1 //===- GlobalOpt.cpp - Optimize Global Variables --------------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This pass transforms simple global variables that never have their address
11 // taken. If obviously true, it marks read/write globals as constant, deletes
12 // variables only stored to, etc.
14 //===----------------------------------------------------------------------===//
16 #define DEBUG_TYPE "globalopt"
17 #include "llvm/Transforms/IPO.h"
18 #include "llvm/CallingConv.h"
19 #include "llvm/Constants.h"
20 #include "llvm/DerivedTypes.h"
21 #include "llvm/Instructions.h"
22 #include "llvm/IntrinsicInst.h"
23 #include "llvm/Module.h"
24 #include "llvm/Operator.h"
25 #include "llvm/Pass.h"
26 #include "llvm/Analysis/ConstantFolding.h"
27 #include "llvm/Analysis/MemoryBuiltins.h"
28 #include "llvm/Target/TargetData.h"
29 #include "llvm/Support/CallSite.h"
30 #include "llvm/Support/Debug.h"
31 #include "llvm/Support/ErrorHandling.h"
32 #include "llvm/Support/GetElementPtrTypeIterator.h"
33 #include "llvm/Support/MathExtras.h"
34 #include "llvm/Support/raw_ostream.h"
35 #include "llvm/ADT/DenseMap.h"
36 #include "llvm/ADT/SmallPtrSet.h"
37 #include "llvm/ADT/SmallVector.h"
38 #include "llvm/ADT/Statistic.h"
39 #include "llvm/ADT/STLExtras.h"
43 STATISTIC(NumMarked , "Number of globals marked constant");
44 STATISTIC(NumUnnamed , "Number of globals marked unnamed_addr");
45 STATISTIC(NumSRA , "Number of aggregate globals broken into scalars");
46 STATISTIC(NumHeapSRA , "Number of heap objects SRA'd");
47 STATISTIC(NumSubstitute,"Number of globals with initializers stored into them");
48 STATISTIC(NumDeleted , "Number of globals deleted");
49 STATISTIC(NumFnDeleted , "Number of functions deleted");
50 STATISTIC(NumGlobUses , "Number of global uses devirtualized");
51 STATISTIC(NumLocalized , "Number of globals localized");
52 STATISTIC(NumShrunkToBool , "Number of global vars shrunk to booleans");
53 STATISTIC(NumFastCallFns , "Number of functions converted to fastcc");
54 STATISTIC(NumCtorsEvaluated, "Number of static ctors evaluated");
55 STATISTIC(NumNestRemoved , "Number of nest attributes removed");
56 STATISTIC(NumAliasesResolved, "Number of global aliases resolved");
57 STATISTIC(NumAliasesRemoved, "Number of global aliases eliminated");
58 STATISTIC(NumCXXDtorsRemoved, "Number of global C++ destructors removed");
62 struct GlobalOpt : public ModulePass {
63 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
65 static char ID; // Pass identification, replacement for typeid
66 GlobalOpt() : ModulePass(ID) {
67 initializeGlobalOptPass(*PassRegistry::getPassRegistry());
70 bool runOnModule(Module &M);
73 GlobalVariable *FindGlobalCtors(Module &M);
74 bool OptimizeFunctions(Module &M);
75 bool OptimizeGlobalVars(Module &M);
76 bool OptimizeGlobalAliases(Module &M);
77 bool OptimizeGlobalCtorsList(GlobalVariable *&GCL);
78 bool ProcessGlobal(GlobalVariable *GV,Module::global_iterator &GVI);
79 bool ProcessInternalGlobal(GlobalVariable *GV,Module::global_iterator &GVI,
80 const SmallPtrSet<const PHINode*, 16> &PHIUsers,
81 const GlobalStatus &GS);
82 bool OptimizeEmptyGlobalCXXDtors(Function *CXAAtExitFn);
86 char GlobalOpt::ID = 0;
87 INITIALIZE_PASS(GlobalOpt, "globalopt",
88 "Global Variable Optimizer", false, false)
90 ModulePass *llvm::createGlobalOptimizerPass() { return new GlobalOpt(); }
94 /// GlobalStatus - As we analyze each global, keep track of some information
95 /// about it. If we find out that the address of the global is taken, none of
96 /// this info will be accurate.
98 /// isCompared - True if the global's address is used in a comparison.
101 /// isLoaded - True if the global is ever loaded. If the global isn't ever
102 /// loaded it can be deleted.
105 /// StoredType - Keep track of what stores to the global look like.
108 /// NotStored - There is no store to this global. It can thus be marked
112 /// isInitializerStored - This global is stored to, but the only thing
113 /// stored is the constant it was initialized with. This is only tracked
114 /// for scalar globals.
117 /// isStoredOnce - This global is stored to, but only its initializer and
118 /// one other value is ever stored to it. If this global isStoredOnce, we
119 /// track the value stored to it in StoredOnceValue below. This is only
120 /// tracked for scalar globals.
123 /// isStored - This global is stored to by multiple values or something else
124 /// that we cannot track.
128 /// StoredOnceValue - If only one value (besides the initializer constant) is
129 /// ever stored to this global, keep track of what value it is.
130 Value *StoredOnceValue;
132 /// AccessingFunction/HasMultipleAccessingFunctions - These start out
133 /// null/false. When the first accessing function is noticed, it is recorded.
134 /// When a second different accessing function is noticed,
135 /// HasMultipleAccessingFunctions is set to true.
136 const Function *AccessingFunction;
137 bool HasMultipleAccessingFunctions;
139 /// HasNonInstructionUser - Set to true if this global has a user that is not
140 /// an instruction (e.g. a constant expr or GV initializer).
141 bool HasNonInstructionUser;
143 /// HasPHIUser - Set to true if this global has a user that is a PHI node.
146 GlobalStatus() : isCompared(false), isLoaded(false), StoredType(NotStored),
147 StoredOnceValue(0), AccessingFunction(0),
148 HasMultipleAccessingFunctions(false), HasNonInstructionUser(false),
154 // SafeToDestroyConstant - It is safe to destroy a constant iff it is only used
155 // by constants itself. Note that constants cannot be cyclic, so this test is
156 // pretty easy to implement recursively.
158 static bool SafeToDestroyConstant(const Constant *C) {
159 if (isa<GlobalValue>(C)) return false;
161 for (Value::const_use_iterator UI = C->use_begin(), E = C->use_end(); UI != E;
163 if (const Constant *CU = dyn_cast<Constant>(*UI)) {
164 if (!SafeToDestroyConstant(CU)) return false;
171 /// AnalyzeGlobal - Look at all uses of the global and fill in the GlobalStatus
172 /// structure. If the global has its address taken, return true to indicate we
173 /// can't do anything with it.
175 static bool AnalyzeGlobal(const Value *V, GlobalStatus &GS,
176 SmallPtrSet<const PHINode*, 16> &PHIUsers) {
177 for (Value::const_use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;
180 if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(U)) {
181 GS.HasNonInstructionUser = true;
183 // If the result of the constantexpr isn't pointer type, then we won't
184 // know to expect it in various places. Just reject early.
185 if (!isa<PointerType>(CE->getType())) return true;
187 if (AnalyzeGlobal(CE, GS, PHIUsers)) return true;
188 } else if (const Instruction *I = dyn_cast<Instruction>(U)) {
189 if (!GS.HasMultipleAccessingFunctions) {
190 const Function *F = I->getParent()->getParent();
191 if (GS.AccessingFunction == 0)
192 GS.AccessingFunction = F;
193 else if (GS.AccessingFunction != F)
194 GS.HasMultipleAccessingFunctions = true;
196 if (const LoadInst *LI = dyn_cast<LoadInst>(I)) {
198 if (LI->isVolatile()) return true; // Don't hack on volatile loads.
199 } else if (const StoreInst *SI = dyn_cast<StoreInst>(I)) {
200 // Don't allow a store OF the address, only stores TO the address.
201 if (SI->getOperand(0) == V) return true;
203 if (SI->isVolatile()) return true; // Don't hack on volatile stores.
205 // If this is a direct store to the global (i.e., the global is a scalar
206 // value, not an aggregate), keep more specific information about
208 if (GS.StoredType != GlobalStatus::isStored) {
209 if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(
210 SI->getOperand(1))) {
211 Value *StoredVal = SI->getOperand(0);
212 if (StoredVal == GV->getInitializer()) {
213 if (GS.StoredType < GlobalStatus::isInitializerStored)
214 GS.StoredType = GlobalStatus::isInitializerStored;
215 } else if (isa<LoadInst>(StoredVal) &&
216 cast<LoadInst>(StoredVal)->getOperand(0) == GV) {
217 if (GS.StoredType < GlobalStatus::isInitializerStored)
218 GS.StoredType = GlobalStatus::isInitializerStored;
219 } else if (GS.StoredType < GlobalStatus::isStoredOnce) {
220 GS.StoredType = GlobalStatus::isStoredOnce;
221 GS.StoredOnceValue = StoredVal;
222 } else if (GS.StoredType == GlobalStatus::isStoredOnce &&
223 GS.StoredOnceValue == StoredVal) {
226 GS.StoredType = GlobalStatus::isStored;
229 GS.StoredType = GlobalStatus::isStored;
232 } else if (isa<GetElementPtrInst>(I)) {
233 if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
234 } else if (isa<SelectInst>(I)) {
235 if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
236 } else if (const PHINode *PN = dyn_cast<PHINode>(I)) {
237 // PHI nodes we can check just like select or GEP instructions, but we
238 // have to be careful about infinite recursion.
239 if (PHIUsers.insert(PN)) // Not already visited.
240 if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
241 GS.HasPHIUser = true;
242 } else if (isa<CmpInst>(I)) {
243 GS.isCompared = true;
244 } else if (const MemTransferInst *MTI = dyn_cast<MemTransferInst>(I)) {
245 if (MTI->isVolatile()) return true;
246 if (MTI->getArgOperand(0) == V)
247 GS.StoredType = GlobalStatus::isStored;
248 if (MTI->getArgOperand(1) == V)
250 } else if (const MemSetInst *MSI = dyn_cast<MemSetInst>(I)) {
251 assert(MSI->getArgOperand(0) == V && "Memset only takes one pointer!");
252 if (MSI->isVolatile()) return true;
253 GS.StoredType = GlobalStatus::isStored;
255 return true; // Any other non-load instruction might take address!
257 } else if (const Constant *C = dyn_cast<Constant>(U)) {
258 GS.HasNonInstructionUser = true;
259 // We might have a dead and dangling constant hanging off of here.
260 if (!SafeToDestroyConstant(C))
263 GS.HasNonInstructionUser = true;
264 // Otherwise must be some other user.
272 static Constant *getAggregateConstantElement(Constant *Agg, Constant *Idx) {
273 ConstantInt *CI = dyn_cast<ConstantInt>(Idx);
275 unsigned IdxV = CI->getZExtValue();
277 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(Agg)) {
278 if (IdxV < CS->getNumOperands()) return CS->getOperand(IdxV);
279 } else if (ConstantArray *CA = dyn_cast<ConstantArray>(Agg)) {
280 if (IdxV < CA->getNumOperands()) return CA->getOperand(IdxV);
281 } else if (ConstantVector *CP = dyn_cast<ConstantVector>(Agg)) {
282 if (IdxV < CP->getNumOperands()) return CP->getOperand(IdxV);
283 } else if (isa<ConstantAggregateZero>(Agg)) {
284 if (StructType *STy = dyn_cast<StructType>(Agg->getType())) {
285 if (IdxV < STy->getNumElements())
286 return Constant::getNullValue(STy->getElementType(IdxV));
287 } else if (SequentialType *STy =
288 dyn_cast<SequentialType>(Agg->getType())) {
289 return Constant::getNullValue(STy->getElementType());
291 } else if (isa<UndefValue>(Agg)) {
292 if (StructType *STy = dyn_cast<StructType>(Agg->getType())) {
293 if (IdxV < STy->getNumElements())
294 return UndefValue::get(STy->getElementType(IdxV));
295 } else if (SequentialType *STy =
296 dyn_cast<SequentialType>(Agg->getType())) {
297 return UndefValue::get(STy->getElementType());
304 /// CleanupConstantGlobalUsers - We just marked GV constant. Loop over all
305 /// users of the global, cleaning up the obvious ones. This is largely just a
306 /// quick scan over the use list to clean up the easy and obvious cruft. This
307 /// returns true if it made a change.
308 static bool CleanupConstantGlobalUsers(Value *V, Constant *Init) {
309 bool Changed = false;
310 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;) {
313 if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
315 // Replace the load with the initializer.
316 LI->replaceAllUsesWith(Init);
317 LI->eraseFromParent();
320 } else if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
321 // Store must be unreachable or storing Init into the global.
322 SI->eraseFromParent();
324 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U)) {
325 if (CE->getOpcode() == Instruction::GetElementPtr) {
326 Constant *SubInit = 0;
328 SubInit = ConstantFoldLoadThroughGEPConstantExpr(Init, CE);
329 Changed |= CleanupConstantGlobalUsers(CE, SubInit);
330 } else if (CE->getOpcode() == Instruction::BitCast &&
331 CE->getType()->isPointerTy()) {
332 // Pointer cast, delete any stores and memsets to the global.
333 Changed |= CleanupConstantGlobalUsers(CE, 0);
336 if (CE->use_empty()) {
337 CE->destroyConstant();
340 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) {
341 // Do not transform "gepinst (gep constexpr (GV))" here, because forming
342 // "gepconstexpr (gep constexpr (GV))" will cause the two gep's to fold
343 // and will invalidate our notion of what Init is.
344 Constant *SubInit = 0;
345 if (!isa<ConstantExpr>(GEP->getOperand(0))) {
347 dyn_cast_or_null<ConstantExpr>(ConstantFoldInstruction(GEP));
348 if (Init && CE && CE->getOpcode() == Instruction::GetElementPtr)
349 SubInit = ConstantFoldLoadThroughGEPConstantExpr(Init, CE);
351 Changed |= CleanupConstantGlobalUsers(GEP, SubInit);
353 if (GEP->use_empty()) {
354 GEP->eraseFromParent();
357 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(U)) { // memset/cpy/mv
358 if (MI->getRawDest() == V) {
359 MI->eraseFromParent();
363 } else if (Constant *C = dyn_cast<Constant>(U)) {
364 // If we have a chain of dead constantexprs or other things dangling from
365 // us, and if they are all dead, nuke them without remorse.
366 if (SafeToDestroyConstant(C)) {
367 C->destroyConstant();
368 // This could have invalidated UI, start over from scratch.
369 CleanupConstantGlobalUsers(V, Init);
377 /// isSafeSROAElementUse - Return true if the specified instruction is a safe
378 /// user of a derived expression from a global that we want to SROA.
379 static bool isSafeSROAElementUse(Value *V) {
380 // We might have a dead and dangling constant hanging off of here.
381 if (Constant *C = dyn_cast<Constant>(V))
382 return SafeToDestroyConstant(C);
384 Instruction *I = dyn_cast<Instruction>(V);
385 if (!I) return false;
388 if (isa<LoadInst>(I)) return true;
390 // Stores *to* the pointer are ok.
391 if (StoreInst *SI = dyn_cast<StoreInst>(I))
392 return SI->getOperand(0) != V;
394 // Otherwise, it must be a GEP.
395 GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I);
396 if (GEPI == 0) return false;
398 if (GEPI->getNumOperands() < 3 || !isa<Constant>(GEPI->getOperand(1)) ||
399 !cast<Constant>(GEPI->getOperand(1))->isNullValue())
402 for (Value::use_iterator I = GEPI->use_begin(), E = GEPI->use_end();
404 if (!isSafeSROAElementUse(*I))
410 /// IsUserOfGlobalSafeForSRA - U is a direct user of the specified global value.
411 /// Look at it and its uses and decide whether it is safe to SROA this global.
413 static bool IsUserOfGlobalSafeForSRA(User *U, GlobalValue *GV) {
414 // The user of the global must be a GEP Inst or a ConstantExpr GEP.
415 if (!isa<GetElementPtrInst>(U) &&
416 (!isa<ConstantExpr>(U) ||
417 cast<ConstantExpr>(U)->getOpcode() != Instruction::GetElementPtr))
420 // Check to see if this ConstantExpr GEP is SRA'able. In particular, we
421 // don't like < 3 operand CE's, and we don't like non-constant integer
422 // indices. This enforces that all uses are 'gep GV, 0, C, ...' for some
424 if (U->getNumOperands() < 3 || !isa<Constant>(U->getOperand(1)) ||
425 !cast<Constant>(U->getOperand(1))->isNullValue() ||
426 !isa<ConstantInt>(U->getOperand(2)))
429 gep_type_iterator GEPI = gep_type_begin(U), E = gep_type_end(U);
430 ++GEPI; // Skip over the pointer index.
432 // If this is a use of an array allocation, do a bit more checking for sanity.
433 if (ArrayType *AT = dyn_cast<ArrayType>(*GEPI)) {
434 uint64_t NumElements = AT->getNumElements();
435 ConstantInt *Idx = cast<ConstantInt>(U->getOperand(2));
437 // Check to make sure that index falls within the array. If not,
438 // something funny is going on, so we won't do the optimization.
440 if (Idx->getZExtValue() >= NumElements)
443 // We cannot scalar repl this level of the array unless any array
444 // sub-indices are in-range constants. In particular, consider:
445 // A[0][i]. We cannot know that the user isn't doing invalid things like
446 // allowing i to index an out-of-range subscript that accesses A[1].
448 // Scalar replacing *just* the outer index of the array is probably not
449 // going to be a win anyway, so just give up.
450 for (++GEPI; // Skip array index.
453 uint64_t NumElements;
454 if (ArrayType *SubArrayTy = dyn_cast<ArrayType>(*GEPI))
455 NumElements = SubArrayTy->getNumElements();
456 else if (VectorType *SubVectorTy = dyn_cast<VectorType>(*GEPI))
457 NumElements = SubVectorTy->getNumElements();
459 assert((*GEPI)->isStructTy() &&
460 "Indexed GEP type is not array, vector, or struct!");
464 ConstantInt *IdxVal = dyn_cast<ConstantInt>(GEPI.getOperand());
465 if (!IdxVal || IdxVal->getZExtValue() >= NumElements)
470 for (Value::use_iterator I = U->use_begin(), E = U->use_end(); I != E; ++I)
471 if (!isSafeSROAElementUse(*I))
476 /// GlobalUsersSafeToSRA - Look at all uses of the global and decide whether it
477 /// is safe for us to perform this transformation.
479 static bool GlobalUsersSafeToSRA(GlobalValue *GV) {
480 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end();
482 if (!IsUserOfGlobalSafeForSRA(*UI, GV))
489 /// SRAGlobal - Perform scalar replacement of aggregates on the specified global
490 /// variable. This opens the door for other optimizations by exposing the
491 /// behavior of the program in a more fine-grained way. We have determined that
492 /// this transformation is safe already. We return the first global variable we
493 /// insert so that the caller can reprocess it.
494 static GlobalVariable *SRAGlobal(GlobalVariable *GV, const TargetData &TD) {
495 // Make sure this global only has simple uses that we can SRA.
496 if (!GlobalUsersSafeToSRA(GV))
499 assert(GV->hasLocalLinkage() && !GV->isConstant());
500 Constant *Init = GV->getInitializer();
501 Type *Ty = Init->getType();
503 std::vector<GlobalVariable*> NewGlobals;
504 Module::GlobalListType &Globals = GV->getParent()->getGlobalList();
506 // Get the alignment of the global, either explicit or target-specific.
507 unsigned StartAlignment = GV->getAlignment();
508 if (StartAlignment == 0)
509 StartAlignment = TD.getABITypeAlignment(GV->getType());
511 if (StructType *STy = dyn_cast<StructType>(Ty)) {
512 NewGlobals.reserve(STy->getNumElements());
513 const StructLayout &Layout = *TD.getStructLayout(STy);
514 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
515 Constant *In = getAggregateConstantElement(Init,
516 ConstantInt::get(Type::getInt32Ty(STy->getContext()), i));
517 assert(In && "Couldn't get element of initializer?");
518 GlobalVariable *NGV = new GlobalVariable(STy->getElementType(i), false,
519 GlobalVariable::InternalLinkage,
520 In, GV->getName()+"."+Twine(i),
522 GV->getType()->getAddressSpace());
523 Globals.insert(GV, NGV);
524 NewGlobals.push_back(NGV);
526 // Calculate the known alignment of the field. If the original aggregate
527 // had 256 byte alignment for example, something might depend on that:
528 // propagate info to each field.
529 uint64_t FieldOffset = Layout.getElementOffset(i);
530 unsigned NewAlign = (unsigned)MinAlign(StartAlignment, FieldOffset);
531 if (NewAlign > TD.getABITypeAlignment(STy->getElementType(i)))
532 NGV->setAlignment(NewAlign);
534 } else if (SequentialType *STy = dyn_cast<SequentialType>(Ty)) {
535 unsigned NumElements = 0;
536 if (ArrayType *ATy = dyn_cast<ArrayType>(STy))
537 NumElements = ATy->getNumElements();
539 NumElements = cast<VectorType>(STy)->getNumElements();
541 if (NumElements > 16 && GV->hasNUsesOrMore(16))
542 return 0; // It's not worth it.
543 NewGlobals.reserve(NumElements);
545 uint64_t EltSize = TD.getTypeAllocSize(STy->getElementType());
546 unsigned EltAlign = TD.getABITypeAlignment(STy->getElementType());
547 for (unsigned i = 0, e = NumElements; i != e; ++i) {
548 Constant *In = getAggregateConstantElement(Init,
549 ConstantInt::get(Type::getInt32Ty(Init->getContext()), i));
550 assert(In && "Couldn't get element of initializer?");
552 GlobalVariable *NGV = new GlobalVariable(STy->getElementType(), false,
553 GlobalVariable::InternalLinkage,
554 In, GV->getName()+"."+Twine(i),
556 GV->getType()->getAddressSpace());
557 Globals.insert(GV, NGV);
558 NewGlobals.push_back(NGV);
560 // Calculate the known alignment of the field. If the original aggregate
561 // had 256 byte alignment for example, something might depend on that:
562 // propagate info to each field.
563 unsigned NewAlign = (unsigned)MinAlign(StartAlignment, EltSize*i);
564 if (NewAlign > EltAlign)
565 NGV->setAlignment(NewAlign);
569 if (NewGlobals.empty())
572 DEBUG(dbgs() << "PERFORMING GLOBAL SRA ON: " << *GV);
574 Constant *NullInt =Constant::getNullValue(Type::getInt32Ty(GV->getContext()));
576 // Loop over all of the uses of the global, replacing the constantexpr geps,
577 // with smaller constantexpr geps or direct references.
578 while (!GV->use_empty()) {
579 User *GEP = GV->use_back();
580 assert(((isa<ConstantExpr>(GEP) &&
581 cast<ConstantExpr>(GEP)->getOpcode()==Instruction::GetElementPtr)||
582 isa<GetElementPtrInst>(GEP)) && "NonGEP CE's are not SRAable!");
584 // Ignore the 1th operand, which has to be zero or else the program is quite
585 // broken (undefined). Get the 2nd operand, which is the structure or array
587 unsigned Val = cast<ConstantInt>(GEP->getOperand(2))->getZExtValue();
588 if (Val >= NewGlobals.size()) Val = 0; // Out of bound array access.
590 Value *NewPtr = NewGlobals[Val];
592 // Form a shorter GEP if needed.
593 if (GEP->getNumOperands() > 3) {
594 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GEP)) {
595 SmallVector<Constant*, 8> Idxs;
596 Idxs.push_back(NullInt);
597 for (unsigned i = 3, e = CE->getNumOperands(); i != e; ++i)
598 Idxs.push_back(CE->getOperand(i));
599 NewPtr = ConstantExpr::getGetElementPtr(cast<Constant>(NewPtr), Idxs);
601 GetElementPtrInst *GEPI = cast<GetElementPtrInst>(GEP);
602 SmallVector<Value*, 8> Idxs;
603 Idxs.push_back(NullInt);
604 for (unsigned i = 3, e = GEPI->getNumOperands(); i != e; ++i)
605 Idxs.push_back(GEPI->getOperand(i));
606 NewPtr = GetElementPtrInst::Create(NewPtr, Idxs,
607 GEPI->getName()+"."+Twine(Val),GEPI);
610 GEP->replaceAllUsesWith(NewPtr);
612 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(GEP))
613 GEPI->eraseFromParent();
615 cast<ConstantExpr>(GEP)->destroyConstant();
618 // Delete the old global, now that it is dead.
622 // Loop over the new globals array deleting any globals that are obviously
623 // dead. This can arise due to scalarization of a structure or an array that
624 // has elements that are dead.
625 unsigned FirstGlobal = 0;
626 for (unsigned i = 0, e = NewGlobals.size(); i != e; ++i)
627 if (NewGlobals[i]->use_empty()) {
628 Globals.erase(NewGlobals[i]);
629 if (FirstGlobal == i) ++FirstGlobal;
632 return FirstGlobal != NewGlobals.size() ? NewGlobals[FirstGlobal] : 0;
635 /// AllUsesOfValueWillTrapIfNull - Return true if all users of the specified
636 /// value will trap if the value is dynamically null. PHIs keeps track of any
637 /// phi nodes we've seen to avoid reprocessing them.
638 static bool AllUsesOfValueWillTrapIfNull(const Value *V,
639 SmallPtrSet<const PHINode*, 8> &PHIs) {
640 for (Value::const_use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;
644 if (isa<LoadInst>(U)) {
646 } else if (const StoreInst *SI = dyn_cast<StoreInst>(U)) {
647 if (SI->getOperand(0) == V) {
648 //cerr << "NONTRAPPING USE: " << *U;
649 return false; // Storing the value.
651 } else if (const CallInst *CI = dyn_cast<CallInst>(U)) {
652 if (CI->getCalledValue() != V) {
653 //cerr << "NONTRAPPING USE: " << *U;
654 return false; // Not calling the ptr
656 } else if (const InvokeInst *II = dyn_cast<InvokeInst>(U)) {
657 if (II->getCalledValue() != V) {
658 //cerr << "NONTRAPPING USE: " << *U;
659 return false; // Not calling the ptr
661 } else if (const BitCastInst *CI = dyn_cast<BitCastInst>(U)) {
662 if (!AllUsesOfValueWillTrapIfNull(CI, PHIs)) return false;
663 } else if (const GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(U)) {
664 if (!AllUsesOfValueWillTrapIfNull(GEPI, PHIs)) return false;
665 } else if (const PHINode *PN = dyn_cast<PHINode>(U)) {
666 // If we've already seen this phi node, ignore it, it has already been
668 if (PHIs.insert(PN) && !AllUsesOfValueWillTrapIfNull(PN, PHIs))
670 } else if (isa<ICmpInst>(U) &&
671 isa<ConstantPointerNull>(UI->getOperand(1))) {
672 // Ignore icmp X, null
674 //cerr << "NONTRAPPING USE: " << *U;
681 /// AllUsesOfLoadedValueWillTrapIfNull - Return true if all uses of any loads
682 /// from GV will trap if the loaded value is null. Note that this also permits
683 /// comparisons of the loaded value against null, as a special case.
684 static bool AllUsesOfLoadedValueWillTrapIfNull(const GlobalVariable *GV) {
685 for (Value::const_use_iterator UI = GV->use_begin(), E = GV->use_end();
689 if (const LoadInst *LI = dyn_cast<LoadInst>(U)) {
690 SmallPtrSet<const PHINode*, 8> PHIs;
691 if (!AllUsesOfValueWillTrapIfNull(LI, PHIs))
693 } else if (isa<StoreInst>(U)) {
694 // Ignore stores to the global.
696 // We don't know or understand this user, bail out.
697 //cerr << "UNKNOWN USER OF GLOBAL!: " << *U;
704 static bool OptimizeAwayTrappingUsesOfValue(Value *V, Constant *NewV) {
705 bool Changed = false;
706 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ) {
707 Instruction *I = cast<Instruction>(*UI++);
708 if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
709 LI->setOperand(0, NewV);
711 } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
712 if (SI->getOperand(1) == V) {
713 SI->setOperand(1, NewV);
716 } else if (isa<CallInst>(I) || isa<InvokeInst>(I)) {
718 if (CS.getCalledValue() == V) {
719 // Calling through the pointer! Turn into a direct call, but be careful
720 // that the pointer is not also being passed as an argument.
721 CS.setCalledFunction(NewV);
723 bool PassedAsArg = false;
724 for (unsigned i = 0, e = CS.arg_size(); i != e; ++i)
725 if (CS.getArgument(i) == V) {
727 CS.setArgument(i, NewV);
731 // Being passed as an argument also. Be careful to not invalidate UI!
735 } else if (CastInst *CI = dyn_cast<CastInst>(I)) {
736 Changed |= OptimizeAwayTrappingUsesOfValue(CI,
737 ConstantExpr::getCast(CI->getOpcode(),
738 NewV, CI->getType()));
739 if (CI->use_empty()) {
741 CI->eraseFromParent();
743 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I)) {
744 // Should handle GEP here.
745 SmallVector<Constant*, 8> Idxs;
746 Idxs.reserve(GEPI->getNumOperands()-1);
747 for (User::op_iterator i = GEPI->op_begin() + 1, e = GEPI->op_end();
749 if (Constant *C = dyn_cast<Constant>(*i))
753 if (Idxs.size() == GEPI->getNumOperands()-1)
754 Changed |= OptimizeAwayTrappingUsesOfValue(GEPI,
755 ConstantExpr::getGetElementPtr(NewV, Idxs));
756 if (GEPI->use_empty()) {
758 GEPI->eraseFromParent();
767 /// OptimizeAwayTrappingUsesOfLoads - The specified global has only one non-null
768 /// value stored into it. If there are uses of the loaded value that would trap
769 /// if the loaded value is dynamically null, then we know that they cannot be
770 /// reachable with a null optimize away the load.
771 static bool OptimizeAwayTrappingUsesOfLoads(GlobalVariable *GV, Constant *LV) {
772 bool Changed = false;
774 // Keep track of whether we are able to remove all the uses of the global
775 // other than the store that defines it.
776 bool AllNonStoreUsesGone = true;
778 // Replace all uses of loads with uses of uses of the stored value.
779 for (Value::use_iterator GUI = GV->use_begin(), E = GV->use_end(); GUI != E;){
780 User *GlobalUser = *GUI++;
781 if (LoadInst *LI = dyn_cast<LoadInst>(GlobalUser)) {
782 Changed |= OptimizeAwayTrappingUsesOfValue(LI, LV);
783 // If we were able to delete all uses of the loads
784 if (LI->use_empty()) {
785 LI->eraseFromParent();
788 AllNonStoreUsesGone = false;
790 } else if (isa<StoreInst>(GlobalUser)) {
791 // Ignore the store that stores "LV" to the global.
792 assert(GlobalUser->getOperand(1) == GV &&
793 "Must be storing *to* the global");
795 AllNonStoreUsesGone = false;
797 // If we get here we could have other crazy uses that are transitively
799 assert((isa<PHINode>(GlobalUser) || isa<SelectInst>(GlobalUser) ||
800 isa<ConstantExpr>(GlobalUser) || isa<CmpInst>(GlobalUser)) &&
801 "Only expect load and stores!");
806 DEBUG(dbgs() << "OPTIMIZED LOADS FROM STORED ONCE POINTER: " << *GV);
810 // If we nuked all of the loads, then none of the stores are needed either,
811 // nor is the global.
812 if (AllNonStoreUsesGone) {
813 DEBUG(dbgs() << " *** GLOBAL NOW DEAD!\n");
814 CleanupConstantGlobalUsers(GV, 0);
815 if (GV->use_empty()) {
816 GV->eraseFromParent();
824 /// ConstantPropUsersOf - Walk the use list of V, constant folding all of the
825 /// instructions that are foldable.
826 static void ConstantPropUsersOf(Value *V) {
827 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; )
828 if (Instruction *I = dyn_cast<Instruction>(*UI++))
829 if (Constant *NewC = ConstantFoldInstruction(I)) {
830 I->replaceAllUsesWith(NewC);
832 // Advance UI to the next non-I use to avoid invalidating it!
833 // Instructions could multiply use V.
834 while (UI != E && *UI == I)
836 I->eraseFromParent();
840 /// OptimizeGlobalAddressOfMalloc - This function takes the specified global
841 /// variable, and transforms the program as if it always contained the result of
842 /// the specified malloc. Because it is always the result of the specified
843 /// malloc, there is no reason to actually DO the malloc. Instead, turn the
844 /// malloc into a global, and any loads of GV as uses of the new global.
845 static GlobalVariable *OptimizeGlobalAddressOfMalloc(GlobalVariable *GV,
848 ConstantInt *NElements,
850 DEBUG(errs() << "PROMOTING GLOBAL: " << *GV << " CALL = " << *CI << '\n');
853 if (NElements->getZExtValue() == 1)
854 GlobalType = AllocTy;
856 // If we have an array allocation, the global variable is of an array.
857 GlobalType = ArrayType::get(AllocTy, NElements->getZExtValue());
859 // Create the new global variable. The contents of the malloc'd memory is
860 // undefined, so initialize with an undef value.
861 GlobalVariable *NewGV = new GlobalVariable(*GV->getParent(),
863 GlobalValue::InternalLinkage,
864 UndefValue::get(GlobalType),
865 GV->getName()+".body",
867 GV->isThreadLocal());
869 // If there are bitcast users of the malloc (which is typical, usually we have
870 // a malloc + bitcast) then replace them with uses of the new global. Update
871 // other users to use the global as well.
872 BitCastInst *TheBC = 0;
873 while (!CI->use_empty()) {
874 Instruction *User = cast<Instruction>(CI->use_back());
875 if (BitCastInst *BCI = dyn_cast<BitCastInst>(User)) {
876 if (BCI->getType() == NewGV->getType()) {
877 BCI->replaceAllUsesWith(NewGV);
878 BCI->eraseFromParent();
880 BCI->setOperand(0, NewGV);
884 TheBC = new BitCastInst(NewGV, CI->getType(), "newgv", CI);
885 User->replaceUsesOfWith(CI, TheBC);
889 Constant *RepValue = NewGV;
890 if (NewGV->getType() != GV->getType()->getElementType())
891 RepValue = ConstantExpr::getBitCast(RepValue,
892 GV->getType()->getElementType());
894 // If there is a comparison against null, we will insert a global bool to
895 // keep track of whether the global was initialized yet or not.
896 GlobalVariable *InitBool =
897 new GlobalVariable(Type::getInt1Ty(GV->getContext()), false,
898 GlobalValue::InternalLinkage,
899 ConstantInt::getFalse(GV->getContext()),
900 GV->getName()+".init", GV->isThreadLocal());
901 bool InitBoolUsed = false;
903 // Loop over all uses of GV, processing them in turn.
904 while (!GV->use_empty()) {
905 if (StoreInst *SI = dyn_cast<StoreInst>(GV->use_back())) {
906 // The global is initialized when the store to it occurs.
907 new StoreInst(ConstantInt::getTrue(GV->getContext()), InitBool, SI);
908 SI->eraseFromParent();
912 LoadInst *LI = cast<LoadInst>(GV->use_back());
913 while (!LI->use_empty()) {
914 Use &LoadUse = LI->use_begin().getUse();
915 if (!isa<ICmpInst>(LoadUse.getUser())) {
920 ICmpInst *ICI = cast<ICmpInst>(LoadUse.getUser());
921 // Replace the cmp X, 0 with a use of the bool value.
922 Value *LV = new LoadInst(InitBool, InitBool->getName()+".val", ICI);
924 switch (ICI->getPredicate()) {
925 default: llvm_unreachable("Unknown ICmp Predicate!");
926 case ICmpInst::ICMP_ULT:
927 case ICmpInst::ICMP_SLT: // X < null -> always false
928 LV = ConstantInt::getFalse(GV->getContext());
930 case ICmpInst::ICMP_ULE:
931 case ICmpInst::ICMP_SLE:
932 case ICmpInst::ICMP_EQ:
933 LV = BinaryOperator::CreateNot(LV, "notinit", ICI);
935 case ICmpInst::ICMP_NE:
936 case ICmpInst::ICMP_UGE:
937 case ICmpInst::ICMP_SGE:
938 case ICmpInst::ICMP_UGT:
939 case ICmpInst::ICMP_SGT:
942 ICI->replaceAllUsesWith(LV);
943 ICI->eraseFromParent();
945 LI->eraseFromParent();
948 // If the initialization boolean was used, insert it, otherwise delete it.
950 while (!InitBool->use_empty()) // Delete initializations
951 cast<StoreInst>(InitBool->use_back())->eraseFromParent();
954 GV->getParent()->getGlobalList().insert(GV, InitBool);
956 // Now the GV is dead, nuke it and the malloc..
957 GV->eraseFromParent();
958 CI->eraseFromParent();
960 // To further other optimizations, loop over all users of NewGV and try to
961 // constant prop them. This will promote GEP instructions with constant
962 // indices into GEP constant-exprs, which will allow global-opt to hack on it.
963 ConstantPropUsersOf(NewGV);
964 if (RepValue != NewGV)
965 ConstantPropUsersOf(RepValue);
970 /// ValueIsOnlyUsedLocallyOrStoredToOneGlobal - Scan the use-list of V checking
971 /// to make sure that there are no complex uses of V. We permit simple things
972 /// like dereferencing the pointer, but not storing through the address, unless
973 /// it is to the specified global.
974 static bool ValueIsOnlyUsedLocallyOrStoredToOneGlobal(const Instruction *V,
975 const GlobalVariable *GV,
976 SmallPtrSet<const PHINode*, 8> &PHIs) {
977 for (Value::const_use_iterator UI = V->use_begin(), E = V->use_end();
979 const Instruction *Inst = cast<Instruction>(*UI);
981 if (isa<LoadInst>(Inst) || isa<CmpInst>(Inst)) {
982 continue; // Fine, ignore.
985 if (const StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
986 if (SI->getOperand(0) == V && SI->getOperand(1) != GV)
987 return false; // Storing the pointer itself... bad.
988 continue; // Otherwise, storing through it, or storing into GV... fine.
991 // Must index into the array and into the struct.
992 if (isa<GetElementPtrInst>(Inst) && Inst->getNumOperands() >= 3) {
993 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(Inst, GV, PHIs))
998 if (const PHINode *PN = dyn_cast<PHINode>(Inst)) {
999 // PHIs are ok if all uses are ok. Don't infinitely recurse through PHI
1001 if (PHIs.insert(PN))
1002 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(PN, GV, PHIs))
1007 if (const BitCastInst *BCI = dyn_cast<BitCastInst>(Inst)) {
1008 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(BCI, GV, PHIs))
1018 /// ReplaceUsesOfMallocWithGlobal - The Alloc pointer is stored into GV
1019 /// somewhere. Transform all uses of the allocation into loads from the
1020 /// global and uses of the resultant pointer. Further, delete the store into
1021 /// GV. This assumes that these value pass the
1022 /// 'ValueIsOnlyUsedLocallyOrStoredToOneGlobal' predicate.
1023 static void ReplaceUsesOfMallocWithGlobal(Instruction *Alloc,
1024 GlobalVariable *GV) {
1025 while (!Alloc->use_empty()) {
1026 Instruction *U = cast<Instruction>(*Alloc->use_begin());
1027 Instruction *InsertPt = U;
1028 if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
1029 // If this is the store of the allocation into the global, remove it.
1030 if (SI->getOperand(1) == GV) {
1031 SI->eraseFromParent();
1034 } else if (PHINode *PN = dyn_cast<PHINode>(U)) {
1035 // Insert the load in the corresponding predecessor, not right before the
1037 InsertPt = PN->getIncomingBlock(Alloc->use_begin())->getTerminator();
1038 } else if (isa<BitCastInst>(U)) {
1039 // Must be bitcast between the malloc and store to initialize the global.
1040 ReplaceUsesOfMallocWithGlobal(U, GV);
1041 U->eraseFromParent();
1043 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(U)) {
1044 // If this is a "GEP bitcast" and the user is a store to the global, then
1045 // just process it as a bitcast.
1046 if (GEPI->hasAllZeroIndices() && GEPI->hasOneUse())
1047 if (StoreInst *SI = dyn_cast<StoreInst>(GEPI->use_back()))
1048 if (SI->getOperand(1) == GV) {
1049 // Must be bitcast GEP between the malloc and store to initialize
1051 ReplaceUsesOfMallocWithGlobal(GEPI, GV);
1052 GEPI->eraseFromParent();
1057 // Insert a load from the global, and use it instead of the malloc.
1058 Value *NL = new LoadInst(GV, GV->getName()+".val", InsertPt);
1059 U->replaceUsesOfWith(Alloc, NL);
1063 /// LoadUsesSimpleEnoughForHeapSRA - Verify that all uses of V (a load, or a phi
1064 /// of a load) are simple enough to perform heap SRA on. This permits GEP's
1065 /// that index through the array and struct field, icmps of null, and PHIs.
1066 static bool LoadUsesSimpleEnoughForHeapSRA(const Value *V,
1067 SmallPtrSet<const PHINode*, 32> &LoadUsingPHIs,
1068 SmallPtrSet<const PHINode*, 32> &LoadUsingPHIsPerLoad) {
1069 // We permit two users of the load: setcc comparing against the null
1070 // pointer, and a getelementptr of a specific form.
1071 for (Value::const_use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;
1073 const Instruction *User = cast<Instruction>(*UI);
1075 // Comparison against null is ok.
1076 if (const ICmpInst *ICI = dyn_cast<ICmpInst>(User)) {
1077 if (!isa<ConstantPointerNull>(ICI->getOperand(1)))
1082 // getelementptr is also ok, but only a simple form.
1083 if (const GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
1084 // Must index into the array and into the struct.
1085 if (GEPI->getNumOperands() < 3)
1088 // Otherwise the GEP is ok.
1092 if (const PHINode *PN = dyn_cast<PHINode>(User)) {
1093 if (!LoadUsingPHIsPerLoad.insert(PN))
1094 // This means some phi nodes are dependent on each other.
1095 // Avoid infinite looping!
1097 if (!LoadUsingPHIs.insert(PN))
1098 // If we have already analyzed this PHI, then it is safe.
1101 // Make sure all uses of the PHI are simple enough to transform.
1102 if (!LoadUsesSimpleEnoughForHeapSRA(PN,
1103 LoadUsingPHIs, LoadUsingPHIsPerLoad))
1109 // Otherwise we don't know what this is, not ok.
1117 /// AllGlobalLoadUsesSimpleEnoughForHeapSRA - If all users of values loaded from
1118 /// GV are simple enough to perform HeapSRA, return true.
1119 static bool AllGlobalLoadUsesSimpleEnoughForHeapSRA(const GlobalVariable *GV,
1120 Instruction *StoredVal) {
1121 SmallPtrSet<const PHINode*, 32> LoadUsingPHIs;
1122 SmallPtrSet<const PHINode*, 32> LoadUsingPHIsPerLoad;
1123 for (Value::const_use_iterator UI = GV->use_begin(), E = GV->use_end();
1125 if (const LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
1126 if (!LoadUsesSimpleEnoughForHeapSRA(LI, LoadUsingPHIs,
1127 LoadUsingPHIsPerLoad))
1129 LoadUsingPHIsPerLoad.clear();
1132 // If we reach here, we know that all uses of the loads and transitive uses
1133 // (through PHI nodes) are simple enough to transform. However, we don't know
1134 // that all inputs the to the PHI nodes are in the same equivalence sets.
1135 // Check to verify that all operands of the PHIs are either PHIS that can be
1136 // transformed, loads from GV, or MI itself.
1137 for (SmallPtrSet<const PHINode*, 32>::const_iterator I = LoadUsingPHIs.begin()
1138 , E = LoadUsingPHIs.end(); I != E; ++I) {
1139 const PHINode *PN = *I;
1140 for (unsigned op = 0, e = PN->getNumIncomingValues(); op != e; ++op) {
1141 Value *InVal = PN->getIncomingValue(op);
1143 // PHI of the stored value itself is ok.
1144 if (InVal == StoredVal) continue;
1146 if (const PHINode *InPN = dyn_cast<PHINode>(InVal)) {
1147 // One of the PHIs in our set is (optimistically) ok.
1148 if (LoadUsingPHIs.count(InPN))
1153 // Load from GV is ok.
1154 if (const LoadInst *LI = dyn_cast<LoadInst>(InVal))
1155 if (LI->getOperand(0) == GV)
1160 // Anything else is rejected.
1168 static Value *GetHeapSROAValue(Value *V, unsigned FieldNo,
1169 DenseMap<Value*, std::vector<Value*> > &InsertedScalarizedValues,
1170 std::vector<std::pair<PHINode*, unsigned> > &PHIsToRewrite) {
1171 std::vector<Value*> &FieldVals = InsertedScalarizedValues[V];
1173 if (FieldNo >= FieldVals.size())
1174 FieldVals.resize(FieldNo+1);
1176 // If we already have this value, just reuse the previously scalarized
1178 if (Value *FieldVal = FieldVals[FieldNo])
1181 // Depending on what instruction this is, we have several cases.
1183 if (LoadInst *LI = dyn_cast<LoadInst>(V)) {
1184 // This is a scalarized version of the load from the global. Just create
1185 // a new Load of the scalarized global.
1186 Result = new LoadInst(GetHeapSROAValue(LI->getOperand(0), FieldNo,
1187 InsertedScalarizedValues,
1189 LI->getName()+".f"+Twine(FieldNo), LI);
1190 } else if (PHINode *PN = dyn_cast<PHINode>(V)) {
1191 // PN's type is pointer to struct. Make a new PHI of pointer to struct
1194 cast<StructType>(cast<PointerType>(PN->getType())->getElementType());
1197 PHINode::Create(PointerType::getUnqual(ST->getElementType(FieldNo)),
1198 PN->getNumIncomingValues(),
1199 PN->getName()+".f"+Twine(FieldNo), PN);
1201 PHIsToRewrite.push_back(std::make_pair(PN, FieldNo));
1203 llvm_unreachable("Unknown usable value");
1207 return FieldVals[FieldNo] = Result;
1210 /// RewriteHeapSROALoadUser - Given a load instruction and a value derived from
1211 /// the load, rewrite the derived value to use the HeapSRoA'd load.
1212 static void RewriteHeapSROALoadUser(Instruction *LoadUser,
1213 DenseMap<Value*, std::vector<Value*> > &InsertedScalarizedValues,
1214 std::vector<std::pair<PHINode*, unsigned> > &PHIsToRewrite) {
1215 // If this is a comparison against null, handle it.
1216 if (ICmpInst *SCI = dyn_cast<ICmpInst>(LoadUser)) {
1217 assert(isa<ConstantPointerNull>(SCI->getOperand(1)));
1218 // If we have a setcc of the loaded pointer, we can use a setcc of any
1220 Value *NPtr = GetHeapSROAValue(SCI->getOperand(0), 0,
1221 InsertedScalarizedValues, PHIsToRewrite);
1223 Value *New = new ICmpInst(SCI, SCI->getPredicate(), NPtr,
1224 Constant::getNullValue(NPtr->getType()),
1226 SCI->replaceAllUsesWith(New);
1227 SCI->eraseFromParent();
1231 // Handle 'getelementptr Ptr, Idx, i32 FieldNo ...'
1232 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(LoadUser)) {
1233 assert(GEPI->getNumOperands() >= 3 && isa<ConstantInt>(GEPI->getOperand(2))
1234 && "Unexpected GEPI!");
1236 // Load the pointer for this field.
1237 unsigned FieldNo = cast<ConstantInt>(GEPI->getOperand(2))->getZExtValue();
1238 Value *NewPtr = GetHeapSROAValue(GEPI->getOperand(0), FieldNo,
1239 InsertedScalarizedValues, PHIsToRewrite);
1241 // Create the new GEP idx vector.
1242 SmallVector<Value*, 8> GEPIdx;
1243 GEPIdx.push_back(GEPI->getOperand(1));
1244 GEPIdx.append(GEPI->op_begin()+3, GEPI->op_end());
1246 Value *NGEPI = GetElementPtrInst::Create(NewPtr, GEPIdx,
1247 GEPI->getName(), GEPI);
1248 GEPI->replaceAllUsesWith(NGEPI);
1249 GEPI->eraseFromParent();
1253 // Recursively transform the users of PHI nodes. This will lazily create the
1254 // PHIs that are needed for individual elements. Keep track of what PHIs we
1255 // see in InsertedScalarizedValues so that we don't get infinite loops (very
1256 // antisocial). If the PHI is already in InsertedScalarizedValues, it has
1257 // already been seen first by another load, so its uses have already been
1259 PHINode *PN = cast<PHINode>(LoadUser);
1260 if (!InsertedScalarizedValues.insert(std::make_pair(PN,
1261 std::vector<Value*>())).second)
1264 // If this is the first time we've seen this PHI, recursively process all
1266 for (Value::use_iterator UI = PN->use_begin(), E = PN->use_end(); UI != E; ) {
1267 Instruction *User = cast<Instruction>(*UI++);
1268 RewriteHeapSROALoadUser(User, InsertedScalarizedValues, PHIsToRewrite);
1272 /// RewriteUsesOfLoadForHeapSRoA - We are performing Heap SRoA on a global. Ptr
1273 /// is a value loaded from the global. Eliminate all uses of Ptr, making them
1274 /// use FieldGlobals instead. All uses of loaded values satisfy
1275 /// AllGlobalLoadUsesSimpleEnoughForHeapSRA.
1276 static void RewriteUsesOfLoadForHeapSRoA(LoadInst *Load,
1277 DenseMap<Value*, std::vector<Value*> > &InsertedScalarizedValues,
1278 std::vector<std::pair<PHINode*, unsigned> > &PHIsToRewrite) {
1279 for (Value::use_iterator UI = Load->use_begin(), E = Load->use_end();
1281 Instruction *User = cast<Instruction>(*UI++);
1282 RewriteHeapSROALoadUser(User, InsertedScalarizedValues, PHIsToRewrite);
1285 if (Load->use_empty()) {
1286 Load->eraseFromParent();
1287 InsertedScalarizedValues.erase(Load);
1291 /// PerformHeapAllocSRoA - CI is an allocation of an array of structures. Break
1292 /// it up into multiple allocations of arrays of the fields.
1293 static GlobalVariable *PerformHeapAllocSRoA(GlobalVariable *GV, CallInst *CI,
1294 Value* NElems, TargetData *TD) {
1295 DEBUG(dbgs() << "SROA HEAP ALLOC: " << *GV << " MALLOC = " << *CI << '\n');
1296 Type* MAT = getMallocAllocatedType(CI);
1297 StructType *STy = cast<StructType>(MAT);
1299 // There is guaranteed to be at least one use of the malloc (storing
1300 // it into GV). If there are other uses, change them to be uses of
1301 // the global to simplify later code. This also deletes the store
1303 ReplaceUsesOfMallocWithGlobal(CI, GV);
1305 // Okay, at this point, there are no users of the malloc. Insert N
1306 // new mallocs at the same place as CI, and N globals.
1307 std::vector<Value*> FieldGlobals;
1308 std::vector<Value*> FieldMallocs;
1310 for (unsigned FieldNo = 0, e = STy->getNumElements(); FieldNo != e;++FieldNo){
1311 Type *FieldTy = STy->getElementType(FieldNo);
1312 PointerType *PFieldTy = PointerType::getUnqual(FieldTy);
1314 GlobalVariable *NGV =
1315 new GlobalVariable(*GV->getParent(),
1316 PFieldTy, false, GlobalValue::InternalLinkage,
1317 Constant::getNullValue(PFieldTy),
1318 GV->getName() + ".f" + Twine(FieldNo), GV,
1319 GV->isThreadLocal());
1320 FieldGlobals.push_back(NGV);
1322 unsigned TypeSize = TD->getTypeAllocSize(FieldTy);
1323 if (StructType *ST = dyn_cast<StructType>(FieldTy))
1324 TypeSize = TD->getStructLayout(ST)->getSizeInBytes();
1325 Type *IntPtrTy = TD->getIntPtrType(CI->getContext());
1326 Value *NMI = CallInst::CreateMalloc(CI, IntPtrTy, FieldTy,
1327 ConstantInt::get(IntPtrTy, TypeSize),
1329 CI->getName() + ".f" + Twine(FieldNo));
1330 FieldMallocs.push_back(NMI);
1331 new StoreInst(NMI, NGV, CI);
1334 // The tricky aspect of this transformation is handling the case when malloc
1335 // fails. In the original code, malloc failing would set the result pointer
1336 // of malloc to null. In this case, some mallocs could succeed and others
1337 // could fail. As such, we emit code that looks like this:
1338 // F0 = malloc(field0)
1339 // F1 = malloc(field1)
1340 // F2 = malloc(field2)
1341 // if (F0 == 0 || F1 == 0 || F2 == 0) {
1342 // if (F0) { free(F0); F0 = 0; }
1343 // if (F1) { free(F1); F1 = 0; }
1344 // if (F2) { free(F2); F2 = 0; }
1346 // The malloc can also fail if its argument is too large.
1347 Constant *ConstantZero = ConstantInt::get(CI->getArgOperand(0)->getType(), 0);
1348 Value *RunningOr = new ICmpInst(CI, ICmpInst::ICMP_SLT, CI->getArgOperand(0),
1349 ConstantZero, "isneg");
1350 for (unsigned i = 0, e = FieldMallocs.size(); i != e; ++i) {
1351 Value *Cond = new ICmpInst(CI, ICmpInst::ICMP_EQ, FieldMallocs[i],
1352 Constant::getNullValue(FieldMallocs[i]->getType()),
1354 RunningOr = BinaryOperator::CreateOr(RunningOr, Cond, "tmp", CI);
1357 // Split the basic block at the old malloc.
1358 BasicBlock *OrigBB = CI->getParent();
1359 BasicBlock *ContBB = OrigBB->splitBasicBlock(CI, "malloc_cont");
1361 // Create the block to check the first condition. Put all these blocks at the
1362 // end of the function as they are unlikely to be executed.
1363 BasicBlock *NullPtrBlock = BasicBlock::Create(OrigBB->getContext(),
1365 OrigBB->getParent());
1367 // Remove the uncond branch from OrigBB to ContBB, turning it into a cond
1368 // branch on RunningOr.
1369 OrigBB->getTerminator()->eraseFromParent();
1370 BranchInst::Create(NullPtrBlock, ContBB, RunningOr, OrigBB);
1372 // Within the NullPtrBlock, we need to emit a comparison and branch for each
1373 // pointer, because some may be null while others are not.
1374 for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) {
1375 Value *GVVal = new LoadInst(FieldGlobals[i], "tmp", NullPtrBlock);
1376 Value *Cmp = new ICmpInst(*NullPtrBlock, ICmpInst::ICMP_NE, GVVal,
1377 Constant::getNullValue(GVVal->getType()),
1379 BasicBlock *FreeBlock = BasicBlock::Create(Cmp->getContext(), "free_it",
1380 OrigBB->getParent());
1381 BasicBlock *NextBlock = BasicBlock::Create(Cmp->getContext(), "next",
1382 OrigBB->getParent());
1383 Instruction *BI = BranchInst::Create(FreeBlock, NextBlock,
1386 // Fill in FreeBlock.
1387 CallInst::CreateFree(GVVal, BI);
1388 new StoreInst(Constant::getNullValue(GVVal->getType()), FieldGlobals[i],
1390 BranchInst::Create(NextBlock, FreeBlock);
1392 NullPtrBlock = NextBlock;
1395 BranchInst::Create(ContBB, NullPtrBlock);
1397 // CI is no longer needed, remove it.
1398 CI->eraseFromParent();
1400 /// InsertedScalarizedLoads - As we process loads, if we can't immediately
1401 /// update all uses of the load, keep track of what scalarized loads are
1402 /// inserted for a given load.
1403 DenseMap<Value*, std::vector<Value*> > InsertedScalarizedValues;
1404 InsertedScalarizedValues[GV] = FieldGlobals;
1406 std::vector<std::pair<PHINode*, unsigned> > PHIsToRewrite;
1408 // Okay, the malloc site is completely handled. All of the uses of GV are now
1409 // loads, and all uses of those loads are simple. Rewrite them to use loads
1410 // of the per-field globals instead.
1411 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); UI != E;) {
1412 Instruction *User = cast<Instruction>(*UI++);
1414 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1415 RewriteUsesOfLoadForHeapSRoA(LI, InsertedScalarizedValues, PHIsToRewrite);
1419 // Must be a store of null.
1420 StoreInst *SI = cast<StoreInst>(User);
1421 assert(isa<ConstantPointerNull>(SI->getOperand(0)) &&
1422 "Unexpected heap-sra user!");
1424 // Insert a store of null into each global.
1425 for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) {
1426 PointerType *PT = cast<PointerType>(FieldGlobals[i]->getType());
1427 Constant *Null = Constant::getNullValue(PT->getElementType());
1428 new StoreInst(Null, FieldGlobals[i], SI);
1430 // Erase the original store.
1431 SI->eraseFromParent();
1434 // While we have PHIs that are interesting to rewrite, do it.
1435 while (!PHIsToRewrite.empty()) {
1436 PHINode *PN = PHIsToRewrite.back().first;
1437 unsigned FieldNo = PHIsToRewrite.back().second;
1438 PHIsToRewrite.pop_back();
1439 PHINode *FieldPN = cast<PHINode>(InsertedScalarizedValues[PN][FieldNo]);
1440 assert(FieldPN->getNumIncomingValues() == 0 &&"Already processed this phi");
1442 // Add all the incoming values. This can materialize more phis.
1443 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
1444 Value *InVal = PN->getIncomingValue(i);
1445 InVal = GetHeapSROAValue(InVal, FieldNo, InsertedScalarizedValues,
1447 FieldPN->addIncoming(InVal, PN->getIncomingBlock(i));
1451 // Drop all inter-phi links and any loads that made it this far.
1452 for (DenseMap<Value*, std::vector<Value*> >::iterator
1453 I = InsertedScalarizedValues.begin(), E = InsertedScalarizedValues.end();
1455 if (PHINode *PN = dyn_cast<PHINode>(I->first))
1456 PN->dropAllReferences();
1457 else if (LoadInst *LI = dyn_cast<LoadInst>(I->first))
1458 LI->dropAllReferences();
1461 // Delete all the phis and loads now that inter-references are dead.
1462 for (DenseMap<Value*, std::vector<Value*> >::iterator
1463 I = InsertedScalarizedValues.begin(), E = InsertedScalarizedValues.end();
1465 if (PHINode *PN = dyn_cast<PHINode>(I->first))
1466 PN->eraseFromParent();
1467 else if (LoadInst *LI = dyn_cast<LoadInst>(I->first))
1468 LI->eraseFromParent();
1471 // The old global is now dead, remove it.
1472 GV->eraseFromParent();
1475 return cast<GlobalVariable>(FieldGlobals[0]);
1478 /// TryToOptimizeStoreOfMallocToGlobal - This function is called when we see a
1479 /// pointer global variable with a single value stored it that is a malloc or
1481 static bool TryToOptimizeStoreOfMallocToGlobal(GlobalVariable *GV,
1484 Module::global_iterator &GVI,
1489 // If this is a malloc of an abstract type, don't touch it.
1490 if (!AllocTy->isSized())
1493 // We can't optimize this global unless all uses of it are *known* to be
1494 // of the malloc value, not of the null initializer value (consider a use
1495 // that compares the global's value against zero to see if the malloc has
1496 // been reached). To do this, we check to see if all uses of the global
1497 // would trap if the global were null: this proves that they must all
1498 // happen after the malloc.
1499 if (!AllUsesOfLoadedValueWillTrapIfNull(GV))
1502 // We can't optimize this if the malloc itself is used in a complex way,
1503 // for example, being stored into multiple globals. This allows the
1504 // malloc to be stored into the specified global, loaded setcc'd, and
1505 // GEP'd. These are all things we could transform to using the global
1507 SmallPtrSet<const PHINode*, 8> PHIs;
1508 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(CI, GV, PHIs))
1511 // If we have a global that is only initialized with a fixed size malloc,
1512 // transform the program to use global memory instead of malloc'd memory.
1513 // This eliminates dynamic allocation, avoids an indirection accessing the
1514 // data, and exposes the resultant global to further GlobalOpt.
1515 // We cannot optimize the malloc if we cannot determine malloc array size.
1516 Value *NElems = getMallocArraySize(CI, TD, true);
1520 if (ConstantInt *NElements = dyn_cast<ConstantInt>(NElems))
1521 // Restrict this transformation to only working on small allocations
1522 // (2048 bytes currently), as we don't want to introduce a 16M global or
1524 if (NElements->getZExtValue() * TD->getTypeAllocSize(AllocTy) < 2048) {
1525 GVI = OptimizeGlobalAddressOfMalloc(GV, CI, AllocTy, NElements, TD);
1529 // If the allocation is an array of structures, consider transforming this
1530 // into multiple malloc'd arrays, one for each field. This is basically
1531 // SRoA for malloc'd memory.
1533 // If this is an allocation of a fixed size array of structs, analyze as a
1534 // variable size array. malloc [100 x struct],1 -> malloc struct, 100
1535 if (NElems == ConstantInt::get(CI->getArgOperand(0)->getType(), 1))
1536 if (ArrayType *AT = dyn_cast<ArrayType>(AllocTy))
1537 AllocTy = AT->getElementType();
1539 StructType *AllocSTy = dyn_cast<StructType>(AllocTy);
1543 // This the structure has an unreasonable number of fields, leave it
1545 if (AllocSTy->getNumElements() <= 16 && AllocSTy->getNumElements() != 0 &&
1546 AllGlobalLoadUsesSimpleEnoughForHeapSRA(GV, CI)) {
1548 // If this is a fixed size array, transform the Malloc to be an alloc of
1549 // structs. malloc [100 x struct],1 -> malloc struct, 100
1550 if (ArrayType *AT = dyn_cast<ArrayType>(getMallocAllocatedType(CI))) {
1551 Type *IntPtrTy = TD->getIntPtrType(CI->getContext());
1552 unsigned TypeSize = TD->getStructLayout(AllocSTy)->getSizeInBytes();
1553 Value *AllocSize = ConstantInt::get(IntPtrTy, TypeSize);
1554 Value *NumElements = ConstantInt::get(IntPtrTy, AT->getNumElements());
1555 Instruction *Malloc = CallInst::CreateMalloc(CI, IntPtrTy, AllocSTy,
1556 AllocSize, NumElements,
1558 Instruction *Cast = new BitCastInst(Malloc, CI->getType(), "tmp", CI);
1559 CI->replaceAllUsesWith(Cast);
1560 CI->eraseFromParent();
1561 CI = dyn_cast<BitCastInst>(Malloc) ?
1562 extractMallocCallFromBitCast(Malloc) : cast<CallInst>(Malloc);
1565 GVI = PerformHeapAllocSRoA(GV, CI, getMallocArraySize(CI, TD, true),TD);
1572 // OptimizeOnceStoredGlobal - Try to optimize globals based on the knowledge
1573 // that only one value (besides its initializer) is ever stored to the global.
1574 static bool OptimizeOnceStoredGlobal(GlobalVariable *GV, Value *StoredOnceVal,
1575 Module::global_iterator &GVI,
1577 // Ignore no-op GEPs and bitcasts.
1578 StoredOnceVal = StoredOnceVal->stripPointerCasts();
1580 // If we are dealing with a pointer global that is initialized to null and
1581 // only has one (non-null) value stored into it, then we can optimize any
1582 // users of the loaded value (often calls and loads) that would trap if the
1584 if (GV->getInitializer()->getType()->isPointerTy() &&
1585 GV->getInitializer()->isNullValue()) {
1586 if (Constant *SOVC = dyn_cast<Constant>(StoredOnceVal)) {
1587 if (GV->getInitializer()->getType() != SOVC->getType())
1588 SOVC = ConstantExpr::getBitCast(SOVC, GV->getInitializer()->getType());
1590 // Optimize away any trapping uses of the loaded value.
1591 if (OptimizeAwayTrappingUsesOfLoads(GV, SOVC))
1593 } else if (CallInst *CI = extractMallocCall(StoredOnceVal)) {
1594 Type* MallocType = getMallocAllocatedType(CI);
1595 if (MallocType && TryToOptimizeStoreOfMallocToGlobal(GV, CI, MallocType,
1604 /// TryToShrinkGlobalToBoolean - At this point, we have learned that the only
1605 /// two values ever stored into GV are its initializer and OtherVal. See if we
1606 /// can shrink the global into a boolean and select between the two values
1607 /// whenever it is used. This exposes the values to other scalar optimizations.
1608 static bool TryToShrinkGlobalToBoolean(GlobalVariable *GV, Constant *OtherVal) {
1609 Type *GVElType = GV->getType()->getElementType();
1611 // If GVElType is already i1, it is already shrunk. If the type of the GV is
1612 // an FP value, pointer or vector, don't do this optimization because a select
1613 // between them is very expensive and unlikely to lead to later
1614 // simplification. In these cases, we typically end up with "cond ? v1 : v2"
1615 // where v1 and v2 both require constant pool loads, a big loss.
1616 if (GVElType == Type::getInt1Ty(GV->getContext()) ||
1617 GVElType->isFloatingPointTy() ||
1618 GVElType->isPointerTy() || GVElType->isVectorTy())
1621 // Walk the use list of the global seeing if all the uses are load or store.
1622 // If there is anything else, bail out.
1623 for (Value::use_iterator I = GV->use_begin(), E = GV->use_end(); I != E; ++I){
1625 if (!isa<LoadInst>(U) && !isa<StoreInst>(U))
1629 DEBUG(dbgs() << " *** SHRINKING TO BOOL: " << *GV);
1631 // Create the new global, initializing it to false.
1632 GlobalVariable *NewGV = new GlobalVariable(Type::getInt1Ty(GV->getContext()),
1634 GlobalValue::InternalLinkage,
1635 ConstantInt::getFalse(GV->getContext()),
1637 GV->isThreadLocal());
1638 GV->getParent()->getGlobalList().insert(GV, NewGV);
1640 Constant *InitVal = GV->getInitializer();
1641 assert(InitVal->getType() != Type::getInt1Ty(GV->getContext()) &&
1642 "No reason to shrink to bool!");
1644 // If initialized to zero and storing one into the global, we can use a cast
1645 // instead of a select to synthesize the desired value.
1646 bool IsOneZero = false;
1647 if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal))
1648 IsOneZero = InitVal->isNullValue() && CI->isOne();
1650 while (!GV->use_empty()) {
1651 Instruction *UI = cast<Instruction>(GV->use_back());
1652 if (StoreInst *SI = dyn_cast<StoreInst>(UI)) {
1653 // Change the store into a boolean store.
1654 bool StoringOther = SI->getOperand(0) == OtherVal;
1655 // Only do this if we weren't storing a loaded value.
1657 if (StoringOther || SI->getOperand(0) == InitVal)
1658 StoreVal = ConstantInt::get(Type::getInt1Ty(GV->getContext()),
1661 // Otherwise, we are storing a previously loaded copy. To do this,
1662 // change the copy from copying the original value to just copying the
1664 Instruction *StoredVal = cast<Instruction>(SI->getOperand(0));
1666 // If we've already replaced the input, StoredVal will be a cast or
1667 // select instruction. If not, it will be a load of the original
1669 if (LoadInst *LI = dyn_cast<LoadInst>(StoredVal)) {
1670 assert(LI->getOperand(0) == GV && "Not a copy!");
1671 // Insert a new load, to preserve the saved value.
1672 StoreVal = new LoadInst(NewGV, LI->getName()+".b", LI);
1674 assert((isa<CastInst>(StoredVal) || isa<SelectInst>(StoredVal)) &&
1675 "This is not a form that we understand!");
1676 StoreVal = StoredVal->getOperand(0);
1677 assert(isa<LoadInst>(StoreVal) && "Not a load of NewGV!");
1680 new StoreInst(StoreVal, NewGV, SI);
1682 // Change the load into a load of bool then a select.
1683 LoadInst *LI = cast<LoadInst>(UI);
1684 LoadInst *NLI = new LoadInst(NewGV, LI->getName()+".b", LI);
1687 NSI = new ZExtInst(NLI, LI->getType(), "", LI);
1689 NSI = SelectInst::Create(NLI, OtherVal, InitVal, "", LI);
1691 LI->replaceAllUsesWith(NSI);
1693 UI->eraseFromParent();
1696 GV->eraseFromParent();
1701 /// ProcessInternalGlobal - Analyze the specified global variable and optimize
1702 /// it if possible. If we make a change, return true.
1703 bool GlobalOpt::ProcessGlobal(GlobalVariable *GV,
1704 Module::global_iterator &GVI) {
1705 if (!GV->hasLocalLinkage())
1708 // Do more involved optimizations if the global is internal.
1709 GV->removeDeadConstantUsers();
1711 if (GV->use_empty()) {
1712 DEBUG(dbgs() << "GLOBAL DEAD: " << *GV);
1713 GV->eraseFromParent();
1718 SmallPtrSet<const PHINode*, 16> PHIUsers;
1721 if (AnalyzeGlobal(GV, GS, PHIUsers))
1724 if (!GS.isCompared && !GV->hasUnnamedAddr()) {
1725 GV->setUnnamedAddr(true);
1729 if (GV->isConstant() || !GV->hasInitializer())
1732 return ProcessInternalGlobal(GV, GVI, PHIUsers, GS);
1735 /// ProcessInternalGlobal - Analyze the specified global variable and optimize
1736 /// it if possible. If we make a change, return true.
1737 bool GlobalOpt::ProcessInternalGlobal(GlobalVariable *GV,
1738 Module::global_iterator &GVI,
1739 const SmallPtrSet<const PHINode*, 16> &PHIUsers,
1740 const GlobalStatus &GS) {
1741 // If this is a first class global and has only one accessing function
1742 // and this function is main (which we know is not recursive we can make
1743 // this global a local variable) we replace the global with a local alloca
1744 // in this function.
1746 // NOTE: It doesn't make sense to promote non single-value types since we
1747 // are just replacing static memory to stack memory.
1749 // If the global is in different address space, don't bring it to stack.
1750 if (!GS.HasMultipleAccessingFunctions &&
1751 GS.AccessingFunction && !GS.HasNonInstructionUser &&
1752 GV->getType()->getElementType()->isSingleValueType() &&
1753 GS.AccessingFunction->getName() == "main" &&
1754 GS.AccessingFunction->hasExternalLinkage() &&
1755 GV->getType()->getAddressSpace() == 0) {
1756 DEBUG(dbgs() << "LOCALIZING GLOBAL: " << *GV);
1757 Instruction& FirstI = const_cast<Instruction&>(*GS.AccessingFunction
1758 ->getEntryBlock().begin());
1759 Type* ElemTy = GV->getType()->getElementType();
1760 // FIXME: Pass Global's alignment when globals have alignment
1761 AllocaInst* Alloca = new AllocaInst(ElemTy, NULL, GV->getName(), &FirstI);
1762 if (!isa<UndefValue>(GV->getInitializer()))
1763 new StoreInst(GV->getInitializer(), Alloca, &FirstI);
1765 GV->replaceAllUsesWith(Alloca);
1766 GV->eraseFromParent();
1771 // If the global is never loaded (but may be stored to), it is dead.
1774 DEBUG(dbgs() << "GLOBAL NEVER LOADED: " << *GV);
1776 // Delete any stores we can find to the global. We may not be able to
1777 // make it completely dead though.
1778 bool Changed = CleanupConstantGlobalUsers(GV, GV->getInitializer());
1780 // If the global is dead now, delete it.
1781 if (GV->use_empty()) {
1782 GV->eraseFromParent();
1788 } else if (GS.StoredType <= GlobalStatus::isInitializerStored) {
1789 DEBUG(dbgs() << "MARKING CONSTANT: " << *GV);
1790 GV->setConstant(true);
1792 // Clean up any obviously simplifiable users now.
1793 CleanupConstantGlobalUsers(GV, GV->getInitializer());
1795 // If the global is dead now, just nuke it.
1796 if (GV->use_empty()) {
1797 DEBUG(dbgs() << " *** Marking constant allowed us to simplify "
1798 << "all users and delete global!\n");
1799 GV->eraseFromParent();
1805 } else if (!GV->getInitializer()->getType()->isSingleValueType()) {
1806 if (TargetData *TD = getAnalysisIfAvailable<TargetData>())
1807 if (GlobalVariable *FirstNewGV = SRAGlobal(GV, *TD)) {
1808 GVI = FirstNewGV; // Don't skip the newly produced globals!
1811 } else if (GS.StoredType == GlobalStatus::isStoredOnce) {
1812 // If the initial value for the global was an undef value, and if only
1813 // one other value was stored into it, we can just change the
1814 // initializer to be the stored value, then delete all stores to the
1815 // global. This allows us to mark it constant.
1816 if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue))
1817 if (isa<UndefValue>(GV->getInitializer())) {
1818 // Change the initial value here.
1819 GV->setInitializer(SOVConstant);
1821 // Clean up any obviously simplifiable users now.
1822 CleanupConstantGlobalUsers(GV, GV->getInitializer());
1824 if (GV->use_empty()) {
1825 DEBUG(dbgs() << " *** Substituting initializer allowed us to "
1826 << "simplify all users and delete global!\n");
1827 GV->eraseFromParent();
1836 // Try to optimize globals based on the knowledge that only one value
1837 // (besides its initializer) is ever stored to the global.
1838 if (OptimizeOnceStoredGlobal(GV, GS.StoredOnceValue, GVI,
1839 getAnalysisIfAvailable<TargetData>()))
1842 // Otherwise, if the global was not a boolean, we can shrink it to be a
1844 if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue))
1845 if (TryToShrinkGlobalToBoolean(GV, SOVConstant)) {
1854 /// ChangeCalleesToFastCall - Walk all of the direct calls of the specified
1855 /// function, changing them to FastCC.
1856 static void ChangeCalleesToFastCall(Function *F) {
1857 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){
1858 CallSite User(cast<Instruction>(*UI));
1859 User.setCallingConv(CallingConv::Fast);
1863 static AttrListPtr StripNest(const AttrListPtr &Attrs) {
1864 for (unsigned i = 0, e = Attrs.getNumSlots(); i != e; ++i) {
1865 if ((Attrs.getSlot(i).Attrs & Attribute::Nest) == 0)
1868 // There can be only one.
1869 return Attrs.removeAttr(Attrs.getSlot(i).Index, Attribute::Nest);
1875 static void RemoveNestAttribute(Function *F) {
1876 F->setAttributes(StripNest(F->getAttributes()));
1877 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){
1878 CallSite User(cast<Instruction>(*UI));
1879 User.setAttributes(StripNest(User.getAttributes()));
1883 bool GlobalOpt::OptimizeFunctions(Module &M) {
1884 bool Changed = false;
1885 // Optimize functions.
1886 for (Module::iterator FI = M.begin(), E = M.end(); FI != E; ) {
1888 // Functions without names cannot be referenced outside this module.
1889 if (!F->hasName() && !F->isDeclaration())
1890 F->setLinkage(GlobalValue::InternalLinkage);
1891 F->removeDeadConstantUsers();
1892 if (F->use_empty() && (F->hasLocalLinkage() || F->hasLinkOnceLinkage())) {
1893 F->eraseFromParent();
1896 } else if (F->hasLocalLinkage()) {
1897 if (F->getCallingConv() == CallingConv::C && !F->isVarArg() &&
1898 !F->hasAddressTaken()) {
1899 // If this function has C calling conventions, is not a varargs
1900 // function, and is only called directly, promote it to use the Fast
1901 // calling convention.
1902 F->setCallingConv(CallingConv::Fast);
1903 ChangeCalleesToFastCall(F);
1908 if (F->getAttributes().hasAttrSomewhere(Attribute::Nest) &&
1909 !F->hasAddressTaken()) {
1910 // The function is not used by a trampoline intrinsic, so it is safe
1911 // to remove the 'nest' attribute.
1912 RemoveNestAttribute(F);
1921 bool GlobalOpt::OptimizeGlobalVars(Module &M) {
1922 bool Changed = false;
1923 for (Module::global_iterator GVI = M.global_begin(), E = M.global_end();
1925 GlobalVariable *GV = GVI++;
1926 // Global variables without names cannot be referenced outside this module.
1927 if (!GV->hasName() && !GV->isDeclaration())
1928 GV->setLinkage(GlobalValue::InternalLinkage);
1929 // Simplify the initializer.
1930 if (GV->hasInitializer())
1931 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GV->getInitializer())) {
1932 TargetData *TD = getAnalysisIfAvailable<TargetData>();
1933 Constant *New = ConstantFoldConstantExpression(CE, TD);
1934 if (New && New != CE)
1935 GV->setInitializer(New);
1938 Changed |= ProcessGlobal(GV, GVI);
1943 /// FindGlobalCtors - Find the llvm.global_ctors list, verifying that all
1944 /// initializers have an init priority of 65535.
1945 GlobalVariable *GlobalOpt::FindGlobalCtors(Module &M) {
1946 GlobalVariable *GV = M.getGlobalVariable("llvm.global_ctors");
1947 if (GV == 0) return 0;
1949 // Verify that the initializer is simple enough for us to handle. We are
1950 // only allowed to optimize the initializer if it is unique.
1951 if (!GV->hasUniqueInitializer()) return 0;
1953 if (isa<ConstantAggregateZero>(GV->getInitializer()))
1955 ConstantArray *CA = cast<ConstantArray>(GV->getInitializer());
1957 for (User::op_iterator i = CA->op_begin(), e = CA->op_end(); i != e; ++i) {
1958 if (isa<ConstantAggregateZero>(*i))
1960 ConstantStruct *CS = cast<ConstantStruct>(*i);
1961 if (isa<ConstantPointerNull>(CS->getOperand(1)))
1964 // Must have a function or null ptr.
1965 if (!isa<Function>(CS->getOperand(1)))
1968 // Init priority must be standard.
1969 ConstantInt *CI = cast<ConstantInt>(CS->getOperand(0));
1970 if (CI->getZExtValue() != 65535)
1977 /// ParseGlobalCtors - Given a llvm.global_ctors list that we can understand,
1978 /// return a list of the functions and null terminator as a vector.
1979 static std::vector<Function*> ParseGlobalCtors(GlobalVariable *GV) {
1980 if (GV->getInitializer()->isNullValue())
1981 return std::vector<Function*>();
1982 ConstantArray *CA = cast<ConstantArray>(GV->getInitializer());
1983 std::vector<Function*> Result;
1984 Result.reserve(CA->getNumOperands());
1985 for (User::op_iterator i = CA->op_begin(), e = CA->op_end(); i != e; ++i) {
1986 ConstantStruct *CS = cast<ConstantStruct>(*i);
1987 Result.push_back(dyn_cast<Function>(CS->getOperand(1)));
1992 /// InstallGlobalCtors - Given a specified llvm.global_ctors list, install the
1993 /// specified array, returning the new global to use.
1994 static GlobalVariable *InstallGlobalCtors(GlobalVariable *GCL,
1995 const std::vector<Function*> &Ctors) {
1996 // If we made a change, reassemble the initializer list.
1997 Constant *CSVals[2];
1998 CSVals[0] = ConstantInt::get(Type::getInt32Ty(GCL->getContext()), 65535);
2001 StructType *StructTy =
2003 cast<ArrayType>(GCL->getType()->getElementType())->getElementType());
2005 // Create the new init list.
2006 std::vector<Constant*> CAList;
2007 for (unsigned i = 0, e = Ctors.size(); i != e; ++i) {
2009 CSVals[1] = Ctors[i];
2011 Type *FTy = FunctionType::get(Type::getVoidTy(GCL->getContext()),
2013 PointerType *PFTy = PointerType::getUnqual(FTy);
2014 CSVals[1] = Constant::getNullValue(PFTy);
2015 CSVals[0] = ConstantInt::get(Type::getInt32Ty(GCL->getContext()),
2018 CAList.push_back(ConstantStruct::get(StructTy, CSVals));
2021 // Create the array initializer.
2022 Constant *CA = ConstantArray::get(ArrayType::get(StructTy,
2023 CAList.size()), CAList);
2025 // If we didn't change the number of elements, don't create a new GV.
2026 if (CA->getType() == GCL->getInitializer()->getType()) {
2027 GCL->setInitializer(CA);
2031 // Create the new global and insert it next to the existing list.
2032 GlobalVariable *NGV = new GlobalVariable(CA->getType(), GCL->isConstant(),
2033 GCL->getLinkage(), CA, "",
2034 GCL->isThreadLocal());
2035 GCL->getParent()->getGlobalList().insert(GCL, NGV);
2038 // Nuke the old list, replacing any uses with the new one.
2039 if (!GCL->use_empty()) {
2041 if (V->getType() != GCL->getType())
2042 V = ConstantExpr::getBitCast(V, GCL->getType());
2043 GCL->replaceAllUsesWith(V);
2045 GCL->eraseFromParent();
2054 static Constant *getVal(DenseMap<Value*, Constant*> &ComputedValues, Value *V) {
2055 if (Constant *CV = dyn_cast<Constant>(V)) return CV;
2056 Constant *R = ComputedValues[V];
2057 assert(R && "Reference to an uncomputed value!");
2062 isSimpleEnoughValueToCommit(Constant *C,
2063 SmallPtrSet<Constant*, 8> &SimpleConstants);
2066 /// isSimpleEnoughValueToCommit - Return true if the specified constant can be
2067 /// handled by the code generator. We don't want to generate something like:
2068 /// void *X = &X/42;
2069 /// because the code generator doesn't have a relocation that can handle that.
2071 /// This function should be called if C was not found (but just got inserted)
2072 /// in SimpleConstants to avoid having to rescan the same constants all the
2074 static bool isSimpleEnoughValueToCommitHelper(Constant *C,
2075 SmallPtrSet<Constant*, 8> &SimpleConstants) {
2076 // Simple integer, undef, constant aggregate zero, global addresses, etc are
2078 if (C->getNumOperands() == 0 || isa<BlockAddress>(C) ||
2079 isa<GlobalValue>(C))
2082 // Aggregate values are safe if all their elements are.
2083 if (isa<ConstantArray>(C) || isa<ConstantStruct>(C) ||
2084 isa<ConstantVector>(C)) {
2085 for (unsigned i = 0, e = C->getNumOperands(); i != e; ++i) {
2086 Constant *Op = cast<Constant>(C->getOperand(i));
2087 if (!isSimpleEnoughValueToCommit(Op, SimpleConstants))
2093 // We don't know exactly what relocations are allowed in constant expressions,
2094 // so we allow &global+constantoffset, which is safe and uniformly supported
2096 ConstantExpr *CE = cast<ConstantExpr>(C);
2097 switch (CE->getOpcode()) {
2098 case Instruction::BitCast:
2099 case Instruction::IntToPtr:
2100 case Instruction::PtrToInt:
2101 // These casts are always fine if the casted value is.
2102 return isSimpleEnoughValueToCommit(CE->getOperand(0), SimpleConstants);
2104 // GEP is fine if it is simple + constant offset.
2105 case Instruction::GetElementPtr:
2106 for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i)
2107 if (!isa<ConstantInt>(CE->getOperand(i)))
2109 return isSimpleEnoughValueToCommit(CE->getOperand(0), SimpleConstants);
2111 case Instruction::Add:
2112 // We allow simple+cst.
2113 if (!isa<ConstantInt>(CE->getOperand(1)))
2115 return isSimpleEnoughValueToCommit(CE->getOperand(0), SimpleConstants);
2121 isSimpleEnoughValueToCommit(Constant *C,
2122 SmallPtrSet<Constant*, 8> &SimpleConstants) {
2123 // If we already checked this constant, we win.
2124 if (!SimpleConstants.insert(C)) return true;
2125 // Check the constant.
2126 return isSimpleEnoughValueToCommitHelper(C, SimpleConstants);
2130 /// isSimpleEnoughPointerToCommit - Return true if this constant is simple
2131 /// enough for us to understand. In particular, if it is a cast to anything
2132 /// other than from one pointer type to another pointer type, we punt.
2133 /// We basically just support direct accesses to globals and GEP's of
2134 /// globals. This should be kept up to date with CommitValueTo.
2135 static bool isSimpleEnoughPointerToCommit(Constant *C) {
2136 // Conservatively, avoid aggregate types. This is because we don't
2137 // want to worry about them partially overlapping other stores.
2138 if (!cast<PointerType>(C->getType())->getElementType()->isSingleValueType())
2141 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C))
2142 // Do not allow weak/*_odr/linkonce/dllimport/dllexport linkage or
2143 // external globals.
2144 return GV->hasUniqueInitializer();
2146 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) {
2147 // Handle a constantexpr gep.
2148 if (CE->getOpcode() == Instruction::GetElementPtr &&
2149 isa<GlobalVariable>(CE->getOperand(0)) &&
2150 cast<GEPOperator>(CE)->isInBounds()) {
2151 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
2152 // Do not allow weak/*_odr/linkonce/dllimport/dllexport linkage or
2153 // external globals.
2154 if (!GV->hasUniqueInitializer())
2157 // The first index must be zero.
2158 ConstantInt *CI = dyn_cast<ConstantInt>(*llvm::next(CE->op_begin()));
2159 if (!CI || !CI->isZero()) return false;
2161 // The remaining indices must be compile-time known integers within the
2162 // notional bounds of the corresponding static array types.
2163 if (!CE->isGEPWithNoNotionalOverIndexing())
2166 return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE);
2168 // A constantexpr bitcast from a pointer to another pointer is a no-op,
2169 // and we know how to evaluate it by moving the bitcast from the pointer
2170 // operand to the value operand.
2171 } else if (CE->getOpcode() == Instruction::BitCast &&
2172 isa<GlobalVariable>(CE->getOperand(0))) {
2173 // Do not allow weak/*_odr/linkonce/dllimport/dllexport linkage or
2174 // external globals.
2175 return cast<GlobalVariable>(CE->getOperand(0))->hasUniqueInitializer();
2182 /// EvaluateStoreInto - Evaluate a piece of a constantexpr store into a global
2183 /// initializer. This returns 'Init' modified to reflect 'Val' stored into it.
2184 /// At this point, the GEP operands of Addr [0, OpNo) have been stepped into.
2185 static Constant *EvaluateStoreInto(Constant *Init, Constant *Val,
2186 ConstantExpr *Addr, unsigned OpNo) {
2187 // Base case of the recursion.
2188 if (OpNo == Addr->getNumOperands()) {
2189 assert(Val->getType() == Init->getType() && "Type mismatch!");
2193 std::vector<Constant*> Elts;
2194 if (StructType *STy = dyn_cast<StructType>(Init->getType())) {
2196 // Break up the constant into its elements.
2197 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(Init)) {
2198 for (User::op_iterator i = CS->op_begin(), e = CS->op_end(); i != e; ++i)
2199 Elts.push_back(cast<Constant>(*i));
2200 } else if (isa<ConstantAggregateZero>(Init)) {
2201 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
2202 Elts.push_back(Constant::getNullValue(STy->getElementType(i)));
2203 } else if (isa<UndefValue>(Init)) {
2204 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
2205 Elts.push_back(UndefValue::get(STy->getElementType(i)));
2207 llvm_unreachable("This code is out of sync with "
2208 " ConstantFoldLoadThroughGEPConstantExpr");
2211 // Replace the element that we are supposed to.
2212 ConstantInt *CU = cast<ConstantInt>(Addr->getOperand(OpNo));
2213 unsigned Idx = CU->getZExtValue();
2214 assert(Idx < STy->getNumElements() && "Struct index out of range!");
2215 Elts[Idx] = EvaluateStoreInto(Elts[Idx], Val, Addr, OpNo+1);
2217 // Return the modified struct.
2218 return ConstantStruct::get(STy, Elts);
2221 ConstantInt *CI = cast<ConstantInt>(Addr->getOperand(OpNo));
2222 SequentialType *InitTy = cast<SequentialType>(Init->getType());
2225 if (ArrayType *ATy = dyn_cast<ArrayType>(InitTy))
2226 NumElts = ATy->getNumElements();
2228 NumElts = cast<VectorType>(InitTy)->getNumElements();
2230 // Break up the array into elements.
2231 if (ConstantArray *CA = dyn_cast<ConstantArray>(Init)) {
2232 for (User::op_iterator i = CA->op_begin(), e = CA->op_end(); i != e; ++i)
2233 Elts.push_back(cast<Constant>(*i));
2234 } else if (ConstantVector *CV = dyn_cast<ConstantVector>(Init)) {
2235 for (User::op_iterator i = CV->op_begin(), e = CV->op_end(); i != e; ++i)
2236 Elts.push_back(cast<Constant>(*i));
2237 } else if (isa<ConstantAggregateZero>(Init)) {
2238 Elts.assign(NumElts, Constant::getNullValue(InitTy->getElementType()));
2240 assert(isa<UndefValue>(Init) && "This code is out of sync with "
2241 " ConstantFoldLoadThroughGEPConstantExpr");
2242 Elts.assign(NumElts, UndefValue::get(InitTy->getElementType()));
2245 assert(CI->getZExtValue() < NumElts);
2246 Elts[CI->getZExtValue()] =
2247 EvaluateStoreInto(Elts[CI->getZExtValue()], Val, Addr, OpNo+1);
2249 if (Init->getType()->isArrayTy())
2250 return ConstantArray::get(cast<ArrayType>(InitTy), Elts);
2251 return ConstantVector::get(Elts);
2254 /// CommitValueTo - We have decided that Addr (which satisfies the predicate
2255 /// isSimpleEnoughPointerToCommit) should get Val as its value. Make it happen.
2256 static void CommitValueTo(Constant *Val, Constant *Addr) {
2257 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Addr)) {
2258 assert(GV->hasInitializer());
2259 GV->setInitializer(Val);
2263 ConstantExpr *CE = cast<ConstantExpr>(Addr);
2264 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
2265 GV->setInitializer(EvaluateStoreInto(GV->getInitializer(), Val, CE, 2));
2268 /// ComputeLoadResult - Return the value that would be computed by a load from
2269 /// P after the stores reflected by 'memory' have been performed. If we can't
2270 /// decide, return null.
2271 static Constant *ComputeLoadResult(Constant *P,
2272 const DenseMap<Constant*, Constant*> &Memory) {
2273 // If this memory location has been recently stored, use the stored value: it
2274 // is the most up-to-date.
2275 DenseMap<Constant*, Constant*>::const_iterator I = Memory.find(P);
2276 if (I != Memory.end()) return I->second;
2279 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(P)) {
2280 if (GV->hasDefinitiveInitializer())
2281 return GV->getInitializer();
2285 // Handle a constantexpr getelementptr.
2286 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(P))
2287 if (CE->getOpcode() == Instruction::GetElementPtr &&
2288 isa<GlobalVariable>(CE->getOperand(0))) {
2289 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
2290 if (GV->hasDefinitiveInitializer())
2291 return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE);
2294 return 0; // don't know how to evaluate.
2297 /// EvaluateFunction - Evaluate a call to function F, returning true if
2298 /// successful, false if we can't evaluate it. ActualArgs contains the formal
2299 /// arguments for the function.
2300 static bool EvaluateFunction(Function *F, Constant *&RetVal,
2301 const SmallVectorImpl<Constant*> &ActualArgs,
2302 std::vector<Function*> &CallStack,
2303 DenseMap<Constant*, Constant*> &MutatedMemory,
2304 std::vector<GlobalVariable*> &AllocaTmps,
2305 SmallPtrSet<Constant*, 8> &SimpleConstants,
2306 const TargetData *TD) {
2307 // Check to see if this function is already executing (recursion). If so,
2308 // bail out. TODO: we might want to accept limited recursion.
2309 if (std::find(CallStack.begin(), CallStack.end(), F) != CallStack.end())
2312 CallStack.push_back(F);
2314 /// Values - As we compute SSA register values, we store their contents here.
2315 DenseMap<Value*, Constant*> Values;
2317 // Initialize arguments to the incoming values specified.
2319 for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end(); AI != E;
2321 Values[AI] = ActualArgs[ArgNo];
2323 /// ExecutedBlocks - We only handle non-looping, non-recursive code. As such,
2324 /// we can only evaluate any one basic block at most once. This set keeps
2325 /// track of what we have executed so we can detect recursive cases etc.
2326 SmallPtrSet<BasicBlock*, 32> ExecutedBlocks;
2328 // CurInst - The current instruction we're evaluating.
2329 BasicBlock::iterator CurInst = F->begin()->begin();
2331 // This is the main evaluation loop.
2333 Constant *InstResult = 0;
2335 if (StoreInst *SI = dyn_cast<StoreInst>(CurInst)) {
2336 if (SI->isVolatile()) return false; // no volatile accesses.
2337 Constant *Ptr = getVal(Values, SI->getOperand(1));
2338 if (!isSimpleEnoughPointerToCommit(Ptr))
2339 // If this is too complex for us to commit, reject it.
2342 Constant *Val = getVal(Values, SI->getOperand(0));
2344 // If this might be too difficult for the backend to handle (e.g. the addr
2345 // of one global variable divided by another) then we can't commit it.
2346 if (!isSimpleEnoughValueToCommit(Val, SimpleConstants))
2349 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr))
2350 if (CE->getOpcode() == Instruction::BitCast) {
2351 // If we're evaluating a store through a bitcast, then we need
2352 // to pull the bitcast off the pointer type and push it onto the
2354 Ptr = CE->getOperand(0);
2356 Type *NewTy=cast<PointerType>(Ptr->getType())->getElementType();
2358 // In order to push the bitcast onto the stored value, a bitcast
2359 // from NewTy to Val's type must be legal. If it's not, we can try
2360 // introspecting NewTy to find a legal conversion.
2361 while (!Val->getType()->canLosslesslyBitCastTo(NewTy)) {
2362 // If NewTy is a struct, we can convert the pointer to the struct
2363 // into a pointer to its first member.
2364 // FIXME: This could be extended to support arrays as well.
2365 if (StructType *STy = dyn_cast<StructType>(NewTy)) {
2366 NewTy = STy->getTypeAtIndex(0U);
2368 IntegerType *IdxTy =IntegerType::get(NewTy->getContext(), 32);
2369 Constant *IdxZero = ConstantInt::get(IdxTy, 0, false);
2370 Constant * const IdxList[] = {IdxZero, IdxZero};
2372 Ptr = ConstantExpr::getGetElementPtr(Ptr, IdxList);
2374 // If we can't improve the situation by introspecting NewTy,
2375 // we have to give up.
2381 // If we found compatible types, go ahead and push the bitcast
2382 // onto the stored value.
2383 Val = ConstantExpr::getBitCast(Val, NewTy);
2386 MutatedMemory[Ptr] = Val;
2387 } else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(CurInst)) {
2388 InstResult = ConstantExpr::get(BO->getOpcode(),
2389 getVal(Values, BO->getOperand(0)),
2390 getVal(Values, BO->getOperand(1)));
2391 } else if (CmpInst *CI = dyn_cast<CmpInst>(CurInst)) {
2392 InstResult = ConstantExpr::getCompare(CI->getPredicate(),
2393 getVal(Values, CI->getOperand(0)),
2394 getVal(Values, CI->getOperand(1)));
2395 } else if (CastInst *CI = dyn_cast<CastInst>(CurInst)) {
2396 InstResult = ConstantExpr::getCast(CI->getOpcode(),
2397 getVal(Values, CI->getOperand(0)),
2399 } else if (SelectInst *SI = dyn_cast<SelectInst>(CurInst)) {
2400 InstResult = ConstantExpr::getSelect(getVal(Values, SI->getOperand(0)),
2401 getVal(Values, SI->getOperand(1)),
2402 getVal(Values, SI->getOperand(2)));
2403 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(CurInst)) {
2404 Constant *P = getVal(Values, GEP->getOperand(0));
2405 SmallVector<Constant*, 8> GEPOps;
2406 for (User::op_iterator i = GEP->op_begin() + 1, e = GEP->op_end();
2408 GEPOps.push_back(getVal(Values, *i));
2410 ConstantExpr::getGetElementPtr(P, GEPOps,
2411 cast<GEPOperator>(GEP)->isInBounds());
2412 } else if (LoadInst *LI = dyn_cast<LoadInst>(CurInst)) {
2413 if (LI->isVolatile()) return false; // no volatile accesses.
2414 InstResult = ComputeLoadResult(getVal(Values, LI->getOperand(0)),
2416 if (InstResult == 0) return false; // Could not evaluate load.
2417 } else if (AllocaInst *AI = dyn_cast<AllocaInst>(CurInst)) {
2418 if (AI->isArrayAllocation()) return false; // Cannot handle array allocs.
2419 Type *Ty = AI->getType()->getElementType();
2420 AllocaTmps.push_back(new GlobalVariable(Ty, false,
2421 GlobalValue::InternalLinkage,
2422 UndefValue::get(Ty),
2424 InstResult = AllocaTmps.back();
2425 } else if (CallInst *CI = dyn_cast<CallInst>(CurInst)) {
2427 // Debug info can safely be ignored here.
2428 if (isa<DbgInfoIntrinsic>(CI)) {
2433 // Cannot handle inline asm.
2434 if (isa<InlineAsm>(CI->getCalledValue())) return false;
2436 if (MemSetInst *MSI = dyn_cast<MemSetInst>(CI)) {
2437 if (MSI->isVolatile()) return false;
2438 Constant *Ptr = getVal(Values, MSI->getDest());
2439 Constant *Val = getVal(Values, MSI->getValue());
2440 Constant *DestVal = ComputeLoadResult(getVal(Values, Ptr),
2442 if (Val->isNullValue() && DestVal && DestVal->isNullValue()) {
2443 // This memset is a no-op.
2450 // Resolve function pointers.
2451 Function *Callee = dyn_cast<Function>(getVal(Values,
2452 CI->getCalledValue()));
2453 if (!Callee) return false; // Cannot resolve.
2455 SmallVector<Constant*, 8> Formals;
2457 for (User::op_iterator i = CS.arg_begin(), e = CS.arg_end();
2459 Formals.push_back(getVal(Values, *i));
2461 if (Callee->isDeclaration()) {
2462 // If this is a function we can constant fold, do it.
2463 if (Constant *C = ConstantFoldCall(Callee, Formals)) {
2469 if (Callee->getFunctionType()->isVarArg())
2473 // Execute the call, if successful, use the return value.
2474 if (!EvaluateFunction(Callee, RetVal, Formals, CallStack,
2475 MutatedMemory, AllocaTmps, SimpleConstants, TD))
2477 InstResult = RetVal;
2479 } else if (isa<TerminatorInst>(CurInst)) {
2480 BasicBlock *NewBB = 0;
2481 if (BranchInst *BI = dyn_cast<BranchInst>(CurInst)) {
2482 if (BI->isUnconditional()) {
2483 NewBB = BI->getSuccessor(0);
2486 dyn_cast<ConstantInt>(getVal(Values, BI->getCondition()));
2487 if (!Cond) return false; // Cannot determine.
2489 NewBB = BI->getSuccessor(!Cond->getZExtValue());
2491 } else if (SwitchInst *SI = dyn_cast<SwitchInst>(CurInst)) {
2493 dyn_cast<ConstantInt>(getVal(Values, SI->getCondition()));
2494 if (!Val) return false; // Cannot determine.
2495 NewBB = SI->getSuccessor(SI->findCaseValue(Val));
2496 } else if (IndirectBrInst *IBI = dyn_cast<IndirectBrInst>(CurInst)) {
2497 Value *Val = getVal(Values, IBI->getAddress())->stripPointerCasts();
2498 if (BlockAddress *BA = dyn_cast<BlockAddress>(Val))
2499 NewBB = BA->getBasicBlock();
2501 return false; // Cannot determine.
2502 } else if (ReturnInst *RI = dyn_cast<ReturnInst>(CurInst)) {
2503 if (RI->getNumOperands())
2504 RetVal = getVal(Values, RI->getOperand(0));
2506 CallStack.pop_back(); // return from fn.
2507 return true; // We succeeded at evaluating this ctor!
2509 // invoke, unwind, unreachable.
2510 return false; // Cannot handle this terminator.
2513 // Okay, we succeeded in evaluating this control flow. See if we have
2514 // executed the new block before. If so, we have a looping function,
2515 // which we cannot evaluate in reasonable time.
2516 if (!ExecutedBlocks.insert(NewBB))
2517 return false; // looped!
2519 // Okay, we have never been in this block before. Check to see if there
2520 // are any PHI nodes. If so, evaluate them with information about where
2522 BasicBlock *OldBB = CurInst->getParent();
2523 CurInst = NewBB->begin();
2525 for (; (PN = dyn_cast<PHINode>(CurInst)); ++CurInst)
2526 Values[PN] = getVal(Values, PN->getIncomingValueForBlock(OldBB));
2528 // Do NOT increment CurInst. We know that the terminator had no value.
2531 // Did not know how to evaluate this!
2535 if (!CurInst->use_empty()) {
2536 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(InstResult))
2537 InstResult = ConstantFoldConstantExpression(CE, TD);
2539 Values[CurInst] = InstResult;
2542 // Advance program counter.
2547 /// EvaluateStaticConstructor - Evaluate static constructors in the function, if
2548 /// we can. Return true if we can, false otherwise.
2549 static bool EvaluateStaticConstructor(Function *F, const TargetData *TD) {
2550 /// MutatedMemory - For each store we execute, we update this map. Loads
2551 /// check this to get the most up-to-date value. If evaluation is successful,
2552 /// this state is committed to the process.
2553 DenseMap<Constant*, Constant*> MutatedMemory;
2555 /// AllocaTmps - To 'execute' an alloca, we create a temporary global variable
2556 /// to represent its body. This vector is needed so we can delete the
2557 /// temporary globals when we are done.
2558 std::vector<GlobalVariable*> AllocaTmps;
2560 /// CallStack - This is used to detect recursion. In pathological situations
2561 /// we could hit exponential behavior, but at least there is nothing
2563 std::vector<Function*> CallStack;
2565 /// SimpleConstants - These are constants we have checked and know to be
2566 /// simple enough to live in a static initializer of a global.
2567 SmallPtrSet<Constant*, 8> SimpleConstants;
2569 // Call the function.
2570 Constant *RetValDummy;
2571 bool EvalSuccess = EvaluateFunction(F, RetValDummy,
2572 SmallVector<Constant*, 0>(), CallStack,
2573 MutatedMemory, AllocaTmps,
2574 SimpleConstants, TD);
2577 // We succeeded at evaluation: commit the result.
2578 DEBUG(dbgs() << "FULLY EVALUATED GLOBAL CTOR FUNCTION '"
2579 << F->getName() << "' to " << MutatedMemory.size()
2581 for (DenseMap<Constant*, Constant*>::iterator I = MutatedMemory.begin(),
2582 E = MutatedMemory.end(); I != E; ++I)
2583 CommitValueTo(I->second, I->first);
2586 // At this point, we are done interpreting. If we created any 'alloca'
2587 // temporaries, release them now.
2588 while (!AllocaTmps.empty()) {
2589 GlobalVariable *Tmp = AllocaTmps.back();
2590 AllocaTmps.pop_back();
2592 // If there are still users of the alloca, the program is doing something
2593 // silly, e.g. storing the address of the alloca somewhere and using it
2594 // later. Since this is undefined, we'll just make it be null.
2595 if (!Tmp->use_empty())
2596 Tmp->replaceAllUsesWith(Constant::getNullValue(Tmp->getType()));
2605 /// OptimizeGlobalCtorsList - Simplify and evaluation global ctors if possible.
2606 /// Return true if anything changed.
2607 bool GlobalOpt::OptimizeGlobalCtorsList(GlobalVariable *&GCL) {
2608 std::vector<Function*> Ctors = ParseGlobalCtors(GCL);
2609 bool MadeChange = false;
2610 if (Ctors.empty()) return false;
2612 const TargetData *TD = getAnalysisIfAvailable<TargetData>();
2613 // Loop over global ctors, optimizing them when we can.
2614 for (unsigned i = 0; i != Ctors.size(); ++i) {
2615 Function *F = Ctors[i];
2616 // Found a null terminator in the middle of the list, prune off the rest of
2619 if (i != Ctors.size()-1) {
2626 // We cannot simplify external ctor functions.
2627 if (F->empty()) continue;
2629 // If we can evaluate the ctor at compile time, do.
2630 if (EvaluateStaticConstructor(F, TD)) {
2631 Ctors.erase(Ctors.begin()+i);
2634 ++NumCtorsEvaluated;
2639 if (!MadeChange) return false;
2641 GCL = InstallGlobalCtors(GCL, Ctors);
2645 bool GlobalOpt::OptimizeGlobalAliases(Module &M) {
2646 bool Changed = false;
2648 for (Module::alias_iterator I = M.alias_begin(), E = M.alias_end();
2650 Module::alias_iterator J = I++;
2651 // Aliases without names cannot be referenced outside this module.
2652 if (!J->hasName() && !J->isDeclaration())
2653 J->setLinkage(GlobalValue::InternalLinkage);
2654 // If the aliasee may change at link time, nothing can be done - bail out.
2655 if (J->mayBeOverridden())
2658 Constant *Aliasee = J->getAliasee();
2659 GlobalValue *Target = cast<GlobalValue>(Aliasee->stripPointerCasts());
2660 Target->removeDeadConstantUsers();
2661 bool hasOneUse = Target->hasOneUse() && Aliasee->hasOneUse();
2663 // Make all users of the alias use the aliasee instead.
2664 if (!J->use_empty()) {
2665 J->replaceAllUsesWith(Aliasee);
2666 ++NumAliasesResolved;
2670 // If the alias is externally visible, we may still be able to simplify it.
2671 if (!J->hasLocalLinkage()) {
2672 // If the aliasee has internal linkage, give it the name and linkage
2673 // of the alias, and delete the alias. This turns:
2674 // define internal ... @f(...)
2675 // @a = alias ... @f
2677 // define ... @a(...)
2678 if (!Target->hasLocalLinkage())
2681 // Do not perform the transform if multiple aliases potentially target the
2682 // aliasee. This check also ensures that it is safe to replace the section
2683 // and other attributes of the aliasee with those of the alias.
2687 // Give the aliasee the name, linkage and other attributes of the alias.
2688 Target->takeName(J);
2689 Target->setLinkage(J->getLinkage());
2690 Target->GlobalValue::copyAttributesFrom(J);
2693 // Delete the alias.
2694 M.getAliasList().erase(J);
2695 ++NumAliasesRemoved;
2702 static Function *FindCXAAtExit(Module &M) {
2703 Function *Fn = M.getFunction("__cxa_atexit");
2708 FunctionType *FTy = Fn->getFunctionType();
2710 // Checking that the function has the right return type, the right number of
2711 // parameters and that they all have pointer types should be enough.
2712 if (!FTy->getReturnType()->isIntegerTy() ||
2713 FTy->getNumParams() != 3 ||
2714 !FTy->getParamType(0)->isPointerTy() ||
2715 !FTy->getParamType(1)->isPointerTy() ||
2716 !FTy->getParamType(2)->isPointerTy())
2722 /// cxxDtorIsEmpty - Returns whether the given function is an empty C++
2723 /// destructor and can therefore be eliminated.
2724 /// Note that we assume that other optimization passes have already simplified
2725 /// the code so we only look for a function with a single basic block, where
2726 /// the only allowed instructions are 'ret' or 'call' to empty C++ dtor.
2727 static bool cxxDtorIsEmpty(const Function &Fn,
2728 SmallPtrSet<const Function *, 8> &CalledFunctions) {
2729 // FIXME: We could eliminate C++ destructors if they're readonly/readnone and
2730 // nounwind, but that doesn't seem worth doing.
2731 if (Fn.isDeclaration())
2734 if (++Fn.begin() != Fn.end())
2737 const BasicBlock &EntryBlock = Fn.getEntryBlock();
2738 for (BasicBlock::const_iterator I = EntryBlock.begin(), E = EntryBlock.end();
2740 if (const CallInst *CI = dyn_cast<CallInst>(I)) {
2741 // Ignore debug intrinsics.
2742 if (isa<DbgInfoIntrinsic>(CI))
2745 const Function *CalledFn = CI->getCalledFunction();
2750 SmallPtrSet<const Function *, 8> NewCalledFunctions(CalledFunctions);
2752 // Don't treat recursive functions as empty.
2753 if (!NewCalledFunctions.insert(CalledFn))
2756 if (!cxxDtorIsEmpty(*CalledFn, NewCalledFunctions))
2758 } else if (isa<ReturnInst>(*I))
2767 bool GlobalOpt::OptimizeEmptyGlobalCXXDtors(Function *CXAAtExitFn) {
2768 /// Itanium C++ ABI p3.3.5:
2770 /// After constructing a global (or local static) object, that will require
2771 /// destruction on exit, a termination function is registered as follows:
2773 /// extern "C" int __cxa_atexit ( void (*f)(void *), void *p, void *d );
2775 /// This registration, e.g. __cxa_atexit(f,p,d), is intended to cause the
2776 /// call f(p) when DSO d is unloaded, before all such termination calls
2777 /// registered before this one. It returns zero if registration is
2778 /// successful, nonzero on failure.
2780 // This pass will look for calls to __cxa_atexit where the function is trivial
2782 bool Changed = false;
2784 for (Function::use_iterator I = CXAAtExitFn->use_begin(),
2785 E = CXAAtExitFn->use_end(); I != E;) {
2786 // We're only interested in calls. Theoretically, we could handle invoke
2787 // instructions as well, but neither llvm-gcc nor clang generate invokes
2789 CallInst *CI = dyn_cast<CallInst>(*I++);
2794 dyn_cast<Function>(CI->getArgOperand(0)->stripPointerCasts());
2798 SmallPtrSet<const Function *, 8> CalledFunctions;
2799 if (!cxxDtorIsEmpty(*DtorFn, CalledFunctions))
2802 // Just remove the call.
2803 CI->replaceAllUsesWith(Constant::getNullValue(CI->getType()));
2804 CI->eraseFromParent();
2806 ++NumCXXDtorsRemoved;
2814 bool GlobalOpt::runOnModule(Module &M) {
2815 bool Changed = false;
2817 // Try to find the llvm.globalctors list.
2818 GlobalVariable *GlobalCtors = FindGlobalCtors(M);
2820 Function *CXAAtExitFn = FindCXAAtExit(M);
2822 bool LocalChange = true;
2823 while (LocalChange) {
2824 LocalChange = false;
2826 // Delete functions that are trivially dead, ccc -> fastcc
2827 LocalChange |= OptimizeFunctions(M);
2829 // Optimize global_ctors list.
2831 LocalChange |= OptimizeGlobalCtorsList(GlobalCtors);
2833 // Optimize non-address-taken globals.
2834 LocalChange |= OptimizeGlobalVars(M);
2836 // Resolve aliases, when possible.
2837 LocalChange |= OptimizeGlobalAliases(M);
2839 // Try to remove trivial global destructors.
2841 LocalChange |= OptimizeEmptyGlobalCXXDtors(CXAAtExitFn);
2843 Changed |= LocalChange;
2846 // TODO: Move all global ctors functions to the end of the module for code