ScalarReplAggregates.cpp revision d01a0da090407762fe3b770d84f049d72d06467e
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/Dominators.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 hasDT, char &ID) 58 : FunctionPass(ID), HasDomTree(hasDT) { 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 HasDomTree; 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 /// hasSubelementAccess - This is true if a subelement of the alloca is 92 /// ever accessed, or false if the alloca is only accessed with mem 93 /// intrinsics or load/store that only access the entire alloca at once. 94 bool hasSubelementAccess : 1; 95 96 /// hasALoadOrStore - This is true if there are any loads or stores to it. 97 /// The alloca may just be accessed with memcpy, for example, which would 98 /// not set this. 99 bool hasALoadOrStore : 1; 100 101 AllocaInfo() 102 : isUnsafe(false), isMemCpySrc(false), isMemCpyDst(false), 103 hasSubelementAccess(false), hasALoadOrStore(false) {} 104 }; 105 106 unsigned SRThreshold; 107 108 void MarkUnsafe(AllocaInfo &I, Instruction *User) { 109 I.isUnsafe = true; 110 DEBUG(dbgs() << " Transformation preventing inst: " << *User << '\n'); 111 } 112 113 bool isSafeAllocaToScalarRepl(AllocaInst *AI); 114 115 void isSafeForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset, 116 AllocaInfo &Info); 117 void isSafeGEP(GetElementPtrInst *GEPI, AllocaInst *AI, uint64_t &Offset, 118 AllocaInfo &Info); 119 void isSafeMemAccess(AllocaInst *AI, uint64_t Offset, uint64_t MemSize, 120 const Type *MemOpType, bool isStore, AllocaInfo &Info, 121 Instruction *TheAccess); 122 bool TypeHasComponent(const Type *T, uint64_t Offset, uint64_t Size); 123 uint64_t FindElementAndOffset(const Type *&T, uint64_t &Offset, 124 const Type *&IdxTy); 125 126 void DoScalarReplacement(AllocaInst *AI, 127 std::vector<AllocaInst*> &WorkList); 128 void DeleteDeadInstructions(); 129 130 void RewriteForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset, 131 SmallVector<AllocaInst*, 32> &NewElts); 132 void RewriteBitCast(BitCastInst *BC, AllocaInst *AI, uint64_t Offset, 133 SmallVector<AllocaInst*, 32> &NewElts); 134 void RewriteGEP(GetElementPtrInst *GEPI, AllocaInst *AI, uint64_t Offset, 135 SmallVector<AllocaInst*, 32> &NewElts); 136 void RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *Inst, 137 AllocaInst *AI, 138 SmallVector<AllocaInst*, 32> &NewElts); 139 void RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocaInst *AI, 140 SmallVector<AllocaInst*, 32> &NewElts); 141 void RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocaInst *AI, 142 SmallVector<AllocaInst*, 32> &NewElts); 143 144 static MemTransferInst *isOnlyCopiedFromConstantGlobal(AllocaInst *AI); 145 }; 146 147 // SROA_DT - SROA that uses DominatorTree. 148 struct SROA_DT : public SROA { 149 static char ID; 150 public: 151 SROA_DT(int T = -1) : SROA(T, true, ID) { 152 initializeSROA_DTPass(*PassRegistry::getPassRegistry()); 153 } 154 155 // getAnalysisUsage - This pass does not require any passes, but we know it 156 // will not alter the CFG, so say so. 157 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 158 AU.addRequired<DominatorTree>(); 159 AU.setPreservesCFG(); 160 } 161 }; 162 163 // SROA_SSAUp - SROA that uses SSAUpdater. 164 struct SROA_SSAUp : public SROA { 165 static char ID; 166 public: 167 SROA_SSAUp(int T = -1) : SROA(T, false, ID) { 168 initializeSROA_SSAUpPass(*PassRegistry::getPassRegistry()); 169 } 170 171 // getAnalysisUsage - This pass does not require any passes, but we know it 172 // will not alter the CFG, so say so. 173 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 174 AU.setPreservesCFG(); 175 } 176 }; 177 178} 179 180char SROA_DT::ID = 0; 181char SROA_SSAUp::ID = 0; 182 183INITIALIZE_PASS_BEGIN(SROA_DT, "scalarrepl", 184 "Scalar Replacement of Aggregates (DT)", false, false) 185INITIALIZE_PASS_DEPENDENCY(DominatorTree) 186INITIALIZE_PASS_END(SROA_DT, "scalarrepl", 187 "Scalar Replacement of Aggregates (DT)", false, false) 188 189INITIALIZE_PASS_BEGIN(SROA_SSAUp, "scalarrepl-ssa", 190 "Scalar Replacement of Aggregates (SSAUp)", false, false) 191INITIALIZE_PASS_END(SROA_SSAUp, "scalarrepl-ssa", 192 "Scalar Replacement of Aggregates (SSAUp)", false, false) 193 194// Public interface to the ScalarReplAggregates pass 195FunctionPass *llvm::createScalarReplAggregatesPass(int Threshold, 196 bool UseDomTree) { 197 if (UseDomTree) 198 return new SROA_DT(Threshold); 199 return new SROA_SSAUp(Threshold); 200} 201 202 203//===----------------------------------------------------------------------===// 204// Convert To Scalar Optimization. 205//===----------------------------------------------------------------------===// 206 207namespace { 208/// ConvertToScalarInfo - This class implements the "Convert To Scalar" 209/// optimization, which scans the uses of an alloca and determines if it can 210/// rewrite it in terms of a single new alloca that can be mem2reg'd. 211class ConvertToScalarInfo { 212 /// AllocaSize - The size of the alloca being considered. 213 unsigned AllocaSize; 214 const TargetData &TD; 215 216 /// IsNotTrivial - This is set to true if there is some access to the object 217 /// which means that mem2reg can't promote it. 218 bool IsNotTrivial; 219 220 /// VectorTy - This tracks the type that we should promote the vector to if 221 /// it is possible to turn it into a vector. This starts out null, and if it 222 /// isn't possible to turn into a vector type, it gets set to VoidTy. 223 const Type *VectorTy; 224 225 /// HadAVector - True if there is at least one vector access to the alloca. 226 /// We don't want to turn random arrays into vectors and use vector element 227 /// insert/extract, but if there are element accesses to something that is 228 /// also declared as a vector, we do want to promote to a vector. 229 bool HadAVector; 230 231public: 232 explicit ConvertToScalarInfo(unsigned Size, const TargetData &td) 233 : AllocaSize(Size), TD(td) { 234 IsNotTrivial = false; 235 VectorTy = 0; 236 HadAVector = false; 237 } 238 239 AllocaInst *TryConvert(AllocaInst *AI); 240 241private: 242 bool CanConvertToScalar(Value *V, uint64_t Offset); 243 void MergeInType(const Type *In, uint64_t Offset); 244 void ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, uint64_t Offset); 245 246 Value *ConvertScalar_ExtractValue(Value *NV, const Type *ToType, 247 uint64_t Offset, IRBuilder<> &Builder); 248 Value *ConvertScalar_InsertValue(Value *StoredVal, Value *ExistingVal, 249 uint64_t Offset, IRBuilder<> &Builder); 250}; 251} // end anonymous namespace. 252 253 254/// TryConvert - Analyze the specified alloca, and if it is safe to do so, 255/// rewrite it to be a new alloca which is mem2reg'able. This returns the new 256/// alloca if possible or null if not. 257AllocaInst *ConvertToScalarInfo::TryConvert(AllocaInst *AI) { 258 // If we can't convert this scalar, or if mem2reg can trivially do it, bail 259 // out. 260 if (!CanConvertToScalar(AI, 0) || !IsNotTrivial) 261 return 0; 262 263 // If we were able to find a vector type that can handle this with 264 // insert/extract elements, and if there was at least one use that had 265 // a vector type, promote this to a vector. We don't want to promote 266 // random stuff that doesn't use vectors (e.g. <9 x double>) because then 267 // we just get a lot of insert/extracts. If at least one vector is 268 // involved, then we probably really do have a union of vector/array. 269 const Type *NewTy; 270 if (VectorTy && VectorTy->isVectorTy() && HadAVector) { 271 DEBUG(dbgs() << "CONVERT TO VECTOR: " << *AI << "\n TYPE = " 272 << *VectorTy << '\n'); 273 NewTy = VectorTy; // Use the vector type. 274 } else { 275 DEBUG(dbgs() << "CONVERT TO SCALAR INTEGER: " << *AI << "\n"); 276 // Create and insert the integer alloca. 277 NewTy = IntegerType::get(AI->getContext(), AllocaSize*8); 278 } 279 AllocaInst *NewAI = new AllocaInst(NewTy, 0, "", AI->getParent()->begin()); 280 ConvertUsesToScalar(AI, NewAI, 0); 281 return NewAI; 282} 283 284/// MergeInType - Add the 'In' type to the accumulated vector type (VectorTy) 285/// so far at the offset specified by Offset (which is specified in bytes). 286/// 287/// There are two cases we handle here: 288/// 1) A union of vector types of the same size and potentially its elements. 289/// Here we turn element accesses into insert/extract element operations. 290/// This promotes a <4 x float> with a store of float to the third element 291/// into a <4 x float> that uses insert element. 292/// 2) A fully general blob of memory, which we turn into some (potentially 293/// large) integer type with extract and insert operations where the loads 294/// and stores would mutate the memory. We mark this by setting VectorTy 295/// to VoidTy. 296void ConvertToScalarInfo::MergeInType(const Type *In, uint64_t Offset) { 297 // If we already decided to turn this into a blob of integer memory, there is 298 // nothing to be done. 299 if (VectorTy && VectorTy->isVoidTy()) 300 return; 301 302 // If this could be contributing to a vector, analyze it. 303 304 // If the In type is a vector that is the same size as the alloca, see if it 305 // matches the existing VecTy. 306 if (const VectorType *VInTy = dyn_cast<VectorType>(In)) { 307 // Remember if we saw a vector type. 308 HadAVector = true; 309 310 if (VInTy->getBitWidth()/8 == AllocaSize && Offset == 0) { 311 // If we're storing/loading a vector of the right size, allow it as a 312 // vector. If this the first vector we see, remember the type so that 313 // we know the element size. If this is a subsequent access, ignore it 314 // even if it is a differing type but the same size. Worst case we can 315 // bitcast the resultant vectors. 316 if (VectorTy == 0) 317 VectorTy = VInTy; 318 return; 319 } 320 } else if (In->isFloatTy() || In->isDoubleTy() || 321 (In->isIntegerTy() && In->getPrimitiveSizeInBits() >= 8 && 322 isPowerOf2_32(In->getPrimitiveSizeInBits()))) { 323 // If we're accessing something that could be an element of a vector, see 324 // if the implied vector agrees with what we already have and if Offset is 325 // compatible with it. 326 unsigned EltSize = In->getPrimitiveSizeInBits()/8; 327 if (Offset % EltSize == 0 && AllocaSize % EltSize == 0 && 328 (VectorTy == 0 || 329 cast<VectorType>(VectorTy)->getElementType() 330 ->getPrimitiveSizeInBits()/8 == EltSize)) { 331 if (VectorTy == 0) 332 VectorTy = VectorType::get(In, AllocaSize/EltSize); 333 return; 334 } 335 } 336 337 // Otherwise, we have a case that we can't handle with an optimized vector 338 // form. We can still turn this into a large integer. 339 VectorTy = Type::getVoidTy(In->getContext()); 340} 341 342/// CanConvertToScalar - V is a pointer. If we can convert the pointee and all 343/// its accesses to a single vector type, return true and set VecTy to 344/// the new type. If we could convert the alloca into a single promotable 345/// integer, return true but set VecTy to VoidTy. Further, if the use is not a 346/// completely trivial use that mem2reg could promote, set IsNotTrivial. Offset 347/// is the current offset from the base of the alloca being analyzed. 348/// 349/// If we see at least one access to the value that is as a vector type, set the 350/// SawVec flag. 351bool ConvertToScalarInfo::CanConvertToScalar(Value *V, uint64_t Offset) { 352 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) { 353 Instruction *User = cast<Instruction>(*UI); 354 355 if (LoadInst *LI = dyn_cast<LoadInst>(User)) { 356 // Don't break volatile loads. 357 if (LI->isVolatile()) 358 return false; 359 // Don't touch MMX operations. 360 if (LI->getType()->isX86_MMXTy()) 361 return false; 362 MergeInType(LI->getType(), Offset); 363 continue; 364 } 365 366 if (StoreInst *SI = dyn_cast<StoreInst>(User)) { 367 // Storing the pointer, not into the value? 368 if (SI->getOperand(0) == V || SI->isVolatile()) return false; 369 // Don't touch MMX operations. 370 if (SI->getOperand(0)->getType()->isX86_MMXTy()) 371 return false; 372 MergeInType(SI->getOperand(0)->getType(), Offset); 373 continue; 374 } 375 376 if (BitCastInst *BCI = dyn_cast<BitCastInst>(User)) { 377 IsNotTrivial = true; // Can't be mem2reg'd. 378 if (!CanConvertToScalar(BCI, Offset)) 379 return false; 380 continue; 381 } 382 383 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) { 384 // If this is a GEP with a variable indices, we can't handle it. 385 if (!GEP->hasAllConstantIndices()) 386 return false; 387 388 // Compute the offset that this GEP adds to the pointer. 389 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end()); 390 uint64_t GEPOffset = TD.getIndexedOffset(GEP->getPointerOperandType(), 391 &Indices[0], Indices.size()); 392 // See if all uses can be converted. 393 if (!CanConvertToScalar(GEP, Offset+GEPOffset)) 394 return false; 395 IsNotTrivial = true; // Can't be mem2reg'd. 396 continue; 397 } 398 399 // If this is a constant sized memset of a constant value (e.g. 0) we can 400 // handle it. 401 if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) { 402 // Store of constant value and constant size. 403 if (!isa<ConstantInt>(MSI->getValue()) || 404 !isa<ConstantInt>(MSI->getLength())) 405 return false; 406 IsNotTrivial = true; // Can't be mem2reg'd. 407 continue; 408 } 409 410 // If this is a memcpy or memmove into or out of the whole allocation, we 411 // can handle it like a load or store of the scalar type. 412 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) { 413 ConstantInt *Len = dyn_cast<ConstantInt>(MTI->getLength()); 414 if (Len == 0 || Len->getZExtValue() != AllocaSize || Offset != 0) 415 return false; 416 417 IsNotTrivial = true; // Can't be mem2reg'd. 418 continue; 419 } 420 421 // Otherwise, we cannot handle this! 422 return false; 423 } 424 425 return true; 426} 427 428/// ConvertUsesToScalar - Convert all of the users of Ptr to use the new alloca 429/// directly. This happens when we are converting an "integer union" to a 430/// single integer scalar, or when we are converting a "vector union" to a 431/// vector with insert/extractelement instructions. 432/// 433/// Offset is an offset from the original alloca, in bits that need to be 434/// shifted to the right. By the end of this, there should be no uses of Ptr. 435void ConvertToScalarInfo::ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, 436 uint64_t Offset) { 437 while (!Ptr->use_empty()) { 438 Instruction *User = cast<Instruction>(Ptr->use_back()); 439 440 if (BitCastInst *CI = dyn_cast<BitCastInst>(User)) { 441 ConvertUsesToScalar(CI, NewAI, Offset); 442 CI->eraseFromParent(); 443 continue; 444 } 445 446 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) { 447 // Compute the offset that this GEP adds to the pointer. 448 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end()); 449 uint64_t GEPOffset = TD.getIndexedOffset(GEP->getPointerOperandType(), 450 &Indices[0], Indices.size()); 451 ConvertUsesToScalar(GEP, NewAI, Offset+GEPOffset*8); 452 GEP->eraseFromParent(); 453 continue; 454 } 455 456 IRBuilder<> Builder(User); 457 458 if (LoadInst *LI = dyn_cast<LoadInst>(User)) { 459 // The load is a bit extract from NewAI shifted right by Offset bits. 460 Value *LoadedVal = Builder.CreateLoad(NewAI, "tmp"); 461 Value *NewLoadVal 462 = ConvertScalar_ExtractValue(LoadedVal, LI->getType(), Offset, Builder); 463 LI->replaceAllUsesWith(NewLoadVal); 464 LI->eraseFromParent(); 465 continue; 466 } 467 468 if (StoreInst *SI = dyn_cast<StoreInst>(User)) { 469 assert(SI->getOperand(0) != Ptr && "Consistency error!"); 470 Instruction *Old = Builder.CreateLoad(NewAI, NewAI->getName()+".in"); 471 Value *New = ConvertScalar_InsertValue(SI->getOperand(0), Old, Offset, 472 Builder); 473 Builder.CreateStore(New, NewAI); 474 SI->eraseFromParent(); 475 476 // If the load we just inserted is now dead, then the inserted store 477 // overwrote the entire thing. 478 if (Old->use_empty()) 479 Old->eraseFromParent(); 480 continue; 481 } 482 483 // If this is a constant sized memset of a constant value (e.g. 0) we can 484 // transform it into a store of the expanded constant value. 485 if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) { 486 assert(MSI->getRawDest() == Ptr && "Consistency error!"); 487 unsigned NumBytes = cast<ConstantInt>(MSI->getLength())->getZExtValue(); 488 if (NumBytes != 0) { 489 unsigned Val = cast<ConstantInt>(MSI->getValue())->getZExtValue(); 490 491 // Compute the value replicated the right number of times. 492 APInt APVal(NumBytes*8, Val); 493 494 // Splat the value if non-zero. 495 if (Val) 496 for (unsigned i = 1; i != NumBytes; ++i) 497 APVal |= APVal << 8; 498 499 Instruction *Old = Builder.CreateLoad(NewAI, NewAI->getName()+".in"); 500 Value *New = ConvertScalar_InsertValue( 501 ConstantInt::get(User->getContext(), APVal), 502 Old, Offset, Builder); 503 Builder.CreateStore(New, NewAI); 504 505 // If the load we just inserted is now dead, then the memset overwrote 506 // the entire thing. 507 if (Old->use_empty()) 508 Old->eraseFromParent(); 509 } 510 MSI->eraseFromParent(); 511 continue; 512 } 513 514 // If this is a memcpy or memmove into or out of the whole allocation, we 515 // can handle it like a load or store of the scalar type. 516 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) { 517 assert(Offset == 0 && "must be store to start of alloca"); 518 519 // If the source and destination are both to the same alloca, then this is 520 // a noop copy-to-self, just delete it. Otherwise, emit a load and store 521 // as appropriate. 522 AllocaInst *OrigAI = cast<AllocaInst>(GetUnderlyingObject(Ptr, 0)); 523 524 if (GetUnderlyingObject(MTI->getSource(), 0) != OrigAI) { 525 // Dest must be OrigAI, change this to be a load from the original 526 // pointer (bitcasted), then a store to our new alloca. 527 assert(MTI->getRawDest() == Ptr && "Neither use is of pointer?"); 528 Value *SrcPtr = MTI->getSource(); 529 const PointerType* SPTy = cast<PointerType>(SrcPtr->getType()); 530 const PointerType* AIPTy = cast<PointerType>(NewAI->getType()); 531 if (SPTy->getAddressSpace() != AIPTy->getAddressSpace()) { 532 AIPTy = PointerType::get(AIPTy->getElementType(), 533 SPTy->getAddressSpace()); 534 } 535 SrcPtr = Builder.CreateBitCast(SrcPtr, AIPTy); 536 537 LoadInst *SrcVal = Builder.CreateLoad(SrcPtr, "srcval"); 538 SrcVal->setAlignment(MTI->getAlignment()); 539 Builder.CreateStore(SrcVal, NewAI); 540 } else if (GetUnderlyingObject(MTI->getDest(), 0) != OrigAI) { 541 // Src must be OrigAI, change this to be a load from NewAI then a store 542 // through the original dest pointer (bitcasted). 543 assert(MTI->getRawSource() == Ptr && "Neither use is of pointer?"); 544 LoadInst *SrcVal = Builder.CreateLoad(NewAI, "srcval"); 545 546 const PointerType* DPTy = cast<PointerType>(MTI->getDest()->getType()); 547 const PointerType* AIPTy = cast<PointerType>(NewAI->getType()); 548 if (DPTy->getAddressSpace() != AIPTy->getAddressSpace()) { 549 AIPTy = PointerType::get(AIPTy->getElementType(), 550 DPTy->getAddressSpace()); 551 } 552 Value *DstPtr = Builder.CreateBitCast(MTI->getDest(), AIPTy); 553 554 StoreInst *NewStore = Builder.CreateStore(SrcVal, DstPtr); 555 NewStore->setAlignment(MTI->getAlignment()); 556 } else { 557 // Noop transfer. Src == Dst 558 } 559 560 MTI->eraseFromParent(); 561 continue; 562 } 563 564 llvm_unreachable("Unsupported operation!"); 565 } 566} 567 568/// ConvertScalar_ExtractValue - Extract a value of type ToType from an integer 569/// or vector value FromVal, extracting the bits from the offset specified by 570/// Offset. This returns the value, which is of type ToType. 571/// 572/// This happens when we are converting an "integer union" to a single 573/// integer scalar, or when we are converting a "vector union" to a vector with 574/// insert/extractelement instructions. 575/// 576/// Offset is an offset from the original alloca, in bits that need to be 577/// shifted to the right. 578Value *ConvertToScalarInfo:: 579ConvertScalar_ExtractValue(Value *FromVal, const Type *ToType, 580 uint64_t Offset, IRBuilder<> &Builder) { 581 // If the load is of the whole new alloca, no conversion is needed. 582 if (FromVal->getType() == ToType && Offset == 0) 583 return FromVal; 584 585 // If the result alloca is a vector type, this is either an element 586 // access or a bitcast to another vector type of the same size. 587 if (const VectorType *VTy = dyn_cast<VectorType>(FromVal->getType())) { 588 if (ToType->isVectorTy()) 589 return Builder.CreateBitCast(FromVal, ToType, "tmp"); 590 591 // Otherwise it must be an element access. 592 unsigned Elt = 0; 593 if (Offset) { 594 unsigned EltSize = TD.getTypeAllocSizeInBits(VTy->getElementType()); 595 Elt = Offset/EltSize; 596 assert(EltSize*Elt == Offset && "Invalid modulus in validity checking"); 597 } 598 // Return the element extracted out of it. 599 Value *V = Builder.CreateExtractElement(FromVal, ConstantInt::get( 600 Type::getInt32Ty(FromVal->getContext()), Elt), "tmp"); 601 if (V->getType() != ToType) 602 V = Builder.CreateBitCast(V, ToType, "tmp"); 603 return V; 604 } 605 606 // If ToType is a first class aggregate, extract out each of the pieces and 607 // use insertvalue's to form the FCA. 608 if (const StructType *ST = dyn_cast<StructType>(ToType)) { 609 const StructLayout &Layout = *TD.getStructLayout(ST); 610 Value *Res = UndefValue::get(ST); 611 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) { 612 Value *Elt = ConvertScalar_ExtractValue(FromVal, ST->getElementType(i), 613 Offset+Layout.getElementOffsetInBits(i), 614 Builder); 615 Res = Builder.CreateInsertValue(Res, Elt, i, "tmp"); 616 } 617 return Res; 618 } 619 620 if (const ArrayType *AT = dyn_cast<ArrayType>(ToType)) { 621 uint64_t EltSize = TD.getTypeAllocSizeInBits(AT->getElementType()); 622 Value *Res = UndefValue::get(AT); 623 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) { 624 Value *Elt = ConvertScalar_ExtractValue(FromVal, AT->getElementType(), 625 Offset+i*EltSize, Builder); 626 Res = Builder.CreateInsertValue(Res, Elt, i, "tmp"); 627 } 628 return Res; 629 } 630 631 // Otherwise, this must be a union that was converted to an integer value. 632 const IntegerType *NTy = cast<IntegerType>(FromVal->getType()); 633 634 // If this is a big-endian system and the load is narrower than the 635 // full alloca type, we need to do a shift to get the right bits. 636 int ShAmt = 0; 637 if (TD.isBigEndian()) { 638 // On big-endian machines, the lowest bit is stored at the bit offset 639 // from the pointer given by getTypeStoreSizeInBits. This matters for 640 // integers with a bitwidth that is not a multiple of 8. 641 ShAmt = TD.getTypeStoreSizeInBits(NTy) - 642 TD.getTypeStoreSizeInBits(ToType) - Offset; 643 } else { 644 ShAmt = Offset; 645 } 646 647 // Note: we support negative bitwidths (with shl) which are not defined. 648 // We do this to support (f.e.) loads off the end of a structure where 649 // only some bits are used. 650 if (ShAmt > 0 && (unsigned)ShAmt < NTy->getBitWidth()) 651 FromVal = Builder.CreateLShr(FromVal, 652 ConstantInt::get(FromVal->getType(), 653 ShAmt), "tmp"); 654 else if (ShAmt < 0 && (unsigned)-ShAmt < NTy->getBitWidth()) 655 FromVal = Builder.CreateShl(FromVal, 656 ConstantInt::get(FromVal->getType(), 657 -ShAmt), "tmp"); 658 659 // Finally, unconditionally truncate the integer to the right width. 660 unsigned LIBitWidth = TD.getTypeSizeInBits(ToType); 661 if (LIBitWidth < NTy->getBitWidth()) 662 FromVal = 663 Builder.CreateTrunc(FromVal, IntegerType::get(FromVal->getContext(), 664 LIBitWidth), "tmp"); 665 else if (LIBitWidth > NTy->getBitWidth()) 666 FromVal = 667 Builder.CreateZExt(FromVal, IntegerType::get(FromVal->getContext(), 668 LIBitWidth), "tmp"); 669 670 // If the result is an integer, this is a trunc or bitcast. 671 if (ToType->isIntegerTy()) { 672 // Should be done. 673 } else if (ToType->isFloatingPointTy() || ToType->isVectorTy()) { 674 // Just do a bitcast, we know the sizes match up. 675 FromVal = Builder.CreateBitCast(FromVal, ToType, "tmp"); 676 } else { 677 // Otherwise must be a pointer. 678 FromVal = Builder.CreateIntToPtr(FromVal, ToType, "tmp"); 679 } 680 assert(FromVal->getType() == ToType && "Didn't convert right?"); 681 return FromVal; 682} 683 684/// ConvertScalar_InsertValue - Insert the value "SV" into the existing integer 685/// or vector value "Old" at the offset specified by Offset. 686/// 687/// This happens when we are converting an "integer union" to a 688/// single integer scalar, or when we are converting a "vector union" to a 689/// vector with insert/extractelement instructions. 690/// 691/// Offset is an offset from the original alloca, in bits that need to be 692/// shifted to the right. 693Value *ConvertToScalarInfo:: 694ConvertScalar_InsertValue(Value *SV, Value *Old, 695 uint64_t Offset, IRBuilder<> &Builder) { 696 // Convert the stored type to the actual type, shift it left to insert 697 // then 'or' into place. 698 const Type *AllocaType = Old->getType(); 699 LLVMContext &Context = Old->getContext(); 700 701 if (const VectorType *VTy = dyn_cast<VectorType>(AllocaType)) { 702 uint64_t VecSize = TD.getTypeAllocSizeInBits(VTy); 703 uint64_t ValSize = TD.getTypeAllocSizeInBits(SV->getType()); 704 705 // Changing the whole vector with memset or with an access of a different 706 // vector type? 707 if (ValSize == VecSize) 708 return Builder.CreateBitCast(SV, AllocaType, "tmp"); 709 710 uint64_t EltSize = TD.getTypeAllocSizeInBits(VTy->getElementType()); 711 712 // Must be an element insertion. 713 unsigned Elt = Offset/EltSize; 714 715 if (SV->getType() != VTy->getElementType()) 716 SV = Builder.CreateBitCast(SV, VTy->getElementType(), "tmp"); 717 718 SV = Builder.CreateInsertElement(Old, SV, 719 ConstantInt::get(Type::getInt32Ty(SV->getContext()), Elt), 720 "tmp"); 721 return SV; 722 } 723 724 // If SV is a first-class aggregate value, insert each value recursively. 725 if (const StructType *ST = dyn_cast<StructType>(SV->getType())) { 726 const StructLayout &Layout = *TD.getStructLayout(ST); 727 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) { 728 Value *Elt = Builder.CreateExtractValue(SV, i, "tmp"); 729 Old = ConvertScalar_InsertValue(Elt, Old, 730 Offset+Layout.getElementOffsetInBits(i), 731 Builder); 732 } 733 return Old; 734 } 735 736 if (const ArrayType *AT = dyn_cast<ArrayType>(SV->getType())) { 737 uint64_t EltSize = TD.getTypeAllocSizeInBits(AT->getElementType()); 738 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) { 739 Value *Elt = Builder.CreateExtractValue(SV, i, "tmp"); 740 Old = ConvertScalar_InsertValue(Elt, Old, Offset+i*EltSize, Builder); 741 } 742 return Old; 743 } 744 745 // If SV is a float, convert it to the appropriate integer type. 746 // If it is a pointer, do the same. 747 unsigned SrcWidth = TD.getTypeSizeInBits(SV->getType()); 748 unsigned DestWidth = TD.getTypeSizeInBits(AllocaType); 749 unsigned SrcStoreWidth = TD.getTypeStoreSizeInBits(SV->getType()); 750 unsigned DestStoreWidth = TD.getTypeStoreSizeInBits(AllocaType); 751 if (SV->getType()->isFloatingPointTy() || SV->getType()->isVectorTy()) 752 SV = Builder.CreateBitCast(SV, 753 IntegerType::get(SV->getContext(),SrcWidth), "tmp"); 754 else if (SV->getType()->isPointerTy()) 755 SV = Builder.CreatePtrToInt(SV, TD.getIntPtrType(SV->getContext()), "tmp"); 756 757 // Zero extend or truncate the value if needed. 758 if (SV->getType() != AllocaType) { 759 if (SV->getType()->getPrimitiveSizeInBits() < 760 AllocaType->getPrimitiveSizeInBits()) 761 SV = Builder.CreateZExt(SV, AllocaType, "tmp"); 762 else { 763 // Truncation may be needed if storing more than the alloca can hold 764 // (undefined behavior). 765 SV = Builder.CreateTrunc(SV, AllocaType, "tmp"); 766 SrcWidth = DestWidth; 767 SrcStoreWidth = DestStoreWidth; 768 } 769 } 770 771 // If this is a big-endian system and the store is narrower than the 772 // full alloca type, we need to do a shift to get the right bits. 773 int ShAmt = 0; 774 if (TD.isBigEndian()) { 775 // On big-endian machines, the lowest bit is stored at the bit offset 776 // from the pointer given by getTypeStoreSizeInBits. This matters for 777 // integers with a bitwidth that is not a multiple of 8. 778 ShAmt = DestStoreWidth - SrcStoreWidth - Offset; 779 } else { 780 ShAmt = Offset; 781 } 782 783 // Note: we support negative bitwidths (with shr) which are not defined. 784 // We do this to support (f.e.) stores off the end of a structure where 785 // only some bits in the structure are set. 786 APInt Mask(APInt::getLowBitsSet(DestWidth, SrcWidth)); 787 if (ShAmt > 0 && (unsigned)ShAmt < DestWidth) { 788 SV = Builder.CreateShl(SV, ConstantInt::get(SV->getType(), 789 ShAmt), "tmp"); 790 Mask <<= ShAmt; 791 } else if (ShAmt < 0 && (unsigned)-ShAmt < DestWidth) { 792 SV = Builder.CreateLShr(SV, ConstantInt::get(SV->getType(), 793 -ShAmt), "tmp"); 794 Mask = Mask.lshr(-ShAmt); 795 } 796 797 // Mask out the bits we are about to insert from the old value, and or 798 // in the new bits. 799 if (SrcWidth != DestWidth) { 800 assert(DestWidth > SrcWidth); 801 Old = Builder.CreateAnd(Old, ConstantInt::get(Context, ~Mask), "mask"); 802 SV = Builder.CreateOr(Old, SV, "ins"); 803 } 804 return SV; 805} 806 807 808//===----------------------------------------------------------------------===// 809// SRoA Driver 810//===----------------------------------------------------------------------===// 811 812 813bool SROA::runOnFunction(Function &F) { 814 TD = getAnalysisIfAvailable<TargetData>(); 815 816 bool Changed = performPromotion(F); 817 818 // FIXME: ScalarRepl currently depends on TargetData more than it 819 // theoretically needs to. It should be refactored in order to support 820 // target-independent IR. Until this is done, just skip the actual 821 // scalar-replacement portion of this pass. 822 if (!TD) return Changed; 823 824 while (1) { 825 bool LocalChange = performScalarRepl(F); 826 if (!LocalChange) break; // No need to repromote if no scalarrepl 827 Changed = true; 828 LocalChange = performPromotion(F); 829 if (!LocalChange) break; // No need to re-scalarrepl if no promotion 830 } 831 832 return Changed; 833} 834 835namespace { 836class AllocaPromoter : public LoadAndStorePromoter { 837 AllocaInst *AI; 838public: 839 AllocaPromoter(const SmallVectorImpl<Instruction*> &Insts, SSAUpdater &S) 840 : LoadAndStorePromoter(Insts, S), AI(0) {} 841 842 void run(AllocaInst *AI, const SmallVectorImpl<Instruction*> &Insts) { 843 // Remember which alloca we're promoting (for isInstInList). 844 this->AI = AI; 845 LoadAndStorePromoter::run(Insts); 846 AI->eraseFromParent(); 847 } 848 849 virtual bool isInstInList(Instruction *I, 850 const SmallVectorImpl<Instruction*> &Insts) const { 851 if (LoadInst *LI = dyn_cast<LoadInst>(I)) 852 return LI->getOperand(0) == AI; 853 return cast<StoreInst>(I)->getPointerOperand() == AI; 854 } 855}; 856} // end anon namespace 857 858bool SROA::performPromotion(Function &F) { 859 std::vector<AllocaInst*> Allocas; 860 DominatorTree *DT = 0; 861 if (HasDomTree) 862 DT = &getAnalysis<DominatorTree>(); 863 864 BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function 865 866 bool Changed = false; 867 SmallVector<Instruction*, 64> Insts; 868 while (1) { 869 Allocas.clear(); 870 871 // Find allocas that are safe to promote, by looking at all instructions in 872 // the entry node 873 for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I) 874 if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) // Is it an alloca? 875 if (isAllocaPromotable(AI)) 876 Allocas.push_back(AI); 877 878 if (Allocas.empty()) break; 879 880 if (HasDomTree) 881 PromoteMemToReg(Allocas, *DT); 882 else { 883 SSAUpdater SSA; 884 for (unsigned i = 0, e = Allocas.size(); i != e; ++i) { 885 AllocaInst *AI = Allocas[i]; 886 887 // Build list of instructions to promote. 888 for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end(); 889 UI != E; ++UI) 890 Insts.push_back(cast<Instruction>(*UI)); 891 892 AllocaPromoter(Insts, SSA).run(AI, Insts); 893 Insts.clear(); 894 } 895 } 896 NumPromoted += Allocas.size(); 897 Changed = true; 898 } 899 900 return Changed; 901} 902 903 904/// ShouldAttemptScalarRepl - Decide if an alloca is a good candidate for 905/// SROA. It must be a struct or array type with a small number of elements. 906static bool ShouldAttemptScalarRepl(AllocaInst *AI) { 907 const Type *T = AI->getAllocatedType(); 908 // Do not promote any struct into more than 32 separate vars. 909 if (const StructType *ST = dyn_cast<StructType>(T)) 910 return ST->getNumElements() <= 32; 911 // Arrays are much less likely to be safe for SROA; only consider 912 // them if they are very small. 913 if (const ArrayType *AT = dyn_cast<ArrayType>(T)) 914 return AT->getNumElements() <= 8; 915 return false; 916} 917 918 919// performScalarRepl - This algorithm is a simple worklist driven algorithm, 920// which runs on all of the malloc/alloca instructions in the function, removing 921// them if they are only used by getelementptr instructions. 922// 923bool SROA::performScalarRepl(Function &F) { 924 std::vector<AllocaInst*> WorkList; 925 926 // Scan the entry basic block, adding allocas to the worklist. 927 BasicBlock &BB = F.getEntryBlock(); 928 for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I) 929 if (AllocaInst *A = dyn_cast<AllocaInst>(I)) 930 WorkList.push_back(A); 931 932 // Process the worklist 933 bool Changed = false; 934 while (!WorkList.empty()) { 935 AllocaInst *AI = WorkList.back(); 936 WorkList.pop_back(); 937 938 // Handle dead allocas trivially. These can be formed by SROA'ing arrays 939 // with unused elements. 940 if (AI->use_empty()) { 941 AI->eraseFromParent(); 942 Changed = true; 943 continue; 944 } 945 946 // If this alloca is impossible for us to promote, reject it early. 947 if (AI->isArrayAllocation() || !AI->getAllocatedType()->isSized()) 948 continue; 949 950 // Check to see if this allocation is only modified by a memcpy/memmove from 951 // a constant global. If this is the case, we can change all users to use 952 // the constant global instead. This is commonly produced by the CFE by 953 // constructs like "void foo() { int A[] = {1,2,3,4,5,6,7,8,9...}; }" if 'A' 954 // is only subsequently read. 955 if (MemTransferInst *TheCopy = isOnlyCopiedFromConstantGlobal(AI)) { 956 DEBUG(dbgs() << "Found alloca equal to global: " << *AI << '\n'); 957 DEBUG(dbgs() << " memcpy = " << *TheCopy << '\n'); 958 Constant *TheSrc = cast<Constant>(TheCopy->getSource()); 959 AI->replaceAllUsesWith(ConstantExpr::getBitCast(TheSrc, AI->getType())); 960 TheCopy->eraseFromParent(); // Don't mutate the global. 961 AI->eraseFromParent(); 962 ++NumGlobals; 963 Changed = true; 964 continue; 965 } 966 967 // Check to see if we can perform the core SROA transformation. We cannot 968 // transform the allocation instruction if it is an array allocation 969 // (allocations OF arrays are ok though), and an allocation of a scalar 970 // value cannot be decomposed at all. 971 uint64_t AllocaSize = TD->getTypeAllocSize(AI->getAllocatedType()); 972 973 // Do not promote [0 x %struct]. 974 if (AllocaSize == 0) continue; 975 976 // Do not promote any struct whose size is too big. 977 if (AllocaSize > SRThreshold) continue; 978 979 // If the alloca looks like a good candidate for scalar replacement, and if 980 // all its users can be transformed, then split up the aggregate into its 981 // separate elements. 982 if (ShouldAttemptScalarRepl(AI) && isSafeAllocaToScalarRepl(AI)) { 983 DoScalarReplacement(AI, WorkList); 984 Changed = true; 985 continue; 986 } 987 988 // If we can turn this aggregate value (potentially with casts) into a 989 // simple scalar value that can be mem2reg'd into a register value. 990 // IsNotTrivial tracks whether this is something that mem2reg could have 991 // promoted itself. If so, we don't want to transform it needlessly. Note 992 // that we can't just check based on the type: the alloca may be of an i32 993 // but that has pointer arithmetic to set byte 3 of it or something. 994 if (AllocaInst *NewAI = 995 ConvertToScalarInfo((unsigned)AllocaSize, *TD).TryConvert(AI)) { 996 NewAI->takeName(AI); 997 AI->eraseFromParent(); 998 ++NumConverted; 999 Changed = true; 1000 continue; 1001 } 1002 1003 // Otherwise, couldn't process this alloca. 1004 } 1005 1006 return Changed; 1007} 1008 1009/// DoScalarReplacement - This alloca satisfied the isSafeAllocaToScalarRepl 1010/// predicate, do SROA now. 1011void SROA::DoScalarReplacement(AllocaInst *AI, 1012 std::vector<AllocaInst*> &WorkList) { 1013 DEBUG(dbgs() << "Found inst to SROA: " << *AI << '\n'); 1014 SmallVector<AllocaInst*, 32> ElementAllocas; 1015 if (const StructType *ST = dyn_cast<StructType>(AI->getAllocatedType())) { 1016 ElementAllocas.reserve(ST->getNumContainedTypes()); 1017 for (unsigned i = 0, e = ST->getNumContainedTypes(); i != e; ++i) { 1018 AllocaInst *NA = new AllocaInst(ST->getContainedType(i), 0, 1019 AI->getAlignment(), 1020 AI->getName() + "." + Twine(i), AI); 1021 ElementAllocas.push_back(NA); 1022 WorkList.push_back(NA); // Add to worklist for recursive processing 1023 } 1024 } else { 1025 const ArrayType *AT = cast<ArrayType>(AI->getAllocatedType()); 1026 ElementAllocas.reserve(AT->getNumElements()); 1027 const Type *ElTy = AT->getElementType(); 1028 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) { 1029 AllocaInst *NA = new AllocaInst(ElTy, 0, 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 } 1035 1036 // Now that we have created the new alloca instructions, rewrite all the 1037 // uses of the old alloca. 1038 RewriteForScalarRepl(AI, AI, 0, ElementAllocas); 1039 1040 // Now erase any instructions that were made dead while rewriting the alloca. 1041 DeleteDeadInstructions(); 1042 AI->eraseFromParent(); 1043 1044 ++NumReplaced; 1045} 1046 1047/// DeleteDeadInstructions - Erase instructions on the DeadInstrs list, 1048/// recursively including all their operands that become trivially dead. 1049void SROA::DeleteDeadInstructions() { 1050 while (!DeadInsts.empty()) { 1051 Instruction *I = cast<Instruction>(DeadInsts.pop_back_val()); 1052 1053 for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI) 1054 if (Instruction *U = dyn_cast<Instruction>(*OI)) { 1055 // Zero out the operand and see if it becomes trivially dead. 1056 // (But, don't add allocas to the dead instruction list -- they are 1057 // already on the worklist and will be deleted separately.) 1058 *OI = 0; 1059 if (isInstructionTriviallyDead(U) && !isa<AllocaInst>(U)) 1060 DeadInsts.push_back(U); 1061 } 1062 1063 I->eraseFromParent(); 1064 } 1065} 1066 1067/// isSafeForScalarRepl - Check if instruction I is a safe use with regard to 1068/// performing scalar replacement of alloca AI. The results are flagged in 1069/// the Info parameter. Offset indicates the position within AI that is 1070/// referenced by this instruction. 1071void SROA::isSafeForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset, 1072 AllocaInfo &Info) { 1073 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E; ++UI) { 1074 Instruction *User = cast<Instruction>(*UI); 1075 1076 if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) { 1077 isSafeForScalarRepl(BC, AI, Offset, Info); 1078 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) { 1079 uint64_t GEPOffset = Offset; 1080 isSafeGEP(GEPI, AI, GEPOffset, Info); 1081 if (!Info.isUnsafe) 1082 isSafeForScalarRepl(GEPI, AI, GEPOffset, Info); 1083 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) { 1084 ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength()); 1085 if (Length == 0) 1086 return MarkUnsafe(Info, User); 1087 isSafeMemAccess(AI, Offset, Length->getZExtValue(), 0, 1088 UI.getOperandNo() == 0, Info, MI); 1089 } else if (LoadInst *LI = dyn_cast<LoadInst>(User)) { 1090 if (LI->isVolatile()) 1091 return MarkUnsafe(Info, User); 1092 const Type *LIType = LI->getType(); 1093 isSafeMemAccess(AI, Offset, TD->getTypeAllocSize(LIType), 1094 LIType, false, Info, LI); 1095 Info.hasALoadOrStore = true; 1096 1097 } else if (StoreInst *SI = dyn_cast<StoreInst>(User)) { 1098 // Store is ok if storing INTO the pointer, not storing the pointer 1099 if (SI->isVolatile() || SI->getOperand(0) == I) 1100 return MarkUnsafe(Info, User); 1101 1102 const Type *SIType = SI->getOperand(0)->getType(); 1103 isSafeMemAccess(AI, Offset, TD->getTypeAllocSize(SIType), 1104 SIType, true, Info, SI); 1105 Info.hasALoadOrStore = true; 1106 } else { 1107 return MarkUnsafe(Info, User); 1108 } 1109 if (Info.isUnsafe) return; 1110 } 1111} 1112 1113/// isSafeGEP - Check if a GEP instruction can be handled for scalar 1114/// replacement. It is safe when all the indices are constant, in-bounds 1115/// references, and when the resulting offset corresponds to an element within 1116/// the alloca type. The results are flagged in the Info parameter. Upon 1117/// return, Offset is adjusted as specified by the GEP indices. 1118void SROA::isSafeGEP(GetElementPtrInst *GEPI, AllocaInst *AI, 1119 uint64_t &Offset, AllocaInfo &Info) { 1120 gep_type_iterator GEPIt = gep_type_begin(GEPI), E = gep_type_end(GEPI); 1121 if (GEPIt == E) 1122 return; 1123 1124 // Walk through the GEP type indices, checking the types that this indexes 1125 // into. 1126 for (; GEPIt != E; ++GEPIt) { 1127 // Ignore struct elements, no extra checking needed for these. 1128 if ((*GEPIt)->isStructTy()) 1129 continue; 1130 1131 ConstantInt *IdxVal = dyn_cast<ConstantInt>(GEPIt.getOperand()); 1132 if (!IdxVal) 1133 return MarkUnsafe(Info, GEPI); 1134 } 1135 1136 // Compute the offset due to this GEP and check if the alloca has a 1137 // component element at that offset. 1138 SmallVector<Value*, 8> Indices(GEPI->op_begin() + 1, GEPI->op_end()); 1139 Offset += TD->getIndexedOffset(GEPI->getPointerOperandType(), 1140 &Indices[0], Indices.size()); 1141 if (!TypeHasComponent(AI->getAllocatedType(), Offset, 0)) 1142 MarkUnsafe(Info, GEPI); 1143} 1144 1145/// isHomogeneousAggregate - Check if type T is a struct or array containing 1146/// elements of the same type (which is always true for arrays). If so, 1147/// return true with NumElts and EltTy set to the number of elements and the 1148/// element type, respectively. 1149static bool isHomogeneousAggregate(const Type *T, unsigned &NumElts, 1150 const Type *&EltTy) { 1151 if (const ArrayType *AT = dyn_cast<ArrayType>(T)) { 1152 NumElts = AT->getNumElements(); 1153 EltTy = (NumElts == 0 ? 0 : AT->getElementType()); 1154 return true; 1155 } 1156 if (const StructType *ST = dyn_cast<StructType>(T)) { 1157 NumElts = ST->getNumContainedTypes(); 1158 EltTy = (NumElts == 0 ? 0 : ST->getContainedType(0)); 1159 for (unsigned n = 1; n < NumElts; ++n) { 1160 if (ST->getContainedType(n) != EltTy) 1161 return false; 1162 } 1163 return true; 1164 } 1165 return false; 1166} 1167 1168/// isCompatibleAggregate - Check if T1 and T2 are either the same type or are 1169/// "homogeneous" aggregates with the same element type and number of elements. 1170static bool isCompatibleAggregate(const Type *T1, const Type *T2) { 1171 if (T1 == T2) 1172 return true; 1173 1174 unsigned NumElts1, NumElts2; 1175 const Type *EltTy1, *EltTy2; 1176 if (isHomogeneousAggregate(T1, NumElts1, EltTy1) && 1177 isHomogeneousAggregate(T2, NumElts2, EltTy2) && 1178 NumElts1 == NumElts2 && 1179 EltTy1 == EltTy2) 1180 return true; 1181 1182 return false; 1183} 1184 1185/// isSafeMemAccess - Check if a load/store/memcpy operates on the entire AI 1186/// alloca or has an offset and size that corresponds to a component element 1187/// within it. The offset checked here may have been formed from a GEP with a 1188/// pointer bitcasted to a different type. 1189void SROA::isSafeMemAccess(AllocaInst *AI, uint64_t Offset, uint64_t MemSize, 1190 const Type *MemOpType, bool isStore, 1191 AllocaInfo &Info, Instruction *TheAccess) { 1192 // Check if this is a load/store of the entire alloca. 1193 if (Offset == 0 && MemSize == TD->getTypeAllocSize(AI->getAllocatedType())) { 1194 // This can be safe for MemIntrinsics (where MemOpType is 0) and integer 1195 // loads/stores (which are essentially the same as the MemIntrinsics with 1196 // regard to copying padding between elements). But, if an alloca is 1197 // flagged as both a source and destination of such operations, we'll need 1198 // to check later for padding between elements. 1199 if (!MemOpType || MemOpType->isIntegerTy()) { 1200 if (isStore) 1201 Info.isMemCpyDst = true; 1202 else 1203 Info.isMemCpySrc = true; 1204 return; 1205 } 1206 // This is also safe for references using a type that is compatible with 1207 // the type of the alloca, so that loads/stores can be rewritten using 1208 // insertvalue/extractvalue. 1209 if (isCompatibleAggregate(MemOpType, AI->getAllocatedType())) { 1210 Info.hasSubelementAccess = true; 1211 return; 1212 } 1213 } 1214 // Check if the offset/size correspond to a component within the alloca type. 1215 const Type *T = AI->getAllocatedType(); 1216 if (TypeHasComponent(T, Offset, MemSize)) { 1217 Info.hasSubelementAccess = true; 1218 return; 1219 } 1220 1221 return MarkUnsafe(Info, TheAccess); 1222} 1223 1224/// TypeHasComponent - Return true if T has a component type with the 1225/// specified offset and size. If Size is zero, do not check the size. 1226bool SROA::TypeHasComponent(const Type *T, uint64_t Offset, uint64_t Size) { 1227 const Type *EltTy; 1228 uint64_t EltSize; 1229 if (const StructType *ST = dyn_cast<StructType>(T)) { 1230 const StructLayout *Layout = TD->getStructLayout(ST); 1231 unsigned EltIdx = Layout->getElementContainingOffset(Offset); 1232 EltTy = ST->getContainedType(EltIdx); 1233 EltSize = TD->getTypeAllocSize(EltTy); 1234 Offset -= Layout->getElementOffset(EltIdx); 1235 } else if (const ArrayType *AT = dyn_cast<ArrayType>(T)) { 1236 EltTy = AT->getElementType(); 1237 EltSize = TD->getTypeAllocSize(EltTy); 1238 if (Offset >= AT->getNumElements() * EltSize) 1239 return false; 1240 Offset %= EltSize; 1241 } else { 1242 return false; 1243 } 1244 if (Offset == 0 && (Size == 0 || EltSize == Size)) 1245 return true; 1246 // Check if the component spans multiple elements. 1247 if (Offset + Size > EltSize) 1248 return false; 1249 return TypeHasComponent(EltTy, Offset, Size); 1250} 1251 1252/// RewriteForScalarRepl - Alloca AI is being split into NewElts, so rewrite 1253/// the instruction I, which references it, to use the separate elements. 1254/// Offset indicates the position within AI that is referenced by this 1255/// instruction. 1256void SROA::RewriteForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset, 1257 SmallVector<AllocaInst*, 32> &NewElts) { 1258 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E; ++UI) { 1259 Instruction *User = cast<Instruction>(*UI); 1260 1261 if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) { 1262 RewriteBitCast(BC, AI, Offset, NewElts); 1263 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) { 1264 RewriteGEP(GEPI, AI, Offset, NewElts); 1265 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) { 1266 ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength()); 1267 uint64_t MemSize = Length->getZExtValue(); 1268 if (Offset == 0 && 1269 MemSize == TD->getTypeAllocSize(AI->getAllocatedType())) 1270 RewriteMemIntrinUserOfAlloca(MI, I, AI, NewElts); 1271 // Otherwise the intrinsic can only touch a single element and the 1272 // address operand will be updated, so nothing else needs to be done. 1273 } else if (LoadInst *LI = dyn_cast<LoadInst>(User)) { 1274 const Type *LIType = LI->getType(); 1275 1276 if (isCompatibleAggregate(LIType, AI->getAllocatedType())) { 1277 // Replace: 1278 // %res = load { i32, i32 }* %alloc 1279 // with: 1280 // %load.0 = load i32* %alloc.0 1281 // %insert.0 insertvalue { i32, i32 } zeroinitializer, i32 %load.0, 0 1282 // %load.1 = load i32* %alloc.1 1283 // %insert = insertvalue { i32, i32 } %insert.0, i32 %load.1, 1 1284 // (Also works for arrays instead of structs) 1285 Value *Insert = UndefValue::get(LIType); 1286 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { 1287 Value *Load = new LoadInst(NewElts[i], "load", LI); 1288 Insert = InsertValueInst::Create(Insert, Load, i, "insert", LI); 1289 } 1290 LI->replaceAllUsesWith(Insert); 1291 DeadInsts.push_back(LI); 1292 } else if (LIType->isIntegerTy() && 1293 TD->getTypeAllocSize(LIType) == 1294 TD->getTypeAllocSize(AI->getAllocatedType())) { 1295 // If this is a load of the entire alloca to an integer, rewrite it. 1296 RewriteLoadUserOfWholeAlloca(LI, AI, NewElts); 1297 } 1298 } else if (StoreInst *SI = dyn_cast<StoreInst>(User)) { 1299 Value *Val = SI->getOperand(0); 1300 const Type *SIType = Val->getType(); 1301 if (isCompatibleAggregate(SIType, AI->getAllocatedType())) { 1302 // Replace: 1303 // store { i32, i32 } %val, { i32, i32 }* %alloc 1304 // with: 1305 // %val.0 = extractvalue { i32, i32 } %val, 0 1306 // store i32 %val.0, i32* %alloc.0 1307 // %val.1 = extractvalue { i32, i32 } %val, 1 1308 // store i32 %val.1, i32* %alloc.1 1309 // (Also works for arrays instead of structs) 1310 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { 1311 Value *Extract = ExtractValueInst::Create(Val, i, Val->getName(), SI); 1312 new StoreInst(Extract, NewElts[i], SI); 1313 } 1314 DeadInsts.push_back(SI); 1315 } else if (SIType->isIntegerTy() && 1316 TD->getTypeAllocSize(SIType) == 1317 TD->getTypeAllocSize(AI->getAllocatedType())) { 1318 // If this is a store of the entire alloca from an integer, rewrite it. 1319 RewriteStoreUserOfWholeAlloca(SI, AI, NewElts); 1320 } 1321 } 1322 } 1323} 1324 1325/// RewriteBitCast - Update a bitcast reference to the alloca being replaced 1326/// and recursively continue updating all of its uses. 1327void SROA::RewriteBitCast(BitCastInst *BC, AllocaInst *AI, uint64_t Offset, 1328 SmallVector<AllocaInst*, 32> &NewElts) { 1329 RewriteForScalarRepl(BC, AI, Offset, NewElts); 1330 if (BC->getOperand(0) != AI) 1331 return; 1332 1333 // The bitcast references the original alloca. Replace its uses with 1334 // references to the first new element alloca. 1335 Instruction *Val = NewElts[0]; 1336 if (Val->getType() != BC->getDestTy()) { 1337 Val = new BitCastInst(Val, BC->getDestTy(), "", BC); 1338 Val->takeName(BC); 1339 } 1340 BC->replaceAllUsesWith(Val); 1341 DeadInsts.push_back(BC); 1342} 1343 1344/// FindElementAndOffset - Return the index of the element containing Offset 1345/// within the specified type, which must be either a struct or an array. 1346/// Sets T to the type of the element and Offset to the offset within that 1347/// element. IdxTy is set to the type of the index result to be used in a 1348/// GEP instruction. 1349uint64_t SROA::FindElementAndOffset(const Type *&T, uint64_t &Offset, 1350 const Type *&IdxTy) { 1351 uint64_t Idx = 0; 1352 if (const StructType *ST = dyn_cast<StructType>(T)) { 1353 const StructLayout *Layout = TD->getStructLayout(ST); 1354 Idx = Layout->getElementContainingOffset(Offset); 1355 T = ST->getContainedType(Idx); 1356 Offset -= Layout->getElementOffset(Idx); 1357 IdxTy = Type::getInt32Ty(T->getContext()); 1358 return Idx; 1359 } 1360 const ArrayType *AT = cast<ArrayType>(T); 1361 T = AT->getElementType(); 1362 uint64_t EltSize = TD->getTypeAllocSize(T); 1363 Idx = Offset / EltSize; 1364 Offset -= Idx * EltSize; 1365 IdxTy = Type::getInt64Ty(T->getContext()); 1366 return Idx; 1367} 1368 1369/// RewriteGEP - Check if this GEP instruction moves the pointer across 1370/// elements of the alloca that are being split apart, and if so, rewrite 1371/// the GEP to be relative to the new element. 1372void SROA::RewriteGEP(GetElementPtrInst *GEPI, AllocaInst *AI, uint64_t Offset, 1373 SmallVector<AllocaInst*, 32> &NewElts) { 1374 uint64_t OldOffset = Offset; 1375 SmallVector<Value*, 8> Indices(GEPI->op_begin() + 1, GEPI->op_end()); 1376 Offset += TD->getIndexedOffset(GEPI->getPointerOperandType(), 1377 &Indices[0], Indices.size()); 1378 1379 RewriteForScalarRepl(GEPI, AI, Offset, NewElts); 1380 1381 const Type *T = AI->getAllocatedType(); 1382 const Type *IdxTy; 1383 uint64_t OldIdx = FindElementAndOffset(T, OldOffset, IdxTy); 1384 if (GEPI->getOperand(0) == AI) 1385 OldIdx = ~0ULL; // Force the GEP to be rewritten. 1386 1387 T = AI->getAllocatedType(); 1388 uint64_t EltOffset = Offset; 1389 uint64_t Idx = FindElementAndOffset(T, EltOffset, IdxTy); 1390 1391 // If this GEP does not move the pointer across elements of the alloca 1392 // being split, then it does not needs to be rewritten. 1393 if (Idx == OldIdx) 1394 return; 1395 1396 const Type *i32Ty = Type::getInt32Ty(AI->getContext()); 1397 SmallVector<Value*, 8> NewArgs; 1398 NewArgs.push_back(Constant::getNullValue(i32Ty)); 1399 while (EltOffset != 0) { 1400 uint64_t EltIdx = FindElementAndOffset(T, EltOffset, IdxTy); 1401 NewArgs.push_back(ConstantInt::get(IdxTy, EltIdx)); 1402 } 1403 Instruction *Val = NewElts[Idx]; 1404 if (NewArgs.size() > 1) { 1405 Val = GetElementPtrInst::CreateInBounds(Val, NewArgs.begin(), 1406 NewArgs.end(), "", GEPI); 1407 Val->takeName(GEPI); 1408 } 1409 if (Val->getType() != GEPI->getType()) 1410 Val = new BitCastInst(Val, GEPI->getType(), Val->getName(), GEPI); 1411 GEPI->replaceAllUsesWith(Val); 1412 DeadInsts.push_back(GEPI); 1413} 1414 1415/// RewriteMemIntrinUserOfAlloca - MI is a memcpy/memset/memmove from or to AI. 1416/// Rewrite it to copy or set the elements of the scalarized memory. 1417void SROA::RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *Inst, 1418 AllocaInst *AI, 1419 SmallVector<AllocaInst*, 32> &NewElts) { 1420 // If this is a memcpy/memmove, construct the other pointer as the 1421 // appropriate type. The "Other" pointer is the pointer that goes to memory 1422 // that doesn't have anything to do with the alloca that we are promoting. For 1423 // memset, this Value* stays null. 1424 Value *OtherPtr = 0; 1425 unsigned MemAlignment = MI->getAlignment(); 1426 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(MI)) { // memmove/memcopy 1427 if (Inst == MTI->getRawDest()) 1428 OtherPtr = MTI->getRawSource(); 1429 else { 1430 assert(Inst == MTI->getRawSource()); 1431 OtherPtr = MTI->getRawDest(); 1432 } 1433 } 1434 1435 // If there is an other pointer, we want to convert it to the same pointer 1436 // type as AI has, so we can GEP through it safely. 1437 if (OtherPtr) { 1438 unsigned AddrSpace = 1439 cast<PointerType>(OtherPtr->getType())->getAddressSpace(); 1440 1441 // Remove bitcasts and all-zero GEPs from OtherPtr. This is an 1442 // optimization, but it's also required to detect the corner case where 1443 // both pointer operands are referencing the same memory, and where 1444 // OtherPtr may be a bitcast or GEP that currently being rewritten. (This 1445 // function is only called for mem intrinsics that access the whole 1446 // aggregate, so non-zero GEPs are not an issue here.) 1447 OtherPtr = OtherPtr->stripPointerCasts(); 1448 1449 // Copying the alloca to itself is a no-op: just delete it. 1450 if (OtherPtr == AI || OtherPtr == NewElts[0]) { 1451 // This code will run twice for a no-op memcpy -- once for each operand. 1452 // Put only one reference to MI on the DeadInsts list. 1453 for (SmallVector<Value*, 32>::const_iterator I = DeadInsts.begin(), 1454 E = DeadInsts.end(); I != E; ++I) 1455 if (*I == MI) return; 1456 DeadInsts.push_back(MI); 1457 return; 1458 } 1459 1460 // If the pointer is not the right type, insert a bitcast to the right 1461 // type. 1462 const Type *NewTy = 1463 PointerType::get(AI->getType()->getElementType(), AddrSpace); 1464 1465 if (OtherPtr->getType() != NewTy) 1466 OtherPtr = new BitCastInst(OtherPtr, NewTy, OtherPtr->getName(), MI); 1467 } 1468 1469 // Process each element of the aggregate. 1470 bool SROADest = MI->getRawDest() == Inst; 1471 1472 Constant *Zero = Constant::getNullValue(Type::getInt32Ty(MI->getContext())); 1473 1474 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { 1475 // If this is a memcpy/memmove, emit a GEP of the other element address. 1476 Value *OtherElt = 0; 1477 unsigned OtherEltAlign = MemAlignment; 1478 1479 if (OtherPtr) { 1480 Value *Idx[2] = { Zero, 1481 ConstantInt::get(Type::getInt32Ty(MI->getContext()), i) }; 1482 OtherElt = GetElementPtrInst::CreateInBounds(OtherPtr, Idx, Idx + 2, 1483 OtherPtr->getName()+"."+Twine(i), 1484 MI); 1485 uint64_t EltOffset; 1486 const PointerType *OtherPtrTy = cast<PointerType>(OtherPtr->getType()); 1487 const Type *OtherTy = OtherPtrTy->getElementType(); 1488 if (const StructType *ST = dyn_cast<StructType>(OtherTy)) { 1489 EltOffset = TD->getStructLayout(ST)->getElementOffset(i); 1490 } else { 1491 const Type *EltTy = cast<SequentialType>(OtherTy)->getElementType(); 1492 EltOffset = TD->getTypeAllocSize(EltTy)*i; 1493 } 1494 1495 // The alignment of the other pointer is the guaranteed alignment of the 1496 // element, which is affected by both the known alignment of the whole 1497 // mem intrinsic and the alignment of the element. If the alignment of 1498 // the memcpy (f.e.) is 32 but the element is at a 4-byte offset, then the 1499 // known alignment is just 4 bytes. 1500 OtherEltAlign = (unsigned)MinAlign(OtherEltAlign, EltOffset); 1501 } 1502 1503 Value *EltPtr = NewElts[i]; 1504 const Type *EltTy = cast<PointerType>(EltPtr->getType())->getElementType(); 1505 1506 // If we got down to a scalar, insert a load or store as appropriate. 1507 if (EltTy->isSingleValueType()) { 1508 if (isa<MemTransferInst>(MI)) { 1509 if (SROADest) { 1510 // From Other to Alloca. 1511 Value *Elt = new LoadInst(OtherElt, "tmp", false, OtherEltAlign, MI); 1512 new StoreInst(Elt, EltPtr, MI); 1513 } else { 1514 // From Alloca to Other. 1515 Value *Elt = new LoadInst(EltPtr, "tmp", MI); 1516 new StoreInst(Elt, OtherElt, false, OtherEltAlign, MI); 1517 } 1518 continue; 1519 } 1520 assert(isa<MemSetInst>(MI)); 1521 1522 // If the stored element is zero (common case), just store a null 1523 // constant. 1524 Constant *StoreVal; 1525 if (ConstantInt *CI = dyn_cast<ConstantInt>(MI->getArgOperand(1))) { 1526 if (CI->isZero()) { 1527 StoreVal = Constant::getNullValue(EltTy); // 0.0, null, 0, <0,0> 1528 } else { 1529 // If EltTy is a vector type, get the element type. 1530 const Type *ValTy = EltTy->getScalarType(); 1531 1532 // Construct an integer with the right value. 1533 unsigned EltSize = TD->getTypeSizeInBits(ValTy); 1534 APInt OneVal(EltSize, CI->getZExtValue()); 1535 APInt TotalVal(OneVal); 1536 // Set each byte. 1537 for (unsigned i = 0; 8*i < EltSize; ++i) { 1538 TotalVal = TotalVal.shl(8); 1539 TotalVal |= OneVal; 1540 } 1541 1542 // Convert the integer value to the appropriate type. 1543 StoreVal = ConstantInt::get(CI->getContext(), TotalVal); 1544 if (ValTy->isPointerTy()) 1545 StoreVal = ConstantExpr::getIntToPtr(StoreVal, ValTy); 1546 else if (ValTy->isFloatingPointTy()) 1547 StoreVal = ConstantExpr::getBitCast(StoreVal, ValTy); 1548 assert(StoreVal->getType() == ValTy && "Type mismatch!"); 1549 1550 // If the requested value was a vector constant, create it. 1551 if (EltTy != ValTy) { 1552 unsigned NumElts = cast<VectorType>(ValTy)->getNumElements(); 1553 SmallVector<Constant*, 16> Elts(NumElts, StoreVal); 1554 StoreVal = ConstantVector::get(&Elts[0], NumElts); 1555 } 1556 } 1557 new StoreInst(StoreVal, EltPtr, MI); 1558 continue; 1559 } 1560 // Otherwise, if we're storing a byte variable, use a memset call for 1561 // this element. 1562 } 1563 1564 unsigned EltSize = TD->getTypeAllocSize(EltTy); 1565 1566 IRBuilder<> Builder(MI); 1567 1568 // Finally, insert the meminst for this element. 1569 if (isa<MemSetInst>(MI)) { 1570 Builder.CreateMemSet(EltPtr, MI->getArgOperand(1), EltSize, 1571 MI->isVolatile()); 1572 } else { 1573 assert(isa<MemTransferInst>(MI)); 1574 Value *Dst = SROADest ? EltPtr : OtherElt; // Dest ptr 1575 Value *Src = SROADest ? OtherElt : EltPtr; // Src ptr 1576 1577 if (isa<MemCpyInst>(MI)) 1578 Builder.CreateMemCpy(Dst, Src, EltSize, OtherEltAlign,MI->isVolatile()); 1579 else 1580 Builder.CreateMemMove(Dst, Src, EltSize,OtherEltAlign,MI->isVolatile()); 1581 } 1582 } 1583 DeadInsts.push_back(MI); 1584} 1585 1586/// RewriteStoreUserOfWholeAlloca - We found a store of an integer that 1587/// overwrites the entire allocation. Extract out the pieces of the stored 1588/// integer and store them individually. 1589void SROA::RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocaInst *AI, 1590 SmallVector<AllocaInst*, 32> &NewElts){ 1591 // Extract each element out of the integer according to its structure offset 1592 // and store the element value to the individual alloca. 1593 Value *SrcVal = SI->getOperand(0); 1594 const Type *AllocaEltTy = AI->getAllocatedType(); 1595 uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy); 1596 1597 IRBuilder<> Builder(SI); 1598 1599 // Handle tail padding by extending the operand 1600 if (TD->getTypeSizeInBits(SrcVal->getType()) != AllocaSizeBits) 1601 SrcVal = Builder.CreateZExt(SrcVal, 1602 IntegerType::get(SI->getContext(), AllocaSizeBits)); 1603 1604 DEBUG(dbgs() << "PROMOTING STORE TO WHOLE ALLOCA: " << *AI << '\n' << *SI 1605 << '\n'); 1606 1607 // There are two forms here: AI could be an array or struct. Both cases 1608 // have different ways to compute the element offset. 1609 if (const StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) { 1610 const StructLayout *Layout = TD->getStructLayout(EltSTy); 1611 1612 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { 1613 // Get the number of bits to shift SrcVal to get the value. 1614 const Type *FieldTy = EltSTy->getElementType(i); 1615 uint64_t Shift = Layout->getElementOffsetInBits(i); 1616 1617 if (TD->isBigEndian()) 1618 Shift = AllocaSizeBits-Shift-TD->getTypeAllocSizeInBits(FieldTy); 1619 1620 Value *EltVal = SrcVal; 1621 if (Shift) { 1622 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift); 1623 EltVal = Builder.CreateLShr(EltVal, ShiftVal, "sroa.store.elt"); 1624 } 1625 1626 // Truncate down to an integer of the right size. 1627 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy); 1628 1629 // Ignore zero sized fields like {}, they obviously contain no data. 1630 if (FieldSizeBits == 0) continue; 1631 1632 if (FieldSizeBits != AllocaSizeBits) 1633 EltVal = Builder.CreateTrunc(EltVal, 1634 IntegerType::get(SI->getContext(), FieldSizeBits)); 1635 Value *DestField = NewElts[i]; 1636 if (EltVal->getType() == FieldTy) { 1637 // Storing to an integer field of this size, just do it. 1638 } else if (FieldTy->isFloatingPointTy() || FieldTy->isVectorTy()) { 1639 // Bitcast to the right element type (for fp/vector values). 1640 EltVal = Builder.CreateBitCast(EltVal, FieldTy); 1641 } else { 1642 // Otherwise, bitcast the dest pointer (for aggregates). 1643 DestField = Builder.CreateBitCast(DestField, 1644 PointerType::getUnqual(EltVal->getType())); 1645 } 1646 new StoreInst(EltVal, DestField, SI); 1647 } 1648 1649 } else { 1650 const ArrayType *ATy = cast<ArrayType>(AllocaEltTy); 1651 const Type *ArrayEltTy = ATy->getElementType(); 1652 uint64_t ElementOffset = TD->getTypeAllocSizeInBits(ArrayEltTy); 1653 uint64_t ElementSizeBits = TD->getTypeSizeInBits(ArrayEltTy); 1654 1655 uint64_t Shift; 1656 1657 if (TD->isBigEndian()) 1658 Shift = AllocaSizeBits-ElementOffset; 1659 else 1660 Shift = 0; 1661 1662 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { 1663 // Ignore zero sized fields like {}, they obviously contain no data. 1664 if (ElementSizeBits == 0) continue; 1665 1666 Value *EltVal = SrcVal; 1667 if (Shift) { 1668 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift); 1669 EltVal = Builder.CreateLShr(EltVal, ShiftVal, "sroa.store.elt"); 1670 } 1671 1672 // Truncate down to an integer of the right size. 1673 if (ElementSizeBits != AllocaSizeBits) 1674 EltVal = Builder.CreateTrunc(EltVal, 1675 IntegerType::get(SI->getContext(), 1676 ElementSizeBits)); 1677 Value *DestField = NewElts[i]; 1678 if (EltVal->getType() == ArrayEltTy) { 1679 // Storing to an integer field of this size, just do it. 1680 } else if (ArrayEltTy->isFloatingPointTy() || 1681 ArrayEltTy->isVectorTy()) { 1682 // Bitcast to the right element type (for fp/vector values). 1683 EltVal = Builder.CreateBitCast(EltVal, ArrayEltTy); 1684 } else { 1685 // Otherwise, bitcast the dest pointer (for aggregates). 1686 DestField = Builder.CreateBitCast(DestField, 1687 PointerType::getUnqual(EltVal->getType())); 1688 } 1689 new StoreInst(EltVal, DestField, SI); 1690 1691 if (TD->isBigEndian()) 1692 Shift -= ElementOffset; 1693 else 1694 Shift += ElementOffset; 1695 } 1696 } 1697 1698 DeadInsts.push_back(SI); 1699} 1700 1701/// RewriteLoadUserOfWholeAlloca - We found a load of the entire allocation to 1702/// an integer. Load the individual pieces to form the aggregate value. 1703void SROA::RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocaInst *AI, 1704 SmallVector<AllocaInst*, 32> &NewElts) { 1705 // Extract each element out of the NewElts according to its structure offset 1706 // and form the result value. 1707 const Type *AllocaEltTy = AI->getAllocatedType(); 1708 uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy); 1709 1710 DEBUG(dbgs() << "PROMOTING LOAD OF WHOLE ALLOCA: " << *AI << '\n' << *LI 1711 << '\n'); 1712 1713 // There are two forms here: AI could be an array or struct. Both cases 1714 // have different ways to compute the element offset. 1715 const StructLayout *Layout = 0; 1716 uint64_t ArrayEltBitOffset = 0; 1717 if (const StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) { 1718 Layout = TD->getStructLayout(EltSTy); 1719 } else { 1720 const Type *ArrayEltTy = cast<ArrayType>(AllocaEltTy)->getElementType(); 1721 ArrayEltBitOffset = TD->getTypeAllocSizeInBits(ArrayEltTy); 1722 } 1723 1724 Value *ResultVal = 1725 Constant::getNullValue(IntegerType::get(LI->getContext(), AllocaSizeBits)); 1726 1727 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { 1728 // Load the value from the alloca. If the NewElt is an aggregate, cast 1729 // the pointer to an integer of the same size before doing the load. 1730 Value *SrcField = NewElts[i]; 1731 const Type *FieldTy = 1732 cast<PointerType>(SrcField->getType())->getElementType(); 1733 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy); 1734 1735 // Ignore zero sized fields like {}, they obviously contain no data. 1736 if (FieldSizeBits == 0) continue; 1737 1738 const IntegerType *FieldIntTy = IntegerType::get(LI->getContext(), 1739 FieldSizeBits); 1740 if (!FieldTy->isIntegerTy() && !FieldTy->isFloatingPointTy() && 1741 !FieldTy->isVectorTy()) 1742 SrcField = new BitCastInst(SrcField, 1743 PointerType::getUnqual(FieldIntTy), 1744 "", LI); 1745 SrcField = new LoadInst(SrcField, "sroa.load.elt", LI); 1746 1747 // If SrcField is a fp or vector of the right size but that isn't an 1748 // integer type, bitcast to an integer so we can shift it. 1749 if (SrcField->getType() != FieldIntTy) 1750 SrcField = new BitCastInst(SrcField, FieldIntTy, "", LI); 1751 1752 // Zero extend the field to be the same size as the final alloca so that 1753 // we can shift and insert it. 1754 if (SrcField->getType() != ResultVal->getType()) 1755 SrcField = new ZExtInst(SrcField, ResultVal->getType(), "", LI); 1756 1757 // Determine the number of bits to shift SrcField. 1758 uint64_t Shift; 1759 if (Layout) // Struct case. 1760 Shift = Layout->getElementOffsetInBits(i); 1761 else // Array case. 1762 Shift = i*ArrayEltBitOffset; 1763 1764 if (TD->isBigEndian()) 1765 Shift = AllocaSizeBits-Shift-FieldIntTy->getBitWidth(); 1766 1767 if (Shift) { 1768 Value *ShiftVal = ConstantInt::get(SrcField->getType(), Shift); 1769 SrcField = BinaryOperator::CreateShl(SrcField, ShiftVal, "", LI); 1770 } 1771 1772 // Don't create an 'or x, 0' on the first iteration. 1773 if (!isa<Constant>(ResultVal) || 1774 !cast<Constant>(ResultVal)->isNullValue()) 1775 ResultVal = BinaryOperator::CreateOr(SrcField, ResultVal, "", LI); 1776 else 1777 ResultVal = SrcField; 1778 } 1779 1780 // Handle tail padding by truncating the result 1781 if (TD->getTypeSizeInBits(LI->getType()) != AllocaSizeBits) 1782 ResultVal = new TruncInst(ResultVal, LI->getType(), "", LI); 1783 1784 LI->replaceAllUsesWith(ResultVal); 1785 DeadInsts.push_back(LI); 1786} 1787 1788/// HasPadding - Return true if the specified type has any structure or 1789/// alignment padding in between the elements that would be split apart 1790/// by SROA; return false otherwise. 1791static bool HasPadding(const Type *Ty, const TargetData &TD) { 1792 if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) { 1793 Ty = ATy->getElementType(); 1794 return TD.getTypeSizeInBits(Ty) != TD.getTypeAllocSizeInBits(Ty); 1795 } 1796 1797 // SROA currently handles only Arrays and Structs. 1798 const StructType *STy = cast<StructType>(Ty); 1799 const StructLayout *SL = TD.getStructLayout(STy); 1800 unsigned PrevFieldBitOffset = 0; 1801 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) { 1802 unsigned FieldBitOffset = SL->getElementOffsetInBits(i); 1803 1804 // Check to see if there is any padding between this element and the 1805 // previous one. 1806 if (i) { 1807 unsigned PrevFieldEnd = 1808 PrevFieldBitOffset+TD.getTypeSizeInBits(STy->getElementType(i-1)); 1809 if (PrevFieldEnd < FieldBitOffset) 1810 return true; 1811 } 1812 PrevFieldBitOffset = FieldBitOffset; 1813 } 1814 // Check for tail padding. 1815 if (unsigned EltCount = STy->getNumElements()) { 1816 unsigned PrevFieldEnd = PrevFieldBitOffset + 1817 TD.getTypeSizeInBits(STy->getElementType(EltCount-1)); 1818 if (PrevFieldEnd < SL->getSizeInBits()) 1819 return true; 1820 } 1821 return false; 1822} 1823 1824/// isSafeStructAllocaToScalarRepl - Check to see if the specified allocation of 1825/// an aggregate can be broken down into elements. Return 0 if not, 3 if safe, 1826/// or 1 if safe after canonicalization has been performed. 1827bool SROA::isSafeAllocaToScalarRepl(AllocaInst *AI) { 1828 // Loop over the use list of the alloca. We can only transform it if all of 1829 // the users are safe to transform. 1830 AllocaInfo Info; 1831 1832 isSafeForScalarRepl(AI, AI, 0, Info); 1833 if (Info.isUnsafe) { 1834 DEBUG(dbgs() << "Cannot transform: " << *AI << '\n'); 1835 return false; 1836 } 1837 1838 // Okay, we know all the users are promotable. If the aggregate is a memcpy 1839 // source and destination, we have to be careful. In particular, the memcpy 1840 // could be moving around elements that live in structure padding of the LLVM 1841 // types, but may actually be used. In these cases, we refuse to promote the 1842 // struct. 1843 if (Info.isMemCpySrc && Info.isMemCpyDst && 1844 HasPadding(AI->getAllocatedType(), *TD)) 1845 return false; 1846 1847 // If the alloca never has an access to just *part* of it, but is accessed 1848 // via loads and stores, then we should use ConvertToScalarInfo to promote 1849 // the alloca instead of promoting each piece at a time and inserting fission 1850 // and fusion code. 1851 if (!Info.hasSubelementAccess && Info.hasALoadOrStore) { 1852 // If the struct/array just has one element, use basic SRoA. 1853 if (const StructType *ST = dyn_cast<StructType>(AI->getAllocatedType())) { 1854 if (ST->getNumElements() > 1) return false; 1855 } else { 1856 if (cast<ArrayType>(AI->getAllocatedType())->getNumElements() > 1) 1857 return false; 1858 } 1859 } 1860 return true; 1861} 1862 1863 1864 1865/// PointsToConstantGlobal - Return true if V (possibly indirectly) points to 1866/// some part of a constant global variable. This intentionally only accepts 1867/// constant expressions because we don't can't rewrite arbitrary instructions. 1868static bool PointsToConstantGlobal(Value *V) { 1869 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V)) 1870 return GV->isConstant(); 1871 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) 1872 if (CE->getOpcode() == Instruction::BitCast || 1873 CE->getOpcode() == Instruction::GetElementPtr) 1874 return PointsToConstantGlobal(CE->getOperand(0)); 1875 return false; 1876} 1877 1878/// isOnlyCopiedFromConstantGlobal - Recursively walk the uses of a (derived) 1879/// pointer to an alloca. Ignore any reads of the pointer, return false if we 1880/// see any stores or other unknown uses. If we see pointer arithmetic, keep 1881/// track of whether it moves the pointer (with isOffset) but otherwise traverse 1882/// the uses. If we see a memcpy/memmove that targets an unoffseted pointer to 1883/// the alloca, and if the source pointer is a pointer to a constant global, we 1884/// can optimize this. 1885static bool isOnlyCopiedFromConstantGlobal(Value *V, MemTransferInst *&TheCopy, 1886 bool isOffset) { 1887 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) { 1888 User *U = cast<Instruction>(*UI); 1889 1890 if (LoadInst *LI = dyn_cast<LoadInst>(U)) { 1891 // Ignore non-volatile loads, they are always ok. 1892 if (LI->isVolatile()) return false; 1893 continue; 1894 } 1895 1896 if (BitCastInst *BCI = dyn_cast<BitCastInst>(U)) { 1897 // If uses of the bitcast are ok, we are ok. 1898 if (!isOnlyCopiedFromConstantGlobal(BCI, TheCopy, isOffset)) 1899 return false; 1900 continue; 1901 } 1902 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) { 1903 // If the GEP has all zero indices, it doesn't offset the pointer. If it 1904 // doesn't, it does. 1905 if (!isOnlyCopiedFromConstantGlobal(GEP, TheCopy, 1906 isOffset || !GEP->hasAllZeroIndices())) 1907 return false; 1908 continue; 1909 } 1910 1911 if (CallSite CS = U) { 1912 // If this is a readonly/readnone call site, then we know it is just a 1913 // load and we can ignore it. 1914 if (CS.onlyReadsMemory()) 1915 continue; 1916 1917 // If this is the function being called then we treat it like a load and 1918 // ignore it. 1919 if (CS.isCallee(UI)) 1920 continue; 1921 1922 // If this is being passed as a byval argument, the caller is making a 1923 // copy, so it is only a read of the alloca. 1924 unsigned ArgNo = CS.getArgumentNo(UI); 1925 if (CS.paramHasAttr(ArgNo+1, Attribute::ByVal)) 1926 continue; 1927 } 1928 1929 // If this is isn't our memcpy/memmove, reject it as something we can't 1930 // handle. 1931 MemTransferInst *MI = dyn_cast<MemTransferInst>(U); 1932 if (MI == 0) 1933 return false; 1934 1935 // If the transfer is using the alloca as a source of the transfer, then 1936 // ignore it since it is a load (unless the transfer is volatile). 1937 if (UI.getOperandNo() == 1) { 1938 if (MI->isVolatile()) return false; 1939 continue; 1940 } 1941 1942 // If we already have seen a copy, reject the second one. 1943 if (TheCopy) return false; 1944 1945 // If the pointer has been offset from the start of the alloca, we can't 1946 // safely handle this. 1947 if (isOffset) return false; 1948 1949 // If the memintrinsic isn't using the alloca as the dest, reject it. 1950 if (UI.getOperandNo() != 0) return false; 1951 1952 // If the source of the memcpy/move is not a constant global, reject it. 1953 if (!PointsToConstantGlobal(MI->getSource())) 1954 return false; 1955 1956 // Otherwise, the transform is safe. Remember the copy instruction. 1957 TheCopy = MI; 1958 } 1959 return true; 1960} 1961 1962/// isOnlyCopiedFromConstantGlobal - Return true if the specified alloca is only 1963/// modified by a copy from a constant global. If we can prove this, we can 1964/// replace any uses of the alloca with uses of the global directly. 1965MemTransferInst *SROA::isOnlyCopiedFromConstantGlobal(AllocaInst *AI) { 1966 MemTransferInst *TheCopy = 0; 1967 if (::isOnlyCopiedFromConstantGlobal(AI, TheCopy, false)) 1968 return TheCopy; 1969 return 0; 1970} 1971