| //===-- Analysis.cpp - CodeGen LLVM IR Analysis Utilities -----------------===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This file defines several CodeGen-specific LLVM IR analysis utilities. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "llvm/CodeGen/Analysis.h" |
| #include "llvm/Analysis/ValueTracking.h" |
| #include "llvm/CodeGen/MachineFunction.h" |
| #include "llvm/CodeGen/SelectionDAG.h" |
| #include "llvm/IR/DataLayout.h" |
| #include "llvm/IR/DerivedTypes.h" |
| #include "llvm/IR/Function.h" |
| #include "llvm/IR/Instructions.h" |
| #include "llvm/IR/IntrinsicInst.h" |
| #include "llvm/IR/LLVMContext.h" |
| #include "llvm/IR/Module.h" |
| #include "llvm/Support/ErrorHandling.h" |
| #include "llvm/Support/MathExtras.h" |
| #include "llvm/Target/TargetLowering.h" |
| using namespace llvm; |
| |
| /// ComputeLinearIndex - Given an LLVM IR aggregate type and a sequence |
| /// of insertvalue or extractvalue indices that identify a member, return |
| /// the linearized index of the start of the member. |
| /// |
| unsigned llvm::ComputeLinearIndex(Type *Ty, |
| const unsigned *Indices, |
| const unsigned *IndicesEnd, |
| unsigned CurIndex) { |
| // Base case: We're done. |
| if (Indices && Indices == IndicesEnd) |
| return CurIndex; |
| |
| // Given a struct type, recursively traverse the elements. |
| if (StructType *STy = dyn_cast<StructType>(Ty)) { |
| for (StructType::element_iterator EB = STy->element_begin(), |
| EI = EB, |
| EE = STy->element_end(); |
| EI != EE; ++EI) { |
| if (Indices && *Indices == unsigned(EI - EB)) |
| return ComputeLinearIndex(*EI, Indices+1, IndicesEnd, CurIndex); |
| CurIndex = ComputeLinearIndex(*EI, nullptr, nullptr, CurIndex); |
| } |
| return CurIndex; |
| } |
| // Given an array type, recursively traverse the elements. |
| else if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) { |
| Type *EltTy = ATy->getElementType(); |
| for (unsigned i = 0, e = ATy->getNumElements(); i != e; ++i) { |
| if (Indices && *Indices == i) |
| return ComputeLinearIndex(EltTy, Indices+1, IndicesEnd, CurIndex); |
| CurIndex = ComputeLinearIndex(EltTy, nullptr, nullptr, CurIndex); |
| } |
| return CurIndex; |
| } |
| // We haven't found the type we're looking for, so keep searching. |
| return CurIndex + 1; |
| } |
| |
| /// ComputeValueVTs - Given an LLVM IR type, compute a sequence of |
| /// EVTs that represent all the individual underlying |
| /// non-aggregate types that comprise it. |
| /// |
| /// If Offsets is non-null, it points to a vector to be filled in |
| /// with the in-memory offsets of each of the individual values. |
| /// |
| void llvm::ComputeValueVTs(const TargetLowering &TLI, Type *Ty, |
| SmallVectorImpl<EVT> &ValueVTs, |
| SmallVectorImpl<uint64_t> *Offsets, |
| uint64_t StartingOffset) { |
| // Given a struct type, recursively traverse the elements. |
| if (StructType *STy = dyn_cast<StructType>(Ty)) { |
| const StructLayout *SL = TLI.getDataLayout()->getStructLayout(STy); |
| for (StructType::element_iterator EB = STy->element_begin(), |
| EI = EB, |
| EE = STy->element_end(); |
| EI != EE; ++EI) |
| ComputeValueVTs(TLI, *EI, ValueVTs, Offsets, |
| StartingOffset + SL->getElementOffset(EI - EB)); |
| return; |
| } |
| // Given an array type, recursively traverse the elements. |
| if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) { |
| Type *EltTy = ATy->getElementType(); |
| uint64_t EltSize = TLI.getDataLayout()->getTypeAllocSize(EltTy); |
| for (unsigned i = 0, e = ATy->getNumElements(); i != e; ++i) |
| ComputeValueVTs(TLI, EltTy, ValueVTs, Offsets, |
| StartingOffset + i * EltSize); |
| return; |
| } |
| // Interpret void as zero return values. |
| if (Ty->isVoidTy()) |
| return; |
| // Base case: we can get an EVT for this LLVM IR type. |
| ValueVTs.push_back(TLI.getValueType(Ty)); |
| if (Offsets) |
| Offsets->push_back(StartingOffset); |
| } |
| |
| /// ExtractTypeInfo - Returns the type info, possibly bitcast, encoded in V. |
| GlobalVariable *llvm::ExtractTypeInfo(Value *V) { |
| V = V->stripPointerCasts(); |
| GlobalVariable *GV = dyn_cast<GlobalVariable>(V); |
| |
| if (GV && GV->getName() == "llvm.eh.catch.all.value") { |
| assert(GV->hasInitializer() && |
| "The EH catch-all value must have an initializer"); |
| Value *Init = GV->getInitializer(); |
| GV = dyn_cast<GlobalVariable>(Init); |
| if (!GV) V = cast<ConstantPointerNull>(Init); |
| } |
| |
| assert((GV || isa<ConstantPointerNull>(V)) && |
| "TypeInfo must be a global variable or NULL"); |
| return GV; |
| } |
| |
| /// hasInlineAsmMemConstraint - Return true if the inline asm instruction being |
| /// processed uses a memory 'm' constraint. |
| bool |
| llvm::hasInlineAsmMemConstraint(InlineAsm::ConstraintInfoVector &CInfos, |
| const TargetLowering &TLI) { |
| for (unsigned i = 0, e = CInfos.size(); i != e; ++i) { |
| InlineAsm::ConstraintInfo &CI = CInfos[i]; |
| for (unsigned j = 0, ee = CI.Codes.size(); j != ee; ++j) { |
| TargetLowering::ConstraintType CType = TLI.getConstraintType(CI.Codes[j]); |
| if (CType == TargetLowering::C_Memory) |
| return true; |
| } |
| |
| // Indirect operand accesses access memory. |
| if (CI.isIndirect) |
| return true; |
| } |
| |
| return false; |
| } |
| |
| /// getFCmpCondCode - Return the ISD condition code corresponding to |
| /// the given LLVM IR floating-point condition code. This includes |
| /// consideration of global floating-point math flags. |
| /// |
| ISD::CondCode llvm::getFCmpCondCode(FCmpInst::Predicate Pred) { |
| switch (Pred) { |
| case FCmpInst::FCMP_FALSE: return ISD::SETFALSE; |
| case FCmpInst::FCMP_OEQ: return ISD::SETOEQ; |
| case FCmpInst::FCMP_OGT: return ISD::SETOGT; |
| case FCmpInst::FCMP_OGE: return ISD::SETOGE; |
| case FCmpInst::FCMP_OLT: return ISD::SETOLT; |
| case FCmpInst::FCMP_OLE: return ISD::SETOLE; |
| case FCmpInst::FCMP_ONE: return ISD::SETONE; |
| case FCmpInst::FCMP_ORD: return ISD::SETO; |
| case FCmpInst::FCMP_UNO: return ISD::SETUO; |
| case FCmpInst::FCMP_UEQ: return ISD::SETUEQ; |
| case FCmpInst::FCMP_UGT: return ISD::SETUGT; |
| case FCmpInst::FCMP_UGE: return ISD::SETUGE; |
| case FCmpInst::FCMP_ULT: return ISD::SETULT; |
| case FCmpInst::FCMP_ULE: return ISD::SETULE; |
| case FCmpInst::FCMP_UNE: return ISD::SETUNE; |
| case FCmpInst::FCMP_TRUE: return ISD::SETTRUE; |
| default: llvm_unreachable("Invalid FCmp predicate opcode!"); |
| } |
| } |
| |
| ISD::CondCode llvm::getFCmpCodeWithoutNaN(ISD::CondCode CC) { |
| switch (CC) { |
| case ISD::SETOEQ: case ISD::SETUEQ: return ISD::SETEQ; |
| case ISD::SETONE: case ISD::SETUNE: return ISD::SETNE; |
| case ISD::SETOLT: case ISD::SETULT: return ISD::SETLT; |
| case ISD::SETOLE: case ISD::SETULE: return ISD::SETLE; |
| case ISD::SETOGT: case ISD::SETUGT: return ISD::SETGT; |
| case ISD::SETOGE: case ISD::SETUGE: return ISD::SETGE; |
| default: return CC; |
| } |
| } |
| |
| /// getICmpCondCode - Return the ISD condition code corresponding to |
| /// the given LLVM IR integer condition code. |
| /// |
| ISD::CondCode llvm::getICmpCondCode(ICmpInst::Predicate Pred) { |
| switch (Pred) { |
| case ICmpInst::ICMP_EQ: return ISD::SETEQ; |
| case ICmpInst::ICMP_NE: return ISD::SETNE; |
| case ICmpInst::ICMP_SLE: return ISD::SETLE; |
| case ICmpInst::ICMP_ULE: return ISD::SETULE; |
| case ICmpInst::ICMP_SGE: return ISD::SETGE; |
| case ICmpInst::ICMP_UGE: return ISD::SETUGE; |
| case ICmpInst::ICMP_SLT: return ISD::SETLT; |
| case ICmpInst::ICMP_ULT: return ISD::SETULT; |
| case ICmpInst::ICMP_SGT: return ISD::SETGT; |
| case ICmpInst::ICMP_UGT: return ISD::SETUGT; |
| default: |
| llvm_unreachable("Invalid ICmp predicate opcode!"); |
| } |
| } |
| |
| static bool isNoopBitcast(Type *T1, Type *T2, |
| const TargetLoweringBase& TLI) { |
| return T1 == T2 || (T1->isPointerTy() && T2->isPointerTy()) || |
| (isa<VectorType>(T1) && isa<VectorType>(T2) && |
| TLI.isTypeLegal(EVT::getEVT(T1)) && TLI.isTypeLegal(EVT::getEVT(T2))); |
| } |
| |
| /// Look through operations that will be free to find the earliest source of |
| /// this value. |
| /// |
| /// @param ValLoc If V has aggegate type, we will be interested in a particular |
| /// scalar component. This records its address; the reverse of this list gives a |
| /// sequence of indices appropriate for an extractvalue to locate the important |
| /// value. This value is updated during the function and on exit will indicate |
| /// similar information for the Value returned. |
| /// |
| /// @param DataBits If this function looks through truncate instructions, this |
| /// will record the smallest size attained. |
| static const Value *getNoopInput(const Value *V, |
| SmallVectorImpl<unsigned> &ValLoc, |
| unsigned &DataBits, |
| const TargetLoweringBase &TLI) { |
| while (true) { |
| // Try to look through V1; if V1 is not an instruction, it can't be looked |
| // through. |
| const Instruction *I = dyn_cast<Instruction>(V); |
| if (!I || I->getNumOperands() == 0) return V; |
| const Value *NoopInput = nullptr; |
| |
| Value *Op = I->getOperand(0); |
| if (isa<BitCastInst>(I)) { |
| // Look through truly no-op bitcasts. |
| if (isNoopBitcast(Op->getType(), I->getType(), TLI)) |
| NoopInput = Op; |
| } else if (isa<GetElementPtrInst>(I)) { |
| // Look through getelementptr |
| if (cast<GetElementPtrInst>(I)->hasAllZeroIndices()) |
| NoopInput = Op; |
| } else if (isa<IntToPtrInst>(I)) { |
| // Look through inttoptr. |
| // Make sure this isn't a truncating or extending cast. We could |
| // support this eventually, but don't bother for now. |
| if (!isa<VectorType>(I->getType()) && |
| TLI.getPointerTy().getSizeInBits() == |
| cast<IntegerType>(Op->getType())->getBitWidth()) |
| NoopInput = Op; |
| } else if (isa<PtrToIntInst>(I)) { |
| // Look through ptrtoint. |
| // Make sure this isn't a truncating or extending cast. We could |
| // support this eventually, but don't bother for now. |
| if (!isa<VectorType>(I->getType()) && |
| TLI.getPointerTy().getSizeInBits() == |
| cast<IntegerType>(I->getType())->getBitWidth()) |
| NoopInput = Op; |
| } else if (isa<TruncInst>(I) && |
| TLI.allowTruncateForTailCall(Op->getType(), I->getType())) { |
| DataBits = std::min(DataBits, I->getType()->getPrimitiveSizeInBits()); |
| NoopInput = Op; |
| } else if (isa<CallInst>(I)) { |
| // Look through call (skipping callee) |
| for (User::const_op_iterator i = I->op_begin(), e = I->op_end() - 1; |
| i != e; ++i) { |
| unsigned attrInd = i - I->op_begin() + 1; |
| if (cast<CallInst>(I)->paramHasAttr(attrInd, Attribute::Returned) && |
| isNoopBitcast((*i)->getType(), I->getType(), TLI)) { |
| NoopInput = *i; |
| break; |
| } |
| } |
| } else if (isa<InvokeInst>(I)) { |
| // Look through invoke (skipping BB, BB, Callee) |
| for (User::const_op_iterator i = I->op_begin(), e = I->op_end() - 3; |
| i != e; ++i) { |
| unsigned attrInd = i - I->op_begin() + 1; |
| if (cast<InvokeInst>(I)->paramHasAttr(attrInd, Attribute::Returned) && |
| isNoopBitcast((*i)->getType(), I->getType(), TLI)) { |
| NoopInput = *i; |
| break; |
| } |
| } |
| } else if (const InsertValueInst *IVI = dyn_cast<InsertValueInst>(V)) { |
| // Value may come from either the aggregate or the scalar |
| ArrayRef<unsigned> InsertLoc = IVI->getIndices(); |
| if (std::equal(InsertLoc.rbegin(), InsertLoc.rend(), |
| ValLoc.rbegin())) { |
| // The type being inserted is a nested sub-type of the aggregate; we |
| // have to remove those initial indices to get the location we're |
| // interested in for the operand. |
| ValLoc.resize(ValLoc.size() - InsertLoc.size()); |
| NoopInput = IVI->getInsertedValueOperand(); |
| } else { |
| // The struct we're inserting into has the value we're interested in, no |
| // change of address. |
| NoopInput = Op; |
| } |
| } else if (const ExtractValueInst *EVI = dyn_cast<ExtractValueInst>(V)) { |
| // The part we're interested in will inevitably be some sub-section of the |
| // previous aggregate. Combine the two paths to obtain the true address of |
| // our element. |
| ArrayRef<unsigned> ExtractLoc = EVI->getIndices(); |
| std::copy(ExtractLoc.rbegin(), ExtractLoc.rend(), |
| std::back_inserter(ValLoc)); |
| NoopInput = Op; |
| } |
| // Terminate if we couldn't find anything to look through. |
| if (!NoopInput) |
| return V; |
| |
| V = NoopInput; |
| } |
| } |
| |
| /// Return true if this scalar return value only has bits discarded on its path |
| /// from the "tail call" to the "ret". This includes the obvious noop |
| /// instructions handled by getNoopInput above as well as free truncations (or |
| /// extensions prior to the call). |
| static bool slotOnlyDiscardsData(const Value *RetVal, const Value *CallVal, |
| SmallVectorImpl<unsigned> &RetIndices, |
| SmallVectorImpl<unsigned> &CallIndices, |
| bool AllowDifferingSizes, |
| const TargetLoweringBase &TLI) { |
| |
| // Trace the sub-value needed by the return value as far back up the graph as |
| // possible, in the hope that it will intersect with the value produced by the |
| // call. In the simple case with no "returned" attribute, the hope is actually |
| // that we end up back at the tail call instruction itself. |
| unsigned BitsRequired = UINT_MAX; |
| RetVal = getNoopInput(RetVal, RetIndices, BitsRequired, TLI); |
| |
| // If this slot in the value returned is undef, it doesn't matter what the |
| // call puts there, it'll be fine. |
| if (isa<UndefValue>(RetVal)) |
| return true; |
| |
| // Now do a similar search up through the graph to find where the value |
| // actually returned by the "tail call" comes from. In the simple case without |
| // a "returned" attribute, the search will be blocked immediately and the loop |
| // a Noop. |
| unsigned BitsProvided = UINT_MAX; |
| CallVal = getNoopInput(CallVal, CallIndices, BitsProvided, TLI); |
| |
| // There's no hope if we can't actually trace them to (the same part of!) the |
| // same value. |
| if (CallVal != RetVal || CallIndices != RetIndices) |
| return false; |
| |
| // However, intervening truncates may have made the call non-tail. Make sure |
| // all the bits that are needed by the "ret" have been provided by the "tail |
| // call". FIXME: with sufficiently cunning bit-tracking, we could look through |
| // extensions too. |
| if (BitsProvided < BitsRequired || |
| (!AllowDifferingSizes && BitsProvided != BitsRequired)) |
| return false; |
| |
| return true; |
| } |
| |
| /// For an aggregate type, determine whether a given index is within bounds or |
| /// not. |
| static bool indexReallyValid(CompositeType *T, unsigned Idx) { |
| if (ArrayType *AT = dyn_cast<ArrayType>(T)) |
| return Idx < AT->getNumElements(); |
| |
| return Idx < cast<StructType>(T)->getNumElements(); |
| } |
| |
| /// Move the given iterators to the next leaf type in depth first traversal. |
| /// |
| /// Performs a depth-first traversal of the type as specified by its arguments, |
| /// stopping at the next leaf node (which may be a legitimate scalar type or an |
| /// empty struct or array). |
| /// |
| /// @param SubTypes List of the partial components making up the type from |
| /// outermost to innermost non-empty aggregate. The element currently |
| /// represented is SubTypes.back()->getTypeAtIndex(Path.back() - 1). |
| /// |
| /// @param Path Set of extractvalue indices leading from the outermost type |
| /// (SubTypes[0]) to the leaf node currently represented. |
| /// |
| /// @returns true if a new type was found, false otherwise. Calling this |
| /// function again on a finished iterator will repeatedly return |
| /// false. SubTypes.back()->getTypeAtIndex(Path.back()) is either an empty |
| /// aggregate or a non-aggregate |
| static bool advanceToNextLeafType(SmallVectorImpl<CompositeType *> &SubTypes, |
| SmallVectorImpl<unsigned> &Path) { |
| // First march back up the tree until we can successfully increment one of the |
| // coordinates in Path. |
| while (!Path.empty() && !indexReallyValid(SubTypes.back(), Path.back() + 1)) { |
| Path.pop_back(); |
| SubTypes.pop_back(); |
| } |
| |
| // If we reached the top, then the iterator is done. |
| if (Path.empty()) |
| return false; |
| |
| // We know there's *some* valid leaf now, so march back down the tree picking |
| // out the left-most element at each node. |
| ++Path.back(); |
| Type *DeeperType = SubTypes.back()->getTypeAtIndex(Path.back()); |
| while (DeeperType->isAggregateType()) { |
| CompositeType *CT = cast<CompositeType>(DeeperType); |
| if (!indexReallyValid(CT, 0)) |
| return true; |
| |
| SubTypes.push_back(CT); |
| Path.push_back(0); |
| |
| DeeperType = CT->getTypeAtIndex(0U); |
| } |
| |
| return true; |
| } |
| |
| /// Find the first non-empty, scalar-like type in Next and setup the iterator |
| /// components. |
| /// |
| /// Assuming Next is an aggregate of some kind, this function will traverse the |
| /// tree from left to right (i.e. depth-first) looking for the first |
| /// non-aggregate type which will play a role in function return. |
| /// |
| /// For example, if Next was {[0 x i64], {{}, i32, {}}, i32} then we would setup |
| /// Path as [1, 1] and SubTypes as [Next, {{}, i32, {}}] to represent the first |
| /// i32 in that type. |
| static bool firstRealType(Type *Next, |
| SmallVectorImpl<CompositeType *> &SubTypes, |
| SmallVectorImpl<unsigned> &Path) { |
| // First initialise the iterator components to the first "leaf" node |
| // (i.e. node with no valid sub-type at any index, so {} does count as a leaf |
| // despite nominally being an aggregate). |
| while (Next->isAggregateType() && |
| indexReallyValid(cast<CompositeType>(Next), 0)) { |
| SubTypes.push_back(cast<CompositeType>(Next)); |
| Path.push_back(0); |
| Next = cast<CompositeType>(Next)->getTypeAtIndex(0U); |
| } |
| |
| // If there's no Path now, Next was originally scalar already (or empty |
| // leaf). We're done. |
| if (Path.empty()) |
| return true; |
| |
| // Otherwise, use normal iteration to keep looking through the tree until we |
| // find a non-aggregate type. |
| while (SubTypes.back()->getTypeAtIndex(Path.back())->isAggregateType()) { |
| if (!advanceToNextLeafType(SubTypes, Path)) |
| return false; |
| } |
| |
| return true; |
| } |
| |
| /// Set the iterator data-structures to the next non-empty, non-aggregate |
| /// subtype. |
| static bool nextRealType(SmallVectorImpl<CompositeType *> &SubTypes, |
| SmallVectorImpl<unsigned> &Path) { |
| do { |
| if (!advanceToNextLeafType(SubTypes, Path)) |
| return false; |
| |
| assert(!Path.empty() && "found a leaf but didn't set the path?"); |
| } while (SubTypes.back()->getTypeAtIndex(Path.back())->isAggregateType()); |
| |
| return true; |
| } |
| |
| |
| /// Test if the given instruction is in a position to be optimized |
| /// with a tail-call. This roughly means that it's in a block with |
| /// a return and there's nothing that needs to be scheduled |
| /// between it and the return. |
| /// |
| /// This function only tests target-independent requirements. |
| bool llvm::isInTailCallPosition(ImmutableCallSite CS, const TargetMachine &TM) { |
| const Instruction *I = CS.getInstruction(); |
| const BasicBlock *ExitBB = I->getParent(); |
| const TerminatorInst *Term = ExitBB->getTerminator(); |
| const ReturnInst *Ret = dyn_cast<ReturnInst>(Term); |
| |
| // The block must end in a return statement or unreachable. |
| // |
| // FIXME: Decline tailcall if it's not guaranteed and if the block ends in |
| // an unreachable, for now. The way tailcall optimization is currently |
| // implemented means it will add an epilogue followed by a jump. That is |
| // not profitable. Also, if the callee is a special function (e.g. |
| // longjmp on x86), it can end up causing miscompilation that has not |
| // been fully understood. |
| if (!Ret && |
| (!TM.Options.GuaranteedTailCallOpt || !isa<UnreachableInst>(Term))) |
| return false; |
| |
| // If I will have a chain, make sure no other instruction that will have a |
| // chain interposes between I and the return. |
| if (I->mayHaveSideEffects() || I->mayReadFromMemory() || |
| !isSafeToSpeculativelyExecute(I)) |
| for (BasicBlock::const_iterator BBI = std::prev(ExitBB->end(), 2);; --BBI) { |
| if (&*BBI == I) |
| break; |
| // Debug info intrinsics do not get in the way of tail call optimization. |
| if (isa<DbgInfoIntrinsic>(BBI)) |
| continue; |
| if (BBI->mayHaveSideEffects() || BBI->mayReadFromMemory() || |
| !isSafeToSpeculativelyExecute(BBI)) |
| return false; |
| } |
| |
| return returnTypeIsEligibleForTailCall(ExitBB->getParent(), I, Ret, |
| *TM.getTargetLowering()); |
| } |
| |
| bool llvm::returnTypeIsEligibleForTailCall(const Function *F, |
| const Instruction *I, |
| const ReturnInst *Ret, |
| const TargetLoweringBase &TLI) { |
| // If the block ends with a void return or unreachable, it doesn't matter |
| // what the call's return type is. |
| if (!Ret || Ret->getNumOperands() == 0) return true; |
| |
| // If the return value is undef, it doesn't matter what the call's |
| // return type is. |
| if (isa<UndefValue>(Ret->getOperand(0))) return true; |
| |
| // Make sure the attributes attached to each return are compatible. |
| AttrBuilder CallerAttrs(F->getAttributes(), |
| AttributeSet::ReturnIndex); |
| AttrBuilder CalleeAttrs(cast<CallInst>(I)->getAttributes(), |
| AttributeSet::ReturnIndex); |
| |
| // Noalias is completely benign as far as calling convention goes, it |
| // shouldn't affect whether the call is a tail call. |
| CallerAttrs = CallerAttrs.removeAttribute(Attribute::NoAlias); |
| CalleeAttrs = CalleeAttrs.removeAttribute(Attribute::NoAlias); |
| |
| bool AllowDifferingSizes = true; |
| if (CallerAttrs.contains(Attribute::ZExt)) { |
| if (!CalleeAttrs.contains(Attribute::ZExt)) |
| return false; |
| |
| AllowDifferingSizes = false; |
| CallerAttrs.removeAttribute(Attribute::ZExt); |
| CalleeAttrs.removeAttribute(Attribute::ZExt); |
| } else if (CallerAttrs.contains(Attribute::SExt)) { |
| if (!CalleeAttrs.contains(Attribute::SExt)) |
| return false; |
| |
| AllowDifferingSizes = false; |
| CallerAttrs.removeAttribute(Attribute::SExt); |
| CalleeAttrs.removeAttribute(Attribute::SExt); |
| } |
| |
| // If they're still different, there's some facet we don't understand |
| // (currently only "inreg", but in future who knows). It may be OK but the |
| // only safe option is to reject the tail call. |
| if (CallerAttrs != CalleeAttrs) |
| return false; |
| |
| const Value *RetVal = Ret->getOperand(0), *CallVal = I; |
| SmallVector<unsigned, 4> RetPath, CallPath; |
| SmallVector<CompositeType *, 4> RetSubTypes, CallSubTypes; |
| |
| bool RetEmpty = !firstRealType(RetVal->getType(), RetSubTypes, RetPath); |
| bool CallEmpty = !firstRealType(CallVal->getType(), CallSubTypes, CallPath); |
| |
| // Nothing's actually returned, it doesn't matter what the callee put there |
| // it's a valid tail call. |
| if (RetEmpty) |
| return true; |
| |
| // Iterate pairwise through each of the value types making up the tail call |
| // and the corresponding return. For each one we want to know whether it's |
| // essentially going directly from the tail call to the ret, via operations |
| // that end up not generating any code. |
| // |
| // We allow a certain amount of covariance here. For example it's permitted |
| // for the tail call to define more bits than the ret actually cares about |
| // (e.g. via a truncate). |
| do { |
| if (CallEmpty) { |
| // We've exhausted the values produced by the tail call instruction, the |
| // rest are essentially undef. The type doesn't really matter, but we need |
| // *something*. |
| Type *SlotType = RetSubTypes.back()->getTypeAtIndex(RetPath.back()); |
| CallVal = UndefValue::get(SlotType); |
| } |
| |
| // The manipulations performed when we're looking through an insertvalue or |
| // an extractvalue would happen at the front of the RetPath list, so since |
| // we have to copy it anyway it's more efficient to create a reversed copy. |
| using std::copy; |
| SmallVector<unsigned, 4> TmpRetPath, TmpCallPath; |
| copy(RetPath.rbegin(), RetPath.rend(), std::back_inserter(TmpRetPath)); |
| copy(CallPath.rbegin(), CallPath.rend(), std::back_inserter(TmpCallPath)); |
| |
| // Finally, we can check whether the value produced by the tail call at this |
| // index is compatible with the value we return. |
| if (!slotOnlyDiscardsData(RetVal, CallVal, TmpRetPath, TmpCallPath, |
| AllowDifferingSizes, TLI)) |
| return false; |
| |
| CallEmpty = !nextRealType(CallSubTypes, CallPath); |
| } while(nextRealType(RetSubTypes, RetPath)); |
| |
| return true; |
| } |
