ScalarReplAggregates.cpp revision 9adc0abad3c3ed40a268ccbcee0c74cb9e1359fe
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" 44#include "llvm/ADT/StringExtras.h" 45using namespace llvm; 46 47STATISTIC(NumReplaced, "Number of allocas broken up"); 48STATISTIC(NumPromoted, "Number of allocas promoted"); 49STATISTIC(NumConverted, "Number of aggregates converted to scalar"); 50STATISTIC(NumGlobals, "Number of allocas copied from constant global"); 51 52namespace { 53 struct VISIBILITY_HIDDEN SROA : public FunctionPass { 54 static char ID; // Pass identification, replacement for typeid 55 explicit SROA(signed T = -1) : FunctionPass(&ID) { 56 if (T == -1) 57 SRThreshold = 128; 58 else 59 SRThreshold = T; 60 } 61 62 bool runOnFunction(Function &F); 63 64 bool performScalarRepl(Function &F); 65 bool performPromotion(Function &F); 66 67 // getAnalysisUsage - This pass does not require any passes, but we know it 68 // will not alter the CFG, so say so. 69 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 70 AU.addRequired<DominatorTree>(); 71 AU.addRequired<DominanceFrontier>(); 72 AU.addRequired<TargetData>(); 73 AU.setPreservesCFG(); 74 } 75 76 private: 77 TargetData *TD; 78 79 /// AllocaInfo - When analyzing uses of an alloca instruction, this captures 80 /// information about the uses. All these fields are initialized to false 81 /// and set to true when something is learned. 82 struct AllocaInfo { 83 /// isUnsafe - This is set to true if the alloca cannot be SROA'd. 84 bool isUnsafe : 1; 85 86 /// needsCleanup - This is set to true if there is some use of the alloca 87 /// that requires cleanup. 88 bool needsCleanup : 1; 89 90 /// isMemCpySrc - This is true if this aggregate is memcpy'd from. 91 bool isMemCpySrc : 1; 92 93 /// isMemCpyDst - This is true if this aggregate is memcpy'd into. 94 bool isMemCpyDst : 1; 95 96 AllocaInfo() 97 : isUnsafe(false), needsCleanup(false), 98 isMemCpySrc(false), isMemCpyDst(false) {} 99 }; 100 101 unsigned SRThreshold; 102 103 void MarkUnsafe(AllocaInfo &I) { I.isUnsafe = true; } 104 105 int isSafeAllocaToScalarRepl(AllocationInst *AI); 106 107 void isSafeUseOfAllocation(Instruction *User, AllocationInst *AI, 108 AllocaInfo &Info); 109 void isSafeElementUse(Value *Ptr, bool isFirstElt, AllocationInst *AI, 110 AllocaInfo &Info); 111 void isSafeMemIntrinsicOnAllocation(MemIntrinsic *MI, AllocationInst *AI, 112 unsigned OpNo, AllocaInfo &Info); 113 void isSafeUseOfBitCastedAllocation(BitCastInst *User, AllocationInst *AI, 114 AllocaInfo &Info); 115 116 void DoScalarReplacement(AllocationInst *AI, 117 std::vector<AllocationInst*> &WorkList); 118 void CleanupGEP(GetElementPtrInst *GEP); 119 void CleanupAllocaUsers(AllocationInst *AI); 120 AllocaInst *AddNewAlloca(Function &F, const Type *Ty, AllocationInst *Base); 121 122 void RewriteBitCastUserOfAlloca(Instruction *BCInst, AllocationInst *AI, 123 SmallVector<AllocaInst*, 32> &NewElts); 124 125 void RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *BCInst, 126 AllocationInst *AI, 127 SmallVector<AllocaInst*, 32> &NewElts); 128 void RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocationInst *AI, 129 SmallVector<AllocaInst*, 32> &NewElts); 130 void RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocationInst *AI, 131 SmallVector<AllocaInst*, 32> &NewElts); 132 133 bool CanConvertToScalar(Value *V, bool &IsNotTrivial, const Type *&VecTy, 134 bool &SawVec, uint64_t Offset, unsigned AllocaSize); 135 void ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, uint64_t Offset); 136 Value *ConvertScalar_ExtractValue(Value *NV, const Type *ToType, 137 uint64_t Offset, IRBuilder<> &Builder); 138 Value *ConvertScalar_InsertValue(Value *StoredVal, Value *ExistingVal, 139 uint64_t Offset, IRBuilder<> &Builder); 140 static Instruction *isOnlyCopiedFromConstantGlobal(AllocationInst *AI); 141 }; 142} 143 144char SROA::ID = 0; 145static RegisterPass<SROA> X("scalarrepl", "Scalar Replacement of Aggregates"); 146 147// Public interface to the ScalarReplAggregates pass 148FunctionPass *llvm::createScalarReplAggregatesPass(signed int Threshold) { 149 return new SROA(Threshold); 150} 151 152 153bool SROA::runOnFunction(Function &F) { 154 TD = &getAnalysis<TargetData>(); 155 156 bool Changed = performPromotion(F); 157 while (1) { 158 bool LocalChange = performScalarRepl(F); 159 if (!LocalChange) break; // No need to repromote if no scalarrepl 160 Changed = true; 161 LocalChange = performPromotion(F); 162 if (!LocalChange) break; // No need to re-scalarrepl if no promotion 163 } 164 165 return Changed; 166} 167 168 169bool SROA::performPromotion(Function &F) { 170 std::vector<AllocaInst*> Allocas; 171 DominatorTree &DT = getAnalysis<DominatorTree>(); 172 DominanceFrontier &DF = getAnalysis<DominanceFrontier>(); 173 174 BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function 175 176 bool Changed = false; 177 178 while (1) { 179 Allocas.clear(); 180 181 // Find allocas that are safe to promote, by looking at all instructions in 182 // the entry node 183 for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I) 184 if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) // Is it an alloca? 185 if (isAllocaPromotable(AI)) 186 Allocas.push_back(AI); 187 188 if (Allocas.empty()) break; 189 190 PromoteMemToReg(Allocas, DT, DF, Context); 191 NumPromoted += Allocas.size(); 192 Changed = true; 193 } 194 195 return Changed; 196} 197 198/// getNumSAElements - Return the number of elements in the specific struct or 199/// array. 200static uint64_t getNumSAElements(const Type *T) { 201 if (const StructType *ST = dyn_cast<StructType>(T)) 202 return ST->getNumElements(); 203 return cast<ArrayType>(T)->getNumElements(); 204} 205 206// performScalarRepl - This algorithm is a simple worklist driven algorithm, 207// which runs on all of the malloc/alloca instructions in the function, removing 208// them if they are only used by getelementptr instructions. 209// 210bool SROA::performScalarRepl(Function &F) { 211 std::vector<AllocationInst*> WorkList; 212 213 // Scan the entry basic block, adding any alloca's and mallocs to the worklist 214 BasicBlock &BB = F.getEntryBlock(); 215 for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I) 216 if (AllocationInst *A = dyn_cast<AllocationInst>(I)) 217 WorkList.push_back(A); 218 219 // Process the worklist 220 bool Changed = false; 221 while (!WorkList.empty()) { 222 AllocationInst *AI = WorkList.back(); 223 WorkList.pop_back(); 224 225 // Handle dead allocas trivially. These can be formed by SROA'ing arrays 226 // with unused elements. 227 if (AI->use_empty()) { 228 AI->eraseFromParent(); 229 continue; 230 } 231 232 // If this alloca is impossible for us to promote, reject it early. 233 if (AI->isArrayAllocation() || !AI->getAllocatedType()->isSized()) 234 continue; 235 236 // Check to see if this allocation is only modified by a memcpy/memmove from 237 // a constant global. If this is the case, we can change all users to use 238 // the constant global instead. This is commonly produced by the CFE by 239 // constructs like "void foo() { int A[] = {1,2,3,4,5,6,7,8,9...}; }" if 'A' 240 // is only subsequently read. 241 if (Instruction *TheCopy = isOnlyCopiedFromConstantGlobal(AI)) { 242 DOUT << "Found alloca equal to global: " << *AI; 243 DOUT << " memcpy = " << *TheCopy; 244 Constant *TheSrc = cast<Constant>(TheCopy->getOperand(2)); 245 AI->replaceAllUsesWith( 246 Context->getConstantExprBitCast(TheSrc, AI->getType())); 247 TheCopy->eraseFromParent(); // Don't mutate the global. 248 AI->eraseFromParent(); 249 ++NumGlobals; 250 Changed = true; 251 continue; 252 } 253 254 // Check to see if we can perform the core SROA transformation. We cannot 255 // transform the allocation instruction if it is an array allocation 256 // (allocations OF arrays are ok though), and an allocation of a scalar 257 // value cannot be decomposed at all. 258 uint64_t AllocaSize = TD->getTypeAllocSize(AI->getAllocatedType()); 259 260 // Do not promote any struct whose size is too big. 261 if (AllocaSize > SRThreshold) continue; 262 263 if ((isa<StructType>(AI->getAllocatedType()) || 264 isa<ArrayType>(AI->getAllocatedType())) && 265 // Do not promote any struct into more than "32" separate vars. 266 getNumSAElements(AI->getAllocatedType()) <= SRThreshold/4) { 267 // Check that all of the users of the allocation are capable of being 268 // transformed. 269 switch (isSafeAllocaToScalarRepl(AI)) { 270 default: llvm_unreachable("Unexpected value!"); 271 case 0: // Not safe to scalar replace. 272 break; 273 case 1: // Safe, but requires cleanup/canonicalizations first 274 CleanupAllocaUsers(AI); 275 // FALL THROUGH. 276 case 3: // Safe to scalar replace. 277 DoScalarReplacement(AI, WorkList); 278 Changed = true; 279 continue; 280 } 281 } 282 283 // If we can turn this aggregate value (potentially with casts) into a 284 // simple scalar value that can be mem2reg'd into a register value. 285 // IsNotTrivial tracks whether this is something that mem2reg could have 286 // promoted itself. If so, we don't want to transform it needlessly. Note 287 // that we can't just check based on the type: the alloca may be of an i32 288 // but that has pointer arithmetic to set byte 3 of it or something. 289 bool IsNotTrivial = false; 290 const Type *VectorTy = 0; 291 bool HadAVector = false; 292 if (CanConvertToScalar(AI, IsNotTrivial, VectorTy, HadAVector, 293 0, unsigned(AllocaSize)) && IsNotTrivial) { 294 AllocaInst *NewAI; 295 // If we were able to find a vector type that can handle this with 296 // insert/extract elements, and if there was at least one use that had 297 // a vector type, promote this to a vector. We don't want to promote 298 // random stuff that doesn't use vectors (e.g. <9 x double>) because then 299 // we just get a lot of insert/extracts. If at least one vector is 300 // involved, then we probably really do have a union of vector/array. 301 if (VectorTy && isa<VectorType>(VectorTy) && HadAVector) { 302 DOUT << "CONVERT TO VECTOR: " << *AI << " TYPE = " << *VectorTy <<"\n"; 303 304 // Create and insert the vector alloca. 305 NewAI = new AllocaInst(*Context, VectorTy, 0, "", 306 AI->getParent()->begin()); 307 ConvertUsesToScalar(AI, NewAI, 0); 308 } else { 309 DOUT << "CONVERT TO SCALAR INTEGER: " << *AI << "\n"; 310 311 // Create and insert the integer alloca. 312 const Type *NewTy = Context->getIntegerType(AllocaSize*8); 313 NewAI = new AllocaInst(*Context, NewTy, 0, "", 314 AI->getParent()->begin()); 315 ConvertUsesToScalar(AI, NewAI, 0); 316 } 317 NewAI->takeName(AI); 318 AI->eraseFromParent(); 319 ++NumConverted; 320 Changed = true; 321 continue; 322 } 323 324 // Otherwise, couldn't process this alloca. 325 } 326 327 return Changed; 328} 329 330/// DoScalarReplacement - This alloca satisfied the isSafeAllocaToScalarRepl 331/// predicate, do SROA now. 332void SROA::DoScalarReplacement(AllocationInst *AI, 333 std::vector<AllocationInst*> &WorkList) { 334 DOUT << "Found inst to SROA: " << *AI; 335 SmallVector<AllocaInst*, 32> ElementAllocas; 336 if (const StructType *ST = dyn_cast<StructType>(AI->getAllocatedType())) { 337 ElementAllocas.reserve(ST->getNumContainedTypes()); 338 for (unsigned i = 0, e = ST->getNumContainedTypes(); i != e; ++i) { 339 AllocaInst *NA = new AllocaInst(*Context, 340 ST->getContainedType(i), 0, 341 AI->getAlignment(), 342 AI->getName() + "." + utostr(i), AI); 343 ElementAllocas.push_back(NA); 344 WorkList.push_back(NA); // Add to worklist for recursive processing 345 } 346 } else { 347 const ArrayType *AT = cast<ArrayType>(AI->getAllocatedType()); 348 ElementAllocas.reserve(AT->getNumElements()); 349 const Type *ElTy = AT->getElementType(); 350 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) { 351 AllocaInst *NA = new AllocaInst(*Context, ElTy, 0, AI->getAlignment(), 352 AI->getName() + "." + utostr(i), AI); 353 ElementAllocas.push_back(NA); 354 WorkList.push_back(NA); // Add to worklist for recursive processing 355 } 356 } 357 358 // Now that we have created the alloca instructions that we want to use, 359 // expand the getelementptr instructions to use them. 360 // 361 while (!AI->use_empty()) { 362 Instruction *User = cast<Instruction>(AI->use_back()); 363 if (BitCastInst *BCInst = dyn_cast<BitCastInst>(User)) { 364 RewriteBitCastUserOfAlloca(BCInst, AI, ElementAllocas); 365 BCInst->eraseFromParent(); 366 continue; 367 } 368 369 // Replace: 370 // %res = load { i32, i32 }* %alloc 371 // with: 372 // %load.0 = load i32* %alloc.0 373 // %insert.0 insertvalue { i32, i32 } zeroinitializer, i32 %load.0, 0 374 // %load.1 = load i32* %alloc.1 375 // %insert = insertvalue { i32, i32 } %insert.0, i32 %load.1, 1 376 // (Also works for arrays instead of structs) 377 if (LoadInst *LI = dyn_cast<LoadInst>(User)) { 378 Value *Insert = Context->getUndef(LI->getType()); 379 for (unsigned i = 0, e = ElementAllocas.size(); i != e; ++i) { 380 Value *Load = new LoadInst(ElementAllocas[i], "load", LI); 381 Insert = InsertValueInst::Create(Insert, Load, i, "insert", LI); 382 } 383 LI->replaceAllUsesWith(Insert); 384 LI->eraseFromParent(); 385 continue; 386 } 387 388 // Replace: 389 // store { i32, i32 } %val, { i32, i32 }* %alloc 390 // with: 391 // %val.0 = extractvalue { i32, i32 } %val, 0 392 // store i32 %val.0, i32* %alloc.0 393 // %val.1 = extractvalue { i32, i32 } %val, 1 394 // store i32 %val.1, i32* %alloc.1 395 // (Also works for arrays instead of structs) 396 if (StoreInst *SI = dyn_cast<StoreInst>(User)) { 397 Value *Val = SI->getOperand(0); 398 for (unsigned i = 0, e = ElementAllocas.size(); i != e; ++i) { 399 Value *Extract = ExtractValueInst::Create(Val, i, Val->getName(), SI); 400 new StoreInst(Extract, ElementAllocas[i], SI); 401 } 402 SI->eraseFromParent(); 403 continue; 404 } 405 406 GetElementPtrInst *GEPI = cast<GetElementPtrInst>(User); 407 // We now know that the GEP is of the form: GEP <ptr>, 0, <cst> 408 unsigned Idx = 409 (unsigned)cast<ConstantInt>(GEPI->getOperand(2))->getZExtValue(); 410 411 assert(Idx < ElementAllocas.size() && "Index out of range?"); 412 AllocaInst *AllocaToUse = ElementAllocas[Idx]; 413 414 Value *RepValue; 415 if (GEPI->getNumOperands() == 3) { 416 // Do not insert a new getelementptr instruction with zero indices, only 417 // to have it optimized out later. 418 RepValue = AllocaToUse; 419 } else { 420 // We are indexing deeply into the structure, so we still need a 421 // getelement ptr instruction to finish the indexing. This may be 422 // expanded itself once the worklist is rerun. 423 // 424 SmallVector<Value*, 8> NewArgs; 425 NewArgs.push_back(Context->getNullValue(Type::Int32Ty)); 426 NewArgs.append(GEPI->op_begin()+3, GEPI->op_end()); 427 RepValue = GetElementPtrInst::Create(AllocaToUse, NewArgs.begin(), 428 NewArgs.end(), "", GEPI); 429 RepValue->takeName(GEPI); 430 } 431 432 // If this GEP is to the start of the aggregate, check for memcpys. 433 if (Idx == 0 && GEPI->hasAllZeroIndices()) 434 RewriteBitCastUserOfAlloca(GEPI, AI, ElementAllocas); 435 436 // Move all of the users over to the new GEP. 437 GEPI->replaceAllUsesWith(RepValue); 438 // Delete the old GEP 439 GEPI->eraseFromParent(); 440 } 441 442 // Finally, delete the Alloca instruction 443 AI->eraseFromParent(); 444 NumReplaced++; 445} 446 447 448/// isSafeElementUse - Check to see if this use is an allowed use for a 449/// getelementptr instruction of an array aggregate allocation. isFirstElt 450/// indicates whether Ptr is known to the start of the aggregate. 451/// 452void SROA::isSafeElementUse(Value *Ptr, bool isFirstElt, AllocationInst *AI, 453 AllocaInfo &Info) { 454 for (Value::use_iterator I = Ptr->use_begin(), E = Ptr->use_end(); 455 I != E; ++I) { 456 Instruction *User = cast<Instruction>(*I); 457 switch (User->getOpcode()) { 458 case Instruction::Load: break; 459 case Instruction::Store: 460 // Store is ok if storing INTO the pointer, not storing the pointer 461 if (User->getOperand(0) == Ptr) return MarkUnsafe(Info); 462 break; 463 case Instruction::GetElementPtr: { 464 GetElementPtrInst *GEP = cast<GetElementPtrInst>(User); 465 bool AreAllZeroIndices = isFirstElt; 466 if (GEP->getNumOperands() > 1) { 467 if (!isa<ConstantInt>(GEP->getOperand(1)) || 468 !cast<ConstantInt>(GEP->getOperand(1))->isZero()) 469 // Using pointer arithmetic to navigate the array. 470 return MarkUnsafe(Info); 471 472 if (AreAllZeroIndices) 473 AreAllZeroIndices = GEP->hasAllZeroIndices(); 474 } 475 isSafeElementUse(GEP, AreAllZeroIndices, AI, Info); 476 if (Info.isUnsafe) return; 477 break; 478 } 479 case Instruction::BitCast: 480 if (isFirstElt) { 481 isSafeUseOfBitCastedAllocation(cast<BitCastInst>(User), AI, Info); 482 if (Info.isUnsafe) return; 483 break; 484 } 485 DOUT << " Transformation preventing inst: " << *User; 486 return MarkUnsafe(Info); 487 case Instruction::Call: 488 if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) { 489 if (isFirstElt) { 490 isSafeMemIntrinsicOnAllocation(MI, AI, I.getOperandNo(), Info); 491 if (Info.isUnsafe) return; 492 break; 493 } 494 } 495 DOUT << " Transformation preventing inst: " << *User; 496 return MarkUnsafe(Info); 497 default: 498 DOUT << " Transformation preventing inst: " << *User; 499 return MarkUnsafe(Info); 500 } 501 } 502 return; // All users look ok :) 503} 504 505/// AllUsersAreLoads - Return true if all users of this value are loads. 506static bool AllUsersAreLoads(Value *Ptr) { 507 for (Value::use_iterator I = Ptr->use_begin(), E = Ptr->use_end(); 508 I != E; ++I) 509 if (cast<Instruction>(*I)->getOpcode() != Instruction::Load) 510 return false; 511 return true; 512} 513 514/// isSafeUseOfAllocation - Check to see if this user is an allowed use for an 515/// aggregate allocation. 516/// 517void SROA::isSafeUseOfAllocation(Instruction *User, AllocationInst *AI, 518 AllocaInfo &Info) { 519 if (BitCastInst *C = dyn_cast<BitCastInst>(User)) 520 return isSafeUseOfBitCastedAllocation(C, AI, Info); 521 522 if (LoadInst *LI = dyn_cast<LoadInst>(User)) 523 if (!LI->isVolatile()) 524 return;// Loads (returning a first class aggregrate) are always rewritable 525 526 if (StoreInst *SI = dyn_cast<StoreInst>(User)) 527 if (!SI->isVolatile() && SI->getOperand(0) != AI) 528 return;// Store is ok if storing INTO the pointer, not storing the pointer 529 530 GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User); 531 if (GEPI == 0) 532 return MarkUnsafe(Info); 533 534 gep_type_iterator I = gep_type_begin(GEPI), E = gep_type_end(GEPI); 535 536 // The GEP is not safe to transform if not of the form "GEP <ptr>, 0, <cst>". 537 if (I == E || 538 I.getOperand() != Context->getNullValue(I.getOperand()->getType())) { 539 return MarkUnsafe(Info); 540 } 541 542 ++I; 543 if (I == E) return MarkUnsafe(Info); // ran out of GEP indices?? 544 545 bool IsAllZeroIndices = true; 546 547 // If the first index is a non-constant index into an array, see if we can 548 // handle it as a special case. 549 if (const ArrayType *AT = dyn_cast<ArrayType>(*I)) { 550 if (!isa<ConstantInt>(I.getOperand())) { 551 IsAllZeroIndices = 0; 552 uint64_t NumElements = AT->getNumElements(); 553 554 // If this is an array index and the index is not constant, we cannot 555 // promote... that is unless the array has exactly one or two elements in 556 // it, in which case we CAN promote it, but we have to canonicalize this 557 // out if this is the only problem. 558 if ((NumElements == 1 || NumElements == 2) && 559 AllUsersAreLoads(GEPI)) { 560 Info.needsCleanup = true; 561 return; // Canonicalization required! 562 } 563 return MarkUnsafe(Info); 564 } 565 } 566 567 // Walk through the GEP type indices, checking the types that this indexes 568 // into. 569 for (; I != E; ++I) { 570 // Ignore struct elements, no extra checking needed for these. 571 if (isa<StructType>(*I)) 572 continue; 573 574 ConstantInt *IdxVal = dyn_cast<ConstantInt>(I.getOperand()); 575 if (!IdxVal) return MarkUnsafe(Info); 576 577 // Are all indices still zero? 578 IsAllZeroIndices &= IdxVal->isZero(); 579 580 if (const ArrayType *AT = dyn_cast<ArrayType>(*I)) { 581 // This GEP indexes an array. Verify that this is an in-range constant 582 // integer. Specifically, consider A[0][i]. We cannot know that the user 583 // isn't doing invalid things like allowing i to index an out-of-range 584 // subscript that accesses A[1]. Because of this, we have to reject SROA 585 // of any accesses into structs where any of the components are variables. 586 if (IdxVal->getZExtValue() >= AT->getNumElements()) 587 return MarkUnsafe(Info); 588 } else if (const VectorType *VT = dyn_cast<VectorType>(*I)) { 589 if (IdxVal->getZExtValue() >= VT->getNumElements()) 590 return MarkUnsafe(Info); 591 } 592 } 593 594 // If there are any non-simple uses of this getelementptr, make sure to reject 595 // them. 596 return isSafeElementUse(GEPI, IsAllZeroIndices, AI, Info); 597} 598 599/// isSafeMemIntrinsicOnAllocation - Return true if the specified memory 600/// intrinsic can be promoted by SROA. At this point, we know that the operand 601/// of the memintrinsic is a pointer to the beginning of the allocation. 602void SROA::isSafeMemIntrinsicOnAllocation(MemIntrinsic *MI, AllocationInst *AI, 603 unsigned OpNo, AllocaInfo &Info) { 604 // If not constant length, give up. 605 ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength()); 606 if (!Length) return MarkUnsafe(Info); 607 608 // If not the whole aggregate, give up. 609 if (Length->getZExtValue() != 610 TD->getTypeAllocSize(AI->getType()->getElementType())) 611 return MarkUnsafe(Info); 612 613 // We only know about memcpy/memset/memmove. 614 if (!isa<MemIntrinsic>(MI)) 615 return MarkUnsafe(Info); 616 617 // Otherwise, we can transform it. Determine whether this is a memcpy/set 618 // into or out of the aggregate. 619 if (OpNo == 1) 620 Info.isMemCpyDst = true; 621 else { 622 assert(OpNo == 2); 623 Info.isMemCpySrc = true; 624 } 625} 626 627/// isSafeUseOfBitCastedAllocation - Return true if all users of this bitcast 628/// are 629void SROA::isSafeUseOfBitCastedAllocation(BitCastInst *BC, AllocationInst *AI, 630 AllocaInfo &Info) { 631 for (Value::use_iterator UI = BC->use_begin(), E = BC->use_end(); 632 UI != E; ++UI) { 633 if (BitCastInst *BCU = dyn_cast<BitCastInst>(UI)) { 634 isSafeUseOfBitCastedAllocation(BCU, AI, Info); 635 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(UI)) { 636 isSafeMemIntrinsicOnAllocation(MI, AI, UI.getOperandNo(), Info); 637 } else if (StoreInst *SI = dyn_cast<StoreInst>(UI)) { 638 if (SI->isVolatile()) 639 return MarkUnsafe(Info); 640 641 // If storing the entire alloca in one chunk through a bitcasted pointer 642 // to integer, we can transform it. This happens (for example) when you 643 // cast a {i32,i32}* to i64* and store through it. This is similar to the 644 // memcpy case and occurs in various "byval" cases and emulated memcpys. 645 if (isa<IntegerType>(SI->getOperand(0)->getType()) && 646 TD->getTypeAllocSize(SI->getOperand(0)->getType()) == 647 TD->getTypeAllocSize(AI->getType()->getElementType())) { 648 Info.isMemCpyDst = true; 649 continue; 650 } 651 return MarkUnsafe(Info); 652 } else if (LoadInst *LI = dyn_cast<LoadInst>(UI)) { 653 if (LI->isVolatile()) 654 return MarkUnsafe(Info); 655 656 // If loading the entire alloca in one chunk through a bitcasted pointer 657 // to integer, we can transform it. This happens (for example) when you 658 // cast a {i32,i32}* to i64* and load through it. This is similar to the 659 // memcpy case and occurs in various "byval" cases and emulated memcpys. 660 if (isa<IntegerType>(LI->getType()) && 661 TD->getTypeAllocSize(LI->getType()) == 662 TD->getTypeAllocSize(AI->getType()->getElementType())) { 663 Info.isMemCpySrc = true; 664 continue; 665 } 666 return MarkUnsafe(Info); 667 } else if (isa<DbgInfoIntrinsic>(UI)) { 668 // If one user is DbgInfoIntrinsic then check if all users are 669 // DbgInfoIntrinsics. 670 if (OnlyUsedByDbgInfoIntrinsics(BC)) { 671 Info.needsCleanup = true; 672 return; 673 } 674 else 675 MarkUnsafe(Info); 676 } 677 else { 678 return MarkUnsafe(Info); 679 } 680 if (Info.isUnsafe) return; 681 } 682} 683 684/// RewriteBitCastUserOfAlloca - BCInst (transitively) bitcasts AI, or indexes 685/// to its first element. Transform users of the cast to use the new values 686/// instead. 687void SROA::RewriteBitCastUserOfAlloca(Instruction *BCInst, AllocationInst *AI, 688 SmallVector<AllocaInst*, 32> &NewElts) { 689 Value::use_iterator UI = BCInst->use_begin(), UE = BCInst->use_end(); 690 while (UI != UE) { 691 Instruction *User = cast<Instruction>(*UI++); 692 if (BitCastInst *BCU = dyn_cast<BitCastInst>(User)) { 693 RewriteBitCastUserOfAlloca(BCU, AI, NewElts); 694 if (BCU->use_empty()) BCU->eraseFromParent(); 695 continue; 696 } 697 698 if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) { 699 // This must be memcpy/memmove/memset of the entire aggregate. 700 // Split into one per element. 701 RewriteMemIntrinUserOfAlloca(MI, BCInst, AI, NewElts); 702 continue; 703 } 704 705 if (StoreInst *SI = dyn_cast<StoreInst>(User)) { 706 // If this is a store of the entire alloca from an integer, rewrite it. 707 RewriteStoreUserOfWholeAlloca(SI, AI, NewElts); 708 continue; 709 } 710 711 if (LoadInst *LI = dyn_cast<LoadInst>(User)) { 712 // If this is a load of the entire alloca to an integer, rewrite it. 713 RewriteLoadUserOfWholeAlloca(LI, AI, NewElts); 714 continue; 715 } 716 717 // Otherwise it must be some other user of a gep of the first pointer. Just 718 // leave these alone. 719 continue; 720 } 721} 722 723/// RewriteMemIntrinUserOfAlloca - MI is a memcpy/memset/memmove from or to AI. 724/// Rewrite it to copy or set the elements of the scalarized memory. 725void SROA::RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *BCInst, 726 AllocationInst *AI, 727 SmallVector<AllocaInst*, 32> &NewElts) { 728 729 // If this is a memcpy/memmove, construct the other pointer as the 730 // appropriate type. The "Other" pointer is the pointer that goes to memory 731 // that doesn't have anything to do with the alloca that we are promoting. For 732 // memset, this Value* stays null. 733 Value *OtherPtr = 0; 734 unsigned MemAlignment = MI->getAlignment(); 735 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(MI)) { // memmove/memcopy 736 if (BCInst == MTI->getRawDest()) 737 OtherPtr = MTI->getRawSource(); 738 else { 739 assert(BCInst == MTI->getRawSource()); 740 OtherPtr = MTI->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 = Context->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, Context->getConstantInt(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->getTypeAllocSize(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<MemTransferInst>(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 = Context->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->getScalarType(); 830 831 // Construct an integer with the right value. 832 unsigned EltSize = TD->getTypeSizeInBits(ValTy); 833 APInt OneVal(EltSize, CI->getZExtValue()); 834 APInt TotalVal(OneVal); 835 // Set each byte. 836 for (unsigned i = 0; 8*i < EltSize; ++i) { 837 TotalVal = TotalVal.shl(8); 838 TotalVal |= OneVal; 839 } 840 841 // Convert the integer value to the appropriate type. 842 StoreVal = Context->getConstantInt(TotalVal); 843 if (isa<PointerType>(ValTy)) 844 StoreVal = Context->getConstantExprIntToPtr(StoreVal, ValTy); 845 else if (ValTy->isFloatingPoint()) 846 StoreVal = Context->getConstantExprBitCast(StoreVal, ValTy); 847 assert(StoreVal->getType() == ValTy && "Type mismatch!"); 848 849 // If the requested value was a vector constant, create it. 850 if (EltTy != ValTy) { 851 unsigned NumElts = cast<VectorType>(ValTy)->getNumElements(); 852 SmallVector<Constant*, 16> Elts(NumElts, StoreVal); 853 StoreVal = Context->getConstantVector(&Elts[0], NumElts); 854 } 855 } 856 new StoreInst(StoreVal, EltPtr, MI); 857 continue; 858 } 859 // Otherwise, if we're storing a byte variable, use a memset call for 860 // this element. 861 } 862 863 // Cast the element pointer to BytePtrTy. 864 if (EltPtr->getType() != BytePtrTy) 865 EltPtr = new BitCastInst(EltPtr, BytePtrTy, EltPtr->getNameStr(), MI); 866 867 // Cast the other pointer (if we have one) to BytePtrTy. 868 if (OtherElt && OtherElt->getType() != BytePtrTy) 869 OtherElt = new BitCastInst(OtherElt, BytePtrTy,OtherElt->getNameStr(), 870 MI); 871 872 unsigned EltSize = TD->getTypeAllocSize(EltTy); 873 874 // Finally, insert the meminst for this element. 875 if (isa<MemTransferInst>(MI)) { 876 Value *Ops[] = { 877 SROADest ? EltPtr : OtherElt, // Dest ptr 878 SROADest ? OtherElt : EltPtr, // Src ptr 879 Context->getConstantInt(MI->getOperand(3)->getType(), EltSize), // Size 880 Context->getConstantInt(Type::Int32Ty, OtherEltAlign) // Align 881 }; 882 CallInst::Create(TheFn, Ops, Ops + 4, "", MI); 883 } else { 884 assert(isa<MemSetInst>(MI)); 885 Value *Ops[] = { 886 EltPtr, MI->getOperand(2), // Dest, Value, 887 Context->getConstantInt(MI->getOperand(3)->getType(), EltSize), // Size 888 Zero // Align 889 }; 890 CallInst::Create(TheFn, Ops, Ops + 4, "", MI); 891 } 892 } 893 MI->eraseFromParent(); 894} 895 896/// RewriteStoreUserOfWholeAlloca - We found an store of an integer that 897/// overwrites the entire allocation. Extract out the pieces of the stored 898/// integer and store them individually. 899void SROA::RewriteStoreUserOfWholeAlloca(StoreInst *SI, 900 AllocationInst *AI, 901 SmallVector<AllocaInst*, 32> &NewElts){ 902 // Extract each element out of the integer according to its structure offset 903 // and store the element value to the individual alloca. 904 Value *SrcVal = SI->getOperand(0); 905 const Type *AllocaEltTy = AI->getType()->getElementType(); 906 uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy); 907 908 // If this isn't a store of an integer to the whole alloca, it may be a store 909 // to the first element. Just ignore the store in this case and normal SROA 910 // will handle it. 911 if (!isa<IntegerType>(SrcVal->getType()) || 912 TD->getTypeAllocSizeInBits(SrcVal->getType()) != AllocaSizeBits) 913 return; 914 // Handle tail padding by extending the operand 915 if (TD->getTypeSizeInBits(SrcVal->getType()) != AllocaSizeBits) 916 SrcVal = new ZExtInst(SrcVal, 917 Context->getIntegerType(AllocaSizeBits), "", 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 = Context->getConstantInt(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 Context->getIntegerType(FieldSizeBits), "", SI); 950 Value *DestField = NewElts[i]; 951 if (EltVal->getType() == FieldTy) { 952 // Storing to an integer field of this size, just do it. 953 } else if (FieldTy->isFloatingPoint() || isa<VectorType>(FieldTy)) { 954 // Bitcast to the right element type (for fp/vector values). 955 EltVal = new BitCastInst(EltVal, FieldTy, "", SI); 956 } else { 957 // Otherwise, bitcast the dest pointer (for aggregates). 958 DestField = new BitCastInst(DestField, 959 Context->getPointerTypeUnqual(EltVal->getType()), 960 "", SI); 961 } 962 new StoreInst(EltVal, DestField, SI); 963 } 964 965 } else { 966 const ArrayType *ATy = cast<ArrayType>(AllocaEltTy); 967 const Type *ArrayEltTy = ATy->getElementType(); 968 uint64_t ElementOffset = TD->getTypeAllocSizeInBits(ArrayEltTy); 969 uint64_t ElementSizeBits = TD->getTypeSizeInBits(ArrayEltTy); 970 971 uint64_t Shift; 972 973 if (TD->isBigEndian()) 974 Shift = AllocaSizeBits-ElementOffset; 975 else 976 Shift = 0; 977 978 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { 979 // Ignore zero sized fields like {}, they obviously contain no data. 980 if (ElementSizeBits == 0) continue; 981 982 Value *EltVal = SrcVal; 983 if (Shift) { 984 Value *ShiftVal = Context->getConstantInt(EltVal->getType(), Shift); 985 EltVal = BinaryOperator::CreateLShr(EltVal, ShiftVal, 986 "sroa.store.elt", SI); 987 } 988 989 // Truncate down to an integer of the right size. 990 if (ElementSizeBits != AllocaSizeBits) 991 EltVal = new TruncInst(EltVal, 992 Context->getIntegerType(ElementSizeBits),"",SI); 993 Value *DestField = NewElts[i]; 994 if (EltVal->getType() == ArrayEltTy) { 995 // Storing to an integer field of this size, just do it. 996 } else if (ArrayEltTy->isFloatingPoint() || isa<VectorType>(ArrayEltTy)) { 997 // Bitcast to the right element type (for fp/vector values). 998 EltVal = new BitCastInst(EltVal, ArrayEltTy, "", SI); 999 } else { 1000 // Otherwise, bitcast the dest pointer (for aggregates). 1001 DestField = new BitCastInst(DestField, 1002 Context->getPointerTypeUnqual(EltVal->getType()), 1003 "", SI); 1004 } 1005 new StoreInst(EltVal, DestField, SI); 1006 1007 if (TD->isBigEndian()) 1008 Shift -= ElementOffset; 1009 else 1010 Shift += ElementOffset; 1011 } 1012 } 1013 1014 SI->eraseFromParent(); 1015} 1016 1017/// RewriteLoadUserOfWholeAlloca - We found an load of the entire allocation to 1018/// an integer. Load the individual pieces to form the aggregate value. 1019void SROA::RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocationInst *AI, 1020 SmallVector<AllocaInst*, 32> &NewElts) { 1021 // Extract each element out of the NewElts according to its structure offset 1022 // and form the result value. 1023 const Type *AllocaEltTy = AI->getType()->getElementType(); 1024 uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy); 1025 1026 // If this isn't a load of the whole alloca to an integer, it may be a load 1027 // of the first element. Just ignore the load in this case and normal SROA 1028 // will handle it. 1029 if (!isa<IntegerType>(LI->getType()) || 1030 TD->getTypeAllocSizeInBits(LI->getType()) != AllocaSizeBits) 1031 return; 1032 1033 DOUT << "PROMOTING LOAD OF WHOLE ALLOCA: " << *AI << *LI; 1034 1035 // There are two forms here: AI could be an array or struct. Both cases 1036 // have different ways to compute the element offset. 1037 const StructLayout *Layout = 0; 1038 uint64_t ArrayEltBitOffset = 0; 1039 if (const StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) { 1040 Layout = TD->getStructLayout(EltSTy); 1041 } else { 1042 const Type *ArrayEltTy = cast<ArrayType>(AllocaEltTy)->getElementType(); 1043 ArrayEltBitOffset = TD->getTypeAllocSizeInBits(ArrayEltTy); 1044 } 1045 1046 Value *ResultVal = 1047 Context->getNullValue(Context->getIntegerType(AllocaSizeBits)); 1048 1049 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { 1050 // Load the value from the alloca. If the NewElt is an aggregate, cast 1051 // the pointer to an integer of the same size before doing the load. 1052 Value *SrcField = NewElts[i]; 1053 const Type *FieldTy = 1054 cast<PointerType>(SrcField->getType())->getElementType(); 1055 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy); 1056 1057 // Ignore zero sized fields like {}, they obviously contain no data. 1058 if (FieldSizeBits == 0) continue; 1059 1060 const IntegerType *FieldIntTy = Context->getIntegerType(FieldSizeBits); 1061 if (!isa<IntegerType>(FieldTy) && !FieldTy->isFloatingPoint() && 1062 !isa<VectorType>(FieldTy)) 1063 SrcField = new BitCastInst(SrcField, 1064 Context->getPointerTypeUnqual(FieldIntTy), 1065 "", LI); 1066 SrcField = new LoadInst(SrcField, "sroa.load.elt", LI); 1067 1068 // If SrcField is a fp or vector of the right size but that isn't an 1069 // integer type, bitcast to an integer so we can shift it. 1070 if (SrcField->getType() != FieldIntTy) 1071 SrcField = new BitCastInst(SrcField, FieldIntTy, "", LI); 1072 1073 // Zero extend the field to be the same size as the final alloca so that 1074 // we can shift and insert it. 1075 if (SrcField->getType() != ResultVal->getType()) 1076 SrcField = new ZExtInst(SrcField, ResultVal->getType(), "", LI); 1077 1078 // Determine the number of bits to shift SrcField. 1079 uint64_t Shift; 1080 if (Layout) // Struct case. 1081 Shift = Layout->getElementOffsetInBits(i); 1082 else // Array case. 1083 Shift = i*ArrayEltBitOffset; 1084 1085 if (TD->isBigEndian()) 1086 Shift = AllocaSizeBits-Shift-FieldIntTy->getBitWidth(); 1087 1088 if (Shift) { 1089 Value *ShiftVal = Context->getConstantInt(SrcField->getType(), Shift); 1090 SrcField = BinaryOperator::CreateShl(SrcField, ShiftVal, "", LI); 1091 } 1092 1093 ResultVal = BinaryOperator::CreateOr(SrcField, ResultVal, "", LI); 1094 } 1095 1096 // Handle tail padding by truncating the result 1097 if (TD->getTypeSizeInBits(LI->getType()) != AllocaSizeBits) 1098 ResultVal = new TruncInst(ResultVal, LI->getType(), "", LI); 1099 1100 LI->replaceAllUsesWith(ResultVal); 1101 LI->eraseFromParent(); 1102} 1103 1104 1105/// HasPadding - Return true if the specified type has any structure or 1106/// alignment padding, false otherwise. 1107static bool HasPadding(const Type *Ty, const TargetData &TD) { 1108 if (const StructType *STy = dyn_cast<StructType>(Ty)) { 1109 const StructLayout *SL = TD.getStructLayout(STy); 1110 unsigned PrevFieldBitOffset = 0; 1111 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) { 1112 unsigned FieldBitOffset = SL->getElementOffsetInBits(i); 1113 1114 // Padding in sub-elements? 1115 if (HasPadding(STy->getElementType(i), TD)) 1116 return true; 1117 1118 // Check to see if there is any padding between this element and the 1119 // previous one. 1120 if (i) { 1121 unsigned PrevFieldEnd = 1122 PrevFieldBitOffset+TD.getTypeSizeInBits(STy->getElementType(i-1)); 1123 if (PrevFieldEnd < FieldBitOffset) 1124 return true; 1125 } 1126 1127 PrevFieldBitOffset = FieldBitOffset; 1128 } 1129 1130 // Check for tail padding. 1131 if (unsigned EltCount = STy->getNumElements()) { 1132 unsigned PrevFieldEnd = PrevFieldBitOffset + 1133 TD.getTypeSizeInBits(STy->getElementType(EltCount-1)); 1134 if (PrevFieldEnd < SL->getSizeInBits()) 1135 return true; 1136 } 1137 1138 } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) { 1139 return HasPadding(ATy->getElementType(), TD); 1140 } else if (const VectorType *VTy = dyn_cast<VectorType>(Ty)) { 1141 return HasPadding(VTy->getElementType(), TD); 1142 } 1143 return TD.getTypeSizeInBits(Ty) != TD.getTypeAllocSizeInBits(Ty); 1144} 1145 1146/// isSafeStructAllocaToScalarRepl - Check to see if the specified allocation of 1147/// an aggregate can be broken down into elements. Return 0 if not, 3 if safe, 1148/// or 1 if safe after canonicalization has been performed. 1149/// 1150int SROA::isSafeAllocaToScalarRepl(AllocationInst *AI) { 1151 // Loop over the use list of the alloca. We can only transform it if all of 1152 // the users are safe to transform. 1153 AllocaInfo Info; 1154 1155 for (Value::use_iterator I = AI->use_begin(), E = AI->use_end(); 1156 I != E; ++I) { 1157 isSafeUseOfAllocation(cast<Instruction>(*I), AI, Info); 1158 if (Info.isUnsafe) { 1159 DOUT << "Cannot transform: " << *AI << " due to user: " << **I; 1160 return 0; 1161 } 1162 } 1163 1164 // Okay, we know all the users are promotable. If the aggregate is a memcpy 1165 // source and destination, we have to be careful. In particular, the memcpy 1166 // could be moving around elements that live in structure padding of the LLVM 1167 // types, but may actually be used. In these cases, we refuse to promote the 1168 // struct. 1169 if (Info.isMemCpySrc && Info.isMemCpyDst && 1170 HasPadding(AI->getType()->getElementType(), *TD)) 1171 return 0; 1172 1173 // If we require cleanup, return 1, otherwise return 3. 1174 return Info.needsCleanup ? 1 : 3; 1175} 1176 1177/// CleanupGEP - GEP is used by an Alloca, which can be prompted after the GEP 1178/// is canonicalized here. 1179void SROA::CleanupGEP(GetElementPtrInst *GEPI) { 1180 gep_type_iterator I = gep_type_begin(GEPI); 1181 ++I; 1182 1183 const ArrayType *AT = dyn_cast<ArrayType>(*I); 1184 if (!AT) 1185 return; 1186 1187 uint64_t NumElements = AT->getNumElements(); 1188 1189 if (isa<ConstantInt>(I.getOperand())) 1190 return; 1191 1192 if (NumElements == 1) { 1193 GEPI->setOperand(2, Context->getNullValue(Type::Int32Ty)); 1194 return; 1195 } 1196 1197 assert(NumElements == 2 && "Unhandled case!"); 1198 // All users of the GEP must be loads. At each use of the GEP, insert 1199 // two loads of the appropriate indexed GEP and select between them. 1200 Value *IsOne = new ICmpInst(GEPI, ICmpInst::ICMP_NE, I.getOperand(), 1201 Context->getNullValue(I.getOperand()->getType()), 1202 "isone"); 1203 // Insert the new GEP instructions, which are properly indexed. 1204 SmallVector<Value*, 8> Indices(GEPI->op_begin()+1, GEPI->op_end()); 1205 Indices[1] = Context->getNullValue(Type::Int32Ty); 1206 Value *ZeroIdx = GetElementPtrInst::Create(GEPI->getOperand(0), 1207 Indices.begin(), 1208 Indices.end(), 1209 GEPI->getName()+".0", GEPI); 1210 Indices[1] = Context->getConstantInt(Type::Int32Ty, 1); 1211 Value *OneIdx = GetElementPtrInst::Create(GEPI->getOperand(0), 1212 Indices.begin(), 1213 Indices.end(), 1214 GEPI->getName()+".1", GEPI); 1215 // Replace all loads of the variable index GEP with loads from both 1216 // indexes and a select. 1217 while (!GEPI->use_empty()) { 1218 LoadInst *LI = cast<LoadInst>(GEPI->use_back()); 1219 Value *Zero = new LoadInst(ZeroIdx, LI->getName()+".0", LI); 1220 Value *One = new LoadInst(OneIdx , LI->getName()+".1", LI); 1221 Value *R = SelectInst::Create(IsOne, One, Zero, LI->getName(), LI); 1222 LI->replaceAllUsesWith(R); 1223 LI->eraseFromParent(); 1224 } 1225 GEPI->eraseFromParent(); 1226} 1227 1228 1229/// CleanupAllocaUsers - If SROA reported that it can promote the specified 1230/// allocation, but only if cleaned up, perform the cleanups required. 1231void SROA::CleanupAllocaUsers(AllocationInst *AI) { 1232 // At this point, we know that the end result will be SROA'd and promoted, so 1233 // we can insert ugly code if required so long as sroa+mem2reg will clean it 1234 // up. 1235 for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end(); 1236 UI != E; ) { 1237 User *U = *UI++; 1238 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(U)) 1239 CleanupGEP(GEPI); 1240 else { 1241 Instruction *I = cast<Instruction>(U); 1242 SmallVector<DbgInfoIntrinsic *, 2> DbgInUses; 1243 if (!isa<StoreInst>(I) && OnlyUsedByDbgInfoIntrinsics(I, &DbgInUses)) { 1244 // Safe to remove debug info uses. 1245 while (!DbgInUses.empty()) { 1246 DbgInfoIntrinsic *DI = DbgInUses.back(); DbgInUses.pop_back(); 1247 DI->eraseFromParent(); 1248 } 1249 I->eraseFromParent(); 1250 } 1251 } 1252 } 1253} 1254 1255/// MergeInType - Add the 'In' type to the accumulated type (Accum) so far at 1256/// the offset specified by Offset (which is specified in bytes). 1257/// 1258/// There are two cases we handle here: 1259/// 1) A union of vector types of the same size and potentially its elements. 1260/// Here we turn element accesses into insert/extract element operations. 1261/// This promotes a <4 x float> with a store of float to the third element 1262/// into a <4 x float> that uses insert element. 1263/// 2) A fully general blob of memory, which we turn into some (potentially 1264/// large) integer type with extract and insert operations where the loads 1265/// and stores would mutate the memory. 1266static void MergeInType(const Type *In, uint64_t Offset, const Type *&VecTy, 1267 unsigned AllocaSize, const TargetData &TD, 1268 LLVMContext *Context) { 1269 // If this could be contributing to a vector, analyze it. 1270 if (VecTy != Type::VoidTy) { // either null or a vector type. 1271 1272 // If the In type is a vector that is the same size as the alloca, see if it 1273 // matches the existing VecTy. 1274 if (const VectorType *VInTy = dyn_cast<VectorType>(In)) { 1275 if (VInTy->getBitWidth()/8 == AllocaSize && Offset == 0) { 1276 // If we're storing/loading a vector of the right size, allow it as a 1277 // vector. If this the first vector we see, remember the type so that 1278 // we know the element size. 1279 if (VecTy == 0) 1280 VecTy = VInTy; 1281 return; 1282 } 1283 } else if (In == Type::FloatTy || In == Type::DoubleTy || 1284 (isa<IntegerType>(In) && In->getPrimitiveSizeInBits() >= 8 && 1285 isPowerOf2_32(In->getPrimitiveSizeInBits()))) { 1286 // If we're accessing something that could be an element of a vector, see 1287 // if the implied vector agrees with what we already have and if Offset is 1288 // compatible with it. 1289 unsigned EltSize = In->getPrimitiveSizeInBits()/8; 1290 if (Offset % EltSize == 0 && 1291 AllocaSize % EltSize == 0 && 1292 (VecTy == 0 || 1293 cast<VectorType>(VecTy)->getElementType() 1294 ->getPrimitiveSizeInBits()/8 == EltSize)) { 1295 if (VecTy == 0) 1296 VecTy = Context->getVectorType(In, AllocaSize/EltSize); 1297 return; 1298 } 1299 } 1300 } 1301 1302 // Otherwise, we have a case that we can't handle with an optimized vector 1303 // form. We can still turn this into a large integer. 1304 VecTy = Type::VoidTy; 1305} 1306 1307/// CanConvertToScalar - V is a pointer. If we can convert the pointee and all 1308/// its accesses to use a to single vector type, return true, and set VecTy to 1309/// the new type. If we could convert the alloca into a single promotable 1310/// integer, return true but set VecTy to VoidTy. Further, if the use is not a 1311/// completely trivial use that mem2reg could promote, set IsNotTrivial. Offset 1312/// is the current offset from the base of the alloca being analyzed. 1313/// 1314/// If we see at least one access to the value that is as a vector type, set the 1315/// SawVec flag. 1316/// 1317bool SROA::CanConvertToScalar(Value *V, bool &IsNotTrivial, const Type *&VecTy, 1318 bool &SawVec, uint64_t Offset, 1319 unsigned AllocaSize) { 1320 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) { 1321 Instruction *User = cast<Instruction>(*UI); 1322 1323 if (LoadInst *LI = dyn_cast<LoadInst>(User)) { 1324 // Don't break volatile loads. 1325 if (LI->isVolatile()) 1326 return false; 1327 MergeInType(LI->getType(), Offset, VecTy, AllocaSize, *TD, Context); 1328 SawVec |= isa<VectorType>(LI->getType()); 1329 continue; 1330 } 1331 1332 if (StoreInst *SI = dyn_cast<StoreInst>(User)) { 1333 // Storing the pointer, not into the value? 1334 if (SI->getOperand(0) == V || SI->isVolatile()) return 0; 1335 MergeInType(SI->getOperand(0)->getType(), Offset, 1336 VecTy, AllocaSize, *TD, Context); 1337 SawVec |= isa<VectorType>(SI->getOperand(0)->getType()); 1338 continue; 1339 } 1340 1341 if (BitCastInst *BCI = dyn_cast<BitCastInst>(User)) { 1342 if (!CanConvertToScalar(BCI, IsNotTrivial, VecTy, SawVec, Offset, 1343 AllocaSize)) 1344 return false; 1345 IsNotTrivial = true; 1346 continue; 1347 } 1348 1349 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) { 1350 // If this is a GEP with a variable indices, we can't handle it. 1351 if (!GEP->hasAllConstantIndices()) 1352 return false; 1353 1354 // Compute the offset that this GEP adds to the pointer. 1355 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end()); 1356 uint64_t GEPOffset = TD->getIndexedOffset(GEP->getOperand(0)->getType(), 1357 &Indices[0], Indices.size()); 1358 // See if all uses can be converted. 1359 if (!CanConvertToScalar(GEP, IsNotTrivial, VecTy, SawVec,Offset+GEPOffset, 1360 AllocaSize)) 1361 return false; 1362 IsNotTrivial = true; 1363 continue; 1364 } 1365 1366 // If this is a constant sized memset of a constant value (e.g. 0) we can 1367 // handle it. 1368 if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) { 1369 // Store of constant value and constant size. 1370 if (isa<ConstantInt>(MSI->getValue()) && 1371 isa<ConstantInt>(MSI->getLength())) { 1372 IsNotTrivial = true; 1373 continue; 1374 } 1375 } 1376 1377 // If this is a memcpy or memmove into or out of the whole allocation, we 1378 // can handle it like a load or store of the scalar type. 1379 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) { 1380 if (ConstantInt *Len = dyn_cast<ConstantInt>(MTI->getLength())) 1381 if (Len->getZExtValue() == AllocaSize && Offset == 0) { 1382 IsNotTrivial = true; 1383 continue; 1384 } 1385 } 1386 1387 // Ignore dbg intrinsic. 1388 if (isa<DbgInfoIntrinsic>(User)) 1389 continue; 1390 1391 // Otherwise, we cannot handle this! 1392 return false; 1393 } 1394 1395 return true; 1396} 1397 1398 1399/// ConvertUsesToScalar - Convert all of the users of Ptr to use the new alloca 1400/// directly. This happens when we are converting an "integer union" to a 1401/// single integer scalar, or when we are converting a "vector union" to a 1402/// vector with insert/extractelement instructions. 1403/// 1404/// Offset is an offset from the original alloca, in bits that need to be 1405/// shifted to the right. By the end of this, there should be no uses of Ptr. 1406void SROA::ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, uint64_t Offset) { 1407 while (!Ptr->use_empty()) { 1408 Instruction *User = cast<Instruction>(Ptr->use_back()); 1409 1410 if (BitCastInst *CI = dyn_cast<BitCastInst>(User)) { 1411 ConvertUsesToScalar(CI, NewAI, Offset); 1412 CI->eraseFromParent(); 1413 continue; 1414 } 1415 1416 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) { 1417 // Compute the offset that this GEP adds to the pointer. 1418 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end()); 1419 uint64_t GEPOffset = TD->getIndexedOffset(GEP->getOperand(0)->getType(), 1420 &Indices[0], Indices.size()); 1421 ConvertUsesToScalar(GEP, NewAI, Offset+GEPOffset*8); 1422 GEP->eraseFromParent(); 1423 continue; 1424 } 1425 1426 IRBuilder<> Builder(User->getParent(), User); 1427 1428 if (LoadInst *LI = dyn_cast<LoadInst>(User)) { 1429 // The load is a bit extract from NewAI shifted right by Offset bits. 1430 Value *LoadedVal = Builder.CreateLoad(NewAI, "tmp"); 1431 Value *NewLoadVal 1432 = ConvertScalar_ExtractValue(LoadedVal, LI->getType(), Offset, Builder); 1433 LI->replaceAllUsesWith(NewLoadVal); 1434 LI->eraseFromParent(); 1435 continue; 1436 } 1437 1438 if (StoreInst *SI = dyn_cast<StoreInst>(User)) { 1439 assert(SI->getOperand(0) != Ptr && "Consistency error!"); 1440 Value *Old = Builder.CreateLoad(NewAI, (NewAI->getName()+".in").c_str()); 1441 Value *New = ConvertScalar_InsertValue(SI->getOperand(0), Old, Offset, 1442 Builder); 1443 Builder.CreateStore(New, NewAI); 1444 SI->eraseFromParent(); 1445 continue; 1446 } 1447 1448 // If this is a constant sized memset of a constant value (e.g. 0) we can 1449 // transform it into a store of the expanded constant value. 1450 if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) { 1451 assert(MSI->getRawDest() == Ptr && "Consistency error!"); 1452 unsigned NumBytes = cast<ConstantInt>(MSI->getLength())->getZExtValue(); 1453 if (NumBytes != 0) { 1454 unsigned Val = cast<ConstantInt>(MSI->getValue())->getZExtValue(); 1455 1456 // Compute the value replicated the right number of times. 1457 APInt APVal(NumBytes*8, Val); 1458 1459 // Splat the value if non-zero. 1460 if (Val) 1461 for (unsigned i = 1; i != NumBytes; ++i) 1462 APVal |= APVal << 8; 1463 1464 Value *Old = Builder.CreateLoad(NewAI, (NewAI->getName()+".in").c_str()); 1465 Value *New = ConvertScalar_InsertValue(Context->getConstantInt(APVal), 1466 Old, Offset, Builder); 1467 Builder.CreateStore(New, NewAI); 1468 } 1469 MSI->eraseFromParent(); 1470 continue; 1471 } 1472 1473 // If this is a memcpy or memmove into or out of the whole allocation, we 1474 // can handle it like a load or store of the scalar type. 1475 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) { 1476 assert(Offset == 0 && "must be store to start of alloca"); 1477 1478 // If the source and destination are both to the same alloca, then this is 1479 // a noop copy-to-self, just delete it. Otherwise, emit a load and store 1480 // as appropriate. 1481 AllocaInst *OrigAI = cast<AllocaInst>(Ptr->getUnderlyingObject()); 1482 1483 if (MTI->getSource()->getUnderlyingObject() != OrigAI) { 1484 // Dest must be OrigAI, change this to be a load from the original 1485 // pointer (bitcasted), then a store to our new alloca. 1486 assert(MTI->getRawDest() == Ptr && "Neither use is of pointer?"); 1487 Value *SrcPtr = MTI->getSource(); 1488 SrcPtr = Builder.CreateBitCast(SrcPtr, NewAI->getType()); 1489 1490 LoadInst *SrcVal = Builder.CreateLoad(SrcPtr, "srcval"); 1491 SrcVal->setAlignment(MTI->getAlignment()); 1492 Builder.CreateStore(SrcVal, NewAI); 1493 } else if (MTI->getDest()->getUnderlyingObject() != OrigAI) { 1494 // Src must be OrigAI, change this to be a load from NewAI then a store 1495 // through the original dest pointer (bitcasted). 1496 assert(MTI->getRawSource() == Ptr && "Neither use is of pointer?"); 1497 LoadInst *SrcVal = Builder.CreateLoad(NewAI, "srcval"); 1498 1499 Value *DstPtr = Builder.CreateBitCast(MTI->getDest(), NewAI->getType()); 1500 StoreInst *NewStore = Builder.CreateStore(SrcVal, DstPtr); 1501 NewStore->setAlignment(MTI->getAlignment()); 1502 } else { 1503 // Noop transfer. Src == Dst 1504 } 1505 1506 1507 MTI->eraseFromParent(); 1508 continue; 1509 } 1510 1511 // If user is a dbg info intrinsic then it is safe to remove it. 1512 if (isa<DbgInfoIntrinsic>(User)) { 1513 User->eraseFromParent(); 1514 continue; 1515 } 1516 1517 llvm_unreachable("Unsupported operation!"); 1518 } 1519} 1520 1521/// ConvertScalar_ExtractValue - Extract a value of type ToType from an integer 1522/// or vector value FromVal, extracting the bits from the offset specified by 1523/// Offset. This returns the value, which is of type ToType. 1524/// 1525/// This happens when we are converting an "integer union" to a single 1526/// integer scalar, or when we are converting a "vector union" to a vector with 1527/// insert/extractelement instructions. 1528/// 1529/// Offset is an offset from the original alloca, in bits that need to be 1530/// shifted to the right. 1531Value *SROA::ConvertScalar_ExtractValue(Value *FromVal, const Type *ToType, 1532 uint64_t Offset, IRBuilder<> &Builder) { 1533 // If the load is of the whole new alloca, no conversion is needed. 1534 if (FromVal->getType() == ToType && Offset == 0) 1535 return FromVal; 1536 1537 // If the result alloca is a vector type, this is either an element 1538 // access or a bitcast to another vector type of the same size. 1539 if (const VectorType *VTy = dyn_cast<VectorType>(FromVal->getType())) { 1540 if (isa<VectorType>(ToType)) 1541 return Builder.CreateBitCast(FromVal, ToType, "tmp"); 1542 1543 // Otherwise it must be an element access. 1544 unsigned Elt = 0; 1545 if (Offset) { 1546 unsigned EltSize = TD->getTypeAllocSizeInBits(VTy->getElementType()); 1547 Elt = Offset/EltSize; 1548 assert(EltSize*Elt == Offset && "Invalid modulus in validity checking"); 1549 } 1550 // Return the element extracted out of it. 1551 Value *V = Builder.CreateExtractElement(FromVal, 1552 Context->getConstantInt(Type::Int32Ty,Elt), 1553 "tmp"); 1554 if (V->getType() != ToType) 1555 V = Builder.CreateBitCast(V, ToType, "tmp"); 1556 return V; 1557 } 1558 1559 // If ToType is a first class aggregate, extract out each of the pieces and 1560 // use insertvalue's to form the FCA. 1561 if (const StructType *ST = dyn_cast<StructType>(ToType)) { 1562 const StructLayout &Layout = *TD->getStructLayout(ST); 1563 Value *Res = Context->getUndef(ST); 1564 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) { 1565 Value *Elt = ConvertScalar_ExtractValue(FromVal, ST->getElementType(i), 1566 Offset+Layout.getElementOffsetInBits(i), 1567 Builder); 1568 Res = Builder.CreateInsertValue(Res, Elt, i, "tmp"); 1569 } 1570 return Res; 1571 } 1572 1573 if (const ArrayType *AT = dyn_cast<ArrayType>(ToType)) { 1574 uint64_t EltSize = TD->getTypeAllocSizeInBits(AT->getElementType()); 1575 Value *Res = Context->getUndef(AT); 1576 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) { 1577 Value *Elt = ConvertScalar_ExtractValue(FromVal, AT->getElementType(), 1578 Offset+i*EltSize, Builder); 1579 Res = Builder.CreateInsertValue(Res, Elt, i, "tmp"); 1580 } 1581 return Res; 1582 } 1583 1584 // Otherwise, this must be a union that was converted to an integer value. 1585 const IntegerType *NTy = cast<IntegerType>(FromVal->getType()); 1586 1587 // If this is a big-endian system and the load is narrower than the 1588 // full alloca type, we need to do a shift to get the right bits. 1589 int ShAmt = 0; 1590 if (TD->isBigEndian()) { 1591 // On big-endian machines, the lowest bit is stored at the bit offset 1592 // from the pointer given by getTypeStoreSizeInBits. This matters for 1593 // integers with a bitwidth that is not a multiple of 8. 1594 ShAmt = TD->getTypeStoreSizeInBits(NTy) - 1595 TD->getTypeStoreSizeInBits(ToType) - Offset; 1596 } else { 1597 ShAmt = Offset; 1598 } 1599 1600 // Note: we support negative bitwidths (with shl) which are not defined. 1601 // We do this to support (f.e.) loads off the end of a structure where 1602 // only some bits are used. 1603 if (ShAmt > 0 && (unsigned)ShAmt < NTy->getBitWidth()) 1604 FromVal = Builder.CreateLShr(FromVal, 1605 Context->getConstantInt(FromVal->getType(), 1606 ShAmt), "tmp"); 1607 else if (ShAmt < 0 && (unsigned)-ShAmt < NTy->getBitWidth()) 1608 FromVal = Builder.CreateShl(FromVal, 1609 Context->getConstantInt(FromVal->getType(), 1610 -ShAmt), "tmp"); 1611 1612 // Finally, unconditionally truncate the integer to the right width. 1613 unsigned LIBitWidth = TD->getTypeSizeInBits(ToType); 1614 if (LIBitWidth < NTy->getBitWidth()) 1615 FromVal = 1616 Builder.CreateTrunc(FromVal, Context->getIntegerType(LIBitWidth), "tmp"); 1617 else if (LIBitWidth > NTy->getBitWidth()) 1618 FromVal = 1619 Builder.CreateZExt(FromVal, Context->getIntegerType(LIBitWidth), "tmp"); 1620 1621 // If the result is an integer, this is a trunc or bitcast. 1622 if (isa<IntegerType>(ToType)) { 1623 // Should be done. 1624 } else if (ToType->isFloatingPoint() || isa<VectorType>(ToType)) { 1625 // Just do a bitcast, we know the sizes match up. 1626 FromVal = Builder.CreateBitCast(FromVal, ToType, "tmp"); 1627 } else { 1628 // Otherwise must be a pointer. 1629 FromVal = Builder.CreateIntToPtr(FromVal, ToType, "tmp"); 1630 } 1631 assert(FromVal->getType() == ToType && "Didn't convert right?"); 1632 return FromVal; 1633} 1634 1635 1636/// ConvertScalar_InsertValue - Insert the value "SV" into the existing integer 1637/// or vector value "Old" at the offset specified by Offset. 1638/// 1639/// This happens when we are converting an "integer union" to a 1640/// single integer scalar, or when we are converting a "vector union" to a 1641/// vector with insert/extractelement instructions. 1642/// 1643/// Offset is an offset from the original alloca, in bits that need to be 1644/// shifted to the right. 1645Value *SROA::ConvertScalar_InsertValue(Value *SV, Value *Old, 1646 uint64_t Offset, IRBuilder<> &Builder) { 1647 1648 // Convert the stored type to the actual type, shift it left to insert 1649 // then 'or' into place. 1650 const Type *AllocaType = Old->getType(); 1651 1652 if (const VectorType *VTy = dyn_cast<VectorType>(AllocaType)) { 1653 uint64_t VecSize = TD->getTypeAllocSizeInBits(VTy); 1654 uint64_t ValSize = TD->getTypeAllocSizeInBits(SV->getType()); 1655 1656 // Changing the whole vector with memset or with an access of a different 1657 // vector type? 1658 if (ValSize == VecSize) 1659 return Builder.CreateBitCast(SV, AllocaType, "tmp"); 1660 1661 uint64_t EltSize = TD->getTypeAllocSizeInBits(VTy->getElementType()); 1662 1663 // Must be an element insertion. 1664 unsigned Elt = Offset/EltSize; 1665 1666 if (SV->getType() != VTy->getElementType()) 1667 SV = Builder.CreateBitCast(SV, VTy->getElementType(), "tmp"); 1668 1669 SV = Builder.CreateInsertElement(Old, SV, 1670 Context->getConstantInt(Type::Int32Ty, Elt), 1671 "tmp"); 1672 return SV; 1673 } 1674 1675 // If SV is a first-class aggregate value, insert each value recursively. 1676 if (const StructType *ST = dyn_cast<StructType>(SV->getType())) { 1677 const StructLayout &Layout = *TD->getStructLayout(ST); 1678 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) { 1679 Value *Elt = Builder.CreateExtractValue(SV, i, "tmp"); 1680 Old = ConvertScalar_InsertValue(Elt, Old, 1681 Offset+Layout.getElementOffsetInBits(i), 1682 Builder); 1683 } 1684 return Old; 1685 } 1686 1687 if (const ArrayType *AT = dyn_cast<ArrayType>(SV->getType())) { 1688 uint64_t EltSize = TD->getTypeAllocSizeInBits(AT->getElementType()); 1689 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) { 1690 Value *Elt = Builder.CreateExtractValue(SV, i, "tmp"); 1691 Old = ConvertScalar_InsertValue(Elt, Old, Offset+i*EltSize, Builder); 1692 } 1693 return Old; 1694 } 1695 1696 // If SV is a float, convert it to the appropriate integer type. 1697 // If it is a pointer, do the same. 1698 unsigned SrcWidth = TD->getTypeSizeInBits(SV->getType()); 1699 unsigned DestWidth = TD->getTypeSizeInBits(AllocaType); 1700 unsigned SrcStoreWidth = TD->getTypeStoreSizeInBits(SV->getType()); 1701 unsigned DestStoreWidth = TD->getTypeStoreSizeInBits(AllocaType); 1702 if (SV->getType()->isFloatingPoint() || isa<VectorType>(SV->getType())) 1703 SV = Builder.CreateBitCast(SV, Context->getIntegerType(SrcWidth), "tmp"); 1704 else if (isa<PointerType>(SV->getType())) 1705 SV = Builder.CreatePtrToInt(SV, TD->getIntPtrType(), "tmp"); 1706 1707 // Zero extend or truncate the value if needed. 1708 if (SV->getType() != AllocaType) { 1709 if (SV->getType()->getPrimitiveSizeInBits() < 1710 AllocaType->getPrimitiveSizeInBits()) 1711 SV = Builder.CreateZExt(SV, AllocaType, "tmp"); 1712 else { 1713 // Truncation may be needed if storing more than the alloca can hold 1714 // (undefined behavior). 1715 SV = Builder.CreateTrunc(SV, AllocaType, "tmp"); 1716 SrcWidth = DestWidth; 1717 SrcStoreWidth = DestStoreWidth; 1718 } 1719 } 1720 1721 // If this is a big-endian system and the store is narrower than the 1722 // full alloca type, we need to do a shift to get the right bits. 1723 int ShAmt = 0; 1724 if (TD->isBigEndian()) { 1725 // On big-endian machines, the lowest bit is stored at the bit offset 1726 // from the pointer given by getTypeStoreSizeInBits. This matters for 1727 // integers with a bitwidth that is not a multiple of 8. 1728 ShAmt = DestStoreWidth - SrcStoreWidth - Offset; 1729 } else { 1730 ShAmt = Offset; 1731 } 1732 1733 // Note: we support negative bitwidths (with shr) which are not defined. 1734 // We do this to support (f.e.) stores off the end of a structure where 1735 // only some bits in the structure are set. 1736 APInt Mask(APInt::getLowBitsSet(DestWidth, SrcWidth)); 1737 if (ShAmt > 0 && (unsigned)ShAmt < DestWidth) { 1738 SV = Builder.CreateShl(SV, Context->getConstantInt(SV->getType(), 1739 ShAmt), "tmp"); 1740 Mask <<= ShAmt; 1741 } else if (ShAmt < 0 && (unsigned)-ShAmt < DestWidth) { 1742 SV = Builder.CreateLShr(SV, Context->getConstantInt(SV->getType(), 1743 -ShAmt), "tmp"); 1744 Mask = Mask.lshr(-ShAmt); 1745 } 1746 1747 // Mask out the bits we are about to insert from the old value, and or 1748 // in the new bits. 1749 if (SrcWidth != DestWidth) { 1750 assert(DestWidth > SrcWidth); 1751 Old = Builder.CreateAnd(Old, Context->getConstantInt(~Mask), "mask"); 1752 SV = Builder.CreateOr(Old, SV, "ins"); 1753 } 1754 return SV; 1755} 1756 1757 1758 1759/// PointsToConstantGlobal - Return true if V (possibly indirectly) points to 1760/// some part of a constant global variable. This intentionally only accepts 1761/// constant expressions because we don't can't rewrite arbitrary instructions. 1762static bool PointsToConstantGlobal(Value *V) { 1763 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V)) 1764 return GV->isConstant(); 1765 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) 1766 if (CE->getOpcode() == Instruction::BitCast || 1767 CE->getOpcode() == Instruction::GetElementPtr) 1768 return PointsToConstantGlobal(CE->getOperand(0)); 1769 return false; 1770} 1771 1772/// isOnlyCopiedFromConstantGlobal - Recursively walk the uses of a (derived) 1773/// pointer to an alloca. Ignore any reads of the pointer, return false if we 1774/// see any stores or other unknown uses. If we see pointer arithmetic, keep 1775/// track of whether it moves the pointer (with isOffset) but otherwise traverse 1776/// the uses. If we see a memcpy/memmove that targets an unoffseted pointer to 1777/// the alloca, and if the source pointer is a pointer to a constant global, we 1778/// can optimize this. 1779static bool isOnlyCopiedFromConstantGlobal(Value *V, Instruction *&TheCopy, 1780 bool isOffset) { 1781 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) { 1782 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) 1783 // Ignore non-volatile loads, they are always ok. 1784 if (!LI->isVolatile()) 1785 continue; 1786 1787 if (BitCastInst *BCI = dyn_cast<BitCastInst>(*UI)) { 1788 // If uses of the bitcast are ok, we are ok. 1789 if (!isOnlyCopiedFromConstantGlobal(BCI, TheCopy, isOffset)) 1790 return false; 1791 continue; 1792 } 1793 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(*UI)) { 1794 // If the GEP has all zero indices, it doesn't offset the pointer. If it 1795 // doesn't, it does. 1796 if (!isOnlyCopiedFromConstantGlobal(GEP, TheCopy, 1797 isOffset || !GEP->hasAllZeroIndices())) 1798 return false; 1799 continue; 1800 } 1801 1802 // If this is isn't our memcpy/memmove, reject it as something we can't 1803 // handle. 1804 if (!isa<MemTransferInst>(*UI)) 1805 return false; 1806 1807 // If we already have seen a copy, reject the second one. 1808 if (TheCopy) return false; 1809 1810 // If the pointer has been offset from the start of the alloca, we can't 1811 // safely handle this. 1812 if (isOffset) return false; 1813 1814 // If the memintrinsic isn't using the alloca as the dest, reject it. 1815 if (UI.getOperandNo() != 1) return false; 1816 1817 MemIntrinsic *MI = cast<MemIntrinsic>(*UI); 1818 1819 // If the source of the memcpy/move is not a constant global, reject it. 1820 if (!PointsToConstantGlobal(MI->getOperand(2))) 1821 return false; 1822 1823 // Otherwise, the transform is safe. Remember the copy instruction. 1824 TheCopy = MI; 1825 } 1826 return true; 1827} 1828 1829/// isOnlyCopiedFromConstantGlobal - Return true if the specified alloca is only 1830/// modified by a copy from a constant global. If we can prove this, we can 1831/// replace any uses of the alloca with uses of the global directly. 1832Instruction *SROA::isOnlyCopiedFromConstantGlobal(AllocationInst *AI) { 1833 Instruction *TheCopy = 0; 1834 if (::isOnlyCopiedFromConstantGlobal(AI, TheCopy, false)) 1835 return TheCopy; 1836 return 0; 1837} 1838