ScalarReplAggregates.cpp revision 1541e0f7da2de6ae84434060df81e93b64000924
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/Pass.h" 31#include "llvm/Analysis/Dominators.h" 32#include "llvm/Target/TargetData.h" 33#include "llvm/Transforms/Utils/PromoteMemToReg.h" 34#include "llvm/Transforms/Utils/Local.h" 35#include "llvm/Support/Debug.h" 36#include "llvm/Support/GetElementPtrTypeIterator.h" 37#include "llvm/Support/IRBuilder.h" 38#include "llvm/Support/MathExtras.h" 39#include "llvm/Support/Compiler.h" 40#include "llvm/ADT/SmallVector.h" 41#include "llvm/ADT/Statistic.h" 42#include "llvm/ADT/StringExtras.h" 43using namespace llvm; 44 45STATISTIC(NumReplaced, "Number of allocas broken up"); 46STATISTIC(NumPromoted, "Number of allocas promoted"); 47STATISTIC(NumConverted, "Number of aggregates converted to scalar"); 48STATISTIC(NumGlobals, "Number of allocas copied from constant global"); 49 50namespace { 51 struct VISIBILITY_HIDDEN SROA : public FunctionPass { 52 static char ID; // Pass identification, replacement for typeid 53 explicit SROA(signed T = -1) : FunctionPass(&ID) { 54 if (T == -1) 55 SRThreshold = 128; 56 else 57 SRThreshold = T; 58 } 59 60 bool runOnFunction(Function &F); 61 62 bool performScalarRepl(Function &F); 63 bool performPromotion(Function &F); 64 65 // getAnalysisUsage - This pass does not require any passes, but we know it 66 // will not alter the CFG, so say so. 67 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 68 AU.addRequired<DominatorTree>(); 69 AU.addRequired<DominanceFrontier>(); 70 AU.addRequired<TargetData>(); 71 AU.setPreservesCFG(); 72 } 73 74 private: 75 TargetData *TD; 76 77 /// AllocaInfo - When analyzing uses of an alloca instruction, this captures 78 /// information about the uses. All these fields are initialized to false 79 /// and set to true when something is learned. 80 struct AllocaInfo { 81 /// isUnsafe - This is set to true if the alloca cannot be SROA'd. 82 bool isUnsafe : 1; 83 84 /// needsCleanup - This is set to true if there is some use of the alloca 85 /// that requires cleanup. 86 bool needsCleanup : 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), needsCleanup(false), 96 isMemCpySrc(false), isMemCpyDst(false) {} 97 }; 98 99 unsigned SRThreshold; 100 101 void MarkUnsafe(AllocaInfo &I) { I.isUnsafe = true; } 102 103 int isSafeAllocaToScalarRepl(AllocationInst *AI); 104 105 void isSafeUseOfAllocation(Instruction *User, AllocationInst *AI, 106 AllocaInfo &Info); 107 void isSafeElementUse(Value *Ptr, bool isFirstElt, AllocationInst *AI, 108 AllocaInfo &Info); 109 void isSafeMemIntrinsicOnAllocation(MemIntrinsic *MI, AllocationInst *AI, 110 unsigned OpNo, AllocaInfo &Info); 111 void isSafeUseOfBitCastedAllocation(BitCastInst *User, AllocationInst *AI, 112 AllocaInfo &Info); 113 114 void DoScalarReplacement(AllocationInst *AI, 115 std::vector<AllocationInst*> &WorkList); 116 void CleanupGEP(GetElementPtrInst *GEP); 117 void CleanupAllocaUsers(AllocationInst *AI); 118 AllocaInst *AddNewAlloca(Function &F, const Type *Ty, AllocationInst *Base); 119 120 void RewriteBitCastUserOfAlloca(Instruction *BCInst, AllocationInst *AI, 121 SmallVector<AllocaInst*, 32> &NewElts); 122 123 void RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *BCInst, 124 AllocationInst *AI, 125 SmallVector<AllocaInst*, 32> &NewElts); 126 void RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocationInst *AI, 127 SmallVector<AllocaInst*, 32> &NewElts); 128 void RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocationInst *AI, 129 SmallVector<AllocaInst*, 32> &NewElts); 130 131 bool CanConvertToScalar(Value *V, bool &IsNotTrivial, const Type *&VecTy, 132 bool &SawVec, uint64_t Offset, unsigned AllocaSize); 133 void ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, uint64_t Offset); 134 Value *ConvertScalar_ExtractValue(Value *NV, const Type *ToType, 135 uint64_t Offset, IRBuilder<> &Builder); 136 Value *ConvertScalar_InsertValue(Value *StoredVal, Value *ExistingVal, 137 uint64_t Offset, IRBuilder<> &Builder); 138 static Instruction *isOnlyCopiedFromConstantGlobal(AllocationInst *AI); 139 }; 140} 141 142char SROA::ID = 0; 143static RegisterPass<SROA> X("scalarrepl", "Scalar Replacement of Aggregates"); 144 145// Public interface to the ScalarReplAggregates pass 146FunctionPass *llvm::createScalarReplAggregatesPass(signed int Threshold) { 147 return new SROA(Threshold); 148} 149 150 151bool SROA::runOnFunction(Function &F) { 152 TD = &getAnalysis<TargetData>(); 153 154 bool Changed = performPromotion(F); 155 while (1) { 156 bool LocalChange = performScalarRepl(F); 157 if (!LocalChange) break; // No need to repromote if no scalarrepl 158 Changed = true; 159 LocalChange = performPromotion(F); 160 if (!LocalChange) break; // No need to re-scalarrepl if no promotion 161 } 162 163 return Changed; 164} 165 166 167bool SROA::performPromotion(Function &F) { 168 std::vector<AllocaInst*> Allocas; 169 DominatorTree &DT = getAnalysis<DominatorTree>(); 170 DominanceFrontier &DF = getAnalysis<DominanceFrontier>(); 171 172 BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function 173 174 bool Changed = false; 175 176 while (1) { 177 Allocas.clear(); 178 179 // Find allocas that are safe to promote, by looking at all instructions in 180 // the entry node 181 for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I) 182 if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) // Is it an alloca? 183 if (isAllocaPromotable(AI)) 184 Allocas.push_back(AI); 185 186 if (Allocas.empty()) break; 187 188 PromoteMemToReg(Allocas, DT, DF); 189 NumPromoted += Allocas.size(); 190 Changed = true; 191 } 192 193 return Changed; 194} 195 196/// getNumSAElements - Return the number of elements in the specific struct or 197/// array. 198static uint64_t getNumSAElements(const Type *T) { 199 if (const StructType *ST = dyn_cast<StructType>(T)) 200 return ST->getNumElements(); 201 return cast<ArrayType>(T)->getNumElements(); 202} 203 204// performScalarRepl - This algorithm is a simple worklist driven algorithm, 205// which runs on all of the malloc/alloca instructions in the function, removing 206// them if they are only used by getelementptr instructions. 207// 208bool SROA::performScalarRepl(Function &F) { 209 std::vector<AllocationInst*> WorkList; 210 211 // Scan the entry basic block, adding any alloca's and mallocs to the worklist 212 BasicBlock &BB = F.getEntryBlock(); 213 for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I) 214 if (AllocationInst *A = dyn_cast<AllocationInst>(I)) 215 WorkList.push_back(A); 216 217 // Process the worklist 218 bool Changed = false; 219 while (!WorkList.empty()) { 220 AllocationInst *AI = WorkList.back(); 221 WorkList.pop_back(); 222 223 // Handle dead allocas trivially. These can be formed by SROA'ing arrays 224 // with unused elements. 225 if (AI->use_empty()) { 226 AI->eraseFromParent(); 227 continue; 228 } 229 230 // If this alloca is impossible for us to promote, reject it early. 231 if (AI->isArrayAllocation() || !AI->getAllocatedType()->isSized()) 232 continue; 233 234 // Check to see if this allocation is only modified by a memcpy/memmove from 235 // a constant global. If this is the case, we can change all users to use 236 // the constant global instead. This is commonly produced by the CFE by 237 // constructs like "void foo() { int A[] = {1,2,3,4,5,6,7,8,9...}; }" if 'A' 238 // is only subsequently read. 239 if (Instruction *TheCopy = isOnlyCopiedFromConstantGlobal(AI)) { 240 DOUT << "Found alloca equal to global: " << *AI; 241 DOUT << " memcpy = " << *TheCopy; 242 Constant *TheSrc = cast<Constant>(TheCopy->getOperand(2)); 243 AI->replaceAllUsesWith(ConstantExpr::getBitCast(TheSrc, AI->getType())); 244 TheCopy->eraseFromParent(); // Don't mutate the global. 245 AI->eraseFromParent(); 246 ++NumGlobals; 247 Changed = true; 248 continue; 249 } 250 251 // Check to see if we can perform the core SROA transformation. We cannot 252 // transform the allocation instruction if it is an array allocation 253 // (allocations OF arrays are ok though), and an allocation of a scalar 254 // value cannot be decomposed at all. 255 uint64_t AllocaSize = TD->getTypePaddedSize(AI->getAllocatedType()); 256 257 // Do not promote any struct whose size is too big. 258 if (AllocaSize > SRThreshold) continue; 259 260 if ((isa<StructType>(AI->getAllocatedType()) || 261 isa<ArrayType>(AI->getAllocatedType())) && 262 // Do not promote any struct into more than "32" separate vars. 263 getNumSAElements(AI->getAllocatedType()) < SRThreshold/4) { 264 // Check that all of the users of the allocation are capable of being 265 // transformed. 266 switch (isSafeAllocaToScalarRepl(AI)) { 267 default: assert(0 && "Unexpected value!"); 268 case 0: // Not safe to scalar replace. 269 break; 270 case 1: // Safe, but requires cleanup/canonicalizations first 271 CleanupAllocaUsers(AI); 272 // FALL THROUGH. 273 case 3: // Safe to scalar replace. 274 DoScalarReplacement(AI, WorkList); 275 Changed = true; 276 continue; 277 } 278 } 279 280 // If we can turn this aggregate value (potentially with casts) into a 281 // simple scalar value that can be mem2reg'd into a register value. 282 // IsNotTrivial tracks whether this is something that mem2reg could have 283 // promoted itself. If so, we don't want to transform it needlessly. Note 284 // that we can't just check based on the type: the alloca may be of an i32 285 // but that has pointer arithmetic to set byte 3 of it or something. 286 bool IsNotTrivial = false; 287 const Type *VectorTy = 0; 288 bool HadAVector = false; 289 if (CanConvertToScalar(AI, IsNotTrivial, VectorTy, HadAVector, 290 0, unsigned(AllocaSize)) && IsNotTrivial && 291 AllocaSize <= 128) { 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(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() + "." + utostr(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() + "." + utostr(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(Type::Int32Ty)); 421 NewArgs.append(GEPI->op_begin()+3, GEPI->op_end()); 422 RepValue = GetElementPtrInst::Create(AllocaToUse, NewArgs.begin(), 423 NewArgs.end(), "", GEPI); 424 RepValue->takeName(GEPI); 425 } 426 427 // If this GEP is to the start of the aggregate, check for memcpys. 428 if (Idx == 0 && GEPI->hasAllZeroIndices()) 429 RewriteBitCastUserOfAlloca(GEPI, AI, ElementAllocas); 430 431 // Move all of the users over to the new GEP. 432 GEPI->replaceAllUsesWith(RepValue); 433 // Delete the old GEP 434 GEPI->eraseFromParent(); 435 } 436 437 // Finally, delete the Alloca instruction 438 AI->eraseFromParent(); 439 NumReplaced++; 440} 441 442 443/// isSafeElementUse - Check to see if this use is an allowed use for a 444/// getelementptr instruction of an array aggregate allocation. isFirstElt 445/// indicates whether Ptr is known to the start of the aggregate. 446/// 447void SROA::isSafeElementUse(Value *Ptr, bool isFirstElt, AllocationInst *AI, 448 AllocaInfo &Info) { 449 for (Value::use_iterator I = Ptr->use_begin(), E = Ptr->use_end(); 450 I != E; ++I) { 451 Instruction *User = cast<Instruction>(*I); 452 switch (User->getOpcode()) { 453 case Instruction::Load: break; 454 case Instruction::Store: 455 // Store is ok if storing INTO the pointer, not storing the pointer 456 if (User->getOperand(0) == Ptr) return MarkUnsafe(Info); 457 break; 458 case Instruction::GetElementPtr: { 459 GetElementPtrInst *GEP = cast<GetElementPtrInst>(User); 460 bool AreAllZeroIndices = isFirstElt; 461 if (GEP->getNumOperands() > 1) { 462 if (!isa<ConstantInt>(GEP->getOperand(1)) || 463 !cast<ConstantInt>(GEP->getOperand(1))->isZero()) 464 // Using pointer arithmetic to navigate the array. 465 return MarkUnsafe(Info); 466 467 if (AreAllZeroIndices) 468 AreAllZeroIndices = GEP->hasAllZeroIndices(); 469 } 470 isSafeElementUse(GEP, AreAllZeroIndices, AI, Info); 471 if (Info.isUnsafe) return; 472 break; 473 } 474 case Instruction::BitCast: 475 if (isFirstElt) { 476 isSafeUseOfBitCastedAllocation(cast<BitCastInst>(User), AI, Info); 477 if (Info.isUnsafe) return; 478 break; 479 } 480 DOUT << " Transformation preventing inst: " << *User; 481 return MarkUnsafe(Info); 482 case Instruction::Call: 483 if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) { 484 if (isFirstElt) { 485 isSafeMemIntrinsicOnAllocation(MI, AI, I.getOperandNo(), Info); 486 if (Info.isUnsafe) return; 487 break; 488 } 489 } 490 DOUT << " Transformation preventing inst: " << *User; 491 return MarkUnsafe(Info); 492 default: 493 DOUT << " Transformation preventing inst: " << *User; 494 return MarkUnsafe(Info); 495 } 496 } 497 return; // All users look ok :) 498} 499 500/// AllUsersAreLoads - Return true if all users of this value are loads. 501static bool AllUsersAreLoads(Value *Ptr) { 502 for (Value::use_iterator I = Ptr->use_begin(), E = Ptr->use_end(); 503 I != E; ++I) 504 if (cast<Instruction>(*I)->getOpcode() != Instruction::Load) 505 return false; 506 return true; 507} 508 509/// isSafeUseOfAllocation - Check to see if this user is an allowed use for an 510/// aggregate allocation. 511/// 512void SROA::isSafeUseOfAllocation(Instruction *User, AllocationInst *AI, 513 AllocaInfo &Info) { 514 if (BitCastInst *C = dyn_cast<BitCastInst>(User)) 515 return isSafeUseOfBitCastedAllocation(C, AI, Info); 516 517 if (LoadInst *LI = dyn_cast<LoadInst>(User)) 518 if (!LI->isVolatile()) 519 return;// Loads (returning a first class aggregrate) are always rewritable 520 521 if (StoreInst *SI = dyn_cast<StoreInst>(User)) 522 if (!SI->isVolatile() && SI->getOperand(0) != AI) 523 return;// Store is ok if storing INTO the pointer, not storing the pointer 524 525 GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User); 526 if (GEPI == 0) 527 return MarkUnsafe(Info); 528 529 gep_type_iterator I = gep_type_begin(GEPI), E = gep_type_end(GEPI); 530 531 // The GEP is not safe to transform if not of the form "GEP <ptr>, 0, <cst>". 532 if (I == E || 533 I.getOperand() != Constant::getNullValue(I.getOperand()->getType())) { 534 return MarkUnsafe(Info); 535 } 536 537 ++I; 538 if (I == E) return MarkUnsafe(Info); // ran out of GEP indices?? 539 540 bool IsAllZeroIndices = true; 541 542 // If the first index is a non-constant index into an array, see if we can 543 // handle it as a special case. 544 if (const ArrayType *AT = dyn_cast<ArrayType>(*I)) { 545 if (!isa<ConstantInt>(I.getOperand())) { 546 IsAllZeroIndices = 0; 547 uint64_t NumElements = AT->getNumElements(); 548 549 // If this is an array index and the index is not constant, we cannot 550 // promote... that is unless the array has exactly one or two elements in 551 // it, in which case we CAN promote it, but we have to canonicalize this 552 // out if this is the only problem. 553 if ((NumElements == 1 || NumElements == 2) && 554 AllUsersAreLoads(GEPI)) { 555 Info.needsCleanup = true; 556 return; // Canonicalization required! 557 } 558 return MarkUnsafe(Info); 559 } 560 } 561 562 // Walk through the GEP type indices, checking the types that this indexes 563 // into. 564 for (; I != E; ++I) { 565 // Ignore struct elements, no extra checking needed for these. 566 if (isa<StructType>(*I)) 567 continue; 568 569 ConstantInt *IdxVal = dyn_cast<ConstantInt>(I.getOperand()); 570 if (!IdxVal) return MarkUnsafe(Info); 571 572 // Are all indices still zero? 573 IsAllZeroIndices &= IdxVal->isZero(); 574 575 if (const ArrayType *AT = dyn_cast<ArrayType>(*I)) { 576 // This GEP indexes an array. Verify that this is an in-range constant 577 // integer. Specifically, consider A[0][i]. We cannot know that the user 578 // isn't doing invalid things like allowing i to index an out-of-range 579 // subscript that accesses A[1]. Because of this, we have to reject SROA 580 // of any accesses into structs where any of the components are variables. 581 if (IdxVal->getZExtValue() >= AT->getNumElements()) 582 return MarkUnsafe(Info); 583 } else if (const VectorType *VT = dyn_cast<VectorType>(*I)) { 584 if (IdxVal->getZExtValue() >= VT->getNumElements()) 585 return MarkUnsafe(Info); 586 } 587 } 588 589 // If there are any non-simple uses of this getelementptr, make sure to reject 590 // them. 591 return isSafeElementUse(GEPI, IsAllZeroIndices, AI, Info); 592} 593 594/// isSafeMemIntrinsicOnAllocation - Return true if the specified memory 595/// intrinsic can be promoted by SROA. At this point, we know that the operand 596/// of the memintrinsic is a pointer to the beginning of the allocation. 597void SROA::isSafeMemIntrinsicOnAllocation(MemIntrinsic *MI, AllocationInst *AI, 598 unsigned OpNo, AllocaInfo &Info) { 599 // If not constant length, give up. 600 ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength()); 601 if (!Length) return MarkUnsafe(Info); 602 603 // If not the whole aggregate, give up. 604 if (Length->getZExtValue() != 605 TD->getTypePaddedSize(AI->getType()->getElementType())) 606 return MarkUnsafe(Info); 607 608 // We only know about memcpy/memset/memmove. 609 if (!isa<MemCpyInst>(MI) && !isa<MemSetInst>(MI) && !isa<MemMoveInst>(MI)) 610 return MarkUnsafe(Info); 611 612 // Otherwise, we can transform it. Determine whether this is a memcpy/set 613 // into or out of the aggregate. 614 if (OpNo == 1) 615 Info.isMemCpyDst = true; 616 else { 617 assert(OpNo == 2); 618 Info.isMemCpySrc = true; 619 } 620} 621 622/// isSafeUseOfBitCastedAllocation - Return true if all users of this bitcast 623/// are 624void SROA::isSafeUseOfBitCastedAllocation(BitCastInst *BC, AllocationInst *AI, 625 AllocaInfo &Info) { 626 for (Value::use_iterator UI = BC->use_begin(), E = BC->use_end(); 627 UI != E; ++UI) { 628 if (BitCastInst *BCU = dyn_cast<BitCastInst>(UI)) { 629 isSafeUseOfBitCastedAllocation(BCU, AI, Info); 630 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(UI)) { 631 isSafeMemIntrinsicOnAllocation(MI, AI, UI.getOperandNo(), Info); 632 } else if (StoreInst *SI = dyn_cast<StoreInst>(UI)) { 633 if (SI->isVolatile()) 634 return MarkUnsafe(Info); 635 636 // If storing the entire alloca in one chunk through a bitcasted pointer 637 // to integer, we can transform it. This happens (for example) when you 638 // cast a {i32,i32}* to i64* and store through it. This is similar to the 639 // memcpy case and occurs in various "byval" cases and emulated memcpys. 640 if (isa<IntegerType>(SI->getOperand(0)->getType()) && 641 TD->getTypePaddedSize(SI->getOperand(0)->getType()) == 642 TD->getTypePaddedSize(AI->getType()->getElementType())) { 643 Info.isMemCpyDst = true; 644 continue; 645 } 646 return MarkUnsafe(Info); 647 } else if (LoadInst *LI = dyn_cast<LoadInst>(UI)) { 648 if (LI->isVolatile()) 649 return MarkUnsafe(Info); 650 651 // If loading the entire alloca in one chunk through a bitcasted pointer 652 // to integer, we can transform it. This happens (for example) when you 653 // cast a {i32,i32}* to i64* and load through it. This is similar to the 654 // memcpy case and occurs in various "byval" cases and emulated memcpys. 655 if (isa<IntegerType>(LI->getType()) && 656 TD->getTypePaddedSize(LI->getType()) == 657 TD->getTypePaddedSize(AI->getType()->getElementType())) { 658 Info.isMemCpySrc = true; 659 continue; 660 } 661 return MarkUnsafe(Info); 662 } else if (isa<DbgInfoIntrinsic>(UI)) { 663 // If one user is DbgInfoIntrinsic then check if all users are 664 // DbgInfoIntrinsics. 665 if (OnlyUsedByDbgInfoIntrinsics(BC)) { 666 Info.needsCleanup = true; 667 return; 668 } 669 else 670 MarkUnsafe(Info); 671 } 672 else { 673 return MarkUnsafe(Info); 674 } 675 if (Info.isUnsafe) return; 676 } 677} 678 679/// RewriteBitCastUserOfAlloca - BCInst (transitively) bitcasts AI, or indexes 680/// to its first element. Transform users of the cast to use the new values 681/// instead. 682void SROA::RewriteBitCastUserOfAlloca(Instruction *BCInst, AllocationInst *AI, 683 SmallVector<AllocaInst*, 32> &NewElts) { 684 Value::use_iterator UI = BCInst->use_begin(), UE = BCInst->use_end(); 685 while (UI != UE) { 686 Instruction *User = cast<Instruction>(*UI++); 687 if (BitCastInst *BCU = dyn_cast<BitCastInst>(User)) { 688 RewriteBitCastUserOfAlloca(BCU, AI, NewElts); 689 if (BCU->use_empty()) BCU->eraseFromParent(); 690 continue; 691 } 692 693 if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) { 694 // This must be memcpy/memmove/memset of the entire aggregate. 695 // Split into one per element. 696 RewriteMemIntrinUserOfAlloca(MI, BCInst, AI, NewElts); 697 continue; 698 } 699 700 if (StoreInst *SI = dyn_cast<StoreInst>(User)) { 701 // If this is a store of the entire alloca from an integer, rewrite it. 702 RewriteStoreUserOfWholeAlloca(SI, AI, NewElts); 703 continue; 704 } 705 706 if (LoadInst *LI = dyn_cast<LoadInst>(User)) { 707 // If this is a load of the entire alloca to an integer, rewrite it. 708 RewriteLoadUserOfWholeAlloca(LI, AI, NewElts); 709 continue; 710 } 711 712 // Otherwise it must be some other user of a gep of the first pointer. Just 713 // leave these alone. 714 continue; 715 } 716} 717 718/// RewriteMemIntrinUserOfAlloca - MI is a memcpy/memset/memmove from or to AI. 719/// Rewrite it to copy or set the elements of the scalarized memory. 720void SROA::RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *BCInst, 721 AllocationInst *AI, 722 SmallVector<AllocaInst*, 32> &NewElts) { 723 724 // If this is a memcpy/memmove, construct the other pointer as the 725 // appropriate type. The "Other" pointer is the pointer that goes to 726 Value *OtherPtr = 0; 727 unsigned MemAlignment = MI->getAlignment()->getZExtValue(); 728 if (MemCpyInst *MCI = dyn_cast<MemCpyInst>(MI)) { 729 if (BCInst == MCI->getRawDest()) 730 OtherPtr = MCI->getRawSource(); 731 else { 732 assert(BCInst == MCI->getRawSource()); 733 OtherPtr = MCI->getRawDest(); 734 } 735 } else if (MemMoveInst *MMI = dyn_cast<MemMoveInst>(MI)) { 736 if (BCInst == MMI->getRawDest()) 737 OtherPtr = MMI->getRawSource(); 738 else { 739 assert(BCInst == MMI->getRawSource()); 740 OtherPtr = MMI->getRawDest(); 741 } 742 } 743 744 // If there is an other pointer, we want to convert it to the same pointer 745 // type as AI has, so we can GEP through it safely. 746 if (OtherPtr) { 747 // It is likely that OtherPtr is a bitcast, if so, remove it. 748 if (BitCastInst *BC = dyn_cast<BitCastInst>(OtherPtr)) 749 OtherPtr = BC->getOperand(0); 750 // All zero GEPs are effectively bitcasts. 751 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(OtherPtr)) 752 if (GEP->hasAllZeroIndices()) 753 OtherPtr = GEP->getOperand(0); 754 755 if (ConstantExpr *BCE = dyn_cast<ConstantExpr>(OtherPtr)) 756 if (BCE->getOpcode() == Instruction::BitCast) 757 OtherPtr = BCE->getOperand(0); 758 759 // If the pointer is not the right type, insert a bitcast to the right 760 // type. 761 if (OtherPtr->getType() != AI->getType()) 762 OtherPtr = new BitCastInst(OtherPtr, AI->getType(), OtherPtr->getName(), 763 MI); 764 } 765 766 // Process each element of the aggregate. 767 Value *TheFn = MI->getOperand(0); 768 const Type *BytePtrTy = MI->getRawDest()->getType(); 769 bool SROADest = MI->getRawDest() == BCInst; 770 771 Constant *Zero = Constant::getNullValue(Type::Int32Ty); 772 773 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { 774 // If this is a memcpy/memmove, emit a GEP of the other element address. 775 Value *OtherElt = 0; 776 unsigned OtherEltAlign = MemAlignment; 777 778 if (OtherPtr) { 779 Value *Idx[2] = { Zero, ConstantInt::get(Type::Int32Ty, i) }; 780 OtherElt = GetElementPtrInst::Create(OtherPtr, Idx, Idx + 2, 781 OtherPtr->getNameStr()+"."+utostr(i), 782 MI); 783 uint64_t EltOffset; 784 const PointerType *OtherPtrTy = cast<PointerType>(OtherPtr->getType()); 785 if (const StructType *ST = 786 dyn_cast<StructType>(OtherPtrTy->getElementType())) { 787 EltOffset = TD->getStructLayout(ST)->getElementOffset(i); 788 } else { 789 const Type *EltTy = 790 cast<SequentialType>(OtherPtr->getType())->getElementType(); 791 EltOffset = TD->getTypePaddedSize(EltTy)*i; 792 } 793 794 // The alignment of the other pointer is the guaranteed alignment of the 795 // element, which is affected by both the known alignment of the whole 796 // mem intrinsic and the alignment of the element. If the alignment of 797 // the memcpy (f.e.) is 32 but the element is at a 4-byte offset, then the 798 // known alignment is just 4 bytes. 799 OtherEltAlign = (unsigned)MinAlign(OtherEltAlign, EltOffset); 800 } 801 802 Value *EltPtr = NewElts[i]; 803 const Type *EltTy = cast<PointerType>(EltPtr->getType())->getElementType(); 804 805 // If we got down to a scalar, insert a load or store as appropriate. 806 if (EltTy->isSingleValueType()) { 807 if (isa<MemCpyInst>(MI) || isa<MemMoveInst>(MI)) { 808 if (SROADest) { 809 // From Other to Alloca. 810 Value *Elt = new LoadInst(OtherElt, "tmp", false, OtherEltAlign, MI); 811 new StoreInst(Elt, EltPtr, MI); 812 } else { 813 // From Alloca to Other. 814 Value *Elt = new LoadInst(EltPtr, "tmp", MI); 815 new StoreInst(Elt, OtherElt, false, OtherEltAlign, MI); 816 } 817 continue; 818 } 819 assert(isa<MemSetInst>(MI)); 820 821 // If the stored element is zero (common case), just store a null 822 // constant. 823 Constant *StoreVal; 824 if (ConstantInt *CI = dyn_cast<ConstantInt>(MI->getOperand(2))) { 825 if (CI->isZero()) { 826 StoreVal = Constant::getNullValue(EltTy); // 0.0, null, 0, <0,0> 827 } else { 828 // If EltTy is a vector type, get the element type. 829 const Type *ValTy = EltTy; 830 if (const VectorType *VTy = dyn_cast<VectorType>(ValTy)) 831 ValTy = VTy->getElementType(); 832 833 // Construct an integer with the right value. 834 unsigned EltSize = TD->getTypeSizeInBits(ValTy); 835 APInt OneVal(EltSize, CI->getZExtValue()); 836 APInt TotalVal(OneVal); 837 // Set each byte. 838 for (unsigned i = 0; 8*i < EltSize; ++i) { 839 TotalVal = TotalVal.shl(8); 840 TotalVal |= OneVal; 841 } 842 843 // Convert the integer value to the appropriate type. 844 StoreVal = ConstantInt::get(TotalVal); 845 if (isa<PointerType>(ValTy)) 846 StoreVal = ConstantExpr::getIntToPtr(StoreVal, ValTy); 847 else if (ValTy->isFloatingPoint()) 848 StoreVal = ConstantExpr::getBitCast(StoreVal, ValTy); 849 assert(StoreVal->getType() == ValTy && "Type mismatch!"); 850 851 // If the requested value was a vector constant, create it. 852 if (EltTy != ValTy) { 853 unsigned NumElts = cast<VectorType>(ValTy)->getNumElements(); 854 SmallVector<Constant*, 16> Elts(NumElts, StoreVal); 855 StoreVal = ConstantVector::get(&Elts[0], NumElts); 856 } 857 } 858 new StoreInst(StoreVal, EltPtr, MI); 859 continue; 860 } 861 // Otherwise, if we're storing a byte variable, use a memset call for 862 // this element. 863 } 864 865 // Cast the element pointer to BytePtrTy. 866 if (EltPtr->getType() != BytePtrTy) 867 EltPtr = new BitCastInst(EltPtr, BytePtrTy, EltPtr->getNameStr(), MI); 868 869 // Cast the other pointer (if we have one) to BytePtrTy. 870 if (OtherElt && OtherElt->getType() != BytePtrTy) 871 OtherElt = new BitCastInst(OtherElt, BytePtrTy,OtherElt->getNameStr(), 872 MI); 873 874 unsigned EltSize = TD->getTypePaddedSize(EltTy); 875 876 // Finally, insert the meminst for this element. 877 if (isa<MemCpyInst>(MI) || isa<MemMoveInst>(MI)) { 878 Value *Ops[] = { 879 SROADest ? EltPtr : OtherElt, // Dest ptr 880 SROADest ? OtherElt : EltPtr, // Src ptr 881 ConstantInt::get(MI->getOperand(3)->getType(), EltSize), // Size 882 ConstantInt::get(Type::Int32Ty, OtherEltAlign) // Align 883 }; 884 CallInst::Create(TheFn, Ops, Ops + 4, "", MI); 885 } else { 886 assert(isa<MemSetInst>(MI)); 887 Value *Ops[] = { 888 EltPtr, MI->getOperand(2), // Dest, Value, 889 ConstantInt::get(MI->getOperand(3)->getType(), EltSize), // Size 890 Zero // Align 891 }; 892 CallInst::Create(TheFn, Ops, Ops + 4, "", MI); 893 } 894 } 895 MI->eraseFromParent(); 896} 897 898/// RewriteStoreUserOfWholeAlloca - We found an store of an integer that 899/// overwrites the entire allocation. Extract out the pieces of the stored 900/// integer and store them individually. 901void SROA::RewriteStoreUserOfWholeAlloca(StoreInst *SI, 902 AllocationInst *AI, 903 SmallVector<AllocaInst*, 32> &NewElts){ 904 // Extract each element out of the integer according to its structure offset 905 // and store the element value to the individual alloca. 906 Value *SrcVal = SI->getOperand(0); 907 const Type *AllocaEltTy = AI->getType()->getElementType(); 908 uint64_t AllocaSizeBits = TD->getTypePaddedSizeInBits(AllocaEltTy); 909 910 // If this isn't a store of an integer to the whole alloca, it may be a store 911 // to the first element. Just ignore the store in this case and normal SROA 912 // will handle it. 913 if (!isa<IntegerType>(SrcVal->getType()) || 914 TD->getTypePaddedSizeInBits(SrcVal->getType()) != AllocaSizeBits) 915 return; 916 917 DOUT << "PROMOTING STORE TO WHOLE ALLOCA: " << *AI << *SI; 918 919 // There are two forms here: AI could be an array or struct. Both cases 920 // have different ways to compute the element offset. 921 if (const StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) { 922 const StructLayout *Layout = TD->getStructLayout(EltSTy); 923 924 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { 925 // Get the number of bits to shift SrcVal to get the value. 926 const Type *FieldTy = EltSTy->getElementType(i); 927 uint64_t Shift = Layout->getElementOffsetInBits(i); 928 929 if (TD->isBigEndian()) 930 Shift = AllocaSizeBits-Shift-TD->getTypePaddedSizeInBits(FieldTy); 931 932 Value *EltVal = SrcVal; 933 if (Shift) { 934 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift); 935 EltVal = BinaryOperator::CreateLShr(EltVal, ShiftVal, 936 "sroa.store.elt", SI); 937 } 938 939 // Truncate down to an integer of the right size. 940 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy); 941 942 // Ignore zero sized fields like {}, they obviously contain no data. 943 if (FieldSizeBits == 0) continue; 944 945 if (FieldSizeBits != AllocaSizeBits) 946 EltVal = new TruncInst(EltVal, IntegerType::get(FieldSizeBits), "", SI); 947 Value *DestField = NewElts[i]; 948 if (EltVal->getType() == FieldTy) { 949 // Storing to an integer field of this size, just do it. 950 } else if (FieldTy->isFloatingPoint() || isa<VectorType>(FieldTy)) { 951 // Bitcast to the right element type (for fp/vector values). 952 EltVal = new BitCastInst(EltVal, FieldTy, "", SI); 953 } else { 954 // Otherwise, bitcast the dest pointer (for aggregates). 955 DestField = new BitCastInst(DestField, 956 PointerType::getUnqual(EltVal->getType()), 957 "", SI); 958 } 959 new StoreInst(EltVal, DestField, SI); 960 } 961 962 } else { 963 const ArrayType *ATy = cast<ArrayType>(AllocaEltTy); 964 const Type *ArrayEltTy = ATy->getElementType(); 965 uint64_t ElementOffset = TD->getTypePaddedSizeInBits(ArrayEltTy); 966 uint64_t ElementSizeBits = TD->getTypeSizeInBits(ArrayEltTy); 967 968 uint64_t Shift; 969 970 if (TD->isBigEndian()) 971 Shift = AllocaSizeBits-ElementOffset; 972 else 973 Shift = 0; 974 975 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { 976 // Ignore zero sized fields like {}, they obviously contain no data. 977 if (ElementSizeBits == 0) continue; 978 979 Value *EltVal = SrcVal; 980 if (Shift) { 981 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift); 982 EltVal = BinaryOperator::CreateLShr(EltVal, ShiftVal, 983 "sroa.store.elt", SI); 984 } 985 986 // Truncate down to an integer of the right size. 987 if (ElementSizeBits != AllocaSizeBits) 988 EltVal = new TruncInst(EltVal, IntegerType::get(ElementSizeBits),"",SI); 989 Value *DestField = NewElts[i]; 990 if (EltVal->getType() == ArrayEltTy) { 991 // Storing to an integer field of this size, just do it. 992 } else if (ArrayEltTy->isFloatingPoint() || isa<VectorType>(ArrayEltTy)) { 993 // Bitcast to the right element type (for fp/vector values). 994 EltVal = new BitCastInst(EltVal, ArrayEltTy, "", SI); 995 } else { 996 // Otherwise, bitcast the dest pointer (for aggregates). 997 DestField = new BitCastInst(DestField, 998 PointerType::getUnqual(EltVal->getType()), 999 "", SI); 1000 } 1001 new StoreInst(EltVal, DestField, SI); 1002 1003 if (TD->isBigEndian()) 1004 Shift -= ElementOffset; 1005 else 1006 Shift += ElementOffset; 1007 } 1008 } 1009 1010 SI->eraseFromParent(); 1011} 1012 1013/// RewriteLoadUserOfWholeAlloca - We found an load of the entire allocation to 1014/// an integer. Load the individual pieces to form the aggregate value. 1015void SROA::RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocationInst *AI, 1016 SmallVector<AllocaInst*, 32> &NewElts) { 1017 // Extract each element out of the NewElts according to its structure offset 1018 // and form the result value. 1019 const Type *AllocaEltTy = AI->getType()->getElementType(); 1020 uint64_t AllocaSizeBits = TD->getTypePaddedSizeInBits(AllocaEltTy); 1021 1022 // If this isn't a load of the whole alloca to an integer, it may be a load 1023 // of the first element. Just ignore the load in this case and normal SROA 1024 // will handle it. 1025 if (!isa<IntegerType>(LI->getType()) || 1026 TD->getTypePaddedSizeInBits(LI->getType()) != AllocaSizeBits) 1027 return; 1028 1029 DOUT << "PROMOTING LOAD OF WHOLE ALLOCA: " << *AI << *LI; 1030 1031 // There are two forms here: AI could be an array or struct. Both cases 1032 // have different ways to compute the element offset. 1033 const StructLayout *Layout = 0; 1034 uint64_t ArrayEltBitOffset = 0; 1035 if (const StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) { 1036 Layout = TD->getStructLayout(EltSTy); 1037 } else { 1038 const Type *ArrayEltTy = cast<ArrayType>(AllocaEltTy)->getElementType(); 1039 ArrayEltBitOffset = TD->getTypePaddedSizeInBits(ArrayEltTy); 1040 } 1041 1042 Value *ResultVal = Constant::getNullValue(LI->getType()); 1043 1044 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { 1045 // Load the value from the alloca. If the NewElt is an aggregate, cast 1046 // the pointer to an integer of the same size before doing the load. 1047 Value *SrcField = NewElts[i]; 1048 const Type *FieldTy = 1049 cast<PointerType>(SrcField->getType())->getElementType(); 1050 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy); 1051 1052 // Ignore zero sized fields like {}, they obviously contain no data. 1053 if (FieldSizeBits == 0) continue; 1054 1055 const IntegerType *FieldIntTy = IntegerType::get(FieldSizeBits); 1056 if (!isa<IntegerType>(FieldTy) && !FieldTy->isFloatingPoint() && 1057 !isa<VectorType>(FieldTy)) 1058 SrcField = new BitCastInst(SrcField, PointerType::getUnqual(FieldIntTy), 1059 "", LI); 1060 SrcField = new LoadInst(SrcField, "sroa.load.elt", LI); 1061 1062 // If SrcField is a fp or vector of the right size but that isn't an 1063 // integer type, bitcast to an integer so we can shift it. 1064 if (SrcField->getType() != FieldIntTy) 1065 SrcField = new BitCastInst(SrcField, FieldIntTy, "", LI); 1066 1067 // Zero extend the field to be the same size as the final alloca so that 1068 // we can shift and insert it. 1069 if (SrcField->getType() != ResultVal->getType()) 1070 SrcField = new ZExtInst(SrcField, ResultVal->getType(), "", LI); 1071 1072 // Determine the number of bits to shift SrcField. 1073 uint64_t Shift; 1074 if (Layout) // Struct case. 1075 Shift = Layout->getElementOffsetInBits(i); 1076 else // Array case. 1077 Shift = i*ArrayEltBitOffset; 1078 1079 if (TD->isBigEndian()) 1080 Shift = AllocaSizeBits-Shift-FieldIntTy->getBitWidth(); 1081 1082 if (Shift) { 1083 Value *ShiftVal = ConstantInt::get(SrcField->getType(), Shift); 1084 SrcField = BinaryOperator::CreateShl(SrcField, ShiftVal, "", LI); 1085 } 1086 1087 ResultVal = BinaryOperator::CreateOr(SrcField, ResultVal, "", LI); 1088 } 1089 1090 LI->replaceAllUsesWith(ResultVal); 1091 LI->eraseFromParent(); 1092} 1093 1094 1095/// HasPadding - Return true if the specified type has any structure or 1096/// alignment padding, false otherwise. 1097static bool HasPadding(const Type *Ty, const TargetData &TD) { 1098 if (const StructType *STy = dyn_cast<StructType>(Ty)) { 1099 const StructLayout *SL = TD.getStructLayout(STy); 1100 unsigned PrevFieldBitOffset = 0; 1101 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) { 1102 unsigned FieldBitOffset = SL->getElementOffsetInBits(i); 1103 1104 // Padding in sub-elements? 1105 if (HasPadding(STy->getElementType(i), TD)) 1106 return true; 1107 1108 // Check to see if there is any padding between this element and the 1109 // previous one. 1110 if (i) { 1111 unsigned PrevFieldEnd = 1112 PrevFieldBitOffset+TD.getTypeSizeInBits(STy->getElementType(i-1)); 1113 if (PrevFieldEnd < FieldBitOffset) 1114 return true; 1115 } 1116 1117 PrevFieldBitOffset = FieldBitOffset; 1118 } 1119 1120 // Check for tail padding. 1121 if (unsigned EltCount = STy->getNumElements()) { 1122 unsigned PrevFieldEnd = PrevFieldBitOffset + 1123 TD.getTypeSizeInBits(STy->getElementType(EltCount-1)); 1124 if (PrevFieldEnd < SL->getSizeInBits()) 1125 return true; 1126 } 1127 1128 } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) { 1129 return HasPadding(ATy->getElementType(), TD); 1130 } else if (const VectorType *VTy = dyn_cast<VectorType>(Ty)) { 1131 return HasPadding(VTy->getElementType(), TD); 1132 } 1133 return TD.getTypeSizeInBits(Ty) != TD.getTypePaddedSizeInBits(Ty); 1134} 1135 1136/// isSafeStructAllocaToScalarRepl - Check to see if the specified allocation of 1137/// an aggregate can be broken down into elements. Return 0 if not, 3 if safe, 1138/// or 1 if safe after canonicalization has been performed. 1139/// 1140int SROA::isSafeAllocaToScalarRepl(AllocationInst *AI) { 1141 // Loop over the use list of the alloca. We can only transform it if all of 1142 // the users are safe to transform. 1143 AllocaInfo Info; 1144 1145 for (Value::use_iterator I = AI->use_begin(), E = AI->use_end(); 1146 I != E; ++I) { 1147 isSafeUseOfAllocation(cast<Instruction>(*I), AI, Info); 1148 if (Info.isUnsafe) { 1149 DOUT << "Cannot transform: " << *AI << " due to user: " << **I; 1150 return 0; 1151 } 1152 } 1153 1154 // Okay, we know all the users are promotable. If the aggregate is a memcpy 1155 // source and destination, we have to be careful. In particular, the memcpy 1156 // could be moving around elements that live in structure padding of the LLVM 1157 // types, but may actually be used. In these cases, we refuse to promote the 1158 // struct. 1159 if (Info.isMemCpySrc && Info.isMemCpyDst && 1160 HasPadding(AI->getType()->getElementType(), *TD)) 1161 return 0; 1162 1163 // If we require cleanup, return 1, otherwise return 3. 1164 return Info.needsCleanup ? 1 : 3; 1165} 1166 1167/// CleanupGEP - GEP is used by an Alloca, which can be prompted after the GEP 1168/// is canonicalized here. 1169void SROA::CleanupGEP(GetElementPtrInst *GEPI) { 1170 gep_type_iterator I = gep_type_begin(GEPI); 1171 ++I; 1172 1173 const ArrayType *AT = dyn_cast<ArrayType>(*I); 1174 if (!AT) 1175 return; 1176 1177 uint64_t NumElements = AT->getNumElements(); 1178 1179 if (isa<ConstantInt>(I.getOperand())) 1180 return; 1181 1182 if (NumElements == 1) { 1183 GEPI->setOperand(2, Constant::getNullValue(Type::Int32Ty)); 1184 return; 1185 } 1186 1187 assert(NumElements == 2 && "Unhandled case!"); 1188 // All users of the GEP must be loads. At each use of the GEP, insert 1189 // two loads of the appropriate indexed GEP and select between them. 1190 Value *IsOne = new ICmpInst(ICmpInst::ICMP_NE, I.getOperand(), 1191 Constant::getNullValue(I.getOperand()->getType()), 1192 "isone", GEPI); 1193 // Insert the new GEP instructions, which are properly indexed. 1194 SmallVector<Value*, 8> Indices(GEPI->op_begin()+1, GEPI->op_end()); 1195 Indices[1] = Constant::getNullValue(Type::Int32Ty); 1196 Value *ZeroIdx = GetElementPtrInst::Create(GEPI->getOperand(0), 1197 Indices.begin(), 1198 Indices.end(), 1199 GEPI->getName()+".0", GEPI); 1200 Indices[1] = ConstantInt::get(Type::Int32Ty, 1); 1201 Value *OneIdx = GetElementPtrInst::Create(GEPI->getOperand(0), 1202 Indices.begin(), 1203 Indices.end(), 1204 GEPI->getName()+".1", GEPI); 1205 // Replace all loads of the variable index GEP with loads from both 1206 // indexes and a select. 1207 while (!GEPI->use_empty()) { 1208 LoadInst *LI = cast<LoadInst>(GEPI->use_back()); 1209 Value *Zero = new LoadInst(ZeroIdx, LI->getName()+".0", LI); 1210 Value *One = new LoadInst(OneIdx , LI->getName()+".1", LI); 1211 Value *R = SelectInst::Create(IsOne, One, Zero, LI->getName(), LI); 1212 LI->replaceAllUsesWith(R); 1213 LI->eraseFromParent(); 1214 } 1215 GEPI->eraseFromParent(); 1216} 1217 1218 1219/// CleanupAllocaUsers - If SROA reported that it can promote the specified 1220/// allocation, but only if cleaned up, perform the cleanups required. 1221void SROA::CleanupAllocaUsers(AllocationInst *AI) { 1222 // At this point, we know that the end result will be SROA'd and promoted, so 1223 // we can insert ugly code if required so long as sroa+mem2reg will clean it 1224 // up. 1225 for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end(); 1226 UI != E; ) { 1227 User *U = *UI++; 1228 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(U)) 1229 CleanupGEP(GEPI); 1230 else if (Instruction *I = dyn_cast<Instruction>(U)) { 1231 SmallVector<DbgInfoIntrinsic *, 2> DbgInUses; 1232 if (OnlyUsedByDbgInfoIntrinsics(I, &DbgInUses)) { 1233 // Safe to remove debug info uses. 1234 while (!DbgInUses.empty()) { 1235 DbgInfoIntrinsic *DI = DbgInUses.back(); DbgInUses.pop_back(); 1236 DI->eraseFromParent(); 1237 } 1238 I->eraseFromParent(); 1239 } 1240 } 1241 } 1242} 1243 1244/// MergeInType - Add the 'In' type to the accumulated type (Accum) so far at 1245/// the offset specified by Offset (which is specified in bytes). 1246/// 1247/// There are two cases we handle here: 1248/// 1) A union of vector types of the same size and potentially its elements. 1249/// Here we turn element accesses into insert/extract element operations. 1250/// This promotes a <4 x float> with a store of float to the third element 1251/// into a <4 x float> that uses insert element. 1252/// 2) A fully general blob of memory, which we turn into some (potentially 1253/// large) integer type with extract and insert operations where the loads 1254/// and stores would mutate the memory. 1255static void MergeInType(const Type *In, uint64_t Offset, const Type *&VecTy, 1256 unsigned AllocaSize, const TargetData &TD) { 1257 // If this could be contributing to a vector, analyze it. 1258 if (VecTy != Type::VoidTy) { // either null or a vector type. 1259 1260 // If the In type is a vector that is the same size as the alloca, see if it 1261 // matches the existing VecTy. 1262 if (const VectorType *VInTy = dyn_cast<VectorType>(In)) { 1263 if (VInTy->getBitWidth()/8 == AllocaSize && Offset == 0) { 1264 // If we're storing/loading a vector of the right size, allow it as a 1265 // vector. If this the first vector we see, remember the type so that 1266 // we know the element size. 1267 if (VecTy == 0) 1268 VecTy = VInTy; 1269 return; 1270 } 1271 } else if (In == Type::FloatTy || In == Type::DoubleTy || 1272 (isa<IntegerType>(In) && In->getPrimitiveSizeInBits() >= 8 && 1273 isPowerOf2_32(In->getPrimitiveSizeInBits()))) { 1274 // If we're accessing something that could be an element of a vector, see 1275 // if the implied vector agrees with what we already have and if Offset is 1276 // compatible with it. 1277 unsigned EltSize = In->getPrimitiveSizeInBits()/8; 1278 if (Offset % EltSize == 0 && 1279 AllocaSize % EltSize == 0 && 1280 (VecTy == 0 || 1281 cast<VectorType>(VecTy)->getElementType() 1282 ->getPrimitiveSizeInBits()/8 == EltSize)) { 1283 if (VecTy == 0) 1284 VecTy = VectorType::get(In, AllocaSize/EltSize); 1285 return; 1286 } 1287 } 1288 } 1289 1290 // Otherwise, we have a case that we can't handle with an optimized vector 1291 // form. We can still turn this into a large integer. 1292 VecTy = Type::VoidTy; 1293} 1294 1295/// CanConvertToScalar - V is a pointer. If we can convert the pointee and all 1296/// its accesses to use a to single vector type, return true, and set VecTy to 1297/// the new type. If we could convert the alloca into a single promotable 1298/// integer, return true but set VecTy to VoidTy. Further, if the use is not a 1299/// completely trivial use that mem2reg could promote, set IsNotTrivial. Offset 1300/// is the current offset from the base of the alloca being analyzed. 1301/// 1302/// If we see at least one access to the value that is as a vector type, set the 1303/// SawVec flag. 1304/// 1305bool SROA::CanConvertToScalar(Value *V, bool &IsNotTrivial, const Type *&VecTy, 1306 bool &SawVec, uint64_t Offset, 1307 unsigned AllocaSize) { 1308 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) { 1309 Instruction *User = cast<Instruction>(*UI); 1310 1311 if (LoadInst *LI = dyn_cast<LoadInst>(User)) { 1312 // Don't break volatile loads. 1313 if (LI->isVolatile()) 1314 return false; 1315 MergeInType(LI->getType(), Offset, VecTy, AllocaSize, *TD); 1316 SawVec |= isa<VectorType>(LI->getType()); 1317 continue; 1318 } 1319 1320 if (StoreInst *SI = dyn_cast<StoreInst>(User)) { 1321 // Storing the pointer, not into the value? 1322 if (SI->getOperand(0) == V || SI->isVolatile()) return 0; 1323 MergeInType(SI->getOperand(0)->getType(), Offset, VecTy, AllocaSize, *TD); 1324 SawVec |= isa<VectorType>(SI->getOperand(0)->getType()); 1325 continue; 1326 } 1327 1328 if (BitCastInst *BCI = dyn_cast<BitCastInst>(User)) { 1329 if (!CanConvertToScalar(BCI, IsNotTrivial, VecTy, SawVec, Offset, 1330 AllocaSize)) 1331 return false; 1332 IsNotTrivial = true; 1333 continue; 1334 } 1335 1336 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) { 1337 // If this is a GEP with a variable indices, we can't handle it. 1338 if (!GEP->hasAllConstantIndices()) 1339 return false; 1340 1341 // Compute the offset that this GEP adds to the pointer. 1342 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end()); 1343 uint64_t GEPOffset = TD->getIndexedOffset(GEP->getOperand(0)->getType(), 1344 &Indices[0], Indices.size()); 1345 // See if all uses can be converted. 1346 if (!CanConvertToScalar(GEP, IsNotTrivial, VecTy, SawVec,Offset+GEPOffset, 1347 AllocaSize)) 1348 return false; 1349 IsNotTrivial = true; 1350 continue; 1351 } 1352 1353 // If this is a constant sized memset of a constant value (e.g. 0) we can 1354 // handle it. 1355 if (isa<MemSetInst>(User) && 1356 // Store of constant value. 1357 isa<ConstantInt>(User->getOperand(2)) && 1358 // Store with constant size. 1359 isa<ConstantInt>(User->getOperand(3))) { 1360 VecTy = Type::VoidTy; 1361 IsNotTrivial = true; 1362 continue; 1363 } 1364 1365 // Otherwise, we cannot handle this! 1366 return false; 1367 } 1368 1369 return true; 1370} 1371 1372 1373/// ConvertUsesToScalar - Convert all of the users of Ptr to use the new alloca 1374/// directly. This happens when we are converting an "integer union" to a 1375/// single integer scalar, or when we are converting a "vector union" to a 1376/// vector with insert/extractelement instructions. 1377/// 1378/// Offset is an offset from the original alloca, in bits that need to be 1379/// shifted to the right. By the end of this, there should be no uses of Ptr. 1380void SROA::ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, uint64_t Offset) { 1381 while (!Ptr->use_empty()) { 1382 Instruction *User = cast<Instruction>(Ptr->use_back()); 1383 1384 if (BitCastInst *CI = dyn_cast<BitCastInst>(User)) { 1385 ConvertUsesToScalar(CI, NewAI, Offset); 1386 CI->eraseFromParent(); 1387 continue; 1388 } 1389 1390 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) { 1391 // Compute the offset that this GEP adds to the pointer. 1392 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end()); 1393 uint64_t GEPOffset = TD->getIndexedOffset(GEP->getOperand(0)->getType(), 1394 &Indices[0], Indices.size()); 1395 ConvertUsesToScalar(GEP, NewAI, Offset+GEPOffset*8); 1396 GEP->eraseFromParent(); 1397 continue; 1398 } 1399 1400 IRBuilder<> Builder(User->getParent(), User); 1401 1402 if (LoadInst *LI = dyn_cast<LoadInst>(User)) { 1403 // The load is a bit extract from NewAI shifted right by Offset bits. 1404 Value *LoadedVal = Builder.CreateLoad(NewAI, "tmp"); 1405 Value *NewLoadVal 1406 = ConvertScalar_ExtractValue(LoadedVal, LI->getType(), Offset, Builder); 1407 LI->replaceAllUsesWith(NewLoadVal); 1408 LI->eraseFromParent(); 1409 continue; 1410 } 1411 1412 if (StoreInst *SI = dyn_cast<StoreInst>(User)) { 1413 assert(SI->getOperand(0) != Ptr && "Consistency error!"); 1414 Value *Old = Builder.CreateLoad(NewAI, (NewAI->getName()+".in").c_str()); 1415 Value *New = ConvertScalar_InsertValue(SI->getOperand(0), Old, Offset, 1416 Builder); 1417 Builder.CreateStore(New, NewAI); 1418 SI->eraseFromParent(); 1419 continue; 1420 } 1421 1422 // If this is a constant sized memset of a constant value (e.g. 0) we can 1423 // transform it into a store of the expanded constant value. 1424 if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) { 1425 assert(MSI->getRawDest() == Ptr && "Consistency error!"); 1426 unsigned NumBytes = cast<ConstantInt>(MSI->getLength())->getZExtValue(); 1427 unsigned Val = cast<ConstantInt>(MSI->getValue())->getZExtValue(); 1428 1429 // Compute the value replicated the right number of times. 1430 APInt APVal(NumBytes*8, Val); 1431 1432 // Splat the value if non-zero. 1433 if (Val) 1434 for (unsigned i = 1; i != NumBytes; ++i) 1435 APVal |= APVal << 8; 1436 1437 Value *Old = Builder.CreateLoad(NewAI, (NewAI->getName()+".in").c_str()); 1438 Value *New = ConvertScalar_InsertValue(ConstantInt::get(APVal), Old, 1439 Offset, Builder); 1440 Builder.CreateStore(New, NewAI); 1441 MSI->eraseFromParent(); 1442 continue; 1443 } 1444 1445 1446 assert(0 && "Unsupported operation!"); 1447 abort(); 1448 } 1449} 1450 1451/// ConvertScalar_ExtractValue - Extract a value of type ToType from an integer 1452/// or vector value FromVal, extracting the bits from the offset specified by 1453/// Offset. This returns the value, which is of type ToType. 1454/// 1455/// This happens when we are converting an "integer union" to a single 1456/// integer scalar, or when we are converting a "vector union" to a vector with 1457/// insert/extractelement instructions. 1458/// 1459/// Offset is an offset from the original alloca, in bits that need to be 1460/// shifted to the right. 1461Value *SROA::ConvertScalar_ExtractValue(Value *FromVal, const Type *ToType, 1462 uint64_t Offset, IRBuilder<> &Builder) { 1463 // If the load is of the whole new alloca, no conversion is needed. 1464 if (FromVal->getType() == ToType && Offset == 0) 1465 return FromVal; 1466 1467 // If the result alloca is a vector type, this is either an element 1468 // access or a bitcast to another vector type of the same size. 1469 if (const VectorType *VTy = dyn_cast<VectorType>(FromVal->getType())) { 1470 if (isa<VectorType>(ToType)) 1471 return Builder.CreateBitCast(FromVal, ToType, "tmp"); 1472 1473 // Otherwise it must be an element access. 1474 unsigned Elt = 0; 1475 if (Offset) { 1476 unsigned EltSize = TD->getTypePaddedSizeInBits(VTy->getElementType()); 1477 Elt = Offset/EltSize; 1478 assert(EltSize*Elt == Offset && "Invalid modulus in validity checking"); 1479 } 1480 // Return the element extracted out of it. 1481 Value *V = Builder.CreateExtractElement(FromVal, 1482 ConstantInt::get(Type::Int32Ty,Elt), 1483 "tmp"); 1484 if (V->getType() != ToType) 1485 V = Builder.CreateBitCast(V, ToType, "tmp"); 1486 return V; 1487 } 1488 1489 // If ToType is a first class aggregate, extract out each of the pieces and 1490 // use insertvalue's to form the FCA. 1491 if (const StructType *ST = dyn_cast<StructType>(ToType)) { 1492 const StructLayout &Layout = *TD->getStructLayout(ST); 1493 Value *Res = UndefValue::get(ST); 1494 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) { 1495 Value *Elt = ConvertScalar_ExtractValue(FromVal, ST->getElementType(i), 1496 Offset+Layout.getElementOffsetInBits(i), 1497 Builder); 1498 Res = Builder.CreateInsertValue(Res, Elt, i, "tmp"); 1499 } 1500 return Res; 1501 } 1502 1503 if (const ArrayType *AT = dyn_cast<ArrayType>(ToType)) { 1504 uint64_t EltSize = TD->getTypePaddedSizeInBits(AT->getElementType()); 1505 Value *Res = UndefValue::get(AT); 1506 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) { 1507 Value *Elt = ConvertScalar_ExtractValue(FromVal, AT->getElementType(), 1508 Offset+i*EltSize, Builder); 1509 Res = Builder.CreateInsertValue(Res, Elt, i, "tmp"); 1510 } 1511 return Res; 1512 } 1513 1514 // Otherwise, this must be a union that was converted to an integer value. 1515 const IntegerType *NTy = cast<IntegerType>(FromVal->getType()); 1516 1517 // If this is a big-endian system and the load is narrower than the 1518 // full alloca type, we need to do a shift to get the right bits. 1519 int ShAmt = 0; 1520 if (TD->isBigEndian()) { 1521 // On big-endian machines, the lowest bit is stored at the bit offset 1522 // from the pointer given by getTypeStoreSizeInBits. This matters for 1523 // integers with a bitwidth that is not a multiple of 8. 1524 ShAmt = TD->getTypeStoreSizeInBits(NTy) - 1525 TD->getTypeStoreSizeInBits(ToType) - Offset; 1526 } else { 1527 ShAmt = Offset; 1528 } 1529 1530 // Note: we support negative bitwidths (with shl) which are not defined. 1531 // We do this to support (f.e.) loads off the end of a structure where 1532 // only some bits are used. 1533 if (ShAmt > 0 && (unsigned)ShAmt < NTy->getBitWidth()) 1534 FromVal = Builder.CreateLShr(FromVal, ConstantInt::get(FromVal->getType(), 1535 ShAmt), "tmp"); 1536 else if (ShAmt < 0 && (unsigned)-ShAmt < NTy->getBitWidth()) 1537 FromVal = Builder.CreateShl(FromVal, ConstantInt::get(FromVal->getType(), 1538 -ShAmt), "tmp"); 1539 1540 // Finally, unconditionally truncate the integer to the right width. 1541 unsigned LIBitWidth = TD->getTypeSizeInBits(ToType); 1542 if (LIBitWidth < NTy->getBitWidth()) 1543 FromVal = Builder.CreateTrunc(FromVal, IntegerType::get(LIBitWidth), "tmp"); 1544 else if (LIBitWidth > NTy->getBitWidth()) 1545 FromVal = Builder.CreateZExt(FromVal, IntegerType::get(LIBitWidth), "tmp"); 1546 1547 // If the result is an integer, this is a trunc or bitcast. 1548 if (isa<IntegerType>(ToType)) { 1549 // Should be done. 1550 } else if (ToType->isFloatingPoint() || isa<VectorType>(ToType)) { 1551 // Just do a bitcast, we know the sizes match up. 1552 FromVal = Builder.CreateBitCast(FromVal, ToType, "tmp"); 1553 } else { 1554 // Otherwise must be a pointer. 1555 FromVal = Builder.CreateIntToPtr(FromVal, ToType, "tmp"); 1556 } 1557 assert(FromVal->getType() == ToType && "Didn't convert right?"); 1558 return FromVal; 1559} 1560 1561 1562/// ConvertScalar_InsertValue - Insert the value "SV" into the existing integer 1563/// or vector value "Old" at the offset specified by Offset. 1564/// 1565/// This happens when we are converting an "integer union" to a 1566/// single integer scalar, or when we are converting a "vector union" to a 1567/// vector with insert/extractelement instructions. 1568/// 1569/// Offset is an offset from the original alloca, in bits that need to be 1570/// shifted to the right. 1571Value *SROA::ConvertScalar_InsertValue(Value *SV, Value *Old, 1572 uint64_t Offset, IRBuilder<> &Builder) { 1573 1574 // Convert the stored type to the actual type, shift it left to insert 1575 // then 'or' into place. 1576 const Type *AllocaType = Old->getType(); 1577 1578 if (const VectorType *VTy = dyn_cast<VectorType>(AllocaType)) { 1579 // If the result alloca is a vector type, this is either an element 1580 // access or a bitcast to another vector type. 1581 if (isa<VectorType>(SV->getType())) { 1582 SV = Builder.CreateBitCast(SV, AllocaType, "tmp"); 1583 } else { 1584 // Must be an element insertion. 1585 unsigned Elt = Offset/TD->getTypePaddedSizeInBits(VTy->getElementType()); 1586 1587 if (SV->getType() != VTy->getElementType()) 1588 SV = Builder.CreateBitCast(SV, VTy->getElementType(), "tmp"); 1589 1590 SV = Builder.CreateInsertElement(Old, SV, 1591 ConstantInt::get(Type::Int32Ty, Elt), 1592 "tmp"); 1593 } 1594 return SV; 1595 } 1596 1597 // If SV is a first-class aggregate value, insert each value recursively. 1598 if (const StructType *ST = dyn_cast<StructType>(SV->getType())) { 1599 const StructLayout &Layout = *TD->getStructLayout(ST); 1600 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) { 1601 Value *Elt = Builder.CreateExtractValue(SV, i, "tmp"); 1602 Old = ConvertScalar_InsertValue(Elt, Old, 1603 Offset+Layout.getElementOffsetInBits(i), 1604 Builder); 1605 } 1606 return Old; 1607 } 1608 1609 if (const ArrayType *AT = dyn_cast<ArrayType>(SV->getType())) { 1610 uint64_t EltSize = TD->getTypePaddedSizeInBits(AT->getElementType()); 1611 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) { 1612 Value *Elt = Builder.CreateExtractValue(SV, i, "tmp"); 1613 Old = ConvertScalar_InsertValue(Elt, Old, Offset+i*EltSize, Builder); 1614 } 1615 return Old; 1616 } 1617 1618 // If SV is a float, convert it to the appropriate integer type. 1619 // If it is a pointer, do the same. 1620 unsigned SrcWidth = TD->getTypeSizeInBits(SV->getType()); 1621 unsigned DestWidth = TD->getTypeSizeInBits(AllocaType); 1622 unsigned SrcStoreWidth = TD->getTypeStoreSizeInBits(SV->getType()); 1623 unsigned DestStoreWidth = TD->getTypeStoreSizeInBits(AllocaType); 1624 if (SV->getType()->isFloatingPoint() || isa<VectorType>(SV->getType())) 1625 SV = Builder.CreateBitCast(SV, IntegerType::get(SrcWidth), "tmp"); 1626 else if (isa<PointerType>(SV->getType())) 1627 SV = Builder.CreatePtrToInt(SV, TD->getIntPtrType(), "tmp"); 1628 1629 // Zero extend or truncate the value if needed. 1630 if (SV->getType() != AllocaType) { 1631 if (SV->getType()->getPrimitiveSizeInBits() < 1632 AllocaType->getPrimitiveSizeInBits()) 1633 SV = Builder.CreateZExt(SV, AllocaType, "tmp"); 1634 else { 1635 // Truncation may be needed if storing more than the alloca can hold 1636 // (undefined behavior). 1637 SV = Builder.CreateTrunc(SV, AllocaType, "tmp"); 1638 SrcWidth = DestWidth; 1639 SrcStoreWidth = DestStoreWidth; 1640 } 1641 } 1642 1643 // If this is a big-endian system and the store is narrower than the 1644 // full alloca type, we need to do a shift to get the right bits. 1645 int ShAmt = 0; 1646 if (TD->isBigEndian()) { 1647 // On big-endian machines, the lowest bit is stored at the bit offset 1648 // from the pointer given by getTypeStoreSizeInBits. This matters for 1649 // integers with a bitwidth that is not a multiple of 8. 1650 ShAmt = DestStoreWidth - SrcStoreWidth - Offset; 1651 } else { 1652 ShAmt = Offset; 1653 } 1654 1655 // Note: we support negative bitwidths (with shr) which are not defined. 1656 // We do this to support (f.e.) stores off the end of a structure where 1657 // only some bits in the structure are set. 1658 APInt Mask(APInt::getLowBitsSet(DestWidth, SrcWidth)); 1659 if (ShAmt > 0 && (unsigned)ShAmt < DestWidth) { 1660 SV = Builder.CreateShl(SV, ConstantInt::get(SV->getType(), ShAmt), "tmp"); 1661 Mask <<= ShAmt; 1662 } else if (ShAmt < 0 && (unsigned)-ShAmt < DestWidth) { 1663 SV = Builder.CreateLShr(SV, ConstantInt::get(SV->getType(), -ShAmt), "tmp"); 1664 Mask = Mask.lshr(-ShAmt); 1665 } 1666 1667 // Mask out the bits we are about to insert from the old value, and or 1668 // in the new bits. 1669 if (SrcWidth != DestWidth) { 1670 assert(DestWidth > SrcWidth); 1671 Old = Builder.CreateAnd(Old, ConstantInt::get(~Mask), "mask"); 1672 SV = Builder.CreateOr(Old, SV, "ins"); 1673 } 1674 return SV; 1675} 1676 1677 1678 1679/// PointsToConstantGlobal - Return true if V (possibly indirectly) points to 1680/// some part of a constant global variable. This intentionally only accepts 1681/// constant expressions because we don't can't rewrite arbitrary instructions. 1682static bool PointsToConstantGlobal(Value *V) { 1683 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V)) 1684 return GV->isConstant(); 1685 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) 1686 if (CE->getOpcode() == Instruction::BitCast || 1687 CE->getOpcode() == Instruction::GetElementPtr) 1688 return PointsToConstantGlobal(CE->getOperand(0)); 1689 return false; 1690} 1691 1692/// isOnlyCopiedFromConstantGlobal - Recursively walk the uses of a (derived) 1693/// pointer to an alloca. Ignore any reads of the pointer, return false if we 1694/// see any stores or other unknown uses. If we see pointer arithmetic, keep 1695/// track of whether it moves the pointer (with isOffset) but otherwise traverse 1696/// the uses. If we see a memcpy/memmove that targets an unoffseted pointer to 1697/// the alloca, and if the source pointer is a pointer to a constant global, we 1698/// can optimize this. 1699static bool isOnlyCopiedFromConstantGlobal(Value *V, Instruction *&TheCopy, 1700 bool isOffset) { 1701 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) { 1702 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) 1703 // Ignore non-volatile loads, they are always ok. 1704 if (!LI->isVolatile()) 1705 continue; 1706 1707 if (BitCastInst *BCI = dyn_cast<BitCastInst>(*UI)) { 1708 // If uses of the bitcast are ok, we are ok. 1709 if (!isOnlyCopiedFromConstantGlobal(BCI, TheCopy, isOffset)) 1710 return false; 1711 continue; 1712 } 1713 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(*UI)) { 1714 // If the GEP has all zero indices, it doesn't offset the pointer. If it 1715 // doesn't, it does. 1716 if (!isOnlyCopiedFromConstantGlobal(GEP, TheCopy, 1717 isOffset || !GEP->hasAllZeroIndices())) 1718 return false; 1719 continue; 1720 } 1721 1722 // If this is isn't our memcpy/memmove, reject it as something we can't 1723 // handle. 1724 if (!isa<MemCpyInst>(*UI) && !isa<MemMoveInst>(*UI)) 1725 return false; 1726 1727 // If we already have seen a copy, reject the second one. 1728 if (TheCopy) return false; 1729 1730 // If the pointer has been offset from the start of the alloca, we can't 1731 // safely handle this. 1732 if (isOffset) return false; 1733 1734 // If the memintrinsic isn't using the alloca as the dest, reject it. 1735 if (UI.getOperandNo() != 1) return false; 1736 1737 MemIntrinsic *MI = cast<MemIntrinsic>(*UI); 1738 1739 // If the source of the memcpy/move is not a constant global, reject it. 1740 if (!PointsToConstantGlobal(MI->getOperand(2))) 1741 return false; 1742 1743 // Otherwise, the transform is safe. Remember the copy instruction. 1744 TheCopy = MI; 1745 } 1746 return true; 1747} 1748 1749/// isOnlyCopiedFromConstantGlobal - Return true if the specified alloca is only 1750/// modified by a copy from a constant global. If we can prove this, we can 1751/// replace any uses of the alloca with uses of the global directly. 1752Instruction *SROA::isOnlyCopiedFromConstantGlobal(AllocationInst *AI) { 1753 Instruction *TheCopy = 0; 1754 if (::isOnlyCopiedFromConstantGlobal(AI, TheCopy, false)) 1755 return TheCopy; 1756 return 0; 1757} 1758