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.
92 : isUnsafe(false), isMemCpySrc(false), isMemCpyDst(false) {}
97 void MarkUnsafe(AllocaInfo &I) { I.isUnsafe = true; }
99 bool isSafeAllocaToScalarRepl(AllocaInst *AI);
101 void isSafeForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset,
103 void isSafeGEP(GetElementPtrInst *GEPI, AllocaInst *AI, uint64_t &Offset,
105 void isSafeMemAccess(AllocaInst *AI, uint64_t Offset, uint64_t MemSize,
106 const Type *MemOpType, bool isStore, AllocaInfo &Info);
107 bool TypeHasComponent(const Type *T, uint64_t Offset, uint64_t Size);
108 uint64_t FindElementAndOffset(const Type *&T, uint64_t &Offset,
111 void DoScalarReplacement(AllocaInst *AI,
112 std::vector<AllocaInst*> &WorkList);
113 void DeleteDeadInstructions();
115 void RewriteForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset,
116 SmallVector<AllocaInst*, 32> &NewElts);
117 void RewriteBitCast(BitCastInst *BC, AllocaInst *AI, uint64_t Offset,
118 SmallVector<AllocaInst*, 32> &NewElts);
119 void RewriteGEP(GetElementPtrInst *GEPI, AllocaInst *AI, uint64_t Offset,
120 SmallVector<AllocaInst*, 32> &NewElts);
121 void RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *Inst,
123 SmallVector<AllocaInst*, 32> &NewElts);
124 void RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocaInst *AI,
125 SmallVector<AllocaInst*, 32> &NewElts);
126 void RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocaInst *AI,
127 SmallVector<AllocaInst*, 32> &NewElts);
129 static MemTransferInst *isOnlyCopiedFromConstantGlobal(AllocaInst *AI);
132 // SROA_DF - SROA that uses DominanceFrontier.
133 struct SROA_DF : public SROA {
136 SROA_DF(int T = -1) : SROA(T, true, ID) {
137 initializeSROA_DFPass(*PassRegistry::getPassRegistry());
140 // getAnalysisUsage - This pass does not require any passes, but we know it
141 // will not alter the CFG, so say so.
142 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
143 AU.addRequired<DominatorTree>();
144 AU.addRequired<DominanceFrontier>();
145 AU.setPreservesCFG();
149 // SROA_SSAUp - SROA that uses SSAUpdater.
150 struct SROA_SSAUp : public SROA {
153 SROA_SSAUp(int T = -1) : SROA(T, false, ID) {
154 initializeSROA_SSAUpPass(*PassRegistry::getPassRegistry());
157 // getAnalysisUsage - This pass does not require any passes, but we know it
158 // will not alter the CFG, so say so.
159 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
160 AU.setPreservesCFG();
166 char SROA_DF::ID = 0;
167 char SROA_SSAUp::ID = 0;
169 INITIALIZE_PASS_BEGIN(SROA_DF, "scalarrepl",
170 "Scalar Replacement of Aggregates (DF)", false, false)
171 INITIALIZE_PASS_DEPENDENCY(DominatorTree)
172 INITIALIZE_PASS_DEPENDENCY(DominanceFrontier)
173 INITIALIZE_PASS_END(SROA_DF, "scalarrepl",
174 "Scalar Replacement of Aggregates (DF)", false, false)
176 INITIALIZE_PASS_BEGIN(SROA_SSAUp, "scalarrepl-ssa",
177 "Scalar Replacement of Aggregates (SSAUp)", false, false)
178 INITIALIZE_PASS_END(SROA_SSAUp, "scalarrepl-ssa",
179 "Scalar Replacement of Aggregates (SSAUp)", false, false)
181 // Public interface to the ScalarReplAggregates pass
182 FunctionPass *llvm::createScalarReplAggregatesPass(int Threshold,
183 bool UseDomFrontier) {
185 return new SROA_DF(Threshold);
186 return new SROA_SSAUp(Threshold);
190 //===----------------------------------------------------------------------===//
191 // Convert To Scalar Optimization.
192 //===----------------------------------------------------------------------===//
195 /// ConvertToScalarInfo - This class implements the "Convert To Scalar"
196 /// optimization, which scans the uses of an alloca and determines if it can
197 /// rewrite it in terms of a single new alloca that can be mem2reg'd.
198 class ConvertToScalarInfo {
199 /// AllocaSize - The size of the alloca being considered.
201 const TargetData &TD;
203 /// IsNotTrivial - This is set to true if there is some access to the object
204 /// which means that mem2reg can't promote it.
207 /// VectorTy - This tracks the type that we should promote the vector to if
208 /// it is possible to turn it into a vector. This starts out null, and if it
209 /// isn't possible to turn into a vector type, it gets set to VoidTy.
210 const Type *VectorTy;
212 /// HadAVector - True if there is at least one vector access to the alloca.
213 /// We don't want to turn random arrays into vectors and use vector element
214 /// insert/extract, but if there are element accesses to something that is
215 /// also declared as a vector, we do want to promote to a vector.
219 explicit ConvertToScalarInfo(unsigned Size, const TargetData &td)
220 : AllocaSize(Size), TD(td) {
221 IsNotTrivial = false;
226 AllocaInst *TryConvert(AllocaInst *AI);
229 bool CanConvertToScalar(Value *V, uint64_t Offset);
230 void MergeInType(const Type *In, uint64_t Offset);
231 void ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, uint64_t Offset);
233 Value *ConvertScalar_ExtractValue(Value *NV, const Type *ToType,
234 uint64_t Offset, IRBuilder<> &Builder);
235 Value *ConvertScalar_InsertValue(Value *StoredVal, Value *ExistingVal,
236 uint64_t Offset, IRBuilder<> &Builder);
238 } // end anonymous namespace.
241 /// IsVerbotenVectorType - Return true if this is a vector type ScalarRepl isn't
242 /// allowed to form. We do this to avoid MMX types, which is a complete hack,
243 /// but is required until the backend is fixed.
244 static bool IsVerbotenVectorType(const VectorType *VTy, const Instruction *I) {
245 StringRef Triple(I->getParent()->getParent()->getParent()->getTargetTriple());
246 if (!Triple.startswith("i386") &&
247 !Triple.startswith("x86_64"))
250 // Reject all the MMX vector types.
251 switch (VTy->getNumElements()) {
252 default: return false;
253 case 1: return VTy->getElementType()->isIntegerTy(64);
254 case 2: return VTy->getElementType()->isIntegerTy(32);
255 case 4: return VTy->getElementType()->isIntegerTy(16);
256 case 8: return VTy->getElementType()->isIntegerTy(8);
261 /// TryConvert - Analyze the specified alloca, and if it is safe to do so,
262 /// rewrite it to be a new alloca which is mem2reg'able. This returns the new
263 /// alloca if possible or null if not.
264 AllocaInst *ConvertToScalarInfo::TryConvert(AllocaInst *AI) {
265 // If we can't convert this scalar, or if mem2reg can trivially do it, bail
267 if (!CanConvertToScalar(AI, 0) || !IsNotTrivial)
270 // If we were able to find a vector type that can handle this with
271 // insert/extract elements, and if there was at least one use that had
272 // a vector type, promote this to a vector. We don't want to promote
273 // random stuff that doesn't use vectors (e.g. <9 x double>) because then
274 // we just get a lot of insert/extracts. If at least one vector is
275 // involved, then we probably really do have a union of vector/array.
277 if (VectorTy && VectorTy->isVectorTy() && HadAVector &&
278 !IsVerbotenVectorType(cast<VectorType>(VectorTy), AI)) {
279 DEBUG(dbgs() << "CONVERT TO VECTOR: " << *AI << "\n TYPE = "
280 << *VectorTy << '\n');
281 NewTy = VectorTy; // Use the vector type.
283 DEBUG(dbgs() << "CONVERT TO SCALAR INTEGER: " << *AI << "\n");
284 // Create and insert the integer alloca.
285 NewTy = IntegerType::get(AI->getContext(), AllocaSize*8);
287 AllocaInst *NewAI = new AllocaInst(NewTy, 0, "", AI->getParent()->begin());
288 ConvertUsesToScalar(AI, NewAI, 0);
292 /// MergeInType - Add the 'In' type to the accumulated vector type (VectorTy)
293 /// so far at the offset specified by Offset (which is specified in bytes).
295 /// There are two cases we handle here:
296 /// 1) A union of vector types of the same size and potentially its elements.
297 /// Here we turn element accesses into insert/extract element operations.
298 /// This promotes a <4 x float> with a store of float to the third element
299 /// into a <4 x float> that uses insert element.
300 /// 2) A fully general blob of memory, which we turn into some (potentially
301 /// large) integer type with extract and insert operations where the loads
302 /// and stores would mutate the memory. We mark this by setting VectorTy
304 void ConvertToScalarInfo::MergeInType(const Type *In, uint64_t Offset) {
305 // If we already decided to turn this into a blob of integer memory, there is
306 // nothing to be done.
307 if (VectorTy && VectorTy->isVoidTy())
310 // If this could be contributing to a vector, analyze it.
312 // If the In type is a vector that is the same size as the alloca, see if it
313 // matches the existing VecTy.
314 if (const VectorType *VInTy = dyn_cast<VectorType>(In)) {
315 // Remember if we saw a vector type.
318 if (VInTy->getBitWidth()/8 == AllocaSize && Offset == 0) {
319 // If we're storing/loading a vector of the right size, allow it as a
320 // vector. If this the first vector we see, remember the type so that
321 // we know the element size. If this is a subsequent access, ignore it
322 // even if it is a differing type but the same size. Worst case we can
323 // bitcast the resultant vectors.
328 } else if (In->isFloatTy() || In->isDoubleTy() ||
329 (In->isIntegerTy() && In->getPrimitiveSizeInBits() >= 8 &&
330 isPowerOf2_32(In->getPrimitiveSizeInBits()))) {
331 // If we're accessing something that could be an element of a vector, see
332 // if the implied vector agrees with what we already have and if Offset is
333 // compatible with it.
334 unsigned EltSize = In->getPrimitiveSizeInBits()/8;
335 if (Offset % EltSize == 0 && AllocaSize % EltSize == 0 &&
337 cast<VectorType>(VectorTy)->getElementType()
338 ->getPrimitiveSizeInBits()/8 == EltSize)) {
340 VectorTy = VectorType::get(In, AllocaSize/EltSize);
345 // Otherwise, we have a case that we can't handle with an optimized vector
346 // form. We can still turn this into a large integer.
347 VectorTy = Type::getVoidTy(In->getContext());
350 /// CanConvertToScalar - V is a pointer. If we can convert the pointee and all
351 /// its accesses to a single vector type, return true and set VecTy to
352 /// the new type. If we could convert the alloca into a single promotable
353 /// integer, return true but set VecTy to VoidTy. Further, if the use is not a
354 /// completely trivial use that mem2reg could promote, set IsNotTrivial. Offset
355 /// is the current offset from the base of the alloca being analyzed.
357 /// If we see at least one access to the value that is as a vector type, set the
359 bool ConvertToScalarInfo::CanConvertToScalar(Value *V, uint64_t Offset) {
360 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) {
361 Instruction *User = cast<Instruction>(*UI);
363 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
364 // Don't break volatile loads.
365 if (LI->isVolatile())
367 // Don't touch MMX operations.
368 if (LI->getType()->isX86_MMXTy())
370 MergeInType(LI->getType(), Offset);
374 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
375 // Storing the pointer, not into the value?
376 if (SI->getOperand(0) == V || SI->isVolatile()) return false;
377 // Don't touch MMX operations.
378 if (SI->getOperand(0)->getType()->isX86_MMXTy())
380 MergeInType(SI->getOperand(0)->getType(), Offset);
384 if (BitCastInst *BCI = dyn_cast<BitCastInst>(User)) {
385 IsNotTrivial = true; // Can't be mem2reg'd.
386 if (!CanConvertToScalar(BCI, Offset))
391 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) {
392 // If this is a GEP with a variable indices, we can't handle it.
393 if (!GEP->hasAllConstantIndices())
396 // Compute the offset that this GEP adds to the pointer.
397 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end());
398 uint64_t GEPOffset = TD.getIndexedOffset(GEP->getPointerOperandType(),
399 &Indices[0], Indices.size());
400 // See if all uses can be converted.
401 if (!CanConvertToScalar(GEP, Offset+GEPOffset))
403 IsNotTrivial = true; // Can't be mem2reg'd.
407 // If this is a constant sized memset of a constant value (e.g. 0) we can
409 if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) {
410 // Store of constant value and constant size.
411 if (!isa<ConstantInt>(MSI->getValue()) ||
412 !isa<ConstantInt>(MSI->getLength()))
414 IsNotTrivial = true; // Can't be mem2reg'd.
418 // If this is a memcpy or memmove into or out of the whole allocation, we
419 // can handle it like a load or store of the scalar type.
420 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) {
421 ConstantInt *Len = dyn_cast<ConstantInt>(MTI->getLength());
422 if (Len == 0 || Len->getZExtValue() != AllocaSize || Offset != 0)
425 IsNotTrivial = true; // Can't be mem2reg'd.
429 // Otherwise, we cannot handle this!
436 /// ConvertUsesToScalar - Convert all of the users of Ptr to use the new alloca
437 /// directly. This happens when we are converting an "integer union" to a
438 /// single integer scalar, or when we are converting a "vector union" to a
439 /// vector with insert/extractelement instructions.
441 /// Offset is an offset from the original alloca, in bits that need to be
442 /// shifted to the right. By the end of this, there should be no uses of Ptr.
443 void ConvertToScalarInfo::ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI,
445 while (!Ptr->use_empty()) {
446 Instruction *User = cast<Instruction>(Ptr->use_back());
448 if (BitCastInst *CI = dyn_cast<BitCastInst>(User)) {
449 ConvertUsesToScalar(CI, NewAI, Offset);
450 CI->eraseFromParent();
454 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) {
455 // Compute the offset that this GEP adds to the pointer.
456 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end());
457 uint64_t GEPOffset = TD.getIndexedOffset(GEP->getPointerOperandType(),
458 &Indices[0], Indices.size());
459 ConvertUsesToScalar(GEP, NewAI, Offset+GEPOffset*8);
460 GEP->eraseFromParent();
464 IRBuilder<> Builder(User);
466 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
467 // The load is a bit extract from NewAI shifted right by Offset bits.
468 Value *LoadedVal = Builder.CreateLoad(NewAI, "tmp");
470 = ConvertScalar_ExtractValue(LoadedVal, LI->getType(), Offset, Builder);
471 LI->replaceAllUsesWith(NewLoadVal);
472 LI->eraseFromParent();
476 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
477 assert(SI->getOperand(0) != Ptr && "Consistency error!");
478 Instruction *Old = Builder.CreateLoad(NewAI, NewAI->getName()+".in");
479 Value *New = ConvertScalar_InsertValue(SI->getOperand(0), Old, Offset,
481 Builder.CreateStore(New, NewAI);
482 SI->eraseFromParent();
484 // If the load we just inserted is now dead, then the inserted store
485 // overwrote the entire thing.
486 if (Old->use_empty())
487 Old->eraseFromParent();
491 // If this is a constant sized memset of a constant value (e.g. 0) we can
492 // transform it into a store of the expanded constant value.
493 if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) {
494 assert(MSI->getRawDest() == Ptr && "Consistency error!");
495 unsigned NumBytes = cast<ConstantInt>(MSI->getLength())->getZExtValue();
497 unsigned Val = cast<ConstantInt>(MSI->getValue())->getZExtValue();
499 // Compute the value replicated the right number of times.
500 APInt APVal(NumBytes*8, Val);
502 // Splat the value if non-zero.
504 for (unsigned i = 1; i != NumBytes; ++i)
507 Instruction *Old = Builder.CreateLoad(NewAI, NewAI->getName()+".in");
508 Value *New = ConvertScalar_InsertValue(
509 ConstantInt::get(User->getContext(), APVal),
510 Old, Offset, Builder);
511 Builder.CreateStore(New, NewAI);
513 // If the load we just inserted is now dead, then the memset overwrote
515 if (Old->use_empty())
516 Old->eraseFromParent();
518 MSI->eraseFromParent();
522 // If this is a memcpy or memmove into or out of the whole allocation, we
523 // can handle it like a load or store of the scalar type.
524 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) {
525 assert(Offset == 0 && "must be store to start of alloca");
527 // If the source and destination are both to the same alloca, then this is
528 // a noop copy-to-self, just delete it. Otherwise, emit a load and store
530 AllocaInst *OrigAI = cast<AllocaInst>(GetUnderlyingObject(Ptr, 0));
532 if (GetUnderlyingObject(MTI->getSource(), 0) != OrigAI) {
533 // Dest must be OrigAI, change this to be a load from the original
534 // pointer (bitcasted), then a store to our new alloca.
535 assert(MTI->getRawDest() == Ptr && "Neither use is of pointer?");
536 Value *SrcPtr = MTI->getSource();
537 const PointerType* SPTy = cast<PointerType>(SrcPtr->getType());
538 const PointerType* AIPTy = cast<PointerType>(NewAI->getType());
539 if (SPTy->getAddressSpace() != AIPTy->getAddressSpace()) {
540 AIPTy = PointerType::get(AIPTy->getElementType(),
541 SPTy->getAddressSpace());
543 SrcPtr = Builder.CreateBitCast(SrcPtr, AIPTy);
545 LoadInst *SrcVal = Builder.CreateLoad(SrcPtr, "srcval");
546 SrcVal->setAlignment(MTI->getAlignment());
547 Builder.CreateStore(SrcVal, NewAI);
548 } else if (GetUnderlyingObject(MTI->getDest(), 0) != OrigAI) {
549 // Src must be OrigAI, change this to be a load from NewAI then a store
550 // through the original dest pointer (bitcasted).
551 assert(MTI->getRawSource() == Ptr && "Neither use is of pointer?");
552 LoadInst *SrcVal = Builder.CreateLoad(NewAI, "srcval");
554 const PointerType* DPTy = cast<PointerType>(MTI->getDest()->getType());
555 const PointerType* AIPTy = cast<PointerType>(NewAI->getType());
556 if (DPTy->getAddressSpace() != AIPTy->getAddressSpace()) {
557 AIPTy = PointerType::get(AIPTy->getElementType(),
558 DPTy->getAddressSpace());
560 Value *DstPtr = Builder.CreateBitCast(MTI->getDest(), AIPTy);
562 StoreInst *NewStore = Builder.CreateStore(SrcVal, DstPtr);
563 NewStore->setAlignment(MTI->getAlignment());
565 // Noop transfer. Src == Dst
568 MTI->eraseFromParent();
572 llvm_unreachable("Unsupported operation!");
576 /// ConvertScalar_ExtractValue - Extract a value of type ToType from an integer
577 /// or vector value FromVal, extracting the bits from the offset specified by
578 /// Offset. This returns the value, which is of type ToType.
580 /// This happens when we are converting an "integer union" to a single
581 /// integer scalar, or when we are converting a "vector union" to a vector with
582 /// insert/extractelement instructions.
584 /// Offset is an offset from the original alloca, in bits that need to be
585 /// shifted to the right.
586 Value *ConvertToScalarInfo::
587 ConvertScalar_ExtractValue(Value *FromVal, const Type *ToType,
588 uint64_t Offset, IRBuilder<> &Builder) {
589 // If the load is of the whole new alloca, no conversion is needed.
590 if (FromVal->getType() == ToType && Offset == 0)
593 // If the result alloca is a vector type, this is either an element
594 // access or a bitcast to another vector type of the same size.
595 if (const VectorType *VTy = dyn_cast<VectorType>(FromVal->getType())) {
596 if (ToType->isVectorTy())
597 return Builder.CreateBitCast(FromVal, ToType, "tmp");
599 // Otherwise it must be an element access.
602 unsigned EltSize = TD.getTypeAllocSizeInBits(VTy->getElementType());
603 Elt = Offset/EltSize;
604 assert(EltSize*Elt == Offset && "Invalid modulus in validity checking");
606 // Return the element extracted out of it.
607 Value *V = Builder.CreateExtractElement(FromVal, ConstantInt::get(
608 Type::getInt32Ty(FromVal->getContext()), Elt), "tmp");
609 if (V->getType() != ToType)
610 V = Builder.CreateBitCast(V, ToType, "tmp");
614 // If ToType is a first class aggregate, extract out each of the pieces and
615 // use insertvalue's to form the FCA.
616 if (const StructType *ST = dyn_cast<StructType>(ToType)) {
617 const StructLayout &Layout = *TD.getStructLayout(ST);
618 Value *Res = UndefValue::get(ST);
619 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) {
620 Value *Elt = ConvertScalar_ExtractValue(FromVal, ST->getElementType(i),
621 Offset+Layout.getElementOffsetInBits(i),
623 Res = Builder.CreateInsertValue(Res, Elt, i, "tmp");
628 if (const ArrayType *AT = dyn_cast<ArrayType>(ToType)) {
629 uint64_t EltSize = TD.getTypeAllocSizeInBits(AT->getElementType());
630 Value *Res = UndefValue::get(AT);
631 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
632 Value *Elt = ConvertScalar_ExtractValue(FromVal, AT->getElementType(),
633 Offset+i*EltSize, Builder);
634 Res = Builder.CreateInsertValue(Res, Elt, i, "tmp");
639 // Otherwise, this must be a union that was converted to an integer value.
640 const IntegerType *NTy = cast<IntegerType>(FromVal->getType());
642 // If this is a big-endian system and the load is narrower than the
643 // full alloca type, we need to do a shift to get the right bits.
645 if (TD.isBigEndian()) {
646 // On big-endian machines, the lowest bit is stored at the bit offset
647 // from the pointer given by getTypeStoreSizeInBits. This matters for
648 // integers with a bitwidth that is not a multiple of 8.
649 ShAmt = TD.getTypeStoreSizeInBits(NTy) -
650 TD.getTypeStoreSizeInBits(ToType) - Offset;
655 // Note: we support negative bitwidths (with shl) which are not defined.
656 // We do this to support (f.e.) loads off the end of a structure where
657 // only some bits are used.
658 if (ShAmt > 0 && (unsigned)ShAmt < NTy->getBitWidth())
659 FromVal = Builder.CreateLShr(FromVal,
660 ConstantInt::get(FromVal->getType(),
662 else if (ShAmt < 0 && (unsigned)-ShAmt < NTy->getBitWidth())
663 FromVal = Builder.CreateShl(FromVal,
664 ConstantInt::get(FromVal->getType(),
667 // Finally, unconditionally truncate the integer to the right width.
668 unsigned LIBitWidth = TD.getTypeSizeInBits(ToType);
669 if (LIBitWidth < NTy->getBitWidth())
671 Builder.CreateTrunc(FromVal, IntegerType::get(FromVal->getContext(),
673 else if (LIBitWidth > NTy->getBitWidth())
675 Builder.CreateZExt(FromVal, IntegerType::get(FromVal->getContext(),
678 // If the result is an integer, this is a trunc or bitcast.
679 if (ToType->isIntegerTy()) {
681 } else if (ToType->isFloatingPointTy() || ToType->isVectorTy()) {
682 // Just do a bitcast, we know the sizes match up.
683 FromVal = Builder.CreateBitCast(FromVal, ToType, "tmp");
685 // Otherwise must be a pointer.
686 FromVal = Builder.CreateIntToPtr(FromVal, ToType, "tmp");
688 assert(FromVal->getType() == ToType && "Didn't convert right?");
692 /// ConvertScalar_InsertValue - Insert the value "SV" into the existing integer
693 /// or vector value "Old" at the offset specified by Offset.
695 /// This happens when we are converting an "integer union" to a
696 /// single integer scalar, or when we are converting a "vector union" to a
697 /// vector with insert/extractelement instructions.
699 /// Offset is an offset from the original alloca, in bits that need to be
700 /// shifted to the right.
701 Value *ConvertToScalarInfo::
702 ConvertScalar_InsertValue(Value *SV, Value *Old,
703 uint64_t Offset, IRBuilder<> &Builder) {
704 // Convert the stored type to the actual type, shift it left to insert
705 // then 'or' into place.
706 const Type *AllocaType = Old->getType();
707 LLVMContext &Context = Old->getContext();
709 if (const VectorType *VTy = dyn_cast<VectorType>(AllocaType)) {
710 uint64_t VecSize = TD.getTypeAllocSizeInBits(VTy);
711 uint64_t ValSize = TD.getTypeAllocSizeInBits(SV->getType());
713 // Changing the whole vector with memset or with an access of a different
715 if (ValSize == VecSize)
716 return Builder.CreateBitCast(SV, AllocaType, "tmp");
718 uint64_t EltSize = TD.getTypeAllocSizeInBits(VTy->getElementType());
720 // Must be an element insertion.
721 unsigned Elt = Offset/EltSize;
723 if (SV->getType() != VTy->getElementType())
724 SV = Builder.CreateBitCast(SV, VTy->getElementType(), "tmp");
726 SV = Builder.CreateInsertElement(Old, SV,
727 ConstantInt::get(Type::getInt32Ty(SV->getContext()), Elt),
732 // If SV is a first-class aggregate value, insert each value recursively.
733 if (const StructType *ST = dyn_cast<StructType>(SV->getType())) {
734 const StructLayout &Layout = *TD.getStructLayout(ST);
735 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) {
736 Value *Elt = Builder.CreateExtractValue(SV, i, "tmp");
737 Old = ConvertScalar_InsertValue(Elt, Old,
738 Offset+Layout.getElementOffsetInBits(i),
744 if (const ArrayType *AT = dyn_cast<ArrayType>(SV->getType())) {
745 uint64_t EltSize = TD.getTypeAllocSizeInBits(AT->getElementType());
746 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
747 Value *Elt = Builder.CreateExtractValue(SV, i, "tmp");
748 Old = ConvertScalar_InsertValue(Elt, Old, Offset+i*EltSize, Builder);
753 // If SV is a float, convert it to the appropriate integer type.
754 // If it is a pointer, do the same.
755 unsigned SrcWidth = TD.getTypeSizeInBits(SV->getType());
756 unsigned DestWidth = TD.getTypeSizeInBits(AllocaType);
757 unsigned SrcStoreWidth = TD.getTypeStoreSizeInBits(SV->getType());
758 unsigned DestStoreWidth = TD.getTypeStoreSizeInBits(AllocaType);
759 if (SV->getType()->isFloatingPointTy() || SV->getType()->isVectorTy())
760 SV = Builder.CreateBitCast(SV,
761 IntegerType::get(SV->getContext(),SrcWidth), "tmp");
762 else if (SV->getType()->isPointerTy())
763 SV = Builder.CreatePtrToInt(SV, TD.getIntPtrType(SV->getContext()), "tmp");
765 // Zero extend or truncate the value if needed.
766 if (SV->getType() != AllocaType) {
767 if (SV->getType()->getPrimitiveSizeInBits() <
768 AllocaType->getPrimitiveSizeInBits())
769 SV = Builder.CreateZExt(SV, AllocaType, "tmp");
771 // Truncation may be needed if storing more than the alloca can hold
772 // (undefined behavior).
773 SV = Builder.CreateTrunc(SV, AllocaType, "tmp");
774 SrcWidth = DestWidth;
775 SrcStoreWidth = DestStoreWidth;
779 // If this is a big-endian system and the store is narrower than the
780 // full alloca type, we need to do a shift to get the right bits.
782 if (TD.isBigEndian()) {
783 // On big-endian machines, the lowest bit is stored at the bit offset
784 // from the pointer given by getTypeStoreSizeInBits. This matters for
785 // integers with a bitwidth that is not a multiple of 8.
786 ShAmt = DestStoreWidth - SrcStoreWidth - Offset;
791 // Note: we support negative bitwidths (with shr) which are not defined.
792 // We do this to support (f.e.) stores off the end of a structure where
793 // only some bits in the structure are set.
794 APInt Mask(APInt::getLowBitsSet(DestWidth, SrcWidth));
795 if (ShAmt > 0 && (unsigned)ShAmt < DestWidth) {
796 SV = Builder.CreateShl(SV, ConstantInt::get(SV->getType(),
799 } else if (ShAmt < 0 && (unsigned)-ShAmt < DestWidth) {
800 SV = Builder.CreateLShr(SV, ConstantInt::get(SV->getType(),
802 Mask = Mask.lshr(-ShAmt);
805 // Mask out the bits we are about to insert from the old value, and or
807 if (SrcWidth != DestWidth) {
808 assert(DestWidth > SrcWidth);
809 Old = Builder.CreateAnd(Old, ConstantInt::get(Context, ~Mask), "mask");
810 SV = Builder.CreateOr(Old, SV, "ins");
816 //===----------------------------------------------------------------------===//
818 //===----------------------------------------------------------------------===//
821 bool SROA::runOnFunction(Function &F) {
822 TD = getAnalysisIfAvailable<TargetData>();
824 bool Changed = performPromotion(F);
826 // FIXME: ScalarRepl currently depends on TargetData more than it
827 // theoretically needs to. It should be refactored in order to support
828 // target-independent IR. Until this is done, just skip the actual
829 // scalar-replacement portion of this pass.
830 if (!TD) return Changed;
833 bool LocalChange = performScalarRepl(F);
834 if (!LocalChange) break; // No need to repromote if no scalarrepl
836 LocalChange = performPromotion(F);
837 if (!LocalChange) break; // No need to re-scalarrepl if no promotion
843 /// PromoteAlloca - Promote an alloca to registers, using SSAUpdater.
844 static void PromoteAlloca(AllocaInst *AI, SSAUpdater &SSA) {
845 SSA.Initialize(AI->getType()->getElementType(), AI->getName());
847 // First step: bucket up uses of the alloca by the block they occur in.
848 // This is important because we have to handle multiple defs/uses in a block
849 // ourselves: SSAUpdater is purely for cross-block references.
850 // FIXME: Want a TinyVector<Instruction*> since there is often 0/1 element.
851 DenseMap<BasicBlock*, std::vector<Instruction*> > UsesByBlock;
853 for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end();
855 Instruction *User = cast<Instruction>(*UI);
856 UsesByBlock[User->getParent()].push_back(User);
859 // Okay, now we can iterate over all the blocks in the function with uses,
860 // processing them. Keep track of which loads are loading a live-in value.
861 // Walk the uses in the use-list order to be determinstic.
862 SmallVector<LoadInst*, 32> LiveInLoads;
863 DenseMap<Value*, Value*> ReplacedLoads;
865 for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end();
867 Instruction *User = cast<Instruction>(*UI);
868 BasicBlock *BB = User->getParent();
869 std::vector<Instruction*> &BlockUses = UsesByBlock[BB];
871 // If this block has already been processed, ignore this repeat use.
872 if (BlockUses.empty()) continue;
874 // Okay, this is the first use in the block. If this block just has a
875 // single user in it, we can rewrite it trivially.
876 if (BlockUses.size() == 1) {
877 // If it is a store, it is a trivial def of the value in the block.
878 if (StoreInst *SI = dyn_cast<StoreInst>(User))
879 SSA.AddAvailableValue(BB, SI->getOperand(0));
881 // Otherwise it is a load, queue it to rewrite as a live-in load.
882 LiveInLoads.push_back(cast<LoadInst>(User));
887 // Otherwise, check to see if this block is all loads.
888 bool HasStore = false;
889 for (unsigned i = 0, e = BlockUses.size(); i != e; ++i) {
890 if (isa<StoreInst>(BlockUses[i])) {
896 // If so, we can queue them all as live in loads. We don't have an
897 // efficient way to tell which on is first in the block and don't want to
898 // scan large blocks, so just add all loads as live ins.
900 for (unsigned i = 0, e = BlockUses.size(); i != e; ++i)
901 LiveInLoads.push_back(cast<LoadInst>(BlockUses[i]));
906 // Otherwise, we have mixed loads and stores (or just a bunch of stores).
907 // Since SSAUpdater is purely for cross-block values, we need to determine
908 // the order of these instructions in the block. If the first use in the
909 // block is a load, then it uses the live in value. The last store defines
910 // the live out value. We handle this by doing a linear scan of the block.
911 Value *StoredValue = 0;
912 for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E; ++II) {
913 if (LoadInst *L = dyn_cast<LoadInst>(II)) {
914 // If this is a load from an unrelated pointer, ignore it.
915 if (L->getOperand(0) != AI) continue;
917 // If we haven't seen a store yet, this is a live in use, otherwise
918 // use the stored value.
920 L->replaceAllUsesWith(StoredValue);
921 ReplacedLoads[L] = StoredValue;
923 LiveInLoads.push_back(L);
928 if (StoreInst *S = dyn_cast<StoreInst>(II)) {
929 // If this is a store to an unrelated pointer, ignore it.
930 if (S->getPointerOperand() != AI) continue;
932 // Remember that this is the active value in the block.
933 StoredValue = S->getOperand(0);
937 // The last stored value that happened is the live-out for the block.
938 assert(StoredValue && "Already checked that there is a store in block");
939 SSA.AddAvailableValue(BB, StoredValue);
943 // Okay, now we rewrite all loads that use live-in values in the loop,
944 // inserting PHI nodes as necessary.
945 for (unsigned i = 0, e = LiveInLoads.size(); i != e; ++i) {
946 LoadInst *ALoad = LiveInLoads[i];
947 Value *NewVal = SSA.GetValueInMiddleOfBlock(ALoad->getParent());
948 ALoad->replaceAllUsesWith(NewVal);
949 ReplacedLoads[ALoad] = NewVal;
952 // Now that everything is rewritten, delete the old instructions from the
953 // function. They should all be dead now.
954 for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end(); UI != E; ) {
955 Instruction *User = cast<Instruction>(*UI++);
957 // If this is a load that still has uses, then the load must have been added
958 // as a live value in the SSAUpdate data structure for a block (e.g. because
959 // the loaded value was stored later). In this case, we need to recursively
960 // propagate the updates until we get to the real value.
961 if (!User->use_empty()) {
962 Value *NewVal = ReplacedLoads[User];
963 assert(NewVal && "not a replaced load?");
965 // Propagate down to the ultimate replacee. The intermediately loads
966 // could theoretically already have been deleted, so we don't want to
967 // dereference the Value*'s.
968 DenseMap<Value*, Value*>::iterator RLI = ReplacedLoads.find(NewVal);
969 while (RLI != ReplacedLoads.end()) {
970 NewVal = RLI->second;
971 RLI = ReplacedLoads.find(NewVal);
974 User->replaceAllUsesWith(NewVal);
977 User->eraseFromParent();
982 bool SROA::performPromotion(Function &F) {
983 std::vector<AllocaInst*> Allocas;
984 DominatorTree *DT = 0;
985 DominanceFrontier *DF = 0;
986 if (HasDomFrontiers) {
987 DT = &getAnalysis<DominatorTree>();
988 DF = &getAnalysis<DominanceFrontier>();
991 BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function
993 bool Changed = false;
998 // Find allocas that are safe to promote, by looking at all instructions in
1000 for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I)
1001 if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) // Is it an alloca?
1002 if (isAllocaPromotable(AI))
1003 Allocas.push_back(AI);
1005 if (Allocas.empty()) break;
1007 if (HasDomFrontiers)
1008 PromoteMemToReg(Allocas, *DT, *DF);
1011 for (unsigned i = 0, e = Allocas.size(); i != e; ++i) {
1012 PromoteAlloca(Allocas[i], SSA);
1013 Allocas[i]->eraseFromParent();
1016 NumPromoted += Allocas.size();
1024 /// ShouldAttemptScalarRepl - Decide if an alloca is a good candidate for
1025 /// SROA. It must be a struct or array type with a small number of elements.
1026 static bool ShouldAttemptScalarRepl(AllocaInst *AI) {
1027 const Type *T = AI->getAllocatedType();
1028 // Do not promote any struct into more than 32 separate vars.
1029 if (const StructType *ST = dyn_cast<StructType>(T))
1030 return ST->getNumElements() <= 32;
1031 // Arrays are much less likely to be safe for SROA; only consider
1032 // them if they are very small.
1033 if (const ArrayType *AT = dyn_cast<ArrayType>(T))
1034 return AT->getNumElements() <= 8;
1039 // performScalarRepl - This algorithm is a simple worklist driven algorithm,
1040 // which runs on all of the malloc/alloca instructions in the function, removing
1041 // them if they are only used by getelementptr instructions.
1043 bool SROA::performScalarRepl(Function &F) {
1044 std::vector<AllocaInst*> WorkList;
1046 // Scan the entry basic block, adding allocas to the worklist.
1047 BasicBlock &BB = F.getEntryBlock();
1048 for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I)
1049 if (AllocaInst *A = dyn_cast<AllocaInst>(I))
1050 WorkList.push_back(A);
1052 // Process the worklist
1053 bool Changed = false;
1054 while (!WorkList.empty()) {
1055 AllocaInst *AI = WorkList.back();
1056 WorkList.pop_back();
1058 // Handle dead allocas trivially. These can be formed by SROA'ing arrays
1059 // with unused elements.
1060 if (AI->use_empty()) {
1061 AI->eraseFromParent();
1066 // If this alloca is impossible for us to promote, reject it early.
1067 if (AI->isArrayAllocation() || !AI->getAllocatedType()->isSized())
1070 // Check to see if this allocation is only modified by a memcpy/memmove from
1071 // a constant global. If this is the case, we can change all users to use
1072 // the constant global instead. This is commonly produced by the CFE by
1073 // constructs like "void foo() { int A[] = {1,2,3,4,5,6,7,8,9...}; }" if 'A'
1074 // is only subsequently read.
1075 if (MemTransferInst *TheCopy = isOnlyCopiedFromConstantGlobal(AI)) {
1076 DEBUG(dbgs() << "Found alloca equal to global: " << *AI << '\n');
1077 DEBUG(dbgs() << " memcpy = " << *TheCopy << '\n');
1078 Constant *TheSrc = cast<Constant>(TheCopy->getSource());
1079 AI->replaceAllUsesWith(ConstantExpr::getBitCast(TheSrc, AI->getType()));
1080 TheCopy->eraseFromParent(); // Don't mutate the global.
1081 AI->eraseFromParent();
1087 // Check to see if we can perform the core SROA transformation. We cannot
1088 // transform the allocation instruction if it is an array allocation
1089 // (allocations OF arrays are ok though), and an allocation of a scalar
1090 // value cannot be decomposed at all.
1091 uint64_t AllocaSize = TD->getTypeAllocSize(AI->getAllocatedType());
1093 // Do not promote [0 x %struct].
1094 if (AllocaSize == 0) continue;
1096 // Do not promote any struct whose size is too big.
1097 if (AllocaSize > SRThreshold) continue;
1099 // If the alloca looks like a good candidate for scalar replacement, and if
1100 // all its users can be transformed, then split up the aggregate into its
1101 // separate elements.
1102 if (ShouldAttemptScalarRepl(AI) && isSafeAllocaToScalarRepl(AI)) {
1103 DoScalarReplacement(AI, WorkList);
1108 // If we can turn this aggregate value (potentially with casts) into a
1109 // simple scalar value that can be mem2reg'd into a register value.
1110 // IsNotTrivial tracks whether this is something that mem2reg could have
1111 // promoted itself. If so, we don't want to transform it needlessly. Note
1112 // that we can't just check based on the type: the alloca may be of an i32
1113 // but that has pointer arithmetic to set byte 3 of it or something.
1114 if (AllocaInst *NewAI =
1115 ConvertToScalarInfo((unsigned)AllocaSize, *TD).TryConvert(AI)) {
1116 NewAI->takeName(AI);
1117 AI->eraseFromParent();
1123 // Otherwise, couldn't process this alloca.
1129 /// DoScalarReplacement - This alloca satisfied the isSafeAllocaToScalarRepl
1130 /// predicate, do SROA now.
1131 void SROA::DoScalarReplacement(AllocaInst *AI,
1132 std::vector<AllocaInst*> &WorkList) {
1133 DEBUG(dbgs() << "Found inst to SROA: " << *AI << '\n');
1134 SmallVector<AllocaInst*, 32> ElementAllocas;
1135 if (const StructType *ST = dyn_cast<StructType>(AI->getAllocatedType())) {
1136 ElementAllocas.reserve(ST->getNumContainedTypes());
1137 for (unsigned i = 0, e = ST->getNumContainedTypes(); i != e; ++i) {
1138 AllocaInst *NA = new AllocaInst(ST->getContainedType(i), 0,
1140 AI->getName() + "." + Twine(i), AI);
1141 ElementAllocas.push_back(NA);
1142 WorkList.push_back(NA); // Add to worklist for recursive processing
1145 const ArrayType *AT = cast<ArrayType>(AI->getAllocatedType());
1146 ElementAllocas.reserve(AT->getNumElements());
1147 const Type *ElTy = AT->getElementType();
1148 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
1149 AllocaInst *NA = new AllocaInst(ElTy, 0, AI->getAlignment(),
1150 AI->getName() + "." + Twine(i), AI);
1151 ElementAllocas.push_back(NA);
1152 WorkList.push_back(NA); // Add to worklist for recursive processing
1156 // Now that we have created the new alloca instructions, rewrite all the
1157 // uses of the old alloca.
1158 RewriteForScalarRepl(AI, AI, 0, ElementAllocas);
1160 // Now erase any instructions that were made dead while rewriting the alloca.
1161 DeleteDeadInstructions();
1162 AI->eraseFromParent();
1167 /// DeleteDeadInstructions - Erase instructions on the DeadInstrs list,
1168 /// recursively including all their operands that become trivially dead.
1169 void SROA::DeleteDeadInstructions() {
1170 while (!DeadInsts.empty()) {
1171 Instruction *I = cast<Instruction>(DeadInsts.pop_back_val());
1173 for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI)
1174 if (Instruction *U = dyn_cast<Instruction>(*OI)) {
1175 // Zero out the operand and see if it becomes trivially dead.
1176 // (But, don't add allocas to the dead instruction list -- they are
1177 // already on the worklist and will be deleted separately.)
1179 if (isInstructionTriviallyDead(U) && !isa<AllocaInst>(U))
1180 DeadInsts.push_back(U);
1183 I->eraseFromParent();
1187 /// isSafeForScalarRepl - Check if instruction I is a safe use with regard to
1188 /// performing scalar replacement of alloca AI. The results are flagged in
1189 /// the Info parameter. Offset indicates the position within AI that is
1190 /// referenced by this instruction.
1191 void SROA::isSafeForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset,
1193 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E; ++UI) {
1194 Instruction *User = cast<Instruction>(*UI);
1196 if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) {
1197 isSafeForScalarRepl(BC, AI, Offset, Info);
1198 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
1199 uint64_t GEPOffset = Offset;
1200 isSafeGEP(GEPI, AI, GEPOffset, Info);
1202 isSafeForScalarRepl(GEPI, AI, GEPOffset, Info);
1203 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) {
1204 ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength());
1206 isSafeMemAccess(AI, Offset, Length->getZExtValue(), 0,
1207 UI.getOperandNo() == 0, Info);
1210 } else if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1211 if (!LI->isVolatile()) {
1212 const Type *LIType = LI->getType();
1213 isSafeMemAccess(AI, Offset, TD->getTypeAllocSize(LIType),
1214 LIType, false, Info);
1217 } else if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
1218 // Store is ok if storing INTO the pointer, not storing the pointer
1219 if (!SI->isVolatile() && SI->getOperand(0) != I) {
1220 const Type *SIType = SI->getOperand(0)->getType();
1221 isSafeMemAccess(AI, Offset, TD->getTypeAllocSize(SIType),
1222 SIType, true, Info);
1226 DEBUG(errs() << " Transformation preventing inst: " << *User << '\n');
1229 if (Info.isUnsafe) return;
1233 /// isSafeGEP - Check if a GEP instruction can be handled for scalar
1234 /// replacement. It is safe when all the indices are constant, in-bounds
1235 /// references, and when the resulting offset corresponds to an element within
1236 /// the alloca type. The results are flagged in the Info parameter. Upon
1237 /// return, Offset is adjusted as specified by the GEP indices.
1238 void SROA::isSafeGEP(GetElementPtrInst *GEPI, AllocaInst *AI,
1239 uint64_t &Offset, AllocaInfo &Info) {
1240 gep_type_iterator GEPIt = gep_type_begin(GEPI), E = gep_type_end(GEPI);
1244 // Walk through the GEP type indices, checking the types that this indexes
1246 for (; GEPIt != E; ++GEPIt) {
1247 // Ignore struct elements, no extra checking needed for these.
1248 if ((*GEPIt)->isStructTy())
1251 ConstantInt *IdxVal = dyn_cast<ConstantInt>(GEPIt.getOperand());
1253 return MarkUnsafe(Info);
1256 // Compute the offset due to this GEP and check if the alloca has a
1257 // component element at that offset.
1258 SmallVector<Value*, 8> Indices(GEPI->op_begin() + 1, GEPI->op_end());
1259 Offset += TD->getIndexedOffset(GEPI->getPointerOperandType(),
1260 &Indices[0], Indices.size());
1261 if (!TypeHasComponent(AI->getAllocatedType(), Offset, 0))
1265 /// isHomogeneousAggregate - Check if type T is a struct or array containing
1266 /// elements of the same type (which is always true for arrays). If so,
1267 /// return true with NumElts and EltTy set to the number of elements and the
1268 /// element type, respectively.
1269 static bool isHomogeneousAggregate(const Type *T, unsigned &NumElts,
1270 const Type *&EltTy) {
1271 if (const ArrayType *AT = dyn_cast<ArrayType>(T)) {
1272 NumElts = AT->getNumElements();
1273 EltTy = (NumElts == 0 ? 0 : AT->getElementType());
1276 if (const StructType *ST = dyn_cast<StructType>(T)) {
1277 NumElts = ST->getNumContainedTypes();
1278 EltTy = (NumElts == 0 ? 0 : ST->getContainedType(0));
1279 for (unsigned n = 1; n < NumElts; ++n) {
1280 if (ST->getContainedType(n) != EltTy)
1288 /// isCompatibleAggregate - Check if T1 and T2 are either the same type or are
1289 /// "homogeneous" aggregates with the same element type and number of elements.
1290 static bool isCompatibleAggregate(const Type *T1, const Type *T2) {
1294 unsigned NumElts1, NumElts2;
1295 const Type *EltTy1, *EltTy2;
1296 if (isHomogeneousAggregate(T1, NumElts1, EltTy1) &&
1297 isHomogeneousAggregate(T2, NumElts2, EltTy2) &&
1298 NumElts1 == NumElts2 &&
1305 /// isSafeMemAccess - Check if a load/store/memcpy operates on the entire AI
1306 /// alloca or has an offset and size that corresponds to a component element
1307 /// within it. The offset checked here may have been formed from a GEP with a
1308 /// pointer bitcasted to a different type.
1309 void SROA::isSafeMemAccess(AllocaInst *AI, uint64_t Offset, uint64_t MemSize,
1310 const Type *MemOpType, bool isStore,
1312 // Check if this is a load/store of the entire alloca.
1313 if (Offset == 0 && MemSize == TD->getTypeAllocSize(AI->getAllocatedType())) {
1314 // This can be safe for MemIntrinsics (where MemOpType is 0) and integer
1315 // loads/stores (which are essentially the same as the MemIntrinsics with
1316 // regard to copying padding between elements). But, if an alloca is
1317 // flagged as both a source and destination of such operations, we'll need
1318 // to check later for padding between elements.
1319 if (!MemOpType || MemOpType->isIntegerTy()) {
1321 Info.isMemCpyDst = true;
1323 Info.isMemCpySrc = true;
1326 // This is also safe for references using a type that is compatible with
1327 // the type of the alloca, so that loads/stores can be rewritten using
1328 // insertvalue/extractvalue.
1329 if (isCompatibleAggregate(MemOpType, AI->getAllocatedType()))
1332 // Check if the offset/size correspond to a component within the alloca type.
1333 const Type *T = AI->getAllocatedType();
1334 if (TypeHasComponent(T, Offset, MemSize))
1337 return MarkUnsafe(Info);
1340 /// TypeHasComponent - Return true if T has a component type with the
1341 /// specified offset and size. If Size is zero, do not check the size.
1342 bool SROA::TypeHasComponent(const Type *T, uint64_t Offset, uint64_t Size) {
1345 if (const StructType *ST = dyn_cast<StructType>(T)) {
1346 const StructLayout *Layout = TD->getStructLayout(ST);
1347 unsigned EltIdx = Layout->getElementContainingOffset(Offset);
1348 EltTy = ST->getContainedType(EltIdx);
1349 EltSize = TD->getTypeAllocSize(EltTy);
1350 Offset -= Layout->getElementOffset(EltIdx);
1351 } else if (const ArrayType *AT = dyn_cast<ArrayType>(T)) {
1352 EltTy = AT->getElementType();
1353 EltSize = TD->getTypeAllocSize(EltTy);
1354 if (Offset >= AT->getNumElements() * EltSize)
1360 if (Offset == 0 && (Size == 0 || EltSize == Size))
1362 // Check if the component spans multiple elements.
1363 if (Offset + Size > EltSize)
1365 return TypeHasComponent(EltTy, Offset, Size);
1368 /// RewriteForScalarRepl - Alloca AI is being split into NewElts, so rewrite
1369 /// the instruction I, which references it, to use the separate elements.
1370 /// Offset indicates the position within AI that is referenced by this
1372 void SROA::RewriteForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset,
1373 SmallVector<AllocaInst*, 32> &NewElts) {
1374 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E; ++UI) {
1375 Instruction *User = cast<Instruction>(*UI);
1377 if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) {
1378 RewriteBitCast(BC, AI, Offset, NewElts);
1379 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
1380 RewriteGEP(GEPI, AI, Offset, NewElts);
1381 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) {
1382 ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength());
1383 uint64_t MemSize = Length->getZExtValue();
1385 MemSize == TD->getTypeAllocSize(AI->getAllocatedType()))
1386 RewriteMemIntrinUserOfAlloca(MI, I, AI, NewElts);
1387 // Otherwise the intrinsic can only touch a single element and the
1388 // address operand will be updated, so nothing else needs to be done.
1389 } else if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1390 const Type *LIType = LI->getType();
1391 if (isCompatibleAggregate(LIType, AI->getAllocatedType())) {
1393 // %res = load { i32, i32 }* %alloc
1395 // %load.0 = load i32* %alloc.0
1396 // %insert.0 insertvalue { i32, i32 } zeroinitializer, i32 %load.0, 0
1397 // %load.1 = load i32* %alloc.1
1398 // %insert = insertvalue { i32, i32 } %insert.0, i32 %load.1, 1
1399 // (Also works for arrays instead of structs)
1400 Value *Insert = UndefValue::get(LIType);
1401 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
1402 Value *Load = new LoadInst(NewElts[i], "load", LI);
1403 Insert = InsertValueInst::Create(Insert, Load, i, "insert", LI);
1405 LI->replaceAllUsesWith(Insert);
1406 DeadInsts.push_back(LI);
1407 } else if (LIType->isIntegerTy() &&
1408 TD->getTypeAllocSize(LIType) ==
1409 TD->getTypeAllocSize(AI->getAllocatedType())) {
1410 // If this is a load of the entire alloca to an integer, rewrite it.
1411 RewriteLoadUserOfWholeAlloca(LI, AI, NewElts);
1413 } else if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
1414 Value *Val = SI->getOperand(0);
1415 const Type *SIType = Val->getType();
1416 if (isCompatibleAggregate(SIType, AI->getAllocatedType())) {
1418 // store { i32, i32 } %val, { i32, i32 }* %alloc
1420 // %val.0 = extractvalue { i32, i32 } %val, 0
1421 // store i32 %val.0, i32* %alloc.0
1422 // %val.1 = extractvalue { i32, i32 } %val, 1
1423 // store i32 %val.1, i32* %alloc.1
1424 // (Also works for arrays instead of structs)
1425 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
1426 Value *Extract = ExtractValueInst::Create(Val, i, Val->getName(), SI);
1427 new StoreInst(Extract, NewElts[i], SI);
1429 DeadInsts.push_back(SI);
1430 } else if (SIType->isIntegerTy() &&
1431 TD->getTypeAllocSize(SIType) ==
1432 TD->getTypeAllocSize(AI->getAllocatedType())) {
1433 // If this is a store of the entire alloca from an integer, rewrite it.
1434 RewriteStoreUserOfWholeAlloca(SI, AI, NewElts);
1440 /// RewriteBitCast - Update a bitcast reference to the alloca being replaced
1441 /// and recursively continue updating all of its uses.
1442 void SROA::RewriteBitCast(BitCastInst *BC, AllocaInst *AI, uint64_t Offset,
1443 SmallVector<AllocaInst*, 32> &NewElts) {
1444 RewriteForScalarRepl(BC, AI, Offset, NewElts);
1445 if (BC->getOperand(0) != AI)
1448 // The bitcast references the original alloca. Replace its uses with
1449 // references to the first new element alloca.
1450 Instruction *Val = NewElts[0];
1451 if (Val->getType() != BC->getDestTy()) {
1452 Val = new BitCastInst(Val, BC->getDestTy(), "", BC);
1455 BC->replaceAllUsesWith(Val);
1456 DeadInsts.push_back(BC);
1459 /// FindElementAndOffset - Return the index of the element containing Offset
1460 /// within the specified type, which must be either a struct or an array.
1461 /// Sets T to the type of the element and Offset to the offset within that
1462 /// element. IdxTy is set to the type of the index result to be used in a
1463 /// GEP instruction.
1464 uint64_t SROA::FindElementAndOffset(const Type *&T, uint64_t &Offset,
1465 const Type *&IdxTy) {
1467 if (const StructType *ST = dyn_cast<StructType>(T)) {
1468 const StructLayout *Layout = TD->getStructLayout(ST);
1469 Idx = Layout->getElementContainingOffset(Offset);
1470 T = ST->getContainedType(Idx);
1471 Offset -= Layout->getElementOffset(Idx);
1472 IdxTy = Type::getInt32Ty(T->getContext());
1475 const ArrayType *AT = cast<ArrayType>(T);
1476 T = AT->getElementType();
1477 uint64_t EltSize = TD->getTypeAllocSize(T);
1478 Idx = Offset / EltSize;
1479 Offset -= Idx * EltSize;
1480 IdxTy = Type::getInt64Ty(T->getContext());
1484 /// RewriteGEP - Check if this GEP instruction moves the pointer across
1485 /// elements of the alloca that are being split apart, and if so, rewrite
1486 /// the GEP to be relative to the new element.
1487 void SROA::RewriteGEP(GetElementPtrInst *GEPI, AllocaInst *AI, uint64_t Offset,
1488 SmallVector<AllocaInst*, 32> &NewElts) {
1489 uint64_t OldOffset = Offset;
1490 SmallVector<Value*, 8> Indices(GEPI->op_begin() + 1, GEPI->op_end());
1491 Offset += TD->getIndexedOffset(GEPI->getPointerOperandType(),
1492 &Indices[0], Indices.size());
1494 RewriteForScalarRepl(GEPI, AI, Offset, NewElts);
1496 const Type *T = AI->getAllocatedType();
1498 uint64_t OldIdx = FindElementAndOffset(T, OldOffset, IdxTy);
1499 if (GEPI->getOperand(0) == AI)
1500 OldIdx = ~0ULL; // Force the GEP to be rewritten.
1502 T = AI->getAllocatedType();
1503 uint64_t EltOffset = Offset;
1504 uint64_t Idx = FindElementAndOffset(T, EltOffset, IdxTy);
1506 // If this GEP does not move the pointer across elements of the alloca
1507 // being split, then it does not needs to be rewritten.
1511 const Type *i32Ty = Type::getInt32Ty(AI->getContext());
1512 SmallVector<Value*, 8> NewArgs;
1513 NewArgs.push_back(Constant::getNullValue(i32Ty));
1514 while (EltOffset != 0) {
1515 uint64_t EltIdx = FindElementAndOffset(T, EltOffset, IdxTy);
1516 NewArgs.push_back(ConstantInt::get(IdxTy, EltIdx));
1518 Instruction *Val = NewElts[Idx];
1519 if (NewArgs.size() > 1) {
1520 Val = GetElementPtrInst::CreateInBounds(Val, NewArgs.begin(),
1521 NewArgs.end(), "", GEPI);
1522 Val->takeName(GEPI);
1524 if (Val->getType() != GEPI->getType())
1525 Val = new BitCastInst(Val, GEPI->getType(), Val->getName(), GEPI);
1526 GEPI->replaceAllUsesWith(Val);
1527 DeadInsts.push_back(GEPI);
1530 /// RewriteMemIntrinUserOfAlloca - MI is a memcpy/memset/memmove from or to AI.
1531 /// Rewrite it to copy or set the elements of the scalarized memory.
1532 void SROA::RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *Inst,
1534 SmallVector<AllocaInst*, 32> &NewElts) {
1535 // If this is a memcpy/memmove, construct the other pointer as the
1536 // appropriate type. The "Other" pointer is the pointer that goes to memory
1537 // that doesn't have anything to do with the alloca that we are promoting. For
1538 // memset, this Value* stays null.
1539 Value *OtherPtr = 0;
1540 unsigned MemAlignment = MI->getAlignment();
1541 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(MI)) { // memmove/memcopy
1542 if (Inst == MTI->getRawDest())
1543 OtherPtr = MTI->getRawSource();
1545 assert(Inst == MTI->getRawSource());
1546 OtherPtr = MTI->getRawDest();
1550 // If there is an other pointer, we want to convert it to the same pointer
1551 // type as AI has, so we can GEP through it safely.
1553 unsigned AddrSpace =
1554 cast<PointerType>(OtherPtr->getType())->getAddressSpace();
1556 // Remove bitcasts and all-zero GEPs from OtherPtr. This is an
1557 // optimization, but it's also required to detect the corner case where
1558 // both pointer operands are referencing the same memory, and where
1559 // OtherPtr may be a bitcast or GEP that currently being rewritten. (This
1560 // function is only called for mem intrinsics that access the whole
1561 // aggregate, so non-zero GEPs are not an issue here.)
1562 OtherPtr = OtherPtr->stripPointerCasts();
1564 // Copying the alloca to itself is a no-op: just delete it.
1565 if (OtherPtr == AI || OtherPtr == NewElts[0]) {
1566 // This code will run twice for a no-op memcpy -- once for each operand.
1567 // Put only one reference to MI on the DeadInsts list.
1568 for (SmallVector<Value*, 32>::const_iterator I = DeadInsts.begin(),
1569 E = DeadInsts.end(); I != E; ++I)
1570 if (*I == MI) return;
1571 DeadInsts.push_back(MI);
1575 // If the pointer is not the right type, insert a bitcast to the right
1578 PointerType::get(AI->getType()->getElementType(), AddrSpace);
1580 if (OtherPtr->getType() != NewTy)
1581 OtherPtr = new BitCastInst(OtherPtr, NewTy, OtherPtr->getName(), MI);
1584 // Process each element of the aggregate.
1585 bool SROADest = MI->getRawDest() == Inst;
1587 Constant *Zero = Constant::getNullValue(Type::getInt32Ty(MI->getContext()));
1589 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
1590 // If this is a memcpy/memmove, emit a GEP of the other element address.
1591 Value *OtherElt = 0;
1592 unsigned OtherEltAlign = MemAlignment;
1595 Value *Idx[2] = { Zero,
1596 ConstantInt::get(Type::getInt32Ty(MI->getContext()), i) };
1597 OtherElt = GetElementPtrInst::CreateInBounds(OtherPtr, Idx, Idx + 2,
1598 OtherPtr->getName()+"."+Twine(i),
1601 const PointerType *OtherPtrTy = cast<PointerType>(OtherPtr->getType());
1602 const Type *OtherTy = OtherPtrTy->getElementType();
1603 if (const StructType *ST = dyn_cast<StructType>(OtherTy)) {
1604 EltOffset = TD->getStructLayout(ST)->getElementOffset(i);
1606 const Type *EltTy = cast<SequentialType>(OtherTy)->getElementType();
1607 EltOffset = TD->getTypeAllocSize(EltTy)*i;
1610 // The alignment of the other pointer is the guaranteed alignment of the
1611 // element, which is affected by both the known alignment of the whole
1612 // mem intrinsic and the alignment of the element. If the alignment of
1613 // the memcpy (f.e.) is 32 but the element is at a 4-byte offset, then the
1614 // known alignment is just 4 bytes.
1615 OtherEltAlign = (unsigned)MinAlign(OtherEltAlign, EltOffset);
1618 Value *EltPtr = NewElts[i];
1619 const Type *EltTy = cast<PointerType>(EltPtr->getType())->getElementType();
1621 // If we got down to a scalar, insert a load or store as appropriate.
1622 if (EltTy->isSingleValueType()) {
1623 if (isa<MemTransferInst>(MI)) {
1625 // From Other to Alloca.
1626 Value *Elt = new LoadInst(OtherElt, "tmp", false, OtherEltAlign, MI);
1627 new StoreInst(Elt, EltPtr, MI);
1629 // From Alloca to Other.
1630 Value *Elt = new LoadInst(EltPtr, "tmp", MI);
1631 new StoreInst(Elt, OtherElt, false, OtherEltAlign, MI);
1635 assert(isa<MemSetInst>(MI));
1637 // If the stored element is zero (common case), just store a null
1640 if (ConstantInt *CI = dyn_cast<ConstantInt>(MI->getArgOperand(1))) {
1642 StoreVal = Constant::getNullValue(EltTy); // 0.0, null, 0, <0,0>
1644 // If EltTy is a vector type, get the element type.
1645 const Type *ValTy = EltTy->getScalarType();
1647 // Construct an integer with the right value.
1648 unsigned EltSize = TD->getTypeSizeInBits(ValTy);
1649 APInt OneVal(EltSize, CI->getZExtValue());
1650 APInt TotalVal(OneVal);
1652 for (unsigned i = 0; 8*i < EltSize; ++i) {
1653 TotalVal = TotalVal.shl(8);
1657 // Convert the integer value to the appropriate type.
1658 StoreVal = ConstantInt::get(CI->getContext(), TotalVal);
1659 if (ValTy->isPointerTy())
1660 StoreVal = ConstantExpr::getIntToPtr(StoreVal, ValTy);
1661 else if (ValTy->isFloatingPointTy())
1662 StoreVal = ConstantExpr::getBitCast(StoreVal, ValTy);
1663 assert(StoreVal->getType() == ValTy && "Type mismatch!");
1665 // If the requested value was a vector constant, create it.
1666 if (EltTy != ValTy) {
1667 unsigned NumElts = cast<VectorType>(ValTy)->getNumElements();
1668 SmallVector<Constant*, 16> Elts(NumElts, StoreVal);
1669 StoreVal = ConstantVector::get(&Elts[0], NumElts);
1672 new StoreInst(StoreVal, EltPtr, MI);
1675 // Otherwise, if we're storing a byte variable, use a memset call for
1679 unsigned EltSize = TD->getTypeAllocSize(EltTy);
1681 IRBuilder<> Builder(MI);
1683 // Finally, insert the meminst for this element.
1684 if (isa<MemSetInst>(MI)) {
1685 Builder.CreateMemSet(EltPtr, MI->getArgOperand(1), EltSize,
1688 assert(isa<MemTransferInst>(MI));
1689 Value *Dst = SROADest ? EltPtr : OtherElt; // Dest ptr
1690 Value *Src = SROADest ? OtherElt : EltPtr; // Src ptr
1692 if (isa<MemCpyInst>(MI))
1693 Builder.CreateMemCpy(Dst, Src, EltSize, OtherEltAlign,MI->isVolatile());
1695 Builder.CreateMemMove(Dst, Src, EltSize,OtherEltAlign,MI->isVolatile());
1698 DeadInsts.push_back(MI);
1701 /// RewriteStoreUserOfWholeAlloca - We found a store of an integer that
1702 /// overwrites the entire allocation. Extract out the pieces of the stored
1703 /// integer and store them individually.
1704 void SROA::RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocaInst *AI,
1705 SmallVector<AllocaInst*, 32> &NewElts){
1706 // Extract each element out of the integer according to its structure offset
1707 // and store the element value to the individual alloca.
1708 Value *SrcVal = SI->getOperand(0);
1709 const Type *AllocaEltTy = AI->getAllocatedType();
1710 uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy);
1712 // Handle tail padding by extending the operand
1713 if (TD->getTypeSizeInBits(SrcVal->getType()) != AllocaSizeBits)
1714 SrcVal = new ZExtInst(SrcVal,
1715 IntegerType::get(SI->getContext(), AllocaSizeBits),
1718 DEBUG(dbgs() << "PROMOTING STORE TO WHOLE ALLOCA: " << *AI << '\n' << *SI
1721 // There are two forms here: AI could be an array or struct. Both cases
1722 // have different ways to compute the element offset.
1723 if (const StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) {
1724 const StructLayout *Layout = TD->getStructLayout(EltSTy);
1726 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
1727 // Get the number of bits to shift SrcVal to get the value.
1728 const Type *FieldTy = EltSTy->getElementType(i);
1729 uint64_t Shift = Layout->getElementOffsetInBits(i);
1731 if (TD->isBigEndian())
1732 Shift = AllocaSizeBits-Shift-TD->getTypeAllocSizeInBits(FieldTy);
1734 Value *EltVal = SrcVal;
1736 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift);
1737 EltVal = BinaryOperator::CreateLShr(EltVal, ShiftVal,
1738 "sroa.store.elt", SI);
1741 // Truncate down to an integer of the right size.
1742 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy);
1744 // Ignore zero sized fields like {}, they obviously contain no data.
1745 if (FieldSizeBits == 0) continue;
1747 if (FieldSizeBits != AllocaSizeBits)
1748 EltVal = new TruncInst(EltVal,
1749 IntegerType::get(SI->getContext(), FieldSizeBits),
1751 Value *DestField = NewElts[i];
1752 if (EltVal->getType() == FieldTy) {
1753 // Storing to an integer field of this size, just do it.
1754 } else if (FieldTy->isFloatingPointTy() || FieldTy->isVectorTy()) {
1755 // Bitcast to the right element type (for fp/vector values).
1756 EltVal = new BitCastInst(EltVal, FieldTy, "", SI);
1758 // Otherwise, bitcast the dest pointer (for aggregates).
1759 DestField = new BitCastInst(DestField,
1760 PointerType::getUnqual(EltVal->getType()),
1763 new StoreInst(EltVal, DestField, SI);
1767 const ArrayType *ATy = cast<ArrayType>(AllocaEltTy);
1768 const Type *ArrayEltTy = ATy->getElementType();
1769 uint64_t ElementOffset = TD->getTypeAllocSizeInBits(ArrayEltTy);
1770 uint64_t ElementSizeBits = TD->getTypeSizeInBits(ArrayEltTy);
1774 if (TD->isBigEndian())
1775 Shift = AllocaSizeBits-ElementOffset;
1779 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
1780 // Ignore zero sized fields like {}, they obviously contain no data.
1781 if (ElementSizeBits == 0) continue;
1783 Value *EltVal = SrcVal;
1785 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift);
1786 EltVal = BinaryOperator::CreateLShr(EltVal, ShiftVal,
1787 "sroa.store.elt", SI);
1790 // Truncate down to an integer of the right size.
1791 if (ElementSizeBits != AllocaSizeBits)
1792 EltVal = new TruncInst(EltVal,
1793 IntegerType::get(SI->getContext(),
1794 ElementSizeBits), "", SI);
1795 Value *DestField = NewElts[i];
1796 if (EltVal->getType() == ArrayEltTy) {
1797 // Storing to an integer field of this size, just do it.
1798 } else if (ArrayEltTy->isFloatingPointTy() ||
1799 ArrayEltTy->isVectorTy()) {
1800 // Bitcast to the right element type (for fp/vector values).
1801 EltVal = new BitCastInst(EltVal, ArrayEltTy, "", SI);
1803 // Otherwise, bitcast the dest pointer (for aggregates).
1804 DestField = new BitCastInst(DestField,
1805 PointerType::getUnqual(EltVal->getType()),
1808 new StoreInst(EltVal, DestField, SI);
1810 if (TD->isBigEndian())
1811 Shift -= ElementOffset;
1813 Shift += ElementOffset;
1817 DeadInsts.push_back(SI);
1820 /// RewriteLoadUserOfWholeAlloca - We found a load of the entire allocation to
1821 /// an integer. Load the individual pieces to form the aggregate value.
1822 void SROA::RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocaInst *AI,
1823 SmallVector<AllocaInst*, 32> &NewElts) {
1824 // Extract each element out of the NewElts according to its structure offset
1825 // and form the result value.
1826 const Type *AllocaEltTy = AI->getAllocatedType();
1827 uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy);
1829 DEBUG(dbgs() << "PROMOTING LOAD OF WHOLE ALLOCA: " << *AI << '\n' << *LI
1832 // There are two forms here: AI could be an array or struct. Both cases
1833 // have different ways to compute the element offset.
1834 const StructLayout *Layout = 0;
1835 uint64_t ArrayEltBitOffset = 0;
1836 if (const StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) {
1837 Layout = TD->getStructLayout(EltSTy);
1839 const Type *ArrayEltTy = cast<ArrayType>(AllocaEltTy)->getElementType();
1840 ArrayEltBitOffset = TD->getTypeAllocSizeInBits(ArrayEltTy);
1844 Constant::getNullValue(IntegerType::get(LI->getContext(), AllocaSizeBits));
1846 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
1847 // Load the value from the alloca. If the NewElt is an aggregate, cast
1848 // the pointer to an integer of the same size before doing the load.
1849 Value *SrcField = NewElts[i];
1850 const Type *FieldTy =
1851 cast<PointerType>(SrcField->getType())->getElementType();
1852 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy);
1854 // Ignore zero sized fields like {}, they obviously contain no data.
1855 if (FieldSizeBits == 0) continue;
1857 const IntegerType *FieldIntTy = IntegerType::get(LI->getContext(),
1859 if (!FieldTy->isIntegerTy() && !FieldTy->isFloatingPointTy() &&
1860 !FieldTy->isVectorTy())
1861 SrcField = new BitCastInst(SrcField,
1862 PointerType::getUnqual(FieldIntTy),
1864 SrcField = new LoadInst(SrcField, "sroa.load.elt", LI);
1866 // If SrcField is a fp or vector of the right size but that isn't an
1867 // integer type, bitcast to an integer so we can shift it.
1868 if (SrcField->getType() != FieldIntTy)
1869 SrcField = new BitCastInst(SrcField, FieldIntTy, "", LI);
1871 // Zero extend the field to be the same size as the final alloca so that
1872 // we can shift and insert it.
1873 if (SrcField->getType() != ResultVal->getType())
1874 SrcField = new ZExtInst(SrcField, ResultVal->getType(), "", LI);
1876 // Determine the number of bits to shift SrcField.
1878 if (Layout) // Struct case.
1879 Shift = Layout->getElementOffsetInBits(i);
1881 Shift = i*ArrayEltBitOffset;
1883 if (TD->isBigEndian())
1884 Shift = AllocaSizeBits-Shift-FieldIntTy->getBitWidth();
1887 Value *ShiftVal = ConstantInt::get(SrcField->getType(), Shift);
1888 SrcField = BinaryOperator::CreateShl(SrcField, ShiftVal, "", LI);
1891 // Don't create an 'or x, 0' on the first iteration.
1892 if (!isa<Constant>(ResultVal) ||
1893 !cast<Constant>(ResultVal)->isNullValue())
1894 ResultVal = BinaryOperator::CreateOr(SrcField, ResultVal, "", LI);
1896 ResultVal = SrcField;
1899 // Handle tail padding by truncating the result
1900 if (TD->getTypeSizeInBits(LI->getType()) != AllocaSizeBits)
1901 ResultVal = new TruncInst(ResultVal, LI->getType(), "", LI);
1903 LI->replaceAllUsesWith(ResultVal);
1904 DeadInsts.push_back(LI);
1907 /// HasPadding - Return true if the specified type has any structure or
1908 /// alignment padding in between the elements that would be split apart
1909 /// by SROA; return false otherwise.
1910 static bool HasPadding(const Type *Ty, const TargetData &TD) {
1911 if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
1912 Ty = ATy->getElementType();
1913 return TD.getTypeSizeInBits(Ty) != TD.getTypeAllocSizeInBits(Ty);
1916 // SROA currently handles only Arrays and Structs.
1917 const StructType *STy = cast<StructType>(Ty);
1918 const StructLayout *SL = TD.getStructLayout(STy);
1919 unsigned PrevFieldBitOffset = 0;
1920 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
1921 unsigned FieldBitOffset = SL->getElementOffsetInBits(i);
1923 // Check to see if there is any padding between this element and the
1926 unsigned PrevFieldEnd =
1927 PrevFieldBitOffset+TD.getTypeSizeInBits(STy->getElementType(i-1));
1928 if (PrevFieldEnd < FieldBitOffset)
1931 PrevFieldBitOffset = FieldBitOffset;
1933 // Check for tail padding.
1934 if (unsigned EltCount = STy->getNumElements()) {
1935 unsigned PrevFieldEnd = PrevFieldBitOffset +
1936 TD.getTypeSizeInBits(STy->getElementType(EltCount-1));
1937 if (PrevFieldEnd < SL->getSizeInBits())
1943 /// isSafeStructAllocaToScalarRepl - Check to see if the specified allocation of
1944 /// an aggregate can be broken down into elements. Return 0 if not, 3 if safe,
1945 /// or 1 if safe after canonicalization has been performed.
1946 bool SROA::isSafeAllocaToScalarRepl(AllocaInst *AI) {
1947 // Loop over the use list of the alloca. We can only transform it if all of
1948 // the users are safe to transform.
1951 isSafeForScalarRepl(AI, AI, 0, Info);
1952 if (Info.isUnsafe) {
1953 DEBUG(dbgs() << "Cannot transform: " << *AI << '\n');
1957 // Okay, we know all the users are promotable. If the aggregate is a memcpy
1958 // source and destination, we have to be careful. In particular, the memcpy
1959 // could be moving around elements that live in structure padding of the LLVM
1960 // types, but may actually be used. In these cases, we refuse to promote the
1962 if (Info.isMemCpySrc && Info.isMemCpyDst &&
1963 HasPadding(AI->getAllocatedType(), *TD))
1971 /// PointsToConstantGlobal - Return true if V (possibly indirectly) points to
1972 /// some part of a constant global variable. This intentionally only accepts
1973 /// constant expressions because we don't can't rewrite arbitrary instructions.
1974 static bool PointsToConstantGlobal(Value *V) {
1975 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
1976 return GV->isConstant();
1977 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
1978 if (CE->getOpcode() == Instruction::BitCast ||
1979 CE->getOpcode() == Instruction::GetElementPtr)
1980 return PointsToConstantGlobal(CE->getOperand(0));
1984 /// isOnlyCopiedFromConstantGlobal - Recursively walk the uses of a (derived)
1985 /// pointer to an alloca. Ignore any reads of the pointer, return false if we
1986 /// see any stores or other unknown uses. If we see pointer arithmetic, keep
1987 /// track of whether it moves the pointer (with isOffset) but otherwise traverse
1988 /// the uses. If we see a memcpy/memmove that targets an unoffseted pointer to
1989 /// the alloca, and if the source pointer is a pointer to a constant global, we
1990 /// can optimize this.
1991 static bool isOnlyCopiedFromConstantGlobal(Value *V, MemTransferInst *&TheCopy,
1993 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) {
1994 User *U = cast<Instruction>(*UI);
1996 if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
1997 // Ignore non-volatile loads, they are always ok.
1998 if (LI->isVolatile()) return false;
2002 if (BitCastInst *BCI = dyn_cast<BitCastInst>(U)) {
2003 // If uses of the bitcast are ok, we are ok.
2004 if (!isOnlyCopiedFromConstantGlobal(BCI, TheCopy, isOffset))
2008 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) {
2009 // If the GEP has all zero indices, it doesn't offset the pointer. If it
2010 // doesn't, it does.
2011 if (!isOnlyCopiedFromConstantGlobal(GEP, TheCopy,
2012 isOffset || !GEP->hasAllZeroIndices()))
2017 if (CallSite CS = U) {
2018 // If this is a readonly/readnone call site, then we know it is just a
2019 // load and we can ignore it.
2020 if (CS.onlyReadsMemory())
2023 // If this is the function being called then we treat it like a load and
2025 if (CS.isCallee(UI))
2028 // If this is being passed as a byval argument, the caller is making a
2029 // copy, so it is only a read of the alloca.
2030 unsigned ArgNo = CS.getArgumentNo(UI);
2031 if (CS.paramHasAttr(ArgNo+1, Attribute::ByVal))
2035 // If this is isn't our memcpy/memmove, reject it as something we can't
2037 MemTransferInst *MI = dyn_cast<MemTransferInst>(U);
2041 // If the transfer is using the alloca as a source of the transfer, then
2042 // ignore it since it is a load (unless the transfer is volatile).
2043 if (UI.getOperandNo() == 1) {
2044 if (MI->isVolatile()) return false;
2048 // If we already have seen a copy, reject the second one.
2049 if (TheCopy) return false;
2051 // If the pointer has been offset from the start of the alloca, we can't
2052 // safely handle this.
2053 if (isOffset) return false;
2055 // If the memintrinsic isn't using the alloca as the dest, reject it.
2056 if (UI.getOperandNo() != 0) return false;
2058 // If the source of the memcpy/move is not a constant global, reject it.
2059 if (!PointsToConstantGlobal(MI->getSource()))
2062 // Otherwise, the transform is safe. Remember the copy instruction.
2068 /// isOnlyCopiedFromConstantGlobal - Return true if the specified alloca is only
2069 /// modified by a copy from a constant global. If we can prove this, we can
2070 /// replace any uses of the alloca with uses of the global directly.
2071 MemTransferInst *SROA::isOnlyCopiedFromConstantGlobal(AllocaInst *AI) {
2072 MemTransferInst *TheCopy = 0;
2073 if (::isOnlyCopiedFromConstantGlobal(AI, TheCopy, false))