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/DominanceFrontier.h"
34 #include "llvm/Analysis/ValueTracking.h"
35 #include "llvm/Target/TargetData.h"
36 #include "llvm/Transforms/Utils/PromoteMemToReg.h"
37 #include "llvm/Transforms/Utils/Local.h"
38 #include "llvm/Support/CallSite.h"
39 #include "llvm/Support/Debug.h"
40 #include "llvm/Support/ErrorHandling.h"
41 #include "llvm/Support/GetElementPtrTypeIterator.h"
42 #include "llvm/Support/IRBuilder.h"
43 #include "llvm/Support/MathExtras.h"
44 #include "llvm/Support/raw_ostream.h"
45 #include "llvm/ADT/SmallVector.h"
46 #include "llvm/ADT/Statistic.h"
49 STATISTIC(NumReplaced, "Number of allocas broken up");
50 STATISTIC(NumPromoted, "Number of allocas promoted");
51 STATISTIC(NumConverted, "Number of aggregates converted to scalar");
52 STATISTIC(NumGlobals, "Number of allocas copied from constant global");
55 struct SROA : public FunctionPass {
56 static char ID; // Pass identification, replacement for typeid
57 explicit SROA(signed T = -1) : FunctionPass(ID) {
58 initializeSROAPass(*PassRegistry::getPassRegistry());
65 bool runOnFunction(Function &F);
67 bool performScalarRepl(Function &F);
68 bool performPromotion(Function &F);
70 // getAnalysisUsage - This pass does not require any passes, but we know it
71 // will not alter the CFG, so say so.
72 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
73 AU.addRequired<DominatorTree>();
74 AU.addRequired<DominanceFrontier>();
81 /// DeadInsts - Keep track of instructions we have made dead, so that
82 /// we can remove them after we are done working.
83 SmallVector<Value*, 32> DeadInsts;
85 /// AllocaInfo - When analyzing uses of an alloca instruction, this captures
86 /// information about the uses. All these fields are initialized to false
87 /// and set to true when something is learned.
89 /// isUnsafe - This is set to true if the alloca cannot be SROA'd.
92 /// isMemCpySrc - This is true if this aggregate is memcpy'd from.
95 /// isMemCpyDst - This is true if this aggregate is memcpy'd into.
99 : isUnsafe(false), isMemCpySrc(false), isMemCpyDst(false) {}
102 unsigned SRThreshold;
104 void MarkUnsafe(AllocaInfo &I) { I.isUnsafe = true; }
106 bool isSafeAllocaToScalarRepl(AllocaInst *AI);
108 void isSafeForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset,
110 void isSafeGEP(GetElementPtrInst *GEPI, AllocaInst *AI, uint64_t &Offset,
112 void isSafeMemAccess(AllocaInst *AI, uint64_t Offset, uint64_t MemSize,
113 const Type *MemOpType, bool isStore, AllocaInfo &Info);
114 bool TypeHasComponent(const Type *T, uint64_t Offset, uint64_t Size);
115 uint64_t FindElementAndOffset(const Type *&T, uint64_t &Offset,
118 void DoScalarReplacement(AllocaInst *AI,
119 std::vector<AllocaInst*> &WorkList);
120 void DeleteDeadInstructions();
122 void RewriteForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset,
123 SmallVector<AllocaInst*, 32> &NewElts);
124 void RewriteBitCast(BitCastInst *BC, AllocaInst *AI, uint64_t Offset,
125 SmallVector<AllocaInst*, 32> &NewElts);
126 void RewriteGEP(GetElementPtrInst *GEPI, AllocaInst *AI, uint64_t Offset,
127 SmallVector<AllocaInst*, 32> &NewElts);
128 void RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *Inst,
130 SmallVector<AllocaInst*, 32> &NewElts);
131 void RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocaInst *AI,
132 SmallVector<AllocaInst*, 32> &NewElts);
133 void RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocaInst *AI,
134 SmallVector<AllocaInst*, 32> &NewElts);
136 static MemTransferInst *isOnlyCopiedFromConstantGlobal(AllocaInst *AI);
141 INITIALIZE_PASS_BEGIN(SROA, "scalarrepl",
142 "Scalar Replacement of Aggregates", false, false)
143 INITIALIZE_PASS_DEPENDENCY(DominatorTree)
144 INITIALIZE_PASS_DEPENDENCY(DominanceFrontier)
145 INITIALIZE_PASS_END(SROA, "scalarrepl",
146 "Scalar Replacement of Aggregates", false, false)
148 // Public interface to the ScalarReplAggregates pass
149 FunctionPass *llvm::createScalarReplAggregatesPass(signed int Threshold) {
150 return new SROA(Threshold);
154 //===----------------------------------------------------------------------===//
155 // Convert To Scalar Optimization.
156 //===----------------------------------------------------------------------===//
159 /// ConvertToScalarInfo - This class implements the "Convert To Scalar"
160 /// optimization, which scans the uses of an alloca and determines if it can
161 /// rewrite it in terms of a single new alloca that can be mem2reg'd.
162 class ConvertToScalarInfo {
163 /// AllocaSize - The size of the alloca being considered.
165 const TargetData &TD;
167 /// IsNotTrivial - This is set to true if there is some access to the object
168 /// which means that mem2reg can't promote it.
171 /// VectorTy - This tracks the type that we should promote the vector to if
172 /// it is possible to turn it into a vector. This starts out null, and if it
173 /// isn't possible to turn into a vector type, it gets set to VoidTy.
174 const Type *VectorTy;
176 /// HadAVector - True if there is at least one vector access to the alloca.
177 /// We don't want to turn random arrays into vectors and use vector element
178 /// insert/extract, but if there are element accesses to something that is
179 /// also declared as a vector, we do want to promote to a vector.
183 explicit ConvertToScalarInfo(unsigned Size, const TargetData &td)
184 : AllocaSize(Size), TD(td) {
185 IsNotTrivial = false;
190 AllocaInst *TryConvert(AllocaInst *AI);
193 bool CanConvertToScalar(Value *V, uint64_t Offset);
194 void MergeInType(const Type *In, uint64_t Offset);
195 void ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, uint64_t Offset);
197 Value *ConvertScalar_ExtractValue(Value *NV, const Type *ToType,
198 uint64_t Offset, IRBuilder<> &Builder);
199 Value *ConvertScalar_InsertValue(Value *StoredVal, Value *ExistingVal,
200 uint64_t Offset, IRBuilder<> &Builder);
202 } // end anonymous namespace.
205 /// IsVerbotenVectorType - Return true if this is a vector type ScalarRepl isn't
206 /// allowed to form. We do this to avoid MMX types, which is a complete hack,
207 /// but is required until the backend is fixed.
208 static bool IsVerbotenVectorType(const VectorType *VTy, const Instruction *I) {
209 StringRef Triple(I->getParent()->getParent()->getParent()->getTargetTriple());
210 if (!Triple.startswith("i386") &&
211 !Triple.startswith("x86_64"))
214 // Reject all the MMX vector types.
215 switch (VTy->getNumElements()) {
216 default: return false;
217 case 1: return VTy->getElementType()->isIntegerTy(64);
218 case 2: return VTy->getElementType()->isIntegerTy(32);
219 case 4: return VTy->getElementType()->isIntegerTy(16);
220 case 8: return VTy->getElementType()->isIntegerTy(8);
225 /// TryConvert - Analyze the specified alloca, and if it is safe to do so,
226 /// rewrite it to be a new alloca which is mem2reg'able. This returns the new
227 /// alloca if possible or null if not.
228 AllocaInst *ConvertToScalarInfo::TryConvert(AllocaInst *AI) {
229 // If we can't convert this scalar, or if mem2reg can trivially do it, bail
231 if (!CanConvertToScalar(AI, 0) || !IsNotTrivial)
234 // If we were able to find a vector type that can handle this with
235 // insert/extract elements, and if there was at least one use that had
236 // a vector type, promote this to a vector. We don't want to promote
237 // random stuff that doesn't use vectors (e.g. <9 x double>) because then
238 // we just get a lot of insert/extracts. If at least one vector is
239 // involved, then we probably really do have a union of vector/array.
241 if (VectorTy && VectorTy->isVectorTy() && HadAVector &&
242 !IsVerbotenVectorType(cast<VectorType>(VectorTy), AI)) {
243 DEBUG(dbgs() << "CONVERT TO VECTOR: " << *AI << "\n TYPE = "
244 << *VectorTy << '\n');
245 NewTy = VectorTy; // Use the vector type.
247 DEBUG(dbgs() << "CONVERT TO SCALAR INTEGER: " << *AI << "\n");
248 // Create and insert the integer alloca.
249 NewTy = IntegerType::get(AI->getContext(), AllocaSize*8);
251 AllocaInst *NewAI = new AllocaInst(NewTy, 0, "", AI->getParent()->begin());
252 ConvertUsesToScalar(AI, NewAI, 0);
256 /// MergeInType - Add the 'In' type to the accumulated vector type (VectorTy)
257 /// so far at the offset specified by Offset (which is specified in bytes).
259 /// There are two cases we handle here:
260 /// 1) A union of vector types of the same size and potentially its elements.
261 /// Here we turn element accesses into insert/extract element operations.
262 /// This promotes a <4 x float> with a store of float to the third element
263 /// into a <4 x float> that uses insert element.
264 /// 2) A fully general blob of memory, which we turn into some (potentially
265 /// large) integer type with extract and insert operations where the loads
266 /// and stores would mutate the memory. We mark this by setting VectorTy
268 void ConvertToScalarInfo::MergeInType(const Type *In, uint64_t Offset) {
269 // If we already decided to turn this into a blob of integer memory, there is
270 // nothing to be done.
271 if (VectorTy && VectorTy->isVoidTy())
274 // If this could be contributing to a vector, analyze it.
276 // If the In type is a vector that is the same size as the alloca, see if it
277 // matches the existing VecTy.
278 if (const VectorType *VInTy = dyn_cast<VectorType>(In)) {
279 // Remember if we saw a vector type.
282 if (VInTy->getBitWidth()/8 == AllocaSize && Offset == 0) {
283 // If we're storing/loading a vector of the right size, allow it as a
284 // vector. If this the first vector we see, remember the type so that
285 // we know the element size. If this is a subsequent access, ignore it
286 // even if it is a differing type but the same size. Worst case we can
287 // bitcast the resultant vectors.
292 } else if (In->isFloatTy() || In->isDoubleTy() ||
293 (In->isIntegerTy() && In->getPrimitiveSizeInBits() >= 8 &&
294 isPowerOf2_32(In->getPrimitiveSizeInBits()))) {
295 // If we're accessing something that could be an element of a vector, see
296 // if the implied vector agrees with what we already have and if Offset is
297 // compatible with it.
298 unsigned EltSize = In->getPrimitiveSizeInBits()/8;
299 if (Offset % EltSize == 0 && AllocaSize % EltSize == 0 &&
301 cast<VectorType>(VectorTy)->getElementType()
302 ->getPrimitiveSizeInBits()/8 == EltSize)) {
304 VectorTy = VectorType::get(In, AllocaSize/EltSize);
309 // Otherwise, we have a case that we can't handle with an optimized vector
310 // form. We can still turn this into a large integer.
311 VectorTy = Type::getVoidTy(In->getContext());
314 /// CanConvertToScalar - V is a pointer. If we can convert the pointee and all
315 /// its accesses to a single vector type, return true and set VecTy to
316 /// the new type. If we could convert the alloca into a single promotable
317 /// integer, return true but set VecTy to VoidTy. Further, if the use is not a
318 /// completely trivial use that mem2reg could promote, set IsNotTrivial. Offset
319 /// is the current offset from the base of the alloca being analyzed.
321 /// If we see at least one access to the value that is as a vector type, set the
323 bool ConvertToScalarInfo::CanConvertToScalar(Value *V, uint64_t Offset) {
324 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) {
325 Instruction *User = cast<Instruction>(*UI);
327 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
328 // Don't break volatile loads.
329 if (LI->isVolatile())
331 // Don't touch MMX operations.
332 if (LI->getType()->isX86_MMXTy())
334 MergeInType(LI->getType(), Offset);
338 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
339 // Storing the pointer, not into the value?
340 if (SI->getOperand(0) == V || SI->isVolatile()) return false;
341 // Don't touch MMX operations.
342 if (SI->getOperand(0)->getType()->isX86_MMXTy())
344 MergeInType(SI->getOperand(0)->getType(), Offset);
348 if (BitCastInst *BCI = dyn_cast<BitCastInst>(User)) {
349 IsNotTrivial = true; // Can't be mem2reg'd.
350 if (!CanConvertToScalar(BCI, Offset))
355 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) {
356 // If this is a GEP with a variable indices, we can't handle it.
357 if (!GEP->hasAllConstantIndices())
360 // Compute the offset that this GEP adds to the pointer.
361 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end());
362 uint64_t GEPOffset = TD.getIndexedOffset(GEP->getPointerOperandType(),
363 &Indices[0], Indices.size());
364 // See if all uses can be converted.
365 if (!CanConvertToScalar(GEP, Offset+GEPOffset))
367 IsNotTrivial = true; // Can't be mem2reg'd.
371 // If this is a constant sized memset of a constant value (e.g. 0) we can
373 if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) {
374 // Store of constant value and constant size.
375 if (!isa<ConstantInt>(MSI->getValue()) ||
376 !isa<ConstantInt>(MSI->getLength()))
378 IsNotTrivial = true; // Can't be mem2reg'd.
382 // If this is a memcpy or memmove into or out of the whole allocation, we
383 // can handle it like a load or store of the scalar type.
384 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) {
385 ConstantInt *Len = dyn_cast<ConstantInt>(MTI->getLength());
386 if (Len == 0 || Len->getZExtValue() != AllocaSize || Offset != 0)
389 IsNotTrivial = true; // Can't be mem2reg'd.
393 // Otherwise, we cannot handle this!
400 /// ConvertUsesToScalar - Convert all of the users of Ptr to use the new alloca
401 /// directly. This happens when we are converting an "integer union" to a
402 /// single integer scalar, or when we are converting a "vector union" to a
403 /// vector with insert/extractelement instructions.
405 /// Offset is an offset from the original alloca, in bits that need to be
406 /// shifted to the right. By the end of this, there should be no uses of Ptr.
407 void ConvertToScalarInfo::ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI,
409 while (!Ptr->use_empty()) {
410 Instruction *User = cast<Instruction>(Ptr->use_back());
412 if (BitCastInst *CI = dyn_cast<BitCastInst>(User)) {
413 ConvertUsesToScalar(CI, NewAI, Offset);
414 CI->eraseFromParent();
418 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) {
419 // Compute the offset that this GEP adds to the pointer.
420 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end());
421 uint64_t GEPOffset = TD.getIndexedOffset(GEP->getPointerOperandType(),
422 &Indices[0], Indices.size());
423 ConvertUsesToScalar(GEP, NewAI, Offset+GEPOffset*8);
424 GEP->eraseFromParent();
428 IRBuilder<> Builder(User);
430 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
431 // The load is a bit extract from NewAI shifted right by Offset bits.
432 Value *LoadedVal = Builder.CreateLoad(NewAI, "tmp");
434 = ConvertScalar_ExtractValue(LoadedVal, LI->getType(), Offset, Builder);
435 LI->replaceAllUsesWith(NewLoadVal);
436 LI->eraseFromParent();
440 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
441 assert(SI->getOperand(0) != Ptr && "Consistency error!");
442 Instruction *Old = Builder.CreateLoad(NewAI, NewAI->getName()+".in");
443 Value *New = ConvertScalar_InsertValue(SI->getOperand(0), Old, Offset,
445 Builder.CreateStore(New, NewAI);
446 SI->eraseFromParent();
448 // If the load we just inserted is now dead, then the inserted store
449 // overwrote the entire thing.
450 if (Old->use_empty())
451 Old->eraseFromParent();
455 // If this is a constant sized memset of a constant value (e.g. 0) we can
456 // transform it into a store of the expanded constant value.
457 if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) {
458 assert(MSI->getRawDest() == Ptr && "Consistency error!");
459 unsigned NumBytes = cast<ConstantInt>(MSI->getLength())->getZExtValue();
461 unsigned Val = cast<ConstantInt>(MSI->getValue())->getZExtValue();
463 // Compute the value replicated the right number of times.
464 APInt APVal(NumBytes*8, Val);
466 // Splat the value if non-zero.
468 for (unsigned i = 1; i != NumBytes; ++i)
471 Instruction *Old = Builder.CreateLoad(NewAI, NewAI->getName()+".in");
472 Value *New = ConvertScalar_InsertValue(
473 ConstantInt::get(User->getContext(), APVal),
474 Old, Offset, Builder);
475 Builder.CreateStore(New, NewAI);
477 // If the load we just inserted is now dead, then the memset overwrote
479 if (Old->use_empty())
480 Old->eraseFromParent();
482 MSI->eraseFromParent();
486 // If this is a memcpy or memmove into or out of the whole allocation, we
487 // can handle it like a load or store of the scalar type.
488 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) {
489 assert(Offset == 0 && "must be store to start of alloca");
491 // If the source and destination are both to the same alloca, then this is
492 // a noop copy-to-self, just delete it. Otherwise, emit a load and store
494 AllocaInst *OrigAI = cast<AllocaInst>(GetUnderlyingObject(Ptr, 0));
496 if (GetUnderlyingObject(MTI->getSource(), 0) != OrigAI) {
497 // Dest must be OrigAI, change this to be a load from the original
498 // pointer (bitcasted), then a store to our new alloca.
499 assert(MTI->getRawDest() == Ptr && "Neither use is of pointer?");
500 Value *SrcPtr = MTI->getSource();
501 const PointerType* SPTy = cast<PointerType>(SrcPtr->getType());
502 const PointerType* AIPTy = cast<PointerType>(NewAI->getType());
503 if (SPTy->getAddressSpace() != AIPTy->getAddressSpace()) {
504 AIPTy = PointerType::get(AIPTy->getElementType(),
505 SPTy->getAddressSpace());
507 SrcPtr = Builder.CreateBitCast(SrcPtr, AIPTy);
509 LoadInst *SrcVal = Builder.CreateLoad(SrcPtr, "srcval");
510 SrcVal->setAlignment(MTI->getAlignment());
511 Builder.CreateStore(SrcVal, NewAI);
512 } else if (GetUnderlyingObject(MTI->getDest(), 0) != OrigAI) {
513 // Src must be OrigAI, change this to be a load from NewAI then a store
514 // through the original dest pointer (bitcasted).
515 assert(MTI->getRawSource() == Ptr && "Neither use is of pointer?");
516 LoadInst *SrcVal = Builder.CreateLoad(NewAI, "srcval");
518 const PointerType* DPTy = cast<PointerType>(MTI->getDest()->getType());
519 const PointerType* AIPTy = cast<PointerType>(NewAI->getType());
520 if (DPTy->getAddressSpace() != AIPTy->getAddressSpace()) {
521 AIPTy = PointerType::get(AIPTy->getElementType(),
522 DPTy->getAddressSpace());
524 Value *DstPtr = Builder.CreateBitCast(MTI->getDest(), AIPTy);
526 StoreInst *NewStore = Builder.CreateStore(SrcVal, DstPtr);
527 NewStore->setAlignment(MTI->getAlignment());
529 // Noop transfer. Src == Dst
532 MTI->eraseFromParent();
536 llvm_unreachable("Unsupported operation!");
540 /// ConvertScalar_ExtractValue - Extract a value of type ToType from an integer
541 /// or vector value FromVal, extracting the bits from the offset specified by
542 /// Offset. This returns the value, which is of type ToType.
544 /// This happens when we are converting an "integer union" to a single
545 /// integer scalar, or when we are converting a "vector union" to a vector with
546 /// insert/extractelement instructions.
548 /// Offset is an offset from the original alloca, in bits that need to be
549 /// shifted to the right.
550 Value *ConvertToScalarInfo::
551 ConvertScalar_ExtractValue(Value *FromVal, const Type *ToType,
552 uint64_t Offset, IRBuilder<> &Builder) {
553 // If the load is of the whole new alloca, no conversion is needed.
554 if (FromVal->getType() == ToType && Offset == 0)
557 // If the result alloca is a vector type, this is either an element
558 // access or a bitcast to another vector type of the same size.
559 if (const VectorType *VTy = dyn_cast<VectorType>(FromVal->getType())) {
560 if (ToType->isVectorTy())
561 return Builder.CreateBitCast(FromVal, ToType, "tmp");
563 // Otherwise it must be an element access.
566 unsigned EltSize = TD.getTypeAllocSizeInBits(VTy->getElementType());
567 Elt = Offset/EltSize;
568 assert(EltSize*Elt == Offset && "Invalid modulus in validity checking");
570 // Return the element extracted out of it.
571 Value *V = Builder.CreateExtractElement(FromVal, ConstantInt::get(
572 Type::getInt32Ty(FromVal->getContext()), Elt), "tmp");
573 if (V->getType() != ToType)
574 V = Builder.CreateBitCast(V, ToType, "tmp");
578 // If ToType is a first class aggregate, extract out each of the pieces and
579 // use insertvalue's to form the FCA.
580 if (const StructType *ST = dyn_cast<StructType>(ToType)) {
581 const StructLayout &Layout = *TD.getStructLayout(ST);
582 Value *Res = UndefValue::get(ST);
583 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) {
584 Value *Elt = ConvertScalar_ExtractValue(FromVal, ST->getElementType(i),
585 Offset+Layout.getElementOffsetInBits(i),
587 Res = Builder.CreateInsertValue(Res, Elt, i, "tmp");
592 if (const ArrayType *AT = dyn_cast<ArrayType>(ToType)) {
593 uint64_t EltSize = TD.getTypeAllocSizeInBits(AT->getElementType());
594 Value *Res = UndefValue::get(AT);
595 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
596 Value *Elt = ConvertScalar_ExtractValue(FromVal, AT->getElementType(),
597 Offset+i*EltSize, Builder);
598 Res = Builder.CreateInsertValue(Res, Elt, i, "tmp");
603 // Otherwise, this must be a union that was converted to an integer value.
604 const IntegerType *NTy = cast<IntegerType>(FromVal->getType());
606 // If this is a big-endian system and the load is narrower than the
607 // full alloca type, we need to do a shift to get the right bits.
609 if (TD.isBigEndian()) {
610 // On big-endian machines, the lowest bit is stored at the bit offset
611 // from the pointer given by getTypeStoreSizeInBits. This matters for
612 // integers with a bitwidth that is not a multiple of 8.
613 ShAmt = TD.getTypeStoreSizeInBits(NTy) -
614 TD.getTypeStoreSizeInBits(ToType) - Offset;
619 // Note: we support negative bitwidths (with shl) which are not defined.
620 // We do this to support (f.e.) loads off the end of a structure where
621 // only some bits are used.
622 if (ShAmt > 0 && (unsigned)ShAmt < NTy->getBitWidth())
623 FromVal = Builder.CreateLShr(FromVal,
624 ConstantInt::get(FromVal->getType(),
626 else if (ShAmt < 0 && (unsigned)-ShAmt < NTy->getBitWidth())
627 FromVal = Builder.CreateShl(FromVal,
628 ConstantInt::get(FromVal->getType(),
631 // Finally, unconditionally truncate the integer to the right width.
632 unsigned LIBitWidth = TD.getTypeSizeInBits(ToType);
633 if (LIBitWidth < NTy->getBitWidth())
635 Builder.CreateTrunc(FromVal, IntegerType::get(FromVal->getContext(),
637 else if (LIBitWidth > NTy->getBitWidth())
639 Builder.CreateZExt(FromVal, IntegerType::get(FromVal->getContext(),
642 // If the result is an integer, this is a trunc or bitcast.
643 if (ToType->isIntegerTy()) {
645 } else if (ToType->isFloatingPointTy() || ToType->isVectorTy()) {
646 // Just do a bitcast, we know the sizes match up.
647 FromVal = Builder.CreateBitCast(FromVal, ToType, "tmp");
649 // Otherwise must be a pointer.
650 FromVal = Builder.CreateIntToPtr(FromVal, ToType, "tmp");
652 assert(FromVal->getType() == ToType && "Didn't convert right?");
656 /// ConvertScalar_InsertValue - Insert the value "SV" into the existing integer
657 /// or vector value "Old" at the offset specified by Offset.
659 /// This happens when we are converting an "integer union" to a
660 /// single integer scalar, or when we are converting a "vector union" to a
661 /// vector with insert/extractelement instructions.
663 /// Offset is an offset from the original alloca, in bits that need to be
664 /// shifted to the right.
665 Value *ConvertToScalarInfo::
666 ConvertScalar_InsertValue(Value *SV, Value *Old,
667 uint64_t Offset, IRBuilder<> &Builder) {
668 // Convert the stored type to the actual type, shift it left to insert
669 // then 'or' into place.
670 const Type *AllocaType = Old->getType();
671 LLVMContext &Context = Old->getContext();
673 if (const VectorType *VTy = dyn_cast<VectorType>(AllocaType)) {
674 uint64_t VecSize = TD.getTypeAllocSizeInBits(VTy);
675 uint64_t ValSize = TD.getTypeAllocSizeInBits(SV->getType());
677 // Changing the whole vector with memset or with an access of a different
679 if (ValSize == VecSize)
680 return Builder.CreateBitCast(SV, AllocaType, "tmp");
682 uint64_t EltSize = TD.getTypeAllocSizeInBits(VTy->getElementType());
684 // Must be an element insertion.
685 unsigned Elt = Offset/EltSize;
687 if (SV->getType() != VTy->getElementType())
688 SV = Builder.CreateBitCast(SV, VTy->getElementType(), "tmp");
690 SV = Builder.CreateInsertElement(Old, SV,
691 ConstantInt::get(Type::getInt32Ty(SV->getContext()), Elt),
696 // If SV is a first-class aggregate value, insert each value recursively.
697 if (const StructType *ST = dyn_cast<StructType>(SV->getType())) {
698 const StructLayout &Layout = *TD.getStructLayout(ST);
699 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) {
700 Value *Elt = Builder.CreateExtractValue(SV, i, "tmp");
701 Old = ConvertScalar_InsertValue(Elt, Old,
702 Offset+Layout.getElementOffsetInBits(i),
708 if (const ArrayType *AT = dyn_cast<ArrayType>(SV->getType())) {
709 uint64_t EltSize = TD.getTypeAllocSizeInBits(AT->getElementType());
710 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
711 Value *Elt = Builder.CreateExtractValue(SV, i, "tmp");
712 Old = ConvertScalar_InsertValue(Elt, Old, Offset+i*EltSize, Builder);
717 // If SV is a float, convert it to the appropriate integer type.
718 // If it is a pointer, do the same.
719 unsigned SrcWidth = TD.getTypeSizeInBits(SV->getType());
720 unsigned DestWidth = TD.getTypeSizeInBits(AllocaType);
721 unsigned SrcStoreWidth = TD.getTypeStoreSizeInBits(SV->getType());
722 unsigned DestStoreWidth = TD.getTypeStoreSizeInBits(AllocaType);
723 if (SV->getType()->isFloatingPointTy() || SV->getType()->isVectorTy())
724 SV = Builder.CreateBitCast(SV,
725 IntegerType::get(SV->getContext(),SrcWidth), "tmp");
726 else if (SV->getType()->isPointerTy())
727 SV = Builder.CreatePtrToInt(SV, TD.getIntPtrType(SV->getContext()), "tmp");
729 // Zero extend or truncate the value if needed.
730 if (SV->getType() != AllocaType) {
731 if (SV->getType()->getPrimitiveSizeInBits() <
732 AllocaType->getPrimitiveSizeInBits())
733 SV = Builder.CreateZExt(SV, AllocaType, "tmp");
735 // Truncation may be needed if storing more than the alloca can hold
736 // (undefined behavior).
737 SV = Builder.CreateTrunc(SV, AllocaType, "tmp");
738 SrcWidth = DestWidth;
739 SrcStoreWidth = DestStoreWidth;
743 // If this is a big-endian system and the store is narrower than the
744 // full alloca type, we need to do a shift to get the right bits.
746 if (TD.isBigEndian()) {
747 // On big-endian machines, the lowest bit is stored at the bit offset
748 // from the pointer given by getTypeStoreSizeInBits. This matters for
749 // integers with a bitwidth that is not a multiple of 8.
750 ShAmt = DestStoreWidth - SrcStoreWidth - Offset;
755 // Note: we support negative bitwidths (with shr) which are not defined.
756 // We do this to support (f.e.) stores off the end of a structure where
757 // only some bits in the structure are set.
758 APInt Mask(APInt::getLowBitsSet(DestWidth, SrcWidth));
759 if (ShAmt > 0 && (unsigned)ShAmt < DestWidth) {
760 SV = Builder.CreateShl(SV, ConstantInt::get(SV->getType(),
763 } else if (ShAmt < 0 && (unsigned)-ShAmt < DestWidth) {
764 SV = Builder.CreateLShr(SV, ConstantInt::get(SV->getType(),
766 Mask = Mask.lshr(-ShAmt);
769 // Mask out the bits we are about to insert from the old value, and or
771 if (SrcWidth != DestWidth) {
772 assert(DestWidth > SrcWidth);
773 Old = Builder.CreateAnd(Old, ConstantInt::get(Context, ~Mask), "mask");
774 SV = Builder.CreateOr(Old, SV, "ins");
780 //===----------------------------------------------------------------------===//
782 //===----------------------------------------------------------------------===//
785 bool SROA::runOnFunction(Function &F) {
786 TD = getAnalysisIfAvailable<TargetData>();
788 bool Changed = performPromotion(F);
790 // FIXME: ScalarRepl currently depends on TargetData more than it
791 // theoretically needs to. It should be refactored in order to support
792 // target-independent IR. Until this is done, just skip the actual
793 // scalar-replacement portion of this pass.
794 if (!TD) return Changed;
797 bool LocalChange = performScalarRepl(F);
798 if (!LocalChange) break; // No need to repromote if no scalarrepl
800 LocalChange = performPromotion(F);
801 if (!LocalChange) break; // No need to re-scalarrepl if no promotion
808 bool SROA::performPromotion(Function &F) {
809 std::vector<AllocaInst*> Allocas;
810 DominatorTree &DT = getAnalysis<DominatorTree>();
811 DominanceFrontier &DF = getAnalysis<DominanceFrontier>();
813 BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function
815 bool Changed = false;
820 // Find allocas that are safe to promote, by looking at all instructions in
822 for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I)
823 if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) // Is it an alloca?
824 if (isAllocaPromotable(AI))
825 Allocas.push_back(AI);
827 if (Allocas.empty()) break;
829 PromoteMemToReg(Allocas, DT, DF);
830 NumPromoted += Allocas.size();
838 /// ShouldAttemptScalarRepl - Decide if an alloca is a good candidate for
839 /// SROA. It must be a struct or array type with a small number of elements.
840 static bool ShouldAttemptScalarRepl(AllocaInst *AI) {
841 const Type *T = AI->getAllocatedType();
842 // Do not promote any struct into more than 32 separate vars.
843 if (const StructType *ST = dyn_cast<StructType>(T))
844 return ST->getNumElements() <= 32;
845 // Arrays are much less likely to be safe for SROA; only consider
846 // them if they are very small.
847 if (const ArrayType *AT = dyn_cast<ArrayType>(T))
848 return AT->getNumElements() <= 8;
853 // performScalarRepl - This algorithm is a simple worklist driven algorithm,
854 // which runs on all of the malloc/alloca instructions in the function, removing
855 // them if they are only used by getelementptr instructions.
857 bool SROA::performScalarRepl(Function &F) {
858 std::vector<AllocaInst*> WorkList;
860 // Scan the entry basic block, adding allocas to the worklist.
861 BasicBlock &BB = F.getEntryBlock();
862 for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I)
863 if (AllocaInst *A = dyn_cast<AllocaInst>(I))
864 WorkList.push_back(A);
866 // Process the worklist
867 bool Changed = false;
868 while (!WorkList.empty()) {
869 AllocaInst *AI = WorkList.back();
872 // Handle dead allocas trivially. These can be formed by SROA'ing arrays
873 // with unused elements.
874 if (AI->use_empty()) {
875 AI->eraseFromParent();
880 // If this alloca is impossible for us to promote, reject it early.
881 if (AI->isArrayAllocation() || !AI->getAllocatedType()->isSized())
884 // Check to see if this allocation is only modified by a memcpy/memmove from
885 // a constant global. If this is the case, we can change all users to use
886 // the constant global instead. This is commonly produced by the CFE by
887 // constructs like "void foo() { int A[] = {1,2,3,4,5,6,7,8,9...}; }" if 'A'
888 // is only subsequently read.
889 if (MemTransferInst *TheCopy = isOnlyCopiedFromConstantGlobal(AI)) {
890 DEBUG(dbgs() << "Found alloca equal to global: " << *AI << '\n');
891 DEBUG(dbgs() << " memcpy = " << *TheCopy << '\n');
892 Constant *TheSrc = cast<Constant>(TheCopy->getSource());
893 AI->replaceAllUsesWith(ConstantExpr::getBitCast(TheSrc, AI->getType()));
894 TheCopy->eraseFromParent(); // Don't mutate the global.
895 AI->eraseFromParent();
901 // Check to see if we can perform the core SROA transformation. We cannot
902 // transform the allocation instruction if it is an array allocation
903 // (allocations OF arrays are ok though), and an allocation of a scalar
904 // value cannot be decomposed at all.
905 uint64_t AllocaSize = TD->getTypeAllocSize(AI->getAllocatedType());
907 // Do not promote [0 x %struct].
908 if (AllocaSize == 0) continue;
910 // Do not promote any struct whose size is too big.
911 if (AllocaSize > SRThreshold) continue;
913 // If the alloca looks like a good candidate for scalar replacement, and if
914 // all its users can be transformed, then split up the aggregate into its
915 // separate elements.
916 if (ShouldAttemptScalarRepl(AI) && isSafeAllocaToScalarRepl(AI)) {
917 DoScalarReplacement(AI, WorkList);
922 // If we can turn this aggregate value (potentially with casts) into a
923 // simple scalar value that can be mem2reg'd into a register value.
924 // IsNotTrivial tracks whether this is something that mem2reg could have
925 // promoted itself. If so, we don't want to transform it needlessly. Note
926 // that we can't just check based on the type: the alloca may be of an i32
927 // but that has pointer arithmetic to set byte 3 of it or something.
928 if (AllocaInst *NewAI =
929 ConvertToScalarInfo((unsigned)AllocaSize, *TD).TryConvert(AI)) {
931 AI->eraseFromParent();
937 // Otherwise, couldn't process this alloca.
943 /// DoScalarReplacement - This alloca satisfied the isSafeAllocaToScalarRepl
944 /// predicate, do SROA now.
945 void SROA::DoScalarReplacement(AllocaInst *AI,
946 std::vector<AllocaInst*> &WorkList) {
947 DEBUG(dbgs() << "Found inst to SROA: " << *AI << '\n');
948 SmallVector<AllocaInst*, 32> ElementAllocas;
949 if (const StructType *ST = dyn_cast<StructType>(AI->getAllocatedType())) {
950 ElementAllocas.reserve(ST->getNumContainedTypes());
951 for (unsigned i = 0, e = ST->getNumContainedTypes(); i != e; ++i) {
952 AllocaInst *NA = new AllocaInst(ST->getContainedType(i), 0,
954 AI->getName() + "." + Twine(i), AI);
955 ElementAllocas.push_back(NA);
956 WorkList.push_back(NA); // Add to worklist for recursive processing
959 const ArrayType *AT = cast<ArrayType>(AI->getAllocatedType());
960 ElementAllocas.reserve(AT->getNumElements());
961 const Type *ElTy = AT->getElementType();
962 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
963 AllocaInst *NA = new AllocaInst(ElTy, 0, AI->getAlignment(),
964 AI->getName() + "." + Twine(i), AI);
965 ElementAllocas.push_back(NA);
966 WorkList.push_back(NA); // Add to worklist for recursive processing
970 // Now that we have created the new alloca instructions, rewrite all the
971 // uses of the old alloca.
972 RewriteForScalarRepl(AI, AI, 0, ElementAllocas);
974 // Now erase any instructions that were made dead while rewriting the alloca.
975 DeleteDeadInstructions();
976 AI->eraseFromParent();
981 /// DeleteDeadInstructions - Erase instructions on the DeadInstrs list,
982 /// recursively including all their operands that become trivially dead.
983 void SROA::DeleteDeadInstructions() {
984 while (!DeadInsts.empty()) {
985 Instruction *I = cast<Instruction>(DeadInsts.pop_back_val());
987 for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI)
988 if (Instruction *U = dyn_cast<Instruction>(*OI)) {
989 // Zero out the operand and see if it becomes trivially dead.
990 // (But, don't add allocas to the dead instruction list -- they are
991 // already on the worklist and will be deleted separately.)
993 if (isInstructionTriviallyDead(U) && !isa<AllocaInst>(U))
994 DeadInsts.push_back(U);
997 I->eraseFromParent();
1001 /// isSafeForScalarRepl - Check if instruction I is a safe use with regard to
1002 /// performing scalar replacement of alloca AI. The results are flagged in
1003 /// the Info parameter. Offset indicates the position within AI that is
1004 /// referenced by this instruction.
1005 void SROA::isSafeForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset,
1007 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E; ++UI) {
1008 Instruction *User = cast<Instruction>(*UI);
1010 if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) {
1011 isSafeForScalarRepl(BC, AI, Offset, Info);
1012 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
1013 uint64_t GEPOffset = Offset;
1014 isSafeGEP(GEPI, AI, GEPOffset, Info);
1016 isSafeForScalarRepl(GEPI, AI, GEPOffset, Info);
1017 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) {
1018 ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength());
1020 isSafeMemAccess(AI, Offset, Length->getZExtValue(), 0,
1021 UI.getOperandNo() == 0, Info);
1024 } else if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1025 if (!LI->isVolatile()) {
1026 const Type *LIType = LI->getType();
1027 isSafeMemAccess(AI, Offset, TD->getTypeAllocSize(LIType),
1028 LIType, false, Info);
1031 } else if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
1032 // Store is ok if storing INTO the pointer, not storing the pointer
1033 if (!SI->isVolatile() && SI->getOperand(0) != I) {
1034 const Type *SIType = SI->getOperand(0)->getType();
1035 isSafeMemAccess(AI, Offset, TD->getTypeAllocSize(SIType),
1036 SIType, true, Info);
1040 DEBUG(errs() << " Transformation preventing inst: " << *User << '\n');
1043 if (Info.isUnsafe) return;
1047 /// isSafeGEP - Check if a GEP instruction can be handled for scalar
1048 /// replacement. It is safe when all the indices are constant, in-bounds
1049 /// references, and when the resulting offset corresponds to an element within
1050 /// the alloca type. The results are flagged in the Info parameter. Upon
1051 /// return, Offset is adjusted as specified by the GEP indices.
1052 void SROA::isSafeGEP(GetElementPtrInst *GEPI, AllocaInst *AI,
1053 uint64_t &Offset, AllocaInfo &Info) {
1054 gep_type_iterator GEPIt = gep_type_begin(GEPI), E = gep_type_end(GEPI);
1058 // Walk through the GEP type indices, checking the types that this indexes
1060 for (; GEPIt != E; ++GEPIt) {
1061 // Ignore struct elements, no extra checking needed for these.
1062 if ((*GEPIt)->isStructTy())
1065 ConstantInt *IdxVal = dyn_cast<ConstantInt>(GEPIt.getOperand());
1067 return MarkUnsafe(Info);
1070 // Compute the offset due to this GEP and check if the alloca has a
1071 // component element at that offset.
1072 SmallVector<Value*, 8> Indices(GEPI->op_begin() + 1, GEPI->op_end());
1073 Offset += TD->getIndexedOffset(GEPI->getPointerOperandType(),
1074 &Indices[0], Indices.size());
1075 if (!TypeHasComponent(AI->getAllocatedType(), Offset, 0))
1079 /// isHomogeneousAggregate - Check if type T is a struct or array containing
1080 /// elements of the same type (which is always true for arrays). If so,
1081 /// return true with NumElts and EltTy set to the number of elements and the
1082 /// element type, respectively.
1083 static bool isHomogeneousAggregate(const Type *T, unsigned &NumElts,
1084 const Type *&EltTy) {
1085 if (const ArrayType *AT = dyn_cast<ArrayType>(T)) {
1086 NumElts = AT->getNumElements();
1087 EltTy = AT->getElementType();
1090 if (const StructType *ST = dyn_cast<StructType>(T)) {
1091 NumElts = ST->getNumContainedTypes();
1092 EltTy = ST->getContainedType(0);
1093 for (unsigned n = 1; n < NumElts; ++n) {
1094 if (ST->getContainedType(n) != EltTy)
1102 /// isCompatibleAggregate - Check if T1 and T2 are either the same type or are
1103 /// "homogeneous" aggregates with the same element type and number of elements.
1104 static bool isCompatibleAggregate(const Type *T1, const Type *T2) {
1108 unsigned NumElts1, NumElts2;
1109 const Type *EltTy1, *EltTy2;
1110 if (isHomogeneousAggregate(T1, NumElts1, EltTy1) &&
1111 isHomogeneousAggregate(T2, NumElts2, EltTy2) &&
1112 NumElts1 == NumElts2 &&
1119 /// isSafeMemAccess - Check if a load/store/memcpy operates on the entire AI
1120 /// alloca or has an offset and size that corresponds to a component element
1121 /// within it. The offset checked here may have been formed from a GEP with a
1122 /// pointer bitcasted to a different type.
1123 void SROA::isSafeMemAccess(AllocaInst *AI, uint64_t Offset, uint64_t MemSize,
1124 const Type *MemOpType, bool isStore,
1126 // Check if this is a load/store of the entire alloca.
1127 if (Offset == 0 && MemSize == TD->getTypeAllocSize(AI->getAllocatedType())) {
1128 // This can be safe for MemIntrinsics (where MemOpType is 0) and integer
1129 // loads/stores (which are essentially the same as the MemIntrinsics with
1130 // regard to copying padding between elements). But, if an alloca is
1131 // flagged as both a source and destination of such operations, we'll need
1132 // to check later for padding between elements.
1133 if (!MemOpType || MemOpType->isIntegerTy()) {
1135 Info.isMemCpyDst = true;
1137 Info.isMemCpySrc = true;
1140 // This is also safe for references using a type that is compatible with
1141 // the type of the alloca, so that loads/stores can be rewritten using
1142 // insertvalue/extractvalue.
1143 if (isCompatibleAggregate(MemOpType, AI->getAllocatedType()))
1146 // Check if the offset/size correspond to a component within the alloca type.
1147 const Type *T = AI->getAllocatedType();
1148 if (TypeHasComponent(T, Offset, MemSize))
1151 return MarkUnsafe(Info);
1154 /// TypeHasComponent - Return true if T has a component type with the
1155 /// specified offset and size. If Size is zero, do not check the size.
1156 bool SROA::TypeHasComponent(const Type *T, uint64_t Offset, uint64_t Size) {
1159 if (const StructType *ST = dyn_cast<StructType>(T)) {
1160 const StructLayout *Layout = TD->getStructLayout(ST);
1161 unsigned EltIdx = Layout->getElementContainingOffset(Offset);
1162 EltTy = ST->getContainedType(EltIdx);
1163 EltSize = TD->getTypeAllocSize(EltTy);
1164 Offset -= Layout->getElementOffset(EltIdx);
1165 } else if (const ArrayType *AT = dyn_cast<ArrayType>(T)) {
1166 EltTy = AT->getElementType();
1167 EltSize = TD->getTypeAllocSize(EltTy);
1168 if (Offset >= AT->getNumElements() * EltSize)
1174 if (Offset == 0 && (Size == 0 || EltSize == Size))
1176 // Check if the component spans multiple elements.
1177 if (Offset + Size > EltSize)
1179 return TypeHasComponent(EltTy, Offset, Size);
1182 /// RewriteForScalarRepl - Alloca AI is being split into NewElts, so rewrite
1183 /// the instruction I, which references it, to use the separate elements.
1184 /// Offset indicates the position within AI that is referenced by this
1186 void SROA::RewriteForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset,
1187 SmallVector<AllocaInst*, 32> &NewElts) {
1188 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E; ++UI) {
1189 Instruction *User = cast<Instruction>(*UI);
1191 if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) {
1192 RewriteBitCast(BC, AI, Offset, NewElts);
1193 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
1194 RewriteGEP(GEPI, AI, Offset, NewElts);
1195 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) {
1196 ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength());
1197 uint64_t MemSize = Length->getZExtValue();
1199 MemSize == TD->getTypeAllocSize(AI->getAllocatedType()))
1200 RewriteMemIntrinUserOfAlloca(MI, I, AI, NewElts);
1201 // Otherwise the intrinsic can only touch a single element and the
1202 // address operand will be updated, so nothing else needs to be done.
1203 } else if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1204 const Type *LIType = LI->getType();
1205 if (isCompatibleAggregate(LIType, AI->getAllocatedType())) {
1207 // %res = load { i32, i32 }* %alloc
1209 // %load.0 = load i32* %alloc.0
1210 // %insert.0 insertvalue { i32, i32 } zeroinitializer, i32 %load.0, 0
1211 // %load.1 = load i32* %alloc.1
1212 // %insert = insertvalue { i32, i32 } %insert.0, i32 %load.1, 1
1213 // (Also works for arrays instead of structs)
1214 Value *Insert = UndefValue::get(LIType);
1215 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
1216 Value *Load = new LoadInst(NewElts[i], "load", LI);
1217 Insert = InsertValueInst::Create(Insert, Load, i, "insert", LI);
1219 LI->replaceAllUsesWith(Insert);
1220 DeadInsts.push_back(LI);
1221 } else if (LIType->isIntegerTy() &&
1222 TD->getTypeAllocSize(LIType) ==
1223 TD->getTypeAllocSize(AI->getAllocatedType())) {
1224 // If this is a load of the entire alloca to an integer, rewrite it.
1225 RewriteLoadUserOfWholeAlloca(LI, AI, NewElts);
1227 } else if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
1228 Value *Val = SI->getOperand(0);
1229 const Type *SIType = Val->getType();
1230 if (isCompatibleAggregate(SIType, AI->getAllocatedType())) {
1232 // store { i32, i32 } %val, { i32, i32 }* %alloc
1234 // %val.0 = extractvalue { i32, i32 } %val, 0
1235 // store i32 %val.0, i32* %alloc.0
1236 // %val.1 = extractvalue { i32, i32 } %val, 1
1237 // store i32 %val.1, i32* %alloc.1
1238 // (Also works for arrays instead of structs)
1239 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
1240 Value *Extract = ExtractValueInst::Create(Val, i, Val->getName(), SI);
1241 new StoreInst(Extract, NewElts[i], SI);
1243 DeadInsts.push_back(SI);
1244 } else if (SIType->isIntegerTy() &&
1245 TD->getTypeAllocSize(SIType) ==
1246 TD->getTypeAllocSize(AI->getAllocatedType())) {
1247 // If this is a store of the entire alloca from an integer, rewrite it.
1248 RewriteStoreUserOfWholeAlloca(SI, AI, NewElts);
1254 /// RewriteBitCast - Update a bitcast reference to the alloca being replaced
1255 /// and recursively continue updating all of its uses.
1256 void SROA::RewriteBitCast(BitCastInst *BC, AllocaInst *AI, uint64_t Offset,
1257 SmallVector<AllocaInst*, 32> &NewElts) {
1258 RewriteForScalarRepl(BC, AI, Offset, NewElts);
1259 if (BC->getOperand(0) != AI)
1262 // The bitcast references the original alloca. Replace its uses with
1263 // references to the first new element alloca.
1264 Instruction *Val = NewElts[0];
1265 if (Val->getType() != BC->getDestTy()) {
1266 Val = new BitCastInst(Val, BC->getDestTy(), "", BC);
1269 BC->replaceAllUsesWith(Val);
1270 DeadInsts.push_back(BC);
1273 /// FindElementAndOffset - Return the index of the element containing Offset
1274 /// within the specified type, which must be either a struct or an array.
1275 /// Sets T to the type of the element and Offset to the offset within that
1276 /// element. IdxTy is set to the type of the index result to be used in a
1277 /// GEP instruction.
1278 uint64_t SROA::FindElementAndOffset(const Type *&T, uint64_t &Offset,
1279 const Type *&IdxTy) {
1281 if (const StructType *ST = dyn_cast<StructType>(T)) {
1282 const StructLayout *Layout = TD->getStructLayout(ST);
1283 Idx = Layout->getElementContainingOffset(Offset);
1284 T = ST->getContainedType(Idx);
1285 Offset -= Layout->getElementOffset(Idx);
1286 IdxTy = Type::getInt32Ty(T->getContext());
1289 const ArrayType *AT = cast<ArrayType>(T);
1290 T = AT->getElementType();
1291 uint64_t EltSize = TD->getTypeAllocSize(T);
1292 Idx = Offset / EltSize;
1293 Offset -= Idx * EltSize;
1294 IdxTy = Type::getInt64Ty(T->getContext());
1298 /// RewriteGEP - Check if this GEP instruction moves the pointer across
1299 /// elements of the alloca that are being split apart, and if so, rewrite
1300 /// the GEP to be relative to the new element.
1301 void SROA::RewriteGEP(GetElementPtrInst *GEPI, AllocaInst *AI, uint64_t Offset,
1302 SmallVector<AllocaInst*, 32> &NewElts) {
1303 uint64_t OldOffset = Offset;
1304 SmallVector<Value*, 8> Indices(GEPI->op_begin() + 1, GEPI->op_end());
1305 Offset += TD->getIndexedOffset(GEPI->getPointerOperandType(),
1306 &Indices[0], Indices.size());
1308 RewriteForScalarRepl(GEPI, AI, Offset, NewElts);
1310 const Type *T = AI->getAllocatedType();
1312 uint64_t OldIdx = FindElementAndOffset(T, OldOffset, IdxTy);
1313 if (GEPI->getOperand(0) == AI)
1314 OldIdx = ~0ULL; // Force the GEP to be rewritten.
1316 T = AI->getAllocatedType();
1317 uint64_t EltOffset = Offset;
1318 uint64_t Idx = FindElementAndOffset(T, EltOffset, IdxTy);
1320 // If this GEP does not move the pointer across elements of the alloca
1321 // being split, then it does not needs to be rewritten.
1325 const Type *i32Ty = Type::getInt32Ty(AI->getContext());
1326 SmallVector<Value*, 8> NewArgs;
1327 NewArgs.push_back(Constant::getNullValue(i32Ty));
1328 while (EltOffset != 0) {
1329 uint64_t EltIdx = FindElementAndOffset(T, EltOffset, IdxTy);
1330 NewArgs.push_back(ConstantInt::get(IdxTy, EltIdx));
1332 Instruction *Val = NewElts[Idx];
1333 if (NewArgs.size() > 1) {
1334 Val = GetElementPtrInst::CreateInBounds(Val, NewArgs.begin(),
1335 NewArgs.end(), "", GEPI);
1336 Val->takeName(GEPI);
1338 if (Val->getType() != GEPI->getType())
1339 Val = new BitCastInst(Val, GEPI->getType(), Val->getName(), GEPI);
1340 GEPI->replaceAllUsesWith(Val);
1341 DeadInsts.push_back(GEPI);
1344 /// RewriteMemIntrinUserOfAlloca - MI is a memcpy/memset/memmove from or to AI.
1345 /// Rewrite it to copy or set the elements of the scalarized memory.
1346 void SROA::RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *Inst,
1348 SmallVector<AllocaInst*, 32> &NewElts) {
1349 // If this is a memcpy/memmove, construct the other pointer as the
1350 // appropriate type. The "Other" pointer is the pointer that goes to memory
1351 // that doesn't have anything to do with the alloca that we are promoting. For
1352 // memset, this Value* stays null.
1353 Value *OtherPtr = 0;
1354 unsigned MemAlignment = MI->getAlignment();
1355 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(MI)) { // memmove/memcopy
1356 if (Inst == MTI->getRawDest())
1357 OtherPtr = MTI->getRawSource();
1359 assert(Inst == MTI->getRawSource());
1360 OtherPtr = MTI->getRawDest();
1364 // If there is an other pointer, we want to convert it to the same pointer
1365 // type as AI has, so we can GEP through it safely.
1367 unsigned AddrSpace =
1368 cast<PointerType>(OtherPtr->getType())->getAddressSpace();
1370 // Remove bitcasts and all-zero GEPs from OtherPtr. This is an
1371 // optimization, but it's also required to detect the corner case where
1372 // both pointer operands are referencing the same memory, and where
1373 // OtherPtr may be a bitcast or GEP that currently being rewritten. (This
1374 // function is only called for mem intrinsics that access the whole
1375 // aggregate, so non-zero GEPs are not an issue here.)
1376 OtherPtr = OtherPtr->stripPointerCasts();
1378 // Copying the alloca to itself is a no-op: just delete it.
1379 if (OtherPtr == AI || OtherPtr == NewElts[0]) {
1380 // This code will run twice for a no-op memcpy -- once for each operand.
1381 // Put only one reference to MI on the DeadInsts list.
1382 for (SmallVector<Value*, 32>::const_iterator I = DeadInsts.begin(),
1383 E = DeadInsts.end(); I != E; ++I)
1384 if (*I == MI) return;
1385 DeadInsts.push_back(MI);
1389 // If the pointer is not the right type, insert a bitcast to the right
1392 PointerType::get(AI->getType()->getElementType(), AddrSpace);
1394 if (OtherPtr->getType() != NewTy)
1395 OtherPtr = new BitCastInst(OtherPtr, NewTy, OtherPtr->getName(), MI);
1398 // Process each element of the aggregate.
1399 bool SROADest = MI->getRawDest() == Inst;
1401 Constant *Zero = Constant::getNullValue(Type::getInt32Ty(MI->getContext()));
1403 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
1404 // If this is a memcpy/memmove, emit a GEP of the other element address.
1405 Value *OtherElt = 0;
1406 unsigned OtherEltAlign = MemAlignment;
1409 Value *Idx[2] = { Zero,
1410 ConstantInt::get(Type::getInt32Ty(MI->getContext()), i) };
1411 OtherElt = GetElementPtrInst::CreateInBounds(OtherPtr, Idx, Idx + 2,
1412 OtherPtr->getName()+"."+Twine(i),
1415 const PointerType *OtherPtrTy = cast<PointerType>(OtherPtr->getType());
1416 const Type *OtherTy = OtherPtrTy->getElementType();
1417 if (const StructType *ST = dyn_cast<StructType>(OtherTy)) {
1418 EltOffset = TD->getStructLayout(ST)->getElementOffset(i);
1420 const Type *EltTy = cast<SequentialType>(OtherTy)->getElementType();
1421 EltOffset = TD->getTypeAllocSize(EltTy)*i;
1424 // The alignment of the other pointer is the guaranteed alignment of the
1425 // element, which is affected by both the known alignment of the whole
1426 // mem intrinsic and the alignment of the element. If the alignment of
1427 // the memcpy (f.e.) is 32 but the element is at a 4-byte offset, then the
1428 // known alignment is just 4 bytes.
1429 OtherEltAlign = (unsigned)MinAlign(OtherEltAlign, EltOffset);
1432 Value *EltPtr = NewElts[i];
1433 const Type *EltTy = cast<PointerType>(EltPtr->getType())->getElementType();
1435 // If we got down to a scalar, insert a load or store as appropriate.
1436 if (EltTy->isSingleValueType()) {
1437 if (isa<MemTransferInst>(MI)) {
1439 // From Other to Alloca.
1440 Value *Elt = new LoadInst(OtherElt, "tmp", false, OtherEltAlign, MI);
1441 new StoreInst(Elt, EltPtr, MI);
1443 // From Alloca to Other.
1444 Value *Elt = new LoadInst(EltPtr, "tmp", MI);
1445 new StoreInst(Elt, OtherElt, false, OtherEltAlign, MI);
1449 assert(isa<MemSetInst>(MI));
1451 // If the stored element is zero (common case), just store a null
1454 if (ConstantInt *CI = dyn_cast<ConstantInt>(MI->getArgOperand(1))) {
1456 StoreVal = Constant::getNullValue(EltTy); // 0.0, null, 0, <0,0>
1458 // If EltTy is a vector type, get the element type.
1459 const Type *ValTy = EltTy->getScalarType();
1461 // Construct an integer with the right value.
1462 unsigned EltSize = TD->getTypeSizeInBits(ValTy);
1463 APInt OneVal(EltSize, CI->getZExtValue());
1464 APInt TotalVal(OneVal);
1466 for (unsigned i = 0; 8*i < EltSize; ++i) {
1467 TotalVal = TotalVal.shl(8);
1471 // Convert the integer value to the appropriate type.
1472 StoreVal = ConstantInt::get(CI->getContext(), TotalVal);
1473 if (ValTy->isPointerTy())
1474 StoreVal = ConstantExpr::getIntToPtr(StoreVal, ValTy);
1475 else if (ValTy->isFloatingPointTy())
1476 StoreVal = ConstantExpr::getBitCast(StoreVal, ValTy);
1477 assert(StoreVal->getType() == ValTy && "Type mismatch!");
1479 // If the requested value was a vector constant, create it.
1480 if (EltTy != ValTy) {
1481 unsigned NumElts = cast<VectorType>(ValTy)->getNumElements();
1482 SmallVector<Constant*, 16> Elts(NumElts, StoreVal);
1483 StoreVal = ConstantVector::get(&Elts[0], NumElts);
1486 new StoreInst(StoreVal, EltPtr, MI);
1489 // Otherwise, if we're storing a byte variable, use a memset call for
1493 unsigned EltSize = TD->getTypeAllocSize(EltTy);
1495 IRBuilder<> Builder(MI);
1497 // Finally, insert the meminst for this element.
1498 if (isa<MemSetInst>(MI)) {
1499 Builder.CreateMemSet(EltPtr, MI->getArgOperand(1), EltSize,
1502 assert(isa<MemTransferInst>(MI));
1503 Value *Dst = SROADest ? EltPtr : OtherElt; // Dest ptr
1504 Value *Src = SROADest ? OtherElt : EltPtr; // Src ptr
1506 if (isa<MemCpyInst>(MI))
1507 Builder.CreateMemCpy(Dst, Src, EltSize, OtherEltAlign,MI->isVolatile());
1509 Builder.CreateMemMove(Dst, Src, EltSize,OtherEltAlign,MI->isVolatile());
1512 DeadInsts.push_back(MI);
1515 /// RewriteStoreUserOfWholeAlloca - We found a store of an integer that
1516 /// overwrites the entire allocation. Extract out the pieces of the stored
1517 /// integer and store them individually.
1518 void SROA::RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocaInst *AI,
1519 SmallVector<AllocaInst*, 32> &NewElts){
1520 // Extract each element out of the integer according to its structure offset
1521 // and store the element value to the individual alloca.
1522 Value *SrcVal = SI->getOperand(0);
1523 const Type *AllocaEltTy = AI->getAllocatedType();
1524 uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy);
1526 // Handle tail padding by extending the operand
1527 if (TD->getTypeSizeInBits(SrcVal->getType()) != AllocaSizeBits)
1528 SrcVal = new ZExtInst(SrcVal,
1529 IntegerType::get(SI->getContext(), AllocaSizeBits),
1532 DEBUG(dbgs() << "PROMOTING STORE TO WHOLE ALLOCA: " << *AI << '\n' << *SI
1535 // There are two forms here: AI could be an array or struct. Both cases
1536 // have different ways to compute the element offset.
1537 if (const StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) {
1538 const StructLayout *Layout = TD->getStructLayout(EltSTy);
1540 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
1541 // Get the number of bits to shift SrcVal to get the value.
1542 const Type *FieldTy = EltSTy->getElementType(i);
1543 uint64_t Shift = Layout->getElementOffsetInBits(i);
1545 if (TD->isBigEndian())
1546 Shift = AllocaSizeBits-Shift-TD->getTypeAllocSizeInBits(FieldTy);
1548 Value *EltVal = SrcVal;
1550 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift);
1551 EltVal = BinaryOperator::CreateLShr(EltVal, ShiftVal,
1552 "sroa.store.elt", SI);
1555 // Truncate down to an integer of the right size.
1556 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy);
1558 // Ignore zero sized fields like {}, they obviously contain no data.
1559 if (FieldSizeBits == 0) continue;
1561 if (FieldSizeBits != AllocaSizeBits)
1562 EltVal = new TruncInst(EltVal,
1563 IntegerType::get(SI->getContext(), FieldSizeBits),
1565 Value *DestField = NewElts[i];
1566 if (EltVal->getType() == FieldTy) {
1567 // Storing to an integer field of this size, just do it.
1568 } else if (FieldTy->isFloatingPointTy() || FieldTy->isVectorTy()) {
1569 // Bitcast to the right element type (for fp/vector values).
1570 EltVal = new BitCastInst(EltVal, FieldTy, "", SI);
1572 // Otherwise, bitcast the dest pointer (for aggregates).
1573 DestField = new BitCastInst(DestField,
1574 PointerType::getUnqual(EltVal->getType()),
1577 new StoreInst(EltVal, DestField, SI);
1581 const ArrayType *ATy = cast<ArrayType>(AllocaEltTy);
1582 const Type *ArrayEltTy = ATy->getElementType();
1583 uint64_t ElementOffset = TD->getTypeAllocSizeInBits(ArrayEltTy);
1584 uint64_t ElementSizeBits = TD->getTypeSizeInBits(ArrayEltTy);
1588 if (TD->isBigEndian())
1589 Shift = AllocaSizeBits-ElementOffset;
1593 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
1594 // Ignore zero sized fields like {}, they obviously contain no data.
1595 if (ElementSizeBits == 0) continue;
1597 Value *EltVal = SrcVal;
1599 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift);
1600 EltVal = BinaryOperator::CreateLShr(EltVal, ShiftVal,
1601 "sroa.store.elt", SI);
1604 // Truncate down to an integer of the right size.
1605 if (ElementSizeBits != AllocaSizeBits)
1606 EltVal = new TruncInst(EltVal,
1607 IntegerType::get(SI->getContext(),
1608 ElementSizeBits),"",SI);
1609 Value *DestField = NewElts[i];
1610 if (EltVal->getType() == ArrayEltTy) {
1611 // Storing to an integer field of this size, just do it.
1612 } else if (ArrayEltTy->isFloatingPointTy() ||
1613 ArrayEltTy->isVectorTy()) {
1614 // Bitcast to the right element type (for fp/vector values).
1615 EltVal = new BitCastInst(EltVal, ArrayEltTy, "", SI);
1617 // Otherwise, bitcast the dest pointer (for aggregates).
1618 DestField = new BitCastInst(DestField,
1619 PointerType::getUnqual(EltVal->getType()),
1622 new StoreInst(EltVal, DestField, SI);
1624 if (TD->isBigEndian())
1625 Shift -= ElementOffset;
1627 Shift += ElementOffset;
1631 DeadInsts.push_back(SI);
1634 /// RewriteLoadUserOfWholeAlloca - We found a load of the entire allocation to
1635 /// an integer. Load the individual pieces to form the aggregate value.
1636 void SROA::RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocaInst *AI,
1637 SmallVector<AllocaInst*, 32> &NewElts) {
1638 // Extract each element out of the NewElts according to its structure offset
1639 // and form the result value.
1640 const Type *AllocaEltTy = AI->getAllocatedType();
1641 uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy);
1643 DEBUG(dbgs() << "PROMOTING LOAD OF WHOLE ALLOCA: " << *AI << '\n' << *LI
1646 // There are two forms here: AI could be an array or struct. Both cases
1647 // have different ways to compute the element offset.
1648 const StructLayout *Layout = 0;
1649 uint64_t ArrayEltBitOffset = 0;
1650 if (const StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) {
1651 Layout = TD->getStructLayout(EltSTy);
1653 const Type *ArrayEltTy = cast<ArrayType>(AllocaEltTy)->getElementType();
1654 ArrayEltBitOffset = TD->getTypeAllocSizeInBits(ArrayEltTy);
1658 Constant::getNullValue(IntegerType::get(LI->getContext(), AllocaSizeBits));
1660 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
1661 // Load the value from the alloca. If the NewElt is an aggregate, cast
1662 // the pointer to an integer of the same size before doing the load.
1663 Value *SrcField = NewElts[i];
1664 const Type *FieldTy =
1665 cast<PointerType>(SrcField->getType())->getElementType();
1666 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy);
1668 // Ignore zero sized fields like {}, they obviously contain no data.
1669 if (FieldSizeBits == 0) continue;
1671 const IntegerType *FieldIntTy = IntegerType::get(LI->getContext(),
1673 if (!FieldTy->isIntegerTy() && !FieldTy->isFloatingPointTy() &&
1674 !FieldTy->isVectorTy())
1675 SrcField = new BitCastInst(SrcField,
1676 PointerType::getUnqual(FieldIntTy),
1678 SrcField = new LoadInst(SrcField, "sroa.load.elt", LI);
1680 // If SrcField is a fp or vector of the right size but that isn't an
1681 // integer type, bitcast to an integer so we can shift it.
1682 if (SrcField->getType() != FieldIntTy)
1683 SrcField = new BitCastInst(SrcField, FieldIntTy, "", LI);
1685 // Zero extend the field to be the same size as the final alloca so that
1686 // we can shift and insert it.
1687 if (SrcField->getType() != ResultVal->getType())
1688 SrcField = new ZExtInst(SrcField, ResultVal->getType(), "", LI);
1690 // Determine the number of bits to shift SrcField.
1692 if (Layout) // Struct case.
1693 Shift = Layout->getElementOffsetInBits(i);
1695 Shift = i*ArrayEltBitOffset;
1697 if (TD->isBigEndian())
1698 Shift = AllocaSizeBits-Shift-FieldIntTy->getBitWidth();
1701 Value *ShiftVal = ConstantInt::get(SrcField->getType(), Shift);
1702 SrcField = BinaryOperator::CreateShl(SrcField, ShiftVal, "", LI);
1705 // Don't create an 'or x, 0' on the first iteration.
1706 if (!isa<Constant>(ResultVal) ||
1707 !cast<Constant>(ResultVal)->isNullValue())
1708 ResultVal = BinaryOperator::CreateOr(SrcField, ResultVal, "", LI);
1710 ResultVal = SrcField;
1713 // Handle tail padding by truncating the result
1714 if (TD->getTypeSizeInBits(LI->getType()) != AllocaSizeBits)
1715 ResultVal = new TruncInst(ResultVal, LI->getType(), "", LI);
1717 LI->replaceAllUsesWith(ResultVal);
1718 DeadInsts.push_back(LI);
1721 /// HasPadding - Return true if the specified type has any structure or
1722 /// alignment padding in between the elements that would be split apart
1723 /// by SROA; return false otherwise.
1724 static bool HasPadding(const Type *Ty, const TargetData &TD) {
1725 if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
1726 Ty = ATy->getElementType();
1727 return TD.getTypeSizeInBits(Ty) != TD.getTypeAllocSizeInBits(Ty);
1730 // SROA currently handles only Arrays and Structs.
1731 const StructType *STy = cast<StructType>(Ty);
1732 const StructLayout *SL = TD.getStructLayout(STy);
1733 unsigned PrevFieldBitOffset = 0;
1734 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
1735 unsigned FieldBitOffset = SL->getElementOffsetInBits(i);
1737 // Check to see if there is any padding between this element and the
1740 unsigned PrevFieldEnd =
1741 PrevFieldBitOffset+TD.getTypeSizeInBits(STy->getElementType(i-1));
1742 if (PrevFieldEnd < FieldBitOffset)
1745 PrevFieldBitOffset = FieldBitOffset;
1747 // Check for tail padding.
1748 if (unsigned EltCount = STy->getNumElements()) {
1749 unsigned PrevFieldEnd = PrevFieldBitOffset +
1750 TD.getTypeSizeInBits(STy->getElementType(EltCount-1));
1751 if (PrevFieldEnd < SL->getSizeInBits())
1757 /// isSafeStructAllocaToScalarRepl - Check to see if the specified allocation of
1758 /// an aggregate can be broken down into elements. Return 0 if not, 3 if safe,
1759 /// or 1 if safe after canonicalization has been performed.
1760 bool SROA::isSafeAllocaToScalarRepl(AllocaInst *AI) {
1761 // Loop over the use list of the alloca. We can only transform it if all of
1762 // the users are safe to transform.
1765 isSafeForScalarRepl(AI, AI, 0, Info);
1766 if (Info.isUnsafe) {
1767 DEBUG(dbgs() << "Cannot transform: " << *AI << '\n');
1771 // Okay, we know all the users are promotable. If the aggregate is a memcpy
1772 // source and destination, we have to be careful. In particular, the memcpy
1773 // could be moving around elements that live in structure padding of the LLVM
1774 // types, but may actually be used. In these cases, we refuse to promote the
1776 if (Info.isMemCpySrc && Info.isMemCpyDst &&
1777 HasPadding(AI->getAllocatedType(), *TD))
1785 /// PointsToConstantGlobal - Return true if V (possibly indirectly) points to
1786 /// some part of a constant global variable. This intentionally only accepts
1787 /// constant expressions because we don't can't rewrite arbitrary instructions.
1788 static bool PointsToConstantGlobal(Value *V) {
1789 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
1790 return GV->isConstant();
1791 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
1792 if (CE->getOpcode() == Instruction::BitCast ||
1793 CE->getOpcode() == Instruction::GetElementPtr)
1794 return PointsToConstantGlobal(CE->getOperand(0));
1798 /// isOnlyCopiedFromConstantGlobal - Recursively walk the uses of a (derived)
1799 /// pointer to an alloca. Ignore any reads of the pointer, return false if we
1800 /// see any stores or other unknown uses. If we see pointer arithmetic, keep
1801 /// track of whether it moves the pointer (with isOffset) but otherwise traverse
1802 /// the uses. If we see a memcpy/memmove that targets an unoffseted pointer to
1803 /// the alloca, and if the source pointer is a pointer to a constant global, we
1804 /// can optimize this.
1805 static bool isOnlyCopiedFromConstantGlobal(Value *V, MemTransferInst *&TheCopy,
1807 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) {
1808 User *U = cast<Instruction>(*UI);
1810 if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
1811 // Ignore non-volatile loads, they are always ok.
1812 if (LI->isVolatile()) return false;
1816 if (BitCastInst *BCI = dyn_cast<BitCastInst>(U)) {
1817 // If uses of the bitcast are ok, we are ok.
1818 if (!isOnlyCopiedFromConstantGlobal(BCI, TheCopy, isOffset))
1822 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) {
1823 // If the GEP has all zero indices, it doesn't offset the pointer. If it
1824 // doesn't, it does.
1825 if (!isOnlyCopiedFromConstantGlobal(GEP, TheCopy,
1826 isOffset || !GEP->hasAllZeroIndices()))
1831 if (CallSite CS = U) {
1832 // If this is a readonly/readnone call site, then we know it is just a
1833 // load and we can ignore it.
1834 if (CS.onlyReadsMemory())
1837 // If this is the function being called then we treat it like a load and
1839 if (CS.isCallee(UI))
1842 // If this is being passed as a byval argument, the caller is making a
1843 // copy, so it is only a read of the alloca.
1844 unsigned ArgNo = CS.getArgumentNo(UI);
1845 if (CS.paramHasAttr(ArgNo+1, Attribute::ByVal))
1849 // If this is isn't our memcpy/memmove, reject it as something we can't
1851 MemTransferInst *MI = dyn_cast<MemTransferInst>(U);
1855 // If the transfer is using the alloca as a source of the transfer, then
1856 // ignore it since it is a load (unless the transfer is volatile).
1857 if (UI.getOperandNo() == 1) {
1858 if (MI->isVolatile()) return false;
1862 // If we already have seen a copy, reject the second one.
1863 if (TheCopy) return false;
1865 // If the pointer has been offset from the start of the alloca, we can't
1866 // safely handle this.
1867 if (isOffset) return false;
1869 // If the memintrinsic isn't using the alloca as the dest, reject it.
1870 if (UI.getOperandNo() != 0) return false;
1872 // If the source of the memcpy/move is not a constant global, reject it.
1873 if (!PointsToConstantGlobal(MI->getSource()))
1876 // Otherwise, the transform is safe. Remember the copy instruction.
1882 /// isOnlyCopiedFromConstantGlobal - Return true if the specified alloca is only
1883 /// modified by a copy from a constant global. If we can prove this, we can
1884 /// replace any uses of the alloca with uses of the global directly.
1885 MemTransferInst *SROA::isOnlyCopiedFromConstantGlobal(AllocaInst *AI) {
1886 MemTransferInst *TheCopy = 0;
1887 if (::isOnlyCopiedFromConstantGlobal(AI, TheCopy, false))