| //===- InstCombineSelect.cpp ----------------------------------------------===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This file implements the visitSelect function. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "InstCombineInternal.h" |
| #include "llvm/Analysis/ConstantFolding.h" |
| #include "llvm/Analysis/InstructionSimplify.h" |
| #include "llvm/Analysis/ValueTracking.h" |
| #include "llvm/IR/PatternMatch.h" |
| using namespace llvm; |
| using namespace PatternMatch; |
| |
| #define DEBUG_TYPE "instcombine" |
| |
| static SelectPatternFlavor |
| getInverseMinMaxSelectPattern(SelectPatternFlavor SPF) { |
| switch (SPF) { |
| default: |
| llvm_unreachable("unhandled!"); |
| |
| case SPF_SMIN: |
| return SPF_SMAX; |
| case SPF_UMIN: |
| return SPF_UMAX; |
| case SPF_SMAX: |
| return SPF_SMIN; |
| case SPF_UMAX: |
| return SPF_UMIN; |
| } |
| } |
| |
| static CmpInst::Predicate getCmpPredicateForMinMax(SelectPatternFlavor SPF, |
| bool Ordered=false) { |
| switch (SPF) { |
| default: |
| llvm_unreachable("unhandled!"); |
| |
| case SPF_SMIN: |
| return ICmpInst::ICMP_SLT; |
| case SPF_UMIN: |
| return ICmpInst::ICMP_ULT; |
| case SPF_SMAX: |
| return ICmpInst::ICMP_SGT; |
| case SPF_UMAX: |
| return ICmpInst::ICMP_UGT; |
| case SPF_FMINNUM: |
| return Ordered ? FCmpInst::FCMP_OLT : FCmpInst::FCMP_ULT; |
| case SPF_FMAXNUM: |
| return Ordered ? FCmpInst::FCMP_OGT : FCmpInst::FCMP_UGT; |
| } |
| } |
| |
| static Value *generateMinMaxSelectPattern(InstCombiner::BuilderTy *Builder, |
| SelectPatternFlavor SPF, Value *A, |
| Value *B) { |
| CmpInst::Predicate Pred = getCmpPredicateForMinMax(SPF); |
| assert(CmpInst::isIntPredicate(Pred)); |
| return Builder->CreateSelect(Builder->CreateICmp(Pred, A, B), A, B); |
| } |
| |
| /// We want to turn code that looks like this: |
| /// %C = or %A, %B |
| /// %D = select %cond, %C, %A |
| /// into: |
| /// %C = select %cond, %B, 0 |
| /// %D = or %A, %C |
| /// |
| /// Assuming that the specified instruction is an operand to the select, return |
| /// a bitmask indicating which operands of this instruction are foldable if they |
| /// equal the other incoming value of the select. |
| /// |
| static unsigned GetSelectFoldableOperands(Instruction *I) { |
| switch (I->getOpcode()) { |
| case Instruction::Add: |
| case Instruction::Mul: |
| case Instruction::And: |
| case Instruction::Or: |
| case Instruction::Xor: |
| return 3; // Can fold through either operand. |
| case Instruction::Sub: // Can only fold on the amount subtracted. |
| case Instruction::Shl: // Can only fold on the shift amount. |
| case Instruction::LShr: |
| case Instruction::AShr: |
| return 1; |
| default: |
| return 0; // Cannot fold |
| } |
| } |
| |
| /// For the same transformation as the previous function, return the identity |
| /// constant that goes into the select. |
| static Constant *GetSelectFoldableConstant(Instruction *I) { |
| switch (I->getOpcode()) { |
| default: llvm_unreachable("This cannot happen!"); |
| case Instruction::Add: |
| case Instruction::Sub: |
| case Instruction::Or: |
| case Instruction::Xor: |
| case Instruction::Shl: |
| case Instruction::LShr: |
| case Instruction::AShr: |
| return Constant::getNullValue(I->getType()); |
| case Instruction::And: |
| return Constant::getAllOnesValue(I->getType()); |
| case Instruction::Mul: |
| return ConstantInt::get(I->getType(), 1); |
| } |
| } |
| |
| /// We have (select c, TI, FI), and we know that TI and FI have the same opcode. |
| Instruction *InstCombiner::FoldSelectOpOp(SelectInst &SI, Instruction *TI, |
| Instruction *FI) { |
| // If this is a cast from the same type, merge. |
| if (TI->getNumOperands() == 1 && TI->isCast()) { |
| Type *FIOpndTy = FI->getOperand(0)->getType(); |
| if (TI->getOperand(0)->getType() != FIOpndTy) |
| return nullptr; |
| |
| // The select condition may be a vector. We may only change the operand |
| // type if the vector width remains the same (and matches the condition). |
| Type *CondTy = SI.getCondition()->getType(); |
| if (CondTy->isVectorTy()) { |
| if (!FIOpndTy->isVectorTy()) |
| return nullptr; |
| if (CondTy->getVectorNumElements() != FIOpndTy->getVectorNumElements()) |
| return nullptr; |
| |
| // TODO: If the backend knew how to deal with casts better, we could |
| // remove this limitation. For now, there's too much potential to create |
| // worse codegen by promoting the select ahead of size-altering casts |
| // (PR28160). |
| // |
| // Note that ValueTracking's matchSelectPattern() looks through casts |
| // without checking 'hasOneUse' when it matches min/max patterns, so this |
| // transform may end up happening anyway. |
| if (TI->getOpcode() != Instruction::BitCast && |
| (!TI->hasOneUse() || !FI->hasOneUse())) |
| return nullptr; |
| |
| } else if (!TI->hasOneUse() || !FI->hasOneUse()) { |
| // TODO: The one-use restrictions for a scalar select could be eased if |
| // the fold of a select in visitLoadInst() was enhanced to match a pattern |
| // that includes a cast. |
| return nullptr; |
| } |
| |
| // Fold this by inserting a select from the input values. |
| Value *NewSI = Builder->CreateSelect(SI.getCondition(), TI->getOperand(0), |
| FI->getOperand(0), SI.getName()+".v"); |
| return CastInst::Create(Instruction::CastOps(TI->getOpcode()), NewSI, |
| TI->getType()); |
| } |
| |
| // TODO: This function ends awkwardly in unreachable - fix to be more normal. |
| |
| // Only handle binary operators with one-use here. As with the cast case |
| // above, it may be possible to relax the one-use constraint, but that needs |
| // be examined carefully since it may not reduce the total number of |
| // instructions. |
| if (!isa<BinaryOperator>(TI) || !TI->hasOneUse() || !FI->hasOneUse()) |
| return nullptr; |
| |
| // Figure out if the operations have any operands in common. |
| Value *MatchOp, *OtherOpT, *OtherOpF; |
| bool MatchIsOpZero; |
| if (TI->getOperand(0) == FI->getOperand(0)) { |
| MatchOp = TI->getOperand(0); |
| OtherOpT = TI->getOperand(1); |
| OtherOpF = FI->getOperand(1); |
| MatchIsOpZero = true; |
| } else if (TI->getOperand(1) == FI->getOperand(1)) { |
| MatchOp = TI->getOperand(1); |
| OtherOpT = TI->getOperand(0); |
| OtherOpF = FI->getOperand(0); |
| MatchIsOpZero = false; |
| } else if (!TI->isCommutative()) { |
| return nullptr; |
| } else if (TI->getOperand(0) == FI->getOperand(1)) { |
| MatchOp = TI->getOperand(0); |
| OtherOpT = TI->getOperand(1); |
| OtherOpF = FI->getOperand(0); |
| MatchIsOpZero = true; |
| } else if (TI->getOperand(1) == FI->getOperand(0)) { |
| MatchOp = TI->getOperand(1); |
| OtherOpT = TI->getOperand(0); |
| OtherOpF = FI->getOperand(1); |
| MatchIsOpZero = true; |
| } else { |
| return nullptr; |
| } |
| |
| // If we reach here, they do have operations in common. |
| Value *NewSI = Builder->CreateSelect(SI.getCondition(), OtherOpT, |
| OtherOpF, SI.getName()+".v"); |
| |
| if (BinaryOperator *BO = dyn_cast<BinaryOperator>(TI)) { |
| if (MatchIsOpZero) |
| return BinaryOperator::Create(BO->getOpcode(), MatchOp, NewSI); |
| else |
| return BinaryOperator::Create(BO->getOpcode(), NewSI, MatchOp); |
| } |
| llvm_unreachable("Shouldn't get here"); |
| } |
| |
| static bool isSelect01(Constant *C1, Constant *C2) { |
| ConstantInt *C1I = dyn_cast<ConstantInt>(C1); |
| if (!C1I) |
| return false; |
| ConstantInt *C2I = dyn_cast<ConstantInt>(C2); |
| if (!C2I) |
| return false; |
| if (!C1I->isZero() && !C2I->isZero()) // One side must be zero. |
| return false; |
| return C1I->isOne() || C1I->isAllOnesValue() || |
| C2I->isOne() || C2I->isAllOnesValue(); |
| } |
| |
| /// Try to fold the select into one of the operands to allow further |
| /// optimization. |
| Instruction *InstCombiner::FoldSelectIntoOp(SelectInst &SI, Value *TrueVal, |
| Value *FalseVal) { |
| // See the comment above GetSelectFoldableOperands for a description of the |
| // transformation we are doing here. |
| if (Instruction *TVI = dyn_cast<Instruction>(TrueVal)) { |
| if (TVI->hasOneUse() && TVI->getNumOperands() == 2 && |
| !isa<Constant>(FalseVal)) { |
| if (unsigned SFO = GetSelectFoldableOperands(TVI)) { |
| unsigned OpToFold = 0; |
| if ((SFO & 1) && FalseVal == TVI->getOperand(0)) { |
| OpToFold = 1; |
| } else if ((SFO & 2) && FalseVal == TVI->getOperand(1)) { |
| OpToFold = 2; |
| } |
| |
| if (OpToFold) { |
| Constant *C = GetSelectFoldableConstant(TVI); |
| Value *OOp = TVI->getOperand(2-OpToFold); |
| // Avoid creating select between 2 constants unless it's selecting |
| // between 0, 1 and -1. |
| if (!isa<Constant>(OOp) || isSelect01(C, cast<Constant>(OOp))) { |
| Value *NewSel = Builder->CreateSelect(SI.getCondition(), OOp, C); |
| NewSel->takeName(TVI); |
| BinaryOperator *TVI_BO = cast<BinaryOperator>(TVI); |
| BinaryOperator *BO = BinaryOperator::Create(TVI_BO->getOpcode(), |
| FalseVal, NewSel); |
| BO->copyIRFlags(TVI_BO); |
| return BO; |
| } |
| } |
| } |
| } |
| } |
| |
| if (Instruction *FVI = dyn_cast<Instruction>(FalseVal)) { |
| if (FVI->hasOneUse() && FVI->getNumOperands() == 2 && |
| !isa<Constant>(TrueVal)) { |
| if (unsigned SFO = GetSelectFoldableOperands(FVI)) { |
| unsigned OpToFold = 0; |
| if ((SFO & 1) && TrueVal == FVI->getOperand(0)) { |
| OpToFold = 1; |
| } else if ((SFO & 2) && TrueVal == FVI->getOperand(1)) { |
| OpToFold = 2; |
| } |
| |
| if (OpToFold) { |
| Constant *C = GetSelectFoldableConstant(FVI); |
| Value *OOp = FVI->getOperand(2-OpToFold); |
| // Avoid creating select between 2 constants unless it's selecting |
| // between 0, 1 and -1. |
| if (!isa<Constant>(OOp) || isSelect01(C, cast<Constant>(OOp))) { |
| Value *NewSel = Builder->CreateSelect(SI.getCondition(), C, OOp); |
| NewSel->takeName(FVI); |
| BinaryOperator *FVI_BO = cast<BinaryOperator>(FVI); |
| BinaryOperator *BO = BinaryOperator::Create(FVI_BO->getOpcode(), |
| TrueVal, NewSel); |
| BO->copyIRFlags(FVI_BO); |
| return BO; |
| } |
| } |
| } |
| } |
| } |
| |
| return nullptr; |
| } |
| |
| /// We want to turn: |
| /// (select (icmp eq (and X, C1), 0), Y, (or Y, C2)) |
| /// into: |
| /// (or (shl (and X, C1), C3), y) |
| /// iff: |
| /// C1 and C2 are both powers of 2 |
| /// where: |
| /// C3 = Log(C2) - Log(C1) |
| /// |
| /// This transform handles cases where: |
| /// 1. The icmp predicate is inverted |
| /// 2. The select operands are reversed |
| /// 3. The magnitude of C2 and C1 are flipped |
| static Value *foldSelectICmpAndOr(const SelectInst &SI, Value *TrueVal, |
| Value *FalseVal, |
| InstCombiner::BuilderTy *Builder) { |
| const ICmpInst *IC = dyn_cast<ICmpInst>(SI.getCondition()); |
| if (!IC || !IC->isEquality() || !SI.getType()->isIntegerTy()) |
| return nullptr; |
| |
| Value *CmpLHS = IC->getOperand(0); |
| Value *CmpRHS = IC->getOperand(1); |
| |
| if (!match(CmpRHS, m_Zero())) |
| return nullptr; |
| |
| Value *X; |
| const APInt *C1; |
| if (!match(CmpLHS, m_And(m_Value(X), m_Power2(C1)))) |
| return nullptr; |
| |
| const APInt *C2; |
| bool OrOnTrueVal = false; |
| bool OrOnFalseVal = match(FalseVal, m_Or(m_Specific(TrueVal), m_Power2(C2))); |
| if (!OrOnFalseVal) |
| OrOnTrueVal = match(TrueVal, m_Or(m_Specific(FalseVal), m_Power2(C2))); |
| |
| if (!OrOnFalseVal && !OrOnTrueVal) |
| return nullptr; |
| |
| Value *V = CmpLHS; |
| Value *Y = OrOnFalseVal ? TrueVal : FalseVal; |
| |
| unsigned C1Log = C1->logBase2(); |
| unsigned C2Log = C2->logBase2(); |
| if (C2Log > C1Log) { |
| V = Builder->CreateZExtOrTrunc(V, Y->getType()); |
| V = Builder->CreateShl(V, C2Log - C1Log); |
| } else if (C1Log > C2Log) { |
| V = Builder->CreateLShr(V, C1Log - C2Log); |
| V = Builder->CreateZExtOrTrunc(V, Y->getType()); |
| } else |
| V = Builder->CreateZExtOrTrunc(V, Y->getType()); |
| |
| ICmpInst::Predicate Pred = IC->getPredicate(); |
| if ((Pred == ICmpInst::ICMP_NE && OrOnFalseVal) || |
| (Pred == ICmpInst::ICMP_EQ && OrOnTrueVal)) |
| V = Builder->CreateXor(V, *C2); |
| |
| return Builder->CreateOr(V, Y); |
| } |
| |
| /// Attempt to fold a cttz/ctlz followed by a icmp plus select into a single |
| /// call to cttz/ctlz with flag 'is_zero_undef' cleared. |
| /// |
| /// For example, we can fold the following code sequence: |
| /// \code |
| /// %0 = tail call i32 @llvm.cttz.i32(i32 %x, i1 true) |
| /// %1 = icmp ne i32 %x, 0 |
| /// %2 = select i1 %1, i32 %0, i32 32 |
| /// \code |
| /// |
| /// into: |
| /// %0 = tail call i32 @llvm.cttz.i32(i32 %x, i1 false) |
| static Value *foldSelectCttzCtlz(ICmpInst *ICI, Value *TrueVal, Value *FalseVal, |
| InstCombiner::BuilderTy *Builder) { |
| ICmpInst::Predicate Pred = ICI->getPredicate(); |
| Value *CmpLHS = ICI->getOperand(0); |
| Value *CmpRHS = ICI->getOperand(1); |
| |
| // Check if the condition value compares a value for equality against zero. |
| if (!ICI->isEquality() || !match(CmpRHS, m_Zero())) |
| return nullptr; |
| |
| Value *Count = FalseVal; |
| Value *ValueOnZero = TrueVal; |
| if (Pred == ICmpInst::ICMP_NE) |
| std::swap(Count, ValueOnZero); |
| |
| // Skip zero extend/truncate. |
| Value *V = nullptr; |
| if (match(Count, m_ZExt(m_Value(V))) || |
| match(Count, m_Trunc(m_Value(V)))) |
| Count = V; |
| |
| // Check if the value propagated on zero is a constant number equal to the |
| // sizeof in bits of 'Count'. |
| unsigned SizeOfInBits = Count->getType()->getScalarSizeInBits(); |
| if (!match(ValueOnZero, m_SpecificInt(SizeOfInBits))) |
| return nullptr; |
| |
| // Check that 'Count' is a call to intrinsic cttz/ctlz. Also check that the |
| // input to the cttz/ctlz is used as LHS for the compare instruction. |
| if (match(Count, m_Intrinsic<Intrinsic::cttz>(m_Specific(CmpLHS))) || |
| match(Count, m_Intrinsic<Intrinsic::ctlz>(m_Specific(CmpLHS)))) { |
| IntrinsicInst *II = cast<IntrinsicInst>(Count); |
| IRBuilder<> Builder(II); |
| // Explicitly clear the 'undef_on_zero' flag. |
| IntrinsicInst *NewI = cast<IntrinsicInst>(II->clone()); |
| Type *Ty = NewI->getArgOperand(1)->getType(); |
| NewI->setArgOperand(1, Constant::getNullValue(Ty)); |
| Builder.Insert(NewI); |
| return Builder.CreateZExtOrTrunc(NewI, ValueOnZero->getType()); |
| } |
| |
| return nullptr; |
| } |
| |
| /// Visit a SelectInst that has an ICmpInst as its first operand. |
| Instruction *InstCombiner::visitSelectInstWithICmp(SelectInst &SI, |
| ICmpInst *ICI) { |
| bool Changed = false; |
| ICmpInst::Predicate Pred = ICI->getPredicate(); |
| Value *CmpLHS = ICI->getOperand(0); |
| Value *CmpRHS = ICI->getOperand(1); |
| Value *TrueVal = SI.getTrueValue(); |
| Value *FalseVal = SI.getFalseValue(); |
| |
| // Check cases where the comparison is with a constant that |
| // can be adjusted to fit the min/max idiom. We may move or edit ICI |
| // here, so make sure the select is the only user. |
| if (ICI->hasOneUse()) |
| if (ConstantInt *CI = dyn_cast<ConstantInt>(CmpRHS)) { |
| switch (Pred) { |
| default: break; |
| case ICmpInst::ICMP_ULT: |
| case ICmpInst::ICMP_SLT: |
| case ICmpInst::ICMP_UGT: |
| case ICmpInst::ICMP_SGT: { |
| // These transformations only work for selects over integers. |
| IntegerType *SelectTy = dyn_cast<IntegerType>(SI.getType()); |
| if (!SelectTy) |
| break; |
| |
| Constant *AdjustedRHS; |
| if (Pred == ICmpInst::ICMP_UGT || Pred == ICmpInst::ICMP_SGT) |
| AdjustedRHS = ConstantInt::get(CI->getContext(), CI->getValue() + 1); |
| else // (Pred == ICmpInst::ICMP_ULT || Pred == ICmpInst::ICMP_SLT) |
| AdjustedRHS = ConstantInt::get(CI->getContext(), CI->getValue() - 1); |
| |
| // X > C ? X : C+1 --> X < C+1 ? C+1 : X |
| // X < C ? X : C-1 --> X > C-1 ? C-1 : X |
| if ((CmpLHS == TrueVal && AdjustedRHS == FalseVal) || |
| (CmpLHS == FalseVal && AdjustedRHS == TrueVal)) |
| ; // Nothing to do here. Values match without any sign/zero extension. |
| |
| // Types do not match. Instead of calculating this with mixed types |
| // promote all to the larger type. This enables scalar evolution to |
| // analyze this expression. |
| else if (CmpRHS->getType()->getScalarSizeInBits() |
| < SelectTy->getBitWidth()) { |
| Constant *sextRHS = ConstantExpr::getSExt(AdjustedRHS, SelectTy); |
| |
| // X = sext x; x >s c ? X : C+1 --> X = sext x; X <s C+1 ? C+1 : X |
| // X = sext x; x <s c ? X : C-1 --> X = sext x; X >s C-1 ? C-1 : X |
| // X = sext x; x >u c ? X : C+1 --> X = sext x; X <u C+1 ? C+1 : X |
| // X = sext x; x <u c ? X : C-1 --> X = sext x; X >u C-1 ? C-1 : X |
| if (match(TrueVal, m_SExt(m_Specific(CmpLHS))) && |
| sextRHS == FalseVal) { |
| CmpLHS = TrueVal; |
| AdjustedRHS = sextRHS; |
| } else if (match(FalseVal, m_SExt(m_Specific(CmpLHS))) && |
| sextRHS == TrueVal) { |
| CmpLHS = FalseVal; |
| AdjustedRHS = sextRHS; |
| } else if (ICI->isUnsigned()) { |
| Constant *zextRHS = ConstantExpr::getZExt(AdjustedRHS, SelectTy); |
| // X = zext x; x >u c ? X : C+1 --> X = zext x; X <u C+1 ? C+1 : X |
| // X = zext x; x <u c ? X : C-1 --> X = zext x; X >u C-1 ? C-1 : X |
| // zext + signed compare cannot be changed: |
| // 0xff <s 0x00, but 0x00ff >s 0x0000 |
| if (match(TrueVal, m_ZExt(m_Specific(CmpLHS))) && |
| zextRHS == FalseVal) { |
| CmpLHS = TrueVal; |
| AdjustedRHS = zextRHS; |
| } else if (match(FalseVal, m_ZExt(m_Specific(CmpLHS))) && |
| zextRHS == TrueVal) { |
| CmpLHS = FalseVal; |
| AdjustedRHS = zextRHS; |
| } else |
| break; |
| } else |
| break; |
| } else |
| break; |
| |
| Pred = ICmpInst::getSwappedPredicate(Pred); |
| CmpRHS = AdjustedRHS; |
| std::swap(FalseVal, TrueVal); |
| ICI->setPredicate(Pred); |
| ICI->setOperand(0, CmpLHS); |
| ICI->setOperand(1, CmpRHS); |
| SI.setOperand(1, TrueVal); |
| SI.setOperand(2, FalseVal); |
| |
| // Move ICI instruction right before the select instruction. Otherwise |
| // the sext/zext value may be defined after the ICI instruction uses it. |
| ICI->moveBefore(&SI); |
| |
| Changed = true; |
| break; |
| } |
| } |
| } |
| |
| // Transform (X >s -1) ? C1 : C2 --> ((X >>s 31) & (C2 - C1)) + C1 |
| // and (X <s 0) ? C2 : C1 --> ((X >>s 31) & (C2 - C1)) + C1 |
| // FIXME: Type and constness constraints could be lifted, but we have to |
| // watch code size carefully. We should consider xor instead of |
| // sub/add when we decide to do that. |
| if (IntegerType *Ty = dyn_cast<IntegerType>(CmpLHS->getType())) { |
| if (TrueVal->getType() == Ty) { |
| if (ConstantInt *Cmp = dyn_cast<ConstantInt>(CmpRHS)) { |
| ConstantInt *C1 = nullptr, *C2 = nullptr; |
| if (Pred == ICmpInst::ICMP_SGT && Cmp->isAllOnesValue()) { |
| C1 = dyn_cast<ConstantInt>(TrueVal); |
| C2 = dyn_cast<ConstantInt>(FalseVal); |
| } else if (Pred == ICmpInst::ICMP_SLT && Cmp->isNullValue()) { |
| C1 = dyn_cast<ConstantInt>(FalseVal); |
| C2 = dyn_cast<ConstantInt>(TrueVal); |
| } |
| if (C1 && C2) { |
| // This shift results in either -1 or 0. |
| Value *AShr = Builder->CreateAShr(CmpLHS, Ty->getBitWidth()-1); |
| |
| // Check if we can express the operation with a single or. |
| if (C2->isAllOnesValue()) |
| return replaceInstUsesWith(SI, Builder->CreateOr(AShr, C1)); |
| |
| Value *And = Builder->CreateAnd(AShr, C2->getValue()-C1->getValue()); |
| return replaceInstUsesWith(SI, Builder->CreateAdd(And, C1)); |
| } |
| } |
| } |
| } |
| |
| // NOTE: if we wanted to, this is where to detect integer MIN/MAX |
| |
| if (CmpRHS != CmpLHS && isa<Constant>(CmpRHS)) { |
| if (CmpLHS == TrueVal && Pred == ICmpInst::ICMP_EQ) { |
| // Transform (X == C) ? X : Y -> (X == C) ? C : Y |
| SI.setOperand(1, CmpRHS); |
| Changed = true; |
| } else if (CmpLHS == FalseVal && Pred == ICmpInst::ICMP_NE) { |
| // Transform (X != C) ? Y : X -> (X != C) ? Y : C |
| SI.setOperand(2, CmpRHS); |
| Changed = true; |
| } |
| } |
| |
| { |
| unsigned BitWidth = DL.getTypeSizeInBits(TrueVal->getType()); |
| APInt MinSignedValue = APInt::getSignBit(BitWidth); |
| Value *X; |
| const APInt *Y, *C; |
| bool TrueWhenUnset; |
| bool IsBitTest = false; |
| if (ICmpInst::isEquality(Pred) && |
| match(CmpLHS, m_And(m_Value(X), m_Power2(Y))) && |
| match(CmpRHS, m_Zero())) { |
| IsBitTest = true; |
| TrueWhenUnset = Pred == ICmpInst::ICMP_EQ; |
| } else if (Pred == ICmpInst::ICMP_SLT && match(CmpRHS, m_Zero())) { |
| X = CmpLHS; |
| Y = &MinSignedValue; |
| IsBitTest = true; |
| TrueWhenUnset = false; |
| } else if (Pred == ICmpInst::ICMP_SGT && match(CmpRHS, m_AllOnes())) { |
| X = CmpLHS; |
| Y = &MinSignedValue; |
| IsBitTest = true; |
| TrueWhenUnset = true; |
| } |
| if (IsBitTest) { |
| Value *V = nullptr; |
| // (X & Y) == 0 ? X : X ^ Y --> X & ~Y |
| if (TrueWhenUnset && TrueVal == X && |
| match(FalseVal, m_Xor(m_Specific(X), m_APInt(C))) && *Y == *C) |
| V = Builder->CreateAnd(X, ~(*Y)); |
| // (X & Y) != 0 ? X ^ Y : X --> X & ~Y |
| else if (!TrueWhenUnset && FalseVal == X && |
| match(TrueVal, m_Xor(m_Specific(X), m_APInt(C))) && *Y == *C) |
| V = Builder->CreateAnd(X, ~(*Y)); |
| // (X & Y) == 0 ? X ^ Y : X --> X | Y |
| else if (TrueWhenUnset && FalseVal == X && |
| match(TrueVal, m_Xor(m_Specific(X), m_APInt(C))) && *Y == *C) |
| V = Builder->CreateOr(X, *Y); |
| // (X & Y) != 0 ? X : X ^ Y --> X | Y |
| else if (!TrueWhenUnset && TrueVal == X && |
| match(FalseVal, m_Xor(m_Specific(X), m_APInt(C))) && *Y == *C) |
| V = Builder->CreateOr(X, *Y); |
| |
| if (V) |
| return replaceInstUsesWith(SI, V); |
| } |
| } |
| |
| if (Value *V = foldSelectICmpAndOr(SI, TrueVal, FalseVal, Builder)) |
| return replaceInstUsesWith(SI, V); |
| |
| if (Value *V = foldSelectCttzCtlz(ICI, TrueVal, FalseVal, Builder)) |
| return replaceInstUsesWith(SI, V); |
| |
| return Changed ? &SI : nullptr; |
| } |
| |
| |
| /// SI is a select whose condition is a PHI node (but the two may be in |
| /// different blocks). See if the true/false values (V) are live in all of the |
| /// predecessor blocks of the PHI. For example, cases like this can't be mapped: |
| /// |
| /// X = phi [ C1, BB1], [C2, BB2] |
| /// Y = add |
| /// Z = select X, Y, 0 |
| /// |
| /// because Y is not live in BB1/BB2. |
| /// |
| static bool CanSelectOperandBeMappingIntoPredBlock(const Value *V, |
| const SelectInst &SI) { |
| // If the value is a non-instruction value like a constant or argument, it |
| // can always be mapped. |
| const Instruction *I = dyn_cast<Instruction>(V); |
| if (!I) return true; |
| |
| // If V is a PHI node defined in the same block as the condition PHI, we can |
| // map the arguments. |
| const PHINode *CondPHI = cast<PHINode>(SI.getCondition()); |
| |
| if (const PHINode *VP = dyn_cast<PHINode>(I)) |
| if (VP->getParent() == CondPHI->getParent()) |
| return true; |
| |
| // Otherwise, if the PHI and select are defined in the same block and if V is |
| // defined in a different block, then we can transform it. |
| if (SI.getParent() == CondPHI->getParent() && |
| I->getParent() != CondPHI->getParent()) |
| return true; |
| |
| // Otherwise we have a 'hard' case and we can't tell without doing more |
| // detailed dominator based analysis, punt. |
| return false; |
| } |
| |
| /// We have an SPF (e.g. a min or max) of an SPF of the form: |
| /// SPF2(SPF1(A, B), C) |
| Instruction *InstCombiner::FoldSPFofSPF(Instruction *Inner, |
| SelectPatternFlavor SPF1, |
| Value *A, Value *B, |
| Instruction &Outer, |
| SelectPatternFlavor SPF2, Value *C) { |
| if (Outer.getType() != Inner->getType()) |
| return nullptr; |
| |
| if (C == A || C == B) { |
| // MAX(MAX(A, B), B) -> MAX(A, B) |
| // MIN(MIN(a, b), a) -> MIN(a, b) |
| if (SPF1 == SPF2) |
| return replaceInstUsesWith(Outer, Inner); |
| |
| // MAX(MIN(a, b), a) -> a |
| // MIN(MAX(a, b), a) -> a |
| if ((SPF1 == SPF_SMIN && SPF2 == SPF_SMAX) || |
| (SPF1 == SPF_SMAX && SPF2 == SPF_SMIN) || |
| (SPF1 == SPF_UMIN && SPF2 == SPF_UMAX) || |
| (SPF1 == SPF_UMAX && SPF2 == SPF_UMIN)) |
| return replaceInstUsesWith(Outer, C); |
| } |
| |
| if (SPF1 == SPF2) { |
| if (ConstantInt *CB = dyn_cast<ConstantInt>(B)) { |
| if (ConstantInt *CC = dyn_cast<ConstantInt>(C)) { |
| const APInt &ACB = CB->getValue(); |
| const APInt &ACC = CC->getValue(); |
| |
| // MIN(MIN(A, 23), 97) -> MIN(A, 23) |
| // MAX(MAX(A, 97), 23) -> MAX(A, 97) |
| if ((SPF1 == SPF_UMIN && ACB.ule(ACC)) || |
| (SPF1 == SPF_SMIN && ACB.sle(ACC)) || |
| (SPF1 == SPF_UMAX && ACB.uge(ACC)) || |
| (SPF1 == SPF_SMAX && ACB.sge(ACC))) |
| return replaceInstUsesWith(Outer, Inner); |
| |
| // MIN(MIN(A, 97), 23) -> MIN(A, 23) |
| // MAX(MAX(A, 23), 97) -> MAX(A, 97) |
| if ((SPF1 == SPF_UMIN && ACB.ugt(ACC)) || |
| (SPF1 == SPF_SMIN && ACB.sgt(ACC)) || |
| (SPF1 == SPF_UMAX && ACB.ult(ACC)) || |
| (SPF1 == SPF_SMAX && ACB.slt(ACC))) { |
| Outer.replaceUsesOfWith(Inner, A); |
| return &Outer; |
| } |
| } |
| } |
| } |
| |
| // ABS(ABS(X)) -> ABS(X) |
| // NABS(NABS(X)) -> NABS(X) |
| if (SPF1 == SPF2 && (SPF1 == SPF_ABS || SPF1 == SPF_NABS)) { |
| return replaceInstUsesWith(Outer, Inner); |
| } |
| |
| // ABS(NABS(X)) -> ABS(X) |
| // NABS(ABS(X)) -> NABS(X) |
| if ((SPF1 == SPF_ABS && SPF2 == SPF_NABS) || |
| (SPF1 == SPF_NABS && SPF2 == SPF_ABS)) { |
| SelectInst *SI = cast<SelectInst>(Inner); |
| Value *NewSI = Builder->CreateSelect( |
| SI->getCondition(), SI->getFalseValue(), SI->getTrueValue()); |
| return replaceInstUsesWith(Outer, NewSI); |
| } |
| |
| auto IsFreeOrProfitableToInvert = |
| [&](Value *V, Value *&NotV, bool &ElidesXor) { |
| if (match(V, m_Not(m_Value(NotV)))) { |
| // If V has at most 2 uses then we can get rid of the xor operation |
| // entirely. |
| ElidesXor |= !V->hasNUsesOrMore(3); |
| return true; |
| } |
| |
| if (IsFreeToInvert(V, !V->hasNUsesOrMore(3))) { |
| NotV = nullptr; |
| return true; |
| } |
| |
| return false; |
| }; |
| |
| Value *NotA, *NotB, *NotC; |
| bool ElidesXor = false; |
| |
| // MIN(MIN(~A, ~B), ~C) == ~MAX(MAX(A, B), C) |
| // MIN(MAX(~A, ~B), ~C) == ~MAX(MIN(A, B), C) |
| // MAX(MIN(~A, ~B), ~C) == ~MIN(MAX(A, B), C) |
| // MAX(MAX(~A, ~B), ~C) == ~MIN(MIN(A, B), C) |
| // |
| // This transform is performance neutral if we can elide at least one xor from |
| // the set of three operands, since we'll be tacking on an xor at the very |
| // end. |
| if (IsFreeOrProfitableToInvert(A, NotA, ElidesXor) && |
| IsFreeOrProfitableToInvert(B, NotB, ElidesXor) && |
| IsFreeOrProfitableToInvert(C, NotC, ElidesXor) && ElidesXor) { |
| if (!NotA) |
| NotA = Builder->CreateNot(A); |
| if (!NotB) |
| NotB = Builder->CreateNot(B); |
| if (!NotC) |
| NotC = Builder->CreateNot(C); |
| |
| Value *NewInner = generateMinMaxSelectPattern( |
| Builder, getInverseMinMaxSelectPattern(SPF1), NotA, NotB); |
| Value *NewOuter = Builder->CreateNot(generateMinMaxSelectPattern( |
| Builder, getInverseMinMaxSelectPattern(SPF2), NewInner, NotC)); |
| return replaceInstUsesWith(Outer, NewOuter); |
| } |
| |
| return nullptr; |
| } |
| |
| /// If one of the constants is zero (we know they can't both be) and we have an |
| /// icmp instruction with zero, and we have an 'and' with the non-constant value |
| /// and a power of two we can turn the select into a shift on the result of the |
| /// 'and'. |
| static Value *foldSelectICmpAnd(const SelectInst &SI, ConstantInt *TrueVal, |
| ConstantInt *FalseVal, |
| InstCombiner::BuilderTy *Builder) { |
| const ICmpInst *IC = dyn_cast<ICmpInst>(SI.getCondition()); |
| if (!IC || !IC->isEquality() || !SI.getType()->isIntegerTy()) |
| return nullptr; |
| |
| if (!match(IC->getOperand(1), m_Zero())) |
| return nullptr; |
| |
| ConstantInt *AndRHS; |
| Value *LHS = IC->getOperand(0); |
| if (!match(LHS, m_And(m_Value(), m_ConstantInt(AndRHS)))) |
| return nullptr; |
| |
| // If both select arms are non-zero see if we have a select of the form |
| // 'x ? 2^n + C : C'. Then we can offset both arms by C, use the logic |
| // for 'x ? 2^n : 0' and fix the thing up at the end. |
| ConstantInt *Offset = nullptr; |
| if (!TrueVal->isZero() && !FalseVal->isZero()) { |
| if ((TrueVal->getValue() - FalseVal->getValue()).isPowerOf2()) |
| Offset = FalseVal; |
| else if ((FalseVal->getValue() - TrueVal->getValue()).isPowerOf2()) |
| Offset = TrueVal; |
| else |
| return nullptr; |
| |
| // Adjust TrueVal and FalseVal to the offset. |
| TrueVal = ConstantInt::get(Builder->getContext(), |
| TrueVal->getValue() - Offset->getValue()); |
| FalseVal = ConstantInt::get(Builder->getContext(), |
| FalseVal->getValue() - Offset->getValue()); |
| } |
| |
| // Make sure the mask in the 'and' and one of the select arms is a power of 2. |
| if (!AndRHS->getValue().isPowerOf2() || |
| (!TrueVal->getValue().isPowerOf2() && |
| !FalseVal->getValue().isPowerOf2())) |
| return nullptr; |
| |
| // Determine which shift is needed to transform result of the 'and' into the |
| // desired result. |
| ConstantInt *ValC = !TrueVal->isZero() ? TrueVal : FalseVal; |
| unsigned ValZeros = ValC->getValue().logBase2(); |
| unsigned AndZeros = AndRHS->getValue().logBase2(); |
| |
| // If types don't match we can still convert the select by introducing a zext |
| // or a trunc of the 'and'. The trunc case requires that all of the truncated |
| // bits are zero, we can figure that out by looking at the 'and' mask. |
| if (AndZeros >= ValC->getBitWidth()) |
| return nullptr; |
| |
| Value *V = Builder->CreateZExtOrTrunc(LHS, SI.getType()); |
| if (ValZeros > AndZeros) |
| V = Builder->CreateShl(V, ValZeros - AndZeros); |
| else if (ValZeros < AndZeros) |
| V = Builder->CreateLShr(V, AndZeros - ValZeros); |
| |
| // Okay, now we know that everything is set up, we just don't know whether we |
| // have a icmp_ne or icmp_eq and whether the true or false val is the zero. |
| bool ShouldNotVal = !TrueVal->isZero(); |
| ShouldNotVal ^= IC->getPredicate() == ICmpInst::ICMP_NE; |
| if (ShouldNotVal) |
| V = Builder->CreateXor(V, ValC); |
| |
| // Apply an offset if needed. |
| if (Offset) |
| V = Builder->CreateAdd(V, Offset); |
| return V; |
| } |
| |
| /// Turn select C, (X + Y), (X - Y) --> (X + (select C, Y, (-Y))). |
| /// This is even legal for FP. |
| static Instruction *foldAddSubSelect(SelectInst &SI, |
| InstCombiner::BuilderTy &Builder) { |
| Value *CondVal = SI.getCondition(); |
| Value *TrueVal = SI.getTrueValue(); |
| Value *FalseVal = SI.getFalseValue(); |
| auto *TI = dyn_cast<Instruction>(TrueVal); |
| auto *FI = dyn_cast<Instruction>(FalseVal); |
| if (!TI || !FI || !TI->hasOneUse() || !FI->hasOneUse()) |
| return nullptr; |
| |
| Instruction *AddOp = nullptr, *SubOp = nullptr; |
| if ((TI->getOpcode() == Instruction::Sub && |
| FI->getOpcode() == Instruction::Add) || |
| (TI->getOpcode() == Instruction::FSub && |
| FI->getOpcode() == Instruction::FAdd)) { |
| AddOp = FI; |
| SubOp = TI; |
| } else if ((FI->getOpcode() == Instruction::Sub && |
| TI->getOpcode() == Instruction::Add) || |
| (FI->getOpcode() == Instruction::FSub && |
| TI->getOpcode() == Instruction::FAdd)) { |
| AddOp = TI; |
| SubOp = FI; |
| } |
| |
| if (AddOp) { |
| Value *OtherAddOp = nullptr; |
| if (SubOp->getOperand(0) == AddOp->getOperand(0)) { |
| OtherAddOp = AddOp->getOperand(1); |
| } else if (SubOp->getOperand(0) == AddOp->getOperand(1)) { |
| OtherAddOp = AddOp->getOperand(0); |
| } |
| |
| if (OtherAddOp) { |
| // So at this point we know we have (Y -> OtherAddOp): |
| // select C, (add X, Y), (sub X, Z) |
| Value *NegVal; // Compute -Z |
| if (SI.getType()->isFPOrFPVectorTy()) { |
| NegVal = Builder.CreateFNeg(SubOp->getOperand(1)); |
| if (Instruction *NegInst = dyn_cast<Instruction>(NegVal)) { |
| FastMathFlags Flags = AddOp->getFastMathFlags(); |
| Flags &= SubOp->getFastMathFlags(); |
| NegInst->setFastMathFlags(Flags); |
| } |
| } else { |
| NegVal = Builder.CreateNeg(SubOp->getOperand(1)); |
| } |
| |
| Value *NewTrueOp = OtherAddOp; |
| Value *NewFalseOp = NegVal; |
| if (AddOp != TI) |
| std::swap(NewTrueOp, NewFalseOp); |
| Value *NewSel = Builder.CreateSelect(CondVal, NewTrueOp, NewFalseOp, |
| SI.getName() + ".p"); |
| |
| if (SI.getType()->isFPOrFPVectorTy()) { |
| Instruction *RI = |
| BinaryOperator::CreateFAdd(SubOp->getOperand(0), NewSel); |
| |
| FastMathFlags Flags = AddOp->getFastMathFlags(); |
| Flags &= SubOp->getFastMathFlags(); |
| RI->setFastMathFlags(Flags); |
| return RI; |
| } else |
| return BinaryOperator::CreateAdd(SubOp->getOperand(0), NewSel); |
| } |
| } |
| return nullptr; |
| } |
| |
| Instruction *InstCombiner::visitSelectInst(SelectInst &SI) { |
| Value *CondVal = SI.getCondition(); |
| Value *TrueVal = SI.getTrueValue(); |
| Value *FalseVal = SI.getFalseValue(); |
| Type *SelType = SI.getType(); |
| |
| if (Value *V = |
| SimplifySelectInst(CondVal, TrueVal, FalseVal, DL, TLI, DT, AC)) |
| return replaceInstUsesWith(SI, V); |
| |
| if (SelType->getScalarType()->isIntegerTy(1) && |
| TrueVal->getType() == CondVal->getType()) { |
| if (match(TrueVal, m_One())) { |
| // Change: A = select B, true, C --> A = or B, C |
| return BinaryOperator::CreateOr(CondVal, FalseVal); |
| } |
| if (match(TrueVal, m_Zero())) { |
| // Change: A = select B, false, C --> A = and !B, C |
| Value *NotCond = Builder->CreateNot(CondVal, "not." + CondVal->getName()); |
| return BinaryOperator::CreateAnd(NotCond, FalseVal); |
| } |
| if (match(FalseVal, m_Zero())) { |
| // Change: A = select B, C, false --> A = and B, C |
| return BinaryOperator::CreateAnd(CondVal, TrueVal); |
| } |
| if (match(FalseVal, m_One())) { |
| // Change: A = select B, C, true --> A = or !B, C |
| Value *NotCond = Builder->CreateNot(CondVal, "not." + CondVal->getName()); |
| return BinaryOperator::CreateOr(NotCond, TrueVal); |
| } |
| |
| // select a, a, b -> a | b |
| // select a, b, a -> a & b |
| if (CondVal == TrueVal) |
| return BinaryOperator::CreateOr(CondVal, FalseVal); |
| if (CondVal == FalseVal) |
| return BinaryOperator::CreateAnd(CondVal, TrueVal); |
| |
| // select a, ~a, b -> (~a) & b |
| // select a, b, ~a -> (~a) | b |
| if (match(TrueVal, m_Not(m_Specific(CondVal)))) |
| return BinaryOperator::CreateAnd(TrueVal, FalseVal); |
| if (match(FalseVal, m_Not(m_Specific(CondVal)))) |
| return BinaryOperator::CreateOr(TrueVal, FalseVal); |
| } |
| |
| // Selecting between two integer or vector splat integer constants? |
| // |
| // Note that we don't handle a scalar select of vectors: |
| // select i1 %c, <2 x i8> <1, 1>, <2 x i8> <0, 0> |
| // because that may need 3 instructions to splat the condition value: |
| // extend, insertelement, shufflevector. |
| if (CondVal->getType()->isVectorTy() == SelType->isVectorTy()) { |
| // select C, 1, 0 -> zext C to int |
| if (match(TrueVal, m_One()) && match(FalseVal, m_Zero())) |
| return new ZExtInst(CondVal, SelType); |
| |
| // select C, -1, 0 -> sext C to int |
| if (match(TrueVal, m_AllOnes()) && match(FalseVal, m_Zero())) |
| return new SExtInst(CondVal, SelType); |
| |
| // select C, 0, 1 -> zext !C to int |
| if (match(TrueVal, m_Zero()) && match(FalseVal, m_One())) { |
| Value *NotCond = Builder->CreateNot(CondVal, "not." + CondVal->getName()); |
| return new ZExtInst(NotCond, SelType); |
| } |
| |
| // select C, 0, -1 -> sext !C to int |
| if (match(TrueVal, m_Zero()) && match(FalseVal, m_AllOnes())) { |
| Value *NotCond = Builder->CreateNot(CondVal, "not." + CondVal->getName()); |
| return new SExtInst(NotCond, SelType); |
| } |
| } |
| |
| if (ConstantInt *TrueValC = dyn_cast<ConstantInt>(TrueVal)) |
| if (ConstantInt *FalseValC = dyn_cast<ConstantInt>(FalseVal)) |
| if (Value *V = foldSelectICmpAnd(SI, TrueValC, FalseValC, Builder)) |
| return replaceInstUsesWith(SI, V); |
| |
| // See if we are selecting two values based on a comparison of the two values. |
| if (FCmpInst *FCI = dyn_cast<FCmpInst>(CondVal)) { |
| if (FCI->getOperand(0) == TrueVal && FCI->getOperand(1) == FalseVal) { |
| // Transform (X == Y) ? X : Y -> Y |
| if (FCI->getPredicate() == FCmpInst::FCMP_OEQ) { |
| // This is not safe in general for floating point: |
| // consider X== -0, Y== +0. |
| // It becomes safe if either operand is a nonzero constant. |
| ConstantFP *CFPt, *CFPf; |
| if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) && |
| !CFPt->getValueAPF().isZero()) || |
| ((CFPf = dyn_cast<ConstantFP>(FalseVal)) && |
| !CFPf->getValueAPF().isZero())) |
| return replaceInstUsesWith(SI, FalseVal); |
| } |
| // Transform (X une Y) ? X : Y -> X |
| if (FCI->getPredicate() == FCmpInst::FCMP_UNE) { |
| // This is not safe in general for floating point: |
| // consider X== -0, Y== +0. |
| // It becomes safe if either operand is a nonzero constant. |
| ConstantFP *CFPt, *CFPf; |
| if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) && |
| !CFPt->getValueAPF().isZero()) || |
| ((CFPf = dyn_cast<ConstantFP>(FalseVal)) && |
| !CFPf->getValueAPF().isZero())) |
| return replaceInstUsesWith(SI, TrueVal); |
| } |
| |
| // Canonicalize to use ordered comparisons by swapping the select |
| // operands. |
| // |
| // e.g. |
| // (X ugt Y) ? X : Y -> (X ole Y) ? Y : X |
| if (FCI->hasOneUse() && FCmpInst::isUnordered(FCI->getPredicate())) { |
| FCmpInst::Predicate InvPred = FCI->getInversePredicate(); |
| IRBuilder<>::FastMathFlagGuard FMFG(*Builder); |
| Builder->setFastMathFlags(FCI->getFastMathFlags()); |
| Value *NewCond = Builder->CreateFCmp(InvPred, TrueVal, FalseVal, |
| FCI->getName() + ".inv"); |
| |
| return SelectInst::Create(NewCond, FalseVal, TrueVal, |
| SI.getName() + ".p"); |
| } |
| |
| // NOTE: if we wanted to, this is where to detect MIN/MAX |
| } else if (FCI->getOperand(0) == FalseVal && FCI->getOperand(1) == TrueVal){ |
| // Transform (X == Y) ? Y : X -> X |
| if (FCI->getPredicate() == FCmpInst::FCMP_OEQ) { |
| // This is not safe in general for floating point: |
| // consider X== -0, Y== +0. |
| // It becomes safe if either operand is a nonzero constant. |
| ConstantFP *CFPt, *CFPf; |
| if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) && |
| !CFPt->getValueAPF().isZero()) || |
| ((CFPf = dyn_cast<ConstantFP>(FalseVal)) && |
| !CFPf->getValueAPF().isZero())) |
| return replaceInstUsesWith(SI, FalseVal); |
| } |
| // Transform (X une Y) ? Y : X -> Y |
| if (FCI->getPredicate() == FCmpInst::FCMP_UNE) { |
| // This is not safe in general for floating point: |
| // consider X== -0, Y== +0. |
| // It becomes safe if either operand is a nonzero constant. |
| ConstantFP *CFPt, *CFPf; |
| if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) && |
| !CFPt->getValueAPF().isZero()) || |
| ((CFPf = dyn_cast<ConstantFP>(FalseVal)) && |
| !CFPf->getValueAPF().isZero())) |
| return replaceInstUsesWith(SI, TrueVal); |
| } |
| |
| // Canonicalize to use ordered comparisons by swapping the select |
| // operands. |
| // |
| // e.g. |
| // (X ugt Y) ? X : Y -> (X ole Y) ? X : Y |
| if (FCI->hasOneUse() && FCmpInst::isUnordered(FCI->getPredicate())) { |
| FCmpInst::Predicate InvPred = FCI->getInversePredicate(); |
| IRBuilder<>::FastMathFlagGuard FMFG(*Builder); |
| Builder->setFastMathFlags(FCI->getFastMathFlags()); |
| Value *NewCond = Builder->CreateFCmp(InvPred, FalseVal, TrueVal, |
| FCI->getName() + ".inv"); |
| |
| return SelectInst::Create(NewCond, FalseVal, TrueVal, |
| SI.getName() + ".p"); |
| } |
| |
| // NOTE: if we wanted to, this is where to detect MIN/MAX |
| } |
| // NOTE: if we wanted to, this is where to detect ABS |
| } |
| |
| // See if we are selecting two values based on a comparison of the two values. |
| if (ICmpInst *ICI = dyn_cast<ICmpInst>(CondVal)) |
| if (Instruction *Result = visitSelectInstWithICmp(SI, ICI)) |
| return Result; |
| |
| if (Instruction *Add = foldAddSubSelect(SI, *Builder)) |
| return Add; |
| |
| // Turn (select C, (op X, Y), (op X, Z)) -> (op X, (select C, Y, Z)) |
| auto *TI = dyn_cast<Instruction>(TrueVal); |
| auto *FI = dyn_cast<Instruction>(FalseVal); |
| if (TI && FI && TI->getOpcode() == FI->getOpcode()) |
| if (Instruction *IV = FoldSelectOpOp(SI, TI, FI)) |
| return IV; |
| |
| // See if we can fold the select into one of our operands. |
| if (SelType->isIntOrIntVectorTy() || SelType->isFPOrFPVectorTy()) { |
| if (Instruction *FoldI = FoldSelectIntoOp(SI, TrueVal, FalseVal)) |
| return FoldI; |
| |
| Value *LHS, *RHS, *LHS2, *RHS2; |
| Instruction::CastOps CastOp; |
| SelectPatternResult SPR = matchSelectPattern(&SI, LHS, RHS, &CastOp); |
| auto SPF = SPR.Flavor; |
| |
| if (SelectPatternResult::isMinOrMax(SPF)) { |
| // Canonicalize so that type casts are outside select patterns. |
| if (LHS->getType()->getPrimitiveSizeInBits() != |
| SelType->getPrimitiveSizeInBits()) { |
| CmpInst::Predicate Pred = getCmpPredicateForMinMax(SPF, SPR.Ordered); |
| |
| Value *Cmp; |
| if (CmpInst::isIntPredicate(Pred)) { |
| Cmp = Builder->CreateICmp(Pred, LHS, RHS); |
| } else { |
| IRBuilder<>::FastMathFlagGuard FMFG(*Builder); |
| auto FMF = cast<FPMathOperator>(SI.getCondition())->getFastMathFlags(); |
| Builder->setFastMathFlags(FMF); |
| Cmp = Builder->CreateFCmp(Pred, LHS, RHS); |
| } |
| |
| Value *NewSI = Builder->CreateCast(CastOp, |
| Builder->CreateSelect(Cmp, LHS, RHS), |
| SelType); |
| return replaceInstUsesWith(SI, NewSI); |
| } |
| } |
| |
| if (SPF) { |
| // MAX(MAX(a, b), a) -> MAX(a, b) |
| // MIN(MIN(a, b), a) -> MIN(a, b) |
| // MAX(MIN(a, b), a) -> a |
| // MIN(MAX(a, b), a) -> a |
| // ABS(ABS(a)) -> ABS(a) |
| // NABS(NABS(a)) -> NABS(a) |
| if (SelectPatternFlavor SPF2 = matchSelectPattern(LHS, LHS2, RHS2).Flavor) |
| if (Instruction *R = FoldSPFofSPF(cast<Instruction>(LHS),SPF2,LHS2,RHS2, |
| SI, SPF, RHS)) |
| return R; |
| if (SelectPatternFlavor SPF2 = matchSelectPattern(RHS, LHS2, RHS2).Flavor) |
| if (Instruction *R = FoldSPFofSPF(cast<Instruction>(RHS),SPF2,LHS2,RHS2, |
| SI, SPF, LHS)) |
| return R; |
| } |
| |
| // MAX(~a, ~b) -> ~MIN(a, b) |
| if (SPF == SPF_SMAX || SPF == SPF_UMAX) { |
| if (IsFreeToInvert(LHS, LHS->hasNUses(2)) && |
| IsFreeToInvert(RHS, RHS->hasNUses(2))) { |
| |
| // This transform adds a xor operation and that extra cost needs to be |
| // justified. We look for simplifications that will result from |
| // applying this rule: |
| |
| bool Profitable = |
| (LHS->hasNUses(2) && match(LHS, m_Not(m_Value()))) || |
| (RHS->hasNUses(2) && match(RHS, m_Not(m_Value()))) || |
| (SI.hasOneUse() && match(*SI.user_begin(), m_Not(m_Value()))); |
| |
| if (Profitable) { |
| Value *NewLHS = Builder->CreateNot(LHS); |
| Value *NewRHS = Builder->CreateNot(RHS); |
| Value *NewCmp = SPF == SPF_SMAX |
| ? Builder->CreateICmpSLT(NewLHS, NewRHS) |
| : Builder->CreateICmpULT(NewLHS, NewRHS); |
| Value *NewSI = |
| Builder->CreateNot(Builder->CreateSelect(NewCmp, NewLHS, NewRHS)); |
| return replaceInstUsesWith(SI, NewSI); |
| } |
| } |
| } |
| |
| // TODO. |
| // ABS(-X) -> ABS(X) |
| } |
| |
| // See if we can fold the select into a phi node if the condition is a select. |
| if (isa<PHINode>(SI.getCondition())) |
| // The true/false values have to be live in the PHI predecessor's blocks. |
| if (CanSelectOperandBeMappingIntoPredBlock(TrueVal, SI) && |
| CanSelectOperandBeMappingIntoPredBlock(FalseVal, SI)) |
| if (Instruction *NV = FoldOpIntoPhi(SI)) |
| return NV; |
| |
| if (SelectInst *TrueSI = dyn_cast<SelectInst>(TrueVal)) { |
| if (TrueSI->getCondition()->getType() == CondVal->getType()) { |
| // select(C, select(C, a, b), c) -> select(C, a, c) |
| if (TrueSI->getCondition() == CondVal) { |
| if (SI.getTrueValue() == TrueSI->getTrueValue()) |
| return nullptr; |
| SI.setOperand(1, TrueSI->getTrueValue()); |
| return &SI; |
| } |
| // select(C0, select(C1, a, b), b) -> select(C0&C1, a, b) |
| // We choose this as normal form to enable folding on the And and shortening |
| // paths for the values (this helps GetUnderlyingObjects() for example). |
| if (TrueSI->getFalseValue() == FalseVal && TrueSI->hasOneUse()) { |
| Value *And = Builder->CreateAnd(CondVal, TrueSI->getCondition()); |
| SI.setOperand(0, And); |
| SI.setOperand(1, TrueSI->getTrueValue()); |
| return &SI; |
| } |
| } |
| } |
| if (SelectInst *FalseSI = dyn_cast<SelectInst>(FalseVal)) { |
| if (FalseSI->getCondition()->getType() == CondVal->getType()) { |
| // select(C, a, select(C, b, c)) -> select(C, a, c) |
| if (FalseSI->getCondition() == CondVal) { |
| if (SI.getFalseValue() == FalseSI->getFalseValue()) |
| return nullptr; |
| SI.setOperand(2, FalseSI->getFalseValue()); |
| return &SI; |
| } |
| // select(C0, a, select(C1, a, b)) -> select(C0|C1, a, b) |
| if (FalseSI->getTrueValue() == TrueVal && FalseSI->hasOneUse()) { |
| Value *Or = Builder->CreateOr(CondVal, FalseSI->getCondition()); |
| SI.setOperand(0, Or); |
| SI.setOperand(2, FalseSI->getFalseValue()); |
| return &SI; |
| } |
| } |
| } |
| |
| if (BinaryOperator::isNot(CondVal)) { |
| SI.setOperand(0, BinaryOperator::getNotArgument(CondVal)); |
| SI.setOperand(1, FalseVal); |
| SI.setOperand(2, TrueVal); |
| return &SI; |
| } |
| |
| if (VectorType* VecTy = dyn_cast<VectorType>(SelType)) { |
| unsigned VWidth = VecTy->getNumElements(); |
| APInt UndefElts(VWidth, 0); |
| APInt AllOnesEltMask(APInt::getAllOnesValue(VWidth)); |
| if (Value *V = SimplifyDemandedVectorElts(&SI, AllOnesEltMask, UndefElts)) { |
| if (V != &SI) |
| return replaceInstUsesWith(SI, V); |
| return &SI; |
| } |
| |
| if (isa<ConstantAggregateZero>(CondVal)) { |
| return replaceInstUsesWith(SI, FalseVal); |
| } |
| } |
| |
| // See if we can determine the result of this select based on a dominating |
| // condition. |
| BasicBlock *Parent = SI.getParent(); |
| if (BasicBlock *Dom = Parent->getSinglePredecessor()) { |
| auto *PBI = dyn_cast_or_null<BranchInst>(Dom->getTerminator()); |
| if (PBI && PBI->isConditional() && |
| PBI->getSuccessor(0) != PBI->getSuccessor(1) && |
| (PBI->getSuccessor(0) == Parent || PBI->getSuccessor(1) == Parent)) { |
| bool CondIsFalse = PBI->getSuccessor(1) == Parent; |
| Optional<bool> Implication = isImpliedCondition( |
| PBI->getCondition(), SI.getCondition(), DL, CondIsFalse); |
| if (Implication) { |
| Value *V = *Implication ? TrueVal : FalseVal; |
| return replaceInstUsesWith(SI, V); |
| } |
| } |
| } |
| |
| return nullptr; |
| } |
