1//===- ScalarReplAggregates.cpp - Scalar Replacement of Aggregates --------===//
2//
3// The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
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.
15//
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.
19//
20//===----------------------------------------------------------------------===//
21
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/Pass.h"
31#include "llvm/Analysis/Dominators.h"
32#include "llvm/Target/TargetData.h"
33#include "llvm/Transforms/Utils/PromoteMemToReg.h"
34#include "llvm/Transforms/Utils/Local.h"
35#include "llvm/Support/Debug.h"
36#include "llvm/Support/GetElementPtrTypeIterator.h"
37#include "llvm/Support/IRBuilder.h"
38#include "llvm/Support/MathExtras.h"
39#include "llvm/Support/Compiler.h"
40#include "llvm/ADT/SmallVector.h"
41#include "llvm/ADT/Statistic.h"
42#include "llvm/ADT/StringExtras.h"
43using namespace llvm;
44
45STATISTIC(NumReplaced, "Number of allocas broken up");
46STATISTIC(NumPromoted, "Number of allocas promoted");
47STATISTIC(NumConverted, "Number of aggregates converted to scalar");
48STATISTIC(NumGlobals, "Number of allocas copied from constant global");
49
50namespace {
51 struct VISIBILITY_HIDDEN SROA : public FunctionPass {
52 static char ID; // Pass identification, replacement for typeid
53 explicit SROA(signed T = -1) : FunctionPass(&ID) {
54 if (T == -1)
55 SRThreshold = 128;
56 else
57 SRThreshold = T;
58 }
59
60 bool runOnFunction(Function &F);
61
62 bool performScalarRepl(Function &F);
63 bool performPromotion(Function &F);
64
65 // getAnalysisUsage - This pass does not require any passes, but we know it
66 // will not alter the CFG, so say so.
67 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
68 AU.addRequired<DominatorTree>();
69 AU.addRequired<DominanceFrontier>();
70 AU.addRequired<TargetData>();
71 AU.setPreservesCFG();
72 }
73
74 private:
75 TargetData *TD;
76
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.
80 struct AllocaInfo {
81 /// isUnsafe - This is set to true if the alloca cannot be SROA'd.
82 bool isUnsafe : 1;
83
84 /// needsCleanup - This is set to true if there is some use of the alloca
85 /// that requires cleanup.
86 bool needsCleanup : 1;
87
88 /// isMemCpySrc - This is true if this aggregate is memcpy'd from.
89 bool isMemCpySrc : 1;
90
91 /// isMemCpyDst - This is true if this aggregate is memcpy'd into.
92 bool isMemCpyDst : 1;
93
94 AllocaInfo()
95 : isUnsafe(false), needsCleanup(false),
96 isMemCpySrc(false), isMemCpyDst(false) {}
97 };
98
99 unsigned SRThreshold;
100
101 void MarkUnsafe(AllocaInfo &I) { I.isUnsafe = true; }
102
103 int isSafeAllocaToScalarRepl(AllocationInst *AI);
104
105 void isSafeUseOfAllocation(Instruction *User, AllocationInst *AI,
106 AllocaInfo &Info);
107 void isSafeElementUse(Value *Ptr, bool isFirstElt, AllocationInst *AI,
108 AllocaInfo &Info);
109 void isSafeMemIntrinsicOnAllocation(MemIntrinsic *MI, AllocationInst *AI,
110 unsigned OpNo, AllocaInfo &Info);
111 void isSafeUseOfBitCastedAllocation(BitCastInst *User, AllocationInst *AI,
112 AllocaInfo &Info);
113
114 void DoScalarReplacement(AllocationInst *AI,
115 std::vector<AllocationInst*> &WorkList);
116 void CleanupGEP(GetElementPtrInst *GEP);
117 void CleanupAllocaUsers(AllocationInst *AI);
118 AllocaInst *AddNewAlloca(Function &F, const Type *Ty, AllocationInst *Base);
119
120 void RewriteBitCastUserOfAlloca(Instruction *BCInst, AllocationInst *AI,
121 SmallVector<AllocaInst*, 32> &NewElts);
122
123 void RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *BCInst,
124 AllocationInst *AI,
125 SmallVector<AllocaInst*, 32> &NewElts);
126 void RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocationInst *AI,
127 SmallVector<AllocaInst*, 32> &NewElts);
128 void RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocationInst *AI,
129 SmallVector<AllocaInst*, 32> &NewElts);
130
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(AllocationInst *AI);
139 };
140}
141
142char SROA::ID = 0;
143static RegisterPass<SROA> X("scalarrepl", "Scalar Replacement of Aggregates");
144
145// Public interface to the ScalarReplAggregates pass
146FunctionPass *llvm::createScalarReplAggregatesPass(signed int Threshold) {
147 return new SROA(Threshold);
148}
149
150
151bool SROA::runOnFunction(Function &F) {
152 TD = &getAnalysis<TargetData>();
153
154 bool Changed = performPromotion(F);
155 while (1) {
156 bool LocalChange = performScalarRepl(F);
157 if (!LocalChange) break; // No need to repromote if no scalarrepl
158 Changed = true;
159 LocalChange = performPromotion(F);
160 if (!LocalChange) break; // No need to re-scalarrepl if no promotion
161 }
162
163 return Changed;
164}
165
166
167bool SROA::performPromotion(Function &F) {
168 std::vector<AllocaInst*> Allocas;
169 DominatorTree &DT = getAnalysis<DominatorTree>();
170 DominanceFrontier &DF = getAnalysis<DominanceFrontier>();
171
172 BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function
173
174 bool Changed = false;
175
176 while (1) {
177 Allocas.clear();
178
179 // Find allocas that are safe to promote, by looking at all instructions in
180 // the entry node
181 for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I)
182 if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) // Is it an alloca?
183 if (isAllocaPromotable(AI))
184 Allocas.push_back(AI);
185
186 if (Allocas.empty()) break;
187
188 PromoteMemToReg(Allocas, DT, DF);
189 NumPromoted += Allocas.size();
190 Changed = true;
191 }
192
193 return Changed;
194}
195
196/// getNumSAElements - Return the number of elements in the specific struct or
197/// array.
198static uint64_t getNumSAElements(const Type *T) {
199 if (const StructType *ST = dyn_cast<StructType>(T))
200 return ST->getNumElements();
201 return cast<ArrayType>(T)->getNumElements();
202}
203
204// performScalarRepl - This algorithm is a simple worklist driven algorithm,
205// which runs on all of the malloc/alloca instructions in the function, removing
206// them if they are only used by getelementptr instructions.
207//
208bool SROA::performScalarRepl(Function &F) {
209 std::vector<AllocationInst*> WorkList;
210
211 // Scan the entry basic block, adding any alloca's and mallocs to the worklist
212 BasicBlock &BB = F.getEntryBlock();
213 for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I)
214 if (AllocationInst *A = dyn_cast<AllocationInst>(I))
215 WorkList.push_back(A);
216
217 // Process the worklist
218 bool Changed = false;
219 while (!WorkList.empty()) {
220 AllocationInst *AI = WorkList.back();
221 WorkList.pop_back();
222
223 // Handle dead allocas trivially. These can be formed by SROA'ing arrays
224 // with unused elements.
225 if (AI->use_empty()) {
226 AI->eraseFromParent();
227 continue;
228 }
229
230 // If this alloca is impossible for us to promote, reject it early.
231 if (AI->isArrayAllocation() || !AI->getAllocatedType()->isSized())
232 continue;
233
234 // Check to see if this allocation is only modified by a memcpy/memmove from
235 // a constant global. If this is the case, we can change all users to use
236 // the constant global instead. This is commonly produced by the CFE by
237 // constructs like "void foo() { int A[] = {1,2,3,4,5,6,7,8,9...}; }" if 'A'
238 // is only subsequently read.
239 if (Instruction *TheCopy = isOnlyCopiedFromConstantGlobal(AI)) {
240 DOUT << "Found alloca equal to global: " << *AI;
241 DOUT << " memcpy = " << *TheCopy;
242 Constant *TheSrc = cast<Constant>(TheCopy->getOperand(2));
243 AI->replaceAllUsesWith(ConstantExpr::getBitCast(TheSrc, AI->getType()));
244 TheCopy->eraseFromParent(); // Don't mutate the global.
245 AI->eraseFromParent();
246 ++NumGlobals;
247 Changed = true;
248 continue;
249 }
250
251 // Check to see if we can perform the core SROA transformation. We cannot
252 // transform the allocation instruction if it is an array allocation
253 // (allocations OF arrays are ok though), and an allocation of a scalar
254 // value cannot be decomposed at all.
255 uint64_t AllocaSize = TD->getTypeAllocSize(AI->getAllocatedType());
256
257 // Do not promote any struct whose size is too big.
258 if (AllocaSize > SRThreshold) continue;
259
260 if ((isa<StructType>(AI->getAllocatedType()) ||
261 isa<ArrayType>(AI->getAllocatedType())) &&
262 // Do not promote any struct into more than "32" separate vars.
263 getNumSAElements(AI->getAllocatedType()) <= SRThreshold/4) {
264 // Check that all of the users of the allocation are capable of being
265 // transformed.
266 switch (isSafeAllocaToScalarRepl(AI)) {
267 default: assert(0 && "Unexpected value!");
268 case 0: // Not safe to scalar replace.
269 break;
270 case 1: // Safe, but requires cleanup/canonicalizations first
271 CleanupAllocaUsers(AI);
272 // FALL THROUGH.
273 case 3: // Safe to scalar replace.
274 DoScalarReplacement(AI, WorkList);
275 Changed = true;
276 continue;
277 }
278 }
279
280 // If we can turn this aggregate value (potentially with casts) into a
281 // simple scalar value that can be mem2reg'd into a register value.
282 // IsNotTrivial tracks whether this is something that mem2reg could have
283 // promoted itself. If so, we don't want to transform it needlessly. Note
284 // that we can't just check based on the type: the alloca may be of an i32
285 // but that has pointer arithmetic to set byte 3 of it or something.
286 bool IsNotTrivial = false;
287 const Type *VectorTy = 0;
288 bool HadAVector = false;
289 if (CanConvertToScalar(AI, IsNotTrivial, VectorTy, HadAVector,
290 0, unsigned(AllocaSize)) && IsNotTrivial) {
291 AllocaInst *NewAI;
292 // If we were able to find a vector type that can handle this with
293 // insert/extract elements, and if there was at least one use that had
294 // a vector type, promote this to a vector. We don't want to promote
295 // random stuff that doesn't use vectors (e.g. <9 x double>) because then
296 // we just get a lot of insert/extracts. If at least one vector is
297 // involved, then we probably really do have a union of vector/array.
298 if (VectorTy && isa<VectorType>(VectorTy) && HadAVector) {
299 DOUT << "CONVERT TO VECTOR: " << *AI << " TYPE = " << *VectorTy <<"\n";
300
301 // Create and insert the vector alloca.
302 NewAI = new AllocaInst(VectorTy, 0, "", AI->getParent()->begin());
303 ConvertUsesToScalar(AI, NewAI, 0);
304 } else {
305 DOUT << "CONVERT TO SCALAR INTEGER: " << *AI << "\n";
306
307 // Create and insert the integer alloca.
308 const Type *NewTy = IntegerType::get(AllocaSize*8);
309 NewAI = new AllocaInst(NewTy, 0, "", AI->getParent()->begin());
310 ConvertUsesToScalar(AI, NewAI, 0);
311 }
312 NewAI->takeName(AI);
313 AI->eraseFromParent();
314 ++NumConverted;
315 Changed = true;
316 continue;
317 }
318
319 // Otherwise, couldn't process this alloca.
320 }
321
322 return Changed;
323}
324
325/// DoScalarReplacement - This alloca satisfied the isSafeAllocaToScalarRepl
326/// predicate, do SROA now.
327void SROA::DoScalarReplacement(AllocationInst *AI,
328 std::vector<AllocationInst*> &WorkList) {
329 DOUT << "Found inst to SROA: " << *AI;
330 SmallVector<AllocaInst*, 32> ElementAllocas;
331 if (const StructType *ST = dyn_cast<StructType>(AI->getAllocatedType())) {
332 ElementAllocas.reserve(ST->getNumContainedTypes());
333 for (unsigned i = 0, e = ST->getNumContainedTypes(); i != e; ++i) {
334 AllocaInst *NA = new AllocaInst(ST->getContainedType(i), 0,
335 AI->getAlignment(),
336 AI->getName() + "." + utostr(i), AI);
337 ElementAllocas.push_back(NA);
338 WorkList.push_back(NA); // Add to worklist for recursive processing
339 }
340 } else {
341 const ArrayType *AT = cast<ArrayType>(AI->getAllocatedType());
342 ElementAllocas.reserve(AT->getNumElements());
343 const Type *ElTy = AT->getElementType();
344 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
345 AllocaInst *NA = new AllocaInst(ElTy, 0, AI->getAlignment(),
346 AI->getName() + "." + utostr(i), AI);
347 ElementAllocas.push_back(NA);
348 WorkList.push_back(NA); // Add to worklist for recursive processing
349 }
350 }
351
352 // Now that we have created the alloca instructions that we want to use,
353 // expand the getelementptr instructions to use them.
354 //
355 while (!AI->use_empty()) {
356 Instruction *User = cast<Instruction>(AI->use_back());
357 if (BitCastInst *BCInst = dyn_cast<BitCastInst>(User)) {
358 RewriteBitCastUserOfAlloca(BCInst, AI, ElementAllocas);
359 BCInst->eraseFromParent();
360 continue;
361 }
362
363 // Replace:
364 // %res = load { i32, i32 }* %alloc
365 // with:
366 // %load.0 = load i32* %alloc.0
367 // %insert.0 insertvalue { i32, i32 } zeroinitializer, i32 %load.0, 0
368 // %load.1 = load i32* %alloc.1
369 // %insert = insertvalue { i32, i32 } %insert.0, i32 %load.1, 1
370 // (Also works for arrays instead of structs)
371 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
372 Value *Insert = UndefValue::get(LI->getType());
373 for (unsigned i = 0, e = ElementAllocas.size(); i != e; ++i) {
374 Value *Load = new LoadInst(ElementAllocas[i], "load", LI);
375 Insert = InsertValueInst::Create(Insert, Load, i, "insert", LI);
376 }
377 LI->replaceAllUsesWith(Insert);
378 LI->eraseFromParent();
379 continue;
380 }
381
382 // Replace:
383 // store { i32, i32 } %val, { i32, i32 }* %alloc
384 // with:
385 // %val.0 = extractvalue { i32, i32 } %val, 0
386 // store i32 %val.0, i32* %alloc.0
387 // %val.1 = extractvalue { i32, i32 } %val, 1
388 // store i32 %val.1, i32* %alloc.1
389 // (Also works for arrays instead of structs)
390 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
391 Value *Val = SI->getOperand(0);
392 for (unsigned i = 0, e = ElementAllocas.size(); i != e; ++i) {
393 Value *Extract = ExtractValueInst::Create(Val, i, Val->getName(), SI);
394 new StoreInst(Extract, ElementAllocas[i], SI);
395 }
396 SI->eraseFromParent();
397 continue;
398 }
399
400 GetElementPtrInst *GEPI = cast<GetElementPtrInst>(User);
401 // We now know that the GEP is of the form: GEP <ptr>, 0, <cst>
402 unsigned Idx =
403 (unsigned)cast<ConstantInt>(GEPI->getOperand(2))->getZExtValue();
404
405 assert(Idx < ElementAllocas.size() && "Index out of range?");
406 AllocaInst *AllocaToUse = ElementAllocas[Idx];
407
408 Value *RepValue;
409 if (GEPI->getNumOperands() == 3) {
410 // Do not insert a new getelementptr instruction with zero indices, only
411 // to have it optimized out later.
412 RepValue = AllocaToUse;
413 } else {
414 // We are indexing deeply into the structure, so we still need a
415 // getelement ptr instruction to finish the indexing. This may be
416 // expanded itself once the worklist is rerun.
417 //
418 SmallVector<Value*, 8> NewArgs;
419 NewArgs.push_back(Constant::getNullValue(Type::Int32Ty));
420 NewArgs.append(GEPI->op_begin()+3, GEPI->op_end());
421 RepValue = GetElementPtrInst::Create(AllocaToUse, NewArgs.begin(),
422 NewArgs.end(), "", GEPI);
423 RepValue->takeName(GEPI);
424 }
425
426 // If this GEP is to the start of the aggregate, check for memcpys.
427 if (Idx == 0 && GEPI->hasAllZeroIndices())
428 RewriteBitCastUserOfAlloca(GEPI, AI, ElementAllocas);
429
430 // Move all of the users over to the new GEP.
431 GEPI->replaceAllUsesWith(RepValue);
432 // Delete the old GEP
433 GEPI->eraseFromParent();
434 }
435
436 // Finally, delete the Alloca instruction
437 AI->eraseFromParent();
438 NumReplaced++;
439}
440
441
442/// isSafeElementUse - Check to see if this use is an allowed use for a
443/// getelementptr instruction of an array aggregate allocation. isFirstElt
444/// indicates whether Ptr is known to the start of the aggregate.
445///
446void SROA::isSafeElementUse(Value *Ptr, bool isFirstElt, AllocationInst *AI,
447 AllocaInfo &Info) {
448 for (Value::use_iterator I = Ptr->use_begin(), E = Ptr->use_end();
449 I != E; ++I) {
450 Instruction *User = cast<Instruction>(*I);
451 switch (User->getOpcode()) {
452 case Instruction::Load: break;
453 case Instruction::Store:
454 // Store is ok if storing INTO the pointer, not storing the pointer
455 if (User->getOperand(0) == Ptr) return MarkUnsafe(Info);
456 break;
457 case Instruction::GetElementPtr: {
458 GetElementPtrInst *GEP = cast<GetElementPtrInst>(User);
459 bool AreAllZeroIndices = isFirstElt;
460 if (GEP->getNumOperands() > 1) {
461 if (!isa<ConstantInt>(GEP->getOperand(1)) ||
462 !cast<ConstantInt>(GEP->getOperand(1))->isZero())
463 // Using pointer arithmetic to navigate the array.
464 return MarkUnsafe(Info);
465
466 if (AreAllZeroIndices)
467 AreAllZeroIndices = GEP->hasAllZeroIndices();
468 }
469 isSafeElementUse(GEP, AreAllZeroIndices, AI, Info);
470 if (Info.isUnsafe) return;
471 break;
472 }
473 case Instruction::BitCast:
474 if (isFirstElt) {
475 isSafeUseOfBitCastedAllocation(cast<BitCastInst>(User), AI, Info);
476 if (Info.isUnsafe) return;
477 break;
478 }
479 DOUT << " Transformation preventing inst: " << *User;
480 return MarkUnsafe(Info);
481 case Instruction::Call:
482 if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) {
483 if (isFirstElt) {
484 isSafeMemIntrinsicOnAllocation(MI, AI, I.getOperandNo(), Info);
485 if (Info.isUnsafe) return;
486 break;
487 }
488 }
489 DOUT << " Transformation preventing inst: " << *User;
490 return MarkUnsafe(Info);
491 default:
492 DOUT << " Transformation preventing inst: " << *User;
493 return MarkUnsafe(Info);
494 }
495 }
496 return; // All users look ok :)
497}
498
499/// AllUsersAreLoads - Return true if all users of this value are loads.
500static bool AllUsersAreLoads(Value *Ptr) {
501 for (Value::use_iterator I = Ptr->use_begin(), E = Ptr->use_end();
502 I != E; ++I)
503 if (cast<Instruction>(*I)->getOpcode() != Instruction::Load)
504 return false;
505 return true;
506}
507
508/// isSafeUseOfAllocation - Check to see if this user is an allowed use for an
509/// aggregate allocation.
510///
511void SROA::isSafeUseOfAllocation(Instruction *User, AllocationInst *AI,
512 AllocaInfo &Info) {
513 if (BitCastInst *C = dyn_cast<BitCastInst>(User))
514 return isSafeUseOfBitCastedAllocation(C, AI, Info);
515
516 if (LoadInst *LI = dyn_cast<LoadInst>(User))
517 if (!LI->isVolatile())
518 return;// Loads (returning a first class aggregrate) are always rewritable
519
520 if (StoreInst *SI = dyn_cast<StoreInst>(User))
521 if (!SI->isVolatile() && SI->getOperand(0) != AI)
522 return;// Store is ok if storing INTO the pointer, not storing the pointer
523
524 GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User);
525 if (GEPI == 0)
526 return MarkUnsafe(Info);
527
528 gep_type_iterator I = gep_type_begin(GEPI), E = gep_type_end(GEPI);
529
530 // The GEP is not safe to transform if not of the form "GEP <ptr>, 0, <cst>".
531 if (I == E ||
532 I.getOperand() != Constant::getNullValue(I.getOperand()->getType())) {
533 return MarkUnsafe(Info);
534 }
535
536 ++I;
537 if (I == E) return MarkUnsafe(Info); // ran out of GEP indices??
538
539 bool IsAllZeroIndices = true;
540
541 // If the first index is a non-constant index into an array, see if we can
542 // handle it as a special case.
543 if (const ArrayType *AT = dyn_cast<ArrayType>(*I)) {
544 if (!isa<ConstantInt>(I.getOperand())) {
545 IsAllZeroIndices = 0;
546 uint64_t NumElements = AT->getNumElements();
547
548 // If this is an array index and the index is not constant, we cannot
549 // promote... that is unless the array has exactly one or two elements in
550 // it, in which case we CAN promote it, but we have to canonicalize this
551 // out if this is the only problem.
552 if ((NumElements == 1 || NumElements == 2) &&
553 AllUsersAreLoads(GEPI)) {
554 Info.needsCleanup = true;
555 return; // Canonicalization required!
556 }
557 return MarkUnsafe(Info);
558 }
559 }
560
561 // Walk through the GEP type indices, checking the types that this indexes
562 // into.
563 for (; I != E; ++I) {
564 // Ignore struct elements, no extra checking needed for these.
565 if (isa<StructType>(*I))
566 continue;
567
568 ConstantInt *IdxVal = dyn_cast<ConstantInt>(I.getOperand());
569 if (!IdxVal) return MarkUnsafe(Info);
570
571 // Are all indices still zero?
572 IsAllZeroIndices &= IdxVal->isZero();
573
574 if (const ArrayType *AT = dyn_cast<ArrayType>(*I)) {
575 // This GEP indexes an array. Verify that this is an in-range constant
576 // integer. Specifically, consider A[0][i]. We cannot know that the user
577 // isn't doing invalid things like allowing i to index an out-of-range
578 // subscript that accesses A[1]. Because of this, we have to reject SROA
579 // of any accesses into structs where any of the components are variables.
580 if (IdxVal->getZExtValue() >= AT->getNumElements())
581 return MarkUnsafe(Info);
582 } else if (const VectorType *VT = dyn_cast<VectorType>(*I)) {
583 if (IdxVal->getZExtValue() >= VT->getNumElements())
584 return MarkUnsafe(Info);
585 }
586 }
587
588 // If there are any non-simple uses of this getelementptr, make sure to reject
589 // them.
590 return isSafeElementUse(GEPI, IsAllZeroIndices, AI, Info);
591}
592
593/// isSafeMemIntrinsicOnAllocation - Return true if the specified memory
594/// intrinsic can be promoted by SROA. At this point, we know that the operand
595/// of the memintrinsic is a pointer to the beginning of the allocation.
596void SROA::isSafeMemIntrinsicOnAllocation(MemIntrinsic *MI, AllocationInst *AI,
597 unsigned OpNo, AllocaInfo &Info) {
598 // If not constant length, give up.
599 ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength());
600 if (!Length) return MarkUnsafe(Info);
601
602 // If not the whole aggregate, give up.
603 if (Length->getZExtValue() !=
604 TD->getTypeAllocSize(AI->getType()->getElementType()))
605 return MarkUnsafe(Info);
606
607 // We only know about memcpy/memset/memmove.
608 if (!isa<MemIntrinsic>(MI))
609 return MarkUnsafe(Info);
610
611 // Otherwise, we can transform it. Determine whether this is a memcpy/set
612 // into or out of the aggregate.
613 if (OpNo == 1)
614 Info.isMemCpyDst = true;
615 else {
616 assert(OpNo == 2);
617 Info.isMemCpySrc = true;
618 }
619}
620
621/// isSafeUseOfBitCastedAllocation - Return true if all users of this bitcast
622/// are
623void SROA::isSafeUseOfBitCastedAllocation(BitCastInst *BC, AllocationInst *AI,
624 AllocaInfo &Info) {
625 for (Value::use_iterator UI = BC->use_begin(), E = BC->use_end();
626 UI != E; ++UI) {
627 if (BitCastInst *BCU = dyn_cast<BitCastInst>(UI)) {
628 isSafeUseOfBitCastedAllocation(BCU, AI, Info);
629 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(UI)) {
630 isSafeMemIntrinsicOnAllocation(MI, AI, UI.getOperandNo(), Info);
631 } else if (StoreInst *SI = dyn_cast<StoreInst>(UI)) {
632 if (SI->isVolatile())
633 return MarkUnsafe(Info);
634
635 // If storing the entire alloca in one chunk through a bitcasted pointer
636 // to integer, we can transform it. This happens (for example) when you
637 // cast a {i32,i32}* to i64* and store through it. This is similar to the
638 // memcpy case and occurs in various "byval" cases and emulated memcpys.
639 if (isa<IntegerType>(SI->getOperand(0)->getType()) &&
640 TD->getTypeAllocSize(SI->getOperand(0)->getType()) ==
641 TD->getTypeAllocSize(AI->getType()->getElementType())) {
642 Info.isMemCpyDst = true;
643 continue;
644 }
645 return MarkUnsafe(Info);
646 } else if (LoadInst *LI = dyn_cast<LoadInst>(UI)) {
647 if (LI->isVolatile())
648 return MarkUnsafe(Info);
649
650 // If loading the entire alloca in one chunk through a bitcasted pointer
651 // to integer, we can transform it. This happens (for example) when you
652 // cast a {i32,i32}* to i64* and load through it. This is similar to the
653 // memcpy case and occurs in various "byval" cases and emulated memcpys.
654 if (isa<IntegerType>(LI->getType()) &&
655 TD->getTypeAllocSize(LI->getType()) ==
656 TD->getTypeAllocSize(AI->getType()->getElementType())) {
657 Info.isMemCpySrc = true;
658 continue;
659 }
660 return MarkUnsafe(Info);
661 } else if (isa<DbgInfoIntrinsic>(UI)) {
662 // If one user is DbgInfoIntrinsic then check if all users are
663 // DbgInfoIntrinsics.
664 if (OnlyUsedByDbgInfoIntrinsics(BC)) {
665 Info.needsCleanup = true;
666 return;
667 }
668 else
669 MarkUnsafe(Info);
670 }
671 else {
672 return MarkUnsafe(Info);
673 }
674 if (Info.isUnsafe) return;
675 }
676}
677
678/// RewriteBitCastUserOfAlloca - BCInst (transitively) bitcasts AI, or indexes
679/// to its first element. Transform users of the cast to use the new values
680/// instead.
681void SROA::RewriteBitCastUserOfAlloca(Instruction *BCInst, AllocationInst *AI,
682 SmallVector<AllocaInst*, 32> &NewElts) {
683 Value::use_iterator UI = BCInst->use_begin(), UE = BCInst->use_end();
684 while (UI != UE) {
685 Instruction *User = cast<Instruction>(*UI++);
686 if (BitCastInst *BCU = dyn_cast<BitCastInst>(User)) {
687 RewriteBitCastUserOfAlloca(BCU, AI, NewElts);
688 if (BCU->use_empty()) BCU->eraseFromParent();
689 continue;
690 }
691
692 if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) {
693 // This must be memcpy/memmove/memset of the entire aggregate.
694 // Split into one per element.
695 RewriteMemIntrinUserOfAlloca(MI, BCInst, AI, NewElts);
696 continue;
697 }
698
699 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
700 // If this is a store of the entire alloca from an integer, rewrite it.
701 RewriteStoreUserOfWholeAlloca(SI, AI, NewElts);
702 continue;
703 }
704
705 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
706 // If this is a load of the entire alloca to an integer, rewrite it.
707 RewriteLoadUserOfWholeAlloca(LI, AI, NewElts);
708 continue;
709 }
710
711 // Otherwise it must be some other user of a gep of the first pointer. Just
712 // leave these alone.
713 continue;
714 }
715}
716
717/// RewriteMemIntrinUserOfAlloca - MI is a memcpy/memset/memmove from or to AI.
718/// Rewrite it to copy or set the elements of the scalarized memory.
719void SROA::RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *BCInst,
720 AllocationInst *AI,
721 SmallVector<AllocaInst*, 32> &NewElts) {
722
723 // If this is a memcpy/memmove, construct the other pointer as the
724 // appropriate type. The "Other" pointer is the pointer that goes to memory
725 // that doesn't have anything to do with the alloca that we are promoting. For
726 // memset, this Value* stays null.
727 Value *OtherPtr = 0;
728 unsigned MemAlignment = MI->getAlignment();
729 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(MI)) { // memmove/memcopy
730 if (BCInst == MTI->getRawDest())
731 OtherPtr = MTI->getRawSource();
732 else {
733 assert(BCInst == MTI->getRawSource());
734 OtherPtr = MTI->getRawDest();
735 }
736 }
737
738 // If there is an other pointer, we want to convert it to the same pointer
739 // type as AI has, so we can GEP through it safely.
740 if (OtherPtr) {
741 // It is likely that OtherPtr is a bitcast, if so, remove it.
742 if (BitCastInst *BC = dyn_cast<BitCastInst>(OtherPtr))
743 OtherPtr = BC->getOperand(0);
744 // All zero GEPs are effectively bitcasts.
745 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(OtherPtr))
746 if (GEP->hasAllZeroIndices())
747 OtherPtr = GEP->getOperand(0);
748
749 if (ConstantExpr *BCE = dyn_cast<ConstantExpr>(OtherPtr))
750 if (BCE->getOpcode() == Instruction::BitCast)
751 OtherPtr = BCE->getOperand(0);
752
753 // If the pointer is not the right type, insert a bitcast to the right
754 // type.
755 if (OtherPtr->getType() != AI->getType())
756 OtherPtr = new BitCastInst(OtherPtr, AI->getType(), OtherPtr->getName(),
757 MI);
758 }
759
760 // Process each element of the aggregate.
761 Value *TheFn = MI->getOperand(0);
762 const Type *BytePtrTy = MI->getRawDest()->getType();
763 bool SROADest = MI->getRawDest() == BCInst;
764
765 Constant *Zero = Constant::getNullValue(Type::Int32Ty);
766
767 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
768 // If this is a memcpy/memmove, emit a GEP of the other element address.
769 Value *OtherElt = 0;
770 unsigned OtherEltAlign = MemAlignment;
771
772 if (OtherPtr) {
773 Value *Idx[2] = { Zero, ConstantInt::get(Type::Int32Ty, i) };
774 OtherElt = GetElementPtrInst::Create(OtherPtr, Idx, Idx + 2,
775 OtherPtr->getNameStr()+"."+utostr(i),
776 MI);
777 uint64_t EltOffset;
778 const PointerType *OtherPtrTy = cast<PointerType>(OtherPtr->getType());
779 if (const StructType *ST =
780 dyn_cast<StructType>(OtherPtrTy->getElementType())) {
781 EltOffset = TD->getStructLayout(ST)->getElementOffset(i);
782 } else {
783 const Type *EltTy =
784 cast<SequentialType>(OtherPtr->getType())->getElementType();
785 EltOffset = TD->getTypeAllocSize(EltTy)*i;
786 }
787
788 // The alignment of the other pointer is the guaranteed alignment of the
789 // element, which is affected by both the known alignment of the whole
790 // mem intrinsic and the alignment of the element. If the alignment of
791 // the memcpy (f.e.) is 32 but the element is at a 4-byte offset, then the
792 // known alignment is just 4 bytes.
793 OtherEltAlign = (unsigned)MinAlign(OtherEltAlign, EltOffset);
794 }
795
796 Value *EltPtr = NewElts[i];
797 const Type *EltTy = cast<PointerType>(EltPtr->getType())->getElementType();
798
799 // If we got down to a scalar, insert a load or store as appropriate.
800 if (EltTy->isSingleValueType()) {
801 if (isa<MemTransferInst>(MI)) {
802 if (SROADest) {
803 // From Other to Alloca.
804 Value *Elt = new LoadInst(OtherElt, "tmp", false, OtherEltAlign, MI);
805 new StoreInst(Elt, EltPtr, MI);
806 } else {
807 // From Alloca to Other.
808 Value *Elt = new LoadInst(EltPtr, "tmp", MI);
809 new StoreInst(Elt, OtherElt, false, OtherEltAlign, MI);
810 }
811 continue;
812 }
813 assert(isa<MemSetInst>(MI));
814
815 // If the stored element is zero (common case), just store a null
816 // constant.
817 Constant *StoreVal;
818 if (ConstantInt *CI = dyn_cast<ConstantInt>(MI->getOperand(2))) {
819 if (CI->isZero()) {
820 StoreVal = Constant::getNullValue(EltTy); // 0.0, null, 0, <0,0>
821 } else {
822 // If EltTy is a vector type, get the element type.
823 const Type *ValTy = EltTy;
824 if (const VectorType *VTy = dyn_cast<VectorType>(ValTy))
825 ValTy = VTy->getElementType();
826
827 // Construct an integer with the right value.
828 unsigned EltSize = TD->getTypeSizeInBits(ValTy);
829 APInt OneVal(EltSize, CI->getZExtValue());
830 APInt TotalVal(OneVal);
831 // Set each byte.
832 for (unsigned i = 0; 8*i < EltSize; ++i) {
833 TotalVal = TotalVal.shl(8);
834 TotalVal |= OneVal;
835 }
836
837 // Convert the integer value to the appropriate type.
838 StoreVal = ConstantInt::get(TotalVal);
839 if (isa<PointerType>(ValTy))
840 StoreVal = ConstantExpr::getIntToPtr(StoreVal, ValTy);
841 else if (ValTy->isFloatingPoint())
842 StoreVal = ConstantExpr::getBitCast(StoreVal, ValTy);
843 assert(StoreVal->getType() == ValTy && "Type mismatch!");
844
845 // If the requested value was a vector constant, create it.
846 if (EltTy != ValTy) {
847 unsigned NumElts = cast<VectorType>(ValTy)->getNumElements();
848 SmallVector<Constant*, 16> Elts(NumElts, StoreVal);
849 StoreVal = ConstantVector::get(&Elts[0], NumElts);
850 }
851 }
852 new StoreInst(StoreVal, EltPtr, MI);
853 continue;
854 }
855 // Otherwise, if we're storing a byte variable, use a memset call for
856 // this element.
857 }
858
859 // Cast the element pointer to BytePtrTy.
860 if (EltPtr->getType() != BytePtrTy)
861 EltPtr = new BitCastInst(EltPtr, BytePtrTy, EltPtr->getNameStr(), MI);
862
863 // Cast the other pointer (if we have one) to BytePtrTy.
864 if (OtherElt && OtherElt->getType() != BytePtrTy)
865 OtherElt = new BitCastInst(OtherElt, BytePtrTy,OtherElt->getNameStr(),
866 MI);
867
868 unsigned EltSize = TD->getTypeAllocSize(EltTy);
869
870 // Finally, insert the meminst for this element.
871 if (isa<MemTransferInst>(MI)) {
872 Value *Ops[] = {
873 SROADest ? EltPtr : OtherElt, // Dest ptr
874 SROADest ? OtherElt : EltPtr, // Src ptr
875 ConstantInt::get(MI->getOperand(3)->getType(), EltSize), // Size
876 ConstantInt::get(Type::Int32Ty, OtherEltAlign) // Align
877 };
878 CallInst::Create(TheFn, Ops, Ops + 4, "", MI);
879 } else {
880 assert(isa<MemSetInst>(MI));
881 Value *Ops[] = {
882 EltPtr, MI->getOperand(2), // Dest, Value,
883 ConstantInt::get(MI->getOperand(3)->getType(), EltSize), // Size
884 Zero // Align
885 };
886 CallInst::Create(TheFn, Ops, Ops + 4, "", MI);
887 }
888 }
889 MI->eraseFromParent();
890}
891
892/// RewriteStoreUserOfWholeAlloca - We found an store of an integer that
893/// overwrites the entire allocation. Extract out the pieces of the stored
894/// integer and store them individually.
895void SROA::RewriteStoreUserOfWholeAlloca(StoreInst *SI,
896 AllocationInst *AI,
897 SmallVector<AllocaInst*, 32> &NewElts){
898 // Extract each element out of the integer according to its structure offset
899 // and store the element value to the individual alloca.
900 Value *SrcVal = SI->getOperand(0);
901 const Type *AllocaEltTy = AI->getType()->getElementType();
902 uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy);
903
904 // If this isn't a store of an integer to the whole alloca, it may be a store
905 // to the first element. Just ignore the store in this case and normal SROA
906 // will handle it.
907 if (!isa<IntegerType>(SrcVal->getType()) ||
908 TD->getTypeAllocSizeInBits(SrcVal->getType()) != AllocaSizeBits)
909 return;
910 // Handle tail padding by extending the operand
911 if (TD->getTypeSizeInBits(SrcVal->getType()) != AllocaSizeBits)
912 SrcVal = new ZExtInst(SrcVal, IntegerType::get(AllocaSizeBits), "", SI);
913
914 DOUT << "PROMOTING STORE TO WHOLE ALLOCA: " << *AI << *SI;
915
916 // There are two forms here: AI could be an array or struct. Both cases
917 // have different ways to compute the element offset.
918 if (const StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) {
919 const StructLayout *Layout = TD->getStructLayout(EltSTy);
920
921 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
922 // Get the number of bits to shift SrcVal to get the value.
923 const Type *FieldTy = EltSTy->getElementType(i);
924 uint64_t Shift = Layout->getElementOffsetInBits(i);
925
926 if (TD->isBigEndian())
927 Shift = AllocaSizeBits-Shift-TD->getTypeAllocSizeInBits(FieldTy);
928
929 Value *EltVal = SrcVal;
930 if (Shift) {
931 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift);
932 EltVal = BinaryOperator::CreateLShr(EltVal, ShiftVal,
933 "sroa.store.elt", SI);
934 }
935
936 // Truncate down to an integer of the right size.
937 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy);
938
939 // Ignore zero sized fields like {}, they obviously contain no data.
940 if (FieldSizeBits == 0) continue;
941
942 if (FieldSizeBits != AllocaSizeBits)
943 EltVal = new TruncInst(EltVal, IntegerType::get(FieldSizeBits), "", SI);
944 Value *DestField = NewElts[i];
945 if (EltVal->getType() == FieldTy) {
946 // Storing to an integer field of this size, just do it.
947 } else if (FieldTy->isFloatingPoint() || isa<VectorType>(FieldTy)) {
948 // Bitcast to the right element type (for fp/vector values).
949 EltVal = new BitCastInst(EltVal, FieldTy, "", SI);
950 } else {
951 // Otherwise, bitcast the dest pointer (for aggregates).
952 DestField = new BitCastInst(DestField,
953 PointerType::getUnqual(EltVal->getType()),
954 "", SI);
955 }
956 new StoreInst(EltVal, DestField, SI);
957 }
958
959 } else {
960 const ArrayType *ATy = cast<ArrayType>(AllocaEltTy);
961 const Type *ArrayEltTy = ATy->getElementType();
962 uint64_t ElementOffset = TD->getTypeAllocSizeInBits(ArrayEltTy);
963 uint64_t ElementSizeBits = TD->getTypeSizeInBits(ArrayEltTy);
964
965 uint64_t Shift;
966
967 if (TD->isBigEndian())
968 Shift = AllocaSizeBits-ElementOffset;
969 else
970 Shift = 0;
971
972 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
973 // Ignore zero sized fields like {}, they obviously contain no data.
974 if (ElementSizeBits == 0) continue;
975
976 Value *EltVal = SrcVal;
977 if (Shift) {
978 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift);
979 EltVal = BinaryOperator::CreateLShr(EltVal, ShiftVal,
980 "sroa.store.elt", SI);
981 }
982
983 // Truncate down to an integer of the right size.
984 if (ElementSizeBits != AllocaSizeBits)
985 EltVal = new TruncInst(EltVal, IntegerType::get(ElementSizeBits),"",SI);
986 Value *DestField = NewElts[i];
987 if (EltVal->getType() == ArrayEltTy) {
988 // Storing to an integer field of this size, just do it.
989 } else if (ArrayEltTy->isFloatingPoint() || isa<VectorType>(ArrayEltTy)) {
990 // Bitcast to the right element type (for fp/vector values).
991 EltVal = new BitCastInst(EltVal, ArrayEltTy, "", SI);
992 } else {
993 // Otherwise, bitcast the dest pointer (for aggregates).
994 DestField = new BitCastInst(DestField,
995 PointerType::getUnqual(EltVal->getType()),
996 "", SI);
997 }
998 new StoreInst(EltVal, DestField, SI);
999
1000 if (TD->isBigEndian())
1001 Shift -= ElementOffset;
1002 else
1003 Shift += ElementOffset;
1004 }
1005 }
1006
1007 SI->eraseFromParent();
1008}
1009
1010/// RewriteLoadUserOfWholeAlloca - We found an load of the entire allocation to
1011/// an integer. Load the individual pieces to form the aggregate value.
1012void SROA::RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocationInst *AI,
1013 SmallVector<AllocaInst*, 32> &NewElts) {
1014 // Extract each element out of the NewElts according to its structure offset
1015 // and form the result value.
1016 const Type *AllocaEltTy = AI->getType()->getElementType();
1017 uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy);
1018
1019 // If this isn't a load of the whole alloca to an integer, it may be a load
1020 // of the first element. Just ignore the load in this case and normal SROA
1021 // will handle it.
1022 if (!isa<IntegerType>(LI->getType()) ||
1023 TD->getTypeAllocSizeInBits(LI->getType()) != AllocaSizeBits)
1024 return;
1025
1026 DOUT << "PROMOTING LOAD OF WHOLE ALLOCA: " << *AI << *LI;
1027
1028 // There are two forms here: AI could be an array or struct. Both cases
1029 // have different ways to compute the element offset.
1030 const StructLayout *Layout = 0;
1031 uint64_t ArrayEltBitOffset = 0;
1032 if (const StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) {
1033 Layout = TD->getStructLayout(EltSTy);
1034 } else {
1035 const Type *ArrayEltTy = cast<ArrayType>(AllocaEltTy)->getElementType();
1036 ArrayEltBitOffset = TD->getTypeAllocSizeInBits(ArrayEltTy);
1037 }
1038
1039 Value *ResultVal = Constant::getNullValue(IntegerType::get(AllocaSizeBits));
1040
1041 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
1042 // Load the value from the alloca. If the NewElt is an aggregate, cast
1043 // the pointer to an integer of the same size before doing the load.
1044 Value *SrcField = NewElts[i];
1045 const Type *FieldTy =
1046 cast<PointerType>(SrcField->getType())->getElementType();
1047 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy);
1048
1049 // Ignore zero sized fields like {}, they obviously contain no data.
1050 if (FieldSizeBits == 0) continue;
1051
1052 const IntegerType *FieldIntTy = IntegerType::get(FieldSizeBits);
1053 if (!isa<IntegerType>(FieldTy) && !FieldTy->isFloatingPoint() &&
1054 !isa<VectorType>(FieldTy))
1055 SrcField = new BitCastInst(SrcField, PointerType::getUnqual(FieldIntTy),
1056 "", LI);
1057 SrcField = new LoadInst(SrcField, "sroa.load.elt", LI);
1058
1059 // If SrcField is a fp or vector of the right size but that isn't an
1060 // integer type, bitcast to an integer so we can shift it.
1061 if (SrcField->getType() != FieldIntTy)
1062 SrcField = new BitCastInst(SrcField, FieldIntTy, "", LI);
1063
1064 // Zero extend the field to be the same size as the final alloca so that
1065 // we can shift and insert it.
1066 if (SrcField->getType() != ResultVal->getType())
1067 SrcField = new ZExtInst(SrcField, ResultVal->getType(), "", LI);
1068
1069 // Determine the number of bits to shift SrcField.
1070 uint64_t Shift;
1071 if (Layout) // Struct case.
1072 Shift = Layout->getElementOffsetInBits(i);
1073 else // Array case.
1074 Shift = i*ArrayEltBitOffset;
1075
1076 if (TD->isBigEndian())
1077 Shift = AllocaSizeBits-Shift-FieldIntTy->getBitWidth();
1078
1079 if (Shift) {
1080 Value *ShiftVal = ConstantInt::get(SrcField->getType(), Shift);
1081 SrcField = BinaryOperator::CreateShl(SrcField, ShiftVal, "", LI);
1082 }
1083
1084 ResultVal = BinaryOperator::CreateOr(SrcField, ResultVal, "", LI);
1085 }
1086
1087 // Handle tail padding by truncating the result
1088 if (TD->getTypeSizeInBits(LI->getType()) != AllocaSizeBits)
1089 ResultVal = new TruncInst(ResultVal, LI->getType(), "", LI);
1090
1091 LI->replaceAllUsesWith(ResultVal);
1092 LI->eraseFromParent();
1093}
1094
1095
1096/// HasPadding - Return true if the specified type has any structure or
1097/// alignment padding, false otherwise.
1098static bool HasPadding(const Type *Ty, const TargetData &TD) {
1099 if (const StructType *STy = dyn_cast<StructType>(Ty)) {
1100 const StructLayout *SL = TD.getStructLayout(STy);
1101 unsigned PrevFieldBitOffset = 0;
1102 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
1103 unsigned FieldBitOffset = SL->getElementOffsetInBits(i);
1104
1105 // Padding in sub-elements?
1106 if (HasPadding(STy->getElementType(i), TD))
1107 return true;
1108
1109 // Check to see if there is any padding between this element and the
1110 // previous one.
1111 if (i) {
1112 unsigned PrevFieldEnd =
1113 PrevFieldBitOffset+TD.getTypeSizeInBits(STy->getElementType(i-1));
1114 if (PrevFieldEnd < FieldBitOffset)
1115 return true;
1116 }
1117
1118 PrevFieldBitOffset = FieldBitOffset;
1119 }
1120
1121 // Check for tail padding.
1122 if (unsigned EltCount = STy->getNumElements()) {
1123 unsigned PrevFieldEnd = PrevFieldBitOffset +
1124 TD.getTypeSizeInBits(STy->getElementType(EltCount-1));
1125 if (PrevFieldEnd < SL->getSizeInBits())
1126 return true;
1127 }
1128
1129 } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
1130 return HasPadding(ATy->getElementType(), TD);
1131 } else if (const VectorType *VTy = dyn_cast<VectorType>(Ty)) {
1132 return HasPadding(VTy->getElementType(), TD);
1133 }
1134 return TD.getTypeSizeInBits(Ty) != TD.getTypeAllocSizeInBits(Ty);
1135}
1136
1137/// isSafeStructAllocaToScalarRepl - Check to see if the specified allocation of
1138/// an aggregate can be broken down into elements. Return 0 if not, 3 if safe,
1139/// or 1 if safe after canonicalization has been performed.
1140///
1141int SROA::isSafeAllocaToScalarRepl(AllocationInst *AI) {
1142 // Loop over the use list of the alloca. We can only transform it if all of
1143 // the users are safe to transform.
1144 AllocaInfo Info;
1145
1146 for (Value::use_iterator I = AI->use_begin(), E = AI->use_end();
1147 I != E; ++I) {
1148 isSafeUseOfAllocation(cast<Instruction>(*I), AI, Info);
1149 if (Info.isUnsafe) {
1150 DOUT << "Cannot transform: " << *AI << " due to user: " << **I;
1151 return 0;
1152 }
1153 }
1154
1155 // Okay, we know all the users are promotable. If the aggregate is a memcpy
1156 // source and destination, we have to be careful. In particular, the memcpy
1157 // could be moving around elements that live in structure padding of the LLVM
1158 // types, but may actually be used. In these cases, we refuse to promote the
1159 // struct.
1160 if (Info.isMemCpySrc && Info.isMemCpyDst &&
1161 HasPadding(AI->getType()->getElementType(), *TD))
1162 return 0;
1163
1164 // If we require cleanup, return 1, otherwise return 3.
1165 return Info.needsCleanup ? 1 : 3;
1166}
1167
1168/// CleanupGEP - GEP is used by an Alloca, which can be prompted after the GEP
1169/// is canonicalized here.
1170void SROA::CleanupGEP(GetElementPtrInst *GEPI) {
1171 gep_type_iterator I = gep_type_begin(GEPI);
1172 ++I;
1173
1174 const ArrayType *AT = dyn_cast<ArrayType>(*I);
1175 if (!AT)
1176 return;
1177
1178 uint64_t NumElements = AT->getNumElements();
1179
1180 if (isa<ConstantInt>(I.getOperand()))
1181 return;
1182
1183 if (NumElements == 1) {
1184 GEPI->setOperand(2, Constant::getNullValue(Type::Int32Ty));
1185 return;
1186 }
1187
1188 assert(NumElements == 2 && "Unhandled case!");
1189 // All users of the GEP must be loads. At each use of the GEP, insert
1190 // two loads of the appropriate indexed GEP and select between them.
1191 Value *IsOne = new ICmpInst(ICmpInst::ICMP_NE, I.getOperand(),
1192 Constant::getNullValue(I.getOperand()->getType()),
1193 "isone", GEPI);
1194 // Insert the new GEP instructions, which are properly indexed.
1195 SmallVector<Value*, 8> Indices(GEPI->op_begin()+1, GEPI->op_end());
1196 Indices[1] = Constant::getNullValue(Type::Int32Ty);
1197 Value *ZeroIdx = GetElementPtrInst::Create(GEPI->getOperand(0),
1198 Indices.begin(),
1199 Indices.end(),
1200 GEPI->getName()+".0", GEPI);
1201 Indices[1] = ConstantInt::get(Type::Int32Ty, 1);
1202 Value *OneIdx = GetElementPtrInst::Create(GEPI->getOperand(0),
1203 Indices.begin(),
1204 Indices.end(),
1205 GEPI->getName()+".1", GEPI);
1206 // Replace all loads of the variable index GEP with loads from both
1207 // indexes and a select.
1208 while (!GEPI->use_empty()) {
1209 LoadInst *LI = cast<LoadInst>(GEPI->use_back());
1210 Value *Zero = new LoadInst(ZeroIdx, LI->getName()+".0", LI);
1211 Value *One = new LoadInst(OneIdx , LI->getName()+".1", LI);
1212 Value *R = SelectInst::Create(IsOne, One, Zero, LI->getName(), LI);
1213 LI->replaceAllUsesWith(R);
1214 LI->eraseFromParent();
1215 }
1216 GEPI->eraseFromParent();
1217}
1218
1219
1220/// CleanupAllocaUsers - If SROA reported that it can promote the specified
1221/// allocation, but only if cleaned up, perform the cleanups required.
1222void SROA::CleanupAllocaUsers(AllocationInst *AI) {
1223 // At this point, we know that the end result will be SROA'd and promoted, so
1224 // we can insert ugly code if required so long as sroa+mem2reg will clean it
1225 // up.
1226 for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end();
1227 UI != E; ) {
1228 User *U = *UI++;
1229 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(U))
1230 CleanupGEP(GEPI);
| 1//===- ScalarReplAggregates.cpp - Scalar Replacement of Aggregates --------===//
2//
3// The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
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.
15//
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.
19//
20//===----------------------------------------------------------------------===//
21
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/Pass.h"
31#include "llvm/Analysis/Dominators.h"
32#include "llvm/Target/TargetData.h"
33#include "llvm/Transforms/Utils/PromoteMemToReg.h"
34#include "llvm/Transforms/Utils/Local.h"
35#include "llvm/Support/Debug.h"
36#include "llvm/Support/GetElementPtrTypeIterator.h"
37#include "llvm/Support/IRBuilder.h"
38#include "llvm/Support/MathExtras.h"
39#include "llvm/Support/Compiler.h"
40#include "llvm/ADT/SmallVector.h"
41#include "llvm/ADT/Statistic.h"
42#include "llvm/ADT/StringExtras.h"
43using namespace llvm;
44
45STATISTIC(NumReplaced, "Number of allocas broken up");
46STATISTIC(NumPromoted, "Number of allocas promoted");
47STATISTIC(NumConverted, "Number of aggregates converted to scalar");
48STATISTIC(NumGlobals, "Number of allocas copied from constant global");
49
50namespace {
51 struct VISIBILITY_HIDDEN SROA : public FunctionPass {
52 static char ID; // Pass identification, replacement for typeid
53 explicit SROA(signed T = -1) : FunctionPass(&ID) {
54 if (T == -1)
55 SRThreshold = 128;
56 else
57 SRThreshold = T;
58 }
59
60 bool runOnFunction(Function &F);
61
62 bool performScalarRepl(Function &F);
63 bool performPromotion(Function &F);
64
65 // getAnalysisUsage - This pass does not require any passes, but we know it
66 // will not alter the CFG, so say so.
67 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
68 AU.addRequired<DominatorTree>();
69 AU.addRequired<DominanceFrontier>();
70 AU.addRequired<TargetData>();
71 AU.setPreservesCFG();
72 }
73
74 private:
75 TargetData *TD;
76
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.
80 struct AllocaInfo {
81 /// isUnsafe - This is set to true if the alloca cannot be SROA'd.
82 bool isUnsafe : 1;
83
84 /// needsCleanup - This is set to true if there is some use of the alloca
85 /// that requires cleanup.
86 bool needsCleanup : 1;
87
88 /// isMemCpySrc - This is true if this aggregate is memcpy'd from.
89 bool isMemCpySrc : 1;
90
91 /// isMemCpyDst - This is true if this aggregate is memcpy'd into.
92 bool isMemCpyDst : 1;
93
94 AllocaInfo()
95 : isUnsafe(false), needsCleanup(false),
96 isMemCpySrc(false), isMemCpyDst(false) {}
97 };
98
99 unsigned SRThreshold;
100
101 void MarkUnsafe(AllocaInfo &I) { I.isUnsafe = true; }
102
103 int isSafeAllocaToScalarRepl(AllocationInst *AI);
104
105 void isSafeUseOfAllocation(Instruction *User, AllocationInst *AI,
106 AllocaInfo &Info);
107 void isSafeElementUse(Value *Ptr, bool isFirstElt, AllocationInst *AI,
108 AllocaInfo &Info);
109 void isSafeMemIntrinsicOnAllocation(MemIntrinsic *MI, AllocationInst *AI,
110 unsigned OpNo, AllocaInfo &Info);
111 void isSafeUseOfBitCastedAllocation(BitCastInst *User, AllocationInst *AI,
112 AllocaInfo &Info);
113
114 void DoScalarReplacement(AllocationInst *AI,
115 std::vector<AllocationInst*> &WorkList);
116 void CleanupGEP(GetElementPtrInst *GEP);
117 void CleanupAllocaUsers(AllocationInst *AI);
118 AllocaInst *AddNewAlloca(Function &F, const Type *Ty, AllocationInst *Base);
119
120 void RewriteBitCastUserOfAlloca(Instruction *BCInst, AllocationInst *AI,
121 SmallVector<AllocaInst*, 32> &NewElts);
122
123 void RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *BCInst,
124 AllocationInst *AI,
125 SmallVector<AllocaInst*, 32> &NewElts);
126 void RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocationInst *AI,
127 SmallVector<AllocaInst*, 32> &NewElts);
128 void RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocationInst *AI,
129 SmallVector<AllocaInst*, 32> &NewElts);
130
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(AllocationInst *AI);
139 };
140}
141
142char SROA::ID = 0;
143static RegisterPass<SROA> X("scalarrepl", "Scalar Replacement of Aggregates");
144
145// Public interface to the ScalarReplAggregates pass
146FunctionPass *llvm::createScalarReplAggregatesPass(signed int Threshold) {
147 return new SROA(Threshold);
148}
149
150
151bool SROA::runOnFunction(Function &F) {
152 TD = &getAnalysis<TargetData>();
153
154 bool Changed = performPromotion(F);
155 while (1) {
156 bool LocalChange = performScalarRepl(F);
157 if (!LocalChange) break; // No need to repromote if no scalarrepl
158 Changed = true;
159 LocalChange = performPromotion(F);
160 if (!LocalChange) break; // No need to re-scalarrepl if no promotion
161 }
162
163 return Changed;
164}
165
166
167bool SROA::performPromotion(Function &F) {
168 std::vector<AllocaInst*> Allocas;
169 DominatorTree &DT = getAnalysis<DominatorTree>();
170 DominanceFrontier &DF = getAnalysis<DominanceFrontier>();
171
172 BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function
173
174 bool Changed = false;
175
176 while (1) {
177 Allocas.clear();
178
179 // Find allocas that are safe to promote, by looking at all instructions in
180 // the entry node
181 for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I)
182 if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) // Is it an alloca?
183 if (isAllocaPromotable(AI))
184 Allocas.push_back(AI);
185
186 if (Allocas.empty()) break;
187
188 PromoteMemToReg(Allocas, DT, DF);
189 NumPromoted += Allocas.size();
190 Changed = true;
191 }
192
193 return Changed;
194}
195
196/// getNumSAElements - Return the number of elements in the specific struct or
197/// array.
198static uint64_t getNumSAElements(const Type *T) {
199 if (const StructType *ST = dyn_cast<StructType>(T))
200 return ST->getNumElements();
201 return cast<ArrayType>(T)->getNumElements();
202}
203
204// performScalarRepl - This algorithm is a simple worklist driven algorithm,
205// which runs on all of the malloc/alloca instructions in the function, removing
206// them if they are only used by getelementptr instructions.
207//
208bool SROA::performScalarRepl(Function &F) {
209 std::vector<AllocationInst*> WorkList;
210
211 // Scan the entry basic block, adding any alloca's and mallocs to the worklist
212 BasicBlock &BB = F.getEntryBlock();
213 for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I)
214 if (AllocationInst *A = dyn_cast<AllocationInst>(I))
215 WorkList.push_back(A);
216
217 // Process the worklist
218 bool Changed = false;
219 while (!WorkList.empty()) {
220 AllocationInst *AI = WorkList.back();
221 WorkList.pop_back();
222
223 // Handle dead allocas trivially. These can be formed by SROA'ing arrays
224 // with unused elements.
225 if (AI->use_empty()) {
226 AI->eraseFromParent();
227 continue;
228 }
229
230 // If this alloca is impossible for us to promote, reject it early.
231 if (AI->isArrayAllocation() || !AI->getAllocatedType()->isSized())
232 continue;
233
234 // Check to see if this allocation is only modified by a memcpy/memmove from
235 // a constant global. If this is the case, we can change all users to use
236 // the constant global instead. This is commonly produced by the CFE by
237 // constructs like "void foo() { int A[] = {1,2,3,4,5,6,7,8,9...}; }" if 'A'
238 // is only subsequently read.
239 if (Instruction *TheCopy = isOnlyCopiedFromConstantGlobal(AI)) {
240 DOUT << "Found alloca equal to global: " << *AI;
241 DOUT << " memcpy = " << *TheCopy;
242 Constant *TheSrc = cast<Constant>(TheCopy->getOperand(2));
243 AI->replaceAllUsesWith(ConstantExpr::getBitCast(TheSrc, AI->getType()));
244 TheCopy->eraseFromParent(); // Don't mutate the global.
245 AI->eraseFromParent();
246 ++NumGlobals;
247 Changed = true;
248 continue;
249 }
250
251 // Check to see if we can perform the core SROA transformation. We cannot
252 // transform the allocation instruction if it is an array allocation
253 // (allocations OF arrays are ok though), and an allocation of a scalar
254 // value cannot be decomposed at all.
255 uint64_t AllocaSize = TD->getTypeAllocSize(AI->getAllocatedType());
256
257 // Do not promote any struct whose size is too big.
258 if (AllocaSize > SRThreshold) continue;
259
260 if ((isa<StructType>(AI->getAllocatedType()) ||
261 isa<ArrayType>(AI->getAllocatedType())) &&
262 // Do not promote any struct into more than "32" separate vars.
263 getNumSAElements(AI->getAllocatedType()) <= SRThreshold/4) {
264 // Check that all of the users of the allocation are capable of being
265 // transformed.
266 switch (isSafeAllocaToScalarRepl(AI)) {
267 default: assert(0 && "Unexpected value!");
268 case 0: // Not safe to scalar replace.
269 break;
270 case 1: // Safe, but requires cleanup/canonicalizations first
271 CleanupAllocaUsers(AI);
272 // FALL THROUGH.
273 case 3: // Safe to scalar replace.
274 DoScalarReplacement(AI, WorkList);
275 Changed = true;
276 continue;
277 }
278 }
279
280 // If we can turn this aggregate value (potentially with casts) into a
281 // simple scalar value that can be mem2reg'd into a register value.
282 // IsNotTrivial tracks whether this is something that mem2reg could have
283 // promoted itself. If so, we don't want to transform it needlessly. Note
284 // that we can't just check based on the type: the alloca may be of an i32
285 // but that has pointer arithmetic to set byte 3 of it or something.
286 bool IsNotTrivial = false;
287 const Type *VectorTy = 0;
288 bool HadAVector = false;
289 if (CanConvertToScalar(AI, IsNotTrivial, VectorTy, HadAVector,
290 0, unsigned(AllocaSize)) && IsNotTrivial) {
291 AllocaInst *NewAI;
292 // If we were able to find a vector type that can handle this with
293 // insert/extract elements, and if there was at least one use that had
294 // a vector type, promote this to a vector. We don't want to promote
295 // random stuff that doesn't use vectors (e.g. <9 x double>) because then
296 // we just get a lot of insert/extracts. If at least one vector is
297 // involved, then we probably really do have a union of vector/array.
298 if (VectorTy && isa<VectorType>(VectorTy) && HadAVector) {
299 DOUT << "CONVERT TO VECTOR: " << *AI << " TYPE = " << *VectorTy <<"\n";
300
301 // Create and insert the vector alloca.
302 NewAI = new AllocaInst(VectorTy, 0, "", AI->getParent()->begin());
303 ConvertUsesToScalar(AI, NewAI, 0);
304 } else {
305 DOUT << "CONVERT TO SCALAR INTEGER: " << *AI << "\n";
306
307 // Create and insert the integer alloca.
308 const Type *NewTy = IntegerType::get(AllocaSize*8);
309 NewAI = new AllocaInst(NewTy, 0, "", AI->getParent()->begin());
310 ConvertUsesToScalar(AI, NewAI, 0);
311 }
312 NewAI->takeName(AI);
313 AI->eraseFromParent();
314 ++NumConverted;
315 Changed = true;
316 continue;
317 }
318
319 // Otherwise, couldn't process this alloca.
320 }
321
322 return Changed;
323}
324
325/// DoScalarReplacement - This alloca satisfied the isSafeAllocaToScalarRepl
326/// predicate, do SROA now.
327void SROA::DoScalarReplacement(AllocationInst *AI,
328 std::vector<AllocationInst*> &WorkList) {
329 DOUT << "Found inst to SROA: " << *AI;
330 SmallVector<AllocaInst*, 32> ElementAllocas;
331 if (const StructType *ST = dyn_cast<StructType>(AI->getAllocatedType())) {
332 ElementAllocas.reserve(ST->getNumContainedTypes());
333 for (unsigned i = 0, e = ST->getNumContainedTypes(); i != e; ++i) {
334 AllocaInst *NA = new AllocaInst(ST->getContainedType(i), 0,
335 AI->getAlignment(),
336 AI->getName() + "." + utostr(i), AI);
337 ElementAllocas.push_back(NA);
338 WorkList.push_back(NA); // Add to worklist for recursive processing
339 }
340 } else {
341 const ArrayType *AT = cast<ArrayType>(AI->getAllocatedType());
342 ElementAllocas.reserve(AT->getNumElements());
343 const Type *ElTy = AT->getElementType();
344 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
345 AllocaInst *NA = new AllocaInst(ElTy, 0, AI->getAlignment(),
346 AI->getName() + "." + utostr(i), AI);
347 ElementAllocas.push_back(NA);
348 WorkList.push_back(NA); // Add to worklist for recursive processing
349 }
350 }
351
352 // Now that we have created the alloca instructions that we want to use,
353 // expand the getelementptr instructions to use them.
354 //
355 while (!AI->use_empty()) {
356 Instruction *User = cast<Instruction>(AI->use_back());
357 if (BitCastInst *BCInst = dyn_cast<BitCastInst>(User)) {
358 RewriteBitCastUserOfAlloca(BCInst, AI, ElementAllocas);
359 BCInst->eraseFromParent();
360 continue;
361 }
362
363 // Replace:
364 // %res = load { i32, i32 }* %alloc
365 // with:
366 // %load.0 = load i32* %alloc.0
367 // %insert.0 insertvalue { i32, i32 } zeroinitializer, i32 %load.0, 0
368 // %load.1 = load i32* %alloc.1
369 // %insert = insertvalue { i32, i32 } %insert.0, i32 %load.1, 1
370 // (Also works for arrays instead of structs)
371 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
372 Value *Insert = UndefValue::get(LI->getType());
373 for (unsigned i = 0, e = ElementAllocas.size(); i != e; ++i) {
374 Value *Load = new LoadInst(ElementAllocas[i], "load", LI);
375 Insert = InsertValueInst::Create(Insert, Load, i, "insert", LI);
376 }
377 LI->replaceAllUsesWith(Insert);
378 LI->eraseFromParent();
379 continue;
380 }
381
382 // Replace:
383 // store { i32, i32 } %val, { i32, i32 }* %alloc
384 // with:
385 // %val.0 = extractvalue { i32, i32 } %val, 0
386 // store i32 %val.0, i32* %alloc.0
387 // %val.1 = extractvalue { i32, i32 } %val, 1
388 // store i32 %val.1, i32* %alloc.1
389 // (Also works for arrays instead of structs)
390 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
391 Value *Val = SI->getOperand(0);
392 for (unsigned i = 0, e = ElementAllocas.size(); i != e; ++i) {
393 Value *Extract = ExtractValueInst::Create(Val, i, Val->getName(), SI);
394 new StoreInst(Extract, ElementAllocas[i], SI);
395 }
396 SI->eraseFromParent();
397 continue;
398 }
399
400 GetElementPtrInst *GEPI = cast<GetElementPtrInst>(User);
401 // We now know that the GEP is of the form: GEP <ptr>, 0, <cst>
402 unsigned Idx =
403 (unsigned)cast<ConstantInt>(GEPI->getOperand(2))->getZExtValue();
404
405 assert(Idx < ElementAllocas.size() && "Index out of range?");
406 AllocaInst *AllocaToUse = ElementAllocas[Idx];
407
408 Value *RepValue;
409 if (GEPI->getNumOperands() == 3) {
410 // Do not insert a new getelementptr instruction with zero indices, only
411 // to have it optimized out later.
412 RepValue = AllocaToUse;
413 } else {
414 // We are indexing deeply into the structure, so we still need a
415 // getelement ptr instruction to finish the indexing. This may be
416 // expanded itself once the worklist is rerun.
417 //
418 SmallVector<Value*, 8> NewArgs;
419 NewArgs.push_back(Constant::getNullValue(Type::Int32Ty));
420 NewArgs.append(GEPI->op_begin()+3, GEPI->op_end());
421 RepValue = GetElementPtrInst::Create(AllocaToUse, NewArgs.begin(),
422 NewArgs.end(), "", GEPI);
423 RepValue->takeName(GEPI);
424 }
425
426 // If this GEP is to the start of the aggregate, check for memcpys.
427 if (Idx == 0 && GEPI->hasAllZeroIndices())
428 RewriteBitCastUserOfAlloca(GEPI, AI, ElementAllocas);
429
430 // Move all of the users over to the new GEP.
431 GEPI->replaceAllUsesWith(RepValue);
432 // Delete the old GEP
433 GEPI->eraseFromParent();
434 }
435
436 // Finally, delete the Alloca instruction
437 AI->eraseFromParent();
438 NumReplaced++;
439}
440
441
442/// isSafeElementUse - Check to see if this use is an allowed use for a
443/// getelementptr instruction of an array aggregate allocation. isFirstElt
444/// indicates whether Ptr is known to the start of the aggregate.
445///
446void SROA::isSafeElementUse(Value *Ptr, bool isFirstElt, AllocationInst *AI,
447 AllocaInfo &Info) {
448 for (Value::use_iterator I = Ptr->use_begin(), E = Ptr->use_end();
449 I != E; ++I) {
450 Instruction *User = cast<Instruction>(*I);
451 switch (User->getOpcode()) {
452 case Instruction::Load: break;
453 case Instruction::Store:
454 // Store is ok if storing INTO the pointer, not storing the pointer
455 if (User->getOperand(0) == Ptr) return MarkUnsafe(Info);
456 break;
457 case Instruction::GetElementPtr: {
458 GetElementPtrInst *GEP = cast<GetElementPtrInst>(User);
459 bool AreAllZeroIndices = isFirstElt;
460 if (GEP->getNumOperands() > 1) {
461 if (!isa<ConstantInt>(GEP->getOperand(1)) ||
462 !cast<ConstantInt>(GEP->getOperand(1))->isZero())
463 // Using pointer arithmetic to navigate the array.
464 return MarkUnsafe(Info);
465
466 if (AreAllZeroIndices)
467 AreAllZeroIndices = GEP->hasAllZeroIndices();
468 }
469 isSafeElementUse(GEP, AreAllZeroIndices, AI, Info);
470 if (Info.isUnsafe) return;
471 break;
472 }
473 case Instruction::BitCast:
474 if (isFirstElt) {
475 isSafeUseOfBitCastedAllocation(cast<BitCastInst>(User), AI, Info);
476 if (Info.isUnsafe) return;
477 break;
478 }
479 DOUT << " Transformation preventing inst: " << *User;
480 return MarkUnsafe(Info);
481 case Instruction::Call:
482 if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) {
483 if (isFirstElt) {
484 isSafeMemIntrinsicOnAllocation(MI, AI, I.getOperandNo(), Info);
485 if (Info.isUnsafe) return;
486 break;
487 }
488 }
489 DOUT << " Transformation preventing inst: " << *User;
490 return MarkUnsafe(Info);
491 default:
492 DOUT << " Transformation preventing inst: " << *User;
493 return MarkUnsafe(Info);
494 }
495 }
496 return; // All users look ok :)
497}
498
499/// AllUsersAreLoads - Return true if all users of this value are loads.
500static bool AllUsersAreLoads(Value *Ptr) {
501 for (Value::use_iterator I = Ptr->use_begin(), E = Ptr->use_end();
502 I != E; ++I)
503 if (cast<Instruction>(*I)->getOpcode() != Instruction::Load)
504 return false;
505 return true;
506}
507
508/// isSafeUseOfAllocation - Check to see if this user is an allowed use for an
509/// aggregate allocation.
510///
511void SROA::isSafeUseOfAllocation(Instruction *User, AllocationInst *AI,
512 AllocaInfo &Info) {
513 if (BitCastInst *C = dyn_cast<BitCastInst>(User))
514 return isSafeUseOfBitCastedAllocation(C, AI, Info);
515
516 if (LoadInst *LI = dyn_cast<LoadInst>(User))
517 if (!LI->isVolatile())
518 return;// Loads (returning a first class aggregrate) are always rewritable
519
520 if (StoreInst *SI = dyn_cast<StoreInst>(User))
521 if (!SI->isVolatile() && SI->getOperand(0) != AI)
522 return;// Store is ok if storing INTO the pointer, not storing the pointer
523
524 GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User);
525 if (GEPI == 0)
526 return MarkUnsafe(Info);
527
528 gep_type_iterator I = gep_type_begin(GEPI), E = gep_type_end(GEPI);
529
530 // The GEP is not safe to transform if not of the form "GEP <ptr>, 0, <cst>".
531 if (I == E ||
532 I.getOperand() != Constant::getNullValue(I.getOperand()->getType())) {
533 return MarkUnsafe(Info);
534 }
535
536 ++I;
537 if (I == E) return MarkUnsafe(Info); // ran out of GEP indices??
538
539 bool IsAllZeroIndices = true;
540
541 // If the first index is a non-constant index into an array, see if we can
542 // handle it as a special case.
543 if (const ArrayType *AT = dyn_cast<ArrayType>(*I)) {
544 if (!isa<ConstantInt>(I.getOperand())) {
545 IsAllZeroIndices = 0;
546 uint64_t NumElements = AT->getNumElements();
547
548 // If this is an array index and the index is not constant, we cannot
549 // promote... that is unless the array has exactly one or two elements in
550 // it, in which case we CAN promote it, but we have to canonicalize this
551 // out if this is the only problem.
552 if ((NumElements == 1 || NumElements == 2) &&
553 AllUsersAreLoads(GEPI)) {
554 Info.needsCleanup = true;
555 return; // Canonicalization required!
556 }
557 return MarkUnsafe(Info);
558 }
559 }
560
561 // Walk through the GEP type indices, checking the types that this indexes
562 // into.
563 for (; I != E; ++I) {
564 // Ignore struct elements, no extra checking needed for these.
565 if (isa<StructType>(*I))
566 continue;
567
568 ConstantInt *IdxVal = dyn_cast<ConstantInt>(I.getOperand());
569 if (!IdxVal) return MarkUnsafe(Info);
570
571 // Are all indices still zero?
572 IsAllZeroIndices &= IdxVal->isZero();
573
574 if (const ArrayType *AT = dyn_cast<ArrayType>(*I)) {
575 // This GEP indexes an array. Verify that this is an in-range constant
576 // integer. Specifically, consider A[0][i]. We cannot know that the user
577 // isn't doing invalid things like allowing i to index an out-of-range
578 // subscript that accesses A[1]. Because of this, we have to reject SROA
579 // of any accesses into structs where any of the components are variables.
580 if (IdxVal->getZExtValue() >= AT->getNumElements())
581 return MarkUnsafe(Info);
582 } else if (const VectorType *VT = dyn_cast<VectorType>(*I)) {
583 if (IdxVal->getZExtValue() >= VT->getNumElements())
584 return MarkUnsafe(Info);
585 }
586 }
587
588 // If there are any non-simple uses of this getelementptr, make sure to reject
589 // them.
590 return isSafeElementUse(GEPI, IsAllZeroIndices, AI, Info);
591}
592
593/// isSafeMemIntrinsicOnAllocation - Return true if the specified memory
594/// intrinsic can be promoted by SROA. At this point, we know that the operand
595/// of the memintrinsic is a pointer to the beginning of the allocation.
596void SROA::isSafeMemIntrinsicOnAllocation(MemIntrinsic *MI, AllocationInst *AI,
597 unsigned OpNo, AllocaInfo &Info) {
598 // If not constant length, give up.
599 ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength());
600 if (!Length) return MarkUnsafe(Info);
601
602 // If not the whole aggregate, give up.
603 if (Length->getZExtValue() !=
604 TD->getTypeAllocSize(AI->getType()->getElementType()))
605 return MarkUnsafe(Info);
606
607 // We only know about memcpy/memset/memmove.
608 if (!isa<MemIntrinsic>(MI))
609 return MarkUnsafe(Info);
610
611 // Otherwise, we can transform it. Determine whether this is a memcpy/set
612 // into or out of the aggregate.
613 if (OpNo == 1)
614 Info.isMemCpyDst = true;
615 else {
616 assert(OpNo == 2);
617 Info.isMemCpySrc = true;
618 }
619}
620
621/// isSafeUseOfBitCastedAllocation - Return true if all users of this bitcast
622/// are
623void SROA::isSafeUseOfBitCastedAllocation(BitCastInst *BC, AllocationInst *AI,
624 AllocaInfo &Info) {
625 for (Value::use_iterator UI = BC->use_begin(), E = BC->use_end();
626 UI != E; ++UI) {
627 if (BitCastInst *BCU = dyn_cast<BitCastInst>(UI)) {
628 isSafeUseOfBitCastedAllocation(BCU, AI, Info);
629 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(UI)) {
630 isSafeMemIntrinsicOnAllocation(MI, AI, UI.getOperandNo(), Info);
631 } else if (StoreInst *SI = dyn_cast<StoreInst>(UI)) {
632 if (SI->isVolatile())
633 return MarkUnsafe(Info);
634
635 // If storing the entire alloca in one chunk through a bitcasted pointer
636 // to integer, we can transform it. This happens (for example) when you
637 // cast a {i32,i32}* to i64* and store through it. This is similar to the
638 // memcpy case and occurs in various "byval" cases and emulated memcpys.
639 if (isa<IntegerType>(SI->getOperand(0)->getType()) &&
640 TD->getTypeAllocSize(SI->getOperand(0)->getType()) ==
641 TD->getTypeAllocSize(AI->getType()->getElementType())) {
642 Info.isMemCpyDst = true;
643 continue;
644 }
645 return MarkUnsafe(Info);
646 } else if (LoadInst *LI = dyn_cast<LoadInst>(UI)) {
647 if (LI->isVolatile())
648 return MarkUnsafe(Info);
649
650 // If loading the entire alloca in one chunk through a bitcasted pointer
651 // to integer, we can transform it. This happens (for example) when you
652 // cast a {i32,i32}* to i64* and load through it. This is similar to the
653 // memcpy case and occurs in various "byval" cases and emulated memcpys.
654 if (isa<IntegerType>(LI->getType()) &&
655 TD->getTypeAllocSize(LI->getType()) ==
656 TD->getTypeAllocSize(AI->getType()->getElementType())) {
657 Info.isMemCpySrc = true;
658 continue;
659 }
660 return MarkUnsafe(Info);
661 } else if (isa<DbgInfoIntrinsic>(UI)) {
662 // If one user is DbgInfoIntrinsic then check if all users are
663 // DbgInfoIntrinsics.
664 if (OnlyUsedByDbgInfoIntrinsics(BC)) {
665 Info.needsCleanup = true;
666 return;
667 }
668 else
669 MarkUnsafe(Info);
670 }
671 else {
672 return MarkUnsafe(Info);
673 }
674 if (Info.isUnsafe) return;
675 }
676}
677
678/// RewriteBitCastUserOfAlloca - BCInst (transitively) bitcasts AI, or indexes
679/// to its first element. Transform users of the cast to use the new values
680/// instead.
681void SROA::RewriteBitCastUserOfAlloca(Instruction *BCInst, AllocationInst *AI,
682 SmallVector<AllocaInst*, 32> &NewElts) {
683 Value::use_iterator UI = BCInst->use_begin(), UE = BCInst->use_end();
684 while (UI != UE) {
685 Instruction *User = cast<Instruction>(*UI++);
686 if (BitCastInst *BCU = dyn_cast<BitCastInst>(User)) {
687 RewriteBitCastUserOfAlloca(BCU, AI, NewElts);
688 if (BCU->use_empty()) BCU->eraseFromParent();
689 continue;
690 }
691
692 if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) {
693 // This must be memcpy/memmove/memset of the entire aggregate.
694 // Split into one per element.
695 RewriteMemIntrinUserOfAlloca(MI, BCInst, AI, NewElts);
696 continue;
697 }
698
699 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
700 // If this is a store of the entire alloca from an integer, rewrite it.
701 RewriteStoreUserOfWholeAlloca(SI, AI, NewElts);
702 continue;
703 }
704
705 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
706 // If this is a load of the entire alloca to an integer, rewrite it.
707 RewriteLoadUserOfWholeAlloca(LI, AI, NewElts);
708 continue;
709 }
710
711 // Otherwise it must be some other user of a gep of the first pointer. Just
712 // leave these alone.
713 continue;
714 }
715}
716
717/// RewriteMemIntrinUserOfAlloca - MI is a memcpy/memset/memmove from or to AI.
718/// Rewrite it to copy or set the elements of the scalarized memory.
719void SROA::RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *BCInst,
720 AllocationInst *AI,
721 SmallVector<AllocaInst*, 32> &NewElts) {
722
723 // If this is a memcpy/memmove, construct the other pointer as the
724 // appropriate type. The "Other" pointer is the pointer that goes to memory
725 // that doesn't have anything to do with the alloca that we are promoting. For
726 // memset, this Value* stays null.
727 Value *OtherPtr = 0;
728 unsigned MemAlignment = MI->getAlignment();
729 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(MI)) { // memmove/memcopy
730 if (BCInst == MTI->getRawDest())
731 OtherPtr = MTI->getRawSource();
732 else {
733 assert(BCInst == MTI->getRawSource());
734 OtherPtr = MTI->getRawDest();
735 }
736 }
737
738 // If there is an other pointer, we want to convert it to the same pointer
739 // type as AI has, so we can GEP through it safely.
740 if (OtherPtr) {
741 // It is likely that OtherPtr is a bitcast, if so, remove it.
742 if (BitCastInst *BC = dyn_cast<BitCastInst>(OtherPtr))
743 OtherPtr = BC->getOperand(0);
744 // All zero GEPs are effectively bitcasts.
745 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(OtherPtr))
746 if (GEP->hasAllZeroIndices())
747 OtherPtr = GEP->getOperand(0);
748
749 if (ConstantExpr *BCE = dyn_cast<ConstantExpr>(OtherPtr))
750 if (BCE->getOpcode() == Instruction::BitCast)
751 OtherPtr = BCE->getOperand(0);
752
753 // If the pointer is not the right type, insert a bitcast to the right
754 // type.
755 if (OtherPtr->getType() != AI->getType())
756 OtherPtr = new BitCastInst(OtherPtr, AI->getType(), OtherPtr->getName(),
757 MI);
758 }
759
760 // Process each element of the aggregate.
761 Value *TheFn = MI->getOperand(0);
762 const Type *BytePtrTy = MI->getRawDest()->getType();
763 bool SROADest = MI->getRawDest() == BCInst;
764
765 Constant *Zero = Constant::getNullValue(Type::Int32Ty);
766
767 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
768 // If this is a memcpy/memmove, emit a GEP of the other element address.
769 Value *OtherElt = 0;
770 unsigned OtherEltAlign = MemAlignment;
771
772 if (OtherPtr) {
773 Value *Idx[2] = { Zero, ConstantInt::get(Type::Int32Ty, i) };
774 OtherElt = GetElementPtrInst::Create(OtherPtr, Idx, Idx + 2,
775 OtherPtr->getNameStr()+"."+utostr(i),
776 MI);
777 uint64_t EltOffset;
778 const PointerType *OtherPtrTy = cast<PointerType>(OtherPtr->getType());
779 if (const StructType *ST =
780 dyn_cast<StructType>(OtherPtrTy->getElementType())) {
781 EltOffset = TD->getStructLayout(ST)->getElementOffset(i);
782 } else {
783 const Type *EltTy =
784 cast<SequentialType>(OtherPtr->getType())->getElementType();
785 EltOffset = TD->getTypeAllocSize(EltTy)*i;
786 }
787
788 // The alignment of the other pointer is the guaranteed alignment of the
789 // element, which is affected by both the known alignment of the whole
790 // mem intrinsic and the alignment of the element. If the alignment of
791 // the memcpy (f.e.) is 32 but the element is at a 4-byte offset, then the
792 // known alignment is just 4 bytes.
793 OtherEltAlign = (unsigned)MinAlign(OtherEltAlign, EltOffset);
794 }
795
796 Value *EltPtr = NewElts[i];
797 const Type *EltTy = cast<PointerType>(EltPtr->getType())->getElementType();
798
799 // If we got down to a scalar, insert a load or store as appropriate.
800 if (EltTy->isSingleValueType()) {
801 if (isa<MemTransferInst>(MI)) {
802 if (SROADest) {
803 // From Other to Alloca.
804 Value *Elt = new LoadInst(OtherElt, "tmp", false, OtherEltAlign, MI);
805 new StoreInst(Elt, EltPtr, MI);
806 } else {
807 // From Alloca to Other.
808 Value *Elt = new LoadInst(EltPtr, "tmp", MI);
809 new StoreInst(Elt, OtherElt, false, OtherEltAlign, MI);
810 }
811 continue;
812 }
813 assert(isa<MemSetInst>(MI));
814
815 // If the stored element is zero (common case), just store a null
816 // constant.
817 Constant *StoreVal;
818 if (ConstantInt *CI = dyn_cast<ConstantInt>(MI->getOperand(2))) {
819 if (CI->isZero()) {
820 StoreVal = Constant::getNullValue(EltTy); // 0.0, null, 0, <0,0>
821 } else {
822 // If EltTy is a vector type, get the element type.
823 const Type *ValTy = EltTy;
824 if (const VectorType *VTy = dyn_cast<VectorType>(ValTy))
825 ValTy = VTy->getElementType();
826
827 // Construct an integer with the right value.
828 unsigned EltSize = TD->getTypeSizeInBits(ValTy);
829 APInt OneVal(EltSize, CI->getZExtValue());
830 APInt TotalVal(OneVal);
831 // Set each byte.
832 for (unsigned i = 0; 8*i < EltSize; ++i) {
833 TotalVal = TotalVal.shl(8);
834 TotalVal |= OneVal;
835 }
836
837 // Convert the integer value to the appropriate type.
838 StoreVal = ConstantInt::get(TotalVal);
839 if (isa<PointerType>(ValTy))
840 StoreVal = ConstantExpr::getIntToPtr(StoreVal, ValTy);
841 else if (ValTy->isFloatingPoint())
842 StoreVal = ConstantExpr::getBitCast(StoreVal, ValTy);
843 assert(StoreVal->getType() == ValTy && "Type mismatch!");
844
845 // If the requested value was a vector constant, create it.
846 if (EltTy != ValTy) {
847 unsigned NumElts = cast<VectorType>(ValTy)->getNumElements();
848 SmallVector<Constant*, 16> Elts(NumElts, StoreVal);
849 StoreVal = ConstantVector::get(&Elts[0], NumElts);
850 }
851 }
852 new StoreInst(StoreVal, EltPtr, MI);
853 continue;
854 }
855 // Otherwise, if we're storing a byte variable, use a memset call for
856 // this element.
857 }
858
859 // Cast the element pointer to BytePtrTy.
860 if (EltPtr->getType() != BytePtrTy)
861 EltPtr = new BitCastInst(EltPtr, BytePtrTy, EltPtr->getNameStr(), MI);
862
863 // Cast the other pointer (if we have one) to BytePtrTy.
864 if (OtherElt && OtherElt->getType() != BytePtrTy)
865 OtherElt = new BitCastInst(OtherElt, BytePtrTy,OtherElt->getNameStr(),
866 MI);
867
868 unsigned EltSize = TD->getTypeAllocSize(EltTy);
869
870 // Finally, insert the meminst for this element.
871 if (isa<MemTransferInst>(MI)) {
872 Value *Ops[] = {
873 SROADest ? EltPtr : OtherElt, // Dest ptr
874 SROADest ? OtherElt : EltPtr, // Src ptr
875 ConstantInt::get(MI->getOperand(3)->getType(), EltSize), // Size
876 ConstantInt::get(Type::Int32Ty, OtherEltAlign) // Align
877 };
878 CallInst::Create(TheFn, Ops, Ops + 4, "", MI);
879 } else {
880 assert(isa<MemSetInst>(MI));
881 Value *Ops[] = {
882 EltPtr, MI->getOperand(2), // Dest, Value,
883 ConstantInt::get(MI->getOperand(3)->getType(), EltSize), // Size
884 Zero // Align
885 };
886 CallInst::Create(TheFn, Ops, Ops + 4, "", MI);
887 }
888 }
889 MI->eraseFromParent();
890}
891
892/// RewriteStoreUserOfWholeAlloca - We found an store of an integer that
893/// overwrites the entire allocation. Extract out the pieces of the stored
894/// integer and store them individually.
895void SROA::RewriteStoreUserOfWholeAlloca(StoreInst *SI,
896 AllocationInst *AI,
897 SmallVector<AllocaInst*, 32> &NewElts){
898 // Extract each element out of the integer according to its structure offset
899 // and store the element value to the individual alloca.
900 Value *SrcVal = SI->getOperand(0);
901 const Type *AllocaEltTy = AI->getType()->getElementType();
902 uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy);
903
904 // If this isn't a store of an integer to the whole alloca, it may be a store
905 // to the first element. Just ignore the store in this case and normal SROA
906 // will handle it.
907 if (!isa<IntegerType>(SrcVal->getType()) ||
908 TD->getTypeAllocSizeInBits(SrcVal->getType()) != AllocaSizeBits)
909 return;
910 // Handle tail padding by extending the operand
911 if (TD->getTypeSizeInBits(SrcVal->getType()) != AllocaSizeBits)
912 SrcVal = new ZExtInst(SrcVal, IntegerType::get(AllocaSizeBits), "", SI);
913
914 DOUT << "PROMOTING STORE TO WHOLE ALLOCA: " << *AI << *SI;
915
916 // There are two forms here: AI could be an array or struct. Both cases
917 // have different ways to compute the element offset.
918 if (const StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) {
919 const StructLayout *Layout = TD->getStructLayout(EltSTy);
920
921 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
922 // Get the number of bits to shift SrcVal to get the value.
923 const Type *FieldTy = EltSTy->getElementType(i);
924 uint64_t Shift = Layout->getElementOffsetInBits(i);
925
926 if (TD->isBigEndian())
927 Shift = AllocaSizeBits-Shift-TD->getTypeAllocSizeInBits(FieldTy);
928
929 Value *EltVal = SrcVal;
930 if (Shift) {
931 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift);
932 EltVal = BinaryOperator::CreateLShr(EltVal, ShiftVal,
933 "sroa.store.elt", SI);
934 }
935
936 // Truncate down to an integer of the right size.
937 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy);
938
939 // Ignore zero sized fields like {}, they obviously contain no data.
940 if (FieldSizeBits == 0) continue;
941
942 if (FieldSizeBits != AllocaSizeBits)
943 EltVal = new TruncInst(EltVal, IntegerType::get(FieldSizeBits), "", SI);
944 Value *DestField = NewElts[i];
945 if (EltVal->getType() == FieldTy) {
946 // Storing to an integer field of this size, just do it.
947 } else if (FieldTy->isFloatingPoint() || isa<VectorType>(FieldTy)) {
948 // Bitcast to the right element type (for fp/vector values).
949 EltVal = new BitCastInst(EltVal, FieldTy, "", SI);
950 } else {
951 // Otherwise, bitcast the dest pointer (for aggregates).
952 DestField = new BitCastInst(DestField,
953 PointerType::getUnqual(EltVal->getType()),
954 "", SI);
955 }
956 new StoreInst(EltVal, DestField, SI);
957 }
958
959 } else {
960 const ArrayType *ATy = cast<ArrayType>(AllocaEltTy);
961 const Type *ArrayEltTy = ATy->getElementType();
962 uint64_t ElementOffset = TD->getTypeAllocSizeInBits(ArrayEltTy);
963 uint64_t ElementSizeBits = TD->getTypeSizeInBits(ArrayEltTy);
964
965 uint64_t Shift;
966
967 if (TD->isBigEndian())
968 Shift = AllocaSizeBits-ElementOffset;
969 else
970 Shift = 0;
971
972 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
973 // Ignore zero sized fields like {}, they obviously contain no data.
974 if (ElementSizeBits == 0) continue;
975
976 Value *EltVal = SrcVal;
977 if (Shift) {
978 Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift);
979 EltVal = BinaryOperator::CreateLShr(EltVal, ShiftVal,
980 "sroa.store.elt", SI);
981 }
982
983 // Truncate down to an integer of the right size.
984 if (ElementSizeBits != AllocaSizeBits)
985 EltVal = new TruncInst(EltVal, IntegerType::get(ElementSizeBits),"",SI);
986 Value *DestField = NewElts[i];
987 if (EltVal->getType() == ArrayEltTy) {
988 // Storing to an integer field of this size, just do it.
989 } else if (ArrayEltTy->isFloatingPoint() || isa<VectorType>(ArrayEltTy)) {
990 // Bitcast to the right element type (for fp/vector values).
991 EltVal = new BitCastInst(EltVal, ArrayEltTy, "", SI);
992 } else {
993 // Otherwise, bitcast the dest pointer (for aggregates).
994 DestField = new BitCastInst(DestField,
995 PointerType::getUnqual(EltVal->getType()),
996 "", SI);
997 }
998 new StoreInst(EltVal, DestField, SI);
999
1000 if (TD->isBigEndian())
1001 Shift -= ElementOffset;
1002 else
1003 Shift += ElementOffset;
1004 }
1005 }
1006
1007 SI->eraseFromParent();
1008}
1009
1010/// RewriteLoadUserOfWholeAlloca - We found an load of the entire allocation to
1011/// an integer. Load the individual pieces to form the aggregate value.
1012void SROA::RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocationInst *AI,
1013 SmallVector<AllocaInst*, 32> &NewElts) {
1014 // Extract each element out of the NewElts according to its structure offset
1015 // and form the result value.
1016 const Type *AllocaEltTy = AI->getType()->getElementType();
1017 uint64_t AllocaSizeBits = TD->getTypeAllocSizeInBits(AllocaEltTy);
1018
1019 // If this isn't a load of the whole alloca to an integer, it may be a load
1020 // of the first element. Just ignore the load in this case and normal SROA
1021 // will handle it.
1022 if (!isa<IntegerType>(LI->getType()) ||
1023 TD->getTypeAllocSizeInBits(LI->getType()) != AllocaSizeBits)
1024 return;
1025
1026 DOUT << "PROMOTING LOAD OF WHOLE ALLOCA: " << *AI << *LI;
1027
1028 // There are two forms here: AI could be an array or struct. Both cases
1029 // have different ways to compute the element offset.
1030 const StructLayout *Layout = 0;
1031 uint64_t ArrayEltBitOffset = 0;
1032 if (const StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) {
1033 Layout = TD->getStructLayout(EltSTy);
1034 } else {
1035 const Type *ArrayEltTy = cast<ArrayType>(AllocaEltTy)->getElementType();
1036 ArrayEltBitOffset = TD->getTypeAllocSizeInBits(ArrayEltTy);
1037 }
1038
1039 Value *ResultVal = Constant::getNullValue(IntegerType::get(AllocaSizeBits));
1040
1041 for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
1042 // Load the value from the alloca. If the NewElt is an aggregate, cast
1043 // the pointer to an integer of the same size before doing the load.
1044 Value *SrcField = NewElts[i];
1045 const Type *FieldTy =
1046 cast<PointerType>(SrcField->getType())->getElementType();
1047 uint64_t FieldSizeBits = TD->getTypeSizeInBits(FieldTy);
1048
1049 // Ignore zero sized fields like {}, they obviously contain no data.
1050 if (FieldSizeBits == 0) continue;
1051
1052 const IntegerType *FieldIntTy = IntegerType::get(FieldSizeBits);
1053 if (!isa<IntegerType>(FieldTy) && !FieldTy->isFloatingPoint() &&
1054 !isa<VectorType>(FieldTy))
1055 SrcField = new BitCastInst(SrcField, PointerType::getUnqual(FieldIntTy),
1056 "", LI);
1057 SrcField = new LoadInst(SrcField, "sroa.load.elt", LI);
1058
1059 // If SrcField is a fp or vector of the right size but that isn't an
1060 // integer type, bitcast to an integer so we can shift it.
1061 if (SrcField->getType() != FieldIntTy)
1062 SrcField = new BitCastInst(SrcField, FieldIntTy, "", LI);
1063
1064 // Zero extend the field to be the same size as the final alloca so that
1065 // we can shift and insert it.
1066 if (SrcField->getType() != ResultVal->getType())
1067 SrcField = new ZExtInst(SrcField, ResultVal->getType(), "", LI);
1068
1069 // Determine the number of bits to shift SrcField.
1070 uint64_t Shift;
1071 if (Layout) // Struct case.
1072 Shift = Layout->getElementOffsetInBits(i);
1073 else // Array case.
1074 Shift = i*ArrayEltBitOffset;
1075
1076 if (TD->isBigEndian())
1077 Shift = AllocaSizeBits-Shift-FieldIntTy->getBitWidth();
1078
1079 if (Shift) {
1080 Value *ShiftVal = ConstantInt::get(SrcField->getType(), Shift);
1081 SrcField = BinaryOperator::CreateShl(SrcField, ShiftVal, "", LI);
1082 }
1083
1084 ResultVal = BinaryOperator::CreateOr(SrcField, ResultVal, "", LI);
1085 }
1086
1087 // Handle tail padding by truncating the result
1088 if (TD->getTypeSizeInBits(LI->getType()) != AllocaSizeBits)
1089 ResultVal = new TruncInst(ResultVal, LI->getType(), "", LI);
1090
1091 LI->replaceAllUsesWith(ResultVal);
1092 LI->eraseFromParent();
1093}
1094
1095
1096/// HasPadding - Return true if the specified type has any structure or
1097/// alignment padding, false otherwise.
1098static bool HasPadding(const Type *Ty, const TargetData &TD) {
1099 if (const StructType *STy = dyn_cast<StructType>(Ty)) {
1100 const StructLayout *SL = TD.getStructLayout(STy);
1101 unsigned PrevFieldBitOffset = 0;
1102 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
1103 unsigned FieldBitOffset = SL->getElementOffsetInBits(i);
1104
1105 // Padding in sub-elements?
1106 if (HasPadding(STy->getElementType(i), TD))
1107 return true;
1108
1109 // Check to see if there is any padding between this element and the
1110 // previous one.
1111 if (i) {
1112 unsigned PrevFieldEnd =
1113 PrevFieldBitOffset+TD.getTypeSizeInBits(STy->getElementType(i-1));
1114 if (PrevFieldEnd < FieldBitOffset)
1115 return true;
1116 }
1117
1118 PrevFieldBitOffset = FieldBitOffset;
1119 }
1120
1121 // Check for tail padding.
1122 if (unsigned EltCount = STy->getNumElements()) {
1123 unsigned PrevFieldEnd = PrevFieldBitOffset +
1124 TD.getTypeSizeInBits(STy->getElementType(EltCount-1));
1125 if (PrevFieldEnd < SL->getSizeInBits())
1126 return true;
1127 }
1128
1129 } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
1130 return HasPadding(ATy->getElementType(), TD);
1131 } else if (const VectorType *VTy = dyn_cast<VectorType>(Ty)) {
1132 return HasPadding(VTy->getElementType(), TD);
1133 }
1134 return TD.getTypeSizeInBits(Ty) != TD.getTypeAllocSizeInBits(Ty);
1135}
1136
1137/// isSafeStructAllocaToScalarRepl - Check to see if the specified allocation of
1138/// an aggregate can be broken down into elements. Return 0 if not, 3 if safe,
1139/// or 1 if safe after canonicalization has been performed.
1140///
1141int SROA::isSafeAllocaToScalarRepl(AllocationInst *AI) {
1142 // Loop over the use list of the alloca. We can only transform it if all of
1143 // the users are safe to transform.
1144 AllocaInfo Info;
1145
1146 for (Value::use_iterator I = AI->use_begin(), E = AI->use_end();
1147 I != E; ++I) {
1148 isSafeUseOfAllocation(cast<Instruction>(*I), AI, Info);
1149 if (Info.isUnsafe) {
1150 DOUT << "Cannot transform: " << *AI << " due to user: " << **I;
1151 return 0;
1152 }
1153 }
1154
1155 // Okay, we know all the users are promotable. If the aggregate is a memcpy
1156 // source and destination, we have to be careful. In particular, the memcpy
1157 // could be moving around elements that live in structure padding of the LLVM
1158 // types, but may actually be used. In these cases, we refuse to promote the
1159 // struct.
1160 if (Info.isMemCpySrc && Info.isMemCpyDst &&
1161 HasPadding(AI->getType()->getElementType(), *TD))
1162 return 0;
1163
1164 // If we require cleanup, return 1, otherwise return 3.
1165 return Info.needsCleanup ? 1 : 3;
1166}
1167
1168/// CleanupGEP - GEP is used by an Alloca, which can be prompted after the GEP
1169/// is canonicalized here.
1170void SROA::CleanupGEP(GetElementPtrInst *GEPI) {
1171 gep_type_iterator I = gep_type_begin(GEPI);
1172 ++I;
1173
1174 const ArrayType *AT = dyn_cast<ArrayType>(*I);
1175 if (!AT)
1176 return;
1177
1178 uint64_t NumElements = AT->getNumElements();
1179
1180 if (isa<ConstantInt>(I.getOperand()))
1181 return;
1182
1183 if (NumElements == 1) {
1184 GEPI->setOperand(2, Constant::getNullValue(Type::Int32Ty));
1185 return;
1186 }
1187
1188 assert(NumElements == 2 && "Unhandled case!");
1189 // All users of the GEP must be loads. At each use of the GEP, insert
1190 // two loads of the appropriate indexed GEP and select between them.
1191 Value *IsOne = new ICmpInst(ICmpInst::ICMP_NE, I.getOperand(),
1192 Constant::getNullValue(I.getOperand()->getType()),
1193 "isone", GEPI);
1194 // Insert the new GEP instructions, which are properly indexed.
1195 SmallVector<Value*, 8> Indices(GEPI->op_begin()+1, GEPI->op_end());
1196 Indices[1] = Constant::getNullValue(Type::Int32Ty);
1197 Value *ZeroIdx = GetElementPtrInst::Create(GEPI->getOperand(0),
1198 Indices.begin(),
1199 Indices.end(),
1200 GEPI->getName()+".0", GEPI);
1201 Indices[1] = ConstantInt::get(Type::Int32Ty, 1);
1202 Value *OneIdx = GetElementPtrInst::Create(GEPI->getOperand(0),
1203 Indices.begin(),
1204 Indices.end(),
1205 GEPI->getName()+".1", GEPI);
1206 // Replace all loads of the variable index GEP with loads from both
1207 // indexes and a select.
1208 while (!GEPI->use_empty()) {
1209 LoadInst *LI = cast<LoadInst>(GEPI->use_back());
1210 Value *Zero = new LoadInst(ZeroIdx, LI->getName()+".0", LI);
1211 Value *One = new LoadInst(OneIdx , LI->getName()+".1", LI);
1212 Value *R = SelectInst::Create(IsOne, One, Zero, LI->getName(), LI);
1213 LI->replaceAllUsesWith(R);
1214 LI->eraseFromParent();
1215 }
1216 GEPI->eraseFromParent();
1217}
1218
1219
1220/// CleanupAllocaUsers - If SROA reported that it can promote the specified
1221/// allocation, but only if cleaned up, perform the cleanups required.
1222void SROA::CleanupAllocaUsers(AllocationInst *AI) {
1223 // At this point, we know that the end result will be SROA'd and promoted, so
1224 // we can insert ugly code if required so long as sroa+mem2reg will clean it
1225 // up.
1226 for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end();
1227 UI != E; ) {
1228 User *U = *UI++;
1229 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(U))
1230 CleanupGEP(GEPI);
|
1232 SmallVector<DbgInfoIntrinsic *, 2> DbgInUses;
1233 if (!isa<StoreInst>(I) && OnlyUsedByDbgInfoIntrinsics(I, &DbgInUses)) {
1234 // Safe to remove debug info uses.
1235 while (!DbgInUses.empty()) {
1236 DbgInfoIntrinsic *DI = DbgInUses.back(); DbgInUses.pop_back();
1237 DI->eraseFromParent();
1238 }
1239 I->eraseFromParent();
1240 }
1241 }
1242 }
1243}
1244
1245/// MergeInType - Add the 'In' type to the accumulated type (Accum) so far at
1246/// the offset specified by Offset (which is specified in bytes).
1247///
1248/// There are two cases we handle here:
1249/// 1) A union of vector types of the same size and potentially its elements.
1250/// Here we turn element accesses into insert/extract element operations.
1251/// This promotes a <4 x float> with a store of float to the third element
1252/// into a <4 x float> that uses insert element.
1253/// 2) A fully general blob of memory, which we turn into some (potentially
1254/// large) integer type with extract and insert operations where the loads
1255/// and stores would mutate the memory.
1256static void MergeInType(const Type *In, uint64_t Offset, const Type *&VecTy,
1257 unsigned AllocaSize, const TargetData &TD) {
1258 // If this could be contributing to a vector, analyze it.
1259 if (VecTy != Type::VoidTy) { // either null or a vector type.
1260
1261 // If the In type is a vector that is the same size as the alloca, see if it
1262 // matches the existing VecTy.
1263 if (const VectorType *VInTy = dyn_cast<VectorType>(In)) {
1264 if (VInTy->getBitWidth()/8 == AllocaSize && Offset == 0) {
1265 // If we're storing/loading a vector of the right size, allow it as a
1266 // vector. If this the first vector we see, remember the type so that
1267 // we know the element size.
1268 if (VecTy == 0)
1269 VecTy = VInTy;
1270 return;
1271 }
1272 } else if (In == Type::FloatTy || In == Type::DoubleTy ||
1273 (isa<IntegerType>(In) && In->getPrimitiveSizeInBits() >= 8 &&
1274 isPowerOf2_32(In->getPrimitiveSizeInBits()))) {
1275 // If we're accessing something that could be an element of a vector, see
1276 // if the implied vector agrees with what we already have and if Offset is
1277 // compatible with it.
1278 unsigned EltSize = In->getPrimitiveSizeInBits()/8;
1279 if (Offset % EltSize == 0 &&
1280 AllocaSize % EltSize == 0 &&
1281 (VecTy == 0 ||
1282 cast<VectorType>(VecTy)->getElementType()
1283 ->getPrimitiveSizeInBits()/8 == EltSize)) {
1284 if (VecTy == 0)
1285 VecTy = VectorType::get(In, AllocaSize/EltSize);
1286 return;
1287 }
1288 }
1289 }
1290
1291 // Otherwise, we have a case that we can't handle with an optimized vector
1292 // form. We can still turn this into a large integer.
1293 VecTy = Type::VoidTy;
1294}
1295
1296/// CanConvertToScalar - V is a pointer. If we can convert the pointee and all
1297/// its accesses to use a to single vector type, return true, and set VecTy to
1298/// the new type. If we could convert the alloca into a single promotable
1299/// integer, return true but set VecTy to VoidTy. Further, if the use is not a
1300/// completely trivial use that mem2reg could promote, set IsNotTrivial. Offset
1301/// is the current offset from the base of the alloca being analyzed.
1302///
1303/// If we see at least one access to the value that is as a vector type, set the
1304/// SawVec flag.
1305///
1306bool SROA::CanConvertToScalar(Value *V, bool &IsNotTrivial, const Type *&VecTy,
1307 bool &SawVec, uint64_t Offset,
1308 unsigned AllocaSize) {
1309 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) {
1310 Instruction *User = cast<Instruction>(*UI);
1311
1312 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1313 // Don't break volatile loads.
1314 if (LI->isVolatile())
1315 return false;
1316 MergeInType(LI->getType(), Offset, VecTy, AllocaSize, *TD);
1317 SawVec |= isa<VectorType>(LI->getType());
1318 continue;
1319 }
1320
1321 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
1322 // Storing the pointer, not into the value?
1323 if (SI->getOperand(0) == V || SI->isVolatile()) return 0;
1324 MergeInType(SI->getOperand(0)->getType(), Offset, VecTy, AllocaSize, *TD);
1325 SawVec |= isa<VectorType>(SI->getOperand(0)->getType());
1326 continue;
1327 }
1328
1329 if (BitCastInst *BCI = dyn_cast<BitCastInst>(User)) {
1330 if (!CanConvertToScalar(BCI, IsNotTrivial, VecTy, SawVec, Offset,
1331 AllocaSize))
1332 return false;
1333 IsNotTrivial = true;
1334 continue;
1335 }
1336
1337 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) {
1338 // If this is a GEP with a variable indices, we can't handle it.
1339 if (!GEP->hasAllConstantIndices())
1340 return false;
1341
1342 // Compute the offset that this GEP adds to the pointer.
1343 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end());
1344 uint64_t GEPOffset = TD->getIndexedOffset(GEP->getOperand(0)->getType(),
1345 &Indices[0], Indices.size());
1346 // See if all uses can be converted.
1347 if (!CanConvertToScalar(GEP, IsNotTrivial, VecTy, SawVec,Offset+GEPOffset,
1348 AllocaSize))
1349 return false;
1350 IsNotTrivial = true;
1351 continue;
1352 }
1353
1354 // If this is a constant sized memset of a constant value (e.g. 0) we can
1355 // handle it.
1356 if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) {
1357 // Store of constant value and constant size.
1358 if (isa<ConstantInt>(MSI->getValue()) &&
1359 isa<ConstantInt>(MSI->getLength())) {
1360 IsNotTrivial = true;
1361 continue;
1362 }
1363 }
1364
1365 // If this is a memcpy or memmove into or out of the whole allocation, we
1366 // can handle it like a load or store of the scalar type.
1367 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) {
1368 if (ConstantInt *Len = dyn_cast<ConstantInt>(MTI->getLength()))
1369 if (Len->getZExtValue() == AllocaSize && Offset == 0) {
1370 IsNotTrivial = true;
1371 continue;
1372 }
1373 }
1374
1375 // Ignore dbg intrinsic.
1376 if (isa<DbgInfoIntrinsic>(User))
1377 continue;
1378
1379 // Otherwise, we cannot handle this!
1380 return false;
1381 }
1382
1383 return true;
1384}
1385
1386
1387/// ConvertUsesToScalar - Convert all of the users of Ptr to use the new alloca
1388/// directly. This happens when we are converting an "integer union" to a
1389/// single integer scalar, or when we are converting a "vector union" to a
1390/// vector with insert/extractelement instructions.
1391///
1392/// Offset is an offset from the original alloca, in bits that need to be
1393/// shifted to the right. By the end of this, there should be no uses of Ptr.
1394void SROA::ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, uint64_t Offset) {
1395 while (!Ptr->use_empty()) {
1396 Instruction *User = cast<Instruction>(Ptr->use_back());
1397
1398 if (BitCastInst *CI = dyn_cast<BitCastInst>(User)) {
1399 ConvertUsesToScalar(CI, NewAI, Offset);
1400 CI->eraseFromParent();
1401 continue;
1402 }
1403
1404 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) {
1405 // Compute the offset that this GEP adds to the pointer.
1406 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end());
1407 uint64_t GEPOffset = TD->getIndexedOffset(GEP->getOperand(0)->getType(),
1408 &Indices[0], Indices.size());
1409 ConvertUsesToScalar(GEP, NewAI, Offset+GEPOffset*8);
1410 GEP->eraseFromParent();
1411 continue;
1412 }
1413
1414 IRBuilder<> Builder(User->getParent(), User);
1415
1416 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1417 // The load is a bit extract from NewAI shifted right by Offset bits.
1418 Value *LoadedVal = Builder.CreateLoad(NewAI, "tmp");
1419 Value *NewLoadVal
1420 = ConvertScalar_ExtractValue(LoadedVal, LI->getType(), Offset, Builder);
1421 LI->replaceAllUsesWith(NewLoadVal);
1422 LI->eraseFromParent();
1423 continue;
1424 }
1425
1426 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
1427 assert(SI->getOperand(0) != Ptr && "Consistency error!");
1428 Value *Old = Builder.CreateLoad(NewAI, (NewAI->getName()+".in").c_str());
1429 Value *New = ConvertScalar_InsertValue(SI->getOperand(0), Old, Offset,
1430 Builder);
1431 Builder.CreateStore(New, NewAI);
1432 SI->eraseFromParent();
1433 continue;
1434 }
1435
1436 // If this is a constant sized memset of a constant value (e.g. 0) we can
1437 // transform it into a store of the expanded constant value.
1438 if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) {
1439 assert(MSI->getRawDest() == Ptr && "Consistency error!");
1440 unsigned NumBytes = cast<ConstantInt>(MSI->getLength())->getZExtValue();
1441 if (NumBytes != 0) {
1442 unsigned Val = cast<ConstantInt>(MSI->getValue())->getZExtValue();
1443
1444 // Compute the value replicated the right number of times.
1445 APInt APVal(NumBytes*8, Val);
1446
1447 // Splat the value if non-zero.
1448 if (Val)
1449 for (unsigned i = 1; i != NumBytes; ++i)
1450 APVal |= APVal << 8;
1451
1452 Value *Old = Builder.CreateLoad(NewAI, (NewAI->getName()+".in").c_str());
1453 Value *New = ConvertScalar_InsertValue(ConstantInt::get(APVal), Old,
1454 Offset, Builder);
1455 Builder.CreateStore(New, NewAI);
1456 }
1457 MSI->eraseFromParent();
1458 continue;
1459 }
1460
1461 // If this is a memcpy or memmove into or out of the whole allocation, we
1462 // can handle it like a load or store of the scalar type.
1463 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) {
1464 assert(Offset == 0 && "must be store to start of alloca");
1465
1466 // If the source and destination are both to the same alloca, then this is
1467 // a noop copy-to-self, just delete it. Otherwise, emit a load and store
1468 // as appropriate.
1469 AllocaInst *OrigAI = cast<AllocaInst>(Ptr->getUnderlyingObject());
1470
1471 if (MTI->getSource()->getUnderlyingObject() != OrigAI) {
1472 // Dest must be OrigAI, change this to be a load from the original
1473 // pointer (bitcasted), then a store to our new alloca.
1474 assert(MTI->getRawDest() == Ptr && "Neither use is of pointer?");
1475 Value *SrcPtr = MTI->getSource();
1476 SrcPtr = Builder.CreateBitCast(SrcPtr, NewAI->getType());
1477
1478 LoadInst *SrcVal = Builder.CreateLoad(SrcPtr, "srcval");
1479 SrcVal->setAlignment(MTI->getAlignment());
1480 Builder.CreateStore(SrcVal, NewAI);
1481 } else if (MTI->getDest()->getUnderlyingObject() != OrigAI) {
1482 // Src must be OrigAI, change this to be a load from NewAI then a store
1483 // through the original dest pointer (bitcasted).
1484 assert(MTI->getRawSource() == Ptr && "Neither use is of pointer?");
1485 LoadInst *SrcVal = Builder.CreateLoad(NewAI, "srcval");
1486
1487 Value *DstPtr = Builder.CreateBitCast(MTI->getDest(), NewAI->getType());
1488 StoreInst *NewStore = Builder.CreateStore(SrcVal, DstPtr);
1489 NewStore->setAlignment(MTI->getAlignment());
1490 } else {
1491 // Noop transfer. Src == Dst
1492 }
1493
1494
1495 MTI->eraseFromParent();
1496 continue;
1497 }
1498
1499 // If user is a dbg info intrinsic then it is safe to remove it.
1500 if (isa<DbgInfoIntrinsic>(User)) {
1501 User->eraseFromParent();
1502 continue;
1503 }
1504
1505 assert(0 && "Unsupported operation!");
1506 abort();
1507 }
1508}
1509
1510/// ConvertScalar_ExtractValue - Extract a value of type ToType from an integer
1511/// or vector value FromVal, extracting the bits from the offset specified by
1512/// Offset. This returns the value, which is of type ToType.
1513///
1514/// This happens when we are converting an "integer union" to a single
1515/// integer scalar, or when we are converting a "vector union" to a vector with
1516/// insert/extractelement instructions.
1517///
1518/// Offset is an offset from the original alloca, in bits that need to be
1519/// shifted to the right.
1520Value *SROA::ConvertScalar_ExtractValue(Value *FromVal, const Type *ToType,
1521 uint64_t Offset, IRBuilder<> &Builder) {
1522 // If the load is of the whole new alloca, no conversion is needed.
1523 if (FromVal->getType() == ToType && Offset == 0)
1524 return FromVal;
1525
1526 // If the result alloca is a vector type, this is either an element
1527 // access or a bitcast to another vector type of the same size.
1528 if (const VectorType *VTy = dyn_cast<VectorType>(FromVal->getType())) {
1529 if (isa<VectorType>(ToType))
1530 return Builder.CreateBitCast(FromVal, ToType, "tmp");
1531
1532 // Otherwise it must be an element access.
1533 unsigned Elt = 0;
1534 if (Offset) {
1535 unsigned EltSize = TD->getTypeAllocSizeInBits(VTy->getElementType());
1536 Elt = Offset/EltSize;
1537 assert(EltSize*Elt == Offset && "Invalid modulus in validity checking");
1538 }
1539 // Return the element extracted out of it.
1540 Value *V = Builder.CreateExtractElement(FromVal,
1541 ConstantInt::get(Type::Int32Ty,Elt),
1542 "tmp");
1543 if (V->getType() != ToType)
1544 V = Builder.CreateBitCast(V, ToType, "tmp");
1545 return V;
1546 }
1547
1548 // If ToType is a first class aggregate, extract out each of the pieces and
1549 // use insertvalue's to form the FCA.
1550 if (const StructType *ST = dyn_cast<StructType>(ToType)) {
1551 const StructLayout &Layout = *TD->getStructLayout(ST);
1552 Value *Res = UndefValue::get(ST);
1553 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) {
1554 Value *Elt = ConvertScalar_ExtractValue(FromVal, ST->getElementType(i),
1555 Offset+Layout.getElementOffsetInBits(i),
1556 Builder);
1557 Res = Builder.CreateInsertValue(Res, Elt, i, "tmp");
1558 }
1559 return Res;
1560 }
1561
1562 if (const ArrayType *AT = dyn_cast<ArrayType>(ToType)) {
1563 uint64_t EltSize = TD->getTypeAllocSizeInBits(AT->getElementType());
1564 Value *Res = UndefValue::get(AT);
1565 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
1566 Value *Elt = ConvertScalar_ExtractValue(FromVal, AT->getElementType(),
1567 Offset+i*EltSize, Builder);
1568 Res = Builder.CreateInsertValue(Res, Elt, i, "tmp");
1569 }
1570 return Res;
1571 }
1572
1573 // Otherwise, this must be a union that was converted to an integer value.
1574 const IntegerType *NTy = cast<IntegerType>(FromVal->getType());
1575
1576 // If this is a big-endian system and the load is narrower than the
1577 // full alloca type, we need to do a shift to get the right bits.
1578 int ShAmt = 0;
1579 if (TD->isBigEndian()) {
1580 // On big-endian machines, the lowest bit is stored at the bit offset
1581 // from the pointer given by getTypeStoreSizeInBits. This matters for
1582 // integers with a bitwidth that is not a multiple of 8.
1583 ShAmt = TD->getTypeStoreSizeInBits(NTy) -
1584 TD->getTypeStoreSizeInBits(ToType) - Offset;
1585 } else {
1586 ShAmt = Offset;
1587 }
1588
1589 // Note: we support negative bitwidths (with shl) which are not defined.
1590 // We do this to support (f.e.) loads off the end of a structure where
1591 // only some bits are used.
1592 if (ShAmt > 0 && (unsigned)ShAmt < NTy->getBitWidth())
1593 FromVal = Builder.CreateLShr(FromVal, ConstantInt::get(FromVal->getType(),
1594 ShAmt), "tmp");
1595 else if (ShAmt < 0 && (unsigned)-ShAmt < NTy->getBitWidth())
1596 FromVal = Builder.CreateShl(FromVal, ConstantInt::get(FromVal->getType(),
1597 -ShAmt), "tmp");
1598
1599 // Finally, unconditionally truncate the integer to the right width.
1600 unsigned LIBitWidth = TD->getTypeSizeInBits(ToType);
1601 if (LIBitWidth < NTy->getBitWidth())
1602 FromVal = Builder.CreateTrunc(FromVal, IntegerType::get(LIBitWidth), "tmp");
1603 else if (LIBitWidth > NTy->getBitWidth())
1604 FromVal = Builder.CreateZExt(FromVal, IntegerType::get(LIBitWidth), "tmp");
1605
1606 // If the result is an integer, this is a trunc or bitcast.
1607 if (isa<IntegerType>(ToType)) {
1608 // Should be done.
1609 } else if (ToType->isFloatingPoint() || isa<VectorType>(ToType)) {
1610 // Just do a bitcast, we know the sizes match up.
1611 FromVal = Builder.CreateBitCast(FromVal, ToType, "tmp");
1612 } else {
1613 // Otherwise must be a pointer.
1614 FromVal = Builder.CreateIntToPtr(FromVal, ToType, "tmp");
1615 }
1616 assert(FromVal->getType() == ToType && "Didn't convert right?");
1617 return FromVal;
1618}
1619
1620
1621/// ConvertScalar_InsertValue - Insert the value "SV" into the existing integer
1622/// or vector value "Old" at the offset specified by Offset.
1623///
1624/// This happens when we are converting an "integer union" to a
1625/// single integer scalar, or when we are converting a "vector union" to a
1626/// vector with insert/extractelement instructions.
1627///
1628/// Offset is an offset from the original alloca, in bits that need to be
1629/// shifted to the right.
1630Value *SROA::ConvertScalar_InsertValue(Value *SV, Value *Old,
1631 uint64_t Offset, IRBuilder<> &Builder) {
1632
1633 // Convert the stored type to the actual type, shift it left to insert
1634 // then 'or' into place.
1635 const Type *AllocaType = Old->getType();
1636
1637 if (const VectorType *VTy = dyn_cast<VectorType>(AllocaType)) {
1638 uint64_t VecSize = TD->getTypeAllocSizeInBits(VTy);
1639 uint64_t ValSize = TD->getTypeAllocSizeInBits(SV->getType());
1640
1641 // Changing the whole vector with memset or with an access of a different
1642 // vector type?
1643 if (ValSize == VecSize)
1644 return Builder.CreateBitCast(SV, AllocaType, "tmp");
1645
1646 uint64_t EltSize = TD->getTypeAllocSizeInBits(VTy->getElementType());
1647
1648 // Must be an element insertion.
1649 unsigned Elt = Offset/EltSize;
1650
1651 if (SV->getType() != VTy->getElementType())
1652 SV = Builder.CreateBitCast(SV, VTy->getElementType(), "tmp");
1653
1654 SV = Builder.CreateInsertElement(Old, SV,
1655 ConstantInt::get(Type::Int32Ty, Elt),
1656 "tmp");
1657 return SV;
1658 }
1659
1660 // If SV is a first-class aggregate value, insert each value recursively.
1661 if (const StructType *ST = dyn_cast<StructType>(SV->getType())) {
1662 const StructLayout &Layout = *TD->getStructLayout(ST);
1663 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) {
1664 Value *Elt = Builder.CreateExtractValue(SV, i, "tmp");
1665 Old = ConvertScalar_InsertValue(Elt, Old,
1666 Offset+Layout.getElementOffsetInBits(i),
1667 Builder);
1668 }
1669 return Old;
1670 }
1671
1672 if (const ArrayType *AT = dyn_cast<ArrayType>(SV->getType())) {
1673 uint64_t EltSize = TD->getTypeAllocSizeInBits(AT->getElementType());
1674 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
1675 Value *Elt = Builder.CreateExtractValue(SV, i, "tmp");
1676 Old = ConvertScalar_InsertValue(Elt, Old, Offset+i*EltSize, Builder);
1677 }
1678 return Old;
1679 }
1680
1681 // If SV is a float, convert it to the appropriate integer type.
1682 // If it is a pointer, do the same.
1683 unsigned SrcWidth = TD->getTypeSizeInBits(SV->getType());
1684 unsigned DestWidth = TD->getTypeSizeInBits(AllocaType);
1685 unsigned SrcStoreWidth = TD->getTypeStoreSizeInBits(SV->getType());
1686 unsigned DestStoreWidth = TD->getTypeStoreSizeInBits(AllocaType);
1687 if (SV->getType()->isFloatingPoint() || isa<VectorType>(SV->getType()))
1688 SV = Builder.CreateBitCast(SV, IntegerType::get(SrcWidth), "tmp");
1689 else if (isa<PointerType>(SV->getType()))
1690 SV = Builder.CreatePtrToInt(SV, TD->getIntPtrType(), "tmp");
1691
1692 // Zero extend or truncate the value if needed.
1693 if (SV->getType() != AllocaType) {
1694 if (SV->getType()->getPrimitiveSizeInBits() <
1695 AllocaType->getPrimitiveSizeInBits())
1696 SV = Builder.CreateZExt(SV, AllocaType, "tmp");
1697 else {
1698 // Truncation may be needed if storing more than the alloca can hold
1699 // (undefined behavior).
1700 SV = Builder.CreateTrunc(SV, AllocaType, "tmp");
1701 SrcWidth = DestWidth;
1702 SrcStoreWidth = DestStoreWidth;
1703 }
1704 }
1705
1706 // If this is a big-endian system and the store is narrower than the
1707 // full alloca type, we need to do a shift to get the right bits.
1708 int ShAmt = 0;
1709 if (TD->isBigEndian()) {
1710 // On big-endian machines, the lowest bit is stored at the bit offset
1711 // from the pointer given by getTypeStoreSizeInBits. This matters for
1712 // integers with a bitwidth that is not a multiple of 8.
1713 ShAmt = DestStoreWidth - SrcStoreWidth - Offset;
1714 } else {
1715 ShAmt = Offset;
1716 }
1717
1718 // Note: we support negative bitwidths (with shr) which are not defined.
1719 // We do this to support (f.e.) stores off the end of a structure where
1720 // only some bits in the structure are set.
1721 APInt Mask(APInt::getLowBitsSet(DestWidth, SrcWidth));
1722 if (ShAmt > 0 && (unsigned)ShAmt < DestWidth) {
1723 SV = Builder.CreateShl(SV, ConstantInt::get(SV->getType(), ShAmt), "tmp");
1724 Mask <<= ShAmt;
1725 } else if (ShAmt < 0 && (unsigned)-ShAmt < DestWidth) {
1726 SV = Builder.CreateLShr(SV, ConstantInt::get(SV->getType(), -ShAmt), "tmp");
1727 Mask = Mask.lshr(-ShAmt);
1728 }
1729
1730 // Mask out the bits we are about to insert from the old value, and or
1731 // in the new bits.
1732 if (SrcWidth != DestWidth) {
1733 assert(DestWidth > SrcWidth);
1734 Old = Builder.CreateAnd(Old, ConstantInt::get(~Mask), "mask");
1735 SV = Builder.CreateOr(Old, SV, "ins");
1736 }
1737 return SV;
1738}
1739
1740
1741
1742/// PointsToConstantGlobal - Return true if V (possibly indirectly) points to
1743/// some part of a constant global variable. This intentionally only accepts
1744/// constant expressions because we don't can't rewrite arbitrary instructions.
1745static bool PointsToConstantGlobal(Value *V) {
1746 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
1747 return GV->isConstant();
1748 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
1749 if (CE->getOpcode() == Instruction::BitCast ||
1750 CE->getOpcode() == Instruction::GetElementPtr)
1751 return PointsToConstantGlobal(CE->getOperand(0));
1752 return false;
1753}
1754
1755/// isOnlyCopiedFromConstantGlobal - Recursively walk the uses of a (derived)
1756/// pointer to an alloca. Ignore any reads of the pointer, return false if we
1757/// see any stores or other unknown uses. If we see pointer arithmetic, keep
1758/// track of whether it moves the pointer (with isOffset) but otherwise traverse
1759/// the uses. If we see a memcpy/memmove that targets an unoffseted pointer to
1760/// the alloca, and if the source pointer is a pointer to a constant global, we
1761/// can optimize this.
1762static bool isOnlyCopiedFromConstantGlobal(Value *V, Instruction *&TheCopy,
1763 bool isOffset) {
1764 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) {
1765 if (LoadInst *LI = dyn_cast<LoadInst>(*UI))
1766 // Ignore non-volatile loads, they are always ok.
1767 if (!LI->isVolatile())
1768 continue;
1769
1770 if (BitCastInst *BCI = dyn_cast<BitCastInst>(*UI)) {
1771 // If uses of the bitcast are ok, we are ok.
1772 if (!isOnlyCopiedFromConstantGlobal(BCI, TheCopy, isOffset))
1773 return false;
1774 continue;
1775 }
1776 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(*UI)) {
1777 // If the GEP has all zero indices, it doesn't offset the pointer. If it
1778 // doesn't, it does.
1779 if (!isOnlyCopiedFromConstantGlobal(GEP, TheCopy,
1780 isOffset || !GEP->hasAllZeroIndices()))
1781 return false;
1782 continue;
1783 }
1784
1785 // If this is isn't our memcpy/memmove, reject it as something we can't
1786 // handle.
1787 if (!isa<MemTransferInst>(*UI))
1788 return false;
1789
1790 // If we already have seen a copy, reject the second one.
1791 if (TheCopy) return false;
1792
1793 // If the pointer has been offset from the start of the alloca, we can't
1794 // safely handle this.
1795 if (isOffset) return false;
1796
1797 // If the memintrinsic isn't using the alloca as the dest, reject it.
1798 if (UI.getOperandNo() != 1) return false;
1799
1800 MemIntrinsic *MI = cast<MemIntrinsic>(*UI);
1801
1802 // If the source of the memcpy/move is not a constant global, reject it.
1803 if (!PointsToConstantGlobal(MI->getOperand(2)))
1804 return false;
1805
1806 // Otherwise, the transform is safe. Remember the copy instruction.
1807 TheCopy = MI;
1808 }
1809 return true;
1810}
1811
1812/// isOnlyCopiedFromConstantGlobal - Return true if the specified alloca is only
1813/// modified by a copy from a constant global. If we can prove this, we can
1814/// replace any uses of the alloca with uses of the global directly.
1815Instruction *SROA::isOnlyCopiedFromConstantGlobal(AllocationInst *AI) {
1816 Instruction *TheCopy = 0;
1817 if (::isOnlyCopiedFromConstantGlobal(AI, TheCopy, false))
1818 return TheCopy;
1819 return 0;
1820}
| 1233 SmallVector<DbgInfoIntrinsic *, 2> DbgInUses;
1234 if (!isa<StoreInst>(I) && OnlyUsedByDbgInfoIntrinsics(I, &DbgInUses)) {
1235 // Safe to remove debug info uses.
1236 while (!DbgInUses.empty()) {
1237 DbgInfoIntrinsic *DI = DbgInUses.back(); DbgInUses.pop_back();
1238 DI->eraseFromParent();
1239 }
1240 I->eraseFromParent();
1241 }
1242 }
1243 }
1244}
1245
1246/// MergeInType - Add the 'In' type to the accumulated type (Accum) so far at
1247/// the offset specified by Offset (which is specified in bytes).
1248///
1249/// There are two cases we handle here:
1250/// 1) A union of vector types of the same size and potentially its elements.
1251/// Here we turn element accesses into insert/extract element operations.
1252/// This promotes a <4 x float> with a store of float to the third element
1253/// into a <4 x float> that uses insert element.
1254/// 2) A fully general blob of memory, which we turn into some (potentially
1255/// large) integer type with extract and insert operations where the loads
1256/// and stores would mutate the memory.
1257static void MergeInType(const Type *In, uint64_t Offset, const Type *&VecTy,
1258 unsigned AllocaSize, const TargetData &TD) {
1259 // If this could be contributing to a vector, analyze it.
1260 if (VecTy != Type::VoidTy) { // either null or a vector type.
1261
1262 // If the In type is a vector that is the same size as the alloca, see if it
1263 // matches the existing VecTy.
1264 if (const VectorType *VInTy = dyn_cast<VectorType>(In)) {
1265 if (VInTy->getBitWidth()/8 == AllocaSize && Offset == 0) {
1266 // If we're storing/loading a vector of the right size, allow it as a
1267 // vector. If this the first vector we see, remember the type so that
1268 // we know the element size.
1269 if (VecTy == 0)
1270 VecTy = VInTy;
1271 return;
1272 }
1273 } else if (In == Type::FloatTy || In == Type::DoubleTy ||
1274 (isa<IntegerType>(In) && In->getPrimitiveSizeInBits() >= 8 &&
1275 isPowerOf2_32(In->getPrimitiveSizeInBits()))) {
1276 // If we're accessing something that could be an element of a vector, see
1277 // if the implied vector agrees with what we already have and if Offset is
1278 // compatible with it.
1279 unsigned EltSize = In->getPrimitiveSizeInBits()/8;
1280 if (Offset % EltSize == 0 &&
1281 AllocaSize % EltSize == 0 &&
1282 (VecTy == 0 ||
1283 cast<VectorType>(VecTy)->getElementType()
1284 ->getPrimitiveSizeInBits()/8 == EltSize)) {
1285 if (VecTy == 0)
1286 VecTy = VectorType::get(In, AllocaSize/EltSize);
1287 return;
1288 }
1289 }
1290 }
1291
1292 // Otherwise, we have a case that we can't handle with an optimized vector
1293 // form. We can still turn this into a large integer.
1294 VecTy = Type::VoidTy;
1295}
1296
1297/// CanConvertToScalar - V is a pointer. If we can convert the pointee and all
1298/// its accesses to use a to single vector type, return true, and set VecTy to
1299/// the new type. If we could convert the alloca into a single promotable
1300/// integer, return true but set VecTy to VoidTy. Further, if the use is not a
1301/// completely trivial use that mem2reg could promote, set IsNotTrivial. Offset
1302/// is the current offset from the base of the alloca being analyzed.
1303///
1304/// If we see at least one access to the value that is as a vector type, set the
1305/// SawVec flag.
1306///
1307bool SROA::CanConvertToScalar(Value *V, bool &IsNotTrivial, const Type *&VecTy,
1308 bool &SawVec, uint64_t Offset,
1309 unsigned AllocaSize) {
1310 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) {
1311 Instruction *User = cast<Instruction>(*UI);
1312
1313 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1314 // Don't break volatile loads.
1315 if (LI->isVolatile())
1316 return false;
1317 MergeInType(LI->getType(), Offset, VecTy, AllocaSize, *TD);
1318 SawVec |= isa<VectorType>(LI->getType());
1319 continue;
1320 }
1321
1322 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
1323 // Storing the pointer, not into the value?
1324 if (SI->getOperand(0) == V || SI->isVolatile()) return 0;
1325 MergeInType(SI->getOperand(0)->getType(), Offset, VecTy, AllocaSize, *TD);
1326 SawVec |= isa<VectorType>(SI->getOperand(0)->getType());
1327 continue;
1328 }
1329
1330 if (BitCastInst *BCI = dyn_cast<BitCastInst>(User)) {
1331 if (!CanConvertToScalar(BCI, IsNotTrivial, VecTy, SawVec, Offset,
1332 AllocaSize))
1333 return false;
1334 IsNotTrivial = true;
1335 continue;
1336 }
1337
1338 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) {
1339 // If this is a GEP with a variable indices, we can't handle it.
1340 if (!GEP->hasAllConstantIndices())
1341 return false;
1342
1343 // Compute the offset that this GEP adds to the pointer.
1344 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end());
1345 uint64_t GEPOffset = TD->getIndexedOffset(GEP->getOperand(0)->getType(),
1346 &Indices[0], Indices.size());
1347 // See if all uses can be converted.
1348 if (!CanConvertToScalar(GEP, IsNotTrivial, VecTy, SawVec,Offset+GEPOffset,
1349 AllocaSize))
1350 return false;
1351 IsNotTrivial = true;
1352 continue;
1353 }
1354
1355 // If this is a constant sized memset of a constant value (e.g. 0) we can
1356 // handle it.
1357 if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) {
1358 // Store of constant value and constant size.
1359 if (isa<ConstantInt>(MSI->getValue()) &&
1360 isa<ConstantInt>(MSI->getLength())) {
1361 IsNotTrivial = true;
1362 continue;
1363 }
1364 }
1365
1366 // If this is a memcpy or memmove into or out of the whole allocation, we
1367 // can handle it like a load or store of the scalar type.
1368 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) {
1369 if (ConstantInt *Len = dyn_cast<ConstantInt>(MTI->getLength()))
1370 if (Len->getZExtValue() == AllocaSize && Offset == 0) {
1371 IsNotTrivial = true;
1372 continue;
1373 }
1374 }
1375
1376 // Ignore dbg intrinsic.
1377 if (isa<DbgInfoIntrinsic>(User))
1378 continue;
1379
1380 // Otherwise, we cannot handle this!
1381 return false;
1382 }
1383
1384 return true;
1385}
1386
1387
1388/// ConvertUsesToScalar - Convert all of the users of Ptr to use the new alloca
1389/// directly. This happens when we are converting an "integer union" to a
1390/// single integer scalar, or when we are converting a "vector union" to a
1391/// vector with insert/extractelement instructions.
1392///
1393/// Offset is an offset from the original alloca, in bits that need to be
1394/// shifted to the right. By the end of this, there should be no uses of Ptr.
1395void SROA::ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, uint64_t Offset) {
1396 while (!Ptr->use_empty()) {
1397 Instruction *User = cast<Instruction>(Ptr->use_back());
1398
1399 if (BitCastInst *CI = dyn_cast<BitCastInst>(User)) {
1400 ConvertUsesToScalar(CI, NewAI, Offset);
1401 CI->eraseFromParent();
1402 continue;
1403 }
1404
1405 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) {
1406 // Compute the offset that this GEP adds to the pointer.
1407 SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end());
1408 uint64_t GEPOffset = TD->getIndexedOffset(GEP->getOperand(0)->getType(),
1409 &Indices[0], Indices.size());
1410 ConvertUsesToScalar(GEP, NewAI, Offset+GEPOffset*8);
1411 GEP->eraseFromParent();
1412 continue;
1413 }
1414
1415 IRBuilder<> Builder(User->getParent(), User);
1416
1417 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1418 // The load is a bit extract from NewAI shifted right by Offset bits.
1419 Value *LoadedVal = Builder.CreateLoad(NewAI, "tmp");
1420 Value *NewLoadVal
1421 = ConvertScalar_ExtractValue(LoadedVal, LI->getType(), Offset, Builder);
1422 LI->replaceAllUsesWith(NewLoadVal);
1423 LI->eraseFromParent();
1424 continue;
1425 }
1426
1427 if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
1428 assert(SI->getOperand(0) != Ptr && "Consistency error!");
1429 Value *Old = Builder.CreateLoad(NewAI, (NewAI->getName()+".in").c_str());
1430 Value *New = ConvertScalar_InsertValue(SI->getOperand(0), Old, Offset,
1431 Builder);
1432 Builder.CreateStore(New, NewAI);
1433 SI->eraseFromParent();
1434 continue;
1435 }
1436
1437 // If this is a constant sized memset of a constant value (e.g. 0) we can
1438 // transform it into a store of the expanded constant value.
1439 if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) {
1440 assert(MSI->getRawDest() == Ptr && "Consistency error!");
1441 unsigned NumBytes = cast<ConstantInt>(MSI->getLength())->getZExtValue();
1442 if (NumBytes != 0) {
1443 unsigned Val = cast<ConstantInt>(MSI->getValue())->getZExtValue();
1444
1445 // Compute the value replicated the right number of times.
1446 APInt APVal(NumBytes*8, Val);
1447
1448 // Splat the value if non-zero.
1449 if (Val)
1450 for (unsigned i = 1; i != NumBytes; ++i)
1451 APVal |= APVal << 8;
1452
1453 Value *Old = Builder.CreateLoad(NewAI, (NewAI->getName()+".in").c_str());
1454 Value *New = ConvertScalar_InsertValue(ConstantInt::get(APVal), Old,
1455 Offset, Builder);
1456 Builder.CreateStore(New, NewAI);
1457 }
1458 MSI->eraseFromParent();
1459 continue;
1460 }
1461
1462 // If this is a memcpy or memmove into or out of the whole allocation, we
1463 // can handle it like a load or store of the scalar type.
1464 if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) {
1465 assert(Offset == 0 && "must be store to start of alloca");
1466
1467 // If the source and destination are both to the same alloca, then this is
1468 // a noop copy-to-self, just delete it. Otherwise, emit a load and store
1469 // as appropriate.
1470 AllocaInst *OrigAI = cast<AllocaInst>(Ptr->getUnderlyingObject());
1471
1472 if (MTI->getSource()->getUnderlyingObject() != OrigAI) {
1473 // Dest must be OrigAI, change this to be a load from the original
1474 // pointer (bitcasted), then a store to our new alloca.
1475 assert(MTI->getRawDest() == Ptr && "Neither use is of pointer?");
1476 Value *SrcPtr = MTI->getSource();
1477 SrcPtr = Builder.CreateBitCast(SrcPtr, NewAI->getType());
1478
1479 LoadInst *SrcVal = Builder.CreateLoad(SrcPtr, "srcval");
1480 SrcVal->setAlignment(MTI->getAlignment());
1481 Builder.CreateStore(SrcVal, NewAI);
1482 } else if (MTI->getDest()->getUnderlyingObject() != OrigAI) {
1483 // Src must be OrigAI, change this to be a load from NewAI then a store
1484 // through the original dest pointer (bitcasted).
1485 assert(MTI->getRawSource() == Ptr && "Neither use is of pointer?");
1486 LoadInst *SrcVal = Builder.CreateLoad(NewAI, "srcval");
1487
1488 Value *DstPtr = Builder.CreateBitCast(MTI->getDest(), NewAI->getType());
1489 StoreInst *NewStore = Builder.CreateStore(SrcVal, DstPtr);
1490 NewStore->setAlignment(MTI->getAlignment());
1491 } else {
1492 // Noop transfer. Src == Dst
1493 }
1494
1495
1496 MTI->eraseFromParent();
1497 continue;
1498 }
1499
1500 // If user is a dbg info intrinsic then it is safe to remove it.
1501 if (isa<DbgInfoIntrinsic>(User)) {
1502 User->eraseFromParent();
1503 continue;
1504 }
1505
1506 assert(0 && "Unsupported operation!");
1507 abort();
1508 }
1509}
1510
1511/// ConvertScalar_ExtractValue - Extract a value of type ToType from an integer
1512/// or vector value FromVal, extracting the bits from the offset specified by
1513/// Offset. This returns the value, which is of type ToType.
1514///
1515/// This happens when we are converting an "integer union" to a single
1516/// integer scalar, or when we are converting a "vector union" to a vector with
1517/// insert/extractelement instructions.
1518///
1519/// Offset is an offset from the original alloca, in bits that need to be
1520/// shifted to the right.
1521Value *SROA::ConvertScalar_ExtractValue(Value *FromVal, const Type *ToType,
1522 uint64_t Offset, IRBuilder<> &Builder) {
1523 // If the load is of the whole new alloca, no conversion is needed.
1524 if (FromVal->getType() == ToType && Offset == 0)
1525 return FromVal;
1526
1527 // If the result alloca is a vector type, this is either an element
1528 // access or a bitcast to another vector type of the same size.
1529 if (const VectorType *VTy = dyn_cast<VectorType>(FromVal->getType())) {
1530 if (isa<VectorType>(ToType))
1531 return Builder.CreateBitCast(FromVal, ToType, "tmp");
1532
1533 // Otherwise it must be an element access.
1534 unsigned Elt = 0;
1535 if (Offset) {
1536 unsigned EltSize = TD->getTypeAllocSizeInBits(VTy->getElementType());
1537 Elt = Offset/EltSize;
1538 assert(EltSize*Elt == Offset && "Invalid modulus in validity checking");
1539 }
1540 // Return the element extracted out of it.
1541 Value *V = Builder.CreateExtractElement(FromVal,
1542 ConstantInt::get(Type::Int32Ty,Elt),
1543 "tmp");
1544 if (V->getType() != ToType)
1545 V = Builder.CreateBitCast(V, ToType, "tmp");
1546 return V;
1547 }
1548
1549 // If ToType is a first class aggregate, extract out each of the pieces and
1550 // use insertvalue's to form the FCA.
1551 if (const StructType *ST = dyn_cast<StructType>(ToType)) {
1552 const StructLayout &Layout = *TD->getStructLayout(ST);
1553 Value *Res = UndefValue::get(ST);
1554 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) {
1555 Value *Elt = ConvertScalar_ExtractValue(FromVal, ST->getElementType(i),
1556 Offset+Layout.getElementOffsetInBits(i),
1557 Builder);
1558 Res = Builder.CreateInsertValue(Res, Elt, i, "tmp");
1559 }
1560 return Res;
1561 }
1562
1563 if (const ArrayType *AT = dyn_cast<ArrayType>(ToType)) {
1564 uint64_t EltSize = TD->getTypeAllocSizeInBits(AT->getElementType());
1565 Value *Res = UndefValue::get(AT);
1566 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
1567 Value *Elt = ConvertScalar_ExtractValue(FromVal, AT->getElementType(),
1568 Offset+i*EltSize, Builder);
1569 Res = Builder.CreateInsertValue(Res, Elt, i, "tmp");
1570 }
1571 return Res;
1572 }
1573
1574 // Otherwise, this must be a union that was converted to an integer value.
1575 const IntegerType *NTy = cast<IntegerType>(FromVal->getType());
1576
1577 // If this is a big-endian system and the load is narrower than the
1578 // full alloca type, we need to do a shift to get the right bits.
1579 int ShAmt = 0;
1580 if (TD->isBigEndian()) {
1581 // On big-endian machines, the lowest bit is stored at the bit offset
1582 // from the pointer given by getTypeStoreSizeInBits. This matters for
1583 // integers with a bitwidth that is not a multiple of 8.
1584 ShAmt = TD->getTypeStoreSizeInBits(NTy) -
1585 TD->getTypeStoreSizeInBits(ToType) - Offset;
1586 } else {
1587 ShAmt = Offset;
1588 }
1589
1590 // Note: we support negative bitwidths (with shl) which are not defined.
1591 // We do this to support (f.e.) loads off the end of a structure where
1592 // only some bits are used.
1593 if (ShAmt > 0 && (unsigned)ShAmt < NTy->getBitWidth())
1594 FromVal = Builder.CreateLShr(FromVal, ConstantInt::get(FromVal->getType(),
1595 ShAmt), "tmp");
1596 else if (ShAmt < 0 && (unsigned)-ShAmt < NTy->getBitWidth())
1597 FromVal = Builder.CreateShl(FromVal, ConstantInt::get(FromVal->getType(),
1598 -ShAmt), "tmp");
1599
1600 // Finally, unconditionally truncate the integer to the right width.
1601 unsigned LIBitWidth = TD->getTypeSizeInBits(ToType);
1602 if (LIBitWidth < NTy->getBitWidth())
1603 FromVal = Builder.CreateTrunc(FromVal, IntegerType::get(LIBitWidth), "tmp");
1604 else if (LIBitWidth > NTy->getBitWidth())
1605 FromVal = Builder.CreateZExt(FromVal, IntegerType::get(LIBitWidth), "tmp");
1606
1607 // If the result is an integer, this is a trunc or bitcast.
1608 if (isa<IntegerType>(ToType)) {
1609 // Should be done.
1610 } else if (ToType->isFloatingPoint() || isa<VectorType>(ToType)) {
1611 // Just do a bitcast, we know the sizes match up.
1612 FromVal = Builder.CreateBitCast(FromVal, ToType, "tmp");
1613 } else {
1614 // Otherwise must be a pointer.
1615 FromVal = Builder.CreateIntToPtr(FromVal, ToType, "tmp");
1616 }
1617 assert(FromVal->getType() == ToType && "Didn't convert right?");
1618 return FromVal;
1619}
1620
1621
1622/// ConvertScalar_InsertValue - Insert the value "SV" into the existing integer
1623/// or vector value "Old" at the offset specified by Offset.
1624///
1625/// This happens when we are converting an "integer union" to a
1626/// single integer scalar, or when we are converting a "vector union" to a
1627/// vector with insert/extractelement instructions.
1628///
1629/// Offset is an offset from the original alloca, in bits that need to be
1630/// shifted to the right.
1631Value *SROA::ConvertScalar_InsertValue(Value *SV, Value *Old,
1632 uint64_t Offset, IRBuilder<> &Builder) {
1633
1634 // Convert the stored type to the actual type, shift it left to insert
1635 // then 'or' into place.
1636 const Type *AllocaType = Old->getType();
1637
1638 if (const VectorType *VTy = dyn_cast<VectorType>(AllocaType)) {
1639 uint64_t VecSize = TD->getTypeAllocSizeInBits(VTy);
1640 uint64_t ValSize = TD->getTypeAllocSizeInBits(SV->getType());
1641
1642 // Changing the whole vector with memset or with an access of a different
1643 // vector type?
1644 if (ValSize == VecSize)
1645 return Builder.CreateBitCast(SV, AllocaType, "tmp");
1646
1647 uint64_t EltSize = TD->getTypeAllocSizeInBits(VTy->getElementType());
1648
1649 // Must be an element insertion.
1650 unsigned Elt = Offset/EltSize;
1651
1652 if (SV->getType() != VTy->getElementType())
1653 SV = Builder.CreateBitCast(SV, VTy->getElementType(), "tmp");
1654
1655 SV = Builder.CreateInsertElement(Old, SV,
1656 ConstantInt::get(Type::Int32Ty, Elt),
1657 "tmp");
1658 return SV;
1659 }
1660
1661 // If SV is a first-class aggregate value, insert each value recursively.
1662 if (const StructType *ST = dyn_cast<StructType>(SV->getType())) {
1663 const StructLayout &Layout = *TD->getStructLayout(ST);
1664 for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) {
1665 Value *Elt = Builder.CreateExtractValue(SV, i, "tmp");
1666 Old = ConvertScalar_InsertValue(Elt, Old,
1667 Offset+Layout.getElementOffsetInBits(i),
1668 Builder);
1669 }
1670 return Old;
1671 }
1672
1673 if (const ArrayType *AT = dyn_cast<ArrayType>(SV->getType())) {
1674 uint64_t EltSize = TD->getTypeAllocSizeInBits(AT->getElementType());
1675 for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
1676 Value *Elt = Builder.CreateExtractValue(SV, i, "tmp");
1677 Old = ConvertScalar_InsertValue(Elt, Old, Offset+i*EltSize, Builder);
1678 }
1679 return Old;
1680 }
1681
1682 // If SV is a float, convert it to the appropriate integer type.
1683 // If it is a pointer, do the same.
1684 unsigned SrcWidth = TD->getTypeSizeInBits(SV->getType());
1685 unsigned DestWidth = TD->getTypeSizeInBits(AllocaType);
1686 unsigned SrcStoreWidth = TD->getTypeStoreSizeInBits(SV->getType());
1687 unsigned DestStoreWidth = TD->getTypeStoreSizeInBits(AllocaType);
1688 if (SV->getType()->isFloatingPoint() || isa<VectorType>(SV->getType()))
1689 SV = Builder.CreateBitCast(SV, IntegerType::get(SrcWidth), "tmp");
1690 else if (isa<PointerType>(SV->getType()))
1691 SV = Builder.CreatePtrToInt(SV, TD->getIntPtrType(), "tmp");
1692
1693 // Zero extend or truncate the value if needed.
1694 if (SV->getType() != AllocaType) {
1695 if (SV->getType()->getPrimitiveSizeInBits() <
1696 AllocaType->getPrimitiveSizeInBits())
1697 SV = Builder.CreateZExt(SV, AllocaType, "tmp");
1698 else {
1699 // Truncation may be needed if storing more than the alloca can hold
1700 // (undefined behavior).
1701 SV = Builder.CreateTrunc(SV, AllocaType, "tmp");
1702 SrcWidth = DestWidth;
1703 SrcStoreWidth = DestStoreWidth;
1704 }
1705 }
1706
1707 // If this is a big-endian system and the store is narrower than the
1708 // full alloca type, we need to do a shift to get the right bits.
1709 int ShAmt = 0;
1710 if (TD->isBigEndian()) {
1711 // On big-endian machines, the lowest bit is stored at the bit offset
1712 // from the pointer given by getTypeStoreSizeInBits. This matters for
1713 // integers with a bitwidth that is not a multiple of 8.
1714 ShAmt = DestStoreWidth - SrcStoreWidth - Offset;
1715 } else {
1716 ShAmt = Offset;
1717 }
1718
1719 // Note: we support negative bitwidths (with shr) which are not defined.
1720 // We do this to support (f.e.) stores off the end of a structure where
1721 // only some bits in the structure are set.
1722 APInt Mask(APInt::getLowBitsSet(DestWidth, SrcWidth));
1723 if (ShAmt > 0 && (unsigned)ShAmt < DestWidth) {
1724 SV = Builder.CreateShl(SV, ConstantInt::get(SV->getType(), ShAmt), "tmp");
1725 Mask <<= ShAmt;
1726 } else if (ShAmt < 0 && (unsigned)-ShAmt < DestWidth) {
1727 SV = Builder.CreateLShr(SV, ConstantInt::get(SV->getType(), -ShAmt), "tmp");
1728 Mask = Mask.lshr(-ShAmt);
1729 }
1730
1731 // Mask out the bits we are about to insert from the old value, and or
1732 // in the new bits.
1733 if (SrcWidth != DestWidth) {
1734 assert(DestWidth > SrcWidth);
1735 Old = Builder.CreateAnd(Old, ConstantInt::get(~Mask), "mask");
1736 SV = Builder.CreateOr(Old, SV, "ins");
1737 }
1738 return SV;
1739}
1740
1741
1742
1743/// PointsToConstantGlobal - Return true if V (possibly indirectly) points to
1744/// some part of a constant global variable. This intentionally only accepts
1745/// constant expressions because we don't can't rewrite arbitrary instructions.
1746static bool PointsToConstantGlobal(Value *V) {
1747 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
1748 return GV->isConstant();
1749 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
1750 if (CE->getOpcode() == Instruction::BitCast ||
1751 CE->getOpcode() == Instruction::GetElementPtr)
1752 return PointsToConstantGlobal(CE->getOperand(0));
1753 return false;
1754}
1755
1756/// isOnlyCopiedFromConstantGlobal - Recursively walk the uses of a (derived)
1757/// pointer to an alloca. Ignore any reads of the pointer, return false if we
1758/// see any stores or other unknown uses. If we see pointer arithmetic, keep
1759/// track of whether it moves the pointer (with isOffset) but otherwise traverse
1760/// the uses. If we see a memcpy/memmove that targets an unoffseted pointer to
1761/// the alloca, and if the source pointer is a pointer to a constant global, we
1762/// can optimize this.
1763static bool isOnlyCopiedFromConstantGlobal(Value *V, Instruction *&TheCopy,
1764 bool isOffset) {
1765 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) {
1766 if (LoadInst *LI = dyn_cast<LoadInst>(*UI))
1767 // Ignore non-volatile loads, they are always ok.
1768 if (!LI->isVolatile())
1769 continue;
1770
1771 if (BitCastInst *BCI = dyn_cast<BitCastInst>(*UI)) {
1772 // If uses of the bitcast are ok, we are ok.
1773 if (!isOnlyCopiedFromConstantGlobal(BCI, TheCopy, isOffset))
1774 return false;
1775 continue;
1776 }
1777 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(*UI)) {
1778 // If the GEP has all zero indices, it doesn't offset the pointer. If it
1779 // doesn't, it does.
1780 if (!isOnlyCopiedFromConstantGlobal(GEP, TheCopy,
1781 isOffset || !GEP->hasAllZeroIndices()))
1782 return false;
1783 continue;
1784 }
1785
1786 // If this is isn't our memcpy/memmove, reject it as something we can't
1787 // handle.
1788 if (!isa<MemTransferInst>(*UI))
1789 return false;
1790
1791 // If we already have seen a copy, reject the second one.
1792 if (TheCopy) return false;
1793
1794 // If the pointer has been offset from the start of the alloca, we can't
1795 // safely handle this.
1796 if (isOffset) return false;
1797
1798 // If the memintrinsic isn't using the alloca as the dest, reject it.
1799 if (UI.getOperandNo() != 1) return false;
1800
1801 MemIntrinsic *MI = cast<MemIntrinsic>(*UI);
1802
1803 // If the source of the memcpy/move is not a constant global, reject it.
1804 if (!PointsToConstantGlobal(MI->getOperand(2)))
1805 return false;
1806
1807 // Otherwise, the transform is safe. Remember the copy instruction.
1808 TheCopy = MI;
1809 }
1810 return true;
1811}
1812
1813/// isOnlyCopiedFromConstantGlobal - Return true if the specified alloca is only
1814/// modified by a copy from a constant global. If we can prove this, we can
1815/// replace any uses of the alloca with uses of the global directly.
1816Instruction *SROA::isOnlyCopiedFromConstantGlobal(AllocationInst *AI) {
1817 Instruction *TheCopy = 0;
1818 if (::isOnlyCopiedFromConstantGlobal(AI, TheCopy, false))
1819 return TheCopy;
1820 return 0;
1821}
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