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/Pass.h"
25 #include "llvm/Analysis/ConstantFolding.h"
26 #include "llvm/Analysis/MemoryBuiltins.h"
27 #include "llvm/Target/TargetData.h"
28 #include "llvm/Support/CallSite.h"
29 #include "llvm/Support/Debug.h"
30 #include "llvm/Support/ErrorHandling.h"
31 #include "llvm/Support/GetElementPtrTypeIterator.h"
32 #include "llvm/Support/MathExtras.h"
33 #include "llvm/Support/raw_ostream.h"
34 #include "llvm/ADT/DenseMap.h"
35 #include "llvm/ADT/SmallPtrSet.h"
36 #include "llvm/ADT/SmallVector.h"
37 #include "llvm/ADT/Statistic.h"
38 #include "llvm/ADT/STLExtras.h"
42 STATISTIC(NumMarked , "Number of globals marked constant");
43 STATISTIC(NumSRA , "Number of aggregate globals broken into scalars");
44 STATISTIC(NumHeapSRA , "Number of heap objects SRA'd");
45 STATISTIC(NumSubstitute,"Number of globals with initializers stored into them");
46 STATISTIC(NumDeleted , "Number of globals deleted");
47 STATISTIC(NumFnDeleted , "Number of functions deleted");
48 STATISTIC(NumGlobUses , "Number of global uses devirtualized");
49 STATISTIC(NumLocalized , "Number of globals localized");
50 STATISTIC(NumShrunkToBool , "Number of global vars shrunk to booleans");
51 STATISTIC(NumFastCallFns , "Number of functions converted to fastcc");
52 STATISTIC(NumCtorsEvaluated, "Number of static ctors evaluated");
53 STATISTIC(NumNestRemoved , "Number of nest attributes removed");
54 STATISTIC(NumAliasesResolved, "Number of global aliases resolved");
55 STATISTIC(NumAliasesRemoved, "Number of global aliases eliminated");
58 struct GlobalOpt : public ModulePass {
59 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
61 static char ID; // Pass identification, replacement for typeid
62 GlobalOpt() : ModulePass(&ID) {}
64 bool runOnModule(Module &M);
67 GlobalVariable *FindGlobalCtors(Module &M);
68 bool OptimizeFunctions(Module &M);
69 bool OptimizeGlobalVars(Module &M);
70 bool OptimizeGlobalAliases(Module &M);
71 bool OptimizeGlobalCtorsList(GlobalVariable *&GCL);
72 bool ProcessInternalGlobal(GlobalVariable *GV,Module::global_iterator &GVI);
76 char GlobalOpt::ID = 0;
77 static RegisterPass<GlobalOpt> X("globalopt", "Global Variable Optimizer");
79 ModulePass *llvm::createGlobalOptimizerPass() { return new GlobalOpt(); }
83 /// GlobalStatus - As we analyze each global, keep track of some information
84 /// about it. If we find out that the address of the global is taken, none of
85 /// this info will be accurate.
87 /// isLoaded - True if the global is ever loaded. If the global isn't ever
88 /// loaded it can be deleted.
91 /// StoredType - Keep track of what stores to the global look like.
94 /// NotStored - There is no store to this global. It can thus be marked
98 /// isInitializerStored - This global is stored to, but the only thing
99 /// stored is the constant it was initialized with. This is only tracked
100 /// for scalar globals.
103 /// isStoredOnce - This global is stored to, but only its initializer and
104 /// one other value is ever stored to it. If this global isStoredOnce, we
105 /// track the value stored to it in StoredOnceValue below. This is only
106 /// tracked for scalar globals.
109 /// isStored - This global is stored to by multiple values or something else
110 /// that we cannot track.
114 /// StoredOnceValue - If only one value (besides the initializer constant) is
115 /// ever stored to this global, keep track of what value it is.
116 Value *StoredOnceValue;
118 /// AccessingFunction/HasMultipleAccessingFunctions - These start out
119 /// null/false. When the first accessing function is noticed, it is recorded.
120 /// When a second different accessing function is noticed,
121 /// HasMultipleAccessingFunctions is set to true.
122 Function *AccessingFunction;
123 bool HasMultipleAccessingFunctions;
125 /// HasNonInstructionUser - Set to true if this global has a user that is not
126 /// an instruction (e.g. a constant expr or GV initializer).
127 bool HasNonInstructionUser;
129 /// HasPHIUser - Set to true if this global has a user that is a PHI node.
132 GlobalStatus() : isLoaded(false), StoredType(NotStored), StoredOnceValue(0),
133 AccessingFunction(0), HasMultipleAccessingFunctions(false),
134 HasNonInstructionUser(false), HasPHIUser(false) {}
139 // SafeToDestroyConstant - It is safe to destroy a constant iff it is only used
140 // by constants itself. Note that constants cannot be cyclic, so this test is
141 // pretty easy to implement recursively.
143 static bool SafeToDestroyConstant(Constant *C) {
144 if (isa<GlobalValue>(C)) return false;
146 for (Value::use_iterator UI = C->use_begin(), E = C->use_end(); UI != E; ++UI)
147 if (Constant *CU = dyn_cast<Constant>(*UI)) {
148 if (!SafeToDestroyConstant(CU)) return false;
155 /// AnalyzeGlobal - Look at all uses of the global and fill in the GlobalStatus
156 /// structure. If the global has its address taken, return true to indicate we
157 /// can't do anything with it.
159 static bool AnalyzeGlobal(Value *V, GlobalStatus &GS,
160 SmallPtrSet<PHINode*, 16> &PHIUsers) {
161 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ++UI)
162 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(*UI)) {
163 GS.HasNonInstructionUser = true;
165 if (AnalyzeGlobal(CE, GS, PHIUsers)) return true;
167 } else if (Instruction *I = dyn_cast<Instruction>(*UI)) {
168 if (!GS.HasMultipleAccessingFunctions) {
169 Function *F = I->getParent()->getParent();
170 if (GS.AccessingFunction == 0)
171 GS.AccessingFunction = F;
172 else if (GS.AccessingFunction != F)
173 GS.HasMultipleAccessingFunctions = true;
175 if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
177 if (LI->isVolatile()) return true; // Don't hack on volatile loads.
178 } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
179 // Don't allow a store OF the address, only stores TO the address.
180 if (SI->getOperand(0) == V) return true;
182 if (SI->isVolatile()) return true; // Don't hack on volatile stores.
184 // If this is a direct store to the global (i.e., the global is a scalar
185 // value, not an aggregate), keep more specific information about
187 if (GS.StoredType != GlobalStatus::isStored) {
188 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(SI->getOperand(1))){
189 Value *StoredVal = SI->getOperand(0);
190 if (StoredVal == GV->getInitializer()) {
191 if (GS.StoredType < GlobalStatus::isInitializerStored)
192 GS.StoredType = GlobalStatus::isInitializerStored;
193 } else if (isa<LoadInst>(StoredVal) &&
194 cast<LoadInst>(StoredVal)->getOperand(0) == GV) {
196 if (GS.StoredType < GlobalStatus::isInitializerStored)
197 GS.StoredType = GlobalStatus::isInitializerStored;
198 } else if (GS.StoredType < GlobalStatus::isStoredOnce) {
199 GS.StoredType = GlobalStatus::isStoredOnce;
200 GS.StoredOnceValue = StoredVal;
201 } else if (GS.StoredType == GlobalStatus::isStoredOnce &&
202 GS.StoredOnceValue == StoredVal) {
205 GS.StoredType = GlobalStatus::isStored;
208 GS.StoredType = GlobalStatus::isStored;
211 } else if (isa<GetElementPtrInst>(I)) {
212 if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
213 } else if (isa<SelectInst>(I)) {
214 if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
215 } else if (PHINode *PN = dyn_cast<PHINode>(I)) {
216 // PHI nodes we can check just like select or GEP instructions, but we
217 // have to be careful about infinite recursion.
218 if (PHIUsers.insert(PN)) // Not already visited.
219 if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
220 GS.HasPHIUser = true;
221 } else if (isa<CmpInst>(I)) {
222 } else if (isa<MemTransferInst>(I)) {
223 if (I->getOperand(1) == V)
224 GS.StoredType = GlobalStatus::isStored;
225 if (I->getOperand(2) == V)
227 } else if (isa<MemSetInst>(I)) {
228 assert(I->getOperand(1) == V && "Memset only takes one pointer!");
229 GS.StoredType = GlobalStatus::isStored;
231 return true; // Any other non-load instruction might take address!
233 } else if (Constant *C = dyn_cast<Constant>(*UI)) {
234 GS.HasNonInstructionUser = true;
235 // We might have a dead and dangling constant hanging off of here.
236 if (!SafeToDestroyConstant(C))
239 GS.HasNonInstructionUser = true;
240 // Otherwise must be some other user.
247 static Constant *getAggregateConstantElement(Constant *Agg, Constant *Idx) {
248 ConstantInt *CI = dyn_cast<ConstantInt>(Idx);
250 unsigned IdxV = CI->getZExtValue();
252 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(Agg)) {
253 if (IdxV < CS->getNumOperands()) return CS->getOperand(IdxV);
254 } else if (ConstantArray *CA = dyn_cast<ConstantArray>(Agg)) {
255 if (IdxV < CA->getNumOperands()) return CA->getOperand(IdxV);
256 } else if (ConstantVector *CP = dyn_cast<ConstantVector>(Agg)) {
257 if (IdxV < CP->getNumOperands()) return CP->getOperand(IdxV);
258 } else if (isa<ConstantAggregateZero>(Agg)) {
259 if (const StructType *STy = dyn_cast<StructType>(Agg->getType())) {
260 if (IdxV < STy->getNumElements())
261 return Constant::getNullValue(STy->getElementType(IdxV));
262 } else if (const SequentialType *STy =
263 dyn_cast<SequentialType>(Agg->getType())) {
264 return Constant::getNullValue(STy->getElementType());
266 } else if (isa<UndefValue>(Agg)) {
267 if (const StructType *STy = dyn_cast<StructType>(Agg->getType())) {
268 if (IdxV < STy->getNumElements())
269 return UndefValue::get(STy->getElementType(IdxV));
270 } else if (const SequentialType *STy =
271 dyn_cast<SequentialType>(Agg->getType())) {
272 return UndefValue::get(STy->getElementType());
279 /// CleanupConstantGlobalUsers - We just marked GV constant. Loop over all
280 /// users of the global, cleaning up the obvious ones. This is largely just a
281 /// quick scan over the use list to clean up the easy and obvious cruft. This
282 /// returns true if it made a change.
283 static bool CleanupConstantGlobalUsers(Value *V, Constant *Init) {
284 bool Changed = false;
285 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;) {
288 if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
290 // Replace the load with the initializer.
291 LI->replaceAllUsesWith(Init);
292 LI->eraseFromParent();
295 } else if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
296 // Store must be unreachable or storing Init into the global.
297 SI->eraseFromParent();
299 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U)) {
300 if (CE->getOpcode() == Instruction::GetElementPtr) {
301 Constant *SubInit = 0;
303 SubInit = ConstantFoldLoadThroughGEPConstantExpr(Init, CE);
304 Changed |= CleanupConstantGlobalUsers(CE, SubInit);
305 } else if (CE->getOpcode() == Instruction::BitCast &&
306 CE->getType()->isPointerTy()) {
307 // Pointer cast, delete any stores and memsets to the global.
308 Changed |= CleanupConstantGlobalUsers(CE, 0);
311 if (CE->use_empty()) {
312 CE->destroyConstant();
315 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) {
316 // Do not transform "gepinst (gep constexpr (GV))" here, because forming
317 // "gepconstexpr (gep constexpr (GV))" will cause the two gep's to fold
318 // and will invalidate our notion of what Init is.
319 Constant *SubInit = 0;
320 if (!isa<ConstantExpr>(GEP->getOperand(0))) {
322 dyn_cast_or_null<ConstantExpr>(ConstantFoldInstruction(GEP));
323 if (Init && CE && CE->getOpcode() == Instruction::GetElementPtr)
324 SubInit = ConstantFoldLoadThroughGEPConstantExpr(Init, CE);
326 Changed |= CleanupConstantGlobalUsers(GEP, SubInit);
328 if (GEP->use_empty()) {
329 GEP->eraseFromParent();
332 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(U)) { // memset/cpy/mv
333 if (MI->getRawDest() == V) {
334 MI->eraseFromParent();
338 } else if (Constant *C = dyn_cast<Constant>(U)) {
339 // If we have a chain of dead constantexprs or other things dangling from
340 // us, and if they are all dead, nuke them without remorse.
341 if (SafeToDestroyConstant(C)) {
342 C->destroyConstant();
343 // This could have invalidated UI, start over from scratch.
344 CleanupConstantGlobalUsers(V, Init);
352 /// isSafeSROAElementUse - Return true if the specified instruction is a safe
353 /// user of a derived expression from a global that we want to SROA.
354 static bool isSafeSROAElementUse(Value *V) {
355 // We might have a dead and dangling constant hanging off of here.
356 if (Constant *C = dyn_cast<Constant>(V))
357 return SafeToDestroyConstant(C);
359 Instruction *I = dyn_cast<Instruction>(V);
360 if (!I) return false;
363 if (isa<LoadInst>(I)) return true;
365 // Stores *to* the pointer are ok.
366 if (StoreInst *SI = dyn_cast<StoreInst>(I))
367 return SI->getOperand(0) != V;
369 // Otherwise, it must be a GEP.
370 GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I);
371 if (GEPI == 0) return false;
373 if (GEPI->getNumOperands() < 3 || !isa<Constant>(GEPI->getOperand(1)) ||
374 !cast<Constant>(GEPI->getOperand(1))->isNullValue())
377 for (Value::use_iterator I = GEPI->use_begin(), E = GEPI->use_end();
379 if (!isSafeSROAElementUse(*I))
385 /// IsUserOfGlobalSafeForSRA - U is a direct user of the specified global value.
386 /// Look at it and its uses and decide whether it is safe to SROA this global.
388 static bool IsUserOfGlobalSafeForSRA(User *U, GlobalValue *GV) {
389 // The user of the global must be a GEP Inst or a ConstantExpr GEP.
390 if (!isa<GetElementPtrInst>(U) &&
391 (!isa<ConstantExpr>(U) ||
392 cast<ConstantExpr>(U)->getOpcode() != Instruction::GetElementPtr))
395 // Check to see if this ConstantExpr GEP is SRA'able. In particular, we
396 // don't like < 3 operand CE's, and we don't like non-constant integer
397 // indices. This enforces that all uses are 'gep GV, 0, C, ...' for some
399 if (U->getNumOperands() < 3 || !isa<Constant>(U->getOperand(1)) ||
400 !cast<Constant>(U->getOperand(1))->isNullValue() ||
401 !isa<ConstantInt>(U->getOperand(2)))
404 gep_type_iterator GEPI = gep_type_begin(U), E = gep_type_end(U);
405 ++GEPI; // Skip over the pointer index.
407 // If this is a use of an array allocation, do a bit more checking for sanity.
408 if (const ArrayType *AT = dyn_cast<ArrayType>(*GEPI)) {
409 uint64_t NumElements = AT->getNumElements();
410 ConstantInt *Idx = cast<ConstantInt>(U->getOperand(2));
412 // Check to make sure that index falls within the array. If not,
413 // something funny is going on, so we won't do the optimization.
415 if (Idx->getZExtValue() >= NumElements)
418 // We cannot scalar repl this level of the array unless any array
419 // sub-indices are in-range constants. In particular, consider:
420 // A[0][i]. We cannot know that the user isn't doing invalid things like
421 // allowing i to index an out-of-range subscript that accesses A[1].
423 // Scalar replacing *just* the outer index of the array is probably not
424 // going to be a win anyway, so just give up.
425 for (++GEPI; // Skip array index.
428 uint64_t NumElements;
429 if (const ArrayType *SubArrayTy = dyn_cast<ArrayType>(*GEPI))
430 NumElements = SubArrayTy->getNumElements();
431 else if (const VectorType *SubVectorTy = dyn_cast<VectorType>(*GEPI))
432 NumElements = SubVectorTy->getNumElements();
434 assert((*GEPI)->isStructTy() &&
435 "Indexed GEP type is not array, vector, or struct!");
439 ConstantInt *IdxVal = dyn_cast<ConstantInt>(GEPI.getOperand());
440 if (!IdxVal || IdxVal->getZExtValue() >= NumElements)
445 for (Value::use_iterator I = U->use_begin(), E = U->use_end(); I != E; ++I)
446 if (!isSafeSROAElementUse(*I))
451 /// GlobalUsersSafeToSRA - Look at all uses of the global and decide whether it
452 /// is safe for us to perform this transformation.
454 static bool GlobalUsersSafeToSRA(GlobalValue *GV) {
455 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end();
457 if (!IsUserOfGlobalSafeForSRA(*UI, GV))
464 /// SRAGlobal - Perform scalar replacement of aggregates on the specified global
465 /// variable. This opens the door for other optimizations by exposing the
466 /// behavior of the program in a more fine-grained way. We have determined that
467 /// this transformation is safe already. We return the first global variable we
468 /// insert so that the caller can reprocess it.
469 static GlobalVariable *SRAGlobal(GlobalVariable *GV, const TargetData &TD) {
470 // Make sure this global only has simple uses that we can SRA.
471 if (!GlobalUsersSafeToSRA(GV))
474 assert(GV->hasLocalLinkage() && !GV->isConstant());
475 Constant *Init = GV->getInitializer();
476 const Type *Ty = Init->getType();
478 std::vector<GlobalVariable*> NewGlobals;
479 Module::GlobalListType &Globals = GV->getParent()->getGlobalList();
481 // Get the alignment of the global, either explicit or target-specific.
482 unsigned StartAlignment = GV->getAlignment();
483 if (StartAlignment == 0)
484 StartAlignment = TD.getABITypeAlignment(GV->getType());
486 if (const StructType *STy = dyn_cast<StructType>(Ty)) {
487 NewGlobals.reserve(STy->getNumElements());
488 const StructLayout &Layout = *TD.getStructLayout(STy);
489 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
490 Constant *In = getAggregateConstantElement(Init,
491 ConstantInt::get(Type::getInt32Ty(STy->getContext()), i));
492 assert(In && "Couldn't get element of initializer?");
493 GlobalVariable *NGV = new GlobalVariable(STy->getElementType(i), false,
494 GlobalVariable::InternalLinkage,
495 In, GV->getName()+"."+Twine(i),
497 GV->getType()->getAddressSpace());
498 Globals.insert(GV, NGV);
499 NewGlobals.push_back(NGV);
501 // Calculate the known alignment of the field. If the original aggregate
502 // had 256 byte alignment for example, something might depend on that:
503 // propagate info to each field.
504 uint64_t FieldOffset = Layout.getElementOffset(i);
505 unsigned NewAlign = (unsigned)MinAlign(StartAlignment, FieldOffset);
506 if (NewAlign > TD.getABITypeAlignment(STy->getElementType(i)))
507 NGV->setAlignment(NewAlign);
509 } else if (const SequentialType *STy = dyn_cast<SequentialType>(Ty)) {
510 unsigned NumElements = 0;
511 if (const ArrayType *ATy = dyn_cast<ArrayType>(STy))
512 NumElements = ATy->getNumElements();
514 NumElements = cast<VectorType>(STy)->getNumElements();
516 if (NumElements > 16 && GV->hasNUsesOrMore(16))
517 return 0; // It's not worth it.
518 NewGlobals.reserve(NumElements);
520 uint64_t EltSize = TD.getTypeAllocSize(STy->getElementType());
521 unsigned EltAlign = TD.getABITypeAlignment(STy->getElementType());
522 for (unsigned i = 0, e = NumElements; i != e; ++i) {
523 Constant *In = getAggregateConstantElement(Init,
524 ConstantInt::get(Type::getInt32Ty(Init->getContext()), i));
525 assert(In && "Couldn't get element of initializer?");
527 GlobalVariable *NGV = new GlobalVariable(STy->getElementType(), false,
528 GlobalVariable::InternalLinkage,
529 In, GV->getName()+"."+Twine(i),
531 GV->getType()->getAddressSpace());
532 Globals.insert(GV, NGV);
533 NewGlobals.push_back(NGV);
535 // Calculate the known alignment of the field. If the original aggregate
536 // had 256 byte alignment for example, something might depend on that:
537 // propagate info to each field.
538 unsigned NewAlign = (unsigned)MinAlign(StartAlignment, EltSize*i);
539 if (NewAlign > EltAlign)
540 NGV->setAlignment(NewAlign);
544 if (NewGlobals.empty())
547 DEBUG(dbgs() << "PERFORMING GLOBAL SRA ON: " << *GV);
549 Constant *NullInt =Constant::getNullValue(Type::getInt32Ty(GV->getContext()));
551 // Loop over all of the uses of the global, replacing the constantexpr geps,
552 // with smaller constantexpr geps or direct references.
553 while (!GV->use_empty()) {
554 User *GEP = GV->use_back();
555 assert(((isa<ConstantExpr>(GEP) &&
556 cast<ConstantExpr>(GEP)->getOpcode()==Instruction::GetElementPtr)||
557 isa<GetElementPtrInst>(GEP)) && "NonGEP CE's are not SRAable!");
559 // Ignore the 1th operand, which has to be zero or else the program is quite
560 // broken (undefined). Get the 2nd operand, which is the structure or array
562 unsigned Val = cast<ConstantInt>(GEP->getOperand(2))->getZExtValue();
563 if (Val >= NewGlobals.size()) Val = 0; // Out of bound array access.
565 Value *NewPtr = NewGlobals[Val];
567 // Form a shorter GEP if needed.
568 if (GEP->getNumOperands() > 3) {
569 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GEP)) {
570 SmallVector<Constant*, 8> Idxs;
571 Idxs.push_back(NullInt);
572 for (unsigned i = 3, e = CE->getNumOperands(); i != e; ++i)
573 Idxs.push_back(CE->getOperand(i));
574 NewPtr = ConstantExpr::getGetElementPtr(cast<Constant>(NewPtr),
575 &Idxs[0], Idxs.size());
577 GetElementPtrInst *GEPI = cast<GetElementPtrInst>(GEP);
578 SmallVector<Value*, 8> Idxs;
579 Idxs.push_back(NullInt);
580 for (unsigned i = 3, e = GEPI->getNumOperands(); i != e; ++i)
581 Idxs.push_back(GEPI->getOperand(i));
582 NewPtr = GetElementPtrInst::Create(NewPtr, Idxs.begin(), Idxs.end(),
583 GEPI->getName()+"."+Twine(Val),GEPI);
586 GEP->replaceAllUsesWith(NewPtr);
588 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(GEP))
589 GEPI->eraseFromParent();
591 cast<ConstantExpr>(GEP)->destroyConstant();
594 // Delete the old global, now that it is dead.
598 // Loop over the new globals array deleting any globals that are obviously
599 // dead. This can arise due to scalarization of a structure or an array that
600 // has elements that are dead.
601 unsigned FirstGlobal = 0;
602 for (unsigned i = 0, e = NewGlobals.size(); i != e; ++i)
603 if (NewGlobals[i]->use_empty()) {
604 Globals.erase(NewGlobals[i]);
605 if (FirstGlobal == i) ++FirstGlobal;
608 return FirstGlobal != NewGlobals.size() ? NewGlobals[FirstGlobal] : 0;
611 /// AllUsesOfValueWillTrapIfNull - Return true if all users of the specified
612 /// value will trap if the value is dynamically null. PHIs keeps track of any
613 /// phi nodes we've seen to avoid reprocessing them.
614 static bool AllUsesOfValueWillTrapIfNull(Value *V,
615 SmallPtrSet<PHINode*, 8> &PHIs) {
616 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ++UI)
617 if (isa<LoadInst>(*UI)) {
619 } else if (StoreInst *SI = dyn_cast<StoreInst>(*UI)) {
620 if (SI->getOperand(0) == V) {
621 //cerr << "NONTRAPPING USE: " << **UI;
622 return false; // Storing the value.
624 } else if (CallInst *CI = dyn_cast<CallInst>(*UI)) {
625 if (CI->getOperand(0) != V) {
626 //cerr << "NONTRAPPING USE: " << **UI;
627 return false; // Not calling the ptr
629 } else if (InvokeInst *II = dyn_cast<InvokeInst>(*UI)) {
630 if (II->getOperand(0) != V) {
631 //cerr << "NONTRAPPING USE: " << **UI;
632 return false; // Not calling the ptr
634 } else if (BitCastInst *CI = dyn_cast<BitCastInst>(*UI)) {
635 if (!AllUsesOfValueWillTrapIfNull(CI, PHIs)) return false;
636 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(*UI)) {
637 if (!AllUsesOfValueWillTrapIfNull(GEPI, PHIs)) return false;
638 } else if (PHINode *PN = dyn_cast<PHINode>(*UI)) {
639 // If we've already seen this phi node, ignore it, it has already been
641 if (PHIs.insert(PN) && !AllUsesOfValueWillTrapIfNull(PN, PHIs))
643 } else if (isa<ICmpInst>(*UI) &&
644 isa<ConstantPointerNull>(UI->getOperand(1))) {
645 // Ignore icmp X, null
647 //cerr << "NONTRAPPING USE: " << **UI;
653 /// AllUsesOfLoadedValueWillTrapIfNull - Return true if all uses of any loads
654 /// from GV will trap if the loaded value is null. Note that this also permits
655 /// comparisons of the loaded value against null, as a special case.
656 static bool AllUsesOfLoadedValueWillTrapIfNull(GlobalVariable *GV) {
657 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); UI!=E; ++UI)
658 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
659 SmallPtrSet<PHINode*, 8> PHIs;
660 if (!AllUsesOfValueWillTrapIfNull(LI, PHIs))
662 } else if (isa<StoreInst>(*UI)) {
663 // Ignore stores to the global.
665 // We don't know or understand this user, bail out.
666 //cerr << "UNKNOWN USER OF GLOBAL!: " << **UI;
673 static bool OptimizeAwayTrappingUsesOfValue(Value *V, Constant *NewV) {
674 bool Changed = false;
675 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ) {
676 Instruction *I = cast<Instruction>(*UI++);
677 if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
678 LI->setOperand(0, NewV);
680 } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
681 if (SI->getOperand(1) == V) {
682 SI->setOperand(1, NewV);
685 } else if (isa<CallInst>(I) || isa<InvokeInst>(I)) {
686 if (I->getOperand(0) == V) {
687 // Calling through the pointer! Turn into a direct call, but be careful
688 // that the pointer is not also being passed as an argument.
689 I->setOperand(0, NewV);
691 bool PassedAsArg = false;
692 for (unsigned i = 1, e = I->getNumOperands(); i != e; ++i)
693 if (I->getOperand(i) == V) {
695 I->setOperand(i, NewV);
699 // Being passed as an argument also. Be careful to not invalidate UI!
703 } else if (CastInst *CI = dyn_cast<CastInst>(I)) {
704 Changed |= OptimizeAwayTrappingUsesOfValue(CI,
705 ConstantExpr::getCast(CI->getOpcode(),
706 NewV, CI->getType()));
707 if (CI->use_empty()) {
709 CI->eraseFromParent();
711 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I)) {
712 // Should handle GEP here.
713 SmallVector<Constant*, 8> Idxs;
714 Idxs.reserve(GEPI->getNumOperands()-1);
715 for (User::op_iterator i = GEPI->op_begin() + 1, e = GEPI->op_end();
717 if (Constant *C = dyn_cast<Constant>(*i))
721 if (Idxs.size() == GEPI->getNumOperands()-1)
722 Changed |= OptimizeAwayTrappingUsesOfValue(GEPI,
723 ConstantExpr::getGetElementPtr(NewV, &Idxs[0],
725 if (GEPI->use_empty()) {
727 GEPI->eraseFromParent();
736 /// OptimizeAwayTrappingUsesOfLoads - The specified global has only one non-null
737 /// value stored into it. If there are uses of the loaded value that would trap
738 /// if the loaded value is dynamically null, then we know that they cannot be
739 /// reachable with a null optimize away the load.
740 static bool OptimizeAwayTrappingUsesOfLoads(GlobalVariable *GV, Constant *LV) {
741 bool Changed = false;
743 // Keep track of whether we are able to remove all the uses of the global
744 // other than the store that defines it.
745 bool AllNonStoreUsesGone = true;
747 // Replace all uses of loads with uses of uses of the stored value.
748 for (Value::use_iterator GUI = GV->use_begin(), E = GV->use_end(); GUI != E;){
749 User *GlobalUser = *GUI++;
750 if (LoadInst *LI = dyn_cast<LoadInst>(GlobalUser)) {
751 Changed |= OptimizeAwayTrappingUsesOfValue(LI, LV);
752 // If we were able to delete all uses of the loads
753 if (LI->use_empty()) {
754 LI->eraseFromParent();
757 AllNonStoreUsesGone = false;
759 } else if (isa<StoreInst>(GlobalUser)) {
760 // Ignore the store that stores "LV" to the global.
761 assert(GlobalUser->getOperand(1) == GV &&
762 "Must be storing *to* the global");
764 AllNonStoreUsesGone = false;
766 // If we get here we could have other crazy uses that are transitively
768 assert((isa<PHINode>(GlobalUser) || isa<SelectInst>(GlobalUser) ||
769 isa<ConstantExpr>(GlobalUser)) && "Only expect load and stores!");
774 DEBUG(dbgs() << "OPTIMIZED LOADS FROM STORED ONCE POINTER: " << *GV);
778 // If we nuked all of the loads, then none of the stores are needed either,
779 // nor is the global.
780 if (AllNonStoreUsesGone) {
781 DEBUG(dbgs() << " *** GLOBAL NOW DEAD!\n");
782 CleanupConstantGlobalUsers(GV, 0);
783 if (GV->use_empty()) {
784 GV->eraseFromParent();
792 /// ConstantPropUsersOf - Walk the use list of V, constant folding all of the
793 /// instructions that are foldable.
794 static void ConstantPropUsersOf(Value *V) {
795 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; )
796 if (Instruction *I = dyn_cast<Instruction>(*UI++))
797 if (Constant *NewC = ConstantFoldInstruction(I)) {
798 I->replaceAllUsesWith(NewC);
800 // Advance UI to the next non-I use to avoid invalidating it!
801 // Instructions could multiply use V.
802 while (UI != E && *UI == I)
804 I->eraseFromParent();
808 /// OptimizeGlobalAddressOfMalloc - This function takes the specified global
809 /// variable, and transforms the program as if it always contained the result of
810 /// the specified malloc. Because it is always the result of the specified
811 /// malloc, there is no reason to actually DO the malloc. Instead, turn the
812 /// malloc into a global, and any loads of GV as uses of the new global.
813 static GlobalVariable *OptimizeGlobalAddressOfMalloc(GlobalVariable *GV,
816 ConstantInt *NElements,
818 DEBUG(errs() << "PROMOTING GLOBAL: " << *GV << " CALL = " << *CI << '\n');
820 const Type *GlobalType;
821 if (NElements->getZExtValue() == 1)
822 GlobalType = AllocTy;
824 // If we have an array allocation, the global variable is of an array.
825 GlobalType = ArrayType::get(AllocTy, NElements->getZExtValue());
827 // Create the new global variable. The contents of the malloc'd memory is
828 // undefined, so initialize with an undef value.
829 const Type *MAT = getMallocAllocatedType(CI);
830 GlobalVariable *NewGV = new GlobalVariable(*GV->getParent(),
832 GlobalValue::InternalLinkage,
833 UndefValue::get(MAT),
834 GV->getName()+".body",
836 GV->isThreadLocal());
838 // If there are bitcast users of the malloc (which is typical, usually we have
839 // a malloc + bitcast) then replace them with uses of the new global. Update
840 // other users to use the global as well.
841 BitCastInst *TheBC = 0;
842 while (!CI->use_empty()) {
843 Instruction *User = cast<Instruction>(CI->use_back());
844 if (BitCastInst *BCI = dyn_cast<BitCastInst>(User)) {
845 if (BCI->getType() == NewGV->getType()) {
846 BCI->replaceAllUsesWith(NewGV);
847 BCI->eraseFromParent();
849 BCI->setOperand(0, NewGV);
853 TheBC = new BitCastInst(NewGV, CI->getType(), "newgv", CI);
854 User->replaceUsesOfWith(CI, TheBC);
858 Constant *RepValue = NewGV;
859 if (NewGV->getType() != GV->getType()->getElementType())
860 RepValue = ConstantExpr::getBitCast(RepValue,
861 GV->getType()->getElementType());
863 // If there is a comparison against null, we will insert a global bool to
864 // keep track of whether the global was initialized yet or not.
865 GlobalVariable *InitBool =
866 new GlobalVariable(Type::getInt1Ty(GV->getContext()), false,
867 GlobalValue::InternalLinkage,
868 ConstantInt::getFalse(GV->getContext()),
869 GV->getName()+".init", GV->isThreadLocal());
870 bool InitBoolUsed = false;
872 // Loop over all uses of GV, processing them in turn.
873 while (!GV->use_empty()) {
874 if (StoreInst *SI = dyn_cast<StoreInst>(GV->use_back())) {
875 // The global is initialized when the store to it occurs.
876 new StoreInst(ConstantInt::getTrue(GV->getContext()), InitBool, SI);
877 SI->eraseFromParent();
881 LoadInst *LI = cast<LoadInst>(GV->use_back());
882 while (!LI->use_empty()) {
883 Use &LoadUse = LI->use_begin().getUse();
884 if (!isa<ICmpInst>(LoadUse.getUser())) {
889 ICmpInst *ICI = cast<ICmpInst>(LoadUse.getUser());
890 // Replace the cmp X, 0 with a use of the bool value.
891 Value *LV = new LoadInst(InitBool, InitBool->getName()+".val", ICI);
893 switch (ICI->getPredicate()) {
894 default: llvm_unreachable("Unknown ICmp Predicate!");
895 case ICmpInst::ICMP_ULT:
896 case ICmpInst::ICMP_SLT: // X < null -> always false
897 LV = ConstantInt::getFalse(GV->getContext());
899 case ICmpInst::ICMP_ULE:
900 case ICmpInst::ICMP_SLE:
901 case ICmpInst::ICMP_EQ:
902 LV = BinaryOperator::CreateNot(LV, "notinit", ICI);
904 case ICmpInst::ICMP_NE:
905 case ICmpInst::ICMP_UGE:
906 case ICmpInst::ICMP_SGE:
907 case ICmpInst::ICMP_UGT:
908 case ICmpInst::ICMP_SGT:
911 ICI->replaceAllUsesWith(LV);
912 ICI->eraseFromParent();
914 LI->eraseFromParent();
917 // If the initialization boolean was used, insert it, otherwise delete it.
919 while (!InitBool->use_empty()) // Delete initializations
920 cast<StoreInst>(InitBool->use_back())->eraseFromParent();
923 GV->getParent()->getGlobalList().insert(GV, InitBool);
925 // Now the GV is dead, nuke it and the malloc..
926 GV->eraseFromParent();
927 CI->eraseFromParent();
929 // To further other optimizations, loop over all users of NewGV and try to
930 // constant prop them. This will promote GEP instructions with constant
931 // indices into GEP constant-exprs, which will allow global-opt to hack on it.
932 ConstantPropUsersOf(NewGV);
933 if (RepValue != NewGV)
934 ConstantPropUsersOf(RepValue);
939 /// ValueIsOnlyUsedLocallyOrStoredToOneGlobal - Scan the use-list of V checking
940 /// to make sure that there are no complex uses of V. We permit simple things
941 /// like dereferencing the pointer, but not storing through the address, unless
942 /// it is to the specified global.
943 static bool ValueIsOnlyUsedLocallyOrStoredToOneGlobal(Instruction *V,
945 SmallPtrSet<PHINode*, 8> &PHIs) {
946 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;++UI){
947 Instruction *Inst = cast<Instruction>(*UI);
949 if (isa<LoadInst>(Inst) || isa<CmpInst>(Inst)) {
950 continue; // Fine, ignore.
953 if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
954 if (SI->getOperand(0) == V && SI->getOperand(1) != GV)
955 return false; // Storing the pointer itself... bad.
956 continue; // Otherwise, storing through it, or storing into GV... fine.
959 if (isa<GetElementPtrInst>(Inst)) {
960 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(Inst, GV, PHIs))
965 if (PHINode *PN = dyn_cast<PHINode>(Inst)) {
966 // PHIs are ok if all uses are ok. Don't infinitely recurse through PHI
969 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(PN, GV, PHIs))
974 if (BitCastInst *BCI = dyn_cast<BitCastInst>(Inst)) {
975 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(BCI, GV, PHIs))
985 /// ReplaceUsesOfMallocWithGlobal - The Alloc pointer is stored into GV
986 /// somewhere. Transform all uses of the allocation into loads from the
987 /// global and uses of the resultant pointer. Further, delete the store into
988 /// GV. This assumes that these value pass the
989 /// 'ValueIsOnlyUsedLocallyOrStoredToOneGlobal' predicate.
990 static void ReplaceUsesOfMallocWithGlobal(Instruction *Alloc,
991 GlobalVariable *GV) {
992 while (!Alloc->use_empty()) {
993 Instruction *U = cast<Instruction>(*Alloc->use_begin());
994 Instruction *InsertPt = U;
995 if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
996 // If this is the store of the allocation into the global, remove it.
997 if (SI->getOperand(1) == GV) {
998 SI->eraseFromParent();
1001 } else if (PHINode *PN = dyn_cast<PHINode>(U)) {
1002 // Insert the load in the corresponding predecessor, not right before the
1004 InsertPt = PN->getIncomingBlock(Alloc->use_begin())->getTerminator();
1005 } else if (isa<BitCastInst>(U)) {
1006 // Must be bitcast between the malloc and store to initialize the global.
1007 ReplaceUsesOfMallocWithGlobal(U, GV);
1008 U->eraseFromParent();
1010 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(U)) {
1011 // If this is a "GEP bitcast" and the user is a store to the global, then
1012 // just process it as a bitcast.
1013 if (GEPI->hasAllZeroIndices() && GEPI->hasOneUse())
1014 if (StoreInst *SI = dyn_cast<StoreInst>(GEPI->use_back()))
1015 if (SI->getOperand(1) == GV) {
1016 // Must be bitcast GEP between the malloc and store to initialize
1018 ReplaceUsesOfMallocWithGlobal(GEPI, GV);
1019 GEPI->eraseFromParent();
1024 // Insert a load from the global, and use it instead of the malloc.
1025 Value *NL = new LoadInst(GV, GV->getName()+".val", InsertPt);
1026 U->replaceUsesOfWith(Alloc, NL);
1030 /// LoadUsesSimpleEnoughForHeapSRA - Verify that all uses of V (a load, or a phi
1031 /// of a load) are simple enough to perform heap SRA on. This permits GEP's
1032 /// that index through the array and struct field, icmps of null, and PHIs.
1033 static bool LoadUsesSimpleEnoughForHeapSRA(Value *V,
1034 SmallPtrSet<PHINode*, 32> &LoadUsingPHIs,
1035 SmallPtrSet<PHINode*, 32> &LoadUsingPHIsPerLoad) {
1036 // We permit two users of the load: setcc comparing against the null
1037 // pointer, and a getelementptr of a specific form.
1038 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;++UI){
1039 Instruction *User = cast<Instruction>(*UI);
1041 // Comparison against null is ok.
1042 if (ICmpInst *ICI = dyn_cast<ICmpInst>(User)) {
1043 if (!isa<ConstantPointerNull>(ICI->getOperand(1)))
1048 // getelementptr is also ok, but only a simple form.
1049 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
1050 // Must index into the array and into the struct.
1051 if (GEPI->getNumOperands() < 3)
1054 // Otherwise the GEP is ok.
1058 if (PHINode *PN = dyn_cast<PHINode>(User)) {
1059 if (!LoadUsingPHIsPerLoad.insert(PN))
1060 // This means some phi nodes are dependent on each other.
1061 // Avoid infinite looping!
1063 if (!LoadUsingPHIs.insert(PN))
1064 // If we have already analyzed this PHI, then it is safe.
1067 // Make sure all uses of the PHI are simple enough to transform.
1068 if (!LoadUsesSimpleEnoughForHeapSRA(PN,
1069 LoadUsingPHIs, LoadUsingPHIsPerLoad))
1075 // Otherwise we don't know what this is, not ok.
1083 /// AllGlobalLoadUsesSimpleEnoughForHeapSRA - If all users of values loaded from
1084 /// GV are simple enough to perform HeapSRA, return true.
1085 static bool AllGlobalLoadUsesSimpleEnoughForHeapSRA(GlobalVariable *GV,
1086 Instruction *StoredVal) {
1087 SmallPtrSet<PHINode*, 32> LoadUsingPHIs;
1088 SmallPtrSet<PHINode*, 32> LoadUsingPHIsPerLoad;
1089 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); UI != E;
1091 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
1092 if (!LoadUsesSimpleEnoughForHeapSRA(LI, LoadUsingPHIs,
1093 LoadUsingPHIsPerLoad))
1095 LoadUsingPHIsPerLoad.clear();
1098 // If we reach here, we know that all uses of the loads and transitive uses
1099 // (through PHI nodes) are simple enough to transform. However, we don't know
1100 // that all inputs the to the PHI nodes are in the same equivalence sets.
1101 // Check to verify that all operands of the PHIs are either PHIS that can be
1102 // transformed, loads from GV, or MI itself.
1103 for (SmallPtrSet<PHINode*, 32>::iterator I = LoadUsingPHIs.begin(),
1104 E = LoadUsingPHIs.end(); I != E; ++I) {
1106 for (unsigned op = 0, e = PN->getNumIncomingValues(); op != e; ++op) {
1107 Value *InVal = PN->getIncomingValue(op);
1109 // PHI of the stored value itself is ok.
1110 if (InVal == StoredVal) continue;
1112 if (PHINode *InPN = dyn_cast<PHINode>(InVal)) {
1113 // One of the PHIs in our set is (optimistically) ok.
1114 if (LoadUsingPHIs.count(InPN))
1119 // Load from GV is ok.
1120 if (LoadInst *LI = dyn_cast<LoadInst>(InVal))
1121 if (LI->getOperand(0) == GV)
1126 // Anything else is rejected.
1134 static Value *GetHeapSROAValue(Value *V, unsigned FieldNo,
1135 DenseMap<Value*, std::vector<Value*> > &InsertedScalarizedValues,
1136 std::vector<std::pair<PHINode*, unsigned> > &PHIsToRewrite) {
1137 std::vector<Value*> &FieldVals = InsertedScalarizedValues[V];
1139 if (FieldNo >= FieldVals.size())
1140 FieldVals.resize(FieldNo+1);
1142 // If we already have this value, just reuse the previously scalarized
1144 if (Value *FieldVal = FieldVals[FieldNo])
1147 // Depending on what instruction this is, we have several cases.
1149 if (LoadInst *LI = dyn_cast<LoadInst>(V)) {
1150 // This is a scalarized version of the load from the global. Just create
1151 // a new Load of the scalarized global.
1152 Result = new LoadInst(GetHeapSROAValue(LI->getOperand(0), FieldNo,
1153 InsertedScalarizedValues,
1155 LI->getName()+".f"+Twine(FieldNo), LI);
1156 } else if (PHINode *PN = dyn_cast<PHINode>(V)) {
1157 // PN's type is pointer to struct. Make a new PHI of pointer to struct
1159 const StructType *ST =
1160 cast<StructType>(cast<PointerType>(PN->getType())->getElementType());
1163 PHINode::Create(PointerType::getUnqual(ST->getElementType(FieldNo)),
1164 PN->getName()+".f"+Twine(FieldNo), PN);
1165 PHIsToRewrite.push_back(std::make_pair(PN, FieldNo));
1167 llvm_unreachable("Unknown usable value");
1171 return FieldVals[FieldNo] = Result;
1174 /// RewriteHeapSROALoadUser - Given a load instruction and a value derived from
1175 /// the load, rewrite the derived value to use the HeapSRoA'd load.
1176 static void RewriteHeapSROALoadUser(Instruction *LoadUser,
1177 DenseMap<Value*, std::vector<Value*> > &InsertedScalarizedValues,
1178 std::vector<std::pair<PHINode*, unsigned> > &PHIsToRewrite) {
1179 // If this is a comparison against null, handle it.
1180 if (ICmpInst *SCI = dyn_cast<ICmpInst>(LoadUser)) {
1181 assert(isa<ConstantPointerNull>(SCI->getOperand(1)));
1182 // If we have a setcc of the loaded pointer, we can use a setcc of any
1184 Value *NPtr = GetHeapSROAValue(SCI->getOperand(0), 0,
1185 InsertedScalarizedValues, PHIsToRewrite);
1187 Value *New = new ICmpInst(SCI, SCI->getPredicate(), NPtr,
1188 Constant::getNullValue(NPtr->getType()),
1190 SCI->replaceAllUsesWith(New);
1191 SCI->eraseFromParent();
1195 // Handle 'getelementptr Ptr, Idx, i32 FieldNo ...'
1196 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(LoadUser)) {
1197 assert(GEPI->getNumOperands() >= 3 && isa<ConstantInt>(GEPI->getOperand(2))
1198 && "Unexpected GEPI!");
1200 // Load the pointer for this field.
1201 unsigned FieldNo = cast<ConstantInt>(GEPI->getOperand(2))->getZExtValue();
1202 Value *NewPtr = GetHeapSROAValue(GEPI->getOperand(0), FieldNo,
1203 InsertedScalarizedValues, PHIsToRewrite);
1205 // Create the new GEP idx vector.
1206 SmallVector<Value*, 8> GEPIdx;
1207 GEPIdx.push_back(GEPI->getOperand(1));
1208 GEPIdx.append(GEPI->op_begin()+3, GEPI->op_end());
1210 Value *NGEPI = GetElementPtrInst::Create(NewPtr,
1211 GEPIdx.begin(), GEPIdx.end(),
1212 GEPI->getName(), GEPI);
1213 GEPI->replaceAllUsesWith(NGEPI);
1214 GEPI->eraseFromParent();
1218 // Recursively transform the users of PHI nodes. This will lazily create the
1219 // PHIs that are needed for individual elements. Keep track of what PHIs we
1220 // see in InsertedScalarizedValues so that we don't get infinite loops (very
1221 // antisocial). If the PHI is already in InsertedScalarizedValues, it has
1222 // already been seen first by another load, so its uses have already been
1224 PHINode *PN = cast<PHINode>(LoadUser);
1226 DenseMap<Value*, std::vector<Value*> >::iterator InsertPos;
1227 tie(InsertPos, Inserted) =
1228 InsertedScalarizedValues.insert(std::make_pair(PN, std::vector<Value*>()));
1229 if (!Inserted) return;
1231 // If this is the first time we've seen this PHI, recursively process all
1233 for (Value::use_iterator UI = PN->use_begin(), E = PN->use_end(); UI != E; ) {
1234 Instruction *User = cast<Instruction>(*UI++);
1235 RewriteHeapSROALoadUser(User, InsertedScalarizedValues, PHIsToRewrite);
1239 /// RewriteUsesOfLoadForHeapSRoA - We are performing Heap SRoA on a global. Ptr
1240 /// is a value loaded from the global. Eliminate all uses of Ptr, making them
1241 /// use FieldGlobals instead. All uses of loaded values satisfy
1242 /// AllGlobalLoadUsesSimpleEnoughForHeapSRA.
1243 static void RewriteUsesOfLoadForHeapSRoA(LoadInst *Load,
1244 DenseMap<Value*, std::vector<Value*> > &InsertedScalarizedValues,
1245 std::vector<std::pair<PHINode*, unsigned> > &PHIsToRewrite) {
1246 for (Value::use_iterator UI = Load->use_begin(), E = Load->use_end();
1248 Instruction *User = cast<Instruction>(*UI++);
1249 RewriteHeapSROALoadUser(User, InsertedScalarizedValues, PHIsToRewrite);
1252 if (Load->use_empty()) {
1253 Load->eraseFromParent();
1254 InsertedScalarizedValues.erase(Load);
1258 /// PerformHeapAllocSRoA - CI is an allocation of an array of structures. Break
1259 /// it up into multiple allocations of arrays of the fields.
1260 static GlobalVariable *PerformHeapAllocSRoA(GlobalVariable *GV, CallInst *CI,
1261 Value* NElems, TargetData *TD) {
1262 DEBUG(dbgs() << "SROA HEAP ALLOC: " << *GV << " MALLOC = " << *CI << '\n');
1263 const Type* MAT = getMallocAllocatedType(CI);
1264 const StructType *STy = cast<StructType>(MAT);
1266 // There is guaranteed to be at least one use of the malloc (storing
1267 // it into GV). If there are other uses, change them to be uses of
1268 // the global to simplify later code. This also deletes the store
1270 ReplaceUsesOfMallocWithGlobal(CI, GV);
1272 // Okay, at this point, there are no users of the malloc. Insert N
1273 // new mallocs at the same place as CI, and N globals.
1274 std::vector<Value*> FieldGlobals;
1275 std::vector<Value*> FieldMallocs;
1277 for (unsigned FieldNo = 0, e = STy->getNumElements(); FieldNo != e;++FieldNo){
1278 const Type *FieldTy = STy->getElementType(FieldNo);
1279 const PointerType *PFieldTy = PointerType::getUnqual(FieldTy);
1281 GlobalVariable *NGV =
1282 new GlobalVariable(*GV->getParent(),
1283 PFieldTy, false, GlobalValue::InternalLinkage,
1284 Constant::getNullValue(PFieldTy),
1285 GV->getName() + ".f" + Twine(FieldNo), GV,
1286 GV->isThreadLocal());
1287 FieldGlobals.push_back(NGV);
1289 unsigned TypeSize = TD->getTypeAllocSize(FieldTy);
1290 if (const StructType *ST = dyn_cast<StructType>(FieldTy))
1291 TypeSize = TD->getStructLayout(ST)->getSizeInBytes();
1292 const Type *IntPtrTy = TD->getIntPtrType(CI->getContext());
1293 Value *NMI = CallInst::CreateMalloc(CI, IntPtrTy, FieldTy,
1294 ConstantInt::get(IntPtrTy, TypeSize),
1296 CI->getName() + ".f" + Twine(FieldNo));
1297 FieldMallocs.push_back(NMI);
1298 new StoreInst(NMI, NGV, CI);
1301 // The tricky aspect of this transformation is handling the case when malloc
1302 // fails. In the original code, malloc failing would set the result pointer
1303 // of malloc to null. In this case, some mallocs could succeed and others
1304 // could fail. As such, we emit code that looks like this:
1305 // F0 = malloc(field0)
1306 // F1 = malloc(field1)
1307 // F2 = malloc(field2)
1308 // if (F0 == 0 || F1 == 0 || F2 == 0) {
1309 // if (F0) { free(F0); F0 = 0; }
1310 // if (F1) { free(F1); F1 = 0; }
1311 // if (F2) { free(F2); F2 = 0; }
1313 // The malloc can also fail if its argument is too large.
1314 Constant *ConstantZero = ConstantInt::get(CI->getOperand(1)->getType(), 0);
1315 Value *RunningOr = new ICmpInst(CI, ICmpInst::ICMP_SLT, CI->getOperand(1),
1316 ConstantZero, "isneg");
1317 for (unsigned i = 0, e = FieldMallocs.size(); i != e; ++i) {
1318 Value *Cond = new ICmpInst(CI, ICmpInst::ICMP_EQ, FieldMallocs[i],
1319 Constant::getNullValue(FieldMallocs[i]->getType()),
1321 RunningOr = BinaryOperator::CreateOr(RunningOr, Cond, "tmp", CI);
1324 // Split the basic block at the old malloc.
1325 BasicBlock *OrigBB = CI->getParent();
1326 BasicBlock *ContBB = OrigBB->splitBasicBlock(CI, "malloc_cont");
1328 // Create the block to check the first condition. Put all these blocks at the
1329 // end of the function as they are unlikely to be executed.
1330 BasicBlock *NullPtrBlock = BasicBlock::Create(OrigBB->getContext(),
1332 OrigBB->getParent());
1334 // Remove the uncond branch from OrigBB to ContBB, turning it into a cond
1335 // branch on RunningOr.
1336 OrigBB->getTerminator()->eraseFromParent();
1337 BranchInst::Create(NullPtrBlock, ContBB, RunningOr, OrigBB);
1339 // Within the NullPtrBlock, we need to emit a comparison and branch for each
1340 // pointer, because some may be null while others are not.
1341 for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) {
1342 Value *GVVal = new LoadInst(FieldGlobals[i], "tmp", NullPtrBlock);
1343 Value *Cmp = new ICmpInst(*NullPtrBlock, ICmpInst::ICMP_NE, GVVal,
1344 Constant::getNullValue(GVVal->getType()),
1346 BasicBlock *FreeBlock = BasicBlock::Create(Cmp->getContext(), "free_it",
1347 OrigBB->getParent());
1348 BasicBlock *NextBlock = BasicBlock::Create(Cmp->getContext(), "next",
1349 OrigBB->getParent());
1350 Instruction *BI = BranchInst::Create(FreeBlock, NextBlock,
1353 // Fill in FreeBlock.
1354 CallInst::CreateFree(GVVal, BI);
1355 new StoreInst(Constant::getNullValue(GVVal->getType()), FieldGlobals[i],
1357 BranchInst::Create(NextBlock, FreeBlock);
1359 NullPtrBlock = NextBlock;
1362 BranchInst::Create(ContBB, NullPtrBlock);
1364 // CI is no longer needed, remove it.
1365 CI->eraseFromParent();
1367 /// InsertedScalarizedLoads - As we process loads, if we can't immediately
1368 /// update all uses of the load, keep track of what scalarized loads are
1369 /// inserted for a given load.
1370 DenseMap<Value*, std::vector<Value*> > InsertedScalarizedValues;
1371 InsertedScalarizedValues[GV] = FieldGlobals;
1373 std::vector<std::pair<PHINode*, unsigned> > PHIsToRewrite;
1375 // Okay, the malloc site is completely handled. All of the uses of GV are now
1376 // loads, and all uses of those loads are simple. Rewrite them to use loads
1377 // of the per-field globals instead.
1378 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); UI != E;) {
1379 Instruction *User = cast<Instruction>(*UI++);
1381 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1382 RewriteUsesOfLoadForHeapSRoA(LI, InsertedScalarizedValues, PHIsToRewrite);
1386 // Must be a store of null.
1387 StoreInst *SI = cast<StoreInst>(User);
1388 assert(isa<ConstantPointerNull>(SI->getOperand(0)) &&
1389 "Unexpected heap-sra user!");
1391 // Insert a store of null into each global.
1392 for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) {
1393 const PointerType *PT = cast<PointerType>(FieldGlobals[i]->getType());
1394 Constant *Null = Constant::getNullValue(PT->getElementType());
1395 new StoreInst(Null, FieldGlobals[i], SI);
1397 // Erase the original store.
1398 SI->eraseFromParent();
1401 // While we have PHIs that are interesting to rewrite, do it.
1402 while (!PHIsToRewrite.empty()) {
1403 PHINode *PN = PHIsToRewrite.back().first;
1404 unsigned FieldNo = PHIsToRewrite.back().second;
1405 PHIsToRewrite.pop_back();
1406 PHINode *FieldPN = cast<PHINode>(InsertedScalarizedValues[PN][FieldNo]);
1407 assert(FieldPN->getNumIncomingValues() == 0 &&"Already processed this phi");
1409 // Add all the incoming values. This can materialize more phis.
1410 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
1411 Value *InVal = PN->getIncomingValue(i);
1412 InVal = GetHeapSROAValue(InVal, FieldNo, InsertedScalarizedValues,
1414 FieldPN->addIncoming(InVal, PN->getIncomingBlock(i));
1418 // Drop all inter-phi links and any loads that made it this far.
1419 for (DenseMap<Value*, std::vector<Value*> >::iterator
1420 I = InsertedScalarizedValues.begin(), E = InsertedScalarizedValues.end();
1422 if (PHINode *PN = dyn_cast<PHINode>(I->first))
1423 PN->dropAllReferences();
1424 else if (LoadInst *LI = dyn_cast<LoadInst>(I->first))
1425 LI->dropAllReferences();
1428 // Delete all the phis and loads now that inter-references are dead.
1429 for (DenseMap<Value*, std::vector<Value*> >::iterator
1430 I = InsertedScalarizedValues.begin(), E = InsertedScalarizedValues.end();
1432 if (PHINode *PN = dyn_cast<PHINode>(I->first))
1433 PN->eraseFromParent();
1434 else if (LoadInst *LI = dyn_cast<LoadInst>(I->first))
1435 LI->eraseFromParent();
1438 // The old global is now dead, remove it.
1439 GV->eraseFromParent();
1442 return cast<GlobalVariable>(FieldGlobals[0]);
1445 /// TryToOptimizeStoreOfMallocToGlobal - This function is called when we see a
1446 /// pointer global variable with a single value stored it that is a malloc or
1448 static bool TryToOptimizeStoreOfMallocToGlobal(GlobalVariable *GV,
1450 const Type *AllocTy,
1451 Module::global_iterator &GVI,
1453 // If this is a malloc of an abstract type, don't touch it.
1454 if (!AllocTy->isSized())
1457 // We can't optimize this global unless all uses of it are *known* to be
1458 // of the malloc value, not of the null initializer value (consider a use
1459 // that compares the global's value against zero to see if the malloc has
1460 // been reached). To do this, we check to see if all uses of the global
1461 // would trap if the global were null: this proves that they must all
1462 // happen after the malloc.
1463 if (!AllUsesOfLoadedValueWillTrapIfNull(GV))
1466 // We can't optimize this if the malloc itself is used in a complex way,
1467 // for example, being stored into multiple globals. This allows the
1468 // malloc to be stored into the specified global, loaded setcc'd, and
1469 // GEP'd. These are all things we could transform to using the global
1472 SmallPtrSet<PHINode*, 8> PHIs;
1473 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(CI, GV, PHIs))
1477 // If we have a global that is only initialized with a fixed size malloc,
1478 // transform the program to use global memory instead of malloc'd memory.
1479 // This eliminates dynamic allocation, avoids an indirection accessing the
1480 // data, and exposes the resultant global to further GlobalOpt.
1481 // We cannot optimize the malloc if we cannot determine malloc array size.
1482 if (Value *NElems = getMallocArraySize(CI, TD, true)) {
1483 if (ConstantInt *NElements = dyn_cast<ConstantInt>(NElems))
1484 // Restrict this transformation to only working on small allocations
1485 // (2048 bytes currently), as we don't want to introduce a 16M global or
1488 NElements->getZExtValue() * TD->getTypeAllocSize(AllocTy) < 2048) {
1489 GVI = OptimizeGlobalAddressOfMalloc(GV, CI, AllocTy, NElements, TD);
1493 // If the allocation is an array of structures, consider transforming this
1494 // into multiple malloc'd arrays, one for each field. This is basically
1495 // SRoA for malloc'd memory.
1497 // If this is an allocation of a fixed size array of structs, analyze as a
1498 // variable size array. malloc [100 x struct],1 -> malloc struct, 100
1499 if (NElems == ConstantInt::get(CI->getOperand(1)->getType(), 1))
1500 if (const ArrayType *AT = dyn_cast<ArrayType>(AllocTy))
1501 AllocTy = AT->getElementType();
1503 if (const StructType *AllocSTy = dyn_cast<StructType>(AllocTy)) {
1504 // This the structure has an unreasonable number of fields, leave it
1506 if (AllocSTy->getNumElements() <= 16 && AllocSTy->getNumElements() != 0 &&
1507 AllGlobalLoadUsesSimpleEnoughForHeapSRA(GV, CI)) {
1509 // If this is a fixed size array, transform the Malloc to be an alloc of
1510 // structs. malloc [100 x struct],1 -> malloc struct, 100
1511 if (const ArrayType *AT =
1512 dyn_cast<ArrayType>(getMallocAllocatedType(CI))) {
1513 const Type *IntPtrTy = TD->getIntPtrType(CI->getContext());
1514 unsigned TypeSize = TD->getStructLayout(AllocSTy)->getSizeInBytes();
1515 Value *AllocSize = ConstantInt::get(IntPtrTy, TypeSize);
1516 Value *NumElements = ConstantInt::get(IntPtrTy, AT->getNumElements());
1517 Instruction *Malloc = CallInst::CreateMalloc(CI, IntPtrTy, AllocSTy,
1518 AllocSize, NumElements,
1520 Instruction *Cast = new BitCastInst(Malloc, CI->getType(), "tmp", CI);
1521 CI->replaceAllUsesWith(Cast);
1522 CI->eraseFromParent();
1523 CI = dyn_cast<BitCastInst>(Malloc) ?
1524 extractMallocCallFromBitCast(Malloc) : cast<CallInst>(Malloc);
1527 GVI = PerformHeapAllocSRoA(GV, CI, getMallocArraySize(CI, TD, true),TD);
1536 // OptimizeOnceStoredGlobal - Try to optimize globals based on the knowledge
1537 // that only one value (besides its initializer) is ever stored to the global.
1538 static bool OptimizeOnceStoredGlobal(GlobalVariable *GV, Value *StoredOnceVal,
1539 Module::global_iterator &GVI,
1541 // Ignore no-op GEPs and bitcasts.
1542 StoredOnceVal = StoredOnceVal->stripPointerCasts();
1544 // If we are dealing with a pointer global that is initialized to null and
1545 // only has one (non-null) value stored into it, then we can optimize any
1546 // users of the loaded value (often calls and loads) that would trap if the
1548 if (GV->getInitializer()->getType()->isPointerTy() &&
1549 GV->getInitializer()->isNullValue()) {
1550 if (Constant *SOVC = dyn_cast<Constant>(StoredOnceVal)) {
1551 if (GV->getInitializer()->getType() != SOVC->getType())
1553 ConstantExpr::getBitCast(SOVC, GV->getInitializer()->getType());
1555 // Optimize away any trapping uses of the loaded value.
1556 if (OptimizeAwayTrappingUsesOfLoads(GV, SOVC))
1558 } else if (CallInst *CI = extractMallocCall(StoredOnceVal)) {
1559 const Type* MallocType = getMallocAllocatedType(CI);
1560 if (MallocType && TryToOptimizeStoreOfMallocToGlobal(GV, CI, MallocType,
1569 /// TryToShrinkGlobalToBoolean - At this point, we have learned that the only
1570 /// two values ever stored into GV are its initializer and OtherVal. See if we
1571 /// can shrink the global into a boolean and select between the two values
1572 /// whenever it is used. This exposes the values to other scalar optimizations.
1573 static bool TryToShrinkGlobalToBoolean(GlobalVariable *GV, Constant *OtherVal) {
1574 const Type *GVElType = GV->getType()->getElementType();
1576 // If GVElType is already i1, it is already shrunk. If the type of the GV is
1577 // an FP value, pointer or vector, don't do this optimization because a select
1578 // between them is very expensive and unlikely to lead to later
1579 // simplification. In these cases, we typically end up with "cond ? v1 : v2"
1580 // where v1 and v2 both require constant pool loads, a big loss.
1581 if (GVElType == Type::getInt1Ty(GV->getContext()) ||
1582 GVElType->isFloatingPointTy() ||
1583 GVElType->isPointerTy() || GVElType->isVectorTy())
1586 // Walk the use list of the global seeing if all the uses are load or store.
1587 // If there is anything else, bail out.
1588 for (Value::use_iterator I = GV->use_begin(), E = GV->use_end(); I != E; ++I)
1589 if (!isa<LoadInst>(I) && !isa<StoreInst>(I))
1592 DEBUG(dbgs() << " *** SHRINKING TO BOOL: " << *GV);
1594 // Create the new global, initializing it to false.
1595 GlobalVariable *NewGV = new GlobalVariable(Type::getInt1Ty(GV->getContext()),
1597 GlobalValue::InternalLinkage,
1598 ConstantInt::getFalse(GV->getContext()),
1600 GV->isThreadLocal());
1601 GV->getParent()->getGlobalList().insert(GV, NewGV);
1603 Constant *InitVal = GV->getInitializer();
1604 assert(InitVal->getType() != Type::getInt1Ty(GV->getContext()) &&
1605 "No reason to shrink to bool!");
1607 // If initialized to zero and storing one into the global, we can use a cast
1608 // instead of a select to synthesize the desired value.
1609 bool IsOneZero = false;
1610 if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal))
1611 IsOneZero = InitVal->isNullValue() && CI->isOne();
1613 while (!GV->use_empty()) {
1614 Instruction *UI = cast<Instruction>(GV->use_back());
1615 if (StoreInst *SI = dyn_cast<StoreInst>(UI)) {
1616 // Change the store into a boolean store.
1617 bool StoringOther = SI->getOperand(0) == OtherVal;
1618 // Only do this if we weren't storing a loaded value.
1620 if (StoringOther || SI->getOperand(0) == InitVal)
1621 StoreVal = ConstantInt::get(Type::getInt1Ty(GV->getContext()),
1624 // Otherwise, we are storing a previously loaded copy. To do this,
1625 // change the copy from copying the original value to just copying the
1627 Instruction *StoredVal = cast<Instruction>(SI->getOperand(0));
1629 // If we're already replaced the input, StoredVal will be a cast or
1630 // select instruction. If not, it will be a load of the original
1632 if (LoadInst *LI = dyn_cast<LoadInst>(StoredVal)) {
1633 assert(LI->getOperand(0) == GV && "Not a copy!");
1634 // Insert a new load, to preserve the saved value.
1635 StoreVal = new LoadInst(NewGV, LI->getName()+".b", LI);
1637 assert((isa<CastInst>(StoredVal) || isa<SelectInst>(StoredVal)) &&
1638 "This is not a form that we understand!");
1639 StoreVal = StoredVal->getOperand(0);
1640 assert(isa<LoadInst>(StoreVal) && "Not a load of NewGV!");
1643 new StoreInst(StoreVal, NewGV, SI);
1645 // Change the load into a load of bool then a select.
1646 LoadInst *LI = cast<LoadInst>(UI);
1647 LoadInst *NLI = new LoadInst(NewGV, LI->getName()+".b", LI);
1650 NSI = new ZExtInst(NLI, LI->getType(), "", LI);
1652 NSI = SelectInst::Create(NLI, OtherVal, InitVal, "", LI);
1654 LI->replaceAllUsesWith(NSI);
1656 UI->eraseFromParent();
1659 GV->eraseFromParent();
1664 /// ProcessInternalGlobal - Analyze the specified global variable and optimize
1665 /// it if possible. If we make a change, return true.
1666 bool GlobalOpt::ProcessInternalGlobal(GlobalVariable *GV,
1667 Module::global_iterator &GVI) {
1668 SmallPtrSet<PHINode*, 16> PHIUsers;
1670 GV->removeDeadConstantUsers();
1672 if (GV->use_empty()) {
1673 DEBUG(dbgs() << "GLOBAL DEAD: " << *GV);
1674 GV->eraseFromParent();
1679 if (!AnalyzeGlobal(GV, GS, PHIUsers)) {
1681 DEBUG(dbgs() << "Global: " << *GV);
1682 DEBUG(dbgs() << " isLoaded = " << GS.isLoaded << "\n");
1683 DEBUG(dbgs() << " StoredType = ");
1684 switch (GS.StoredType) {
1685 case GlobalStatus::NotStored: DEBUG(dbgs() << "NEVER STORED\n"); break;
1686 case GlobalStatus::isInitializerStored: DEBUG(dbgs() << "INIT STORED\n");
1688 case GlobalStatus::isStoredOnce: DEBUG(dbgs() << "STORED ONCE\n"); break;
1689 case GlobalStatus::isStored: DEBUG(dbgs() << "stored\n"); break;
1691 if (GS.StoredType == GlobalStatus::isStoredOnce && GS.StoredOnceValue)
1692 DEBUG(dbgs() << " StoredOnceValue = " << *GS.StoredOnceValue << "\n");
1693 if (GS.AccessingFunction && !GS.HasMultipleAccessingFunctions)
1694 DEBUG(dbgs() << " AccessingFunction = " << GS.AccessingFunction->getName()
1696 DEBUG(dbgs() << " HasMultipleAccessingFunctions = "
1697 << GS.HasMultipleAccessingFunctions << "\n");
1698 DEBUG(dbgs() << " HasNonInstructionUser = "
1699 << GS.HasNonInstructionUser<<"\n");
1700 DEBUG(dbgs() << "\n");
1703 // If this is a first class global and has only one accessing function
1704 // and this function is main (which we know is not recursive we can make
1705 // this global a local variable) we replace the global with a local alloca
1706 // in this function.
1708 // NOTE: It doesn't make sense to promote non single-value types since we
1709 // are just replacing static memory to stack memory.
1711 // If the global is in different address space, don't bring it to stack.
1712 if (!GS.HasMultipleAccessingFunctions &&
1713 GS.AccessingFunction && !GS.HasNonInstructionUser &&
1714 GV->getType()->getElementType()->isSingleValueType() &&
1715 GS.AccessingFunction->getName() == "main" &&
1716 GS.AccessingFunction->hasExternalLinkage() &&
1717 GV->getType()->getAddressSpace() == 0) {
1718 DEBUG(dbgs() << "LOCALIZING GLOBAL: " << *GV);
1719 Instruction* FirstI = GS.AccessingFunction->getEntryBlock().begin();
1720 const Type* ElemTy = GV->getType()->getElementType();
1721 // FIXME: Pass Global's alignment when globals have alignment
1722 AllocaInst* Alloca = new AllocaInst(ElemTy, NULL, GV->getName(), FirstI);
1723 if (!isa<UndefValue>(GV->getInitializer()))
1724 new StoreInst(GV->getInitializer(), Alloca, FirstI);
1726 GV->replaceAllUsesWith(Alloca);
1727 GV->eraseFromParent();
1732 // If the global is never loaded (but may be stored to), it is dead.
1735 DEBUG(dbgs() << "GLOBAL NEVER LOADED: " << *GV);
1737 // Delete any stores we can find to the global. We may not be able to
1738 // make it completely dead though.
1739 bool Changed = CleanupConstantGlobalUsers(GV, GV->getInitializer());
1741 // If the global is dead now, delete it.
1742 if (GV->use_empty()) {
1743 GV->eraseFromParent();
1749 } else if (GS.StoredType <= GlobalStatus::isInitializerStored) {
1750 DEBUG(dbgs() << "MARKING CONSTANT: " << *GV);
1751 GV->setConstant(true);
1753 // Clean up any obviously simplifiable users now.
1754 CleanupConstantGlobalUsers(GV, GV->getInitializer());
1756 // If the global is dead now, just nuke it.
1757 if (GV->use_empty()) {
1758 DEBUG(dbgs() << " *** Marking constant allowed us to simplify "
1759 << "all users and delete global!\n");
1760 GV->eraseFromParent();
1766 } else if (!GV->getInitializer()->getType()->isSingleValueType()) {
1767 if (TargetData *TD = getAnalysisIfAvailable<TargetData>())
1768 if (GlobalVariable *FirstNewGV = SRAGlobal(GV, *TD)) {
1769 GVI = FirstNewGV; // Don't skip the newly produced globals!
1772 } else if (GS.StoredType == GlobalStatus::isStoredOnce) {
1773 // If the initial value for the global was an undef value, and if only
1774 // one other value was stored into it, we can just change the
1775 // initializer to be the stored value, then delete all stores to the
1776 // global. This allows us to mark it constant.
1777 if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue))
1778 if (isa<UndefValue>(GV->getInitializer())) {
1779 // Change the initial value here.
1780 GV->setInitializer(SOVConstant);
1782 // Clean up any obviously simplifiable users now.
1783 CleanupConstantGlobalUsers(GV, GV->getInitializer());
1785 if (GV->use_empty()) {
1786 DEBUG(dbgs() << " *** Substituting initializer allowed us to "
1787 << "simplify all users and delete global!\n");
1788 GV->eraseFromParent();
1797 // Try to optimize globals based on the knowledge that only one value
1798 // (besides its initializer) is ever stored to the global.
1799 if (OptimizeOnceStoredGlobal(GV, GS.StoredOnceValue, GVI,
1800 getAnalysisIfAvailable<TargetData>()))
1803 // Otherwise, if the global was not a boolean, we can shrink it to be a
1805 if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue))
1806 if (TryToShrinkGlobalToBoolean(GV, SOVConstant)) {
1815 /// ChangeCalleesToFastCall - Walk all of the direct calls of the specified
1816 /// function, changing them to FastCC.
1817 static void ChangeCalleesToFastCall(Function *F) {
1818 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){
1819 CallSite User(cast<Instruction>(*UI));
1820 User.setCallingConv(CallingConv::Fast);
1824 static AttrListPtr StripNest(const AttrListPtr &Attrs) {
1825 for (unsigned i = 0, e = Attrs.getNumSlots(); i != e; ++i) {
1826 if ((Attrs.getSlot(i).Attrs & Attribute::Nest) == 0)
1829 // There can be only one.
1830 return Attrs.removeAttr(Attrs.getSlot(i).Index, Attribute::Nest);
1836 static void RemoveNestAttribute(Function *F) {
1837 F->setAttributes(StripNest(F->getAttributes()));
1838 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){
1839 CallSite User(cast<Instruction>(*UI));
1840 User.setAttributes(StripNest(User.getAttributes()));
1844 bool GlobalOpt::OptimizeFunctions(Module &M) {
1845 bool Changed = false;
1846 // Optimize functions.
1847 for (Module::iterator FI = M.begin(), E = M.end(); FI != E; ) {
1849 // Functions without names cannot be referenced outside this module.
1850 if (!F->hasName() && !F->isDeclaration())
1851 F->setLinkage(GlobalValue::InternalLinkage);
1852 F->removeDeadConstantUsers();
1853 if (F->use_empty() && (F->hasLocalLinkage() || F->hasLinkOnceLinkage())) {
1854 F->eraseFromParent();
1857 } else if (F->hasLocalLinkage()) {
1858 if (F->getCallingConv() == CallingConv::C && !F->isVarArg() &&
1859 !F->hasAddressTaken()) {
1860 // If this function has C calling conventions, is not a varargs
1861 // function, and is only called directly, promote it to use the Fast
1862 // calling convention.
1863 F->setCallingConv(CallingConv::Fast);
1864 ChangeCalleesToFastCall(F);
1869 if (F->getAttributes().hasAttrSomewhere(Attribute::Nest) &&
1870 !F->hasAddressTaken()) {
1871 // The function is not used by a trampoline intrinsic, so it is safe
1872 // to remove the 'nest' attribute.
1873 RemoveNestAttribute(F);
1882 bool GlobalOpt::OptimizeGlobalVars(Module &M) {
1883 bool Changed = false;
1884 for (Module::global_iterator GVI = M.global_begin(), E = M.global_end();
1886 GlobalVariable *GV = GVI++;
1887 // Global variables without names cannot be referenced outside this module.
1888 if (!GV->hasName() && !GV->isDeclaration())
1889 GV->setLinkage(GlobalValue::InternalLinkage);
1890 // Simplify the initializer.
1891 if (GV->hasInitializer())
1892 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GV->getInitializer())) {
1893 TargetData *TD = getAnalysisIfAvailable<TargetData>();
1894 Constant *New = ConstantFoldConstantExpression(CE, TD);
1895 if (New && New != CE)
1896 GV->setInitializer(New);
1898 // Do more involved optimizations if the global is internal.
1899 if (!GV->isConstant() && GV->hasLocalLinkage() &&
1900 GV->hasInitializer())
1901 Changed |= ProcessInternalGlobal(GV, GVI);
1906 /// FindGlobalCtors - Find the llvm.globalctors list, verifying that all
1907 /// initializers have an init priority of 65535.
1908 GlobalVariable *GlobalOpt::FindGlobalCtors(Module &M) {
1909 for (Module::global_iterator I = M.global_begin(), E = M.global_end();
1911 if (I->getName() == "llvm.global_ctors") {
1912 // Found it, verify it's an array of { int, void()* }.
1913 const ArrayType *ATy =dyn_cast<ArrayType>(I->getType()->getElementType());
1915 const StructType *STy = dyn_cast<StructType>(ATy->getElementType());
1916 if (!STy || STy->getNumElements() != 2 ||
1917 !STy->getElementType(0)->isIntegerTy(32)) return 0;
1918 const PointerType *PFTy = dyn_cast<PointerType>(STy->getElementType(1));
1919 if (!PFTy) return 0;
1920 const FunctionType *FTy = dyn_cast<FunctionType>(PFTy->getElementType());
1921 if (!FTy || !FTy->getReturnType()->isVoidTy() ||
1922 FTy->isVarArg() || FTy->getNumParams() != 0)
1925 // Verify that the initializer is simple enough for us to handle.
1926 if (!I->hasDefinitiveInitializer()) return 0;
1927 ConstantArray *CA = dyn_cast<ConstantArray>(I->getInitializer());
1929 for (User::op_iterator i = CA->op_begin(), e = CA->op_end(); i != e; ++i)
1930 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(*i)) {
1931 if (isa<ConstantPointerNull>(CS->getOperand(1)))
1934 // Must have a function or null ptr.
1935 if (!isa<Function>(CS->getOperand(1)))
1938 // Init priority must be standard.
1939 ConstantInt *CI = dyn_cast<ConstantInt>(CS->getOperand(0));
1940 if (!CI || CI->getZExtValue() != 65535)
1951 /// ParseGlobalCtors - Given a llvm.global_ctors list that we can understand,
1952 /// return a list of the functions and null terminator as a vector.
1953 static std::vector<Function*> ParseGlobalCtors(GlobalVariable *GV) {
1954 ConstantArray *CA = cast<ConstantArray>(GV->getInitializer());
1955 std::vector<Function*> Result;
1956 Result.reserve(CA->getNumOperands());
1957 for (User::op_iterator i = CA->op_begin(), e = CA->op_end(); i != e; ++i) {
1958 ConstantStruct *CS = cast<ConstantStruct>(*i);
1959 Result.push_back(dyn_cast<Function>(CS->getOperand(1)));
1964 /// InstallGlobalCtors - Given a specified llvm.global_ctors list, install the
1965 /// specified array, returning the new global to use.
1966 static GlobalVariable *InstallGlobalCtors(GlobalVariable *GCL,
1967 const std::vector<Function*> &Ctors) {
1968 // If we made a change, reassemble the initializer list.
1969 std::vector<Constant*> CSVals;
1970 CSVals.push_back(ConstantInt::get(Type::getInt32Ty(GCL->getContext()),65535));
1971 CSVals.push_back(0);
1973 // Create the new init list.
1974 std::vector<Constant*> CAList;
1975 for (unsigned i = 0, e = Ctors.size(); i != e; ++i) {
1977 CSVals[1] = Ctors[i];
1979 const Type *FTy = FunctionType::get(Type::getVoidTy(GCL->getContext()),
1981 const PointerType *PFTy = PointerType::getUnqual(FTy);
1982 CSVals[1] = Constant::getNullValue(PFTy);
1983 CSVals[0] = ConstantInt::get(Type::getInt32Ty(GCL->getContext()),
1986 CAList.push_back(ConstantStruct::get(GCL->getContext(), CSVals, false));
1989 // Create the array initializer.
1990 const Type *StructTy =
1991 cast<ArrayType>(GCL->getType()->getElementType())->getElementType();
1992 Constant *CA = ConstantArray::get(ArrayType::get(StructTy,
1993 CAList.size()), CAList);
1995 // If we didn't change the number of elements, don't create a new GV.
1996 if (CA->getType() == GCL->getInitializer()->getType()) {
1997 GCL->setInitializer(CA);
2001 // Create the new global and insert it next to the existing list.
2002 GlobalVariable *NGV = new GlobalVariable(CA->getType(), GCL->isConstant(),
2003 GCL->getLinkage(), CA, "",
2004 GCL->isThreadLocal());
2005 GCL->getParent()->getGlobalList().insert(GCL, NGV);
2008 // Nuke the old list, replacing any uses with the new one.
2009 if (!GCL->use_empty()) {
2011 if (V->getType() != GCL->getType())
2012 V = ConstantExpr::getBitCast(V, GCL->getType());
2013 GCL->replaceAllUsesWith(V);
2015 GCL->eraseFromParent();
2024 static Constant *getVal(DenseMap<Value*, Constant*> &ComputedValues,
2026 if (Constant *CV = dyn_cast<Constant>(V)) return CV;
2027 Constant *R = ComputedValues[V];
2028 assert(R && "Reference to an uncomputed value!");
2032 /// isSimpleEnoughPointerToCommit - Return true if this constant is simple
2033 /// enough for us to understand. In particular, if it is a cast of something,
2034 /// we punt. We basically just support direct accesses to globals and GEP's of
2035 /// globals. This should be kept up to date with CommitValueTo.
2036 static bool isSimpleEnoughPointerToCommit(Constant *C) {
2037 // Conservatively, avoid aggregate types. This is because we don't
2038 // want to worry about them partially overlapping other stores.
2039 if (!cast<PointerType>(C->getType())->getElementType()->isSingleValueType())
2042 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C))
2043 // Do not allow weak/linkonce/dllimport/dllexport linkage or
2044 // external globals.
2045 return GV->hasDefinitiveInitializer();
2047 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
2048 // Handle a constantexpr gep.
2049 if (CE->getOpcode() == Instruction::GetElementPtr &&
2050 isa<GlobalVariable>(CE->getOperand(0)) &&
2051 cast<GEPOperator>(CE)->isInBounds()) {
2052 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
2053 // Do not allow weak/linkonce/dllimport/dllexport linkage or
2054 // external globals.
2055 if (!GV->hasDefinitiveInitializer())
2058 // The first index must be zero.
2059 ConstantInt *CI = dyn_cast<ConstantInt>(*next(CE->op_begin()));
2060 if (!CI || !CI->isZero()) return false;
2062 // The remaining indices must be compile-time known integers within the
2063 // notional bounds of the corresponding static array types.
2064 if (!CE->isGEPWithNoNotionalOverIndexing())
2067 return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE);
2072 /// EvaluateStoreInto - Evaluate a piece of a constantexpr store into a global
2073 /// initializer. This returns 'Init' modified to reflect 'Val' stored into it.
2074 /// At this point, the GEP operands of Addr [0, OpNo) have been stepped into.
2075 static Constant *EvaluateStoreInto(Constant *Init, Constant *Val,
2076 ConstantExpr *Addr, unsigned OpNo) {
2077 // Base case of the recursion.
2078 if (OpNo == Addr->getNumOperands()) {
2079 assert(Val->getType() == Init->getType() && "Type mismatch!");
2083 std::vector<Constant*> Elts;
2084 if (const StructType *STy = dyn_cast<StructType>(Init->getType())) {
2086 // Break up the constant into its elements.
2087 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(Init)) {
2088 for (User::op_iterator i = CS->op_begin(), e = CS->op_end(); i != e; ++i)
2089 Elts.push_back(cast<Constant>(*i));
2090 } else if (isa<ConstantAggregateZero>(Init)) {
2091 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
2092 Elts.push_back(Constant::getNullValue(STy->getElementType(i)));
2093 } else if (isa<UndefValue>(Init)) {
2094 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
2095 Elts.push_back(UndefValue::get(STy->getElementType(i)));
2097 llvm_unreachable("This code is out of sync with "
2098 " ConstantFoldLoadThroughGEPConstantExpr");
2101 // Replace the element that we are supposed to.
2102 ConstantInt *CU = cast<ConstantInt>(Addr->getOperand(OpNo));
2103 unsigned Idx = CU->getZExtValue();
2104 assert(Idx < STy->getNumElements() && "Struct index out of range!");
2105 Elts[Idx] = EvaluateStoreInto(Elts[Idx], Val, Addr, OpNo+1);
2107 // Return the modified struct.
2108 return ConstantStruct::get(Init->getContext(), &Elts[0], Elts.size(),
2111 ConstantInt *CI = cast<ConstantInt>(Addr->getOperand(OpNo));
2112 const SequentialType *InitTy = cast<SequentialType>(Init->getType());
2115 if (const ArrayType *ATy = dyn_cast<ArrayType>(InitTy))
2116 NumElts = ATy->getNumElements();
2118 NumElts = cast<VectorType>(InitTy)->getNumElements();
2121 // Break up the array into elements.
2122 if (ConstantArray *CA = dyn_cast<ConstantArray>(Init)) {
2123 for (User::op_iterator i = CA->op_begin(), e = CA->op_end(); i != e; ++i)
2124 Elts.push_back(cast<Constant>(*i));
2125 } else if (ConstantVector *CV = dyn_cast<ConstantVector>(Init)) {
2126 for (User::op_iterator i = CV->op_begin(), e = CV->op_end(); i != e; ++i)
2127 Elts.push_back(cast<Constant>(*i));
2128 } else if (isa<ConstantAggregateZero>(Init)) {
2129 Elts.assign(NumElts, Constant::getNullValue(InitTy->getElementType()));
2131 assert(isa<UndefValue>(Init) && "This code is out of sync with "
2132 " ConstantFoldLoadThroughGEPConstantExpr");
2133 Elts.assign(NumElts, UndefValue::get(InitTy->getElementType()));
2136 assert(CI->getZExtValue() < NumElts);
2137 Elts[CI->getZExtValue()] =
2138 EvaluateStoreInto(Elts[CI->getZExtValue()], Val, Addr, OpNo+1);
2140 if (Init->getType()->isArrayTy())
2141 return ConstantArray::get(cast<ArrayType>(InitTy), Elts);
2143 return ConstantVector::get(&Elts[0], Elts.size());
2147 /// CommitValueTo - We have decided that Addr (which satisfies the predicate
2148 /// isSimpleEnoughPointerToCommit) should get Val as its value. Make it happen.
2149 static void CommitValueTo(Constant *Val, Constant *Addr) {
2150 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Addr)) {
2151 assert(GV->hasInitializer());
2152 GV->setInitializer(Val);
2156 ConstantExpr *CE = cast<ConstantExpr>(Addr);
2157 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
2158 GV->setInitializer(EvaluateStoreInto(GV->getInitializer(), Val, CE, 2));
2161 /// ComputeLoadResult - Return the value that would be computed by a load from
2162 /// P after the stores reflected by 'memory' have been performed. If we can't
2163 /// decide, return null.
2164 static Constant *ComputeLoadResult(Constant *P,
2165 const DenseMap<Constant*, Constant*> &Memory) {
2166 // If this memory location has been recently stored, use the stored value: it
2167 // is the most up-to-date.
2168 DenseMap<Constant*, Constant*>::const_iterator I = Memory.find(P);
2169 if (I != Memory.end()) return I->second;
2172 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(P)) {
2173 if (GV->hasDefinitiveInitializer())
2174 return GV->getInitializer();
2178 // Handle a constantexpr getelementptr.
2179 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(P))
2180 if (CE->getOpcode() == Instruction::GetElementPtr &&
2181 isa<GlobalVariable>(CE->getOperand(0))) {
2182 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
2183 if (GV->hasDefinitiveInitializer())
2184 return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE);
2187 return 0; // don't know how to evaluate.
2190 /// EvaluateFunction - Evaluate a call to function F, returning true if
2191 /// successful, false if we can't evaluate it. ActualArgs contains the formal
2192 /// arguments for the function.
2193 static bool EvaluateFunction(Function *F, Constant *&RetVal,
2194 const SmallVectorImpl<Constant*> &ActualArgs,
2195 std::vector<Function*> &CallStack,
2196 DenseMap<Constant*, Constant*> &MutatedMemory,
2197 std::vector<GlobalVariable*> &AllocaTmps) {
2198 // Check to see if this function is already executing (recursion). If so,
2199 // bail out. TODO: we might want to accept limited recursion.
2200 if (std::find(CallStack.begin(), CallStack.end(), F) != CallStack.end())
2203 CallStack.push_back(F);
2205 /// Values - As we compute SSA register values, we store their contents here.
2206 DenseMap<Value*, Constant*> Values;
2208 // Initialize arguments to the incoming values specified.
2210 for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end(); AI != E;
2212 Values[AI] = ActualArgs[ArgNo];
2214 /// ExecutedBlocks - We only handle non-looping, non-recursive code. As such,
2215 /// we can only evaluate any one basic block at most once. This set keeps
2216 /// track of what we have executed so we can detect recursive cases etc.
2217 SmallPtrSet<BasicBlock*, 32> ExecutedBlocks;
2219 // CurInst - The current instruction we're evaluating.
2220 BasicBlock::iterator CurInst = F->begin()->begin();
2222 // This is the main evaluation loop.
2224 Constant *InstResult = 0;
2226 if (StoreInst *SI = dyn_cast<StoreInst>(CurInst)) {
2227 if (SI->isVolatile()) return false; // no volatile accesses.
2228 Constant *Ptr = getVal(Values, SI->getOperand(1));
2229 if (!isSimpleEnoughPointerToCommit(Ptr))
2230 // If this is too complex for us to commit, reject it.
2232 Constant *Val = getVal(Values, SI->getOperand(0));
2233 MutatedMemory[Ptr] = Val;
2234 } else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(CurInst)) {
2235 InstResult = ConstantExpr::get(BO->getOpcode(),
2236 getVal(Values, BO->getOperand(0)),
2237 getVal(Values, BO->getOperand(1)));
2238 } else if (CmpInst *CI = dyn_cast<CmpInst>(CurInst)) {
2239 InstResult = ConstantExpr::getCompare(CI->getPredicate(),
2240 getVal(Values, CI->getOperand(0)),
2241 getVal(Values, CI->getOperand(1)));
2242 } else if (CastInst *CI = dyn_cast<CastInst>(CurInst)) {
2243 InstResult = ConstantExpr::getCast(CI->getOpcode(),
2244 getVal(Values, CI->getOperand(0)),
2246 } else if (SelectInst *SI = dyn_cast<SelectInst>(CurInst)) {
2248 ConstantExpr::getSelect(getVal(Values, SI->getOperand(0)),
2249 getVal(Values, SI->getOperand(1)),
2250 getVal(Values, SI->getOperand(2)));
2251 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(CurInst)) {
2252 Constant *P = getVal(Values, GEP->getOperand(0));
2253 SmallVector<Constant*, 8> GEPOps;
2254 for (User::op_iterator i = GEP->op_begin() + 1, e = GEP->op_end();
2256 GEPOps.push_back(getVal(Values, *i));
2257 InstResult = cast<GEPOperator>(GEP)->isInBounds() ?
2258 ConstantExpr::getInBoundsGetElementPtr(P, &GEPOps[0], GEPOps.size()) :
2259 ConstantExpr::getGetElementPtr(P, &GEPOps[0], GEPOps.size());
2260 } else if (LoadInst *LI = dyn_cast<LoadInst>(CurInst)) {
2261 if (LI->isVolatile()) return false; // no volatile accesses.
2262 InstResult = ComputeLoadResult(getVal(Values, LI->getOperand(0)),
2264 if (InstResult == 0) return false; // Could not evaluate load.
2265 } else if (AllocaInst *AI = dyn_cast<AllocaInst>(CurInst)) {
2266 if (AI->isArrayAllocation()) return false; // Cannot handle array allocs.
2267 const Type *Ty = AI->getType()->getElementType();
2268 AllocaTmps.push_back(new GlobalVariable(Ty, false,
2269 GlobalValue::InternalLinkage,
2270 UndefValue::get(Ty),
2272 InstResult = AllocaTmps.back();
2273 } else if (CallInst *CI = dyn_cast<CallInst>(CurInst)) {
2275 // Debug info can safely be ignored here.
2276 if (isa<DbgInfoIntrinsic>(CI)) {
2281 // Cannot handle inline asm.
2282 if (isa<InlineAsm>(CI->getOperand(0))) return false;
2284 // Resolve function pointers.
2285 Function *Callee = dyn_cast<Function>(getVal(Values, CI->getOperand(0)));
2286 if (!Callee) return false; // Cannot resolve.
2288 SmallVector<Constant*, 8> Formals;
2289 for (User::op_iterator i = CI->op_begin() + 1, e = CI->op_end();
2291 Formals.push_back(getVal(Values, *i));
2293 if (Callee->isDeclaration()) {
2294 // If this is a function we can constant fold, do it.
2295 if (Constant *C = ConstantFoldCall(Callee, Formals.data(),
2302 if (Callee->getFunctionType()->isVarArg())
2306 // Execute the call, if successful, use the return value.
2307 if (!EvaluateFunction(Callee, RetVal, Formals, CallStack,
2308 MutatedMemory, AllocaTmps))
2310 InstResult = RetVal;
2312 } else if (isa<TerminatorInst>(CurInst)) {
2313 BasicBlock *NewBB = 0;
2314 if (BranchInst *BI = dyn_cast<BranchInst>(CurInst)) {
2315 if (BI->isUnconditional()) {
2316 NewBB = BI->getSuccessor(0);
2319 dyn_cast<ConstantInt>(getVal(Values, BI->getCondition()));
2320 if (!Cond) return false; // Cannot determine.
2322 NewBB = BI->getSuccessor(!Cond->getZExtValue());
2324 } else if (SwitchInst *SI = dyn_cast<SwitchInst>(CurInst)) {
2326 dyn_cast<ConstantInt>(getVal(Values, SI->getCondition()));
2327 if (!Val) return false; // Cannot determine.
2328 NewBB = SI->getSuccessor(SI->findCaseValue(Val));
2329 } else if (IndirectBrInst *IBI = dyn_cast<IndirectBrInst>(CurInst)) {
2330 Value *Val = getVal(Values, IBI->getAddress())->stripPointerCasts();
2331 if (BlockAddress *BA = dyn_cast<BlockAddress>(Val))
2332 NewBB = BA->getBasicBlock();
2334 return false; // Cannot determine.
2335 } else if (ReturnInst *RI = dyn_cast<ReturnInst>(CurInst)) {
2336 if (RI->getNumOperands())
2337 RetVal = getVal(Values, RI->getOperand(0));
2339 CallStack.pop_back(); // return from fn.
2340 return true; // We succeeded at evaluating this ctor!
2342 // invoke, unwind, unreachable.
2343 return false; // Cannot handle this terminator.
2346 // Okay, we succeeded in evaluating this control flow. See if we have
2347 // executed the new block before. If so, we have a looping function,
2348 // which we cannot evaluate in reasonable time.
2349 if (!ExecutedBlocks.insert(NewBB))
2350 return false; // looped!
2352 // Okay, we have never been in this block before. Check to see if there
2353 // are any PHI nodes. If so, evaluate them with information about where
2355 BasicBlock *OldBB = CurInst->getParent();
2356 CurInst = NewBB->begin();
2358 for (; (PN = dyn_cast<PHINode>(CurInst)); ++CurInst)
2359 Values[PN] = getVal(Values, PN->getIncomingValueForBlock(OldBB));
2361 // Do NOT increment CurInst. We know that the terminator had no value.
2364 // Did not know how to evaluate this!
2368 if (!CurInst->use_empty())
2369 Values[CurInst] = InstResult;
2371 // Advance program counter.
2376 /// EvaluateStaticConstructor - Evaluate static constructors in the function, if
2377 /// we can. Return true if we can, false otherwise.
2378 static bool EvaluateStaticConstructor(Function *F) {
2379 /// MutatedMemory - For each store we execute, we update this map. Loads
2380 /// check this to get the most up-to-date value. If evaluation is successful,
2381 /// this state is committed to the process.
2382 DenseMap<Constant*, Constant*> MutatedMemory;
2384 /// AllocaTmps - To 'execute' an alloca, we create a temporary global variable
2385 /// to represent its body. This vector is needed so we can delete the
2386 /// temporary globals when we are done.
2387 std::vector<GlobalVariable*> AllocaTmps;
2389 /// CallStack - This is used to detect recursion. In pathological situations
2390 /// we could hit exponential behavior, but at least there is nothing
2392 std::vector<Function*> CallStack;
2394 // Call the function.
2395 Constant *RetValDummy;
2396 bool EvalSuccess = EvaluateFunction(F, RetValDummy,
2397 SmallVector<Constant*, 0>(), CallStack,
2398 MutatedMemory, AllocaTmps);
2400 // We succeeded at evaluation: commit the result.
2401 DEBUG(dbgs() << "FULLY EVALUATED GLOBAL CTOR FUNCTION '"
2402 << F->getName() << "' to " << MutatedMemory.size()
2404 for (DenseMap<Constant*, Constant*>::iterator I = MutatedMemory.begin(),
2405 E = MutatedMemory.end(); I != E; ++I)
2406 CommitValueTo(I->second, I->first);
2409 // At this point, we are done interpreting. If we created any 'alloca'
2410 // temporaries, release them now.
2411 while (!AllocaTmps.empty()) {
2412 GlobalVariable *Tmp = AllocaTmps.back();
2413 AllocaTmps.pop_back();
2415 // If there are still users of the alloca, the program is doing something
2416 // silly, e.g. storing the address of the alloca somewhere and using it
2417 // later. Since this is undefined, we'll just make it be null.
2418 if (!Tmp->use_empty())
2419 Tmp->replaceAllUsesWith(Constant::getNullValue(Tmp->getType()));
2428 /// OptimizeGlobalCtorsList - Simplify and evaluation global ctors if possible.
2429 /// Return true if anything changed.
2430 bool GlobalOpt::OptimizeGlobalCtorsList(GlobalVariable *&GCL) {
2431 std::vector<Function*> Ctors = ParseGlobalCtors(GCL);
2432 bool MadeChange = false;
2433 if (Ctors.empty()) return false;
2435 // Loop over global ctors, optimizing them when we can.
2436 for (unsigned i = 0; i != Ctors.size(); ++i) {
2437 Function *F = Ctors[i];
2438 // Found a null terminator in the middle of the list, prune off the rest of
2441 if (i != Ctors.size()-1) {
2448 // We cannot simplify external ctor functions.
2449 if (F->empty()) continue;
2451 // If we can evaluate the ctor at compile time, do.
2452 if (EvaluateStaticConstructor(F)) {
2453 Ctors.erase(Ctors.begin()+i);
2456 ++NumCtorsEvaluated;
2461 if (!MadeChange) return false;
2463 GCL = InstallGlobalCtors(GCL, Ctors);
2467 bool GlobalOpt::OptimizeGlobalAliases(Module &M) {
2468 bool Changed = false;
2470 for (Module::alias_iterator I = M.alias_begin(), E = M.alias_end();
2472 Module::alias_iterator J = I++;
2473 // Aliases without names cannot be referenced outside this module.
2474 if (!J->hasName() && !J->isDeclaration())
2475 J->setLinkage(GlobalValue::InternalLinkage);
2476 // If the aliasee may change at link time, nothing can be done - bail out.
2477 if (J->mayBeOverridden())
2480 Constant *Aliasee = J->getAliasee();
2481 GlobalValue *Target = cast<GlobalValue>(Aliasee->stripPointerCasts());
2482 Target->removeDeadConstantUsers();
2483 bool hasOneUse = Target->hasOneUse() && Aliasee->hasOneUse();
2485 // Make all users of the alias use the aliasee instead.
2486 if (!J->use_empty()) {
2487 J->replaceAllUsesWith(Aliasee);
2488 ++NumAliasesResolved;
2492 // If the alias is externally visible, we may still be able to simplify it.
2493 if (!J->hasLocalLinkage()) {
2494 // If the aliasee has internal linkage, give it the name and linkage
2495 // of the alias, and delete the alias. This turns:
2496 // define internal ... @f(...)
2497 // @a = alias ... @f
2499 // define ... @a(...)
2500 if (!Target->hasLocalLinkage())
2503 // Do not perform the transform if multiple aliases potentially target the
2504 // aliasee. This check also ensures that it is safe to replace the section
2505 // and other attributes of the aliasee with those of the alias.
2509 // Give the aliasee the name, linkage and other attributes of the alias.
2510 Target->takeName(J);
2511 Target->setLinkage(J->getLinkage());
2512 Target->GlobalValue::copyAttributesFrom(J);
2515 // Delete the alias.
2516 M.getAliasList().erase(J);
2517 ++NumAliasesRemoved;
2524 bool GlobalOpt::runOnModule(Module &M) {
2525 bool Changed = false;
2527 // Try to find the llvm.globalctors list.
2528 GlobalVariable *GlobalCtors = FindGlobalCtors(M);
2530 bool LocalChange = true;
2531 while (LocalChange) {
2532 LocalChange = false;
2534 // Delete functions that are trivially dead, ccc -> fastcc
2535 LocalChange |= OptimizeFunctions(M);
2537 // Optimize global_ctors list.
2539 LocalChange |= OptimizeGlobalCtorsList(GlobalCtors);
2541 // Optimize non-address-taken globals.
2542 LocalChange |= OptimizeGlobalVars(M);
2544 // Resolve aliases, when possible.
2545 LocalChange |= OptimizeGlobalAliases(M);
2546 Changed |= LocalChange;
2549 // TODO: Move all global ctors functions to the end of the module for code