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/Pass.h"
32 #include "llvm/Analysis/Dominators.h"
33 #include "llvm/Target/TargetData.h"
34 #include "llvm/Transforms/Utils/PromoteMemToReg.h"
35 #include "llvm/Transforms/Utils/Local.h"
36 #include "llvm/Support/Debug.h"
37 #include "llvm/Support/ErrorHandling.h"
38 #include "llvm/Support/GetElementPtrTypeIterator.h"
39 #include "llvm/Support/IRBuilder.h"
40 #include "llvm/Support/MathExtras.h"
41 #include "llvm/Support/raw_ostream.h"
42 #include "llvm/ADT/SmallVector.h"
43 #include "llvm/ADT/Statistic.h"
46 STATISTIC(NumReplaced, "Number of allocas broken up");
47 STATISTIC(NumPromoted, "Number of allocas promoted");
48 STATISTIC(NumConverted, "Number of aggregates converted to scalar");
49 STATISTIC(NumGlobals, "Number of allocas copied from constant global");
52 struct ConvertToScalarInfo;
54 struct SROA : public FunctionPass {
55 static char ID; // Pass identification, replacement for typeid
56 explicit SROA(signed T = -1) : FunctionPass(&ID) {
63 bool runOnFunction(Function &F);
65 bool performScalarRepl(Function &F);
66 bool performPromotion(Function &F);
68 // getAnalysisUsage - This pass does not require any passes, but we know it
69 // will not alter the CFG, so say so.
70 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
71 AU.addRequired<DominatorTree>();
72 AU.addRequired<DominanceFrontier>();
79 /// DeadInsts - Keep track of instructions we have made dead, so that
80 /// we can remove them after we are done working.
81 SmallVector<Value*, 32> DeadInsts;
83 /// AllocaInfo - When analyzing uses of an alloca instruction, this captures
84 /// information about the uses. All these fields are initialized to false
85 /// and set to true when something is learned.
87 /// isUnsafe - This is set to true if the alloca cannot be SROA'd.
90 /// isMemCpySrc - This is true if this aggregate is memcpy'd from.
93 /// isMemCpyDst - This is true if this aggregate is memcpy'd into.
97 : isUnsafe(false), isMemCpySrc(false), isMemCpyDst(false) {}
100 unsigned SRThreshold;
102 void MarkUnsafe(AllocaInfo &I) { I.isUnsafe = true; }
104 bool isSafeAllocaToScalarRepl(AllocaInst *AI);
106 void isSafeForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset,
108 void isSafeGEP(GetElementPtrInst *GEPI, AllocaInst *AI, uint64_t &Offset,
110 void isSafeMemAccess(AllocaInst *AI, uint64_t Offset, uint64_t MemSize,
111 const Type *MemOpType, bool isStore, AllocaInfo &Info);
112 bool TypeHasComponent(const Type *T, uint64_t Offset, uint64_t Size);
113 uint64_t FindElementAndOffset(const Type *&T, uint64_t &Offset,
116 void DoScalarReplacement(AllocaInst *AI,
117 std::vector<AllocaInst*> &WorkList);
118 void DeleteDeadInstructions();
119 AllocaInst *AddNewAlloca(Function &F, const Type *Ty, AllocaInst *Base);
121 void RewriteForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset,
122 SmallVector<AllocaInst*, 32> &NewElts);
123 void RewriteBitCast(BitCastInst *BC, AllocaInst *AI, uint64_t Offset,
124 SmallVector<AllocaInst*, 32> &NewElts);
125 void RewriteGEP(GetElementPtrInst *GEPI, AllocaInst *AI, uint64_t Offset,
126 SmallVector<AllocaInst*, 32> &NewElts);
127 void RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *Inst,
129 SmallVector<AllocaInst*, 32> &NewElts);
130 void RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocaInst *AI,
131 SmallVector<AllocaInst*, 32> &NewElts);
132 void RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocaInst *AI,
133 SmallVector<AllocaInst*, 32> &NewElts);
135 bool CanConvertToScalar(Value *V, ConvertToScalarInfo &ConvertInfo,
137 void ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, uint64_t Offset);
138 Value *ConvertScalar_ExtractValue(Value *NV, const Type *ToType,
139 uint64_t Offset, IRBuilder<> &Builder);
140 Value *ConvertScalar_InsertValue(Value *StoredVal, Value *ExistingVal,
141 uint64_t Offset, IRBuilder<> &Builder);
142 static MemTransferInst *isOnlyCopiedFromConstantGlobal(AllocaInst *AI);
147 static RegisterPass<SROA> X("scalarrepl", "Scalar Replacement of Aggregates");
149 // Public interface to the ScalarReplAggregates pass
150 FunctionPass *llvm::createScalarReplAggregatesPass(signed int Threshold) {
151 return new SROA(Threshold);
155 bool SROA::runOnFunction(Function &F) {
156 TD = getAnalysisIfAvailable<TargetData>();
158 bool Changed = performPromotion(F);
160 // FIXME: ScalarRepl currently depends on TargetData more than it
161 // theoretically needs to. It should be refactored in order to support
162 // target-independent IR. Until this is done, just skip the actual
163 // scalar-replacement portion of this pass.
164 if (!TD) return Changed;
167 bool LocalChange = performScalarRepl(F);
168 if (!LocalChange) break; // No need to repromote if no scalarrepl
170 LocalChange = performPromotion(F);
171 if (!LocalChange) break; // No need to re-scalarrepl if no promotion
178 bool SROA::performPromotion(Function &F) {
179 std::vector<AllocaInst*> Allocas;
180 DominatorTree &DT = getAnalysis<DominatorTree>();
181 DominanceFrontier &DF = getAnalysis<DominanceFrontier>();
183 BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function
185 bool Changed = false;
190 // Find allocas that are safe to promote, by looking at all instructions in
192 for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I)
193 if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) // Is it an alloca?
194 if (isAllocaPromotable(AI))
195 Allocas.push_back(AI);
197 if (Allocas.empty()) break;
199 PromoteMemToReg(Allocas, DT, DF);
200 NumPromoted += Allocas.size();
207 /// ShouldAttemptScalarRepl - Decide if an alloca is a good candidate for
208 /// SROA. It must be a struct or array type with a small number of elements.
209 static bool ShouldAttemptScalarRepl(AllocaInst *AI) {
210 const Type *T = AI->getAllocatedType();
211 // Do not promote any struct into more than 32 separate vars.
212 if (const StructType *ST = dyn_cast<StructType>(T))
213 return ST->getNumElements() <= 32;
214 // Arrays are much less likely to be safe for SROA; only consider
215 // them if they are very small.
216 if (const ArrayType *AT = dyn_cast<ArrayType>(T))
217 return AT->getNumElements() <= 8;
222 struct ConvertToScalarInfo {
223 /// AllocaSize - The size of the alloca being considered.
227 const Type *VectorTy;
230 explicit ConvertToScalarInfo(unsigned Size) : AllocaSize(Size) {
231 IsNotTrivial = false;
236 bool shouldConvertToVector() const {
237 return VectorTy && VectorTy->isVectorTy() && HadAVector;
240 } // end anonymous namespace.
244 // performScalarRepl - This algorithm is a simple worklist driven algorithm,
245 // which runs on all of the malloc/alloca instructions in the function, removing
246 // them if they are only used by getelementptr instructions.
248 bool SROA::performScalarRepl(Function &F) {
249 std::vector<AllocaInst*> WorkList;
251 // Scan the entry basic block, adding allocas to the worklist.
252 BasicBlock &BB = F.getEntryBlock();
253 for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I)
254 if (AllocaInst *A = dyn_cast<AllocaInst>(I))
255 WorkList.push_back(A);
257 // Process the worklist
258 bool Changed = false;
259 while (!WorkList.empty()) {
260 AllocaInst *AI = WorkList.back();
263 // Handle dead allocas trivially. These can be formed by SROA'ing arrays
264 // with unused elements.
265 if (AI->use_empty()) {
266 AI->eraseFromParent();
271 // If this alloca is impossible for us to promote, reject it early.
272 if (AI->isArrayAllocation() || !AI->getAllocatedType()->isSized())
275 // Check to see if this allocation is only modified by a memcpy/memmove from
276 // a constant global. If this is the case, we can change all users to use
277 // the constant global instead. This is commonly produced by the CFE by
278 // constructs like "void foo() { int A[] = {1,2,3,4,5,6,7,8,9...}; }" if 'A'
279 // is only subsequently read.
280 if (MemTransferInst *TheCopy = isOnlyCopiedFromConstantGlobal(AI)) {
281 DEBUG(dbgs() << "Found alloca equal to global: " << *AI << '\n');
282 DEBUG(dbgs() << " memcpy = " << *TheCopy << '\n');
283 Constant *TheSrc = cast<Constant>(TheCopy->getSource());
284 AI->replaceAllUsesWith(ConstantExpr::getBitCast(TheSrc, AI->getType()));
285 TheCopy->eraseFromParent(); // Don't mutate the global.
286 AI->eraseFromParent();
292 // Check to see if we can perform the core SROA transformation. We cannot
293 // transform the allocation instruction if it is an array allocation
294 // (allocations OF arrays are ok though), and an allocation of a scalar
295 // value cannot be decomposed at all.
296 uint64_t AllocaSize = TD->getTypeAllocSize(AI->getAllocatedType());
298 // Do not promote [0 x %struct].
299 if (AllocaSize == 0) continue;
301 // Do not promote any struct whose size is too big.
302 if (AllocaSize > SRThreshold) continue;
304 // If the alloca looks like a good candidate for scalar replacement, and if
305 // all its users can be transformed, then split up the aggregate into its
306 // separate elements.
307 if (ShouldAttemptScalarRepl(AI) && isSafeAllocaToScalarRepl(AI)) {
308 DoScalarReplacement(AI, WorkList);
313 // If we can turn this aggregate value (potentially with casts) into a
314 // simple scalar value that can be mem2reg'd into a register value.
315 // IsNotTrivial tracks whether this is something that mem2reg could have
316 // promoted itself. If so, we don't want to transform it needlessly. Note
317 // that we can't just check based on the type: the alloca may be of an i32
318 // but that has pointer arithmetic to set byte 3 of it or something.
319 ConvertToScalarInfo ConvertInfo((unsigned)AllocaSize);
320 if (CanConvertToScalar(AI, ConvertInfo, 0) && ConvertInfo.IsNotTrivial) {
322 // If we were able to find a vector type that can handle this with
323 // insert/extract elements, and if there was at least one use that had
324 // a vector type, promote this to a vector. We don't want to promote
325 // random stuff that doesn't use vectors (e.g. <9 x double>) because then
326 // we just get a lot of insert/extracts. If at least one vector is
327 // involved, then we probably really do have a union of vector/array.
328 if (ConvertInfo.shouldConvertToVector()) {
329 DEBUG(dbgs() << "CONVERT TO VECTOR: " << *AI << "\n TYPE = "
330 << *ConvertInfo.VectorTy << '\n');
332 // Create and insert the vector alloca.
333 NewAI = new AllocaInst(ConvertInfo.VectorTy, 0, "",
334 AI->getParent()->begin());
335 ConvertUsesToScalar(AI, NewAI, 0);
337 DEBUG(dbgs() << "CONVERT TO SCALAR INTEGER: " << *AI << "\n");
339 // Create and insert the integer alloca.
340 const Type *NewTy = IntegerType::get(AI->getContext(), AllocaSize*8);
341 NewAI = new AllocaInst(NewTy, 0, "", AI->getParent()->begin());
342 ConvertUsesToScalar(AI, NewAI, 0);
345 AI->eraseFromParent();
351 // Otherwise, couldn't process this alloca.
357 /// DoScalarReplacement - This alloca satisfied the isSafeAllocaToScalarRepl
358 /// predicate, do SROA now.
359 void SROA::DoScalarReplacement(AllocaInst *AI,
360 std::vector<AllocaInst*> &WorkList) {
361 DEBUG(dbgs() << "Found inst to SROA: " << *AI << '\n');
362 SmallVector<AllocaInst*, 32> ElementAllocas;
363 if (const StructType *ST = dyn_cast<StructType>(AI->getAllocatedType())) {
364 ElementAllocas.reserve(ST->getNumContainedTypes());
365 for (unsigned i = 0, e = ST->getNumContainedTypes(); i != e; ++i) {
366 AllocaInst *NA = new AllocaInst(ST->getContainedType(i), 0,
368 AI->getName() + "." + Twine(i), AI);
369 ElementAllocas.push_back(NA);
370 WorkList.push_back(NA); // Add to worklist for recursive processing
373 const ArrayType *AT = cast<ArrayType>(AI->getAllocatedType());
374 ElementAllocas.reserve(AT->getNumElements());
375 const Type *ElTy = AT->getElementType();
376 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
377 AllocaInst *NA = new AllocaInst(ElTy, 0, AI->getAlignment(),
378 AI->getName() + "." + Twine(i), AI);
379 ElementAllocas.push_back(NA);
380 WorkList.push_back(NA); // Add to worklist for recursive processing
384 // Now that we have created the new alloca instructions, rewrite all the
385 // uses of the old alloca.
386 RewriteForScalarRepl(AI, AI, 0, ElementAllocas);
388 // Now erase any instructions that were made dead while rewriting the alloca.
389 DeleteDeadInstructions();
390 AI->eraseFromParent();
395 /// DeleteDeadInstructions - Erase instructions on the DeadInstrs list,
396 /// recursively including all their operands that become trivially dead.
397 void SROA::DeleteDeadInstructions() {
398 while (!DeadInsts.empty()) {
399 Instruction *I = cast<Instruction>(DeadInsts.pop_back_val());
401 for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI)
402 if (Instruction *U = dyn_cast<Instruction>(*OI)) {
403 // Zero out the operand and see if it becomes trivially dead.
404 // (But, don't add allocas to the dead instruction list -- they are
405 // already on the worklist and will be deleted separately.)
407 if (isInstructionTriviallyDead(U) && !isa<AllocaInst>(U))
408 DeadInsts.push_back(U);
411 I->eraseFromParent();
415 /// isSafeForScalarRepl - Check if instruction I is a safe use with regard to
416 /// performing scalar replacement of alloca AI. The results are flagged in
417 /// the Info parameter. Offset indicates the position within AI that is
418 /// referenced by this instruction.
419 void SROA::isSafeForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset,
421 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E; ++UI) {
422 Instruction *User = cast<Instruction>(*UI);
424 if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) {
425 isSafeForScalarRepl(BC, AI, Offset, Info);
426 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
427 uint64_t GEPOffset = Offset;
428 isSafeGEP(GEPI, AI, GEPOffset, Info);
430 isSafeForScalarRepl(GEPI, AI, GEPOffset, Info);
431 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) {
432 ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength());
434 isSafeMemAccess(AI, Offset, Length->getZExtValue(), 0,
435 UI.getOperandNo() == 0, Info);
438 } else if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
439 if (!LI->isVolatile()) {
440 const Type *LIType = LI->getType();
441 isSafeMemAccess(AI, Offset, TD->getTypeAllocSize(LIType),
442 LIType, false, Info);
445 } else if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
446 // Store is ok if storing INTO the pointer, not storing the pointer
447 if (!SI->isVolatile() && SI->getOperand(0) != I) {
448 const Type *SIType = SI->getOperand(0)->getType();
449 isSafeMemAccess(AI, Offset, TD->getTypeAllocSize(SIType),
454 DEBUG(errs() << " Transformation preventing inst: " << *User << '\n');
457 if (Info.isUnsafe) return;
461 /// isSafeGEP - Check if a GEP instruction can be handled for scalar
462 /// replacement. It is safe when all the indices are constant, in-bounds
463 /// references, and when the resulting offset corresponds to an element within
464 /// the alloca type. The results are flagged in the Info parameter. Upon
465 /// return, Offset is adjusted as specified by the GEP indices.
466 void SROA::isSafeGEP(GetElementPtrInst *GEPI, AllocaInst *AI,
467 uint64_t &Offset, AllocaInfo &Info) {
468 gep_type_iterator GEPIt = gep_type_begin(GEPI), E = gep_type_end(GEPI);
472 // Walk through the GEP type indices, checking the types that this indexes
474 for (; GEPIt != E; ++GEPIt) {
475 // Ignore struct elements, no extra checking needed for these.
476 if ((*GEPIt)->isStructTy())
479 ConstantInt *IdxVal = dyn_cast<ConstantInt>(GEPIt.getOperand());
481 return MarkUnsafe(Info);
484 // Compute the offset due to this GEP and check if the alloca has a
485 // component element at that offset.
486 SmallVector<Value*, 8> Indices(GEPI->op_begin() + 1, GEPI->op_end());
487 Offset += TD->getIndexedOffset(GEPI->getPointerOperandType(),
488 &Indices[0], Indices.size());
489 if (!TypeHasComponent(AI->getAllocatedType(), Offset, 0))
493 /// isSafeMemAccess - Check if a load/store/memcpy operates on the entire AI
494 /// alloca or has an offset and size that corresponds to a component element
495 /// within it. The offset checked here may have been formed from a GEP with a
496 /// pointer bitcasted to a different type.
497 void SROA::isSafeMemAccess(AllocaInst *AI, uint64_t Offset, uint64_t MemSize,
498 const Type *MemOpType, bool isStore,
500 // Check if this is a load/store of the entire alloca.
501 if (Offset == 0 && MemSize == TD->getTypeAllocSize(AI->getAllocatedType())) {
502 bool UsesAggregateType = (MemOpType == AI->getAllocatedType());
503 // This is safe for MemIntrinsics (where MemOpType is 0), integer types
504 // (which are essentially the same as the MemIntrinsics, especially with
505 // regard to copying padding between elements), or references using the
506 // aggregate type of the alloca.
507 if (!MemOpType || MemOpType->isIntegerTy() || UsesAggregateType) {
508 if (!UsesAggregateType) {
510 Info.isMemCpyDst = true;
512 Info.isMemCpySrc = true;
517 // Check if the offset/size correspond to a component within the alloca type.
518 const Type *T = AI->getAllocatedType();
519 if (TypeHasComponent(T, Offset, MemSize))
522 return MarkUnsafe(Info);
525 /// TypeHasComponent - Return true if T has a component type with the
526 /// specified offset and size. If Size is zero, do not check the size.
527 bool SROA::TypeHasComponent(const Type *T, uint64_t Offset, uint64_t Size) {
530 if (const StructType *ST = dyn_cast<StructType>(T)) {
531 const StructLayout *Layout = TD->getStructLayout(ST);
532 unsigned EltIdx = Layout->getElementContainingOffset(Offset);
533 EltTy = ST->getContainedType(EltIdx);
534 EltSize = TD->getTypeAllocSize(EltTy);
535 Offset -= Layout->getElementOffset(EltIdx);
536 } else if (const ArrayType *AT = dyn_cast<ArrayType>(T)) {
537 EltTy = AT->getElementType();
538 EltSize = TD->getTypeAllocSize(EltTy);
539 if (Offset >= AT->getNumElements() * EltSize)
545 if (Offset == 0 && (Size == 0 || EltSize == Size))
547 // Check if the component spans multiple elements.
548 if (Offset + Size > EltSize)
550 return TypeHasComponent(EltTy, Offset, Size);
553 /// RewriteForScalarRepl - Alloca AI is being split into NewElts, so rewrite
554 /// the instruction I, which references it, to use the separate elements.
555 /// Offset indicates the position within AI that is referenced by this
557 void SROA::RewriteForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset,
558 SmallVector<AllocaInst*, 32> &NewElts) {
559 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E; ++UI) {
560 Instruction *User = cast<Instruction>(*UI);
562 if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) {
563 RewriteBitCast(BC, AI, Offset, NewElts);
564 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
565 RewriteGEP(GEPI, AI, Offset, NewElts);
566 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) {
567 ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength());
568 uint64_t MemSize = Length->getZExtValue();
570 MemSize == TD->getTypeAllocSize(AI->getAllocatedType()))
571 RewriteMemIntrinUserOfAlloca(MI, I, AI, NewElts);
572 // Otherwise the intrinsic can only touch a single element and the
573 // address operand will be updated, so nothing else needs to be done.
574 } else if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
575 const Type *LIType = LI->getType();
576 if (LIType == AI->getAllocatedType()) {
578 // %res = load { i32, i32 }* %alloc
580 // %load.0 = load i32* %alloc.0
581 // %insert.0 insertvalue { i32, i32 } zeroinitializer, i32 %load.0, 0
582 // %load.1 = load i32* %alloc.1
583 // %insert = insertvalue { i32, i32 } %insert.0, i32 %load.1, 1
584 // (Also works for arrays instead of structs)
585 Value *Insert = UndefValue::get(LIType);
586 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
587 Value *Load = new LoadInst(NewElts[i], "load", LI);
588 Insert = InsertValueInst::Create(Insert, Load, i, "insert", LI);
590 LI->replaceAllUsesWith(Insert);
591 DeadInsts.push_back(LI);
592 } else if (LIType->isIntegerTy() &&
593 TD->getTypeAllocSize(LIType) ==
594 TD->getTypeAllocSize(AI->getAllocatedType())) {
595 // If this is a load of the entire alloca to an integer, rewrite it.
596 RewriteLoadUserOfWholeAlloca(LI, AI, NewElts);
598 } else if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
599 Value *Val = SI->getOperand(0);
600 const Type *SIType = Val->getType();
601 if (SIType == AI->getAllocatedType()) {
603 // store { i32, i32 } %val, { i32, i32 }* %alloc
605 // %val.0 = extractvalue { i32, i32 } %val, 0
606 // store i32 %val.0, i32* %alloc.0
607 // %val.1 = extractvalue { i32, i32 } %val, 1
608 // store i32 %val.1, i32* %alloc.1
609 // (Also works for arrays instead of structs)
610 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
611 Value *Extract = ExtractValueInst::Create(Val, i, Val->getName(), SI);
612 new StoreInst(Extract, NewElts[i], SI);
614 DeadInsts.push_back(SI);
615 } else if (SIType->isIntegerTy() &&
616 TD->getTypeAllocSize(SIType) ==
617 TD->getTypeAllocSize(AI->getAllocatedType())) {
618 // If this is a store of the entire alloca from an integer, rewrite it.
619 RewriteStoreUserOfWholeAlloca(SI, AI, NewElts);
625 /// RewriteBitCast - Update a bitcast reference to the alloca being replaced
626 /// and recursively continue updating all of its uses.
627 void SROA::RewriteBitCast(BitCastInst *BC, AllocaInst *AI, uint64_t Offset,
628 SmallVector<AllocaInst*, 32> &NewElts) {
629 RewriteForScalarRepl(BC, AI, Offset, NewElts);
630 if (BC->getOperand(0) != AI)
633 // The bitcast references the original alloca. Replace its uses with
634 // references to the first new element alloca.
635 Instruction *Val = NewElts[0];
636 if (Val->getType() != BC->getDestTy()) {
637 Val = new BitCastInst(Val, BC->getDestTy(), "", BC);
640 BC->replaceAllUsesWith(Val);
641 DeadInsts.push_back(BC);
644 /// FindElementAndOffset - Return the index of the element containing Offset
645 /// within the specified type, which must be either a struct or an array.
646 /// Sets T to the type of the element and Offset to the offset within that
647 /// element. IdxTy is set to the type of the index result to be used in a
649 uint64_t SROA::FindElementAndOffset(const Type *&T, uint64_t &Offset,
650 const Type *&IdxTy) {
652 if (const StructType *ST = dyn_cast<StructType>(T)) {
653 const StructLayout *Layout = TD->getStructLayout(ST);
654 Idx = Layout->getElementContainingOffset(Offset);
655 T = ST->getContainedType(Idx);
656 Offset -= Layout->getElementOffset(Idx);
657 IdxTy = Type::getInt32Ty(T->getContext());
660 const ArrayType *AT = cast<ArrayType>(T);
661 T = AT->getElementType();
662 uint64_t EltSize = TD->getTypeAllocSize(T);
663 Idx = Offset / EltSize;
664 Offset -= Idx * EltSize;
665 IdxTy = Type::getInt64Ty(T->getContext());
669 /// RewriteGEP - Check if this GEP instruction moves the pointer across
670 /// elements of the alloca that are being split apart, and if so, rewrite
671 /// the GEP to be relative to the new element.
672 void SROA::RewriteGEP(GetElementPtrInst *GEPI, AllocaInst *AI, uint64_t Offset,
673 SmallVector<AllocaInst*, 32> &NewElts) {
674 uint64_t OldOffset = Offset;
675 SmallVector<Value*, 8> Indices(GEPI->op_begin() + 1, GEPI->op_end());
676 Offset += TD->getIndexedOffset(GEPI->getPointerOperandType(),
677 &Indices[0], Indices.size());
679 RewriteForScalarRepl(GEPI, AI, Offset, NewElts);
681 const Type *T = AI->getAllocatedType();
683 uint64_t OldIdx = FindElementAndOffset(T, OldOffset, IdxTy);
684 if (GEPI->getOperand(0) == AI)
685 OldIdx = ~0ULL; // Force the GEP to be rewritten.
687 T = AI->getAllocatedType();
688 uint64_t EltOffset = Offset;
689 uint64_t Idx = FindElementAndOffset(T, EltOffset, IdxTy);
691 // If this GEP does not move the pointer across elements of the alloca
692 // being split, then it does not needs to be rewritten.
696 const Type *i32Ty = Type::getInt32Ty(AI->getContext());
697 SmallVector<Value*, 8> NewArgs;
698 NewArgs.push_back(Constant::getNullValue(i32Ty));
699 while (EltOffset != 0) {
700 uint64_t EltIdx = FindElementAndOffset(T, EltOffset, IdxTy);
701 NewArgs.push_back(ConstantInt::get(IdxTy, EltIdx));
703 Instruction *Val = NewElts[Idx];
704 if (NewArgs.size() > 1) {
705 Val = GetElementPtrInst::CreateInBounds(Val, NewArgs.begin(),
706 NewArgs.end(), "", GEPI);
709 if (Val->getType() != GEPI->getType())
710 Val = new BitCastInst(Val, GEPI->getType(), Val->getName(), GEPI);
711 GEPI->replaceAllUsesWith(Val);
712 DeadInsts.push_back(GEPI);
715 /// RewriteMemIntrinUserOfAlloca - MI is a memcpy/memset/memmove from or to AI.
716 /// Rewrite it to copy or set the elements of the scalarized memory.
717 void SROA::RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *Inst,
719 SmallVector<AllocaInst*, 32> &NewElts) {
720 // If this is a memcpy/memmove, construct the other pointer as the
721 // appropriate type. The "Other" pointer is the pointer that goes to memory
722 // that doesn't have anything to do with the alloca that we are promoting. For
723 // memset, this Value* stays null.
725 LLVMContext &Context = MI->getContext();
726 unsigned MemAlignment = MI->getAlignment();
727 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(MI)) { // memmove/memcopy
728 if (Inst == MTI->getRawDest())
729 OtherPtr = MTI->getRawSource();
731 assert(Inst == MTI->getRawSource());
732 OtherPtr = MTI->getRawDest();
736 // If there is an other pointer, we want to convert it to the same pointer
737 // type as AI has, so we can GEP through it safely.
740 // Remove bitcasts and all-zero GEPs from OtherPtr. This is an
741 // optimization, but it's also required to detect the corner case where
742 // both pointer operands are referencing the same memory, and where
743 // OtherPtr may be a bitcast or GEP that currently being rewritten. (This
744 // function is only called for mem intrinsics that access the whole
745 // aggregate, so non-zero GEPs are not an issue here.)
747 if (BitCastInst *BC = dyn_cast<BitCastInst>(OtherPtr)) {
748 OtherPtr = BC->getOperand(0);
751 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(OtherPtr)) {
752 // All zero GEPs are effectively bitcasts.
753 if (GEP->hasAllZeroIndices()) {
754 OtherPtr = GEP->getOperand(0);
760 // Copying the alloca to itself is a no-op: just delete it.
761 if (OtherPtr == AI || OtherPtr == NewElts[0]) {
762 // This code will run twice for a no-op memcpy -- once for each operand.
763 // Put only one reference to MI on the DeadInsts list.
764 for (SmallVector<Value*, 32>::const_iterator I = DeadInsts.begin(),
765 E = DeadInsts.end(); I != E; ++I)
766 if (*I == MI) return;
767 DeadInsts.push_back(MI);
771 if (ConstantExpr *BCE = dyn_cast<ConstantExpr>(OtherPtr))
772 if (BCE->getOpcode() == Instruction::BitCast)
773 OtherPtr = BCE->getOperand(0);
775 // If the pointer is not the right type, insert a bitcast to the right
777 if (OtherPtr->getType() != AI->getType())
778 OtherPtr = new BitCastInst(OtherPtr, AI->getType(), OtherPtr->getName(),
782 // Process each element of the aggregate.
783 Value *TheFn = MI->getCalledValue();
784 const Type *BytePtrTy = MI->getRawDest()->getType();
785 bool SROADest = MI->getRawDest() == Inst;
787 Constant *Zero = Constant::getNullValue(Type::getInt32Ty(MI->getContext()));
789 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
790 // If this is a memcpy/memmove, emit a GEP of the other element address.
792 unsigned OtherEltAlign = MemAlignment;
795 Value *Idx[2] = { Zero,
796 ConstantInt::get(Type::getInt32Ty(MI->getContext()), i) };
797 OtherElt = GetElementPtrInst::CreateInBounds(OtherPtr, Idx, Idx + 2,
798 OtherPtr->getName()+"."+Twine(i),
801 const PointerType *OtherPtrTy = cast<PointerType>(OtherPtr->getType());
802 if (const StructType *ST =
803 dyn_cast<StructType>(OtherPtrTy->getElementType())) {
804 EltOffset = TD->getStructLayout(ST)->getElementOffset(i);
807 cast<SequentialType>(OtherPtr->getType())->getElementType();
808 EltOffset = TD->getTypeAllocSize(EltTy)*i;
811 // The alignment of the other pointer is the guaranteed alignment of the
812 // element, which is affected by both the known alignment of the whole
813 // mem intrinsic and the alignment of the element. If the alignment of
814 // the memcpy (f.e.) is 32 but the element is at a 4-byte offset, then the
815 // known alignment is just 4 bytes.
816 OtherEltAlign = (unsigned)MinAlign(OtherEltAlign, EltOffset);
819 Value *EltPtr = NewElts[i];
820 const Type *EltTy = cast<PointerType>(EltPtr->getType())->getElementType();
822 // If we got down to a scalar, insert a load or store as appropriate.
823 if (EltTy->isSingleValueType()) {
824 if (isa<MemTransferInst>(MI)) {
826 // From Other to Alloca.
827 Value *Elt = new LoadInst(OtherElt, "tmp", false, OtherEltAlign, MI);
828 new StoreInst(Elt, EltPtr, MI);
830 // From Alloca to Other.
831 Value *Elt = new LoadInst(EltPtr, "tmp", MI);
832 new StoreInst(Elt, OtherElt, false, OtherEltAlign, MI);
836 assert(isa<MemSetInst>(MI));
838 // If the stored element is zero (common case), just store a null
841 if (ConstantInt *CI = dyn_cast<ConstantInt>(MI->getOperand(1))) {
843 StoreVal = Constant::getNullValue(EltTy); // 0.0, null, 0, <0,0>
845 // If EltTy is a vector type, get the element type.
846 const Type *ValTy = EltTy->getScalarType();
848 // Construct an integer with the right value.
849 unsigned EltSize = TD->getTypeSizeInBits(ValTy);
850 APInt OneVal(EltSize, CI->getZExtValue());
851 APInt TotalVal(OneVal);
853 for (unsigned i = 0; 8*i < EltSize; ++i) {
854 TotalVal = TotalVal.shl(8);
858 // Convert the integer value to the appropriate type.
859 StoreVal = ConstantInt::get(Context, TotalVal);
860 if (ValTy->isPointerTy())
861 StoreVal = ConstantExpr::getIntToPtr(StoreVal, ValTy);
862 else if (ValTy->isFloatingPointTy())
863 StoreVal = ConstantExpr::getBitCast(StoreVal, ValTy);
864 assert(StoreVal->getType() == ValTy && "Type mismatch!");
866 // If the requested value was a vector constant, create it.
867 if (EltTy != ValTy) {
868 unsigned NumElts = cast<VectorType>(ValTy)->getNumElements();
869 SmallVector<Constant*, 16> Elts(NumElts, StoreVal);
870 StoreVal = ConstantVector::get(&Elts[0], NumElts);
873 new StoreInst(StoreVal, EltPtr, MI);
876 // Otherwise, if we're storing a byte variable, use a memset call for
880 // Cast the element pointer to BytePtrTy.
881 if (EltPtr->getType() != BytePtrTy)
882 EltPtr = new BitCastInst(EltPtr, BytePtrTy, EltPtr->getName(), MI);
884 // Cast the other pointer (if we have one) to BytePtrTy.
885 if (OtherElt && OtherElt->getType() != BytePtrTy) {
886 // Preserve address space of OtherElt
887 const PointerType* OtherPTy = cast<PointerType>(OtherElt->getType());
888 const PointerType* PTy = cast<PointerType>(BytePtrTy);
889 if (OtherPTy->getElementType() != PTy->getElementType()) {
890 Type *NewOtherPTy = PointerType::get(PTy->getElementType(),
891 OtherPTy->getAddressSpace());
892 OtherElt = new BitCastInst(OtherElt, NewOtherPTy,
893 OtherElt->getNameStr(), MI);
897 unsigned EltSize = TD->getTypeAllocSize(EltTy);
899 // Finally, insert the meminst for this element.
900 if (isa<MemTransferInst>(MI)) {
902 SROADest ? EltPtr : OtherElt, // Dest ptr
903 SROADest ? OtherElt : EltPtr, // Src ptr
904 ConstantInt::get(MI->getOperand(2)->getType(), EltSize), // Size
906 ConstantInt::get(Type::getInt32Ty(MI->getContext()), OtherEltAlign),
909 // In case we fold the address space overloaded memcpy of A to B
910 // with memcpy of B to C, change the function to be a memcpy of A to C.
911 const Type *Tys[] = { Ops[0]->getType(), Ops[1]->getType(),
913 Module *M = MI->getParent()->getParent()->getParent();
914 TheFn = Intrinsic::getDeclaration(M, MI->getIntrinsicID(), Tys, 3);
915 CallInst::Create(TheFn, Ops, Ops + 5, "", MI);
917 assert(isa<MemSetInst>(MI));
919 EltPtr, MI->getOperand(1), // Dest, Value,
920 ConstantInt::get(MI->getOperand(2)->getType(), EltSize), // Size
922 ConstantInt::get(Type::getInt1Ty(MI->getContext()), 0) // isVolatile
924 const Type *Tys[] = { Ops[0]->getType(), Ops[2]->getType() };
925 Module *M = MI->getParent()->getParent()->getParent();
926 TheFn = Intrinsic::getDeclaration(M, Intrinsic::memset, Tys, 2);
927 CallInst::Create(TheFn, Ops, Ops + 5, "", MI);
930 DeadInsts.push_back(MI);
933 /// RewriteStoreUserOfWholeAlloca - We found a store of an integer that
934 /// overwrites the entire allocation. Extract out the pieces of the stored
935 /// integer and store them individually.
936 void SROA::RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocaInst *AI,
937 SmallVector<AllocaInst*, 32> &NewElts){
938 // Extract each element out of the integer according to its structure offset
939 // and store the element value to the individual alloca.
940 Value *SrcVal = SI->getOperand(0);
941 const Type *AllocaEltTy = AI->getAllocatedType();
942 uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy);
944 // Handle tail padding by extending the operand
945 if (TD->getTypeSizeInBits(SrcVal->getType()) != AllocaSizeBits)
946 SrcVal = new ZExtInst(SrcVal,
947 IntegerType::get(SI->getContext(), AllocaSizeBits),
950 DEBUG(dbgs() << "PROMOTING STORE TO WHOLE ALLOCA: " << *AI << '\n' << *SI
953 // There are two forms here: AI could be an array or struct. Both cases
954 // have different ways to compute the element offset.
955 if (const StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) {
956 const StructLayout *Layout = TD->getStructLayout(EltSTy);
958 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
959 // Get the number of bits to shift SrcVal to get the value.
960 const Type *FieldTy = EltSTy->getElementType(i);
961 uint64_t Shift = Layout->getElementOffsetInBits(i);
963 if (TD->isBigEndian())
964 Shift = AllocaSizeBits-Shift-TD->getTypeAllocSizeInBits(FieldTy);
966 Value *EltVal = SrcVal;
968 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift);
969 EltVal = BinaryOperator::CreateLShr(EltVal, ShiftVal,
970 "sroa.store.elt", SI);
973 // Truncate down to an integer of the right size.
974 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy);
976 // Ignore zero sized fields like {}, they obviously contain no data.
977 if (FieldSizeBits == 0) continue;
979 if (FieldSizeBits != AllocaSizeBits)
980 EltVal = new TruncInst(EltVal,
981 IntegerType::get(SI->getContext(), FieldSizeBits),
983 Value *DestField = NewElts[i];
984 if (EltVal->getType() == FieldTy) {
985 // Storing to an integer field of this size, just do it.
986 } else if (FieldTy->isFloatingPointTy() || FieldTy->isVectorTy()) {
987 // Bitcast to the right element type (for fp/vector values).
988 EltVal = new BitCastInst(EltVal, FieldTy, "", SI);
990 // Otherwise, bitcast the dest pointer (for aggregates).
991 DestField = new BitCastInst(DestField,
992 PointerType::getUnqual(EltVal->getType()),
995 new StoreInst(EltVal, DestField, SI);
999 const ArrayType *ATy = cast<ArrayType>(AllocaEltTy);
1000 const Type *ArrayEltTy = ATy->getElementType();
1001 uint64_t ElementOffset = TD->getTypeAllocSizeInBits(ArrayEltTy);
1002 uint64_t ElementSizeBits = TD->getTypeSizeInBits(ArrayEltTy);
1006 if (TD->isBigEndian())
1007 Shift = AllocaSizeBits-ElementOffset;
1011 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
1012 // Ignore zero sized fields like {}, they obviously contain no data.
1013 if (ElementSizeBits == 0) continue;
1015 Value *EltVal = SrcVal;
1017 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift);
1018 EltVal = BinaryOperator::CreateLShr(EltVal, ShiftVal,
1019 "sroa.store.elt", SI);
1022 // Truncate down to an integer of the right size.
1023 if (ElementSizeBits != AllocaSizeBits)
1024 EltVal = new TruncInst(EltVal,
1025 IntegerType::get(SI->getContext(),
1026 ElementSizeBits),"",SI);
1027 Value *DestField = NewElts[i];
1028 if (EltVal->getType() == ArrayEltTy) {
1029 // Storing to an integer field of this size, just do it.
1030 } else if (ArrayEltTy->isFloatingPointTy() ||
1031 ArrayEltTy->isVectorTy()) {
1032 // Bitcast to the right element type (for fp/vector values).
1033 EltVal = new BitCastInst(EltVal, ArrayEltTy, "", SI);
1035 // Otherwise, bitcast the dest pointer (for aggregates).
1036 DestField = new BitCastInst(DestField,
1037 PointerType::getUnqual(EltVal->getType()),
1040 new StoreInst(EltVal, DestField, SI);
1042 if (TD->isBigEndian())
1043 Shift -= ElementOffset;
1045 Shift += ElementOffset;
1049 DeadInsts.push_back(SI);
1052 /// RewriteLoadUserOfWholeAlloca - We found a load of the entire allocation to
1053 /// an integer. Load the individual pieces to form the aggregate value.
1054 void SROA::RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocaInst *AI,
1055 SmallVector<AllocaInst*, 32> &NewElts) {
1056 // Extract each element out of the NewElts according to its structure offset
1057 // and form the result value.
1058 const Type *AllocaEltTy = AI->getAllocatedType();
1059 uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy);
1061 DEBUG(dbgs() << "PROMOTING LOAD OF WHOLE ALLOCA: " << *AI << '\n' << *LI
1064 // There are two forms here: AI could be an array or struct. Both cases
1065 // have different ways to compute the element offset.
1066 const StructLayout *Layout = 0;
1067 uint64_t ArrayEltBitOffset = 0;
1068 if (const StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) {
1069 Layout = TD->getStructLayout(EltSTy);
1071 const Type *ArrayEltTy = cast<ArrayType>(AllocaEltTy)->getElementType();
1072 ArrayEltBitOffset = TD->getTypeAllocSizeInBits(ArrayEltTy);
1076 Constant::getNullValue(IntegerType::get(LI->getContext(), AllocaSizeBits));
1078 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
1079 // Load the value from the alloca. If the NewElt is an aggregate, cast
1080 // the pointer to an integer of the same size before doing the load.
1081 Value *SrcField = NewElts[i];
1082 const Type *FieldTy =
1083 cast<PointerType>(SrcField->getType())->getElementType();
1084 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy);
1086 // Ignore zero sized fields like {}, they obviously contain no data.
1087 if (FieldSizeBits == 0) continue;
1089 const IntegerType *FieldIntTy = IntegerType::get(LI->getContext(),
1091 if (!FieldTy->isIntegerTy() && !FieldTy->isFloatingPointTy() &&
1092 !FieldTy->isVectorTy())
1093 SrcField = new BitCastInst(SrcField,
1094 PointerType::getUnqual(FieldIntTy),
1096 SrcField = new LoadInst(SrcField, "sroa.load.elt", LI);
1098 // If SrcField is a fp or vector of the right size but that isn't an
1099 // integer type, bitcast to an integer so we can shift it.
1100 if (SrcField->getType() != FieldIntTy)
1101 SrcField = new BitCastInst(SrcField, FieldIntTy, "", LI);
1103 // Zero extend the field to be the same size as the final alloca so that
1104 // we can shift and insert it.
1105 if (SrcField->getType() != ResultVal->getType())
1106 SrcField = new ZExtInst(SrcField, ResultVal->getType(), "", LI);
1108 // Determine the number of bits to shift SrcField.
1110 if (Layout) // Struct case.
1111 Shift = Layout->getElementOffsetInBits(i);
1113 Shift = i*ArrayEltBitOffset;
1115 if (TD->isBigEndian())
1116 Shift = AllocaSizeBits-Shift-FieldIntTy->getBitWidth();
1119 Value *ShiftVal = ConstantInt::get(SrcField->getType(), Shift);
1120 SrcField = BinaryOperator::CreateShl(SrcField, ShiftVal, "", LI);
1123 ResultVal = BinaryOperator::CreateOr(SrcField, ResultVal, "", LI);
1126 // Handle tail padding by truncating the result
1127 if (TD->getTypeSizeInBits(LI->getType()) != AllocaSizeBits)
1128 ResultVal = new TruncInst(ResultVal, LI->getType(), "", LI);
1130 LI->replaceAllUsesWith(ResultVal);
1131 DeadInsts.push_back(LI);
1134 /// HasPadding - Return true if the specified type has any structure or
1135 /// alignment padding, false otherwise.
1136 static bool HasPadding(const Type *Ty, const TargetData &TD) {
1137 if (const StructType *STy = dyn_cast<StructType>(Ty)) {
1138 const StructLayout *SL = TD.getStructLayout(STy);
1139 unsigned PrevFieldBitOffset = 0;
1140 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
1141 unsigned FieldBitOffset = SL->getElementOffsetInBits(i);
1143 // Padding in sub-elements?
1144 if (HasPadding(STy->getElementType(i), TD))
1147 // Check to see if there is any padding between this element and the
1150 unsigned PrevFieldEnd =
1151 PrevFieldBitOffset+TD.getTypeSizeInBits(STy->getElementType(i-1));
1152 if (PrevFieldEnd < FieldBitOffset)
1156 PrevFieldBitOffset = FieldBitOffset;
1159 // Check for tail padding.
1160 if (unsigned EltCount = STy->getNumElements()) {
1161 unsigned PrevFieldEnd = PrevFieldBitOffset +
1162 TD.getTypeSizeInBits(STy->getElementType(EltCount-1));
1163 if (PrevFieldEnd < SL->getSizeInBits())
1167 } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
1168 return HasPadding(ATy->getElementType(), TD);
1169 } else if (const VectorType *VTy = dyn_cast<VectorType>(Ty)) {
1170 return HasPadding(VTy->getElementType(), TD);
1172 return TD.getTypeSizeInBits(Ty) != TD.getTypeAllocSizeInBits(Ty);
1175 /// isSafeStructAllocaToScalarRepl - Check to see if the specified allocation of
1176 /// an aggregate can be broken down into elements. Return 0 if not, 3 if safe,
1177 /// or 1 if safe after canonicalization has been performed.
1178 bool SROA::isSafeAllocaToScalarRepl(AllocaInst *AI) {
1179 // Loop over the use list of the alloca. We can only transform it if all of
1180 // the users are safe to transform.
1183 isSafeForScalarRepl(AI, AI, 0, Info);
1184 if (Info.isUnsafe) {
1185 DEBUG(dbgs() << "Cannot transform: " << *AI << '\n');
1189 // Okay, we know all the users are promotable. If the aggregate is a memcpy
1190 // source and destination, we have to be careful. In particular, the memcpy
1191 // could be moving around elements that live in structure padding of the LLVM
1192 // types, but may actually be used. In these cases, we refuse to promote the
1194 if (Info.isMemCpySrc && Info.isMemCpyDst &&
1195 HasPadding(AI->getAllocatedType(), *TD))
1201 /// MergeInType - Add the 'In' type to the accumulated type (Accum) so far at
1202 /// the offset specified by Offset (which is specified in bytes).
1204 /// There are two cases we handle here:
1205 /// 1) A union of vector types of the same size and potentially its elements.
1206 /// Here we turn element accesses into insert/extract element operations.
1207 /// This promotes a <4 x float> with a store of float to the third element
1208 /// into a <4 x float> that uses insert element.
1209 /// 2) A fully general blob of memory, which we turn into some (potentially
1210 /// large) integer type with extract and insert operations where the loads
1211 /// and stores would mutate the memory.
1212 static void MergeInType(const Type *In, uint64_t Offset,
1213 ConvertToScalarInfo &ConvertInfo, const TargetData &TD){
1214 // Remember if we saw a vector type.
1215 ConvertInfo.HadAVector |= In->isVectorTy();
1217 if (ConvertInfo.VectorTy && ConvertInfo.VectorTy->isVoidTy())
1220 // If this could be contributing to a vector, analyze it.
1222 // If the In type is a vector that is the same size as the alloca, see if it
1223 // matches the existing VecTy.
1224 if (const VectorType *VInTy = dyn_cast<VectorType>(In)) {
1225 if (VInTy->getBitWidth()/8 == ConvertInfo.AllocaSize && Offset == 0) {
1226 // If we're storing/loading a vector of the right size, allow it as a
1227 // vector. If this the first vector we see, remember the type so that
1228 // we know the element size.
1229 if (ConvertInfo.VectorTy == 0)
1230 ConvertInfo.VectorTy = VInTy;
1233 } else if (In->isFloatTy() || In->isDoubleTy() ||
1234 (In->isIntegerTy() && In->getPrimitiveSizeInBits() >= 8 &&
1235 isPowerOf2_32(In->getPrimitiveSizeInBits()))) {
1236 // If we're accessing something that could be an element of a vector, see
1237 // if the implied vector agrees with what we already have and if Offset is
1238 // compatible with it.
1239 unsigned EltSize = In->getPrimitiveSizeInBits()/8;
1240 if (Offset % EltSize == 0 &&
1241 ConvertInfo.AllocaSize % EltSize == 0 &&
1242 (ConvertInfo.VectorTy == 0 ||
1243 cast<VectorType>(ConvertInfo.VectorTy)->getElementType()
1244 ->getPrimitiveSizeInBits()/8 == EltSize)) {
1245 if (ConvertInfo.VectorTy == 0)
1246 ConvertInfo.VectorTy = VectorType::get(In,
1247 ConvertInfo.AllocaSize/EltSize);
1252 // Otherwise, we have a case that we can't handle with an optimized vector
1253 // form. We can still turn this into a large integer.
1254 ConvertInfo.VectorTy = Type::getVoidTy(In->getContext());
1257 /// CanConvertToScalar - V is a pointer. If we can convert the pointee and all
1258 /// its accesses to a single vector type, return true and set VecTy to
1259 /// the new type. If we could convert the alloca into a single promotable
1260 /// integer, return true but set VecTy to VoidTy. Further, if the use is not a
1261 /// completely trivial use that mem2reg could promote, set IsNotTrivial. Offset
1262 /// is the current offset from the base of the alloca being analyzed.
1264 /// If we see at least one access to the value that is as a vector type, set the
1266 bool SROA::CanConvertToScalar(Value *V, ConvertToScalarInfo &ConvertInfo,
1268 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) {
1269 Instruction *User = cast<Instruction>(*UI);
1271 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1272 // Don't break volatile loads.
1273 if (LI->isVolatile())
1275 MergeInType(LI->getType(), Offset, ConvertInfo, *TD);
1279 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
1280 // Storing the pointer, not into the value?
1281 if (SI->getOperand(0) == V || SI->isVolatile()) return false;
1282 MergeInType(SI->getOperand(0)->getType(), Offset, ConvertInfo, *TD);
1286 if (BitCastInst *BCI = dyn_cast<BitCastInst>(User)) {
1287 if (!CanConvertToScalar(BCI, ConvertInfo, Offset))
1289 ConvertInfo.IsNotTrivial = true;
1293 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) {
1294 // If this is a GEP with a variable indices, we can't handle it.
1295 if (!GEP->hasAllConstantIndices())
1298 // Compute the offset that this GEP adds to the pointer.
1299 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end());
1300 uint64_t GEPOffset = TD->getIndexedOffset(GEP->getPointerOperandType(),
1301 &Indices[0], Indices.size());
1302 // See if all uses can be converted.
1303 if (!CanConvertToScalar(GEP, ConvertInfo, Offset+GEPOffset))
1305 ConvertInfo.IsNotTrivial = true;
1309 // If this is a constant sized memset of a constant value (e.g. 0) we can
1311 if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) {
1312 // Store of constant value and constant size.
1313 if (isa<ConstantInt>(MSI->getValue()) &&
1314 isa<ConstantInt>(MSI->getLength())) {
1315 ConvertInfo.IsNotTrivial = true;
1320 // If this is a memcpy or memmove into or out of the whole allocation, we
1321 // can handle it like a load or store of the scalar type.
1322 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) {
1323 if (ConstantInt *Len = dyn_cast<ConstantInt>(MTI->getLength()))
1324 if (Len->getZExtValue() == ConvertInfo.AllocaSize && Offset == 0) {
1325 ConvertInfo.IsNotTrivial = true;
1330 // Otherwise, we cannot handle this!
1337 /// ConvertUsesToScalar - Convert all of the users of Ptr to use the new alloca
1338 /// directly. This happens when we are converting an "integer union" to a
1339 /// single integer scalar, or when we are converting a "vector union" to a
1340 /// vector with insert/extractelement instructions.
1342 /// Offset is an offset from the original alloca, in bits that need to be
1343 /// shifted to the right. By the end of this, there should be no uses of Ptr.
1344 void SROA::ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, uint64_t Offset) {
1345 while (!Ptr->use_empty()) {
1346 Instruction *User = cast<Instruction>(Ptr->use_back());
1348 if (BitCastInst *CI = dyn_cast<BitCastInst>(User)) {
1349 ConvertUsesToScalar(CI, NewAI, Offset);
1350 CI->eraseFromParent();
1354 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) {
1355 // Compute the offset that this GEP adds to the pointer.
1356 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end());
1357 uint64_t GEPOffset = TD->getIndexedOffset(GEP->getPointerOperandType(),
1358 &Indices[0], Indices.size());
1359 ConvertUsesToScalar(GEP, NewAI, Offset+GEPOffset*8);
1360 GEP->eraseFromParent();
1364 IRBuilder<> Builder(User->getParent(), User);
1366 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1367 // The load is a bit extract from NewAI shifted right by Offset bits.
1368 Value *LoadedVal = Builder.CreateLoad(NewAI, "tmp");
1370 = ConvertScalar_ExtractValue(LoadedVal, LI->getType(), Offset, Builder);
1371 LI->replaceAllUsesWith(NewLoadVal);
1372 LI->eraseFromParent();
1376 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
1377 assert(SI->getOperand(0) != Ptr && "Consistency error!");
1378 Instruction *Old = Builder.CreateLoad(NewAI, NewAI->getName()+".in");
1379 Value *New = ConvertScalar_InsertValue(SI->getOperand(0), Old, Offset,
1381 Builder.CreateStore(New, NewAI);
1382 SI->eraseFromParent();
1384 // If the load we just inserted is now dead, then the inserted store
1385 // overwrote the entire thing.
1386 if (Old->use_empty())
1387 Old->eraseFromParent();
1391 // If this is a constant sized memset of a constant value (e.g. 0) we can
1392 // transform it into a store of the expanded constant value.
1393 if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) {
1394 assert(MSI->getRawDest() == Ptr && "Consistency error!");
1395 unsigned NumBytes = cast<ConstantInt>(MSI->getLength())->getZExtValue();
1396 if (NumBytes != 0) {
1397 unsigned Val = cast<ConstantInt>(MSI->getValue())->getZExtValue();
1399 // Compute the value replicated the right number of times.
1400 APInt APVal(NumBytes*8, Val);
1402 // Splat the value if non-zero.
1404 for (unsigned i = 1; i != NumBytes; ++i)
1405 APVal |= APVal << 8;
1407 Instruction *Old = Builder.CreateLoad(NewAI, NewAI->getName()+".in");
1408 Value *New = ConvertScalar_InsertValue(
1409 ConstantInt::get(User->getContext(), APVal),
1410 Old, Offset, Builder);
1411 Builder.CreateStore(New, NewAI);
1413 // If the load we just inserted is now dead, then the memset overwrote
1414 // the entire thing.
1415 if (Old->use_empty())
1416 Old->eraseFromParent();
1418 MSI->eraseFromParent();
1422 // If this is a memcpy or memmove into or out of the whole allocation, we
1423 // can handle it like a load or store of the scalar type.
1424 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) {
1425 assert(Offset == 0 && "must be store to start of alloca");
1427 // If the source and destination are both to the same alloca, then this is
1428 // a noop copy-to-self, just delete it. Otherwise, emit a load and store
1430 AllocaInst *OrigAI = cast<AllocaInst>(Ptr->getUnderlyingObject(0));
1432 if (MTI->getSource()->getUnderlyingObject(0) != OrigAI) {
1433 // Dest must be OrigAI, change this to be a load from the original
1434 // pointer (bitcasted), then a store to our new alloca.
1435 assert(MTI->getRawDest() == Ptr && "Neither use is of pointer?");
1436 Value *SrcPtr = MTI->getSource();
1437 SrcPtr = Builder.CreateBitCast(SrcPtr, NewAI->getType());
1439 LoadInst *SrcVal = Builder.CreateLoad(SrcPtr, "srcval");
1440 SrcVal->setAlignment(MTI->getAlignment());
1441 Builder.CreateStore(SrcVal, NewAI);
1442 } else if (MTI->getDest()->getUnderlyingObject(0) != OrigAI) {
1443 // Src must be OrigAI, change this to be a load from NewAI then a store
1444 // through the original dest pointer (bitcasted).
1445 assert(MTI->getRawSource() == Ptr && "Neither use is of pointer?");
1446 LoadInst *SrcVal = Builder.CreateLoad(NewAI, "srcval");
1448 Value *DstPtr = Builder.CreateBitCast(MTI->getDest(), NewAI->getType());
1449 StoreInst *NewStore = Builder.CreateStore(SrcVal, DstPtr);
1450 NewStore->setAlignment(MTI->getAlignment());
1452 // Noop transfer. Src == Dst
1455 MTI->eraseFromParent();
1459 llvm_unreachable("Unsupported operation!");
1463 /// ConvertScalar_ExtractValue - Extract a value of type ToType from an integer
1464 /// or vector value FromVal, extracting the bits from the offset specified by
1465 /// Offset. This returns the value, which is of type ToType.
1467 /// This happens when we are converting an "integer union" to a single
1468 /// integer scalar, or when we are converting a "vector union" to a vector with
1469 /// insert/extractelement instructions.
1471 /// Offset is an offset from the original alloca, in bits that need to be
1472 /// shifted to the right.
1473 Value *SROA::ConvertScalar_ExtractValue(Value *FromVal, const Type *ToType,
1474 uint64_t Offset, IRBuilder<> &Builder) {
1475 // If the load is of the whole new alloca, no conversion is needed.
1476 if (FromVal->getType() == ToType && Offset == 0)
1479 // If the result alloca is a vector type, this is either an element
1480 // access or a bitcast to another vector type of the same size.
1481 if (const VectorType *VTy = dyn_cast<VectorType>(FromVal->getType())) {
1482 if (ToType->isVectorTy())
1483 return Builder.CreateBitCast(FromVal, ToType, "tmp");
1485 // Otherwise it must be an element access.
1488 unsigned EltSize = TD->getTypeAllocSizeInBits(VTy->getElementType());
1489 Elt = Offset/EltSize;
1490 assert(EltSize*Elt == Offset && "Invalid modulus in validity checking");
1492 // Return the element extracted out of it.
1493 Value *V = Builder.CreateExtractElement(FromVal, ConstantInt::get(
1494 Type::getInt32Ty(FromVal->getContext()), Elt), "tmp");
1495 if (V->getType() != ToType)
1496 V = Builder.CreateBitCast(V, ToType, "tmp");
1500 // If ToType is a first class aggregate, extract out each of the pieces and
1501 // use insertvalue's to form the FCA.
1502 if (const StructType *ST = dyn_cast<StructType>(ToType)) {
1503 const StructLayout &Layout = *TD->getStructLayout(ST);
1504 Value *Res = UndefValue::get(ST);
1505 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) {
1506 Value *Elt = ConvertScalar_ExtractValue(FromVal, ST->getElementType(i),
1507 Offset+Layout.getElementOffsetInBits(i),
1509 Res = Builder.CreateInsertValue(Res, Elt, i, "tmp");
1514 if (const ArrayType *AT = dyn_cast<ArrayType>(ToType)) {
1515 uint64_t EltSize = TD->getTypeAllocSizeInBits(AT->getElementType());
1516 Value *Res = UndefValue::get(AT);
1517 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
1518 Value *Elt = ConvertScalar_ExtractValue(FromVal, AT->getElementType(),
1519 Offset+i*EltSize, Builder);
1520 Res = Builder.CreateInsertValue(Res, Elt, i, "tmp");
1525 // Otherwise, this must be a union that was converted to an integer value.
1526 const IntegerType *NTy = cast<IntegerType>(FromVal->getType());
1528 // If this is a big-endian system and the load is narrower than the
1529 // full alloca type, we need to do a shift to get the right bits.
1531 if (TD->isBigEndian()) {
1532 // On big-endian machines, the lowest bit is stored at the bit offset
1533 // from the pointer given by getTypeStoreSizeInBits. This matters for
1534 // integers with a bitwidth that is not a multiple of 8.
1535 ShAmt = TD->getTypeStoreSizeInBits(NTy) -
1536 TD->getTypeStoreSizeInBits(ToType) - Offset;
1541 // Note: we support negative bitwidths (with shl) which are not defined.
1542 // We do this to support (f.e.) loads off the end of a structure where
1543 // only some bits are used.
1544 if (ShAmt > 0 && (unsigned)ShAmt < NTy->getBitWidth())
1545 FromVal = Builder.CreateLShr(FromVal,
1546 ConstantInt::get(FromVal->getType(),
1548 else if (ShAmt < 0 && (unsigned)-ShAmt < NTy->getBitWidth())
1549 FromVal = Builder.CreateShl(FromVal,
1550 ConstantInt::get(FromVal->getType(),
1553 // Finally, unconditionally truncate the integer to the right width.
1554 unsigned LIBitWidth = TD->getTypeSizeInBits(ToType);
1555 if (LIBitWidth < NTy->getBitWidth())
1557 Builder.CreateTrunc(FromVal, IntegerType::get(FromVal->getContext(),
1558 LIBitWidth), "tmp");
1559 else if (LIBitWidth > NTy->getBitWidth())
1561 Builder.CreateZExt(FromVal, IntegerType::get(FromVal->getContext(),
1562 LIBitWidth), "tmp");
1564 // If the result is an integer, this is a trunc or bitcast.
1565 if (ToType->isIntegerTy()) {
1567 } else if (ToType->isFloatingPointTy() || ToType->isVectorTy()) {
1568 // Just do a bitcast, we know the sizes match up.
1569 FromVal = Builder.CreateBitCast(FromVal, ToType, "tmp");
1571 // Otherwise must be a pointer.
1572 FromVal = Builder.CreateIntToPtr(FromVal, ToType, "tmp");
1574 assert(FromVal->getType() == ToType && "Didn't convert right?");
1578 /// ConvertScalar_InsertValue - Insert the value "SV" into the existing integer
1579 /// or vector value "Old" at the offset specified by Offset.
1581 /// This happens when we are converting an "integer union" to a
1582 /// single integer scalar, or when we are converting a "vector union" to a
1583 /// vector with insert/extractelement instructions.
1585 /// Offset is an offset from the original alloca, in bits that need to be
1586 /// shifted to the right.
1587 Value *SROA::ConvertScalar_InsertValue(Value *SV, Value *Old,
1588 uint64_t Offset, IRBuilder<> &Builder) {
1590 // Convert the stored type to the actual type, shift it left to insert
1591 // then 'or' into place.
1592 const Type *AllocaType = Old->getType();
1593 LLVMContext &Context = Old->getContext();
1595 if (const VectorType *VTy = dyn_cast<VectorType>(AllocaType)) {
1596 uint64_t VecSize = TD->getTypeAllocSizeInBits(VTy);
1597 uint64_t ValSize = TD->getTypeAllocSizeInBits(SV->getType());
1599 // Changing the whole vector with memset or with an access of a different
1601 if (ValSize == VecSize)
1602 return Builder.CreateBitCast(SV, AllocaType, "tmp");
1604 uint64_t EltSize = TD->getTypeAllocSizeInBits(VTy->getElementType());
1606 // Must be an element insertion.
1607 unsigned Elt = Offset/EltSize;
1609 if (SV->getType() != VTy->getElementType())
1610 SV = Builder.CreateBitCast(SV, VTy->getElementType(), "tmp");
1612 SV = Builder.CreateInsertElement(Old, SV,
1613 ConstantInt::get(Type::getInt32Ty(SV->getContext()), Elt),
1618 // If SV is a first-class aggregate value, insert each value recursively.
1619 if (const StructType *ST = dyn_cast<StructType>(SV->getType())) {
1620 const StructLayout &Layout = *TD->getStructLayout(ST);
1621 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) {
1622 Value *Elt = Builder.CreateExtractValue(SV, i, "tmp");
1623 Old = ConvertScalar_InsertValue(Elt, Old,
1624 Offset+Layout.getElementOffsetInBits(i),
1630 if (const ArrayType *AT = dyn_cast<ArrayType>(SV->getType())) {
1631 uint64_t EltSize = TD->getTypeAllocSizeInBits(AT->getElementType());
1632 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
1633 Value *Elt = Builder.CreateExtractValue(SV, i, "tmp");
1634 Old = ConvertScalar_InsertValue(Elt, Old, Offset+i*EltSize, Builder);
1639 // If SV is a float, convert it to the appropriate integer type.
1640 // If it is a pointer, do the same.
1641 unsigned SrcWidth = TD->getTypeSizeInBits(SV->getType());
1642 unsigned DestWidth = TD->getTypeSizeInBits(AllocaType);
1643 unsigned SrcStoreWidth = TD->getTypeStoreSizeInBits(SV->getType());
1644 unsigned DestStoreWidth = TD->getTypeStoreSizeInBits(AllocaType);
1645 if (SV->getType()->isFloatingPointTy() || SV->getType()->isVectorTy())
1646 SV = Builder.CreateBitCast(SV,
1647 IntegerType::get(SV->getContext(),SrcWidth), "tmp");
1648 else if (SV->getType()->isPointerTy())
1649 SV = Builder.CreatePtrToInt(SV, TD->getIntPtrType(SV->getContext()), "tmp");
1651 // Zero extend or truncate the value if needed.
1652 if (SV->getType() != AllocaType) {
1653 if (SV->getType()->getPrimitiveSizeInBits() <
1654 AllocaType->getPrimitiveSizeInBits())
1655 SV = Builder.CreateZExt(SV, AllocaType, "tmp");
1657 // Truncation may be needed if storing more than the alloca can hold
1658 // (undefined behavior).
1659 SV = Builder.CreateTrunc(SV, AllocaType, "tmp");
1660 SrcWidth = DestWidth;
1661 SrcStoreWidth = DestStoreWidth;
1665 // If this is a big-endian system and the store is narrower than the
1666 // full alloca type, we need to do a shift to get the right bits.
1668 if (TD->isBigEndian()) {
1669 // On big-endian machines, the lowest bit is stored at the bit offset
1670 // from the pointer given by getTypeStoreSizeInBits. This matters for
1671 // integers with a bitwidth that is not a multiple of 8.
1672 ShAmt = DestStoreWidth - SrcStoreWidth - Offset;
1677 // Note: we support negative bitwidths (with shr) which are not defined.
1678 // We do this to support (f.e.) stores off the end of a structure where
1679 // only some bits in the structure are set.
1680 APInt Mask(APInt::getLowBitsSet(DestWidth, SrcWidth));
1681 if (ShAmt > 0 && (unsigned)ShAmt < DestWidth) {
1682 SV = Builder.CreateShl(SV, ConstantInt::get(SV->getType(),
1685 } else if (ShAmt < 0 && (unsigned)-ShAmt < DestWidth) {
1686 SV = Builder.CreateLShr(SV, ConstantInt::get(SV->getType(),
1688 Mask = Mask.lshr(-ShAmt);
1691 // Mask out the bits we are about to insert from the old value, and or
1693 if (SrcWidth != DestWidth) {
1694 assert(DestWidth > SrcWidth);
1695 Old = Builder.CreateAnd(Old, ConstantInt::get(Context, ~Mask), "mask");
1696 SV = Builder.CreateOr(Old, SV, "ins");
1703 /// PointsToConstantGlobal - Return true if V (possibly indirectly) points to
1704 /// some part of a constant global variable. This intentionally only accepts
1705 /// constant expressions because we don't can't rewrite arbitrary instructions.
1706 static bool PointsToConstantGlobal(Value *V) {
1707 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
1708 return GV->isConstant();
1709 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
1710 if (CE->getOpcode() == Instruction::BitCast ||
1711 CE->getOpcode() == Instruction::GetElementPtr)
1712 return PointsToConstantGlobal(CE->getOperand(0));
1716 /// isOnlyCopiedFromConstantGlobal - Recursively walk the uses of a (derived)
1717 /// pointer to an alloca. Ignore any reads of the pointer, return false if we
1718 /// see any stores or other unknown uses. If we see pointer arithmetic, keep
1719 /// track of whether it moves the pointer (with isOffset) but otherwise traverse
1720 /// the uses. If we see a memcpy/memmove that targets an unoffseted pointer to
1721 /// the alloca, and if the source pointer is a pointer to a constant global, we
1722 /// can optimize this.
1723 static bool isOnlyCopiedFromConstantGlobal(Value *V, MemTransferInst *&TheCopy,
1725 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) {
1726 User *U = cast<Instruction>(*UI);
1728 if (LoadInst *LI = dyn_cast<LoadInst>(U))
1729 // Ignore non-volatile loads, they are always ok.
1730 if (!LI->isVolatile())
1733 if (BitCastInst *BCI = dyn_cast<BitCastInst>(U)) {
1734 // If uses of the bitcast are ok, we are ok.
1735 if (!isOnlyCopiedFromConstantGlobal(BCI, TheCopy, isOffset))
1739 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) {
1740 // If the GEP has all zero indices, it doesn't offset the pointer. If it
1741 // doesn't, it does.
1742 if (!isOnlyCopiedFromConstantGlobal(GEP, TheCopy,
1743 isOffset || !GEP->hasAllZeroIndices()))
1748 // If this is isn't our memcpy/memmove, reject it as something we can't
1750 MemTransferInst *MI = dyn_cast<MemTransferInst>(U);
1754 // If we already have seen a copy, reject the second one.
1755 if (TheCopy) return false;
1757 // If the pointer has been offset from the start of the alloca, we can't
1758 // safely handle this.
1759 if (isOffset) return false;
1761 // If the memintrinsic isn't using the alloca as the dest, reject it.
1762 if (UI.getOperandNo() != 0) return false;
1764 // If the source of the memcpy/move is not a constant global, reject it.
1765 if (!PointsToConstantGlobal(MI->getSource()))
1768 // Otherwise, the transform is safe. Remember the copy instruction.
1774 /// isOnlyCopiedFromConstantGlobal - Return true if the specified alloca is only
1775 /// modified by a copy from a constant global. If we can prove this, we can
1776 /// replace any uses of the alloca with uses of the global directly.
1777 MemTransferInst *SROA::isOnlyCopiedFromConstantGlobal(AllocaInst *AI) {
1778 MemTransferInst *TheCopy = 0;
1779 if (::isOnlyCopiedFromConstantGlobal(AI, TheCopy, false))