ScalarReplAggregates.cpp revision 3eeba88631db6da7d45df67f677556297bd93f75
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 they 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/DIBuilder.h" 26#include "llvm/DebugInfo.h" 27#include "llvm/DerivedTypes.h" 28#include "llvm/Function.h" 29#include "llvm/GlobalVariable.h" 30#include "llvm/IRBuilder.h" 31#include "llvm/Instructions.h" 32#include "llvm/IntrinsicInst.h" 33#include "llvm/LLVMContext.h" 34#include "llvm/Module.h" 35#include "llvm/Operator.h" 36#include "llvm/Pass.h" 37#include "llvm/ADT/SetVector.h" 38#include "llvm/ADT/SmallVector.h" 39#include "llvm/ADT/Statistic.h" 40#include "llvm/Analysis/Dominators.h" 41#include "llvm/Analysis/Loads.h" 42#include "llvm/Analysis/ValueTracking.h" 43#include "llvm/Support/CallSite.h" 44#include "llvm/Support/Debug.h" 45#include "llvm/Support/ErrorHandling.h" 46#include "llvm/Support/GetElementPtrTypeIterator.h" 47#include "llvm/Support/MathExtras.h" 48#include "llvm/Support/raw_ostream.h" 49#include "llvm/Target/TargetData.h" 50#include "llvm/Transforms/Utils/Local.h" 51#include "llvm/Transforms/Utils/PromoteMemToReg.h" 52#include "llvm/Transforms/Utils/SSAUpdater.h" 53using namespace llvm; 54 55STATISTIC(NumReplaced, "Number of allocas broken up"); 56STATISTIC(NumPromoted, "Number of allocas promoted"); 57STATISTIC(NumAdjusted, "Number of scalar allocas adjusted to allow promotion"); 58STATISTIC(NumConverted, "Number of aggregates converted to scalar"); 59STATISTIC(NumGlobals, "Number of allocas copied from constant global"); 60 61namespace { 62 struct SROA : public FunctionPass { 63 SROA(int T, bool hasDT, char &ID, int ST, int AT, int SLT) 64 : FunctionPass(ID), HasDomTree(hasDT) { 65 if (T == -1) 66 SRThreshold = 128; 67 else 68 SRThreshold = T; 69 if (ST == -1) 70 StructMemberThreshold = 32; 71 else 72 StructMemberThreshold = ST; 73 if (AT == -1) 74 ArrayElementThreshold = 8; 75 else 76 ArrayElementThreshold = AT; 77 if (SLT == -1) 78 // Do not limit the scalar integer load size if no threshold is given. 79 ScalarLoadThreshold = -1; 80 else 81 ScalarLoadThreshold = SLT; 82 } 83 84 bool runOnFunction(Function &F); 85 86 bool performScalarRepl(Function &F); 87 bool performPromotion(Function &F); 88 89 private: 90 bool HasDomTree; 91 TargetData *TD; 92 93 /// DeadInsts - Keep track of instructions we have made dead, so that 94 /// we can remove them after we are done working. 95 SmallVector<Value*, 32> DeadInsts; 96 97 /// AllocaInfo - When analyzing uses of an alloca instruction, this captures 98 /// information about the uses. All these fields are initialized to false 99 /// and set to true when something is learned. 100 struct AllocaInfo { 101 /// The alloca to promote. 102 AllocaInst *AI; 103 104 /// CheckedPHIs - This is a set of verified PHI nodes, to prevent infinite 105 /// looping and avoid redundant work. 106 SmallPtrSet<PHINode*, 8> CheckedPHIs; 107 108 /// isUnsafe - This is set to true if the alloca cannot be SROA'd. 109 bool isUnsafe : 1; 110 111 /// isMemCpySrc - This is true if this aggregate is memcpy'd from. 112 bool isMemCpySrc : 1; 113 114 /// isMemCpyDst - This is true if this aggregate is memcpy'd into. 115 bool isMemCpyDst : 1; 116 117 /// hasSubelementAccess - This is true if a subelement of the alloca is 118 /// ever accessed, or false if the alloca is only accessed with mem 119 /// intrinsics or load/store that only access the entire alloca at once. 120 bool hasSubelementAccess : 1; 121 122 /// hasALoadOrStore - This is true if there are any loads or stores to it. 123 /// The alloca may just be accessed with memcpy, for example, which would 124 /// not set this. 125 bool hasALoadOrStore : 1; 126 127 explicit AllocaInfo(AllocaInst *ai) 128 : AI(ai), isUnsafe(false), isMemCpySrc(false), isMemCpyDst(false), 129 hasSubelementAccess(false), hasALoadOrStore(false) {} 130 }; 131 132 /// SRThreshold - The maximum alloca size to considered for SROA. 133 unsigned SRThreshold; 134 135 /// StructMemberThreshold - The maximum number of members a struct can 136 /// contain to be considered for SROA. 137 unsigned StructMemberThreshold; 138 139 /// ArrayElementThreshold - The maximum number of elements an array can 140 /// have to be considered for SROA. 141 unsigned ArrayElementThreshold; 142 143 /// ScalarLoadThreshold - The maximum size in bits of scalars to load when 144 /// converting to scalar 145 unsigned ScalarLoadThreshold; 146 147 void MarkUnsafe(AllocaInfo &I, Instruction *User) { 148 I.isUnsafe = true; 149 DEBUG(dbgs() << " Transformation preventing inst: " << *User << '\n'); 150 } 151 152 bool isSafeAllocaToScalarRepl(AllocaInst *AI); 153 154 void isSafeForScalarRepl(Instruction *I, uint64_t Offset, AllocaInfo &Info); 155 void isSafePHISelectUseForScalarRepl(Instruction *User, uint64_t Offset, 156 AllocaInfo &Info); 157 void isSafeGEP(GetElementPtrInst *GEPI, uint64_t &Offset, AllocaInfo &Info); 158 void isSafeMemAccess(uint64_t Offset, uint64_t MemSize, 159 Type *MemOpType, bool isStore, AllocaInfo &Info, 160 Instruction *TheAccess, bool AllowWholeAccess); 161 bool TypeHasComponent(Type *T, uint64_t Offset, uint64_t Size); 162 uint64_t FindElementAndOffset(Type *&T, uint64_t &Offset, 163 Type *&IdxTy); 164 165 void DoScalarReplacement(AllocaInst *AI, 166 std::vector<AllocaInst*> &WorkList); 167 void DeleteDeadInstructions(); 168 169 void RewriteForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset, 170 SmallVector<AllocaInst*, 32> &NewElts); 171 void RewriteBitCast(BitCastInst *BC, AllocaInst *AI, uint64_t Offset, 172 SmallVector<AllocaInst*, 32> &NewElts); 173 void RewriteGEP(GetElementPtrInst *GEPI, AllocaInst *AI, uint64_t Offset, 174 SmallVector<AllocaInst*, 32> &NewElts); 175 void RewriteLifetimeIntrinsic(IntrinsicInst *II, AllocaInst *AI, 176 uint64_t Offset, 177 SmallVector<AllocaInst*, 32> &NewElts); 178 void RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *Inst, 179 AllocaInst *AI, 180 SmallVector<AllocaInst*, 32> &NewElts); 181 void RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocaInst *AI, 182 SmallVector<AllocaInst*, 32> &NewElts); 183 void RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocaInst *AI, 184 SmallVector<AllocaInst*, 32> &NewElts); 185 bool ShouldAttemptScalarRepl(AllocaInst *AI); 186 187 static MemTransferInst *isOnlyCopiedFromConstantGlobal( 188 AllocaInst *AI, SmallVector<Instruction*, 4> &ToDelete); 189 }; 190 191 // SROA_DT - SROA that uses DominatorTree. 192 struct SROA_DT : public SROA { 193 static char ID; 194 public: 195 SROA_DT(int T = -1, int ST = -1, int AT = -1, int SLT = -1) : 196 SROA(T, true, ID, ST, AT, SLT) { 197 initializeSROA_DTPass(*PassRegistry::getPassRegistry()); 198 } 199 200 // getAnalysisUsage - This pass does not require any passes, but we know it 201 // will not alter the CFG, so say so. 202 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 203 AU.addRequired<DominatorTree>(); 204 AU.setPreservesCFG(); 205 } 206 }; 207 208 // SROA_SSAUp - SROA that uses SSAUpdater. 209 struct SROA_SSAUp : public SROA { 210 static char ID; 211 public: 212 SROA_SSAUp(int T = -1, int ST = -1, int AT = -1, int SLT = -1) : 213 SROA(T, false, ID, ST, AT, SLT) { 214 initializeSROA_SSAUpPass(*PassRegistry::getPassRegistry()); 215 } 216 217 // getAnalysisUsage - This pass does not require any passes, but we know it 218 // will not alter the CFG, so say so. 219 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 220 AU.setPreservesCFG(); 221 } 222 }; 223 224} 225 226char SROA_DT::ID = 0; 227char SROA_SSAUp::ID = 0; 228 229INITIALIZE_PASS_BEGIN(SROA_DT, "scalarrepl", 230 "Scalar Replacement of Aggregates (DT)", false, false) 231INITIALIZE_PASS_DEPENDENCY(DominatorTree) 232INITIALIZE_PASS_END(SROA_DT, "scalarrepl", 233 "Scalar Replacement of Aggregates (DT)", false, false) 234 235INITIALIZE_PASS_BEGIN(SROA_SSAUp, "scalarrepl-ssa", 236 "Scalar Replacement of Aggregates (SSAUp)", false, false) 237INITIALIZE_PASS_END(SROA_SSAUp, "scalarrepl-ssa", 238 "Scalar Replacement of Aggregates (SSAUp)", false, false) 239 240// Public interface to the ScalarReplAggregates pass 241FunctionPass *llvm::createScalarReplAggregatesPass(int Threshold, 242 bool UseDomTree, 243 int StructMemberThreshold, 244 int ArrayElementThreshold, 245 int ScalarLoadThreshold) { 246 if (UseDomTree) 247 return new SROA_DT(Threshold, StructMemberThreshold, ArrayElementThreshold, 248 ScalarLoadThreshold); 249 return new SROA_SSAUp(Threshold, StructMemberThreshold, 250 ArrayElementThreshold, ScalarLoadThreshold); 251} 252 253 254//===----------------------------------------------------------------------===// 255// Convert To Scalar Optimization. 256//===----------------------------------------------------------------------===// 257 258namespace { 259/// ConvertToScalarInfo - This class implements the "Convert To Scalar" 260/// optimization, which scans the uses of an alloca and determines if it can 261/// rewrite it in terms of a single new alloca that can be mem2reg'd. 262class ConvertToScalarInfo { 263 /// AllocaSize - The size of the alloca being considered in bytes. 264 unsigned AllocaSize; 265 const TargetData &TD; 266 unsigned ScalarLoadThreshold; 267 268 /// IsNotTrivial - This is set to true if there is some access to the object 269 /// which means that mem2reg can't promote it. 270 bool IsNotTrivial; 271 272 /// ScalarKind - Tracks the kind of alloca being considered for promotion, 273 /// computed based on the uses of the alloca rather than the LLVM type system. 274 enum { 275 Unknown, 276 277 // Accesses via GEPs that are consistent with element access of a vector 278 // type. This will not be converted into a vector unless there is a later 279 // access using an actual vector type. 280 ImplicitVector, 281 282 // Accesses via vector operations and GEPs that are consistent with the 283 // layout of a vector type. 284 Vector, 285 286 // An integer bag-of-bits with bitwise operations for insertion and 287 // extraction. Any combination of types can be converted into this kind 288 // of scalar. 289 Integer 290 } ScalarKind; 291 292 /// VectorTy - This tracks the type that we should promote the vector to if 293 /// it is possible to turn it into a vector. This starts out null, and if it 294 /// isn't possible to turn into a vector type, it gets set to VoidTy. 295 VectorType *VectorTy; 296 297 /// HadNonMemTransferAccess - True if there is at least one access to the 298 /// alloca that is not a MemTransferInst. We don't want to turn structs into 299 /// large integers unless there is some potential for optimization. 300 bool HadNonMemTransferAccess; 301 302 /// HadDynamicAccess - True if some element of this alloca was dynamic. 303 /// We don't yet have support for turning a dynamic access into a large 304 /// integer. 305 bool HadDynamicAccess; 306 307public: 308 explicit ConvertToScalarInfo(unsigned Size, const TargetData &td, 309 unsigned SLT) 310 : AllocaSize(Size), TD(td), ScalarLoadThreshold(SLT), IsNotTrivial(false), 311 ScalarKind(Unknown), VectorTy(0), HadNonMemTransferAccess(false), 312 HadDynamicAccess(false) { } 313 314 AllocaInst *TryConvert(AllocaInst *AI); 315 316private: 317 bool CanConvertToScalar(Value *V, uint64_t Offset, Value* NonConstantIdx); 318 void MergeInTypeForLoadOrStore(Type *In, uint64_t Offset); 319 bool MergeInVectorType(VectorType *VInTy, uint64_t Offset); 320 void ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, uint64_t Offset, 321 Value *NonConstantIdx); 322 323 Value *ConvertScalar_ExtractValue(Value *NV, Type *ToType, 324 uint64_t Offset, Value* NonConstantIdx, 325 IRBuilder<> &Builder); 326 Value *ConvertScalar_InsertValue(Value *StoredVal, Value *ExistingVal, 327 uint64_t Offset, Value* NonConstantIdx, 328 IRBuilder<> &Builder); 329}; 330} // end anonymous namespace. 331 332 333/// TryConvert - Analyze the specified alloca, and if it is safe to do so, 334/// rewrite it to be a new alloca which is mem2reg'able. This returns the new 335/// alloca if possible or null if not. 336AllocaInst *ConvertToScalarInfo::TryConvert(AllocaInst *AI) { 337 // If we can't convert this scalar, or if mem2reg can trivially do it, bail 338 // out. 339 if (!CanConvertToScalar(AI, 0, 0) || !IsNotTrivial) 340 return 0; 341 342 // If an alloca has only memset / memcpy uses, it may still have an Unknown 343 // ScalarKind. Treat it as an Integer below. 344 if (ScalarKind == Unknown) 345 ScalarKind = Integer; 346 347 if (ScalarKind == Vector && VectorTy->getBitWidth() != AllocaSize * 8) 348 ScalarKind = Integer; 349 350 // If we were able to find a vector type that can handle this with 351 // insert/extract elements, and if there was at least one use that had 352 // a vector type, promote this to a vector. We don't want to promote 353 // random stuff that doesn't use vectors (e.g. <9 x double>) because then 354 // we just get a lot of insert/extracts. If at least one vector is 355 // involved, then we probably really do have a union of vector/array. 356 Type *NewTy; 357 if (ScalarKind == Vector) { 358 assert(VectorTy && "Missing type for vector scalar."); 359 DEBUG(dbgs() << "CONVERT TO VECTOR: " << *AI << "\n TYPE = " 360 << *VectorTy << '\n'); 361 NewTy = VectorTy; // Use the vector type. 362 } else { 363 unsigned BitWidth = AllocaSize * 8; 364 365 // Do not convert to scalar integer if the alloca size exceeds the 366 // scalar load threshold. 367 if (BitWidth > ScalarLoadThreshold) 368 return 0; 369 370 if ((ScalarKind == ImplicitVector || ScalarKind == Integer) && 371 !HadNonMemTransferAccess && !TD.fitsInLegalInteger(BitWidth)) 372 return 0; 373 // Dynamic accesses on integers aren't yet supported. They need us to shift 374 // by a dynamic amount which could be difficult to work out as we might not 375 // know whether to use a left or right shift. 376 if (ScalarKind == Integer && HadDynamicAccess) 377 return 0; 378 379 DEBUG(dbgs() << "CONVERT TO SCALAR INTEGER: " << *AI << "\n"); 380 // Create and insert the integer alloca. 381 NewTy = IntegerType::get(AI->getContext(), BitWidth); 382 } 383 AllocaInst *NewAI = new AllocaInst(NewTy, 0, "", AI->getParent()->begin()); 384 ConvertUsesToScalar(AI, NewAI, 0, 0); 385 return NewAI; 386} 387 388/// MergeInTypeForLoadOrStore - Add the 'In' type to the accumulated vector type 389/// (VectorTy) so far at the offset specified by Offset (which is specified in 390/// bytes). 391/// 392/// There are two cases we handle here: 393/// 1) A union of vector types of the same size and potentially its elements. 394/// Here we turn element accesses into insert/extract element operations. 395/// This promotes a <4 x float> with a store of float to the third element 396/// into a <4 x float> that uses insert element. 397/// 2) A fully general blob of memory, which we turn into some (potentially 398/// large) integer type with extract and insert operations where the loads 399/// and stores would mutate the memory. We mark this by setting VectorTy 400/// to VoidTy. 401void ConvertToScalarInfo::MergeInTypeForLoadOrStore(Type *In, 402 uint64_t Offset) { 403 // If we already decided to turn this into a blob of integer memory, there is 404 // nothing to be done. 405 if (ScalarKind == Integer) 406 return; 407 408 // If this could be contributing to a vector, analyze it. 409 410 // If the In type is a vector that is the same size as the alloca, see if it 411 // matches the existing VecTy. 412 if (VectorType *VInTy = dyn_cast<VectorType>(In)) { 413 if (MergeInVectorType(VInTy, Offset)) 414 return; 415 } else if (In->isFloatTy() || In->isDoubleTy() || 416 (In->isIntegerTy() && In->getPrimitiveSizeInBits() >= 8 && 417 isPowerOf2_32(In->getPrimitiveSizeInBits()))) { 418 // Full width accesses can be ignored, because they can always be turned 419 // into bitcasts. 420 unsigned EltSize = In->getPrimitiveSizeInBits()/8; 421 if (EltSize == AllocaSize) 422 return; 423 424 // If we're accessing something that could be an element of a vector, see 425 // if the implied vector agrees with what we already have and if Offset is 426 // compatible with it. 427 if (Offset % EltSize == 0 && AllocaSize % EltSize == 0 && 428 (!VectorTy || EltSize == VectorTy->getElementType() 429 ->getPrimitiveSizeInBits()/8)) { 430 if (!VectorTy) { 431 ScalarKind = ImplicitVector; 432 VectorTy = VectorType::get(In, AllocaSize/EltSize); 433 } 434 return; 435 } 436 } 437 438 // Otherwise, we have a case that we can't handle with an optimized vector 439 // form. We can still turn this into a large integer. 440 ScalarKind = Integer; 441} 442 443/// MergeInVectorType - Handles the vector case of MergeInTypeForLoadOrStore, 444/// returning true if the type was successfully merged and false otherwise. 445bool ConvertToScalarInfo::MergeInVectorType(VectorType *VInTy, 446 uint64_t Offset) { 447 if (VInTy->getBitWidth()/8 == AllocaSize && Offset == 0) { 448 // If we're storing/loading a vector of the right size, allow it as a 449 // vector. If this the first vector we see, remember the type so that 450 // we know the element size. If this is a subsequent access, ignore it 451 // even if it is a differing type but the same size. Worst case we can 452 // bitcast the resultant vectors. 453 if (!VectorTy) 454 VectorTy = VInTy; 455 ScalarKind = Vector; 456 return true; 457 } 458 459 return false; 460} 461 462/// CanConvertToScalar - V is a pointer. If we can convert the pointee and all 463/// its accesses to a single vector type, return true and set VecTy to 464/// the new type. If we could convert the alloca into a single promotable 465/// integer, return true but set VecTy to VoidTy. Further, if the use is not a 466/// completely trivial use that mem2reg could promote, set IsNotTrivial. Offset 467/// is the current offset from the base of the alloca being analyzed. 468/// 469/// If we see at least one access to the value that is as a vector type, set the 470/// SawVec flag. 471bool ConvertToScalarInfo::CanConvertToScalar(Value *V, uint64_t Offset, 472 Value* NonConstantIdx) { 473 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) { 474 Instruction *User = cast<Instruction>(*UI); 475 476 if (LoadInst *LI = dyn_cast<LoadInst>(User)) { 477 // Don't break volatile loads. 478 if (!LI->isSimple()) 479 return false; 480 // Don't touch MMX operations. 481 if (LI->getType()->isX86_MMXTy()) 482 return false; 483 HadNonMemTransferAccess = true; 484 MergeInTypeForLoadOrStore(LI->getType(), Offset); 485 continue; 486 } 487 488 if (StoreInst *SI = dyn_cast<StoreInst>(User)) { 489 // Storing the pointer, not into the value? 490 if (SI->getOperand(0) == V || !SI->isSimple()) return false; 491 // Don't touch MMX operations. 492 if (SI->getOperand(0)->getType()->isX86_MMXTy()) 493 return false; 494 HadNonMemTransferAccess = true; 495 MergeInTypeForLoadOrStore(SI->getOperand(0)->getType(), Offset); 496 continue; 497 } 498 499 if (BitCastInst *BCI = dyn_cast<BitCastInst>(User)) { 500 if (!onlyUsedByLifetimeMarkers(BCI)) 501 IsNotTrivial = true; // Can't be mem2reg'd. 502 if (!CanConvertToScalar(BCI, Offset, NonConstantIdx)) 503 return false; 504 continue; 505 } 506 507 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) { 508 // If this is a GEP with a variable indices, we can't handle it. 509 PointerType* PtrTy = dyn_cast<PointerType>(GEP->getPointerOperandType()); 510 if (!PtrTy) 511 return false; 512 513 // Compute the offset that this GEP adds to the pointer. 514 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end()); 515 Value *GEPNonConstantIdx = 0; 516 if (!GEP->hasAllConstantIndices()) { 517 if (!isa<VectorType>(PtrTy->getElementType())) 518 return false; 519 if (NonConstantIdx) 520 return false; 521 GEPNonConstantIdx = Indices.pop_back_val(); 522 if (!GEPNonConstantIdx->getType()->isIntegerTy(32)) 523 return false; 524 HadDynamicAccess = true; 525 } else 526 GEPNonConstantIdx = NonConstantIdx; 527 uint64_t GEPOffset = TD.getIndexedOffset(PtrTy, 528 Indices); 529 // See if all uses can be converted. 530 if (!CanConvertToScalar(GEP, Offset+GEPOffset, GEPNonConstantIdx)) 531 return false; 532 IsNotTrivial = true; // Can't be mem2reg'd. 533 HadNonMemTransferAccess = true; 534 continue; 535 } 536 537 // If this is a constant sized memset of a constant value (e.g. 0) we can 538 // handle it. 539 if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) { 540 // Store to dynamic index. 541 if (NonConstantIdx) 542 return false; 543 // Store of constant value. 544 if (!isa<ConstantInt>(MSI->getValue())) 545 return false; 546 547 // Store of constant size. 548 ConstantInt *Len = dyn_cast<ConstantInt>(MSI->getLength()); 549 if (!Len) 550 return false; 551 552 // If the size differs from the alloca, we can only convert the alloca to 553 // an integer bag-of-bits. 554 // FIXME: This should handle all of the cases that are currently accepted 555 // as vector element insertions. 556 if (Len->getZExtValue() != AllocaSize || Offset != 0) 557 ScalarKind = Integer; 558 559 IsNotTrivial = true; // Can't be mem2reg'd. 560 HadNonMemTransferAccess = true; 561 continue; 562 } 563 564 // If this is a memcpy or memmove into or out of the whole allocation, we 565 // can handle it like a load or store of the scalar type. 566 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) { 567 // Store to dynamic index. 568 if (NonConstantIdx) 569 return false; 570 ConstantInt *Len = dyn_cast<ConstantInt>(MTI->getLength()); 571 if (Len == 0 || Len->getZExtValue() != AllocaSize || Offset != 0) 572 return false; 573 574 IsNotTrivial = true; // Can't be mem2reg'd. 575 continue; 576 } 577 578 // If this is a lifetime intrinsic, we can handle it. 579 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(User)) { 580 if (II->getIntrinsicID() == Intrinsic::lifetime_start || 581 II->getIntrinsicID() == Intrinsic::lifetime_end) { 582 continue; 583 } 584 } 585 586 // Otherwise, we cannot handle this! 587 return false; 588 } 589 590 return true; 591} 592 593/// ConvertUsesToScalar - Convert all of the users of Ptr to use the new alloca 594/// directly. This happens when we are converting an "integer union" to a 595/// single integer scalar, or when we are converting a "vector union" to a 596/// vector with insert/extractelement instructions. 597/// 598/// Offset is an offset from the original alloca, in bits that need to be 599/// shifted to the right. By the end of this, there should be no uses of Ptr. 600void ConvertToScalarInfo::ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, 601 uint64_t Offset, 602 Value* NonConstantIdx) { 603 while (!Ptr->use_empty()) { 604 Instruction *User = cast<Instruction>(Ptr->use_back()); 605 606 if (BitCastInst *CI = dyn_cast<BitCastInst>(User)) { 607 ConvertUsesToScalar(CI, NewAI, Offset, NonConstantIdx); 608 CI->eraseFromParent(); 609 continue; 610 } 611 612 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) { 613 // Compute the offset that this GEP adds to the pointer. 614 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end()); 615 Value* GEPNonConstantIdx = 0; 616 if (!GEP->hasAllConstantIndices()) { 617 assert(!NonConstantIdx && 618 "Dynamic GEP reading from dynamic GEP unsupported"); 619 GEPNonConstantIdx = Indices.pop_back_val(); 620 } else 621 GEPNonConstantIdx = NonConstantIdx; 622 uint64_t GEPOffset = TD.getIndexedOffset(GEP->getPointerOperandType(), 623 Indices); 624 ConvertUsesToScalar(GEP, NewAI, Offset+GEPOffset*8, GEPNonConstantIdx); 625 GEP->eraseFromParent(); 626 continue; 627 } 628 629 IRBuilder<> Builder(User); 630 631 if (LoadInst *LI = dyn_cast<LoadInst>(User)) { 632 // The load is a bit extract from NewAI shifted right by Offset bits. 633 Value *LoadedVal = Builder.CreateLoad(NewAI); 634 Value *NewLoadVal 635 = ConvertScalar_ExtractValue(LoadedVal, LI->getType(), Offset, 636 NonConstantIdx, Builder); 637 LI->replaceAllUsesWith(NewLoadVal); 638 LI->eraseFromParent(); 639 continue; 640 } 641 642 if (StoreInst *SI = dyn_cast<StoreInst>(User)) { 643 assert(SI->getOperand(0) != Ptr && "Consistency error!"); 644 Instruction *Old = Builder.CreateLoad(NewAI, NewAI->getName()+".in"); 645 Value *New = ConvertScalar_InsertValue(SI->getOperand(0), Old, Offset, 646 NonConstantIdx, Builder); 647 Builder.CreateStore(New, NewAI); 648 SI->eraseFromParent(); 649 650 // If the load we just inserted is now dead, then the inserted store 651 // overwrote the entire thing. 652 if (Old->use_empty()) 653 Old->eraseFromParent(); 654 continue; 655 } 656 657 // If this is a constant sized memset of a constant value (e.g. 0) we can 658 // transform it into a store of the expanded constant value. 659 if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) { 660 assert(MSI->getRawDest() == Ptr && "Consistency error!"); 661 assert(!NonConstantIdx && "Cannot replace dynamic memset with insert"); 662 int64_t SNumBytes = cast<ConstantInt>(MSI->getLength())->getSExtValue(); 663 if (SNumBytes > 0 && (SNumBytes >> 32) == 0) { 664 unsigned NumBytes = static_cast<unsigned>(SNumBytes); 665 unsigned Val = cast<ConstantInt>(MSI->getValue())->getZExtValue(); 666 667 // Compute the value replicated the right number of times. 668 APInt APVal(NumBytes*8, Val); 669 670 // Splat the value if non-zero. 671 if (Val) 672 for (unsigned i = 1; i != NumBytes; ++i) 673 APVal |= APVal << 8; 674 675 Instruction *Old = Builder.CreateLoad(NewAI, NewAI->getName()+".in"); 676 Value *New = ConvertScalar_InsertValue( 677 ConstantInt::get(User->getContext(), APVal), 678 Old, Offset, 0, Builder); 679 Builder.CreateStore(New, NewAI); 680 681 // If the load we just inserted is now dead, then the memset overwrote 682 // the entire thing. 683 if (Old->use_empty()) 684 Old->eraseFromParent(); 685 } 686 MSI->eraseFromParent(); 687 continue; 688 } 689 690 // If this is a memcpy or memmove into or out of the whole allocation, we 691 // can handle it like a load or store of the scalar type. 692 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) { 693 assert(Offset == 0 && "must be store to start of alloca"); 694 assert(!NonConstantIdx && "Cannot replace dynamic transfer with insert"); 695 696 // If the source and destination are both to the same alloca, then this is 697 // a noop copy-to-self, just delete it. Otherwise, emit a load and store 698 // as appropriate. 699 AllocaInst *OrigAI = cast<AllocaInst>(GetUnderlyingObject(Ptr, &TD, 0)); 700 701 if (GetUnderlyingObject(MTI->getSource(), &TD, 0) != OrigAI) { 702 // Dest must be OrigAI, change this to be a load from the original 703 // pointer (bitcasted), then a store to our new alloca. 704 assert(MTI->getRawDest() == Ptr && "Neither use is of pointer?"); 705 Value *SrcPtr = MTI->getSource(); 706 PointerType* SPTy = cast<PointerType>(SrcPtr->getType()); 707 PointerType* AIPTy = cast<PointerType>(NewAI->getType()); 708 if (SPTy->getAddressSpace() != AIPTy->getAddressSpace()) { 709 AIPTy = PointerType::get(AIPTy->getElementType(), 710 SPTy->getAddressSpace()); 711 } 712 SrcPtr = Builder.CreateBitCast(SrcPtr, AIPTy); 713 714 LoadInst *SrcVal = Builder.CreateLoad(SrcPtr, "srcval"); 715 SrcVal->setAlignment(MTI->getAlignment()); 716 Builder.CreateStore(SrcVal, NewAI); 717 } else if (GetUnderlyingObject(MTI->getDest(), &TD, 0) != OrigAI) { 718 // Src must be OrigAI, change this to be a load from NewAI then a store 719 // through the original dest pointer (bitcasted). 720 assert(MTI->getRawSource() == Ptr && "Neither use is of pointer?"); 721 LoadInst *SrcVal = Builder.CreateLoad(NewAI, "srcval"); 722 723 PointerType* DPTy = cast<PointerType>(MTI->getDest()->getType()); 724 PointerType* AIPTy = cast<PointerType>(NewAI->getType()); 725 if (DPTy->getAddressSpace() != AIPTy->getAddressSpace()) { 726 AIPTy = PointerType::get(AIPTy->getElementType(), 727 DPTy->getAddressSpace()); 728 } 729 Value *DstPtr = Builder.CreateBitCast(MTI->getDest(), AIPTy); 730 731 StoreInst *NewStore = Builder.CreateStore(SrcVal, DstPtr); 732 NewStore->setAlignment(MTI->getAlignment()); 733 } else { 734 // Noop transfer. Src == Dst 735 } 736 737 MTI->eraseFromParent(); 738 continue; 739 } 740 741 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(User)) { 742 if (II->getIntrinsicID() == Intrinsic::lifetime_start || 743 II->getIntrinsicID() == Intrinsic::lifetime_end) { 744 // There's no need to preserve these, as the resulting alloca will be 745 // converted to a register anyways. 746 II->eraseFromParent(); 747 continue; 748 } 749 } 750 751 llvm_unreachable("Unsupported operation!"); 752 } 753} 754 755/// ConvertScalar_ExtractValue - Extract a value of type ToType from an integer 756/// or vector value FromVal, extracting the bits from the offset specified by 757/// Offset. This returns the value, which is of type ToType. 758/// 759/// This happens when we are converting an "integer union" to a single 760/// integer scalar, or when we are converting a "vector union" to a vector with 761/// insert/extractelement instructions. 762/// 763/// Offset is an offset from the original alloca, in bits that need to be 764/// shifted to the right. 765Value *ConvertToScalarInfo:: 766ConvertScalar_ExtractValue(Value *FromVal, Type *ToType, 767 uint64_t Offset, Value* NonConstantIdx, 768 IRBuilder<> &Builder) { 769 // If the load is of the whole new alloca, no conversion is needed. 770 Type *FromType = FromVal->getType(); 771 if (FromType == ToType && Offset == 0) 772 return FromVal; 773 774 // If the result alloca is a vector type, this is either an element 775 // access or a bitcast to another vector type of the same size. 776 if (VectorType *VTy = dyn_cast<VectorType>(FromType)) { 777 unsigned FromTypeSize = TD.getTypeAllocSize(FromType); 778 unsigned ToTypeSize = TD.getTypeAllocSize(ToType); 779 if (FromTypeSize == ToTypeSize) 780 return Builder.CreateBitCast(FromVal, ToType); 781 782 // Otherwise it must be an element access. 783 unsigned Elt = 0; 784 if (Offset) { 785 unsigned EltSize = TD.getTypeAllocSizeInBits(VTy->getElementType()); 786 Elt = Offset/EltSize; 787 assert(EltSize*Elt == Offset && "Invalid modulus in validity checking"); 788 } 789 // Return the element extracted out of it. 790 Value *Idx; 791 if (NonConstantIdx) { 792 if (Elt) 793 Idx = Builder.CreateAdd(NonConstantIdx, 794 Builder.getInt32(Elt), 795 "dyn.offset"); 796 else 797 Idx = NonConstantIdx; 798 } else 799 Idx = Builder.getInt32(Elt); 800 Value *V = Builder.CreateExtractElement(FromVal, Idx); 801 if (V->getType() != ToType) 802 V = Builder.CreateBitCast(V, ToType); 803 return V; 804 } 805 806 // If ToType is a first class aggregate, extract out each of the pieces and 807 // use insertvalue's to form the FCA. 808 if (StructType *ST = dyn_cast<StructType>(ToType)) { 809 assert(!NonConstantIdx && 810 "Dynamic indexing into struct types not supported"); 811 const StructLayout &Layout = *TD.getStructLayout(ST); 812 Value *Res = UndefValue::get(ST); 813 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) { 814 Value *Elt = ConvertScalar_ExtractValue(FromVal, ST->getElementType(i), 815 Offset+Layout.getElementOffsetInBits(i), 816 0, Builder); 817 Res = Builder.CreateInsertValue(Res, Elt, i); 818 } 819 return Res; 820 } 821 822 if (ArrayType *AT = dyn_cast<ArrayType>(ToType)) { 823 assert(!NonConstantIdx && 824 "Dynamic indexing into array types not supported"); 825 uint64_t EltSize = TD.getTypeAllocSizeInBits(AT->getElementType()); 826 Value *Res = UndefValue::get(AT); 827 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) { 828 Value *Elt = ConvertScalar_ExtractValue(FromVal, AT->getElementType(), 829 Offset+i*EltSize, 0, Builder); 830 Res = Builder.CreateInsertValue(Res, Elt, i); 831 } 832 return Res; 833 } 834 835 // Otherwise, this must be a union that was converted to an integer value. 836 IntegerType *NTy = cast<IntegerType>(FromVal->getType()); 837 838 // If this is a big-endian system and the load is narrower than the 839 // full alloca type, we need to do a shift to get the right bits. 840 int ShAmt = 0; 841 if (TD.isBigEndian()) { 842 // On big-endian machines, the lowest bit is stored at the bit offset 843 // from the pointer given by getTypeStoreSizeInBits. This matters for 844 // integers with a bitwidth that is not a multiple of 8. 845 ShAmt = TD.getTypeStoreSizeInBits(NTy) - 846 TD.getTypeStoreSizeInBits(ToType) - Offset; 847 } else { 848 ShAmt = Offset; 849 } 850 851 // Note: we support negative bitwidths (with shl) which are not defined. 852 // We do this to support (f.e.) loads off the end of a structure where 853 // only some bits are used. 854 if (ShAmt > 0 && (unsigned)ShAmt < NTy->getBitWidth()) 855 FromVal = Builder.CreateLShr(FromVal, 856 ConstantInt::get(FromVal->getType(), ShAmt)); 857 else if (ShAmt < 0 && (unsigned)-ShAmt < NTy->getBitWidth()) 858 FromVal = Builder.CreateShl(FromVal, 859 ConstantInt::get(FromVal->getType(), -ShAmt)); 860 861 // Finally, unconditionally truncate the integer to the right width. 862 unsigned LIBitWidth = TD.getTypeSizeInBits(ToType); 863 if (LIBitWidth < NTy->getBitWidth()) 864 FromVal = 865 Builder.CreateTrunc(FromVal, IntegerType::get(FromVal->getContext(), 866 LIBitWidth)); 867 else if (LIBitWidth > NTy->getBitWidth()) 868 FromVal = 869 Builder.CreateZExt(FromVal, IntegerType::get(FromVal->getContext(), 870 LIBitWidth)); 871 872 // If the result is an integer, this is a trunc or bitcast. 873 if (ToType->isIntegerTy()) { 874 // Should be done. 875 } else if (ToType->isFloatingPointTy() || ToType->isVectorTy()) { 876 // Just do a bitcast, we know the sizes match up. 877 FromVal = Builder.CreateBitCast(FromVal, ToType); 878 } else { 879 // Otherwise must be a pointer. 880 FromVal = Builder.CreateIntToPtr(FromVal, ToType); 881 } 882 assert(FromVal->getType() == ToType && "Didn't convert right?"); 883 return FromVal; 884} 885 886/// ConvertScalar_InsertValue - Insert the value "SV" into the existing integer 887/// or vector value "Old" at the offset specified by Offset. 888/// 889/// This happens when we are converting an "integer union" to a 890/// single integer scalar, or when we are converting a "vector union" to a 891/// vector with insert/extractelement instructions. 892/// 893/// Offset is an offset from the original alloca, in bits that need to be 894/// shifted to the right. 895/// 896/// NonConstantIdx is an index value if there was a GEP with a non-constant 897/// index value. If this is 0 then all GEPs used to find this insert address 898/// are constant. 899Value *ConvertToScalarInfo:: 900ConvertScalar_InsertValue(Value *SV, Value *Old, 901 uint64_t Offset, Value* NonConstantIdx, 902 IRBuilder<> &Builder) { 903 // Convert the stored type to the actual type, shift it left to insert 904 // then 'or' into place. 905 Type *AllocaType = Old->getType(); 906 LLVMContext &Context = Old->getContext(); 907 908 if (VectorType *VTy = dyn_cast<VectorType>(AllocaType)) { 909 uint64_t VecSize = TD.getTypeAllocSizeInBits(VTy); 910 uint64_t ValSize = TD.getTypeAllocSizeInBits(SV->getType()); 911 912 // Changing the whole vector with memset or with an access of a different 913 // vector type? 914 if (ValSize == VecSize) 915 return Builder.CreateBitCast(SV, AllocaType); 916 917 // Must be an element insertion. 918 Type *EltTy = VTy->getElementType(); 919 if (SV->getType() != EltTy) 920 SV = Builder.CreateBitCast(SV, EltTy); 921 uint64_t EltSize = TD.getTypeAllocSizeInBits(EltTy); 922 unsigned Elt = Offset/EltSize; 923 Value *Idx; 924 if (NonConstantIdx) { 925 if (Elt) 926 Idx = Builder.CreateAdd(NonConstantIdx, 927 Builder.getInt32(Elt), 928 "dyn.offset"); 929 else 930 Idx = NonConstantIdx; 931 } else 932 Idx = Builder.getInt32(Elt); 933 return Builder.CreateInsertElement(Old, SV, Idx); 934 } 935 936 // If SV is a first-class aggregate value, insert each value recursively. 937 if (StructType *ST = dyn_cast<StructType>(SV->getType())) { 938 assert(!NonConstantIdx && 939 "Dynamic indexing into struct types not supported"); 940 const StructLayout &Layout = *TD.getStructLayout(ST); 941 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) { 942 Value *Elt = Builder.CreateExtractValue(SV, i); 943 Old = ConvertScalar_InsertValue(Elt, Old, 944 Offset+Layout.getElementOffsetInBits(i), 945 0, Builder); 946 } 947 return Old; 948 } 949 950 if (ArrayType *AT = dyn_cast<ArrayType>(SV->getType())) { 951 assert(!NonConstantIdx && 952 "Dynamic indexing into array types not supported"); 953 uint64_t EltSize = TD.getTypeAllocSizeInBits(AT->getElementType()); 954 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) { 955 Value *Elt = Builder.CreateExtractValue(SV, i); 956 Old = ConvertScalar_InsertValue(Elt, Old, Offset+i*EltSize, 0, Builder); 957 } 958 return Old; 959 } 960 961 // If SV is a float, convert it to the appropriate integer type. 962 // If it is a pointer, do the same. 963 unsigned SrcWidth = TD.getTypeSizeInBits(SV->getType()); 964 unsigned DestWidth = TD.getTypeSizeInBits(AllocaType); 965 unsigned SrcStoreWidth = TD.getTypeStoreSizeInBits(SV->getType()); 966 unsigned DestStoreWidth = TD.getTypeStoreSizeInBits(AllocaType); 967 if (SV->getType()->isFloatingPointTy() || SV->getType()->isVectorTy()) 968 SV = Builder.CreateBitCast(SV, IntegerType::get(SV->getContext(),SrcWidth)); 969 else if (SV->getType()->isPointerTy()) 970 SV = Builder.CreatePtrToInt(SV, TD.getIntPtrType(SV->getContext())); 971 972 // Zero extend or truncate the value if needed. 973 if (SV->getType() != AllocaType) { 974 if (SV->getType()->getPrimitiveSizeInBits() < 975 AllocaType->getPrimitiveSizeInBits()) 976 SV = Builder.CreateZExt(SV, AllocaType); 977 else { 978 // Truncation may be needed if storing more than the alloca can hold 979 // (undefined behavior). 980 SV = Builder.CreateTrunc(SV, AllocaType); 981 SrcWidth = DestWidth; 982 SrcStoreWidth = DestStoreWidth; 983 } 984 } 985 986 // If this is a big-endian system and the store is narrower than the 987 // full alloca type, we need to do a shift to get the right bits. 988 int ShAmt = 0; 989 if (TD.isBigEndian()) { 990 // On big-endian machines, the lowest bit is stored at the bit offset 991 // from the pointer given by getTypeStoreSizeInBits. This matters for 992 // integers with a bitwidth that is not a multiple of 8. 993 ShAmt = DestStoreWidth - SrcStoreWidth - Offset; 994 } else { 995 ShAmt = Offset; 996 } 997 998 // Note: we support negative bitwidths (with shr) which are not defined. 999 // We do this to support (f.e.) stores off the end of a structure where 1000 // only some bits in the structure are set. 1001 APInt Mask(APInt::getLowBitsSet(DestWidth, SrcWidth)); 1002 if (ShAmt > 0 && (unsigned)ShAmt < DestWidth) { 1003 SV = Builder.CreateShl(SV, ConstantInt::get(SV->getType(), ShAmt)); 1004 Mask <<= ShAmt; 1005 } else if (ShAmt < 0 && (unsigned)-ShAmt < DestWidth) { 1006 SV = Builder.CreateLShr(SV, ConstantInt::get(SV->getType(), -ShAmt)); 1007 Mask = Mask.lshr(-ShAmt); 1008 } 1009 1010 // Mask out the bits we are about to insert from the old value, and or 1011 // in the new bits. 1012 if (SrcWidth != DestWidth) { 1013 assert(DestWidth > SrcWidth); 1014 Old = Builder.CreateAnd(Old, ConstantInt::get(Context, ~Mask), "mask"); 1015 SV = Builder.CreateOr(Old, SV, "ins"); 1016 } 1017 return SV; 1018} 1019 1020 1021//===----------------------------------------------------------------------===// 1022// SRoA Driver 1023//===----------------------------------------------------------------------===// 1024 1025 1026bool SROA::runOnFunction(Function &F) { 1027 TD = getAnalysisIfAvailable<TargetData>(); 1028 1029 bool Changed = performPromotion(F); 1030 1031 // FIXME: ScalarRepl currently depends on TargetData more than it 1032 // theoretically needs to. It should be refactored in order to support 1033 // target-independent IR. Until this is done, just skip the actual 1034 // scalar-replacement portion of this pass. 1035 if (!TD) return Changed; 1036 1037 while (1) { 1038 bool LocalChange = performScalarRepl(F); 1039 if (!LocalChange) break; // No need to repromote if no scalarrepl 1040 Changed = true; 1041 LocalChange = performPromotion(F); 1042 if (!LocalChange) break; // No need to re-scalarrepl if no promotion 1043 } 1044 1045 return Changed; 1046} 1047 1048namespace { 1049class AllocaPromoter : public LoadAndStorePromoter { 1050 AllocaInst *AI; 1051 DIBuilder *DIB; 1052 SmallVector<DbgDeclareInst *, 4> DDIs; 1053 SmallVector<DbgValueInst *, 4> DVIs; 1054public: 1055 AllocaPromoter(const SmallVectorImpl<Instruction*> &Insts, SSAUpdater &S, 1056 DIBuilder *DB) 1057 : LoadAndStorePromoter(Insts, S), AI(0), DIB(DB) {} 1058 1059 void run(AllocaInst *AI, const SmallVectorImpl<Instruction*> &Insts) { 1060 // Remember which alloca we're promoting (for isInstInList). 1061 this->AI = AI; 1062 if (MDNode *DebugNode = MDNode::getIfExists(AI->getContext(), AI)) { 1063 for (Value::use_iterator UI = DebugNode->use_begin(), 1064 E = DebugNode->use_end(); UI != E; ++UI) 1065 if (DbgDeclareInst *DDI = dyn_cast<DbgDeclareInst>(*UI)) 1066 DDIs.push_back(DDI); 1067 else if (DbgValueInst *DVI = dyn_cast<DbgValueInst>(*UI)) 1068 DVIs.push_back(DVI); 1069 } 1070 1071 LoadAndStorePromoter::run(Insts); 1072 AI->eraseFromParent(); 1073 for (SmallVector<DbgDeclareInst *, 4>::iterator I = DDIs.begin(), 1074 E = DDIs.end(); I != E; ++I) { 1075 DbgDeclareInst *DDI = *I; 1076 DDI->eraseFromParent(); 1077 } 1078 for (SmallVector<DbgValueInst *, 4>::iterator I = DVIs.begin(), 1079 E = DVIs.end(); I != E; ++I) { 1080 DbgValueInst *DVI = *I; 1081 DVI->eraseFromParent(); 1082 } 1083 } 1084 1085 virtual bool isInstInList(Instruction *I, 1086 const SmallVectorImpl<Instruction*> &Insts) const { 1087 if (LoadInst *LI = dyn_cast<LoadInst>(I)) 1088 return LI->getOperand(0) == AI; 1089 return cast<StoreInst>(I)->getPointerOperand() == AI; 1090 } 1091 1092 virtual void updateDebugInfo(Instruction *Inst) const { 1093 for (SmallVector<DbgDeclareInst *, 4>::const_iterator I = DDIs.begin(), 1094 E = DDIs.end(); I != E; ++I) { 1095 DbgDeclareInst *DDI = *I; 1096 if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) 1097 ConvertDebugDeclareToDebugValue(DDI, SI, *DIB); 1098 else if (LoadInst *LI = dyn_cast<LoadInst>(Inst)) 1099 ConvertDebugDeclareToDebugValue(DDI, LI, *DIB); 1100 } 1101 for (SmallVector<DbgValueInst *, 4>::const_iterator I = DVIs.begin(), 1102 E = DVIs.end(); I != E; ++I) { 1103 DbgValueInst *DVI = *I; 1104 Value *Arg = NULL; 1105 if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) { 1106 // If an argument is zero extended then use argument directly. The ZExt 1107 // may be zapped by an optimization pass in future. 1108 if (ZExtInst *ZExt = dyn_cast<ZExtInst>(SI->getOperand(0))) 1109 Arg = dyn_cast<Argument>(ZExt->getOperand(0)); 1110 if (SExtInst *SExt = dyn_cast<SExtInst>(SI->getOperand(0))) 1111 Arg = dyn_cast<Argument>(SExt->getOperand(0)); 1112 if (!Arg) 1113 Arg = SI->getOperand(0); 1114 } else if (LoadInst *LI = dyn_cast<LoadInst>(Inst)) { 1115 Arg = LI->getOperand(0); 1116 } else { 1117 continue; 1118 } 1119 Instruction *DbgVal = 1120 DIB->insertDbgValueIntrinsic(Arg, 0, DIVariable(DVI->getVariable()), 1121 Inst); 1122 DbgVal->setDebugLoc(DVI->getDebugLoc()); 1123 } 1124 } 1125}; 1126} // end anon namespace 1127 1128/// isSafeSelectToSpeculate - Select instructions that use an alloca and are 1129/// subsequently loaded can be rewritten to load both input pointers and then 1130/// select between the result, allowing the load of the alloca to be promoted. 1131/// From this: 1132/// %P2 = select i1 %cond, i32* %Alloca, i32* %Other 1133/// %V = load i32* %P2 1134/// to: 1135/// %V1 = load i32* %Alloca -> will be mem2reg'd 1136/// %V2 = load i32* %Other 1137/// %V = select i1 %cond, i32 %V1, i32 %V2 1138/// 1139/// We can do this to a select if its only uses are loads and if the operand to 1140/// the select can be loaded unconditionally. 1141static bool isSafeSelectToSpeculate(SelectInst *SI, const TargetData *TD) { 1142 bool TDerefable = SI->getTrueValue()->isDereferenceablePointer(); 1143 bool FDerefable = SI->getFalseValue()->isDereferenceablePointer(); 1144 1145 for (Value::use_iterator UI = SI->use_begin(), UE = SI->use_end(); 1146 UI != UE; ++UI) { 1147 LoadInst *LI = dyn_cast<LoadInst>(*UI); 1148 if (LI == 0 || !LI->isSimple()) return false; 1149 1150 // Both operands to the select need to be dereferencable, either absolutely 1151 // (e.g. allocas) or at this point because we can see other accesses to it. 1152 if (!TDerefable && !isSafeToLoadUnconditionally(SI->getTrueValue(), LI, 1153 LI->getAlignment(), TD)) 1154 return false; 1155 if (!FDerefable && !isSafeToLoadUnconditionally(SI->getFalseValue(), LI, 1156 LI->getAlignment(), TD)) 1157 return false; 1158 } 1159 1160 return true; 1161} 1162 1163/// isSafePHIToSpeculate - PHI instructions that use an alloca and are 1164/// subsequently loaded can be rewritten to load both input pointers in the pred 1165/// blocks and then PHI the results, allowing the load of the alloca to be 1166/// promoted. 1167/// From this: 1168/// %P2 = phi [i32* %Alloca, i32* %Other] 1169/// %V = load i32* %P2 1170/// to: 1171/// %V1 = load i32* %Alloca -> will be mem2reg'd 1172/// ... 1173/// %V2 = load i32* %Other 1174/// ... 1175/// %V = phi [i32 %V1, i32 %V2] 1176/// 1177/// We can do this to a select if its only uses are loads and if the operand to 1178/// the select can be loaded unconditionally. 1179static bool isSafePHIToSpeculate(PHINode *PN, const TargetData *TD) { 1180 // For now, we can only do this promotion if the load is in the same block as 1181 // the PHI, and if there are no stores between the phi and load. 1182 // TODO: Allow recursive phi users. 1183 // TODO: Allow stores. 1184 BasicBlock *BB = PN->getParent(); 1185 unsigned MaxAlign = 0; 1186 for (Value::use_iterator UI = PN->use_begin(), UE = PN->use_end(); 1187 UI != UE; ++UI) { 1188 LoadInst *LI = dyn_cast<LoadInst>(*UI); 1189 if (LI == 0 || !LI->isSimple()) return false; 1190 1191 // For now we only allow loads in the same block as the PHI. This is a 1192 // common case that happens when instcombine merges two loads through a PHI. 1193 if (LI->getParent() != BB) return false; 1194 1195 // Ensure that there are no instructions between the PHI and the load that 1196 // could store. 1197 for (BasicBlock::iterator BBI = PN; &*BBI != LI; ++BBI) 1198 if (BBI->mayWriteToMemory()) 1199 return false; 1200 1201 MaxAlign = std::max(MaxAlign, LI->getAlignment()); 1202 } 1203 1204 // Okay, we know that we have one or more loads in the same block as the PHI. 1205 // We can transform this if it is safe to push the loads into the predecessor 1206 // blocks. The only thing to watch out for is that we can't put a possibly 1207 // trapping load in the predecessor if it is a critical edge. 1208 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) { 1209 BasicBlock *Pred = PN->getIncomingBlock(i); 1210 Value *InVal = PN->getIncomingValue(i); 1211 1212 // If the terminator of the predecessor has side-effects (an invoke), 1213 // there is no safe place to put a load in the predecessor. 1214 if (Pred->getTerminator()->mayHaveSideEffects()) 1215 return false; 1216 1217 // If the value is produced by the terminator of the predecessor 1218 // (an invoke), there is no valid place to put a load in the predecessor. 1219 if (Pred->getTerminator() == InVal) 1220 return false; 1221 1222 // If the predecessor has a single successor, then the edge isn't critical. 1223 if (Pred->getTerminator()->getNumSuccessors() == 1) 1224 continue; 1225 1226 // If this pointer is always safe to load, or if we can prove that there is 1227 // already a load in the block, then we can move the load to the pred block. 1228 if (InVal->isDereferenceablePointer() || 1229 isSafeToLoadUnconditionally(InVal, Pred->getTerminator(), MaxAlign, TD)) 1230 continue; 1231 1232 return false; 1233 } 1234 1235 return true; 1236} 1237 1238 1239/// tryToMakeAllocaBePromotable - This returns true if the alloca only has 1240/// direct (non-volatile) loads and stores to it. If the alloca is close but 1241/// not quite there, this will transform the code to allow promotion. As such, 1242/// it is a non-pure predicate. 1243static bool tryToMakeAllocaBePromotable(AllocaInst *AI, const TargetData *TD) { 1244 SetVector<Instruction*, SmallVector<Instruction*, 4>, 1245 SmallPtrSet<Instruction*, 4> > InstsToRewrite; 1246 1247 for (Value::use_iterator UI = AI->use_begin(), UE = AI->use_end(); 1248 UI != UE; ++UI) { 1249 User *U = *UI; 1250 if (LoadInst *LI = dyn_cast<LoadInst>(U)) { 1251 if (!LI->isSimple()) 1252 return false; 1253 continue; 1254 } 1255 1256 if (StoreInst *SI = dyn_cast<StoreInst>(U)) { 1257 if (SI->getOperand(0) == AI || !SI->isSimple()) 1258 return false; // Don't allow a store OF the AI, only INTO the AI. 1259 continue; 1260 } 1261 1262 if (SelectInst *SI = dyn_cast<SelectInst>(U)) { 1263 // If the condition being selected on is a constant, fold the select, yes 1264 // this does (rarely) happen early on. 1265 if (ConstantInt *CI = dyn_cast<ConstantInt>(SI->getCondition())) { 1266 Value *Result = SI->getOperand(1+CI->isZero()); 1267 SI->replaceAllUsesWith(Result); 1268 SI->eraseFromParent(); 1269 1270 // This is very rare and we just scrambled the use list of AI, start 1271 // over completely. 1272 return tryToMakeAllocaBePromotable(AI, TD); 1273 } 1274 1275 // If it is safe to turn "load (select c, AI, ptr)" into a select of two 1276 // loads, then we can transform this by rewriting the select. 1277 if (!isSafeSelectToSpeculate(SI, TD)) 1278 return false; 1279 1280 InstsToRewrite.insert(SI); 1281 continue; 1282 } 1283 1284 if (PHINode *PN = dyn_cast<PHINode>(U)) { 1285 if (PN->use_empty()) { // Dead PHIs can be stripped. 1286 InstsToRewrite.insert(PN); 1287 continue; 1288 } 1289 1290 // If it is safe to turn "load (phi [AI, ptr, ...])" into a PHI of loads 1291 // in the pred blocks, then we can transform this by rewriting the PHI. 1292 if (!isSafePHIToSpeculate(PN, TD)) 1293 return false; 1294 1295 InstsToRewrite.insert(PN); 1296 continue; 1297 } 1298 1299 if (BitCastInst *BCI = dyn_cast<BitCastInst>(U)) { 1300 if (onlyUsedByLifetimeMarkers(BCI)) { 1301 InstsToRewrite.insert(BCI); 1302 continue; 1303 } 1304 } 1305 1306 return false; 1307 } 1308 1309 // If there are no instructions to rewrite, then all uses are load/stores and 1310 // we're done! 1311 if (InstsToRewrite.empty()) 1312 return true; 1313 1314 // If we have instructions that need to be rewritten for this to be promotable 1315 // take care of it now. 1316 for (unsigned i = 0, e = InstsToRewrite.size(); i != e; ++i) { 1317 if (BitCastInst *BCI = dyn_cast<BitCastInst>(InstsToRewrite[i])) { 1318 // This could only be a bitcast used by nothing but lifetime intrinsics. 1319 for (BitCastInst::use_iterator I = BCI->use_begin(), E = BCI->use_end(); 1320 I != E;) { 1321 Use &U = I.getUse(); 1322 ++I; 1323 cast<Instruction>(U.getUser())->eraseFromParent(); 1324 } 1325 BCI->eraseFromParent(); 1326 continue; 1327 } 1328 1329 if (SelectInst *SI = dyn_cast<SelectInst>(InstsToRewrite[i])) { 1330 // Selects in InstsToRewrite only have load uses. Rewrite each as two 1331 // loads with a new select. 1332 while (!SI->use_empty()) { 1333 LoadInst *LI = cast<LoadInst>(SI->use_back()); 1334 1335 IRBuilder<> Builder(LI); 1336 LoadInst *TrueLoad = 1337 Builder.CreateLoad(SI->getTrueValue(), LI->getName()+".t"); 1338 LoadInst *FalseLoad = 1339 Builder.CreateLoad(SI->getFalseValue(), LI->getName()+".f"); 1340 1341 // Transfer alignment and TBAA info if present. 1342 TrueLoad->setAlignment(LI->getAlignment()); 1343 FalseLoad->setAlignment(LI->getAlignment()); 1344 if (MDNode *Tag = LI->getMetadata(LLVMContext::MD_tbaa)) { 1345 TrueLoad->setMetadata(LLVMContext::MD_tbaa, Tag); 1346 FalseLoad->setMetadata(LLVMContext::MD_tbaa, Tag); 1347 } 1348 1349 Value *V = Builder.CreateSelect(SI->getCondition(), TrueLoad, FalseLoad); 1350 V->takeName(LI); 1351 LI->replaceAllUsesWith(V); 1352 LI->eraseFromParent(); 1353 } 1354 1355 // Now that all the loads are gone, the select is gone too. 1356 SI->eraseFromParent(); 1357 continue; 1358 } 1359 1360 // Otherwise, we have a PHI node which allows us to push the loads into the 1361 // predecessors. 1362 PHINode *PN = cast<PHINode>(InstsToRewrite[i]); 1363 if (PN->use_empty()) { 1364 PN->eraseFromParent(); 1365 continue; 1366 } 1367 1368 Type *LoadTy = cast<PointerType>(PN->getType())->getElementType(); 1369 PHINode *NewPN = PHINode::Create(LoadTy, PN->getNumIncomingValues(), 1370 PN->getName()+".ld", PN); 1371 1372 // Get the TBAA tag and alignment to use from one of the loads. It doesn't 1373 // matter which one we get and if any differ, it doesn't matter. 1374 LoadInst *SomeLoad = cast<LoadInst>(PN->use_back()); 1375 MDNode *TBAATag = SomeLoad->getMetadata(LLVMContext::MD_tbaa); 1376 unsigned Align = SomeLoad->getAlignment(); 1377 1378 // Rewrite all loads of the PN to use the new PHI. 1379 while (!PN->use_empty()) { 1380 LoadInst *LI = cast<LoadInst>(PN->use_back()); 1381 LI->replaceAllUsesWith(NewPN); 1382 LI->eraseFromParent(); 1383 } 1384 1385 // Inject loads into all of the pred blocks. Keep track of which blocks we 1386 // insert them into in case we have multiple edges from the same block. 1387 DenseMap<BasicBlock*, LoadInst*> InsertedLoads; 1388 1389 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) { 1390 BasicBlock *Pred = PN->getIncomingBlock(i); 1391 LoadInst *&Load = InsertedLoads[Pred]; 1392 if (Load == 0) { 1393 Load = new LoadInst(PN->getIncomingValue(i), 1394 PN->getName() + "." + Pred->getName(), 1395 Pred->getTerminator()); 1396 Load->setAlignment(Align); 1397 if (TBAATag) Load->setMetadata(LLVMContext::MD_tbaa, TBAATag); 1398 } 1399 1400 NewPN->addIncoming(Load, Pred); 1401 } 1402 1403 PN->eraseFromParent(); 1404 } 1405 1406 ++NumAdjusted; 1407 return true; 1408} 1409 1410bool SROA::performPromotion(Function &F) { 1411 std::vector<AllocaInst*> Allocas; 1412 DominatorTree *DT = 0; 1413 if (HasDomTree) 1414 DT = &getAnalysis<DominatorTree>(); 1415 1416 BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function 1417 DIBuilder DIB(*F.getParent()); 1418 bool Changed = false; 1419 SmallVector<Instruction*, 64> Insts; 1420 while (1) { 1421 Allocas.clear(); 1422 1423 // Find allocas that are safe to promote, by looking at all instructions in 1424 // the entry node 1425 for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I) 1426 if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) // Is it an alloca? 1427 if (tryToMakeAllocaBePromotable(AI, TD)) 1428 Allocas.push_back(AI); 1429 1430 if (Allocas.empty()) break; 1431 1432 if (HasDomTree) 1433 PromoteMemToReg(Allocas, *DT); 1434 else { 1435 SSAUpdater SSA; 1436 for (unsigned i = 0, e = Allocas.size(); i != e; ++i) { 1437 AllocaInst *AI = Allocas[i]; 1438 1439 // Build list of instructions to promote. 1440 for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end(); 1441 UI != E; ++UI) 1442 Insts.push_back(cast<Instruction>(*UI)); 1443 AllocaPromoter(Insts, SSA, &DIB).run(AI, Insts); 1444 Insts.clear(); 1445 } 1446 } 1447 NumPromoted += Allocas.size(); 1448 Changed = true; 1449 } 1450 1451 return Changed; 1452} 1453 1454 1455/// ShouldAttemptScalarRepl - Decide if an alloca is a good candidate for 1456/// SROA. It must be a struct or array type with a small number of elements. 1457bool SROA::ShouldAttemptScalarRepl(AllocaInst *AI) { 1458 Type *T = AI->getAllocatedType(); 1459 // Do not promote any struct that has too many members. 1460 if (StructType *ST = dyn_cast<StructType>(T)) 1461 return ST->getNumElements() <= StructMemberThreshold; 1462 // Do not promote any array that has too many elements. 1463 if (ArrayType *AT = dyn_cast<ArrayType>(T)) 1464 return AT->getNumElements() <= ArrayElementThreshold; 1465 return false; 1466} 1467 1468/// getPointeeAlignment - Compute the minimum alignment of the value pointed 1469/// to by the given pointer. 1470static unsigned getPointeeAlignment(Value *V, const TargetData &TD) { 1471 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) 1472 if (CE->getOpcode() == Instruction::BitCast || 1473 (CE->getOpcode() == Instruction::GetElementPtr && 1474 cast<GEPOperator>(CE)->hasAllZeroIndices())) 1475 return getPointeeAlignment(CE->getOperand(0), TD); 1476 1477 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V)) 1478 if (!GV->isDeclaration()) 1479 return TD.getPreferredAlignment(GV); 1480 1481 if (PointerType *PT = dyn_cast<PointerType>(V->getType())) 1482 return TD.getABITypeAlignment(PT->getElementType()); 1483 1484 return 0; 1485} 1486 1487 1488// performScalarRepl - This algorithm is a simple worklist driven algorithm, 1489// which runs on all of the alloca instructions in the function, removing them 1490// if they are only used by getelementptr instructions. 1491// 1492bool SROA::performScalarRepl(Function &F) { 1493 std::vector<AllocaInst*> WorkList; 1494 1495 // Scan the entry basic block, adding allocas to the worklist. 1496 BasicBlock &BB = F.getEntryBlock(); 1497 for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I) 1498 if (AllocaInst *A = dyn_cast<AllocaInst>(I)) 1499 WorkList.push_back(A); 1500 1501 // Process the worklist 1502 bool Changed = false; 1503 while (!WorkList.empty()) { 1504 AllocaInst *AI = WorkList.back(); 1505 WorkList.pop_back(); 1506 1507 // Handle dead allocas trivially. These can be formed by SROA'ing arrays 1508 // with unused elements. 1509 if (AI->use_empty()) { 1510 AI->eraseFromParent(); 1511 Changed = true; 1512 continue; 1513 } 1514 1515 // If this alloca is impossible for us to promote, reject it early. 1516 if (AI->isArrayAllocation() || !AI->getAllocatedType()->isSized()) 1517 continue; 1518 1519 // Check to see if this allocation is only modified by a memcpy/memmove from 1520 // a constant global whose alignment is equal to or exceeds that of the 1521 // allocation. If this is the case, we can change all users to use 1522 // the constant global instead. This is commonly produced by the CFE by 1523 // constructs like "void foo() { int A[] = {1,2,3,4,5,6,7,8,9...}; }" if 'A' 1524 // is only subsequently read. 1525 SmallVector<Instruction *, 4> ToDelete; 1526 if (MemTransferInst *Copy = isOnlyCopiedFromConstantGlobal(AI, ToDelete)) { 1527 if (AI->getAlignment() <= getPointeeAlignment(Copy->getSource(), *TD)) { 1528 DEBUG(dbgs() << "Found alloca equal to global: " << *AI << '\n'); 1529 DEBUG(dbgs() << " memcpy = " << *Copy << '\n'); 1530 for (unsigned i = 0, e = ToDelete.size(); i != e; ++i) 1531 ToDelete[i]->eraseFromParent(); 1532 Constant *TheSrc = cast<Constant>(Copy->getSource()); 1533 AI->replaceAllUsesWith(ConstantExpr::getBitCast(TheSrc, AI->getType())); 1534 Copy->eraseFromParent(); // Don't mutate the global. 1535 AI->eraseFromParent(); 1536 ++NumGlobals; 1537 Changed = true; 1538 continue; 1539 } 1540 } 1541 1542 // Check to see if we can perform the core SROA transformation. We cannot 1543 // transform the allocation instruction if it is an array allocation 1544 // (allocations OF arrays are ok though), and an allocation of a scalar 1545 // value cannot be decomposed at all. 1546 uint64_t AllocaSize = TD->getTypeAllocSize(AI->getAllocatedType()); 1547 1548 // Do not promote [0 x %struct]. 1549 if (AllocaSize == 0) continue; 1550 1551 // Do not promote any struct whose size is too big. 1552 if (AllocaSize > SRThreshold) continue; 1553 1554 // If the alloca looks like a good candidate for scalar replacement, and if 1555 // all its users can be transformed, then split up the aggregate into its 1556 // separate elements. 1557 if (ShouldAttemptScalarRepl(AI) && isSafeAllocaToScalarRepl(AI)) { 1558 DoScalarReplacement(AI, WorkList); 1559 Changed = true; 1560 continue; 1561 } 1562 1563 // If we can turn this aggregate value (potentially with casts) into a 1564 // simple scalar value that can be mem2reg'd into a register value. 1565 // IsNotTrivial tracks whether this is something that mem2reg could have 1566 // promoted itself. If so, we don't want to transform it needlessly. Note 1567 // that we can't just check based on the type: the alloca may be of an i32 1568 // but that has pointer arithmetic to set byte 3 of it or something. 1569 if (AllocaInst *NewAI = ConvertToScalarInfo( 1570 (unsigned)AllocaSize, *TD, ScalarLoadThreshold).TryConvert(AI)) { 1571 NewAI->takeName(AI); 1572 AI->eraseFromParent(); 1573 ++NumConverted; 1574 Changed = true; 1575 continue; 1576 } 1577 1578 // Otherwise, couldn't process this alloca. 1579 } 1580 1581 return Changed; 1582} 1583 1584/// DoScalarReplacement - This alloca satisfied the isSafeAllocaToScalarRepl 1585/// predicate, do SROA now. 1586void SROA::DoScalarReplacement(AllocaInst *AI, 1587 std::vector<AllocaInst*> &WorkList) { 1588 DEBUG(dbgs() << "Found inst to SROA: " << *AI << '\n'); 1589 SmallVector<AllocaInst*, 32> ElementAllocas; 1590 if (StructType *ST = dyn_cast<StructType>(AI->getAllocatedType())) { 1591 ElementAllocas.reserve(ST->getNumContainedTypes()); 1592 for (unsigned i = 0, e = ST->getNumContainedTypes(); i != e; ++i) { 1593 AllocaInst *NA = new AllocaInst(ST->getContainedType(i), 0, 1594 AI->getAlignment(), 1595 AI->getName() + "." + Twine(i), AI); 1596 ElementAllocas.push_back(NA); 1597 WorkList.push_back(NA); // Add to worklist for recursive processing 1598 } 1599 } else { 1600 ArrayType *AT = cast<ArrayType>(AI->getAllocatedType()); 1601 ElementAllocas.reserve(AT->getNumElements()); 1602 Type *ElTy = AT->getElementType(); 1603 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) { 1604 AllocaInst *NA = new AllocaInst(ElTy, 0, AI->getAlignment(), 1605 AI->getName() + "." + Twine(i), AI); 1606 ElementAllocas.push_back(NA); 1607 WorkList.push_back(NA); // Add to worklist for recursive processing 1608 } 1609 } 1610 1611 // Now that we have created the new alloca instructions, rewrite all the 1612 // uses of the old alloca. 1613 RewriteForScalarRepl(AI, AI, 0, ElementAllocas); 1614 1615 // Now erase any instructions that were made dead while rewriting the alloca. 1616 DeleteDeadInstructions(); 1617 AI->eraseFromParent(); 1618 1619 ++NumReplaced; 1620} 1621 1622/// DeleteDeadInstructions - Erase instructions on the DeadInstrs list, 1623/// recursively including all their operands that become trivially dead. 1624void SROA::DeleteDeadInstructions() { 1625 while (!DeadInsts.empty()) { 1626 Instruction *I = cast<Instruction>(DeadInsts.pop_back_val()); 1627 1628 for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI) 1629 if (Instruction *U = dyn_cast<Instruction>(*OI)) { 1630 // Zero out the operand and see if it becomes trivially dead. 1631 // (But, don't add allocas to the dead instruction list -- they are 1632 // already on the worklist and will be deleted separately.) 1633 *OI = 0; 1634 if (isInstructionTriviallyDead(U) && !isa<AllocaInst>(U)) 1635 DeadInsts.push_back(U); 1636 } 1637 1638 I->eraseFromParent(); 1639 } 1640} 1641 1642/// isSafeForScalarRepl - Check if instruction I is a safe use with regard to 1643/// performing scalar replacement of alloca AI. The results are flagged in 1644/// the Info parameter. Offset indicates the position within AI that is 1645/// referenced by this instruction. 1646void SROA::isSafeForScalarRepl(Instruction *I, uint64_t Offset, 1647 AllocaInfo &Info) { 1648 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E; ++UI) { 1649 Instruction *User = cast<Instruction>(*UI); 1650 1651 if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) { 1652 isSafeForScalarRepl(BC, Offset, Info); 1653 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) { 1654 uint64_t GEPOffset = Offset; 1655 isSafeGEP(GEPI, GEPOffset, Info); 1656 if (!Info.isUnsafe) 1657 isSafeForScalarRepl(GEPI, GEPOffset, Info); 1658 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) { 1659 ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength()); 1660 if (Length == 0) 1661 return MarkUnsafe(Info, User); 1662 if (Length->isNegative()) 1663 return MarkUnsafe(Info, User); 1664 1665 isSafeMemAccess(Offset, Length->getZExtValue(), 0, 1666 UI.getOperandNo() == 0, Info, MI, 1667 true /*AllowWholeAccess*/); 1668 } else if (LoadInst *LI = dyn_cast<LoadInst>(User)) { 1669 if (!LI->isSimple()) 1670 return MarkUnsafe(Info, User); 1671 Type *LIType = LI->getType(); 1672 isSafeMemAccess(Offset, TD->getTypeAllocSize(LIType), 1673 LIType, false, Info, LI, true /*AllowWholeAccess*/); 1674 Info.hasALoadOrStore = true; 1675 1676 } else if (StoreInst *SI = dyn_cast<StoreInst>(User)) { 1677 // Store is ok if storing INTO the pointer, not storing the pointer 1678 if (!SI->isSimple() || SI->getOperand(0) == I) 1679 return MarkUnsafe(Info, User); 1680 1681 Type *SIType = SI->getOperand(0)->getType(); 1682 isSafeMemAccess(Offset, TD->getTypeAllocSize(SIType), 1683 SIType, true, Info, SI, true /*AllowWholeAccess*/); 1684 Info.hasALoadOrStore = true; 1685 } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(User)) { 1686 if (II->getIntrinsicID() != Intrinsic::lifetime_start && 1687 II->getIntrinsicID() != Intrinsic::lifetime_end) 1688 return MarkUnsafe(Info, User); 1689 } else if (isa<PHINode>(User) || isa<SelectInst>(User)) { 1690 isSafePHISelectUseForScalarRepl(User, Offset, Info); 1691 } else { 1692 return MarkUnsafe(Info, User); 1693 } 1694 if (Info.isUnsafe) return; 1695 } 1696} 1697 1698 1699/// isSafePHIUseForScalarRepl - If we see a PHI node or select using a pointer 1700/// derived from the alloca, we can often still split the alloca into elements. 1701/// This is useful if we have a large alloca where one element is phi'd 1702/// together somewhere: we can SRoA and promote all the other elements even if 1703/// we end up not being able to promote this one. 1704/// 1705/// All we require is that the uses of the PHI do not index into other parts of 1706/// the alloca. The most important use case for this is single load and stores 1707/// that are PHI'd together, which can happen due to code sinking. 1708void SROA::isSafePHISelectUseForScalarRepl(Instruction *I, uint64_t Offset, 1709 AllocaInfo &Info) { 1710 // If we've already checked this PHI, don't do it again. 1711 if (PHINode *PN = dyn_cast<PHINode>(I)) 1712 if (!Info.CheckedPHIs.insert(PN)) 1713 return; 1714 1715 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E; ++UI) { 1716 Instruction *User = cast<Instruction>(*UI); 1717 1718 if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) { 1719 isSafePHISelectUseForScalarRepl(BC, Offset, Info); 1720 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) { 1721 // Only allow "bitcast" GEPs for simplicity. We could generalize this, 1722 // but would have to prove that we're staying inside of an element being 1723 // promoted. 1724 if (!GEPI->hasAllZeroIndices()) 1725 return MarkUnsafe(Info, User); 1726 isSafePHISelectUseForScalarRepl(GEPI, Offset, Info); 1727 } else if (LoadInst *LI = dyn_cast<LoadInst>(User)) { 1728 if (!LI->isSimple()) 1729 return MarkUnsafe(Info, User); 1730 Type *LIType = LI->getType(); 1731 isSafeMemAccess(Offset, TD->getTypeAllocSize(LIType), 1732 LIType, false, Info, LI, false /*AllowWholeAccess*/); 1733 Info.hasALoadOrStore = true; 1734 1735 } else if (StoreInst *SI = dyn_cast<StoreInst>(User)) { 1736 // Store is ok if storing INTO the pointer, not storing the pointer 1737 if (!SI->isSimple() || SI->getOperand(0) == I) 1738 return MarkUnsafe(Info, User); 1739 1740 Type *SIType = SI->getOperand(0)->getType(); 1741 isSafeMemAccess(Offset, TD->getTypeAllocSize(SIType), 1742 SIType, true, Info, SI, false /*AllowWholeAccess*/); 1743 Info.hasALoadOrStore = true; 1744 } else if (isa<PHINode>(User) || isa<SelectInst>(User)) { 1745 isSafePHISelectUseForScalarRepl(User, Offset, Info); 1746 } else { 1747 return MarkUnsafe(Info, User); 1748 } 1749 if (Info.isUnsafe) return; 1750 } 1751} 1752 1753/// isSafeGEP - Check if a GEP instruction can be handled for scalar 1754/// replacement. It is safe when all the indices are constant, in-bounds 1755/// references, and when the resulting offset corresponds to an element within 1756/// the alloca type. The results are flagged in the Info parameter. Upon 1757/// return, Offset is adjusted as specified by the GEP indices. 1758void SROA::isSafeGEP(GetElementPtrInst *GEPI, 1759 uint64_t &Offset, AllocaInfo &Info) { 1760 gep_type_iterator GEPIt = gep_type_begin(GEPI), E = gep_type_end(GEPI); 1761 if (GEPIt == E) 1762 return; 1763 bool NonConstant = false; 1764 unsigned NonConstantIdxSize = 0; 1765 1766 // Walk through the GEP type indices, checking the types that this indexes 1767 // into. 1768 for (; GEPIt != E; ++GEPIt) { 1769 // Ignore struct elements, no extra checking needed for these. 1770 if ((*GEPIt)->isStructTy()) 1771 continue; 1772 1773 ConstantInt *IdxVal = dyn_cast<ConstantInt>(GEPIt.getOperand()); 1774 if (!IdxVal) { 1775 // Non constant GEPs are only a problem on arrays, structs, and pointers 1776 // Vectors can be dynamically indexed. 1777 // FIXME: Add support for dynamic indexing on arrays. This should be 1778 // ok on any subarrays of the alloca array, eg, a[0][i] is ok, but a[i][0] 1779 // isn't. 1780 if (!(*GEPIt)->isVectorTy()) 1781 return MarkUnsafe(Info, GEPI); 1782 NonConstant = true; 1783 NonConstantIdxSize = TD->getTypeAllocSize(*GEPIt); 1784 } 1785 } 1786 1787 // Compute the offset due to this GEP and check if the alloca has a 1788 // component element at that offset. 1789 SmallVector<Value*, 8> Indices(GEPI->op_begin() + 1, GEPI->op_end()); 1790 // If this GEP is non constant then the last operand must have been a 1791 // dynamic index into a vector. Pop this now as it has no impact on the 1792 // constant part of the offset. 1793 if (NonConstant) 1794 Indices.pop_back(); 1795 Offset += TD->getIndexedOffset(GEPI->getPointerOperandType(), Indices); 1796 if (!TypeHasComponent(Info.AI->getAllocatedType(), Offset, 1797 NonConstantIdxSize)) 1798 MarkUnsafe(Info, GEPI); 1799} 1800 1801/// isHomogeneousAggregate - Check if type T is a struct or array containing 1802/// elements of the same type (which is always true for arrays). If so, 1803/// return true with NumElts and EltTy set to the number of elements and the 1804/// element type, respectively. 1805static bool isHomogeneousAggregate(Type *T, unsigned &NumElts, 1806 Type *&EltTy) { 1807 if (ArrayType *AT = dyn_cast<ArrayType>(T)) { 1808 NumElts = AT->getNumElements(); 1809 EltTy = (NumElts == 0 ? 0 : AT->getElementType()); 1810 return true; 1811 } 1812 if (StructType *ST = dyn_cast<StructType>(T)) { 1813 NumElts = ST->getNumContainedTypes(); 1814 EltTy = (NumElts == 0 ? 0 : ST->getContainedType(0)); 1815 for (unsigned n = 1; n < NumElts; ++n) { 1816 if (ST->getContainedType(n) != EltTy) 1817 return false; 1818 } 1819 return true; 1820 } 1821 return false; 1822} 1823 1824/// isCompatibleAggregate - Check if T1 and T2 are either the same type or are 1825/// "homogeneous" aggregates with the same element type and number of elements. 1826static bool isCompatibleAggregate(Type *T1, Type *T2) { 1827 if (T1 == T2) 1828 return true; 1829 1830 unsigned NumElts1, NumElts2; 1831 Type *EltTy1, *EltTy2; 1832 if (isHomogeneousAggregate(T1, NumElts1, EltTy1) && 1833 isHomogeneousAggregate(T2, NumElts2, EltTy2) && 1834 NumElts1 == NumElts2 && 1835 EltTy1 == EltTy2) 1836 return true; 1837 1838 return false; 1839} 1840 1841/// isSafeMemAccess - Check if a load/store/memcpy operates on the entire AI 1842/// alloca or has an offset and size that corresponds to a component element 1843/// within it. The offset checked here may have been formed from a GEP with a 1844/// pointer bitcasted to a different type. 1845/// 1846/// If AllowWholeAccess is true, then this allows uses of the entire alloca as a 1847/// unit. If false, it only allows accesses known to be in a single element. 1848void SROA::isSafeMemAccess(uint64_t Offset, uint64_t MemSize, 1849 Type *MemOpType, bool isStore, 1850 AllocaInfo &Info, Instruction *TheAccess, 1851 bool AllowWholeAccess) { 1852 // Check if this is a load/store of the entire alloca. 1853 if (Offset == 0 && AllowWholeAccess && 1854 MemSize == TD->getTypeAllocSize(Info.AI->getAllocatedType())) { 1855 // This can be safe for MemIntrinsics (where MemOpType is 0) and integer 1856 // loads/stores (which are essentially the same as the MemIntrinsics with 1857 // regard to copying padding between elements). But, if an alloca is 1858 // flagged as both a source and destination of such operations, we'll need 1859 // to check later for padding between elements. 1860 if (!MemOpType || MemOpType->isIntegerTy()) { 1861 if (isStore) 1862 Info.isMemCpyDst = true; 1863 else 1864 Info.isMemCpySrc = true; 1865 return; 1866 } 1867 // This is also safe for references using a type that is compatible with 1868 // the type of the alloca, so that loads/stores can be rewritten using 1869 // insertvalue/extractvalue. 1870 if (isCompatibleAggregate(MemOpType, Info.AI->getAllocatedType())) { 1871 Info.hasSubelementAccess = true; 1872 return; 1873 } 1874 } 1875 // Check if the offset/size correspond to a component within the alloca type. 1876 Type *T = Info.AI->getAllocatedType(); 1877 if (TypeHasComponent(T, Offset, MemSize)) { 1878 Info.hasSubelementAccess = true; 1879 return; 1880 } 1881 1882 return MarkUnsafe(Info, TheAccess); 1883} 1884 1885/// TypeHasComponent - Return true if T has a component type with the 1886/// specified offset and size. If Size is zero, do not check the size. 1887bool SROA::TypeHasComponent(Type *T, uint64_t Offset, uint64_t Size) { 1888 Type *EltTy; 1889 uint64_t EltSize; 1890 if (StructType *ST = dyn_cast<StructType>(T)) { 1891 const StructLayout *Layout = TD->getStructLayout(ST); 1892 unsigned EltIdx = Layout->getElementContainingOffset(Offset); 1893 EltTy = ST->getContainedType(EltIdx); 1894 EltSize = TD->getTypeAllocSize(EltTy); 1895 Offset -= Layout->getElementOffset(EltIdx); 1896 } else if (ArrayType *AT = dyn_cast<ArrayType>(T)) { 1897 EltTy = AT->getElementType(); 1898 EltSize = TD->getTypeAllocSize(EltTy); 1899 if (Offset >= AT->getNumElements() * EltSize) 1900 return false; 1901 Offset %= EltSize; 1902 } else if (VectorType *VT = dyn_cast<VectorType>(T)) { 1903 EltTy = VT->getElementType(); 1904 EltSize = TD->getTypeAllocSize(EltTy); 1905 if (Offset >= VT->getNumElements() * EltSize) 1906 return false; 1907 Offset %= EltSize; 1908 } else { 1909 return false; 1910 } 1911 if (Offset == 0 && (Size == 0 || EltSize == Size)) 1912 return true; 1913 // Check if the component spans multiple elements. 1914 if (Offset + Size > EltSize) 1915 return false; 1916 return TypeHasComponent(EltTy, Offset, Size); 1917} 1918 1919/// RewriteForScalarRepl - Alloca AI is being split into NewElts, so rewrite 1920/// the instruction I, which references it, to use the separate elements. 1921/// Offset indicates the position within AI that is referenced by this 1922/// instruction. 1923void SROA::RewriteForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset, 1924 SmallVector<AllocaInst*, 32> &NewElts) { 1925 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E;) { 1926 Use &TheUse = UI.getUse(); 1927 Instruction *User = cast<Instruction>(*UI++); 1928 1929 if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) { 1930 RewriteBitCast(BC, AI, Offset, NewElts); 1931 continue; 1932 } 1933 1934 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) { 1935 RewriteGEP(GEPI, AI, Offset, NewElts); 1936 continue; 1937 } 1938 1939 if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) { 1940 ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength()); 1941 uint64_t MemSize = Length->getZExtValue(); 1942 if (Offset == 0 && 1943 MemSize == TD->getTypeAllocSize(AI->getAllocatedType())) 1944 RewriteMemIntrinUserOfAlloca(MI, I, AI, NewElts); 1945 // Otherwise the intrinsic can only touch a single element and the 1946 // address operand will be updated, so nothing else needs to be done. 1947 continue; 1948 } 1949 1950 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(User)) { 1951 if (II->getIntrinsicID() == Intrinsic::lifetime_start || 1952 II->getIntrinsicID() == Intrinsic::lifetime_end) { 1953 RewriteLifetimeIntrinsic(II, AI, Offset, NewElts); 1954 } 1955 continue; 1956 } 1957 1958 if (LoadInst *LI = dyn_cast<LoadInst>(User)) { 1959 Type *LIType = LI->getType(); 1960 1961 if (isCompatibleAggregate(LIType, AI->getAllocatedType())) { 1962 // Replace: 1963 // %res = load { i32, i32 }* %alloc 1964 // with: 1965 // %load.0 = load i32* %alloc.0 1966 // %insert.0 insertvalue { i32, i32 } zeroinitializer, i32 %load.0, 0 1967 // %load.1 = load i32* %alloc.1 1968 // %insert = insertvalue { i32, i32 } %insert.0, i32 %load.1, 1 1969 // (Also works for arrays instead of structs) 1970 Value *Insert = UndefValue::get(LIType); 1971 IRBuilder<> Builder(LI); 1972 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { 1973 Value *Load = Builder.CreateLoad(NewElts[i], "load"); 1974 Insert = Builder.CreateInsertValue(Insert, Load, i, "insert"); 1975 } 1976 LI->replaceAllUsesWith(Insert); 1977 DeadInsts.push_back(LI); 1978 } else if (LIType->isIntegerTy() && 1979 TD->getTypeAllocSize(LIType) == 1980 TD->getTypeAllocSize(AI->getAllocatedType())) { 1981 // If this is a load of the entire alloca to an integer, rewrite it. 1982 RewriteLoadUserOfWholeAlloca(LI, AI, NewElts); 1983 } 1984 continue; 1985 } 1986 1987 if (StoreInst *SI = dyn_cast<StoreInst>(User)) { 1988 Value *Val = SI->getOperand(0); 1989 Type *SIType = Val->getType(); 1990 if (isCompatibleAggregate(SIType, AI->getAllocatedType())) { 1991 // Replace: 1992 // store { i32, i32 } %val, { i32, i32 }* %alloc 1993 // with: 1994 // %val.0 = extractvalue { i32, i32 } %val, 0 1995 // store i32 %val.0, i32* %alloc.0 1996 // %val.1 = extractvalue { i32, i32 } %val, 1 1997 // store i32 %val.1, i32* %alloc.1 1998 // (Also works for arrays instead of structs) 1999 IRBuilder<> Builder(SI); 2000 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { 2001 Value *Extract = Builder.CreateExtractValue(Val, i, Val->getName()); 2002 Builder.CreateStore(Extract, NewElts[i]); 2003 } 2004 DeadInsts.push_back(SI); 2005 } else if (SIType->isIntegerTy() && 2006 TD->getTypeAllocSize(SIType) == 2007 TD->getTypeAllocSize(AI->getAllocatedType())) { 2008 // If this is a store of the entire alloca from an integer, rewrite it. 2009 RewriteStoreUserOfWholeAlloca(SI, AI, NewElts); 2010 } 2011 continue; 2012 } 2013 2014 if (isa<SelectInst>(User) || isa<PHINode>(User)) { 2015 // If we have a PHI user of the alloca itself (as opposed to a GEP or 2016 // bitcast) we have to rewrite it. GEP and bitcast uses will be RAUW'd to 2017 // the new pointer. 2018 if (!isa<AllocaInst>(I)) continue; 2019 2020 assert(Offset == 0 && NewElts[0] && 2021 "Direct alloca use should have a zero offset"); 2022 2023 // If we have a use of the alloca, we know the derived uses will be 2024 // utilizing just the first element of the scalarized result. Insert a 2025 // bitcast of the first alloca before the user as required. 2026 AllocaInst *NewAI = NewElts[0]; 2027 BitCastInst *BCI = new BitCastInst(NewAI, AI->getType(), "", NewAI); 2028 NewAI->moveBefore(BCI); 2029 TheUse = BCI; 2030 continue; 2031 } 2032 } 2033} 2034 2035/// RewriteBitCast - Update a bitcast reference to the alloca being replaced 2036/// and recursively continue updating all of its uses. 2037void SROA::RewriteBitCast(BitCastInst *BC, AllocaInst *AI, uint64_t Offset, 2038 SmallVector<AllocaInst*, 32> &NewElts) { 2039 RewriteForScalarRepl(BC, AI, Offset, NewElts); 2040 if (BC->getOperand(0) != AI) 2041 return; 2042 2043 // The bitcast references the original alloca. Replace its uses with 2044 // references to the alloca containing offset zero (which is normally at 2045 // index zero, but might not be in cases involving structs with elements 2046 // of size zero). 2047 Type *T = AI->getAllocatedType(); 2048 uint64_t EltOffset = 0; 2049 Type *IdxTy; 2050 uint64_t Idx = FindElementAndOffset(T, EltOffset, IdxTy); 2051 Instruction *Val = NewElts[Idx]; 2052 if (Val->getType() != BC->getDestTy()) { 2053 Val = new BitCastInst(Val, BC->getDestTy(), "", BC); 2054 Val->takeName(BC); 2055 } 2056 BC->replaceAllUsesWith(Val); 2057 DeadInsts.push_back(BC); 2058} 2059 2060/// FindElementAndOffset - Return the index of the element containing Offset 2061/// within the specified type, which must be either a struct or an array. 2062/// Sets T to the type of the element and Offset to the offset within that 2063/// element. IdxTy is set to the type of the index result to be used in a 2064/// GEP instruction. 2065uint64_t SROA::FindElementAndOffset(Type *&T, uint64_t &Offset, 2066 Type *&IdxTy) { 2067 uint64_t Idx = 0; 2068 if (StructType *ST = dyn_cast<StructType>(T)) { 2069 const StructLayout *Layout = TD->getStructLayout(ST); 2070 Idx = Layout->getElementContainingOffset(Offset); 2071 T = ST->getContainedType(Idx); 2072 Offset -= Layout->getElementOffset(Idx); 2073 IdxTy = Type::getInt32Ty(T->getContext()); 2074 return Idx; 2075 } else if (ArrayType *AT = dyn_cast<ArrayType>(T)) { 2076 T = AT->getElementType(); 2077 uint64_t EltSize = TD->getTypeAllocSize(T); 2078 Idx = Offset / EltSize; 2079 Offset -= Idx * EltSize; 2080 IdxTy = Type::getInt64Ty(T->getContext()); 2081 return Idx; 2082 } 2083 VectorType *VT = cast<VectorType>(T); 2084 T = VT->getElementType(); 2085 uint64_t EltSize = TD->getTypeAllocSize(T); 2086 Idx = Offset / EltSize; 2087 Offset -= Idx * EltSize; 2088 IdxTy = Type::getInt64Ty(T->getContext()); 2089 return Idx; 2090} 2091 2092/// RewriteGEP - Check if this GEP instruction moves the pointer across 2093/// elements of the alloca that are being split apart, and if so, rewrite 2094/// the GEP to be relative to the new element. 2095void SROA::RewriteGEP(GetElementPtrInst *GEPI, AllocaInst *AI, uint64_t Offset, 2096 SmallVector<AllocaInst*, 32> &NewElts) { 2097 uint64_t OldOffset = Offset; 2098 SmallVector<Value*, 8> Indices(GEPI->op_begin() + 1, GEPI->op_end()); 2099 // If the GEP was dynamic then it must have been a dynamic vector lookup. 2100 // In this case, it must be the last GEP operand which is dynamic so keep that 2101 // aside until we've found the constant GEP offset then add it back in at the 2102 // end. 2103 Value* NonConstantIdx = 0; 2104 if (!GEPI->hasAllConstantIndices()) 2105 NonConstantIdx = Indices.pop_back_val(); 2106 Offset += TD->getIndexedOffset(GEPI->getPointerOperandType(), Indices); 2107 2108 RewriteForScalarRepl(GEPI, AI, Offset, NewElts); 2109 2110 Type *T = AI->getAllocatedType(); 2111 Type *IdxTy; 2112 uint64_t OldIdx = FindElementAndOffset(T, OldOffset, IdxTy); 2113 if (GEPI->getOperand(0) == AI) 2114 OldIdx = ~0ULL; // Force the GEP to be rewritten. 2115 2116 T = AI->getAllocatedType(); 2117 uint64_t EltOffset = Offset; 2118 uint64_t Idx = FindElementAndOffset(T, EltOffset, IdxTy); 2119 2120 // If this GEP does not move the pointer across elements of the alloca 2121 // being split, then it does not needs to be rewritten. 2122 if (Idx == OldIdx) 2123 return; 2124 2125 Type *i32Ty = Type::getInt32Ty(AI->getContext()); 2126 SmallVector<Value*, 8> NewArgs; 2127 NewArgs.push_back(Constant::getNullValue(i32Ty)); 2128 while (EltOffset != 0) { 2129 uint64_t EltIdx = FindElementAndOffset(T, EltOffset, IdxTy); 2130 NewArgs.push_back(ConstantInt::get(IdxTy, EltIdx)); 2131 } 2132 if (NonConstantIdx) { 2133 Type* GepTy = T; 2134 // This GEP has a dynamic index. We need to add "i32 0" to index through 2135 // any structs or arrays in the original type until we get to the vector 2136 // to index. 2137 while (!isa<VectorType>(GepTy)) { 2138 NewArgs.push_back(Constant::getNullValue(i32Ty)); 2139 GepTy = cast<CompositeType>(GepTy)->getTypeAtIndex(0U); 2140 } 2141 NewArgs.push_back(NonConstantIdx); 2142 } 2143 Instruction *Val = NewElts[Idx]; 2144 if (NewArgs.size() > 1) { 2145 Val = GetElementPtrInst::CreateInBounds(Val, NewArgs, "", GEPI); 2146 Val->takeName(GEPI); 2147 } 2148 if (Val->getType() != GEPI->getType()) 2149 Val = new BitCastInst(Val, GEPI->getType(), Val->getName(), GEPI); 2150 GEPI->replaceAllUsesWith(Val); 2151 DeadInsts.push_back(GEPI); 2152} 2153 2154/// RewriteLifetimeIntrinsic - II is a lifetime.start/lifetime.end. Rewrite it 2155/// to mark the lifetime of the scalarized memory. 2156void SROA::RewriteLifetimeIntrinsic(IntrinsicInst *II, AllocaInst *AI, 2157 uint64_t Offset, 2158 SmallVector<AllocaInst*, 32> &NewElts) { 2159 ConstantInt *OldSize = cast<ConstantInt>(II->getArgOperand(0)); 2160 // Put matching lifetime markers on everything from Offset up to 2161 // Offset+OldSize. 2162 Type *AIType = AI->getAllocatedType(); 2163 uint64_t NewOffset = Offset; 2164 Type *IdxTy; 2165 uint64_t Idx = FindElementAndOffset(AIType, NewOffset, IdxTy); 2166 2167 IRBuilder<> Builder(II); 2168 uint64_t Size = OldSize->getLimitedValue(); 2169 2170 if (NewOffset) { 2171 // Splice the first element and index 'NewOffset' bytes in. SROA will 2172 // split the alloca again later. 2173 Value *V = Builder.CreateBitCast(NewElts[Idx], Builder.getInt8PtrTy()); 2174 V = Builder.CreateGEP(V, Builder.getInt64(NewOffset)); 2175 2176 IdxTy = NewElts[Idx]->getAllocatedType(); 2177 uint64_t EltSize = TD->getTypeAllocSize(IdxTy) - NewOffset; 2178 if (EltSize > Size) { 2179 EltSize = Size; 2180 Size = 0; 2181 } else { 2182 Size -= EltSize; 2183 } 2184 if (II->getIntrinsicID() == Intrinsic::lifetime_start) 2185 Builder.CreateLifetimeStart(V, Builder.getInt64(EltSize)); 2186 else 2187 Builder.CreateLifetimeEnd(V, Builder.getInt64(EltSize)); 2188 ++Idx; 2189 } 2190 2191 for (; Idx != NewElts.size() && Size; ++Idx) { 2192 IdxTy = NewElts[Idx]->getAllocatedType(); 2193 uint64_t EltSize = TD->getTypeAllocSize(IdxTy); 2194 if (EltSize > Size) { 2195 EltSize = Size; 2196 Size = 0; 2197 } else { 2198 Size -= EltSize; 2199 } 2200 if (II->getIntrinsicID() == Intrinsic::lifetime_start) 2201 Builder.CreateLifetimeStart(NewElts[Idx], 2202 Builder.getInt64(EltSize)); 2203 else 2204 Builder.CreateLifetimeEnd(NewElts[Idx], 2205 Builder.getInt64(EltSize)); 2206 } 2207 DeadInsts.push_back(II); 2208} 2209 2210/// RewriteMemIntrinUserOfAlloca - MI is a memcpy/memset/memmove from or to AI. 2211/// Rewrite it to copy or set the elements of the scalarized memory. 2212void SROA::RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *Inst, 2213 AllocaInst *AI, 2214 SmallVector<AllocaInst*, 32> &NewElts) { 2215 // If this is a memcpy/memmove, construct the other pointer as the 2216 // appropriate type. The "Other" pointer is the pointer that goes to memory 2217 // that doesn't have anything to do with the alloca that we are promoting. For 2218 // memset, this Value* stays null. 2219 Value *OtherPtr = 0; 2220 unsigned MemAlignment = MI->getAlignment(); 2221 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(MI)) { // memmove/memcopy 2222 if (Inst == MTI->getRawDest()) 2223 OtherPtr = MTI->getRawSource(); 2224 else { 2225 assert(Inst == MTI->getRawSource()); 2226 OtherPtr = MTI->getRawDest(); 2227 } 2228 } 2229 2230 // If there is an other pointer, we want to convert it to the same pointer 2231 // type as AI has, so we can GEP through it safely. 2232 if (OtherPtr) { 2233 unsigned AddrSpace = 2234 cast<PointerType>(OtherPtr->getType())->getAddressSpace(); 2235 2236 // Remove bitcasts and all-zero GEPs from OtherPtr. This is an 2237 // optimization, but it's also required to detect the corner case where 2238 // both pointer operands are referencing the same memory, and where 2239 // OtherPtr may be a bitcast or GEP that currently being rewritten. (This 2240 // function is only called for mem intrinsics that access the whole 2241 // aggregate, so non-zero GEPs are not an issue here.) 2242 OtherPtr = OtherPtr->stripPointerCasts(); 2243 2244 // Copying the alloca to itself is a no-op: just delete it. 2245 if (OtherPtr == AI || OtherPtr == NewElts[0]) { 2246 // This code will run twice for a no-op memcpy -- once for each operand. 2247 // Put only one reference to MI on the DeadInsts list. 2248 for (SmallVector<Value*, 32>::const_iterator I = DeadInsts.begin(), 2249 E = DeadInsts.end(); I != E; ++I) 2250 if (*I == MI) return; 2251 DeadInsts.push_back(MI); 2252 return; 2253 } 2254 2255 // If the pointer is not the right type, insert a bitcast to the right 2256 // type. 2257 Type *NewTy = 2258 PointerType::get(AI->getType()->getElementType(), AddrSpace); 2259 2260 if (OtherPtr->getType() != NewTy) 2261 OtherPtr = new BitCastInst(OtherPtr, NewTy, OtherPtr->getName(), MI); 2262 } 2263 2264 // Process each element of the aggregate. 2265 bool SROADest = MI->getRawDest() == Inst; 2266 2267 Constant *Zero = Constant::getNullValue(Type::getInt32Ty(MI->getContext())); 2268 2269 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { 2270 // If this is a memcpy/memmove, emit a GEP of the other element address. 2271 Value *OtherElt = 0; 2272 unsigned OtherEltAlign = MemAlignment; 2273 2274 if (OtherPtr) { 2275 Value *Idx[2] = { Zero, 2276 ConstantInt::get(Type::getInt32Ty(MI->getContext()), i) }; 2277 OtherElt = GetElementPtrInst::CreateInBounds(OtherPtr, Idx, 2278 OtherPtr->getName()+"."+Twine(i), 2279 MI); 2280 uint64_t EltOffset; 2281 PointerType *OtherPtrTy = cast<PointerType>(OtherPtr->getType()); 2282 Type *OtherTy = OtherPtrTy->getElementType(); 2283 if (StructType *ST = dyn_cast<StructType>(OtherTy)) { 2284 EltOffset = TD->getStructLayout(ST)->getElementOffset(i); 2285 } else { 2286 Type *EltTy = cast<SequentialType>(OtherTy)->getElementType(); 2287 EltOffset = TD->getTypeAllocSize(EltTy)*i; 2288 } 2289 2290 // The alignment of the other pointer is the guaranteed alignment of the 2291 // element, which is affected by both the known alignment of the whole 2292 // mem intrinsic and the alignment of the element. If the alignment of 2293 // the memcpy (f.e.) is 32 but the element is at a 4-byte offset, then the 2294 // known alignment is just 4 bytes. 2295 OtherEltAlign = (unsigned)MinAlign(OtherEltAlign, EltOffset); 2296 } 2297 2298 Value *EltPtr = NewElts[i]; 2299 Type *EltTy = cast<PointerType>(EltPtr->getType())->getElementType(); 2300 2301 // If we got down to a scalar, insert a load or store as appropriate. 2302 if (EltTy->isSingleValueType()) { 2303 if (isa<MemTransferInst>(MI)) { 2304 if (SROADest) { 2305 // From Other to Alloca. 2306 Value *Elt = new LoadInst(OtherElt, "tmp", false, OtherEltAlign, MI); 2307 new StoreInst(Elt, EltPtr, MI); 2308 } else { 2309 // From Alloca to Other. 2310 Value *Elt = new LoadInst(EltPtr, "tmp", MI); 2311 new StoreInst(Elt, OtherElt, false, OtherEltAlign, MI); 2312 } 2313 continue; 2314 } 2315 assert(isa<MemSetInst>(MI)); 2316 2317 // If the stored element is zero (common case), just store a null 2318 // constant. 2319 Constant *StoreVal; 2320 if (ConstantInt *CI = dyn_cast<ConstantInt>(MI->getArgOperand(1))) { 2321 if (CI->isZero()) { 2322 StoreVal = Constant::getNullValue(EltTy); // 0.0, null, 0, <0,0> 2323 } else { 2324 // If EltTy is a vector type, get the element type. 2325 Type *ValTy = EltTy->getScalarType(); 2326 2327 // Construct an integer with the right value. 2328 unsigned EltSize = TD->getTypeSizeInBits(ValTy); 2329 APInt OneVal(EltSize, CI->getZExtValue()); 2330 APInt TotalVal(OneVal); 2331 // Set each byte. 2332 for (unsigned i = 0; 8*i < EltSize; ++i) { 2333 TotalVal = TotalVal.shl(8); 2334 TotalVal |= OneVal; 2335 } 2336 2337 // Convert the integer value to the appropriate type. 2338 StoreVal = ConstantInt::get(CI->getContext(), TotalVal); 2339 if (ValTy->isPointerTy()) 2340 StoreVal = ConstantExpr::getIntToPtr(StoreVal, ValTy); 2341 else if (ValTy->isFloatingPointTy()) 2342 StoreVal = ConstantExpr::getBitCast(StoreVal, ValTy); 2343 assert(StoreVal->getType() == ValTy && "Type mismatch!"); 2344 2345 // If the requested value was a vector constant, create it. 2346 if (EltTy->isVectorTy()) { 2347 unsigned NumElts = cast<VectorType>(EltTy)->getNumElements(); 2348 StoreVal = ConstantVector::getSplat(NumElts, StoreVal); 2349 } 2350 } 2351 new StoreInst(StoreVal, EltPtr, MI); 2352 continue; 2353 } 2354 // Otherwise, if we're storing a byte variable, use a memset call for 2355 // this element. 2356 } 2357 2358 unsigned EltSize = TD->getTypeAllocSize(EltTy); 2359 if (!EltSize) 2360 continue; 2361 2362 IRBuilder<> Builder(MI); 2363 2364 // Finally, insert the meminst for this element. 2365 if (isa<MemSetInst>(MI)) { 2366 Builder.CreateMemSet(EltPtr, MI->getArgOperand(1), EltSize, 2367 MI->isVolatile()); 2368 } else { 2369 assert(isa<MemTransferInst>(MI)); 2370 Value *Dst = SROADest ? EltPtr : OtherElt; // Dest ptr 2371 Value *Src = SROADest ? OtherElt : EltPtr; // Src ptr 2372 2373 if (isa<MemCpyInst>(MI)) 2374 Builder.CreateMemCpy(Dst, Src, EltSize, OtherEltAlign,MI->isVolatile()); 2375 else 2376 Builder.CreateMemMove(Dst, Src, EltSize,OtherEltAlign,MI->isVolatile()); 2377 } 2378 } 2379 DeadInsts.push_back(MI); 2380} 2381 2382/// RewriteStoreUserOfWholeAlloca - We found a store of an integer that 2383/// overwrites the entire allocation. Extract out the pieces of the stored 2384/// integer and store them individually. 2385void SROA::RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocaInst *AI, 2386 SmallVector<AllocaInst*, 32> &NewElts){ 2387 // Extract each element out of the integer according to its structure offset 2388 // and store the element value to the individual alloca. 2389 Value *SrcVal = SI->getOperand(0); 2390 Type *AllocaEltTy = AI->getAllocatedType(); 2391 uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy); 2392 2393 IRBuilder<> Builder(SI); 2394 2395 // Handle tail padding by extending the operand 2396 if (TD->getTypeSizeInBits(SrcVal->getType()) != AllocaSizeBits) 2397 SrcVal = Builder.CreateZExt(SrcVal, 2398 IntegerType::get(SI->getContext(), AllocaSizeBits)); 2399 2400 DEBUG(dbgs() << "PROMOTING STORE TO WHOLE ALLOCA: " << *AI << '\n' << *SI 2401 << '\n'); 2402 2403 // There are two forms here: AI could be an array or struct. Both cases 2404 // have different ways to compute the element offset. 2405 if (StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) { 2406 const StructLayout *Layout = TD->getStructLayout(EltSTy); 2407 2408 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { 2409 // Get the number of bits to shift SrcVal to get the value. 2410 Type *FieldTy = EltSTy->getElementType(i); 2411 uint64_t Shift = Layout->getElementOffsetInBits(i); 2412 2413 if (TD->isBigEndian()) 2414 Shift = AllocaSizeBits-Shift-TD->getTypeAllocSizeInBits(FieldTy); 2415 2416 Value *EltVal = SrcVal; 2417 if (Shift) { 2418 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift); 2419 EltVal = Builder.CreateLShr(EltVal, ShiftVal, "sroa.store.elt"); 2420 } 2421 2422 // Truncate down to an integer of the right size. 2423 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy); 2424 2425 // Ignore zero sized fields like {}, they obviously contain no data. 2426 if (FieldSizeBits == 0) continue; 2427 2428 if (FieldSizeBits != AllocaSizeBits) 2429 EltVal = Builder.CreateTrunc(EltVal, 2430 IntegerType::get(SI->getContext(), FieldSizeBits)); 2431 Value *DestField = NewElts[i]; 2432 if (EltVal->getType() == FieldTy) { 2433 // Storing to an integer field of this size, just do it. 2434 } else if (FieldTy->isFloatingPointTy() || FieldTy->isVectorTy()) { 2435 // Bitcast to the right element type (for fp/vector values). 2436 EltVal = Builder.CreateBitCast(EltVal, FieldTy); 2437 } else { 2438 // Otherwise, bitcast the dest pointer (for aggregates). 2439 DestField = Builder.CreateBitCast(DestField, 2440 PointerType::getUnqual(EltVal->getType())); 2441 } 2442 new StoreInst(EltVal, DestField, SI); 2443 } 2444 2445 } else { 2446 ArrayType *ATy = cast<ArrayType>(AllocaEltTy); 2447 Type *ArrayEltTy = ATy->getElementType(); 2448 uint64_t ElementOffset = TD->getTypeAllocSizeInBits(ArrayEltTy); 2449 uint64_t ElementSizeBits = TD->getTypeSizeInBits(ArrayEltTy); 2450 2451 uint64_t Shift; 2452 2453 if (TD->isBigEndian()) 2454 Shift = AllocaSizeBits-ElementOffset; 2455 else 2456 Shift = 0; 2457 2458 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { 2459 // Ignore zero sized fields like {}, they obviously contain no data. 2460 if (ElementSizeBits == 0) continue; 2461 2462 Value *EltVal = SrcVal; 2463 if (Shift) { 2464 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift); 2465 EltVal = Builder.CreateLShr(EltVal, ShiftVal, "sroa.store.elt"); 2466 } 2467 2468 // Truncate down to an integer of the right size. 2469 if (ElementSizeBits != AllocaSizeBits) 2470 EltVal = Builder.CreateTrunc(EltVal, 2471 IntegerType::get(SI->getContext(), 2472 ElementSizeBits)); 2473 Value *DestField = NewElts[i]; 2474 if (EltVal->getType() == ArrayEltTy) { 2475 // Storing to an integer field of this size, just do it. 2476 } else if (ArrayEltTy->isFloatingPointTy() || 2477 ArrayEltTy->isVectorTy()) { 2478 // Bitcast to the right element type (for fp/vector values). 2479 EltVal = Builder.CreateBitCast(EltVal, ArrayEltTy); 2480 } else { 2481 // Otherwise, bitcast the dest pointer (for aggregates). 2482 DestField = Builder.CreateBitCast(DestField, 2483 PointerType::getUnqual(EltVal->getType())); 2484 } 2485 new StoreInst(EltVal, DestField, SI); 2486 2487 if (TD->isBigEndian()) 2488 Shift -= ElementOffset; 2489 else 2490 Shift += ElementOffset; 2491 } 2492 } 2493 2494 DeadInsts.push_back(SI); 2495} 2496 2497/// RewriteLoadUserOfWholeAlloca - We found a load of the entire allocation to 2498/// an integer. Load the individual pieces to form the aggregate value. 2499void SROA::RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocaInst *AI, 2500 SmallVector<AllocaInst*, 32> &NewElts) { 2501 // Extract each element out of the NewElts according to its structure offset 2502 // and form the result value. 2503 Type *AllocaEltTy = AI->getAllocatedType(); 2504 uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy); 2505 2506 DEBUG(dbgs() << "PROMOTING LOAD OF WHOLE ALLOCA: " << *AI << '\n' << *LI 2507 << '\n'); 2508 2509 // There are two forms here: AI could be an array or struct. Both cases 2510 // have different ways to compute the element offset. 2511 const StructLayout *Layout = 0; 2512 uint64_t ArrayEltBitOffset = 0; 2513 if (StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) { 2514 Layout = TD->getStructLayout(EltSTy); 2515 } else { 2516 Type *ArrayEltTy = cast<ArrayType>(AllocaEltTy)->getElementType(); 2517 ArrayEltBitOffset = TD->getTypeAllocSizeInBits(ArrayEltTy); 2518 } 2519 2520 Value *ResultVal = 2521 Constant::getNullValue(IntegerType::get(LI->getContext(), AllocaSizeBits)); 2522 2523 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) { 2524 // Load the value from the alloca. If the NewElt is an aggregate, cast 2525 // the pointer to an integer of the same size before doing the load. 2526 Value *SrcField = NewElts[i]; 2527 Type *FieldTy = 2528 cast<PointerType>(SrcField->getType())->getElementType(); 2529 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy); 2530 2531 // Ignore zero sized fields like {}, they obviously contain no data. 2532 if (FieldSizeBits == 0) continue; 2533 2534 IntegerType *FieldIntTy = IntegerType::get(LI->getContext(), 2535 FieldSizeBits); 2536 if (!FieldTy->isIntegerTy() && !FieldTy->isFloatingPointTy() && 2537 !FieldTy->isVectorTy()) 2538 SrcField = new BitCastInst(SrcField, 2539 PointerType::getUnqual(FieldIntTy), 2540 "", LI); 2541 SrcField = new LoadInst(SrcField, "sroa.load.elt", LI); 2542 2543 // If SrcField is a fp or vector of the right size but that isn't an 2544 // integer type, bitcast to an integer so we can shift it. 2545 if (SrcField->getType() != FieldIntTy) 2546 SrcField = new BitCastInst(SrcField, FieldIntTy, "", LI); 2547 2548 // Zero extend the field to be the same size as the final alloca so that 2549 // we can shift and insert it. 2550 if (SrcField->getType() != ResultVal->getType()) 2551 SrcField = new ZExtInst(SrcField, ResultVal->getType(), "", LI); 2552 2553 // Determine the number of bits to shift SrcField. 2554 uint64_t Shift; 2555 if (Layout) // Struct case. 2556 Shift = Layout->getElementOffsetInBits(i); 2557 else // Array case. 2558 Shift = i*ArrayEltBitOffset; 2559 2560 if (TD->isBigEndian()) 2561 Shift = AllocaSizeBits-Shift-FieldIntTy->getBitWidth(); 2562 2563 if (Shift) { 2564 Value *ShiftVal = ConstantInt::get(SrcField->getType(), Shift); 2565 SrcField = BinaryOperator::CreateShl(SrcField, ShiftVal, "", LI); 2566 } 2567 2568 // Don't create an 'or x, 0' on the first iteration. 2569 if (!isa<Constant>(ResultVal) || 2570 !cast<Constant>(ResultVal)->isNullValue()) 2571 ResultVal = BinaryOperator::CreateOr(SrcField, ResultVal, "", LI); 2572 else 2573 ResultVal = SrcField; 2574 } 2575 2576 // Handle tail padding by truncating the result 2577 if (TD->getTypeSizeInBits(LI->getType()) != AllocaSizeBits) 2578 ResultVal = new TruncInst(ResultVal, LI->getType(), "", LI); 2579 2580 LI->replaceAllUsesWith(ResultVal); 2581 DeadInsts.push_back(LI); 2582} 2583 2584/// HasPadding - Return true if the specified type has any structure or 2585/// alignment padding in between the elements that would be split apart 2586/// by SROA; return false otherwise. 2587static bool HasPadding(Type *Ty, const TargetData &TD) { 2588 if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) { 2589 Ty = ATy->getElementType(); 2590 return TD.getTypeSizeInBits(Ty) != TD.getTypeAllocSizeInBits(Ty); 2591 } 2592 2593 // SROA currently handles only Arrays and Structs. 2594 StructType *STy = cast<StructType>(Ty); 2595 const StructLayout *SL = TD.getStructLayout(STy); 2596 unsigned PrevFieldBitOffset = 0; 2597 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) { 2598 unsigned FieldBitOffset = SL->getElementOffsetInBits(i); 2599 2600 // Check to see if there is any padding between this element and the 2601 // previous one. 2602 if (i) { 2603 unsigned PrevFieldEnd = 2604 PrevFieldBitOffset+TD.getTypeSizeInBits(STy->getElementType(i-1)); 2605 if (PrevFieldEnd < FieldBitOffset) 2606 return true; 2607 } 2608 PrevFieldBitOffset = FieldBitOffset; 2609 } 2610 // Check for tail padding. 2611 if (unsigned EltCount = STy->getNumElements()) { 2612 unsigned PrevFieldEnd = PrevFieldBitOffset + 2613 TD.getTypeSizeInBits(STy->getElementType(EltCount-1)); 2614 if (PrevFieldEnd < SL->getSizeInBits()) 2615 return true; 2616 } 2617 return false; 2618} 2619 2620/// isSafeStructAllocaToScalarRepl - Check to see if the specified allocation of 2621/// an aggregate can be broken down into elements. Return 0 if not, 3 if safe, 2622/// or 1 if safe after canonicalization has been performed. 2623bool SROA::isSafeAllocaToScalarRepl(AllocaInst *AI) { 2624 // Loop over the use list of the alloca. We can only transform it if all of 2625 // the users are safe to transform. 2626 AllocaInfo Info(AI); 2627 2628 isSafeForScalarRepl(AI, 0, Info); 2629 if (Info.isUnsafe) { 2630 DEBUG(dbgs() << "Cannot transform: " << *AI << '\n'); 2631 return false; 2632 } 2633 2634 // Okay, we know all the users are promotable. If the aggregate is a memcpy 2635 // source and destination, we have to be careful. In particular, the memcpy 2636 // could be moving around elements that live in structure padding of the LLVM 2637 // types, but may actually be used. In these cases, we refuse to promote the 2638 // struct. 2639 if (Info.isMemCpySrc && Info.isMemCpyDst && 2640 HasPadding(AI->getAllocatedType(), *TD)) 2641 return false; 2642 2643 // If the alloca never has an access to just *part* of it, but is accessed 2644 // via loads and stores, then we should use ConvertToScalarInfo to promote 2645 // the alloca instead of promoting each piece at a time and inserting fission 2646 // and fusion code. 2647 if (!Info.hasSubelementAccess && Info.hasALoadOrStore) { 2648 // If the struct/array just has one element, use basic SRoA. 2649 if (StructType *ST = dyn_cast<StructType>(AI->getAllocatedType())) { 2650 if (ST->getNumElements() > 1) return false; 2651 } else { 2652 if (cast<ArrayType>(AI->getAllocatedType())->getNumElements() > 1) 2653 return false; 2654 } 2655 } 2656 2657 return true; 2658} 2659 2660 2661 2662/// PointsToConstantGlobal - Return true if V (possibly indirectly) points to 2663/// some part of a constant global variable. This intentionally only accepts 2664/// constant expressions because we don't can't rewrite arbitrary instructions. 2665static bool PointsToConstantGlobal(Value *V) { 2666 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V)) 2667 return GV->isConstant(); 2668 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) 2669 if (CE->getOpcode() == Instruction::BitCast || 2670 CE->getOpcode() == Instruction::GetElementPtr) 2671 return PointsToConstantGlobal(CE->getOperand(0)); 2672 return false; 2673} 2674 2675/// isOnlyCopiedFromConstantGlobal - Recursively walk the uses of a (derived) 2676/// pointer to an alloca. Ignore any reads of the pointer, return false if we 2677/// see any stores or other unknown uses. If we see pointer arithmetic, keep 2678/// track of whether it moves the pointer (with isOffset) but otherwise traverse 2679/// the uses. If we see a memcpy/memmove that targets an unoffseted pointer to 2680/// the alloca, and if the source pointer is a pointer to a constant global, we 2681/// can optimize this. 2682static bool 2683isOnlyCopiedFromConstantGlobal(Value *V, MemTransferInst *&TheCopy, 2684 bool isOffset, 2685 SmallVector<Instruction *, 4> &LifetimeMarkers) { 2686 // We track lifetime intrinsics as we encounter them. If we decide to go 2687 // ahead and replace the value with the global, this lets the caller quickly 2688 // eliminate the markers. 2689 2690 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) { 2691 User *U = cast<Instruction>(*UI); 2692 2693 if (LoadInst *LI = dyn_cast<LoadInst>(U)) { 2694 // Ignore non-volatile loads, they are always ok. 2695 if (!LI->isSimple()) return false; 2696 continue; 2697 } 2698 2699 if (BitCastInst *BCI = dyn_cast<BitCastInst>(U)) { 2700 // If uses of the bitcast are ok, we are ok. 2701 if (!isOnlyCopiedFromConstantGlobal(BCI, TheCopy, isOffset, 2702 LifetimeMarkers)) 2703 return false; 2704 continue; 2705 } 2706 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) { 2707 // If the GEP has all zero indices, it doesn't offset the pointer. If it 2708 // doesn't, it does. 2709 if (!isOnlyCopiedFromConstantGlobal(GEP, TheCopy, 2710 isOffset || !GEP->hasAllZeroIndices(), 2711 LifetimeMarkers)) 2712 return false; 2713 continue; 2714 } 2715 2716 if (CallSite CS = U) { 2717 // If this is the function being called then we treat it like a load and 2718 // ignore it. 2719 if (CS.isCallee(UI)) 2720 continue; 2721 2722 // If this is a readonly/readnone call site, then we know it is just a 2723 // load (but one that potentially returns the value itself), so we can 2724 // ignore it if we know that the value isn't captured. 2725 unsigned ArgNo = CS.getArgumentNo(UI); 2726 if (CS.onlyReadsMemory() && 2727 (CS.getInstruction()->use_empty() || CS.doesNotCapture(ArgNo))) 2728 continue; 2729 2730 // If this is being passed as a byval argument, the caller is making a 2731 // copy, so it is only a read of the alloca. 2732 if (CS.isByValArgument(ArgNo)) 2733 continue; 2734 } 2735 2736 // Lifetime intrinsics can be handled by the caller. 2737 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(U)) { 2738 if (II->getIntrinsicID() == Intrinsic::lifetime_start || 2739 II->getIntrinsicID() == Intrinsic::lifetime_end) { 2740 assert(II->use_empty() && "Lifetime markers have no result to use!"); 2741 LifetimeMarkers.push_back(II); 2742 continue; 2743 } 2744 } 2745 2746 // If this is isn't our memcpy/memmove, reject it as something we can't 2747 // handle. 2748 MemTransferInst *MI = dyn_cast<MemTransferInst>(U); 2749 if (MI == 0) 2750 return false; 2751 2752 // If the transfer is using the alloca as a source of the transfer, then 2753 // ignore it since it is a load (unless the transfer is volatile). 2754 if (UI.getOperandNo() == 1) { 2755 if (MI->isVolatile()) return false; 2756 continue; 2757 } 2758 2759 // If we already have seen a copy, reject the second one. 2760 if (TheCopy) return false; 2761 2762 // If the pointer has been offset from the start of the alloca, we can't 2763 // safely handle this. 2764 if (isOffset) return false; 2765 2766 // If the memintrinsic isn't using the alloca as the dest, reject it. 2767 if (UI.getOperandNo() != 0) return false; 2768 2769 // If the source of the memcpy/move is not a constant global, reject it. 2770 if (!PointsToConstantGlobal(MI->getSource())) 2771 return false; 2772 2773 // Otherwise, the transform is safe. Remember the copy instruction. 2774 TheCopy = MI; 2775 } 2776 return true; 2777} 2778 2779/// isOnlyCopiedFromConstantGlobal - Return true if the specified alloca is only 2780/// modified by a copy from a constant global. If we can prove this, we can 2781/// replace any uses of the alloca with uses of the global directly. 2782MemTransferInst * 2783SROA::isOnlyCopiedFromConstantGlobal(AllocaInst *AI, 2784 SmallVector<Instruction*, 4> &ToDelete) { 2785 MemTransferInst *TheCopy = 0; 2786 if (::isOnlyCopiedFromConstantGlobal(AI, TheCopy, false, ToDelete)) 2787 return TheCopy; 2788 return 0; 2789} 2790