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/Target/TargetData.h"
27 #include "llvm/Support/CallSite.h"
28 #include "llvm/Support/Compiler.h"
29 #include "llvm/Support/Debug.h"
30 #include "llvm/Support/GetElementPtrTypeIterator.h"
31 #include "llvm/Support/MathExtras.h"
32 #include "llvm/ADT/DenseMap.h"
33 #include "llvm/ADT/SmallPtrSet.h"
34 #include "llvm/ADT/SmallVector.h"
35 #include "llvm/ADT/Statistic.h"
36 #include "llvm/ADT/StringExtras.h"
37 #include "llvm/ADT/STLExtras.h"
41 STATISTIC(NumMarked , "Number of globals marked constant");
42 STATISTIC(NumSRA , "Number of aggregate globals broken into scalars");
43 STATISTIC(NumHeapSRA , "Number of heap objects SRA'd");
44 STATISTIC(NumSubstitute,"Number of globals with initializers stored into them");
45 STATISTIC(NumDeleted , "Number of globals deleted");
46 STATISTIC(NumFnDeleted , "Number of functions deleted");
47 STATISTIC(NumGlobUses , "Number of global uses devirtualized");
48 STATISTIC(NumLocalized , "Number of globals localized");
49 STATISTIC(NumShrunkToBool , "Number of global vars shrunk to booleans");
50 STATISTIC(NumFastCallFns , "Number of functions converted to fastcc");
51 STATISTIC(NumCtorsEvaluated, "Number of static ctors evaluated");
52 STATISTIC(NumNestRemoved , "Number of nest attributes removed");
53 STATISTIC(NumAliasesResolved, "Number of global aliases resolved");
54 STATISTIC(NumAliasesRemoved, "Number of global aliases eliminated");
57 struct VISIBILITY_HIDDEN GlobalOpt : public ModulePass {
58 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
59 AU.addRequired<TargetData>();
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 ResolveAliases(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.
86 struct VISIBILITY_HIDDEN GlobalStatus {
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 /// ConstantIsDead - Return true if the specified constant is (transitively)
140 /// dead. The constant may be used by other constants (e.g. constant arrays,
141 /// constant exprs, constant global variables) as long as they are dead,
142 /// but it cannot be used by anything else. If DeadGVs is not null then
143 /// record dead constant GV users.
144 static bool ConstantIsDead(Constant *C,
145 SmallPtrSet<GlobalVariable *, 4> *DeadGVs = false) {
146 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C))
147 if (GV->hasLocalLinkage() && GV->use_empty()) {
152 if (isa<GlobalValue>(C)) return false;
154 for (Value::use_iterator UI = C->use_begin(), E = C->use_end(); UI != E; ++UI)
155 if (Constant *CU = dyn_cast<Constant>(*UI)) {
156 if (!ConstantIsDead(CU, DeadGVs)) return false;
163 /// AnalyzeGlobal - Look at all uses of the global and fill in the GlobalStatus
164 /// structure. If the global has its address taken, return true to indicate we
165 /// can't do anything with it.
167 static bool AnalyzeGlobal(Value *V, GlobalStatus &GS,
168 SmallPtrSet<PHINode*, 16> &PHIUsers) {
169 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ++UI)
170 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(*UI)) {
171 GS.HasNonInstructionUser = true;
173 if (AnalyzeGlobal(CE, GS, PHIUsers)) return true;
175 } else if (Instruction *I = dyn_cast<Instruction>(*UI)) {
176 if (!GS.HasMultipleAccessingFunctions) {
177 Function *F = I->getParent()->getParent();
178 if (GS.AccessingFunction == 0)
179 GS.AccessingFunction = F;
180 else if (GS.AccessingFunction != F)
181 GS.HasMultipleAccessingFunctions = true;
183 if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
185 if (LI->isVolatile()) return true; // Don't hack on volatile loads.
186 } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
187 // Don't allow a store OF the address, only stores TO the address.
188 if (SI->getOperand(0) == V) return true;
190 if (SI->isVolatile()) return true; // Don't hack on volatile stores.
192 // If this is a direct store to the global (i.e., the global is a scalar
193 // value, not an aggregate), keep more specific information about
195 if (GS.StoredType != GlobalStatus::isStored) {
196 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(SI->getOperand(1))){
197 Value *StoredVal = SI->getOperand(0);
198 if (StoredVal == GV->getInitializer()) {
199 if (GS.StoredType < GlobalStatus::isInitializerStored)
200 GS.StoredType = GlobalStatus::isInitializerStored;
201 } else if (isa<LoadInst>(StoredVal) &&
202 cast<LoadInst>(StoredVal)->getOperand(0) == GV) {
204 if (GS.StoredType < GlobalStatus::isInitializerStored)
205 GS.StoredType = GlobalStatus::isInitializerStored;
206 } else if (GS.StoredType < GlobalStatus::isStoredOnce) {
207 GS.StoredType = GlobalStatus::isStoredOnce;
208 GS.StoredOnceValue = StoredVal;
209 } else if (GS.StoredType == GlobalStatus::isStoredOnce &&
210 GS.StoredOnceValue == StoredVal) {
213 GS.StoredType = GlobalStatus::isStored;
216 GS.StoredType = GlobalStatus::isStored;
219 } else if (isa<GetElementPtrInst>(I)) {
220 if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
221 } else if (isa<SelectInst>(I)) {
222 if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
223 } else if (PHINode *PN = dyn_cast<PHINode>(I)) {
224 // PHI nodes we can check just like select or GEP instructions, but we
225 // have to be careful about infinite recursion.
226 if (PHIUsers.insert(PN)) // Not already visited.
227 if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
228 GS.HasPHIUser = true;
229 } else if (isa<CmpInst>(I)) {
230 } else if (isa<MemCpyInst>(I) || isa<MemMoveInst>(I)) {
231 if (I->getOperand(1) == V)
232 GS.StoredType = GlobalStatus::isStored;
233 if (I->getOperand(2) == V)
235 } else if (isa<MemSetInst>(I)) {
236 assert(I->getOperand(1) == V && "Memset only takes one pointer!");
237 GS.StoredType = GlobalStatus::isStored;
239 return true; // Any other non-load instruction might take address!
241 } else if (Constant *C = dyn_cast<Constant>(*UI)) {
242 GS.HasNonInstructionUser = true;
243 // We might have a dead and dangling constant hanging off of here.
244 if (!ConstantIsDead(C))
247 GS.HasNonInstructionUser = true;
248 // Otherwise must be some other user.
255 static Constant *getAggregateConstantElement(Constant *Agg, Constant *Idx) {
256 ConstantInt *CI = dyn_cast<ConstantInt>(Idx);
258 unsigned IdxV = CI->getZExtValue();
260 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(Agg)) {
261 if (IdxV < CS->getNumOperands()) return CS->getOperand(IdxV);
262 } else if (ConstantArray *CA = dyn_cast<ConstantArray>(Agg)) {
263 if (IdxV < CA->getNumOperands()) return CA->getOperand(IdxV);
264 } else if (ConstantVector *CP = dyn_cast<ConstantVector>(Agg)) {
265 if (IdxV < CP->getNumOperands()) return CP->getOperand(IdxV);
266 } else if (isa<ConstantAggregateZero>(Agg)) {
267 if (const StructType *STy = dyn_cast<StructType>(Agg->getType())) {
268 if (IdxV < STy->getNumElements())
269 return Constant::getNullValue(STy->getElementType(IdxV));
270 } else if (const SequentialType *STy =
271 dyn_cast<SequentialType>(Agg->getType())) {
272 return Constant::getNullValue(STy->getElementType());
274 } else if (isa<UndefValue>(Agg)) {
275 if (const StructType *STy = dyn_cast<StructType>(Agg->getType())) {
276 if (IdxV < STy->getNumElements())
277 return UndefValue::get(STy->getElementType(IdxV));
278 } else if (const SequentialType *STy =
279 dyn_cast<SequentialType>(Agg->getType())) {
280 return UndefValue::get(STy->getElementType());
287 /// CleanupConstantGlobalUsers - We just marked GV constant. Loop over all
288 /// users of the global, cleaning up the obvious ones. This is largely just a
289 /// quick scan over the use list to clean up the easy and obvious cruft. This
290 /// returns true if it made a change.
291 static bool CleanupConstantGlobalUsers(Value *V, Constant *Init) {
292 bool Changed = false;
293 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;) {
296 if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
298 // Replace the load with the initializer.
299 LI->replaceAllUsesWith(Init);
300 LI->eraseFromParent();
303 } else if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
304 // Store must be unreachable or storing Init into the global.
305 SI->eraseFromParent();
307 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U)) {
308 if (CE->getOpcode() == Instruction::GetElementPtr) {
309 Constant *SubInit = 0;
311 SubInit = ConstantFoldLoadThroughGEPConstantExpr(Init, CE);
312 Changed |= CleanupConstantGlobalUsers(CE, SubInit);
313 } else if (CE->getOpcode() == Instruction::BitCast &&
314 isa<PointerType>(CE->getType())) {
315 // Pointer cast, delete any stores and memsets to the global.
316 Changed |= CleanupConstantGlobalUsers(CE, 0);
319 if (CE->use_empty()) {
320 CE->destroyConstant();
323 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) {
324 // Do not transform "gepinst (gep constexpr (GV))" here, because forming
325 // "gepconstexpr (gep constexpr (GV))" will cause the two gep's to fold
326 // and will invalidate our notion of what Init is.
327 Constant *SubInit = 0;
328 if (!isa<ConstantExpr>(GEP->getOperand(0))) {
330 dyn_cast_or_null<ConstantExpr>(ConstantFoldInstruction(GEP));
331 if (Init && CE && CE->getOpcode() == Instruction::GetElementPtr)
332 SubInit = ConstantFoldLoadThroughGEPConstantExpr(Init, CE);
334 Changed |= CleanupConstantGlobalUsers(GEP, SubInit);
336 if (GEP->use_empty()) {
337 GEP->eraseFromParent();
340 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(U)) { // memset/cpy/mv
341 if (MI->getRawDest() == V) {
342 MI->eraseFromParent();
346 } else if (Constant *C = dyn_cast<Constant>(U)) {
347 // If we have a chain of dead constantexprs or other things dangling from
348 // us, and if they are all dead, nuke them without remorse.
349 SmallPtrSet<GlobalVariable *, 4> DeadGVs;
350 if (ConstantIsDead(C, &DeadGVs)) {
351 for (SmallPtrSet<GlobalVariable *, 4>::iterator TI = DeadGVs.begin(),
352 TE = DeadGVs.end(); TI != TE; ) {
353 GlobalVariable *TGV = *TI; ++TI;
354 TGV->eraseFromParent();
356 C->destroyConstant();
357 // This could have invalidated UI, start over from scratch.
358 CleanupConstantGlobalUsers(V, Init);
366 /// isSafeSROAElementUse - Return true if the specified instruction is a safe
367 /// user of a derived expression from a global that we want to SROA.
368 static bool isSafeSROAElementUse(Value *V) {
369 // We might have a dead and dangling constant hanging off of here.
370 if (Constant *C = dyn_cast<Constant>(V))
371 return ConstantIsDead(C);
373 Instruction *I = dyn_cast<Instruction>(V);
374 if (!I) return false;
377 if (isa<LoadInst>(I)) return true;
379 // Stores *to* the pointer are ok.
380 if (StoreInst *SI = dyn_cast<StoreInst>(I))
381 return SI->getOperand(0) != V;
383 // Otherwise, it must be a GEP.
384 GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I);
385 if (GEPI == 0) return false;
387 if (GEPI->getNumOperands() < 3 || !isa<Constant>(GEPI->getOperand(1)) ||
388 !cast<Constant>(GEPI->getOperand(1))->isNullValue())
391 for (Value::use_iterator I = GEPI->use_begin(), E = GEPI->use_end();
393 if (!isSafeSROAElementUse(*I))
399 /// IsUserOfGlobalSafeForSRA - U is a direct user of the specified global value.
400 /// Look at it and its uses and decide whether it is safe to SROA this global.
402 static bool IsUserOfGlobalSafeForSRA(User *U, GlobalValue *GV) {
403 // The user of the global must be a GEP Inst or a ConstantExpr GEP.
404 if (!isa<GetElementPtrInst>(U) &&
405 (!isa<ConstantExpr>(U) ||
406 cast<ConstantExpr>(U)->getOpcode() != Instruction::GetElementPtr))
409 // Check to see if this ConstantExpr GEP is SRA'able. In particular, we
410 // don't like < 3 operand CE's, and we don't like non-constant integer
411 // indices. This enforces that all uses are 'gep GV, 0, C, ...' for some
413 if (U->getNumOperands() < 3 || !isa<Constant>(U->getOperand(1)) ||
414 !cast<Constant>(U->getOperand(1))->isNullValue() ||
415 !isa<ConstantInt>(U->getOperand(2)))
418 gep_type_iterator GEPI = gep_type_begin(U), E = gep_type_end(U);
419 ++GEPI; // Skip over the pointer index.
421 // If this is a use of an array allocation, do a bit more checking for sanity.
422 if (const ArrayType *AT = dyn_cast<ArrayType>(*GEPI)) {
423 uint64_t NumElements = AT->getNumElements();
424 ConstantInt *Idx = cast<ConstantInt>(U->getOperand(2));
426 // Check to make sure that index falls within the array. If not,
427 // something funny is going on, so we won't do the optimization.
429 if (Idx->getZExtValue() >= NumElements)
432 // We cannot scalar repl this level of the array unless any array
433 // sub-indices are in-range constants. In particular, consider:
434 // A[0][i]. We cannot know that the user isn't doing invalid things like
435 // allowing i to index an out-of-range subscript that accesses A[1].
437 // Scalar replacing *just* the outer index of the array is probably not
438 // going to be a win anyway, so just give up.
439 for (++GEPI; // Skip array index.
440 GEPI != E && (isa<ArrayType>(*GEPI) || isa<VectorType>(*GEPI));
442 uint64_t NumElements;
443 if (const ArrayType *SubArrayTy = dyn_cast<ArrayType>(*GEPI))
444 NumElements = SubArrayTy->getNumElements();
446 NumElements = cast<VectorType>(*GEPI)->getNumElements();
448 ConstantInt *IdxVal = dyn_cast<ConstantInt>(GEPI.getOperand());
449 if (!IdxVal || IdxVal->getZExtValue() >= NumElements)
454 for (Value::use_iterator I = U->use_begin(), E = U->use_end(); I != E; ++I)
455 if (!isSafeSROAElementUse(*I))
460 /// GlobalUsersSafeToSRA - Look at all uses of the global and decide whether it
461 /// is safe for us to perform this transformation.
463 static bool GlobalUsersSafeToSRA(GlobalValue *GV) {
464 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end();
466 if (!IsUserOfGlobalSafeForSRA(*UI, GV))
473 /// SRAGlobal - Perform scalar replacement of aggregates on the specified global
474 /// variable. This opens the door for other optimizations by exposing the
475 /// behavior of the program in a more fine-grained way. We have determined that
476 /// this transformation is safe already. We return the first global variable we
477 /// insert so that the caller can reprocess it.
478 static GlobalVariable *SRAGlobal(GlobalVariable *GV, const TargetData &TD) {
479 // Make sure this global only has simple uses that we can SRA.
480 if (!GlobalUsersSafeToSRA(GV))
483 assert(GV->hasLocalLinkage() && !GV->isConstant());
484 Constant *Init = GV->getInitializer();
485 const Type *Ty = Init->getType();
487 std::vector<GlobalVariable*> NewGlobals;
488 Module::GlobalListType &Globals = GV->getParent()->getGlobalList();
490 // Get the alignment of the global, either explicit or target-specific.
491 unsigned StartAlignment = GV->getAlignment();
492 if (StartAlignment == 0)
493 StartAlignment = TD.getABITypeAlignment(GV->getType());
495 if (const StructType *STy = dyn_cast<StructType>(Ty)) {
496 NewGlobals.reserve(STy->getNumElements());
497 const StructLayout &Layout = *TD.getStructLayout(STy);
498 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
499 Constant *In = getAggregateConstantElement(Init,
500 ConstantInt::get(Type::Int32Ty, i));
501 assert(In && "Couldn't get element of initializer?");
502 GlobalVariable *NGV = new GlobalVariable(STy->getElementType(i), false,
503 GlobalVariable::InternalLinkage,
504 In, GV->getName()+"."+utostr(i),
507 GV->getType()->getAddressSpace());
508 Globals.insert(GV, NGV);
509 NewGlobals.push_back(NGV);
511 // Calculate the known alignment of the field. If the original aggregate
512 // had 256 byte alignment for example, something might depend on that:
513 // propagate info to each field.
514 uint64_t FieldOffset = Layout.getElementOffset(i);
515 unsigned NewAlign = (unsigned)MinAlign(StartAlignment, FieldOffset);
516 if (NewAlign > TD.getABITypeAlignment(STy->getElementType(i)))
517 NGV->setAlignment(NewAlign);
519 } else if (const SequentialType *STy = dyn_cast<SequentialType>(Ty)) {
520 unsigned NumElements = 0;
521 if (const ArrayType *ATy = dyn_cast<ArrayType>(STy))
522 NumElements = ATy->getNumElements();
524 NumElements = cast<VectorType>(STy)->getNumElements();
526 if (NumElements > 16 && GV->hasNUsesOrMore(16))
527 return 0; // It's not worth it.
528 NewGlobals.reserve(NumElements);
530 uint64_t EltSize = TD.getTypePaddedSize(STy->getElementType());
531 unsigned EltAlign = TD.getABITypeAlignment(STy->getElementType());
532 for (unsigned i = 0, e = NumElements; i != e; ++i) {
533 Constant *In = getAggregateConstantElement(Init,
534 ConstantInt::get(Type::Int32Ty, i));
535 assert(In && "Couldn't get element of initializer?");
537 GlobalVariable *NGV = new GlobalVariable(STy->getElementType(), false,
538 GlobalVariable::InternalLinkage,
539 In, GV->getName()+"."+utostr(i),
542 GV->getType()->getAddressSpace());
543 Globals.insert(GV, NGV);
544 NewGlobals.push_back(NGV);
546 // Calculate the known alignment of the field. If the original aggregate
547 // had 256 byte alignment for example, something might depend on that:
548 // propagate info to each field.
549 unsigned NewAlign = (unsigned)MinAlign(StartAlignment, EltSize*i);
550 if (NewAlign > EltAlign)
551 NGV->setAlignment(NewAlign);
555 if (NewGlobals.empty())
558 DOUT << "PERFORMING GLOBAL SRA ON: " << *GV;
560 Constant *NullInt = Constant::getNullValue(Type::Int32Ty);
562 // Loop over all of the uses of the global, replacing the constantexpr geps,
563 // with smaller constantexpr geps or direct references.
564 while (!GV->use_empty()) {
565 User *GEP = GV->use_back();
566 assert(((isa<ConstantExpr>(GEP) &&
567 cast<ConstantExpr>(GEP)->getOpcode()==Instruction::GetElementPtr)||
568 isa<GetElementPtrInst>(GEP)) && "NonGEP CE's are not SRAable!");
570 // Ignore the 1th operand, which has to be zero or else the program is quite
571 // broken (undefined). Get the 2nd operand, which is the structure or array
573 unsigned Val = cast<ConstantInt>(GEP->getOperand(2))->getZExtValue();
574 if (Val >= NewGlobals.size()) Val = 0; // Out of bound array access.
576 Value *NewPtr = NewGlobals[Val];
578 // Form a shorter GEP if needed.
579 if (GEP->getNumOperands() > 3) {
580 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GEP)) {
581 SmallVector<Constant*, 8> Idxs;
582 Idxs.push_back(NullInt);
583 for (unsigned i = 3, e = CE->getNumOperands(); i != e; ++i)
584 Idxs.push_back(CE->getOperand(i));
585 NewPtr = ConstantExpr::getGetElementPtr(cast<Constant>(NewPtr),
586 &Idxs[0], Idxs.size());
588 GetElementPtrInst *GEPI = cast<GetElementPtrInst>(GEP);
589 SmallVector<Value*, 8> Idxs;
590 Idxs.push_back(NullInt);
591 for (unsigned i = 3, e = GEPI->getNumOperands(); i != e; ++i)
592 Idxs.push_back(GEPI->getOperand(i));
593 NewPtr = GetElementPtrInst::Create(NewPtr, Idxs.begin(), Idxs.end(),
594 GEPI->getName()+"."+utostr(Val), GEPI);
597 GEP->replaceAllUsesWith(NewPtr);
599 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(GEP))
600 GEPI->eraseFromParent();
602 cast<ConstantExpr>(GEP)->destroyConstant();
605 // Delete the old global, now that it is dead.
609 // Loop over the new globals array deleting any globals that are obviously
610 // dead. This can arise due to scalarization of a structure or an array that
611 // has elements that are dead.
612 unsigned FirstGlobal = 0;
613 for (unsigned i = 0, e = NewGlobals.size(); i != e; ++i)
614 if (NewGlobals[i]->use_empty()) {
615 Globals.erase(NewGlobals[i]);
616 if (FirstGlobal == i) ++FirstGlobal;
619 return FirstGlobal != NewGlobals.size() ? NewGlobals[FirstGlobal] : 0;
622 /// AllUsesOfValueWillTrapIfNull - Return true if all users of the specified
623 /// value will trap if the value is dynamically null. PHIs keeps track of any
624 /// phi nodes we've seen to avoid reprocessing them.
625 static bool AllUsesOfValueWillTrapIfNull(Value *V,
626 SmallPtrSet<PHINode*, 8> &PHIs) {
627 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ++UI)
628 if (isa<LoadInst>(*UI)) {
630 } else if (StoreInst *SI = dyn_cast<StoreInst>(*UI)) {
631 if (SI->getOperand(0) == V) {
632 //cerr << "NONTRAPPING USE: " << **UI;
633 return false; // Storing the value.
635 } else if (CallInst *CI = dyn_cast<CallInst>(*UI)) {
636 if (CI->getOperand(0) != V) {
637 //cerr << "NONTRAPPING USE: " << **UI;
638 return false; // Not calling the ptr
640 } else if (InvokeInst *II = dyn_cast<InvokeInst>(*UI)) {
641 if (II->getOperand(0) != V) {
642 //cerr << "NONTRAPPING USE: " << **UI;
643 return false; // Not calling the ptr
645 } else if (BitCastInst *CI = dyn_cast<BitCastInst>(*UI)) {
646 if (!AllUsesOfValueWillTrapIfNull(CI, PHIs)) return false;
647 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(*UI)) {
648 if (!AllUsesOfValueWillTrapIfNull(GEPI, PHIs)) return false;
649 } else if (PHINode *PN = dyn_cast<PHINode>(*UI)) {
650 // If we've already seen this phi node, ignore it, it has already been
653 return AllUsesOfValueWillTrapIfNull(PN, PHIs);
654 } else if (isa<ICmpInst>(*UI) &&
655 isa<ConstantPointerNull>(UI->getOperand(1))) {
656 // Ignore setcc X, null
658 //cerr << "NONTRAPPING USE: " << **UI;
664 /// AllUsesOfLoadedValueWillTrapIfNull - Return true if all uses of any loads
665 /// from GV will trap if the loaded value is null. Note that this also permits
666 /// comparisons of the loaded value against null, as a special case.
667 static bool AllUsesOfLoadedValueWillTrapIfNull(GlobalVariable *GV) {
668 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); UI!=E; ++UI)
669 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
670 SmallPtrSet<PHINode*, 8> PHIs;
671 if (!AllUsesOfValueWillTrapIfNull(LI, PHIs))
673 } else if (isa<StoreInst>(*UI)) {
674 // Ignore stores to the global.
676 // We don't know or understand this user, bail out.
677 //cerr << "UNKNOWN USER OF GLOBAL!: " << **UI;
684 static bool OptimizeAwayTrappingUsesOfValue(Value *V, Constant *NewV) {
685 bool Changed = false;
686 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ) {
687 Instruction *I = cast<Instruction>(*UI++);
688 if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
689 LI->setOperand(0, NewV);
691 } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
692 if (SI->getOperand(1) == V) {
693 SI->setOperand(1, NewV);
696 } else if (isa<CallInst>(I) || isa<InvokeInst>(I)) {
697 if (I->getOperand(0) == V) {
698 // Calling through the pointer! Turn into a direct call, but be careful
699 // that the pointer is not also being passed as an argument.
700 I->setOperand(0, NewV);
702 bool PassedAsArg = false;
703 for (unsigned i = 1, e = I->getNumOperands(); i != e; ++i)
704 if (I->getOperand(i) == V) {
706 I->setOperand(i, NewV);
710 // Being passed as an argument also. Be careful to not invalidate UI!
714 } else if (CastInst *CI = dyn_cast<CastInst>(I)) {
715 Changed |= OptimizeAwayTrappingUsesOfValue(CI,
716 ConstantExpr::getCast(CI->getOpcode(),
717 NewV, CI->getType()));
718 if (CI->use_empty()) {
720 CI->eraseFromParent();
722 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I)) {
723 // Should handle GEP here.
724 SmallVector<Constant*, 8> Idxs;
725 Idxs.reserve(GEPI->getNumOperands()-1);
726 for (User::op_iterator i = GEPI->op_begin() + 1, e = GEPI->op_end();
728 if (Constant *C = dyn_cast<Constant>(*i))
732 if (Idxs.size() == GEPI->getNumOperands()-1)
733 Changed |= OptimizeAwayTrappingUsesOfValue(GEPI,
734 ConstantExpr::getGetElementPtr(NewV, &Idxs[0],
736 if (GEPI->use_empty()) {
738 GEPI->eraseFromParent();
747 /// OptimizeAwayTrappingUsesOfLoads - The specified global has only one non-null
748 /// value stored into it. If there are uses of the loaded value that would trap
749 /// if the loaded value is dynamically null, then we know that they cannot be
750 /// reachable with a null optimize away the load.
751 static bool OptimizeAwayTrappingUsesOfLoads(GlobalVariable *GV, Constant *LV) {
752 bool Changed = false;
754 // Keep track of whether we are able to remove all the uses of the global
755 // other than the store that defines it.
756 bool AllNonStoreUsesGone = true;
758 // Replace all uses of loads with uses of uses of the stored value.
759 for (Value::use_iterator GUI = GV->use_begin(), E = GV->use_end(); GUI != E;){
760 User *GlobalUser = *GUI++;
761 if (LoadInst *LI = dyn_cast<LoadInst>(GlobalUser)) {
762 Changed |= OptimizeAwayTrappingUsesOfValue(LI, LV);
763 // If we were able to delete all uses of the loads
764 if (LI->use_empty()) {
765 LI->eraseFromParent();
768 AllNonStoreUsesGone = false;
770 } else if (isa<StoreInst>(GlobalUser)) {
771 // Ignore the store that stores "LV" to the global.
772 assert(GlobalUser->getOperand(1) == GV &&
773 "Must be storing *to* the global");
775 AllNonStoreUsesGone = false;
777 // If we get here we could have other crazy uses that are transitively
779 assert((isa<PHINode>(GlobalUser) || isa<SelectInst>(GlobalUser) ||
780 isa<ConstantExpr>(GlobalUser)) && "Only expect load and stores!");
785 DOUT << "OPTIMIZED LOADS FROM STORED ONCE POINTER: " << *GV;
789 // If we nuked all of the loads, then none of the stores are needed either,
790 // nor is the global.
791 if (AllNonStoreUsesGone) {
792 DOUT << " *** GLOBAL NOW DEAD!\n";
793 CleanupConstantGlobalUsers(GV, 0);
794 if (GV->use_empty()) {
795 GV->eraseFromParent();
803 /// ConstantPropUsersOf - Walk the use list of V, constant folding all of the
804 /// instructions that are foldable.
805 static void ConstantPropUsersOf(Value *V) {
806 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; )
807 if (Instruction *I = dyn_cast<Instruction>(*UI++))
808 if (Constant *NewC = ConstantFoldInstruction(I)) {
809 I->replaceAllUsesWith(NewC);
811 // Advance UI to the next non-I use to avoid invalidating it!
812 // Instructions could multiply use V.
813 while (UI != E && *UI == I)
815 I->eraseFromParent();
819 /// OptimizeGlobalAddressOfMalloc - This function takes the specified global
820 /// variable, and transforms the program as if it always contained the result of
821 /// the specified malloc. Because it is always the result of the specified
822 /// malloc, there is no reason to actually DO the malloc. Instead, turn the
823 /// malloc into a global, and any loads of GV as uses of the new global.
824 static GlobalVariable *OptimizeGlobalAddressOfMalloc(GlobalVariable *GV,
826 DOUT << "PROMOTING MALLOC GLOBAL: " << *GV << " MALLOC = " << *MI;
827 ConstantInt *NElements = cast<ConstantInt>(MI->getArraySize());
829 if (NElements->getZExtValue() != 1) {
830 // If we have an array allocation, transform it to a single element
831 // allocation to make the code below simpler.
832 Type *NewTy = ArrayType::get(MI->getAllocatedType(),
833 NElements->getZExtValue());
835 new MallocInst(NewTy, Constant::getNullValue(Type::Int32Ty),
836 MI->getAlignment(), MI->getName(), MI);
838 Indices[0] = Indices[1] = Constant::getNullValue(Type::Int32Ty);
839 Value *NewGEP = GetElementPtrInst::Create(NewMI, Indices, Indices + 2,
840 NewMI->getName()+".el0", MI);
841 MI->replaceAllUsesWith(NewGEP);
842 MI->eraseFromParent();
846 // Create the new global variable. The contents of the malloc'd memory is
847 // undefined, so initialize with an undef value.
848 Constant *Init = UndefValue::get(MI->getAllocatedType());
849 GlobalVariable *NewGV = new GlobalVariable(MI->getAllocatedType(), false,
850 GlobalValue::InternalLinkage, Init,
851 GV->getName()+".body",
853 GV->isThreadLocal());
854 // FIXME: This new global should have the alignment returned by malloc. Code
855 // could depend on malloc returning large alignment (on the mac, 16 bytes) but
856 // this would only guarantee some lower alignment.
857 GV->getParent()->getGlobalList().insert(GV, NewGV);
859 // Anything that used the malloc now uses the global directly.
860 MI->replaceAllUsesWith(NewGV);
862 Constant *RepValue = NewGV;
863 if (NewGV->getType() != GV->getType()->getElementType())
864 RepValue = ConstantExpr::getBitCast(RepValue,
865 GV->getType()->getElementType());
867 // If there is a comparison against null, we will insert a global bool to
868 // keep track of whether the global was initialized yet or not.
869 GlobalVariable *InitBool =
870 new GlobalVariable(Type::Int1Ty, false, GlobalValue::InternalLinkage,
871 ConstantInt::getFalse(), GV->getName()+".init",
872 (Module *)NULL, GV->isThreadLocal());
873 bool InitBoolUsed = false;
875 // Loop over all uses of GV, processing them in turn.
876 std::vector<StoreInst*> Stores;
877 while (!GV->use_empty())
878 if (LoadInst *LI = dyn_cast<LoadInst>(GV->use_back())) {
879 while (!LI->use_empty()) {
880 Use &LoadUse = LI->use_begin().getUse();
881 if (!isa<ICmpInst>(LoadUse.getUser()))
884 ICmpInst *CI = cast<ICmpInst>(LoadUse.getUser());
885 // Replace the cmp X, 0 with a use of the bool value.
886 Value *LV = new LoadInst(InitBool, InitBool->getName()+".val", CI);
888 switch (CI->getPredicate()) {
889 default: assert(0 && "Unknown ICmp Predicate!");
890 case ICmpInst::ICMP_ULT:
891 case ICmpInst::ICMP_SLT:
892 LV = ConstantInt::getFalse(); // X < null -> always false
894 case ICmpInst::ICMP_ULE:
895 case ICmpInst::ICMP_SLE:
896 case ICmpInst::ICMP_EQ:
897 LV = BinaryOperator::CreateNot(LV, "notinit", CI);
899 case ICmpInst::ICMP_NE:
900 case ICmpInst::ICMP_UGE:
901 case ICmpInst::ICMP_SGE:
902 case ICmpInst::ICMP_UGT:
903 case ICmpInst::ICMP_SGT:
906 CI->replaceAllUsesWith(LV);
907 CI->eraseFromParent();
910 LI->eraseFromParent();
912 StoreInst *SI = cast<StoreInst>(GV->use_back());
913 // The global is initialized when the store to it occurs.
914 new StoreInst(ConstantInt::getTrue(), InitBool, SI);
915 SI->eraseFromParent();
918 // If the initialization boolean was used, insert it, otherwise delete it.
920 while (!InitBool->use_empty()) // Delete initializations
921 cast<Instruction>(InitBool->use_back())->eraseFromParent();
924 GV->getParent()->getGlobalList().insert(GV, InitBool);
927 // Now the GV is dead, nuke it and the malloc.
928 GV->eraseFromParent();
929 MI->eraseFromParent();
931 // To further other optimizations, loop over all users of NewGV and try to
932 // constant prop them. This will promote GEP instructions with constant
933 // indices into GEP constant-exprs, which will allow global-opt to hack on it.
934 ConstantPropUsersOf(NewGV);
935 if (RepValue != NewGV)
936 ConstantPropUsersOf(RepValue);
941 /// ValueIsOnlyUsedLocallyOrStoredToOneGlobal - Scan the use-list of V checking
942 /// to make sure that there are no complex uses of V. We permit simple things
943 /// like dereferencing the pointer, but not storing through the address, unless
944 /// it is to the specified global.
945 static bool ValueIsOnlyUsedLocallyOrStoredToOneGlobal(Instruction *V,
947 SmallPtrSet<PHINode*, 8> &PHIs) {
948 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;++UI){
949 Instruction *Inst = dyn_cast<Instruction>(*UI);
950 if (Inst == 0) return false;
952 if (isa<LoadInst>(Inst) || isa<CmpInst>(Inst)) {
953 continue; // Fine, ignore.
956 if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
957 if (SI->getOperand(0) == V && SI->getOperand(1) != GV)
958 return false; // Storing the pointer itself... bad.
959 continue; // Otherwise, storing through it, or storing into GV... fine.
962 if (isa<GetElementPtrInst>(Inst)) {
963 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(Inst, GV, PHIs))
968 if (PHINode *PN = dyn_cast<PHINode>(Inst)) {
969 // PHIs are ok if all uses are ok. Don't infinitely recurse through PHI
972 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(PN, GV, PHIs))
977 if (BitCastInst *BCI = dyn_cast<BitCastInst>(Inst)) {
978 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(BCI, GV, PHIs))
988 /// ReplaceUsesOfMallocWithGlobal - The Alloc pointer is stored into GV
989 /// somewhere. Transform all uses of the allocation into loads from the
990 /// global and uses of the resultant pointer. Further, delete the store into
991 /// GV. This assumes that these value pass the
992 /// 'ValueIsOnlyUsedLocallyOrStoredToOneGlobal' predicate.
993 static void ReplaceUsesOfMallocWithGlobal(Instruction *Alloc,
994 GlobalVariable *GV) {
995 while (!Alloc->use_empty()) {
996 Instruction *U = cast<Instruction>(*Alloc->use_begin());
997 Instruction *InsertPt = U;
998 if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
999 // If this is the store of the allocation into the global, remove it.
1000 if (SI->getOperand(1) == GV) {
1001 SI->eraseFromParent();
1004 } else if (PHINode *PN = dyn_cast<PHINode>(U)) {
1005 // Insert the load in the corresponding predecessor, not right before the
1007 InsertPt = PN->getIncomingBlock(Alloc->use_begin())->getTerminator();
1008 } else if (isa<BitCastInst>(U)) {
1009 // Must be bitcast between the malloc and store to initialize the global.
1010 ReplaceUsesOfMallocWithGlobal(U, GV);
1011 U->eraseFromParent();
1013 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(U)) {
1014 // If this is a "GEP bitcast" and the user is a store to the global, then
1015 // just process it as a bitcast.
1016 if (GEPI->hasAllZeroIndices() && GEPI->hasOneUse())
1017 if (StoreInst *SI = dyn_cast<StoreInst>(GEPI->use_back()))
1018 if (SI->getOperand(1) == GV) {
1019 // Must be bitcast GEP between the malloc and store to initialize
1021 ReplaceUsesOfMallocWithGlobal(GEPI, GV);
1022 GEPI->eraseFromParent();
1027 // Insert a load from the global, and use it instead of the malloc.
1028 Value *NL = new LoadInst(GV, GV->getName()+".val", InsertPt);
1029 U->replaceUsesOfWith(Alloc, NL);
1033 /// LoadUsesSimpleEnoughForHeapSRA - Verify that all uses of V (a load, or a phi
1034 /// of a load) are simple enough to perform heap SRA on. This permits GEP's
1035 /// that index through the array and struct field, icmps of null, and PHIs.
1036 static bool LoadUsesSimpleEnoughForHeapSRA(Value *V,
1037 SmallPtrSet<PHINode*, 32> &LoadUsingPHIs) {
1038 // We permit two users of the load: setcc comparing against the null
1039 // pointer, and a getelementptr of a specific form.
1040 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;++UI){
1041 Instruction *User = cast<Instruction>(*UI);
1043 // Comparison against null is ok.
1044 if (ICmpInst *ICI = dyn_cast<ICmpInst>(User)) {
1045 if (!isa<ConstantPointerNull>(ICI->getOperand(1)))
1050 // getelementptr is also ok, but only a simple form.
1051 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
1052 // Must index into the array and into the struct.
1053 if (GEPI->getNumOperands() < 3)
1056 // Otherwise the GEP is ok.
1060 if (PHINode *PN = dyn_cast<PHINode>(User)) {
1061 // If we have already recursively analyzed this PHI, then it is safe.
1062 if (LoadUsingPHIs.insert(PN))
1065 // Make sure all uses of the PHI are simple enough to transform.
1066 if (!LoadUsesSimpleEnoughForHeapSRA(PN, LoadUsingPHIs))
1072 // Otherwise we don't know what this is, not ok.
1080 /// AllGlobalLoadUsesSimpleEnoughForHeapSRA - If all users of values loaded from
1081 /// GV are simple enough to perform HeapSRA, return true.
1082 static bool AllGlobalLoadUsesSimpleEnoughForHeapSRA(GlobalVariable *GV,
1084 SmallPtrSet<PHINode*, 32> LoadUsingPHIs;
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))
1091 // If we reach here, we know that all uses of the loads and transitive uses
1092 // (through PHI nodes) are simple enough to transform. However, we don't know
1093 // that all inputs the to the PHI nodes are in the same equivalence sets.
1094 // Check to verify that all operands of the PHIs are either PHIS that can be
1095 // transformed, loads from GV, or MI itself.
1096 for (SmallPtrSet<PHINode*, 32>::iterator I = LoadUsingPHIs.begin(),
1097 E = LoadUsingPHIs.end(); I != E; ++I) {
1099 for (unsigned op = 0, e = PN->getNumIncomingValues(); op != e; ++op) {
1100 Value *InVal = PN->getIncomingValue(op);
1102 // PHI of the stored value itself is ok.
1103 if (InVal == MI) continue;
1105 if (PHINode *InPN = dyn_cast<PHINode>(InVal)) {
1106 // One of the PHIs in our set is (optimistically) ok.
1107 if (LoadUsingPHIs.count(InPN))
1112 // Load from GV is ok.
1113 if (LoadInst *LI = dyn_cast<LoadInst>(InVal))
1114 if (LI->getOperand(0) == GV)
1119 // Anything else is rejected.
1127 static Value *GetHeapSROAValue(Value *V, unsigned FieldNo,
1128 DenseMap<Value*, std::vector<Value*> > &InsertedScalarizedValues,
1129 std::vector<std::pair<PHINode*, unsigned> > &PHIsToRewrite) {
1130 std::vector<Value*> &FieldVals = InsertedScalarizedValues[V];
1132 if (FieldNo >= FieldVals.size())
1133 FieldVals.resize(FieldNo+1);
1135 // If we already have this value, just reuse the previously scalarized
1137 if (Value *FieldVal = FieldVals[FieldNo])
1140 // Depending on what instruction this is, we have several cases.
1142 if (LoadInst *LI = dyn_cast<LoadInst>(V)) {
1143 // This is a scalarized version of the load from the global. Just create
1144 // a new Load of the scalarized global.
1145 Result = new LoadInst(GetHeapSROAValue(LI->getOperand(0), FieldNo,
1146 InsertedScalarizedValues,
1148 LI->getName()+".f" + utostr(FieldNo), LI);
1149 } else if (PHINode *PN = dyn_cast<PHINode>(V)) {
1150 // PN's type is pointer to struct. Make a new PHI of pointer to struct
1152 const StructType *ST =
1153 cast<StructType>(cast<PointerType>(PN->getType())->getElementType());
1155 Result =PHINode::Create(PointerType::getUnqual(ST->getElementType(FieldNo)),
1156 PN->getName()+".f"+utostr(FieldNo), PN);
1157 PHIsToRewrite.push_back(std::make_pair(PN, FieldNo));
1159 assert(0 && "Unknown usable value");
1163 return FieldVals[FieldNo] = Result;
1166 /// RewriteHeapSROALoadUser - Given a load instruction and a value derived from
1167 /// the load, rewrite the derived value to use the HeapSRoA'd load.
1168 static void RewriteHeapSROALoadUser(Instruction *LoadUser,
1169 DenseMap<Value*, std::vector<Value*> > &InsertedScalarizedValues,
1170 std::vector<std::pair<PHINode*, unsigned> > &PHIsToRewrite) {
1171 // If this is a comparison against null, handle it.
1172 if (ICmpInst *SCI = dyn_cast<ICmpInst>(LoadUser)) {
1173 assert(isa<ConstantPointerNull>(SCI->getOperand(1)));
1174 // If we have a setcc of the loaded pointer, we can use a setcc of any
1176 Value *NPtr = GetHeapSROAValue(SCI->getOperand(0), 0,
1177 InsertedScalarizedValues, PHIsToRewrite);
1179 Value *New = new ICmpInst(SCI->getPredicate(), NPtr,
1180 Constant::getNullValue(NPtr->getType()),
1181 SCI->getName(), SCI);
1182 SCI->replaceAllUsesWith(New);
1183 SCI->eraseFromParent();
1187 // Handle 'getelementptr Ptr, Idx, i32 FieldNo ...'
1188 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(LoadUser)) {
1189 assert(GEPI->getNumOperands() >= 3 && isa<ConstantInt>(GEPI->getOperand(2))
1190 && "Unexpected GEPI!");
1192 // Load the pointer for this field.
1193 unsigned FieldNo = cast<ConstantInt>(GEPI->getOperand(2))->getZExtValue();
1194 Value *NewPtr = GetHeapSROAValue(GEPI->getOperand(0), FieldNo,
1195 InsertedScalarizedValues, PHIsToRewrite);
1197 // Create the new GEP idx vector.
1198 SmallVector<Value*, 8> GEPIdx;
1199 GEPIdx.push_back(GEPI->getOperand(1));
1200 GEPIdx.append(GEPI->op_begin()+3, GEPI->op_end());
1202 Value *NGEPI = GetElementPtrInst::Create(NewPtr,
1203 GEPIdx.begin(), GEPIdx.end(),
1204 GEPI->getName(), GEPI);
1205 GEPI->replaceAllUsesWith(NGEPI);
1206 GEPI->eraseFromParent();
1210 // Recursively transform the users of PHI nodes. This will lazily create the
1211 // PHIs that are needed for individual elements. Keep track of what PHIs we
1212 // see in InsertedScalarizedValues so that we don't get infinite loops (very
1213 // antisocial). If the PHI is already in InsertedScalarizedValues, it has
1214 // already been seen first by another load, so its uses have already been
1216 PHINode *PN = cast<PHINode>(LoadUser);
1218 DenseMap<Value*, std::vector<Value*> >::iterator InsertPos;
1219 tie(InsertPos, Inserted) =
1220 InsertedScalarizedValues.insert(std::make_pair(PN, std::vector<Value*>()));
1221 if (!Inserted) return;
1223 // If this is the first time we've seen this PHI, recursively process all
1225 for (Value::use_iterator UI = PN->use_begin(), E = PN->use_end(); UI != E; ) {
1226 Instruction *User = cast<Instruction>(*UI++);
1227 RewriteHeapSROALoadUser(User, InsertedScalarizedValues, PHIsToRewrite);
1231 /// RewriteUsesOfLoadForHeapSRoA - We are performing Heap SRoA on a global. Ptr
1232 /// is a value loaded from the global. Eliminate all uses of Ptr, making them
1233 /// use FieldGlobals instead. All uses of loaded values satisfy
1234 /// AllGlobalLoadUsesSimpleEnoughForHeapSRA.
1235 static void RewriteUsesOfLoadForHeapSRoA(LoadInst *Load,
1236 DenseMap<Value*, std::vector<Value*> > &InsertedScalarizedValues,
1237 std::vector<std::pair<PHINode*, unsigned> > &PHIsToRewrite) {
1238 for (Value::use_iterator UI = Load->use_begin(), E = Load->use_end();
1240 Instruction *User = cast<Instruction>(*UI++);
1241 RewriteHeapSROALoadUser(User, InsertedScalarizedValues, PHIsToRewrite);
1244 if (Load->use_empty()) {
1245 Load->eraseFromParent();
1246 InsertedScalarizedValues.erase(Load);
1250 /// PerformHeapAllocSRoA - MI is an allocation of an array of structures. Break
1251 /// it up into multiple allocations of arrays of the fields.
1252 static GlobalVariable *PerformHeapAllocSRoA(GlobalVariable *GV, MallocInst *MI){
1253 DOUT << "SROA HEAP ALLOC: " << *GV << " MALLOC = " << *MI;
1254 const StructType *STy = cast<StructType>(MI->getAllocatedType());
1256 // There is guaranteed to be at least one use of the malloc (storing
1257 // it into GV). If there are other uses, change them to be uses of
1258 // the global to simplify later code. This also deletes the store
1260 ReplaceUsesOfMallocWithGlobal(MI, GV);
1262 // Okay, at this point, there are no users of the malloc. Insert N
1263 // new mallocs at the same place as MI, and N globals.
1264 std::vector<Value*> FieldGlobals;
1265 std::vector<MallocInst*> FieldMallocs;
1267 for (unsigned FieldNo = 0, e = STy->getNumElements(); FieldNo != e;++FieldNo){
1268 const Type *FieldTy = STy->getElementType(FieldNo);
1269 const Type *PFieldTy = PointerType::getUnqual(FieldTy);
1271 GlobalVariable *NGV =
1272 new GlobalVariable(PFieldTy, false, GlobalValue::InternalLinkage,
1273 Constant::getNullValue(PFieldTy),
1274 GV->getName() + ".f" + utostr(FieldNo), GV,
1275 GV->isThreadLocal());
1276 FieldGlobals.push_back(NGV);
1278 MallocInst *NMI = new MallocInst(FieldTy, MI->getArraySize(),
1279 MI->getName() + ".f" + utostr(FieldNo),MI);
1280 FieldMallocs.push_back(NMI);
1281 new StoreInst(NMI, NGV, MI);
1284 // The tricky aspect of this transformation is handling the case when malloc
1285 // fails. In the original code, malloc failing would set the result pointer
1286 // of malloc to null. In this case, some mallocs could succeed and others
1287 // could fail. As such, we emit code that looks like this:
1288 // F0 = malloc(field0)
1289 // F1 = malloc(field1)
1290 // F2 = malloc(field2)
1291 // if (F0 == 0 || F1 == 0 || F2 == 0) {
1292 // if (F0) { free(F0); F0 = 0; }
1293 // if (F1) { free(F1); F1 = 0; }
1294 // if (F2) { free(F2); F2 = 0; }
1296 Value *RunningOr = 0;
1297 for (unsigned i = 0, e = FieldMallocs.size(); i != e; ++i) {
1298 Value *Cond = new ICmpInst(ICmpInst::ICMP_EQ, FieldMallocs[i],
1299 Constant::getNullValue(FieldMallocs[i]->getType()),
1302 RunningOr = Cond; // First seteq
1304 RunningOr = BinaryOperator::CreateOr(RunningOr, Cond, "tmp", MI);
1307 // Split the basic block at the old malloc.
1308 BasicBlock *OrigBB = MI->getParent();
1309 BasicBlock *ContBB = OrigBB->splitBasicBlock(MI, "malloc_cont");
1311 // Create the block to check the first condition. Put all these blocks at the
1312 // end of the function as they are unlikely to be executed.
1313 BasicBlock *NullPtrBlock = BasicBlock::Create("malloc_ret_null",
1314 OrigBB->getParent());
1316 // Remove the uncond branch from OrigBB to ContBB, turning it into a cond
1317 // branch on RunningOr.
1318 OrigBB->getTerminator()->eraseFromParent();
1319 BranchInst::Create(NullPtrBlock, ContBB, RunningOr, OrigBB);
1321 // Within the NullPtrBlock, we need to emit a comparison and branch for each
1322 // pointer, because some may be null while others are not.
1323 for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) {
1324 Value *GVVal = new LoadInst(FieldGlobals[i], "tmp", NullPtrBlock);
1325 Value *Cmp = new ICmpInst(ICmpInst::ICMP_NE, GVVal,
1326 Constant::getNullValue(GVVal->getType()),
1327 "tmp", NullPtrBlock);
1328 BasicBlock *FreeBlock = BasicBlock::Create("free_it", OrigBB->getParent());
1329 BasicBlock *NextBlock = BasicBlock::Create("next", OrigBB->getParent());
1330 BranchInst::Create(FreeBlock, NextBlock, Cmp, NullPtrBlock);
1332 // Fill in FreeBlock.
1333 new FreeInst(GVVal, FreeBlock);
1334 new StoreInst(Constant::getNullValue(GVVal->getType()), FieldGlobals[i],
1336 BranchInst::Create(NextBlock, FreeBlock);
1338 NullPtrBlock = NextBlock;
1341 BranchInst::Create(ContBB, NullPtrBlock);
1343 // MI is no longer needed, remove it.
1344 MI->eraseFromParent();
1346 /// InsertedScalarizedLoads - As we process loads, if we can't immediately
1347 /// update all uses of the load, keep track of what scalarized loads are
1348 /// inserted for a given load.
1349 DenseMap<Value*, std::vector<Value*> > InsertedScalarizedValues;
1350 InsertedScalarizedValues[GV] = FieldGlobals;
1352 std::vector<std::pair<PHINode*, unsigned> > PHIsToRewrite;
1354 // Okay, the malloc site is completely handled. All of the uses of GV are now
1355 // loads, and all uses of those loads are simple. Rewrite them to use loads
1356 // of the per-field globals instead.
1357 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); UI != E;) {
1358 Instruction *User = cast<Instruction>(*UI++);
1360 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1361 RewriteUsesOfLoadForHeapSRoA(LI, InsertedScalarizedValues, PHIsToRewrite);
1365 // Must be a store of null.
1366 StoreInst *SI = cast<StoreInst>(User);
1367 assert(isa<ConstantPointerNull>(SI->getOperand(0)) &&
1368 "Unexpected heap-sra user!");
1370 // Insert a store of null into each global.
1371 for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) {
1372 const PointerType *PT = cast<PointerType>(FieldGlobals[i]->getType());
1373 Constant *Null = Constant::getNullValue(PT->getElementType());
1374 new StoreInst(Null, FieldGlobals[i], SI);
1376 // Erase the original store.
1377 SI->eraseFromParent();
1380 // While we have PHIs that are interesting to rewrite, do it.
1381 while (!PHIsToRewrite.empty()) {
1382 PHINode *PN = PHIsToRewrite.back().first;
1383 unsigned FieldNo = PHIsToRewrite.back().second;
1384 PHIsToRewrite.pop_back();
1385 PHINode *FieldPN = cast<PHINode>(InsertedScalarizedValues[PN][FieldNo]);
1386 assert(FieldPN->getNumIncomingValues() == 0 &&"Already processed this phi");
1388 // Add all the incoming values. This can materialize more phis.
1389 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
1390 Value *InVal = PN->getIncomingValue(i);
1391 InVal = GetHeapSROAValue(InVal, FieldNo, InsertedScalarizedValues,
1393 FieldPN->addIncoming(InVal, PN->getIncomingBlock(i));
1397 // Drop all inter-phi links and any loads that made it this far.
1398 for (DenseMap<Value*, std::vector<Value*> >::iterator
1399 I = InsertedScalarizedValues.begin(), E = InsertedScalarizedValues.end();
1401 if (PHINode *PN = dyn_cast<PHINode>(I->first))
1402 PN->dropAllReferences();
1403 else if (LoadInst *LI = dyn_cast<LoadInst>(I->first))
1404 LI->dropAllReferences();
1407 // Delete all the phis and loads now that inter-references are dead.
1408 for (DenseMap<Value*, std::vector<Value*> >::iterator
1409 I = InsertedScalarizedValues.begin(), E = InsertedScalarizedValues.end();
1411 if (PHINode *PN = dyn_cast<PHINode>(I->first))
1412 PN->eraseFromParent();
1413 else if (LoadInst *LI = dyn_cast<LoadInst>(I->first))
1414 LI->eraseFromParent();
1417 // The old global is now dead, remove it.
1418 GV->eraseFromParent();
1421 return cast<GlobalVariable>(FieldGlobals[0]);
1424 /// TryToOptimizeStoreOfMallocToGlobal - This function is called when we see a
1425 /// pointer global variable with a single value stored it that is a malloc or
1427 static bool TryToOptimizeStoreOfMallocToGlobal(GlobalVariable *GV,
1429 Module::global_iterator &GVI,
1431 // If this is a malloc of an abstract type, don't touch it.
1432 if (!MI->getAllocatedType()->isSized())
1435 // We can't optimize this global unless all uses of it are *known* to be
1436 // of the malloc value, not of the null initializer value (consider a use
1437 // that compares the global's value against zero to see if the malloc has
1438 // been reached). To do this, we check to see if all uses of the global
1439 // would trap if the global were null: this proves that they must all
1440 // happen after the malloc.
1441 if (!AllUsesOfLoadedValueWillTrapIfNull(GV))
1444 // We can't optimize this if the malloc itself is used in a complex way,
1445 // for example, being stored into multiple globals. This allows the
1446 // malloc to be stored into the specified global, loaded setcc'd, and
1447 // GEP'd. These are all things we could transform to using the global
1450 SmallPtrSet<PHINode*, 8> PHIs;
1451 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(MI, GV, PHIs))
1456 // If we have a global that is only initialized with a fixed size malloc,
1457 // transform the program to use global memory instead of malloc'd memory.
1458 // This eliminates dynamic allocation, avoids an indirection accessing the
1459 // data, and exposes the resultant global to further GlobalOpt.
1460 if (ConstantInt *NElements = dyn_cast<ConstantInt>(MI->getArraySize())) {
1461 // Restrict this transformation to only working on small allocations
1462 // (2048 bytes currently), as we don't want to introduce a 16M global or
1464 if (NElements->getZExtValue()*
1465 TD.getTypePaddedSize(MI->getAllocatedType()) < 2048) {
1466 GVI = OptimizeGlobalAddressOfMalloc(GV, MI);
1471 // If the allocation is an array of structures, consider transforming this
1472 // into multiple malloc'd arrays, one for each field. This is basically
1473 // SRoA for malloc'd memory.
1474 const Type *AllocTy = MI->getAllocatedType();
1476 // If this is an allocation of a fixed size array of structs, analyze as a
1477 // variable size array. malloc [100 x struct],1 -> malloc struct, 100
1478 if (!MI->isArrayAllocation())
1479 if (const ArrayType *AT = dyn_cast<ArrayType>(AllocTy))
1480 AllocTy = AT->getElementType();
1482 if (const StructType *AllocSTy = dyn_cast<StructType>(AllocTy)) {
1483 // This the structure has an unreasonable number of fields, leave it
1485 if (AllocSTy->getNumElements() <= 16 && AllocSTy->getNumElements() != 0 &&
1486 AllGlobalLoadUsesSimpleEnoughForHeapSRA(GV, MI)) {
1488 // If this is a fixed size array, transform the Malloc to be an alloc of
1489 // structs. malloc [100 x struct],1 -> malloc struct, 100
1490 if (const ArrayType *AT = dyn_cast<ArrayType>(MI->getAllocatedType())) {
1492 new MallocInst(AllocSTy,
1493 ConstantInt::get(Type::Int32Ty, AT->getNumElements()),
1495 NewMI->takeName(MI);
1496 Value *Cast = new BitCastInst(NewMI, MI->getType(), "tmp", MI);
1497 MI->replaceAllUsesWith(Cast);
1498 MI->eraseFromParent();
1502 GVI = PerformHeapAllocSRoA(GV, MI);
1510 // OptimizeOnceStoredGlobal - Try to optimize globals based on the knowledge
1511 // that only one value (besides its initializer) is ever stored to the global.
1512 static bool OptimizeOnceStoredGlobal(GlobalVariable *GV, Value *StoredOnceVal,
1513 Module::global_iterator &GVI,
1515 // Ignore no-op GEPs and bitcasts.
1516 StoredOnceVal = StoredOnceVal->stripPointerCasts();
1518 // If we are dealing with a pointer global that is initialized to null and
1519 // only has one (non-null) value stored into it, then we can optimize any
1520 // users of the loaded value (often calls and loads) that would trap if the
1522 if (isa<PointerType>(GV->getInitializer()->getType()) &&
1523 GV->getInitializer()->isNullValue()) {
1524 if (Constant *SOVC = dyn_cast<Constant>(StoredOnceVal)) {
1525 if (GV->getInitializer()->getType() != SOVC->getType())
1526 SOVC = ConstantExpr::getBitCast(SOVC, GV->getInitializer()->getType());
1528 // Optimize away any trapping uses of the loaded value.
1529 if (OptimizeAwayTrappingUsesOfLoads(GV, SOVC))
1531 } else if (MallocInst *MI = dyn_cast<MallocInst>(StoredOnceVal)) {
1532 if (TryToOptimizeStoreOfMallocToGlobal(GV, MI, GVI, TD))
1540 /// TryToShrinkGlobalToBoolean - At this point, we have learned that the only
1541 /// two values ever stored into GV are its initializer and OtherVal. See if we
1542 /// can shrink the global into a boolean and select between the two values
1543 /// whenever it is used. This exposes the values to other scalar optimizations.
1544 static bool TryToShrinkGlobalToBoolean(GlobalVariable *GV, Constant *OtherVal) {
1545 const Type *GVElType = GV->getType()->getElementType();
1547 // If GVElType is already i1, it is already shrunk. If the type of the GV is
1548 // an FP value or vector, don't do this optimization because a select between
1549 // them is very expensive and unlikely to lead to later simplification.
1550 if (GVElType == Type::Int1Ty || GVElType->isFloatingPoint() ||
1551 isa<VectorType>(GVElType))
1554 // Walk the use list of the global seeing if all the uses are load or store.
1555 // If there is anything else, bail out.
1556 for (Value::use_iterator I = GV->use_begin(), E = GV->use_end(); I != E; ++I)
1557 if (!isa<LoadInst>(I) && !isa<StoreInst>(I))
1560 DOUT << " *** SHRINKING TO BOOL: " << *GV;
1562 // Create the new global, initializing it to false.
1563 GlobalVariable *NewGV = new GlobalVariable(Type::Int1Ty, false,
1564 GlobalValue::InternalLinkage, ConstantInt::getFalse(),
1567 GV->isThreadLocal());
1568 GV->getParent()->getGlobalList().insert(GV, NewGV);
1570 Constant *InitVal = GV->getInitializer();
1571 assert(InitVal->getType() != Type::Int1Ty && "No reason to shrink to bool!");
1573 // If initialized to zero and storing one into the global, we can use a cast
1574 // instead of a select to synthesize the desired value.
1575 bool IsOneZero = false;
1576 if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal))
1577 IsOneZero = InitVal->isNullValue() && CI->isOne();
1579 while (!GV->use_empty()) {
1580 Instruction *UI = cast<Instruction>(GV->use_back());
1581 if (StoreInst *SI = dyn_cast<StoreInst>(UI)) {
1582 // Change the store into a boolean store.
1583 bool StoringOther = SI->getOperand(0) == OtherVal;
1584 // Only do this if we weren't storing a loaded value.
1586 if (StoringOther || SI->getOperand(0) == InitVal)
1587 StoreVal = ConstantInt::get(Type::Int1Ty, StoringOther);
1589 // Otherwise, we are storing a previously loaded copy. To do this,
1590 // change the copy from copying the original value to just copying the
1592 Instruction *StoredVal = cast<Instruction>(SI->getOperand(0));
1594 // If we're already replaced the input, StoredVal will be a cast or
1595 // select instruction. If not, it will be a load of the original
1597 if (LoadInst *LI = dyn_cast<LoadInst>(StoredVal)) {
1598 assert(LI->getOperand(0) == GV && "Not a copy!");
1599 // Insert a new load, to preserve the saved value.
1600 StoreVal = new LoadInst(NewGV, LI->getName()+".b", LI);
1602 assert((isa<CastInst>(StoredVal) || isa<SelectInst>(StoredVal)) &&
1603 "This is not a form that we understand!");
1604 StoreVal = StoredVal->getOperand(0);
1605 assert(isa<LoadInst>(StoreVal) && "Not a load of NewGV!");
1608 new StoreInst(StoreVal, NewGV, SI);
1610 // Change the load into a load of bool then a select.
1611 LoadInst *LI = cast<LoadInst>(UI);
1612 LoadInst *NLI = new LoadInst(NewGV, LI->getName()+".b", LI);
1615 NSI = new ZExtInst(NLI, LI->getType(), "", LI);
1617 NSI = SelectInst::Create(NLI, OtherVal, InitVal, "", LI);
1619 LI->replaceAllUsesWith(NSI);
1621 UI->eraseFromParent();
1624 GV->eraseFromParent();
1629 /// ProcessInternalGlobal - Analyze the specified global variable and optimize
1630 /// it if possible. If we make a change, return true.
1631 bool GlobalOpt::ProcessInternalGlobal(GlobalVariable *GV,
1632 Module::global_iterator &GVI) {
1633 SmallPtrSet<PHINode*, 16> PHIUsers;
1635 GV->removeDeadConstantUsers();
1637 if (GV->use_empty()) {
1638 DOUT << "GLOBAL DEAD: " << *GV;
1639 GV->eraseFromParent();
1644 if (!AnalyzeGlobal(GV, GS, PHIUsers)) {
1646 cerr << "Global: " << *GV;
1647 cerr << " isLoaded = " << GS.isLoaded << "\n";
1648 cerr << " StoredType = ";
1649 switch (GS.StoredType) {
1650 case GlobalStatus::NotStored: cerr << "NEVER STORED\n"; break;
1651 case GlobalStatus::isInitializerStored: cerr << "INIT STORED\n"; break;
1652 case GlobalStatus::isStoredOnce: cerr << "STORED ONCE\n"; break;
1653 case GlobalStatus::isStored: cerr << "stored\n"; break;
1655 if (GS.StoredType == GlobalStatus::isStoredOnce && GS.StoredOnceValue)
1656 cerr << " StoredOnceValue = " << *GS.StoredOnceValue << "\n";
1657 if (GS.AccessingFunction && !GS.HasMultipleAccessingFunctions)
1658 cerr << " AccessingFunction = " << GS.AccessingFunction->getName()
1660 cerr << " HasMultipleAccessingFunctions = "
1661 << GS.HasMultipleAccessingFunctions << "\n";
1662 cerr << " HasNonInstructionUser = " << GS.HasNonInstructionUser<<"\n";
1666 // If this is a first class global and has only one accessing function
1667 // and this function is main (which we know is not recursive we can make
1668 // this global a local variable) we replace the global with a local alloca
1669 // in this function.
1671 // NOTE: It doesn't make sense to promote non single-value types since we
1672 // are just replacing static memory to stack memory.
1673 if (!GS.HasMultipleAccessingFunctions &&
1674 GS.AccessingFunction && !GS.HasNonInstructionUser &&
1675 GV->getType()->getElementType()->isSingleValueType() &&
1676 GS.AccessingFunction->getName() == "main" &&
1677 GS.AccessingFunction->hasExternalLinkage()) {
1678 DOUT << "LOCALIZING GLOBAL: " << *GV;
1679 Instruction* FirstI = GS.AccessingFunction->getEntryBlock().begin();
1680 const Type* ElemTy = GV->getType()->getElementType();
1681 // FIXME: Pass Global's alignment when globals have alignment
1682 AllocaInst* Alloca = new AllocaInst(ElemTy, NULL, GV->getName(), FirstI);
1683 if (!isa<UndefValue>(GV->getInitializer()))
1684 new StoreInst(GV->getInitializer(), Alloca, FirstI);
1686 GV->replaceAllUsesWith(Alloca);
1687 GV->eraseFromParent();
1692 // If the global is never loaded (but may be stored to), it is dead.
1695 DOUT << "GLOBAL NEVER LOADED: " << *GV;
1697 // Delete any stores we can find to the global. We may not be able to
1698 // make it completely dead though.
1699 bool Changed = CleanupConstantGlobalUsers(GV, GV->getInitializer());
1701 // If the global is dead now, delete it.
1702 if (GV->use_empty()) {
1703 GV->eraseFromParent();
1709 } else if (GS.StoredType <= GlobalStatus::isInitializerStored) {
1710 DOUT << "MARKING CONSTANT: " << *GV;
1711 GV->setConstant(true);
1713 // Clean up any obviously simplifiable users now.
1714 CleanupConstantGlobalUsers(GV, GV->getInitializer());
1716 // If the global is dead now, just nuke it.
1717 if (GV->use_empty()) {
1718 DOUT << " *** Marking constant allowed us to simplify "
1719 << "all users and delete global!\n";
1720 GV->eraseFromParent();
1726 } else if (!GV->getInitializer()->getType()->isSingleValueType()) {
1727 if (GlobalVariable *FirstNewGV = SRAGlobal(GV,
1728 getAnalysis<TargetData>())) {
1729 GVI = FirstNewGV; // Don't skip the newly produced globals!
1732 } else if (GS.StoredType == GlobalStatus::isStoredOnce) {
1733 // If the initial value for the global was an undef value, and if only
1734 // one other value was stored into it, we can just change the
1735 // initializer to be the stored value, then delete all stores to the
1736 // global. This allows us to mark it constant.
1737 if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue))
1738 if (isa<UndefValue>(GV->getInitializer())) {
1739 // Change the initial value here.
1740 GV->setInitializer(SOVConstant);
1742 // Clean up any obviously simplifiable users now.
1743 CleanupConstantGlobalUsers(GV, GV->getInitializer());
1745 if (GV->use_empty()) {
1746 DOUT << " *** Substituting initializer allowed us to "
1747 << "simplify all users and delete global!\n";
1748 GV->eraseFromParent();
1757 // Try to optimize globals based on the knowledge that only one value
1758 // (besides its initializer) is ever stored to the global.
1759 if (OptimizeOnceStoredGlobal(GV, GS.StoredOnceValue, GVI,
1760 getAnalysis<TargetData>()))
1763 // Otherwise, if the global was not a boolean, we can shrink it to be a
1765 if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue))
1766 if (TryToShrinkGlobalToBoolean(GV, SOVConstant)) {
1775 /// OnlyCalledDirectly - Return true if the specified function is only called
1776 /// directly. In other words, its address is never taken.
1777 static bool OnlyCalledDirectly(Function *F) {
1778 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){
1779 Instruction *User = dyn_cast<Instruction>(*UI);
1780 if (!User) return false;
1781 if (!isa<CallInst>(User) && !isa<InvokeInst>(User)) return false;
1783 // See if the function address is passed as an argument.
1784 for (User::op_iterator i = User->op_begin() + 1, e = User->op_end();
1786 if (*i == F) return false;
1791 /// ChangeCalleesToFastCall - Walk all of the direct calls of the specified
1792 /// function, changing them to FastCC.
1793 static void ChangeCalleesToFastCall(Function *F) {
1794 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){
1795 CallSite User(cast<Instruction>(*UI));
1796 User.setCallingConv(CallingConv::Fast);
1800 static AttrListPtr StripNest(const AttrListPtr &Attrs) {
1801 for (unsigned i = 0, e = Attrs.getNumSlots(); i != e; ++i) {
1802 if ((Attrs.getSlot(i).Attrs & Attribute::Nest) == 0)
1805 // There can be only one.
1806 return Attrs.removeAttr(Attrs.getSlot(i).Index, Attribute::Nest);
1812 static void RemoveNestAttribute(Function *F) {
1813 F->setAttributes(StripNest(F->getAttributes()));
1814 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){
1815 CallSite User(cast<Instruction>(*UI));
1816 User.setAttributes(StripNest(User.getAttributes()));
1820 bool GlobalOpt::OptimizeFunctions(Module &M) {
1821 bool Changed = false;
1822 // Optimize functions.
1823 for (Module::iterator FI = M.begin(), E = M.end(); FI != E; ) {
1825 F->removeDeadConstantUsers();
1826 if (F->use_empty() && (F->hasLocalLinkage() ||
1827 F->hasLinkOnceLinkage())) {
1828 M.getFunctionList().erase(F);
1831 } else if (F->hasLocalLinkage()) {
1832 if (F->getCallingConv() == CallingConv::C && !F->isVarArg() &&
1833 OnlyCalledDirectly(F)) {
1834 // If this function has C calling conventions, is not a varargs
1835 // function, and is only called directly, promote it to use the Fast
1836 // calling convention.
1837 F->setCallingConv(CallingConv::Fast);
1838 ChangeCalleesToFastCall(F);
1843 if (F->getAttributes().hasAttrSomewhere(Attribute::Nest) &&
1844 OnlyCalledDirectly(F)) {
1845 // The function is not used by a trampoline intrinsic, so it is safe
1846 // to remove the 'nest' attribute.
1847 RemoveNestAttribute(F);
1856 bool GlobalOpt::OptimizeGlobalVars(Module &M) {
1857 bool Changed = false;
1858 for (Module::global_iterator GVI = M.global_begin(), E = M.global_end();
1860 GlobalVariable *GV = GVI++;
1861 if (!GV->isConstant() && GV->hasLocalLinkage() &&
1862 GV->hasInitializer())
1863 Changed |= ProcessInternalGlobal(GV, GVI);
1868 /// FindGlobalCtors - Find the llvm.globalctors list, verifying that all
1869 /// initializers have an init priority of 65535.
1870 GlobalVariable *GlobalOpt::FindGlobalCtors(Module &M) {
1871 for (Module::global_iterator I = M.global_begin(), E = M.global_end();
1873 if (I->getName() == "llvm.global_ctors") {
1874 // Found it, verify it's an array of { int, void()* }.
1875 const ArrayType *ATy =dyn_cast<ArrayType>(I->getType()->getElementType());
1877 const StructType *STy = dyn_cast<StructType>(ATy->getElementType());
1878 if (!STy || STy->getNumElements() != 2 ||
1879 STy->getElementType(0) != Type::Int32Ty) return 0;
1880 const PointerType *PFTy = dyn_cast<PointerType>(STy->getElementType(1));
1881 if (!PFTy) return 0;
1882 const FunctionType *FTy = dyn_cast<FunctionType>(PFTy->getElementType());
1883 if (!FTy || FTy->getReturnType() != Type::VoidTy || FTy->isVarArg() ||
1884 FTy->getNumParams() != 0)
1887 // Verify that the initializer is simple enough for us to handle.
1888 if (!I->hasInitializer()) return 0;
1889 ConstantArray *CA = dyn_cast<ConstantArray>(I->getInitializer());
1891 for (User::op_iterator i = CA->op_begin(), e = CA->op_end(); i != e; ++i)
1892 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(*i)) {
1893 if (isa<ConstantPointerNull>(CS->getOperand(1)))
1896 // Must have a function or null ptr.
1897 if (!isa<Function>(CS->getOperand(1)))
1900 // Init priority must be standard.
1901 ConstantInt *CI = dyn_cast<ConstantInt>(CS->getOperand(0));
1902 if (!CI || CI->getZExtValue() != 65535)
1913 /// ParseGlobalCtors - Given a llvm.global_ctors list that we can understand,
1914 /// return a list of the functions and null terminator as a vector.
1915 static std::vector<Function*> ParseGlobalCtors(GlobalVariable *GV) {
1916 ConstantArray *CA = cast<ConstantArray>(GV->getInitializer());
1917 std::vector<Function*> Result;
1918 Result.reserve(CA->getNumOperands());
1919 for (User::op_iterator i = CA->op_begin(), e = CA->op_end(); i != e; ++i) {
1920 ConstantStruct *CS = cast<ConstantStruct>(*i);
1921 Result.push_back(dyn_cast<Function>(CS->getOperand(1)));
1926 /// InstallGlobalCtors - Given a specified llvm.global_ctors list, install the
1927 /// specified array, returning the new global to use.
1928 static GlobalVariable *InstallGlobalCtors(GlobalVariable *GCL,
1929 const std::vector<Function*> &Ctors) {
1930 // If we made a change, reassemble the initializer list.
1931 std::vector<Constant*> CSVals;
1932 CSVals.push_back(ConstantInt::get(Type::Int32Ty, 65535));
1933 CSVals.push_back(0);
1935 // Create the new init list.
1936 std::vector<Constant*> CAList;
1937 for (unsigned i = 0, e = Ctors.size(); i != e; ++i) {
1939 CSVals[1] = Ctors[i];
1941 const Type *FTy = FunctionType::get(Type::VoidTy,
1942 std::vector<const Type*>(), false);
1943 const PointerType *PFTy = PointerType::getUnqual(FTy);
1944 CSVals[1] = Constant::getNullValue(PFTy);
1945 CSVals[0] = ConstantInt::get(Type::Int32Ty, 2147483647);
1947 CAList.push_back(ConstantStruct::get(CSVals));
1950 // Create the array initializer.
1951 const Type *StructTy =
1952 cast<ArrayType>(GCL->getType()->getElementType())->getElementType();
1953 Constant *CA = ConstantArray::get(ArrayType::get(StructTy, CAList.size()),
1956 // If we didn't change the number of elements, don't create a new GV.
1957 if (CA->getType() == GCL->getInitializer()->getType()) {
1958 GCL->setInitializer(CA);
1962 // Create the new global and insert it next to the existing list.
1963 GlobalVariable *NGV = new GlobalVariable(CA->getType(), GCL->isConstant(),
1964 GCL->getLinkage(), CA, "",
1966 GCL->isThreadLocal());
1967 GCL->getParent()->getGlobalList().insert(GCL, NGV);
1970 // Nuke the old list, replacing any uses with the new one.
1971 if (!GCL->use_empty()) {
1973 if (V->getType() != GCL->getType())
1974 V = ConstantExpr::getBitCast(V, GCL->getType());
1975 GCL->replaceAllUsesWith(V);
1977 GCL->eraseFromParent();
1986 static Constant *getVal(DenseMap<Value*, Constant*> &ComputedValues,
1988 if (Constant *CV = dyn_cast<Constant>(V)) return CV;
1989 Constant *R = ComputedValues[V];
1990 assert(R && "Reference to an uncomputed value!");
1994 /// isSimpleEnoughPointerToCommit - Return true if this constant is simple
1995 /// enough for us to understand. In particular, if it is a cast of something,
1996 /// we punt. We basically just support direct accesses to globals and GEP's of
1997 /// globals. This should be kept up to date with CommitValueTo.
1998 static bool isSimpleEnoughPointerToCommit(Constant *C) {
1999 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C)) {
2000 if (!GV->hasExternalLinkage() && !GV->hasLocalLinkage())
2001 return false; // do not allow weak/linkonce/dllimport/dllexport linkage.
2002 return !GV->isDeclaration(); // reject external globals.
2004 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
2005 // Handle a constantexpr gep.
2006 if (CE->getOpcode() == Instruction::GetElementPtr &&
2007 isa<GlobalVariable>(CE->getOperand(0))) {
2008 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
2009 if (!GV->hasExternalLinkage() && !GV->hasLocalLinkage())
2010 return false; // do not allow weak/linkonce/dllimport/dllexport linkage.
2011 return GV->hasInitializer() &&
2012 ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE);
2017 /// EvaluateStoreInto - Evaluate a piece of a constantexpr store into a global
2018 /// initializer. This returns 'Init' modified to reflect 'Val' stored into it.
2019 /// At this point, the GEP operands of Addr [0, OpNo) have been stepped into.
2020 static Constant *EvaluateStoreInto(Constant *Init, Constant *Val,
2021 ConstantExpr *Addr, unsigned OpNo) {
2022 // Base case of the recursion.
2023 if (OpNo == Addr->getNumOperands()) {
2024 assert(Val->getType() == Init->getType() && "Type mismatch!");
2028 if (const StructType *STy = dyn_cast<StructType>(Init->getType())) {
2029 std::vector<Constant*> Elts;
2031 // Break up the constant into its elements.
2032 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(Init)) {
2033 for (User::op_iterator i = CS->op_begin(), e = CS->op_end(); i != e; ++i)
2034 Elts.push_back(cast<Constant>(*i));
2035 } else if (isa<ConstantAggregateZero>(Init)) {
2036 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
2037 Elts.push_back(Constant::getNullValue(STy->getElementType(i)));
2038 } else if (isa<UndefValue>(Init)) {
2039 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
2040 Elts.push_back(UndefValue::get(STy->getElementType(i)));
2042 assert(0 && "This code is out of sync with "
2043 " ConstantFoldLoadThroughGEPConstantExpr");
2046 // Replace the element that we are supposed to.
2047 ConstantInt *CU = cast<ConstantInt>(Addr->getOperand(OpNo));
2048 unsigned Idx = CU->getZExtValue();
2049 assert(Idx < STy->getNumElements() && "Struct index out of range!");
2050 Elts[Idx] = EvaluateStoreInto(Elts[Idx], Val, Addr, OpNo+1);
2052 // Return the modified struct.
2053 return ConstantStruct::get(&Elts[0], Elts.size(), STy->isPacked());
2055 ConstantInt *CI = cast<ConstantInt>(Addr->getOperand(OpNo));
2056 const ArrayType *ATy = cast<ArrayType>(Init->getType());
2058 // Break up the array into elements.
2059 std::vector<Constant*> Elts;
2060 if (ConstantArray *CA = dyn_cast<ConstantArray>(Init)) {
2061 for (User::op_iterator i = CA->op_begin(), e = CA->op_end(); i != e; ++i)
2062 Elts.push_back(cast<Constant>(*i));
2063 } else if (isa<ConstantAggregateZero>(Init)) {
2064 Constant *Elt = Constant::getNullValue(ATy->getElementType());
2065 Elts.assign(ATy->getNumElements(), Elt);
2066 } else if (isa<UndefValue>(Init)) {
2067 Constant *Elt = UndefValue::get(ATy->getElementType());
2068 Elts.assign(ATy->getNumElements(), Elt);
2070 assert(0 && "This code is out of sync with "
2071 " ConstantFoldLoadThroughGEPConstantExpr");
2074 assert(CI->getZExtValue() < ATy->getNumElements());
2075 Elts[CI->getZExtValue()] =
2076 EvaluateStoreInto(Elts[CI->getZExtValue()], Val, Addr, OpNo+1);
2077 return ConstantArray::get(ATy, Elts);
2081 /// CommitValueTo - We have decided that Addr (which satisfies the predicate
2082 /// isSimpleEnoughPointerToCommit) should get Val as its value. Make it happen.
2083 static void CommitValueTo(Constant *Val, Constant *Addr) {
2084 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Addr)) {
2085 assert(GV->hasInitializer());
2086 GV->setInitializer(Val);
2090 ConstantExpr *CE = cast<ConstantExpr>(Addr);
2091 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
2093 Constant *Init = GV->getInitializer();
2094 Init = EvaluateStoreInto(Init, Val, CE, 2);
2095 GV->setInitializer(Init);
2098 /// ComputeLoadResult - Return the value that would be computed by a load from
2099 /// P after the stores reflected by 'memory' have been performed. If we can't
2100 /// decide, return null.
2101 static Constant *ComputeLoadResult(Constant *P,
2102 const DenseMap<Constant*, Constant*> &Memory) {
2103 // If this memory location has been recently stored, use the stored value: it
2104 // is the most up-to-date.
2105 DenseMap<Constant*, Constant*>::const_iterator I = Memory.find(P);
2106 if (I != Memory.end()) return I->second;
2109 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(P)) {
2110 if (GV->hasInitializer())
2111 return GV->getInitializer();
2115 // Handle a constantexpr getelementptr.
2116 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(P))
2117 if (CE->getOpcode() == Instruction::GetElementPtr &&
2118 isa<GlobalVariable>(CE->getOperand(0))) {
2119 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
2120 if (GV->hasInitializer())
2121 return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE);
2124 return 0; // don't know how to evaluate.
2127 /// EvaluateFunction - Evaluate a call to function F, returning true if
2128 /// successful, false if we can't evaluate it. ActualArgs contains the formal
2129 /// arguments for the function.
2130 static bool EvaluateFunction(Function *F, Constant *&RetVal,
2131 const std::vector<Constant*> &ActualArgs,
2132 std::vector<Function*> &CallStack,
2133 DenseMap<Constant*, Constant*> &MutatedMemory,
2134 std::vector<GlobalVariable*> &AllocaTmps) {
2135 // Check to see if this function is already executing (recursion). If so,
2136 // bail out. TODO: we might want to accept limited recursion.
2137 if (std::find(CallStack.begin(), CallStack.end(), F) != CallStack.end())
2140 CallStack.push_back(F);
2142 /// Values - As we compute SSA register values, we store their contents here.
2143 DenseMap<Value*, Constant*> Values;
2145 // Initialize arguments to the incoming values specified.
2147 for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end(); AI != E;
2149 Values[AI] = ActualArgs[ArgNo];
2151 /// ExecutedBlocks - We only handle non-looping, non-recursive code. As such,
2152 /// we can only evaluate any one basic block at most once. This set keeps
2153 /// track of what we have executed so we can detect recursive cases etc.
2154 SmallPtrSet<BasicBlock*, 32> ExecutedBlocks;
2156 // CurInst - The current instruction we're evaluating.
2157 BasicBlock::iterator CurInst = F->begin()->begin();
2159 // This is the main evaluation loop.
2161 Constant *InstResult = 0;
2163 if (StoreInst *SI = dyn_cast<StoreInst>(CurInst)) {
2164 if (SI->isVolatile()) return false; // no volatile accesses.
2165 Constant *Ptr = getVal(Values, SI->getOperand(1));
2166 if (!isSimpleEnoughPointerToCommit(Ptr))
2167 // If this is too complex for us to commit, reject it.
2169 Constant *Val = getVal(Values, SI->getOperand(0));
2170 MutatedMemory[Ptr] = Val;
2171 } else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(CurInst)) {
2172 InstResult = ConstantExpr::get(BO->getOpcode(),
2173 getVal(Values, BO->getOperand(0)),
2174 getVal(Values, BO->getOperand(1)));
2175 } else if (CmpInst *CI = dyn_cast<CmpInst>(CurInst)) {
2176 InstResult = ConstantExpr::getCompare(CI->getPredicate(),
2177 getVal(Values, CI->getOperand(0)),
2178 getVal(Values, CI->getOperand(1)));
2179 } else if (CastInst *CI = dyn_cast<CastInst>(CurInst)) {
2180 InstResult = ConstantExpr::getCast(CI->getOpcode(),
2181 getVal(Values, CI->getOperand(0)),
2183 } else if (SelectInst *SI = dyn_cast<SelectInst>(CurInst)) {
2184 InstResult = ConstantExpr::getSelect(getVal(Values, SI->getOperand(0)),
2185 getVal(Values, SI->getOperand(1)),
2186 getVal(Values, SI->getOperand(2)));
2187 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(CurInst)) {
2188 Constant *P = getVal(Values, GEP->getOperand(0));
2189 SmallVector<Constant*, 8> GEPOps;
2190 for (User::op_iterator i = GEP->op_begin() + 1, e = GEP->op_end();
2192 GEPOps.push_back(getVal(Values, *i));
2193 InstResult = ConstantExpr::getGetElementPtr(P, &GEPOps[0], GEPOps.size());
2194 } else if (LoadInst *LI = dyn_cast<LoadInst>(CurInst)) {
2195 if (LI->isVolatile()) return false; // no volatile accesses.
2196 InstResult = ComputeLoadResult(getVal(Values, LI->getOperand(0)),
2198 if (InstResult == 0) return false; // Could not evaluate load.
2199 } else if (AllocaInst *AI = dyn_cast<AllocaInst>(CurInst)) {
2200 if (AI->isArrayAllocation()) return false; // Cannot handle array allocs.
2201 const Type *Ty = AI->getType()->getElementType();
2202 AllocaTmps.push_back(new GlobalVariable(Ty, false,
2203 GlobalValue::InternalLinkage,
2204 UndefValue::get(Ty),
2206 InstResult = AllocaTmps.back();
2207 } else if (CallInst *CI = dyn_cast<CallInst>(CurInst)) {
2208 // Cannot handle inline asm.
2209 if (isa<InlineAsm>(CI->getOperand(0))) return false;
2211 // Resolve function pointers.
2212 Function *Callee = dyn_cast<Function>(getVal(Values, CI->getOperand(0)));
2213 if (!Callee) return false; // Cannot resolve.
2215 std::vector<Constant*> Formals;
2216 for (User::op_iterator i = CI->op_begin() + 1, e = CI->op_end();
2218 Formals.push_back(getVal(Values, *i));
2220 if (Callee->isDeclaration()) {
2221 // If this is a function we can constant fold, do it.
2222 if (Constant *C = ConstantFoldCall(Callee, &Formals[0],
2229 if (Callee->getFunctionType()->isVarArg())
2234 // Execute the call, if successful, use the return value.
2235 if (!EvaluateFunction(Callee, RetVal, Formals, CallStack,
2236 MutatedMemory, AllocaTmps))
2238 InstResult = RetVal;
2240 } else if (isa<TerminatorInst>(CurInst)) {
2241 BasicBlock *NewBB = 0;
2242 if (BranchInst *BI = dyn_cast<BranchInst>(CurInst)) {
2243 if (BI->isUnconditional()) {
2244 NewBB = BI->getSuccessor(0);
2247 dyn_cast<ConstantInt>(getVal(Values, BI->getCondition()));
2248 if (!Cond) return false; // Cannot determine.
2250 NewBB = BI->getSuccessor(!Cond->getZExtValue());
2252 } else if (SwitchInst *SI = dyn_cast<SwitchInst>(CurInst)) {
2254 dyn_cast<ConstantInt>(getVal(Values, SI->getCondition()));
2255 if (!Val) return false; // Cannot determine.
2256 NewBB = SI->getSuccessor(SI->findCaseValue(Val));
2257 } else if (ReturnInst *RI = dyn_cast<ReturnInst>(CurInst)) {
2258 if (RI->getNumOperands())
2259 RetVal = getVal(Values, RI->getOperand(0));
2261 CallStack.pop_back(); // return from fn.
2262 return true; // We succeeded at evaluating this ctor!
2264 // invoke, unwind, unreachable.
2265 return false; // Cannot handle this terminator.
2268 // Okay, we succeeded in evaluating this control flow. See if we have
2269 // executed the new block before. If so, we have a looping function,
2270 // which we cannot evaluate in reasonable time.
2271 if (!ExecutedBlocks.insert(NewBB))
2272 return false; // looped!
2274 // Okay, we have never been in this block before. Check to see if there
2275 // are any PHI nodes. If so, evaluate them with information about where
2277 BasicBlock *OldBB = CurInst->getParent();
2278 CurInst = NewBB->begin();
2280 for (; (PN = dyn_cast<PHINode>(CurInst)); ++CurInst)
2281 Values[PN] = getVal(Values, PN->getIncomingValueForBlock(OldBB));
2283 // Do NOT increment CurInst. We know that the terminator had no value.
2286 // Did not know how to evaluate this!
2290 if (!CurInst->use_empty())
2291 Values[CurInst] = InstResult;
2293 // Advance program counter.
2298 /// EvaluateStaticConstructor - Evaluate static constructors in the function, if
2299 /// we can. Return true if we can, false otherwise.
2300 static bool EvaluateStaticConstructor(Function *F) {
2301 /// MutatedMemory - For each store we execute, we update this map. Loads
2302 /// check this to get the most up-to-date value. If evaluation is successful,
2303 /// this state is committed to the process.
2304 DenseMap<Constant*, Constant*> MutatedMemory;
2306 /// AllocaTmps - To 'execute' an alloca, we create a temporary global variable
2307 /// to represent its body. This vector is needed so we can delete the
2308 /// temporary globals when we are done.
2309 std::vector<GlobalVariable*> AllocaTmps;
2311 /// CallStack - This is used to detect recursion. In pathological situations
2312 /// we could hit exponential behavior, but at least there is nothing
2314 std::vector<Function*> CallStack;
2316 // Call the function.
2317 Constant *RetValDummy;
2318 bool EvalSuccess = EvaluateFunction(F, RetValDummy, std::vector<Constant*>(),
2319 CallStack, MutatedMemory, AllocaTmps);
2321 // We succeeded at evaluation: commit the result.
2322 DOUT << "FULLY EVALUATED GLOBAL CTOR FUNCTION '"
2323 << F->getName() << "' to " << MutatedMemory.size()
2325 for (DenseMap<Constant*, Constant*>::iterator I = MutatedMemory.begin(),
2326 E = MutatedMemory.end(); I != E; ++I)
2327 CommitValueTo(I->second, I->first);
2330 // At this point, we are done interpreting. If we created any 'alloca'
2331 // temporaries, release them now.
2332 while (!AllocaTmps.empty()) {
2333 GlobalVariable *Tmp = AllocaTmps.back();
2334 AllocaTmps.pop_back();
2336 // If there are still users of the alloca, the program is doing something
2337 // silly, e.g. storing the address of the alloca somewhere and using it
2338 // later. Since this is undefined, we'll just make it be null.
2339 if (!Tmp->use_empty())
2340 Tmp->replaceAllUsesWith(Constant::getNullValue(Tmp->getType()));
2349 /// OptimizeGlobalCtorsList - Simplify and evaluation global ctors if possible.
2350 /// Return true if anything changed.
2351 bool GlobalOpt::OptimizeGlobalCtorsList(GlobalVariable *&GCL) {
2352 std::vector<Function*> Ctors = ParseGlobalCtors(GCL);
2353 bool MadeChange = false;
2354 if (Ctors.empty()) return false;
2356 // Loop over global ctors, optimizing them when we can.
2357 for (unsigned i = 0; i != Ctors.size(); ++i) {
2358 Function *F = Ctors[i];
2359 // Found a null terminator in the middle of the list, prune off the rest of
2362 if (i != Ctors.size()-1) {
2369 // We cannot simplify external ctor functions.
2370 if (F->empty()) continue;
2372 // If we can evaluate the ctor at compile time, do.
2373 if (EvaluateStaticConstructor(F)) {
2374 Ctors.erase(Ctors.begin()+i);
2377 ++NumCtorsEvaluated;
2382 if (!MadeChange) return false;
2384 GCL = InstallGlobalCtors(GCL, Ctors);
2388 bool GlobalOpt::ResolveAliases(Module &M) {
2389 bool Changed = false;
2391 for (Module::alias_iterator I = M.alias_begin(), E = M.alias_end();
2393 Module::alias_iterator J = I++;
2394 // If the aliasee may change at link time, nothing can be done - bail out.
2395 if (J->mayBeOverridden())
2398 Constant *Aliasee = J->getAliasee();
2399 GlobalValue *Target = cast<GlobalValue>(Aliasee->stripPointerCasts());
2400 Target->removeDeadConstantUsers();
2401 bool hasOneUse = Target->hasOneUse() && Aliasee->hasOneUse();
2403 // Make all users of the alias use the aliasee instead.
2404 if (!J->use_empty()) {
2405 J->replaceAllUsesWith(Aliasee);
2406 ++NumAliasesResolved;
2410 // If the aliasee has internal linkage, give it the name and linkage
2411 // of the alias, and delete the alias. This turns:
2412 // define internal ... @f(...)
2413 // @a = alias ... @f
2415 // define ... @a(...)
2416 if (!Target->hasLocalLinkage())
2419 // The transform is only useful if the alias does not have internal linkage.
2420 if (J->hasLocalLinkage())
2423 // Do not perform the transform if multiple aliases potentially target the
2424 // aliasee. This check also ensures that it is safe to replace the section
2425 // and other attributes of the aliasee with those of the alias.
2429 // Give the aliasee the name, linkage and other attributes of the alias.
2430 Target->takeName(J);
2431 Target->setLinkage(J->getLinkage());
2432 Target->GlobalValue::copyAttributesFrom(J);
2434 // Delete the alias.
2435 M.getAliasList().erase(J);
2436 ++NumAliasesRemoved;
2443 bool GlobalOpt::runOnModule(Module &M) {
2444 bool Changed = false;
2446 // Try to find the llvm.globalctors list.
2447 GlobalVariable *GlobalCtors = FindGlobalCtors(M);
2449 bool LocalChange = true;
2450 while (LocalChange) {
2451 LocalChange = false;
2453 // Delete functions that are trivially dead, ccc -> fastcc
2454 LocalChange |= OptimizeFunctions(M);
2456 // Optimize global_ctors list.
2458 LocalChange |= OptimizeGlobalCtorsList(GlobalCtors);
2460 // Optimize non-address-taken globals.
2461 LocalChange |= OptimizeGlobalVars(M);
2463 // Resolve aliases, when possible.
2464 LocalChange |= ResolveAliases(M);
2465 Changed |= LocalChange;
2468 // TODO: Move all global ctors functions to the end of the module for code