ScalarReplAggregates.cpp revision d0f56132cfa6e25fb9692e84ea12444c86b92ae4
1//===- ScalarReplAggregates.cpp - Scalar Replacement of Aggregates --------===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This transformation implements the well known scalar replacement of 11// aggregates transformation. This xform breaks up alloca instructions of 12// aggregate type (structure or array) into individual alloca instructions for 13// each member (if possible). Then, if possible, it transforms the individual 14// alloca instructions into nice clean scalar SSA form. 15// 16// This combines a simple SRoA algorithm with the Mem2Reg algorithm because 17// often interact, especially for C++ programs. As such, iterating between 18// SRoA, then Mem2Reg until we run out of things to promote works well. 19// 20//===----------------------------------------------------------------------===// 21 22#define DEBUG_TYPE "scalarrepl" 23#include "llvm/Transforms/Scalar.h" 24#include "llvm/Constants.h" 25#include "llvm/DerivedTypes.h" 26#include "llvm/Function.h" 27#include "llvm/GlobalVariable.h" 28#include "llvm/Instructions.h" 29#include "llvm/IntrinsicInst.h" 30#include "llvm/LLVMContext.h" 31#include "llvm/Module.h" 32#include "llvm/Pass.h" 33#include "llvm/Analysis/DominanceFrontier.h" 34#include "llvm/Analysis/ValueTracking.h" 35#include "llvm/Target/TargetData.h" 36#include "llvm/Transforms/Utils/PromoteMemToReg.h" 37#include "llvm/Transforms/Utils/Local.h" 38#include "llvm/Transforms/Utils/SSAUpdater.h" 39#include "llvm/Support/CallSite.h" 40#include "llvm/Support/Debug.h" 41#include "llvm/Support/ErrorHandling.h" 42#include "llvm/Support/GetElementPtrTypeIterator.h" 43#include "llvm/Support/IRBuilder.h" 44#include "llvm/Support/MathExtras.h" 45#include "llvm/Support/raw_ostream.h" 46#include "llvm/ADT/SmallVector.h" 47#include "llvm/ADT/Statistic.h" 48using namespace llvm; 49 50STATISTIC(NumReplaced, "Number of allocas broken up"); 51STATISTIC(NumPromoted, "Number of allocas promoted"); 52STATISTIC(NumConverted, "Number of aggregates converted to scalar"); 53STATISTIC(NumGlobals, "Number of allocas copied from constant global"); 54 55namespace { 56 struct SROA : public FunctionPass { 57 SROA(int T, bool hasDF, char &ID) 58 : FunctionPass(ID), HasDomFrontiers(hasDF) { 59 if (T == -1) 60 SRThreshold = 128; 61 else 62 SRThreshold = T; 63 } 64 65 bool runOnFunction(Function &F); 66 67 bool performScalarRepl(Function &F); 68 bool performPromotion(Function &F); 69 70 private: 71 bool HasDomFrontiers; 72 TargetData *TD; 73 74 /// DeadInsts - Keep track of instructions we have made dead, so that 75 /// we can remove them after we are done working. 76 SmallVector<Value*, 32> DeadInsts; 77 78 /// AllocaInfo - When analyzing uses of an alloca instruction, this captures 79 /// information about the uses. All these fields are initialized to false 80 /// and set to true when something is learned. 81 struct AllocaInfo { 82 /// isUnsafe - This is set to true if the alloca cannot be SROA'd. 83 bool isUnsafe : 1; 84 85 /// isMemCpySrc - This is true if this aggregate is memcpy'd from. 86 bool isMemCpySrc : 1; 87 88 /// isMemCpyDst - This is true if this aggregate is memcpy'd into. 89 bool isMemCpyDst : 1; 90 91 AllocaInfo() 92 : isUnsafe(false), isMemCpySrc(false), isMemCpyDst(false) {} 93 }; 94 95 unsigned SRThreshold; 96 97 void MarkUnsafe(AllocaInfo &I) { I.isUnsafe = true; } 98 99 bool isSafeAllocaToScalarRepl(AllocaInst *AI); 100 101 void isSafeForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset, 102 AllocaInfo &Info); 103 void isSafeGEP(GetElementPtrInst *GEPI, AllocaInst *AI, uint64_t &Offset, 104 AllocaInfo &Info); 105 void isSafeMemAccess(AllocaInst *AI, uint64_t Offset, uint64_t MemSize, 106 const Type *MemOpType, bool isStore, AllocaInfo &Info); 107 bool TypeHasComponent(const Type *T, uint64_t Offset, uint64_t Size); 108 uint64_t FindElementAndOffset(const Type *&T, uint64_t &Offset, 109 const Type *&IdxTy); 110 111 void DoScalarReplacement(AllocaInst *AI, 112 std::vector<AllocaInst*> &WorkList); 113 void DeleteDeadInstructions(); 114 115 void RewriteForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset, 116 SmallVector<AllocaInst*, 32> &NewElts); 117 void RewriteBitCast(BitCastInst *BC, AllocaInst *AI, uint64_t Offset, 118 SmallVector<AllocaInst*, 32> &NewElts); 119 void RewriteGEP(GetElementPtrInst *GEPI, AllocaInst *AI, uint64_t Offset, 120 SmallVector<AllocaInst*, 32> &NewElts); 121 void RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *Inst, 122 AllocaInst *AI, 123 SmallVector<AllocaInst*, 32> &NewElts); 124 void RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocaInst *AI, 125 SmallVector<AllocaInst*, 32> &NewElts); 126 void RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocaInst *AI, 127 SmallVector<AllocaInst*, 32> &NewElts); 128 129 static MemTransferInst *isOnlyCopiedFromConstantGlobal(AllocaInst *AI); 130 }; 131 132 // SROA_DF - SROA that uses DominanceFrontier. 133 struct SROA_DF : public SROA { 134 static char ID; 135 public: 136 SROA_DF(int T = -1) : SROA(T, true, ID) { 137 initializeSROA_DFPass(*PassRegistry::getPassRegistry()); 138 } 139 140 // getAnalysisUsage - This pass does not require any passes, but we know it 141 // will not alter the CFG, so say so. 142 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 143 AU.addRequired<DominatorTree>(); 144 AU.addRequired<DominanceFrontier>(); 145 AU.setPreservesCFG(); 146 } 147 }; 148 149 // SROA_SSAUp - SROA that uses SSAUpdater. 150 struct SROA_SSAUp : public SROA { 151 static char ID; 152 public: 153 SROA_SSAUp(int T = -1) : SROA(T, false, ID) { 154 initializeSROA_SSAUpPass(*PassRegistry::getPassRegistry()); 155 } 156 157 // getAnalysisUsage - This pass does not require any passes, but we know it 158 // will not alter the CFG, so say so. 159 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 160 AU.setPreservesCFG(); 161 } 162 }; 163 164} 165 166char SROA_DF::ID = 0; 167char SROA_SSAUp::ID = 0; 168 169INITIALIZE_PASS_BEGIN(SROA_DF, "scalarrepl", 170 "Scalar Replacement of Aggregates (DF)", false, false) 171INITIALIZE_PASS_DEPENDENCY(DominatorTree) 172INITIALIZE_PASS_DEPENDENCY(DominanceFrontier) 173INITIALIZE_PASS_END(SROA_DF, "scalarrepl", 174 "Scalar Replacement of Aggregates (DF)", false, false) 175 176INITIALIZE_PASS_BEGIN(SROA_SSAUp, "scalarrepl-ssa", 177 "Scalar Replacement of Aggregates (SSAUp)", false, false) 178INITIALIZE_PASS_END(SROA_SSAUp, "scalarrepl-ssa", 179 "Scalar Replacement of Aggregates (SSAUp)", false, false) 180 181// Public interface to the ScalarReplAggregates pass 182FunctionPass *llvm::createScalarReplAggregatesPass(int Threshold, 183 bool UseDomFrontier) { 184 if (UseDomFrontier) 185 return new SROA_DF(Threshold); 186 return new SROA_SSAUp(Threshold); 187} 188 189 190//===----------------------------------------------------------------------===// 191// Convert To Scalar Optimization. 192//===----------------------------------------------------------------------===// 193 194namespace { 195/// ConvertToScalarInfo - This class implements the "Convert To Scalar" 196/// optimization, which scans the uses of an alloca and determines if it can 197/// rewrite it in terms of a single new alloca that can be mem2reg'd. 198class ConvertToScalarInfo { 199 /// AllocaSize - The size of the alloca being considered. 200 unsigned AllocaSize; 201 const TargetData &TD; 202 203 /// IsNotTrivial - This is set to true if there is some access to the object 204 /// which means that mem2reg can't promote it. 205 bool IsNotTrivial; 206 207 /// VectorTy - This tracks the type that we should promote the vector to if 208 /// it is possible to turn it into a vector. This starts out null, and if it 209 /// isn't possible to turn into a vector type, it gets set to VoidTy. 210 const Type *VectorTy; 211 212 /// HadAVector - True if there is at least one vector access to the alloca. 213 /// We don't want to turn random arrays into vectors and use vector element 214 /// insert/extract, but if there are element accesses to something that is 215 /// also declared as a vector, we do want to promote to a vector. 216 bool HadAVector; 217 218public: 219 explicit ConvertToScalarInfo(unsigned Size, const TargetData &td) 220 : AllocaSize(Size), TD(td) { 221 IsNotTrivial = false; 222 VectorTy = 0; 223 HadAVector = false; 224 } 225 226 AllocaInst *TryConvert(AllocaInst *AI); 227 228private: 229 bool CanConvertToScalar(Value *V, uint64_t Offset); 230 void MergeInType(const Type *In, uint64_t Offset); 231 void ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, uint64_t Offset); 232 233 Value *ConvertScalar_ExtractValue(Value *NV, const Type *ToType, 234 uint64_t Offset, IRBuilder<> &Builder); 235 Value *ConvertScalar_InsertValue(Value *StoredVal, Value *ExistingVal, 236 uint64_t Offset, IRBuilder<> &Builder); 237}; 238} // end anonymous namespace. 239 240 241/// IsVerbotenVectorType - Return true if this is a vector type ScalarRepl isn't 242/// allowed to form. We do this to avoid MMX types, which is a complete hack, 243/// but is required until the backend is fixed. 244static bool IsVerbotenVectorType(const VectorType *VTy, const Instruction *I) { 245 StringRef Triple(I->getParent()->getParent()->getParent()->getTargetTriple()); 246 if (!Triple.startswith("i386") && 247 !Triple.startswith("x86_64")) 248 return false; 249 250 // Reject all the MMX vector types. 251 switch (VTy->getNumElements()) { 252 default: return false; 253 case 1: return VTy->getElementType()->isIntegerTy(64); 254 case 2: return VTy->getElementType()->isIntegerTy(32); 255 case 4: return VTy->getElementType()->isIntegerTy(16); 256 case 8: return VTy->getElementType()->isIntegerTy(8); 257 } 258} 259 260 261/// TryConvert - Analyze the specified alloca, and if it is safe to do so, 262/// rewrite it to be a new alloca which is mem2reg'able. This returns the new 263/// alloca if possible or null if not. 264AllocaInst *ConvertToScalarInfo::TryConvert(AllocaInst *AI) { 265 // If we can't convert this scalar, or if mem2reg can trivially do it, bail 266 // out. 267 if (!CanConvertToScalar(AI, 0) || !IsNotTrivial) 268 return 0; 269 270 // If we were able to find a vector type that can handle this with 271 // insert/extract elements, and if there was at least one use that had 272 // a vector type, promote this to a vector. We don't want to promote 273 // random stuff that doesn't use vectors (e.g. <9 x double>) because then 274 // we just get a lot of insert/extracts. If at least one vector is 275 // involved, then we probably really do have a union of vector/array. 276 const Type *NewTy; 277 if (VectorTy && VectorTy->isVectorTy() && HadAVector && 278 !IsVerbotenVectorType(cast<VectorType>(VectorTy), AI)) { 279 DEBUG(dbgs() << "CONVERT TO VECTOR: " << *AI << "\n TYPE = " 280 << *VectorTy << '\n'); 281 NewTy = VectorTy; // Use the vector type. 282 } else { 283 DEBUG(dbgs() << "CONVERT TO SCALAR INTEGER: " << *AI << "\n"); 284 // Create and insert the integer alloca. 285 NewTy = IntegerType::get(AI->getContext(), AllocaSize*8); 286 } 287 AllocaInst *NewAI = new AllocaInst(NewTy, 0, "", AI->getParent()->begin()); 288 ConvertUsesToScalar(AI, NewAI, 0); 289 return NewAI; 290} 291 292/// MergeInType - Add the 'In' type to the accumulated vector type (VectorTy) 293/// so far at the offset specified by Offset (which is specified in bytes). 294/// 295/// There are two cases we handle here: 296/// 1) A union of vector types of the same size and potentially its elements. 297/// Here we turn element accesses into insert/extract element operations. 298/// This promotes a <4 x float> with a store of float to the third element 299/// into a <4 x float> that uses insert element. 300/// 2) A fully general blob of memory, which we turn into some (potentially 301/// large) integer type with extract and insert operations where the loads 302/// and stores would mutate the memory. We mark this by setting VectorTy 303/// to VoidTy. 304void ConvertToScalarInfo::MergeInType(const Type *In, uint64_t Offset) { 305 // If we already decided to turn this into a blob of integer memory, there is 306 // nothing to be done. 307 if (VectorTy && VectorTy->isVoidTy()) 308 return; 309 310 // If this could be contributing to a vector, analyze it. 311 312 // If the In type is a vector that is the same size as the alloca, see if it 313 // matches the existing VecTy. 314 if (const VectorType *VInTy = dyn_cast<VectorType>(In)) { 315 // Remember if we saw a vector type. 316 HadAVector = true; 317 318 if (VInTy->getBitWidth()/8 == AllocaSize && Offset == 0) { 319 // If we're storing/loading a vector of the right size, allow it as a 320 // vector. If this the first vector we see, remember the type so that 321 // we know the element size. If this is a subsequent access, ignore it 322 // even if it is a differing type but the same size. Worst case we can 323 // bitcast the resultant vectors. 324 if (VectorTy == 0) 325 VectorTy = VInTy; 326 return; 327 } 328 } else if (In->isFloatTy() || In->isDoubleTy() || 329 (In->isIntegerTy() && In->getPrimitiveSizeInBits() >= 8 && 330 isPowerOf2_32(In->getPrimitiveSizeInBits()))) { 331 // If we're accessing something that could be an element of a vector, see 332 // if the implied vector agrees with what we already have and if Offset is 333 // compatible with it. 334 unsigned EltSize = In->getPrimitiveSizeInBits()/8; 335 if (Offset % EltSize == 0 && AllocaSize % EltSize == 0 && 336 (VectorTy == 0 || 337 cast<VectorType>(VectorTy)->getElementType() 338 ->getPrimitiveSizeInBits()/8 == EltSize)) { 339 if (VectorTy == 0) 340 VectorTy = VectorType::get(In, AllocaSize/EltSize); 341 return; 342 } 343 } 344 345 // Otherwise, we have a case that we can't handle with an optimized vector 346 // form. We can still turn this into a large integer. 347 VectorTy = Type::getVoidTy(In->getContext()); 348} 349 350/// CanConvertToScalar - V is a pointer. If we can convert the pointee and all 351/// its accesses to a single vector type, return true and set VecTy to 352/// the new type. If we could convert the alloca into a single promotable 353/// integer, return true but set VecTy to VoidTy. Further, if the use is not a 354/// completely trivial use that mem2reg could promote, set IsNotTrivial. Offset 355/// is the current offset from the base of the alloca being analyzed. 356/// 357/// If we see at least one access to the value that is as a vector type, set the 358/// SawVec flag. 359bool ConvertToScalarInfo::CanConvertToScalar(Value *V, uint64_t Offset) { 360 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) { 361 Instruction *User = cast<Instruction>(*UI); 362 363 if (LoadInst *LI = dyn_cast<LoadInst>(User)) { 364 // Don't break volatile loads. 365 if (LI->isVolatile()) 366 return false; 367 // Don't touch MMX operations. 368 if (LI->getType()->isX86_MMXTy()) 369 return false; 370 MergeInType(LI->getType(), Offset); 371 continue; 372 } 373 374 if (StoreInst *SI = dyn_cast<StoreInst>(User)) { 375 // Storing the pointer, not into the value? 376 if (SI->getOperand(0) == V || SI->isVolatile()) return false; 377 // Don't touch MMX operations. 378 if (SI->getOperand(0)->getType()->isX86_MMXTy()) 379 return false; 380 MergeInType(SI->getOperand(0)->getType(), Offset); 381 continue; 382 } 383 384 if (BitCastInst *BCI = dyn_cast<BitCastInst>(User)) { 385 IsNotTrivial = true; // Can't be mem2reg'd. 386 if (!CanConvertToScalar(BCI, Offset)) 387 return false; 388 continue; 389 } 390 391 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) { 392 // If this is a GEP with a variable indices, we can't handle it. 393 if (!GEP->hasAllConstantIndices()) 394 return false; 395 396 // Compute the offset that this GEP adds to the pointer. 397 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end()); 398 uint64_t GEPOffset = TD.getIndexedOffset(GEP->getPointerOperandType(), 399 &Indices[0], Indices.size()); 400 // See if all uses can be converted. 401 if (!CanConvertToScalar(GEP, Offset+GEPOffset)) 402 return false; 403 IsNotTrivial = true; // Can't be mem2reg'd. 404 continue; 405 } 406 407 // If this is a constant sized memset of a constant value (e.g. 0) we can 408 // handle it. 409 if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) { 410 // Store of constant value and constant size. 411 if (!isa<ConstantInt>(MSI->getValue()) || 412 !isa<ConstantInt>(MSI->getLength())) 413 return false; 414 IsNotTrivial = true; // Can't be mem2reg'd. 415 continue; 416 } 417 418 // If this is a memcpy or memmove into or out of the whole allocation, we 419 // can handle it like a load or store of the scalar type. 420 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) { 421 ConstantInt *Len = dyn_cast<ConstantInt>(MTI->getLength()); 422 if (Len == 0 || Len->getZExtValue() != AllocaSize || Offset != 0) 423 return false; 424 425 IsNotTrivial = true; // Can't be mem2reg'd. 426 continue; 427 } 428 429 // Otherwise, we cannot handle this! 430 return false; 431 } 432 433 return true; 434} 435 436/// ConvertUsesToScalar - Convert all of the users of Ptr to use the new alloca 437/// directly. This happens when we are converting an "integer union" to a 438/// single integer scalar, or when we are converting a "vector union" to a 439/// vector with insert/extractelement instructions. 440/// 441/// Offset is an offset from the original alloca, in bits that need to be 442/// shifted to the right. By the end of this, there should be no uses of Ptr. 443void ConvertToScalarInfo::ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, 444 uint64_t Offset) { 445 while (!Ptr->use_empty()) { 446 Instruction *User = cast<Instruction>(Ptr->use_back()); 447 448 if (BitCastInst *CI = dyn_cast<BitCastInst>(User)) { 449 ConvertUsesToScalar(CI, NewAI, Offset); 450 CI->eraseFromParent(); 451 continue; 452 } 453 454 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) { 455 // Compute the offset that this GEP adds to the pointer. 456 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end()); 457 uint64_t GEPOffset = TD.getIndexedOffset(GEP->getPointerOperandType(), 458 &Indices[0], Indices.size()); 459 ConvertUsesToScalar(GEP, NewAI, Offset+GEPOffset*8); 460 GEP->eraseFromParent(); 461 continue; 462 } 463 464 IRBuilder<> Builder(User); 465 466 if (LoadInst *LI = dyn_cast<LoadInst>(User)) { 467 // The load is a bit extract from NewAI shifted right by Offset bits. 468 Value *LoadedVal = Builder.CreateLoad(NewAI, "tmp"); 469 Value *NewLoadVal 470 = ConvertScalar_ExtractValue(LoadedVal, LI->getType(), Offset, Builder); 471 LI->replaceAllUsesWith(NewLoadVal); 472 LI->eraseFromParent(); 473 continue; 474 } 475 476 if (StoreInst *SI = dyn_cast<StoreInst>(User)) { 477 assert(SI->getOperand(0) != Ptr && "Consistency error!"); 478 Instruction *Old = Builder.CreateLoad(NewAI, NewAI->getName()+".in"); 479 Value *New = ConvertScalar_InsertValue(SI->getOperand(0), Old, Offset, 480 Builder); 481 Builder.CreateStore(New, NewAI); 482 SI->eraseFromParent(); 483 484 // If the load we just inserted is now dead, then the inserted store 485 // overwrote the entire thing. 486 if (Old->use_empty()) 487 Old->eraseFromParent(); 488 continue; 489 } 490 491 // If this is a constant sized memset of a constant value (e.g. 0) we can 492 // transform it into a store of the expanded constant value. 493 if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) { 494 assert(MSI->getRawDest() == Ptr && "Consistency error!"); 495 unsigned NumBytes = cast<ConstantInt>(MSI->getLength())->getZExtValue(); 496 if (NumBytes != 0) { 497 unsigned Val = cast<ConstantInt>(MSI->getValue())->getZExtValue(); 498 499 // Compute the value replicated the right number of times. 500 APInt APVal(NumBytes*8, Val); 501 502 // Splat the value if non-zero. 503 if (Val) 504 for (unsigned i = 1; i != NumBytes; ++i) 505 APVal |= APVal << 8; 506 507 Instruction *Old = Builder.CreateLoad(NewAI, NewAI->getName()+".in"); 508 Value *New = ConvertScalar_InsertValue( 509 ConstantInt::get(User->getContext(), APVal), 510 Old, Offset, Builder); 511 Builder.CreateStore(New, NewAI); 512 513 // If the load we just inserted is now dead, then the memset overwrote 514 // the entire thing. 515 if (Old->use_empty()) 516 Old->eraseFromParent(); 517 } 518 MSI->eraseFromParent(); 519 continue; 520 } 521 522 // If this is a memcpy or memmove into or out of the whole allocation, we 523 // can handle it like a load or store of the scalar type. 524 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) { 525 assert(Offset == 0 && "must be store to start of alloca"); 526 527 // If the source and destination are both to the same alloca, then this is 528 // a noop copy-to-self, just delete it. Otherwise, emit a load and store 529 // as appropriate. 530 AllocaInst *OrigAI = cast<AllocaInst>(GetUnderlyingObject(Ptr, 0)); 531 532 if (GetUnderlyingObject(MTI->getSource(), 0) != OrigAI) { 533 // Dest must be OrigAI, change this to be a load from the original 534 // pointer (bitcasted), then a store to our new alloca. 535 assert(MTI->getRawDest() == Ptr && "Neither use is of pointer?"); 536 Value *SrcPtr = MTI->getSource(); 537 const PointerType* SPTy = cast<PointerType>(SrcPtr->getType()); 538 const PointerType* AIPTy = cast<PointerType>(NewAI->getType()); 539 if (SPTy->getAddressSpace() != AIPTy->getAddressSpace()) { 540 AIPTy = PointerType::get(AIPTy->getElementType(), 541 SPTy->getAddressSpace()); 542 } 543 SrcPtr = Builder.CreateBitCast(SrcPtr, AIPTy); 544 545 LoadInst *SrcVal = Builder.CreateLoad(SrcPtr, "srcval"); 546 SrcVal->setAlignment(MTI->getAlignment()); 547 Builder.CreateStore(SrcVal, NewAI); 548 } else if (GetUnderlyingObject(MTI->getDest(), 0) != OrigAI) { 549 // Src must be OrigAI, change this to be a load from NewAI then a store 550 // through the original dest pointer (bitcasted). 551 assert(MTI->getRawSource() == Ptr && "Neither use is of pointer?"); 552 LoadInst *SrcVal = Builder.CreateLoad(NewAI, "srcval"); 553 554 const PointerType* DPTy = cast<PointerType>(MTI->getDest()->getType()); 555 const PointerType* AIPTy = cast<PointerType>(NewAI->getType()); 556 if (DPTy->getAddressSpace() != AIPTy->getAddressSpace()) { 557 AIPTy = PointerType::get(AIPTy->getElementType(), 558 DPTy->getAddressSpace()); 559 } 560 Value *DstPtr = Builder.CreateBitCast(MTI->getDest(), AIPTy); 561 562 StoreInst *NewStore = Builder.CreateStore(SrcVal, DstPtr); 563 NewStore->setAlignment(MTI->getAlignment()); 564 } else { 565 // Noop transfer. Src == Dst 566 } 567 568 MTI->eraseFromParent(); 569 continue; 570 } 571 572 llvm_unreachable("Unsupported operation!"); 573 } 574} 575 576/// ConvertScalar_ExtractValue - Extract a value of type ToType from an integer 577/// or vector value FromVal, extracting the bits from the offset specified by 578/// Offset. This returns the value, which is of type ToType. 579/// 580/// This happens when we are converting an "integer union" to a single 581/// integer scalar, or when we are converting a "vector union" to a vector with 582/// insert/extractelement instructions. 583/// 584/// Offset is an offset from the original alloca, in bits that need to be 585/// shifted to the right. 586Value *ConvertToScalarInfo:: 587ConvertScalar_ExtractValue(Value *FromVal, const Type *ToType, 588 uint64_t Offset, IRBuilder<> &Builder) { 589 // If the load is of the whole new alloca, no conversion is needed. 590 if (FromVal->getType() == ToType && Offset == 0) 591 return FromVal; 592 593 // If the result alloca is a vector type, this is either an element 594 // access or a bitcast to another vector type of the same size. 595 if (const VectorType *VTy = dyn_cast<VectorType>(FromVal->getType())) { 596 if (ToType->isVectorTy()) 597 return Builder.CreateBitCast(FromVal, ToType, "tmp"); 598 599 // Otherwise it must be an element access. 600 unsigned Elt = 0; 601 if (Offset) { 602 unsigned EltSize = TD.getTypeAllocSizeInBits(VTy->getElementType()); 603 Elt = Offset/EltSize; 604 assert(EltSize*Elt == Offset && "Invalid modulus in validity checking"); 605 } 606 // Return the element extracted out of it. 607 Value *V = Builder.CreateExtractElement(FromVal, ConstantInt::get( 608 Type::getInt32Ty(FromVal->getContext()), Elt), "tmp"); 609 if (V->getType() != ToType) 610 V = Builder.CreateBitCast(V, ToType, "tmp"); 611 return V; 612 } 613 614 // If ToType is a first class aggregate, extract out each of the pieces and 615 // use insertvalue's to form the FCA. 616 if (const StructType *ST = dyn_cast<StructType>(ToType)) { 617 const StructLayout &Layout = *TD.getStructLayout(ST); 618 Value *Res = UndefValue::get(ST); 619 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) { 620 Value *Elt = ConvertScalar_ExtractValue(FromVal, ST->getElementType(i), 621 Offset+Layout.getElementOffsetInBits(i), 622 Builder); 623 Res = Builder.CreateInsertValue(Res, Elt, i, "tmp"); 624 } 625 return Res; 626 } 627 628 if (const ArrayType *AT = dyn_cast<ArrayType>(ToType)) { 629 uint64_t EltSize = TD.getTypeAllocSizeInBits(AT->getElementType()); 630 Value *Res = UndefValue::get(AT); 631 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) { 632 Value *Elt = ConvertScalar_ExtractValue(FromVal, AT->getElementType(), 633 Offset+i*EltSize, Builder); 634 Res = Builder.CreateInsertValue(Res, Elt, i, "tmp"); 635 } 636 return Res; 637 } 638 639 // Otherwise, this must be a union that was converted to an integer value. 640 const IntegerType *NTy = cast<IntegerType>(FromVal->getType()); 641 642 // If this is a big-endian system and the load is narrower than the 643 // full alloca type, we need to do a shift to get the right bits. 644 int ShAmt = 0; 645 if (TD.isBigEndian()) { 646 // On big-endian machines, the lowest bit is stored at the bit offset 647 // from the pointer given by getTypeStoreSizeInBits. This matters for 648 // integers with a bitwidth that is not a multiple of 8. 649 ShAmt = TD.getTypeStoreSizeInBits(NTy) - 650 TD.getTypeStoreSizeInBits(ToType) - Offset; 651 } else { 652 ShAmt = Offset; 653 } 654 655 // Note: we support negative bitwidths (with shl) which are not defined. 656 // We do this to support (f.e.) loads off the end of a structure where 657 // only some bits are used. 658 if (ShAmt > 0 && (unsigned)ShAmt < NTy->getBitWidth()) 659 FromVal = Builder.CreateLShr(FromVal, 660 ConstantInt::get(FromVal->getType(), 661 ShAmt), "tmp"); 662 else if (ShAmt < 0 && (unsigned)-ShAmt < NTy->getBitWidth()) 663 FromVal = Builder.CreateShl(FromVal, 664 ConstantInt::get(FromVal->getType(), 665 -ShAmt), "tmp"); 666 667 // Finally, unconditionally truncate the integer to the right width. 668 unsigned LIBitWidth = TD.getTypeSizeInBits(ToType); 669 if (LIBitWidth < NTy->getBitWidth()) 670 FromVal = 671 Builder.CreateTrunc(FromVal, IntegerType::get(FromVal->getContext(), 672 LIBitWidth), "tmp"); 673 else if (LIBitWidth > NTy->getBitWidth()) 674 FromVal = 675 Builder.CreateZExt(FromVal, IntegerType::get(FromVal->getContext(), 676 LIBitWidth), "tmp"); 677 678 // If the result is an integer, this is a trunc or bitcast. 679 if (ToType->isIntegerTy()) { 680 // Should be done. 681 } else if (ToType->isFloatingPointTy() || ToType->isVectorTy()) { 682 // Just do a bitcast, we know the sizes match up. 683 FromVal = Builder.CreateBitCast(FromVal, ToType, "tmp"); 684 } else { 685 // Otherwise must be a pointer. 686 FromVal = Builder.CreateIntToPtr(FromVal, ToType, "tmp"); 687 } 688 assert(FromVal->getType() == ToType && "Didn't convert right?"); 689 return FromVal; 690} 691 692/// ConvertScalar_InsertValue - Insert the value "SV" into the existing integer 693/// or vector value "Old" at the offset specified by Offset. 694/// 695/// This happens when we are converting an "integer union" to a 696/// single integer scalar, or when we are converting a "vector union" to a 697/// vector with insert/extractelement instructions. 698/// 699/// Offset is an offset from the original alloca, in bits that need to be 700/// shifted to the right. 701Value *ConvertToScalarInfo:: 702ConvertScalar_InsertValue(Value *SV, Value *Old, 703 uint64_t Offset, IRBuilder<> &Builder) { 704 // Convert the stored type to the actual type, shift it left to insert 705 // then 'or' into place. 706 const Type *AllocaType = Old->getType(); 707 LLVMContext &Context = Old->getContext(); 708 709 if (const VectorType *VTy = dyn_cast<VectorType>(AllocaType)) { 710 uint64_t VecSize = TD.getTypeAllocSizeInBits(VTy); 711 uint64_t ValSize = TD.getTypeAllocSizeInBits(SV->getType()); 712 713 // Changing the whole vector with memset or with an access of a different 714 // vector type? 715 if (ValSize == VecSize) 716 return Builder.CreateBitCast(SV, AllocaType, "tmp"); 717 718 uint64_t EltSize = TD.getTypeAllocSizeInBits(VTy->getElementType()); 719 720 // Must be an element insertion. 721 unsigned Elt = Offset/EltSize; 722 723 if (SV->getType() != VTy->getElementType()) 724 SV = Builder.CreateBitCast(SV, VTy->getElementType(), "tmp"); 725 726 SV = Builder.CreateInsertElement(Old, SV, 727 ConstantInt::get(Type::getInt32Ty(SV->getContext()), Elt), 728 "tmp"); 729 return SV; 730 } 731 732 // If SV is a first-class aggregate value, insert each value recursively. 733 if (const StructType *ST = dyn_cast<StructType>(SV->getType())) { 734 const StructLayout &Layout = *TD.getStructLayout(ST); 735 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) { 736 Value *Elt = Builder.CreateExtractValue(SV, i, "tmp"); 737 Old = ConvertScalar_InsertValue(Elt, Old, 738 Offset+Layout.getElementOffsetInBits(i), 739 Builder); 740 } 741 return Old; 742 } 743 744 if (const ArrayType *AT = dyn_cast<ArrayType>(SV->getType())) { 745 uint64_t EltSize = TD.getTypeAllocSizeInBits(AT->getElementType()); 746 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) { 747 Value *Elt = Builder.CreateExtractValue(SV, i, "tmp"); 748 Old = ConvertScalar_InsertValue(Elt, Old, Offset+i*EltSize, Builder); 749 } 750 return Old; 751 } 752 753 // If SV is a float, convert it to the appropriate integer type. 754 // If it is a pointer, do the same. 755 unsigned SrcWidth = TD.getTypeSizeInBits(SV->getType()); 756 unsigned DestWidth = TD.getTypeSizeInBits(AllocaType); 757 unsigned SrcStoreWidth = TD.getTypeStoreSizeInBits(SV->getType()); 758 unsigned DestStoreWidth = TD.getTypeStoreSizeInBits(AllocaType); 759 if (SV->getType()->isFloatingPointTy() || SV->getType()->isVectorTy()) 760 SV = Builder.CreateBitCast(SV, 761 IntegerType::get(SV->getContext(),SrcWidth), "tmp"); 762 else if (SV->getType()->isPointerTy()) 763 SV = Builder.CreatePtrToInt(SV, TD.getIntPtrType(SV->getContext()), "tmp"); 764 765 // Zero extend or truncate the value if needed. 766 if (SV->getType() != AllocaType) { 767 if (SV->getType()->getPrimitiveSizeInBits() < 768 AllocaType->getPrimitiveSizeInBits()) 769 SV = Builder.CreateZExt(SV, AllocaType, "tmp"); 770 else { 771 // Truncation may be needed if storing more than the alloca can hold 772 // (undefined behavior). 773 SV = Builder.CreateTrunc(SV, AllocaType, "tmp"); 774 SrcWidth = DestWidth; 775 SrcStoreWidth = DestStoreWidth; 776 } 777 } 778 779 // If this is a big-endian system and the store is narrower than the 780 // full alloca type, we need to do a shift to get the right bits. 781 int ShAmt = 0; 782 if (TD.isBigEndian()) { 783 // On big-endian machines, the lowest bit is stored at the bit offset 784 // from the pointer given by getTypeStoreSizeInBits. This matters for 785 // integers with a bitwidth that is not a multiple of 8. 786 ShAmt = DestStoreWidth - SrcStoreWidth - Offset; 787 } else { 788 ShAmt = Offset; 789 } 790 791 // Note: we support negative bitwidths (with shr) which are not defined. 792 // We do this to support (f.e.) stores off the end of a structure where 793 // only some bits in the structure are set. 794 APInt Mask(APInt::getLowBitsSet(DestWidth, SrcWidth)); 795 if (ShAmt > 0 && (unsigned)ShAmt < DestWidth) { 796 SV = Builder.CreateShl(SV, ConstantInt::get(SV->getType(), 797 ShAmt), "tmp"); 798 Mask <<= ShAmt; 799 } else if (ShAmt < 0 && (unsigned)-ShAmt < DestWidth) { 800 SV = Builder.CreateLShr(SV, ConstantInt::get(SV->getType(), 801 -ShAmt), "tmp"); 802 Mask = Mask.lshr(-ShAmt); 803 } 804 805 // Mask out the bits we are about to insert from the old value, and or 806 // in the new bits. 807 if (SrcWidth != DestWidth) { 808 assert(DestWidth > SrcWidth); 809 Old = Builder.CreateAnd(Old, ConstantInt::get(Context, ~Mask), "mask"); 810 SV = Builder.CreateOr(Old, SV, "ins"); 811 } 812 return SV; 813} 814 815 816//===----------------------------------------------------------------------===// 817// SRoA Driver 818//===----------------------------------------------------------------------===// 819 820 821bool SROA::runOnFunction(Function &F) { 822 TD = getAnalysisIfAvailable<TargetData>(); 823 824 bool Changed = performPromotion(F); 825 826 // FIXME: ScalarRepl currently depends on TargetData more than it 827 // theoretically needs to. It should be refactored in order to support 828 // target-independent IR. Until this is done, just skip the actual 829 // scalar-replacement portion of this pass. 830 if (!TD) return Changed; 831 832 while (1) { 833 bool LocalChange = performScalarRepl(F); 834 if (!LocalChange) break; // No need to repromote if no scalarrepl 835 Changed = true; 836 LocalChange = performPromotion(F); 837 if (!LocalChange) break; // No need to re-scalarrepl if no promotion 838 } 839 840 return Changed; 841} 842 843namespace { 844class AllocaPromoter : public LoadAndStorePromoter { 845 AllocaInst *AI; 846public: 847 AllocaPromoter() : AI(0) {} 848 849 void run(AllocaInst *AI, SSAUpdater &SSA) { 850 // Remember which alloca we're promoting (for isInstInList). 851 this->AI = AI; 852 853 // Build the list of instructions to promote. 854 SmallVector<Instruction*, 64> Insts; 855 for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end(); 856 UI != E; ++UI) 857 Insts.push_back(cast<Instruction>(*UI)); 858 859 LoadAndStorePromoter::run(AI->getName(), Insts, &SSA); 860 861 AI->eraseFromParent(); 862 } 863 864 virtual bool isInstInList(Instruction *I, 865 const SmallVectorImpl<Instruction*> &Insts) const { 866 if (LoadInst *LI = dyn_cast<LoadInst>(I)) 867 return LI->getOperand(0) == AI; 868 return cast<StoreInst>(I)->getPointerOperand() == AI; 869 } 870}; 871} // end anon namespace 872 873bool SROA::performPromotion(Function &F) { 874 std::vector<AllocaInst*> Allocas; 875 DominatorTree *DT = 0; 876 DominanceFrontier *DF = 0; 877 if (HasDomFrontiers) { 878 DT = &getAnalysis<DominatorTree>(); 879 DF = &getAnalysis<DominanceFrontier>(); 880 } 881 882 BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function 883 884 bool Changed = false; 885 886 while (1) { 887 Allocas.clear(); 888 889 // Find allocas that are safe to promote, by looking at all instructions in 890 // the entry node 891 for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I) 892 if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) // Is it an alloca? 893 if (isAllocaPromotable(AI)) 894 Allocas.push_back(AI); 895 896 if (Allocas.empty()) break; 897 898 if (HasDomFrontiers) 899 PromoteMemToReg(Allocas, *DT, *DF); 900 else { 901 SSAUpdater SSA; 902 AllocaPromoter Promoter; 903 for (unsigned i = 0, e = Allocas.size(); i != e; ++i) 904 Promoter.run(Allocas[i], SSA); 905 } 906 NumPromoted += Allocas.size(); 907 Changed = true; 908 } 909 910 return Changed; 911} 912 913 914/// ShouldAttemptScalarRepl - Decide if an alloca is a good candidate for 915/// SROA. It must be a struct or array type with a small number of elements. 916static bool ShouldAttemptScalarRepl(AllocaInst *AI) { 917 const Type *T = AI->getAllocatedType(); 918 // Do not promote any struct into more than 32 separate vars. 919 if (const StructType *ST = dyn_cast<StructType>(T)) 920 return ST->getNumElements() <= 32; 921 // Arrays are much less likely to be safe for SROA; only consider 922 // them if they are very small. 923 if (const ArrayType *AT = dyn_cast<ArrayType>(T)) 924 return AT->getNumElements() <= 8; 925 return false; 926} 927 928 929// performScalarRepl - This algorithm is a simple worklist driven algorithm, 930// which runs on all of the malloc/alloca instructions in the function, removing 931// them if they are only used by getelementptr instructions. 932// 933bool SROA::performScalarRepl(Function &F) { 934 std::vector<AllocaInst*> WorkList; 935 936 // Scan the entry basic block, adding allocas to the worklist. 937 BasicBlock &BB = F.getEntryBlock(); 938 for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I) 939 if (AllocaInst *A = dyn_cast<AllocaInst>(I)) 940 WorkList.push_back(A); 941 942 // Process the worklist 943 bool Changed = false; 944 while (!WorkList.empty()) { 945 AllocaInst *AI = WorkList.back(); 946 WorkList.pop_back(); 947 948 // Handle dead allocas trivially. These can be formed by SROA'ing arrays 949 // with unused elements. 950 if (AI->use_empty()) { 951 AI->eraseFromParent(); 952 Changed = true; 953 continue; 954 } 955 956 // If this alloca is impossible for us to promote, reject it early. 957 if (AI->isArrayAllocation() || !AI->getAllocatedType()->isSized()) 958 continue; 959 960 // Check to see if this allocation is only modified by a memcpy/memmove from 961 // a constant global. If this is the case, we can change all users to use 962 // the constant global instead. This is commonly produced by the CFE by 963 // constructs like "void foo() { int A[] = {1,2,3,4,5,6,7,8,9...}; }" if 'A' 964 // is only subsequently read. 965 if (MemTransferInst *TheCopy = isOnlyCopiedFromConstantGlobal(AI)) { 966 DEBUG(dbgs() << "Found alloca equal to global: " << *AI << '\n'); 967 DEBUG(dbgs() << " memcpy = " << *TheCopy << '\n'); 968 Constant *TheSrc = cast<Constant>(TheCopy->getSource()); 969 AI->replaceAllUsesWith(ConstantExpr::getBitCast(TheSrc, AI->getType())); 970 TheCopy->eraseFromParent(); // Don't mutate the global. 971 AI->eraseFromParent(); 972 ++NumGlobals; 973 Changed = true; 974 continue; 975 } 976 977 // Check to see if we can perform the core SROA transformation. We cannot 978 // transform the allocation instruction if it is an array allocation 979 // (allocations OF arrays are ok though), and an allocation of a scalar 980 // value cannot be decomposed at all. 981 uint64_t AllocaSize = TD->getTypeAllocSize(AI->getAllocatedType()); 982 983 // Do not promote [0 x %struct]. 984 if (AllocaSize == 0) continue; 985 986 // Do not promote any struct whose size is too big. 987 if (AllocaSize > SRThreshold) continue; 988 989 // If the alloca looks like a good candidate for scalar replacement, and if 990 // all its users can be transformed, then split up the aggregate into its 991 // separate elements. 992 if (ShouldAttemptScalarRepl(AI) && isSafeAllocaToScalarRepl(AI)) { 993 DoScalarReplacement(AI, WorkList); 994 Changed = true; 995 continue; 996 } 997 998 // If we can turn this aggregate value (potentially with casts) into a 999 // simple scalar value that can be mem2reg'd into a register value. 1000 // IsNotTrivial tracks whether this is something that mem2reg could have 1001 // promoted itself. If so, we don't want to transform it needlessly. Note 1002 // that we can't just check based on the type: the alloca may be of an i32 1003 // but that has pointer arithmetic to set byte 3 of it or something. 1004 if (AllocaInst *NewAI = 1005 ConvertToScalarInfo((unsigned)AllocaSize, *TD).TryConvert(AI)) { 1006 NewAI->takeName(AI); 1007 AI->eraseFromParent(); 1008 ++NumConverted; 1009 Changed = true; 1010 continue; 1011 } 1012 1013 // Otherwise, couldn't process this alloca. 1014 } 1015 1016 return Changed; 1017} 1018 1019/// DoScalarReplacement - This alloca satisfied the isSafeAllocaToScalarRepl 1020/// predicate, do SROA now. 1021void SROA::DoScalarReplacement(AllocaInst *AI, 1022 std::vector<AllocaInst*> &WorkList) { 1023 DEBUG(dbgs() << "Found inst to SROA: " << *AI << '\n'); 1024 SmallVector<AllocaInst*, 32> ElementAllocas; 1025 if (const StructType *ST = dyn_cast<StructType>(AI->getAllocatedType())) { 1026 ElementAllocas.reserve(ST->getNumContainedTypes()); 1027 for (unsigned i = 0, e = ST->getNumContainedTypes(); i != e; ++i) { 1028 AllocaInst *NA = new AllocaInst(ST->getContainedType(i), 0, 1029 AI->getAlignment(), 1030 AI->getName() + "." + Twine(i), AI); 1031 ElementAllocas.push_back(NA); 1032 WorkList.push_back(NA); // Add to worklist for recursive processing 1033 } 1034 } else { 1035 const ArrayType *AT = cast<ArrayType>(AI->getAllocatedType()); 1036 ElementAllocas.reserve(AT->getNumElements()); 1037 const Type *ElTy = AT->getElementType(); 1038 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) { 1039 AllocaInst *NA = new AllocaInst(ElTy, 0, AI->getAlignment(), 1040 AI->getName() + "." + Twine(i), AI); 1041 ElementAllocas.push_back(NA); 1042 WorkList.push_back(NA); // Add to worklist for recursive processing 1043 } 1044 } 1045 1046 // Now that we have created the new alloca instructions, rewrite all the 1047 // uses of the old alloca. 1048 RewriteForScalarRepl(AI, AI, 0, ElementAllocas); 1049 1050 // Now erase any instructions that were made dead while rewriting the alloca. 1051 DeleteDeadInstructions(); 1052 AI->eraseFromParent(); 1053 1054 ++NumReplaced; 1055} 1056 1057/// DeleteDeadInstructions - Erase instructions on the DeadInstrs list, 1058/// recursively including all their operands that become trivially dead. 1059void SROA::DeleteDeadInstructions() { 1060 while (!DeadInsts.empty()) { 1061 Instruction *I = cast<Instruction>(DeadInsts.pop_back_val()); 1062 1063 for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI) 1064 if (Instruction *U = dyn_cast<Instruction>(*OI)) { 1065 // Zero out the operand and see if it becomes trivially dead. 1066 // (But, don't add allocas to the dead instruction list -- they are 1067 // already on the worklist and will be deleted separately.) 1068 *OI = 0; 1069 if (isInstructionTriviallyDead(U) && !isa<AllocaInst>(U)) 1070 DeadInsts.push_back(U); 1071 } 1072 1073 I->eraseFromParent(); 1074 } 1075} 1076 1077/// isSafeForScalarRepl - Check if instruction I is a safe use with regard to 1078/// performing scalar replacement of alloca AI. The results are flagged in 1079/// the Info parameter. Offset indicates the position within AI that is 1080/// referenced by this instruction. 1081void SROA::isSafeForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset, 1082 AllocaInfo &Info) { 1083 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E; ++UI) { 1084 Instruction *User = cast<Instruction>(*UI); 1085 1086 if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) { 1087 isSafeForScalarRepl(BC, AI, Offset, Info); 1088 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) { 1089 uint64_t GEPOffset = Offset; 1090 isSafeGEP(GEPI, AI, GEPOffset, Info); 1091 if (!Info.isUnsafe) 1092 isSafeForScalarRepl(GEPI, AI, GEPOffset, Info); 1093 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) { 1094 ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength()); 1095 if (Length) 1096 isSafeMemAccess(AI, Offset, Length->getZExtValue(), 0, 1097 UI.getOperandNo() == 0, Info); 1098 else 1099 MarkUnsafe(Info); 1100 } else if (LoadInst *LI = dyn_cast<LoadInst>(User)) { 1101 if (!LI->isVolatile()) { 1102 const Type *LIType = LI->getType(); 1103 isSafeMemAccess(AI, Offset, TD->getTypeAllocSize(LIType), 1104 LIType, false, Info); 1105 } else 1106 MarkUnsafe(Info); 1107 } else if (StoreInst *SI = dyn_cast<StoreInst>(User)) { 1108 // Store is ok if storing INTO the pointer, not storing the pointer 1109 if (!SI->isVolatile() && SI->getOperand(0) != I) { 1110 const Type *SIType = SI->getOperand(0)->getType(); 1111 isSafeMemAccess(AI, Offset, TD->getTypeAllocSize(SIType), 1112 SIType, true, Info); 1113 } else 1114 MarkUnsafe(Info); 1115 } else { 1116 DEBUG(errs() << " Transformation preventing inst: " << *User << '\n'); 1117 MarkUnsafe(Info); 1118 } 1119 if (Info.isUnsafe) return; 1120 } 1121} 1122 1123/// isSafeGEP - Check if a GEP instruction can be handled for scalar 1124/// replacement. It is safe when all the indices are constant, in-bounds 1125/// references, and when the resulting offset corresponds to an element within 1126/// the alloca type. The results are flagged in the Info parameter. Upon 1127/// return, Offset is adjusted as specified by the GEP indices. 1128void SROA::isSafeGEP(GetElementPtrInst *GEPI, AllocaInst *AI, 1129 uint64_t &Offset, AllocaInfo &Info) { 1130 gep_type_iterator GEPIt = gep_type_begin(GEPI), E = gep_type_end(GEPI); 1131 if (GEPIt == E) 1132 return; 1133 1134 // Walk through the GEP type indices, checking the types that this indexes 1135 // into. 1136 for (; GEPIt != E; ++GEPIt) { 1137 // Ignore struct elements, no extra checking needed for these. 1138 if ((*GEPIt)->isStructTy()) 1139 continue; 1140 1141 ConstantInt *IdxVal = dyn_cast<ConstantInt>(GEPIt.getOperand()); 1142 if (!IdxVal) 1143 return MarkUnsafe(Info); 1144 } 1145 1146 // Compute the offset due to this GEP and check if the alloca has a 1147 // component element at that offset. 1148 SmallVector<Value*, 8> Indices(GEPI->op_begin() + 1, GEPI->op_end()); 1149 Offset += TD->getIndexedOffset(GEPI->getPointerOperandType(), 1150 &Indices[0], Indices.size()); 1151 if (!TypeHasComponent(AI->getAllocatedType(), Offset, 0)) 1152 MarkUnsafe(Info); 1153} 1154 1155/// isHomogeneousAggregate - Check if type T is a struct or array containing 1156/// elements of the same type (which is always true for arrays). If so, 1157/// return true with NumElts and EltTy set to the number of elements and the 1158/// element type, respectively. 1159static bool isHomogeneousAggregate(const Type *T, unsigned &NumElts, 1160 const Type *&EltTy) { 1161 if (const ArrayType *AT = dyn_cast<ArrayType>(T)) { 1162 NumElts = AT->getNumElements(); 1163 EltTy = (NumElts == 0 ? 0 : AT->getElementType()); 1164 return true; 1165 } 1166 if (const StructType *ST = dyn_cast<StructType>(T)) { 1167 NumElts = ST->getNumContainedTypes(); 1168 EltTy = (NumElts == 0 ? 0 : ST->getContainedType(0)); 1169 for (unsigned n = 1; n < NumElts; ++n) { 1170 if (ST->getContainedType(n) != EltTy) 1171 return false; 1172 } 1173 return true; 1174 } 1175 return false; 1176} 1177 1178/// isCompatibleAggregate - Check if T1 and T2 are either the same type or are 1179/// "homogeneous" aggregates with the same element type and number of elements. 1180static bool isCompatibleAggregate(const Type *T1, const Type *T2) { 1181 if (T1 == T2) 1182 return true; 1183 1184 unsigned NumElts1, NumElts2; 1185 const Type *EltTy1, *EltTy2; 1186 if (isHomogeneousAggregate(T1, NumElts1, EltTy1) && 1187 isHomogeneousAggregate(T2, NumElts2, EltTy2) && 1188 NumElts1 == NumElts2 && 1189 EltTy1 == EltTy2) 1190 return true; 1191 1192 return false; 1193} 1194 1195/// isSafeMemAccess - Check if a load/store/memcpy operates on the entire AI 1196/// alloca or has an offset and size that corresponds to a component element 1197/// within it. The offset checked here may have been formed from a GEP with a 1198/// pointer bitcasted to a different type. 1199void SROA::isSafeMemAccess(AllocaInst *AI, uint64_t Offset, uint64_t MemSize, 1200 const Type *MemOpType, bool isStore, 1201 AllocaInfo &Info) { 1202 // Check if this is a load/store of the entire alloca. 1203 if (Offset == 0 && MemSize == TD->getTypeAllocSize(AI->getAllocatedType())) { 1204 // This can be safe for MemIntrinsics (where MemOpType is 0) and integer 1205 // loads/stores (which are essentially the same as the MemIntrinsics with 1206 // regard to copying padding between elements). But, if an alloca is 1207 // flagged as both a source and destination of such operations, we'll need 1208 // to check later for padding between elements. 1209 if (!MemOpType || MemOpType->isIntegerTy()) { 1210 if (isStore) 1211 Info.isMemCpyDst = true; 1212 else 1213 Info.isMemCpySrc = true; 1214 return; 1215 } 1216 // This is also safe for references using a type that is compatible with 1217 // the type of the alloca, so that loads/stores can be rewritten using 1218 // insertvalue/extractvalue. 1219 if (isCompatibleAggregate(MemOpType, AI->getAllocatedType())) 1220 return; 1221 } 1222 // Check if the offset/size correspond to a component within the alloca type. 1223 const Type *T = AI->getAllocatedType(); 1224 if (TypeHasComponent(T, Offset, MemSize)) 1225 return; 1226 1227 return MarkUnsafe(Info); 1228} 1229 1230/// TypeHasComponent - Return true if T has a component type with the 1231/// specified offset and size. If Size is zero, do not check the size. 1232bool SROA::TypeHasComponent(const Type *T, uint64_t Offset, uint64_t Size) { 1233 const Type *EltTy; 1234 uint64_t EltSize; 1235 if (const StructType *ST = dyn_cast<StructType>(T)) { 1236 const StructLayout *Layout = TD->getStructLayout(ST); 1237 unsigned EltIdx = Layout->getElementContainingOffset(Offset); 1238 EltTy = ST->getContainedType(EltIdx); 1239 EltSize = TD->getTypeAllocSize(EltTy); 1240 Offset -= Layout->getElementOffset(EltIdx); 1241 } else if (const ArrayType *AT = dyn_cast<ArrayType>(T)) { 1242 EltTy = AT->getElementType(); 1243 EltSize = TD->getTypeAllocSize(EltTy); 1244 if (Offset >= AT->getNumElements() * EltSize) 1245 return false; 1246 Offset %= EltSize; 1247 } else { 1248 return false; 1249 } 1250 if (Offset == 0 && (Size == 0 || EltSize == Size)) 1251 return true; 1252 // Check if the component spans multiple elements. 1253 if (Offset + Size > EltSize) 1254 return false; 1255 return TypeHasComponent(EltTy, Offset, Size); 1256} 1257 1258/// RewriteForScalarRepl - Alloca AI is being split into NewElts, so rewrite 1259/// the instruction I, which references it, to use the separate elements. 1260/// Offset indicates the position within AI that is referenced by this 1261/// instruction. 1262void SROA::RewriteForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset, 1263 SmallVector<AllocaInst*, 32> &NewElts) { 1264 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E; ++UI) { 1265 Instruction *User = cast<Instruction>(*UI); 1266 1267 if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) { 1268 RewriteBitCast(BC, AI, Offset, NewElts); 1269 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) { 1270 RewriteGEP(GEPI, AI, Offset, NewElts); 1271 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) { 1272 ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength()); 1273 uint64_t MemSize = Length->getZExtValue(); 1274 if (Offset == 0 && 1275 MemSize == TD->getTypeAllocSize(AI->getAllocatedType())) 1276 RewriteMemIntrinUserOfAlloca(MI, I, AI, NewElts); 1277 // Otherwise the intrinsic can only touch a single element and the 1278 // address operand will be updated, so nothing else needs to be done. 1279 } else if (LoadInst *LI = dyn_cast<LoadInst>(User)) { 1280 const Type *LIType = LI->getType(); 1281 if (isCompatibleAggregate(LIType, AI->getAllocatedType())) { 1282 // Replace: 1283 // %res = load { i32, i32 }* %alloc 1284 // with: 1285 // %load.0 = load i32* %alloc.0 1286 // %insert.0 insertvalue { i32, i32 } zeroinitializer, i32 %load.0, 0 1287 // %load.1 = load i32* %alloc.1 1288 // %insert = insertvalue { i32, i32 } %insert.0, i32 %load.1, 1 1289 // (Also works for arrays instead of structs) 1290 Value *Insert = UndefValue::get(LIType); 1291 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { 1292 Value *Load = new LoadInst(NewElts[i], "load", LI); 1293 Insert = InsertValueInst::Create(Insert, Load, i, "insert", LI); 1294 } 1295 LI->replaceAllUsesWith(Insert); 1296 DeadInsts.push_back(LI); 1297 } else if (LIType->isIntegerTy() && 1298 TD->getTypeAllocSize(LIType) == 1299 TD->getTypeAllocSize(AI->getAllocatedType())) { 1300 // If this is a load of the entire alloca to an integer, rewrite it. 1301 RewriteLoadUserOfWholeAlloca(LI, AI, NewElts); 1302 } 1303 } else if (StoreInst *SI = dyn_cast<StoreInst>(User)) { 1304 Value *Val = SI->getOperand(0); 1305 const Type *SIType = Val->getType(); 1306 if (isCompatibleAggregate(SIType, AI->getAllocatedType())) { 1307 // Replace: 1308 // store { i32, i32 } %val, { i32, i32 }* %alloc 1309 // with: 1310 // %val.0 = extractvalue { i32, i32 } %val, 0 1311 // store i32 %val.0, i32* %alloc.0 1312 // %val.1 = extractvalue { i32, i32 } %val, 1 1313 // store i32 %val.1, i32* %alloc.1 1314 // (Also works for arrays instead of structs) 1315 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { 1316 Value *Extract = ExtractValueInst::Create(Val, i, Val->getName(), SI); 1317 new StoreInst(Extract, NewElts[i], SI); 1318 } 1319 DeadInsts.push_back(SI); 1320 } else if (SIType->isIntegerTy() && 1321 TD->getTypeAllocSize(SIType) == 1322 TD->getTypeAllocSize(AI->getAllocatedType())) { 1323 // If this is a store of the entire alloca from an integer, rewrite it. 1324 RewriteStoreUserOfWholeAlloca(SI, AI, NewElts); 1325 } 1326 } 1327 } 1328} 1329 1330/// RewriteBitCast - Update a bitcast reference to the alloca being replaced 1331/// and recursively continue updating all of its uses. 1332void SROA::RewriteBitCast(BitCastInst *BC, AllocaInst *AI, uint64_t Offset, 1333 SmallVector<AllocaInst*, 32> &NewElts) { 1334 RewriteForScalarRepl(BC, AI, Offset, NewElts); 1335 if (BC->getOperand(0) != AI) 1336 return; 1337 1338 // The bitcast references the original alloca. Replace its uses with 1339 // references to the first new element alloca. 1340 Instruction *Val = NewElts[0]; 1341 if (Val->getType() != BC->getDestTy()) { 1342 Val = new BitCastInst(Val, BC->getDestTy(), "", BC); 1343 Val->takeName(BC); 1344 } 1345 BC->replaceAllUsesWith(Val); 1346 DeadInsts.push_back(BC); 1347} 1348 1349/// FindElementAndOffset - Return the index of the element containing Offset 1350/// within the specified type, which must be either a struct or an array. 1351/// Sets T to the type of the element and Offset to the offset within that 1352/// element. IdxTy is set to the type of the index result to be used in a 1353/// GEP instruction. 1354uint64_t SROA::FindElementAndOffset(const Type *&T, uint64_t &Offset, 1355 const Type *&IdxTy) { 1356 uint64_t Idx = 0; 1357 if (const StructType *ST = dyn_cast<StructType>(T)) { 1358 const StructLayout *Layout = TD->getStructLayout(ST); 1359 Idx = Layout->getElementContainingOffset(Offset); 1360 T = ST->getContainedType(Idx); 1361 Offset -= Layout->getElementOffset(Idx); 1362 IdxTy = Type::getInt32Ty(T->getContext()); 1363 return Idx; 1364 } 1365 const ArrayType *AT = cast<ArrayType>(T); 1366 T = AT->getElementType(); 1367 uint64_t EltSize = TD->getTypeAllocSize(T); 1368 Idx = Offset / EltSize; 1369 Offset -= Idx * EltSize; 1370 IdxTy = Type::getInt64Ty(T->getContext()); 1371 return Idx; 1372} 1373 1374/// RewriteGEP - Check if this GEP instruction moves the pointer across 1375/// elements of the alloca that are being split apart, and if so, rewrite 1376/// the GEP to be relative to the new element. 1377void SROA::RewriteGEP(GetElementPtrInst *GEPI, AllocaInst *AI, uint64_t Offset, 1378 SmallVector<AllocaInst*, 32> &NewElts) { 1379 uint64_t OldOffset = Offset; 1380 SmallVector<Value*, 8> Indices(GEPI->op_begin() + 1, GEPI->op_end()); 1381 Offset += TD->getIndexedOffset(GEPI->getPointerOperandType(), 1382 &Indices[0], Indices.size()); 1383 1384 RewriteForScalarRepl(GEPI, AI, Offset, NewElts); 1385 1386 const Type *T = AI->getAllocatedType(); 1387 const Type *IdxTy; 1388 uint64_t OldIdx = FindElementAndOffset(T, OldOffset, IdxTy); 1389 if (GEPI->getOperand(0) == AI) 1390 OldIdx = ~0ULL; // Force the GEP to be rewritten. 1391 1392 T = AI->getAllocatedType(); 1393 uint64_t EltOffset = Offset; 1394 uint64_t Idx = FindElementAndOffset(T, EltOffset, IdxTy); 1395 1396 // If this GEP does not move the pointer across elements of the alloca 1397 // being split, then it does not needs to be rewritten. 1398 if (Idx == OldIdx) 1399 return; 1400 1401 const Type *i32Ty = Type::getInt32Ty(AI->getContext()); 1402 SmallVector<Value*, 8> NewArgs; 1403 NewArgs.push_back(Constant::getNullValue(i32Ty)); 1404 while (EltOffset != 0) { 1405 uint64_t EltIdx = FindElementAndOffset(T, EltOffset, IdxTy); 1406 NewArgs.push_back(ConstantInt::get(IdxTy, EltIdx)); 1407 } 1408 Instruction *Val = NewElts[Idx]; 1409 if (NewArgs.size() > 1) { 1410 Val = GetElementPtrInst::CreateInBounds(Val, NewArgs.begin(), 1411 NewArgs.end(), "", GEPI); 1412 Val->takeName(GEPI); 1413 } 1414 if (Val->getType() != GEPI->getType()) 1415 Val = new BitCastInst(Val, GEPI->getType(), Val->getName(), GEPI); 1416 GEPI->replaceAllUsesWith(Val); 1417 DeadInsts.push_back(GEPI); 1418} 1419 1420/// RewriteMemIntrinUserOfAlloca - MI is a memcpy/memset/memmove from or to AI. 1421/// Rewrite it to copy or set the elements of the scalarized memory. 1422void SROA::RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *Inst, 1423 AllocaInst *AI, 1424 SmallVector<AllocaInst*, 32> &NewElts) { 1425 // If this is a memcpy/memmove, construct the other pointer as the 1426 // appropriate type. The "Other" pointer is the pointer that goes to memory 1427 // that doesn't have anything to do with the alloca that we are promoting. For 1428 // memset, this Value* stays null. 1429 Value *OtherPtr = 0; 1430 unsigned MemAlignment = MI->getAlignment(); 1431 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(MI)) { // memmove/memcopy 1432 if (Inst == MTI->getRawDest()) 1433 OtherPtr = MTI->getRawSource(); 1434 else { 1435 assert(Inst == MTI->getRawSource()); 1436 OtherPtr = MTI->getRawDest(); 1437 } 1438 } 1439 1440 // If there is an other pointer, we want to convert it to the same pointer 1441 // type as AI has, so we can GEP through it safely. 1442 if (OtherPtr) { 1443 unsigned AddrSpace = 1444 cast<PointerType>(OtherPtr->getType())->getAddressSpace(); 1445 1446 // Remove bitcasts and all-zero GEPs from OtherPtr. This is an 1447 // optimization, but it's also required to detect the corner case where 1448 // both pointer operands are referencing the same memory, and where 1449 // OtherPtr may be a bitcast or GEP that currently being rewritten. (This 1450 // function is only called for mem intrinsics that access the whole 1451 // aggregate, so non-zero GEPs are not an issue here.) 1452 OtherPtr = OtherPtr->stripPointerCasts(); 1453 1454 // Copying the alloca to itself is a no-op: just delete it. 1455 if (OtherPtr == AI || OtherPtr == NewElts[0]) { 1456 // This code will run twice for a no-op memcpy -- once for each operand. 1457 // Put only one reference to MI on the DeadInsts list. 1458 for (SmallVector<Value*, 32>::const_iterator I = DeadInsts.begin(), 1459 E = DeadInsts.end(); I != E; ++I) 1460 if (*I == MI) return; 1461 DeadInsts.push_back(MI); 1462 return; 1463 } 1464 1465 // If the pointer is not the right type, insert a bitcast to the right 1466 // type. 1467 const Type *NewTy = 1468 PointerType::get(AI->getType()->getElementType(), AddrSpace); 1469 1470 if (OtherPtr->getType() != NewTy) 1471 OtherPtr = new BitCastInst(OtherPtr, NewTy, OtherPtr->getName(), MI); 1472 } 1473 1474 // Process each element of the aggregate. 1475 bool SROADest = MI->getRawDest() == Inst; 1476 1477 Constant *Zero = Constant::getNullValue(Type::getInt32Ty(MI->getContext())); 1478 1479 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { 1480 // If this is a memcpy/memmove, emit a GEP of the other element address. 1481 Value *OtherElt = 0; 1482 unsigned OtherEltAlign = MemAlignment; 1483 1484 if (OtherPtr) { 1485 Value *Idx[2] = { Zero, 1486 ConstantInt::get(Type::getInt32Ty(MI->getContext()), i) }; 1487 OtherElt = GetElementPtrInst::CreateInBounds(OtherPtr, Idx, Idx + 2, 1488 OtherPtr->getName()+"."+Twine(i), 1489 MI); 1490 uint64_t EltOffset; 1491 const PointerType *OtherPtrTy = cast<PointerType>(OtherPtr->getType()); 1492 const Type *OtherTy = OtherPtrTy->getElementType(); 1493 if (const StructType *ST = dyn_cast<StructType>(OtherTy)) { 1494 EltOffset = TD->getStructLayout(ST)->getElementOffset(i); 1495 } else { 1496 const Type *EltTy = cast<SequentialType>(OtherTy)->getElementType(); 1497 EltOffset = TD->getTypeAllocSize(EltTy)*i; 1498 } 1499 1500 // The alignment of the other pointer is the guaranteed alignment of the 1501 // element, which is affected by both the known alignment of the whole 1502 // mem intrinsic and the alignment of the element. If the alignment of 1503 // the memcpy (f.e.) is 32 but the element is at a 4-byte offset, then the 1504 // known alignment is just 4 bytes. 1505 OtherEltAlign = (unsigned)MinAlign(OtherEltAlign, EltOffset); 1506 } 1507 1508 Value *EltPtr = NewElts[i]; 1509 const Type *EltTy = cast<PointerType>(EltPtr->getType())->getElementType(); 1510 1511 // If we got down to a scalar, insert a load or store as appropriate. 1512 if (EltTy->isSingleValueType()) { 1513 if (isa<MemTransferInst>(MI)) { 1514 if (SROADest) { 1515 // From Other to Alloca. 1516 Value *Elt = new LoadInst(OtherElt, "tmp", false, OtherEltAlign, MI); 1517 new StoreInst(Elt, EltPtr, MI); 1518 } else { 1519 // From Alloca to Other. 1520 Value *Elt = new LoadInst(EltPtr, "tmp", MI); 1521 new StoreInst(Elt, OtherElt, false, OtherEltAlign, MI); 1522 } 1523 continue; 1524 } 1525 assert(isa<MemSetInst>(MI)); 1526 1527 // If the stored element is zero (common case), just store a null 1528 // constant. 1529 Constant *StoreVal; 1530 if (ConstantInt *CI = dyn_cast<ConstantInt>(MI->getArgOperand(1))) { 1531 if (CI->isZero()) { 1532 StoreVal = Constant::getNullValue(EltTy); // 0.0, null, 0, <0,0> 1533 } else { 1534 // If EltTy is a vector type, get the element type. 1535 const Type *ValTy = EltTy->getScalarType(); 1536 1537 // Construct an integer with the right value. 1538 unsigned EltSize = TD->getTypeSizeInBits(ValTy); 1539 APInt OneVal(EltSize, CI->getZExtValue()); 1540 APInt TotalVal(OneVal); 1541 // Set each byte. 1542 for (unsigned i = 0; 8*i < EltSize; ++i) { 1543 TotalVal = TotalVal.shl(8); 1544 TotalVal |= OneVal; 1545 } 1546 1547 // Convert the integer value to the appropriate type. 1548 StoreVal = ConstantInt::get(CI->getContext(), TotalVal); 1549 if (ValTy->isPointerTy()) 1550 StoreVal = ConstantExpr::getIntToPtr(StoreVal, ValTy); 1551 else if (ValTy->isFloatingPointTy()) 1552 StoreVal = ConstantExpr::getBitCast(StoreVal, ValTy); 1553 assert(StoreVal->getType() == ValTy && "Type mismatch!"); 1554 1555 // If the requested value was a vector constant, create it. 1556 if (EltTy != ValTy) { 1557 unsigned NumElts = cast<VectorType>(ValTy)->getNumElements(); 1558 SmallVector<Constant*, 16> Elts(NumElts, StoreVal); 1559 StoreVal = ConstantVector::get(&Elts[0], NumElts); 1560 } 1561 } 1562 new StoreInst(StoreVal, EltPtr, MI); 1563 continue; 1564 } 1565 // Otherwise, if we're storing a byte variable, use a memset call for 1566 // this element. 1567 } 1568 1569 unsigned EltSize = TD->getTypeAllocSize(EltTy); 1570 1571 IRBuilder<> Builder(MI); 1572 1573 // Finally, insert the meminst for this element. 1574 if (isa<MemSetInst>(MI)) { 1575 Builder.CreateMemSet(EltPtr, MI->getArgOperand(1), EltSize, 1576 MI->isVolatile()); 1577 } else { 1578 assert(isa<MemTransferInst>(MI)); 1579 Value *Dst = SROADest ? EltPtr : OtherElt; // Dest ptr 1580 Value *Src = SROADest ? OtherElt : EltPtr; // Src ptr 1581 1582 if (isa<MemCpyInst>(MI)) 1583 Builder.CreateMemCpy(Dst, Src, EltSize, OtherEltAlign,MI->isVolatile()); 1584 else 1585 Builder.CreateMemMove(Dst, Src, EltSize,OtherEltAlign,MI->isVolatile()); 1586 } 1587 } 1588 DeadInsts.push_back(MI); 1589} 1590 1591/// RewriteStoreUserOfWholeAlloca - We found a store of an integer that 1592/// overwrites the entire allocation. Extract out the pieces of the stored 1593/// integer and store them individually. 1594void SROA::RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocaInst *AI, 1595 SmallVector<AllocaInst*, 32> &NewElts){ 1596 // Extract each element out of the integer according to its structure offset 1597 // and store the element value to the individual alloca. 1598 Value *SrcVal = SI->getOperand(0); 1599 const Type *AllocaEltTy = AI->getAllocatedType(); 1600 uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy); 1601 1602 // Handle tail padding by extending the operand 1603 if (TD->getTypeSizeInBits(SrcVal->getType()) != AllocaSizeBits) 1604 SrcVal = new ZExtInst(SrcVal, 1605 IntegerType::get(SI->getContext(), AllocaSizeBits), 1606 "", SI); 1607 1608 DEBUG(dbgs() << "PROMOTING STORE TO WHOLE ALLOCA: " << *AI << '\n' << *SI 1609 << '\n'); 1610 1611 // There are two forms here: AI could be an array or struct. Both cases 1612 // have different ways to compute the element offset. 1613 if (const StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) { 1614 const StructLayout *Layout = TD->getStructLayout(EltSTy); 1615 1616 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { 1617 // Get the number of bits to shift SrcVal to get the value. 1618 const Type *FieldTy = EltSTy->getElementType(i); 1619 uint64_t Shift = Layout->getElementOffsetInBits(i); 1620 1621 if (TD->isBigEndian()) 1622 Shift = AllocaSizeBits-Shift-TD->getTypeAllocSizeInBits(FieldTy); 1623 1624 Value *EltVal = SrcVal; 1625 if (Shift) { 1626 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift); 1627 EltVal = BinaryOperator::CreateLShr(EltVal, ShiftVal, 1628 "sroa.store.elt", SI); 1629 } 1630 1631 // Truncate down to an integer of the right size. 1632 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy); 1633 1634 // Ignore zero sized fields like {}, they obviously contain no data. 1635 if (FieldSizeBits == 0) continue; 1636 1637 if (FieldSizeBits != AllocaSizeBits) 1638 EltVal = new TruncInst(EltVal, 1639 IntegerType::get(SI->getContext(), FieldSizeBits), 1640 "", SI); 1641 Value *DestField = NewElts[i]; 1642 if (EltVal->getType() == FieldTy) { 1643 // Storing to an integer field of this size, just do it. 1644 } else if (FieldTy->isFloatingPointTy() || FieldTy->isVectorTy()) { 1645 // Bitcast to the right element type (for fp/vector values). 1646 EltVal = new BitCastInst(EltVal, FieldTy, "", SI); 1647 } else { 1648 // Otherwise, bitcast the dest pointer (for aggregates). 1649 DestField = new BitCastInst(DestField, 1650 PointerType::getUnqual(EltVal->getType()), 1651 "", SI); 1652 } 1653 new StoreInst(EltVal, DestField, SI); 1654 } 1655 1656 } else { 1657 const ArrayType *ATy = cast<ArrayType>(AllocaEltTy); 1658 const Type *ArrayEltTy = ATy->getElementType(); 1659 uint64_t ElementOffset = TD->getTypeAllocSizeInBits(ArrayEltTy); 1660 uint64_t ElementSizeBits = TD->getTypeSizeInBits(ArrayEltTy); 1661 1662 uint64_t Shift; 1663 1664 if (TD->isBigEndian()) 1665 Shift = AllocaSizeBits-ElementOffset; 1666 else 1667 Shift = 0; 1668 1669 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { 1670 // Ignore zero sized fields like {}, they obviously contain no data. 1671 if (ElementSizeBits == 0) continue; 1672 1673 Value *EltVal = SrcVal; 1674 if (Shift) { 1675 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift); 1676 EltVal = BinaryOperator::CreateLShr(EltVal, ShiftVal, 1677 "sroa.store.elt", SI); 1678 } 1679 1680 // Truncate down to an integer of the right size. 1681 if (ElementSizeBits != AllocaSizeBits) 1682 EltVal = new TruncInst(EltVal, 1683 IntegerType::get(SI->getContext(), 1684 ElementSizeBits), "", SI); 1685 Value *DestField = NewElts[i]; 1686 if (EltVal->getType() == ArrayEltTy) { 1687 // Storing to an integer field of this size, just do it. 1688 } else if (ArrayEltTy->isFloatingPointTy() || 1689 ArrayEltTy->isVectorTy()) { 1690 // Bitcast to the right element type (for fp/vector values). 1691 EltVal = new BitCastInst(EltVal, ArrayEltTy, "", SI); 1692 } else { 1693 // Otherwise, bitcast the dest pointer (for aggregates). 1694 DestField = new BitCastInst(DestField, 1695 PointerType::getUnqual(EltVal->getType()), 1696 "", SI); 1697 } 1698 new StoreInst(EltVal, DestField, SI); 1699 1700 if (TD->isBigEndian()) 1701 Shift -= ElementOffset; 1702 else 1703 Shift += ElementOffset; 1704 } 1705 } 1706 1707 DeadInsts.push_back(SI); 1708} 1709 1710/// RewriteLoadUserOfWholeAlloca - We found a load of the entire allocation to 1711/// an integer. Load the individual pieces to form the aggregate value. 1712void SROA::RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocaInst *AI, 1713 SmallVector<AllocaInst*, 32> &NewElts) { 1714 // Extract each element out of the NewElts according to its structure offset 1715 // and form the result value. 1716 const Type *AllocaEltTy = AI->getAllocatedType(); 1717 uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy); 1718 1719 DEBUG(dbgs() << "PROMOTING LOAD OF WHOLE ALLOCA: " << *AI << '\n' << *LI 1720 << '\n'); 1721 1722 // There are two forms here: AI could be an array or struct. Both cases 1723 // have different ways to compute the element offset. 1724 const StructLayout *Layout = 0; 1725 uint64_t ArrayEltBitOffset = 0; 1726 if (const StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) { 1727 Layout = TD->getStructLayout(EltSTy); 1728 } else { 1729 const Type *ArrayEltTy = cast<ArrayType>(AllocaEltTy)->getElementType(); 1730 ArrayEltBitOffset = TD->getTypeAllocSizeInBits(ArrayEltTy); 1731 } 1732 1733 Value *ResultVal = 1734 Constant::getNullValue(IntegerType::get(LI->getContext(), AllocaSizeBits)); 1735 1736 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { 1737 // Load the value from the alloca. If the NewElt is an aggregate, cast 1738 // the pointer to an integer of the same size before doing the load. 1739 Value *SrcField = NewElts[i]; 1740 const Type *FieldTy = 1741 cast<PointerType>(SrcField->getType())->getElementType(); 1742 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy); 1743 1744 // Ignore zero sized fields like {}, they obviously contain no data. 1745 if (FieldSizeBits == 0) continue; 1746 1747 const IntegerType *FieldIntTy = IntegerType::get(LI->getContext(), 1748 FieldSizeBits); 1749 if (!FieldTy->isIntegerTy() && !FieldTy->isFloatingPointTy() && 1750 !FieldTy->isVectorTy()) 1751 SrcField = new BitCastInst(SrcField, 1752 PointerType::getUnqual(FieldIntTy), 1753 "", LI); 1754 SrcField = new LoadInst(SrcField, "sroa.load.elt", LI); 1755 1756 // If SrcField is a fp or vector of the right size but that isn't an 1757 // integer type, bitcast to an integer so we can shift it. 1758 if (SrcField->getType() != FieldIntTy) 1759 SrcField = new BitCastInst(SrcField, FieldIntTy, "", LI); 1760 1761 // Zero extend the field to be the same size as the final alloca so that 1762 // we can shift and insert it. 1763 if (SrcField->getType() != ResultVal->getType()) 1764 SrcField = new ZExtInst(SrcField, ResultVal->getType(), "", LI); 1765 1766 // Determine the number of bits to shift SrcField. 1767 uint64_t Shift; 1768 if (Layout) // Struct case. 1769 Shift = Layout->getElementOffsetInBits(i); 1770 else // Array case. 1771 Shift = i*ArrayEltBitOffset; 1772 1773 if (TD->isBigEndian()) 1774 Shift = AllocaSizeBits-Shift-FieldIntTy->getBitWidth(); 1775 1776 if (Shift) { 1777 Value *ShiftVal = ConstantInt::get(SrcField->getType(), Shift); 1778 SrcField = BinaryOperator::CreateShl(SrcField, ShiftVal, "", LI); 1779 } 1780 1781 // Don't create an 'or x, 0' on the first iteration. 1782 if (!isa<Constant>(ResultVal) || 1783 !cast<Constant>(ResultVal)->isNullValue()) 1784 ResultVal = BinaryOperator::CreateOr(SrcField, ResultVal, "", LI); 1785 else 1786 ResultVal = SrcField; 1787 } 1788 1789 // Handle tail padding by truncating the result 1790 if (TD->getTypeSizeInBits(LI->getType()) != AllocaSizeBits) 1791 ResultVal = new TruncInst(ResultVal, LI->getType(), "", LI); 1792 1793 LI->replaceAllUsesWith(ResultVal); 1794 DeadInsts.push_back(LI); 1795} 1796 1797/// HasPadding - Return true if the specified type has any structure or 1798/// alignment padding in between the elements that would be split apart 1799/// by SROA; return false otherwise. 1800static bool HasPadding(const Type *Ty, const TargetData &TD) { 1801 if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) { 1802 Ty = ATy->getElementType(); 1803 return TD.getTypeSizeInBits(Ty) != TD.getTypeAllocSizeInBits(Ty); 1804 } 1805 1806 // SROA currently handles only Arrays and Structs. 1807 const StructType *STy = cast<StructType>(Ty); 1808 const StructLayout *SL = TD.getStructLayout(STy); 1809 unsigned PrevFieldBitOffset = 0; 1810 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) { 1811 unsigned FieldBitOffset = SL->getElementOffsetInBits(i); 1812 1813 // Check to see if there is any padding between this element and the 1814 // previous one. 1815 if (i) { 1816 unsigned PrevFieldEnd = 1817 PrevFieldBitOffset+TD.getTypeSizeInBits(STy->getElementType(i-1)); 1818 if (PrevFieldEnd < FieldBitOffset) 1819 return true; 1820 } 1821 PrevFieldBitOffset = FieldBitOffset; 1822 } 1823 // Check for tail padding. 1824 if (unsigned EltCount = STy->getNumElements()) { 1825 unsigned PrevFieldEnd = PrevFieldBitOffset + 1826 TD.getTypeSizeInBits(STy->getElementType(EltCount-1)); 1827 if (PrevFieldEnd < SL->getSizeInBits()) 1828 return true; 1829 } 1830 return false; 1831} 1832 1833/// isSafeStructAllocaToScalarRepl - Check to see if the specified allocation of 1834/// an aggregate can be broken down into elements. Return 0 if not, 3 if safe, 1835/// or 1 if safe after canonicalization has been performed. 1836bool SROA::isSafeAllocaToScalarRepl(AllocaInst *AI) { 1837 // Loop over the use list of the alloca. We can only transform it if all of 1838 // the users are safe to transform. 1839 AllocaInfo Info; 1840 1841 isSafeForScalarRepl(AI, AI, 0, Info); 1842 if (Info.isUnsafe) { 1843 DEBUG(dbgs() << "Cannot transform: " << *AI << '\n'); 1844 return false; 1845 } 1846 1847 // Okay, we know all the users are promotable. If the aggregate is a memcpy 1848 // source and destination, we have to be careful. In particular, the memcpy 1849 // could be moving around elements that live in structure padding of the LLVM 1850 // types, but may actually be used. In these cases, we refuse to promote the 1851 // struct. 1852 if (Info.isMemCpySrc && Info.isMemCpyDst && 1853 HasPadding(AI->getAllocatedType(), *TD)) 1854 return false; 1855 1856 return true; 1857} 1858 1859 1860 1861/// PointsToConstantGlobal - Return true if V (possibly indirectly) points to 1862/// some part of a constant global variable. This intentionally only accepts 1863/// constant expressions because we don't can't rewrite arbitrary instructions. 1864static bool PointsToConstantGlobal(Value *V) { 1865 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V)) 1866 return GV->isConstant(); 1867 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) 1868 if (CE->getOpcode() == Instruction::BitCast || 1869 CE->getOpcode() == Instruction::GetElementPtr) 1870 return PointsToConstantGlobal(CE->getOperand(0)); 1871 return false; 1872} 1873 1874/// isOnlyCopiedFromConstantGlobal - Recursively walk the uses of a (derived) 1875/// pointer to an alloca. Ignore any reads of the pointer, return false if we 1876/// see any stores or other unknown uses. If we see pointer arithmetic, keep 1877/// track of whether it moves the pointer (with isOffset) but otherwise traverse 1878/// the uses. If we see a memcpy/memmove that targets an unoffseted pointer to 1879/// the alloca, and if the source pointer is a pointer to a constant global, we 1880/// can optimize this. 1881static bool isOnlyCopiedFromConstantGlobal(Value *V, MemTransferInst *&TheCopy, 1882 bool isOffset) { 1883 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) { 1884 User *U = cast<Instruction>(*UI); 1885 1886 if (LoadInst *LI = dyn_cast<LoadInst>(U)) { 1887 // Ignore non-volatile loads, they are always ok. 1888 if (LI->isVolatile()) return false; 1889 continue; 1890 } 1891 1892 if (BitCastInst *BCI = dyn_cast<BitCastInst>(U)) { 1893 // If uses of the bitcast are ok, we are ok. 1894 if (!isOnlyCopiedFromConstantGlobal(BCI, TheCopy, isOffset)) 1895 return false; 1896 continue; 1897 } 1898 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) { 1899 // If the GEP has all zero indices, it doesn't offset the pointer. If it 1900 // doesn't, it does. 1901 if (!isOnlyCopiedFromConstantGlobal(GEP, TheCopy, 1902 isOffset || !GEP->hasAllZeroIndices())) 1903 return false; 1904 continue; 1905 } 1906 1907 if (CallSite CS = U) { 1908 // If this is a readonly/readnone call site, then we know it is just a 1909 // load and we can ignore it. 1910 if (CS.onlyReadsMemory()) 1911 continue; 1912 1913 // If this is the function being called then we treat it like a load and 1914 // ignore it. 1915 if (CS.isCallee(UI)) 1916 continue; 1917 1918 // If this is being passed as a byval argument, the caller is making a 1919 // copy, so it is only a read of the alloca. 1920 unsigned ArgNo = CS.getArgumentNo(UI); 1921 if (CS.paramHasAttr(ArgNo+1, Attribute::ByVal)) 1922 continue; 1923 } 1924 1925 // If this is isn't our memcpy/memmove, reject it as something we can't 1926 // handle. 1927 MemTransferInst *MI = dyn_cast<MemTransferInst>(U); 1928 if (MI == 0) 1929 return false; 1930 1931 // If the transfer is using the alloca as a source of the transfer, then 1932 // ignore it since it is a load (unless the transfer is volatile). 1933 if (UI.getOperandNo() == 1) { 1934 if (MI->isVolatile()) return false; 1935 continue; 1936 } 1937 1938 // If we already have seen a copy, reject the second one. 1939 if (TheCopy) return false; 1940 1941 // If the pointer has been offset from the start of the alloca, we can't 1942 // safely handle this. 1943 if (isOffset) return false; 1944 1945 // If the memintrinsic isn't using the alloca as the dest, reject it. 1946 if (UI.getOperandNo() != 0) return false; 1947 1948 // If the source of the memcpy/move is not a constant global, reject it. 1949 if (!PointsToConstantGlobal(MI->getSource())) 1950 return false; 1951 1952 // Otherwise, the transform is safe. Remember the copy instruction. 1953 TheCopy = MI; 1954 } 1955 return true; 1956} 1957 1958/// isOnlyCopiedFromConstantGlobal - Return true if the specified alloca is only 1959/// modified by a copy from a constant global. If we can prove this, we can 1960/// replace any uses of the alloca with uses of the global directly. 1961MemTransferInst *SROA::isOnlyCopiedFromConstantGlobal(AllocaInst *AI) { 1962 MemTransferInst *TheCopy = 0; 1963 if (::isOnlyCopiedFromConstantGlobal(AI, TheCopy, false)) 1964 return TheCopy; 1965 return 0; 1966} 1967