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 SROA : public FunctionPass {
53 static char ID; // Pass identification, replacement for typeid
54 explicit SROA(signed T = -1) : FunctionPass(&ID) {
61 bool runOnFunction(Function &F);
63 bool performScalarRepl(Function &F);
64 bool performPromotion(Function &F);
66 // getAnalysisUsage - This pass does not require any passes, but we know it
67 // will not alter the CFG, so say so.
68 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
69 AU.addRequired<DominatorTree>();
70 AU.addRequired<DominanceFrontier>();
77 /// DeadInsts - Keep track of instructions we have made dead, so that
78 /// we can remove them after we are done working.
79 SmallVector<WeakVH, 16> DeadInsts;
81 /// AllocaInfo - When analyzing uses of an alloca instruction, this captures
82 /// information about the uses. All these fields are initialized to false
83 /// and set to true when something is learned.
85 /// isUnsafe - This is set to true if the alloca cannot be SROA'd.
88 /// needsCleanup - This is set to true if there is some use of the alloca
89 /// that requires cleanup.
90 bool needsCleanup : 1;
92 /// isMemCpySrc - This is true if this aggregate is memcpy'd from.
95 /// isMemCpyDst - This is true if this aggregate is memcpy'd into.
99 : isUnsafe(false), needsCleanup(false),
100 isMemCpySrc(false), isMemCpyDst(false) {}
103 unsigned SRThreshold;
105 void MarkUnsafe(AllocaInfo &I) { I.isUnsafe = true; }
107 int isSafeAllocaToScalarRepl(AllocaInst *AI);
109 void isSafeForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset,
110 uint64_t ArrayOffset, AllocaInfo &Info);
111 void isSafeGEP(GetElementPtrInst *GEPI, AllocaInst *AI, uint64_t &Offset,
112 uint64_t &ArrayOffset, AllocaInfo &Info);
113 void isSafeMemAccess(AllocaInst *AI, uint64_t Offset, uint64_t ArrayOffset,
114 uint64_t MemSize, const Type *MemOpType, bool isStore,
116 bool TypeHasComponent(const Type *T, uint64_t Offset, uint64_t Size);
117 unsigned FindElementAndOffset(const Type *&T, uint64_t &Offset);
119 void DoScalarReplacement(AllocaInst *AI,
120 std::vector<AllocaInst*> &WorkList);
121 void DeleteDeadInstructions();
122 void CleanupGEP(GetElementPtrInst *GEP);
123 void CleanupAllocaUsers(Value *V);
124 AllocaInst *AddNewAlloca(Function &F, const Type *Ty, AllocaInst *Base);
126 void RewriteForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset,
127 SmallVector<AllocaInst*, 32> &NewElts);
128 void RewriteBitCast(BitCastInst *BC, AllocaInst *AI, uint64_t Offset,
129 SmallVector<AllocaInst*, 32> &NewElts);
130 void RewriteGEP(GetElementPtrInst *GEPI, AllocaInst *AI, uint64_t Offset,
131 SmallVector<AllocaInst*, 32> &NewElts);
132 void RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *Inst,
134 SmallVector<AllocaInst*, 32> &NewElts);
135 void RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocaInst *AI,
136 SmallVector<AllocaInst*, 32> &NewElts);
137 void RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocaInst *AI,
138 SmallVector<AllocaInst*, 32> &NewElts);
140 bool CanConvertToScalar(Value *V, bool &IsNotTrivial, const Type *&VecTy,
141 bool &SawVec, uint64_t Offset, unsigned AllocaSize);
142 void ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, uint64_t Offset);
143 Value *ConvertScalar_ExtractValue(Value *NV, const Type *ToType,
144 uint64_t Offset, IRBuilder<> &Builder);
145 Value *ConvertScalar_InsertValue(Value *StoredVal, Value *ExistingVal,
146 uint64_t Offset, IRBuilder<> &Builder);
147 static Instruction *isOnlyCopiedFromConstantGlobal(AllocaInst *AI);
152 static RegisterPass<SROA> X("scalarrepl", "Scalar Replacement of Aggregates");
154 // Public interface to the ScalarReplAggregates pass
155 FunctionPass *llvm::createScalarReplAggregatesPass(signed int Threshold) {
156 return new SROA(Threshold);
160 bool SROA::runOnFunction(Function &F) {
161 TD = getAnalysisIfAvailable<TargetData>();
163 bool Changed = performPromotion(F);
165 // FIXME: ScalarRepl currently depends on TargetData more than it
166 // theoretically needs to. It should be refactored in order to support
167 // target-independent IR. Until this is done, just skip the actual
168 // scalar-replacement portion of this pass.
169 if (!TD) return Changed;
172 bool LocalChange = performScalarRepl(F);
173 if (!LocalChange) break; // No need to repromote if no scalarrepl
175 LocalChange = performPromotion(F);
176 if (!LocalChange) break; // No need to re-scalarrepl if no promotion
183 bool SROA::performPromotion(Function &F) {
184 std::vector<AllocaInst*> Allocas;
185 DominatorTree &DT = getAnalysis<DominatorTree>();
186 DominanceFrontier &DF = getAnalysis<DominanceFrontier>();
188 BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function
190 bool Changed = false;
195 // Find allocas that are safe to promote, by looking at all instructions in
197 for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I)
198 if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) // Is it an alloca?
199 if (isAllocaPromotable(AI))
200 Allocas.push_back(AI);
202 if (Allocas.empty()) break;
204 PromoteMemToReg(Allocas, DT, DF);
205 NumPromoted += Allocas.size();
212 /// getNumSAElements - Return the number of elements in the specific struct or
214 static uint64_t getNumSAElements(const Type *T) {
215 if (const StructType *ST = dyn_cast<StructType>(T))
216 return ST->getNumElements();
217 return cast<ArrayType>(T)->getNumElements();
220 // performScalarRepl - This algorithm is a simple worklist driven algorithm,
221 // which runs on all of the malloc/alloca instructions in the function, removing
222 // them if they are only used by getelementptr instructions.
224 bool SROA::performScalarRepl(Function &F) {
225 std::vector<AllocaInst*> WorkList;
227 // Scan the entry basic block, adding any alloca's and mallocs to the worklist
228 BasicBlock &BB = F.getEntryBlock();
229 for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I)
230 if (AllocaInst *A = dyn_cast<AllocaInst>(I))
231 WorkList.push_back(A);
233 // Process the worklist
234 bool Changed = false;
235 while (!WorkList.empty()) {
236 AllocaInst *AI = WorkList.back();
239 // Handle dead allocas trivially. These can be formed by SROA'ing arrays
240 // with unused elements.
241 if (AI->use_empty()) {
242 AI->eraseFromParent();
246 // If this alloca is impossible for us to promote, reject it early.
247 if (AI->isArrayAllocation() || !AI->getAllocatedType()->isSized())
250 // Check to see if this allocation is only modified by a memcpy/memmove from
251 // a constant global. If this is the case, we can change all users to use
252 // the constant global instead. This is commonly produced by the CFE by
253 // constructs like "void foo() { int A[] = {1,2,3,4,5,6,7,8,9...}; }" if 'A'
254 // is only subsequently read.
255 if (Instruction *TheCopy = isOnlyCopiedFromConstantGlobal(AI)) {
256 DEBUG(errs() << "Found alloca equal to global: " << *AI << '\n');
257 DEBUG(errs() << " memcpy = " << *TheCopy << '\n');
258 Constant *TheSrc = cast<Constant>(TheCopy->getOperand(2));
259 AI->replaceAllUsesWith(ConstantExpr::getBitCast(TheSrc, AI->getType()));
260 TheCopy->eraseFromParent(); // Don't mutate the global.
261 AI->eraseFromParent();
267 // Check to see if we can perform the core SROA transformation. We cannot
268 // transform the allocation instruction if it is an array allocation
269 // (allocations OF arrays are ok though), and an allocation of a scalar
270 // value cannot be decomposed at all.
271 uint64_t AllocaSize = TD->getTypeAllocSize(AI->getAllocatedType());
273 // Do not promote [0 x %struct].
274 if (AllocaSize == 0) continue;
276 // Do not promote any struct whose size is too big.
277 if (AllocaSize > SRThreshold) continue;
279 if ((isa<StructType>(AI->getAllocatedType()) ||
280 isa<ArrayType>(AI->getAllocatedType())) &&
281 // Do not promote any struct into more than "32" separate vars.
282 getNumSAElements(AI->getAllocatedType()) <= SRThreshold/4) {
283 // Check that all of the users of the allocation are capable of being
285 switch (isSafeAllocaToScalarRepl(AI)) {
286 default: llvm_unreachable("Unexpected value!");
287 case 0: // Not safe to scalar replace.
289 case 1: // Safe, but requires cleanup/canonicalizations first
290 CleanupAllocaUsers(AI);
292 case 3: // Safe to scalar replace.
293 DoScalarReplacement(AI, WorkList);
299 // If we can turn this aggregate value (potentially with casts) into a
300 // simple scalar value that can be mem2reg'd into a register value.
301 // IsNotTrivial tracks whether this is something that mem2reg could have
302 // promoted itself. If so, we don't want to transform it needlessly. Note
303 // that we can't just check based on the type: the alloca may be of an i32
304 // but that has pointer arithmetic to set byte 3 of it or something.
305 bool IsNotTrivial = false;
306 const Type *VectorTy = 0;
307 bool HadAVector = false;
308 if (CanConvertToScalar(AI, IsNotTrivial, VectorTy, HadAVector,
309 0, unsigned(AllocaSize)) && IsNotTrivial) {
311 // If we were able to find a vector type that can handle this with
312 // insert/extract elements, and if there was at least one use that had
313 // a vector type, promote this to a vector. We don't want to promote
314 // random stuff that doesn't use vectors (e.g. <9 x double>) because then
315 // we just get a lot of insert/extracts. If at least one vector is
316 // involved, then we probably really do have a union of vector/array.
317 if (VectorTy && isa<VectorType>(VectorTy) && HadAVector) {
318 DEBUG(errs() << "CONVERT TO VECTOR: " << *AI << "\n TYPE = "
319 << *VectorTy << '\n');
321 // Create and insert the vector alloca.
322 NewAI = new AllocaInst(VectorTy, 0, "", AI->getParent()->begin());
323 ConvertUsesToScalar(AI, NewAI, 0);
325 DEBUG(errs() << "CONVERT TO SCALAR INTEGER: " << *AI << "\n");
327 // Create and insert the integer alloca.
328 const Type *NewTy = IntegerType::get(AI->getContext(), AllocaSize*8);
329 NewAI = new AllocaInst(NewTy, 0, "", AI->getParent()->begin());
330 ConvertUsesToScalar(AI, NewAI, 0);
333 AI->eraseFromParent();
339 // Otherwise, couldn't process this alloca.
345 /// DoScalarReplacement - This alloca satisfied the isSafeAllocaToScalarRepl
346 /// predicate, do SROA now.
347 void SROA::DoScalarReplacement(AllocaInst *AI,
348 std::vector<AllocaInst*> &WorkList) {
349 DEBUG(errs() << "Found inst to SROA: " << *AI << '\n');
350 SmallVector<AllocaInst*, 32> ElementAllocas;
351 if (const StructType *ST = dyn_cast<StructType>(AI->getAllocatedType())) {
352 ElementAllocas.reserve(ST->getNumContainedTypes());
353 for (unsigned i = 0, e = ST->getNumContainedTypes(); i != e; ++i) {
354 AllocaInst *NA = new AllocaInst(ST->getContainedType(i), 0,
356 AI->getName() + "." + Twine(i), AI);
357 ElementAllocas.push_back(NA);
358 WorkList.push_back(NA); // Add to worklist for recursive processing
361 const ArrayType *AT = cast<ArrayType>(AI->getAllocatedType());
362 ElementAllocas.reserve(AT->getNumElements());
363 const Type *ElTy = AT->getElementType();
364 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
365 AllocaInst *NA = new AllocaInst(ElTy, 0, AI->getAlignment(),
366 AI->getName() + "." + Twine(i), AI);
367 ElementAllocas.push_back(NA);
368 WorkList.push_back(NA); // Add to worklist for recursive processing
372 // Now that we have created the new alloca instructions, rewrite all the
373 // uses of the old alloca.
374 DeadInsts.push_back(AI);
375 RewriteForScalarRepl(AI, AI, 0, ElementAllocas);
377 // Now erase any instructions that were made dead while rewriting the alloca.
378 DeleteDeadInstructions();
383 /// DeleteDeadInstructions - Erase instructions on the DeadInstrs list,
384 /// recursively including all their operands that become trivially dead.
385 void SROA::DeleteDeadInstructions() {
386 while (!DeadInsts.empty()) {
387 Instruction *I = dyn_cast_or_null<Instruction>(DeadInsts.pop_back_val());
391 for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI)
392 if (Instruction *U = dyn_cast<Instruction>(*OI)) {
393 // Zero out the operand and see if it becomes trivially dead.
395 if (isInstructionTriviallyDead(U))
396 DeadInsts.push_back(U);
399 I->eraseFromParent();
403 /// AllUsersAreLoads - Return true if all users of this value are loads.
404 static bool AllUsersAreLoads(Value *Ptr) {
405 for (Value::use_iterator I = Ptr->use_begin(), E = Ptr->use_end();
407 if (cast<Instruction>(*I)->getOpcode() != Instruction::Load)
412 /// isSafeForScalarRepl - Check if instruction I is a safe use with regard to
413 /// performing scalar replacement of alloca AI. The results are flagged in
414 /// the Info parameter. Offset and ArrayOffset indicate the position within
415 /// AI that is referenced by this instruction.
416 void SROA::isSafeForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset,
417 uint64_t ArrayOffset, AllocaInfo &Info) {
418 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E; ++UI) {
419 Instruction *User = cast<Instruction>(*UI);
421 if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) {
422 isSafeForScalarRepl(BC, AI, Offset, ArrayOffset, Info);
423 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
424 uint64_t GEPArrayOffset = ArrayOffset;
425 uint64_t GEPOffset = Offset;
426 isSafeGEP(GEPI, AI, GEPOffset, GEPArrayOffset, Info);
428 isSafeForScalarRepl(GEPI, AI, GEPOffset, GEPArrayOffset, Info);
429 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(UI)) {
430 ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength());
432 isSafeMemAccess(AI, Offset, ArrayOffset, Length->getZExtValue(), 0,
433 UI.getOperandNo() == 1, Info);
436 } else if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
437 if (!LI->isVolatile()) {
438 const Type *LIType = LI->getType();
439 isSafeMemAccess(AI, Offset, ArrayOffset, TD->getTypeAllocSize(LIType),
440 LIType, false, Info);
443 } else if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
444 // Store is ok if storing INTO the pointer, not storing the pointer
445 if (!SI->isVolatile() && SI->getOperand(0) != I) {
446 const Type *SIType = SI->getOperand(0)->getType();
447 isSafeMemAccess(AI, Offset, ArrayOffset, TD->getTypeAllocSize(SIType),
451 } else if (isa<DbgInfoIntrinsic>(UI)) {
452 // If one user is DbgInfoIntrinsic then check if all users are
453 // DbgInfoIntrinsics.
454 if (OnlyUsedByDbgInfoIntrinsics(I)) {
455 Info.needsCleanup = true;
460 DEBUG(errs() << " Transformation preventing inst: " << *User << '\n');
463 if (Info.isUnsafe) return;
467 /// isSafeGEP - Check if a GEP instruction can be handled for scalar
468 /// replacement. It is safe when all the indices are constant, in-bounds
469 /// references, and when the resulting offset corresponds to an element within
470 /// the alloca type. The results are flagged in the Info parameter. Upon
471 /// return, Offset is adjusted as specified by the GEP indices. For the
472 /// special case of a variable index to a 2-element array, ArrayOffset is set
473 /// to the array element size.
474 void SROA::isSafeGEP(GetElementPtrInst *GEPI, AllocaInst *AI,
475 uint64_t &Offset, uint64_t &ArrayOffset,
477 gep_type_iterator GEPIt = gep_type_begin(GEPI), E = gep_type_end(GEPI);
481 // The first GEP index must be zero.
482 if (!isa<ConstantInt>(GEPIt.getOperand()) ||
483 !cast<ConstantInt>(GEPIt.getOperand())->isZero())
484 return MarkUnsafe(Info);
488 // If the first index is a non-constant index into an array, see if we can
489 // handle it as a special case.
490 const Type *ArrayEltTy = 0;
491 if (ArrayOffset == 0 && Offset == 0) {
492 if (const ArrayType *AT = dyn_cast<ArrayType>(*GEPIt)) {
493 if (!isa<ConstantInt>(GEPIt.getOperand())) {
494 uint64_t NumElements = AT->getNumElements();
496 // If this is an array index and the index is not constant, we cannot
497 // promote... that is unless the array has exactly one or two elements
498 // in it, in which case we CAN promote it, but we have to canonicalize
499 // this out if this is the only problem.
500 if ((NumElements != 1 && NumElements != 2) || !AllUsersAreLoads(GEPI))
501 return MarkUnsafe(Info);
502 Info.needsCleanup = true;
503 ArrayOffset = TD->getTypeAllocSizeInBits(AT->getElementType());
504 ArrayEltTy = AT->getElementType();
510 // Walk through the GEP type indices, checking the types that this indexes
512 for (; GEPIt != E; ++GEPIt) {
513 // Ignore struct elements, no extra checking needed for these.
514 if (isa<StructType>(*GEPIt))
517 ConstantInt *IdxVal = dyn_cast<ConstantInt>(GEPIt.getOperand());
519 return MarkUnsafe(Info);
521 if (const ArrayType *AT = dyn_cast<ArrayType>(*GEPIt)) {
522 // This GEP indexes an array. Verify that this is an in-range constant
523 // integer. Specifically, consider A[0][i]. We cannot know that the user
524 // isn't doing invalid things like allowing i to index an out-of-range
525 // subscript that accesses A[1]. Because of this, we have to reject SROA
526 // of any accesses into structs where any of the components are variables.
527 if (IdxVal->getZExtValue() >= AT->getNumElements())
528 return MarkUnsafe(Info);
530 const VectorType *VT = dyn_cast<VectorType>(*GEPIt);
531 assert(VT && "unexpected type in GEP type iterator");
532 if (IdxVal->getZExtValue() >= VT->getNumElements())
533 return MarkUnsafe(Info);
537 // All the indices are safe. Now compute the offset due to this GEP and
538 // check if the alloca has a component element at that offset.
539 if (ArrayOffset == 0) {
540 SmallVector<Value*, 8> Indices(GEPI->op_begin() + 1, GEPI->op_end());
541 Offset += TD->getIndexedOffset(GEPI->getPointerOperandType(),
542 &Indices[0], Indices.size());
544 // Both array elements have the same type, so it suffices to check one of
545 // them. Copy the GEP indices starting from the array index, but replace
546 // that variable index with a constant zero.
547 SmallVector<Value*, 8> Indices(GEPI->op_begin() + 2, GEPI->op_end());
548 Indices[0] = Constant::getNullValue(Type::getInt32Ty(GEPI->getContext()));
549 const Type *ArrayEltPtr = PointerType::getUnqual(ArrayEltTy);
550 Offset += TD->getIndexedOffset(ArrayEltPtr, &Indices[0], Indices.size());
552 if (!TypeHasComponent(AI->getAllocatedType(), Offset, 0))
556 /// isSafeMemAccess - Check if a load/store/memcpy operates on the entire AI
557 /// alloca or has an offset and size that corresponds to a component element
558 /// within it. The offset checked here may have been formed from a GEP with a
559 /// pointer bitcasted to a different type.
560 void SROA::isSafeMemAccess(AllocaInst *AI, uint64_t Offset,
561 uint64_t ArrayOffset, uint64_t MemSize,
562 const Type *MemOpType, bool isStore,
564 // Check if this is a load/store of the entire alloca.
565 if (Offset == 0 && ArrayOffset == 0 &&
566 MemSize == TD->getTypeAllocSize(AI->getAllocatedType())) {
567 bool UsesAggregateType = (MemOpType == AI->getAllocatedType());
568 // This is safe for MemIntrinsics (where MemOpType is 0), integer types
569 // (which are essentially the same as the MemIntrinsics, especially with
570 // regard to copying padding between elements), or references using the
571 // aggregate type of the alloca.
572 if (!MemOpType || isa<IntegerType>(MemOpType) || UsesAggregateType) {
573 if (!UsesAggregateType) {
575 Info.isMemCpyDst = true;
577 Info.isMemCpySrc = true;
582 // Check if the offset/size correspond to a component within the alloca type.
583 const Type *T = AI->getAllocatedType();
584 if (TypeHasComponent(T, Offset, MemSize) &&
585 (ArrayOffset == 0 || TypeHasComponent(T, Offset + ArrayOffset, MemSize)))
588 return MarkUnsafe(Info);
591 /// TypeHasComponent - Return true if T has a component type with the
592 /// specified offset and size. If Size is zero, do not check the size.
593 bool SROA::TypeHasComponent(const Type *T, uint64_t Offset, uint64_t Size) {
596 if (const StructType *ST = dyn_cast<StructType>(T)) {
597 const StructLayout *Layout = TD->getStructLayout(ST);
598 unsigned EltIdx = Layout->getElementContainingOffset(Offset);
599 EltTy = ST->getContainedType(EltIdx);
600 EltSize = TD->getTypeAllocSize(EltTy);
601 Offset -= Layout->getElementOffset(EltIdx);
602 } else if (const ArrayType *AT = dyn_cast<ArrayType>(T)) {
603 EltTy = AT->getElementType();
604 EltSize = TD->getTypeAllocSize(EltTy);
609 if (Offset == 0 && (Size == 0 || EltSize == Size))
611 // Check if the component spans multiple elements.
612 if (Offset + Size > EltSize)
614 return TypeHasComponent(EltTy, Offset, Size);
617 /// RewriteForScalarRepl - Alloca AI is being split into NewElts, so rewrite
618 /// the instruction I, which references it, to use the separate elements.
619 /// Offset indicates the position within AI that is referenced by this
621 void SROA::RewriteForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset,
622 SmallVector<AllocaInst*, 32> &NewElts) {
623 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E; ++UI) {
624 Instruction *User = cast<Instruction>(*UI);
626 if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) {
627 RewriteBitCast(BC, AI, Offset, NewElts);
628 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
629 RewriteGEP(GEPI, AI, Offset, NewElts);
630 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) {
631 ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength());
632 uint64_t MemSize = Length->getZExtValue();
634 MemSize == TD->getTypeAllocSize(AI->getAllocatedType()))
635 RewriteMemIntrinUserOfAlloca(MI, I, AI, NewElts);
636 } else if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
637 const Type *LIType = LI->getType();
638 if (LIType == AI->getAllocatedType()) {
640 // %res = load { i32, i32 }* %alloc
642 // %load.0 = load i32* %alloc.0
643 // %insert.0 insertvalue { i32, i32 } zeroinitializer, i32 %load.0, 0
644 // %load.1 = load i32* %alloc.1
645 // %insert = insertvalue { i32, i32 } %insert.0, i32 %load.1, 1
646 // (Also works for arrays instead of structs)
647 Value *Insert = UndefValue::get(LIType);
648 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
649 Value *Load = new LoadInst(NewElts[i], "load", LI);
650 Insert = InsertValueInst::Create(Insert, Load, i, "insert", LI);
652 LI->replaceAllUsesWith(Insert);
653 DeadInsts.push_back(LI);
654 } else if (isa<IntegerType>(LIType) &&
655 TD->getTypeAllocSize(LIType) ==
656 TD->getTypeAllocSize(AI->getAllocatedType())) {
657 // If this is a load of the entire alloca to an integer, rewrite it.
658 RewriteLoadUserOfWholeAlloca(LI, AI, NewElts);
660 } else if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
661 Value *Val = SI->getOperand(0);
662 const Type *SIType = Val->getType();
663 if (SIType == AI->getAllocatedType()) {
665 // store { i32, i32 } %val, { i32, i32 }* %alloc
667 // %val.0 = extractvalue { i32, i32 } %val, 0
668 // store i32 %val.0, i32* %alloc.0
669 // %val.1 = extractvalue { i32, i32 } %val, 1
670 // store i32 %val.1, i32* %alloc.1
671 // (Also works for arrays instead of structs)
672 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
673 Value *Extract = ExtractValueInst::Create(Val, i, Val->getName(), SI);
674 new StoreInst(Extract, NewElts[i], SI);
676 DeadInsts.push_back(SI);
677 } else if (isa<IntegerType>(SIType) &&
678 TD->getTypeAllocSize(SIType) ==
679 TD->getTypeAllocSize(AI->getAllocatedType())) {
680 // If this is a store of the entire alloca from an integer, rewrite it.
681 RewriteStoreUserOfWholeAlloca(SI, AI, NewElts);
687 /// RewriteBitCast - Update a bitcast reference to the alloca being replaced
688 /// and recursively continue updating all of its uses.
689 void SROA::RewriteBitCast(BitCastInst *BC, AllocaInst *AI, uint64_t Offset,
690 SmallVector<AllocaInst*, 32> &NewElts) {
691 RewriteForScalarRepl(BC, AI, Offset, NewElts);
692 if (BC->getOperand(0) != AI)
695 // The bitcast references the original alloca. Replace its uses with
696 // references to the first new element alloca.
697 Instruction *Val = NewElts[0];
698 if (Val->getType() != BC->getDestTy()) {
699 Val = new BitCastInst(Val, BC->getDestTy(), "", BC);
702 BC->replaceAllUsesWith(Val);
703 DeadInsts.push_back(BC);
706 /// FindElementAndOffset - Return the index of the element containing Offset
707 /// within the specified type, which must be either a struct or an array.
708 /// Sets T to the type of the element and Offset to the offset within that
710 unsigned SROA::FindElementAndOffset(const Type *&T, uint64_t &Offset) {
712 if (const StructType *ST = dyn_cast<StructType>(T)) {
713 const StructLayout *Layout = TD->getStructLayout(ST);
714 Idx = Layout->getElementContainingOffset(Offset);
715 T = ST->getContainedType(Idx);
716 Offset -= Layout->getElementOffset(Idx);
718 const ArrayType *AT = dyn_cast<ArrayType>(T);
719 assert(AT && "unexpected type for scalar replacement");
720 T = AT->getElementType();
721 uint64_t EltSize = TD->getTypeAllocSize(T);
722 Idx = (unsigned)(Offset / EltSize);
723 Offset -= Idx * EltSize;
728 /// RewriteGEP - Check if this GEP instruction moves the pointer across
729 /// elements of the alloca that are being split apart, and if so, rewrite
730 /// the GEP to be relative to the new element.
731 void SROA::RewriteGEP(GetElementPtrInst *GEPI, AllocaInst *AI, uint64_t Offset,
732 SmallVector<AllocaInst*, 32> &NewElts) {
733 uint64_t OldOffset = Offset;
734 SmallVector<Value*, 8> Indices(GEPI->op_begin() + 1, GEPI->op_end());
735 Offset += TD->getIndexedOffset(GEPI->getPointerOperandType(),
736 &Indices[0], Indices.size());
738 RewriteForScalarRepl(GEPI, AI, Offset, NewElts);
740 const Type *T = AI->getAllocatedType();
741 unsigned OldIdx = FindElementAndOffset(T, OldOffset);
742 if (GEPI->getOperand(0) == AI)
743 OldIdx = ~0U; // Force the GEP to be rewritten.
745 T = AI->getAllocatedType();
746 uint64_t EltOffset = Offset;
747 unsigned Idx = FindElementAndOffset(T, EltOffset);
749 // If this GEP does not move the pointer across elements of the alloca
750 // being split, then it does not needs to be rewritten.
754 const Type *i32Ty = Type::getInt32Ty(AI->getContext());
755 SmallVector<Value*, 8> NewArgs;
756 NewArgs.push_back(Constant::getNullValue(i32Ty));
757 while (EltOffset != 0) {
758 unsigned EltIdx = FindElementAndOffset(T, EltOffset);
759 NewArgs.push_back(ConstantInt::get(i32Ty, EltIdx));
761 Instruction *Val = NewElts[Idx];
762 if (NewArgs.size() > 1) {
763 Val = GetElementPtrInst::CreateInBounds(Val, NewArgs.begin(),
764 NewArgs.end(), "", GEPI);
767 if (Val->getType() != GEPI->getType())
768 Val = new BitCastInst(Val, GEPI->getType(), Val->getNameStr(), GEPI);
769 GEPI->replaceAllUsesWith(Val);
770 DeadInsts.push_back(GEPI);
773 /// RewriteMemIntrinUserOfAlloca - MI is a memcpy/memset/memmove from or to AI.
774 /// Rewrite it to copy or set the elements of the scalarized memory.
775 void SROA::RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *Inst,
777 SmallVector<AllocaInst*, 32> &NewElts) {
778 // If this is a memcpy/memmove, construct the other pointer as the
779 // appropriate type. The "Other" pointer is the pointer that goes to memory
780 // that doesn't have anything to do with the alloca that we are promoting. For
781 // memset, this Value* stays null.
783 LLVMContext &Context = MI->getContext();
784 unsigned MemAlignment = MI->getAlignment();
785 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(MI)) { // memmove/memcopy
786 if (Inst == MTI->getRawDest())
787 OtherPtr = MTI->getRawSource();
789 assert(Inst == MTI->getRawSource());
790 OtherPtr = MTI->getRawDest();
794 // If there is an other pointer, we want to convert it to the same pointer
795 // type as AI has, so we can GEP through it safely.
798 // Remove bitcasts and all-zero GEPs from OtherPtr. This is an
799 // optimization, but it's also required to detect the corner case where
800 // both pointer operands are referencing the same memory, and where
801 // OtherPtr may be a bitcast or GEP that currently being rewritten. (This
802 // function is only called for mem intrinsics that access the whole
803 // aggregate, so non-zero GEPs are not an issue here.)
805 if (BitCastInst *BC = dyn_cast<BitCastInst>(OtherPtr)) {
806 OtherPtr = BC->getOperand(0);
809 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(OtherPtr)) {
810 // All zero GEPs are effectively bitcasts.
811 if (GEP->hasAllZeroIndices()) {
812 OtherPtr = GEP->getOperand(0);
818 // If OtherPtr has already been rewritten, this intrinsic will be dead.
819 if (OtherPtr == NewElts[0])
822 if (ConstantExpr *BCE = dyn_cast<ConstantExpr>(OtherPtr))
823 if (BCE->getOpcode() == Instruction::BitCast)
824 OtherPtr = BCE->getOperand(0);
826 // If the pointer is not the right type, insert a bitcast to the right
828 if (OtherPtr->getType() != AI->getType())
829 OtherPtr = new BitCastInst(OtherPtr, AI->getType(), OtherPtr->getName(),
833 // Process each element of the aggregate.
834 Value *TheFn = MI->getOperand(0);
835 const Type *BytePtrTy = MI->getRawDest()->getType();
836 bool SROADest = MI->getRawDest() == Inst;
838 Constant *Zero = Constant::getNullValue(Type::getInt32Ty(MI->getContext()));
840 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
841 // If this is a memcpy/memmove, emit a GEP of the other element address.
843 unsigned OtherEltAlign = MemAlignment;
845 if (OtherPtr == AI) {
846 OtherElt = NewElts[i];
848 } else if (OtherPtr) {
849 Value *Idx[2] = { Zero,
850 ConstantInt::get(Type::getInt32Ty(MI->getContext()), i) };
851 OtherElt = GetElementPtrInst::CreateInBounds(OtherPtr, Idx, Idx + 2,
852 OtherPtr->getNameStr()+"."+Twine(i),
855 const PointerType *OtherPtrTy = cast<PointerType>(OtherPtr->getType());
856 if (const StructType *ST =
857 dyn_cast<StructType>(OtherPtrTy->getElementType())) {
858 EltOffset = TD->getStructLayout(ST)->getElementOffset(i);
861 cast<SequentialType>(OtherPtr->getType())->getElementType();
862 EltOffset = TD->getTypeAllocSize(EltTy)*i;
865 // The alignment of the other pointer is the guaranteed alignment of the
866 // element, which is affected by both the known alignment of the whole
867 // mem intrinsic and the alignment of the element. If the alignment of
868 // the memcpy (f.e.) is 32 but the element is at a 4-byte offset, then the
869 // known alignment is just 4 bytes.
870 OtherEltAlign = (unsigned)MinAlign(OtherEltAlign, EltOffset);
873 Value *EltPtr = NewElts[i];
874 const Type *EltTy = cast<PointerType>(EltPtr->getType())->getElementType();
876 // If we got down to a scalar, insert a load or store as appropriate.
877 if (EltTy->isSingleValueType()) {
878 if (isa<MemTransferInst>(MI)) {
880 // From Other to Alloca.
881 Value *Elt = new LoadInst(OtherElt, "tmp", false, OtherEltAlign, MI);
882 new StoreInst(Elt, EltPtr, MI);
884 // From Alloca to Other.
885 Value *Elt = new LoadInst(EltPtr, "tmp", MI);
886 new StoreInst(Elt, OtherElt, false, OtherEltAlign, MI);
890 assert(isa<MemSetInst>(MI));
892 // If the stored element is zero (common case), just store a null
895 if (ConstantInt *CI = dyn_cast<ConstantInt>(MI->getOperand(2))) {
897 StoreVal = Constant::getNullValue(EltTy); // 0.0, null, 0, <0,0>
899 // If EltTy is a vector type, get the element type.
900 const Type *ValTy = EltTy->getScalarType();
902 // Construct an integer with the right value.
903 unsigned EltSize = TD->getTypeSizeInBits(ValTy);
904 APInt OneVal(EltSize, CI->getZExtValue());
905 APInt TotalVal(OneVal);
907 for (unsigned i = 0; 8*i < EltSize; ++i) {
908 TotalVal = TotalVal.shl(8);
912 // Convert the integer value to the appropriate type.
913 StoreVal = ConstantInt::get(Context, TotalVal);
914 if (isa<PointerType>(ValTy))
915 StoreVal = ConstantExpr::getIntToPtr(StoreVal, ValTy);
916 else if (ValTy->isFloatingPoint())
917 StoreVal = ConstantExpr::getBitCast(StoreVal, ValTy);
918 assert(StoreVal->getType() == ValTy && "Type mismatch!");
920 // If the requested value was a vector constant, create it.
921 if (EltTy != ValTy) {
922 unsigned NumElts = cast<VectorType>(ValTy)->getNumElements();
923 SmallVector<Constant*, 16> Elts(NumElts, StoreVal);
924 StoreVal = ConstantVector::get(&Elts[0], NumElts);
927 new StoreInst(StoreVal, EltPtr, MI);
930 // Otherwise, if we're storing a byte variable, use a memset call for
934 // Cast the element pointer to BytePtrTy.
935 if (EltPtr->getType() != BytePtrTy)
936 EltPtr = new BitCastInst(EltPtr, BytePtrTy, EltPtr->getNameStr(), MI);
938 // Cast the other pointer (if we have one) to BytePtrTy.
939 if (OtherElt && OtherElt->getType() != BytePtrTy)
940 OtherElt = new BitCastInst(OtherElt, BytePtrTy,OtherElt->getNameStr(),
943 unsigned EltSize = TD->getTypeAllocSize(EltTy);
945 // Finally, insert the meminst for this element.
946 if (isa<MemTransferInst>(MI)) {
948 SROADest ? EltPtr : OtherElt, // Dest ptr
949 SROADest ? OtherElt : EltPtr, // Src ptr
950 ConstantInt::get(MI->getOperand(3)->getType(), EltSize), // Size
952 ConstantInt::get(Type::getInt32Ty(MI->getContext()), OtherEltAlign)
954 CallInst::Create(TheFn, Ops, Ops + 4, "", MI);
956 assert(isa<MemSetInst>(MI));
958 EltPtr, MI->getOperand(2), // Dest, Value,
959 ConstantInt::get(MI->getOperand(3)->getType(), EltSize), // Size
962 CallInst::Create(TheFn, Ops, Ops + 4, "", MI);
965 DeadInsts.push_back(MI);
968 /// RewriteStoreUserOfWholeAlloca - We found a store of an integer that
969 /// overwrites the entire allocation. Extract out the pieces of the stored
970 /// integer and store them individually.
971 void SROA::RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocaInst *AI,
972 SmallVector<AllocaInst*, 32> &NewElts){
973 // Extract each element out of the integer according to its structure offset
974 // and store the element value to the individual alloca.
975 Value *SrcVal = SI->getOperand(0);
976 const Type *AllocaEltTy = AI->getAllocatedType();
977 uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy);
979 // Handle tail padding by extending the operand
980 if (TD->getTypeSizeInBits(SrcVal->getType()) != AllocaSizeBits)
981 SrcVal = new ZExtInst(SrcVal,
982 IntegerType::get(SI->getContext(), AllocaSizeBits),
985 DEBUG(errs() << "PROMOTING STORE TO WHOLE ALLOCA: " << *AI << '\n' << *SI
988 // There are two forms here: AI could be an array or struct. Both cases
989 // have different ways to compute the element offset.
990 if (const StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) {
991 const StructLayout *Layout = TD->getStructLayout(EltSTy);
993 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
994 // Get the number of bits to shift SrcVal to get the value.
995 const Type *FieldTy = EltSTy->getElementType(i);
996 uint64_t Shift = Layout->getElementOffsetInBits(i);
998 if (TD->isBigEndian())
999 Shift = AllocaSizeBits-Shift-TD->getTypeAllocSizeInBits(FieldTy);
1001 Value *EltVal = SrcVal;
1003 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift);
1004 EltVal = BinaryOperator::CreateLShr(EltVal, ShiftVal,
1005 "sroa.store.elt", SI);
1008 // Truncate down to an integer of the right size.
1009 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy);
1011 // Ignore zero sized fields like {}, they obviously contain no data.
1012 if (FieldSizeBits == 0) continue;
1014 if (FieldSizeBits != AllocaSizeBits)
1015 EltVal = new TruncInst(EltVal,
1016 IntegerType::get(SI->getContext(), FieldSizeBits),
1018 Value *DestField = NewElts[i];
1019 if (EltVal->getType() == FieldTy) {
1020 // Storing to an integer field of this size, just do it.
1021 } else if (FieldTy->isFloatingPoint() || isa<VectorType>(FieldTy)) {
1022 // Bitcast to the right element type (for fp/vector values).
1023 EltVal = new BitCastInst(EltVal, FieldTy, "", SI);
1025 // Otherwise, bitcast the dest pointer (for aggregates).
1026 DestField = new BitCastInst(DestField,
1027 PointerType::getUnqual(EltVal->getType()),
1030 new StoreInst(EltVal, DestField, SI);
1034 const ArrayType *ATy = cast<ArrayType>(AllocaEltTy);
1035 const Type *ArrayEltTy = ATy->getElementType();
1036 uint64_t ElementOffset = TD->getTypeAllocSizeInBits(ArrayEltTy);
1037 uint64_t ElementSizeBits = TD->getTypeSizeInBits(ArrayEltTy);
1041 if (TD->isBigEndian())
1042 Shift = AllocaSizeBits-ElementOffset;
1046 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
1047 // Ignore zero sized fields like {}, they obviously contain no data.
1048 if (ElementSizeBits == 0) continue;
1050 Value *EltVal = SrcVal;
1052 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift);
1053 EltVal = BinaryOperator::CreateLShr(EltVal, ShiftVal,
1054 "sroa.store.elt", SI);
1057 // Truncate down to an integer of the right size.
1058 if (ElementSizeBits != AllocaSizeBits)
1059 EltVal = new TruncInst(EltVal,
1060 IntegerType::get(SI->getContext(),
1061 ElementSizeBits),"",SI);
1062 Value *DestField = NewElts[i];
1063 if (EltVal->getType() == ArrayEltTy) {
1064 // Storing to an integer field of this size, just do it.
1065 } else if (ArrayEltTy->isFloatingPoint() || isa<VectorType>(ArrayEltTy)) {
1066 // Bitcast to the right element type (for fp/vector values).
1067 EltVal = new BitCastInst(EltVal, ArrayEltTy, "", SI);
1069 // Otherwise, bitcast the dest pointer (for aggregates).
1070 DestField = new BitCastInst(DestField,
1071 PointerType::getUnqual(EltVal->getType()),
1074 new StoreInst(EltVal, DestField, SI);
1076 if (TD->isBigEndian())
1077 Shift -= ElementOffset;
1079 Shift += ElementOffset;
1083 DeadInsts.push_back(SI);
1086 /// RewriteLoadUserOfWholeAlloca - We found a load of the entire allocation to
1087 /// an integer. Load the individual pieces to form the aggregate value.
1088 void SROA::RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocaInst *AI,
1089 SmallVector<AllocaInst*, 32> &NewElts) {
1090 // Extract each element out of the NewElts according to its structure offset
1091 // and form the result value.
1092 const Type *AllocaEltTy = AI->getAllocatedType();
1093 uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy);
1095 DEBUG(errs() << "PROMOTING LOAD OF WHOLE ALLOCA: " << *AI << '\n' << *LI
1098 // There are two forms here: AI could be an array or struct. Both cases
1099 // have different ways to compute the element offset.
1100 const StructLayout *Layout = 0;
1101 uint64_t ArrayEltBitOffset = 0;
1102 if (const StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) {
1103 Layout = TD->getStructLayout(EltSTy);
1105 const Type *ArrayEltTy = cast<ArrayType>(AllocaEltTy)->getElementType();
1106 ArrayEltBitOffset = TD->getTypeAllocSizeInBits(ArrayEltTy);
1110 Constant::getNullValue(IntegerType::get(LI->getContext(), AllocaSizeBits));
1112 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
1113 // Load the value from the alloca. If the NewElt is an aggregate, cast
1114 // the pointer to an integer of the same size before doing the load.
1115 Value *SrcField = NewElts[i];
1116 const Type *FieldTy =
1117 cast<PointerType>(SrcField->getType())->getElementType();
1118 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy);
1120 // Ignore zero sized fields like {}, they obviously contain no data.
1121 if (FieldSizeBits == 0) continue;
1123 const IntegerType *FieldIntTy = IntegerType::get(LI->getContext(),
1125 if (!isa<IntegerType>(FieldTy) && !FieldTy->isFloatingPoint() &&
1126 !isa<VectorType>(FieldTy))
1127 SrcField = new BitCastInst(SrcField,
1128 PointerType::getUnqual(FieldIntTy),
1130 SrcField = new LoadInst(SrcField, "sroa.load.elt", LI);
1132 // If SrcField is a fp or vector of the right size but that isn't an
1133 // integer type, bitcast to an integer so we can shift it.
1134 if (SrcField->getType() != FieldIntTy)
1135 SrcField = new BitCastInst(SrcField, FieldIntTy, "", LI);
1137 // Zero extend the field to be the same size as the final alloca so that
1138 // we can shift and insert it.
1139 if (SrcField->getType() != ResultVal->getType())
1140 SrcField = new ZExtInst(SrcField, ResultVal->getType(), "", LI);
1142 // Determine the number of bits to shift SrcField.
1144 if (Layout) // Struct case.
1145 Shift = Layout->getElementOffsetInBits(i);
1147 Shift = i*ArrayEltBitOffset;
1149 if (TD->isBigEndian())
1150 Shift = AllocaSizeBits-Shift-FieldIntTy->getBitWidth();
1153 Value *ShiftVal = ConstantInt::get(SrcField->getType(), Shift);
1154 SrcField = BinaryOperator::CreateShl(SrcField, ShiftVal, "", LI);
1157 ResultVal = BinaryOperator::CreateOr(SrcField, ResultVal, "", LI);
1160 // Handle tail padding by truncating the result
1161 if (TD->getTypeSizeInBits(LI->getType()) != AllocaSizeBits)
1162 ResultVal = new TruncInst(ResultVal, LI->getType(), "", LI);
1164 LI->replaceAllUsesWith(ResultVal);
1165 DeadInsts.push_back(LI);
1168 /// HasPadding - Return true if the specified type has any structure or
1169 /// alignment padding, false otherwise.
1170 static bool HasPadding(const Type *Ty, const TargetData &TD) {
1171 if (const StructType *STy = dyn_cast<StructType>(Ty)) {
1172 const StructLayout *SL = TD.getStructLayout(STy);
1173 unsigned PrevFieldBitOffset = 0;
1174 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
1175 unsigned FieldBitOffset = SL->getElementOffsetInBits(i);
1177 // Padding in sub-elements?
1178 if (HasPadding(STy->getElementType(i), TD))
1181 // Check to see if there is any padding between this element and the
1184 unsigned PrevFieldEnd =
1185 PrevFieldBitOffset+TD.getTypeSizeInBits(STy->getElementType(i-1));
1186 if (PrevFieldEnd < FieldBitOffset)
1190 PrevFieldBitOffset = FieldBitOffset;
1193 // Check for tail padding.
1194 if (unsigned EltCount = STy->getNumElements()) {
1195 unsigned PrevFieldEnd = PrevFieldBitOffset +
1196 TD.getTypeSizeInBits(STy->getElementType(EltCount-1));
1197 if (PrevFieldEnd < SL->getSizeInBits())
1201 } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
1202 return HasPadding(ATy->getElementType(), TD);
1203 } else if (const VectorType *VTy = dyn_cast<VectorType>(Ty)) {
1204 return HasPadding(VTy->getElementType(), TD);
1206 return TD.getTypeSizeInBits(Ty) != TD.getTypeAllocSizeInBits(Ty);
1209 /// isSafeStructAllocaToScalarRepl - Check to see if the specified allocation of
1210 /// an aggregate can be broken down into elements. Return 0 if not, 3 if safe,
1211 /// or 1 if safe after canonicalization has been performed.
1212 int SROA::isSafeAllocaToScalarRepl(AllocaInst *AI) {
1213 // Loop over the use list of the alloca. We can only transform it if all of
1214 // the users are safe to transform.
1217 isSafeForScalarRepl(AI, AI, 0, 0, Info);
1218 if (Info.isUnsafe) {
1219 DEBUG(errs() << "Cannot transform: " << *AI << '\n');
1223 // Okay, we know all the users are promotable. If the aggregate is a memcpy
1224 // source and destination, we have to be careful. In particular, the memcpy
1225 // could be moving around elements that live in structure padding of the LLVM
1226 // types, but may actually be used. In these cases, we refuse to promote the
1228 if (Info.isMemCpySrc && Info.isMemCpyDst &&
1229 HasPadding(AI->getAllocatedType(), *TD))
1232 // If we require cleanup, return 1, otherwise return 3.
1233 return Info.needsCleanup ? 1 : 3;
1236 /// CleanupGEP - GEP is used by an Alloca, which can be promoted after the GEP
1237 /// is canonicalized here.
1238 void SROA::CleanupGEP(GetElementPtrInst *GEPI) {
1239 gep_type_iterator I = gep_type_begin(GEPI);
1242 const ArrayType *AT = dyn_cast<ArrayType>(*I);
1246 uint64_t NumElements = AT->getNumElements();
1248 if (isa<ConstantInt>(I.getOperand()))
1251 if (NumElements == 1) {
1253 Constant::getNullValue(Type::getInt32Ty(GEPI->getContext())));
1257 assert(NumElements == 2 && "Unhandled case!");
1258 // All users of the GEP must be loads. At each use of the GEP, insert
1259 // two loads of the appropriate indexed GEP and select between them.
1260 Value *IsOne = new ICmpInst(GEPI, ICmpInst::ICMP_NE, I.getOperand(),
1261 Constant::getNullValue(I.getOperand()->getType()),
1263 // Insert the new GEP instructions, which are properly indexed.
1264 SmallVector<Value*, 8> Indices(GEPI->op_begin()+1, GEPI->op_end());
1265 Indices[1] = Constant::getNullValue(Type::getInt32Ty(GEPI->getContext()));
1266 Value *ZeroIdx = GetElementPtrInst::CreateInBounds(GEPI->getOperand(0),
1269 GEPI->getName()+".0",GEPI);
1270 Indices[1] = ConstantInt::get(Type::getInt32Ty(GEPI->getContext()), 1);
1271 Value *OneIdx = GetElementPtrInst::CreateInBounds(GEPI->getOperand(0),
1274 GEPI->getName()+".1", GEPI);
1275 // Replace all loads of the variable index GEP with loads from both
1276 // indexes and a select.
1277 while (!GEPI->use_empty()) {
1278 LoadInst *LI = cast<LoadInst>(GEPI->use_back());
1279 Value *Zero = new LoadInst(ZeroIdx, LI->getName()+".0", LI);
1280 Value *One = new LoadInst(OneIdx , LI->getName()+".1", LI);
1281 Value *R = SelectInst::Create(IsOne, One, Zero, LI->getName(), LI);
1282 LI->replaceAllUsesWith(R);
1283 LI->eraseFromParent();
1287 /// CleanupAllocaUsers - If SROA reported that it can promote the specified
1288 /// allocation, but only if cleaned up, perform the cleanups required.
1289 void SROA::CleanupAllocaUsers(Value *V) {
1290 // At this point, we know that the end result will be SROA'd and promoted, so
1291 // we can insert ugly code if required so long as sroa+mem2reg will clean it
1293 for (Value::use_iterator UI = V->use_begin(), E = V->use_end();
1296 if (isa<BitCastInst>(U)) {
1297 CleanupAllocaUsers(U);
1298 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(U)) {
1300 CleanupAllocaUsers(GEPI);
1301 if (GEPI->use_empty()) GEPI->eraseFromParent();
1303 Instruction *I = cast<Instruction>(U);
1304 SmallVector<DbgInfoIntrinsic *, 2> DbgInUses;
1305 if (!isa<StoreInst>(I) && OnlyUsedByDbgInfoIntrinsics(I, &DbgInUses)) {
1306 // Safe to remove debug info uses.
1307 while (!DbgInUses.empty()) {
1308 DbgInfoIntrinsic *DI = DbgInUses.back(); DbgInUses.pop_back();
1309 DI->eraseFromParent();
1311 I->eraseFromParent();
1317 /// MergeInType - Add the 'In' type to the accumulated type (Accum) so far at
1318 /// the offset specified by Offset (which is specified in bytes).
1320 /// There are two cases we handle here:
1321 /// 1) A union of vector types of the same size and potentially its elements.
1322 /// Here we turn element accesses into insert/extract element operations.
1323 /// This promotes a <4 x float> with a store of float to the third element
1324 /// into a <4 x float> that uses insert element.
1325 /// 2) A fully general blob of memory, which we turn into some (potentially
1326 /// large) integer type with extract and insert operations where the loads
1327 /// and stores would mutate the memory.
1328 static void MergeInType(const Type *In, uint64_t Offset, const Type *&VecTy,
1329 unsigned AllocaSize, const TargetData &TD,
1330 LLVMContext &Context) {
1331 // If this could be contributing to a vector, analyze it.
1332 if (VecTy != Type::getVoidTy(Context)) { // either null or a vector type.
1334 // If the In type is a vector that is the same size as the alloca, see if it
1335 // matches the existing VecTy.
1336 if (const VectorType *VInTy = dyn_cast<VectorType>(In)) {
1337 if (VInTy->getBitWidth()/8 == AllocaSize && Offset == 0) {
1338 // If we're storing/loading a vector of the right size, allow it as a
1339 // vector. If this the first vector we see, remember the type so that
1340 // we know the element size.
1345 } else if (In->isFloatTy() || In->isDoubleTy() ||
1346 (isa<IntegerType>(In) && In->getPrimitiveSizeInBits() >= 8 &&
1347 isPowerOf2_32(In->getPrimitiveSizeInBits()))) {
1348 // If we're accessing something that could be an element of a vector, see
1349 // if the implied vector agrees with what we already have and if Offset is
1350 // compatible with it.
1351 unsigned EltSize = In->getPrimitiveSizeInBits()/8;
1352 if (Offset % EltSize == 0 &&
1353 AllocaSize % EltSize == 0 &&
1355 cast<VectorType>(VecTy)->getElementType()
1356 ->getPrimitiveSizeInBits()/8 == EltSize)) {
1358 VecTy = VectorType::get(In, AllocaSize/EltSize);
1364 // Otherwise, we have a case that we can't handle with an optimized vector
1365 // form. We can still turn this into a large integer.
1366 VecTy = Type::getVoidTy(Context);
1369 /// CanConvertToScalar - V is a pointer. If we can convert the pointee and all
1370 /// its accesses to a single vector type, return true and set VecTy to
1371 /// the new type. If we could convert the alloca into a single promotable
1372 /// integer, return true but set VecTy to VoidTy. Further, if the use is not a
1373 /// completely trivial use that mem2reg could promote, set IsNotTrivial. Offset
1374 /// is the current offset from the base of the alloca being analyzed.
1376 /// If we see at least one access to the value that is as a vector type, set the
1378 bool SROA::CanConvertToScalar(Value *V, bool &IsNotTrivial, const Type *&VecTy,
1379 bool &SawVec, uint64_t Offset,
1380 unsigned AllocaSize) {
1381 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) {
1382 Instruction *User = cast<Instruction>(*UI);
1384 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1385 // Don't break volatile loads.
1386 if (LI->isVolatile())
1388 MergeInType(LI->getType(), Offset, VecTy,
1389 AllocaSize, *TD, V->getContext());
1390 SawVec |= isa<VectorType>(LI->getType());
1394 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
1395 // Storing the pointer, not into the value?
1396 if (SI->getOperand(0) == V || SI->isVolatile()) return 0;
1397 MergeInType(SI->getOperand(0)->getType(), Offset,
1398 VecTy, AllocaSize, *TD, V->getContext());
1399 SawVec |= isa<VectorType>(SI->getOperand(0)->getType());
1403 if (BitCastInst *BCI = dyn_cast<BitCastInst>(User)) {
1404 if (!CanConvertToScalar(BCI, IsNotTrivial, VecTy, SawVec, Offset,
1407 IsNotTrivial = true;
1411 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) {
1412 // If this is a GEP with a variable indices, we can't handle it.
1413 if (!GEP->hasAllConstantIndices())
1416 // Compute the offset that this GEP adds to the pointer.
1417 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end());
1418 uint64_t GEPOffset = TD->getIndexedOffset(GEP->getPointerOperandType(),
1419 &Indices[0], Indices.size());
1420 // See if all uses can be converted.
1421 if (!CanConvertToScalar(GEP, IsNotTrivial, VecTy, SawVec,Offset+GEPOffset,
1424 IsNotTrivial = true;
1428 // If this is a constant sized memset of a constant value (e.g. 0) we can
1430 if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) {
1431 // Store of constant value and constant size.
1432 if (isa<ConstantInt>(MSI->getValue()) &&
1433 isa<ConstantInt>(MSI->getLength())) {
1434 IsNotTrivial = true;
1439 // If this is a memcpy or memmove into or out of the whole allocation, we
1440 // can handle it like a load or store of the scalar type.
1441 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) {
1442 if (ConstantInt *Len = dyn_cast<ConstantInt>(MTI->getLength()))
1443 if (Len->getZExtValue() == AllocaSize && Offset == 0) {
1444 IsNotTrivial = true;
1449 // Ignore dbg intrinsic.
1450 if (isa<DbgInfoIntrinsic>(User))
1453 // Otherwise, we cannot handle this!
1460 /// ConvertUsesToScalar - Convert all of the users of Ptr to use the new alloca
1461 /// directly. This happens when we are converting an "integer union" to a
1462 /// single integer scalar, or when we are converting a "vector union" to a
1463 /// vector with insert/extractelement instructions.
1465 /// Offset is an offset from the original alloca, in bits that need to be
1466 /// shifted to the right. By the end of this, there should be no uses of Ptr.
1467 void SROA::ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, uint64_t Offset) {
1468 while (!Ptr->use_empty()) {
1469 Instruction *User = cast<Instruction>(Ptr->use_back());
1471 if (BitCastInst *CI = dyn_cast<BitCastInst>(User)) {
1472 ConvertUsesToScalar(CI, NewAI, Offset);
1473 CI->eraseFromParent();
1477 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) {
1478 // Compute the offset that this GEP adds to the pointer.
1479 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end());
1480 uint64_t GEPOffset = TD->getIndexedOffset(GEP->getPointerOperandType(),
1481 &Indices[0], Indices.size());
1482 ConvertUsesToScalar(GEP, NewAI, Offset+GEPOffset*8);
1483 GEP->eraseFromParent();
1487 IRBuilder<> Builder(User->getParent(), User);
1489 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1490 // The load is a bit extract from NewAI shifted right by Offset bits.
1491 Value *LoadedVal = Builder.CreateLoad(NewAI, "tmp");
1493 = ConvertScalar_ExtractValue(LoadedVal, LI->getType(), Offset, Builder);
1494 LI->replaceAllUsesWith(NewLoadVal);
1495 LI->eraseFromParent();
1499 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
1500 assert(SI->getOperand(0) != Ptr && "Consistency error!");
1501 // FIXME: Remove once builder has Twine API.
1502 Value *Old = Builder.CreateLoad(NewAI,
1503 (NewAI->getName()+".in").str().c_str());
1504 Value *New = ConvertScalar_InsertValue(SI->getOperand(0), Old, Offset,
1506 Builder.CreateStore(New, NewAI);
1507 SI->eraseFromParent();
1511 // If this is a constant sized memset of a constant value (e.g. 0) we can
1512 // transform it into a store of the expanded constant value.
1513 if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) {
1514 assert(MSI->getRawDest() == Ptr && "Consistency error!");
1515 unsigned NumBytes = cast<ConstantInt>(MSI->getLength())->getZExtValue();
1516 if (NumBytes != 0) {
1517 unsigned Val = cast<ConstantInt>(MSI->getValue())->getZExtValue();
1519 // Compute the value replicated the right number of times.
1520 APInt APVal(NumBytes*8, Val);
1522 // Splat the value if non-zero.
1524 for (unsigned i = 1; i != NumBytes; ++i)
1525 APVal |= APVal << 8;
1527 // FIXME: Remove once builder has Twine API.
1528 Value *Old = Builder.CreateLoad(NewAI,
1529 (NewAI->getName()+".in").str().c_str());
1530 Value *New = ConvertScalar_InsertValue(
1531 ConstantInt::get(User->getContext(), APVal),
1532 Old, Offset, Builder);
1533 Builder.CreateStore(New, NewAI);
1535 MSI->eraseFromParent();
1539 // If this is a memcpy or memmove into or out of the whole allocation, we
1540 // can handle it like a load or store of the scalar type.
1541 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) {
1542 assert(Offset == 0 && "must be store to start of alloca");
1544 // If the source and destination are both to the same alloca, then this is
1545 // a noop copy-to-self, just delete it. Otherwise, emit a load and store
1547 AllocaInst *OrigAI = cast<AllocaInst>(Ptr->getUnderlyingObject());
1549 if (MTI->getSource()->getUnderlyingObject() != OrigAI) {
1550 // Dest must be OrigAI, change this to be a load from the original
1551 // pointer (bitcasted), then a store to our new alloca.
1552 assert(MTI->getRawDest() == Ptr && "Neither use is of pointer?");
1553 Value *SrcPtr = MTI->getSource();
1554 SrcPtr = Builder.CreateBitCast(SrcPtr, NewAI->getType());
1556 LoadInst *SrcVal = Builder.CreateLoad(SrcPtr, "srcval");
1557 SrcVal->setAlignment(MTI->getAlignment());
1558 Builder.CreateStore(SrcVal, NewAI);
1559 } else if (MTI->getDest()->getUnderlyingObject() != OrigAI) {
1560 // Src must be OrigAI, change this to be a load from NewAI then a store
1561 // through the original dest pointer (bitcasted).
1562 assert(MTI->getRawSource() == Ptr && "Neither use is of pointer?");
1563 LoadInst *SrcVal = Builder.CreateLoad(NewAI, "srcval");
1565 Value *DstPtr = Builder.CreateBitCast(MTI->getDest(), NewAI->getType());
1566 StoreInst *NewStore = Builder.CreateStore(SrcVal, DstPtr);
1567 NewStore->setAlignment(MTI->getAlignment());
1569 // Noop transfer. Src == Dst
1573 MTI->eraseFromParent();
1577 // If user is a dbg info intrinsic then it is safe to remove it.
1578 if (isa<DbgInfoIntrinsic>(User)) {
1579 User->eraseFromParent();
1583 llvm_unreachable("Unsupported operation!");
1587 /// ConvertScalar_ExtractValue - Extract a value of type ToType from an integer
1588 /// or vector value FromVal, extracting the bits from the offset specified by
1589 /// Offset. This returns the value, which is of type ToType.
1591 /// This happens when we are converting an "integer union" to a single
1592 /// integer scalar, or when we are converting a "vector union" to a vector with
1593 /// insert/extractelement instructions.
1595 /// Offset is an offset from the original alloca, in bits that need to be
1596 /// shifted to the right.
1597 Value *SROA::ConvertScalar_ExtractValue(Value *FromVal, const Type *ToType,
1598 uint64_t Offset, IRBuilder<> &Builder) {
1599 // If the load is of the whole new alloca, no conversion is needed.
1600 if (FromVal->getType() == ToType && Offset == 0)
1603 // If the result alloca is a vector type, this is either an element
1604 // access or a bitcast to another vector type of the same size.
1605 if (const VectorType *VTy = dyn_cast<VectorType>(FromVal->getType())) {
1606 if (isa<VectorType>(ToType))
1607 return Builder.CreateBitCast(FromVal, ToType, "tmp");
1609 // Otherwise it must be an element access.
1612 unsigned EltSize = TD->getTypeAllocSizeInBits(VTy->getElementType());
1613 Elt = Offset/EltSize;
1614 assert(EltSize*Elt == Offset && "Invalid modulus in validity checking");
1616 // Return the element extracted out of it.
1617 Value *V = Builder.CreateExtractElement(FromVal, ConstantInt::get(
1618 Type::getInt32Ty(FromVal->getContext()), Elt), "tmp");
1619 if (V->getType() != ToType)
1620 V = Builder.CreateBitCast(V, ToType, "tmp");
1624 // If ToType is a first class aggregate, extract out each of the pieces and
1625 // use insertvalue's to form the FCA.
1626 if (const StructType *ST = dyn_cast<StructType>(ToType)) {
1627 const StructLayout &Layout = *TD->getStructLayout(ST);
1628 Value *Res = UndefValue::get(ST);
1629 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) {
1630 Value *Elt = ConvertScalar_ExtractValue(FromVal, ST->getElementType(i),
1631 Offset+Layout.getElementOffsetInBits(i),
1633 Res = Builder.CreateInsertValue(Res, Elt, i, "tmp");
1638 if (const ArrayType *AT = dyn_cast<ArrayType>(ToType)) {
1639 uint64_t EltSize = TD->getTypeAllocSizeInBits(AT->getElementType());
1640 Value *Res = UndefValue::get(AT);
1641 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
1642 Value *Elt = ConvertScalar_ExtractValue(FromVal, AT->getElementType(),
1643 Offset+i*EltSize, Builder);
1644 Res = Builder.CreateInsertValue(Res, Elt, i, "tmp");
1649 // Otherwise, this must be a union that was converted to an integer value.
1650 const IntegerType *NTy = cast<IntegerType>(FromVal->getType());
1652 // If this is a big-endian system and the load is narrower than the
1653 // full alloca type, we need to do a shift to get the right bits.
1655 if (TD->isBigEndian()) {
1656 // On big-endian machines, the lowest bit is stored at the bit offset
1657 // from the pointer given by getTypeStoreSizeInBits. This matters for
1658 // integers with a bitwidth that is not a multiple of 8.
1659 ShAmt = TD->getTypeStoreSizeInBits(NTy) -
1660 TD->getTypeStoreSizeInBits(ToType) - Offset;
1665 // Note: we support negative bitwidths (with shl) which are not defined.
1666 // We do this to support (f.e.) loads off the end of a structure where
1667 // only some bits are used.
1668 if (ShAmt > 0 && (unsigned)ShAmt < NTy->getBitWidth())
1669 FromVal = Builder.CreateLShr(FromVal,
1670 ConstantInt::get(FromVal->getType(),
1672 else if (ShAmt < 0 && (unsigned)-ShAmt < NTy->getBitWidth())
1673 FromVal = Builder.CreateShl(FromVal,
1674 ConstantInt::get(FromVal->getType(),
1677 // Finally, unconditionally truncate the integer to the right width.
1678 unsigned LIBitWidth = TD->getTypeSizeInBits(ToType);
1679 if (LIBitWidth < NTy->getBitWidth())
1681 Builder.CreateTrunc(FromVal, IntegerType::get(FromVal->getContext(),
1682 LIBitWidth), "tmp");
1683 else if (LIBitWidth > NTy->getBitWidth())
1685 Builder.CreateZExt(FromVal, IntegerType::get(FromVal->getContext(),
1686 LIBitWidth), "tmp");
1688 // If the result is an integer, this is a trunc or bitcast.
1689 if (isa<IntegerType>(ToType)) {
1691 } else if (ToType->isFloatingPoint() || isa<VectorType>(ToType)) {
1692 // Just do a bitcast, we know the sizes match up.
1693 FromVal = Builder.CreateBitCast(FromVal, ToType, "tmp");
1695 // Otherwise must be a pointer.
1696 FromVal = Builder.CreateIntToPtr(FromVal, ToType, "tmp");
1698 assert(FromVal->getType() == ToType && "Didn't convert right?");
1702 /// ConvertScalar_InsertValue - Insert the value "SV" into the existing integer
1703 /// or vector value "Old" at the offset specified by Offset.
1705 /// This happens when we are converting an "integer union" to a
1706 /// single integer scalar, or when we are converting a "vector union" to a
1707 /// vector with insert/extractelement instructions.
1709 /// Offset is an offset from the original alloca, in bits that need to be
1710 /// shifted to the right.
1711 Value *SROA::ConvertScalar_InsertValue(Value *SV, Value *Old,
1712 uint64_t Offset, IRBuilder<> &Builder) {
1714 // Convert the stored type to the actual type, shift it left to insert
1715 // then 'or' into place.
1716 const Type *AllocaType = Old->getType();
1717 LLVMContext &Context = Old->getContext();
1719 if (const VectorType *VTy = dyn_cast<VectorType>(AllocaType)) {
1720 uint64_t VecSize = TD->getTypeAllocSizeInBits(VTy);
1721 uint64_t ValSize = TD->getTypeAllocSizeInBits(SV->getType());
1723 // Changing the whole vector with memset or with an access of a different
1725 if (ValSize == VecSize)
1726 return Builder.CreateBitCast(SV, AllocaType, "tmp");
1728 uint64_t EltSize = TD->getTypeAllocSizeInBits(VTy->getElementType());
1730 // Must be an element insertion.
1731 unsigned Elt = Offset/EltSize;
1733 if (SV->getType() != VTy->getElementType())
1734 SV = Builder.CreateBitCast(SV, VTy->getElementType(), "tmp");
1736 SV = Builder.CreateInsertElement(Old, SV,
1737 ConstantInt::get(Type::getInt32Ty(SV->getContext()), Elt),
1742 // If SV is a first-class aggregate value, insert each value recursively.
1743 if (const StructType *ST = dyn_cast<StructType>(SV->getType())) {
1744 const StructLayout &Layout = *TD->getStructLayout(ST);
1745 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) {
1746 Value *Elt = Builder.CreateExtractValue(SV, i, "tmp");
1747 Old = ConvertScalar_InsertValue(Elt, Old,
1748 Offset+Layout.getElementOffsetInBits(i),
1754 if (const ArrayType *AT = dyn_cast<ArrayType>(SV->getType())) {
1755 uint64_t EltSize = TD->getTypeAllocSizeInBits(AT->getElementType());
1756 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
1757 Value *Elt = Builder.CreateExtractValue(SV, i, "tmp");
1758 Old = ConvertScalar_InsertValue(Elt, Old, Offset+i*EltSize, Builder);
1763 // If SV is a float, convert it to the appropriate integer type.
1764 // If it is a pointer, do the same.
1765 unsigned SrcWidth = TD->getTypeSizeInBits(SV->getType());
1766 unsigned DestWidth = TD->getTypeSizeInBits(AllocaType);
1767 unsigned SrcStoreWidth = TD->getTypeStoreSizeInBits(SV->getType());
1768 unsigned DestStoreWidth = TD->getTypeStoreSizeInBits(AllocaType);
1769 if (SV->getType()->isFloatingPoint() || isa<VectorType>(SV->getType()))
1770 SV = Builder.CreateBitCast(SV,
1771 IntegerType::get(SV->getContext(),SrcWidth), "tmp");
1772 else if (isa<PointerType>(SV->getType()))
1773 SV = Builder.CreatePtrToInt(SV, TD->getIntPtrType(SV->getContext()), "tmp");
1775 // Zero extend or truncate the value if needed.
1776 if (SV->getType() != AllocaType) {
1777 if (SV->getType()->getPrimitiveSizeInBits() <
1778 AllocaType->getPrimitiveSizeInBits())
1779 SV = Builder.CreateZExt(SV, AllocaType, "tmp");
1781 // Truncation may be needed if storing more than the alloca can hold
1782 // (undefined behavior).
1783 SV = Builder.CreateTrunc(SV, AllocaType, "tmp");
1784 SrcWidth = DestWidth;
1785 SrcStoreWidth = DestStoreWidth;
1789 // If this is a big-endian system and the store is narrower than the
1790 // full alloca type, we need to do a shift to get the right bits.
1792 if (TD->isBigEndian()) {
1793 // On big-endian machines, the lowest bit is stored at the bit offset
1794 // from the pointer given by getTypeStoreSizeInBits. This matters for
1795 // integers with a bitwidth that is not a multiple of 8.
1796 ShAmt = DestStoreWidth - SrcStoreWidth - Offset;
1801 // Note: we support negative bitwidths (with shr) which are not defined.
1802 // We do this to support (f.e.) stores off the end of a structure where
1803 // only some bits in the structure are set.
1804 APInt Mask(APInt::getLowBitsSet(DestWidth, SrcWidth));
1805 if (ShAmt > 0 && (unsigned)ShAmt < DestWidth) {
1806 SV = Builder.CreateShl(SV, ConstantInt::get(SV->getType(),
1809 } else if (ShAmt < 0 && (unsigned)-ShAmt < DestWidth) {
1810 SV = Builder.CreateLShr(SV, ConstantInt::get(SV->getType(),
1812 Mask = Mask.lshr(-ShAmt);
1815 // Mask out the bits we are about to insert from the old value, and or
1817 if (SrcWidth != DestWidth) {
1818 assert(DestWidth > SrcWidth);
1819 Old = Builder.CreateAnd(Old, ConstantInt::get(Context, ~Mask), "mask");
1820 SV = Builder.CreateOr(Old, SV, "ins");
1827 /// PointsToConstantGlobal - Return true if V (possibly indirectly) points to
1828 /// some part of a constant global variable. This intentionally only accepts
1829 /// constant expressions because we don't can't rewrite arbitrary instructions.
1830 static bool PointsToConstantGlobal(Value *V) {
1831 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
1832 return GV->isConstant();
1833 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
1834 if (CE->getOpcode() == Instruction::BitCast ||
1835 CE->getOpcode() == Instruction::GetElementPtr)
1836 return PointsToConstantGlobal(CE->getOperand(0));
1840 /// isOnlyCopiedFromConstantGlobal - Recursively walk the uses of a (derived)
1841 /// pointer to an alloca. Ignore any reads of the pointer, return false if we
1842 /// see any stores or other unknown uses. If we see pointer arithmetic, keep
1843 /// track of whether it moves the pointer (with isOffset) but otherwise traverse
1844 /// the uses. If we see a memcpy/memmove that targets an unoffseted pointer to
1845 /// the alloca, and if the source pointer is a pointer to a constant global, we
1846 /// can optimize this.
1847 static bool isOnlyCopiedFromConstantGlobal(Value *V, Instruction *&TheCopy,
1849 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) {
1850 if (LoadInst *LI = dyn_cast<LoadInst>(*UI))
1851 // Ignore non-volatile loads, they are always ok.
1852 if (!LI->isVolatile())
1855 if (BitCastInst *BCI = dyn_cast<BitCastInst>(*UI)) {
1856 // If uses of the bitcast are ok, we are ok.
1857 if (!isOnlyCopiedFromConstantGlobal(BCI, TheCopy, isOffset))
1861 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(*UI)) {
1862 // If the GEP has all zero indices, it doesn't offset the pointer. If it
1863 // doesn't, it does.
1864 if (!isOnlyCopiedFromConstantGlobal(GEP, TheCopy,
1865 isOffset || !GEP->hasAllZeroIndices()))
1870 // If this is isn't our memcpy/memmove, reject it as something we can't
1872 if (!isa<MemTransferInst>(*UI))
1875 // If we already have seen a copy, reject the second one.
1876 if (TheCopy) return false;
1878 // If the pointer has been offset from the start of the alloca, we can't
1879 // safely handle this.
1880 if (isOffset) return false;
1882 // If the memintrinsic isn't using the alloca as the dest, reject it.
1883 if (UI.getOperandNo() != 1) return false;
1885 MemIntrinsic *MI = cast<MemIntrinsic>(*UI);
1887 // If the source of the memcpy/move is not a constant global, reject it.
1888 if (!PointsToConstantGlobal(MI->getOperand(2)))
1891 // Otherwise, the transform is safe. Remember the copy instruction.
1897 /// isOnlyCopiedFromConstantGlobal - Return true if the specified alloca is only
1898 /// modified by a copy from a constant global. If we can prove this, we can
1899 /// replace any uses of the alloca with uses of the global directly.
1900 Instruction *SROA::isOnlyCopiedFromConstantGlobal(AllocaInst *AI) {
1901 Instruction *TheCopy = 0;
1902 if (::isOnlyCopiedFromConstantGlobal(AI, TheCopy, false))