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/Dominators.h"
34 #include "llvm/Analysis/Loads.h"
35 #include "llvm/Analysis/ValueTracking.h"
36 #include "llvm/Target/TargetData.h"
37 #include "llvm/Transforms/Utils/PromoteMemToReg.h"
38 #include "llvm/Transforms/Utils/Local.h"
39 #include "llvm/Transforms/Utils/SSAUpdater.h"
40 #include "llvm/Support/CallSite.h"
41 #include "llvm/Support/Debug.h"
42 #include "llvm/Support/ErrorHandling.h"
43 #include "llvm/Support/GetElementPtrTypeIterator.h"
44 #include "llvm/Support/IRBuilder.h"
45 #include "llvm/Support/MathExtras.h"
46 #include "llvm/Support/raw_ostream.h"
47 #include "llvm/ADT/SetVector.h"
48 #include "llvm/ADT/SmallVector.h"
49 #include "llvm/ADT/Statistic.h"
52 STATISTIC(NumReplaced, "Number of allocas broken up");
53 STATISTIC(NumPromoted, "Number of allocas promoted");
54 STATISTIC(NumAdjusted, "Number of scalar allocas adjusted to allow promotion");
55 STATISTIC(NumConverted, "Number of aggregates converted to scalar");
56 STATISTIC(NumGlobals, "Number of allocas copied from constant global");
59 struct SROA : public FunctionPass {
60 SROA(int T, bool hasDT, char &ID)
61 : FunctionPass(ID), HasDomTree(hasDT) {
68 bool runOnFunction(Function &F);
70 bool performScalarRepl(Function &F);
71 bool performPromotion(Function &F);
77 /// DeadInsts - Keep track of instructions we have made dead, so that
78 /// we can remove them after we are done working.
79 SmallVector<Value*, 32> DeadInsts;
81 /// AllocaInfo - When analyzing uses of an alloca instruction, this captures
82 /// information about the uses. All these fields are initialized to false
83 /// and set to true when something is learned.
85 /// The alloca to promote.
88 /// CheckedPHIs - This is a set of verified PHI nodes, to prevent infinite
89 /// looping and avoid redundant work.
90 SmallPtrSet<PHINode*, 8> CheckedPHIs;
92 /// isUnsafe - This is set to true if the alloca cannot be SROA'd.
95 /// isMemCpySrc - This is true if this aggregate is memcpy'd from.
98 /// isMemCpyDst - This is true if this aggregate is memcpy'd into.
101 /// hasSubelementAccess - This is true if a subelement of the alloca is
102 /// ever accessed, or false if the alloca is only accessed with mem
103 /// intrinsics or load/store that only access the entire alloca at once.
104 bool hasSubelementAccess : 1;
106 /// hasALoadOrStore - This is true if there are any loads or stores to it.
107 /// The alloca may just be accessed with memcpy, for example, which would
109 bool hasALoadOrStore : 1;
111 explicit AllocaInfo(AllocaInst *ai)
112 : AI(ai), isUnsafe(false), isMemCpySrc(false), isMemCpyDst(false),
113 hasSubelementAccess(false), hasALoadOrStore(false) {}
116 unsigned SRThreshold;
118 void MarkUnsafe(AllocaInfo &I, Instruction *User) {
120 DEBUG(dbgs() << " Transformation preventing inst: " << *User << '\n');
123 bool isSafeAllocaToScalarRepl(AllocaInst *AI);
125 void isSafeForScalarRepl(Instruction *I, uint64_t Offset, AllocaInfo &Info);
126 void isSafePHISelectUseForScalarRepl(Instruction *User, uint64_t Offset,
128 void isSafeGEP(GetElementPtrInst *GEPI, uint64_t &Offset, AllocaInfo &Info);
129 void isSafeMemAccess(uint64_t Offset, uint64_t MemSize,
130 const Type *MemOpType, bool isStore, AllocaInfo &Info,
131 Instruction *TheAccess, bool AllowWholeAccess);
132 bool TypeHasComponent(const Type *T, uint64_t Offset, uint64_t Size);
133 uint64_t FindElementAndOffset(const Type *&T, uint64_t &Offset,
136 void DoScalarReplacement(AllocaInst *AI,
137 std::vector<AllocaInst*> &WorkList);
138 void DeleteDeadInstructions();
140 void RewriteForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset,
141 SmallVector<AllocaInst*, 32> &NewElts);
142 void RewriteBitCast(BitCastInst *BC, AllocaInst *AI, uint64_t Offset,
143 SmallVector<AllocaInst*, 32> &NewElts);
144 void RewriteGEP(GetElementPtrInst *GEPI, AllocaInst *AI, uint64_t Offset,
145 SmallVector<AllocaInst*, 32> &NewElts);
146 void RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *Inst,
148 SmallVector<AllocaInst*, 32> &NewElts);
149 void RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocaInst *AI,
150 SmallVector<AllocaInst*, 32> &NewElts);
151 void RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocaInst *AI,
152 SmallVector<AllocaInst*, 32> &NewElts);
154 static MemTransferInst *isOnlyCopiedFromConstantGlobal(AllocaInst *AI);
157 // SROA_DT - SROA that uses DominatorTree.
158 struct SROA_DT : public SROA {
161 SROA_DT(int T = -1) : SROA(T, true, ID) {
162 initializeSROA_DTPass(*PassRegistry::getPassRegistry());
165 // getAnalysisUsage - This pass does not require any passes, but we know it
166 // will not alter the CFG, so say so.
167 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
168 AU.addRequired<DominatorTree>();
169 AU.setPreservesCFG();
173 // SROA_SSAUp - SROA that uses SSAUpdater.
174 struct SROA_SSAUp : public SROA {
177 SROA_SSAUp(int T = -1) : SROA(T, false, ID) {
178 initializeSROA_SSAUpPass(*PassRegistry::getPassRegistry());
181 // getAnalysisUsage - This pass does not require any passes, but we know it
182 // will not alter the CFG, so say so.
183 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
184 AU.setPreservesCFG();
190 char SROA_DT::ID = 0;
191 char SROA_SSAUp::ID = 0;
193 INITIALIZE_PASS_BEGIN(SROA_DT, "scalarrepl",
194 "Scalar Replacement of Aggregates (DT)", false, false)
195 INITIALIZE_PASS_DEPENDENCY(DominatorTree)
196 INITIALIZE_PASS_END(SROA_DT, "scalarrepl",
197 "Scalar Replacement of Aggregates (DT)", false, false)
199 INITIALIZE_PASS_BEGIN(SROA_SSAUp, "scalarrepl-ssa",
200 "Scalar Replacement of Aggregates (SSAUp)", false, false)
201 INITIALIZE_PASS_END(SROA_SSAUp, "scalarrepl-ssa",
202 "Scalar Replacement of Aggregates (SSAUp)", false, false)
204 // Public interface to the ScalarReplAggregates pass
205 FunctionPass *llvm::createScalarReplAggregatesPass(int Threshold,
208 return new SROA_DT(Threshold);
209 return new SROA_SSAUp(Threshold);
213 //===----------------------------------------------------------------------===//
214 // Convert To Scalar Optimization.
215 //===----------------------------------------------------------------------===//
218 /// ConvertToScalarInfo - This class implements the "Convert To Scalar"
219 /// optimization, which scans the uses of an alloca and determines if it can
220 /// rewrite it in terms of a single new alloca that can be mem2reg'd.
221 class ConvertToScalarInfo {
222 /// AllocaSize - The size of the alloca being considered.
224 const TargetData &TD;
226 /// IsNotTrivial - This is set to true if there is some access to the object
227 /// which means that mem2reg can't promote it.
230 /// VectorTy - This tracks the type that we should promote the vector to if
231 /// it is possible to turn it into a vector. This starts out null, and if it
232 /// isn't possible to turn into a vector type, it gets set to VoidTy.
233 const Type *VectorTy;
235 /// HadAVector - True if there is at least one vector access to the alloca.
236 /// We don't want to turn random arrays into vectors and use vector element
237 /// insert/extract, but if there are element accesses to something that is
238 /// also declared as a vector, we do want to promote to a vector.
242 explicit ConvertToScalarInfo(unsigned Size, const TargetData &td)
243 : AllocaSize(Size), TD(td) {
244 IsNotTrivial = false;
249 AllocaInst *TryConvert(AllocaInst *AI);
252 bool CanConvertToScalar(Value *V, uint64_t Offset);
253 void MergeInType(const Type *In, uint64_t Offset);
254 bool MergeInVectorType(const VectorType *VInTy, uint64_t Offset);
255 void ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, uint64_t Offset);
257 Value *ConvertScalar_ExtractValue(Value *NV, const Type *ToType,
258 uint64_t Offset, IRBuilder<> &Builder);
259 Value *ConvertScalar_InsertValue(Value *StoredVal, Value *ExistingVal,
260 uint64_t Offset, IRBuilder<> &Builder);
262 } // end anonymous namespace.
265 /// TryConvert - Analyze the specified alloca, and if it is safe to do so,
266 /// rewrite it to be a new alloca which is mem2reg'able. This returns the new
267 /// alloca if possible or null if not.
268 AllocaInst *ConvertToScalarInfo::TryConvert(AllocaInst *AI) {
269 // If we can't convert this scalar, or if mem2reg can trivially do it, bail
271 if (!CanConvertToScalar(AI, 0) || !IsNotTrivial)
274 // If we were able to find a vector type that can handle this with
275 // insert/extract elements, and if there was at least one use that had
276 // a vector type, promote this to a vector. We don't want to promote
277 // random stuff that doesn't use vectors (e.g. <9 x double>) because then
278 // we just get a lot of insert/extracts. If at least one vector is
279 // involved, then we probably really do have a union of vector/array.
281 if (VectorTy && VectorTy->isVectorTy() && HadAVector) {
282 DEBUG(dbgs() << "CONVERT TO VECTOR: " << *AI << "\n TYPE = "
283 << *VectorTy << '\n');
284 NewTy = VectorTy; // Use the vector type.
286 DEBUG(dbgs() << "CONVERT TO SCALAR INTEGER: " << *AI << "\n");
287 // Create and insert the integer alloca.
288 NewTy = IntegerType::get(AI->getContext(), AllocaSize*8);
290 AllocaInst *NewAI = new AllocaInst(NewTy, 0, "", AI->getParent()->begin());
291 ConvertUsesToScalar(AI, NewAI, 0);
295 /// MergeInType - Add the 'In' type to the accumulated vector type (VectorTy)
296 /// so far at the offset specified by Offset (which is specified in bytes).
298 /// There are three cases we handle here:
299 /// 1) A union of vector types of the same size and potentially its elements.
300 /// Here we turn element accesses into insert/extract element operations.
301 /// This promotes a <4 x float> with a store of float to the third element
302 /// into a <4 x float> that uses insert element.
303 /// 2) A union of vector types with power-of-2 size differences, e.g. a float,
304 /// <2 x float> and <4 x float>. Here we turn element accesses into insert
305 /// and extract element operations, and <2 x float> accesses into a cast to
306 /// <2 x double>, an extract, and a cast back to <2 x float>.
307 /// 3) A fully general blob of memory, which we turn into some (potentially
308 /// large) integer type with extract and insert operations where the loads
309 /// and stores would mutate the memory. We mark this by setting VectorTy
311 void ConvertToScalarInfo::MergeInType(const Type *In, uint64_t Offset) {
312 // If we already decided to turn this into a blob of integer memory, there is
313 // nothing to be done.
314 if (VectorTy && VectorTy->isVoidTy())
317 // If this could be contributing to a vector, analyze it.
319 // If the In type is a vector that is the same size as the alloca, see if it
320 // matches the existing VecTy.
321 if (const VectorType *VInTy = dyn_cast<VectorType>(In)) {
322 if (MergeInVectorType(VInTy, Offset))
324 } else if (In->isFloatTy() || In->isDoubleTy() ||
325 (In->isIntegerTy() && In->getPrimitiveSizeInBits() >= 8 &&
326 isPowerOf2_32(In->getPrimitiveSizeInBits()))) {
327 // If we're accessing something that could be an element of a vector, see
328 // if the implied vector agrees with what we already have and if Offset is
329 // compatible with it.
330 unsigned EltSize = In->getPrimitiveSizeInBits()/8;
331 if (Offset % EltSize == 0 && AllocaSize % EltSize == 0 &&
333 cast<VectorType>(VectorTy)->getElementType()
334 ->getPrimitiveSizeInBits()/8 == EltSize)) {
336 VectorTy = VectorType::get(In, AllocaSize/EltSize);
341 // Otherwise, we have a case that we can't handle with an optimized vector
342 // form. We can still turn this into a large integer.
343 VectorTy = Type::getVoidTy(In->getContext());
346 /// MergeInVectorType - Handles the vector case of MergeInType, returning true
347 /// if the type was successfully merged and false otherwise.
348 bool ConvertToScalarInfo::MergeInVectorType(const VectorType *VInTy,
350 // Remember if we saw a vector type.
353 // TODO: Support nonzero offsets?
357 // Only allow vectors that are a power-of-2 away from the size of the alloca.
358 if (!isPowerOf2_64(AllocaSize / (VInTy->getBitWidth() / 8)))
361 // If this the first vector we see, remember the type so that we know the
368 unsigned BitWidth = cast<VectorType>(VectorTy)->getBitWidth();
369 unsigned InBitWidth = VInTy->getBitWidth();
371 // Vectors of the same size can be converted using a simple bitcast.
372 if (InBitWidth == BitWidth && AllocaSize == (InBitWidth / 8))
375 const Type *ElementTy = cast<VectorType>(VectorTy)->getElementType();
376 const Type *InElementTy = cast<VectorType>(VectorTy)->getElementType();
378 // Do not allow mixed integer and floating-point accesses from vectors of
380 if (ElementTy->isFloatingPointTy() != InElementTy->isFloatingPointTy())
383 if (ElementTy->isFloatingPointTy()) {
384 // Only allow floating-point vectors of different sizes if they have the
385 // same element type.
386 // TODO: This could be loosened a bit, but would anything benefit?
387 if (ElementTy != InElementTy)
390 // There are no arbitrary-precision floating-point types, which limits the
391 // number of legal vector types with larger element types that we can form
392 // to bitcast and extract a subvector.
393 // TODO: We could support some more cases with mixed fp128 and double here.
394 if (!(BitWidth == 64 || BitWidth == 128) ||
395 !(InBitWidth == 64 || InBitWidth == 128))
398 assert(ElementTy->isIntegerTy() && "Vector elements must be either integer "
399 "or floating-point.");
400 unsigned BitWidth = ElementTy->getPrimitiveSizeInBits();
401 unsigned InBitWidth = InElementTy->getPrimitiveSizeInBits();
403 // Do not allow integer types smaller than a byte or types whose widths are
404 // not a multiple of a byte.
405 if (BitWidth < 8 || InBitWidth < 8 ||
406 BitWidth % 8 != 0 || InBitWidth % 8 != 0)
410 // Pick the largest of the two vector types.
411 if (InBitWidth > BitWidth)
417 /// CanConvertToScalar - V is a pointer. If we can convert the pointee and all
418 /// its accesses to a single vector type, return true and set VecTy to
419 /// the new type. If we could convert the alloca into a single promotable
420 /// integer, return true but set VecTy to VoidTy. Further, if the use is not a
421 /// completely trivial use that mem2reg could promote, set IsNotTrivial. Offset
422 /// is the current offset from the base of the alloca being analyzed.
424 /// If we see at least one access to the value that is as a vector type, set the
426 bool ConvertToScalarInfo::CanConvertToScalar(Value *V, uint64_t Offset) {
427 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) {
428 Instruction *User = cast<Instruction>(*UI);
430 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
431 // Don't break volatile loads.
432 if (LI->isVolatile())
434 // Don't touch MMX operations.
435 if (LI->getType()->isX86_MMXTy())
437 MergeInType(LI->getType(), Offset);
441 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
442 // Storing the pointer, not into the value?
443 if (SI->getOperand(0) == V || SI->isVolatile()) return false;
444 // Don't touch MMX operations.
445 if (SI->getOperand(0)->getType()->isX86_MMXTy())
447 MergeInType(SI->getOperand(0)->getType(), Offset);
451 if (BitCastInst *BCI = dyn_cast<BitCastInst>(User)) {
452 IsNotTrivial = true; // Can't be mem2reg'd.
453 if (!CanConvertToScalar(BCI, Offset))
458 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) {
459 // If this is a GEP with a variable indices, we can't handle it.
460 if (!GEP->hasAllConstantIndices())
463 // Compute the offset that this GEP adds to the pointer.
464 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end());
465 uint64_t GEPOffset = TD.getIndexedOffset(GEP->getPointerOperandType(),
466 &Indices[0], Indices.size());
467 // See if all uses can be converted.
468 if (!CanConvertToScalar(GEP, Offset+GEPOffset))
470 IsNotTrivial = true; // Can't be mem2reg'd.
474 // If this is a constant sized memset of a constant value (e.g. 0) we can
476 if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) {
477 // Store of constant value and constant size.
478 if (!isa<ConstantInt>(MSI->getValue()) ||
479 !isa<ConstantInt>(MSI->getLength()))
481 IsNotTrivial = true; // Can't be mem2reg'd.
485 // If this is a memcpy or memmove into or out of the whole allocation, we
486 // can handle it like a load or store of the scalar type.
487 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) {
488 ConstantInt *Len = dyn_cast<ConstantInt>(MTI->getLength());
489 if (Len == 0 || Len->getZExtValue() != AllocaSize || Offset != 0)
492 IsNotTrivial = true; // Can't be mem2reg'd.
496 // Otherwise, we cannot handle this!
503 /// ConvertUsesToScalar - Convert all of the users of Ptr to use the new alloca
504 /// directly. This happens when we are converting an "integer union" to a
505 /// single integer scalar, or when we are converting a "vector union" to a
506 /// vector with insert/extractelement instructions.
508 /// Offset is an offset from the original alloca, in bits that need to be
509 /// shifted to the right. By the end of this, there should be no uses of Ptr.
510 void ConvertToScalarInfo::ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI,
512 while (!Ptr->use_empty()) {
513 Instruction *User = cast<Instruction>(Ptr->use_back());
515 if (BitCastInst *CI = dyn_cast<BitCastInst>(User)) {
516 ConvertUsesToScalar(CI, NewAI, Offset);
517 CI->eraseFromParent();
521 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) {
522 // Compute the offset that this GEP adds to the pointer.
523 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end());
524 uint64_t GEPOffset = TD.getIndexedOffset(GEP->getPointerOperandType(),
525 &Indices[0], Indices.size());
526 ConvertUsesToScalar(GEP, NewAI, Offset+GEPOffset*8);
527 GEP->eraseFromParent();
531 IRBuilder<> Builder(User);
533 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
534 // The load is a bit extract from NewAI shifted right by Offset bits.
535 Value *LoadedVal = Builder.CreateLoad(NewAI, "tmp");
537 = ConvertScalar_ExtractValue(LoadedVal, LI->getType(), Offset, Builder);
538 LI->replaceAllUsesWith(NewLoadVal);
539 LI->eraseFromParent();
543 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
544 assert(SI->getOperand(0) != Ptr && "Consistency error!");
545 Instruction *Old = Builder.CreateLoad(NewAI, NewAI->getName()+".in");
546 Value *New = ConvertScalar_InsertValue(SI->getOperand(0), Old, Offset,
548 Builder.CreateStore(New, NewAI);
549 SI->eraseFromParent();
551 // If the load we just inserted is now dead, then the inserted store
552 // overwrote the entire thing.
553 if (Old->use_empty())
554 Old->eraseFromParent();
558 // If this is a constant sized memset of a constant value (e.g. 0) we can
559 // transform it into a store of the expanded constant value.
560 if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) {
561 assert(MSI->getRawDest() == Ptr && "Consistency error!");
562 unsigned NumBytes = cast<ConstantInt>(MSI->getLength())->getZExtValue();
564 unsigned Val = cast<ConstantInt>(MSI->getValue())->getZExtValue();
566 // Compute the value replicated the right number of times.
567 APInt APVal(NumBytes*8, Val);
569 // Splat the value if non-zero.
571 for (unsigned i = 1; i != NumBytes; ++i)
574 Instruction *Old = Builder.CreateLoad(NewAI, NewAI->getName()+".in");
575 Value *New = ConvertScalar_InsertValue(
576 ConstantInt::get(User->getContext(), APVal),
577 Old, Offset, Builder);
578 Builder.CreateStore(New, NewAI);
580 // If the load we just inserted is now dead, then the memset overwrote
582 if (Old->use_empty())
583 Old->eraseFromParent();
585 MSI->eraseFromParent();
589 // If this is a memcpy or memmove into or out of the whole allocation, we
590 // can handle it like a load or store of the scalar type.
591 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) {
592 assert(Offset == 0 && "must be store to start of alloca");
594 // If the source and destination are both to the same alloca, then this is
595 // a noop copy-to-self, just delete it. Otherwise, emit a load and store
597 AllocaInst *OrigAI = cast<AllocaInst>(GetUnderlyingObject(Ptr, &TD, 0));
599 if (GetUnderlyingObject(MTI->getSource(), &TD, 0) != OrigAI) {
600 // Dest must be OrigAI, change this to be a load from the original
601 // pointer (bitcasted), then a store to our new alloca.
602 assert(MTI->getRawDest() == Ptr && "Neither use is of pointer?");
603 Value *SrcPtr = MTI->getSource();
604 const PointerType* SPTy = cast<PointerType>(SrcPtr->getType());
605 const PointerType* AIPTy = cast<PointerType>(NewAI->getType());
606 if (SPTy->getAddressSpace() != AIPTy->getAddressSpace()) {
607 AIPTy = PointerType::get(AIPTy->getElementType(),
608 SPTy->getAddressSpace());
610 SrcPtr = Builder.CreateBitCast(SrcPtr, AIPTy);
612 LoadInst *SrcVal = Builder.CreateLoad(SrcPtr, "srcval");
613 SrcVal->setAlignment(MTI->getAlignment());
614 Builder.CreateStore(SrcVal, NewAI);
615 } else if (GetUnderlyingObject(MTI->getDest(), &TD, 0) != OrigAI) {
616 // Src must be OrigAI, change this to be a load from NewAI then a store
617 // through the original dest pointer (bitcasted).
618 assert(MTI->getRawSource() == Ptr && "Neither use is of pointer?");
619 LoadInst *SrcVal = Builder.CreateLoad(NewAI, "srcval");
621 const PointerType* DPTy = cast<PointerType>(MTI->getDest()->getType());
622 const PointerType* AIPTy = cast<PointerType>(NewAI->getType());
623 if (DPTy->getAddressSpace() != AIPTy->getAddressSpace()) {
624 AIPTy = PointerType::get(AIPTy->getElementType(),
625 DPTy->getAddressSpace());
627 Value *DstPtr = Builder.CreateBitCast(MTI->getDest(), AIPTy);
629 StoreInst *NewStore = Builder.CreateStore(SrcVal, DstPtr);
630 NewStore->setAlignment(MTI->getAlignment());
632 // Noop transfer. Src == Dst
635 MTI->eraseFromParent();
639 llvm_unreachable("Unsupported operation!");
643 /// getScaledElementType - Gets a scaled element type for a partial vector
644 /// access of an alloca. The input type must be an integer or float, and
645 /// the resulting type must be an integer, float or double.
646 static const Type *getScaledElementType(const Type *OldTy, unsigned Scale) {
647 assert((OldTy->isIntegerTy() || OldTy->isFloatTy()) && "Partial vector "
648 "accesses must be scaled from integer or float elements.");
650 LLVMContext &Context = OldTy->getContext();
651 unsigned Size = OldTy->getPrimitiveSizeInBits() * Scale;
653 if (OldTy->isIntegerTy())
654 return Type::getIntNTy(Context, Size);
656 return Type::getFloatTy(Context);
658 return Type::getDoubleTy(Context);
660 llvm_unreachable("Invalid type for a partial vector access of an alloca!");
663 /// ConvertScalar_ExtractValue - Extract a value of type ToType from an integer
664 /// or vector value FromVal, extracting the bits from the offset specified by
665 /// Offset. This returns the value, which is of type ToType.
667 /// This happens when we are converting an "integer union" to a single
668 /// integer scalar, or when we are converting a "vector union" to a vector with
669 /// insert/extractelement instructions.
671 /// Offset is an offset from the original alloca, in bits that need to be
672 /// shifted to the right.
673 Value *ConvertToScalarInfo::
674 ConvertScalar_ExtractValue(Value *FromVal, const Type *ToType,
675 uint64_t Offset, IRBuilder<> &Builder) {
676 // If the load is of the whole new alloca, no conversion is needed.
677 if (FromVal->getType() == ToType && Offset == 0)
680 // If the result alloca is a vector type, this is either an element
681 // access or a bitcast to another vector type of the same size.
682 if (const VectorType *VTy = dyn_cast<VectorType>(FromVal->getType())) {
683 if (ToType->isVectorTy()) {
684 unsigned ToTypeSize = TD.getTypeAllocSize(ToType);
685 if (ToTypeSize == AllocaSize)
686 return Builder.CreateBitCast(FromVal, ToType, "tmp");
688 assert(isPowerOf2_64(AllocaSize / ToTypeSize) &&
689 "Partial vector access of an alloca must have a power-of-2 size "
691 assert(Offset == 0 && "Can't extract a value of a smaller vector type "
692 "from a nonzero offset.");
694 const Type *ToElementTy = cast<VectorType>(ToType)->getElementType();
695 unsigned Scale = AllocaSize / ToTypeSize;
696 const Type *CastElementTy = getScaledElementType(ToElementTy, Scale);
697 unsigned NumCastVectorElements = VTy->getNumElements() / Scale;
699 LLVMContext &Context = FromVal->getContext();
700 const Type *CastTy = VectorType::get(CastElementTy,
701 NumCastVectorElements);
702 Value *Cast = Builder.CreateBitCast(FromVal, CastTy, "tmp");
703 Value *Extract = Builder.CreateExtractElement(Cast, ConstantInt::get(
704 Type::getInt32Ty(Context), 0), "tmp");
705 return Builder.CreateBitCast(Extract, ToType, "tmp");
708 // Otherwise it must be an element access.
711 unsigned EltSize = TD.getTypeAllocSizeInBits(VTy->getElementType());
712 Elt = Offset/EltSize;
713 assert(EltSize*Elt == Offset && "Invalid modulus in validity checking");
715 // Return the element extracted out of it.
716 Value *V = Builder.CreateExtractElement(FromVal, ConstantInt::get(
717 Type::getInt32Ty(FromVal->getContext()), Elt), "tmp");
718 if (V->getType() != ToType)
719 V = Builder.CreateBitCast(V, ToType, "tmp");
723 // If ToType is a first class aggregate, extract out each of the pieces and
724 // use insertvalue's to form the FCA.
725 if (const StructType *ST = dyn_cast<StructType>(ToType)) {
726 const StructLayout &Layout = *TD.getStructLayout(ST);
727 Value *Res = UndefValue::get(ST);
728 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) {
729 Value *Elt = ConvertScalar_ExtractValue(FromVal, ST->getElementType(i),
730 Offset+Layout.getElementOffsetInBits(i),
732 Res = Builder.CreateInsertValue(Res, Elt, i, "tmp");
737 if (const ArrayType *AT = dyn_cast<ArrayType>(ToType)) {
738 uint64_t EltSize = TD.getTypeAllocSizeInBits(AT->getElementType());
739 Value *Res = UndefValue::get(AT);
740 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
741 Value *Elt = ConvertScalar_ExtractValue(FromVal, AT->getElementType(),
742 Offset+i*EltSize, Builder);
743 Res = Builder.CreateInsertValue(Res, Elt, i, "tmp");
748 // Otherwise, this must be a union that was converted to an integer value.
749 const IntegerType *NTy = cast<IntegerType>(FromVal->getType());
751 // If this is a big-endian system and the load is narrower than the
752 // full alloca type, we need to do a shift to get the right bits.
754 if (TD.isBigEndian()) {
755 // On big-endian machines, the lowest bit is stored at the bit offset
756 // from the pointer given by getTypeStoreSizeInBits. This matters for
757 // integers with a bitwidth that is not a multiple of 8.
758 ShAmt = TD.getTypeStoreSizeInBits(NTy) -
759 TD.getTypeStoreSizeInBits(ToType) - Offset;
764 // Note: we support negative bitwidths (with shl) which are not defined.
765 // We do this to support (f.e.) loads off the end of a structure where
766 // only some bits are used.
767 if (ShAmt > 0 && (unsigned)ShAmt < NTy->getBitWidth())
768 FromVal = Builder.CreateLShr(FromVal,
769 ConstantInt::get(FromVal->getType(),
771 else if (ShAmt < 0 && (unsigned)-ShAmt < NTy->getBitWidth())
772 FromVal = Builder.CreateShl(FromVal,
773 ConstantInt::get(FromVal->getType(),
776 // Finally, unconditionally truncate the integer to the right width.
777 unsigned LIBitWidth = TD.getTypeSizeInBits(ToType);
778 if (LIBitWidth < NTy->getBitWidth())
780 Builder.CreateTrunc(FromVal, IntegerType::get(FromVal->getContext(),
782 else if (LIBitWidth > NTy->getBitWidth())
784 Builder.CreateZExt(FromVal, IntegerType::get(FromVal->getContext(),
787 // If the result is an integer, this is a trunc or bitcast.
788 if (ToType->isIntegerTy()) {
790 } else if (ToType->isFloatingPointTy() || ToType->isVectorTy()) {
791 // Just do a bitcast, we know the sizes match up.
792 FromVal = Builder.CreateBitCast(FromVal, ToType, "tmp");
794 // Otherwise must be a pointer.
795 FromVal = Builder.CreateIntToPtr(FromVal, ToType, "tmp");
797 assert(FromVal->getType() == ToType && "Didn't convert right?");
801 /// ConvertScalar_InsertValue - Insert the value "SV" into the existing integer
802 /// or vector value "Old" at the offset specified by Offset.
804 /// This happens when we are converting an "integer union" to a
805 /// single integer scalar, or when we are converting a "vector union" to a
806 /// vector with insert/extractelement instructions.
808 /// Offset is an offset from the original alloca, in bits that need to be
809 /// shifted to the right.
810 Value *ConvertToScalarInfo::
811 ConvertScalar_InsertValue(Value *SV, Value *Old,
812 uint64_t Offset, IRBuilder<> &Builder) {
813 // Convert the stored type to the actual type, shift it left to insert
814 // then 'or' into place.
815 const Type *AllocaType = Old->getType();
816 LLVMContext &Context = Old->getContext();
818 if (const VectorType *VTy = dyn_cast<VectorType>(AllocaType)) {
819 uint64_t VecSize = TD.getTypeAllocSizeInBits(VTy);
820 uint64_t ValSize = TD.getTypeAllocSizeInBits(SV->getType());
822 // Changing the whole vector with memset or with an access of a different
824 if (ValSize == VecSize)
825 return Builder.CreateBitCast(SV, AllocaType, "tmp");
827 if (SV->getType()->isVectorTy() && isPowerOf2_64(VecSize / ValSize)) {
828 assert(Offset == 0 && "Can't insert a value of a smaller vector type at "
829 "a nonzero offset.");
831 const Type *ToElementTy =
832 cast<VectorType>(SV->getType())->getElementType();
833 unsigned Scale = VecSize / ValSize;
834 const Type *CastElementTy = getScaledElementType(ToElementTy, Scale);
835 unsigned NumCastVectorElements = VTy->getNumElements() / Scale;
837 LLVMContext &Context = SV->getContext();
838 const Type *OldCastTy = VectorType::get(CastElementTy,
839 NumCastVectorElements);
840 Value *OldCast = Builder.CreateBitCast(Old, OldCastTy, "tmp");
842 Value *SVCast = Builder.CreateBitCast(SV, CastElementTy, "tmp");
844 Builder.CreateInsertElement(OldCast, SVCast, ConstantInt::get(
845 Type::getInt32Ty(Context), 0), "tmp");
846 return Builder.CreateBitCast(Insert, AllocaType, "tmp");
849 uint64_t EltSize = TD.getTypeAllocSizeInBits(VTy->getElementType());
851 // Must be an element insertion.
852 unsigned Elt = Offset/EltSize;
854 if (SV->getType() != VTy->getElementType())
855 SV = Builder.CreateBitCast(SV, VTy->getElementType(), "tmp");
857 SV = Builder.CreateInsertElement(Old, SV,
858 ConstantInt::get(Type::getInt32Ty(SV->getContext()), Elt),
863 // If SV is a first-class aggregate value, insert each value recursively.
864 if (const StructType *ST = dyn_cast<StructType>(SV->getType())) {
865 const StructLayout &Layout = *TD.getStructLayout(ST);
866 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) {
867 Value *Elt = Builder.CreateExtractValue(SV, i, "tmp");
868 Old = ConvertScalar_InsertValue(Elt, Old,
869 Offset+Layout.getElementOffsetInBits(i),
875 if (const ArrayType *AT = dyn_cast<ArrayType>(SV->getType())) {
876 uint64_t EltSize = TD.getTypeAllocSizeInBits(AT->getElementType());
877 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
878 Value *Elt = Builder.CreateExtractValue(SV, i, "tmp");
879 Old = ConvertScalar_InsertValue(Elt, Old, Offset+i*EltSize, Builder);
884 // If SV is a float, convert it to the appropriate integer type.
885 // If it is a pointer, do the same.
886 unsigned SrcWidth = TD.getTypeSizeInBits(SV->getType());
887 unsigned DestWidth = TD.getTypeSizeInBits(AllocaType);
888 unsigned SrcStoreWidth = TD.getTypeStoreSizeInBits(SV->getType());
889 unsigned DestStoreWidth = TD.getTypeStoreSizeInBits(AllocaType);
890 if (SV->getType()->isFloatingPointTy() || SV->getType()->isVectorTy())
891 SV = Builder.CreateBitCast(SV,
892 IntegerType::get(SV->getContext(),SrcWidth), "tmp");
893 else if (SV->getType()->isPointerTy())
894 SV = Builder.CreatePtrToInt(SV, TD.getIntPtrType(SV->getContext()), "tmp");
896 // Zero extend or truncate the value if needed.
897 if (SV->getType() != AllocaType) {
898 if (SV->getType()->getPrimitiveSizeInBits() <
899 AllocaType->getPrimitiveSizeInBits())
900 SV = Builder.CreateZExt(SV, AllocaType, "tmp");
902 // Truncation may be needed if storing more than the alloca can hold
903 // (undefined behavior).
904 SV = Builder.CreateTrunc(SV, AllocaType, "tmp");
905 SrcWidth = DestWidth;
906 SrcStoreWidth = DestStoreWidth;
910 // If this is a big-endian system and the store is narrower than the
911 // full alloca type, we need to do a shift to get the right bits.
913 if (TD.isBigEndian()) {
914 // On big-endian machines, the lowest bit is stored at the bit offset
915 // from the pointer given by getTypeStoreSizeInBits. This matters for
916 // integers with a bitwidth that is not a multiple of 8.
917 ShAmt = DestStoreWidth - SrcStoreWidth - Offset;
922 // Note: we support negative bitwidths (with shr) which are not defined.
923 // We do this to support (f.e.) stores off the end of a structure where
924 // only some bits in the structure are set.
925 APInt Mask(APInt::getLowBitsSet(DestWidth, SrcWidth));
926 if (ShAmt > 0 && (unsigned)ShAmt < DestWidth) {
927 SV = Builder.CreateShl(SV, ConstantInt::get(SV->getType(),
930 } else if (ShAmt < 0 && (unsigned)-ShAmt < DestWidth) {
931 SV = Builder.CreateLShr(SV, ConstantInt::get(SV->getType(),
933 Mask = Mask.lshr(-ShAmt);
936 // Mask out the bits we are about to insert from the old value, and or
938 if (SrcWidth != DestWidth) {
939 assert(DestWidth > SrcWidth);
940 Old = Builder.CreateAnd(Old, ConstantInt::get(Context, ~Mask), "mask");
941 SV = Builder.CreateOr(Old, SV, "ins");
947 //===----------------------------------------------------------------------===//
949 //===----------------------------------------------------------------------===//
952 bool SROA::runOnFunction(Function &F) {
953 TD = getAnalysisIfAvailable<TargetData>();
955 bool Changed = performPromotion(F);
957 // FIXME: ScalarRepl currently depends on TargetData more than it
958 // theoretically needs to. It should be refactored in order to support
959 // target-independent IR. Until this is done, just skip the actual
960 // scalar-replacement portion of this pass.
961 if (!TD) return Changed;
964 bool LocalChange = performScalarRepl(F);
965 if (!LocalChange) break; // No need to repromote if no scalarrepl
967 LocalChange = performPromotion(F);
968 if (!LocalChange) break; // No need to re-scalarrepl if no promotion
975 class AllocaPromoter : public LoadAndStorePromoter {
978 AllocaPromoter(const SmallVectorImpl<Instruction*> &Insts, SSAUpdater &S)
979 : LoadAndStorePromoter(Insts, S), AI(0) {}
981 void run(AllocaInst *AI, const SmallVectorImpl<Instruction*> &Insts) {
982 // Remember which alloca we're promoting (for isInstInList).
984 LoadAndStorePromoter::run(Insts);
985 AI->eraseFromParent();
988 virtual bool isInstInList(Instruction *I,
989 const SmallVectorImpl<Instruction*> &Insts) const {
990 if (LoadInst *LI = dyn_cast<LoadInst>(I))
991 return LI->getOperand(0) == AI;
992 return cast<StoreInst>(I)->getPointerOperand() == AI;
995 } // end anon namespace
997 /// isSafeSelectToSpeculate - Select instructions that use an alloca and are
998 /// subsequently loaded can be rewritten to load both input pointers and then
999 /// select between the result, allowing the load of the alloca to be promoted.
1001 /// %P2 = select i1 %cond, i32* %Alloca, i32* %Other
1002 /// %V = load i32* %P2
1004 /// %V1 = load i32* %Alloca -> will be mem2reg'd
1005 /// %V2 = load i32* %Other
1006 /// %V = select i1 %cond, i32 %V1, i32 %V2
1008 /// We can do this to a select if its only uses are loads and if the operand to
1009 /// the select can be loaded unconditionally.
1010 static bool isSafeSelectToSpeculate(SelectInst *SI, const TargetData *TD) {
1011 bool TDerefable = SI->getTrueValue()->isDereferenceablePointer();
1012 bool FDerefable = SI->getFalseValue()->isDereferenceablePointer();
1014 for (Value::use_iterator UI = SI->use_begin(), UE = SI->use_end();
1016 LoadInst *LI = dyn_cast<LoadInst>(*UI);
1017 if (LI == 0 || LI->isVolatile()) return false;
1019 // Both operands to the select need to be dereferencable, either absolutely
1020 // (e.g. allocas) or at this point because we can see other accesses to it.
1021 if (!TDerefable && !isSafeToLoadUnconditionally(SI->getTrueValue(), LI,
1022 LI->getAlignment(), TD))
1024 if (!FDerefable && !isSafeToLoadUnconditionally(SI->getFalseValue(), LI,
1025 LI->getAlignment(), TD))
1032 /// isSafePHIToSpeculate - PHI instructions that use an alloca and are
1033 /// subsequently loaded can be rewritten to load both input pointers in the pred
1034 /// blocks and then PHI the results, allowing the load of the alloca to be
1037 /// %P2 = phi [i32* %Alloca, i32* %Other]
1038 /// %V = load i32* %P2
1040 /// %V1 = load i32* %Alloca -> will be mem2reg'd
1042 /// %V2 = load i32* %Other
1044 /// %V = phi [i32 %V1, i32 %V2]
1046 /// We can do this to a select if its only uses are loads and if the operand to
1047 /// the select can be loaded unconditionally.
1048 static bool isSafePHIToSpeculate(PHINode *PN, const TargetData *TD) {
1049 // For now, we can only do this promotion if the load is in the same block as
1050 // the PHI, and if there are no stores between the phi and load.
1051 // TODO: Allow recursive phi users.
1052 // TODO: Allow stores.
1053 BasicBlock *BB = PN->getParent();
1054 unsigned MaxAlign = 0;
1055 for (Value::use_iterator UI = PN->use_begin(), UE = PN->use_end();
1057 LoadInst *LI = dyn_cast<LoadInst>(*UI);
1058 if (LI == 0 || LI->isVolatile()) return false;
1060 // For now we only allow loads in the same block as the PHI. This is a
1061 // common case that happens when instcombine merges two loads through a PHI.
1062 if (LI->getParent() != BB) return false;
1064 // Ensure that there are no instructions between the PHI and the load that
1066 for (BasicBlock::iterator BBI = PN; &*BBI != LI; ++BBI)
1067 if (BBI->mayWriteToMemory())
1070 MaxAlign = std::max(MaxAlign, LI->getAlignment());
1073 // Okay, we know that we have one or more loads in the same block as the PHI.
1074 // We can transform this if it is safe to push the loads into the predecessor
1075 // blocks. The only thing to watch out for is that we can't put a possibly
1076 // trapping load in the predecessor if it is a critical edge.
1077 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
1078 BasicBlock *Pred = PN->getIncomingBlock(i);
1080 // If the predecessor has a single successor, then the edge isn't critical.
1081 if (Pred->getTerminator()->getNumSuccessors() == 1)
1084 Value *InVal = PN->getIncomingValue(i);
1086 // If the InVal is an invoke in the pred, we can't put a load on the edge.
1087 if (InvokeInst *II = dyn_cast<InvokeInst>(InVal))
1088 if (II->getParent() == Pred)
1091 // If this pointer is always safe to load, or if we can prove that there is
1092 // already a load in the block, then we can move the load to the pred block.
1093 if (InVal->isDereferenceablePointer() ||
1094 isSafeToLoadUnconditionally(InVal, Pred->getTerminator(), MaxAlign, TD))
1104 /// tryToMakeAllocaBePromotable - This returns true if the alloca only has
1105 /// direct (non-volatile) loads and stores to it. If the alloca is close but
1106 /// not quite there, this will transform the code to allow promotion. As such,
1107 /// it is a non-pure predicate.
1108 static bool tryToMakeAllocaBePromotable(AllocaInst *AI, const TargetData *TD) {
1109 SetVector<Instruction*, SmallVector<Instruction*, 4>,
1110 SmallPtrSet<Instruction*, 4> > InstsToRewrite;
1112 for (Value::use_iterator UI = AI->use_begin(), UE = AI->use_end();
1115 if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
1116 if (LI->isVolatile())
1121 if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
1122 if (SI->getOperand(0) == AI || SI->isVolatile())
1123 return false; // Don't allow a store OF the AI, only INTO the AI.
1127 if (SelectInst *SI = dyn_cast<SelectInst>(U)) {
1128 // If the condition being selected on is a constant, fold the select, yes
1129 // this does (rarely) happen early on.
1130 if (ConstantInt *CI = dyn_cast<ConstantInt>(SI->getCondition())) {
1131 Value *Result = SI->getOperand(1+CI->isZero());
1132 SI->replaceAllUsesWith(Result);
1133 SI->eraseFromParent();
1135 // This is very rare and we just scrambled the use list of AI, start
1137 return tryToMakeAllocaBePromotable(AI, TD);
1140 // If it is safe to turn "load (select c, AI, ptr)" into a select of two
1141 // loads, then we can transform this by rewriting the select.
1142 if (!isSafeSelectToSpeculate(SI, TD))
1145 InstsToRewrite.insert(SI);
1149 if (PHINode *PN = dyn_cast<PHINode>(U)) {
1150 if (PN->use_empty()) { // Dead PHIs can be stripped.
1151 InstsToRewrite.insert(PN);
1155 // If it is safe to turn "load (phi [AI, ptr, ...])" into a PHI of loads
1156 // in the pred blocks, then we can transform this by rewriting the PHI.
1157 if (!isSafePHIToSpeculate(PN, TD))
1160 InstsToRewrite.insert(PN);
1167 // If there are no instructions to rewrite, then all uses are load/stores and
1169 if (InstsToRewrite.empty())
1172 // If we have instructions that need to be rewritten for this to be promotable
1173 // take care of it now.
1174 for (unsigned i = 0, e = InstsToRewrite.size(); i != e; ++i) {
1175 if (SelectInst *SI = dyn_cast<SelectInst>(InstsToRewrite[i])) {
1176 // Selects in InstsToRewrite only have load uses. Rewrite each as two
1177 // loads with a new select.
1178 while (!SI->use_empty()) {
1179 LoadInst *LI = cast<LoadInst>(SI->use_back());
1181 IRBuilder<> Builder(LI);
1182 LoadInst *TrueLoad =
1183 Builder.CreateLoad(SI->getTrueValue(), LI->getName()+".t");
1184 LoadInst *FalseLoad =
1185 Builder.CreateLoad(SI->getFalseValue(), LI->getName()+".t");
1187 // Transfer alignment and TBAA info if present.
1188 TrueLoad->setAlignment(LI->getAlignment());
1189 FalseLoad->setAlignment(LI->getAlignment());
1190 if (MDNode *Tag = LI->getMetadata(LLVMContext::MD_tbaa)) {
1191 TrueLoad->setMetadata(LLVMContext::MD_tbaa, Tag);
1192 FalseLoad->setMetadata(LLVMContext::MD_tbaa, Tag);
1195 Value *V = Builder.CreateSelect(SI->getCondition(), TrueLoad, FalseLoad);
1197 LI->replaceAllUsesWith(V);
1198 LI->eraseFromParent();
1201 // Now that all the loads are gone, the select is gone too.
1202 SI->eraseFromParent();
1206 // Otherwise, we have a PHI node which allows us to push the loads into the
1208 PHINode *PN = cast<PHINode>(InstsToRewrite[i]);
1209 if (PN->use_empty()) {
1210 PN->eraseFromParent();
1214 const Type *LoadTy = cast<PointerType>(PN->getType())->getElementType();
1215 PHINode *NewPN = PHINode::Create(LoadTy, PN->getName()+".ld", PN);
1217 // Get the TBAA tag and alignment to use from one of the loads. It doesn't
1218 // matter which one we get and if any differ, it doesn't matter.
1219 LoadInst *SomeLoad = cast<LoadInst>(PN->use_back());
1220 MDNode *TBAATag = SomeLoad->getMetadata(LLVMContext::MD_tbaa);
1221 unsigned Align = SomeLoad->getAlignment();
1223 // Rewrite all loads of the PN to use the new PHI.
1224 while (!PN->use_empty()) {
1225 LoadInst *LI = cast<LoadInst>(PN->use_back());
1226 LI->replaceAllUsesWith(NewPN);
1227 LI->eraseFromParent();
1230 // Inject loads into all of the pred blocks. Keep track of which blocks we
1231 // insert them into in case we have multiple edges from the same block.
1232 DenseMap<BasicBlock*, LoadInst*> InsertedLoads;
1234 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
1235 BasicBlock *Pred = PN->getIncomingBlock(i);
1236 LoadInst *&Load = InsertedLoads[Pred];
1238 Load = new LoadInst(PN->getIncomingValue(i),
1239 PN->getName() + "." + Pred->getName(),
1240 Pred->getTerminator());
1241 Load->setAlignment(Align);
1242 if (TBAATag) Load->setMetadata(LLVMContext::MD_tbaa, TBAATag);
1245 NewPN->addIncoming(Load, Pred);
1248 PN->eraseFromParent();
1256 bool SROA::performPromotion(Function &F) {
1257 std::vector<AllocaInst*> Allocas;
1258 DominatorTree *DT = 0;
1260 DT = &getAnalysis<DominatorTree>();
1262 BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function
1264 bool Changed = false;
1265 SmallVector<Instruction*, 64> Insts;
1269 // Find allocas that are safe to promote, by looking at all instructions in
1271 for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I)
1272 if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) // Is it an alloca?
1273 if (tryToMakeAllocaBePromotable(AI, TD))
1274 Allocas.push_back(AI);
1276 if (Allocas.empty()) break;
1279 PromoteMemToReg(Allocas, *DT);
1282 for (unsigned i = 0, e = Allocas.size(); i != e; ++i) {
1283 AllocaInst *AI = Allocas[i];
1285 // Build list of instructions to promote.
1286 for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end();
1288 Insts.push_back(cast<Instruction>(*UI));
1290 AllocaPromoter(Insts, SSA).run(AI, Insts);
1294 NumPromoted += Allocas.size();
1302 /// ShouldAttemptScalarRepl - Decide if an alloca is a good candidate for
1303 /// SROA. It must be a struct or array type with a small number of elements.
1304 static bool ShouldAttemptScalarRepl(AllocaInst *AI) {
1305 const Type *T = AI->getAllocatedType();
1306 // Do not promote any struct into more than 32 separate vars.
1307 if (const StructType *ST = dyn_cast<StructType>(T))
1308 return ST->getNumElements() <= 32;
1309 // Arrays are much less likely to be safe for SROA; only consider
1310 // them if they are very small.
1311 if (const ArrayType *AT = dyn_cast<ArrayType>(T))
1312 return AT->getNumElements() <= 8;
1317 // performScalarRepl - This algorithm is a simple worklist driven algorithm,
1318 // which runs on all of the malloc/alloca instructions in the function, removing
1319 // them if they are only used by getelementptr instructions.
1321 bool SROA::performScalarRepl(Function &F) {
1322 std::vector<AllocaInst*> WorkList;
1324 // Scan the entry basic block, adding allocas to the worklist.
1325 BasicBlock &BB = F.getEntryBlock();
1326 for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I)
1327 if (AllocaInst *A = dyn_cast<AllocaInst>(I))
1328 WorkList.push_back(A);
1330 // Process the worklist
1331 bool Changed = false;
1332 while (!WorkList.empty()) {
1333 AllocaInst *AI = WorkList.back();
1334 WorkList.pop_back();
1336 // Handle dead allocas trivially. These can be formed by SROA'ing arrays
1337 // with unused elements.
1338 if (AI->use_empty()) {
1339 AI->eraseFromParent();
1344 // If this alloca is impossible for us to promote, reject it early.
1345 if (AI->isArrayAllocation() || !AI->getAllocatedType()->isSized())
1348 // Check to see if this allocation is only modified by a memcpy/memmove from
1349 // a constant global. If this is the case, we can change all users to use
1350 // the constant global instead. This is commonly produced by the CFE by
1351 // constructs like "void foo() { int A[] = {1,2,3,4,5,6,7,8,9...}; }" if 'A'
1352 // is only subsequently read.
1353 if (MemTransferInst *TheCopy = isOnlyCopiedFromConstantGlobal(AI)) {
1354 DEBUG(dbgs() << "Found alloca equal to global: " << *AI << '\n');
1355 DEBUG(dbgs() << " memcpy = " << *TheCopy << '\n');
1356 Constant *TheSrc = cast<Constant>(TheCopy->getSource());
1357 AI->replaceAllUsesWith(ConstantExpr::getBitCast(TheSrc, AI->getType()));
1358 TheCopy->eraseFromParent(); // Don't mutate the global.
1359 AI->eraseFromParent();
1365 // Check to see if we can perform the core SROA transformation. We cannot
1366 // transform the allocation instruction if it is an array allocation
1367 // (allocations OF arrays are ok though), and an allocation of a scalar
1368 // value cannot be decomposed at all.
1369 uint64_t AllocaSize = TD->getTypeAllocSize(AI->getAllocatedType());
1371 // Do not promote [0 x %struct].
1372 if (AllocaSize == 0) continue;
1374 // Do not promote any struct whose size is too big.
1375 if (AllocaSize > SRThreshold) continue;
1377 // If the alloca looks like a good candidate for scalar replacement, and if
1378 // all its users can be transformed, then split up the aggregate into its
1379 // separate elements.
1380 if (ShouldAttemptScalarRepl(AI) && isSafeAllocaToScalarRepl(AI)) {
1381 DoScalarReplacement(AI, WorkList);
1386 // If we can turn this aggregate value (potentially with casts) into a
1387 // simple scalar value that can be mem2reg'd into a register value.
1388 // IsNotTrivial tracks whether this is something that mem2reg could have
1389 // promoted itself. If so, we don't want to transform it needlessly. Note
1390 // that we can't just check based on the type: the alloca may be of an i32
1391 // but that has pointer arithmetic to set byte 3 of it or something.
1392 if (AllocaInst *NewAI =
1393 ConvertToScalarInfo((unsigned)AllocaSize, *TD).TryConvert(AI)) {
1394 NewAI->takeName(AI);
1395 AI->eraseFromParent();
1401 // Otherwise, couldn't process this alloca.
1407 /// DoScalarReplacement - This alloca satisfied the isSafeAllocaToScalarRepl
1408 /// predicate, do SROA now.
1409 void SROA::DoScalarReplacement(AllocaInst *AI,
1410 std::vector<AllocaInst*> &WorkList) {
1411 DEBUG(dbgs() << "Found inst to SROA: " << *AI << '\n');
1412 SmallVector<AllocaInst*, 32> ElementAllocas;
1413 if (const StructType *ST = dyn_cast<StructType>(AI->getAllocatedType())) {
1414 ElementAllocas.reserve(ST->getNumContainedTypes());
1415 for (unsigned i = 0, e = ST->getNumContainedTypes(); i != e; ++i) {
1416 AllocaInst *NA = new AllocaInst(ST->getContainedType(i), 0,
1418 AI->getName() + "." + Twine(i), AI);
1419 ElementAllocas.push_back(NA);
1420 WorkList.push_back(NA); // Add to worklist for recursive processing
1423 const ArrayType *AT = cast<ArrayType>(AI->getAllocatedType());
1424 ElementAllocas.reserve(AT->getNumElements());
1425 const Type *ElTy = AT->getElementType();
1426 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
1427 AllocaInst *NA = new AllocaInst(ElTy, 0, AI->getAlignment(),
1428 AI->getName() + "." + Twine(i), AI);
1429 ElementAllocas.push_back(NA);
1430 WorkList.push_back(NA); // Add to worklist for recursive processing
1434 // Now that we have created the new alloca instructions, rewrite all the
1435 // uses of the old alloca.
1436 RewriteForScalarRepl(AI, AI, 0, ElementAllocas);
1438 // Now erase any instructions that were made dead while rewriting the alloca.
1439 DeleteDeadInstructions();
1440 AI->eraseFromParent();
1445 /// DeleteDeadInstructions - Erase instructions on the DeadInstrs list,
1446 /// recursively including all their operands that become trivially dead.
1447 void SROA::DeleteDeadInstructions() {
1448 while (!DeadInsts.empty()) {
1449 Instruction *I = cast<Instruction>(DeadInsts.pop_back_val());
1451 for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI)
1452 if (Instruction *U = dyn_cast<Instruction>(*OI)) {
1453 // Zero out the operand and see if it becomes trivially dead.
1454 // (But, don't add allocas to the dead instruction list -- they are
1455 // already on the worklist and will be deleted separately.)
1457 if (isInstructionTriviallyDead(U) && !isa<AllocaInst>(U))
1458 DeadInsts.push_back(U);
1461 I->eraseFromParent();
1465 /// isSafeForScalarRepl - Check if instruction I is a safe use with regard to
1466 /// performing scalar replacement of alloca AI. The results are flagged in
1467 /// the Info parameter. Offset indicates the position within AI that is
1468 /// referenced by this instruction.
1469 void SROA::isSafeForScalarRepl(Instruction *I, uint64_t Offset,
1471 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E; ++UI) {
1472 Instruction *User = cast<Instruction>(*UI);
1474 if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) {
1475 isSafeForScalarRepl(BC, Offset, Info);
1476 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
1477 uint64_t GEPOffset = Offset;
1478 isSafeGEP(GEPI, GEPOffset, Info);
1480 isSafeForScalarRepl(GEPI, GEPOffset, Info);
1481 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) {
1482 ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength());
1484 return MarkUnsafe(Info, User);
1485 isSafeMemAccess(Offset, Length->getZExtValue(), 0,
1486 UI.getOperandNo() == 0, Info, MI,
1487 true /*AllowWholeAccess*/);
1488 } else if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1489 if (LI->isVolatile())
1490 return MarkUnsafe(Info, User);
1491 const Type *LIType = LI->getType();
1492 isSafeMemAccess(Offset, TD->getTypeAllocSize(LIType),
1493 LIType, false, Info, LI, true /*AllowWholeAccess*/);
1494 Info.hasALoadOrStore = true;
1496 } else if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
1497 // Store is ok if storing INTO the pointer, not storing the pointer
1498 if (SI->isVolatile() || SI->getOperand(0) == I)
1499 return MarkUnsafe(Info, User);
1501 const Type *SIType = SI->getOperand(0)->getType();
1502 isSafeMemAccess(Offset, TD->getTypeAllocSize(SIType),
1503 SIType, true, Info, SI, true /*AllowWholeAccess*/);
1504 Info.hasALoadOrStore = true;
1505 } else if (isa<PHINode>(User) || isa<SelectInst>(User)) {
1506 isSafePHISelectUseForScalarRepl(User, Offset, Info);
1508 return MarkUnsafe(Info, User);
1510 if (Info.isUnsafe) return;
1515 /// isSafePHIUseForScalarRepl - If we see a PHI node or select using a pointer
1516 /// derived from the alloca, we can often still split the alloca into elements.
1517 /// This is useful if we have a large alloca where one element is phi'd
1518 /// together somewhere: we can SRoA and promote all the other elements even if
1519 /// we end up not being able to promote this one.
1521 /// All we require is that the uses of the PHI do not index into other parts of
1522 /// the alloca. The most important use case for this is single load and stores
1523 /// that are PHI'd together, which can happen due to code sinking.
1524 void SROA::isSafePHISelectUseForScalarRepl(Instruction *I, uint64_t Offset,
1526 // If we've already checked this PHI, don't do it again.
1527 if (PHINode *PN = dyn_cast<PHINode>(I))
1528 if (!Info.CheckedPHIs.insert(PN))
1531 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E; ++UI) {
1532 Instruction *User = cast<Instruction>(*UI);
1534 if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) {
1535 isSafePHISelectUseForScalarRepl(BC, Offset, Info);
1536 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
1537 // Only allow "bitcast" GEPs for simplicity. We could generalize this,
1538 // but would have to prove that we're staying inside of an element being
1540 if (!GEPI->hasAllZeroIndices())
1541 return MarkUnsafe(Info, User);
1542 isSafePHISelectUseForScalarRepl(GEPI, Offset, Info);
1543 } else if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1544 if (LI->isVolatile())
1545 return MarkUnsafe(Info, User);
1546 const Type *LIType = LI->getType();
1547 isSafeMemAccess(Offset, TD->getTypeAllocSize(LIType),
1548 LIType, false, Info, LI, false /*AllowWholeAccess*/);
1549 Info.hasALoadOrStore = true;
1551 } else if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
1552 // Store is ok if storing INTO the pointer, not storing the pointer
1553 if (SI->isVolatile() || SI->getOperand(0) == I)
1554 return MarkUnsafe(Info, User);
1556 const Type *SIType = SI->getOperand(0)->getType();
1557 isSafeMemAccess(Offset, TD->getTypeAllocSize(SIType),
1558 SIType, true, Info, SI, false /*AllowWholeAccess*/);
1559 Info.hasALoadOrStore = true;
1560 } else if (isa<PHINode>(User) || isa<SelectInst>(User)) {
1561 isSafePHISelectUseForScalarRepl(User, Offset, Info);
1563 return MarkUnsafe(Info, User);
1565 if (Info.isUnsafe) return;
1569 /// isSafeGEP - Check if a GEP instruction can be handled for scalar
1570 /// replacement. It is safe when all the indices are constant, in-bounds
1571 /// references, and when the resulting offset corresponds to an element within
1572 /// the alloca type. The results are flagged in the Info parameter. Upon
1573 /// return, Offset is adjusted as specified by the GEP indices.
1574 void SROA::isSafeGEP(GetElementPtrInst *GEPI,
1575 uint64_t &Offset, AllocaInfo &Info) {
1576 gep_type_iterator GEPIt = gep_type_begin(GEPI), E = gep_type_end(GEPI);
1580 // Walk through the GEP type indices, checking the types that this indexes
1582 for (; GEPIt != E; ++GEPIt) {
1583 // Ignore struct elements, no extra checking needed for these.
1584 if ((*GEPIt)->isStructTy())
1587 ConstantInt *IdxVal = dyn_cast<ConstantInt>(GEPIt.getOperand());
1589 return MarkUnsafe(Info, GEPI);
1592 // Compute the offset due to this GEP and check if the alloca has a
1593 // component element at that offset.
1594 SmallVector<Value*, 8> Indices(GEPI->op_begin() + 1, GEPI->op_end());
1595 Offset += TD->getIndexedOffset(GEPI->getPointerOperandType(),
1596 &Indices[0], Indices.size());
1597 if (!TypeHasComponent(Info.AI->getAllocatedType(), Offset, 0))
1598 MarkUnsafe(Info, GEPI);
1601 /// isHomogeneousAggregate - Check if type T is a struct or array containing
1602 /// elements of the same type (which is always true for arrays). If so,
1603 /// return true with NumElts and EltTy set to the number of elements and the
1604 /// element type, respectively.
1605 static bool isHomogeneousAggregate(const Type *T, unsigned &NumElts,
1606 const Type *&EltTy) {
1607 if (const ArrayType *AT = dyn_cast<ArrayType>(T)) {
1608 NumElts = AT->getNumElements();
1609 EltTy = (NumElts == 0 ? 0 : AT->getElementType());
1612 if (const StructType *ST = dyn_cast<StructType>(T)) {
1613 NumElts = ST->getNumContainedTypes();
1614 EltTy = (NumElts == 0 ? 0 : ST->getContainedType(0));
1615 for (unsigned n = 1; n < NumElts; ++n) {
1616 if (ST->getContainedType(n) != EltTy)
1624 /// isCompatibleAggregate - Check if T1 and T2 are either the same type or are
1625 /// "homogeneous" aggregates with the same element type and number of elements.
1626 static bool isCompatibleAggregate(const Type *T1, const Type *T2) {
1630 unsigned NumElts1, NumElts2;
1631 const Type *EltTy1, *EltTy2;
1632 if (isHomogeneousAggregate(T1, NumElts1, EltTy1) &&
1633 isHomogeneousAggregate(T2, NumElts2, EltTy2) &&
1634 NumElts1 == NumElts2 &&
1641 /// isSafeMemAccess - Check if a load/store/memcpy operates on the entire AI
1642 /// alloca or has an offset and size that corresponds to a component element
1643 /// within it. The offset checked here may have been formed from a GEP with a
1644 /// pointer bitcasted to a different type.
1646 /// If AllowWholeAccess is true, then this allows uses of the entire alloca as a
1647 /// unit. If false, it only allows accesses known to be in a single element.
1648 void SROA::isSafeMemAccess(uint64_t Offset, uint64_t MemSize,
1649 const Type *MemOpType, bool isStore,
1650 AllocaInfo &Info, Instruction *TheAccess,
1651 bool AllowWholeAccess) {
1652 // Check if this is a load/store of the entire alloca.
1653 if (Offset == 0 && AllowWholeAccess &&
1654 MemSize == TD->getTypeAllocSize(Info.AI->getAllocatedType())) {
1655 // This can be safe for MemIntrinsics (where MemOpType is 0) and integer
1656 // loads/stores (which are essentially the same as the MemIntrinsics with
1657 // regard to copying padding between elements). But, if an alloca is
1658 // flagged as both a source and destination of such operations, we'll need
1659 // to check later for padding between elements.
1660 if (!MemOpType || MemOpType->isIntegerTy()) {
1662 Info.isMemCpyDst = true;
1664 Info.isMemCpySrc = true;
1667 // This is also safe for references using a type that is compatible with
1668 // the type of the alloca, so that loads/stores can be rewritten using
1669 // insertvalue/extractvalue.
1670 if (isCompatibleAggregate(MemOpType, Info.AI->getAllocatedType())) {
1671 Info.hasSubelementAccess = true;
1675 // Check if the offset/size correspond to a component within the alloca type.
1676 const Type *T = Info.AI->getAllocatedType();
1677 if (TypeHasComponent(T, Offset, MemSize)) {
1678 Info.hasSubelementAccess = true;
1682 return MarkUnsafe(Info, TheAccess);
1685 /// TypeHasComponent - Return true if T has a component type with the
1686 /// specified offset and size. If Size is zero, do not check the size.
1687 bool SROA::TypeHasComponent(const Type *T, uint64_t Offset, uint64_t Size) {
1690 if (const StructType *ST = dyn_cast<StructType>(T)) {
1691 const StructLayout *Layout = TD->getStructLayout(ST);
1692 unsigned EltIdx = Layout->getElementContainingOffset(Offset);
1693 EltTy = ST->getContainedType(EltIdx);
1694 EltSize = TD->getTypeAllocSize(EltTy);
1695 Offset -= Layout->getElementOffset(EltIdx);
1696 } else if (const ArrayType *AT = dyn_cast<ArrayType>(T)) {
1697 EltTy = AT->getElementType();
1698 EltSize = TD->getTypeAllocSize(EltTy);
1699 if (Offset >= AT->getNumElements() * EltSize)
1705 if (Offset == 0 && (Size == 0 || EltSize == Size))
1707 // Check if the component spans multiple elements.
1708 if (Offset + Size > EltSize)
1710 return TypeHasComponent(EltTy, Offset, Size);
1713 /// RewriteForScalarRepl - Alloca AI is being split into NewElts, so rewrite
1714 /// the instruction I, which references it, to use the separate elements.
1715 /// Offset indicates the position within AI that is referenced by this
1717 void SROA::RewriteForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset,
1718 SmallVector<AllocaInst*, 32> &NewElts) {
1719 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E;) {
1720 Use &TheUse = UI.getUse();
1721 Instruction *User = cast<Instruction>(*UI++);
1723 if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) {
1724 RewriteBitCast(BC, AI, Offset, NewElts);
1728 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
1729 RewriteGEP(GEPI, AI, Offset, NewElts);
1733 if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) {
1734 ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength());
1735 uint64_t MemSize = Length->getZExtValue();
1737 MemSize == TD->getTypeAllocSize(AI->getAllocatedType()))
1738 RewriteMemIntrinUserOfAlloca(MI, I, AI, NewElts);
1739 // Otherwise the intrinsic can only touch a single element and the
1740 // address operand will be updated, so nothing else needs to be done.
1744 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1745 const Type *LIType = LI->getType();
1747 if (isCompatibleAggregate(LIType, AI->getAllocatedType())) {
1749 // %res = load { i32, i32 }* %alloc
1751 // %load.0 = load i32* %alloc.0
1752 // %insert.0 insertvalue { i32, i32 } zeroinitializer, i32 %load.0, 0
1753 // %load.1 = load i32* %alloc.1
1754 // %insert = insertvalue { i32, i32 } %insert.0, i32 %load.1, 1
1755 // (Also works for arrays instead of structs)
1756 Value *Insert = UndefValue::get(LIType);
1757 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
1758 Value *Load = new LoadInst(NewElts[i], "load", LI);
1759 Insert = InsertValueInst::Create(Insert, Load, i, "insert", LI);
1761 LI->replaceAllUsesWith(Insert);
1762 DeadInsts.push_back(LI);
1763 } else if (LIType->isIntegerTy() &&
1764 TD->getTypeAllocSize(LIType) ==
1765 TD->getTypeAllocSize(AI->getAllocatedType())) {
1766 // If this is a load of the entire alloca to an integer, rewrite it.
1767 RewriteLoadUserOfWholeAlloca(LI, AI, NewElts);
1772 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
1773 Value *Val = SI->getOperand(0);
1774 const Type *SIType = Val->getType();
1775 if (isCompatibleAggregate(SIType, AI->getAllocatedType())) {
1777 // store { i32, i32 } %val, { i32, i32 }* %alloc
1779 // %val.0 = extractvalue { i32, i32 } %val, 0
1780 // store i32 %val.0, i32* %alloc.0
1781 // %val.1 = extractvalue { i32, i32 } %val, 1
1782 // store i32 %val.1, i32* %alloc.1
1783 // (Also works for arrays instead of structs)
1784 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
1785 Value *Extract = ExtractValueInst::Create(Val, i, Val->getName(), SI);
1786 new StoreInst(Extract, NewElts[i], SI);
1788 DeadInsts.push_back(SI);
1789 } else if (SIType->isIntegerTy() &&
1790 TD->getTypeAllocSize(SIType) ==
1791 TD->getTypeAllocSize(AI->getAllocatedType())) {
1792 // If this is a store of the entire alloca from an integer, rewrite it.
1793 RewriteStoreUserOfWholeAlloca(SI, AI, NewElts);
1798 if (isa<SelectInst>(User) || isa<PHINode>(User)) {
1799 // If we have a PHI user of the alloca itself (as opposed to a GEP or
1800 // bitcast) we have to rewrite it. GEP and bitcast uses will be RAUW'd to
1802 if (!isa<AllocaInst>(I)) continue;
1804 assert(Offset == 0 && NewElts[0] &&
1805 "Direct alloca use should have a zero offset");
1807 // If we have a use of the alloca, we know the derived uses will be
1808 // utilizing just the first element of the scalarized result. Insert a
1809 // bitcast of the first alloca before the user as required.
1810 AllocaInst *NewAI = NewElts[0];
1811 BitCastInst *BCI = new BitCastInst(NewAI, AI->getType(), "", NewAI);
1812 NewAI->moveBefore(BCI);
1819 /// RewriteBitCast - Update a bitcast reference to the alloca being replaced
1820 /// and recursively continue updating all of its uses.
1821 void SROA::RewriteBitCast(BitCastInst *BC, AllocaInst *AI, uint64_t Offset,
1822 SmallVector<AllocaInst*, 32> &NewElts) {
1823 RewriteForScalarRepl(BC, AI, Offset, NewElts);
1824 if (BC->getOperand(0) != AI)
1827 // The bitcast references the original alloca. Replace its uses with
1828 // references to the first new element alloca.
1829 Instruction *Val = NewElts[0];
1830 if (Val->getType() != BC->getDestTy()) {
1831 Val = new BitCastInst(Val, BC->getDestTy(), "", BC);
1834 BC->replaceAllUsesWith(Val);
1835 DeadInsts.push_back(BC);
1838 /// FindElementAndOffset - Return the index of the element containing Offset
1839 /// within the specified type, which must be either a struct or an array.
1840 /// Sets T to the type of the element and Offset to the offset within that
1841 /// element. IdxTy is set to the type of the index result to be used in a
1842 /// GEP instruction.
1843 uint64_t SROA::FindElementAndOffset(const Type *&T, uint64_t &Offset,
1844 const Type *&IdxTy) {
1846 if (const StructType *ST = dyn_cast<StructType>(T)) {
1847 const StructLayout *Layout = TD->getStructLayout(ST);
1848 Idx = Layout->getElementContainingOffset(Offset);
1849 T = ST->getContainedType(Idx);
1850 Offset -= Layout->getElementOffset(Idx);
1851 IdxTy = Type::getInt32Ty(T->getContext());
1854 const ArrayType *AT = cast<ArrayType>(T);
1855 T = AT->getElementType();
1856 uint64_t EltSize = TD->getTypeAllocSize(T);
1857 Idx = Offset / EltSize;
1858 Offset -= Idx * EltSize;
1859 IdxTy = Type::getInt64Ty(T->getContext());
1863 /// RewriteGEP - Check if this GEP instruction moves the pointer across
1864 /// elements of the alloca that are being split apart, and if so, rewrite
1865 /// the GEP to be relative to the new element.
1866 void SROA::RewriteGEP(GetElementPtrInst *GEPI, AllocaInst *AI, uint64_t Offset,
1867 SmallVector<AllocaInst*, 32> &NewElts) {
1868 uint64_t OldOffset = Offset;
1869 SmallVector<Value*, 8> Indices(GEPI->op_begin() + 1, GEPI->op_end());
1870 Offset += TD->getIndexedOffset(GEPI->getPointerOperandType(),
1871 &Indices[0], Indices.size());
1873 RewriteForScalarRepl(GEPI, AI, Offset, NewElts);
1875 const Type *T = AI->getAllocatedType();
1877 uint64_t OldIdx = FindElementAndOffset(T, OldOffset, IdxTy);
1878 if (GEPI->getOperand(0) == AI)
1879 OldIdx = ~0ULL; // Force the GEP to be rewritten.
1881 T = AI->getAllocatedType();
1882 uint64_t EltOffset = Offset;
1883 uint64_t Idx = FindElementAndOffset(T, EltOffset, IdxTy);
1885 // If this GEP does not move the pointer across elements of the alloca
1886 // being split, then it does not needs to be rewritten.
1890 const Type *i32Ty = Type::getInt32Ty(AI->getContext());
1891 SmallVector<Value*, 8> NewArgs;
1892 NewArgs.push_back(Constant::getNullValue(i32Ty));
1893 while (EltOffset != 0) {
1894 uint64_t EltIdx = FindElementAndOffset(T, EltOffset, IdxTy);
1895 NewArgs.push_back(ConstantInt::get(IdxTy, EltIdx));
1897 Instruction *Val = NewElts[Idx];
1898 if (NewArgs.size() > 1) {
1899 Val = GetElementPtrInst::CreateInBounds(Val, NewArgs.begin(),
1900 NewArgs.end(), "", GEPI);
1901 Val->takeName(GEPI);
1903 if (Val->getType() != GEPI->getType())
1904 Val = new BitCastInst(Val, GEPI->getType(), Val->getName(), GEPI);
1905 GEPI->replaceAllUsesWith(Val);
1906 DeadInsts.push_back(GEPI);
1909 /// RewriteMemIntrinUserOfAlloca - MI is a memcpy/memset/memmove from or to AI.
1910 /// Rewrite it to copy or set the elements of the scalarized memory.
1911 void SROA::RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *Inst,
1913 SmallVector<AllocaInst*, 32> &NewElts) {
1914 // If this is a memcpy/memmove, construct the other pointer as the
1915 // appropriate type. The "Other" pointer is the pointer that goes to memory
1916 // that doesn't have anything to do with the alloca that we are promoting. For
1917 // memset, this Value* stays null.
1918 Value *OtherPtr = 0;
1919 unsigned MemAlignment = MI->getAlignment();
1920 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(MI)) { // memmove/memcopy
1921 if (Inst == MTI->getRawDest())
1922 OtherPtr = MTI->getRawSource();
1924 assert(Inst == MTI->getRawSource());
1925 OtherPtr = MTI->getRawDest();
1929 // If there is an other pointer, we want to convert it to the same pointer
1930 // type as AI has, so we can GEP through it safely.
1932 unsigned AddrSpace =
1933 cast<PointerType>(OtherPtr->getType())->getAddressSpace();
1935 // Remove bitcasts and all-zero GEPs from OtherPtr. This is an
1936 // optimization, but it's also required to detect the corner case where
1937 // both pointer operands are referencing the same memory, and where
1938 // OtherPtr may be a bitcast or GEP that currently being rewritten. (This
1939 // function is only called for mem intrinsics that access the whole
1940 // aggregate, so non-zero GEPs are not an issue here.)
1941 OtherPtr = OtherPtr->stripPointerCasts();
1943 // Copying the alloca to itself is a no-op: just delete it.
1944 if (OtherPtr == AI || OtherPtr == NewElts[0]) {
1945 // This code will run twice for a no-op memcpy -- once for each operand.
1946 // Put only one reference to MI on the DeadInsts list.
1947 for (SmallVector<Value*, 32>::const_iterator I = DeadInsts.begin(),
1948 E = DeadInsts.end(); I != E; ++I)
1949 if (*I == MI) return;
1950 DeadInsts.push_back(MI);
1954 // If the pointer is not the right type, insert a bitcast to the right
1957 PointerType::get(AI->getType()->getElementType(), AddrSpace);
1959 if (OtherPtr->getType() != NewTy)
1960 OtherPtr = new BitCastInst(OtherPtr, NewTy, OtherPtr->getName(), MI);
1963 // Process each element of the aggregate.
1964 bool SROADest = MI->getRawDest() == Inst;
1966 Constant *Zero = Constant::getNullValue(Type::getInt32Ty(MI->getContext()));
1968 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
1969 // If this is a memcpy/memmove, emit a GEP of the other element address.
1970 Value *OtherElt = 0;
1971 unsigned OtherEltAlign = MemAlignment;
1974 Value *Idx[2] = { Zero,
1975 ConstantInt::get(Type::getInt32Ty(MI->getContext()), i) };
1976 OtherElt = GetElementPtrInst::CreateInBounds(OtherPtr, Idx, Idx + 2,
1977 OtherPtr->getName()+"."+Twine(i),
1980 const PointerType *OtherPtrTy = cast<PointerType>(OtherPtr->getType());
1981 const Type *OtherTy = OtherPtrTy->getElementType();
1982 if (const StructType *ST = dyn_cast<StructType>(OtherTy)) {
1983 EltOffset = TD->getStructLayout(ST)->getElementOffset(i);
1985 const Type *EltTy = cast<SequentialType>(OtherTy)->getElementType();
1986 EltOffset = TD->getTypeAllocSize(EltTy)*i;
1989 // The alignment of the other pointer is the guaranteed alignment of the
1990 // element, which is affected by both the known alignment of the whole
1991 // mem intrinsic and the alignment of the element. If the alignment of
1992 // the memcpy (f.e.) is 32 but the element is at a 4-byte offset, then the
1993 // known alignment is just 4 bytes.
1994 OtherEltAlign = (unsigned)MinAlign(OtherEltAlign, EltOffset);
1997 Value *EltPtr = NewElts[i];
1998 const Type *EltTy = cast<PointerType>(EltPtr->getType())->getElementType();
2000 // If we got down to a scalar, insert a load or store as appropriate.
2001 if (EltTy->isSingleValueType()) {
2002 if (isa<MemTransferInst>(MI)) {
2004 // From Other to Alloca.
2005 Value *Elt = new LoadInst(OtherElt, "tmp", false, OtherEltAlign, MI);
2006 new StoreInst(Elt, EltPtr, MI);
2008 // From Alloca to Other.
2009 Value *Elt = new LoadInst(EltPtr, "tmp", MI);
2010 new StoreInst(Elt, OtherElt, false, OtherEltAlign, MI);
2014 assert(isa<MemSetInst>(MI));
2016 // If the stored element is zero (common case), just store a null
2019 if (ConstantInt *CI = dyn_cast<ConstantInt>(MI->getArgOperand(1))) {
2021 StoreVal = Constant::getNullValue(EltTy); // 0.0, null, 0, <0,0>
2023 // If EltTy is a vector type, get the element type.
2024 const Type *ValTy = EltTy->getScalarType();
2026 // Construct an integer with the right value.
2027 unsigned EltSize = TD->getTypeSizeInBits(ValTy);
2028 APInt OneVal(EltSize, CI->getZExtValue());
2029 APInt TotalVal(OneVal);
2031 for (unsigned i = 0; 8*i < EltSize; ++i) {
2032 TotalVal = TotalVal.shl(8);
2036 // Convert the integer value to the appropriate type.
2037 StoreVal = ConstantInt::get(CI->getContext(), TotalVal);
2038 if (ValTy->isPointerTy())
2039 StoreVal = ConstantExpr::getIntToPtr(StoreVal, ValTy);
2040 else if (ValTy->isFloatingPointTy())
2041 StoreVal = ConstantExpr::getBitCast(StoreVal, ValTy);
2042 assert(StoreVal->getType() == ValTy && "Type mismatch!");
2044 // If the requested value was a vector constant, create it.
2045 if (EltTy != ValTy) {
2046 unsigned NumElts = cast<VectorType>(ValTy)->getNumElements();
2047 SmallVector<Constant*, 16> Elts(NumElts, StoreVal);
2048 StoreVal = ConstantVector::get(Elts);
2051 new StoreInst(StoreVal, EltPtr, MI);
2054 // Otherwise, if we're storing a byte variable, use a memset call for
2058 unsigned EltSize = TD->getTypeAllocSize(EltTy);
2060 IRBuilder<> Builder(MI);
2062 // Finally, insert the meminst for this element.
2063 if (isa<MemSetInst>(MI)) {
2064 Builder.CreateMemSet(EltPtr, MI->getArgOperand(1), EltSize,
2067 assert(isa<MemTransferInst>(MI));
2068 Value *Dst = SROADest ? EltPtr : OtherElt; // Dest ptr
2069 Value *Src = SROADest ? OtherElt : EltPtr; // Src ptr
2071 if (isa<MemCpyInst>(MI))
2072 Builder.CreateMemCpy(Dst, Src, EltSize, OtherEltAlign,MI->isVolatile());
2074 Builder.CreateMemMove(Dst, Src, EltSize,OtherEltAlign,MI->isVolatile());
2077 DeadInsts.push_back(MI);
2080 /// RewriteStoreUserOfWholeAlloca - We found a store of an integer that
2081 /// overwrites the entire allocation. Extract out the pieces of the stored
2082 /// integer and store them individually.
2083 void SROA::RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocaInst *AI,
2084 SmallVector<AllocaInst*, 32> &NewElts){
2085 // Extract each element out of the integer according to its structure offset
2086 // and store the element value to the individual alloca.
2087 Value *SrcVal = SI->getOperand(0);
2088 const Type *AllocaEltTy = AI->getAllocatedType();
2089 uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy);
2091 IRBuilder<> Builder(SI);
2093 // Handle tail padding by extending the operand
2094 if (TD->getTypeSizeInBits(SrcVal->getType()) != AllocaSizeBits)
2095 SrcVal = Builder.CreateZExt(SrcVal,
2096 IntegerType::get(SI->getContext(), AllocaSizeBits));
2098 DEBUG(dbgs() << "PROMOTING STORE TO WHOLE ALLOCA: " << *AI << '\n' << *SI
2101 // There are two forms here: AI could be an array or struct. Both cases
2102 // have different ways to compute the element offset.
2103 if (const StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) {
2104 const StructLayout *Layout = TD->getStructLayout(EltSTy);
2106 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
2107 // Get the number of bits to shift SrcVal to get the value.
2108 const Type *FieldTy = EltSTy->getElementType(i);
2109 uint64_t Shift = Layout->getElementOffsetInBits(i);
2111 if (TD->isBigEndian())
2112 Shift = AllocaSizeBits-Shift-TD->getTypeAllocSizeInBits(FieldTy);
2114 Value *EltVal = SrcVal;
2116 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift);
2117 EltVal = Builder.CreateLShr(EltVal, ShiftVal, "sroa.store.elt");
2120 // Truncate down to an integer of the right size.
2121 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy);
2123 // Ignore zero sized fields like {}, they obviously contain no data.
2124 if (FieldSizeBits == 0) continue;
2126 if (FieldSizeBits != AllocaSizeBits)
2127 EltVal = Builder.CreateTrunc(EltVal,
2128 IntegerType::get(SI->getContext(), FieldSizeBits));
2129 Value *DestField = NewElts[i];
2130 if (EltVal->getType() == FieldTy) {
2131 // Storing to an integer field of this size, just do it.
2132 } else if (FieldTy->isFloatingPointTy() || FieldTy->isVectorTy()) {
2133 // Bitcast to the right element type (for fp/vector values).
2134 EltVal = Builder.CreateBitCast(EltVal, FieldTy);
2136 // Otherwise, bitcast the dest pointer (for aggregates).
2137 DestField = Builder.CreateBitCast(DestField,
2138 PointerType::getUnqual(EltVal->getType()));
2140 new StoreInst(EltVal, DestField, SI);
2144 const ArrayType *ATy = cast<ArrayType>(AllocaEltTy);
2145 const Type *ArrayEltTy = ATy->getElementType();
2146 uint64_t ElementOffset = TD->getTypeAllocSizeInBits(ArrayEltTy);
2147 uint64_t ElementSizeBits = TD->getTypeSizeInBits(ArrayEltTy);
2151 if (TD->isBigEndian())
2152 Shift = AllocaSizeBits-ElementOffset;
2156 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
2157 // Ignore zero sized fields like {}, they obviously contain no data.
2158 if (ElementSizeBits == 0) continue;
2160 Value *EltVal = SrcVal;
2162 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift);
2163 EltVal = Builder.CreateLShr(EltVal, ShiftVal, "sroa.store.elt");
2166 // Truncate down to an integer of the right size.
2167 if (ElementSizeBits != AllocaSizeBits)
2168 EltVal = Builder.CreateTrunc(EltVal,
2169 IntegerType::get(SI->getContext(),
2171 Value *DestField = NewElts[i];
2172 if (EltVal->getType() == ArrayEltTy) {
2173 // Storing to an integer field of this size, just do it.
2174 } else if (ArrayEltTy->isFloatingPointTy() ||
2175 ArrayEltTy->isVectorTy()) {
2176 // Bitcast to the right element type (for fp/vector values).
2177 EltVal = Builder.CreateBitCast(EltVal, ArrayEltTy);
2179 // Otherwise, bitcast the dest pointer (for aggregates).
2180 DestField = Builder.CreateBitCast(DestField,
2181 PointerType::getUnqual(EltVal->getType()));
2183 new StoreInst(EltVal, DestField, SI);
2185 if (TD->isBigEndian())
2186 Shift -= ElementOffset;
2188 Shift += ElementOffset;
2192 DeadInsts.push_back(SI);
2195 /// RewriteLoadUserOfWholeAlloca - We found a load of the entire allocation to
2196 /// an integer. Load the individual pieces to form the aggregate value.
2197 void SROA::RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocaInst *AI,
2198 SmallVector<AllocaInst*, 32> &NewElts) {
2199 // Extract each element out of the NewElts according to its structure offset
2200 // and form the result value.
2201 const Type *AllocaEltTy = AI->getAllocatedType();
2202 uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy);
2204 DEBUG(dbgs() << "PROMOTING LOAD OF WHOLE ALLOCA: " << *AI << '\n' << *LI
2207 // There are two forms here: AI could be an array or struct. Both cases
2208 // have different ways to compute the element offset.
2209 const StructLayout *Layout = 0;
2210 uint64_t ArrayEltBitOffset = 0;
2211 if (const StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) {
2212 Layout = TD->getStructLayout(EltSTy);
2214 const Type *ArrayEltTy = cast<ArrayType>(AllocaEltTy)->getElementType();
2215 ArrayEltBitOffset = TD->getTypeAllocSizeInBits(ArrayEltTy);
2219 Constant::getNullValue(IntegerType::get(LI->getContext(), AllocaSizeBits));
2221 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
2222 // Load the value from the alloca. If the NewElt is an aggregate, cast
2223 // the pointer to an integer of the same size before doing the load.
2224 Value *SrcField = NewElts[i];
2225 const Type *FieldTy =
2226 cast<PointerType>(SrcField->getType())->getElementType();
2227 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy);
2229 // Ignore zero sized fields like {}, they obviously contain no data.
2230 if (FieldSizeBits == 0) continue;
2232 const IntegerType *FieldIntTy = IntegerType::get(LI->getContext(),
2234 if (!FieldTy->isIntegerTy() && !FieldTy->isFloatingPointTy() &&
2235 !FieldTy->isVectorTy())
2236 SrcField = new BitCastInst(SrcField,
2237 PointerType::getUnqual(FieldIntTy),
2239 SrcField = new LoadInst(SrcField, "sroa.load.elt", LI);
2241 // If SrcField is a fp or vector of the right size but that isn't an
2242 // integer type, bitcast to an integer so we can shift it.
2243 if (SrcField->getType() != FieldIntTy)
2244 SrcField = new BitCastInst(SrcField, FieldIntTy, "", LI);
2246 // Zero extend the field to be the same size as the final alloca so that
2247 // we can shift and insert it.
2248 if (SrcField->getType() != ResultVal->getType())
2249 SrcField = new ZExtInst(SrcField, ResultVal->getType(), "", LI);
2251 // Determine the number of bits to shift SrcField.
2253 if (Layout) // Struct case.
2254 Shift = Layout->getElementOffsetInBits(i);
2256 Shift = i*ArrayEltBitOffset;
2258 if (TD->isBigEndian())
2259 Shift = AllocaSizeBits-Shift-FieldIntTy->getBitWidth();
2262 Value *ShiftVal = ConstantInt::get(SrcField->getType(), Shift);
2263 SrcField = BinaryOperator::CreateShl(SrcField, ShiftVal, "", LI);
2266 // Don't create an 'or x, 0' on the first iteration.
2267 if (!isa<Constant>(ResultVal) ||
2268 !cast<Constant>(ResultVal)->isNullValue())
2269 ResultVal = BinaryOperator::CreateOr(SrcField, ResultVal, "", LI);
2271 ResultVal = SrcField;
2274 // Handle tail padding by truncating the result
2275 if (TD->getTypeSizeInBits(LI->getType()) != AllocaSizeBits)
2276 ResultVal = new TruncInst(ResultVal, LI->getType(), "", LI);
2278 LI->replaceAllUsesWith(ResultVal);
2279 DeadInsts.push_back(LI);
2282 /// HasPadding - Return true if the specified type has any structure or
2283 /// alignment padding in between the elements that would be split apart
2284 /// by SROA; return false otherwise.
2285 static bool HasPadding(const Type *Ty, const TargetData &TD) {
2286 if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
2287 Ty = ATy->getElementType();
2288 return TD.getTypeSizeInBits(Ty) != TD.getTypeAllocSizeInBits(Ty);
2291 // SROA currently handles only Arrays and Structs.
2292 const StructType *STy = cast<StructType>(Ty);
2293 const StructLayout *SL = TD.getStructLayout(STy);
2294 unsigned PrevFieldBitOffset = 0;
2295 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
2296 unsigned FieldBitOffset = SL->getElementOffsetInBits(i);
2298 // Check to see if there is any padding between this element and the
2301 unsigned PrevFieldEnd =
2302 PrevFieldBitOffset+TD.getTypeSizeInBits(STy->getElementType(i-1));
2303 if (PrevFieldEnd < FieldBitOffset)
2306 PrevFieldBitOffset = FieldBitOffset;
2308 // Check for tail padding.
2309 if (unsigned EltCount = STy->getNumElements()) {
2310 unsigned PrevFieldEnd = PrevFieldBitOffset +
2311 TD.getTypeSizeInBits(STy->getElementType(EltCount-1));
2312 if (PrevFieldEnd < SL->getSizeInBits())
2318 /// isSafeStructAllocaToScalarRepl - Check to see if the specified allocation of
2319 /// an aggregate can be broken down into elements. Return 0 if not, 3 if safe,
2320 /// or 1 if safe after canonicalization has been performed.
2321 bool SROA::isSafeAllocaToScalarRepl(AllocaInst *AI) {
2322 // Loop over the use list of the alloca. We can only transform it if all of
2323 // the users are safe to transform.
2324 AllocaInfo Info(AI);
2326 isSafeForScalarRepl(AI, 0, Info);
2327 if (Info.isUnsafe) {
2328 DEBUG(dbgs() << "Cannot transform: " << *AI << '\n');
2332 // Okay, we know all the users are promotable. If the aggregate is a memcpy
2333 // source and destination, we have to be careful. In particular, the memcpy
2334 // could be moving around elements that live in structure padding of the LLVM
2335 // types, but may actually be used. In these cases, we refuse to promote the
2337 if (Info.isMemCpySrc && Info.isMemCpyDst &&
2338 HasPadding(AI->getAllocatedType(), *TD))
2341 // If the alloca never has an access to just *part* of it, but is accessed
2342 // via loads and stores, then we should use ConvertToScalarInfo to promote
2343 // the alloca instead of promoting each piece at a time and inserting fission
2345 if (!Info.hasSubelementAccess && Info.hasALoadOrStore) {
2346 // If the struct/array just has one element, use basic SRoA.
2347 if (const StructType *ST = dyn_cast<StructType>(AI->getAllocatedType())) {
2348 if (ST->getNumElements() > 1) return false;
2350 if (cast<ArrayType>(AI->getAllocatedType())->getNumElements() > 1)
2360 /// PointsToConstantGlobal - Return true if V (possibly indirectly) points to
2361 /// some part of a constant global variable. This intentionally only accepts
2362 /// constant expressions because we don't can't rewrite arbitrary instructions.
2363 static bool PointsToConstantGlobal(Value *V) {
2364 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
2365 return GV->isConstant();
2366 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
2367 if (CE->getOpcode() == Instruction::BitCast ||
2368 CE->getOpcode() == Instruction::GetElementPtr)
2369 return PointsToConstantGlobal(CE->getOperand(0));
2373 /// isOnlyCopiedFromConstantGlobal - Recursively walk the uses of a (derived)
2374 /// pointer to an alloca. Ignore any reads of the pointer, return false if we
2375 /// see any stores or other unknown uses. If we see pointer arithmetic, keep
2376 /// track of whether it moves the pointer (with isOffset) but otherwise traverse
2377 /// the uses. If we see a memcpy/memmove that targets an unoffseted pointer to
2378 /// the alloca, and if the source pointer is a pointer to a constant global, we
2379 /// can optimize this.
2380 static bool isOnlyCopiedFromConstantGlobal(Value *V, MemTransferInst *&TheCopy,
2382 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) {
2383 User *U = cast<Instruction>(*UI);
2385 if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
2386 // Ignore non-volatile loads, they are always ok.
2387 if (LI->isVolatile()) return false;
2391 if (BitCastInst *BCI = dyn_cast<BitCastInst>(U)) {
2392 // If uses of the bitcast are ok, we are ok.
2393 if (!isOnlyCopiedFromConstantGlobal(BCI, TheCopy, isOffset))
2397 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) {
2398 // If the GEP has all zero indices, it doesn't offset the pointer. If it
2399 // doesn't, it does.
2400 if (!isOnlyCopiedFromConstantGlobal(GEP, TheCopy,
2401 isOffset || !GEP->hasAllZeroIndices()))
2406 if (CallSite CS = U) {
2407 // If this is a readonly/readnone call site, then we know it is just a
2408 // load and we can ignore it.
2409 if (CS.onlyReadsMemory())
2412 // If this is the function being called then we treat it like a load and
2414 if (CS.isCallee(UI))
2417 // If this is being passed as a byval argument, the caller is making a
2418 // copy, so it is only a read of the alloca.
2419 unsigned ArgNo = CS.getArgumentNo(UI);
2420 if (CS.paramHasAttr(ArgNo+1, Attribute::ByVal))
2424 // If this is isn't our memcpy/memmove, reject it as something we can't
2426 MemTransferInst *MI = dyn_cast<MemTransferInst>(U);
2430 // If the transfer is using the alloca as a source of the transfer, then
2431 // ignore it since it is a load (unless the transfer is volatile).
2432 if (UI.getOperandNo() == 1) {
2433 if (MI->isVolatile()) return false;
2437 // If we already have seen a copy, reject the second one.
2438 if (TheCopy) return false;
2440 // If the pointer has been offset from the start of the alloca, we can't
2441 // safely handle this.
2442 if (isOffset) return false;
2444 // If the memintrinsic isn't using the alloca as the dest, reject it.
2445 if (UI.getOperandNo() != 0) return false;
2447 // If the source of the memcpy/move is not a constant global, reject it.
2448 if (!PointsToConstantGlobal(MI->getSource()))
2451 // Otherwise, the transform is safe. Remember the copy instruction.
2457 /// isOnlyCopiedFromConstantGlobal - Return true if the specified alloca is only
2458 /// modified by a copy from a constant global. If we can prove this, we can
2459 /// replace any uses of the alloca with uses of the global directly.
2460 MemTransferInst *SROA::isOnlyCopiedFromConstantGlobal(AllocaInst *AI) {
2461 MemTransferInst *TheCopy = 0;
2462 if (::isOnlyCopiedFromConstantGlobal(AI, TheCopy, false))