1 //===- ScalarReplAggregates.cpp - Scalar Replacement of Aggregates --------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This transformation implements the well known scalar replacement of
11 // aggregates transformation. This xform breaks up alloca instructions of
12 // aggregate type (structure or array) into individual alloca instructions for
13 // each member (if possible). Then, if possible, it transforms the individual
14 // alloca instructions into nice clean scalar SSA form.
16 // This combines a simple SRoA algorithm with the Mem2Reg algorithm because
17 // often interact, especially for C++ programs. As such, iterating between
18 // SRoA, then Mem2Reg until we run out of things to promote works well.
20 //===----------------------------------------------------------------------===//
22 #define DEBUG_TYPE "scalarrepl"
23 #include "llvm/Transforms/Scalar.h"
24 #include "llvm/Constants.h"
25 #include "llvm/DerivedTypes.h"
26 #include "llvm/Function.h"
27 #include "llvm/GlobalVariable.h"
28 #include "llvm/Instructions.h"
29 #include "llvm/IntrinsicInst.h"
30 #include "llvm/LLVMContext.h"
31 #include "llvm/Pass.h"
32 #include "llvm/Analysis/Dominators.h"
33 #include "llvm/Target/TargetData.h"
34 #include "llvm/Transforms/Utils/PromoteMemToReg.h"
35 #include "llvm/Transforms/Utils/Local.h"
36 #include "llvm/Support/Debug.h"
37 #include "llvm/Support/ErrorHandling.h"
38 #include "llvm/Support/GetElementPtrTypeIterator.h"
39 #include "llvm/Support/IRBuilder.h"
40 #include "llvm/Support/MathExtras.h"
41 #include "llvm/Support/raw_ostream.h"
42 #include "llvm/ADT/SmallVector.h"
43 #include "llvm/ADT/Statistic.h"
46 STATISTIC(NumReplaced, "Number of allocas broken up");
47 STATISTIC(NumPromoted, "Number of allocas promoted");
48 STATISTIC(NumConverted, "Number of aggregates converted to scalar");
49 STATISTIC(NumGlobals, "Number of allocas copied from constant global");
52 struct SROA : public FunctionPass {
53 static char ID; // Pass identification, replacement for typeid
54 explicit SROA(signed T = -1) : FunctionPass(&ID) {
61 bool runOnFunction(Function &F);
63 bool performScalarRepl(Function &F);
64 bool performPromotion(Function &F);
66 // getAnalysisUsage - This pass does not require any passes, but we know it
67 // will not alter the CFG, so say so.
68 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
69 AU.addRequired<DominatorTree>();
70 AU.addRequired<DominanceFrontier>();
77 /// AllocaInfo - When analyzing uses of an alloca instruction, this captures
78 /// information about the uses. All these fields are initialized to false
79 /// and set to true when something is learned.
81 /// isUnsafe - This is set to true if the alloca cannot be SROA'd.
84 /// needsCleanup - This is set to true if there is some use of the alloca
85 /// that requires cleanup.
86 bool needsCleanup : 1;
88 /// isMemCpySrc - This is true if this aggregate is memcpy'd from.
91 /// isMemCpyDst - This is true if this aggregate is memcpy'd into.
95 : isUnsafe(false), needsCleanup(false),
96 isMemCpySrc(false), isMemCpyDst(false) {}
101 void MarkUnsafe(AllocaInfo &I) { I.isUnsafe = true; }
103 int isSafeAllocaToScalarRepl(AllocaInst *AI);
105 void isSafeUseOfAllocation(Instruction *User, AllocaInst *AI,
107 void isSafeElementUse(Value *Ptr, bool isFirstElt, AllocaInst *AI,
109 void isSafeMemIntrinsicOnAllocation(MemIntrinsic *MI, AllocaInst *AI,
110 unsigned OpNo, AllocaInfo &Info);
111 void isSafeUseOfBitCastedAllocation(BitCastInst *User, AllocaInst *AI,
114 void DoScalarReplacement(AllocaInst *AI,
115 std::vector<AllocaInst*> &WorkList);
116 void CleanupGEP(GetElementPtrInst *GEP);
117 void CleanupAllocaUsers(AllocaInst *AI);
118 AllocaInst *AddNewAlloca(Function &F, const Type *Ty, AllocaInst *Base);
120 void RewriteBitCastUserOfAlloca(Instruction *BCInst, AllocaInst *AI,
121 SmallVector<AllocaInst*, 32> &NewElts);
123 void RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *BCInst,
125 SmallVector<AllocaInst*, 32> &NewElts);
126 void RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocaInst *AI,
127 SmallVector<AllocaInst*, 32> &NewElts);
128 void RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocaInst *AI,
129 SmallVector<AllocaInst*, 32> &NewElts);
131 bool CanConvertToScalar(Value *V, bool &IsNotTrivial, const Type *&VecTy,
132 bool &SawVec, uint64_t Offset, unsigned AllocaSize);
133 void ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, uint64_t Offset);
134 Value *ConvertScalar_ExtractValue(Value *NV, const Type *ToType,
135 uint64_t Offset, IRBuilder<> &Builder);
136 Value *ConvertScalar_InsertValue(Value *StoredVal, Value *ExistingVal,
137 uint64_t Offset, IRBuilder<> &Builder);
138 static Instruction *isOnlyCopiedFromConstantGlobal(AllocaInst *AI);
143 static RegisterPass<SROA> X("scalarrepl", "Scalar Replacement of Aggregates");
145 // Public interface to the ScalarReplAggregates pass
146 FunctionPass *llvm::createScalarReplAggregatesPass(signed int Threshold) {
147 return new SROA(Threshold);
151 bool SROA::runOnFunction(Function &F) {
152 TD = getAnalysisIfAvailable<TargetData>();
154 bool Changed = performPromotion(F);
156 // FIXME: ScalarRepl currently depends on TargetData more than it
157 // theoretically needs to. It should be refactored in order to support
158 // target-independent IR. Until this is done, just skip the actual
159 // scalar-replacement portion of this pass.
160 if (!TD) return Changed;
163 bool LocalChange = performScalarRepl(F);
164 if (!LocalChange) break; // No need to repromote if no scalarrepl
166 LocalChange = performPromotion(F);
167 if (!LocalChange) break; // No need to re-scalarrepl if no promotion
174 bool SROA::performPromotion(Function &F) {
175 std::vector<AllocaInst*> Allocas;
176 DominatorTree &DT = getAnalysis<DominatorTree>();
177 DominanceFrontier &DF = getAnalysis<DominanceFrontier>();
179 BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function
181 bool Changed = false;
186 // Find allocas that are safe to promote, by looking at all instructions in
188 for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I)
189 if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) // Is it an alloca?
190 if (isAllocaPromotable(AI))
191 Allocas.push_back(AI);
193 if (Allocas.empty()) break;
195 PromoteMemToReg(Allocas, DT, DF);
196 NumPromoted += Allocas.size();
203 /// getNumSAElements - Return the number of elements in the specific struct or
205 static uint64_t getNumSAElements(const Type *T) {
206 if (const StructType *ST = dyn_cast<StructType>(T))
207 return ST->getNumElements();
208 return cast<ArrayType>(T)->getNumElements();
211 // performScalarRepl - This algorithm is a simple worklist driven algorithm,
212 // which runs on all of the malloc/alloca instructions in the function, removing
213 // them if they are only used by getelementptr instructions.
215 bool SROA::performScalarRepl(Function &F) {
216 std::vector<AllocaInst*> WorkList;
218 // Scan the entry basic block, adding any alloca's and mallocs to the worklist
219 BasicBlock &BB = F.getEntryBlock();
220 for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I)
221 if (AllocaInst *A = dyn_cast<AllocaInst>(I))
222 WorkList.push_back(A);
224 // Process the worklist
225 bool Changed = false;
226 while (!WorkList.empty()) {
227 AllocaInst *AI = WorkList.back();
230 // Handle dead allocas trivially. These can be formed by SROA'ing arrays
231 // with unused elements.
232 if (AI->use_empty()) {
233 AI->eraseFromParent();
237 // If this alloca is impossible for us to promote, reject it early.
238 if (AI->isArrayAllocation() || !AI->getAllocatedType()->isSized())
241 // Check to see if this allocation is only modified by a memcpy/memmove from
242 // a constant global. If this is the case, we can change all users to use
243 // the constant global instead. This is commonly produced by the CFE by
244 // constructs like "void foo() { int A[] = {1,2,3,4,5,6,7,8,9...}; }" if 'A'
245 // is only subsequently read.
246 if (Instruction *TheCopy = isOnlyCopiedFromConstantGlobal(AI)) {
247 DEBUG(errs() << "Found alloca equal to global: " << *AI << '\n');
248 DEBUG(errs() << " memcpy = " << *TheCopy << '\n');
249 Constant *TheSrc = cast<Constant>(TheCopy->getOperand(2));
250 AI->replaceAllUsesWith(ConstantExpr::getBitCast(TheSrc, AI->getType()));
251 TheCopy->eraseFromParent(); // Don't mutate the global.
252 AI->eraseFromParent();
258 // Check to see if we can perform the core SROA transformation. We cannot
259 // transform the allocation instruction if it is an array allocation
260 // (allocations OF arrays are ok though), and an allocation of a scalar
261 // value cannot be decomposed at all.
262 uint64_t AllocaSize = TD->getTypeAllocSize(AI->getAllocatedType());
264 // Do not promote [0 x %struct].
265 if (AllocaSize == 0) continue;
267 // Do not promote any struct whose size is too big.
268 if (AllocaSize > SRThreshold) continue;
270 if ((isa<StructType>(AI->getAllocatedType()) ||
271 isa<ArrayType>(AI->getAllocatedType())) &&
272 // Do not promote any struct into more than "32" separate vars.
273 getNumSAElements(AI->getAllocatedType()) <= SRThreshold/4) {
274 // Check that all of the users of the allocation are capable of being
276 switch (isSafeAllocaToScalarRepl(AI)) {
277 default: llvm_unreachable("Unexpected value!");
278 case 0: // Not safe to scalar replace.
280 case 1: // Safe, but requires cleanup/canonicalizations first
281 CleanupAllocaUsers(AI);
283 case 3: // Safe to scalar replace.
284 DoScalarReplacement(AI, WorkList);
290 // If we can turn this aggregate value (potentially with casts) into a
291 // simple scalar value that can be mem2reg'd into a register value.
292 // IsNotTrivial tracks whether this is something that mem2reg could have
293 // promoted itself. If so, we don't want to transform it needlessly. Note
294 // that we can't just check based on the type: the alloca may be of an i32
295 // but that has pointer arithmetic to set byte 3 of it or something.
296 bool IsNotTrivial = false;
297 const Type *VectorTy = 0;
298 bool HadAVector = false;
299 if (CanConvertToScalar(AI, IsNotTrivial, VectorTy, HadAVector,
300 0, unsigned(AllocaSize)) && IsNotTrivial) {
302 // If we were able to find a vector type that can handle this with
303 // insert/extract elements, and if there was at least one use that had
304 // a vector type, promote this to a vector. We don't want to promote
305 // random stuff that doesn't use vectors (e.g. <9 x double>) because then
306 // we just get a lot of insert/extracts. If at least one vector is
307 // involved, then we probably really do have a union of vector/array.
308 if (VectorTy && isa<VectorType>(VectorTy) && HadAVector) {
309 DEBUG(errs() << "CONVERT TO VECTOR: " << *AI << "\n TYPE = "
310 << *VectorTy << '\n');
312 // Create and insert the vector alloca.
313 NewAI = new AllocaInst(VectorTy, 0, "", AI->getParent()->begin());
314 ConvertUsesToScalar(AI, NewAI, 0);
316 DEBUG(errs() << "CONVERT TO SCALAR INTEGER: " << *AI << "\n");
318 // Create and insert the integer alloca.
319 const Type *NewTy = IntegerType::get(AI->getContext(), AllocaSize*8);
320 NewAI = new AllocaInst(NewTy, 0, "", AI->getParent()->begin());
321 ConvertUsesToScalar(AI, NewAI, 0);
324 AI->eraseFromParent();
330 // Otherwise, couldn't process this alloca.
336 /// DoScalarReplacement - This alloca satisfied the isSafeAllocaToScalarRepl
337 /// predicate, do SROA now.
338 void SROA::DoScalarReplacement(AllocaInst *AI,
339 std::vector<AllocaInst*> &WorkList) {
340 DEBUG(errs() << "Found inst to SROA: " << *AI << '\n');
341 SmallVector<AllocaInst*, 32> ElementAllocas;
342 if (const StructType *ST = dyn_cast<StructType>(AI->getAllocatedType())) {
343 ElementAllocas.reserve(ST->getNumContainedTypes());
344 for (unsigned i = 0, e = ST->getNumContainedTypes(); i != e; ++i) {
345 AllocaInst *NA = new AllocaInst(ST->getContainedType(i), 0,
347 AI->getName() + "." + Twine(i), AI);
348 ElementAllocas.push_back(NA);
349 WorkList.push_back(NA); // Add to worklist for recursive processing
352 const ArrayType *AT = cast<ArrayType>(AI->getAllocatedType());
353 ElementAllocas.reserve(AT->getNumElements());
354 const Type *ElTy = AT->getElementType();
355 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
356 AllocaInst *NA = new AllocaInst(ElTy, 0, AI->getAlignment(),
357 AI->getName() + "." + Twine(i), AI);
358 ElementAllocas.push_back(NA);
359 WorkList.push_back(NA); // Add to worklist for recursive processing
363 // Now that we have created the alloca instructions that we want to use,
364 // expand the getelementptr instructions to use them.
366 while (!AI->use_empty()) {
367 Instruction *User = cast<Instruction>(AI->use_back());
368 if (BitCastInst *BCInst = dyn_cast<BitCastInst>(User)) {
369 RewriteBitCastUserOfAlloca(BCInst, AI, ElementAllocas);
370 BCInst->eraseFromParent();
375 // %res = load { i32, i32 }* %alloc
377 // %load.0 = load i32* %alloc.0
378 // %insert.0 insertvalue { i32, i32 } zeroinitializer, i32 %load.0, 0
379 // %load.1 = load i32* %alloc.1
380 // %insert = insertvalue { i32, i32 } %insert.0, i32 %load.1, 1
381 // (Also works for arrays instead of structs)
382 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
383 Value *Insert = UndefValue::get(LI->getType());
384 for (unsigned i = 0, e = ElementAllocas.size(); i != e; ++i) {
385 Value *Load = new LoadInst(ElementAllocas[i], "load", LI);
386 Insert = InsertValueInst::Create(Insert, Load, i, "insert", LI);
388 LI->replaceAllUsesWith(Insert);
389 LI->eraseFromParent();
394 // store { i32, i32 } %val, { i32, i32 }* %alloc
396 // %val.0 = extractvalue { i32, i32 } %val, 0
397 // store i32 %val.0, i32* %alloc.0
398 // %val.1 = extractvalue { i32, i32 } %val, 1
399 // store i32 %val.1, i32* %alloc.1
400 // (Also works for arrays instead of structs)
401 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
402 Value *Val = SI->getOperand(0);
403 for (unsigned i = 0, e = ElementAllocas.size(); i != e; ++i) {
404 Value *Extract = ExtractValueInst::Create(Val, i, Val->getName(), SI);
405 new StoreInst(Extract, ElementAllocas[i], SI);
407 SI->eraseFromParent();
411 GetElementPtrInst *GEPI = cast<GetElementPtrInst>(User);
412 // We now know that the GEP is of the form: GEP <ptr>, 0, <cst>
414 (unsigned)cast<ConstantInt>(GEPI->getOperand(2))->getZExtValue();
416 assert(Idx < ElementAllocas.size() && "Index out of range?");
417 AllocaInst *AllocaToUse = ElementAllocas[Idx];
420 if (GEPI->getNumOperands() == 3) {
421 // Do not insert a new getelementptr instruction with zero indices, only
422 // to have it optimized out later.
423 RepValue = AllocaToUse;
425 // We are indexing deeply into the structure, so we still need a
426 // getelement ptr instruction to finish the indexing. This may be
427 // expanded itself once the worklist is rerun.
429 SmallVector<Value*, 8> NewArgs;
430 NewArgs.push_back(Constant::getNullValue(
431 Type::getInt32Ty(AI->getContext())));
432 NewArgs.append(GEPI->op_begin()+3, GEPI->op_end());
433 RepValue = GetElementPtrInst::Create(AllocaToUse, NewArgs.begin(),
434 NewArgs.end(), "", GEPI);
435 RepValue->takeName(GEPI);
438 // If this GEP is to the start of the aggregate, check for memcpys.
439 if (Idx == 0 && GEPI->hasAllZeroIndices())
440 RewriteBitCastUserOfAlloca(GEPI, AI, ElementAllocas);
442 // Move all of the users over to the new GEP.
443 GEPI->replaceAllUsesWith(RepValue);
444 // Delete the old GEP
445 GEPI->eraseFromParent();
448 // Finally, delete the Alloca instruction
449 AI->eraseFromParent();
453 /// isSafeElementUse - Check to see if this use is an allowed use for a
454 /// getelementptr instruction of an array aggregate allocation. isFirstElt
455 /// indicates whether Ptr is known to the start of the aggregate.
456 void SROA::isSafeElementUse(Value *Ptr, bool isFirstElt, AllocaInst *AI,
458 for (Value::use_iterator I = Ptr->use_begin(), E = Ptr->use_end();
460 Instruction *User = cast<Instruction>(*I);
461 switch (User->getOpcode()) {
462 case Instruction::Load: break;
463 case Instruction::Store:
464 // Store is ok if storing INTO the pointer, not storing the pointer
465 if (User->getOperand(0) == Ptr) return MarkUnsafe(Info);
467 case Instruction::GetElementPtr: {
468 GetElementPtrInst *GEP = cast<GetElementPtrInst>(User);
469 bool AreAllZeroIndices = isFirstElt;
470 if (GEP->getNumOperands() > 1 &&
471 (!isa<ConstantInt>(GEP->getOperand(1)) ||
472 !cast<ConstantInt>(GEP->getOperand(1))->isZero()))
473 // Using pointer arithmetic to navigate the array.
474 return MarkUnsafe(Info);
476 // Verify that any array subscripts are in range.
477 for (gep_type_iterator GEPIt = gep_type_begin(GEP),
478 E = gep_type_end(GEP); GEPIt != E; ++GEPIt) {
479 // Ignore struct elements, no extra checking needed for these.
480 if (isa<StructType>(*GEPIt))
483 // This GEP indexes an array. Verify that this is an in-range
484 // constant integer. Specifically, consider A[0][i]. We cannot know that
485 // the user isn't doing invalid things like allowing i to index an
486 // out-of-range subscript that accesses A[1]. Because of this, we have
487 // to reject SROA of any accesses into structs where any of the
488 // components are variables.
489 ConstantInt *IdxVal = dyn_cast<ConstantInt>(GEPIt.getOperand());
490 if (!IdxVal) return MarkUnsafe(Info);
492 // Are all indices still zero?
493 AreAllZeroIndices &= IdxVal->isZero();
495 if (const ArrayType *AT = dyn_cast<ArrayType>(*GEPIt)) {
496 if (IdxVal->getZExtValue() >= AT->getNumElements())
497 return MarkUnsafe(Info);
498 } else if (const VectorType *VT = dyn_cast<VectorType>(*GEPIt)) {
499 if (IdxVal->getZExtValue() >= VT->getNumElements())
500 return MarkUnsafe(Info);
504 isSafeElementUse(GEP, AreAllZeroIndices, AI, Info);
505 if (Info.isUnsafe) return;
508 case Instruction::BitCast:
510 isSafeUseOfBitCastedAllocation(cast<BitCastInst>(User), AI, Info);
511 if (Info.isUnsafe) return;
514 DEBUG(errs() << " Transformation preventing inst: " << *User << '\n');
515 return MarkUnsafe(Info);
516 case Instruction::Call:
517 if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) {
519 isSafeMemIntrinsicOnAllocation(MI, AI, I.getOperandNo(), Info);
520 if (Info.isUnsafe) return;
524 DEBUG(errs() << " Transformation preventing inst: " << *User << '\n');
525 return MarkUnsafe(Info);
527 DEBUG(errs() << " Transformation preventing inst: " << *User << '\n');
528 return MarkUnsafe(Info);
531 return; // All users look ok :)
534 /// AllUsersAreLoads - Return true if all users of this value are loads.
535 static bool AllUsersAreLoads(Value *Ptr) {
536 for (Value::use_iterator I = Ptr->use_begin(), E = Ptr->use_end();
538 if (cast<Instruction>(*I)->getOpcode() != Instruction::Load)
543 /// isSafeUseOfAllocation - Check to see if this user is an allowed use for an
544 /// aggregate allocation.
545 void SROA::isSafeUseOfAllocation(Instruction *User, AllocaInst *AI,
547 if (BitCastInst *C = dyn_cast<BitCastInst>(User))
548 return isSafeUseOfBitCastedAllocation(C, AI, Info);
550 if (LoadInst *LI = dyn_cast<LoadInst>(User))
551 if (!LI->isVolatile())
552 return;// Loads (returning a first class aggregrate) are always rewritable
554 if (StoreInst *SI = dyn_cast<StoreInst>(User))
555 if (!SI->isVolatile() && SI->getOperand(0) != AI)
556 return;// Store is ok if storing INTO the pointer, not storing the pointer
558 GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User);
560 return MarkUnsafe(Info);
562 gep_type_iterator I = gep_type_begin(GEPI), E = gep_type_end(GEPI);
564 // The GEP is not safe to transform if not of the form "GEP <ptr>, 0, <cst>".
566 I.getOperand() != Constant::getNullValue(I.getOperand()->getType())) {
567 return MarkUnsafe(Info);
571 if (I == E) return MarkUnsafe(Info); // ran out of GEP indices??
573 bool IsAllZeroIndices = true;
575 // If the first index is a non-constant index into an array, see if we can
576 // handle it as a special case.
577 if (const ArrayType *AT = dyn_cast<ArrayType>(*I)) {
578 if (!isa<ConstantInt>(I.getOperand())) {
579 IsAllZeroIndices = 0;
580 uint64_t NumElements = AT->getNumElements();
582 // If this is an array index and the index is not constant, we cannot
583 // promote... that is unless the array has exactly one or two elements in
584 // it, in which case we CAN promote it, but we have to canonicalize this
585 // out if this is the only problem.
586 if ((NumElements == 1 || NumElements == 2) &&
587 AllUsersAreLoads(GEPI)) {
588 Info.needsCleanup = true;
589 return; // Canonicalization required!
591 return MarkUnsafe(Info);
595 // Walk through the GEP type indices, checking the types that this indexes
597 for (; I != E; ++I) {
598 // Ignore struct elements, no extra checking needed for these.
599 if (isa<StructType>(*I))
602 ConstantInt *IdxVal = dyn_cast<ConstantInt>(I.getOperand());
603 if (!IdxVal) return MarkUnsafe(Info);
605 // Are all indices still zero?
606 IsAllZeroIndices &= IdxVal->isZero();
608 if (const ArrayType *AT = dyn_cast<ArrayType>(*I)) {
609 // This GEP indexes an array. Verify that this is an in-range constant
610 // integer. Specifically, consider A[0][i]. We cannot know that the user
611 // isn't doing invalid things like allowing i to index an out-of-range
612 // subscript that accesses A[1]. Because of this, we have to reject SROA
613 // of any accesses into structs where any of the components are variables.
614 if (IdxVal->getZExtValue() >= AT->getNumElements())
615 return MarkUnsafe(Info);
616 } else if (const VectorType *VT = dyn_cast<VectorType>(*I)) {
617 if (IdxVal->getZExtValue() >= VT->getNumElements())
618 return MarkUnsafe(Info);
622 // If there are any non-simple uses of this getelementptr, make sure to reject
624 return isSafeElementUse(GEPI, IsAllZeroIndices, AI, Info);
627 /// isSafeMemIntrinsicOnAllocation - Check if the specified memory
628 /// intrinsic can be promoted by SROA. At this point, we know that the operand
629 /// of the memintrinsic is a pointer to the beginning of the allocation.
630 void SROA::isSafeMemIntrinsicOnAllocation(MemIntrinsic *MI, AllocaInst *AI,
631 unsigned OpNo, AllocaInfo &Info) {
632 // If not constant length, give up.
633 ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength());
634 if (!Length) return MarkUnsafe(Info);
636 // If not the whole aggregate, give up.
637 if (Length->getZExtValue() !=
638 TD->getTypeAllocSize(AI->getType()->getElementType()))
639 return MarkUnsafe(Info);
641 // We only know about memcpy/memset/memmove.
642 if (!isa<MemIntrinsic>(MI))
643 return MarkUnsafe(Info);
645 // Otherwise, we can transform it. Determine whether this is a memcpy/set
646 // into or out of the aggregate.
648 Info.isMemCpyDst = true;
651 Info.isMemCpySrc = true;
655 /// isSafeUseOfBitCastedAllocation - Check if all users of this bitcast
656 /// from an alloca are safe for SROA of that alloca.
657 void SROA::isSafeUseOfBitCastedAllocation(BitCastInst *BC, AllocaInst *AI,
659 for (Value::use_iterator UI = BC->use_begin(), E = BC->use_end();
661 if (BitCastInst *BCU = dyn_cast<BitCastInst>(UI)) {
662 isSafeUseOfBitCastedAllocation(BCU, AI, Info);
663 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(UI)) {
664 isSafeMemIntrinsicOnAllocation(MI, AI, UI.getOperandNo(), Info);
665 } else if (StoreInst *SI = dyn_cast<StoreInst>(UI)) {
666 if (SI->isVolatile())
667 return MarkUnsafe(Info);
669 // If storing the entire alloca in one chunk through a bitcasted pointer
670 // to integer, we can transform it. This happens (for example) when you
671 // cast a {i32,i32}* to i64* and store through it. This is similar to the
672 // memcpy case and occurs in various "byval" cases and emulated memcpys.
673 if (isa<IntegerType>(SI->getOperand(0)->getType()) &&
674 TD->getTypeAllocSize(SI->getOperand(0)->getType()) ==
675 TD->getTypeAllocSize(AI->getType()->getElementType())) {
676 Info.isMemCpyDst = true;
679 return MarkUnsafe(Info);
680 } else if (LoadInst *LI = dyn_cast<LoadInst>(UI)) {
681 if (LI->isVolatile())
682 return MarkUnsafe(Info);
684 // If loading the entire alloca in one chunk through a bitcasted pointer
685 // to integer, we can transform it. This happens (for example) when you
686 // cast a {i32,i32}* to i64* and load through it. This is similar to the
687 // memcpy case and occurs in various "byval" cases and emulated memcpys.
688 if (isa<IntegerType>(LI->getType()) &&
689 TD->getTypeAllocSize(LI->getType()) ==
690 TD->getTypeAllocSize(AI->getType()->getElementType())) {
691 Info.isMemCpySrc = true;
694 return MarkUnsafe(Info);
695 } else if (isa<DbgInfoIntrinsic>(UI)) {
696 // If one user is DbgInfoIntrinsic then check if all users are
697 // DbgInfoIntrinsics.
698 if (OnlyUsedByDbgInfoIntrinsics(BC)) {
699 Info.needsCleanup = true;
706 return MarkUnsafe(Info);
708 if (Info.isUnsafe) return;
712 /// RewriteBitCastUserOfAlloca - BCInst (transitively) bitcasts AI, or indexes
713 /// to its first element. Transform users of the cast to use the new values
715 void SROA::RewriteBitCastUserOfAlloca(Instruction *BCInst, AllocaInst *AI,
716 SmallVector<AllocaInst*, 32> &NewElts) {
717 Value::use_iterator UI = BCInst->use_begin(), UE = BCInst->use_end();
719 Instruction *User = cast<Instruction>(*UI++);
720 if (BitCastInst *BCU = dyn_cast<BitCastInst>(User)) {
721 RewriteBitCastUserOfAlloca(BCU, AI, NewElts);
722 if (BCU->use_empty()) BCU->eraseFromParent();
726 if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) {
727 // This must be memcpy/memmove/memset of the entire aggregate.
728 // Split into one per element.
729 RewriteMemIntrinUserOfAlloca(MI, BCInst, AI, NewElts);
733 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
734 // If this is a store of the entire alloca from an integer, rewrite it.
735 RewriteStoreUserOfWholeAlloca(SI, AI, NewElts);
739 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
740 // If this is a load of the entire alloca to an integer, rewrite it.
741 RewriteLoadUserOfWholeAlloca(LI, AI, NewElts);
745 // Otherwise it must be some other user of a gep of the first pointer. Just
746 // leave these alone.
751 /// RewriteMemIntrinUserOfAlloca - MI is a memcpy/memset/memmove from or to AI.
752 /// Rewrite it to copy or set the elements of the scalarized memory.
753 void SROA::RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *BCInst,
755 SmallVector<AllocaInst*, 32> &NewElts) {
757 // If this is a memcpy/memmove, construct the other pointer as the
758 // appropriate type. The "Other" pointer is the pointer that goes to memory
759 // that doesn't have anything to do with the alloca that we are promoting. For
760 // memset, this Value* stays null.
762 LLVMContext &Context = MI->getContext();
763 unsigned MemAlignment = MI->getAlignment();
764 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(MI)) { // memmove/memcopy
765 if (BCInst == MTI->getRawDest())
766 OtherPtr = MTI->getRawSource();
768 assert(BCInst == MTI->getRawSource());
769 OtherPtr = MTI->getRawDest();
773 // If there is an other pointer, we want to convert it to the same pointer
774 // type as AI has, so we can GEP through it safely.
776 // It is likely that OtherPtr is a bitcast, if so, remove it.
777 if (BitCastInst *BC = dyn_cast<BitCastInst>(OtherPtr))
778 OtherPtr = BC->getOperand(0);
779 // All zero GEPs are effectively bitcasts.
780 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(OtherPtr))
781 if (GEP->hasAllZeroIndices())
782 OtherPtr = GEP->getOperand(0);
784 if (ConstantExpr *BCE = dyn_cast<ConstantExpr>(OtherPtr))
785 if (BCE->getOpcode() == Instruction::BitCast)
786 OtherPtr = BCE->getOperand(0);
788 // If the pointer is not the right type, insert a bitcast to the right
790 if (OtherPtr->getType() != AI->getType())
791 OtherPtr = new BitCastInst(OtherPtr, AI->getType(), OtherPtr->getName(),
795 // Process each element of the aggregate.
796 Value *TheFn = MI->getOperand(0);
797 const Type *BytePtrTy = MI->getRawDest()->getType();
798 bool SROADest = MI->getRawDest() == BCInst;
800 Constant *Zero = Constant::getNullValue(Type::getInt32Ty(MI->getContext()));
802 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
803 // If this is a memcpy/memmove, emit a GEP of the other element address.
805 unsigned OtherEltAlign = MemAlignment;
808 Value *Idx[2] = { Zero,
809 ConstantInt::get(Type::getInt32Ty(MI->getContext()), i) };
810 OtherElt = GetElementPtrInst::Create(OtherPtr, Idx, Idx + 2,
811 OtherPtr->getNameStr()+"."+Twine(i),
814 const PointerType *OtherPtrTy = cast<PointerType>(OtherPtr->getType());
815 if (const StructType *ST =
816 dyn_cast<StructType>(OtherPtrTy->getElementType())) {
817 EltOffset = TD->getStructLayout(ST)->getElementOffset(i);
820 cast<SequentialType>(OtherPtr->getType())->getElementType();
821 EltOffset = TD->getTypeAllocSize(EltTy)*i;
824 // The alignment of the other pointer is the guaranteed alignment of the
825 // element, which is affected by both the known alignment of the whole
826 // mem intrinsic and the alignment of the element. If the alignment of
827 // the memcpy (f.e.) is 32 but the element is at a 4-byte offset, then the
828 // known alignment is just 4 bytes.
829 OtherEltAlign = (unsigned)MinAlign(OtherEltAlign, EltOffset);
832 Value *EltPtr = NewElts[i];
833 const Type *EltTy = cast<PointerType>(EltPtr->getType())->getElementType();
835 // If we got down to a scalar, insert a load or store as appropriate.
836 if (EltTy->isSingleValueType()) {
837 if (isa<MemTransferInst>(MI)) {
839 // From Other to Alloca.
840 Value *Elt = new LoadInst(OtherElt, "tmp", false, OtherEltAlign, MI);
841 new StoreInst(Elt, EltPtr, MI);
843 // From Alloca to Other.
844 Value *Elt = new LoadInst(EltPtr, "tmp", MI);
845 new StoreInst(Elt, OtherElt, false, OtherEltAlign, MI);
849 assert(isa<MemSetInst>(MI));
851 // If the stored element is zero (common case), just store a null
854 if (ConstantInt *CI = dyn_cast<ConstantInt>(MI->getOperand(2))) {
856 StoreVal = Constant::getNullValue(EltTy); // 0.0, null, 0, <0,0>
858 // If EltTy is a vector type, get the element type.
859 const Type *ValTy = EltTy->getScalarType();
861 // Construct an integer with the right value.
862 unsigned EltSize = TD->getTypeSizeInBits(ValTy);
863 APInt OneVal(EltSize, CI->getZExtValue());
864 APInt TotalVal(OneVal);
866 for (unsigned i = 0; 8*i < EltSize; ++i) {
867 TotalVal = TotalVal.shl(8);
871 // Convert the integer value to the appropriate type.
872 StoreVal = ConstantInt::get(Context, TotalVal);
873 if (isa<PointerType>(ValTy))
874 StoreVal = ConstantExpr::getIntToPtr(StoreVal, ValTy);
875 else if (ValTy->isFloatingPoint())
876 StoreVal = ConstantExpr::getBitCast(StoreVal, ValTy);
877 assert(StoreVal->getType() == ValTy && "Type mismatch!");
879 // If the requested value was a vector constant, create it.
880 if (EltTy != ValTy) {
881 unsigned NumElts = cast<VectorType>(ValTy)->getNumElements();
882 SmallVector<Constant*, 16> Elts(NumElts, StoreVal);
883 StoreVal = ConstantVector::get(&Elts[0], NumElts);
886 new StoreInst(StoreVal, EltPtr, MI);
889 // Otherwise, if we're storing a byte variable, use a memset call for
893 // Cast the element pointer to BytePtrTy.
894 if (EltPtr->getType() != BytePtrTy)
895 EltPtr = new BitCastInst(EltPtr, BytePtrTy, EltPtr->getNameStr(), MI);
897 // Cast the other pointer (if we have one) to BytePtrTy.
898 if (OtherElt && OtherElt->getType() != BytePtrTy)
899 OtherElt = new BitCastInst(OtherElt, BytePtrTy,OtherElt->getNameStr(),
902 unsigned EltSize = TD->getTypeAllocSize(EltTy);
904 // Finally, insert the meminst for this element.
905 if (isa<MemTransferInst>(MI)) {
907 SROADest ? EltPtr : OtherElt, // Dest ptr
908 SROADest ? OtherElt : EltPtr, // Src ptr
909 ConstantInt::get(MI->getOperand(3)->getType(), EltSize), // Size
911 ConstantInt::get(Type::getInt32Ty(MI->getContext()), OtherEltAlign)
913 CallInst::Create(TheFn, Ops, Ops + 4, "", MI);
915 assert(isa<MemSetInst>(MI));
917 EltPtr, MI->getOperand(2), // Dest, Value,
918 ConstantInt::get(MI->getOperand(3)->getType(), EltSize), // Size
921 CallInst::Create(TheFn, Ops, Ops + 4, "", MI);
924 MI->eraseFromParent();
927 /// RewriteStoreUserOfWholeAlloca - We found a store of an integer that
928 /// overwrites the entire allocation. Extract out the pieces of the stored
929 /// integer and store them individually.
930 void SROA::RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocaInst *AI,
931 SmallVector<AllocaInst*, 32> &NewElts){
932 // Extract each element out of the integer according to its structure offset
933 // and store the element value to the individual alloca.
934 Value *SrcVal = SI->getOperand(0);
935 const Type *AllocaEltTy = AI->getType()->getElementType();
936 uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy);
938 // If this isn't a store of an integer to the whole alloca, it may be a store
939 // to the first element. Just ignore the store in this case and normal SROA
941 if (!isa<IntegerType>(SrcVal->getType()) ||
942 TD->getTypeAllocSizeInBits(SrcVal->getType()) != AllocaSizeBits)
944 // Handle tail padding by extending the operand
945 if (TD->getTypeSizeInBits(SrcVal->getType()) != AllocaSizeBits)
946 SrcVal = new ZExtInst(SrcVal,
947 IntegerType::get(SI->getContext(), AllocaSizeBits),
950 DEBUG(errs() << "PROMOTING STORE TO WHOLE ALLOCA: " << *AI << '\n' << *SI
953 // There are two forms here: AI could be an array or struct. Both cases
954 // have different ways to compute the element offset.
955 if (const StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) {
956 const StructLayout *Layout = TD->getStructLayout(EltSTy);
958 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
959 // Get the number of bits to shift SrcVal to get the value.
960 const Type *FieldTy = EltSTy->getElementType(i);
961 uint64_t Shift = Layout->getElementOffsetInBits(i);
963 if (TD->isBigEndian())
964 Shift = AllocaSizeBits-Shift-TD->getTypeAllocSizeInBits(FieldTy);
966 Value *EltVal = SrcVal;
968 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift);
969 EltVal = BinaryOperator::CreateLShr(EltVal, ShiftVal,
970 "sroa.store.elt", SI);
973 // Truncate down to an integer of the right size.
974 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy);
976 // Ignore zero sized fields like {}, they obviously contain no data.
977 if (FieldSizeBits == 0) continue;
979 if (FieldSizeBits != AllocaSizeBits)
980 EltVal = new TruncInst(EltVal,
981 IntegerType::get(SI->getContext(), FieldSizeBits),
983 Value *DestField = NewElts[i];
984 if (EltVal->getType() == FieldTy) {
985 // Storing to an integer field of this size, just do it.
986 } else if (FieldTy->isFloatingPoint() || isa<VectorType>(FieldTy)) {
987 // Bitcast to the right element type (for fp/vector values).
988 EltVal = new BitCastInst(EltVal, FieldTy, "", SI);
990 // Otherwise, bitcast the dest pointer (for aggregates).
991 DestField = new BitCastInst(DestField,
992 PointerType::getUnqual(EltVal->getType()),
995 new StoreInst(EltVal, DestField, SI);
999 const ArrayType *ATy = cast<ArrayType>(AllocaEltTy);
1000 const Type *ArrayEltTy = ATy->getElementType();
1001 uint64_t ElementOffset = TD->getTypeAllocSizeInBits(ArrayEltTy);
1002 uint64_t ElementSizeBits = TD->getTypeSizeInBits(ArrayEltTy);
1006 if (TD->isBigEndian())
1007 Shift = AllocaSizeBits-ElementOffset;
1011 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
1012 // Ignore zero sized fields like {}, they obviously contain no data.
1013 if (ElementSizeBits == 0) continue;
1015 Value *EltVal = SrcVal;
1017 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift);
1018 EltVal = BinaryOperator::CreateLShr(EltVal, ShiftVal,
1019 "sroa.store.elt", SI);
1022 // Truncate down to an integer of the right size.
1023 if (ElementSizeBits != AllocaSizeBits)
1024 EltVal = new TruncInst(EltVal,
1025 IntegerType::get(SI->getContext(),
1026 ElementSizeBits),"",SI);
1027 Value *DestField = NewElts[i];
1028 if (EltVal->getType() == ArrayEltTy) {
1029 // Storing to an integer field of this size, just do it.
1030 } else if (ArrayEltTy->isFloatingPoint() || isa<VectorType>(ArrayEltTy)) {
1031 // Bitcast to the right element type (for fp/vector values).
1032 EltVal = new BitCastInst(EltVal, ArrayEltTy, "", SI);
1034 // Otherwise, bitcast the dest pointer (for aggregates).
1035 DestField = new BitCastInst(DestField,
1036 PointerType::getUnqual(EltVal->getType()),
1039 new StoreInst(EltVal, DestField, SI);
1041 if (TD->isBigEndian())
1042 Shift -= ElementOffset;
1044 Shift += ElementOffset;
1048 SI->eraseFromParent();
1051 /// RewriteLoadUserOfWholeAlloca - We found a load of the entire allocation to
1052 /// an integer. Load the individual pieces to form the aggregate value.
1053 void SROA::RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocaInst *AI,
1054 SmallVector<AllocaInst*, 32> &NewElts) {
1055 // Extract each element out of the NewElts according to its structure offset
1056 // and form the result value.
1057 const Type *AllocaEltTy = AI->getType()->getElementType();
1058 uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy);
1060 // If this isn't a load of the whole alloca to an integer, it may be a load
1061 // of the first element. Just ignore the load in this case and normal SROA
1063 if (!isa<IntegerType>(LI->getType()) ||
1064 TD->getTypeAllocSizeInBits(LI->getType()) != AllocaSizeBits)
1067 DEBUG(errs() << "PROMOTING LOAD OF WHOLE ALLOCA: " << *AI << '\n' << *LI
1070 // There are two forms here: AI could be an array or struct. Both cases
1071 // have different ways to compute the element offset.
1072 const StructLayout *Layout = 0;
1073 uint64_t ArrayEltBitOffset = 0;
1074 if (const StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) {
1075 Layout = TD->getStructLayout(EltSTy);
1077 const Type *ArrayEltTy = cast<ArrayType>(AllocaEltTy)->getElementType();
1078 ArrayEltBitOffset = TD->getTypeAllocSizeInBits(ArrayEltTy);
1082 Constant::getNullValue(IntegerType::get(LI->getContext(), AllocaSizeBits));
1084 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
1085 // Load the value from the alloca. If the NewElt is an aggregate, cast
1086 // the pointer to an integer of the same size before doing the load.
1087 Value *SrcField = NewElts[i];
1088 const Type *FieldTy =
1089 cast<PointerType>(SrcField->getType())->getElementType();
1090 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy);
1092 // Ignore zero sized fields like {}, they obviously contain no data.
1093 if (FieldSizeBits == 0) continue;
1095 const IntegerType *FieldIntTy = IntegerType::get(LI->getContext(),
1097 if (!isa<IntegerType>(FieldTy) && !FieldTy->isFloatingPoint() &&
1098 !isa<VectorType>(FieldTy))
1099 SrcField = new BitCastInst(SrcField,
1100 PointerType::getUnqual(FieldIntTy),
1102 SrcField = new LoadInst(SrcField, "sroa.load.elt", LI);
1104 // If SrcField is a fp or vector of the right size but that isn't an
1105 // integer type, bitcast to an integer so we can shift it.
1106 if (SrcField->getType() != FieldIntTy)
1107 SrcField = new BitCastInst(SrcField, FieldIntTy, "", LI);
1109 // Zero extend the field to be the same size as the final alloca so that
1110 // we can shift and insert it.
1111 if (SrcField->getType() != ResultVal->getType())
1112 SrcField = new ZExtInst(SrcField, ResultVal->getType(), "", LI);
1114 // Determine the number of bits to shift SrcField.
1116 if (Layout) // Struct case.
1117 Shift = Layout->getElementOffsetInBits(i);
1119 Shift = i*ArrayEltBitOffset;
1121 if (TD->isBigEndian())
1122 Shift = AllocaSizeBits-Shift-FieldIntTy->getBitWidth();
1125 Value *ShiftVal = ConstantInt::get(SrcField->getType(), Shift);
1126 SrcField = BinaryOperator::CreateShl(SrcField, ShiftVal, "", LI);
1129 ResultVal = BinaryOperator::CreateOr(SrcField, ResultVal, "", LI);
1132 // Handle tail padding by truncating the result
1133 if (TD->getTypeSizeInBits(LI->getType()) != AllocaSizeBits)
1134 ResultVal = new TruncInst(ResultVal, LI->getType(), "", LI);
1136 LI->replaceAllUsesWith(ResultVal);
1137 LI->eraseFromParent();
1141 /// HasPadding - Return true if the specified type has any structure or
1142 /// alignment padding, false otherwise.
1143 static bool HasPadding(const Type *Ty, const TargetData &TD) {
1144 if (const StructType *STy = dyn_cast<StructType>(Ty)) {
1145 const StructLayout *SL = TD.getStructLayout(STy);
1146 unsigned PrevFieldBitOffset = 0;
1147 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
1148 unsigned FieldBitOffset = SL->getElementOffsetInBits(i);
1150 // Padding in sub-elements?
1151 if (HasPadding(STy->getElementType(i), TD))
1154 // Check to see if there is any padding between this element and the
1157 unsigned PrevFieldEnd =
1158 PrevFieldBitOffset+TD.getTypeSizeInBits(STy->getElementType(i-1));
1159 if (PrevFieldEnd < FieldBitOffset)
1163 PrevFieldBitOffset = FieldBitOffset;
1166 // Check for tail padding.
1167 if (unsigned EltCount = STy->getNumElements()) {
1168 unsigned PrevFieldEnd = PrevFieldBitOffset +
1169 TD.getTypeSizeInBits(STy->getElementType(EltCount-1));
1170 if (PrevFieldEnd < SL->getSizeInBits())
1174 } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
1175 return HasPadding(ATy->getElementType(), TD);
1176 } else if (const VectorType *VTy = dyn_cast<VectorType>(Ty)) {
1177 return HasPadding(VTy->getElementType(), TD);
1179 return TD.getTypeSizeInBits(Ty) != TD.getTypeAllocSizeInBits(Ty);
1182 /// isSafeStructAllocaToScalarRepl - Check to see if the specified allocation of
1183 /// an aggregate can be broken down into elements. Return 0 if not, 3 if safe,
1184 /// or 1 if safe after canonicalization has been performed.
1185 int SROA::isSafeAllocaToScalarRepl(AllocaInst *AI) {
1186 // Loop over the use list of the alloca. We can only transform it if all of
1187 // the users are safe to transform.
1190 for (Value::use_iterator I = AI->use_begin(), E = AI->use_end();
1192 isSafeUseOfAllocation(cast<Instruction>(*I), AI, Info);
1193 if (Info.isUnsafe) {
1194 DEBUG(errs() << "Cannot transform: " << *AI << "\n due to user: "
1200 // Okay, we know all the users are promotable. If the aggregate is a memcpy
1201 // source and destination, we have to be careful. In particular, the memcpy
1202 // could be moving around elements that live in structure padding of the LLVM
1203 // types, but may actually be used. In these cases, we refuse to promote the
1205 if (Info.isMemCpySrc && Info.isMemCpyDst &&
1206 HasPadding(AI->getType()->getElementType(), *TD))
1209 // If we require cleanup, return 1, otherwise return 3.
1210 return Info.needsCleanup ? 1 : 3;
1213 /// CleanupGEP - GEP is used by an Alloca, which can be prompted after the GEP
1214 /// is canonicalized here.
1215 void SROA::CleanupGEP(GetElementPtrInst *GEPI) {
1216 gep_type_iterator I = gep_type_begin(GEPI);
1219 const ArrayType *AT = dyn_cast<ArrayType>(*I);
1223 uint64_t NumElements = AT->getNumElements();
1225 if (isa<ConstantInt>(I.getOperand()))
1228 if (NumElements == 1) {
1230 Constant::getNullValue(Type::getInt32Ty(GEPI->getContext())));
1234 assert(NumElements == 2 && "Unhandled case!");
1235 // All users of the GEP must be loads. At each use of the GEP, insert
1236 // two loads of the appropriate indexed GEP and select between them.
1237 Value *IsOne = new ICmpInst(GEPI, ICmpInst::ICMP_NE, I.getOperand(),
1238 Constant::getNullValue(I.getOperand()->getType()),
1240 // Insert the new GEP instructions, which are properly indexed.
1241 SmallVector<Value*, 8> Indices(GEPI->op_begin()+1, GEPI->op_end());
1242 Indices[1] = Constant::getNullValue(Type::getInt32Ty(GEPI->getContext()));
1243 Value *ZeroIdx = GetElementPtrInst::Create(GEPI->getOperand(0),
1246 GEPI->getName()+".0", GEPI);
1247 Indices[1] = ConstantInt::get(Type::getInt32Ty(GEPI->getContext()), 1);
1248 Value *OneIdx = GetElementPtrInst::Create(GEPI->getOperand(0),
1251 GEPI->getName()+".1", GEPI);
1252 // Replace all loads of the variable index GEP with loads from both
1253 // indexes and a select.
1254 while (!GEPI->use_empty()) {
1255 LoadInst *LI = cast<LoadInst>(GEPI->use_back());
1256 Value *Zero = new LoadInst(ZeroIdx, LI->getName()+".0", LI);
1257 Value *One = new LoadInst(OneIdx , LI->getName()+".1", LI);
1258 Value *R = SelectInst::Create(IsOne, One, Zero, LI->getName(), LI);
1259 LI->replaceAllUsesWith(R);
1260 LI->eraseFromParent();
1262 GEPI->eraseFromParent();
1266 /// CleanupAllocaUsers - If SROA reported that it can promote the specified
1267 /// allocation, but only if cleaned up, perform the cleanups required.
1268 void SROA::CleanupAllocaUsers(AllocaInst *AI) {
1269 // At this point, we know that the end result will be SROA'd and promoted, so
1270 // we can insert ugly code if required so long as sroa+mem2reg will clean it
1272 for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end();
1275 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(U))
1278 Instruction *I = cast<Instruction>(U);
1279 SmallVector<DbgInfoIntrinsic *, 2> DbgInUses;
1280 if (!isa<StoreInst>(I) && OnlyUsedByDbgInfoIntrinsics(I, &DbgInUses)) {
1281 // Safe to remove debug info uses.
1282 while (!DbgInUses.empty()) {
1283 DbgInfoIntrinsic *DI = DbgInUses.back(); DbgInUses.pop_back();
1284 DI->eraseFromParent();
1286 I->eraseFromParent();
1292 /// MergeInType - Add the 'In' type to the accumulated type (Accum) so far at
1293 /// the offset specified by Offset (which is specified in bytes).
1295 /// There are two cases we handle here:
1296 /// 1) A union of vector types of the same size and potentially its elements.
1297 /// Here we turn element accesses into insert/extract element operations.
1298 /// This promotes a <4 x float> with a store of float to the third element
1299 /// into a <4 x float> that uses insert element.
1300 /// 2) A fully general blob of memory, which we turn into some (potentially
1301 /// large) integer type with extract and insert operations where the loads
1302 /// and stores would mutate the memory.
1303 static void MergeInType(const Type *In, uint64_t Offset, const Type *&VecTy,
1304 unsigned AllocaSize, const TargetData &TD,
1305 LLVMContext &Context) {
1306 // If this could be contributing to a vector, analyze it.
1307 if (VecTy != Type::getVoidTy(Context)) { // either null or a vector type.
1309 // If the In type is a vector that is the same size as the alloca, see if it
1310 // matches the existing VecTy.
1311 if (const VectorType *VInTy = dyn_cast<VectorType>(In)) {
1312 if (VInTy->getBitWidth()/8 == AllocaSize && Offset == 0) {
1313 // If we're storing/loading a vector of the right size, allow it as a
1314 // vector. If this the first vector we see, remember the type so that
1315 // we know the element size.
1320 } else if (In->isFloatTy() || In->isDoubleTy() ||
1321 (isa<IntegerType>(In) && In->getPrimitiveSizeInBits() >= 8 &&
1322 isPowerOf2_32(In->getPrimitiveSizeInBits()))) {
1323 // If we're accessing something that could be an element of a vector, see
1324 // if the implied vector agrees with what we already have and if Offset is
1325 // compatible with it.
1326 unsigned EltSize = In->getPrimitiveSizeInBits()/8;
1327 if (Offset % EltSize == 0 &&
1328 AllocaSize % EltSize == 0 &&
1330 cast<VectorType>(VecTy)->getElementType()
1331 ->getPrimitiveSizeInBits()/8 == EltSize)) {
1333 VecTy = VectorType::get(In, AllocaSize/EltSize);
1339 // Otherwise, we have a case that we can't handle with an optimized vector
1340 // form. We can still turn this into a large integer.
1341 VecTy = Type::getVoidTy(Context);
1344 /// CanConvertToScalar - V is a pointer. If we can convert the pointee and all
1345 /// its accesses to use a to single vector type, return true, and set VecTy to
1346 /// the new type. If we could convert the alloca into a single promotable
1347 /// integer, return true but set VecTy to VoidTy. Further, if the use is not a
1348 /// completely trivial use that mem2reg could promote, set IsNotTrivial. Offset
1349 /// is the current offset from the base of the alloca being analyzed.
1351 /// If we see at least one access to the value that is as a vector type, set the
1353 bool SROA::CanConvertToScalar(Value *V, bool &IsNotTrivial, const Type *&VecTy,
1354 bool &SawVec, uint64_t Offset,
1355 unsigned AllocaSize) {
1356 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) {
1357 Instruction *User = cast<Instruction>(*UI);
1359 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1360 // Don't break volatile loads.
1361 if (LI->isVolatile())
1363 MergeInType(LI->getType(), Offset, VecTy,
1364 AllocaSize, *TD, V->getContext());
1365 SawVec |= isa<VectorType>(LI->getType());
1369 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
1370 // Storing the pointer, not into the value?
1371 if (SI->getOperand(0) == V || SI->isVolatile()) return 0;
1372 MergeInType(SI->getOperand(0)->getType(), Offset,
1373 VecTy, AllocaSize, *TD, V->getContext());
1374 SawVec |= isa<VectorType>(SI->getOperand(0)->getType());
1378 if (BitCastInst *BCI = dyn_cast<BitCastInst>(User)) {
1379 if (!CanConvertToScalar(BCI, IsNotTrivial, VecTy, SawVec, Offset,
1382 IsNotTrivial = true;
1386 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) {
1387 // If this is a GEP with a variable indices, we can't handle it.
1388 if (!GEP->hasAllConstantIndices())
1391 // Compute the offset that this GEP adds to the pointer.
1392 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end());
1393 uint64_t GEPOffset = TD->getIndexedOffset(GEP->getOperand(0)->getType(),
1394 &Indices[0], Indices.size());
1395 // See if all uses can be converted.
1396 if (!CanConvertToScalar(GEP, IsNotTrivial, VecTy, SawVec,Offset+GEPOffset,
1399 IsNotTrivial = true;
1403 // If this is a constant sized memset of a constant value (e.g. 0) we can
1405 if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) {
1406 // Store of constant value and constant size.
1407 if (isa<ConstantInt>(MSI->getValue()) &&
1408 isa<ConstantInt>(MSI->getLength())) {
1409 IsNotTrivial = true;
1414 // If this is a memcpy or memmove into or out of the whole allocation, we
1415 // can handle it like a load or store of the scalar type.
1416 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) {
1417 if (ConstantInt *Len = dyn_cast<ConstantInt>(MTI->getLength()))
1418 if (Len->getZExtValue() == AllocaSize && Offset == 0) {
1419 IsNotTrivial = true;
1424 // Ignore dbg intrinsic.
1425 if (isa<DbgInfoIntrinsic>(User))
1428 // Otherwise, we cannot handle this!
1435 /// ConvertUsesToScalar - Convert all of the users of Ptr to use the new alloca
1436 /// directly. This happens when we are converting an "integer union" to a
1437 /// single integer scalar, or when we are converting a "vector union" to a
1438 /// vector with insert/extractelement instructions.
1440 /// Offset is an offset from the original alloca, in bits that need to be
1441 /// shifted to the right. By the end of this, there should be no uses of Ptr.
1442 void SROA::ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, uint64_t Offset) {
1443 while (!Ptr->use_empty()) {
1444 Instruction *User = cast<Instruction>(Ptr->use_back());
1446 if (BitCastInst *CI = dyn_cast<BitCastInst>(User)) {
1447 ConvertUsesToScalar(CI, NewAI, Offset);
1448 CI->eraseFromParent();
1452 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) {
1453 // Compute the offset that this GEP adds to the pointer.
1454 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end());
1455 uint64_t GEPOffset = TD->getIndexedOffset(GEP->getOperand(0)->getType(),
1456 &Indices[0], Indices.size());
1457 ConvertUsesToScalar(GEP, NewAI, Offset+GEPOffset*8);
1458 GEP->eraseFromParent();
1462 IRBuilder<> Builder(User->getParent(), User);
1464 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1465 // The load is a bit extract from NewAI shifted right by Offset bits.
1466 Value *LoadedVal = Builder.CreateLoad(NewAI, "tmp");
1468 = ConvertScalar_ExtractValue(LoadedVal, LI->getType(), Offset, Builder);
1469 LI->replaceAllUsesWith(NewLoadVal);
1470 LI->eraseFromParent();
1474 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
1475 assert(SI->getOperand(0) != Ptr && "Consistency error!");
1476 // FIXME: Remove once builder has Twine API.
1477 Value *Old = Builder.CreateLoad(NewAI,
1478 (NewAI->getName()+".in").str().c_str());
1479 Value *New = ConvertScalar_InsertValue(SI->getOperand(0), Old, Offset,
1481 Builder.CreateStore(New, NewAI);
1482 SI->eraseFromParent();
1486 // If this is a constant sized memset of a constant value (e.g. 0) we can
1487 // transform it into a store of the expanded constant value.
1488 if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) {
1489 assert(MSI->getRawDest() == Ptr && "Consistency error!");
1490 unsigned NumBytes = cast<ConstantInt>(MSI->getLength())->getZExtValue();
1491 if (NumBytes != 0) {
1492 unsigned Val = cast<ConstantInt>(MSI->getValue())->getZExtValue();
1494 // Compute the value replicated the right number of times.
1495 APInt APVal(NumBytes*8, Val);
1497 // Splat the value if non-zero.
1499 for (unsigned i = 1; i != NumBytes; ++i)
1500 APVal |= APVal << 8;
1502 // FIXME: Remove once builder has Twine API.
1503 Value *Old = Builder.CreateLoad(NewAI,
1504 (NewAI->getName()+".in").str().c_str());
1505 Value *New = ConvertScalar_InsertValue(
1506 ConstantInt::get(User->getContext(), APVal),
1507 Old, Offset, Builder);
1508 Builder.CreateStore(New, NewAI);
1510 MSI->eraseFromParent();
1514 // If this is a memcpy or memmove into or out of the whole allocation, we
1515 // can handle it like a load or store of the scalar type.
1516 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) {
1517 assert(Offset == 0 && "must be store to start of alloca");
1519 // If the source and destination are both to the same alloca, then this is
1520 // a noop copy-to-self, just delete it. Otherwise, emit a load and store
1522 AllocaInst *OrigAI = cast<AllocaInst>(Ptr->getUnderlyingObject());
1524 if (MTI->getSource()->getUnderlyingObject() != OrigAI) {
1525 // Dest must be OrigAI, change this to be a load from the original
1526 // pointer (bitcasted), then a store to our new alloca.
1527 assert(MTI->getRawDest() == Ptr && "Neither use is of pointer?");
1528 Value *SrcPtr = MTI->getSource();
1529 SrcPtr = Builder.CreateBitCast(SrcPtr, NewAI->getType());
1531 LoadInst *SrcVal = Builder.CreateLoad(SrcPtr, "srcval");
1532 SrcVal->setAlignment(MTI->getAlignment());
1533 Builder.CreateStore(SrcVal, NewAI);
1534 } else if (MTI->getDest()->getUnderlyingObject() != OrigAI) {
1535 // Src must be OrigAI, change this to be a load from NewAI then a store
1536 // through the original dest pointer (bitcasted).
1537 assert(MTI->getRawSource() == Ptr && "Neither use is of pointer?");
1538 LoadInst *SrcVal = Builder.CreateLoad(NewAI, "srcval");
1540 Value *DstPtr = Builder.CreateBitCast(MTI->getDest(), NewAI->getType());
1541 StoreInst *NewStore = Builder.CreateStore(SrcVal, DstPtr);
1542 NewStore->setAlignment(MTI->getAlignment());
1544 // Noop transfer. Src == Dst
1548 MTI->eraseFromParent();
1552 // If user is a dbg info intrinsic then it is safe to remove it.
1553 if (isa<DbgInfoIntrinsic>(User)) {
1554 User->eraseFromParent();
1558 llvm_unreachable("Unsupported operation!");
1562 /// ConvertScalar_ExtractValue - Extract a value of type ToType from an integer
1563 /// or vector value FromVal, extracting the bits from the offset specified by
1564 /// Offset. This returns the value, which is of type ToType.
1566 /// This happens when we are converting an "integer union" to a single
1567 /// integer scalar, or when we are converting a "vector union" to a vector with
1568 /// insert/extractelement instructions.
1570 /// Offset is an offset from the original alloca, in bits that need to be
1571 /// shifted to the right.
1572 Value *SROA::ConvertScalar_ExtractValue(Value *FromVal, const Type *ToType,
1573 uint64_t Offset, IRBuilder<> &Builder) {
1574 // If the load is of the whole new alloca, no conversion is needed.
1575 if (FromVal->getType() == ToType && Offset == 0)
1578 // If the result alloca is a vector type, this is either an element
1579 // access or a bitcast to another vector type of the same size.
1580 if (const VectorType *VTy = dyn_cast<VectorType>(FromVal->getType())) {
1581 if (isa<VectorType>(ToType))
1582 return Builder.CreateBitCast(FromVal, ToType, "tmp");
1584 // Otherwise it must be an element access.
1587 unsigned EltSize = TD->getTypeAllocSizeInBits(VTy->getElementType());
1588 Elt = Offset/EltSize;
1589 assert(EltSize*Elt == Offset && "Invalid modulus in validity checking");
1591 // Return the element extracted out of it.
1592 Value *V = Builder.CreateExtractElement(FromVal, ConstantInt::get(
1593 Type::getInt32Ty(FromVal->getContext()), Elt), "tmp");
1594 if (V->getType() != ToType)
1595 V = Builder.CreateBitCast(V, ToType, "tmp");
1599 // If ToType is a first class aggregate, extract out each of the pieces and
1600 // use insertvalue's to form the FCA.
1601 if (const StructType *ST = dyn_cast<StructType>(ToType)) {
1602 const StructLayout &Layout = *TD->getStructLayout(ST);
1603 Value *Res = UndefValue::get(ST);
1604 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) {
1605 Value *Elt = ConvertScalar_ExtractValue(FromVal, ST->getElementType(i),
1606 Offset+Layout.getElementOffsetInBits(i),
1608 Res = Builder.CreateInsertValue(Res, Elt, i, "tmp");
1613 if (const ArrayType *AT = dyn_cast<ArrayType>(ToType)) {
1614 uint64_t EltSize = TD->getTypeAllocSizeInBits(AT->getElementType());
1615 Value *Res = UndefValue::get(AT);
1616 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
1617 Value *Elt = ConvertScalar_ExtractValue(FromVal, AT->getElementType(),
1618 Offset+i*EltSize, Builder);
1619 Res = Builder.CreateInsertValue(Res, Elt, i, "tmp");
1624 // Otherwise, this must be a union that was converted to an integer value.
1625 const IntegerType *NTy = cast<IntegerType>(FromVal->getType());
1627 // If this is a big-endian system and the load is narrower than the
1628 // full alloca type, we need to do a shift to get the right bits.
1630 if (TD->isBigEndian()) {
1631 // On big-endian machines, the lowest bit is stored at the bit offset
1632 // from the pointer given by getTypeStoreSizeInBits. This matters for
1633 // integers with a bitwidth that is not a multiple of 8.
1634 ShAmt = TD->getTypeStoreSizeInBits(NTy) -
1635 TD->getTypeStoreSizeInBits(ToType) - Offset;
1640 // Note: we support negative bitwidths (with shl) which are not defined.
1641 // We do this to support (f.e.) loads off the end of a structure where
1642 // only some bits are used.
1643 if (ShAmt > 0 && (unsigned)ShAmt < NTy->getBitWidth())
1644 FromVal = Builder.CreateLShr(FromVal,
1645 ConstantInt::get(FromVal->getType(),
1647 else if (ShAmt < 0 && (unsigned)-ShAmt < NTy->getBitWidth())
1648 FromVal = Builder.CreateShl(FromVal,
1649 ConstantInt::get(FromVal->getType(),
1652 // Finally, unconditionally truncate the integer to the right width.
1653 unsigned LIBitWidth = TD->getTypeSizeInBits(ToType);
1654 if (LIBitWidth < NTy->getBitWidth())
1656 Builder.CreateTrunc(FromVal, IntegerType::get(FromVal->getContext(),
1657 LIBitWidth), "tmp");
1658 else if (LIBitWidth > NTy->getBitWidth())
1660 Builder.CreateZExt(FromVal, IntegerType::get(FromVal->getContext(),
1661 LIBitWidth), "tmp");
1663 // If the result is an integer, this is a trunc or bitcast.
1664 if (isa<IntegerType>(ToType)) {
1666 } else if (ToType->isFloatingPoint() || isa<VectorType>(ToType)) {
1667 // Just do a bitcast, we know the sizes match up.
1668 FromVal = Builder.CreateBitCast(FromVal, ToType, "tmp");
1670 // Otherwise must be a pointer.
1671 FromVal = Builder.CreateIntToPtr(FromVal, ToType, "tmp");
1673 assert(FromVal->getType() == ToType && "Didn't convert right?");
1677 /// ConvertScalar_InsertValue - Insert the value "SV" into the existing integer
1678 /// or vector value "Old" at the offset specified by Offset.
1680 /// This happens when we are converting an "integer union" to a
1681 /// single integer scalar, or when we are converting a "vector union" to a
1682 /// vector with insert/extractelement instructions.
1684 /// Offset is an offset from the original alloca, in bits that need to be
1685 /// shifted to the right.
1686 Value *SROA::ConvertScalar_InsertValue(Value *SV, Value *Old,
1687 uint64_t Offset, IRBuilder<> &Builder) {
1689 // Convert the stored type to the actual type, shift it left to insert
1690 // then 'or' into place.
1691 const Type *AllocaType = Old->getType();
1692 LLVMContext &Context = Old->getContext();
1694 if (const VectorType *VTy = dyn_cast<VectorType>(AllocaType)) {
1695 uint64_t VecSize = TD->getTypeAllocSizeInBits(VTy);
1696 uint64_t ValSize = TD->getTypeAllocSizeInBits(SV->getType());
1698 // Changing the whole vector with memset or with an access of a different
1700 if (ValSize == VecSize)
1701 return Builder.CreateBitCast(SV, AllocaType, "tmp");
1703 uint64_t EltSize = TD->getTypeAllocSizeInBits(VTy->getElementType());
1705 // Must be an element insertion.
1706 unsigned Elt = Offset/EltSize;
1708 if (SV->getType() != VTy->getElementType())
1709 SV = Builder.CreateBitCast(SV, VTy->getElementType(), "tmp");
1711 SV = Builder.CreateInsertElement(Old, SV,
1712 ConstantInt::get(Type::getInt32Ty(SV->getContext()), Elt),
1717 // If SV is a first-class aggregate value, insert each value recursively.
1718 if (const StructType *ST = dyn_cast<StructType>(SV->getType())) {
1719 const StructLayout &Layout = *TD->getStructLayout(ST);
1720 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) {
1721 Value *Elt = Builder.CreateExtractValue(SV, i, "tmp");
1722 Old = ConvertScalar_InsertValue(Elt, Old,
1723 Offset+Layout.getElementOffsetInBits(i),
1729 if (const ArrayType *AT = dyn_cast<ArrayType>(SV->getType())) {
1730 uint64_t EltSize = TD->getTypeAllocSizeInBits(AT->getElementType());
1731 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
1732 Value *Elt = Builder.CreateExtractValue(SV, i, "tmp");
1733 Old = ConvertScalar_InsertValue(Elt, Old, Offset+i*EltSize, Builder);
1738 // If SV is a float, convert it to the appropriate integer type.
1739 // If it is a pointer, do the same.
1740 unsigned SrcWidth = TD->getTypeSizeInBits(SV->getType());
1741 unsigned DestWidth = TD->getTypeSizeInBits(AllocaType);
1742 unsigned SrcStoreWidth = TD->getTypeStoreSizeInBits(SV->getType());
1743 unsigned DestStoreWidth = TD->getTypeStoreSizeInBits(AllocaType);
1744 if (SV->getType()->isFloatingPoint() || isa<VectorType>(SV->getType()))
1745 SV = Builder.CreateBitCast(SV,
1746 IntegerType::get(SV->getContext(),SrcWidth), "tmp");
1747 else if (isa<PointerType>(SV->getType()))
1748 SV = Builder.CreatePtrToInt(SV, TD->getIntPtrType(SV->getContext()), "tmp");
1750 // Zero extend or truncate the value if needed.
1751 if (SV->getType() != AllocaType) {
1752 if (SV->getType()->getPrimitiveSizeInBits() <
1753 AllocaType->getPrimitiveSizeInBits())
1754 SV = Builder.CreateZExt(SV, AllocaType, "tmp");
1756 // Truncation may be needed if storing more than the alloca can hold
1757 // (undefined behavior).
1758 SV = Builder.CreateTrunc(SV, AllocaType, "tmp");
1759 SrcWidth = DestWidth;
1760 SrcStoreWidth = DestStoreWidth;
1764 // If this is a big-endian system and the store is narrower than the
1765 // full alloca type, we need to do a shift to get the right bits.
1767 if (TD->isBigEndian()) {
1768 // On big-endian machines, the lowest bit is stored at the bit offset
1769 // from the pointer given by getTypeStoreSizeInBits. This matters for
1770 // integers with a bitwidth that is not a multiple of 8.
1771 ShAmt = DestStoreWidth - SrcStoreWidth - Offset;
1776 // Note: we support negative bitwidths (with shr) which are not defined.
1777 // We do this to support (f.e.) stores off the end of a structure where
1778 // only some bits in the structure are set.
1779 APInt Mask(APInt::getLowBitsSet(DestWidth, SrcWidth));
1780 if (ShAmt > 0 && (unsigned)ShAmt < DestWidth) {
1781 SV = Builder.CreateShl(SV, ConstantInt::get(SV->getType(),
1784 } else if (ShAmt < 0 && (unsigned)-ShAmt < DestWidth) {
1785 SV = Builder.CreateLShr(SV, ConstantInt::get(SV->getType(),
1787 Mask = Mask.lshr(-ShAmt);
1790 // Mask out the bits we are about to insert from the old value, and or
1792 if (SrcWidth != DestWidth) {
1793 assert(DestWidth > SrcWidth);
1794 Old = Builder.CreateAnd(Old, ConstantInt::get(Context, ~Mask), "mask");
1795 SV = Builder.CreateOr(Old, SV, "ins");
1802 /// PointsToConstantGlobal - Return true if V (possibly indirectly) points to
1803 /// some part of a constant global variable. This intentionally only accepts
1804 /// constant expressions because we don't can't rewrite arbitrary instructions.
1805 static bool PointsToConstantGlobal(Value *V) {
1806 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
1807 return GV->isConstant();
1808 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
1809 if (CE->getOpcode() == Instruction::BitCast ||
1810 CE->getOpcode() == Instruction::GetElementPtr)
1811 return PointsToConstantGlobal(CE->getOperand(0));
1815 /// isOnlyCopiedFromConstantGlobal - Recursively walk the uses of a (derived)
1816 /// pointer to an alloca. Ignore any reads of the pointer, return false if we
1817 /// see any stores or other unknown uses. If we see pointer arithmetic, keep
1818 /// track of whether it moves the pointer (with isOffset) but otherwise traverse
1819 /// the uses. If we see a memcpy/memmove that targets an unoffseted pointer to
1820 /// the alloca, and if the source pointer is a pointer to a constant global, we
1821 /// can optimize this.
1822 static bool isOnlyCopiedFromConstantGlobal(Value *V, Instruction *&TheCopy,
1824 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) {
1825 if (LoadInst *LI = dyn_cast<LoadInst>(*UI))
1826 // Ignore non-volatile loads, they are always ok.
1827 if (!LI->isVolatile())
1830 if (BitCastInst *BCI = dyn_cast<BitCastInst>(*UI)) {
1831 // If uses of the bitcast are ok, we are ok.
1832 if (!isOnlyCopiedFromConstantGlobal(BCI, TheCopy, isOffset))
1836 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(*UI)) {
1837 // If the GEP has all zero indices, it doesn't offset the pointer. If it
1838 // doesn't, it does.
1839 if (!isOnlyCopiedFromConstantGlobal(GEP, TheCopy,
1840 isOffset || !GEP->hasAllZeroIndices()))
1845 // If this is isn't our memcpy/memmove, reject it as something we can't
1847 if (!isa<MemTransferInst>(*UI))
1850 // If we already have seen a copy, reject the second one.
1851 if (TheCopy) return false;
1853 // If the pointer has been offset from the start of the alloca, we can't
1854 // safely handle this.
1855 if (isOffset) return false;
1857 // If the memintrinsic isn't using the alloca as the dest, reject it.
1858 if (UI.getOperandNo() != 1) return false;
1860 MemIntrinsic *MI = cast<MemIntrinsic>(*UI);
1862 // If the source of the memcpy/move is not a constant global, reject it.
1863 if (!PointsToConstantGlobal(MI->getOperand(2)))
1866 // Otherwise, the transform is safe. Remember the copy instruction.
1872 /// isOnlyCopiedFromConstantGlobal - Return true if the specified alloca is only
1873 /// modified by a copy from a constant global. If we can prove this, we can
1874 /// replace any uses of the alloca with uses of the global directly.
1875 Instruction *SROA::isOnlyCopiedFromConstantGlobal(AllocaInst *AI) {
1876 Instruction *TheCopy = 0;
1877 if (::isOnlyCopiedFromConstantGlobal(AI, TheCopy, false))