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/Compiler.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 VISIBILITY_HIDDEN 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>();
71 AU.addRequired<TargetData>();
78 /// AllocaInfo - When analyzing uses of an alloca instruction, this captures
79 /// information about the uses. All these fields are initialized to false
80 /// and set to true when something is learned.
82 /// isUnsafe - This is set to true if the alloca cannot be SROA'd.
85 /// needsCleanup - This is set to true if there is some use of the alloca
86 /// that requires cleanup.
87 bool needsCleanup : 1;
89 /// isMemCpySrc - This is true if this aggregate is memcpy'd from.
92 /// isMemCpyDst - This is true if this aggregate is memcpy'd into.
96 : isUnsafe(false), needsCleanup(false),
97 isMemCpySrc(false), isMemCpyDst(false) {}
100 unsigned SRThreshold;
102 void MarkUnsafe(AllocaInfo &I) { I.isUnsafe = true; }
104 int isSafeAllocaToScalarRepl(AllocationInst *AI);
106 void isSafeUseOfAllocation(Instruction *User, AllocationInst *AI,
108 void isSafeElementUse(Value *Ptr, bool isFirstElt, AllocationInst *AI,
110 void isSafeMemIntrinsicOnAllocation(MemIntrinsic *MI, AllocationInst *AI,
111 unsigned OpNo, AllocaInfo &Info);
112 void isSafeUseOfBitCastedAllocation(BitCastInst *User, AllocationInst *AI,
115 void DoScalarReplacement(AllocationInst *AI,
116 std::vector<AllocationInst*> &WorkList);
117 void CleanupGEP(GetElementPtrInst *GEP);
118 void CleanupAllocaUsers(AllocationInst *AI);
119 AllocaInst *AddNewAlloca(Function &F, const Type *Ty, AllocationInst *Base);
121 void RewriteBitCastUserOfAlloca(Instruction *BCInst, AllocationInst *AI,
122 SmallVector<AllocaInst*, 32> &NewElts);
124 void RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *BCInst,
126 SmallVector<AllocaInst*, 32> &NewElts);
127 void RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocationInst *AI,
128 SmallVector<AllocaInst*, 32> &NewElts);
129 void RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocationInst *AI,
130 SmallVector<AllocaInst*, 32> &NewElts);
132 bool CanConvertToScalar(Value *V, bool &IsNotTrivial, const Type *&VecTy,
133 bool &SawVec, uint64_t Offset, unsigned AllocaSize);
134 void ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, uint64_t Offset);
135 Value *ConvertScalar_ExtractValue(Value *NV, const Type *ToType,
136 uint64_t Offset, IRBuilder<> &Builder);
137 Value *ConvertScalar_InsertValue(Value *StoredVal, Value *ExistingVal,
138 uint64_t Offset, IRBuilder<> &Builder);
139 static Instruction *isOnlyCopiedFromConstantGlobal(AllocationInst *AI);
144 static RegisterPass<SROA> X("scalarrepl", "Scalar Replacement of Aggregates");
146 // Public interface to the ScalarReplAggregates pass
147 FunctionPass *llvm::createScalarReplAggregatesPass(signed int Threshold) {
148 return new SROA(Threshold);
152 bool SROA::runOnFunction(Function &F) {
153 TD = &getAnalysis<TargetData>();
155 bool Changed = performPromotion(F);
157 bool LocalChange = performScalarRepl(F);
158 if (!LocalChange) break; // No need to repromote if no scalarrepl
160 LocalChange = performPromotion(F);
161 if (!LocalChange) break; // No need to re-scalarrepl if no promotion
168 bool SROA::performPromotion(Function &F) {
169 std::vector<AllocaInst*> Allocas;
170 DominatorTree &DT = getAnalysis<DominatorTree>();
171 DominanceFrontier &DF = getAnalysis<DominanceFrontier>();
173 BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function
175 bool Changed = false;
180 // Find allocas that are safe to promote, by looking at all instructions in
182 for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I)
183 if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) // Is it an alloca?
184 if (isAllocaPromotable(AI))
185 Allocas.push_back(AI);
187 if (Allocas.empty()) break;
189 PromoteMemToReg(Allocas, DT, DF, F.getContext());
190 NumPromoted += Allocas.size();
197 /// getNumSAElements - Return the number of elements in the specific struct or
199 static uint64_t getNumSAElements(const Type *T) {
200 if (const StructType *ST = dyn_cast<StructType>(T))
201 return ST->getNumElements();
202 return cast<ArrayType>(T)->getNumElements();
205 // performScalarRepl - This algorithm is a simple worklist driven algorithm,
206 // which runs on all of the malloc/alloca instructions in the function, removing
207 // them if they are only used by getelementptr instructions.
209 bool SROA::performScalarRepl(Function &F) {
210 std::vector<AllocationInst*> WorkList;
212 // Scan the entry basic block, adding any alloca's and mallocs to the worklist
213 BasicBlock &BB = F.getEntryBlock();
214 for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I)
215 if (AllocationInst *A = dyn_cast<AllocationInst>(I))
216 WorkList.push_back(A);
218 // Process the worklist
219 bool Changed = false;
220 while (!WorkList.empty()) {
221 AllocationInst *AI = WorkList.back();
224 // Handle dead allocas trivially. These can be formed by SROA'ing arrays
225 // with unused elements.
226 if (AI->use_empty()) {
227 AI->eraseFromParent();
231 // If this alloca is impossible for us to promote, reject it early.
232 if (AI->isArrayAllocation() || !AI->getAllocatedType()->isSized())
235 // Check to see if this allocation is only modified by a memcpy/memmove from
236 // a constant global. If this is the case, we can change all users to use
237 // the constant global instead. This is commonly produced by the CFE by
238 // constructs like "void foo() { int A[] = {1,2,3,4,5,6,7,8,9...}; }" if 'A'
239 // is only subsequently read.
240 if (Instruction *TheCopy = isOnlyCopiedFromConstantGlobal(AI)) {
241 DOUT << "Found alloca equal to global: " << *AI;
242 DOUT << " memcpy = " << *TheCopy;
243 Constant *TheSrc = cast<Constant>(TheCopy->getOperand(2));
244 AI->replaceAllUsesWith(ConstantExpr::getBitCast(TheSrc, AI->getType()));
245 TheCopy->eraseFromParent(); // Don't mutate the global.
246 AI->eraseFromParent();
252 // Check to see if we can perform the core SROA transformation. We cannot
253 // transform the allocation instruction if it is an array allocation
254 // (allocations OF arrays are ok though), and an allocation of a scalar
255 // value cannot be decomposed at all.
256 uint64_t AllocaSize = TD->getTypeAllocSize(AI->getAllocatedType());
258 // Do not promote any struct whose size is too big.
259 if (AllocaSize > SRThreshold) continue;
261 if ((isa<StructType>(AI->getAllocatedType()) ||
262 isa<ArrayType>(AI->getAllocatedType())) &&
263 // Do not promote any struct into more than "32" separate vars.
264 getNumSAElements(AI->getAllocatedType()) <= SRThreshold/4) {
265 // Check that all of the users of the allocation are capable of being
267 switch (isSafeAllocaToScalarRepl(AI)) {
268 default: llvm_unreachable("Unexpected value!");
269 case 0: // Not safe to scalar replace.
271 case 1: // Safe, but requires cleanup/canonicalizations first
272 CleanupAllocaUsers(AI);
274 case 3: // Safe to scalar replace.
275 DoScalarReplacement(AI, WorkList);
281 // If we can turn this aggregate value (potentially with casts) into a
282 // simple scalar value that can be mem2reg'd into a register value.
283 // IsNotTrivial tracks whether this is something that mem2reg could have
284 // promoted itself. If so, we don't want to transform it needlessly. Note
285 // that we can't just check based on the type: the alloca may be of an i32
286 // but that has pointer arithmetic to set byte 3 of it or something.
287 bool IsNotTrivial = false;
288 const Type *VectorTy = 0;
289 bool HadAVector = false;
290 if (CanConvertToScalar(AI, IsNotTrivial, VectorTy, HadAVector,
291 0, unsigned(AllocaSize)) && IsNotTrivial) {
293 // If we were able to find a vector type that can handle this with
294 // insert/extract elements, and if there was at least one use that had
295 // a vector type, promote this to a vector. We don't want to promote
296 // random stuff that doesn't use vectors (e.g. <9 x double>) because then
297 // we just get a lot of insert/extracts. If at least one vector is
298 // involved, then we probably really do have a union of vector/array.
299 if (VectorTy && isa<VectorType>(VectorTy) && HadAVector) {
300 DOUT << "CONVERT TO VECTOR: " << *AI << " TYPE = " << *VectorTy <<"\n";
302 // Create and insert the vector alloca.
303 NewAI = new AllocaInst(VectorTy, 0, "", AI->getParent()->begin());
304 ConvertUsesToScalar(AI, NewAI, 0);
306 DOUT << "CONVERT TO SCALAR INTEGER: " << *AI << "\n";
308 // Create and insert the integer alloca.
309 const Type *NewTy = IntegerType::get(AI->getContext(), AllocaSize*8);
310 NewAI = new AllocaInst(NewTy, 0, "", AI->getParent()->begin());
311 ConvertUsesToScalar(AI, NewAI, 0);
314 AI->eraseFromParent();
320 // Otherwise, couldn't process this alloca.
326 /// DoScalarReplacement - This alloca satisfied the isSafeAllocaToScalarRepl
327 /// predicate, do SROA now.
328 void SROA::DoScalarReplacement(AllocationInst *AI,
329 std::vector<AllocationInst*> &WorkList) {
330 DOUT << "Found inst to SROA: " << *AI;
331 SmallVector<AllocaInst*, 32> ElementAllocas;
332 if (const StructType *ST = dyn_cast<StructType>(AI->getAllocatedType())) {
333 ElementAllocas.reserve(ST->getNumContainedTypes());
334 for (unsigned i = 0, e = ST->getNumContainedTypes(); i != e; ++i) {
335 AllocaInst *NA = new AllocaInst(ST->getContainedType(i), 0,
337 AI->getName() + "." + Twine(i), AI);
338 ElementAllocas.push_back(NA);
339 WorkList.push_back(NA); // Add to worklist for recursive processing
342 const ArrayType *AT = cast<ArrayType>(AI->getAllocatedType());
343 ElementAllocas.reserve(AT->getNumElements());
344 const Type *ElTy = AT->getElementType();
345 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
346 AllocaInst *NA = new AllocaInst(ElTy, 0, AI->getAlignment(),
347 AI->getName() + "." + Twine(i), AI);
348 ElementAllocas.push_back(NA);
349 WorkList.push_back(NA); // Add to worklist for recursive processing
353 // Now that we have created the alloca instructions that we want to use,
354 // expand the getelementptr instructions to use them.
356 while (!AI->use_empty()) {
357 Instruction *User = cast<Instruction>(AI->use_back());
358 if (BitCastInst *BCInst = dyn_cast<BitCastInst>(User)) {
359 RewriteBitCastUserOfAlloca(BCInst, AI, ElementAllocas);
360 BCInst->eraseFromParent();
365 // %res = load { i32, i32 }* %alloc
367 // %load.0 = load i32* %alloc.0
368 // %insert.0 insertvalue { i32, i32 } zeroinitializer, i32 %load.0, 0
369 // %load.1 = load i32* %alloc.1
370 // %insert = insertvalue { i32, i32 } %insert.0, i32 %load.1, 1
371 // (Also works for arrays instead of structs)
372 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
373 Value *Insert = UndefValue::get(LI->getType());
374 for (unsigned i = 0, e = ElementAllocas.size(); i != e; ++i) {
375 Value *Load = new LoadInst(ElementAllocas[i], "load", LI);
376 Insert = InsertValueInst::Create(Insert, Load, i, "insert", LI);
378 LI->replaceAllUsesWith(Insert);
379 LI->eraseFromParent();
384 // store { i32, i32 } %val, { i32, i32 }* %alloc
386 // %val.0 = extractvalue { i32, i32 } %val, 0
387 // store i32 %val.0, i32* %alloc.0
388 // %val.1 = extractvalue { i32, i32 } %val, 1
389 // store i32 %val.1, i32* %alloc.1
390 // (Also works for arrays instead of structs)
391 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
392 Value *Val = SI->getOperand(0);
393 for (unsigned i = 0, e = ElementAllocas.size(); i != e; ++i) {
394 Value *Extract = ExtractValueInst::Create(Val, i, Val->getName(), SI);
395 new StoreInst(Extract, ElementAllocas[i], SI);
397 SI->eraseFromParent();
401 GetElementPtrInst *GEPI = cast<GetElementPtrInst>(User);
402 // We now know that the GEP is of the form: GEP <ptr>, 0, <cst>
404 (unsigned)cast<ConstantInt>(GEPI->getOperand(2))->getZExtValue();
406 assert(Idx < ElementAllocas.size() && "Index out of range?");
407 AllocaInst *AllocaToUse = ElementAllocas[Idx];
410 if (GEPI->getNumOperands() == 3) {
411 // Do not insert a new getelementptr instruction with zero indices, only
412 // to have it optimized out later.
413 RepValue = AllocaToUse;
415 // We are indexing deeply into the structure, so we still need a
416 // getelement ptr instruction to finish the indexing. This may be
417 // expanded itself once the worklist is rerun.
419 SmallVector<Value*, 8> NewArgs;
420 NewArgs.push_back(Constant::getNullValue(
421 Type::getInt32Ty(AI->getContext())));
422 NewArgs.append(GEPI->op_begin()+3, GEPI->op_end());
423 RepValue = GetElementPtrInst::Create(AllocaToUse, NewArgs.begin(),
424 NewArgs.end(), "", GEPI);
425 RepValue->takeName(GEPI);
428 // If this GEP is to the start of the aggregate, check for memcpys.
429 if (Idx == 0 && GEPI->hasAllZeroIndices())
430 RewriteBitCastUserOfAlloca(GEPI, AI, ElementAllocas);
432 // Move all of the users over to the new GEP.
433 GEPI->replaceAllUsesWith(RepValue);
434 // Delete the old GEP
435 GEPI->eraseFromParent();
438 // Finally, delete the Alloca instruction
439 AI->eraseFromParent();
444 /// isSafeElementUse - Check to see if this use is an allowed use for a
445 /// getelementptr instruction of an array aggregate allocation. isFirstElt
446 /// indicates whether Ptr is known to the start of the aggregate.
448 void SROA::isSafeElementUse(Value *Ptr, bool isFirstElt, AllocationInst *AI,
450 for (Value::use_iterator I = Ptr->use_begin(), E = Ptr->use_end();
452 Instruction *User = cast<Instruction>(*I);
453 switch (User->getOpcode()) {
454 case Instruction::Load: break;
455 case Instruction::Store:
456 // Store is ok if storing INTO the pointer, not storing the pointer
457 if (User->getOperand(0) == Ptr) return MarkUnsafe(Info);
459 case Instruction::GetElementPtr: {
460 GetElementPtrInst *GEP = cast<GetElementPtrInst>(User);
461 bool AreAllZeroIndices = isFirstElt;
462 if (GEP->getNumOperands() > 1) {
463 if (!isa<ConstantInt>(GEP->getOperand(1)) ||
464 !cast<ConstantInt>(GEP->getOperand(1))->isZero())
465 // Using pointer arithmetic to navigate the array.
466 return MarkUnsafe(Info);
468 if (AreAllZeroIndices)
469 AreAllZeroIndices = GEP->hasAllZeroIndices();
471 isSafeElementUse(GEP, AreAllZeroIndices, AI, Info);
472 if (Info.isUnsafe) return;
475 case Instruction::BitCast:
477 isSafeUseOfBitCastedAllocation(cast<BitCastInst>(User), AI, Info);
478 if (Info.isUnsafe) return;
481 DOUT << " Transformation preventing inst: " << *User;
482 return MarkUnsafe(Info);
483 case Instruction::Call:
484 if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) {
486 isSafeMemIntrinsicOnAllocation(MI, AI, I.getOperandNo(), Info);
487 if (Info.isUnsafe) return;
491 DOUT << " Transformation preventing inst: " << *User;
492 return MarkUnsafe(Info);
494 DOUT << " Transformation preventing inst: " << *User;
495 return MarkUnsafe(Info);
498 return; // All users look ok :)
501 /// AllUsersAreLoads - Return true if all users of this value are loads.
502 static bool AllUsersAreLoads(Value *Ptr) {
503 for (Value::use_iterator I = Ptr->use_begin(), E = Ptr->use_end();
505 if (cast<Instruction>(*I)->getOpcode() != Instruction::Load)
510 /// isSafeUseOfAllocation - Check to see if this user is an allowed use for an
511 /// aggregate allocation.
513 void SROA::isSafeUseOfAllocation(Instruction *User, AllocationInst *AI,
515 if (BitCastInst *C = dyn_cast<BitCastInst>(User))
516 return isSafeUseOfBitCastedAllocation(C, AI, Info);
518 if (LoadInst *LI = dyn_cast<LoadInst>(User))
519 if (!LI->isVolatile())
520 return;// Loads (returning a first class aggregrate) are always rewritable
522 if (StoreInst *SI = dyn_cast<StoreInst>(User))
523 if (!SI->isVolatile() && SI->getOperand(0) != AI)
524 return;// Store is ok if storing INTO the pointer, not storing the pointer
526 GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User);
528 return MarkUnsafe(Info);
530 gep_type_iterator I = gep_type_begin(GEPI), E = gep_type_end(GEPI);
532 // The GEP is not safe to transform if not of the form "GEP <ptr>, 0, <cst>".
534 I.getOperand() != Constant::getNullValue(I.getOperand()->getType())) {
535 return MarkUnsafe(Info);
539 if (I == E) return MarkUnsafe(Info); // ran out of GEP indices??
541 bool IsAllZeroIndices = true;
543 // If the first index is a non-constant index into an array, see if we can
544 // handle it as a special case.
545 if (const ArrayType *AT = dyn_cast<ArrayType>(*I)) {
546 if (!isa<ConstantInt>(I.getOperand())) {
547 IsAllZeroIndices = 0;
548 uint64_t NumElements = AT->getNumElements();
550 // If this is an array index and the index is not constant, we cannot
551 // promote... that is unless the array has exactly one or two elements in
552 // it, in which case we CAN promote it, but we have to canonicalize this
553 // out if this is the only problem.
554 if ((NumElements == 1 || NumElements == 2) &&
555 AllUsersAreLoads(GEPI)) {
556 Info.needsCleanup = true;
557 return; // Canonicalization required!
559 return MarkUnsafe(Info);
563 // Walk through the GEP type indices, checking the types that this indexes
565 for (; I != E; ++I) {
566 // Ignore struct elements, no extra checking needed for these.
567 if (isa<StructType>(*I))
570 ConstantInt *IdxVal = dyn_cast<ConstantInt>(I.getOperand());
571 if (!IdxVal) return MarkUnsafe(Info);
573 // Are all indices still zero?
574 IsAllZeroIndices &= IdxVal->isZero();
576 if (const ArrayType *AT = dyn_cast<ArrayType>(*I)) {
577 // This GEP indexes an array. Verify that this is an in-range constant
578 // integer. Specifically, consider A[0][i]. We cannot know that the user
579 // isn't doing invalid things like allowing i to index an out-of-range
580 // subscript that accesses A[1]. Because of this, we have to reject SROA
581 // of any accesses into structs where any of the components are variables.
582 if (IdxVal->getZExtValue() >= AT->getNumElements())
583 return MarkUnsafe(Info);
584 } else if (const VectorType *VT = dyn_cast<VectorType>(*I)) {
585 if (IdxVal->getZExtValue() >= VT->getNumElements())
586 return MarkUnsafe(Info);
590 // If there are any non-simple uses of this getelementptr, make sure to reject
592 return isSafeElementUse(GEPI, IsAllZeroIndices, AI, Info);
595 /// isSafeMemIntrinsicOnAllocation - Return true if the specified memory
596 /// intrinsic can be promoted by SROA. At this point, we know that the operand
597 /// of the memintrinsic is a pointer to the beginning of the allocation.
598 void SROA::isSafeMemIntrinsicOnAllocation(MemIntrinsic *MI, AllocationInst *AI,
599 unsigned OpNo, AllocaInfo &Info) {
600 // If not constant length, give up.
601 ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength());
602 if (!Length) return MarkUnsafe(Info);
604 // If not the whole aggregate, give up.
605 if (Length->getZExtValue() !=
606 TD->getTypeAllocSize(AI->getType()->getElementType()))
607 return MarkUnsafe(Info);
609 // We only know about memcpy/memset/memmove.
610 if (!isa<MemIntrinsic>(MI))
611 return MarkUnsafe(Info);
613 // Otherwise, we can transform it. Determine whether this is a memcpy/set
614 // into or out of the aggregate.
616 Info.isMemCpyDst = true;
619 Info.isMemCpySrc = true;
623 /// isSafeUseOfBitCastedAllocation - Return true if all users of this bitcast
625 void SROA::isSafeUseOfBitCastedAllocation(BitCastInst *BC, AllocationInst *AI,
627 for (Value::use_iterator UI = BC->use_begin(), E = BC->use_end();
629 if (BitCastInst *BCU = dyn_cast<BitCastInst>(UI)) {
630 isSafeUseOfBitCastedAllocation(BCU, AI, Info);
631 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(UI)) {
632 isSafeMemIntrinsicOnAllocation(MI, AI, UI.getOperandNo(), Info);
633 } else if (StoreInst *SI = dyn_cast<StoreInst>(UI)) {
634 if (SI->isVolatile())
635 return MarkUnsafe(Info);
637 // If storing the entire alloca in one chunk through a bitcasted pointer
638 // to integer, we can transform it. This happens (for example) when you
639 // cast a {i32,i32}* to i64* and store through it. This is similar to the
640 // memcpy case and occurs in various "byval" cases and emulated memcpys.
641 if (isa<IntegerType>(SI->getOperand(0)->getType()) &&
642 TD->getTypeAllocSize(SI->getOperand(0)->getType()) ==
643 TD->getTypeAllocSize(AI->getType()->getElementType())) {
644 Info.isMemCpyDst = true;
647 return MarkUnsafe(Info);
648 } else if (LoadInst *LI = dyn_cast<LoadInst>(UI)) {
649 if (LI->isVolatile())
650 return MarkUnsafe(Info);
652 // If loading the entire alloca in one chunk through a bitcasted pointer
653 // to integer, we can transform it. This happens (for example) when you
654 // cast a {i32,i32}* to i64* and load through it. This is similar to the
655 // memcpy case and occurs in various "byval" cases and emulated memcpys.
656 if (isa<IntegerType>(LI->getType()) &&
657 TD->getTypeAllocSize(LI->getType()) ==
658 TD->getTypeAllocSize(AI->getType()->getElementType())) {
659 Info.isMemCpySrc = true;
662 return MarkUnsafe(Info);
663 } else if (isa<DbgInfoIntrinsic>(UI)) {
664 // If one user is DbgInfoIntrinsic then check if all users are
665 // DbgInfoIntrinsics.
666 if (OnlyUsedByDbgInfoIntrinsics(BC)) {
667 Info.needsCleanup = true;
674 return MarkUnsafe(Info);
676 if (Info.isUnsafe) return;
680 /// RewriteBitCastUserOfAlloca - BCInst (transitively) bitcasts AI, or indexes
681 /// to its first element. Transform users of the cast to use the new values
683 void SROA::RewriteBitCastUserOfAlloca(Instruction *BCInst, AllocationInst *AI,
684 SmallVector<AllocaInst*, 32> &NewElts) {
685 Value::use_iterator UI = BCInst->use_begin(), UE = BCInst->use_end();
687 Instruction *User = cast<Instruction>(*UI++);
688 if (BitCastInst *BCU = dyn_cast<BitCastInst>(User)) {
689 RewriteBitCastUserOfAlloca(BCU, AI, NewElts);
690 if (BCU->use_empty()) BCU->eraseFromParent();
694 if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) {
695 // This must be memcpy/memmove/memset of the entire aggregate.
696 // Split into one per element.
697 RewriteMemIntrinUserOfAlloca(MI, BCInst, AI, NewElts);
701 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
702 // If this is a store of the entire alloca from an integer, rewrite it.
703 RewriteStoreUserOfWholeAlloca(SI, AI, NewElts);
707 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
708 // If this is a load of the entire alloca to an integer, rewrite it.
709 RewriteLoadUserOfWholeAlloca(LI, AI, NewElts);
713 // Otherwise it must be some other user of a gep of the first pointer. Just
714 // leave these alone.
719 /// RewriteMemIntrinUserOfAlloca - MI is a memcpy/memset/memmove from or to AI.
720 /// Rewrite it to copy or set the elements of the scalarized memory.
721 void SROA::RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *BCInst,
723 SmallVector<AllocaInst*, 32> &NewElts) {
725 // If this is a memcpy/memmove, construct the other pointer as the
726 // appropriate type. The "Other" pointer is the pointer that goes to memory
727 // that doesn't have anything to do with the alloca that we are promoting. For
728 // memset, this Value* stays null.
730 LLVMContext &Context = MI->getContext();
731 unsigned MemAlignment = MI->getAlignment();
732 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(MI)) { // memmove/memcopy
733 if (BCInst == MTI->getRawDest())
734 OtherPtr = MTI->getRawSource();
736 assert(BCInst == MTI->getRawSource());
737 OtherPtr = MTI->getRawDest();
741 // If there is an other pointer, we want to convert it to the same pointer
742 // type as AI has, so we can GEP through it safely.
744 // It is likely that OtherPtr is a bitcast, if so, remove it.
745 if (BitCastInst *BC = dyn_cast<BitCastInst>(OtherPtr))
746 OtherPtr = BC->getOperand(0);
747 // All zero GEPs are effectively bitcasts.
748 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(OtherPtr))
749 if (GEP->hasAllZeroIndices())
750 OtherPtr = GEP->getOperand(0);
752 if (ConstantExpr *BCE = dyn_cast<ConstantExpr>(OtherPtr))
753 if (BCE->getOpcode() == Instruction::BitCast)
754 OtherPtr = BCE->getOperand(0);
756 // If the pointer is not the right type, insert a bitcast to the right
758 if (OtherPtr->getType() != AI->getType())
759 OtherPtr = new BitCastInst(OtherPtr, AI->getType(), OtherPtr->getName(),
763 // Process each element of the aggregate.
764 Value *TheFn = MI->getOperand(0);
765 const Type *BytePtrTy = MI->getRawDest()->getType();
766 bool SROADest = MI->getRawDest() == BCInst;
768 Constant *Zero = Constant::getNullValue(Type::getInt32Ty(MI->getContext()));
770 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
771 // If this is a memcpy/memmove, emit a GEP of the other element address.
773 unsigned OtherEltAlign = MemAlignment;
776 Value *Idx[2] = { Zero,
777 ConstantInt::get(Type::getInt32Ty(MI->getContext()), i) };
778 OtherElt = GetElementPtrInst::Create(OtherPtr, Idx, Idx + 2,
779 OtherPtr->getNameStr()+"."+Twine(i),
782 const PointerType *OtherPtrTy = cast<PointerType>(OtherPtr->getType());
783 if (const StructType *ST =
784 dyn_cast<StructType>(OtherPtrTy->getElementType())) {
785 EltOffset = TD->getStructLayout(ST)->getElementOffset(i);
788 cast<SequentialType>(OtherPtr->getType())->getElementType();
789 EltOffset = TD->getTypeAllocSize(EltTy)*i;
792 // The alignment of the other pointer is the guaranteed alignment of the
793 // element, which is affected by both the known alignment of the whole
794 // mem intrinsic and the alignment of the element. If the alignment of
795 // the memcpy (f.e.) is 32 but the element is at a 4-byte offset, then the
796 // known alignment is just 4 bytes.
797 OtherEltAlign = (unsigned)MinAlign(OtherEltAlign, EltOffset);
800 Value *EltPtr = NewElts[i];
801 const Type *EltTy = cast<PointerType>(EltPtr->getType())->getElementType();
803 // If we got down to a scalar, insert a load or store as appropriate.
804 if (EltTy->isSingleValueType()) {
805 if (isa<MemTransferInst>(MI)) {
807 // From Other to Alloca.
808 Value *Elt = new LoadInst(OtherElt, "tmp", false, OtherEltAlign, MI);
809 new StoreInst(Elt, EltPtr, MI);
811 // From Alloca to Other.
812 Value *Elt = new LoadInst(EltPtr, "tmp", MI);
813 new StoreInst(Elt, OtherElt, false, OtherEltAlign, MI);
817 assert(isa<MemSetInst>(MI));
819 // If the stored element is zero (common case), just store a null
822 if (ConstantInt *CI = dyn_cast<ConstantInt>(MI->getOperand(2))) {
824 StoreVal = Constant::getNullValue(EltTy); // 0.0, null, 0, <0,0>
826 // If EltTy is a vector type, get the element type.
827 const Type *ValTy = EltTy->getScalarType();
829 // Construct an integer with the right value.
830 unsigned EltSize = TD->getTypeSizeInBits(ValTy);
831 APInt OneVal(EltSize, CI->getZExtValue());
832 APInt TotalVal(OneVal);
834 for (unsigned i = 0; 8*i < EltSize; ++i) {
835 TotalVal = TotalVal.shl(8);
839 // Convert the integer value to the appropriate type.
840 StoreVal = ConstantInt::get(Context, TotalVal);
841 if (isa<PointerType>(ValTy))
842 StoreVal = ConstantExpr::getIntToPtr(StoreVal, ValTy);
843 else if (ValTy->isFloatingPoint())
844 StoreVal = ConstantExpr::getBitCast(StoreVal, ValTy);
845 assert(StoreVal->getType() == ValTy && "Type mismatch!");
847 // If the requested value was a vector constant, create it.
848 if (EltTy != ValTy) {
849 unsigned NumElts = cast<VectorType>(ValTy)->getNumElements();
850 SmallVector<Constant*, 16> Elts(NumElts, StoreVal);
851 StoreVal = ConstantVector::get(&Elts[0], NumElts);
854 new StoreInst(StoreVal, EltPtr, MI);
857 // Otherwise, if we're storing a byte variable, use a memset call for
861 // Cast the element pointer to BytePtrTy.
862 if (EltPtr->getType() != BytePtrTy)
863 EltPtr = new BitCastInst(EltPtr, BytePtrTy, EltPtr->getNameStr(), MI);
865 // Cast the other pointer (if we have one) to BytePtrTy.
866 if (OtherElt && OtherElt->getType() != BytePtrTy)
867 OtherElt = new BitCastInst(OtherElt, BytePtrTy,OtherElt->getNameStr(),
870 unsigned EltSize = TD->getTypeAllocSize(EltTy);
872 // Finally, insert the meminst for this element.
873 if (isa<MemTransferInst>(MI)) {
875 SROADest ? EltPtr : OtherElt, // Dest ptr
876 SROADest ? OtherElt : EltPtr, // Src ptr
877 ConstantInt::get(MI->getOperand(3)->getType(), EltSize), // Size
879 ConstantInt::get(Type::getInt32Ty(MI->getContext()), OtherEltAlign)
881 CallInst::Create(TheFn, Ops, Ops + 4, "", MI);
883 assert(isa<MemSetInst>(MI));
885 EltPtr, MI->getOperand(2), // Dest, Value,
886 ConstantInt::get(MI->getOperand(3)->getType(), EltSize), // Size
889 CallInst::Create(TheFn, Ops, Ops + 4, "", MI);
892 MI->eraseFromParent();
895 /// RewriteStoreUserOfWholeAlloca - We found an store of an integer that
896 /// overwrites the entire allocation. Extract out the pieces of the stored
897 /// integer and store them individually.
898 void SROA::RewriteStoreUserOfWholeAlloca(StoreInst *SI,
900 SmallVector<AllocaInst*, 32> &NewElts){
901 // Extract each element out of the integer according to its structure offset
902 // and store the element value to the individual alloca.
903 Value *SrcVal = SI->getOperand(0);
904 const Type *AllocaEltTy = AI->getType()->getElementType();
905 uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy);
907 // If this isn't a store of an integer to the whole alloca, it may be a store
908 // to the first element. Just ignore the store in this case and normal SROA
910 if (!isa<IntegerType>(SrcVal->getType()) ||
911 TD->getTypeAllocSizeInBits(SrcVal->getType()) != AllocaSizeBits)
913 // Handle tail padding by extending the operand
914 if (TD->getTypeSizeInBits(SrcVal->getType()) != AllocaSizeBits)
915 SrcVal = new ZExtInst(SrcVal,
916 IntegerType::get(SI->getContext(), AllocaSizeBits),
919 DOUT << "PROMOTING STORE TO WHOLE ALLOCA: " << *AI << *SI;
921 // There are two forms here: AI could be an array or struct. Both cases
922 // have different ways to compute the element offset.
923 if (const StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) {
924 const StructLayout *Layout = TD->getStructLayout(EltSTy);
926 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
927 // Get the number of bits to shift SrcVal to get the value.
928 const Type *FieldTy = EltSTy->getElementType(i);
929 uint64_t Shift = Layout->getElementOffsetInBits(i);
931 if (TD->isBigEndian())
932 Shift = AllocaSizeBits-Shift-TD->getTypeAllocSizeInBits(FieldTy);
934 Value *EltVal = SrcVal;
936 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift);
937 EltVal = BinaryOperator::CreateLShr(EltVal, ShiftVal,
938 "sroa.store.elt", SI);
941 // Truncate down to an integer of the right size.
942 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy);
944 // Ignore zero sized fields like {}, they obviously contain no data.
945 if (FieldSizeBits == 0) continue;
947 if (FieldSizeBits != AllocaSizeBits)
948 EltVal = new TruncInst(EltVal,
949 IntegerType::get(SI->getContext(), FieldSizeBits),
951 Value *DestField = NewElts[i];
952 if (EltVal->getType() == FieldTy) {
953 // Storing to an integer field of this size, just do it.
954 } else if (FieldTy->isFloatingPoint() || isa<VectorType>(FieldTy)) {
955 // Bitcast to the right element type (for fp/vector values).
956 EltVal = new BitCastInst(EltVal, FieldTy, "", SI);
958 // Otherwise, bitcast the dest pointer (for aggregates).
959 DestField = new BitCastInst(DestField,
960 PointerType::getUnqual(EltVal->getType()),
963 new StoreInst(EltVal, DestField, SI);
967 const ArrayType *ATy = cast<ArrayType>(AllocaEltTy);
968 const Type *ArrayEltTy = ATy->getElementType();
969 uint64_t ElementOffset = TD->getTypeAllocSizeInBits(ArrayEltTy);
970 uint64_t ElementSizeBits = TD->getTypeSizeInBits(ArrayEltTy);
974 if (TD->isBigEndian())
975 Shift = AllocaSizeBits-ElementOffset;
979 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
980 // Ignore zero sized fields like {}, they obviously contain no data.
981 if (ElementSizeBits == 0) continue;
983 Value *EltVal = SrcVal;
985 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift);
986 EltVal = BinaryOperator::CreateLShr(EltVal, ShiftVal,
987 "sroa.store.elt", SI);
990 // Truncate down to an integer of the right size.
991 if (ElementSizeBits != AllocaSizeBits)
992 EltVal = new TruncInst(EltVal,
993 IntegerType::get(SI->getContext(),
994 ElementSizeBits),"",SI);
995 Value *DestField = NewElts[i];
996 if (EltVal->getType() == ArrayEltTy) {
997 // Storing to an integer field of this size, just do it.
998 } else if (ArrayEltTy->isFloatingPoint() || isa<VectorType>(ArrayEltTy)) {
999 // Bitcast to the right element type (for fp/vector values).
1000 EltVal = new BitCastInst(EltVal, ArrayEltTy, "", SI);
1002 // Otherwise, bitcast the dest pointer (for aggregates).
1003 DestField = new BitCastInst(DestField,
1004 PointerType::getUnqual(EltVal->getType()),
1007 new StoreInst(EltVal, DestField, SI);
1009 if (TD->isBigEndian())
1010 Shift -= ElementOffset;
1012 Shift += ElementOffset;
1016 SI->eraseFromParent();
1019 /// RewriteLoadUserOfWholeAlloca - We found an load of the entire allocation to
1020 /// an integer. Load the individual pieces to form the aggregate value.
1021 void SROA::RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocationInst *AI,
1022 SmallVector<AllocaInst*, 32> &NewElts) {
1023 // Extract each element out of the NewElts according to its structure offset
1024 // and form the result value.
1025 const Type *AllocaEltTy = AI->getType()->getElementType();
1026 uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy);
1028 // If this isn't a load of the whole alloca to an integer, it may be a load
1029 // of the first element. Just ignore the load in this case and normal SROA
1031 if (!isa<IntegerType>(LI->getType()) ||
1032 TD->getTypeAllocSizeInBits(LI->getType()) != AllocaSizeBits)
1035 DOUT << "PROMOTING LOAD OF WHOLE ALLOCA: " << *AI << *LI;
1037 // There are two forms here: AI could be an array or struct. Both cases
1038 // have different ways to compute the element offset.
1039 const StructLayout *Layout = 0;
1040 uint64_t ArrayEltBitOffset = 0;
1041 if (const StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) {
1042 Layout = TD->getStructLayout(EltSTy);
1044 const Type *ArrayEltTy = cast<ArrayType>(AllocaEltTy)->getElementType();
1045 ArrayEltBitOffset = TD->getTypeAllocSizeInBits(ArrayEltTy);
1049 Constant::getNullValue(IntegerType::get(LI->getContext(), AllocaSizeBits));
1051 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
1052 // Load the value from the alloca. If the NewElt is an aggregate, cast
1053 // the pointer to an integer of the same size before doing the load.
1054 Value *SrcField = NewElts[i];
1055 const Type *FieldTy =
1056 cast<PointerType>(SrcField->getType())->getElementType();
1057 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy);
1059 // Ignore zero sized fields like {}, they obviously contain no data.
1060 if (FieldSizeBits == 0) continue;
1062 const IntegerType *FieldIntTy = IntegerType::get(LI->getContext(),
1064 if (!isa<IntegerType>(FieldTy) && !FieldTy->isFloatingPoint() &&
1065 !isa<VectorType>(FieldTy))
1066 SrcField = new BitCastInst(SrcField,
1067 PointerType::getUnqual(FieldIntTy),
1069 SrcField = new LoadInst(SrcField, "sroa.load.elt", LI);
1071 // If SrcField is a fp or vector of the right size but that isn't an
1072 // integer type, bitcast to an integer so we can shift it.
1073 if (SrcField->getType() != FieldIntTy)
1074 SrcField = new BitCastInst(SrcField, FieldIntTy, "", LI);
1076 // Zero extend the field to be the same size as the final alloca so that
1077 // we can shift and insert it.
1078 if (SrcField->getType() != ResultVal->getType())
1079 SrcField = new ZExtInst(SrcField, ResultVal->getType(), "", LI);
1081 // Determine the number of bits to shift SrcField.
1083 if (Layout) // Struct case.
1084 Shift = Layout->getElementOffsetInBits(i);
1086 Shift = i*ArrayEltBitOffset;
1088 if (TD->isBigEndian())
1089 Shift = AllocaSizeBits-Shift-FieldIntTy->getBitWidth();
1092 Value *ShiftVal = ConstantInt::get(SrcField->getType(), Shift);
1093 SrcField = BinaryOperator::CreateShl(SrcField, ShiftVal, "", LI);
1096 ResultVal = BinaryOperator::CreateOr(SrcField, ResultVal, "", LI);
1099 // Handle tail padding by truncating the result
1100 if (TD->getTypeSizeInBits(LI->getType()) != AllocaSizeBits)
1101 ResultVal = new TruncInst(ResultVal, LI->getType(), "", LI);
1103 LI->replaceAllUsesWith(ResultVal);
1104 LI->eraseFromParent();
1108 /// HasPadding - Return true if the specified type has any structure or
1109 /// alignment padding, false otherwise.
1110 static bool HasPadding(const Type *Ty, const TargetData &TD) {
1111 if (const StructType *STy = dyn_cast<StructType>(Ty)) {
1112 const StructLayout *SL = TD.getStructLayout(STy);
1113 unsigned PrevFieldBitOffset = 0;
1114 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
1115 unsigned FieldBitOffset = SL->getElementOffsetInBits(i);
1117 // Padding in sub-elements?
1118 if (HasPadding(STy->getElementType(i), TD))
1121 // Check to see if there is any padding between this element and the
1124 unsigned PrevFieldEnd =
1125 PrevFieldBitOffset+TD.getTypeSizeInBits(STy->getElementType(i-1));
1126 if (PrevFieldEnd < FieldBitOffset)
1130 PrevFieldBitOffset = FieldBitOffset;
1133 // Check for tail padding.
1134 if (unsigned EltCount = STy->getNumElements()) {
1135 unsigned PrevFieldEnd = PrevFieldBitOffset +
1136 TD.getTypeSizeInBits(STy->getElementType(EltCount-1));
1137 if (PrevFieldEnd < SL->getSizeInBits())
1141 } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
1142 return HasPadding(ATy->getElementType(), TD);
1143 } else if (const VectorType *VTy = dyn_cast<VectorType>(Ty)) {
1144 return HasPadding(VTy->getElementType(), TD);
1146 return TD.getTypeSizeInBits(Ty) != TD.getTypeAllocSizeInBits(Ty);
1149 /// isSafeStructAllocaToScalarRepl - Check to see if the specified allocation of
1150 /// an aggregate can be broken down into elements. Return 0 if not, 3 if safe,
1151 /// or 1 if safe after canonicalization has been performed.
1153 int SROA::isSafeAllocaToScalarRepl(AllocationInst *AI) {
1154 // Loop over the use list of the alloca. We can only transform it if all of
1155 // the users are safe to transform.
1158 for (Value::use_iterator I = AI->use_begin(), E = AI->use_end();
1160 isSafeUseOfAllocation(cast<Instruction>(*I), AI, Info);
1161 if (Info.isUnsafe) {
1162 DOUT << "Cannot transform: " << *AI << " due to user: " << **I;
1167 // Okay, we know all the users are promotable. If the aggregate is a memcpy
1168 // source and destination, we have to be careful. In particular, the memcpy
1169 // could be moving around elements that live in structure padding of the LLVM
1170 // types, but may actually be used. In these cases, we refuse to promote the
1172 if (Info.isMemCpySrc && Info.isMemCpyDst &&
1173 HasPadding(AI->getType()->getElementType(), *TD))
1176 // If we require cleanup, return 1, otherwise return 3.
1177 return Info.needsCleanup ? 1 : 3;
1180 /// CleanupGEP - GEP is used by an Alloca, which can be prompted after the GEP
1181 /// is canonicalized here.
1182 void SROA::CleanupGEP(GetElementPtrInst *GEPI) {
1183 gep_type_iterator I = gep_type_begin(GEPI);
1186 const ArrayType *AT = dyn_cast<ArrayType>(*I);
1190 uint64_t NumElements = AT->getNumElements();
1192 if (isa<ConstantInt>(I.getOperand()))
1195 if (NumElements == 1) {
1197 Constant::getNullValue(Type::getInt32Ty(GEPI->getContext())));
1201 assert(NumElements == 2 && "Unhandled case!");
1202 // All users of the GEP must be loads. At each use of the GEP, insert
1203 // two loads of the appropriate indexed GEP and select between them.
1204 Value *IsOne = new ICmpInst(GEPI, ICmpInst::ICMP_NE, I.getOperand(),
1205 Constant::getNullValue(I.getOperand()->getType()),
1207 // Insert the new GEP instructions, which are properly indexed.
1208 SmallVector<Value*, 8> Indices(GEPI->op_begin()+1, GEPI->op_end());
1209 Indices[1] = Constant::getNullValue(Type::getInt32Ty(GEPI->getContext()));
1210 Value *ZeroIdx = GetElementPtrInst::Create(GEPI->getOperand(0),
1213 GEPI->getName()+".0", GEPI);
1214 Indices[1] = ConstantInt::get(Type::getInt32Ty(GEPI->getContext()), 1);
1215 Value *OneIdx = GetElementPtrInst::Create(GEPI->getOperand(0),
1218 GEPI->getName()+".1", GEPI);
1219 // Replace all loads of the variable index GEP with loads from both
1220 // indexes and a select.
1221 while (!GEPI->use_empty()) {
1222 LoadInst *LI = cast<LoadInst>(GEPI->use_back());
1223 Value *Zero = new LoadInst(ZeroIdx, LI->getName()+".0", LI);
1224 Value *One = new LoadInst(OneIdx , LI->getName()+".1", LI);
1225 Value *R = SelectInst::Create(IsOne, One, Zero, LI->getName(), LI);
1226 LI->replaceAllUsesWith(R);
1227 LI->eraseFromParent();
1229 GEPI->eraseFromParent();
1233 /// CleanupAllocaUsers - If SROA reported that it can promote the specified
1234 /// allocation, but only if cleaned up, perform the cleanups required.
1235 void SROA::CleanupAllocaUsers(AllocationInst *AI) {
1236 // At this point, we know that the end result will be SROA'd and promoted, so
1237 // we can insert ugly code if required so long as sroa+mem2reg will clean it
1239 for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end();
1242 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(U))
1245 Instruction *I = cast<Instruction>(U);
1246 SmallVector<DbgInfoIntrinsic *, 2> DbgInUses;
1247 if (!isa<StoreInst>(I) && OnlyUsedByDbgInfoIntrinsics(I, &DbgInUses)) {
1248 // Safe to remove debug info uses.
1249 while (!DbgInUses.empty()) {
1250 DbgInfoIntrinsic *DI = DbgInUses.back(); DbgInUses.pop_back();
1251 DI->eraseFromParent();
1253 I->eraseFromParent();
1259 /// MergeInType - Add the 'In' type to the accumulated type (Accum) so far at
1260 /// the offset specified by Offset (which is specified in bytes).
1262 /// There are two cases we handle here:
1263 /// 1) A union of vector types of the same size and potentially its elements.
1264 /// Here we turn element accesses into insert/extract element operations.
1265 /// This promotes a <4 x float> with a store of float to the third element
1266 /// into a <4 x float> that uses insert element.
1267 /// 2) A fully general blob of memory, which we turn into some (potentially
1268 /// large) integer type with extract and insert operations where the loads
1269 /// and stores would mutate the memory.
1270 static void MergeInType(const Type *In, uint64_t Offset, const Type *&VecTy,
1271 unsigned AllocaSize, const TargetData &TD,
1272 LLVMContext &Context) {
1273 // If this could be contributing to a vector, analyze it.
1274 if (VecTy != Type::getVoidTy(Context)) { // either null or a vector type.
1276 // If the In type is a vector that is the same size as the alloca, see if it
1277 // matches the existing VecTy.
1278 if (const VectorType *VInTy = dyn_cast<VectorType>(In)) {
1279 if (VInTy->getBitWidth()/8 == AllocaSize && Offset == 0) {
1280 // If we're storing/loading a vector of the right size, allow it as a
1281 // vector. If this the first vector we see, remember the type so that
1282 // we know the element size.
1287 } else if (In == Type::getFloatTy(Context) ||
1288 In == Type::getDoubleTy(Context) ||
1289 (isa<IntegerType>(In) && In->getPrimitiveSizeInBits() >= 8 &&
1290 isPowerOf2_32(In->getPrimitiveSizeInBits()))) {
1291 // If we're accessing something that could be an element of a vector, see
1292 // if the implied vector agrees with what we already have and if Offset is
1293 // compatible with it.
1294 unsigned EltSize = In->getPrimitiveSizeInBits()/8;
1295 if (Offset % EltSize == 0 &&
1296 AllocaSize % EltSize == 0 &&
1298 cast<VectorType>(VecTy)->getElementType()
1299 ->getPrimitiveSizeInBits()/8 == EltSize)) {
1301 VecTy = VectorType::get(In, AllocaSize/EltSize);
1307 // Otherwise, we have a case that we can't handle with an optimized vector
1308 // form. We can still turn this into a large integer.
1309 VecTy = Type::getVoidTy(Context);
1312 /// CanConvertToScalar - V is a pointer. If we can convert the pointee and all
1313 /// its accesses to use a to single vector type, return true, and set VecTy to
1314 /// the new type. If we could convert the alloca into a single promotable
1315 /// integer, return true but set VecTy to VoidTy. Further, if the use is not a
1316 /// completely trivial use that mem2reg could promote, set IsNotTrivial. Offset
1317 /// is the current offset from the base of the alloca being analyzed.
1319 /// If we see at least one access to the value that is as a vector type, set the
1322 bool SROA::CanConvertToScalar(Value *V, bool &IsNotTrivial, const Type *&VecTy,
1323 bool &SawVec, uint64_t Offset,
1324 unsigned AllocaSize) {
1325 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) {
1326 Instruction *User = cast<Instruction>(*UI);
1328 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1329 // Don't break volatile loads.
1330 if (LI->isVolatile())
1332 MergeInType(LI->getType(), Offset, VecTy,
1333 AllocaSize, *TD, V->getContext());
1334 SawVec |= isa<VectorType>(LI->getType());
1338 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
1339 // Storing the pointer, not into the value?
1340 if (SI->getOperand(0) == V || SI->isVolatile()) return 0;
1341 MergeInType(SI->getOperand(0)->getType(), Offset,
1342 VecTy, AllocaSize, *TD, V->getContext());
1343 SawVec |= isa<VectorType>(SI->getOperand(0)->getType());
1347 if (BitCastInst *BCI = dyn_cast<BitCastInst>(User)) {
1348 if (!CanConvertToScalar(BCI, IsNotTrivial, VecTy, SawVec, Offset,
1351 IsNotTrivial = true;
1355 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) {
1356 // If this is a GEP with a variable indices, we can't handle it.
1357 if (!GEP->hasAllConstantIndices())
1360 // Compute the offset that this GEP adds to the pointer.
1361 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end());
1362 uint64_t GEPOffset = TD->getIndexedOffset(GEP->getOperand(0)->getType(),
1363 &Indices[0], Indices.size());
1364 // See if all uses can be converted.
1365 if (!CanConvertToScalar(GEP, IsNotTrivial, VecTy, SawVec,Offset+GEPOffset,
1368 IsNotTrivial = true;
1372 // If this is a constant sized memset of a constant value (e.g. 0) we can
1374 if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) {
1375 // Store of constant value and constant size.
1376 if (isa<ConstantInt>(MSI->getValue()) &&
1377 isa<ConstantInt>(MSI->getLength())) {
1378 IsNotTrivial = true;
1383 // If this is a memcpy or memmove into or out of the whole allocation, we
1384 // can handle it like a load or store of the scalar type.
1385 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) {
1386 if (ConstantInt *Len = dyn_cast<ConstantInt>(MTI->getLength()))
1387 if (Len->getZExtValue() == AllocaSize && Offset == 0) {
1388 IsNotTrivial = true;
1393 // Ignore dbg intrinsic.
1394 if (isa<DbgInfoIntrinsic>(User))
1397 // Otherwise, we cannot handle this!
1405 /// ConvertUsesToScalar - Convert all of the users of Ptr to use the new alloca
1406 /// directly. This happens when we are converting an "integer union" to a
1407 /// single integer scalar, or when we are converting a "vector union" to a
1408 /// vector with insert/extractelement instructions.
1410 /// Offset is an offset from the original alloca, in bits that need to be
1411 /// shifted to the right. By the end of this, there should be no uses of Ptr.
1412 void SROA::ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, uint64_t Offset) {
1413 while (!Ptr->use_empty()) {
1414 Instruction *User = cast<Instruction>(Ptr->use_back());
1416 if (BitCastInst *CI = dyn_cast<BitCastInst>(User)) {
1417 ConvertUsesToScalar(CI, NewAI, Offset);
1418 CI->eraseFromParent();
1422 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) {
1423 // Compute the offset that this GEP adds to the pointer.
1424 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end());
1425 uint64_t GEPOffset = TD->getIndexedOffset(GEP->getOperand(0)->getType(),
1426 &Indices[0], Indices.size());
1427 ConvertUsesToScalar(GEP, NewAI, Offset+GEPOffset*8);
1428 GEP->eraseFromParent();
1432 IRBuilder<> Builder(User->getParent(), User);
1434 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1435 // The load is a bit extract from NewAI shifted right by Offset bits.
1436 Value *LoadedVal = Builder.CreateLoad(NewAI, "tmp");
1438 = ConvertScalar_ExtractValue(LoadedVal, LI->getType(), Offset, Builder);
1439 LI->replaceAllUsesWith(NewLoadVal);
1440 LI->eraseFromParent();
1444 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
1445 assert(SI->getOperand(0) != Ptr && "Consistency error!");
1446 // FIXME: Remove once builder has Twine API.
1447 Value *Old = Builder.CreateLoad(NewAI, (NewAI->getName()+".in").str().c_str());
1448 Value *New = ConvertScalar_InsertValue(SI->getOperand(0), Old, Offset,
1450 Builder.CreateStore(New, NewAI);
1451 SI->eraseFromParent();
1455 // If this is a constant sized memset of a constant value (e.g. 0) we can
1456 // transform it into a store of the expanded constant value.
1457 if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) {
1458 assert(MSI->getRawDest() == Ptr && "Consistency error!");
1459 unsigned NumBytes = cast<ConstantInt>(MSI->getLength())->getZExtValue();
1460 if (NumBytes != 0) {
1461 unsigned Val = cast<ConstantInt>(MSI->getValue())->getZExtValue();
1463 // Compute the value replicated the right number of times.
1464 APInt APVal(NumBytes*8, Val);
1466 // Splat the value if non-zero.
1468 for (unsigned i = 1; i != NumBytes; ++i)
1469 APVal |= APVal << 8;
1471 // FIXME: Remove once builder has Twine API.
1472 Value *Old = Builder.CreateLoad(NewAI, (NewAI->getName()+".in").str().c_str());
1473 Value *New = ConvertScalar_InsertValue(
1474 ConstantInt::get(User->getContext(), APVal),
1475 Old, Offset, Builder);
1476 Builder.CreateStore(New, NewAI);
1478 MSI->eraseFromParent();
1482 // If this is a memcpy or memmove into or out of the whole allocation, we
1483 // can handle it like a load or store of the scalar type.
1484 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) {
1485 assert(Offset == 0 && "must be store to start of alloca");
1487 // If the source and destination are both to the same alloca, then this is
1488 // a noop copy-to-self, just delete it. Otherwise, emit a load and store
1490 AllocaInst *OrigAI = cast<AllocaInst>(Ptr->getUnderlyingObject());
1492 if (MTI->getSource()->getUnderlyingObject() != OrigAI) {
1493 // Dest must be OrigAI, change this to be a load from the original
1494 // pointer (bitcasted), then a store to our new alloca.
1495 assert(MTI->getRawDest() == Ptr && "Neither use is of pointer?");
1496 Value *SrcPtr = MTI->getSource();
1497 SrcPtr = Builder.CreateBitCast(SrcPtr, NewAI->getType());
1499 LoadInst *SrcVal = Builder.CreateLoad(SrcPtr, "srcval");
1500 SrcVal->setAlignment(MTI->getAlignment());
1501 Builder.CreateStore(SrcVal, NewAI);
1502 } else if (MTI->getDest()->getUnderlyingObject() != OrigAI) {
1503 // Src must be OrigAI, change this to be a load from NewAI then a store
1504 // through the original dest pointer (bitcasted).
1505 assert(MTI->getRawSource() == Ptr && "Neither use is of pointer?");
1506 LoadInst *SrcVal = Builder.CreateLoad(NewAI, "srcval");
1508 Value *DstPtr = Builder.CreateBitCast(MTI->getDest(), NewAI->getType());
1509 StoreInst *NewStore = Builder.CreateStore(SrcVal, DstPtr);
1510 NewStore->setAlignment(MTI->getAlignment());
1512 // Noop transfer. Src == Dst
1516 MTI->eraseFromParent();
1520 // If user is a dbg info intrinsic then it is safe to remove it.
1521 if (isa<DbgInfoIntrinsic>(User)) {
1522 User->eraseFromParent();
1526 llvm_unreachable("Unsupported operation!");
1530 /// ConvertScalar_ExtractValue - Extract a value of type ToType from an integer
1531 /// or vector value FromVal, extracting the bits from the offset specified by
1532 /// Offset. This returns the value, which is of type ToType.
1534 /// This happens when we are converting an "integer union" to a single
1535 /// integer scalar, or when we are converting a "vector union" to a vector with
1536 /// insert/extractelement instructions.
1538 /// Offset is an offset from the original alloca, in bits that need to be
1539 /// shifted to the right.
1540 Value *SROA::ConvertScalar_ExtractValue(Value *FromVal, const Type *ToType,
1541 uint64_t Offset, IRBuilder<> &Builder) {
1542 // If the load is of the whole new alloca, no conversion is needed.
1543 if (FromVal->getType() == ToType && Offset == 0)
1546 // If the result alloca is a vector type, this is either an element
1547 // access or a bitcast to another vector type of the same size.
1548 if (const VectorType *VTy = dyn_cast<VectorType>(FromVal->getType())) {
1549 if (isa<VectorType>(ToType))
1550 return Builder.CreateBitCast(FromVal, ToType, "tmp");
1552 // Otherwise it must be an element access.
1555 unsigned EltSize = TD->getTypeAllocSizeInBits(VTy->getElementType());
1556 Elt = Offset/EltSize;
1557 assert(EltSize*Elt == Offset && "Invalid modulus in validity checking");
1559 // Return the element extracted out of it.
1560 Value *V = Builder.CreateExtractElement(FromVal, ConstantInt::get(
1561 Type::getInt32Ty(FromVal->getContext()), Elt), "tmp");
1562 if (V->getType() != ToType)
1563 V = Builder.CreateBitCast(V, ToType, "tmp");
1567 // If ToType is a first class aggregate, extract out each of the pieces and
1568 // use insertvalue's to form the FCA.
1569 if (const StructType *ST = dyn_cast<StructType>(ToType)) {
1570 const StructLayout &Layout = *TD->getStructLayout(ST);
1571 Value *Res = UndefValue::get(ST);
1572 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) {
1573 Value *Elt = ConvertScalar_ExtractValue(FromVal, ST->getElementType(i),
1574 Offset+Layout.getElementOffsetInBits(i),
1576 Res = Builder.CreateInsertValue(Res, Elt, i, "tmp");
1581 if (const ArrayType *AT = dyn_cast<ArrayType>(ToType)) {
1582 uint64_t EltSize = TD->getTypeAllocSizeInBits(AT->getElementType());
1583 Value *Res = UndefValue::get(AT);
1584 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
1585 Value *Elt = ConvertScalar_ExtractValue(FromVal, AT->getElementType(),
1586 Offset+i*EltSize, Builder);
1587 Res = Builder.CreateInsertValue(Res, Elt, i, "tmp");
1592 // Otherwise, this must be a union that was converted to an integer value.
1593 const IntegerType *NTy = cast<IntegerType>(FromVal->getType());
1595 // If this is a big-endian system and the load is narrower than the
1596 // full alloca type, we need to do a shift to get the right bits.
1598 if (TD->isBigEndian()) {
1599 // On big-endian machines, the lowest bit is stored at the bit offset
1600 // from the pointer given by getTypeStoreSizeInBits. This matters for
1601 // integers with a bitwidth that is not a multiple of 8.
1602 ShAmt = TD->getTypeStoreSizeInBits(NTy) -
1603 TD->getTypeStoreSizeInBits(ToType) - Offset;
1608 // Note: we support negative bitwidths (with shl) which are not defined.
1609 // We do this to support (f.e.) loads off the end of a structure where
1610 // only some bits are used.
1611 if (ShAmt > 0 && (unsigned)ShAmt < NTy->getBitWidth())
1612 FromVal = Builder.CreateLShr(FromVal,
1613 ConstantInt::get(FromVal->getType(),
1615 else if (ShAmt < 0 && (unsigned)-ShAmt < NTy->getBitWidth())
1616 FromVal = Builder.CreateShl(FromVal,
1617 ConstantInt::get(FromVal->getType(),
1620 // Finally, unconditionally truncate the integer to the right width.
1621 unsigned LIBitWidth = TD->getTypeSizeInBits(ToType);
1622 if (LIBitWidth < NTy->getBitWidth())
1624 Builder.CreateTrunc(FromVal, IntegerType::get(FromVal->getContext(),
1625 LIBitWidth), "tmp");
1626 else if (LIBitWidth > NTy->getBitWidth())
1628 Builder.CreateZExt(FromVal, IntegerType::get(FromVal->getContext(),
1629 LIBitWidth), "tmp");
1631 // If the result is an integer, this is a trunc or bitcast.
1632 if (isa<IntegerType>(ToType)) {
1634 } else if (ToType->isFloatingPoint() || isa<VectorType>(ToType)) {
1635 // Just do a bitcast, we know the sizes match up.
1636 FromVal = Builder.CreateBitCast(FromVal, ToType, "tmp");
1638 // Otherwise must be a pointer.
1639 FromVal = Builder.CreateIntToPtr(FromVal, ToType, "tmp");
1641 assert(FromVal->getType() == ToType && "Didn't convert right?");
1646 /// ConvertScalar_InsertValue - Insert the value "SV" into the existing integer
1647 /// or vector value "Old" at the offset specified by Offset.
1649 /// This happens when we are converting an "integer union" to a
1650 /// single integer scalar, or when we are converting a "vector union" to a
1651 /// vector with insert/extractelement instructions.
1653 /// Offset is an offset from the original alloca, in bits that need to be
1654 /// shifted to the right.
1655 Value *SROA::ConvertScalar_InsertValue(Value *SV, Value *Old,
1656 uint64_t Offset, IRBuilder<> &Builder) {
1658 // Convert the stored type to the actual type, shift it left to insert
1659 // then 'or' into place.
1660 const Type *AllocaType = Old->getType();
1661 LLVMContext &Context = Old->getContext();
1663 if (const VectorType *VTy = dyn_cast<VectorType>(AllocaType)) {
1664 uint64_t VecSize = TD->getTypeAllocSizeInBits(VTy);
1665 uint64_t ValSize = TD->getTypeAllocSizeInBits(SV->getType());
1667 // Changing the whole vector with memset or with an access of a different
1669 if (ValSize == VecSize)
1670 return Builder.CreateBitCast(SV, AllocaType, "tmp");
1672 uint64_t EltSize = TD->getTypeAllocSizeInBits(VTy->getElementType());
1674 // Must be an element insertion.
1675 unsigned Elt = Offset/EltSize;
1677 if (SV->getType() != VTy->getElementType())
1678 SV = Builder.CreateBitCast(SV, VTy->getElementType(), "tmp");
1680 SV = Builder.CreateInsertElement(Old, SV,
1681 ConstantInt::get(Type::getInt32Ty(SV->getContext()), Elt),
1686 // If SV is a first-class aggregate value, insert each value recursively.
1687 if (const StructType *ST = dyn_cast<StructType>(SV->getType())) {
1688 const StructLayout &Layout = *TD->getStructLayout(ST);
1689 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) {
1690 Value *Elt = Builder.CreateExtractValue(SV, i, "tmp");
1691 Old = ConvertScalar_InsertValue(Elt, Old,
1692 Offset+Layout.getElementOffsetInBits(i),
1698 if (const ArrayType *AT = dyn_cast<ArrayType>(SV->getType())) {
1699 uint64_t EltSize = TD->getTypeAllocSizeInBits(AT->getElementType());
1700 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
1701 Value *Elt = Builder.CreateExtractValue(SV, i, "tmp");
1702 Old = ConvertScalar_InsertValue(Elt, Old, Offset+i*EltSize, Builder);
1707 // If SV is a float, convert it to the appropriate integer type.
1708 // If it is a pointer, do the same.
1709 unsigned SrcWidth = TD->getTypeSizeInBits(SV->getType());
1710 unsigned DestWidth = TD->getTypeSizeInBits(AllocaType);
1711 unsigned SrcStoreWidth = TD->getTypeStoreSizeInBits(SV->getType());
1712 unsigned DestStoreWidth = TD->getTypeStoreSizeInBits(AllocaType);
1713 if (SV->getType()->isFloatingPoint() || isa<VectorType>(SV->getType()))
1714 SV = Builder.CreateBitCast(SV,
1715 IntegerType::get(SV->getContext(),SrcWidth), "tmp");
1716 else if (isa<PointerType>(SV->getType()))
1717 SV = Builder.CreatePtrToInt(SV, TD->getIntPtrType(SV->getContext()), "tmp");
1719 // Zero extend or truncate the value if needed.
1720 if (SV->getType() != AllocaType) {
1721 if (SV->getType()->getPrimitiveSizeInBits() <
1722 AllocaType->getPrimitiveSizeInBits())
1723 SV = Builder.CreateZExt(SV, AllocaType, "tmp");
1725 // Truncation may be needed if storing more than the alloca can hold
1726 // (undefined behavior).
1727 SV = Builder.CreateTrunc(SV, AllocaType, "tmp");
1728 SrcWidth = DestWidth;
1729 SrcStoreWidth = DestStoreWidth;
1733 // If this is a big-endian system and the store is narrower than the
1734 // full alloca type, we need to do a shift to get the right bits.
1736 if (TD->isBigEndian()) {
1737 // On big-endian machines, the lowest bit is stored at the bit offset
1738 // from the pointer given by getTypeStoreSizeInBits. This matters for
1739 // integers with a bitwidth that is not a multiple of 8.
1740 ShAmt = DestStoreWidth - SrcStoreWidth - Offset;
1745 // Note: we support negative bitwidths (with shr) which are not defined.
1746 // We do this to support (f.e.) stores off the end of a structure where
1747 // only some bits in the structure are set.
1748 APInt Mask(APInt::getLowBitsSet(DestWidth, SrcWidth));
1749 if (ShAmt > 0 && (unsigned)ShAmt < DestWidth) {
1750 SV = Builder.CreateShl(SV, ConstantInt::get(SV->getType(),
1753 } else if (ShAmt < 0 && (unsigned)-ShAmt < DestWidth) {
1754 SV = Builder.CreateLShr(SV, ConstantInt::get(SV->getType(),
1756 Mask = Mask.lshr(-ShAmt);
1759 // Mask out the bits we are about to insert from the old value, and or
1761 if (SrcWidth != DestWidth) {
1762 assert(DestWidth > SrcWidth);
1763 Old = Builder.CreateAnd(Old, ConstantInt::get(Context, ~Mask), "mask");
1764 SV = Builder.CreateOr(Old, SV, "ins");
1771 /// PointsToConstantGlobal - Return true if V (possibly indirectly) points to
1772 /// some part of a constant global variable. This intentionally only accepts
1773 /// constant expressions because we don't can't rewrite arbitrary instructions.
1774 static bool PointsToConstantGlobal(Value *V) {
1775 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
1776 return GV->isConstant();
1777 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
1778 if (CE->getOpcode() == Instruction::BitCast ||
1779 CE->getOpcode() == Instruction::GetElementPtr)
1780 return PointsToConstantGlobal(CE->getOperand(0));
1784 /// isOnlyCopiedFromConstantGlobal - Recursively walk the uses of a (derived)
1785 /// pointer to an alloca. Ignore any reads of the pointer, return false if we
1786 /// see any stores or other unknown uses. If we see pointer arithmetic, keep
1787 /// track of whether it moves the pointer (with isOffset) but otherwise traverse
1788 /// the uses. If we see a memcpy/memmove that targets an unoffseted pointer to
1789 /// the alloca, and if the source pointer is a pointer to a constant global, we
1790 /// can optimize this.
1791 static bool isOnlyCopiedFromConstantGlobal(Value *V, Instruction *&TheCopy,
1793 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) {
1794 if (LoadInst *LI = dyn_cast<LoadInst>(*UI))
1795 // Ignore non-volatile loads, they are always ok.
1796 if (!LI->isVolatile())
1799 if (BitCastInst *BCI = dyn_cast<BitCastInst>(*UI)) {
1800 // If uses of the bitcast are ok, we are ok.
1801 if (!isOnlyCopiedFromConstantGlobal(BCI, TheCopy, isOffset))
1805 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(*UI)) {
1806 // If the GEP has all zero indices, it doesn't offset the pointer. If it
1807 // doesn't, it does.
1808 if (!isOnlyCopiedFromConstantGlobal(GEP, TheCopy,
1809 isOffset || !GEP->hasAllZeroIndices()))
1814 // If this is isn't our memcpy/memmove, reject it as something we can't
1816 if (!isa<MemTransferInst>(*UI))
1819 // If we already have seen a copy, reject the second one.
1820 if (TheCopy) return false;
1822 // If the pointer has been offset from the start of the alloca, we can't
1823 // safely handle this.
1824 if (isOffset) return false;
1826 // If the memintrinsic isn't using the alloca as the dest, reject it.
1827 if (UI.getOperandNo() != 1) return false;
1829 MemIntrinsic *MI = cast<MemIntrinsic>(*UI);
1831 // If the source of the memcpy/move is not a constant global, reject it.
1832 if (!PointsToConstantGlobal(MI->getOperand(2)))
1835 // Otherwise, the transform is safe. Remember the copy instruction.
1841 /// isOnlyCopiedFromConstantGlobal - Return true if the specified alloca is only
1842 /// modified by a copy from a constant global. If we can prove this, we can
1843 /// replace any uses of the alloca with uses of the global directly.
1844 Instruction *SROA::isOnlyCopiedFromConstantGlobal(AllocationInst *AI) {
1845 Instruction *TheCopy = 0;
1846 if (::isOnlyCopiedFromConstantGlobal(AI, TheCopy, false))