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/LLVMContext.h"
24 #include "llvm/Module.h"
25 #include "llvm/Pass.h"
26 #include "llvm/Analysis/ConstantFolding.h"
27 #include "llvm/Target/TargetData.h"
28 #include "llvm/Support/CallSite.h"
29 #include "llvm/Support/Compiler.h"
30 #include "llvm/Support/Debug.h"
31 #include "llvm/Support/GetElementPtrTypeIterator.h"
32 #include "llvm/Support/MathExtras.h"
33 #include "llvm/ADT/DenseMap.h"
34 #include "llvm/ADT/SmallPtrSet.h"
35 #include "llvm/ADT/SmallVector.h"
36 #include "llvm/ADT/Statistic.h"
37 #include "llvm/ADT/StringExtras.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 VISIBILITY_HIDDEN GlobalOpt : public ModulePass {
59 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
60 AU.addRequired<TargetData>();
62 static char ID; // Pass identification, replacement for typeid
63 GlobalOpt() : ModulePass(&ID) {}
65 bool runOnModule(Module &M);
68 GlobalVariable *FindGlobalCtors(Module &M);
69 bool OptimizeFunctions(Module &M);
70 bool OptimizeGlobalVars(Module &M);
71 bool OptimizeGlobalAliases(Module &M);
72 bool OptimizeGlobalCtorsList(GlobalVariable *&GCL);
73 bool ProcessInternalGlobal(GlobalVariable *GV,Module::global_iterator &GVI);
77 char GlobalOpt::ID = 0;
78 static RegisterPass<GlobalOpt> X("globalopt", "Global Variable Optimizer");
80 ModulePass *llvm::createGlobalOptimizerPass() { return new GlobalOpt(); }
84 /// GlobalStatus - As we analyze each global, keep track of some information
85 /// about it. If we find out that the address of the global is taken, none of
86 /// this info will be accurate.
87 struct VISIBILITY_HIDDEN GlobalStatus {
88 /// isLoaded - True if the global is ever loaded. If the global isn't ever
89 /// loaded it can be deleted.
92 /// StoredType - Keep track of what stores to the global look like.
95 /// NotStored - There is no store to this global. It can thus be marked
99 /// isInitializerStored - This global is stored to, but the only thing
100 /// stored is the constant it was initialized with. This is only tracked
101 /// for scalar globals.
104 /// isStoredOnce - This global is stored to, but only its initializer and
105 /// one other value is ever stored to it. If this global isStoredOnce, we
106 /// track the value stored to it in StoredOnceValue below. This is only
107 /// tracked for scalar globals.
110 /// isStored - This global is stored to by multiple values or something else
111 /// that we cannot track.
115 /// StoredOnceValue - If only one value (besides the initializer constant) is
116 /// ever stored to this global, keep track of what value it is.
117 Value *StoredOnceValue;
119 /// AccessingFunction/HasMultipleAccessingFunctions - These start out
120 /// null/false. When the first accessing function is noticed, it is recorded.
121 /// When a second different accessing function is noticed,
122 /// HasMultipleAccessingFunctions is set to true.
123 Function *AccessingFunction;
124 bool HasMultipleAccessingFunctions;
126 /// HasNonInstructionUser - Set to true if this global has a user that is not
127 /// an instruction (e.g. a constant expr or GV initializer).
128 bool HasNonInstructionUser;
130 /// HasPHIUser - Set to true if this global has a user that is a PHI node.
133 GlobalStatus() : isLoaded(false), StoredType(NotStored), StoredOnceValue(0),
134 AccessingFunction(0), HasMultipleAccessingFunctions(false),
135 HasNonInstructionUser(false), HasPHIUser(false) {}
140 // SafeToDestroyConstant - It is safe to destroy a constant iff it is only used
141 // by constants itself. Note that constants cannot be cyclic, so this test is
142 // pretty easy to implement recursively.
144 static bool SafeToDestroyConstant(Constant *C) {
145 if (isa<GlobalValue>(C)) return false;
147 for (Value::use_iterator UI = C->use_begin(), E = C->use_end(); UI != E; ++UI)
148 if (Constant *CU = dyn_cast<Constant>(*UI)) {
149 if (!SafeToDestroyConstant(CU)) return false;
156 /// AnalyzeGlobal - Look at all uses of the global and fill in the GlobalStatus
157 /// structure. If the global has its address taken, return true to indicate we
158 /// can't do anything with it.
160 static bool AnalyzeGlobal(Value *V, GlobalStatus &GS,
161 SmallPtrSet<PHINode*, 16> &PHIUsers) {
162 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ++UI)
163 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(*UI)) {
164 GS.HasNonInstructionUser = true;
166 if (AnalyzeGlobal(CE, GS, PHIUsers)) return true;
168 } else if (Instruction *I = dyn_cast<Instruction>(*UI)) {
169 if (!GS.HasMultipleAccessingFunctions) {
170 Function *F = I->getParent()->getParent();
171 if (GS.AccessingFunction == 0)
172 GS.AccessingFunction = F;
173 else if (GS.AccessingFunction != F)
174 GS.HasMultipleAccessingFunctions = true;
176 if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
178 if (LI->isVolatile()) return true; // Don't hack on volatile loads.
179 } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
180 // Don't allow a store OF the address, only stores TO the address.
181 if (SI->getOperand(0) == V) return true;
183 if (SI->isVolatile()) return true; // Don't hack on volatile stores.
185 // If this is a direct store to the global (i.e., the global is a scalar
186 // value, not an aggregate), keep more specific information about
188 if (GS.StoredType != GlobalStatus::isStored) {
189 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(SI->getOperand(1))){
190 Value *StoredVal = SI->getOperand(0);
191 if (StoredVal == GV->getInitializer()) {
192 if (GS.StoredType < GlobalStatus::isInitializerStored)
193 GS.StoredType = GlobalStatus::isInitializerStored;
194 } else if (isa<LoadInst>(StoredVal) &&
195 cast<LoadInst>(StoredVal)->getOperand(0) == GV) {
197 if (GS.StoredType < GlobalStatus::isInitializerStored)
198 GS.StoredType = GlobalStatus::isInitializerStored;
199 } else if (GS.StoredType < GlobalStatus::isStoredOnce) {
200 GS.StoredType = GlobalStatus::isStoredOnce;
201 GS.StoredOnceValue = StoredVal;
202 } else if (GS.StoredType == GlobalStatus::isStoredOnce &&
203 GS.StoredOnceValue == StoredVal) {
206 GS.StoredType = GlobalStatus::isStored;
209 GS.StoredType = GlobalStatus::isStored;
212 } else if (isa<GetElementPtrInst>(I)) {
213 if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
214 } else if (isa<SelectInst>(I)) {
215 if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
216 } else if (PHINode *PN = dyn_cast<PHINode>(I)) {
217 // PHI nodes we can check just like select or GEP instructions, but we
218 // have to be careful about infinite recursion.
219 if (PHIUsers.insert(PN)) // Not already visited.
220 if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
221 GS.HasPHIUser = true;
222 } else if (isa<CmpInst>(I)) {
223 } else if (isa<MemTransferInst>(I)) {
224 if (I->getOperand(1) == V)
225 GS.StoredType = GlobalStatus::isStored;
226 if (I->getOperand(2) == V)
228 } else if (isa<MemSetInst>(I)) {
229 assert(I->getOperand(1) == V && "Memset only takes one pointer!");
230 GS.StoredType = GlobalStatus::isStored;
232 return true; // Any other non-load instruction might take address!
234 } else if (Constant *C = dyn_cast<Constant>(*UI)) {
235 GS.HasNonInstructionUser = true;
236 // We might have a dead and dangling constant hanging off of here.
237 if (!SafeToDestroyConstant(C))
240 GS.HasNonInstructionUser = true;
241 // Otherwise must be some other user.
248 static Constant *getAggregateConstantElement(Constant *Agg, Constant *Idx,
249 LLVMContext* Context) {
250 ConstantInt *CI = dyn_cast<ConstantInt>(Idx);
252 unsigned IdxV = CI->getZExtValue();
254 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(Agg)) {
255 if (IdxV < CS->getNumOperands()) return CS->getOperand(IdxV);
256 } else if (ConstantArray *CA = dyn_cast<ConstantArray>(Agg)) {
257 if (IdxV < CA->getNumOperands()) return CA->getOperand(IdxV);
258 } else if (ConstantVector *CP = dyn_cast<ConstantVector>(Agg)) {
259 if (IdxV < CP->getNumOperands()) return CP->getOperand(IdxV);
260 } else if (isa<ConstantAggregateZero>(Agg)) {
261 if (const StructType *STy = dyn_cast<StructType>(Agg->getType())) {
262 if (IdxV < STy->getNumElements())
263 return Context->getNullValue(STy->getElementType(IdxV));
264 } else if (const SequentialType *STy =
265 dyn_cast<SequentialType>(Agg->getType())) {
266 return Context->getNullValue(STy->getElementType());
268 } else if (isa<UndefValue>(Agg)) {
269 if (const StructType *STy = dyn_cast<StructType>(Agg->getType())) {
270 if (IdxV < STy->getNumElements())
271 return Context->getUndef(STy->getElementType(IdxV));
272 } else if (const SequentialType *STy =
273 dyn_cast<SequentialType>(Agg->getType())) {
274 return Context->getUndef(STy->getElementType());
281 /// CleanupConstantGlobalUsers - We just marked GV constant. Loop over all
282 /// users of the global, cleaning up the obvious ones. This is largely just a
283 /// quick scan over the use list to clean up the easy and obvious cruft. This
284 /// returns true if it made a change.
285 static bool CleanupConstantGlobalUsers(Value *V, Constant *Init) {
286 bool Changed = false;
287 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;) {
290 if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
292 // Replace the load with the initializer.
293 LI->replaceAllUsesWith(Init);
294 LI->eraseFromParent();
297 } else if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
298 // Store must be unreachable or storing Init into the global.
299 SI->eraseFromParent();
301 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U)) {
302 if (CE->getOpcode() == Instruction::GetElementPtr) {
303 Constant *SubInit = 0;
305 SubInit = ConstantFoldLoadThroughGEPConstantExpr(Init, CE);
306 Changed |= CleanupConstantGlobalUsers(CE, SubInit);
307 } else if (CE->getOpcode() == Instruction::BitCast &&
308 isa<PointerType>(CE->getType())) {
309 // Pointer cast, delete any stores and memsets to the global.
310 Changed |= CleanupConstantGlobalUsers(CE, 0);
313 if (CE->use_empty()) {
314 CE->destroyConstant();
317 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) {
318 // Do not transform "gepinst (gep constexpr (GV))" here, because forming
319 // "gepconstexpr (gep constexpr (GV))" will cause the two gep's to fold
320 // and will invalidate our notion of what Init is.
321 Constant *SubInit = 0;
322 if (!isa<ConstantExpr>(GEP->getOperand(0))) {
324 dyn_cast_or_null<ConstantExpr>(ConstantFoldInstruction(GEP));
325 if (Init && CE && CE->getOpcode() == Instruction::GetElementPtr)
326 SubInit = ConstantFoldLoadThroughGEPConstantExpr(Init, CE);
328 Changed |= CleanupConstantGlobalUsers(GEP, SubInit);
330 if (GEP->use_empty()) {
331 GEP->eraseFromParent();
334 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(U)) { // memset/cpy/mv
335 if (MI->getRawDest() == V) {
336 MI->eraseFromParent();
340 } else if (Constant *C = dyn_cast<Constant>(U)) {
341 // If we have a chain of dead constantexprs or other things dangling from
342 // us, and if they are all dead, nuke them without remorse.
343 if (SafeToDestroyConstant(C)) {
344 C->destroyConstant();
345 // This could have invalidated UI, start over from scratch.
346 CleanupConstantGlobalUsers(V, Init);
354 /// isSafeSROAElementUse - Return true if the specified instruction is a safe
355 /// user of a derived expression from a global that we want to SROA.
356 static bool isSafeSROAElementUse(Value *V) {
357 // We might have a dead and dangling constant hanging off of here.
358 if (Constant *C = dyn_cast<Constant>(V))
359 return SafeToDestroyConstant(C);
361 Instruction *I = dyn_cast<Instruction>(V);
362 if (!I) return false;
365 if (isa<LoadInst>(I)) return true;
367 // Stores *to* the pointer are ok.
368 if (StoreInst *SI = dyn_cast<StoreInst>(I))
369 return SI->getOperand(0) != V;
371 // Otherwise, it must be a GEP.
372 GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I);
373 if (GEPI == 0) return false;
375 if (GEPI->getNumOperands() < 3 || !isa<Constant>(GEPI->getOperand(1)) ||
376 !cast<Constant>(GEPI->getOperand(1))->isNullValue())
379 for (Value::use_iterator I = GEPI->use_begin(), E = GEPI->use_end();
381 if (!isSafeSROAElementUse(*I))
387 /// IsUserOfGlobalSafeForSRA - U is a direct user of the specified global value.
388 /// Look at it and its uses and decide whether it is safe to SROA this global.
390 static bool IsUserOfGlobalSafeForSRA(User *U, GlobalValue *GV) {
391 // The user of the global must be a GEP Inst or a ConstantExpr GEP.
392 if (!isa<GetElementPtrInst>(U) &&
393 (!isa<ConstantExpr>(U) ||
394 cast<ConstantExpr>(U)->getOpcode() != Instruction::GetElementPtr))
397 // Check to see if this ConstantExpr GEP is SRA'able. In particular, we
398 // don't like < 3 operand CE's, and we don't like non-constant integer
399 // indices. This enforces that all uses are 'gep GV, 0, C, ...' for some
401 if (U->getNumOperands() < 3 || !isa<Constant>(U->getOperand(1)) ||
402 !cast<Constant>(U->getOperand(1))->isNullValue() ||
403 !isa<ConstantInt>(U->getOperand(2)))
406 gep_type_iterator GEPI = gep_type_begin(U), E = gep_type_end(U);
407 ++GEPI; // Skip over the pointer index.
409 // If this is a use of an array allocation, do a bit more checking for sanity.
410 if (const ArrayType *AT = dyn_cast<ArrayType>(*GEPI)) {
411 uint64_t NumElements = AT->getNumElements();
412 ConstantInt *Idx = cast<ConstantInt>(U->getOperand(2));
414 // Check to make sure that index falls within the array. If not,
415 // something funny is going on, so we won't do the optimization.
417 if (Idx->getZExtValue() >= NumElements)
420 // We cannot scalar repl this level of the array unless any array
421 // sub-indices are in-range constants. In particular, consider:
422 // A[0][i]. We cannot know that the user isn't doing invalid things like
423 // allowing i to index an out-of-range subscript that accesses A[1].
425 // Scalar replacing *just* the outer index of the array is probably not
426 // going to be a win anyway, so just give up.
427 for (++GEPI; // Skip array index.
428 GEPI != E && (isa<ArrayType>(*GEPI) || isa<VectorType>(*GEPI));
430 uint64_t NumElements;
431 if (const ArrayType *SubArrayTy = dyn_cast<ArrayType>(*GEPI))
432 NumElements = SubArrayTy->getNumElements();
434 NumElements = cast<VectorType>(*GEPI)->getNumElements();
436 ConstantInt *IdxVal = dyn_cast<ConstantInt>(GEPI.getOperand());
437 if (!IdxVal || IdxVal->getZExtValue() >= NumElements)
442 for (Value::use_iterator I = U->use_begin(), E = U->use_end(); I != E; ++I)
443 if (!isSafeSROAElementUse(*I))
448 /// GlobalUsersSafeToSRA - Look at all uses of the global and decide whether it
449 /// is safe for us to perform this transformation.
451 static bool GlobalUsersSafeToSRA(GlobalValue *GV) {
452 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end();
454 if (!IsUserOfGlobalSafeForSRA(*UI, GV))
461 /// SRAGlobal - Perform scalar replacement of aggregates on the specified global
462 /// variable. This opens the door for other optimizations by exposing the
463 /// behavior of the program in a more fine-grained way. We have determined that
464 /// this transformation is safe already. We return the first global variable we
465 /// insert so that the caller can reprocess it.
466 static GlobalVariable *SRAGlobal(GlobalVariable *GV, const TargetData &TD,
467 LLVMContext* Context) {
468 // Make sure this global only has simple uses that we can SRA.
469 if (!GlobalUsersSafeToSRA(GV))
472 assert(GV->hasLocalLinkage() && !GV->isConstant());
473 Constant *Init = GV->getInitializer();
474 const Type *Ty = Init->getType();
476 std::vector<GlobalVariable*> NewGlobals;
477 Module::GlobalListType &Globals = GV->getParent()->getGlobalList();
479 // Get the alignment of the global, either explicit or target-specific.
480 unsigned StartAlignment = GV->getAlignment();
481 if (StartAlignment == 0)
482 StartAlignment = TD.getABITypeAlignment(GV->getType());
484 if (const StructType *STy = dyn_cast<StructType>(Ty)) {
485 NewGlobals.reserve(STy->getNumElements());
486 const StructLayout &Layout = *TD.getStructLayout(STy);
487 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
488 Constant *In = getAggregateConstantElement(Init,
489 Context->getConstantInt(Type::Int32Ty, i),
491 assert(In && "Couldn't get element of initializer?");
492 GlobalVariable *NGV = new GlobalVariable(STy->getElementType(i), false,
493 GlobalVariable::InternalLinkage,
494 In, GV->getName()+"."+utostr(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 Context->getConstantInt(Type::Int32Ty, i),
526 assert(In && "Couldn't get element of initializer?");
528 GlobalVariable *NGV = new GlobalVariable(STy->getElementType(), false,
529 GlobalVariable::InternalLinkage,
530 In, GV->getName()+"."+utostr(i),
533 GV->getType()->getAddressSpace());
534 Globals.insert(GV, NGV);
535 NewGlobals.push_back(NGV);
537 // Calculate the known alignment of the field. If the original aggregate
538 // had 256 byte alignment for example, something might depend on that:
539 // propagate info to each field.
540 unsigned NewAlign = (unsigned)MinAlign(StartAlignment, EltSize*i);
541 if (NewAlign > EltAlign)
542 NGV->setAlignment(NewAlign);
546 if (NewGlobals.empty())
549 DOUT << "PERFORMING GLOBAL SRA ON: " << *GV;
551 Constant *NullInt = Context->getNullValue(Type::Int32Ty);
553 // Loop over all of the uses of the global, replacing the constantexpr geps,
554 // with smaller constantexpr geps or direct references.
555 while (!GV->use_empty()) {
556 User *GEP = GV->use_back();
557 assert(((isa<ConstantExpr>(GEP) &&
558 cast<ConstantExpr>(GEP)->getOpcode()==Instruction::GetElementPtr)||
559 isa<GetElementPtrInst>(GEP)) && "NonGEP CE's are not SRAable!");
561 // Ignore the 1th operand, which has to be zero or else the program is quite
562 // broken (undefined). Get the 2nd operand, which is the structure or array
564 unsigned Val = cast<ConstantInt>(GEP->getOperand(2))->getZExtValue();
565 if (Val >= NewGlobals.size()) Val = 0; // Out of bound array access.
567 Value *NewPtr = NewGlobals[Val];
569 // Form a shorter GEP if needed.
570 if (GEP->getNumOperands() > 3) {
571 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GEP)) {
572 SmallVector<Constant*, 8> Idxs;
573 Idxs.push_back(NullInt);
574 for (unsigned i = 3, e = CE->getNumOperands(); i != e; ++i)
575 Idxs.push_back(CE->getOperand(i));
576 NewPtr = Context->getConstantExprGetElementPtr(cast<Constant>(NewPtr),
577 &Idxs[0], Idxs.size());
579 GetElementPtrInst *GEPI = cast<GetElementPtrInst>(GEP);
580 SmallVector<Value*, 8> Idxs;
581 Idxs.push_back(NullInt);
582 for (unsigned i = 3, e = GEPI->getNumOperands(); i != e; ++i)
583 Idxs.push_back(GEPI->getOperand(i));
584 NewPtr = GetElementPtrInst::Create(NewPtr, Idxs.begin(), Idxs.end(),
585 GEPI->getName()+"."+utostr(Val), GEPI);
588 GEP->replaceAllUsesWith(NewPtr);
590 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(GEP))
591 GEPI->eraseFromParent();
593 cast<ConstantExpr>(GEP)->destroyConstant();
596 // Delete the old global, now that it is dead.
600 // Loop over the new globals array deleting any globals that are obviously
601 // dead. This can arise due to scalarization of a structure or an array that
602 // has elements that are dead.
603 unsigned FirstGlobal = 0;
604 for (unsigned i = 0, e = NewGlobals.size(); i != e; ++i)
605 if (NewGlobals[i]->use_empty()) {
606 Globals.erase(NewGlobals[i]);
607 if (FirstGlobal == i) ++FirstGlobal;
610 return FirstGlobal != NewGlobals.size() ? NewGlobals[FirstGlobal] : 0;
613 /// AllUsesOfValueWillTrapIfNull - Return true if all users of the specified
614 /// value will trap if the value is dynamically null. PHIs keeps track of any
615 /// phi nodes we've seen to avoid reprocessing them.
616 static bool AllUsesOfValueWillTrapIfNull(Value *V,
617 SmallPtrSet<PHINode*, 8> &PHIs) {
618 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ++UI)
619 if (isa<LoadInst>(*UI)) {
621 } else if (StoreInst *SI = dyn_cast<StoreInst>(*UI)) {
622 if (SI->getOperand(0) == V) {
623 //cerr << "NONTRAPPING USE: " << **UI;
624 return false; // Storing the value.
626 } else if (CallInst *CI = dyn_cast<CallInst>(*UI)) {
627 if (CI->getOperand(0) != V) {
628 //cerr << "NONTRAPPING USE: " << **UI;
629 return false; // Not calling the ptr
631 } else if (InvokeInst *II = dyn_cast<InvokeInst>(*UI)) {
632 if (II->getOperand(0) != V) {
633 //cerr << "NONTRAPPING USE: " << **UI;
634 return false; // Not calling the ptr
636 } else if (BitCastInst *CI = dyn_cast<BitCastInst>(*UI)) {
637 if (!AllUsesOfValueWillTrapIfNull(CI, PHIs)) return false;
638 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(*UI)) {
639 if (!AllUsesOfValueWillTrapIfNull(GEPI, PHIs)) return false;
640 } else if (PHINode *PN = dyn_cast<PHINode>(*UI)) {
641 // If we've already seen this phi node, ignore it, it has already been
644 return AllUsesOfValueWillTrapIfNull(PN, PHIs);
645 } else if (isa<ICmpInst>(*UI) &&
646 isa<ConstantPointerNull>(UI->getOperand(1))) {
647 // Ignore setcc X, null
649 //cerr << "NONTRAPPING USE: " << **UI;
655 /// AllUsesOfLoadedValueWillTrapIfNull - Return true if all uses of any loads
656 /// from GV will trap if the loaded value is null. Note that this also permits
657 /// comparisons of the loaded value against null, as a special case.
658 static bool AllUsesOfLoadedValueWillTrapIfNull(GlobalVariable *GV) {
659 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); UI!=E; ++UI)
660 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
661 SmallPtrSet<PHINode*, 8> PHIs;
662 if (!AllUsesOfValueWillTrapIfNull(LI, PHIs))
664 } else if (isa<StoreInst>(*UI)) {
665 // Ignore stores to the global.
667 // We don't know or understand this user, bail out.
668 //cerr << "UNKNOWN USER OF GLOBAL!: " << **UI;
675 static bool OptimizeAwayTrappingUsesOfValue(Value *V, Constant *NewV,
676 LLVMContext* Context) {
677 bool Changed = false;
678 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ) {
679 Instruction *I = cast<Instruction>(*UI++);
680 if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
681 LI->setOperand(0, NewV);
683 } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
684 if (SI->getOperand(1) == V) {
685 SI->setOperand(1, NewV);
688 } else if (isa<CallInst>(I) || isa<InvokeInst>(I)) {
689 if (I->getOperand(0) == V) {
690 // Calling through the pointer! Turn into a direct call, but be careful
691 // that the pointer is not also being passed as an argument.
692 I->setOperand(0, NewV);
694 bool PassedAsArg = false;
695 for (unsigned i = 1, e = I->getNumOperands(); i != e; ++i)
696 if (I->getOperand(i) == V) {
698 I->setOperand(i, NewV);
702 // Being passed as an argument also. Be careful to not invalidate UI!
706 } else if (CastInst *CI = dyn_cast<CastInst>(I)) {
707 Changed |= OptimizeAwayTrappingUsesOfValue(CI,
708 Context->getConstantExprCast(CI->getOpcode(),
709 NewV, CI->getType()), Context);
710 if (CI->use_empty()) {
712 CI->eraseFromParent();
714 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I)) {
715 // Should handle GEP here.
716 SmallVector<Constant*, 8> Idxs;
717 Idxs.reserve(GEPI->getNumOperands()-1);
718 for (User::op_iterator i = GEPI->op_begin() + 1, e = GEPI->op_end();
720 if (Constant *C = dyn_cast<Constant>(*i))
724 if (Idxs.size() == GEPI->getNumOperands()-1)
725 Changed |= OptimizeAwayTrappingUsesOfValue(GEPI,
726 Context->getConstantExprGetElementPtr(NewV, &Idxs[0],
727 Idxs.size()), Context);
728 if (GEPI->use_empty()) {
730 GEPI->eraseFromParent();
739 /// OptimizeAwayTrappingUsesOfLoads - The specified global has only one non-null
740 /// value stored into it. If there are uses of the loaded value that would trap
741 /// if the loaded value is dynamically null, then we know that they cannot be
742 /// reachable with a null optimize away the load.
743 static bool OptimizeAwayTrappingUsesOfLoads(GlobalVariable *GV, Constant *LV,
744 LLVMContext* Context) {
745 bool Changed = false;
747 // Keep track of whether we are able to remove all the uses of the global
748 // other than the store that defines it.
749 bool AllNonStoreUsesGone = true;
751 // Replace all uses of loads with uses of uses of the stored value.
752 for (Value::use_iterator GUI = GV->use_begin(), E = GV->use_end(); GUI != E;){
753 User *GlobalUser = *GUI++;
754 if (LoadInst *LI = dyn_cast<LoadInst>(GlobalUser)) {
755 Changed |= OptimizeAwayTrappingUsesOfValue(LI, LV, Context);
756 // If we were able to delete all uses of the loads
757 if (LI->use_empty()) {
758 LI->eraseFromParent();
761 AllNonStoreUsesGone = false;
763 } else if (isa<StoreInst>(GlobalUser)) {
764 // Ignore the store that stores "LV" to the global.
765 assert(GlobalUser->getOperand(1) == GV &&
766 "Must be storing *to* the global");
768 AllNonStoreUsesGone = false;
770 // If we get here we could have other crazy uses that are transitively
772 assert((isa<PHINode>(GlobalUser) || isa<SelectInst>(GlobalUser) ||
773 isa<ConstantExpr>(GlobalUser)) && "Only expect load and stores!");
778 DOUT << "OPTIMIZED LOADS FROM STORED ONCE POINTER: " << *GV;
782 // If we nuked all of the loads, then none of the stores are needed either,
783 // nor is the global.
784 if (AllNonStoreUsesGone) {
785 DOUT << " *** GLOBAL NOW DEAD!\n";
786 CleanupConstantGlobalUsers(GV, 0);
787 if (GV->use_empty()) {
788 GV->eraseFromParent();
796 /// ConstantPropUsersOf - Walk the use list of V, constant folding all of the
797 /// instructions that are foldable.
798 static void ConstantPropUsersOf(Value *V) {
799 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; )
800 if (Instruction *I = dyn_cast<Instruction>(*UI++))
801 if (Constant *NewC = ConstantFoldInstruction(I)) {
802 I->replaceAllUsesWith(NewC);
804 // Advance UI to the next non-I use to avoid invalidating it!
805 // Instructions could multiply use V.
806 while (UI != E && *UI == I)
808 I->eraseFromParent();
812 /// OptimizeGlobalAddressOfMalloc - This function takes the specified global
813 /// variable, and transforms the program as if it always contained the result of
814 /// the specified malloc. Because it is always the result of the specified
815 /// malloc, there is no reason to actually DO the malloc. Instead, turn the
816 /// malloc into a global, and any loads of GV as uses of the new global.
817 static GlobalVariable *OptimizeGlobalAddressOfMalloc(GlobalVariable *GV,
819 LLVMContext* Context) {
820 DOUT << "PROMOTING MALLOC GLOBAL: " << *GV << " MALLOC = " << *MI;
821 ConstantInt *NElements = cast<ConstantInt>(MI->getArraySize());
823 if (NElements->getZExtValue() != 1) {
824 // If we have an array allocation, transform it to a single element
825 // allocation to make the code below simpler.
826 Type *NewTy = Context->getArrayType(MI->getAllocatedType(),
827 NElements->getZExtValue());
829 new MallocInst(NewTy, Context->getNullValue(Type::Int32Ty),
830 MI->getAlignment(), MI->getName(), MI);
832 Indices[0] = Indices[1] = Context->getNullValue(Type::Int32Ty);
833 Value *NewGEP = GetElementPtrInst::Create(NewMI, Indices, Indices + 2,
834 NewMI->getName()+".el0", MI);
835 MI->replaceAllUsesWith(NewGEP);
836 MI->eraseFromParent();
840 // Create the new global variable. The contents of the malloc'd memory is
841 // undefined, so initialize with an undef value.
842 Constant *Init = Context->getUndef(MI->getAllocatedType());
843 GlobalVariable *NewGV = new GlobalVariable(MI->getAllocatedType(), false,
844 GlobalValue::InternalLinkage, Init,
845 GV->getName()+".body",
847 GV->isThreadLocal());
848 // FIXME: This new global should have the alignment returned by malloc. Code
849 // could depend on malloc returning large alignment (on the mac, 16 bytes) but
850 // this would only guarantee some lower alignment.
851 GV->getParent()->getGlobalList().insert(GV, NewGV);
853 // Anything that used the malloc now uses the global directly.
854 MI->replaceAllUsesWith(NewGV);
856 Constant *RepValue = NewGV;
857 if (NewGV->getType() != GV->getType()->getElementType())
858 RepValue = Context->getConstantExprBitCast(RepValue,
859 GV->getType()->getElementType());
861 // If there is a comparison against null, we will insert a global bool to
862 // keep track of whether the global was initialized yet or not.
863 GlobalVariable *InitBool =
864 new GlobalVariable(Type::Int1Ty, false, GlobalValue::InternalLinkage,
865 Context->getConstantIntFalse(), GV->getName()+".init",
866 (Module *)NULL, GV->isThreadLocal());
867 bool InitBoolUsed = false;
869 // Loop over all uses of GV, processing them in turn.
870 std::vector<StoreInst*> Stores;
871 while (!GV->use_empty())
872 if (LoadInst *LI = dyn_cast<LoadInst>(GV->use_back())) {
873 while (!LI->use_empty()) {
874 Use &LoadUse = LI->use_begin().getUse();
875 if (!isa<ICmpInst>(LoadUse.getUser()))
878 ICmpInst *CI = cast<ICmpInst>(LoadUse.getUser());
879 // Replace the cmp X, 0 with a use of the bool value.
880 Value *LV = new LoadInst(InitBool, InitBool->getName()+".val", CI);
882 switch (CI->getPredicate()) {
883 default: assert(0 && "Unknown ICmp Predicate!");
884 case ICmpInst::ICMP_ULT:
885 case ICmpInst::ICMP_SLT:
886 LV = Context->getConstantIntFalse(); // X < null -> always false
888 case ICmpInst::ICMP_ULE:
889 case ICmpInst::ICMP_SLE:
890 case ICmpInst::ICMP_EQ:
891 LV = BinaryOperator::CreateNot(LV, "notinit", CI);
893 case ICmpInst::ICMP_NE:
894 case ICmpInst::ICMP_UGE:
895 case ICmpInst::ICMP_SGE:
896 case ICmpInst::ICMP_UGT:
897 case ICmpInst::ICMP_SGT:
900 CI->replaceAllUsesWith(LV);
901 CI->eraseFromParent();
904 LI->eraseFromParent();
906 StoreInst *SI = cast<StoreInst>(GV->use_back());
907 // The global is initialized when the store to it occurs.
908 new StoreInst(Context->getConstantIntTrue(), InitBool, SI);
909 SI->eraseFromParent();
912 // If the initialization boolean was used, insert it, otherwise delete it.
914 while (!InitBool->use_empty()) // Delete initializations
915 cast<Instruction>(InitBool->use_back())->eraseFromParent();
918 GV->getParent()->getGlobalList().insert(GV, InitBool);
921 // Now the GV is dead, nuke it and the malloc.
922 GV->eraseFromParent();
923 MI->eraseFromParent();
925 // To further other optimizations, loop over all users of NewGV and try to
926 // constant prop them. This will promote GEP instructions with constant
927 // indices into GEP constant-exprs, which will allow global-opt to hack on it.
928 ConstantPropUsersOf(NewGV);
929 if (RepValue != NewGV)
930 ConstantPropUsersOf(RepValue);
935 /// ValueIsOnlyUsedLocallyOrStoredToOneGlobal - Scan the use-list of V checking
936 /// to make sure that there are no complex uses of V. We permit simple things
937 /// like dereferencing the pointer, but not storing through the address, unless
938 /// it is to the specified global.
939 static bool ValueIsOnlyUsedLocallyOrStoredToOneGlobal(Instruction *V,
941 SmallPtrSet<PHINode*, 8> &PHIs) {
942 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;++UI){
943 Instruction *Inst = cast<Instruction>(*UI);
945 if (isa<LoadInst>(Inst) || isa<CmpInst>(Inst)) {
946 continue; // Fine, ignore.
949 if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
950 if (SI->getOperand(0) == V && SI->getOperand(1) != GV)
951 return false; // Storing the pointer itself... bad.
952 continue; // Otherwise, storing through it, or storing into GV... fine.
955 if (isa<GetElementPtrInst>(Inst)) {
956 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(Inst, GV, PHIs))
961 if (PHINode *PN = dyn_cast<PHINode>(Inst)) {
962 // PHIs are ok if all uses are ok. Don't infinitely recurse through PHI
965 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(PN, GV, PHIs))
970 if (BitCastInst *BCI = dyn_cast<BitCastInst>(Inst)) {
971 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(BCI, GV, PHIs))
981 /// ReplaceUsesOfMallocWithGlobal - The Alloc pointer is stored into GV
982 /// somewhere. Transform all uses of the allocation into loads from the
983 /// global and uses of the resultant pointer. Further, delete the store into
984 /// GV. This assumes that these value pass the
985 /// 'ValueIsOnlyUsedLocallyOrStoredToOneGlobal' predicate.
986 static void ReplaceUsesOfMallocWithGlobal(Instruction *Alloc,
987 GlobalVariable *GV) {
988 while (!Alloc->use_empty()) {
989 Instruction *U = cast<Instruction>(*Alloc->use_begin());
990 Instruction *InsertPt = U;
991 if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
992 // If this is the store of the allocation into the global, remove it.
993 if (SI->getOperand(1) == GV) {
994 SI->eraseFromParent();
997 } else if (PHINode *PN = dyn_cast<PHINode>(U)) {
998 // Insert the load in the corresponding predecessor, not right before the
1000 InsertPt = PN->getIncomingBlock(Alloc->use_begin())->getTerminator();
1001 } else if (isa<BitCastInst>(U)) {
1002 // Must be bitcast between the malloc and store to initialize the global.
1003 ReplaceUsesOfMallocWithGlobal(U, GV);
1004 U->eraseFromParent();
1006 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(U)) {
1007 // If this is a "GEP bitcast" and the user is a store to the global, then
1008 // just process it as a bitcast.
1009 if (GEPI->hasAllZeroIndices() && GEPI->hasOneUse())
1010 if (StoreInst *SI = dyn_cast<StoreInst>(GEPI->use_back()))
1011 if (SI->getOperand(1) == GV) {
1012 // Must be bitcast GEP between the malloc and store to initialize
1014 ReplaceUsesOfMallocWithGlobal(GEPI, GV);
1015 GEPI->eraseFromParent();
1020 // Insert a load from the global, and use it instead of the malloc.
1021 Value *NL = new LoadInst(GV, GV->getName()+".val", InsertPt);
1022 U->replaceUsesOfWith(Alloc, NL);
1026 /// LoadUsesSimpleEnoughForHeapSRA - Verify that all uses of V (a load, or a phi
1027 /// of a load) are simple enough to perform heap SRA on. This permits GEP's
1028 /// that index through the array and struct field, icmps of null, and PHIs.
1029 static bool LoadUsesSimpleEnoughForHeapSRA(Value *V,
1030 SmallPtrSet<PHINode*, 32> &LoadUsingPHIs,
1031 SmallPtrSet<PHINode*, 32> &LoadUsingPHIsPerLoad) {
1032 // We permit two users of the load: setcc comparing against the null
1033 // pointer, and a getelementptr of a specific form.
1034 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;++UI){
1035 Instruction *User = cast<Instruction>(*UI);
1037 // Comparison against null is ok.
1038 if (ICmpInst *ICI = dyn_cast<ICmpInst>(User)) {
1039 if (!isa<ConstantPointerNull>(ICI->getOperand(1)))
1044 // getelementptr is also ok, but only a simple form.
1045 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
1046 // Must index into the array and into the struct.
1047 if (GEPI->getNumOperands() < 3)
1050 // Otherwise the GEP is ok.
1054 if (PHINode *PN = dyn_cast<PHINode>(User)) {
1055 if (!LoadUsingPHIsPerLoad.insert(PN))
1056 // This means some phi nodes are dependent on each other.
1057 // Avoid infinite looping!
1059 if (!LoadUsingPHIs.insert(PN))
1060 // If we have already analyzed this PHI, then it is safe.
1063 // Make sure all uses of the PHI are simple enough to transform.
1064 if (!LoadUsesSimpleEnoughForHeapSRA(PN,
1065 LoadUsingPHIs, LoadUsingPHIsPerLoad))
1071 // Otherwise we don't know what this is, not ok.
1079 /// AllGlobalLoadUsesSimpleEnoughForHeapSRA - If all users of values loaded from
1080 /// GV are simple enough to perform HeapSRA, return true.
1081 static bool AllGlobalLoadUsesSimpleEnoughForHeapSRA(GlobalVariable *GV,
1083 SmallPtrSet<PHINode*, 32> LoadUsingPHIs;
1084 SmallPtrSet<PHINode*, 32> LoadUsingPHIsPerLoad;
1085 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); UI != E;
1087 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
1088 if (!LoadUsesSimpleEnoughForHeapSRA(LI, LoadUsingPHIs,
1089 LoadUsingPHIsPerLoad))
1091 LoadUsingPHIsPerLoad.clear();
1094 // If we reach here, we know that all uses of the loads and transitive uses
1095 // (through PHI nodes) are simple enough to transform. However, we don't know
1096 // that all inputs the to the PHI nodes are in the same equivalence sets.
1097 // Check to verify that all operands of the PHIs are either PHIS that can be
1098 // transformed, loads from GV, or MI itself.
1099 for (SmallPtrSet<PHINode*, 32>::iterator I = LoadUsingPHIs.begin(),
1100 E = LoadUsingPHIs.end(); I != E; ++I) {
1102 for (unsigned op = 0, e = PN->getNumIncomingValues(); op != e; ++op) {
1103 Value *InVal = PN->getIncomingValue(op);
1105 // PHI of the stored value itself is ok.
1106 if (InVal == MI) continue;
1108 if (PHINode *InPN = dyn_cast<PHINode>(InVal)) {
1109 // One of the PHIs in our set is (optimistically) ok.
1110 if (LoadUsingPHIs.count(InPN))
1115 // Load from GV is ok.
1116 if (LoadInst *LI = dyn_cast<LoadInst>(InVal))
1117 if (LI->getOperand(0) == GV)
1122 // Anything else is rejected.
1130 static Value *GetHeapSROAValue(Value *V, unsigned FieldNo,
1131 DenseMap<Value*, std::vector<Value*> > &InsertedScalarizedValues,
1132 std::vector<std::pair<PHINode*, unsigned> > &PHIsToRewrite,
1133 LLVMContext* Context) {
1134 std::vector<Value*> &FieldVals = InsertedScalarizedValues[V];
1136 if (FieldNo >= FieldVals.size())
1137 FieldVals.resize(FieldNo+1);
1139 // If we already have this value, just reuse the previously scalarized
1141 if (Value *FieldVal = FieldVals[FieldNo])
1144 // Depending on what instruction this is, we have several cases.
1146 if (LoadInst *LI = dyn_cast<LoadInst>(V)) {
1147 // This is a scalarized version of the load from the global. Just create
1148 // a new Load of the scalarized global.
1149 Result = new LoadInst(GetHeapSROAValue(LI->getOperand(0), FieldNo,
1150 InsertedScalarizedValues,
1151 PHIsToRewrite, Context),
1152 LI->getName()+".f" + utostr(FieldNo), LI);
1153 } else if (PHINode *PN = dyn_cast<PHINode>(V)) {
1154 // PN's type is pointer to struct. Make a new PHI of pointer to struct
1156 const StructType *ST =
1157 cast<StructType>(cast<PointerType>(PN->getType())->getElementType());
1160 PHINode::Create(Context->getPointerTypeUnqual(ST->getElementType(FieldNo)),
1161 PN->getName()+".f"+utostr(FieldNo), PN);
1162 PHIsToRewrite.push_back(std::make_pair(PN, FieldNo));
1164 assert(0 && "Unknown usable value");
1168 return FieldVals[FieldNo] = Result;
1171 /// RewriteHeapSROALoadUser - Given a load instruction and a value derived from
1172 /// the load, rewrite the derived value to use the HeapSRoA'd load.
1173 static void RewriteHeapSROALoadUser(Instruction *LoadUser,
1174 DenseMap<Value*, std::vector<Value*> > &InsertedScalarizedValues,
1175 std::vector<std::pair<PHINode*, unsigned> > &PHIsToRewrite,
1176 LLVMContext* Context) {
1177 // If this is a comparison against null, handle it.
1178 if (ICmpInst *SCI = dyn_cast<ICmpInst>(LoadUser)) {
1179 assert(isa<ConstantPointerNull>(SCI->getOperand(1)));
1180 // If we have a setcc of the loaded pointer, we can use a setcc of any
1182 Value *NPtr = GetHeapSROAValue(SCI->getOperand(0), 0,
1183 InsertedScalarizedValues, PHIsToRewrite,
1186 Value *New = new ICmpInst(SCI->getPredicate(), NPtr,
1187 Context->getNullValue(NPtr->getType()),
1188 SCI->getName(), SCI);
1189 SCI->replaceAllUsesWith(New);
1190 SCI->eraseFromParent();
1194 // Handle 'getelementptr Ptr, Idx, i32 FieldNo ...'
1195 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(LoadUser)) {
1196 assert(GEPI->getNumOperands() >= 3 && isa<ConstantInt>(GEPI->getOperand(2))
1197 && "Unexpected GEPI!");
1199 // Load the pointer for this field.
1200 unsigned FieldNo = cast<ConstantInt>(GEPI->getOperand(2))->getZExtValue();
1201 Value *NewPtr = GetHeapSROAValue(GEPI->getOperand(0), FieldNo,
1202 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,
1240 /// RewriteUsesOfLoadForHeapSRoA - We are performing Heap SRoA on a global. Ptr
1241 /// is a value loaded from the global. Eliminate all uses of Ptr, making them
1242 /// use FieldGlobals instead. All uses of loaded values satisfy
1243 /// AllGlobalLoadUsesSimpleEnoughForHeapSRA.
1244 static void RewriteUsesOfLoadForHeapSRoA(LoadInst *Load,
1245 DenseMap<Value*, std::vector<Value*> > &InsertedScalarizedValues,
1246 std::vector<std::pair<PHINode*, unsigned> > &PHIsToRewrite,
1247 LLVMContext* Context) {
1248 for (Value::use_iterator UI = Load->use_begin(), E = Load->use_end();
1250 Instruction *User = cast<Instruction>(*UI++);
1251 RewriteHeapSROALoadUser(User, InsertedScalarizedValues, PHIsToRewrite,
1255 if (Load->use_empty()) {
1256 Load->eraseFromParent();
1257 InsertedScalarizedValues.erase(Load);
1261 /// PerformHeapAllocSRoA - MI is an allocation of an array of structures. Break
1262 /// it up into multiple allocations of arrays of the fields.
1263 static GlobalVariable *PerformHeapAllocSRoA(GlobalVariable *GV, MallocInst *MI,
1264 LLVMContext* Context){
1265 DOUT << "SROA HEAP ALLOC: " << *GV << " MALLOC = " << *MI;
1266 const StructType *STy = cast<StructType>(MI->getAllocatedType());
1268 // There is guaranteed to be at least one use of the malloc (storing
1269 // it into GV). If there are other uses, change them to be uses of
1270 // the global to simplify later code. This also deletes the store
1272 ReplaceUsesOfMallocWithGlobal(MI, GV);
1274 // Okay, at this point, there are no users of the malloc. Insert N
1275 // new mallocs at the same place as MI, and N globals.
1276 std::vector<Value*> FieldGlobals;
1277 std::vector<MallocInst*> FieldMallocs;
1279 for (unsigned FieldNo = 0, e = STy->getNumElements(); FieldNo != e;++FieldNo){
1280 const Type *FieldTy = STy->getElementType(FieldNo);
1281 const Type *PFieldTy = Context->getPointerTypeUnqual(FieldTy);
1283 GlobalVariable *NGV =
1284 new GlobalVariable(PFieldTy, false, GlobalValue::InternalLinkage,
1285 Context->getNullValue(PFieldTy),
1286 GV->getName() + ".f" + utostr(FieldNo), GV,
1287 GV->isThreadLocal());
1288 FieldGlobals.push_back(NGV);
1290 MallocInst *NMI = new MallocInst(FieldTy, MI->getArraySize(),
1291 MI->getName() + ".f" + utostr(FieldNo),MI);
1292 FieldMallocs.push_back(NMI);
1293 new StoreInst(NMI, NGV, MI);
1296 // The tricky aspect of this transformation is handling the case when malloc
1297 // fails. In the original code, malloc failing would set the result pointer
1298 // of malloc to null. In this case, some mallocs could succeed and others
1299 // could fail. As such, we emit code that looks like this:
1300 // F0 = malloc(field0)
1301 // F1 = malloc(field1)
1302 // F2 = malloc(field2)
1303 // if (F0 == 0 || F1 == 0 || F2 == 0) {
1304 // if (F0) { free(F0); F0 = 0; }
1305 // if (F1) { free(F1); F1 = 0; }
1306 // if (F2) { free(F2); F2 = 0; }
1308 Value *RunningOr = 0;
1309 for (unsigned i = 0, e = FieldMallocs.size(); i != e; ++i) {
1310 Value *Cond = new ICmpInst(ICmpInst::ICMP_EQ, FieldMallocs[i],
1311 Context->getNullValue(FieldMallocs[i]->getType()),
1314 RunningOr = Cond; // First seteq
1316 RunningOr = BinaryOperator::CreateOr(RunningOr, Cond, "tmp", MI);
1319 // Split the basic block at the old malloc.
1320 BasicBlock *OrigBB = MI->getParent();
1321 BasicBlock *ContBB = OrigBB->splitBasicBlock(MI, "malloc_cont");
1323 // Create the block to check the first condition. Put all these blocks at the
1324 // end of the function as they are unlikely to be executed.
1325 BasicBlock *NullPtrBlock = BasicBlock::Create("malloc_ret_null",
1326 OrigBB->getParent());
1328 // Remove the uncond branch from OrigBB to ContBB, turning it into a cond
1329 // branch on RunningOr.
1330 OrigBB->getTerminator()->eraseFromParent();
1331 BranchInst::Create(NullPtrBlock, ContBB, RunningOr, OrigBB);
1333 // Within the NullPtrBlock, we need to emit a comparison and branch for each
1334 // pointer, because some may be null while others are not.
1335 for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) {
1336 Value *GVVal = new LoadInst(FieldGlobals[i], "tmp", NullPtrBlock);
1337 Value *Cmp = new ICmpInst(ICmpInst::ICMP_NE, GVVal,
1338 Context->getNullValue(GVVal->getType()),
1339 "tmp", NullPtrBlock);
1340 BasicBlock *FreeBlock = BasicBlock::Create("free_it", OrigBB->getParent());
1341 BasicBlock *NextBlock = BasicBlock::Create("next", OrigBB->getParent());
1342 BranchInst::Create(FreeBlock, NextBlock, Cmp, NullPtrBlock);
1344 // Fill in FreeBlock.
1345 new FreeInst(GVVal, FreeBlock);
1346 new StoreInst(Context->getNullValue(GVVal->getType()), FieldGlobals[i],
1348 BranchInst::Create(NextBlock, FreeBlock);
1350 NullPtrBlock = NextBlock;
1353 BranchInst::Create(ContBB, NullPtrBlock);
1355 // MI is no longer needed, remove it.
1356 MI->eraseFromParent();
1358 /// InsertedScalarizedLoads - As we process loads, if we can't immediately
1359 /// update all uses of the load, keep track of what scalarized loads are
1360 /// inserted for a given load.
1361 DenseMap<Value*, std::vector<Value*> > InsertedScalarizedValues;
1362 InsertedScalarizedValues[GV] = FieldGlobals;
1364 std::vector<std::pair<PHINode*, unsigned> > PHIsToRewrite;
1366 // Okay, the malloc site is completely handled. All of the uses of GV are now
1367 // loads, and all uses of those loads are simple. Rewrite them to use loads
1368 // of the per-field globals instead.
1369 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); UI != E;) {
1370 Instruction *User = cast<Instruction>(*UI++);
1372 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1373 RewriteUsesOfLoadForHeapSRoA(LI, InsertedScalarizedValues, PHIsToRewrite,
1378 // Must be a store of null.
1379 StoreInst *SI = cast<StoreInst>(User);
1380 assert(isa<ConstantPointerNull>(SI->getOperand(0)) &&
1381 "Unexpected heap-sra user!");
1383 // Insert a store of null into each global.
1384 for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) {
1385 const PointerType *PT = cast<PointerType>(FieldGlobals[i]->getType());
1386 Constant *Null = Context->getNullValue(PT->getElementType());
1387 new StoreInst(Null, FieldGlobals[i], SI);
1389 // Erase the original store.
1390 SI->eraseFromParent();
1393 // While we have PHIs that are interesting to rewrite, do it.
1394 while (!PHIsToRewrite.empty()) {
1395 PHINode *PN = PHIsToRewrite.back().first;
1396 unsigned FieldNo = PHIsToRewrite.back().second;
1397 PHIsToRewrite.pop_back();
1398 PHINode *FieldPN = cast<PHINode>(InsertedScalarizedValues[PN][FieldNo]);
1399 assert(FieldPN->getNumIncomingValues() == 0 &&"Already processed this phi");
1401 // Add all the incoming values. This can materialize more phis.
1402 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
1403 Value *InVal = PN->getIncomingValue(i);
1404 InVal = GetHeapSROAValue(InVal, FieldNo, InsertedScalarizedValues,
1405 PHIsToRewrite, Context);
1406 FieldPN->addIncoming(InVal, PN->getIncomingBlock(i));
1410 // Drop all inter-phi links and any loads that made it this far.
1411 for (DenseMap<Value*, std::vector<Value*> >::iterator
1412 I = InsertedScalarizedValues.begin(), E = InsertedScalarizedValues.end();
1414 if (PHINode *PN = dyn_cast<PHINode>(I->first))
1415 PN->dropAllReferences();
1416 else if (LoadInst *LI = dyn_cast<LoadInst>(I->first))
1417 LI->dropAllReferences();
1420 // Delete all the phis and loads now that inter-references are dead.
1421 for (DenseMap<Value*, std::vector<Value*> >::iterator
1422 I = InsertedScalarizedValues.begin(), E = InsertedScalarizedValues.end();
1424 if (PHINode *PN = dyn_cast<PHINode>(I->first))
1425 PN->eraseFromParent();
1426 else if (LoadInst *LI = dyn_cast<LoadInst>(I->first))
1427 LI->eraseFromParent();
1430 // The old global is now dead, remove it.
1431 GV->eraseFromParent();
1434 return cast<GlobalVariable>(FieldGlobals[0]);
1437 /// TryToOptimizeStoreOfMallocToGlobal - This function is called when we see a
1438 /// pointer global variable with a single value stored it that is a malloc or
1440 static bool TryToOptimizeStoreOfMallocToGlobal(GlobalVariable *GV,
1442 Module::global_iterator &GVI,
1444 LLVMContext* Context) {
1445 // If this is a malloc of an abstract type, don't touch it.
1446 if (!MI->getAllocatedType()->isSized())
1449 // We can't optimize this global unless all uses of it are *known* to be
1450 // of the malloc value, not of the null initializer value (consider a use
1451 // that compares the global's value against zero to see if the malloc has
1452 // been reached). To do this, we check to see if all uses of the global
1453 // would trap if the global were null: this proves that they must all
1454 // happen after the malloc.
1455 if (!AllUsesOfLoadedValueWillTrapIfNull(GV))
1458 // We can't optimize this if the malloc itself is used in a complex way,
1459 // for example, being stored into multiple globals. This allows the
1460 // malloc to be stored into the specified global, loaded setcc'd, and
1461 // GEP'd. These are all things we could transform to using the global
1464 SmallPtrSet<PHINode*, 8> PHIs;
1465 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(MI, GV, PHIs))
1470 // If we have a global that is only initialized with a fixed size malloc,
1471 // transform the program to use global memory instead of malloc'd memory.
1472 // This eliminates dynamic allocation, avoids an indirection accessing the
1473 // data, and exposes the resultant global to further GlobalOpt.
1474 if (ConstantInt *NElements = dyn_cast<ConstantInt>(MI->getArraySize())) {
1475 // Restrict this transformation to only working on small allocations
1476 // (2048 bytes currently), as we don't want to introduce a 16M global or
1478 if (NElements->getZExtValue()*
1479 TD.getTypeAllocSize(MI->getAllocatedType()) < 2048) {
1480 GVI = OptimizeGlobalAddressOfMalloc(GV, MI, Context);
1485 // If the allocation is an array of structures, consider transforming this
1486 // into multiple malloc'd arrays, one for each field. This is basically
1487 // SRoA for malloc'd memory.
1488 const Type *AllocTy = MI->getAllocatedType();
1490 // If this is an allocation of a fixed size array of structs, analyze as a
1491 // variable size array. malloc [100 x struct],1 -> malloc struct, 100
1492 if (!MI->isArrayAllocation())
1493 if (const ArrayType *AT = dyn_cast<ArrayType>(AllocTy))
1494 AllocTy = AT->getElementType();
1496 if (const StructType *AllocSTy = dyn_cast<StructType>(AllocTy)) {
1497 // This the structure has an unreasonable number of fields, leave it
1499 if (AllocSTy->getNumElements() <= 16 && AllocSTy->getNumElements() != 0 &&
1500 AllGlobalLoadUsesSimpleEnoughForHeapSRA(GV, MI)) {
1502 // If this is a fixed size array, transform the Malloc to be an alloc of
1503 // structs. malloc [100 x struct],1 -> malloc struct, 100
1504 if (const ArrayType *AT = dyn_cast<ArrayType>(MI->getAllocatedType())) {
1506 new MallocInst(AllocSTy,
1507 Context->getConstantInt(Type::Int32Ty, AT->getNumElements()),
1509 NewMI->takeName(MI);
1510 Value *Cast = new BitCastInst(NewMI, MI->getType(), "tmp", MI);
1511 MI->replaceAllUsesWith(Cast);
1512 MI->eraseFromParent();
1516 GVI = PerformHeapAllocSRoA(GV, MI, Context);
1524 // OptimizeOnceStoredGlobal - Try to optimize globals based on the knowledge
1525 // that only one value (besides its initializer) is ever stored to the global.
1526 static bool OptimizeOnceStoredGlobal(GlobalVariable *GV, Value *StoredOnceVal,
1527 Module::global_iterator &GVI,
1528 TargetData &TD, LLVMContext* Context) {
1529 // Ignore no-op GEPs and bitcasts.
1530 StoredOnceVal = StoredOnceVal->stripPointerCasts();
1532 // If we are dealing with a pointer global that is initialized to null and
1533 // only has one (non-null) value stored into it, then we can optimize any
1534 // users of the loaded value (often calls and loads) that would trap if the
1536 if (isa<PointerType>(GV->getInitializer()->getType()) &&
1537 GV->getInitializer()->isNullValue()) {
1538 if (Constant *SOVC = dyn_cast<Constant>(StoredOnceVal)) {
1539 if (GV->getInitializer()->getType() != SOVC->getType())
1541 Context->getConstantExprBitCast(SOVC, GV->getInitializer()->getType());
1543 // Optimize away any trapping uses of the loaded value.
1544 if (OptimizeAwayTrappingUsesOfLoads(GV, SOVC, Context))
1546 } else if (MallocInst *MI = dyn_cast<MallocInst>(StoredOnceVal)) {
1547 if (TryToOptimizeStoreOfMallocToGlobal(GV, MI, GVI, TD, Context))
1555 /// TryToShrinkGlobalToBoolean - At this point, we have learned that the only
1556 /// two values ever stored into GV are its initializer and OtherVal. See if we
1557 /// can shrink the global into a boolean and select between the two values
1558 /// whenever it is used. This exposes the values to other scalar optimizations.
1559 static bool TryToShrinkGlobalToBoolean(GlobalVariable *GV, Constant *OtherVal,
1560 LLVMContext* Context) {
1561 const Type *GVElType = GV->getType()->getElementType();
1563 // If GVElType is already i1, it is already shrunk. If the type of the GV is
1564 // an FP value, pointer or vector, don't do this optimization because a select
1565 // between them is very expensive and unlikely to lead to later
1566 // simplification. In these cases, we typically end up with "cond ? v1 : v2"
1567 // where v1 and v2 both require constant pool loads, a big loss.
1568 if (GVElType == Type::Int1Ty || GVElType->isFloatingPoint() ||
1569 isa<PointerType>(GVElType) || isa<VectorType>(GVElType))
1572 // Walk the use list of the global seeing if all the uses are load or store.
1573 // If there is anything else, bail out.
1574 for (Value::use_iterator I = GV->use_begin(), E = GV->use_end(); I != E; ++I)
1575 if (!isa<LoadInst>(I) && !isa<StoreInst>(I))
1578 DOUT << " *** SHRINKING TO BOOL: " << *GV;
1580 // Create the new global, initializing it to false.
1581 GlobalVariable *NewGV = new GlobalVariable(Type::Int1Ty, false,
1582 GlobalValue::InternalLinkage, Context->getConstantIntFalse(),
1585 GV->isThreadLocal());
1586 GV->getParent()->getGlobalList().insert(GV, NewGV);
1588 Constant *InitVal = GV->getInitializer();
1589 assert(InitVal->getType() != Type::Int1Ty && "No reason to shrink to bool!");
1591 // If initialized to zero and storing one into the global, we can use a cast
1592 // instead of a select to synthesize the desired value.
1593 bool IsOneZero = false;
1594 if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal))
1595 IsOneZero = InitVal->isNullValue() && CI->isOne();
1597 while (!GV->use_empty()) {
1598 Instruction *UI = cast<Instruction>(GV->use_back());
1599 if (StoreInst *SI = dyn_cast<StoreInst>(UI)) {
1600 // Change the store into a boolean store.
1601 bool StoringOther = SI->getOperand(0) == OtherVal;
1602 // Only do this if we weren't storing a loaded value.
1604 if (StoringOther || SI->getOperand(0) == InitVal)
1605 StoreVal = Context->getConstantInt(Type::Int1Ty, StoringOther);
1607 // Otherwise, we are storing a previously loaded copy. To do this,
1608 // change the copy from copying the original value to just copying the
1610 Instruction *StoredVal = cast<Instruction>(SI->getOperand(0));
1612 // If we're already replaced the input, StoredVal will be a cast or
1613 // select instruction. If not, it will be a load of the original
1615 if (LoadInst *LI = dyn_cast<LoadInst>(StoredVal)) {
1616 assert(LI->getOperand(0) == GV && "Not a copy!");
1617 // Insert a new load, to preserve the saved value.
1618 StoreVal = new LoadInst(NewGV, LI->getName()+".b", LI);
1620 assert((isa<CastInst>(StoredVal) || isa<SelectInst>(StoredVal)) &&
1621 "This is not a form that we understand!");
1622 StoreVal = StoredVal->getOperand(0);
1623 assert(isa<LoadInst>(StoreVal) && "Not a load of NewGV!");
1626 new StoreInst(StoreVal, NewGV, SI);
1628 // Change the load into a load of bool then a select.
1629 LoadInst *LI = cast<LoadInst>(UI);
1630 LoadInst *NLI = new LoadInst(NewGV, LI->getName()+".b", LI);
1633 NSI = new ZExtInst(NLI, LI->getType(), "", LI);
1635 NSI = SelectInst::Create(NLI, OtherVal, InitVal, "", LI);
1637 LI->replaceAllUsesWith(NSI);
1639 UI->eraseFromParent();
1642 GV->eraseFromParent();
1647 /// ProcessInternalGlobal - Analyze the specified global variable and optimize
1648 /// it if possible. If we make a change, return true.
1649 bool GlobalOpt::ProcessInternalGlobal(GlobalVariable *GV,
1650 Module::global_iterator &GVI) {
1651 SmallPtrSet<PHINode*, 16> PHIUsers;
1653 GV->removeDeadConstantUsers();
1655 if (GV->use_empty()) {
1656 DOUT << "GLOBAL DEAD: " << *GV;
1657 GV->eraseFromParent();
1662 if (!AnalyzeGlobal(GV, GS, PHIUsers)) {
1664 cerr << "Global: " << *GV;
1665 cerr << " isLoaded = " << GS.isLoaded << "\n";
1666 cerr << " StoredType = ";
1667 switch (GS.StoredType) {
1668 case GlobalStatus::NotStored: cerr << "NEVER STORED\n"; break;
1669 case GlobalStatus::isInitializerStored: cerr << "INIT STORED\n"; break;
1670 case GlobalStatus::isStoredOnce: cerr << "STORED ONCE\n"; break;
1671 case GlobalStatus::isStored: cerr << "stored\n"; break;
1673 if (GS.StoredType == GlobalStatus::isStoredOnce && GS.StoredOnceValue)
1674 cerr << " StoredOnceValue = " << *GS.StoredOnceValue << "\n";
1675 if (GS.AccessingFunction && !GS.HasMultipleAccessingFunctions)
1676 cerr << " AccessingFunction = " << GS.AccessingFunction->getName()
1678 cerr << " HasMultipleAccessingFunctions = "
1679 << GS.HasMultipleAccessingFunctions << "\n";
1680 cerr << " HasNonInstructionUser = " << GS.HasNonInstructionUser<<"\n";
1684 // If this is a first class global and has only one accessing function
1685 // and this function is main (which we know is not recursive we can make
1686 // this global a local variable) we replace the global with a local alloca
1687 // in this function.
1689 // NOTE: It doesn't make sense to promote non single-value types since we
1690 // are just replacing static memory to stack memory.
1692 // If the global is in different address space, don't bring it to stack.
1693 if (!GS.HasMultipleAccessingFunctions &&
1694 GS.AccessingFunction && !GS.HasNonInstructionUser &&
1695 GV->getType()->getElementType()->isSingleValueType() &&
1696 GS.AccessingFunction->getName() == "main" &&
1697 GS.AccessingFunction->hasExternalLinkage() &&
1698 GV->getType()->getAddressSpace() == 0) {
1699 DOUT << "LOCALIZING GLOBAL: " << *GV;
1700 Instruction* FirstI = GS.AccessingFunction->getEntryBlock().begin();
1701 const Type* ElemTy = GV->getType()->getElementType();
1702 // FIXME: Pass Global's alignment when globals have alignment
1703 AllocaInst* Alloca = new AllocaInst(ElemTy, NULL, GV->getName(), FirstI);
1704 if (!isa<UndefValue>(GV->getInitializer()))
1705 new StoreInst(GV->getInitializer(), Alloca, FirstI);
1707 GV->replaceAllUsesWith(Alloca);
1708 GV->eraseFromParent();
1713 // If the global is never loaded (but may be stored to), it is dead.
1716 DOUT << "GLOBAL NEVER LOADED: " << *GV;
1718 // Delete any stores we can find to the global. We may not be able to
1719 // make it completely dead though.
1720 bool Changed = CleanupConstantGlobalUsers(GV, GV->getInitializer());
1722 // If the global is dead now, delete it.
1723 if (GV->use_empty()) {
1724 GV->eraseFromParent();
1730 } else if (GS.StoredType <= GlobalStatus::isInitializerStored) {
1731 DOUT << "MARKING CONSTANT: " << *GV;
1732 GV->setConstant(true);
1734 // Clean up any obviously simplifiable users now.
1735 CleanupConstantGlobalUsers(GV, GV->getInitializer());
1737 // If the global is dead now, just nuke it.
1738 if (GV->use_empty()) {
1739 DOUT << " *** Marking constant allowed us to simplify "
1740 << "all users and delete global!\n";
1741 GV->eraseFromParent();
1747 } else if (!GV->getInitializer()->getType()->isSingleValueType()) {
1748 if (GlobalVariable *FirstNewGV = SRAGlobal(GV,
1749 getAnalysis<TargetData>(),
1751 GVI = FirstNewGV; // Don't skip the newly produced globals!
1754 } else if (GS.StoredType == GlobalStatus::isStoredOnce) {
1755 // If the initial value for the global was an undef value, and if only
1756 // one other value was stored into it, we can just change the
1757 // initializer to be the stored value, then delete all stores to the
1758 // global. This allows us to mark it constant.
1759 if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue))
1760 if (isa<UndefValue>(GV->getInitializer())) {
1761 // Change the initial value here.
1762 GV->setInitializer(SOVConstant);
1764 // Clean up any obviously simplifiable users now.
1765 CleanupConstantGlobalUsers(GV, GV->getInitializer());
1767 if (GV->use_empty()) {
1768 DOUT << " *** Substituting initializer allowed us to "
1769 << "simplify all users and delete global!\n";
1770 GV->eraseFromParent();
1779 // Try to optimize globals based on the knowledge that only one value
1780 // (besides its initializer) is ever stored to the global.
1781 if (OptimizeOnceStoredGlobal(GV, GS.StoredOnceValue, GVI,
1782 getAnalysis<TargetData>(), Context))
1785 // Otherwise, if the global was not a boolean, we can shrink it to be a
1787 if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue))
1788 if (TryToShrinkGlobalToBoolean(GV, SOVConstant, Context)) {
1797 /// ChangeCalleesToFastCall - Walk all of the direct calls of the specified
1798 /// function, changing them to FastCC.
1799 static void ChangeCalleesToFastCall(Function *F) {
1800 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){
1801 CallSite User(cast<Instruction>(*UI));
1802 User.setCallingConv(CallingConv::Fast);
1806 static AttrListPtr StripNest(const AttrListPtr &Attrs) {
1807 for (unsigned i = 0, e = Attrs.getNumSlots(); i != e; ++i) {
1808 if ((Attrs.getSlot(i).Attrs & Attribute::Nest) == 0)
1811 // There can be only one.
1812 return Attrs.removeAttr(Attrs.getSlot(i).Index, Attribute::Nest);
1818 static void RemoveNestAttribute(Function *F) {
1819 F->setAttributes(StripNest(F->getAttributes()));
1820 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){
1821 CallSite User(cast<Instruction>(*UI));
1822 User.setAttributes(StripNest(User.getAttributes()));
1826 bool GlobalOpt::OptimizeFunctions(Module &M) {
1827 bool Changed = false;
1828 // Optimize functions.
1829 for (Module::iterator FI = M.begin(), E = M.end(); FI != E; ) {
1831 // Functions without names cannot be referenced outside this module.
1832 if (!F->hasName() && !F->isDeclaration())
1833 F->setLinkage(GlobalValue::InternalLinkage);
1834 F->removeDeadConstantUsers();
1835 if (F->use_empty() && (F->hasLocalLinkage() ||
1836 F->hasLinkOnceLinkage())) {
1837 M.getFunctionList().erase(F);
1840 } else if (F->hasLocalLinkage()) {
1841 if (F->getCallingConv() == CallingConv::C && !F->isVarArg() &&
1842 !F->hasAddressTaken()) {
1843 // If this function has C calling conventions, is not a varargs
1844 // function, and is only called directly, promote it to use the Fast
1845 // calling convention.
1846 F->setCallingConv(CallingConv::Fast);
1847 ChangeCalleesToFastCall(F);
1852 if (F->getAttributes().hasAttrSomewhere(Attribute::Nest) &&
1853 !F->hasAddressTaken()) {
1854 // The function is not used by a trampoline intrinsic, so it is safe
1855 // to remove the 'nest' attribute.
1856 RemoveNestAttribute(F);
1865 bool GlobalOpt::OptimizeGlobalVars(Module &M) {
1866 bool Changed = false;
1867 for (Module::global_iterator GVI = M.global_begin(), E = M.global_end();
1869 GlobalVariable *GV = GVI++;
1870 // Global variables without names cannot be referenced outside this module.
1871 if (!GV->hasName() && !GV->isDeclaration())
1872 GV->setLinkage(GlobalValue::InternalLinkage);
1873 if (!GV->isConstant() && GV->hasLocalLinkage() &&
1874 GV->hasInitializer())
1875 Changed |= ProcessInternalGlobal(GV, GVI);
1880 /// FindGlobalCtors - Find the llvm.globalctors list, verifying that all
1881 /// initializers have an init priority of 65535.
1882 GlobalVariable *GlobalOpt::FindGlobalCtors(Module &M) {
1883 for (Module::global_iterator I = M.global_begin(), E = M.global_end();
1885 if (I->getName() == "llvm.global_ctors") {
1886 // Found it, verify it's an array of { int, void()* }.
1887 const ArrayType *ATy =dyn_cast<ArrayType>(I->getType()->getElementType());
1889 const StructType *STy = dyn_cast<StructType>(ATy->getElementType());
1890 if (!STy || STy->getNumElements() != 2 ||
1891 STy->getElementType(0) != Type::Int32Ty) return 0;
1892 const PointerType *PFTy = dyn_cast<PointerType>(STy->getElementType(1));
1893 if (!PFTy) return 0;
1894 const FunctionType *FTy = dyn_cast<FunctionType>(PFTy->getElementType());
1895 if (!FTy || FTy->getReturnType() != Type::VoidTy || FTy->isVarArg() ||
1896 FTy->getNumParams() != 0)
1899 // Verify that the initializer is simple enough for us to handle.
1900 if (!I->hasInitializer()) return 0;
1901 ConstantArray *CA = dyn_cast<ConstantArray>(I->getInitializer());
1903 for (User::op_iterator i = CA->op_begin(), e = CA->op_end(); i != e; ++i)
1904 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(*i)) {
1905 if (isa<ConstantPointerNull>(CS->getOperand(1)))
1908 // Must have a function or null ptr.
1909 if (!isa<Function>(CS->getOperand(1)))
1912 // Init priority must be standard.
1913 ConstantInt *CI = dyn_cast<ConstantInt>(CS->getOperand(0));
1914 if (!CI || CI->getZExtValue() != 65535)
1925 /// ParseGlobalCtors - Given a llvm.global_ctors list that we can understand,
1926 /// return a list of the functions and null terminator as a vector.
1927 static std::vector<Function*> ParseGlobalCtors(GlobalVariable *GV) {
1928 ConstantArray *CA = cast<ConstantArray>(GV->getInitializer());
1929 std::vector<Function*> Result;
1930 Result.reserve(CA->getNumOperands());
1931 for (User::op_iterator i = CA->op_begin(), e = CA->op_end(); i != e; ++i) {
1932 ConstantStruct *CS = cast<ConstantStruct>(*i);
1933 Result.push_back(dyn_cast<Function>(CS->getOperand(1)));
1938 /// InstallGlobalCtors - Given a specified llvm.global_ctors list, install the
1939 /// specified array, returning the new global to use.
1940 static GlobalVariable *InstallGlobalCtors(GlobalVariable *GCL,
1941 const std::vector<Function*> &Ctors,
1942 LLVMContext* Context) {
1943 // If we made a change, reassemble the initializer list.
1944 std::vector<Constant*> CSVals;
1945 CSVals.push_back(Context->getConstantInt(Type::Int32Ty, 65535));
1946 CSVals.push_back(0);
1948 // Create the new init list.
1949 std::vector<Constant*> CAList;
1950 for (unsigned i = 0, e = Ctors.size(); i != e; ++i) {
1952 CSVals[1] = Ctors[i];
1954 const Type *FTy = Context->getFunctionType(Type::VoidTy, false);
1955 const PointerType *PFTy = Context->getPointerTypeUnqual(FTy);
1956 CSVals[1] = Context->getNullValue(PFTy);
1957 CSVals[0] = Context->getConstantInt(Type::Int32Ty, 2147483647);
1959 CAList.push_back(Context->getConstantStruct(CSVals));
1962 // Create the array initializer.
1963 const Type *StructTy =
1964 cast<ArrayType>(GCL->getType()->getElementType())->getElementType();
1965 Constant *CA = Context->getConstantArray(ArrayType::get(StructTy,
1966 CAList.size()), CAList);
1968 // If we didn't change the number of elements, don't create a new GV.
1969 if (CA->getType() == GCL->getInitializer()->getType()) {
1970 GCL->setInitializer(CA);
1974 // Create the new global and insert it next to the existing list.
1975 GlobalVariable *NGV = new GlobalVariable(CA->getType(), GCL->isConstant(),
1976 GCL->getLinkage(), CA, "",
1978 GCL->isThreadLocal());
1979 GCL->getParent()->getGlobalList().insert(GCL, NGV);
1982 // Nuke the old list, replacing any uses with the new one.
1983 if (!GCL->use_empty()) {
1985 if (V->getType() != GCL->getType())
1986 V = Context->getConstantExprBitCast(V, GCL->getType());
1987 GCL->replaceAllUsesWith(V);
1989 GCL->eraseFromParent();
1998 static Constant *getVal(DenseMap<Value*, Constant*> &ComputedValues,
2000 if (Constant *CV = dyn_cast<Constant>(V)) return CV;
2001 Constant *R = ComputedValues[V];
2002 assert(R && "Reference to an uncomputed value!");
2006 /// isSimpleEnoughPointerToCommit - Return true if this constant is simple
2007 /// enough for us to understand. In particular, if it is a cast of something,
2008 /// we punt. We basically just support direct accesses to globals and GEP's of
2009 /// globals. This should be kept up to date with CommitValueTo.
2010 static bool isSimpleEnoughPointerToCommit(Constant *C) {
2011 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C)) {
2012 if (!GV->hasExternalLinkage() && !GV->hasLocalLinkage())
2013 return false; // do not allow weak/linkonce/dllimport/dllexport linkage.
2014 return !GV->isDeclaration(); // reject external globals.
2016 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
2017 // Handle a constantexpr gep.
2018 if (CE->getOpcode() == Instruction::GetElementPtr &&
2019 isa<GlobalVariable>(CE->getOperand(0))) {
2020 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
2021 if (!GV->hasExternalLinkage() && !GV->hasLocalLinkage())
2022 return false; // do not allow weak/linkonce/dllimport/dllexport linkage.
2023 return GV->hasInitializer() &&
2024 ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE);
2029 /// EvaluateStoreInto - Evaluate a piece of a constantexpr store into a global
2030 /// initializer. This returns 'Init' modified to reflect 'Val' stored into it.
2031 /// At this point, the GEP operands of Addr [0, OpNo) have been stepped into.
2032 static Constant *EvaluateStoreInto(Constant *Init, Constant *Val,
2033 ConstantExpr *Addr, unsigned OpNo,
2034 LLVMContext* Context) {
2035 // Base case of the recursion.
2036 if (OpNo == Addr->getNumOperands()) {
2037 assert(Val->getType() == Init->getType() && "Type mismatch!");
2041 if (const StructType *STy = dyn_cast<StructType>(Init->getType())) {
2042 std::vector<Constant*> Elts;
2044 // Break up the constant into its elements.
2045 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(Init)) {
2046 for (User::op_iterator i = CS->op_begin(), e = CS->op_end(); i != e; ++i)
2047 Elts.push_back(cast<Constant>(*i));
2048 } else if (isa<ConstantAggregateZero>(Init)) {
2049 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
2050 Elts.push_back(Context->getNullValue(STy->getElementType(i)));
2051 } else if (isa<UndefValue>(Init)) {
2052 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
2053 Elts.push_back(Context->getUndef(STy->getElementType(i)));
2055 assert(0 && "This code is out of sync with "
2056 " ConstantFoldLoadThroughGEPConstantExpr");
2059 // Replace the element that we are supposed to.
2060 ConstantInt *CU = cast<ConstantInt>(Addr->getOperand(OpNo));
2061 unsigned Idx = CU->getZExtValue();
2062 assert(Idx < STy->getNumElements() && "Struct index out of range!");
2063 Elts[Idx] = EvaluateStoreInto(Elts[Idx], Val, Addr, OpNo+1, Context);
2065 // Return the modified struct.
2066 return Context->getConstantStruct(&Elts[0], Elts.size(), STy->isPacked());
2068 ConstantInt *CI = cast<ConstantInt>(Addr->getOperand(OpNo));
2069 const ArrayType *ATy = cast<ArrayType>(Init->getType());
2071 // Break up the array into elements.
2072 std::vector<Constant*> Elts;
2073 if (ConstantArray *CA = dyn_cast<ConstantArray>(Init)) {
2074 for (User::op_iterator i = CA->op_begin(), e = CA->op_end(); i != e; ++i)
2075 Elts.push_back(cast<Constant>(*i));
2076 } else if (isa<ConstantAggregateZero>(Init)) {
2077 Constant *Elt = Context->getNullValue(ATy->getElementType());
2078 Elts.assign(ATy->getNumElements(), Elt);
2079 } else if (isa<UndefValue>(Init)) {
2080 Constant *Elt = Context->getUndef(ATy->getElementType());
2081 Elts.assign(ATy->getNumElements(), Elt);
2083 assert(0 && "This code is out of sync with "
2084 " ConstantFoldLoadThroughGEPConstantExpr");
2087 assert(CI->getZExtValue() < ATy->getNumElements());
2088 Elts[CI->getZExtValue()] =
2089 EvaluateStoreInto(Elts[CI->getZExtValue()], Val, Addr, OpNo+1, Context);
2090 return Context->getConstantArray(ATy, Elts);
2094 /// CommitValueTo - We have decided that Addr (which satisfies the predicate
2095 /// isSimpleEnoughPointerToCommit) should get Val as its value. Make it happen.
2096 static void CommitValueTo(Constant *Val, Constant *Addr,
2097 LLVMContext* Context) {
2098 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Addr)) {
2099 assert(GV->hasInitializer());
2100 GV->setInitializer(Val);
2104 ConstantExpr *CE = cast<ConstantExpr>(Addr);
2105 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
2107 Constant *Init = GV->getInitializer();
2108 Init = EvaluateStoreInto(Init, Val, CE, 2, Context);
2109 GV->setInitializer(Init);
2112 /// ComputeLoadResult - Return the value that would be computed by a load from
2113 /// P after the stores reflected by 'memory' have been performed. If we can't
2114 /// decide, return null.
2115 static Constant *ComputeLoadResult(Constant *P,
2116 const DenseMap<Constant*, Constant*> &Memory) {
2117 // If this memory location has been recently stored, use the stored value: it
2118 // is the most up-to-date.
2119 DenseMap<Constant*, Constant*>::const_iterator I = Memory.find(P);
2120 if (I != Memory.end()) return I->second;
2123 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(P)) {
2124 if (GV->hasInitializer())
2125 return GV->getInitializer();
2129 // Handle a constantexpr getelementptr.
2130 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(P))
2131 if (CE->getOpcode() == Instruction::GetElementPtr &&
2132 isa<GlobalVariable>(CE->getOperand(0))) {
2133 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
2134 if (GV->hasInitializer())
2135 return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE);
2138 return 0; // don't know how to evaluate.
2141 /// EvaluateFunction - Evaluate a call to function F, returning true if
2142 /// successful, false if we can't evaluate it. ActualArgs contains the formal
2143 /// arguments for the function.
2144 static bool EvaluateFunction(Function *F, Constant *&RetVal,
2145 const std::vector<Constant*> &ActualArgs,
2146 std::vector<Function*> &CallStack,
2147 DenseMap<Constant*, Constant*> &MutatedMemory,
2148 std::vector<GlobalVariable*> &AllocaTmps) {
2149 // Check to see if this function is already executing (recursion). If so,
2150 // bail out. TODO: we might want to accept limited recursion.
2151 if (std::find(CallStack.begin(), CallStack.end(), F) != CallStack.end())
2154 LLVMContext* Context = F->getContext();
2156 CallStack.push_back(F);
2158 /// Values - As we compute SSA register values, we store their contents here.
2159 DenseMap<Value*, Constant*> Values;
2161 // Initialize arguments to the incoming values specified.
2163 for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end(); AI != E;
2165 Values[AI] = ActualArgs[ArgNo];
2167 /// ExecutedBlocks - We only handle non-looping, non-recursive code. As such,
2168 /// we can only evaluate any one basic block at most once. This set keeps
2169 /// track of what we have executed so we can detect recursive cases etc.
2170 SmallPtrSet<BasicBlock*, 32> ExecutedBlocks;
2172 // CurInst - The current instruction we're evaluating.
2173 BasicBlock::iterator CurInst = F->begin()->begin();
2175 // This is the main evaluation loop.
2177 Constant *InstResult = 0;
2179 if (StoreInst *SI = dyn_cast<StoreInst>(CurInst)) {
2180 if (SI->isVolatile()) return false; // no volatile accesses.
2181 Constant *Ptr = getVal(Values, SI->getOperand(1));
2182 if (!isSimpleEnoughPointerToCommit(Ptr))
2183 // If this is too complex for us to commit, reject it.
2185 Constant *Val = getVal(Values, SI->getOperand(0));
2186 MutatedMemory[Ptr] = Val;
2187 } else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(CurInst)) {
2188 InstResult = Context->getConstantExpr(BO->getOpcode(),
2189 getVal(Values, BO->getOperand(0)),
2190 getVal(Values, BO->getOperand(1)));
2191 } else if (CmpInst *CI = dyn_cast<CmpInst>(CurInst)) {
2192 InstResult = Context->getConstantExprCompare(CI->getPredicate(),
2193 getVal(Values, CI->getOperand(0)),
2194 getVal(Values, CI->getOperand(1)));
2195 } else if (CastInst *CI = dyn_cast<CastInst>(CurInst)) {
2196 InstResult = Context->getConstantExprCast(CI->getOpcode(),
2197 getVal(Values, CI->getOperand(0)),
2199 } else if (SelectInst *SI = dyn_cast<SelectInst>(CurInst)) {
2201 Context->getConstantExprSelect(getVal(Values, SI->getOperand(0)),
2202 getVal(Values, SI->getOperand(1)),
2203 getVal(Values, SI->getOperand(2)));
2204 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(CurInst)) {
2205 Constant *P = getVal(Values, GEP->getOperand(0));
2206 SmallVector<Constant*, 8> GEPOps;
2207 for (User::op_iterator i = GEP->op_begin() + 1, e = GEP->op_end();
2209 GEPOps.push_back(getVal(Values, *i));
2211 Context->getConstantExprGetElementPtr(P, &GEPOps[0], GEPOps.size());
2212 } else if (LoadInst *LI = dyn_cast<LoadInst>(CurInst)) {
2213 if (LI->isVolatile()) return false; // no volatile accesses.
2214 InstResult = ComputeLoadResult(getVal(Values, LI->getOperand(0)),
2216 if (InstResult == 0) return false; // Could not evaluate load.
2217 } else if (AllocaInst *AI = dyn_cast<AllocaInst>(CurInst)) {
2218 if (AI->isArrayAllocation()) return false; // Cannot handle array allocs.
2219 const Type *Ty = AI->getType()->getElementType();
2220 AllocaTmps.push_back(new GlobalVariable(Ty, false,
2221 GlobalValue::InternalLinkage,
2222 Context->getUndef(Ty),
2224 InstResult = AllocaTmps.back();
2225 } else if (CallInst *CI = dyn_cast<CallInst>(CurInst)) {
2227 // Debug info can safely be ignored here.
2228 if (isa<DbgInfoIntrinsic>(CI)) {
2233 // Cannot handle inline asm.
2234 if (isa<InlineAsm>(CI->getOperand(0))) return false;
2236 // Resolve function pointers.
2237 Function *Callee = dyn_cast<Function>(getVal(Values, CI->getOperand(0)));
2238 if (!Callee) return false; // Cannot resolve.
2240 std::vector<Constant*> Formals;
2241 for (User::op_iterator i = CI->op_begin() + 1, e = CI->op_end();
2243 Formals.push_back(getVal(Values, *i));
2245 if (Callee->isDeclaration()) {
2246 // If this is a function we can constant fold, do it.
2247 if (Constant *C = ConstantFoldCall(Callee, &Formals[0],
2254 if (Callee->getFunctionType()->isVarArg())
2258 // Execute the call, if successful, use the return value.
2259 if (!EvaluateFunction(Callee, RetVal, Formals, CallStack,
2260 MutatedMemory, AllocaTmps))
2262 InstResult = RetVal;
2264 } else if (isa<TerminatorInst>(CurInst)) {
2265 BasicBlock *NewBB = 0;
2266 if (BranchInst *BI = dyn_cast<BranchInst>(CurInst)) {
2267 if (BI->isUnconditional()) {
2268 NewBB = BI->getSuccessor(0);
2271 dyn_cast<ConstantInt>(getVal(Values, BI->getCondition()));
2272 if (!Cond) return false; // Cannot determine.
2274 NewBB = BI->getSuccessor(!Cond->getZExtValue());
2276 } else if (SwitchInst *SI = dyn_cast<SwitchInst>(CurInst)) {
2278 dyn_cast<ConstantInt>(getVal(Values, SI->getCondition()));
2279 if (!Val) return false; // Cannot determine.
2280 NewBB = SI->getSuccessor(SI->findCaseValue(Val));
2281 } else if (ReturnInst *RI = dyn_cast<ReturnInst>(CurInst)) {
2282 if (RI->getNumOperands())
2283 RetVal = getVal(Values, RI->getOperand(0));
2285 CallStack.pop_back(); // return from fn.
2286 return true; // We succeeded at evaluating this ctor!
2288 // invoke, unwind, unreachable.
2289 return false; // Cannot handle this terminator.
2292 // Okay, we succeeded in evaluating this control flow. See if we have
2293 // executed the new block before. If so, we have a looping function,
2294 // which we cannot evaluate in reasonable time.
2295 if (!ExecutedBlocks.insert(NewBB))
2296 return false; // looped!
2298 // Okay, we have never been in this block before. Check to see if there
2299 // are any PHI nodes. If so, evaluate them with information about where
2301 BasicBlock *OldBB = CurInst->getParent();
2302 CurInst = NewBB->begin();
2304 for (; (PN = dyn_cast<PHINode>(CurInst)); ++CurInst)
2305 Values[PN] = getVal(Values, PN->getIncomingValueForBlock(OldBB));
2307 // Do NOT increment CurInst. We know that the terminator had no value.
2310 // Did not know how to evaluate this!
2314 if (!CurInst->use_empty())
2315 Values[CurInst] = InstResult;
2317 // Advance program counter.
2322 /// EvaluateStaticConstructor - Evaluate static constructors in the function, if
2323 /// we can. Return true if we can, false otherwise.
2324 static bool EvaluateStaticConstructor(Function *F) {
2325 /// MutatedMemory - For each store we execute, we update this map. Loads
2326 /// check this to get the most up-to-date value. If evaluation is successful,
2327 /// this state is committed to the process.
2328 DenseMap<Constant*, Constant*> MutatedMemory;
2330 /// AllocaTmps - To 'execute' an alloca, we create a temporary global variable
2331 /// to represent its body. This vector is needed so we can delete the
2332 /// temporary globals when we are done.
2333 std::vector<GlobalVariable*> AllocaTmps;
2335 /// CallStack - This is used to detect recursion. In pathological situations
2336 /// we could hit exponential behavior, but at least there is nothing
2338 std::vector<Function*> CallStack;
2340 // Call the function.
2341 Constant *RetValDummy;
2342 bool EvalSuccess = EvaluateFunction(F, RetValDummy, std::vector<Constant*>(),
2343 CallStack, MutatedMemory, AllocaTmps);
2345 // We succeeded at evaluation: commit the result.
2346 DOUT << "FULLY EVALUATED GLOBAL CTOR FUNCTION '"
2347 << F->getName() << "' to " << MutatedMemory.size()
2349 for (DenseMap<Constant*, Constant*>::iterator I = MutatedMemory.begin(),
2350 E = MutatedMemory.end(); I != E; ++I)
2351 CommitValueTo(I->second, I->first, F->getContext());
2354 // At this point, we are done interpreting. If we created any 'alloca'
2355 // temporaries, release them now.
2356 while (!AllocaTmps.empty()) {
2357 GlobalVariable *Tmp = AllocaTmps.back();
2358 AllocaTmps.pop_back();
2360 // If there are still users of the alloca, the program is doing something
2361 // silly, e.g. storing the address of the alloca somewhere and using it
2362 // later. Since this is undefined, we'll just make it be null.
2363 if (!Tmp->use_empty())
2364 Tmp->replaceAllUsesWith(F->getContext()->getNullValue(Tmp->getType()));
2373 /// OptimizeGlobalCtorsList - Simplify and evaluation global ctors if possible.
2374 /// Return true if anything changed.
2375 bool GlobalOpt::OptimizeGlobalCtorsList(GlobalVariable *&GCL) {
2376 std::vector<Function*> Ctors = ParseGlobalCtors(GCL);
2377 bool MadeChange = false;
2378 if (Ctors.empty()) return false;
2380 // Loop over global ctors, optimizing them when we can.
2381 for (unsigned i = 0; i != Ctors.size(); ++i) {
2382 Function *F = Ctors[i];
2383 // Found a null terminator in the middle of the list, prune off the rest of
2386 if (i != Ctors.size()-1) {
2393 // We cannot simplify external ctor functions.
2394 if (F->empty()) continue;
2396 // If we can evaluate the ctor at compile time, do.
2397 if (EvaluateStaticConstructor(F)) {
2398 Ctors.erase(Ctors.begin()+i);
2401 ++NumCtorsEvaluated;
2406 if (!MadeChange) return false;
2408 GCL = InstallGlobalCtors(GCL, Ctors, Context);
2412 bool GlobalOpt::OptimizeGlobalAliases(Module &M) {
2413 bool Changed = false;
2415 for (Module::alias_iterator I = M.alias_begin(), E = M.alias_end();
2417 Module::alias_iterator J = I++;
2418 // Aliases without names cannot be referenced outside this module.
2419 if (!J->hasName() && !J->isDeclaration())
2420 J->setLinkage(GlobalValue::InternalLinkage);
2421 // If the aliasee may change at link time, nothing can be done - bail out.
2422 if (J->mayBeOverridden())
2425 Constant *Aliasee = J->getAliasee();
2426 GlobalValue *Target = cast<GlobalValue>(Aliasee->stripPointerCasts());
2427 Target->removeDeadConstantUsers();
2428 bool hasOneUse = Target->hasOneUse() && Aliasee->hasOneUse();
2430 // Make all users of the alias use the aliasee instead.
2431 if (!J->use_empty()) {
2432 J->replaceAllUsesWith(Aliasee);
2433 ++NumAliasesResolved;
2437 // If the aliasee has internal linkage, give it the name and linkage
2438 // of the alias, and delete the alias. This turns:
2439 // define internal ... @f(...)
2440 // @a = alias ... @f
2442 // define ... @a(...)
2443 if (!Target->hasLocalLinkage())
2446 // The transform is only useful if the alias does not have internal linkage.
2447 if (J->hasLocalLinkage())
2450 // Do not perform the transform if multiple aliases potentially target the
2451 // aliasee. This check also ensures that it is safe to replace the section
2452 // and other attributes of the aliasee with those of the alias.
2456 // Give the aliasee the name, linkage and other attributes of the alias.
2457 Target->takeName(J);
2458 Target->setLinkage(J->getLinkage());
2459 Target->GlobalValue::copyAttributesFrom(J);
2461 // Delete the alias.
2462 M.getAliasList().erase(J);
2463 ++NumAliasesRemoved;
2470 bool GlobalOpt::runOnModule(Module &M) {
2471 bool Changed = false;
2473 // Try to find the llvm.globalctors list.
2474 GlobalVariable *GlobalCtors = FindGlobalCtors(M);
2476 bool LocalChange = true;
2477 while (LocalChange) {
2478 LocalChange = false;
2480 // Delete functions that are trivially dead, ccc -> fastcc
2481 LocalChange |= OptimizeFunctions(M);
2483 // Optimize global_ctors list.
2485 LocalChange |= OptimizeGlobalCtorsList(GlobalCtors);
2487 // Optimize non-address-taken globals.
2488 LocalChange |= OptimizeGlobalVars(M);
2490 // Resolve aliases, when possible.
2491 LocalChange |= OptimizeGlobalAliases(M);
2492 Changed |= LocalChange;
2495 // TODO: Move all global ctors functions to the end of the module for code