ScalarReplAggregates.cpp revision 221345
1177633Sdfr//===- ScalarReplAggregates.cpp - Scalar Replacement of Aggregates --------===// 2177633Sdfr// 3177633Sdfr// The LLVM Compiler Infrastructure 4177633Sdfr// 5177633Sdfr// This file is distributed under the University of Illinois Open Source 6177633Sdfr// License. See LICENSE.TXT for details. 7177633Sdfr// 8177633Sdfr//===----------------------------------------------------------------------===// 9177633Sdfr// 10177633Sdfr// This transformation implements the well known scalar replacement of 11177633Sdfr// aggregates transformation. This xform breaks up alloca instructions of 12177633Sdfr// aggregate type (structure or array) into individual alloca instructions for 13177633Sdfr// each member (if possible). Then, if possible, it transforms the individual 14177633Sdfr// alloca instructions into nice clean scalar SSA form. 15177633Sdfr// 16177633Sdfr// This combines a simple SRoA algorithm with the Mem2Reg algorithm because 17177633Sdfr// often interact, especially for C++ programs. As such, iterating between 18177633Sdfr// SRoA, then Mem2Reg until we run out of things to promote works well. 19177633Sdfr// 20177633Sdfr//===----------------------------------------------------------------------===// 21177633Sdfr 22177633Sdfr#define DEBUG_TYPE "scalarrepl" 23177633Sdfr#include "llvm/Transforms/Scalar.h" 24177633Sdfr#include "llvm/Constants.h" 25177633Sdfr#include "llvm/DerivedTypes.h" 26177633Sdfr#include "llvm/Function.h" 27177633Sdfr#include "llvm/GlobalVariable.h" 28177633Sdfr#include "llvm/Instructions.h" 29177633Sdfr#include "llvm/IntrinsicInst.h" 30177633Sdfr#include "llvm/LLVMContext.h" 31177633Sdfr#include "llvm/Module.h" 32177633Sdfr#include "llvm/Pass.h" 33184588Sdfr#include "llvm/Analysis/Dominators.h" 34180025Sdfr#include "llvm/Analysis/Loads.h" 35177633Sdfr#include "llvm/Analysis/ValueTracking.h" 36177633Sdfr#include "llvm/Target/TargetData.h" 37177633Sdfr#include "llvm/Transforms/Utils/PromoteMemToReg.h" 38177633Sdfr#include "llvm/Transforms/Utils/Local.h" 39177633Sdfr#include "llvm/Transforms/Utils/SSAUpdater.h" 40177633Sdfr#include "llvm/Support/CallSite.h" 41177633Sdfr#include "llvm/Support/Debug.h" 42177633Sdfr#include "llvm/Support/ErrorHandling.h" 43177633Sdfr#include "llvm/Support/GetElementPtrTypeIterator.h" 44177633Sdfr#include "llvm/Support/IRBuilder.h" 45177633Sdfr#include "llvm/Support/MathExtras.h" 46177633Sdfr#include "llvm/Support/raw_ostream.h" 47177685Sdfr#include "llvm/ADT/SetVector.h" 48244008Srmacklem#include "llvm/ADT/SmallVector.h" 49177633Sdfr#include "llvm/ADT/Statistic.h" 50180025Sdfrusing namespace llvm; 51184588Sdfr 52177633SdfrSTATISTIC(NumReplaced, "Number of allocas broken up"); 53177633SdfrSTATISTIC(NumPromoted, "Number of allocas promoted"); 54177633SdfrSTATISTIC(NumAdjusted, "Number of scalar allocas adjusted to allow promotion"); 55177633SdfrSTATISTIC(NumConverted, "Number of aggregates converted to scalar"); 56184588SdfrSTATISTIC(NumGlobals, "Number of allocas copied from constant global"); 57177633Sdfr 58177633Sdfrnamespace { 59177633Sdfr struct SROA : public FunctionPass { 60177633Sdfr SROA(int T, bool hasDT, char &ID) 61177633Sdfr : FunctionPass(ID), HasDomTree(hasDT) { 62177633Sdfr if (T == -1) 63177633Sdfr SRThreshold = 128; 64184588Sdfr else 65177633Sdfr SRThreshold = T; 66177633Sdfr } 67177633Sdfr 68177633Sdfr bool runOnFunction(Function &F); 69184588Sdfr 70184588Sdfr bool performScalarRepl(Function &F); 71177633Sdfr bool performPromotion(Function &F); 72177633Sdfr 73177633Sdfr private: 74177633Sdfr bool HasDomTree; 75177633Sdfr TargetData *TD; 76177633Sdfr 77177633Sdfr /// DeadInsts - Keep track of instructions we have made dead, so that 78177633Sdfr /// we can remove them after we are done working. 79177633Sdfr SmallVector<Value*, 32> DeadInsts; 80177633Sdfr 81177633Sdfr /// AllocaInfo - When analyzing uses of an alloca instruction, this captures 82177633Sdfr /// information about the uses. All these fields are initialized to false 83177633Sdfr /// and set to true when something is learned. 84177633Sdfr struct AllocaInfo { 85177633Sdfr /// The alloca to promote. 86177633Sdfr AllocaInst *AI; 87177633Sdfr 88177633Sdfr /// CheckedPHIs - This is a set of verified PHI nodes, to prevent infinite 89177633Sdfr /// looping and avoid redundant work. 90180025Sdfr SmallPtrSet<PHINode*, 8> CheckedPHIs; 91177633Sdfr 92177633Sdfr /// isUnsafe - This is set to true if the alloca cannot be SROA'd. 93177633Sdfr bool isUnsafe : 1; 94177633Sdfr 95177633Sdfr /// isMemCpySrc - This is true if this aggregate is memcpy'd from. 96177633Sdfr bool isMemCpySrc : 1; 97177633Sdfr 98177633Sdfr /// isMemCpyDst - This is true if this aggregate is memcpy'd into. 99180025Sdfr bool isMemCpyDst : 1; 100177633Sdfr 101180025Sdfr /// hasSubelementAccess - This is true if a subelement of the alloca is 102184588Sdfr /// ever accessed, or false if the alloca is only accessed with mem 103177633Sdfr /// intrinsics or load/store that only access the entire alloca at once. 104177633Sdfr bool hasSubelementAccess : 1; 105180025Sdfr 106184588Sdfr /// hasALoadOrStore - This is true if there are any loads or stores to it. 107184588Sdfr /// The alloca may just be accessed with memcpy, for example, which would 108177633Sdfr /// not set this. 109177633Sdfr bool hasALoadOrStore : 1; 110180025Sdfr 111177633Sdfr explicit AllocaInfo(AllocaInst *ai) 112177633Sdfr : AI(ai), isUnsafe(false), isMemCpySrc(false), isMemCpyDst(false), 113177633Sdfr hasSubelementAccess(false), hasALoadOrStore(false) {} 114177633Sdfr }; 115177633Sdfr 116177633Sdfr unsigned SRThreshold; 117177633Sdfr 118177633Sdfr void MarkUnsafe(AllocaInfo &I, Instruction *User) { 119177633Sdfr I.isUnsafe = true; 120177633Sdfr DEBUG(dbgs() << " Transformation preventing inst: " << *User << '\n'); 121177633Sdfr } 122184588Sdfr 123177633Sdfr bool isSafeAllocaToScalarRepl(AllocaInst *AI); 124177633Sdfr 125180025Sdfr void isSafeForScalarRepl(Instruction *I, uint64_t Offset, AllocaInfo &Info); 126180025Sdfr void isSafePHISelectUseForScalarRepl(Instruction *User, uint64_t Offset, 127177633Sdfr AllocaInfo &Info); 128184588Sdfr void isSafeGEP(GetElementPtrInst *GEPI, uint64_t &Offset, AllocaInfo &Info); 129194934Srmacklem void isSafeMemAccess(uint64_t Offset, uint64_t MemSize, 130177633Sdfr const Type *MemOpType, bool isStore, AllocaInfo &Info, 131180025Sdfr Instruction *TheAccess, bool AllowWholeAccess); 132194934Srmacklem bool TypeHasComponent(const Type *T, uint64_t Offset, uint64_t Size); 133194934Srmacklem uint64_t FindElementAndOffset(const Type *&T, uint64_t &Offset, 134194934Srmacklem const Type *&IdxTy); 135194934Srmacklem 136194934Srmacklem void DoScalarReplacement(AllocaInst *AI, 137194934Srmacklem std::vector<AllocaInst*> &WorkList); 138194934Srmacklem void DeleteDeadInstructions(); 139194934Srmacklem 140184588Sdfr void RewriteForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset, 141184588Sdfr SmallVector<AllocaInst*, 32> &NewElts); 142184588Sdfr void RewriteBitCast(BitCastInst *BC, AllocaInst *AI, uint64_t Offset, 143184588Sdfr SmallVector<AllocaInst*, 32> &NewElts); 144194934Srmacklem void RewriteGEP(GetElementPtrInst *GEPI, AllocaInst *AI, uint64_t Offset, 145180025Sdfr SmallVector<AllocaInst*, 32> &NewElts); 146180025Sdfr void RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *Inst, 147180025Sdfr AllocaInst *AI, 148194934Srmacklem SmallVector<AllocaInst*, 32> &NewElts); 149194934Srmacklem void RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocaInst *AI, 150194934Srmacklem SmallVector<AllocaInst*, 32> &NewElts); 151194934Srmacklem void RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocaInst *AI, 152194934Srmacklem SmallVector<AllocaInst*, 32> &NewElts); 153194934Srmacklem 154194934Srmacklem static MemTransferInst *isOnlyCopiedFromConstantGlobal(AllocaInst *AI); 155194934Srmacklem }; 156180025Sdfr 157180025Sdfr // SROA_DT - SROA that uses DominatorTree. 158196503Szec struct SROA_DT : public SROA { 159196503Szec static char ID; 160177633Sdfr public: 161177633Sdfr SROA_DT(int T = -1) : SROA(T, true, ID) { 162180025Sdfr initializeSROA_DTPass(*PassRegistry::getPassRegistry()); 163177633Sdfr } 164196503Szec 165180025Sdfr // getAnalysisUsage - This pass does not require any passes, but we know it 166177633Sdfr // will not alter the CFG, so say so. 167188142Sdfr virtual void getAnalysisUsage(AnalysisUsage &AU) const { 168184588Sdfr AU.addRequired<DominatorTree>(); 169184588Sdfr AU.setPreservesCFG(); 170177633Sdfr } 171177633Sdfr }; 172194934Srmacklem 173177633Sdfr // SROA_SSAUp - SROA that uses SSAUpdater. 174177633Sdfr struct SROA_SSAUp : public SROA { 175177633Sdfr static char ID; 176194934Srmacklem public: 177177633Sdfr SROA_SSAUp(int T = -1) : SROA(T, false, ID) { 178221127Srmacklem initializeSROA_SSAUpPass(*PassRegistry::getPassRegistry()); 179184588Sdfr } 180177633Sdfr 181194934Srmacklem // getAnalysisUsage - This pass does not require any passes, but we know it 182184588Sdfr // will not alter the CFG, so say so. 183184588Sdfr virtual void getAnalysisUsage(AnalysisUsage &AU) const { 184180025Sdfr AU.setPreservesCFG(); 185180025Sdfr } 186180025Sdfr }; 187178112Sdfr 188194934Srmacklem} 189194934Srmacklem 190194934Srmacklemchar SROA_DT::ID = 0; 191194934Srmacklemchar SROA_SSAUp::ID = 0; 192194934Srmacklem 193194934SrmacklemINITIALIZE_PASS_BEGIN(SROA_DT, "scalarrepl", 194244008Srmacklem "Scalar Replacement of Aggregates (DT)", false, false) 195244008SrmacklemINITIALIZE_PASS_DEPENDENCY(DominatorTree) 196180025SdfrINITIALIZE_PASS_END(SROA_DT, "scalarrepl", 197177633Sdfr "Scalar Replacement of Aggregates (DT)", false, false) 198180025Sdfr 199180025SdfrINITIALIZE_PASS_BEGIN(SROA_SSAUp, "scalarrepl-ssa", 200194934Srmacklem "Scalar Replacement of Aggregates (SSAUp)", false, false) 201194934SrmacklemINITIALIZE_PASS_END(SROA_SSAUp, "scalarrepl-ssa", 202194934Srmacklem "Scalar Replacement of Aggregates (SSAUp)", false, false) 203194934Srmacklem 204184588Sdfr// Public interface to the ScalarReplAggregates pass 205180025SdfrFunctionPass *llvm::createScalarReplAggregatesPass(int Threshold, 206180025Sdfr bool UseDomTree) { 207180025Sdfr if (UseDomTree) 208180025Sdfr return new SROA_DT(Threshold); 209194934Srmacklem return new SROA_SSAUp(Threshold); 210194934Srmacklem} 211194934Srmacklem 212194934Srmacklem 213194934Srmacklem//===----------------------------------------------------------------------===// 214194934Srmacklem// Convert To Scalar Optimization. 215194934Srmacklem//===----------------------------------------------------------------------===// 216194934Srmacklem 217194934Srmacklemnamespace { 218194934Srmacklem/// ConvertToScalarInfo - This class implements the "Convert To Scalar" 219194934Srmacklem/// optimization, which scans the uses of an alloca and determines if it can 220180025Sdfr/// rewrite it in terms of a single new alloca that can be mem2reg'd. 221177633Sdfrclass ConvertToScalarInfo { 222177633Sdfr /// AllocaSize - The size of the alloca being considered in bytes. 223177633Sdfr unsigned AllocaSize; 224177633Sdfr const TargetData &TD; 225180025Sdfr 226180025Sdfr /// IsNotTrivial - This is set to true if there is some access to the object 227177633Sdfr /// which means that mem2reg can't promote it. 228184588Sdfr bool IsNotTrivial; 229184588Sdfr 230184588Sdfr /// VectorTy - This tracks the type that we should promote the vector to if 231177633Sdfr /// it is possible to turn it into a vector. This starts out null, and if it 232177633Sdfr /// isn't possible to turn into a vector type, it gets set to VoidTy. 233180025Sdfr const Type *VectorTy; 234177633Sdfr 235194934Srmacklem /// HadAVector - True if there is at least one vector access to the alloca. 236177633Sdfr /// We don't want to turn random arrays into vectors and use vector element 237180025Sdfr /// insert/extract, but if there are element accesses to something that is 238177633Sdfr /// also declared as a vector, we do want to promote to a vector. 239194934Srmacklem bool HadAVector; 240184588Sdfr 241194934Srmacklem /// HadNonMemTransferAccess - True if there is at least one access to the 242184588Sdfr /// alloca that is not a MemTransferInst. We don't want to turn structs into 243184588Sdfr /// large integers unless there is some potential for optimization. 244184588Sdfr bool HadNonMemTransferAccess; 245178112Sdfr 246194934Srmacklempublic: 247178112Sdfr explicit ConvertToScalarInfo(unsigned Size, const TargetData &td) 248184588Sdfr : AllocaSize(Size), TD(td), IsNotTrivial(false), VectorTy(0), 249194934Srmacklem HadAVector(false), HadNonMemTransferAccess(false) { } 250248255Sjhb 251194934Srmacklem AllocaInst *TryConvert(AllocaInst *AI); 252194934Srmacklem 253184588Sdfrprivate: 254184588Sdfr bool CanConvertToScalar(Value *V, uint64_t Offset); 255184588Sdfr void MergeInType(const Type *In, uint64_t Offset, bool IsLoadOrStore); 256184588Sdfr bool MergeInVectorType(const VectorType *VInTy, uint64_t Offset); 257184588Sdfr void ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, uint64_t Offset); 258178112Sdfr 259178112Sdfr Value *ConvertScalar_ExtractValue(Value *NV, const Type *ToType, 260194934Srmacklem uint64_t Offset, IRBuilder<> &Builder); 261178112Sdfr Value *ConvertScalar_InsertValue(Value *StoredVal, Value *ExistingVal, 262177633Sdfr uint64_t Offset, IRBuilder<> &Builder); 263184588Sdfr}; 264184588Sdfr} // end anonymous namespace. 265184588Sdfr 266184588Sdfr 267184588Sdfr/// TryConvert - Analyze the specified alloca, and if it is safe to do so, 268180025Sdfr/// rewrite it to be a new alloca which is mem2reg'able. This returns the new 269180025Sdfr/// alloca if possible or null if not. 270180025SdfrAllocaInst *ConvertToScalarInfo::TryConvert(AllocaInst *AI) { 271184588Sdfr // If we can't convert this scalar, or if mem2reg can trivially do it, bail 272184588Sdfr // out. 273177633Sdfr if (!CanConvertToScalar(AI, 0) || !IsNotTrivial) 274184588Sdfr return 0; 275184588Sdfr 276184588Sdfr // If we were able to find a vector type that can handle this with 277184588Sdfr // insert/extract elements, and if there was at least one use that had 278184588Sdfr // a vector type, promote this to a vector. We don't want to promote 279177633Sdfr // random stuff that doesn't use vectors (e.g. <9 x double>) because then 280177633Sdfr // we just get a lot of insert/extracts. If at least one vector is 281177633Sdfr // involved, then we probably really do have a union of vector/array. 282177633Sdfr const Type *NewTy; 283177633Sdfr if (VectorTy && VectorTy->isVectorTy() && HadAVector) { 284177633Sdfr DEBUG(dbgs() << "CONVERT TO VECTOR: " << *AI << "\n TYPE = " 285177633Sdfr << *VectorTy << '\n'); 286177633Sdfr NewTy = VectorTy; // Use the vector type. 287177633Sdfr } else { 288180025Sdfr unsigned BitWidth = AllocaSize * 8; 289194934Srmacklem if (!HadAVector && !HadNonMemTransferAccess && 290177633Sdfr !TD.fitsInLegalInteger(BitWidth)) 291180025Sdfr return 0; 292177633Sdfr 293177633Sdfr DEBUG(dbgs() << "CONVERT TO SCALAR INTEGER: " << *AI << "\n"); 294184588Sdfr // Create and insert the integer alloca. 295184588Sdfr NewTy = IntegerType::get(AI->getContext(), BitWidth); 296180025Sdfr } 297194934Srmacklem AllocaInst *NewAI = new AllocaInst(NewTy, 0, "", AI->getParent()->begin()); 298194934Srmacklem ConvertUsesToScalar(AI, NewAI, 0); 299180025Sdfr return NewAI; 300194934Srmacklem} 301180025Sdfr 302180025Sdfr/// MergeInType - Add the 'In' type to the accumulated vector type (VectorTy) 303180025Sdfr/// so far at the offset specified by Offset (which is specified in bytes). 304180025Sdfr/// 305180025Sdfr/// There are three cases we handle here: 306180025Sdfr/// 1) A union of vector types of the same size and potentially its elements. 307180025Sdfr/// Here we turn element accesses into insert/extract element operations. 308180025Sdfr/// This promotes a <4 x float> with a store of float to the third element 309194934Srmacklem/// into a <4 x float> that uses insert element. 310194934Srmacklem/// 2) A union of vector types with power-of-2 size differences, e.g. a float, 311194934Srmacklem/// <2 x float> and <4 x float>. Here we turn element accesses into insert 312194934Srmacklem/// and extract element operations, and <2 x float> accesses into a cast to 313194934Srmacklem/// <2 x double>, an extract, and a cast back to <2 x float>. 314180025Sdfr/// 3) A fully general blob of memory, which we turn into some (potentially 315180025Sdfr/// large) integer type with extract and insert operations where the loads 316180025Sdfr/// and stores would mutate the memory. We mark this by setting VectorTy 317194934Srmacklem/// to VoidTy. 318194934Srmacklemvoid ConvertToScalarInfo::MergeInType(const Type *In, uint64_t Offset, 319194934Srmacklem bool IsLoadOrStore) { 320194934Srmacklem // If we already decided to turn this into a blob of integer memory, there is 321180025Sdfr // nothing to be done. 322194934Srmacklem if (VectorTy && VectorTy->isVoidTy()) 323184588Sdfr return; 324194934Srmacklem 325184588Sdfr // If this could be contributing to a vector, analyze it. 326177633Sdfr 327177633Sdfr // If the In type is a vector that is the same size as the alloca, see if it 328177633Sdfr // matches the existing VecTy. 329184588Sdfr if (const VectorType *VInTy = dyn_cast<VectorType>(In)) { 330184588Sdfr if (MergeInVectorType(VInTy, Offset)) 331184588Sdfr return; 332177633Sdfr } else if (In->isFloatTy() || In->isDoubleTy() || 333177633Sdfr (In->isIntegerTy() && In->getPrimitiveSizeInBits() >= 8 && 334177633Sdfr isPowerOf2_32(In->getPrimitiveSizeInBits()))) { 335177633Sdfr // Full width accesses can be ignored, because they can always be turned 336177633Sdfr // into bitcasts. 337177633Sdfr unsigned EltSize = In->getPrimitiveSizeInBits()/8; 338177633Sdfr if (IsLoadOrStore && EltSize == AllocaSize) 339177633Sdfr return; 340184588Sdfr 341177633Sdfr // If we're accessing something that could be an element of a vector, see 342177633Sdfr // if the implied vector agrees with what we already have and if Offset is 343194934Srmacklem // compatible with it. 344194934Srmacklem if (Offset % EltSize == 0 && AllocaSize % EltSize == 0) { 345194934Srmacklem if (!VectorTy) { 346194934Srmacklem VectorTy = VectorType::get(In, AllocaSize/EltSize); 347177633Sdfr return; 348177633Sdfr } 349177633Sdfr 350177633Sdfr unsigned CurrentEltSize = cast<VectorType>(VectorTy)->getElementType() 351177633Sdfr ->getPrimitiveSizeInBits()/8; 352177633Sdfr if (EltSize == CurrentEltSize) 353177633Sdfr return; 354177633Sdfr 355177633Sdfr if (In->isIntegerTy() && isPowerOf2_32(AllocaSize / EltSize)) 356177633Sdfr return; 357177633Sdfr } 358177633Sdfr } 359177633Sdfr 360177633Sdfr // Otherwise, we have a case that we can't handle with an optimized vector 361194934Srmacklem // form. We can still turn this into a large integer. 362194934Srmacklem VectorTy = Type::getVoidTy(In->getContext()); 363194934Srmacklem} 364194934Srmacklem 365177633Sdfr/// MergeInVectorType - Handles the vector case of MergeInType, returning true 366177633Sdfr/// if the type was successfully merged and false otherwise. 367177633Sdfrbool ConvertToScalarInfo::MergeInVectorType(const VectorType *VInTy, 368177633Sdfr uint64_t Offset) { 369244008Srmacklem // Remember if we saw a vector type. 370177633Sdfr HadAVector = true; 371177633Sdfr 372177633Sdfr // TODO: Support nonzero offsets? 373177633Sdfr if (Offset != 0) 374177633Sdfr return false; 375177633Sdfr 376177633Sdfr // Only allow vectors that are a power-of-2 away from the size of the alloca. 377177633Sdfr if (!isPowerOf2_64(AllocaSize / (VInTy->getBitWidth() / 8))) 378177633Sdfr return false; 379177633Sdfr 380177633Sdfr // If this the first vector we see, remember the type so that we know the 381177633Sdfr // element size. 382177633Sdfr if (!VectorTy) { 383177633Sdfr VectorTy = VInTy; 384177633Sdfr return true; 385177633Sdfr } 386177633Sdfr 387177633Sdfr unsigned BitWidth = cast<VectorType>(VectorTy)->getBitWidth(); 388177633Sdfr unsigned InBitWidth = VInTy->getBitWidth(); 389177633Sdfr 390177633Sdfr // Vectors of the same size can be converted using a simple bitcast. 391177633Sdfr if (InBitWidth == BitWidth && AllocaSize == (InBitWidth / 8)) 392177633Sdfr return true; 393177633Sdfr 394177633Sdfr const Type *ElementTy = cast<VectorType>(VectorTy)->getElementType(); 395177633Sdfr const Type *InElementTy = cast<VectorType>(VInTy)->getElementType(); 396177633Sdfr 397177633Sdfr // Do not allow mixed integer and floating-point accesses from vectors of 398177633Sdfr // different sizes. 399177633Sdfr if (ElementTy->isFloatingPointTy() != InElementTy->isFloatingPointTy()) 400177633Sdfr return false; 401177633Sdfr 402177633Sdfr if (ElementTy->isFloatingPointTy()) { 403177633Sdfr // Only allow floating-point vectors of different sizes if they have the 404177633Sdfr // same element type. 405177633Sdfr // TODO: This could be loosened a bit, but would anything benefit? 406177633Sdfr if (ElementTy != InElementTy) 407177633Sdfr return false; 408177633Sdfr 409177633Sdfr // There are no arbitrary-precision floating-point types, which limits the 410177633Sdfr // number of legal vector types with larger element types that we can form 411177633Sdfr // to bitcast and extract a subvector. 412177633Sdfr // TODO: We could support some more cases with mixed fp128 and double here. 413177633Sdfr if (!(BitWidth == 64 || BitWidth == 128) || 414177633Sdfr !(InBitWidth == 64 || InBitWidth == 128)) 415177633Sdfr return false; 416184588Sdfr } else { 417177633Sdfr assert(ElementTy->isIntegerTy() && "Vector elements must be either integer " 418177633Sdfr "or floating-point."); 419177633Sdfr unsigned BitWidth = ElementTy->getPrimitiveSizeInBits(); 420177633Sdfr unsigned InBitWidth = InElementTy->getPrimitiveSizeInBits(); 421177633Sdfr 422177633Sdfr // Do not allow integer types smaller than a byte or types whose widths are 423177633Sdfr // not a multiple of a byte. 424177633Sdfr if (BitWidth < 8 || InBitWidth < 8 || 425177633Sdfr BitWidth % 8 != 0 || InBitWidth % 8 != 0) 426177633Sdfr return false; 427177633Sdfr } 428177633Sdfr 429177633Sdfr // Pick the largest of the two vector types. 430177633Sdfr if (InBitWidth > BitWidth) 431177633Sdfr VectorTy = VInTy; 432177633Sdfr 433177633Sdfr return true; 434177633Sdfr} 435180025Sdfr 436180025Sdfr/// CanConvertToScalar - V is a pointer. If we can convert the pointee and all 437180025Sdfr/// its accesses to a single vector type, return true and set VecTy to 438180025Sdfr/// the new type. If we could convert the alloca into a single promotable 439180025Sdfr/// integer, return true but set VecTy to VoidTy. Further, if the use is not a 440180025Sdfr/// completely trivial use that mem2reg could promote, set IsNotTrivial. Offset 441180025Sdfr/// is the current offset from the base of the alloca being analyzed. 442180025Sdfr/// 443184588Sdfr/// If we see at least one access to the value that is as a vector type, set the 444184588Sdfr/// SawVec flag. 445184588Sdfrbool ConvertToScalarInfo::CanConvertToScalar(Value *V, uint64_t Offset) { 446184588Sdfr for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) { 447184588Sdfr Instruction *User = cast<Instruction>(*UI); 448184588Sdfr 449184588Sdfr if (LoadInst *LI = dyn_cast<LoadInst>(User)) { 450184588Sdfr // Don't break volatile loads. 451244008Srmacklem if (LI->isVolatile()) 452244008Srmacklem return false; 453244008Srmacklem // Don't touch MMX operations. 454244008Srmacklem if (LI->getType()->isX86_MMXTy()) 455244008Srmacklem return false; 456244008Srmacklem HadNonMemTransferAccess = true; 457244008Srmacklem MergeInType(LI->getType(), Offset, true); 458177633Sdfr continue; 459177633Sdfr } 460177633Sdfr 461177633Sdfr if (StoreInst *SI = dyn_cast<StoreInst>(User)) { 462177633Sdfr // Storing the pointer, not into the value? 463177633Sdfr if (SI->getOperand(0) == V || SI->isVolatile()) return false; 464177633Sdfr // Don't touch MMX operations. 465177633Sdfr if (SI->getOperand(0)->getType()->isX86_MMXTy()) 466184588Sdfr return false; 467184588Sdfr HadNonMemTransferAccess = true; 468184588Sdfr MergeInType(SI->getOperand(0)->getType(), Offset, true); 469184588Sdfr continue; 470184588Sdfr } 471184588Sdfr 472184588Sdfr if (BitCastInst *BCI = dyn_cast<BitCastInst>(User)) { 473184588Sdfr IsNotTrivial = true; // Can't be mem2reg'd. 474184588Sdfr if (!CanConvertToScalar(BCI, Offset)) 475184588Sdfr return false; 476184588Sdfr continue; 477184588Sdfr } 478184588Sdfr 479184588Sdfr if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) { 480184588Sdfr // If this is a GEP with a variable indices, we can't handle it. 481184588Sdfr if (!GEP->hasAllConstantIndices()) 482184588Sdfr return false; 483184588Sdfr 484184588Sdfr // Compute the offset that this GEP adds to the pointer. 485184588Sdfr SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end()); 486184588Sdfr uint64_t GEPOffset = TD.getIndexedOffset(GEP->getPointerOperandType(), 487184588Sdfr &Indices[0], Indices.size()); 488184588Sdfr // See if all uses can be converted. 489184588Sdfr if (!CanConvertToScalar(GEP, Offset+GEPOffset)) 490184588Sdfr return false; 491177633Sdfr IsNotTrivial = true; // Can't be mem2reg'd. 492177633Sdfr HadNonMemTransferAccess = true; 493177633Sdfr continue; 494244008Srmacklem } 495177633Sdfr 496177633Sdfr // If this is a constant sized memset of a constant value (e.g. 0) we can 497177633Sdfr // handle it. 498244008Srmacklem if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) { 499244008Srmacklem // Store of constant value and constant size. 500244008Srmacklem if (!isa<ConstantInt>(MSI->getValue()) || 501244008Srmacklem !isa<ConstantInt>(MSI->getLength())) 502244008Srmacklem return false; 503184588Sdfr IsNotTrivial = true; // Can't be mem2reg'd. 504181684Sdfr HadNonMemTransferAccess = true; 505177633Sdfr continue; 506177633Sdfr } 507177633Sdfr 508 // If this is a memcpy or memmove into or out of the whole allocation, we 509 // can handle it like a load or store of the scalar type. 510 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) { 511 ConstantInt *Len = dyn_cast<ConstantInt>(MTI->getLength()); 512 if (Len == 0 || Len->getZExtValue() != AllocaSize || Offset != 0) 513 return false; 514 515 IsNotTrivial = true; // Can't be mem2reg'd. 516 continue; 517 } 518 519 // Otherwise, we cannot handle this! 520 return false; 521 } 522 523 return true; 524} 525 526/// ConvertUsesToScalar - Convert all of the users of Ptr to use the new alloca 527/// directly. This happens when we are converting an "integer union" to a 528/// single integer scalar, or when we are converting a "vector union" to a 529/// vector with insert/extractelement instructions. 530/// 531/// Offset is an offset from the original alloca, in bits that need to be 532/// shifted to the right. By the end of this, there should be no uses of Ptr. 533void ConvertToScalarInfo::ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, 534 uint64_t Offset) { 535 while (!Ptr->use_empty()) { 536 Instruction *User = cast<Instruction>(Ptr->use_back()); 537 538 if (BitCastInst *CI = dyn_cast<BitCastInst>(User)) { 539 ConvertUsesToScalar(CI, NewAI, Offset); 540 CI->eraseFromParent(); 541 continue; 542 } 543 544 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) { 545 // Compute the offset that this GEP adds to the pointer. 546 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end()); 547 uint64_t GEPOffset = TD.getIndexedOffset(GEP->getPointerOperandType(), 548 &Indices[0], Indices.size()); 549 ConvertUsesToScalar(GEP, NewAI, Offset+GEPOffset*8); 550 GEP->eraseFromParent(); 551 continue; 552 } 553 554 IRBuilder<> Builder(User); 555 556 if (LoadInst *LI = dyn_cast<LoadInst>(User)) { 557 // The load is a bit extract from NewAI shifted right by Offset bits. 558 Value *LoadedVal = Builder.CreateLoad(NewAI, "tmp"); 559 Value *NewLoadVal 560 = ConvertScalar_ExtractValue(LoadedVal, LI->getType(), Offset, Builder); 561 LI->replaceAllUsesWith(NewLoadVal); 562 LI->eraseFromParent(); 563 continue; 564 } 565 566 if (StoreInst *SI = dyn_cast<StoreInst>(User)) { 567 assert(SI->getOperand(0) != Ptr && "Consistency error!"); 568 Instruction *Old = Builder.CreateLoad(NewAI, NewAI->getName()+".in"); 569 Value *New = ConvertScalar_InsertValue(SI->getOperand(0), Old, Offset, 570 Builder); 571 Builder.CreateStore(New, NewAI); 572 SI->eraseFromParent(); 573 574 // If the load we just inserted is now dead, then the inserted store 575 // overwrote the entire thing. 576 if (Old->use_empty()) 577 Old->eraseFromParent(); 578 continue; 579 } 580 581 // If this is a constant sized memset of a constant value (e.g. 0) we can 582 // transform it into a store of the expanded constant value. 583 if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) { 584 assert(MSI->getRawDest() == Ptr && "Consistency error!"); 585 unsigned NumBytes = cast<ConstantInt>(MSI->getLength())->getZExtValue(); 586 if (NumBytes != 0) { 587 unsigned Val = cast<ConstantInt>(MSI->getValue())->getZExtValue(); 588 589 // Compute the value replicated the right number of times. 590 APInt APVal(NumBytes*8, Val); 591 592 // Splat the value if non-zero. 593 if (Val) 594 for (unsigned i = 1; i != NumBytes; ++i) 595 APVal |= APVal << 8; 596 597 Instruction *Old = Builder.CreateLoad(NewAI, NewAI->getName()+".in"); 598 Value *New = ConvertScalar_InsertValue( 599 ConstantInt::get(User->getContext(), APVal), 600 Old, Offset, Builder); 601 Builder.CreateStore(New, NewAI); 602 603 // If the load we just inserted is now dead, then the memset overwrote 604 // the entire thing. 605 if (Old->use_empty()) 606 Old->eraseFromParent(); 607 } 608 MSI->eraseFromParent(); 609 continue; 610 } 611 612 // If this is a memcpy or memmove into or out of the whole allocation, we 613 // can handle it like a load or store of the scalar type. 614 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) { 615 assert(Offset == 0 && "must be store to start of alloca"); 616 617 // If the source and destination are both to the same alloca, then this is 618 // a noop copy-to-self, just delete it. Otherwise, emit a load and store 619 // as appropriate. 620 AllocaInst *OrigAI = cast<AllocaInst>(GetUnderlyingObject(Ptr, &TD, 0)); 621 622 if (GetUnderlyingObject(MTI->getSource(), &TD, 0) != OrigAI) { 623 // Dest must be OrigAI, change this to be a load from the original 624 // pointer (bitcasted), then a store to our new alloca. 625 assert(MTI->getRawDest() == Ptr && "Neither use is of pointer?"); 626 Value *SrcPtr = MTI->getSource(); 627 const PointerType* SPTy = cast<PointerType>(SrcPtr->getType()); 628 const PointerType* AIPTy = cast<PointerType>(NewAI->getType()); 629 if (SPTy->getAddressSpace() != AIPTy->getAddressSpace()) { 630 AIPTy = PointerType::get(AIPTy->getElementType(), 631 SPTy->getAddressSpace()); 632 } 633 SrcPtr = Builder.CreateBitCast(SrcPtr, AIPTy); 634 635 LoadInst *SrcVal = Builder.CreateLoad(SrcPtr, "srcval"); 636 SrcVal->setAlignment(MTI->getAlignment()); 637 Builder.CreateStore(SrcVal, NewAI); 638 } else if (GetUnderlyingObject(MTI->getDest(), &TD, 0) != OrigAI) { 639 // Src must be OrigAI, change this to be a load from NewAI then a store 640 // through the original dest pointer (bitcasted). 641 assert(MTI->getRawSource() == Ptr && "Neither use is of pointer?"); 642 LoadInst *SrcVal = Builder.CreateLoad(NewAI, "srcval"); 643 644 const PointerType* DPTy = cast<PointerType>(MTI->getDest()->getType()); 645 const PointerType* AIPTy = cast<PointerType>(NewAI->getType()); 646 if (DPTy->getAddressSpace() != AIPTy->getAddressSpace()) { 647 AIPTy = PointerType::get(AIPTy->getElementType(), 648 DPTy->getAddressSpace()); 649 } 650 Value *DstPtr = Builder.CreateBitCast(MTI->getDest(), AIPTy); 651 652 StoreInst *NewStore = Builder.CreateStore(SrcVal, DstPtr); 653 NewStore->setAlignment(MTI->getAlignment()); 654 } else { 655 // Noop transfer. Src == Dst 656 } 657 658 MTI->eraseFromParent(); 659 continue; 660 } 661 662 llvm_unreachable("Unsupported operation!"); 663 } 664} 665 666/// getScaledElementType - Gets a scaled element type for a partial vector 667/// access of an alloca. The input types must be integer or floating-point 668/// scalar or vector types, and the resulting type is an integer, float or 669/// double. 670static const Type *getScaledElementType(const Type *Ty1, const Type *Ty2, 671 unsigned NewBitWidth) { 672 bool IsFP1 = Ty1->isFloatingPointTy() || 673 (Ty1->isVectorTy() && 674 cast<VectorType>(Ty1)->getElementType()->isFloatingPointTy()); 675 bool IsFP2 = Ty2->isFloatingPointTy() || 676 (Ty2->isVectorTy() && 677 cast<VectorType>(Ty2)->getElementType()->isFloatingPointTy()); 678 679 LLVMContext &Context = Ty1->getContext(); 680 681 // Prefer floating-point types over integer types, as integer types may have 682 // been created by earlier scalar replacement. 683 if (IsFP1 || IsFP2) { 684 if (NewBitWidth == 32) 685 return Type::getFloatTy(Context); 686 if (NewBitWidth == 64) 687 return Type::getDoubleTy(Context); 688 } 689 690 return Type::getIntNTy(Context, NewBitWidth); 691} 692 693/// CreateShuffleVectorCast - Creates a shuffle vector to convert one vector 694/// to another vector of the same element type which has the same allocation 695/// size but different primitive sizes (e.g. <3 x i32> and <4 x i32>). 696static Value *CreateShuffleVectorCast(Value *FromVal, const Type *ToType, 697 IRBuilder<> &Builder) { 698 const Type *FromType = FromVal->getType(); 699 const VectorType *FromVTy = cast<VectorType>(FromType); 700 const VectorType *ToVTy = cast<VectorType>(ToType); 701 assert((ToVTy->getElementType() == FromVTy->getElementType()) && 702 "Vectors must have the same element type"); 703 Value *UnV = UndefValue::get(FromType); 704 unsigned numEltsFrom = FromVTy->getNumElements(); 705 unsigned numEltsTo = ToVTy->getNumElements(); 706 707 SmallVector<Constant*, 3> Args; 708 const Type* Int32Ty = Builder.getInt32Ty(); 709 unsigned minNumElts = std::min(numEltsFrom, numEltsTo); 710 unsigned i; 711 for (i=0; i != minNumElts; ++i) 712 Args.push_back(ConstantInt::get(Int32Ty, i)); 713 714 if (i < numEltsTo) { 715 Constant* UnC = UndefValue::get(Int32Ty); 716 for (; i != numEltsTo; ++i) 717 Args.push_back(UnC); 718 } 719 Constant *Mask = ConstantVector::get(Args); 720 return Builder.CreateShuffleVector(FromVal, UnV, Mask, "tmpV"); 721} 722 723/// ConvertScalar_ExtractValue - Extract a value of type ToType from an integer 724/// or vector value FromVal, extracting the bits from the offset specified by 725/// Offset. This returns the value, which is of type ToType. 726/// 727/// This happens when we are converting an "integer union" to a single 728/// integer scalar, or when we are converting a "vector union" to a vector with 729/// insert/extractelement instructions. 730/// 731/// Offset is an offset from the original alloca, in bits that need to be 732/// shifted to the right. 733Value *ConvertToScalarInfo:: 734ConvertScalar_ExtractValue(Value *FromVal, const Type *ToType, 735 uint64_t Offset, IRBuilder<> &Builder) { 736 // If the load is of the whole new alloca, no conversion is needed. 737 const Type *FromType = FromVal->getType(); 738 if (FromType == ToType && Offset == 0) 739 return FromVal; 740 741 // If the result alloca is a vector type, this is either an element 742 // access or a bitcast to another vector type of the same size. 743 if (const VectorType *VTy = dyn_cast<VectorType>(FromType)) { 744 unsigned ToTypeSize = TD.getTypeAllocSize(ToType); 745 if (ToTypeSize == AllocaSize) { 746 // If the two types have the same primitive size, use a bit cast. 747 // Otherwise, it is two vectors with the same element type that has 748 // the same allocation size but different number of elements so use 749 // a shuffle vector. 750 if (FromType->getPrimitiveSizeInBits() == 751 ToType->getPrimitiveSizeInBits()) 752 return Builder.CreateBitCast(FromVal, ToType, "tmp"); 753 else 754 return CreateShuffleVectorCast(FromVal, ToType, Builder); 755 } 756 757 if (isPowerOf2_64(AllocaSize / ToTypeSize)) { 758 assert(!(ToType->isVectorTy() && Offset != 0) && "Can't extract a value " 759 "of a smaller vector type at a nonzero offset."); 760 761 const Type *CastElementTy = getScaledElementType(FromType, ToType, 762 ToTypeSize * 8); 763 unsigned NumCastVectorElements = AllocaSize / ToTypeSize; 764 765 LLVMContext &Context = FromVal->getContext(); 766 const Type *CastTy = VectorType::get(CastElementTy, 767 NumCastVectorElements); 768 Value *Cast = Builder.CreateBitCast(FromVal, CastTy, "tmp"); 769 770 unsigned EltSize = TD.getTypeAllocSizeInBits(CastElementTy); 771 unsigned Elt = Offset/EltSize; 772 assert(EltSize*Elt == Offset && "Invalid modulus in validity checking"); 773 Value *Extract = Builder.CreateExtractElement(Cast, ConstantInt::get( 774 Type::getInt32Ty(Context), Elt), "tmp"); 775 return Builder.CreateBitCast(Extract, ToType, "tmp"); 776 } 777 778 // Otherwise it must be an element access. 779 unsigned Elt = 0; 780 if (Offset) { 781 unsigned EltSize = TD.getTypeAllocSizeInBits(VTy->getElementType()); 782 Elt = Offset/EltSize; 783 assert(EltSize*Elt == Offset && "Invalid modulus in validity checking"); 784 } 785 // Return the element extracted out of it. 786 Value *V = Builder.CreateExtractElement(FromVal, ConstantInt::get( 787 Type::getInt32Ty(FromVal->getContext()), Elt), "tmp"); 788 if (V->getType() != ToType) 789 V = Builder.CreateBitCast(V, ToType, "tmp"); 790 return V; 791 } 792 793 // If ToType is a first class aggregate, extract out each of the pieces and 794 // use insertvalue's to form the FCA. 795 if (const StructType *ST = dyn_cast<StructType>(ToType)) { 796 const StructLayout &Layout = *TD.getStructLayout(ST); 797 Value *Res = UndefValue::get(ST); 798 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) { 799 Value *Elt = ConvertScalar_ExtractValue(FromVal, ST->getElementType(i), 800 Offset+Layout.getElementOffsetInBits(i), 801 Builder); 802 Res = Builder.CreateInsertValue(Res, Elt, i, "tmp"); 803 } 804 return Res; 805 } 806 807 if (const ArrayType *AT = dyn_cast<ArrayType>(ToType)) { 808 uint64_t EltSize = TD.getTypeAllocSizeInBits(AT->getElementType()); 809 Value *Res = UndefValue::get(AT); 810 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) { 811 Value *Elt = ConvertScalar_ExtractValue(FromVal, AT->getElementType(), 812 Offset+i*EltSize, Builder); 813 Res = Builder.CreateInsertValue(Res, Elt, i, "tmp"); 814 } 815 return Res; 816 } 817 818 // Otherwise, this must be a union that was converted to an integer value. 819 const IntegerType *NTy = cast<IntegerType>(FromVal->getType()); 820 821 // If this is a big-endian system and the load is narrower than the 822 // full alloca type, we need to do a shift to get the right bits. 823 int ShAmt = 0; 824 if (TD.isBigEndian()) { 825 // On big-endian machines, the lowest bit is stored at the bit offset 826 // from the pointer given by getTypeStoreSizeInBits. This matters for 827 // integers with a bitwidth that is not a multiple of 8. 828 ShAmt = TD.getTypeStoreSizeInBits(NTy) - 829 TD.getTypeStoreSizeInBits(ToType) - Offset; 830 } else { 831 ShAmt = Offset; 832 } 833 834 // Note: we support negative bitwidths (with shl) which are not defined. 835 // We do this to support (f.e.) loads off the end of a structure where 836 // only some bits are used. 837 if (ShAmt > 0 && (unsigned)ShAmt < NTy->getBitWidth()) 838 FromVal = Builder.CreateLShr(FromVal, 839 ConstantInt::get(FromVal->getType(), 840 ShAmt), "tmp"); 841 else if (ShAmt < 0 && (unsigned)-ShAmt < NTy->getBitWidth()) 842 FromVal = Builder.CreateShl(FromVal, 843 ConstantInt::get(FromVal->getType(), 844 -ShAmt), "tmp"); 845 846 // Finally, unconditionally truncate the integer to the right width. 847 unsigned LIBitWidth = TD.getTypeSizeInBits(ToType); 848 if (LIBitWidth < NTy->getBitWidth()) 849 FromVal = 850 Builder.CreateTrunc(FromVal, IntegerType::get(FromVal->getContext(), 851 LIBitWidth), "tmp"); 852 else if (LIBitWidth > NTy->getBitWidth()) 853 FromVal = 854 Builder.CreateZExt(FromVal, IntegerType::get(FromVal->getContext(), 855 LIBitWidth), "tmp"); 856 857 // If the result is an integer, this is a trunc or bitcast. 858 if (ToType->isIntegerTy()) { 859 // Should be done. 860 } else if (ToType->isFloatingPointTy() || ToType->isVectorTy()) { 861 // Just do a bitcast, we know the sizes match up. 862 FromVal = Builder.CreateBitCast(FromVal, ToType, "tmp"); 863 } else { 864 // Otherwise must be a pointer. 865 FromVal = Builder.CreateIntToPtr(FromVal, ToType, "tmp"); 866 } 867 assert(FromVal->getType() == ToType && "Didn't convert right?"); 868 return FromVal; 869} 870 871/// ConvertScalar_InsertValue - Insert the value "SV" into the existing integer 872/// or vector value "Old" at the offset specified by Offset. 873/// 874/// This happens when we are converting an "integer union" to a 875/// single integer scalar, or when we are converting a "vector union" to a 876/// vector with insert/extractelement instructions. 877/// 878/// Offset is an offset from the original alloca, in bits that need to be 879/// shifted to the right. 880Value *ConvertToScalarInfo:: 881ConvertScalar_InsertValue(Value *SV, Value *Old, 882 uint64_t Offset, IRBuilder<> &Builder) { 883 // Convert the stored type to the actual type, shift it left to insert 884 // then 'or' into place. 885 const Type *AllocaType = Old->getType(); 886 LLVMContext &Context = Old->getContext(); 887 888 if (const VectorType *VTy = dyn_cast<VectorType>(AllocaType)) { 889 uint64_t VecSize = TD.getTypeAllocSizeInBits(VTy); 890 uint64_t ValSize = TD.getTypeAllocSizeInBits(SV->getType()); 891 892 // Changing the whole vector with memset or with an access of a different 893 // vector type? 894 if (ValSize == VecSize) { 895 // If the two types have the same primitive size, use a bit cast. 896 // Otherwise, it is two vectors with the same element type that has 897 // the same allocation size but different number of elements so use 898 // a shuffle vector. 899 if (VTy->getPrimitiveSizeInBits() == 900 SV->getType()->getPrimitiveSizeInBits()) 901 return Builder.CreateBitCast(SV, AllocaType, "tmp"); 902 else 903 return CreateShuffleVectorCast(SV, VTy, Builder); 904 } 905 906 if (isPowerOf2_64(VecSize / ValSize)) { 907 assert(!(SV->getType()->isVectorTy() && Offset != 0) && "Can't insert a " 908 "value of a smaller vector type at a nonzero offset."); 909 910 const Type *CastElementTy = getScaledElementType(VTy, SV->getType(), 911 ValSize); 912 unsigned NumCastVectorElements = VecSize / ValSize; 913 914 LLVMContext &Context = SV->getContext(); 915 const Type *OldCastTy = VectorType::get(CastElementTy, 916 NumCastVectorElements); 917 Value *OldCast = Builder.CreateBitCast(Old, OldCastTy, "tmp"); 918 919 Value *SVCast = Builder.CreateBitCast(SV, CastElementTy, "tmp"); 920 921 unsigned EltSize = TD.getTypeAllocSizeInBits(CastElementTy); 922 unsigned Elt = Offset/EltSize; 923 assert(EltSize*Elt == Offset && "Invalid modulus in validity checking"); 924 Value *Insert = 925 Builder.CreateInsertElement(OldCast, SVCast, ConstantInt::get( 926 Type::getInt32Ty(Context), Elt), "tmp"); 927 return Builder.CreateBitCast(Insert, AllocaType, "tmp"); 928 } 929 930 // Must be an element insertion. 931 assert(SV->getType() == VTy->getElementType()); 932 uint64_t EltSize = TD.getTypeAllocSizeInBits(VTy->getElementType()); 933 unsigned Elt = Offset/EltSize; 934 return Builder.CreateInsertElement(Old, SV, 935 ConstantInt::get(Type::getInt32Ty(SV->getContext()), Elt), 936 "tmp"); 937 } 938 939 // If SV is a first-class aggregate value, insert each value recursively. 940 if (const StructType *ST = dyn_cast<StructType>(SV->getType())) { 941 const StructLayout &Layout = *TD.getStructLayout(ST); 942 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) { 943 Value *Elt = Builder.CreateExtractValue(SV, i, "tmp"); 944 Old = ConvertScalar_InsertValue(Elt, Old, 945 Offset+Layout.getElementOffsetInBits(i), 946 Builder); 947 } 948 return Old; 949 } 950 951 if (const ArrayType *AT = dyn_cast<ArrayType>(SV->getType())) { 952 uint64_t EltSize = TD.getTypeAllocSizeInBits(AT->getElementType()); 953 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) { 954 Value *Elt = Builder.CreateExtractValue(SV, i, "tmp"); 955 Old = ConvertScalar_InsertValue(Elt, Old, Offset+i*EltSize, Builder); 956 } 957 return Old; 958 } 959 960 // If SV is a float, convert it to the appropriate integer type. 961 // If it is a pointer, do the same. 962 unsigned SrcWidth = TD.getTypeSizeInBits(SV->getType()); 963 unsigned DestWidth = TD.getTypeSizeInBits(AllocaType); 964 unsigned SrcStoreWidth = TD.getTypeStoreSizeInBits(SV->getType()); 965 unsigned DestStoreWidth = TD.getTypeStoreSizeInBits(AllocaType); 966 if (SV->getType()->isFloatingPointTy() || SV->getType()->isVectorTy()) 967 SV = Builder.CreateBitCast(SV, 968 IntegerType::get(SV->getContext(),SrcWidth), "tmp"); 969 else if (SV->getType()->isPointerTy()) 970 SV = Builder.CreatePtrToInt(SV, TD.getIntPtrType(SV->getContext()), "tmp"); 971 972 // Zero extend or truncate the value if needed. 973 if (SV->getType() != AllocaType) { 974 if (SV->getType()->getPrimitiveSizeInBits() < 975 AllocaType->getPrimitiveSizeInBits()) 976 SV = Builder.CreateZExt(SV, AllocaType, "tmp"); 977 else { 978 // Truncation may be needed if storing more than the alloca can hold 979 // (undefined behavior). 980 SV = Builder.CreateTrunc(SV, AllocaType, "tmp"); 981 SrcWidth = DestWidth; 982 SrcStoreWidth = DestStoreWidth; 983 } 984 } 985 986 // If this is a big-endian system and the store is narrower than the 987 // full alloca type, we need to do a shift to get the right bits. 988 int ShAmt = 0; 989 if (TD.isBigEndian()) { 990 // On big-endian machines, the lowest bit is stored at the bit offset 991 // from the pointer given by getTypeStoreSizeInBits. This matters for 992 // integers with a bitwidth that is not a multiple of 8. 993 ShAmt = DestStoreWidth - SrcStoreWidth - Offset; 994 } else { 995 ShAmt = Offset; 996 } 997 998 // Note: we support negative bitwidths (with shr) which are not defined. 999 // We do this to support (f.e.) stores off the end of a structure where 1000 // only some bits in the structure are set. 1001 APInt Mask(APInt::getLowBitsSet(DestWidth, SrcWidth)); 1002 if (ShAmt > 0 && (unsigned)ShAmt < DestWidth) { 1003 SV = Builder.CreateShl(SV, ConstantInt::get(SV->getType(), 1004 ShAmt), "tmp"); 1005 Mask <<= ShAmt; 1006 } else if (ShAmt < 0 && (unsigned)-ShAmt < DestWidth) { 1007 SV = Builder.CreateLShr(SV, ConstantInt::get(SV->getType(), 1008 -ShAmt), "tmp"); 1009 Mask = Mask.lshr(-ShAmt); 1010 } 1011 1012 // Mask out the bits we are about to insert from the old value, and or 1013 // in the new bits. 1014 if (SrcWidth != DestWidth) { 1015 assert(DestWidth > SrcWidth); 1016 Old = Builder.CreateAnd(Old, ConstantInt::get(Context, ~Mask), "mask"); 1017 SV = Builder.CreateOr(Old, SV, "ins"); 1018 } 1019 return SV; 1020} 1021 1022 1023//===----------------------------------------------------------------------===// 1024// SRoA Driver 1025//===----------------------------------------------------------------------===// 1026 1027 1028bool SROA::runOnFunction(Function &F) { 1029 TD = getAnalysisIfAvailable<TargetData>(); 1030 1031 bool Changed = performPromotion(F); 1032 1033 // FIXME: ScalarRepl currently depends on TargetData more than it 1034 // theoretically needs to. It should be refactored in order to support 1035 // target-independent IR. Until this is done, just skip the actual 1036 // scalar-replacement portion of this pass. 1037 if (!TD) return Changed; 1038 1039 while (1) { 1040 bool LocalChange = performScalarRepl(F); 1041 if (!LocalChange) break; // No need to repromote if no scalarrepl 1042 Changed = true; 1043 LocalChange = performPromotion(F); 1044 if (!LocalChange) break; // No need to re-scalarrepl if no promotion 1045 } 1046 1047 return Changed; 1048} 1049 1050namespace { 1051class AllocaPromoter : public LoadAndStorePromoter { 1052 AllocaInst *AI; 1053public: 1054 AllocaPromoter(const SmallVectorImpl<Instruction*> &Insts, SSAUpdater &S) 1055 : LoadAndStorePromoter(Insts, S), AI(0) {} 1056 1057 void run(AllocaInst *AI, const SmallVectorImpl<Instruction*> &Insts) { 1058 // Remember which alloca we're promoting (for isInstInList). 1059 this->AI = AI; 1060 LoadAndStorePromoter::run(Insts); 1061 AI->eraseFromParent(); 1062 } 1063 1064 virtual bool isInstInList(Instruction *I, 1065 const SmallVectorImpl<Instruction*> &Insts) const { 1066 if (LoadInst *LI = dyn_cast<LoadInst>(I)) 1067 return LI->getOperand(0) == AI; 1068 return cast<StoreInst>(I)->getPointerOperand() == AI; 1069 } 1070}; 1071} // end anon namespace 1072 1073/// isSafeSelectToSpeculate - Select instructions that use an alloca and are 1074/// subsequently loaded can be rewritten to load both input pointers and then 1075/// select between the result, allowing the load of the alloca to be promoted. 1076/// From this: 1077/// %P2 = select i1 %cond, i32* %Alloca, i32* %Other 1078/// %V = load i32* %P2 1079/// to: 1080/// %V1 = load i32* %Alloca -> will be mem2reg'd 1081/// %V2 = load i32* %Other 1082/// %V = select i1 %cond, i32 %V1, i32 %V2 1083/// 1084/// We can do this to a select if its only uses are loads and if the operand to 1085/// the select can be loaded unconditionally. 1086static bool isSafeSelectToSpeculate(SelectInst *SI, const TargetData *TD) { 1087 bool TDerefable = SI->getTrueValue()->isDereferenceablePointer(); 1088 bool FDerefable = SI->getFalseValue()->isDereferenceablePointer(); 1089 1090 for (Value::use_iterator UI = SI->use_begin(), UE = SI->use_end(); 1091 UI != UE; ++UI) { 1092 LoadInst *LI = dyn_cast<LoadInst>(*UI); 1093 if (LI == 0 || LI->isVolatile()) return false; 1094 1095 // Both operands to the select need to be dereferencable, either absolutely 1096 // (e.g. allocas) or at this point because we can see other accesses to it. 1097 if (!TDerefable && !isSafeToLoadUnconditionally(SI->getTrueValue(), LI, 1098 LI->getAlignment(), TD)) 1099 return false; 1100 if (!FDerefable && !isSafeToLoadUnconditionally(SI->getFalseValue(), LI, 1101 LI->getAlignment(), TD)) 1102 return false; 1103 } 1104 1105 return true; 1106} 1107 1108/// isSafePHIToSpeculate - PHI instructions that use an alloca and are 1109/// subsequently loaded can be rewritten to load both input pointers in the pred 1110/// blocks and then PHI the results, allowing the load of the alloca to be 1111/// promoted. 1112/// From this: 1113/// %P2 = phi [i32* %Alloca, i32* %Other] 1114/// %V = load i32* %P2 1115/// to: 1116/// %V1 = load i32* %Alloca -> will be mem2reg'd 1117/// ... 1118/// %V2 = load i32* %Other 1119/// ... 1120/// %V = phi [i32 %V1, i32 %V2] 1121/// 1122/// We can do this to a select if its only uses are loads and if the operand to 1123/// the select can be loaded unconditionally. 1124static bool isSafePHIToSpeculate(PHINode *PN, const TargetData *TD) { 1125 // For now, we can only do this promotion if the load is in the same block as 1126 // the PHI, and if there are no stores between the phi and load. 1127 // TODO: Allow recursive phi users. 1128 // TODO: Allow stores. 1129 BasicBlock *BB = PN->getParent(); 1130 unsigned MaxAlign = 0; 1131 for (Value::use_iterator UI = PN->use_begin(), UE = PN->use_end(); 1132 UI != UE; ++UI) { 1133 LoadInst *LI = dyn_cast<LoadInst>(*UI); 1134 if (LI == 0 || LI->isVolatile()) return false; 1135 1136 // For now we only allow loads in the same block as the PHI. This is a 1137 // common case that happens when instcombine merges two loads through a PHI. 1138 if (LI->getParent() != BB) return false; 1139 1140 // Ensure that there are no instructions between the PHI and the load that 1141 // could store. 1142 for (BasicBlock::iterator BBI = PN; &*BBI != LI; ++BBI) 1143 if (BBI->mayWriteToMemory()) 1144 return false; 1145 1146 MaxAlign = std::max(MaxAlign, LI->getAlignment()); 1147 } 1148 1149 // Okay, we know that we have one or more loads in the same block as the PHI. 1150 // We can transform this if it is safe to push the loads into the predecessor 1151 // blocks. The only thing to watch out for is that we can't put a possibly 1152 // trapping load in the predecessor if it is a critical edge. 1153 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) { 1154 BasicBlock *Pred = PN->getIncomingBlock(i); 1155 1156 // If the predecessor has a single successor, then the edge isn't critical. 1157 if (Pred->getTerminator()->getNumSuccessors() == 1) 1158 continue; 1159 1160 Value *InVal = PN->getIncomingValue(i); 1161 1162 // If the InVal is an invoke in the pred, we can't put a load on the edge. 1163 if (InvokeInst *II = dyn_cast<InvokeInst>(InVal)) 1164 if (II->getParent() == Pred) 1165 return false; 1166 1167 // If this pointer is always safe to load, or if we can prove that there is 1168 // already a load in the block, then we can move the load to the pred block. 1169 if (InVal->isDereferenceablePointer() || 1170 isSafeToLoadUnconditionally(InVal, Pred->getTerminator(), MaxAlign, TD)) 1171 continue; 1172 1173 return false; 1174 } 1175 1176 return true; 1177} 1178 1179 1180/// tryToMakeAllocaBePromotable - This returns true if the alloca only has 1181/// direct (non-volatile) loads and stores to it. If the alloca is close but 1182/// not quite there, this will transform the code to allow promotion. As such, 1183/// it is a non-pure predicate. 1184static bool tryToMakeAllocaBePromotable(AllocaInst *AI, const TargetData *TD) { 1185 SetVector<Instruction*, SmallVector<Instruction*, 4>, 1186 SmallPtrSet<Instruction*, 4> > InstsToRewrite; 1187 1188 for (Value::use_iterator UI = AI->use_begin(), UE = AI->use_end(); 1189 UI != UE; ++UI) { 1190 User *U = *UI; 1191 if (LoadInst *LI = dyn_cast<LoadInst>(U)) { 1192 if (LI->isVolatile()) 1193 return false; 1194 continue; 1195 } 1196 1197 if (StoreInst *SI = dyn_cast<StoreInst>(U)) { 1198 if (SI->getOperand(0) == AI || SI->isVolatile()) 1199 return false; // Don't allow a store OF the AI, only INTO the AI. 1200 continue; 1201 } 1202 1203 if (SelectInst *SI = dyn_cast<SelectInst>(U)) { 1204 // If the condition being selected on is a constant, fold the select, yes 1205 // this does (rarely) happen early on. 1206 if (ConstantInt *CI = dyn_cast<ConstantInt>(SI->getCondition())) { 1207 Value *Result = SI->getOperand(1+CI->isZero()); 1208 SI->replaceAllUsesWith(Result); 1209 SI->eraseFromParent(); 1210 1211 // This is very rare and we just scrambled the use list of AI, start 1212 // over completely. 1213 return tryToMakeAllocaBePromotable(AI, TD); 1214 } 1215 1216 // If it is safe to turn "load (select c, AI, ptr)" into a select of two 1217 // loads, then we can transform this by rewriting the select. 1218 if (!isSafeSelectToSpeculate(SI, TD)) 1219 return false; 1220 1221 InstsToRewrite.insert(SI); 1222 continue; 1223 } 1224 1225 if (PHINode *PN = dyn_cast<PHINode>(U)) { 1226 if (PN->use_empty()) { // Dead PHIs can be stripped. 1227 InstsToRewrite.insert(PN); 1228 continue; 1229 } 1230 1231 // If it is safe to turn "load (phi [AI, ptr, ...])" into a PHI of loads 1232 // in the pred blocks, then we can transform this by rewriting the PHI. 1233 if (!isSafePHIToSpeculate(PN, TD)) 1234 return false; 1235 1236 InstsToRewrite.insert(PN); 1237 continue; 1238 } 1239 1240 return false; 1241 } 1242 1243 // If there are no instructions to rewrite, then all uses are load/stores and 1244 // we're done! 1245 if (InstsToRewrite.empty()) 1246 return true; 1247 1248 // If we have instructions that need to be rewritten for this to be promotable 1249 // take care of it now. 1250 for (unsigned i = 0, e = InstsToRewrite.size(); i != e; ++i) { 1251 if (SelectInst *SI = dyn_cast<SelectInst>(InstsToRewrite[i])) { 1252 // Selects in InstsToRewrite only have load uses. Rewrite each as two 1253 // loads with a new select. 1254 while (!SI->use_empty()) { 1255 LoadInst *LI = cast<LoadInst>(SI->use_back()); 1256 1257 IRBuilder<> Builder(LI); 1258 LoadInst *TrueLoad = 1259 Builder.CreateLoad(SI->getTrueValue(), LI->getName()+".t"); 1260 LoadInst *FalseLoad = 1261 Builder.CreateLoad(SI->getFalseValue(), LI->getName()+".t"); 1262 1263 // Transfer alignment and TBAA info if present. 1264 TrueLoad->setAlignment(LI->getAlignment()); 1265 FalseLoad->setAlignment(LI->getAlignment()); 1266 if (MDNode *Tag = LI->getMetadata(LLVMContext::MD_tbaa)) { 1267 TrueLoad->setMetadata(LLVMContext::MD_tbaa, Tag); 1268 FalseLoad->setMetadata(LLVMContext::MD_tbaa, Tag); 1269 } 1270 1271 Value *V = Builder.CreateSelect(SI->getCondition(), TrueLoad, FalseLoad); 1272 V->takeName(LI); 1273 LI->replaceAllUsesWith(V); 1274 LI->eraseFromParent(); 1275 } 1276 1277 // Now that all the loads are gone, the select is gone too. 1278 SI->eraseFromParent(); 1279 continue; 1280 } 1281 1282 // Otherwise, we have a PHI node which allows us to push the loads into the 1283 // predecessors. 1284 PHINode *PN = cast<PHINode>(InstsToRewrite[i]); 1285 if (PN->use_empty()) { 1286 PN->eraseFromParent(); 1287 continue; 1288 } 1289 1290 const Type *LoadTy = cast<PointerType>(PN->getType())->getElementType(); 1291 PHINode *NewPN = PHINode::Create(LoadTy, PN->getNumIncomingValues(), 1292 PN->getName()+".ld", PN); 1293 1294 // Get the TBAA tag and alignment to use from one of the loads. It doesn't 1295 // matter which one we get and if any differ, it doesn't matter. 1296 LoadInst *SomeLoad = cast<LoadInst>(PN->use_back()); 1297 MDNode *TBAATag = SomeLoad->getMetadata(LLVMContext::MD_tbaa); 1298 unsigned Align = SomeLoad->getAlignment(); 1299 1300 // Rewrite all loads of the PN to use the new PHI. 1301 while (!PN->use_empty()) { 1302 LoadInst *LI = cast<LoadInst>(PN->use_back()); 1303 LI->replaceAllUsesWith(NewPN); 1304 LI->eraseFromParent(); 1305 } 1306 1307 // Inject loads into all of the pred blocks. Keep track of which blocks we 1308 // insert them into in case we have multiple edges from the same block. 1309 DenseMap<BasicBlock*, LoadInst*> InsertedLoads; 1310 1311 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) { 1312 BasicBlock *Pred = PN->getIncomingBlock(i); 1313 LoadInst *&Load = InsertedLoads[Pred]; 1314 if (Load == 0) { 1315 Load = new LoadInst(PN->getIncomingValue(i), 1316 PN->getName() + "." + Pred->getName(), 1317 Pred->getTerminator()); 1318 Load->setAlignment(Align); 1319 if (TBAATag) Load->setMetadata(LLVMContext::MD_tbaa, TBAATag); 1320 } 1321 1322 NewPN->addIncoming(Load, Pred); 1323 } 1324 1325 PN->eraseFromParent(); 1326 } 1327 1328 ++NumAdjusted; 1329 return true; 1330} 1331 1332 1333bool SROA::performPromotion(Function &F) { 1334 std::vector<AllocaInst*> Allocas; 1335 DominatorTree *DT = 0; 1336 if (HasDomTree) 1337 DT = &getAnalysis<DominatorTree>(); 1338 1339 BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function 1340 1341 bool Changed = false; 1342 SmallVector<Instruction*, 64> Insts; 1343 while (1) { 1344 Allocas.clear(); 1345 1346 // Find allocas that are safe to promote, by looking at all instructions in 1347 // the entry node 1348 for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I) 1349 if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) // Is it an alloca? 1350 if (tryToMakeAllocaBePromotable(AI, TD)) 1351 Allocas.push_back(AI); 1352 1353 if (Allocas.empty()) break; 1354 1355 if (HasDomTree) 1356 PromoteMemToReg(Allocas, *DT); 1357 else { 1358 SSAUpdater SSA; 1359 for (unsigned i = 0, e = Allocas.size(); i != e; ++i) { 1360 AllocaInst *AI = Allocas[i]; 1361 1362 // Build list of instructions to promote. 1363 for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end(); 1364 UI != E; ++UI) 1365 Insts.push_back(cast<Instruction>(*UI)); 1366 1367 AllocaPromoter(Insts, SSA).run(AI, Insts); 1368 Insts.clear(); 1369 } 1370 } 1371 NumPromoted += Allocas.size(); 1372 Changed = true; 1373 } 1374 1375 return Changed; 1376} 1377 1378 1379/// ShouldAttemptScalarRepl - Decide if an alloca is a good candidate for 1380/// SROA. It must be a struct or array type with a small number of elements. 1381static bool ShouldAttemptScalarRepl(AllocaInst *AI) { 1382 const Type *T = AI->getAllocatedType(); 1383 // Do not promote any struct into more than 32 separate vars. 1384 if (const StructType *ST = dyn_cast<StructType>(T)) 1385 return ST->getNumElements() <= 32; 1386 // Arrays are much less likely to be safe for SROA; only consider 1387 // them if they are very small. 1388 if (const ArrayType *AT = dyn_cast<ArrayType>(T)) 1389 return AT->getNumElements() <= 8; 1390 return false; 1391} 1392 1393 1394// performScalarRepl - This algorithm is a simple worklist driven algorithm, 1395// which runs on all of the malloc/alloca instructions in the function, removing 1396// them if they are only used by getelementptr instructions. 1397// 1398bool SROA::performScalarRepl(Function &F) { 1399 std::vector<AllocaInst*> WorkList; 1400 1401 // Scan the entry basic block, adding allocas to the worklist. 1402 BasicBlock &BB = F.getEntryBlock(); 1403 for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I) 1404 if (AllocaInst *A = dyn_cast<AllocaInst>(I)) 1405 WorkList.push_back(A); 1406 1407 // Process the worklist 1408 bool Changed = false; 1409 while (!WorkList.empty()) { 1410 AllocaInst *AI = WorkList.back(); 1411 WorkList.pop_back(); 1412 1413 // Handle dead allocas trivially. These can be formed by SROA'ing arrays 1414 // with unused elements. 1415 if (AI->use_empty()) { 1416 AI->eraseFromParent(); 1417 Changed = true; 1418 continue; 1419 } 1420 1421 // If this alloca is impossible for us to promote, reject it early. 1422 if (AI->isArrayAllocation() || !AI->getAllocatedType()->isSized()) 1423 continue; 1424 1425 // Check to see if this allocation is only modified by a memcpy/memmove from 1426 // a constant global. If this is the case, we can change all users to use 1427 // the constant global instead. This is commonly produced by the CFE by 1428 // constructs like "void foo() { int A[] = {1,2,3,4,5,6,7,8,9...}; }" if 'A' 1429 // is only subsequently read. 1430 if (MemTransferInst *TheCopy = isOnlyCopiedFromConstantGlobal(AI)) { 1431 DEBUG(dbgs() << "Found alloca equal to global: " << *AI << '\n'); 1432 DEBUG(dbgs() << " memcpy = " << *TheCopy << '\n'); 1433 Constant *TheSrc = cast<Constant>(TheCopy->getSource()); 1434 AI->replaceAllUsesWith(ConstantExpr::getBitCast(TheSrc, AI->getType())); 1435 TheCopy->eraseFromParent(); // Don't mutate the global. 1436 AI->eraseFromParent(); 1437 ++NumGlobals; 1438 Changed = true; 1439 continue; 1440 } 1441 1442 // Check to see if we can perform the core SROA transformation. We cannot 1443 // transform the allocation instruction if it is an array allocation 1444 // (allocations OF arrays are ok though), and an allocation of a scalar 1445 // value cannot be decomposed at all. 1446 uint64_t AllocaSize = TD->getTypeAllocSize(AI->getAllocatedType()); 1447 1448 // Do not promote [0 x %struct]. 1449 if (AllocaSize == 0) continue; 1450 1451 // Do not promote any struct whose size is too big. 1452 if (AllocaSize > SRThreshold) continue; 1453 1454 // If the alloca looks like a good candidate for scalar replacement, and if 1455 // all its users can be transformed, then split up the aggregate into its 1456 // separate elements. 1457 if (ShouldAttemptScalarRepl(AI) && isSafeAllocaToScalarRepl(AI)) { 1458 DoScalarReplacement(AI, WorkList); 1459 Changed = true; 1460 continue; 1461 } 1462 1463 // If we can turn this aggregate value (potentially with casts) into a 1464 // simple scalar value that can be mem2reg'd into a register value. 1465 // IsNotTrivial tracks whether this is something that mem2reg could have 1466 // promoted itself. If so, we don't want to transform it needlessly. Note 1467 // that we can't just check based on the type: the alloca may be of an i32 1468 // but that has pointer arithmetic to set byte 3 of it or something. 1469 if (AllocaInst *NewAI = 1470 ConvertToScalarInfo((unsigned)AllocaSize, *TD).TryConvert(AI)) { 1471 NewAI->takeName(AI); 1472 AI->eraseFromParent(); 1473 ++NumConverted; 1474 Changed = true; 1475 continue; 1476 } 1477 1478 // Otherwise, couldn't process this alloca. 1479 } 1480 1481 return Changed; 1482} 1483 1484/// DoScalarReplacement - This alloca satisfied the isSafeAllocaToScalarRepl 1485/// predicate, do SROA now. 1486void SROA::DoScalarReplacement(AllocaInst *AI, 1487 std::vector<AllocaInst*> &WorkList) { 1488 DEBUG(dbgs() << "Found inst to SROA: " << *AI << '\n'); 1489 SmallVector<AllocaInst*, 32> ElementAllocas; 1490 if (const StructType *ST = dyn_cast<StructType>(AI->getAllocatedType())) { 1491 ElementAllocas.reserve(ST->getNumContainedTypes()); 1492 for (unsigned i = 0, e = ST->getNumContainedTypes(); i != e; ++i) { 1493 AllocaInst *NA = new AllocaInst(ST->getContainedType(i), 0, 1494 AI->getAlignment(), 1495 AI->getName() + "." + Twine(i), AI); 1496 ElementAllocas.push_back(NA); 1497 WorkList.push_back(NA); // Add to worklist for recursive processing 1498 } 1499 } else { 1500 const ArrayType *AT = cast<ArrayType>(AI->getAllocatedType()); 1501 ElementAllocas.reserve(AT->getNumElements()); 1502 const Type *ElTy = AT->getElementType(); 1503 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) { 1504 AllocaInst *NA = new AllocaInst(ElTy, 0, AI->getAlignment(), 1505 AI->getName() + "." + Twine(i), AI); 1506 ElementAllocas.push_back(NA); 1507 WorkList.push_back(NA); // Add to worklist for recursive processing 1508 } 1509 } 1510 1511 // Now that we have created the new alloca instructions, rewrite all the 1512 // uses of the old alloca. 1513 RewriteForScalarRepl(AI, AI, 0, ElementAllocas); 1514 1515 // Now erase any instructions that were made dead while rewriting the alloca. 1516 DeleteDeadInstructions(); 1517 AI->eraseFromParent(); 1518 1519 ++NumReplaced; 1520} 1521 1522/// DeleteDeadInstructions - Erase instructions on the DeadInstrs list, 1523/// recursively including all their operands that become trivially dead. 1524void SROA::DeleteDeadInstructions() { 1525 while (!DeadInsts.empty()) { 1526 Instruction *I = cast<Instruction>(DeadInsts.pop_back_val()); 1527 1528 for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI) 1529 if (Instruction *U = dyn_cast<Instruction>(*OI)) { 1530 // Zero out the operand and see if it becomes trivially dead. 1531 // (But, don't add allocas to the dead instruction list -- they are 1532 // already on the worklist and will be deleted separately.) 1533 *OI = 0; 1534 if (isInstructionTriviallyDead(U) && !isa<AllocaInst>(U)) 1535 DeadInsts.push_back(U); 1536 } 1537 1538 I->eraseFromParent(); 1539 } 1540} 1541 1542/// isSafeForScalarRepl - Check if instruction I is a safe use with regard to 1543/// performing scalar replacement of alloca AI. The results are flagged in 1544/// the Info parameter. Offset indicates the position within AI that is 1545/// referenced by this instruction. 1546void SROA::isSafeForScalarRepl(Instruction *I, uint64_t Offset, 1547 AllocaInfo &Info) { 1548 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E; ++UI) { 1549 Instruction *User = cast<Instruction>(*UI); 1550 1551 if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) { 1552 isSafeForScalarRepl(BC, Offset, Info); 1553 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) { 1554 uint64_t GEPOffset = Offset; 1555 isSafeGEP(GEPI, GEPOffset, Info); 1556 if (!Info.isUnsafe) 1557 isSafeForScalarRepl(GEPI, GEPOffset, Info); 1558 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) { 1559 ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength()); 1560 if (Length == 0) 1561 return MarkUnsafe(Info, User); 1562 isSafeMemAccess(Offset, Length->getZExtValue(), 0, 1563 UI.getOperandNo() == 0, Info, MI, 1564 true /*AllowWholeAccess*/); 1565 } else if (LoadInst *LI = dyn_cast<LoadInst>(User)) { 1566 if (LI->isVolatile()) 1567 return MarkUnsafe(Info, User); 1568 const Type *LIType = LI->getType(); 1569 isSafeMemAccess(Offset, TD->getTypeAllocSize(LIType), 1570 LIType, false, Info, LI, true /*AllowWholeAccess*/); 1571 Info.hasALoadOrStore = true; 1572 1573 } else if (StoreInst *SI = dyn_cast<StoreInst>(User)) { 1574 // Store is ok if storing INTO the pointer, not storing the pointer 1575 if (SI->isVolatile() || SI->getOperand(0) == I) 1576 return MarkUnsafe(Info, User); 1577 1578 const Type *SIType = SI->getOperand(0)->getType(); 1579 isSafeMemAccess(Offset, TD->getTypeAllocSize(SIType), 1580 SIType, true, Info, SI, true /*AllowWholeAccess*/); 1581 Info.hasALoadOrStore = true; 1582 } else if (isa<PHINode>(User) || isa<SelectInst>(User)) { 1583 isSafePHISelectUseForScalarRepl(User, Offset, Info); 1584 } else { 1585 return MarkUnsafe(Info, User); 1586 } 1587 if (Info.isUnsafe) return; 1588 } 1589} 1590 1591 1592/// isSafePHIUseForScalarRepl - If we see a PHI node or select using a pointer 1593/// derived from the alloca, we can often still split the alloca into elements. 1594/// This is useful if we have a large alloca where one element is phi'd 1595/// together somewhere: we can SRoA and promote all the other elements even if 1596/// we end up not being able to promote this one. 1597/// 1598/// All we require is that the uses of the PHI do not index into other parts of 1599/// the alloca. The most important use case for this is single load and stores 1600/// that are PHI'd together, which can happen due to code sinking. 1601void SROA::isSafePHISelectUseForScalarRepl(Instruction *I, uint64_t Offset, 1602 AllocaInfo &Info) { 1603 // If we've already checked this PHI, don't do it again. 1604 if (PHINode *PN = dyn_cast<PHINode>(I)) 1605 if (!Info.CheckedPHIs.insert(PN)) 1606 return; 1607 1608 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E; ++UI) { 1609 Instruction *User = cast<Instruction>(*UI); 1610 1611 if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) { 1612 isSafePHISelectUseForScalarRepl(BC, Offset, Info); 1613 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) { 1614 // Only allow "bitcast" GEPs for simplicity. We could generalize this, 1615 // but would have to prove that we're staying inside of an element being 1616 // promoted. 1617 if (!GEPI->hasAllZeroIndices()) 1618 return MarkUnsafe(Info, User); 1619 isSafePHISelectUseForScalarRepl(GEPI, Offset, Info); 1620 } else if (LoadInst *LI = dyn_cast<LoadInst>(User)) { 1621 if (LI->isVolatile()) 1622 return MarkUnsafe(Info, User); 1623 const Type *LIType = LI->getType(); 1624 isSafeMemAccess(Offset, TD->getTypeAllocSize(LIType), 1625 LIType, false, Info, LI, false /*AllowWholeAccess*/); 1626 Info.hasALoadOrStore = true; 1627 1628 } else if (StoreInst *SI = dyn_cast<StoreInst>(User)) { 1629 // Store is ok if storing INTO the pointer, not storing the pointer 1630 if (SI->isVolatile() || SI->getOperand(0) == I) 1631 return MarkUnsafe(Info, User); 1632 1633 const Type *SIType = SI->getOperand(0)->getType(); 1634 isSafeMemAccess(Offset, TD->getTypeAllocSize(SIType), 1635 SIType, true, Info, SI, false /*AllowWholeAccess*/); 1636 Info.hasALoadOrStore = true; 1637 } else if (isa<PHINode>(User) || isa<SelectInst>(User)) { 1638 isSafePHISelectUseForScalarRepl(User, Offset, Info); 1639 } else { 1640 return MarkUnsafe(Info, User); 1641 } 1642 if (Info.isUnsafe) return; 1643 } 1644} 1645 1646/// isSafeGEP - Check if a GEP instruction can be handled for scalar 1647/// replacement. It is safe when all the indices are constant, in-bounds 1648/// references, and when the resulting offset corresponds to an element within 1649/// the alloca type. The results are flagged in the Info parameter. Upon 1650/// return, Offset is adjusted as specified by the GEP indices. 1651void SROA::isSafeGEP(GetElementPtrInst *GEPI, 1652 uint64_t &Offset, AllocaInfo &Info) { 1653 gep_type_iterator GEPIt = gep_type_begin(GEPI), E = gep_type_end(GEPI); 1654 if (GEPIt == E) 1655 return; 1656 1657 // Walk through the GEP type indices, checking the types that this indexes 1658 // into. 1659 for (; GEPIt != E; ++GEPIt) { 1660 // Ignore struct elements, no extra checking needed for these. 1661 if ((*GEPIt)->isStructTy()) 1662 continue; 1663 1664 ConstantInt *IdxVal = dyn_cast<ConstantInt>(GEPIt.getOperand()); 1665 if (!IdxVal) 1666 return MarkUnsafe(Info, GEPI); 1667 } 1668 1669 // Compute the offset due to this GEP and check if the alloca has a 1670 // component element at that offset. 1671 SmallVector<Value*, 8> Indices(GEPI->op_begin() + 1, GEPI->op_end()); 1672 Offset += TD->getIndexedOffset(GEPI->getPointerOperandType(), 1673 &Indices[0], Indices.size()); 1674 if (!TypeHasComponent(Info.AI->getAllocatedType(), Offset, 0)) 1675 MarkUnsafe(Info, GEPI); 1676} 1677 1678/// isHomogeneousAggregate - Check if type T is a struct or array containing 1679/// elements of the same type (which is always true for arrays). If so, 1680/// return true with NumElts and EltTy set to the number of elements and the 1681/// element type, respectively. 1682static bool isHomogeneousAggregate(const Type *T, unsigned &NumElts, 1683 const Type *&EltTy) { 1684 if (const ArrayType *AT = dyn_cast<ArrayType>(T)) { 1685 NumElts = AT->getNumElements(); 1686 EltTy = (NumElts == 0 ? 0 : AT->getElementType()); 1687 return true; 1688 } 1689 if (const StructType *ST = dyn_cast<StructType>(T)) { 1690 NumElts = ST->getNumContainedTypes(); 1691 EltTy = (NumElts == 0 ? 0 : ST->getContainedType(0)); 1692 for (unsigned n = 1; n < NumElts; ++n) { 1693 if (ST->getContainedType(n) != EltTy) 1694 return false; 1695 } 1696 return true; 1697 } 1698 return false; 1699} 1700 1701/// isCompatibleAggregate - Check if T1 and T2 are either the same type or are 1702/// "homogeneous" aggregates with the same element type and number of elements. 1703static bool isCompatibleAggregate(const Type *T1, const Type *T2) { 1704 if (T1 == T2) 1705 return true; 1706 1707 unsigned NumElts1, NumElts2; 1708 const Type *EltTy1, *EltTy2; 1709 if (isHomogeneousAggregate(T1, NumElts1, EltTy1) && 1710 isHomogeneousAggregate(T2, NumElts2, EltTy2) && 1711 NumElts1 == NumElts2 && 1712 EltTy1 == EltTy2) 1713 return true; 1714 1715 return false; 1716} 1717 1718/// isSafeMemAccess - Check if a load/store/memcpy operates on the entire AI 1719/// alloca or has an offset and size that corresponds to a component element 1720/// within it. The offset checked here may have been formed from a GEP with a 1721/// pointer bitcasted to a different type. 1722/// 1723/// If AllowWholeAccess is true, then this allows uses of the entire alloca as a 1724/// unit. If false, it only allows accesses known to be in a single element. 1725void SROA::isSafeMemAccess(uint64_t Offset, uint64_t MemSize, 1726 const Type *MemOpType, bool isStore, 1727 AllocaInfo &Info, Instruction *TheAccess, 1728 bool AllowWholeAccess) { 1729 // Check if this is a load/store of the entire alloca. 1730 if (Offset == 0 && AllowWholeAccess && 1731 MemSize == TD->getTypeAllocSize(Info.AI->getAllocatedType())) { 1732 // This can be safe for MemIntrinsics (where MemOpType is 0) and integer 1733 // loads/stores (which are essentially the same as the MemIntrinsics with 1734 // regard to copying padding between elements). But, if an alloca is 1735 // flagged as both a source and destination of such operations, we'll need 1736 // to check later for padding between elements. 1737 if (!MemOpType || MemOpType->isIntegerTy()) { 1738 if (isStore) 1739 Info.isMemCpyDst = true; 1740 else 1741 Info.isMemCpySrc = true; 1742 return; 1743 } 1744 // This is also safe for references using a type that is compatible with 1745 // the type of the alloca, so that loads/stores can be rewritten using 1746 // insertvalue/extractvalue. 1747 if (isCompatibleAggregate(MemOpType, Info.AI->getAllocatedType())) { 1748 Info.hasSubelementAccess = true; 1749 return; 1750 } 1751 } 1752 // Check if the offset/size correspond to a component within the alloca type. 1753 const Type *T = Info.AI->getAllocatedType(); 1754 if (TypeHasComponent(T, Offset, MemSize)) { 1755 Info.hasSubelementAccess = true; 1756 return; 1757 } 1758 1759 return MarkUnsafe(Info, TheAccess); 1760} 1761 1762/// TypeHasComponent - Return true if T has a component type with the 1763/// specified offset and size. If Size is zero, do not check the size. 1764bool SROA::TypeHasComponent(const Type *T, uint64_t Offset, uint64_t Size) { 1765 const Type *EltTy; 1766 uint64_t EltSize; 1767 if (const StructType *ST = dyn_cast<StructType>(T)) { 1768 const StructLayout *Layout = TD->getStructLayout(ST); 1769 unsigned EltIdx = Layout->getElementContainingOffset(Offset); 1770 EltTy = ST->getContainedType(EltIdx); 1771 EltSize = TD->getTypeAllocSize(EltTy); 1772 Offset -= Layout->getElementOffset(EltIdx); 1773 } else if (const ArrayType *AT = dyn_cast<ArrayType>(T)) { 1774 EltTy = AT->getElementType(); 1775 EltSize = TD->getTypeAllocSize(EltTy); 1776 if (Offset >= AT->getNumElements() * EltSize) 1777 return false; 1778 Offset %= EltSize; 1779 } else { 1780 return false; 1781 } 1782 if (Offset == 0 && (Size == 0 || EltSize == Size)) 1783 return true; 1784 // Check if the component spans multiple elements. 1785 if (Offset + Size > EltSize) 1786 return false; 1787 return TypeHasComponent(EltTy, Offset, Size); 1788} 1789 1790/// RewriteForScalarRepl - Alloca AI is being split into NewElts, so rewrite 1791/// the instruction I, which references it, to use the separate elements. 1792/// Offset indicates the position within AI that is referenced by this 1793/// instruction. 1794void SROA::RewriteForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset, 1795 SmallVector<AllocaInst*, 32> &NewElts) { 1796 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E;) { 1797 Use &TheUse = UI.getUse(); 1798 Instruction *User = cast<Instruction>(*UI++); 1799 1800 if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) { 1801 RewriteBitCast(BC, AI, Offset, NewElts); 1802 continue; 1803 } 1804 1805 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) { 1806 RewriteGEP(GEPI, AI, Offset, NewElts); 1807 continue; 1808 } 1809 1810 if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) { 1811 ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength()); 1812 uint64_t MemSize = Length->getZExtValue(); 1813 if (Offset == 0 && 1814 MemSize == TD->getTypeAllocSize(AI->getAllocatedType())) 1815 RewriteMemIntrinUserOfAlloca(MI, I, AI, NewElts); 1816 // Otherwise the intrinsic can only touch a single element and the 1817 // address operand will be updated, so nothing else needs to be done. 1818 continue; 1819 } 1820 1821 if (LoadInst *LI = dyn_cast<LoadInst>(User)) { 1822 const Type *LIType = LI->getType(); 1823 1824 if (isCompatibleAggregate(LIType, AI->getAllocatedType())) { 1825 // Replace: 1826 // %res = load { i32, i32 }* %alloc 1827 // with: 1828 // %load.0 = load i32* %alloc.0 1829 // %insert.0 insertvalue { i32, i32 } zeroinitializer, i32 %load.0, 0 1830 // %load.1 = load i32* %alloc.1 1831 // %insert = insertvalue { i32, i32 } %insert.0, i32 %load.1, 1 1832 // (Also works for arrays instead of structs) 1833 Value *Insert = UndefValue::get(LIType); 1834 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { 1835 Value *Load = new LoadInst(NewElts[i], "load", LI); 1836 Insert = InsertValueInst::Create(Insert, Load, i, "insert", LI); 1837 } 1838 LI->replaceAllUsesWith(Insert); 1839 DeadInsts.push_back(LI); 1840 } else if (LIType->isIntegerTy() && 1841 TD->getTypeAllocSize(LIType) == 1842 TD->getTypeAllocSize(AI->getAllocatedType())) { 1843 // If this is a load of the entire alloca to an integer, rewrite it. 1844 RewriteLoadUserOfWholeAlloca(LI, AI, NewElts); 1845 } 1846 continue; 1847 } 1848 1849 if (StoreInst *SI = dyn_cast<StoreInst>(User)) { 1850 Value *Val = SI->getOperand(0); 1851 const Type *SIType = Val->getType(); 1852 if (isCompatibleAggregate(SIType, AI->getAllocatedType())) { 1853 // Replace: 1854 // store { i32, i32 } %val, { i32, i32 }* %alloc 1855 // with: 1856 // %val.0 = extractvalue { i32, i32 } %val, 0 1857 // store i32 %val.0, i32* %alloc.0 1858 // %val.1 = extractvalue { i32, i32 } %val, 1 1859 // store i32 %val.1, i32* %alloc.1 1860 // (Also works for arrays instead of structs) 1861 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { 1862 Value *Extract = ExtractValueInst::Create(Val, i, Val->getName(), SI); 1863 new StoreInst(Extract, NewElts[i], SI); 1864 } 1865 DeadInsts.push_back(SI); 1866 } else if (SIType->isIntegerTy() && 1867 TD->getTypeAllocSize(SIType) == 1868 TD->getTypeAllocSize(AI->getAllocatedType())) { 1869 // If this is a store of the entire alloca from an integer, rewrite it. 1870 RewriteStoreUserOfWholeAlloca(SI, AI, NewElts); 1871 } 1872 continue; 1873 } 1874 1875 if (isa<SelectInst>(User) || isa<PHINode>(User)) { 1876 // If we have a PHI user of the alloca itself (as opposed to a GEP or 1877 // bitcast) we have to rewrite it. GEP and bitcast uses will be RAUW'd to 1878 // the new pointer. 1879 if (!isa<AllocaInst>(I)) continue; 1880 1881 assert(Offset == 0 && NewElts[0] && 1882 "Direct alloca use should have a zero offset"); 1883 1884 // If we have a use of the alloca, we know the derived uses will be 1885 // utilizing just the first element of the scalarized result. Insert a 1886 // bitcast of the first alloca before the user as required. 1887 AllocaInst *NewAI = NewElts[0]; 1888 BitCastInst *BCI = new BitCastInst(NewAI, AI->getType(), "", NewAI); 1889 NewAI->moveBefore(BCI); 1890 TheUse = BCI; 1891 continue; 1892 } 1893 } 1894} 1895 1896/// RewriteBitCast - Update a bitcast reference to the alloca being replaced 1897/// and recursively continue updating all of its uses. 1898void SROA::RewriteBitCast(BitCastInst *BC, AllocaInst *AI, uint64_t Offset, 1899 SmallVector<AllocaInst*, 32> &NewElts) { 1900 RewriteForScalarRepl(BC, AI, Offset, NewElts); 1901 if (BC->getOperand(0) != AI) 1902 return; 1903 1904 // The bitcast references the original alloca. Replace its uses with 1905 // references to the first new element alloca. 1906 Instruction *Val = NewElts[0]; 1907 if (Val->getType() != BC->getDestTy()) { 1908 Val = new BitCastInst(Val, BC->getDestTy(), "", BC); 1909 Val->takeName(BC); 1910 } 1911 BC->replaceAllUsesWith(Val); 1912 DeadInsts.push_back(BC); 1913} 1914 1915/// FindElementAndOffset - Return the index of the element containing Offset 1916/// within the specified type, which must be either a struct or an array. 1917/// Sets T to the type of the element and Offset to the offset within that 1918/// element. IdxTy is set to the type of the index result to be used in a 1919/// GEP instruction. 1920uint64_t SROA::FindElementAndOffset(const Type *&T, uint64_t &Offset, 1921 const Type *&IdxTy) { 1922 uint64_t Idx = 0; 1923 if (const StructType *ST = dyn_cast<StructType>(T)) { 1924 const StructLayout *Layout = TD->getStructLayout(ST); 1925 Idx = Layout->getElementContainingOffset(Offset); 1926 T = ST->getContainedType(Idx); 1927 Offset -= Layout->getElementOffset(Idx); 1928 IdxTy = Type::getInt32Ty(T->getContext()); 1929 return Idx; 1930 } 1931 const ArrayType *AT = cast<ArrayType>(T); 1932 T = AT->getElementType(); 1933 uint64_t EltSize = TD->getTypeAllocSize(T); 1934 Idx = Offset / EltSize; 1935 Offset -= Idx * EltSize; 1936 IdxTy = Type::getInt64Ty(T->getContext()); 1937 return Idx; 1938} 1939 1940/// RewriteGEP - Check if this GEP instruction moves the pointer across 1941/// elements of the alloca that are being split apart, and if so, rewrite 1942/// the GEP to be relative to the new element. 1943void SROA::RewriteGEP(GetElementPtrInst *GEPI, AllocaInst *AI, uint64_t Offset, 1944 SmallVector<AllocaInst*, 32> &NewElts) { 1945 uint64_t OldOffset = Offset; 1946 SmallVector<Value*, 8> Indices(GEPI->op_begin() + 1, GEPI->op_end()); 1947 Offset += TD->getIndexedOffset(GEPI->getPointerOperandType(), 1948 &Indices[0], Indices.size()); 1949 1950 RewriteForScalarRepl(GEPI, AI, Offset, NewElts); 1951 1952 const Type *T = AI->getAllocatedType(); 1953 const Type *IdxTy; 1954 uint64_t OldIdx = FindElementAndOffset(T, OldOffset, IdxTy); 1955 if (GEPI->getOperand(0) == AI) 1956 OldIdx = ~0ULL; // Force the GEP to be rewritten. 1957 1958 T = AI->getAllocatedType(); 1959 uint64_t EltOffset = Offset; 1960 uint64_t Idx = FindElementAndOffset(T, EltOffset, IdxTy); 1961 1962 // If this GEP does not move the pointer across elements of the alloca 1963 // being split, then it does not needs to be rewritten. 1964 if (Idx == OldIdx) 1965 return; 1966 1967 const Type *i32Ty = Type::getInt32Ty(AI->getContext()); 1968 SmallVector<Value*, 8> NewArgs; 1969 NewArgs.push_back(Constant::getNullValue(i32Ty)); 1970 while (EltOffset != 0) { 1971 uint64_t EltIdx = FindElementAndOffset(T, EltOffset, IdxTy); 1972 NewArgs.push_back(ConstantInt::get(IdxTy, EltIdx)); 1973 } 1974 Instruction *Val = NewElts[Idx]; 1975 if (NewArgs.size() > 1) { 1976 Val = GetElementPtrInst::CreateInBounds(Val, NewArgs.begin(), 1977 NewArgs.end(), "", GEPI); 1978 Val->takeName(GEPI); 1979 } 1980 if (Val->getType() != GEPI->getType()) 1981 Val = new BitCastInst(Val, GEPI->getType(), Val->getName(), GEPI); 1982 GEPI->replaceAllUsesWith(Val); 1983 DeadInsts.push_back(GEPI); 1984} 1985 1986/// RewriteMemIntrinUserOfAlloca - MI is a memcpy/memset/memmove from or to AI. 1987/// Rewrite it to copy or set the elements of the scalarized memory. 1988void SROA::RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *Inst, 1989 AllocaInst *AI, 1990 SmallVector<AllocaInst*, 32> &NewElts) { 1991 // If this is a memcpy/memmove, construct the other pointer as the 1992 // appropriate type. The "Other" pointer is the pointer that goes to memory 1993 // that doesn't have anything to do with the alloca that we are promoting. For 1994 // memset, this Value* stays null. 1995 Value *OtherPtr = 0; 1996 unsigned MemAlignment = MI->getAlignment(); 1997 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(MI)) { // memmove/memcopy 1998 if (Inst == MTI->getRawDest()) 1999 OtherPtr = MTI->getRawSource(); 2000 else { 2001 assert(Inst == MTI->getRawSource()); 2002 OtherPtr = MTI->getRawDest(); 2003 } 2004 } 2005 2006 // If there is an other pointer, we want to convert it to the same pointer 2007 // type as AI has, so we can GEP through it safely. 2008 if (OtherPtr) { 2009 unsigned AddrSpace = 2010 cast<PointerType>(OtherPtr->getType())->getAddressSpace(); 2011 2012 // Remove bitcasts and all-zero GEPs from OtherPtr. This is an 2013 // optimization, but it's also required to detect the corner case where 2014 // both pointer operands are referencing the same memory, and where 2015 // OtherPtr may be a bitcast or GEP that currently being rewritten. (This 2016 // function is only called for mem intrinsics that access the whole 2017 // aggregate, so non-zero GEPs are not an issue here.) 2018 OtherPtr = OtherPtr->stripPointerCasts(); 2019 2020 // Copying the alloca to itself is a no-op: just delete it. 2021 if (OtherPtr == AI || OtherPtr == NewElts[0]) { 2022 // This code will run twice for a no-op memcpy -- once for each operand. 2023 // Put only one reference to MI on the DeadInsts list. 2024 for (SmallVector<Value*, 32>::const_iterator I = DeadInsts.begin(), 2025 E = DeadInsts.end(); I != E; ++I) 2026 if (*I == MI) return; 2027 DeadInsts.push_back(MI); 2028 return; 2029 } 2030 2031 // If the pointer is not the right type, insert a bitcast to the right 2032 // type. 2033 const Type *NewTy = 2034 PointerType::get(AI->getType()->getElementType(), AddrSpace); 2035 2036 if (OtherPtr->getType() != NewTy) 2037 OtherPtr = new BitCastInst(OtherPtr, NewTy, OtherPtr->getName(), MI); 2038 } 2039 2040 // Process each element of the aggregate. 2041 bool SROADest = MI->getRawDest() == Inst; 2042 2043 Constant *Zero = Constant::getNullValue(Type::getInt32Ty(MI->getContext())); 2044 2045 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { 2046 // If this is a memcpy/memmove, emit a GEP of the other element address. 2047 Value *OtherElt = 0; 2048 unsigned OtherEltAlign = MemAlignment; 2049 2050 if (OtherPtr) { 2051 Value *Idx[2] = { Zero, 2052 ConstantInt::get(Type::getInt32Ty(MI->getContext()), i) }; 2053 OtherElt = GetElementPtrInst::CreateInBounds(OtherPtr, Idx, Idx + 2, 2054 OtherPtr->getName()+"."+Twine(i), 2055 MI); 2056 uint64_t EltOffset; 2057 const PointerType *OtherPtrTy = cast<PointerType>(OtherPtr->getType()); 2058 const Type *OtherTy = OtherPtrTy->getElementType(); 2059 if (const StructType *ST = dyn_cast<StructType>(OtherTy)) { 2060 EltOffset = TD->getStructLayout(ST)->getElementOffset(i); 2061 } else { 2062 const Type *EltTy = cast<SequentialType>(OtherTy)->getElementType(); 2063 EltOffset = TD->getTypeAllocSize(EltTy)*i; 2064 } 2065 2066 // The alignment of the other pointer is the guaranteed alignment of the 2067 // element, which is affected by both the known alignment of the whole 2068 // mem intrinsic and the alignment of the element. If the alignment of 2069 // the memcpy (f.e.) is 32 but the element is at a 4-byte offset, then the 2070 // known alignment is just 4 bytes. 2071 OtherEltAlign = (unsigned)MinAlign(OtherEltAlign, EltOffset); 2072 } 2073 2074 Value *EltPtr = NewElts[i]; 2075 const Type *EltTy = cast<PointerType>(EltPtr->getType())->getElementType(); 2076 2077 // If we got down to a scalar, insert a load or store as appropriate. 2078 if (EltTy->isSingleValueType()) { 2079 if (isa<MemTransferInst>(MI)) { 2080 if (SROADest) { 2081 // From Other to Alloca. 2082 Value *Elt = new LoadInst(OtherElt, "tmp", false, OtherEltAlign, MI); 2083 new StoreInst(Elt, EltPtr, MI); 2084 } else { 2085 // From Alloca to Other. 2086 Value *Elt = new LoadInst(EltPtr, "tmp", MI); 2087 new StoreInst(Elt, OtherElt, false, OtherEltAlign, MI); 2088 } 2089 continue; 2090 } 2091 assert(isa<MemSetInst>(MI)); 2092 2093 // If the stored element is zero (common case), just store a null 2094 // constant. 2095 Constant *StoreVal; 2096 if (ConstantInt *CI = dyn_cast<ConstantInt>(MI->getArgOperand(1))) { 2097 if (CI->isZero()) { 2098 StoreVal = Constant::getNullValue(EltTy); // 0.0, null, 0, <0,0> 2099 } else { 2100 // If EltTy is a vector type, get the element type. 2101 const Type *ValTy = EltTy->getScalarType(); 2102 2103 // Construct an integer with the right value. 2104 unsigned EltSize = TD->getTypeSizeInBits(ValTy); 2105 APInt OneVal(EltSize, CI->getZExtValue()); 2106 APInt TotalVal(OneVal); 2107 // Set each byte. 2108 for (unsigned i = 0; 8*i < EltSize; ++i) { 2109 TotalVal = TotalVal.shl(8); 2110 TotalVal |= OneVal; 2111 } 2112 2113 // Convert the integer value to the appropriate type. 2114 StoreVal = ConstantInt::get(CI->getContext(), TotalVal); 2115 if (ValTy->isPointerTy()) 2116 StoreVal = ConstantExpr::getIntToPtr(StoreVal, ValTy); 2117 else if (ValTy->isFloatingPointTy()) 2118 StoreVal = ConstantExpr::getBitCast(StoreVal, ValTy); 2119 assert(StoreVal->getType() == ValTy && "Type mismatch!"); 2120 2121 // If the requested value was a vector constant, create it. 2122 if (EltTy != ValTy) { 2123 unsigned NumElts = cast<VectorType>(ValTy)->getNumElements(); 2124 SmallVector<Constant*, 16> Elts(NumElts, StoreVal); 2125 StoreVal = ConstantVector::get(Elts); 2126 } 2127 } 2128 new StoreInst(StoreVal, EltPtr, MI); 2129 continue; 2130 } 2131 // Otherwise, if we're storing a byte variable, use a memset call for 2132 // this element. 2133 } 2134 2135 unsigned EltSize = TD->getTypeAllocSize(EltTy); 2136 2137 IRBuilder<> Builder(MI); 2138 2139 // Finally, insert the meminst for this element. 2140 if (isa<MemSetInst>(MI)) { 2141 Builder.CreateMemSet(EltPtr, MI->getArgOperand(1), EltSize, 2142 MI->isVolatile()); 2143 } else { 2144 assert(isa<MemTransferInst>(MI)); 2145 Value *Dst = SROADest ? EltPtr : OtherElt; // Dest ptr 2146 Value *Src = SROADest ? OtherElt : EltPtr; // Src ptr 2147 2148 if (isa<MemCpyInst>(MI)) 2149 Builder.CreateMemCpy(Dst, Src, EltSize, OtherEltAlign,MI->isVolatile()); 2150 else 2151 Builder.CreateMemMove(Dst, Src, EltSize,OtherEltAlign,MI->isVolatile()); 2152 } 2153 } 2154 DeadInsts.push_back(MI); 2155} 2156 2157/// RewriteStoreUserOfWholeAlloca - We found a store of an integer that 2158/// overwrites the entire allocation. Extract out the pieces of the stored 2159/// integer and store them individually. 2160void SROA::RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocaInst *AI, 2161 SmallVector<AllocaInst*, 32> &NewElts){ 2162 // Extract each element out of the integer according to its structure offset 2163 // and store the element value to the individual alloca. 2164 Value *SrcVal = SI->getOperand(0); 2165 const Type *AllocaEltTy = AI->getAllocatedType(); 2166 uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy); 2167 2168 IRBuilder<> Builder(SI); 2169 2170 // Handle tail padding by extending the operand 2171 if (TD->getTypeSizeInBits(SrcVal->getType()) != AllocaSizeBits) 2172 SrcVal = Builder.CreateZExt(SrcVal, 2173 IntegerType::get(SI->getContext(), AllocaSizeBits)); 2174 2175 DEBUG(dbgs() << "PROMOTING STORE TO WHOLE ALLOCA: " << *AI << '\n' << *SI 2176 << '\n'); 2177 2178 // There are two forms here: AI could be an array or struct. Both cases 2179 // have different ways to compute the element offset. 2180 if (const StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) { 2181 const StructLayout *Layout = TD->getStructLayout(EltSTy); 2182 2183 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { 2184 // Get the number of bits to shift SrcVal to get the value. 2185 const Type *FieldTy = EltSTy->getElementType(i); 2186 uint64_t Shift = Layout->getElementOffsetInBits(i); 2187 2188 if (TD->isBigEndian()) 2189 Shift = AllocaSizeBits-Shift-TD->getTypeAllocSizeInBits(FieldTy); 2190 2191 Value *EltVal = SrcVal; 2192 if (Shift) { 2193 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift); 2194 EltVal = Builder.CreateLShr(EltVal, ShiftVal, "sroa.store.elt"); 2195 } 2196 2197 // Truncate down to an integer of the right size. 2198 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy); 2199 2200 // Ignore zero sized fields like {}, they obviously contain no data. 2201 if (FieldSizeBits == 0) continue; 2202 2203 if (FieldSizeBits != AllocaSizeBits) 2204 EltVal = Builder.CreateTrunc(EltVal, 2205 IntegerType::get(SI->getContext(), FieldSizeBits)); 2206 Value *DestField = NewElts[i]; 2207 if (EltVal->getType() == FieldTy) { 2208 // Storing to an integer field of this size, just do it. 2209 } else if (FieldTy->isFloatingPointTy() || FieldTy->isVectorTy()) { 2210 // Bitcast to the right element type (for fp/vector values). 2211 EltVal = Builder.CreateBitCast(EltVal, FieldTy); 2212 } else { 2213 // Otherwise, bitcast the dest pointer (for aggregates). 2214 DestField = Builder.CreateBitCast(DestField, 2215 PointerType::getUnqual(EltVal->getType())); 2216 } 2217 new StoreInst(EltVal, DestField, SI); 2218 } 2219 2220 } else { 2221 const ArrayType *ATy = cast<ArrayType>(AllocaEltTy); 2222 const Type *ArrayEltTy = ATy->getElementType(); 2223 uint64_t ElementOffset = TD->getTypeAllocSizeInBits(ArrayEltTy); 2224 uint64_t ElementSizeBits = TD->getTypeSizeInBits(ArrayEltTy); 2225 2226 uint64_t Shift; 2227 2228 if (TD->isBigEndian()) 2229 Shift = AllocaSizeBits-ElementOffset; 2230 else 2231 Shift = 0; 2232 2233 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { 2234 // Ignore zero sized fields like {}, they obviously contain no data. 2235 if (ElementSizeBits == 0) continue; 2236 2237 Value *EltVal = SrcVal; 2238 if (Shift) { 2239 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift); 2240 EltVal = Builder.CreateLShr(EltVal, ShiftVal, "sroa.store.elt"); 2241 } 2242 2243 // Truncate down to an integer of the right size. 2244 if (ElementSizeBits != AllocaSizeBits) 2245 EltVal = Builder.CreateTrunc(EltVal, 2246 IntegerType::get(SI->getContext(), 2247 ElementSizeBits)); 2248 Value *DestField = NewElts[i]; 2249 if (EltVal->getType() == ArrayEltTy) { 2250 // Storing to an integer field of this size, just do it. 2251 } else if (ArrayEltTy->isFloatingPointTy() || 2252 ArrayEltTy->isVectorTy()) { 2253 // Bitcast to the right element type (for fp/vector values). 2254 EltVal = Builder.CreateBitCast(EltVal, ArrayEltTy); 2255 } else { 2256 // Otherwise, bitcast the dest pointer (for aggregates). 2257 DestField = Builder.CreateBitCast(DestField, 2258 PointerType::getUnqual(EltVal->getType())); 2259 } 2260 new StoreInst(EltVal, DestField, SI); 2261 2262 if (TD->isBigEndian()) 2263 Shift -= ElementOffset; 2264 else 2265 Shift += ElementOffset; 2266 } 2267 } 2268 2269 DeadInsts.push_back(SI); 2270} 2271 2272/// RewriteLoadUserOfWholeAlloca - We found a load of the entire allocation to 2273/// an integer. Load the individual pieces to form the aggregate value. 2274void SROA::RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocaInst *AI, 2275 SmallVector<AllocaInst*, 32> &NewElts) { 2276 // Extract each element out of the NewElts according to its structure offset 2277 // and form the result value. 2278 const Type *AllocaEltTy = AI->getAllocatedType(); 2279 uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy); 2280 2281 DEBUG(dbgs() << "PROMOTING LOAD OF WHOLE ALLOCA: " << *AI << '\n' << *LI 2282 << '\n'); 2283 2284 // There are two forms here: AI could be an array or struct. Both cases 2285 // have different ways to compute the element offset. 2286 const StructLayout *Layout = 0; 2287 uint64_t ArrayEltBitOffset = 0; 2288 if (const StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) { 2289 Layout = TD->getStructLayout(EltSTy); 2290 } else { 2291 const Type *ArrayEltTy = cast<ArrayType>(AllocaEltTy)->getElementType(); 2292 ArrayEltBitOffset = TD->getTypeAllocSizeInBits(ArrayEltTy); 2293 } 2294 2295 Value *ResultVal = 2296 Constant::getNullValue(IntegerType::get(LI->getContext(), AllocaSizeBits)); 2297 2298 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { 2299 // Load the value from the alloca. If the NewElt is an aggregate, cast 2300 // the pointer to an integer of the same size before doing the load. 2301 Value *SrcField = NewElts[i]; 2302 const Type *FieldTy = 2303 cast<PointerType>(SrcField->getType())->getElementType(); 2304 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy); 2305 2306 // Ignore zero sized fields like {}, they obviously contain no data. 2307 if (FieldSizeBits == 0) continue; 2308 2309 const IntegerType *FieldIntTy = IntegerType::get(LI->getContext(), 2310 FieldSizeBits); 2311 if (!FieldTy->isIntegerTy() && !FieldTy->isFloatingPointTy() && 2312 !FieldTy->isVectorTy()) 2313 SrcField = new BitCastInst(SrcField, 2314 PointerType::getUnqual(FieldIntTy), 2315 "", LI); 2316 SrcField = new LoadInst(SrcField, "sroa.load.elt", LI); 2317 2318 // If SrcField is a fp or vector of the right size but that isn't an 2319 // integer type, bitcast to an integer so we can shift it. 2320 if (SrcField->getType() != FieldIntTy) 2321 SrcField = new BitCastInst(SrcField, FieldIntTy, "", LI); 2322 2323 // Zero extend the field to be the same size as the final alloca so that 2324 // we can shift and insert it. 2325 if (SrcField->getType() != ResultVal->getType()) 2326 SrcField = new ZExtInst(SrcField, ResultVal->getType(), "", LI); 2327 2328 // Determine the number of bits to shift SrcField. 2329 uint64_t Shift; 2330 if (Layout) // Struct case. 2331 Shift = Layout->getElementOffsetInBits(i); 2332 else // Array case. 2333 Shift = i*ArrayEltBitOffset; 2334 2335 if (TD->isBigEndian()) 2336 Shift = AllocaSizeBits-Shift-FieldIntTy->getBitWidth(); 2337 2338 if (Shift) { 2339 Value *ShiftVal = ConstantInt::get(SrcField->getType(), Shift); 2340 SrcField = BinaryOperator::CreateShl(SrcField, ShiftVal, "", LI); 2341 } 2342 2343 // Don't create an 'or x, 0' on the first iteration. 2344 if (!isa<Constant>(ResultVal) || 2345 !cast<Constant>(ResultVal)->isNullValue()) 2346 ResultVal = BinaryOperator::CreateOr(SrcField, ResultVal, "", LI); 2347 else 2348 ResultVal = SrcField; 2349 } 2350 2351 // Handle tail padding by truncating the result 2352 if (TD->getTypeSizeInBits(LI->getType()) != AllocaSizeBits) 2353 ResultVal = new TruncInst(ResultVal, LI->getType(), "", LI); 2354 2355 LI->replaceAllUsesWith(ResultVal); 2356 DeadInsts.push_back(LI); 2357} 2358 2359/// HasPadding - Return true if the specified type has any structure or 2360/// alignment padding in between the elements that would be split apart 2361/// by SROA; return false otherwise. 2362static bool HasPadding(const Type *Ty, const TargetData &TD) { 2363 if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) { 2364 Ty = ATy->getElementType(); 2365 return TD.getTypeSizeInBits(Ty) != TD.getTypeAllocSizeInBits(Ty); 2366 } 2367 2368 // SROA currently handles only Arrays and Structs. 2369 const StructType *STy = cast<StructType>(Ty); 2370 const StructLayout *SL = TD.getStructLayout(STy); 2371 unsigned PrevFieldBitOffset = 0; 2372 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) { 2373 unsigned FieldBitOffset = SL->getElementOffsetInBits(i); 2374 2375 // Check to see if there is any padding between this element and the 2376 // previous one. 2377 if (i) { 2378 unsigned PrevFieldEnd = 2379 PrevFieldBitOffset+TD.getTypeSizeInBits(STy->getElementType(i-1)); 2380 if (PrevFieldEnd < FieldBitOffset) 2381 return true; 2382 } 2383 PrevFieldBitOffset = FieldBitOffset; 2384 } 2385 // Check for tail padding. 2386 if (unsigned EltCount = STy->getNumElements()) { 2387 unsigned PrevFieldEnd = PrevFieldBitOffset + 2388 TD.getTypeSizeInBits(STy->getElementType(EltCount-1)); 2389 if (PrevFieldEnd < SL->getSizeInBits()) 2390 return true; 2391 } 2392 return false; 2393} 2394 2395/// isSafeStructAllocaToScalarRepl - Check to see if the specified allocation of 2396/// an aggregate can be broken down into elements. Return 0 if not, 3 if safe, 2397/// or 1 if safe after canonicalization has been performed. 2398bool SROA::isSafeAllocaToScalarRepl(AllocaInst *AI) { 2399 // Loop over the use list of the alloca. We can only transform it if all of 2400 // the users are safe to transform. 2401 AllocaInfo Info(AI); 2402 2403 isSafeForScalarRepl(AI, 0, Info); 2404 if (Info.isUnsafe) { 2405 DEBUG(dbgs() << "Cannot transform: " << *AI << '\n'); 2406 return false; 2407 } 2408 2409 // Okay, we know all the users are promotable. If the aggregate is a memcpy 2410 // source and destination, we have to be careful. In particular, the memcpy 2411 // could be moving around elements that live in structure padding of the LLVM 2412 // types, but may actually be used. In these cases, we refuse to promote the 2413 // struct. 2414 if (Info.isMemCpySrc && Info.isMemCpyDst && 2415 HasPadding(AI->getAllocatedType(), *TD)) 2416 return false; 2417 2418 // If the alloca never has an access to just *part* of it, but is accessed 2419 // via loads and stores, then we should use ConvertToScalarInfo to promote 2420 // the alloca instead of promoting each piece at a time and inserting fission 2421 // and fusion code. 2422 if (!Info.hasSubelementAccess && Info.hasALoadOrStore) { 2423 // If the struct/array just has one element, use basic SRoA. 2424 if (const StructType *ST = dyn_cast<StructType>(AI->getAllocatedType())) { 2425 if (ST->getNumElements() > 1) return false; 2426 } else { 2427 if (cast<ArrayType>(AI->getAllocatedType())->getNumElements() > 1) 2428 return false; 2429 } 2430 } 2431 2432 return true; 2433} 2434 2435 2436 2437/// PointsToConstantGlobal - Return true if V (possibly indirectly) points to 2438/// some part of a constant global variable. This intentionally only accepts 2439/// constant expressions because we don't can't rewrite arbitrary instructions. 2440static bool PointsToConstantGlobal(Value *V) { 2441 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V)) 2442 return GV->isConstant(); 2443 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) 2444 if (CE->getOpcode() == Instruction::BitCast || 2445 CE->getOpcode() == Instruction::GetElementPtr) 2446 return PointsToConstantGlobal(CE->getOperand(0)); 2447 return false; 2448} 2449 2450/// isOnlyCopiedFromConstantGlobal - Recursively walk the uses of a (derived) 2451/// pointer to an alloca. Ignore any reads of the pointer, return false if we 2452/// see any stores or other unknown uses. If we see pointer arithmetic, keep 2453/// track of whether it moves the pointer (with isOffset) but otherwise traverse 2454/// the uses. If we see a memcpy/memmove that targets an unoffseted pointer to 2455/// the alloca, and if the source pointer is a pointer to a constant global, we 2456/// can optimize this. 2457static bool isOnlyCopiedFromConstantGlobal(Value *V, MemTransferInst *&TheCopy, 2458 bool isOffset) { 2459 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) { 2460 User *U = cast<Instruction>(*UI); 2461 2462 if (LoadInst *LI = dyn_cast<LoadInst>(U)) { 2463 // Ignore non-volatile loads, they are always ok. 2464 if (LI->isVolatile()) return false; 2465 continue; 2466 } 2467 2468 if (BitCastInst *BCI = dyn_cast<BitCastInst>(U)) { 2469 // If uses of the bitcast are ok, we are ok. 2470 if (!isOnlyCopiedFromConstantGlobal(BCI, TheCopy, isOffset)) 2471 return false; 2472 continue; 2473 } 2474 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) { 2475 // If the GEP has all zero indices, it doesn't offset the pointer. If it 2476 // doesn't, it does. 2477 if (!isOnlyCopiedFromConstantGlobal(GEP, TheCopy, 2478 isOffset || !GEP->hasAllZeroIndices())) 2479 return false; 2480 continue; 2481 } 2482 2483 if (CallSite CS = U) { 2484 // If this is a readonly/readnone call site, then we know it is just a 2485 // load and we can ignore it. 2486 if (CS.onlyReadsMemory()) 2487 continue; 2488 2489 // If this is the function being called then we treat it like a load and 2490 // ignore it. 2491 if (CS.isCallee(UI)) 2492 continue; 2493 2494 // If this is being passed as a byval argument, the caller is making a 2495 // copy, so it is only a read of the alloca. 2496 unsigned ArgNo = CS.getArgumentNo(UI); 2497 if (CS.paramHasAttr(ArgNo+1, Attribute::ByVal)) 2498 continue; 2499 } 2500 2501 // If this is isn't our memcpy/memmove, reject it as something we can't 2502 // handle. 2503 MemTransferInst *MI = dyn_cast<MemTransferInst>(U); 2504 if (MI == 0) 2505 return false; 2506 2507 // If the transfer is using the alloca as a source of the transfer, then 2508 // ignore it since it is a load (unless the transfer is volatile). 2509 if (UI.getOperandNo() == 1) { 2510 if (MI->isVolatile()) return false; 2511 continue; 2512 } 2513 2514 // If we already have seen a copy, reject the second one. 2515 if (TheCopy) return false; 2516 2517 // If the pointer has been offset from the start of the alloca, we can't 2518 // safely handle this. 2519 if (isOffset) return false; 2520 2521 // If the memintrinsic isn't using the alloca as the dest, reject it. 2522 if (UI.getOperandNo() != 0) return false; 2523 2524 // If the source of the memcpy/move is not a constant global, reject it. 2525 if (!PointsToConstantGlobal(MI->getSource())) 2526 return false; 2527 2528 // Otherwise, the transform is safe. Remember the copy instruction. 2529 TheCopy = MI; 2530 } 2531 return true; 2532} 2533 2534/// isOnlyCopiedFromConstantGlobal - Return true if the specified alloca is only 2535/// modified by a copy from a constant global. If we can prove this, we can 2536/// replace any uses of the alloca with uses of the global directly. 2537MemTransferInst *SROA::isOnlyCopiedFromConstantGlobal(AllocaInst *AI) { 2538 MemTransferInst *TheCopy = 0; 2539 if (::isOnlyCopiedFromConstantGlobal(AI, TheCopy, false)) 2540 return TheCopy; 2541 return 0; 2542} 2543