ScalarReplAggregates.cpp revision 204642
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/Pass.h" 32#include "llvm/Analysis/Dominators.h" 33#include "llvm/Target/TargetData.h" 34#include "llvm/Transforms/Utils/PromoteMemToReg.h" 35#include "llvm/Transforms/Utils/Local.h" 36#include "llvm/Support/Debug.h" 37#include "llvm/Support/ErrorHandling.h" 38#include "llvm/Support/GetElementPtrTypeIterator.h" 39#include "llvm/Support/IRBuilder.h" 40#include "llvm/Support/MathExtras.h" 41#include "llvm/Support/raw_ostream.h" 42#include "llvm/ADT/SmallVector.h" 43#include "llvm/ADT/Statistic.h" 44using namespace llvm; 45 46STATISTIC(NumReplaced, "Number of allocas broken up"); 47STATISTIC(NumPromoted, "Number of allocas promoted"); 48STATISTIC(NumConverted, "Number of aggregates converted to scalar"); 49STATISTIC(NumGlobals, "Number of allocas copied from constant global"); 50 51namespace { 52 struct SROA : public FunctionPass { 53 static char ID; // Pass identification, replacement for typeid 54 explicit SROA(signed T = -1) : FunctionPass(&ID) { 55 if (T == -1) 56 SRThreshold = 128; 57 else 58 SRThreshold = T; 59 } 60 61 bool runOnFunction(Function &F); 62 63 bool performScalarRepl(Function &F); 64 bool performPromotion(Function &F); 65 66 // getAnalysisUsage - This pass does not require any passes, but we know it 67 // will not alter the CFG, so say so. 68 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 69 AU.addRequired<DominatorTree>(); 70 AU.addRequired<DominanceFrontier>(); 71 AU.setPreservesCFG(); 72 } 73 74 private: 75 TargetData *TD; 76 77 /// DeadInsts - Keep track of instructions we have made dead, so that 78 /// we can remove them after we are done working. 79 SmallVector<Value*, 32> DeadInsts; 80 81 /// AllocaInfo - When analyzing uses of an alloca instruction, this captures 82 /// information about the uses. All these fields are initialized to false 83 /// and set to true when something is learned. 84 struct AllocaInfo { 85 /// isUnsafe - This is set to true if the alloca cannot be SROA'd. 86 bool isUnsafe : 1; 87 88 /// isMemCpySrc - This is true if this aggregate is memcpy'd from. 89 bool isMemCpySrc : 1; 90 91 /// isMemCpyDst - This is true if this aggregate is memcpy'd into. 92 bool isMemCpyDst : 1; 93 94 AllocaInfo() 95 : isUnsafe(false), isMemCpySrc(false), isMemCpyDst(false) {} 96 }; 97 98 unsigned SRThreshold; 99 100 void MarkUnsafe(AllocaInfo &I) { I.isUnsafe = true; } 101 102 bool isSafeAllocaToScalarRepl(AllocaInst *AI); 103 104 void isSafeForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset, 105 AllocaInfo &Info); 106 void isSafeGEP(GetElementPtrInst *GEPI, AllocaInst *AI, uint64_t &Offset, 107 AllocaInfo &Info); 108 void isSafeMemAccess(AllocaInst *AI, uint64_t Offset, uint64_t MemSize, 109 const Type *MemOpType, bool isStore, AllocaInfo &Info); 110 bool TypeHasComponent(const Type *T, uint64_t Offset, uint64_t Size); 111 uint64_t FindElementAndOffset(const Type *&T, uint64_t &Offset, 112 const Type *&IdxTy); 113 114 void DoScalarReplacement(AllocaInst *AI, 115 std::vector<AllocaInst*> &WorkList); 116 void DeleteDeadInstructions(); 117 AllocaInst *AddNewAlloca(Function &F, const Type *Ty, AllocaInst *Base); 118 119 void RewriteForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset, 120 SmallVector<AllocaInst*, 32> &NewElts); 121 void RewriteBitCast(BitCastInst *BC, AllocaInst *AI, uint64_t Offset, 122 SmallVector<AllocaInst*, 32> &NewElts); 123 void RewriteGEP(GetElementPtrInst *GEPI, AllocaInst *AI, uint64_t Offset, 124 SmallVector<AllocaInst*, 32> &NewElts); 125 void RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *Inst, 126 AllocaInst *AI, 127 SmallVector<AllocaInst*, 32> &NewElts); 128 void RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocaInst *AI, 129 SmallVector<AllocaInst*, 32> &NewElts); 130 void RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocaInst *AI, 131 SmallVector<AllocaInst*, 32> &NewElts); 132 133 bool CanConvertToScalar(Value *V, bool &IsNotTrivial, const Type *&VecTy, 134 bool &SawVec, uint64_t Offset, unsigned AllocaSize); 135 void ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, uint64_t Offset); 136 Value *ConvertScalar_ExtractValue(Value *NV, const Type *ToType, 137 uint64_t Offset, IRBuilder<> &Builder); 138 Value *ConvertScalar_InsertValue(Value *StoredVal, Value *ExistingVal, 139 uint64_t Offset, IRBuilder<> &Builder); 140 static Instruction *isOnlyCopiedFromConstantGlobal(AllocaInst *AI); 141 }; 142} 143 144char SROA::ID = 0; 145static RegisterPass<SROA> X("scalarrepl", "Scalar Replacement of Aggregates"); 146 147// Public interface to the ScalarReplAggregates pass 148FunctionPass *llvm::createScalarReplAggregatesPass(signed int Threshold) { 149 return new SROA(Threshold); 150} 151 152 153bool SROA::runOnFunction(Function &F) { 154 TD = getAnalysisIfAvailable<TargetData>(); 155 156 bool Changed = performPromotion(F); 157 158 // FIXME: ScalarRepl currently depends on TargetData more than it 159 // theoretically needs to. It should be refactored in order to support 160 // target-independent IR. Until this is done, just skip the actual 161 // scalar-replacement portion of this pass. 162 if (!TD) return Changed; 163 164 while (1) { 165 bool LocalChange = performScalarRepl(F); 166 if (!LocalChange) break; // No need to repromote if no scalarrepl 167 Changed = true; 168 LocalChange = performPromotion(F); 169 if (!LocalChange) break; // No need to re-scalarrepl if no promotion 170 } 171 172 return Changed; 173} 174 175 176bool SROA::performPromotion(Function &F) { 177 std::vector<AllocaInst*> Allocas; 178 DominatorTree &DT = getAnalysis<DominatorTree>(); 179 DominanceFrontier &DF = getAnalysis<DominanceFrontier>(); 180 181 BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function 182 183 bool Changed = false; 184 185 while (1) { 186 Allocas.clear(); 187 188 // Find allocas that are safe to promote, by looking at all instructions in 189 // the entry node 190 for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I) 191 if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) // Is it an alloca? 192 if (isAllocaPromotable(AI)) 193 Allocas.push_back(AI); 194 195 if (Allocas.empty()) break; 196 197 PromoteMemToReg(Allocas, DT, DF); 198 NumPromoted += Allocas.size(); 199 Changed = true; 200 } 201 202 return Changed; 203} 204 205/// ShouldAttemptScalarRepl - Decide if an alloca is a good candidate for 206/// SROA. It must be a struct or array type with a small number of elements. 207static bool ShouldAttemptScalarRepl(AllocaInst *AI) { 208 const Type *T = AI->getAllocatedType(); 209 // Do not promote any struct into more than 32 separate vars. 210 if (const StructType *ST = dyn_cast<StructType>(T)) 211 return ST->getNumElements() <= 32; 212 // Arrays are much less likely to be safe for SROA; only consider 213 // them if they are very small. 214 if (const ArrayType *AT = dyn_cast<ArrayType>(T)) 215 return AT->getNumElements() <= 8; 216 return false; 217} 218 219// performScalarRepl - This algorithm is a simple worklist driven algorithm, 220// which runs on all of the malloc/alloca instructions in the function, removing 221// them if they are only used by getelementptr instructions. 222// 223bool SROA::performScalarRepl(Function &F) { 224 std::vector<AllocaInst*> WorkList; 225 226 // Scan the entry basic block, adding any alloca's and mallocs to the worklist 227 BasicBlock &BB = F.getEntryBlock(); 228 for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I) 229 if (AllocaInst *A = dyn_cast<AllocaInst>(I)) 230 WorkList.push_back(A); 231 232 // Process the worklist 233 bool Changed = false; 234 while (!WorkList.empty()) { 235 AllocaInst *AI = WorkList.back(); 236 WorkList.pop_back(); 237 238 // Handle dead allocas trivially. These can be formed by SROA'ing arrays 239 // with unused elements. 240 if (AI->use_empty()) { 241 AI->eraseFromParent(); 242 continue; 243 } 244 245 // If this alloca is impossible for us to promote, reject it early. 246 if (AI->isArrayAllocation() || !AI->getAllocatedType()->isSized()) 247 continue; 248 249 // Check to see if this allocation is only modified by a memcpy/memmove from 250 // a constant global. If this is the case, we can change all users to use 251 // the constant global instead. This is commonly produced by the CFE by 252 // constructs like "void foo() { int A[] = {1,2,3,4,5,6,7,8,9...}; }" if 'A' 253 // is only subsequently read. 254 if (Instruction *TheCopy = isOnlyCopiedFromConstantGlobal(AI)) { 255 DEBUG(dbgs() << "Found alloca equal to global: " << *AI << '\n'); 256 DEBUG(dbgs() << " memcpy = " << *TheCopy << '\n'); 257 Constant *TheSrc = cast<Constant>(TheCopy->getOperand(2)); 258 AI->replaceAllUsesWith(ConstantExpr::getBitCast(TheSrc, AI->getType())); 259 TheCopy->eraseFromParent(); // Don't mutate the global. 260 AI->eraseFromParent(); 261 ++NumGlobals; 262 Changed = true; 263 continue; 264 } 265 266 // Check to see if we can perform the core SROA transformation. We cannot 267 // transform the allocation instruction if it is an array allocation 268 // (allocations OF arrays are ok though), and an allocation of a scalar 269 // value cannot be decomposed at all. 270 uint64_t AllocaSize = TD->getTypeAllocSize(AI->getAllocatedType()); 271 272 // Do not promote [0 x %struct]. 273 if (AllocaSize == 0) continue; 274 275 // If the alloca looks like a good candidate for scalar replacement, and if 276 // all its users can be transformed, then split up the aggregate into its 277 // separate elements. 278 if (ShouldAttemptScalarRepl(AI) && isSafeAllocaToScalarRepl(AI)) { 279 DoScalarReplacement(AI, WorkList); 280 Changed = true; 281 continue; 282 } 283 284 // Do not promote any struct whose size is too big. 285 if (AllocaSize > SRThreshold) continue; 286 287 // If we can turn this aggregate value (potentially with casts) into a 288 // simple scalar value that can be mem2reg'd into a register value. 289 // IsNotTrivial tracks whether this is something that mem2reg could have 290 // promoted itself. If so, we don't want to transform it needlessly. Note 291 // that we can't just check based on the type: the alloca may be of an i32 292 // but that has pointer arithmetic to set byte 3 of it or something. 293 bool IsNotTrivial = false; 294 const Type *VectorTy = 0; 295 bool HadAVector = false; 296 if (CanConvertToScalar(AI, IsNotTrivial, VectorTy, HadAVector, 297 0, unsigned(AllocaSize)) && IsNotTrivial) { 298 AllocaInst *NewAI; 299 // If we were able to find a vector type that can handle this with 300 // insert/extract elements, and if there was at least one use that had 301 // a vector type, promote this to a vector. We don't want to promote 302 // random stuff that doesn't use vectors (e.g. <9 x double>) because then 303 // we just get a lot of insert/extracts. If at least one vector is 304 // involved, then we probably really do have a union of vector/array. 305 if (VectorTy && VectorTy->isVectorTy() && HadAVector) { 306 DEBUG(dbgs() << "CONVERT TO VECTOR: " << *AI << "\n TYPE = " 307 << *VectorTy << '\n'); 308 309 // Create and insert the vector alloca. 310 NewAI = new AllocaInst(VectorTy, 0, "", AI->getParent()->begin()); 311 ConvertUsesToScalar(AI, NewAI, 0); 312 } else { 313 DEBUG(dbgs() << "CONVERT TO SCALAR INTEGER: " << *AI << "\n"); 314 315 // Create and insert the integer alloca. 316 const Type *NewTy = IntegerType::get(AI->getContext(), AllocaSize*8); 317 NewAI = new AllocaInst(NewTy, 0, "", AI->getParent()->begin()); 318 ConvertUsesToScalar(AI, NewAI, 0); 319 } 320 NewAI->takeName(AI); 321 AI->eraseFromParent(); 322 ++NumConverted; 323 Changed = true; 324 continue; 325 } 326 327 // Otherwise, couldn't process this alloca. 328 } 329 330 return Changed; 331} 332 333/// DoScalarReplacement - This alloca satisfied the isSafeAllocaToScalarRepl 334/// predicate, do SROA now. 335void SROA::DoScalarReplacement(AllocaInst *AI, 336 std::vector<AllocaInst*> &WorkList) { 337 DEBUG(dbgs() << "Found inst to SROA: " << *AI << '\n'); 338 SmallVector<AllocaInst*, 32> ElementAllocas; 339 if (const StructType *ST = dyn_cast<StructType>(AI->getAllocatedType())) { 340 ElementAllocas.reserve(ST->getNumContainedTypes()); 341 for (unsigned i = 0, e = ST->getNumContainedTypes(); i != e; ++i) { 342 AllocaInst *NA = new AllocaInst(ST->getContainedType(i), 0, 343 AI->getAlignment(), 344 AI->getName() + "." + Twine(i), AI); 345 ElementAllocas.push_back(NA); 346 WorkList.push_back(NA); // Add to worklist for recursive processing 347 } 348 } else { 349 const ArrayType *AT = cast<ArrayType>(AI->getAllocatedType()); 350 ElementAllocas.reserve(AT->getNumElements()); 351 const Type *ElTy = AT->getElementType(); 352 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) { 353 AllocaInst *NA = new AllocaInst(ElTy, 0, AI->getAlignment(), 354 AI->getName() + "." + Twine(i), AI); 355 ElementAllocas.push_back(NA); 356 WorkList.push_back(NA); // Add to worklist for recursive processing 357 } 358 } 359 360 // Now that we have created the new alloca instructions, rewrite all the 361 // uses of the old alloca. 362 RewriteForScalarRepl(AI, AI, 0, ElementAllocas); 363 364 // Now erase any instructions that were made dead while rewriting the alloca. 365 DeleteDeadInstructions(); 366 AI->eraseFromParent(); 367 368 NumReplaced++; 369} 370 371/// DeleteDeadInstructions - Erase instructions on the DeadInstrs list, 372/// recursively including all their operands that become trivially dead. 373void SROA::DeleteDeadInstructions() { 374 while (!DeadInsts.empty()) { 375 Instruction *I = cast<Instruction>(DeadInsts.pop_back_val()); 376 377 for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI) 378 if (Instruction *U = dyn_cast<Instruction>(*OI)) { 379 // Zero out the operand and see if it becomes trivially dead. 380 // (But, don't add allocas to the dead instruction list -- they are 381 // already on the worklist and will be deleted separately.) 382 *OI = 0; 383 if (isInstructionTriviallyDead(U) && !isa<AllocaInst>(U)) 384 DeadInsts.push_back(U); 385 } 386 387 I->eraseFromParent(); 388 } 389} 390 391/// isSafeForScalarRepl - Check if instruction I is a safe use with regard to 392/// performing scalar replacement of alloca AI. The results are flagged in 393/// the Info parameter. Offset indicates the position within AI that is 394/// referenced by this instruction. 395void SROA::isSafeForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset, 396 AllocaInfo &Info) { 397 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E; ++UI) { 398 Instruction *User = cast<Instruction>(*UI); 399 400 if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) { 401 isSafeForScalarRepl(BC, AI, Offset, Info); 402 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) { 403 uint64_t GEPOffset = Offset; 404 isSafeGEP(GEPI, AI, GEPOffset, Info); 405 if (!Info.isUnsafe) 406 isSafeForScalarRepl(GEPI, AI, GEPOffset, Info); 407 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(UI)) { 408 ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength()); 409 if (Length) 410 isSafeMemAccess(AI, Offset, Length->getZExtValue(), 0, 411 UI.getOperandNo() == 1, Info); 412 else 413 MarkUnsafe(Info); 414 } else if (LoadInst *LI = dyn_cast<LoadInst>(User)) { 415 if (!LI->isVolatile()) { 416 const Type *LIType = LI->getType(); 417 isSafeMemAccess(AI, Offset, TD->getTypeAllocSize(LIType), 418 LIType, false, Info); 419 } else 420 MarkUnsafe(Info); 421 } else if (StoreInst *SI = dyn_cast<StoreInst>(User)) { 422 // Store is ok if storing INTO the pointer, not storing the pointer 423 if (!SI->isVolatile() && SI->getOperand(0) != I) { 424 const Type *SIType = SI->getOperand(0)->getType(); 425 isSafeMemAccess(AI, Offset, TD->getTypeAllocSize(SIType), 426 SIType, true, Info); 427 } else 428 MarkUnsafe(Info); 429 } else { 430 DEBUG(errs() << " Transformation preventing inst: " << *User << '\n'); 431 MarkUnsafe(Info); 432 } 433 if (Info.isUnsafe) return; 434 } 435} 436 437/// isSafeGEP - Check if a GEP instruction can be handled for scalar 438/// replacement. It is safe when all the indices are constant, in-bounds 439/// references, and when the resulting offset corresponds to an element within 440/// the alloca type. The results are flagged in the Info parameter. Upon 441/// return, Offset is adjusted as specified by the GEP indices. 442void SROA::isSafeGEP(GetElementPtrInst *GEPI, AllocaInst *AI, 443 uint64_t &Offset, AllocaInfo &Info) { 444 gep_type_iterator GEPIt = gep_type_begin(GEPI), E = gep_type_end(GEPI); 445 if (GEPIt == E) 446 return; 447 448 // Walk through the GEP type indices, checking the types that this indexes 449 // into. 450 for (; GEPIt != E; ++GEPIt) { 451 // Ignore struct elements, no extra checking needed for these. 452 if ((*GEPIt)->isStructTy()) 453 continue; 454 455 ConstantInt *IdxVal = dyn_cast<ConstantInt>(GEPIt.getOperand()); 456 if (!IdxVal) 457 return MarkUnsafe(Info); 458 } 459 460 // Compute the offset due to this GEP and check if the alloca has a 461 // component element at that offset. 462 SmallVector<Value*, 8> Indices(GEPI->op_begin() + 1, GEPI->op_end()); 463 Offset += TD->getIndexedOffset(GEPI->getPointerOperandType(), 464 &Indices[0], Indices.size()); 465 if (!TypeHasComponent(AI->getAllocatedType(), Offset, 0)) 466 MarkUnsafe(Info); 467} 468 469/// isSafeMemAccess - Check if a load/store/memcpy operates on the entire AI 470/// alloca or has an offset and size that corresponds to a component element 471/// within it. The offset checked here may have been formed from a GEP with a 472/// pointer bitcasted to a different type. 473void SROA::isSafeMemAccess(AllocaInst *AI, uint64_t Offset, uint64_t MemSize, 474 const Type *MemOpType, bool isStore, 475 AllocaInfo &Info) { 476 // Check if this is a load/store of the entire alloca. 477 if (Offset == 0 && MemSize == TD->getTypeAllocSize(AI->getAllocatedType())) { 478 bool UsesAggregateType = (MemOpType == AI->getAllocatedType()); 479 // This is safe for MemIntrinsics (where MemOpType is 0), integer types 480 // (which are essentially the same as the MemIntrinsics, especially with 481 // regard to copying padding between elements), or references using the 482 // aggregate type of the alloca. 483 if (!MemOpType || MemOpType->isIntegerTy() || UsesAggregateType) { 484 if (!UsesAggregateType) { 485 if (isStore) 486 Info.isMemCpyDst = true; 487 else 488 Info.isMemCpySrc = true; 489 } 490 return; 491 } 492 } 493 // Check if the offset/size correspond to a component within the alloca type. 494 const Type *T = AI->getAllocatedType(); 495 if (TypeHasComponent(T, Offset, MemSize)) 496 return; 497 498 return MarkUnsafe(Info); 499} 500 501/// TypeHasComponent - Return true if T has a component type with the 502/// specified offset and size. If Size is zero, do not check the size. 503bool SROA::TypeHasComponent(const Type *T, uint64_t Offset, uint64_t Size) { 504 const Type *EltTy; 505 uint64_t EltSize; 506 if (const StructType *ST = dyn_cast<StructType>(T)) { 507 const StructLayout *Layout = TD->getStructLayout(ST); 508 unsigned EltIdx = Layout->getElementContainingOffset(Offset); 509 EltTy = ST->getContainedType(EltIdx); 510 EltSize = TD->getTypeAllocSize(EltTy); 511 Offset -= Layout->getElementOffset(EltIdx); 512 } else if (const ArrayType *AT = dyn_cast<ArrayType>(T)) { 513 EltTy = AT->getElementType(); 514 EltSize = TD->getTypeAllocSize(EltTy); 515 if (Offset >= AT->getNumElements() * EltSize) 516 return false; 517 Offset %= EltSize; 518 } else { 519 return false; 520 } 521 if (Offset == 0 && (Size == 0 || EltSize == Size)) 522 return true; 523 // Check if the component spans multiple elements. 524 if (Offset + Size > EltSize) 525 return false; 526 return TypeHasComponent(EltTy, Offset, Size); 527} 528 529/// RewriteForScalarRepl - Alloca AI is being split into NewElts, so rewrite 530/// the instruction I, which references it, to use the separate elements. 531/// Offset indicates the position within AI that is referenced by this 532/// instruction. 533void SROA::RewriteForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset, 534 SmallVector<AllocaInst*, 32> &NewElts) { 535 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E; ++UI) { 536 Instruction *User = cast<Instruction>(*UI); 537 538 if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) { 539 RewriteBitCast(BC, AI, Offset, NewElts); 540 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) { 541 RewriteGEP(GEPI, AI, Offset, NewElts); 542 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) { 543 ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength()); 544 uint64_t MemSize = Length->getZExtValue(); 545 if (Offset == 0 && 546 MemSize == TD->getTypeAllocSize(AI->getAllocatedType())) 547 RewriteMemIntrinUserOfAlloca(MI, I, AI, NewElts); 548 // Otherwise the intrinsic can only touch a single element and the 549 // address operand will be updated, so nothing else needs to be done. 550 } else if (LoadInst *LI = dyn_cast<LoadInst>(User)) { 551 const Type *LIType = LI->getType(); 552 if (LIType == AI->getAllocatedType()) { 553 // Replace: 554 // %res = load { i32, i32 }* %alloc 555 // with: 556 // %load.0 = load i32* %alloc.0 557 // %insert.0 insertvalue { i32, i32 } zeroinitializer, i32 %load.0, 0 558 // %load.1 = load i32* %alloc.1 559 // %insert = insertvalue { i32, i32 } %insert.0, i32 %load.1, 1 560 // (Also works for arrays instead of structs) 561 Value *Insert = UndefValue::get(LIType); 562 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { 563 Value *Load = new LoadInst(NewElts[i], "load", LI); 564 Insert = InsertValueInst::Create(Insert, Load, i, "insert", LI); 565 } 566 LI->replaceAllUsesWith(Insert); 567 DeadInsts.push_back(LI); 568 } else if (LIType->isIntegerTy() && 569 TD->getTypeAllocSize(LIType) == 570 TD->getTypeAllocSize(AI->getAllocatedType())) { 571 // If this is a load of the entire alloca to an integer, rewrite it. 572 RewriteLoadUserOfWholeAlloca(LI, AI, NewElts); 573 } 574 } else if (StoreInst *SI = dyn_cast<StoreInst>(User)) { 575 Value *Val = SI->getOperand(0); 576 const Type *SIType = Val->getType(); 577 if (SIType == AI->getAllocatedType()) { 578 // Replace: 579 // store { i32, i32 } %val, { i32, i32 }* %alloc 580 // with: 581 // %val.0 = extractvalue { i32, i32 } %val, 0 582 // store i32 %val.0, i32* %alloc.0 583 // %val.1 = extractvalue { i32, i32 } %val, 1 584 // store i32 %val.1, i32* %alloc.1 585 // (Also works for arrays instead of structs) 586 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { 587 Value *Extract = ExtractValueInst::Create(Val, i, Val->getName(), SI); 588 new StoreInst(Extract, NewElts[i], SI); 589 } 590 DeadInsts.push_back(SI); 591 } else if (SIType->isIntegerTy() && 592 TD->getTypeAllocSize(SIType) == 593 TD->getTypeAllocSize(AI->getAllocatedType())) { 594 // If this is a store of the entire alloca from an integer, rewrite it. 595 RewriteStoreUserOfWholeAlloca(SI, AI, NewElts); 596 } 597 } 598 } 599} 600 601/// RewriteBitCast - Update a bitcast reference to the alloca being replaced 602/// and recursively continue updating all of its uses. 603void SROA::RewriteBitCast(BitCastInst *BC, AllocaInst *AI, uint64_t Offset, 604 SmallVector<AllocaInst*, 32> &NewElts) { 605 RewriteForScalarRepl(BC, AI, Offset, NewElts); 606 if (BC->getOperand(0) != AI) 607 return; 608 609 // The bitcast references the original alloca. Replace its uses with 610 // references to the first new element alloca. 611 Instruction *Val = NewElts[0]; 612 if (Val->getType() != BC->getDestTy()) { 613 Val = new BitCastInst(Val, BC->getDestTy(), "", BC); 614 Val->takeName(BC); 615 } 616 BC->replaceAllUsesWith(Val); 617 DeadInsts.push_back(BC); 618} 619 620/// FindElementAndOffset - Return the index of the element containing Offset 621/// within the specified type, which must be either a struct or an array. 622/// Sets T to the type of the element and Offset to the offset within that 623/// element. IdxTy is set to the type of the index result to be used in a 624/// GEP instruction. 625uint64_t SROA::FindElementAndOffset(const Type *&T, uint64_t &Offset, 626 const Type *&IdxTy) { 627 uint64_t Idx = 0; 628 if (const StructType *ST = dyn_cast<StructType>(T)) { 629 const StructLayout *Layout = TD->getStructLayout(ST); 630 Idx = Layout->getElementContainingOffset(Offset); 631 T = ST->getContainedType(Idx); 632 Offset -= Layout->getElementOffset(Idx); 633 IdxTy = Type::getInt32Ty(T->getContext()); 634 return Idx; 635 } 636 const ArrayType *AT = cast<ArrayType>(T); 637 T = AT->getElementType(); 638 uint64_t EltSize = TD->getTypeAllocSize(T); 639 Idx = Offset / EltSize; 640 Offset -= Idx * EltSize; 641 IdxTy = Type::getInt64Ty(T->getContext()); 642 return Idx; 643} 644 645/// RewriteGEP - Check if this GEP instruction moves the pointer across 646/// elements of the alloca that are being split apart, and if so, rewrite 647/// the GEP to be relative to the new element. 648void SROA::RewriteGEP(GetElementPtrInst *GEPI, AllocaInst *AI, uint64_t Offset, 649 SmallVector<AllocaInst*, 32> &NewElts) { 650 uint64_t OldOffset = Offset; 651 SmallVector<Value*, 8> Indices(GEPI->op_begin() + 1, GEPI->op_end()); 652 Offset += TD->getIndexedOffset(GEPI->getPointerOperandType(), 653 &Indices[0], Indices.size()); 654 655 RewriteForScalarRepl(GEPI, AI, Offset, NewElts); 656 657 const Type *T = AI->getAllocatedType(); 658 const Type *IdxTy; 659 uint64_t OldIdx = FindElementAndOffset(T, OldOffset, IdxTy); 660 if (GEPI->getOperand(0) == AI) 661 OldIdx = ~0ULL; // Force the GEP to be rewritten. 662 663 T = AI->getAllocatedType(); 664 uint64_t EltOffset = Offset; 665 uint64_t Idx = FindElementAndOffset(T, EltOffset, IdxTy); 666 667 // If this GEP does not move the pointer across elements of the alloca 668 // being split, then it does not needs to be rewritten. 669 if (Idx == OldIdx) 670 return; 671 672 const Type *i32Ty = Type::getInt32Ty(AI->getContext()); 673 SmallVector<Value*, 8> NewArgs; 674 NewArgs.push_back(Constant::getNullValue(i32Ty)); 675 while (EltOffset != 0) { 676 uint64_t EltIdx = FindElementAndOffset(T, EltOffset, IdxTy); 677 NewArgs.push_back(ConstantInt::get(IdxTy, EltIdx)); 678 } 679 Instruction *Val = NewElts[Idx]; 680 if (NewArgs.size() > 1) { 681 Val = GetElementPtrInst::CreateInBounds(Val, NewArgs.begin(), 682 NewArgs.end(), "", GEPI); 683 Val->takeName(GEPI); 684 } 685 if (Val->getType() != GEPI->getType()) 686 Val = new BitCastInst(Val, GEPI->getType(), Val->getName(), GEPI); 687 GEPI->replaceAllUsesWith(Val); 688 DeadInsts.push_back(GEPI); 689} 690 691/// RewriteMemIntrinUserOfAlloca - MI is a memcpy/memset/memmove from or to AI. 692/// Rewrite it to copy or set the elements of the scalarized memory. 693void SROA::RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *Inst, 694 AllocaInst *AI, 695 SmallVector<AllocaInst*, 32> &NewElts) { 696 // If this is a memcpy/memmove, construct the other pointer as the 697 // appropriate type. The "Other" pointer is the pointer that goes to memory 698 // that doesn't have anything to do with the alloca that we are promoting. For 699 // memset, this Value* stays null. 700 Value *OtherPtr = 0; 701 LLVMContext &Context = MI->getContext(); 702 unsigned MemAlignment = MI->getAlignment(); 703 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(MI)) { // memmove/memcopy 704 if (Inst == MTI->getRawDest()) 705 OtherPtr = MTI->getRawSource(); 706 else { 707 assert(Inst == MTI->getRawSource()); 708 OtherPtr = MTI->getRawDest(); 709 } 710 } 711 712 // If there is an other pointer, we want to convert it to the same pointer 713 // type as AI has, so we can GEP through it safely. 714 if (OtherPtr) { 715 716 // Remove bitcasts and all-zero GEPs from OtherPtr. This is an 717 // optimization, but it's also required to detect the corner case where 718 // both pointer operands are referencing the same memory, and where 719 // OtherPtr may be a bitcast or GEP that currently being rewritten. (This 720 // function is only called for mem intrinsics that access the whole 721 // aggregate, so non-zero GEPs are not an issue here.) 722 while (1) { 723 if (BitCastInst *BC = dyn_cast<BitCastInst>(OtherPtr)) { 724 OtherPtr = BC->getOperand(0); 725 continue; 726 } 727 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(OtherPtr)) { 728 // All zero GEPs are effectively bitcasts. 729 if (GEP->hasAllZeroIndices()) { 730 OtherPtr = GEP->getOperand(0); 731 continue; 732 } 733 } 734 break; 735 } 736 // Copying the alloca to itself is a no-op: just delete it. 737 if (OtherPtr == AI || OtherPtr == NewElts[0]) { 738 // This code will run twice for a no-op memcpy -- once for each operand. 739 // Put only one reference to MI on the DeadInsts list. 740 for (SmallVector<Value*, 32>::const_iterator I = DeadInsts.begin(), 741 E = DeadInsts.end(); I != E; ++I) 742 if (*I == MI) return; 743 DeadInsts.push_back(MI); 744 return; 745 } 746 747 if (ConstantExpr *BCE = dyn_cast<ConstantExpr>(OtherPtr)) 748 if (BCE->getOpcode() == Instruction::BitCast) 749 OtherPtr = BCE->getOperand(0); 750 751 // If the pointer is not the right type, insert a bitcast to the right 752 // type. 753 if (OtherPtr->getType() != AI->getType()) 754 OtherPtr = new BitCastInst(OtherPtr, AI->getType(), OtherPtr->getName(), 755 MI); 756 } 757 758 // Process each element of the aggregate. 759 Value *TheFn = MI->getOperand(0); 760 const Type *BytePtrTy = MI->getRawDest()->getType(); 761 bool SROADest = MI->getRawDest() == Inst; 762 763 Constant *Zero = Constant::getNullValue(Type::getInt32Ty(MI->getContext())); 764 765 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { 766 // If this is a memcpy/memmove, emit a GEP of the other element address. 767 Value *OtherElt = 0; 768 unsigned OtherEltAlign = MemAlignment; 769 770 if (OtherPtr) { 771 Value *Idx[2] = { Zero, 772 ConstantInt::get(Type::getInt32Ty(MI->getContext()), i) }; 773 OtherElt = GetElementPtrInst::CreateInBounds(OtherPtr, Idx, Idx + 2, 774 OtherPtr->getName()+"."+Twine(i), 775 MI); 776 uint64_t EltOffset; 777 const PointerType *OtherPtrTy = cast<PointerType>(OtherPtr->getType()); 778 if (const StructType *ST = 779 dyn_cast<StructType>(OtherPtrTy->getElementType())) { 780 EltOffset = TD->getStructLayout(ST)->getElementOffset(i); 781 } else { 782 const Type *EltTy = 783 cast<SequentialType>(OtherPtr->getType())->getElementType(); 784 EltOffset = TD->getTypeAllocSize(EltTy)*i; 785 } 786 787 // The alignment of the other pointer is the guaranteed alignment of the 788 // element, which is affected by both the known alignment of the whole 789 // mem intrinsic and the alignment of the element. If the alignment of 790 // the memcpy (f.e.) is 32 but the element is at a 4-byte offset, then the 791 // known alignment is just 4 bytes. 792 OtherEltAlign = (unsigned)MinAlign(OtherEltAlign, EltOffset); 793 } 794 795 Value *EltPtr = NewElts[i]; 796 const Type *EltTy = cast<PointerType>(EltPtr->getType())->getElementType(); 797 798 // If we got down to a scalar, insert a load or store as appropriate. 799 if (EltTy->isSingleValueType()) { 800 if (isa<MemTransferInst>(MI)) { 801 if (SROADest) { 802 // From Other to Alloca. 803 Value *Elt = new LoadInst(OtherElt, "tmp", false, OtherEltAlign, MI); 804 new StoreInst(Elt, EltPtr, MI); 805 } else { 806 // From Alloca to Other. 807 Value *Elt = new LoadInst(EltPtr, "tmp", MI); 808 new StoreInst(Elt, OtherElt, false, OtherEltAlign, MI); 809 } 810 continue; 811 } 812 assert(isa<MemSetInst>(MI)); 813 814 // If the stored element is zero (common case), just store a null 815 // constant. 816 Constant *StoreVal; 817 if (ConstantInt *CI = dyn_cast<ConstantInt>(MI->getOperand(2))) { 818 if (CI->isZero()) { 819 StoreVal = Constant::getNullValue(EltTy); // 0.0, null, 0, <0,0> 820 } else { 821 // If EltTy is a vector type, get the element type. 822 const Type *ValTy = EltTy->getScalarType(); 823 824 // Construct an integer with the right value. 825 unsigned EltSize = TD->getTypeSizeInBits(ValTy); 826 APInt OneVal(EltSize, CI->getZExtValue()); 827 APInt TotalVal(OneVal); 828 // Set each byte. 829 for (unsigned i = 0; 8*i < EltSize; ++i) { 830 TotalVal = TotalVal.shl(8); 831 TotalVal |= OneVal; 832 } 833 834 // Convert the integer value to the appropriate type. 835 StoreVal = ConstantInt::get(Context, TotalVal); 836 if (ValTy->isPointerTy()) 837 StoreVal = ConstantExpr::getIntToPtr(StoreVal, ValTy); 838 else if (ValTy->isFloatingPointTy()) 839 StoreVal = ConstantExpr::getBitCast(StoreVal, ValTy); 840 assert(StoreVal->getType() == ValTy && "Type mismatch!"); 841 842 // If the requested value was a vector constant, create it. 843 if (EltTy != ValTy) { 844 unsigned NumElts = cast<VectorType>(ValTy)->getNumElements(); 845 SmallVector<Constant*, 16> Elts(NumElts, StoreVal); 846 StoreVal = ConstantVector::get(&Elts[0], NumElts); 847 } 848 } 849 new StoreInst(StoreVal, EltPtr, MI); 850 continue; 851 } 852 // Otherwise, if we're storing a byte variable, use a memset call for 853 // this element. 854 } 855 856 // Cast the element pointer to BytePtrTy. 857 if (EltPtr->getType() != BytePtrTy) 858 EltPtr = new BitCastInst(EltPtr, BytePtrTy, EltPtr->getName(), MI); 859 860 // Cast the other pointer (if we have one) to BytePtrTy. 861 if (OtherElt && OtherElt->getType() != BytePtrTy) 862 OtherElt = new BitCastInst(OtherElt, BytePtrTy, OtherElt->getName(), MI); 863 864 unsigned EltSize = TD->getTypeAllocSize(EltTy); 865 866 // Finally, insert the meminst for this element. 867 if (isa<MemTransferInst>(MI)) { 868 Value *Ops[] = { 869 SROADest ? EltPtr : OtherElt, // Dest ptr 870 SROADest ? OtherElt : EltPtr, // Src ptr 871 ConstantInt::get(MI->getOperand(3)->getType(), EltSize), // Size 872 // Align 873 ConstantInt::get(Type::getInt32Ty(MI->getContext()), OtherEltAlign) 874 }; 875 CallInst::Create(TheFn, Ops, Ops + 4, "", MI); 876 } else { 877 assert(isa<MemSetInst>(MI)); 878 Value *Ops[] = { 879 EltPtr, MI->getOperand(2), // Dest, Value, 880 ConstantInt::get(MI->getOperand(3)->getType(), EltSize), // Size 881 Zero // Align 882 }; 883 CallInst::Create(TheFn, Ops, Ops + 4, "", MI); 884 } 885 } 886 DeadInsts.push_back(MI); 887} 888 889/// RewriteStoreUserOfWholeAlloca - We found a store of an integer that 890/// overwrites the entire allocation. Extract out the pieces of the stored 891/// integer and store them individually. 892void SROA::RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocaInst *AI, 893 SmallVector<AllocaInst*, 32> &NewElts){ 894 // Extract each element out of the integer according to its structure offset 895 // and store the element value to the individual alloca. 896 Value *SrcVal = SI->getOperand(0); 897 const Type *AllocaEltTy = AI->getAllocatedType(); 898 uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy); 899 900 // Handle tail padding by extending the operand 901 if (TD->getTypeSizeInBits(SrcVal->getType()) != AllocaSizeBits) 902 SrcVal = new ZExtInst(SrcVal, 903 IntegerType::get(SI->getContext(), AllocaSizeBits), 904 "", SI); 905 906 DEBUG(dbgs() << "PROMOTING STORE TO WHOLE ALLOCA: " << *AI << '\n' << *SI 907 << '\n'); 908 909 // There are two forms here: AI could be an array or struct. Both cases 910 // have different ways to compute the element offset. 911 if (const StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) { 912 const StructLayout *Layout = TD->getStructLayout(EltSTy); 913 914 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { 915 // Get the number of bits to shift SrcVal to get the value. 916 const Type *FieldTy = EltSTy->getElementType(i); 917 uint64_t Shift = Layout->getElementOffsetInBits(i); 918 919 if (TD->isBigEndian()) 920 Shift = AllocaSizeBits-Shift-TD->getTypeAllocSizeInBits(FieldTy); 921 922 Value *EltVal = SrcVal; 923 if (Shift) { 924 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift); 925 EltVal = BinaryOperator::CreateLShr(EltVal, ShiftVal, 926 "sroa.store.elt", SI); 927 } 928 929 // Truncate down to an integer of the right size. 930 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy); 931 932 // Ignore zero sized fields like {}, they obviously contain no data. 933 if (FieldSizeBits == 0) continue; 934 935 if (FieldSizeBits != AllocaSizeBits) 936 EltVal = new TruncInst(EltVal, 937 IntegerType::get(SI->getContext(), FieldSizeBits), 938 "", SI); 939 Value *DestField = NewElts[i]; 940 if (EltVal->getType() == FieldTy) { 941 // Storing to an integer field of this size, just do it. 942 } else if (FieldTy->isFloatingPointTy() || FieldTy->isVectorTy()) { 943 // Bitcast to the right element type (for fp/vector values). 944 EltVal = new BitCastInst(EltVal, FieldTy, "", SI); 945 } else { 946 // Otherwise, bitcast the dest pointer (for aggregates). 947 DestField = new BitCastInst(DestField, 948 PointerType::getUnqual(EltVal->getType()), 949 "", SI); 950 } 951 new StoreInst(EltVal, DestField, SI); 952 } 953 954 } else { 955 const ArrayType *ATy = cast<ArrayType>(AllocaEltTy); 956 const Type *ArrayEltTy = ATy->getElementType(); 957 uint64_t ElementOffset = TD->getTypeAllocSizeInBits(ArrayEltTy); 958 uint64_t ElementSizeBits = TD->getTypeSizeInBits(ArrayEltTy); 959 960 uint64_t Shift; 961 962 if (TD->isBigEndian()) 963 Shift = AllocaSizeBits-ElementOffset; 964 else 965 Shift = 0; 966 967 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { 968 // Ignore zero sized fields like {}, they obviously contain no data. 969 if (ElementSizeBits == 0) continue; 970 971 Value *EltVal = SrcVal; 972 if (Shift) { 973 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift); 974 EltVal = BinaryOperator::CreateLShr(EltVal, ShiftVal, 975 "sroa.store.elt", SI); 976 } 977 978 // Truncate down to an integer of the right size. 979 if (ElementSizeBits != AllocaSizeBits) 980 EltVal = new TruncInst(EltVal, 981 IntegerType::get(SI->getContext(), 982 ElementSizeBits),"",SI); 983 Value *DestField = NewElts[i]; 984 if (EltVal->getType() == ArrayEltTy) { 985 // Storing to an integer field of this size, just do it. 986 } else if (ArrayEltTy->isFloatingPointTy() || 987 ArrayEltTy->isVectorTy()) { 988 // Bitcast to the right element type (for fp/vector values). 989 EltVal = new BitCastInst(EltVal, ArrayEltTy, "", SI); 990 } else { 991 // Otherwise, bitcast the dest pointer (for aggregates). 992 DestField = new BitCastInst(DestField, 993 PointerType::getUnqual(EltVal->getType()), 994 "", SI); 995 } 996 new StoreInst(EltVal, DestField, SI); 997 998 if (TD->isBigEndian()) 999 Shift -= ElementOffset; 1000 else 1001 Shift += ElementOffset; 1002 } 1003 } 1004 1005 DeadInsts.push_back(SI); 1006} 1007 1008/// RewriteLoadUserOfWholeAlloca - We found a load of the entire allocation to 1009/// an integer. Load the individual pieces to form the aggregate value. 1010void SROA::RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocaInst *AI, 1011 SmallVector<AllocaInst*, 32> &NewElts) { 1012 // Extract each element out of the NewElts according to its structure offset 1013 // and form the result value. 1014 const Type *AllocaEltTy = AI->getAllocatedType(); 1015 uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy); 1016 1017 DEBUG(dbgs() << "PROMOTING LOAD OF WHOLE ALLOCA: " << *AI << '\n' << *LI 1018 << '\n'); 1019 1020 // There are two forms here: AI could be an array or struct. Both cases 1021 // have different ways to compute the element offset. 1022 const StructLayout *Layout = 0; 1023 uint64_t ArrayEltBitOffset = 0; 1024 if (const StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) { 1025 Layout = TD->getStructLayout(EltSTy); 1026 } else { 1027 const Type *ArrayEltTy = cast<ArrayType>(AllocaEltTy)->getElementType(); 1028 ArrayEltBitOffset = TD->getTypeAllocSizeInBits(ArrayEltTy); 1029 } 1030 1031 Value *ResultVal = 1032 Constant::getNullValue(IntegerType::get(LI->getContext(), AllocaSizeBits)); 1033 1034 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { 1035 // Load the value from the alloca. If the NewElt is an aggregate, cast 1036 // the pointer to an integer of the same size before doing the load. 1037 Value *SrcField = NewElts[i]; 1038 const Type *FieldTy = 1039 cast<PointerType>(SrcField->getType())->getElementType(); 1040 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy); 1041 1042 // Ignore zero sized fields like {}, they obviously contain no data. 1043 if (FieldSizeBits == 0) continue; 1044 1045 const IntegerType *FieldIntTy = IntegerType::get(LI->getContext(), 1046 FieldSizeBits); 1047 if (!FieldTy->isIntegerTy() && !FieldTy->isFloatingPointTy() && 1048 !FieldTy->isVectorTy()) 1049 SrcField = new BitCastInst(SrcField, 1050 PointerType::getUnqual(FieldIntTy), 1051 "", LI); 1052 SrcField = new LoadInst(SrcField, "sroa.load.elt", LI); 1053 1054 // If SrcField is a fp or vector of the right size but that isn't an 1055 // integer type, bitcast to an integer so we can shift it. 1056 if (SrcField->getType() != FieldIntTy) 1057 SrcField = new BitCastInst(SrcField, FieldIntTy, "", LI); 1058 1059 // Zero extend the field to be the same size as the final alloca so that 1060 // we can shift and insert it. 1061 if (SrcField->getType() != ResultVal->getType()) 1062 SrcField = new ZExtInst(SrcField, ResultVal->getType(), "", LI); 1063 1064 // Determine the number of bits to shift SrcField. 1065 uint64_t Shift; 1066 if (Layout) // Struct case. 1067 Shift = Layout->getElementOffsetInBits(i); 1068 else // Array case. 1069 Shift = i*ArrayEltBitOffset; 1070 1071 if (TD->isBigEndian()) 1072 Shift = AllocaSizeBits-Shift-FieldIntTy->getBitWidth(); 1073 1074 if (Shift) { 1075 Value *ShiftVal = ConstantInt::get(SrcField->getType(), Shift); 1076 SrcField = BinaryOperator::CreateShl(SrcField, ShiftVal, "", LI); 1077 } 1078 1079 ResultVal = BinaryOperator::CreateOr(SrcField, ResultVal, "", LI); 1080 } 1081 1082 // Handle tail padding by truncating the result 1083 if (TD->getTypeSizeInBits(LI->getType()) != AllocaSizeBits) 1084 ResultVal = new TruncInst(ResultVal, LI->getType(), "", LI); 1085 1086 LI->replaceAllUsesWith(ResultVal); 1087 DeadInsts.push_back(LI); 1088} 1089 1090/// HasPadding - Return true if the specified type has any structure or 1091/// alignment padding, false otherwise. 1092static bool HasPadding(const Type *Ty, const TargetData &TD) { 1093 if (const StructType *STy = dyn_cast<StructType>(Ty)) { 1094 const StructLayout *SL = TD.getStructLayout(STy); 1095 unsigned PrevFieldBitOffset = 0; 1096 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) { 1097 unsigned FieldBitOffset = SL->getElementOffsetInBits(i); 1098 1099 // Padding in sub-elements? 1100 if (HasPadding(STy->getElementType(i), TD)) 1101 return true; 1102 1103 // Check to see if there is any padding between this element and the 1104 // previous one. 1105 if (i) { 1106 unsigned PrevFieldEnd = 1107 PrevFieldBitOffset+TD.getTypeSizeInBits(STy->getElementType(i-1)); 1108 if (PrevFieldEnd < FieldBitOffset) 1109 return true; 1110 } 1111 1112 PrevFieldBitOffset = FieldBitOffset; 1113 } 1114 1115 // Check for tail padding. 1116 if (unsigned EltCount = STy->getNumElements()) { 1117 unsigned PrevFieldEnd = PrevFieldBitOffset + 1118 TD.getTypeSizeInBits(STy->getElementType(EltCount-1)); 1119 if (PrevFieldEnd < SL->getSizeInBits()) 1120 return true; 1121 } 1122 1123 } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) { 1124 return HasPadding(ATy->getElementType(), TD); 1125 } else if (const VectorType *VTy = dyn_cast<VectorType>(Ty)) { 1126 return HasPadding(VTy->getElementType(), TD); 1127 } 1128 return TD.getTypeSizeInBits(Ty) != TD.getTypeAllocSizeInBits(Ty); 1129} 1130 1131/// isSafeStructAllocaToScalarRepl - Check to see if the specified allocation of 1132/// an aggregate can be broken down into elements. Return 0 if not, 3 if safe, 1133/// or 1 if safe after canonicalization has been performed. 1134bool SROA::isSafeAllocaToScalarRepl(AllocaInst *AI) { 1135 // Loop over the use list of the alloca. We can only transform it if all of 1136 // the users are safe to transform. 1137 AllocaInfo Info; 1138 1139 isSafeForScalarRepl(AI, AI, 0, Info); 1140 if (Info.isUnsafe) { 1141 DEBUG(dbgs() << "Cannot transform: " << *AI << '\n'); 1142 return false; 1143 } 1144 1145 // Okay, we know all the users are promotable. If the aggregate is a memcpy 1146 // source and destination, we have to be careful. In particular, the memcpy 1147 // could be moving around elements that live in structure padding of the LLVM 1148 // types, but may actually be used. In these cases, we refuse to promote the 1149 // struct. 1150 if (Info.isMemCpySrc && Info.isMemCpyDst && 1151 HasPadding(AI->getAllocatedType(), *TD)) 1152 return false; 1153 1154 return true; 1155} 1156 1157/// MergeInType - Add the 'In' type to the accumulated type (Accum) so far at 1158/// the offset specified by Offset (which is specified in bytes). 1159/// 1160/// There are two cases we handle here: 1161/// 1) A union of vector types of the same size and potentially its elements. 1162/// Here we turn element accesses into insert/extract element operations. 1163/// This promotes a <4 x float> with a store of float to the third element 1164/// into a <4 x float> that uses insert element. 1165/// 2) A fully general blob of memory, which we turn into some (potentially 1166/// large) integer type with extract and insert operations where the loads 1167/// and stores would mutate the memory. 1168static void MergeInType(const Type *In, uint64_t Offset, const Type *&VecTy, 1169 unsigned AllocaSize, const TargetData &TD, 1170 LLVMContext &Context) { 1171 // If this could be contributing to a vector, analyze it. 1172 if (VecTy != Type::getVoidTy(Context)) { // either null or a vector type. 1173 1174 // If the In type is a vector that is the same size as the alloca, see if it 1175 // matches the existing VecTy. 1176 if (const VectorType *VInTy = dyn_cast<VectorType>(In)) { 1177 if (VInTy->getBitWidth()/8 == AllocaSize && Offset == 0) { 1178 // If we're storing/loading a vector of the right size, allow it as a 1179 // vector. If this the first vector we see, remember the type so that 1180 // we know the element size. 1181 if (VecTy == 0) 1182 VecTy = VInTy; 1183 return; 1184 } 1185 } else if (In->isFloatTy() || In->isDoubleTy() || 1186 (In->isIntegerTy() && In->getPrimitiveSizeInBits() >= 8 && 1187 isPowerOf2_32(In->getPrimitiveSizeInBits()))) { 1188 // If we're accessing something that could be an element of a vector, see 1189 // if the implied vector agrees with what we already have and if Offset is 1190 // compatible with it. 1191 unsigned EltSize = In->getPrimitiveSizeInBits()/8; 1192 if (Offset % EltSize == 0 && 1193 AllocaSize % EltSize == 0 && 1194 (VecTy == 0 || 1195 cast<VectorType>(VecTy)->getElementType() 1196 ->getPrimitiveSizeInBits()/8 == EltSize)) { 1197 if (VecTy == 0) 1198 VecTy = VectorType::get(In, AllocaSize/EltSize); 1199 return; 1200 } 1201 } 1202 } 1203 1204 // Otherwise, we have a case that we can't handle with an optimized vector 1205 // form. We can still turn this into a large integer. 1206 VecTy = Type::getVoidTy(Context); 1207} 1208 1209/// CanConvertToScalar - V is a pointer. If we can convert the pointee and all 1210/// its accesses to a single vector type, return true and set VecTy to 1211/// the new type. If we could convert the alloca into a single promotable 1212/// integer, return true but set VecTy to VoidTy. Further, if the use is not a 1213/// completely trivial use that mem2reg could promote, set IsNotTrivial. Offset 1214/// is the current offset from the base of the alloca being analyzed. 1215/// 1216/// If we see at least one access to the value that is as a vector type, set the 1217/// SawVec flag. 1218bool SROA::CanConvertToScalar(Value *V, bool &IsNotTrivial, const Type *&VecTy, 1219 bool &SawVec, uint64_t Offset, 1220 unsigned AllocaSize) { 1221 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) { 1222 Instruction *User = cast<Instruction>(*UI); 1223 1224 if (LoadInst *LI = dyn_cast<LoadInst>(User)) { 1225 // Don't break volatile loads. 1226 if (LI->isVolatile()) 1227 return false; 1228 MergeInType(LI->getType(), Offset, VecTy, 1229 AllocaSize, *TD, V->getContext()); 1230 SawVec |= LI->getType()->isVectorTy(); 1231 continue; 1232 } 1233 1234 if (StoreInst *SI = dyn_cast<StoreInst>(User)) { 1235 // Storing the pointer, not into the value? 1236 if (SI->getOperand(0) == V || SI->isVolatile()) return 0; 1237 MergeInType(SI->getOperand(0)->getType(), Offset, 1238 VecTy, AllocaSize, *TD, V->getContext()); 1239 SawVec |= SI->getOperand(0)->getType()->isVectorTy(); 1240 continue; 1241 } 1242 1243 if (BitCastInst *BCI = dyn_cast<BitCastInst>(User)) { 1244 if (!CanConvertToScalar(BCI, IsNotTrivial, VecTy, SawVec, Offset, 1245 AllocaSize)) 1246 return false; 1247 IsNotTrivial = true; 1248 continue; 1249 } 1250 1251 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) { 1252 // If this is a GEP with a variable indices, we can't handle it. 1253 if (!GEP->hasAllConstantIndices()) 1254 return false; 1255 1256 // Compute the offset that this GEP adds to the pointer. 1257 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end()); 1258 uint64_t GEPOffset = TD->getIndexedOffset(GEP->getPointerOperandType(), 1259 &Indices[0], Indices.size()); 1260 // See if all uses can be converted. 1261 if (!CanConvertToScalar(GEP, IsNotTrivial, VecTy, SawVec,Offset+GEPOffset, 1262 AllocaSize)) 1263 return false; 1264 IsNotTrivial = true; 1265 continue; 1266 } 1267 1268 // If this is a constant sized memset of a constant value (e.g. 0) we can 1269 // handle it. 1270 if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) { 1271 // Store of constant value and constant size. 1272 if (isa<ConstantInt>(MSI->getValue()) && 1273 isa<ConstantInt>(MSI->getLength())) { 1274 IsNotTrivial = true; 1275 continue; 1276 } 1277 } 1278 1279 // If this is a memcpy or memmove into or out of the whole allocation, we 1280 // can handle it like a load or store of the scalar type. 1281 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) { 1282 if (ConstantInt *Len = dyn_cast<ConstantInt>(MTI->getLength())) 1283 if (Len->getZExtValue() == AllocaSize && Offset == 0) { 1284 IsNotTrivial = true; 1285 continue; 1286 } 1287 } 1288 1289 // Otherwise, we cannot handle this! 1290 return false; 1291 } 1292 1293 return true; 1294} 1295 1296/// ConvertUsesToScalar - Convert all of the users of Ptr to use the new alloca 1297/// directly. This happens when we are converting an "integer union" to a 1298/// single integer scalar, or when we are converting a "vector union" to a 1299/// vector with insert/extractelement instructions. 1300/// 1301/// Offset is an offset from the original alloca, in bits that need to be 1302/// shifted to the right. By the end of this, there should be no uses of Ptr. 1303void SROA::ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, uint64_t Offset) { 1304 while (!Ptr->use_empty()) { 1305 Instruction *User = cast<Instruction>(Ptr->use_back()); 1306 1307 if (BitCastInst *CI = dyn_cast<BitCastInst>(User)) { 1308 ConvertUsesToScalar(CI, NewAI, Offset); 1309 CI->eraseFromParent(); 1310 continue; 1311 } 1312 1313 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) { 1314 // Compute the offset that this GEP adds to the pointer. 1315 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end()); 1316 uint64_t GEPOffset = TD->getIndexedOffset(GEP->getPointerOperandType(), 1317 &Indices[0], Indices.size()); 1318 ConvertUsesToScalar(GEP, NewAI, Offset+GEPOffset*8); 1319 GEP->eraseFromParent(); 1320 continue; 1321 } 1322 1323 IRBuilder<> Builder(User->getParent(), User); 1324 1325 if (LoadInst *LI = dyn_cast<LoadInst>(User)) { 1326 // The load is a bit extract from NewAI shifted right by Offset bits. 1327 Value *LoadedVal = Builder.CreateLoad(NewAI, "tmp"); 1328 Value *NewLoadVal 1329 = ConvertScalar_ExtractValue(LoadedVal, LI->getType(), Offset, Builder); 1330 LI->replaceAllUsesWith(NewLoadVal); 1331 LI->eraseFromParent(); 1332 continue; 1333 } 1334 1335 if (StoreInst *SI = dyn_cast<StoreInst>(User)) { 1336 assert(SI->getOperand(0) != Ptr && "Consistency error!"); 1337 Instruction *Old = Builder.CreateLoad(NewAI, NewAI->getName()+".in"); 1338 Value *New = ConvertScalar_InsertValue(SI->getOperand(0), Old, Offset, 1339 Builder); 1340 Builder.CreateStore(New, NewAI); 1341 SI->eraseFromParent(); 1342 1343 // If the load we just inserted is now dead, then the inserted store 1344 // overwrote the entire thing. 1345 if (Old->use_empty()) 1346 Old->eraseFromParent(); 1347 continue; 1348 } 1349 1350 // If this is a constant sized memset of a constant value (e.g. 0) we can 1351 // transform it into a store of the expanded constant value. 1352 if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) { 1353 assert(MSI->getRawDest() == Ptr && "Consistency error!"); 1354 unsigned NumBytes = cast<ConstantInt>(MSI->getLength())->getZExtValue(); 1355 if (NumBytes != 0) { 1356 unsigned Val = cast<ConstantInt>(MSI->getValue())->getZExtValue(); 1357 1358 // Compute the value replicated the right number of times. 1359 APInt APVal(NumBytes*8, Val); 1360 1361 // Splat the value if non-zero. 1362 if (Val) 1363 for (unsigned i = 1; i != NumBytes; ++i) 1364 APVal |= APVal << 8; 1365 1366 Instruction *Old = Builder.CreateLoad(NewAI, NewAI->getName()+".in"); 1367 Value *New = ConvertScalar_InsertValue( 1368 ConstantInt::get(User->getContext(), APVal), 1369 Old, Offset, Builder); 1370 Builder.CreateStore(New, NewAI); 1371 1372 // If the load we just inserted is now dead, then the memset overwrote 1373 // the entire thing. 1374 if (Old->use_empty()) 1375 Old->eraseFromParent(); 1376 } 1377 MSI->eraseFromParent(); 1378 continue; 1379 } 1380 1381 // If this is a memcpy or memmove into or out of the whole allocation, we 1382 // can handle it like a load or store of the scalar type. 1383 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) { 1384 assert(Offset == 0 && "must be store to start of alloca"); 1385 1386 // If the source and destination are both to the same alloca, then this is 1387 // a noop copy-to-self, just delete it. Otherwise, emit a load and store 1388 // as appropriate. 1389 AllocaInst *OrigAI = cast<AllocaInst>(Ptr->getUnderlyingObject(0)); 1390 1391 if (MTI->getSource()->getUnderlyingObject(0) != OrigAI) { 1392 // Dest must be OrigAI, change this to be a load from the original 1393 // pointer (bitcasted), then a store to our new alloca. 1394 assert(MTI->getRawDest() == Ptr && "Neither use is of pointer?"); 1395 Value *SrcPtr = MTI->getSource(); 1396 SrcPtr = Builder.CreateBitCast(SrcPtr, NewAI->getType()); 1397 1398 LoadInst *SrcVal = Builder.CreateLoad(SrcPtr, "srcval"); 1399 SrcVal->setAlignment(MTI->getAlignment()); 1400 Builder.CreateStore(SrcVal, NewAI); 1401 } else if (MTI->getDest()->getUnderlyingObject(0) != OrigAI) { 1402 // Src must be OrigAI, change this to be a load from NewAI then a store 1403 // through the original dest pointer (bitcasted). 1404 assert(MTI->getRawSource() == Ptr && "Neither use is of pointer?"); 1405 LoadInst *SrcVal = Builder.CreateLoad(NewAI, "srcval"); 1406 1407 Value *DstPtr = Builder.CreateBitCast(MTI->getDest(), NewAI->getType()); 1408 StoreInst *NewStore = Builder.CreateStore(SrcVal, DstPtr); 1409 NewStore->setAlignment(MTI->getAlignment()); 1410 } else { 1411 // Noop transfer. Src == Dst 1412 } 1413 1414 MTI->eraseFromParent(); 1415 continue; 1416 } 1417 1418 llvm_unreachable("Unsupported operation!"); 1419 } 1420} 1421 1422/// ConvertScalar_ExtractValue - Extract a value of type ToType from an integer 1423/// or vector value FromVal, extracting the bits from the offset specified by 1424/// Offset. This returns the value, which is of type ToType. 1425/// 1426/// This happens when we are converting an "integer union" to a single 1427/// integer scalar, or when we are converting a "vector union" to a vector with 1428/// insert/extractelement instructions. 1429/// 1430/// Offset is an offset from the original alloca, in bits that need to be 1431/// shifted to the right. 1432Value *SROA::ConvertScalar_ExtractValue(Value *FromVal, const Type *ToType, 1433 uint64_t Offset, IRBuilder<> &Builder) { 1434 // If the load is of the whole new alloca, no conversion is needed. 1435 if (FromVal->getType() == ToType && Offset == 0) 1436 return FromVal; 1437 1438 // If the result alloca is a vector type, this is either an element 1439 // access or a bitcast to another vector type of the same size. 1440 if (const VectorType *VTy = dyn_cast<VectorType>(FromVal->getType())) { 1441 if (ToType->isVectorTy()) 1442 return Builder.CreateBitCast(FromVal, ToType, "tmp"); 1443 1444 // Otherwise it must be an element access. 1445 unsigned Elt = 0; 1446 if (Offset) { 1447 unsigned EltSize = TD->getTypeAllocSizeInBits(VTy->getElementType()); 1448 Elt = Offset/EltSize; 1449 assert(EltSize*Elt == Offset && "Invalid modulus in validity checking"); 1450 } 1451 // Return the element extracted out of it. 1452 Value *V = Builder.CreateExtractElement(FromVal, ConstantInt::get( 1453 Type::getInt32Ty(FromVal->getContext()), Elt), "tmp"); 1454 if (V->getType() != ToType) 1455 V = Builder.CreateBitCast(V, ToType, "tmp"); 1456 return V; 1457 } 1458 1459 // If ToType is a first class aggregate, extract out each of the pieces and 1460 // use insertvalue's to form the FCA. 1461 if (const StructType *ST = dyn_cast<StructType>(ToType)) { 1462 const StructLayout &Layout = *TD->getStructLayout(ST); 1463 Value *Res = UndefValue::get(ST); 1464 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) { 1465 Value *Elt = ConvertScalar_ExtractValue(FromVal, ST->getElementType(i), 1466 Offset+Layout.getElementOffsetInBits(i), 1467 Builder); 1468 Res = Builder.CreateInsertValue(Res, Elt, i, "tmp"); 1469 } 1470 return Res; 1471 } 1472 1473 if (const ArrayType *AT = dyn_cast<ArrayType>(ToType)) { 1474 uint64_t EltSize = TD->getTypeAllocSizeInBits(AT->getElementType()); 1475 Value *Res = UndefValue::get(AT); 1476 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) { 1477 Value *Elt = ConvertScalar_ExtractValue(FromVal, AT->getElementType(), 1478 Offset+i*EltSize, Builder); 1479 Res = Builder.CreateInsertValue(Res, Elt, i, "tmp"); 1480 } 1481 return Res; 1482 } 1483 1484 // Otherwise, this must be a union that was converted to an integer value. 1485 const IntegerType *NTy = cast<IntegerType>(FromVal->getType()); 1486 1487 // If this is a big-endian system and the load is narrower than the 1488 // full alloca type, we need to do a shift to get the right bits. 1489 int ShAmt = 0; 1490 if (TD->isBigEndian()) { 1491 // On big-endian machines, the lowest bit is stored at the bit offset 1492 // from the pointer given by getTypeStoreSizeInBits. This matters for 1493 // integers with a bitwidth that is not a multiple of 8. 1494 ShAmt = TD->getTypeStoreSizeInBits(NTy) - 1495 TD->getTypeStoreSizeInBits(ToType) - Offset; 1496 } else { 1497 ShAmt = Offset; 1498 } 1499 1500 // Note: we support negative bitwidths (with shl) which are not defined. 1501 // We do this to support (f.e.) loads off the end of a structure where 1502 // only some bits are used. 1503 if (ShAmt > 0 && (unsigned)ShAmt < NTy->getBitWidth()) 1504 FromVal = Builder.CreateLShr(FromVal, 1505 ConstantInt::get(FromVal->getType(), 1506 ShAmt), "tmp"); 1507 else if (ShAmt < 0 && (unsigned)-ShAmt < NTy->getBitWidth()) 1508 FromVal = Builder.CreateShl(FromVal, 1509 ConstantInt::get(FromVal->getType(), 1510 -ShAmt), "tmp"); 1511 1512 // Finally, unconditionally truncate the integer to the right width. 1513 unsigned LIBitWidth = TD->getTypeSizeInBits(ToType); 1514 if (LIBitWidth < NTy->getBitWidth()) 1515 FromVal = 1516 Builder.CreateTrunc(FromVal, IntegerType::get(FromVal->getContext(), 1517 LIBitWidth), "tmp"); 1518 else if (LIBitWidth > NTy->getBitWidth()) 1519 FromVal = 1520 Builder.CreateZExt(FromVal, IntegerType::get(FromVal->getContext(), 1521 LIBitWidth), "tmp"); 1522 1523 // If the result is an integer, this is a trunc or bitcast. 1524 if (ToType->isIntegerTy()) { 1525 // Should be done. 1526 } else if (ToType->isFloatingPointTy() || ToType->isVectorTy()) { 1527 // Just do a bitcast, we know the sizes match up. 1528 FromVal = Builder.CreateBitCast(FromVal, ToType, "tmp"); 1529 } else { 1530 // Otherwise must be a pointer. 1531 FromVal = Builder.CreateIntToPtr(FromVal, ToType, "tmp"); 1532 } 1533 assert(FromVal->getType() == ToType && "Didn't convert right?"); 1534 return FromVal; 1535} 1536 1537/// ConvertScalar_InsertValue - Insert the value "SV" into the existing integer 1538/// or vector value "Old" at the offset specified by Offset. 1539/// 1540/// This happens when we are converting an "integer union" to a 1541/// single integer scalar, or when we are converting a "vector union" to a 1542/// vector with insert/extractelement instructions. 1543/// 1544/// Offset is an offset from the original alloca, in bits that need to be 1545/// shifted to the right. 1546Value *SROA::ConvertScalar_InsertValue(Value *SV, Value *Old, 1547 uint64_t Offset, IRBuilder<> &Builder) { 1548 1549 // Convert the stored type to the actual type, shift it left to insert 1550 // then 'or' into place. 1551 const Type *AllocaType = Old->getType(); 1552 LLVMContext &Context = Old->getContext(); 1553 1554 if (const VectorType *VTy = dyn_cast<VectorType>(AllocaType)) { 1555 uint64_t VecSize = TD->getTypeAllocSizeInBits(VTy); 1556 uint64_t ValSize = TD->getTypeAllocSizeInBits(SV->getType()); 1557 1558 // Changing the whole vector with memset or with an access of a different 1559 // vector type? 1560 if (ValSize == VecSize) 1561 return Builder.CreateBitCast(SV, AllocaType, "tmp"); 1562 1563 uint64_t EltSize = TD->getTypeAllocSizeInBits(VTy->getElementType()); 1564 1565 // Must be an element insertion. 1566 unsigned Elt = Offset/EltSize; 1567 1568 if (SV->getType() != VTy->getElementType()) 1569 SV = Builder.CreateBitCast(SV, VTy->getElementType(), "tmp"); 1570 1571 SV = Builder.CreateInsertElement(Old, SV, 1572 ConstantInt::get(Type::getInt32Ty(SV->getContext()), Elt), 1573 "tmp"); 1574 return SV; 1575 } 1576 1577 // If SV is a first-class aggregate value, insert each value recursively. 1578 if (const StructType *ST = dyn_cast<StructType>(SV->getType())) { 1579 const StructLayout &Layout = *TD->getStructLayout(ST); 1580 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) { 1581 Value *Elt = Builder.CreateExtractValue(SV, i, "tmp"); 1582 Old = ConvertScalar_InsertValue(Elt, Old, 1583 Offset+Layout.getElementOffsetInBits(i), 1584 Builder); 1585 } 1586 return Old; 1587 } 1588 1589 if (const ArrayType *AT = dyn_cast<ArrayType>(SV->getType())) { 1590 uint64_t EltSize = TD->getTypeAllocSizeInBits(AT->getElementType()); 1591 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) { 1592 Value *Elt = Builder.CreateExtractValue(SV, i, "tmp"); 1593 Old = ConvertScalar_InsertValue(Elt, Old, Offset+i*EltSize, Builder); 1594 } 1595 return Old; 1596 } 1597 1598 // If SV is a float, convert it to the appropriate integer type. 1599 // If it is a pointer, do the same. 1600 unsigned SrcWidth = TD->getTypeSizeInBits(SV->getType()); 1601 unsigned DestWidth = TD->getTypeSizeInBits(AllocaType); 1602 unsigned SrcStoreWidth = TD->getTypeStoreSizeInBits(SV->getType()); 1603 unsigned DestStoreWidth = TD->getTypeStoreSizeInBits(AllocaType); 1604 if (SV->getType()->isFloatingPointTy() || SV->getType()->isVectorTy()) 1605 SV = Builder.CreateBitCast(SV, 1606 IntegerType::get(SV->getContext(),SrcWidth), "tmp"); 1607 else if (SV->getType()->isPointerTy()) 1608 SV = Builder.CreatePtrToInt(SV, TD->getIntPtrType(SV->getContext()), "tmp"); 1609 1610 // Zero extend or truncate the value if needed. 1611 if (SV->getType() != AllocaType) { 1612 if (SV->getType()->getPrimitiveSizeInBits() < 1613 AllocaType->getPrimitiveSizeInBits()) 1614 SV = Builder.CreateZExt(SV, AllocaType, "tmp"); 1615 else { 1616 // Truncation may be needed if storing more than the alloca can hold 1617 // (undefined behavior). 1618 SV = Builder.CreateTrunc(SV, AllocaType, "tmp"); 1619 SrcWidth = DestWidth; 1620 SrcStoreWidth = DestStoreWidth; 1621 } 1622 } 1623 1624 // If this is a big-endian system and the store is narrower than the 1625 // full alloca type, we need to do a shift to get the right bits. 1626 int ShAmt = 0; 1627 if (TD->isBigEndian()) { 1628 // On big-endian machines, the lowest bit is stored at the bit offset 1629 // from the pointer given by getTypeStoreSizeInBits. This matters for 1630 // integers with a bitwidth that is not a multiple of 8. 1631 ShAmt = DestStoreWidth - SrcStoreWidth - Offset; 1632 } else { 1633 ShAmt = Offset; 1634 } 1635 1636 // Note: we support negative bitwidths (with shr) which are not defined. 1637 // We do this to support (f.e.) stores off the end of a structure where 1638 // only some bits in the structure are set. 1639 APInt Mask(APInt::getLowBitsSet(DestWidth, SrcWidth)); 1640 if (ShAmt > 0 && (unsigned)ShAmt < DestWidth) { 1641 SV = Builder.CreateShl(SV, ConstantInt::get(SV->getType(), 1642 ShAmt), "tmp"); 1643 Mask <<= ShAmt; 1644 } else if (ShAmt < 0 && (unsigned)-ShAmt < DestWidth) { 1645 SV = Builder.CreateLShr(SV, ConstantInt::get(SV->getType(), 1646 -ShAmt), "tmp"); 1647 Mask = Mask.lshr(-ShAmt); 1648 } 1649 1650 // Mask out the bits we are about to insert from the old value, and or 1651 // in the new bits. 1652 if (SrcWidth != DestWidth) { 1653 assert(DestWidth > SrcWidth); 1654 Old = Builder.CreateAnd(Old, ConstantInt::get(Context, ~Mask), "mask"); 1655 SV = Builder.CreateOr(Old, SV, "ins"); 1656 } 1657 return SV; 1658} 1659 1660 1661 1662/// PointsToConstantGlobal - Return true if V (possibly indirectly) points to 1663/// some part of a constant global variable. This intentionally only accepts 1664/// constant expressions because we don't can't rewrite arbitrary instructions. 1665static bool PointsToConstantGlobal(Value *V) { 1666 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V)) 1667 return GV->isConstant(); 1668 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) 1669 if (CE->getOpcode() == Instruction::BitCast || 1670 CE->getOpcode() == Instruction::GetElementPtr) 1671 return PointsToConstantGlobal(CE->getOperand(0)); 1672 return false; 1673} 1674 1675/// isOnlyCopiedFromConstantGlobal - Recursively walk the uses of a (derived) 1676/// pointer to an alloca. Ignore any reads of the pointer, return false if we 1677/// see any stores or other unknown uses. If we see pointer arithmetic, keep 1678/// track of whether it moves the pointer (with isOffset) but otherwise traverse 1679/// the uses. If we see a memcpy/memmove that targets an unoffseted pointer to 1680/// the alloca, and if the source pointer is a pointer to a constant global, we 1681/// can optimize this. 1682static bool isOnlyCopiedFromConstantGlobal(Value *V, Instruction *&TheCopy, 1683 bool isOffset) { 1684 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) { 1685 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) 1686 // Ignore non-volatile loads, they are always ok. 1687 if (!LI->isVolatile()) 1688 continue; 1689 1690 if (BitCastInst *BCI = dyn_cast<BitCastInst>(*UI)) { 1691 // If uses of the bitcast are ok, we are ok. 1692 if (!isOnlyCopiedFromConstantGlobal(BCI, TheCopy, isOffset)) 1693 return false; 1694 continue; 1695 } 1696 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(*UI)) { 1697 // If the GEP has all zero indices, it doesn't offset the pointer. If it 1698 // doesn't, it does. 1699 if (!isOnlyCopiedFromConstantGlobal(GEP, TheCopy, 1700 isOffset || !GEP->hasAllZeroIndices())) 1701 return false; 1702 continue; 1703 } 1704 1705 // If this is isn't our memcpy/memmove, reject it as something we can't 1706 // handle. 1707 if (!isa<MemTransferInst>(*UI)) 1708 return false; 1709 1710 // If we already have seen a copy, reject the second one. 1711 if (TheCopy) return false; 1712 1713 // If the pointer has been offset from the start of the alloca, we can't 1714 // safely handle this. 1715 if (isOffset) return false; 1716 1717 // If the memintrinsic isn't using the alloca as the dest, reject it. 1718 if (UI.getOperandNo() != 1) return false; 1719 1720 MemIntrinsic *MI = cast<MemIntrinsic>(*UI); 1721 1722 // If the source of the memcpy/move is not a constant global, reject it. 1723 if (!PointsToConstantGlobal(MI->getOperand(2))) 1724 return false; 1725 1726 // Otherwise, the transform is safe. Remember the copy instruction. 1727 TheCopy = MI; 1728 } 1729 return true; 1730} 1731 1732/// isOnlyCopiedFromConstantGlobal - Return true if the specified alloca is only 1733/// modified by a copy from a constant global. If we can prove this, we can 1734/// replace any uses of the alloca with uses of the global directly. 1735Instruction *SROA::isOnlyCopiedFromConstantGlobal(AllocaInst *AI) { 1736 Instruction *TheCopy = 0; 1737 if (::isOnlyCopiedFromConstantGlobal(AI, TheCopy, false)) 1738 return TheCopy; 1739 return 0; 1740} 1741