ScalarReplAggregates.cpp revision 1d0be15f89cb5056e20e2d24faa8d6afb1573bca
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/Compiler.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 VISIBILITY_HIDDEN 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.addRequired<TargetData>(); 72 AU.setPreservesCFG(); 73 } 74 75 private: 76 TargetData *TD; 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 /// needsCleanup - This is set to true if there is some use of the alloca 86 /// that requires cleanup. 87 bool needsCleanup : 1; 88 89 /// isMemCpySrc - This is true if this aggregate is memcpy'd from. 90 bool isMemCpySrc : 1; 91 92 /// isMemCpyDst - This is true if this aggregate is memcpy'd into. 93 bool isMemCpyDst : 1; 94 95 AllocaInfo() 96 : isUnsafe(false), needsCleanup(false), 97 isMemCpySrc(false), isMemCpyDst(false) {} 98 }; 99 100 unsigned SRThreshold; 101 102 void MarkUnsafe(AllocaInfo &I) { I.isUnsafe = true; } 103 104 int isSafeAllocaToScalarRepl(AllocationInst *AI); 105 106 void isSafeUseOfAllocation(Instruction *User, AllocationInst *AI, 107 AllocaInfo &Info); 108 void isSafeElementUse(Value *Ptr, bool isFirstElt, AllocationInst *AI, 109 AllocaInfo &Info); 110 void isSafeMemIntrinsicOnAllocation(MemIntrinsic *MI, AllocationInst *AI, 111 unsigned OpNo, AllocaInfo &Info); 112 void isSafeUseOfBitCastedAllocation(BitCastInst *User, AllocationInst *AI, 113 AllocaInfo &Info); 114 115 void DoScalarReplacement(AllocationInst *AI, 116 std::vector<AllocationInst*> &WorkList); 117 void CleanupGEP(GetElementPtrInst *GEP); 118 void CleanupAllocaUsers(AllocationInst *AI); 119 AllocaInst *AddNewAlloca(Function &F, const Type *Ty, AllocationInst *Base); 120 121 void RewriteBitCastUserOfAlloca(Instruction *BCInst, AllocationInst *AI, 122 SmallVector<AllocaInst*, 32> &NewElts); 123 124 void RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *BCInst, 125 AllocationInst *AI, 126 SmallVector<AllocaInst*, 32> &NewElts); 127 void RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocationInst *AI, 128 SmallVector<AllocaInst*, 32> &NewElts); 129 void RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocationInst *AI, 130 SmallVector<AllocaInst*, 32> &NewElts); 131 132 bool CanConvertToScalar(Value *V, bool &IsNotTrivial, const Type *&VecTy, 133 bool &SawVec, uint64_t Offset, unsigned AllocaSize); 134 void ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, uint64_t Offset); 135 Value *ConvertScalar_ExtractValue(Value *NV, const Type *ToType, 136 uint64_t Offset, IRBuilder<> &Builder); 137 Value *ConvertScalar_InsertValue(Value *StoredVal, Value *ExistingVal, 138 uint64_t Offset, IRBuilder<> &Builder); 139 static Instruction *isOnlyCopiedFromConstantGlobal(AllocationInst *AI); 140 }; 141} 142 143char SROA::ID = 0; 144static RegisterPass<SROA> X("scalarrepl", "Scalar Replacement of Aggregates"); 145 146// Public interface to the ScalarReplAggregates pass 147FunctionPass *llvm::createScalarReplAggregatesPass(signed int Threshold) { 148 return new SROA(Threshold); 149} 150 151 152bool SROA::runOnFunction(Function &F) { 153 TD = &getAnalysis<TargetData>(); 154 155 bool Changed = performPromotion(F); 156 while (1) { 157 bool LocalChange = performScalarRepl(F); 158 if (!LocalChange) break; // No need to repromote if no scalarrepl 159 Changed = true; 160 LocalChange = performPromotion(F); 161 if (!LocalChange) break; // No need to re-scalarrepl if no promotion 162 } 163 164 return Changed; 165} 166 167 168bool SROA::performPromotion(Function &F) { 169 std::vector<AllocaInst*> Allocas; 170 DominatorTree &DT = getAnalysis<DominatorTree>(); 171 DominanceFrontier &DF = getAnalysis<DominanceFrontier>(); 172 173 BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function 174 175 bool Changed = false; 176 177 while (1) { 178 Allocas.clear(); 179 180 // Find allocas that are safe to promote, by looking at all instructions in 181 // the entry node 182 for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I) 183 if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) // Is it an alloca? 184 if (isAllocaPromotable(AI)) 185 Allocas.push_back(AI); 186 187 if (Allocas.empty()) break; 188 189 PromoteMemToReg(Allocas, DT, DF, F.getContext()); 190 NumPromoted += Allocas.size(); 191 Changed = true; 192 } 193 194 return Changed; 195} 196 197/// getNumSAElements - Return the number of elements in the specific struct or 198/// array. 199static uint64_t getNumSAElements(const Type *T) { 200 if (const StructType *ST = dyn_cast<StructType>(T)) 201 return ST->getNumElements(); 202 return cast<ArrayType>(T)->getNumElements(); 203} 204 205// performScalarRepl - This algorithm is a simple worklist driven algorithm, 206// which runs on all of the malloc/alloca instructions in the function, removing 207// them if they are only used by getelementptr instructions. 208// 209bool SROA::performScalarRepl(Function &F) { 210 std::vector<AllocationInst*> WorkList; 211 212 // Scan the entry basic block, adding any alloca's and mallocs to the worklist 213 BasicBlock &BB = F.getEntryBlock(); 214 for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I) 215 if (AllocationInst *A = dyn_cast<AllocationInst>(I)) 216 WorkList.push_back(A); 217 218 // Process the worklist 219 bool Changed = false; 220 while (!WorkList.empty()) { 221 AllocationInst *AI = WorkList.back(); 222 WorkList.pop_back(); 223 224 // Handle dead allocas trivially. These can be formed by SROA'ing arrays 225 // with unused elements. 226 if (AI->use_empty()) { 227 AI->eraseFromParent(); 228 continue; 229 } 230 231 // If this alloca is impossible for us to promote, reject it early. 232 if (AI->isArrayAllocation() || !AI->getAllocatedType()->isSized()) 233 continue; 234 235 // Check to see if this allocation is only modified by a memcpy/memmove from 236 // a constant global. If this is the case, we can change all users to use 237 // the constant global instead. This is commonly produced by the CFE by 238 // constructs like "void foo() { int A[] = {1,2,3,4,5,6,7,8,9...}; }" if 'A' 239 // is only subsequently read. 240 if (Instruction *TheCopy = isOnlyCopiedFromConstantGlobal(AI)) { 241 DOUT << "Found alloca equal to global: " << *AI; 242 DOUT << " memcpy = " << *TheCopy; 243 Constant *TheSrc = cast<Constant>(TheCopy->getOperand(2)); 244 AI->replaceAllUsesWith(ConstantExpr::getBitCast(TheSrc, AI->getType())); 245 TheCopy->eraseFromParent(); // Don't mutate the global. 246 AI->eraseFromParent(); 247 ++NumGlobals; 248 Changed = true; 249 continue; 250 } 251 252 // Check to see if we can perform the core SROA transformation. We cannot 253 // transform the allocation instruction if it is an array allocation 254 // (allocations OF arrays are ok though), and an allocation of a scalar 255 // value cannot be decomposed at all. 256 uint64_t AllocaSize = TD->getTypeAllocSize(AI->getAllocatedType()); 257 258 // Do not promote any struct whose size is too big. 259 if (AllocaSize > SRThreshold) continue; 260 261 if ((isa<StructType>(AI->getAllocatedType()) || 262 isa<ArrayType>(AI->getAllocatedType())) && 263 // Do not promote any struct into more than "32" separate vars. 264 getNumSAElements(AI->getAllocatedType()) <= SRThreshold/4) { 265 // Check that all of the users of the allocation are capable of being 266 // transformed. 267 switch (isSafeAllocaToScalarRepl(AI)) { 268 default: llvm_unreachable("Unexpected value!"); 269 case 0: // Not safe to scalar replace. 270 break; 271 case 1: // Safe, but requires cleanup/canonicalizations first 272 CleanupAllocaUsers(AI); 273 // FALL THROUGH. 274 case 3: // Safe to scalar replace. 275 DoScalarReplacement(AI, WorkList); 276 Changed = true; 277 continue; 278 } 279 } 280 281 // If we can turn this aggregate value (potentially with casts) into a 282 // simple scalar value that can be mem2reg'd into a register value. 283 // IsNotTrivial tracks whether this is something that mem2reg could have 284 // promoted itself. If so, we don't want to transform it needlessly. Note 285 // that we can't just check based on the type: the alloca may be of an i32 286 // but that has pointer arithmetic to set byte 3 of it or something. 287 bool IsNotTrivial = false; 288 const Type *VectorTy = 0; 289 bool HadAVector = false; 290 if (CanConvertToScalar(AI, IsNotTrivial, VectorTy, HadAVector, 291 0, unsigned(AllocaSize)) && IsNotTrivial) { 292 AllocaInst *NewAI; 293 // If we were able to find a vector type that can handle this with 294 // insert/extract elements, and if there was at least one use that had 295 // a vector type, promote this to a vector. We don't want to promote 296 // random stuff that doesn't use vectors (e.g. <9 x double>) because then 297 // we just get a lot of insert/extracts. If at least one vector is 298 // involved, then we probably really do have a union of vector/array. 299 if (VectorTy && isa<VectorType>(VectorTy) && HadAVector) { 300 DOUT << "CONVERT TO VECTOR: " << *AI << " TYPE = " << *VectorTy <<"\n"; 301 302 // Create and insert the vector alloca. 303 NewAI = new AllocaInst(VectorTy, 0, "", AI->getParent()->begin()); 304 ConvertUsesToScalar(AI, NewAI, 0); 305 } else { 306 DOUT << "CONVERT TO SCALAR INTEGER: " << *AI << "\n"; 307 308 // Create and insert the integer alloca. 309 const Type *NewTy = IntegerType::get(AI->getContext(), AllocaSize*8); 310 NewAI = new AllocaInst(NewTy, 0, "", AI->getParent()->begin()); 311 ConvertUsesToScalar(AI, NewAI, 0); 312 } 313 NewAI->takeName(AI); 314 AI->eraseFromParent(); 315 ++NumConverted; 316 Changed = true; 317 continue; 318 } 319 320 // Otherwise, couldn't process this alloca. 321 } 322 323 return Changed; 324} 325 326/// DoScalarReplacement - This alloca satisfied the isSafeAllocaToScalarRepl 327/// predicate, do SROA now. 328void SROA::DoScalarReplacement(AllocationInst *AI, 329 std::vector<AllocationInst*> &WorkList) { 330 DOUT << "Found inst to SROA: " << *AI; 331 SmallVector<AllocaInst*, 32> ElementAllocas; 332 if (const StructType *ST = dyn_cast<StructType>(AI->getAllocatedType())) { 333 ElementAllocas.reserve(ST->getNumContainedTypes()); 334 for (unsigned i = 0, e = ST->getNumContainedTypes(); i != e; ++i) { 335 AllocaInst *NA = new AllocaInst(ST->getContainedType(i), 0, 336 AI->getAlignment(), 337 AI->getName() + "." + Twine(i), AI); 338 ElementAllocas.push_back(NA); 339 WorkList.push_back(NA); // Add to worklist for recursive processing 340 } 341 } else { 342 const ArrayType *AT = cast<ArrayType>(AI->getAllocatedType()); 343 ElementAllocas.reserve(AT->getNumElements()); 344 const Type *ElTy = AT->getElementType(); 345 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) { 346 AllocaInst *NA = new AllocaInst(ElTy, 0, AI->getAlignment(), 347 AI->getName() + "." + Twine(i), AI); 348 ElementAllocas.push_back(NA); 349 WorkList.push_back(NA); // Add to worklist for recursive processing 350 } 351 } 352 353 // Now that we have created the alloca instructions that we want to use, 354 // expand the getelementptr instructions to use them. 355 // 356 while (!AI->use_empty()) { 357 Instruction *User = cast<Instruction>(AI->use_back()); 358 if (BitCastInst *BCInst = dyn_cast<BitCastInst>(User)) { 359 RewriteBitCastUserOfAlloca(BCInst, AI, ElementAllocas); 360 BCInst->eraseFromParent(); 361 continue; 362 } 363 364 // Replace: 365 // %res = load { i32, i32 }* %alloc 366 // with: 367 // %load.0 = load i32* %alloc.0 368 // %insert.0 insertvalue { i32, i32 } zeroinitializer, i32 %load.0, 0 369 // %load.1 = load i32* %alloc.1 370 // %insert = insertvalue { i32, i32 } %insert.0, i32 %load.1, 1 371 // (Also works for arrays instead of structs) 372 if (LoadInst *LI = dyn_cast<LoadInst>(User)) { 373 Value *Insert = UndefValue::get(LI->getType()); 374 for (unsigned i = 0, e = ElementAllocas.size(); i != e; ++i) { 375 Value *Load = new LoadInst(ElementAllocas[i], "load", LI); 376 Insert = InsertValueInst::Create(Insert, Load, i, "insert", LI); 377 } 378 LI->replaceAllUsesWith(Insert); 379 LI->eraseFromParent(); 380 continue; 381 } 382 383 // Replace: 384 // store { i32, i32 } %val, { i32, i32 }* %alloc 385 // with: 386 // %val.0 = extractvalue { i32, i32 } %val, 0 387 // store i32 %val.0, i32* %alloc.0 388 // %val.1 = extractvalue { i32, i32 } %val, 1 389 // store i32 %val.1, i32* %alloc.1 390 // (Also works for arrays instead of structs) 391 if (StoreInst *SI = dyn_cast<StoreInst>(User)) { 392 Value *Val = SI->getOperand(0); 393 for (unsigned i = 0, e = ElementAllocas.size(); i != e; ++i) { 394 Value *Extract = ExtractValueInst::Create(Val, i, Val->getName(), SI); 395 new StoreInst(Extract, ElementAllocas[i], SI); 396 } 397 SI->eraseFromParent(); 398 continue; 399 } 400 401 GetElementPtrInst *GEPI = cast<GetElementPtrInst>(User); 402 // We now know that the GEP is of the form: GEP <ptr>, 0, <cst> 403 unsigned Idx = 404 (unsigned)cast<ConstantInt>(GEPI->getOperand(2))->getZExtValue(); 405 406 assert(Idx < ElementAllocas.size() && "Index out of range?"); 407 AllocaInst *AllocaToUse = ElementAllocas[Idx]; 408 409 Value *RepValue; 410 if (GEPI->getNumOperands() == 3) { 411 // Do not insert a new getelementptr instruction with zero indices, only 412 // to have it optimized out later. 413 RepValue = AllocaToUse; 414 } else { 415 // We are indexing deeply into the structure, so we still need a 416 // getelement ptr instruction to finish the indexing. This may be 417 // expanded itself once the worklist is rerun. 418 // 419 SmallVector<Value*, 8> NewArgs; 420 NewArgs.push_back(Constant::getNullValue( 421 Type::getInt32Ty(AI->getContext()))); 422 NewArgs.append(GEPI->op_begin()+3, GEPI->op_end()); 423 RepValue = GetElementPtrInst::Create(AllocaToUse, NewArgs.begin(), 424 NewArgs.end(), "", GEPI); 425 RepValue->takeName(GEPI); 426 } 427 428 // If this GEP is to the start of the aggregate, check for memcpys. 429 if (Idx == 0 && GEPI->hasAllZeroIndices()) 430 RewriteBitCastUserOfAlloca(GEPI, AI, ElementAllocas); 431 432 // Move all of the users over to the new GEP. 433 GEPI->replaceAllUsesWith(RepValue); 434 // Delete the old GEP 435 GEPI->eraseFromParent(); 436 } 437 438 // Finally, delete the Alloca instruction 439 AI->eraseFromParent(); 440 NumReplaced++; 441} 442 443 444/// isSafeElementUse - Check to see if this use is an allowed use for a 445/// getelementptr instruction of an array aggregate allocation. isFirstElt 446/// indicates whether Ptr is known to the start of the aggregate. 447/// 448void SROA::isSafeElementUse(Value *Ptr, bool isFirstElt, AllocationInst *AI, 449 AllocaInfo &Info) { 450 for (Value::use_iterator I = Ptr->use_begin(), E = Ptr->use_end(); 451 I != E; ++I) { 452 Instruction *User = cast<Instruction>(*I); 453 switch (User->getOpcode()) { 454 case Instruction::Load: break; 455 case Instruction::Store: 456 // Store is ok if storing INTO the pointer, not storing the pointer 457 if (User->getOperand(0) == Ptr) return MarkUnsafe(Info); 458 break; 459 case Instruction::GetElementPtr: { 460 GetElementPtrInst *GEP = cast<GetElementPtrInst>(User); 461 bool AreAllZeroIndices = isFirstElt; 462 if (GEP->getNumOperands() > 1) { 463 if (!isa<ConstantInt>(GEP->getOperand(1)) || 464 !cast<ConstantInt>(GEP->getOperand(1))->isZero()) 465 // Using pointer arithmetic to navigate the array. 466 return MarkUnsafe(Info); 467 468 if (AreAllZeroIndices) 469 AreAllZeroIndices = GEP->hasAllZeroIndices(); 470 } 471 isSafeElementUse(GEP, AreAllZeroIndices, AI, Info); 472 if (Info.isUnsafe) return; 473 break; 474 } 475 case Instruction::BitCast: 476 if (isFirstElt) { 477 isSafeUseOfBitCastedAllocation(cast<BitCastInst>(User), AI, Info); 478 if (Info.isUnsafe) return; 479 break; 480 } 481 DOUT << " Transformation preventing inst: " << *User; 482 return MarkUnsafe(Info); 483 case Instruction::Call: 484 if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) { 485 if (isFirstElt) { 486 isSafeMemIntrinsicOnAllocation(MI, AI, I.getOperandNo(), Info); 487 if (Info.isUnsafe) return; 488 break; 489 } 490 } 491 DOUT << " Transformation preventing inst: " << *User; 492 return MarkUnsafe(Info); 493 default: 494 DOUT << " Transformation preventing inst: " << *User; 495 return MarkUnsafe(Info); 496 } 497 } 498 return; // All users look ok :) 499} 500 501/// AllUsersAreLoads - Return true if all users of this value are loads. 502static bool AllUsersAreLoads(Value *Ptr) { 503 for (Value::use_iterator I = Ptr->use_begin(), E = Ptr->use_end(); 504 I != E; ++I) 505 if (cast<Instruction>(*I)->getOpcode() != Instruction::Load) 506 return false; 507 return true; 508} 509 510/// isSafeUseOfAllocation - Check to see if this user is an allowed use for an 511/// aggregate allocation. 512/// 513void SROA::isSafeUseOfAllocation(Instruction *User, AllocationInst *AI, 514 AllocaInfo &Info) { 515 if (BitCastInst *C = dyn_cast<BitCastInst>(User)) 516 return isSafeUseOfBitCastedAllocation(C, AI, Info); 517 518 if (LoadInst *LI = dyn_cast<LoadInst>(User)) 519 if (!LI->isVolatile()) 520 return;// Loads (returning a first class aggregrate) are always rewritable 521 522 if (StoreInst *SI = dyn_cast<StoreInst>(User)) 523 if (!SI->isVolatile() && SI->getOperand(0) != AI) 524 return;// Store is ok if storing INTO the pointer, not storing the pointer 525 526 GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User); 527 if (GEPI == 0) 528 return MarkUnsafe(Info); 529 530 gep_type_iterator I = gep_type_begin(GEPI), E = gep_type_end(GEPI); 531 532 // The GEP is not safe to transform if not of the form "GEP <ptr>, 0, <cst>". 533 if (I == E || 534 I.getOperand() != Constant::getNullValue(I.getOperand()->getType())) { 535 return MarkUnsafe(Info); 536 } 537 538 ++I; 539 if (I == E) return MarkUnsafe(Info); // ran out of GEP indices?? 540 541 bool IsAllZeroIndices = true; 542 543 // If the first index is a non-constant index into an array, see if we can 544 // handle it as a special case. 545 if (const ArrayType *AT = dyn_cast<ArrayType>(*I)) { 546 if (!isa<ConstantInt>(I.getOperand())) { 547 IsAllZeroIndices = 0; 548 uint64_t NumElements = AT->getNumElements(); 549 550 // If this is an array index and the index is not constant, we cannot 551 // promote... that is unless the array has exactly one or two elements in 552 // it, in which case we CAN promote it, but we have to canonicalize this 553 // out if this is the only problem. 554 if ((NumElements == 1 || NumElements == 2) && 555 AllUsersAreLoads(GEPI)) { 556 Info.needsCleanup = true; 557 return; // Canonicalization required! 558 } 559 return MarkUnsafe(Info); 560 } 561 } 562 563 // Walk through the GEP type indices, checking the types that this indexes 564 // into. 565 for (; I != E; ++I) { 566 // Ignore struct elements, no extra checking needed for these. 567 if (isa<StructType>(*I)) 568 continue; 569 570 ConstantInt *IdxVal = dyn_cast<ConstantInt>(I.getOperand()); 571 if (!IdxVal) return MarkUnsafe(Info); 572 573 // Are all indices still zero? 574 IsAllZeroIndices &= IdxVal->isZero(); 575 576 if (const ArrayType *AT = dyn_cast<ArrayType>(*I)) { 577 // This GEP indexes an array. Verify that this is an in-range constant 578 // integer. Specifically, consider A[0][i]. We cannot know that the user 579 // isn't doing invalid things like allowing i to index an out-of-range 580 // subscript that accesses A[1]. Because of this, we have to reject SROA 581 // of any accesses into structs where any of the components are variables. 582 if (IdxVal->getZExtValue() >= AT->getNumElements()) 583 return MarkUnsafe(Info); 584 } else if (const VectorType *VT = dyn_cast<VectorType>(*I)) { 585 if (IdxVal->getZExtValue() >= VT->getNumElements()) 586 return MarkUnsafe(Info); 587 } 588 } 589 590 // If there are any non-simple uses of this getelementptr, make sure to reject 591 // them. 592 return isSafeElementUse(GEPI, IsAllZeroIndices, AI, Info); 593} 594 595/// isSafeMemIntrinsicOnAllocation - Return true if the specified memory 596/// intrinsic can be promoted by SROA. At this point, we know that the operand 597/// of the memintrinsic is a pointer to the beginning of the allocation. 598void SROA::isSafeMemIntrinsicOnAllocation(MemIntrinsic *MI, AllocationInst *AI, 599 unsigned OpNo, AllocaInfo &Info) { 600 // If not constant length, give up. 601 ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength()); 602 if (!Length) return MarkUnsafe(Info); 603 604 // If not the whole aggregate, give up. 605 if (Length->getZExtValue() != 606 TD->getTypeAllocSize(AI->getType()->getElementType())) 607 return MarkUnsafe(Info); 608 609 // We only know about memcpy/memset/memmove. 610 if (!isa<MemIntrinsic>(MI)) 611 return MarkUnsafe(Info); 612 613 // Otherwise, we can transform it. Determine whether this is a memcpy/set 614 // into or out of the aggregate. 615 if (OpNo == 1) 616 Info.isMemCpyDst = true; 617 else { 618 assert(OpNo == 2); 619 Info.isMemCpySrc = true; 620 } 621} 622 623/// isSafeUseOfBitCastedAllocation - Return true if all users of this bitcast 624/// are 625void SROA::isSafeUseOfBitCastedAllocation(BitCastInst *BC, AllocationInst *AI, 626 AllocaInfo &Info) { 627 for (Value::use_iterator UI = BC->use_begin(), E = BC->use_end(); 628 UI != E; ++UI) { 629 if (BitCastInst *BCU = dyn_cast<BitCastInst>(UI)) { 630 isSafeUseOfBitCastedAllocation(BCU, AI, Info); 631 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(UI)) { 632 isSafeMemIntrinsicOnAllocation(MI, AI, UI.getOperandNo(), Info); 633 } else if (StoreInst *SI = dyn_cast<StoreInst>(UI)) { 634 if (SI->isVolatile()) 635 return MarkUnsafe(Info); 636 637 // If storing the entire alloca in one chunk through a bitcasted pointer 638 // to integer, we can transform it. This happens (for example) when you 639 // cast a {i32,i32}* to i64* and store through it. This is similar to the 640 // memcpy case and occurs in various "byval" cases and emulated memcpys. 641 if (isa<IntegerType>(SI->getOperand(0)->getType()) && 642 TD->getTypeAllocSize(SI->getOperand(0)->getType()) == 643 TD->getTypeAllocSize(AI->getType()->getElementType())) { 644 Info.isMemCpyDst = true; 645 continue; 646 } 647 return MarkUnsafe(Info); 648 } else if (LoadInst *LI = dyn_cast<LoadInst>(UI)) { 649 if (LI->isVolatile()) 650 return MarkUnsafe(Info); 651 652 // If loading the entire alloca in one chunk through a bitcasted pointer 653 // to integer, we can transform it. This happens (for example) when you 654 // cast a {i32,i32}* to i64* and load through it. This is similar to the 655 // memcpy case and occurs in various "byval" cases and emulated memcpys. 656 if (isa<IntegerType>(LI->getType()) && 657 TD->getTypeAllocSize(LI->getType()) == 658 TD->getTypeAllocSize(AI->getType()->getElementType())) { 659 Info.isMemCpySrc = true; 660 continue; 661 } 662 return MarkUnsafe(Info); 663 } else if (isa<DbgInfoIntrinsic>(UI)) { 664 // If one user is DbgInfoIntrinsic then check if all users are 665 // DbgInfoIntrinsics. 666 if (OnlyUsedByDbgInfoIntrinsics(BC)) { 667 Info.needsCleanup = true; 668 return; 669 } 670 else 671 MarkUnsafe(Info); 672 } 673 else { 674 return MarkUnsafe(Info); 675 } 676 if (Info.isUnsafe) return; 677 } 678} 679 680/// RewriteBitCastUserOfAlloca - BCInst (transitively) bitcasts AI, or indexes 681/// to its first element. Transform users of the cast to use the new values 682/// instead. 683void SROA::RewriteBitCastUserOfAlloca(Instruction *BCInst, AllocationInst *AI, 684 SmallVector<AllocaInst*, 32> &NewElts) { 685 Value::use_iterator UI = BCInst->use_begin(), UE = BCInst->use_end(); 686 while (UI != UE) { 687 Instruction *User = cast<Instruction>(*UI++); 688 if (BitCastInst *BCU = dyn_cast<BitCastInst>(User)) { 689 RewriteBitCastUserOfAlloca(BCU, AI, NewElts); 690 if (BCU->use_empty()) BCU->eraseFromParent(); 691 continue; 692 } 693 694 if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) { 695 // This must be memcpy/memmove/memset of the entire aggregate. 696 // Split into one per element. 697 RewriteMemIntrinUserOfAlloca(MI, BCInst, AI, NewElts); 698 continue; 699 } 700 701 if (StoreInst *SI = dyn_cast<StoreInst>(User)) { 702 // If this is a store of the entire alloca from an integer, rewrite it. 703 RewriteStoreUserOfWholeAlloca(SI, AI, NewElts); 704 continue; 705 } 706 707 if (LoadInst *LI = dyn_cast<LoadInst>(User)) { 708 // If this is a load of the entire alloca to an integer, rewrite it. 709 RewriteLoadUserOfWholeAlloca(LI, AI, NewElts); 710 continue; 711 } 712 713 // Otherwise it must be some other user of a gep of the first pointer. Just 714 // leave these alone. 715 continue; 716 } 717} 718 719/// RewriteMemIntrinUserOfAlloca - MI is a memcpy/memset/memmove from or to AI. 720/// Rewrite it to copy or set the elements of the scalarized memory. 721void SROA::RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *BCInst, 722 AllocationInst *AI, 723 SmallVector<AllocaInst*, 32> &NewElts) { 724 725 // If this is a memcpy/memmove, construct the other pointer as the 726 // appropriate type. The "Other" pointer is the pointer that goes to memory 727 // that doesn't have anything to do with the alloca that we are promoting. For 728 // memset, this Value* stays null. 729 Value *OtherPtr = 0; 730 LLVMContext &Context = MI->getContext(); 731 unsigned MemAlignment = MI->getAlignment(); 732 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(MI)) { // memmove/memcopy 733 if (BCInst == MTI->getRawDest()) 734 OtherPtr = MTI->getRawSource(); 735 else { 736 assert(BCInst == MTI->getRawSource()); 737 OtherPtr = MTI->getRawDest(); 738 } 739 } 740 741 // If there is an other pointer, we want to convert it to the same pointer 742 // type as AI has, so we can GEP through it safely. 743 if (OtherPtr) { 744 // It is likely that OtherPtr is a bitcast, if so, remove it. 745 if (BitCastInst *BC = dyn_cast<BitCastInst>(OtherPtr)) 746 OtherPtr = BC->getOperand(0); 747 // All zero GEPs are effectively bitcasts. 748 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(OtherPtr)) 749 if (GEP->hasAllZeroIndices()) 750 OtherPtr = GEP->getOperand(0); 751 752 if (ConstantExpr *BCE = dyn_cast<ConstantExpr>(OtherPtr)) 753 if (BCE->getOpcode() == Instruction::BitCast) 754 OtherPtr = BCE->getOperand(0); 755 756 // If the pointer is not the right type, insert a bitcast to the right 757 // type. 758 if (OtherPtr->getType() != AI->getType()) 759 OtherPtr = new BitCastInst(OtherPtr, AI->getType(), OtherPtr->getName(), 760 MI); 761 } 762 763 // Process each element of the aggregate. 764 Value *TheFn = MI->getOperand(0); 765 const Type *BytePtrTy = MI->getRawDest()->getType(); 766 bool SROADest = MI->getRawDest() == BCInst; 767 768 Constant *Zero = Constant::getNullValue(Type::getInt32Ty(MI->getContext())); 769 770 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { 771 // If this is a memcpy/memmove, emit a GEP of the other element address. 772 Value *OtherElt = 0; 773 unsigned OtherEltAlign = MemAlignment; 774 775 if (OtherPtr) { 776 Value *Idx[2] = { Zero, 777 ConstantInt::get(Type::getInt32Ty(MI->getContext()), i) }; 778 OtherElt = GetElementPtrInst::Create(OtherPtr, Idx, Idx + 2, 779 OtherPtr->getNameStr()+"."+Twine(i), 780 MI); 781 uint64_t EltOffset; 782 const PointerType *OtherPtrTy = cast<PointerType>(OtherPtr->getType()); 783 if (const StructType *ST = 784 dyn_cast<StructType>(OtherPtrTy->getElementType())) { 785 EltOffset = TD->getStructLayout(ST)->getElementOffset(i); 786 } else { 787 const Type *EltTy = 788 cast<SequentialType>(OtherPtr->getType())->getElementType(); 789 EltOffset = TD->getTypeAllocSize(EltTy)*i; 790 } 791 792 // The alignment of the other pointer is the guaranteed alignment of the 793 // element, which is affected by both the known alignment of the whole 794 // mem intrinsic and the alignment of the element. If the alignment of 795 // the memcpy (f.e.) is 32 but the element is at a 4-byte offset, then the 796 // known alignment is just 4 bytes. 797 OtherEltAlign = (unsigned)MinAlign(OtherEltAlign, EltOffset); 798 } 799 800 Value *EltPtr = NewElts[i]; 801 const Type *EltTy = cast<PointerType>(EltPtr->getType())->getElementType(); 802 803 // If we got down to a scalar, insert a load or store as appropriate. 804 if (EltTy->isSingleValueType()) { 805 if (isa<MemTransferInst>(MI)) { 806 if (SROADest) { 807 // From Other to Alloca. 808 Value *Elt = new LoadInst(OtherElt, "tmp", false, OtherEltAlign, MI); 809 new StoreInst(Elt, EltPtr, MI); 810 } else { 811 // From Alloca to Other. 812 Value *Elt = new LoadInst(EltPtr, "tmp", MI); 813 new StoreInst(Elt, OtherElt, false, OtherEltAlign, MI); 814 } 815 continue; 816 } 817 assert(isa<MemSetInst>(MI)); 818 819 // If the stored element is zero (common case), just store a null 820 // constant. 821 Constant *StoreVal; 822 if (ConstantInt *CI = dyn_cast<ConstantInt>(MI->getOperand(2))) { 823 if (CI->isZero()) { 824 StoreVal = Constant::getNullValue(EltTy); // 0.0, null, 0, <0,0> 825 } else { 826 // If EltTy is a vector type, get the element type. 827 const Type *ValTy = EltTy->getScalarType(); 828 829 // Construct an integer with the right value. 830 unsigned EltSize = TD->getTypeSizeInBits(ValTy); 831 APInt OneVal(EltSize, CI->getZExtValue()); 832 APInt TotalVal(OneVal); 833 // Set each byte. 834 for (unsigned i = 0; 8*i < EltSize; ++i) { 835 TotalVal = TotalVal.shl(8); 836 TotalVal |= OneVal; 837 } 838 839 // Convert the integer value to the appropriate type. 840 StoreVal = ConstantInt::get(Context, TotalVal); 841 if (isa<PointerType>(ValTy)) 842 StoreVal = ConstantExpr::getIntToPtr(StoreVal, ValTy); 843 else if (ValTy->isFloatingPoint()) 844 StoreVal = ConstantExpr::getBitCast(StoreVal, ValTy); 845 assert(StoreVal->getType() == ValTy && "Type mismatch!"); 846 847 // If the requested value was a vector constant, create it. 848 if (EltTy != ValTy) { 849 unsigned NumElts = cast<VectorType>(ValTy)->getNumElements(); 850 SmallVector<Constant*, 16> Elts(NumElts, StoreVal); 851 StoreVal = ConstantVector::get(&Elts[0], NumElts); 852 } 853 } 854 new StoreInst(StoreVal, EltPtr, MI); 855 continue; 856 } 857 // Otherwise, if we're storing a byte variable, use a memset call for 858 // this element. 859 } 860 861 // Cast the element pointer to BytePtrTy. 862 if (EltPtr->getType() != BytePtrTy) 863 EltPtr = new BitCastInst(EltPtr, BytePtrTy, EltPtr->getNameStr(), MI); 864 865 // Cast the other pointer (if we have one) to BytePtrTy. 866 if (OtherElt && OtherElt->getType() != BytePtrTy) 867 OtherElt = new BitCastInst(OtherElt, BytePtrTy,OtherElt->getNameStr(), 868 MI); 869 870 unsigned EltSize = TD->getTypeAllocSize(EltTy); 871 872 // Finally, insert the meminst for this element. 873 if (isa<MemTransferInst>(MI)) { 874 Value *Ops[] = { 875 SROADest ? EltPtr : OtherElt, // Dest ptr 876 SROADest ? OtherElt : EltPtr, // Src ptr 877 ConstantInt::get(MI->getOperand(3)->getType(), EltSize), // Size 878 // Align 879 ConstantInt::get(Type::getInt32Ty(MI->getContext()), OtherEltAlign) 880 }; 881 CallInst::Create(TheFn, Ops, Ops + 4, "", MI); 882 } else { 883 assert(isa<MemSetInst>(MI)); 884 Value *Ops[] = { 885 EltPtr, MI->getOperand(2), // Dest, Value, 886 ConstantInt::get(MI->getOperand(3)->getType(), EltSize), // Size 887 Zero // Align 888 }; 889 CallInst::Create(TheFn, Ops, Ops + 4, "", MI); 890 } 891 } 892 MI->eraseFromParent(); 893} 894 895/// RewriteStoreUserOfWholeAlloca - We found an store of an integer that 896/// overwrites the entire allocation. Extract out the pieces of the stored 897/// integer and store them individually. 898void SROA::RewriteStoreUserOfWholeAlloca(StoreInst *SI, 899 AllocationInst *AI, 900 SmallVector<AllocaInst*, 32> &NewElts){ 901 // Extract each element out of the integer according to its structure offset 902 // and store the element value to the individual alloca. 903 Value *SrcVal = SI->getOperand(0); 904 const Type *AllocaEltTy = AI->getType()->getElementType(); 905 uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy); 906 907 // If this isn't a store of an integer to the whole alloca, it may be a store 908 // to the first element. Just ignore the store in this case and normal SROA 909 // will handle it. 910 if (!isa<IntegerType>(SrcVal->getType()) || 911 TD->getTypeAllocSizeInBits(SrcVal->getType()) != AllocaSizeBits) 912 return; 913 // Handle tail padding by extending the operand 914 if (TD->getTypeSizeInBits(SrcVal->getType()) != AllocaSizeBits) 915 SrcVal = new ZExtInst(SrcVal, 916 IntegerType::get(SI->getContext(), AllocaSizeBits), 917 "", SI); 918 919 DOUT << "PROMOTING STORE TO WHOLE ALLOCA: " << *AI << *SI; 920 921 // There are two forms here: AI could be an array or struct. Both cases 922 // have different ways to compute the element offset. 923 if (const StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) { 924 const StructLayout *Layout = TD->getStructLayout(EltSTy); 925 926 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { 927 // Get the number of bits to shift SrcVal to get the value. 928 const Type *FieldTy = EltSTy->getElementType(i); 929 uint64_t Shift = Layout->getElementOffsetInBits(i); 930 931 if (TD->isBigEndian()) 932 Shift = AllocaSizeBits-Shift-TD->getTypeAllocSizeInBits(FieldTy); 933 934 Value *EltVal = SrcVal; 935 if (Shift) { 936 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift); 937 EltVal = BinaryOperator::CreateLShr(EltVal, ShiftVal, 938 "sroa.store.elt", SI); 939 } 940 941 // Truncate down to an integer of the right size. 942 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy); 943 944 // Ignore zero sized fields like {}, they obviously contain no data. 945 if (FieldSizeBits == 0) continue; 946 947 if (FieldSizeBits != AllocaSizeBits) 948 EltVal = new TruncInst(EltVal, 949 IntegerType::get(SI->getContext(), FieldSizeBits), 950 "", SI); 951 Value *DestField = NewElts[i]; 952 if (EltVal->getType() == FieldTy) { 953 // Storing to an integer field of this size, just do it. 954 } else if (FieldTy->isFloatingPoint() || isa<VectorType>(FieldTy)) { 955 // Bitcast to the right element type (for fp/vector values). 956 EltVal = new BitCastInst(EltVal, FieldTy, "", SI); 957 } else { 958 // Otherwise, bitcast the dest pointer (for aggregates). 959 DestField = new BitCastInst(DestField, 960 PointerType::getUnqual(EltVal->getType()), 961 "", SI); 962 } 963 new StoreInst(EltVal, DestField, SI); 964 } 965 966 } else { 967 const ArrayType *ATy = cast<ArrayType>(AllocaEltTy); 968 const Type *ArrayEltTy = ATy->getElementType(); 969 uint64_t ElementOffset = TD->getTypeAllocSizeInBits(ArrayEltTy); 970 uint64_t ElementSizeBits = TD->getTypeSizeInBits(ArrayEltTy); 971 972 uint64_t Shift; 973 974 if (TD->isBigEndian()) 975 Shift = AllocaSizeBits-ElementOffset; 976 else 977 Shift = 0; 978 979 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { 980 // Ignore zero sized fields like {}, they obviously contain no data. 981 if (ElementSizeBits == 0) continue; 982 983 Value *EltVal = SrcVal; 984 if (Shift) { 985 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift); 986 EltVal = BinaryOperator::CreateLShr(EltVal, ShiftVal, 987 "sroa.store.elt", SI); 988 } 989 990 // Truncate down to an integer of the right size. 991 if (ElementSizeBits != AllocaSizeBits) 992 EltVal = new TruncInst(EltVal, 993 IntegerType::get(SI->getContext(), 994 ElementSizeBits),"",SI); 995 Value *DestField = NewElts[i]; 996 if (EltVal->getType() == ArrayEltTy) { 997 // Storing to an integer field of this size, just do it. 998 } else if (ArrayEltTy->isFloatingPoint() || isa<VectorType>(ArrayEltTy)) { 999 // Bitcast to the right element type (for fp/vector values). 1000 EltVal = new BitCastInst(EltVal, ArrayEltTy, "", SI); 1001 } else { 1002 // Otherwise, bitcast the dest pointer (for aggregates). 1003 DestField = new BitCastInst(DestField, 1004 PointerType::getUnqual(EltVal->getType()), 1005 "", SI); 1006 } 1007 new StoreInst(EltVal, DestField, SI); 1008 1009 if (TD->isBigEndian()) 1010 Shift -= ElementOffset; 1011 else 1012 Shift += ElementOffset; 1013 } 1014 } 1015 1016 SI->eraseFromParent(); 1017} 1018 1019/// RewriteLoadUserOfWholeAlloca - We found an load of the entire allocation to 1020/// an integer. Load the individual pieces to form the aggregate value. 1021void SROA::RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocationInst *AI, 1022 SmallVector<AllocaInst*, 32> &NewElts) { 1023 // Extract each element out of the NewElts according to its structure offset 1024 // and form the result value. 1025 const Type *AllocaEltTy = AI->getType()->getElementType(); 1026 uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy); 1027 1028 // If this isn't a load of the whole alloca to an integer, it may be a load 1029 // of the first element. Just ignore the load in this case and normal SROA 1030 // will handle it. 1031 if (!isa<IntegerType>(LI->getType()) || 1032 TD->getTypeAllocSizeInBits(LI->getType()) != AllocaSizeBits) 1033 return; 1034 1035 DOUT << "PROMOTING LOAD OF WHOLE ALLOCA: " << *AI << *LI; 1036 1037 // There are two forms here: AI could be an array or struct. Both cases 1038 // have different ways to compute the element offset. 1039 const StructLayout *Layout = 0; 1040 uint64_t ArrayEltBitOffset = 0; 1041 if (const StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) { 1042 Layout = TD->getStructLayout(EltSTy); 1043 } else { 1044 const Type *ArrayEltTy = cast<ArrayType>(AllocaEltTy)->getElementType(); 1045 ArrayEltBitOffset = TD->getTypeAllocSizeInBits(ArrayEltTy); 1046 } 1047 1048 Value *ResultVal = 1049 Constant::getNullValue(IntegerType::get(LI->getContext(), AllocaSizeBits)); 1050 1051 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { 1052 // Load the value from the alloca. If the NewElt is an aggregate, cast 1053 // the pointer to an integer of the same size before doing the load. 1054 Value *SrcField = NewElts[i]; 1055 const Type *FieldTy = 1056 cast<PointerType>(SrcField->getType())->getElementType(); 1057 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy); 1058 1059 // Ignore zero sized fields like {}, they obviously contain no data. 1060 if (FieldSizeBits == 0) continue; 1061 1062 const IntegerType *FieldIntTy = IntegerType::get(LI->getContext(), 1063 FieldSizeBits); 1064 if (!isa<IntegerType>(FieldTy) && !FieldTy->isFloatingPoint() && 1065 !isa<VectorType>(FieldTy)) 1066 SrcField = new BitCastInst(SrcField, 1067 PointerType::getUnqual(FieldIntTy), 1068 "", LI); 1069 SrcField = new LoadInst(SrcField, "sroa.load.elt", LI); 1070 1071 // If SrcField is a fp or vector of the right size but that isn't an 1072 // integer type, bitcast to an integer so we can shift it. 1073 if (SrcField->getType() != FieldIntTy) 1074 SrcField = new BitCastInst(SrcField, FieldIntTy, "", LI); 1075 1076 // Zero extend the field to be the same size as the final alloca so that 1077 // we can shift and insert it. 1078 if (SrcField->getType() != ResultVal->getType()) 1079 SrcField = new ZExtInst(SrcField, ResultVal->getType(), "", LI); 1080 1081 // Determine the number of bits to shift SrcField. 1082 uint64_t Shift; 1083 if (Layout) // Struct case. 1084 Shift = Layout->getElementOffsetInBits(i); 1085 else // Array case. 1086 Shift = i*ArrayEltBitOffset; 1087 1088 if (TD->isBigEndian()) 1089 Shift = AllocaSizeBits-Shift-FieldIntTy->getBitWidth(); 1090 1091 if (Shift) { 1092 Value *ShiftVal = ConstantInt::get(SrcField->getType(), Shift); 1093 SrcField = BinaryOperator::CreateShl(SrcField, ShiftVal, "", LI); 1094 } 1095 1096 ResultVal = BinaryOperator::CreateOr(SrcField, ResultVal, "", LI); 1097 } 1098 1099 // Handle tail padding by truncating the result 1100 if (TD->getTypeSizeInBits(LI->getType()) != AllocaSizeBits) 1101 ResultVal = new TruncInst(ResultVal, LI->getType(), "", LI); 1102 1103 LI->replaceAllUsesWith(ResultVal); 1104 LI->eraseFromParent(); 1105} 1106 1107 1108/// HasPadding - Return true if the specified type has any structure or 1109/// alignment padding, false otherwise. 1110static bool HasPadding(const Type *Ty, const TargetData &TD) { 1111 if (const StructType *STy = dyn_cast<StructType>(Ty)) { 1112 const StructLayout *SL = TD.getStructLayout(STy); 1113 unsigned PrevFieldBitOffset = 0; 1114 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) { 1115 unsigned FieldBitOffset = SL->getElementOffsetInBits(i); 1116 1117 // Padding in sub-elements? 1118 if (HasPadding(STy->getElementType(i), TD)) 1119 return true; 1120 1121 // Check to see if there is any padding between this element and the 1122 // previous one. 1123 if (i) { 1124 unsigned PrevFieldEnd = 1125 PrevFieldBitOffset+TD.getTypeSizeInBits(STy->getElementType(i-1)); 1126 if (PrevFieldEnd < FieldBitOffset) 1127 return true; 1128 } 1129 1130 PrevFieldBitOffset = FieldBitOffset; 1131 } 1132 1133 // Check for tail padding. 1134 if (unsigned EltCount = STy->getNumElements()) { 1135 unsigned PrevFieldEnd = PrevFieldBitOffset + 1136 TD.getTypeSizeInBits(STy->getElementType(EltCount-1)); 1137 if (PrevFieldEnd < SL->getSizeInBits()) 1138 return true; 1139 } 1140 1141 } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) { 1142 return HasPadding(ATy->getElementType(), TD); 1143 } else if (const VectorType *VTy = dyn_cast<VectorType>(Ty)) { 1144 return HasPadding(VTy->getElementType(), TD); 1145 } 1146 return TD.getTypeSizeInBits(Ty) != TD.getTypeAllocSizeInBits(Ty); 1147} 1148 1149/// isSafeStructAllocaToScalarRepl - Check to see if the specified allocation of 1150/// an aggregate can be broken down into elements. Return 0 if not, 3 if safe, 1151/// or 1 if safe after canonicalization has been performed. 1152/// 1153int SROA::isSafeAllocaToScalarRepl(AllocationInst *AI) { 1154 // Loop over the use list of the alloca. We can only transform it if all of 1155 // the users are safe to transform. 1156 AllocaInfo Info; 1157 1158 for (Value::use_iterator I = AI->use_begin(), E = AI->use_end(); 1159 I != E; ++I) { 1160 isSafeUseOfAllocation(cast<Instruction>(*I), AI, Info); 1161 if (Info.isUnsafe) { 1162 DOUT << "Cannot transform: " << *AI << " due to user: " << **I; 1163 return 0; 1164 } 1165 } 1166 1167 // Okay, we know all the users are promotable. If the aggregate is a memcpy 1168 // source and destination, we have to be careful. In particular, the memcpy 1169 // could be moving around elements that live in structure padding of the LLVM 1170 // types, but may actually be used. In these cases, we refuse to promote the 1171 // struct. 1172 if (Info.isMemCpySrc && Info.isMemCpyDst && 1173 HasPadding(AI->getType()->getElementType(), *TD)) 1174 return 0; 1175 1176 // If we require cleanup, return 1, otherwise return 3. 1177 return Info.needsCleanup ? 1 : 3; 1178} 1179 1180/// CleanupGEP - GEP is used by an Alloca, which can be prompted after the GEP 1181/// is canonicalized here. 1182void SROA::CleanupGEP(GetElementPtrInst *GEPI) { 1183 gep_type_iterator I = gep_type_begin(GEPI); 1184 ++I; 1185 1186 const ArrayType *AT = dyn_cast<ArrayType>(*I); 1187 if (!AT) 1188 return; 1189 1190 uint64_t NumElements = AT->getNumElements(); 1191 1192 if (isa<ConstantInt>(I.getOperand())) 1193 return; 1194 1195 if (NumElements == 1) { 1196 GEPI->setOperand(2, 1197 Constant::getNullValue(Type::getInt32Ty(GEPI->getContext()))); 1198 return; 1199 } 1200 1201 assert(NumElements == 2 && "Unhandled case!"); 1202 // All users of the GEP must be loads. At each use of the GEP, insert 1203 // two loads of the appropriate indexed GEP and select between them. 1204 Value *IsOne = new ICmpInst(GEPI, ICmpInst::ICMP_NE, I.getOperand(), 1205 Constant::getNullValue(I.getOperand()->getType()), 1206 "isone"); 1207 // Insert the new GEP instructions, which are properly indexed. 1208 SmallVector<Value*, 8> Indices(GEPI->op_begin()+1, GEPI->op_end()); 1209 Indices[1] = Constant::getNullValue(Type::getInt32Ty(GEPI->getContext())); 1210 Value *ZeroIdx = GetElementPtrInst::Create(GEPI->getOperand(0), 1211 Indices.begin(), 1212 Indices.end(), 1213 GEPI->getName()+".0", GEPI); 1214 Indices[1] = ConstantInt::get(Type::getInt32Ty(GEPI->getContext()), 1); 1215 Value *OneIdx = GetElementPtrInst::Create(GEPI->getOperand(0), 1216 Indices.begin(), 1217 Indices.end(), 1218 GEPI->getName()+".1", GEPI); 1219 // Replace all loads of the variable index GEP with loads from both 1220 // indexes and a select. 1221 while (!GEPI->use_empty()) { 1222 LoadInst *LI = cast<LoadInst>(GEPI->use_back()); 1223 Value *Zero = new LoadInst(ZeroIdx, LI->getName()+".0", LI); 1224 Value *One = new LoadInst(OneIdx , LI->getName()+".1", LI); 1225 Value *R = SelectInst::Create(IsOne, One, Zero, LI->getName(), LI); 1226 LI->replaceAllUsesWith(R); 1227 LI->eraseFromParent(); 1228 } 1229 GEPI->eraseFromParent(); 1230} 1231 1232 1233/// CleanupAllocaUsers - If SROA reported that it can promote the specified 1234/// allocation, but only if cleaned up, perform the cleanups required. 1235void SROA::CleanupAllocaUsers(AllocationInst *AI) { 1236 // At this point, we know that the end result will be SROA'd and promoted, so 1237 // we can insert ugly code if required so long as sroa+mem2reg will clean it 1238 // up. 1239 for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end(); 1240 UI != E; ) { 1241 User *U = *UI++; 1242 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(U)) 1243 CleanupGEP(GEPI); 1244 else { 1245 Instruction *I = cast<Instruction>(U); 1246 SmallVector<DbgInfoIntrinsic *, 2> DbgInUses; 1247 if (!isa<StoreInst>(I) && OnlyUsedByDbgInfoIntrinsics(I, &DbgInUses)) { 1248 // Safe to remove debug info uses. 1249 while (!DbgInUses.empty()) { 1250 DbgInfoIntrinsic *DI = DbgInUses.back(); DbgInUses.pop_back(); 1251 DI->eraseFromParent(); 1252 } 1253 I->eraseFromParent(); 1254 } 1255 } 1256 } 1257} 1258 1259/// MergeInType - Add the 'In' type to the accumulated type (Accum) so far at 1260/// the offset specified by Offset (which is specified in bytes). 1261/// 1262/// There are two cases we handle here: 1263/// 1) A union of vector types of the same size and potentially its elements. 1264/// Here we turn element accesses into insert/extract element operations. 1265/// This promotes a <4 x float> with a store of float to the third element 1266/// into a <4 x float> that uses insert element. 1267/// 2) A fully general blob of memory, which we turn into some (potentially 1268/// large) integer type with extract and insert operations where the loads 1269/// and stores would mutate the memory. 1270static void MergeInType(const Type *In, uint64_t Offset, const Type *&VecTy, 1271 unsigned AllocaSize, const TargetData &TD, 1272 LLVMContext &Context) { 1273 // If this could be contributing to a vector, analyze it. 1274 if (VecTy != Type::getVoidTy(Context)) { // either null or a vector type. 1275 1276 // If the In type is a vector that is the same size as the alloca, see if it 1277 // matches the existing VecTy. 1278 if (const VectorType *VInTy = dyn_cast<VectorType>(In)) { 1279 if (VInTy->getBitWidth()/8 == AllocaSize && Offset == 0) { 1280 // If we're storing/loading a vector of the right size, allow it as a 1281 // vector. If this the first vector we see, remember the type so that 1282 // we know the element size. 1283 if (VecTy == 0) 1284 VecTy = VInTy; 1285 return; 1286 } 1287 } else if (In == Type::getFloatTy(Context) || 1288 In == Type::getDoubleTy(Context) || 1289 (isa<IntegerType>(In) && In->getPrimitiveSizeInBits() >= 8 && 1290 isPowerOf2_32(In->getPrimitiveSizeInBits()))) { 1291 // If we're accessing something that could be an element of a vector, see 1292 // if the implied vector agrees with what we already have and if Offset is 1293 // compatible with it. 1294 unsigned EltSize = In->getPrimitiveSizeInBits()/8; 1295 if (Offset % EltSize == 0 && 1296 AllocaSize % EltSize == 0 && 1297 (VecTy == 0 || 1298 cast<VectorType>(VecTy)->getElementType() 1299 ->getPrimitiveSizeInBits()/8 == EltSize)) { 1300 if (VecTy == 0) 1301 VecTy = VectorType::get(In, AllocaSize/EltSize); 1302 return; 1303 } 1304 } 1305 } 1306 1307 // Otherwise, we have a case that we can't handle with an optimized vector 1308 // form. We can still turn this into a large integer. 1309 VecTy = Type::getVoidTy(Context); 1310} 1311 1312/// CanConvertToScalar - V is a pointer. If we can convert the pointee and all 1313/// its accesses to use a to single vector type, return true, and set VecTy to 1314/// the new type. If we could convert the alloca into a single promotable 1315/// integer, return true but set VecTy to VoidTy. Further, if the use is not a 1316/// completely trivial use that mem2reg could promote, set IsNotTrivial. Offset 1317/// is the current offset from the base of the alloca being analyzed. 1318/// 1319/// If we see at least one access to the value that is as a vector type, set the 1320/// SawVec flag. 1321/// 1322bool SROA::CanConvertToScalar(Value *V, bool &IsNotTrivial, const Type *&VecTy, 1323 bool &SawVec, uint64_t Offset, 1324 unsigned AllocaSize) { 1325 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) { 1326 Instruction *User = cast<Instruction>(*UI); 1327 1328 if (LoadInst *LI = dyn_cast<LoadInst>(User)) { 1329 // Don't break volatile loads. 1330 if (LI->isVolatile()) 1331 return false; 1332 MergeInType(LI->getType(), Offset, VecTy, 1333 AllocaSize, *TD, V->getContext()); 1334 SawVec |= isa<VectorType>(LI->getType()); 1335 continue; 1336 } 1337 1338 if (StoreInst *SI = dyn_cast<StoreInst>(User)) { 1339 // Storing the pointer, not into the value? 1340 if (SI->getOperand(0) == V || SI->isVolatile()) return 0; 1341 MergeInType(SI->getOperand(0)->getType(), Offset, 1342 VecTy, AllocaSize, *TD, V->getContext()); 1343 SawVec |= isa<VectorType>(SI->getOperand(0)->getType()); 1344 continue; 1345 } 1346 1347 if (BitCastInst *BCI = dyn_cast<BitCastInst>(User)) { 1348 if (!CanConvertToScalar(BCI, IsNotTrivial, VecTy, SawVec, Offset, 1349 AllocaSize)) 1350 return false; 1351 IsNotTrivial = true; 1352 continue; 1353 } 1354 1355 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) { 1356 // If this is a GEP with a variable indices, we can't handle it. 1357 if (!GEP->hasAllConstantIndices()) 1358 return false; 1359 1360 // Compute the offset that this GEP adds to the pointer. 1361 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end()); 1362 uint64_t GEPOffset = TD->getIndexedOffset(GEP->getOperand(0)->getType(), 1363 &Indices[0], Indices.size()); 1364 // See if all uses can be converted. 1365 if (!CanConvertToScalar(GEP, IsNotTrivial, VecTy, SawVec,Offset+GEPOffset, 1366 AllocaSize)) 1367 return false; 1368 IsNotTrivial = true; 1369 continue; 1370 } 1371 1372 // If this is a constant sized memset of a constant value (e.g. 0) we can 1373 // handle it. 1374 if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) { 1375 // Store of constant value and constant size. 1376 if (isa<ConstantInt>(MSI->getValue()) && 1377 isa<ConstantInt>(MSI->getLength())) { 1378 IsNotTrivial = true; 1379 continue; 1380 } 1381 } 1382 1383 // If this is a memcpy or memmove into or out of the whole allocation, we 1384 // can handle it like a load or store of the scalar type. 1385 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) { 1386 if (ConstantInt *Len = dyn_cast<ConstantInt>(MTI->getLength())) 1387 if (Len->getZExtValue() == AllocaSize && Offset == 0) { 1388 IsNotTrivial = true; 1389 continue; 1390 } 1391 } 1392 1393 // Ignore dbg intrinsic. 1394 if (isa<DbgInfoIntrinsic>(User)) 1395 continue; 1396 1397 // Otherwise, we cannot handle this! 1398 return false; 1399 } 1400 1401 return true; 1402} 1403 1404 1405/// ConvertUsesToScalar - Convert all of the users of Ptr to use the new alloca 1406/// directly. This happens when we are converting an "integer union" to a 1407/// single integer scalar, or when we are converting a "vector union" to a 1408/// vector with insert/extractelement instructions. 1409/// 1410/// Offset is an offset from the original alloca, in bits that need to be 1411/// shifted to the right. By the end of this, there should be no uses of Ptr. 1412void SROA::ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, uint64_t Offset) { 1413 while (!Ptr->use_empty()) { 1414 Instruction *User = cast<Instruction>(Ptr->use_back()); 1415 1416 if (BitCastInst *CI = dyn_cast<BitCastInst>(User)) { 1417 ConvertUsesToScalar(CI, NewAI, Offset); 1418 CI->eraseFromParent(); 1419 continue; 1420 } 1421 1422 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) { 1423 // Compute the offset that this GEP adds to the pointer. 1424 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end()); 1425 uint64_t GEPOffset = TD->getIndexedOffset(GEP->getOperand(0)->getType(), 1426 &Indices[0], Indices.size()); 1427 ConvertUsesToScalar(GEP, NewAI, Offset+GEPOffset*8); 1428 GEP->eraseFromParent(); 1429 continue; 1430 } 1431 1432 IRBuilder<> Builder(User->getParent(), User); 1433 1434 if (LoadInst *LI = dyn_cast<LoadInst>(User)) { 1435 // The load is a bit extract from NewAI shifted right by Offset bits. 1436 Value *LoadedVal = Builder.CreateLoad(NewAI, "tmp"); 1437 Value *NewLoadVal 1438 = ConvertScalar_ExtractValue(LoadedVal, LI->getType(), Offset, Builder); 1439 LI->replaceAllUsesWith(NewLoadVal); 1440 LI->eraseFromParent(); 1441 continue; 1442 } 1443 1444 if (StoreInst *SI = dyn_cast<StoreInst>(User)) { 1445 assert(SI->getOperand(0) != Ptr && "Consistency error!"); 1446 // FIXME: Remove once builder has Twine API. 1447 Value *Old = Builder.CreateLoad(NewAI, (NewAI->getName()+".in").str().c_str()); 1448 Value *New = ConvertScalar_InsertValue(SI->getOperand(0), Old, Offset, 1449 Builder); 1450 Builder.CreateStore(New, NewAI); 1451 SI->eraseFromParent(); 1452 continue; 1453 } 1454 1455 // If this is a constant sized memset of a constant value (e.g. 0) we can 1456 // transform it into a store of the expanded constant value. 1457 if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) { 1458 assert(MSI->getRawDest() == Ptr && "Consistency error!"); 1459 unsigned NumBytes = cast<ConstantInt>(MSI->getLength())->getZExtValue(); 1460 if (NumBytes != 0) { 1461 unsigned Val = cast<ConstantInt>(MSI->getValue())->getZExtValue(); 1462 1463 // Compute the value replicated the right number of times. 1464 APInt APVal(NumBytes*8, Val); 1465 1466 // Splat the value if non-zero. 1467 if (Val) 1468 for (unsigned i = 1; i != NumBytes; ++i) 1469 APVal |= APVal << 8; 1470 1471 // FIXME: Remove once builder has Twine API. 1472 Value *Old = Builder.CreateLoad(NewAI, (NewAI->getName()+".in").str().c_str()); 1473 Value *New = ConvertScalar_InsertValue( 1474 ConstantInt::get(User->getContext(), APVal), 1475 Old, Offset, Builder); 1476 Builder.CreateStore(New, NewAI); 1477 } 1478 MSI->eraseFromParent(); 1479 continue; 1480 } 1481 1482 // If this is a memcpy or memmove into or out of the whole allocation, we 1483 // can handle it like a load or store of the scalar type. 1484 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) { 1485 assert(Offset == 0 && "must be store to start of alloca"); 1486 1487 // If the source and destination are both to the same alloca, then this is 1488 // a noop copy-to-self, just delete it. Otherwise, emit a load and store 1489 // as appropriate. 1490 AllocaInst *OrigAI = cast<AllocaInst>(Ptr->getUnderlyingObject()); 1491 1492 if (MTI->getSource()->getUnderlyingObject() != OrigAI) { 1493 // Dest must be OrigAI, change this to be a load from the original 1494 // pointer (bitcasted), then a store to our new alloca. 1495 assert(MTI->getRawDest() == Ptr && "Neither use is of pointer?"); 1496 Value *SrcPtr = MTI->getSource(); 1497 SrcPtr = Builder.CreateBitCast(SrcPtr, NewAI->getType()); 1498 1499 LoadInst *SrcVal = Builder.CreateLoad(SrcPtr, "srcval"); 1500 SrcVal->setAlignment(MTI->getAlignment()); 1501 Builder.CreateStore(SrcVal, NewAI); 1502 } else if (MTI->getDest()->getUnderlyingObject() != OrigAI) { 1503 // Src must be OrigAI, change this to be a load from NewAI then a store 1504 // through the original dest pointer (bitcasted). 1505 assert(MTI->getRawSource() == Ptr && "Neither use is of pointer?"); 1506 LoadInst *SrcVal = Builder.CreateLoad(NewAI, "srcval"); 1507 1508 Value *DstPtr = Builder.CreateBitCast(MTI->getDest(), NewAI->getType()); 1509 StoreInst *NewStore = Builder.CreateStore(SrcVal, DstPtr); 1510 NewStore->setAlignment(MTI->getAlignment()); 1511 } else { 1512 // Noop transfer. Src == Dst 1513 } 1514 1515 1516 MTI->eraseFromParent(); 1517 continue; 1518 } 1519 1520 // If user is a dbg info intrinsic then it is safe to remove it. 1521 if (isa<DbgInfoIntrinsic>(User)) { 1522 User->eraseFromParent(); 1523 continue; 1524 } 1525 1526 llvm_unreachable("Unsupported operation!"); 1527 } 1528} 1529 1530/// ConvertScalar_ExtractValue - Extract a value of type ToType from an integer 1531/// or vector value FromVal, extracting the bits from the offset specified by 1532/// Offset. This returns the value, which is of type ToType. 1533/// 1534/// This happens when we are converting an "integer union" to a single 1535/// integer scalar, or when we are converting a "vector union" to a vector with 1536/// insert/extractelement instructions. 1537/// 1538/// Offset is an offset from the original alloca, in bits that need to be 1539/// shifted to the right. 1540Value *SROA::ConvertScalar_ExtractValue(Value *FromVal, const Type *ToType, 1541 uint64_t Offset, IRBuilder<> &Builder) { 1542 // If the load is of the whole new alloca, no conversion is needed. 1543 if (FromVal->getType() == ToType && Offset == 0) 1544 return FromVal; 1545 1546 // If the result alloca is a vector type, this is either an element 1547 // access or a bitcast to another vector type of the same size. 1548 if (const VectorType *VTy = dyn_cast<VectorType>(FromVal->getType())) { 1549 if (isa<VectorType>(ToType)) 1550 return Builder.CreateBitCast(FromVal, ToType, "tmp"); 1551 1552 // Otherwise it must be an element access. 1553 unsigned Elt = 0; 1554 if (Offset) { 1555 unsigned EltSize = TD->getTypeAllocSizeInBits(VTy->getElementType()); 1556 Elt = Offset/EltSize; 1557 assert(EltSize*Elt == Offset && "Invalid modulus in validity checking"); 1558 } 1559 // Return the element extracted out of it. 1560 Value *V = Builder.CreateExtractElement(FromVal, ConstantInt::get( 1561 Type::getInt32Ty(FromVal->getContext()), Elt), "tmp"); 1562 if (V->getType() != ToType) 1563 V = Builder.CreateBitCast(V, ToType, "tmp"); 1564 return V; 1565 } 1566 1567 // If ToType is a first class aggregate, extract out each of the pieces and 1568 // use insertvalue's to form the FCA. 1569 if (const StructType *ST = dyn_cast<StructType>(ToType)) { 1570 const StructLayout &Layout = *TD->getStructLayout(ST); 1571 Value *Res = UndefValue::get(ST); 1572 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) { 1573 Value *Elt = ConvertScalar_ExtractValue(FromVal, ST->getElementType(i), 1574 Offset+Layout.getElementOffsetInBits(i), 1575 Builder); 1576 Res = Builder.CreateInsertValue(Res, Elt, i, "tmp"); 1577 } 1578 return Res; 1579 } 1580 1581 if (const ArrayType *AT = dyn_cast<ArrayType>(ToType)) { 1582 uint64_t EltSize = TD->getTypeAllocSizeInBits(AT->getElementType()); 1583 Value *Res = UndefValue::get(AT); 1584 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) { 1585 Value *Elt = ConvertScalar_ExtractValue(FromVal, AT->getElementType(), 1586 Offset+i*EltSize, Builder); 1587 Res = Builder.CreateInsertValue(Res, Elt, i, "tmp"); 1588 } 1589 return Res; 1590 } 1591 1592 // Otherwise, this must be a union that was converted to an integer value. 1593 const IntegerType *NTy = cast<IntegerType>(FromVal->getType()); 1594 1595 // If this is a big-endian system and the load is narrower than the 1596 // full alloca type, we need to do a shift to get the right bits. 1597 int ShAmt = 0; 1598 if (TD->isBigEndian()) { 1599 // On big-endian machines, the lowest bit is stored at the bit offset 1600 // from the pointer given by getTypeStoreSizeInBits. This matters for 1601 // integers with a bitwidth that is not a multiple of 8. 1602 ShAmt = TD->getTypeStoreSizeInBits(NTy) - 1603 TD->getTypeStoreSizeInBits(ToType) - Offset; 1604 } else { 1605 ShAmt = Offset; 1606 } 1607 1608 // Note: we support negative bitwidths (with shl) which are not defined. 1609 // We do this to support (f.e.) loads off the end of a structure where 1610 // only some bits are used. 1611 if (ShAmt > 0 && (unsigned)ShAmt < NTy->getBitWidth()) 1612 FromVal = Builder.CreateLShr(FromVal, 1613 ConstantInt::get(FromVal->getType(), 1614 ShAmt), "tmp"); 1615 else if (ShAmt < 0 && (unsigned)-ShAmt < NTy->getBitWidth()) 1616 FromVal = Builder.CreateShl(FromVal, 1617 ConstantInt::get(FromVal->getType(), 1618 -ShAmt), "tmp"); 1619 1620 // Finally, unconditionally truncate the integer to the right width. 1621 unsigned LIBitWidth = TD->getTypeSizeInBits(ToType); 1622 if (LIBitWidth < NTy->getBitWidth()) 1623 FromVal = 1624 Builder.CreateTrunc(FromVal, IntegerType::get(FromVal->getContext(), 1625 LIBitWidth), "tmp"); 1626 else if (LIBitWidth > NTy->getBitWidth()) 1627 FromVal = 1628 Builder.CreateZExt(FromVal, IntegerType::get(FromVal->getContext(), 1629 LIBitWidth), "tmp"); 1630 1631 // If the result is an integer, this is a trunc or bitcast. 1632 if (isa<IntegerType>(ToType)) { 1633 // Should be done. 1634 } else if (ToType->isFloatingPoint() || isa<VectorType>(ToType)) { 1635 // Just do a bitcast, we know the sizes match up. 1636 FromVal = Builder.CreateBitCast(FromVal, ToType, "tmp"); 1637 } else { 1638 // Otherwise must be a pointer. 1639 FromVal = Builder.CreateIntToPtr(FromVal, ToType, "tmp"); 1640 } 1641 assert(FromVal->getType() == ToType && "Didn't convert right?"); 1642 return FromVal; 1643} 1644 1645 1646/// ConvertScalar_InsertValue - Insert the value "SV" into the existing integer 1647/// or vector value "Old" at the offset specified by Offset. 1648/// 1649/// This happens when we are converting an "integer union" to a 1650/// single integer scalar, or when we are converting a "vector union" to a 1651/// vector with insert/extractelement instructions. 1652/// 1653/// Offset is an offset from the original alloca, in bits that need to be 1654/// shifted to the right. 1655Value *SROA::ConvertScalar_InsertValue(Value *SV, Value *Old, 1656 uint64_t Offset, IRBuilder<> &Builder) { 1657 1658 // Convert the stored type to the actual type, shift it left to insert 1659 // then 'or' into place. 1660 const Type *AllocaType = Old->getType(); 1661 LLVMContext &Context = Old->getContext(); 1662 1663 if (const VectorType *VTy = dyn_cast<VectorType>(AllocaType)) { 1664 uint64_t VecSize = TD->getTypeAllocSizeInBits(VTy); 1665 uint64_t ValSize = TD->getTypeAllocSizeInBits(SV->getType()); 1666 1667 // Changing the whole vector with memset or with an access of a different 1668 // vector type? 1669 if (ValSize == VecSize) 1670 return Builder.CreateBitCast(SV, AllocaType, "tmp"); 1671 1672 uint64_t EltSize = TD->getTypeAllocSizeInBits(VTy->getElementType()); 1673 1674 // Must be an element insertion. 1675 unsigned Elt = Offset/EltSize; 1676 1677 if (SV->getType() != VTy->getElementType()) 1678 SV = Builder.CreateBitCast(SV, VTy->getElementType(), "tmp"); 1679 1680 SV = Builder.CreateInsertElement(Old, SV, 1681 ConstantInt::get(Type::getInt32Ty(SV->getContext()), Elt), 1682 "tmp"); 1683 return SV; 1684 } 1685 1686 // If SV is a first-class aggregate value, insert each value recursively. 1687 if (const StructType *ST = dyn_cast<StructType>(SV->getType())) { 1688 const StructLayout &Layout = *TD->getStructLayout(ST); 1689 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) { 1690 Value *Elt = Builder.CreateExtractValue(SV, i, "tmp"); 1691 Old = ConvertScalar_InsertValue(Elt, Old, 1692 Offset+Layout.getElementOffsetInBits(i), 1693 Builder); 1694 } 1695 return Old; 1696 } 1697 1698 if (const ArrayType *AT = dyn_cast<ArrayType>(SV->getType())) { 1699 uint64_t EltSize = TD->getTypeAllocSizeInBits(AT->getElementType()); 1700 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) { 1701 Value *Elt = Builder.CreateExtractValue(SV, i, "tmp"); 1702 Old = ConvertScalar_InsertValue(Elt, Old, Offset+i*EltSize, Builder); 1703 } 1704 return Old; 1705 } 1706 1707 // If SV is a float, convert it to the appropriate integer type. 1708 // If it is a pointer, do the same. 1709 unsigned SrcWidth = TD->getTypeSizeInBits(SV->getType()); 1710 unsigned DestWidth = TD->getTypeSizeInBits(AllocaType); 1711 unsigned SrcStoreWidth = TD->getTypeStoreSizeInBits(SV->getType()); 1712 unsigned DestStoreWidth = TD->getTypeStoreSizeInBits(AllocaType); 1713 if (SV->getType()->isFloatingPoint() || isa<VectorType>(SV->getType())) 1714 SV = Builder.CreateBitCast(SV, 1715 IntegerType::get(SV->getContext(),SrcWidth), "tmp"); 1716 else if (isa<PointerType>(SV->getType())) 1717 SV = Builder.CreatePtrToInt(SV, TD->getIntPtrType(SV->getContext()), "tmp"); 1718 1719 // Zero extend or truncate the value if needed. 1720 if (SV->getType() != AllocaType) { 1721 if (SV->getType()->getPrimitiveSizeInBits() < 1722 AllocaType->getPrimitiveSizeInBits()) 1723 SV = Builder.CreateZExt(SV, AllocaType, "tmp"); 1724 else { 1725 // Truncation may be needed if storing more than the alloca can hold 1726 // (undefined behavior). 1727 SV = Builder.CreateTrunc(SV, AllocaType, "tmp"); 1728 SrcWidth = DestWidth; 1729 SrcStoreWidth = DestStoreWidth; 1730 } 1731 } 1732 1733 // If this is a big-endian system and the store is narrower than the 1734 // full alloca type, we need to do a shift to get the right bits. 1735 int ShAmt = 0; 1736 if (TD->isBigEndian()) { 1737 // On big-endian machines, the lowest bit is stored at the bit offset 1738 // from the pointer given by getTypeStoreSizeInBits. This matters for 1739 // integers with a bitwidth that is not a multiple of 8. 1740 ShAmt = DestStoreWidth - SrcStoreWidth - Offset; 1741 } else { 1742 ShAmt = Offset; 1743 } 1744 1745 // Note: we support negative bitwidths (with shr) which are not defined. 1746 // We do this to support (f.e.) stores off the end of a structure where 1747 // only some bits in the structure are set. 1748 APInt Mask(APInt::getLowBitsSet(DestWidth, SrcWidth)); 1749 if (ShAmt > 0 && (unsigned)ShAmt < DestWidth) { 1750 SV = Builder.CreateShl(SV, ConstantInt::get(SV->getType(), 1751 ShAmt), "tmp"); 1752 Mask <<= ShAmt; 1753 } else if (ShAmt < 0 && (unsigned)-ShAmt < DestWidth) { 1754 SV = Builder.CreateLShr(SV, ConstantInt::get(SV->getType(), 1755 -ShAmt), "tmp"); 1756 Mask = Mask.lshr(-ShAmt); 1757 } 1758 1759 // Mask out the bits we are about to insert from the old value, and or 1760 // in the new bits. 1761 if (SrcWidth != DestWidth) { 1762 assert(DestWidth > SrcWidth); 1763 Old = Builder.CreateAnd(Old, ConstantInt::get(Context, ~Mask), "mask"); 1764 SV = Builder.CreateOr(Old, SV, "ins"); 1765 } 1766 return SV; 1767} 1768 1769 1770 1771/// PointsToConstantGlobal - Return true if V (possibly indirectly) points to 1772/// some part of a constant global variable. This intentionally only accepts 1773/// constant expressions because we don't can't rewrite arbitrary instructions. 1774static bool PointsToConstantGlobal(Value *V) { 1775 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V)) 1776 return GV->isConstant(); 1777 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) 1778 if (CE->getOpcode() == Instruction::BitCast || 1779 CE->getOpcode() == Instruction::GetElementPtr) 1780 return PointsToConstantGlobal(CE->getOperand(0)); 1781 return false; 1782} 1783 1784/// isOnlyCopiedFromConstantGlobal - Recursively walk the uses of a (derived) 1785/// pointer to an alloca. Ignore any reads of the pointer, return false if we 1786/// see any stores or other unknown uses. If we see pointer arithmetic, keep 1787/// track of whether it moves the pointer (with isOffset) but otherwise traverse 1788/// the uses. If we see a memcpy/memmove that targets an unoffseted pointer to 1789/// the alloca, and if the source pointer is a pointer to a constant global, we 1790/// can optimize this. 1791static bool isOnlyCopiedFromConstantGlobal(Value *V, Instruction *&TheCopy, 1792 bool isOffset) { 1793 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) { 1794 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) 1795 // Ignore non-volatile loads, they are always ok. 1796 if (!LI->isVolatile()) 1797 continue; 1798 1799 if (BitCastInst *BCI = dyn_cast<BitCastInst>(*UI)) { 1800 // If uses of the bitcast are ok, we are ok. 1801 if (!isOnlyCopiedFromConstantGlobal(BCI, TheCopy, isOffset)) 1802 return false; 1803 continue; 1804 } 1805 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(*UI)) { 1806 // If the GEP has all zero indices, it doesn't offset the pointer. If it 1807 // doesn't, it does. 1808 if (!isOnlyCopiedFromConstantGlobal(GEP, TheCopy, 1809 isOffset || !GEP->hasAllZeroIndices())) 1810 return false; 1811 continue; 1812 } 1813 1814 // If this is isn't our memcpy/memmove, reject it as something we can't 1815 // handle. 1816 if (!isa<MemTransferInst>(*UI)) 1817 return false; 1818 1819 // If we already have seen a copy, reject the second one. 1820 if (TheCopy) return false; 1821 1822 // If the pointer has been offset from the start of the alloca, we can't 1823 // safely handle this. 1824 if (isOffset) return false; 1825 1826 // If the memintrinsic isn't using the alloca as the dest, reject it. 1827 if (UI.getOperandNo() != 1) return false; 1828 1829 MemIntrinsic *MI = cast<MemIntrinsic>(*UI); 1830 1831 // If the source of the memcpy/move is not a constant global, reject it. 1832 if (!PointsToConstantGlobal(MI->getOperand(2))) 1833 return false; 1834 1835 // Otherwise, the transform is safe. Remember the copy instruction. 1836 TheCopy = MI; 1837 } 1838 return true; 1839} 1840 1841/// isOnlyCopiedFromConstantGlobal - Return true if the specified alloca is only 1842/// modified by a copy from a constant global. If we can prove this, we can 1843/// replace any uses of the alloca with uses of the global directly. 1844Instruction *SROA::isOnlyCopiedFromConstantGlobal(AllocationInst *AI) { 1845 Instruction *TheCopy = 0; 1846 if (::isOnlyCopiedFromConstantGlobal(AI, TheCopy, false)) 1847 return TheCopy; 1848 return 0; 1849} 1850