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 // Don't hack on volatile/atomic loads.
199 if (!LI->isSimple()) return true;
200 } else if (const StoreInst *SI = dyn_cast<StoreInst>(I)) {
201 // Don't allow a store OF the address, only stores TO the address.
202 if (SI->getOperand(0) == V) return true;
204 // Don't hack on volatile/atomic stores.
205 if (!SI->isSimple()) return true;
207 // If this is a direct store to the global (i.e., the global is a scalar
208 // value, not an aggregate), keep more specific information about
210 if (GS.StoredType != GlobalStatus::isStored) {
211 if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(
212 SI->getOperand(1))) {
213 Value *StoredVal = SI->getOperand(0);
214 if (StoredVal == GV->getInitializer()) {
215 if (GS.StoredType < GlobalStatus::isInitializerStored)
216 GS.StoredType = GlobalStatus::isInitializerStored;
217 } else if (isa<LoadInst>(StoredVal) &&
218 cast<LoadInst>(StoredVal)->getOperand(0) == GV) {
219 if (GS.StoredType < GlobalStatus::isInitializerStored)
220 GS.StoredType = GlobalStatus::isInitializerStored;
221 } else if (GS.StoredType < GlobalStatus::isStoredOnce) {
222 GS.StoredType = GlobalStatus::isStoredOnce;
223 GS.StoredOnceValue = StoredVal;
224 } else if (GS.StoredType == GlobalStatus::isStoredOnce &&
225 GS.StoredOnceValue == StoredVal) {
228 GS.StoredType = GlobalStatus::isStored;
231 GS.StoredType = GlobalStatus::isStored;
234 } else if (isa<GetElementPtrInst>(I)) {
235 if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
236 } else if (isa<SelectInst>(I)) {
237 if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
238 } else if (const PHINode *PN = dyn_cast<PHINode>(I)) {
239 // PHI nodes we can check just like select or GEP instructions, but we
240 // have to be careful about infinite recursion.
241 if (PHIUsers.insert(PN)) // Not already visited.
242 if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
243 GS.HasPHIUser = true;
244 } else if (isa<CmpInst>(I)) {
245 GS.isCompared = true;
246 } else if (const MemTransferInst *MTI = dyn_cast<MemTransferInst>(I)) {
247 if (MTI->isVolatile()) return true;
248 if (MTI->getArgOperand(0) == V)
249 GS.StoredType = GlobalStatus::isStored;
250 if (MTI->getArgOperand(1) == V)
252 } else if (const MemSetInst *MSI = dyn_cast<MemSetInst>(I)) {
253 assert(MSI->getArgOperand(0) == V && "Memset only takes one pointer!");
254 if (MSI->isVolatile()) return true;
255 GS.StoredType = GlobalStatus::isStored;
257 return true; // Any other non-load instruction might take address!
259 } else if (const Constant *C = dyn_cast<Constant>(U)) {
260 GS.HasNonInstructionUser = true;
261 // We might have a dead and dangling constant hanging off of here.
262 if (!SafeToDestroyConstant(C))
265 GS.HasNonInstructionUser = true;
266 // Otherwise must be some other user.
274 static Constant *getAggregateConstantElement(Constant *Agg, Constant *Idx) {
275 ConstantInt *CI = dyn_cast<ConstantInt>(Idx);
277 unsigned IdxV = CI->getZExtValue();
279 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(Agg)) {
280 if (IdxV < CS->getNumOperands()) return CS->getOperand(IdxV);
281 } else if (ConstantArray *CA = dyn_cast<ConstantArray>(Agg)) {
282 if (IdxV < CA->getNumOperands()) return CA->getOperand(IdxV);
283 } else if (ConstantVector *CP = dyn_cast<ConstantVector>(Agg)) {
284 if (IdxV < CP->getNumOperands()) return CP->getOperand(IdxV);
285 } else if (isa<ConstantAggregateZero>(Agg)) {
286 if (StructType *STy = dyn_cast<StructType>(Agg->getType())) {
287 if (IdxV < STy->getNumElements())
288 return Constant::getNullValue(STy->getElementType(IdxV));
289 } else if (SequentialType *STy =
290 dyn_cast<SequentialType>(Agg->getType())) {
291 return Constant::getNullValue(STy->getElementType());
293 } else if (isa<UndefValue>(Agg)) {
294 if (StructType *STy = dyn_cast<StructType>(Agg->getType())) {
295 if (IdxV < STy->getNumElements())
296 return UndefValue::get(STy->getElementType(IdxV));
297 } else if (SequentialType *STy =
298 dyn_cast<SequentialType>(Agg->getType())) {
299 return UndefValue::get(STy->getElementType());
306 /// CleanupConstantGlobalUsers - We just marked GV constant. Loop over all
307 /// users of the global, cleaning up the obvious ones. This is largely just a
308 /// quick scan over the use list to clean up the easy and obvious cruft. This
309 /// returns true if it made a change.
310 static bool CleanupConstantGlobalUsers(Value *V, Constant *Init) {
311 bool Changed = false;
312 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;) {
315 if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
317 // Replace the load with the initializer.
318 LI->replaceAllUsesWith(Init);
319 LI->eraseFromParent();
322 } else if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
323 // Store must be unreachable or storing Init into the global.
324 SI->eraseFromParent();
326 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U)) {
327 if (CE->getOpcode() == Instruction::GetElementPtr) {
328 Constant *SubInit = 0;
330 SubInit = ConstantFoldLoadThroughGEPConstantExpr(Init, CE);
331 Changed |= CleanupConstantGlobalUsers(CE, SubInit);
332 } else if (CE->getOpcode() == Instruction::BitCast &&
333 CE->getType()->isPointerTy()) {
334 // Pointer cast, delete any stores and memsets to the global.
335 Changed |= CleanupConstantGlobalUsers(CE, 0);
338 if (CE->use_empty()) {
339 CE->destroyConstant();
342 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) {
343 // Do not transform "gepinst (gep constexpr (GV))" here, because forming
344 // "gepconstexpr (gep constexpr (GV))" will cause the two gep's to fold
345 // and will invalidate our notion of what Init is.
346 Constant *SubInit = 0;
347 if (!isa<ConstantExpr>(GEP->getOperand(0))) {
349 dyn_cast_or_null<ConstantExpr>(ConstantFoldInstruction(GEP));
350 if (Init && CE && CE->getOpcode() == Instruction::GetElementPtr)
351 SubInit = ConstantFoldLoadThroughGEPConstantExpr(Init, CE);
353 Changed |= CleanupConstantGlobalUsers(GEP, SubInit);
355 if (GEP->use_empty()) {
356 GEP->eraseFromParent();
359 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(U)) { // memset/cpy/mv
360 if (MI->getRawDest() == V) {
361 MI->eraseFromParent();
365 } else if (Constant *C = dyn_cast<Constant>(U)) {
366 // If we have a chain of dead constantexprs or other things dangling from
367 // us, and if they are all dead, nuke them without remorse.
368 if (SafeToDestroyConstant(C)) {
369 C->destroyConstant();
370 // This could have invalidated UI, start over from scratch.
371 CleanupConstantGlobalUsers(V, Init);
379 /// isSafeSROAElementUse - Return true if the specified instruction is a safe
380 /// user of a derived expression from a global that we want to SROA.
381 static bool isSafeSROAElementUse(Value *V) {
382 // We might have a dead and dangling constant hanging off of here.
383 if (Constant *C = dyn_cast<Constant>(V))
384 return SafeToDestroyConstant(C);
386 Instruction *I = dyn_cast<Instruction>(V);
387 if (!I) return false;
390 if (isa<LoadInst>(I)) return true;
392 // Stores *to* the pointer are ok.
393 if (StoreInst *SI = dyn_cast<StoreInst>(I))
394 return SI->getOperand(0) != V;
396 // Otherwise, it must be a GEP.
397 GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I);
398 if (GEPI == 0) return false;
400 if (GEPI->getNumOperands() < 3 || !isa<Constant>(GEPI->getOperand(1)) ||
401 !cast<Constant>(GEPI->getOperand(1))->isNullValue())
404 for (Value::use_iterator I = GEPI->use_begin(), E = GEPI->use_end();
406 if (!isSafeSROAElementUse(*I))
412 /// IsUserOfGlobalSafeForSRA - U is a direct user of the specified global value.
413 /// Look at it and its uses and decide whether it is safe to SROA this global.
415 static bool IsUserOfGlobalSafeForSRA(User *U, GlobalValue *GV) {
416 // The user of the global must be a GEP Inst or a ConstantExpr GEP.
417 if (!isa<GetElementPtrInst>(U) &&
418 (!isa<ConstantExpr>(U) ||
419 cast<ConstantExpr>(U)->getOpcode() != Instruction::GetElementPtr))
422 // Check to see if this ConstantExpr GEP is SRA'able. In particular, we
423 // don't like < 3 operand CE's, and we don't like non-constant integer
424 // indices. This enforces that all uses are 'gep GV, 0, C, ...' for some
426 if (U->getNumOperands() < 3 || !isa<Constant>(U->getOperand(1)) ||
427 !cast<Constant>(U->getOperand(1))->isNullValue() ||
428 !isa<ConstantInt>(U->getOperand(2)))
431 gep_type_iterator GEPI = gep_type_begin(U), E = gep_type_end(U);
432 ++GEPI; // Skip over the pointer index.
434 // If this is a use of an array allocation, do a bit more checking for sanity.
435 if (ArrayType *AT = dyn_cast<ArrayType>(*GEPI)) {
436 uint64_t NumElements = AT->getNumElements();
437 ConstantInt *Idx = cast<ConstantInt>(U->getOperand(2));
439 // Check to make sure that index falls within the array. If not,
440 // something funny is going on, so we won't do the optimization.
442 if (Idx->getZExtValue() >= NumElements)
445 // We cannot scalar repl this level of the array unless any array
446 // sub-indices are in-range constants. In particular, consider:
447 // A[0][i]. We cannot know that the user isn't doing invalid things like
448 // allowing i to index an out-of-range subscript that accesses A[1].
450 // Scalar replacing *just* the outer index of the array is probably not
451 // going to be a win anyway, so just give up.
452 for (++GEPI; // Skip array index.
455 uint64_t NumElements;
456 if (ArrayType *SubArrayTy = dyn_cast<ArrayType>(*GEPI))
457 NumElements = SubArrayTy->getNumElements();
458 else if (VectorType *SubVectorTy = dyn_cast<VectorType>(*GEPI))
459 NumElements = SubVectorTy->getNumElements();
461 assert((*GEPI)->isStructTy() &&
462 "Indexed GEP type is not array, vector, or struct!");
466 ConstantInt *IdxVal = dyn_cast<ConstantInt>(GEPI.getOperand());
467 if (!IdxVal || IdxVal->getZExtValue() >= NumElements)
472 for (Value::use_iterator I = U->use_begin(), E = U->use_end(); I != E; ++I)
473 if (!isSafeSROAElementUse(*I))
478 /// GlobalUsersSafeToSRA - Look at all uses of the global and decide whether it
479 /// is safe for us to perform this transformation.
481 static bool GlobalUsersSafeToSRA(GlobalValue *GV) {
482 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end();
484 if (!IsUserOfGlobalSafeForSRA(*UI, GV))
491 /// SRAGlobal - Perform scalar replacement of aggregates on the specified global
492 /// variable. This opens the door for other optimizations by exposing the
493 /// behavior of the program in a more fine-grained way. We have determined that
494 /// this transformation is safe already. We return the first global variable we
495 /// insert so that the caller can reprocess it.
496 static GlobalVariable *SRAGlobal(GlobalVariable *GV, const TargetData &TD) {
497 // Make sure this global only has simple uses that we can SRA.
498 if (!GlobalUsersSafeToSRA(GV))
501 assert(GV->hasLocalLinkage() && !GV->isConstant());
502 Constant *Init = GV->getInitializer();
503 Type *Ty = Init->getType();
505 std::vector<GlobalVariable*> NewGlobals;
506 Module::GlobalListType &Globals = GV->getParent()->getGlobalList();
508 // Get the alignment of the global, either explicit or target-specific.
509 unsigned StartAlignment = GV->getAlignment();
510 if (StartAlignment == 0)
511 StartAlignment = TD.getABITypeAlignment(GV->getType());
513 if (StructType *STy = dyn_cast<StructType>(Ty)) {
514 NewGlobals.reserve(STy->getNumElements());
515 const StructLayout &Layout = *TD.getStructLayout(STy);
516 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
517 Constant *In = getAggregateConstantElement(Init,
518 ConstantInt::get(Type::getInt32Ty(STy->getContext()), i));
519 assert(In && "Couldn't get element of initializer?");
520 GlobalVariable *NGV = new GlobalVariable(STy->getElementType(i), false,
521 GlobalVariable::InternalLinkage,
522 In, GV->getName()+"."+Twine(i),
524 GV->getType()->getAddressSpace());
525 Globals.insert(GV, NGV);
526 NewGlobals.push_back(NGV);
528 // Calculate the known alignment of the field. If the original aggregate
529 // had 256 byte alignment for example, something might depend on that:
530 // propagate info to each field.
531 uint64_t FieldOffset = Layout.getElementOffset(i);
532 unsigned NewAlign = (unsigned)MinAlign(StartAlignment, FieldOffset);
533 if (NewAlign > TD.getABITypeAlignment(STy->getElementType(i)))
534 NGV->setAlignment(NewAlign);
536 } else if (SequentialType *STy = dyn_cast<SequentialType>(Ty)) {
537 unsigned NumElements = 0;
538 if (ArrayType *ATy = dyn_cast<ArrayType>(STy))
539 NumElements = ATy->getNumElements();
541 NumElements = cast<VectorType>(STy)->getNumElements();
543 if (NumElements > 16 && GV->hasNUsesOrMore(16))
544 return 0; // It's not worth it.
545 NewGlobals.reserve(NumElements);
547 uint64_t EltSize = TD.getTypeAllocSize(STy->getElementType());
548 unsigned EltAlign = TD.getABITypeAlignment(STy->getElementType());
549 for (unsigned i = 0, e = NumElements; i != e; ++i) {
550 Constant *In = getAggregateConstantElement(Init,
551 ConstantInt::get(Type::getInt32Ty(Init->getContext()), i));
552 assert(In && "Couldn't get element of initializer?");
554 GlobalVariable *NGV = new GlobalVariable(STy->getElementType(), false,
555 GlobalVariable::InternalLinkage,
556 In, GV->getName()+"."+Twine(i),
558 GV->getType()->getAddressSpace());
559 Globals.insert(GV, NGV);
560 NewGlobals.push_back(NGV);
562 // Calculate the known alignment of the field. If the original aggregate
563 // had 256 byte alignment for example, something might depend on that:
564 // propagate info to each field.
565 unsigned NewAlign = (unsigned)MinAlign(StartAlignment, EltSize*i);
566 if (NewAlign > EltAlign)
567 NGV->setAlignment(NewAlign);
571 if (NewGlobals.empty())
574 DEBUG(dbgs() << "PERFORMING GLOBAL SRA ON: " << *GV);
576 Constant *NullInt =Constant::getNullValue(Type::getInt32Ty(GV->getContext()));
578 // Loop over all of the uses of the global, replacing the constantexpr geps,
579 // with smaller constantexpr geps or direct references.
580 while (!GV->use_empty()) {
581 User *GEP = GV->use_back();
582 assert(((isa<ConstantExpr>(GEP) &&
583 cast<ConstantExpr>(GEP)->getOpcode()==Instruction::GetElementPtr)||
584 isa<GetElementPtrInst>(GEP)) && "NonGEP CE's are not SRAable!");
586 // Ignore the 1th operand, which has to be zero or else the program is quite
587 // broken (undefined). Get the 2nd operand, which is the structure or array
589 unsigned Val = cast<ConstantInt>(GEP->getOperand(2))->getZExtValue();
590 if (Val >= NewGlobals.size()) Val = 0; // Out of bound array access.
592 Value *NewPtr = NewGlobals[Val];
594 // Form a shorter GEP if needed.
595 if (GEP->getNumOperands() > 3) {
596 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GEP)) {
597 SmallVector<Constant*, 8> Idxs;
598 Idxs.push_back(NullInt);
599 for (unsigned i = 3, e = CE->getNumOperands(); i != e; ++i)
600 Idxs.push_back(CE->getOperand(i));
601 NewPtr = ConstantExpr::getGetElementPtr(cast<Constant>(NewPtr), Idxs);
603 GetElementPtrInst *GEPI = cast<GetElementPtrInst>(GEP);
604 SmallVector<Value*, 8> Idxs;
605 Idxs.push_back(NullInt);
606 for (unsigned i = 3, e = GEPI->getNumOperands(); i != e; ++i)
607 Idxs.push_back(GEPI->getOperand(i));
608 NewPtr = GetElementPtrInst::Create(NewPtr, Idxs,
609 GEPI->getName()+"."+Twine(Val),GEPI);
612 GEP->replaceAllUsesWith(NewPtr);
614 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(GEP))
615 GEPI->eraseFromParent();
617 cast<ConstantExpr>(GEP)->destroyConstant();
620 // Delete the old global, now that it is dead.
624 // Loop over the new globals array deleting any globals that are obviously
625 // dead. This can arise due to scalarization of a structure or an array that
626 // has elements that are dead.
627 unsigned FirstGlobal = 0;
628 for (unsigned i = 0, e = NewGlobals.size(); i != e; ++i)
629 if (NewGlobals[i]->use_empty()) {
630 Globals.erase(NewGlobals[i]);
631 if (FirstGlobal == i) ++FirstGlobal;
634 return FirstGlobal != NewGlobals.size() ? NewGlobals[FirstGlobal] : 0;
637 /// AllUsesOfValueWillTrapIfNull - Return true if all users of the specified
638 /// value will trap if the value is dynamically null. PHIs keeps track of any
639 /// phi nodes we've seen to avoid reprocessing them.
640 static bool AllUsesOfValueWillTrapIfNull(const Value *V,
641 SmallPtrSet<const PHINode*, 8> &PHIs) {
642 for (Value::const_use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;
646 if (isa<LoadInst>(U)) {
648 } else if (const StoreInst *SI = dyn_cast<StoreInst>(U)) {
649 if (SI->getOperand(0) == V) {
650 //cerr << "NONTRAPPING USE: " << *U;
651 return false; // Storing the value.
653 } else if (const CallInst *CI = dyn_cast<CallInst>(U)) {
654 if (CI->getCalledValue() != V) {
655 //cerr << "NONTRAPPING USE: " << *U;
656 return false; // Not calling the ptr
658 } else if (const InvokeInst *II = dyn_cast<InvokeInst>(U)) {
659 if (II->getCalledValue() != V) {
660 //cerr << "NONTRAPPING USE: " << *U;
661 return false; // Not calling the ptr
663 } else if (const BitCastInst *CI = dyn_cast<BitCastInst>(U)) {
664 if (!AllUsesOfValueWillTrapIfNull(CI, PHIs)) return false;
665 } else if (const GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(U)) {
666 if (!AllUsesOfValueWillTrapIfNull(GEPI, PHIs)) return false;
667 } else if (const PHINode *PN = dyn_cast<PHINode>(U)) {
668 // If we've already seen this phi node, ignore it, it has already been
670 if (PHIs.insert(PN) && !AllUsesOfValueWillTrapIfNull(PN, PHIs))
672 } else if (isa<ICmpInst>(U) &&
673 isa<ConstantPointerNull>(UI->getOperand(1))) {
674 // Ignore icmp X, null
676 //cerr << "NONTRAPPING USE: " << *U;
683 /// AllUsesOfLoadedValueWillTrapIfNull - Return true if all uses of any loads
684 /// from GV will trap if the loaded value is null. Note that this also permits
685 /// comparisons of the loaded value against null, as a special case.
686 static bool AllUsesOfLoadedValueWillTrapIfNull(const GlobalVariable *GV) {
687 for (Value::const_use_iterator UI = GV->use_begin(), E = GV->use_end();
691 if (const LoadInst *LI = dyn_cast<LoadInst>(U)) {
692 SmallPtrSet<const PHINode*, 8> PHIs;
693 if (!AllUsesOfValueWillTrapIfNull(LI, PHIs))
695 } else if (isa<StoreInst>(U)) {
696 // Ignore stores to the global.
698 // We don't know or understand this user, bail out.
699 //cerr << "UNKNOWN USER OF GLOBAL!: " << *U;
706 static bool OptimizeAwayTrappingUsesOfValue(Value *V, Constant *NewV) {
707 bool Changed = false;
708 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ) {
709 Instruction *I = cast<Instruction>(*UI++);
710 if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
711 LI->setOperand(0, NewV);
713 } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
714 if (SI->getOperand(1) == V) {
715 SI->setOperand(1, NewV);
718 } else if (isa<CallInst>(I) || isa<InvokeInst>(I)) {
720 if (CS.getCalledValue() == V) {
721 // Calling through the pointer! Turn into a direct call, but be careful
722 // that the pointer is not also being passed as an argument.
723 CS.setCalledFunction(NewV);
725 bool PassedAsArg = false;
726 for (unsigned i = 0, e = CS.arg_size(); i != e; ++i)
727 if (CS.getArgument(i) == V) {
729 CS.setArgument(i, NewV);
733 // Being passed as an argument also. Be careful to not invalidate UI!
737 } else if (CastInst *CI = dyn_cast<CastInst>(I)) {
738 Changed |= OptimizeAwayTrappingUsesOfValue(CI,
739 ConstantExpr::getCast(CI->getOpcode(),
740 NewV, CI->getType()));
741 if (CI->use_empty()) {
743 CI->eraseFromParent();
745 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I)) {
746 // Should handle GEP here.
747 SmallVector<Constant*, 8> Idxs;
748 Idxs.reserve(GEPI->getNumOperands()-1);
749 for (User::op_iterator i = GEPI->op_begin() + 1, e = GEPI->op_end();
751 if (Constant *C = dyn_cast<Constant>(*i))
755 if (Idxs.size() == GEPI->getNumOperands()-1)
756 Changed |= OptimizeAwayTrappingUsesOfValue(GEPI,
757 ConstantExpr::getGetElementPtr(NewV, Idxs));
758 if (GEPI->use_empty()) {
760 GEPI->eraseFromParent();
769 /// OptimizeAwayTrappingUsesOfLoads - The specified global has only one non-null
770 /// value stored into it. If there are uses of the loaded value that would trap
771 /// if the loaded value is dynamically null, then we know that they cannot be
772 /// reachable with a null optimize away the load.
773 static bool OptimizeAwayTrappingUsesOfLoads(GlobalVariable *GV, Constant *LV) {
774 bool Changed = false;
776 // Keep track of whether we are able to remove all the uses of the global
777 // other than the store that defines it.
778 bool AllNonStoreUsesGone = true;
780 // Replace all uses of loads with uses of uses of the stored value.
781 for (Value::use_iterator GUI = GV->use_begin(), E = GV->use_end(); GUI != E;){
782 User *GlobalUser = *GUI++;
783 if (LoadInst *LI = dyn_cast<LoadInst>(GlobalUser)) {
784 Changed |= OptimizeAwayTrappingUsesOfValue(LI, LV);
785 // If we were able to delete all uses of the loads
786 if (LI->use_empty()) {
787 LI->eraseFromParent();
790 AllNonStoreUsesGone = false;
792 } else if (isa<StoreInst>(GlobalUser)) {
793 // Ignore the store that stores "LV" to the global.
794 assert(GlobalUser->getOperand(1) == GV &&
795 "Must be storing *to* the global");
797 AllNonStoreUsesGone = false;
799 // If we get here we could have other crazy uses that are transitively
801 assert((isa<PHINode>(GlobalUser) || isa<SelectInst>(GlobalUser) ||
802 isa<ConstantExpr>(GlobalUser) || isa<CmpInst>(GlobalUser)) &&
803 "Only expect load and stores!");
808 DEBUG(dbgs() << "OPTIMIZED LOADS FROM STORED ONCE POINTER: " << *GV);
812 // If we nuked all of the loads, then none of the stores are needed either,
813 // nor is the global.
814 if (AllNonStoreUsesGone) {
815 DEBUG(dbgs() << " *** GLOBAL NOW DEAD!\n");
816 CleanupConstantGlobalUsers(GV, 0);
817 if (GV->use_empty()) {
818 GV->eraseFromParent();
826 /// ConstantPropUsersOf - Walk the use list of V, constant folding all of the
827 /// instructions that are foldable.
828 static void ConstantPropUsersOf(Value *V) {
829 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; )
830 if (Instruction *I = dyn_cast<Instruction>(*UI++))
831 if (Constant *NewC = ConstantFoldInstruction(I)) {
832 I->replaceAllUsesWith(NewC);
834 // Advance UI to the next non-I use to avoid invalidating it!
835 // Instructions could multiply use V.
836 while (UI != E && *UI == I)
838 I->eraseFromParent();
842 /// OptimizeGlobalAddressOfMalloc - This function takes the specified global
843 /// variable, and transforms the program as if it always contained the result of
844 /// the specified malloc. Because it is always the result of the specified
845 /// malloc, there is no reason to actually DO the malloc. Instead, turn the
846 /// malloc into a global, and any loads of GV as uses of the new global.
847 static GlobalVariable *OptimizeGlobalAddressOfMalloc(GlobalVariable *GV,
850 ConstantInt *NElements,
852 DEBUG(errs() << "PROMOTING GLOBAL: " << *GV << " CALL = " << *CI << '\n');
855 if (NElements->getZExtValue() == 1)
856 GlobalType = AllocTy;
858 // If we have an array allocation, the global variable is of an array.
859 GlobalType = ArrayType::get(AllocTy, NElements->getZExtValue());
861 // Create the new global variable. The contents of the malloc'd memory is
862 // undefined, so initialize with an undef value.
863 GlobalVariable *NewGV = new GlobalVariable(*GV->getParent(),
865 GlobalValue::InternalLinkage,
866 UndefValue::get(GlobalType),
867 GV->getName()+".body",
869 GV->isThreadLocal());
871 // If there are bitcast users of the malloc (which is typical, usually we have
872 // a malloc + bitcast) then replace them with uses of the new global. Update
873 // other users to use the global as well.
874 BitCastInst *TheBC = 0;
875 while (!CI->use_empty()) {
876 Instruction *User = cast<Instruction>(CI->use_back());
877 if (BitCastInst *BCI = dyn_cast<BitCastInst>(User)) {
878 if (BCI->getType() == NewGV->getType()) {
879 BCI->replaceAllUsesWith(NewGV);
880 BCI->eraseFromParent();
882 BCI->setOperand(0, NewGV);
886 TheBC = new BitCastInst(NewGV, CI->getType(), "newgv", CI);
887 User->replaceUsesOfWith(CI, TheBC);
891 Constant *RepValue = NewGV;
892 if (NewGV->getType() != GV->getType()->getElementType())
893 RepValue = ConstantExpr::getBitCast(RepValue,
894 GV->getType()->getElementType());
896 // If there is a comparison against null, we will insert a global bool to
897 // keep track of whether the global was initialized yet or not.
898 GlobalVariable *InitBool =
899 new GlobalVariable(Type::getInt1Ty(GV->getContext()), false,
900 GlobalValue::InternalLinkage,
901 ConstantInt::getFalse(GV->getContext()),
902 GV->getName()+".init", GV->isThreadLocal());
903 bool InitBoolUsed = false;
905 // Loop over all uses of GV, processing them in turn.
906 while (!GV->use_empty()) {
907 if (StoreInst *SI = dyn_cast<StoreInst>(GV->use_back())) {
908 // The global is initialized when the store to it occurs.
909 new StoreInst(ConstantInt::getTrue(GV->getContext()), InitBool, SI);
910 SI->eraseFromParent();
914 LoadInst *LI = cast<LoadInst>(GV->use_back());
915 while (!LI->use_empty()) {
916 Use &LoadUse = LI->use_begin().getUse();
917 if (!isa<ICmpInst>(LoadUse.getUser())) {
922 ICmpInst *ICI = cast<ICmpInst>(LoadUse.getUser());
923 // Replace the cmp X, 0 with a use of the bool value.
924 Value *LV = new LoadInst(InitBool, InitBool->getName()+".val", ICI);
926 switch (ICI->getPredicate()) {
927 default: llvm_unreachable("Unknown ICmp Predicate!");
928 case ICmpInst::ICMP_ULT:
929 case ICmpInst::ICMP_SLT: // X < null -> always false
930 LV = ConstantInt::getFalse(GV->getContext());
932 case ICmpInst::ICMP_ULE:
933 case ICmpInst::ICMP_SLE:
934 case ICmpInst::ICMP_EQ:
935 LV = BinaryOperator::CreateNot(LV, "notinit", ICI);
937 case ICmpInst::ICMP_NE:
938 case ICmpInst::ICMP_UGE:
939 case ICmpInst::ICMP_SGE:
940 case ICmpInst::ICMP_UGT:
941 case ICmpInst::ICMP_SGT:
944 ICI->replaceAllUsesWith(LV);
945 ICI->eraseFromParent();
947 LI->eraseFromParent();
950 // If the initialization boolean was used, insert it, otherwise delete it.
952 while (!InitBool->use_empty()) // Delete initializations
953 cast<StoreInst>(InitBool->use_back())->eraseFromParent();
956 GV->getParent()->getGlobalList().insert(GV, InitBool);
958 // Now the GV is dead, nuke it and the malloc..
959 GV->eraseFromParent();
960 CI->eraseFromParent();
962 // To further other optimizations, loop over all users of NewGV and try to
963 // constant prop them. This will promote GEP instructions with constant
964 // indices into GEP constant-exprs, which will allow global-opt to hack on it.
965 ConstantPropUsersOf(NewGV);
966 if (RepValue != NewGV)
967 ConstantPropUsersOf(RepValue);
972 /// ValueIsOnlyUsedLocallyOrStoredToOneGlobal - Scan the use-list of V checking
973 /// to make sure that there are no complex uses of V. We permit simple things
974 /// like dereferencing the pointer, but not storing through the address, unless
975 /// it is to the specified global.
976 static bool ValueIsOnlyUsedLocallyOrStoredToOneGlobal(const Instruction *V,
977 const GlobalVariable *GV,
978 SmallPtrSet<const PHINode*, 8> &PHIs) {
979 for (Value::const_use_iterator UI = V->use_begin(), E = V->use_end();
981 const Instruction *Inst = cast<Instruction>(*UI);
983 if (isa<LoadInst>(Inst) || isa<CmpInst>(Inst)) {
984 continue; // Fine, ignore.
987 if (const StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
988 if (SI->getOperand(0) == V && SI->getOperand(1) != GV)
989 return false; // Storing the pointer itself... bad.
990 continue; // Otherwise, storing through it, or storing into GV... fine.
993 // Must index into the array and into the struct.
994 if (isa<GetElementPtrInst>(Inst) && Inst->getNumOperands() >= 3) {
995 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(Inst, GV, PHIs))
1000 if (const PHINode *PN = dyn_cast<PHINode>(Inst)) {
1001 // PHIs are ok if all uses are ok. Don't infinitely recurse through PHI
1003 if (PHIs.insert(PN))
1004 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(PN, GV, PHIs))
1009 if (const BitCastInst *BCI = dyn_cast<BitCastInst>(Inst)) {
1010 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(BCI, GV, PHIs))
1020 /// ReplaceUsesOfMallocWithGlobal - The Alloc pointer is stored into GV
1021 /// somewhere. Transform all uses of the allocation into loads from the
1022 /// global and uses of the resultant pointer. Further, delete the store into
1023 /// GV. This assumes that these value pass the
1024 /// 'ValueIsOnlyUsedLocallyOrStoredToOneGlobal' predicate.
1025 static void ReplaceUsesOfMallocWithGlobal(Instruction *Alloc,
1026 GlobalVariable *GV) {
1027 while (!Alloc->use_empty()) {
1028 Instruction *U = cast<Instruction>(*Alloc->use_begin());
1029 Instruction *InsertPt = U;
1030 if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
1031 // If this is the store of the allocation into the global, remove it.
1032 if (SI->getOperand(1) == GV) {
1033 SI->eraseFromParent();
1036 } else if (PHINode *PN = dyn_cast<PHINode>(U)) {
1037 // Insert the load in the corresponding predecessor, not right before the
1039 InsertPt = PN->getIncomingBlock(Alloc->use_begin())->getTerminator();
1040 } else if (isa<BitCastInst>(U)) {
1041 // Must be bitcast between the malloc and store to initialize the global.
1042 ReplaceUsesOfMallocWithGlobal(U, GV);
1043 U->eraseFromParent();
1045 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(U)) {
1046 // If this is a "GEP bitcast" and the user is a store to the global, then
1047 // just process it as a bitcast.
1048 if (GEPI->hasAllZeroIndices() && GEPI->hasOneUse())
1049 if (StoreInst *SI = dyn_cast<StoreInst>(GEPI->use_back()))
1050 if (SI->getOperand(1) == GV) {
1051 // Must be bitcast GEP between the malloc and store to initialize
1053 ReplaceUsesOfMallocWithGlobal(GEPI, GV);
1054 GEPI->eraseFromParent();
1059 // Insert a load from the global, and use it instead of the malloc.
1060 Value *NL = new LoadInst(GV, GV->getName()+".val", InsertPt);
1061 U->replaceUsesOfWith(Alloc, NL);
1065 /// LoadUsesSimpleEnoughForHeapSRA - Verify that all uses of V (a load, or a phi
1066 /// of a load) are simple enough to perform heap SRA on. This permits GEP's
1067 /// that index through the array and struct field, icmps of null, and PHIs.
1068 static bool LoadUsesSimpleEnoughForHeapSRA(const Value *V,
1069 SmallPtrSet<const PHINode*, 32> &LoadUsingPHIs,
1070 SmallPtrSet<const PHINode*, 32> &LoadUsingPHIsPerLoad) {
1071 // We permit two users of the load: setcc comparing against the null
1072 // pointer, and a getelementptr of a specific form.
1073 for (Value::const_use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;
1075 const Instruction *User = cast<Instruction>(*UI);
1077 // Comparison against null is ok.
1078 if (const ICmpInst *ICI = dyn_cast<ICmpInst>(User)) {
1079 if (!isa<ConstantPointerNull>(ICI->getOperand(1)))
1084 // getelementptr is also ok, but only a simple form.
1085 if (const GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
1086 // Must index into the array and into the struct.
1087 if (GEPI->getNumOperands() < 3)
1090 // Otherwise the GEP is ok.
1094 if (const PHINode *PN = dyn_cast<PHINode>(User)) {
1095 if (!LoadUsingPHIsPerLoad.insert(PN))
1096 // This means some phi nodes are dependent on each other.
1097 // Avoid infinite looping!
1099 if (!LoadUsingPHIs.insert(PN))
1100 // If we have already analyzed this PHI, then it is safe.
1103 // Make sure all uses of the PHI are simple enough to transform.
1104 if (!LoadUsesSimpleEnoughForHeapSRA(PN,
1105 LoadUsingPHIs, LoadUsingPHIsPerLoad))
1111 // Otherwise we don't know what this is, not ok.
1119 /// AllGlobalLoadUsesSimpleEnoughForHeapSRA - If all users of values loaded from
1120 /// GV are simple enough to perform HeapSRA, return true.
1121 static bool AllGlobalLoadUsesSimpleEnoughForHeapSRA(const GlobalVariable *GV,
1122 Instruction *StoredVal) {
1123 SmallPtrSet<const PHINode*, 32> LoadUsingPHIs;
1124 SmallPtrSet<const PHINode*, 32> LoadUsingPHIsPerLoad;
1125 for (Value::const_use_iterator UI = GV->use_begin(), E = GV->use_end();
1127 if (const LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
1128 if (!LoadUsesSimpleEnoughForHeapSRA(LI, LoadUsingPHIs,
1129 LoadUsingPHIsPerLoad))
1131 LoadUsingPHIsPerLoad.clear();
1134 // If we reach here, we know that all uses of the loads and transitive uses
1135 // (through PHI nodes) are simple enough to transform. However, we don't know
1136 // that all inputs the to the PHI nodes are in the same equivalence sets.
1137 // Check to verify that all operands of the PHIs are either PHIS that can be
1138 // transformed, loads from GV, or MI itself.
1139 for (SmallPtrSet<const PHINode*, 32>::const_iterator I = LoadUsingPHIs.begin()
1140 , E = LoadUsingPHIs.end(); I != E; ++I) {
1141 const PHINode *PN = *I;
1142 for (unsigned op = 0, e = PN->getNumIncomingValues(); op != e; ++op) {
1143 Value *InVal = PN->getIncomingValue(op);
1145 // PHI of the stored value itself is ok.
1146 if (InVal == StoredVal) continue;
1148 if (const PHINode *InPN = dyn_cast<PHINode>(InVal)) {
1149 // One of the PHIs in our set is (optimistically) ok.
1150 if (LoadUsingPHIs.count(InPN))
1155 // Load from GV is ok.
1156 if (const LoadInst *LI = dyn_cast<LoadInst>(InVal))
1157 if (LI->getOperand(0) == GV)
1162 // Anything else is rejected.
1170 static Value *GetHeapSROAValue(Value *V, unsigned FieldNo,
1171 DenseMap<Value*, std::vector<Value*> > &InsertedScalarizedValues,
1172 std::vector<std::pair<PHINode*, unsigned> > &PHIsToRewrite) {
1173 std::vector<Value*> &FieldVals = InsertedScalarizedValues[V];
1175 if (FieldNo >= FieldVals.size())
1176 FieldVals.resize(FieldNo+1);
1178 // If we already have this value, just reuse the previously scalarized
1180 if (Value *FieldVal = FieldVals[FieldNo])
1183 // Depending on what instruction this is, we have several cases.
1185 if (LoadInst *LI = dyn_cast<LoadInst>(V)) {
1186 // This is a scalarized version of the load from the global. Just create
1187 // a new Load of the scalarized global.
1188 Result = new LoadInst(GetHeapSROAValue(LI->getOperand(0), FieldNo,
1189 InsertedScalarizedValues,
1191 LI->getName()+".f"+Twine(FieldNo), LI);
1192 } else if (PHINode *PN = dyn_cast<PHINode>(V)) {
1193 // PN's type is pointer to struct. Make a new PHI of pointer to struct
1196 cast<StructType>(cast<PointerType>(PN->getType())->getElementType());
1199 PHINode::Create(PointerType::getUnqual(ST->getElementType(FieldNo)),
1200 PN->getNumIncomingValues(),
1201 PN->getName()+".f"+Twine(FieldNo), PN);
1203 PHIsToRewrite.push_back(std::make_pair(PN, FieldNo));
1205 llvm_unreachable("Unknown usable value");
1209 return FieldVals[FieldNo] = Result;
1212 /// RewriteHeapSROALoadUser - Given a load instruction and a value derived from
1213 /// the load, rewrite the derived value to use the HeapSRoA'd load.
1214 static void RewriteHeapSROALoadUser(Instruction *LoadUser,
1215 DenseMap<Value*, std::vector<Value*> > &InsertedScalarizedValues,
1216 std::vector<std::pair<PHINode*, unsigned> > &PHIsToRewrite) {
1217 // If this is a comparison against null, handle it.
1218 if (ICmpInst *SCI = dyn_cast<ICmpInst>(LoadUser)) {
1219 assert(isa<ConstantPointerNull>(SCI->getOperand(1)));
1220 // If we have a setcc of the loaded pointer, we can use a setcc of any
1222 Value *NPtr = GetHeapSROAValue(SCI->getOperand(0), 0,
1223 InsertedScalarizedValues, PHIsToRewrite);
1225 Value *New = new ICmpInst(SCI, SCI->getPredicate(), NPtr,
1226 Constant::getNullValue(NPtr->getType()),
1228 SCI->replaceAllUsesWith(New);
1229 SCI->eraseFromParent();
1233 // Handle 'getelementptr Ptr, Idx, i32 FieldNo ...'
1234 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(LoadUser)) {
1235 assert(GEPI->getNumOperands() >= 3 && isa<ConstantInt>(GEPI->getOperand(2))
1236 && "Unexpected GEPI!");
1238 // Load the pointer for this field.
1239 unsigned FieldNo = cast<ConstantInt>(GEPI->getOperand(2))->getZExtValue();
1240 Value *NewPtr = GetHeapSROAValue(GEPI->getOperand(0), FieldNo,
1241 InsertedScalarizedValues, PHIsToRewrite);
1243 // Create the new GEP idx vector.
1244 SmallVector<Value*, 8> GEPIdx;
1245 GEPIdx.push_back(GEPI->getOperand(1));
1246 GEPIdx.append(GEPI->op_begin()+3, GEPI->op_end());
1248 Value *NGEPI = GetElementPtrInst::Create(NewPtr, GEPIdx,
1249 GEPI->getName(), GEPI);
1250 GEPI->replaceAllUsesWith(NGEPI);
1251 GEPI->eraseFromParent();
1255 // Recursively transform the users of PHI nodes. This will lazily create the
1256 // PHIs that are needed for individual elements. Keep track of what PHIs we
1257 // see in InsertedScalarizedValues so that we don't get infinite loops (very
1258 // antisocial). If the PHI is already in InsertedScalarizedValues, it has
1259 // already been seen first by another load, so its uses have already been
1261 PHINode *PN = cast<PHINode>(LoadUser);
1262 if (!InsertedScalarizedValues.insert(std::make_pair(PN,
1263 std::vector<Value*>())).second)
1266 // If this is the first time we've seen this PHI, recursively process all
1268 for (Value::use_iterator UI = PN->use_begin(), E = PN->use_end(); UI != E; ) {
1269 Instruction *User = cast<Instruction>(*UI++);
1270 RewriteHeapSROALoadUser(User, InsertedScalarizedValues, PHIsToRewrite);
1274 /// RewriteUsesOfLoadForHeapSRoA - We are performing Heap SRoA on a global. Ptr
1275 /// is a value loaded from the global. Eliminate all uses of Ptr, making them
1276 /// use FieldGlobals instead. All uses of loaded values satisfy
1277 /// AllGlobalLoadUsesSimpleEnoughForHeapSRA.
1278 static void RewriteUsesOfLoadForHeapSRoA(LoadInst *Load,
1279 DenseMap<Value*, std::vector<Value*> > &InsertedScalarizedValues,
1280 std::vector<std::pair<PHINode*, unsigned> > &PHIsToRewrite) {
1281 for (Value::use_iterator UI = Load->use_begin(), E = Load->use_end();
1283 Instruction *User = cast<Instruction>(*UI++);
1284 RewriteHeapSROALoadUser(User, InsertedScalarizedValues, PHIsToRewrite);
1287 if (Load->use_empty()) {
1288 Load->eraseFromParent();
1289 InsertedScalarizedValues.erase(Load);
1293 /// PerformHeapAllocSRoA - CI is an allocation of an array of structures. Break
1294 /// it up into multiple allocations of arrays of the fields.
1295 static GlobalVariable *PerformHeapAllocSRoA(GlobalVariable *GV, CallInst *CI,
1296 Value* NElems, TargetData *TD) {
1297 DEBUG(dbgs() << "SROA HEAP ALLOC: " << *GV << " MALLOC = " << *CI << '\n');
1298 Type* MAT = getMallocAllocatedType(CI);
1299 StructType *STy = cast<StructType>(MAT);
1301 // There is guaranteed to be at least one use of the malloc (storing
1302 // it into GV). If there are other uses, change them to be uses of
1303 // the global to simplify later code. This also deletes the store
1305 ReplaceUsesOfMallocWithGlobal(CI, GV);
1307 // Okay, at this point, there are no users of the malloc. Insert N
1308 // new mallocs at the same place as CI, and N globals.
1309 std::vector<Value*> FieldGlobals;
1310 std::vector<Value*> FieldMallocs;
1312 for (unsigned FieldNo = 0, e = STy->getNumElements(); FieldNo != e;++FieldNo){
1313 Type *FieldTy = STy->getElementType(FieldNo);
1314 PointerType *PFieldTy = PointerType::getUnqual(FieldTy);
1316 GlobalVariable *NGV =
1317 new GlobalVariable(*GV->getParent(),
1318 PFieldTy, false, GlobalValue::InternalLinkage,
1319 Constant::getNullValue(PFieldTy),
1320 GV->getName() + ".f" + Twine(FieldNo), GV,
1321 GV->isThreadLocal());
1322 FieldGlobals.push_back(NGV);
1324 unsigned TypeSize = TD->getTypeAllocSize(FieldTy);
1325 if (StructType *ST = dyn_cast<StructType>(FieldTy))
1326 TypeSize = TD->getStructLayout(ST)->getSizeInBytes();
1327 Type *IntPtrTy = TD->getIntPtrType(CI->getContext());
1328 Value *NMI = CallInst::CreateMalloc(CI, IntPtrTy, FieldTy,
1329 ConstantInt::get(IntPtrTy, TypeSize),
1331 CI->getName() + ".f" + Twine(FieldNo));
1332 FieldMallocs.push_back(NMI);
1333 new StoreInst(NMI, NGV, CI);
1336 // The tricky aspect of this transformation is handling the case when malloc
1337 // fails. In the original code, malloc failing would set the result pointer
1338 // of malloc to null. In this case, some mallocs could succeed and others
1339 // could fail. As such, we emit code that looks like this:
1340 // F0 = malloc(field0)
1341 // F1 = malloc(field1)
1342 // F2 = malloc(field2)
1343 // if (F0 == 0 || F1 == 0 || F2 == 0) {
1344 // if (F0) { free(F0); F0 = 0; }
1345 // if (F1) { free(F1); F1 = 0; }
1346 // if (F2) { free(F2); F2 = 0; }
1348 // The malloc can also fail if its argument is too large.
1349 Constant *ConstantZero = ConstantInt::get(CI->getArgOperand(0)->getType(), 0);
1350 Value *RunningOr = new ICmpInst(CI, ICmpInst::ICMP_SLT, CI->getArgOperand(0),
1351 ConstantZero, "isneg");
1352 for (unsigned i = 0, e = FieldMallocs.size(); i != e; ++i) {
1353 Value *Cond = new ICmpInst(CI, ICmpInst::ICMP_EQ, FieldMallocs[i],
1354 Constant::getNullValue(FieldMallocs[i]->getType()),
1356 RunningOr = BinaryOperator::CreateOr(RunningOr, Cond, "tmp", CI);
1359 // Split the basic block at the old malloc.
1360 BasicBlock *OrigBB = CI->getParent();
1361 BasicBlock *ContBB = OrigBB->splitBasicBlock(CI, "malloc_cont");
1363 // Create the block to check the first condition. Put all these blocks at the
1364 // end of the function as they are unlikely to be executed.
1365 BasicBlock *NullPtrBlock = BasicBlock::Create(OrigBB->getContext(),
1367 OrigBB->getParent());
1369 // Remove the uncond branch from OrigBB to ContBB, turning it into a cond
1370 // branch on RunningOr.
1371 OrigBB->getTerminator()->eraseFromParent();
1372 BranchInst::Create(NullPtrBlock, ContBB, RunningOr, OrigBB);
1374 // Within the NullPtrBlock, we need to emit a comparison and branch for each
1375 // pointer, because some may be null while others are not.
1376 for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) {
1377 Value *GVVal = new LoadInst(FieldGlobals[i], "tmp", NullPtrBlock);
1378 Value *Cmp = new ICmpInst(*NullPtrBlock, ICmpInst::ICMP_NE, GVVal,
1379 Constant::getNullValue(GVVal->getType()),
1381 BasicBlock *FreeBlock = BasicBlock::Create(Cmp->getContext(), "free_it",
1382 OrigBB->getParent());
1383 BasicBlock *NextBlock = BasicBlock::Create(Cmp->getContext(), "next",
1384 OrigBB->getParent());
1385 Instruction *BI = BranchInst::Create(FreeBlock, NextBlock,
1388 // Fill in FreeBlock.
1389 CallInst::CreateFree(GVVal, BI);
1390 new StoreInst(Constant::getNullValue(GVVal->getType()), FieldGlobals[i],
1392 BranchInst::Create(NextBlock, FreeBlock);
1394 NullPtrBlock = NextBlock;
1397 BranchInst::Create(ContBB, NullPtrBlock);
1399 // CI is no longer needed, remove it.
1400 CI->eraseFromParent();
1402 /// InsertedScalarizedLoads - As we process loads, if we can't immediately
1403 /// update all uses of the load, keep track of what scalarized loads are
1404 /// inserted for a given load.
1405 DenseMap<Value*, std::vector<Value*> > InsertedScalarizedValues;
1406 InsertedScalarizedValues[GV] = FieldGlobals;
1408 std::vector<std::pair<PHINode*, unsigned> > PHIsToRewrite;
1410 // Okay, the malloc site is completely handled. All of the uses of GV are now
1411 // loads, and all uses of those loads are simple. Rewrite them to use loads
1412 // of the per-field globals instead.
1413 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); UI != E;) {
1414 Instruction *User = cast<Instruction>(*UI++);
1416 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1417 RewriteUsesOfLoadForHeapSRoA(LI, InsertedScalarizedValues, PHIsToRewrite);
1421 // Must be a store of null.
1422 StoreInst *SI = cast<StoreInst>(User);
1423 assert(isa<ConstantPointerNull>(SI->getOperand(0)) &&
1424 "Unexpected heap-sra user!");
1426 // Insert a store of null into each global.
1427 for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) {
1428 PointerType *PT = cast<PointerType>(FieldGlobals[i]->getType());
1429 Constant *Null = Constant::getNullValue(PT->getElementType());
1430 new StoreInst(Null, FieldGlobals[i], SI);
1432 // Erase the original store.
1433 SI->eraseFromParent();
1436 // While we have PHIs that are interesting to rewrite, do it.
1437 while (!PHIsToRewrite.empty()) {
1438 PHINode *PN = PHIsToRewrite.back().first;
1439 unsigned FieldNo = PHIsToRewrite.back().second;
1440 PHIsToRewrite.pop_back();
1441 PHINode *FieldPN = cast<PHINode>(InsertedScalarizedValues[PN][FieldNo]);
1442 assert(FieldPN->getNumIncomingValues() == 0 &&"Already processed this phi");
1444 // Add all the incoming values. This can materialize more phis.
1445 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
1446 Value *InVal = PN->getIncomingValue(i);
1447 InVal = GetHeapSROAValue(InVal, FieldNo, InsertedScalarizedValues,
1449 FieldPN->addIncoming(InVal, PN->getIncomingBlock(i));
1453 // Drop all inter-phi links and any loads that made it this far.
1454 for (DenseMap<Value*, std::vector<Value*> >::iterator
1455 I = InsertedScalarizedValues.begin(), E = InsertedScalarizedValues.end();
1457 if (PHINode *PN = dyn_cast<PHINode>(I->first))
1458 PN->dropAllReferences();
1459 else if (LoadInst *LI = dyn_cast<LoadInst>(I->first))
1460 LI->dropAllReferences();
1463 // Delete all the phis and loads now that inter-references are dead.
1464 for (DenseMap<Value*, std::vector<Value*> >::iterator
1465 I = InsertedScalarizedValues.begin(), E = InsertedScalarizedValues.end();
1467 if (PHINode *PN = dyn_cast<PHINode>(I->first))
1468 PN->eraseFromParent();
1469 else if (LoadInst *LI = dyn_cast<LoadInst>(I->first))
1470 LI->eraseFromParent();
1473 // The old global is now dead, remove it.
1474 GV->eraseFromParent();
1477 return cast<GlobalVariable>(FieldGlobals[0]);
1480 /// TryToOptimizeStoreOfMallocToGlobal - This function is called when we see a
1481 /// pointer global variable with a single value stored it that is a malloc or
1483 static bool TryToOptimizeStoreOfMallocToGlobal(GlobalVariable *GV,
1486 Module::global_iterator &GVI,
1491 // If this is a malloc of an abstract type, don't touch it.
1492 if (!AllocTy->isSized())
1495 // We can't optimize this global unless all uses of it are *known* to be
1496 // of the malloc value, not of the null initializer value (consider a use
1497 // that compares the global's value against zero to see if the malloc has
1498 // been reached). To do this, we check to see if all uses of the global
1499 // would trap if the global were null: this proves that they must all
1500 // happen after the malloc.
1501 if (!AllUsesOfLoadedValueWillTrapIfNull(GV))
1504 // We can't optimize this if the malloc itself is used in a complex way,
1505 // for example, being stored into multiple globals. This allows the
1506 // malloc to be stored into the specified global, loaded setcc'd, and
1507 // GEP'd. These are all things we could transform to using the global
1509 SmallPtrSet<const PHINode*, 8> PHIs;
1510 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(CI, GV, PHIs))
1513 // If we have a global that is only initialized with a fixed size malloc,
1514 // transform the program to use global memory instead of malloc'd memory.
1515 // This eliminates dynamic allocation, avoids an indirection accessing the
1516 // data, and exposes the resultant global to further GlobalOpt.
1517 // We cannot optimize the malloc if we cannot determine malloc array size.
1518 Value *NElems = getMallocArraySize(CI, TD, true);
1522 if (ConstantInt *NElements = dyn_cast<ConstantInt>(NElems))
1523 // Restrict this transformation to only working on small allocations
1524 // (2048 bytes currently), as we don't want to introduce a 16M global or
1526 if (NElements->getZExtValue() * TD->getTypeAllocSize(AllocTy) < 2048) {
1527 GVI = OptimizeGlobalAddressOfMalloc(GV, CI, AllocTy, NElements, TD);
1531 // If the allocation is an array of structures, consider transforming this
1532 // into multiple malloc'd arrays, one for each field. This is basically
1533 // SRoA for malloc'd memory.
1535 // If this is an allocation of a fixed size array of structs, analyze as a
1536 // variable size array. malloc [100 x struct],1 -> malloc struct, 100
1537 if (NElems == ConstantInt::get(CI->getArgOperand(0)->getType(), 1))
1538 if (ArrayType *AT = dyn_cast<ArrayType>(AllocTy))
1539 AllocTy = AT->getElementType();
1541 StructType *AllocSTy = dyn_cast<StructType>(AllocTy);
1545 // This the structure has an unreasonable number of fields, leave it
1547 if (AllocSTy->getNumElements() <= 16 && AllocSTy->getNumElements() != 0 &&
1548 AllGlobalLoadUsesSimpleEnoughForHeapSRA(GV, CI)) {
1550 // If this is a fixed size array, transform the Malloc to be an alloc of
1551 // structs. malloc [100 x struct],1 -> malloc struct, 100
1552 if (ArrayType *AT = dyn_cast<ArrayType>(getMallocAllocatedType(CI))) {
1553 Type *IntPtrTy = TD->getIntPtrType(CI->getContext());
1554 unsigned TypeSize = TD->getStructLayout(AllocSTy)->getSizeInBytes();
1555 Value *AllocSize = ConstantInt::get(IntPtrTy, TypeSize);
1556 Value *NumElements = ConstantInt::get(IntPtrTy, AT->getNumElements());
1557 Instruction *Malloc = CallInst::CreateMalloc(CI, IntPtrTy, AllocSTy,
1558 AllocSize, NumElements,
1560 Instruction *Cast = new BitCastInst(Malloc, CI->getType(), "tmp", CI);
1561 CI->replaceAllUsesWith(Cast);
1562 CI->eraseFromParent();
1563 CI = dyn_cast<BitCastInst>(Malloc) ?
1564 extractMallocCallFromBitCast(Malloc) : cast<CallInst>(Malloc);
1567 GVI = PerformHeapAllocSRoA(GV, CI, getMallocArraySize(CI, TD, true),TD);
1574 // OptimizeOnceStoredGlobal - Try to optimize globals based on the knowledge
1575 // that only one value (besides its initializer) is ever stored to the global.
1576 static bool OptimizeOnceStoredGlobal(GlobalVariable *GV, Value *StoredOnceVal,
1577 Module::global_iterator &GVI,
1579 // Ignore no-op GEPs and bitcasts.
1580 StoredOnceVal = StoredOnceVal->stripPointerCasts();
1582 // If we are dealing with a pointer global that is initialized to null and
1583 // only has one (non-null) value stored into it, then we can optimize any
1584 // users of the loaded value (often calls and loads) that would trap if the
1586 if (GV->getInitializer()->getType()->isPointerTy() &&
1587 GV->getInitializer()->isNullValue()) {
1588 if (Constant *SOVC = dyn_cast<Constant>(StoredOnceVal)) {
1589 if (GV->getInitializer()->getType() != SOVC->getType())
1590 SOVC = ConstantExpr::getBitCast(SOVC, GV->getInitializer()->getType());
1592 // Optimize away any trapping uses of the loaded value.
1593 if (OptimizeAwayTrappingUsesOfLoads(GV, SOVC))
1595 } else if (CallInst *CI = extractMallocCall(StoredOnceVal)) {
1596 Type* MallocType = getMallocAllocatedType(CI);
1597 if (MallocType && TryToOptimizeStoreOfMallocToGlobal(GV, CI, MallocType,
1606 /// TryToShrinkGlobalToBoolean - At this point, we have learned that the only
1607 /// two values ever stored into GV are its initializer and OtherVal. See if we
1608 /// can shrink the global into a boolean and select between the two values
1609 /// whenever it is used. This exposes the values to other scalar optimizations.
1610 static bool TryToShrinkGlobalToBoolean(GlobalVariable *GV, Constant *OtherVal) {
1611 Type *GVElType = GV->getType()->getElementType();
1613 // If GVElType is already i1, it is already shrunk. If the type of the GV is
1614 // an FP value, pointer or vector, don't do this optimization because a select
1615 // between them is very expensive and unlikely to lead to later
1616 // simplification. In these cases, we typically end up with "cond ? v1 : v2"
1617 // where v1 and v2 both require constant pool loads, a big loss.
1618 if (GVElType == Type::getInt1Ty(GV->getContext()) ||
1619 GVElType->isFloatingPointTy() ||
1620 GVElType->isPointerTy() || GVElType->isVectorTy())
1623 // Walk the use list of the global seeing if all the uses are load or store.
1624 // If there is anything else, bail out.
1625 for (Value::use_iterator I = GV->use_begin(), E = GV->use_end(); I != E; ++I){
1627 if (!isa<LoadInst>(U) && !isa<StoreInst>(U))
1631 DEBUG(dbgs() << " *** SHRINKING TO BOOL: " << *GV);
1633 // Create the new global, initializing it to false.
1634 GlobalVariable *NewGV = new GlobalVariable(Type::getInt1Ty(GV->getContext()),
1636 GlobalValue::InternalLinkage,
1637 ConstantInt::getFalse(GV->getContext()),
1639 GV->isThreadLocal());
1640 GV->getParent()->getGlobalList().insert(GV, NewGV);
1642 Constant *InitVal = GV->getInitializer();
1643 assert(InitVal->getType() != Type::getInt1Ty(GV->getContext()) &&
1644 "No reason to shrink to bool!");
1646 // If initialized to zero and storing one into the global, we can use a cast
1647 // instead of a select to synthesize the desired value.
1648 bool IsOneZero = false;
1649 if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal))
1650 IsOneZero = InitVal->isNullValue() && CI->isOne();
1652 while (!GV->use_empty()) {
1653 Instruction *UI = cast<Instruction>(GV->use_back());
1654 if (StoreInst *SI = dyn_cast<StoreInst>(UI)) {
1655 // Change the store into a boolean store.
1656 bool StoringOther = SI->getOperand(0) == OtherVal;
1657 // Only do this if we weren't storing a loaded value.
1659 if (StoringOther || SI->getOperand(0) == InitVal)
1660 StoreVal = ConstantInt::get(Type::getInt1Ty(GV->getContext()),
1663 // Otherwise, we are storing a previously loaded copy. To do this,
1664 // change the copy from copying the original value to just copying the
1666 Instruction *StoredVal = cast<Instruction>(SI->getOperand(0));
1668 // If we've already replaced the input, StoredVal will be a cast or
1669 // select instruction. If not, it will be a load of the original
1671 if (LoadInst *LI = dyn_cast<LoadInst>(StoredVal)) {
1672 assert(LI->getOperand(0) == GV && "Not a copy!");
1673 // Insert a new load, to preserve the saved value.
1674 StoreVal = new LoadInst(NewGV, LI->getName()+".b", LI);
1676 assert((isa<CastInst>(StoredVal) || isa<SelectInst>(StoredVal)) &&
1677 "This is not a form that we understand!");
1678 StoreVal = StoredVal->getOperand(0);
1679 assert(isa<LoadInst>(StoreVal) && "Not a load of NewGV!");
1682 new StoreInst(StoreVal, NewGV, SI);
1684 // Change the load into a load of bool then a select.
1685 LoadInst *LI = cast<LoadInst>(UI);
1686 LoadInst *NLI = new LoadInst(NewGV, LI->getName()+".b", LI);
1689 NSI = new ZExtInst(NLI, LI->getType(), "", LI);
1691 NSI = SelectInst::Create(NLI, OtherVal, InitVal, "", LI);
1693 LI->replaceAllUsesWith(NSI);
1695 UI->eraseFromParent();
1698 GV->eraseFromParent();
1703 /// ProcessInternalGlobal - Analyze the specified global variable and optimize
1704 /// it if possible. If we make a change, return true.
1705 bool GlobalOpt::ProcessGlobal(GlobalVariable *GV,
1706 Module::global_iterator &GVI) {
1707 if (!GV->hasLocalLinkage())
1710 // Do more involved optimizations if the global is internal.
1711 GV->removeDeadConstantUsers();
1713 if (GV->use_empty()) {
1714 DEBUG(dbgs() << "GLOBAL DEAD: " << *GV);
1715 GV->eraseFromParent();
1720 SmallPtrSet<const PHINode*, 16> PHIUsers;
1723 if (AnalyzeGlobal(GV, GS, PHIUsers))
1726 if (!GS.isCompared && !GV->hasUnnamedAddr()) {
1727 GV->setUnnamedAddr(true);
1731 if (GV->isConstant() || !GV->hasInitializer())
1734 return ProcessInternalGlobal(GV, GVI, PHIUsers, GS);
1737 /// ProcessInternalGlobal - Analyze the specified global variable and optimize
1738 /// it if possible. If we make a change, return true.
1739 bool GlobalOpt::ProcessInternalGlobal(GlobalVariable *GV,
1740 Module::global_iterator &GVI,
1741 const SmallPtrSet<const PHINode*, 16> &PHIUsers,
1742 const GlobalStatus &GS) {
1743 // If this is a first class global and has only one accessing function
1744 // and this function is main (which we know is not recursive we can make
1745 // this global a local variable) we replace the global with a local alloca
1746 // in this function.
1748 // NOTE: It doesn't make sense to promote non single-value types since we
1749 // are just replacing static memory to stack memory.
1751 // If the global is in different address space, don't bring it to stack.
1752 if (!GS.HasMultipleAccessingFunctions &&
1753 GS.AccessingFunction && !GS.HasNonInstructionUser &&
1754 GV->getType()->getElementType()->isSingleValueType() &&
1755 GS.AccessingFunction->getName() == "main" &&
1756 GS.AccessingFunction->hasExternalLinkage() &&
1757 GV->getType()->getAddressSpace() == 0) {
1758 DEBUG(dbgs() << "LOCALIZING GLOBAL: " << *GV);
1759 Instruction& FirstI = const_cast<Instruction&>(*GS.AccessingFunction
1760 ->getEntryBlock().begin());
1761 Type* ElemTy = GV->getType()->getElementType();
1762 // FIXME: Pass Global's alignment when globals have alignment
1763 AllocaInst* Alloca = new AllocaInst(ElemTy, NULL, GV->getName(), &FirstI);
1764 if (!isa<UndefValue>(GV->getInitializer()))
1765 new StoreInst(GV->getInitializer(), Alloca, &FirstI);
1767 GV->replaceAllUsesWith(Alloca);
1768 GV->eraseFromParent();
1773 // If the global is never loaded (but may be stored to), it is dead.
1776 DEBUG(dbgs() << "GLOBAL NEVER LOADED: " << *GV);
1778 // Delete any stores we can find to the global. We may not be able to
1779 // make it completely dead though.
1780 bool Changed = CleanupConstantGlobalUsers(GV, GV->getInitializer());
1782 // If the global is dead now, delete it.
1783 if (GV->use_empty()) {
1784 GV->eraseFromParent();
1790 } else if (GS.StoredType <= GlobalStatus::isInitializerStored) {
1791 DEBUG(dbgs() << "MARKING CONSTANT: " << *GV);
1792 GV->setConstant(true);
1794 // Clean up any obviously simplifiable users now.
1795 CleanupConstantGlobalUsers(GV, GV->getInitializer());
1797 // If the global is dead now, just nuke it.
1798 if (GV->use_empty()) {
1799 DEBUG(dbgs() << " *** Marking constant allowed us to simplify "
1800 << "all users and delete global!\n");
1801 GV->eraseFromParent();
1807 } else if (!GV->getInitializer()->getType()->isSingleValueType()) {
1808 if (TargetData *TD = getAnalysisIfAvailable<TargetData>())
1809 if (GlobalVariable *FirstNewGV = SRAGlobal(GV, *TD)) {
1810 GVI = FirstNewGV; // Don't skip the newly produced globals!
1813 } else if (GS.StoredType == GlobalStatus::isStoredOnce) {
1814 // If the initial value for the global was an undef value, and if only
1815 // one other value was stored into it, we can just change the
1816 // initializer to be the stored value, then delete all stores to the
1817 // global. This allows us to mark it constant.
1818 if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue))
1819 if (isa<UndefValue>(GV->getInitializer())) {
1820 // Change the initial value here.
1821 GV->setInitializer(SOVConstant);
1823 // Clean up any obviously simplifiable users now.
1824 CleanupConstantGlobalUsers(GV, GV->getInitializer());
1826 if (GV->use_empty()) {
1827 DEBUG(dbgs() << " *** Substituting initializer allowed us to "
1828 << "simplify all users and delete global!\n");
1829 GV->eraseFromParent();
1838 // Try to optimize globals based on the knowledge that only one value
1839 // (besides its initializer) is ever stored to the global.
1840 if (OptimizeOnceStoredGlobal(GV, GS.StoredOnceValue, GVI,
1841 getAnalysisIfAvailable<TargetData>()))
1844 // Otherwise, if the global was not a boolean, we can shrink it to be a
1846 if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue))
1847 if (TryToShrinkGlobalToBoolean(GV, SOVConstant)) {
1856 /// ChangeCalleesToFastCall - Walk all of the direct calls of the specified
1857 /// function, changing them to FastCC.
1858 static void ChangeCalleesToFastCall(Function *F) {
1859 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){
1860 CallSite User(cast<Instruction>(*UI));
1861 User.setCallingConv(CallingConv::Fast);
1865 static AttrListPtr StripNest(const AttrListPtr &Attrs) {
1866 for (unsigned i = 0, e = Attrs.getNumSlots(); i != e; ++i) {
1867 if ((Attrs.getSlot(i).Attrs & Attribute::Nest) == 0)
1870 // There can be only one.
1871 return Attrs.removeAttr(Attrs.getSlot(i).Index, Attribute::Nest);
1877 static void RemoveNestAttribute(Function *F) {
1878 F->setAttributes(StripNest(F->getAttributes()));
1879 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){
1880 CallSite User(cast<Instruction>(*UI));
1881 User.setAttributes(StripNest(User.getAttributes()));
1885 bool GlobalOpt::OptimizeFunctions(Module &M) {
1886 bool Changed = false;
1887 // Optimize functions.
1888 for (Module::iterator FI = M.begin(), E = M.end(); FI != E; ) {
1890 // Functions without names cannot be referenced outside this module.
1891 if (!F->hasName() && !F->isDeclaration())
1892 F->setLinkage(GlobalValue::InternalLinkage);
1893 F->removeDeadConstantUsers();
1894 if (F->use_empty() && (F->hasLocalLinkage() || F->hasLinkOnceLinkage())) {
1895 F->eraseFromParent();
1898 } else if (F->hasLocalLinkage()) {
1899 if (F->getCallingConv() == CallingConv::C && !F->isVarArg() &&
1900 !F->hasAddressTaken()) {
1901 // If this function has C calling conventions, is not a varargs
1902 // function, and is only called directly, promote it to use the Fast
1903 // calling convention.
1904 F->setCallingConv(CallingConv::Fast);
1905 ChangeCalleesToFastCall(F);
1910 if (F->getAttributes().hasAttrSomewhere(Attribute::Nest) &&
1911 !F->hasAddressTaken()) {
1912 // The function is not used by a trampoline intrinsic, so it is safe
1913 // to remove the 'nest' attribute.
1914 RemoveNestAttribute(F);
1923 bool GlobalOpt::OptimizeGlobalVars(Module &M) {
1924 bool Changed = false;
1925 for (Module::global_iterator GVI = M.global_begin(), E = M.global_end();
1927 GlobalVariable *GV = GVI++;
1928 // Global variables without names cannot be referenced outside this module.
1929 if (!GV->hasName() && !GV->isDeclaration())
1930 GV->setLinkage(GlobalValue::InternalLinkage);
1931 // Simplify the initializer.
1932 if (GV->hasInitializer())
1933 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GV->getInitializer())) {
1934 TargetData *TD = getAnalysisIfAvailable<TargetData>();
1935 Constant *New = ConstantFoldConstantExpression(CE, TD);
1936 if (New && New != CE)
1937 GV->setInitializer(New);
1940 Changed |= ProcessGlobal(GV, GVI);
1945 /// FindGlobalCtors - Find the llvm.global_ctors list, verifying that all
1946 /// initializers have an init priority of 65535.
1947 GlobalVariable *GlobalOpt::FindGlobalCtors(Module &M) {
1948 GlobalVariable *GV = M.getGlobalVariable("llvm.global_ctors");
1949 if (GV == 0) return 0;
1951 // Verify that the initializer is simple enough for us to handle. We are
1952 // only allowed to optimize the initializer if it is unique.
1953 if (!GV->hasUniqueInitializer()) return 0;
1955 if (isa<ConstantAggregateZero>(GV->getInitializer()))
1957 ConstantArray *CA = cast<ConstantArray>(GV->getInitializer());
1959 for (User::op_iterator i = CA->op_begin(), e = CA->op_end(); i != e; ++i) {
1960 if (isa<ConstantAggregateZero>(*i))
1962 ConstantStruct *CS = cast<ConstantStruct>(*i);
1963 if (isa<ConstantPointerNull>(CS->getOperand(1)))
1966 // Must have a function or null ptr.
1967 if (!isa<Function>(CS->getOperand(1)))
1970 // Init priority must be standard.
1971 ConstantInt *CI = cast<ConstantInt>(CS->getOperand(0));
1972 if (CI->getZExtValue() != 65535)
1979 /// ParseGlobalCtors - Given a llvm.global_ctors list that we can understand,
1980 /// return a list of the functions and null terminator as a vector.
1981 static std::vector<Function*> ParseGlobalCtors(GlobalVariable *GV) {
1982 if (GV->getInitializer()->isNullValue())
1983 return std::vector<Function*>();
1984 ConstantArray *CA = cast<ConstantArray>(GV->getInitializer());
1985 std::vector<Function*> Result;
1986 Result.reserve(CA->getNumOperands());
1987 for (User::op_iterator i = CA->op_begin(), e = CA->op_end(); i != e; ++i) {
1988 ConstantStruct *CS = cast<ConstantStruct>(*i);
1989 Result.push_back(dyn_cast<Function>(CS->getOperand(1)));
1994 /// InstallGlobalCtors - Given a specified llvm.global_ctors list, install the
1995 /// specified array, returning the new global to use.
1996 static GlobalVariable *InstallGlobalCtors(GlobalVariable *GCL,
1997 const std::vector<Function*> &Ctors) {
1998 // If we made a change, reassemble the initializer list.
1999 Constant *CSVals[2];
2000 CSVals[0] = ConstantInt::get(Type::getInt32Ty(GCL->getContext()), 65535);
2003 StructType *StructTy =
2005 cast<ArrayType>(GCL->getType()->getElementType())->getElementType());
2007 // Create the new init list.
2008 std::vector<Constant*> CAList;
2009 for (unsigned i = 0, e = Ctors.size(); i != e; ++i) {
2011 CSVals[1] = Ctors[i];
2013 Type *FTy = FunctionType::get(Type::getVoidTy(GCL->getContext()),
2015 PointerType *PFTy = PointerType::getUnqual(FTy);
2016 CSVals[1] = Constant::getNullValue(PFTy);
2017 CSVals[0] = ConstantInt::get(Type::getInt32Ty(GCL->getContext()),
2020 CAList.push_back(ConstantStruct::get(StructTy, CSVals));
2023 // Create the array initializer.
2024 Constant *CA = ConstantArray::get(ArrayType::get(StructTy,
2025 CAList.size()), CAList);
2027 // If we didn't change the number of elements, don't create a new GV.
2028 if (CA->getType() == GCL->getInitializer()->getType()) {
2029 GCL->setInitializer(CA);
2033 // Create the new global and insert it next to the existing list.
2034 GlobalVariable *NGV = new GlobalVariable(CA->getType(), GCL->isConstant(),
2035 GCL->getLinkage(), CA, "",
2036 GCL->isThreadLocal());
2037 GCL->getParent()->getGlobalList().insert(GCL, NGV);
2040 // Nuke the old list, replacing any uses with the new one.
2041 if (!GCL->use_empty()) {
2043 if (V->getType() != GCL->getType())
2044 V = ConstantExpr::getBitCast(V, GCL->getType());
2045 GCL->replaceAllUsesWith(V);
2047 GCL->eraseFromParent();
2056 static Constant *getVal(DenseMap<Value*, Constant*> &ComputedValues, Value *V) {
2057 if (Constant *CV = dyn_cast<Constant>(V)) return CV;
2058 Constant *R = ComputedValues[V];
2059 assert(R && "Reference to an uncomputed value!");
2064 isSimpleEnoughValueToCommit(Constant *C,
2065 SmallPtrSet<Constant*, 8> &SimpleConstants);
2068 /// isSimpleEnoughValueToCommit - Return true if the specified constant can be
2069 /// handled by the code generator. We don't want to generate something like:
2070 /// void *X = &X/42;
2071 /// because the code generator doesn't have a relocation that can handle that.
2073 /// This function should be called if C was not found (but just got inserted)
2074 /// in SimpleConstants to avoid having to rescan the same constants all the
2076 static bool isSimpleEnoughValueToCommitHelper(Constant *C,
2077 SmallPtrSet<Constant*, 8> &SimpleConstants) {
2078 // Simple integer, undef, constant aggregate zero, global addresses, etc are
2080 if (C->getNumOperands() == 0 || isa<BlockAddress>(C) ||
2081 isa<GlobalValue>(C))
2084 // Aggregate values are safe if all their elements are.
2085 if (isa<ConstantArray>(C) || isa<ConstantStruct>(C) ||
2086 isa<ConstantVector>(C)) {
2087 for (unsigned i = 0, e = C->getNumOperands(); i != e; ++i) {
2088 Constant *Op = cast<Constant>(C->getOperand(i));
2089 if (!isSimpleEnoughValueToCommit(Op, SimpleConstants))
2095 // We don't know exactly what relocations are allowed in constant expressions,
2096 // so we allow &global+constantoffset, which is safe and uniformly supported
2098 ConstantExpr *CE = cast<ConstantExpr>(C);
2099 switch (CE->getOpcode()) {
2100 case Instruction::BitCast:
2101 case Instruction::IntToPtr:
2102 case Instruction::PtrToInt:
2103 // These casts are always fine if the casted value is.
2104 return isSimpleEnoughValueToCommit(CE->getOperand(0), SimpleConstants);
2106 // GEP is fine if it is simple + constant offset.
2107 case Instruction::GetElementPtr:
2108 for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i)
2109 if (!isa<ConstantInt>(CE->getOperand(i)))
2111 return isSimpleEnoughValueToCommit(CE->getOperand(0), SimpleConstants);
2113 case Instruction::Add:
2114 // We allow simple+cst.
2115 if (!isa<ConstantInt>(CE->getOperand(1)))
2117 return isSimpleEnoughValueToCommit(CE->getOperand(0), SimpleConstants);
2123 isSimpleEnoughValueToCommit(Constant *C,
2124 SmallPtrSet<Constant*, 8> &SimpleConstants) {
2125 // If we already checked this constant, we win.
2126 if (!SimpleConstants.insert(C)) return true;
2127 // Check the constant.
2128 return isSimpleEnoughValueToCommitHelper(C, SimpleConstants);
2132 /// isSimpleEnoughPointerToCommit - Return true if this constant is simple
2133 /// enough for us to understand. In particular, if it is a cast to anything
2134 /// other than from one pointer type to another pointer type, we punt.
2135 /// We basically just support direct accesses to globals and GEP's of
2136 /// globals. This should be kept up to date with CommitValueTo.
2137 static bool isSimpleEnoughPointerToCommit(Constant *C) {
2138 // Conservatively, avoid aggregate types. This is because we don't
2139 // want to worry about them partially overlapping other stores.
2140 if (!cast<PointerType>(C->getType())->getElementType()->isSingleValueType())
2143 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C))
2144 // Do not allow weak/*_odr/linkonce/dllimport/dllexport linkage or
2145 // external globals.
2146 return GV->hasUniqueInitializer();
2148 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) {
2149 // Handle a constantexpr gep.
2150 if (CE->getOpcode() == Instruction::GetElementPtr &&
2151 isa<GlobalVariable>(CE->getOperand(0)) &&
2152 cast<GEPOperator>(CE)->isInBounds()) {
2153 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
2154 // Do not allow weak/*_odr/linkonce/dllimport/dllexport linkage or
2155 // external globals.
2156 if (!GV->hasUniqueInitializer())
2159 // The first index must be zero.
2160 ConstantInt *CI = dyn_cast<ConstantInt>(*llvm::next(CE->op_begin()));
2161 if (!CI || !CI->isZero()) return false;
2163 // The remaining indices must be compile-time known integers within the
2164 // notional bounds of the corresponding static array types.
2165 if (!CE->isGEPWithNoNotionalOverIndexing())
2168 return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE);
2170 // A constantexpr bitcast from a pointer to another pointer is a no-op,
2171 // and we know how to evaluate it by moving the bitcast from the pointer
2172 // operand to the value operand.
2173 } else if (CE->getOpcode() == Instruction::BitCast &&
2174 isa<GlobalVariable>(CE->getOperand(0))) {
2175 // Do not allow weak/*_odr/linkonce/dllimport/dllexport linkage or
2176 // external globals.
2177 return cast<GlobalVariable>(CE->getOperand(0))->hasUniqueInitializer();
2184 /// EvaluateStoreInto - Evaluate a piece of a constantexpr store into a global
2185 /// initializer. This returns 'Init' modified to reflect 'Val' stored into it.
2186 /// At this point, the GEP operands of Addr [0, OpNo) have been stepped into.
2187 static Constant *EvaluateStoreInto(Constant *Init, Constant *Val,
2188 ConstantExpr *Addr, unsigned OpNo) {
2189 // Base case of the recursion.
2190 if (OpNo == Addr->getNumOperands()) {
2191 assert(Val->getType() == Init->getType() && "Type mismatch!");
2195 std::vector<Constant*> Elts;
2196 if (StructType *STy = dyn_cast<StructType>(Init->getType())) {
2198 // Break up the constant into its elements.
2199 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(Init)) {
2200 for (User::op_iterator i = CS->op_begin(), e = CS->op_end(); i != e; ++i)
2201 Elts.push_back(cast<Constant>(*i));
2202 } else if (isa<ConstantAggregateZero>(Init)) {
2203 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
2204 Elts.push_back(Constant::getNullValue(STy->getElementType(i)));
2205 } else if (isa<UndefValue>(Init)) {
2206 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
2207 Elts.push_back(UndefValue::get(STy->getElementType(i)));
2209 llvm_unreachable("This code is out of sync with "
2210 " ConstantFoldLoadThroughGEPConstantExpr");
2213 // Replace the element that we are supposed to.
2214 ConstantInt *CU = cast<ConstantInt>(Addr->getOperand(OpNo));
2215 unsigned Idx = CU->getZExtValue();
2216 assert(Idx < STy->getNumElements() && "Struct index out of range!");
2217 Elts[Idx] = EvaluateStoreInto(Elts[Idx], Val, Addr, OpNo+1);
2219 // Return the modified struct.
2220 return ConstantStruct::get(STy, Elts);
2223 ConstantInt *CI = cast<ConstantInt>(Addr->getOperand(OpNo));
2224 SequentialType *InitTy = cast<SequentialType>(Init->getType());
2227 if (ArrayType *ATy = dyn_cast<ArrayType>(InitTy))
2228 NumElts = ATy->getNumElements();
2230 NumElts = cast<VectorType>(InitTy)->getNumElements();
2232 // Break up the array into elements.
2233 if (ConstantArray *CA = dyn_cast<ConstantArray>(Init)) {
2234 for (User::op_iterator i = CA->op_begin(), e = CA->op_end(); i != e; ++i)
2235 Elts.push_back(cast<Constant>(*i));
2236 } else if (ConstantVector *CV = dyn_cast<ConstantVector>(Init)) {
2237 for (User::op_iterator i = CV->op_begin(), e = CV->op_end(); i != e; ++i)
2238 Elts.push_back(cast<Constant>(*i));
2239 } else if (isa<ConstantAggregateZero>(Init)) {
2240 Elts.assign(NumElts, Constant::getNullValue(InitTy->getElementType()));
2242 assert(isa<UndefValue>(Init) && "This code is out of sync with "
2243 " ConstantFoldLoadThroughGEPConstantExpr");
2244 Elts.assign(NumElts, UndefValue::get(InitTy->getElementType()));
2247 assert(CI->getZExtValue() < NumElts);
2248 Elts[CI->getZExtValue()] =
2249 EvaluateStoreInto(Elts[CI->getZExtValue()], Val, Addr, OpNo+1);
2251 if (Init->getType()->isArrayTy())
2252 return ConstantArray::get(cast<ArrayType>(InitTy), Elts);
2253 return ConstantVector::get(Elts);
2256 /// CommitValueTo - We have decided that Addr (which satisfies the predicate
2257 /// isSimpleEnoughPointerToCommit) should get Val as its value. Make it happen.
2258 static void CommitValueTo(Constant *Val, Constant *Addr) {
2259 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Addr)) {
2260 assert(GV->hasInitializer());
2261 GV->setInitializer(Val);
2265 ConstantExpr *CE = cast<ConstantExpr>(Addr);
2266 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
2267 GV->setInitializer(EvaluateStoreInto(GV->getInitializer(), Val, CE, 2));
2270 /// ComputeLoadResult - Return the value that would be computed by a load from
2271 /// P after the stores reflected by 'memory' have been performed. If we can't
2272 /// decide, return null.
2273 static Constant *ComputeLoadResult(Constant *P,
2274 const DenseMap<Constant*, Constant*> &Memory) {
2275 // If this memory location has been recently stored, use the stored value: it
2276 // is the most up-to-date.
2277 DenseMap<Constant*, Constant*>::const_iterator I = Memory.find(P);
2278 if (I != Memory.end()) return I->second;
2281 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(P)) {
2282 if (GV->hasDefinitiveInitializer())
2283 return GV->getInitializer();
2287 // Handle a constantexpr getelementptr.
2288 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(P))
2289 if (CE->getOpcode() == Instruction::GetElementPtr &&
2290 isa<GlobalVariable>(CE->getOperand(0))) {
2291 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
2292 if (GV->hasDefinitiveInitializer())
2293 return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE);
2296 return 0; // don't know how to evaluate.
2299 /// EvaluateFunction - Evaluate a call to function F, returning true if
2300 /// successful, false if we can't evaluate it. ActualArgs contains the formal
2301 /// arguments for the function.
2302 static bool EvaluateFunction(Function *F, Constant *&RetVal,
2303 const SmallVectorImpl<Constant*> &ActualArgs,
2304 std::vector<Function*> &CallStack,
2305 DenseMap<Constant*, Constant*> &MutatedMemory,
2306 std::vector<GlobalVariable*> &AllocaTmps,
2307 SmallPtrSet<Constant*, 8> &SimpleConstants,
2308 const TargetData *TD) {
2309 // Check to see if this function is already executing (recursion). If so,
2310 // bail out. TODO: we might want to accept limited recursion.
2311 if (std::find(CallStack.begin(), CallStack.end(), F) != CallStack.end())
2314 CallStack.push_back(F);
2316 /// Values - As we compute SSA register values, we store their contents here.
2317 DenseMap<Value*, Constant*> Values;
2319 // Initialize arguments to the incoming values specified.
2321 for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end(); AI != E;
2323 Values[AI] = ActualArgs[ArgNo];
2325 /// ExecutedBlocks - We only handle non-looping, non-recursive code. As such,
2326 /// we can only evaluate any one basic block at most once. This set keeps
2327 /// track of what we have executed so we can detect recursive cases etc.
2328 SmallPtrSet<BasicBlock*, 32> ExecutedBlocks;
2330 // CurInst - The current instruction we're evaluating.
2331 BasicBlock::iterator CurInst = F->begin()->begin();
2333 // This is the main evaluation loop.
2335 Constant *InstResult = 0;
2337 if (StoreInst *SI = dyn_cast<StoreInst>(CurInst)) {
2338 if (!SI->isSimple()) return false; // no volatile/atomic accesses.
2339 Constant *Ptr = getVal(Values, SI->getOperand(1));
2340 if (!isSimpleEnoughPointerToCommit(Ptr))
2341 // If this is too complex for us to commit, reject it.
2344 Constant *Val = getVal(Values, SI->getOperand(0));
2346 // If this might be too difficult for the backend to handle (e.g. the addr
2347 // of one global variable divided by another) then we can't commit it.
2348 if (!isSimpleEnoughValueToCommit(Val, SimpleConstants))
2351 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr))
2352 if (CE->getOpcode() == Instruction::BitCast) {
2353 // If we're evaluating a store through a bitcast, then we need
2354 // to pull the bitcast off the pointer type and push it onto the
2356 Ptr = CE->getOperand(0);
2358 Type *NewTy=cast<PointerType>(Ptr->getType())->getElementType();
2360 // In order to push the bitcast onto the stored value, a bitcast
2361 // from NewTy to Val's type must be legal. If it's not, we can try
2362 // introspecting NewTy to find a legal conversion.
2363 while (!Val->getType()->canLosslesslyBitCastTo(NewTy)) {
2364 // If NewTy is a struct, we can convert the pointer to the struct
2365 // into a pointer to its first member.
2366 // FIXME: This could be extended to support arrays as well.
2367 if (StructType *STy = dyn_cast<StructType>(NewTy)) {
2368 NewTy = STy->getTypeAtIndex(0U);
2370 IntegerType *IdxTy =IntegerType::get(NewTy->getContext(), 32);
2371 Constant *IdxZero = ConstantInt::get(IdxTy, 0, false);
2372 Constant * const IdxList[] = {IdxZero, IdxZero};
2374 Ptr = ConstantExpr::getGetElementPtr(Ptr, IdxList);
2376 // If we can't improve the situation by introspecting NewTy,
2377 // we have to give up.
2383 // If we found compatible types, go ahead and push the bitcast
2384 // onto the stored value.
2385 Val = ConstantExpr::getBitCast(Val, NewTy);
2388 MutatedMemory[Ptr] = Val;
2389 } else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(CurInst)) {
2390 InstResult = ConstantExpr::get(BO->getOpcode(),
2391 getVal(Values, BO->getOperand(0)),
2392 getVal(Values, BO->getOperand(1)));
2393 } else if (CmpInst *CI = dyn_cast<CmpInst>(CurInst)) {
2394 InstResult = ConstantExpr::getCompare(CI->getPredicate(),
2395 getVal(Values, CI->getOperand(0)),
2396 getVal(Values, CI->getOperand(1)));
2397 } else if (CastInst *CI = dyn_cast<CastInst>(CurInst)) {
2398 InstResult = ConstantExpr::getCast(CI->getOpcode(),
2399 getVal(Values, CI->getOperand(0)),
2401 } else if (SelectInst *SI = dyn_cast<SelectInst>(CurInst)) {
2402 InstResult = ConstantExpr::getSelect(getVal(Values, SI->getOperand(0)),
2403 getVal(Values, SI->getOperand(1)),
2404 getVal(Values, SI->getOperand(2)));
2405 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(CurInst)) {
2406 Constant *P = getVal(Values, GEP->getOperand(0));
2407 SmallVector<Constant*, 8> GEPOps;
2408 for (User::op_iterator i = GEP->op_begin() + 1, e = GEP->op_end();
2410 GEPOps.push_back(getVal(Values, *i));
2412 ConstantExpr::getGetElementPtr(P, GEPOps,
2413 cast<GEPOperator>(GEP)->isInBounds());
2414 } else if (LoadInst *LI = dyn_cast<LoadInst>(CurInst)) {
2415 if (!LI->isSimple()) return false; // no volatile/atomic accesses.
2416 InstResult = ComputeLoadResult(getVal(Values, LI->getOperand(0)),
2418 if (InstResult == 0) return false; // Could not evaluate load.
2419 } else if (AllocaInst *AI = dyn_cast<AllocaInst>(CurInst)) {
2420 if (AI->isArrayAllocation()) return false; // Cannot handle array allocs.
2421 Type *Ty = AI->getType()->getElementType();
2422 AllocaTmps.push_back(new GlobalVariable(Ty, false,
2423 GlobalValue::InternalLinkage,
2424 UndefValue::get(Ty),
2426 InstResult = AllocaTmps.back();
2427 } else if (CallInst *CI = dyn_cast<CallInst>(CurInst)) {
2429 // Debug info can safely be ignored here.
2430 if (isa<DbgInfoIntrinsic>(CI)) {
2435 // Cannot handle inline asm.
2436 if (isa<InlineAsm>(CI->getCalledValue())) return false;
2438 if (MemSetInst *MSI = dyn_cast<MemSetInst>(CI)) {
2439 if (MSI->isVolatile()) return false;
2440 Constant *Ptr = getVal(Values, MSI->getDest());
2441 Constant *Val = getVal(Values, MSI->getValue());
2442 Constant *DestVal = ComputeLoadResult(getVal(Values, Ptr),
2444 if (Val->isNullValue() && DestVal && DestVal->isNullValue()) {
2445 // This memset is a no-op.
2452 // Resolve function pointers.
2453 Function *Callee = dyn_cast<Function>(getVal(Values,
2454 CI->getCalledValue()));
2455 if (!Callee) return false; // Cannot resolve.
2457 SmallVector<Constant*, 8> Formals;
2459 for (User::op_iterator i = CS.arg_begin(), e = CS.arg_end();
2461 Formals.push_back(getVal(Values, *i));
2463 if (Callee->isDeclaration()) {
2464 // If this is a function we can constant fold, do it.
2465 if (Constant *C = ConstantFoldCall(Callee, Formals)) {
2471 if (Callee->getFunctionType()->isVarArg())
2475 // Execute the call, if successful, use the return value.
2476 if (!EvaluateFunction(Callee, RetVal, Formals, CallStack,
2477 MutatedMemory, AllocaTmps, SimpleConstants, TD))
2479 InstResult = RetVal;
2481 } else if (isa<TerminatorInst>(CurInst)) {
2482 BasicBlock *NewBB = 0;
2483 if (BranchInst *BI = dyn_cast<BranchInst>(CurInst)) {
2484 if (BI->isUnconditional()) {
2485 NewBB = BI->getSuccessor(0);
2488 dyn_cast<ConstantInt>(getVal(Values, BI->getCondition()));
2489 if (!Cond) return false; // Cannot determine.
2491 NewBB = BI->getSuccessor(!Cond->getZExtValue());
2493 } else if (SwitchInst *SI = dyn_cast<SwitchInst>(CurInst)) {
2495 dyn_cast<ConstantInt>(getVal(Values, SI->getCondition()));
2496 if (!Val) return false; // Cannot determine.
2497 NewBB = SI->getSuccessor(SI->findCaseValue(Val));
2498 } else if (IndirectBrInst *IBI = dyn_cast<IndirectBrInst>(CurInst)) {
2499 Value *Val = getVal(Values, IBI->getAddress())->stripPointerCasts();
2500 if (BlockAddress *BA = dyn_cast<BlockAddress>(Val))
2501 NewBB = BA->getBasicBlock();
2503 return false; // Cannot determine.
2504 } else if (ReturnInst *RI = dyn_cast<ReturnInst>(CurInst)) {
2505 if (RI->getNumOperands())
2506 RetVal = getVal(Values, RI->getOperand(0));
2508 CallStack.pop_back(); // return from fn.
2509 return true; // We succeeded at evaluating this ctor!
2511 // invoke, unwind, resume, unreachable.
2512 return false; // Cannot handle this terminator.
2515 // Okay, we succeeded in evaluating this control flow. See if we have
2516 // executed the new block before. If so, we have a looping function,
2517 // which we cannot evaluate in reasonable time.
2518 if (!ExecutedBlocks.insert(NewBB))
2519 return false; // looped!
2521 // Okay, we have never been in this block before. Check to see if there
2522 // are any PHI nodes. If so, evaluate them with information about where
2524 BasicBlock *OldBB = CurInst->getParent();
2525 CurInst = NewBB->begin();
2527 for (; (PN = dyn_cast<PHINode>(CurInst)); ++CurInst)
2528 Values[PN] = getVal(Values, PN->getIncomingValueForBlock(OldBB));
2530 // Do NOT increment CurInst. We know that the terminator had no value.
2533 // Did not know how to evaluate this!
2537 if (!CurInst->use_empty()) {
2538 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(InstResult))
2539 InstResult = ConstantFoldConstantExpression(CE, TD);
2541 Values[CurInst] = InstResult;
2544 // Advance program counter.
2549 /// EvaluateStaticConstructor - Evaluate static constructors in the function, if
2550 /// we can. Return true if we can, false otherwise.
2551 static bool EvaluateStaticConstructor(Function *F, const TargetData *TD) {
2552 /// MutatedMemory - For each store we execute, we update this map. Loads
2553 /// check this to get the most up-to-date value. If evaluation is successful,
2554 /// this state is committed to the process.
2555 DenseMap<Constant*, Constant*> MutatedMemory;
2557 /// AllocaTmps - To 'execute' an alloca, we create a temporary global variable
2558 /// to represent its body. This vector is needed so we can delete the
2559 /// temporary globals when we are done.
2560 std::vector<GlobalVariable*> AllocaTmps;
2562 /// CallStack - This is used to detect recursion. In pathological situations
2563 /// we could hit exponential behavior, but at least there is nothing
2565 std::vector<Function*> CallStack;
2567 /// SimpleConstants - These are constants we have checked and know to be
2568 /// simple enough to live in a static initializer of a global.
2569 SmallPtrSet<Constant*, 8> SimpleConstants;
2571 // Call the function.
2572 Constant *RetValDummy;
2573 bool EvalSuccess = EvaluateFunction(F, RetValDummy,
2574 SmallVector<Constant*, 0>(), CallStack,
2575 MutatedMemory, AllocaTmps,
2576 SimpleConstants, TD);
2579 // We succeeded at evaluation: commit the result.
2580 DEBUG(dbgs() << "FULLY EVALUATED GLOBAL CTOR FUNCTION '"
2581 << F->getName() << "' to " << MutatedMemory.size()
2583 for (DenseMap<Constant*, Constant*>::iterator I = MutatedMemory.begin(),
2584 E = MutatedMemory.end(); I != E; ++I)
2585 CommitValueTo(I->second, I->first);
2588 // At this point, we are done interpreting. If we created any 'alloca'
2589 // temporaries, release them now.
2590 while (!AllocaTmps.empty()) {
2591 GlobalVariable *Tmp = AllocaTmps.back();
2592 AllocaTmps.pop_back();
2594 // If there are still users of the alloca, the program is doing something
2595 // silly, e.g. storing the address of the alloca somewhere and using it
2596 // later. Since this is undefined, we'll just make it be null.
2597 if (!Tmp->use_empty())
2598 Tmp->replaceAllUsesWith(Constant::getNullValue(Tmp->getType()));
2607 /// OptimizeGlobalCtorsList - Simplify and evaluation global ctors if possible.
2608 /// Return true if anything changed.
2609 bool GlobalOpt::OptimizeGlobalCtorsList(GlobalVariable *&GCL) {
2610 std::vector<Function*> Ctors = ParseGlobalCtors(GCL);
2611 bool MadeChange = false;
2612 if (Ctors.empty()) return false;
2614 const TargetData *TD = getAnalysisIfAvailable<TargetData>();
2615 // Loop over global ctors, optimizing them when we can.
2616 for (unsigned i = 0; i != Ctors.size(); ++i) {
2617 Function *F = Ctors[i];
2618 // Found a null terminator in the middle of the list, prune off the rest of
2621 if (i != Ctors.size()-1) {
2628 // We cannot simplify external ctor functions.
2629 if (F->empty()) continue;
2631 // If we can evaluate the ctor at compile time, do.
2632 if (EvaluateStaticConstructor(F, TD)) {
2633 Ctors.erase(Ctors.begin()+i);
2636 ++NumCtorsEvaluated;
2641 if (!MadeChange) return false;
2643 GCL = InstallGlobalCtors(GCL, Ctors);
2647 bool GlobalOpt::OptimizeGlobalAliases(Module &M) {
2648 bool Changed = false;
2650 for (Module::alias_iterator I = M.alias_begin(), E = M.alias_end();
2652 Module::alias_iterator J = I++;
2653 // Aliases without names cannot be referenced outside this module.
2654 if (!J->hasName() && !J->isDeclaration())
2655 J->setLinkage(GlobalValue::InternalLinkage);
2656 // If the aliasee may change at link time, nothing can be done - bail out.
2657 if (J->mayBeOverridden())
2660 Constant *Aliasee = J->getAliasee();
2661 GlobalValue *Target = cast<GlobalValue>(Aliasee->stripPointerCasts());
2662 Target->removeDeadConstantUsers();
2663 bool hasOneUse = Target->hasOneUse() && Aliasee->hasOneUse();
2665 // Make all users of the alias use the aliasee instead.
2666 if (!J->use_empty()) {
2667 J->replaceAllUsesWith(Aliasee);
2668 ++NumAliasesResolved;
2672 // If the alias is externally visible, we may still be able to simplify it.
2673 if (!J->hasLocalLinkage()) {
2674 // If the aliasee has internal linkage, give it the name and linkage
2675 // of the alias, and delete the alias. This turns:
2676 // define internal ... @f(...)
2677 // @a = alias ... @f
2679 // define ... @a(...)
2680 if (!Target->hasLocalLinkage())
2683 // Do not perform the transform if multiple aliases potentially target the
2684 // aliasee. This check also ensures that it is safe to replace the section
2685 // and other attributes of the aliasee with those of the alias.
2689 // Give the aliasee the name, linkage and other attributes of the alias.
2690 Target->takeName(J);
2691 Target->setLinkage(J->getLinkage());
2692 Target->GlobalValue::copyAttributesFrom(J);
2695 // Delete the alias.
2696 M.getAliasList().erase(J);
2697 ++NumAliasesRemoved;
2704 static Function *FindCXAAtExit(Module &M) {
2705 Function *Fn = M.getFunction("__cxa_atexit");
2710 FunctionType *FTy = Fn->getFunctionType();
2712 // Checking that the function has the right return type, the right number of
2713 // parameters and that they all have pointer types should be enough.
2714 if (!FTy->getReturnType()->isIntegerTy() ||
2715 FTy->getNumParams() != 3 ||
2716 !FTy->getParamType(0)->isPointerTy() ||
2717 !FTy->getParamType(1)->isPointerTy() ||
2718 !FTy->getParamType(2)->isPointerTy())
2724 /// cxxDtorIsEmpty - Returns whether the given function is an empty C++
2725 /// destructor and can therefore be eliminated.
2726 /// Note that we assume that other optimization passes have already simplified
2727 /// the code so we only look for a function with a single basic block, where
2728 /// the only allowed instructions are 'ret' or 'call' to empty C++ dtor.
2729 static bool cxxDtorIsEmpty(const Function &Fn,
2730 SmallPtrSet<const Function *, 8> &CalledFunctions) {
2731 // FIXME: We could eliminate C++ destructors if they're readonly/readnone and
2732 // nounwind, but that doesn't seem worth doing.
2733 if (Fn.isDeclaration())
2736 if (++Fn.begin() != Fn.end())
2739 const BasicBlock &EntryBlock = Fn.getEntryBlock();
2740 for (BasicBlock::const_iterator I = EntryBlock.begin(), E = EntryBlock.end();
2742 if (const CallInst *CI = dyn_cast<CallInst>(I)) {
2743 // Ignore debug intrinsics.
2744 if (isa<DbgInfoIntrinsic>(CI))
2747 const Function *CalledFn = CI->getCalledFunction();
2752 SmallPtrSet<const Function *, 8> NewCalledFunctions(CalledFunctions);
2754 // Don't treat recursive functions as empty.
2755 if (!NewCalledFunctions.insert(CalledFn))
2758 if (!cxxDtorIsEmpty(*CalledFn, NewCalledFunctions))
2760 } else if (isa<ReturnInst>(*I))
2769 bool GlobalOpt::OptimizeEmptyGlobalCXXDtors(Function *CXAAtExitFn) {
2770 /// Itanium C++ ABI p3.3.5:
2772 /// After constructing a global (or local static) object, that will require
2773 /// destruction on exit, a termination function is registered as follows:
2775 /// extern "C" int __cxa_atexit ( void (*f)(void *), void *p, void *d );
2777 /// This registration, e.g. __cxa_atexit(f,p,d), is intended to cause the
2778 /// call f(p) when DSO d is unloaded, before all such termination calls
2779 /// registered before this one. It returns zero if registration is
2780 /// successful, nonzero on failure.
2782 // This pass will look for calls to __cxa_atexit where the function is trivial
2784 bool Changed = false;
2786 for (Function::use_iterator I = CXAAtExitFn->use_begin(),
2787 E = CXAAtExitFn->use_end(); I != E;) {
2788 // We're only interested in calls. Theoretically, we could handle invoke
2789 // instructions as well, but neither llvm-gcc nor clang generate invokes
2791 CallInst *CI = dyn_cast<CallInst>(*I++);
2796 dyn_cast<Function>(CI->getArgOperand(0)->stripPointerCasts());
2800 SmallPtrSet<const Function *, 8> CalledFunctions;
2801 if (!cxxDtorIsEmpty(*DtorFn, CalledFunctions))
2804 // Just remove the call.
2805 CI->replaceAllUsesWith(Constant::getNullValue(CI->getType()));
2806 CI->eraseFromParent();
2808 ++NumCXXDtorsRemoved;
2816 bool GlobalOpt::runOnModule(Module &M) {
2817 bool Changed = false;
2819 // Try to find the llvm.globalctors list.
2820 GlobalVariable *GlobalCtors = FindGlobalCtors(M);
2822 Function *CXAAtExitFn = FindCXAAtExit(M);
2824 bool LocalChange = true;
2825 while (LocalChange) {
2826 LocalChange = false;
2828 // Delete functions that are trivially dead, ccc -> fastcc
2829 LocalChange |= OptimizeFunctions(M);
2831 // Optimize global_ctors list.
2833 LocalChange |= OptimizeGlobalCtorsList(GlobalCtors);
2835 // Optimize non-address-taken globals.
2836 LocalChange |= OptimizeGlobalVars(M);
2838 // Resolve aliases, when possible.
2839 LocalChange |= OptimizeGlobalAliases(M);
2841 // Try to remove trivial global destructors.
2843 LocalChange |= OptimizeEmptyGlobalCXXDtors(CXAAtExitFn);
2845 Changed |= LocalChange;
2848 // TODO: Move all global ctors functions to the end of the module for code