1 //===- GlobalOpt.cpp - Optimize Global Variables --------------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source 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/Support/Debug.h"
26 #include "llvm/Target/TargetData.h"
27 #include "llvm/Transforms/Utils/Local.h"
28 #include "llvm/ADT/Statistic.h"
29 #include "llvm/ADT/StringExtras.h"
35 Statistic<> NumMarked ("globalopt", "Number of globals marked constant");
36 Statistic<> NumSRA ("globalopt", "Number of aggregate globals broken "
38 Statistic<> NumSubstitute("globalopt",
39 "Number of globals with initializers stored into them");
40 Statistic<> NumDeleted ("globalopt", "Number of globals deleted");
41 Statistic<> NumFnDeleted("globalopt", "Number of functions deleted");
42 Statistic<> NumGlobUses ("globalopt", "Number of global uses devirtualized");
43 Statistic<> NumLocalized("globalopt", "Number of globals localized");
44 Statistic<> NumShrunkToBool("globalopt",
45 "Number of global vars shrunk to booleans");
46 Statistic<> NumFastCallFns("globalopt",
47 "Number of functions converted to fastcc");
48 Statistic<> NumEmptyCtor ("globalopt", "Number of empty ctors removed");
49 Statistic<> NumCtorsEvaluated("globalopt","Number of static ctors evaluated");
51 struct GlobalOpt : public ModulePass {
52 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
53 AU.addRequired<TargetData>();
56 bool runOnModule(Module &M);
59 GlobalVariable *FindGlobalCtors(Module &M);
60 bool OptimizeFunctions(Module &M);
61 bool OptimizeGlobalVars(Module &M);
62 bool OptimizeGlobalCtorsList(GlobalVariable *&GCL);
63 bool ProcessInternalGlobal(GlobalVariable *GV, Module::global_iterator &GVI);
66 RegisterOpt<GlobalOpt> X("globalopt", "Global Variable Optimizer");
69 ModulePass *llvm::createGlobalOptimizerPass() { return new GlobalOpt(); }
71 /// GlobalStatus - As we analyze each global, keep track of some information
72 /// about it. If we find out that the address of the global is taken, none of
73 /// this info will be accurate.
75 /// isLoaded - True if the global is ever loaded. If the global isn't ever
76 /// loaded it can be deleted.
79 /// StoredType - Keep track of what stores to the global look like.
82 /// NotStored - There is no store to this global. It can thus be marked
86 /// isInitializerStored - This global is stored to, but the only thing
87 /// stored is the constant it was initialized with. This is only tracked
88 /// for scalar globals.
91 /// isStoredOnce - This global is stored to, but only its initializer and
92 /// one other value is ever stored to it. If this global isStoredOnce, we
93 /// track the value stored to it in StoredOnceValue below. This is only
94 /// tracked for scalar globals.
97 /// isStored - This global is stored to by multiple values or something else
98 /// that we cannot track.
102 /// StoredOnceValue - If only one value (besides the initializer constant) is
103 /// ever stored to this global, keep track of what value it is.
104 Value *StoredOnceValue;
106 // AccessingFunction/HasMultipleAccessingFunctions - These start out
107 // null/false. When the first accessing function is noticed, it is recorded.
108 // When a second different accessing function is noticed,
109 // HasMultipleAccessingFunctions is set to true.
110 Function *AccessingFunction;
111 bool HasMultipleAccessingFunctions;
113 // HasNonInstructionUser - Set to true if this global has a user that is not
114 // an instruction (e.g. a constant expr or GV initializer).
115 bool HasNonInstructionUser;
117 /// isNotSuitableForSRA - Keep track of whether any SRA preventing users of
118 /// the global exist. Such users include GEP instruction with variable
119 /// indexes, and non-gep/load/store users like constant expr casts.
120 bool isNotSuitableForSRA;
122 GlobalStatus() : isLoaded(false), StoredType(NotStored), StoredOnceValue(0),
123 AccessingFunction(0), HasMultipleAccessingFunctions(false),
124 HasNonInstructionUser(false), isNotSuitableForSRA(false) {}
129 /// ConstantIsDead - Return true if the specified constant is (transitively)
130 /// dead. The constant may be used by other constants (e.g. constant arrays and
131 /// constant exprs) as long as they are dead, but it cannot be used by anything
133 static bool ConstantIsDead(Constant *C) {
134 if (isa<GlobalValue>(C)) return false;
136 for (Value::use_iterator UI = C->use_begin(), E = C->use_end(); UI != E; ++UI)
137 if (Constant *CU = dyn_cast<Constant>(*UI)) {
138 if (!ConstantIsDead(CU)) return false;
145 /// AnalyzeGlobal - Look at all uses of the global and fill in the GlobalStatus
146 /// structure. If the global has its address taken, return true to indicate we
147 /// can't do anything with it.
149 static bool AnalyzeGlobal(Value *V, GlobalStatus &GS,
150 std::set<PHINode*> &PHIUsers) {
151 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ++UI)
152 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(*UI)) {
153 GS.HasNonInstructionUser = true;
155 if (AnalyzeGlobal(CE, GS, PHIUsers)) return true;
156 if (CE->getOpcode() != Instruction::GetElementPtr)
157 GS.isNotSuitableForSRA = true;
158 else if (!GS.isNotSuitableForSRA) {
159 // Check to see if this ConstantExpr GEP is SRA'able. In particular, we
160 // don't like < 3 operand CE's, and we don't like non-constant integer
162 if (CE->getNumOperands() < 3 || !CE->getOperand(1)->isNullValue())
163 GS.isNotSuitableForSRA = true;
165 for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i)
166 if (!isa<ConstantInt>(CE->getOperand(i))) {
167 GS.isNotSuitableForSRA = true;
173 } else if (Instruction *I = dyn_cast<Instruction>(*UI)) {
174 if (!GS.HasMultipleAccessingFunctions) {
175 Function *F = I->getParent()->getParent();
176 if (GS.AccessingFunction == 0)
177 GS.AccessingFunction = F;
178 else if (GS.AccessingFunction != F)
179 GS.HasMultipleAccessingFunctions = true;
181 if (isa<LoadInst>(I)) {
183 } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
184 // Don't allow a store OF the address, only stores TO the address.
185 if (SI->getOperand(0) == V) return true;
187 // If this is a direct store to the global (i.e., the global is a scalar
188 // value, not an aggregate), keep more specific information about
190 if (GS.StoredType != GlobalStatus::isStored)
191 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(SI->getOperand(1))){
192 Value *StoredVal = SI->getOperand(0);
193 if (StoredVal == GV->getInitializer()) {
194 if (GS.StoredType < GlobalStatus::isInitializerStored)
195 GS.StoredType = GlobalStatus::isInitializerStored;
196 } else if (isa<LoadInst>(StoredVal) &&
197 cast<LoadInst>(StoredVal)->getOperand(0) == GV) {
199 if (GS.StoredType < GlobalStatus::isInitializerStored)
200 GS.StoredType = GlobalStatus::isInitializerStored;
201 } else if (GS.StoredType < GlobalStatus::isStoredOnce) {
202 GS.StoredType = GlobalStatus::isStoredOnce;
203 GS.StoredOnceValue = StoredVal;
204 } else if (GS.StoredType == GlobalStatus::isStoredOnce &&
205 GS.StoredOnceValue == StoredVal) {
208 GS.StoredType = GlobalStatus::isStored;
211 GS.StoredType = GlobalStatus::isStored;
213 } else if (isa<GetElementPtrInst>(I)) {
214 if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
216 // If the first two indices are constants, this can be SRA'd.
217 if (isa<GlobalVariable>(I->getOperand(0))) {
218 if (I->getNumOperands() < 3 || !isa<Constant>(I->getOperand(1)) ||
219 !cast<Constant>(I->getOperand(1))->isNullValue() ||
220 !isa<ConstantInt>(I->getOperand(2)))
221 GS.isNotSuitableForSRA = true;
222 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(I->getOperand(0))){
223 if (CE->getOpcode() != Instruction::GetElementPtr ||
224 CE->getNumOperands() < 3 || I->getNumOperands() < 2 ||
225 !isa<Constant>(I->getOperand(0)) ||
226 !cast<Constant>(I->getOperand(0))->isNullValue())
227 GS.isNotSuitableForSRA = true;
229 GS.isNotSuitableForSRA = true;
231 } else if (isa<SelectInst>(I)) {
232 if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
233 GS.isNotSuitableForSRA = true;
234 } else if (PHINode *PN = dyn_cast<PHINode>(I)) {
235 // PHI nodes we can check just like select or GEP instructions, but we
236 // have to be careful about infinite recursion.
237 if (PHIUsers.insert(PN).second) // Not already visited.
238 if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
239 GS.isNotSuitableForSRA = true;
240 } else if (isa<SetCondInst>(I)) {
241 GS.isNotSuitableForSRA = true;
242 } else if (isa<MemCpyInst>(I) || isa<MemMoveInst>(I)) {
243 if (I->getOperand(1) == V)
244 GS.StoredType = GlobalStatus::isStored;
245 if (I->getOperand(2) == V)
247 GS.isNotSuitableForSRA = true;
248 } else if (isa<MemSetInst>(I)) {
249 assert(I->getOperand(1) == V && "Memset only takes one pointer!");
250 GS.StoredType = GlobalStatus::isStored;
251 GS.isNotSuitableForSRA = true;
253 return true; // Any other non-load instruction might take address!
255 } else if (Constant *C = dyn_cast<Constant>(*UI)) {
256 GS.HasNonInstructionUser = true;
257 // We might have a dead and dangling constant hanging off of here.
258 if (!ConstantIsDead(C))
261 GS.HasNonInstructionUser = true;
262 // Otherwise must be some other user.
269 static Constant *getAggregateConstantElement(Constant *Agg, Constant *Idx) {
270 ConstantInt *CI = dyn_cast<ConstantInt>(Idx);
272 unsigned IdxV = (unsigned)CI->getRawValue();
274 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(Agg)) {
275 if (IdxV < CS->getNumOperands()) return CS->getOperand(IdxV);
276 } else if (ConstantArray *CA = dyn_cast<ConstantArray>(Agg)) {
277 if (IdxV < CA->getNumOperands()) return CA->getOperand(IdxV);
278 } else if (ConstantPacked *CP = dyn_cast<ConstantPacked>(Agg)) {
279 if (IdxV < CP->getNumOperands()) return CP->getOperand(IdxV);
280 } else if (isa<ConstantAggregateZero>(Agg)) {
281 if (const StructType *STy = dyn_cast<StructType>(Agg->getType())) {
282 if (IdxV < STy->getNumElements())
283 return Constant::getNullValue(STy->getElementType(IdxV));
284 } else if (const SequentialType *STy =
285 dyn_cast<SequentialType>(Agg->getType())) {
286 return Constant::getNullValue(STy->getElementType());
288 } else if (isa<UndefValue>(Agg)) {
289 if (const StructType *STy = dyn_cast<StructType>(Agg->getType())) {
290 if (IdxV < STy->getNumElements())
291 return UndefValue::get(STy->getElementType(IdxV));
292 } else if (const SequentialType *STy =
293 dyn_cast<SequentialType>(Agg->getType())) {
294 return UndefValue::get(STy->getElementType());
300 static Constant *TraverseGEPInitializer(User *GEP, Constant *Init) {
301 if (Init == 0) return 0;
302 if (GEP->getNumOperands() == 1 ||
303 !isa<Constant>(GEP->getOperand(1)) ||
304 !cast<Constant>(GEP->getOperand(1))->isNullValue())
307 for (unsigned i = 2, e = GEP->getNumOperands(); i != e; ++i) {
308 ConstantInt *Idx = dyn_cast<ConstantInt>(GEP->getOperand(i));
310 Init = getAggregateConstantElement(Init, Idx);
311 if (Init == 0) return 0;
316 /// CleanupConstantGlobalUsers - We just marked GV constant. Loop over all
317 /// users of the global, cleaning up the obvious ones. This is largely just a
318 /// quick scan over the use list to clean up the easy and obvious cruft. This
319 /// returns true if it made a change.
320 static bool CleanupConstantGlobalUsers(Value *V, Constant *Init) {
321 bool Changed = false;
322 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;) {
325 if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
327 // Replace the load with the initializer.
328 LI->replaceAllUsesWith(Init);
329 LI->eraseFromParent();
332 } else if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
333 // Store must be unreachable or storing Init into the global.
334 SI->eraseFromParent();
336 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U)) {
337 if (CE->getOpcode() == Instruction::GetElementPtr) {
338 Constant *SubInit = TraverseGEPInitializer(CE, Init);
339 Changed |= CleanupConstantGlobalUsers(CE, SubInit);
340 } else if (CE->getOpcode() == Instruction::Cast &&
341 isa<PointerType>(CE->getType())) {
342 // Pointer cast, delete any stores and memsets to the global.
343 Changed |= CleanupConstantGlobalUsers(CE, 0);
346 if (CE->use_empty()) {
347 CE->destroyConstant();
350 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) {
351 Constant *SubInit = TraverseGEPInitializer(GEP, Init);
352 Changed |= CleanupConstantGlobalUsers(GEP, SubInit);
354 if (GEP->use_empty()) {
355 GEP->eraseFromParent();
358 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(U)) { // memset/cpy/mv
359 if (MI->getRawDest() == V) {
360 MI->eraseFromParent();
364 } else if (Constant *C = dyn_cast<Constant>(U)) {
365 // If we have a chain of dead constantexprs or other things dangling from
366 // us, and if they are all dead, nuke them without remorse.
367 if (ConstantIsDead(C)) {
368 C->destroyConstant();
369 // This could have invalidated UI, start over from scratch.
370 CleanupConstantGlobalUsers(V, Init);
378 /// SRAGlobal - Perform scalar replacement of aggregates on the specified global
379 /// variable. This opens the door for other optimizations by exposing the
380 /// behavior of the program in a more fine-grained way. We have determined that
381 /// this transformation is safe already. We return the first global variable we
382 /// insert so that the caller can reprocess it.
383 static GlobalVariable *SRAGlobal(GlobalVariable *GV) {
384 assert(GV->hasInternalLinkage() && !GV->isConstant());
385 Constant *Init = GV->getInitializer();
386 const Type *Ty = Init->getType();
388 std::vector<GlobalVariable*> NewGlobals;
389 Module::GlobalListType &Globals = GV->getParent()->getGlobalList();
391 if (const StructType *STy = dyn_cast<StructType>(Ty)) {
392 NewGlobals.reserve(STy->getNumElements());
393 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
394 Constant *In = getAggregateConstantElement(Init,
395 ConstantUInt::get(Type::UIntTy, i));
396 assert(In && "Couldn't get element of initializer?");
397 GlobalVariable *NGV = new GlobalVariable(STy->getElementType(i), false,
398 GlobalVariable::InternalLinkage,
399 In, GV->getName()+"."+utostr(i));
400 Globals.insert(GV, NGV);
401 NewGlobals.push_back(NGV);
403 } else if (const SequentialType *STy = dyn_cast<SequentialType>(Ty)) {
404 unsigned NumElements = 0;
405 if (const ArrayType *ATy = dyn_cast<ArrayType>(STy))
406 NumElements = ATy->getNumElements();
407 else if (const PackedType *PTy = dyn_cast<PackedType>(STy))
408 NumElements = PTy->getNumElements();
410 assert(0 && "Unknown aggregate sequential type!");
412 if (NumElements > 16 && GV->hasNUsesOrMore(16))
413 return 0; // It's not worth it.
414 NewGlobals.reserve(NumElements);
415 for (unsigned i = 0, e = NumElements; i != e; ++i) {
416 Constant *In = getAggregateConstantElement(Init,
417 ConstantUInt::get(Type::UIntTy, i));
418 assert(In && "Couldn't get element of initializer?");
420 GlobalVariable *NGV = new GlobalVariable(STy->getElementType(), false,
421 GlobalVariable::InternalLinkage,
422 In, GV->getName()+"."+utostr(i));
423 Globals.insert(GV, NGV);
424 NewGlobals.push_back(NGV);
428 if (NewGlobals.empty())
431 DEBUG(std::cerr << "PERFORMING GLOBAL SRA ON: " << *GV);
433 Constant *NullInt = Constant::getNullValue(Type::IntTy);
435 // Loop over all of the uses of the global, replacing the constantexpr geps,
436 // with smaller constantexpr geps or direct references.
437 while (!GV->use_empty()) {
438 User *GEP = GV->use_back();
439 assert(((isa<ConstantExpr>(GEP) &&
440 cast<ConstantExpr>(GEP)->getOpcode()==Instruction::GetElementPtr)||
441 isa<GetElementPtrInst>(GEP)) && "NonGEP CE's are not SRAable!");
443 // Ignore the 1th operand, which has to be zero or else the program is quite
444 // broken (undefined). Get the 2nd operand, which is the structure or array
447 (unsigned)cast<ConstantInt>(GEP->getOperand(2))->getRawValue();
448 if (Val >= NewGlobals.size()) Val = 0; // Out of bound array access.
450 Value *NewPtr = NewGlobals[Val];
452 // Form a shorter GEP if needed.
453 if (GEP->getNumOperands() > 3)
454 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GEP)) {
455 std::vector<Constant*> Idxs;
456 Idxs.push_back(NullInt);
457 for (unsigned i = 3, e = CE->getNumOperands(); i != e; ++i)
458 Idxs.push_back(CE->getOperand(i));
459 NewPtr = ConstantExpr::getGetElementPtr(cast<Constant>(NewPtr), Idxs);
461 GetElementPtrInst *GEPI = cast<GetElementPtrInst>(GEP);
462 std::vector<Value*> Idxs;
463 Idxs.push_back(NullInt);
464 for (unsigned i = 3, e = GEPI->getNumOperands(); i != e; ++i)
465 Idxs.push_back(GEPI->getOperand(i));
466 NewPtr = new GetElementPtrInst(NewPtr, Idxs,
467 GEPI->getName()+"."+utostr(Val), GEPI);
469 GEP->replaceAllUsesWith(NewPtr);
471 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(GEP))
472 GEPI->eraseFromParent();
474 cast<ConstantExpr>(GEP)->destroyConstant();
477 // Delete the old global, now that it is dead.
481 // Loop over the new globals array deleting any globals that are obviously
482 // dead. This can arise due to scalarization of a structure or an array that
483 // has elements that are dead.
484 unsigned FirstGlobal = 0;
485 for (unsigned i = 0, e = NewGlobals.size(); i != e; ++i)
486 if (NewGlobals[i]->use_empty()) {
487 Globals.erase(NewGlobals[i]);
488 if (FirstGlobal == i) ++FirstGlobal;
491 return FirstGlobal != NewGlobals.size() ? NewGlobals[FirstGlobal] : 0;
494 /// AllUsesOfValueWillTrapIfNull - Return true if all users of the specified
495 /// value will trap if the value is dynamically null.
496 static bool AllUsesOfValueWillTrapIfNull(Value *V) {
497 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ++UI)
498 if (isa<LoadInst>(*UI)) {
500 } else if (StoreInst *SI = dyn_cast<StoreInst>(*UI)) {
501 if (SI->getOperand(0) == V) {
502 //std::cerr << "NONTRAPPING USE: " << **UI;
503 return false; // Storing the value.
505 } else if (CallInst *CI = dyn_cast<CallInst>(*UI)) {
506 if (CI->getOperand(0) != V) {
507 //std::cerr << "NONTRAPPING USE: " << **UI;
508 return false; // Not calling the ptr
510 } else if (InvokeInst *II = dyn_cast<InvokeInst>(*UI)) {
511 if (II->getOperand(0) != V) {
512 //std::cerr << "NONTRAPPING USE: " << **UI;
513 return false; // Not calling the ptr
515 } else if (CastInst *CI = dyn_cast<CastInst>(*UI)) {
516 if (!AllUsesOfValueWillTrapIfNull(CI)) return false;
517 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(*UI)) {
518 if (!AllUsesOfValueWillTrapIfNull(GEPI)) return false;
519 } else if (isa<SetCondInst>(*UI) &&
520 isa<ConstantPointerNull>(UI->getOperand(1))) {
521 // Ignore setcc X, null
523 //std::cerr << "NONTRAPPING USE: " << **UI;
529 /// AllUsesOfLoadedValueWillTrapIfNull - Return true if all uses of any loads
530 /// from GV will trap if the loaded value is null. Note that this also permits
531 /// comparisons of the loaded value against null, as a special case.
532 static bool AllUsesOfLoadedValueWillTrapIfNull(GlobalVariable *GV) {
533 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); UI!=E; ++UI)
534 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
535 if (!AllUsesOfValueWillTrapIfNull(LI))
537 } else if (isa<StoreInst>(*UI)) {
538 // Ignore stores to the global.
540 // We don't know or understand this user, bail out.
541 //std::cerr << "UNKNOWN USER OF GLOBAL!: " << **UI;
548 static bool OptimizeAwayTrappingUsesOfValue(Value *V, Constant *NewV) {
549 bool Changed = false;
550 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ) {
551 Instruction *I = cast<Instruction>(*UI++);
552 if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
553 LI->setOperand(0, NewV);
555 } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
556 if (SI->getOperand(1) == V) {
557 SI->setOperand(1, NewV);
560 } else if (isa<CallInst>(I) || isa<InvokeInst>(I)) {
561 if (I->getOperand(0) == V) {
562 // Calling through the pointer! Turn into a direct call, but be careful
563 // that the pointer is not also being passed as an argument.
564 I->setOperand(0, NewV);
566 bool PassedAsArg = false;
567 for (unsigned i = 1, e = I->getNumOperands(); i != e; ++i)
568 if (I->getOperand(i) == V) {
570 I->setOperand(i, NewV);
574 // Being passed as an argument also. Be careful to not invalidate UI!
578 } else if (CastInst *CI = dyn_cast<CastInst>(I)) {
579 Changed |= OptimizeAwayTrappingUsesOfValue(CI,
580 ConstantExpr::getCast(NewV, CI->getType()));
581 if (CI->use_empty()) {
583 CI->eraseFromParent();
585 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I)) {
586 // Should handle GEP here.
587 std::vector<Constant*> Indices;
588 Indices.reserve(GEPI->getNumOperands()-1);
589 for (unsigned i = 1, e = GEPI->getNumOperands(); i != e; ++i)
590 if (Constant *C = dyn_cast<Constant>(GEPI->getOperand(i)))
591 Indices.push_back(C);
594 if (Indices.size() == GEPI->getNumOperands()-1)
595 Changed |= OptimizeAwayTrappingUsesOfValue(GEPI,
596 ConstantExpr::getGetElementPtr(NewV, Indices));
597 if (GEPI->use_empty()) {
599 GEPI->eraseFromParent();
608 /// OptimizeAwayTrappingUsesOfLoads - The specified global has only one non-null
609 /// value stored into it. If there are uses of the loaded value that would trap
610 /// if the loaded value is dynamically null, then we know that they cannot be
611 /// reachable with a null optimize away the load.
612 static bool OptimizeAwayTrappingUsesOfLoads(GlobalVariable *GV, Constant *LV) {
613 std::vector<LoadInst*> Loads;
614 bool Changed = false;
616 // Replace all uses of loads with uses of uses of the stored value.
617 for (Value::use_iterator GUI = GV->use_begin(), E = GV->use_end();
619 if (LoadInst *LI = dyn_cast<LoadInst>(*GUI)) {
621 Changed |= OptimizeAwayTrappingUsesOfValue(LI, LV);
623 assert(isa<StoreInst>(*GUI) && "Only expect load and stores!");
627 DEBUG(std::cerr << "OPTIMIZED LOADS FROM STORED ONCE POINTER: " << *GV);
631 // Delete all of the loads we can, keeping track of whether we nuked them all!
632 bool AllLoadsGone = true;
633 while (!Loads.empty()) {
634 LoadInst *L = Loads.back();
635 if (L->use_empty()) {
636 L->eraseFromParent();
639 AllLoadsGone = false;
644 // If we nuked all of the loads, then none of the stores are needed either,
645 // nor is the global.
647 DEBUG(std::cerr << " *** GLOBAL NOW DEAD!\n");
648 CleanupConstantGlobalUsers(GV, 0);
649 if (GV->use_empty()) {
650 GV->eraseFromParent();
658 /// ConstantPropUsersOf - Walk the use list of V, constant folding all of the
659 /// instructions that are foldable.
660 static void ConstantPropUsersOf(Value *V) {
661 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; )
662 if (Instruction *I = dyn_cast<Instruction>(*UI++))
663 if (Constant *NewC = ConstantFoldInstruction(I)) {
664 I->replaceAllUsesWith(NewC);
666 // Advance UI to the next non-I use to avoid invalidating it!
667 // Instructions could multiply use V.
668 while (UI != E && *UI == I)
670 I->eraseFromParent();
674 /// OptimizeGlobalAddressOfMalloc - This function takes the specified global
675 /// variable, and transforms the program as if it always contained the result of
676 /// the specified malloc. Because it is always the result of the specified
677 /// malloc, there is no reason to actually DO the malloc. Instead, turn the
678 /// malloc into a global, and any laods of GV as uses of the new global.
679 static GlobalVariable *OptimizeGlobalAddressOfMalloc(GlobalVariable *GV,
681 DEBUG(std::cerr << "PROMOTING MALLOC GLOBAL: " << *GV << " MALLOC = " <<*MI);
682 ConstantInt *NElements = cast<ConstantInt>(MI->getArraySize());
684 if (NElements->getRawValue() != 1) {
685 // If we have an array allocation, transform it to a single element
686 // allocation to make the code below simpler.
687 Type *NewTy = ArrayType::get(MI->getAllocatedType(),
688 (unsigned)NElements->getRawValue());
690 new MallocInst(NewTy, Constant::getNullValue(Type::UIntTy),
692 std::vector<Value*> Indices;
693 Indices.push_back(Constant::getNullValue(Type::IntTy));
694 Indices.push_back(Indices[0]);
695 Value *NewGEP = new GetElementPtrInst(NewMI, Indices,
696 NewMI->getName()+".el0", MI);
697 MI->replaceAllUsesWith(NewGEP);
698 MI->eraseFromParent();
702 // Create the new global variable. The contents of the malloc'd memory is
703 // undefined, so initialize with an undef value.
704 Constant *Init = UndefValue::get(MI->getAllocatedType());
705 GlobalVariable *NewGV = new GlobalVariable(MI->getAllocatedType(), false,
706 GlobalValue::InternalLinkage, Init,
707 GV->getName()+".body");
708 GV->getParent()->getGlobalList().insert(GV, NewGV);
710 // Anything that used the malloc now uses the global directly.
711 MI->replaceAllUsesWith(NewGV);
713 Constant *RepValue = NewGV;
714 if (NewGV->getType() != GV->getType()->getElementType())
715 RepValue = ConstantExpr::getCast(RepValue, GV->getType()->getElementType());
717 // If there is a comparison against null, we will insert a global bool to
718 // keep track of whether the global was initialized yet or not.
719 GlobalVariable *InitBool =
720 new GlobalVariable(Type::BoolTy, false, GlobalValue::InternalLinkage,
721 ConstantBool::False, GV->getName()+".init");
722 bool InitBoolUsed = false;
724 // Loop over all uses of GV, processing them in turn.
725 std::vector<StoreInst*> Stores;
726 while (!GV->use_empty())
727 if (LoadInst *LI = dyn_cast<LoadInst>(GV->use_back())) {
728 while (!LI->use_empty()) {
729 Use &LoadUse = LI->use_begin().getUse();
730 if (!isa<SetCondInst>(LoadUse.getUser()))
733 // Replace the setcc X, 0 with a use of the bool value.
734 SetCondInst *SCI = cast<SetCondInst>(LoadUse.getUser());
735 Value *LV = new LoadInst(InitBool, InitBool->getName()+".val", SCI);
737 switch (SCI->getOpcode()) {
738 default: assert(0 && "Unknown opcode!");
739 case Instruction::SetLT:
740 LV = ConstantBool::False; // X < null -> always false
742 case Instruction::SetEQ:
743 case Instruction::SetLE:
744 LV = BinaryOperator::createNot(LV, "notinit", SCI);
746 case Instruction::SetNE:
747 case Instruction::SetGE:
748 case Instruction::SetGT:
751 SCI->replaceAllUsesWith(LV);
752 SCI->eraseFromParent();
755 LI->eraseFromParent();
757 StoreInst *SI = cast<StoreInst>(GV->use_back());
758 // The global is initialized when the store to it occurs.
759 new StoreInst(ConstantBool::True, InitBool, SI);
760 SI->eraseFromParent();
763 // If the initialization boolean was used, insert it, otherwise delete it.
765 while (!InitBool->use_empty()) // Delete initializations
766 cast<Instruction>(InitBool->use_back())->eraseFromParent();
769 GV->getParent()->getGlobalList().insert(GV, InitBool);
772 // Now the GV is dead, nuke it and the malloc.
773 GV->eraseFromParent();
774 MI->eraseFromParent();
776 // To further other optimizations, loop over all users of NewGV and try to
777 // constant prop them. This will promote GEP instructions with constant
778 // indices into GEP constant-exprs, which will allow global-opt to hack on it.
779 ConstantPropUsersOf(NewGV);
780 if (RepValue != NewGV)
781 ConstantPropUsersOf(RepValue);
786 /// ValueIsOnlyUsedLocallyOrStoredToOneGlobal - Scan the use-list of V checking
787 /// to make sure that there are no complex uses of V. We permit simple things
788 /// like dereferencing the pointer, but not storing through the address, unless
789 /// it is to the specified global.
790 static bool ValueIsOnlyUsedLocallyOrStoredToOneGlobal(Instruction *V,
791 GlobalVariable *GV) {
792 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;++UI)
793 if (isa<LoadInst>(*UI) || isa<SetCondInst>(*UI)) {
795 } else if (StoreInst *SI = dyn_cast<StoreInst>(*UI)) {
796 if (SI->getOperand(0) == V && SI->getOperand(1) != GV)
797 return false; // Storing the pointer itself... bad.
798 // Otherwise, storing through it, or storing into GV... fine.
799 } else if (isa<GetElementPtrInst>(*UI) || isa<SelectInst>(*UI)) {
800 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(cast<Instruction>(*UI),GV))
809 // OptimizeOnceStoredGlobal - Try to optimize globals based on the knowledge
810 // that only one value (besides its initializer) is ever stored to the global.
811 static bool OptimizeOnceStoredGlobal(GlobalVariable *GV, Value *StoredOnceVal,
812 Module::global_iterator &GVI, TargetData &TD) {
813 if (CastInst *CI = dyn_cast<CastInst>(StoredOnceVal))
814 StoredOnceVal = CI->getOperand(0);
815 else if (GetElementPtrInst *GEPI =dyn_cast<GetElementPtrInst>(StoredOnceVal)){
816 // "getelementptr Ptr, 0, 0, 0" is really just a cast.
817 bool IsJustACast = true;
818 for (unsigned i = 1, e = GEPI->getNumOperands(); i != e; ++i)
819 if (!isa<Constant>(GEPI->getOperand(i)) ||
820 !cast<Constant>(GEPI->getOperand(i))->isNullValue()) {
825 StoredOnceVal = GEPI->getOperand(0);
828 // If we are dealing with a pointer global that is initialized to null and
829 // only has one (non-null) value stored into it, then we can optimize any
830 // users of the loaded value (often calls and loads) that would trap if the
832 if (isa<PointerType>(GV->getInitializer()->getType()) &&
833 GV->getInitializer()->isNullValue()) {
834 if (Constant *SOVC = dyn_cast<Constant>(StoredOnceVal)) {
835 if (GV->getInitializer()->getType() != SOVC->getType())
836 SOVC = ConstantExpr::getCast(SOVC, GV->getInitializer()->getType());
838 // Optimize away any trapping uses of the loaded value.
839 if (OptimizeAwayTrappingUsesOfLoads(GV, SOVC))
841 } else if (MallocInst *MI = dyn_cast<MallocInst>(StoredOnceVal)) {
842 // If we have a global that is only initialized with a fixed size malloc,
843 // and if all users of the malloc trap, and if the malloc'd address is not
844 // put anywhere else, transform the program to use global memory instead
845 // of malloc'd memory. This eliminates dynamic allocation (good) and
846 // exposes the resultant global to further GlobalOpt (even better). Note
847 // that we restrict this transformation to only working on small
848 // allocations (2048 bytes currently), as we don't want to introduce a 16M
849 // global or something.
850 if (ConstantInt *NElements = dyn_cast<ConstantInt>(MI->getArraySize()))
851 if (MI->getAllocatedType()->isSized() &&
852 NElements->getRawValue()*
853 TD.getTypeSize(MI->getAllocatedType()) < 2048 &&
854 AllUsesOfLoadedValueWillTrapIfNull(GV) &&
855 ValueIsOnlyUsedLocallyOrStoredToOneGlobal(MI, GV)) {
856 GVI = OptimizeGlobalAddressOfMalloc(GV, MI);
865 /// ShrinkGlobalToBoolean - At this point, we have learned that the only two
866 /// values ever stored into GV are its initializer and OtherVal.
867 static void ShrinkGlobalToBoolean(GlobalVariable *GV, Constant *OtherVal) {
868 // Create the new global, initializing it to false.
869 GlobalVariable *NewGV = new GlobalVariable(Type::BoolTy, false,
870 GlobalValue::InternalLinkage, ConstantBool::False, GV->getName()+".b");
871 GV->getParent()->getGlobalList().insert(GV, NewGV);
873 Constant *InitVal = GV->getInitializer();
874 assert(InitVal->getType() != Type::BoolTy && "No reason to shrink to bool!");
876 // If initialized to zero and storing one into the global, we can use a cast
877 // instead of a select to synthesize the desired value.
878 bool IsOneZero = false;
879 if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal))
880 IsOneZero = InitVal->isNullValue() && CI->equalsInt(1);
882 while (!GV->use_empty()) {
883 Instruction *UI = cast<Instruction>(GV->use_back());
884 if (StoreInst *SI = dyn_cast<StoreInst>(UI)) {
885 // Change the store into a boolean store.
886 bool StoringOther = SI->getOperand(0) == OtherVal;
887 // Only do this if we weren't storing a loaded value.
889 if (StoringOther || SI->getOperand(0) == InitVal)
890 StoreVal = ConstantBool::get(StoringOther);
892 // Otherwise, we are storing a previously loaded copy. To do this,
893 // change the copy from copying the original value to just copying the
895 Instruction *StoredVal = cast<Instruction>(SI->getOperand(0));
897 // If we're already replaced the input, StoredVal will be a cast or
898 // select instruction. If not, it will be a load of the original
900 if (LoadInst *LI = dyn_cast<LoadInst>(StoredVal)) {
901 assert(LI->getOperand(0) == GV && "Not a copy!");
902 // Insert a new load, to preserve the saved value.
903 StoreVal = new LoadInst(NewGV, LI->getName()+".b", LI);
905 assert((isa<CastInst>(StoredVal) || isa<SelectInst>(StoredVal)) &&
906 "This is not a form that we understand!");
907 StoreVal = StoredVal->getOperand(0);
908 assert(isa<LoadInst>(StoreVal) && "Not a load of NewGV!");
911 new StoreInst(StoreVal, NewGV, SI);
912 } else if (!UI->use_empty()) {
913 // Change the load into a load of bool then a select.
914 LoadInst *LI = cast<LoadInst>(UI);
916 std::string Name = LI->getName(); LI->setName("");
917 LoadInst *NLI = new LoadInst(NewGV, Name+".b", LI);
920 NSI = new CastInst(NLI, LI->getType(), Name, LI);
922 NSI = new SelectInst(NLI, OtherVal, InitVal, Name, LI);
923 LI->replaceAllUsesWith(NSI);
925 UI->eraseFromParent();
928 GV->eraseFromParent();
932 /// ProcessInternalGlobal - Analyze the specified global variable and optimize
933 /// it if possible. If we make a change, return true.
934 bool GlobalOpt::ProcessInternalGlobal(GlobalVariable *GV,
935 Module::global_iterator &GVI) {
936 std::set<PHINode*> PHIUsers;
939 GV->removeDeadConstantUsers();
941 if (GV->use_empty()) {
942 DEBUG(std::cerr << "GLOBAL DEAD: " << *GV);
943 GV->eraseFromParent();
948 if (!AnalyzeGlobal(GV, GS, PHIUsers)) {
949 // If this is a first class global and has only one accessing function
950 // and this function is main (which we know is not recursive we can make
951 // this global a local variable) we replace the global with a local alloca
954 // NOTE: It doesn't make sense to promote non first class types since we
955 // are just replacing static memory to stack memory.
956 if (!GS.HasMultipleAccessingFunctions &&
957 GS.AccessingFunction && !GS.HasNonInstructionUser &&
958 GV->getType()->getElementType()->isFirstClassType() &&
959 GS.AccessingFunction->getName() == "main" &&
960 GS.AccessingFunction->hasExternalLinkage()) {
961 DEBUG(std::cerr << "LOCALIZING GLOBAL: " << *GV);
962 Instruction* FirstI = GS.AccessingFunction->getEntryBlock().begin();
963 const Type* ElemTy = GV->getType()->getElementType();
964 AllocaInst* Alloca = new AllocaInst(ElemTy, NULL, GV->getName(), FirstI);
965 if (!isa<UndefValue>(GV->getInitializer()))
966 new StoreInst(GV->getInitializer(), Alloca, FirstI);
968 GV->replaceAllUsesWith(Alloca);
969 GV->eraseFromParent();
973 // If the global is never loaded (but may be stored to), it is dead.
976 DEBUG(std::cerr << "GLOBAL NEVER LOADED: " << *GV);
978 // Delete any stores we can find to the global. We may not be able to
979 // make it completely dead though.
980 bool Changed = CleanupConstantGlobalUsers(GV, GV->getInitializer());
982 // If the global is dead now, delete it.
983 if (GV->use_empty()) {
984 GV->eraseFromParent();
990 } else if (GS.StoredType <= GlobalStatus::isInitializerStored) {
991 DEBUG(std::cerr << "MARKING CONSTANT: " << *GV);
992 GV->setConstant(true);
994 // Clean up any obviously simplifiable users now.
995 CleanupConstantGlobalUsers(GV, GV->getInitializer());
997 // If the global is dead now, just nuke it.
998 if (GV->use_empty()) {
999 DEBUG(std::cerr << " *** Marking constant allowed us to simplify "
1000 "all users and delete global!\n");
1001 GV->eraseFromParent();
1007 } else if (!GS.isNotSuitableForSRA &&
1008 !GV->getInitializer()->getType()->isFirstClassType()) {
1009 if (GlobalVariable *FirstNewGV = SRAGlobal(GV)) {
1010 GVI = FirstNewGV; // Don't skip the newly produced globals!
1013 } else if (GS.StoredType == GlobalStatus::isStoredOnce) {
1014 // If the initial value for the global was an undef value, and if only
1015 // one other value was stored into it, we can just change the
1016 // initializer to be an undef value, then delete all stores to the
1017 // global. This allows us to mark it constant.
1018 if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue))
1019 if (isa<UndefValue>(GV->getInitializer())) {
1020 // Change the initial value here.
1021 GV->setInitializer(SOVConstant);
1023 // Clean up any obviously simplifiable users now.
1024 CleanupConstantGlobalUsers(GV, GV->getInitializer());
1026 if (GV->use_empty()) {
1027 DEBUG(std::cerr << " *** Substituting initializer allowed us to "
1028 "simplify all users and delete global!\n");
1029 GV->eraseFromParent();
1038 // Try to optimize globals based on the knowledge that only one value
1039 // (besides its initializer) is ever stored to the global.
1040 if (OptimizeOnceStoredGlobal(GV, GS.StoredOnceValue, GVI,
1041 getAnalysis<TargetData>()))
1044 // Otherwise, if the global was not a boolean, we can shrink it to be a
1046 if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue))
1047 if (GV->getType()->getElementType() != Type::BoolTy &&
1048 !GV->getType()->getElementType()->isFloatingPoint()) {
1049 DEBUG(std::cerr << " *** SHRINKING TO BOOL: " << *GV);
1050 ShrinkGlobalToBoolean(GV, SOVConstant);
1059 /// OnlyCalledDirectly - Return true if the specified function is only called
1060 /// directly. In other words, its address is never taken.
1061 static bool OnlyCalledDirectly(Function *F) {
1062 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){
1063 Instruction *User = dyn_cast<Instruction>(*UI);
1064 if (!User) return false;
1065 if (!isa<CallInst>(User) && !isa<InvokeInst>(User)) return false;
1067 // See if the function address is passed as an argument.
1068 for (unsigned i = 1, e = User->getNumOperands(); i != e; ++i)
1069 if (User->getOperand(i) == F) return false;
1074 /// ChangeCalleesToFastCall - Walk all of the direct calls of the specified
1075 /// function, changing them to FastCC.
1076 static void ChangeCalleesToFastCall(Function *F) {
1077 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){
1078 Instruction *User = cast<Instruction>(*UI);
1079 if (CallInst *CI = dyn_cast<CallInst>(User))
1080 CI->setCallingConv(CallingConv::Fast);
1082 cast<InvokeInst>(User)->setCallingConv(CallingConv::Fast);
1086 bool GlobalOpt::OptimizeFunctions(Module &M) {
1087 bool Changed = false;
1088 // Optimize functions.
1089 for (Module::iterator FI = M.begin(), E = M.end(); FI != E; ) {
1091 F->removeDeadConstantUsers();
1092 if (F->use_empty() && (F->hasInternalLinkage() ||
1093 F->hasLinkOnceLinkage())) {
1094 M.getFunctionList().erase(F);
1097 } else if (F->hasInternalLinkage() &&
1098 F->getCallingConv() == CallingConv::C && !F->isVarArg() &&
1099 OnlyCalledDirectly(F)) {
1100 // If this function has C calling conventions, is not a varargs
1101 // function, and is only called directly, promote it to use the Fast
1102 // calling convention.
1103 F->setCallingConv(CallingConv::Fast);
1104 ChangeCalleesToFastCall(F);
1112 bool GlobalOpt::OptimizeGlobalVars(Module &M) {
1113 bool Changed = false;
1114 for (Module::global_iterator GVI = M.global_begin(), E = M.global_end();
1116 GlobalVariable *GV = GVI++;
1117 if (!GV->isConstant() && GV->hasInternalLinkage() &&
1118 GV->hasInitializer())
1119 Changed |= ProcessInternalGlobal(GV, GVI);
1124 /// FindGlobalCtors - Find the llvm.globalctors list, verifying that all
1125 /// initializers have an init priority of 65535.
1126 GlobalVariable *GlobalOpt::FindGlobalCtors(Module &M) {
1127 for (Module::giterator I = M.global_begin(), E = M.global_end(); I != E; ++I)
1128 if (I->getName() == "llvm.global_ctors") {
1129 // Found it, verify it's an array of { int, void()* }.
1130 const ArrayType *ATy =dyn_cast<ArrayType>(I->getType()->getElementType());
1132 const StructType *STy = dyn_cast<StructType>(ATy->getElementType());
1133 if (!STy || STy->getNumElements() != 2 ||
1134 STy->getElementType(0) != Type::IntTy) return 0;
1135 const PointerType *PFTy = dyn_cast<PointerType>(STy->getElementType(1));
1136 if (!PFTy) return 0;
1137 const FunctionType *FTy = dyn_cast<FunctionType>(PFTy->getElementType());
1138 if (!FTy || FTy->getReturnType() != Type::VoidTy || FTy->isVarArg() ||
1139 FTy->getNumParams() != 0)
1142 // Verify that the initializer is simple enough for us to handle.
1143 if (!I->hasInitializer()) return 0;
1144 ConstantArray *CA = dyn_cast<ConstantArray>(I->getInitializer());
1146 for (unsigned i = 0, e = CA->getNumOperands(); i != e; ++i)
1147 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(CA->getOperand(i))) {
1148 if (isa<ConstantPointerNull>(CS->getOperand(1)))
1151 // Must have a function or null ptr.
1152 if (!isa<Function>(CS->getOperand(1)))
1155 // Init priority must be standard.
1156 ConstantInt *CI = dyn_cast<ConstantInt>(CS->getOperand(0));
1157 if (!CI || CI->getRawValue() != 65535)
1168 /// ParseGlobalCtors - Given a llvm.global_ctors list that we can understand,
1169 /// return a list of the functions and null terminator as a vector.
1170 static std::vector<Function*> ParseGlobalCtors(GlobalVariable *GV) {
1171 ConstantArray *CA = cast<ConstantArray>(GV->getInitializer());
1172 std::vector<Function*> Result;
1173 Result.reserve(CA->getNumOperands());
1174 for (unsigned i = 0, e = CA->getNumOperands(); i != e; ++i) {
1175 ConstantStruct *CS = cast<ConstantStruct>(CA->getOperand(i));
1176 Result.push_back(dyn_cast<Function>(CS->getOperand(1)));
1181 /// InstallGlobalCtors - Given a specified llvm.global_ctors list, install the
1182 /// specified array, returning the new global to use.
1183 static GlobalVariable *InstallGlobalCtors(GlobalVariable *GCL,
1184 const std::vector<Function*> &Ctors) {
1185 // If we made a change, reassemble the initializer list.
1186 std::vector<Constant*> CSVals;
1187 CSVals.push_back(ConstantSInt::get(Type::IntTy, 65535));
1188 CSVals.push_back(0);
1190 // Create the new init list.
1191 std::vector<Constant*> CAList;
1192 for (unsigned i = 0, e = Ctors.size(); i != e; ++i) {
1194 CSVals[1] = Ctors[i];
1196 const Type *FTy = FunctionType::get(Type::VoidTy,
1197 std::vector<const Type*>(), false);
1198 const PointerType *PFTy = PointerType::get(FTy);
1199 CSVals[1] = Constant::getNullValue(PFTy);
1200 CSVals[0] = ConstantSInt::get(Type::IntTy, 2147483647);
1202 CAList.push_back(ConstantStruct::get(CSVals));
1205 // Create the array initializer.
1206 const Type *StructTy =
1207 cast<ArrayType>(GCL->getType()->getElementType())->getElementType();
1208 Constant *CA = ConstantArray::get(ArrayType::get(StructTy, CAList.size()),
1211 // If we didn't change the number of elements, don't create a new GV.
1212 if (CA->getType() == GCL->getInitializer()->getType()) {
1213 GCL->setInitializer(CA);
1217 // Create the new global and insert it next to the existing list.
1218 GlobalVariable *NGV = new GlobalVariable(CA->getType(), GCL->isConstant(),
1219 GCL->getLinkage(), CA,
1222 GCL->getParent()->getGlobalList().insert(GCL, NGV);
1224 // Nuke the old list, replacing any uses with the new one.
1225 if (!GCL->use_empty()) {
1227 if (V->getType() != GCL->getType())
1228 V = ConstantExpr::getCast(V, GCL->getType());
1229 GCL->replaceAllUsesWith(V);
1231 GCL->eraseFromParent();
1240 static Constant *getVal(std::map<Value*, Constant*> &ComputedValues,
1242 if (Constant *CV = dyn_cast<Constant>(V)) return CV;
1243 Constant *R = ComputedValues[V];
1244 assert(R && "Reference to an uncomputed value!");
1248 /// isSimpleEnoughPointerToCommit - Return true if this constant is simple
1249 /// enough for us to understand. In particular, if it is a cast of something,
1250 /// we punt. We basically just support direct accesses to globals and GEP's of
1251 /// globals. This should be kept up to date with CommitValueTo.
1252 static bool isSimpleEnoughPointerToCommit(Constant *C) {
1253 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C))
1254 return !GV->isExternal(); // reject external globals.
1258 /// CommitValueTo - We have decided that Addr (which satisfies the predicate
1259 /// isSimpleEnoughPointerToCommit) should get Val as its value. Make it happen.
1260 static void CommitValueTo(Constant *Val, Constant *Addr) {
1261 GlobalVariable *GV = cast<GlobalVariable>(Addr);
1262 assert(GV->hasInitializer());
1263 GV->setInitializer(Val);
1266 /// EvaluateStaticConstructor - Evaluate static constructors in the function, if
1267 /// we can. Return true if we can, false otherwise.
1268 static bool EvaluateStaticConstructor(Function *F) {
1269 /// Values - As we compute SSA register values, we store their contents here.
1270 std::map<Value*, Constant*> Values;
1272 /// MutatedMemory - For each store we execute, we update this map. Loads
1273 /// check this to get the most up-to-date value. If evaluation is successful,
1274 /// this state is committed to the process.
1275 std::map<Constant*, Constant*> MutatedMemory;
1277 // CurInst - The current instruction we're evaluating.
1278 BasicBlock::iterator CurInst = F->begin()->begin();
1280 // This is the main evaluation loop.
1282 Constant *InstResult = 0;
1284 if (StoreInst *SI = dyn_cast<StoreInst>(CurInst)) {
1285 Constant *Ptr = getVal(Values, SI->getOperand(1));
1286 if (!isSimpleEnoughPointerToCommit(Ptr))
1287 // If this is too complex for us to commit, reject it.
1289 Constant *Val = getVal(Values, SI->getOperand(0));
1290 MutatedMemory[Ptr] = Val;
1291 } else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(CurInst)) {
1292 InstResult = ConstantExpr::get(BO->getOpcode(),
1293 getVal(Values, BO->getOperand(0)),
1294 getVal(Values, BO->getOperand(1)));
1295 } else if (ShiftInst *SI = dyn_cast<ShiftInst>(CurInst)) {
1296 InstResult = ConstantExpr::get(SI->getOpcode(),
1297 getVal(Values, SI->getOperand(0)),
1298 getVal(Values, SI->getOperand(1)));
1299 } else if (CastInst *CI = dyn_cast<CastInst>(CurInst)) {
1300 InstResult = ConstantExpr::getCast(getVal(Values, CI->getOperand(0)),
1302 } else if (SelectInst *SI = dyn_cast<SelectInst>(CurInst)) {
1303 InstResult = ConstantExpr::getSelect(getVal(Values, SI->getOperand(0)),
1304 getVal(Values, SI->getOperand(1)),
1305 getVal(Values, SI->getOperand(2)));
1306 } else if (ReturnInst *RI = dyn_cast<ReturnInst>(CurInst)) {
1307 assert(RI->getNumOperands() == 0);
1308 break; // We succeeded at evaluating this ctor!
1310 // TODO: use ConstantFoldCall for function calls.
1312 // Did not know how to evaluate this!
1316 if (!CurInst->use_empty())
1317 Values[CurInst] = InstResult;
1319 // Advance program counter.
1323 // If we get here, we know that we succeeded at evaluation: commit the result.
1325 for (std::map<Constant*, Constant*>::iterator I = MutatedMemory.begin(),
1326 E = MutatedMemory.end(); I != E; ++I)
1327 CommitValueTo(I->second, I->first);
1332 /// OptimizeGlobalCtorsList - Simplify and evaluation global ctors if possible.
1333 /// Return true if anything changed.
1334 bool GlobalOpt::OptimizeGlobalCtorsList(GlobalVariable *&GCL) {
1335 std::vector<Function*> Ctors = ParseGlobalCtors(GCL);
1336 bool MadeChange = false;
1337 if (Ctors.empty()) return false;
1339 // Loop over global ctors, optimizing them when we can.
1340 for (unsigned i = 0; i != Ctors.size(); ++i) {
1341 Function *F = Ctors[i];
1342 // Found a null terminator in the middle of the list, prune off the rest of
1345 if (i != Ctors.size()-1) {
1352 // We cannot simplify external ctor functions.
1353 if (F->empty()) continue;
1355 // If we can evaluate the ctor at compile time, do.
1356 if (EvaluateStaticConstructor(F)) {
1357 Ctors.erase(Ctors.begin()+i);
1360 ++NumCtorsEvaluated;
1364 // If the function is empty, just remove it from the ctor list.
1365 if (isa<ReturnInst>(F->begin()->getTerminator()) &&
1366 &F->begin()->front() == F->begin()->getTerminator()) {
1367 Ctors.erase(Ctors.begin()+i);
1375 if (!MadeChange) return false;
1377 GCL = InstallGlobalCtors(GCL, Ctors);
1382 bool GlobalOpt::runOnModule(Module &M) {
1383 bool Changed = false;
1385 // Try to find the llvm.globalctors list.
1386 GlobalVariable *GlobalCtors = FindGlobalCtors(M);
1388 bool LocalChange = true;
1389 while (LocalChange) {
1390 LocalChange = false;
1392 // Delete functions that are trivially dead, ccc -> fastcc
1393 LocalChange |= OptimizeFunctions(M);
1395 // Optimize global_ctors list.
1397 LocalChange |= OptimizeGlobalCtorsList(GlobalCtors);
1399 // Optimize non-address-taken globals.
1400 LocalChange |= OptimizeGlobalVars(M);
1401 Changed |= LocalChange;
1404 // TODO: Move all global ctors functions to the end of the module for code