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/Transforms/Utils/SSAUpdater.h"
39 #include "llvm/Support/CallSite.h"
40 #include "llvm/Support/Debug.h"
41 #include "llvm/Support/ErrorHandling.h"
42 #include "llvm/Support/GetElementPtrTypeIterator.h"
43 #include "llvm/Support/IRBuilder.h"
44 #include "llvm/Support/MathExtras.h"
45 #include "llvm/Support/raw_ostream.h"
46 #include "llvm/ADT/SmallVector.h"
47 #include "llvm/ADT/Statistic.h"
50 STATISTIC(NumReplaced, "Number of allocas broken up");
51 STATISTIC(NumPromoted, "Number of allocas promoted");
52 STATISTIC(NumConverted, "Number of aggregates converted to scalar");
53 STATISTIC(NumGlobals, "Number of allocas copied from constant global");
56 struct SROA : public FunctionPass {
57 SROA(int T, bool hasDF, char &ID)
58 : FunctionPass(ID), HasDomFrontiers(hasDF) {
65 bool runOnFunction(Function &F);
67 bool performScalarRepl(Function &F);
68 bool performPromotion(Function &F);
74 /// DeadInsts - Keep track of instructions we have made dead, so that
75 /// we can remove them after we are done working.
76 SmallVector<Value*, 32> DeadInsts;
78 /// AllocaInfo - When analyzing uses of an alloca instruction, this captures
79 /// information about the uses. All these fields are initialized to false
80 /// and set to true when something is learned.
82 /// isUnsafe - This is set to true if the alloca cannot be SROA'd.
85 /// isMemCpySrc - This is true if this aggregate is memcpy'd from.
88 /// isMemCpyDst - This is true if this aggregate is memcpy'd into.
91 /// hasSubelementAccess - This is true if a subelement of the alloca is
92 /// ever accessed, or false if the alloca is only accessed with mem
93 /// intrinsics or load/store that only access the entire alloca at once.
94 bool hasSubelementAccess : 1;
96 /// hasALoadOrStore - This is true if there are any loads or stores to it.
97 /// The alloca may just be accessed with memcpy, for example, which would
99 bool hasALoadOrStore : 1;
102 : isUnsafe(false), isMemCpySrc(false), isMemCpyDst(false),
103 hasSubelementAccess(false), hasALoadOrStore(false) {}
106 unsigned SRThreshold;
108 void MarkUnsafe(AllocaInfo &I) { I.isUnsafe = true; }
110 bool isSafeAllocaToScalarRepl(AllocaInst *AI);
112 void isSafeForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset,
114 void isSafeGEP(GetElementPtrInst *GEPI, AllocaInst *AI, uint64_t &Offset,
116 void isSafeMemAccess(AllocaInst *AI, uint64_t Offset, uint64_t MemSize,
117 const Type *MemOpType, bool isStore, AllocaInfo &Info);
118 bool TypeHasComponent(const Type *T, uint64_t Offset, uint64_t Size);
119 uint64_t FindElementAndOffset(const Type *&T, uint64_t &Offset,
122 void DoScalarReplacement(AllocaInst *AI,
123 std::vector<AllocaInst*> &WorkList);
124 void DeleteDeadInstructions();
126 void RewriteForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset,
127 SmallVector<AllocaInst*, 32> &NewElts);
128 void RewriteBitCast(BitCastInst *BC, AllocaInst *AI, uint64_t Offset,
129 SmallVector<AllocaInst*, 32> &NewElts);
130 void RewriteGEP(GetElementPtrInst *GEPI, AllocaInst *AI, uint64_t Offset,
131 SmallVector<AllocaInst*, 32> &NewElts);
132 void RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *Inst,
134 SmallVector<AllocaInst*, 32> &NewElts);
135 void RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocaInst *AI,
136 SmallVector<AllocaInst*, 32> &NewElts);
137 void RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocaInst *AI,
138 SmallVector<AllocaInst*, 32> &NewElts);
140 static MemTransferInst *isOnlyCopiedFromConstantGlobal(AllocaInst *AI);
143 // SROA_DF - SROA that uses DominanceFrontier.
144 struct SROA_DF : public SROA {
147 SROA_DF(int T = -1) : SROA(T, true, ID) {
148 initializeSROA_DFPass(*PassRegistry::getPassRegistry());
151 // getAnalysisUsage - This pass does not require any passes, but we know it
152 // will not alter the CFG, so say so.
153 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
154 AU.addRequired<DominatorTree>();
155 AU.addRequired<DominanceFrontier>();
156 AU.setPreservesCFG();
160 // SROA_SSAUp - SROA that uses SSAUpdater.
161 struct SROA_SSAUp : public SROA {
164 SROA_SSAUp(int T = -1) : SROA(T, false, ID) {
165 initializeSROA_SSAUpPass(*PassRegistry::getPassRegistry());
168 // getAnalysisUsage - This pass does not require any passes, but we know it
169 // will not alter the CFG, so say so.
170 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
171 AU.setPreservesCFG();
177 char SROA_DF::ID = 0;
178 char SROA_SSAUp::ID = 0;
180 INITIALIZE_PASS_BEGIN(SROA_DF, "scalarrepl",
181 "Scalar Replacement of Aggregates (DF)", false, false)
182 INITIALIZE_PASS_DEPENDENCY(DominatorTree)
183 INITIALIZE_PASS_DEPENDENCY(DominanceFrontier)
184 INITIALIZE_PASS_END(SROA_DF, "scalarrepl",
185 "Scalar Replacement of Aggregates (DF)", false, false)
187 INITIALIZE_PASS_BEGIN(SROA_SSAUp, "scalarrepl-ssa",
188 "Scalar Replacement of Aggregates (SSAUp)", false, false)
189 INITIALIZE_PASS_END(SROA_SSAUp, "scalarrepl-ssa",
190 "Scalar Replacement of Aggregates (SSAUp)", false, false)
192 // Public interface to the ScalarReplAggregates pass
193 FunctionPass *llvm::createScalarReplAggregatesPass(int Threshold,
194 bool UseDomFrontier) {
196 return new SROA_DF(Threshold);
197 return new SROA_SSAUp(Threshold);
201 //===----------------------------------------------------------------------===//
202 // Convert To Scalar Optimization.
203 //===----------------------------------------------------------------------===//
206 /// ConvertToScalarInfo - This class implements the "Convert To Scalar"
207 /// optimization, which scans the uses of an alloca and determines if it can
208 /// rewrite it in terms of a single new alloca that can be mem2reg'd.
209 class ConvertToScalarInfo {
210 /// AllocaSize - The size of the alloca being considered.
212 const TargetData &TD;
214 /// IsNotTrivial - This is set to true if there is some access to the object
215 /// which means that mem2reg can't promote it.
218 /// VectorTy - This tracks the type that we should promote the vector to if
219 /// it is possible to turn it into a vector. This starts out null, and if it
220 /// isn't possible to turn into a vector type, it gets set to VoidTy.
221 const Type *VectorTy;
223 /// HadAVector - True if there is at least one vector access to the alloca.
224 /// We don't want to turn random arrays into vectors and use vector element
225 /// insert/extract, but if there are element accesses to something that is
226 /// also declared as a vector, we do want to promote to a vector.
230 explicit ConvertToScalarInfo(unsigned Size, const TargetData &td)
231 : AllocaSize(Size), TD(td) {
232 IsNotTrivial = false;
237 AllocaInst *TryConvert(AllocaInst *AI);
240 bool CanConvertToScalar(Value *V, uint64_t Offset);
241 void MergeInType(const Type *In, uint64_t Offset);
242 void ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, uint64_t Offset);
244 Value *ConvertScalar_ExtractValue(Value *NV, const Type *ToType,
245 uint64_t Offset, IRBuilder<> &Builder);
246 Value *ConvertScalar_InsertValue(Value *StoredVal, Value *ExistingVal,
247 uint64_t Offset, IRBuilder<> &Builder);
249 } // end anonymous namespace.
252 /// IsVerbotenVectorType - Return true if this is a vector type ScalarRepl isn't
253 /// allowed to form. We do this to avoid MMX types, which is a complete hack,
254 /// but is required until the backend is fixed.
255 static bool IsVerbotenVectorType(const VectorType *VTy, const Instruction *I) {
256 StringRef Triple(I->getParent()->getParent()->getParent()->getTargetTriple());
257 if (!Triple.startswith("i386") &&
258 !Triple.startswith("x86_64"))
261 // Reject all the MMX vector types.
262 switch (VTy->getNumElements()) {
263 default: return false;
264 case 1: return VTy->getElementType()->isIntegerTy(64);
265 case 2: return VTy->getElementType()->isIntegerTy(32);
266 case 4: return VTy->getElementType()->isIntegerTy(16);
267 case 8: return VTy->getElementType()->isIntegerTy(8);
272 /// TryConvert - Analyze the specified alloca, and if it is safe to do so,
273 /// rewrite it to be a new alloca which is mem2reg'able. This returns the new
274 /// alloca if possible or null if not.
275 AllocaInst *ConvertToScalarInfo::TryConvert(AllocaInst *AI) {
276 // If we can't convert this scalar, or if mem2reg can trivially do it, bail
278 if (!CanConvertToScalar(AI, 0) || !IsNotTrivial)
281 // If we were able to find a vector type that can handle this with
282 // insert/extract elements, and if there was at least one use that had
283 // a vector type, promote this to a vector. We don't want to promote
284 // random stuff that doesn't use vectors (e.g. <9 x double>) because then
285 // we just get a lot of insert/extracts. If at least one vector is
286 // involved, then we probably really do have a union of vector/array.
288 if (VectorTy && VectorTy->isVectorTy() && HadAVector &&
289 !IsVerbotenVectorType(cast<VectorType>(VectorTy), AI)) {
290 DEBUG(dbgs() << "CONVERT TO VECTOR: " << *AI << "\n TYPE = "
291 << *VectorTy << '\n');
292 NewTy = VectorTy; // Use the vector type.
294 DEBUG(dbgs() << "CONVERT TO SCALAR INTEGER: " << *AI << "\n");
295 // Create and insert the integer alloca.
296 NewTy = IntegerType::get(AI->getContext(), AllocaSize*8);
298 AllocaInst *NewAI = new AllocaInst(NewTy, 0, "", AI->getParent()->begin());
299 ConvertUsesToScalar(AI, NewAI, 0);
303 /// MergeInType - Add the 'In' type to the accumulated vector type (VectorTy)
304 /// so far at the offset specified by Offset (which is specified in bytes).
306 /// There are two cases we handle here:
307 /// 1) A union of vector types of the same size and potentially its elements.
308 /// Here we turn element accesses into insert/extract element operations.
309 /// This promotes a <4 x float> with a store of float to the third element
310 /// into a <4 x float> that uses insert element.
311 /// 2) A fully general blob of memory, which we turn into some (potentially
312 /// large) integer type with extract and insert operations where the loads
313 /// and stores would mutate the memory. We mark this by setting VectorTy
315 void ConvertToScalarInfo::MergeInType(const Type *In, uint64_t Offset) {
316 // If we already decided to turn this into a blob of integer memory, there is
317 // nothing to be done.
318 if (VectorTy && VectorTy->isVoidTy())
321 // If this could be contributing to a vector, analyze it.
323 // If the In type is a vector that is the same size as the alloca, see if it
324 // matches the existing VecTy.
325 if (const VectorType *VInTy = dyn_cast<VectorType>(In)) {
326 // Remember if we saw a vector type.
329 if (VInTy->getBitWidth()/8 == AllocaSize && Offset == 0) {
330 // If we're storing/loading a vector of the right size, allow it as a
331 // vector. If this the first vector we see, remember the type so that
332 // we know the element size. If this is a subsequent access, ignore it
333 // even if it is a differing type but the same size. Worst case we can
334 // bitcast the resultant vectors.
339 } else if (In->isFloatTy() || In->isDoubleTy() ||
340 (In->isIntegerTy() && In->getPrimitiveSizeInBits() >= 8 &&
341 isPowerOf2_32(In->getPrimitiveSizeInBits()))) {
342 // If we're accessing something that could be an element of a vector, see
343 // if the implied vector agrees with what we already have and if Offset is
344 // compatible with it.
345 unsigned EltSize = In->getPrimitiveSizeInBits()/8;
346 if (Offset % EltSize == 0 && AllocaSize % EltSize == 0 &&
348 cast<VectorType>(VectorTy)->getElementType()
349 ->getPrimitiveSizeInBits()/8 == EltSize)) {
351 VectorTy = VectorType::get(In, AllocaSize/EltSize);
356 // Otherwise, we have a case that we can't handle with an optimized vector
357 // form. We can still turn this into a large integer.
358 VectorTy = Type::getVoidTy(In->getContext());
361 /// CanConvertToScalar - V is a pointer. If we can convert the pointee and all
362 /// its accesses to a single vector type, return true and set VecTy to
363 /// the new type. If we could convert the alloca into a single promotable
364 /// integer, return true but set VecTy to VoidTy. Further, if the use is not a
365 /// completely trivial use that mem2reg could promote, set IsNotTrivial. Offset
366 /// is the current offset from the base of the alloca being analyzed.
368 /// If we see at least one access to the value that is as a vector type, set the
370 bool ConvertToScalarInfo::CanConvertToScalar(Value *V, uint64_t Offset) {
371 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) {
372 Instruction *User = cast<Instruction>(*UI);
374 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
375 // Don't break volatile loads.
376 if (LI->isVolatile())
378 // Don't touch MMX operations.
379 if (LI->getType()->isX86_MMXTy())
381 MergeInType(LI->getType(), Offset);
385 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
386 // Storing the pointer, not into the value?
387 if (SI->getOperand(0) == V || SI->isVolatile()) return false;
388 // Don't touch MMX operations.
389 if (SI->getOperand(0)->getType()->isX86_MMXTy())
391 MergeInType(SI->getOperand(0)->getType(), Offset);
395 if (BitCastInst *BCI = dyn_cast<BitCastInst>(User)) {
396 IsNotTrivial = true; // Can't be mem2reg'd.
397 if (!CanConvertToScalar(BCI, Offset))
402 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) {
403 // If this is a GEP with a variable indices, we can't handle it.
404 if (!GEP->hasAllConstantIndices())
407 // Compute the offset that this GEP adds to the pointer.
408 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end());
409 uint64_t GEPOffset = TD.getIndexedOffset(GEP->getPointerOperandType(),
410 &Indices[0], Indices.size());
411 // See if all uses can be converted.
412 if (!CanConvertToScalar(GEP, Offset+GEPOffset))
414 IsNotTrivial = true; // Can't be mem2reg'd.
418 // If this is a constant sized memset of a constant value (e.g. 0) we can
420 if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) {
421 // Store of constant value and constant size.
422 if (!isa<ConstantInt>(MSI->getValue()) ||
423 !isa<ConstantInt>(MSI->getLength()))
425 IsNotTrivial = true; // Can't be mem2reg'd.
429 // If this is a memcpy or memmove into or out of the whole allocation, we
430 // can handle it like a load or store of the scalar type.
431 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) {
432 ConstantInt *Len = dyn_cast<ConstantInt>(MTI->getLength());
433 if (Len == 0 || Len->getZExtValue() != AllocaSize || Offset != 0)
436 IsNotTrivial = true; // Can't be mem2reg'd.
440 // Otherwise, we cannot handle this!
447 /// ConvertUsesToScalar - Convert all of the users of Ptr to use the new alloca
448 /// directly. This happens when we are converting an "integer union" to a
449 /// single integer scalar, or when we are converting a "vector union" to a
450 /// vector with insert/extractelement instructions.
452 /// Offset is an offset from the original alloca, in bits that need to be
453 /// shifted to the right. By the end of this, there should be no uses of Ptr.
454 void ConvertToScalarInfo::ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI,
456 while (!Ptr->use_empty()) {
457 Instruction *User = cast<Instruction>(Ptr->use_back());
459 if (BitCastInst *CI = dyn_cast<BitCastInst>(User)) {
460 ConvertUsesToScalar(CI, NewAI, Offset);
461 CI->eraseFromParent();
465 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) {
466 // Compute the offset that this GEP adds to the pointer.
467 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end());
468 uint64_t GEPOffset = TD.getIndexedOffset(GEP->getPointerOperandType(),
469 &Indices[0], Indices.size());
470 ConvertUsesToScalar(GEP, NewAI, Offset+GEPOffset*8);
471 GEP->eraseFromParent();
475 IRBuilder<> Builder(User);
477 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
478 // The load is a bit extract from NewAI shifted right by Offset bits.
479 Value *LoadedVal = Builder.CreateLoad(NewAI, "tmp");
481 = ConvertScalar_ExtractValue(LoadedVal, LI->getType(), Offset, Builder);
482 LI->replaceAllUsesWith(NewLoadVal);
483 LI->eraseFromParent();
487 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
488 assert(SI->getOperand(0) != Ptr && "Consistency error!");
489 Instruction *Old = Builder.CreateLoad(NewAI, NewAI->getName()+".in");
490 Value *New = ConvertScalar_InsertValue(SI->getOperand(0), Old, Offset,
492 Builder.CreateStore(New, NewAI);
493 SI->eraseFromParent();
495 // If the load we just inserted is now dead, then the inserted store
496 // overwrote the entire thing.
497 if (Old->use_empty())
498 Old->eraseFromParent();
502 // If this is a constant sized memset of a constant value (e.g. 0) we can
503 // transform it into a store of the expanded constant value.
504 if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) {
505 assert(MSI->getRawDest() == Ptr && "Consistency error!");
506 unsigned NumBytes = cast<ConstantInt>(MSI->getLength())->getZExtValue();
508 unsigned Val = cast<ConstantInt>(MSI->getValue())->getZExtValue();
510 // Compute the value replicated the right number of times.
511 APInt APVal(NumBytes*8, Val);
513 // Splat the value if non-zero.
515 for (unsigned i = 1; i != NumBytes; ++i)
518 Instruction *Old = Builder.CreateLoad(NewAI, NewAI->getName()+".in");
519 Value *New = ConvertScalar_InsertValue(
520 ConstantInt::get(User->getContext(), APVal),
521 Old, Offset, Builder);
522 Builder.CreateStore(New, NewAI);
524 // If the load we just inserted is now dead, then the memset overwrote
526 if (Old->use_empty())
527 Old->eraseFromParent();
529 MSI->eraseFromParent();
533 // If this is a memcpy or memmove into or out of the whole allocation, we
534 // can handle it like a load or store of the scalar type.
535 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) {
536 assert(Offset == 0 && "must be store to start of alloca");
538 // If the source and destination are both to the same alloca, then this is
539 // a noop copy-to-self, just delete it. Otherwise, emit a load and store
541 AllocaInst *OrigAI = cast<AllocaInst>(GetUnderlyingObject(Ptr, 0));
543 if (GetUnderlyingObject(MTI->getSource(), 0) != OrigAI) {
544 // Dest must be OrigAI, change this to be a load from the original
545 // pointer (bitcasted), then a store to our new alloca.
546 assert(MTI->getRawDest() == Ptr && "Neither use is of pointer?");
547 Value *SrcPtr = MTI->getSource();
548 const PointerType* SPTy = cast<PointerType>(SrcPtr->getType());
549 const PointerType* AIPTy = cast<PointerType>(NewAI->getType());
550 if (SPTy->getAddressSpace() != AIPTy->getAddressSpace()) {
551 AIPTy = PointerType::get(AIPTy->getElementType(),
552 SPTy->getAddressSpace());
554 SrcPtr = Builder.CreateBitCast(SrcPtr, AIPTy);
556 LoadInst *SrcVal = Builder.CreateLoad(SrcPtr, "srcval");
557 SrcVal->setAlignment(MTI->getAlignment());
558 Builder.CreateStore(SrcVal, NewAI);
559 } else if (GetUnderlyingObject(MTI->getDest(), 0) != OrigAI) {
560 // Src must be OrigAI, change this to be a load from NewAI then a store
561 // through the original dest pointer (bitcasted).
562 assert(MTI->getRawSource() == Ptr && "Neither use is of pointer?");
563 LoadInst *SrcVal = Builder.CreateLoad(NewAI, "srcval");
565 const PointerType* DPTy = cast<PointerType>(MTI->getDest()->getType());
566 const PointerType* AIPTy = cast<PointerType>(NewAI->getType());
567 if (DPTy->getAddressSpace() != AIPTy->getAddressSpace()) {
568 AIPTy = PointerType::get(AIPTy->getElementType(),
569 DPTy->getAddressSpace());
571 Value *DstPtr = Builder.CreateBitCast(MTI->getDest(), AIPTy);
573 StoreInst *NewStore = Builder.CreateStore(SrcVal, DstPtr);
574 NewStore->setAlignment(MTI->getAlignment());
576 // Noop transfer. Src == Dst
579 MTI->eraseFromParent();
583 llvm_unreachable("Unsupported operation!");
587 /// ConvertScalar_ExtractValue - Extract a value of type ToType from an integer
588 /// or vector value FromVal, extracting the bits from the offset specified by
589 /// Offset. This returns the value, which is of type ToType.
591 /// This happens when we are converting an "integer union" to a single
592 /// integer scalar, or when we are converting a "vector union" to a vector with
593 /// insert/extractelement instructions.
595 /// Offset is an offset from the original alloca, in bits that need to be
596 /// shifted to the right.
597 Value *ConvertToScalarInfo::
598 ConvertScalar_ExtractValue(Value *FromVal, const Type *ToType,
599 uint64_t Offset, IRBuilder<> &Builder) {
600 // If the load is of the whole new alloca, no conversion is needed.
601 if (FromVal->getType() == ToType && Offset == 0)
604 // If the result alloca is a vector type, this is either an element
605 // access or a bitcast to another vector type of the same size.
606 if (const VectorType *VTy = dyn_cast<VectorType>(FromVal->getType())) {
607 if (ToType->isVectorTy())
608 return Builder.CreateBitCast(FromVal, ToType, "tmp");
610 // Otherwise it must be an element access.
613 unsigned EltSize = TD.getTypeAllocSizeInBits(VTy->getElementType());
614 Elt = Offset/EltSize;
615 assert(EltSize*Elt == Offset && "Invalid modulus in validity checking");
617 // Return the element extracted out of it.
618 Value *V = Builder.CreateExtractElement(FromVal, ConstantInt::get(
619 Type::getInt32Ty(FromVal->getContext()), Elt), "tmp");
620 if (V->getType() != ToType)
621 V = Builder.CreateBitCast(V, ToType, "tmp");
625 // If ToType is a first class aggregate, extract out each of the pieces and
626 // use insertvalue's to form the FCA.
627 if (const StructType *ST = dyn_cast<StructType>(ToType)) {
628 const StructLayout &Layout = *TD.getStructLayout(ST);
629 Value *Res = UndefValue::get(ST);
630 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) {
631 Value *Elt = ConvertScalar_ExtractValue(FromVal, ST->getElementType(i),
632 Offset+Layout.getElementOffsetInBits(i),
634 Res = Builder.CreateInsertValue(Res, Elt, i, "tmp");
639 if (const ArrayType *AT = dyn_cast<ArrayType>(ToType)) {
640 uint64_t EltSize = TD.getTypeAllocSizeInBits(AT->getElementType());
641 Value *Res = UndefValue::get(AT);
642 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
643 Value *Elt = ConvertScalar_ExtractValue(FromVal, AT->getElementType(),
644 Offset+i*EltSize, Builder);
645 Res = Builder.CreateInsertValue(Res, Elt, i, "tmp");
650 // Otherwise, this must be a union that was converted to an integer value.
651 const IntegerType *NTy = cast<IntegerType>(FromVal->getType());
653 // If this is a big-endian system and the load is narrower than the
654 // full alloca type, we need to do a shift to get the right bits.
656 if (TD.isBigEndian()) {
657 // On big-endian machines, the lowest bit is stored at the bit offset
658 // from the pointer given by getTypeStoreSizeInBits. This matters for
659 // integers with a bitwidth that is not a multiple of 8.
660 ShAmt = TD.getTypeStoreSizeInBits(NTy) -
661 TD.getTypeStoreSizeInBits(ToType) - Offset;
666 // Note: we support negative bitwidths (with shl) which are not defined.
667 // We do this to support (f.e.) loads off the end of a structure where
668 // only some bits are used.
669 if (ShAmt > 0 && (unsigned)ShAmt < NTy->getBitWidth())
670 FromVal = Builder.CreateLShr(FromVal,
671 ConstantInt::get(FromVal->getType(),
673 else if (ShAmt < 0 && (unsigned)-ShAmt < NTy->getBitWidth())
674 FromVal = Builder.CreateShl(FromVal,
675 ConstantInt::get(FromVal->getType(),
678 // Finally, unconditionally truncate the integer to the right width.
679 unsigned LIBitWidth = TD.getTypeSizeInBits(ToType);
680 if (LIBitWidth < NTy->getBitWidth())
682 Builder.CreateTrunc(FromVal, IntegerType::get(FromVal->getContext(),
684 else if (LIBitWidth > NTy->getBitWidth())
686 Builder.CreateZExt(FromVal, IntegerType::get(FromVal->getContext(),
689 // If the result is an integer, this is a trunc or bitcast.
690 if (ToType->isIntegerTy()) {
692 } else if (ToType->isFloatingPointTy() || ToType->isVectorTy()) {
693 // Just do a bitcast, we know the sizes match up.
694 FromVal = Builder.CreateBitCast(FromVal, ToType, "tmp");
696 // Otherwise must be a pointer.
697 FromVal = Builder.CreateIntToPtr(FromVal, ToType, "tmp");
699 assert(FromVal->getType() == ToType && "Didn't convert right?");
703 /// ConvertScalar_InsertValue - Insert the value "SV" into the existing integer
704 /// or vector value "Old" at the offset specified by Offset.
706 /// This happens when we are converting an "integer union" to a
707 /// single integer scalar, or when we are converting a "vector union" to a
708 /// vector with insert/extractelement instructions.
710 /// Offset is an offset from the original alloca, in bits that need to be
711 /// shifted to the right.
712 Value *ConvertToScalarInfo::
713 ConvertScalar_InsertValue(Value *SV, Value *Old,
714 uint64_t Offset, IRBuilder<> &Builder) {
715 // Convert the stored type to the actual type, shift it left to insert
716 // then 'or' into place.
717 const Type *AllocaType = Old->getType();
718 LLVMContext &Context = Old->getContext();
720 if (const VectorType *VTy = dyn_cast<VectorType>(AllocaType)) {
721 uint64_t VecSize = TD.getTypeAllocSizeInBits(VTy);
722 uint64_t ValSize = TD.getTypeAllocSizeInBits(SV->getType());
724 // Changing the whole vector with memset or with an access of a different
726 if (ValSize == VecSize)
727 return Builder.CreateBitCast(SV, AllocaType, "tmp");
729 uint64_t EltSize = TD.getTypeAllocSizeInBits(VTy->getElementType());
731 // Must be an element insertion.
732 unsigned Elt = Offset/EltSize;
734 if (SV->getType() != VTy->getElementType())
735 SV = Builder.CreateBitCast(SV, VTy->getElementType(), "tmp");
737 SV = Builder.CreateInsertElement(Old, SV,
738 ConstantInt::get(Type::getInt32Ty(SV->getContext()), Elt),
743 // If SV is a first-class aggregate value, insert each value recursively.
744 if (const StructType *ST = dyn_cast<StructType>(SV->getType())) {
745 const StructLayout &Layout = *TD.getStructLayout(ST);
746 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) {
747 Value *Elt = Builder.CreateExtractValue(SV, i, "tmp");
748 Old = ConvertScalar_InsertValue(Elt, Old,
749 Offset+Layout.getElementOffsetInBits(i),
755 if (const ArrayType *AT = dyn_cast<ArrayType>(SV->getType())) {
756 uint64_t EltSize = TD.getTypeAllocSizeInBits(AT->getElementType());
757 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
758 Value *Elt = Builder.CreateExtractValue(SV, i, "tmp");
759 Old = ConvertScalar_InsertValue(Elt, Old, Offset+i*EltSize, Builder);
764 // If SV is a float, convert it to the appropriate integer type.
765 // If it is a pointer, do the same.
766 unsigned SrcWidth = TD.getTypeSizeInBits(SV->getType());
767 unsigned DestWidth = TD.getTypeSizeInBits(AllocaType);
768 unsigned SrcStoreWidth = TD.getTypeStoreSizeInBits(SV->getType());
769 unsigned DestStoreWidth = TD.getTypeStoreSizeInBits(AllocaType);
770 if (SV->getType()->isFloatingPointTy() || SV->getType()->isVectorTy())
771 SV = Builder.CreateBitCast(SV,
772 IntegerType::get(SV->getContext(),SrcWidth), "tmp");
773 else if (SV->getType()->isPointerTy())
774 SV = Builder.CreatePtrToInt(SV, TD.getIntPtrType(SV->getContext()), "tmp");
776 // Zero extend or truncate the value if needed.
777 if (SV->getType() != AllocaType) {
778 if (SV->getType()->getPrimitiveSizeInBits() <
779 AllocaType->getPrimitiveSizeInBits())
780 SV = Builder.CreateZExt(SV, AllocaType, "tmp");
782 // Truncation may be needed if storing more than the alloca can hold
783 // (undefined behavior).
784 SV = Builder.CreateTrunc(SV, AllocaType, "tmp");
785 SrcWidth = DestWidth;
786 SrcStoreWidth = DestStoreWidth;
790 // If this is a big-endian system and the store is narrower than the
791 // full alloca type, we need to do a shift to get the right bits.
793 if (TD.isBigEndian()) {
794 // On big-endian machines, the lowest bit is stored at the bit offset
795 // from the pointer given by getTypeStoreSizeInBits. This matters for
796 // integers with a bitwidth that is not a multiple of 8.
797 ShAmt = DestStoreWidth - SrcStoreWidth - Offset;
802 // Note: we support negative bitwidths (with shr) which are not defined.
803 // We do this to support (f.e.) stores off the end of a structure where
804 // only some bits in the structure are set.
805 APInt Mask(APInt::getLowBitsSet(DestWidth, SrcWidth));
806 if (ShAmt > 0 && (unsigned)ShAmt < DestWidth) {
807 SV = Builder.CreateShl(SV, ConstantInt::get(SV->getType(),
810 } else if (ShAmt < 0 && (unsigned)-ShAmt < DestWidth) {
811 SV = Builder.CreateLShr(SV, ConstantInt::get(SV->getType(),
813 Mask = Mask.lshr(-ShAmt);
816 // Mask out the bits we are about to insert from the old value, and or
818 if (SrcWidth != DestWidth) {
819 assert(DestWidth > SrcWidth);
820 Old = Builder.CreateAnd(Old, ConstantInt::get(Context, ~Mask), "mask");
821 SV = Builder.CreateOr(Old, SV, "ins");
827 //===----------------------------------------------------------------------===//
829 //===----------------------------------------------------------------------===//
832 bool SROA::runOnFunction(Function &F) {
833 TD = getAnalysisIfAvailable<TargetData>();
835 bool Changed = performPromotion(F);
837 // FIXME: ScalarRepl currently depends on TargetData more than it
838 // theoretically needs to. It should be refactored in order to support
839 // target-independent IR. Until this is done, just skip the actual
840 // scalar-replacement portion of this pass.
841 if (!TD) return Changed;
844 bool LocalChange = performScalarRepl(F);
845 if (!LocalChange) break; // No need to repromote if no scalarrepl
847 LocalChange = performPromotion(F);
848 if (!LocalChange) break; // No need to re-scalarrepl if no promotion
855 class AllocaPromoter : public LoadAndStorePromoter {
858 AllocaPromoter(const SmallVectorImpl<Instruction*> &Insts, SSAUpdater &S)
859 : LoadAndStorePromoter(Insts, S), AI(0) {}
861 void run(AllocaInst *AI, const SmallVectorImpl<Instruction*> &Insts) {
862 // Remember which alloca we're promoting (for isInstInList).
864 LoadAndStorePromoter::run(Insts);
865 AI->eraseFromParent();
868 virtual bool isInstInList(Instruction *I,
869 const SmallVectorImpl<Instruction*> &Insts) const {
870 if (LoadInst *LI = dyn_cast<LoadInst>(I))
871 return LI->getOperand(0) == AI;
872 return cast<StoreInst>(I)->getPointerOperand() == AI;
875 } // end anon namespace
877 bool SROA::performPromotion(Function &F) {
878 std::vector<AllocaInst*> Allocas;
879 DominatorTree *DT = 0;
880 DominanceFrontier *DF = 0;
881 if (HasDomFrontiers) {
882 DT = &getAnalysis<DominatorTree>();
883 DF = &getAnalysis<DominanceFrontier>();
886 BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function
888 bool Changed = false;
889 SmallVector<Instruction*, 64> Insts;
893 // Find allocas that are safe to promote, by looking at all instructions in
895 for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I)
896 if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) // Is it an alloca?
897 if (isAllocaPromotable(AI))
898 Allocas.push_back(AI);
900 if (Allocas.empty()) break;
903 PromoteMemToReg(Allocas, *DT, *DF);
906 for (unsigned i = 0, e = Allocas.size(); i != e; ++i) {
907 AllocaInst *AI = Allocas[i];
909 // Build list of instructions to promote.
910 for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end();
912 Insts.push_back(cast<Instruction>(*UI));
914 AllocaPromoter(Insts, SSA).run(AI, Insts);
918 NumPromoted += Allocas.size();
926 /// ShouldAttemptScalarRepl - Decide if an alloca is a good candidate for
927 /// SROA. It must be a struct or array type with a small number of elements.
928 static bool ShouldAttemptScalarRepl(AllocaInst *AI) {
929 const Type *T = AI->getAllocatedType();
930 // Do not promote any struct into more than 32 separate vars.
931 if (const StructType *ST = dyn_cast<StructType>(T))
932 return ST->getNumElements() <= 32;
933 // Arrays are much less likely to be safe for SROA; only consider
934 // them if they are very small.
935 if (const ArrayType *AT = dyn_cast<ArrayType>(T))
936 return AT->getNumElements() <= 8;
941 // performScalarRepl - This algorithm is a simple worklist driven algorithm,
942 // which runs on all of the malloc/alloca instructions in the function, removing
943 // them if they are only used by getelementptr instructions.
945 bool SROA::performScalarRepl(Function &F) {
946 std::vector<AllocaInst*> WorkList;
948 // Scan the entry basic block, adding allocas to the worklist.
949 BasicBlock &BB = F.getEntryBlock();
950 for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I)
951 if (AllocaInst *A = dyn_cast<AllocaInst>(I))
952 WorkList.push_back(A);
954 // Process the worklist
955 bool Changed = false;
956 while (!WorkList.empty()) {
957 AllocaInst *AI = WorkList.back();
960 // Handle dead allocas trivially. These can be formed by SROA'ing arrays
961 // with unused elements.
962 if (AI->use_empty()) {
963 AI->eraseFromParent();
968 // If this alloca is impossible for us to promote, reject it early.
969 if (AI->isArrayAllocation() || !AI->getAllocatedType()->isSized())
972 // Check to see if this allocation is only modified by a memcpy/memmove from
973 // a constant global. If this is the case, we can change all users to use
974 // the constant global instead. This is commonly produced by the CFE by
975 // constructs like "void foo() { int A[] = {1,2,3,4,5,6,7,8,9...}; }" if 'A'
976 // is only subsequently read.
977 if (MemTransferInst *TheCopy = isOnlyCopiedFromConstantGlobal(AI)) {
978 DEBUG(dbgs() << "Found alloca equal to global: " << *AI << '\n');
979 DEBUG(dbgs() << " memcpy = " << *TheCopy << '\n');
980 Constant *TheSrc = cast<Constant>(TheCopy->getSource());
981 AI->replaceAllUsesWith(ConstantExpr::getBitCast(TheSrc, AI->getType()));
982 TheCopy->eraseFromParent(); // Don't mutate the global.
983 AI->eraseFromParent();
989 // Check to see if we can perform the core SROA transformation. We cannot
990 // transform the allocation instruction if it is an array allocation
991 // (allocations OF arrays are ok though), and an allocation of a scalar
992 // value cannot be decomposed at all.
993 uint64_t AllocaSize = TD->getTypeAllocSize(AI->getAllocatedType());
995 // Do not promote [0 x %struct].
996 if (AllocaSize == 0) continue;
998 // Do not promote any struct whose size is too big.
999 if (AllocaSize > SRThreshold) continue;
1001 // If the alloca looks like a good candidate for scalar replacement, and if
1002 // all its users can be transformed, then split up the aggregate into its
1003 // separate elements.
1004 if (ShouldAttemptScalarRepl(AI) && isSafeAllocaToScalarRepl(AI)) {
1005 DoScalarReplacement(AI, WorkList);
1010 // If we can turn this aggregate value (potentially with casts) into a
1011 // simple scalar value that can be mem2reg'd into a register value.
1012 // IsNotTrivial tracks whether this is something that mem2reg could have
1013 // promoted itself. If so, we don't want to transform it needlessly. Note
1014 // that we can't just check based on the type: the alloca may be of an i32
1015 // but that has pointer arithmetic to set byte 3 of it or something.
1016 if (AllocaInst *NewAI =
1017 ConvertToScalarInfo((unsigned)AllocaSize, *TD).TryConvert(AI)) {
1018 NewAI->takeName(AI);
1019 AI->eraseFromParent();
1025 // Otherwise, couldn't process this alloca.
1031 /// DoScalarReplacement - This alloca satisfied the isSafeAllocaToScalarRepl
1032 /// predicate, do SROA now.
1033 void SROA::DoScalarReplacement(AllocaInst *AI,
1034 std::vector<AllocaInst*> &WorkList) {
1035 DEBUG(dbgs() << "Found inst to SROA: " << *AI << '\n');
1036 SmallVector<AllocaInst*, 32> ElementAllocas;
1037 if (const StructType *ST = dyn_cast<StructType>(AI->getAllocatedType())) {
1038 ElementAllocas.reserve(ST->getNumContainedTypes());
1039 for (unsigned i = 0, e = ST->getNumContainedTypes(); i != e; ++i) {
1040 AllocaInst *NA = new AllocaInst(ST->getContainedType(i), 0,
1042 AI->getName() + "." + Twine(i), AI);
1043 ElementAllocas.push_back(NA);
1044 WorkList.push_back(NA); // Add to worklist for recursive processing
1047 const ArrayType *AT = cast<ArrayType>(AI->getAllocatedType());
1048 ElementAllocas.reserve(AT->getNumElements());
1049 const Type *ElTy = AT->getElementType();
1050 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
1051 AllocaInst *NA = new AllocaInst(ElTy, 0, AI->getAlignment(),
1052 AI->getName() + "." + Twine(i), AI);
1053 ElementAllocas.push_back(NA);
1054 WorkList.push_back(NA); // Add to worklist for recursive processing
1058 // Now that we have created the new alloca instructions, rewrite all the
1059 // uses of the old alloca.
1060 RewriteForScalarRepl(AI, AI, 0, ElementAllocas);
1062 // Now erase any instructions that were made dead while rewriting the alloca.
1063 DeleteDeadInstructions();
1064 AI->eraseFromParent();
1069 /// DeleteDeadInstructions - Erase instructions on the DeadInstrs list,
1070 /// recursively including all their operands that become trivially dead.
1071 void SROA::DeleteDeadInstructions() {
1072 while (!DeadInsts.empty()) {
1073 Instruction *I = cast<Instruction>(DeadInsts.pop_back_val());
1075 for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI)
1076 if (Instruction *U = dyn_cast<Instruction>(*OI)) {
1077 // Zero out the operand and see if it becomes trivially dead.
1078 // (But, don't add allocas to the dead instruction list -- they are
1079 // already on the worklist and will be deleted separately.)
1081 if (isInstructionTriviallyDead(U) && !isa<AllocaInst>(U))
1082 DeadInsts.push_back(U);
1085 I->eraseFromParent();
1089 /// isSafeForScalarRepl - Check if instruction I is a safe use with regard to
1090 /// performing scalar replacement of alloca AI. The results are flagged in
1091 /// the Info parameter. Offset indicates the position within AI that is
1092 /// referenced by this instruction.
1093 void SROA::isSafeForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset,
1095 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E; ++UI) {
1096 Instruction *User = cast<Instruction>(*UI);
1098 if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) {
1099 isSafeForScalarRepl(BC, AI, Offset, Info);
1100 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
1101 uint64_t GEPOffset = Offset;
1102 isSafeGEP(GEPI, AI, GEPOffset, Info);
1104 isSafeForScalarRepl(GEPI, AI, GEPOffset, Info);
1105 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) {
1106 ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength());
1108 isSafeMemAccess(AI, Offset, Length->getZExtValue(), 0,
1109 UI.getOperandNo() == 0, Info);
1112 } else if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1113 if (!LI->isVolatile()) {
1114 const Type *LIType = LI->getType();
1115 isSafeMemAccess(AI, Offset, TD->getTypeAllocSize(LIType),
1116 LIType, false, Info);
1117 Info.hasALoadOrStore = true;
1120 } else if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
1121 // Store is ok if storing INTO the pointer, not storing the pointer
1122 if (!SI->isVolatile() && SI->getOperand(0) != I) {
1123 const Type *SIType = SI->getOperand(0)->getType();
1124 isSafeMemAccess(AI, Offset, TD->getTypeAllocSize(SIType),
1125 SIType, true, Info);
1126 Info.hasALoadOrStore = true;
1130 DEBUG(errs() << " Transformation preventing inst: " << *User << '\n');
1133 if (Info.isUnsafe) return;
1137 /// isSafeGEP - Check if a GEP instruction can be handled for scalar
1138 /// replacement. It is safe when all the indices are constant, in-bounds
1139 /// references, and when the resulting offset corresponds to an element within
1140 /// the alloca type. The results are flagged in the Info parameter. Upon
1141 /// return, Offset is adjusted as specified by the GEP indices.
1142 void SROA::isSafeGEP(GetElementPtrInst *GEPI, AllocaInst *AI,
1143 uint64_t &Offset, AllocaInfo &Info) {
1144 gep_type_iterator GEPIt = gep_type_begin(GEPI), E = gep_type_end(GEPI);
1148 // Walk through the GEP type indices, checking the types that this indexes
1150 for (; GEPIt != E; ++GEPIt) {
1151 // Ignore struct elements, no extra checking needed for these.
1152 if ((*GEPIt)->isStructTy())
1155 ConstantInt *IdxVal = dyn_cast<ConstantInt>(GEPIt.getOperand());
1157 return MarkUnsafe(Info);
1160 // Compute the offset due to this GEP and check if the alloca has a
1161 // component element at that offset.
1162 SmallVector<Value*, 8> Indices(GEPI->op_begin() + 1, GEPI->op_end());
1163 Offset += TD->getIndexedOffset(GEPI->getPointerOperandType(),
1164 &Indices[0], Indices.size());
1165 if (!TypeHasComponent(AI->getAllocatedType(), Offset, 0))
1169 /// isHomogeneousAggregate - Check if type T is a struct or array containing
1170 /// elements of the same type (which is always true for arrays). If so,
1171 /// return true with NumElts and EltTy set to the number of elements and the
1172 /// element type, respectively.
1173 static bool isHomogeneousAggregate(const Type *T, unsigned &NumElts,
1174 const Type *&EltTy) {
1175 if (const ArrayType *AT = dyn_cast<ArrayType>(T)) {
1176 NumElts = AT->getNumElements();
1177 EltTy = (NumElts == 0 ? 0 : AT->getElementType());
1180 if (const StructType *ST = dyn_cast<StructType>(T)) {
1181 NumElts = ST->getNumContainedTypes();
1182 EltTy = (NumElts == 0 ? 0 : ST->getContainedType(0));
1183 for (unsigned n = 1; n < NumElts; ++n) {
1184 if (ST->getContainedType(n) != EltTy)
1192 /// isCompatibleAggregate - Check if T1 and T2 are either the same type or are
1193 /// "homogeneous" aggregates with the same element type and number of elements.
1194 static bool isCompatibleAggregate(const Type *T1, const Type *T2) {
1198 unsigned NumElts1, NumElts2;
1199 const Type *EltTy1, *EltTy2;
1200 if (isHomogeneousAggregate(T1, NumElts1, EltTy1) &&
1201 isHomogeneousAggregate(T2, NumElts2, EltTy2) &&
1202 NumElts1 == NumElts2 &&
1209 /// isSafeMemAccess - Check if a load/store/memcpy operates on the entire AI
1210 /// alloca or has an offset and size that corresponds to a component element
1211 /// within it. The offset checked here may have been formed from a GEP with a
1212 /// pointer bitcasted to a different type.
1213 void SROA::isSafeMemAccess(AllocaInst *AI, uint64_t Offset, uint64_t MemSize,
1214 const Type *MemOpType, bool isStore,
1216 // Check if this is a load/store of the entire alloca.
1217 if (Offset == 0 && MemSize == TD->getTypeAllocSize(AI->getAllocatedType())) {
1218 // This can be safe for MemIntrinsics (where MemOpType is 0) and integer
1219 // loads/stores (which are essentially the same as the MemIntrinsics with
1220 // regard to copying padding between elements). But, if an alloca is
1221 // flagged as both a source and destination of such operations, we'll need
1222 // to check later for padding between elements.
1223 if (!MemOpType || MemOpType->isIntegerTy()) {
1225 Info.isMemCpyDst = true;
1227 Info.isMemCpySrc = true;
1230 // This is also safe for references using a type that is compatible with
1231 // the type of the alloca, so that loads/stores can be rewritten using
1232 // insertvalue/extractvalue.
1233 if (isCompatibleAggregate(MemOpType, AI->getAllocatedType())) {
1234 Info.hasSubelementAccess = true;
1238 // Check if the offset/size correspond to a component within the alloca type.
1239 const Type *T = AI->getAllocatedType();
1240 if (TypeHasComponent(T, Offset, MemSize)) {
1241 Info.hasSubelementAccess = true;
1245 return MarkUnsafe(Info);
1248 /// TypeHasComponent - Return true if T has a component type with the
1249 /// specified offset and size. If Size is zero, do not check the size.
1250 bool SROA::TypeHasComponent(const Type *T, uint64_t Offset, uint64_t Size) {
1253 if (const StructType *ST = dyn_cast<StructType>(T)) {
1254 const StructLayout *Layout = TD->getStructLayout(ST);
1255 unsigned EltIdx = Layout->getElementContainingOffset(Offset);
1256 EltTy = ST->getContainedType(EltIdx);
1257 EltSize = TD->getTypeAllocSize(EltTy);
1258 Offset -= Layout->getElementOffset(EltIdx);
1259 } else if (const ArrayType *AT = dyn_cast<ArrayType>(T)) {
1260 EltTy = AT->getElementType();
1261 EltSize = TD->getTypeAllocSize(EltTy);
1262 if (Offset >= AT->getNumElements() * EltSize)
1268 if (Offset == 0 && (Size == 0 || EltSize == Size))
1270 // Check if the component spans multiple elements.
1271 if (Offset + Size > EltSize)
1273 return TypeHasComponent(EltTy, Offset, Size);
1276 /// RewriteForScalarRepl - Alloca AI is being split into NewElts, so rewrite
1277 /// the instruction I, which references it, to use the separate elements.
1278 /// Offset indicates the position within AI that is referenced by this
1280 void SROA::RewriteForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset,
1281 SmallVector<AllocaInst*, 32> &NewElts) {
1282 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E; ++UI) {
1283 Instruction *User = cast<Instruction>(*UI);
1285 if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) {
1286 RewriteBitCast(BC, AI, Offset, NewElts);
1287 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
1288 RewriteGEP(GEPI, AI, Offset, NewElts);
1289 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) {
1290 ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength());
1291 uint64_t MemSize = Length->getZExtValue();
1293 MemSize == TD->getTypeAllocSize(AI->getAllocatedType()))
1294 RewriteMemIntrinUserOfAlloca(MI, I, AI, NewElts);
1295 // Otherwise the intrinsic can only touch a single element and the
1296 // address operand will be updated, so nothing else needs to be done.
1297 } else if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1298 const Type *LIType = LI->getType();
1300 if (isCompatibleAggregate(LIType, AI->getAllocatedType())) {
1302 // %res = load { i32, i32 }* %alloc
1304 // %load.0 = load i32* %alloc.0
1305 // %insert.0 insertvalue { i32, i32 } zeroinitializer, i32 %load.0, 0
1306 // %load.1 = load i32* %alloc.1
1307 // %insert = insertvalue { i32, i32 } %insert.0, i32 %load.1, 1
1308 // (Also works for arrays instead of structs)
1309 Value *Insert = UndefValue::get(LIType);
1310 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
1311 Value *Load = new LoadInst(NewElts[i], "load", LI);
1312 Insert = InsertValueInst::Create(Insert, Load, i, "insert", LI);
1314 LI->replaceAllUsesWith(Insert);
1315 DeadInsts.push_back(LI);
1316 } else if (LIType->isIntegerTy() &&
1317 TD->getTypeAllocSize(LIType) ==
1318 TD->getTypeAllocSize(AI->getAllocatedType())) {
1319 // If this is a load of the entire alloca to an integer, rewrite it.
1320 RewriteLoadUserOfWholeAlloca(LI, AI, NewElts);
1322 } else if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
1323 Value *Val = SI->getOperand(0);
1324 const Type *SIType = Val->getType();
1325 if (isCompatibleAggregate(SIType, AI->getAllocatedType())) {
1327 // store { i32, i32 } %val, { i32, i32 }* %alloc
1329 // %val.0 = extractvalue { i32, i32 } %val, 0
1330 // store i32 %val.0, i32* %alloc.0
1331 // %val.1 = extractvalue { i32, i32 } %val, 1
1332 // store i32 %val.1, i32* %alloc.1
1333 // (Also works for arrays instead of structs)
1334 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
1335 Value *Extract = ExtractValueInst::Create(Val, i, Val->getName(), SI);
1336 new StoreInst(Extract, NewElts[i], SI);
1338 DeadInsts.push_back(SI);
1339 } else if (SIType->isIntegerTy() &&
1340 TD->getTypeAllocSize(SIType) ==
1341 TD->getTypeAllocSize(AI->getAllocatedType())) {
1342 // If this is a store of the entire alloca from an integer, rewrite it.
1343 RewriteStoreUserOfWholeAlloca(SI, AI, NewElts);
1349 /// RewriteBitCast - Update a bitcast reference to the alloca being replaced
1350 /// and recursively continue updating all of its uses.
1351 void SROA::RewriteBitCast(BitCastInst *BC, AllocaInst *AI, uint64_t Offset,
1352 SmallVector<AllocaInst*, 32> &NewElts) {
1353 RewriteForScalarRepl(BC, AI, Offset, NewElts);
1354 if (BC->getOperand(0) != AI)
1357 // The bitcast references the original alloca. Replace its uses with
1358 // references to the first new element alloca.
1359 Instruction *Val = NewElts[0];
1360 if (Val->getType() != BC->getDestTy()) {
1361 Val = new BitCastInst(Val, BC->getDestTy(), "", BC);
1364 BC->replaceAllUsesWith(Val);
1365 DeadInsts.push_back(BC);
1368 /// FindElementAndOffset - Return the index of the element containing Offset
1369 /// within the specified type, which must be either a struct or an array.
1370 /// Sets T to the type of the element and Offset to the offset within that
1371 /// element. IdxTy is set to the type of the index result to be used in a
1372 /// GEP instruction.
1373 uint64_t SROA::FindElementAndOffset(const Type *&T, uint64_t &Offset,
1374 const Type *&IdxTy) {
1376 if (const StructType *ST = dyn_cast<StructType>(T)) {
1377 const StructLayout *Layout = TD->getStructLayout(ST);
1378 Idx = Layout->getElementContainingOffset(Offset);
1379 T = ST->getContainedType(Idx);
1380 Offset -= Layout->getElementOffset(Idx);
1381 IdxTy = Type::getInt32Ty(T->getContext());
1384 const ArrayType *AT = cast<ArrayType>(T);
1385 T = AT->getElementType();
1386 uint64_t EltSize = TD->getTypeAllocSize(T);
1387 Idx = Offset / EltSize;
1388 Offset -= Idx * EltSize;
1389 IdxTy = Type::getInt64Ty(T->getContext());
1393 /// RewriteGEP - Check if this GEP instruction moves the pointer across
1394 /// elements of the alloca that are being split apart, and if so, rewrite
1395 /// the GEP to be relative to the new element.
1396 void SROA::RewriteGEP(GetElementPtrInst *GEPI, AllocaInst *AI, uint64_t Offset,
1397 SmallVector<AllocaInst*, 32> &NewElts) {
1398 uint64_t OldOffset = Offset;
1399 SmallVector<Value*, 8> Indices(GEPI->op_begin() + 1, GEPI->op_end());
1400 Offset += TD->getIndexedOffset(GEPI->getPointerOperandType(),
1401 &Indices[0], Indices.size());
1403 RewriteForScalarRepl(GEPI, AI, Offset, NewElts);
1405 const Type *T = AI->getAllocatedType();
1407 uint64_t OldIdx = FindElementAndOffset(T, OldOffset, IdxTy);
1408 if (GEPI->getOperand(0) == AI)
1409 OldIdx = ~0ULL; // Force the GEP to be rewritten.
1411 T = AI->getAllocatedType();
1412 uint64_t EltOffset = Offset;
1413 uint64_t Idx = FindElementAndOffset(T, EltOffset, IdxTy);
1415 // If this GEP does not move the pointer across elements of the alloca
1416 // being split, then it does not needs to be rewritten.
1420 const Type *i32Ty = Type::getInt32Ty(AI->getContext());
1421 SmallVector<Value*, 8> NewArgs;
1422 NewArgs.push_back(Constant::getNullValue(i32Ty));
1423 while (EltOffset != 0) {
1424 uint64_t EltIdx = FindElementAndOffset(T, EltOffset, IdxTy);
1425 NewArgs.push_back(ConstantInt::get(IdxTy, EltIdx));
1427 Instruction *Val = NewElts[Idx];
1428 if (NewArgs.size() > 1) {
1429 Val = GetElementPtrInst::CreateInBounds(Val, NewArgs.begin(),
1430 NewArgs.end(), "", GEPI);
1431 Val->takeName(GEPI);
1433 if (Val->getType() != GEPI->getType())
1434 Val = new BitCastInst(Val, GEPI->getType(), Val->getName(), GEPI);
1435 GEPI->replaceAllUsesWith(Val);
1436 DeadInsts.push_back(GEPI);
1439 /// RewriteMemIntrinUserOfAlloca - MI is a memcpy/memset/memmove from or to AI.
1440 /// Rewrite it to copy or set the elements of the scalarized memory.
1441 void SROA::RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *Inst,
1443 SmallVector<AllocaInst*, 32> &NewElts) {
1444 // If this is a memcpy/memmove, construct the other pointer as the
1445 // appropriate type. The "Other" pointer is the pointer that goes to memory
1446 // that doesn't have anything to do with the alloca that we are promoting. For
1447 // memset, this Value* stays null.
1448 Value *OtherPtr = 0;
1449 unsigned MemAlignment = MI->getAlignment();
1450 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(MI)) { // memmove/memcopy
1451 if (Inst == MTI->getRawDest())
1452 OtherPtr = MTI->getRawSource();
1454 assert(Inst == MTI->getRawSource());
1455 OtherPtr = MTI->getRawDest();
1459 // If there is an other pointer, we want to convert it to the same pointer
1460 // type as AI has, so we can GEP through it safely.
1462 unsigned AddrSpace =
1463 cast<PointerType>(OtherPtr->getType())->getAddressSpace();
1465 // Remove bitcasts and all-zero GEPs from OtherPtr. This is an
1466 // optimization, but it's also required to detect the corner case where
1467 // both pointer operands are referencing the same memory, and where
1468 // OtherPtr may be a bitcast or GEP that currently being rewritten. (This
1469 // function is only called for mem intrinsics that access the whole
1470 // aggregate, so non-zero GEPs are not an issue here.)
1471 OtherPtr = OtherPtr->stripPointerCasts();
1473 // Copying the alloca to itself is a no-op: just delete it.
1474 if (OtherPtr == AI || OtherPtr == NewElts[0]) {
1475 // This code will run twice for a no-op memcpy -- once for each operand.
1476 // Put only one reference to MI on the DeadInsts list.
1477 for (SmallVector<Value*, 32>::const_iterator I = DeadInsts.begin(),
1478 E = DeadInsts.end(); I != E; ++I)
1479 if (*I == MI) return;
1480 DeadInsts.push_back(MI);
1484 // If the pointer is not the right type, insert a bitcast to the right
1487 PointerType::get(AI->getType()->getElementType(), AddrSpace);
1489 if (OtherPtr->getType() != NewTy)
1490 OtherPtr = new BitCastInst(OtherPtr, NewTy, OtherPtr->getName(), MI);
1493 // Process each element of the aggregate.
1494 bool SROADest = MI->getRawDest() == Inst;
1496 Constant *Zero = Constant::getNullValue(Type::getInt32Ty(MI->getContext()));
1498 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
1499 // If this is a memcpy/memmove, emit a GEP of the other element address.
1500 Value *OtherElt = 0;
1501 unsigned OtherEltAlign = MemAlignment;
1504 Value *Idx[2] = { Zero,
1505 ConstantInt::get(Type::getInt32Ty(MI->getContext()), i) };
1506 OtherElt = GetElementPtrInst::CreateInBounds(OtherPtr, Idx, Idx + 2,
1507 OtherPtr->getName()+"."+Twine(i),
1510 const PointerType *OtherPtrTy = cast<PointerType>(OtherPtr->getType());
1511 const Type *OtherTy = OtherPtrTy->getElementType();
1512 if (const StructType *ST = dyn_cast<StructType>(OtherTy)) {
1513 EltOffset = TD->getStructLayout(ST)->getElementOffset(i);
1515 const Type *EltTy = cast<SequentialType>(OtherTy)->getElementType();
1516 EltOffset = TD->getTypeAllocSize(EltTy)*i;
1519 // The alignment of the other pointer is the guaranteed alignment of the
1520 // element, which is affected by both the known alignment of the whole
1521 // mem intrinsic and the alignment of the element. If the alignment of
1522 // the memcpy (f.e.) is 32 but the element is at a 4-byte offset, then the
1523 // known alignment is just 4 bytes.
1524 OtherEltAlign = (unsigned)MinAlign(OtherEltAlign, EltOffset);
1527 Value *EltPtr = NewElts[i];
1528 const Type *EltTy = cast<PointerType>(EltPtr->getType())->getElementType();
1530 // If we got down to a scalar, insert a load or store as appropriate.
1531 if (EltTy->isSingleValueType()) {
1532 if (isa<MemTransferInst>(MI)) {
1534 // From Other to Alloca.
1535 Value *Elt = new LoadInst(OtherElt, "tmp", false, OtherEltAlign, MI);
1536 new StoreInst(Elt, EltPtr, MI);
1538 // From Alloca to Other.
1539 Value *Elt = new LoadInst(EltPtr, "tmp", MI);
1540 new StoreInst(Elt, OtherElt, false, OtherEltAlign, MI);
1544 assert(isa<MemSetInst>(MI));
1546 // If the stored element is zero (common case), just store a null
1549 if (ConstantInt *CI = dyn_cast<ConstantInt>(MI->getArgOperand(1))) {
1551 StoreVal = Constant::getNullValue(EltTy); // 0.0, null, 0, <0,0>
1553 // If EltTy is a vector type, get the element type.
1554 const Type *ValTy = EltTy->getScalarType();
1556 // Construct an integer with the right value.
1557 unsigned EltSize = TD->getTypeSizeInBits(ValTy);
1558 APInt OneVal(EltSize, CI->getZExtValue());
1559 APInt TotalVal(OneVal);
1561 for (unsigned i = 0; 8*i < EltSize; ++i) {
1562 TotalVal = TotalVal.shl(8);
1566 // Convert the integer value to the appropriate type.
1567 StoreVal = ConstantInt::get(CI->getContext(), TotalVal);
1568 if (ValTy->isPointerTy())
1569 StoreVal = ConstantExpr::getIntToPtr(StoreVal, ValTy);
1570 else if (ValTy->isFloatingPointTy())
1571 StoreVal = ConstantExpr::getBitCast(StoreVal, ValTy);
1572 assert(StoreVal->getType() == ValTy && "Type mismatch!");
1574 // If the requested value was a vector constant, create it.
1575 if (EltTy != ValTy) {
1576 unsigned NumElts = cast<VectorType>(ValTy)->getNumElements();
1577 SmallVector<Constant*, 16> Elts(NumElts, StoreVal);
1578 StoreVal = ConstantVector::get(&Elts[0], NumElts);
1581 new StoreInst(StoreVal, EltPtr, MI);
1584 // Otherwise, if we're storing a byte variable, use a memset call for
1588 unsigned EltSize = TD->getTypeAllocSize(EltTy);
1590 IRBuilder<> Builder(MI);
1592 // Finally, insert the meminst for this element.
1593 if (isa<MemSetInst>(MI)) {
1594 Builder.CreateMemSet(EltPtr, MI->getArgOperand(1), EltSize,
1597 assert(isa<MemTransferInst>(MI));
1598 Value *Dst = SROADest ? EltPtr : OtherElt; // Dest ptr
1599 Value *Src = SROADest ? OtherElt : EltPtr; // Src ptr
1601 if (isa<MemCpyInst>(MI))
1602 Builder.CreateMemCpy(Dst, Src, EltSize, OtherEltAlign,MI->isVolatile());
1604 Builder.CreateMemMove(Dst, Src, EltSize,OtherEltAlign,MI->isVolatile());
1607 DeadInsts.push_back(MI);
1610 /// RewriteStoreUserOfWholeAlloca - We found a store of an integer that
1611 /// overwrites the entire allocation. Extract out the pieces of the stored
1612 /// integer and store them individually.
1613 void SROA::RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocaInst *AI,
1614 SmallVector<AllocaInst*, 32> &NewElts){
1615 // Extract each element out of the integer according to its structure offset
1616 // and store the element value to the individual alloca.
1617 Value *SrcVal = SI->getOperand(0);
1618 const Type *AllocaEltTy = AI->getAllocatedType();
1619 uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy);
1621 IRBuilder<> Builder(SI);
1623 // Handle tail padding by extending the operand
1624 if (TD->getTypeSizeInBits(SrcVal->getType()) != AllocaSizeBits)
1625 SrcVal = Builder.CreateZExt(SrcVal,
1626 IntegerType::get(SI->getContext(), AllocaSizeBits));
1628 DEBUG(dbgs() << "PROMOTING STORE TO WHOLE ALLOCA: " << *AI << '\n' << *SI
1631 // There are two forms here: AI could be an array or struct. Both cases
1632 // have different ways to compute the element offset.
1633 if (const StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) {
1634 const StructLayout *Layout = TD->getStructLayout(EltSTy);
1636 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
1637 // Get the number of bits to shift SrcVal to get the value.
1638 const Type *FieldTy = EltSTy->getElementType(i);
1639 uint64_t Shift = Layout->getElementOffsetInBits(i);
1641 if (TD->isBigEndian())
1642 Shift = AllocaSizeBits-Shift-TD->getTypeAllocSizeInBits(FieldTy);
1644 Value *EltVal = SrcVal;
1646 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift);
1647 EltVal = Builder.CreateLShr(EltVal, ShiftVal, "sroa.store.elt");
1650 // Truncate down to an integer of the right size.
1651 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy);
1653 // Ignore zero sized fields like {}, they obviously contain no data.
1654 if (FieldSizeBits == 0) continue;
1656 if (FieldSizeBits != AllocaSizeBits)
1657 EltVal = Builder.CreateTrunc(EltVal,
1658 IntegerType::get(SI->getContext(), FieldSizeBits));
1659 Value *DestField = NewElts[i];
1660 if (EltVal->getType() == FieldTy) {
1661 // Storing to an integer field of this size, just do it.
1662 } else if (FieldTy->isFloatingPointTy() || FieldTy->isVectorTy()) {
1663 // Bitcast to the right element type (for fp/vector values).
1664 EltVal = Builder.CreateBitCast(EltVal, FieldTy);
1666 // Otherwise, bitcast the dest pointer (for aggregates).
1667 DestField = Builder.CreateBitCast(DestField,
1668 PointerType::getUnqual(EltVal->getType()));
1670 new StoreInst(EltVal, DestField, SI);
1674 const ArrayType *ATy = cast<ArrayType>(AllocaEltTy);
1675 const Type *ArrayEltTy = ATy->getElementType();
1676 uint64_t ElementOffset = TD->getTypeAllocSizeInBits(ArrayEltTy);
1677 uint64_t ElementSizeBits = TD->getTypeSizeInBits(ArrayEltTy);
1681 if (TD->isBigEndian())
1682 Shift = AllocaSizeBits-ElementOffset;
1686 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
1687 // Ignore zero sized fields like {}, they obviously contain no data.
1688 if (ElementSizeBits == 0) continue;
1690 Value *EltVal = SrcVal;
1692 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift);
1693 EltVal = Builder.CreateLShr(EltVal, ShiftVal, "sroa.store.elt");
1696 // Truncate down to an integer of the right size.
1697 if (ElementSizeBits != AllocaSizeBits)
1698 EltVal = Builder.CreateTrunc(EltVal,
1699 IntegerType::get(SI->getContext(),
1701 Value *DestField = NewElts[i];
1702 if (EltVal->getType() == ArrayEltTy) {
1703 // Storing to an integer field of this size, just do it.
1704 } else if (ArrayEltTy->isFloatingPointTy() ||
1705 ArrayEltTy->isVectorTy()) {
1706 // Bitcast to the right element type (for fp/vector values).
1707 EltVal = Builder.CreateBitCast(EltVal, ArrayEltTy);
1709 // Otherwise, bitcast the dest pointer (for aggregates).
1710 DestField = Builder.CreateBitCast(DestField,
1711 PointerType::getUnqual(EltVal->getType()));
1713 new StoreInst(EltVal, DestField, SI);
1715 if (TD->isBigEndian())
1716 Shift -= ElementOffset;
1718 Shift += ElementOffset;
1722 DeadInsts.push_back(SI);
1725 /// RewriteLoadUserOfWholeAlloca - We found a load of the entire allocation to
1726 /// an integer. Load the individual pieces to form the aggregate value.
1727 void SROA::RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocaInst *AI,
1728 SmallVector<AllocaInst*, 32> &NewElts) {
1729 // Extract each element out of the NewElts according to its structure offset
1730 // and form the result value.
1731 const Type *AllocaEltTy = AI->getAllocatedType();
1732 uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy);
1734 DEBUG(dbgs() << "PROMOTING LOAD OF WHOLE ALLOCA: " << *AI << '\n' << *LI
1737 // There are two forms here: AI could be an array or struct. Both cases
1738 // have different ways to compute the element offset.
1739 const StructLayout *Layout = 0;
1740 uint64_t ArrayEltBitOffset = 0;
1741 if (const StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) {
1742 Layout = TD->getStructLayout(EltSTy);
1744 const Type *ArrayEltTy = cast<ArrayType>(AllocaEltTy)->getElementType();
1745 ArrayEltBitOffset = TD->getTypeAllocSizeInBits(ArrayEltTy);
1749 Constant::getNullValue(IntegerType::get(LI->getContext(), AllocaSizeBits));
1751 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
1752 // Load the value from the alloca. If the NewElt is an aggregate, cast
1753 // the pointer to an integer of the same size before doing the load.
1754 Value *SrcField = NewElts[i];
1755 const Type *FieldTy =
1756 cast<PointerType>(SrcField->getType())->getElementType();
1757 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy);
1759 // Ignore zero sized fields like {}, they obviously contain no data.
1760 if (FieldSizeBits == 0) continue;
1762 const IntegerType *FieldIntTy = IntegerType::get(LI->getContext(),
1764 if (!FieldTy->isIntegerTy() && !FieldTy->isFloatingPointTy() &&
1765 !FieldTy->isVectorTy())
1766 SrcField = new BitCastInst(SrcField,
1767 PointerType::getUnqual(FieldIntTy),
1769 SrcField = new LoadInst(SrcField, "sroa.load.elt", LI);
1771 // If SrcField is a fp or vector of the right size but that isn't an
1772 // integer type, bitcast to an integer so we can shift it.
1773 if (SrcField->getType() != FieldIntTy)
1774 SrcField = new BitCastInst(SrcField, FieldIntTy, "", LI);
1776 // Zero extend the field to be the same size as the final alloca so that
1777 // we can shift and insert it.
1778 if (SrcField->getType() != ResultVal->getType())
1779 SrcField = new ZExtInst(SrcField, ResultVal->getType(), "", LI);
1781 // Determine the number of bits to shift SrcField.
1783 if (Layout) // Struct case.
1784 Shift = Layout->getElementOffsetInBits(i);
1786 Shift = i*ArrayEltBitOffset;
1788 if (TD->isBigEndian())
1789 Shift = AllocaSizeBits-Shift-FieldIntTy->getBitWidth();
1792 Value *ShiftVal = ConstantInt::get(SrcField->getType(), Shift);
1793 SrcField = BinaryOperator::CreateShl(SrcField, ShiftVal, "", LI);
1796 // Don't create an 'or x, 0' on the first iteration.
1797 if (!isa<Constant>(ResultVal) ||
1798 !cast<Constant>(ResultVal)->isNullValue())
1799 ResultVal = BinaryOperator::CreateOr(SrcField, ResultVal, "", LI);
1801 ResultVal = SrcField;
1804 // Handle tail padding by truncating the result
1805 if (TD->getTypeSizeInBits(LI->getType()) != AllocaSizeBits)
1806 ResultVal = new TruncInst(ResultVal, LI->getType(), "", LI);
1808 LI->replaceAllUsesWith(ResultVal);
1809 DeadInsts.push_back(LI);
1812 /// HasPadding - Return true if the specified type has any structure or
1813 /// alignment padding in between the elements that would be split apart
1814 /// by SROA; return false otherwise.
1815 static bool HasPadding(const Type *Ty, const TargetData &TD) {
1816 if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
1817 Ty = ATy->getElementType();
1818 return TD.getTypeSizeInBits(Ty) != TD.getTypeAllocSizeInBits(Ty);
1821 // SROA currently handles only Arrays and Structs.
1822 const StructType *STy = cast<StructType>(Ty);
1823 const StructLayout *SL = TD.getStructLayout(STy);
1824 unsigned PrevFieldBitOffset = 0;
1825 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
1826 unsigned FieldBitOffset = SL->getElementOffsetInBits(i);
1828 // Check to see if there is any padding between this element and the
1831 unsigned PrevFieldEnd =
1832 PrevFieldBitOffset+TD.getTypeSizeInBits(STy->getElementType(i-1));
1833 if (PrevFieldEnd < FieldBitOffset)
1836 PrevFieldBitOffset = FieldBitOffset;
1838 // Check for tail padding.
1839 if (unsigned EltCount = STy->getNumElements()) {
1840 unsigned PrevFieldEnd = PrevFieldBitOffset +
1841 TD.getTypeSizeInBits(STy->getElementType(EltCount-1));
1842 if (PrevFieldEnd < SL->getSizeInBits())
1848 /// isSafeStructAllocaToScalarRepl - Check to see if the specified allocation of
1849 /// an aggregate can be broken down into elements. Return 0 if not, 3 if safe,
1850 /// or 1 if safe after canonicalization has been performed.
1851 bool SROA::isSafeAllocaToScalarRepl(AllocaInst *AI) {
1852 // Loop over the use list of the alloca. We can only transform it if all of
1853 // the users are safe to transform.
1856 isSafeForScalarRepl(AI, AI, 0, Info);
1857 if (Info.isUnsafe) {
1858 DEBUG(dbgs() << "Cannot transform: " << *AI << '\n');
1862 // Okay, we know all the users are promotable. If the aggregate is a memcpy
1863 // source and destination, we have to be careful. In particular, the memcpy
1864 // could be moving around elements that live in structure padding of the LLVM
1865 // types, but may actually be used. In these cases, we refuse to promote the
1867 if (Info.isMemCpySrc && Info.isMemCpyDst &&
1868 HasPadding(AI->getAllocatedType(), *TD))
1871 // If the alloca is never has an access to just *part* of it, but is accessed
1872 // with loads and stores, then we should use ConvertToScalarInfo to promote
1873 // the alloca instead of promoting each piece at a time and inserting fission
1875 if (!Info.hasSubelementAccess && Info.hasALoadOrStore) {
1876 // If the struct/array just has one element, use basic SRoA.
1877 if (const StructType *ST = dyn_cast<StructType>(AI->getAllocatedType())) {
1878 if (ST->getNumElements() > 1) return false;
1880 if (cast<ArrayType>(AI->getAllocatedType())->getNumElements() > 1)
1889 /// PointsToConstantGlobal - Return true if V (possibly indirectly) points to
1890 /// some part of a constant global variable. This intentionally only accepts
1891 /// constant expressions because we don't can't rewrite arbitrary instructions.
1892 static bool PointsToConstantGlobal(Value *V) {
1893 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
1894 return GV->isConstant();
1895 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
1896 if (CE->getOpcode() == Instruction::BitCast ||
1897 CE->getOpcode() == Instruction::GetElementPtr)
1898 return PointsToConstantGlobal(CE->getOperand(0));
1902 /// isOnlyCopiedFromConstantGlobal - Recursively walk the uses of a (derived)
1903 /// pointer to an alloca. Ignore any reads of the pointer, return false if we
1904 /// see any stores or other unknown uses. If we see pointer arithmetic, keep
1905 /// track of whether it moves the pointer (with isOffset) but otherwise traverse
1906 /// the uses. If we see a memcpy/memmove that targets an unoffseted pointer to
1907 /// the alloca, and if the source pointer is a pointer to a constant global, we
1908 /// can optimize this.
1909 static bool isOnlyCopiedFromConstantGlobal(Value *V, MemTransferInst *&TheCopy,
1911 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) {
1912 User *U = cast<Instruction>(*UI);
1914 if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
1915 // Ignore non-volatile loads, they are always ok.
1916 if (LI->isVolatile()) return false;
1920 if (BitCastInst *BCI = dyn_cast<BitCastInst>(U)) {
1921 // If uses of the bitcast are ok, we are ok.
1922 if (!isOnlyCopiedFromConstantGlobal(BCI, TheCopy, isOffset))
1926 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) {
1927 // If the GEP has all zero indices, it doesn't offset the pointer. If it
1928 // doesn't, it does.
1929 if (!isOnlyCopiedFromConstantGlobal(GEP, TheCopy,
1930 isOffset || !GEP->hasAllZeroIndices()))
1935 if (CallSite CS = U) {
1936 // If this is a readonly/readnone call site, then we know it is just a
1937 // load and we can ignore it.
1938 if (CS.onlyReadsMemory())
1941 // If this is the function being called then we treat it like a load and
1943 if (CS.isCallee(UI))
1946 // If this is being passed as a byval argument, the caller is making a
1947 // copy, so it is only a read of the alloca.
1948 unsigned ArgNo = CS.getArgumentNo(UI);
1949 if (CS.paramHasAttr(ArgNo+1, Attribute::ByVal))
1953 // If this is isn't our memcpy/memmove, reject it as something we can't
1955 MemTransferInst *MI = dyn_cast<MemTransferInst>(U);
1959 // If the transfer is using the alloca as a source of the transfer, then
1960 // ignore it since it is a load (unless the transfer is volatile).
1961 if (UI.getOperandNo() == 1) {
1962 if (MI->isVolatile()) return false;
1966 // If we already have seen a copy, reject the second one.
1967 if (TheCopy) return false;
1969 // If the pointer has been offset from the start of the alloca, we can't
1970 // safely handle this.
1971 if (isOffset) return false;
1973 // If the memintrinsic isn't using the alloca as the dest, reject it.
1974 if (UI.getOperandNo() != 0) return false;
1976 // If the source of the memcpy/move is not a constant global, reject it.
1977 if (!PointsToConstantGlobal(MI->getSource()))
1980 // Otherwise, the transform is safe. Remember the copy instruction.
1986 /// isOnlyCopiedFromConstantGlobal - Return true if the specified alloca is only
1987 /// modified by a copy from a constant global. If we can prove this, we can
1988 /// replace any uses of the alloca with uses of the global directly.
1989 MemTransferInst *SROA::isOnlyCopiedFromConstantGlobal(AllocaInst *AI) {
1990 MemTransferInst *TheCopy = 0;
1991 if (::isOnlyCopiedFromConstantGlobal(AI, TheCopy, false))