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 in bytes.
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.
241 /// HadNonMemTransferAccess - True if there is at least one access to the
242 /// alloca that is not a MemTransferInst. We don't want to turn structs into
243 /// large integers unless there is some potential for optimization.
244 bool HadNonMemTransferAccess;
247 explicit ConvertToScalarInfo(unsigned Size, const TargetData &td)
248 : AllocaSize(Size), TD(td), IsNotTrivial(false), VectorTy(0),
249 HadAVector(false), HadNonMemTransferAccess(false) { }
251 AllocaInst *TryConvert(AllocaInst *AI);
254 bool CanConvertToScalar(Value *V, uint64_t Offset);
255 void MergeInType(const Type *In, uint64_t Offset, bool IsLoadOrStore);
256 bool MergeInVectorType(const VectorType *VInTy, uint64_t Offset);
257 void ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, uint64_t Offset);
259 Value *ConvertScalar_ExtractValue(Value *NV, const Type *ToType,
260 uint64_t Offset, IRBuilder<> &Builder);
261 Value *ConvertScalar_InsertValue(Value *StoredVal, Value *ExistingVal,
262 uint64_t Offset, IRBuilder<> &Builder);
264 } // end anonymous namespace.
267 /// TryConvert - Analyze the specified alloca, and if it is safe to do so,
268 /// rewrite it to be a new alloca which is mem2reg'able. This returns the new
269 /// alloca if possible or null if not.
270 AllocaInst *ConvertToScalarInfo::TryConvert(AllocaInst *AI) {
271 // If we can't convert this scalar, or if mem2reg can trivially do it, bail
273 if (!CanConvertToScalar(AI, 0) || !IsNotTrivial)
276 // If we were able to find a vector type that can handle this with
277 // insert/extract elements, and if there was at least one use that had
278 // a vector type, promote this to a vector. We don't want to promote
279 // random stuff that doesn't use vectors (e.g. <9 x double>) because then
280 // we just get a lot of insert/extracts. If at least one vector is
281 // involved, then we probably really do have a union of vector/array.
283 if (VectorTy && VectorTy->isVectorTy() && HadAVector) {
284 DEBUG(dbgs() << "CONVERT TO VECTOR: " << *AI << "\n TYPE = "
285 << *VectorTy << '\n');
286 NewTy = VectorTy; // Use the vector type.
288 unsigned BitWidth = AllocaSize * 8;
289 if (!HadAVector && !HadNonMemTransferAccess &&
290 !TD.fitsInLegalInteger(BitWidth))
293 DEBUG(dbgs() << "CONVERT TO SCALAR INTEGER: " << *AI << "\n");
294 // Create and insert the integer alloca.
295 NewTy = IntegerType::get(AI->getContext(), BitWidth);
297 AllocaInst *NewAI = new AllocaInst(NewTy, 0, "", AI->getParent()->begin());
298 ConvertUsesToScalar(AI, NewAI, 0);
302 /// MergeInType - Add the 'In' type to the accumulated vector type (VectorTy)
303 /// so far at the offset specified by Offset (which is specified in bytes).
305 /// There are three cases we handle here:
306 /// 1) A union of vector types of the same size and potentially its elements.
307 /// Here we turn element accesses into insert/extract element operations.
308 /// This promotes a <4 x float> with a store of float to the third element
309 /// into a <4 x float> that uses insert element.
310 /// 2) A union of vector types with power-of-2 size differences, e.g. a float,
311 /// <2 x float> and <4 x float>. Here we turn element accesses into insert
312 /// and extract element operations, and <2 x float> accesses into a cast to
313 /// <2 x double>, an extract, and a cast back to <2 x float>.
314 /// 3) A fully general blob of memory, which we turn into some (potentially
315 /// large) integer type with extract and insert operations where the loads
316 /// and stores would mutate the memory. We mark this by setting VectorTy
318 void ConvertToScalarInfo::MergeInType(const Type *In, uint64_t Offset,
319 bool IsLoadOrStore) {
320 // If we already decided to turn this into a blob of integer memory, there is
321 // nothing to be done.
322 if (VectorTy && VectorTy->isVoidTy())
325 // If this could be contributing to a vector, analyze it.
327 // If the In type is a vector that is the same size as the alloca, see if it
328 // matches the existing VecTy.
329 if (const VectorType *VInTy = dyn_cast<VectorType>(In)) {
330 if (MergeInVectorType(VInTy, Offset))
332 } else if (In->isFloatTy() || In->isDoubleTy() ||
333 (In->isIntegerTy() && In->getPrimitiveSizeInBits() >= 8 &&
334 isPowerOf2_32(In->getPrimitiveSizeInBits()))) {
335 // Full width accesses can be ignored, because they can always be turned
337 unsigned EltSize = In->getPrimitiveSizeInBits()/8;
338 if (IsLoadOrStore && EltSize == AllocaSize)
341 // If we're accessing something that could be an element of a vector, see
342 // if the implied vector agrees with what we already have and if Offset is
343 // compatible with it.
344 if (Offset % EltSize == 0 && AllocaSize % EltSize == 0) {
346 VectorTy = VectorType::get(In, AllocaSize/EltSize);
350 unsigned CurrentEltSize = cast<VectorType>(VectorTy)->getElementType()
351 ->getPrimitiveSizeInBits()/8;
352 if (EltSize == CurrentEltSize)
357 // Otherwise, we have a case that we can't handle with an optimized vector
358 // form. We can still turn this into a large integer.
359 VectorTy = Type::getVoidTy(In->getContext());
362 /// MergeInVectorType - Handles the vector case of MergeInType, returning true
363 /// if the type was successfully merged and false otherwise.
364 bool ConvertToScalarInfo::MergeInVectorType(const VectorType *VInTy,
366 // Remember if we saw a vector type.
369 // TODO: Support nonzero offsets?
373 // Only allow vectors that are a power-of-2 away from the size of the alloca.
374 if (!isPowerOf2_64(AllocaSize / (VInTy->getBitWidth() / 8)))
377 // If this the first vector we see, remember the type so that we know the
384 unsigned BitWidth = cast<VectorType>(VectorTy)->getBitWidth();
385 unsigned InBitWidth = VInTy->getBitWidth();
387 // Vectors of the same size can be converted using a simple bitcast.
388 if (InBitWidth == BitWidth && AllocaSize == (InBitWidth / 8))
391 const Type *ElementTy = cast<VectorType>(VectorTy)->getElementType();
392 const Type *InElementTy = cast<VectorType>(VInTy)->getElementType();
394 // Do not allow mixed integer and floating-point accesses from vectors of
396 if (ElementTy->isFloatingPointTy() != InElementTy->isFloatingPointTy())
399 if (ElementTy->isFloatingPointTy()) {
400 // Only allow floating-point vectors of different sizes if they have the
401 // same element type.
402 // TODO: This could be loosened a bit, but would anything benefit?
403 if (ElementTy != InElementTy)
406 // There are no arbitrary-precision floating-point types, which limits the
407 // number of legal vector types with larger element types that we can form
408 // to bitcast and extract a subvector.
409 // TODO: We could support some more cases with mixed fp128 and double here.
410 if (!(BitWidth == 64 || BitWidth == 128) ||
411 !(InBitWidth == 64 || InBitWidth == 128))
414 assert(ElementTy->isIntegerTy() && "Vector elements must be either integer "
415 "or floating-point.");
416 unsigned BitWidth = ElementTy->getPrimitiveSizeInBits();
417 unsigned InBitWidth = InElementTy->getPrimitiveSizeInBits();
419 // Do not allow integer types smaller than a byte or types whose widths are
420 // not a multiple of a byte.
421 if (BitWidth < 8 || InBitWidth < 8 ||
422 BitWidth % 8 != 0 || InBitWidth % 8 != 0)
426 // Pick the largest of the two vector types.
427 if (InBitWidth > BitWidth)
433 /// CanConvertToScalar - V is a pointer. If we can convert the pointee and all
434 /// its accesses to a single vector type, return true and set VecTy to
435 /// the new type. If we could convert the alloca into a single promotable
436 /// integer, return true but set VecTy to VoidTy. Further, if the use is not a
437 /// completely trivial use that mem2reg could promote, set IsNotTrivial. Offset
438 /// is the current offset from the base of the alloca being analyzed.
440 /// If we see at least one access to the value that is as a vector type, set the
442 bool ConvertToScalarInfo::CanConvertToScalar(Value *V, uint64_t Offset) {
443 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) {
444 Instruction *User = cast<Instruction>(*UI);
446 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
447 // Don't break volatile loads.
448 if (LI->isVolatile())
450 // Don't touch MMX operations.
451 if (LI->getType()->isX86_MMXTy())
453 HadNonMemTransferAccess = true;
454 MergeInType(LI->getType(), Offset, true);
458 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
459 // Storing the pointer, not into the value?
460 if (SI->getOperand(0) == V || SI->isVolatile()) return false;
461 // Don't touch MMX operations.
462 if (SI->getOperand(0)->getType()->isX86_MMXTy())
464 HadNonMemTransferAccess = true;
465 MergeInType(SI->getOperand(0)->getType(), Offset, true);
469 if (BitCastInst *BCI = dyn_cast<BitCastInst>(User)) {
470 IsNotTrivial = true; // Can't be mem2reg'd.
471 if (!CanConvertToScalar(BCI, Offset))
476 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) {
477 // If this is a GEP with a variable indices, we can't handle it.
478 if (!GEP->hasAllConstantIndices())
481 // Compute the offset that this GEP adds to the pointer.
482 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end());
483 uint64_t GEPOffset = TD.getIndexedOffset(GEP->getPointerOperandType(),
484 &Indices[0], Indices.size());
485 // See if all uses can be converted.
486 if (!CanConvertToScalar(GEP, Offset+GEPOffset))
488 IsNotTrivial = true; // Can't be mem2reg'd.
489 HadNonMemTransferAccess = true;
493 // If this is a constant sized memset of a constant value (e.g. 0) we can
495 if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) {
496 // Store of constant value and constant size.
497 if (!isa<ConstantInt>(MSI->getValue()) ||
498 !isa<ConstantInt>(MSI->getLength()))
500 IsNotTrivial = true; // Can't be mem2reg'd.
501 HadNonMemTransferAccess = true;
505 // If this is a memcpy or memmove into or out of the whole allocation, we
506 // can handle it like a load or store of the scalar type.
507 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) {
508 ConstantInt *Len = dyn_cast<ConstantInt>(MTI->getLength());
509 if (Len == 0 || Len->getZExtValue() != AllocaSize || Offset != 0)
512 IsNotTrivial = true; // Can't be mem2reg'd.
516 // Otherwise, we cannot handle this!
523 /// ConvertUsesToScalar - Convert all of the users of Ptr to use the new alloca
524 /// directly. This happens when we are converting an "integer union" to a
525 /// single integer scalar, or when we are converting a "vector union" to a
526 /// vector with insert/extractelement instructions.
528 /// Offset is an offset from the original alloca, in bits that need to be
529 /// shifted to the right. By the end of this, there should be no uses of Ptr.
530 void ConvertToScalarInfo::ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI,
532 while (!Ptr->use_empty()) {
533 Instruction *User = cast<Instruction>(Ptr->use_back());
535 if (BitCastInst *CI = dyn_cast<BitCastInst>(User)) {
536 ConvertUsesToScalar(CI, NewAI, Offset);
537 CI->eraseFromParent();
541 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) {
542 // Compute the offset that this GEP adds to the pointer.
543 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end());
544 uint64_t GEPOffset = TD.getIndexedOffset(GEP->getPointerOperandType(),
545 &Indices[0], Indices.size());
546 ConvertUsesToScalar(GEP, NewAI, Offset+GEPOffset*8);
547 GEP->eraseFromParent();
551 IRBuilder<> Builder(User);
553 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
554 // The load is a bit extract from NewAI shifted right by Offset bits.
555 Value *LoadedVal = Builder.CreateLoad(NewAI, "tmp");
557 = ConvertScalar_ExtractValue(LoadedVal, LI->getType(), Offset, Builder);
558 LI->replaceAllUsesWith(NewLoadVal);
559 LI->eraseFromParent();
563 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
564 assert(SI->getOperand(0) != Ptr && "Consistency error!");
565 Instruction *Old = Builder.CreateLoad(NewAI, NewAI->getName()+".in");
566 Value *New = ConvertScalar_InsertValue(SI->getOperand(0), Old, Offset,
568 Builder.CreateStore(New, NewAI);
569 SI->eraseFromParent();
571 // If the load we just inserted is now dead, then the inserted store
572 // overwrote the entire thing.
573 if (Old->use_empty())
574 Old->eraseFromParent();
578 // If this is a constant sized memset of a constant value (e.g. 0) we can
579 // transform it into a store of the expanded constant value.
580 if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) {
581 assert(MSI->getRawDest() == Ptr && "Consistency error!");
582 unsigned NumBytes = cast<ConstantInt>(MSI->getLength())->getZExtValue();
584 unsigned Val = cast<ConstantInt>(MSI->getValue())->getZExtValue();
586 // Compute the value replicated the right number of times.
587 APInt APVal(NumBytes*8, Val);
589 // Splat the value if non-zero.
591 for (unsigned i = 1; i != NumBytes; ++i)
594 Instruction *Old = Builder.CreateLoad(NewAI, NewAI->getName()+".in");
595 Value *New = ConvertScalar_InsertValue(
596 ConstantInt::get(User->getContext(), APVal),
597 Old, Offset, Builder);
598 Builder.CreateStore(New, NewAI);
600 // If the load we just inserted is now dead, then the memset overwrote
602 if (Old->use_empty())
603 Old->eraseFromParent();
605 MSI->eraseFromParent();
609 // If this is a memcpy or memmove into or out of the whole allocation, we
610 // can handle it like a load or store of the scalar type.
611 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) {
612 assert(Offset == 0 && "must be store to start of alloca");
614 // If the source and destination are both to the same alloca, then this is
615 // a noop copy-to-self, just delete it. Otherwise, emit a load and store
617 AllocaInst *OrigAI = cast<AllocaInst>(GetUnderlyingObject(Ptr, &TD, 0));
619 if (GetUnderlyingObject(MTI->getSource(), &TD, 0) != OrigAI) {
620 // Dest must be OrigAI, change this to be a load from the original
621 // pointer (bitcasted), then a store to our new alloca.
622 assert(MTI->getRawDest() == Ptr && "Neither use is of pointer?");
623 Value *SrcPtr = MTI->getSource();
624 const PointerType* SPTy = cast<PointerType>(SrcPtr->getType());
625 const PointerType* AIPTy = cast<PointerType>(NewAI->getType());
626 if (SPTy->getAddressSpace() != AIPTy->getAddressSpace()) {
627 AIPTy = PointerType::get(AIPTy->getElementType(),
628 SPTy->getAddressSpace());
630 SrcPtr = Builder.CreateBitCast(SrcPtr, AIPTy);
632 LoadInst *SrcVal = Builder.CreateLoad(SrcPtr, "srcval");
633 SrcVal->setAlignment(MTI->getAlignment());
634 Builder.CreateStore(SrcVal, NewAI);
635 } else if (GetUnderlyingObject(MTI->getDest(), &TD, 0) != OrigAI) {
636 // Src must be OrigAI, change this to be a load from NewAI then a store
637 // through the original dest pointer (bitcasted).
638 assert(MTI->getRawSource() == Ptr && "Neither use is of pointer?");
639 LoadInst *SrcVal = Builder.CreateLoad(NewAI, "srcval");
641 const PointerType* DPTy = cast<PointerType>(MTI->getDest()->getType());
642 const PointerType* AIPTy = cast<PointerType>(NewAI->getType());
643 if (DPTy->getAddressSpace() != AIPTy->getAddressSpace()) {
644 AIPTy = PointerType::get(AIPTy->getElementType(),
645 DPTy->getAddressSpace());
647 Value *DstPtr = Builder.CreateBitCast(MTI->getDest(), AIPTy);
649 StoreInst *NewStore = Builder.CreateStore(SrcVal, DstPtr);
650 NewStore->setAlignment(MTI->getAlignment());
652 // Noop transfer. Src == Dst
655 MTI->eraseFromParent();
659 llvm_unreachable("Unsupported operation!");
663 /// getScaledElementType - Gets a scaled element type for a partial vector
664 /// access of an alloca. The input type must be an integer or float, and
665 /// the resulting type must be an integer, float or double.
666 static const Type *getScaledElementType(const Type *OldTy,
667 unsigned NewBitWidth) {
668 assert((OldTy->isIntegerTy() || OldTy->isFloatTy()) && "Partial vector "
669 "accesses must be scaled from integer or float elements.");
671 LLVMContext &Context = OldTy->getContext();
673 if (OldTy->isIntegerTy())
674 return Type::getIntNTy(Context, NewBitWidth);
675 if (NewBitWidth == 32)
676 return Type::getFloatTy(Context);
677 if (NewBitWidth == 64)
678 return Type::getDoubleTy(Context);
680 llvm_unreachable("Invalid type for a partial vector access of an alloca!");
683 /// CreateShuffleVectorCast - Creates a shuffle vector to convert one vector
684 /// to another vector of the same element type which has the same allocation
685 /// size but different primitive sizes (e.g. <3 x i32> and <4 x i32>).
686 static Value *CreateShuffleVectorCast(Value *FromVal, const Type *ToType,
687 IRBuilder<> &Builder) {
688 const Type *FromType = FromVal->getType();
689 const VectorType *FromVTy = cast<VectorType>(FromType);
690 const VectorType *ToVTy = cast<VectorType>(ToType);
691 assert((ToVTy->getElementType() == FromVTy->getElementType()) &&
692 "Vectors must have the same element type");
693 Value *UnV = UndefValue::get(FromType);
694 unsigned numEltsFrom = FromVTy->getNumElements();
695 unsigned numEltsTo = ToVTy->getNumElements();
697 SmallVector<Constant*, 3> Args;
698 const Type* Int32Ty = Builder.getInt32Ty();
699 unsigned minNumElts = std::min(numEltsFrom, numEltsTo);
701 for (i=0; i != minNumElts; ++i)
702 Args.push_back(ConstantInt::get(Int32Ty, i));
705 Constant* UnC = UndefValue::get(Int32Ty);
706 for (; i != numEltsTo; ++i)
709 Constant *Mask = ConstantVector::get(Args);
710 return Builder.CreateShuffleVector(FromVal, UnV, Mask, "tmpV");
713 /// ConvertScalar_ExtractValue - Extract a value of type ToType from an integer
714 /// or vector value FromVal, extracting the bits from the offset specified by
715 /// Offset. This returns the value, which is of type ToType.
717 /// This happens when we are converting an "integer union" to a single
718 /// integer scalar, or when we are converting a "vector union" to a vector with
719 /// insert/extractelement instructions.
721 /// Offset is an offset from the original alloca, in bits that need to be
722 /// shifted to the right.
723 Value *ConvertToScalarInfo::
724 ConvertScalar_ExtractValue(Value *FromVal, const Type *ToType,
725 uint64_t Offset, IRBuilder<> &Builder) {
726 // If the load is of the whole new alloca, no conversion is needed.
727 const Type *FromType = FromVal->getType();
728 if (FromType == ToType && Offset == 0)
731 // If the result alloca is a vector type, this is either an element
732 // access or a bitcast to another vector type of the same size.
733 if (const VectorType *VTy = dyn_cast<VectorType>(FromType)) {
734 unsigned ToTypeSize = TD.getTypeAllocSize(ToType);
735 if (ToTypeSize == AllocaSize) {
736 // If the two types have the same primitive size, use a bit cast.
737 // Otherwise, it is two vectors with the same element type that has
738 // the same allocation size but different number of elements so use
740 if (FromType->getPrimitiveSizeInBits() ==
741 ToType->getPrimitiveSizeInBits())
742 return Builder.CreateBitCast(FromVal, ToType, "tmp");
744 return CreateShuffleVectorCast(FromVal, ToType, Builder);
747 if (ToType->isVectorTy()) {
748 assert(isPowerOf2_64(AllocaSize / ToTypeSize) &&
749 "Partial vector access of an alloca must have a power-of-2 size "
751 assert(Offset == 0 && "Can't extract a value of a smaller vector type "
752 "from a nonzero offset.");
754 const Type *ToElementTy = cast<VectorType>(ToType)->getElementType();
755 const Type *CastElementTy = getScaledElementType(ToElementTy,
757 unsigned NumCastVectorElements = AllocaSize / ToTypeSize;
759 LLVMContext &Context = FromVal->getContext();
760 const Type *CastTy = VectorType::get(CastElementTy,
761 NumCastVectorElements);
762 Value *Cast = Builder.CreateBitCast(FromVal, CastTy, "tmp");
763 Value *Extract = Builder.CreateExtractElement(Cast, ConstantInt::get(
764 Type::getInt32Ty(Context), 0), "tmp");
765 return Builder.CreateBitCast(Extract, ToType, "tmp");
768 // Otherwise it must be an element access.
771 unsigned EltSize = TD.getTypeAllocSizeInBits(VTy->getElementType());
772 Elt = Offset/EltSize;
773 assert(EltSize*Elt == Offset && "Invalid modulus in validity checking");
775 // Return the element extracted out of it.
776 Value *V = Builder.CreateExtractElement(FromVal, ConstantInt::get(
777 Type::getInt32Ty(FromVal->getContext()), Elt), "tmp");
778 if (V->getType() != ToType)
779 V = Builder.CreateBitCast(V, ToType, "tmp");
783 // If ToType is a first class aggregate, extract out each of the pieces and
784 // use insertvalue's to form the FCA.
785 if (const StructType *ST = dyn_cast<StructType>(ToType)) {
786 const StructLayout &Layout = *TD.getStructLayout(ST);
787 Value *Res = UndefValue::get(ST);
788 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) {
789 Value *Elt = ConvertScalar_ExtractValue(FromVal, ST->getElementType(i),
790 Offset+Layout.getElementOffsetInBits(i),
792 Res = Builder.CreateInsertValue(Res, Elt, i, "tmp");
797 if (const ArrayType *AT = dyn_cast<ArrayType>(ToType)) {
798 uint64_t EltSize = TD.getTypeAllocSizeInBits(AT->getElementType());
799 Value *Res = UndefValue::get(AT);
800 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
801 Value *Elt = ConvertScalar_ExtractValue(FromVal, AT->getElementType(),
802 Offset+i*EltSize, Builder);
803 Res = Builder.CreateInsertValue(Res, Elt, i, "tmp");
808 // Otherwise, this must be a union that was converted to an integer value.
809 const IntegerType *NTy = cast<IntegerType>(FromVal->getType());
811 // If this is a big-endian system and the load is narrower than the
812 // full alloca type, we need to do a shift to get the right bits.
814 if (TD.isBigEndian()) {
815 // On big-endian machines, the lowest bit is stored at the bit offset
816 // from the pointer given by getTypeStoreSizeInBits. This matters for
817 // integers with a bitwidth that is not a multiple of 8.
818 ShAmt = TD.getTypeStoreSizeInBits(NTy) -
819 TD.getTypeStoreSizeInBits(ToType) - Offset;
824 // Note: we support negative bitwidths (with shl) which are not defined.
825 // We do this to support (f.e.) loads off the end of a structure where
826 // only some bits are used.
827 if (ShAmt > 0 && (unsigned)ShAmt < NTy->getBitWidth())
828 FromVal = Builder.CreateLShr(FromVal,
829 ConstantInt::get(FromVal->getType(),
831 else if (ShAmt < 0 && (unsigned)-ShAmt < NTy->getBitWidth())
832 FromVal = Builder.CreateShl(FromVal,
833 ConstantInt::get(FromVal->getType(),
836 // Finally, unconditionally truncate the integer to the right width.
837 unsigned LIBitWidth = TD.getTypeSizeInBits(ToType);
838 if (LIBitWidth < NTy->getBitWidth())
840 Builder.CreateTrunc(FromVal, IntegerType::get(FromVal->getContext(),
842 else if (LIBitWidth > NTy->getBitWidth())
844 Builder.CreateZExt(FromVal, IntegerType::get(FromVal->getContext(),
847 // If the result is an integer, this is a trunc or bitcast.
848 if (ToType->isIntegerTy()) {
850 } else if (ToType->isFloatingPointTy() || ToType->isVectorTy()) {
851 // Just do a bitcast, we know the sizes match up.
852 FromVal = Builder.CreateBitCast(FromVal, ToType, "tmp");
854 // Otherwise must be a pointer.
855 FromVal = Builder.CreateIntToPtr(FromVal, ToType, "tmp");
857 assert(FromVal->getType() == ToType && "Didn't convert right?");
861 /// ConvertScalar_InsertValue - Insert the value "SV" into the existing integer
862 /// or vector value "Old" at the offset specified by Offset.
864 /// This happens when we are converting an "integer union" to a
865 /// single integer scalar, or when we are converting a "vector union" to a
866 /// vector with insert/extractelement instructions.
868 /// Offset is an offset from the original alloca, in bits that need to be
869 /// shifted to the right.
870 Value *ConvertToScalarInfo::
871 ConvertScalar_InsertValue(Value *SV, Value *Old,
872 uint64_t Offset, IRBuilder<> &Builder) {
873 // Convert the stored type to the actual type, shift it left to insert
874 // then 'or' into place.
875 const Type *AllocaType = Old->getType();
876 LLVMContext &Context = Old->getContext();
878 if (const VectorType *VTy = dyn_cast<VectorType>(AllocaType)) {
879 uint64_t VecSize = TD.getTypeAllocSizeInBits(VTy);
880 uint64_t ValSize = TD.getTypeAllocSizeInBits(SV->getType());
882 // Changing the whole vector with memset or with an access of a different
884 if (ValSize == VecSize) {
885 // If the two types have the same primitive size, use a bit cast.
886 // Otherwise, it is two vectors with the same element type that has
887 // the same allocation size but different number of elements so use
889 if (VTy->getPrimitiveSizeInBits() ==
890 SV->getType()->getPrimitiveSizeInBits())
891 return Builder.CreateBitCast(SV, AllocaType, "tmp");
893 return CreateShuffleVectorCast(SV, VTy, Builder);
896 if (SV->getType()->isVectorTy() && isPowerOf2_64(VecSize / ValSize)) {
897 assert(Offset == 0 && "Can't insert a value of a smaller vector type at "
898 "a nonzero offset.");
900 const Type *ToElementTy =
901 cast<VectorType>(SV->getType())->getElementType();
902 const Type *CastElementTy = getScaledElementType(ToElementTy, ValSize);
903 unsigned NumCastVectorElements = VecSize / ValSize;
905 LLVMContext &Context = SV->getContext();
906 const Type *OldCastTy = VectorType::get(CastElementTy,
907 NumCastVectorElements);
908 Value *OldCast = Builder.CreateBitCast(Old, OldCastTy, "tmp");
910 Value *SVCast = Builder.CreateBitCast(SV, CastElementTy, "tmp");
912 Builder.CreateInsertElement(OldCast, SVCast, ConstantInt::get(
913 Type::getInt32Ty(Context), 0), "tmp");
914 return Builder.CreateBitCast(Insert, AllocaType, "tmp");
917 // Must be an element insertion.
918 assert(SV->getType() == VTy->getElementType());
919 uint64_t EltSize = TD.getTypeAllocSizeInBits(VTy->getElementType());
920 unsigned Elt = Offset/EltSize;
921 return Builder.CreateInsertElement(Old, SV,
922 ConstantInt::get(Type::getInt32Ty(SV->getContext()), Elt),
926 // If SV is a first-class aggregate value, insert each value recursively.
927 if (const StructType *ST = dyn_cast<StructType>(SV->getType())) {
928 const StructLayout &Layout = *TD.getStructLayout(ST);
929 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) {
930 Value *Elt = Builder.CreateExtractValue(SV, i, "tmp");
931 Old = ConvertScalar_InsertValue(Elt, Old,
932 Offset+Layout.getElementOffsetInBits(i),
938 if (const ArrayType *AT = dyn_cast<ArrayType>(SV->getType())) {
939 uint64_t EltSize = TD.getTypeAllocSizeInBits(AT->getElementType());
940 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
941 Value *Elt = Builder.CreateExtractValue(SV, i, "tmp");
942 Old = ConvertScalar_InsertValue(Elt, Old, Offset+i*EltSize, Builder);
947 // If SV is a float, convert it to the appropriate integer type.
948 // If it is a pointer, do the same.
949 unsigned SrcWidth = TD.getTypeSizeInBits(SV->getType());
950 unsigned DestWidth = TD.getTypeSizeInBits(AllocaType);
951 unsigned SrcStoreWidth = TD.getTypeStoreSizeInBits(SV->getType());
952 unsigned DestStoreWidth = TD.getTypeStoreSizeInBits(AllocaType);
953 if (SV->getType()->isFloatingPointTy() || SV->getType()->isVectorTy())
954 SV = Builder.CreateBitCast(SV,
955 IntegerType::get(SV->getContext(),SrcWidth), "tmp");
956 else if (SV->getType()->isPointerTy())
957 SV = Builder.CreatePtrToInt(SV, TD.getIntPtrType(SV->getContext()), "tmp");
959 // Zero extend or truncate the value if needed.
960 if (SV->getType() != AllocaType) {
961 if (SV->getType()->getPrimitiveSizeInBits() <
962 AllocaType->getPrimitiveSizeInBits())
963 SV = Builder.CreateZExt(SV, AllocaType, "tmp");
965 // Truncation may be needed if storing more than the alloca can hold
966 // (undefined behavior).
967 SV = Builder.CreateTrunc(SV, AllocaType, "tmp");
968 SrcWidth = DestWidth;
969 SrcStoreWidth = DestStoreWidth;
973 // If this is a big-endian system and the store is narrower than the
974 // full alloca type, we need to do a shift to get the right bits.
976 if (TD.isBigEndian()) {
977 // On big-endian machines, the lowest bit is stored at the bit offset
978 // from the pointer given by getTypeStoreSizeInBits. This matters for
979 // integers with a bitwidth that is not a multiple of 8.
980 ShAmt = DestStoreWidth - SrcStoreWidth - Offset;
985 // Note: we support negative bitwidths (with shr) which are not defined.
986 // We do this to support (f.e.) stores off the end of a structure where
987 // only some bits in the structure are set.
988 APInt Mask(APInt::getLowBitsSet(DestWidth, SrcWidth));
989 if (ShAmt > 0 && (unsigned)ShAmt < DestWidth) {
990 SV = Builder.CreateShl(SV, ConstantInt::get(SV->getType(),
993 } else if (ShAmt < 0 && (unsigned)-ShAmt < DestWidth) {
994 SV = Builder.CreateLShr(SV, ConstantInt::get(SV->getType(),
996 Mask = Mask.lshr(-ShAmt);
999 // Mask out the bits we are about to insert from the old value, and or
1001 if (SrcWidth != DestWidth) {
1002 assert(DestWidth > SrcWidth);
1003 Old = Builder.CreateAnd(Old, ConstantInt::get(Context, ~Mask), "mask");
1004 SV = Builder.CreateOr(Old, SV, "ins");
1010 //===----------------------------------------------------------------------===//
1012 //===----------------------------------------------------------------------===//
1015 bool SROA::runOnFunction(Function &F) {
1016 TD = getAnalysisIfAvailable<TargetData>();
1018 bool Changed = performPromotion(F);
1020 // FIXME: ScalarRepl currently depends on TargetData more than it
1021 // theoretically needs to. It should be refactored in order to support
1022 // target-independent IR. Until this is done, just skip the actual
1023 // scalar-replacement portion of this pass.
1024 if (!TD) return Changed;
1027 bool LocalChange = performScalarRepl(F);
1028 if (!LocalChange) break; // No need to repromote if no scalarrepl
1030 LocalChange = performPromotion(F);
1031 if (!LocalChange) break; // No need to re-scalarrepl if no promotion
1038 class AllocaPromoter : public LoadAndStorePromoter {
1041 AllocaPromoter(const SmallVectorImpl<Instruction*> &Insts, SSAUpdater &S)
1042 : LoadAndStorePromoter(Insts, S), AI(0) {}
1044 void run(AllocaInst *AI, const SmallVectorImpl<Instruction*> &Insts) {
1045 // Remember which alloca we're promoting (for isInstInList).
1047 LoadAndStorePromoter::run(Insts);
1048 AI->eraseFromParent();
1051 virtual bool isInstInList(Instruction *I,
1052 const SmallVectorImpl<Instruction*> &Insts) const {
1053 if (LoadInst *LI = dyn_cast<LoadInst>(I))
1054 return LI->getOperand(0) == AI;
1055 return cast<StoreInst>(I)->getPointerOperand() == AI;
1058 } // end anon namespace
1060 /// isSafeSelectToSpeculate - Select instructions that use an alloca and are
1061 /// subsequently loaded can be rewritten to load both input pointers and then
1062 /// select between the result, allowing the load of the alloca to be promoted.
1064 /// %P2 = select i1 %cond, i32* %Alloca, i32* %Other
1065 /// %V = load i32* %P2
1067 /// %V1 = load i32* %Alloca -> will be mem2reg'd
1068 /// %V2 = load i32* %Other
1069 /// %V = select i1 %cond, i32 %V1, i32 %V2
1071 /// We can do this to a select if its only uses are loads and if the operand to
1072 /// the select can be loaded unconditionally.
1073 static bool isSafeSelectToSpeculate(SelectInst *SI, const TargetData *TD) {
1074 bool TDerefable = SI->getTrueValue()->isDereferenceablePointer();
1075 bool FDerefable = SI->getFalseValue()->isDereferenceablePointer();
1077 for (Value::use_iterator UI = SI->use_begin(), UE = SI->use_end();
1079 LoadInst *LI = dyn_cast<LoadInst>(*UI);
1080 if (LI == 0 || LI->isVolatile()) return false;
1082 // Both operands to the select need to be dereferencable, either absolutely
1083 // (e.g. allocas) or at this point because we can see other accesses to it.
1084 if (!TDerefable && !isSafeToLoadUnconditionally(SI->getTrueValue(), LI,
1085 LI->getAlignment(), TD))
1087 if (!FDerefable && !isSafeToLoadUnconditionally(SI->getFalseValue(), LI,
1088 LI->getAlignment(), TD))
1095 /// isSafePHIToSpeculate - PHI instructions that use an alloca and are
1096 /// subsequently loaded can be rewritten to load both input pointers in the pred
1097 /// blocks and then PHI the results, allowing the load of the alloca to be
1100 /// %P2 = phi [i32* %Alloca, i32* %Other]
1101 /// %V = load i32* %P2
1103 /// %V1 = load i32* %Alloca -> will be mem2reg'd
1105 /// %V2 = load i32* %Other
1107 /// %V = phi [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 isSafePHIToSpeculate(PHINode *PN, const TargetData *TD) {
1112 // For now, we can only do this promotion if the load is in the same block as
1113 // the PHI, and if there are no stores between the phi and load.
1114 // TODO: Allow recursive phi users.
1115 // TODO: Allow stores.
1116 BasicBlock *BB = PN->getParent();
1117 unsigned MaxAlign = 0;
1118 for (Value::use_iterator UI = PN->use_begin(), UE = PN->use_end();
1120 LoadInst *LI = dyn_cast<LoadInst>(*UI);
1121 if (LI == 0 || LI->isVolatile()) return false;
1123 // For now we only allow loads in the same block as the PHI. This is a
1124 // common case that happens when instcombine merges two loads through a PHI.
1125 if (LI->getParent() != BB) return false;
1127 // Ensure that there are no instructions between the PHI and the load that
1129 for (BasicBlock::iterator BBI = PN; &*BBI != LI; ++BBI)
1130 if (BBI->mayWriteToMemory())
1133 MaxAlign = std::max(MaxAlign, LI->getAlignment());
1136 // Okay, we know that we have one or more loads in the same block as the PHI.
1137 // We can transform this if it is safe to push the loads into the predecessor
1138 // blocks. The only thing to watch out for is that we can't put a possibly
1139 // trapping load in the predecessor if it is a critical edge.
1140 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
1141 BasicBlock *Pred = PN->getIncomingBlock(i);
1143 // If the predecessor has a single successor, then the edge isn't critical.
1144 if (Pred->getTerminator()->getNumSuccessors() == 1)
1147 Value *InVal = PN->getIncomingValue(i);
1149 // If the InVal is an invoke in the pred, we can't put a load on the edge.
1150 if (InvokeInst *II = dyn_cast<InvokeInst>(InVal))
1151 if (II->getParent() == Pred)
1154 // If this pointer is always safe to load, or if we can prove that there is
1155 // already a load in the block, then we can move the load to the pred block.
1156 if (InVal->isDereferenceablePointer() ||
1157 isSafeToLoadUnconditionally(InVal, Pred->getTerminator(), MaxAlign, TD))
1167 /// tryToMakeAllocaBePromotable - This returns true if the alloca only has
1168 /// direct (non-volatile) loads and stores to it. If the alloca is close but
1169 /// not quite there, this will transform the code to allow promotion. As such,
1170 /// it is a non-pure predicate.
1171 static bool tryToMakeAllocaBePromotable(AllocaInst *AI, const TargetData *TD) {
1172 SetVector<Instruction*, SmallVector<Instruction*, 4>,
1173 SmallPtrSet<Instruction*, 4> > InstsToRewrite;
1175 for (Value::use_iterator UI = AI->use_begin(), UE = AI->use_end();
1178 if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
1179 if (LI->isVolatile())
1184 if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
1185 if (SI->getOperand(0) == AI || SI->isVolatile())
1186 return false; // Don't allow a store OF the AI, only INTO the AI.
1190 if (SelectInst *SI = dyn_cast<SelectInst>(U)) {
1191 // If the condition being selected on is a constant, fold the select, yes
1192 // this does (rarely) happen early on.
1193 if (ConstantInt *CI = dyn_cast<ConstantInt>(SI->getCondition())) {
1194 Value *Result = SI->getOperand(1+CI->isZero());
1195 SI->replaceAllUsesWith(Result);
1196 SI->eraseFromParent();
1198 // This is very rare and we just scrambled the use list of AI, start
1200 return tryToMakeAllocaBePromotable(AI, TD);
1203 // If it is safe to turn "load (select c, AI, ptr)" into a select of two
1204 // loads, then we can transform this by rewriting the select.
1205 if (!isSafeSelectToSpeculate(SI, TD))
1208 InstsToRewrite.insert(SI);
1212 if (PHINode *PN = dyn_cast<PHINode>(U)) {
1213 if (PN->use_empty()) { // Dead PHIs can be stripped.
1214 InstsToRewrite.insert(PN);
1218 // If it is safe to turn "load (phi [AI, ptr, ...])" into a PHI of loads
1219 // in the pred blocks, then we can transform this by rewriting the PHI.
1220 if (!isSafePHIToSpeculate(PN, TD))
1223 InstsToRewrite.insert(PN);
1230 // If there are no instructions to rewrite, then all uses are load/stores and
1232 if (InstsToRewrite.empty())
1235 // If we have instructions that need to be rewritten for this to be promotable
1236 // take care of it now.
1237 for (unsigned i = 0, e = InstsToRewrite.size(); i != e; ++i) {
1238 if (SelectInst *SI = dyn_cast<SelectInst>(InstsToRewrite[i])) {
1239 // Selects in InstsToRewrite only have load uses. Rewrite each as two
1240 // loads with a new select.
1241 while (!SI->use_empty()) {
1242 LoadInst *LI = cast<LoadInst>(SI->use_back());
1244 IRBuilder<> Builder(LI);
1245 LoadInst *TrueLoad =
1246 Builder.CreateLoad(SI->getTrueValue(), LI->getName()+".t");
1247 LoadInst *FalseLoad =
1248 Builder.CreateLoad(SI->getFalseValue(), LI->getName()+".t");
1250 // Transfer alignment and TBAA info if present.
1251 TrueLoad->setAlignment(LI->getAlignment());
1252 FalseLoad->setAlignment(LI->getAlignment());
1253 if (MDNode *Tag = LI->getMetadata(LLVMContext::MD_tbaa)) {
1254 TrueLoad->setMetadata(LLVMContext::MD_tbaa, Tag);
1255 FalseLoad->setMetadata(LLVMContext::MD_tbaa, Tag);
1258 Value *V = Builder.CreateSelect(SI->getCondition(), TrueLoad, FalseLoad);
1260 LI->replaceAllUsesWith(V);
1261 LI->eraseFromParent();
1264 // Now that all the loads are gone, the select is gone too.
1265 SI->eraseFromParent();
1269 // Otherwise, we have a PHI node which allows us to push the loads into the
1271 PHINode *PN = cast<PHINode>(InstsToRewrite[i]);
1272 if (PN->use_empty()) {
1273 PN->eraseFromParent();
1277 const Type *LoadTy = cast<PointerType>(PN->getType())->getElementType();
1278 PHINode *NewPN = PHINode::Create(LoadTy, PN->getNumIncomingValues(),
1279 PN->getName()+".ld", PN);
1281 // Get the TBAA tag and alignment to use from one of the loads. It doesn't
1282 // matter which one we get and if any differ, it doesn't matter.
1283 LoadInst *SomeLoad = cast<LoadInst>(PN->use_back());
1284 MDNode *TBAATag = SomeLoad->getMetadata(LLVMContext::MD_tbaa);
1285 unsigned Align = SomeLoad->getAlignment();
1287 // Rewrite all loads of the PN to use the new PHI.
1288 while (!PN->use_empty()) {
1289 LoadInst *LI = cast<LoadInst>(PN->use_back());
1290 LI->replaceAllUsesWith(NewPN);
1291 LI->eraseFromParent();
1294 // Inject loads into all of the pred blocks. Keep track of which blocks we
1295 // insert them into in case we have multiple edges from the same block.
1296 DenseMap<BasicBlock*, LoadInst*> InsertedLoads;
1298 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
1299 BasicBlock *Pred = PN->getIncomingBlock(i);
1300 LoadInst *&Load = InsertedLoads[Pred];
1302 Load = new LoadInst(PN->getIncomingValue(i),
1303 PN->getName() + "." + Pred->getName(),
1304 Pred->getTerminator());
1305 Load->setAlignment(Align);
1306 if (TBAATag) Load->setMetadata(LLVMContext::MD_tbaa, TBAATag);
1309 NewPN->addIncoming(Load, Pred);
1312 PN->eraseFromParent();
1320 bool SROA::performPromotion(Function &F) {
1321 std::vector<AllocaInst*> Allocas;
1322 DominatorTree *DT = 0;
1324 DT = &getAnalysis<DominatorTree>();
1326 BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function
1328 bool Changed = false;
1329 SmallVector<Instruction*, 64> Insts;
1333 // Find allocas that are safe to promote, by looking at all instructions in
1335 for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I)
1336 if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) // Is it an alloca?
1337 if (tryToMakeAllocaBePromotable(AI, TD))
1338 Allocas.push_back(AI);
1340 if (Allocas.empty()) break;
1343 PromoteMemToReg(Allocas, *DT);
1346 for (unsigned i = 0, e = Allocas.size(); i != e; ++i) {
1347 AllocaInst *AI = Allocas[i];
1349 // Build list of instructions to promote.
1350 for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end();
1352 Insts.push_back(cast<Instruction>(*UI));
1354 AllocaPromoter(Insts, SSA).run(AI, Insts);
1358 NumPromoted += Allocas.size();
1366 /// ShouldAttemptScalarRepl - Decide if an alloca is a good candidate for
1367 /// SROA. It must be a struct or array type with a small number of elements.
1368 static bool ShouldAttemptScalarRepl(AllocaInst *AI) {
1369 const Type *T = AI->getAllocatedType();
1370 // Do not promote any struct into more than 32 separate vars.
1371 if (const StructType *ST = dyn_cast<StructType>(T))
1372 return ST->getNumElements() <= 32;
1373 // Arrays are much less likely to be safe for SROA; only consider
1374 // them if they are very small.
1375 if (const ArrayType *AT = dyn_cast<ArrayType>(T))
1376 return AT->getNumElements() <= 8;
1381 // performScalarRepl - This algorithm is a simple worklist driven algorithm,
1382 // which runs on all of the malloc/alloca instructions in the function, removing
1383 // them if they are only used by getelementptr instructions.
1385 bool SROA::performScalarRepl(Function &F) {
1386 std::vector<AllocaInst*> WorkList;
1388 // Scan the entry basic block, adding allocas to the worklist.
1389 BasicBlock &BB = F.getEntryBlock();
1390 for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I)
1391 if (AllocaInst *A = dyn_cast<AllocaInst>(I))
1392 WorkList.push_back(A);
1394 // Process the worklist
1395 bool Changed = false;
1396 while (!WorkList.empty()) {
1397 AllocaInst *AI = WorkList.back();
1398 WorkList.pop_back();
1400 // Handle dead allocas trivially. These can be formed by SROA'ing arrays
1401 // with unused elements.
1402 if (AI->use_empty()) {
1403 AI->eraseFromParent();
1408 // If this alloca is impossible for us to promote, reject it early.
1409 if (AI->isArrayAllocation() || !AI->getAllocatedType()->isSized())
1412 // Check to see if this allocation is only modified by a memcpy/memmove from
1413 // a constant global. If this is the case, we can change all users to use
1414 // the constant global instead. This is commonly produced by the CFE by
1415 // constructs like "void foo() { int A[] = {1,2,3,4,5,6,7,8,9...}; }" if 'A'
1416 // is only subsequently read.
1417 if (MemTransferInst *TheCopy = isOnlyCopiedFromConstantGlobal(AI)) {
1418 DEBUG(dbgs() << "Found alloca equal to global: " << *AI << '\n');
1419 DEBUG(dbgs() << " memcpy = " << *TheCopy << '\n');
1420 Constant *TheSrc = cast<Constant>(TheCopy->getSource());
1421 AI->replaceAllUsesWith(ConstantExpr::getBitCast(TheSrc, AI->getType()));
1422 TheCopy->eraseFromParent(); // Don't mutate the global.
1423 AI->eraseFromParent();
1429 // Check to see if we can perform the core SROA transformation. We cannot
1430 // transform the allocation instruction if it is an array allocation
1431 // (allocations OF arrays are ok though), and an allocation of a scalar
1432 // value cannot be decomposed at all.
1433 uint64_t AllocaSize = TD->getTypeAllocSize(AI->getAllocatedType());
1435 // Do not promote [0 x %struct].
1436 if (AllocaSize == 0) continue;
1438 // Do not promote any struct whose size is too big.
1439 if (AllocaSize > SRThreshold) continue;
1441 // If the alloca looks like a good candidate for scalar replacement, and if
1442 // all its users can be transformed, then split up the aggregate into its
1443 // separate elements.
1444 if (ShouldAttemptScalarRepl(AI) && isSafeAllocaToScalarRepl(AI)) {
1445 DoScalarReplacement(AI, WorkList);
1450 // If we can turn this aggregate value (potentially with casts) into a
1451 // simple scalar value that can be mem2reg'd into a register value.
1452 // IsNotTrivial tracks whether this is something that mem2reg could have
1453 // promoted itself. If so, we don't want to transform it needlessly. Note
1454 // that we can't just check based on the type: the alloca may be of an i32
1455 // but that has pointer arithmetic to set byte 3 of it or something.
1456 if (AllocaInst *NewAI =
1457 ConvertToScalarInfo((unsigned)AllocaSize, *TD).TryConvert(AI)) {
1458 NewAI->takeName(AI);
1459 AI->eraseFromParent();
1465 // Otherwise, couldn't process this alloca.
1471 /// DoScalarReplacement - This alloca satisfied the isSafeAllocaToScalarRepl
1472 /// predicate, do SROA now.
1473 void SROA::DoScalarReplacement(AllocaInst *AI,
1474 std::vector<AllocaInst*> &WorkList) {
1475 DEBUG(dbgs() << "Found inst to SROA: " << *AI << '\n');
1476 SmallVector<AllocaInst*, 32> ElementAllocas;
1477 if (const StructType *ST = dyn_cast<StructType>(AI->getAllocatedType())) {
1478 ElementAllocas.reserve(ST->getNumContainedTypes());
1479 for (unsigned i = 0, e = ST->getNumContainedTypes(); i != e; ++i) {
1480 AllocaInst *NA = new AllocaInst(ST->getContainedType(i), 0,
1482 AI->getName() + "." + Twine(i), AI);
1483 ElementAllocas.push_back(NA);
1484 WorkList.push_back(NA); // Add to worklist for recursive processing
1487 const ArrayType *AT = cast<ArrayType>(AI->getAllocatedType());
1488 ElementAllocas.reserve(AT->getNumElements());
1489 const Type *ElTy = AT->getElementType();
1490 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
1491 AllocaInst *NA = new AllocaInst(ElTy, 0, AI->getAlignment(),
1492 AI->getName() + "." + Twine(i), AI);
1493 ElementAllocas.push_back(NA);
1494 WorkList.push_back(NA); // Add to worklist for recursive processing
1498 // Now that we have created the new alloca instructions, rewrite all the
1499 // uses of the old alloca.
1500 RewriteForScalarRepl(AI, AI, 0, ElementAllocas);
1502 // Now erase any instructions that were made dead while rewriting the alloca.
1503 DeleteDeadInstructions();
1504 AI->eraseFromParent();
1509 /// DeleteDeadInstructions - Erase instructions on the DeadInstrs list,
1510 /// recursively including all their operands that become trivially dead.
1511 void SROA::DeleteDeadInstructions() {
1512 while (!DeadInsts.empty()) {
1513 Instruction *I = cast<Instruction>(DeadInsts.pop_back_val());
1515 for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI)
1516 if (Instruction *U = dyn_cast<Instruction>(*OI)) {
1517 // Zero out the operand and see if it becomes trivially dead.
1518 // (But, don't add allocas to the dead instruction list -- they are
1519 // already on the worklist and will be deleted separately.)
1521 if (isInstructionTriviallyDead(U) && !isa<AllocaInst>(U))
1522 DeadInsts.push_back(U);
1525 I->eraseFromParent();
1529 /// isSafeForScalarRepl - Check if instruction I is a safe use with regard to
1530 /// performing scalar replacement of alloca AI. The results are flagged in
1531 /// the Info parameter. Offset indicates the position within AI that is
1532 /// referenced by this instruction.
1533 void SROA::isSafeForScalarRepl(Instruction *I, uint64_t Offset,
1535 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E; ++UI) {
1536 Instruction *User = cast<Instruction>(*UI);
1538 if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) {
1539 isSafeForScalarRepl(BC, Offset, Info);
1540 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
1541 uint64_t GEPOffset = Offset;
1542 isSafeGEP(GEPI, GEPOffset, Info);
1544 isSafeForScalarRepl(GEPI, GEPOffset, Info);
1545 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) {
1546 ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength());
1548 return MarkUnsafe(Info, User);
1549 isSafeMemAccess(Offset, Length->getZExtValue(), 0,
1550 UI.getOperandNo() == 0, Info, MI,
1551 true /*AllowWholeAccess*/);
1552 } else if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1553 if (LI->isVolatile())
1554 return MarkUnsafe(Info, User);
1555 const Type *LIType = LI->getType();
1556 isSafeMemAccess(Offset, TD->getTypeAllocSize(LIType),
1557 LIType, false, Info, LI, true /*AllowWholeAccess*/);
1558 Info.hasALoadOrStore = true;
1560 } else if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
1561 // Store is ok if storing INTO the pointer, not storing the pointer
1562 if (SI->isVolatile() || SI->getOperand(0) == I)
1563 return MarkUnsafe(Info, User);
1565 const Type *SIType = SI->getOperand(0)->getType();
1566 isSafeMemAccess(Offset, TD->getTypeAllocSize(SIType),
1567 SIType, true, Info, SI, true /*AllowWholeAccess*/);
1568 Info.hasALoadOrStore = true;
1569 } else if (isa<PHINode>(User) || isa<SelectInst>(User)) {
1570 isSafePHISelectUseForScalarRepl(User, Offset, Info);
1572 return MarkUnsafe(Info, User);
1574 if (Info.isUnsafe) return;
1579 /// isSafePHIUseForScalarRepl - If we see a PHI node or select using a pointer
1580 /// derived from the alloca, we can often still split the alloca into elements.
1581 /// This is useful if we have a large alloca where one element is phi'd
1582 /// together somewhere: we can SRoA and promote all the other elements even if
1583 /// we end up not being able to promote this one.
1585 /// All we require is that the uses of the PHI do not index into other parts of
1586 /// the alloca. The most important use case for this is single load and stores
1587 /// that are PHI'd together, which can happen due to code sinking.
1588 void SROA::isSafePHISelectUseForScalarRepl(Instruction *I, uint64_t Offset,
1590 // If we've already checked this PHI, don't do it again.
1591 if (PHINode *PN = dyn_cast<PHINode>(I))
1592 if (!Info.CheckedPHIs.insert(PN))
1595 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E; ++UI) {
1596 Instruction *User = cast<Instruction>(*UI);
1598 if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) {
1599 isSafePHISelectUseForScalarRepl(BC, Offset, Info);
1600 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
1601 // Only allow "bitcast" GEPs for simplicity. We could generalize this,
1602 // but would have to prove that we're staying inside of an element being
1604 if (!GEPI->hasAllZeroIndices())
1605 return MarkUnsafe(Info, User);
1606 isSafePHISelectUseForScalarRepl(GEPI, Offset, Info);
1607 } else if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1608 if (LI->isVolatile())
1609 return MarkUnsafe(Info, User);
1610 const Type *LIType = LI->getType();
1611 isSafeMemAccess(Offset, TD->getTypeAllocSize(LIType),
1612 LIType, false, Info, LI, false /*AllowWholeAccess*/);
1613 Info.hasALoadOrStore = true;
1615 } else if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
1616 // Store is ok if storing INTO the pointer, not storing the pointer
1617 if (SI->isVolatile() || SI->getOperand(0) == I)
1618 return MarkUnsafe(Info, User);
1620 const Type *SIType = SI->getOperand(0)->getType();
1621 isSafeMemAccess(Offset, TD->getTypeAllocSize(SIType),
1622 SIType, true, Info, SI, false /*AllowWholeAccess*/);
1623 Info.hasALoadOrStore = true;
1624 } else if (isa<PHINode>(User) || isa<SelectInst>(User)) {
1625 isSafePHISelectUseForScalarRepl(User, Offset, Info);
1627 return MarkUnsafe(Info, User);
1629 if (Info.isUnsafe) return;
1633 /// isSafeGEP - Check if a GEP instruction can be handled for scalar
1634 /// replacement. It is safe when all the indices are constant, in-bounds
1635 /// references, and when the resulting offset corresponds to an element within
1636 /// the alloca type. The results are flagged in the Info parameter. Upon
1637 /// return, Offset is adjusted as specified by the GEP indices.
1638 void SROA::isSafeGEP(GetElementPtrInst *GEPI,
1639 uint64_t &Offset, AllocaInfo &Info) {
1640 gep_type_iterator GEPIt = gep_type_begin(GEPI), E = gep_type_end(GEPI);
1644 // Walk through the GEP type indices, checking the types that this indexes
1646 for (; GEPIt != E; ++GEPIt) {
1647 // Ignore struct elements, no extra checking needed for these.
1648 if ((*GEPIt)->isStructTy())
1651 ConstantInt *IdxVal = dyn_cast<ConstantInt>(GEPIt.getOperand());
1653 return MarkUnsafe(Info, GEPI);
1656 // Compute the offset due to this GEP and check if the alloca has a
1657 // component element at that offset.
1658 SmallVector<Value*, 8> Indices(GEPI->op_begin() + 1, GEPI->op_end());
1659 Offset += TD->getIndexedOffset(GEPI->getPointerOperandType(),
1660 &Indices[0], Indices.size());
1661 if (!TypeHasComponent(Info.AI->getAllocatedType(), Offset, 0))
1662 MarkUnsafe(Info, GEPI);
1665 /// isHomogeneousAggregate - Check if type T is a struct or array containing
1666 /// elements of the same type (which is always true for arrays). If so,
1667 /// return true with NumElts and EltTy set to the number of elements and the
1668 /// element type, respectively.
1669 static bool isHomogeneousAggregate(const Type *T, unsigned &NumElts,
1670 const Type *&EltTy) {
1671 if (const ArrayType *AT = dyn_cast<ArrayType>(T)) {
1672 NumElts = AT->getNumElements();
1673 EltTy = (NumElts == 0 ? 0 : AT->getElementType());
1676 if (const StructType *ST = dyn_cast<StructType>(T)) {
1677 NumElts = ST->getNumContainedTypes();
1678 EltTy = (NumElts == 0 ? 0 : ST->getContainedType(0));
1679 for (unsigned n = 1; n < NumElts; ++n) {
1680 if (ST->getContainedType(n) != EltTy)
1688 /// isCompatibleAggregate - Check if T1 and T2 are either the same type or are
1689 /// "homogeneous" aggregates with the same element type and number of elements.
1690 static bool isCompatibleAggregate(const Type *T1, const Type *T2) {
1694 unsigned NumElts1, NumElts2;
1695 const Type *EltTy1, *EltTy2;
1696 if (isHomogeneousAggregate(T1, NumElts1, EltTy1) &&
1697 isHomogeneousAggregate(T2, NumElts2, EltTy2) &&
1698 NumElts1 == NumElts2 &&
1705 /// isSafeMemAccess - Check if a load/store/memcpy operates on the entire AI
1706 /// alloca or has an offset and size that corresponds to a component element
1707 /// within it. The offset checked here may have been formed from a GEP with a
1708 /// pointer bitcasted to a different type.
1710 /// If AllowWholeAccess is true, then this allows uses of the entire alloca as a
1711 /// unit. If false, it only allows accesses known to be in a single element.
1712 void SROA::isSafeMemAccess(uint64_t Offset, uint64_t MemSize,
1713 const Type *MemOpType, bool isStore,
1714 AllocaInfo &Info, Instruction *TheAccess,
1715 bool AllowWholeAccess) {
1716 // Check if this is a load/store of the entire alloca.
1717 if (Offset == 0 && AllowWholeAccess &&
1718 MemSize == TD->getTypeAllocSize(Info.AI->getAllocatedType())) {
1719 // This can be safe for MemIntrinsics (where MemOpType is 0) and integer
1720 // loads/stores (which are essentially the same as the MemIntrinsics with
1721 // regard to copying padding between elements). But, if an alloca is
1722 // flagged as both a source and destination of such operations, we'll need
1723 // to check later for padding between elements.
1724 if (!MemOpType || MemOpType->isIntegerTy()) {
1726 Info.isMemCpyDst = true;
1728 Info.isMemCpySrc = true;
1731 // This is also safe for references using a type that is compatible with
1732 // the type of the alloca, so that loads/stores can be rewritten using
1733 // insertvalue/extractvalue.
1734 if (isCompatibleAggregate(MemOpType, Info.AI->getAllocatedType())) {
1735 Info.hasSubelementAccess = true;
1739 // Check if the offset/size correspond to a component within the alloca type.
1740 const Type *T = Info.AI->getAllocatedType();
1741 if (TypeHasComponent(T, Offset, MemSize)) {
1742 Info.hasSubelementAccess = true;
1746 return MarkUnsafe(Info, TheAccess);
1749 /// TypeHasComponent - Return true if T has a component type with the
1750 /// specified offset and size. If Size is zero, do not check the size.
1751 bool SROA::TypeHasComponent(const Type *T, uint64_t Offset, uint64_t Size) {
1754 if (const StructType *ST = dyn_cast<StructType>(T)) {
1755 const StructLayout *Layout = TD->getStructLayout(ST);
1756 unsigned EltIdx = Layout->getElementContainingOffset(Offset);
1757 EltTy = ST->getContainedType(EltIdx);
1758 EltSize = TD->getTypeAllocSize(EltTy);
1759 Offset -= Layout->getElementOffset(EltIdx);
1760 } else if (const ArrayType *AT = dyn_cast<ArrayType>(T)) {
1761 EltTy = AT->getElementType();
1762 EltSize = TD->getTypeAllocSize(EltTy);
1763 if (Offset >= AT->getNumElements() * EltSize)
1769 if (Offset == 0 && (Size == 0 || EltSize == Size))
1771 // Check if the component spans multiple elements.
1772 if (Offset + Size > EltSize)
1774 return TypeHasComponent(EltTy, Offset, Size);
1777 /// RewriteForScalarRepl - Alloca AI is being split into NewElts, so rewrite
1778 /// the instruction I, which references it, to use the separate elements.
1779 /// Offset indicates the position within AI that is referenced by this
1781 void SROA::RewriteForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset,
1782 SmallVector<AllocaInst*, 32> &NewElts) {
1783 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E;) {
1784 Use &TheUse = UI.getUse();
1785 Instruction *User = cast<Instruction>(*UI++);
1787 if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) {
1788 RewriteBitCast(BC, AI, Offset, NewElts);
1792 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
1793 RewriteGEP(GEPI, AI, Offset, NewElts);
1797 if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) {
1798 ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength());
1799 uint64_t MemSize = Length->getZExtValue();
1801 MemSize == TD->getTypeAllocSize(AI->getAllocatedType()))
1802 RewriteMemIntrinUserOfAlloca(MI, I, AI, NewElts);
1803 // Otherwise the intrinsic can only touch a single element and the
1804 // address operand will be updated, so nothing else needs to be done.
1808 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1809 const Type *LIType = LI->getType();
1811 if (isCompatibleAggregate(LIType, AI->getAllocatedType())) {
1813 // %res = load { i32, i32 }* %alloc
1815 // %load.0 = load i32* %alloc.0
1816 // %insert.0 insertvalue { i32, i32 } zeroinitializer, i32 %load.0, 0
1817 // %load.1 = load i32* %alloc.1
1818 // %insert = insertvalue { i32, i32 } %insert.0, i32 %load.1, 1
1819 // (Also works for arrays instead of structs)
1820 Value *Insert = UndefValue::get(LIType);
1821 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
1822 Value *Load = new LoadInst(NewElts[i], "load", LI);
1823 Insert = InsertValueInst::Create(Insert, Load, i, "insert", LI);
1825 LI->replaceAllUsesWith(Insert);
1826 DeadInsts.push_back(LI);
1827 } else if (LIType->isIntegerTy() &&
1828 TD->getTypeAllocSize(LIType) ==
1829 TD->getTypeAllocSize(AI->getAllocatedType())) {
1830 // If this is a load of the entire alloca to an integer, rewrite it.
1831 RewriteLoadUserOfWholeAlloca(LI, AI, NewElts);
1836 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
1837 Value *Val = SI->getOperand(0);
1838 const Type *SIType = Val->getType();
1839 if (isCompatibleAggregate(SIType, AI->getAllocatedType())) {
1841 // store { i32, i32 } %val, { i32, i32 }* %alloc
1843 // %val.0 = extractvalue { i32, i32 } %val, 0
1844 // store i32 %val.0, i32* %alloc.0
1845 // %val.1 = extractvalue { i32, i32 } %val, 1
1846 // store i32 %val.1, i32* %alloc.1
1847 // (Also works for arrays instead of structs)
1848 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
1849 Value *Extract = ExtractValueInst::Create(Val, i, Val->getName(), SI);
1850 new StoreInst(Extract, NewElts[i], SI);
1852 DeadInsts.push_back(SI);
1853 } else if (SIType->isIntegerTy() &&
1854 TD->getTypeAllocSize(SIType) ==
1855 TD->getTypeAllocSize(AI->getAllocatedType())) {
1856 // If this is a store of the entire alloca from an integer, rewrite it.
1857 RewriteStoreUserOfWholeAlloca(SI, AI, NewElts);
1862 if (isa<SelectInst>(User) || isa<PHINode>(User)) {
1863 // If we have a PHI user of the alloca itself (as opposed to a GEP or
1864 // bitcast) we have to rewrite it. GEP and bitcast uses will be RAUW'd to
1866 if (!isa<AllocaInst>(I)) continue;
1868 assert(Offset == 0 && NewElts[0] &&
1869 "Direct alloca use should have a zero offset");
1871 // If we have a use of the alloca, we know the derived uses will be
1872 // utilizing just the first element of the scalarized result. Insert a
1873 // bitcast of the first alloca before the user as required.
1874 AllocaInst *NewAI = NewElts[0];
1875 BitCastInst *BCI = new BitCastInst(NewAI, AI->getType(), "", NewAI);
1876 NewAI->moveBefore(BCI);
1883 /// RewriteBitCast - Update a bitcast reference to the alloca being replaced
1884 /// and recursively continue updating all of its uses.
1885 void SROA::RewriteBitCast(BitCastInst *BC, AllocaInst *AI, uint64_t Offset,
1886 SmallVector<AllocaInst*, 32> &NewElts) {
1887 RewriteForScalarRepl(BC, AI, Offset, NewElts);
1888 if (BC->getOperand(0) != AI)
1891 // The bitcast references the original alloca. Replace its uses with
1892 // references to the first new element alloca.
1893 Instruction *Val = NewElts[0];
1894 if (Val->getType() != BC->getDestTy()) {
1895 Val = new BitCastInst(Val, BC->getDestTy(), "", BC);
1898 BC->replaceAllUsesWith(Val);
1899 DeadInsts.push_back(BC);
1902 /// FindElementAndOffset - Return the index of the element containing Offset
1903 /// within the specified type, which must be either a struct or an array.
1904 /// Sets T to the type of the element and Offset to the offset within that
1905 /// element. IdxTy is set to the type of the index result to be used in a
1906 /// GEP instruction.
1907 uint64_t SROA::FindElementAndOffset(const Type *&T, uint64_t &Offset,
1908 const Type *&IdxTy) {
1910 if (const StructType *ST = dyn_cast<StructType>(T)) {
1911 const StructLayout *Layout = TD->getStructLayout(ST);
1912 Idx = Layout->getElementContainingOffset(Offset);
1913 T = ST->getContainedType(Idx);
1914 Offset -= Layout->getElementOffset(Idx);
1915 IdxTy = Type::getInt32Ty(T->getContext());
1918 const ArrayType *AT = cast<ArrayType>(T);
1919 T = AT->getElementType();
1920 uint64_t EltSize = TD->getTypeAllocSize(T);
1921 Idx = Offset / EltSize;
1922 Offset -= Idx * EltSize;
1923 IdxTy = Type::getInt64Ty(T->getContext());
1927 /// RewriteGEP - Check if this GEP instruction moves the pointer across
1928 /// elements of the alloca that are being split apart, and if so, rewrite
1929 /// the GEP to be relative to the new element.
1930 void SROA::RewriteGEP(GetElementPtrInst *GEPI, AllocaInst *AI, uint64_t Offset,
1931 SmallVector<AllocaInst*, 32> &NewElts) {
1932 uint64_t OldOffset = Offset;
1933 SmallVector<Value*, 8> Indices(GEPI->op_begin() + 1, GEPI->op_end());
1934 Offset += TD->getIndexedOffset(GEPI->getPointerOperandType(),
1935 &Indices[0], Indices.size());
1937 RewriteForScalarRepl(GEPI, AI, Offset, NewElts);
1939 const Type *T = AI->getAllocatedType();
1941 uint64_t OldIdx = FindElementAndOffset(T, OldOffset, IdxTy);
1942 if (GEPI->getOperand(0) == AI)
1943 OldIdx = ~0ULL; // Force the GEP to be rewritten.
1945 T = AI->getAllocatedType();
1946 uint64_t EltOffset = Offset;
1947 uint64_t Idx = FindElementAndOffset(T, EltOffset, IdxTy);
1949 // If this GEP does not move the pointer across elements of the alloca
1950 // being split, then it does not needs to be rewritten.
1954 const Type *i32Ty = Type::getInt32Ty(AI->getContext());
1955 SmallVector<Value*, 8> NewArgs;
1956 NewArgs.push_back(Constant::getNullValue(i32Ty));
1957 while (EltOffset != 0) {
1958 uint64_t EltIdx = FindElementAndOffset(T, EltOffset, IdxTy);
1959 NewArgs.push_back(ConstantInt::get(IdxTy, EltIdx));
1961 Instruction *Val = NewElts[Idx];
1962 if (NewArgs.size() > 1) {
1963 Val = GetElementPtrInst::CreateInBounds(Val, NewArgs.begin(),
1964 NewArgs.end(), "", GEPI);
1965 Val->takeName(GEPI);
1967 if (Val->getType() != GEPI->getType())
1968 Val = new BitCastInst(Val, GEPI->getType(), Val->getName(), GEPI);
1969 GEPI->replaceAllUsesWith(Val);
1970 DeadInsts.push_back(GEPI);
1973 /// RewriteMemIntrinUserOfAlloca - MI is a memcpy/memset/memmove from or to AI.
1974 /// Rewrite it to copy or set the elements of the scalarized memory.
1975 void SROA::RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *Inst,
1977 SmallVector<AllocaInst*, 32> &NewElts) {
1978 // If this is a memcpy/memmove, construct the other pointer as the
1979 // appropriate type. The "Other" pointer is the pointer that goes to memory
1980 // that doesn't have anything to do with the alloca that we are promoting. For
1981 // memset, this Value* stays null.
1982 Value *OtherPtr = 0;
1983 unsigned MemAlignment = MI->getAlignment();
1984 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(MI)) { // memmove/memcopy
1985 if (Inst == MTI->getRawDest())
1986 OtherPtr = MTI->getRawSource();
1988 assert(Inst == MTI->getRawSource());
1989 OtherPtr = MTI->getRawDest();
1993 // If there is an other pointer, we want to convert it to the same pointer
1994 // type as AI has, so we can GEP through it safely.
1996 unsigned AddrSpace =
1997 cast<PointerType>(OtherPtr->getType())->getAddressSpace();
1999 // Remove bitcasts and all-zero GEPs from OtherPtr. This is an
2000 // optimization, but it's also required to detect the corner case where
2001 // both pointer operands are referencing the same memory, and where
2002 // OtherPtr may be a bitcast or GEP that currently being rewritten. (This
2003 // function is only called for mem intrinsics that access the whole
2004 // aggregate, so non-zero GEPs are not an issue here.)
2005 OtherPtr = OtherPtr->stripPointerCasts();
2007 // Copying the alloca to itself is a no-op: just delete it.
2008 if (OtherPtr == AI || OtherPtr == NewElts[0]) {
2009 // This code will run twice for a no-op memcpy -- once for each operand.
2010 // Put only one reference to MI on the DeadInsts list.
2011 for (SmallVector<Value*, 32>::const_iterator I = DeadInsts.begin(),
2012 E = DeadInsts.end(); I != E; ++I)
2013 if (*I == MI) return;
2014 DeadInsts.push_back(MI);
2018 // If the pointer is not the right type, insert a bitcast to the right
2021 PointerType::get(AI->getType()->getElementType(), AddrSpace);
2023 if (OtherPtr->getType() != NewTy)
2024 OtherPtr = new BitCastInst(OtherPtr, NewTy, OtherPtr->getName(), MI);
2027 // Process each element of the aggregate.
2028 bool SROADest = MI->getRawDest() == Inst;
2030 Constant *Zero = Constant::getNullValue(Type::getInt32Ty(MI->getContext()));
2032 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
2033 // If this is a memcpy/memmove, emit a GEP of the other element address.
2034 Value *OtherElt = 0;
2035 unsigned OtherEltAlign = MemAlignment;
2038 Value *Idx[2] = { Zero,
2039 ConstantInt::get(Type::getInt32Ty(MI->getContext()), i) };
2040 OtherElt = GetElementPtrInst::CreateInBounds(OtherPtr, Idx, Idx + 2,
2041 OtherPtr->getName()+"."+Twine(i),
2044 const PointerType *OtherPtrTy = cast<PointerType>(OtherPtr->getType());
2045 const Type *OtherTy = OtherPtrTy->getElementType();
2046 if (const StructType *ST = dyn_cast<StructType>(OtherTy)) {
2047 EltOffset = TD->getStructLayout(ST)->getElementOffset(i);
2049 const Type *EltTy = cast<SequentialType>(OtherTy)->getElementType();
2050 EltOffset = TD->getTypeAllocSize(EltTy)*i;
2053 // The alignment of the other pointer is the guaranteed alignment of the
2054 // element, which is affected by both the known alignment of the whole
2055 // mem intrinsic and the alignment of the element. If the alignment of
2056 // the memcpy (f.e.) is 32 but the element is at a 4-byte offset, then the
2057 // known alignment is just 4 bytes.
2058 OtherEltAlign = (unsigned)MinAlign(OtherEltAlign, EltOffset);
2061 Value *EltPtr = NewElts[i];
2062 const Type *EltTy = cast<PointerType>(EltPtr->getType())->getElementType();
2064 // If we got down to a scalar, insert a load or store as appropriate.
2065 if (EltTy->isSingleValueType()) {
2066 if (isa<MemTransferInst>(MI)) {
2068 // From Other to Alloca.
2069 Value *Elt = new LoadInst(OtherElt, "tmp", false, OtherEltAlign, MI);
2070 new StoreInst(Elt, EltPtr, MI);
2072 // From Alloca to Other.
2073 Value *Elt = new LoadInst(EltPtr, "tmp", MI);
2074 new StoreInst(Elt, OtherElt, false, OtherEltAlign, MI);
2078 assert(isa<MemSetInst>(MI));
2080 // If the stored element is zero (common case), just store a null
2083 if (ConstantInt *CI = dyn_cast<ConstantInt>(MI->getArgOperand(1))) {
2085 StoreVal = Constant::getNullValue(EltTy); // 0.0, null, 0, <0,0>
2087 // If EltTy is a vector type, get the element type.
2088 const Type *ValTy = EltTy->getScalarType();
2090 // Construct an integer with the right value.
2091 unsigned EltSize = TD->getTypeSizeInBits(ValTy);
2092 APInt OneVal(EltSize, CI->getZExtValue());
2093 APInt TotalVal(OneVal);
2095 for (unsigned i = 0; 8*i < EltSize; ++i) {
2096 TotalVal = TotalVal.shl(8);
2100 // Convert the integer value to the appropriate type.
2101 StoreVal = ConstantInt::get(CI->getContext(), TotalVal);
2102 if (ValTy->isPointerTy())
2103 StoreVal = ConstantExpr::getIntToPtr(StoreVal, ValTy);
2104 else if (ValTy->isFloatingPointTy())
2105 StoreVal = ConstantExpr::getBitCast(StoreVal, ValTy);
2106 assert(StoreVal->getType() == ValTy && "Type mismatch!");
2108 // If the requested value was a vector constant, create it.
2109 if (EltTy != ValTy) {
2110 unsigned NumElts = cast<VectorType>(ValTy)->getNumElements();
2111 SmallVector<Constant*, 16> Elts(NumElts, StoreVal);
2112 StoreVal = ConstantVector::get(Elts);
2115 new StoreInst(StoreVal, EltPtr, MI);
2118 // Otherwise, if we're storing a byte variable, use a memset call for
2122 unsigned EltSize = TD->getTypeAllocSize(EltTy);
2124 IRBuilder<> Builder(MI);
2126 // Finally, insert the meminst for this element.
2127 if (isa<MemSetInst>(MI)) {
2128 Builder.CreateMemSet(EltPtr, MI->getArgOperand(1), EltSize,
2131 assert(isa<MemTransferInst>(MI));
2132 Value *Dst = SROADest ? EltPtr : OtherElt; // Dest ptr
2133 Value *Src = SROADest ? OtherElt : EltPtr; // Src ptr
2135 if (isa<MemCpyInst>(MI))
2136 Builder.CreateMemCpy(Dst, Src, EltSize, OtherEltAlign,MI->isVolatile());
2138 Builder.CreateMemMove(Dst, Src, EltSize,OtherEltAlign,MI->isVolatile());
2141 DeadInsts.push_back(MI);
2144 /// RewriteStoreUserOfWholeAlloca - We found a store of an integer that
2145 /// overwrites the entire allocation. Extract out the pieces of the stored
2146 /// integer and store them individually.
2147 void SROA::RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocaInst *AI,
2148 SmallVector<AllocaInst*, 32> &NewElts){
2149 // Extract each element out of the integer according to its structure offset
2150 // and store the element value to the individual alloca.
2151 Value *SrcVal = SI->getOperand(0);
2152 const Type *AllocaEltTy = AI->getAllocatedType();
2153 uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy);
2155 IRBuilder<> Builder(SI);
2157 // Handle tail padding by extending the operand
2158 if (TD->getTypeSizeInBits(SrcVal->getType()) != AllocaSizeBits)
2159 SrcVal = Builder.CreateZExt(SrcVal,
2160 IntegerType::get(SI->getContext(), AllocaSizeBits));
2162 DEBUG(dbgs() << "PROMOTING STORE TO WHOLE ALLOCA: " << *AI << '\n' << *SI
2165 // There are two forms here: AI could be an array or struct. Both cases
2166 // have different ways to compute the element offset.
2167 if (const StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) {
2168 const StructLayout *Layout = TD->getStructLayout(EltSTy);
2170 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
2171 // Get the number of bits to shift SrcVal to get the value.
2172 const Type *FieldTy = EltSTy->getElementType(i);
2173 uint64_t Shift = Layout->getElementOffsetInBits(i);
2175 if (TD->isBigEndian())
2176 Shift = AllocaSizeBits-Shift-TD->getTypeAllocSizeInBits(FieldTy);
2178 Value *EltVal = SrcVal;
2180 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift);
2181 EltVal = Builder.CreateLShr(EltVal, ShiftVal, "sroa.store.elt");
2184 // Truncate down to an integer of the right size.
2185 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy);
2187 // Ignore zero sized fields like {}, they obviously contain no data.
2188 if (FieldSizeBits == 0) continue;
2190 if (FieldSizeBits != AllocaSizeBits)
2191 EltVal = Builder.CreateTrunc(EltVal,
2192 IntegerType::get(SI->getContext(), FieldSizeBits));
2193 Value *DestField = NewElts[i];
2194 if (EltVal->getType() == FieldTy) {
2195 // Storing to an integer field of this size, just do it.
2196 } else if (FieldTy->isFloatingPointTy() || FieldTy->isVectorTy()) {
2197 // Bitcast to the right element type (for fp/vector values).
2198 EltVal = Builder.CreateBitCast(EltVal, FieldTy);
2200 // Otherwise, bitcast the dest pointer (for aggregates).
2201 DestField = Builder.CreateBitCast(DestField,
2202 PointerType::getUnqual(EltVal->getType()));
2204 new StoreInst(EltVal, DestField, SI);
2208 const ArrayType *ATy = cast<ArrayType>(AllocaEltTy);
2209 const Type *ArrayEltTy = ATy->getElementType();
2210 uint64_t ElementOffset = TD->getTypeAllocSizeInBits(ArrayEltTy);
2211 uint64_t ElementSizeBits = TD->getTypeSizeInBits(ArrayEltTy);
2215 if (TD->isBigEndian())
2216 Shift = AllocaSizeBits-ElementOffset;
2220 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
2221 // Ignore zero sized fields like {}, they obviously contain no data.
2222 if (ElementSizeBits == 0) continue;
2224 Value *EltVal = SrcVal;
2226 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift);
2227 EltVal = Builder.CreateLShr(EltVal, ShiftVal, "sroa.store.elt");
2230 // Truncate down to an integer of the right size.
2231 if (ElementSizeBits != AllocaSizeBits)
2232 EltVal = Builder.CreateTrunc(EltVal,
2233 IntegerType::get(SI->getContext(),
2235 Value *DestField = NewElts[i];
2236 if (EltVal->getType() == ArrayEltTy) {
2237 // Storing to an integer field of this size, just do it.
2238 } else if (ArrayEltTy->isFloatingPointTy() ||
2239 ArrayEltTy->isVectorTy()) {
2240 // Bitcast to the right element type (for fp/vector values).
2241 EltVal = Builder.CreateBitCast(EltVal, ArrayEltTy);
2243 // Otherwise, bitcast the dest pointer (for aggregates).
2244 DestField = Builder.CreateBitCast(DestField,
2245 PointerType::getUnqual(EltVal->getType()));
2247 new StoreInst(EltVal, DestField, SI);
2249 if (TD->isBigEndian())
2250 Shift -= ElementOffset;
2252 Shift += ElementOffset;
2256 DeadInsts.push_back(SI);
2259 /// RewriteLoadUserOfWholeAlloca - We found a load of the entire allocation to
2260 /// an integer. Load the individual pieces to form the aggregate value.
2261 void SROA::RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocaInst *AI,
2262 SmallVector<AllocaInst*, 32> &NewElts) {
2263 // Extract each element out of the NewElts according to its structure offset
2264 // and form the result value.
2265 const Type *AllocaEltTy = AI->getAllocatedType();
2266 uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy);
2268 DEBUG(dbgs() << "PROMOTING LOAD OF WHOLE ALLOCA: " << *AI << '\n' << *LI
2271 // There are two forms here: AI could be an array or struct. Both cases
2272 // have different ways to compute the element offset.
2273 const StructLayout *Layout = 0;
2274 uint64_t ArrayEltBitOffset = 0;
2275 if (const StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) {
2276 Layout = TD->getStructLayout(EltSTy);
2278 const Type *ArrayEltTy = cast<ArrayType>(AllocaEltTy)->getElementType();
2279 ArrayEltBitOffset = TD->getTypeAllocSizeInBits(ArrayEltTy);
2283 Constant::getNullValue(IntegerType::get(LI->getContext(), AllocaSizeBits));
2285 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
2286 // Load the value from the alloca. If the NewElt is an aggregate, cast
2287 // the pointer to an integer of the same size before doing the load.
2288 Value *SrcField = NewElts[i];
2289 const Type *FieldTy =
2290 cast<PointerType>(SrcField->getType())->getElementType();
2291 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy);
2293 // Ignore zero sized fields like {}, they obviously contain no data.
2294 if (FieldSizeBits == 0) continue;
2296 const IntegerType *FieldIntTy = IntegerType::get(LI->getContext(),
2298 if (!FieldTy->isIntegerTy() && !FieldTy->isFloatingPointTy() &&
2299 !FieldTy->isVectorTy())
2300 SrcField = new BitCastInst(SrcField,
2301 PointerType::getUnqual(FieldIntTy),
2303 SrcField = new LoadInst(SrcField, "sroa.load.elt", LI);
2305 // If SrcField is a fp or vector of the right size but that isn't an
2306 // integer type, bitcast to an integer so we can shift it.
2307 if (SrcField->getType() != FieldIntTy)
2308 SrcField = new BitCastInst(SrcField, FieldIntTy, "", LI);
2310 // Zero extend the field to be the same size as the final alloca so that
2311 // we can shift and insert it.
2312 if (SrcField->getType() != ResultVal->getType())
2313 SrcField = new ZExtInst(SrcField, ResultVal->getType(), "", LI);
2315 // Determine the number of bits to shift SrcField.
2317 if (Layout) // Struct case.
2318 Shift = Layout->getElementOffsetInBits(i);
2320 Shift = i*ArrayEltBitOffset;
2322 if (TD->isBigEndian())
2323 Shift = AllocaSizeBits-Shift-FieldIntTy->getBitWidth();
2326 Value *ShiftVal = ConstantInt::get(SrcField->getType(), Shift);
2327 SrcField = BinaryOperator::CreateShl(SrcField, ShiftVal, "", LI);
2330 // Don't create an 'or x, 0' on the first iteration.
2331 if (!isa<Constant>(ResultVal) ||
2332 !cast<Constant>(ResultVal)->isNullValue())
2333 ResultVal = BinaryOperator::CreateOr(SrcField, ResultVal, "", LI);
2335 ResultVal = SrcField;
2338 // Handle tail padding by truncating the result
2339 if (TD->getTypeSizeInBits(LI->getType()) != AllocaSizeBits)
2340 ResultVal = new TruncInst(ResultVal, LI->getType(), "", LI);
2342 LI->replaceAllUsesWith(ResultVal);
2343 DeadInsts.push_back(LI);
2346 /// HasPadding - Return true if the specified type has any structure or
2347 /// alignment padding in between the elements that would be split apart
2348 /// by SROA; return false otherwise.
2349 static bool HasPadding(const Type *Ty, const TargetData &TD) {
2350 if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
2351 Ty = ATy->getElementType();
2352 return TD.getTypeSizeInBits(Ty) != TD.getTypeAllocSizeInBits(Ty);
2355 // SROA currently handles only Arrays and Structs.
2356 const StructType *STy = cast<StructType>(Ty);
2357 const StructLayout *SL = TD.getStructLayout(STy);
2358 unsigned PrevFieldBitOffset = 0;
2359 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
2360 unsigned FieldBitOffset = SL->getElementOffsetInBits(i);
2362 // Check to see if there is any padding between this element and the
2365 unsigned PrevFieldEnd =
2366 PrevFieldBitOffset+TD.getTypeSizeInBits(STy->getElementType(i-1));
2367 if (PrevFieldEnd < FieldBitOffset)
2370 PrevFieldBitOffset = FieldBitOffset;
2372 // Check for tail padding.
2373 if (unsigned EltCount = STy->getNumElements()) {
2374 unsigned PrevFieldEnd = PrevFieldBitOffset +
2375 TD.getTypeSizeInBits(STy->getElementType(EltCount-1));
2376 if (PrevFieldEnd < SL->getSizeInBits())
2382 /// isSafeStructAllocaToScalarRepl - Check to see if the specified allocation of
2383 /// an aggregate can be broken down into elements. Return 0 if not, 3 if safe,
2384 /// or 1 if safe after canonicalization has been performed.
2385 bool SROA::isSafeAllocaToScalarRepl(AllocaInst *AI) {
2386 // Loop over the use list of the alloca. We can only transform it if all of
2387 // the users are safe to transform.
2388 AllocaInfo Info(AI);
2390 isSafeForScalarRepl(AI, 0, Info);
2391 if (Info.isUnsafe) {
2392 DEBUG(dbgs() << "Cannot transform: " << *AI << '\n');
2396 // Okay, we know all the users are promotable. If the aggregate is a memcpy
2397 // source and destination, we have to be careful. In particular, the memcpy
2398 // could be moving around elements that live in structure padding of the LLVM
2399 // types, but may actually be used. In these cases, we refuse to promote the
2401 if (Info.isMemCpySrc && Info.isMemCpyDst &&
2402 HasPadding(AI->getAllocatedType(), *TD))
2405 // If the alloca never has an access to just *part* of it, but is accessed
2406 // via loads and stores, then we should use ConvertToScalarInfo to promote
2407 // the alloca instead of promoting each piece at a time and inserting fission
2409 if (!Info.hasSubelementAccess && Info.hasALoadOrStore) {
2410 // If the struct/array just has one element, use basic SRoA.
2411 if (const StructType *ST = dyn_cast<StructType>(AI->getAllocatedType())) {
2412 if (ST->getNumElements() > 1) return false;
2414 if (cast<ArrayType>(AI->getAllocatedType())->getNumElements() > 1)
2424 /// PointsToConstantGlobal - Return true if V (possibly indirectly) points to
2425 /// some part of a constant global variable. This intentionally only accepts
2426 /// constant expressions because we don't can't rewrite arbitrary instructions.
2427 static bool PointsToConstantGlobal(Value *V) {
2428 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
2429 return GV->isConstant();
2430 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
2431 if (CE->getOpcode() == Instruction::BitCast ||
2432 CE->getOpcode() == Instruction::GetElementPtr)
2433 return PointsToConstantGlobal(CE->getOperand(0));
2437 /// isOnlyCopiedFromConstantGlobal - Recursively walk the uses of a (derived)
2438 /// pointer to an alloca. Ignore any reads of the pointer, return false if we
2439 /// see any stores or other unknown uses. If we see pointer arithmetic, keep
2440 /// track of whether it moves the pointer (with isOffset) but otherwise traverse
2441 /// the uses. If we see a memcpy/memmove that targets an unoffseted pointer to
2442 /// the alloca, and if the source pointer is a pointer to a constant global, we
2443 /// can optimize this.
2444 static bool isOnlyCopiedFromConstantGlobal(Value *V, MemTransferInst *&TheCopy,
2446 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) {
2447 User *U = cast<Instruction>(*UI);
2449 if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
2450 // Ignore non-volatile loads, they are always ok.
2451 if (LI->isVolatile()) return false;
2455 if (BitCastInst *BCI = dyn_cast<BitCastInst>(U)) {
2456 // If uses of the bitcast are ok, we are ok.
2457 if (!isOnlyCopiedFromConstantGlobal(BCI, TheCopy, isOffset))
2461 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) {
2462 // If the GEP has all zero indices, it doesn't offset the pointer. If it
2463 // doesn't, it does.
2464 if (!isOnlyCopiedFromConstantGlobal(GEP, TheCopy,
2465 isOffset || !GEP->hasAllZeroIndices()))
2470 if (CallSite CS = U) {
2471 // If this is a readonly/readnone call site, then we know it is just a
2472 // load and we can ignore it.
2473 if (CS.onlyReadsMemory())
2476 // If this is the function being called then we treat it like a load and
2478 if (CS.isCallee(UI))
2481 // If this is being passed as a byval argument, the caller is making a
2482 // copy, so it is only a read of the alloca.
2483 unsigned ArgNo = CS.getArgumentNo(UI);
2484 if (CS.paramHasAttr(ArgNo+1, Attribute::ByVal))
2488 // If this is isn't our memcpy/memmove, reject it as something we can't
2490 MemTransferInst *MI = dyn_cast<MemTransferInst>(U);
2494 // If the transfer is using the alloca as a source of the transfer, then
2495 // ignore it since it is a load (unless the transfer is volatile).
2496 if (UI.getOperandNo() == 1) {
2497 if (MI->isVolatile()) return false;
2501 // If we already have seen a copy, reject the second one.
2502 if (TheCopy) return false;
2504 // If the pointer has been offset from the start of the alloca, we can't
2505 // safely handle this.
2506 if (isOffset) return false;
2508 // If the memintrinsic isn't using the alloca as the dest, reject it.
2509 if (UI.getOperandNo() != 0) return false;
2511 // If the source of the memcpy/move is not a constant global, reject it.
2512 if (!PointsToConstantGlobal(MI->getSource()))
2515 // Otherwise, the transform is safe. Remember the copy instruction.
2521 /// isOnlyCopiedFromConstantGlobal - Return true if the specified alloca is only
2522 /// modified by a copy from a constant global. If we can prove this, we can
2523 /// replace any uses of the alloca with uses of the global directly.
2524 MemTransferInst *SROA::isOnlyCopiedFromConstantGlobal(AllocaInst *AI) {
2525 MemTransferInst *TheCopy = 0;
2526 if (::isOnlyCopiedFromConstantGlobal(AI, TheCopy, false))