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//===- LoopVectorize.cpp - A Loop Vectorizer ------------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This is the LLVM loop vectorizer. This pass modifies 'vectorizable' loops
// and generates target-independent LLVM-IR.
// The vectorizer uses the TargetTransformInfo analysis to estimate the costs
// of instructions in order to estimate the profitability of vectorization.
//
// The loop vectorizer combines consecutive loop iterations into a single
// 'wide' iteration. After this transformation the index is incremented
// by the SIMD vector width, and not by one.
//
// This pass has three parts:
// 1. The main loop pass that drives the different parts.
// 2. LoopVectorizationLegality - A unit that checks for the legality
// of the vectorization.
// 3. InnerLoopVectorizer - A unit that performs the actual
// widening of instructions.
// 4. LoopVectorizationCostModel - A unit that checks for the profitability
// of vectorization. It decides on the optimal vector width, which
// can be one, if vectorization is not profitable.
//
// There is a development effort going on to migrate loop vectorizer to the
// VPlan infrastructure and to introduce outer loop vectorization support (see
// docs/Proposal/VectorizationPlan.rst and
// http://lists.llvm.org/pipermail/llvm-dev/2017-December/119523.html). For this
// purpose, we temporarily introduced the VPlan-native vectorization path: an
// alternative vectorization path that is natively implemented on top of the
// VPlan infrastructure. See EnableVPlanNativePath for enabling.
//
//===----------------------------------------------------------------------===//
//
// The reduction-variable vectorization is based on the paper:
// D. Nuzman and R. Henderson. Multi-platform Auto-vectorization.
//
// Variable uniformity checks are inspired by:
// Karrenberg, R. and Hack, S. Whole Function Vectorization.
//
// The interleaved access vectorization is based on the paper:
// Dorit Nuzman, Ira Rosen and Ayal Zaks. Auto-Vectorization of Interleaved
// Data for SIMD
//
// Other ideas/concepts are from:
// A. Zaks and D. Nuzman. Autovectorization in GCC-two years later.
//
// S. Maleki, Y. Gao, M. Garzaran, T. Wong and D. Padua. An Evaluation of
// Vectorizing Compilers.
//
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/Vectorize/LoopVectorize.h"
#include "LoopVectorizationPlanner.h"
#include "llvm/ADT/APInt.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/DenseMapInfo.h"
#include "llvm/ADT/Hashing.h"
#include "llvm/ADT/MapVector.h"
#include "llvm/ADT/None.h"
#include "llvm/ADT/Optional.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/Twine.h"
#include "llvm/ADT/iterator_range.h"
#include "llvm/Analysis/AssumptionCache.h"
#include "llvm/Analysis/BasicAliasAnalysis.h"
#include "llvm/Analysis/BlockFrequencyInfo.h"
#include "llvm/Analysis/CFG.h"
#include "llvm/Analysis/CodeMetrics.h"
#include "llvm/Analysis/DemandedBits.h"
#include "llvm/Analysis/GlobalsModRef.h"
#include "llvm/Analysis/LoopAccessAnalysis.h"
#include "llvm/Analysis/LoopAnalysisManager.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/LoopIterator.h"
#include "llvm/Analysis/OptimizationRemarkEmitter.h"
#include "llvm/Analysis/ScalarEvolution.h"
#include "llvm/Analysis/ScalarEvolutionExpander.h"
#include "llvm/Analysis/ScalarEvolutionExpressions.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/Analysis/VectorUtils.h"
#include "llvm/IR/Attributes.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/CFG.h"
#include "llvm/IR/Constant.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/DebugInfoMetadata.h"
#include "llvm/IR/DebugLoc.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/DiagnosticInfo.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/InstrTypes.h"
#include "llvm/IR/Instruction.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/Metadata.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/Operator.h"
#include "llvm/IR/Type.h"
#include "llvm/IR/Use.h"
#include "llvm/IR/User.h"
#include "llvm/IR/Value.h"
#include "llvm/IR/ValueHandle.h"
#include "llvm/IR/Verifier.h"
#include "llvm/Pass.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/LoopSimplify.h"
#include "llvm/Transforms/Utils/LoopUtils.h"
#include "llvm/Transforms/Utils/LoopVersioning.h"
#include "llvm/Transforms/Vectorize/LoopVectorizationLegality.h"
#include <algorithm>
#include <cassert>
#include <cstdint>
#include <cstdlib>
#include <functional>
#include <iterator>
#include <limits>
#include <memory>
#include <string>
#include <tuple>
#include <utility>
#include <vector>
using namespace llvm;
#define LV_NAME "loop-vectorize"
#define DEBUG_TYPE LV_NAME
STATISTIC(LoopsVectorized, "Number of loops vectorized");
STATISTIC(LoopsAnalyzed, "Number of loops analyzed for vectorization");
/// Loops with a known constant trip count below this number are vectorized only
/// if no scalar iteration overheads are incurred.
static cl::opt<unsigned> TinyTripCountVectorThreshold(
"vectorizer-min-trip-count", cl::init(16), cl::Hidden,
cl::desc("Loops with a constant trip count that is smaller than this "
"value are vectorized only if no scalar iteration overheads "
"are incurred."));
static cl::opt<bool> MaximizeBandwidth(
"vectorizer-maximize-bandwidth", cl::init(false), cl::Hidden,
cl::desc("Maximize bandwidth when selecting vectorization factor which "
"will be determined by the smallest type in loop."));
static cl::opt<bool> EnableInterleavedMemAccesses(
"enable-interleaved-mem-accesses", cl::init(false), cl::Hidden,
cl::desc("Enable vectorization on interleaved memory accesses in a loop"));
/// Maximum factor for an interleaved memory access.
static cl::opt<unsigned> MaxInterleaveGroupFactor(
"max-interleave-group-factor", cl::Hidden,
cl::desc("Maximum factor for an interleaved access group (default = 8)"),
cl::init(8));
/// We don't interleave loops with a known constant trip count below this
/// number.
static const unsigned TinyTripCountInterleaveThreshold = 128;
static cl::opt<unsigned> ForceTargetNumScalarRegs(
"force-target-num-scalar-regs", cl::init(0), cl::Hidden,
cl::desc("A flag that overrides the target's number of scalar registers."));
static cl::opt<unsigned> ForceTargetNumVectorRegs(
"force-target-num-vector-regs", cl::init(0), cl::Hidden,
cl::desc("A flag that overrides the target's number of vector registers."));
static cl::opt<unsigned> ForceTargetMaxScalarInterleaveFactor(
"force-target-max-scalar-interleave", cl::init(0), cl::Hidden,
cl::desc("A flag that overrides the target's max interleave factor for "
"scalar loops."));
static cl::opt<unsigned> ForceTargetMaxVectorInterleaveFactor(
"force-target-max-vector-interleave", cl::init(0), cl::Hidden,
cl::desc("A flag that overrides the target's max interleave factor for "
"vectorized loops."));
static cl::opt<unsigned> ForceTargetInstructionCost(
"force-target-instruction-cost", cl::init(0), cl::Hidden,
cl::desc("A flag that overrides the target's expected cost for "
"an instruction to a single constant value. Mostly "
"useful for getting consistent testing."));
static cl::opt<unsigned> SmallLoopCost(
"small-loop-cost", cl::init(20), cl::Hidden,
cl::desc(
"The cost of a loop that is considered 'small' by the interleaver."));
static cl::opt<bool> LoopVectorizeWithBlockFrequency(
"loop-vectorize-with-block-frequency", cl::init(true), cl::Hidden,
cl::desc("Enable the use of the block frequency analysis to access PGO "
"heuristics minimizing code growth in cold regions and being more "
"aggressive in hot regions."));
// Runtime interleave loops for load/store throughput.
static cl::opt<bool> EnableLoadStoreRuntimeInterleave(
"enable-loadstore-runtime-interleave", cl::init(true), cl::Hidden,
cl::desc(
"Enable runtime interleaving until load/store ports are saturated"));
/// The number of stores in a loop that are allowed to need predication.
static cl::opt<unsigned> NumberOfStoresToPredicate(
"vectorize-num-stores-pred", cl::init(1), cl::Hidden,
cl::desc("Max number of stores to be predicated behind an if."));
static cl::opt<bool> EnableIndVarRegisterHeur(
"enable-ind-var-reg-heur", cl::init(true), cl::Hidden,
cl::desc("Count the induction variable only once when interleaving"));
static cl::opt<bool> EnableCondStoresVectorization(
"enable-cond-stores-vec", cl::init(true), cl::Hidden,
cl::desc("Enable if predication of stores during vectorization."));
static cl::opt<unsigned> MaxNestedScalarReductionIC(
"max-nested-scalar-reduction-interleave", cl::init(2), cl::Hidden,
cl::desc("The maximum interleave count to use when interleaving a scalar "
"reduction in a nested loop."));
static cl::opt<bool> EnableVPlanNativePath(
"enable-vplan-native-path", cl::init(false), cl::Hidden,
cl::desc("Enable VPlan-native vectorization path with "
"support for outer loop vectorization."));
/// A helper function for converting Scalar types to vector types.
/// If the incoming type is void, we return void. If the VF is 1, we return
/// the scalar type.
static Type *ToVectorTy(Type *Scalar, unsigned VF) {
if (Scalar->isVoidTy() || VF == 1)
return Scalar;
return VectorType::get(Scalar, VF);
}
// FIXME: The following helper functions have multiple implementations
// in the project. They can be effectively organized in a common Load/Store
// utilities unit.
/// A helper function that returns the type of loaded or stored value.
static Type *getMemInstValueType(Value *I) {
assert((isa<LoadInst>(I) || isa<StoreInst>(I)) &&
"Expected Load or Store instruction");
if (auto *LI = dyn_cast<LoadInst>(I))
return LI->getType();
return cast<StoreInst>(I)->getValueOperand()->getType();
}
/// A helper function that returns the alignment of load or store instruction.
static unsigned getMemInstAlignment(Value *I) {
assert((isa<LoadInst>(I) || isa<StoreInst>(I)) &&
"Expected Load or Store instruction");
if (auto *LI = dyn_cast<LoadInst>(I))
return LI->getAlignment();
return cast<StoreInst>(I)->getAlignment();
}
/// A helper function that returns the address space of the pointer operand of
/// load or store instruction.
static unsigned getMemInstAddressSpace(Value *I) {
assert((isa<LoadInst>(I) || isa<StoreInst>(I)) &&
"Expected Load or Store instruction");
if (auto *LI = dyn_cast<LoadInst>(I))
return LI->getPointerAddressSpace();
return cast<StoreInst>(I)->getPointerAddressSpace();
}
/// A helper function that returns true if the given type is irregular. The
/// type is irregular if its allocated size doesn't equal the store size of an
/// element of the corresponding vector type at the given vectorization factor.
static bool hasIrregularType(Type *Ty, const DataLayout &DL, unsigned VF) {
// Determine if an array of VF elements of type Ty is "bitcast compatible"
// with a <VF x Ty> vector.
if (VF > 1) {
auto *VectorTy = VectorType::get(Ty, VF);
return VF * DL.getTypeAllocSize(Ty) != DL.getTypeStoreSize(VectorTy);
}
// If the vectorization factor is one, we just check if an array of type Ty
// requires padding between elements.
return DL.getTypeAllocSizeInBits(Ty) != DL.getTypeSizeInBits(Ty);
}
/// A helper function that returns the reciprocal of the block probability of
/// predicated blocks. If we return X, we are assuming the predicated block
/// will execute once for every X iterations of the loop header.
///
/// TODO: We should use actual block probability here, if available. Currently,
/// we always assume predicated blocks have a 50% chance of executing.
static unsigned getReciprocalPredBlockProb() { return 2; }
/// A helper function that adds a 'fast' flag to floating-point operations.
static Value *addFastMathFlag(Value *V) {
if (isa<FPMathOperator>(V)) {
FastMathFlags Flags;
Flags.setFast();
cast<Instruction>(V)->setFastMathFlags(Flags);
}
return V;
}
/// A helper function that returns an integer or floating-point constant with
/// value C.
static Constant *getSignedIntOrFpConstant(Type *Ty, int64_t C) {
return Ty->isIntegerTy() ? ConstantInt::getSigned(Ty, C)
: ConstantFP::get(Ty, C);
}
namespace llvm {
/// InnerLoopVectorizer vectorizes loops which contain only one basic
/// block to a specified vectorization factor (VF).
/// This class performs the widening of scalars into vectors, or multiple
/// scalars. This class also implements the following features:
/// * It inserts an epilogue loop for handling loops that don't have iteration
/// counts that are known to be a multiple of the vectorization factor.
/// * It handles the code generation for reduction variables.
/// * Scalarization (implementation using scalars) of un-vectorizable
/// instructions.
/// InnerLoopVectorizer does not perform any vectorization-legality
/// checks, and relies on the caller to check for the different legality
/// aspects. The InnerLoopVectorizer relies on the
/// LoopVectorizationLegality class to provide information about the induction
/// and reduction variables that were found to a given vectorization factor.
class InnerLoopVectorizer {
public:
InnerLoopVectorizer(Loop *OrigLoop, PredicatedScalarEvolution &PSE,
LoopInfo *LI, DominatorTree *DT,
const TargetLibraryInfo *TLI,
const TargetTransformInfo *TTI, AssumptionCache *AC,
OptimizationRemarkEmitter *ORE, unsigned VecWidth,
unsigned UnrollFactor, LoopVectorizationLegality *LVL,
LoopVectorizationCostModel *CM)
: OrigLoop(OrigLoop), PSE(PSE), LI(LI), DT(DT), TLI(TLI), TTI(TTI),
AC(AC), ORE(ORE), VF(VecWidth), UF(UnrollFactor),
Builder(PSE.getSE()->getContext()),
VectorLoopValueMap(UnrollFactor, VecWidth), Legal(LVL), Cost(CM) {}
virtual ~InnerLoopVectorizer() = default;
/// Create a new empty loop. Unlink the old loop and connect the new one.
/// Return the pre-header block of the new loop.
BasicBlock *createVectorizedLoopSkeleton();
/// Widen a single instruction within the innermost loop.
void widenInstruction(Instruction &I);
/// Fix the vectorized code, taking care of header phi's, live-outs, and more.
void fixVectorizedLoop();
// Return true if any runtime check is added.
bool areSafetyChecksAdded() { return AddedSafetyChecks; }
/// A type for vectorized values in the new loop. Each value from the
/// original loop, when vectorized, is represented by UF vector values in the
/// new unrolled loop, where UF is the unroll factor.
using VectorParts = SmallVector<Value *, 2>;
/// Vectorize a single PHINode in a block. This method handles the induction
/// variable canonicalization. It supports both VF = 1 for unrolled loops and
/// arbitrary length vectors.
void widenPHIInstruction(Instruction *PN, unsigned UF, unsigned VF);
/// A helper function to scalarize a single Instruction in the innermost loop.
/// Generates a sequence of scalar instances for each lane between \p MinLane
/// and \p MaxLane, times each part between \p MinPart and \p MaxPart,
/// inclusive..
void scalarizeInstruction(Instruction *Instr, const VPIteration &Instance,
bool IfPredicateInstr);
/// Widen an integer or floating-point induction variable \p IV. If \p Trunc
/// is provided, the integer induction variable will first be truncated to
/// the corresponding type.
void widenIntOrFpInduction(PHINode *IV, TruncInst *Trunc = nullptr);
/// getOrCreateVectorValue and getOrCreateScalarValue coordinate to generate a
/// vector or scalar value on-demand if one is not yet available. When
/// vectorizing a loop, we visit the definition of an instruction before its
/// uses. When visiting the definition, we either vectorize or scalarize the
/// instruction, creating an entry for it in the corresponding map. (In some
/// cases, such as induction variables, we will create both vector and scalar
/// entries.) Then, as we encounter uses of the definition, we derive values
/// for each scalar or vector use unless such a value is already available.
/// For example, if we scalarize a definition and one of its uses is vector,
/// we build the required vector on-demand with an insertelement sequence
/// when visiting the use. Otherwise, if the use is scalar, we can use the
/// existing scalar definition.
///
/// Return a value in the new loop corresponding to \p V from the original
/// loop at unroll index \p Part. If the value has already been vectorized,
/// the corresponding vector entry in VectorLoopValueMap is returned. If,
/// however, the value has a scalar entry in VectorLoopValueMap, we construct
/// a new vector value on-demand by inserting the scalar values into a vector
/// with an insertelement sequence. If the value has been neither vectorized
/// nor scalarized, it must be loop invariant, so we simply broadcast the
/// value into a vector.
Value *getOrCreateVectorValue(Value *V, unsigned Part);
/// Return a value in the new loop corresponding to \p V from the original
/// loop at unroll and vector indices \p Instance. If the value has been
/// vectorized but not scalarized, the necessary extractelement instruction
/// will be generated.
Value *getOrCreateScalarValue(Value *V, const VPIteration &Instance);
/// Construct the vector value of a scalarized value \p V one lane at a time.
void packScalarIntoVectorValue(Value *V, const VPIteration &Instance);
/// Try to vectorize the interleaved access group that \p Instr belongs to.
void vectorizeInterleaveGroup(Instruction *Instr);
/// Vectorize Load and Store instructions, optionally masking the vector
/// operations if \p BlockInMask is non-null.
void vectorizeMemoryInstruction(Instruction *Instr,
VectorParts *BlockInMask = nullptr);
/// \brief Set the debug location in the builder using the debug location in
/// the instruction.
void setDebugLocFromInst(IRBuilder<> &B, const Value *Ptr);
protected:
friend class LoopVectorizationPlanner;
/// A small list of PHINodes.
using PhiVector = SmallVector<PHINode *, 4>;
/// A type for scalarized values in the new loop. Each value from the
/// original loop, when scalarized, is represented by UF x VF scalar values
/// in the new unrolled loop, where UF is the unroll factor and VF is the
/// vectorization factor.
using ScalarParts = SmallVector<SmallVector<Value *, 4>, 2>;
/// Set up the values of the IVs correctly when exiting the vector loop.
void fixupIVUsers(PHINode *OrigPhi, const InductionDescriptor &II,
Value *CountRoundDown, Value *EndValue,
BasicBlock *MiddleBlock);
/// Create a new induction variable inside L.
PHINode *createInductionVariable(Loop *L, Value *Start, Value *End,
Value *Step, Instruction *DL);
/// Handle all cross-iteration phis in the header.
void fixCrossIterationPHIs();
/// Fix a first-order recurrence. This is the second phase of vectorizing
/// this phi node.
void fixFirstOrderRecurrence(PHINode *Phi);
/// Fix a reduction cross-iteration phi. This is the second phase of
/// vectorizing this phi node.
void fixReduction(PHINode *Phi);
/// \brief The Loop exit block may have single value PHI nodes with some
/// incoming value. While vectorizing we only handled real values
/// that were defined inside the loop and we should have one value for
/// each predecessor of its parent basic block. See PR14725.
void fixLCSSAPHIs();
/// Iteratively sink the scalarized operands of a predicated instruction into
/// the block that was created for it.
void sinkScalarOperands(Instruction *PredInst);
/// Shrinks vector element sizes to the smallest bitwidth they can be legally
/// represented as.
void truncateToMinimalBitwidths();
/// Insert the new loop to the loop hierarchy and pass manager
/// and update the analysis passes.
void updateAnalysis();
/// Create a broadcast instruction. This method generates a broadcast
/// instruction (shuffle) for loop invariant values and for the induction
/// value. If this is the induction variable then we extend it to N, N+1, ...
/// this is needed because each iteration in the loop corresponds to a SIMD
/// element.
virtual Value *getBroadcastInstrs(Value *V);
/// This function adds (StartIdx, StartIdx + Step, StartIdx + 2*Step, ...)
/// to each vector element of Val. The sequence starts at StartIndex.
/// \p Opcode is relevant for FP induction variable.
virtual Value *getStepVector(Value *Val, int StartIdx, Value *Step,
Instruction::BinaryOps Opcode =
Instruction::BinaryOpsEnd);
/// Compute scalar induction steps. \p ScalarIV is the scalar induction
/// variable on which to base the steps, \p Step is the size of the step, and
/// \p EntryVal is the value from the original loop that maps to the steps.
/// Note that \p EntryVal doesn't have to be an induction variable - it
/// can also be a truncate instruction.
void buildScalarSteps(Value *ScalarIV, Value *Step, Instruction *EntryVal,
const InductionDescriptor &ID);
/// Create a vector induction phi node based on an existing scalar one. \p
/// EntryVal is the value from the original loop that maps to the vector phi
/// node, and \p Step is the loop-invariant step. If \p EntryVal is a
/// truncate instruction, instead of widening the original IV, we widen a
/// version of the IV truncated to \p EntryVal's type.
void createVectorIntOrFpInductionPHI(const InductionDescriptor &II,
Value *Step, Instruction *EntryVal);
/// Returns true if an instruction \p I should be scalarized instead of
/// vectorized for the chosen vectorization factor.
bool shouldScalarizeInstruction(Instruction *I) const;
/// Returns true if we should generate a scalar version of \p IV.
bool needsScalarInduction(Instruction *IV) const;
/// If there is a cast involved in the induction variable \p ID, which should
/// be ignored in the vectorized loop body, this function records the
/// VectorLoopValue of the respective Phi also as the VectorLoopValue of the
/// cast. We had already proved that the casted Phi is equal to the uncasted
/// Phi in the vectorized loop (under a runtime guard), and therefore
/// there is no need to vectorize the cast - the same value can be used in the
/// vector loop for both the Phi and the cast.
/// If \p VectorLoopValue is a scalarized value, \p Lane is also specified,
/// Otherwise, \p VectorLoopValue is a widened/vectorized value.
///
/// \p EntryVal is the value from the original loop that maps to the vector
/// phi node and is used to distinguish what is the IV currently being
/// processed - original one (if \p EntryVal is a phi corresponding to the
/// original IV) or the "newly-created" one based on the proof mentioned above
/// (see also buildScalarSteps() and createVectorIntOrFPInductionPHI()). In the
/// latter case \p EntryVal is a TruncInst and we must not record anything for
/// that IV, but it's error-prone to expect callers of this routine to care
/// about that, hence this explicit parameter.
void recordVectorLoopValueForInductionCast(const InductionDescriptor &ID,
const Instruction *EntryVal,
Value *VectorLoopValue,
unsigned Part,
unsigned Lane = UINT_MAX);
/// Generate a shuffle sequence that will reverse the vector Vec.
virtual Value *reverseVector(Value *Vec);
/// Returns (and creates if needed) the original loop trip count.
Value *getOrCreateTripCount(Loop *NewLoop);
/// Returns (and creates if needed) the trip count of the widened loop.
Value *getOrCreateVectorTripCount(Loop *NewLoop);
/// Returns a bitcasted value to the requested vector type.
/// Also handles bitcasts of vector<float> <-> vector<pointer> types.
Value *createBitOrPointerCast(Value *V, VectorType *DstVTy,
const DataLayout &DL);
/// Emit a bypass check to see if the vector trip count is zero, including if
/// it overflows.
void emitMinimumIterationCountCheck(Loop *L, BasicBlock *Bypass);
/// Emit a bypass check to see if all of the SCEV assumptions we've
/// had to make are correct.
void emitSCEVChecks(Loop *L, BasicBlock *Bypass);
/// Emit bypass checks to check any memory assumptions we may have made.
void emitMemRuntimeChecks(Loop *L, BasicBlock *Bypass);
/// Add additional metadata to \p To that was not present on \p Orig.
///
/// Currently this is used to add the noalias annotations based on the
/// inserted memchecks. Use this for instructions that are *cloned* into the
/// vector loop.
void addNewMetadata(Instruction *To, const Instruction *Orig);
/// Add metadata from one instruction to another.
///
/// This includes both the original MDs from \p From and additional ones (\see
/// addNewMetadata). Use this for *newly created* instructions in the vector
/// loop.
void addMetadata(Instruction *To, Instruction *From);
/// \brief Similar to the previous function but it adds the metadata to a
/// vector of instructions.
void addMetadata(ArrayRef<Value *> To, Instruction *From);
/// The original loop.
Loop *OrigLoop;
/// A wrapper around ScalarEvolution used to add runtime SCEV checks. Applies
/// dynamic knowledge to simplify SCEV expressions and converts them to a
/// more usable form.
PredicatedScalarEvolution &PSE;
/// Loop Info.
LoopInfo *LI;
/// Dominator Tree.
DominatorTree *DT;
/// Alias Analysis.
AliasAnalysis *AA;
/// Target Library Info.
const TargetLibraryInfo *TLI;
/// Target Transform Info.
const TargetTransformInfo *TTI;
/// Assumption Cache.
AssumptionCache *AC;
/// Interface to emit optimization remarks.
OptimizationRemarkEmitter *ORE;
/// \brief LoopVersioning. It's only set up (non-null) if memchecks were
/// used.
///
/// This is currently only used to add no-alias metadata based on the
/// memchecks. The actually versioning is performed manually.
std::unique_ptr<LoopVersioning> LVer;
/// The vectorization SIMD factor to use. Each vector will have this many
/// vector elements.
unsigned VF;
/// The vectorization unroll factor to use. Each scalar is vectorized to this
/// many different vector instructions.
unsigned UF;
/// The builder that we use
IRBuilder<> Builder;
// --- Vectorization state ---
/// The vector-loop preheader.
BasicBlock *LoopVectorPreHeader;
/// The scalar-loop preheader.
BasicBlock *LoopScalarPreHeader;
/// Middle Block between the vector and the scalar.
BasicBlock *LoopMiddleBlock;
/// The ExitBlock of the scalar loop.
BasicBlock *LoopExitBlock;
/// The vector loop body.
BasicBlock *LoopVectorBody;
/// The scalar loop body.
BasicBlock *LoopScalarBody;
/// A list of all bypass blocks. The first block is the entry of the loop.
SmallVector<BasicBlock *, 4> LoopBypassBlocks;
/// The new Induction variable which was added to the new block.
PHINode *Induction = nullptr;
/// The induction variable of the old basic block.
PHINode *OldInduction = nullptr;
/// Maps values from the original loop to their corresponding values in the
/// vectorized loop. A key value can map to either vector values, scalar
/// values or both kinds of values, depending on whether the key was
/// vectorized and scalarized.
VectorizerValueMap VectorLoopValueMap;
/// Store instructions that were predicated.
SmallVector<Instruction *, 4> PredicatedInstructions;
/// Trip count of the original loop.
Value *TripCount = nullptr;
/// Trip count of the widened loop (TripCount - TripCount % (VF*UF))
Value *VectorTripCount = nullptr;
/// The legality analysis.
LoopVectorizationLegality *Legal;
/// The profitablity analysis.
LoopVectorizationCostModel *Cost;
// Record whether runtime checks are added.
bool AddedSafetyChecks = false;
// Holds the end values for each induction variable. We save the end values
// so we can later fix-up the external users of the induction variables.
DenseMap<PHINode *, Value *> IVEndValues;
};
class InnerLoopUnroller : public InnerLoopVectorizer {
public:
InnerLoopUnroller(Loop *OrigLoop, PredicatedScalarEvolution &PSE,
LoopInfo *LI, DominatorTree *DT,
const TargetLibraryInfo *TLI,
const TargetTransformInfo *TTI, AssumptionCache *AC,
OptimizationRemarkEmitter *ORE, unsigned UnrollFactor,
LoopVectorizationLegality *LVL,
LoopVectorizationCostModel *CM)
: InnerLoopVectorizer(OrigLoop, PSE, LI, DT, TLI, TTI, AC, ORE, 1,
UnrollFactor, LVL, CM) {}
private:
Value *getBroadcastInstrs(Value *V) override;
Value *getStepVector(Value *Val, int StartIdx, Value *Step,
Instruction::BinaryOps Opcode =
Instruction::BinaryOpsEnd) override;
Value *reverseVector(Value *Vec) override;
};
} // end namespace llvm
/// \brief Look for a meaningful debug location on the instruction or it's
/// operands.
static Instruction *getDebugLocFromInstOrOperands(Instruction *I) {
if (!I)
return I;
DebugLoc Empty;
if (I->getDebugLoc() != Empty)
return I;
for (User::op_iterator OI = I->op_begin(), OE = I->op_end(); OI != OE; ++OI) {
if (Instruction *OpInst = dyn_cast<Instruction>(*OI))
if (OpInst->getDebugLoc() != Empty)
return OpInst;
}
return I;
}
void InnerLoopVectorizer::setDebugLocFromInst(IRBuilder<> &B, const Value *Ptr) {
if (const Instruction *Inst = dyn_cast_or_null<Instruction>(Ptr)) {
const DILocation *DIL = Inst->getDebugLoc();
if (DIL && Inst->getFunction()->isDebugInfoForProfiling() &&
!isa<DbgInfoIntrinsic>(Inst))
B.SetCurrentDebugLocation(DIL->cloneWithDuplicationFactor(UF * VF));
else
B.SetCurrentDebugLocation(DIL);
} else
B.SetCurrentDebugLocation(DebugLoc());
}
#ifndef NDEBUG
/// \return string containing a file name and a line # for the given loop.
static std::string getDebugLocString(const Loop *L) {
std::string Result;
if (L) {
raw_string_ostream OS(Result);
if (const DebugLoc LoopDbgLoc = L->getStartLoc())
LoopDbgLoc.print(OS);
else
// Just print the module name.
OS << L->getHeader()->getParent()->getParent()->getModuleIdentifier();
OS.flush();
}
return Result;
}
#endif
void InnerLoopVectorizer::addNewMetadata(Instruction *To,
const Instruction *Orig) {
// If the loop was versioned with memchecks, add the corresponding no-alias
// metadata.
if (LVer && (isa<LoadInst>(Orig) || isa<StoreInst>(Orig)))
LVer->annotateInstWithNoAlias(To, Orig);
}
void InnerLoopVectorizer::addMetadata(Instruction *To,
Instruction *From) {
propagateMetadata(To, From);
addNewMetadata(To, From);
}
void InnerLoopVectorizer::addMetadata(ArrayRef<Value *> To,
Instruction *From) {
for (Value *V : To) {
if (Instruction *I = dyn_cast<Instruction>(V))
addMetadata(I, From);
}
}
namespace llvm {
/// \brief The group of interleaved loads/stores sharing the same stride and
/// close to each other.
///
/// Each member in this group has an index starting from 0, and the largest
/// index should be less than interleaved factor, which is equal to the absolute
/// value of the access's stride.
///
/// E.g. An interleaved load group of factor 4:
/// for (unsigned i = 0; i < 1024; i+=4) {
/// a = A[i]; // Member of index 0
/// b = A[i+1]; // Member of index 1
/// d = A[i+3]; // Member of index 3
/// ...
/// }
///
/// An interleaved store group of factor 4:
/// for (unsigned i = 0; i < 1024; i+=4) {
/// ...
/// A[i] = a; // Member of index 0
/// A[i+1] = b; // Member of index 1
/// A[i+2] = c; // Member of index 2
/// A[i+3] = d; // Member of index 3
/// }
///
/// Note: the interleaved load group could have gaps (missing members), but
/// the interleaved store group doesn't allow gaps.
class InterleaveGroup {
public:
InterleaveGroup(Instruction *Instr, int Stride, unsigned Align)
: Align(Align), InsertPos(Instr) {
assert(Align && "The alignment should be non-zero");
Factor = std::abs(Stride);
assert(Factor > 1 && "Invalid interleave factor");
Reverse = Stride < 0;
Members[0] = Instr;
}
bool isReverse() const { return Reverse; }
unsigned getFactor() const { return Factor; }
unsigned getAlignment() const { return Align; }
unsigned getNumMembers() const { return Members.size(); }
/// \brief Try to insert a new member \p Instr with index \p Index and
/// alignment \p NewAlign. The index is related to the leader and it could be
/// negative if it is the new leader.
///
/// \returns false if the instruction doesn't belong to the group.
bool insertMember(Instruction *Instr, int Index, unsigned NewAlign) {
assert(NewAlign && "The new member's alignment should be non-zero");
int Key = Index + SmallestKey;
// Skip if there is already a member with the same index.
if (Members.count(Key))
return false;
if (Key > LargestKey) {
// The largest index is always less than the interleave factor.
if (Index >= static_cast<int>(Factor))
return false;
LargestKey = Key;
} else if (Key < SmallestKey) {
// The largest index is always less than the interleave factor.
if (LargestKey - Key >= static_cast<int>(Factor))
return false;
SmallestKey = Key;
}
// It's always safe to select the minimum alignment.
Align = std::min(Align, NewAlign);
Members[Key] = Instr;
return true;
}
/// \brief Get the member with the given index \p Index
///
/// \returns nullptr if contains no such member.
Instruction *getMember(unsigned Index) const {
int Key = SmallestKey + Index;
if (!Members.count(Key))
return nullptr;
return Members.find(Key)->second;
}
/// \brief Get the index for the given member. Unlike the key in the member
/// map, the index starts from 0.
unsigned getIndex(Instruction *Instr) const {
for (auto I : Members)
if (I.second == Instr)
return I.first - SmallestKey;
llvm_unreachable("InterleaveGroup contains no such member");
}
Instruction *getInsertPos() const { return InsertPos; }
void setInsertPos(Instruction *Inst) { InsertPos = Inst; }
/// Add metadata (e.g. alias info) from the instructions in this group to \p
/// NewInst.
///
/// FIXME: this function currently does not add noalias metadata a'la
/// addNewMedata. To do that we need to compute the intersection of the
/// noalias info from all members.
void addMetadata(Instruction *NewInst) const {
SmallVector<Value *, 4> VL;
std::transform(Members.begin(), Members.end(), std::back_inserter(VL),
[](std::pair<int, Instruction *> p) { return p.second; });
propagateMetadata(NewInst, VL);
}
private:
unsigned Factor; // Interleave Factor.
bool Reverse;
unsigned Align;
DenseMap<int, Instruction *> Members;
int SmallestKey = 0;
int LargestKey = 0;
// To avoid breaking dependences, vectorized instructions of an interleave
// group should be inserted at either the first load or the last store in
// program order.
//
// E.g. %even = load i32 // Insert Position
// %add = add i32 %even // Use of %even
// %odd = load i32
//
// store i32 %even
// %odd = add i32 // Def of %odd
// store i32 %odd // Insert Position
Instruction *InsertPos;
};
} // end namespace llvm
namespace {
/// \brief Drive the analysis of interleaved memory accesses in the loop.
///
/// Use this class to analyze interleaved accesses only when we can vectorize
/// a loop. Otherwise it's meaningless to do analysis as the vectorization
/// on interleaved accesses is unsafe.
///
/// The analysis collects interleave groups and records the relationships
/// between the member and the group in a map.
class InterleavedAccessInfo {
public:
InterleavedAccessInfo(PredicatedScalarEvolution &PSE, Loop *L,
DominatorTree *DT, LoopInfo *LI,
const LoopAccessInfo *LAI)
: PSE(PSE), TheLoop(L), DT(DT), LI(LI), LAI(LAI) {}
~InterleavedAccessInfo() {
SmallSet<InterleaveGroup *, 4> DelSet;
// Avoid releasing a pointer twice.
for (auto &I : InterleaveGroupMap)
DelSet.insert(I.second);
for (auto *Ptr : DelSet)
delete Ptr;
}
/// \brief Analyze the interleaved accesses and collect them in interleave
/// groups. Substitute symbolic strides using \p Strides.
void analyzeInterleaving();
/// \brief Check if \p Instr belongs to any interleave group.
bool isInterleaved(Instruction *Instr) const {
return InterleaveGroupMap.count(Instr);
}
/// \brief Get the interleave group that \p Instr belongs to.
///
/// \returns nullptr if doesn't have such group.
InterleaveGroup *getInterleaveGroup(Instruction *Instr) const {
if (InterleaveGroupMap.count(Instr))
return InterleaveGroupMap.find(Instr)->second;
return nullptr;
}
/// \brief Returns true if an interleaved group that may access memory
/// out-of-bounds requires a scalar epilogue iteration for correctness.
bool requiresScalarEpilogue() const { return RequiresScalarEpilogue; }
private:
/// A wrapper around ScalarEvolution, used to add runtime SCEV checks.
/// Simplifies SCEV expressions in the context of existing SCEV assumptions.
/// The interleaved access analysis can also add new predicates (for example
/// by versioning strides of pointers).
PredicatedScalarEvolution &PSE;
Loop *TheLoop;
DominatorTree *DT;
LoopInfo *LI;
const LoopAccessInfo *LAI;
/// True if the loop may contain non-reversed interleaved groups with
/// out-of-bounds accesses. We ensure we don't speculatively access memory
/// out-of-bounds by executing at least one scalar epilogue iteration.
bool RequiresScalarEpilogue = false;
/// Holds the relationships between the members and the interleave group.
DenseMap<Instruction *, InterleaveGroup *> InterleaveGroupMap;
/// Holds dependences among the memory accesses in the loop. It maps a source
/// access to a set of dependent sink accesses.
DenseMap<Instruction *, SmallPtrSet<Instruction *, 2>> Dependences;
/// \brief The descriptor for a strided memory access.
struct StrideDescriptor {
StrideDescriptor() = default;
StrideDescriptor(int64_t Stride, const SCEV *Scev, uint64_t Size,
unsigned Align)
: Stride(Stride), Scev(Scev), Size(Size), Align(Align) {}
// The access's stride. It is negative for a reverse access.
int64_t Stride = 0;
// The scalar expression of this access.
const SCEV *Scev = nullptr;
// The size of the memory object.
uint64_t Size = 0;
// The alignment of this access.
unsigned Align = 0;
};
/// \brief A type for holding instructions and their stride descriptors.
using StrideEntry = std::pair<Instruction *, StrideDescriptor>;
/// \brief Create a new interleave group with the given instruction \p Instr,
/// stride \p Stride and alignment \p Align.
///
/// \returns the newly created interleave group.
InterleaveGroup *createInterleaveGroup(Instruction *Instr, int Stride,
unsigned Align) {
assert(!InterleaveGroupMap.count(Instr) &&
"Already in an interleaved access group");
InterleaveGroupMap[Instr] = new InterleaveGroup(Instr, Stride, Align);
return InterleaveGroupMap[Instr];
}
/// \brief Release the group and remove all the relationships.
void releaseGroup(InterleaveGroup *Group) {
for (unsigned i = 0; i < Group->getFactor(); i++)
if (Instruction *Member = Group->getMember(i))
InterleaveGroupMap.erase(Member);
delete Group;
}
/// \brief Collect all the accesses with a constant stride in program order.
void collectConstStrideAccesses(
MapVector<Instruction *, StrideDescriptor> &AccessStrideInfo,
const ValueToValueMap &Strides);
/// \brief Returns true if \p Stride is allowed in an interleaved group.
static bool isStrided(int Stride) {
unsigned Factor = std::abs(Stride);
return Factor >= 2 && Factor <= MaxInterleaveGroupFactor;
}
/// \brief Returns true if \p BB is a predicated block.
bool isPredicated(BasicBlock *BB) const {
return LoopAccessInfo::blockNeedsPredication(BB, TheLoop, DT);
}
/// \brief Returns true if LoopAccessInfo can be used for dependence queries.
bool areDependencesValid() const {
return LAI && LAI->getDepChecker().getDependences();
}
/// \brief Returns true if memory accesses \p A and \p B can be reordered, if
/// necessary, when constructing interleaved groups.
///
/// \p A must precede \p B in program order. We return false if reordering is
/// not necessary or is prevented because \p A and \p B may be dependent.
bool canReorderMemAccessesForInterleavedGroups(StrideEntry *A,
StrideEntry *B) const {
// Code motion for interleaved accesses can potentially hoist strided loads
// and sink strided stores. The code below checks the legality of the
// following two conditions:
//
// 1. Potentially moving a strided load (B) before any store (A) that
// precedes B, or
//
// 2. Potentially moving a strided store (A) after any load or store (B)
// that A precedes.
//
// It's legal to reorder A and B if we know there isn't a dependence from A
// to B. Note that this determination is conservative since some
// dependences could potentially be reordered safely.
// A is potentially the source of a dependence.
auto *Src = A->first;
auto SrcDes = A->second;
// B is potentially the sink of a dependence.
auto *Sink = B->first;
auto SinkDes = B->second;
// Code motion for interleaved accesses can't violate WAR dependences.
// Thus, reordering is legal if the source isn't a write.
if (!Src->mayWriteToMemory())
return true;
// At least one of the accesses must be strided.
if (!isStrided(SrcDes.Stride) && !isStrided(SinkDes.Stride))
return true;
// If dependence information is not available from LoopAccessInfo,
// conservatively assume the instructions can't be reordered.
if (!areDependencesValid())
return false;
// If we know there is a dependence from source to sink, assume the
// instructions can't be reordered. Otherwise, reordering is legal.
return !Dependences.count(Src) || !Dependences.lookup(Src).count(Sink);
}
/// \brief Collect the dependences from LoopAccessInfo.
///
/// We process the dependences once during the interleaved access analysis to
/// enable constant-time dependence queries.
void collectDependences() {
if (!areDependencesValid())
return;
auto *Deps = LAI->getDepChecker().getDependences();
for (auto Dep : *Deps)
Dependences[Dep.getSource(*LAI)].insert(Dep.getDestination(*LAI));
}
};
} // end anonymous namespace
static void emitMissedWarning(Function *F, Loop *L,
const LoopVectorizeHints &LH,
OptimizationRemarkEmitter *ORE) {
LH.emitRemarkWithHints();
if (LH.getForce() == LoopVectorizeHints::FK_Enabled) {
if (LH.getWidth() != 1)
ORE->emit(DiagnosticInfoOptimizationFailure(
DEBUG_TYPE, "FailedRequestedVectorization",
L->getStartLoc(), L->getHeader())
<< "loop not vectorized: "
<< "failed explicitly specified loop vectorization");
else if (LH.getInterleave() != 1)
ORE->emit(DiagnosticInfoOptimizationFailure(
DEBUG_TYPE, "FailedRequestedInterleaving", L->getStartLoc(),
L->getHeader())
<< "loop not interleaved: "
<< "failed explicitly specified loop interleaving");
}
}
namespace llvm {
/// LoopVectorizationCostModel - estimates the expected speedups due to
/// vectorization.
/// In many cases vectorization is not profitable. This can happen because of
/// a number of reasons. In this class we mainly attempt to predict the
/// expected speedup/slowdowns due to the supported instruction set. We use the
/// TargetTransformInfo to query the different backends for the cost of
/// different operations.
class LoopVectorizationCostModel {
public:
LoopVectorizationCostModel(Loop *L, PredicatedScalarEvolution &PSE,
LoopInfo *LI, LoopVectorizationLegality *Legal,
const TargetTransformInfo &TTI,
const TargetLibraryInfo *TLI, DemandedBits *DB,
AssumptionCache *AC,
OptimizationRemarkEmitter *ORE, const Function *F,
const LoopVectorizeHints *Hints,
InterleavedAccessInfo &IAI)
: TheLoop(L), PSE(PSE), LI(LI), Legal(Legal), TTI(TTI), TLI(TLI), DB(DB),
AC(AC), ORE(ORE), TheFunction(F), Hints(Hints), InterleaveInfo(IAI) {}
/// \return An upper bound for the vectorization factor, or None if
/// vectorization should be avoided up front.
Optional<unsigned> computeMaxVF(bool OptForSize);
/// \return The most profitable vectorization factor and the cost of that VF.
/// This method checks every power of two up to MaxVF. If UserVF is not ZERO
/// then this vectorization factor will be selected if vectorization is
/// possible.
VectorizationFactor selectVectorizationFactor(unsigned MaxVF);
/// Setup cost-based decisions for user vectorization factor.
void selectUserVectorizationFactor(unsigned UserVF) {
collectUniformsAndScalars(UserVF);
collectInstsToScalarize(UserVF);
}
/// \return The size (in bits) of the smallest and widest types in the code
/// that needs to be vectorized. We ignore values that remain scalar such as
/// 64 bit loop indices.
std::pair<unsigned, unsigned> getSmallestAndWidestTypes();
/// \return The desired interleave count.
/// If interleave count has been specified by metadata it will be returned.
/// Otherwise, the interleave count is computed and returned. VF and LoopCost
/// are the selected vectorization factor and the cost of the selected VF.
unsigned selectInterleaveCount(bool OptForSize, unsigned VF,
unsigned LoopCost);
/// Memory access instruction may be vectorized in more than one way.
/// Form of instruction after vectorization depends on cost.
/// This function takes cost-based decisions for Load/Store instructions
/// and collects them in a map. This decisions map is used for building
/// the lists of loop-uniform and loop-scalar instructions.
/// The calculated cost is saved with widening decision in order to
/// avoid redundant calculations.
void setCostBasedWideningDecision(unsigned VF);
/// \brief A struct that represents some properties of the register usage
/// of a loop.
struct RegisterUsage {
/// Holds the number of loop invariant values that are used in the loop.
unsigned LoopInvariantRegs;
/// Holds the maximum number of concurrent live intervals in the loop.
unsigned MaxLocalUsers;
};
/// \return Returns information about the register usages of the loop for the
/// given vectorization factors.
SmallVector<RegisterUsage, 8> calculateRegisterUsage(ArrayRef<unsigned> VFs);
/// Collect values we want to ignore in the cost model.
void collectValuesToIgnore();
/// \returns The smallest bitwidth each instruction can be represented with.
/// The vector equivalents of these instructions should be truncated to this
/// type.
const MapVector<Instruction *, uint64_t> &getMinimalBitwidths() const {
return MinBWs;
}
/// \returns True if it is more profitable to scalarize instruction \p I for
/// vectorization factor \p VF.
bool isProfitableToScalarize(Instruction *I, unsigned VF) const {
assert(VF > 1 && "Profitable to scalarize relevant only for VF > 1.");
auto Scalars = InstsToScalarize.find(VF);
assert(Scalars != InstsToScalarize.end() &&
"VF not yet analyzed for scalarization profitability");
return Scalars->second.count(I);
}
/// Returns true if \p I is known to be uniform after vectorization.
bool isUniformAfterVectorization(Instruction *I, unsigned VF) const {
if (VF == 1)
return true;
assert(Uniforms.count(VF) && "VF not yet analyzed for uniformity");
auto UniformsPerVF = Uniforms.find(VF);
return UniformsPerVF->second.count(I);
}
/// Returns true if \p I is known to be scalar after vectorization.
bool isScalarAfterVectorization(Instruction *I, unsigned VF) const {
if (VF == 1)
return true;
assert(Scalars.count(VF) && "Scalar values are not calculated for VF");
auto ScalarsPerVF = Scalars.find(VF);
return ScalarsPerVF->second.count(I);
}
/// \returns True if instruction \p I can be truncated to a smaller bitwidth
/// for vectorization factor \p VF.
bool canTruncateToMinimalBitwidth(Instruction *I, unsigned VF) const {
return VF > 1 && MinBWs.count(I) && !isProfitableToScalarize(I, VF) &&
!isScalarAfterVectorization(I, VF);
}
/// Decision that was taken during cost calculation for memory instruction.
enum InstWidening {
CM_Unknown,
CM_Widen, // For consecutive accesses with stride +1.
CM_Widen_Reverse, // For consecutive accesses with stride -1.
CM_Interleave,
CM_GatherScatter,
CM_Scalarize
};
/// Save vectorization decision \p W and \p Cost taken by the cost model for
/// instruction \p I and vector width \p VF.
void setWideningDecision(Instruction *I, unsigned VF, InstWidening W,
unsigned Cost) {
assert(VF >= 2 && "Expected VF >=2");
WideningDecisions[std::make_pair(I, VF)] = std::make_pair(W, Cost);
}
/// Save vectorization decision \p W and \p Cost taken by the cost model for
/// interleaving group \p Grp and vector width \p VF.
void setWideningDecision(const InterleaveGroup *Grp, unsigned VF,
InstWidening W, unsigned Cost) {
assert(VF >= 2 && "Expected VF >=2");
/// Broadcast this decicion to all instructions inside the group.
/// But the cost will be assigned to one instruction only.
for (unsigned i = 0; i < Grp->getFactor(); ++i) {
if (auto *I = Grp->getMember(i)) {
if (Grp->getInsertPos() == I)
WideningDecisions[std::make_pair(I, VF)] = std::make_pair(W, Cost);
else
WideningDecisions[std::make_pair(I, VF)] = std::make_pair(W, 0);
}
}
}
/// Return the cost model decision for the given instruction \p I and vector
/// width \p VF. Return CM_Unknown if this instruction did not pass
/// through the cost modeling.
InstWidening getWideningDecision(Instruction *I, unsigned VF) {
assert(VF >= 2 && "Expected VF >=2");
std::pair<Instruction *, unsigned> InstOnVF = std::make_pair(I, VF);
auto Itr = WideningDecisions.find(InstOnVF);
if (Itr == WideningDecisions.end())
return CM_Unknown;
return Itr->second.first;
}
/// Return the vectorization cost for the given instruction \p I and vector
/// width \p VF.
unsigned getWideningCost(Instruction *I, unsigned VF) {
assert(VF >= 2 && "Expected VF >=2");
std::pair<Instruction *, unsigned> InstOnVF = std::make_pair(I, VF);
assert(WideningDecisions.count(InstOnVF) && "The cost is not calculated");
return WideningDecisions[InstOnVF].second;
}
/// Return True if instruction \p I is an optimizable truncate whose operand
/// is an induction variable. Such a truncate will be removed by adding a new
/// induction variable with the destination type.
bool isOptimizableIVTruncate(Instruction *I, unsigned VF) {
// If the instruction is not a truncate, return false.
auto *Trunc = dyn_cast<TruncInst>(I);
if (!Trunc)
return false;
// Get the source and destination types of the truncate.
Type *SrcTy = ToVectorTy(cast<CastInst>(I)->getSrcTy(), VF);
Type *DestTy = ToVectorTy(cast<CastInst>(I)->getDestTy(), VF);
// If the truncate is free for the given types, return false. Replacing a
// free truncate with an induction variable would add an induction variable
// update instruction to each iteration of the loop. We exclude from this
// check the primary induction variable since it will need an update
// instruction regardless.
Value *Op = Trunc->getOperand(0);
if (Op != Legal->getPrimaryInduction() && TTI.isTruncateFree(SrcTy, DestTy))
return false;
// If the truncated value is not an induction variable, return false.
return Legal->isInductionPhi(Op);
}
/// Collects the instructions to scalarize for each predicated instruction in
/// the loop.
void collectInstsToScalarize(unsigned VF);
/// Collect Uniform and Scalar values for the given \p VF.
/// The sets depend on CM decision for Load/Store instructions
/// that may be vectorized as interleave, gather-scatter or scalarized.
void collectUniformsAndScalars(unsigned VF) {
// Do the analysis once.
if (VF == 1 || Uniforms.count(VF))
return;
setCostBasedWideningDecision(VF);
collectLoopUniforms(VF);
collectLoopScalars(VF);
}
/// Returns true if the target machine supports masked store operation
/// for the given \p DataType and kind of access to \p Ptr.
bool isLegalMaskedStore(Type *DataType, Value *Ptr) {
return Legal->isConsecutivePtr(Ptr) && TTI.isLegalMaskedStore(DataType);
}
/// Returns true if the target machine supports masked load operation
/// for the given \p DataType and kind of access to \p Ptr.
bool isLegalMaskedLoad(Type *DataType, Value *Ptr) {
return Legal->isConsecutivePtr(Ptr) && TTI.isLegalMaskedLoad(DataType);
}
/// Returns true if the target machine supports masked scatter operation
/// for the given \p DataType.
bool isLegalMaskedScatter(Type *DataType) {
return TTI.isLegalMaskedScatter(DataType);
}
/// Returns true if the target machine supports masked gather operation
/// for the given \p DataType.
bool isLegalMaskedGather(Type *DataType) {
return TTI.isLegalMaskedGather(DataType);
}
/// Returns true if the target machine can represent \p V as a masked gather
/// or scatter operation.
bool isLegalGatherOrScatter(Value *V) {
bool LI = isa<LoadInst>(V);
bool SI = isa<StoreInst>(V);
if (!LI && !SI)
return false;
auto *Ty = getMemInstValueType(V);
return (LI && isLegalMaskedGather(Ty)) || (SI && isLegalMaskedScatter(Ty));
}
/// Returns true if \p I is an instruction that will be scalarized with
/// predication. Such instructions include conditional stores and
/// instructions that may divide by zero.
bool isScalarWithPredication(Instruction *I);
/// Returns true if \p I is a memory instruction with consecutive memory
/// access that can be widened.
bool memoryInstructionCanBeWidened(Instruction *I, unsigned VF = 1);
/// \brief Check if \p Instr belongs to any interleaved access group.
bool isAccessInterleaved(Instruction *Instr) {
return InterleaveInfo.isInterleaved(Instr);
}
/// \brief Get the interleaved access group that \p Instr belongs to.
const InterleaveGroup *getInterleavedAccessGroup(Instruction *Instr) {
return InterleaveInfo.getInterleaveGroup(Instr);
}
/// \brief Returns true if an interleaved group requires a scalar iteration
/// to handle accesses with gaps.
bool requiresScalarEpilogue() const {
return InterleaveInfo.requiresScalarEpilogue();
}
private:
unsigned NumPredStores = 0;
/// \return An upper bound for the vectorization factor, larger than zero.
/// One is returned if vectorization should best be avoided due to cost.
unsigned computeFeasibleMaxVF(bool OptForSize, unsigned ConstTripCount);
/// The vectorization cost is a combination of the cost itself and a boolean
/// indicating whether any of the contributing operations will actually
/// operate on
/// vector values after type legalization in the backend. If this latter value
/// is
/// false, then all operations will be scalarized (i.e. no vectorization has
/// actually taken place).
using VectorizationCostTy = std::pair<unsigned, bool>;
/// Returns the expected execution cost. The unit of the cost does
/// not matter because we use the 'cost' units to compare different
/// vector widths. The cost that is returned is *not* normalized by
/// the factor width.
VectorizationCostTy expectedCost(unsigned VF);
/// Returns the execution time cost of an instruction for a given vector
/// width. Vector width of one means scalar.
VectorizationCostTy getInstructionCost(Instruction *I, unsigned VF);
/// The cost-computation logic from getInstructionCost which provides
/// the vector type as an output parameter.
unsigned getInstructionCost(Instruction *I, unsigned VF, Type *&VectorTy);
/// Calculate vectorization cost of memory instruction \p I.
unsigned getMemoryInstructionCost(Instruction *I, unsigned VF);
/// The cost computation for scalarized memory instruction.
unsigned getMemInstScalarizationCost(Instruction *I, unsigned VF);
/// The cost computation for interleaving group of memory instructions.
unsigned getInterleaveGroupCost(Instruction *I, unsigned VF);
/// The cost computation for Gather/Scatter instruction.
unsigned getGatherScatterCost(Instruction *I, unsigned VF);
/// The cost computation for widening instruction \p I with consecutive
/// memory access.
unsigned getConsecutiveMemOpCost(Instruction *I, unsigned VF);
/// The cost calculation for Load instruction \p I with uniform pointer -
/// scalar load + broadcast.
unsigned getUniformMemOpCost(Instruction *I, unsigned VF);
/// Returns whether the instruction is a load or store and will be a emitted
/// as a vector operation.
bool isConsecutiveLoadOrStore(Instruction *I);
/// Returns true if an artificially high cost for emulated masked memrefs
/// should be used.
bool useEmulatedMaskMemRefHack(Instruction *I);
/// Create an analysis remark that explains why vectorization failed
///
/// \p RemarkName is the identifier for the remark. \return the remark object
/// that can be streamed to.
OptimizationRemarkAnalysis createMissedAnalysis(StringRef RemarkName) {
return createLVMissedAnalysis(Hints->vectorizeAnalysisPassName(),
RemarkName, TheLoop);
}
/// Map of scalar integer values to the smallest bitwidth they can be legally
/// represented as. The vector equivalents of these values should be truncated
/// to this type.
MapVector<Instruction *, uint64_t> MinBWs;
/// A type representing the costs for instructions if they were to be
/// scalarized rather than vectorized. The entries are Instruction-Cost
/// pairs.
using ScalarCostsTy = DenseMap<Instruction *, unsigned>;
/// A set containing all BasicBlocks that are known to present after
/// vectorization as a predicated block.
SmallPtrSet<BasicBlock *, 4> PredicatedBBsAfterVectorization;
/// A map holding scalar costs for different vectorization factors. The
/// presence of a cost for an instruction in the mapping indicates that the
/// instruction will be scalarized when vectorizing with the associated
/// vectorization factor. The entries are VF-ScalarCostTy pairs.
DenseMap<unsigned, ScalarCostsTy> InstsToScalarize;
/// Holds the instructions known to be uniform after vectorization.
/// The data is collected per VF.
DenseMap<unsigned, SmallPtrSet<Instruction *, 4>> Uniforms;
/// Holds the instructions known to be scalar after vectorization.
/// The data is collected per VF.
DenseMap<unsigned, SmallPtrSet<Instruction *, 4>> Scalars;
/// Holds the instructions (address computations) that are forced to be
/// scalarized.
DenseMap<unsigned, SmallPtrSet<Instruction *, 4>> ForcedScalars;
/// Returns the expected difference in cost from scalarizing the expression
/// feeding a predicated instruction \p PredInst. The instructions to
/// scalarize and their scalar costs are collected in \p ScalarCosts. A
/// non-negative return value implies the expression will be scalarized.
/// Currently, only single-use chains are considered for scalarization.
int computePredInstDiscount(Instruction *PredInst, ScalarCostsTy &ScalarCosts,
unsigned VF);
/// Collect the instructions that are uniform after vectorization. An
/// instruction is uniform if we represent it with a single scalar value in
/// the vectorized loop corresponding to each vector iteration. Examples of
/// uniform instructions include pointer operands of consecutive or
/// interleaved memory accesses. Note that although uniformity implies an
/// instruction will be scalar, the reverse is not true. In general, a
/// scalarized instruction will be represented by VF scalar values in the
/// vectorized loop, each corresponding to an iteration of the original
/// scalar loop.
void collectLoopUniforms(unsigned VF);
/// Collect the instructions that are scalar after vectorization. An
/// instruction is scalar if it is known to be uniform or will be scalarized
/// during vectorization. Non-uniform scalarized instructions will be
/// represented by VF values in the vectorized loop, each corresponding to an
/// iteration of the original scalar loop.
void collectLoopScalars(unsigned VF);
/// Keeps cost model vectorization decision and cost for instructions.
/// Right now it is used for memory instructions only.
using DecisionList = DenseMap<std::pair<Instruction *, unsigned>,
std::pair<InstWidening, unsigned>>;
DecisionList WideningDecisions;
public:
/// The loop that we evaluate.
Loop *TheLoop;
/// Predicated scalar evolution analysis.
PredicatedScalarEvolution &PSE;
/// Loop Info analysis.
LoopInfo *LI;
/// Vectorization legality.
LoopVectorizationLegality *Legal;
/// Vector target information.
const TargetTransformInfo &TTI;
/// Target Library Info.
const TargetLibraryInfo *TLI;
/// Demanded bits analysis.
DemandedBits *DB;
/// Assumption cache.
AssumptionCache *AC;
/// Interface to emit optimization remarks.
OptimizationRemarkEmitter *ORE;
const Function *TheFunction;
/// Loop Vectorize Hint.
const LoopVectorizeHints *Hints;
/// The interleave access information contains groups of interleaved accesses
/// with the same stride and close to each other.
InterleavedAccessInfo &InterleaveInfo;
/// Values to ignore in the cost model.
SmallPtrSet<const Value *, 16> ValuesToIgnore;
/// Values to ignore in the cost model when VF > 1.
SmallPtrSet<const Value *, 16> VecValuesToIgnore;
};
} // end namespace llvm
// Return true if \p OuterLp is an outer loop annotated with hints for explicit
// vectorization. The loop needs to be annotated with #pragma omp simd
// simdlen(#) or #pragma clang vectorize(enable) vectorize_width(#). If the
// vector length information is not provided, vectorization is not considered
// explicit. Interleave hints are not allowed either. These limitations will be
// relaxed in the future.
// Please, note that we are currently forced to abuse the pragma 'clang
// vectorize' semantics. This pragma provides *auto-vectorization hints*
// (i.e., LV must check that vectorization is legal) whereas pragma 'omp simd'
// provides *explicit vectorization hints* (LV can bypass legal checks and
// assume that vectorization is legal). However, both hints are implemented
// using the same metadata (llvm.loop.vectorize, processed by
// LoopVectorizeHints). This will be fixed in the future when the native IR
// representation for pragma 'omp simd' is introduced.
static bool isExplicitVecOuterLoop(Loop *OuterLp,
OptimizationRemarkEmitter *ORE) {
assert(!OuterLp->empty() && "This is not an outer loop");
LoopVectorizeHints Hints(OuterLp, true /*DisableInterleaving*/, *ORE);
// Only outer loops with an explicit vectorization hint are supported.
// Unannotated outer loops are ignored.
if (Hints.getForce() == LoopVectorizeHints::FK_Undefined)
return false;
Function *Fn = OuterLp->getHeader()->getParent();
if (!Hints.allowVectorization(Fn, OuterLp, false /*AlwaysVectorize*/)) {
DEBUG(dbgs() << "LV: Loop hints prevent outer loop vectorization.\n");
return false;
}
if (!Hints.getWidth()) {
DEBUG(dbgs() << "LV: Not vectorizing: No user vector width.\n");
emitMissedWarning(Fn, OuterLp, Hints, ORE);
return false;
}
if (Hints.getInterleave() > 1) {
// TODO: Interleave support is future work.
DEBUG(dbgs() << "LV: Not vectorizing: Interleave is not supported for "
"outer loops.\n");
emitMissedWarning(Fn, OuterLp, Hints, ORE);
return false;
}
return true;
}
static void collectSupportedLoops(Loop &L, LoopInfo *LI,
OptimizationRemarkEmitter *ORE,
SmallVectorImpl<Loop *> &V) {
// Collect inner loops and outer loops without irreducible control flow. For
// now, only collect outer loops that have explicit vectorization hints.
if (L.empty() || (EnableVPlanNativePath && isExplicitVecOuterLoop(&L, ORE))) {
LoopBlocksRPO RPOT(&L);
RPOT.perform(LI);
if (!containsIrreducibleCFG<const BasicBlock *>(RPOT, *LI)) {
V.push_back(&L);
// TODO: Collect inner loops inside marked outer loops in case
// vectorization fails for the outer loop. Do not invoke
// 'containsIrreducibleCFG' again for inner loops when the outer loop is
// already known to be reducible. We can use an inherited attribute for
// that.
return;
}
}
for (Loop *InnerL : L)
collectSupportedLoops(*InnerL, LI, ORE, V);
}
namespace {
/// The LoopVectorize Pass.
struct LoopVectorize : public FunctionPass {
/// Pass identification, replacement for typeid
static char ID;
LoopVectorizePass Impl;
explicit LoopVectorize(bool NoUnrolling = false, bool AlwaysVectorize = true)
: FunctionPass(ID) {
Impl.DisableUnrolling = NoUnrolling;
Impl.AlwaysVectorize = AlwaysVectorize;
initializeLoopVectorizePass(*PassRegistry::getPassRegistry());
}
bool runOnFunction(Function &F) override {
if (skipFunction(F))
return false;
auto *SE = &getAnalysis<ScalarEvolutionWrapperPass>().getSE();
auto *LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
auto *TTI = &getAnalysis<TargetTransformInfoWrapperPass>().getTTI(F);
auto *DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
auto *BFI = &getAnalysis<BlockFrequencyInfoWrapperPass>().getBFI();
auto *TLIP = getAnalysisIfAvailable<TargetLibraryInfoWrapperPass>();
auto *TLI = TLIP ? &TLIP->getTLI() : nullptr;
auto *AA = &getAnalysis<AAResultsWrapperPass>().getAAResults();
auto *AC = &getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F);
auto *LAA = &getAnalysis<LoopAccessLegacyAnalysis>();
auto *DB = &getAnalysis<DemandedBitsWrapperPass>().getDemandedBits();
auto *ORE = &getAnalysis<OptimizationRemarkEmitterWrapperPass>().getORE();
std::function<const LoopAccessInfo &(Loop &)> GetLAA =
[&](Loop &L) -> const LoopAccessInfo & { return LAA->getInfo(&L); };
return Impl.runImpl(F, *SE, *LI, *TTI, *DT, *BFI, TLI, *DB, *AA, *AC,
GetLAA, *ORE);
}
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.addRequired<AssumptionCacheTracker>();
AU.addRequired<BlockFrequencyInfoWrapperPass>();
AU.addRequired<DominatorTreeWrapperPass>();
AU.addRequired<LoopInfoWrapperPass>();
AU.addRequired<ScalarEvolutionWrapperPass>();
AU.addRequired<TargetTransformInfoWrapperPass>();
AU.addRequired<AAResultsWrapperPass>();
AU.addRequired<LoopAccessLegacyAnalysis>();
AU.addRequired<DemandedBitsWrapperPass>();
AU.addRequired<OptimizationRemarkEmitterWrapperPass>();
AU.addPreserved<LoopInfoWrapperPass>();
AU.addPreserved<DominatorTreeWrapperPass>();
AU.addPreserved<BasicAAWrapperPass>();
AU.addPreserved<GlobalsAAWrapperPass>();
}
};
} // end anonymous namespace
//===----------------------------------------------------------------------===//
// Implementation of LoopVectorizationLegality, InnerLoopVectorizer and
// LoopVectorizationCostModel and LoopVectorizationPlanner.
//===----------------------------------------------------------------------===//
Value *InnerLoopVectorizer::getBroadcastInstrs(Value *V) {
// We need to place the broadcast of invariant variables outside the loop.
Instruction *Instr = dyn_cast<Instruction>(V);
bool NewInstr = (Instr && Instr->getParent() == LoopVectorBody);
bool Invariant = OrigLoop->isLoopInvariant(V) && !NewInstr;
// Place the code for broadcasting invariant variables in the new preheader.
IRBuilder<>::InsertPointGuard Guard(Builder);
if (Invariant)
Builder.SetInsertPoint(LoopVectorPreHeader->getTerminator());
// Broadcast the scalar into all locations in the vector.
Value *Shuf = Builder.CreateVectorSplat(VF, V, "broadcast");
return Shuf;
}
void InnerLoopVectorizer::createVectorIntOrFpInductionPHI(
const InductionDescriptor &II, Value *Step, Instruction *EntryVal) {
assert((isa<PHINode>(EntryVal) || isa<TruncInst>(EntryVal)) &&
"Expected either an induction phi-node or a truncate of it!");
Value *Start = II.getStartValue();
// Construct the initial value of the vector IV in the vector loop preheader
auto CurrIP = Builder.saveIP();
Builder.SetInsertPoint(LoopVectorPreHeader->getTerminator());
if (isa<TruncInst>(EntryVal)) {
assert(Start->getType()->isIntegerTy() &&
"Truncation requires an integer type");
auto *TruncType = cast<IntegerType>(EntryVal->getType());
Step = Builder.CreateTrunc(Step, TruncType);
Start = Builder.CreateCast(Instruction::Trunc, Start, TruncType);
}
Value *SplatStart = Builder.CreateVectorSplat(VF, Start);
Value *SteppedStart =
getStepVector(SplatStart, 0, Step, II.getInductionOpcode());
// We create vector phi nodes for both integer and floating-point induction
// variables. Here, we determine the kind of arithmetic we will perform.
Instruction::BinaryOps AddOp;
Instruction::BinaryOps MulOp;
if (Step->getType()->isIntegerTy()) {
AddOp = Instruction::Add;
MulOp = Instruction::Mul;
} else {
AddOp = II.getInductionOpcode();
MulOp = Instruction::FMul;
}
// Multiply the vectorization factor by the step using integer or
// floating-point arithmetic as appropriate.
Value *ConstVF = getSignedIntOrFpConstant(Step->getType(), VF);
Value *Mul = addFastMathFlag(Builder.CreateBinOp(MulOp, Step, ConstVF));
// Create a vector splat to use in the induction update.
//
// FIXME: If the step is non-constant, we create the vector splat with
// IRBuilder. IRBuilder can constant-fold the multiply, but it doesn't
// handle a constant vector splat.
Value *SplatVF = isa<Constant>(Mul)
? ConstantVector::getSplat(VF, cast<Constant>(Mul))
: Builder.CreateVectorSplat(VF, Mul);
Builder.restoreIP(CurrIP);
// We may need to add the step a number of times, depending on the unroll
// factor. The last of those goes into the PHI.
PHINode *VecInd = PHINode::Create(SteppedStart->getType(), 2, "vec.ind",
&*LoopVectorBody->getFirstInsertionPt());
Instruction *LastInduction = VecInd;
for (unsigned Part = 0; Part < UF; ++Part) {
VectorLoopValueMap.setVectorValue(EntryVal, Part, LastInduction);
if (isa<TruncInst>(EntryVal))
addMetadata(LastInduction, EntryVal);
recordVectorLoopValueForInductionCast(II, EntryVal, LastInduction, Part);
LastInduction = cast<Instruction>(addFastMathFlag(
Builder.CreateBinOp(AddOp, LastInduction, SplatVF, "step.add")));
}
// Move the last step to the end of the latch block. This ensures consistent
// placement of all induction updates.
auto *LoopVectorLatch = LI->getLoopFor(LoopVectorBody)->getLoopLatch();
auto *Br = cast<BranchInst>(LoopVectorLatch->getTerminator());
auto *ICmp = cast<Instruction>(Br->getCondition());
LastInduction->moveBefore(ICmp);
LastInduction->setName("vec.ind.next");
VecInd->addIncoming(SteppedStart, LoopVectorPreHeader);
VecInd->addIncoming(LastInduction, LoopVectorLatch);
}
bool InnerLoopVectorizer::shouldScalarizeInstruction(Instruction *I) const {
return Cost->isScalarAfterVectorization(I, VF) ||
Cost->isProfitableToScalarize(I, VF);
}
bool InnerLoopVectorizer::needsScalarInduction(Instruction *IV) const {
if (shouldScalarizeInstruction(IV))
return true;
auto isScalarInst = [&](User *U) -> bool {
auto *I = cast<Instruction>(U);
return (OrigLoop->contains(I) && shouldScalarizeInstruction(I));
};
return llvm::any_of(IV->users(), isScalarInst);
}
void InnerLoopVectorizer::recordVectorLoopValueForInductionCast(
const InductionDescriptor &ID, const Instruction *EntryVal,
Value *VectorLoopVal, unsigned Part, unsigned Lane) {
assert((isa<PHINode>(EntryVal) || isa<TruncInst>(EntryVal)) &&
"Expected either an induction phi-node or a truncate of it!");
// This induction variable is not the phi from the original loop but the
// newly-created IV based on the proof that casted Phi is equal to the
// uncasted Phi in the vectorized loop (under a runtime guard possibly). It
// re-uses the same InductionDescriptor that original IV uses but we don't
// have to do any recording in this case - that is done when original IV is
// processed.
if (isa<TruncInst>(EntryVal))
return;
const SmallVectorImpl<Instruction *> &Casts = ID.getCastInsts();
if (Casts.empty())
return;
// Only the first Cast instruction in the Casts vector is of interest.
// The rest of the Casts (if exist) have no uses outside the
// induction update chain itself.
Instruction *CastInst = *Casts.begin();
if (Lane < UINT_MAX)
VectorLoopValueMap.setScalarValue(CastInst, {Part, Lane}, VectorLoopVal);
else
VectorLoopValueMap.setVectorValue(CastInst, Part, VectorLoopVal);
}
void InnerLoopVectorizer::widenIntOrFpInduction(PHINode *IV, TruncInst *Trunc) {
assert((IV->getType()->isIntegerTy() || IV != OldInduction) &&
"Primary induction variable must have an integer type");
auto II = Legal->getInductionVars()->find(IV);
assert(II != Legal->getInductionVars()->end() && "IV is not an induction");
auto ID = II->second;
assert(IV->getType() == ID.getStartValue()->getType() && "Types must match");
// The scalar value to broadcast. This will be derived from the canonical
// induction variable.
Value *ScalarIV = nullptr;
// The value from the original loop to which we are mapping the new induction
// variable.
Instruction *EntryVal = Trunc ? cast<Instruction>(Trunc) : IV;
// True if we have vectorized the induction variable.
auto VectorizedIV = false;
// Determine if we want a scalar version of the induction variable. This is
// true if the induction variable itself is not widened, or if it has at
// least one user in the loop that is not widened.
auto NeedsScalarIV = VF > 1 && needsScalarInduction(EntryVal);
// Generate code for the induction step. Note that induction steps are
// required to be loop-invariant
assert(PSE.getSE()->isLoopInvariant(ID.getStep(), OrigLoop) &&
"Induction step should be loop invariant");
auto &DL = OrigLoop->getHeader()->getModule()->getDataLayout();
Value *Step = nullptr;
if (PSE.getSE()->isSCEVable(IV->getType())) {
SCEVExpander Exp(*PSE.getSE(), DL, "induction");
Step = Exp.expandCodeFor(ID.getStep(), ID.getStep()->getType(),
LoopVectorPreHeader->getTerminator());
} else {
Step = cast<SCEVUnknown>(ID.getStep())->getValue();
}
// Try to create a new independent vector induction variable. If we can't
// create the phi node, we will splat the scalar induction variable in each
// loop iteration.
if (VF > 1 && !shouldScalarizeInstruction(EntryVal)) {
createVectorIntOrFpInductionPHI(ID, Step, EntryVal);
VectorizedIV = true;
}
// If we haven't yet vectorized the induction variable, or if we will create
// a scalar one, we need to define the scalar induction variable and step
// values. If we were given a truncation type, truncate the canonical
// induction variable and step. Otherwise, derive these values from the
// induction descriptor.
if (!VectorizedIV || NeedsScalarIV) {
ScalarIV = Induction;
if (IV != OldInduction) {
ScalarIV = IV->getType()->isIntegerTy()
? Builder.CreateSExtOrTrunc(Induction, IV->getType())
: Builder.CreateCast(Instruction::SIToFP, Induction,
IV->getType());
ScalarIV = ID.transform(Builder, ScalarIV, PSE.getSE(), DL);
ScalarIV->setName("offset.idx");
}
if (Trunc) {
auto *TruncType = cast<IntegerType>(Trunc->getType());
assert(Step->getType()->isIntegerTy() &&
"Truncation requires an integer step");
ScalarIV = Builder.CreateTrunc(ScalarIV, TruncType);
Step = Builder.CreateTrunc(Step, TruncType);
}
}
// If we haven't yet vectorized the induction variable, splat the scalar
// induction variable, and build the necessary step vectors.
// TODO: Don't do it unless the vectorized IV is really required.
if (!VectorizedIV) {
Value *Broadcasted = getBroadcastInstrs(ScalarIV);
for (unsigned Part = 0; Part < UF; ++Part) {
Value *EntryPart =
getStepVector(Broadcasted, VF * Part, Step, ID.getInductionOpcode());
VectorLoopValueMap.setVectorValue(EntryVal, Part, EntryPart);
if (Trunc)
addMetadata(EntryPart, Trunc);
recordVectorLoopValueForInductionCast(ID, EntryVal, EntryPart, Part);
}
}
// If an induction variable is only used for counting loop iterations or
// calculating addresses, it doesn't need to be widened. Create scalar steps
// that can be used by instructions we will later scalarize. Note that the
// addition of the scalar steps will not increase the number of instructions
// in the loop in the common case prior to InstCombine. We will be trading
// one vector extract for each scalar step.
if (NeedsScalarIV)
buildScalarSteps(ScalarIV, Step, EntryVal, ID);
}
Value *InnerLoopVectorizer::getStepVector(Value *Val, int StartIdx, Value *Step,
Instruction::BinaryOps BinOp) {
// Create and check the types.
assert(Val->getType()->isVectorTy() && "Must be a vector");
int VLen = Val->getType()->getVectorNumElements();
Type *STy = Val->getType()->getScalarType();
assert((STy->isIntegerTy() || STy->isFloatingPointTy()) &&
"Induction Step must be an integer or FP");
assert(Step->getType() == STy && "Step has wrong type");
SmallVector<Constant *, 8> Indices;
if (STy->isIntegerTy()) {
// Create a vector of consecutive numbers from zero to VF.
for (int i = 0; i < VLen; ++i)
Indices.push_back(ConstantInt::get(STy, StartIdx + i));
// Add the consecutive indices to the vector value.
Constant *Cv = ConstantVector::get(Indices);
assert(Cv->getType() == Val->getType() && "Invalid consecutive vec");
Step = Builder.CreateVectorSplat(VLen, Step);
assert(Step->getType() == Val->getType() && "Invalid step vec");
// FIXME: The newly created binary instructions should contain nsw/nuw flags,
// which can be found from the original scalar operations.
Step = Builder.CreateMul(Cv, Step);
return Builder.CreateAdd(Val, Step, "induction");
}
// Floating point induction.
assert((BinOp == Instruction::FAdd || BinOp == Instruction::FSub) &&
"Binary Opcode should be specified for FP induction");
// Create a vector of consecutive numbers from zero to VF.
for (int i = 0; i < VLen; ++i)
Indices.push_back(ConstantFP::get(STy, (double)(StartIdx + i)));
// Add the consecutive indices to the vector value.
Constant *Cv = ConstantVector::get(Indices);
Step = Builder.CreateVectorSplat(VLen, Step);
// Floating point operations had to be 'fast' to enable the induction.
FastMathFlags Flags;
Flags.setFast();
Value *MulOp = Builder.CreateFMul(Cv, Step);
if (isa<Instruction>(MulOp))
// Have to check, MulOp may be a constant
cast<Instruction>(MulOp)->setFastMathFlags(Flags);
Value *BOp = Builder.CreateBinOp(BinOp, Val, MulOp, "induction");
if (isa<Instruction>(BOp))
cast<Instruction>(BOp)->setFastMathFlags(Flags);
return BOp;
}
void InnerLoopVectorizer::buildScalarSteps(Value *ScalarIV, Value *Step,
Instruction *EntryVal,
const InductionDescriptor &ID) {
// We shouldn't have to build scalar steps if we aren't vectorizing.
assert(VF > 1 && "VF should be greater than one");
// Get the value type and ensure it and the step have the same integer type.
Type *ScalarIVTy = ScalarIV->getType()->getScalarType();
assert(ScalarIVTy == Step->getType() &&
"Val and Step should have the same type");
// We build scalar steps for both integer and floating-point induction
// variables. Here, we determine the kind of arithmetic we will perform.
Instruction::BinaryOps AddOp;
Instruction::BinaryOps MulOp;
if (ScalarIVTy->isIntegerTy()) {
AddOp = Instruction::Add;
MulOp = Instruction::Mul;
} else {
AddOp = ID.getInductionOpcode();
MulOp = Instruction::FMul;
}
// Determine the number of scalars we need to generate for each unroll
// iteration. If EntryVal is uniform, we only need to generate the first
// lane. Otherwise, we generate all VF values.
unsigned Lanes =
Cost->isUniformAfterVectorization(cast<Instruction>(EntryVal), VF) ? 1
: VF;
// Compute the scalar steps and save the results in VectorLoopValueMap.
for (unsigned Part = 0; Part < UF; ++Part) {
for (unsigned Lane = 0; Lane < Lanes; ++Lane) {
auto *StartIdx = getSignedIntOrFpConstant(ScalarIVTy, VF * Part + Lane);
auto *Mul = addFastMathFlag(Builder.CreateBinOp(MulOp, StartIdx, Step));
auto *Add = addFastMathFlag(Builder.CreateBinOp(AddOp, ScalarIV, Mul));
VectorLoopValueMap.setScalarValue(EntryVal, {Part, Lane}, Add);
recordVectorLoopValueForInductionCast(ID, EntryVal, Add, Part, Lane);
}
}
}
Value *InnerLoopVectorizer::getOrCreateVectorValue(Value *V, unsigned Part) {
assert(V != Induction && "The new induction variable should not be used.");
assert(!V->getType()->isVectorTy() && "Can't widen a vector");
assert(!V->getType()->isVoidTy() && "Type does not produce a value");
// If we have a stride that is replaced by one, do it here.
if (Legal->hasStride(V))
V = ConstantInt::get(V->getType(), 1);
// If we have a vector mapped to this value, return it.
if (VectorLoopValueMap.hasVectorValue(V, Part))
return VectorLoopValueMap.getVectorValue(V, Part);
// If the value has not been vectorized, check if it has been scalarized
// instead. If it has been scalarized, and we actually need the value in
// vector form, we will construct the vector values on demand.
if (VectorLoopValueMap.hasAnyScalarValue(V)) {
Value *ScalarValue = VectorLoopValueMap.getScalarValue(V, {Part, 0});
// If we've scalarized a value, that value should be an instruction.
auto *I = cast<Instruction>(V);
// If we aren't vectorizing, we can just copy the scalar map values over to
// the vector map.
if (VF == 1) {
VectorLoopValueMap.setVectorValue(V, Part, ScalarValue);
return ScalarValue;
}
// Get the last scalar instruction we generated for V and Part. If the value
// is known to be uniform after vectorization, this corresponds to lane zero
// of the Part unroll iteration. Otherwise, the last instruction is the one
// we created for the last vector lane of the Part unroll iteration.
unsigned LastLane = Cost->isUniformAfterVectorization(I, VF) ? 0 : VF - 1;
auto *LastInst = cast<Instruction>(
VectorLoopValueMap.getScalarValue(V, {Part, LastLane}));
// Set the insert point after the last scalarized instruction. This ensures
// the insertelement sequence will directly follow the scalar definitions.
auto OldIP = Builder.saveIP();
auto NewIP = std::next(BasicBlock::iterator(LastInst));
Builder.SetInsertPoint(&*NewIP);
// However, if we are vectorizing, we need to construct the vector values.
// If the value is known to be uniform after vectorization, we can just
// broadcast the scalar value corresponding to lane zero for each unroll
// iteration. Otherwise, we construct the vector values using insertelement
// instructions. Since the resulting vectors are stored in
// VectorLoopValueMap, we will only generate the insertelements once.
Value *VectorValue = nullptr;
if (Cost->isUniformAfterVectorization(I, VF)) {
VectorValue = getBroadcastInstrs(ScalarValue);
VectorLoopValueMap.setVectorValue(V, Part, VectorValue);
} else {
// Initialize packing with insertelements to start from undef.
Value *Undef = UndefValue::get(VectorType::get(V->getType(), VF));
VectorLoopValueMap.setVectorValue(V, Part, Undef);
for (unsigned Lane = 0; Lane < VF; ++Lane)
packScalarIntoVectorValue(V, {Part, Lane});
VectorValue = VectorLoopValueMap.getVectorValue(V, Part);
}
Builder.restoreIP(OldIP);
return VectorValue;
}
// If this scalar is unknown, assume that it is a constant or that it is
// loop invariant. Broadcast V and save the value for future uses.
Value *B = getBroadcastInstrs(V);
VectorLoopValueMap.setVectorValue(V, Part, B);
return B;
}
Value *
InnerLoopVectorizer::getOrCreateScalarValue(Value *V,
const VPIteration &Instance) {
// If the value is not an instruction contained in the loop, it should
// already be scalar.
if (OrigLoop->isLoopInvariant(V))
return V;
assert(Instance.Lane > 0
? !Cost->isUniformAfterVectorization(cast<Instruction>(V), VF)
: true && "Uniform values only have lane zero");
// If the value from the original loop has not been vectorized, it is
// represented by UF x VF scalar values in the new loop. Return the requested
// scalar value.
if (VectorLoopValueMap.hasScalarValue(V, Instance))
return VectorLoopValueMap.getScalarValue(V, Instance);
// If the value has not been scalarized, get its entry in VectorLoopValueMap
// for the given unroll part. If this entry is not a vector type (i.e., the
// vectorization factor is one), there is no need to generate an
// extractelement instruction.
auto *U = getOrCreateVectorValue(V, Instance.Part);
if (!U->getType()->isVectorTy()) {
assert(VF == 1 && "Value not scalarized has non-vector type");
return U;
}
// Otherwise, the value from the original loop has been vectorized and is
// represented by UF vector values. Extract and return the requested scalar
// value from the appropriate vector lane.
return Builder.CreateExtractElement(U, Builder.getInt32(Instance.Lane));
}
void InnerLoopVectorizer::packScalarIntoVectorValue(
Value *V, const VPIteration &Instance) {
assert(V != Induction && "The new induction variable should not be used.");
assert(!V->getType()->isVectorTy() && "Can't pack a vector");
assert(!V->getType()->isVoidTy() && "Type does not produce a value");
Value *ScalarInst = VectorLoopValueMap.getScalarValue(V, Instance);
Value *VectorValue = VectorLoopValueMap.getVectorValue(V, Instance.Part);
VectorValue = Builder.CreateInsertElement(VectorValue, ScalarInst,
Builder.getInt32(Instance.Lane));
VectorLoopValueMap.resetVectorValue(V, Instance.Part, VectorValue);
}
Value *InnerLoopVectorizer::reverseVector(Value *Vec) {
assert(Vec->getType()->isVectorTy() && "Invalid type");
SmallVector<Constant *, 8> ShuffleMask;
for (unsigned i = 0; i < VF; ++i)
ShuffleMask.push_back(Builder.getInt32(VF - i - 1));
return Builder.CreateShuffleVector(Vec, UndefValue::get(Vec->getType()),
ConstantVector::get(ShuffleMask),
"reverse");
}
// Try to vectorize the interleave group that \p Instr belongs to.
//
// E.g. Translate following interleaved load group (factor = 3):
// for (i = 0; i < N; i+=3) {
// R = Pic[i]; // Member of index 0
// G = Pic[i+1]; // Member of index 1
// B = Pic[i+2]; // Member of index 2
// ... // do something to R, G, B
// }
// To:
// %wide.vec = load <12 x i32> ; Read 4 tuples of R,G,B
// %R.vec = shuffle %wide.vec, undef, <0, 3, 6, 9> ; R elements
// %G.vec = shuffle %wide.vec, undef, <1, 4, 7, 10> ; G elements
// %B.vec = shuffle %wide.vec, undef, <2, 5, 8, 11> ; B elements
//
// Or translate following interleaved store group (factor = 3):
// for (i = 0; i < N; i+=3) {
// ... do something to R, G, B
// Pic[i] = R; // Member of index 0
// Pic[i+1] = G; // Member of index 1
// Pic[i+2] = B; // Member of index 2
// }
// To:
// %R_G.vec = shuffle %R.vec, %G.vec, <0, 1, 2, ..., 7>
// %B_U.vec = shuffle %B.vec, undef, <0, 1, 2, 3, u, u, u, u>
// %interleaved.vec = shuffle %R_G.vec, %B_U.vec,
// <0, 4, 8, 1, 5, 9, 2, 6, 10, 3, 7, 11> ; Interleave R,G,B elements
// store <12 x i32> %interleaved.vec ; Write 4 tuples of R,G,B
void InnerLoopVectorizer::vectorizeInterleaveGroup(Instruction *Instr) {
const InterleaveGroup *Group = Cost->getInterleavedAccessGroup(Instr);
assert(Group && "Fail to get an interleaved access group.");
// Skip if current instruction is not the insert position.
if (Instr != Group->getInsertPos())
return;
const DataLayout &DL = Instr->getModule()->getDataLayout();
Value *Ptr = getLoadStorePointerOperand(Instr);
// Prepare for the vector type of the interleaved load/store.
Type *ScalarTy = getMemInstValueType(Instr);
unsigned InterleaveFactor = Group->getFactor();
Type *VecTy = VectorType::get(ScalarTy, InterleaveFactor * VF);
Type *PtrTy = VecTy->getPointerTo(getMemInstAddressSpace(Instr));
// Prepare for the new pointers.
setDebugLocFromInst(Builder, Ptr);
SmallVector<Value *, 2> NewPtrs;
unsigned Index = Group->getIndex(Instr);
// If the group is reverse, adjust the index to refer to the last vector lane
// instead of the first. We adjust the index from the first vector lane,
// rather than directly getting the pointer for lane VF - 1, because the
// pointer operand of the interleaved access is supposed to be uniform. For
// uniform instructions, we're only required to generate a value for the
// first vector lane in each unroll iteration.
if (Group->isReverse())
Index += (VF - 1) * Group->getFactor();
bool InBounds = false;
if (auto *gep = dyn_cast<GetElementPtrInst>(Ptr->stripPointerCasts()))
InBounds = gep->isInBounds();
for (unsigned Part = 0; Part < UF; Part++) {
Value *NewPtr = getOrCreateScalarValue(Ptr, {Part, 0});
// Notice current instruction could be any index. Need to adjust the address
// to the member of index 0.
//
// E.g. a = A[i+1]; // Member of index 1 (Current instruction)
// b = A[i]; // Member of index 0
// Current pointer is pointed to A[i+1], adjust it to A[i].
//
// E.g. A[i+1] = a; // Member of index 1
// A[i] = b; // Member of index 0
// A[i+2] = c; // Member of index 2 (Current instruction)
// Current pointer is pointed to A[i+2], adjust it to A[i].
NewPtr = Builder.CreateGEP(NewPtr, Builder.getInt32(-Index));
if (InBounds)
cast<GetElementPtrInst>(NewPtr)->setIsInBounds(true);
// Cast to the vector pointer type.
NewPtrs.push_back(Builder.CreateBitCast(NewPtr, PtrTy));
}
setDebugLocFromInst(Builder, Instr);
Value *UndefVec = UndefValue::get(VecTy);
// Vectorize the interleaved load group.
if (isa<LoadInst>(Instr)) {
// For each unroll part, create a wide load for the group.
SmallVector<Value *, 2> NewLoads;
for (unsigned Part = 0; Part < UF; Part++) {
auto *NewLoad = Builder.CreateAlignedLoad(
NewPtrs[Part], Group->getAlignment(), "wide.vec");
Group->addMetadata(NewLoad);
NewLoads.push_back(NewLoad);
}
// For each member in the group, shuffle out the appropriate data from the
// wide loads.
for (unsigned I = 0; I < InterleaveFactor; ++I) {
Instruction *Member = Group->getMember(I);
// Skip the gaps in the group.
if (!Member)
continue;
Constant *StrideMask = createStrideMask(Builder, I, InterleaveFactor, VF);
for (unsigned Part = 0; Part < UF; Part++) {
Value *StridedVec = Builder.CreateShuffleVector(
NewLoads[Part], UndefVec, StrideMask, "strided.vec");
// If this member has different type, cast the result type.
if (Member->getType() != ScalarTy) {
VectorType *OtherVTy = VectorType::get(Member->getType(), VF);
StridedVec = createBitOrPointerCast(StridedVec, OtherVTy, DL);
}
if (Group->isReverse())
StridedVec = reverseVector(StridedVec);
VectorLoopValueMap.setVectorValue(Member, Part, StridedVec);
}
}
return;
}
// The sub vector type for current instruction.
VectorType *SubVT = VectorType::get(ScalarTy, VF);
// Vectorize the interleaved store group.
for (unsigned Part = 0; Part < UF; Part++) {
// Collect the stored vector from each member.
SmallVector<Value *, 4> StoredVecs;
for (unsigned i = 0; i < InterleaveFactor; i++) {
// Interleaved store group doesn't allow a gap, so each index has a member
Instruction *Member = Group->getMember(i);
assert(Member && "Fail to get a member from an interleaved store group");
Value *StoredVec = getOrCreateVectorValue(
cast<StoreInst>(Member)->getValueOperand(), Part);
if (Group->isReverse())
StoredVec = reverseVector(StoredVec);
// If this member has different type, cast it to a unified type.
if (StoredVec->getType() != SubVT)
StoredVec = createBitOrPointerCast(StoredVec, SubVT, DL);
StoredVecs.push_back(StoredVec);
}
// Concatenate all vectors into a wide vector.
Value *WideVec = concatenateVectors(Builder, StoredVecs);
// Interleave the elements in the wide vector.
Constant *IMask = createInterleaveMask(Builder, VF, InterleaveFactor);
Value *IVec = Builder.CreateShuffleVector(WideVec, UndefVec, IMask,
"interleaved.vec");
Instruction *NewStoreInstr =
Builder.CreateAlignedStore(IVec, NewPtrs[Part], Group->getAlignment());
Group->addMetadata(NewStoreInstr);
}
}
void InnerLoopVectorizer::vectorizeMemoryInstruction(Instruction *Instr,
VectorParts *BlockInMask) {
// Attempt to issue a wide load.
LoadInst *LI = dyn_cast<LoadInst>(Instr);
StoreInst *SI = dyn_cast<StoreInst>(Instr);
assert((LI || SI) && "Invalid Load/Store instruction");
LoopVectorizationCostModel::InstWidening Decision =
Cost->getWideningDecision(Instr, VF);
assert(Decision != LoopVectorizationCostModel::CM_Unknown &&
"CM decision should be taken at this point");
if (Decision == LoopVectorizationCostModel::CM_Interleave)
return vectorizeInterleaveGroup(Instr);
Type *ScalarDataTy = getMemInstValueType(Instr);
Type *DataTy = VectorType::get(ScalarDataTy, VF);
Value *Ptr = getLoadStorePointerOperand(Instr);
unsigned Alignment = getMemInstAlignment(Instr);
// An alignment of 0 means target abi alignment. We need to use the scalar's
// target abi alignment in such a case.
const DataLayout &DL = Instr->getModule()->getDataLayout();
if (!Alignment)
Alignment = DL.getABITypeAlignment(ScalarDataTy);
unsigned AddressSpace = getMemInstAddressSpace(Instr);
// Determine if the pointer operand of the access is either consecutive or
// reverse consecutive.
bool Reverse = (Decision == LoopVectorizationCostModel::CM_Widen_Reverse);
bool ConsecutiveStride =
Reverse || (Decision == LoopVectorizationCostModel::CM_Widen);
bool CreateGatherScatter =
(Decision == LoopVectorizationCostModel::CM_GatherScatter);
// Either Ptr feeds a vector load/store, or a vector GEP should feed a vector
// gather/scatter. Otherwise Decision should have been to Scalarize.
assert((ConsecutiveStride || CreateGatherScatter) &&
"The instruction should be scalarized");
// Handle consecutive loads/stores.
if (ConsecutiveStride)
Ptr = getOrCreateScalarValue(Ptr, {0, 0});
VectorParts Mask;
bool isMaskRequired = BlockInMask;
if (isMaskRequired)
Mask = *BlockInMask;
bool InBounds = false;
if (auto *gep = dyn_cast<GetElementPtrInst>(
getLoadStorePointerOperand(Instr)->stripPointerCasts()))
InBounds = gep->isInBounds();
const auto CreateVecPtr = [&](unsigned Part, Value *Ptr) -> Value * {
// Calculate the pointer for the specific unroll-part.
GetElementPtrInst *PartPtr = nullptr;
if (Reverse) {
// If the address is consecutive but reversed, then the
// wide store needs to start at the last vector element.
PartPtr = cast<GetElementPtrInst>(
Builder.CreateGEP(Ptr, Builder.getInt32(-Part * VF)));
PartPtr->setIsInBounds(InBounds);
PartPtr = cast<GetElementPtrInst>(
Builder.CreateGEP(PartPtr, Builder.getInt32(1 - VF)));
PartPtr->setIsInBounds(InBounds);
if (isMaskRequired) // Reverse of a null all-one mask is a null mask.
Mask[Part] = reverseVector(Mask[Part]);
} else {
PartPtr = cast<GetElementPtrInst>(
Builder.CreateGEP(Ptr, Builder.getInt32(Part * VF)));
PartPtr->setIsInBounds(InBounds);
}
return Builder.CreateBitCast(PartPtr, DataTy->getPointerTo(AddressSpace));
};
// Handle Stores:
if (SI) {
setDebugLocFromInst(Builder, SI);
for (unsigned Part = 0; Part < UF; ++Part) {
Instruction *NewSI = nullptr;
Value *StoredVal = getOrCreateVectorValue(SI->getValueOperand(), Part);
if (CreateGatherScatter) {
Value *MaskPart = isMaskRequired ? Mask[Part] : nullptr;
Value *VectorGep = getOrCreateVectorValue(Ptr, Part);
NewSI = Builder.CreateMaskedScatter(StoredVal, VectorGep, Alignment,
MaskPart);
} else {
if (Reverse) {
// If we store to reverse consecutive memory locations, then we need
// to reverse the order of elements in the stored value.
StoredVal = reverseVector(StoredVal);
// We don't want to update the value in the map as it might be used in
// another expression. So don't call resetVectorValue(StoredVal).
}
auto *VecPtr = CreateVecPtr(Part, Ptr);
if (isMaskRequired)
NewSI = Builder.CreateMaskedStore(StoredVal, VecPtr, Alignment,
Mask[Part]);
else
NewSI = Builder.CreateAlignedStore(StoredVal, VecPtr, Alignment);
}
addMetadata(NewSI, SI);
}
return;
}
// Handle loads.
assert(LI && "Must have a load instruction");
setDebugLocFromInst(Builder, LI);
for (unsigned Part = 0; Part < UF; ++Part) {
Value *NewLI;
if (CreateGatherScatter) {
Value *MaskPart = isMaskRequired ? Mask[Part] : nullptr;
Value *VectorGep = getOrCreateVectorValue(Ptr, Part);
NewLI = Builder.CreateMaskedGather(VectorGep, Alignment, MaskPart,
nullptr, "wide.masked.gather");
addMetadata(NewLI, LI);
} else {
auto *VecPtr = CreateVecPtr(Part, Ptr);
if (isMaskRequired)
NewLI = Builder.CreateMaskedLoad(VecPtr, Alignment, Mask[Part],
UndefValue::get(DataTy),
"wide.masked.load");
else
NewLI = Builder.CreateAlignedLoad(VecPtr, Alignment, "wide.load");
// Add metadata to the load, but setVectorValue to the reverse shuffle.
addMetadata(NewLI, LI);
if (Reverse)
NewLI = reverseVector(NewLI);
}
VectorLoopValueMap.setVectorValue(Instr, Part, NewLI);
}
}
void InnerLoopVectorizer::scalarizeInstruction(Instruction *Instr,
const VPIteration &Instance,
bool IfPredicateInstr) {
assert(!Instr->getType()->isAggregateType() && "Can't handle vectors");
setDebugLocFromInst(Builder, Instr);
// Does this instruction return a value ?
bool IsVoidRetTy = Instr->getType()->isVoidTy();
Instruction *Cloned = Instr->clone();
if (!IsVoidRetTy)
Cloned->setName(Instr->getName() + ".cloned");
// Replace the operands of the cloned instructions with their scalar
// equivalents in the new loop.
for (unsigned op = 0, e = Instr->getNumOperands(); op != e; ++op) {
auto *NewOp = getOrCreateScalarValue(Instr->getOperand(op), Instance);
Cloned->setOperand(op, NewOp);
}
addNewMetadata(Cloned, Instr);
// Place the cloned scalar in the new loop.
Builder.Insert(Cloned);
// Add the cloned scalar to the scalar map entry.
VectorLoopValueMap.setScalarValue(Instr, Instance, Cloned);
// If we just cloned a new assumption, add it the assumption cache.
if (auto *II = dyn_cast<IntrinsicInst>(Cloned))
if (II->getIntrinsicID() == Intrinsic::assume)
AC->registerAssumption(II);
// End if-block.
if (IfPredicateInstr)
PredicatedInstructions.push_back(Cloned);
}
PHINode *InnerLoopVectorizer::createInductionVariable(Loop *L, Value *Start,
Value *End, Value *Step,
Instruction *DL) {
BasicBlock *Header = L->getHeader();
BasicBlock *Latch = L->getLoopLatch();
// As we're just creating this loop, it's possible no latch exists
// yet. If so, use the header as this will be a single block loop.
if (!Latch)
Latch = Header;
IRBuilder<> Builder(&*Header->getFirstInsertionPt());
Instruction *OldInst = getDebugLocFromInstOrOperands(OldInduction);
setDebugLocFromInst(Builder, OldInst);
auto *Induction = Builder.CreatePHI(Start->getType(), 2, "index");
Builder.SetInsertPoint(Latch->getTerminator());
setDebugLocFromInst(Builder, OldInst);
// Create i+1 and fill the PHINode.
Value *Next = Builder.CreateAdd(Induction, Step, "index.next");
Induction->addIncoming(Start, L->getLoopPreheader());
Induction->addIncoming(Next, Latch);
// Create the compare.
Value *ICmp = Builder.CreateICmpEQ(Next, End);
Builder.CreateCondBr(ICmp, L->getExitBlock(), Header);
// Now we have two terminators. Remove the old one from the block.
Latch->getTerminator()->eraseFromParent();
return Induction;
}
Value *InnerLoopVectorizer::getOrCreateTripCount(Loop *L) {
if (TripCount)
return TripCount;
IRBuilder<> Builder(L->getLoopPreheader()->getTerminator());
// Find the loop boundaries.
ScalarEvolution *SE = PSE.getSE();
const SCEV *BackedgeTakenCount = PSE.getBackedgeTakenCount();
assert(BackedgeTakenCount != SE->getCouldNotCompute() &&
"Invalid loop count");
Type *IdxTy = Legal->getWidestInductionType();
// The exit count might have the type of i64 while the phi is i32. This can
// happen if we have an induction variable that is sign extended before the
// compare. The only way that we get a backedge taken count is that the
// induction variable was signed and as such will not overflow. In such a case
// truncation is legal.
if (BackedgeTakenCount->getType()->getPrimitiveSizeInBits() >
IdxTy->getPrimitiveSizeInBits())
BackedgeTakenCount = SE->getTruncateOrNoop(BackedgeTakenCount, IdxTy);
BackedgeTakenCount = SE->getNoopOrZeroExtend(BackedgeTakenCount, IdxTy);
// Get the total trip count from the count by adding 1.
const SCEV *ExitCount = SE->getAddExpr(
BackedgeTakenCount, SE->getOne(BackedgeTakenCount->getType()));
const DataLayout &DL = L->getHeader()->getModule()->getDataLayout();
// Expand the trip count and place the new instructions in the preheader.
// Notice that the pre-header does not change, only the loop body.
SCEVExpander Exp(*SE, DL, "induction");
// Count holds the overall loop count (N).
TripCount = Exp.expandCodeFor(ExitCount, ExitCount->getType(),
L->getLoopPreheader()->getTerminator());
if (TripCount->getType()->isPointerTy())
TripCount =
CastInst::CreatePointerCast(TripCount, IdxTy, "exitcount.ptrcnt.to.int",
L->getLoopPreheader()->getTerminator());
return TripCount;
}
Value *InnerLoopVectorizer::getOrCreateVectorTripCount(Loop *L) {
if (VectorTripCount)
return VectorTripCount;
Value *TC = getOrCreateTripCount(L);
IRBuilder<> Builder(L->getLoopPreheader()->getTerminator());
// Now we need to generate the expression for the part of the loop that the
// vectorized body will execute. This is equal to N - (N % Step) if scalar
// iterations are not required for correctness, or N - Step, otherwise. Step
// is equal to the vectorization factor (number of SIMD elements) times the
// unroll factor (number of SIMD instructions).
Constant *Step = ConstantInt::get(TC->getType(), VF * UF);
Value *R = Builder.CreateURem(TC, Step, "n.mod.vf");
// If there is a non-reversed interleaved group that may speculatively access
// memory out-of-bounds, we need to ensure that there will be at least one
// iteration of the scalar epilogue loop. Thus, if the step evenly divides
// the trip count, we set the remainder to be equal to the step. If the step
// does not evenly divide the trip count, no adjustment is necessary since
// there will already be scalar iterations. Note that the minimum iterations
// check ensures that N >= Step.
if (VF > 1 && Cost->requiresScalarEpilogue()) {
auto *IsZero = Builder.CreateICmpEQ(R, ConstantInt::get(R->getType(), 0));
R = Builder.CreateSelect(IsZero, Step, R);
}
VectorTripCount = Builder.CreateSub(TC, R, "n.vec");
return VectorTripCount;
}
Value *InnerLoopVectorizer::createBitOrPointerCast(Value *V, VectorType *DstVTy,
const DataLayout &DL) {
// Verify that V is a vector type with same number of elements as DstVTy.
unsigned VF = DstVTy->getNumElements();
VectorType *SrcVecTy = cast<VectorType>(V->getType());
assert((VF == SrcVecTy->getNumElements()) && "Vector dimensions do not match");
Type *SrcElemTy = SrcVecTy->getElementType();
Type *DstElemTy = DstVTy->getElementType();
assert((DL.getTypeSizeInBits(SrcElemTy) == DL.getTypeSizeInBits(DstElemTy)) &&
"Vector elements must have same size");
// Do a direct cast if element types are castable.
if (CastInst::isBitOrNoopPointerCastable(SrcElemTy, DstElemTy, DL)) {
return Builder.CreateBitOrPointerCast(V, DstVTy);
}
// V cannot be directly casted to desired vector type.
// May happen when V is a floating point vector but DstVTy is a vector of
// pointers or vice-versa. Handle this using a two-step bitcast using an
// intermediate Integer type for the bitcast i.e. Ptr <-> Int <-> Float.
assert((DstElemTy->isPointerTy() != SrcElemTy->isPointerTy()) &&
"Only one type should be a pointer type");
assert((DstElemTy->isFloatingPointTy() != SrcElemTy->isFloatingPointTy()) &&
"Only one type should be a floating point type");
Type *IntTy =
IntegerType::getIntNTy(V->getContext(), DL.getTypeSizeInBits(SrcElemTy));
VectorType *VecIntTy = VectorType::get(IntTy, VF);
Value *CastVal = Builder.CreateBitOrPointerCast(V, VecIntTy);
return Builder.CreateBitOrPointerCast(CastVal, DstVTy);
}
void InnerLoopVectorizer::emitMinimumIterationCountCheck(Loop *L,
BasicBlock *Bypass) {
Value *Count = getOrCreateTripCount(L);
BasicBlock *BB = L->getLoopPreheader();
IRBuilder<> Builder(BB->getTerminator());
// Generate code to check if the loop's trip count is less than VF * UF, or
// equal to it in case a scalar epilogue is required; this implies that the
// vector trip count is zero. This check also covers the case where adding one
// to the backedge-taken count overflowed leading to an incorrect trip count
// of zero. In this case we will also jump to the scalar loop.
auto P = Cost->requiresScalarEpilogue() ? ICmpInst::ICMP_ULE
: ICmpInst::ICMP_ULT;
Value *CheckMinIters = Builder.CreateICmp(
P, Count, ConstantInt::get(Count->getType(), VF * UF), "min.iters.check");
BasicBlock *NewBB = BB->splitBasicBlock(BB->getTerminator(), "vector.ph");
// Update dominator tree immediately if the generated block is a
// LoopBypassBlock because SCEV expansions to generate loop bypass
// checks may query it before the current function is finished.
DT->addNewBlock(NewBB, BB);
if (L->getParentLoop())
L->getParentLoop()->addBasicBlockToLoop(NewBB, *LI);
ReplaceInstWithInst(BB->getTerminator(),
BranchInst::Create(Bypass, NewBB, CheckMinIters));
LoopBypassBlocks.push_back(BB);
}
void InnerLoopVectorizer::emitSCEVChecks(Loop *L, BasicBlock *Bypass) {
BasicBlock *BB = L->getLoopPreheader();
// Generate the code to check that the SCEV assumptions that we made.
// We want the new basic block to start at the first instruction in a
// sequence of instructions that form a check.
SCEVExpander Exp(*PSE.getSE(), Bypass->getModule()->getDataLayout(),
"scev.check");
Value *SCEVCheck =
Exp.expandCodeForPredicate(&PSE.getUnionPredicate(), BB->getTerminator());
if (auto *C = dyn_cast<ConstantInt>(SCEVCheck))
if (C->isZero())
return;
// Create a new block containing the stride check.
BB->setName("vector.scevcheck");
auto *NewBB = BB->splitBasicBlock(BB->getTerminator(), "vector.ph");
// Update dominator tree immediately if the generated block is a
// LoopBypassBlock because SCEV expansions to generate loop bypass
// checks may query it before the current function is finished.
DT->addNewBlock(NewBB, BB);
if (L->getParentLoop())
L->getParentLoop()->addBasicBlockToLoop(NewBB, *LI);
ReplaceInstWithInst(BB->getTerminator(),
BranchInst::Create(Bypass, NewBB, SCEVCheck));
LoopBypassBlocks.push_back(BB);
AddedSafetyChecks = true;
}
void InnerLoopVectorizer::emitMemRuntimeChecks(Loop *L, BasicBlock *Bypass) {
BasicBlock *BB = L->getLoopPreheader();
// Generate the code that checks in runtime if arrays overlap. We put the
// checks into a separate block to make the more common case of few elements
// faster.
Instruction *FirstCheckInst;
Instruction *MemRuntimeCheck;
std::tie(FirstCheckInst, MemRuntimeCheck) =
Legal->getLAI()->addRuntimeChecks(BB->getTerminator());
if (!MemRuntimeCheck)
return;
// Create a new block containing the memory check.
BB->setName("vector.memcheck");
auto *NewBB = BB->splitBasicBlock(BB->getTerminator(), "vector.ph");
// Update dominator tree immediately if the generated block is a
// LoopBypassBlock because SCEV expansions to generate loop bypass
// checks may query it before the current function is finished.
DT->addNewBlock(NewBB, BB);
if (L->getParentLoop())
L->getParentLoop()->addBasicBlockToLoop(NewBB, *LI);
ReplaceInstWithInst(BB->getTerminator(),
BranchInst::Create(Bypass, NewBB, MemRuntimeCheck));
LoopBypassBlocks.push_back(BB);
AddedSafetyChecks = true;
// We currently don't use LoopVersioning for the actual loop cloning but we
// still use it to add the noalias metadata.
LVer = llvm::make_unique<LoopVersioning>(*Legal->getLAI(), OrigLoop, LI, DT,
PSE.getSE());
LVer->prepareNoAliasMetadata();
}
BasicBlock *InnerLoopVectorizer::createVectorizedLoopSkeleton() {
/*
In this function we generate a new loop. The new loop will contain
the vectorized instructions while the old loop will continue to run the
scalar remainder.
[ ] <-- loop iteration number check.
/ |
/ v
| [ ] <-- vector loop bypass (may consist of multiple blocks).
| / |
| / v
|| [ ] <-- vector pre header.
|/ |
| v
| [ ] \
| [ ]_| <-- vector loop.
| |
| v
| -[ ] <--- middle-block.
| / |
| / v
-|- >[ ] <--- new preheader.
| |
| v
| [ ] \
| [ ]_| <-- old scalar loop to handle remainder.
\ |
\ v
>[ ] <-- exit block.
...
*/
BasicBlock *OldBasicBlock = OrigLoop->getHeader();
BasicBlock *VectorPH = OrigLoop->getLoopPreheader();
BasicBlock *ExitBlock = OrigLoop->getExitBlock();
assert(VectorPH && "Invalid loop structure");
assert(ExitBlock && "Must have an exit block");
// Some loops have a single integer induction variable, while other loops
// don't. One example is c++ iterators that often have multiple pointer
// induction variables. In the code below we also support a case where we
// don't have a single induction variable.
//
// We try to obtain an induction variable from the original loop as hard
// as possible. However if we don't find one that:
// - is an integer
// - counts from zero, stepping by one
// - is the size of the widest induction variable type
// then we create a new one.
OldInduction = Legal->getPrimaryInduction();
Type *IdxTy = Legal->getWidestInductionType();
// Split the single block loop into the two loop structure described above.
BasicBlock *VecBody =
VectorPH->splitBasicBlock(VectorPH->getTerminator(), "vector.body");
BasicBlock *MiddleBlock =
VecBody->splitBasicBlock(VecBody->getTerminator(), "middle.block");
BasicBlock *ScalarPH =
MiddleBlock->splitBasicBlock(MiddleBlock->getTerminator(), "scalar.ph");
// Create and register the new vector loop.
Loop *Lp = LI->AllocateLoop();
Loop *ParentLoop = OrigLoop->getParentLoop();
// Insert the new loop into the loop nest and register the new basic blocks
// before calling any utilities such as SCEV that require valid LoopInfo.
if (ParentLoop) {
ParentLoop->addChildLoop(Lp);
ParentLoop->addBasicBlockToLoop(ScalarPH, *LI);
ParentLoop->addBasicBlockToLoop(MiddleBlock, *LI);
} else {
LI->addTopLevelLoop(Lp);
}
Lp->addBasicBlockToLoop(VecBody, *LI);
// Find the loop boundaries.
Value *Count = getOrCreateTripCount(Lp);
Value *StartIdx = ConstantInt::get(IdxTy, 0);
// Now, compare the new count to zero. If it is zero skip the vector loop and
// jump to the scalar loop. This check also covers the case where the
// backedge-taken count is uint##_max: adding one to it will overflow leading
// to an incorrect trip count of zero. In this (rare) case we will also jump
// to the scalar loop.
emitMinimumIterationCountCheck(Lp, ScalarPH);
// Generate the code to check any assumptions that we've made for SCEV
// expressions.
emitSCEVChecks(Lp, ScalarPH);
// Generate the code that checks in runtime if arrays overlap. We put the
// checks into a separate block to make the more common case of few elements
// faster.
emitMemRuntimeChecks(Lp, ScalarPH);
// Generate the induction variable.
// The loop step is equal to the vectorization factor (num of SIMD elements)
// times the unroll factor (num of SIMD instructions).
Value *CountRoundDown = getOrCreateVectorTripCount(Lp);
Constant *Step = ConstantInt::get(IdxTy, VF * UF);
Induction =
createInductionVariable(Lp, StartIdx, CountRoundDown, Step,
getDebugLocFromInstOrOperands(OldInduction));
// We are going to resume the execution of the scalar loop.
// Go over all of the induction variables that we found and fix the
// PHIs that are left in the scalar version of the loop.
// The starting values of PHI nodes depend on the counter of the last
// iteration in the vectorized loop.
// If we come from a bypass edge then we need to start from the original
// start value.
// This variable saves the new starting index for the scalar loop. It is used
// to test if there are any tail iterations left once the vector loop has
// completed.
LoopVectorizationLegality::InductionList *List = Legal->getInductionVars();
for (auto &InductionEntry : *List) {
PHINode *OrigPhi = InductionEntry.first;
InductionDescriptor II = InductionEntry.second;
// Create phi nodes to merge from the backedge-taken check block.
PHINode *BCResumeVal = PHINode::Create(
OrigPhi->getType(), 3, "bc.resume.val", ScalarPH->getTerminator());
Value *&EndValue = IVEndValues[OrigPhi];
if (OrigPhi == OldInduction) {
// We know what the end value is.
EndValue = CountRoundDown;
} else {
IRBuilder<> B(Lp->getLoopPreheader()->getTerminator());
Type *StepType = II.getStep()->getType();
Instruction::CastOps CastOp =
CastInst::getCastOpcode(CountRoundDown, true, StepType, true);
Value *CRD = B.CreateCast(CastOp, CountRoundDown, StepType, "cast.crd");
const DataLayout &DL = OrigLoop->getHeader()->getModule()->getDataLayout();
EndValue = II.transform(B, CRD, PSE.getSE(), DL);
EndValue->setName("ind.end");
}
// The new PHI merges the original incoming value, in case of a bypass,
// or the value at the end of the vectorized loop.
BCResumeVal->addIncoming(EndValue, MiddleBlock);
// Fix the scalar body counter (PHI node).
unsigned BlockIdx = OrigPhi->getBasicBlockIndex(ScalarPH);
// The old induction's phi node in the scalar body needs the truncated
// value.
for (BasicBlock *BB : LoopBypassBlocks)
BCResumeVal->addIncoming(II.getStartValue(), BB);
OrigPhi->setIncomingValue(BlockIdx, BCResumeVal);
}
// Add a check in the middle block to see if we have completed
// all of the iterations in the first vector loop.
// If (N - N%VF) == N, then we *don't* need to run the remainder.
Value *CmpN =
CmpInst::Create(Instruction::ICmp, CmpInst::ICMP_EQ, Count,
CountRoundDown, "cmp.n", MiddleBlock->getTerminator());
ReplaceInstWithInst(MiddleBlock->getTerminator(),
BranchInst::Create(ExitBlock, ScalarPH, CmpN));
// Get ready to start creating new instructions into the vectorized body.
Builder.SetInsertPoint(&*VecBody->getFirstInsertionPt());
// Save the state.
LoopVectorPreHeader = Lp->getLoopPreheader();
LoopScalarPreHeader = ScalarPH;
LoopMiddleBlock = MiddleBlock;
LoopExitBlock = ExitBlock;
LoopVectorBody = VecBody;
LoopScalarBody = OldBasicBlock;
// Keep all loop hints from the original loop on the vector loop (we'll
// replace the vectorizer-specific hints below).
if (MDNode *LID = OrigLoop->getLoopID())
Lp->setLoopID(LID);
LoopVectorizeHints Hints(Lp, true, *ORE);
Hints.setAlreadyVectorized();
return LoopVectorPreHeader;
}
// Fix up external users of the induction variable. At this point, we are
// in LCSSA form, with all external PHIs that use the IV having one input value,
// coming from the remainder loop. We need those PHIs to also have a correct
// value for the IV when arriving directly from the middle block.
void InnerLoopVectorizer::fixupIVUsers(PHINode *OrigPhi,
const InductionDescriptor &II,
Value *CountRoundDown, Value *EndValue,
BasicBlock *MiddleBlock) {
// There are two kinds of external IV usages - those that use the value
// computed in the last iteration (the PHI) and those that use the penultimate
// value (the value that feeds into the phi from the loop latch).
// We allow both, but they, obviously, have different values.
assert(OrigLoop->getExitBlock() && "Expected a single exit block");
DenseMap<Value *, Value *> MissingVals;
// An external user of the last iteration's value should see the value that
// the remainder loop uses to initialize its own IV.
Value *PostInc = OrigPhi->getIncomingValueForBlock(OrigLoop->getLoopLatch());
for (User *U : PostInc->users()) {
Instruction *UI = cast<Instruction>(U);
if (!OrigLoop->contains(UI)) {
assert(isa<PHINode>(UI) && "Expected LCSSA form");
MissingVals[UI] = EndValue;
}
}
// An external user of the penultimate value need to see EndValue - Step.
// The simplest way to get this is to recompute it from the constituent SCEVs,
// that is Start + (Step * (CRD - 1)).
for (User *U : OrigPhi->users()) {
auto *UI = cast<Instruction>(U);
if (!OrigLoop->contains(UI)) {
const DataLayout &DL =
OrigLoop->getHeader()->getModule()->getDataLayout();
assert(isa<PHINode>(UI) && "Expected LCSSA form");
IRBuilder<> B(MiddleBlock->getTerminator());
Value *CountMinusOne = B.CreateSub(
CountRoundDown, ConstantInt::get(CountRoundDown->getType(), 1));
Value *CMO =
!II.getStep()->getType()->isIntegerTy()
? B.CreateCast(Instruction::SIToFP, CountMinusOne,
II.getStep()->getType())
: B.CreateSExtOrTrunc(CountMinusOne, II.getStep()->getType());
CMO->setName("cast.cmo");
Value *Escape = II.transform(B, CMO, PSE.getSE(), DL);
Escape->setName("ind.escape");
MissingVals[UI] = Escape;
}
}
for (auto &I : MissingVals) {
PHINode *PHI = cast<PHINode>(I.first);
// One corner case we have to handle is two IVs "chasing" each-other,
// that is %IV2 = phi [...], [ %IV1, %latch ]
// In this case, if IV1 has an external use, we need to avoid adding both
// "last value of IV1" and "penultimate value of IV2". So, verify that we
// don't already have an incoming value for the middle block.
if (PHI->getBasicBlockIndex(MiddleBlock) == -1)
PHI->addIncoming(I.second, MiddleBlock);
}
}
namespace {
struct CSEDenseMapInfo {
static bool canHandle(const Instruction *I) {
return isa<InsertElementInst>(I) || isa<ExtractElementInst>(I) ||
isa<ShuffleVectorInst>(I) || isa<GetElementPtrInst>(I);
}
static inline Instruction *getEmptyKey() {
return DenseMapInfo<Instruction *>::getEmptyKey();
}
static inline Instruction *getTombstoneKey() {
return DenseMapInfo<Instruction *>::getTombstoneKey();
}
static unsigned getHashValue(const Instruction *I) {
assert(canHandle(I) && "Unknown instruction!");
return hash_combine(I->getOpcode(), hash_combine_range(I->value_op_begin(),
I->value_op_end()));
}
static bool isEqual(const Instruction *LHS, const Instruction *RHS) {
if (LHS == getEmptyKey() || RHS == getEmptyKey() ||
LHS == getTombstoneKey() || RHS == getTombstoneKey())
return LHS == RHS;
return LHS->isIdenticalTo(RHS);
}
};
} // end anonymous namespace
///\brief Perform cse of induction variable instructions.
static void cse(BasicBlock *BB) {
// Perform simple cse.
SmallDenseMap<Instruction *, Instruction *, 4, CSEDenseMapInfo> CSEMap;
for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E;) {
Instruction *In = &*I++;
if (!CSEDenseMapInfo::canHandle(In))
continue;
// Check if we can replace this instruction with any of the
// visited instructions.
if (Instruction *V = CSEMap.lookup(In)) {
In->replaceAllUsesWith(V);
In->eraseFromParent();
continue;
}
CSEMap[In] = In;
}
}
/// \brief Estimate the overhead of scalarizing an instruction. This is a
/// convenience wrapper for the type-based getScalarizationOverhead API.
static unsigned getScalarizationOverhead(Instruction *I, unsigned VF,
const TargetTransformInfo &TTI) {
if (VF == 1)
return 0;
unsigned Cost = 0;
Type *RetTy = ToVectorTy(I->getType(), VF);
if (!RetTy->isVoidTy() &&
(!isa<LoadInst>(I) ||
!TTI.supportsEfficientVectorElementLoadStore()))
Cost += TTI.getScalarizationOverhead(RetTy, true, false);
if (CallInst *CI = dyn_cast<CallInst>(I)) {
SmallVector<const Value *, 4> Operands(CI->arg_operands());
Cost += TTI.getOperandsScalarizationOverhead(Operands, VF);
}
else if (!isa<StoreInst>(I) ||
!TTI.supportsEfficientVectorElementLoadStore()) {
SmallVector<const Value *, 4> Operands(I->operand_values());
Cost += TTI.getOperandsScalarizationOverhead(Operands, VF);
}
return Cost;
}
// Estimate cost of a call instruction CI if it were vectorized with factor VF.
// Return the cost of the instruction, including scalarization overhead if it's
// needed. The flag NeedToScalarize shows if the call needs to be scalarized -
// i.e. either vector version isn't available, or is too expensive.
static unsigned getVectorCallCost(CallInst *CI, unsigned VF,
const TargetTransformInfo &TTI,
const TargetLibraryInfo *TLI,
bool &NeedToScalarize) {
Function *F = CI->getCalledFunction();
StringRef FnName = CI->getCalledFunction()->getName();
Type *ScalarRetTy = CI->getType();
SmallVector<Type *, 4> Tys, ScalarTys;
for (auto &ArgOp : CI->arg_operands())
ScalarTys.push_back(ArgOp->getType());
// Estimate cost of scalarized vector call. The source operands are assumed
// to be vectors, so we need to extract individual elements from there,
// execute VF scalar calls, and then gather the result into the vector return
// value.
unsigned ScalarCallCost = TTI.getCallInstrCost(F, ScalarRetTy, ScalarTys);
if (VF == 1)
return ScalarCallCost;
// Compute corresponding vector type for return value and arguments.
Type *RetTy = ToVectorTy(ScalarRetTy, VF);
for (Type *ScalarTy : ScalarTys)
Tys.push_back(ToVectorTy(ScalarTy, VF));
// Compute costs of unpacking argument values for the scalar calls and
// packing the return values to a vector.
unsigned ScalarizationCost = getScalarizationOverhead(CI, VF, TTI);
unsigned Cost = ScalarCallCost * VF + ScalarizationCost;
// If we can't emit a vector call for this function, then the currently found
// cost is the cost we need to return.
NeedToScalarize = true;
if (!TLI || !TLI->isFunctionVectorizable(FnName, VF) || CI->isNoBuiltin())
return Cost;
// If the corresponding vector cost is cheaper, return its cost.
unsigned VectorCallCost = TTI.getCallInstrCost(nullptr, RetTy, Tys);
if (VectorCallCost < Cost) {
NeedToScalarize = false;
return VectorCallCost;
}
return Cost;
}
// Estimate cost of an intrinsic call instruction CI if it were vectorized with
// factor VF. Return the cost of the instruction, including scalarization
// overhead if it's needed.
static unsigned getVectorIntrinsicCost(CallInst *CI, unsigned VF,
const TargetTransformInfo &TTI,
const TargetLibraryInfo *TLI) {
Intrinsic::ID ID = getVectorIntrinsicIDForCall(CI, TLI);
assert(ID && "Expected intrinsic call!");
FastMathFlags FMF;
if (auto *FPMO = dyn_cast<FPMathOperator>(CI))
FMF = FPMO->getFastMathFlags();
SmallVector<Value *, 4> Operands(CI->arg_operands());
return TTI.getIntrinsicInstrCost(ID, CI->getType(), Operands, FMF, VF);
}
static Type *smallestIntegerVectorType(Type *T1, Type *T2) {
auto *I1 = cast<IntegerType>(T1->getVectorElementType());
auto *I2 = cast<IntegerType>(T2->getVectorElementType());
return I1->getBitWidth() < I2->getBitWidth() ? T1 : T2;
}
static Type *largestIntegerVectorType(Type *T1, Type *T2) {
auto *I1 = cast<IntegerType>(T1->getVectorElementType());
auto *I2 = cast<IntegerType>(T2->getVectorElementType());
return I1->getBitWidth() > I2->getBitWidth() ? T1 : T2;
}
void InnerLoopVectorizer::truncateToMinimalBitwidths() {
// For every instruction `I` in MinBWs, truncate the operands, create a
// truncated version of `I` and reextend its result. InstCombine runs
// later and will remove any ext/trunc pairs.
SmallPtrSet<Value *, 4> Erased;
for (const auto &KV : Cost->getMinimalBitwidths()) {
// If the value wasn't vectorized, we must maintain the original scalar
// type. The absence of the value from VectorLoopValueMap indicates that it
// wasn't vectorized.
if (!VectorLoopValueMap.hasAnyVectorValue(KV.first))
continue;
for (unsigned Part = 0; Part < UF; ++Part) {
Value *I = getOrCreateVectorValue(KV.first, Part);
if (Erased.count(I) || I->use_empty() || !isa<Instruction>(I))
continue;
Type *OriginalTy = I->getType();
Type *ScalarTruncatedTy =
IntegerType::get(OriginalTy->getContext(), KV.second);
Type *TruncatedTy = VectorType::get(ScalarTruncatedTy,
OriginalTy->getVectorNumElements());
if (TruncatedTy == OriginalTy)
continue;
IRBuilder<> B(cast<Instruction>(I));
auto ShrinkOperand = [&](Value *V) -> Value * {
if (auto *ZI = dyn_cast<ZExtInst>(V))
if (ZI->getSrcTy() == TruncatedTy)
return ZI->getOperand(0);
return B.CreateZExtOrTrunc(V, TruncatedTy);
};
// The actual instruction modification depends on the instruction type,
// unfortunately.
Value *NewI = nullptr;
if (auto *BO = dyn_cast<BinaryOperator>(I)) {
NewI = B.CreateBinOp(BO->getOpcode(), ShrinkOperand(BO->getOperand(0)),
ShrinkOperand(BO->getOperand(1)));
// Any wrapping introduced by shrinking this operation shouldn't be
// considered undefined behavior. So, we can't unconditionally copy
// arithmetic wrapping flags to NewI.
cast<BinaryOperator>(NewI)->copyIRFlags(I, /*IncludeWrapFlags=*/false);
} else if (auto *CI = dyn_cast<ICmpInst>(I)) {
NewI =
B.CreateICmp(CI->getPredicate(), ShrinkOperand(CI->getOperand(0)),
ShrinkOperand(CI->getOperand(1)));
} else if (auto *SI = dyn_cast<SelectInst>(I)) {
NewI = B.CreateSelect(SI->getCondition(),
ShrinkOperand(SI->getTrueValue()),
ShrinkOperand(SI->getFalseValue()));
} else if (auto *CI = dyn_cast<CastInst>(I)) {
switch (CI->getOpcode()) {
default:
llvm_unreachable("Unhandled cast!");
case Instruction::Trunc:
NewI = ShrinkOperand(CI->getOperand(0));
break;
case Instruction::SExt:
NewI = B.CreateSExtOrTrunc(
CI->getOperand(0),
smallestIntegerVectorType(OriginalTy, TruncatedTy));
break;
case Instruction::ZExt:
NewI = B.CreateZExtOrTrunc(
CI->getOperand(0),
smallestIntegerVectorType(OriginalTy, TruncatedTy));
break;
}
} else if (auto *SI = dyn_cast<ShuffleVectorInst>(I)) {
auto Elements0 = SI->getOperand(0)->getType()->getVectorNumElements();
auto *O0 = B.CreateZExtOrTrunc(
SI->getOperand(0), VectorType::get(ScalarTruncatedTy, Elements0));
auto Elements1 = SI->getOperand(1)->getType()->getVectorNumElements();
auto *O1 = B.CreateZExtOrTrunc(
SI->getOperand(1), VectorType::get(ScalarTruncatedTy, Elements1));
NewI = B.CreateShuffleVector(O0, O1, SI->getMask());
} else if (isa<LoadInst>(I)) {
// Don't do anything with the operands, just extend the result.
continue;
} else if (auto *IE = dyn_cast<InsertElementInst>(I)) {
auto Elements = IE->getOperand(0)->getType()->getVectorNumElements();
auto *O0 = B.CreateZExtOrTrunc(
IE->getOperand(0), VectorType::get(ScalarTruncatedTy, Elements));
auto *O1 = B.CreateZExtOrTrunc(IE->getOperand(1), ScalarTruncatedTy);
NewI = B.CreateInsertElement(O0, O1, IE->getOperand(2));
} else if (auto *EE = dyn_cast<ExtractElementInst>(I)) {
auto Elements = EE->getOperand(0)->getType()->getVectorNumElements();
auto *O0 = B.CreateZExtOrTrunc(
EE->getOperand(0), VectorType::get(ScalarTruncatedTy, Elements));
NewI = B.CreateExtractElement(O0, EE->getOperand(2));
} else {
llvm_unreachable("Unhandled instruction type!");
}
// Lastly, extend the result.
NewI->takeName(cast<Instruction>(I));
Value *Res = B.CreateZExtOrTrunc(NewI, OriginalTy);
I->replaceAllUsesWith(Res);
cast<Instruction>(I)->eraseFromParent();
Erased.insert(I);
VectorLoopValueMap.resetVectorValue(KV.first, Part, Res);
}
}
// We'll have created a bunch of ZExts that are now parentless. Clean up.
for (const auto &KV : Cost->getMinimalBitwidths()) {
// If the value wasn't vectorized, we must maintain the original scalar
// type. The absence of the value from VectorLoopValueMap indicates that it
// wasn't vectorized.
if (!VectorLoopValueMap.hasAnyVectorValue(KV.first))
continue;
for (unsigned Part = 0; Part < UF; ++Part) {
Value *I = getOrCreateVectorValue(KV.first, Part);
ZExtInst *Inst = dyn_cast<ZExtInst>(I);
if (Inst && Inst->use_empty()) {
Value *NewI = Inst->getOperand(0);
Inst->eraseFromParent();
VectorLoopValueMap.resetVectorValue(KV.first, Part, NewI);
}
}
}
}
void InnerLoopVectorizer::fixVectorizedLoop() {
// Insert truncates and extends for any truncated instructions as hints to
// InstCombine.
if (VF > 1)
truncateToMinimalBitwidths();
// At this point every instruction in the original loop is widened to a
// vector form. Now we need to fix the recurrences in the loop. These PHI
// nodes are currently empty because we did not want to introduce cycles.
// This is the second stage of vectorizing recurrences.
fixCrossIterationPHIs();
// Update the dominator tree.
//
// FIXME: After creating the structure of the new loop, the dominator tree is
// no longer up-to-date, and it remains that way until we update it
// here. An out-of-date dominator tree is problematic for SCEV,
// because SCEVExpander uses it to guide code generation. The
// vectorizer use SCEVExpanders in several places. Instead, we should
// keep the dominator tree up-to-date as we go.
updateAnalysis();
// Fix-up external users of the induction variables.
for (auto &Entry : *Legal->getInductionVars())
fixupIVUsers(Entry.first, Entry.second,
getOrCreateVectorTripCount(LI->getLoopFor(LoopVectorBody)),
IVEndValues[Entry.first], LoopMiddleBlock);
fixLCSSAPHIs();
for (Instruction *PI : PredicatedInstructions)
sinkScalarOperands(&*PI);
// Remove redundant induction instructions.
cse(LoopVectorBody);
}
void InnerLoopVectorizer::fixCrossIterationPHIs() {
// In order to support recurrences we need to be able to vectorize Phi nodes.
// Phi nodes have cycles, so we need to vectorize them in two stages. This is
// stage #2: We now need to fix the recurrences by adding incoming edges to
// the currently empty PHI nodes. At this point every instruction in the
// original loop is widened to a vector form so we can use them to construct
// the incoming edges.
for (PHINode &Phi : OrigLoop->getHeader()->phis()) {
// Handle first-order recurrences and reductions that need to be fixed.
if (Legal->isFirstOrderRecurrence(&Phi))
fixFirstOrderRecurrence(&Phi);
else if (Legal->isReductionVariable(&Phi))
fixReduction(&Phi);
}
}
void InnerLoopVectorizer::fixFirstOrderRecurrence(PHINode *Phi) {
// This is the second phase of vectorizing first-order recurrences. An
// overview of the transformation is described below. Suppose we have the
// following loop.
//
// for (int i = 0; i < n; ++i)
// b[i] = a[i] - a[i - 1];
//
// There is a first-order recurrence on "a". For this loop, the shorthand
// scalar IR looks like:
//
// scalar.ph:
// s_init = a[-1]
// br scalar.body
//
// scalar.body:
// i = phi [0, scalar.ph], [i+1, scalar.body]
// s1 = phi [s_init, scalar.ph], [s2, scalar.body]
// s2 = a[i]
// b[i] = s2 - s1
// br cond, scalar.body, ...
//
// In this example, s1 is a recurrence because it's value depends on the
// previous iteration. In the first phase of vectorization, we created a
// temporary value for s1. We now complete the vectorization and produce the
// shorthand vector IR shown below (for VF = 4, UF = 1).
//
// vector.ph:
// v_init = vector(..., ..., ..., a[-1])
// br vector.body
//
// vector.body
// i = phi [0, vector.ph], [i+4, vector.body]
// v1 = phi [v_init, vector.ph], [v2, vector.body]
// v2 = a[i, i+1, i+2, i+3];
// v3 = vector(v1(3), v2(0, 1, 2))
// b[i, i+1, i+2, i+3] = v2 - v3
// br cond, vector.body, middle.block
//
// middle.block:
// x = v2(3)
// br scalar.ph
//
// scalar.ph:
// s_init = phi [x, middle.block], [a[-1], otherwise]
// br scalar.body
//
// After execution completes the vector loop, we extract the next value of
// the recurrence (x) to use as the initial value in the scalar loop.
// Get the original loop preheader and single loop latch.
auto *Preheader = OrigLoop->getLoopPreheader();
auto *Latch = OrigLoop->getLoopLatch();
// Get the initial and previous values of the scalar recurrence.
auto *ScalarInit = Phi->getIncomingValueForBlock(Preheader);
auto *Previous = Phi->getIncomingValueForBlock(Latch);
// Create a vector from the initial value.
auto *VectorInit = ScalarInit;
if (VF > 1) {
Builder.SetInsertPoint(LoopVectorPreHeader->getTerminator());
VectorInit = Builder.CreateInsertElement(
UndefValue::get(VectorType::get(VectorInit->getType(), VF)), VectorInit,
Builder.getInt32(VF - 1), "vector.recur.init");
}
// We constructed a temporary phi node in the first phase of vectorization.
// This phi node will eventually be deleted.
Builder.SetInsertPoint(
cast<Instruction>(VectorLoopValueMap.getVectorValue(Phi, 0)));
// Create a phi node for the new recurrence. The current value will either be
// the initial value inserted into a vector or loop-varying vector value.
auto *VecPhi = Builder.CreatePHI(VectorInit->getType(), 2, "vector.recur");
VecPhi->addIncoming(VectorInit, LoopVectorPreHeader);
// Get the vectorized previous value of the last part UF - 1. It appears last
// among all unrolled iterations, due to the order of their construction.
Value *PreviousLastPart = getOrCreateVectorValue(Previous, UF - 1);
// Set the insertion point after the previous value if it is an instruction.
// Note that the previous value may have been constant-folded so it is not
// guaranteed to be an instruction in the vector loop. Also, if the previous
// value is a phi node, we should insert after all the phi nodes to avoid
// breaking basic block verification.
if (LI->getLoopFor(LoopVectorBody)->isLoopInvariant(PreviousLastPart) ||
isa<PHINode>(PreviousLastPart))
Builder.SetInsertPoint(&*LoopVectorBody->getFirstInsertionPt());
else
Builder.SetInsertPoint(
&*++BasicBlock::iterator(cast<Instruction>(PreviousLastPart)));
// We will construct a vector for the recurrence by combining the values for
// the current and previous iterations. This is the required shuffle mask.
SmallVector<Constant *, 8> ShuffleMask(VF);
ShuffleMask[0] = Builder.getInt32(VF - 1);
for (unsigned I = 1; I < VF; ++I)
ShuffleMask[I] = Builder.getInt32(I + VF - 1);
// The vector from which to take the initial value for the current iteration
// (actual or unrolled). Initially, this is the vector phi node.
Value *Incoming = VecPhi;
// Shuffle the current and previous vector and update the vector parts.
for (unsigned Part = 0; Part < UF; ++Part) {
Value *PreviousPart = getOrCreateVectorValue(Previous, Part);
Value *PhiPart = VectorLoopValueMap.getVectorValue(Phi, Part);
auto *Shuffle =
VF > 1 ? Builder.CreateShuffleVector(Incoming, PreviousPart,
ConstantVector::get(ShuffleMask))
: Incoming;
PhiPart->replaceAllUsesWith(Shuffle);
cast<Instruction>(PhiPart)->eraseFromParent();
VectorLoopValueMap.resetVectorValue(Phi, Part, Shuffle);
Incoming = PreviousPart;
}
// Fix the latch value of the new recurrence in the vector loop.
VecPhi->addIncoming(Incoming, LI->getLoopFor(LoopVectorBody)->getLoopLatch());
// Extract the last vector element in the middle block. This will be the
// initial value for the recurrence when jumping to the scalar loop.
auto *ExtractForScalar = Incoming;
if (VF > 1) {
Builder.SetInsertPoint(LoopMiddleBlock->getTerminator());
ExtractForScalar = Builder.CreateExtractElement(
ExtractForScalar, Builder.getInt32(VF - 1), "vector.recur.extract");
}
// Extract the second last element in the middle block if the
// Phi is used outside the loop. We need to extract the phi itself
// and not the last element (the phi update in the current iteration). This
// will be the value when jumping to the exit block from the LoopMiddleBlock,
// when the scalar loop is not run at all.
Value *ExtractForPhiUsedOutsideLoop = nullptr;
if (VF > 1)
ExtractForPhiUsedOutsideLoop = Builder.CreateExtractElement(
Incoming, Builder.getInt32(VF - 2), "vector.recur.extract.for.phi");
// When loop is unrolled without vectorizing, initialize
// ExtractForPhiUsedOutsideLoop with the value just prior to unrolled value of
// `Incoming`. This is analogous to the vectorized case above: extracting the
// second last element when VF > 1.
else if (UF > 1)
ExtractForPhiUsedOutsideLoop = getOrCreateVectorValue(Previous, UF - 2);
// Fix the initial value of the original recurrence in the scalar loop.
Builder.SetInsertPoint(&*LoopScalarPreHeader->begin());
auto *Start = Builder.CreatePHI(Phi->getType(), 2, "scalar.recur.init");
for (auto *BB : predecessors(LoopScalarPreHeader)) {
auto *Incoming = BB == LoopMiddleBlock ? ExtractForScalar : ScalarInit;
Start->addIncoming(Incoming, BB);
}
Phi->setIncomingValue(Phi->getBasicBlockIndex(LoopScalarPreHeader), Start);
Phi->setName("scalar.recur");
// Finally, fix users of the recurrence outside the loop. The users will need
// either the last value of the scalar recurrence or the last value of the
// vector recurrence we extracted in the middle block. Since the loop is in
// LCSSA form, we just need to find the phi node for the original scalar
// recurrence in the exit block, and then add an edge for the middle block.
for (PHINode &LCSSAPhi : LoopExitBlock->phis()) {
if (LCSSAPhi.getIncomingValue(0) == Phi) {
LCSSAPhi.addIncoming(ExtractForPhiUsedOutsideLoop, LoopMiddleBlock);
break;
}
}
}
void InnerLoopVectorizer::fixReduction(PHINode *Phi) {
Constant *Zero = Builder.getInt32(0);
// Get it's reduction variable descriptor.
assert(Legal->isReductionVariable(Phi) &&
"Unable to find the reduction variable");
RecurrenceDescriptor RdxDesc = (*Legal->getReductionVars())[Phi];
RecurrenceDescriptor::RecurrenceKind RK = RdxDesc.getRecurrenceKind();
TrackingVH<Value> ReductionStartValue = RdxDesc.getRecurrenceStartValue();
Instruction *LoopExitInst = RdxDesc.getLoopExitInstr();
RecurrenceDescriptor::MinMaxRecurrenceKind MinMaxKind =
RdxDesc.getMinMaxRecurrenceKind();
setDebugLocFromInst(Builder, ReductionStartValue);
// We need to generate a reduction vector from the incoming scalar.
// To do so, we need to generate the 'identity' vector and override
// one of the elements with the incoming scalar reduction. We need
// to do it in the vector-loop preheader.
Builder.SetInsertPoint(LoopVectorPreHeader->getTerminator());
// This is the vector-clone of the value that leaves the loop.
Type *VecTy = getOrCreateVectorValue(LoopExitInst, 0)->getType();
// Find the reduction identity variable. Zero for addition, or, xor,
// one for multiplication, -1 for And.
Value *Identity;
Value *VectorStart;
if (RK == RecurrenceDescriptor::RK_IntegerMinMax ||
RK == RecurrenceDescriptor::RK_FloatMinMax) {
// MinMax reduction have the start value as their identify.
if (VF == 1) {
VectorStart = Identity = ReductionStartValue;
} else {
VectorStart = Identity =
Builder.CreateVectorSplat(VF, ReductionStartValue, "minmax.ident");
}
} else {
// Handle other reduction kinds:
Constant *Iden = RecurrenceDescriptor::getRecurrenceIdentity(
RK, VecTy->getScalarType());
if (VF == 1) {
Identity = Iden;
// This vector is the Identity vector where the first element is the
// incoming scalar reduction.
VectorStart = ReductionStartValue;
} else {
Identity = ConstantVector::getSplat(VF, Iden);
// This vector is the Identity vector where the first element is the
// incoming scalar reduction.
VectorStart =
Builder.CreateInsertElement(Identity, ReductionStartValue, Zero);
}
}
// Fix the vector-loop phi.
// Reductions do not have to start at zero. They can start with
// any loop invariant values.
BasicBlock *Latch = OrigLoop->getLoopLatch();
Value *LoopVal = Phi->getIncomingValueForBlock(Latch);
for (unsigned Part = 0; Part < UF; ++Part) {
Value *VecRdxPhi = getOrCreateVectorValue(Phi, Part);
Value *Val = getOrCreateVectorValue(LoopVal, Part);
// Make sure to add the reduction stat value only to the
// first unroll part.
Value *StartVal = (Part == 0) ? VectorStart : Identity;
cast<PHINode>(VecRdxPhi)->addIncoming(StartVal, LoopVectorPreHeader);
cast<PHINode>(VecRdxPhi)
->addIncoming(Val, LI->getLoopFor(LoopVectorBody)->getLoopLatch());
}
// Before each round, move the insertion point right between
// the PHIs and the values we are going to write.
// This allows us to write both PHINodes and the extractelement
// instructions.
Builder.SetInsertPoint(&*LoopMiddleBlock->getFirstInsertionPt());
setDebugLocFromInst(Builder, LoopExitInst);
// If the vector reduction can be performed in a smaller type, we truncate
// then extend the loop exit value to enable InstCombine to evaluate the
// entire expression in the smaller type.
if (VF > 1 && Phi->getType() != RdxDesc.getRecurrenceType()) {
Type *RdxVecTy = VectorType::get(RdxDesc.getRecurrenceType(), VF);
Builder.SetInsertPoint(
LI->getLoopFor(LoopVectorBody)->getLoopLatch()->getTerminator());
VectorParts RdxParts(UF);
for (unsigned Part = 0; Part < UF; ++Part) {
RdxParts[Part] = VectorLoopValueMap.getVectorValue(LoopExitInst, Part);
Value *Trunc = Builder.CreateTrunc(RdxParts[Part], RdxVecTy);
Value *Extnd = RdxDesc.isSigned() ? Builder.CreateSExt(Trunc, VecTy)
: Builder.CreateZExt(Trunc, VecTy);
for (Value::user_iterator UI = RdxParts[Part]->user_begin();
UI != RdxParts[Part]->user_end();)
if (*UI != Trunc) {
(*UI++)->replaceUsesOfWith(RdxParts[Part], Extnd);
RdxParts[Part] = Extnd;
} else {
++UI;
}
}
Builder.SetInsertPoint(&*LoopMiddleBlock->getFirstInsertionPt());
for (unsigned Part = 0; Part < UF; ++Part) {
RdxParts[Part] = Builder.CreateTrunc(RdxParts[Part], RdxVecTy);
VectorLoopValueMap.resetVectorValue(LoopExitInst, Part, RdxParts[Part]);
}
}
// Reduce all of the unrolled parts into a single vector.
Value *ReducedPartRdx = VectorLoopValueMap.getVectorValue(LoopExitInst, 0);
unsigned Op = RecurrenceDescriptor::getRecurrenceBinOp(RK);
setDebugLocFromInst(Builder, ReducedPartRdx);
for (unsigned Part = 1; Part < UF; ++Part) {
Value *RdxPart = VectorLoopValueMap.getVectorValue(LoopExitInst, Part);
if (Op != Instruction::ICmp && Op != Instruction::FCmp)
// Floating point operations had to be 'fast' to enable the reduction.
ReducedPartRdx = addFastMathFlag(
Builder.CreateBinOp((Instruction::BinaryOps)Op, RdxPart,
ReducedPartRdx, "bin.rdx"));
else
ReducedPartRdx = RecurrenceDescriptor::createMinMaxOp(
Builder, MinMaxKind, ReducedPartRdx, RdxPart);
}
if (VF > 1) {
bool NoNaN = Legal->hasFunNoNaNAttr();
ReducedPartRdx =
createTargetReduction(Builder, TTI, RdxDesc, ReducedPartRdx, NoNaN);
// If the reduction can be performed in a smaller type, we need to extend
// the reduction to the wider type before we branch to the original loop.
if (Phi->getType() != RdxDesc.getRecurrenceType())
ReducedPartRdx =
RdxDesc.isSigned()
? Builder.CreateSExt(ReducedPartRdx, Phi->getType())
: Builder.CreateZExt(ReducedPartRdx, Phi->getType());
}
// Create a phi node that merges control-flow from the backedge-taken check
// block and the middle block.
PHINode *BCBlockPhi = PHINode::Create(Phi->getType(), 2, "bc.merge.rdx",
LoopScalarPreHeader->getTerminator());
for (unsigned I = 0, E = LoopBypassBlocks.size(); I != E; ++I)
BCBlockPhi->addIncoming(ReductionStartValue, LoopBypassBlocks[I]);
BCBlockPhi->addIncoming(ReducedPartRdx, LoopMiddleBlock);
// Now, we need to fix the users of the reduction variable
// inside and outside of the scalar remainder loop.
// We know that the loop is in LCSSA form. We need to update the
// PHI nodes in the exit blocks.
for (PHINode &LCSSAPhi : LoopExitBlock->phis()) {
// All PHINodes need to have a single entry edge, or two if
// we already fixed them.
assert(LCSSAPhi.getNumIncomingValues() < 3 && "Invalid LCSSA PHI");
// We found a reduction value exit-PHI. Update it with the
// incoming bypass edge.
if (LCSSAPhi.getIncomingValue(0) == LoopExitInst)
LCSSAPhi.addIncoming(ReducedPartRdx, LoopMiddleBlock);
} // end of the LCSSA phi scan.
// Fix the scalar loop reduction variable with the incoming reduction sum
// from the vector body and from the backedge value.
int IncomingEdgeBlockIdx =
Phi->getBasicBlockIndex(OrigLoop->getLoopLatch());
assert(IncomingEdgeBlockIdx >= 0 && "Invalid block index");
// Pick the other block.
int SelfEdgeBlockIdx = (IncomingEdgeBlockIdx ? 0 : 1);
Phi->setIncomingValue(SelfEdgeBlockIdx, BCBlockPhi);
Phi->setIncomingValue(IncomingEdgeBlockIdx, LoopExitInst);
}
void InnerLoopVectorizer::fixLCSSAPHIs() {
for (PHINode &LCSSAPhi : LoopExitBlock->phis()) {
if (LCSSAPhi.getNumIncomingValues() == 1) {
assert(OrigLoop->isLoopInvariant(LCSSAPhi.getIncomingValue(0)) &&
"Incoming value isn't loop invariant");
LCSSAPhi.addIncoming(LCSSAPhi.getIncomingValue(0), LoopMiddleBlock);
}
}
}
void InnerLoopVectorizer::sinkScalarOperands(Instruction *PredInst) {
// The basic block and loop containing the predicated instruction.
auto *PredBB = PredInst->getParent();
auto *VectorLoop = LI->getLoopFor(PredBB);
// Initialize a worklist with the operands of the predicated instruction.
SetVector<Value *> Worklist(PredInst->op_begin(), PredInst->op_end());
// Holds instructions that we need to analyze again. An instruction may be
// reanalyzed if we don't yet know if we can sink it or not.
SmallVector<Instruction *, 8> InstsToReanalyze;
// Returns true if a given use occurs in the predicated block. Phi nodes use
// their operands in their corresponding predecessor blocks.
auto isBlockOfUsePredicated = [&](Use &U) -> bool {
auto *I = cast<Instruction>(U.getUser());
BasicBlock *BB = I->getParent();
if (auto *Phi = dyn_cast<PHINode>(I))
BB = Phi->getIncomingBlock(
PHINode::getIncomingValueNumForOperand(U.getOperandNo()));
return BB == PredBB;
};
// Iteratively sink the scalarized operands of the predicated instruction
// into the block we created for it. When an instruction is sunk, it's
// operands are then added to the worklist. The algorithm ends after one pass
// through the worklist doesn't sink a single instruction.
bool Changed;
do {
// Add the instructions that need to be reanalyzed to the worklist, and
// reset the changed indicator.
Worklist.insert(InstsToReanalyze.begin(), InstsToReanalyze.end());
InstsToReanalyze.clear();
Changed = false;
while (!Worklist.empty()) {
auto *I = dyn_cast<Instruction>(Worklist.pop_back_val());
// We can't sink an instruction if it is a phi node, is already in the
// predicated block, is not in the loop, or may have side effects.
if (!I || isa<PHINode>(I) || I->getParent() == PredBB ||
!VectorLoop->contains(I) || I->mayHaveSideEffects())
continue;
// It's legal to sink the instruction if all its uses occur in the
// predicated block. Otherwise, there's nothing to do yet, and we may
// need to reanalyze the instruction.
if (!llvm::all_of(I->uses(), isBlockOfUsePredicated)) {
InstsToReanalyze.push_back(I);
continue;
}
// Move the instruction to the beginning of the predicated block, and add
// it's operands to the worklist.
I->moveBefore(&*PredBB->getFirstInsertionPt());
Worklist.insert(I->op_begin(), I->op_end());
// The sinking may have enabled other instructions to be sunk, so we will
// need to iterate.
Changed = true;
}
} while (Changed);
}
void InnerLoopVectorizer::widenPHIInstruction(Instruction *PN, unsigned UF,
unsigned VF) {
assert(PN->getParent() == OrigLoop->getHeader() &&
"Non-header phis should have been handled elsewhere");
PHINode *P = cast<PHINode>(PN);
// In order to support recurrences we need to be able to vectorize Phi nodes.
// Phi nodes have cycles, so we need to vectorize them in two stages. This is
// stage #1: We create a new vector PHI node with no incoming edges. We'll use
// this value when we vectorize all of the instructions that use the PHI.
if (Legal->isReductionVariable(P) || Legal->isFirstOrderRecurrence(P)) {
for (unsigned Part = 0; Part < UF; ++Part) {
// This is phase one of vectorizing PHIs.
Type *VecTy =
(VF == 1) ? PN->getType() : VectorType::get(PN->getType(), VF);
Value *EntryPart = PHINode::Create(
VecTy, 2, "vec.phi", &*LoopVectorBody->getFirstInsertionPt());
VectorLoopValueMap.setVectorValue(P, Part, EntryPart);
}
return;
}
setDebugLocFromInst(Builder, P);
// This PHINode must be an induction variable.
// Make sure that we know about it.
assert(Legal->getInductionVars()->count(P) && "Not an induction variable");
InductionDescriptor II = Legal->getInductionVars()->lookup(P);
const DataLayout &DL = OrigLoop->getHeader()->getModule()->getDataLayout();
// FIXME: The newly created binary instructions should contain nsw/nuw flags,
// which can be found from the original scalar operations.
switch (II.getKind()) {
case InductionDescriptor::IK_NoInduction:
llvm_unreachable("Unknown induction");
case InductionDescriptor::IK_IntInduction:
case InductionDescriptor::IK_FpInduction:
llvm_unreachable("Integer/fp induction is handled elsewhere.");
case InductionDescriptor::IK_PtrInduction: {
// Handle the pointer induction variable case.
assert(P->getType()->isPointerTy() && "Unexpected type.");
// This is the normalized GEP that starts counting at zero.
Value *PtrInd = Induction;
PtrInd = Builder.CreateSExtOrTrunc(PtrInd, II.getStep()->getType());
// Determine the number of scalars we need to generate for each unroll
// iteration. If the instruction is uniform, we only need to generate the
// first lane. Otherwise, we generate all VF values.
unsigned Lanes = Cost->isUniformAfterVectorization(P, VF) ? 1 : VF;
// These are the scalar results. Notice that we don't generate vector GEPs
// because scalar GEPs result in better code.
for (unsigned Part = 0; Part < UF; ++Part) {
for (unsigned Lane = 0; Lane < Lanes; ++Lane) {
Constant *Idx = ConstantInt::get(PtrInd->getType(), Lane + Part * VF);
Value *GlobalIdx = Builder.CreateAdd(PtrInd, Idx);
Value *SclrGep = II.transform(Builder, GlobalIdx, PSE.getSE(), DL);
SclrGep->setName("next.gep");
VectorLoopValueMap.setScalarValue(P, {Part, Lane}, SclrGep);
}
}
return;
}
}
}
/// A helper function for checking whether an integer division-related
/// instruction may divide by zero (in which case it must be predicated if
/// executed conditionally in the scalar code).
/// TODO: It may be worthwhile to generalize and check isKnownNonZero().
/// Non-zero divisors that are non compile-time constants will not be
/// converted into multiplication, so we will still end up scalarizing
/// the division, but can do so w/o predication.
static bool mayDivideByZero(Instruction &I) {
assert((I.getOpcode() == Instruction::UDiv ||
I.getOpcode() == Instruction::SDiv ||
I.getOpcode() == Instruction::URem ||
I.getOpcode() == Instruction::SRem) &&
"Unexpected instruction");
Value *Divisor = I.getOperand(1);
auto *CInt = dyn_cast<ConstantInt>(Divisor);
return !CInt || CInt->isZero();
}
void InnerLoopVectorizer::widenInstruction(Instruction &I) {
switch (I.getOpcode()) {
case Instruction::Br:
case Instruction::PHI:
llvm_unreachable("This instruction is handled by a different recipe.");
case Instruction::GetElementPtr: {
// Construct a vector GEP by widening the operands of the scalar GEP as
// necessary. We mark the vector GEP 'inbounds' if appropriate. A GEP
// results in a vector of pointers when at least one operand of the GEP
// is vector-typed. Thus, to keep the representation compact, we only use
// vector-typed operands for loop-varying values.
auto *GEP = cast<GetElementPtrInst>(&I);
if (VF > 1 && OrigLoop->hasLoopInvariantOperands(GEP)) {
// If we are vectorizing, but the GEP has only loop-invariant operands,
// the GEP we build (by only using vector-typed operands for
// loop-varying values) would be a scalar pointer. Thus, to ensure we
// produce a vector of pointers, we need to either arbitrarily pick an
// operand to broadcast, or broadcast a clone of the original GEP.
// Here, we broadcast a clone of the original.
//
// TODO: If at some point we decide to scalarize instructions having
// loop-invariant operands, this special case will no longer be
// required. We would add the scalarization decision to
// collectLoopScalars() and teach getVectorValue() to broadcast
// the lane-zero scalar value.
auto *Clone = Builder.Insert(GEP->clone());
for (unsigned Part = 0; Part < UF; ++Part) {
Value *EntryPart = Builder.CreateVectorSplat(VF, Clone);
VectorLoopValueMap.setVectorValue(&I, Part, EntryPart);
addMetadata(EntryPart, GEP);
}
} else {
// If the GEP has at least one loop-varying operand, we are sure to
// produce a vector of pointers. But if we are only unrolling, we want
// to produce a scalar GEP for each unroll part. Thus, the GEP we
// produce with the code below will be scalar (if VF == 1) or vector
// (otherwise). Note that for the unroll-only case, we still maintain
// values in the vector mapping with initVector, as we do for other
// instructions.
for (unsigned Part = 0; Part < UF; ++Part) {
// The pointer operand of the new GEP. If it's loop-invariant, we
// won't broadcast it.
auto *Ptr =
OrigLoop->isLoopInvariant(GEP->getPointerOperand())
? GEP->getPointerOperand()
: getOrCreateVectorValue(GEP->getPointerOperand(), Part);
// Collect all the indices for the new GEP. If any index is
// loop-invariant, we won't broadcast it.
SmallVector<Value *, 4> Indices;
for (auto &U : make_range(GEP->idx_begin(), GEP->idx_end())) {
if (OrigLoop->isLoopInvariant(U.get()))
Indices.push_back(U.get());
else
Indices.push_back(getOrCreateVectorValue(U.get(), Part));
}
// Create the new GEP. Note that this GEP may be a scalar if VF == 1,
// but it should be a vector, otherwise.
auto *NewGEP = GEP->isInBounds()
? Builder.CreateInBoundsGEP(Ptr, Indices)
: Builder.CreateGEP(Ptr, Indices);
assert((VF == 1 || NewGEP->getType()->isVectorTy()) &&
"NewGEP is not a pointer vector");
VectorLoopValueMap.setVectorValue(&I, Part, NewGEP);
addMetadata(NewGEP, GEP);
}
}
break;
}
case Instruction::UDiv:
case Instruction::SDiv:
case Instruction::SRem:
case Instruction::URem:
case Instruction::Add:
case Instruction::FAdd:
case Instruction::Sub:
case Instruction::FSub:
case Instruction::Mul:
case Instruction::FMul:
case Instruction::FDiv:
case Instruction::FRem:
case Instruction::Shl:
case Instruction::LShr:
case Instruction::AShr:
case Instruction::And:
case Instruction::Or:
case Instruction::Xor: {
// Just widen binops.
auto *BinOp = cast<BinaryOperator>(&I);
setDebugLocFromInst(Builder, BinOp);
for (unsigned Part = 0; Part < UF; ++Part) {
Value *A = getOrCreateVectorValue(BinOp->getOperand(0), Part);
Value *B = getOrCreateVectorValue(BinOp->getOperand(1), Part);
Value *V = Builder.CreateBinOp(BinOp->getOpcode(), A, B);
if (BinaryOperator *VecOp = dyn_cast<BinaryOperator>(V))
VecOp->copyIRFlags(BinOp);
// Use this vector value for all users of the original instruction.
VectorLoopValueMap.setVectorValue(&I, Part, V);
addMetadata(V, BinOp);
}
break;
}
case Instruction::Select: {
// Widen selects.
// If the selector is loop invariant we can create a select
// instruction with a scalar condition. Otherwise, use vector-select.
auto *SE = PSE.getSE();
bool InvariantCond =
SE->isLoopInvariant(PSE.getSCEV(I.getOperand(0)), OrigLoop);
setDebugLocFromInst(Builder, &I);
// The condition can be loop invariant but still defined inside the
// loop. This means that we can't just use the original 'cond' value.
// We have to take the 'vectorized' value and pick the first lane.
// Instcombine will make this a no-op.
auto *ScalarCond = getOrCreateScalarValue(I.getOperand(0), {0, 0});
for (unsigned Part = 0; Part < UF; ++Part) {
Value *Cond = getOrCreateVectorValue(I.getOperand(0), Part);
Value *Op0 = getOrCreateVectorValue(I.getOperand(1), Part);
Value *Op1 = getOrCreateVectorValue(I.getOperand(2), Part);
Value *Sel =
Builder.CreateSelect(InvariantCond ? ScalarCond : Cond, Op0, Op1);
VectorLoopValueMap.setVectorValue(&I, Part, Sel);
addMetadata(Sel, &I);
}
break;
}
case Instruction::ICmp:
case Instruction::FCmp: {
// Widen compares. Generate vector compares.
bool FCmp = (I.getOpcode() == Instruction::FCmp);
auto *Cmp = dyn_cast<CmpInst>(&I);
setDebugLocFromInst(Builder, Cmp);
for (unsigned Part = 0; Part < UF; ++Part) {
Value *A = getOrCreateVectorValue(Cmp->getOperand(0), Part);
Value *B = getOrCreateVectorValue(Cmp->getOperand(1), Part);
Value *C = nullptr;
if (FCmp) {
// Propagate fast math flags.
IRBuilder<>::FastMathFlagGuard FMFG(Builder);
Builder.setFastMathFlags(Cmp->getFastMathFlags());
C = Builder.CreateFCmp(Cmp->getPredicate(), A, B);
} else {
C = Builder.CreateICmp(Cmp->getPredicate(), A, B);
}
VectorLoopValueMap.setVectorValue(&I, Part, C);
addMetadata(C, &I);
}
break;
}
case Instruction::ZExt:
case Instruction::SExt:
case Instruction::FPToUI:
case Instruction::FPToSI:
case Instruction::FPExt:
case Instruction::PtrToInt:
case Instruction::IntToPtr:
case Instruction::SIToFP:
case Instruction::UIToFP:
case Instruction::Trunc:
case Instruction::FPTrunc:
case Instruction::BitCast: {
auto *CI = dyn_cast<CastInst>(&I);
setDebugLocFromInst(Builder, CI);
/// Vectorize casts.
Type *DestTy =
(VF == 1) ? CI->getType() : VectorType::get(CI->getType(), VF);
for (unsigned Part = 0; Part < UF; ++Part) {
Value *A = getOrCreateVectorValue(CI->getOperand(0), Part);
Value *Cast = Builder.CreateCast(CI->getOpcode(), A, DestTy);
VectorLoopValueMap.setVectorValue(&I, Part, Cast);
addMetadata(Cast, &I);
}
break;
}
case Instruction::Call: {
// Ignore dbg intrinsics.
if (isa<DbgInfoIntrinsic>(I))
break;
setDebugLocFromInst(Builder, &I);
Module *M = I.getParent()->getParent()->getParent();
auto *CI = cast<CallInst>(&I);
StringRef FnName = CI->getCalledFunction()->getName();
Function *F = CI->getCalledFunction();
Type *RetTy = ToVectorTy(CI->getType(), VF);
SmallVector<Type *, 4> Tys;
for (Value *ArgOperand : CI->arg_operands())
Tys.push_back(ToVectorTy(ArgOperand->getType(), VF));
Intrinsic::ID ID = getVectorIntrinsicIDForCall(CI, TLI);
// The flag shows whether we use Intrinsic or a usual Call for vectorized
// version of the instruction.
// Is it beneficial to perform intrinsic call compared to lib call?
bool NeedToScalarize;
unsigned CallCost = getVectorCallCost(CI, VF, *TTI, TLI, NeedToScalarize);
bool UseVectorIntrinsic =
ID && getVectorIntrinsicCost(CI, VF, *TTI, TLI) <= CallCost;
assert((UseVectorIntrinsic || !NeedToScalarize) &&
"Instruction should be scalarized elsewhere.");
for (unsigned Part = 0; Part < UF; ++Part) {
SmallVector<Value *, 4> Args;
for (unsigned i = 0, ie = CI->getNumArgOperands(); i != ie; ++i) {
Value *Arg = CI->getArgOperand(i);
// Some intrinsics have a scalar argument - don't replace it with a
// vector.
if (!UseVectorIntrinsic || !hasVectorInstrinsicScalarOpd(ID, i))
Arg = getOrCreateVectorValue(CI->getArgOperand(i), Part);
Args.push_back(Arg);
}
Function *VectorF;
if (UseVectorIntrinsic) {
// Use vector version of the intrinsic.
Type *TysForDecl[] = {CI->getType()};
if (VF > 1)
TysForDecl[0] = VectorType::get(CI->getType()->getScalarType(), VF);
VectorF = Intrinsic::getDeclaration(M, ID, TysForDecl);
} else {
// Use vector version of the library call.
StringRef VFnName = TLI->getVectorizedFunction(FnName, VF);
assert(!VFnName.empty() && "Vector function name is empty.");
VectorF = M->getFunction(VFnName);
if (!VectorF) {
// Generate a declaration
FunctionType *FTy = FunctionType::get(RetTy, Tys, false);
VectorF =
Function::Create(FTy, Function::ExternalLinkage, VFnName, M);
VectorF->copyAttributesFrom(F);
}
}
assert(VectorF && "Can't create vector function.");
SmallVector<OperandBundleDef, 1> OpBundles;
CI->getOperandBundlesAsDefs(OpBundles);
CallInst *V = Builder.CreateCall(VectorF, Args, OpBundles);
if (isa<FPMathOperator>(V))
V->copyFastMathFlags(CI);
VectorLoopValueMap.setVectorValue(&I, Part, V);
addMetadata(V, &I);
}
break;
}
default:
// This instruction is not vectorized by simple widening.
DEBUG(dbgs() << "LV: Found an unhandled instruction: " << I);
llvm_unreachable("Unhandled instruction!");
} // end of switch.
}
void InnerLoopVectorizer::updateAnalysis() {
// Forget the original basic block.
PSE.getSE()->forgetLoop(OrigLoop);
// Update the dominator tree information.
assert(DT->properlyDominates(LoopBypassBlocks.front(), LoopExitBlock) &&
"Entry does not dominate exit.");
DT->addNewBlock(LoopMiddleBlock,
LI->getLoopFor(LoopVectorBody)->getLoopLatch());
DT->addNewBlock(LoopScalarPreHeader, LoopBypassBlocks[0]);
DT->changeImmediateDominator(LoopScalarBody, LoopScalarPreHeader);
DT->changeImmediateDominator(LoopExitBlock, LoopBypassBlocks[0]);
assert(DT->verify(DominatorTree::VerificationLevel::Fast));
}
void LoopVectorizationCostModel::collectLoopScalars(unsigned VF) {
// We should not collect Scalars more than once per VF. Right now, this
// function is called from collectUniformsAndScalars(), which already does
// this check. Collecting Scalars for VF=1 does not make any sense.
assert(VF >= 2 && !Scalars.count(VF) &&
"This function should not be visited twice for the same VF");
SmallSetVector<Instruction *, 8> Worklist;
// These sets are used to seed the analysis with pointers used by memory
// accesses that will remain scalar.
SmallSetVector<Instruction *, 8> ScalarPtrs;
SmallPtrSet<Instruction *, 8> PossibleNonScalarPtrs;
// A helper that returns true if the use of Ptr by MemAccess will be scalar.
// The pointer operands of loads and stores will be scalar as long as the
// memory access is not a gather or scatter operation. The value operand of a
// store will remain scalar if the store is scalarized.
auto isScalarUse = [&](Instruction *MemAccess, Value *Ptr) {
InstWidening WideningDecision = getWideningDecision(MemAccess, VF);
assert(WideningDecision != CM_Unknown &&
"Widening decision should be ready at this moment");
if (auto *Store = dyn_cast<StoreInst>(MemAccess))
if (Ptr == Store->getValueOperand())
return WideningDecision == CM_Scalarize;
assert(Ptr == getLoadStorePointerOperand(MemAccess) &&
"Ptr is neither a value or pointer operand");
return WideningDecision != CM_GatherScatter;
};
// A helper that returns true if the given value is a bitcast or
// getelementptr instruction contained in the loop.
auto isLoopVaryingBitCastOrGEP = [&](Value *V) {
return ((isa<BitCastInst>(V) && V->getType()->isPointerTy()) ||
isa<GetElementPtrInst>(V)) &&
!TheLoop->isLoopInvariant(V);
};
// A helper that evaluates a memory access's use of a pointer. If the use
// will be a scalar use, and the pointer is only used by memory accesses, we
// place the pointer in ScalarPtrs. Otherwise, the pointer is placed in
// PossibleNonScalarPtrs.
auto evaluatePtrUse = [&](Instruction *MemAccess, Value *Ptr) {
// We only care about bitcast and getelementptr instructions contained in
// the loop.
if (!isLoopVaryingBitCastOrGEP(Ptr))
return;
// If the pointer has already been identified as scalar (e.g., if it was
// also identified as uniform), there's nothing to do.
auto *I = cast<Instruction>(Ptr);
if (Worklist.count(I))
return;
// If the use of the pointer will be a scalar use, and all users of the
// pointer are memory accesses, place the pointer in ScalarPtrs. Otherwise,
// place the pointer in PossibleNonScalarPtrs.
if (isScalarUse(MemAccess, Ptr) && llvm::all_of(I->users(), [&](User *U) {
return isa<LoadInst>(U) || isa<StoreInst>(U);
}))
ScalarPtrs.insert(I);
else
PossibleNonScalarPtrs.insert(I);
};
// We seed the scalars analysis with three classes of instructions: (1)
// instructions marked uniform-after-vectorization, (2) bitcast and
// getelementptr instructions used by memory accesses requiring a scalar use,
// and (3) pointer induction variables and their update instructions (we
// currently only scalarize these).
//
// (1) Add to the worklist all instructions that have been identified as
// uniform-after-vectorization.
Worklist.insert(Uniforms[VF].begin(), Uniforms[VF].end());
// (2) Add to the worklist all bitcast and getelementptr instructions used by
// memory accesses requiring a scalar use. The pointer operands of loads and
// stores will be scalar as long as the memory accesses is not a gather or
// scatter operation. The value operand of a store will remain scalar if the
// store is scalarized.
for (auto *BB : TheLoop->blocks())
for (auto &I : *BB) {
if (auto *Load = dyn_cast<LoadInst>(&I)) {
evaluatePtrUse(Load, Load->getPointerOperand());
} else if (auto *Store = dyn_cast<StoreInst>(&I)) {
evaluatePtrUse(Store, Store->getPointerOperand());
evaluatePtrUse(Store, Store->getValueOperand());
}
}
for (auto *I : ScalarPtrs)
if (!PossibleNonScalarPtrs.count(I)) {
DEBUG(dbgs() << "LV: Found scalar instruction: " << *I << "\n");
Worklist.insert(I);
}
// (3) Add to the worklist all pointer induction variables and their update
// instructions.
//
// TODO: Once we are able to vectorize pointer induction variables we should
// no longer insert them into the worklist here.
auto *Latch = TheLoop->getLoopLatch();
for (auto &Induction : *Legal->getInductionVars()) {
auto *Ind = Induction.first;
auto *IndUpdate = cast<Instruction>(Ind->getIncomingValueForBlock(Latch));
if (Induction.second.getKind() != InductionDescriptor::IK_PtrInduction)
continue;
Worklist.insert(Ind);
Worklist.insert(IndUpdate);
DEBUG(dbgs() << "LV: Found scalar instruction: " << *Ind << "\n");
DEBUG(dbgs() << "LV: Found scalar instruction: " << *IndUpdate << "\n");
}
// Insert the forced scalars.
// FIXME: Currently widenPHIInstruction() often creates a dead vector
// induction variable when the PHI user is scalarized.
if (ForcedScalars.count(VF))
for (auto *I : ForcedScalars.find(VF)->second)
Worklist.insert(I);
// Expand the worklist by looking through any bitcasts and getelementptr
// instructions we've already identified as scalar. This is similar to the
// expansion step in collectLoopUniforms(); however, here we're only
// expanding to include additional bitcasts and getelementptr instructions.
unsigned Idx = 0;
while (Idx != Worklist.size()) {
Instruction *Dst = Worklist[Idx++];
if (!isLoopVaryingBitCastOrGEP(Dst->getOperand(0)))
continue;
auto *Src = cast<Instruction>(Dst->getOperand(0));
if (llvm::all_of(Src->users(), [&](User *U) -> bool {
auto *J = cast<Instruction>(U);
return !TheLoop->contains(J) || Worklist.count(J) ||
((isa<LoadInst>(J) || isa<StoreInst>(J)) &&
isScalarUse(J, Src));
})) {
Worklist.insert(Src);
DEBUG(dbgs() << "LV: Found scalar instruction: " << *Src << "\n");
}
}
// An induction variable will remain scalar if all users of the induction
// variable and induction variable update remain scalar.
for (auto &Induction : *Legal->getInductionVars()) {
auto *Ind = Induction.first;
auto *IndUpdate = cast<Instruction>(Ind->getIncomingValueForBlock(Latch));
// We already considered pointer induction variables, so there's no reason
// to look at their users again.
//
// TODO: Once we are able to vectorize pointer induction variables we
// should no longer skip over them here.
if (Induction.second.getKind() == InductionDescriptor::IK_PtrInduction)
continue;
// Determine if all users of the induction variable are scalar after
// vectorization.
auto ScalarInd = llvm::all_of(Ind->users(), [&](User *U) -> bool {
auto *I = cast<Instruction>(U);
return I == IndUpdate || !TheLoop->contains(I) || Worklist.count(I);
});
if (!ScalarInd)
continue;
// Determine if all users of the induction variable update instruction are
// scalar after vectorization.
auto ScalarIndUpdate =
llvm::all_of(IndUpdate->users(), [&](User *U) -> bool {
auto *I = cast<Instruction>(U);
return I == Ind || !TheLoop->contains(I) || Worklist.count(I);
});
if (!ScalarIndUpdate)
continue;
// The induction variable and its update instruction will remain scalar.
Worklist.insert(Ind);
Worklist.insert(IndUpdate);
DEBUG(dbgs() << "LV: Found scalar instruction: " << *Ind << "\n");
DEBUG(dbgs() << "LV: Found scalar instruction: " << *IndUpdate << "\n");
}
Scalars[VF].insert(Worklist.begin(), Worklist.end());
}
bool LoopVectorizationCostModel::isScalarWithPredication(Instruction *I) {
if (!Legal->blockNeedsPredication(I->getParent()))
return false;
switch(I->getOpcode()) {
default:
break;
case Instruction::Load:
case Instruction::Store: {
if (!Legal->isMaskRequired(I))
return false;
auto *Ptr = getLoadStorePointerOperand(I);
auto *Ty = getMemInstValueType(I);
return isa<LoadInst>(I) ?
!(isLegalMaskedLoad(Ty, Ptr) || isLegalMaskedGather(Ty))
: !(isLegalMaskedStore(Ty, Ptr) || isLegalMaskedScatter(Ty));
}
case Instruction::UDiv:
case Instruction::SDiv:
case Instruction::SRem:
case Instruction::URem:
return mayDivideByZero(*I);
}
return false;
}
bool LoopVectorizationCostModel::memoryInstructionCanBeWidened(Instruction *I,
unsigned VF) {
// Get and ensure we have a valid memory instruction.
LoadInst *LI = dyn_cast<LoadInst>(I);
StoreInst *SI = dyn_cast<StoreInst>(I);
assert((LI || SI) && "Invalid memory instruction");
auto *Ptr = getLoadStorePointerOperand(I);
// In order to be widened, the pointer should be consecutive, first of all.
if (!Legal->isConsecutivePtr(Ptr))
return false;
// If the instruction is a store located in a predicated block, it will be
// scalarized.
if (isScalarWithPredication(I))
return false;
// If the instruction's allocated size doesn't equal it's type size, it
// requires padding and will be scalarized.
auto &DL = I->getModule()->getDataLayout();
auto *ScalarTy = LI ? LI->getType() : SI->getValueOperand()->getType();
if (hasIrregularType(ScalarTy, DL, VF))
return false;
return true;
}
void LoopVectorizationCostModel::collectLoopUniforms(unsigned VF) {
// We should not collect Uniforms more than once per VF. Right now,
// this function is called from collectUniformsAndScalars(), which
// already does this check. Collecting Uniforms for VF=1 does not make any
// sense.
assert(VF >= 2 && !Uniforms.count(VF) &&
"This function should not be visited twice for the same VF");
// Visit the list of Uniforms. If we'll not find any uniform value, we'll
// not analyze again. Uniforms.count(VF) will return 1.
Uniforms[VF].clear();
// We now know that the loop is vectorizable!
// Collect instructions inside the loop that will remain uniform after
// vectorization.
// Global values, params and instructions outside of current loop are out of
// scope.
auto isOutOfScope = [&](Value *V) -> bool {
Instruction *I = dyn_cast<Instruction>(V);
return (!I || !TheLoop->contains(I));
};
SetVector<Instruction *> Worklist;
BasicBlock *Latch = TheLoop->getLoopLatch();
// Start with the conditional branch. If the branch condition is an
// instruction contained in the loop that is only used by the branch, it is
// uniform.
auto *Cmp = dyn_cast<Instruction>(Latch->getTerminator()->getOperand(0));
if (Cmp && TheLoop->contains(Cmp) && Cmp->hasOneUse()) {
Worklist.insert(Cmp);
DEBUG(dbgs() << "LV: Found uniform instruction: " << *Cmp << "\n");
}
// Holds consecutive and consecutive-like pointers. Consecutive-like pointers
// are pointers that are treated like consecutive pointers during
// vectorization. The pointer operands of interleaved accesses are an
// example.
SmallSetVector<Instruction *, 8> ConsecutiveLikePtrs;
// Holds pointer operands of instructions that are possibly non-uniform.
SmallPtrSet<Instruction *, 8> PossibleNonUniformPtrs;
auto isUniformDecision = [&](Instruction *I, unsigned VF) {
InstWidening WideningDecision = getWideningDecision(I, VF);
assert(WideningDecision != CM_Unknown &&
"Widening decision should be ready at this moment");
return (WideningDecision == CM_Widen ||
WideningDecision == CM_Widen_Reverse ||
WideningDecision == CM_Interleave);
};
// Iterate over the instructions in the loop, and collect all
// consecutive-like pointer operands in ConsecutiveLikePtrs. If it's possible
// that a consecutive-like pointer operand will be scalarized, we collect it
// in PossibleNonUniformPtrs instead. We use two sets here because a single
// getelementptr instruction can be used by both vectorized and scalarized
// memory instructions. For example, if a loop loads and stores from the same
// location, but the store is conditional, the store will be scalarized, and
// the getelementptr won't remain uniform.
for (auto *BB : TheLoop->blocks())
for (auto &I : *BB) {
// If there's no pointer operand, there's nothing to do.
auto *Ptr = dyn_cast_or_null<Instruction>(getLoadStorePointerOperand(&I));
if (!Ptr)
continue;
// True if all users of Ptr are memory accesses that have Ptr as their
// pointer operand.
auto UsersAreMemAccesses =
llvm::all_of(Ptr->users(), [&](User *U) -> bool {
return getLoadStorePointerOperand(U) == Ptr;
});
// Ensure the memory instruction will not be scalarized or used by
// gather/scatter, making its pointer operand non-uniform. If the pointer
// operand is used by any instruction other than a memory access, we
// conservatively assume the pointer operand may be non-uniform.
if (!UsersAreMemAccesses || !isUniformDecision(&I, VF))
PossibleNonUniformPtrs.insert(Ptr);
// If the memory instruction will be vectorized and its pointer operand
// is consecutive-like, or interleaving - the pointer operand should
// remain uniform.
else
ConsecutiveLikePtrs.insert(Ptr);
}
// Add to the Worklist all consecutive and consecutive-like pointers that
// aren't also identified as possibly non-uniform.
for (auto *V : ConsecutiveLikePtrs)
if (!PossibleNonUniformPtrs.count(V)) {
DEBUG(dbgs() << "LV: Found uniform instruction: " << *V << "\n");
Worklist.insert(V);
}
// Expand Worklist in topological order: whenever a new instruction
// is added , its users should be either already inside Worklist, or
// out of scope. It ensures a uniform instruction will only be used
// by uniform instructions or out of scope instructions.
unsigned idx = 0;
while (idx != Worklist.size()) {
Instruction *I = Worklist[idx++];
for (auto OV : I->operand_values()) {
if (isOutOfScope(OV))
continue;
auto *OI = cast<Instruction>(OV);
if (llvm::all_of(OI->users(), [&](User *U) -> bool {
auto *J = cast<Instruction>(U);
return !TheLoop->contains(J) || Worklist.count(J) ||
(OI == getLoadStorePointerOperand(J) &&
isUniformDecision(J, VF));
})) {
Worklist.insert(OI);
DEBUG(dbgs() << "LV: Found uniform instruction: " << *OI << "\n");
}
}
}
// Returns true if Ptr is the pointer operand of a memory access instruction
// I, and I is known to not require scalarization.
auto isVectorizedMemAccessUse = [&](Instruction *I, Value *Ptr) -> bool {
return getLoadStorePointerOperand(I) == Ptr && isUniformDecision(I, VF);
};
// For an instruction to be added into Worklist above, all its users inside
// the loop should also be in Worklist. However, this condition cannot be
// true for phi nodes that form a cyclic dependence. We must process phi
// nodes separately. An induction variable will remain uniform if all users
// of the induction variable and induction variable update remain uniform.
// The code below handles both pointer and non-pointer induction variables.
for (auto &Induction : *Legal->getInductionVars()) {
auto *Ind = Induction.first;
auto *IndUpdate = cast<Instruction>(Ind->getIncomingValueForBlock(Latch));
// Determine if all users of the induction variable are uniform after
// vectorization.
auto UniformInd = llvm::all_of(Ind->users(), [&](User *U) -> bool {
auto *I = cast<Instruction>(U);
return I == IndUpdate || !TheLoop->contains(I) || Worklist.count(I) ||
isVectorizedMemAccessUse(I, Ind);
});
if (!UniformInd)
continue;
// Determine if all users of the induction variable update instruction are
// uniform after vectorization.
auto UniformIndUpdate =
llvm::all_of(IndUpdate->users(), [&](User *U) -> bool {
auto *I = cast<Instruction>(U);
return I == Ind || !TheLoop->contains(I) || Worklist.count(I) ||
isVectorizedMemAccessUse(I, IndUpdate);
});
if (!UniformIndUpdate)
continue;
// The induction variable and its update instruction will remain uniform.
Worklist.insert(Ind);
Worklist.insert(IndUpdate);
DEBUG(dbgs() << "LV: Found uniform instruction: " << *Ind << "\n");
DEBUG(dbgs() << "LV: Found uniform instruction: " << *IndUpdate << "\n");
}
Uniforms[VF].insert(Worklist.begin(), Worklist.end());
}
void InterleavedAccessInfo::collectConstStrideAccesses(
MapVector<Instruction *, StrideDescriptor> &AccessStrideInfo,
const ValueToValueMap &Strides) {
auto &DL = TheLoop->getHeader()->getModule()->getDataLayout();
// Since it's desired that the load/store instructions be maintained in
// "program order" for the interleaved access analysis, we have to visit the
// blocks in the loop in reverse postorder (i.e., in a topological order).
// Such an ordering will ensure that any load/store that may be executed
// before a second load/store will precede the second load/store in
// AccessStrideInfo.
LoopBlocksDFS DFS(TheLoop);
DFS.perform(LI);
for (BasicBlock *BB : make_range(DFS.beginRPO(), DFS.endRPO()))
for (auto &I : *BB) {
auto *LI = dyn_cast<LoadInst>(&I);
auto *SI = dyn_cast<StoreInst>(&I);
if (!LI && !SI)
continue;
Value *Ptr = getLoadStorePointerOperand(&I);
// We don't check wrapping here because we don't know yet if Ptr will be
// part of a full group or a group with gaps. Checking wrapping for all
// pointers (even those that end up in groups with no gaps) will be overly
// conservative. For full groups, wrapping should be ok since if we would
// wrap around the address space we would do a memory access at nullptr
// even without the transformation. The wrapping checks are therefore
// deferred until after we've formed the interleaved groups.
int64_t Stride = getPtrStride(PSE, Ptr, TheLoop, Strides,
/*Assume=*/true, /*ShouldCheckWrap=*/false);
const SCEV *Scev = replaceSymbolicStrideSCEV(PSE, Strides, Ptr);
PointerType *PtrTy = dyn_cast<PointerType>(Ptr->getType());
uint64_t Size = DL.getTypeAllocSize(PtrTy->getElementType());
// An alignment of 0 means target ABI alignment.
unsigned Align = getMemInstAlignment(&I);
if (!Align)
Align = DL.getABITypeAlignment(PtrTy->getElementType());
AccessStrideInfo[&I] = StrideDescriptor(Stride, Scev, Size, Align);
}
}
// Analyze interleaved accesses and collect them into interleaved load and
// store groups.
//
// When generating code for an interleaved load group, we effectively hoist all
// loads in the group to the location of the first load in program order. When
// generating code for an interleaved store group, we sink all stores to the
// location of the last store. This code motion can change the order of load
// and store instructions and may break dependences.
//
// The code generation strategy mentioned above ensures that we won't violate
// any write-after-read (WAR) dependences.
//
// E.g., for the WAR dependence: a = A[i]; // (1)
// A[i] = b; // (2)
//
// The store group of (2) is always inserted at or below (2), and the load
// group of (1) is always inserted at or above (1). Thus, the instructions will
// never be reordered. All other dependences are checked to ensure the
// correctness of the instruction reordering.
//
// The algorithm visits all memory accesses in the loop in bottom-up program
// order. Program order is established by traversing the blocks in the loop in
// reverse postorder when collecting the accesses.
//
// We visit the memory accesses in bottom-up order because it can simplify the
// construction of store groups in the presence of write-after-write (WAW)
// dependences.
//
// E.g., for the WAW dependence: A[i] = a; // (1)
// A[i] = b; // (2)
// A[i + 1] = c; // (3)
//
// We will first create a store group with (3) and (2). (1) can't be added to
// this group because it and (2) are dependent. However, (1) can be grouped
// with other accesses that may precede it in program order. Note that a
// bottom-up order does not imply that WAW dependences should not be checked.
void InterleavedAccessInfo::analyzeInterleaving() {
DEBUG(dbgs() << "LV: Analyzing interleaved accesses...\n");
const ValueToValueMap &Strides = LAI->getSymbolicStrides();
// Holds all accesses with a constant stride.
MapVector<Instruction *, StrideDescriptor> AccessStrideInfo;
collectConstStrideAccesses(AccessStrideInfo, Strides);
if (AccessStrideInfo.empty())
return;
// Collect the dependences in the loop.
collectDependences();
// Holds all interleaved store groups temporarily.
SmallSetVector<InterleaveGroup *, 4> StoreGroups;
// Holds all interleaved load groups temporarily.
SmallSetVector<InterleaveGroup *, 4> LoadGroups;
// Search in bottom-up program order for pairs of accesses (A and B) that can
// form interleaved load or store groups. In the algorithm below, access A
// precedes access B in program order. We initialize a group for B in the
// outer loop of the algorithm, and then in the inner loop, we attempt to
// insert each A into B's group if:
//
// 1. A and B have the same stride,
// 2. A and B have the same memory object size, and
// 3. A belongs in B's group according to its distance from B.
//
// Special care is taken to ensure group formation will not break any
// dependences.
for (auto BI = AccessStrideInfo.rbegin(), E = AccessStrideInfo.rend();
BI != E; ++BI) {
Instruction *B = BI->first;
StrideDescriptor DesB = BI->second;
// Initialize a group for B if it has an allowable stride. Even if we don't
// create a group for B, we continue with the bottom-up algorithm to ensure
// we don't break any of B's dependences.
InterleaveGroup *Group = nullptr;
if (isStrided(DesB.Stride)) {
Group = getInterleaveGroup(B);
if (!Group) {
DEBUG(dbgs() << "LV: Creating an interleave group with:" << *B << '\n');
Group = createInterleaveGroup(B, DesB.Stride, DesB.Align);
}
if (B->mayWriteToMemory())
StoreGroups.insert(Group);
else
LoadGroups.insert(Group);
}
for (auto AI = std::next(BI); AI != E; ++AI) {
Instruction *A = AI->first;
StrideDescriptor DesA = AI->second;
// Our code motion strategy implies that we can't have dependences
// between accesses in an interleaved group and other accesses located
// between the first and last member of the group. Note that this also
// means that a group can't have more than one member at a given offset.
// The accesses in a group can have dependences with other accesses, but
// we must ensure we don't extend the boundaries of the group such that
// we encompass those dependent accesses.
//
// For example, assume we have the sequence of accesses shown below in a
// stride-2 loop:
//
// (1, 2) is a group | A[i] = a; // (1)
// | A[i-1] = b; // (2) |
// A[i-3] = c; // (3)
// A[i] = d; // (4) | (2, 4) is not a group
//
// Because accesses (2) and (3) are dependent, we can group (2) with (1)
// but not with (4). If we did, the dependent access (3) would be within
// the boundaries of the (2, 4) group.
if (!canReorderMemAccessesForInterleavedGroups(&*AI, &*BI)) {
// If a dependence exists and A is already in a group, we know that A
// must be a store since A precedes B and WAR dependences are allowed.
// Thus, A would be sunk below B. We release A's group to prevent this
// illegal code motion. A will then be free to form another group with
// instructions that precede it.
if (isInterleaved(A)) {
InterleaveGroup *StoreGroup = getInterleaveGroup(A);
StoreGroups.remove(StoreGroup);
releaseGroup(StoreGroup);
}
// If a dependence exists and A is not already in a group (or it was
// and we just released it), B might be hoisted above A (if B is a
// load) or another store might be sunk below A (if B is a store). In
// either case, we can't add additional instructions to B's group. B
// will only form a group with instructions that it precedes.
break;
}
// At this point, we've checked for illegal code motion. If either A or B
// isn't strided, there's nothing left to do.
if (!isStrided(DesA.Stride) || !isStrided(DesB.Stride))
continue;
// Ignore A if it's already in a group or isn't the same kind of memory
// operation as B.
// Note that mayReadFromMemory() isn't mutually exclusive to mayWriteToMemory
// in the case of atomic loads. We shouldn't see those here, canVectorizeMemory()
// should have returned false - except for the case we asked for optimization
// remarks.
if (isInterleaved(A) || (A->mayReadFromMemory() != B->mayReadFromMemory())
|| (A->mayWriteToMemory() != B->mayWriteToMemory()))
continue;
// Check rules 1 and 2. Ignore A if its stride or size is different from
// that of B.
if (DesA.Stride != DesB.Stride || DesA.Size != DesB.Size)
continue;
// Ignore A if the memory object of A and B don't belong to the same
// address space
if (getMemInstAddressSpace(A) != getMemInstAddressSpace(B))
continue;
// Calculate the distance from A to B.
const SCEVConstant *DistToB = dyn_cast<SCEVConstant>(
PSE.getSE()->getMinusSCEV(DesA.Scev, DesB.Scev));
if (!DistToB)
continue;
int64_t DistanceToB = DistToB->getAPInt().getSExtValue();
// Check rule 3. Ignore A if its distance to B is not a multiple of the
// size.
if (DistanceToB % static_cast<int64_t>(DesB.Size))
continue;
// Ignore A if either A or B is in a predicated block. Although we
// currently prevent group formation for predicated accesses, we may be
// able to relax this limitation in the future once we handle more
// complicated blocks.
if (isPredicated(A->getParent()) || isPredicated(B->getParent()))
continue;
// The index of A is the index of B plus A's distance to B in multiples
// of the size.
int IndexA =
Group->getIndex(B) + DistanceToB / static_cast<int64_t>(DesB.Size);
// Try to insert A into B's group.
if (Group->insertMember(A, IndexA, DesA.Align)) {
DEBUG(dbgs() << "LV: Inserted:" << *A << '\n'
<< " into the interleave group with" << *B << '\n');
InterleaveGroupMap[A] = Group;
// Set the first load in program order as the insert position.
if (A->mayReadFromMemory())
Group->setInsertPos(A);
}
} // Iteration over A accesses.
} // Iteration over B accesses.
// Remove interleaved store groups with gaps.
for (InterleaveGroup *Group : StoreGroups)
if (Group->getNumMembers() != Group->getFactor()) {
DEBUG(dbgs() << "LV: Invalidate candidate interleaved store group due "
"to gaps.\n");
releaseGroup(Group);
}
// Remove interleaved groups with gaps (currently only loads) whose memory
// accesses may wrap around. We have to revisit the getPtrStride analysis,
// this time with ShouldCheckWrap=true, since collectConstStrideAccesses does
// not check wrapping (see documentation there).
// FORNOW we use Assume=false;
// TODO: Change to Assume=true but making sure we don't exceed the threshold
// of runtime SCEV assumptions checks (thereby potentially failing to
// vectorize altogether).
// Additional optional optimizations:
// TODO: If we are peeling the loop and we know that the first pointer doesn't
// wrap then we can deduce that all pointers in the group don't wrap.
// This means that we can forcefully peel the loop in order to only have to
// check the first pointer for no-wrap. When we'll change to use Assume=true
// we'll only need at most one runtime check per interleaved group.
for (InterleaveGroup *Group : LoadGroups) {
// Case 1: A full group. Can Skip the checks; For full groups, if the wide
// load would wrap around the address space we would do a memory access at
// nullptr even without the transformation.
if (Group->getNumMembers() == Group->getFactor())
continue;
// Case 2: If first and last members of the group don't wrap this implies
// that all the pointers in the group don't wrap.
// So we check only group member 0 (which is always guaranteed to exist),
// and group member Factor - 1; If the latter doesn't exist we rely on
// peeling (if it is a non-reveresed accsess -- see Case 3).
Value *FirstMemberPtr = getLoadStorePointerOperand(Group->getMember(0));
if (!getPtrStride(PSE, FirstMemberPtr, TheLoop, Strides, /*Assume=*/false,
/*ShouldCheckWrap=*/true)) {
DEBUG(dbgs() << "LV: Invalidate candidate interleaved group due to "
"first group member potentially pointer-wrapping.\n");
releaseGroup(Group);
continue;
}
Instruction *LastMember = Group->getMember(Group->getFactor() - 1);
if (LastMember) {
Value *LastMemberPtr = getLoadStorePointerOperand(LastMember);
if (!getPtrStride(PSE, LastMemberPtr, TheLoop, Strides, /*Assume=*/false,
/*ShouldCheckWrap=*/true)) {
DEBUG(dbgs() << "LV: Invalidate candidate interleaved group due to "
"last group member potentially pointer-wrapping.\n");
releaseGroup(Group);
}
} else {
// Case 3: A non-reversed interleaved load group with gaps: We need
// to execute at least one scalar epilogue iteration. This will ensure
// we don't speculatively access memory out-of-bounds. We only need
// to look for a member at index factor - 1, since every group must have
// a member at index zero.
if (Group->isReverse()) {
DEBUG(dbgs() << "LV: Invalidate candidate interleaved group due to "
"a reverse access with gaps.\n");
releaseGroup(Group);
continue;
}
DEBUG(dbgs() << "LV: Interleaved group requires epilogue iteration.\n");
RequiresScalarEpilogue = true;
}
}
}
Optional<unsigned> LoopVectorizationCostModel::computeMaxVF(bool OptForSize) {
if (Legal->getRuntimePointerChecking()->Need && TTI.hasBranchDivergence()) {
// TODO: It may by useful to do since it's still likely to be dynamically
// uniform if the target can skip.
DEBUG(dbgs() << "LV: Not inserting runtime ptr check for divergent target");
ORE->emit(
createMissedAnalysis("CantVersionLoopWithDivergentTarget")
<< "runtime pointer checks needed. Not enabled for divergent target");
return None;
}
unsigned TC = PSE.getSE()->getSmallConstantTripCount(TheLoop);
if (!OptForSize) // Remaining checks deal with scalar loop when OptForSize.
return computeFeasibleMaxVF(OptForSize, TC);
if (Legal->getRuntimePointerChecking()->Need) {
ORE->emit(createMissedAnalysis("CantVersionLoopWithOptForSize")
<< "runtime pointer checks needed. Enable vectorization of this "
"loop with '#pragma clang loop vectorize(enable)' when "
"compiling with -Os/-Oz");
DEBUG(dbgs()
<< "LV: Aborting. Runtime ptr check is required with -Os/-Oz.\n");
return None;
}
// If we optimize the program for size, avoid creating the tail loop.
DEBUG(dbgs() << "LV: Found trip count: " << TC << '\n');
// If we don't know the precise trip count, don't try to vectorize.
if (TC < 2) {
ORE->emit(
createMissedAnalysis("UnknownLoopCountComplexCFG")
<< "unable to calculate the loop count due to complex control flow");
DEBUG(dbgs() << "LV: Aborting. A tail loop is required with -Os/-Oz.\n");
return None;
}
unsigned MaxVF = computeFeasibleMaxVF(OptForSize, TC);
if (TC % MaxVF != 0) {
// If the trip count that we found modulo the vectorization factor is not
// zero then we require a tail.
// FIXME: look for a smaller MaxVF that does divide TC rather than give up.
// FIXME: return None if loop requiresScalarEpilog(<MaxVF>), or look for a
// smaller MaxVF that does not require a scalar epilog.
ORE->emit(createMissedAnalysis("NoTailLoopWithOptForSize")
<< "cannot optimize for size and vectorize at the "
"same time. Enable vectorization of this loop "
"with '#pragma clang loop vectorize(enable)' "
"when compiling with -Os/-Oz");
DEBUG(dbgs() << "LV: Aborting. A tail loop is required with -Os/-Oz.\n");
return None;
}
return MaxVF;
}
unsigned
LoopVectorizationCostModel::computeFeasibleMaxVF(bool OptForSize,
unsigned ConstTripCount) {
MinBWs = computeMinimumValueSizes(TheLoop->getBlocks(), *DB, &TTI);
unsigned SmallestType, WidestType;
std::tie(SmallestType, WidestType) = getSmallestAndWidestTypes();
unsigned WidestRegister = TTI.getRegisterBitWidth(true);
// Get the maximum safe dependence distance in bits computed by LAA.
// It is computed by MaxVF * sizeOf(type) * 8, where type is taken from
// the memory accesses that is most restrictive (involved in the smallest
// dependence distance).
unsigned MaxSafeRegisterWidth = Legal->getMaxSafeRegisterWidth();
WidestRegister = std::min(WidestRegister, MaxSafeRegisterWidth);
unsigned MaxVectorSize = WidestRegister / WidestType;
DEBUG(dbgs() << "LV: The Smallest and Widest types: " << SmallestType << " / "
<< WidestType << " bits.\n");
DEBUG(dbgs() << "LV: The Widest register safe to use is: " << WidestRegister
<< " bits.\n");
assert(MaxVectorSize <= 64 && "Did not expect to pack so many elements"
" into one vector!");
if (MaxVectorSize == 0) {
DEBUG(dbgs() << "LV: The target has no vector registers.\n");
MaxVectorSize = 1;
return MaxVectorSize;
} else if (ConstTripCount && ConstTripCount < MaxVectorSize &&
isPowerOf2_32(ConstTripCount)) {
// We need to clamp the VF to be the ConstTripCount. There is no point in
// choosing a higher viable VF as done in the loop below.
DEBUG(dbgs() << "LV: Clamping the MaxVF to the constant trip count: "
<< ConstTripCount << "\n");
MaxVectorSize = ConstTripCount;
return MaxVectorSize;
}
unsigned MaxVF = MaxVectorSize;
if (TTI.shouldMaximizeVectorBandwidth(OptForSize) ||
(MaximizeBandwidth && !OptForSize)) {
// Collect all viable vectorization factors larger than the default MaxVF
// (i.e. MaxVectorSize).
SmallVector<unsigned, 8> VFs;
unsigned NewMaxVectorSize = WidestRegister / SmallestType;
for (unsigned VS = MaxVectorSize * 2; VS <= NewMaxVectorSize; VS *= 2)
VFs.push_back(VS);
// For each VF calculate its register usage.
auto RUs = calculateRegisterUsage(VFs);
// Select the largest VF which doesn't require more registers than existing
// ones.
unsigned TargetNumRegisters = TTI.getNumberOfRegisters(true);
for (int i = RUs.size() - 1; i >= 0; --i) {
if (RUs[i].MaxLocalUsers <= TargetNumRegisters) {
MaxVF = VFs[i];
break;
}
}
if (unsigned MinVF = TTI.getMinimumVF(SmallestType)) {
if (MaxVF < MinVF) {
DEBUG(dbgs() << "LV: Overriding calculated MaxVF(" << MaxVF
<< ") with target's minimum: " << MinVF << '\n');
MaxVF = MinVF;
}
}
}
return MaxVF;
}
VectorizationFactor
LoopVectorizationCostModel::selectVectorizationFactor(unsigned MaxVF) {
float Cost = expectedCost(1).first;
const float ScalarCost = Cost;
unsigned Width = 1;
DEBUG(dbgs() << "LV: Scalar loop costs: " << (int)ScalarCost << ".\n");
bool ForceVectorization = Hints->getForce() == LoopVectorizeHints::FK_Enabled;
// Ignore scalar width, because the user explicitly wants vectorization.
if (ForceVectorization && MaxVF > 1) {
Width = 2;
Cost = expectedCost(Width).first / (float)Width;
}
for (unsigned i = 2; i <= MaxVF; i *= 2) {
// Notice that the vector loop needs to be executed less times, so
// we need to divide the cost of the vector loops by the width of
// the vector elements.
VectorizationCostTy C = expectedCost(i);
float VectorCost = C.first / (float)i;
DEBUG(dbgs() << "LV: Vector loop of width " << i
<< " costs: " << (int)VectorCost << ".\n");
if (!C.second && !ForceVectorization) {
DEBUG(
dbgs() << "LV: Not considering vector loop of width " << i
<< " because it will not generate any vector instructions.\n");
continue;
}
if (VectorCost < Cost) {
Cost = VectorCost;
Width = i;
}
}
if (!EnableCondStoresVectorization && NumPredStores) {
ORE->emit(createMissedAnalysis("ConditionalStore")
<< "store that is conditionally executed prevents vectorization");
DEBUG(dbgs() << "LV: No vectorization. There are conditional stores.\n");
Width = 1;
Cost = ScalarCost;
}
DEBUG(if (ForceVectorization && Width > 1 && Cost >= ScalarCost) dbgs()
<< "LV: Vectorization seems to be not beneficial, "
<< "but was forced by a user.\n");
DEBUG(dbgs() << "LV: Selecting VF: " << Width << ".\n");
VectorizationFactor Factor = {Width, (unsigned)(Width * Cost)};
return Factor;
}
std::pair<unsigned, unsigned>
LoopVectorizationCostModel::getSmallestAndWidestTypes() {
unsigned MinWidth = -1U;
unsigned MaxWidth = 8;
const DataLayout &DL = TheFunction->getParent()->getDataLayout();
// For each block.
for (BasicBlock *BB : TheLoop->blocks()) {
// For each instruction in the loop.
for (Instruction &I : *BB) {
Type *T = I.getType();
// Skip ignored values.
if (ValuesToIgnore.count(&I))
continue;
// Only examine Loads, Stores and PHINodes.
if (!isa<LoadInst>(I) && !isa<StoreInst>(I) && !isa<PHINode>(I))
continue;
// Examine PHI nodes that are reduction variables. Update the type to
// account for the recurrence type.
if (auto *PN = dyn_cast<PHINode>(&I)) {
if (!Legal->isReductionVariable(PN))
continue;
RecurrenceDescriptor RdxDesc = (*Legal->getReductionVars())[PN];
T = RdxDesc.getRecurrenceType();
}
// Examine the stored values.
if (auto *ST = dyn_cast<StoreInst>(&I))
T = ST->getValueOperand()->getType();
// Ignore loaded pointer types and stored pointer types that are not
// vectorizable.
//
// FIXME: The check here attempts to predict whether a load or store will
// be vectorized. We only know this for certain after a VF has
// been selected. Here, we assume that if an access can be
// vectorized, it will be. We should also look at extending this
// optimization to non-pointer types.
//
if (T->isPointerTy() && !isConsecutiveLoadOrStore(&I) &&
!isAccessInterleaved(&I) && !isLegalGatherOrScatter(&I))
continue;
MinWidth = std::min(MinWidth,
(unsigned)DL.getTypeSizeInBits(T->getScalarType()));
MaxWidth = std::max(MaxWidth,
(unsigned)DL.getTypeSizeInBits(T->getScalarType()));
}
}
return {MinWidth, MaxWidth};
}
unsigned LoopVectorizationCostModel::selectInterleaveCount(bool OptForSize,
unsigned VF,
unsigned LoopCost) {
// -- The interleave heuristics --
// We interleave the loop in order to expose ILP and reduce the loop overhead.
// There are many micro-architectural considerations that we can't predict
// at this level. For example, frontend pressure (on decode or fetch) due to
// code size, or the number and capabilities of the execution ports.
//
// We use the following heuristics to select the interleave count:
// 1. If the code has reductions, then we interleave to break the cross
// iteration dependency.
// 2. If the loop is really small, then we interleave to reduce the loop
// overhead.
// 3. We don't interleave if we think that we will spill registers to memory
// due to the increased register pressure.
// When we optimize for size, we don't interleave.
if (OptForSize)
return 1;
// We used the distance for the interleave count.
if (Legal->getMaxSafeDepDistBytes() != -1U)
return 1;
// Do not interleave loops with a relatively small trip count.
unsigned TC = PSE.getSE()->getSmallConstantTripCount(TheLoop);
if (TC > 1 && TC < TinyTripCountInterleaveThreshold)
return 1;
unsigned TargetNumRegisters = TTI.getNumberOfRegisters(VF > 1);
DEBUG(dbgs() << "LV: The target has " << TargetNumRegisters
<< " registers\n");
if (VF == 1) {
if (ForceTargetNumScalarRegs.getNumOccurrences() > 0)
TargetNumRegisters = ForceTargetNumScalarRegs;
} else {
if (ForceTargetNumVectorRegs.getNumOccurrences() > 0)
TargetNumRegisters = ForceTargetNumVectorRegs;
}
RegisterUsage R = calculateRegisterUsage({VF})[0];
// We divide by these constants so assume that we have at least one
// instruction that uses at least one register.
R.MaxLocalUsers = std::max(R.MaxLocalUsers, 1U);
// We calculate the interleave count using the following formula.
// Subtract the number of loop invariants from the number of available
// registers. These registers are used by all of the interleaved instances.
// Next, divide the remaining registers by the number of registers that is
// required by the loop, in order to estimate how many parallel instances
// fit without causing spills. All of this is rounded down if necessary to be
// a power of two. We want power of two interleave count to simplify any
// addressing operations or alignment considerations.
unsigned IC = PowerOf2Floor((TargetNumRegisters - R.LoopInvariantRegs) /
R.MaxLocalUsers);
// Don't count the induction variable as interleaved.
if (EnableIndVarRegisterHeur)
IC = PowerOf2Floor((TargetNumRegisters - R.LoopInvariantRegs - 1) /
std::max(1U, (R.MaxLocalUsers - 1)));
// Clamp the interleave ranges to reasonable counts.
unsigned MaxInterleaveCount = TTI.getMaxInterleaveFactor(VF);
// Check if the user has overridden the max.
if (VF == 1) {
if (ForceTargetMaxScalarInterleaveFactor.getNumOccurrences() > 0)
MaxInterleaveCount = ForceTargetMaxScalarInterleaveFactor;
} else {
if (ForceTargetMaxVectorInterleaveFactor.getNumOccurrences() > 0)
MaxInterleaveCount = ForceTargetMaxVectorInterleaveFactor;
}
// If we did not calculate the cost for VF (because the user selected the VF)
// then we calculate the cost of VF here.
if (LoopCost == 0)
LoopCost = expectedCost(VF).first;
// Clamp the calculated IC to be between the 1 and the max interleave count
// that the target allows.
if (IC > MaxInterleaveCount)
IC = MaxInterleaveCount;
else if (IC < 1)
IC = 1;
// Interleave if we vectorized this loop and there is a reduction that could
// benefit from interleaving.
if (VF > 1 && !Legal->getReductionVars()->empty()) {
DEBUG(dbgs() << "LV: Interleaving because of reductions.\n");
return IC;
}
// Note that if we've already vectorized the loop we will have done the
// runtime check and so interleaving won't require further checks.
bool InterleavingRequiresRuntimePointerCheck =
(VF == 1 && Legal->getRuntimePointerChecking()->Need);
// We want to interleave small loops in order to reduce the loop overhead and
// potentially expose ILP opportunities.
DEBUG(dbgs() << "LV: Loop cost is " << LoopCost << '\n');
if (!InterleavingRequiresRuntimePointerCheck && LoopCost < SmallLoopCost) {
// We assume that the cost overhead is 1 and we use the cost model
// to estimate the cost of the loop and interleave until the cost of the
// loop overhead is about 5% of the cost of the loop.
unsigned SmallIC =
std::min(IC, (unsigned)PowerOf2Floor(SmallLoopCost / LoopCost));
// Interleave until store/load ports (estimated by max interleave count) are
// saturated.
unsigned NumStores = Legal->getNumStores();
unsigned NumLoads = Legal->getNumLoads();
unsigned StoresIC = IC / (NumStores ? NumStores : 1);
unsigned LoadsIC = IC / (NumLoads ? NumLoads : 1);
// If we have a scalar reduction (vector reductions are already dealt with
// by this point), we can increase the critical path length if the loop
// we're interleaving is inside another loop. Limit, by default to 2, so the
// critical path only gets increased by one reduction operation.
if (!Legal->getReductionVars()->empty() && TheLoop->getLoopDepth() > 1) {
unsigned F = static_cast<unsigned>(MaxNestedScalarReductionIC);
SmallIC = std::min(SmallIC, F);
StoresIC = std::min(StoresIC, F);
LoadsIC = std::min(LoadsIC, F);
}
if (EnableLoadStoreRuntimeInterleave &&
std::max(StoresIC, LoadsIC) > SmallIC) {
DEBUG(dbgs() << "LV: Interleaving to saturate store or load ports.\n");
return std::max(StoresIC, LoadsIC);
}
DEBUG(dbgs() << "LV: Interleaving to reduce branch cost.\n");
return SmallIC;
}
// Interleave if this is a large loop (small loops are already dealt with by
// this point) that could benefit from interleaving.
bool HasReductions = !Legal->getReductionVars()->empty();
if (TTI.enableAggressiveInterleaving(HasReductions)) {
DEBUG(dbgs() << "LV: Interleaving to expose ILP.\n");
return IC;
}
DEBUG(dbgs() << "LV: Not Interleaving.\n");
return 1;
}
SmallVector<LoopVectorizationCostModel::RegisterUsage, 8>
LoopVectorizationCostModel::calculateRegisterUsage(ArrayRef<unsigned> VFs) {
// This function calculates the register usage by measuring the highest number
// of values that are alive at a single location. Obviously, this is a very
// rough estimation. We scan the loop in a topological order in order and
// assign a number to each instruction. We use RPO to ensure that defs are
// met before their users. We assume that each instruction that has in-loop
// users starts an interval. We record every time that an in-loop value is
// used, so we have a list of the first and last occurrences of each
// instruction. Next, we transpose this data structure into a multi map that
// holds the list of intervals that *end* at a specific location. This multi
// map allows us to perform a linear search. We scan the instructions linearly
// and record each time that a new interval starts, by placing it in a set.
// If we find this value in the multi-map then we remove it from the set.
// The max register usage is the maximum size of the set.
// We also search for instructions that are defined outside the loop, but are
// used inside the loop. We need this number separately from the max-interval
// usage number because when we unroll, loop-invariant values do not take
// more register.
LoopBlocksDFS DFS(TheLoop);
DFS.perform(LI);
RegisterUsage RU;
// Each 'key' in the map opens a new interval. The values
// of the map are the index of the 'last seen' usage of the
// instruction that is the key.
using IntervalMap = DenseMap<Instruction *, unsigned>;
// Maps instruction to its index.
DenseMap<unsigned, Instruction *> IdxToInstr;
// Marks the end of each interval.
IntervalMap EndPoint;
// Saves the list of instruction indices that are used in the loop.
SmallSet<Instruction *, 8> Ends;
// Saves the list of values that are used in the loop but are
// defined outside the loop, such as arguments and constants.
SmallPtrSet<Value *, 8> LoopInvariants;
unsigned Index = 0;
for (BasicBlock *BB : make_range(DFS.beginRPO(), DFS.endRPO())) {
for (Instruction &I : *BB) {
IdxToInstr[Index++] = &I;
// Save the end location of each USE.
for (Value *U : I.operands()) {
auto *Instr = dyn_cast<Instruction>(U);
// Ignore non-instruction values such as arguments, constants, etc.
if (!Instr)
continue;
// If this instruction is outside the loop then record it and continue.
if (!TheLoop->contains(Instr)) {
LoopInvariants.insert(Instr);
continue;
}
// Overwrite previous end points.
EndPoint[Instr] = Index;
Ends.insert(Instr);
}
}
}
// Saves the list of intervals that end with the index in 'key'.
using InstrList = SmallVector<Instruction *, 2>;
DenseMap<unsigned, InstrList> TransposeEnds;
// Transpose the EndPoints to a list of values that end at each index.
for (auto &Interval : EndPoint)
TransposeEnds[Interval.second].push_back(Interval.first);
SmallSet<Instruction *, 8> OpenIntervals;
// Get the size of the widest register.
unsigned MaxSafeDepDist = -1U;
if (Legal->getMaxSafeDepDistBytes() != -1U)
MaxSafeDepDist = Legal->getMaxSafeDepDistBytes() * 8;
unsigned WidestRegister =
std::min(TTI.getRegisterBitWidth(true), MaxSafeDepDist);
const DataLayout &DL = TheFunction->getParent()->getDataLayout();
SmallVector<RegisterUsage, 8> RUs(VFs.size());
SmallVector<unsigned, 8> MaxUsages(VFs.size(), 0);
DEBUG(dbgs() << "LV(REG): Calculating max register usage:\n");
// A lambda that gets the register usage for the given type and VF.
auto GetRegUsage = [&DL, WidestRegister](Type *Ty, unsigned VF) {
if (Ty->isTokenTy())
return 0U;
unsigned TypeSize = DL.getTypeSizeInBits(Ty->getScalarType());
return std::max<unsigned>(1, VF * TypeSize / WidestRegister);
};
for (unsigned int i = 0; i < Index; ++i) {
Instruction *I = IdxToInstr[i];
// Remove all of the instructions that end at this location.
InstrList &List = TransposeEnds[i];
for (Instruction *ToRemove : List)
OpenIntervals.erase(ToRemove);
// Ignore instructions that are never used within the loop.
if (!Ends.count(I))
continue;
// Skip ignored values.
if (ValuesToIgnore.count(I))
continue;
// For each VF find the maximum usage of registers.
for (unsigned j = 0, e = VFs.size(); j < e; ++j) {
if (VFs[j] == 1) {
MaxUsages[j] = std::max(MaxUsages[j], OpenIntervals.size());
continue;
}
collectUniformsAndScalars(VFs[j]);
// Count the number of live intervals.
unsigned RegUsage = 0;
for (auto Inst : OpenIntervals) {
// Skip ignored values for VF > 1.
if (VecValuesToIgnore.count(Inst) ||
isScalarAfterVectorization(Inst, VFs[j]))
continue;
RegUsage += GetRegUsage(Inst->getType(), VFs[j]);
}
MaxUsages[j] = std::max(MaxUsages[j], RegUsage);
}
DEBUG(dbgs() << "LV(REG): At #" << i << " Interval # "
<< OpenIntervals.size() << '\n');
// Add the current instruction to the list of open intervals.
OpenIntervals.insert(I);
}
for (unsigned i = 0, e = VFs.size(); i < e; ++i) {
unsigned Invariant = 0;
if (VFs[i] == 1)
Invariant = LoopInvariants.size();
else {
for (auto Inst : LoopInvariants)
Invariant += GetRegUsage(Inst->getType(), VFs[i]);
}
DEBUG(dbgs() << "LV(REG): VF = " << VFs[i] << '\n');
DEBUG(dbgs() << "LV(REG): Found max usage: " << MaxUsages[i] << '\n');
DEBUG(dbgs() << "LV(REG): Found invariant usage: " << Invariant << '\n');
RU.LoopInvariantRegs = Invariant;
RU.MaxLocalUsers = MaxUsages[i];
RUs[i] = RU;
}
return RUs;
}
bool LoopVectorizationCostModel::useEmulatedMaskMemRefHack(Instruction *I){
// TODO: Cost model for emulated masked load/store is completely
// broken. This hack guides the cost model to use an artificially
// high enough value to practically disable vectorization with such
// operations, except where previously deployed legality hack allowed
// using very low cost values. This is to avoid regressions coming simply
// from moving "masked load/store" check from legality to cost model.
// Masked Load/Gather emulation was previously never allowed.
// Limited number of Masked Store/Scatter emulation was allowed.
assert(isScalarWithPredication(I) &&
"Expecting a scalar emulated instruction");
return isa<LoadInst>(I) ||
(isa<StoreInst>(I) &&
NumPredStores > NumberOfStoresToPredicate);
}
void LoopVectorizationCostModel::collectInstsToScalarize(unsigned VF) {
// If we aren't vectorizing the loop, or if we've already collected the
// instructions to scalarize, there's nothing to do. Collection may already
// have occurred if we have a user-selected VF and are now computing the
// expected cost for interleaving.
if (VF < 2 || InstsToScalarize.count(VF))
return;
// Initialize a mapping for VF in InstsToScalalarize. If we find that it's
// not profitable to scalarize any instructions, the presence of VF in the
// map will indicate that we've analyzed it already.
ScalarCostsTy &ScalarCostsVF = InstsToScalarize[VF];
// Find all the instructions that are scalar with predication in the loop and
// determine if it would be better to not if-convert the blocks they are in.
// If so, we also record the instructions to scalarize.
for (BasicBlock *BB : TheLoop->blocks()) {
if (!Legal->blockNeedsPredication(BB))
continue;
for (Instruction &I : *BB)
if (isScalarWithPredication(&I)) {
ScalarCostsTy ScalarCosts;
// Do not apply discount logic if hacked cost is needed
// for emulated masked memrefs.
if (!useEmulatedMaskMemRefHack(&I) &&
computePredInstDiscount(&I, ScalarCosts, VF) >= 0)
ScalarCostsVF.insert(ScalarCosts.begin(), ScalarCosts.end());
// Remember that BB will remain after vectorization.
PredicatedBBsAfterVectorization.insert(BB);
}
}
}
int LoopVectorizationCostModel::computePredInstDiscount(
Instruction *PredInst, DenseMap<Instruction *, unsigned> &ScalarCosts,
unsigned VF) {
assert(!isUniformAfterVectorization(PredInst, VF) &&
"Instruction marked uniform-after-vectorization will be predicated");
// Initialize the discount to zero, meaning that the scalar version and the
// vector version cost the same.
int Discount = 0;
// Holds instructions to analyze. The instructions we visit are mapped in
// ScalarCosts. Those instructions are the ones that would be scalarized if
// we find that the scalar version costs less.
SmallVector<Instruction *, 8> Worklist;
// Returns true if the given instruction can be scalarized.
auto canBeScalarized = [&](Instruction *I) -> bool {
// We only attempt to scalarize instructions forming a single-use chain
// from the original predicated block that would otherwise be vectorized.
// Although not strictly necessary, we give up on instructions we know will
// already be scalar to avoid traversing chains that are unlikely to be
// beneficial.
if (!I->hasOneUse() || PredInst->getParent() != I->getParent() ||
isScalarAfterVectorization(I, VF))
return false;
// If the instruction is scalar with predication, it will be analyzed
// separately. We ignore it within the context of PredInst.
if (isScalarWithPredication(I))
return false;
// If any of the instruction's operands are uniform after vectorization,
// the instruction cannot be scalarized. This prevents, for example, a
// masked load from being scalarized.
//
// We assume we will only emit a value for lane zero of an instruction
// marked uniform after vectorization, rather than VF identical values.
// Thus, if we scalarize an instruction that uses a uniform, we would
// create uses of values corresponding to the lanes we aren't emitting code
// for. This behavior can be changed by allowing getScalarValue to clone
// the lane zero values for uniforms rather than asserting.
for (Use &U : I->operands())
if (auto *J = dyn_cast<Instruction>(U.get()))
if (isUniformAfterVectorization(J, VF))
return false;
// Otherwise, we can scalarize the instruction.
return true;
};
// Returns true if an operand that cannot be scalarized must be extracted
// from a vector. We will account for this scalarization overhead below. Note
// that the non-void predicated instructions are placed in their own blocks,
// and their return values are inserted into vectors. Thus, an extract would
// still be required.
auto needsExtract = [&](Instruction *I) -> bool {
return TheLoop->contains(I) && !isScalarAfterVectorization(I, VF);
};
// Compute the expected cost discount from scalarizing the entire expression
// feeding the predicated instruction. We currently only consider expressions
// that are single-use instruction chains.
Worklist.push_back(PredInst);
while (!Worklist.empty()) {
Instruction *I = Worklist.pop_back_val();
// If we've already analyzed the instruction, there's nothing to do.
if (ScalarCosts.count(I))
continue;
// Compute the cost of the vector instruction. Note that this cost already
// includes the scalarization overhead of the predicated instruction.
unsigned VectorCost = getInstructionCost(I, VF).first;
// Compute the cost of the scalarized instruction. This cost is the cost of
// the instruction as if it wasn't if-converted and instead remained in the
// predicated block. We will scale this cost by block probability after
// computing the scalarization overhead.
unsigned ScalarCost = VF * getInstructionCost(I, 1).first;
// Compute the scalarization overhead of needed insertelement instructions
// and phi nodes.
if (isScalarWithPredication(I) && !I->getType()->isVoidTy()) {
ScalarCost += TTI.getScalarizationOverhead(ToVectorTy(I->getType(), VF),
true, false);
ScalarCost += VF * TTI.getCFInstrCost(Instruction::PHI);
}
// Compute the scalarization overhead of needed extractelement
// instructions. For each of the instruction's operands, if the operand can
// be scalarized, add it to the worklist; otherwise, account for the
// overhead.
for (Use &U : I->operands())
if (auto *J = dyn_cast<Instruction>(U.get())) {
assert(VectorType::isValidElementType(J->getType()) &&
"Instruction has non-scalar type");
if (canBeScalarized(J))
Worklist.push_back(J);
else if (needsExtract(J))
ScalarCost += TTI.getScalarizationOverhead(
ToVectorTy(J->getType(),VF), false, true);
}
// Scale the total scalar cost by block probability.
ScalarCost /= getReciprocalPredBlockProb();
// Compute the discount. A non-negative discount means the vector version
// of the instruction costs more, and scalarizing would be beneficial.
Discount += VectorCost - ScalarCost;
ScalarCosts[I] = ScalarCost;
}
return Discount;
}
LoopVectorizationCostModel::VectorizationCostTy
LoopVectorizationCostModel::expectedCost(unsigned VF) {
VectorizationCostTy Cost;
// For each block.
for (BasicBlock *BB : TheLoop->blocks()) {
VectorizationCostTy BlockCost;
// For each instruction in the old loop.
for (Instruction &I : BB->instructionsWithoutDebug()) {
// Skip ignored values.
if (ValuesToIgnore.count(&I) ||
(VF > 1 && VecValuesToIgnore.count(&I)))
continue;
VectorizationCostTy C = getInstructionCost(&I, VF);
// Check if we should override the cost.
if (ForceTargetInstructionCost.getNumOccurrences() > 0)
C.first = ForceTargetInstructionCost;
BlockCost.first += C.first;
BlockCost.second |= C.second;
DEBUG(dbgs() << "LV: Found an estimated cost of " << C.first << " for VF "
<< VF << " For instruction: " << I << '\n');
}
// If we are vectorizing a predicated block, it will have been
// if-converted. This means that the block's instructions (aside from
// stores and instructions that may divide by zero) will now be
// unconditionally executed. For the scalar case, we may not always execute
// the predicated block. Thus, scale the block's cost by the probability of
// executing it.
if (VF == 1 && Legal->blockNeedsPredication(BB))
BlockCost.first /= getReciprocalPredBlockProb();
Cost.first += BlockCost.first;
Cost.second |= BlockCost.second;
}
return Cost;
}
/// \brief Gets Address Access SCEV after verifying that the access pattern
/// is loop invariant except the induction variable dependence.
///
/// This SCEV can be sent to the Target in order to estimate the address
/// calculation cost.
static const SCEV *getAddressAccessSCEV(
Value *Ptr,
LoopVectorizationLegality *Legal,
PredicatedScalarEvolution &PSE,
const Loop *TheLoop) {
auto *Gep = dyn_cast<GetElementPtrInst>(Ptr);
if (!Gep)
return nullptr;
// We are looking for a gep with all loop invariant indices except for one
// which should be an induction variable.
auto SE = PSE.getSE();
unsigned NumOperands = Gep->getNumOperands();
for (unsigned i = 1; i < NumOperands; ++i) {
Value *Opd = Gep->getOperand(i);
if (!SE->isLoopInvariant(SE->getSCEV(Opd), TheLoop) &&
!Legal->isInductionVariable(Opd))
return nullptr;
}
// Now we know we have a GEP ptr, %inv, %ind, %inv. return the Ptr SCEV.
return PSE.getSCEV(Ptr);
}
static bool isStrideMul(Instruction *I, LoopVectorizationLegality *Legal) {
return Legal->hasStride(I->getOperand(0)) ||
Legal->hasStride(I->getOperand(1));
}
unsigned LoopVectorizationCostModel::getMemInstScalarizationCost(Instruction *I,
unsigned VF) {
Type *ValTy = getMemInstValueType(I);
auto SE = PSE.getSE();
unsigned Alignment = getMemInstAlignment(I);
unsigned AS = getMemInstAddressSpace(I);
Value *Ptr = getLoadStorePointerOperand(I);
Type *PtrTy = ToVectorTy(Ptr->getType(), VF);
// Figure out whether the access is strided and get the stride value
// if it's known in compile time
const SCEV *PtrSCEV = getAddressAccessSCEV(Ptr, Legal, PSE, TheLoop);
// Get the cost of the scalar memory instruction and address computation.
unsigned Cost = VF * TTI.getAddressComputationCost(PtrTy, SE, PtrSCEV);
Cost += VF *
TTI.getMemoryOpCost(I->getOpcode(), ValTy->getScalarType(), Alignment,
AS, I);
// Get the overhead of the extractelement and insertelement instructions
// we might create due to scalarization.
Cost += getScalarizationOverhead(I, VF, TTI);
// If we have a predicated store, it may not be executed for each vector
// lane. Scale the cost by the probability of executing the predicated
// block.
if (isScalarWithPredication(I)) {
Cost /= getReciprocalPredBlockProb();
if (useEmulatedMaskMemRefHack(I))
// Artificially setting to a high enough value to practically disable
// vectorization with such operations.
Cost = 3000000;
}
return Cost;
}
unsigned LoopVectorizationCostModel::getConsecutiveMemOpCost(Instruction *I,
unsigned VF) {
Type *ValTy = getMemInstValueType(I);
Type *VectorTy = ToVectorTy(ValTy, VF);
unsigned Alignment = getMemInstAlignment(I);
Value *Ptr = getLoadStorePointerOperand(I);
unsigned AS = getMemInstAddressSpace(I);
int ConsecutiveStride = Legal->isConsecutivePtr(Ptr);
assert((ConsecutiveStride == 1 || ConsecutiveStride == -1) &&
"Stride should be 1 or -1 for consecutive memory access");
unsigned Cost = 0;
if (Legal->isMaskRequired(I))
Cost += TTI.getMaskedMemoryOpCost(I->getOpcode(), VectorTy, Alignment, AS);
else
Cost += TTI.getMemoryOpCost(I->getOpcode(), VectorTy, Alignment, AS, I);
bool Reverse = ConsecutiveStride < 0;
if (Reverse)
Cost += TTI.getShuffleCost(TargetTransformInfo::SK_Reverse, VectorTy, 0);
return Cost;
}
unsigned LoopVectorizationCostModel::getUniformMemOpCost(Instruction *I,
unsigned VF) {
LoadInst *LI = cast<LoadInst>(I);
Type *ValTy = LI->getType();
Type *VectorTy = ToVectorTy(ValTy, VF);
unsigned Alignment = LI->getAlignment();
unsigned AS = LI->getPointerAddressSpace();
return TTI.getAddressComputationCost(ValTy) +
TTI.getMemoryOpCost(Instruction::Load, ValTy, Alignment, AS) +
TTI.getShuffleCost(TargetTransformInfo::SK_Broadcast, VectorTy);
}
unsigned LoopVectorizationCostModel::getGatherScatterCost(Instruction *I,
unsigned VF) {
Type *ValTy = getMemInstValueType(I);
Type *VectorTy = ToVectorTy(ValTy, VF);
unsigned Alignment = getMemInstAlignment(I);
Value *Ptr = getLoadStorePointerOperand(I);
return TTI.getAddressComputationCost(VectorTy) +
TTI.getGatherScatterOpCost(I->getOpcode(), VectorTy, Ptr,
Legal->isMaskRequired(I), Alignment);
}
unsigned LoopVectorizationCostModel::getInterleaveGroupCost(Instruction *I,
unsigned VF) {
Type *ValTy = getMemInstValueType(I);
Type *VectorTy = ToVectorTy(ValTy, VF);
unsigned AS = getMemInstAddressSpace(I);
auto Group = getInterleavedAccessGroup(I);
assert(Group && "Fail to get an interleaved access group.");
unsigned InterleaveFactor = Group->getFactor();
Type *WideVecTy = VectorType::get(ValTy, VF * InterleaveFactor);
// Holds the indices of existing members in an interleaved load group.
// An interleaved store group doesn't need this as it doesn't allow gaps.
SmallVector<unsigned, 4> Indices;
if (isa<LoadInst>(I)) {
for (unsigned i = 0; i < InterleaveFactor; i++)
if (Group->getMember(i))
Indices.push_back(i);
}
// Calculate the cost of the whole interleaved group.
unsigned Cost = TTI.getInterleavedMemoryOpCost(I->getOpcode(), WideVecTy,
Group->getFactor(), Indices,
Group->getAlignment(), AS);
if (Group->isReverse())
Cost += Group->getNumMembers() *
TTI.getShuffleCost(TargetTransformInfo::SK_Reverse, VectorTy, 0);
return Cost;
}
unsigned LoopVectorizationCostModel::getMemoryInstructionCost(Instruction *I,
unsigned VF) {
// Calculate scalar cost only. Vectorization cost should be ready at this
// moment.
if (VF == 1) {
Type *ValTy = getMemInstValueType(I);
unsigned Alignment = getMemInstAlignment(I);
unsigned AS = getMemInstAddressSpace(I);
return TTI.getAddressComputationCost(ValTy) +
TTI.getMemoryOpCost(I->getOpcode(), ValTy, Alignment, AS, I);
}
return getWideningCost(I, VF);
}
LoopVectorizationCostModel::VectorizationCostTy
LoopVectorizationCostModel::getInstructionCost(Instruction *I, unsigned VF) {
// If we know that this instruction will remain uniform, check the cost of
// the scalar version.
if (isUniformAfterVectorization(I, VF))
VF = 1;
if (VF > 1 && isProfitableToScalarize(I, VF))
return VectorizationCostTy(InstsToScalarize[VF][I], false);
// Forced scalars do not have any scalarization overhead.
if (VF > 1 && ForcedScalars.count(VF) &&
ForcedScalars.find(VF)->second.count(I))
return VectorizationCostTy((getInstructionCost(I, 1).first * VF), false);
Type *VectorTy;
unsigned C = getInstructionCost(I, VF, VectorTy);
bool TypeNotScalarized =
VF > 1 && VectorTy->isVectorTy() && TTI.getNumberOfParts(VectorTy) < VF;
return VectorizationCostTy(C, TypeNotScalarized);
}
void LoopVectorizationCostModel::setCostBasedWideningDecision(unsigned VF) {
if (VF == 1)
return;
NumPredStores = 0;
for (BasicBlock *BB : TheLoop->blocks()) {
// For each instruction in the old loop.
for (Instruction &I : *BB) {
Value *Ptr = getLoadStorePointerOperand(&I);
if (!Ptr)
continue;
if (isa<StoreInst>(&I) && isScalarWithPredication(&I))
NumPredStores++;
if (isa<LoadInst>(&I) && Legal->isUniform(Ptr)) {
// Scalar load + broadcast
unsigned Cost = getUniformMemOpCost(&I, VF);
setWideningDecision(&I, VF, CM_Scalarize, Cost);
continue;
}
// We assume that widening is the best solution when possible.
if (memoryInstructionCanBeWidened(&I, VF)) {
unsigned Cost = getConsecutiveMemOpCost(&I, VF);
int ConsecutiveStride =
Legal->isConsecutivePtr(getLoadStorePointerOperand(&I));
assert((ConsecutiveStride == 1 || ConsecutiveStride == -1) &&
"Expected consecutive stride.");
InstWidening Decision =
ConsecutiveStride == 1 ? CM_Widen : CM_Widen_Reverse;
setWideningDecision(&I, VF, Decision, Cost);
continue;
}
// Choose between Interleaving, Gather/Scatter or Scalarization.
unsigned InterleaveCost = std::numeric_limits<unsigned>::max();
unsigned NumAccesses = 1;
if (isAccessInterleaved(&I)) {
auto Group = getInterleavedAccessGroup(&I);
assert(Group && "Fail to get an interleaved access group.");
// Make one decision for the whole group.
if (getWideningDecision(&I, VF) != CM_Unknown)
continue;
NumAccesses = Group->getNumMembers();
InterleaveCost = getInterleaveGroupCost(&I, VF);
}
unsigned GatherScatterCost =
isLegalGatherOrScatter(&I)
? getGatherScatterCost(&I, VF) * NumAccesses
: std::numeric_limits<unsigned>::max();
unsigned ScalarizationCost =
getMemInstScalarizationCost(&I, VF) * NumAccesses;
// Choose better solution for the current VF,
// write down this decision and use it during vectorization.
unsigned Cost;
InstWidening Decision;
if (InterleaveCost <= GatherScatterCost &&
InterleaveCost < ScalarizationCost) {
Decision = CM_Interleave;
Cost = InterleaveCost;
} else if (GatherScatterCost < ScalarizationCost) {
Decision = CM_GatherScatter;
Cost = GatherScatterCost;
} else {
Decision = CM_Scalarize;
Cost = ScalarizationCost;
}
// If the instructions belongs to an interleave group, the whole group
// receives the same decision. The whole group receives the cost, but
// the cost will actually be assigned to one instruction.
if (auto Group = getInterleavedAccessGroup(&I))
setWideningDecision(Group, VF, Decision, Cost);
else
setWideningDecision(&I, VF, Decision, Cost);
}
}
// Make sure that any load of address and any other address computation
// remains scalar unless there is gather/scatter support. This avoids
// inevitable extracts into address registers, and also has the benefit of
// activating LSR more, since that pass can't optimize vectorized
// addresses.
if (TTI.prefersVectorizedAddressing())
return;
// Start with all scalar pointer uses.
SmallPtrSet<Instruction *, 8> AddrDefs;
for (BasicBlock *BB : TheLoop->blocks())
for (Instruction &I : *BB) {
Instruction *PtrDef =
dyn_cast_or_null<Instruction>(getLoadStorePointerOperand(&I));
if (PtrDef && TheLoop->contains(PtrDef) &&
getWideningDecision(&I, VF) != CM_GatherScatter)
AddrDefs.insert(PtrDef);
}
// Add all instructions used to generate the addresses.
SmallVector<Instruction *, 4> Worklist;
for (auto *I : AddrDefs)
Worklist.push_back(I);
while (!Worklist.empty()) {
Instruction *I = Worklist.pop_back_val();
for (auto &Op : I->operands())
if (auto *InstOp = dyn_cast<Instruction>(Op))
if ((InstOp->getParent() == I->getParent()) && !isa<PHINode>(InstOp) &&
AddrDefs.insert(InstOp).second)
Worklist.push_back(InstOp);
}
for (auto *I : AddrDefs) {
if (isa<LoadInst>(I)) {
// Setting the desired widening decision should ideally be handled in
// by cost functions, but since this involves the task of finding out
// if the loaded register is involved in an address computation, it is
// instead changed here when we know this is the case.
InstWidening Decision = getWideningDecision(I, VF);
if (Decision == CM_Widen || Decision == CM_Widen_Reverse)
// Scalarize a widened load of address.
setWideningDecision(I, VF, CM_Scalarize,
(VF * getMemoryInstructionCost(I, 1)));
else if (auto Group = getInterleavedAccessGroup(I)) {
// Scalarize an interleave group of address loads.
for (unsigned I = 0; I < Group->getFactor(); ++I) {
if (Instruction *Member = Group->getMember(I))
setWideningDecision(Member, VF, CM_Scalarize,
(VF * getMemoryInstructionCost(Member, 1)));
}
}
} else
// Make sure I gets scalarized and a cost estimate without
// scalarization overhead.
ForcedScalars[VF].insert(I);
}
}
unsigned LoopVectorizationCostModel::getInstructionCost(Instruction *I,
unsigned VF,
Type *&VectorTy) {
Type *RetTy = I->getType();
if (canTruncateToMinimalBitwidth(I, VF))
RetTy = IntegerType::get(RetTy->getContext(), MinBWs[I]);
VectorTy = isScalarAfterVectorization(I, VF) ? RetTy : ToVectorTy(RetTy, VF);
auto SE = PSE.getSE();
// TODO: We need to estimate the cost of intrinsic calls.
switch (I->getOpcode()) {
case Instruction::GetElementPtr:
// We mark this instruction as zero-cost because the cost of GEPs in
// vectorized code depends on whether the corresponding memory instruction
// is scalarized or not. Therefore, we handle GEPs with the memory
// instruction cost.
return 0;
case Instruction::Br: {
// In cases of scalarized and predicated instructions, there will be VF
// predicated blocks in the vectorized loop. Each branch around these
// blocks requires also an extract of its vector compare i1 element.
bool ScalarPredicatedBB = false;
BranchInst *BI = cast<BranchInst>(I);
if (VF > 1 && BI->isConditional() &&
(PredicatedBBsAfterVectorization.count(BI->getSuccessor(0)) ||
PredicatedBBsAfterVectorization.count(BI->getSuccessor(1))))
ScalarPredicatedBB = true;
if (ScalarPredicatedBB) {
// Return cost for branches around scalarized and predicated blocks.
Type *Vec_i1Ty =
VectorType::get(IntegerType::getInt1Ty(RetTy->getContext()), VF);
return (TTI.getScalarizationOverhead(Vec_i1Ty, false, true) +
(TTI.getCFInstrCost(Instruction::Br) * VF));
} else if (I->getParent() == TheLoop->getLoopLatch() || VF == 1)
// The back-edge branch will remain, as will all scalar branches.
return TTI.getCFInstrCost(Instruction::Br);
else
// This branch will be eliminated by if-conversion.
return 0;
// Note: We currently assume zero cost for an unconditional branch inside
// a predicated block since it will become a fall-through, although we
// may decide in the future to call TTI for all branches.
}
case Instruction::PHI: {
auto *Phi = cast<PHINode>(I);
// First-order recurrences are replaced by vector shuffles inside the loop.
if (VF > 1 && Legal->isFirstOrderRecurrence(Phi))
return TTI.getShuffleCost(TargetTransformInfo::SK_ExtractSubvector,
VectorTy, VF - 1, VectorTy);
// Phi nodes in non-header blocks (not inductions, reductions, etc.) are
// converted into select instructions. We require N - 1 selects per phi
// node, where N is the number of incoming values.
if (VF > 1 && Phi->getParent() != TheLoop->getHeader())
return (Phi->getNumIncomingValues() - 1) *
TTI.getCmpSelInstrCost(
Instruction::Select, ToVectorTy(Phi->getType(), VF),
ToVectorTy(Type::getInt1Ty(Phi->getContext()), VF));
return TTI.getCFInstrCost(Instruction::PHI);
}
case Instruction::UDiv:
case Instruction::SDiv:
case Instruction::URem:
case Instruction::SRem:
// If we have a predicated instruction, it may not be executed for each
// vector lane. Get the scalarization cost and scale this amount by the
// probability of executing the predicated block. If the instruction is not
// predicated, we fall through to the next case.
if (VF > 1 && isScalarWithPredication(I)) {
unsigned Cost = 0;
// These instructions have a non-void type, so account for the phi nodes
// that we will create. This cost is likely to be zero. The phi node
// cost, if any, should be scaled by the block probability because it
// models a copy at the end of each predicated block.
Cost += VF * TTI.getCFInstrCost(Instruction::PHI);
// The cost of the non-predicated instruction.
Cost += VF * TTI.getArithmeticInstrCost(I->getOpcode(), RetTy);
// The cost of insertelement and extractelement instructions needed for
// scalarization.
Cost += getScalarizationOverhead(I, VF, TTI);
// Scale the cost by the probability of executing the predicated blocks.
// This assumes the predicated block for each vector lane is equally
// likely.
return Cost / getReciprocalPredBlockProb();
}
LLVM_FALLTHROUGH;
case Instruction::Add:
case Instruction::FAdd:
case Instruction::Sub:
case Instruction::FSub:
case Instruction::Mul:
case Instruction::FMul:
case Instruction::FDiv:
case Instruction::FRem:
case Instruction::Shl:
case Instruction::LShr:
case Instruction::AShr:
case Instruction::And:
case Instruction::Or:
case Instruction::Xor: {
// Since we will replace the stride by 1 the multiplication should go away.
if (I->getOpcode() == Instruction::Mul && isStrideMul(I, Legal))
return 0;
// Certain instructions can be cheaper to vectorize if they have a constant
// second vector operand. One example of this are shifts on x86.
TargetTransformInfo::OperandValueKind Op1VK =
TargetTransformInfo::OK_AnyValue;
TargetTransformInfo::OperandValueKind Op2VK =
TargetTransformInfo::OK_AnyValue;
TargetTransformInfo::OperandValueProperties Op1VP =
TargetTransformInfo::OP_None;
TargetTransformInfo::OperandValueProperties Op2VP =
TargetTransformInfo::OP_None;
Value *Op2 = I->getOperand(1);
// Check for a splat or for a non uniform vector of constants.
if (isa<ConstantInt>(Op2)) {
ConstantInt *CInt = cast<ConstantInt>(Op2);
if (CInt && CInt->getValue().isPowerOf2())
Op2VP = TargetTransformInfo::OP_PowerOf2;
Op2VK = TargetTransformInfo::OK_UniformConstantValue;
} else if (isa<ConstantVector>(Op2) || isa<ConstantDataVector>(Op2)) {
Op2VK = TargetTransformInfo::OK_NonUniformConstantValue;
Constant *SplatValue = cast<Constant>(Op2)->getSplatValue();
if (SplatValue) {
ConstantInt *CInt = dyn_cast<ConstantInt>(SplatValue);
if (CInt && CInt->getValue().isPowerOf2())
Op2VP = TargetTransformInfo::OP_PowerOf2;
Op2VK = TargetTransformInfo::OK_UniformConstantValue;
}
} else if (Legal->isUniform(Op2)) {
Op2VK = TargetTransformInfo::OK_UniformValue;
}
SmallVector<const Value *, 4> Operands(I->operand_values());
unsigned N = isScalarAfterVectorization(I, VF) ? VF : 1;
return N * TTI.getArithmeticInstrCost(I->getOpcode(), VectorTy, Op1VK,
Op2VK, Op1VP, Op2VP, Operands);
}
case Instruction::Select: {
SelectInst *SI = cast<SelectInst>(I);
const SCEV *CondSCEV = SE->getSCEV(SI->getCondition());
bool ScalarCond = (SE->isLoopInvariant(CondSCEV, TheLoop));
Type *CondTy = SI->getCondition()->getType();
if (!ScalarCond)
CondTy = VectorType::get(CondTy, VF);
return TTI.getCmpSelInstrCost(I->getOpcode(), VectorTy, CondTy, I);
}
case Instruction::ICmp:
case Instruction::FCmp: {
Type *ValTy = I->getOperand(0)->getType();
Instruction *Op0AsInstruction = dyn_cast<Instruction>(I->getOperand(0));
if (canTruncateToMinimalBitwidth(Op0AsInstruction, VF))
ValTy = IntegerType::get(ValTy->getContext(), MinBWs[Op0AsInstruction]);
VectorTy = ToVectorTy(ValTy, VF);
return TTI.getCmpSelInstrCost(I->getOpcode(), VectorTy, nullptr, I);
}
case Instruction::Store:
case Instruction::Load: {
unsigned Width = VF;
if (Width > 1) {
InstWidening Decision = getWideningDecision(I, Width);
assert(Decision != CM_Unknown &&
"CM decision should be taken at this point");
if (Decision == CM_Scalarize)
Width = 1;
}
VectorTy = ToVectorTy(getMemInstValueType(I), Width);
return getMemoryInstructionCost(I, VF);
}
case Instruction::ZExt:
case Instruction::SExt:
case Instruction::FPToUI:
case Instruction::FPToSI:
case Instruction::FPExt:
case Instruction::PtrToInt:
case Instruction::IntToPtr:
case Instruction::SIToFP:
case Instruction::UIToFP:
case Instruction::Trunc:
case Instruction::FPTrunc:
case Instruction::BitCast: {
// We optimize the truncation of induction variables having constant
// integer steps. The cost of these truncations is the same as the scalar
// operation.
if (isOptimizableIVTruncate(I, VF)) {
auto *Trunc = cast<TruncInst>(I);
return TTI.getCastInstrCost(Instruction::Trunc, Trunc->getDestTy(),
Trunc->getSrcTy(), Trunc);
}
Type *SrcScalarTy = I->getOperand(0)->getType();
Type *SrcVecTy =
VectorTy->isVectorTy() ? ToVectorTy(SrcScalarTy, VF) : SrcScalarTy;
if (canTruncateToMinimalBitwidth(I, VF)) {
// This cast is going to be shrunk. This may remove the cast or it might
// turn it into slightly different cast. For example, if MinBW == 16,
// "zext i8 %1 to i32" becomes "zext i8 %1 to i16".
//
// Calculate the modified src and dest types.
Type *MinVecTy = VectorTy;
if (I->getOpcode() == Instruction::Trunc) {
SrcVecTy = smallestIntegerVectorType(SrcVecTy, MinVecTy);
VectorTy =
largestIntegerVectorType(ToVectorTy(I->getType(), VF), MinVecTy);
} else if (I->getOpcode() == Instruction::ZExt ||
I->getOpcode() == Instruction::SExt) {
SrcVecTy = largestIntegerVectorType(SrcVecTy, MinVecTy);
VectorTy =
smallestIntegerVectorType(ToVectorTy(I->getType(), VF), MinVecTy);
}
}
unsigned N = isScalarAfterVectorization(I, VF) ? VF : 1;
return N * TTI.getCastInstrCost(I->getOpcode(), VectorTy, SrcVecTy, I);
}
case Instruction::Call: {
bool NeedToScalarize;
CallInst *CI = cast<CallInst>(I);
unsigned CallCost = getVectorCallCost(CI, VF, TTI, TLI, NeedToScalarize);
if (getVectorIntrinsicIDForCall(CI, TLI))
return std::min(CallCost, getVectorIntrinsicCost(CI, VF, TTI, TLI));
return CallCost;
}
default:
// The cost of executing VF copies of the scalar instruction. This opcode
// is unknown. Assume that it is the same as 'mul'.
return VF * TTI.getArithmeticInstrCost(Instruction::Mul, VectorTy) +
getScalarizationOverhead(I, VF, TTI);
} // end of switch.
}
char LoopVectorize::ID = 0;
static const char lv_name[] = "Loop Vectorization";
INITIALIZE_PASS_BEGIN(LoopVectorize, LV_NAME, lv_name, false, false)
INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass)
INITIALIZE_PASS_DEPENDENCY(BasicAAWrapperPass)
INITIALIZE_PASS_DEPENDENCY(AAResultsWrapperPass)
INITIALIZE_PASS_DEPENDENCY(GlobalsAAWrapperPass)
INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
INITIALIZE_PASS_DEPENDENCY(BlockFrequencyInfoWrapperPass)
INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
INITIALIZE_PASS_DEPENDENCY(ScalarEvolutionWrapperPass)
INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
INITIALIZE_PASS_DEPENDENCY(LoopAccessLegacyAnalysis)
INITIALIZE_PASS_DEPENDENCY(DemandedBitsWrapperPass)
INITIALIZE_PASS_DEPENDENCY(OptimizationRemarkEmitterWrapperPass)
INITIALIZE_PASS_END(LoopVectorize, LV_NAME, lv_name, false, false)
namespace llvm {
Pass *createLoopVectorizePass(bool NoUnrolling, bool AlwaysVectorize) {
return new LoopVectorize(NoUnrolling, AlwaysVectorize);
}
} // end namespace llvm
bool LoopVectorizationCostModel::isConsecutiveLoadOrStore(Instruction *Inst) {
// Check if the pointer operand of a load or store instruction is
// consecutive.
if (auto *Ptr = getLoadStorePointerOperand(Inst))
return Legal->isConsecutivePtr(Ptr);
return false;
}
void LoopVectorizationCostModel::collectValuesToIgnore() {
// Ignore ephemeral values.
CodeMetrics::collectEphemeralValues(TheLoop, AC, ValuesToIgnore);
// Ignore type-promoting instructions we identified during reduction
// detection.
for (auto &Reduction : *Legal->getReductionVars()) {
RecurrenceDescriptor &RedDes = Reduction.second;
SmallPtrSetImpl<Instruction *> &Casts = RedDes.getCastInsts();
VecValuesToIgnore.insert(Casts.begin(), Casts.end());
}
// Ignore type-casting instructions we identified during induction
// detection.
for (auto &Induction : *Legal->getInductionVars()) {
InductionDescriptor &IndDes = Induction.second;
const SmallVectorImpl<Instruction *> &Casts = IndDes.getCastInsts();
VecValuesToIgnore.insert(Casts.begin(), Casts.end());
}
}
VectorizationFactor
LoopVectorizationPlanner::planInVPlanNativePath(bool OptForSize,
unsigned UserVF) {
// Width 1 means no vectorize, cost 0 means uncomputed cost.
const VectorizationFactor NoVectorization = {1U, 0U};
// Outer loop handling: They may require CFG and instruction level
// transformations before even evaluating whether vectorization is profitable.
// Since we cannot modify the incoming IR, we need to build VPlan upfront in
// the vectorization pipeline.
if (!OrigLoop->empty()) {
assert(EnableVPlanNativePath && "VPlan-native path is not enabled.");
assert(UserVF && "Expected UserVF for outer loop vectorization.");
assert(isPowerOf2_32(UserVF) && "VF needs to be a power of two");
DEBUG(dbgs() << "LV: Using user VF " << UserVF << ".\n");
buildVPlans(UserVF, UserVF);
return {UserVF, 0};
}
DEBUG(dbgs() << "LV: Not vectorizing. Inner loops aren't supported in the "
"VPlan-native path.\n");
return NoVectorization;
}
VectorizationFactor
LoopVectorizationPlanner::plan(bool OptForSize, unsigned UserVF) {
assert(OrigLoop->empty() && "Inner loop expected.");
// Width 1 means no vectorize, cost 0 means uncomputed cost.
const VectorizationFactor NoVectorization = {1U, 0U};
Optional<unsigned> MaybeMaxVF = CM.computeMaxVF(OptForSize);
if (!MaybeMaxVF.hasValue()) // Cases considered too costly to vectorize.
return NoVectorization;
if (UserVF) {
DEBUG(dbgs() << "LV: Using user VF " << UserVF << ".\n");
assert(isPowerOf2_32(UserVF) && "VF needs to be a power of two");
// Collect the instructions (and their associated costs) that will be more
// profitable to scalarize.
CM.selectUserVectorizationFactor(UserVF);
buildVPlans(UserVF, UserVF);
DEBUG(printPlans(dbgs()));
return {UserVF, 0};
}
unsigned MaxVF = MaybeMaxVF.getValue();
assert(MaxVF != 0 && "MaxVF is zero.");
for (unsigned VF = 1; VF <= MaxVF; VF *= 2) {
// Collect Uniform and Scalar instructions after vectorization with VF.
CM.collectUniformsAndScalars(VF);
// Collect the instructions (and their associated costs) that will be more
// profitable to scalarize.
if (VF > 1)
CM.collectInstsToScalarize(VF);
}
buildVPlans(1, MaxVF);
DEBUG(printPlans(dbgs()));
if (MaxVF == 1)
return NoVectorization;
// Select the optimal vectorization factor.
return CM.selectVectorizationFactor(MaxVF);
}
void LoopVectorizationPlanner::setBestPlan(unsigned VF, unsigned UF) {
DEBUG(dbgs() << "Setting best plan to VF=" << VF << ", UF=" << UF << '\n');
BestVF = VF;
BestUF = UF;
erase_if(VPlans, [VF](const VPlanPtr &Plan) {
return !Plan->hasVF(VF);
});
assert(VPlans.size() == 1 && "Best VF has not a single VPlan.");
}
void LoopVectorizationPlanner::executePlan(InnerLoopVectorizer &ILV,
DominatorTree *DT) {
// Perform the actual loop transformation.
// 1. Create a new empty loop. Unlink the old loop and connect the new one.
VPCallbackILV CallbackILV(ILV);
VPTransformState State{BestVF, BestUF, LI,
DT, ILV.Builder, ILV.VectorLoopValueMap,
&ILV, CallbackILV};
State.CFG.PrevBB = ILV.createVectorizedLoopSkeleton();
//===------------------------------------------------===//
//
// Notice: any optimization or new instruction that go
// into the code below should also be implemented in
// the cost-model.
//
//===------------------------------------------------===//
// 2. Copy and widen instructions from the old loop into the new loop.
assert(VPlans.size() == 1 && "Not a single VPlan to execute.");
VPlans.front()->execute(&State);
// 3. Fix the vectorized code: take care of header phi's, live-outs,
// predication, updating analyses.
ILV.fixVectorizedLoop();
}
void LoopVectorizationPlanner::collectTriviallyDeadInstructions(
SmallPtrSetImpl<Instruction *> &DeadInstructions) {
BasicBlock *Latch = OrigLoop->getLoopLatch();
// We create new control-flow for the vectorized loop, so the original
// condition will be dead after vectorization if it's only used by the
// branch.
auto *Cmp = dyn_cast<Instruction>(Latch->getTerminator()->getOperand(0));
if (Cmp && Cmp->hasOneUse())
DeadInstructions.insert(Cmp);
// We create new "steps" for induction variable updates to which the original
// induction variables map. An original update instruction will be dead if
// all its users except the induction variable are dead.
for (auto &Induction : *Legal->getInductionVars()) {
PHINode *Ind = Induction.first;
auto *IndUpdate = cast<Instruction>(Ind->getIncomingValueForBlock(Latch));
if (llvm::all_of(IndUpdate->users(), [&](User *U) -> bool {
return U == Ind || DeadInstructions.count(cast<Instruction>(U));
}))
DeadInstructions.insert(IndUpdate);
// We record as "Dead" also the type-casting instructions we had identified
// during induction analysis. We don't need any handling for them in the
// vectorized loop because we have proven that, under a proper runtime
// test guarding the vectorized loop, the value of the phi, and the casted
// value of the phi, are the same. The last instruction in this casting chain
// will get its scalar/vector/widened def from the scalar/vector/widened def
// of the respective phi node. Any other casts in the induction def-use chain
// have no other uses outside the phi update chain, and will be ignored.
InductionDescriptor &IndDes = Induction.second;
const SmallVectorImpl<Instruction *> &Casts = IndDes.getCastInsts();
DeadInstructions.insert(Casts.begin(), Casts.end());
}
}
Value *InnerLoopUnroller::reverseVector(Value *Vec) { return Vec; }
Value *InnerLoopUnroller::getBroadcastInstrs(Value *V) { return V; }
Value *InnerLoopUnroller::getStepVector(Value *Val, int StartIdx, Value *Step,
Instruction::BinaryOps BinOp) {
// When unrolling and the VF is 1, we only need to add a simple scalar.
Type *Ty = Val->getType();
assert(!Ty->isVectorTy() && "Val must be a scalar");
if (Ty->isFloatingPointTy()) {
Constant *C = ConstantFP::get(Ty, (double)StartIdx);
// Floating point operations had to be 'fast' to enable the unrolling.
Value *MulOp = addFastMathFlag(Builder.CreateFMul(C, Step));
return addFastMathFlag(Builder.CreateBinOp(BinOp, Val, MulOp));
}
Constant *C = ConstantInt::get(Ty, StartIdx);
return Builder.CreateAdd(Val, Builder.CreateMul(C, Step), "induction");
}
static void AddRuntimeUnrollDisableMetaData(Loop *L) {
SmallVector<Metadata *, 4> MDs;
// Reserve first location for self reference to the LoopID metadata node.
MDs.push_back(nullptr);
bool IsUnrollMetadata = false;
MDNode *LoopID = L->getLoopID();
if (LoopID) {
// First find existing loop unrolling disable metadata.
for (unsigned i = 1, ie = LoopID->getNumOperands(); i < ie; ++i) {
auto *MD = dyn_cast<MDNode>(LoopID->getOperand(i));
if (MD) {
const auto *S = dyn_cast<MDString>(MD->getOperand(0));
IsUnrollMetadata =
S && S->getString().startswith("llvm.loop.unroll.disable");
}
MDs.push_back(LoopID->getOperand(i));
}
}
if (!IsUnrollMetadata) {
// Add runtime unroll disable metadata.
LLVMContext &Context = L->getHeader()->getContext();
SmallVector<Metadata *, 1> DisableOperands;
DisableOperands.push_back(
MDString::get(Context, "llvm.loop.unroll.runtime.disable"));
MDNode *DisableNode = MDNode::get(Context, DisableOperands);
MDs.push_back(DisableNode);
MDNode *NewLoopID = MDNode::get(Context, MDs);
// Set operand 0 to refer to the loop id itself.
NewLoopID->replaceOperandWith(0, NewLoopID);
L->setLoopID(NewLoopID);
}
}
bool LoopVectorizationPlanner::getDecisionAndClampRange(
const std::function<bool(unsigned)> &Predicate, VFRange &Range) {
assert(Range.End > Range.Start && "Trying to test an empty VF range.");
bool PredicateAtRangeStart = Predicate(Range.Start);
for (unsigned TmpVF = Range.Start * 2; TmpVF < Range.End; TmpVF *= 2)
if (Predicate(TmpVF) != PredicateAtRangeStart) {
Range.End = TmpVF;
break;
}
return PredicateAtRangeStart;
}
/// Build VPlans for the full range of feasible VF's = {\p MinVF, 2 * \p MinVF,
/// 4 * \p MinVF, ..., \p MaxVF} by repeatedly building a VPlan for a sub-range
/// of VF's starting at a given VF and extending it as much as possible. Each
/// vectorization decision can potentially shorten this sub-range during
/// buildVPlan().
void LoopVectorizationPlanner::buildVPlans(unsigned MinVF, unsigned MaxVF) {
// Collect conditions feeding internal conditional branches; they need to be
// represented in VPlan for it to model masking.
SmallPtrSet<Value *, 1> NeedDef;
auto *Latch = OrigLoop->getLoopLatch();
for (BasicBlock *BB : OrigLoop->blocks()) {
if (BB == Latch)
continue;
BranchInst *Branch = dyn_cast<BranchInst>(BB->getTerminator());
if (Branch && Branch->isConditional())
NeedDef.insert(Branch->getCondition());
}
for (unsigned VF = MinVF; VF < MaxVF + 1;) {
VFRange SubRange = {VF, MaxVF + 1};
VPlans.push_back(buildVPlan(SubRange, NeedDef));
VF = SubRange.End;
}
}
VPValue *LoopVectorizationPlanner::createEdgeMask(BasicBlock *Src,
BasicBlock *Dst,
VPlanPtr &Plan) {
assert(is_contained(predecessors(Dst), Src) && "Invalid edge");
// Look for cached value.
std::pair<BasicBlock *, BasicBlock *> Edge(Src, Dst);
EdgeMaskCacheTy::iterator ECEntryIt = EdgeMaskCache.find(Edge);
if (ECEntryIt != EdgeMaskCache.end())
return ECEntryIt->second;
VPValue *SrcMask = createBlockInMask(Src, Plan);
// The terminator has to be a branch inst!
BranchInst *BI = dyn_cast<BranchInst>(Src->getTerminator());
assert(BI && "Unexpected terminator found");
if (!BI->isConditional())
return EdgeMaskCache[Edge] = SrcMask;
VPValue *EdgeMask = Plan->getVPValue(BI->getCondition());
assert(EdgeMask && "No Edge Mask found for condition");
if (BI->getSuccessor(0) != Dst)
EdgeMask = Builder.createNot(EdgeMask);
if (SrcMask) // Otherwise block in-mask is all-one, no need to AND.
EdgeMask = Builder.createAnd(EdgeMask, SrcMask);
return EdgeMaskCache[Edge] = EdgeMask;
}
VPValue *LoopVectorizationPlanner::createBlockInMask(BasicBlock *BB,
VPlanPtr &Plan) {
assert(OrigLoop->contains(BB) && "Block is not a part of a loop");
// Look for cached value.
BlockMaskCacheTy::iterator BCEntryIt = BlockMaskCache.find(BB);
if (BCEntryIt != BlockMaskCache.end())
return BCEntryIt->second;
// All-one mask is modelled as no-mask following the convention for masked
// load/store/gather/scatter. Initialize BlockMask to no-mask.
VPValue *BlockMask = nullptr;
// Loop incoming mask is all-one.
if (OrigLoop->getHeader() == BB)
return BlockMaskCache[BB] = BlockMask;
// This is the block mask. We OR all incoming edges.
for (auto *Predecessor : predecessors(BB)) {
VPValue *EdgeMask = createEdgeMask(Predecessor, BB, Plan);
if (!EdgeMask) // Mask of predecessor is all-one so mask of block is too.
return BlockMaskCache[BB] = EdgeMask;
if (!BlockMask) { // BlockMask has its initialized nullptr value.
BlockMask = EdgeMask;
continue;
}
BlockMask = Builder.createOr(BlockMask, EdgeMask);
}
return BlockMaskCache[BB] = BlockMask;
}
VPInterleaveRecipe *
LoopVectorizationPlanner::tryToInterleaveMemory(Instruction *I,
VFRange &Range) {
const InterleaveGroup *IG = CM.getInterleavedAccessGroup(I);
if (!IG)
return nullptr;
// Now check if IG is relevant for VF's in the given range.
auto isIGMember = [&](Instruction *I) -> std::function<bool(unsigned)> {
return [=](unsigned VF) -> bool {
return (VF >= 2 && // Query is illegal for VF == 1
CM.getWideningDecision(I, VF) ==
LoopVectorizationCostModel::CM_Interleave);
};
};
if (!getDecisionAndClampRange(isIGMember(I), Range))
return nullptr;
// I is a member of an InterleaveGroup for VF's in the (possibly trimmed)
// range. If it's the primary member of the IG construct a VPInterleaveRecipe.
// Otherwise, it's an adjunct member of the IG, do not construct any Recipe.
assert(I == IG->getInsertPos() &&
"Generating a recipe for an adjunct member of an interleave group");
return new VPInterleaveRecipe(IG);
}
VPWidenMemoryInstructionRecipe *
LoopVectorizationPlanner::tryToWidenMemory(Instruction *I, VFRange &Range,
VPlanPtr &Plan) {
if (!isa<LoadInst>(I) && !isa<StoreInst>(I))
return nullptr;
auto willWiden = [&](unsigned VF) -> bool {
if (VF == 1)
return false;
if (CM.isScalarAfterVectorization(I, VF) ||
CM.isProfitableToScalarize(I, VF))
return false;
LoopVectorizationCostModel::InstWidening Decision =
CM.getWideningDecision(I, VF);
assert(Decision != LoopVectorizationCostModel::CM_Unknown &&
"CM decision should be taken at this point.");
assert(Decision != LoopVectorizationCostModel::CM_Interleave &&
"Interleave memory opportunity should be caught earlier.");
return Decision != LoopVectorizationCostModel::CM_Scalarize;
};
if (!getDecisionAndClampRange(willWiden, Range))
return nullptr;
VPValue *Mask = nullptr;
if (Legal->isMaskRequired(I))
Mask = createBlockInMask(I->getParent(), Plan);
return new VPWidenMemoryInstructionRecipe(*I, Mask);
}
VPWidenIntOrFpInductionRecipe *
LoopVectorizationPlanner::tryToOptimizeInduction(Instruction *I,
VFRange &Range) {
if (PHINode *Phi = dyn_cast<PHINode>(I)) {
// Check if this is an integer or fp induction. If so, build the recipe that
// produces its scalar and vector values.
InductionDescriptor II = Legal->getInductionVars()->lookup(Phi);
if (II.getKind() == InductionDescriptor::IK_IntInduction ||
II.getKind() == InductionDescriptor::IK_FpInduction)
return new VPWidenIntOrFpInductionRecipe(Phi);
return nullptr;
}
// Optimize the special case where the source is a constant integer
// induction variable. Notice that we can only optimize the 'trunc' case
// because (a) FP conversions lose precision, (b) sext/zext may wrap, and
// (c) other casts depend on pointer size.
// Determine whether \p K is a truncation based on an induction variable that
// can be optimized.
auto isOptimizableIVTruncate =
[&](Instruction *K) -> std::function<bool(unsigned)> {
return
[=](unsigned VF) -> bool { return CM.isOptimizableIVTruncate(K, VF); };
};
if (isa<TruncInst>(I) &&
getDecisionAndClampRange(isOptimizableIVTruncate(I), Range))
return new VPWidenIntOrFpInductionRecipe(cast<PHINode>(I->getOperand(0)),
cast<TruncInst>(I));
return nullptr;
}
VPBlendRecipe *
LoopVectorizationPlanner::tryToBlend(Instruction *I, VPlanPtr &Plan) {
PHINode *Phi = dyn_cast<PHINode>(I);
if (!Phi || Phi->getParent() == OrigLoop->getHeader())
return nullptr;
// We know that all PHIs in non-header blocks are converted into selects, so
// we don't have to worry about the insertion order and we can just use the
// builder. At this point we generate the predication tree. There may be
// duplications since this is a simple recursive scan, but future
// optimizations will clean it up.
SmallVector<VPValue *, 2> Masks;
unsigned NumIncoming = Phi->getNumIncomingValues();
for (unsigned In = 0; In < NumIncoming; In++) {
VPValue *EdgeMask =
createEdgeMask(Phi->getIncomingBlock(In), Phi->getParent(), Plan);
assert((EdgeMask || NumIncoming == 1) &&
"Multiple predecessors with one having a full mask");
if (EdgeMask)
Masks.push_back(EdgeMask);
}
return new VPBlendRecipe(Phi, Masks);
}
bool LoopVectorizationPlanner::tryToWiden(Instruction *I, VPBasicBlock *VPBB,
VFRange &Range) {
if (CM.isScalarWithPredication(I))
return false;
auto IsVectorizableOpcode = [](unsigned Opcode) {
switch (Opcode) {
case Instruction::Add:
case Instruction::And:
case Instruction::AShr:
case Instruction::BitCast:
case Instruction::Br:
case Instruction::Call:
case Instruction::FAdd:
case Instruction::FCmp:
case Instruction::FDiv:
case Instruction::FMul:
case Instruction::FPExt:
case Instruction::FPToSI:
case Instruction::FPToUI:
case Instruction::FPTrunc:
case Instruction::FRem:
case Instruction::FSub:
case Instruction::GetElementPtr:
case Instruction::ICmp:
case Instruction::IntToPtr:
case Instruction::Load:
case Instruction::LShr:
case Instruction::Mul:
case Instruction::Or:
case Instruction::PHI:
case Instruction::PtrToInt:
case Instruction::SDiv:
case Instruction::Select:
case Instruction::SExt:
case Instruction::Shl:
case Instruction::SIToFP:
case Instruction::SRem:
case Instruction::Store:
case Instruction::Sub:
case Instruction::Trunc:
case Instruction::UDiv:
case Instruction::UIToFP:
case Instruction::URem:
case Instruction::Xor:
case Instruction::ZExt:
return true;
}
return false;
};
if (!IsVectorizableOpcode(I->getOpcode()))
return false;
if (CallInst *CI = dyn_cast<CallInst>(I)) {
Intrinsic::ID ID = getVectorIntrinsicIDForCall(CI, TLI);
if (ID && (ID == Intrinsic::assume || ID == Intrinsic::lifetime_end ||
ID == Intrinsic::lifetime_start || ID == Intrinsic::sideeffect))
return false;
}
auto willWiden = [&](unsigned VF) -> bool {
if (!isa<PHINode>(I) && (CM.isScalarAfterVectorization(I, VF) ||
CM.isProfitableToScalarize(I, VF)))
return false;
if (CallInst *CI = dyn_cast<CallInst>(I)) {
Intrinsic::ID ID = getVectorIntrinsicIDForCall(CI, TLI);
// The following case may be scalarized depending on the VF.
// The flag shows whether we use Intrinsic or a usual Call for vectorized
// version of the instruction.
// Is it beneficial to perform intrinsic call compared to lib call?
bool NeedToScalarize;
unsigned CallCost = getVectorCallCost(CI, VF, *TTI, TLI, NeedToScalarize);
bool UseVectorIntrinsic =
ID && getVectorIntrinsicCost(CI, VF, *TTI, TLI) <= CallCost;
return UseVectorIntrinsic || !NeedToScalarize;
}
if (isa<LoadInst>(I) || isa<StoreInst>(I)) {
assert(CM.getWideningDecision(I, VF) ==
LoopVectorizationCostModel::CM_Scalarize &&
"Memory widening decisions should have been taken care by now");
return false;
}
return true;
};
if (!getDecisionAndClampRange(willWiden, Range))
return false;
// Success: widen this instruction. We optimize the common case where
// consecutive instructions can be represented by a single recipe.
if (!VPBB->empty()) {
VPWidenRecipe *LastWidenRecipe = dyn_cast<VPWidenRecipe>(&VPBB->back());
if (LastWidenRecipe && LastWidenRecipe->appendInstruction(I))
return true;
}
VPBB->appendRecipe(new VPWidenRecipe(I));
return true;
}
VPBasicBlock *LoopVectorizationPlanner::handleReplication(
Instruction *I, VFRange &Range, VPBasicBlock *VPBB,
DenseMap<Instruction *, VPReplicateRecipe *> &PredInst2Recipe,
VPlanPtr &Plan) {
bool IsUniform = getDecisionAndClampRange(
[&](unsigned VF) { return CM.isUniformAfterVectorization(I, VF); },
Range);
bool IsPredicated = CM.isScalarWithPredication(I);
auto *Recipe = new VPReplicateRecipe(I, IsUniform, IsPredicated);
// Find if I uses a predicated instruction. If so, it will use its scalar
// value. Avoid hoisting the insert-element which packs the scalar value into
// a vector value, as that happens iff all users use the vector value.
for (auto &Op : I->operands())
if (auto *PredInst = dyn_cast<Instruction>(Op))
if (PredInst2Recipe.find(PredInst) != PredInst2Recipe.end())
PredInst2Recipe[PredInst]->setAlsoPack(false);
// Finalize the recipe for Instr, first if it is not predicated.
if (!IsPredicated) {
DEBUG(dbgs() << "LV: Scalarizing:" << *I << "\n");
VPBB->appendRecipe(Recipe);
return VPBB;
}
DEBUG(dbgs() << "LV: Scalarizing and predicating:" << *I << "\n");
assert(VPBB->getSuccessors().empty() &&
"VPBB has successors when handling predicated replication.");
// Record predicated instructions for above packing optimizations.
PredInst2Recipe[I] = Recipe;
VPBlockBase *Region =
VPBB->setOneSuccessor(createReplicateRegion(I, Recipe, Plan));
return cast<VPBasicBlock>(Region->setOneSuccessor(new VPBasicBlock()));
}
VPRegionBlock *
LoopVectorizationPlanner::createReplicateRegion(Instruction *Instr,
VPRecipeBase *PredRecipe,
VPlanPtr &Plan) {
// Instructions marked for predication are replicated and placed under an
// if-then construct to prevent side-effects.
// Generate recipes to compute the block mask for this region.
VPValue *BlockInMask = createBlockInMask(Instr->getParent(), Plan);
// Build the triangular if-then region.
std::string RegionName = (Twine("pred.") + Instr->getOpcodeName()).str();
assert(Instr->getParent() && "Predicated instruction not in any basic block");
auto *BOMRecipe = new VPBranchOnMaskRecipe(BlockInMask);
auto *Entry = new VPBasicBlock(Twine(RegionName) + ".entry", BOMRecipe);
auto *PHIRecipe =
Instr->getType()->isVoidTy() ? nullptr : new VPPredInstPHIRecipe(Instr);
auto *Exit = new VPBasicBlock(Twine(RegionName) + ".continue", PHIRecipe);
auto *Pred = new VPBasicBlock(Twine(RegionName) + ".if", PredRecipe);
VPRegionBlock *Region = new VPRegionBlock(Entry, Exit, RegionName, true);
// Note: first set Entry as region entry and then connect successors starting
// from it in order, to propagate the "parent" of each VPBasicBlock.
Entry->setTwoSuccessors(Pred, Exit);
Pred->setOneSuccessor(Exit);
return Region;
}
LoopVectorizationPlanner::VPlanPtr
LoopVectorizationPlanner::buildVPlan(VFRange &Range,
const SmallPtrSetImpl<Value *> &NeedDef) {
// Outer loop handling: They may require CFG and instruction level
// transformations before even evaluating whether vectorization is profitable.
// Since we cannot modify the incoming IR, we need to build VPlan upfront in
// the vectorization pipeline.
if (!OrigLoop->empty()) {
assert(EnableVPlanNativePath && "VPlan-native path is not enabled.");
// Create new empty VPlan
auto Plan = llvm::make_unique<VPlan>();
return Plan;
}
assert(OrigLoop->empty() && "Inner loop expected.");
EdgeMaskCache.clear();
BlockMaskCache.clear();
DenseMap<Instruction *, Instruction *> &SinkAfter = Legal->getSinkAfter();
DenseMap<Instruction *, Instruction *> SinkAfterInverse;
// Collect instructions from the original loop that will become trivially dead
// in the vectorized loop. We don't need to vectorize these instructions. For
// example, original induction update instructions can become dead because we
// separately emit induction "steps" when generating code for the new loop.
// Similarly, we create a new latch condition when setting up the structure
// of the new loop, so the old one can become dead.
SmallPtrSet<Instruction *, 4> DeadInstructions;
collectTriviallyDeadInstructions(DeadInstructions);
// Hold a mapping from predicated instructions to their recipes, in order to
// fix their AlsoPack behavior if a user is determined to replicate and use a
// scalar instead of vector value.
DenseMap<Instruction *, VPReplicateRecipe *> PredInst2Recipe;
// Create a dummy pre-entry VPBasicBlock to start building the VPlan.
VPBasicBlock *VPBB = new VPBasicBlock("Pre-Entry");
auto Plan = llvm::make_unique<VPlan>(VPBB);
// Represent values that will have defs inside VPlan.
for (Value *V : NeedDef)
Plan->addVPValue(V);
// Scan the body of the loop in a topological order to visit each basic block
// after having visited its predecessor basic blocks.
LoopBlocksDFS DFS(OrigLoop);
DFS.perform(LI);
for (BasicBlock *BB : make_range(DFS.beginRPO(), DFS.endRPO())) {
// Relevant instructions from basic block BB will be grouped into VPRecipe
// ingredients and fill a new VPBasicBlock.
unsigned VPBBsForBB = 0;
auto *FirstVPBBForBB = new VPBasicBlock(BB->getName());
VPBB->setOneSuccessor(FirstVPBBForBB);
VPBB = FirstVPBBForBB;
Builder.setInsertPoint(VPBB);
std::vector<Instruction *> Ingredients;
// Organize the ingredients to vectorize from current basic block in the
// right order.
for (Instruction &I : BB->instructionsWithoutDebug()) {
Instruction *Instr = &I;
// First filter out irrelevant instructions, to ensure no recipes are
// built for them.
if (isa<BranchInst>(Instr) || DeadInstructions.count(Instr))
continue;
// I is a member of an InterleaveGroup for Range.Start. If it's an adjunct
// member of the IG, do not construct any Recipe for it.
const InterleaveGroup *IG = CM.getInterleavedAccessGroup(Instr);
if (IG && Instr != IG->getInsertPos() &&
Range.Start >= 2 && // Query is illegal for VF == 1
CM.getWideningDecision(Instr, Range.Start) ==
LoopVectorizationCostModel::CM_Interleave) {
if (SinkAfterInverse.count(Instr))
Ingredients.push_back(SinkAfterInverse.find(Instr)->second);
continue;
}
// Move instructions to handle first-order recurrences, step 1: avoid
// handling this instruction until after we've handled the instruction it
// should follow.
auto SAIt = SinkAfter.find(Instr);
if (SAIt != SinkAfter.end()) {
DEBUG(dbgs() << "Sinking" << *SAIt->first << " after" << *SAIt->second
<< " to vectorize a 1st order recurrence.\n");
SinkAfterInverse[SAIt->second] = Instr;
continue;
}
Ingredients.push_back(Instr);
// Move instructions to handle first-order recurrences, step 2: push the
// instruction to be sunk at its insertion point.
auto SAInvIt = SinkAfterInverse.find(Instr);
if (SAInvIt != SinkAfterInverse.end())
Ingredients.push_back(SAInvIt->second);
}
// Introduce each ingredient into VPlan.
for (Instruction *Instr : Ingredients) {
VPRecipeBase *Recipe = nullptr;
// Check if Instr should belong to an interleave memory recipe, or already
// does. In the latter case Instr is irrelevant.
if ((Recipe = tryToInterleaveMemory(Instr, Range))) {
VPBB->appendRecipe(Recipe);
continue;
}
// Check if Instr is a memory operation that should be widened.
if ((Recipe = tryToWidenMemory(Instr, Range, Plan))) {
VPBB->appendRecipe(Recipe);
continue;
}
// Check if Instr should form some PHI recipe.
if ((Recipe = tryToOptimizeInduction(Instr, Range))) {
VPBB->appendRecipe(Recipe);
continue;
}
if ((Recipe = tryToBlend(Instr, Plan))) {
VPBB->appendRecipe(Recipe);
continue;
}
if (PHINode *Phi = dyn_cast<PHINode>(Instr)) {
VPBB->appendRecipe(new VPWidenPHIRecipe(Phi));
continue;
}
// Check if Instr is to be widened by a general VPWidenRecipe, after
// having first checked for specific widening recipes that deal with
// Interleave Groups, Inductions and Phi nodes.
if (tryToWiden(Instr, VPBB, Range))
continue;
// Otherwise, if all widening options failed, Instruction is to be
// replicated. This may create a successor for VPBB.
VPBasicBlock *NextVPBB =
handleReplication(Instr, Range, VPBB, PredInst2Recipe, Plan);
if (NextVPBB != VPBB) {
VPBB = NextVPBB;
VPBB->setName(BB->hasName() ? BB->getName() + "." + Twine(VPBBsForBB++)
: "");
}
}
}
// Discard empty dummy pre-entry VPBasicBlock. Note that other VPBasicBlocks
// may also be empty, such as the last one VPBB, reflecting original
// basic-blocks with no recipes.
VPBasicBlock *PreEntry = cast<VPBasicBlock>(Plan->getEntry());
assert(PreEntry->empty() && "Expecting empty pre-entry block.");
VPBlockBase *Entry = Plan->setEntry(PreEntry->getSingleSuccessor());
PreEntry->disconnectSuccessor(Entry);
delete PreEntry;
std::string PlanName;
raw_string_ostream RSO(PlanName);
unsigned VF = Range.Start;
Plan->addVF(VF);
RSO << "Initial VPlan for VF={" << VF;
for (VF *= 2; VF < Range.End; VF *= 2) {
Plan->addVF(VF);
RSO << "," << VF;
}
RSO << "},UF>=1";
RSO.flush();
Plan->setName(PlanName);
return Plan;
}
Value* LoopVectorizationPlanner::VPCallbackILV::
getOrCreateVectorValues(Value *V, unsigned Part) {
return ILV.getOrCreateVectorValue(V, Part);
}
void VPInterleaveRecipe::print(raw_ostream &O, const Twine &Indent) const {
O << " +\n"
<< Indent << "\"INTERLEAVE-GROUP with factor " << IG->getFactor() << " at ";
IG->getInsertPos()->printAsOperand(O, false);
O << "\\l\"";
for (unsigned i = 0; i < IG->getFactor(); ++i)
if (Instruction *I = IG->getMember(i))
O << " +\n"
<< Indent << "\" " << VPlanIngredient(I) << " " << i << "\\l\"";
}
void VPWidenRecipe::execute(VPTransformState &State) {
for (auto &Instr : make_range(Begin, End))
State.ILV->widenInstruction(Instr);
}
void VPWidenIntOrFpInductionRecipe::execute(VPTransformState &State) {
assert(!State.Instance && "Int or FP induction being replicated.");
State.ILV->widenIntOrFpInduction(IV, Trunc);
}
void VPWidenPHIRecipe::execute(VPTransformState &State) {
State.ILV->widenPHIInstruction(Phi, State.UF, State.VF);
}
void VPBlendRecipe::execute(VPTransformState &State) {
State.ILV->setDebugLocFromInst(State.Builder, Phi);
// We know that all PHIs in non-header blocks are converted into
// selects, so we don't have to worry about the insertion order and we
// can just use the builder.
// At this point we generate the predication tree. There may be
// duplications since this is a simple recursive scan, but future
// optimizations will clean it up.
unsigned NumIncoming = Phi->getNumIncomingValues();
assert((User || NumIncoming == 1) &&
"Multiple predecessors with predecessors having a full mask");
// Generate a sequence of selects of the form:
// SELECT(Mask3, In3,
// SELECT(Mask2, In2,
// ( ...)))
InnerLoopVectorizer::VectorParts Entry(State.UF);
for (unsigned In = 0; In < NumIncoming; ++In) {
for (unsigned Part = 0; Part < State.UF; ++Part) {
// We might have single edge PHIs (blocks) - use an identity
// 'select' for the first PHI operand.
Value *In0 =
State.ILV->getOrCreateVectorValue(Phi->getIncomingValue(In), Part);
if (In == 0)
Entry[Part] = In0; // Initialize with the first incoming value.
else {
// Select between the current value and the previous incoming edge
// based on the incoming mask.
Value *Cond = State.get(User->getOperand(In), Part);
Entry[Part] =
State.Builder.CreateSelect(Cond, In0, Entry[Part], "predphi");
}
}
}
for (unsigned Part = 0; Part < State.UF; ++Part)
State.ValueMap.setVectorValue(Phi, Part, Entry[Part]);
}
void VPInterleaveRecipe::execute(VPTransformState &State) {
assert(!State.Instance && "Interleave group being replicated.");
State.ILV->vectorizeInterleaveGroup(IG->getInsertPos());
}
void VPReplicateRecipe::execute(VPTransformState &State) {
if (State.Instance) { // Generate a single instance.
State.ILV->scalarizeInstruction(Ingredient, *State.Instance, IsPredicated);
// Insert scalar instance packing it into a vector.
if (AlsoPack && State.VF > 1) {
// If we're constructing lane 0, initialize to start from undef.
if (State.Instance->Lane == 0) {
Value *Undef =
UndefValue::get(VectorType::get(Ingredient->getType(), State.VF));
State.ValueMap.setVectorValue(Ingredient, State.Instance->Part, Undef);
}
State.ILV->packScalarIntoVectorValue(Ingredient, *State.Instance);
}
return;
}
// Generate scalar instances for all VF lanes of all UF parts, unless the
// instruction is uniform inwhich case generate only the first lane for each
// of the UF parts.
unsigned EndLane = IsUniform ? 1 : State.VF;
for (unsigned Part = 0; Part < State.UF; ++Part)
for (unsigned Lane = 0; Lane < EndLane; ++Lane)
State.ILV->scalarizeInstruction(Ingredient, {Part, Lane}, IsPredicated);
}
void VPBranchOnMaskRecipe::execute(VPTransformState &State) {
assert(State.Instance && "Branch on Mask works only on single instance.");
unsigned Part = State.Instance->Part;
unsigned Lane = State.Instance->Lane;
Value *ConditionBit = nullptr;
if (!User) // Block in mask is all-one.
ConditionBit = State.Builder.getTrue();
else {
VPValue *BlockInMask = User->getOperand(0);
ConditionBit = State.get(BlockInMask, Part);
if (ConditionBit->getType()->isVectorTy())
ConditionBit = State.Builder.CreateExtractElement(
ConditionBit, State.Builder.getInt32(Lane));
}
// Replace the temporary unreachable terminator with a new conditional branch,
// whose two destinations will be set later when they are created.
auto *CurrentTerminator = State.CFG.PrevBB->getTerminator();
assert(isa<UnreachableInst>(CurrentTerminator) &&
"Expected to replace unreachable terminator with conditional branch.");
auto *CondBr = BranchInst::Create(State.CFG.PrevBB, nullptr, ConditionBit);
CondBr->setSuccessor(0, nullptr);
ReplaceInstWithInst(CurrentTerminator, CondBr);
}
void VPPredInstPHIRecipe::execute(VPTransformState &State) {
assert(State.Instance && "Predicated instruction PHI works per instance.");
Instruction *ScalarPredInst = cast<Instruction>(
State.ValueMap.getScalarValue(PredInst, *State.Instance));
BasicBlock *PredicatedBB = ScalarPredInst->getParent();
BasicBlock *PredicatingBB = PredicatedBB->getSinglePredecessor();
assert(PredicatingBB && "Predicated block has no single predecessor.");
// By current pack/unpack logic we need to generate only a single phi node: if
// a vector value for the predicated instruction exists at this point it means
// the instruction has vector users only, and a phi for the vector value is
// needed. In this case the recipe of the predicated instruction is marked to
// also do that packing, thereby "hoisting" the insert-element sequence.
// Otherwise, a phi node for the scalar value is needed.
unsigned Part = State.Instance->Part;
if (State.ValueMap.hasVectorValue(PredInst, Part)) {
Value *VectorValue = State.ValueMap.getVectorValue(PredInst, Part);
InsertElementInst *IEI = cast<InsertElementInst>(VectorValue);
PHINode *VPhi = State.Builder.CreatePHI(IEI->getType(), 2);
VPhi->addIncoming(IEI->getOperand(0), PredicatingBB); // Unmodified vector.
VPhi->addIncoming(IEI, PredicatedBB); // New vector with inserted element.
State.ValueMap.resetVectorValue(PredInst, Part, VPhi); // Update cache.
} else {
Type *PredInstType = PredInst->getType();
PHINode *Phi = State.Builder.CreatePHI(PredInstType, 2);
Phi->addIncoming(UndefValue::get(ScalarPredInst->getType()), PredicatingBB);
Phi->addIncoming(ScalarPredInst, PredicatedBB);
State.ValueMap.resetScalarValue(PredInst, *State.Instance, Phi);
}
}
void VPWidenMemoryInstructionRecipe::execute(VPTransformState &State) {
if (!User)
return State.ILV->vectorizeMemoryInstruction(&Instr);
// Last (and currently only) operand is a mask.
InnerLoopVectorizer::VectorParts MaskValues(State.UF);
VPValue *Mask = User->getOperand(User->getNumOperands() - 1);
for (unsigned Part = 0; Part < State.UF; ++Part)
MaskValues[Part] = State.get(Mask, Part);
State.ILV->vectorizeMemoryInstruction(&Instr, &MaskValues);
}
// Process the loop in the VPlan-native vectorization path. This path builds
// VPlan upfront in the vectorization pipeline, which allows to apply
// VPlan-to-VPlan transformations from the very beginning without modifying the
// input LLVM IR.
static bool processLoopInVPlanNativePath(
Loop *L, PredicatedScalarEvolution &PSE, LoopInfo *LI, DominatorTree *DT,
LoopVectorizationLegality *LVL, TargetTransformInfo *TTI,
TargetLibraryInfo *TLI, DemandedBits *DB, AssumptionCache *AC,
OptimizationRemarkEmitter *ORE, LoopVectorizeHints &Hints) {
assert(EnableVPlanNativePath && "VPlan-native path is disabled.");
Function *F = L->getHeader()->getParent();
InterleavedAccessInfo IAI(PSE, L, DT, LI, LVL->getLAI());
LoopVectorizationCostModel CM(L, PSE, LI, LVL, *TTI, TLI, DB, AC, ORE, F,
&Hints, IAI);
// Use the planner for outer loop vectorization.
// TODO: CM is not used at this point inside the planner. Turn CM into an
// optional argument if we don't need it in the future.
LoopVectorizationPlanner LVP(L, LI, TLI, TTI, LVL, CM);
// Get user vectorization factor.
unsigned UserVF = Hints.getWidth();
// Check the function attributes to find out if this function should be
// optimized for size.
bool OptForSize =
Hints.getForce() != LoopVectorizeHints::FK_Enabled && F->optForSize();
// Plan how to best vectorize, return the best VF and its cost.
LVP.planInVPlanNativePath(OptForSize, UserVF);
// Returning false. We are currently not generating vector code in the VPlan
// native path.
return false;
}
bool LoopVectorizePass::processLoop(Loop *L) {
assert((EnableVPlanNativePath || L->empty()) &&
"VPlan-native path is not enabled. Only process inner loops.");
#ifndef NDEBUG
const std::string DebugLocStr = getDebugLocString(L);
#endif /* NDEBUG */
DEBUG(dbgs() << "\nLV: Checking a loop in \""
<< L->getHeader()->getParent()->getName() << "\" from "
<< DebugLocStr << "\n");
LoopVectorizeHints Hints(L, DisableUnrolling, *ORE);
DEBUG(dbgs() << "LV: Loop hints:"
<< " force="
<< (Hints.getForce() == LoopVectorizeHints::FK_Disabled
? "disabled"
: (Hints.getForce() == LoopVectorizeHints::FK_Enabled
? "enabled"
: "?"))
<< " width=" << Hints.getWidth()
<< " unroll=" << Hints.getInterleave() << "\n");
// Function containing loop
Function *F = L->getHeader()->getParent();
// Looking at the diagnostic output is the only way to determine if a loop
// was vectorized (other than looking at the IR or machine code), so it
// is important to generate an optimization remark for each loop. Most of
// these messages are generated as OptimizationRemarkAnalysis. Remarks
// generated as OptimizationRemark and OptimizationRemarkMissed are
// less verbose reporting vectorized loops and unvectorized loops that may
// benefit from vectorization, respectively.
if (!Hints.allowVectorization(F, L, AlwaysVectorize)) {
DEBUG(dbgs() << "LV: Loop hints prevent vectorization.\n");
return false;
}
PredicatedScalarEvolution PSE(*SE, *L);
// Check if it is legal to vectorize the loop.
LoopVectorizationRequirements Requirements(*ORE);
LoopVectorizationLegality LVL(L, PSE, DT, TLI, AA, F, GetLAA, LI, ORE,
&Requirements, &Hints, DB, AC);
if (!LVL.canVectorize(EnableVPlanNativePath)) {
DEBUG(dbgs() << "LV: Not vectorizing: Cannot prove legality.\n");
emitMissedWarning(F, L, Hints, ORE);
return false;
}
// Check the function attributes to find out if this function should be
// optimized for size.
bool OptForSize =
Hints.getForce() != LoopVectorizeHints::FK_Enabled && F->optForSize();
// Entrance to the VPlan-native vectorization path. Outer loops are processed
// here. They may require CFG and instruction level transformations before
// even evaluating whether vectorization is profitable. Since we cannot modify
// the incoming IR, we need to build VPlan upfront in the vectorization
// pipeline.
if (!L->empty())
return processLoopInVPlanNativePath(L, PSE, LI, DT, &LVL, TTI, TLI, DB, AC,
ORE, Hints);
assert(L->empty() && "Inner loop expected.");
// Check the loop for a trip count threshold: vectorize loops with a tiny trip
// count by optimizing for size, to minimize overheads.
// Prefer constant trip counts over profile data, over upper bound estimate.
unsigned ExpectedTC = 0;
bool HasExpectedTC = false;
if (const SCEVConstant *ConstExits =
dyn_cast<SCEVConstant>(SE->getBackedgeTakenCount(L))) {
const APInt &ExitsCount = ConstExits->getAPInt();
// We are interested in small values for ExpectedTC. Skip over those that
// can't fit an unsigned.
if (ExitsCount.ult(std::numeric_limits<unsigned>::max())) {
ExpectedTC = static_cast<unsigned>(ExitsCount.getZExtValue()) + 1;
HasExpectedTC = true;
}
}
// ExpectedTC may be large because it's bound by a variable. Check
// profiling information to validate we should vectorize.
if (!HasExpectedTC && LoopVectorizeWithBlockFrequency) {
auto EstimatedTC = getLoopEstimatedTripCount(L);
if (EstimatedTC) {
ExpectedTC = *EstimatedTC;
HasExpectedTC = true;
}
}
if (!HasExpectedTC) {
ExpectedTC = SE->getSmallConstantMaxTripCount(L);
HasExpectedTC = (ExpectedTC > 0);
}
if (HasExpectedTC && ExpectedTC < TinyTripCountVectorThreshold) {
DEBUG(dbgs() << "LV: Found a loop with a very small trip count. "
<< "This loop is worth vectorizing only if no scalar "
<< "iteration overheads are incurred.");
if (Hints.getForce() == LoopVectorizeHints::FK_Enabled)
DEBUG(dbgs() << " But vectorizing was explicitly forced.\n");
else {
DEBUG(dbgs() << "\n");
// Loops with a very small trip count are considered for vectorization
// under OptForSize, thereby making sure the cost of their loop body is
// dominant, free of runtime guards and scalar iteration overheads.
OptForSize = true;
}
}
// Check the function attributes to see if implicit floats are allowed.
// FIXME: This check doesn't seem possibly correct -- what if the loop is
// an integer loop and the vector instructions selected are purely integer
// vector instructions?
if (F->hasFnAttribute(Attribute::NoImplicitFloat)) {
DEBUG(dbgs() << "LV: Can't vectorize when the NoImplicitFloat"
"attribute is used.\n");
ORE->emit(createLVMissedAnalysis(Hints.vectorizeAnalysisPassName(),
"NoImplicitFloat", L)
<< "loop not vectorized due to NoImplicitFloat attribute");
emitMissedWarning(F, L, Hints, ORE);
return false;
}
// Check if the target supports potentially unsafe FP vectorization.
// FIXME: Add a check for the type of safety issue (denormal, signaling)
// for the target we're vectorizing for, to make sure none of the
// additional fp-math flags can help.
if (Hints.isPotentiallyUnsafe() &&
TTI->isFPVectorizationPotentiallyUnsafe()) {
DEBUG(dbgs() << "LV: Potentially unsafe FP op prevents vectorization.\n");
ORE->emit(
createLVMissedAnalysis(Hints.vectorizeAnalysisPassName(), "UnsafeFP", L)
<< "loop not vectorized due to unsafe FP support.");
emitMissedWarning(F, L, Hints, ORE);
return false;
}
bool UseInterleaved = TTI->enableInterleavedAccessVectorization();
InterleavedAccessInfo IAI(PSE, L, DT, LI, LVL.getLAI());
// If an override option has been passed in for interleaved accesses, use it.
if (EnableInterleavedMemAccesses.getNumOccurrences() > 0)
UseInterleaved = EnableInterleavedMemAccesses;
// Analyze interleaved memory accesses.
if (UseInterleaved) {
IAI.analyzeInterleaving();
}
// Use the cost model.
LoopVectorizationCostModel CM(L, PSE, LI, &LVL, *TTI, TLI, DB, AC, ORE, F,
&Hints, IAI);
CM.collectValuesToIgnore();
// Use the planner for vectorization.
LoopVectorizationPlanner LVP(L, LI, TLI, TTI, &LVL, CM);
// Get user vectorization factor.
unsigned UserVF = Hints.getWidth();
// Plan how to best vectorize, return the best VF and its cost.
VectorizationFactor VF = LVP.plan(OptForSize, UserVF);
// Select the interleave count.
unsigned IC = CM.selectInterleaveCount(OptForSize, VF.Width, VF.Cost);
// Get user interleave count.
unsigned UserIC = Hints.getInterleave();
// Identify the diagnostic messages that should be produced.
std::pair<StringRef, std::string> VecDiagMsg, IntDiagMsg;
bool VectorizeLoop = true, InterleaveLoop = true;
if (Requirements.doesNotMeet(F, L, Hints)) {
DEBUG(dbgs() << "LV: Not vectorizing: loop did not meet vectorization "
"requirements.\n");
emitMissedWarning(F, L, Hints, ORE);
return false;
}
if (VF.Width == 1) {
DEBUG(dbgs() << "LV: Vectorization is possible but not beneficial.\n");
VecDiagMsg = std::make_pair(
"VectorizationNotBeneficial",
"the cost-model indicates that vectorization is not beneficial");
VectorizeLoop = false;
}
if (IC == 1 && UserIC <= 1) {
// Tell the user interleaving is not beneficial.
DEBUG(dbgs() << "LV: Interleaving is not beneficial.\n");
IntDiagMsg = std::make_pair(
"InterleavingNotBeneficial",
"the cost-model indicates that interleaving is not beneficial");
InterleaveLoop = false;
if (UserIC == 1) {
IntDiagMsg.first = "InterleavingNotBeneficialAndDisabled";
IntDiagMsg.second +=
" and is explicitly disabled or interleave count is set to 1";
}
} else if (IC > 1 && UserIC == 1) {
// Tell the user interleaving is beneficial, but it explicitly disabled.
DEBUG(dbgs()
<< "LV: Interleaving is beneficial but is explicitly disabled.");
IntDiagMsg = std::make_pair(
"InterleavingBeneficialButDisabled",
"the cost-model indicates that interleaving is beneficial "
"but is explicitly disabled or interleave count is set to 1");
InterleaveLoop = false;
}
// Override IC if user provided an interleave count.
IC = UserIC > 0 ? UserIC : IC;
// Emit diagnostic messages, if any.
const char *VAPassName = Hints.vectorizeAnalysisPassName();
if (!VectorizeLoop && !InterleaveLoop) {
// Do not vectorize or interleaving the loop.
ORE->emit([&]() {
return OptimizationRemarkMissed(VAPassName, VecDiagMsg.first,
L->getStartLoc(), L->getHeader())
<< VecDiagMsg.second;
});
ORE->emit([&]() {
return OptimizationRemarkMissed(LV_NAME, IntDiagMsg.first,
L->getStartLoc(), L->getHeader())
<< IntDiagMsg.second;
});
return false;
} else if (!VectorizeLoop && InterleaveLoop) {
DEBUG(dbgs() << "LV: Interleave Count is " << IC << '\n');
ORE->emit([&]() {
return OptimizationRemarkAnalysis(VAPassName, VecDiagMsg.first,
L->getStartLoc(), L->getHeader())
<< VecDiagMsg.second;
});
} else if (VectorizeLoop && !InterleaveLoop) {
DEBUG(dbgs() << "LV: Found a vectorizable loop (" << VF.Width << ") in "
<< DebugLocStr << '\n');
ORE->emit([&]() {
return OptimizationRemarkAnalysis(LV_NAME, IntDiagMsg.first,
L->getStartLoc(), L->getHeader())
<< IntDiagMsg.second;
});
} else if (VectorizeLoop && InterleaveLoop) {
DEBUG(dbgs() << "LV: Found a vectorizable loop (" << VF.Width << ") in "
<< DebugLocStr << '\n');
DEBUG(dbgs() << "LV: Interleave Count is " << IC << '\n');
}
LVP.setBestPlan(VF.Width, IC);
using namespace ore;
if (!VectorizeLoop) {
assert(IC > 1 && "interleave count should not be 1 or 0");
// If we decided that it is not legal to vectorize the loop, then
// interleave it.
InnerLoopUnroller Unroller(L, PSE, LI, DT, TLI, TTI, AC, ORE, IC, &LVL,
&CM);
LVP.executePlan(Unroller, DT);
ORE->emit([&]() {
return OptimizationRemark(LV_NAME, "Interleaved", L->getStartLoc(),
L->getHeader())
<< "interleaved loop (interleaved count: "
<< NV("InterleaveCount", IC) << ")";
});
} else {
// If we decided that it is *legal* to vectorize the loop, then do it.
InnerLoopVectorizer LB(L, PSE, LI, DT, TLI, TTI, AC, ORE, VF.Width, IC,
&LVL, &CM);
LVP.executePlan(LB, DT);
++LoopsVectorized;
// Add metadata to disable runtime unrolling a scalar loop when there are
// no runtime checks about strides and memory. A scalar loop that is
// rarely used is not worth unrolling.
if (!LB.areSafetyChecksAdded())
AddRuntimeUnrollDisableMetaData(L);
// Report the vectorization decision.
ORE->emit([&]() {
return OptimizationRemark(LV_NAME, "Vectorized", L->getStartLoc(),
L->getHeader())
<< "vectorized loop (vectorization width: "
<< NV("VectorizationFactor", VF.Width)
<< ", interleaved count: " << NV("InterleaveCount", IC) << ")";
});
}
// Mark the loop as already vectorized to avoid vectorizing again.
Hints.setAlreadyVectorized();
DEBUG(verifyFunction(*L->getHeader()->getParent()));
return true;
}
bool LoopVectorizePass::runImpl(
Function &F, ScalarEvolution &SE_, LoopInfo &LI_, TargetTransformInfo &TTI_,
DominatorTree &DT_, BlockFrequencyInfo &BFI_, TargetLibraryInfo *TLI_,
DemandedBits &DB_, AliasAnalysis &AA_, AssumptionCache &AC_,
std::function<const LoopAccessInfo &(Loop &)> &GetLAA_,
OptimizationRemarkEmitter &ORE_) {
SE = &SE_;
LI = &LI_;
TTI = &TTI_;
DT = &DT_;
BFI = &BFI_;
TLI = TLI_;
AA = &AA_;
AC = &AC_;
GetLAA = &GetLAA_;
DB = &DB_;
ORE = &ORE_;
// Don't attempt if
// 1. the target claims to have no vector registers, and
// 2. interleaving won't help ILP.
//
// The second condition is necessary because, even if the target has no
// vector registers, loop vectorization may still enable scalar
// interleaving.
if (!TTI->getNumberOfRegisters(true) && TTI->getMaxInterleaveFactor(1) < 2)
return false;
bool Changed = false;
// The vectorizer requires loops to be in simplified form.
// Since simplification may add new inner loops, it has to run before the
// legality and profitability checks. This means running the loop vectorizer
// will simplify all loops, regardless of whether anything end up being
// vectorized.
for (auto &L : *LI)
Changed |= simplifyLoop(L, DT, LI, SE, AC, false /* PreserveLCSSA */);
// Build up a worklist of inner-loops to vectorize. This is necessary as
// the act of vectorizing or partially unrolling a loop creates new loops
// and can invalidate iterators across the loops.
SmallVector<Loop *, 8> Worklist;
for (Loop *L : *LI)
collectSupportedLoops(*L, LI, ORE, Worklist);
LoopsAnalyzed += Worklist.size();
// Now walk the identified inner loops.
while (!Worklist.empty()) {
Loop *L = Worklist.pop_back_val();
// For the inner loops we actually process, form LCSSA to simplify the
// transform.
Changed |= formLCSSARecursively(*L, *DT, LI, SE);
Changed |= processLoop(L);
}
// Process each loop nest in the function.
return Changed;
}
PreservedAnalyses LoopVectorizePass::run(Function &F,
FunctionAnalysisManager &AM) {
auto &SE = AM.getResult<ScalarEvolutionAnalysis>(F);
auto &LI = AM.getResult<LoopAnalysis>(F);
auto &TTI = AM.getResult<TargetIRAnalysis>(F);
auto &DT = AM.getResult<DominatorTreeAnalysis>(F);
auto &BFI = AM.getResult<BlockFrequencyAnalysis>(F);
auto &TLI = AM.getResult<TargetLibraryAnalysis>(F);
auto &AA = AM.getResult<AAManager>(F);
auto &AC = AM.getResult<AssumptionAnalysis>(F);
auto &DB = AM.getResult<DemandedBitsAnalysis>(F);
auto &ORE = AM.getResult<OptimizationRemarkEmitterAnalysis>(F);
auto &LAM = AM.getResult<LoopAnalysisManagerFunctionProxy>(F).getManager();
std::function<const LoopAccessInfo &(Loop &)> GetLAA =
[&](Loop &L) -> const LoopAccessInfo & {
LoopStandardAnalysisResults AR = {AA, AC, DT, LI, SE, TLI, TTI, nullptr};
return LAM.getResult<LoopAccessAnalysis>(L, AR);
};
bool Changed =
runImpl(F, SE, LI, TTI, DT, BFI, &TLI, DB, AA, AC, GetLAA, ORE);
if (!Changed)
return PreservedAnalyses::all();
PreservedAnalyses PA;
PA.preserve<LoopAnalysis>();
PA.preserve<DominatorTreeAnalysis>();
PA.preserve<BasicAA>();
PA.preserve<GlobalsAA>();
return PA;
}