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"
44 #include "llvm/ADT/StringExtras.h"
47 STATISTIC(NumReplaced, "Number of allocas broken up");
48 STATISTIC(NumPromoted, "Number of allocas promoted");
49 STATISTIC(NumConverted, "Number of aggregates converted to scalar");
50 STATISTIC(NumGlobals, "Number of allocas copied from constant global");
53 struct VISIBILITY_HIDDEN SROA : public FunctionPass {
54 static char ID; // Pass identification, replacement for typeid
55 explicit SROA(signed T = -1) : FunctionPass(&ID) {
62 bool runOnFunction(Function &F);
64 bool performScalarRepl(Function &F);
65 bool performPromotion(Function &F);
67 // getAnalysisUsage - This pass does not require any passes, but we know it
68 // will not alter the CFG, so say so.
69 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
70 AU.addRequired<DominatorTree>();
71 AU.addRequired<DominanceFrontier>();
72 AU.addRequired<TargetData>();
79 /// AllocaInfo - When analyzing uses of an alloca instruction, this captures
80 /// information about the uses. All these fields are initialized to false
81 /// and set to true when something is learned.
83 /// isUnsafe - This is set to true if the alloca cannot be SROA'd.
86 /// needsCleanup - This is set to true if there is some use of the alloca
87 /// that requires cleanup.
88 bool needsCleanup : 1;
90 /// isMemCpySrc - This is true if this aggregate is memcpy'd from.
93 /// isMemCpyDst - This is true if this aggregate is memcpy'd into.
97 : isUnsafe(false), needsCleanup(false),
98 isMemCpySrc(false), isMemCpyDst(false) {}
101 unsigned SRThreshold;
103 void MarkUnsafe(AllocaInfo &I) { I.isUnsafe = true; }
105 int isSafeAllocaToScalarRepl(AllocationInst *AI);
107 void isSafeUseOfAllocation(Instruction *User, AllocationInst *AI,
109 void isSafeElementUse(Value *Ptr, bool isFirstElt, AllocationInst *AI,
111 void isSafeMemIntrinsicOnAllocation(MemIntrinsic *MI, AllocationInst *AI,
112 unsigned OpNo, AllocaInfo &Info);
113 void isSafeUseOfBitCastedAllocation(BitCastInst *User, AllocationInst *AI,
116 void DoScalarReplacement(AllocationInst *AI,
117 std::vector<AllocationInst*> &WorkList);
118 void CleanupGEP(GetElementPtrInst *GEP);
119 void CleanupAllocaUsers(AllocationInst *AI);
120 AllocaInst *AddNewAlloca(Function &F, const Type *Ty, AllocationInst *Base);
122 void RewriteBitCastUserOfAlloca(Instruction *BCInst, AllocationInst *AI,
123 SmallVector<AllocaInst*, 32> &NewElts);
125 void RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *BCInst,
127 SmallVector<AllocaInst*, 32> &NewElts);
128 void RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocationInst *AI,
129 SmallVector<AllocaInst*, 32> &NewElts);
130 void RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocationInst *AI,
131 SmallVector<AllocaInst*, 32> &NewElts);
133 bool CanConvertToScalar(Value *V, bool &IsNotTrivial, const Type *&VecTy,
134 bool &SawVec, uint64_t Offset, unsigned AllocaSize);
135 void ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, uint64_t Offset);
136 Value *ConvertScalar_ExtractValue(Value *NV, const Type *ToType,
137 uint64_t Offset, IRBuilder<> &Builder);
138 Value *ConvertScalar_InsertValue(Value *StoredVal, Value *ExistingVal,
139 uint64_t Offset, IRBuilder<> &Builder);
140 static Instruction *isOnlyCopiedFromConstantGlobal(AllocationInst *AI);
145 static RegisterPass<SROA> X("scalarrepl", "Scalar Replacement of Aggregates");
147 // Public interface to the ScalarReplAggregates pass
148 FunctionPass *llvm::createScalarReplAggregatesPass(signed int Threshold) {
149 return new SROA(Threshold);
153 bool SROA::runOnFunction(Function &F) {
154 TD = &getAnalysis<TargetData>();
156 bool Changed = performPromotion(F);
158 bool LocalChange = performScalarRepl(F);
159 if (!LocalChange) break; // No need to repromote if no scalarrepl
161 LocalChange = performPromotion(F);
162 if (!LocalChange) break; // No need to re-scalarrepl if no promotion
169 bool SROA::performPromotion(Function &F) {
170 std::vector<AllocaInst*> Allocas;
171 DominatorTree &DT = getAnalysis<DominatorTree>();
172 DominanceFrontier &DF = getAnalysis<DominanceFrontier>();
174 BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function
176 bool Changed = false;
181 // Find allocas that are safe to promote, by looking at all instructions in
183 for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I)
184 if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) // Is it an alloca?
185 if (isAllocaPromotable(AI))
186 Allocas.push_back(AI);
188 if (Allocas.empty()) break;
190 PromoteMemToReg(Allocas, DT, DF, Context);
191 NumPromoted += Allocas.size();
198 /// getNumSAElements - Return the number of elements in the specific struct or
200 static uint64_t getNumSAElements(const Type *T) {
201 if (const StructType *ST = dyn_cast<StructType>(T))
202 return ST->getNumElements();
203 return cast<ArrayType>(T)->getNumElements();
206 // performScalarRepl - This algorithm is a simple worklist driven algorithm,
207 // which runs on all of the malloc/alloca instructions in the function, removing
208 // them if they are only used by getelementptr instructions.
210 bool SROA::performScalarRepl(Function &F) {
211 std::vector<AllocationInst*> WorkList;
213 // Scan the entry basic block, adding any alloca's and mallocs to the worklist
214 BasicBlock &BB = F.getEntryBlock();
215 for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I)
216 if (AllocationInst *A = dyn_cast<AllocationInst>(I))
217 WorkList.push_back(A);
219 // Process the worklist
220 bool Changed = false;
221 while (!WorkList.empty()) {
222 AllocationInst *AI = WorkList.back();
225 // Handle dead allocas trivially. These can be formed by SROA'ing arrays
226 // with unused elements.
227 if (AI->use_empty()) {
228 AI->eraseFromParent();
232 // If this alloca is impossible for us to promote, reject it early.
233 if (AI->isArrayAllocation() || !AI->getAllocatedType()->isSized())
236 // Check to see if this allocation is only modified by a memcpy/memmove from
237 // a constant global. If this is the case, we can change all users to use
238 // the constant global instead. This is commonly produced by the CFE by
239 // constructs like "void foo() { int A[] = {1,2,3,4,5,6,7,8,9...}; }" if 'A'
240 // is only subsequently read.
241 if (Instruction *TheCopy = isOnlyCopiedFromConstantGlobal(AI)) {
242 DOUT << "Found alloca equal to global: " << *AI;
243 DOUT << " memcpy = " << *TheCopy;
244 Constant *TheSrc = cast<Constant>(TheCopy->getOperand(2));
245 AI->replaceAllUsesWith(
246 Context->getConstantExprBitCast(TheSrc, AI->getType()));
247 TheCopy->eraseFromParent(); // Don't mutate the global.
248 AI->eraseFromParent();
254 // Check to see if we can perform the core SROA transformation. We cannot
255 // transform the allocation instruction if it is an array allocation
256 // (allocations OF arrays are ok though), and an allocation of a scalar
257 // value cannot be decomposed at all.
258 uint64_t AllocaSize = TD->getTypeAllocSize(AI->getAllocatedType());
260 // Do not promote any struct whose size is too big.
261 if (AllocaSize > SRThreshold) continue;
263 if ((isa<StructType>(AI->getAllocatedType()) ||
264 isa<ArrayType>(AI->getAllocatedType())) &&
265 // Do not promote any struct into more than "32" separate vars.
266 getNumSAElements(AI->getAllocatedType()) <= SRThreshold/4) {
267 // Check that all of the users of the allocation are capable of being
269 switch (isSafeAllocaToScalarRepl(AI)) {
270 default: LLVM_UNREACHABLE("Unexpected value!");
271 case 0: // Not safe to scalar replace.
273 case 1: // Safe, but requires cleanup/canonicalizations first
274 CleanupAllocaUsers(AI);
276 case 3: // Safe to scalar replace.
277 DoScalarReplacement(AI, WorkList);
283 // If we can turn this aggregate value (potentially with casts) into a
284 // simple scalar value that can be mem2reg'd into a register value.
285 // IsNotTrivial tracks whether this is something that mem2reg could have
286 // promoted itself. If so, we don't want to transform it needlessly. Note
287 // that we can't just check based on the type: the alloca may be of an i32
288 // but that has pointer arithmetic to set byte 3 of it or something.
289 bool IsNotTrivial = false;
290 const Type *VectorTy = 0;
291 bool HadAVector = false;
292 if (CanConvertToScalar(AI, IsNotTrivial, VectorTy, HadAVector,
293 0, unsigned(AllocaSize)) && IsNotTrivial) {
295 // If we were able to find a vector type that can handle this with
296 // insert/extract elements, and if there was at least one use that had
297 // a vector type, promote this to a vector. We don't want to promote
298 // random stuff that doesn't use vectors (e.g. <9 x double>) because then
299 // we just get a lot of insert/extracts. If at least one vector is
300 // involved, then we probably really do have a union of vector/array.
301 if (VectorTy && isa<VectorType>(VectorTy) && HadAVector) {
302 DOUT << "CONVERT TO VECTOR: " << *AI << " TYPE = " << *VectorTy <<"\n";
304 // Create and insert the vector alloca.
305 NewAI = new AllocaInst(VectorTy, 0, "", AI->getParent()->begin());
306 ConvertUsesToScalar(AI, NewAI, 0);
308 DOUT << "CONVERT TO SCALAR INTEGER: " << *AI << "\n";
310 // Create and insert the integer alloca.
311 const Type *NewTy = Context->getIntegerType(AllocaSize*8);
312 NewAI = new AllocaInst(NewTy, 0, "", AI->getParent()->begin());
313 ConvertUsesToScalar(AI, NewAI, 0);
316 AI->eraseFromParent();
322 // Otherwise, couldn't process this alloca.
328 /// DoScalarReplacement - This alloca satisfied the isSafeAllocaToScalarRepl
329 /// predicate, do SROA now.
330 void SROA::DoScalarReplacement(AllocationInst *AI,
331 std::vector<AllocationInst*> &WorkList) {
332 DOUT << "Found inst to SROA: " << *AI;
333 SmallVector<AllocaInst*, 32> ElementAllocas;
334 if (const StructType *ST = dyn_cast<StructType>(AI->getAllocatedType())) {
335 ElementAllocas.reserve(ST->getNumContainedTypes());
336 for (unsigned i = 0, e = ST->getNumContainedTypes(); i != e; ++i) {
337 AllocaInst *NA = new AllocaInst(ST->getContainedType(i), 0,
339 AI->getName() + "." + utostr(i), AI);
340 ElementAllocas.push_back(NA);
341 WorkList.push_back(NA); // Add to worklist for recursive processing
344 const ArrayType *AT = cast<ArrayType>(AI->getAllocatedType());
345 ElementAllocas.reserve(AT->getNumElements());
346 const Type *ElTy = AT->getElementType();
347 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
348 AllocaInst *NA = new AllocaInst(ElTy, 0, AI->getAlignment(),
349 AI->getName() + "." + utostr(i), AI);
350 ElementAllocas.push_back(NA);
351 WorkList.push_back(NA); // Add to worklist for recursive processing
355 // Now that we have created the alloca instructions that we want to use,
356 // expand the getelementptr instructions to use them.
358 while (!AI->use_empty()) {
359 Instruction *User = cast<Instruction>(AI->use_back());
360 if (BitCastInst *BCInst = dyn_cast<BitCastInst>(User)) {
361 RewriteBitCastUserOfAlloca(BCInst, AI, ElementAllocas);
362 BCInst->eraseFromParent();
367 // %res = load { i32, i32 }* %alloc
369 // %load.0 = load i32* %alloc.0
370 // %insert.0 insertvalue { i32, i32 } zeroinitializer, i32 %load.0, 0
371 // %load.1 = load i32* %alloc.1
372 // %insert = insertvalue { i32, i32 } %insert.0, i32 %load.1, 1
373 // (Also works for arrays instead of structs)
374 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
375 Value *Insert = Context->getUndef(LI->getType());
376 for (unsigned i = 0, e = ElementAllocas.size(); i != e; ++i) {
377 Value *Load = new LoadInst(ElementAllocas[i], "load", LI);
378 Insert = InsertValueInst::Create(Insert, Load, i, "insert", LI);
380 LI->replaceAllUsesWith(Insert);
381 LI->eraseFromParent();
386 // store { i32, i32 } %val, { i32, i32 }* %alloc
388 // %val.0 = extractvalue { i32, i32 } %val, 0
389 // store i32 %val.0, i32* %alloc.0
390 // %val.1 = extractvalue { i32, i32 } %val, 1
391 // store i32 %val.1, i32* %alloc.1
392 // (Also works for arrays instead of structs)
393 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
394 Value *Val = SI->getOperand(0);
395 for (unsigned i = 0, e = ElementAllocas.size(); i != e; ++i) {
396 Value *Extract = ExtractValueInst::Create(Val, i, Val->getName(), SI);
397 new StoreInst(Extract, ElementAllocas[i], SI);
399 SI->eraseFromParent();
403 GetElementPtrInst *GEPI = cast<GetElementPtrInst>(User);
404 // We now know that the GEP is of the form: GEP <ptr>, 0, <cst>
406 (unsigned)cast<ConstantInt>(GEPI->getOperand(2))->getZExtValue();
408 assert(Idx < ElementAllocas.size() && "Index out of range?");
409 AllocaInst *AllocaToUse = ElementAllocas[Idx];
412 if (GEPI->getNumOperands() == 3) {
413 // Do not insert a new getelementptr instruction with zero indices, only
414 // to have it optimized out later.
415 RepValue = AllocaToUse;
417 // We are indexing deeply into the structure, so we still need a
418 // getelement ptr instruction to finish the indexing. This may be
419 // expanded itself once the worklist is rerun.
421 SmallVector<Value*, 8> NewArgs;
422 NewArgs.push_back(Context->getNullValue(Type::Int32Ty));
423 NewArgs.append(GEPI->op_begin()+3, GEPI->op_end());
424 RepValue = GetElementPtrInst::Create(AllocaToUse, NewArgs.begin(),
425 NewArgs.end(), "", GEPI);
426 RepValue->takeName(GEPI);
429 // If this GEP is to the start of the aggregate, check for memcpys.
430 if (Idx == 0 && GEPI->hasAllZeroIndices())
431 RewriteBitCastUserOfAlloca(GEPI, AI, ElementAllocas);
433 // Move all of the users over to the new GEP.
434 GEPI->replaceAllUsesWith(RepValue);
435 // Delete the old GEP
436 GEPI->eraseFromParent();
439 // Finally, delete the Alloca instruction
440 AI->eraseFromParent();
445 /// isSafeElementUse - Check to see if this use is an allowed use for a
446 /// getelementptr instruction of an array aggregate allocation. isFirstElt
447 /// indicates whether Ptr is known to the start of the aggregate.
449 void SROA::isSafeElementUse(Value *Ptr, bool isFirstElt, AllocationInst *AI,
451 for (Value::use_iterator I = Ptr->use_begin(), E = Ptr->use_end();
453 Instruction *User = cast<Instruction>(*I);
454 switch (User->getOpcode()) {
455 case Instruction::Load: break;
456 case Instruction::Store:
457 // Store is ok if storing INTO the pointer, not storing the pointer
458 if (User->getOperand(0) == Ptr) return MarkUnsafe(Info);
460 case Instruction::GetElementPtr: {
461 GetElementPtrInst *GEP = cast<GetElementPtrInst>(User);
462 bool AreAllZeroIndices = isFirstElt;
463 if (GEP->getNumOperands() > 1) {
464 if (!isa<ConstantInt>(GEP->getOperand(1)) ||
465 !cast<ConstantInt>(GEP->getOperand(1))->isZero())
466 // Using pointer arithmetic to navigate the array.
467 return MarkUnsafe(Info);
469 if (AreAllZeroIndices)
470 AreAllZeroIndices = GEP->hasAllZeroIndices();
472 isSafeElementUse(GEP, AreAllZeroIndices, AI, Info);
473 if (Info.isUnsafe) return;
476 case Instruction::BitCast:
478 isSafeUseOfBitCastedAllocation(cast<BitCastInst>(User), AI, Info);
479 if (Info.isUnsafe) return;
482 DOUT << " Transformation preventing inst: " << *User;
483 return MarkUnsafe(Info);
484 case Instruction::Call:
485 if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) {
487 isSafeMemIntrinsicOnAllocation(MI, AI, I.getOperandNo(), Info);
488 if (Info.isUnsafe) return;
492 DOUT << " Transformation preventing inst: " << *User;
493 return MarkUnsafe(Info);
495 DOUT << " Transformation preventing inst: " << *User;
496 return MarkUnsafe(Info);
499 return; // All users look ok :)
502 /// AllUsersAreLoads - Return true if all users of this value are loads.
503 static bool AllUsersAreLoads(Value *Ptr) {
504 for (Value::use_iterator I = Ptr->use_begin(), E = Ptr->use_end();
506 if (cast<Instruction>(*I)->getOpcode() != Instruction::Load)
511 /// isSafeUseOfAllocation - Check to see if this user is an allowed use for an
512 /// aggregate allocation.
514 void SROA::isSafeUseOfAllocation(Instruction *User, AllocationInst *AI,
516 if (BitCastInst *C = dyn_cast<BitCastInst>(User))
517 return isSafeUseOfBitCastedAllocation(C, AI, Info);
519 if (LoadInst *LI = dyn_cast<LoadInst>(User))
520 if (!LI->isVolatile())
521 return;// Loads (returning a first class aggregrate) are always rewritable
523 if (StoreInst *SI = dyn_cast<StoreInst>(User))
524 if (!SI->isVolatile() && SI->getOperand(0) != AI)
525 return;// Store is ok if storing INTO the pointer, not storing the pointer
527 GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User);
529 return MarkUnsafe(Info);
531 gep_type_iterator I = gep_type_begin(GEPI), E = gep_type_end(GEPI);
533 // The GEP is not safe to transform if not of the form "GEP <ptr>, 0, <cst>".
535 I.getOperand() != Context->getNullValue(I.getOperand()->getType())) {
536 return MarkUnsafe(Info);
540 if (I == E) return MarkUnsafe(Info); // ran out of GEP indices??
542 bool IsAllZeroIndices = true;
544 // If the first index is a non-constant index into an array, see if we can
545 // handle it as a special case.
546 if (const ArrayType *AT = dyn_cast<ArrayType>(*I)) {
547 if (!isa<ConstantInt>(I.getOperand())) {
548 IsAllZeroIndices = 0;
549 uint64_t NumElements = AT->getNumElements();
551 // If this is an array index and the index is not constant, we cannot
552 // promote... that is unless the array has exactly one or two elements in
553 // it, in which case we CAN promote it, but we have to canonicalize this
554 // out if this is the only problem.
555 if ((NumElements == 1 || NumElements == 2) &&
556 AllUsersAreLoads(GEPI)) {
557 Info.needsCleanup = true;
558 return; // Canonicalization required!
560 return MarkUnsafe(Info);
564 // Walk through the GEP type indices, checking the types that this indexes
566 for (; I != E; ++I) {
567 // Ignore struct elements, no extra checking needed for these.
568 if (isa<StructType>(*I))
571 ConstantInt *IdxVal = dyn_cast<ConstantInt>(I.getOperand());
572 if (!IdxVal) return MarkUnsafe(Info);
574 // Are all indices still zero?
575 IsAllZeroIndices &= IdxVal->isZero();
577 if (const ArrayType *AT = dyn_cast<ArrayType>(*I)) {
578 // This GEP indexes an array. Verify that this is an in-range constant
579 // integer. Specifically, consider A[0][i]. We cannot know that the user
580 // isn't doing invalid things like allowing i to index an out-of-range
581 // subscript that accesses A[1]. Because of this, we have to reject SROA
582 // of any accesses into structs where any of the components are variables.
583 if (IdxVal->getZExtValue() >= AT->getNumElements())
584 return MarkUnsafe(Info);
585 } else if (const VectorType *VT = dyn_cast<VectorType>(*I)) {
586 if (IdxVal->getZExtValue() >= VT->getNumElements())
587 return MarkUnsafe(Info);
591 // If there are any non-simple uses of this getelementptr, make sure to reject
593 return isSafeElementUse(GEPI, IsAllZeroIndices, AI, Info);
596 /// isSafeMemIntrinsicOnAllocation - Return true if the specified memory
597 /// intrinsic can be promoted by SROA. At this point, we know that the operand
598 /// of the memintrinsic is a pointer to the beginning of the allocation.
599 void SROA::isSafeMemIntrinsicOnAllocation(MemIntrinsic *MI, AllocationInst *AI,
600 unsigned OpNo, AllocaInfo &Info) {
601 // If not constant length, give up.
602 ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength());
603 if (!Length) return MarkUnsafe(Info);
605 // If not the whole aggregate, give up.
606 if (Length->getZExtValue() !=
607 TD->getTypeAllocSize(AI->getType()->getElementType()))
608 return MarkUnsafe(Info);
610 // We only know about memcpy/memset/memmove.
611 if (!isa<MemIntrinsic>(MI))
612 return MarkUnsafe(Info);
614 // Otherwise, we can transform it. Determine whether this is a memcpy/set
615 // into or out of the aggregate.
617 Info.isMemCpyDst = true;
620 Info.isMemCpySrc = true;
624 /// isSafeUseOfBitCastedAllocation - Return true if all users of this bitcast
626 void SROA::isSafeUseOfBitCastedAllocation(BitCastInst *BC, AllocationInst *AI,
628 for (Value::use_iterator UI = BC->use_begin(), E = BC->use_end();
630 if (BitCastInst *BCU = dyn_cast<BitCastInst>(UI)) {
631 isSafeUseOfBitCastedAllocation(BCU, AI, Info);
632 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(UI)) {
633 isSafeMemIntrinsicOnAllocation(MI, AI, UI.getOperandNo(), Info);
634 } else if (StoreInst *SI = dyn_cast<StoreInst>(UI)) {
635 if (SI->isVolatile())
636 return MarkUnsafe(Info);
638 // If storing the entire alloca in one chunk through a bitcasted pointer
639 // to integer, we can transform it. This happens (for example) when you
640 // cast a {i32,i32}* to i64* and store through it. This is similar to the
641 // memcpy case and occurs in various "byval" cases and emulated memcpys.
642 if (isa<IntegerType>(SI->getOperand(0)->getType()) &&
643 TD->getTypeAllocSize(SI->getOperand(0)->getType()) ==
644 TD->getTypeAllocSize(AI->getType()->getElementType())) {
645 Info.isMemCpyDst = true;
648 return MarkUnsafe(Info);
649 } else if (LoadInst *LI = dyn_cast<LoadInst>(UI)) {
650 if (LI->isVolatile())
651 return MarkUnsafe(Info);
653 // If loading the entire alloca in one chunk through a bitcasted pointer
654 // to integer, we can transform it. This happens (for example) when you
655 // cast a {i32,i32}* to i64* and load through it. This is similar to the
656 // memcpy case and occurs in various "byval" cases and emulated memcpys.
657 if (isa<IntegerType>(LI->getType()) &&
658 TD->getTypeAllocSize(LI->getType()) ==
659 TD->getTypeAllocSize(AI->getType()->getElementType())) {
660 Info.isMemCpySrc = true;
663 return MarkUnsafe(Info);
664 } else if (isa<DbgInfoIntrinsic>(UI)) {
665 // If one user is DbgInfoIntrinsic then check if all users are
666 // DbgInfoIntrinsics.
667 if (OnlyUsedByDbgInfoIntrinsics(BC)) {
668 Info.needsCleanup = true;
675 return MarkUnsafe(Info);
677 if (Info.isUnsafe) return;
681 /// RewriteBitCastUserOfAlloca - BCInst (transitively) bitcasts AI, or indexes
682 /// to its first element. Transform users of the cast to use the new values
684 void SROA::RewriteBitCastUserOfAlloca(Instruction *BCInst, AllocationInst *AI,
685 SmallVector<AllocaInst*, 32> &NewElts) {
686 Value::use_iterator UI = BCInst->use_begin(), UE = BCInst->use_end();
688 Instruction *User = cast<Instruction>(*UI++);
689 if (BitCastInst *BCU = dyn_cast<BitCastInst>(User)) {
690 RewriteBitCastUserOfAlloca(BCU, AI, NewElts);
691 if (BCU->use_empty()) BCU->eraseFromParent();
695 if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) {
696 // This must be memcpy/memmove/memset of the entire aggregate.
697 // Split into one per element.
698 RewriteMemIntrinUserOfAlloca(MI, BCInst, AI, NewElts);
702 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
703 // If this is a store of the entire alloca from an integer, rewrite it.
704 RewriteStoreUserOfWholeAlloca(SI, AI, NewElts);
708 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
709 // If this is a load of the entire alloca to an integer, rewrite it.
710 RewriteLoadUserOfWholeAlloca(LI, AI, NewElts);
714 // Otherwise it must be some other user of a gep of the first pointer. Just
715 // leave these alone.
720 /// RewriteMemIntrinUserOfAlloca - MI is a memcpy/memset/memmove from or to AI.
721 /// Rewrite it to copy or set the elements of the scalarized memory.
722 void SROA::RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *BCInst,
724 SmallVector<AllocaInst*, 32> &NewElts) {
726 // If this is a memcpy/memmove, construct the other pointer as the
727 // appropriate type. The "Other" pointer is the pointer that goes to memory
728 // that doesn't have anything to do with the alloca that we are promoting. For
729 // memset, this Value* stays null.
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 = Context->getNullValue(Type::Int32Ty);
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, Context->getConstantInt(Type::Int32Ty, i) };
777 OtherElt = GetElementPtrInst::Create(OtherPtr, Idx, Idx + 2,
778 OtherPtr->getNameStr()+"."+utostr(i),
781 const PointerType *OtherPtrTy = cast<PointerType>(OtherPtr->getType());
782 if (const StructType *ST =
783 dyn_cast<StructType>(OtherPtrTy->getElementType())) {
784 EltOffset = TD->getStructLayout(ST)->getElementOffset(i);
787 cast<SequentialType>(OtherPtr->getType())->getElementType();
788 EltOffset = TD->getTypeAllocSize(EltTy)*i;
791 // The alignment of the other pointer is the guaranteed alignment of the
792 // element, which is affected by both the known alignment of the whole
793 // mem intrinsic and the alignment of the element. If the alignment of
794 // the memcpy (f.e.) is 32 but the element is at a 4-byte offset, then the
795 // known alignment is just 4 bytes.
796 OtherEltAlign = (unsigned)MinAlign(OtherEltAlign, EltOffset);
799 Value *EltPtr = NewElts[i];
800 const Type *EltTy = cast<PointerType>(EltPtr->getType())->getElementType();
802 // If we got down to a scalar, insert a load or store as appropriate.
803 if (EltTy->isSingleValueType()) {
804 if (isa<MemTransferInst>(MI)) {
806 // From Other to Alloca.
807 Value *Elt = new LoadInst(OtherElt, "tmp", false, OtherEltAlign, MI);
808 new StoreInst(Elt, EltPtr, MI);
810 // From Alloca to Other.
811 Value *Elt = new LoadInst(EltPtr, "tmp", MI);
812 new StoreInst(Elt, OtherElt, false, OtherEltAlign, MI);
816 assert(isa<MemSetInst>(MI));
818 // If the stored element is zero (common case), just store a null
821 if (ConstantInt *CI = dyn_cast<ConstantInt>(MI->getOperand(2))) {
823 StoreVal = Context->getNullValue(EltTy); // 0.0, null, 0, <0,0>
825 // If EltTy is a vector type, get the element type.
826 const Type *ValTy = EltTy->getScalarType();
828 // Construct an integer with the right value.
829 unsigned EltSize = TD->getTypeSizeInBits(ValTy);
830 APInt OneVal(EltSize, CI->getZExtValue());
831 APInt TotalVal(OneVal);
833 for (unsigned i = 0; 8*i < EltSize; ++i) {
834 TotalVal = TotalVal.shl(8);
838 // Convert the integer value to the appropriate type.
839 StoreVal = Context->getConstantInt(TotalVal);
840 if (isa<PointerType>(ValTy))
841 StoreVal = Context->getConstantExprIntToPtr(StoreVal, ValTy);
842 else if (ValTy->isFloatingPoint())
843 StoreVal = Context->getConstantExprBitCast(StoreVal, ValTy);
844 assert(StoreVal->getType() == ValTy && "Type mismatch!");
846 // If the requested value was a vector constant, create it.
847 if (EltTy != ValTy) {
848 unsigned NumElts = cast<VectorType>(ValTy)->getNumElements();
849 SmallVector<Constant*, 16> Elts(NumElts, StoreVal);
850 StoreVal = Context->getConstantVector(&Elts[0], NumElts);
853 new StoreInst(StoreVal, EltPtr, MI);
856 // Otherwise, if we're storing a byte variable, use a memset call for
860 // Cast the element pointer to BytePtrTy.
861 if (EltPtr->getType() != BytePtrTy)
862 EltPtr = new BitCastInst(EltPtr, BytePtrTy, EltPtr->getNameStr(), MI);
864 // Cast the other pointer (if we have one) to BytePtrTy.
865 if (OtherElt && OtherElt->getType() != BytePtrTy)
866 OtherElt = new BitCastInst(OtherElt, BytePtrTy,OtherElt->getNameStr(),
869 unsigned EltSize = TD->getTypeAllocSize(EltTy);
871 // Finally, insert the meminst for this element.
872 if (isa<MemTransferInst>(MI)) {
874 SROADest ? EltPtr : OtherElt, // Dest ptr
875 SROADest ? OtherElt : EltPtr, // Src ptr
876 Context->getConstantInt(MI->getOperand(3)->getType(), EltSize), // Size
877 Context->getConstantInt(Type::Int32Ty, OtherEltAlign) // Align
879 CallInst::Create(TheFn, Ops, Ops + 4, "", MI);
881 assert(isa<MemSetInst>(MI));
883 EltPtr, MI->getOperand(2), // Dest, Value,
884 Context->getConstantInt(MI->getOperand(3)->getType(), EltSize), // Size
887 CallInst::Create(TheFn, Ops, Ops + 4, "", MI);
890 MI->eraseFromParent();
893 /// RewriteStoreUserOfWholeAlloca - We found an store of an integer that
894 /// overwrites the entire allocation. Extract out the pieces of the stored
895 /// integer and store them individually.
896 void SROA::RewriteStoreUserOfWholeAlloca(StoreInst *SI,
898 SmallVector<AllocaInst*, 32> &NewElts){
899 // Extract each element out of the integer according to its structure offset
900 // and store the element value to the individual alloca.
901 Value *SrcVal = SI->getOperand(0);
902 const Type *AllocaEltTy = AI->getType()->getElementType();
903 uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy);
905 // If this isn't a store of an integer to the whole alloca, it may be a store
906 // to the first element. Just ignore the store in this case and normal SROA
908 if (!isa<IntegerType>(SrcVal->getType()) ||
909 TD->getTypeAllocSizeInBits(SrcVal->getType()) != AllocaSizeBits)
911 // Handle tail padding by extending the operand
912 if (TD->getTypeSizeInBits(SrcVal->getType()) != AllocaSizeBits)
913 SrcVal = new ZExtInst(SrcVal,
914 Context->getIntegerType(AllocaSizeBits), "", SI);
916 DOUT << "PROMOTING STORE TO WHOLE ALLOCA: " << *AI << *SI;
918 // There are two forms here: AI could be an array or struct. Both cases
919 // have different ways to compute the element offset.
920 if (const StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) {
921 const StructLayout *Layout = TD->getStructLayout(EltSTy);
923 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
924 // Get the number of bits to shift SrcVal to get the value.
925 const Type *FieldTy = EltSTy->getElementType(i);
926 uint64_t Shift = Layout->getElementOffsetInBits(i);
928 if (TD->isBigEndian())
929 Shift = AllocaSizeBits-Shift-TD->getTypeAllocSizeInBits(FieldTy);
931 Value *EltVal = SrcVal;
933 Value *ShiftVal = Context->getConstantInt(EltVal->getType(), Shift);
934 EltVal = BinaryOperator::CreateLShr(EltVal, ShiftVal,
935 "sroa.store.elt", SI);
938 // Truncate down to an integer of the right size.
939 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy);
941 // Ignore zero sized fields like {}, they obviously contain no data.
942 if (FieldSizeBits == 0) continue;
944 if (FieldSizeBits != AllocaSizeBits)
945 EltVal = new TruncInst(EltVal,
946 Context->getIntegerType(FieldSizeBits), "", SI);
947 Value *DestField = NewElts[i];
948 if (EltVal->getType() == FieldTy) {
949 // Storing to an integer field of this size, just do it.
950 } else if (FieldTy->isFloatingPoint() || isa<VectorType>(FieldTy)) {
951 // Bitcast to the right element type (for fp/vector values).
952 EltVal = new BitCastInst(EltVal, FieldTy, "", SI);
954 // Otherwise, bitcast the dest pointer (for aggregates).
955 DestField = new BitCastInst(DestField,
956 Context->getPointerTypeUnqual(EltVal->getType()),
959 new StoreInst(EltVal, DestField, SI);
963 const ArrayType *ATy = cast<ArrayType>(AllocaEltTy);
964 const Type *ArrayEltTy = ATy->getElementType();
965 uint64_t ElementOffset = TD->getTypeAllocSizeInBits(ArrayEltTy);
966 uint64_t ElementSizeBits = TD->getTypeSizeInBits(ArrayEltTy);
970 if (TD->isBigEndian())
971 Shift = AllocaSizeBits-ElementOffset;
975 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
976 // Ignore zero sized fields like {}, they obviously contain no data.
977 if (ElementSizeBits == 0) continue;
979 Value *EltVal = SrcVal;
981 Value *ShiftVal = Context->getConstantInt(EltVal->getType(), Shift);
982 EltVal = BinaryOperator::CreateLShr(EltVal, ShiftVal,
983 "sroa.store.elt", SI);
986 // Truncate down to an integer of the right size.
987 if (ElementSizeBits != AllocaSizeBits)
988 EltVal = new TruncInst(EltVal,
989 Context->getIntegerType(ElementSizeBits),"",SI);
990 Value *DestField = NewElts[i];
991 if (EltVal->getType() == ArrayEltTy) {
992 // Storing to an integer field of this size, just do it.
993 } else if (ArrayEltTy->isFloatingPoint() || isa<VectorType>(ArrayEltTy)) {
994 // Bitcast to the right element type (for fp/vector values).
995 EltVal = new BitCastInst(EltVal, ArrayEltTy, "", SI);
997 // Otherwise, bitcast the dest pointer (for aggregates).
998 DestField = new BitCastInst(DestField,
999 Context->getPointerTypeUnqual(EltVal->getType()),
1002 new StoreInst(EltVal, DestField, SI);
1004 if (TD->isBigEndian())
1005 Shift -= ElementOffset;
1007 Shift += ElementOffset;
1011 SI->eraseFromParent();
1014 /// RewriteLoadUserOfWholeAlloca - We found an load of the entire allocation to
1015 /// an integer. Load the individual pieces to form the aggregate value.
1016 void SROA::RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocationInst *AI,
1017 SmallVector<AllocaInst*, 32> &NewElts) {
1018 // Extract each element out of the NewElts according to its structure offset
1019 // and form the result value.
1020 const Type *AllocaEltTy = AI->getType()->getElementType();
1021 uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy);
1023 // If this isn't a load of the whole alloca to an integer, it may be a load
1024 // of the first element. Just ignore the load in this case and normal SROA
1026 if (!isa<IntegerType>(LI->getType()) ||
1027 TD->getTypeAllocSizeInBits(LI->getType()) != AllocaSizeBits)
1030 DOUT << "PROMOTING LOAD OF WHOLE ALLOCA: " << *AI << *LI;
1032 // There are two forms here: AI could be an array or struct. Both cases
1033 // have different ways to compute the element offset.
1034 const StructLayout *Layout = 0;
1035 uint64_t ArrayEltBitOffset = 0;
1036 if (const StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) {
1037 Layout = TD->getStructLayout(EltSTy);
1039 const Type *ArrayEltTy = cast<ArrayType>(AllocaEltTy)->getElementType();
1040 ArrayEltBitOffset = TD->getTypeAllocSizeInBits(ArrayEltTy);
1044 Context->getNullValue(Context->getIntegerType(AllocaSizeBits));
1046 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
1047 // Load the value from the alloca. If the NewElt is an aggregate, cast
1048 // the pointer to an integer of the same size before doing the load.
1049 Value *SrcField = NewElts[i];
1050 const Type *FieldTy =
1051 cast<PointerType>(SrcField->getType())->getElementType();
1052 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy);
1054 // Ignore zero sized fields like {}, they obviously contain no data.
1055 if (FieldSizeBits == 0) continue;
1057 const IntegerType *FieldIntTy = Context->getIntegerType(FieldSizeBits);
1058 if (!isa<IntegerType>(FieldTy) && !FieldTy->isFloatingPoint() &&
1059 !isa<VectorType>(FieldTy))
1060 SrcField = new BitCastInst(SrcField,
1061 Context->getPointerTypeUnqual(FieldIntTy),
1063 SrcField = new LoadInst(SrcField, "sroa.load.elt", LI);
1065 // If SrcField is a fp or vector of the right size but that isn't an
1066 // integer type, bitcast to an integer so we can shift it.
1067 if (SrcField->getType() != FieldIntTy)
1068 SrcField = new BitCastInst(SrcField, FieldIntTy, "", LI);
1070 // Zero extend the field to be the same size as the final alloca so that
1071 // we can shift and insert it.
1072 if (SrcField->getType() != ResultVal->getType())
1073 SrcField = new ZExtInst(SrcField, ResultVal->getType(), "", LI);
1075 // Determine the number of bits to shift SrcField.
1077 if (Layout) // Struct case.
1078 Shift = Layout->getElementOffsetInBits(i);
1080 Shift = i*ArrayEltBitOffset;
1082 if (TD->isBigEndian())
1083 Shift = AllocaSizeBits-Shift-FieldIntTy->getBitWidth();
1086 Value *ShiftVal = Context->getConstantInt(SrcField->getType(), Shift);
1087 SrcField = BinaryOperator::CreateShl(SrcField, ShiftVal, "", LI);
1090 ResultVal = BinaryOperator::CreateOr(SrcField, ResultVal, "", LI);
1093 // Handle tail padding by truncating the result
1094 if (TD->getTypeSizeInBits(LI->getType()) != AllocaSizeBits)
1095 ResultVal = new TruncInst(ResultVal, LI->getType(), "", LI);
1097 LI->replaceAllUsesWith(ResultVal);
1098 LI->eraseFromParent();
1102 /// HasPadding - Return true if the specified type has any structure or
1103 /// alignment padding, false otherwise.
1104 static bool HasPadding(const Type *Ty, const TargetData &TD) {
1105 if (const StructType *STy = dyn_cast<StructType>(Ty)) {
1106 const StructLayout *SL = TD.getStructLayout(STy);
1107 unsigned PrevFieldBitOffset = 0;
1108 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
1109 unsigned FieldBitOffset = SL->getElementOffsetInBits(i);
1111 // Padding in sub-elements?
1112 if (HasPadding(STy->getElementType(i), TD))
1115 // Check to see if there is any padding between this element and the
1118 unsigned PrevFieldEnd =
1119 PrevFieldBitOffset+TD.getTypeSizeInBits(STy->getElementType(i-1));
1120 if (PrevFieldEnd < FieldBitOffset)
1124 PrevFieldBitOffset = FieldBitOffset;
1127 // Check for tail padding.
1128 if (unsigned EltCount = STy->getNumElements()) {
1129 unsigned PrevFieldEnd = PrevFieldBitOffset +
1130 TD.getTypeSizeInBits(STy->getElementType(EltCount-1));
1131 if (PrevFieldEnd < SL->getSizeInBits())
1135 } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
1136 return HasPadding(ATy->getElementType(), TD);
1137 } else if (const VectorType *VTy = dyn_cast<VectorType>(Ty)) {
1138 return HasPadding(VTy->getElementType(), TD);
1140 return TD.getTypeSizeInBits(Ty) != TD.getTypeAllocSizeInBits(Ty);
1143 /// isSafeStructAllocaToScalarRepl - Check to see if the specified allocation of
1144 /// an aggregate can be broken down into elements. Return 0 if not, 3 if safe,
1145 /// or 1 if safe after canonicalization has been performed.
1147 int SROA::isSafeAllocaToScalarRepl(AllocationInst *AI) {
1148 // Loop over the use list of the alloca. We can only transform it if all of
1149 // the users are safe to transform.
1152 for (Value::use_iterator I = AI->use_begin(), E = AI->use_end();
1154 isSafeUseOfAllocation(cast<Instruction>(*I), AI, Info);
1155 if (Info.isUnsafe) {
1156 DOUT << "Cannot transform: " << *AI << " due to user: " << **I;
1161 // Okay, we know all the users are promotable. If the aggregate is a memcpy
1162 // source and destination, we have to be careful. In particular, the memcpy
1163 // could be moving around elements that live in structure padding of the LLVM
1164 // types, but may actually be used. In these cases, we refuse to promote the
1166 if (Info.isMemCpySrc && Info.isMemCpyDst &&
1167 HasPadding(AI->getType()->getElementType(), *TD))
1170 // If we require cleanup, return 1, otherwise return 3.
1171 return Info.needsCleanup ? 1 : 3;
1174 /// CleanupGEP - GEP is used by an Alloca, which can be prompted after the GEP
1175 /// is canonicalized here.
1176 void SROA::CleanupGEP(GetElementPtrInst *GEPI) {
1177 gep_type_iterator I = gep_type_begin(GEPI);
1180 const ArrayType *AT = dyn_cast<ArrayType>(*I);
1184 uint64_t NumElements = AT->getNumElements();
1186 if (isa<ConstantInt>(I.getOperand()))
1189 if (NumElements == 1) {
1190 GEPI->setOperand(2, Context->getNullValue(Type::Int32Ty));
1194 assert(NumElements == 2 && "Unhandled case!");
1195 // All users of the GEP must be loads. At each use of the GEP, insert
1196 // two loads of the appropriate indexed GEP and select between them.
1197 Value *IsOne = new ICmpInst(GEPI, ICmpInst::ICMP_NE, I.getOperand(),
1198 Context->getNullValue(I.getOperand()->getType()),
1200 // Insert the new GEP instructions, which are properly indexed.
1201 SmallVector<Value*, 8> Indices(GEPI->op_begin()+1, GEPI->op_end());
1202 Indices[1] = Context->getNullValue(Type::Int32Ty);
1203 Value *ZeroIdx = GetElementPtrInst::Create(GEPI->getOperand(0),
1206 GEPI->getName()+".0", GEPI);
1207 Indices[1] = Context->getConstantInt(Type::Int32Ty, 1);
1208 Value *OneIdx = GetElementPtrInst::Create(GEPI->getOperand(0),
1211 GEPI->getName()+".1", GEPI);
1212 // Replace all loads of the variable index GEP with loads from both
1213 // indexes and a select.
1214 while (!GEPI->use_empty()) {
1215 LoadInst *LI = cast<LoadInst>(GEPI->use_back());
1216 Value *Zero = new LoadInst(ZeroIdx, LI->getName()+".0", LI);
1217 Value *One = new LoadInst(OneIdx , LI->getName()+".1", LI);
1218 Value *R = SelectInst::Create(IsOne, One, Zero, LI->getName(), LI);
1219 LI->replaceAllUsesWith(R);
1220 LI->eraseFromParent();
1222 GEPI->eraseFromParent();
1226 /// CleanupAllocaUsers - If SROA reported that it can promote the specified
1227 /// allocation, but only if cleaned up, perform the cleanups required.
1228 void SROA::CleanupAllocaUsers(AllocationInst *AI) {
1229 // At this point, we know that the end result will be SROA'd and promoted, so
1230 // we can insert ugly code if required so long as sroa+mem2reg will clean it
1232 for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end();
1235 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(U))
1238 Instruction *I = cast<Instruction>(U);
1239 SmallVector<DbgInfoIntrinsic *, 2> DbgInUses;
1240 if (!isa<StoreInst>(I) && OnlyUsedByDbgInfoIntrinsics(I, &DbgInUses)) {
1241 // Safe to remove debug info uses.
1242 while (!DbgInUses.empty()) {
1243 DbgInfoIntrinsic *DI = DbgInUses.back(); DbgInUses.pop_back();
1244 DI->eraseFromParent();
1246 I->eraseFromParent();
1252 /// MergeInType - Add the 'In' type to the accumulated type (Accum) so far at
1253 /// the offset specified by Offset (which is specified in bytes).
1255 /// There are two cases we handle here:
1256 /// 1) A union of vector types of the same size and potentially its elements.
1257 /// Here we turn element accesses into insert/extract element operations.
1258 /// This promotes a <4 x float> with a store of float to the third element
1259 /// into a <4 x float> that uses insert element.
1260 /// 2) A fully general blob of memory, which we turn into some (potentially
1261 /// large) integer type with extract and insert operations where the loads
1262 /// and stores would mutate the memory.
1263 static void MergeInType(const Type *In, uint64_t Offset, const Type *&VecTy,
1264 unsigned AllocaSize, const TargetData &TD,
1265 LLVMContext *Context) {
1266 // If this could be contributing to a vector, analyze it.
1267 if (VecTy != Type::VoidTy) { // either null or a vector type.
1269 // If the In type is a vector that is the same size as the alloca, see if it
1270 // matches the existing VecTy.
1271 if (const VectorType *VInTy = dyn_cast<VectorType>(In)) {
1272 if (VInTy->getBitWidth()/8 == AllocaSize && Offset == 0) {
1273 // If we're storing/loading a vector of the right size, allow it as a
1274 // vector. If this the first vector we see, remember the type so that
1275 // we know the element size.
1280 } else if (In == Type::FloatTy || In == Type::DoubleTy ||
1281 (isa<IntegerType>(In) && In->getPrimitiveSizeInBits() >= 8 &&
1282 isPowerOf2_32(In->getPrimitiveSizeInBits()))) {
1283 // If we're accessing something that could be an element of a vector, see
1284 // if the implied vector agrees with what we already have and if Offset is
1285 // compatible with it.
1286 unsigned EltSize = In->getPrimitiveSizeInBits()/8;
1287 if (Offset % EltSize == 0 &&
1288 AllocaSize % EltSize == 0 &&
1290 cast<VectorType>(VecTy)->getElementType()
1291 ->getPrimitiveSizeInBits()/8 == EltSize)) {
1293 VecTy = Context->getVectorType(In, AllocaSize/EltSize);
1299 // Otherwise, we have a case that we can't handle with an optimized vector
1300 // form. We can still turn this into a large integer.
1301 VecTy = Type::VoidTy;
1304 /// CanConvertToScalar - V is a pointer. If we can convert the pointee and all
1305 /// its accesses to use a to single vector type, return true, and set VecTy to
1306 /// the new type. If we could convert the alloca into a single promotable
1307 /// integer, return true but set VecTy to VoidTy. Further, if the use is not a
1308 /// completely trivial use that mem2reg could promote, set IsNotTrivial. Offset
1309 /// is the current offset from the base of the alloca being analyzed.
1311 /// If we see at least one access to the value that is as a vector type, set the
1314 bool SROA::CanConvertToScalar(Value *V, bool &IsNotTrivial, const Type *&VecTy,
1315 bool &SawVec, uint64_t Offset,
1316 unsigned AllocaSize) {
1317 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) {
1318 Instruction *User = cast<Instruction>(*UI);
1320 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1321 // Don't break volatile loads.
1322 if (LI->isVolatile())
1324 MergeInType(LI->getType(), Offset, VecTy, AllocaSize, *TD, Context);
1325 SawVec |= isa<VectorType>(LI->getType());
1329 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
1330 // Storing the pointer, not into the value?
1331 if (SI->getOperand(0) == V || SI->isVolatile()) return 0;
1332 MergeInType(SI->getOperand(0)->getType(), Offset,
1333 VecTy, AllocaSize, *TD, Context);
1334 SawVec |= isa<VectorType>(SI->getOperand(0)->getType());
1338 if (BitCastInst *BCI = dyn_cast<BitCastInst>(User)) {
1339 if (!CanConvertToScalar(BCI, IsNotTrivial, VecTy, SawVec, Offset,
1342 IsNotTrivial = true;
1346 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) {
1347 // If this is a GEP with a variable indices, we can't handle it.
1348 if (!GEP->hasAllConstantIndices())
1351 // Compute the offset that this GEP adds to the pointer.
1352 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end());
1353 uint64_t GEPOffset = TD->getIndexedOffset(GEP->getOperand(0)->getType(),
1354 &Indices[0], Indices.size());
1355 // See if all uses can be converted.
1356 if (!CanConvertToScalar(GEP, IsNotTrivial, VecTy, SawVec,Offset+GEPOffset,
1359 IsNotTrivial = true;
1363 // If this is a constant sized memset of a constant value (e.g. 0) we can
1365 if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) {
1366 // Store of constant value and constant size.
1367 if (isa<ConstantInt>(MSI->getValue()) &&
1368 isa<ConstantInt>(MSI->getLength())) {
1369 IsNotTrivial = true;
1374 // If this is a memcpy or memmove into or out of the whole allocation, we
1375 // can handle it like a load or store of the scalar type.
1376 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) {
1377 if (ConstantInt *Len = dyn_cast<ConstantInt>(MTI->getLength()))
1378 if (Len->getZExtValue() == AllocaSize && Offset == 0) {
1379 IsNotTrivial = true;
1384 // Ignore dbg intrinsic.
1385 if (isa<DbgInfoIntrinsic>(User))
1388 // Otherwise, we cannot handle this!
1396 /// ConvertUsesToScalar - Convert all of the users of Ptr to use the new alloca
1397 /// directly. This happens when we are converting an "integer union" to a
1398 /// single integer scalar, or when we are converting a "vector union" to a
1399 /// vector with insert/extractelement instructions.
1401 /// Offset is an offset from the original alloca, in bits that need to be
1402 /// shifted to the right. By the end of this, there should be no uses of Ptr.
1403 void SROA::ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, uint64_t Offset) {
1404 while (!Ptr->use_empty()) {
1405 Instruction *User = cast<Instruction>(Ptr->use_back());
1407 if (BitCastInst *CI = dyn_cast<BitCastInst>(User)) {
1408 ConvertUsesToScalar(CI, NewAI, Offset);
1409 CI->eraseFromParent();
1413 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) {
1414 // Compute the offset that this GEP adds to the pointer.
1415 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end());
1416 uint64_t GEPOffset = TD->getIndexedOffset(GEP->getOperand(0)->getType(),
1417 &Indices[0], Indices.size());
1418 ConvertUsesToScalar(GEP, NewAI, Offset+GEPOffset*8);
1419 GEP->eraseFromParent();
1423 IRBuilder<> Builder(User->getParent(), User);
1425 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1426 // The load is a bit extract from NewAI shifted right by Offset bits.
1427 Value *LoadedVal = Builder.CreateLoad(NewAI, "tmp");
1429 = ConvertScalar_ExtractValue(LoadedVal, LI->getType(), Offset, Builder);
1430 LI->replaceAllUsesWith(NewLoadVal);
1431 LI->eraseFromParent();
1435 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
1436 assert(SI->getOperand(0) != Ptr && "Consistency error!");
1437 Value *Old = Builder.CreateLoad(NewAI, (NewAI->getName()+".in").c_str());
1438 Value *New = ConvertScalar_InsertValue(SI->getOperand(0), Old, Offset,
1440 Builder.CreateStore(New, NewAI);
1441 SI->eraseFromParent();
1445 // If this is a constant sized memset of a constant value (e.g. 0) we can
1446 // transform it into a store of the expanded constant value.
1447 if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) {
1448 assert(MSI->getRawDest() == Ptr && "Consistency error!");
1449 unsigned NumBytes = cast<ConstantInt>(MSI->getLength())->getZExtValue();
1450 if (NumBytes != 0) {
1451 unsigned Val = cast<ConstantInt>(MSI->getValue())->getZExtValue();
1453 // Compute the value replicated the right number of times.
1454 APInt APVal(NumBytes*8, Val);
1456 // Splat the value if non-zero.
1458 for (unsigned i = 1; i != NumBytes; ++i)
1459 APVal |= APVal << 8;
1461 Value *Old = Builder.CreateLoad(NewAI, (NewAI->getName()+".in").c_str());
1462 Value *New = ConvertScalar_InsertValue(Context->getConstantInt(APVal),
1463 Old, Offset, Builder);
1464 Builder.CreateStore(New, NewAI);
1466 MSI->eraseFromParent();
1470 // If this is a memcpy or memmove into or out of the whole allocation, we
1471 // can handle it like a load or store of the scalar type.
1472 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) {
1473 assert(Offset == 0 && "must be store to start of alloca");
1475 // If the source and destination are both to the same alloca, then this is
1476 // a noop copy-to-self, just delete it. Otherwise, emit a load and store
1478 AllocaInst *OrigAI = cast<AllocaInst>(Ptr->getUnderlyingObject());
1480 if (MTI->getSource()->getUnderlyingObject() != OrigAI) {
1481 // Dest must be OrigAI, change this to be a load from the original
1482 // pointer (bitcasted), then a store to our new alloca.
1483 assert(MTI->getRawDest() == Ptr && "Neither use is of pointer?");
1484 Value *SrcPtr = MTI->getSource();
1485 SrcPtr = Builder.CreateBitCast(SrcPtr, NewAI->getType());
1487 LoadInst *SrcVal = Builder.CreateLoad(SrcPtr, "srcval");
1488 SrcVal->setAlignment(MTI->getAlignment());
1489 Builder.CreateStore(SrcVal, NewAI);
1490 } else if (MTI->getDest()->getUnderlyingObject() != OrigAI) {
1491 // Src must be OrigAI, change this to be a load from NewAI then a store
1492 // through the original dest pointer (bitcasted).
1493 assert(MTI->getRawSource() == Ptr && "Neither use is of pointer?");
1494 LoadInst *SrcVal = Builder.CreateLoad(NewAI, "srcval");
1496 Value *DstPtr = Builder.CreateBitCast(MTI->getDest(), NewAI->getType());
1497 StoreInst *NewStore = Builder.CreateStore(SrcVal, DstPtr);
1498 NewStore->setAlignment(MTI->getAlignment());
1500 // Noop transfer. Src == Dst
1504 MTI->eraseFromParent();
1508 // If user is a dbg info intrinsic then it is safe to remove it.
1509 if (isa<DbgInfoIntrinsic>(User)) {
1510 User->eraseFromParent();
1514 LLVM_UNREACHABLE("Unsupported operation!");
1518 /// ConvertScalar_ExtractValue - Extract a value of type ToType from an integer
1519 /// or vector value FromVal, extracting the bits from the offset specified by
1520 /// Offset. This returns the value, which is of type ToType.
1522 /// This happens when we are converting an "integer union" to a single
1523 /// integer scalar, or when we are converting a "vector union" to a vector with
1524 /// insert/extractelement instructions.
1526 /// Offset is an offset from the original alloca, in bits that need to be
1527 /// shifted to the right.
1528 Value *SROA::ConvertScalar_ExtractValue(Value *FromVal, const Type *ToType,
1529 uint64_t Offset, IRBuilder<> &Builder) {
1530 // If the load is of the whole new alloca, no conversion is needed.
1531 if (FromVal->getType() == ToType && Offset == 0)
1534 // If the result alloca is a vector type, this is either an element
1535 // access or a bitcast to another vector type of the same size.
1536 if (const VectorType *VTy = dyn_cast<VectorType>(FromVal->getType())) {
1537 if (isa<VectorType>(ToType))
1538 return Builder.CreateBitCast(FromVal, ToType, "tmp");
1540 // Otherwise it must be an element access.
1543 unsigned EltSize = TD->getTypeAllocSizeInBits(VTy->getElementType());
1544 Elt = Offset/EltSize;
1545 assert(EltSize*Elt == Offset && "Invalid modulus in validity checking");
1547 // Return the element extracted out of it.
1548 Value *V = Builder.CreateExtractElement(FromVal,
1549 Context->getConstantInt(Type::Int32Ty,Elt),
1551 if (V->getType() != ToType)
1552 V = Builder.CreateBitCast(V, ToType, "tmp");
1556 // If ToType is a first class aggregate, extract out each of the pieces and
1557 // use insertvalue's to form the FCA.
1558 if (const StructType *ST = dyn_cast<StructType>(ToType)) {
1559 const StructLayout &Layout = *TD->getStructLayout(ST);
1560 Value *Res = Context->getUndef(ST);
1561 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) {
1562 Value *Elt = ConvertScalar_ExtractValue(FromVal, ST->getElementType(i),
1563 Offset+Layout.getElementOffsetInBits(i),
1565 Res = Builder.CreateInsertValue(Res, Elt, i, "tmp");
1570 if (const ArrayType *AT = dyn_cast<ArrayType>(ToType)) {
1571 uint64_t EltSize = TD->getTypeAllocSizeInBits(AT->getElementType());
1572 Value *Res = Context->getUndef(AT);
1573 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
1574 Value *Elt = ConvertScalar_ExtractValue(FromVal, AT->getElementType(),
1575 Offset+i*EltSize, Builder);
1576 Res = Builder.CreateInsertValue(Res, Elt, i, "tmp");
1581 // Otherwise, this must be a union that was converted to an integer value.
1582 const IntegerType *NTy = cast<IntegerType>(FromVal->getType());
1584 // If this is a big-endian system and the load is narrower than the
1585 // full alloca type, we need to do a shift to get the right bits.
1587 if (TD->isBigEndian()) {
1588 // On big-endian machines, the lowest bit is stored at the bit offset
1589 // from the pointer given by getTypeStoreSizeInBits. This matters for
1590 // integers with a bitwidth that is not a multiple of 8.
1591 ShAmt = TD->getTypeStoreSizeInBits(NTy) -
1592 TD->getTypeStoreSizeInBits(ToType) - Offset;
1597 // Note: we support negative bitwidths (with shl) which are not defined.
1598 // We do this to support (f.e.) loads off the end of a structure where
1599 // only some bits are used.
1600 if (ShAmt > 0 && (unsigned)ShAmt < NTy->getBitWidth())
1601 FromVal = Builder.CreateLShr(FromVal,
1602 Context->getConstantInt(FromVal->getType(),
1604 else if (ShAmt < 0 && (unsigned)-ShAmt < NTy->getBitWidth())
1605 FromVal = Builder.CreateShl(FromVal,
1606 Context->getConstantInt(FromVal->getType(),
1609 // Finally, unconditionally truncate the integer to the right width.
1610 unsigned LIBitWidth = TD->getTypeSizeInBits(ToType);
1611 if (LIBitWidth < NTy->getBitWidth())
1613 Builder.CreateTrunc(FromVal, Context->getIntegerType(LIBitWidth), "tmp");
1614 else if (LIBitWidth > NTy->getBitWidth())
1616 Builder.CreateZExt(FromVal, Context->getIntegerType(LIBitWidth), "tmp");
1618 // If the result is an integer, this is a trunc or bitcast.
1619 if (isa<IntegerType>(ToType)) {
1621 } else if (ToType->isFloatingPoint() || isa<VectorType>(ToType)) {
1622 // Just do a bitcast, we know the sizes match up.
1623 FromVal = Builder.CreateBitCast(FromVal, ToType, "tmp");
1625 // Otherwise must be a pointer.
1626 FromVal = Builder.CreateIntToPtr(FromVal, ToType, "tmp");
1628 assert(FromVal->getType() == ToType && "Didn't convert right?");
1633 /// ConvertScalar_InsertValue - Insert the value "SV" into the existing integer
1634 /// or vector value "Old" at the offset specified by Offset.
1636 /// This happens when we are converting an "integer union" to a
1637 /// single integer scalar, or when we are converting a "vector union" to a
1638 /// vector with insert/extractelement instructions.
1640 /// Offset is an offset from the original alloca, in bits that need to be
1641 /// shifted to the right.
1642 Value *SROA::ConvertScalar_InsertValue(Value *SV, Value *Old,
1643 uint64_t Offset, IRBuilder<> &Builder) {
1645 // Convert the stored type to the actual type, shift it left to insert
1646 // then 'or' into place.
1647 const Type *AllocaType = Old->getType();
1649 if (const VectorType *VTy = dyn_cast<VectorType>(AllocaType)) {
1650 uint64_t VecSize = TD->getTypeAllocSizeInBits(VTy);
1651 uint64_t ValSize = TD->getTypeAllocSizeInBits(SV->getType());
1653 // Changing the whole vector with memset or with an access of a different
1655 if (ValSize == VecSize)
1656 return Builder.CreateBitCast(SV, AllocaType, "tmp");
1658 uint64_t EltSize = TD->getTypeAllocSizeInBits(VTy->getElementType());
1660 // Must be an element insertion.
1661 unsigned Elt = Offset/EltSize;
1663 if (SV->getType() != VTy->getElementType())
1664 SV = Builder.CreateBitCast(SV, VTy->getElementType(), "tmp");
1666 SV = Builder.CreateInsertElement(Old, SV,
1667 Context->getConstantInt(Type::Int32Ty, Elt),
1672 // If SV is a first-class aggregate value, insert each value recursively.
1673 if (const StructType *ST = dyn_cast<StructType>(SV->getType())) {
1674 const StructLayout &Layout = *TD->getStructLayout(ST);
1675 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) {
1676 Value *Elt = Builder.CreateExtractValue(SV, i, "tmp");
1677 Old = ConvertScalar_InsertValue(Elt, Old,
1678 Offset+Layout.getElementOffsetInBits(i),
1684 if (const ArrayType *AT = dyn_cast<ArrayType>(SV->getType())) {
1685 uint64_t EltSize = TD->getTypeAllocSizeInBits(AT->getElementType());
1686 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
1687 Value *Elt = Builder.CreateExtractValue(SV, i, "tmp");
1688 Old = ConvertScalar_InsertValue(Elt, Old, Offset+i*EltSize, Builder);
1693 // If SV is a float, convert it to the appropriate integer type.
1694 // If it is a pointer, do the same.
1695 unsigned SrcWidth = TD->getTypeSizeInBits(SV->getType());
1696 unsigned DestWidth = TD->getTypeSizeInBits(AllocaType);
1697 unsigned SrcStoreWidth = TD->getTypeStoreSizeInBits(SV->getType());
1698 unsigned DestStoreWidth = TD->getTypeStoreSizeInBits(AllocaType);
1699 if (SV->getType()->isFloatingPoint() || isa<VectorType>(SV->getType()))
1700 SV = Builder.CreateBitCast(SV, Context->getIntegerType(SrcWidth), "tmp");
1701 else if (isa<PointerType>(SV->getType()))
1702 SV = Builder.CreatePtrToInt(SV, TD->getIntPtrType(), "tmp");
1704 // Zero extend or truncate the value if needed.
1705 if (SV->getType() != AllocaType) {
1706 if (SV->getType()->getPrimitiveSizeInBits() <
1707 AllocaType->getPrimitiveSizeInBits())
1708 SV = Builder.CreateZExt(SV, AllocaType, "tmp");
1710 // Truncation may be needed if storing more than the alloca can hold
1711 // (undefined behavior).
1712 SV = Builder.CreateTrunc(SV, AllocaType, "tmp");
1713 SrcWidth = DestWidth;
1714 SrcStoreWidth = DestStoreWidth;
1718 // If this is a big-endian system and the store is narrower than the
1719 // full alloca type, we need to do a shift to get the right bits.
1721 if (TD->isBigEndian()) {
1722 // On big-endian machines, the lowest bit is stored at the bit offset
1723 // from the pointer given by getTypeStoreSizeInBits. This matters for
1724 // integers with a bitwidth that is not a multiple of 8.
1725 ShAmt = DestStoreWidth - SrcStoreWidth - Offset;
1730 // Note: we support negative bitwidths (with shr) which are not defined.
1731 // We do this to support (f.e.) stores off the end of a structure where
1732 // only some bits in the structure are set.
1733 APInt Mask(APInt::getLowBitsSet(DestWidth, SrcWidth));
1734 if (ShAmt > 0 && (unsigned)ShAmt < DestWidth) {
1735 SV = Builder.CreateShl(SV, Context->getConstantInt(SV->getType(),
1738 } else if (ShAmt < 0 && (unsigned)-ShAmt < DestWidth) {
1739 SV = Builder.CreateLShr(SV, Context->getConstantInt(SV->getType(),
1741 Mask = Mask.lshr(-ShAmt);
1744 // Mask out the bits we are about to insert from the old value, and or
1746 if (SrcWidth != DestWidth) {
1747 assert(DestWidth > SrcWidth);
1748 Old = Builder.CreateAnd(Old, Context->getConstantInt(~Mask), "mask");
1749 SV = Builder.CreateOr(Old, SV, "ins");
1756 /// PointsToConstantGlobal - Return true if V (possibly indirectly) points to
1757 /// some part of a constant global variable. This intentionally only accepts
1758 /// constant expressions because we don't can't rewrite arbitrary instructions.
1759 static bool PointsToConstantGlobal(Value *V) {
1760 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
1761 return GV->isConstant();
1762 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
1763 if (CE->getOpcode() == Instruction::BitCast ||
1764 CE->getOpcode() == Instruction::GetElementPtr)
1765 return PointsToConstantGlobal(CE->getOperand(0));
1769 /// isOnlyCopiedFromConstantGlobal - Recursively walk the uses of a (derived)
1770 /// pointer to an alloca. Ignore any reads of the pointer, return false if we
1771 /// see any stores or other unknown uses. If we see pointer arithmetic, keep
1772 /// track of whether it moves the pointer (with isOffset) but otherwise traverse
1773 /// the uses. If we see a memcpy/memmove that targets an unoffseted pointer to
1774 /// the alloca, and if the source pointer is a pointer to a constant global, we
1775 /// can optimize this.
1776 static bool isOnlyCopiedFromConstantGlobal(Value *V, Instruction *&TheCopy,
1778 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) {
1779 if (LoadInst *LI = dyn_cast<LoadInst>(*UI))
1780 // Ignore non-volatile loads, they are always ok.
1781 if (!LI->isVolatile())
1784 if (BitCastInst *BCI = dyn_cast<BitCastInst>(*UI)) {
1785 // If uses of the bitcast are ok, we are ok.
1786 if (!isOnlyCopiedFromConstantGlobal(BCI, TheCopy, isOffset))
1790 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(*UI)) {
1791 // If the GEP has all zero indices, it doesn't offset the pointer. If it
1792 // doesn't, it does.
1793 if (!isOnlyCopiedFromConstantGlobal(GEP, TheCopy,
1794 isOffset || !GEP->hasAllZeroIndices()))
1799 // If this is isn't our memcpy/memmove, reject it as something we can't
1801 if (!isa<MemTransferInst>(*UI))
1804 // If we already have seen a copy, reject the second one.
1805 if (TheCopy) return false;
1807 // If the pointer has been offset from the start of the alloca, we can't
1808 // safely handle this.
1809 if (isOffset) return false;
1811 // If the memintrinsic isn't using the alloca as the dest, reject it.
1812 if (UI.getOperandNo() != 1) return false;
1814 MemIntrinsic *MI = cast<MemIntrinsic>(*UI);
1816 // If the source of the memcpy/move is not a constant global, reject it.
1817 if (!PointsToConstantGlobal(MI->getOperand(2)))
1820 // Otherwise, the transform is safe. Remember the copy instruction.
1826 /// isOnlyCopiedFromConstantGlobal - Return true if the specified alloca is only
1827 /// modified by a copy from a constant global. If we can prove this, we can
1828 /// replace any uses of the alloca with uses of the global directly.
1829 Instruction *SROA::isOnlyCopiedFromConstantGlobal(AllocationInst *AI) {
1830 Instruction *TheCopy = 0;
1831 if (::isOnlyCopiedFromConstantGlobal(AI, TheCopy, false))