| //===- ScalarReplAggregates.cpp - Scalar Replacement of Aggregates --------===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This transformation implements the well known scalar replacement of |
| // aggregates transformation. This xform breaks up alloca instructions of |
| // aggregate type (structure or array) into individual alloca instructions for |
| // each member (if possible). Then, if possible, it transforms the individual |
| // alloca instructions into nice clean scalar SSA form. |
| // |
| // This combines a simple SRoA algorithm with the Mem2Reg algorithm because |
| // often interact, especially for C++ programs. As such, iterating between |
| // SRoA, then Mem2Reg until we run out of things to promote works well. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #define DEBUG_TYPE "scalarrepl" |
| #include "llvm/Transforms/Scalar.h" |
| #include "llvm/Constants.h" |
| #include "llvm/DerivedTypes.h" |
| #include "llvm/Function.h" |
| #include "llvm/GlobalVariable.h" |
| #include "llvm/Instructions.h" |
| #include "llvm/IntrinsicInst.h" |
| #include "llvm/LLVMContext.h" |
| #include "llvm/Module.h" |
| #include "llvm/Pass.h" |
| #include "llvm/Analysis/DebugInfo.h" |
| #include "llvm/Analysis/DIBuilder.h" |
| #include "llvm/Analysis/Dominators.h" |
| #include "llvm/Analysis/Loads.h" |
| #include "llvm/Analysis/ValueTracking.h" |
| #include "llvm/Target/TargetData.h" |
| #include "llvm/Transforms/Utils/PromoteMemToReg.h" |
| #include "llvm/Transforms/Utils/Local.h" |
| #include "llvm/Transforms/Utils/SSAUpdater.h" |
| #include "llvm/Support/CallSite.h" |
| #include "llvm/Support/Debug.h" |
| #include "llvm/Support/ErrorHandling.h" |
| #include "llvm/Support/GetElementPtrTypeIterator.h" |
| #include "llvm/Support/IRBuilder.h" |
| #include "llvm/Support/MathExtras.h" |
| #include "llvm/Support/raw_ostream.h" |
| #include "llvm/ADT/SetVector.h" |
| #include "llvm/ADT/SmallVector.h" |
| #include "llvm/ADT/Statistic.h" |
| using namespace llvm; |
| |
| STATISTIC(NumReplaced, "Number of allocas broken up"); |
| STATISTIC(NumPromoted, "Number of allocas promoted"); |
| STATISTIC(NumAdjusted, "Number of scalar allocas adjusted to allow promotion"); |
| STATISTIC(NumConverted, "Number of aggregates converted to scalar"); |
| STATISTIC(NumGlobals, "Number of allocas copied from constant global"); |
| |
| namespace { |
| struct SROA : public FunctionPass { |
| SROA(int T, bool hasDT, char &ID) |
| : FunctionPass(ID), HasDomTree(hasDT) { |
| if (T == -1) |
| SRThreshold = 128; |
| else |
| SRThreshold = T; |
| } |
| |
| bool runOnFunction(Function &F); |
| |
| bool performScalarRepl(Function &F); |
| bool performPromotion(Function &F); |
| |
| private: |
| bool HasDomTree; |
| TargetData *TD; |
| |
| /// DeadInsts - Keep track of instructions we have made dead, so that |
| /// we can remove them after we are done working. |
| SmallVector<Value*, 32> DeadInsts; |
| |
| /// AllocaInfo - When analyzing uses of an alloca instruction, this captures |
| /// information about the uses. All these fields are initialized to false |
| /// and set to true when something is learned. |
| struct AllocaInfo { |
| /// The alloca to promote. |
| AllocaInst *AI; |
| |
| /// CheckedPHIs - This is a set of verified PHI nodes, to prevent infinite |
| /// looping and avoid redundant work. |
| SmallPtrSet<PHINode*, 8> CheckedPHIs; |
| |
| /// isUnsafe - This is set to true if the alloca cannot be SROA'd. |
| bool isUnsafe : 1; |
| |
| /// isMemCpySrc - This is true if this aggregate is memcpy'd from. |
| bool isMemCpySrc : 1; |
| |
| /// isMemCpyDst - This is true if this aggregate is memcpy'd into. |
| bool isMemCpyDst : 1; |
| |
| /// hasSubelementAccess - This is true if a subelement of the alloca is |
| /// ever accessed, or false if the alloca is only accessed with mem |
| /// intrinsics or load/store that only access the entire alloca at once. |
| bool hasSubelementAccess : 1; |
| |
| /// hasALoadOrStore - This is true if there are any loads or stores to it. |
| /// The alloca may just be accessed with memcpy, for example, which would |
| /// not set this. |
| bool hasALoadOrStore : 1; |
| |
| explicit AllocaInfo(AllocaInst *ai) |
| : AI(ai), isUnsafe(false), isMemCpySrc(false), isMemCpyDst(false), |
| hasSubelementAccess(false), hasALoadOrStore(false) {} |
| }; |
| |
| unsigned SRThreshold; |
| |
| void MarkUnsafe(AllocaInfo &I, Instruction *User) { |
| I.isUnsafe = true; |
| DEBUG(dbgs() << " Transformation preventing inst: " << *User << '\n'); |
| } |
| |
| bool isSafeAllocaToScalarRepl(AllocaInst *AI); |
| |
| void isSafeForScalarRepl(Instruction *I, uint64_t Offset, AllocaInfo &Info); |
| void isSafePHISelectUseForScalarRepl(Instruction *User, uint64_t Offset, |
| AllocaInfo &Info); |
| void isSafeGEP(GetElementPtrInst *GEPI, uint64_t &Offset, AllocaInfo &Info); |
| void isSafeMemAccess(uint64_t Offset, uint64_t MemSize, |
| Type *MemOpType, bool isStore, AllocaInfo &Info, |
| Instruction *TheAccess, bool AllowWholeAccess); |
| bool TypeHasComponent(Type *T, uint64_t Offset, uint64_t Size); |
| uint64_t FindElementAndOffset(Type *&T, uint64_t &Offset, |
| Type *&IdxTy); |
| |
| void DoScalarReplacement(AllocaInst *AI, |
| std::vector<AllocaInst*> &WorkList); |
| void DeleteDeadInstructions(); |
| |
| void RewriteForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset, |
| SmallVector<AllocaInst*, 32> &NewElts); |
| void RewriteBitCast(BitCastInst *BC, AllocaInst *AI, uint64_t Offset, |
| SmallVector<AllocaInst*, 32> &NewElts); |
| void RewriteGEP(GetElementPtrInst *GEPI, AllocaInst *AI, uint64_t Offset, |
| SmallVector<AllocaInst*, 32> &NewElts); |
| void RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *Inst, |
| AllocaInst *AI, |
| SmallVector<AllocaInst*, 32> &NewElts); |
| void RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocaInst *AI, |
| SmallVector<AllocaInst*, 32> &NewElts); |
| void RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocaInst *AI, |
| SmallVector<AllocaInst*, 32> &NewElts); |
| |
| static MemTransferInst *isOnlyCopiedFromConstantGlobal( |
| AllocaInst *AI, SmallVector<Instruction*, 4> &ToDelete); |
| }; |
| |
| // SROA_DT - SROA that uses DominatorTree. |
| struct SROA_DT : public SROA { |
| static char ID; |
| public: |
| SROA_DT(int T = -1) : SROA(T, true, ID) { |
| initializeSROA_DTPass(*PassRegistry::getPassRegistry()); |
| } |
| |
| // getAnalysisUsage - This pass does not require any passes, but we know it |
| // will not alter the CFG, so say so. |
| virtual void getAnalysisUsage(AnalysisUsage &AU) const { |
| AU.addRequired<DominatorTree>(); |
| AU.setPreservesCFG(); |
| } |
| }; |
| |
| // SROA_SSAUp - SROA that uses SSAUpdater. |
| struct SROA_SSAUp : public SROA { |
| static char ID; |
| public: |
| SROA_SSAUp(int T = -1) : SROA(T, false, ID) { |
| initializeSROA_SSAUpPass(*PassRegistry::getPassRegistry()); |
| } |
| |
| // getAnalysisUsage - This pass does not require any passes, but we know it |
| // will not alter the CFG, so say so. |
| virtual void getAnalysisUsage(AnalysisUsage &AU) const { |
| AU.setPreservesCFG(); |
| } |
| }; |
| |
| } |
| |
| char SROA_DT::ID = 0; |
| char SROA_SSAUp::ID = 0; |
| |
| INITIALIZE_PASS_BEGIN(SROA_DT, "scalarrepl", |
| "Scalar Replacement of Aggregates (DT)", false, false) |
| INITIALIZE_PASS_DEPENDENCY(DominatorTree) |
| INITIALIZE_PASS_END(SROA_DT, "scalarrepl", |
| "Scalar Replacement of Aggregates (DT)", false, false) |
| |
| INITIALIZE_PASS_BEGIN(SROA_SSAUp, "scalarrepl-ssa", |
| "Scalar Replacement of Aggregates (SSAUp)", false, false) |
| INITIALIZE_PASS_END(SROA_SSAUp, "scalarrepl-ssa", |
| "Scalar Replacement of Aggregates (SSAUp)", false, false) |
| |
| // Public interface to the ScalarReplAggregates pass |
| FunctionPass *llvm::createScalarReplAggregatesPass(int Threshold, |
| bool UseDomTree) { |
| if (UseDomTree) |
| return new SROA_DT(Threshold); |
| return new SROA_SSAUp(Threshold); |
| } |
| |
| |
| //===----------------------------------------------------------------------===// |
| // Convert To Scalar Optimization. |
| //===----------------------------------------------------------------------===// |
| |
| namespace { |
| /// ConvertToScalarInfo - This class implements the "Convert To Scalar" |
| /// optimization, which scans the uses of an alloca and determines if it can |
| /// rewrite it in terms of a single new alloca that can be mem2reg'd. |
| class ConvertToScalarInfo { |
| /// AllocaSize - The size of the alloca being considered in bytes. |
| unsigned AllocaSize; |
| const TargetData &TD; |
| |
| /// IsNotTrivial - This is set to true if there is some access to the object |
| /// which means that mem2reg can't promote it. |
| bool IsNotTrivial; |
| |
| /// ScalarKind - Tracks the kind of alloca being considered for promotion, |
| /// computed based on the uses of the alloca rather than the LLVM type system. |
| enum { |
| Unknown, |
| |
| // Accesses via GEPs that are consistent with element access of a vector |
| // type. This will not be converted into a vector unless there is a later |
| // access using an actual vector type. |
| ImplicitVector, |
| |
| // Accesses via vector operations and GEPs that are consistent with the |
| // layout of a vector type. |
| Vector, |
| |
| // An integer bag-of-bits with bitwise operations for insertion and |
| // extraction. Any combination of types can be converted into this kind |
| // of scalar. |
| Integer |
| } ScalarKind; |
| |
| /// VectorTy - This tracks the type that we should promote the vector to if |
| /// it is possible to turn it into a vector. This starts out null, and if it |
| /// isn't possible to turn into a vector type, it gets set to VoidTy. |
| VectorType *VectorTy; |
| |
| /// HadNonMemTransferAccess - True if there is at least one access to the |
| /// alloca that is not a MemTransferInst. We don't want to turn structs into |
| /// large integers unless there is some potential for optimization. |
| bool HadNonMemTransferAccess; |
| |
| public: |
| explicit ConvertToScalarInfo(unsigned Size, const TargetData &td) |
| : AllocaSize(Size), TD(td), IsNotTrivial(false), ScalarKind(Unknown), |
| VectorTy(0), HadNonMemTransferAccess(false) { } |
| |
| AllocaInst *TryConvert(AllocaInst *AI); |
| |
| private: |
| bool CanConvertToScalar(Value *V, uint64_t Offset); |
| void MergeInTypeForLoadOrStore(Type *In, uint64_t Offset); |
| bool MergeInVectorType(VectorType *VInTy, uint64_t Offset); |
| void ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, uint64_t Offset); |
| |
| Value *ConvertScalar_ExtractValue(Value *NV, Type *ToType, |
| uint64_t Offset, IRBuilder<> &Builder); |
| Value *ConvertScalar_InsertValue(Value *StoredVal, Value *ExistingVal, |
| uint64_t Offset, IRBuilder<> &Builder); |
| }; |
| } // end anonymous namespace. |
| |
| |
| /// TryConvert - Analyze the specified alloca, and if it is safe to do so, |
| /// rewrite it to be a new alloca which is mem2reg'able. This returns the new |
| /// alloca if possible or null if not. |
| AllocaInst *ConvertToScalarInfo::TryConvert(AllocaInst *AI) { |
| // If we can't convert this scalar, or if mem2reg can trivially do it, bail |
| // out. |
| if (!CanConvertToScalar(AI, 0) || !IsNotTrivial) |
| return 0; |
| |
| // If an alloca has only memset / memcpy uses, it may still have an Unknown |
| // ScalarKind. Treat it as an Integer below. |
| if (ScalarKind == Unknown) |
| ScalarKind = Integer; |
| |
| // FIXME: It should be possible to promote the vector type up to the alloca's |
| // size. |
| if (ScalarKind == Vector && VectorTy->getBitWidth() != AllocaSize * 8) |
| ScalarKind = Integer; |
| |
| // If we were able to find a vector type that can handle this with |
| // insert/extract elements, and if there was at least one use that had |
| // a vector type, promote this to a vector. We don't want to promote |
| // random stuff that doesn't use vectors (e.g. <9 x double>) because then |
| // we just get a lot of insert/extracts. If at least one vector is |
| // involved, then we probably really do have a union of vector/array. |
| Type *NewTy; |
| if (ScalarKind == Vector) { |
| assert(VectorTy && "Missing type for vector scalar."); |
| DEBUG(dbgs() << "CONVERT TO VECTOR: " << *AI << "\n TYPE = " |
| << *VectorTy << '\n'); |
| NewTy = VectorTy; // Use the vector type. |
| } else { |
| unsigned BitWidth = AllocaSize * 8; |
| if ((ScalarKind == ImplicitVector || ScalarKind == Integer) && |
| !HadNonMemTransferAccess && !TD.fitsInLegalInteger(BitWidth)) |
| return 0; |
| |
| DEBUG(dbgs() << "CONVERT TO SCALAR INTEGER: " << *AI << "\n"); |
| // Create and insert the integer alloca. |
| NewTy = IntegerType::get(AI->getContext(), BitWidth); |
| } |
| AllocaInst *NewAI = new AllocaInst(NewTy, 0, "", AI->getParent()->begin()); |
| ConvertUsesToScalar(AI, NewAI, 0); |
| return NewAI; |
| } |
| |
| /// MergeInTypeForLoadOrStore - Add the 'In' type to the accumulated vector type |
| /// (VectorTy) so far at the offset specified by Offset (which is specified in |
| /// bytes). |
| /// |
| /// There are three cases we handle here: |
| /// 1) A union of vector types of the same size and potentially its elements. |
| /// Here we turn element accesses into insert/extract element operations. |
| /// This promotes a <4 x float> with a store of float to the third element |
| /// into a <4 x float> that uses insert element. |
| /// 2) A union of vector types with power-of-2 size differences, e.g. a float, |
| /// <2 x float> and <4 x float>. Here we turn element accesses into insert |
| /// and extract element operations, and <2 x float> accesses into a cast to |
| /// <2 x double>, an extract, and a cast back to <2 x float>. |
| /// 3) A fully general blob of memory, which we turn into some (potentially |
| /// large) integer type with extract and insert operations where the loads |
| /// and stores would mutate the memory. We mark this by setting VectorTy |
| /// to VoidTy. |
| void ConvertToScalarInfo::MergeInTypeForLoadOrStore(Type *In, |
| uint64_t Offset) { |
| // If we already decided to turn this into a blob of integer memory, there is |
| // nothing to be done. |
| if (ScalarKind == Integer) |
| return; |
| |
| // If this could be contributing to a vector, analyze it. |
| |
| // If the In type is a vector that is the same size as the alloca, see if it |
| // matches the existing VecTy. |
| if (VectorType *VInTy = dyn_cast<VectorType>(In)) { |
| if (MergeInVectorType(VInTy, Offset)) |
| return; |
| } else if (In->isFloatTy() || In->isDoubleTy() || |
| (In->isIntegerTy() && In->getPrimitiveSizeInBits() >= 8 && |
| isPowerOf2_32(In->getPrimitiveSizeInBits()))) { |
| // Full width accesses can be ignored, because they can always be turned |
| // into bitcasts. |
| unsigned EltSize = In->getPrimitiveSizeInBits()/8; |
| if (EltSize == AllocaSize) |
| return; |
| |
| // If we're accessing something that could be an element of a vector, see |
| // if the implied vector agrees with what we already have and if Offset is |
| // compatible with it. |
| if (Offset % EltSize == 0 && AllocaSize % EltSize == 0 && |
| (!VectorTy || Offset * 8 < VectorTy->getPrimitiveSizeInBits())) { |
| if (!VectorTy) { |
| ScalarKind = ImplicitVector; |
| VectorTy = VectorType::get(In, AllocaSize/EltSize); |
| return; |
| } |
| |
| unsigned CurrentEltSize = VectorTy->getElementType() |
| ->getPrimitiveSizeInBits()/8; |
| if (EltSize == CurrentEltSize) |
| return; |
| |
| if (In->isIntegerTy() && isPowerOf2_32(AllocaSize / EltSize)) |
| return; |
| } |
| } |
| |
| // Otherwise, we have a case that we can't handle with an optimized vector |
| // form. We can still turn this into a large integer. |
| ScalarKind = Integer; |
| } |
| |
| /// MergeInVectorType - Handles the vector case of MergeInTypeForLoadOrStore, |
| /// returning true if the type was successfully merged and false otherwise. |
| bool ConvertToScalarInfo::MergeInVectorType(VectorType *VInTy, |
| uint64_t Offset) { |
| // TODO: Support nonzero offsets? |
| if (Offset != 0) |
| return false; |
| |
| // Only allow vectors that are a power-of-2 away from the size of the alloca. |
| if (!isPowerOf2_64(AllocaSize / (VInTy->getBitWidth() / 8))) |
| return false; |
| |
| // If this the first vector we see, remember the type so that we know the |
| // element size. |
| if (!VectorTy) { |
| ScalarKind = Vector; |
| VectorTy = VInTy; |
| return true; |
| } |
| |
| unsigned BitWidth = VectorTy->getBitWidth(); |
| unsigned InBitWidth = VInTy->getBitWidth(); |
| |
| // Vectors of the same size can be converted using a simple bitcast. |
| if (InBitWidth == BitWidth && AllocaSize == (InBitWidth / 8)) { |
| ScalarKind = Vector; |
| return true; |
| } |
| |
| Type *ElementTy = VectorTy->getElementType(); |
| Type *InElementTy = VInTy->getElementType(); |
| |
| // If they're the same alloc size, we'll be attempting to convert between |
| // them with a vector shuffle, which requires the element types to match. |
| if (TD.getTypeAllocSize(VectorTy) == TD.getTypeAllocSize(VInTy) && |
| ElementTy != InElementTy) |
| return false; |
| |
| // Do not allow mixed integer and floating-point accesses from vectors of |
| // different sizes. |
| if (ElementTy->isFloatingPointTy() != InElementTy->isFloatingPointTy()) |
| return false; |
| |
| if (ElementTy->isFloatingPointTy()) { |
| // Only allow floating-point vectors of different sizes if they have the |
| // same element type. |
| // TODO: This could be loosened a bit, but would anything benefit? |
| if (ElementTy != InElementTy) |
| return false; |
| |
| // There are no arbitrary-precision floating-point types, which limits the |
| // number of legal vector types with larger element types that we can form |
| // to bitcast and extract a subvector. |
| // TODO: We could support some more cases with mixed fp128 and double here. |
| if (!(BitWidth == 64 || BitWidth == 128) || |
| !(InBitWidth == 64 || InBitWidth == 128)) |
| return false; |
| } else { |
| assert(ElementTy->isIntegerTy() && "Vector elements must be either integer " |
| "or floating-point."); |
| unsigned BitWidth = ElementTy->getPrimitiveSizeInBits(); |
| unsigned InBitWidth = InElementTy->getPrimitiveSizeInBits(); |
| |
| // Do not allow integer types smaller than a byte or types whose widths are |
| // not a multiple of a byte. |
| if (BitWidth < 8 || InBitWidth < 8 || |
| BitWidth % 8 != 0 || InBitWidth % 8 != 0) |
| return false; |
| } |
| |
| // Pick the largest of the two vector types. |
| ScalarKind = Vector; |
| if (InBitWidth > BitWidth) |
| VectorTy = VInTy; |
| |
| return true; |
| } |
| |
| /// CanConvertToScalar - V is a pointer. If we can convert the pointee and all |
| /// its accesses to a single vector type, return true and set VecTy to |
| /// the new type. If we could convert the alloca into a single promotable |
| /// integer, return true but set VecTy to VoidTy. Further, if the use is not a |
| /// completely trivial use that mem2reg could promote, set IsNotTrivial. Offset |
| /// is the current offset from the base of the alloca being analyzed. |
| /// |
| /// If we see at least one access to the value that is as a vector type, set the |
| /// SawVec flag. |
| bool ConvertToScalarInfo::CanConvertToScalar(Value *V, uint64_t Offset) { |
| for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) { |
| Instruction *User = cast<Instruction>(*UI); |
| |
| if (LoadInst *LI = dyn_cast<LoadInst>(User)) { |
| // Don't break volatile loads. |
| if (LI->isVolatile()) |
| return false; |
| // Don't touch MMX operations. |
| if (LI->getType()->isX86_MMXTy()) |
| return false; |
| HadNonMemTransferAccess = true; |
| MergeInTypeForLoadOrStore(LI->getType(), Offset); |
| continue; |
| } |
| |
| if (StoreInst *SI = dyn_cast<StoreInst>(User)) { |
| // Storing the pointer, not into the value? |
| if (SI->getOperand(0) == V || SI->isVolatile()) return false; |
| // Don't touch MMX operations. |
| if (SI->getOperand(0)->getType()->isX86_MMXTy()) |
| return false; |
| HadNonMemTransferAccess = true; |
| MergeInTypeForLoadOrStore(SI->getOperand(0)->getType(), Offset); |
| continue; |
| } |
| |
| if (BitCastInst *BCI = dyn_cast<BitCastInst>(User)) { |
| IsNotTrivial = true; // Can't be mem2reg'd. |
| if (!CanConvertToScalar(BCI, Offset)) |
| return false; |
| continue; |
| } |
| |
| if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) { |
| // If this is a GEP with a variable indices, we can't handle it. |
| if (!GEP->hasAllConstantIndices()) |
| return false; |
| |
| // Compute the offset that this GEP adds to the pointer. |
| SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end()); |
| uint64_t GEPOffset = TD.getIndexedOffset(GEP->getPointerOperandType(), |
| Indices); |
| // See if all uses can be converted. |
| if (!CanConvertToScalar(GEP, Offset+GEPOffset)) |
| return false; |
| IsNotTrivial = true; // Can't be mem2reg'd. |
| HadNonMemTransferAccess = true; |
| continue; |
| } |
| |
| // If this is a constant sized memset of a constant value (e.g. 0) we can |
| // handle it. |
| if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) { |
| // Store of constant value. |
| if (!isa<ConstantInt>(MSI->getValue())) |
| return false; |
| |
| // Store of constant size. |
| ConstantInt *Len = dyn_cast<ConstantInt>(MSI->getLength()); |
| if (!Len) |
| return false; |
| |
| // If the size differs from the alloca, we can only convert the alloca to |
| // an integer bag-of-bits. |
| // FIXME: This should handle all of the cases that are currently accepted |
| // as vector element insertions. |
| if (Len->getZExtValue() != AllocaSize || Offset != 0) |
| ScalarKind = Integer; |
| |
| IsNotTrivial = true; // Can't be mem2reg'd. |
| HadNonMemTransferAccess = true; |
| continue; |
| } |
| |
| // If this is a memcpy or memmove into or out of the whole allocation, we |
| // can handle it like a load or store of the scalar type. |
| if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) { |
| ConstantInt *Len = dyn_cast<ConstantInt>(MTI->getLength()); |
| if (Len == 0 || Len->getZExtValue() != AllocaSize || Offset != 0) |
| return false; |
| |
| IsNotTrivial = true; // Can't be mem2reg'd. |
| continue; |
| } |
| |
| // Otherwise, we cannot handle this! |
| return false; |
| } |
| |
| return true; |
| } |
| |
| /// ConvertUsesToScalar - Convert all of the users of Ptr to use the new alloca |
| /// directly. This happens when we are converting an "integer union" to a |
| /// single integer scalar, or when we are converting a "vector union" to a |
| /// vector with insert/extractelement instructions. |
| /// |
| /// Offset is an offset from the original alloca, in bits that need to be |
| /// shifted to the right. By the end of this, there should be no uses of Ptr. |
| void ConvertToScalarInfo::ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, |
| uint64_t Offset) { |
| while (!Ptr->use_empty()) { |
| Instruction *User = cast<Instruction>(Ptr->use_back()); |
| |
| if (BitCastInst *CI = dyn_cast<BitCastInst>(User)) { |
| ConvertUsesToScalar(CI, NewAI, Offset); |
| CI->eraseFromParent(); |
| continue; |
| } |
| |
| if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) { |
| // Compute the offset that this GEP adds to the pointer. |
| SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end()); |
| uint64_t GEPOffset = TD.getIndexedOffset(GEP->getPointerOperandType(), |
| Indices); |
| ConvertUsesToScalar(GEP, NewAI, Offset+GEPOffset*8); |
| GEP->eraseFromParent(); |
| continue; |
| } |
| |
| IRBuilder<> Builder(User); |
| |
| if (LoadInst *LI = dyn_cast<LoadInst>(User)) { |
| // The load is a bit extract from NewAI shifted right by Offset bits. |
| Value *LoadedVal = Builder.CreateLoad(NewAI, "tmp"); |
| Value *NewLoadVal |
| = ConvertScalar_ExtractValue(LoadedVal, LI->getType(), Offset, Builder); |
| LI->replaceAllUsesWith(NewLoadVal); |
| LI->eraseFromParent(); |
| continue; |
| } |
| |
| if (StoreInst *SI = dyn_cast<StoreInst>(User)) { |
| assert(SI->getOperand(0) != Ptr && "Consistency error!"); |
| Instruction *Old = Builder.CreateLoad(NewAI, NewAI->getName()+".in"); |
| Value *New = ConvertScalar_InsertValue(SI->getOperand(0), Old, Offset, |
| Builder); |
| Builder.CreateStore(New, NewAI); |
| SI->eraseFromParent(); |
| |
| // If the load we just inserted is now dead, then the inserted store |
| // overwrote the entire thing. |
| if (Old->use_empty()) |
| Old->eraseFromParent(); |
| continue; |
| } |
| |
| // If this is a constant sized memset of a constant value (e.g. 0) we can |
| // transform it into a store of the expanded constant value. |
| if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) { |
| assert(MSI->getRawDest() == Ptr && "Consistency error!"); |
| unsigned NumBytes = cast<ConstantInt>(MSI->getLength())->getZExtValue(); |
| if (NumBytes != 0) { |
| unsigned Val = cast<ConstantInt>(MSI->getValue())->getZExtValue(); |
| |
| // Compute the value replicated the right number of times. |
| APInt APVal(NumBytes*8, Val); |
| |
| // Splat the value if non-zero. |
| if (Val) |
| for (unsigned i = 1; i != NumBytes; ++i) |
| APVal |= APVal << 8; |
| |
| Instruction *Old = Builder.CreateLoad(NewAI, NewAI->getName()+".in"); |
| Value *New = ConvertScalar_InsertValue( |
| ConstantInt::get(User->getContext(), APVal), |
| Old, Offset, Builder); |
| Builder.CreateStore(New, NewAI); |
| |
| // If the load we just inserted is now dead, then the memset overwrote |
| // the entire thing. |
| if (Old->use_empty()) |
| Old->eraseFromParent(); |
| } |
| MSI->eraseFromParent(); |
| continue; |
| } |
| |
| // If this is a memcpy or memmove into or out of the whole allocation, we |
| // can handle it like a load or store of the scalar type. |
| if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) { |
| assert(Offset == 0 && "must be store to start of alloca"); |
| |
| // If the source and destination are both to the same alloca, then this is |
| // a noop copy-to-self, just delete it. Otherwise, emit a load and store |
| // as appropriate. |
| AllocaInst *OrigAI = cast<AllocaInst>(GetUnderlyingObject(Ptr, &TD, 0)); |
| |
| if (GetUnderlyingObject(MTI->getSource(), &TD, 0) != OrigAI) { |
| // Dest must be OrigAI, change this to be a load from the original |
| // pointer (bitcasted), then a store to our new alloca. |
| assert(MTI->getRawDest() == Ptr && "Neither use is of pointer?"); |
| Value *SrcPtr = MTI->getSource(); |
| PointerType* SPTy = cast<PointerType>(SrcPtr->getType()); |
| PointerType* AIPTy = cast<PointerType>(NewAI->getType()); |
| if (SPTy->getAddressSpace() != AIPTy->getAddressSpace()) { |
| AIPTy = PointerType::get(AIPTy->getElementType(), |
| SPTy->getAddressSpace()); |
| } |
| SrcPtr = Builder.CreateBitCast(SrcPtr, AIPTy); |
| |
| LoadInst *SrcVal = Builder.CreateLoad(SrcPtr, "srcval"); |
| SrcVal->setAlignment(MTI->getAlignment()); |
| Builder.CreateStore(SrcVal, NewAI); |
| } else if (GetUnderlyingObject(MTI->getDest(), &TD, 0) != OrigAI) { |
| // Src must be OrigAI, change this to be a load from NewAI then a store |
| // through the original dest pointer (bitcasted). |
| assert(MTI->getRawSource() == Ptr && "Neither use is of pointer?"); |
| LoadInst *SrcVal = Builder.CreateLoad(NewAI, "srcval"); |
| |
| PointerType* DPTy = cast<PointerType>(MTI->getDest()->getType()); |
| PointerType* AIPTy = cast<PointerType>(NewAI->getType()); |
| if (DPTy->getAddressSpace() != AIPTy->getAddressSpace()) { |
| AIPTy = PointerType::get(AIPTy->getElementType(), |
| DPTy->getAddressSpace()); |
| } |
| Value *DstPtr = Builder.CreateBitCast(MTI->getDest(), AIPTy); |
| |
| StoreInst *NewStore = Builder.CreateStore(SrcVal, DstPtr); |
| NewStore->setAlignment(MTI->getAlignment()); |
| } else { |
| // Noop transfer. Src == Dst |
| } |
| |
| MTI->eraseFromParent(); |
| continue; |
| } |
| |
| llvm_unreachable("Unsupported operation!"); |
| } |
| } |
| |
| /// getScaledElementType - Gets a scaled element type for a partial vector |
| /// access of an alloca. The input types must be integer or floating-point |
| /// scalar or vector types, and the resulting type is an integer, float or |
| /// double. |
| static Type *getScaledElementType(Type *Ty1, Type *Ty2, |
| unsigned NewBitWidth) { |
| bool IsFP1 = Ty1->isFloatingPointTy() || |
| (Ty1->isVectorTy() && |
| cast<VectorType>(Ty1)->getElementType()->isFloatingPointTy()); |
| bool IsFP2 = Ty2->isFloatingPointTy() || |
| (Ty2->isVectorTy() && |
| cast<VectorType>(Ty2)->getElementType()->isFloatingPointTy()); |
| |
| LLVMContext &Context = Ty1->getContext(); |
| |
| // Prefer floating-point types over integer types, as integer types may have |
| // been created by earlier scalar replacement. |
| if (IsFP1 || IsFP2) { |
| if (NewBitWidth == 32) |
| return Type::getFloatTy(Context); |
| if (NewBitWidth == 64) |
| return Type::getDoubleTy(Context); |
| } |
| |
| return Type::getIntNTy(Context, NewBitWidth); |
| } |
| |
| /// CreateShuffleVectorCast - Creates a shuffle vector to convert one vector |
| /// to another vector of the same element type which has the same allocation |
| /// size but different primitive sizes (e.g. <3 x i32> and <4 x i32>). |
| static Value *CreateShuffleVectorCast(Value *FromVal, Type *ToType, |
| IRBuilder<> &Builder) { |
| Type *FromType = FromVal->getType(); |
| VectorType *FromVTy = cast<VectorType>(FromType); |
| VectorType *ToVTy = cast<VectorType>(ToType); |
| assert((ToVTy->getElementType() == FromVTy->getElementType()) && |
| "Vectors must have the same element type"); |
| Value *UnV = UndefValue::get(FromType); |
| unsigned numEltsFrom = FromVTy->getNumElements(); |
| unsigned numEltsTo = ToVTy->getNumElements(); |
| |
| SmallVector<Constant*, 3> Args; |
| Type* Int32Ty = Builder.getInt32Ty(); |
| unsigned minNumElts = std::min(numEltsFrom, numEltsTo); |
| unsigned i; |
| for (i=0; i != minNumElts; ++i) |
| Args.push_back(ConstantInt::get(Int32Ty, i)); |
| |
| if (i < numEltsTo) { |
| Constant* UnC = UndefValue::get(Int32Ty); |
| for (; i != numEltsTo; ++i) |
| Args.push_back(UnC); |
| } |
| Constant *Mask = ConstantVector::get(Args); |
| return Builder.CreateShuffleVector(FromVal, UnV, Mask, "tmpV"); |
| } |
| |
| /// ConvertScalar_ExtractValue - Extract a value of type ToType from an integer |
| /// or vector value FromVal, extracting the bits from the offset specified by |
| /// Offset. This returns the value, which is of type ToType. |
| /// |
| /// This happens when we are converting an "integer union" to a single |
| /// integer scalar, or when we are converting a "vector union" to a vector with |
| /// insert/extractelement instructions. |
| /// |
| /// Offset is an offset from the original alloca, in bits that need to be |
| /// shifted to the right. |
| Value *ConvertToScalarInfo:: |
| ConvertScalar_ExtractValue(Value *FromVal, Type *ToType, |
| uint64_t Offset, IRBuilder<> &Builder) { |
| // If the load is of the whole new alloca, no conversion is needed. |
| Type *FromType = FromVal->getType(); |
| if (FromType == ToType && Offset == 0) |
| return FromVal; |
| |
| // If the result alloca is a vector type, this is either an element |
| // access or a bitcast to another vector type of the same size. |
| if (VectorType *VTy = dyn_cast<VectorType>(FromType)) { |
| unsigned FromTypeSize = TD.getTypeAllocSize(FromType); |
| unsigned ToTypeSize = TD.getTypeAllocSize(ToType); |
| if (FromTypeSize == ToTypeSize) { |
| // If the two types have the same primitive size, use a bit cast. |
| // Otherwise, it is two vectors with the same element type that has |
| // the same allocation size but different number of elements so use |
| // a shuffle vector. |
| if (FromType->getPrimitiveSizeInBits() == |
| ToType->getPrimitiveSizeInBits()) |
| return Builder.CreateBitCast(FromVal, ToType, "tmp"); |
| else |
| return CreateShuffleVectorCast(FromVal, ToType, Builder); |
| } |
| |
| if (isPowerOf2_64(FromTypeSize / ToTypeSize)) { |
| assert(!(ToType->isVectorTy() && Offset != 0) && "Can't extract a value " |
| "of a smaller vector type at a nonzero offset."); |
| |
| Type *CastElementTy = getScaledElementType(FromType, ToType, |
| ToTypeSize * 8); |
| unsigned NumCastVectorElements = FromTypeSize / ToTypeSize; |
| |
| LLVMContext &Context = FromVal->getContext(); |
| Type *CastTy = VectorType::get(CastElementTy, |
| NumCastVectorElements); |
| Value *Cast = Builder.CreateBitCast(FromVal, CastTy, "tmp"); |
| |
| unsigned EltSize = TD.getTypeAllocSizeInBits(CastElementTy); |
| unsigned Elt = Offset/EltSize; |
| assert(EltSize*Elt == Offset && "Invalid modulus in validity checking"); |
| Value *Extract = Builder.CreateExtractElement(Cast, ConstantInt::get( |
| Type::getInt32Ty(Context), Elt), "tmp"); |
| return Builder.CreateBitCast(Extract, ToType, "tmp"); |
| } |
| |
| // Otherwise it must be an element access. |
| unsigned Elt = 0; |
| if (Offset) { |
| unsigned EltSize = TD.getTypeAllocSizeInBits(VTy->getElementType()); |
| Elt = Offset/EltSize; |
| assert(EltSize*Elt == Offset && "Invalid modulus in validity checking"); |
| } |
| // Return the element extracted out of it. |
| Value *V = Builder.CreateExtractElement(FromVal, ConstantInt::get( |
| Type::getInt32Ty(FromVal->getContext()), Elt), "tmp"); |
| if (V->getType() != ToType) |
| V = Builder.CreateBitCast(V, ToType, "tmp"); |
| return V; |
| } |
| |
| // If ToType is a first class aggregate, extract out each of the pieces and |
| // use insertvalue's to form the FCA. |
| if (StructType *ST = dyn_cast<StructType>(ToType)) { |
| const StructLayout &Layout = *TD.getStructLayout(ST); |
| Value *Res = UndefValue::get(ST); |
| for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) { |
| Value *Elt = ConvertScalar_ExtractValue(FromVal, ST->getElementType(i), |
| Offset+Layout.getElementOffsetInBits(i), |
| Builder); |
| Res = Builder.CreateInsertValue(Res, Elt, i, "tmp"); |
| } |
| return Res; |
| } |
| |
| if (ArrayType *AT = dyn_cast<ArrayType>(ToType)) { |
| uint64_t EltSize = TD.getTypeAllocSizeInBits(AT->getElementType()); |
| Value *Res = UndefValue::get(AT); |
| for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) { |
| Value *Elt = ConvertScalar_ExtractValue(FromVal, AT->getElementType(), |
| Offset+i*EltSize, Builder); |
| Res = Builder.CreateInsertValue(Res, Elt, i, "tmp"); |
| } |
| return Res; |
| } |
| |
| // Otherwise, this must be a union that was converted to an integer value. |
| IntegerType *NTy = cast<IntegerType>(FromVal->getType()); |
| |
| // If this is a big-endian system and the load is narrower than the |
| // full alloca type, we need to do a shift to get the right bits. |
| int ShAmt = 0; |
| if (TD.isBigEndian()) { |
| // On big-endian machines, the lowest bit is stored at the bit offset |
| // from the pointer given by getTypeStoreSizeInBits. This matters for |
| // integers with a bitwidth that is not a multiple of 8. |
| ShAmt = TD.getTypeStoreSizeInBits(NTy) - |
| TD.getTypeStoreSizeInBits(ToType) - Offset; |
| } else { |
| ShAmt = Offset; |
| } |
| |
| // Note: we support negative bitwidths (with shl) which are not defined. |
| // We do this to support (f.e.) loads off the end of a structure where |
| // only some bits are used. |
| if (ShAmt > 0 && (unsigned)ShAmt < NTy->getBitWidth()) |
| FromVal = Builder.CreateLShr(FromVal, |
| ConstantInt::get(FromVal->getType(), |
| ShAmt), "tmp"); |
| else if (ShAmt < 0 && (unsigned)-ShAmt < NTy->getBitWidth()) |
| FromVal = Builder.CreateShl(FromVal, |
| ConstantInt::get(FromVal->getType(), |
| -ShAmt), "tmp"); |
| |
| // Finally, unconditionally truncate the integer to the right width. |
| unsigned LIBitWidth = TD.getTypeSizeInBits(ToType); |
| if (LIBitWidth < NTy->getBitWidth()) |
| FromVal = |
| Builder.CreateTrunc(FromVal, IntegerType::get(FromVal->getContext(), |
| LIBitWidth), "tmp"); |
| else if (LIBitWidth > NTy->getBitWidth()) |
| FromVal = |
| Builder.CreateZExt(FromVal, IntegerType::get(FromVal->getContext(), |
| LIBitWidth), "tmp"); |
| |
| // If the result is an integer, this is a trunc or bitcast. |
| if (ToType->isIntegerTy()) { |
| // Should be done. |
| } else if (ToType->isFloatingPointTy() || ToType->isVectorTy()) { |
| // Just do a bitcast, we know the sizes match up. |
| FromVal = Builder.CreateBitCast(FromVal, ToType, "tmp"); |
| } else { |
| // Otherwise must be a pointer. |
| FromVal = Builder.CreateIntToPtr(FromVal, ToType, "tmp"); |
| } |
| assert(FromVal->getType() == ToType && "Didn't convert right?"); |
| return FromVal; |
| } |
| |
| /// ConvertScalar_InsertValue - Insert the value "SV" into the existing integer |
| /// or vector value "Old" at the offset specified by Offset. |
| /// |
| /// This happens when we are converting an "integer union" to a |
| /// single integer scalar, or when we are converting a "vector union" to a |
| /// vector with insert/extractelement instructions. |
| /// |
| /// Offset is an offset from the original alloca, in bits that need to be |
| /// shifted to the right. |
| Value *ConvertToScalarInfo:: |
| ConvertScalar_InsertValue(Value *SV, Value *Old, |
| uint64_t Offset, IRBuilder<> &Builder) { |
| // Convert the stored type to the actual type, shift it left to insert |
| // then 'or' into place. |
| Type *AllocaType = Old->getType(); |
| LLVMContext &Context = Old->getContext(); |
| |
| if (VectorType *VTy = dyn_cast<VectorType>(AllocaType)) { |
| uint64_t VecSize = TD.getTypeAllocSizeInBits(VTy); |
| uint64_t ValSize = TD.getTypeAllocSizeInBits(SV->getType()); |
| |
| // Changing the whole vector with memset or with an access of a different |
| // vector type? |
| if (ValSize == VecSize) { |
| // If the two types have the same primitive size, use a bit cast. |
| // Otherwise, it is two vectors with the same element type that has |
| // the same allocation size but different number of elements so use |
| // a shuffle vector. |
| if (VTy->getPrimitiveSizeInBits() == |
| SV->getType()->getPrimitiveSizeInBits()) |
| return Builder.CreateBitCast(SV, AllocaType, "tmp"); |
| else |
| return CreateShuffleVectorCast(SV, VTy, Builder); |
| } |
| |
| if (isPowerOf2_64(VecSize / ValSize)) { |
| assert(!(SV->getType()->isVectorTy() && Offset != 0) && "Can't insert a " |
| "value of a smaller vector type at a nonzero offset."); |
| |
| Type *CastElementTy = getScaledElementType(VTy, SV->getType(), |
| ValSize); |
| unsigned NumCastVectorElements = VecSize / ValSize; |
| |
| LLVMContext &Context = SV->getContext(); |
| Type *OldCastTy = VectorType::get(CastElementTy, |
| NumCastVectorElements); |
| Value *OldCast = Builder.CreateBitCast(Old, OldCastTy, "tmp"); |
| |
| Value *SVCast = Builder.CreateBitCast(SV, CastElementTy, "tmp"); |
| |
| unsigned EltSize = TD.getTypeAllocSizeInBits(CastElementTy); |
| unsigned Elt = Offset/EltSize; |
| assert(EltSize*Elt == Offset && "Invalid modulus in validity checking"); |
| Value *Insert = |
| Builder.CreateInsertElement(OldCast, SVCast, ConstantInt::get( |
| Type::getInt32Ty(Context), Elt), "tmp"); |
| return Builder.CreateBitCast(Insert, AllocaType, "tmp"); |
| } |
| |
| // Must be an element insertion. |
| assert(SV->getType() == VTy->getElementType()); |
| uint64_t EltSize = TD.getTypeAllocSizeInBits(VTy->getElementType()); |
| unsigned Elt = Offset/EltSize; |
| return Builder.CreateInsertElement(Old, SV, |
| ConstantInt::get(Type::getInt32Ty(SV->getContext()), Elt), |
| "tmp"); |
| } |
| |
| // If SV is a first-class aggregate value, insert each value recursively. |
| if (StructType *ST = dyn_cast<StructType>(SV->getType())) { |
| const StructLayout &Layout = *TD.getStructLayout(ST); |
| for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) { |
| Value *Elt = Builder.CreateExtractValue(SV, i, "tmp"); |
| Old = ConvertScalar_InsertValue(Elt, Old, |
| Offset+Layout.getElementOffsetInBits(i), |
| Builder); |
| } |
| return Old; |
| } |
| |
| if (ArrayType *AT = dyn_cast<ArrayType>(SV->getType())) { |
| uint64_t EltSize = TD.getTypeAllocSizeInBits(AT->getElementType()); |
| for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) { |
| Value *Elt = Builder.CreateExtractValue(SV, i, "tmp"); |
| Old = ConvertScalar_InsertValue(Elt, Old, Offset+i*EltSize, Builder); |
| } |
| return Old; |
| } |
| |
| // If SV is a float, convert it to the appropriate integer type. |
| // If it is a pointer, do the same. |
| unsigned SrcWidth = TD.getTypeSizeInBits(SV->getType()); |
| unsigned DestWidth = TD.getTypeSizeInBits(AllocaType); |
| unsigned SrcStoreWidth = TD.getTypeStoreSizeInBits(SV->getType()); |
| unsigned DestStoreWidth = TD.getTypeStoreSizeInBits(AllocaType); |
| if (SV->getType()->isFloatingPointTy() || SV->getType()->isVectorTy()) |
| SV = Builder.CreateBitCast(SV, |
| IntegerType::get(SV->getContext(),SrcWidth), "tmp"); |
| else if (SV->getType()->isPointerTy()) |
| SV = Builder.CreatePtrToInt(SV, TD.getIntPtrType(SV->getContext()), "tmp"); |
| |
| // Zero extend or truncate the value if needed. |
| if (SV->getType() != AllocaType) { |
| if (SV->getType()->getPrimitiveSizeInBits() < |
| AllocaType->getPrimitiveSizeInBits()) |
| SV = Builder.CreateZExt(SV, AllocaType, "tmp"); |
| else { |
| // Truncation may be needed if storing more than the alloca can hold |
| // (undefined behavior). |
| SV = Builder.CreateTrunc(SV, AllocaType, "tmp"); |
| SrcWidth = DestWidth; |
| SrcStoreWidth = DestStoreWidth; |
| } |
| } |
| |
| // If this is a big-endian system and the store is narrower than the |
| // full alloca type, we need to do a shift to get the right bits. |
| int ShAmt = 0; |
| if (TD.isBigEndian()) { |
| // On big-endian machines, the lowest bit is stored at the bit offset |
| // from the pointer given by getTypeStoreSizeInBits. This matters for |
| // integers with a bitwidth that is not a multiple of 8. |
| ShAmt = DestStoreWidth - SrcStoreWidth - Offset; |
| } else { |
| ShAmt = Offset; |
| } |
| |
| // Note: we support negative bitwidths (with shr) which are not defined. |
| // We do this to support (f.e.) stores off the end of a structure where |
| // only some bits in the structure are set. |
| APInt Mask(APInt::getLowBitsSet(DestWidth, SrcWidth)); |
| if (ShAmt > 0 && (unsigned)ShAmt < DestWidth) { |
| SV = Builder.CreateShl(SV, ConstantInt::get(SV->getType(), |
| ShAmt), "tmp"); |
| Mask <<= ShAmt; |
| } else if (ShAmt < 0 && (unsigned)-ShAmt < DestWidth) { |
| SV = Builder.CreateLShr(SV, ConstantInt::get(SV->getType(), |
| -ShAmt), "tmp"); |
| Mask = Mask.lshr(-ShAmt); |
| } |
| |
| // Mask out the bits we are about to insert from the old value, and or |
| // in the new bits. |
| if (SrcWidth != DestWidth) { |
| assert(DestWidth > SrcWidth); |
| Old = Builder.CreateAnd(Old, ConstantInt::get(Context, ~Mask), "mask"); |
| SV = Builder.CreateOr(Old, SV, "ins"); |
| } |
| return SV; |
| } |
| |
| |
| //===----------------------------------------------------------------------===// |
| // SRoA Driver |
| //===----------------------------------------------------------------------===// |
| |
| |
| bool SROA::runOnFunction(Function &F) { |
| TD = getAnalysisIfAvailable<TargetData>(); |
| |
| bool Changed = performPromotion(F); |
| |
| // FIXME: ScalarRepl currently depends on TargetData more than it |
| // theoretically needs to. It should be refactored in order to support |
| // target-independent IR. Until this is done, just skip the actual |
| // scalar-replacement portion of this pass. |
| if (!TD) return Changed; |
| |
| while (1) { |
| bool LocalChange = performScalarRepl(F); |
| if (!LocalChange) break; // No need to repromote if no scalarrepl |
| Changed = true; |
| LocalChange = performPromotion(F); |
| if (!LocalChange) break; // No need to re-scalarrepl if no promotion |
| } |
| |
| return Changed; |
| } |
| |
| namespace { |
| class AllocaPromoter : public LoadAndStorePromoter { |
| AllocaInst *AI; |
| DIBuilder *DIB; |
| SmallVector<DbgDeclareInst *, 4> DDIs; |
| SmallVector<DbgValueInst *, 4> DVIs; |
| public: |
| AllocaPromoter(const SmallVectorImpl<Instruction*> &Insts, SSAUpdater &S, |
| DIBuilder *DB) |
| : LoadAndStorePromoter(Insts, S), AI(0), DIB(DB) {} |
| |
| void run(AllocaInst *AI, const SmallVectorImpl<Instruction*> &Insts) { |
| // Remember which alloca we're promoting (for isInstInList). |
| this->AI = AI; |
| if (MDNode *DebugNode = MDNode::getIfExists(AI->getContext(), AI)) |
| for (Value::use_iterator UI = DebugNode->use_begin(), |
| E = DebugNode->use_end(); UI != E; ++UI) |
| if (DbgDeclareInst *DDI = dyn_cast<DbgDeclareInst>(*UI)) |
| DDIs.push_back(DDI); |
| else if (DbgValueInst *DVI = dyn_cast<DbgValueInst>(*UI)) |
| DVIs.push_back(DVI); |
| |
| LoadAndStorePromoter::run(Insts); |
| AI->eraseFromParent(); |
| for (SmallVector<DbgDeclareInst *, 4>::iterator I = DDIs.begin(), |
| E = DDIs.end(); I != E; ++I) { |
| DbgDeclareInst *DDI = *I; |
| DDI->eraseFromParent(); |
| } |
| for (SmallVector<DbgValueInst *, 4>::iterator I = DVIs.begin(), |
| E = DVIs.end(); I != E; ++I) { |
| DbgValueInst *DVI = *I; |
| DVI->eraseFromParent(); |
| } |
| } |
| |
| virtual bool isInstInList(Instruction *I, |
| const SmallVectorImpl<Instruction*> &Insts) const { |
| if (LoadInst *LI = dyn_cast<LoadInst>(I)) |
| return LI->getOperand(0) == AI; |
| return cast<StoreInst>(I)->getPointerOperand() == AI; |
| } |
| |
| virtual void updateDebugInfo(Instruction *Inst) const { |
| for (SmallVector<DbgDeclareInst *, 4>::const_iterator I = DDIs.begin(), |
| E = DDIs.end(); I != E; ++I) { |
| DbgDeclareInst *DDI = *I; |
| if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) |
| ConvertDebugDeclareToDebugValue(DDI, SI, *DIB); |
| else if (LoadInst *LI = dyn_cast<LoadInst>(Inst)) |
| ConvertDebugDeclareToDebugValue(DDI, LI, *DIB); |
| } |
| for (SmallVector<DbgValueInst *, 4>::const_iterator I = DVIs.begin(), |
| E = DVIs.end(); I != E; ++I) { |
| DbgValueInst *DVI = *I; |
| if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) { |
| Instruction *DbgVal = NULL; |
| // If an argument is zero extended then use argument directly. The ZExt |
| // may be zapped by an optimization pass in future. |
| Argument *ExtendedArg = NULL; |
| if (ZExtInst *ZExt = dyn_cast<ZExtInst>(SI->getOperand(0))) |
| ExtendedArg = dyn_cast<Argument>(ZExt->getOperand(0)); |
| if (SExtInst *SExt = dyn_cast<SExtInst>(SI->getOperand(0))) |
| ExtendedArg = dyn_cast<Argument>(SExt->getOperand(0)); |
| if (ExtendedArg) |
| DbgVal = DIB->insertDbgValueIntrinsic(ExtendedArg, 0, |
| DIVariable(DVI->getVariable()), |
| SI); |
| else |
| DbgVal = DIB->insertDbgValueIntrinsic(SI->getOperand(0), 0, |
| DIVariable(DVI->getVariable()), |
| SI); |
| DbgVal->setDebugLoc(DVI->getDebugLoc()); |
| } else if (LoadInst *LI = dyn_cast<LoadInst>(Inst)) { |
| Instruction *DbgVal = |
| DIB->insertDbgValueIntrinsic(LI->getOperand(0), 0, |
| DIVariable(DVI->getVariable()), LI); |
| DbgVal->setDebugLoc(DVI->getDebugLoc()); |
| } |
| } |
| } |
| }; |
| } // end anon namespace |
| |
| /// isSafeSelectToSpeculate - Select instructions that use an alloca and are |
| /// subsequently loaded can be rewritten to load both input pointers and then |
| /// select between the result, allowing the load of the alloca to be promoted. |
| /// From this: |
| /// %P2 = select i1 %cond, i32* %Alloca, i32* %Other |
| /// %V = load i32* %P2 |
| /// to: |
| /// %V1 = load i32* %Alloca -> will be mem2reg'd |
| /// %V2 = load i32* %Other |
| /// %V = select i1 %cond, i32 %V1, i32 %V2 |
| /// |
| /// We can do this to a select if its only uses are loads and if the operand to |
| /// the select can be loaded unconditionally. |
| static bool isSafeSelectToSpeculate(SelectInst *SI, const TargetData *TD) { |
| bool TDerefable = SI->getTrueValue()->isDereferenceablePointer(); |
| bool FDerefable = SI->getFalseValue()->isDereferenceablePointer(); |
| |
| for (Value::use_iterator UI = SI->use_begin(), UE = SI->use_end(); |
| UI != UE; ++UI) { |
| LoadInst *LI = dyn_cast<LoadInst>(*UI); |
| if (LI == 0 || LI->isVolatile()) return false; |
| |
| // Both operands to the select need to be dereferencable, either absolutely |
| // (e.g. allocas) or at this point because we can see other accesses to it. |
| if (!TDerefable && !isSafeToLoadUnconditionally(SI->getTrueValue(), LI, |
| LI->getAlignment(), TD)) |
| return false; |
| if (!FDerefable && !isSafeToLoadUnconditionally(SI->getFalseValue(), LI, |
| LI->getAlignment(), TD)) |
| return false; |
| } |
| |
| return true; |
| } |
| |
| /// isSafePHIToSpeculate - PHI instructions that use an alloca and are |
| /// subsequently loaded can be rewritten to load both input pointers in the pred |
| /// blocks and then PHI the results, allowing the load of the alloca to be |
| /// promoted. |
| /// From this: |
| /// %P2 = phi [i32* %Alloca, i32* %Other] |
| /// %V = load i32* %P2 |
| /// to: |
| /// %V1 = load i32* %Alloca -> will be mem2reg'd |
| /// ... |
| /// %V2 = load i32* %Other |
| /// ... |
| /// %V = phi [i32 %V1, i32 %V2] |
| /// |
| /// We can do this to a select if its only uses are loads and if the operand to |
| /// the select can be loaded unconditionally. |
| static bool isSafePHIToSpeculate(PHINode *PN, const TargetData *TD) { |
| // For now, we can only do this promotion if the load is in the same block as |
| // the PHI, and if there are no stores between the phi and load. |
| // TODO: Allow recursive phi users. |
| // TODO: Allow stores. |
| BasicBlock *BB = PN->getParent(); |
| unsigned MaxAlign = 0; |
| for (Value::use_iterator UI = PN->use_begin(), UE = PN->use_end(); |
| UI != UE; ++UI) { |
| LoadInst *LI = dyn_cast<LoadInst>(*UI); |
| if (LI == 0 || LI->isVolatile()) return false; |
| |
| // For now we only allow loads in the same block as the PHI. This is a |
| // common case that happens when instcombine merges two loads through a PHI. |
| if (LI->getParent() != BB) return false; |
| |
| // Ensure that there are no instructions between the PHI and the load that |
| // could store. |
| for (BasicBlock::iterator BBI = PN; &*BBI != LI; ++BBI) |
| if (BBI->mayWriteToMemory()) |
| return false; |
| |
| MaxAlign = std::max(MaxAlign, LI->getAlignment()); |
| } |
| |
| // Okay, we know that we have one or more loads in the same block as the PHI. |
| // We can transform this if it is safe to push the loads into the predecessor |
| // blocks. The only thing to watch out for is that we can't put a possibly |
| // trapping load in the predecessor if it is a critical edge. |
| for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) { |
| BasicBlock *Pred = PN->getIncomingBlock(i); |
| |
| // If the predecessor has a single successor, then the edge isn't critical. |
| if (Pred->getTerminator()->getNumSuccessors() == 1) |
| continue; |
| |
| Value *InVal = PN->getIncomingValue(i); |
| |
| // If the InVal is an invoke in the pred, we can't put a load on the edge. |
| if (InvokeInst *II = dyn_cast<InvokeInst>(InVal)) |
| if (II->getParent() == Pred) |
| return false; |
| |
| // If this pointer is always safe to load, or if we can prove that there is |
| // already a load in the block, then we can move the load to the pred block. |
| if (InVal->isDereferenceablePointer() || |
| isSafeToLoadUnconditionally(InVal, Pred->getTerminator(), MaxAlign, TD)) |
| continue; |
| |
| return false; |
| } |
| |
| return true; |
| } |
| |
| |
| /// tryToMakeAllocaBePromotable - This returns true if the alloca only has |
| /// direct (non-volatile) loads and stores to it. If the alloca is close but |
| /// not quite there, this will transform the code to allow promotion. As such, |
| /// it is a non-pure predicate. |
| static bool tryToMakeAllocaBePromotable(AllocaInst *AI, const TargetData *TD) { |
| SetVector<Instruction*, SmallVector<Instruction*, 4>, |
| SmallPtrSet<Instruction*, 4> > InstsToRewrite; |
| |
| for (Value::use_iterator UI = AI->use_begin(), UE = AI->use_end(); |
| UI != UE; ++UI) { |
| User *U = *UI; |
| if (LoadInst *LI = dyn_cast<LoadInst>(U)) { |
| if (LI->isVolatile()) |
| return false; |
| continue; |
| } |
| |
| if (StoreInst *SI = dyn_cast<StoreInst>(U)) { |
| if (SI->getOperand(0) == AI || SI->isVolatile()) |
| return false; // Don't allow a store OF the AI, only INTO the AI. |
| continue; |
| } |
| |
| if (SelectInst *SI = dyn_cast<SelectInst>(U)) { |
| // If the condition being selected on is a constant, fold the select, yes |
| // this does (rarely) happen early on. |
| if (ConstantInt *CI = dyn_cast<ConstantInt>(SI->getCondition())) { |
| Value *Result = SI->getOperand(1+CI->isZero()); |
| SI->replaceAllUsesWith(Result); |
| SI->eraseFromParent(); |
| |
| // This is very rare and we just scrambled the use list of AI, start |
| // over completely. |
| return tryToMakeAllocaBePromotable(AI, TD); |
| } |
| |
| // If it is safe to turn "load (select c, AI, ptr)" into a select of two |
| // loads, then we can transform this by rewriting the select. |
| if (!isSafeSelectToSpeculate(SI, TD)) |
| return false; |
| |
| InstsToRewrite.insert(SI); |
| continue; |
| } |
| |
| if (PHINode *PN = dyn_cast<PHINode>(U)) { |
| if (PN->use_empty()) { // Dead PHIs can be stripped. |
| InstsToRewrite.insert(PN); |
| continue; |
| } |
| |
| // If it is safe to turn "load (phi [AI, ptr, ...])" into a PHI of loads |
| // in the pred blocks, then we can transform this by rewriting the PHI. |
| if (!isSafePHIToSpeculate(PN, TD)) |
| return false; |
| |
| InstsToRewrite.insert(PN); |
| continue; |
| } |
| |
| return false; |
| } |
| |
| // If there are no instructions to rewrite, then all uses are load/stores and |
| // we're done! |
| if (InstsToRewrite.empty()) |
| return true; |
| |
| // If we have instructions that need to be rewritten for this to be promotable |
| // take care of it now. |
| for (unsigned i = 0, e = InstsToRewrite.size(); i != e; ++i) { |
| if (SelectInst *SI = dyn_cast<SelectInst>(InstsToRewrite[i])) { |
| // Selects in InstsToRewrite only have load uses. Rewrite each as two |
| // loads with a new select. |
| while (!SI->use_empty()) { |
| LoadInst *LI = cast<LoadInst>(SI->use_back()); |
| |
| IRBuilder<> Builder(LI); |
| LoadInst *TrueLoad = |
| Builder.CreateLoad(SI->getTrueValue(), LI->getName()+".t"); |
| LoadInst *FalseLoad = |
| Builder.CreateLoad(SI->getFalseValue(), LI->getName()+".f"); |
| |
| // Transfer alignment and TBAA info if present. |
| TrueLoad->setAlignment(LI->getAlignment()); |
| FalseLoad->setAlignment(LI->getAlignment()); |
| if (MDNode *Tag = LI->getMetadata(LLVMContext::MD_tbaa)) { |
| TrueLoad->setMetadata(LLVMContext::MD_tbaa, Tag); |
| FalseLoad->setMetadata(LLVMContext::MD_tbaa, Tag); |
| } |
| |
| Value *V = Builder.CreateSelect(SI->getCondition(), TrueLoad, FalseLoad); |
| V->takeName(LI); |
| LI->replaceAllUsesWith(V); |
| LI->eraseFromParent(); |
| } |
| |
| // Now that all the loads are gone, the select is gone too. |
| SI->eraseFromParent(); |
| continue; |
| } |
| |
| // Otherwise, we have a PHI node which allows us to push the loads into the |
| // predecessors. |
| PHINode *PN = cast<PHINode>(InstsToRewrite[i]); |
| if (PN->use_empty()) { |
| PN->eraseFromParent(); |
| continue; |
| } |
| |
| Type *LoadTy = cast<PointerType>(PN->getType())->getElementType(); |
| PHINode *NewPN = PHINode::Create(LoadTy, PN->getNumIncomingValues(), |
| PN->getName()+".ld", PN); |
| |
| // Get the TBAA tag and alignment to use from one of the loads. It doesn't |
| // matter which one we get and if any differ, it doesn't matter. |
| LoadInst *SomeLoad = cast<LoadInst>(PN->use_back()); |
| MDNode *TBAATag = SomeLoad->getMetadata(LLVMContext::MD_tbaa); |
| unsigned Align = SomeLoad->getAlignment(); |
| |
| // Rewrite all loads of the PN to use the new PHI. |
| while (!PN->use_empty()) { |
| LoadInst *LI = cast<LoadInst>(PN->use_back()); |
| LI->replaceAllUsesWith(NewPN); |
| LI->eraseFromParent(); |
| } |
| |
| // Inject loads into all of the pred blocks. Keep track of which blocks we |
| // insert them into in case we have multiple edges from the same block. |
| DenseMap<BasicBlock*, LoadInst*> InsertedLoads; |
| |
| for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) { |
| BasicBlock *Pred = PN->getIncomingBlock(i); |
| LoadInst *&Load = InsertedLoads[Pred]; |
| if (Load == 0) { |
| Load = new LoadInst(PN->getIncomingValue(i), |
| PN->getName() + "." + Pred->getName(), |
| Pred->getTerminator()); |
| Load->setAlignment(Align); |
| if (TBAATag) Load->setMetadata(LLVMContext::MD_tbaa, TBAATag); |
| } |
| |
| NewPN->addIncoming(Load, Pred); |
| } |
| |
| PN->eraseFromParent(); |
| } |
| |
| ++NumAdjusted; |
| return true; |
| } |
| |
| bool SROA::performPromotion(Function &F) { |
| std::vector<AllocaInst*> Allocas; |
| DominatorTree *DT = 0; |
| if (HasDomTree) |
| DT = &getAnalysis<DominatorTree>(); |
| |
| BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function |
| DIBuilder DIB(*F.getParent()); |
| bool Changed = false; |
| SmallVector<Instruction*, 64> Insts; |
| while (1) { |
| Allocas.clear(); |
| |
| // Find allocas that are safe to promote, by looking at all instructions in |
| // the entry node |
| for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I) |
| if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) // Is it an alloca? |
| if (tryToMakeAllocaBePromotable(AI, TD)) |
| Allocas.push_back(AI); |
| |
| if (Allocas.empty()) break; |
| |
| if (HasDomTree) |
| PromoteMemToReg(Allocas, *DT); |
| else { |
| SSAUpdater SSA; |
| for (unsigned i = 0, e = Allocas.size(); i != e; ++i) { |
| AllocaInst *AI = Allocas[i]; |
| |
| // Build list of instructions to promote. |
| for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end(); |
| UI != E; ++UI) |
| Insts.push_back(cast<Instruction>(*UI)); |
| AllocaPromoter(Insts, SSA, &DIB).run(AI, Insts); |
| Insts.clear(); |
| } |
| } |
| NumPromoted += Allocas.size(); |
| Changed = true; |
| } |
| |
| return Changed; |
| } |
| |
| |
| /// ShouldAttemptScalarRepl - Decide if an alloca is a good candidate for |
| /// SROA. It must be a struct or array type with a small number of elements. |
| static bool ShouldAttemptScalarRepl(AllocaInst *AI) { |
| Type *T = AI->getAllocatedType(); |
| // Do not promote any struct into more than 32 separate vars. |
| if (StructType *ST = dyn_cast<StructType>(T)) |
| return ST->getNumElements() <= 32; |
| // Arrays are much less likely to be safe for SROA; only consider |
| // them if they are very small. |
| if (ArrayType *AT = dyn_cast<ArrayType>(T)) |
| return AT->getNumElements() <= 8; |
| return false; |
| } |
| |
| |
| // performScalarRepl - This algorithm is a simple worklist driven algorithm, |
| // which runs on all of the alloca instructions in the function, removing them |
| // if they are only used by getelementptr instructions. |
| // |
| bool SROA::performScalarRepl(Function &F) { |
| std::vector<AllocaInst*> WorkList; |
| |
| // Scan the entry basic block, adding allocas to the worklist. |
| BasicBlock &BB = F.getEntryBlock(); |
| for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I) |
| if (AllocaInst *A = dyn_cast<AllocaInst>(I)) |
| WorkList.push_back(A); |
| |
| // Process the worklist |
| bool Changed = false; |
| while (!WorkList.empty()) { |
| AllocaInst *AI = WorkList.back(); |
| WorkList.pop_back(); |
| |
| // Handle dead allocas trivially. These can be formed by SROA'ing arrays |
| // with unused elements. |
| if (AI->use_empty()) { |
| AI->eraseFromParent(); |
| Changed = true; |
| continue; |
| } |
| |
| // If this alloca is impossible for us to promote, reject it early. |
| if (AI->isArrayAllocation() || !AI->getAllocatedType()->isSized()) |
| continue; |
| |
| // Check to see if this allocation is only modified by a memcpy/memmove from |
| // a constant global. If this is the case, we can change all users to use |
| // the constant global instead. This is commonly produced by the CFE by |
| // constructs like "void foo() { int A[] = {1,2,3,4,5,6,7,8,9...}; }" if 'A' |
| // is only subsequently read. |
| SmallVector<Instruction *, 4> ToDelete; |
| if (MemTransferInst *Copy = isOnlyCopiedFromConstantGlobal(AI, ToDelete)) { |
| DEBUG(dbgs() << "Found alloca equal to global: " << *AI << '\n'); |
| DEBUG(dbgs() << " memcpy = " << *Copy << '\n'); |
| for (unsigned i = 0, e = ToDelete.size(); i != e; ++i) |
| ToDelete[i]->eraseFromParent(); |
| Constant *TheSrc = cast<Constant>(Copy->getSource()); |
| AI->replaceAllUsesWith(ConstantExpr::getBitCast(TheSrc, AI->getType())); |
| Copy->eraseFromParent(); // Don't mutate the global. |
| AI->eraseFromParent(); |
| ++NumGlobals; |
| Changed = true; |
| continue; |
| } |
| |
| // Check to see if we can perform the core SROA transformation. We cannot |
| // transform the allocation instruction if it is an array allocation |
| // (allocations OF arrays are ok though), and an allocation of a scalar |
| // value cannot be decomposed at all. |
| uint64_t AllocaSize = TD->getTypeAllocSize(AI->getAllocatedType()); |
| |
| // Do not promote [0 x %struct]. |
| if (AllocaSize == 0) continue; |
| |
| // Do not promote any struct whose size is too big. |
| if (AllocaSize > SRThreshold) continue; |
| |
| // If the alloca looks like a good candidate for scalar replacement, and if |
| // all its users can be transformed, then split up the aggregate into its |
| // separate elements. |
| if (ShouldAttemptScalarRepl(AI) && isSafeAllocaToScalarRepl(AI)) { |
| DoScalarReplacement(AI, WorkList); |
| Changed = true; |
| continue; |
| } |
| |
| // If we can turn this aggregate value (potentially with casts) into a |
| // simple scalar value that can be mem2reg'd into a register value. |
| // IsNotTrivial tracks whether this is something that mem2reg could have |
| // promoted itself. If so, we don't want to transform it needlessly. Note |
| // that we can't just check based on the type: the alloca may be of an i32 |
| // but that has pointer arithmetic to set byte 3 of it or something. |
| if (AllocaInst *NewAI = |
| ConvertToScalarInfo((unsigned)AllocaSize, *TD).TryConvert(AI)) { |
| NewAI->takeName(AI); |
| AI->eraseFromParent(); |
| ++NumConverted; |
| Changed = true; |
| continue; |
| } |
| |
| // Otherwise, couldn't process this alloca. |
| } |
| |
| return Changed; |
| } |
| |
| /// DoScalarReplacement - This alloca satisfied the isSafeAllocaToScalarRepl |
| /// predicate, do SROA now. |
| void SROA::DoScalarReplacement(AllocaInst *AI, |
| std::vector<AllocaInst*> &WorkList) { |
| DEBUG(dbgs() << "Found inst to SROA: " << *AI << '\n'); |
| SmallVector<AllocaInst*, 32> ElementAllocas; |
| if (StructType *ST = dyn_cast<StructType>(AI->getAllocatedType())) { |
| ElementAllocas.reserve(ST->getNumContainedTypes()); |
| for (unsigned i = 0, e = ST->getNumContainedTypes(); i != e; ++i) { |
| AllocaInst *NA = new AllocaInst(ST->getContainedType(i), 0, |
| AI->getAlignment(), |
| AI->getName() + "." + Twine(i), AI); |
| ElementAllocas.push_back(NA); |
| WorkList.push_back(NA); // Add to worklist for recursive processing |
| } |
| } else { |
| ArrayType *AT = cast<ArrayType>(AI->getAllocatedType()); |
| ElementAllocas.reserve(AT->getNumElements()); |
| Type *ElTy = AT->getElementType(); |
| for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) { |
| AllocaInst *NA = new AllocaInst(ElTy, 0, AI->getAlignment(), |
| AI->getName() + "." + Twine(i), AI); |
| ElementAllocas.push_back(NA); |
| WorkList.push_back(NA); // Add to worklist for recursive processing |
| } |
| } |
| |
| // Now that we have created the new alloca instructions, rewrite all the |
| // uses of the old alloca. |
| RewriteForScalarRepl(AI, AI, 0, ElementAllocas); |
| |
| // Now erase any instructions that were made dead while rewriting the alloca. |
| DeleteDeadInstructions(); |
| AI->eraseFromParent(); |
| |
| ++NumReplaced; |
| } |
| |
| /// DeleteDeadInstructions - Erase instructions on the DeadInstrs list, |
| /// recursively including all their operands that become trivially dead. |
| void SROA::DeleteDeadInstructions() { |
| while (!DeadInsts.empty()) { |
| Instruction *I = cast<Instruction>(DeadInsts.pop_back_val()); |
| |
| for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI) |
| if (Instruction *U = dyn_cast<Instruction>(*OI)) { |
| // Zero out the operand and see if it becomes trivially dead. |
| // (But, don't add allocas to the dead instruction list -- they are |
| // already on the worklist and will be deleted separately.) |
| *OI = 0; |
| if (isInstructionTriviallyDead(U) && !isa<AllocaInst>(U)) |
| DeadInsts.push_back(U); |
| } |
| |
| I->eraseFromParent(); |
| } |
| } |
| |
| /// isSafeForScalarRepl - Check if instruction I is a safe use with regard to |
| /// performing scalar replacement of alloca AI. The results are flagged in |
| /// the Info parameter. Offset indicates the position within AI that is |
| /// referenced by this instruction. |
| void SROA::isSafeForScalarRepl(Instruction *I, uint64_t Offset, |
| AllocaInfo &Info) { |
| for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E; ++UI) { |
| Instruction *User = cast<Instruction>(*UI); |
| |
| if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) { |
| isSafeForScalarRepl(BC, Offset, Info); |
| } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) { |
| uint64_t GEPOffset = Offset; |
| isSafeGEP(GEPI, GEPOffset, Info); |
| if (!Info.isUnsafe) |
| isSafeForScalarRepl(GEPI, GEPOffset, Info); |
| } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) { |
| ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength()); |
| if (Length == 0) |
| return MarkUnsafe(Info, User); |
| isSafeMemAccess(Offset, Length->getZExtValue(), 0, |
| UI.getOperandNo() == 0, Info, MI, |
| true /*AllowWholeAccess*/); |
| } else if (LoadInst *LI = dyn_cast<LoadInst>(User)) { |
| if (LI->isVolatile()) |
| return MarkUnsafe(Info, User); |
| Type *LIType = LI->getType(); |
| isSafeMemAccess(Offset, TD->getTypeAllocSize(LIType), |
| LIType, false, Info, LI, true /*AllowWholeAccess*/); |
| Info.hasALoadOrStore = true; |
| |
| } else if (StoreInst *SI = dyn_cast<StoreInst>(User)) { |
| // Store is ok if storing INTO the pointer, not storing the pointer |
| if (SI->isVolatile() || SI->getOperand(0) == I) |
| return MarkUnsafe(Info, User); |
| |
| Type *SIType = SI->getOperand(0)->getType(); |
| isSafeMemAccess(Offset, TD->getTypeAllocSize(SIType), |
| SIType, true, Info, SI, true /*AllowWholeAccess*/); |
| Info.hasALoadOrStore = true; |
| } else if (isa<PHINode>(User) || isa<SelectInst>(User)) { |
| isSafePHISelectUseForScalarRepl(User, Offset, Info); |
| } else { |
| return MarkUnsafe(Info, User); |
| } |
| if (Info.isUnsafe) return; |
| } |
| } |
| |
| |
| /// isSafePHIUseForScalarRepl - If we see a PHI node or select using a pointer |
| /// derived from the alloca, we can often still split the alloca into elements. |
| /// This is useful if we have a large alloca where one element is phi'd |
| /// together somewhere: we can SRoA and promote all the other elements even if |
| /// we end up not being able to promote this one. |
| /// |
| /// All we require is that the uses of the PHI do not index into other parts of |
| /// the alloca. The most important use case for this is single load and stores |
| /// that are PHI'd together, which can happen due to code sinking. |
| void SROA::isSafePHISelectUseForScalarRepl(Instruction *I, uint64_t Offset, |
| AllocaInfo &Info) { |
| // If we've already checked this PHI, don't do it again. |
| if (PHINode *PN = dyn_cast<PHINode>(I)) |
| if (!Info.CheckedPHIs.insert(PN)) |
| return; |
| |
| for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E; ++UI) { |
| Instruction *User = cast<Instruction>(*UI); |
| |
| if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) { |
| isSafePHISelectUseForScalarRepl(BC, Offset, Info); |
| } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) { |
| // Only allow "bitcast" GEPs for simplicity. We could generalize this, |
| // but would have to prove that we're staying inside of an element being |
| // promoted. |
| if (!GEPI->hasAllZeroIndices()) |
| return MarkUnsafe(Info, User); |
| isSafePHISelectUseForScalarRepl(GEPI, Offset, Info); |
| } else if (LoadInst *LI = dyn_cast<LoadInst>(User)) { |
| if (LI->isVolatile()) |
| return MarkUnsafe(Info, User); |
| Type *LIType = LI->getType(); |
| isSafeMemAccess(Offset, TD->getTypeAllocSize(LIType), |
| LIType, false, Info, LI, false /*AllowWholeAccess*/); |
| Info.hasALoadOrStore = true; |
| |
| } else if (StoreInst *SI = dyn_cast<StoreInst>(User)) { |
| // Store is ok if storing INTO the pointer, not storing the pointer |
| if (SI->isVolatile() || SI->getOperand(0) == I) |
| return MarkUnsafe(Info, User); |
| |
| Type *SIType = SI->getOperand(0)->getType(); |
| isSafeMemAccess(Offset, TD->getTypeAllocSize(SIType), |
| SIType, true, Info, SI, false /*AllowWholeAccess*/); |
| Info.hasALoadOrStore = true; |
| } else if (isa<PHINode>(User) || isa<SelectInst>(User)) { |
| isSafePHISelectUseForScalarRepl(User, Offset, Info); |
| } else { |
| return MarkUnsafe(Info, User); |
| } |
| if (Info.isUnsafe) return; |
| } |
| } |
| |
| /// isSafeGEP - Check if a GEP instruction can be handled for scalar |
| /// replacement. It is safe when all the indices are constant, in-bounds |
| /// references, and when the resulting offset corresponds to an element within |
| /// the alloca type. The results are flagged in the Info parameter. Upon |
| /// return, Offset is adjusted as specified by the GEP indices. |
| void SROA::isSafeGEP(GetElementPtrInst *GEPI, |
| uint64_t &Offset, AllocaInfo &Info) { |
| gep_type_iterator GEPIt = gep_type_begin(GEPI), E = gep_type_end(GEPI); |
| if (GEPIt == E) |
| return; |
| |
| // Walk through the GEP type indices, checking the types that this indexes |
| // into. |
| for (; GEPIt != E; ++GEPIt) { |
| // Ignore struct elements, no extra checking needed for these. |
| if ((*GEPIt)->isStructTy()) |
| continue; |
| |
| ConstantInt *IdxVal = dyn_cast<ConstantInt>(GEPIt.getOperand()); |
| if (!IdxVal) |
| return MarkUnsafe(Info, GEPI); |
| } |
| |
| // Compute the offset due to this GEP and check if the alloca has a |
| // component element at that offset. |
| SmallVector<Value*, 8> Indices(GEPI->op_begin() + 1, GEPI->op_end()); |
| Offset += TD->getIndexedOffset(GEPI->getPointerOperandType(), Indices); |
| if (!TypeHasComponent(Info.AI->getAllocatedType(), Offset, 0)) |
| MarkUnsafe(Info, GEPI); |
| } |
| |
| /// isHomogeneousAggregate - Check if type T is a struct or array containing |
| /// elements of the same type (which is always true for arrays). If so, |
| /// return true with NumElts and EltTy set to the number of elements and the |
| /// element type, respectively. |
| static bool isHomogeneousAggregate(Type *T, unsigned &NumElts, |
| Type *&EltTy) { |
| if (ArrayType *AT = dyn_cast<ArrayType>(T)) { |
| NumElts = AT->getNumElements(); |
| EltTy = (NumElts == 0 ? 0 : AT->getElementType()); |
| return true; |
| } |
| if (StructType *ST = dyn_cast<StructType>(T)) { |
| NumElts = ST->getNumContainedTypes(); |
| EltTy = (NumElts == 0 ? 0 : ST->getContainedType(0)); |
| for (unsigned n = 1; n < NumElts; ++n) { |
| if (ST->getContainedType(n) != EltTy) |
| return false; |
| } |
| return true; |
| } |
| return false; |
| } |
| |
| /// isCompatibleAggregate - Check if T1 and T2 are either the same type or are |
| /// "homogeneous" aggregates with the same element type and number of elements. |
| static bool isCompatibleAggregate(Type *T1, Type *T2) { |
| if (T1 == T2) |
| return true; |
| |
| unsigned NumElts1, NumElts2; |
| Type *EltTy1, *EltTy2; |
| if (isHomogeneousAggregate(T1, NumElts1, EltTy1) && |
| isHomogeneousAggregate(T2, NumElts2, EltTy2) && |
| NumElts1 == NumElts2 && |
| EltTy1 == EltTy2) |
| return true; |
| |
| return false; |
| } |
| |
| /// isSafeMemAccess - Check if a load/store/memcpy operates on the entire AI |
| /// alloca or has an offset and size that corresponds to a component element |
| /// within it. The offset checked here may have been formed from a GEP with a |
| /// pointer bitcasted to a different type. |
| /// |
| /// If AllowWholeAccess is true, then this allows uses of the entire alloca as a |
| /// unit. If false, it only allows accesses known to be in a single element. |
| void SROA::isSafeMemAccess(uint64_t Offset, uint64_t MemSize, |
| Type *MemOpType, bool isStore, |
| AllocaInfo &Info, Instruction *TheAccess, |
| bool AllowWholeAccess) { |
| // Check if this is a load/store of the entire alloca. |
| if (Offset == 0 && AllowWholeAccess && |
| MemSize == TD->getTypeAllocSize(Info.AI->getAllocatedType())) { |
| // This can be safe for MemIntrinsics (where MemOpType is 0) and integer |
| // loads/stores (which are essentially the same as the MemIntrinsics with |
| // regard to copying padding between elements). But, if an alloca is |
| // flagged as both a source and destination of such operations, we'll need |
| // to check later for padding between elements. |
| if (!MemOpType || MemOpType->isIntegerTy()) { |
| if (isStore) |
| Info.isMemCpyDst = true; |
| else |
| Info.isMemCpySrc = true; |
| return; |
| } |
| // This is also safe for references using a type that is compatible with |
| // the type of the alloca, so that loads/stores can be rewritten using |
| // insertvalue/extractvalue. |
| if (isCompatibleAggregate(MemOpType, Info.AI->getAllocatedType())) { |
| Info.hasSubelementAccess = true; |
| return; |
| } |
| } |
| // Check if the offset/size correspond to a component within the alloca type. |
| Type *T = Info.AI->getAllocatedType(); |
| if (TypeHasComponent(T, Offset, MemSize)) { |
| Info.hasSubelementAccess = true; |
| return; |
| } |
| |
| return MarkUnsafe(Info, TheAccess); |
| } |
| |
| /// TypeHasComponent - Return true if T has a component type with the |
| /// specified offset and size. If Size is zero, do not check the size. |
| bool SROA::TypeHasComponent(Type *T, uint64_t Offset, uint64_t Size) { |
| Type *EltTy; |
| uint64_t EltSize; |
| if (StructType *ST = dyn_cast<StructType>(T)) { |
| const StructLayout *Layout = TD->getStructLayout(ST); |
| unsigned EltIdx = Layout->getElementContainingOffset(Offset); |
| EltTy = ST->getContainedType(EltIdx); |
| EltSize = TD->getTypeAllocSize(EltTy); |
| Offset -= Layout->getElementOffset(EltIdx); |
| } else if (ArrayType *AT = dyn_cast<ArrayType>(T)) { |
| EltTy = AT->getElementType(); |
| EltSize = TD->getTypeAllocSize(EltTy); |
| if (Offset >= AT->getNumElements() * EltSize) |
| return false; |
| Offset %= EltSize; |
| } else { |
| return false; |
| } |
| if (Offset == 0 && (Size == 0 || EltSize == Size)) |
| return true; |
| // Check if the component spans multiple elements. |
| if (Offset + Size > EltSize) |
| return false; |
| return TypeHasComponent(EltTy, Offset, Size); |
| } |
| |
| /// RewriteForScalarRepl - Alloca AI is being split into NewElts, so rewrite |
| /// the instruction I, which references it, to use the separate elements. |
| /// Offset indicates the position within AI that is referenced by this |
| /// instruction. |
| void SROA::RewriteForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset, |
| SmallVector<AllocaInst*, 32> &NewElts) { |
| for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E;) { |
| Use &TheUse = UI.getUse(); |
| Instruction *User = cast<Instruction>(*UI++); |
| |
| if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) { |
| RewriteBitCast(BC, AI, Offset, NewElts); |
| continue; |
| } |
| |
| if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) { |
| RewriteGEP(GEPI, AI, Offset, NewElts); |
| continue; |
| } |
| |
| if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) { |
| ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength()); |
| uint64_t MemSize = Length->getZExtValue(); |
| if (Offset == 0 && |
| MemSize == TD->getTypeAllocSize(AI->getAllocatedType())) |
| RewriteMemIntrinUserOfAlloca(MI, I, AI, NewElts); |
| // Otherwise the intrinsic can only touch a single element and the |
| // address operand will be updated, so nothing else needs to be done. |
| continue; |
| } |
| |
| if (LoadInst *LI = dyn_cast<LoadInst>(User)) { |
| Type *LIType = LI->getType(); |
| |
| if (isCompatibleAggregate(LIType, AI->getAllocatedType())) { |
| // Replace: |
| // %res = load { i32, i32 }* %alloc |
| // with: |
| // %load.0 = load i32* %alloc.0 |
| // %insert.0 insertvalue { i32, i32 } zeroinitializer, i32 %load.0, 0 |
| // %load.1 = load i32* %alloc.1 |
| // %insert = insertvalue { i32, i32 } %insert.0, i32 %load.1, 1 |
| // (Also works for arrays instead of structs) |
| Value *Insert = UndefValue::get(LIType); |
| IRBuilder<> Builder(LI); |
| for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { |
| Value *Load = Builder.CreateLoad(NewElts[i], "load"); |
| Insert = Builder.CreateInsertValue(Insert, Load, i, "insert"); |
| } |
| LI->replaceAllUsesWith(Insert); |
| DeadInsts.push_back(LI); |
| } else if (LIType->isIntegerTy() && |
| TD->getTypeAllocSize(LIType) == |
| TD->getTypeAllocSize(AI->getAllocatedType())) { |
| // If this is a load of the entire alloca to an integer, rewrite it. |
| RewriteLoadUserOfWholeAlloca(LI, AI, NewElts); |
| } |
| continue; |
| } |
| |
| if (StoreInst *SI = dyn_cast<StoreInst>(User)) { |
| Value *Val = SI->getOperand(0); |
| Type *SIType = Val->getType(); |
| if (isCompatibleAggregate(SIType, AI->getAllocatedType())) { |
| // Replace: |
| // store { i32, i32 } %val, { i32, i32 }* %alloc |
| // with: |
| // %val.0 = extractvalue { i32, i32 } %val, 0 |
| // store i32 %val.0, i32* %alloc.0 |
| // %val.1 = extractvalue { i32, i32 } %val, 1 |
| // store i32 %val.1, i32* %alloc.1 |
| // (Also works for arrays instead of structs) |
| IRBuilder<> Builder(SI); |
| for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { |
| Value *Extract = Builder.CreateExtractValue(Val, i, Val->getName()); |
| Builder.CreateStore(Extract, NewElts[i]); |
| } |
| DeadInsts.push_back(SI); |
| } else if (SIType->isIntegerTy() && |
| TD->getTypeAllocSize(SIType) == |
| TD->getTypeAllocSize(AI->getAllocatedType())) { |
| // If this is a store of the entire alloca from an integer, rewrite it. |
| RewriteStoreUserOfWholeAlloca(SI, AI, NewElts); |
| } |
| continue; |
| } |
| |
| if (isa<SelectInst>(User) || isa<PHINode>(User)) { |
| // If we have a PHI user of the alloca itself (as opposed to a GEP or |
| // bitcast) we have to rewrite it. GEP and bitcast uses will be RAUW'd to |
| // the new pointer. |
| if (!isa<AllocaInst>(I)) continue; |
| |
| assert(Offset == 0 && NewElts[0] && |
| "Direct alloca use should have a zero offset"); |
| |
| // If we have a use of the alloca, we know the derived uses will be |
| // utilizing just the first element of the scalarized result. Insert a |
| // bitcast of the first alloca before the user as required. |
| AllocaInst *NewAI = NewElts[0]; |
| BitCastInst *BCI = new BitCastInst(NewAI, AI->getType(), "", NewAI); |
| NewAI->moveBefore(BCI); |
| TheUse = BCI; |
| continue; |
| } |
| } |
| } |
| |
| /// RewriteBitCast - Update a bitcast reference to the alloca being replaced |
| /// and recursively continue updating all of its uses. |
| void SROA::RewriteBitCast(BitCastInst *BC, AllocaInst *AI, uint64_t Offset, |
| SmallVector<AllocaInst*, 32> &NewElts) { |
| RewriteForScalarRepl(BC, AI, Offset, NewElts); |
| if (BC->getOperand(0) != AI) |
| return; |
| |
| // The bitcast references the original alloca. Replace its uses with |
| // references to the first new element alloca. |
| Instruction *Val = NewElts[0]; |
| if (Val->getType() != BC->getDestTy()) { |
| Val = new BitCastInst(Val, BC->getDestTy(), "", BC); |
| Val->takeName(BC); |
| } |
| BC->replaceAllUsesWith(Val); |
| DeadInsts.push_back(BC); |
| } |
| |
| /// FindElementAndOffset - Return the index of the element containing Offset |
| /// within the specified type, which must be either a struct or an array. |
| /// Sets T to the type of the element and Offset to the offset within that |
| /// element. IdxTy is set to the type of the index result to be used in a |
| /// GEP instruction. |
| uint64_t SROA::FindElementAndOffset(Type *&T, uint64_t &Offset, |
| Type *&IdxTy) { |
| uint64_t Idx = 0; |
| if (StructType *ST = dyn_cast<StructType>(T)) { |
| const StructLayout *Layout = TD->getStructLayout(ST); |
| Idx = Layout->getElementContainingOffset(Offset); |
| T = ST->getContainedType(Idx); |
| Offset -= Layout->getElementOffset(Idx); |
| IdxTy = Type::getInt32Ty(T->getContext()); |
| return Idx; |
| } |
| ArrayType *AT = cast<ArrayType>(T); |
| T = AT->getElementType(); |
| uint64_t EltSize = TD->getTypeAllocSize(T); |
| Idx = Offset / EltSize; |
| Offset -= Idx * EltSize; |
| IdxTy = Type::getInt64Ty(T->getContext()); |
| return Idx; |
| } |
| |
| /// RewriteGEP - Check if this GEP instruction moves the pointer across |
| /// elements of the alloca that are being split apart, and if so, rewrite |
| /// the GEP to be relative to the new element. |
| void SROA::RewriteGEP(GetElementPtrInst *GEPI, AllocaInst *AI, uint64_t Offset, |
| SmallVector<AllocaInst*, 32> &NewElts) { |
| uint64_t OldOffset = Offset; |
| SmallVector<Value*, 8> Indices(GEPI->op_begin() + 1, GEPI->op_end()); |
| Offset += TD->getIndexedOffset(GEPI->getPointerOperandType(), Indices); |
| |
| RewriteForScalarRepl(GEPI, AI, Offset, NewElts); |
| |
| Type *T = AI->getAllocatedType(); |
| Type *IdxTy; |
| uint64_t OldIdx = FindElementAndOffset(T, OldOffset, IdxTy); |
| if (GEPI->getOperand(0) == AI) |
| OldIdx = ~0ULL; // Force the GEP to be rewritten. |
| |
| T = AI->getAllocatedType(); |
| uint64_t EltOffset = Offset; |
| uint64_t Idx = FindElementAndOffset(T, EltOffset, IdxTy); |
| |
| // If this GEP does not move the pointer across elements of the alloca |
| // being split, then it does not needs to be rewritten. |
| if (Idx == OldIdx) |
| return; |
| |
| Type *i32Ty = Type::getInt32Ty(AI->getContext()); |
| SmallVector<Value*, 8> NewArgs; |
| NewArgs.push_back(Constant::getNullValue(i32Ty)); |
| while (EltOffset != 0) { |
| uint64_t EltIdx = FindElementAndOffset(T, EltOffset, IdxTy); |
| NewArgs.push_back(ConstantInt::get(IdxTy, EltIdx)); |
| } |
| Instruction *Val = NewElts[Idx]; |
| if (NewArgs.size() > 1) { |
| Val = GetElementPtrInst::CreateInBounds(Val, NewArgs, "", GEPI); |
| Val->takeName(GEPI); |
| } |
| if (Val->getType() != GEPI->getType()) |
| Val = new BitCastInst(Val, GEPI->getType(), Val->getName(), GEPI); |
| GEPI->replaceAllUsesWith(Val); |
| DeadInsts.push_back(GEPI); |
| } |
| |
| /// RewriteMemIntrinUserOfAlloca - MI is a memcpy/memset/memmove from or to AI. |
| /// Rewrite it to copy or set the elements of the scalarized memory. |
| void SROA::RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *Inst, |
| AllocaInst *AI, |
| SmallVector<AllocaInst*, 32> &NewElts) { |
| // If this is a memcpy/memmove, construct the other pointer as the |
| // appropriate type. The "Other" pointer is the pointer that goes to memory |
| // that doesn't have anything to do with the alloca that we are promoting. For |
| // memset, this Value* stays null. |
| Value *OtherPtr = 0; |
| unsigned MemAlignment = MI->getAlignment(); |
| if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(MI)) { // memmove/memcopy |
| if (Inst == MTI->getRawDest()) |
| OtherPtr = MTI->getRawSource(); |
| else { |
| assert(Inst == MTI->getRawSource()); |
| OtherPtr = MTI->getRawDest(); |
| } |
| } |
| |
| // If there is an other pointer, we want to convert it to the same pointer |
| // type as AI has, so we can GEP through it safely. |
| if (OtherPtr) { |
| unsigned AddrSpace = |
| cast<PointerType>(OtherPtr->getType())->getAddressSpace(); |
| |
| // Remove bitcasts and all-zero GEPs from OtherPtr. This is an |
| // optimization, but it's also required to detect the corner case where |
| // both pointer operands are referencing the same memory, and where |
| // OtherPtr may be a bitcast or GEP that currently being rewritten. (This |
| // function is only called for mem intrinsics that access the whole |
| // aggregate, so non-zero GEPs are not an issue here.) |
| OtherPtr = OtherPtr->stripPointerCasts(); |
| |
| // Copying the alloca to itself is a no-op: just delete it. |
| if (OtherPtr == AI || OtherPtr == NewElts[0]) { |
| // This code will run twice for a no-op memcpy -- once for each operand. |
| // Put only one reference to MI on the DeadInsts list. |
| for (SmallVector<Value*, 32>::const_iterator I = DeadInsts.begin(), |
| E = DeadInsts.end(); I != E; ++I) |
| if (*I == MI) return; |
| DeadInsts.push_back(MI); |
| return; |
| } |
| |
| // If the pointer is not the right type, insert a bitcast to the right |
| // type. |
| Type *NewTy = |
| PointerType::get(AI->getType()->getElementType(), AddrSpace); |
| |
| if (OtherPtr->getType() != NewTy) |
| OtherPtr = new BitCastInst(OtherPtr, NewTy, OtherPtr->getName(), MI); |
| } |
| |
| // Process each element of the aggregate. |
| bool SROADest = MI->getRawDest() == Inst; |
| |
| Constant *Zero = Constant::getNullValue(Type::getInt32Ty(MI->getContext())); |
| |
| for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { |
| // If this is a memcpy/memmove, emit a GEP of the other element address. |
| Value *OtherElt = 0; |
| unsigned OtherEltAlign = MemAlignment; |
| |
| if (OtherPtr) { |
| Value *Idx[2] = { Zero, |
| ConstantInt::get(Type::getInt32Ty(MI->getContext()), i) }; |
| OtherElt = GetElementPtrInst::CreateInBounds(OtherPtr, Idx, |
| OtherPtr->getName()+"."+Twine(i), |
| MI); |
| uint64_t EltOffset; |
| PointerType *OtherPtrTy = cast<PointerType>(OtherPtr->getType()); |
| Type *OtherTy = OtherPtrTy->getElementType(); |
| if (StructType *ST = dyn_cast<StructType>(OtherTy)) { |
| EltOffset = TD->getStructLayout(ST)->getElementOffset(i); |
| } else { |
| Type *EltTy = cast<SequentialType>(OtherTy)->getElementType(); |
| EltOffset = TD->getTypeAllocSize(EltTy)*i; |
| } |
| |
| // The alignment of the other pointer is the guaranteed alignment of the |
| // element, which is affected by both the known alignment of the whole |
| // mem intrinsic and the alignment of the element. If the alignment of |
| // the memcpy (f.e.) is 32 but the element is at a 4-byte offset, then the |
| // known alignment is just 4 bytes. |
| OtherEltAlign = (unsigned)MinAlign(OtherEltAlign, EltOffset); |
| } |
| |
| Value *EltPtr = NewElts[i]; |
| Type *EltTy = cast<PointerType>(EltPtr->getType())->getElementType(); |
| |
| // If we got down to a scalar, insert a load or store as appropriate. |
| if (EltTy->isSingleValueType()) { |
| if (isa<MemTransferInst>(MI)) { |
| if (SROADest) { |
| // From Other to Alloca. |
| Value *Elt = new LoadInst(OtherElt, "tmp", false, OtherEltAlign, MI); |
| new StoreInst(Elt, EltPtr, MI); |
| } else { |
| // From Alloca to Other. |
| Value *Elt = new LoadInst(EltPtr, "tmp", MI); |
| new StoreInst(Elt, OtherElt, false, OtherEltAlign, MI); |
| } |
| continue; |
| } |
| assert(isa<MemSetInst>(MI)); |
| |
| // If the stored element is zero (common case), just store a null |
| // constant. |
| Constant *StoreVal; |
| if (ConstantInt *CI = dyn_cast<ConstantInt>(MI->getArgOperand(1))) { |
| if (CI->isZero()) { |
| StoreVal = Constant::getNullValue(EltTy); // 0.0, null, 0, <0,0> |
| } else { |
| // If EltTy is a vector type, get the element type. |
| Type *ValTy = EltTy->getScalarType(); |
| |
| // Construct an integer with the right value. |
| unsigned EltSize = TD->getTypeSizeInBits(ValTy); |
| APInt OneVal(EltSize, CI->getZExtValue()); |
| APInt TotalVal(OneVal); |
| // Set each byte. |
| for (unsigned i = 0; 8*i < EltSize; ++i) { |
| TotalVal = TotalVal.shl(8); |
| TotalVal |= OneVal; |
| } |
| |
| // Convert the integer value to the appropriate type. |
| StoreVal = ConstantInt::get(CI->getContext(), TotalVal); |
| if (ValTy->isPointerTy()) |
| StoreVal = ConstantExpr::getIntToPtr(StoreVal, ValTy); |
| else if (ValTy->isFloatingPointTy()) |
| StoreVal = ConstantExpr::getBitCast(StoreVal, ValTy); |
| assert(StoreVal->getType() == ValTy && "Type mismatch!"); |
| |
| // If the requested value was a vector constant, create it. |
| if (EltTy != ValTy) { |
| unsigned NumElts = cast<VectorType>(ValTy)->getNumElements(); |
| SmallVector<Constant*, 16> Elts(NumElts, StoreVal); |
| StoreVal = ConstantVector::get(Elts); |
| } |
| } |
| new StoreInst(StoreVal, EltPtr, MI); |
| continue; |
| } |
| // Otherwise, if we're storing a byte variable, use a memset call for |
| // this element. |
| } |
| |
| unsigned EltSize = TD->getTypeAllocSize(EltTy); |
| |
| IRBuilder<> Builder(MI); |
| |
| // Finally, insert the meminst for this element. |
| if (isa<MemSetInst>(MI)) { |
| Builder.CreateMemSet(EltPtr, MI->getArgOperand(1), EltSize, |
| MI->isVolatile()); |
| } else { |
| assert(isa<MemTransferInst>(MI)); |
| Value *Dst = SROADest ? EltPtr : OtherElt; // Dest ptr |
| Value *Src = SROADest ? OtherElt : EltPtr; // Src ptr |
| |
| if (isa<MemCpyInst>(MI)) |
| Builder.CreateMemCpy(Dst, Src, EltSize, OtherEltAlign,MI->isVolatile()); |
| else |
| Builder.CreateMemMove(Dst, Src, EltSize,OtherEltAlign,MI->isVolatile()); |
| } |
| } |
| DeadInsts.push_back(MI); |
| } |
| |
| /// RewriteStoreUserOfWholeAlloca - We found a store of an integer that |
| /// overwrites the entire allocation. Extract out the pieces of the stored |
| /// integer and store them individually. |
| void SROA::RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocaInst *AI, |
| SmallVector<AllocaInst*, 32> &NewElts){ |
| // Extract each element out of the integer according to its structure offset |
| // and store the element value to the individual alloca. |
| Value *SrcVal = SI->getOperand(0); |
| Type *AllocaEltTy = AI->getAllocatedType(); |
| uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy); |
| |
| IRBuilder<> Builder(SI); |
| |
| // Handle tail padding by extending the operand |
| if (TD->getTypeSizeInBits(SrcVal->getType()) != AllocaSizeBits) |
| SrcVal = Builder.CreateZExt(SrcVal, |
| IntegerType::get(SI->getContext(), AllocaSizeBits)); |
| |
| DEBUG(dbgs() << "PROMOTING STORE TO WHOLE ALLOCA: " << *AI << '\n' << *SI |
| << '\n'); |
| |
| // There are two forms here: AI could be an array or struct. Both cases |
| // have different ways to compute the element offset. |
| if (StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) { |
| const StructLayout *Layout = TD->getStructLayout(EltSTy); |
| |
| for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { |
| // Get the number of bits to shift SrcVal to get the value. |
| Type *FieldTy = EltSTy->getElementType(i); |
| uint64_t Shift = Layout->getElementOffsetInBits(i); |
| |
| if (TD->isBigEndian()) |
| Shift = AllocaSizeBits-Shift-TD->getTypeAllocSizeInBits(FieldTy); |
| |
| Value *EltVal = SrcVal; |
| if (Shift) { |
| Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift); |
| EltVal = Builder.CreateLShr(EltVal, ShiftVal, "sroa.store.elt"); |
| } |
| |
| // Truncate down to an integer of the right size. |
| uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy); |
| |
| // Ignore zero sized fields like {}, they obviously contain no data. |
| if (FieldSizeBits == 0) continue; |
| |
| if (FieldSizeBits != AllocaSizeBits) |
| EltVal = Builder.CreateTrunc(EltVal, |
| IntegerType::get(SI->getContext(), FieldSizeBits)); |
| Value *DestField = NewElts[i]; |
| if (EltVal->getType() == FieldTy) { |
| // Storing to an integer field of this size, just do it. |
| } else if (FieldTy->isFloatingPointTy() || FieldTy->isVectorTy()) { |
| // Bitcast to the right element type (for fp/vector values). |
| EltVal = Builder.CreateBitCast(EltVal, FieldTy); |
| } else { |
| // Otherwise, bitcast the dest pointer (for aggregates). |
| DestField = Builder.CreateBitCast(DestField, |
| PointerType::getUnqual(EltVal->getType())); |
| } |
| new StoreInst(EltVal, DestField, SI); |
| } |
| |
| } else { |
| ArrayType *ATy = cast<ArrayType>(AllocaEltTy); |
| Type *ArrayEltTy = ATy->getElementType(); |
| uint64_t ElementOffset = TD->getTypeAllocSizeInBits(ArrayEltTy); |
| uint64_t ElementSizeBits = TD->getTypeSizeInBits(ArrayEltTy); |
| |
| uint64_t Shift; |
| |
| if (TD->isBigEndian()) |
| Shift = AllocaSizeBits-ElementOffset; |
| else |
| Shift = 0; |
| |
| for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { |
| // Ignore zero sized fields like {}, they obviously contain no data. |
| if (ElementSizeBits == 0) continue; |
| |
| Value *EltVal = SrcVal; |
| if (Shift) { |
| Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift); |
| EltVal = Builder.CreateLShr(EltVal, ShiftVal, "sroa.store.elt"); |
| } |
| |
| // Truncate down to an integer of the right size. |
| if (ElementSizeBits != AllocaSizeBits) |
| EltVal = Builder.CreateTrunc(EltVal, |
| IntegerType::get(SI->getContext(), |
| ElementSizeBits)); |
| Value *DestField = NewElts[i]; |
| if (EltVal->getType() == ArrayEltTy) { |
| // Storing to an integer field of this size, just do it. |
| } else if (ArrayEltTy->isFloatingPointTy() || |
| ArrayEltTy->isVectorTy()) { |
| // Bitcast to the right element type (for fp/vector values). |
| EltVal = Builder.CreateBitCast(EltVal, ArrayEltTy); |
| } else { |
| // Otherwise, bitcast the dest pointer (for aggregates). |
| DestField = Builder.CreateBitCast(DestField, |
| PointerType::getUnqual(EltVal->getType())); |
| } |
| new StoreInst(EltVal, DestField, SI); |
| |
| if (TD->isBigEndian()) |
| Shift -= ElementOffset; |
| else |
| Shift += ElementOffset; |
| } |
| } |
| |
| DeadInsts.push_back(SI); |
| } |
| |
| /// RewriteLoadUserOfWholeAlloca - We found a load of the entire allocation to |
| /// an integer. Load the individual pieces to form the aggregate value. |
| void SROA::RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocaInst *AI, |
| SmallVector<AllocaInst*, 32> &NewElts) { |
| // Extract each element out of the NewElts according to its structure offset |
| // and form the result value. |
| Type *AllocaEltTy = AI->getAllocatedType(); |
| uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy); |
| |
| DEBUG(dbgs() << "PROMOTING LOAD OF WHOLE ALLOCA: " << *AI << '\n' << *LI |
| << '\n'); |
| |
| // There are two forms here: AI could be an array or struct. Both cases |
| // have different ways to compute the element offset. |
| const StructLayout *Layout = 0; |
| uint64_t ArrayEltBitOffset = 0; |
| if (StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) { |
| Layout = TD->getStructLayout(EltSTy); |
| } else { |
| Type *ArrayEltTy = cast<ArrayType>(AllocaEltTy)->getElementType(); |
| ArrayEltBitOffset = TD->getTypeAllocSizeInBits(ArrayEltTy); |
| } |
| |
| Value *ResultVal = |
| Constant::getNullValue(IntegerType::get(LI->getContext(), AllocaSizeBits)); |
| |
| for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { |
| // Load the value from the alloca. If the NewElt is an aggregate, cast |
| // the pointer to an integer of the same size before doing the load. |
| Value *SrcField = NewElts[i]; |
| Type *FieldTy = |
| cast<PointerType>(SrcField->getType())->getElementType(); |
| uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy); |
| |
| // Ignore zero sized fields like {}, they obviously contain no data. |
| if (FieldSizeBits == 0) continue; |
| |
| IntegerType *FieldIntTy = IntegerType::get(LI->getContext(), |
| FieldSizeBits); |
| if (!FieldTy->isIntegerTy() && !FieldTy->isFloatingPointTy() && |
| !FieldTy->isVectorTy()) |
| SrcField = new BitCastInst(SrcField, |
| PointerType::getUnqual(FieldIntTy), |
| "", LI); |
| SrcField = new LoadInst(SrcField, "sroa.load.elt", LI); |
| |
| // If SrcField is a fp or vector of the right size but that isn't an |
| // integer type, bitcast to an integer so we can shift it. |
| if (SrcField->getType() != FieldIntTy) |
| SrcField = new BitCastInst(SrcField, FieldIntTy, "", LI); |
| |
| // Zero extend the field to be the same size as the final alloca so that |
| // we can shift and insert it. |
| if (SrcField->getType() != ResultVal->getType()) |
| SrcField = new ZExtInst(SrcField, ResultVal->getType(), "", LI); |
| |
| // Determine the number of bits to shift SrcField. |
| uint64_t Shift; |
| if (Layout) // Struct case. |
| Shift = Layout->getElementOffsetInBits(i); |
| else // Array case. |
| Shift = i*ArrayEltBitOffset; |
| |
| if (TD->isBigEndian()) |
| Shift = AllocaSizeBits-Shift-FieldIntTy->getBitWidth(); |
| |
| if (Shift) { |
| Value *ShiftVal = ConstantInt::get(SrcField->getType(), Shift); |
| SrcField = BinaryOperator::CreateShl(SrcField, ShiftVal, "", LI); |
| } |
| |
| // Don't create an 'or x, 0' on the first iteration. |
| if (!isa<Constant>(ResultVal) || |
| !cast<Constant>(ResultVal)->isNullValue()) |
| ResultVal = BinaryOperator::CreateOr(SrcField, ResultVal, "", LI); |
| else |
| ResultVal = SrcField; |
| } |
| |
| // Handle tail padding by truncating the result |
| if (TD->getTypeSizeInBits(LI->getType()) != AllocaSizeBits) |
| ResultVal = new TruncInst(ResultVal, LI->getType(), "", LI); |
| |
| LI->replaceAllUsesWith(ResultVal); |
| DeadInsts.push_back(LI); |
| } |
| |
| /// HasPadding - Return true if the specified type has any structure or |
| /// alignment padding in between the elements that would be split apart |
| /// by SROA; return false otherwise. |
| static bool HasPadding(Type *Ty, const TargetData &TD) { |
| if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) { |
| Ty = ATy->getElementType(); |
| return TD.getTypeSizeInBits(Ty) != TD.getTypeAllocSizeInBits(Ty); |
| } |
| |
| // SROA currently handles only Arrays and Structs. |
| StructType *STy = cast<StructType>(Ty); |
| const StructLayout *SL = TD.getStructLayout(STy); |
| unsigned PrevFieldBitOffset = 0; |
| for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) { |
| unsigned FieldBitOffset = SL->getElementOffsetInBits(i); |
| |
| // Check to see if there is any padding between this element and the |
| // previous one. |
| if (i) { |
| unsigned PrevFieldEnd = |
| PrevFieldBitOffset+TD.getTypeSizeInBits(STy->getElementType(i-1)); |
| if (PrevFieldEnd < FieldBitOffset) |
| return true; |
| } |
| PrevFieldBitOffset = FieldBitOffset; |
| } |
| // Check for tail padding. |
| if (unsigned EltCount = STy->getNumElements()) { |
| unsigned PrevFieldEnd = PrevFieldBitOffset + |
| TD.getTypeSizeInBits(STy->getElementType(EltCount-1)); |
| if (PrevFieldEnd < SL->getSizeInBits()) |
| return true; |
| } |
| return false; |
| } |
| |
| /// isSafeStructAllocaToScalarRepl - Check to see if the specified allocation of |
| /// an aggregate can be broken down into elements. Return 0 if not, 3 if safe, |
| /// or 1 if safe after canonicalization has been performed. |
| bool SROA::isSafeAllocaToScalarRepl(AllocaInst *AI) { |
| // Loop over the use list of the alloca. We can only transform it if all of |
| // the users are safe to transform. |
| AllocaInfo Info(AI); |
| |
| isSafeForScalarRepl(AI, 0, Info); |
| if (Info.isUnsafe) { |
| DEBUG(dbgs() << "Cannot transform: " << *AI << '\n'); |
| return false; |
| } |
| |
| // Okay, we know all the users are promotable. If the aggregate is a memcpy |
| // source and destination, we have to be careful. In particular, the memcpy |
| // could be moving around elements that live in structure padding of the LLVM |
| // types, but may actually be used. In these cases, we refuse to promote the |
| // struct. |
| if (Info.isMemCpySrc && Info.isMemCpyDst && |
| HasPadding(AI->getAllocatedType(), *TD)) |
| return false; |
| |
| // If the alloca never has an access to just *part* of it, but is accessed |
| // via loads and stores, then we should use ConvertToScalarInfo to promote |
| // the alloca instead of promoting each piece at a time and inserting fission |
| // and fusion code. |
| if (!Info.hasSubelementAccess && Info.hasALoadOrStore) { |
| // If the struct/array just has one element, use basic SRoA. |
| if (StructType *ST = dyn_cast<StructType>(AI->getAllocatedType())) { |
| if (ST->getNumElements() > 1) return false; |
| } else { |
| if (cast<ArrayType>(AI->getAllocatedType())->getNumElements() > 1) |
| return false; |
| } |
| } |
| |
| return true; |
| } |
| |
| |
| |
| /// PointsToConstantGlobal - Return true if V (possibly indirectly) points to |
| /// some part of a constant global variable. This intentionally only accepts |
| /// constant expressions because we don't can't rewrite arbitrary instructions. |
| static bool PointsToConstantGlobal(Value *V) { |
| if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V)) |
| return GV->isConstant(); |
| if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) |
| if (CE->getOpcode() == Instruction::BitCast || |
| CE->getOpcode() == Instruction::GetElementPtr) |
| return PointsToConstantGlobal(CE->getOperand(0)); |
| return false; |
| } |
| |
| /// isOnlyCopiedFromConstantGlobal - Recursively walk the uses of a (derived) |
| /// pointer to an alloca. Ignore any reads of the pointer, return false if we |
| /// see any stores or other unknown uses. If we see pointer arithmetic, keep |
| /// track of whether it moves the pointer (with isOffset) but otherwise traverse |
| /// the uses. If we see a memcpy/memmove that targets an unoffseted pointer to |
| /// the alloca, and if the source pointer is a pointer to a constant global, we |
| /// can optimize this. |
| static bool |
| isOnlyCopiedFromConstantGlobal(Value *V, MemTransferInst *&TheCopy, |
| bool isOffset, |
| SmallVector<Instruction *, 4> &LifetimeMarkers) { |
| // We track lifetime intrinsics as we encounter them. If we decide to go |
| // ahead and replace the value with the global, this lets the caller quickly |
| // eliminate the markers. |
| |
| for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) { |
| User *U = cast<Instruction>(*UI); |
| |
| if (LoadInst *LI = dyn_cast<LoadInst>(U)) { |
| // Ignore non-volatile loads, they are always ok. |
| if (LI->isVolatile()) return false; |
| continue; |
| } |
| |
| if (BitCastInst *BCI = dyn_cast<BitCastInst>(U)) { |
| // If uses of the bitcast are ok, we are ok. |
| if (!isOnlyCopiedFromConstantGlobal(BCI, TheCopy, isOffset, |
| LifetimeMarkers)) |
| return false; |
| continue; |
| } |
| if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) { |
| // If the GEP has all zero indices, it doesn't offset the pointer. If it |
| // doesn't, it does. |
| if (!isOnlyCopiedFromConstantGlobal(GEP, TheCopy, |
| isOffset || !GEP->hasAllZeroIndices(), |
| LifetimeMarkers)) |
| return false; |
| continue; |
| } |
| |
| if (CallSite CS = U) { |
| // If this is the function being called then we treat it like a load and |
| // ignore it. |
| if (CS.isCallee(UI)) |
| continue; |
| |
| // If this is a readonly/readnone call site, then we know it is just a |
| // load (but one that potentially returns the value itself), so we can |
| // ignore it if we know that the value isn't captured. |
| unsigned ArgNo = CS.getArgumentNo(UI); |
| if (CS.onlyReadsMemory() && |
| (CS.getInstruction()->use_empty() || |
| CS.paramHasAttr(ArgNo+1, Attribute::NoCapture))) |
| continue; |
| |
| // If this is being passed as a byval argument, the caller is making a |
| // copy, so it is only a read of the alloca. |
| if (CS.paramHasAttr(ArgNo+1, Attribute::ByVal)) |
| continue; |
| } |
| |
| // Lifetime intrinsics can be handled by the caller. |
| if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(U)) { |
| if (II->getIntrinsicID() == Intrinsic::lifetime_start || |
| II->getIntrinsicID() == Intrinsic::lifetime_end) { |
| assert(II->use_empty() && "Lifetime markers have no result to use!"); |
| LifetimeMarkers.push_back(II); |
| continue; |
| } |
| } |
| |
| // If this is isn't our memcpy/memmove, reject it as something we can't |
| // handle. |
| MemTransferInst *MI = dyn_cast<MemTransferInst>(U); |
| if (MI == 0) |
| return false; |
| |
| // If the transfer is using the alloca as a source of the transfer, then |
| // ignore it since it is a load (unless the transfer is volatile). |
| if (UI.getOperandNo() == 1) { |
| if (MI->isVolatile()) return false; |
| continue; |
| } |
| |
| // If we already have seen a copy, reject the second one. |
| if (TheCopy) return false; |
| |
| // If the pointer has been offset from the start of the alloca, we can't |
| // safely handle this. |
| if (isOffset) return false; |
| |
| // If the memintrinsic isn't using the alloca as the dest, reject it. |
| if (UI.getOperandNo() != 0) return false; |
| |
| // If the source of the memcpy/move is not a constant global, reject it. |
| if (!PointsToConstantGlobal(MI->getSource())) |
| return false; |
| |
| // Otherwise, the transform is safe. Remember the copy instruction. |
| TheCopy = MI; |
| } |
| return true; |
| } |
| |
| /// isOnlyCopiedFromConstantGlobal - Return true if the specified alloca is only |
| /// modified by a copy from a constant global. If we can prove this, we can |
| /// replace any uses of the alloca with uses of the global directly. |
| MemTransferInst * |
| SROA::isOnlyCopiedFromConstantGlobal(AllocaInst *AI, |
| SmallVector<Instruction*, 4> &ToDelete) { |
| MemTransferInst *TheCopy = 0; |
| if (::isOnlyCopiedFromConstantGlobal(AI, TheCopy, false, ToDelete)) |
| return TheCopy; |
| return 0; |
| } |