| //===-- 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/Module.h" |
| #include "llvm/Support/ErrorHandling.h" |
| #include "llvm/Target/TargetMachine.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<StructType>(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<ArrayType>(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<EVT> &ValueVTs, |
| SmallVectorImpl<EVT> *MemVTs, |
| SmallVectorImpl<uint64_t> *Offsets, |
| uint64_t StartingOffset) { |
| // Given a struct type, recursively traverse the elements. |
| if (StructType *STy = dyn_cast<StructType>(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<ArrayType>(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<EVT> &ValueVTs, |
| SmallVectorImpl<uint64_t> *Offsets, |
| uint64_t StartingOffset) { |
| return ComputeValueVTs(TLI, DL, Ty, ValueVTs, /*MemVTs=*/nullptr, Offsets, |
| StartingOffset); |
| } |
| |
| void llvm::computeValueLLTs(const DataLayout &DL, Type &Ty, |
| SmallVectorImpl<LLT> &ValueTys, |
| SmallVectorImpl<uint64_t> *Offsets, |
| uint64_t StartingOffset) { |
| // Given a struct type, recursively traverse the elements. |
| if (StructType *STy = dyn_cast<StructType>(&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<ArrayType>(&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<GlobalValue>(V); |
| GlobalVariable *Var = dyn_cast<GlobalVariable>(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<GlobalValue>(Init); |
| if (!GV) V = cast<ConstantPointerNull>(Init); |
| } |
| |
| assert((GV || isa<ConstantPointerNull>(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; |
| } |
| } |
| |
| 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!"); |
| } |
| } |
| |
| ICmpInst::Predicate llvm::getICmpCondCode(ISD::CondCode Pred) { |
| switch (Pred) { |
| case ISD::SETEQ: |
| return ICmpInst::ICMP_EQ; |
| case ISD::SETNE: |
| return ICmpInst::ICMP_NE; |
| case ISD::SETLE: |
| return ICmpInst::ICMP_SLE; |
| case ISD::SETULE: |
| return ICmpInst::ICMP_ULE; |
| case ISD::SETGE: |
| return ICmpInst::ICMP_SGE; |
| case ISD::SETUGE: |
| return ICmpInst::ICMP_UGE; |
| case ISD::SETLT: |
| return ICmpInst::ICMP_SLT; |
| case ISD::SETULT: |
| return ICmpInst::ICMP_ULT; |
| case ISD::SETGT: |
| return ICmpInst::ICMP_SGT; |
| case ISD::SETUGT: |
| return ICmpInst::ICMP_UGT; |
| default: |
| llvm_unreachable("Invalid ISD integer condition code!"); |
| } |
| } |
| |
| 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 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<unsigned> &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<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()) && |
| DL.getPointerSizeInBits() == |
| 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()) && |
| DL.getPointerSizeInBits() == |
| cast<IntegerType>(I->getType())->getBitWidth()) |
| NoopInput = Op; |
| } else if (isa<TruncInst>(I) && |
| TLI.allowTruncateForTailCall(Op->getType(), I->getType())) { |
| DataBits = |
| std::min((uint64_t)DataBits, |
| I->getType()->getPrimitiveSizeInBits().getFixedValue()); |
| NoopInput = Op; |
| } else if (auto *CB = dyn_cast<CallBase>(I)) { |
| const Value *ReturnedOp = CB->getReturnedArgOperand(); |
| if (ReturnedOp && isNoopBitcast(ReturnedOp->getType(), I->getType(), TLI)) |
| NoopInput = ReturnedOp; |
| } 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 (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<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(); |
| 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<unsigned> &RetIndices, |
| SmallVectorImpl<unsigned> &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<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, 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<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<Type *> &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 = |
| 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<Type *> &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 (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<Type *> &SubTypes, |
| SmallVectorImpl<unsigned> &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<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 && |
| Call.getCallingConv() != CallingConv::Tail && |
| Call.getCallingConv() != CallingConv::SwiftTail) || |
| !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. |
| // 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. |
| // Pseudo probe intrinsics do not block tail call optimization either. |
| if (BBI->isDebugOrPseudoInst()) |
| continue; |
| // A lifetime end, assume or noalias.decl intrinsic should not stop tail |
| // call optimization. |
| if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(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->getContext(), F->getAttributes().getRetAttrs()); |
| AttrBuilder CalleeAttrs(F->getContext(), |
| cast<CallInst>(I)->getAttributes().getRetAttrs()); |
| |
| // 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, Attribute::NoUndef}) { |
| 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<BitCastInst>(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<UndefValue>(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<CallInst>(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<unsigned, 4> RetPath, CallPath; |
| SmallVector<Type *, 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 = |
| 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<unsigned, 4> TmpRetPath(llvm::reverse(RetPath)); |
| SmallVector<unsigned, 4> TmpCallPath(llvm::reverse(CallPath)); |
| |
| // 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<const MachineBasicBlock *, int> &EHScopeMembership, int EHScope, |
| const MachineBasicBlock *MBB) { |
| SmallVector<const MachineBasicBlock *, 16> 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<const MachineBasicBlock *, int> |
| llvm::getEHScopeMembership(const MachineFunction &MF) { |
| DenseMap<const MachineBasicBlock *, int> 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<const MachineBasicBlock *, 16> EHScopeBlocks; |
| SmallVector<const MachineBasicBlock *, 16> UnreachableBlocks; |
| SmallVector<const MachineBasicBlock *, 16> SEHCatchPads; |
| SmallVector<std::pair<const MachineBasicBlock *, int>, 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<const MachineBasicBlock *, int> CatchRetPair : |
| CatchRetSuccessors) |
| collectEHScopeMembers(EHScopeMembership, CatchRetPair.second, |
| CatchRetPair.first); |
| return EHScopeMembership; |
| } |
