//===-- Analysis.cpp - CodeGen LLVM IR Analysis Utilities -----------------===// // // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. // See https://llvm.org/LICENSE.txt for license information. // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception // //===----------------------------------------------------------------------===// // // 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/TargetInstrInfo.h" #include "llvm/CodeGen/TargetLowering.h" #include "llvm/CodeGen/TargetSubtargetInfo.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/TargetMachine.h" #include "llvm/Transforms/Utils/GlobalStatus.h" using namespace llvm; /// Compute the linearized index of a member in a nested aggregate/struct/array /// by recursing and accumulating CurIndex as long as there are indices in the /// index list. 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(Ty)) { for (auto I : llvm::enumerate(STy->elements())) { Type *ET = I.value(); if (Indices && *Indices == I.index()) return ComputeLinearIndex(ET, Indices + 1, IndicesEnd, CurIndex); CurIndex = ComputeLinearIndex(ET, nullptr, nullptr, CurIndex); } assert(!Indices && "Unexpected out of bound"); return CurIndex; } // Given an array type, recursively traverse the elements. else if (ArrayType *ATy = dyn_cast(Ty)) { Type *EltTy = ATy->getElementType(); unsigned NumElts = ATy->getNumElements(); // Compute the Linear offset when jumping one element of the array unsigned EltLinearOffset = ComputeLinearIndex(EltTy, nullptr, nullptr, 0); if (Indices) { assert(*Indices < NumElts && "Unexpected out of bound"); // If the indice is inside the array, compute the index to the requested // elt and recurse inside the element with the end of the indices list CurIndex += EltLinearOffset* *Indices; return ComputeLinearIndex(EltTy, Indices+1, IndicesEnd, CurIndex); } CurIndex += EltLinearOffset*NumElts; 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, const DataLayout &DL, Type *Ty, SmallVectorImpl &ValueVTs, SmallVectorImpl *MemVTs, SmallVectorImpl *Offsets, uint64_t StartingOffset) { // Given a struct type, recursively traverse the elements. if (StructType *STy = dyn_cast(Ty)) { // If the Offsets aren't needed, don't query the struct layout. This allows // us to support structs with scalable vectors for operations that don't // need offsets. const StructLayout *SL = Offsets ? DL.getStructLayout(STy) : nullptr; for (StructType::element_iterator EB = STy->element_begin(), EI = EB, EE = STy->element_end(); EI != EE; ++EI) { // Don't compute the element offset if we didn't get a StructLayout above. uint64_t EltOffset = SL ? SL->getElementOffset(EI - EB) : 0; ComputeValueVTs(TLI, DL, *EI, ValueVTs, MemVTs, Offsets, StartingOffset + EltOffset); } return; } // Given an array type, recursively traverse the elements. if (ArrayType *ATy = dyn_cast(Ty)) { Type *EltTy = ATy->getElementType(); uint64_t EltSize = DL.getTypeAllocSize(EltTy).getFixedValue(); for (unsigned i = 0, e = ATy->getNumElements(); i != e; ++i) ComputeValueVTs(TLI, DL, EltTy, ValueVTs, MemVTs, 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(DL, Ty)); if (MemVTs) MemVTs->push_back(TLI.getMemValueType(DL, Ty)); if (Offsets) Offsets->push_back(StartingOffset); } void llvm::ComputeValueVTs(const TargetLowering &TLI, const DataLayout &DL, Type *Ty, SmallVectorImpl &ValueVTs, SmallVectorImpl *Offsets, uint64_t StartingOffset) { return ComputeValueVTs(TLI, DL, Ty, ValueVTs, /*MemVTs=*/nullptr, Offsets, StartingOffset); } void llvm::computeValueLLTs(const DataLayout &DL, Type &Ty, SmallVectorImpl &ValueTys, SmallVectorImpl *Offsets, uint64_t StartingOffset) { // Given a struct type, recursively traverse the elements. if (StructType *STy = dyn_cast(&Ty)) { // If the Offsets aren't needed, don't query the struct layout. This allows // us to support structs with scalable vectors for operations that don't // need offsets. const StructLayout *SL = Offsets ? DL.getStructLayout(STy) : nullptr; for (unsigned I = 0, E = STy->getNumElements(); I != E; ++I) { uint64_t EltOffset = SL ? SL->getElementOffset(I) : 0; computeValueLLTs(DL, *STy->getElementType(I), ValueTys, Offsets, StartingOffset + EltOffset); } return; } // Given an array type, recursively traverse the elements. if (ArrayType *ATy = dyn_cast(&Ty)) { Type *EltTy = ATy->getElementType(); uint64_t EltSize = DL.getTypeAllocSize(EltTy).getFixedValue(); for (unsigned i = 0, e = ATy->getNumElements(); i != e; ++i) computeValueLLTs(DL, *EltTy, ValueTys, Offsets, StartingOffset + i * EltSize); return; } // Interpret void as zero return values. if (Ty.isVoidTy()) return; // Base case: we can get an LLT for this LLVM IR type. ValueTys.push_back(getLLTForType(Ty, DL)); if (Offsets != nullptr) Offsets->push_back(StartingOffset * 8); } /// ExtractTypeInfo - Returns the type info, possibly bitcast, encoded in V. GlobalValue *llvm::ExtractTypeInfo(Value *V) { V = V->stripPointerCasts(); GlobalValue *GV = dyn_cast(V); GlobalVariable *Var = dyn_cast(V); if (Var && Var->getName() == "llvm.eh.catch.all.value") { assert(Var->hasInitializer() && "The EH catch-all value must have an initializer"); Value *Init = Var->getInitializer(); GV = dyn_cast(Init); if (!GV) V = cast(Init); } assert((GV || isa(V)) && "TypeInfo must be a global variable or NULL"); return GV; } /// 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(T1) && isa(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 aggregate 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 &ValLoc, unsigned &DataBits, const TargetLoweringBase &TLI, const DataLayout &DL) { while (true) { // Try to look through V1; if V1 is not an instruction, it can't be looked // through. const Instruction *I = dyn_cast(V); if (!I || I->getNumOperands() == 0) return V; const Value *NoopInput = nullptr; Value *Op = I->getOperand(0); if (isa(I)) { // Look through truly no-op bitcasts. if (isNoopBitcast(Op->getType(), I->getType(), TLI)) NoopInput = Op; } else if (isa(I)) { // Look through getelementptr if (cast(I)->hasAllZeroIndices()) NoopInput = Op; } else if (isa(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(I->getType()) && DL.getPointerSizeInBits() == cast(Op->getType())->getBitWidth()) NoopInput = Op; } else if (isa(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(I->getType()) && DL.getPointerSizeInBits() == cast(I->getType())->getBitWidth()) NoopInput = Op; } else if (isa(I) && TLI.allowTruncateForTailCall(Op->getType(), I->getType())) { DataBits = std::min((uint64_t)DataBits, I->getType()->getPrimitiveSizeInBits().getFixedSize()); NoopInput = Op; } else if (auto *CB = dyn_cast(I)) { const Value *ReturnedOp = CB->getReturnedArgOperand(); if (ReturnedOp && isNoopBitcast(ReturnedOp->getType(), I->getType(), TLI)) NoopInput = ReturnedOp; } else if (const InsertValueInst *IVI = dyn_cast(V)) { // Value may come from either the aggregate or the scalar ArrayRef InsertLoc = IVI->getIndices(); if (ValLoc.size() >= InsertLoc.size() && std::equal(InsertLoc.begin(), InsertLoc.end(), 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(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 ExtractLoc = EVI->getIndices(); ValLoc.append(ExtractLoc.rbegin(), ExtractLoc.rend()); 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 &RetIndices, SmallVectorImpl &CallIndices, bool AllowDifferingSizes, const TargetLoweringBase &TLI, const DataLayout &DL) { // 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, DL); // If this slot in the value returned is undef, it doesn't matter what the // call puts there, it'll be fine. if (isa(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, DL); // 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(Type *T, unsigned Idx) { if (ArrayType *AT = dyn_cast(T)) return Idx < AT->getNumElements(); return Idx < cast(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 &SubTypes, SmallVectorImpl &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 = ExtractValueInst::getIndexedType(SubTypes.back(), Path.back()); while (DeeperType->isAggregateType()) { if (!indexReallyValid(DeeperType, 0)) return true; SubTypes.push_back(DeeperType); Path.push_back(0); DeeperType = ExtractValueInst::getIndexedType(DeeperType, 0); } 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 &SubTypes, SmallVectorImpl &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 (Type *FirstInner = ExtractValueInst::getIndexedType(Next, 0)) { SubTypes.push_back(Next); Path.push_back(0); Next = FirstInner; } // 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 (ExtractValueInst::getIndexedType(SubTypes.back(), 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 &SubTypes, SmallVectorImpl &Path) { do { if (!advanceToNextLeafType(SubTypes, Path)) return false; assert(!Path.empty() && "found a leaf but didn't set the path?"); } while (ExtractValueInst::getIndexedType(SubTypes.back(), 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(const CallBase &Call, const TargetMachine &TM) { const BasicBlock *ExitBB = Call.getParent(); const Instruction *Term = ExitBB->getTerminator(); const ReturnInst *Ret = dyn_cast(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 && Call.getCallingConv() != CallingConv::Tail && Call.getCallingConv() != CallingConv::SwiftTail) || !isa(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. // Check for all calls including speculatable functions. for (BasicBlock::const_iterator BBI = std::prev(ExitBB->end(), 2);; --BBI) { if (&*BBI == &Call) break; // Debug info intrinsics do not get in the way of tail call optimization. if (isa(BBI)) continue; // Pseudo probe intrinsics do not block tail call optimization either. if (isa(BBI)) continue; // A lifetime end, assume or noalias.decl intrinsic should not stop tail // call optimization. if (const IntrinsicInst *II = dyn_cast(BBI)) if (II->getIntrinsicID() == Intrinsic::lifetime_end || II->getIntrinsicID() == Intrinsic::assume || II->getIntrinsicID() == Intrinsic::experimental_noalias_scope_decl) continue; if (BBI->mayHaveSideEffects() || BBI->mayReadFromMemory() || !isSafeToSpeculativelyExecute(&*BBI)) return false; } const Function *F = ExitBB->getParent(); return returnTypeIsEligibleForTailCall( F, &Call, Ret, *TM.getSubtargetImpl(*F)->getTargetLowering()); } bool llvm::attributesPermitTailCall(const Function *F, const Instruction *I, const ReturnInst *Ret, const TargetLoweringBase &TLI, bool *AllowDifferingSizes) { // ADS may be null, so don't write to it directly. bool DummyADS; bool &ADS = AllowDifferingSizes ? *AllowDifferingSizes : DummyADS; ADS = true; AttrBuilder CallerAttrs(F->getAttributes(), AttributeList::ReturnIndex); AttrBuilder CalleeAttrs(cast(I)->getAttributes(), AttributeList::ReturnIndex); // Following attributes are completely benign as far as calling convention // goes, they shouldn't affect whether the call is a tail call. for (const auto &Attr : {Attribute::Alignment, Attribute::Dereferenceable, Attribute::DereferenceableOrNull, Attribute::NoAlias, Attribute::NonNull}) { CallerAttrs.removeAttribute(Attr); CalleeAttrs.removeAttribute(Attr); } if (CallerAttrs.contains(Attribute::ZExt)) { if (!CalleeAttrs.contains(Attribute::ZExt)) return false; ADS = false; CallerAttrs.removeAttribute(Attribute::ZExt); CalleeAttrs.removeAttribute(Attribute::ZExt); } else if (CallerAttrs.contains(Attribute::SExt)) { if (!CalleeAttrs.contains(Attribute::SExt)) return false; ADS = false; CallerAttrs.removeAttribute(Attribute::SExt); CalleeAttrs.removeAttribute(Attribute::SExt); } // Drop sext and zext return attributes if the result is not used. // This enables tail calls for code like: // // define void @caller() { // entry: // %unused_result = tail call zeroext i1 @callee() // br label %retlabel // retlabel: // ret void // } if (I->use_empty()) { CalleeAttrs.removeAttribute(Attribute::SExt); CalleeAttrs.removeAttribute(Attribute::ZExt); } // 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. return CallerAttrs == CalleeAttrs; } /// Check whether B is a bitcast of a pointer type to another pointer type, /// which is equal to A. static bool isPointerBitcastEqualTo(const Value *A, const Value *B) { assert(A && B && "Expected non-null inputs!"); auto *BitCastIn = dyn_cast(B); if (!BitCastIn) return false; if (!A->getType()->isPointerTy() || !B->getType()->isPointerTy()) return false; return A == BitCastIn->getOperand(0); } 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(Ret->getOperand(0))) return true; // Make sure the attributes attached to each return are compatible. bool AllowDifferingSizes; if (!attributesPermitTailCall(F, I, Ret, TLI, &AllowDifferingSizes)) return false; const Value *RetVal = Ret->getOperand(0), *CallVal = I; // Intrinsic like llvm.memcpy has no return value, but the expanded // libcall may or may not have return value. On most platforms, it // will be expanded as memcpy in libc, which returns the first // argument. On other platforms like arm-none-eabi, memcpy may be // expanded as library call without return value, like __aeabi_memcpy. const CallInst *Call = cast(I); if (Function *F = Call->getCalledFunction()) { Intrinsic::ID IID = F->getIntrinsicID(); if (((IID == Intrinsic::memcpy && TLI.getLibcallName(RTLIB::MEMCPY) == StringRef("memcpy")) || (IID == Intrinsic::memmove && TLI.getLibcallName(RTLIB::MEMMOVE) == StringRef("memmove")) || (IID == Intrinsic::memset && TLI.getLibcallName(RTLIB::MEMSET) == StringRef("memset"))) && (RetVal == Call->getArgOperand(0) || isPointerBitcastEqualTo(RetVal, Call->getArgOperand(0)))) return true; } SmallVector RetPath, CallPath; SmallVector 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 = ExtractValueInst::getIndexedType(RetSubTypes.back(), 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. SmallVector TmpRetPath(RetPath.rbegin(), RetPath.rend()); SmallVector TmpCallPath(CallPath.rbegin(), CallPath.rend()); // 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, F->getParent()->getDataLayout())) return false; CallEmpty = !nextRealType(CallSubTypes, CallPath); } while(nextRealType(RetSubTypes, RetPath)); return true; } static void collectEHScopeMembers( DenseMap &EHScopeMembership, int EHScope, const MachineBasicBlock *MBB) { SmallVector Worklist = {MBB}; while (!Worklist.empty()) { const MachineBasicBlock *Visiting = Worklist.pop_back_val(); // Don't follow blocks which start new scopes. if (Visiting->isEHPad() && Visiting != MBB) continue; // Add this MBB to our scope. auto P = EHScopeMembership.insert(std::make_pair(Visiting, EHScope)); // Don't revisit blocks. if (!P.second) { assert(P.first->second == EHScope && "MBB is part of two scopes!"); continue; } // Returns are boundaries where scope transfer can occur, don't follow // successors. if (Visiting->isEHScopeReturnBlock()) continue; append_range(Worklist, Visiting->successors()); } } DenseMap llvm::getEHScopeMembership(const MachineFunction &MF) { DenseMap EHScopeMembership; // We don't have anything to do if there aren't any EH pads. if (!MF.hasEHScopes()) return EHScopeMembership; int EntryBBNumber = MF.front().getNumber(); bool IsSEH = isAsynchronousEHPersonality( classifyEHPersonality(MF.getFunction().getPersonalityFn())); const TargetInstrInfo *TII = MF.getSubtarget().getInstrInfo(); SmallVector EHScopeBlocks; SmallVector UnreachableBlocks; SmallVector SEHCatchPads; SmallVector, 16> CatchRetSuccessors; for (const MachineBasicBlock &MBB : MF) { if (MBB.isEHScopeEntry()) { EHScopeBlocks.push_back(&MBB); } else if (IsSEH && MBB.isEHPad()) { SEHCatchPads.push_back(&MBB); } else if (MBB.pred_empty()) { UnreachableBlocks.push_back(&MBB); } MachineBasicBlock::const_iterator MBBI = MBB.getFirstTerminator(); // CatchPads are not scopes for SEH so do not consider CatchRet to // transfer control to another scope. if (MBBI == MBB.end() || MBBI->getOpcode() != TII->getCatchReturnOpcode()) continue; // FIXME: SEH CatchPads are not necessarily in the parent function: // they could be inside a finally block. const MachineBasicBlock *Successor = MBBI->getOperand(0).getMBB(); const MachineBasicBlock *SuccessorColor = MBBI->getOperand(1).getMBB(); CatchRetSuccessors.push_back( {Successor, IsSEH ? EntryBBNumber : SuccessorColor->getNumber()}); } // We don't have anything to do if there aren't any EH pads. if (EHScopeBlocks.empty()) return EHScopeMembership; // Identify all the basic blocks reachable from the function entry. collectEHScopeMembers(EHScopeMembership, EntryBBNumber, &MF.front()); // All blocks not part of a scope are in the parent function. for (const MachineBasicBlock *MBB : UnreachableBlocks) collectEHScopeMembers(EHScopeMembership, EntryBBNumber, MBB); // Next, identify all the blocks inside the scopes. for (const MachineBasicBlock *MBB : EHScopeBlocks) collectEHScopeMembers(EHScopeMembership, MBB->getNumber(), MBB); // SEH CatchPads aren't really scopes, handle them separately. for (const MachineBasicBlock *MBB : SEHCatchPads) collectEHScopeMembers(EHScopeMembership, EntryBBNumber, MBB); // Finally, identify all the targets of a catchret. for (std::pair CatchRetPair : CatchRetSuccessors) collectEHScopeMembers(EHScopeMembership, CatchRetPair.second, CatchRetPair.first); return EHScopeMembership; }