1 //===- SROA.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 /// \file 10 /// This transformation implements the well known scalar replacement of 11 /// aggregates transformation. It tries to identify promotable elements of an 12 /// aggregate alloca, and promote them to registers. It will also try to 13 /// convert uses of an element (or set of elements) of an alloca into a vector 14 /// or bitfield-style integer scalar if appropriate. 15 /// 16 /// It works to do this with minimal slicing of the alloca so that regions 17 /// which are merely transferred in and out of external memory remain unchanged 18 /// and are not decomposed to scalar code. 19 /// 20 /// Because this also performs alloca promotion, it can be thought of as also 21 /// serving the purpose of SSA formation. The algorithm iterates on the 22 /// function until all opportunities for promotion have been realized. 23 /// 24 //===----------------------------------------------------------------------===// 25 26 #define DEBUG_TYPE "sroa" 27 #include "llvm/Transforms/Scalar.h" 28 #include "llvm/ADT/STLExtras.h" 29 #include "llvm/ADT/SetVector.h" 30 #include "llvm/ADT/SmallVector.h" 31 #include "llvm/ADT/Statistic.h" 32 #include "llvm/Analysis/Dominators.h" 33 #include "llvm/Analysis/Loads.h" 34 #include "llvm/Analysis/PtrUseVisitor.h" 35 #include "llvm/Analysis/ValueTracking.h" 36 #include "llvm/DIBuilder.h" 37 #include "llvm/DebugInfo.h" 38 #include "llvm/IR/Constants.h" 39 #include "llvm/IR/DataLayout.h" 40 #include "llvm/IR/DerivedTypes.h" 41 #include "llvm/IR/Function.h" 42 #include "llvm/IR/IRBuilder.h" 43 #include "llvm/IR/Instructions.h" 44 #include "llvm/IR/IntrinsicInst.h" 45 #include "llvm/IR/LLVMContext.h" 46 #include "llvm/IR/Operator.h" 47 #include "llvm/InstVisitor.h" 48 #include "llvm/Pass.h" 49 #include "llvm/Support/CommandLine.h" 50 #include "llvm/Support/Compiler.h" 51 #include "llvm/Support/Debug.h" 52 #include "llvm/Support/ErrorHandling.h" 53 #include "llvm/Support/MathExtras.h" 54 #include "llvm/Support/raw_ostream.h" 55 #include "llvm/Transforms/Utils/Local.h" 56 #include "llvm/Transforms/Utils/PromoteMemToReg.h" 57 #include "llvm/Transforms/Utils/SSAUpdater.h" 58 using namespace llvm; 59 60 STATISTIC(NumAllocasAnalyzed, "Number of allocas analyzed for replacement"); 61 STATISTIC(NumAllocaPartitions, "Number of alloca partitions formed"); 62 STATISTIC(MaxPartitionsPerAlloca, "Maximum number of partitions per alloca"); 63 STATISTIC(NumAllocaPartitionUses, "Number of alloca partition uses rewritten"); 64 STATISTIC(MaxUsesPerAllocaPartition, "Maximum number of uses of a partition"); 65 STATISTIC(NumNewAllocas, "Number of new, smaller allocas introduced"); 66 STATISTIC(NumPromoted, "Number of allocas promoted to SSA values"); 67 STATISTIC(NumLoadsSpeculated, "Number of loads speculated to allow promotion"); 68 STATISTIC(NumDeleted, "Number of instructions deleted"); 69 STATISTIC(NumVectorized, "Number of vectorized aggregates"); 70 71 /// Hidden option to force the pass to not use DomTree and mem2reg, instead 72 /// forming SSA values through the SSAUpdater infrastructure. 73 static cl::opt<bool> 74 ForceSSAUpdater("force-ssa-updater", cl::init(false), cl::Hidden); 75 76 namespace { 77 /// \brief A custom IRBuilder inserter which prefixes all names if they are 78 /// preserved. 79 template <bool preserveNames = true> 80 class IRBuilderPrefixedInserter : 81 public IRBuilderDefaultInserter<preserveNames> { 82 std::string Prefix; 83 84 public: 85 void SetNamePrefix(const Twine &P) { Prefix = P.str(); } 86 87 protected: 88 void InsertHelper(Instruction *I, const Twine &Name, BasicBlock *BB, 89 BasicBlock::iterator InsertPt) const { 90 IRBuilderDefaultInserter<preserveNames>::InsertHelper( 91 I, Name.isTriviallyEmpty() ? Name : Prefix + Name, BB, InsertPt); 92 } 93 }; 94 95 // Specialization for not preserving the name is trivial. 96 template <> 97 class IRBuilderPrefixedInserter<false> : 98 public IRBuilderDefaultInserter<false> { 99 public: 100 void SetNamePrefix(const Twine &P) {} 101 }; 102 103 /// \brief Provide a typedef for IRBuilder that drops names in release builds. 104 #ifndef NDEBUG 105 typedef llvm::IRBuilder<true, ConstantFolder, 106 IRBuilderPrefixedInserter<true> > IRBuilderTy; 107 #else 108 typedef llvm::IRBuilder<false, ConstantFolder, 109 IRBuilderPrefixedInserter<false> > IRBuilderTy; 110 #endif 111 } 112 113 namespace { 114 /// \brief A used slice of an alloca. 115 /// 116 /// This structure represents a slice of an alloca used by some instruction. It 117 /// stores both the begin and end offsets of this use, a pointer to the use 118 /// itself, and a flag indicating whether we can classify the use as splittable 119 /// or not when forming partitions of the alloca. 120 class Slice { 121 /// \brief The beginning offset of the range. 122 uint64_t BeginOffset; 123 124 /// \brief The ending offset, not included in the range. 125 uint64_t EndOffset; 126 127 /// \brief Storage for both the use of this slice and whether it can be 128 /// split. 129 PointerIntPair<Use *, 1, bool> UseAndIsSplittable; 130 131 public: 132 Slice() : BeginOffset(), EndOffset() {} 133 Slice(uint64_t BeginOffset, uint64_t EndOffset, Use *U, bool IsSplittable) 134 : BeginOffset(BeginOffset), EndOffset(EndOffset), 135 UseAndIsSplittable(U, IsSplittable) {} 136 137 uint64_t beginOffset() const { return BeginOffset; } 138 uint64_t endOffset() const { return EndOffset; } 139 140 bool isSplittable() const { return UseAndIsSplittable.getInt(); } 141 void makeUnsplittable() { UseAndIsSplittable.setInt(false); } 142 143 Use *getUse() const { return UseAndIsSplittable.getPointer(); } 144 145 bool isDead() const { return getUse() == 0; } 146 void kill() { UseAndIsSplittable.setPointer(0); } 147 148 /// \brief Support for ordering ranges. 149 /// 150 /// This provides an ordering over ranges such that start offsets are 151 /// always increasing, and within equal start offsets, the end offsets are 152 /// decreasing. Thus the spanning range comes first in a cluster with the 153 /// same start position. 154 bool operator<(const Slice &RHS) const { 155 if (beginOffset() < RHS.beginOffset()) return true; 156 if (beginOffset() > RHS.beginOffset()) return false; 157 if (isSplittable() != RHS.isSplittable()) return !isSplittable(); 158 if (endOffset() > RHS.endOffset()) return true; 159 return false; 160 } 161 162 /// \brief Support comparison with a single offset to allow binary searches. 163 friend LLVM_ATTRIBUTE_UNUSED bool operator<(const Slice &LHS, 164 uint64_t RHSOffset) { 165 return LHS.beginOffset() < RHSOffset; 166 } 167 friend LLVM_ATTRIBUTE_UNUSED bool operator<(uint64_t LHSOffset, 168 const Slice &RHS) { 169 return LHSOffset < RHS.beginOffset(); 170 } 171 172 bool operator==(const Slice &RHS) const { 173 return isSplittable() == RHS.isSplittable() && 174 beginOffset() == RHS.beginOffset() && endOffset() == RHS.endOffset(); 175 } 176 bool operator!=(const Slice &RHS) const { return !operator==(RHS); } 177 }; 178 } // end anonymous namespace 179 180 namespace llvm { 181 template <typename T> struct isPodLike; 182 template <> struct isPodLike<Slice> { 183 static const bool value = true; 184 }; 185 } 186 187 namespace { 188 /// \brief Representation of the alloca slices. 189 /// 190 /// This class represents the slices of an alloca which are formed by its 191 /// various uses. If a pointer escapes, we can't fully build a representation 192 /// for the slices used and we reflect that in this structure. The uses are 193 /// stored, sorted by increasing beginning offset and with unsplittable slices 194 /// starting at a particular offset before splittable slices. 195 class AllocaSlices { 196 public: 197 /// \brief Construct the slices of a particular alloca. 198 AllocaSlices(const DataLayout &DL, AllocaInst &AI); 199 200 /// \brief Test whether a pointer to the allocation escapes our analysis. 201 /// 202 /// If this is true, the slices are never fully built and should be 203 /// ignored. 204 bool isEscaped() const { return PointerEscapingInstr; } 205 206 /// \brief Support for iterating over the slices. 207 /// @{ 208 typedef SmallVectorImpl<Slice>::iterator iterator; 209 iterator begin() { return Slices.begin(); } 210 iterator end() { return Slices.end(); } 211 212 typedef SmallVectorImpl<Slice>::const_iterator const_iterator; 213 const_iterator begin() const { return Slices.begin(); } 214 const_iterator end() const { return Slices.end(); } 215 /// @} 216 217 /// \brief Allow iterating the dead users for this alloca. 218 /// 219 /// These are instructions which will never actually use the alloca as they 220 /// are outside the allocated range. They are safe to replace with undef and 221 /// delete. 222 /// @{ 223 typedef SmallVectorImpl<Instruction *>::const_iterator dead_user_iterator; 224 dead_user_iterator dead_user_begin() const { return DeadUsers.begin(); } 225 dead_user_iterator dead_user_end() const { return DeadUsers.end(); } 226 /// @} 227 228 /// \brief Allow iterating the dead expressions referring to this alloca. 229 /// 230 /// These are operands which have cannot actually be used to refer to the 231 /// alloca as they are outside its range and the user doesn't correct for 232 /// that. These mostly consist of PHI node inputs and the like which we just 233 /// need to replace with undef. 234 /// @{ 235 typedef SmallVectorImpl<Use *>::const_iterator dead_op_iterator; 236 dead_op_iterator dead_op_begin() const { return DeadOperands.begin(); } 237 dead_op_iterator dead_op_end() const { return DeadOperands.end(); } 238 /// @} 239 240 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP) 241 void print(raw_ostream &OS, const_iterator I, StringRef Indent = " ") const; 242 void printSlice(raw_ostream &OS, const_iterator I, 243 StringRef Indent = " ") const; 244 void printUse(raw_ostream &OS, const_iterator I, 245 StringRef Indent = " ") const; 246 void print(raw_ostream &OS) const; 247 void LLVM_ATTRIBUTE_NOINLINE LLVM_ATTRIBUTE_USED dump(const_iterator I) const; 248 void LLVM_ATTRIBUTE_NOINLINE LLVM_ATTRIBUTE_USED dump() const; 249 #endif 250 251 private: 252 template <typename DerivedT, typename RetT = void> class BuilderBase; 253 class SliceBuilder; 254 friend class AllocaSlices::SliceBuilder; 255 256 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP) 257 /// \brief Handle to alloca instruction to simplify method interfaces. 258 AllocaInst &AI; 259 #endif 260 261 /// \brief The instruction responsible for this alloca not having a known set 262 /// of slices. 263 /// 264 /// When an instruction (potentially) escapes the pointer to the alloca, we 265 /// store a pointer to that here and abort trying to form slices of the 266 /// alloca. This will be null if the alloca slices are analyzed successfully. 267 Instruction *PointerEscapingInstr; 268 269 /// \brief The slices of the alloca. 270 /// 271 /// We store a vector of the slices formed by uses of the alloca here. This 272 /// vector is sorted by increasing begin offset, and then the unsplittable 273 /// slices before the splittable ones. See the Slice inner class for more 274 /// details. 275 SmallVector<Slice, 8> Slices; 276 277 /// \brief Instructions which will become dead if we rewrite the alloca. 278 /// 279 /// Note that these are not separated by slice. This is because we expect an 280 /// alloca to be completely rewritten or not rewritten at all. If rewritten, 281 /// all these instructions can simply be removed and replaced with undef as 282 /// they come from outside of the allocated space. 283 SmallVector<Instruction *, 8> DeadUsers; 284 285 /// \brief Operands which will become dead if we rewrite the alloca. 286 /// 287 /// These are operands that in their particular use can be replaced with 288 /// undef when we rewrite the alloca. These show up in out-of-bounds inputs 289 /// to PHI nodes and the like. They aren't entirely dead (there might be 290 /// a GEP back into the bounds using it elsewhere) and nor is the PHI, but we 291 /// want to swap this particular input for undef to simplify the use lists of 292 /// the alloca. 293 SmallVector<Use *, 8> DeadOperands; 294 }; 295 } 296 297 static Value *foldSelectInst(SelectInst &SI) { 298 // If the condition being selected on is a constant or the same value is 299 // being selected between, fold the select. Yes this does (rarely) happen 300 // early on. 301 if (ConstantInt *CI = dyn_cast<ConstantInt>(SI.getCondition())) 302 return SI.getOperand(1+CI->isZero()); 303 if (SI.getOperand(1) == SI.getOperand(2)) 304 return SI.getOperand(1); 305 306 return 0; 307 } 308 309 /// \brief Builder for the alloca slices. 310 /// 311 /// This class builds a set of alloca slices by recursively visiting the uses 312 /// of an alloca and making a slice for each load and store at each offset. 313 class AllocaSlices::SliceBuilder : public PtrUseVisitor<SliceBuilder> { 314 friend class PtrUseVisitor<SliceBuilder>; 315 friend class InstVisitor<SliceBuilder>; 316 typedef PtrUseVisitor<SliceBuilder> Base; 317 318 const uint64_t AllocSize; 319 AllocaSlices &S; 320 321 SmallDenseMap<Instruction *, unsigned> MemTransferSliceMap; 322 SmallDenseMap<Instruction *, uint64_t> PHIOrSelectSizes; 323 324 /// \brief Set to de-duplicate dead instructions found in the use walk. 325 SmallPtrSet<Instruction *, 4> VisitedDeadInsts; 326 327 public: 328 SliceBuilder(const DataLayout &DL, AllocaInst &AI, AllocaSlices &S) 329 : PtrUseVisitor<SliceBuilder>(DL), 330 AllocSize(DL.getTypeAllocSize(AI.getAllocatedType())), S(S) {} 331 332 private: 333 void markAsDead(Instruction &I) { 334 if (VisitedDeadInsts.insert(&I)) 335 S.DeadUsers.push_back(&I); 336 } 337 338 void insertUse(Instruction &I, const APInt &Offset, uint64_t Size, 339 bool IsSplittable = false) { 340 // Completely skip uses which have a zero size or start either before or 341 // past the end of the allocation. 342 if (Size == 0 || Offset.isNegative() || Offset.uge(AllocSize)) { 343 DEBUG(dbgs() << "WARNING: Ignoring " << Size << " byte use @" << Offset 344 << " which has zero size or starts outside of the " 345 << AllocSize << " byte alloca:\n" 346 << " alloca: " << S.AI << "\n" 347 << " use: " << I << "\n"); 348 return markAsDead(I); 349 } 350 351 uint64_t BeginOffset = Offset.getZExtValue(); 352 uint64_t EndOffset = BeginOffset + Size; 353 354 // Clamp the end offset to the end of the allocation. Note that this is 355 // formulated to handle even the case where "BeginOffset + Size" overflows. 356 // This may appear superficially to be something we could ignore entirely, 357 // but that is not so! There may be widened loads or PHI-node uses where 358 // some instructions are dead but not others. We can't completely ignore 359 // them, and so have to record at least the information here. 360 assert(AllocSize >= BeginOffset); // Established above. 361 if (Size > AllocSize - BeginOffset) { 362 DEBUG(dbgs() << "WARNING: Clamping a " << Size << " byte use @" << Offset 363 << " to remain within the " << AllocSize << " byte alloca:\n" 364 << " alloca: " << S.AI << "\n" 365 << " use: " << I << "\n"); 366 EndOffset = AllocSize; 367 } 368 369 S.Slices.push_back(Slice(BeginOffset, EndOffset, U, IsSplittable)); 370 } 371 372 void visitBitCastInst(BitCastInst &BC) { 373 if (BC.use_empty()) 374 return markAsDead(BC); 375 376 return Base::visitBitCastInst(BC); 377 } 378 379 void visitGetElementPtrInst(GetElementPtrInst &GEPI) { 380 if (GEPI.use_empty()) 381 return markAsDead(GEPI); 382 383 return Base::visitGetElementPtrInst(GEPI); 384 } 385 386 void handleLoadOrStore(Type *Ty, Instruction &I, const APInt &Offset, 387 uint64_t Size, bool IsVolatile) { 388 // We allow splitting of loads and stores where the type is an integer type 389 // and cover the entire alloca. This prevents us from splitting over 390 // eagerly. 391 // FIXME: In the great blue eventually, we should eagerly split all integer 392 // loads and stores, and then have a separate step that merges adjacent 393 // alloca partitions into a single partition suitable for integer widening. 394 // Or we should skip the merge step and rely on GVN and other passes to 395 // merge adjacent loads and stores that survive mem2reg. 396 bool IsSplittable = 397 Ty->isIntegerTy() && !IsVolatile && Offset == 0 && Size >= AllocSize; 398 399 insertUse(I, Offset, Size, IsSplittable); 400 } 401 402 void visitLoadInst(LoadInst &LI) { 403 assert((!LI.isSimple() || LI.getType()->isSingleValueType()) && 404 "All simple FCA loads should have been pre-split"); 405 406 if (!IsOffsetKnown) 407 return PI.setAborted(&LI); 408 409 uint64_t Size = DL.getTypeStoreSize(LI.getType()); 410 return handleLoadOrStore(LI.getType(), LI, Offset, Size, LI.isVolatile()); 411 } 412 413 void visitStoreInst(StoreInst &SI) { 414 Value *ValOp = SI.getValueOperand(); 415 if (ValOp == *U) 416 return PI.setEscapedAndAborted(&SI); 417 if (!IsOffsetKnown) 418 return PI.setAborted(&SI); 419 420 uint64_t Size = DL.getTypeStoreSize(ValOp->getType()); 421 422 // If this memory access can be shown to *statically* extend outside the 423 // bounds of of the allocation, it's behavior is undefined, so simply 424 // ignore it. Note that this is more strict than the generic clamping 425 // behavior of insertUse. We also try to handle cases which might run the 426 // risk of overflow. 427 // FIXME: We should instead consider the pointer to have escaped if this 428 // function is being instrumented for addressing bugs or race conditions. 429 if (Offset.isNegative() || Size > AllocSize || 430 Offset.ugt(AllocSize - Size)) { 431 DEBUG(dbgs() << "WARNING: Ignoring " << Size << " byte store @" << Offset 432 << " which extends past the end of the " << AllocSize 433 << " byte alloca:\n" 434 << " alloca: " << S.AI << "\n" 435 << " use: " << SI << "\n"); 436 return markAsDead(SI); 437 } 438 439 assert((!SI.isSimple() || ValOp->getType()->isSingleValueType()) && 440 "All simple FCA stores should have been pre-split"); 441 handleLoadOrStore(ValOp->getType(), SI, Offset, Size, SI.isVolatile()); 442 } 443 444 445 void visitMemSetInst(MemSetInst &II) { 446 assert(II.getRawDest() == *U && "Pointer use is not the destination?"); 447 ConstantInt *Length = dyn_cast<ConstantInt>(II.getLength()); 448 if ((Length && Length->getValue() == 0) || 449 (IsOffsetKnown && !Offset.isNegative() && Offset.uge(AllocSize))) 450 // Zero-length mem transfer intrinsics can be ignored entirely. 451 return markAsDead(II); 452 453 if (!IsOffsetKnown) 454 return PI.setAborted(&II); 455 456 insertUse(II, Offset, 457 Length ? Length->getLimitedValue() 458 : AllocSize - Offset.getLimitedValue(), 459 (bool)Length); 460 } 461 462 void visitMemTransferInst(MemTransferInst &II) { 463 ConstantInt *Length = dyn_cast<ConstantInt>(II.getLength()); 464 if ((Length && Length->getValue() == 0) || 465 (IsOffsetKnown && !Offset.isNegative() && Offset.uge(AllocSize))) 466 // Zero-length mem transfer intrinsics can be ignored entirely. 467 return markAsDead(II); 468 469 if (!IsOffsetKnown) 470 return PI.setAborted(&II); 471 472 uint64_t RawOffset = Offset.getLimitedValue(); 473 uint64_t Size = Length ? Length->getLimitedValue() 474 : AllocSize - RawOffset; 475 476 // Check for the special case where the same exact value is used for both 477 // source and dest. 478 if (*U == II.getRawDest() && *U == II.getRawSource()) { 479 // For non-volatile transfers this is a no-op. 480 if (!II.isVolatile()) 481 return markAsDead(II); 482 483 return insertUse(II, Offset, Size, /*IsSplittable=*/false); 484 } 485 486 // If we have seen both source and destination for a mem transfer, then 487 // they both point to the same alloca. 488 bool Inserted; 489 SmallDenseMap<Instruction *, unsigned>::iterator MTPI; 490 llvm::tie(MTPI, Inserted) = 491 MemTransferSliceMap.insert(std::make_pair(&II, S.Slices.size())); 492 unsigned PrevIdx = MTPI->second; 493 if (!Inserted) { 494 Slice &PrevP = S.Slices[PrevIdx]; 495 496 // Check if the begin offsets match and this is a non-volatile transfer. 497 // In that case, we can completely elide the transfer. 498 if (!II.isVolatile() && PrevP.beginOffset() == RawOffset) { 499 PrevP.kill(); 500 return markAsDead(II); 501 } 502 503 // Otherwise we have an offset transfer within the same alloca. We can't 504 // split those. 505 PrevP.makeUnsplittable(); 506 } 507 508 // Insert the use now that we've fixed up the splittable nature. 509 insertUse(II, Offset, Size, /*IsSplittable=*/Inserted && Length); 510 511 // Check that we ended up with a valid index in the map. 512 assert(S.Slices[PrevIdx].getUse()->getUser() == &II && 513 "Map index doesn't point back to a slice with this user."); 514 } 515 516 // Disable SRoA for any intrinsics except for lifetime invariants. 517 // FIXME: What about debug intrinsics? This matches old behavior, but 518 // doesn't make sense. 519 void visitIntrinsicInst(IntrinsicInst &II) { 520 if (!IsOffsetKnown) 521 return PI.setAborted(&II); 522 523 if (II.getIntrinsicID() == Intrinsic::lifetime_start || 524 II.getIntrinsicID() == Intrinsic::lifetime_end) { 525 ConstantInt *Length = cast<ConstantInt>(II.getArgOperand(0)); 526 uint64_t Size = std::min(AllocSize - Offset.getLimitedValue(), 527 Length->getLimitedValue()); 528 insertUse(II, Offset, Size, true); 529 return; 530 } 531 532 Base::visitIntrinsicInst(II); 533 } 534 535 Instruction *hasUnsafePHIOrSelectUse(Instruction *Root, uint64_t &Size) { 536 // We consider any PHI or select that results in a direct load or store of 537 // the same offset to be a viable use for slicing purposes. These uses 538 // are considered unsplittable and the size is the maximum loaded or stored 539 // size. 540 SmallPtrSet<Instruction *, 4> Visited; 541 SmallVector<std::pair<Instruction *, Instruction *>, 4> Uses; 542 Visited.insert(Root); 543 Uses.push_back(std::make_pair(cast<Instruction>(*U), Root)); 544 // If there are no loads or stores, the access is dead. We mark that as 545 // a size zero access. 546 Size = 0; 547 do { 548 Instruction *I, *UsedI; 549 llvm::tie(UsedI, I) = Uses.pop_back_val(); 550 551 if (LoadInst *LI = dyn_cast<LoadInst>(I)) { 552 Size = std::max(Size, DL.getTypeStoreSize(LI->getType())); 553 continue; 554 } 555 if (StoreInst *SI = dyn_cast<StoreInst>(I)) { 556 Value *Op = SI->getOperand(0); 557 if (Op == UsedI) 558 return SI; 559 Size = std::max(Size, DL.getTypeStoreSize(Op->getType())); 560 continue; 561 } 562 563 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(I)) { 564 if (!GEP->hasAllZeroIndices()) 565 return GEP; 566 } else if (!isa<BitCastInst>(I) && !isa<PHINode>(I) && 567 !isa<SelectInst>(I)) { 568 return I; 569 } 570 571 for (Value::use_iterator UI = I->use_begin(), UE = I->use_end(); UI != UE; 572 ++UI) 573 if (Visited.insert(cast<Instruction>(*UI))) 574 Uses.push_back(std::make_pair(I, cast<Instruction>(*UI))); 575 } while (!Uses.empty()); 576 577 return 0; 578 } 579 580 void visitPHINode(PHINode &PN) { 581 if (PN.use_empty()) 582 return markAsDead(PN); 583 if (!IsOffsetKnown) 584 return PI.setAborted(&PN); 585 586 // See if we already have computed info on this node. 587 uint64_t &PHISize = PHIOrSelectSizes[&PN]; 588 if (!PHISize) { 589 // This is a new PHI node, check for an unsafe use of the PHI node. 590 if (Instruction *UnsafeI = hasUnsafePHIOrSelectUse(&PN, PHISize)) 591 return PI.setAborted(UnsafeI); 592 } 593 594 // For PHI and select operands outside the alloca, we can't nuke the entire 595 // phi or select -- the other side might still be relevant, so we special 596 // case them here and use a separate structure to track the operands 597 // themselves which should be replaced with undef. 598 // FIXME: This should instead be escaped in the event we're instrumenting 599 // for address sanitization. 600 if ((Offset.isNegative() && (-Offset).uge(PHISize)) || 601 (!Offset.isNegative() && Offset.uge(AllocSize))) { 602 S.DeadOperands.push_back(U); 603 return; 604 } 605 606 insertUse(PN, Offset, PHISize); 607 } 608 609 void visitSelectInst(SelectInst &SI) { 610 if (SI.use_empty()) 611 return markAsDead(SI); 612 if (Value *Result = foldSelectInst(SI)) { 613 if (Result == *U) 614 // If the result of the constant fold will be the pointer, recurse 615 // through the select as if we had RAUW'ed it. 616 enqueueUsers(SI); 617 else 618 // Otherwise the operand to the select is dead, and we can replace it 619 // with undef. 620 S.DeadOperands.push_back(U); 621 622 return; 623 } 624 if (!IsOffsetKnown) 625 return PI.setAborted(&SI); 626 627 // See if we already have computed info on this node. 628 uint64_t &SelectSize = PHIOrSelectSizes[&SI]; 629 if (!SelectSize) { 630 // This is a new Select, check for an unsafe use of it. 631 if (Instruction *UnsafeI = hasUnsafePHIOrSelectUse(&SI, SelectSize)) 632 return PI.setAborted(UnsafeI); 633 } 634 635 // For PHI and select operands outside the alloca, we can't nuke the entire 636 // phi or select -- the other side might still be relevant, so we special 637 // case them here and use a separate structure to track the operands 638 // themselves which should be replaced with undef. 639 // FIXME: This should instead be escaped in the event we're instrumenting 640 // for address sanitization. 641 if ((Offset.isNegative() && Offset.uge(SelectSize)) || 642 (!Offset.isNegative() && Offset.uge(AllocSize))) { 643 S.DeadOperands.push_back(U); 644 return; 645 } 646 647 insertUse(SI, Offset, SelectSize); 648 } 649 650 /// \brief Disable SROA entirely if there are unhandled users of the alloca. 651 void visitInstruction(Instruction &I) { 652 PI.setAborted(&I); 653 } 654 }; 655 656 AllocaSlices::AllocaSlices(const DataLayout &DL, AllocaInst &AI) 657 : 658 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP) 659 AI(AI), 660 #endif 661 PointerEscapingInstr(0) { 662 SliceBuilder PB(DL, AI, *this); 663 SliceBuilder::PtrInfo PtrI = PB.visitPtr(AI); 664 if (PtrI.isEscaped() || PtrI.isAborted()) { 665 // FIXME: We should sink the escape vs. abort info into the caller nicely, 666 // possibly by just storing the PtrInfo in the AllocaSlices. 667 PointerEscapingInstr = PtrI.getEscapingInst() ? PtrI.getEscapingInst() 668 : PtrI.getAbortingInst(); 669 assert(PointerEscapingInstr && "Did not track a bad instruction"); 670 return; 671 } 672 673 Slices.erase(std::remove_if(Slices.begin(), Slices.end(), 674 std::mem_fun_ref(&Slice::isDead)), 675 Slices.end()); 676 677 // Sort the uses. This arranges for the offsets to be in ascending order, 678 // and the sizes to be in descending order. 679 std::sort(Slices.begin(), Slices.end()); 680 } 681 682 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP) 683 684 void AllocaSlices::print(raw_ostream &OS, const_iterator I, 685 StringRef Indent) const { 686 printSlice(OS, I, Indent); 687 printUse(OS, I, Indent); 688 } 689 690 void AllocaSlices::printSlice(raw_ostream &OS, const_iterator I, 691 StringRef Indent) const { 692 OS << Indent << "[" << I->beginOffset() << "," << I->endOffset() << ")" 693 << " slice #" << (I - begin()) 694 << (I->isSplittable() ? " (splittable)" : "") << "\n"; 695 } 696 697 void AllocaSlices::printUse(raw_ostream &OS, const_iterator I, 698 StringRef Indent) const { 699 OS << Indent << " used by: " << *I->getUse()->getUser() << "\n"; 700 } 701 702 void AllocaSlices::print(raw_ostream &OS) const { 703 if (PointerEscapingInstr) { 704 OS << "Can't analyze slices for alloca: " << AI << "\n" 705 << " A pointer to this alloca escaped by:\n" 706 << " " << *PointerEscapingInstr << "\n"; 707 return; 708 } 709 710 OS << "Slices of alloca: " << AI << "\n"; 711 for (const_iterator I = begin(), E = end(); I != E; ++I) 712 print(OS, I); 713 } 714 715 void AllocaSlices::dump(const_iterator I) const { print(dbgs(), I); } 716 void AllocaSlices::dump() const { print(dbgs()); } 717 718 #endif // !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP) 719 720 namespace { 721 /// \brief Implementation of LoadAndStorePromoter for promoting allocas. 722 /// 723 /// This subclass of LoadAndStorePromoter adds overrides to handle promoting 724 /// the loads and stores of an alloca instruction, as well as updating its 725 /// debug information. This is used when a domtree is unavailable and thus 726 /// mem2reg in its full form can't be used to handle promotion of allocas to 727 /// scalar values. 728 class AllocaPromoter : public LoadAndStorePromoter { 729 AllocaInst &AI; 730 DIBuilder &DIB; 731 732 SmallVector<DbgDeclareInst *, 4> DDIs; 733 SmallVector<DbgValueInst *, 4> DVIs; 734 735 public: 736 AllocaPromoter(const SmallVectorImpl<Instruction *> &Insts, SSAUpdater &S, 737 AllocaInst &AI, DIBuilder &DIB) 738 : LoadAndStorePromoter(Insts, S), AI(AI), DIB(DIB) {} 739 740 void run(const SmallVectorImpl<Instruction*> &Insts) { 741 // Retain the debug information attached to the alloca for use when 742 // rewriting loads and stores. 743 if (MDNode *DebugNode = MDNode::getIfExists(AI.getContext(), &AI)) { 744 for (Value::use_iterator UI = DebugNode->use_begin(), 745 UE = DebugNode->use_end(); 746 UI != UE; ++UI) 747 if (DbgDeclareInst *DDI = dyn_cast<DbgDeclareInst>(*UI)) 748 DDIs.push_back(DDI); 749 else if (DbgValueInst *DVI = dyn_cast<DbgValueInst>(*UI)) 750 DVIs.push_back(DVI); 751 } 752 753 LoadAndStorePromoter::run(Insts); 754 755 // While we have the debug information, clear it off of the alloca. The 756 // caller takes care of deleting the alloca. 757 while (!DDIs.empty()) 758 DDIs.pop_back_val()->eraseFromParent(); 759 while (!DVIs.empty()) 760 DVIs.pop_back_val()->eraseFromParent(); 761 } 762 763 virtual bool isInstInList(Instruction *I, 764 const SmallVectorImpl<Instruction*> &Insts) const { 765 Value *Ptr; 766 if (LoadInst *LI = dyn_cast<LoadInst>(I)) 767 Ptr = LI->getOperand(0); 768 else 769 Ptr = cast<StoreInst>(I)->getPointerOperand(); 770 771 // Only used to detect cycles, which will be rare and quickly found as 772 // we're walking up a chain of defs rather than down through uses. 773 SmallPtrSet<Value *, 4> Visited; 774 775 do { 776 if (Ptr == &AI) 777 return true; 778 779 if (BitCastInst *BCI = dyn_cast<BitCastInst>(Ptr)) 780 Ptr = BCI->getOperand(0); 781 else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(Ptr)) 782 Ptr = GEPI->getPointerOperand(); 783 else 784 return false; 785 786 } while (Visited.insert(Ptr)); 787 788 return false; 789 } 790 791 virtual void updateDebugInfo(Instruction *Inst) const { 792 for (SmallVectorImpl<DbgDeclareInst *>::const_iterator I = DDIs.begin(), 793 E = DDIs.end(); I != E; ++I) { 794 DbgDeclareInst *DDI = *I; 795 if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) 796 ConvertDebugDeclareToDebugValue(DDI, SI, DIB); 797 else if (LoadInst *LI = dyn_cast<LoadInst>(Inst)) 798 ConvertDebugDeclareToDebugValue(DDI, LI, DIB); 799 } 800 for (SmallVectorImpl<DbgValueInst *>::const_iterator I = DVIs.begin(), 801 E = DVIs.end(); I != E; ++I) { 802 DbgValueInst *DVI = *I; 803 Value *Arg = 0; 804 if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) { 805 // If an argument is zero extended then use argument directly. The ZExt 806 // may be zapped by an optimization pass in future. 807 if (ZExtInst *ZExt = dyn_cast<ZExtInst>(SI->getOperand(0))) 808 Arg = dyn_cast<Argument>(ZExt->getOperand(0)); 809 else if (SExtInst *SExt = dyn_cast<SExtInst>(SI->getOperand(0))) 810 Arg = dyn_cast<Argument>(SExt->getOperand(0)); 811 if (!Arg) 812 Arg = SI->getValueOperand(); 813 } else if (LoadInst *LI = dyn_cast<LoadInst>(Inst)) { 814 Arg = LI->getPointerOperand(); 815 } else { 816 continue; 817 } 818 Instruction *DbgVal = 819 DIB.insertDbgValueIntrinsic(Arg, 0, DIVariable(DVI->getVariable()), 820 Inst); 821 DbgVal->setDebugLoc(DVI->getDebugLoc()); 822 } 823 } 824 }; 825 } // end anon namespace 826 827 828 namespace { 829 /// \brief An optimization pass providing Scalar Replacement of Aggregates. 830 /// 831 /// This pass takes allocations which can be completely analyzed (that is, they 832 /// don't escape) and tries to turn them into scalar SSA values. There are 833 /// a few steps to this process. 834 /// 835 /// 1) It takes allocations of aggregates and analyzes the ways in which they 836 /// are used to try to split them into smaller allocations, ideally of 837 /// a single scalar data type. It will split up memcpy and memset accesses 838 /// as necessary and try to isolate individual scalar accesses. 839 /// 2) It will transform accesses into forms which are suitable for SSA value 840 /// promotion. This can be replacing a memset with a scalar store of an 841 /// integer value, or it can involve speculating operations on a PHI or 842 /// select to be a PHI or select of the results. 843 /// 3) Finally, this will try to detect a pattern of accesses which map cleanly 844 /// onto insert and extract operations on a vector value, and convert them to 845 /// this form. By doing so, it will enable promotion of vector aggregates to 846 /// SSA vector values. 847 class SROA : public FunctionPass { 848 const bool RequiresDomTree; 849 850 LLVMContext *C; 851 const DataLayout *DL; 852 DominatorTree *DT; 853 854 /// \brief Worklist of alloca instructions to simplify. 855 /// 856 /// Each alloca in the function is added to this. Each new alloca formed gets 857 /// added to it as well to recursively simplify unless that alloca can be 858 /// directly promoted. Finally, each time we rewrite a use of an alloca other 859 /// the one being actively rewritten, we add it back onto the list if not 860 /// already present to ensure it is re-visited. 861 SetVector<AllocaInst *, SmallVector<AllocaInst *, 16> > Worklist; 862 863 /// \brief A collection of instructions to delete. 864 /// We try to batch deletions to simplify code and make things a bit more 865 /// efficient. 866 SetVector<Instruction *, SmallVector<Instruction *, 8> > DeadInsts; 867 868 /// \brief Post-promotion worklist. 869 /// 870 /// Sometimes we discover an alloca which has a high probability of becoming 871 /// viable for SROA after a round of promotion takes place. In those cases, 872 /// the alloca is enqueued here for re-processing. 873 /// 874 /// Note that we have to be very careful to clear allocas out of this list in 875 /// the event they are deleted. 876 SetVector<AllocaInst *, SmallVector<AllocaInst *, 16> > PostPromotionWorklist; 877 878 /// \brief A collection of alloca instructions we can directly promote. 879 std::vector<AllocaInst *> PromotableAllocas; 880 881 /// \brief A worklist of PHIs to speculate prior to promoting allocas. 882 /// 883 /// All of these PHIs have been checked for the safety of speculation and by 884 /// being speculated will allow promoting allocas currently in the promotable 885 /// queue. 886 SetVector<PHINode *, SmallVector<PHINode *, 2> > SpeculatablePHIs; 887 888 /// \brief A worklist of select instructions to speculate prior to promoting 889 /// allocas. 890 /// 891 /// All of these select instructions have been checked for the safety of 892 /// speculation and by being speculated will allow promoting allocas 893 /// currently in the promotable queue. 894 SetVector<SelectInst *, SmallVector<SelectInst *, 2> > SpeculatableSelects; 895 896 public: 897 SROA(bool RequiresDomTree = true) 898 : FunctionPass(ID), RequiresDomTree(RequiresDomTree), 899 C(0), DL(0), DT(0) { 900 initializeSROAPass(*PassRegistry::getPassRegistry()); 901 } 902 bool runOnFunction(Function &F); 903 void getAnalysisUsage(AnalysisUsage &AU) const; 904 905 const char *getPassName() const { return "SROA"; } 906 static char ID; 907 908 private: 909 friend class PHIOrSelectSpeculator; 910 friend class AllocaSliceRewriter; 911 912 bool rewritePartition(AllocaInst &AI, AllocaSlices &S, 913 AllocaSlices::iterator B, AllocaSlices::iterator E, 914 int64_t BeginOffset, int64_t EndOffset, 915 ArrayRef<AllocaSlices::iterator> SplitUses); 916 bool splitAlloca(AllocaInst &AI, AllocaSlices &S); 917 bool runOnAlloca(AllocaInst &AI); 918 void deleteDeadInstructions(SmallPtrSet<AllocaInst *, 4> &DeletedAllocas); 919 bool promoteAllocas(Function &F); 920 }; 921 } 922 923 char SROA::ID = 0; 924 925 FunctionPass *llvm::createSROAPass(bool RequiresDomTree) { 926 return new SROA(RequiresDomTree); 927 } 928 929 INITIALIZE_PASS_BEGIN(SROA, "sroa", "Scalar Replacement Of Aggregates", 930 false, false) 931 INITIALIZE_PASS_DEPENDENCY(DominatorTree) 932 INITIALIZE_PASS_END(SROA, "sroa", "Scalar Replacement Of Aggregates", 933 false, false) 934 935 /// Walk the range of a partitioning looking for a common type to cover this 936 /// sequence of slices. 937 static Type *findCommonType(AllocaSlices::const_iterator B, 938 AllocaSlices::const_iterator E, 939 uint64_t EndOffset) { 940 Type *Ty = 0; 941 bool IgnoreNonIntegralTypes = false; 942 for (AllocaSlices::const_iterator I = B; I != E; ++I) { 943 Use *U = I->getUse(); 944 if (isa<IntrinsicInst>(*U->getUser())) 945 continue; 946 if (I->beginOffset() != B->beginOffset() || I->endOffset() != EndOffset) 947 continue; 948 949 Type *UserTy = 0; 950 if (LoadInst *LI = dyn_cast<LoadInst>(U->getUser())) { 951 UserTy = LI->getType(); 952 } else if (StoreInst *SI = dyn_cast<StoreInst>(U->getUser())) { 953 UserTy = SI->getValueOperand()->getType(); 954 } else { 955 IgnoreNonIntegralTypes = true; // Give up on anything but an iN type. 956 continue; 957 } 958 959 if (IntegerType *ITy = dyn_cast<IntegerType>(UserTy)) { 960 // If the type is larger than the partition, skip it. We only encounter 961 // this for split integer operations where we want to use the type of the 962 // entity causing the split. Also skip if the type is not a byte width 963 // multiple. 964 if (ITy->getBitWidth() % 8 != 0 || 965 ITy->getBitWidth() / 8 > (EndOffset - B->beginOffset())) 966 continue; 967 968 // If we have found an integer type use covering the alloca, use that 969 // regardless of the other types, as integers are often used for 970 // a "bucket of bits" type. 971 // 972 // NB: This *must* be the only return from inside the loop so that the 973 // order of slices doesn't impact the computed type. 974 return ITy; 975 } else if (IgnoreNonIntegralTypes) { 976 continue; 977 } 978 979 if (Ty && Ty != UserTy) 980 IgnoreNonIntegralTypes = true; // Give up on anything but an iN type. 981 982 Ty = UserTy; 983 } 984 return Ty; 985 } 986 987 /// PHI instructions that use an alloca and are subsequently loaded can be 988 /// rewritten to load both input pointers in the pred blocks and then PHI the 989 /// results, allowing the load of the alloca to be promoted. 990 /// From this: 991 /// %P2 = phi [i32* %Alloca, i32* %Other] 992 /// %V = load i32* %P2 993 /// to: 994 /// %V1 = load i32* %Alloca -> will be mem2reg'd 995 /// ... 996 /// %V2 = load i32* %Other 997 /// ... 998 /// %V = phi [i32 %V1, i32 %V2] 999 /// 1000 /// We can do this to a select if its only uses are loads and if the operands 1001 /// to the select can be loaded unconditionally. 1002 /// 1003 /// FIXME: This should be hoisted into a generic utility, likely in 1004 /// Transforms/Util/Local.h 1005 static bool isSafePHIToSpeculate(PHINode &PN, 1006 const DataLayout *DL = 0) { 1007 // For now, we can only do this promotion if the load is in the same block 1008 // as the PHI, and if there are no stores between the phi and load. 1009 // TODO: Allow recursive phi users. 1010 // TODO: Allow stores. 1011 BasicBlock *BB = PN.getParent(); 1012 unsigned MaxAlign = 0; 1013 bool HaveLoad = false; 1014 for (Value::use_iterator UI = PN.use_begin(), UE = PN.use_end(); UI != UE; 1015 ++UI) { 1016 LoadInst *LI = dyn_cast<LoadInst>(*UI); 1017 if (LI == 0 || !LI->isSimple()) 1018 return false; 1019 1020 // For now we only allow loads in the same block as the PHI. This is 1021 // a common case that happens when instcombine merges two loads through 1022 // a PHI. 1023 if (LI->getParent() != BB) 1024 return false; 1025 1026 // Ensure that there are no instructions between the PHI and the load that 1027 // could store. 1028 for (BasicBlock::iterator BBI = &PN; &*BBI != LI; ++BBI) 1029 if (BBI->mayWriteToMemory()) 1030 return false; 1031 1032 MaxAlign = std::max(MaxAlign, LI->getAlignment()); 1033 HaveLoad = true; 1034 } 1035 1036 if (!HaveLoad) 1037 return false; 1038 1039 // We can only transform this if it is safe to push the loads into the 1040 // predecessor blocks. The only thing to watch out for is that we can't put 1041 // a possibly trapping load in the predecessor if it is a critical edge. 1042 for (unsigned Idx = 0, Num = PN.getNumIncomingValues(); Idx != Num; ++Idx) { 1043 TerminatorInst *TI = PN.getIncomingBlock(Idx)->getTerminator(); 1044 Value *InVal = PN.getIncomingValue(Idx); 1045 1046 // If the value is produced by the terminator of the predecessor (an 1047 // invoke) or it has side-effects, there is no valid place to put a load 1048 // in the predecessor. 1049 if (TI == InVal || TI->mayHaveSideEffects()) 1050 return false; 1051 1052 // If the predecessor has a single successor, then the edge isn't 1053 // critical. 1054 if (TI->getNumSuccessors() == 1) 1055 continue; 1056 1057 // If this pointer is always safe to load, or if we can prove that there 1058 // is already a load in the block, then we can move the load to the pred 1059 // block. 1060 if (InVal->isDereferenceablePointer() || 1061 isSafeToLoadUnconditionally(InVal, TI, MaxAlign, DL)) 1062 continue; 1063 1064 return false; 1065 } 1066 1067 return true; 1068 } 1069 1070 static void speculatePHINodeLoads(PHINode &PN) { 1071 DEBUG(dbgs() << " original: " << PN << "\n"); 1072 1073 Type *LoadTy = cast<PointerType>(PN.getType())->getElementType(); 1074 IRBuilderTy PHIBuilder(&PN); 1075 PHINode *NewPN = PHIBuilder.CreatePHI(LoadTy, PN.getNumIncomingValues(), 1076 PN.getName() + ".sroa.speculated"); 1077 1078 // Get the TBAA tag and alignment to use from one of the loads. It doesn't 1079 // matter which one we get and if any differ. 1080 LoadInst *SomeLoad = cast<LoadInst>(*PN.use_begin()); 1081 MDNode *TBAATag = SomeLoad->getMetadata(LLVMContext::MD_tbaa); 1082 unsigned Align = SomeLoad->getAlignment(); 1083 1084 // Rewrite all loads of the PN to use the new PHI. 1085 while (!PN.use_empty()) { 1086 LoadInst *LI = cast<LoadInst>(*PN.use_begin()); 1087 LI->replaceAllUsesWith(NewPN); 1088 LI->eraseFromParent(); 1089 } 1090 1091 // Inject loads into all of the pred blocks. 1092 for (unsigned Idx = 0, Num = PN.getNumIncomingValues(); Idx != Num; ++Idx) { 1093 BasicBlock *Pred = PN.getIncomingBlock(Idx); 1094 TerminatorInst *TI = Pred->getTerminator(); 1095 Value *InVal = PN.getIncomingValue(Idx); 1096 IRBuilderTy PredBuilder(TI); 1097 1098 LoadInst *Load = PredBuilder.CreateLoad( 1099 InVal, (PN.getName() + ".sroa.speculate.load." + Pred->getName())); 1100 ++NumLoadsSpeculated; 1101 Load->setAlignment(Align); 1102 if (TBAATag) 1103 Load->setMetadata(LLVMContext::MD_tbaa, TBAATag); 1104 NewPN->addIncoming(Load, Pred); 1105 } 1106 1107 DEBUG(dbgs() << " speculated to: " << *NewPN << "\n"); 1108 PN.eraseFromParent(); 1109 } 1110 1111 /// Select instructions that use an alloca and are subsequently loaded can be 1112 /// rewritten to load both input pointers and then select between the result, 1113 /// allowing the load of the alloca to be promoted. 1114 /// From this: 1115 /// %P2 = select i1 %cond, i32* %Alloca, i32* %Other 1116 /// %V = load i32* %P2 1117 /// to: 1118 /// %V1 = load i32* %Alloca -> will be mem2reg'd 1119 /// %V2 = load i32* %Other 1120 /// %V = select i1 %cond, i32 %V1, i32 %V2 1121 /// 1122 /// We can do this to a select if its only uses are loads and if the operand 1123 /// to the select can be loaded unconditionally. 1124 static bool isSafeSelectToSpeculate(SelectInst &SI, const DataLayout *DL = 0) { 1125 Value *TValue = SI.getTrueValue(); 1126 Value *FValue = SI.getFalseValue(); 1127 bool TDerefable = TValue->isDereferenceablePointer(); 1128 bool FDerefable = FValue->isDereferenceablePointer(); 1129 1130 for (Value::use_iterator UI = SI.use_begin(), UE = SI.use_end(); UI != UE; 1131 ++UI) { 1132 LoadInst *LI = dyn_cast<LoadInst>(*UI); 1133 if (LI == 0 || !LI->isSimple()) 1134 return false; 1135 1136 // Both operands to the select need to be dereferencable, either 1137 // absolutely (e.g. allocas) or at this point because we can see other 1138 // accesses to it. 1139 if (!TDerefable && 1140 !isSafeToLoadUnconditionally(TValue, LI, LI->getAlignment(), DL)) 1141 return false; 1142 if (!FDerefable && 1143 !isSafeToLoadUnconditionally(FValue, LI, LI->getAlignment(), DL)) 1144 return false; 1145 } 1146 1147 return true; 1148 } 1149 1150 static void speculateSelectInstLoads(SelectInst &SI) { 1151 DEBUG(dbgs() << " original: " << SI << "\n"); 1152 1153 IRBuilderTy IRB(&SI); 1154 Value *TV = SI.getTrueValue(); 1155 Value *FV = SI.getFalseValue(); 1156 // Replace the loads of the select with a select of two loads. 1157 while (!SI.use_empty()) { 1158 LoadInst *LI = cast<LoadInst>(*SI.use_begin()); 1159 assert(LI->isSimple() && "We only speculate simple loads"); 1160 1161 IRB.SetInsertPoint(LI); 1162 LoadInst *TL = 1163 IRB.CreateLoad(TV, LI->getName() + ".sroa.speculate.load.true"); 1164 LoadInst *FL = 1165 IRB.CreateLoad(FV, LI->getName() + ".sroa.speculate.load.false"); 1166 NumLoadsSpeculated += 2; 1167 1168 // Transfer alignment and TBAA info if present. 1169 TL->setAlignment(LI->getAlignment()); 1170 FL->setAlignment(LI->getAlignment()); 1171 if (MDNode *Tag = LI->getMetadata(LLVMContext::MD_tbaa)) { 1172 TL->setMetadata(LLVMContext::MD_tbaa, Tag); 1173 FL->setMetadata(LLVMContext::MD_tbaa, Tag); 1174 } 1175 1176 Value *V = IRB.CreateSelect(SI.getCondition(), TL, FL, 1177 LI->getName() + ".sroa.speculated"); 1178 1179 DEBUG(dbgs() << " speculated to: " << *V << "\n"); 1180 LI->replaceAllUsesWith(V); 1181 LI->eraseFromParent(); 1182 } 1183 SI.eraseFromParent(); 1184 } 1185 1186 /// \brief Build a GEP out of a base pointer and indices. 1187 /// 1188 /// This will return the BasePtr if that is valid, or build a new GEP 1189 /// instruction using the IRBuilder if GEP-ing is needed. 1190 static Value *buildGEP(IRBuilderTy &IRB, Value *BasePtr, 1191 SmallVectorImpl<Value *> &Indices) { 1192 if (Indices.empty()) 1193 return BasePtr; 1194 1195 // A single zero index is a no-op, so check for this and avoid building a GEP 1196 // in that case. 1197 if (Indices.size() == 1 && cast<ConstantInt>(Indices.back())->isZero()) 1198 return BasePtr; 1199 1200 return IRB.CreateInBoundsGEP(BasePtr, Indices, "idx"); 1201 } 1202 1203 /// \brief Get a natural GEP off of the BasePtr walking through Ty toward 1204 /// TargetTy without changing the offset of the pointer. 1205 /// 1206 /// This routine assumes we've already established a properly offset GEP with 1207 /// Indices, and arrived at the Ty type. The goal is to continue to GEP with 1208 /// zero-indices down through type layers until we find one the same as 1209 /// TargetTy. If we can't find one with the same type, we at least try to use 1210 /// one with the same size. If none of that works, we just produce the GEP as 1211 /// indicated by Indices to have the correct offset. 1212 static Value *getNaturalGEPWithType(IRBuilderTy &IRB, const DataLayout &DL, 1213 Value *BasePtr, Type *Ty, Type *TargetTy, 1214 SmallVectorImpl<Value *> &Indices) { 1215 if (Ty == TargetTy) 1216 return buildGEP(IRB, BasePtr, Indices); 1217 1218 // See if we can descend into a struct and locate a field with the correct 1219 // type. 1220 unsigned NumLayers = 0; 1221 Type *ElementTy = Ty; 1222 do { 1223 if (ElementTy->isPointerTy()) 1224 break; 1225 if (SequentialType *SeqTy = dyn_cast<SequentialType>(ElementTy)) { 1226 ElementTy = SeqTy->getElementType(); 1227 // Note that we use the default address space as this index is over an 1228 // array or a vector, not a pointer. 1229 Indices.push_back(IRB.getInt(APInt(DL.getPointerSizeInBits(0), 0))); 1230 } else if (StructType *STy = dyn_cast<StructType>(ElementTy)) { 1231 if (STy->element_begin() == STy->element_end()) 1232 break; // Nothing left to descend into. 1233 ElementTy = *STy->element_begin(); 1234 Indices.push_back(IRB.getInt32(0)); 1235 } else { 1236 break; 1237 } 1238 ++NumLayers; 1239 } while (ElementTy != TargetTy); 1240 if (ElementTy != TargetTy) 1241 Indices.erase(Indices.end() - NumLayers, Indices.end()); 1242 1243 return buildGEP(IRB, BasePtr, Indices); 1244 } 1245 1246 /// \brief Recursively compute indices for a natural GEP. 1247 /// 1248 /// This is the recursive step for getNaturalGEPWithOffset that walks down the 1249 /// element types adding appropriate indices for the GEP. 1250 static Value *getNaturalGEPRecursively(IRBuilderTy &IRB, const DataLayout &DL, 1251 Value *Ptr, Type *Ty, APInt &Offset, 1252 Type *TargetTy, 1253 SmallVectorImpl<Value *> &Indices) { 1254 if (Offset == 0) 1255 return getNaturalGEPWithType(IRB, DL, Ptr, Ty, TargetTy, Indices); 1256 1257 // We can't recurse through pointer types. 1258 if (Ty->isPointerTy()) 1259 return 0; 1260 1261 // We try to analyze GEPs over vectors here, but note that these GEPs are 1262 // extremely poorly defined currently. The long-term goal is to remove GEPing 1263 // over a vector from the IR completely. 1264 if (VectorType *VecTy = dyn_cast<VectorType>(Ty)) { 1265 unsigned ElementSizeInBits = DL.getTypeSizeInBits(VecTy->getScalarType()); 1266 if (ElementSizeInBits % 8) 1267 return 0; // GEPs over non-multiple of 8 size vector elements are invalid. 1268 APInt ElementSize(Offset.getBitWidth(), ElementSizeInBits / 8); 1269 APInt NumSkippedElements = Offset.sdiv(ElementSize); 1270 if (NumSkippedElements.ugt(VecTy->getNumElements())) 1271 return 0; 1272 Offset -= NumSkippedElements * ElementSize; 1273 Indices.push_back(IRB.getInt(NumSkippedElements)); 1274 return getNaturalGEPRecursively(IRB, DL, Ptr, VecTy->getElementType(), 1275 Offset, TargetTy, Indices); 1276 } 1277 1278 if (ArrayType *ArrTy = dyn_cast<ArrayType>(Ty)) { 1279 Type *ElementTy = ArrTy->getElementType(); 1280 APInt ElementSize(Offset.getBitWidth(), DL.getTypeAllocSize(ElementTy)); 1281 APInt NumSkippedElements = Offset.sdiv(ElementSize); 1282 if (NumSkippedElements.ugt(ArrTy->getNumElements())) 1283 return 0; 1284 1285 Offset -= NumSkippedElements * ElementSize; 1286 Indices.push_back(IRB.getInt(NumSkippedElements)); 1287 return getNaturalGEPRecursively(IRB, DL, Ptr, ElementTy, Offset, TargetTy, 1288 Indices); 1289 } 1290 1291 StructType *STy = dyn_cast<StructType>(Ty); 1292 if (!STy) 1293 return 0; 1294 1295 const StructLayout *SL = DL.getStructLayout(STy); 1296 uint64_t StructOffset = Offset.getZExtValue(); 1297 if (StructOffset >= SL->getSizeInBytes()) 1298 return 0; 1299 unsigned Index = SL->getElementContainingOffset(StructOffset); 1300 Offset -= APInt(Offset.getBitWidth(), SL->getElementOffset(Index)); 1301 Type *ElementTy = STy->getElementType(Index); 1302 if (Offset.uge(DL.getTypeAllocSize(ElementTy))) 1303 return 0; // The offset points into alignment padding. 1304 1305 Indices.push_back(IRB.getInt32(Index)); 1306 return getNaturalGEPRecursively(IRB, DL, Ptr, ElementTy, Offset, TargetTy, 1307 Indices); 1308 } 1309 1310 /// \brief Get a natural GEP from a base pointer to a particular offset and 1311 /// resulting in a particular type. 1312 /// 1313 /// The goal is to produce a "natural" looking GEP that works with the existing 1314 /// composite types to arrive at the appropriate offset and element type for 1315 /// a pointer. TargetTy is the element type the returned GEP should point-to if 1316 /// possible. We recurse by decreasing Offset, adding the appropriate index to 1317 /// Indices, and setting Ty to the result subtype. 1318 /// 1319 /// If no natural GEP can be constructed, this function returns null. 1320 static Value *getNaturalGEPWithOffset(IRBuilderTy &IRB, const DataLayout &DL, 1321 Value *Ptr, APInt Offset, Type *TargetTy, 1322 SmallVectorImpl<Value *> &Indices) { 1323 PointerType *Ty = cast<PointerType>(Ptr->getType()); 1324 1325 // Don't consider any GEPs through an i8* as natural unless the TargetTy is 1326 // an i8. 1327 if (Ty == IRB.getInt8PtrTy() && TargetTy->isIntegerTy(8)) 1328 return 0; 1329 1330 Type *ElementTy = Ty->getElementType(); 1331 if (!ElementTy->isSized()) 1332 return 0; // We can't GEP through an unsized element. 1333 APInt ElementSize(Offset.getBitWidth(), DL.getTypeAllocSize(ElementTy)); 1334 if (ElementSize == 0) 1335 return 0; // Zero-length arrays can't help us build a natural GEP. 1336 APInt NumSkippedElements = Offset.sdiv(ElementSize); 1337 1338 Offset -= NumSkippedElements * ElementSize; 1339 Indices.push_back(IRB.getInt(NumSkippedElements)); 1340 return getNaturalGEPRecursively(IRB, DL, Ptr, ElementTy, Offset, TargetTy, 1341 Indices); 1342 } 1343 1344 /// \brief Compute an adjusted pointer from Ptr by Offset bytes where the 1345 /// resulting pointer has PointerTy. 1346 /// 1347 /// This tries very hard to compute a "natural" GEP which arrives at the offset 1348 /// and produces the pointer type desired. Where it cannot, it will try to use 1349 /// the natural GEP to arrive at the offset and bitcast to the type. Where that 1350 /// fails, it will try to use an existing i8* and GEP to the byte offset and 1351 /// bitcast to the type. 1352 /// 1353 /// The strategy for finding the more natural GEPs is to peel off layers of the 1354 /// pointer, walking back through bit casts and GEPs, searching for a base 1355 /// pointer from which we can compute a natural GEP with the desired 1356 /// properties. The algorithm tries to fold as many constant indices into 1357 /// a single GEP as possible, thus making each GEP more independent of the 1358 /// surrounding code. 1359 static Value *getAdjustedPtr(IRBuilderTy &IRB, const DataLayout &DL, 1360 Value *Ptr, APInt Offset, Type *PointerTy) { 1361 // Even though we don't look through PHI nodes, we could be called on an 1362 // instruction in an unreachable block, which may be on a cycle. 1363 SmallPtrSet<Value *, 4> Visited; 1364 Visited.insert(Ptr); 1365 SmallVector<Value *, 4> Indices; 1366 1367 // We may end up computing an offset pointer that has the wrong type. If we 1368 // never are able to compute one directly that has the correct type, we'll 1369 // fall back to it, so keep it around here. 1370 Value *OffsetPtr = 0; 1371 1372 // Remember any i8 pointer we come across to re-use if we need to do a raw 1373 // byte offset. 1374 Value *Int8Ptr = 0; 1375 APInt Int8PtrOffset(Offset.getBitWidth(), 0); 1376 1377 Type *TargetTy = PointerTy->getPointerElementType(); 1378 1379 do { 1380 // First fold any existing GEPs into the offset. 1381 while (GEPOperator *GEP = dyn_cast<GEPOperator>(Ptr)) { 1382 APInt GEPOffset(Offset.getBitWidth(), 0); 1383 if (!GEP->accumulateConstantOffset(DL, GEPOffset)) 1384 break; 1385 Offset += GEPOffset; 1386 Ptr = GEP->getPointerOperand(); 1387 if (!Visited.insert(Ptr)) 1388 break; 1389 } 1390 1391 // See if we can perform a natural GEP here. 1392 Indices.clear(); 1393 if (Value *P = getNaturalGEPWithOffset(IRB, DL, Ptr, Offset, TargetTy, 1394 Indices)) { 1395 if (P->getType() == PointerTy) { 1396 // Zap any offset pointer that we ended up computing in previous rounds. 1397 if (OffsetPtr && OffsetPtr->use_empty()) 1398 if (Instruction *I = dyn_cast<Instruction>(OffsetPtr)) 1399 I->eraseFromParent(); 1400 return P; 1401 } 1402 if (!OffsetPtr) { 1403 OffsetPtr = P; 1404 } 1405 } 1406 1407 // Stash this pointer if we've found an i8*. 1408 if (Ptr->getType()->isIntegerTy(8)) { 1409 Int8Ptr = Ptr; 1410 Int8PtrOffset = Offset; 1411 } 1412 1413 // Peel off a layer of the pointer and update the offset appropriately. 1414 if (Operator::getOpcode(Ptr) == Instruction::BitCast) { 1415 Ptr = cast<Operator>(Ptr)->getOperand(0); 1416 } else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(Ptr)) { 1417 if (GA->mayBeOverridden()) 1418 break; 1419 Ptr = GA->getAliasee(); 1420 } else { 1421 break; 1422 } 1423 assert(Ptr->getType()->isPointerTy() && "Unexpected operand type!"); 1424 } while (Visited.insert(Ptr)); 1425 1426 if (!OffsetPtr) { 1427 if (!Int8Ptr) { 1428 Int8Ptr = IRB.CreateBitCast(Ptr, IRB.getInt8PtrTy(), 1429 "raw_cast"); 1430 Int8PtrOffset = Offset; 1431 } 1432 1433 OffsetPtr = Int8PtrOffset == 0 ? Int8Ptr : 1434 IRB.CreateInBoundsGEP(Int8Ptr, IRB.getInt(Int8PtrOffset), 1435 "raw_idx"); 1436 } 1437 Ptr = OffsetPtr; 1438 1439 // On the off chance we were targeting i8*, guard the bitcast here. 1440 if (Ptr->getType() != PointerTy) 1441 Ptr = IRB.CreateBitCast(Ptr, PointerTy, "cast"); 1442 1443 return Ptr; 1444 } 1445 1446 /// \brief Test whether we can convert a value from the old to the new type. 1447 /// 1448 /// This predicate should be used to guard calls to convertValue in order to 1449 /// ensure that we only try to convert viable values. The strategy is that we 1450 /// will peel off single element struct and array wrappings to get to an 1451 /// underlying value, and convert that value. 1452 static bool canConvertValue(const DataLayout &DL, Type *OldTy, Type *NewTy) { 1453 if (OldTy == NewTy) 1454 return true; 1455 if (IntegerType *OldITy = dyn_cast<IntegerType>(OldTy)) 1456 if (IntegerType *NewITy = dyn_cast<IntegerType>(NewTy)) 1457 if (NewITy->getBitWidth() >= OldITy->getBitWidth()) 1458 return true; 1459 if (DL.getTypeSizeInBits(NewTy) != DL.getTypeSizeInBits(OldTy)) 1460 return false; 1461 if (!NewTy->isSingleValueType() || !OldTy->isSingleValueType()) 1462 return false; 1463 1464 // We can convert pointers to integers and vice-versa. Same for vectors 1465 // of pointers and integers. 1466 OldTy = OldTy->getScalarType(); 1467 NewTy = NewTy->getScalarType(); 1468 if (NewTy->isPointerTy() || OldTy->isPointerTy()) { 1469 if (NewTy->isPointerTy() && OldTy->isPointerTy()) 1470 return true; 1471 if (NewTy->isIntegerTy() || OldTy->isIntegerTy()) 1472 return true; 1473 return false; 1474 } 1475 1476 return true; 1477 } 1478 1479 /// \brief Generic routine to convert an SSA value to a value of a different 1480 /// type. 1481 /// 1482 /// This will try various different casting techniques, such as bitcasts, 1483 /// inttoptr, and ptrtoint casts. Use the \c canConvertValue predicate to test 1484 /// two types for viability with this routine. 1485 static Value *convertValue(const DataLayout &DL, IRBuilderTy &IRB, Value *V, 1486 Type *NewTy) { 1487 Type *OldTy = V->getType(); 1488 assert(canConvertValue(DL, OldTy, NewTy) && "Value not convertable to type"); 1489 1490 if (OldTy == NewTy) 1491 return V; 1492 1493 if (IntegerType *OldITy = dyn_cast<IntegerType>(OldTy)) 1494 if (IntegerType *NewITy = dyn_cast<IntegerType>(NewTy)) 1495 if (NewITy->getBitWidth() > OldITy->getBitWidth()) 1496 return IRB.CreateZExt(V, NewITy); 1497 1498 // See if we need inttoptr for this type pair. A cast involving both scalars 1499 // and vectors requires and additional bitcast. 1500 if (OldTy->getScalarType()->isIntegerTy() && 1501 NewTy->getScalarType()->isPointerTy()) { 1502 // Expand <2 x i32> to i8* --> <2 x i32> to i64 to i8* 1503 if (OldTy->isVectorTy() && !NewTy->isVectorTy()) 1504 return IRB.CreateIntToPtr(IRB.CreateBitCast(V, DL.getIntPtrType(NewTy)), 1505 NewTy); 1506 1507 // Expand i128 to <2 x i8*> --> i128 to <2 x i64> to <2 x i8*> 1508 if (!OldTy->isVectorTy() && NewTy->isVectorTy()) 1509 return IRB.CreateIntToPtr(IRB.CreateBitCast(V, DL.getIntPtrType(NewTy)), 1510 NewTy); 1511 1512 return IRB.CreateIntToPtr(V, NewTy); 1513 } 1514 1515 // See if we need ptrtoint for this type pair. A cast involving both scalars 1516 // and vectors requires and additional bitcast. 1517 if (OldTy->getScalarType()->isPointerTy() && 1518 NewTy->getScalarType()->isIntegerTy()) { 1519 // Expand <2 x i8*> to i128 --> <2 x i8*> to <2 x i64> to i128 1520 if (OldTy->isVectorTy() && !NewTy->isVectorTy()) 1521 return IRB.CreateBitCast(IRB.CreatePtrToInt(V, DL.getIntPtrType(OldTy)), 1522 NewTy); 1523 1524 // Expand i8* to <2 x i32> --> i8* to i64 to <2 x i32> 1525 if (!OldTy->isVectorTy() && NewTy->isVectorTy()) 1526 return IRB.CreateBitCast(IRB.CreatePtrToInt(V, DL.getIntPtrType(OldTy)), 1527 NewTy); 1528 1529 return IRB.CreatePtrToInt(V, NewTy); 1530 } 1531 1532 return IRB.CreateBitCast(V, NewTy); 1533 } 1534 1535 /// \brief Test whether the given slice use can be promoted to a vector. 1536 /// 1537 /// This function is called to test each entry in a partioning which is slated 1538 /// for a single slice. 1539 static bool isVectorPromotionViableForSlice( 1540 const DataLayout &DL, AllocaSlices &S, uint64_t SliceBeginOffset, 1541 uint64_t SliceEndOffset, VectorType *Ty, uint64_t ElementSize, 1542 AllocaSlices::const_iterator I) { 1543 // First validate the slice offsets. 1544 uint64_t BeginOffset = 1545 std::max(I->beginOffset(), SliceBeginOffset) - SliceBeginOffset; 1546 uint64_t BeginIndex = BeginOffset / ElementSize; 1547 if (BeginIndex * ElementSize != BeginOffset || 1548 BeginIndex >= Ty->getNumElements()) 1549 return false; 1550 uint64_t EndOffset = 1551 std::min(I->endOffset(), SliceEndOffset) - SliceBeginOffset; 1552 uint64_t EndIndex = EndOffset / ElementSize; 1553 if (EndIndex * ElementSize != EndOffset || EndIndex > Ty->getNumElements()) 1554 return false; 1555 1556 assert(EndIndex > BeginIndex && "Empty vector!"); 1557 uint64_t NumElements = EndIndex - BeginIndex; 1558 Type *SliceTy = 1559 (NumElements == 1) ? Ty->getElementType() 1560 : VectorType::get(Ty->getElementType(), NumElements); 1561 1562 Type *SplitIntTy = 1563 Type::getIntNTy(Ty->getContext(), NumElements * ElementSize * 8); 1564 1565 Use *U = I->getUse(); 1566 1567 if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(U->getUser())) { 1568 if (MI->isVolatile()) 1569 return false; 1570 if (!I->isSplittable()) 1571 return false; // Skip any unsplittable intrinsics. 1572 } else if (U->get()->getType()->getPointerElementType()->isStructTy()) { 1573 // Disable vector promotion when there are loads or stores of an FCA. 1574 return false; 1575 } else if (LoadInst *LI = dyn_cast<LoadInst>(U->getUser())) { 1576 if (LI->isVolatile()) 1577 return false; 1578 Type *LTy = LI->getType(); 1579 if (SliceBeginOffset > I->beginOffset() || 1580 SliceEndOffset < I->endOffset()) { 1581 assert(LTy->isIntegerTy()); 1582 LTy = SplitIntTy; 1583 } 1584 if (!canConvertValue(DL, SliceTy, LTy)) 1585 return false; 1586 } else if (StoreInst *SI = dyn_cast<StoreInst>(U->getUser())) { 1587 if (SI->isVolatile()) 1588 return false; 1589 Type *STy = SI->getValueOperand()->getType(); 1590 if (SliceBeginOffset > I->beginOffset() || 1591 SliceEndOffset < I->endOffset()) { 1592 assert(STy->isIntegerTy()); 1593 STy = SplitIntTy; 1594 } 1595 if (!canConvertValue(DL, STy, SliceTy)) 1596 return false; 1597 } else { 1598 return false; 1599 } 1600 1601 return true; 1602 } 1603 1604 /// \brief Test whether the given alloca partitioning and range of slices can be 1605 /// promoted to a vector. 1606 /// 1607 /// This is a quick test to check whether we can rewrite a particular alloca 1608 /// partition (and its newly formed alloca) into a vector alloca with only 1609 /// whole-vector loads and stores such that it could be promoted to a vector 1610 /// SSA value. We only can ensure this for a limited set of operations, and we 1611 /// don't want to do the rewrites unless we are confident that the result will 1612 /// be promotable, so we have an early test here. 1613 static bool 1614 isVectorPromotionViable(const DataLayout &DL, Type *AllocaTy, AllocaSlices &S, 1615 uint64_t SliceBeginOffset, uint64_t SliceEndOffset, 1616 AllocaSlices::const_iterator I, 1617 AllocaSlices::const_iterator E, 1618 ArrayRef<AllocaSlices::iterator> SplitUses) { 1619 VectorType *Ty = dyn_cast<VectorType>(AllocaTy); 1620 if (!Ty) 1621 return false; 1622 1623 uint64_t ElementSize = DL.getTypeSizeInBits(Ty->getScalarType()); 1624 1625 // While the definition of LLVM vectors is bitpacked, we don't support sizes 1626 // that aren't byte sized. 1627 if (ElementSize % 8) 1628 return false; 1629 assert((DL.getTypeSizeInBits(Ty) % 8) == 0 && 1630 "vector size not a multiple of element size?"); 1631 ElementSize /= 8; 1632 1633 for (; I != E; ++I) 1634 if (!isVectorPromotionViableForSlice(DL, S, SliceBeginOffset, 1635 SliceEndOffset, Ty, ElementSize, I)) 1636 return false; 1637 1638 for (ArrayRef<AllocaSlices::iterator>::const_iterator SUI = SplitUses.begin(), 1639 SUE = SplitUses.end(); 1640 SUI != SUE; ++SUI) 1641 if (!isVectorPromotionViableForSlice(DL, S, SliceBeginOffset, 1642 SliceEndOffset, Ty, ElementSize, *SUI)) 1643 return false; 1644 1645 return true; 1646 } 1647 1648 /// \brief Test whether a slice of an alloca is valid for integer widening. 1649 /// 1650 /// This implements the necessary checking for the \c isIntegerWideningViable 1651 /// test below on a single slice of the alloca. 1652 static bool isIntegerWideningViableForSlice(const DataLayout &DL, 1653 Type *AllocaTy, 1654 uint64_t AllocBeginOffset, 1655 uint64_t Size, AllocaSlices &S, 1656 AllocaSlices::const_iterator I, 1657 bool &WholeAllocaOp) { 1658 uint64_t RelBegin = I->beginOffset() - AllocBeginOffset; 1659 uint64_t RelEnd = I->endOffset() - AllocBeginOffset; 1660 1661 // We can't reasonably handle cases where the load or store extends past 1662 // the end of the aloca's type and into its padding. 1663 if (RelEnd > Size) 1664 return false; 1665 1666 Use *U = I->getUse(); 1667 1668 if (LoadInst *LI = dyn_cast<LoadInst>(U->getUser())) { 1669 if (LI->isVolatile()) 1670 return false; 1671 if (RelBegin == 0 && RelEnd == Size) 1672 WholeAllocaOp = true; 1673 if (IntegerType *ITy = dyn_cast<IntegerType>(LI->getType())) { 1674 if (ITy->getBitWidth() < DL.getTypeStoreSizeInBits(ITy)) 1675 return false; 1676 } else if (RelBegin != 0 || RelEnd != Size || 1677 !canConvertValue(DL, AllocaTy, LI->getType())) { 1678 // Non-integer loads need to be convertible from the alloca type so that 1679 // they are promotable. 1680 return false; 1681 } 1682 } else if (StoreInst *SI = dyn_cast<StoreInst>(U->getUser())) { 1683 Type *ValueTy = SI->getValueOperand()->getType(); 1684 if (SI->isVolatile()) 1685 return false; 1686 if (RelBegin == 0 && RelEnd == Size) 1687 WholeAllocaOp = true; 1688 if (IntegerType *ITy = dyn_cast<IntegerType>(ValueTy)) { 1689 if (ITy->getBitWidth() < DL.getTypeStoreSizeInBits(ITy)) 1690 return false; 1691 } else if (RelBegin != 0 || RelEnd != Size || 1692 !canConvertValue(DL, ValueTy, AllocaTy)) { 1693 // Non-integer stores need to be convertible to the alloca type so that 1694 // they are promotable. 1695 return false; 1696 } 1697 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(U->getUser())) { 1698 if (MI->isVolatile() || !isa<Constant>(MI->getLength())) 1699 return false; 1700 if (!I->isSplittable()) 1701 return false; // Skip any unsplittable intrinsics. 1702 } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(U->getUser())) { 1703 if (II->getIntrinsicID() != Intrinsic::lifetime_start && 1704 II->getIntrinsicID() != Intrinsic::lifetime_end) 1705 return false; 1706 } else { 1707 return false; 1708 } 1709 1710 return true; 1711 } 1712 1713 /// \brief Test whether the given alloca partition's integer operations can be 1714 /// widened to promotable ones. 1715 /// 1716 /// This is a quick test to check whether we can rewrite the integer loads and 1717 /// stores to a particular alloca into wider loads and stores and be able to 1718 /// promote the resulting alloca. 1719 static bool 1720 isIntegerWideningViable(const DataLayout &DL, Type *AllocaTy, 1721 uint64_t AllocBeginOffset, AllocaSlices &S, 1722 AllocaSlices::const_iterator I, 1723 AllocaSlices::const_iterator E, 1724 ArrayRef<AllocaSlices::iterator> SplitUses) { 1725 uint64_t SizeInBits = DL.getTypeSizeInBits(AllocaTy); 1726 // Don't create integer types larger than the maximum bitwidth. 1727 if (SizeInBits > IntegerType::MAX_INT_BITS) 1728 return false; 1729 1730 // Don't try to handle allocas with bit-padding. 1731 if (SizeInBits != DL.getTypeStoreSizeInBits(AllocaTy)) 1732 return false; 1733 1734 // We need to ensure that an integer type with the appropriate bitwidth can 1735 // be converted to the alloca type, whatever that is. We don't want to force 1736 // the alloca itself to have an integer type if there is a more suitable one. 1737 Type *IntTy = Type::getIntNTy(AllocaTy->getContext(), SizeInBits); 1738 if (!canConvertValue(DL, AllocaTy, IntTy) || 1739 !canConvertValue(DL, IntTy, AllocaTy)) 1740 return false; 1741 1742 uint64_t Size = DL.getTypeStoreSize(AllocaTy); 1743 1744 // While examining uses, we ensure that the alloca has a covering load or 1745 // store. We don't want to widen the integer operations only to fail to 1746 // promote due to some other unsplittable entry (which we may make splittable 1747 // later). However, if there are only splittable uses, go ahead and assume 1748 // that we cover the alloca. 1749 bool WholeAllocaOp = (I != E) ? false : DL.isLegalInteger(SizeInBits); 1750 1751 for (; I != E; ++I) 1752 if (!isIntegerWideningViableForSlice(DL, AllocaTy, AllocBeginOffset, Size, 1753 S, I, WholeAllocaOp)) 1754 return false; 1755 1756 for (ArrayRef<AllocaSlices::iterator>::const_iterator SUI = SplitUses.begin(), 1757 SUE = SplitUses.end(); 1758 SUI != SUE; ++SUI) 1759 if (!isIntegerWideningViableForSlice(DL, AllocaTy, AllocBeginOffset, Size, 1760 S, *SUI, WholeAllocaOp)) 1761 return false; 1762 1763 return WholeAllocaOp; 1764 } 1765 1766 static Value *extractInteger(const DataLayout &DL, IRBuilderTy &IRB, Value *V, 1767 IntegerType *Ty, uint64_t Offset, 1768 const Twine &Name) { 1769 DEBUG(dbgs() << " start: " << *V << "\n"); 1770 IntegerType *IntTy = cast<IntegerType>(V->getType()); 1771 assert(DL.getTypeStoreSize(Ty) + Offset <= DL.getTypeStoreSize(IntTy) && 1772 "Element extends past full value"); 1773 uint64_t ShAmt = 8*Offset; 1774 if (DL.isBigEndian()) 1775 ShAmt = 8*(DL.getTypeStoreSize(IntTy) - DL.getTypeStoreSize(Ty) - Offset); 1776 if (ShAmt) { 1777 V = IRB.CreateLShr(V, ShAmt, Name + ".shift"); 1778 DEBUG(dbgs() << " shifted: " << *V << "\n"); 1779 } 1780 assert(Ty->getBitWidth() <= IntTy->getBitWidth() && 1781 "Cannot extract to a larger integer!"); 1782 if (Ty != IntTy) { 1783 V = IRB.CreateTrunc(V, Ty, Name + ".trunc"); 1784 DEBUG(dbgs() << " trunced: " << *V << "\n"); 1785 } 1786 return V; 1787 } 1788 1789 static Value *insertInteger(const DataLayout &DL, IRBuilderTy &IRB, Value *Old, 1790 Value *V, uint64_t Offset, const Twine &Name) { 1791 IntegerType *IntTy = cast<IntegerType>(Old->getType()); 1792 IntegerType *Ty = cast<IntegerType>(V->getType()); 1793 assert(Ty->getBitWidth() <= IntTy->getBitWidth() && 1794 "Cannot insert a larger integer!"); 1795 DEBUG(dbgs() << " start: " << *V << "\n"); 1796 if (Ty != IntTy) { 1797 V = IRB.CreateZExt(V, IntTy, Name + ".ext"); 1798 DEBUG(dbgs() << " extended: " << *V << "\n"); 1799 } 1800 assert(DL.getTypeStoreSize(Ty) + Offset <= DL.getTypeStoreSize(IntTy) && 1801 "Element store outside of alloca store"); 1802 uint64_t ShAmt = 8*Offset; 1803 if (DL.isBigEndian()) 1804 ShAmt = 8*(DL.getTypeStoreSize(IntTy) - DL.getTypeStoreSize(Ty) - Offset); 1805 if (ShAmt) { 1806 V = IRB.CreateShl(V, ShAmt, Name + ".shift"); 1807 DEBUG(dbgs() << " shifted: " << *V << "\n"); 1808 } 1809 1810 if (ShAmt || Ty->getBitWidth() < IntTy->getBitWidth()) { 1811 APInt Mask = ~Ty->getMask().zext(IntTy->getBitWidth()).shl(ShAmt); 1812 Old = IRB.CreateAnd(Old, Mask, Name + ".mask"); 1813 DEBUG(dbgs() << " masked: " << *Old << "\n"); 1814 V = IRB.CreateOr(Old, V, Name + ".insert"); 1815 DEBUG(dbgs() << " inserted: " << *V << "\n"); 1816 } 1817 return V; 1818 } 1819 1820 static Value *extractVector(IRBuilderTy &IRB, Value *V, 1821 unsigned BeginIndex, unsigned EndIndex, 1822 const Twine &Name) { 1823 VectorType *VecTy = cast<VectorType>(V->getType()); 1824 unsigned NumElements = EndIndex - BeginIndex; 1825 assert(NumElements <= VecTy->getNumElements() && "Too many elements!"); 1826 1827 if (NumElements == VecTy->getNumElements()) 1828 return V; 1829 1830 if (NumElements == 1) { 1831 V = IRB.CreateExtractElement(V, IRB.getInt32(BeginIndex), 1832 Name + ".extract"); 1833 DEBUG(dbgs() << " extract: " << *V << "\n"); 1834 return V; 1835 } 1836 1837 SmallVector<Constant*, 8> Mask; 1838 Mask.reserve(NumElements); 1839 for (unsigned i = BeginIndex; i != EndIndex; ++i) 1840 Mask.push_back(IRB.getInt32(i)); 1841 V = IRB.CreateShuffleVector(V, UndefValue::get(V->getType()), 1842 ConstantVector::get(Mask), 1843 Name + ".extract"); 1844 DEBUG(dbgs() << " shuffle: " << *V << "\n"); 1845 return V; 1846 } 1847 1848 static Value *insertVector(IRBuilderTy &IRB, Value *Old, Value *V, 1849 unsigned BeginIndex, const Twine &Name) { 1850 VectorType *VecTy = cast<VectorType>(Old->getType()); 1851 assert(VecTy && "Can only insert a vector into a vector"); 1852 1853 VectorType *Ty = dyn_cast<VectorType>(V->getType()); 1854 if (!Ty) { 1855 // Single element to insert. 1856 V = IRB.CreateInsertElement(Old, V, IRB.getInt32(BeginIndex), 1857 Name + ".insert"); 1858 DEBUG(dbgs() << " insert: " << *V << "\n"); 1859 return V; 1860 } 1861 1862 assert(Ty->getNumElements() <= VecTy->getNumElements() && 1863 "Too many elements!"); 1864 if (Ty->getNumElements() == VecTy->getNumElements()) { 1865 assert(V->getType() == VecTy && "Vector type mismatch"); 1866 return V; 1867 } 1868 unsigned EndIndex = BeginIndex + Ty->getNumElements(); 1869 1870 // When inserting a smaller vector into the larger to store, we first 1871 // use a shuffle vector to widen it with undef elements, and then 1872 // a second shuffle vector to select between the loaded vector and the 1873 // incoming vector. 1874 SmallVector<Constant*, 8> Mask; 1875 Mask.reserve(VecTy->getNumElements()); 1876 for (unsigned i = 0; i != VecTy->getNumElements(); ++i) 1877 if (i >= BeginIndex && i < EndIndex) 1878 Mask.push_back(IRB.getInt32(i - BeginIndex)); 1879 else 1880 Mask.push_back(UndefValue::get(IRB.getInt32Ty())); 1881 V = IRB.CreateShuffleVector(V, UndefValue::get(V->getType()), 1882 ConstantVector::get(Mask), 1883 Name + ".expand"); 1884 DEBUG(dbgs() << " shuffle: " << *V << "\n"); 1885 1886 Mask.clear(); 1887 for (unsigned i = 0; i != VecTy->getNumElements(); ++i) 1888 Mask.push_back(IRB.getInt1(i >= BeginIndex && i < EndIndex)); 1889 1890 V = IRB.CreateSelect(ConstantVector::get(Mask), V, Old, Name + "blend"); 1891 1892 DEBUG(dbgs() << " blend: " << *V << "\n"); 1893 return V; 1894 } 1895 1896 namespace { 1897 /// \brief Visitor to rewrite instructions using p particular slice of an alloca 1898 /// to use a new alloca. 1899 /// 1900 /// Also implements the rewriting to vector-based accesses when the partition 1901 /// passes the isVectorPromotionViable predicate. Most of the rewriting logic 1902 /// lives here. 1903 class AllocaSliceRewriter : public InstVisitor<AllocaSliceRewriter, bool> { 1904 // Befriend the base class so it can delegate to private visit methods. 1905 friend class llvm::InstVisitor<AllocaSliceRewriter, bool>; 1906 typedef llvm::InstVisitor<AllocaSliceRewriter, bool> Base; 1907 1908 const DataLayout &DL; 1909 AllocaSlices &S; 1910 SROA &Pass; 1911 AllocaInst &OldAI, &NewAI; 1912 const uint64_t NewAllocaBeginOffset, NewAllocaEndOffset; 1913 Type *NewAllocaTy; 1914 1915 // If we are rewriting an alloca partition which can be written as pure 1916 // vector operations, we stash extra information here. When VecTy is 1917 // non-null, we have some strict guarantees about the rewritten alloca: 1918 // - The new alloca is exactly the size of the vector type here. 1919 // - The accesses all either map to the entire vector or to a single 1920 // element. 1921 // - The set of accessing instructions is only one of those handled above 1922 // in isVectorPromotionViable. Generally these are the same access kinds 1923 // which are promotable via mem2reg. 1924 VectorType *VecTy; 1925 Type *ElementTy; 1926 uint64_t ElementSize; 1927 1928 // This is a convenience and flag variable that will be null unless the new 1929 // alloca's integer operations should be widened to this integer type due to 1930 // passing isIntegerWideningViable above. If it is non-null, the desired 1931 // integer type will be stored here for easy access during rewriting. 1932 IntegerType *IntTy; 1933 1934 // The offset of the slice currently being rewritten. 1935 uint64_t BeginOffset, EndOffset; 1936 bool IsSplittable; 1937 bool IsSplit; 1938 Use *OldUse; 1939 Instruction *OldPtr; 1940 1941 // Output members carrying state about the result of visiting and rewriting 1942 // the slice of the alloca. 1943 bool IsUsedByRewrittenSpeculatableInstructions; 1944 1945 // Utility IR builder, whose name prefix is setup for each visited use, and 1946 // the insertion point is set to point to the user. 1947 IRBuilderTy IRB; 1948 1949 public: 1950 AllocaSliceRewriter(const DataLayout &DL, AllocaSlices &S, SROA &Pass, 1951 AllocaInst &OldAI, AllocaInst &NewAI, 1952 uint64_t NewBeginOffset, uint64_t NewEndOffset, 1953 bool IsVectorPromotable = false, 1954 bool IsIntegerPromotable = false) 1955 : DL(DL), S(S), Pass(Pass), OldAI(OldAI), NewAI(NewAI), 1956 NewAllocaBeginOffset(NewBeginOffset), NewAllocaEndOffset(NewEndOffset), 1957 NewAllocaTy(NewAI.getAllocatedType()), 1958 VecTy(IsVectorPromotable ? cast<VectorType>(NewAllocaTy) : 0), 1959 ElementTy(VecTy ? VecTy->getElementType() : 0), 1960 ElementSize(VecTy ? DL.getTypeSizeInBits(ElementTy) / 8 : 0), 1961 IntTy(IsIntegerPromotable 1962 ? Type::getIntNTy( 1963 NewAI.getContext(), 1964 DL.getTypeSizeInBits(NewAI.getAllocatedType())) 1965 : 0), 1966 BeginOffset(), EndOffset(), IsSplittable(), IsSplit(), OldUse(), 1967 OldPtr(), IsUsedByRewrittenSpeculatableInstructions(false), 1968 IRB(NewAI.getContext(), ConstantFolder()) { 1969 if (VecTy) { 1970 assert((DL.getTypeSizeInBits(ElementTy) % 8) == 0 && 1971 "Only multiple-of-8 sized vector elements are viable"); 1972 ++NumVectorized; 1973 } 1974 assert((!IsVectorPromotable && !IsIntegerPromotable) || 1975 IsVectorPromotable != IsIntegerPromotable); 1976 } 1977 1978 bool visit(AllocaSlices::const_iterator I) { 1979 bool CanSROA = true; 1980 BeginOffset = I->beginOffset(); 1981 EndOffset = I->endOffset(); 1982 IsSplittable = I->isSplittable(); 1983 IsSplit = 1984 BeginOffset < NewAllocaBeginOffset || EndOffset > NewAllocaEndOffset; 1985 1986 OldUse = I->getUse(); 1987 OldPtr = cast<Instruction>(OldUse->get()); 1988 1989 Instruction *OldUserI = cast<Instruction>(OldUse->getUser()); 1990 IRB.SetInsertPoint(OldUserI); 1991 IRB.SetCurrentDebugLocation(OldUserI->getDebugLoc()); 1992 IRB.SetNamePrefix(Twine(NewAI.getName()) + "." + Twine(BeginOffset) + "."); 1993 1994 CanSROA &= visit(cast<Instruction>(OldUse->getUser())); 1995 if (VecTy || IntTy) 1996 assert(CanSROA); 1997 return CanSROA; 1998 } 1999 2000 /// \brief Query whether this slice is used by speculatable instructions after 2001 /// rewriting. 2002 /// 2003 /// These instructions (PHIs and Selects currently) require the alloca slice 2004 /// to run back through the rewriter. Thus, they are promotable, but not on 2005 /// this iteration. This is distinct from a slice which is unpromotable for 2006 /// some other reason, in which case we don't even want to perform the 2007 /// speculation. This can be querried at any time and reflects whether (at 2008 /// that point) a visit call has rewritten a speculatable instruction on the 2009 /// current slice. 2010 bool isUsedByRewrittenSpeculatableInstructions() const { 2011 return IsUsedByRewrittenSpeculatableInstructions; 2012 } 2013 2014 private: 2015 // Make sure the other visit overloads are visible. 2016 using Base::visit; 2017 2018 // Every instruction which can end up as a user must have a rewrite rule. 2019 bool visitInstruction(Instruction &I) { 2020 DEBUG(dbgs() << " !!!! Cannot rewrite: " << I << "\n"); 2021 llvm_unreachable("No rewrite rule for this instruction!"); 2022 } 2023 2024 Value *getAdjustedAllocaPtr(IRBuilderTy &IRB, uint64_t Offset, 2025 Type *PointerTy) { 2026 assert(Offset >= NewAllocaBeginOffset); 2027 return getAdjustedPtr(IRB, DL, &NewAI, APInt(DL.getPointerSizeInBits(), 2028 Offset - NewAllocaBeginOffset), 2029 PointerTy); 2030 } 2031 2032 /// \brief Compute suitable alignment to access an offset into the new alloca. 2033 unsigned getOffsetAlign(uint64_t Offset) { 2034 unsigned NewAIAlign = NewAI.getAlignment(); 2035 if (!NewAIAlign) 2036 NewAIAlign = DL.getABITypeAlignment(NewAI.getAllocatedType()); 2037 return MinAlign(NewAIAlign, Offset); 2038 } 2039 2040 /// \brief Compute suitable alignment to access a type at an offset of the 2041 /// new alloca. 2042 /// 2043 /// \returns zero if the type's ABI alignment is a suitable alignment, 2044 /// otherwise returns the maximal suitable alignment. 2045 unsigned getOffsetTypeAlign(Type *Ty, uint64_t Offset) { 2046 unsigned Align = getOffsetAlign(Offset); 2047 return Align == DL.getABITypeAlignment(Ty) ? 0 : Align; 2048 } 2049 2050 unsigned getIndex(uint64_t Offset) { 2051 assert(VecTy && "Can only call getIndex when rewriting a vector"); 2052 uint64_t RelOffset = Offset - NewAllocaBeginOffset; 2053 assert(RelOffset / ElementSize < UINT32_MAX && "Index out of bounds"); 2054 uint32_t Index = RelOffset / ElementSize; 2055 assert(Index * ElementSize == RelOffset); 2056 return Index; 2057 } 2058 2059 void deleteIfTriviallyDead(Value *V) { 2060 Instruction *I = cast<Instruction>(V); 2061 if (isInstructionTriviallyDead(I)) 2062 Pass.DeadInsts.insert(I); 2063 } 2064 2065 Value *rewriteVectorizedLoadInst(uint64_t NewBeginOffset, 2066 uint64_t NewEndOffset) { 2067 unsigned BeginIndex = getIndex(NewBeginOffset); 2068 unsigned EndIndex = getIndex(NewEndOffset); 2069 assert(EndIndex > BeginIndex && "Empty vector!"); 2070 2071 Value *V = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(), 2072 "load"); 2073 return extractVector(IRB, V, BeginIndex, EndIndex, "vec"); 2074 } 2075 2076 Value *rewriteIntegerLoad(LoadInst &LI, uint64_t NewBeginOffset, 2077 uint64_t NewEndOffset) { 2078 assert(IntTy && "We cannot insert an integer to the alloca"); 2079 assert(!LI.isVolatile()); 2080 Value *V = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(), 2081 "load"); 2082 V = convertValue(DL, IRB, V, IntTy); 2083 assert(NewBeginOffset >= NewAllocaBeginOffset && "Out of bounds offset"); 2084 uint64_t Offset = NewBeginOffset - NewAllocaBeginOffset; 2085 if (Offset > 0 || NewEndOffset < NewAllocaEndOffset) 2086 V = extractInteger(DL, IRB, V, cast<IntegerType>(LI.getType()), Offset, 2087 "extract"); 2088 return V; 2089 } 2090 2091 bool visitLoadInst(LoadInst &LI) { 2092 DEBUG(dbgs() << " original: " << LI << "\n"); 2093 Value *OldOp = LI.getOperand(0); 2094 assert(OldOp == OldPtr); 2095 2096 // Compute the intersecting offset range. 2097 assert(BeginOffset < NewAllocaEndOffset); 2098 assert(EndOffset > NewAllocaBeginOffset); 2099 uint64_t NewBeginOffset = std::max(BeginOffset, NewAllocaBeginOffset); 2100 uint64_t NewEndOffset = std::min(EndOffset, NewAllocaEndOffset); 2101 2102 uint64_t Size = NewEndOffset - NewBeginOffset; 2103 2104 Type *TargetTy = IsSplit ? Type::getIntNTy(LI.getContext(), Size * 8) 2105 : LI.getType(); 2106 bool IsPtrAdjusted = false; 2107 Value *V; 2108 if (VecTy) { 2109 V = rewriteVectorizedLoadInst(NewBeginOffset, NewEndOffset); 2110 } else if (IntTy && LI.getType()->isIntegerTy()) { 2111 V = rewriteIntegerLoad(LI, NewBeginOffset, NewEndOffset); 2112 } else if (NewBeginOffset == NewAllocaBeginOffset && 2113 canConvertValue(DL, NewAllocaTy, LI.getType())) { 2114 V = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(), 2115 LI.isVolatile(), "load"); 2116 } else { 2117 Type *LTy = TargetTy->getPointerTo(); 2118 V = IRB.CreateAlignedLoad( 2119 getAdjustedAllocaPtr(IRB, NewBeginOffset, LTy), 2120 getOffsetTypeAlign(TargetTy, NewBeginOffset - NewAllocaBeginOffset), 2121 LI.isVolatile(), "load"); 2122 IsPtrAdjusted = true; 2123 } 2124 V = convertValue(DL, IRB, V, TargetTy); 2125 2126 if (IsSplit) { 2127 assert(!LI.isVolatile()); 2128 assert(LI.getType()->isIntegerTy() && 2129 "Only integer type loads and stores are split"); 2130 assert(Size < DL.getTypeStoreSize(LI.getType()) && 2131 "Split load isn't smaller than original load"); 2132 assert(LI.getType()->getIntegerBitWidth() == 2133 DL.getTypeStoreSizeInBits(LI.getType()) && 2134 "Non-byte-multiple bit width"); 2135 // Move the insertion point just past the load so that we can refer to it. 2136 IRB.SetInsertPoint(llvm::next(BasicBlock::iterator(&LI))); 2137 // Create a placeholder value with the same type as LI to use as the 2138 // basis for the new value. This allows us to replace the uses of LI with 2139 // the computed value, and then replace the placeholder with LI, leaving 2140 // LI only used for this computation. 2141 Value *Placeholder 2142 = new LoadInst(UndefValue::get(LI.getType()->getPointerTo())); 2143 V = insertInteger(DL, IRB, Placeholder, V, NewBeginOffset, 2144 "insert"); 2145 LI.replaceAllUsesWith(V); 2146 Placeholder->replaceAllUsesWith(&LI); 2147 delete Placeholder; 2148 } else { 2149 LI.replaceAllUsesWith(V); 2150 } 2151 2152 Pass.DeadInsts.insert(&LI); 2153 deleteIfTriviallyDead(OldOp); 2154 DEBUG(dbgs() << " to: " << *V << "\n"); 2155 return !LI.isVolatile() && !IsPtrAdjusted; 2156 } 2157 2158 bool rewriteVectorizedStoreInst(Value *V, StoreInst &SI, Value *OldOp, 2159 uint64_t NewBeginOffset, 2160 uint64_t NewEndOffset) { 2161 if (V->getType() != VecTy) { 2162 unsigned BeginIndex = getIndex(NewBeginOffset); 2163 unsigned EndIndex = getIndex(NewEndOffset); 2164 assert(EndIndex > BeginIndex && "Empty vector!"); 2165 unsigned NumElements = EndIndex - BeginIndex; 2166 assert(NumElements <= VecTy->getNumElements() && "Too many elements!"); 2167 Type *SliceTy = 2168 (NumElements == 1) ? ElementTy 2169 : VectorType::get(ElementTy, NumElements); 2170 if (V->getType() != SliceTy) 2171 V = convertValue(DL, IRB, V, SliceTy); 2172 2173 // Mix in the existing elements. 2174 Value *Old = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(), 2175 "load"); 2176 V = insertVector(IRB, Old, V, BeginIndex, "vec"); 2177 } 2178 StoreInst *Store = IRB.CreateAlignedStore(V, &NewAI, NewAI.getAlignment()); 2179 Pass.DeadInsts.insert(&SI); 2180 2181 (void)Store; 2182 DEBUG(dbgs() << " to: " << *Store << "\n"); 2183 return true; 2184 } 2185 2186 bool rewriteIntegerStore(Value *V, StoreInst &SI, 2187 uint64_t NewBeginOffset, uint64_t NewEndOffset) { 2188 assert(IntTy && "We cannot extract an integer from the alloca"); 2189 assert(!SI.isVolatile()); 2190 if (DL.getTypeSizeInBits(V->getType()) != IntTy->getBitWidth()) { 2191 Value *Old = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(), 2192 "oldload"); 2193 Old = convertValue(DL, IRB, Old, IntTy); 2194 assert(BeginOffset >= NewAllocaBeginOffset && "Out of bounds offset"); 2195 uint64_t Offset = BeginOffset - NewAllocaBeginOffset; 2196 V = insertInteger(DL, IRB, Old, SI.getValueOperand(), Offset, 2197 "insert"); 2198 } 2199 V = convertValue(DL, IRB, V, NewAllocaTy); 2200 StoreInst *Store = IRB.CreateAlignedStore(V, &NewAI, NewAI.getAlignment()); 2201 Pass.DeadInsts.insert(&SI); 2202 (void)Store; 2203 DEBUG(dbgs() << " to: " << *Store << "\n"); 2204 return true; 2205 } 2206 2207 bool visitStoreInst(StoreInst &SI) { 2208 DEBUG(dbgs() << " original: " << SI << "\n"); 2209 Value *OldOp = SI.getOperand(1); 2210 assert(OldOp == OldPtr); 2211 2212 Value *V = SI.getValueOperand(); 2213 2214 // Strip all inbounds GEPs and pointer casts to try to dig out any root 2215 // alloca that should be re-examined after promoting this alloca. 2216 if (V->getType()->isPointerTy()) 2217 if (AllocaInst *AI = dyn_cast<AllocaInst>(V->stripInBoundsOffsets())) 2218 Pass.PostPromotionWorklist.insert(AI); 2219 2220 // Compute the intersecting offset range. 2221 assert(BeginOffset < NewAllocaEndOffset); 2222 assert(EndOffset > NewAllocaBeginOffset); 2223 uint64_t NewBeginOffset = std::max(BeginOffset, NewAllocaBeginOffset); 2224 uint64_t NewEndOffset = std::min(EndOffset, NewAllocaEndOffset); 2225 2226 uint64_t Size = NewEndOffset - NewBeginOffset; 2227 if (Size < DL.getTypeStoreSize(V->getType())) { 2228 assert(!SI.isVolatile()); 2229 assert(V->getType()->isIntegerTy() && 2230 "Only integer type loads and stores are split"); 2231 assert(V->getType()->getIntegerBitWidth() == 2232 DL.getTypeStoreSizeInBits(V->getType()) && 2233 "Non-byte-multiple bit width"); 2234 IntegerType *NarrowTy = Type::getIntNTy(SI.getContext(), Size * 8); 2235 V = extractInteger(DL, IRB, V, NarrowTy, NewBeginOffset, 2236 "extract"); 2237 } 2238 2239 if (VecTy) 2240 return rewriteVectorizedStoreInst(V, SI, OldOp, NewBeginOffset, 2241 NewEndOffset); 2242 if (IntTy && V->getType()->isIntegerTy()) 2243 return rewriteIntegerStore(V, SI, NewBeginOffset, NewEndOffset); 2244 2245 StoreInst *NewSI; 2246 if (NewBeginOffset == NewAllocaBeginOffset && 2247 NewEndOffset == NewAllocaEndOffset && 2248 canConvertValue(DL, V->getType(), NewAllocaTy)) { 2249 V = convertValue(DL, IRB, V, NewAllocaTy); 2250 NewSI = IRB.CreateAlignedStore(V, &NewAI, NewAI.getAlignment(), 2251 SI.isVolatile()); 2252 } else { 2253 Value *NewPtr = getAdjustedAllocaPtr(IRB, NewBeginOffset, 2254 V->getType()->getPointerTo()); 2255 NewSI = IRB.CreateAlignedStore( 2256 V, NewPtr, getOffsetTypeAlign( 2257 V->getType(), NewBeginOffset - NewAllocaBeginOffset), 2258 SI.isVolatile()); 2259 } 2260 (void)NewSI; 2261 Pass.DeadInsts.insert(&SI); 2262 deleteIfTriviallyDead(OldOp); 2263 2264 DEBUG(dbgs() << " to: " << *NewSI << "\n"); 2265 return NewSI->getPointerOperand() == &NewAI && !SI.isVolatile(); 2266 } 2267 2268 /// \brief Compute an integer value from splatting an i8 across the given 2269 /// number of bytes. 2270 /// 2271 /// Note that this routine assumes an i8 is a byte. If that isn't true, don't 2272 /// call this routine. 2273 /// FIXME: Heed the advice above. 2274 /// 2275 /// \param V The i8 value to splat. 2276 /// \param Size The number of bytes in the output (assuming i8 is one byte) 2277 Value *getIntegerSplat(Value *V, unsigned Size) { 2278 assert(Size > 0 && "Expected a positive number of bytes."); 2279 IntegerType *VTy = cast<IntegerType>(V->getType()); 2280 assert(VTy->getBitWidth() == 8 && "Expected an i8 value for the byte"); 2281 if (Size == 1) 2282 return V; 2283 2284 Type *SplatIntTy = Type::getIntNTy(VTy->getContext(), Size*8); 2285 V = IRB.CreateMul(IRB.CreateZExt(V, SplatIntTy, "zext"), 2286 ConstantExpr::getUDiv( 2287 Constant::getAllOnesValue(SplatIntTy), 2288 ConstantExpr::getZExt( 2289 Constant::getAllOnesValue(V->getType()), 2290 SplatIntTy)), 2291 "isplat"); 2292 return V; 2293 } 2294 2295 /// \brief Compute a vector splat for a given element value. 2296 Value *getVectorSplat(Value *V, unsigned NumElements) { 2297 V = IRB.CreateVectorSplat(NumElements, V, "vsplat"); 2298 DEBUG(dbgs() << " splat: " << *V << "\n"); 2299 return V; 2300 } 2301 2302 bool visitMemSetInst(MemSetInst &II) { 2303 DEBUG(dbgs() << " original: " << II << "\n"); 2304 assert(II.getRawDest() == OldPtr); 2305 2306 // If the memset has a variable size, it cannot be split, just adjust the 2307 // pointer to the new alloca. 2308 if (!isa<Constant>(II.getLength())) { 2309 assert(!IsSplit); 2310 assert(BeginOffset >= NewAllocaBeginOffset); 2311 II.setDest( 2312 getAdjustedAllocaPtr(IRB, BeginOffset, II.getRawDest()->getType())); 2313 Type *CstTy = II.getAlignmentCst()->getType(); 2314 II.setAlignment(ConstantInt::get(CstTy, getOffsetAlign(BeginOffset))); 2315 2316 deleteIfTriviallyDead(OldPtr); 2317 return false; 2318 } 2319 2320 // Record this instruction for deletion. 2321 Pass.DeadInsts.insert(&II); 2322 2323 Type *AllocaTy = NewAI.getAllocatedType(); 2324 Type *ScalarTy = AllocaTy->getScalarType(); 2325 2326 // Compute the intersecting offset range. 2327 assert(BeginOffset < NewAllocaEndOffset); 2328 assert(EndOffset > NewAllocaBeginOffset); 2329 uint64_t NewBeginOffset = std::max(BeginOffset, NewAllocaBeginOffset); 2330 uint64_t NewEndOffset = std::min(EndOffset, NewAllocaEndOffset); 2331 uint64_t SliceOffset = NewBeginOffset - NewAllocaBeginOffset; 2332 2333 // If this doesn't map cleanly onto the alloca type, and that type isn't 2334 // a single value type, just emit a memset. 2335 if (!VecTy && !IntTy && 2336 (BeginOffset > NewAllocaBeginOffset || 2337 EndOffset < NewAllocaEndOffset || 2338 !AllocaTy->isSingleValueType() || 2339 !DL.isLegalInteger(DL.getTypeSizeInBits(ScalarTy)) || 2340 DL.getTypeSizeInBits(ScalarTy)%8 != 0)) { 2341 Type *SizeTy = II.getLength()->getType(); 2342 Constant *Size = ConstantInt::get(SizeTy, NewEndOffset - NewBeginOffset); 2343 CallInst *New = IRB.CreateMemSet( 2344 getAdjustedAllocaPtr(IRB, NewBeginOffset, II.getRawDest()->getType()), 2345 II.getValue(), Size, getOffsetAlign(SliceOffset), II.isVolatile()); 2346 (void)New; 2347 DEBUG(dbgs() << " to: " << *New << "\n"); 2348 return false; 2349 } 2350 2351 // If we can represent this as a simple value, we have to build the actual 2352 // value to store, which requires expanding the byte present in memset to 2353 // a sensible representation for the alloca type. This is essentially 2354 // splatting the byte to a sufficiently wide integer, splatting it across 2355 // any desired vector width, and bitcasting to the final type. 2356 Value *V; 2357 2358 if (VecTy) { 2359 // If this is a memset of a vectorized alloca, insert it. 2360 assert(ElementTy == ScalarTy); 2361 2362 unsigned BeginIndex = getIndex(NewBeginOffset); 2363 unsigned EndIndex = getIndex(NewEndOffset); 2364 assert(EndIndex > BeginIndex && "Empty vector!"); 2365 unsigned NumElements = EndIndex - BeginIndex; 2366 assert(NumElements <= VecTy->getNumElements() && "Too many elements!"); 2367 2368 Value *Splat = 2369 getIntegerSplat(II.getValue(), DL.getTypeSizeInBits(ElementTy) / 8); 2370 Splat = convertValue(DL, IRB, Splat, ElementTy); 2371 if (NumElements > 1) 2372 Splat = getVectorSplat(Splat, NumElements); 2373 2374 Value *Old = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(), 2375 "oldload"); 2376 V = insertVector(IRB, Old, Splat, BeginIndex, "vec"); 2377 } else if (IntTy) { 2378 // If this is a memset on an alloca where we can widen stores, insert the 2379 // set integer. 2380 assert(!II.isVolatile()); 2381 2382 uint64_t Size = NewEndOffset - NewBeginOffset; 2383 V = getIntegerSplat(II.getValue(), Size); 2384 2385 if (IntTy && (BeginOffset != NewAllocaBeginOffset || 2386 EndOffset != NewAllocaBeginOffset)) { 2387 Value *Old = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(), 2388 "oldload"); 2389 Old = convertValue(DL, IRB, Old, IntTy); 2390 uint64_t Offset = NewBeginOffset - NewAllocaBeginOffset; 2391 V = insertInteger(DL, IRB, Old, V, Offset, "insert"); 2392 } else { 2393 assert(V->getType() == IntTy && 2394 "Wrong type for an alloca wide integer!"); 2395 } 2396 V = convertValue(DL, IRB, V, AllocaTy); 2397 } else { 2398 // Established these invariants above. 2399 assert(NewBeginOffset == NewAllocaBeginOffset); 2400 assert(NewEndOffset == NewAllocaEndOffset); 2401 2402 V = getIntegerSplat(II.getValue(), DL.getTypeSizeInBits(ScalarTy) / 8); 2403 if (VectorType *AllocaVecTy = dyn_cast<VectorType>(AllocaTy)) 2404 V = getVectorSplat(V, AllocaVecTy->getNumElements()); 2405 2406 V = convertValue(DL, IRB, V, AllocaTy); 2407 } 2408 2409 Value *New = IRB.CreateAlignedStore(V, &NewAI, NewAI.getAlignment(), 2410 II.isVolatile()); 2411 (void)New; 2412 DEBUG(dbgs() << " to: " << *New << "\n"); 2413 return !II.isVolatile(); 2414 } 2415 2416 bool visitMemTransferInst(MemTransferInst &II) { 2417 // Rewriting of memory transfer instructions can be a bit tricky. We break 2418 // them into two categories: split intrinsics and unsplit intrinsics. 2419 2420 DEBUG(dbgs() << " original: " << II << "\n"); 2421 2422 // Compute the intersecting offset range. 2423 assert(BeginOffset < NewAllocaEndOffset); 2424 assert(EndOffset > NewAllocaBeginOffset); 2425 uint64_t NewBeginOffset = std::max(BeginOffset, NewAllocaBeginOffset); 2426 uint64_t NewEndOffset = std::min(EndOffset, NewAllocaEndOffset); 2427 2428 assert(II.getRawSource() == OldPtr || II.getRawDest() == OldPtr); 2429 bool IsDest = II.getRawDest() == OldPtr; 2430 2431 // Compute the relative offset within the transfer. 2432 unsigned IntPtrWidth = DL.getPointerSizeInBits(); 2433 APInt RelOffset(IntPtrWidth, NewBeginOffset - BeginOffset); 2434 2435 unsigned Align = II.getAlignment(); 2436 uint64_t SliceOffset = NewBeginOffset - NewAllocaBeginOffset; 2437 if (Align > 1) 2438 Align = 2439 MinAlign(RelOffset.zextOrTrunc(64).getZExtValue(), 2440 MinAlign(II.getAlignment(), getOffsetAlign(SliceOffset))); 2441 2442 // For unsplit intrinsics, we simply modify the source and destination 2443 // pointers in place. This isn't just an optimization, it is a matter of 2444 // correctness. With unsplit intrinsics we may be dealing with transfers 2445 // within a single alloca before SROA ran, or with transfers that have 2446 // a variable length. We may also be dealing with memmove instead of 2447 // memcpy, and so simply updating the pointers is the necessary for us to 2448 // update both source and dest of a single call. 2449 if (!IsSplittable) { 2450 Value *OldOp = IsDest ? II.getRawDest() : II.getRawSource(); 2451 if (IsDest) 2452 II.setDest( 2453 getAdjustedAllocaPtr(IRB, BeginOffset, II.getRawDest()->getType())); 2454 else 2455 II.setSource(getAdjustedAllocaPtr(IRB, BeginOffset, 2456 II.getRawSource()->getType())); 2457 2458 Type *CstTy = II.getAlignmentCst()->getType(); 2459 II.setAlignment(ConstantInt::get(CstTy, Align)); 2460 2461 DEBUG(dbgs() << " to: " << II << "\n"); 2462 deleteIfTriviallyDead(OldOp); 2463 return false; 2464 } 2465 // For split transfer intrinsics we have an incredibly useful assurance: 2466 // the source and destination do not reside within the same alloca, and at 2467 // least one of them does not escape. This means that we can replace 2468 // memmove with memcpy, and we don't need to worry about all manner of 2469 // downsides to splitting and transforming the operations. 2470 2471 // If this doesn't map cleanly onto the alloca type, and that type isn't 2472 // a single value type, just emit a memcpy. 2473 bool EmitMemCpy 2474 = !VecTy && !IntTy && (BeginOffset > NewAllocaBeginOffset || 2475 EndOffset < NewAllocaEndOffset || 2476 !NewAI.getAllocatedType()->isSingleValueType()); 2477 2478 // If we're just going to emit a memcpy, the alloca hasn't changed, and the 2479 // size hasn't been shrunk based on analysis of the viable range, this is 2480 // a no-op. 2481 if (EmitMemCpy && &OldAI == &NewAI) { 2482 // Ensure the start lines up. 2483 assert(NewBeginOffset == BeginOffset); 2484 2485 // Rewrite the size as needed. 2486 if (NewEndOffset != EndOffset) 2487 II.setLength(ConstantInt::get(II.getLength()->getType(), 2488 NewEndOffset - NewBeginOffset)); 2489 return false; 2490 } 2491 // Record this instruction for deletion. 2492 Pass.DeadInsts.insert(&II); 2493 2494 // Strip all inbounds GEPs and pointer casts to try to dig out any root 2495 // alloca that should be re-examined after rewriting this instruction. 2496 Value *OtherPtr = IsDest ? II.getRawSource() : II.getRawDest(); 2497 if (AllocaInst *AI 2498 = dyn_cast<AllocaInst>(OtherPtr->stripInBoundsOffsets())) 2499 Pass.Worklist.insert(AI); 2500 2501 if (EmitMemCpy) { 2502 Type *OtherPtrTy = IsDest ? II.getRawSource()->getType() 2503 : II.getRawDest()->getType(); 2504 2505 // Compute the other pointer, folding as much as possible to produce 2506 // a single, simple GEP in most cases. 2507 OtherPtr = getAdjustedPtr(IRB, DL, OtherPtr, RelOffset, OtherPtrTy); 2508 2509 Value *OurPtr = getAdjustedAllocaPtr( 2510 IRB, NewBeginOffset, 2511 IsDest ? II.getRawDest()->getType() : II.getRawSource()->getType()); 2512 Type *SizeTy = II.getLength()->getType(); 2513 Constant *Size = ConstantInt::get(SizeTy, NewEndOffset - NewBeginOffset); 2514 2515 CallInst *New = IRB.CreateMemCpy(IsDest ? OurPtr : OtherPtr, 2516 IsDest ? OtherPtr : OurPtr, 2517 Size, Align, II.isVolatile()); 2518 (void)New; 2519 DEBUG(dbgs() << " to: " << *New << "\n"); 2520 return false; 2521 } 2522 2523 // Note that we clamp the alignment to 1 here as a 0 alignment for a memcpy 2524 // is equivalent to 1, but that isn't true if we end up rewriting this as 2525 // a load or store. 2526 if (!Align) 2527 Align = 1; 2528 2529 bool IsWholeAlloca = NewBeginOffset == NewAllocaBeginOffset && 2530 NewEndOffset == NewAllocaEndOffset; 2531 uint64_t Size = NewEndOffset - NewBeginOffset; 2532 unsigned BeginIndex = VecTy ? getIndex(NewBeginOffset) : 0; 2533 unsigned EndIndex = VecTy ? getIndex(NewEndOffset) : 0; 2534 unsigned NumElements = EndIndex - BeginIndex; 2535 IntegerType *SubIntTy 2536 = IntTy ? Type::getIntNTy(IntTy->getContext(), Size*8) : 0; 2537 2538 Type *OtherPtrTy = NewAI.getType(); 2539 if (VecTy && !IsWholeAlloca) { 2540 if (NumElements == 1) 2541 OtherPtrTy = VecTy->getElementType(); 2542 else 2543 OtherPtrTy = VectorType::get(VecTy->getElementType(), NumElements); 2544 2545 OtherPtrTy = OtherPtrTy->getPointerTo(); 2546 } else if (IntTy && !IsWholeAlloca) { 2547 OtherPtrTy = SubIntTy->getPointerTo(); 2548 } 2549 2550 Value *SrcPtr = getAdjustedPtr(IRB, DL, OtherPtr, RelOffset, OtherPtrTy); 2551 Value *DstPtr = &NewAI; 2552 if (!IsDest) 2553 std::swap(SrcPtr, DstPtr); 2554 2555 Value *Src; 2556 if (VecTy && !IsWholeAlloca && !IsDest) { 2557 Src = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(), 2558 "load"); 2559 Src = extractVector(IRB, Src, BeginIndex, EndIndex, "vec"); 2560 } else if (IntTy && !IsWholeAlloca && !IsDest) { 2561 Src = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(), 2562 "load"); 2563 Src = convertValue(DL, IRB, Src, IntTy); 2564 uint64_t Offset = NewBeginOffset - NewAllocaBeginOffset; 2565 Src = extractInteger(DL, IRB, Src, SubIntTy, Offset, "extract"); 2566 } else { 2567 Src = IRB.CreateAlignedLoad(SrcPtr, Align, II.isVolatile(), 2568 "copyload"); 2569 } 2570 2571 if (VecTy && !IsWholeAlloca && IsDest) { 2572 Value *Old = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(), 2573 "oldload"); 2574 Src = insertVector(IRB, Old, Src, BeginIndex, "vec"); 2575 } else if (IntTy && !IsWholeAlloca && IsDest) { 2576 Value *Old = IRB.CreateAlignedLoad(&NewAI, NewAI.getAlignment(), 2577 "oldload"); 2578 Old = convertValue(DL, IRB, Old, IntTy); 2579 uint64_t Offset = NewBeginOffset - NewAllocaBeginOffset; 2580 Src = insertInteger(DL, IRB, Old, Src, Offset, "insert"); 2581 Src = convertValue(DL, IRB, Src, NewAllocaTy); 2582 } 2583 2584 StoreInst *Store = cast<StoreInst>( 2585 IRB.CreateAlignedStore(Src, DstPtr, Align, II.isVolatile())); 2586 (void)Store; 2587 DEBUG(dbgs() << " to: " << *Store << "\n"); 2588 return !II.isVolatile(); 2589 } 2590 2591 bool visitIntrinsicInst(IntrinsicInst &II) { 2592 assert(II.getIntrinsicID() == Intrinsic::lifetime_start || 2593 II.getIntrinsicID() == Intrinsic::lifetime_end); 2594 DEBUG(dbgs() << " original: " << II << "\n"); 2595 assert(II.getArgOperand(1) == OldPtr); 2596 2597 // Compute the intersecting offset range. 2598 assert(BeginOffset < NewAllocaEndOffset); 2599 assert(EndOffset > NewAllocaBeginOffset); 2600 uint64_t NewBeginOffset = std::max(BeginOffset, NewAllocaBeginOffset); 2601 uint64_t NewEndOffset = std::min(EndOffset, NewAllocaEndOffset); 2602 2603 // Record this instruction for deletion. 2604 Pass.DeadInsts.insert(&II); 2605 2606 ConstantInt *Size 2607 = ConstantInt::get(cast<IntegerType>(II.getArgOperand(0)->getType()), 2608 NewEndOffset - NewBeginOffset); 2609 Value *Ptr = 2610 getAdjustedAllocaPtr(IRB, NewBeginOffset, II.getArgOperand(1)->getType()); 2611 Value *New; 2612 if (II.getIntrinsicID() == Intrinsic::lifetime_start) 2613 New = IRB.CreateLifetimeStart(Ptr, Size); 2614 else 2615 New = IRB.CreateLifetimeEnd(Ptr, Size); 2616 2617 (void)New; 2618 DEBUG(dbgs() << " to: " << *New << "\n"); 2619 return true; 2620 } 2621 2622 bool visitPHINode(PHINode &PN) { 2623 DEBUG(dbgs() << " original: " << PN << "\n"); 2624 assert(BeginOffset >= NewAllocaBeginOffset && "PHIs are unsplittable"); 2625 assert(EndOffset <= NewAllocaEndOffset && "PHIs are unsplittable"); 2626 2627 // We would like to compute a new pointer in only one place, but have it be 2628 // as local as possible to the PHI. To do that, we re-use the location of 2629 // the old pointer, which necessarily must be in the right position to 2630 // dominate the PHI. 2631 IRBuilderTy PtrBuilder(OldPtr); 2632 PtrBuilder.SetNamePrefix(Twine(NewAI.getName()) + "." + Twine(BeginOffset) + 2633 "."); 2634 2635 Value *NewPtr = 2636 getAdjustedAllocaPtr(PtrBuilder, BeginOffset, OldPtr->getType()); 2637 // Replace the operands which were using the old pointer. 2638 std::replace(PN.op_begin(), PN.op_end(), cast<Value>(OldPtr), NewPtr); 2639 2640 DEBUG(dbgs() << " to: " << PN << "\n"); 2641 deleteIfTriviallyDead(OldPtr); 2642 2643 // Check whether we can speculate this PHI node, and if so remember that 2644 // fact and queue it up for another iteration after the speculation 2645 // occurs. 2646 if (isSafePHIToSpeculate(PN, &DL)) { 2647 Pass.SpeculatablePHIs.insert(&PN); 2648 IsUsedByRewrittenSpeculatableInstructions = true; 2649 return true; 2650 } 2651 2652 return false; // PHIs can't be promoted on their own. 2653 } 2654 2655 bool visitSelectInst(SelectInst &SI) { 2656 DEBUG(dbgs() << " original: " << SI << "\n"); 2657 assert((SI.getTrueValue() == OldPtr || SI.getFalseValue() == OldPtr) && 2658 "Pointer isn't an operand!"); 2659 assert(BeginOffset >= NewAllocaBeginOffset && "Selects are unsplittable"); 2660 assert(EndOffset <= NewAllocaEndOffset && "Selects are unsplittable"); 2661 2662 Value *NewPtr = getAdjustedAllocaPtr(IRB, BeginOffset, OldPtr->getType()); 2663 // Replace the operands which were using the old pointer. 2664 if (SI.getOperand(1) == OldPtr) 2665 SI.setOperand(1, NewPtr); 2666 if (SI.getOperand(2) == OldPtr) 2667 SI.setOperand(2, NewPtr); 2668 2669 DEBUG(dbgs() << " to: " << SI << "\n"); 2670 deleteIfTriviallyDead(OldPtr); 2671 2672 // Check whether we can speculate this select instruction, and if so 2673 // remember that fact and queue it up for another iteration after the 2674 // speculation occurs. 2675 if (isSafeSelectToSpeculate(SI, &DL)) { 2676 Pass.SpeculatableSelects.insert(&SI); 2677 IsUsedByRewrittenSpeculatableInstructions = true; 2678 return true; 2679 } 2680 2681 return false; // Selects can't be promoted on their own. 2682 } 2683 2684 }; 2685 } 2686 2687 namespace { 2688 /// \brief Visitor to rewrite aggregate loads and stores as scalar. 2689 /// 2690 /// This pass aggressively rewrites all aggregate loads and stores on 2691 /// a particular pointer (or any pointer derived from it which we can identify) 2692 /// with scalar loads and stores. 2693 class AggLoadStoreRewriter : public InstVisitor<AggLoadStoreRewriter, bool> { 2694 // Befriend the base class so it can delegate to private visit methods. 2695 friend class llvm::InstVisitor<AggLoadStoreRewriter, bool>; 2696 2697 const DataLayout &DL; 2698 2699 /// Queue of pointer uses to analyze and potentially rewrite. 2700 SmallVector<Use *, 8> Queue; 2701 2702 /// Set to prevent us from cycling with phi nodes and loops. 2703 SmallPtrSet<User *, 8> Visited; 2704 2705 /// The current pointer use being rewritten. This is used to dig up the used 2706 /// value (as opposed to the user). 2707 Use *U; 2708 2709 public: 2710 AggLoadStoreRewriter(const DataLayout &DL) : DL(DL) {} 2711 2712 /// Rewrite loads and stores through a pointer and all pointers derived from 2713 /// it. 2714 bool rewrite(Instruction &I) { 2715 DEBUG(dbgs() << " Rewriting FCA loads and stores...\n"); 2716 enqueueUsers(I); 2717 bool Changed = false; 2718 while (!Queue.empty()) { 2719 U = Queue.pop_back_val(); 2720 Changed |= visit(cast<Instruction>(U->getUser())); 2721 } 2722 return Changed; 2723 } 2724 2725 private: 2726 /// Enqueue all the users of the given instruction for further processing. 2727 /// This uses a set to de-duplicate users. 2728 void enqueueUsers(Instruction &I) { 2729 for (Value::use_iterator UI = I.use_begin(), UE = I.use_end(); UI != UE; 2730 ++UI) 2731 if (Visited.insert(*UI)) 2732 Queue.push_back(&UI.getUse()); 2733 } 2734 2735 // Conservative default is to not rewrite anything. 2736 bool visitInstruction(Instruction &I) { return false; } 2737 2738 /// \brief Generic recursive split emission class. 2739 template <typename Derived> 2740 class OpSplitter { 2741 protected: 2742 /// The builder used to form new instructions. 2743 IRBuilderTy IRB; 2744 /// The indices which to be used with insert- or extractvalue to select the 2745 /// appropriate value within the aggregate. 2746 SmallVector<unsigned, 4> Indices; 2747 /// The indices to a GEP instruction which will move Ptr to the correct slot 2748 /// within the aggregate. 2749 SmallVector<Value *, 4> GEPIndices; 2750 /// The base pointer of the original op, used as a base for GEPing the 2751 /// split operations. 2752 Value *Ptr; 2753 2754 /// Initialize the splitter with an insertion point, Ptr and start with a 2755 /// single zero GEP index. 2756 OpSplitter(Instruction *InsertionPoint, Value *Ptr) 2757 : IRB(InsertionPoint), GEPIndices(1, IRB.getInt32(0)), Ptr(Ptr) {} 2758 2759 public: 2760 /// \brief Generic recursive split emission routine. 2761 /// 2762 /// This method recursively splits an aggregate op (load or store) into 2763 /// scalar or vector ops. It splits recursively until it hits a single value 2764 /// and emits that single value operation via the template argument. 2765 /// 2766 /// The logic of this routine relies on GEPs and insertvalue and 2767 /// extractvalue all operating with the same fundamental index list, merely 2768 /// formatted differently (GEPs need actual values). 2769 /// 2770 /// \param Ty The type being split recursively into smaller ops. 2771 /// \param Agg The aggregate value being built up or stored, depending on 2772 /// whether this is splitting a load or a store respectively. 2773 void emitSplitOps(Type *Ty, Value *&Agg, const Twine &Name) { 2774 if (Ty->isSingleValueType()) 2775 return static_cast<Derived *>(this)->emitFunc(Ty, Agg, Name); 2776 2777 if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) { 2778 unsigned OldSize = Indices.size(); 2779 (void)OldSize; 2780 for (unsigned Idx = 0, Size = ATy->getNumElements(); Idx != Size; 2781 ++Idx) { 2782 assert(Indices.size() == OldSize && "Did not return to the old size"); 2783 Indices.push_back(Idx); 2784 GEPIndices.push_back(IRB.getInt32(Idx)); 2785 emitSplitOps(ATy->getElementType(), Agg, Name + "." + Twine(Idx)); 2786 GEPIndices.pop_back(); 2787 Indices.pop_back(); 2788 } 2789 return; 2790 } 2791 2792 if (StructType *STy = dyn_cast<StructType>(Ty)) { 2793 unsigned OldSize = Indices.size(); 2794 (void)OldSize; 2795 for (unsigned Idx = 0, Size = STy->getNumElements(); Idx != Size; 2796 ++Idx) { 2797 assert(Indices.size() == OldSize && "Did not return to the old size"); 2798 Indices.push_back(Idx); 2799 GEPIndices.push_back(IRB.getInt32(Idx)); 2800 emitSplitOps(STy->getElementType(Idx), Agg, Name + "." + Twine(Idx)); 2801 GEPIndices.pop_back(); 2802 Indices.pop_back(); 2803 } 2804 return; 2805 } 2806 2807 llvm_unreachable("Only arrays and structs are aggregate loadable types"); 2808 } 2809 }; 2810 2811 struct LoadOpSplitter : public OpSplitter<LoadOpSplitter> { 2812 LoadOpSplitter(Instruction *InsertionPoint, Value *Ptr) 2813 : OpSplitter<LoadOpSplitter>(InsertionPoint, Ptr) {} 2814 2815 /// Emit a leaf load of a single value. This is called at the leaves of the 2816 /// recursive emission to actually load values. 2817 void emitFunc(Type *Ty, Value *&Agg, const Twine &Name) { 2818 assert(Ty->isSingleValueType()); 2819 // Load the single value and insert it using the indices. 2820 Value *GEP = IRB.CreateInBoundsGEP(Ptr, GEPIndices, Name + ".gep"); 2821 Value *Load = IRB.CreateLoad(GEP, Name + ".load"); 2822 Agg = IRB.CreateInsertValue(Agg, Load, Indices, Name + ".insert"); 2823 DEBUG(dbgs() << " to: " << *Load << "\n"); 2824 } 2825 }; 2826 2827 bool visitLoadInst(LoadInst &LI) { 2828 assert(LI.getPointerOperand() == *U); 2829 if (!LI.isSimple() || LI.getType()->isSingleValueType()) 2830 return false; 2831 2832 // We have an aggregate being loaded, split it apart. 2833 DEBUG(dbgs() << " original: " << LI << "\n"); 2834 LoadOpSplitter Splitter(&LI, *U); 2835 Value *V = UndefValue::get(LI.getType()); 2836 Splitter.emitSplitOps(LI.getType(), V, LI.getName() + ".fca"); 2837 LI.replaceAllUsesWith(V); 2838 LI.eraseFromParent(); 2839 return true; 2840 } 2841 2842 struct StoreOpSplitter : public OpSplitter<StoreOpSplitter> { 2843 StoreOpSplitter(Instruction *InsertionPoint, Value *Ptr) 2844 : OpSplitter<StoreOpSplitter>(InsertionPoint, Ptr) {} 2845 2846 /// Emit a leaf store of a single value. This is called at the leaves of the 2847 /// recursive emission to actually produce stores. 2848 void emitFunc(Type *Ty, Value *&Agg, const Twine &Name) { 2849 assert(Ty->isSingleValueType()); 2850 // Extract the single value and store it using the indices. 2851 Value *Store = IRB.CreateStore( 2852 IRB.CreateExtractValue(Agg, Indices, Name + ".extract"), 2853 IRB.CreateInBoundsGEP(Ptr, GEPIndices, Name + ".gep")); 2854 (void)Store; 2855 DEBUG(dbgs() << " to: " << *Store << "\n"); 2856 } 2857 }; 2858 2859 bool visitStoreInst(StoreInst &SI) { 2860 if (!SI.isSimple() || SI.getPointerOperand() != *U) 2861 return false; 2862 Value *V = SI.getValueOperand(); 2863 if (V->getType()->isSingleValueType()) 2864 return false; 2865 2866 // We have an aggregate being stored, split it apart. 2867 DEBUG(dbgs() << " original: " << SI << "\n"); 2868 StoreOpSplitter Splitter(&SI, *U); 2869 Splitter.emitSplitOps(V->getType(), V, V->getName() + ".fca"); 2870 SI.eraseFromParent(); 2871 return true; 2872 } 2873 2874 bool visitBitCastInst(BitCastInst &BC) { 2875 enqueueUsers(BC); 2876 return false; 2877 } 2878 2879 bool visitGetElementPtrInst(GetElementPtrInst &GEPI) { 2880 enqueueUsers(GEPI); 2881 return false; 2882 } 2883 2884 bool visitPHINode(PHINode &PN) { 2885 enqueueUsers(PN); 2886 return false; 2887 } 2888 2889 bool visitSelectInst(SelectInst &SI) { 2890 enqueueUsers(SI); 2891 return false; 2892 } 2893 }; 2894 } 2895 2896 /// \brief Strip aggregate type wrapping. 2897 /// 2898 /// This removes no-op aggregate types wrapping an underlying type. It will 2899 /// strip as many layers of types as it can without changing either the type 2900 /// size or the allocated size. 2901 static Type *stripAggregateTypeWrapping(const DataLayout &DL, Type *Ty) { 2902 if (Ty->isSingleValueType()) 2903 return Ty; 2904 2905 uint64_t AllocSize = DL.getTypeAllocSize(Ty); 2906 uint64_t TypeSize = DL.getTypeSizeInBits(Ty); 2907 2908 Type *InnerTy; 2909 if (ArrayType *ArrTy = dyn_cast<ArrayType>(Ty)) { 2910 InnerTy = ArrTy->getElementType(); 2911 } else if (StructType *STy = dyn_cast<StructType>(Ty)) { 2912 const StructLayout *SL = DL.getStructLayout(STy); 2913 unsigned Index = SL->getElementContainingOffset(0); 2914 InnerTy = STy->getElementType(Index); 2915 } else { 2916 return Ty; 2917 } 2918 2919 if (AllocSize > DL.getTypeAllocSize(InnerTy) || 2920 TypeSize > DL.getTypeSizeInBits(InnerTy)) 2921 return Ty; 2922 2923 return stripAggregateTypeWrapping(DL, InnerTy); 2924 } 2925 2926 /// \brief Try to find a partition of the aggregate type passed in for a given 2927 /// offset and size. 2928 /// 2929 /// This recurses through the aggregate type and tries to compute a subtype 2930 /// based on the offset and size. When the offset and size span a sub-section 2931 /// of an array, it will even compute a new array type for that sub-section, 2932 /// and the same for structs. 2933 /// 2934 /// Note that this routine is very strict and tries to find a partition of the 2935 /// type which produces the *exact* right offset and size. It is not forgiving 2936 /// when the size or offset cause either end of type-based partition to be off. 2937 /// Also, this is a best-effort routine. It is reasonable to give up and not 2938 /// return a type if necessary. 2939 static Type *getTypePartition(const DataLayout &DL, Type *Ty, 2940 uint64_t Offset, uint64_t Size) { 2941 if (Offset == 0 && DL.getTypeAllocSize(Ty) == Size) 2942 return stripAggregateTypeWrapping(DL, Ty); 2943 if (Offset > DL.getTypeAllocSize(Ty) || 2944 (DL.getTypeAllocSize(Ty) - Offset) < Size) 2945 return 0; 2946 2947 if (SequentialType *SeqTy = dyn_cast<SequentialType>(Ty)) { 2948 // We can't partition pointers... 2949 if (SeqTy->isPointerTy()) 2950 return 0; 2951 2952 Type *ElementTy = SeqTy->getElementType(); 2953 uint64_t ElementSize = DL.getTypeAllocSize(ElementTy); 2954 uint64_t NumSkippedElements = Offset / ElementSize; 2955 if (ArrayType *ArrTy = dyn_cast<ArrayType>(SeqTy)) { 2956 if (NumSkippedElements >= ArrTy->getNumElements()) 2957 return 0; 2958 } else if (VectorType *VecTy = dyn_cast<VectorType>(SeqTy)) { 2959 if (NumSkippedElements >= VecTy->getNumElements()) 2960 return 0; 2961 } 2962 Offset -= NumSkippedElements * ElementSize; 2963 2964 // First check if we need to recurse. 2965 if (Offset > 0 || Size < ElementSize) { 2966 // Bail if the partition ends in a different array element. 2967 if ((Offset + Size) > ElementSize) 2968 return 0; 2969 // Recurse through the element type trying to peel off offset bytes. 2970 return getTypePartition(DL, ElementTy, Offset, Size); 2971 } 2972 assert(Offset == 0); 2973 2974 if (Size == ElementSize) 2975 return stripAggregateTypeWrapping(DL, ElementTy); 2976 assert(Size > ElementSize); 2977 uint64_t NumElements = Size / ElementSize; 2978 if (NumElements * ElementSize != Size) 2979 return 0; 2980 return ArrayType::get(ElementTy, NumElements); 2981 } 2982 2983 StructType *STy = dyn_cast<StructType>(Ty); 2984 if (!STy) 2985 return 0; 2986 2987 const StructLayout *SL = DL.getStructLayout(STy); 2988 if (Offset >= SL->getSizeInBytes()) 2989 return 0; 2990 uint64_t EndOffset = Offset + Size; 2991 if (EndOffset > SL->getSizeInBytes()) 2992 return 0; 2993 2994 unsigned Index = SL->getElementContainingOffset(Offset); 2995 Offset -= SL->getElementOffset(Index); 2996 2997 Type *ElementTy = STy->getElementType(Index); 2998 uint64_t ElementSize = DL.getTypeAllocSize(ElementTy); 2999 if (Offset >= ElementSize) 3000 return 0; // The offset points into alignment padding. 3001 3002 // See if any partition must be contained by the element. 3003 if (Offset > 0 || Size < ElementSize) { 3004 if ((Offset + Size) > ElementSize) 3005 return 0; 3006 return getTypePartition(DL, ElementTy, Offset, Size); 3007 } 3008 assert(Offset == 0); 3009 3010 if (Size == ElementSize) 3011 return stripAggregateTypeWrapping(DL, ElementTy); 3012 3013 StructType::element_iterator EI = STy->element_begin() + Index, 3014 EE = STy->element_end(); 3015 if (EndOffset < SL->getSizeInBytes()) { 3016 unsigned EndIndex = SL->getElementContainingOffset(EndOffset); 3017 if (Index == EndIndex) 3018 return 0; // Within a single element and its padding. 3019 3020 // Don't try to form "natural" types if the elements don't line up with the 3021 // expected size. 3022 // FIXME: We could potentially recurse down through the last element in the 3023 // sub-struct to find a natural end point. 3024 if (SL->getElementOffset(EndIndex) != EndOffset) 3025 return 0; 3026 3027 assert(Index < EndIndex); 3028 EE = STy->element_begin() + EndIndex; 3029 } 3030 3031 // Try to build up a sub-structure. 3032 StructType *SubTy = StructType::get(STy->getContext(), makeArrayRef(EI, EE), 3033 STy->isPacked()); 3034 const StructLayout *SubSL = DL.getStructLayout(SubTy); 3035 if (Size != SubSL->getSizeInBytes()) 3036 return 0; // The sub-struct doesn't have quite the size needed. 3037 3038 return SubTy; 3039 } 3040 3041 /// \brief Rewrite an alloca partition's users. 3042 /// 3043 /// This routine drives both of the rewriting goals of the SROA pass. It tries 3044 /// to rewrite uses of an alloca partition to be conducive for SSA value 3045 /// promotion. If the partition needs a new, more refined alloca, this will 3046 /// build that new alloca, preserving as much type information as possible, and 3047 /// rewrite the uses of the old alloca to point at the new one and have the 3048 /// appropriate new offsets. It also evaluates how successful the rewrite was 3049 /// at enabling promotion and if it was successful queues the alloca to be 3050 /// promoted. 3051 bool SROA::rewritePartition(AllocaInst &AI, AllocaSlices &S, 3052 AllocaSlices::iterator B, AllocaSlices::iterator E, 3053 int64_t BeginOffset, int64_t EndOffset, 3054 ArrayRef<AllocaSlices::iterator> SplitUses) { 3055 assert(BeginOffset < EndOffset); 3056 uint64_t SliceSize = EndOffset - BeginOffset; 3057 3058 // Try to compute a friendly type for this partition of the alloca. This 3059 // won't always succeed, in which case we fall back to a legal integer type 3060 // or an i8 array of an appropriate size. 3061 Type *SliceTy = 0; 3062 if (Type *CommonUseTy = findCommonType(B, E, EndOffset)) 3063 if (DL->getTypeAllocSize(CommonUseTy) >= SliceSize) 3064 SliceTy = CommonUseTy; 3065 if (!SliceTy) 3066 if (Type *TypePartitionTy = getTypePartition(*DL, AI.getAllocatedType(), 3067 BeginOffset, SliceSize)) 3068 SliceTy = TypePartitionTy; 3069 if ((!SliceTy || (SliceTy->isArrayTy() && 3070 SliceTy->getArrayElementType()->isIntegerTy())) && 3071 DL->isLegalInteger(SliceSize * 8)) 3072 SliceTy = Type::getIntNTy(*C, SliceSize * 8); 3073 if (!SliceTy) 3074 SliceTy = ArrayType::get(Type::getInt8Ty(*C), SliceSize); 3075 assert(DL->getTypeAllocSize(SliceTy) >= SliceSize); 3076 3077 bool IsVectorPromotable = isVectorPromotionViable( 3078 *DL, SliceTy, S, BeginOffset, EndOffset, B, E, SplitUses); 3079 3080 bool IsIntegerPromotable = 3081 !IsVectorPromotable && 3082 isIntegerWideningViable(*DL, SliceTy, BeginOffset, S, B, E, SplitUses); 3083 3084 // Check for the case where we're going to rewrite to a new alloca of the 3085 // exact same type as the original, and with the same access offsets. In that 3086 // case, re-use the existing alloca, but still run through the rewriter to 3087 // perform phi and select speculation. 3088 AllocaInst *NewAI; 3089 if (SliceTy == AI.getAllocatedType()) { 3090 assert(BeginOffset == 0 && 3091 "Non-zero begin offset but same alloca type"); 3092 NewAI = &AI; 3093 // FIXME: We should be able to bail at this point with "nothing changed". 3094 // FIXME: We might want to defer PHI speculation until after here. 3095 } else { 3096 unsigned Alignment = AI.getAlignment(); 3097 if (!Alignment) { 3098 // The minimum alignment which users can rely on when the explicit 3099 // alignment is omitted or zero is that required by the ABI for this 3100 // type. 3101 Alignment = DL->getABITypeAlignment(AI.getAllocatedType()); 3102 } 3103 Alignment = MinAlign(Alignment, BeginOffset); 3104 // If we will get at least this much alignment from the type alone, leave 3105 // the alloca's alignment unconstrained. 3106 if (Alignment <= DL->getABITypeAlignment(SliceTy)) 3107 Alignment = 0; 3108 NewAI = new AllocaInst(SliceTy, 0, Alignment, 3109 AI.getName() + ".sroa." + Twine(B - S.begin()), &AI); 3110 ++NumNewAllocas; 3111 } 3112 3113 DEBUG(dbgs() << "Rewriting alloca partition " 3114 << "[" << BeginOffset << "," << EndOffset << ") to: " << *NewAI 3115 << "\n"); 3116 3117 // Track the high watermark on several worklists that are only relevant for 3118 // promoted allocas. We will reset it to this point if the alloca is not in 3119 // fact scheduled for promotion. 3120 unsigned PPWOldSize = PostPromotionWorklist.size(); 3121 unsigned SPOldSize = SpeculatablePHIs.size(); 3122 unsigned SSOldSize = SpeculatableSelects.size(); 3123 unsigned NumUses = 0; 3124 3125 AllocaSliceRewriter Rewriter(*DL, S, *this, AI, *NewAI, BeginOffset, 3126 EndOffset, IsVectorPromotable, 3127 IsIntegerPromotable); 3128 bool Promotable = true; 3129 for (ArrayRef<AllocaSlices::iterator>::const_iterator SUI = SplitUses.begin(), 3130 SUE = SplitUses.end(); 3131 SUI != SUE; ++SUI) { 3132 DEBUG(dbgs() << " rewriting split "); 3133 DEBUG(S.printSlice(dbgs(), *SUI, "")); 3134 Promotable &= Rewriter.visit(*SUI); 3135 ++NumUses; 3136 } 3137 for (AllocaSlices::iterator I = B; I != E; ++I) { 3138 DEBUG(dbgs() << " rewriting "); 3139 DEBUG(S.printSlice(dbgs(), I, "")); 3140 Promotable &= Rewriter.visit(I); 3141 ++NumUses; 3142 } 3143 3144 NumAllocaPartitionUses += NumUses; 3145 MaxUsesPerAllocaPartition = 3146 std::max<unsigned>(NumUses, MaxUsesPerAllocaPartition); 3147 3148 if (Promotable && !Rewriter.isUsedByRewrittenSpeculatableInstructions()) { 3149 DEBUG(dbgs() << " and queuing for promotion\n"); 3150 PromotableAllocas.push_back(NewAI); 3151 } else if (NewAI != &AI || 3152 (Promotable && 3153 Rewriter.isUsedByRewrittenSpeculatableInstructions())) { 3154 // If we can't promote the alloca, iterate on it to check for new 3155 // refinements exposed by splitting the current alloca. Don't iterate on an 3156 // alloca which didn't actually change and didn't get promoted. 3157 // 3158 // Alternatively, if we could promote the alloca but have speculatable 3159 // instructions then we will speculate them after finishing our processing 3160 // of the original alloca. Mark the new one for re-visiting in the next 3161 // iteration so the speculated operations can be rewritten. 3162 // 3163 // FIXME: We should actually track whether the rewriter changed anything. 3164 Worklist.insert(NewAI); 3165 } 3166 3167 // Drop any post-promotion work items if promotion didn't happen. 3168 if (!Promotable) { 3169 while (PostPromotionWorklist.size() > PPWOldSize) 3170 PostPromotionWorklist.pop_back(); 3171 while (SpeculatablePHIs.size() > SPOldSize) 3172 SpeculatablePHIs.pop_back(); 3173 while (SpeculatableSelects.size() > SSOldSize) 3174 SpeculatableSelects.pop_back(); 3175 } 3176 3177 return true; 3178 } 3179 3180 namespace { 3181 struct IsSliceEndLessOrEqualTo { 3182 uint64_t UpperBound; 3183 3184 IsSliceEndLessOrEqualTo(uint64_t UpperBound) : UpperBound(UpperBound) {} 3185 3186 bool operator()(const AllocaSlices::iterator &I) { 3187 return I->endOffset() <= UpperBound; 3188 } 3189 }; 3190 } 3191 3192 static void 3193 removeFinishedSplitUses(SmallVectorImpl<AllocaSlices::iterator> &SplitUses, 3194 uint64_t &MaxSplitUseEndOffset, uint64_t Offset) { 3195 if (Offset >= MaxSplitUseEndOffset) { 3196 SplitUses.clear(); 3197 MaxSplitUseEndOffset = 0; 3198 return; 3199 } 3200 3201 size_t SplitUsesOldSize = SplitUses.size(); 3202 SplitUses.erase(std::remove_if(SplitUses.begin(), SplitUses.end(), 3203 IsSliceEndLessOrEqualTo(Offset)), 3204 SplitUses.end()); 3205 if (SplitUsesOldSize == SplitUses.size()) 3206 return; 3207 3208 // Recompute the max. While this is linear, so is remove_if. 3209 MaxSplitUseEndOffset = 0; 3210 for (SmallVectorImpl<AllocaSlices::iterator>::iterator 3211 SUI = SplitUses.begin(), 3212 SUE = SplitUses.end(); 3213 SUI != SUE; ++SUI) 3214 MaxSplitUseEndOffset = std::max((*SUI)->endOffset(), MaxSplitUseEndOffset); 3215 } 3216 3217 /// \brief Walks the slices of an alloca and form partitions based on them, 3218 /// rewriting each of their uses. 3219 bool SROA::splitAlloca(AllocaInst &AI, AllocaSlices &S) { 3220 if (S.begin() == S.end()) 3221 return false; 3222 3223 unsigned NumPartitions = 0; 3224 bool Changed = false; 3225 SmallVector<AllocaSlices::iterator, 4> SplitUses; 3226 uint64_t MaxSplitUseEndOffset = 0; 3227 3228 uint64_t BeginOffset = S.begin()->beginOffset(); 3229 3230 for (AllocaSlices::iterator SI = S.begin(), SJ = llvm::next(SI), SE = S.end(); 3231 SI != SE; SI = SJ) { 3232 uint64_t MaxEndOffset = SI->endOffset(); 3233 3234 if (!SI->isSplittable()) { 3235 // When we're forming an unsplittable region, it must always start at the 3236 // first slice and will extend through its end. 3237 assert(BeginOffset == SI->beginOffset()); 3238 3239 // Form a partition including all of the overlapping slices with this 3240 // unsplittable slice. 3241 while (SJ != SE && SJ->beginOffset() < MaxEndOffset) { 3242 if (!SJ->isSplittable()) 3243 MaxEndOffset = std::max(MaxEndOffset, SJ->endOffset()); 3244 ++SJ; 3245 } 3246 } else { 3247 assert(SI->isSplittable()); // Established above. 3248 3249 // Collect all of the overlapping splittable slices. 3250 while (SJ != SE && SJ->beginOffset() < MaxEndOffset && 3251 SJ->isSplittable()) { 3252 MaxEndOffset = std::max(MaxEndOffset, SJ->endOffset()); 3253 ++SJ; 3254 } 3255 3256 // Back up MaxEndOffset and SJ if we ended the span early when 3257 // encountering an unsplittable slice. 3258 if (SJ != SE && SJ->beginOffset() < MaxEndOffset) { 3259 assert(!SJ->isSplittable()); 3260 MaxEndOffset = SJ->beginOffset(); 3261 } 3262 } 3263 3264 // Check if we have managed to move the end offset forward yet. If so, 3265 // we'll have to rewrite uses and erase old split uses. 3266 if (BeginOffset < MaxEndOffset) { 3267 // Rewrite a sequence of overlapping slices. 3268 Changed |= 3269 rewritePartition(AI, S, SI, SJ, BeginOffset, MaxEndOffset, SplitUses); 3270 ++NumPartitions; 3271 3272 removeFinishedSplitUses(SplitUses, MaxSplitUseEndOffset, MaxEndOffset); 3273 } 3274 3275 // Accumulate all the splittable slices from the [SI,SJ) region which 3276 // overlap going forward. 3277 for (AllocaSlices::iterator SK = SI; SK != SJ; ++SK) 3278 if (SK->isSplittable() && SK->endOffset() > MaxEndOffset) { 3279 SplitUses.push_back(SK); 3280 MaxSplitUseEndOffset = std::max(SK->endOffset(), MaxSplitUseEndOffset); 3281 } 3282 3283 // If we're already at the end and we have no split uses, we're done. 3284 if (SJ == SE && SplitUses.empty()) 3285 break; 3286 3287 // If we have no split uses or no gap in offsets, we're ready to move to 3288 // the next slice. 3289 if (SplitUses.empty() || (SJ != SE && MaxEndOffset == SJ->beginOffset())) { 3290 BeginOffset = SJ->beginOffset(); 3291 continue; 3292 } 3293 3294 // Even if we have split slices, if the next slice is splittable and the 3295 // split slices reach it, we can simply set up the beginning offset of the 3296 // next iteration to bridge between them. 3297 if (SJ != SE && SJ->isSplittable() && 3298 MaxSplitUseEndOffset > SJ->beginOffset()) { 3299 BeginOffset = MaxEndOffset; 3300 continue; 3301 } 3302 3303 // Otherwise, we have a tail of split slices. Rewrite them with an empty 3304 // range of slices. 3305 uint64_t PostSplitEndOffset = 3306 SJ == SE ? MaxSplitUseEndOffset : SJ->beginOffset(); 3307 3308 Changed |= rewritePartition(AI, S, SJ, SJ, MaxEndOffset, PostSplitEndOffset, 3309 SplitUses); 3310 ++NumPartitions; 3311 3312 if (SJ == SE) 3313 break; // Skip the rest, we don't need to do any cleanup. 3314 3315 removeFinishedSplitUses(SplitUses, MaxSplitUseEndOffset, 3316 PostSplitEndOffset); 3317 3318 // Now just reset the begin offset for the next iteration. 3319 BeginOffset = SJ->beginOffset(); 3320 } 3321 3322 NumAllocaPartitions += NumPartitions; 3323 MaxPartitionsPerAlloca = 3324 std::max<unsigned>(NumPartitions, MaxPartitionsPerAlloca); 3325 3326 return Changed; 3327 } 3328 3329 /// \brief Analyze an alloca for SROA. 3330 /// 3331 /// This analyzes the alloca to ensure we can reason about it, builds 3332 /// the slices of the alloca, and then hands it off to be split and 3333 /// rewritten as needed. 3334 bool SROA::runOnAlloca(AllocaInst &AI) { 3335 DEBUG(dbgs() << "SROA alloca: " << AI << "\n"); 3336 ++NumAllocasAnalyzed; 3337 3338 // Special case dead allocas, as they're trivial. 3339 if (AI.use_empty()) { 3340 AI.eraseFromParent(); 3341 return true; 3342 } 3343 3344 // Skip alloca forms that this analysis can't handle. 3345 if (AI.isArrayAllocation() || !AI.getAllocatedType()->isSized() || 3346 DL->getTypeAllocSize(AI.getAllocatedType()) == 0) 3347 return false; 3348 3349 bool Changed = false; 3350 3351 // First, split any FCA loads and stores touching this alloca to promote 3352 // better splitting and promotion opportunities. 3353 AggLoadStoreRewriter AggRewriter(*DL); 3354 Changed |= AggRewriter.rewrite(AI); 3355 3356 // Build the slices using a recursive instruction-visiting builder. 3357 AllocaSlices S(*DL, AI); 3358 DEBUG(S.print(dbgs())); 3359 if (S.isEscaped()) 3360 return Changed; 3361 3362 // Delete all the dead users of this alloca before splitting and rewriting it. 3363 for (AllocaSlices::dead_user_iterator DI = S.dead_user_begin(), 3364 DE = S.dead_user_end(); 3365 DI != DE; ++DI) { 3366 Changed = true; 3367 (*DI)->replaceAllUsesWith(UndefValue::get((*DI)->getType())); 3368 DeadInsts.insert(*DI); 3369 } 3370 for (AllocaSlices::dead_op_iterator DO = S.dead_op_begin(), 3371 DE = S.dead_op_end(); 3372 DO != DE; ++DO) { 3373 Value *OldV = **DO; 3374 // Clobber the use with an undef value. 3375 **DO = UndefValue::get(OldV->getType()); 3376 if (Instruction *OldI = dyn_cast<Instruction>(OldV)) 3377 if (isInstructionTriviallyDead(OldI)) { 3378 Changed = true; 3379 DeadInsts.insert(OldI); 3380 } 3381 } 3382 3383 // No slices to split. Leave the dead alloca for a later pass to clean up. 3384 if (S.begin() == S.end()) 3385 return Changed; 3386 3387 Changed |= splitAlloca(AI, S); 3388 3389 DEBUG(dbgs() << " Speculating PHIs\n"); 3390 while (!SpeculatablePHIs.empty()) 3391 speculatePHINodeLoads(*SpeculatablePHIs.pop_back_val()); 3392 3393 DEBUG(dbgs() << " Speculating Selects\n"); 3394 while (!SpeculatableSelects.empty()) 3395 speculateSelectInstLoads(*SpeculatableSelects.pop_back_val()); 3396 3397 return Changed; 3398 } 3399 3400 /// \brief Delete the dead instructions accumulated in this run. 3401 /// 3402 /// Recursively deletes the dead instructions we've accumulated. This is done 3403 /// at the very end to maximize locality of the recursive delete and to 3404 /// minimize the problems of invalidated instruction pointers as such pointers 3405 /// are used heavily in the intermediate stages of the algorithm. 3406 /// 3407 /// We also record the alloca instructions deleted here so that they aren't 3408 /// subsequently handed to mem2reg to promote. 3409 void SROA::deleteDeadInstructions(SmallPtrSet<AllocaInst*, 4> &DeletedAllocas) { 3410 while (!DeadInsts.empty()) { 3411 Instruction *I = DeadInsts.pop_back_val(); 3412 DEBUG(dbgs() << "Deleting dead instruction: " << *I << "\n"); 3413 3414 I->replaceAllUsesWith(UndefValue::get(I->getType())); 3415 3416 for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI) 3417 if (Instruction *U = dyn_cast<Instruction>(*OI)) { 3418 // Zero out the operand and see if it becomes trivially dead. 3419 *OI = 0; 3420 if (isInstructionTriviallyDead(U)) 3421 DeadInsts.insert(U); 3422 } 3423 3424 if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) 3425 DeletedAllocas.insert(AI); 3426 3427 ++NumDeleted; 3428 I->eraseFromParent(); 3429 } 3430 } 3431 3432 static void enqueueUsersInWorklist(Instruction &I, 3433 SmallVectorImpl<Instruction *> &Worklist, 3434 SmallPtrSet<Instruction *, 8> &Visited) { 3435 for (Value::use_iterator UI = I.use_begin(), UE = I.use_end(); UI != UE; 3436 ++UI) 3437 if (Visited.insert(cast<Instruction>(*UI))) 3438 Worklist.push_back(cast<Instruction>(*UI)); 3439 } 3440 3441 /// \brief Promote the allocas, using the best available technique. 3442 /// 3443 /// This attempts to promote whatever allocas have been identified as viable in 3444 /// the PromotableAllocas list. If that list is empty, there is nothing to do. 3445 /// If there is a domtree available, we attempt to promote using the full power 3446 /// of mem2reg. Otherwise, we build and use the AllocaPromoter above which is 3447 /// based on the SSAUpdater utilities. This function returns whether any 3448 /// promotion occurred. 3449 bool SROA::promoteAllocas(Function &F) { 3450 if (PromotableAllocas.empty()) 3451 return false; 3452 3453 NumPromoted += PromotableAllocas.size(); 3454 3455 if (DT && !ForceSSAUpdater) { 3456 DEBUG(dbgs() << "Promoting allocas with mem2reg...\n"); 3457 PromoteMemToReg(PromotableAllocas, *DT); 3458 PromotableAllocas.clear(); 3459 return true; 3460 } 3461 3462 DEBUG(dbgs() << "Promoting allocas with SSAUpdater...\n"); 3463 SSAUpdater SSA; 3464 DIBuilder DIB(*F.getParent()); 3465 SmallVector<Instruction *, 64> Insts; 3466 3467 // We need a worklist to walk the uses of each alloca. 3468 SmallVector<Instruction *, 8> Worklist; 3469 SmallPtrSet<Instruction *, 8> Visited; 3470 SmallVector<Instruction *, 32> DeadInsts; 3471 3472 for (unsigned Idx = 0, Size = PromotableAllocas.size(); Idx != Size; ++Idx) { 3473 AllocaInst *AI = PromotableAllocas[Idx]; 3474 Insts.clear(); 3475 Worklist.clear(); 3476 Visited.clear(); 3477 3478 enqueueUsersInWorklist(*AI, Worklist, Visited); 3479 3480 while (!Worklist.empty()) { 3481 Instruction *I = Worklist.pop_back_val(); 3482 3483 // FIXME: Currently the SSAUpdater infrastructure doesn't reason about 3484 // lifetime intrinsics and so we strip them (and the bitcasts+GEPs 3485 // leading to them) here. Eventually it should use them to optimize the 3486 // scalar values produced. 3487 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) { 3488 assert(II->getIntrinsicID() == Intrinsic::lifetime_start || 3489 II->getIntrinsicID() == Intrinsic::lifetime_end); 3490 II->eraseFromParent(); 3491 continue; 3492 } 3493 3494 // Push the loads and stores we find onto the list. SROA will already 3495 // have validated that all loads and stores are viable candidates for 3496 // promotion. 3497 if (LoadInst *LI = dyn_cast<LoadInst>(I)) { 3498 assert(LI->getType() == AI->getAllocatedType()); 3499 Insts.push_back(LI); 3500 continue; 3501 } 3502 if (StoreInst *SI = dyn_cast<StoreInst>(I)) { 3503 assert(SI->getValueOperand()->getType() == AI->getAllocatedType()); 3504 Insts.push_back(SI); 3505 continue; 3506 } 3507 3508 // For everything else, we know that only no-op bitcasts and GEPs will 3509 // make it this far, just recurse through them and recall them for later 3510 // removal. 3511 DeadInsts.push_back(I); 3512 enqueueUsersInWorklist(*I, Worklist, Visited); 3513 } 3514 AllocaPromoter(Insts, SSA, *AI, DIB).run(Insts); 3515 while (!DeadInsts.empty()) 3516 DeadInsts.pop_back_val()->eraseFromParent(); 3517 AI->eraseFromParent(); 3518 } 3519 3520 PromotableAllocas.clear(); 3521 return true; 3522 } 3523 3524 namespace { 3525 /// \brief A predicate to test whether an alloca belongs to a set. 3526 class IsAllocaInSet { 3527 typedef SmallPtrSet<AllocaInst *, 4> SetType; 3528 const SetType &Set; 3529 3530 public: 3531 typedef AllocaInst *argument_type; 3532 3533 IsAllocaInSet(const SetType &Set) : Set(Set) {} 3534 bool operator()(AllocaInst *AI) const { return Set.count(AI); } 3535 }; 3536 } 3537 3538 bool SROA::runOnFunction(Function &F) { 3539 DEBUG(dbgs() << "SROA function: " << F.getName() << "\n"); 3540 C = &F.getContext(); 3541 DL = getAnalysisIfAvailable<DataLayout>(); 3542 if (!DL) { 3543 DEBUG(dbgs() << " Skipping SROA -- no target data!\n"); 3544 return false; 3545 } 3546 DT = getAnalysisIfAvailable<DominatorTree>(); 3547 3548 BasicBlock &EntryBB = F.getEntryBlock(); 3549 for (BasicBlock::iterator I = EntryBB.begin(), E = llvm::prior(EntryBB.end()); 3550 I != E; ++I) 3551 if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) 3552 Worklist.insert(AI); 3553 3554 bool Changed = false; 3555 // A set of deleted alloca instruction pointers which should be removed from 3556 // the list of promotable allocas. 3557 SmallPtrSet<AllocaInst *, 4> DeletedAllocas; 3558 3559 do { 3560 while (!Worklist.empty()) { 3561 Changed |= runOnAlloca(*Worklist.pop_back_val()); 3562 deleteDeadInstructions(DeletedAllocas); 3563 3564 // Remove the deleted allocas from various lists so that we don't try to 3565 // continue processing them. 3566 if (!DeletedAllocas.empty()) { 3567 Worklist.remove_if(IsAllocaInSet(DeletedAllocas)); 3568 PostPromotionWorklist.remove_if(IsAllocaInSet(DeletedAllocas)); 3569 PromotableAllocas.erase(std::remove_if(PromotableAllocas.begin(), 3570 PromotableAllocas.end(), 3571 IsAllocaInSet(DeletedAllocas)), 3572 PromotableAllocas.end()); 3573 DeletedAllocas.clear(); 3574 } 3575 } 3576 3577 Changed |= promoteAllocas(F); 3578 3579 Worklist = PostPromotionWorklist; 3580 PostPromotionWorklist.clear(); 3581 } while (!Worklist.empty()); 3582 3583 return Changed; 3584 } 3585 3586 void SROA::getAnalysisUsage(AnalysisUsage &AU) const { 3587 if (RequiresDomTree) 3588 AU.addRequired<DominatorTree>(); 3589 AU.setPreservesCFG(); 3590 } 3591