1 //===- ScalarReplAggregates.cpp - Scalar Replacement of Aggregates --------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This transformation implements the well known scalar replacement of
11 // aggregates transformation. This xform breaks up alloca instructions of
12 // aggregate type (structure or array) into individual alloca instructions for
13 // each member (if possible). Then, if possible, it transforms the individual
14 // alloca instructions into nice clean scalar SSA form.
16 // This combines a simple SRoA algorithm with the Mem2Reg algorithm because
17 // often interact, especially for C++ programs. As such, iterating between
18 // SRoA, then Mem2Reg until we run out of things to promote works well.
20 //===----------------------------------------------------------------------===//
22 #define DEBUG_TYPE "scalarrepl"
23 #include "llvm/Transforms/Scalar.h"
24 #include "llvm/Constants.h"
25 #include "llvm/DerivedTypes.h"
26 #include "llvm/Function.h"
27 #include "llvm/GlobalVariable.h"
28 #include "llvm/Instructions.h"
29 #include "llvm/IntrinsicInst.h"
30 #include "llvm/LLVMContext.h"
31 #include "llvm/Module.h"
32 #include "llvm/Pass.h"
33 #include "llvm/Analysis/DIBuilder.h"
34 #include "llvm/Analysis/Dominators.h"
35 #include "llvm/Analysis/Loads.h"
36 #include "llvm/Analysis/ValueTracking.h"
37 #include "llvm/Target/TargetData.h"
38 #include "llvm/Transforms/Utils/PromoteMemToReg.h"
39 #include "llvm/Transforms/Utils/Local.h"
40 #include "llvm/Transforms/Utils/SSAUpdater.h"
41 #include "llvm/Support/CallSite.h"
42 #include "llvm/Support/Debug.h"
43 #include "llvm/Support/ErrorHandling.h"
44 #include "llvm/Support/GetElementPtrTypeIterator.h"
45 #include "llvm/Support/IRBuilder.h"
46 #include "llvm/Support/MathExtras.h"
47 #include "llvm/Support/raw_ostream.h"
48 #include "llvm/ADT/SetVector.h"
49 #include "llvm/ADT/SmallVector.h"
50 #include "llvm/ADT/Statistic.h"
53 STATISTIC(NumReplaced, "Number of allocas broken up");
54 STATISTIC(NumPromoted, "Number of allocas promoted");
55 STATISTIC(NumAdjusted, "Number of scalar allocas adjusted to allow promotion");
56 STATISTIC(NumConverted, "Number of aggregates converted to scalar");
57 STATISTIC(NumGlobals, "Number of allocas copied from constant global");
60 struct SROA : public FunctionPass {
61 SROA(int T, bool hasDT, char &ID)
62 : FunctionPass(ID), HasDomTree(hasDT) {
69 bool runOnFunction(Function &F);
71 bool performScalarRepl(Function &F);
72 bool performPromotion(Function &F);
78 /// DeadInsts - Keep track of instructions we have made dead, so that
79 /// we can remove them after we are done working.
80 SmallVector<Value*, 32> DeadInsts;
82 /// AllocaInfo - When analyzing uses of an alloca instruction, this captures
83 /// information about the uses. All these fields are initialized to false
84 /// and set to true when something is learned.
86 /// The alloca to promote.
89 /// CheckedPHIs - This is a set of verified PHI nodes, to prevent infinite
90 /// looping and avoid redundant work.
91 SmallPtrSet<PHINode*, 8> CheckedPHIs;
93 /// isUnsafe - This is set to true if the alloca cannot be SROA'd.
96 /// isMemCpySrc - This is true if this aggregate is memcpy'd from.
99 /// isMemCpyDst - This is true if this aggregate is memcpy'd into.
100 bool isMemCpyDst : 1;
102 /// hasSubelementAccess - This is true if a subelement of the alloca is
103 /// ever accessed, or false if the alloca is only accessed with mem
104 /// intrinsics or load/store that only access the entire alloca at once.
105 bool hasSubelementAccess : 1;
107 /// hasALoadOrStore - This is true if there are any loads or stores to it.
108 /// The alloca may just be accessed with memcpy, for example, which would
110 bool hasALoadOrStore : 1;
112 explicit AllocaInfo(AllocaInst *ai)
113 : AI(ai), isUnsafe(false), isMemCpySrc(false), isMemCpyDst(false),
114 hasSubelementAccess(false), hasALoadOrStore(false) {}
117 unsigned SRThreshold;
119 void MarkUnsafe(AllocaInfo &I, Instruction *User) {
121 DEBUG(dbgs() << " Transformation preventing inst: " << *User << '\n');
124 bool isSafeAllocaToScalarRepl(AllocaInst *AI);
126 void isSafeForScalarRepl(Instruction *I, uint64_t Offset, AllocaInfo &Info);
127 void isSafePHISelectUseForScalarRepl(Instruction *User, uint64_t Offset,
129 void isSafeGEP(GetElementPtrInst *GEPI, uint64_t &Offset, AllocaInfo &Info);
130 void isSafeMemAccess(uint64_t Offset, uint64_t MemSize,
131 const Type *MemOpType, bool isStore, AllocaInfo &Info,
132 Instruction *TheAccess, bool AllowWholeAccess);
133 bool TypeHasComponent(const Type *T, uint64_t Offset, uint64_t Size);
134 uint64_t FindElementAndOffset(const Type *&T, uint64_t &Offset,
137 void DoScalarReplacement(AllocaInst *AI,
138 std::vector<AllocaInst*> &WorkList);
139 void DeleteDeadInstructions();
141 void RewriteForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset,
142 SmallVector<AllocaInst*, 32> &NewElts);
143 void RewriteBitCast(BitCastInst *BC, AllocaInst *AI, uint64_t Offset,
144 SmallVector<AllocaInst*, 32> &NewElts);
145 void RewriteGEP(GetElementPtrInst *GEPI, AllocaInst *AI, uint64_t Offset,
146 SmallVector<AllocaInst*, 32> &NewElts);
147 void RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *Inst,
149 SmallVector<AllocaInst*, 32> &NewElts);
150 void RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocaInst *AI,
151 SmallVector<AllocaInst*, 32> &NewElts);
152 void RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocaInst *AI,
153 SmallVector<AllocaInst*, 32> &NewElts);
155 static MemTransferInst *isOnlyCopiedFromConstantGlobal(AllocaInst *AI);
158 // SROA_DT - SROA that uses DominatorTree.
159 struct SROA_DT : public SROA {
162 SROA_DT(int T = -1) : SROA(T, true, ID) {
163 initializeSROA_DTPass(*PassRegistry::getPassRegistry());
166 // getAnalysisUsage - This pass does not require any passes, but we know it
167 // will not alter the CFG, so say so.
168 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
169 AU.addRequired<DominatorTree>();
170 AU.setPreservesCFG();
174 // SROA_SSAUp - SROA that uses SSAUpdater.
175 struct SROA_SSAUp : public SROA {
178 SROA_SSAUp(int T = -1) : SROA(T, false, ID) {
179 initializeSROA_SSAUpPass(*PassRegistry::getPassRegistry());
182 // getAnalysisUsage - This pass does not require any passes, but we know it
183 // will not alter the CFG, so say so.
184 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
185 AU.setPreservesCFG();
191 char SROA_DT::ID = 0;
192 char SROA_SSAUp::ID = 0;
194 INITIALIZE_PASS_BEGIN(SROA_DT, "scalarrepl",
195 "Scalar Replacement of Aggregates (DT)", false, false)
196 INITIALIZE_PASS_DEPENDENCY(DominatorTree)
197 INITIALIZE_PASS_END(SROA_DT, "scalarrepl",
198 "Scalar Replacement of Aggregates (DT)", false, false)
200 INITIALIZE_PASS_BEGIN(SROA_SSAUp, "scalarrepl-ssa",
201 "Scalar Replacement of Aggregates (SSAUp)", false, false)
202 INITIALIZE_PASS_END(SROA_SSAUp, "scalarrepl-ssa",
203 "Scalar Replacement of Aggregates (SSAUp)", false, false)
205 // Public interface to the ScalarReplAggregates pass
206 FunctionPass *llvm::createScalarReplAggregatesPass(int Threshold,
209 return new SROA_DT(Threshold);
210 return new SROA_SSAUp(Threshold);
214 //===----------------------------------------------------------------------===//
215 // Convert To Scalar Optimization.
216 //===----------------------------------------------------------------------===//
219 /// ConvertToScalarInfo - This class implements the "Convert To Scalar"
220 /// optimization, which scans the uses of an alloca and determines if it can
221 /// rewrite it in terms of a single new alloca that can be mem2reg'd.
222 class ConvertToScalarInfo {
223 /// AllocaSize - The size of the alloca being considered in bytes.
225 const TargetData &TD;
227 /// IsNotTrivial - This is set to true if there is some access to the object
228 /// which means that mem2reg can't promote it.
231 /// ScalarKind - Tracks the kind of alloca being considered for promotion,
232 /// computed based on the uses of the alloca rather than the LLVM type system.
236 // An access via GEPs that is consistent with element access of a vector
237 // type. This will not be converted into a vector unless there is a later
238 // access using an actual vector type.
241 // An access via vector operations and possibly GEPs that are consistent
242 // with the layout of the vector type.
245 // An integer bag-of-bits with bitwise operations for insertion and
246 // extraction. Any combination of types can be converted into this kind
251 /// VectorTy - This tracks the type that we should promote the vector to if
252 /// it is possible to turn it into a vector. This starts out null, and if it
253 /// isn't possible to turn into a vector type, it gets set to VoidTy.
254 const VectorType *VectorTy;
256 /// HadNonMemTransferAccess - True if there is at least one access to the
257 /// alloca that is not a MemTransferInst. We don't want to turn structs into
258 /// large integers unless there is some potential for optimization.
259 bool HadNonMemTransferAccess;
262 explicit ConvertToScalarInfo(unsigned Size, const TargetData &td)
263 : AllocaSize(Size), TD(td), IsNotTrivial(false), ScalarKind(Unknown),
264 VectorTy(0), HadNonMemTransferAccess(false) { }
266 AllocaInst *TryConvert(AllocaInst *AI);
269 bool CanConvertToScalar(Value *V, uint64_t Offset);
270 void MergeInType(const Type *In, uint64_t Offset);
271 bool MergeInVectorType(const VectorType *VInTy, uint64_t Offset);
272 void ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, uint64_t Offset);
274 Value *ConvertScalar_ExtractValue(Value *NV, const Type *ToType,
275 uint64_t Offset, IRBuilder<> &Builder);
276 Value *ConvertScalar_InsertValue(Value *StoredVal, Value *ExistingVal,
277 uint64_t Offset, IRBuilder<> &Builder);
279 } // end anonymous namespace.
282 /// TryConvert - Analyze the specified alloca, and if it is safe to do so,
283 /// rewrite it to be a new alloca which is mem2reg'able. This returns the new
284 /// alloca if possible or null if not.
285 AllocaInst *ConvertToScalarInfo::TryConvert(AllocaInst *AI) {
286 // If we can't convert this scalar, or if mem2reg can trivially do it, bail
288 if (!CanConvertToScalar(AI, 0) || !IsNotTrivial)
291 // If an alloca has only memset / memcpy uses, it may still have an Unknown
292 // ScalarKind. Treat it as an Integer below.
293 if (ScalarKind == Unknown)
294 ScalarKind = Integer;
296 // If we were able to find a vector type that can handle this with
297 // insert/extract elements, and if there was at least one use that had
298 // a vector type, promote this to a vector. We don't want to promote
299 // random stuff that doesn't use vectors (e.g. <9 x double>) because then
300 // we just get a lot of insert/extracts. If at least one vector is
301 // involved, then we probably really do have a union of vector/array.
303 if (VectorTy && ScalarKind != ImplicitVector) {
304 DEBUG(dbgs() << "CONVERT TO VECTOR: " << *AI << "\n TYPE = "
305 << *VectorTy << '\n');
306 NewTy = VectorTy; // Use the vector type.
308 unsigned BitWidth = AllocaSize * 8;
309 if ((ScalarKind == ImplicitVector || ScalarKind == Integer) &&
310 !HadNonMemTransferAccess && !TD.fitsInLegalInteger(BitWidth))
313 DEBUG(dbgs() << "CONVERT TO SCALAR INTEGER: " << *AI << "\n");
314 // Create and insert the integer alloca.
315 NewTy = IntegerType::get(AI->getContext(), BitWidth);
317 AllocaInst *NewAI = new AllocaInst(NewTy, 0, "", AI->getParent()->begin());
318 ConvertUsesToScalar(AI, NewAI, 0);
322 /// MergeInType - Add the 'In' type to the accumulated vector type (VectorTy)
323 /// so far at the offset specified by Offset (which is specified in bytes).
325 /// There are three cases we handle here:
326 /// 1) A union of vector types of the same size and potentially its elements.
327 /// Here we turn element accesses into insert/extract element operations.
328 /// This promotes a <4 x float> with a store of float to the third element
329 /// into a <4 x float> that uses insert element.
330 /// 2) A union of vector types with power-of-2 size differences, e.g. a float,
331 /// <2 x float> and <4 x float>. Here we turn element accesses into insert
332 /// and extract element operations, and <2 x float> accesses into a cast to
333 /// <2 x double>, an extract, and a cast back to <2 x float>.
334 /// 3) A fully general blob of memory, which we turn into some (potentially
335 /// large) integer type with extract and insert operations where the loads
336 /// and stores would mutate the memory. We mark this by setting VectorTy
338 void ConvertToScalarInfo::MergeInType(const Type *In, uint64_t Offset) {
339 // If we already decided to turn this into a blob of integer memory, there is
340 // nothing to be done.
341 if (ScalarKind == Integer)
344 // If this could be contributing to a vector, analyze it.
346 // If the In type is a vector that is the same size as the alloca, see if it
347 // matches the existing VecTy.
348 if (const VectorType *VInTy = dyn_cast<VectorType>(In)) {
349 if (MergeInVectorType(VInTy, Offset))
351 } else if (In->isFloatTy() || In->isDoubleTy() ||
352 (In->isIntegerTy() && In->getPrimitiveSizeInBits() >= 8 &&
353 isPowerOf2_32(In->getPrimitiveSizeInBits()))) {
354 // Full width accesses can be ignored, because they can always be turned
356 unsigned EltSize = In->getPrimitiveSizeInBits()/8;
357 if (EltSize == AllocaSize)
360 // If we're accessing something that could be an element of a vector, see
361 // if the implied vector agrees with what we already have and if Offset is
362 // compatible with it.
363 if (Offset % EltSize == 0 && AllocaSize % EltSize == 0 &&
364 (!VectorTy || Offset * 8 < VectorTy->getPrimitiveSizeInBits())) {
366 ScalarKind = ImplicitVector;
367 VectorTy = VectorType::get(In, AllocaSize/EltSize);
371 unsigned CurrentEltSize = VectorTy->getElementType()
372 ->getPrimitiveSizeInBits()/8;
373 if (EltSize == CurrentEltSize)
376 if (In->isIntegerTy() && isPowerOf2_32(AllocaSize / EltSize))
381 // Otherwise, we have a case that we can't handle with an optimized vector
382 // form. We can still turn this into a large integer.
383 ScalarKind = Integer;
387 /// MergeInVectorType - Handles the vector case of MergeInType, returning true
388 /// if the type was successfully merged and false otherwise.
389 bool ConvertToScalarInfo::MergeInVectorType(const VectorType *VInTy,
391 // TODO: Support nonzero offsets?
395 // Only allow vectors that are a power-of-2 away from the size of the alloca.
396 if (!isPowerOf2_64(AllocaSize / (VInTy->getBitWidth() / 8)))
399 // If this the first vector we see, remember the type so that we know the
407 unsigned BitWidth = VectorTy->getBitWidth();
408 unsigned InBitWidth = VInTy->getBitWidth();
410 // Vectors of the same size can be converted using a simple bitcast.
411 if (InBitWidth == BitWidth && AllocaSize == (InBitWidth / 8)) {
416 const Type *ElementTy = VectorTy->getElementType();
417 const Type *InElementTy = VInTy->getElementType();
419 // Do not allow mixed integer and floating-point accesses from vectors of
421 if (ElementTy->isFloatingPointTy() != InElementTy->isFloatingPointTy())
424 if (ElementTy->isFloatingPointTy()) {
425 // Only allow floating-point vectors of different sizes if they have the
426 // same element type.
427 // TODO: This could be loosened a bit, but would anything benefit?
428 if (ElementTy != InElementTy)
431 // There are no arbitrary-precision floating-point types, which limits the
432 // number of legal vector types with larger element types that we can form
433 // to bitcast and extract a subvector.
434 // TODO: We could support some more cases with mixed fp128 and double here.
435 if (!(BitWidth == 64 || BitWidth == 128) ||
436 !(InBitWidth == 64 || InBitWidth == 128))
439 assert(ElementTy->isIntegerTy() && "Vector elements must be either integer "
440 "or floating-point.");
441 unsigned BitWidth = ElementTy->getPrimitiveSizeInBits();
442 unsigned InBitWidth = InElementTy->getPrimitiveSizeInBits();
444 // Do not allow integer types smaller than a byte or types whose widths are
445 // not a multiple of a byte.
446 if (BitWidth < 8 || InBitWidth < 8 ||
447 BitWidth % 8 != 0 || InBitWidth % 8 != 0)
451 // Pick the largest of the two vector types.
453 if (InBitWidth > BitWidth)
459 /// CanConvertToScalar - V is a pointer. If we can convert the pointee and all
460 /// its accesses to a single vector type, return true and set VecTy to
461 /// the new type. If we could convert the alloca into a single promotable
462 /// integer, return true but set VecTy to VoidTy. Further, if the use is not a
463 /// completely trivial use that mem2reg could promote, set IsNotTrivial. Offset
464 /// is the current offset from the base of the alloca being analyzed.
466 /// If we see at least one access to the value that is as a vector type, set the
468 bool ConvertToScalarInfo::CanConvertToScalar(Value *V, uint64_t Offset) {
469 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) {
470 Instruction *User = cast<Instruction>(*UI);
472 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
473 // Don't break volatile loads.
474 if (LI->isVolatile())
476 // Don't touch MMX operations.
477 if (LI->getType()->isX86_MMXTy())
479 HadNonMemTransferAccess = true;
480 MergeInType(LI->getType(), Offset);
484 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
485 // Storing the pointer, not into the value?
486 if (SI->getOperand(0) == V || SI->isVolatile()) return false;
487 // Don't touch MMX operations.
488 if (SI->getOperand(0)->getType()->isX86_MMXTy())
490 HadNonMemTransferAccess = true;
491 MergeInType(SI->getOperand(0)->getType(), Offset);
495 if (BitCastInst *BCI = dyn_cast<BitCastInst>(User)) {
496 IsNotTrivial = true; // Can't be mem2reg'd.
497 if (!CanConvertToScalar(BCI, Offset))
502 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) {
503 // If this is a GEP with a variable indices, we can't handle it.
504 if (!GEP->hasAllConstantIndices())
507 // Compute the offset that this GEP adds to the pointer.
508 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end());
509 uint64_t GEPOffset = TD.getIndexedOffset(GEP->getPointerOperandType(),
510 &Indices[0], Indices.size());
511 // See if all uses can be converted.
512 if (!CanConvertToScalar(GEP, Offset+GEPOffset))
514 IsNotTrivial = true; // Can't be mem2reg'd.
515 HadNonMemTransferAccess = true;
519 // If this is a constant sized memset of a constant value (e.g. 0) we can
521 if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) {
522 // Store of constant value and constant size.
523 if (!isa<ConstantInt>(MSI->getValue()) ||
524 !isa<ConstantInt>(MSI->getLength()))
526 IsNotTrivial = true; // Can't be mem2reg'd.
527 HadNonMemTransferAccess = true;
531 // If this is a memcpy or memmove into or out of the whole allocation, we
532 // can handle it like a load or store of the scalar type.
533 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) {
534 ConstantInt *Len = dyn_cast<ConstantInt>(MTI->getLength());
535 if (Len == 0 || Len->getZExtValue() != AllocaSize || Offset != 0)
538 IsNotTrivial = true; // Can't be mem2reg'd.
542 // Otherwise, we cannot handle this!
549 /// ConvertUsesToScalar - Convert all of the users of Ptr to use the new alloca
550 /// directly. This happens when we are converting an "integer union" to a
551 /// single integer scalar, or when we are converting a "vector union" to a
552 /// vector with insert/extractelement instructions.
554 /// Offset is an offset from the original alloca, in bits that need to be
555 /// shifted to the right. By the end of this, there should be no uses of Ptr.
556 void ConvertToScalarInfo::ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI,
558 while (!Ptr->use_empty()) {
559 Instruction *User = cast<Instruction>(Ptr->use_back());
561 if (BitCastInst *CI = dyn_cast<BitCastInst>(User)) {
562 ConvertUsesToScalar(CI, NewAI, Offset);
563 CI->eraseFromParent();
567 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) {
568 // Compute the offset that this GEP adds to the pointer.
569 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end());
570 uint64_t GEPOffset = TD.getIndexedOffset(GEP->getPointerOperandType(),
571 &Indices[0], Indices.size());
572 ConvertUsesToScalar(GEP, NewAI, Offset+GEPOffset*8);
573 GEP->eraseFromParent();
577 IRBuilder<> Builder(User);
579 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
580 // The load is a bit extract from NewAI shifted right by Offset bits.
581 Value *LoadedVal = Builder.CreateLoad(NewAI, "tmp");
583 = ConvertScalar_ExtractValue(LoadedVal, LI->getType(), Offset, Builder);
584 LI->replaceAllUsesWith(NewLoadVal);
585 LI->eraseFromParent();
589 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
590 assert(SI->getOperand(0) != Ptr && "Consistency error!");
591 Instruction *Old = Builder.CreateLoad(NewAI, NewAI->getName()+".in");
592 Value *New = ConvertScalar_InsertValue(SI->getOperand(0), Old, Offset,
594 Builder.CreateStore(New, NewAI);
595 SI->eraseFromParent();
597 // If the load we just inserted is now dead, then the inserted store
598 // overwrote the entire thing.
599 if (Old->use_empty())
600 Old->eraseFromParent();
604 // If this is a constant sized memset of a constant value (e.g. 0) we can
605 // transform it into a store of the expanded constant value.
606 if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) {
607 assert(MSI->getRawDest() == Ptr && "Consistency error!");
608 unsigned NumBytes = cast<ConstantInt>(MSI->getLength())->getZExtValue();
610 unsigned Val = cast<ConstantInt>(MSI->getValue())->getZExtValue();
612 // Compute the value replicated the right number of times.
613 APInt APVal(NumBytes*8, Val);
615 // Splat the value if non-zero.
617 for (unsigned i = 1; i != NumBytes; ++i)
620 Instruction *Old = Builder.CreateLoad(NewAI, NewAI->getName()+".in");
621 Value *New = ConvertScalar_InsertValue(
622 ConstantInt::get(User->getContext(), APVal),
623 Old, Offset, Builder);
624 Builder.CreateStore(New, NewAI);
626 // If the load we just inserted is now dead, then the memset overwrote
628 if (Old->use_empty())
629 Old->eraseFromParent();
631 MSI->eraseFromParent();
635 // If this is a memcpy or memmove into or out of the whole allocation, we
636 // can handle it like a load or store of the scalar type.
637 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) {
638 assert(Offset == 0 && "must be store to start of alloca");
640 // If the source and destination are both to the same alloca, then this is
641 // a noop copy-to-self, just delete it. Otherwise, emit a load and store
643 AllocaInst *OrigAI = cast<AllocaInst>(GetUnderlyingObject(Ptr, &TD, 0));
645 if (GetUnderlyingObject(MTI->getSource(), &TD, 0) != OrigAI) {
646 // Dest must be OrigAI, change this to be a load from the original
647 // pointer (bitcasted), then a store to our new alloca.
648 assert(MTI->getRawDest() == Ptr && "Neither use is of pointer?");
649 Value *SrcPtr = MTI->getSource();
650 const PointerType* SPTy = cast<PointerType>(SrcPtr->getType());
651 const PointerType* AIPTy = cast<PointerType>(NewAI->getType());
652 if (SPTy->getAddressSpace() != AIPTy->getAddressSpace()) {
653 AIPTy = PointerType::get(AIPTy->getElementType(),
654 SPTy->getAddressSpace());
656 SrcPtr = Builder.CreateBitCast(SrcPtr, AIPTy);
658 LoadInst *SrcVal = Builder.CreateLoad(SrcPtr, "srcval");
659 SrcVal->setAlignment(MTI->getAlignment());
660 Builder.CreateStore(SrcVal, NewAI);
661 } else if (GetUnderlyingObject(MTI->getDest(), &TD, 0) != OrigAI) {
662 // Src must be OrigAI, change this to be a load from NewAI then a store
663 // through the original dest pointer (bitcasted).
664 assert(MTI->getRawSource() == Ptr && "Neither use is of pointer?");
665 LoadInst *SrcVal = Builder.CreateLoad(NewAI, "srcval");
667 const PointerType* DPTy = cast<PointerType>(MTI->getDest()->getType());
668 const PointerType* AIPTy = cast<PointerType>(NewAI->getType());
669 if (DPTy->getAddressSpace() != AIPTy->getAddressSpace()) {
670 AIPTy = PointerType::get(AIPTy->getElementType(),
671 DPTy->getAddressSpace());
673 Value *DstPtr = Builder.CreateBitCast(MTI->getDest(), AIPTy);
675 StoreInst *NewStore = Builder.CreateStore(SrcVal, DstPtr);
676 NewStore->setAlignment(MTI->getAlignment());
678 // Noop transfer. Src == Dst
681 MTI->eraseFromParent();
685 llvm_unreachable("Unsupported operation!");
689 /// getScaledElementType - Gets a scaled element type for a partial vector
690 /// access of an alloca. The input types must be integer or floating-point
691 /// scalar or vector types, and the resulting type is an integer, float or
693 static const Type *getScaledElementType(const Type *Ty1, const Type *Ty2,
694 unsigned NewBitWidth) {
695 bool IsFP1 = Ty1->isFloatingPointTy() ||
696 (Ty1->isVectorTy() &&
697 cast<VectorType>(Ty1)->getElementType()->isFloatingPointTy());
698 bool IsFP2 = Ty2->isFloatingPointTy() ||
699 (Ty2->isVectorTy() &&
700 cast<VectorType>(Ty2)->getElementType()->isFloatingPointTy());
702 LLVMContext &Context = Ty1->getContext();
704 // Prefer floating-point types over integer types, as integer types may have
705 // been created by earlier scalar replacement.
706 if (IsFP1 || IsFP2) {
707 if (NewBitWidth == 32)
708 return Type::getFloatTy(Context);
709 if (NewBitWidth == 64)
710 return Type::getDoubleTy(Context);
713 return Type::getIntNTy(Context, NewBitWidth);
716 /// CreateShuffleVectorCast - Creates a shuffle vector to convert one vector
717 /// to another vector of the same element type which has the same allocation
718 /// size but different primitive sizes (e.g. <3 x i32> and <4 x i32>).
719 static Value *CreateShuffleVectorCast(Value *FromVal, const Type *ToType,
720 IRBuilder<> &Builder) {
721 const Type *FromType = FromVal->getType();
722 const VectorType *FromVTy = cast<VectorType>(FromType);
723 const VectorType *ToVTy = cast<VectorType>(ToType);
724 assert((ToVTy->getElementType() == FromVTy->getElementType()) &&
725 "Vectors must have the same element type");
726 Value *UnV = UndefValue::get(FromType);
727 unsigned numEltsFrom = FromVTy->getNumElements();
728 unsigned numEltsTo = ToVTy->getNumElements();
730 SmallVector<Constant*, 3> Args;
731 const Type* Int32Ty = Builder.getInt32Ty();
732 unsigned minNumElts = std::min(numEltsFrom, numEltsTo);
734 for (i=0; i != minNumElts; ++i)
735 Args.push_back(ConstantInt::get(Int32Ty, i));
738 Constant* UnC = UndefValue::get(Int32Ty);
739 for (; i != numEltsTo; ++i)
742 Constant *Mask = ConstantVector::get(Args);
743 return Builder.CreateShuffleVector(FromVal, UnV, Mask, "tmpV");
746 /// ConvertScalar_ExtractValue - Extract a value of type ToType from an integer
747 /// or vector value FromVal, extracting the bits from the offset specified by
748 /// Offset. This returns the value, which is of type ToType.
750 /// This happens when we are converting an "integer union" to a single
751 /// integer scalar, or when we are converting a "vector union" to a vector with
752 /// insert/extractelement instructions.
754 /// Offset is an offset from the original alloca, in bits that need to be
755 /// shifted to the right.
756 Value *ConvertToScalarInfo::
757 ConvertScalar_ExtractValue(Value *FromVal, const Type *ToType,
758 uint64_t Offset, IRBuilder<> &Builder) {
759 // If the load is of the whole new alloca, no conversion is needed.
760 const Type *FromType = FromVal->getType();
761 if (FromType == ToType && Offset == 0)
764 // If the result alloca is a vector type, this is either an element
765 // access or a bitcast to another vector type of the same size.
766 if (const VectorType *VTy = dyn_cast<VectorType>(FromType)) {
767 unsigned FromTypeSize = TD.getTypeAllocSize(FromType);
768 unsigned ToTypeSize = TD.getTypeAllocSize(ToType);
769 if (FromTypeSize == ToTypeSize) {
770 // If the two types have the same primitive size, use a bit cast.
771 // Otherwise, it is two vectors with the same element type that has
772 // the same allocation size but different number of elements so use
774 if (FromType->getPrimitiveSizeInBits() ==
775 ToType->getPrimitiveSizeInBits())
776 return Builder.CreateBitCast(FromVal, ToType, "tmp");
778 return CreateShuffleVectorCast(FromVal, ToType, Builder);
781 if (isPowerOf2_64(FromTypeSize / ToTypeSize)) {
782 assert(!(ToType->isVectorTy() && Offset != 0) && "Can't extract a value "
783 "of a smaller vector type at a nonzero offset.");
785 const Type *CastElementTy = getScaledElementType(FromType, ToType,
787 unsigned NumCastVectorElements = FromTypeSize / ToTypeSize;
789 LLVMContext &Context = FromVal->getContext();
790 const Type *CastTy = VectorType::get(CastElementTy,
791 NumCastVectorElements);
792 Value *Cast = Builder.CreateBitCast(FromVal, CastTy, "tmp");
794 unsigned EltSize = TD.getTypeAllocSizeInBits(CastElementTy);
795 unsigned Elt = Offset/EltSize;
796 assert(EltSize*Elt == Offset && "Invalid modulus in validity checking");
797 Value *Extract = Builder.CreateExtractElement(Cast, ConstantInt::get(
798 Type::getInt32Ty(Context), Elt), "tmp");
799 return Builder.CreateBitCast(Extract, ToType, "tmp");
802 // Otherwise it must be an element access.
805 unsigned EltSize = TD.getTypeAllocSizeInBits(VTy->getElementType());
806 Elt = Offset/EltSize;
807 assert(EltSize*Elt == Offset && "Invalid modulus in validity checking");
809 // Return the element extracted out of it.
810 Value *V = Builder.CreateExtractElement(FromVal, ConstantInt::get(
811 Type::getInt32Ty(FromVal->getContext()), Elt), "tmp");
812 if (V->getType() != ToType)
813 V = Builder.CreateBitCast(V, ToType, "tmp");
817 // If ToType is a first class aggregate, extract out each of the pieces and
818 // use insertvalue's to form the FCA.
819 if (const StructType *ST = dyn_cast<StructType>(ToType)) {
820 const StructLayout &Layout = *TD.getStructLayout(ST);
821 Value *Res = UndefValue::get(ST);
822 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) {
823 Value *Elt = ConvertScalar_ExtractValue(FromVal, ST->getElementType(i),
824 Offset+Layout.getElementOffsetInBits(i),
826 Res = Builder.CreateInsertValue(Res, Elt, i, "tmp");
831 if (const ArrayType *AT = dyn_cast<ArrayType>(ToType)) {
832 uint64_t EltSize = TD.getTypeAllocSizeInBits(AT->getElementType());
833 Value *Res = UndefValue::get(AT);
834 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
835 Value *Elt = ConvertScalar_ExtractValue(FromVal, AT->getElementType(),
836 Offset+i*EltSize, Builder);
837 Res = Builder.CreateInsertValue(Res, Elt, i, "tmp");
842 // Otherwise, this must be a union that was converted to an integer value.
843 const IntegerType *NTy = cast<IntegerType>(FromVal->getType());
845 // If this is a big-endian system and the load is narrower than the
846 // full alloca type, we need to do a shift to get the right bits.
848 if (TD.isBigEndian()) {
849 // On big-endian machines, the lowest bit is stored at the bit offset
850 // from the pointer given by getTypeStoreSizeInBits. This matters for
851 // integers with a bitwidth that is not a multiple of 8.
852 ShAmt = TD.getTypeStoreSizeInBits(NTy) -
853 TD.getTypeStoreSizeInBits(ToType) - Offset;
858 // Note: we support negative bitwidths (with shl) which are not defined.
859 // We do this to support (f.e.) loads off the end of a structure where
860 // only some bits are used.
861 if (ShAmt > 0 && (unsigned)ShAmt < NTy->getBitWidth())
862 FromVal = Builder.CreateLShr(FromVal,
863 ConstantInt::get(FromVal->getType(),
865 else if (ShAmt < 0 && (unsigned)-ShAmt < NTy->getBitWidth())
866 FromVal = Builder.CreateShl(FromVal,
867 ConstantInt::get(FromVal->getType(),
870 // Finally, unconditionally truncate the integer to the right width.
871 unsigned LIBitWidth = TD.getTypeSizeInBits(ToType);
872 if (LIBitWidth < NTy->getBitWidth())
874 Builder.CreateTrunc(FromVal, IntegerType::get(FromVal->getContext(),
876 else if (LIBitWidth > NTy->getBitWidth())
878 Builder.CreateZExt(FromVal, IntegerType::get(FromVal->getContext(),
881 // If the result is an integer, this is a trunc or bitcast.
882 if (ToType->isIntegerTy()) {
884 } else if (ToType->isFloatingPointTy() || ToType->isVectorTy()) {
885 // Just do a bitcast, we know the sizes match up.
886 FromVal = Builder.CreateBitCast(FromVal, ToType, "tmp");
888 // Otherwise must be a pointer.
889 FromVal = Builder.CreateIntToPtr(FromVal, ToType, "tmp");
891 assert(FromVal->getType() == ToType && "Didn't convert right?");
895 /// ConvertScalar_InsertValue - Insert the value "SV" into the existing integer
896 /// or vector value "Old" at the offset specified by Offset.
898 /// This happens when we are converting an "integer union" to a
899 /// single integer scalar, or when we are converting a "vector union" to a
900 /// vector with insert/extractelement instructions.
902 /// Offset is an offset from the original alloca, in bits that need to be
903 /// shifted to the right.
904 Value *ConvertToScalarInfo::
905 ConvertScalar_InsertValue(Value *SV, Value *Old,
906 uint64_t Offset, IRBuilder<> &Builder) {
907 // Convert the stored type to the actual type, shift it left to insert
908 // then 'or' into place.
909 const Type *AllocaType = Old->getType();
910 LLVMContext &Context = Old->getContext();
912 if (const VectorType *VTy = dyn_cast<VectorType>(AllocaType)) {
913 uint64_t VecSize = TD.getTypeAllocSizeInBits(VTy);
914 uint64_t ValSize = TD.getTypeAllocSizeInBits(SV->getType());
916 // Changing the whole vector with memset or with an access of a different
918 if (ValSize == VecSize) {
919 // If the two types have the same primitive size, use a bit cast.
920 // Otherwise, it is two vectors with the same element type that has
921 // the same allocation size but different number of elements so use
923 if (VTy->getPrimitiveSizeInBits() ==
924 SV->getType()->getPrimitiveSizeInBits())
925 return Builder.CreateBitCast(SV, AllocaType, "tmp");
927 return CreateShuffleVectorCast(SV, VTy, Builder);
930 if (isPowerOf2_64(VecSize / ValSize)) {
931 assert(!(SV->getType()->isVectorTy() && Offset != 0) && "Can't insert a "
932 "value of a smaller vector type at a nonzero offset.");
934 const Type *CastElementTy = getScaledElementType(VTy, SV->getType(),
936 unsigned NumCastVectorElements = VecSize / ValSize;
938 LLVMContext &Context = SV->getContext();
939 const Type *OldCastTy = VectorType::get(CastElementTy,
940 NumCastVectorElements);
941 Value *OldCast = Builder.CreateBitCast(Old, OldCastTy, "tmp");
943 Value *SVCast = Builder.CreateBitCast(SV, CastElementTy, "tmp");
945 unsigned EltSize = TD.getTypeAllocSizeInBits(CastElementTy);
946 unsigned Elt = Offset/EltSize;
947 assert(EltSize*Elt == Offset && "Invalid modulus in validity checking");
949 Builder.CreateInsertElement(OldCast, SVCast, ConstantInt::get(
950 Type::getInt32Ty(Context), Elt), "tmp");
951 return Builder.CreateBitCast(Insert, AllocaType, "tmp");
954 // Must be an element insertion.
955 assert(SV->getType() == VTy->getElementType());
956 uint64_t EltSize = TD.getTypeAllocSizeInBits(VTy->getElementType());
957 unsigned Elt = Offset/EltSize;
958 return Builder.CreateInsertElement(Old, SV,
959 ConstantInt::get(Type::getInt32Ty(SV->getContext()), Elt),
963 // If SV is a first-class aggregate value, insert each value recursively.
964 if (const StructType *ST = dyn_cast<StructType>(SV->getType())) {
965 const StructLayout &Layout = *TD.getStructLayout(ST);
966 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) {
967 Value *Elt = Builder.CreateExtractValue(SV, i, "tmp");
968 Old = ConvertScalar_InsertValue(Elt, Old,
969 Offset+Layout.getElementOffsetInBits(i),
975 if (const ArrayType *AT = dyn_cast<ArrayType>(SV->getType())) {
976 uint64_t EltSize = TD.getTypeAllocSizeInBits(AT->getElementType());
977 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
978 Value *Elt = Builder.CreateExtractValue(SV, i, "tmp");
979 Old = ConvertScalar_InsertValue(Elt, Old, Offset+i*EltSize, Builder);
984 // If SV is a float, convert it to the appropriate integer type.
985 // If it is a pointer, do the same.
986 unsigned SrcWidth = TD.getTypeSizeInBits(SV->getType());
987 unsigned DestWidth = TD.getTypeSizeInBits(AllocaType);
988 unsigned SrcStoreWidth = TD.getTypeStoreSizeInBits(SV->getType());
989 unsigned DestStoreWidth = TD.getTypeStoreSizeInBits(AllocaType);
990 if (SV->getType()->isFloatingPointTy() || SV->getType()->isVectorTy())
991 SV = Builder.CreateBitCast(SV,
992 IntegerType::get(SV->getContext(),SrcWidth), "tmp");
993 else if (SV->getType()->isPointerTy())
994 SV = Builder.CreatePtrToInt(SV, TD.getIntPtrType(SV->getContext()), "tmp");
996 // Zero extend or truncate the value if needed.
997 if (SV->getType() != AllocaType) {
998 if (SV->getType()->getPrimitiveSizeInBits() <
999 AllocaType->getPrimitiveSizeInBits())
1000 SV = Builder.CreateZExt(SV, AllocaType, "tmp");
1002 // Truncation may be needed if storing more than the alloca can hold
1003 // (undefined behavior).
1004 SV = Builder.CreateTrunc(SV, AllocaType, "tmp");
1005 SrcWidth = DestWidth;
1006 SrcStoreWidth = DestStoreWidth;
1010 // If this is a big-endian system and the store is narrower than the
1011 // full alloca type, we need to do a shift to get the right bits.
1013 if (TD.isBigEndian()) {
1014 // On big-endian machines, the lowest bit is stored at the bit offset
1015 // from the pointer given by getTypeStoreSizeInBits. This matters for
1016 // integers with a bitwidth that is not a multiple of 8.
1017 ShAmt = DestStoreWidth - SrcStoreWidth - Offset;
1022 // Note: we support negative bitwidths (with shr) which are not defined.
1023 // We do this to support (f.e.) stores off the end of a structure where
1024 // only some bits in the structure are set.
1025 APInt Mask(APInt::getLowBitsSet(DestWidth, SrcWidth));
1026 if (ShAmt > 0 && (unsigned)ShAmt < DestWidth) {
1027 SV = Builder.CreateShl(SV, ConstantInt::get(SV->getType(),
1030 } else if (ShAmt < 0 && (unsigned)-ShAmt < DestWidth) {
1031 SV = Builder.CreateLShr(SV, ConstantInt::get(SV->getType(),
1033 Mask = Mask.lshr(-ShAmt);
1036 // Mask out the bits we are about to insert from the old value, and or
1038 if (SrcWidth != DestWidth) {
1039 assert(DestWidth > SrcWidth);
1040 Old = Builder.CreateAnd(Old, ConstantInt::get(Context, ~Mask), "mask");
1041 SV = Builder.CreateOr(Old, SV, "ins");
1047 //===----------------------------------------------------------------------===//
1049 //===----------------------------------------------------------------------===//
1052 bool SROA::runOnFunction(Function &F) {
1053 TD = getAnalysisIfAvailable<TargetData>();
1055 bool Changed = performPromotion(F);
1057 // FIXME: ScalarRepl currently depends on TargetData more than it
1058 // theoretically needs to. It should be refactored in order to support
1059 // target-independent IR. Until this is done, just skip the actual
1060 // scalar-replacement portion of this pass.
1061 if (!TD) return Changed;
1064 bool LocalChange = performScalarRepl(F);
1065 if (!LocalChange) break; // No need to repromote if no scalarrepl
1067 LocalChange = performPromotion(F);
1068 if (!LocalChange) break; // No need to re-scalarrepl if no promotion
1075 class AllocaPromoter : public LoadAndStorePromoter {
1078 AllocaPromoter(const SmallVectorImpl<Instruction*> &Insts, SSAUpdater &S,
1079 DbgDeclareInst *DD, DIBuilder *&DB)
1080 : LoadAndStorePromoter(Insts, S, DD, DB), AI(0) {}
1082 void run(AllocaInst *AI, const SmallVectorImpl<Instruction*> &Insts) {
1083 // Remember which alloca we're promoting (for isInstInList).
1085 LoadAndStorePromoter::run(Insts);
1086 AI->eraseFromParent();
1089 virtual bool isInstInList(Instruction *I,
1090 const SmallVectorImpl<Instruction*> &Insts) const {
1091 if (LoadInst *LI = dyn_cast<LoadInst>(I))
1092 return LI->getOperand(0) == AI;
1093 return cast<StoreInst>(I)->getPointerOperand() == AI;
1096 } // end anon namespace
1098 /// isSafeSelectToSpeculate - Select instructions that use an alloca and are
1099 /// subsequently loaded can be rewritten to load both input pointers and then
1100 /// select between the result, allowing the load of the alloca to be promoted.
1102 /// %P2 = select i1 %cond, i32* %Alloca, i32* %Other
1103 /// %V = load i32* %P2
1105 /// %V1 = load i32* %Alloca -> will be mem2reg'd
1106 /// %V2 = load i32* %Other
1107 /// %V = select i1 %cond, i32 %V1, i32 %V2
1109 /// We can do this to a select if its only uses are loads and if the operand to
1110 /// the select can be loaded unconditionally.
1111 static bool isSafeSelectToSpeculate(SelectInst *SI, const TargetData *TD) {
1112 bool TDerefable = SI->getTrueValue()->isDereferenceablePointer();
1113 bool FDerefable = SI->getFalseValue()->isDereferenceablePointer();
1115 for (Value::use_iterator UI = SI->use_begin(), UE = SI->use_end();
1117 LoadInst *LI = dyn_cast<LoadInst>(*UI);
1118 if (LI == 0 || LI->isVolatile()) return false;
1120 // Both operands to the select need to be dereferencable, either absolutely
1121 // (e.g. allocas) or at this point because we can see other accesses to it.
1122 if (!TDerefable && !isSafeToLoadUnconditionally(SI->getTrueValue(), LI,
1123 LI->getAlignment(), TD))
1125 if (!FDerefable && !isSafeToLoadUnconditionally(SI->getFalseValue(), LI,
1126 LI->getAlignment(), TD))
1133 /// isSafePHIToSpeculate - PHI instructions that use an alloca and are
1134 /// subsequently loaded can be rewritten to load both input pointers in the pred
1135 /// blocks and then PHI the results, allowing the load of the alloca to be
1138 /// %P2 = phi [i32* %Alloca, i32* %Other]
1139 /// %V = load i32* %P2
1141 /// %V1 = load i32* %Alloca -> will be mem2reg'd
1143 /// %V2 = load i32* %Other
1145 /// %V = phi [i32 %V1, i32 %V2]
1147 /// We can do this to a select if its only uses are loads and if the operand to
1148 /// the select can be loaded unconditionally.
1149 static bool isSafePHIToSpeculate(PHINode *PN, const TargetData *TD) {
1150 // For now, we can only do this promotion if the load is in the same block as
1151 // the PHI, and if there are no stores between the phi and load.
1152 // TODO: Allow recursive phi users.
1153 // TODO: Allow stores.
1154 BasicBlock *BB = PN->getParent();
1155 unsigned MaxAlign = 0;
1156 for (Value::use_iterator UI = PN->use_begin(), UE = PN->use_end();
1158 LoadInst *LI = dyn_cast<LoadInst>(*UI);
1159 if (LI == 0 || LI->isVolatile()) return false;
1161 // For now we only allow loads in the same block as the PHI. This is a
1162 // common case that happens when instcombine merges two loads through a PHI.
1163 if (LI->getParent() != BB) return false;
1165 // Ensure that there are no instructions between the PHI and the load that
1167 for (BasicBlock::iterator BBI = PN; &*BBI != LI; ++BBI)
1168 if (BBI->mayWriteToMemory())
1171 MaxAlign = std::max(MaxAlign, LI->getAlignment());
1174 // Okay, we know that we have one or more loads in the same block as the PHI.
1175 // We can transform this if it is safe to push the loads into the predecessor
1176 // blocks. The only thing to watch out for is that we can't put a possibly
1177 // trapping load in the predecessor if it is a critical edge.
1178 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
1179 BasicBlock *Pred = PN->getIncomingBlock(i);
1181 // If the predecessor has a single successor, then the edge isn't critical.
1182 if (Pred->getTerminator()->getNumSuccessors() == 1)
1185 Value *InVal = PN->getIncomingValue(i);
1187 // If the InVal is an invoke in the pred, we can't put a load on the edge.
1188 if (InvokeInst *II = dyn_cast<InvokeInst>(InVal))
1189 if (II->getParent() == Pred)
1192 // If this pointer is always safe to load, or if we can prove that there is
1193 // already a load in the block, then we can move the load to the pred block.
1194 if (InVal->isDereferenceablePointer() ||
1195 isSafeToLoadUnconditionally(InVal, Pred->getTerminator(), MaxAlign, TD))
1205 /// tryToMakeAllocaBePromotable - This returns true if the alloca only has
1206 /// direct (non-volatile) loads and stores to it. If the alloca is close but
1207 /// not quite there, this will transform the code to allow promotion. As such,
1208 /// it is a non-pure predicate.
1209 static bool tryToMakeAllocaBePromotable(AllocaInst *AI, const TargetData *TD) {
1210 SetVector<Instruction*, SmallVector<Instruction*, 4>,
1211 SmallPtrSet<Instruction*, 4> > InstsToRewrite;
1213 for (Value::use_iterator UI = AI->use_begin(), UE = AI->use_end();
1216 if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
1217 if (LI->isVolatile())
1222 if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
1223 if (SI->getOperand(0) == AI || SI->isVolatile())
1224 return false; // Don't allow a store OF the AI, only INTO the AI.
1228 if (SelectInst *SI = dyn_cast<SelectInst>(U)) {
1229 // If the condition being selected on is a constant, fold the select, yes
1230 // this does (rarely) happen early on.
1231 if (ConstantInt *CI = dyn_cast<ConstantInt>(SI->getCondition())) {
1232 Value *Result = SI->getOperand(1+CI->isZero());
1233 SI->replaceAllUsesWith(Result);
1234 SI->eraseFromParent();
1236 // This is very rare and we just scrambled the use list of AI, start
1238 return tryToMakeAllocaBePromotable(AI, TD);
1241 // If it is safe to turn "load (select c, AI, ptr)" into a select of two
1242 // loads, then we can transform this by rewriting the select.
1243 if (!isSafeSelectToSpeculate(SI, TD))
1246 InstsToRewrite.insert(SI);
1250 if (PHINode *PN = dyn_cast<PHINode>(U)) {
1251 if (PN->use_empty()) { // Dead PHIs can be stripped.
1252 InstsToRewrite.insert(PN);
1256 // If it is safe to turn "load (phi [AI, ptr, ...])" into a PHI of loads
1257 // in the pred blocks, then we can transform this by rewriting the PHI.
1258 if (!isSafePHIToSpeculate(PN, TD))
1261 InstsToRewrite.insert(PN);
1268 // If there are no instructions to rewrite, then all uses are load/stores and
1270 if (InstsToRewrite.empty())
1273 // If we have instructions that need to be rewritten for this to be promotable
1274 // take care of it now.
1275 for (unsigned i = 0, e = InstsToRewrite.size(); i != e; ++i) {
1276 if (SelectInst *SI = dyn_cast<SelectInst>(InstsToRewrite[i])) {
1277 // Selects in InstsToRewrite only have load uses. Rewrite each as two
1278 // loads with a new select.
1279 while (!SI->use_empty()) {
1280 LoadInst *LI = cast<LoadInst>(SI->use_back());
1282 IRBuilder<> Builder(LI);
1283 LoadInst *TrueLoad =
1284 Builder.CreateLoad(SI->getTrueValue(), LI->getName()+".t");
1285 LoadInst *FalseLoad =
1286 Builder.CreateLoad(SI->getFalseValue(), LI->getName()+".t");
1288 // Transfer alignment and TBAA info if present.
1289 TrueLoad->setAlignment(LI->getAlignment());
1290 FalseLoad->setAlignment(LI->getAlignment());
1291 if (MDNode *Tag = LI->getMetadata(LLVMContext::MD_tbaa)) {
1292 TrueLoad->setMetadata(LLVMContext::MD_tbaa, Tag);
1293 FalseLoad->setMetadata(LLVMContext::MD_tbaa, Tag);
1296 Value *V = Builder.CreateSelect(SI->getCondition(), TrueLoad, FalseLoad);
1298 LI->replaceAllUsesWith(V);
1299 LI->eraseFromParent();
1302 // Now that all the loads are gone, the select is gone too.
1303 SI->eraseFromParent();
1307 // Otherwise, we have a PHI node which allows us to push the loads into the
1309 PHINode *PN = cast<PHINode>(InstsToRewrite[i]);
1310 if (PN->use_empty()) {
1311 PN->eraseFromParent();
1315 const Type *LoadTy = cast<PointerType>(PN->getType())->getElementType();
1316 PHINode *NewPN = PHINode::Create(LoadTy, PN->getNumIncomingValues(),
1317 PN->getName()+".ld", PN);
1319 // Get the TBAA tag and alignment to use from one of the loads. It doesn't
1320 // matter which one we get and if any differ, it doesn't matter.
1321 LoadInst *SomeLoad = cast<LoadInst>(PN->use_back());
1322 MDNode *TBAATag = SomeLoad->getMetadata(LLVMContext::MD_tbaa);
1323 unsigned Align = SomeLoad->getAlignment();
1325 // Rewrite all loads of the PN to use the new PHI.
1326 while (!PN->use_empty()) {
1327 LoadInst *LI = cast<LoadInst>(PN->use_back());
1328 LI->replaceAllUsesWith(NewPN);
1329 LI->eraseFromParent();
1332 // Inject loads into all of the pred blocks. Keep track of which blocks we
1333 // insert them into in case we have multiple edges from the same block.
1334 DenseMap<BasicBlock*, LoadInst*> InsertedLoads;
1336 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
1337 BasicBlock *Pred = PN->getIncomingBlock(i);
1338 LoadInst *&Load = InsertedLoads[Pred];
1340 Load = new LoadInst(PN->getIncomingValue(i),
1341 PN->getName() + "." + Pred->getName(),
1342 Pred->getTerminator());
1343 Load->setAlignment(Align);
1344 if (TBAATag) Load->setMetadata(LLVMContext::MD_tbaa, TBAATag);
1347 NewPN->addIncoming(Load, Pred);
1350 PN->eraseFromParent();
1357 bool SROA::performPromotion(Function &F) {
1358 std::vector<AllocaInst*> Allocas;
1359 DominatorTree *DT = 0;
1361 DT = &getAnalysis<DominatorTree>();
1363 BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function
1365 bool Changed = false;
1366 SmallVector<Instruction*, 64> Insts;
1371 // Find allocas that are safe to promote, by looking at all instructions in
1373 for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I)
1374 if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) // Is it an alloca?
1375 if (tryToMakeAllocaBePromotable(AI, TD))
1376 Allocas.push_back(AI);
1378 if (Allocas.empty()) break;
1381 PromoteMemToReg(Allocas, *DT);
1384 for (unsigned i = 0, e = Allocas.size(); i != e; ++i) {
1385 AllocaInst *AI = Allocas[i];
1387 // Build list of instructions to promote.
1388 for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end();
1390 Insts.push_back(cast<Instruction>(*UI));
1392 DbgDeclareInst *DDI = FindAllocaDbgDeclare(AI);
1394 DIB = new DIBuilder(*AI->getParent()->getParent()->getParent());
1395 AllocaPromoter(Insts, SSA, DDI, DIB).run(AI, Insts);
1399 NumPromoted += Allocas.size();
1403 // FIXME: Is there a better way to handle the lazy initialization of DIB
1404 // so that there doesn't need to be an explicit delete?
1411 /// ShouldAttemptScalarRepl - Decide if an alloca is a good candidate for
1412 /// SROA. It must be a struct or array type with a small number of elements.
1413 static bool ShouldAttemptScalarRepl(AllocaInst *AI) {
1414 const Type *T = AI->getAllocatedType();
1415 // Do not promote any struct into more than 32 separate vars.
1416 if (const StructType *ST = dyn_cast<StructType>(T))
1417 return ST->getNumElements() <= 32;
1418 // Arrays are much less likely to be safe for SROA; only consider
1419 // them if they are very small.
1420 if (const ArrayType *AT = dyn_cast<ArrayType>(T))
1421 return AT->getNumElements() <= 8;
1426 // performScalarRepl - This algorithm is a simple worklist driven algorithm,
1427 // which runs on all of the malloc/alloca instructions in the function, removing
1428 // them if they are only used by getelementptr instructions.
1430 bool SROA::performScalarRepl(Function &F) {
1431 std::vector<AllocaInst*> WorkList;
1433 // Scan the entry basic block, adding allocas to the worklist.
1434 BasicBlock &BB = F.getEntryBlock();
1435 for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I)
1436 if (AllocaInst *A = dyn_cast<AllocaInst>(I))
1437 WorkList.push_back(A);
1439 // Process the worklist
1440 bool Changed = false;
1441 while (!WorkList.empty()) {
1442 AllocaInst *AI = WorkList.back();
1443 WorkList.pop_back();
1445 // Handle dead allocas trivially. These can be formed by SROA'ing arrays
1446 // with unused elements.
1447 if (AI->use_empty()) {
1448 AI->eraseFromParent();
1453 // If this alloca is impossible for us to promote, reject it early.
1454 if (AI->isArrayAllocation() || !AI->getAllocatedType()->isSized())
1457 // Check to see if this allocation is only modified by a memcpy/memmove from
1458 // a constant global. If this is the case, we can change all users to use
1459 // the constant global instead. This is commonly produced by the CFE by
1460 // constructs like "void foo() { int A[] = {1,2,3,4,5,6,7,8,9...}; }" if 'A'
1461 // is only subsequently read.
1462 if (MemTransferInst *TheCopy = isOnlyCopiedFromConstantGlobal(AI)) {
1463 DEBUG(dbgs() << "Found alloca equal to global: " << *AI << '\n');
1464 DEBUG(dbgs() << " memcpy = " << *TheCopy << '\n');
1465 Constant *TheSrc = cast<Constant>(TheCopy->getSource());
1466 AI->replaceAllUsesWith(ConstantExpr::getBitCast(TheSrc, AI->getType()));
1467 TheCopy->eraseFromParent(); // Don't mutate the global.
1468 AI->eraseFromParent();
1474 // Check to see if we can perform the core SROA transformation. We cannot
1475 // transform the allocation instruction if it is an array allocation
1476 // (allocations OF arrays are ok though), and an allocation of a scalar
1477 // value cannot be decomposed at all.
1478 uint64_t AllocaSize = TD->getTypeAllocSize(AI->getAllocatedType());
1480 // Do not promote [0 x %struct].
1481 if (AllocaSize == 0) continue;
1483 // Do not promote any struct whose size is too big.
1484 if (AllocaSize > SRThreshold) continue;
1486 // If the alloca looks like a good candidate for scalar replacement, and if
1487 // all its users can be transformed, then split up the aggregate into its
1488 // separate elements.
1489 if (ShouldAttemptScalarRepl(AI) && isSafeAllocaToScalarRepl(AI)) {
1490 DoScalarReplacement(AI, WorkList);
1495 // If we can turn this aggregate value (potentially with casts) into a
1496 // simple scalar value that can be mem2reg'd into a register value.
1497 // IsNotTrivial tracks whether this is something that mem2reg could have
1498 // promoted itself. If so, we don't want to transform it needlessly. Note
1499 // that we can't just check based on the type: the alloca may be of an i32
1500 // but that has pointer arithmetic to set byte 3 of it or something.
1501 if (AllocaInst *NewAI =
1502 ConvertToScalarInfo((unsigned)AllocaSize, *TD).TryConvert(AI)) {
1503 NewAI->takeName(AI);
1504 AI->eraseFromParent();
1510 // Otherwise, couldn't process this alloca.
1516 /// DoScalarReplacement - This alloca satisfied the isSafeAllocaToScalarRepl
1517 /// predicate, do SROA now.
1518 void SROA::DoScalarReplacement(AllocaInst *AI,
1519 std::vector<AllocaInst*> &WorkList) {
1520 DEBUG(dbgs() << "Found inst to SROA: " << *AI << '\n');
1521 SmallVector<AllocaInst*, 32> ElementAllocas;
1522 if (const StructType *ST = dyn_cast<StructType>(AI->getAllocatedType())) {
1523 ElementAllocas.reserve(ST->getNumContainedTypes());
1524 for (unsigned i = 0, e = ST->getNumContainedTypes(); i != e; ++i) {
1525 AllocaInst *NA = new AllocaInst(ST->getContainedType(i), 0,
1527 AI->getName() + "." + Twine(i), AI);
1528 ElementAllocas.push_back(NA);
1529 WorkList.push_back(NA); // Add to worklist for recursive processing
1532 const ArrayType *AT = cast<ArrayType>(AI->getAllocatedType());
1533 ElementAllocas.reserve(AT->getNumElements());
1534 const Type *ElTy = AT->getElementType();
1535 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
1536 AllocaInst *NA = new AllocaInst(ElTy, 0, AI->getAlignment(),
1537 AI->getName() + "." + Twine(i), AI);
1538 ElementAllocas.push_back(NA);
1539 WorkList.push_back(NA); // Add to worklist for recursive processing
1543 // Now that we have created the new alloca instructions, rewrite all the
1544 // uses of the old alloca.
1545 RewriteForScalarRepl(AI, AI, 0, ElementAllocas);
1547 // Now erase any instructions that were made dead while rewriting the alloca.
1548 DeleteDeadInstructions();
1549 AI->eraseFromParent();
1554 /// DeleteDeadInstructions - Erase instructions on the DeadInstrs list,
1555 /// recursively including all their operands that become trivially dead.
1556 void SROA::DeleteDeadInstructions() {
1557 while (!DeadInsts.empty()) {
1558 Instruction *I = cast<Instruction>(DeadInsts.pop_back_val());
1560 for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI)
1561 if (Instruction *U = dyn_cast<Instruction>(*OI)) {
1562 // Zero out the operand and see if it becomes trivially dead.
1563 // (But, don't add allocas to the dead instruction list -- they are
1564 // already on the worklist and will be deleted separately.)
1566 if (isInstructionTriviallyDead(U) && !isa<AllocaInst>(U))
1567 DeadInsts.push_back(U);
1570 I->eraseFromParent();
1574 /// isSafeForScalarRepl - Check if instruction I is a safe use with regard to
1575 /// performing scalar replacement of alloca AI. The results are flagged in
1576 /// the Info parameter. Offset indicates the position within AI that is
1577 /// referenced by this instruction.
1578 void SROA::isSafeForScalarRepl(Instruction *I, uint64_t Offset,
1580 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E; ++UI) {
1581 Instruction *User = cast<Instruction>(*UI);
1583 if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) {
1584 isSafeForScalarRepl(BC, Offset, Info);
1585 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
1586 uint64_t GEPOffset = Offset;
1587 isSafeGEP(GEPI, GEPOffset, Info);
1589 isSafeForScalarRepl(GEPI, GEPOffset, Info);
1590 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) {
1591 ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength());
1593 return MarkUnsafe(Info, User);
1594 isSafeMemAccess(Offset, Length->getZExtValue(), 0,
1595 UI.getOperandNo() == 0, Info, MI,
1596 true /*AllowWholeAccess*/);
1597 } else if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1598 if (LI->isVolatile())
1599 return MarkUnsafe(Info, User);
1600 const Type *LIType = LI->getType();
1601 isSafeMemAccess(Offset, TD->getTypeAllocSize(LIType),
1602 LIType, false, Info, LI, true /*AllowWholeAccess*/);
1603 Info.hasALoadOrStore = true;
1605 } else if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
1606 // Store is ok if storing INTO the pointer, not storing the pointer
1607 if (SI->isVolatile() || SI->getOperand(0) == I)
1608 return MarkUnsafe(Info, User);
1610 const Type *SIType = SI->getOperand(0)->getType();
1611 isSafeMemAccess(Offset, TD->getTypeAllocSize(SIType),
1612 SIType, true, Info, SI, true /*AllowWholeAccess*/);
1613 Info.hasALoadOrStore = true;
1614 } else if (isa<PHINode>(User) || isa<SelectInst>(User)) {
1615 isSafePHISelectUseForScalarRepl(User, Offset, Info);
1617 return MarkUnsafe(Info, User);
1619 if (Info.isUnsafe) return;
1624 /// isSafePHIUseForScalarRepl - If we see a PHI node or select using a pointer
1625 /// derived from the alloca, we can often still split the alloca into elements.
1626 /// This is useful if we have a large alloca where one element is phi'd
1627 /// together somewhere: we can SRoA and promote all the other elements even if
1628 /// we end up not being able to promote this one.
1630 /// All we require is that the uses of the PHI do not index into other parts of
1631 /// the alloca. The most important use case for this is single load and stores
1632 /// that are PHI'd together, which can happen due to code sinking.
1633 void SROA::isSafePHISelectUseForScalarRepl(Instruction *I, uint64_t Offset,
1635 // If we've already checked this PHI, don't do it again.
1636 if (PHINode *PN = dyn_cast<PHINode>(I))
1637 if (!Info.CheckedPHIs.insert(PN))
1640 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E; ++UI) {
1641 Instruction *User = cast<Instruction>(*UI);
1643 if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) {
1644 isSafePHISelectUseForScalarRepl(BC, Offset, Info);
1645 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
1646 // Only allow "bitcast" GEPs for simplicity. We could generalize this,
1647 // but would have to prove that we're staying inside of an element being
1649 if (!GEPI->hasAllZeroIndices())
1650 return MarkUnsafe(Info, User);
1651 isSafePHISelectUseForScalarRepl(GEPI, Offset, Info);
1652 } else if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1653 if (LI->isVolatile())
1654 return MarkUnsafe(Info, User);
1655 const Type *LIType = LI->getType();
1656 isSafeMemAccess(Offset, TD->getTypeAllocSize(LIType),
1657 LIType, false, Info, LI, false /*AllowWholeAccess*/);
1658 Info.hasALoadOrStore = true;
1660 } else if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
1661 // Store is ok if storing INTO the pointer, not storing the pointer
1662 if (SI->isVolatile() || SI->getOperand(0) == I)
1663 return MarkUnsafe(Info, User);
1665 const Type *SIType = SI->getOperand(0)->getType();
1666 isSafeMemAccess(Offset, TD->getTypeAllocSize(SIType),
1667 SIType, true, Info, SI, false /*AllowWholeAccess*/);
1668 Info.hasALoadOrStore = true;
1669 } else if (isa<PHINode>(User) || isa<SelectInst>(User)) {
1670 isSafePHISelectUseForScalarRepl(User, Offset, Info);
1672 return MarkUnsafe(Info, User);
1674 if (Info.isUnsafe) return;
1678 /// isSafeGEP - Check if a GEP instruction can be handled for scalar
1679 /// replacement. It is safe when all the indices are constant, in-bounds
1680 /// references, and when the resulting offset corresponds to an element within
1681 /// the alloca type. The results are flagged in the Info parameter. Upon
1682 /// return, Offset is adjusted as specified by the GEP indices.
1683 void SROA::isSafeGEP(GetElementPtrInst *GEPI,
1684 uint64_t &Offset, AllocaInfo &Info) {
1685 gep_type_iterator GEPIt = gep_type_begin(GEPI), E = gep_type_end(GEPI);
1689 // Walk through the GEP type indices, checking the types that this indexes
1691 for (; GEPIt != E; ++GEPIt) {
1692 // Ignore struct elements, no extra checking needed for these.
1693 if ((*GEPIt)->isStructTy())
1696 ConstantInt *IdxVal = dyn_cast<ConstantInt>(GEPIt.getOperand());
1698 return MarkUnsafe(Info, GEPI);
1701 // Compute the offset due to this GEP and check if the alloca has a
1702 // component element at that offset.
1703 SmallVector<Value*, 8> Indices(GEPI->op_begin() + 1, GEPI->op_end());
1704 Offset += TD->getIndexedOffset(GEPI->getPointerOperandType(),
1705 &Indices[0], Indices.size());
1706 if (!TypeHasComponent(Info.AI->getAllocatedType(), Offset, 0))
1707 MarkUnsafe(Info, GEPI);
1710 /// isHomogeneousAggregate - Check if type T is a struct or array containing
1711 /// elements of the same type (which is always true for arrays). If so,
1712 /// return true with NumElts and EltTy set to the number of elements and the
1713 /// element type, respectively.
1714 static bool isHomogeneousAggregate(const Type *T, unsigned &NumElts,
1715 const Type *&EltTy) {
1716 if (const ArrayType *AT = dyn_cast<ArrayType>(T)) {
1717 NumElts = AT->getNumElements();
1718 EltTy = (NumElts == 0 ? 0 : AT->getElementType());
1721 if (const StructType *ST = dyn_cast<StructType>(T)) {
1722 NumElts = ST->getNumContainedTypes();
1723 EltTy = (NumElts == 0 ? 0 : ST->getContainedType(0));
1724 for (unsigned n = 1; n < NumElts; ++n) {
1725 if (ST->getContainedType(n) != EltTy)
1733 /// isCompatibleAggregate - Check if T1 and T2 are either the same type or are
1734 /// "homogeneous" aggregates with the same element type and number of elements.
1735 static bool isCompatibleAggregate(const Type *T1, const Type *T2) {
1739 unsigned NumElts1, NumElts2;
1740 const Type *EltTy1, *EltTy2;
1741 if (isHomogeneousAggregate(T1, NumElts1, EltTy1) &&
1742 isHomogeneousAggregate(T2, NumElts2, EltTy2) &&
1743 NumElts1 == NumElts2 &&
1750 /// isSafeMemAccess - Check if a load/store/memcpy operates on the entire AI
1751 /// alloca or has an offset and size that corresponds to a component element
1752 /// within it. The offset checked here may have been formed from a GEP with a
1753 /// pointer bitcasted to a different type.
1755 /// If AllowWholeAccess is true, then this allows uses of the entire alloca as a
1756 /// unit. If false, it only allows accesses known to be in a single element.
1757 void SROA::isSafeMemAccess(uint64_t Offset, uint64_t MemSize,
1758 const Type *MemOpType, bool isStore,
1759 AllocaInfo &Info, Instruction *TheAccess,
1760 bool AllowWholeAccess) {
1761 // Check if this is a load/store of the entire alloca.
1762 if (Offset == 0 && AllowWholeAccess &&
1763 MemSize == TD->getTypeAllocSize(Info.AI->getAllocatedType())) {
1764 // This can be safe for MemIntrinsics (where MemOpType is 0) and integer
1765 // loads/stores (which are essentially the same as the MemIntrinsics with
1766 // regard to copying padding between elements). But, if an alloca is
1767 // flagged as both a source and destination of such operations, we'll need
1768 // to check later for padding between elements.
1769 if (!MemOpType || MemOpType->isIntegerTy()) {
1771 Info.isMemCpyDst = true;
1773 Info.isMemCpySrc = true;
1776 // This is also safe for references using a type that is compatible with
1777 // the type of the alloca, so that loads/stores can be rewritten using
1778 // insertvalue/extractvalue.
1779 if (isCompatibleAggregate(MemOpType, Info.AI->getAllocatedType())) {
1780 Info.hasSubelementAccess = true;
1784 // Check if the offset/size correspond to a component within the alloca type.
1785 const Type *T = Info.AI->getAllocatedType();
1786 if (TypeHasComponent(T, Offset, MemSize)) {
1787 Info.hasSubelementAccess = true;
1791 return MarkUnsafe(Info, TheAccess);
1794 /// TypeHasComponent - Return true if T has a component type with the
1795 /// specified offset and size. If Size is zero, do not check the size.
1796 bool SROA::TypeHasComponent(const Type *T, uint64_t Offset, uint64_t Size) {
1799 if (const StructType *ST = dyn_cast<StructType>(T)) {
1800 const StructLayout *Layout = TD->getStructLayout(ST);
1801 unsigned EltIdx = Layout->getElementContainingOffset(Offset);
1802 EltTy = ST->getContainedType(EltIdx);
1803 EltSize = TD->getTypeAllocSize(EltTy);
1804 Offset -= Layout->getElementOffset(EltIdx);
1805 } else if (const ArrayType *AT = dyn_cast<ArrayType>(T)) {
1806 EltTy = AT->getElementType();
1807 EltSize = TD->getTypeAllocSize(EltTy);
1808 if (Offset >= AT->getNumElements() * EltSize)
1814 if (Offset == 0 && (Size == 0 || EltSize == Size))
1816 // Check if the component spans multiple elements.
1817 if (Offset + Size > EltSize)
1819 return TypeHasComponent(EltTy, Offset, Size);
1822 /// RewriteForScalarRepl - Alloca AI is being split into NewElts, so rewrite
1823 /// the instruction I, which references it, to use the separate elements.
1824 /// Offset indicates the position within AI that is referenced by this
1826 void SROA::RewriteForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset,
1827 SmallVector<AllocaInst*, 32> &NewElts) {
1828 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E;) {
1829 Use &TheUse = UI.getUse();
1830 Instruction *User = cast<Instruction>(*UI++);
1832 if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) {
1833 RewriteBitCast(BC, AI, Offset, NewElts);
1837 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
1838 RewriteGEP(GEPI, AI, Offset, NewElts);
1842 if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) {
1843 ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength());
1844 uint64_t MemSize = Length->getZExtValue();
1846 MemSize == TD->getTypeAllocSize(AI->getAllocatedType()))
1847 RewriteMemIntrinUserOfAlloca(MI, I, AI, NewElts);
1848 // Otherwise the intrinsic can only touch a single element and the
1849 // address operand will be updated, so nothing else needs to be done.
1853 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1854 const Type *LIType = LI->getType();
1856 if (isCompatibleAggregate(LIType, AI->getAllocatedType())) {
1858 // %res = load { i32, i32 }* %alloc
1860 // %load.0 = load i32* %alloc.0
1861 // %insert.0 insertvalue { i32, i32 } zeroinitializer, i32 %load.0, 0
1862 // %load.1 = load i32* %alloc.1
1863 // %insert = insertvalue { i32, i32 } %insert.0, i32 %load.1, 1
1864 // (Also works for arrays instead of structs)
1865 Value *Insert = UndefValue::get(LIType);
1866 IRBuilder<> Builder(LI);
1867 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
1868 Value *Load = Builder.CreateLoad(NewElts[i], "load");
1869 Insert = Builder.CreateInsertValue(Insert, Load, i, "insert");
1871 LI->replaceAllUsesWith(Insert);
1872 DeadInsts.push_back(LI);
1873 } else if (LIType->isIntegerTy() &&
1874 TD->getTypeAllocSize(LIType) ==
1875 TD->getTypeAllocSize(AI->getAllocatedType())) {
1876 // If this is a load of the entire alloca to an integer, rewrite it.
1877 RewriteLoadUserOfWholeAlloca(LI, AI, NewElts);
1882 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
1883 Value *Val = SI->getOperand(0);
1884 const Type *SIType = Val->getType();
1885 if (isCompatibleAggregate(SIType, AI->getAllocatedType())) {
1887 // store { i32, i32 } %val, { i32, i32 }* %alloc
1889 // %val.0 = extractvalue { i32, i32 } %val, 0
1890 // store i32 %val.0, i32* %alloc.0
1891 // %val.1 = extractvalue { i32, i32 } %val, 1
1892 // store i32 %val.1, i32* %alloc.1
1893 // (Also works for arrays instead of structs)
1894 IRBuilder<> Builder(SI);
1895 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
1896 Value *Extract = Builder.CreateExtractValue(Val, i, Val->getName());
1897 Builder.CreateStore(Extract, NewElts[i]);
1899 DeadInsts.push_back(SI);
1900 } else if (SIType->isIntegerTy() &&
1901 TD->getTypeAllocSize(SIType) ==
1902 TD->getTypeAllocSize(AI->getAllocatedType())) {
1903 // If this is a store of the entire alloca from an integer, rewrite it.
1904 RewriteStoreUserOfWholeAlloca(SI, AI, NewElts);
1909 if (isa<SelectInst>(User) || isa<PHINode>(User)) {
1910 // If we have a PHI user of the alloca itself (as opposed to a GEP or
1911 // bitcast) we have to rewrite it. GEP and bitcast uses will be RAUW'd to
1913 if (!isa<AllocaInst>(I)) continue;
1915 assert(Offset == 0 && NewElts[0] &&
1916 "Direct alloca use should have a zero offset");
1918 // If we have a use of the alloca, we know the derived uses will be
1919 // utilizing just the first element of the scalarized result. Insert a
1920 // bitcast of the first alloca before the user as required.
1921 AllocaInst *NewAI = NewElts[0];
1922 BitCastInst *BCI = new BitCastInst(NewAI, AI->getType(), "", NewAI);
1923 NewAI->moveBefore(BCI);
1930 /// RewriteBitCast - Update a bitcast reference to the alloca being replaced
1931 /// and recursively continue updating all of its uses.
1932 void SROA::RewriteBitCast(BitCastInst *BC, AllocaInst *AI, uint64_t Offset,
1933 SmallVector<AllocaInst*, 32> &NewElts) {
1934 RewriteForScalarRepl(BC, AI, Offset, NewElts);
1935 if (BC->getOperand(0) != AI)
1938 // The bitcast references the original alloca. Replace its uses with
1939 // references to the first new element alloca.
1940 Instruction *Val = NewElts[0];
1941 if (Val->getType() != BC->getDestTy()) {
1942 Val = new BitCastInst(Val, BC->getDestTy(), "", BC);
1945 BC->replaceAllUsesWith(Val);
1946 DeadInsts.push_back(BC);
1949 /// FindElementAndOffset - Return the index of the element containing Offset
1950 /// within the specified type, which must be either a struct or an array.
1951 /// Sets T to the type of the element and Offset to the offset within that
1952 /// element. IdxTy is set to the type of the index result to be used in a
1953 /// GEP instruction.
1954 uint64_t SROA::FindElementAndOffset(const Type *&T, uint64_t &Offset,
1955 const Type *&IdxTy) {
1957 if (const StructType *ST = dyn_cast<StructType>(T)) {
1958 const StructLayout *Layout = TD->getStructLayout(ST);
1959 Idx = Layout->getElementContainingOffset(Offset);
1960 T = ST->getContainedType(Idx);
1961 Offset -= Layout->getElementOffset(Idx);
1962 IdxTy = Type::getInt32Ty(T->getContext());
1965 const ArrayType *AT = cast<ArrayType>(T);
1966 T = AT->getElementType();
1967 uint64_t EltSize = TD->getTypeAllocSize(T);
1968 Idx = Offset / EltSize;
1969 Offset -= Idx * EltSize;
1970 IdxTy = Type::getInt64Ty(T->getContext());
1974 /// RewriteGEP - Check if this GEP instruction moves the pointer across
1975 /// elements of the alloca that are being split apart, and if so, rewrite
1976 /// the GEP to be relative to the new element.
1977 void SROA::RewriteGEP(GetElementPtrInst *GEPI, AllocaInst *AI, uint64_t Offset,
1978 SmallVector<AllocaInst*, 32> &NewElts) {
1979 uint64_t OldOffset = Offset;
1980 SmallVector<Value*, 8> Indices(GEPI->op_begin() + 1, GEPI->op_end());
1981 Offset += TD->getIndexedOffset(GEPI->getPointerOperandType(),
1982 &Indices[0], Indices.size());
1984 RewriteForScalarRepl(GEPI, AI, Offset, NewElts);
1986 const Type *T = AI->getAllocatedType();
1988 uint64_t OldIdx = FindElementAndOffset(T, OldOffset, IdxTy);
1989 if (GEPI->getOperand(0) == AI)
1990 OldIdx = ~0ULL; // Force the GEP to be rewritten.
1992 T = AI->getAllocatedType();
1993 uint64_t EltOffset = Offset;
1994 uint64_t Idx = FindElementAndOffset(T, EltOffset, IdxTy);
1996 // If this GEP does not move the pointer across elements of the alloca
1997 // being split, then it does not needs to be rewritten.
2001 const Type *i32Ty = Type::getInt32Ty(AI->getContext());
2002 SmallVector<Value*, 8> NewArgs;
2003 NewArgs.push_back(Constant::getNullValue(i32Ty));
2004 while (EltOffset != 0) {
2005 uint64_t EltIdx = FindElementAndOffset(T, EltOffset, IdxTy);
2006 NewArgs.push_back(ConstantInt::get(IdxTy, EltIdx));
2008 Instruction *Val = NewElts[Idx];
2009 if (NewArgs.size() > 1) {
2010 Val = GetElementPtrInst::CreateInBounds(Val, NewArgs.begin(),
2011 NewArgs.end(), "", GEPI);
2012 Val->takeName(GEPI);
2014 if (Val->getType() != GEPI->getType())
2015 Val = new BitCastInst(Val, GEPI->getType(), Val->getName(), GEPI);
2016 GEPI->replaceAllUsesWith(Val);
2017 DeadInsts.push_back(GEPI);
2020 /// RewriteMemIntrinUserOfAlloca - MI is a memcpy/memset/memmove from or to AI.
2021 /// Rewrite it to copy or set the elements of the scalarized memory.
2022 void SROA::RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *Inst,
2024 SmallVector<AllocaInst*, 32> &NewElts) {
2025 // If this is a memcpy/memmove, construct the other pointer as the
2026 // appropriate type. The "Other" pointer is the pointer that goes to memory
2027 // that doesn't have anything to do with the alloca that we are promoting. For
2028 // memset, this Value* stays null.
2029 Value *OtherPtr = 0;
2030 unsigned MemAlignment = MI->getAlignment();
2031 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(MI)) { // memmove/memcopy
2032 if (Inst == MTI->getRawDest())
2033 OtherPtr = MTI->getRawSource();
2035 assert(Inst == MTI->getRawSource());
2036 OtherPtr = MTI->getRawDest();
2040 // If there is an other pointer, we want to convert it to the same pointer
2041 // type as AI has, so we can GEP through it safely.
2043 unsigned AddrSpace =
2044 cast<PointerType>(OtherPtr->getType())->getAddressSpace();
2046 // Remove bitcasts and all-zero GEPs from OtherPtr. This is an
2047 // optimization, but it's also required to detect the corner case where
2048 // both pointer operands are referencing the same memory, and where
2049 // OtherPtr may be a bitcast or GEP that currently being rewritten. (This
2050 // function is only called for mem intrinsics that access the whole
2051 // aggregate, so non-zero GEPs are not an issue here.)
2052 OtherPtr = OtherPtr->stripPointerCasts();
2054 // Copying the alloca to itself is a no-op: just delete it.
2055 if (OtherPtr == AI || OtherPtr == NewElts[0]) {
2056 // This code will run twice for a no-op memcpy -- once for each operand.
2057 // Put only one reference to MI on the DeadInsts list.
2058 for (SmallVector<Value*, 32>::const_iterator I = DeadInsts.begin(),
2059 E = DeadInsts.end(); I != E; ++I)
2060 if (*I == MI) return;
2061 DeadInsts.push_back(MI);
2065 // If the pointer is not the right type, insert a bitcast to the right
2068 PointerType::get(AI->getType()->getElementType(), AddrSpace);
2070 if (OtherPtr->getType() != NewTy)
2071 OtherPtr = new BitCastInst(OtherPtr, NewTy, OtherPtr->getName(), MI);
2074 // Process each element of the aggregate.
2075 bool SROADest = MI->getRawDest() == Inst;
2077 Constant *Zero = Constant::getNullValue(Type::getInt32Ty(MI->getContext()));
2079 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
2080 // If this is a memcpy/memmove, emit a GEP of the other element address.
2081 Value *OtherElt = 0;
2082 unsigned OtherEltAlign = MemAlignment;
2085 Value *Idx[2] = { Zero,
2086 ConstantInt::get(Type::getInt32Ty(MI->getContext()), i) };
2087 OtherElt = GetElementPtrInst::CreateInBounds(OtherPtr, Idx, Idx + 2,
2088 OtherPtr->getName()+"."+Twine(i),
2091 const PointerType *OtherPtrTy = cast<PointerType>(OtherPtr->getType());
2092 const Type *OtherTy = OtherPtrTy->getElementType();
2093 if (const StructType *ST = dyn_cast<StructType>(OtherTy)) {
2094 EltOffset = TD->getStructLayout(ST)->getElementOffset(i);
2096 const Type *EltTy = cast<SequentialType>(OtherTy)->getElementType();
2097 EltOffset = TD->getTypeAllocSize(EltTy)*i;
2100 // The alignment of the other pointer is the guaranteed alignment of the
2101 // element, which is affected by both the known alignment of the whole
2102 // mem intrinsic and the alignment of the element. If the alignment of
2103 // the memcpy (f.e.) is 32 but the element is at a 4-byte offset, then the
2104 // known alignment is just 4 bytes.
2105 OtherEltAlign = (unsigned)MinAlign(OtherEltAlign, EltOffset);
2108 Value *EltPtr = NewElts[i];
2109 const Type *EltTy = cast<PointerType>(EltPtr->getType())->getElementType();
2111 // If we got down to a scalar, insert a load or store as appropriate.
2112 if (EltTy->isSingleValueType()) {
2113 if (isa<MemTransferInst>(MI)) {
2115 // From Other to Alloca.
2116 Value *Elt = new LoadInst(OtherElt, "tmp", false, OtherEltAlign, MI);
2117 new StoreInst(Elt, EltPtr, MI);
2119 // From Alloca to Other.
2120 Value *Elt = new LoadInst(EltPtr, "tmp", MI);
2121 new StoreInst(Elt, OtherElt, false, OtherEltAlign, MI);
2125 assert(isa<MemSetInst>(MI));
2127 // If the stored element is zero (common case), just store a null
2130 if (ConstantInt *CI = dyn_cast<ConstantInt>(MI->getArgOperand(1))) {
2132 StoreVal = Constant::getNullValue(EltTy); // 0.0, null, 0, <0,0>
2134 // If EltTy is a vector type, get the element type.
2135 const Type *ValTy = EltTy->getScalarType();
2137 // Construct an integer with the right value.
2138 unsigned EltSize = TD->getTypeSizeInBits(ValTy);
2139 APInt OneVal(EltSize, CI->getZExtValue());
2140 APInt TotalVal(OneVal);
2142 for (unsigned i = 0; 8*i < EltSize; ++i) {
2143 TotalVal = TotalVal.shl(8);
2147 // Convert the integer value to the appropriate type.
2148 StoreVal = ConstantInt::get(CI->getContext(), TotalVal);
2149 if (ValTy->isPointerTy())
2150 StoreVal = ConstantExpr::getIntToPtr(StoreVal, ValTy);
2151 else if (ValTy->isFloatingPointTy())
2152 StoreVal = ConstantExpr::getBitCast(StoreVal, ValTy);
2153 assert(StoreVal->getType() == ValTy && "Type mismatch!");
2155 // If the requested value was a vector constant, create it.
2156 if (EltTy != ValTy) {
2157 unsigned NumElts = cast<VectorType>(ValTy)->getNumElements();
2158 SmallVector<Constant*, 16> Elts(NumElts, StoreVal);
2159 StoreVal = ConstantVector::get(Elts);
2162 new StoreInst(StoreVal, EltPtr, MI);
2165 // Otherwise, if we're storing a byte variable, use a memset call for
2169 unsigned EltSize = TD->getTypeAllocSize(EltTy);
2171 IRBuilder<> Builder(MI);
2173 // Finally, insert the meminst for this element.
2174 if (isa<MemSetInst>(MI)) {
2175 Builder.CreateMemSet(EltPtr, MI->getArgOperand(1), EltSize,
2178 assert(isa<MemTransferInst>(MI));
2179 Value *Dst = SROADest ? EltPtr : OtherElt; // Dest ptr
2180 Value *Src = SROADest ? OtherElt : EltPtr; // Src ptr
2182 if (isa<MemCpyInst>(MI))
2183 Builder.CreateMemCpy(Dst, Src, EltSize, OtherEltAlign,MI->isVolatile());
2185 Builder.CreateMemMove(Dst, Src, EltSize,OtherEltAlign,MI->isVolatile());
2188 DeadInsts.push_back(MI);
2191 /// RewriteStoreUserOfWholeAlloca - We found a store of an integer that
2192 /// overwrites the entire allocation. Extract out the pieces of the stored
2193 /// integer and store them individually.
2194 void SROA::RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocaInst *AI,
2195 SmallVector<AllocaInst*, 32> &NewElts){
2196 // Extract each element out of the integer according to its structure offset
2197 // and store the element value to the individual alloca.
2198 Value *SrcVal = SI->getOperand(0);
2199 const Type *AllocaEltTy = AI->getAllocatedType();
2200 uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy);
2202 IRBuilder<> Builder(SI);
2204 // Handle tail padding by extending the operand
2205 if (TD->getTypeSizeInBits(SrcVal->getType()) != AllocaSizeBits)
2206 SrcVal = Builder.CreateZExt(SrcVal,
2207 IntegerType::get(SI->getContext(), AllocaSizeBits));
2209 DEBUG(dbgs() << "PROMOTING STORE TO WHOLE ALLOCA: " << *AI << '\n' << *SI
2212 // There are two forms here: AI could be an array or struct. Both cases
2213 // have different ways to compute the element offset.
2214 if (const StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) {
2215 const StructLayout *Layout = TD->getStructLayout(EltSTy);
2217 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
2218 // Get the number of bits to shift SrcVal to get the value.
2219 const Type *FieldTy = EltSTy->getElementType(i);
2220 uint64_t Shift = Layout->getElementOffsetInBits(i);
2222 if (TD->isBigEndian())
2223 Shift = AllocaSizeBits-Shift-TD->getTypeAllocSizeInBits(FieldTy);
2225 Value *EltVal = SrcVal;
2227 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift);
2228 EltVal = Builder.CreateLShr(EltVal, ShiftVal, "sroa.store.elt");
2231 // Truncate down to an integer of the right size.
2232 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy);
2234 // Ignore zero sized fields like {}, they obviously contain no data.
2235 if (FieldSizeBits == 0) continue;
2237 if (FieldSizeBits != AllocaSizeBits)
2238 EltVal = Builder.CreateTrunc(EltVal,
2239 IntegerType::get(SI->getContext(), FieldSizeBits));
2240 Value *DestField = NewElts[i];
2241 if (EltVal->getType() == FieldTy) {
2242 // Storing to an integer field of this size, just do it.
2243 } else if (FieldTy->isFloatingPointTy() || FieldTy->isVectorTy()) {
2244 // Bitcast to the right element type (for fp/vector values).
2245 EltVal = Builder.CreateBitCast(EltVal, FieldTy);
2247 // Otherwise, bitcast the dest pointer (for aggregates).
2248 DestField = Builder.CreateBitCast(DestField,
2249 PointerType::getUnqual(EltVal->getType()));
2251 new StoreInst(EltVal, DestField, SI);
2255 const ArrayType *ATy = cast<ArrayType>(AllocaEltTy);
2256 const Type *ArrayEltTy = ATy->getElementType();
2257 uint64_t ElementOffset = TD->getTypeAllocSizeInBits(ArrayEltTy);
2258 uint64_t ElementSizeBits = TD->getTypeSizeInBits(ArrayEltTy);
2262 if (TD->isBigEndian())
2263 Shift = AllocaSizeBits-ElementOffset;
2267 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
2268 // Ignore zero sized fields like {}, they obviously contain no data.
2269 if (ElementSizeBits == 0) continue;
2271 Value *EltVal = SrcVal;
2273 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift);
2274 EltVal = Builder.CreateLShr(EltVal, ShiftVal, "sroa.store.elt");
2277 // Truncate down to an integer of the right size.
2278 if (ElementSizeBits != AllocaSizeBits)
2279 EltVal = Builder.CreateTrunc(EltVal,
2280 IntegerType::get(SI->getContext(),
2282 Value *DestField = NewElts[i];
2283 if (EltVal->getType() == ArrayEltTy) {
2284 // Storing to an integer field of this size, just do it.
2285 } else if (ArrayEltTy->isFloatingPointTy() ||
2286 ArrayEltTy->isVectorTy()) {
2287 // Bitcast to the right element type (for fp/vector values).
2288 EltVal = Builder.CreateBitCast(EltVal, ArrayEltTy);
2290 // Otherwise, bitcast the dest pointer (for aggregates).
2291 DestField = Builder.CreateBitCast(DestField,
2292 PointerType::getUnqual(EltVal->getType()));
2294 new StoreInst(EltVal, DestField, SI);
2296 if (TD->isBigEndian())
2297 Shift -= ElementOffset;
2299 Shift += ElementOffset;
2303 DeadInsts.push_back(SI);
2306 /// RewriteLoadUserOfWholeAlloca - We found a load of the entire allocation to
2307 /// an integer. Load the individual pieces to form the aggregate value.
2308 void SROA::RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocaInst *AI,
2309 SmallVector<AllocaInst*, 32> &NewElts) {
2310 // Extract each element out of the NewElts according to its structure offset
2311 // and form the result value.
2312 const Type *AllocaEltTy = AI->getAllocatedType();
2313 uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy);
2315 DEBUG(dbgs() << "PROMOTING LOAD OF WHOLE ALLOCA: " << *AI << '\n' << *LI
2318 // There are two forms here: AI could be an array or struct. Both cases
2319 // have different ways to compute the element offset.
2320 const StructLayout *Layout = 0;
2321 uint64_t ArrayEltBitOffset = 0;
2322 if (const StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) {
2323 Layout = TD->getStructLayout(EltSTy);
2325 const Type *ArrayEltTy = cast<ArrayType>(AllocaEltTy)->getElementType();
2326 ArrayEltBitOffset = TD->getTypeAllocSizeInBits(ArrayEltTy);
2330 Constant::getNullValue(IntegerType::get(LI->getContext(), AllocaSizeBits));
2332 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
2333 // Load the value from the alloca. If the NewElt is an aggregate, cast
2334 // the pointer to an integer of the same size before doing the load.
2335 Value *SrcField = NewElts[i];
2336 const Type *FieldTy =
2337 cast<PointerType>(SrcField->getType())->getElementType();
2338 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy);
2340 // Ignore zero sized fields like {}, they obviously contain no data.
2341 if (FieldSizeBits == 0) continue;
2343 const IntegerType *FieldIntTy = IntegerType::get(LI->getContext(),
2345 if (!FieldTy->isIntegerTy() && !FieldTy->isFloatingPointTy() &&
2346 !FieldTy->isVectorTy())
2347 SrcField = new BitCastInst(SrcField,
2348 PointerType::getUnqual(FieldIntTy),
2350 SrcField = new LoadInst(SrcField, "sroa.load.elt", LI);
2352 // If SrcField is a fp or vector of the right size but that isn't an
2353 // integer type, bitcast to an integer so we can shift it.
2354 if (SrcField->getType() != FieldIntTy)
2355 SrcField = new BitCastInst(SrcField, FieldIntTy, "", LI);
2357 // Zero extend the field to be the same size as the final alloca so that
2358 // we can shift and insert it.
2359 if (SrcField->getType() != ResultVal->getType())
2360 SrcField = new ZExtInst(SrcField, ResultVal->getType(), "", LI);
2362 // Determine the number of bits to shift SrcField.
2364 if (Layout) // Struct case.
2365 Shift = Layout->getElementOffsetInBits(i);
2367 Shift = i*ArrayEltBitOffset;
2369 if (TD->isBigEndian())
2370 Shift = AllocaSizeBits-Shift-FieldIntTy->getBitWidth();
2373 Value *ShiftVal = ConstantInt::get(SrcField->getType(), Shift);
2374 SrcField = BinaryOperator::CreateShl(SrcField, ShiftVal, "", LI);
2377 // Don't create an 'or x, 0' on the first iteration.
2378 if (!isa<Constant>(ResultVal) ||
2379 !cast<Constant>(ResultVal)->isNullValue())
2380 ResultVal = BinaryOperator::CreateOr(SrcField, ResultVal, "", LI);
2382 ResultVal = SrcField;
2385 // Handle tail padding by truncating the result
2386 if (TD->getTypeSizeInBits(LI->getType()) != AllocaSizeBits)
2387 ResultVal = new TruncInst(ResultVal, LI->getType(), "", LI);
2389 LI->replaceAllUsesWith(ResultVal);
2390 DeadInsts.push_back(LI);
2393 /// HasPadding - Return true if the specified type has any structure or
2394 /// alignment padding in between the elements that would be split apart
2395 /// by SROA; return false otherwise.
2396 static bool HasPadding(const Type *Ty, const TargetData &TD) {
2397 if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
2398 Ty = ATy->getElementType();
2399 return TD.getTypeSizeInBits(Ty) != TD.getTypeAllocSizeInBits(Ty);
2402 // SROA currently handles only Arrays and Structs.
2403 const StructType *STy = cast<StructType>(Ty);
2404 const StructLayout *SL = TD.getStructLayout(STy);
2405 unsigned PrevFieldBitOffset = 0;
2406 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
2407 unsigned FieldBitOffset = SL->getElementOffsetInBits(i);
2409 // Check to see if there is any padding between this element and the
2412 unsigned PrevFieldEnd =
2413 PrevFieldBitOffset+TD.getTypeSizeInBits(STy->getElementType(i-1));
2414 if (PrevFieldEnd < FieldBitOffset)
2417 PrevFieldBitOffset = FieldBitOffset;
2419 // Check for tail padding.
2420 if (unsigned EltCount = STy->getNumElements()) {
2421 unsigned PrevFieldEnd = PrevFieldBitOffset +
2422 TD.getTypeSizeInBits(STy->getElementType(EltCount-1));
2423 if (PrevFieldEnd < SL->getSizeInBits())
2429 /// isSafeStructAllocaToScalarRepl - Check to see if the specified allocation of
2430 /// an aggregate can be broken down into elements. Return 0 if not, 3 if safe,
2431 /// or 1 if safe after canonicalization has been performed.
2432 bool SROA::isSafeAllocaToScalarRepl(AllocaInst *AI) {
2433 // Loop over the use list of the alloca. We can only transform it if all of
2434 // the users are safe to transform.
2435 AllocaInfo Info(AI);
2437 isSafeForScalarRepl(AI, 0, Info);
2438 if (Info.isUnsafe) {
2439 DEBUG(dbgs() << "Cannot transform: " << *AI << '\n');
2443 // Okay, we know all the users are promotable. If the aggregate is a memcpy
2444 // source and destination, we have to be careful. In particular, the memcpy
2445 // could be moving around elements that live in structure padding of the LLVM
2446 // types, but may actually be used. In these cases, we refuse to promote the
2448 if (Info.isMemCpySrc && Info.isMemCpyDst &&
2449 HasPadding(AI->getAllocatedType(), *TD))
2452 // If the alloca never has an access to just *part* of it, but is accessed
2453 // via loads and stores, then we should use ConvertToScalarInfo to promote
2454 // the alloca instead of promoting each piece at a time and inserting fission
2456 if (!Info.hasSubelementAccess && Info.hasALoadOrStore) {
2457 // If the struct/array just has one element, use basic SRoA.
2458 if (const StructType *ST = dyn_cast<StructType>(AI->getAllocatedType())) {
2459 if (ST->getNumElements() > 1) return false;
2461 if (cast<ArrayType>(AI->getAllocatedType())->getNumElements() > 1)
2471 /// PointsToConstantGlobal - Return true if V (possibly indirectly) points to
2472 /// some part of a constant global variable. This intentionally only accepts
2473 /// constant expressions because we don't can't rewrite arbitrary instructions.
2474 static bool PointsToConstantGlobal(Value *V) {
2475 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
2476 return GV->isConstant();
2477 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
2478 if (CE->getOpcode() == Instruction::BitCast ||
2479 CE->getOpcode() == Instruction::GetElementPtr)
2480 return PointsToConstantGlobal(CE->getOperand(0));
2484 /// isOnlyCopiedFromConstantGlobal - Recursively walk the uses of a (derived)
2485 /// pointer to an alloca. Ignore any reads of the pointer, return false if we
2486 /// see any stores or other unknown uses. If we see pointer arithmetic, keep
2487 /// track of whether it moves the pointer (with isOffset) but otherwise traverse
2488 /// the uses. If we see a memcpy/memmove that targets an unoffseted pointer to
2489 /// the alloca, and if the source pointer is a pointer to a constant global, we
2490 /// can optimize this.
2491 static bool isOnlyCopiedFromConstantGlobal(Value *V, MemTransferInst *&TheCopy,
2493 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) {
2494 User *U = cast<Instruction>(*UI);
2496 if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
2497 // Ignore non-volatile loads, they are always ok.
2498 if (LI->isVolatile()) return false;
2502 if (BitCastInst *BCI = dyn_cast<BitCastInst>(U)) {
2503 // If uses of the bitcast are ok, we are ok.
2504 if (!isOnlyCopiedFromConstantGlobal(BCI, TheCopy, isOffset))
2508 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) {
2509 // If the GEP has all zero indices, it doesn't offset the pointer. If it
2510 // doesn't, it does.
2511 if (!isOnlyCopiedFromConstantGlobal(GEP, TheCopy,
2512 isOffset || !GEP->hasAllZeroIndices()))
2517 if (CallSite CS = U) {
2518 // If this is the function being called then we treat it like a load and
2520 if (CS.isCallee(UI))
2523 // If this is a readonly/readnone call site, then we know it is just a
2524 // load (but one that potentially returns the value itself), so we can
2525 // ignore it if we know that the value isn't captured.
2526 unsigned ArgNo = CS.getArgumentNo(UI);
2527 if (CS.onlyReadsMemory() &&
2528 (CS.getInstruction()->use_empty() ||
2529 CS.paramHasAttr(ArgNo+1, Attribute::NoCapture)))
2532 // If this is being passed as a byval argument, the caller is making a
2533 // copy, so it is only a read of the alloca.
2534 if (CS.paramHasAttr(ArgNo+1, Attribute::ByVal))
2538 // If this is isn't our memcpy/memmove, reject it as something we can't
2540 MemTransferInst *MI = dyn_cast<MemTransferInst>(U);
2544 // If the transfer is using the alloca as a source of the transfer, then
2545 // ignore it since it is a load (unless the transfer is volatile).
2546 if (UI.getOperandNo() == 1) {
2547 if (MI->isVolatile()) return false;
2551 // If we already have seen a copy, reject the second one.
2552 if (TheCopy) return false;
2554 // If the pointer has been offset from the start of the alloca, we can't
2555 // safely handle this.
2556 if (isOffset) return false;
2558 // If the memintrinsic isn't using the alloca as the dest, reject it.
2559 if (UI.getOperandNo() != 0) return false;
2561 // If the source of the memcpy/move is not a constant global, reject it.
2562 if (!PointsToConstantGlobal(MI->getSource()))
2565 // Otherwise, the transform is safe. Remember the copy instruction.
2571 /// isOnlyCopiedFromConstantGlobal - Return true if the specified alloca is only
2572 /// modified by a copy from a constant global. If we can prove this, we can
2573 /// replace any uses of the alloca with uses of the global directly.
2574 MemTransferInst *SROA::isOnlyCopiedFromConstantGlobal(AllocaInst *AI) {
2575 MemTransferInst *TheCopy = 0;
2576 if (::isOnlyCopiedFromConstantGlobal(AI, TheCopy, false))