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/Analysis/ConstantFolding.h"
26 #include "llvm/Target/TargetData.h"
27 #include "llvm/Support/Compiler.h"
28 #include "llvm/Support/Debug.h"
29 #include "llvm/ADT/SmallPtrSet.h"
30 #include "llvm/ADT/SmallVector.h"
31 #include "llvm/ADT/Statistic.h"
32 #include "llvm/ADT/StringExtras.h"
37 STATISTIC(NumMarked , "Number of globals marked constant");
38 STATISTIC(NumSRA , "Number of aggregate globals broken into scalars");
39 STATISTIC(NumHeapSRA , "Number of heap objects SRA'd");
40 STATISTIC(NumSubstitute,"Number of globals with initializers stored into them");
41 STATISTIC(NumDeleted , "Number of globals deleted");
42 STATISTIC(NumFnDeleted , "Number of functions deleted");
43 STATISTIC(NumGlobUses , "Number of global uses devirtualized");
44 STATISTIC(NumLocalized , "Number of globals localized");
45 STATISTIC(NumShrunkToBool , "Number of global vars shrunk to booleans");
46 STATISTIC(NumFastCallFns , "Number of functions converted to fastcc");
47 STATISTIC(NumCtorsEvaluated, "Number of static ctors evaluated");
50 struct VISIBILITY_HIDDEN GlobalOpt : public ModulePass {
51 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
52 AU.addRequired<TargetData>();
54 static char ID; // Pass identification, replacement for typeid
55 GlobalOpt() : ModulePass((intptr_t)&ID) {}
57 bool runOnModule(Module &M);
60 GlobalVariable *FindGlobalCtors(Module &M);
61 bool OptimizeFunctions(Module &M);
62 bool OptimizeGlobalVars(Module &M);
63 bool OptimizeGlobalCtorsList(GlobalVariable *&GCL);
64 bool ProcessInternalGlobal(GlobalVariable *GV,Module::global_iterator &GVI);
67 char GlobalOpt::ID = 0;
68 RegisterPass<GlobalOpt> X("globalopt", "Global Variable Optimizer");
71 ModulePass *llvm::createGlobalOptimizerPass() { return new GlobalOpt(); }
73 /// GlobalStatus - As we analyze each global, keep track of some information
74 /// about it. If we find out that the address of the global is taken, none of
75 /// this info will be accurate.
76 struct VISIBILITY_HIDDEN GlobalStatus {
77 /// isLoaded - True if the global is ever loaded. If the global isn't ever
78 /// loaded it can be deleted.
81 /// StoredType - Keep track of what stores to the global look like.
84 /// NotStored - There is no store to this global. It can thus be marked
88 /// isInitializerStored - This global is stored to, but the only thing
89 /// stored is the constant it was initialized with. This is only tracked
90 /// for scalar globals.
93 /// isStoredOnce - This global is stored to, but only its initializer and
94 /// one other value is ever stored to it. If this global isStoredOnce, we
95 /// track the value stored to it in StoredOnceValue below. This is only
96 /// tracked for scalar globals.
99 /// isStored - This global is stored to by multiple values or something else
100 /// that we cannot track.
104 /// StoredOnceValue - If only one value (besides the initializer constant) is
105 /// ever stored to this global, keep track of what value it is.
106 Value *StoredOnceValue;
108 /// AccessingFunction/HasMultipleAccessingFunctions - These start out
109 /// null/false. When the first accessing function is noticed, it is recorded.
110 /// When a second different accessing function is noticed,
111 /// HasMultipleAccessingFunctions is set to true.
112 Function *AccessingFunction;
113 bool HasMultipleAccessingFunctions;
115 /// HasNonInstructionUser - Set to true if this global has a user that is not
116 /// an instruction (e.g. a constant expr or GV initializer).
117 bool HasNonInstructionUser;
119 /// HasPHIUser - Set to true if this global has a user that is a PHI node.
122 /// isNotSuitableForSRA - Keep track of whether any SRA preventing users of
123 /// the global exist. Such users include GEP instruction with variable
124 /// indexes, and non-gep/load/store users like constant expr casts.
125 bool isNotSuitableForSRA;
127 GlobalStatus() : isLoaded(false), StoredType(NotStored), StoredOnceValue(0),
128 AccessingFunction(0), HasMultipleAccessingFunctions(false),
129 HasNonInstructionUser(false), HasPHIUser(false),
130 isNotSuitableForSRA(false) {}
135 /// ConstantIsDead - Return true if the specified constant is (transitively)
136 /// dead. The constant may be used by other constants (e.g. constant arrays and
137 /// constant exprs) as long as they are dead, but it cannot be used by anything
139 static bool ConstantIsDead(Constant *C) {
140 if (isa<GlobalValue>(C)) return false;
142 for (Value::use_iterator UI = C->use_begin(), E = C->use_end(); UI != E; ++UI)
143 if (Constant *CU = dyn_cast<Constant>(*UI)) {
144 if (!ConstantIsDead(CU)) return false;
151 /// AnalyzeGlobal - Look at all uses of the global and fill in the GlobalStatus
152 /// structure. If the global has its address taken, return true to indicate we
153 /// can't do anything with it.
155 static bool AnalyzeGlobal(Value *V, GlobalStatus &GS,
156 std::set<PHINode*> &PHIUsers) {
157 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ++UI)
158 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(*UI)) {
159 GS.HasNonInstructionUser = true;
161 if (AnalyzeGlobal(CE, GS, PHIUsers)) return true;
162 if (CE->getOpcode() != Instruction::GetElementPtr)
163 GS.isNotSuitableForSRA = true;
164 else if (!GS.isNotSuitableForSRA) {
165 // Check to see if this ConstantExpr GEP is SRA'able. In particular, we
166 // don't like < 3 operand CE's, and we don't like non-constant integer
168 if (CE->getNumOperands() < 3 || !CE->getOperand(1)->isNullValue())
169 GS.isNotSuitableForSRA = true;
171 for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i)
172 if (!isa<ConstantInt>(CE->getOperand(i))) {
173 GS.isNotSuitableForSRA = true;
179 } else if (Instruction *I = dyn_cast<Instruction>(*UI)) {
180 if (!GS.HasMultipleAccessingFunctions) {
181 Function *F = I->getParent()->getParent();
182 if (GS.AccessingFunction == 0)
183 GS.AccessingFunction = F;
184 else if (GS.AccessingFunction != F)
185 GS.HasMultipleAccessingFunctions = true;
187 if (isa<LoadInst>(I)) {
189 } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
190 // Don't allow a store OF the address, only stores TO the address.
191 if (SI->getOperand(0) == V) return true;
193 // If this is a direct store to the global (i.e., the global is a scalar
194 // value, not an aggregate), keep more specific information about
196 if (GS.StoredType != GlobalStatus::isStored)
197 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(SI->getOperand(1))){
198 Value *StoredVal = SI->getOperand(0);
199 if (StoredVal == GV->getInitializer()) {
200 if (GS.StoredType < GlobalStatus::isInitializerStored)
201 GS.StoredType = GlobalStatus::isInitializerStored;
202 } else if (isa<LoadInst>(StoredVal) &&
203 cast<LoadInst>(StoredVal)->getOperand(0) == GV) {
205 if (GS.StoredType < GlobalStatus::isInitializerStored)
206 GS.StoredType = GlobalStatus::isInitializerStored;
207 } else if (GS.StoredType < GlobalStatus::isStoredOnce) {
208 GS.StoredType = GlobalStatus::isStoredOnce;
209 GS.StoredOnceValue = StoredVal;
210 } else if (GS.StoredType == GlobalStatus::isStoredOnce &&
211 GS.StoredOnceValue == StoredVal) {
214 GS.StoredType = GlobalStatus::isStored;
217 GS.StoredType = GlobalStatus::isStored;
219 } else if (isa<GetElementPtrInst>(I)) {
220 if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
222 // If the first two indices are constants, this can be SRA'd.
223 if (isa<GlobalVariable>(I->getOperand(0))) {
224 if (I->getNumOperands() < 3 || !isa<Constant>(I->getOperand(1)) ||
225 !cast<Constant>(I->getOperand(1))->isNullValue() ||
226 !isa<ConstantInt>(I->getOperand(2)))
227 GS.isNotSuitableForSRA = true;
228 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(I->getOperand(0))){
229 if (CE->getOpcode() != Instruction::GetElementPtr ||
230 CE->getNumOperands() < 3 || I->getNumOperands() < 2 ||
231 !isa<Constant>(I->getOperand(0)) ||
232 !cast<Constant>(I->getOperand(0))->isNullValue())
233 GS.isNotSuitableForSRA = true;
235 GS.isNotSuitableForSRA = true;
237 } else if (isa<SelectInst>(I)) {
238 if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
239 GS.isNotSuitableForSRA = true;
240 } else if (PHINode *PN = dyn_cast<PHINode>(I)) {
241 // PHI nodes we can check just like select or GEP instructions, but we
242 // have to be careful about infinite recursion.
243 if (PHIUsers.insert(PN).second) // Not already visited.
244 if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
245 GS.isNotSuitableForSRA = true;
246 GS.HasPHIUser = true;
247 } else if (isa<CmpInst>(I)) {
248 GS.isNotSuitableForSRA = true;
249 } else if (isa<MemCpyInst>(I) || isa<MemMoveInst>(I)) {
250 if (I->getOperand(1) == V)
251 GS.StoredType = GlobalStatus::isStored;
252 if (I->getOperand(2) == V)
254 GS.isNotSuitableForSRA = true;
255 } else if (isa<MemSetInst>(I)) {
256 assert(I->getOperand(1) == V && "Memset only takes one pointer!");
257 GS.StoredType = GlobalStatus::isStored;
258 GS.isNotSuitableForSRA = true;
260 return true; // Any other non-load instruction might take address!
262 } else if (Constant *C = dyn_cast<Constant>(*UI)) {
263 GS.HasNonInstructionUser = true;
264 // We might have a dead and dangling constant hanging off of here.
265 if (!ConstantIsDead(C))
268 GS.HasNonInstructionUser = true;
269 // Otherwise must be some other user.
276 static Constant *getAggregateConstantElement(Constant *Agg, Constant *Idx) {
277 ConstantInt *CI = dyn_cast<ConstantInt>(Idx);
279 unsigned IdxV = CI->getZExtValue();
281 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(Agg)) {
282 if (IdxV < CS->getNumOperands()) return CS->getOperand(IdxV);
283 } else if (ConstantArray *CA = dyn_cast<ConstantArray>(Agg)) {
284 if (IdxV < CA->getNumOperands()) return CA->getOperand(IdxV);
285 } else if (ConstantVector *CP = dyn_cast<ConstantVector>(Agg)) {
286 if (IdxV < CP->getNumOperands()) return CP->getOperand(IdxV);
287 } else if (isa<ConstantAggregateZero>(Agg)) {
288 if (const StructType *STy = dyn_cast<StructType>(Agg->getType())) {
289 if (IdxV < STy->getNumElements())
290 return Constant::getNullValue(STy->getElementType(IdxV));
291 } else if (const SequentialType *STy =
292 dyn_cast<SequentialType>(Agg->getType())) {
293 return Constant::getNullValue(STy->getElementType());
295 } else if (isa<UndefValue>(Agg)) {
296 if (const StructType *STy = dyn_cast<StructType>(Agg->getType())) {
297 if (IdxV < STy->getNumElements())
298 return UndefValue::get(STy->getElementType(IdxV));
299 } else if (const SequentialType *STy =
300 dyn_cast<SequentialType>(Agg->getType())) {
301 return UndefValue::get(STy->getElementType());
308 /// CleanupConstantGlobalUsers - We just marked GV constant. Loop over all
309 /// users of the global, cleaning up the obvious ones. This is largely just a
310 /// quick scan over the use list to clean up the easy and obvious cruft. This
311 /// returns true if it made a change.
312 static bool CleanupConstantGlobalUsers(Value *V, Constant *Init) {
313 bool Changed = false;
314 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;) {
317 if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
319 // Replace the load with the initializer.
320 LI->replaceAllUsesWith(Init);
321 LI->eraseFromParent();
324 } else if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
325 // Store must be unreachable or storing Init into the global.
326 SI->eraseFromParent();
328 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U)) {
329 if (CE->getOpcode() == Instruction::GetElementPtr) {
330 Constant *SubInit = 0;
332 SubInit = ConstantFoldLoadThroughGEPConstantExpr(Init, CE);
333 Changed |= CleanupConstantGlobalUsers(CE, SubInit);
334 } else if (CE->getOpcode() == Instruction::BitCast &&
335 isa<PointerType>(CE->getType())) {
336 // Pointer cast, delete any stores and memsets to the global.
337 Changed |= CleanupConstantGlobalUsers(CE, 0);
340 if (CE->use_empty()) {
341 CE->destroyConstant();
344 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) {
345 // Do not transform "gepinst (gep constexpr (GV))" here, because forming
346 // "gepconstexpr (gep constexpr (GV))" will cause the two gep's to fold
347 // and will invalidate our notion of what Init is.
348 Constant *SubInit = 0;
349 if (!isa<ConstantExpr>(GEP->getOperand(0))) {
351 dyn_cast_or_null<ConstantExpr>(ConstantFoldInstruction(GEP));
352 if (Init && CE && CE->getOpcode() == Instruction::GetElementPtr)
353 SubInit = ConstantFoldLoadThroughGEPConstantExpr(Init, CE);
355 Changed |= CleanupConstantGlobalUsers(GEP, SubInit);
357 if (GEP->use_empty()) {
358 GEP->eraseFromParent();
361 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(U)) { // memset/cpy/mv
362 if (MI->getRawDest() == V) {
363 MI->eraseFromParent();
367 } else if (Constant *C = dyn_cast<Constant>(U)) {
368 // If we have a chain of dead constantexprs or other things dangling from
369 // us, and if they are all dead, nuke them without remorse.
370 if (ConstantIsDead(C)) {
371 C->destroyConstant();
372 // This could have invalidated UI, start over from scratch.
373 CleanupConstantGlobalUsers(V, Init);
381 /// SRAGlobal - Perform scalar replacement of aggregates on the specified global
382 /// variable. This opens the door for other optimizations by exposing the
383 /// behavior of the program in a more fine-grained way. We have determined that
384 /// this transformation is safe already. We return the first global variable we
385 /// insert so that the caller can reprocess it.
386 static GlobalVariable *SRAGlobal(GlobalVariable *GV) {
387 assert(GV->hasInternalLinkage() && !GV->isConstant());
388 Constant *Init = GV->getInitializer();
389 const Type *Ty = Init->getType();
391 std::vector<GlobalVariable*> NewGlobals;
392 Module::GlobalListType &Globals = GV->getParent()->getGlobalList();
394 if (const StructType *STy = dyn_cast<StructType>(Ty)) {
395 NewGlobals.reserve(STy->getNumElements());
396 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
397 Constant *In = getAggregateConstantElement(Init,
398 ConstantInt::get(Type::Int32Ty, i));
399 assert(In && "Couldn't get element of initializer?");
400 GlobalVariable *NGV = new GlobalVariable(STy->getElementType(i), false,
401 GlobalVariable::InternalLinkage,
402 In, GV->getName()+"."+utostr(i),
404 GV->isThreadLocal());
405 Globals.insert(GV, NGV);
406 NewGlobals.push_back(NGV);
408 } else if (const SequentialType *STy = dyn_cast<SequentialType>(Ty)) {
409 unsigned NumElements = 0;
410 if (const ArrayType *ATy = dyn_cast<ArrayType>(STy))
411 NumElements = ATy->getNumElements();
412 else if (const VectorType *PTy = dyn_cast<VectorType>(STy))
413 NumElements = PTy->getNumElements();
415 assert(0 && "Unknown aggregate sequential type!");
417 if (NumElements > 16 && GV->hasNUsesOrMore(16))
418 return 0; // It's not worth it.
419 NewGlobals.reserve(NumElements);
420 for (unsigned i = 0, e = NumElements; i != e; ++i) {
421 Constant *In = getAggregateConstantElement(Init,
422 ConstantInt::get(Type::Int32Ty, i));
423 assert(In && "Couldn't get element of initializer?");
425 GlobalVariable *NGV = new GlobalVariable(STy->getElementType(), false,
426 GlobalVariable::InternalLinkage,
427 In, GV->getName()+"."+utostr(i),
429 GV->isThreadLocal());
430 Globals.insert(GV, NGV);
431 NewGlobals.push_back(NGV);
435 if (NewGlobals.empty())
438 DOUT << "PERFORMING GLOBAL SRA ON: " << *GV;
440 Constant *NullInt = Constant::getNullValue(Type::Int32Ty);
442 // Loop over all of the uses of the global, replacing the constantexpr geps,
443 // with smaller constantexpr geps or direct references.
444 while (!GV->use_empty()) {
445 User *GEP = GV->use_back();
446 assert(((isa<ConstantExpr>(GEP) &&
447 cast<ConstantExpr>(GEP)->getOpcode()==Instruction::GetElementPtr)||
448 isa<GetElementPtrInst>(GEP)) && "NonGEP CE's are not SRAable!");
450 // Ignore the 1th operand, which has to be zero or else the program is quite
451 // broken (undefined). Get the 2nd operand, which is the structure or array
453 unsigned Val = cast<ConstantInt>(GEP->getOperand(2))->getZExtValue();
454 if (Val >= NewGlobals.size()) Val = 0; // Out of bound array access.
456 Value *NewPtr = NewGlobals[Val];
458 // Form a shorter GEP if needed.
459 if (GEP->getNumOperands() > 3)
460 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GEP)) {
461 SmallVector<Constant*, 8> Idxs;
462 Idxs.push_back(NullInt);
463 for (unsigned i = 3, e = CE->getNumOperands(); i != e; ++i)
464 Idxs.push_back(CE->getOperand(i));
465 NewPtr = ConstantExpr::getGetElementPtr(cast<Constant>(NewPtr),
466 &Idxs[0], Idxs.size());
468 GetElementPtrInst *GEPI = cast<GetElementPtrInst>(GEP);
469 SmallVector<Value*, 8> Idxs;
470 Idxs.push_back(NullInt);
471 for (unsigned i = 3, e = GEPI->getNumOperands(); i != e; ++i)
472 Idxs.push_back(GEPI->getOperand(i));
473 NewPtr = new GetElementPtrInst(NewPtr, Idxs.begin(), Idxs.end(),
474 GEPI->getName()+"."+utostr(Val), GEPI);
476 GEP->replaceAllUsesWith(NewPtr);
478 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(GEP))
479 GEPI->eraseFromParent();
481 cast<ConstantExpr>(GEP)->destroyConstant();
484 // Delete the old global, now that it is dead.
488 // Loop over the new globals array deleting any globals that are obviously
489 // dead. This can arise due to scalarization of a structure or an array that
490 // has elements that are dead.
491 unsigned FirstGlobal = 0;
492 for (unsigned i = 0, e = NewGlobals.size(); i != e; ++i)
493 if (NewGlobals[i]->use_empty()) {
494 Globals.erase(NewGlobals[i]);
495 if (FirstGlobal == i) ++FirstGlobal;
498 return FirstGlobal != NewGlobals.size() ? NewGlobals[FirstGlobal] : 0;
501 /// AllUsesOfValueWillTrapIfNull - Return true if all users of the specified
502 /// value will trap if the value is dynamically null. PHIs keeps track of any
503 /// phi nodes we've seen to avoid reprocessing them.
504 static bool AllUsesOfValueWillTrapIfNull(Value *V,
505 SmallPtrSet<PHINode*, 8> &PHIs) {
506 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ++UI)
507 if (isa<LoadInst>(*UI)) {
509 } else if (StoreInst *SI = dyn_cast<StoreInst>(*UI)) {
510 if (SI->getOperand(0) == V) {
511 //cerr << "NONTRAPPING USE: " << **UI;
512 return false; // Storing the value.
514 } else if (CallInst *CI = dyn_cast<CallInst>(*UI)) {
515 if (CI->getOperand(0) != V) {
516 //cerr << "NONTRAPPING USE: " << **UI;
517 return false; // Not calling the ptr
519 } else if (InvokeInst *II = dyn_cast<InvokeInst>(*UI)) {
520 if (II->getOperand(0) != V) {
521 //cerr << "NONTRAPPING USE: " << **UI;
522 return false; // Not calling the ptr
524 } else if (BitCastInst *CI = dyn_cast<BitCastInst>(*UI)) {
525 if (!AllUsesOfValueWillTrapIfNull(CI, PHIs)) return false;
526 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(*UI)) {
527 if (!AllUsesOfValueWillTrapIfNull(GEPI, PHIs)) return false;
528 } else if (PHINode *PN = dyn_cast<PHINode>(*UI)) {
529 // If we've already seen this phi node, ignore it, it has already been
532 return AllUsesOfValueWillTrapIfNull(PN, PHIs);
533 } else if (isa<ICmpInst>(*UI) &&
534 isa<ConstantPointerNull>(UI->getOperand(1))) {
535 // Ignore setcc X, null
537 //cerr << "NONTRAPPING USE: " << **UI;
543 /// AllUsesOfLoadedValueWillTrapIfNull - Return true if all uses of any loads
544 /// from GV will trap if the loaded value is null. Note that this also permits
545 /// comparisons of the loaded value against null, as a special case.
546 static bool AllUsesOfLoadedValueWillTrapIfNull(GlobalVariable *GV) {
547 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); UI!=E; ++UI)
548 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
549 SmallPtrSet<PHINode*, 8> PHIs;
550 if (!AllUsesOfValueWillTrapIfNull(LI, PHIs))
552 } else if (isa<StoreInst>(*UI)) {
553 // Ignore stores to the global.
555 // We don't know or understand this user, bail out.
556 //cerr << "UNKNOWN USER OF GLOBAL!: " << **UI;
563 static bool OptimizeAwayTrappingUsesOfValue(Value *V, Constant *NewV) {
564 bool Changed = false;
565 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ) {
566 Instruction *I = cast<Instruction>(*UI++);
567 if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
568 LI->setOperand(0, NewV);
570 } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
571 if (SI->getOperand(1) == V) {
572 SI->setOperand(1, NewV);
575 } else if (isa<CallInst>(I) || isa<InvokeInst>(I)) {
576 if (I->getOperand(0) == V) {
577 // Calling through the pointer! Turn into a direct call, but be careful
578 // that the pointer is not also being passed as an argument.
579 I->setOperand(0, NewV);
581 bool PassedAsArg = false;
582 for (unsigned i = 1, e = I->getNumOperands(); i != e; ++i)
583 if (I->getOperand(i) == V) {
585 I->setOperand(i, NewV);
589 // Being passed as an argument also. Be careful to not invalidate UI!
593 } else if (CastInst *CI = dyn_cast<CastInst>(I)) {
594 Changed |= OptimizeAwayTrappingUsesOfValue(CI,
595 ConstantExpr::getCast(CI->getOpcode(),
596 NewV, CI->getType()));
597 if (CI->use_empty()) {
599 CI->eraseFromParent();
601 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I)) {
602 // Should handle GEP here.
603 SmallVector<Constant*, 8> Idxs;
604 Idxs.reserve(GEPI->getNumOperands()-1);
605 for (unsigned i = 1, e = GEPI->getNumOperands(); i != e; ++i)
606 if (Constant *C = dyn_cast<Constant>(GEPI->getOperand(i)))
610 if (Idxs.size() == GEPI->getNumOperands()-1)
611 Changed |= OptimizeAwayTrappingUsesOfValue(GEPI,
612 ConstantExpr::getGetElementPtr(NewV, &Idxs[0],
614 if (GEPI->use_empty()) {
616 GEPI->eraseFromParent();
625 /// OptimizeAwayTrappingUsesOfLoads - The specified global has only one non-null
626 /// value stored into it. If there are uses of the loaded value that would trap
627 /// if the loaded value is dynamically null, then we know that they cannot be
628 /// reachable with a null optimize away the load.
629 static bool OptimizeAwayTrappingUsesOfLoads(GlobalVariable *GV, Constant *LV) {
630 std::vector<LoadInst*> Loads;
631 bool Changed = false;
633 // Replace all uses of loads with uses of uses of the stored value.
634 for (Value::use_iterator GUI = GV->use_begin(), E = GV->use_end();
636 if (LoadInst *LI = dyn_cast<LoadInst>(*GUI)) {
638 Changed |= OptimizeAwayTrappingUsesOfValue(LI, LV);
640 // If we get here we could have stores, selects, or phi nodes whose values
642 assert((isa<StoreInst>(*GUI) || isa<PHINode>(*GUI) ||
643 isa<SelectInst>(*GUI)) &&
644 "Only expect load and stores!");
648 DOUT << "OPTIMIZED LOADS FROM STORED ONCE POINTER: " << *GV;
652 // Delete all of the loads we can, keeping track of whether we nuked them all!
653 bool AllLoadsGone = true;
654 while (!Loads.empty()) {
655 LoadInst *L = Loads.back();
656 if (L->use_empty()) {
657 L->eraseFromParent();
660 AllLoadsGone = false;
665 // If we nuked all of the loads, then none of the stores are needed either,
666 // nor is the global.
668 DOUT << " *** GLOBAL NOW DEAD!\n";
669 CleanupConstantGlobalUsers(GV, 0);
670 if (GV->use_empty()) {
671 GV->eraseFromParent();
679 /// ConstantPropUsersOf - Walk the use list of V, constant folding all of the
680 /// instructions that are foldable.
681 static void ConstantPropUsersOf(Value *V) {
682 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; )
683 if (Instruction *I = dyn_cast<Instruction>(*UI++))
684 if (Constant *NewC = ConstantFoldInstruction(I)) {
685 I->replaceAllUsesWith(NewC);
687 // Advance UI to the next non-I use to avoid invalidating it!
688 // Instructions could multiply use V.
689 while (UI != E && *UI == I)
691 I->eraseFromParent();
695 /// OptimizeGlobalAddressOfMalloc - This function takes the specified global
696 /// variable, and transforms the program as if it always contained the result of
697 /// the specified malloc. Because it is always the result of the specified
698 /// malloc, there is no reason to actually DO the malloc. Instead, turn the
699 /// malloc into a global, and any loads of GV as uses of the new global.
700 static GlobalVariable *OptimizeGlobalAddressOfMalloc(GlobalVariable *GV,
702 DOUT << "PROMOTING MALLOC GLOBAL: " << *GV << " MALLOC = " << *MI;
703 ConstantInt *NElements = cast<ConstantInt>(MI->getArraySize());
705 if (NElements->getZExtValue() != 1) {
706 // If we have an array allocation, transform it to a single element
707 // allocation to make the code below simpler.
708 Type *NewTy = ArrayType::get(MI->getAllocatedType(),
709 NElements->getZExtValue());
711 new MallocInst(NewTy, Constant::getNullValue(Type::Int32Ty),
712 MI->getAlignment(), MI->getName(), MI);
714 Indices[0] = Indices[1] = Constant::getNullValue(Type::Int32Ty);
715 Value *NewGEP = new GetElementPtrInst(NewMI, Indices, Indices + 2,
716 NewMI->getName()+".el0", MI);
717 MI->replaceAllUsesWith(NewGEP);
718 MI->eraseFromParent();
722 // Create the new global variable. The contents of the malloc'd memory is
723 // undefined, so initialize with an undef value.
724 Constant *Init = UndefValue::get(MI->getAllocatedType());
725 GlobalVariable *NewGV = new GlobalVariable(MI->getAllocatedType(), false,
726 GlobalValue::InternalLinkage, Init,
727 GV->getName()+".body",
729 GV->isThreadLocal());
730 GV->getParent()->getGlobalList().insert(GV, NewGV);
732 // Anything that used the malloc now uses the global directly.
733 MI->replaceAllUsesWith(NewGV);
735 Constant *RepValue = NewGV;
736 if (NewGV->getType() != GV->getType()->getElementType())
737 RepValue = ConstantExpr::getBitCast(RepValue,
738 GV->getType()->getElementType());
740 // If there is a comparison against null, we will insert a global bool to
741 // keep track of whether the global was initialized yet or not.
742 GlobalVariable *InitBool =
743 new GlobalVariable(Type::Int1Ty, false, GlobalValue::InternalLinkage,
744 ConstantInt::getFalse(), GV->getName()+".init",
745 (Module *)NULL, GV->isThreadLocal());
746 bool InitBoolUsed = false;
748 // Loop over all uses of GV, processing them in turn.
749 std::vector<StoreInst*> Stores;
750 while (!GV->use_empty())
751 if (LoadInst *LI = dyn_cast<LoadInst>(GV->use_back())) {
752 while (!LI->use_empty()) {
753 Use &LoadUse = LI->use_begin().getUse();
754 if (!isa<ICmpInst>(LoadUse.getUser()))
757 ICmpInst *CI = cast<ICmpInst>(LoadUse.getUser());
758 // Replace the cmp X, 0 with a use of the bool value.
759 Value *LV = new LoadInst(InitBool, InitBool->getName()+".val", CI);
761 switch (CI->getPredicate()) {
762 default: assert(0 && "Unknown ICmp Predicate!");
763 case ICmpInst::ICMP_ULT:
764 case ICmpInst::ICMP_SLT:
765 LV = ConstantInt::getFalse(); // X < null -> always false
767 case ICmpInst::ICMP_ULE:
768 case ICmpInst::ICMP_SLE:
769 case ICmpInst::ICMP_EQ:
770 LV = BinaryOperator::createNot(LV, "notinit", CI);
772 case ICmpInst::ICMP_NE:
773 case ICmpInst::ICMP_UGE:
774 case ICmpInst::ICMP_SGE:
775 case ICmpInst::ICMP_UGT:
776 case ICmpInst::ICMP_SGT:
779 CI->replaceAllUsesWith(LV);
780 CI->eraseFromParent();
783 LI->eraseFromParent();
785 StoreInst *SI = cast<StoreInst>(GV->use_back());
786 // The global is initialized when the store to it occurs.
787 new StoreInst(ConstantInt::getTrue(), InitBool, SI);
788 SI->eraseFromParent();
791 // If the initialization boolean was used, insert it, otherwise delete it.
793 while (!InitBool->use_empty()) // Delete initializations
794 cast<Instruction>(InitBool->use_back())->eraseFromParent();
797 GV->getParent()->getGlobalList().insert(GV, InitBool);
800 // Now the GV is dead, nuke it and the malloc.
801 GV->eraseFromParent();
802 MI->eraseFromParent();
804 // To further other optimizations, loop over all users of NewGV and try to
805 // constant prop them. This will promote GEP instructions with constant
806 // indices into GEP constant-exprs, which will allow global-opt to hack on it.
807 ConstantPropUsersOf(NewGV);
808 if (RepValue != NewGV)
809 ConstantPropUsersOf(RepValue);
814 /// ValueIsOnlyUsedLocallyOrStoredToOneGlobal - Scan the use-list of V checking
815 /// to make sure that there are no complex uses of V. We permit simple things
816 /// like dereferencing the pointer, but not storing through the address, unless
817 /// it is to the specified global.
818 static bool ValueIsOnlyUsedLocallyOrStoredToOneGlobal(Instruction *V,
820 SmallPtrSet<PHINode*, 8> &PHIs) {
821 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ++UI)
822 if (isa<LoadInst>(*UI) || isa<CmpInst>(*UI)) {
824 } else if (StoreInst *SI = dyn_cast<StoreInst>(*UI)) {
825 if (SI->getOperand(0) == V && SI->getOperand(1) != GV)
826 return false; // Storing the pointer itself... bad.
827 // Otherwise, storing through it, or storing into GV... fine.
828 } else if (isa<GetElementPtrInst>(*UI)) {
829 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(cast<Instruction>(*UI),
832 } else if (PHINode *PN = dyn_cast<PHINode>(*UI)) {
833 // PHIs are ok if all uses are ok. Don't infinitely recurse through PHI
836 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(PN, GV, PHIs))
844 /// ReplaceUsesOfMallocWithGlobal - The Alloc pointer is stored into GV
845 /// somewhere. Transform all uses of the allocation into loads from the
846 /// global and uses of the resultant pointer. Further, delete the store into
847 /// GV. This assumes that these value pass the
848 /// 'ValueIsOnlyUsedLocallyOrStoredToOneGlobal' predicate.
849 static void ReplaceUsesOfMallocWithGlobal(Instruction *Alloc,
850 GlobalVariable *GV) {
851 while (!Alloc->use_empty()) {
852 Instruction *U = cast<Instruction>(*Alloc->use_begin());
853 Instruction *InsertPt = U;
854 if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
855 // If this is the store of the allocation into the global, remove it.
856 if (SI->getOperand(1) == GV) {
857 SI->eraseFromParent();
860 } else if (PHINode *PN = dyn_cast<PHINode>(U)) {
861 // Insert the load in the corresponding predecessor, not right before the
863 unsigned PredNo = Alloc->use_begin().getOperandNo()/2;
864 InsertPt = PN->getIncomingBlock(PredNo)->getTerminator();
867 // Insert a load from the global, and use it instead of the malloc.
868 Value *NL = new LoadInst(GV, GV->getName()+".val", InsertPt);
869 U->replaceUsesOfWith(Alloc, NL);
873 /// GlobalLoadUsesSimpleEnoughForHeapSRA - If all users of values loaded from
874 /// GV are simple enough to perform HeapSRA, return true.
875 static bool GlobalLoadUsesSimpleEnoughForHeapSRA(GlobalVariable *GV,
877 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); UI != E;
879 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
880 // We permit two users of the load: setcc comparing against the null
881 // pointer, and a getelementptr of a specific form.
882 for (Value::use_iterator UI = LI->use_begin(), E = LI->use_end(); UI != E;
884 // Comparison against null is ok.
885 if (ICmpInst *ICI = dyn_cast<ICmpInst>(*UI)) {
886 if (!isa<ConstantPointerNull>(ICI->getOperand(1)))
891 // getelementptr is also ok, but only a simple form.
892 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(*UI)) {
893 // Must index into the array and into the struct.
894 if (GEPI->getNumOperands() < 3)
897 // Otherwise the GEP is ok.
901 if (PHINode *PN = dyn_cast<PHINode>(*UI)) {
902 // We have a phi of a load from the global. We can only handle this
903 // if the other PHI'd values are actually the same. In this case,
904 // the rewriter will just drop the phi entirely.
905 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
906 Value *IV = PN->getIncomingValue(i);
907 if (IV == LI) continue; // Trivial the same.
909 // If the phi'd value is from the malloc that initializes the value,
911 if (IV == MI) continue;
913 // Otherwise, we don't know what it is.
919 // Otherwise we don't know what this is, not ok.
926 /// GetHeapSROALoad - Return the load for the specified field of the HeapSROA'd
927 /// value, lazily creating it on demand.
928 static Value *GetHeapSROALoad(Instruction *Load, unsigned FieldNo,
929 const std::vector<GlobalVariable*> &FieldGlobals,
930 std::vector<Value *> &InsertedLoadsForPtr) {
931 if (InsertedLoadsForPtr.size() <= FieldNo)
932 InsertedLoadsForPtr.resize(FieldNo+1);
933 if (InsertedLoadsForPtr[FieldNo] == 0)
934 InsertedLoadsForPtr[FieldNo] = new LoadInst(FieldGlobals[FieldNo],
935 Load->getName()+".f" +
936 utostr(FieldNo), Load);
937 return InsertedLoadsForPtr[FieldNo];
940 /// RewriteHeapSROALoadUser - Given a load instruction and a value derived from
941 /// the load, rewrite the derived value to use the HeapSRoA'd load.
942 static void RewriteHeapSROALoadUser(LoadInst *Load, Instruction *LoadUser,
943 const std::vector<GlobalVariable*> &FieldGlobals,
944 std::vector<Value *> &InsertedLoadsForPtr) {
945 // If this is a comparison against null, handle it.
946 if (ICmpInst *SCI = dyn_cast<ICmpInst>(LoadUser)) {
947 assert(isa<ConstantPointerNull>(SCI->getOperand(1)));
948 // If we have a setcc of the loaded pointer, we can use a setcc of any
951 if (InsertedLoadsForPtr.empty()) {
952 NPtr = GetHeapSROALoad(Load, 0, FieldGlobals, InsertedLoadsForPtr);
954 NPtr = InsertedLoadsForPtr.back();
957 Value *New = new ICmpInst(SCI->getPredicate(), NPtr,
958 Constant::getNullValue(NPtr->getType()),
959 SCI->getName(), SCI);
960 SCI->replaceAllUsesWith(New);
961 SCI->eraseFromParent();
965 // Handle 'getelementptr Ptr, Idx, uint FieldNo ...'
966 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(LoadUser)) {
967 assert(GEPI->getNumOperands() >= 3 && isa<ConstantInt>(GEPI->getOperand(2))
968 && "Unexpected GEPI!");
970 // Load the pointer for this field.
971 unsigned FieldNo = cast<ConstantInt>(GEPI->getOperand(2))->getZExtValue();
972 Value *NewPtr = GetHeapSROALoad(Load, FieldNo,
973 FieldGlobals, InsertedLoadsForPtr);
975 // Create the new GEP idx vector.
976 SmallVector<Value*, 8> GEPIdx;
977 GEPIdx.push_back(GEPI->getOperand(1));
978 GEPIdx.append(GEPI->op_begin()+3, GEPI->op_end());
980 Value *NGEPI = new GetElementPtrInst(NewPtr, GEPIdx.begin(), GEPIdx.end(),
981 GEPI->getName(), GEPI);
982 GEPI->replaceAllUsesWith(NGEPI);
983 GEPI->eraseFromParent();
987 // Handle PHI nodes. PHI nodes must be merging in the same values, plus
988 // potentially the original malloc. Insert phi nodes for each field, then
989 // process uses of the PHI.
990 PHINode *PN = cast<PHINode>(LoadUser);
991 std::vector<Value *> PHIsForField;
992 PHIsForField.resize(FieldGlobals.size());
993 for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) {
994 Value *LoadV = GetHeapSROALoad(Load, i, FieldGlobals, InsertedLoadsForPtr);
996 PHINode *FieldPN = new PHINode(LoadV->getType(),
997 PN->getName()+"."+utostr(i), PN);
998 // Fill in the predecessor values.
999 for (unsigned pred = 0, e = PN->getNumIncomingValues(); pred != e; ++pred) {
1000 // Each predecessor either uses the load or the original malloc.
1001 Value *InVal = PN->getIncomingValue(pred);
1002 BasicBlock *BB = PN->getIncomingBlock(pred);
1004 if (isa<MallocInst>(InVal)) {
1005 // Insert a reload from the global in the predecessor.
1006 NewVal = GetHeapSROALoad(BB->getTerminator(), i, FieldGlobals,
1009 NewVal = InsertedLoadsForPtr[i];
1011 FieldPN->addIncoming(NewVal, BB);
1013 PHIsForField[i] = FieldPN;
1016 // Since PHIsForField specifies a phi for every input value, the lazy inserter
1017 // will never insert a load.
1018 while (!PN->use_empty())
1019 RewriteHeapSROALoadUser(Load, PN->use_back(), FieldGlobals, PHIsForField);
1020 PN->eraseFromParent();
1023 /// RewriteUsesOfLoadForHeapSRoA - We are performing Heap SRoA on a global. Ptr
1024 /// is a value loaded from the global. Eliminate all uses of Ptr, making them
1025 /// use FieldGlobals instead. All uses of loaded values satisfy
1026 /// GlobalLoadUsesSimpleEnoughForHeapSRA.
1027 static void RewriteUsesOfLoadForHeapSRoA(LoadInst *Load,
1028 const std::vector<GlobalVariable*> &FieldGlobals) {
1029 std::vector<Value *> InsertedLoadsForPtr;
1030 //InsertedLoadsForPtr.resize(FieldGlobals.size());
1031 while (!Load->use_empty())
1032 RewriteHeapSROALoadUser(Load, Load->use_back(),
1033 FieldGlobals, InsertedLoadsForPtr);
1036 /// PerformHeapAllocSRoA - MI is an allocation of an array of structures. Break
1037 /// it up into multiple allocations of arrays of the fields.
1038 static GlobalVariable *PerformHeapAllocSRoA(GlobalVariable *GV, MallocInst *MI){
1039 DOUT << "SROA HEAP ALLOC: " << *GV << " MALLOC = " << *MI;
1040 const StructType *STy = cast<StructType>(MI->getAllocatedType());
1042 // There is guaranteed to be at least one use of the malloc (storing
1043 // it into GV). If there are other uses, change them to be uses of
1044 // the global to simplify later code. This also deletes the store
1046 ReplaceUsesOfMallocWithGlobal(MI, GV);
1048 // Okay, at this point, there are no users of the malloc. Insert N
1049 // new mallocs at the same place as MI, and N globals.
1050 std::vector<GlobalVariable*> FieldGlobals;
1051 std::vector<MallocInst*> FieldMallocs;
1053 for (unsigned FieldNo = 0, e = STy->getNumElements(); FieldNo != e;++FieldNo){
1054 const Type *FieldTy = STy->getElementType(FieldNo);
1055 const Type *PFieldTy = PointerType::get(FieldTy);
1057 GlobalVariable *NGV =
1058 new GlobalVariable(PFieldTy, false, GlobalValue::InternalLinkage,
1059 Constant::getNullValue(PFieldTy),
1060 GV->getName() + ".f" + utostr(FieldNo), GV,
1061 GV->isThreadLocal());
1062 FieldGlobals.push_back(NGV);
1064 MallocInst *NMI = new MallocInst(FieldTy, MI->getArraySize(),
1065 MI->getName() + ".f" + utostr(FieldNo),MI);
1066 FieldMallocs.push_back(NMI);
1067 new StoreInst(NMI, NGV, MI);
1070 // The tricky aspect of this transformation is handling the case when malloc
1071 // fails. In the original code, malloc failing would set the result pointer
1072 // of malloc to null. In this case, some mallocs could succeed and others
1073 // could fail. As such, we emit code that looks like this:
1074 // F0 = malloc(field0)
1075 // F1 = malloc(field1)
1076 // F2 = malloc(field2)
1077 // if (F0 == 0 || F1 == 0 || F2 == 0) {
1078 // if (F0) { free(F0); F0 = 0; }
1079 // if (F1) { free(F1); F1 = 0; }
1080 // if (F2) { free(F2); F2 = 0; }
1082 Value *RunningOr = 0;
1083 for (unsigned i = 0, e = FieldMallocs.size(); i != e; ++i) {
1084 Value *Cond = new ICmpInst(ICmpInst::ICMP_EQ, FieldMallocs[i],
1085 Constant::getNullValue(FieldMallocs[i]->getType()),
1088 RunningOr = Cond; // First seteq
1090 RunningOr = BinaryOperator::createOr(RunningOr, Cond, "tmp", MI);
1093 // Split the basic block at the old malloc.
1094 BasicBlock *OrigBB = MI->getParent();
1095 BasicBlock *ContBB = OrigBB->splitBasicBlock(MI, "malloc_cont");
1097 // Create the block to check the first condition. Put all these blocks at the
1098 // end of the function as they are unlikely to be executed.
1099 BasicBlock *NullPtrBlock = new BasicBlock("malloc_ret_null",
1100 OrigBB->getParent());
1102 // Remove the uncond branch from OrigBB to ContBB, turning it into a cond
1103 // branch on RunningOr.
1104 OrigBB->getTerminator()->eraseFromParent();
1105 new BranchInst(NullPtrBlock, ContBB, RunningOr, OrigBB);
1107 // Within the NullPtrBlock, we need to emit a comparison and branch for each
1108 // pointer, because some may be null while others are not.
1109 for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) {
1110 Value *GVVal = new LoadInst(FieldGlobals[i], "tmp", NullPtrBlock);
1111 Value *Cmp = new ICmpInst(ICmpInst::ICMP_NE, GVVal,
1112 Constant::getNullValue(GVVal->getType()),
1113 "tmp", NullPtrBlock);
1114 BasicBlock *FreeBlock = new BasicBlock("free_it", OrigBB->getParent());
1115 BasicBlock *NextBlock = new BasicBlock("next", OrigBB->getParent());
1116 new BranchInst(FreeBlock, NextBlock, Cmp, NullPtrBlock);
1118 // Fill in FreeBlock.
1119 new FreeInst(GVVal, FreeBlock);
1120 new StoreInst(Constant::getNullValue(GVVal->getType()), FieldGlobals[i],
1122 new BranchInst(NextBlock, FreeBlock);
1124 NullPtrBlock = NextBlock;
1127 new BranchInst(ContBB, NullPtrBlock);
1130 // MI is no longer needed, remove it.
1131 MI->eraseFromParent();
1134 // Okay, the malloc site is completely handled. All of the uses of GV are now
1135 // loads, and all uses of those loads are simple. Rewrite them to use loads
1136 // of the per-field globals instead.
1137 while (!GV->use_empty()) {
1138 if (LoadInst *LI = dyn_cast<LoadInst>(GV->use_back())) {
1139 RewriteUsesOfLoadForHeapSRoA(LI, FieldGlobals);
1140 LI->eraseFromParent();
1142 // Must be a store of null.
1143 StoreInst *SI = cast<StoreInst>(GV->use_back());
1144 assert(isa<Constant>(SI->getOperand(0)) &&
1145 cast<Constant>(SI->getOperand(0))->isNullValue() &&
1146 "Unexpected heap-sra user!");
1148 // Insert a store of null into each global.
1149 for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) {
1151 Constant::getNullValue(FieldGlobals[i]->getType()->getElementType());
1152 new StoreInst(Null, FieldGlobals[i], SI);
1154 // Erase the original store.
1155 SI->eraseFromParent();
1159 // The old global is now dead, remove it.
1160 GV->eraseFromParent();
1163 return FieldGlobals[0];
1167 // OptimizeOnceStoredGlobal - Try to optimize globals based on the knowledge
1168 // that only one value (besides its initializer) is ever stored to the global.
1169 static bool OptimizeOnceStoredGlobal(GlobalVariable *GV, Value *StoredOnceVal,
1170 Module::global_iterator &GVI,
1172 if (CastInst *CI = dyn_cast<CastInst>(StoredOnceVal))
1173 StoredOnceVal = CI->getOperand(0);
1174 else if (GetElementPtrInst *GEPI =dyn_cast<GetElementPtrInst>(StoredOnceVal)){
1175 // "getelementptr Ptr, 0, 0, 0" is really just a cast.
1176 bool IsJustACast = true;
1177 for (unsigned i = 1, e = GEPI->getNumOperands(); i != e; ++i)
1178 if (!isa<Constant>(GEPI->getOperand(i)) ||
1179 !cast<Constant>(GEPI->getOperand(i))->isNullValue()) {
1180 IsJustACast = false;
1184 StoredOnceVal = GEPI->getOperand(0);
1187 // If we are dealing with a pointer global that is initialized to null and
1188 // only has one (non-null) value stored into it, then we can optimize any
1189 // users of the loaded value (often calls and loads) that would trap if the
1191 if (isa<PointerType>(GV->getInitializer()->getType()) &&
1192 GV->getInitializer()->isNullValue()) {
1193 if (Constant *SOVC = dyn_cast<Constant>(StoredOnceVal)) {
1194 if (GV->getInitializer()->getType() != SOVC->getType())
1195 SOVC = ConstantExpr::getBitCast(SOVC, GV->getInitializer()->getType());
1197 // Optimize away any trapping uses of the loaded value.
1198 if (OptimizeAwayTrappingUsesOfLoads(GV, SOVC))
1200 } else if (MallocInst *MI = dyn_cast<MallocInst>(StoredOnceVal)) {
1201 // If this is a malloc of an abstract type, don't touch it.
1202 if (!MI->getAllocatedType()->isSized())
1205 // We can't optimize this global unless all uses of it are *known* to be
1206 // of the malloc value, not of the null initializer value (consider a use
1207 // that compares the global's value against zero to see if the malloc has
1208 // been reached). To do this, we check to see if all uses of the global
1209 // would trap if the global were null: this proves that they must all
1210 // happen after the malloc.
1211 if (!AllUsesOfLoadedValueWillTrapIfNull(GV))
1214 // We can't optimize this if the malloc itself is used in a complex way,
1215 // for example, being stored into multiple globals. This allows the
1216 // malloc to be stored into the specified global, loaded setcc'd, and
1217 // GEP'd. These are all things we could transform to using the global
1220 SmallPtrSet<PHINode*, 8> PHIs;
1221 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(MI, GV, PHIs))
1226 // If we have a global that is only initialized with a fixed size malloc,
1227 // transform the program to use global memory instead of malloc'd memory.
1228 // This eliminates dynamic allocation, avoids an indirection accessing the
1229 // data, and exposes the resultant global to further GlobalOpt.
1230 if (ConstantInt *NElements = dyn_cast<ConstantInt>(MI->getArraySize())) {
1231 // Restrict this transformation to only working on small allocations
1232 // (2048 bytes currently), as we don't want to introduce a 16M global or
1234 if (NElements->getZExtValue()*
1235 TD.getABITypeSize(MI->getAllocatedType()) < 2048) {
1236 GVI = OptimizeGlobalAddressOfMalloc(GV, MI);
1241 // If the allocation is an array of structures, consider transforming this
1242 // into multiple malloc'd arrays, one for each field. This is basically
1243 // SRoA for malloc'd memory.
1244 if (const StructType *AllocTy =
1245 dyn_cast<StructType>(MI->getAllocatedType())) {
1246 // This the structure has an unreasonable number of fields, leave it
1248 if (AllocTy->getNumElements() <= 16 && AllocTy->getNumElements() > 0 &&
1249 GlobalLoadUsesSimpleEnoughForHeapSRA(GV, MI)) {
1250 GVI = PerformHeapAllocSRoA(GV, MI);
1260 /// ShrinkGlobalToBoolean - At this point, we have learned that the only two
1261 /// values ever stored into GV are its initializer and OtherVal.
1262 static void ShrinkGlobalToBoolean(GlobalVariable *GV, Constant *OtherVal) {
1263 // Create the new global, initializing it to false.
1264 GlobalVariable *NewGV = new GlobalVariable(Type::Int1Ty, false,
1265 GlobalValue::InternalLinkage, ConstantInt::getFalse(),
1268 GV->isThreadLocal());
1269 GV->getParent()->getGlobalList().insert(GV, NewGV);
1271 Constant *InitVal = GV->getInitializer();
1272 assert(InitVal->getType() != Type::Int1Ty && "No reason to shrink to bool!");
1274 // If initialized to zero and storing one into the global, we can use a cast
1275 // instead of a select to synthesize the desired value.
1276 bool IsOneZero = false;
1277 if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal))
1278 IsOneZero = InitVal->isNullValue() && CI->isOne();
1280 while (!GV->use_empty()) {
1281 Instruction *UI = cast<Instruction>(GV->use_back());
1282 if (StoreInst *SI = dyn_cast<StoreInst>(UI)) {
1283 // Change the store into a boolean store.
1284 bool StoringOther = SI->getOperand(0) == OtherVal;
1285 // Only do this if we weren't storing a loaded value.
1287 if (StoringOther || SI->getOperand(0) == InitVal)
1288 StoreVal = ConstantInt::get(Type::Int1Ty, StoringOther);
1290 // Otherwise, we are storing a previously loaded copy. To do this,
1291 // change the copy from copying the original value to just copying the
1293 Instruction *StoredVal = cast<Instruction>(SI->getOperand(0));
1295 // If we're already replaced the input, StoredVal will be a cast or
1296 // select instruction. If not, it will be a load of the original
1298 if (LoadInst *LI = dyn_cast<LoadInst>(StoredVal)) {
1299 assert(LI->getOperand(0) == GV && "Not a copy!");
1300 // Insert a new load, to preserve the saved value.
1301 StoreVal = new LoadInst(NewGV, LI->getName()+".b", LI);
1303 assert((isa<CastInst>(StoredVal) || isa<SelectInst>(StoredVal)) &&
1304 "This is not a form that we understand!");
1305 StoreVal = StoredVal->getOperand(0);
1306 assert(isa<LoadInst>(StoreVal) && "Not a load of NewGV!");
1309 new StoreInst(StoreVal, NewGV, SI);
1310 } else if (!UI->use_empty()) {
1311 // Change the load into a load of bool then a select.
1312 LoadInst *LI = cast<LoadInst>(UI);
1313 LoadInst *NLI = new LoadInst(NewGV, LI->getName()+".b", LI);
1316 NSI = new ZExtInst(NLI, LI->getType(), "", LI);
1318 NSI = new SelectInst(NLI, OtherVal, InitVal, "", LI);
1320 LI->replaceAllUsesWith(NSI);
1322 UI->eraseFromParent();
1325 GV->eraseFromParent();
1329 /// ProcessInternalGlobal - Analyze the specified global variable and optimize
1330 /// it if possible. If we make a change, return true.
1331 bool GlobalOpt::ProcessInternalGlobal(GlobalVariable *GV,
1332 Module::global_iterator &GVI) {
1333 std::set<PHINode*> PHIUsers;
1335 GV->removeDeadConstantUsers();
1337 if (GV->use_empty()) {
1338 DOUT << "GLOBAL DEAD: " << *GV;
1339 GV->eraseFromParent();
1344 if (!AnalyzeGlobal(GV, GS, PHIUsers)) {
1346 cerr << "Global: " << *GV;
1347 cerr << " isLoaded = " << GS.isLoaded << "\n";
1348 cerr << " StoredType = ";
1349 switch (GS.StoredType) {
1350 case GlobalStatus::NotStored: cerr << "NEVER STORED\n"; break;
1351 case GlobalStatus::isInitializerStored: cerr << "INIT STORED\n"; break;
1352 case GlobalStatus::isStoredOnce: cerr << "STORED ONCE\n"; break;
1353 case GlobalStatus::isStored: cerr << "stored\n"; break;
1355 if (GS.StoredType == GlobalStatus::isStoredOnce && GS.StoredOnceValue)
1356 cerr << " StoredOnceValue = " << *GS.StoredOnceValue << "\n";
1357 if (GS.AccessingFunction && !GS.HasMultipleAccessingFunctions)
1358 cerr << " AccessingFunction = " << GS.AccessingFunction->getName()
1360 cerr << " HasMultipleAccessingFunctions = "
1361 << GS.HasMultipleAccessingFunctions << "\n";
1362 cerr << " HasNonInstructionUser = " << GS.HasNonInstructionUser<<"\n";
1363 cerr << " isNotSuitableForSRA = " << GS.isNotSuitableForSRA << "\n";
1367 // If this is a first class global and has only one accessing function
1368 // and this function is main (which we know is not recursive we can make
1369 // this global a local variable) we replace the global with a local alloca
1370 // in this function.
1372 // NOTE: It doesn't make sense to promote non first class types since we
1373 // are just replacing static memory to stack memory.
1374 if (!GS.HasMultipleAccessingFunctions &&
1375 GS.AccessingFunction && !GS.HasNonInstructionUser &&
1376 GV->getType()->getElementType()->isFirstClassType() &&
1377 GS.AccessingFunction->getName() == "main" &&
1378 GS.AccessingFunction->hasExternalLinkage()) {
1379 DOUT << "LOCALIZING GLOBAL: " << *GV;
1380 Instruction* FirstI = GS.AccessingFunction->getEntryBlock().begin();
1381 const Type* ElemTy = GV->getType()->getElementType();
1382 // FIXME: Pass Global's alignment when globals have alignment
1383 AllocaInst* Alloca = new AllocaInst(ElemTy, NULL, GV->getName(), FirstI);
1384 if (!isa<UndefValue>(GV->getInitializer()))
1385 new StoreInst(GV->getInitializer(), Alloca, FirstI);
1387 GV->replaceAllUsesWith(Alloca);
1388 GV->eraseFromParent();
1393 // If the global is never loaded (but may be stored to), it is dead.
1396 DOUT << "GLOBAL NEVER LOADED: " << *GV;
1398 // Delete any stores we can find to the global. We may not be able to
1399 // make it completely dead though.
1400 bool Changed = CleanupConstantGlobalUsers(GV, GV->getInitializer());
1402 // If the global is dead now, delete it.
1403 if (GV->use_empty()) {
1404 GV->eraseFromParent();
1410 } else if (GS.StoredType <= GlobalStatus::isInitializerStored) {
1411 DOUT << "MARKING CONSTANT: " << *GV;
1412 GV->setConstant(true);
1414 // Clean up any obviously simplifiable users now.
1415 CleanupConstantGlobalUsers(GV, GV->getInitializer());
1417 // If the global is dead now, just nuke it.
1418 if (GV->use_empty()) {
1419 DOUT << " *** Marking constant allowed us to simplify "
1420 << "all users and delete global!\n";
1421 GV->eraseFromParent();
1427 } else if (!GS.isNotSuitableForSRA &&
1428 !GV->getInitializer()->getType()->isFirstClassType()) {
1429 if (GlobalVariable *FirstNewGV = SRAGlobal(GV)) {
1430 GVI = FirstNewGV; // Don't skip the newly produced globals!
1433 } else if (GS.StoredType == GlobalStatus::isStoredOnce) {
1434 // If the initial value for the global was an undef value, and if only
1435 // one other value was stored into it, we can just change the
1436 // initializer to be an undef value, then delete all stores to the
1437 // global. This allows us to mark it constant.
1438 if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue))
1439 if (isa<UndefValue>(GV->getInitializer())) {
1440 // Change the initial value here.
1441 GV->setInitializer(SOVConstant);
1443 // Clean up any obviously simplifiable users now.
1444 CleanupConstantGlobalUsers(GV, GV->getInitializer());
1446 if (GV->use_empty()) {
1447 DOUT << " *** Substituting initializer allowed us to "
1448 << "simplify all users and delete global!\n";
1449 GV->eraseFromParent();
1458 // Try to optimize globals based on the knowledge that only one value
1459 // (besides its initializer) is ever stored to the global.
1460 if (OptimizeOnceStoredGlobal(GV, GS.StoredOnceValue, GVI,
1461 getAnalysis<TargetData>()))
1464 // Otherwise, if the global was not a boolean, we can shrink it to be a
1466 if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue))
1467 if (GV->getType()->getElementType() != Type::Int1Ty &&
1468 !GV->getType()->getElementType()->isFloatingPoint() &&
1469 !isa<VectorType>(GV->getType()->getElementType()) &&
1470 !GS.HasPHIUser && !GS.isNotSuitableForSRA) {
1471 DOUT << " *** SHRINKING TO BOOL: " << *GV;
1472 ShrinkGlobalToBoolean(GV, SOVConstant);
1481 /// OnlyCalledDirectly - Return true if the specified function is only called
1482 /// directly. In other words, its address is never taken.
1483 static bool OnlyCalledDirectly(Function *F) {
1484 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){
1485 Instruction *User = dyn_cast<Instruction>(*UI);
1486 if (!User) return false;
1487 if (!isa<CallInst>(User) && !isa<InvokeInst>(User)) return false;
1489 // See if the function address is passed as an argument.
1490 for (unsigned i = 1, e = User->getNumOperands(); i != e; ++i)
1491 if (User->getOperand(i) == F) return false;
1496 /// ChangeCalleesToFastCall - Walk all of the direct calls of the specified
1497 /// function, changing them to FastCC.
1498 static void ChangeCalleesToFastCall(Function *F) {
1499 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){
1500 Instruction *User = cast<Instruction>(*UI);
1501 if (CallInst *CI = dyn_cast<CallInst>(User))
1502 CI->setCallingConv(CallingConv::Fast);
1504 cast<InvokeInst>(User)->setCallingConv(CallingConv::Fast);
1508 bool GlobalOpt::OptimizeFunctions(Module &M) {
1509 bool Changed = false;
1510 // Optimize functions.
1511 for (Module::iterator FI = M.begin(), E = M.end(); FI != E; ) {
1513 F->removeDeadConstantUsers();
1514 if (F->use_empty() && (F->hasInternalLinkage() ||
1515 F->hasLinkOnceLinkage())) {
1516 M.getFunctionList().erase(F);
1519 } else if (F->hasInternalLinkage() &&
1520 F->getCallingConv() == CallingConv::C && !F->isVarArg() &&
1521 OnlyCalledDirectly(F)) {
1522 // If this function has C calling conventions, is not a varargs
1523 // function, and is only called directly, promote it to use the Fast
1524 // calling convention.
1525 F->setCallingConv(CallingConv::Fast);
1526 ChangeCalleesToFastCall(F);
1534 bool GlobalOpt::OptimizeGlobalVars(Module &M) {
1535 bool Changed = false;
1536 for (Module::global_iterator GVI = M.global_begin(), E = M.global_end();
1538 GlobalVariable *GV = GVI++;
1539 if (!GV->isConstant() && GV->hasInternalLinkage() &&
1540 GV->hasInitializer())
1541 Changed |= ProcessInternalGlobal(GV, GVI);
1546 /// FindGlobalCtors - Find the llvm.globalctors list, verifying that all
1547 /// initializers have an init priority of 65535.
1548 GlobalVariable *GlobalOpt::FindGlobalCtors(Module &M) {
1549 for (Module::global_iterator I = M.global_begin(), E = M.global_end();
1551 if (I->getName() == "llvm.global_ctors") {
1552 // Found it, verify it's an array of { int, void()* }.
1553 const ArrayType *ATy =dyn_cast<ArrayType>(I->getType()->getElementType());
1555 const StructType *STy = dyn_cast<StructType>(ATy->getElementType());
1556 if (!STy || STy->getNumElements() != 2 ||
1557 STy->getElementType(0) != Type::Int32Ty) return 0;
1558 const PointerType *PFTy = dyn_cast<PointerType>(STy->getElementType(1));
1559 if (!PFTy) return 0;
1560 const FunctionType *FTy = dyn_cast<FunctionType>(PFTy->getElementType());
1561 if (!FTy || FTy->getReturnType() != Type::VoidTy || FTy->isVarArg() ||
1562 FTy->getNumParams() != 0)
1565 // Verify that the initializer is simple enough for us to handle.
1566 if (!I->hasInitializer()) return 0;
1567 ConstantArray *CA = dyn_cast<ConstantArray>(I->getInitializer());
1569 for (unsigned i = 0, e = CA->getNumOperands(); i != e; ++i)
1570 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(CA->getOperand(i))) {
1571 if (isa<ConstantPointerNull>(CS->getOperand(1)))
1574 // Must have a function or null ptr.
1575 if (!isa<Function>(CS->getOperand(1)))
1578 // Init priority must be standard.
1579 ConstantInt *CI = dyn_cast<ConstantInt>(CS->getOperand(0));
1580 if (!CI || CI->getZExtValue() != 65535)
1591 /// ParseGlobalCtors - Given a llvm.global_ctors list that we can understand,
1592 /// return a list of the functions and null terminator as a vector.
1593 static std::vector<Function*> ParseGlobalCtors(GlobalVariable *GV) {
1594 ConstantArray *CA = cast<ConstantArray>(GV->getInitializer());
1595 std::vector<Function*> Result;
1596 Result.reserve(CA->getNumOperands());
1597 for (unsigned i = 0, e = CA->getNumOperands(); i != e; ++i) {
1598 ConstantStruct *CS = cast<ConstantStruct>(CA->getOperand(i));
1599 Result.push_back(dyn_cast<Function>(CS->getOperand(1)));
1604 /// InstallGlobalCtors - Given a specified llvm.global_ctors list, install the
1605 /// specified array, returning the new global to use.
1606 static GlobalVariable *InstallGlobalCtors(GlobalVariable *GCL,
1607 const std::vector<Function*> &Ctors) {
1608 // If we made a change, reassemble the initializer list.
1609 std::vector<Constant*> CSVals;
1610 CSVals.push_back(ConstantInt::get(Type::Int32Ty, 65535));
1611 CSVals.push_back(0);
1613 // Create the new init list.
1614 std::vector<Constant*> CAList;
1615 for (unsigned i = 0, e = Ctors.size(); i != e; ++i) {
1617 CSVals[1] = Ctors[i];
1619 const Type *FTy = FunctionType::get(Type::VoidTy,
1620 std::vector<const Type*>(), false);
1621 const PointerType *PFTy = PointerType::get(FTy);
1622 CSVals[1] = Constant::getNullValue(PFTy);
1623 CSVals[0] = ConstantInt::get(Type::Int32Ty, 2147483647);
1625 CAList.push_back(ConstantStruct::get(CSVals));
1628 // Create the array initializer.
1629 const Type *StructTy =
1630 cast<ArrayType>(GCL->getType()->getElementType())->getElementType();
1631 Constant *CA = ConstantArray::get(ArrayType::get(StructTy, CAList.size()),
1634 // If we didn't change the number of elements, don't create a new GV.
1635 if (CA->getType() == GCL->getInitializer()->getType()) {
1636 GCL->setInitializer(CA);
1640 // Create the new global and insert it next to the existing list.
1641 GlobalVariable *NGV = new GlobalVariable(CA->getType(), GCL->isConstant(),
1642 GCL->getLinkage(), CA, "",
1644 GCL->isThreadLocal());
1645 GCL->getParent()->getGlobalList().insert(GCL, NGV);
1648 // Nuke the old list, replacing any uses with the new one.
1649 if (!GCL->use_empty()) {
1651 if (V->getType() != GCL->getType())
1652 V = ConstantExpr::getBitCast(V, GCL->getType());
1653 GCL->replaceAllUsesWith(V);
1655 GCL->eraseFromParent();
1664 static Constant *getVal(std::map<Value*, Constant*> &ComputedValues,
1666 if (Constant *CV = dyn_cast<Constant>(V)) return CV;
1667 Constant *R = ComputedValues[V];
1668 assert(R && "Reference to an uncomputed value!");
1672 /// isSimpleEnoughPointerToCommit - Return true if this constant is simple
1673 /// enough for us to understand. In particular, if it is a cast of something,
1674 /// we punt. We basically just support direct accesses to globals and GEP's of
1675 /// globals. This should be kept up to date with CommitValueTo.
1676 static bool isSimpleEnoughPointerToCommit(Constant *C) {
1677 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C)) {
1678 if (!GV->hasExternalLinkage() && !GV->hasInternalLinkage())
1679 return false; // do not allow weak/linkonce/dllimport/dllexport linkage.
1680 return !GV->isDeclaration(); // reject external globals.
1682 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
1683 // Handle a constantexpr gep.
1684 if (CE->getOpcode() == Instruction::GetElementPtr &&
1685 isa<GlobalVariable>(CE->getOperand(0))) {
1686 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
1687 if (!GV->hasExternalLinkage() && !GV->hasInternalLinkage())
1688 return false; // do not allow weak/linkonce/dllimport/dllexport linkage.
1689 return GV->hasInitializer() &&
1690 ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE);
1695 /// EvaluateStoreInto - Evaluate a piece of a constantexpr store into a global
1696 /// initializer. This returns 'Init' modified to reflect 'Val' stored into it.
1697 /// At this point, the GEP operands of Addr [0, OpNo) have been stepped into.
1698 static Constant *EvaluateStoreInto(Constant *Init, Constant *Val,
1699 ConstantExpr *Addr, unsigned OpNo) {
1700 // Base case of the recursion.
1701 if (OpNo == Addr->getNumOperands()) {
1702 assert(Val->getType() == Init->getType() && "Type mismatch!");
1706 if (const StructType *STy = dyn_cast<StructType>(Init->getType())) {
1707 std::vector<Constant*> Elts;
1709 // Break up the constant into its elements.
1710 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(Init)) {
1711 for (unsigned i = 0, e = CS->getNumOperands(); i != e; ++i)
1712 Elts.push_back(CS->getOperand(i));
1713 } else if (isa<ConstantAggregateZero>(Init)) {
1714 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
1715 Elts.push_back(Constant::getNullValue(STy->getElementType(i)));
1716 } else if (isa<UndefValue>(Init)) {
1717 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
1718 Elts.push_back(UndefValue::get(STy->getElementType(i)));
1720 assert(0 && "This code is out of sync with "
1721 " ConstantFoldLoadThroughGEPConstantExpr");
1724 // Replace the element that we are supposed to.
1725 ConstantInt *CU = cast<ConstantInt>(Addr->getOperand(OpNo));
1726 unsigned Idx = CU->getZExtValue();
1727 assert(Idx < STy->getNumElements() && "Struct index out of range!");
1728 Elts[Idx] = EvaluateStoreInto(Elts[Idx], Val, Addr, OpNo+1);
1730 // Return the modified struct.
1731 return ConstantStruct::get(&Elts[0], Elts.size(), STy->isPacked());
1733 ConstantInt *CI = cast<ConstantInt>(Addr->getOperand(OpNo));
1734 const ArrayType *ATy = cast<ArrayType>(Init->getType());
1736 // Break up the array into elements.
1737 std::vector<Constant*> Elts;
1738 if (ConstantArray *CA = dyn_cast<ConstantArray>(Init)) {
1739 for (unsigned i = 0, e = CA->getNumOperands(); i != e; ++i)
1740 Elts.push_back(CA->getOperand(i));
1741 } else if (isa<ConstantAggregateZero>(Init)) {
1742 Constant *Elt = Constant::getNullValue(ATy->getElementType());
1743 Elts.assign(ATy->getNumElements(), Elt);
1744 } else if (isa<UndefValue>(Init)) {
1745 Constant *Elt = UndefValue::get(ATy->getElementType());
1746 Elts.assign(ATy->getNumElements(), Elt);
1748 assert(0 && "This code is out of sync with "
1749 " ConstantFoldLoadThroughGEPConstantExpr");
1752 assert(CI->getZExtValue() < ATy->getNumElements());
1753 Elts[CI->getZExtValue()] =
1754 EvaluateStoreInto(Elts[CI->getZExtValue()], Val, Addr, OpNo+1);
1755 return ConstantArray::get(ATy, Elts);
1759 /// CommitValueTo - We have decided that Addr (which satisfies the predicate
1760 /// isSimpleEnoughPointerToCommit) should get Val as its value. Make it happen.
1761 static void CommitValueTo(Constant *Val, Constant *Addr) {
1762 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Addr)) {
1763 assert(GV->hasInitializer());
1764 GV->setInitializer(Val);
1768 ConstantExpr *CE = cast<ConstantExpr>(Addr);
1769 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
1771 Constant *Init = GV->getInitializer();
1772 Init = EvaluateStoreInto(Init, Val, CE, 2);
1773 GV->setInitializer(Init);
1776 /// ComputeLoadResult - Return the value that would be computed by a load from
1777 /// P after the stores reflected by 'memory' have been performed. If we can't
1778 /// decide, return null.
1779 static Constant *ComputeLoadResult(Constant *P,
1780 const std::map<Constant*, Constant*> &Memory) {
1781 // If this memory location has been recently stored, use the stored value: it
1782 // is the most up-to-date.
1783 std::map<Constant*, Constant*>::const_iterator I = Memory.find(P);
1784 if (I != Memory.end()) return I->second;
1787 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(P)) {
1788 if (GV->hasInitializer())
1789 return GV->getInitializer();
1793 // Handle a constantexpr getelementptr.
1794 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(P))
1795 if (CE->getOpcode() == Instruction::GetElementPtr &&
1796 isa<GlobalVariable>(CE->getOperand(0))) {
1797 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
1798 if (GV->hasInitializer())
1799 return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE);
1802 return 0; // don't know how to evaluate.
1805 /// EvaluateFunction - Evaluate a call to function F, returning true if
1806 /// successful, false if we can't evaluate it. ActualArgs contains the formal
1807 /// arguments for the function.
1808 static bool EvaluateFunction(Function *F, Constant *&RetVal,
1809 const std::vector<Constant*> &ActualArgs,
1810 std::vector<Function*> &CallStack,
1811 std::map<Constant*, Constant*> &MutatedMemory,
1812 std::vector<GlobalVariable*> &AllocaTmps) {
1813 // Check to see if this function is already executing (recursion). If so,
1814 // bail out. TODO: we might want to accept limited recursion.
1815 if (std::find(CallStack.begin(), CallStack.end(), F) != CallStack.end())
1818 CallStack.push_back(F);
1820 /// Values - As we compute SSA register values, we store their contents here.
1821 std::map<Value*, Constant*> Values;
1823 // Initialize arguments to the incoming values specified.
1825 for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end(); AI != E;
1827 Values[AI] = ActualArgs[ArgNo];
1829 /// ExecutedBlocks - We only handle non-looping, non-recursive code. As such,
1830 /// we can only evaluate any one basic block at most once. This set keeps
1831 /// track of what we have executed so we can detect recursive cases etc.
1832 std::set<BasicBlock*> ExecutedBlocks;
1834 // CurInst - The current instruction we're evaluating.
1835 BasicBlock::iterator CurInst = F->begin()->begin();
1837 // This is the main evaluation loop.
1839 Constant *InstResult = 0;
1841 if (StoreInst *SI = dyn_cast<StoreInst>(CurInst)) {
1842 if (SI->isVolatile()) return false; // no volatile accesses.
1843 Constant *Ptr = getVal(Values, SI->getOperand(1));
1844 if (!isSimpleEnoughPointerToCommit(Ptr))
1845 // If this is too complex for us to commit, reject it.
1847 Constant *Val = getVal(Values, SI->getOperand(0));
1848 MutatedMemory[Ptr] = Val;
1849 } else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(CurInst)) {
1850 InstResult = ConstantExpr::get(BO->getOpcode(),
1851 getVal(Values, BO->getOperand(0)),
1852 getVal(Values, BO->getOperand(1)));
1853 } else if (CmpInst *CI = dyn_cast<CmpInst>(CurInst)) {
1854 InstResult = ConstantExpr::getCompare(CI->getPredicate(),
1855 getVal(Values, CI->getOperand(0)),
1856 getVal(Values, CI->getOperand(1)));
1857 } else if (CastInst *CI = dyn_cast<CastInst>(CurInst)) {
1858 InstResult = ConstantExpr::getCast(CI->getOpcode(),
1859 getVal(Values, CI->getOperand(0)),
1861 } else if (SelectInst *SI = dyn_cast<SelectInst>(CurInst)) {
1862 InstResult = ConstantExpr::getSelect(getVal(Values, SI->getOperand(0)),
1863 getVal(Values, SI->getOperand(1)),
1864 getVal(Values, SI->getOperand(2)));
1865 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(CurInst)) {
1866 Constant *P = getVal(Values, GEP->getOperand(0));
1867 SmallVector<Constant*, 8> GEPOps;
1868 for (unsigned i = 1, e = GEP->getNumOperands(); i != e; ++i)
1869 GEPOps.push_back(getVal(Values, GEP->getOperand(i)));
1870 InstResult = ConstantExpr::getGetElementPtr(P, &GEPOps[0], GEPOps.size());
1871 } else if (LoadInst *LI = dyn_cast<LoadInst>(CurInst)) {
1872 if (LI->isVolatile()) return false; // no volatile accesses.
1873 InstResult = ComputeLoadResult(getVal(Values, LI->getOperand(0)),
1875 if (InstResult == 0) return false; // Could not evaluate load.
1876 } else if (AllocaInst *AI = dyn_cast<AllocaInst>(CurInst)) {
1877 if (AI->isArrayAllocation()) return false; // Cannot handle array allocs.
1878 const Type *Ty = AI->getType()->getElementType();
1879 AllocaTmps.push_back(new GlobalVariable(Ty, false,
1880 GlobalValue::InternalLinkage,
1881 UndefValue::get(Ty),
1883 InstResult = AllocaTmps.back();
1884 } else if (CallInst *CI = dyn_cast<CallInst>(CurInst)) {
1885 // Cannot handle inline asm.
1886 if (isa<InlineAsm>(CI->getOperand(0))) return false;
1888 // Resolve function pointers.
1889 Function *Callee = dyn_cast<Function>(getVal(Values, CI->getOperand(0)));
1890 if (!Callee) return false; // Cannot resolve.
1892 std::vector<Constant*> Formals;
1893 for (unsigned i = 1, e = CI->getNumOperands(); i != e; ++i)
1894 Formals.push_back(getVal(Values, CI->getOperand(i)));
1896 if (Callee->isDeclaration()) {
1897 // If this is a function we can constant fold, do it.
1898 if (Constant *C = ConstantFoldCall(Callee, &Formals[0],
1905 if (Callee->getFunctionType()->isVarArg())
1910 // Execute the call, if successful, use the return value.
1911 if (!EvaluateFunction(Callee, RetVal, Formals, CallStack,
1912 MutatedMemory, AllocaTmps))
1914 InstResult = RetVal;
1916 } else if (isa<TerminatorInst>(CurInst)) {
1917 BasicBlock *NewBB = 0;
1918 if (BranchInst *BI = dyn_cast<BranchInst>(CurInst)) {
1919 if (BI->isUnconditional()) {
1920 NewBB = BI->getSuccessor(0);
1923 dyn_cast<ConstantInt>(getVal(Values, BI->getCondition()));
1924 if (!Cond) return false; // Cannot determine.
1926 NewBB = BI->getSuccessor(!Cond->getZExtValue());
1928 } else if (SwitchInst *SI = dyn_cast<SwitchInst>(CurInst)) {
1930 dyn_cast<ConstantInt>(getVal(Values, SI->getCondition()));
1931 if (!Val) return false; // Cannot determine.
1932 NewBB = SI->getSuccessor(SI->findCaseValue(Val));
1933 } else if (ReturnInst *RI = dyn_cast<ReturnInst>(CurInst)) {
1934 if (RI->getNumOperands())
1935 RetVal = getVal(Values, RI->getOperand(0));
1937 CallStack.pop_back(); // return from fn.
1938 return true; // We succeeded at evaluating this ctor!
1940 // invoke, unwind, unreachable.
1941 return false; // Cannot handle this terminator.
1944 // Okay, we succeeded in evaluating this control flow. See if we have
1945 // executed the new block before. If so, we have a looping function,
1946 // which we cannot evaluate in reasonable time.
1947 if (!ExecutedBlocks.insert(NewBB).second)
1948 return false; // looped!
1950 // Okay, we have never been in this block before. Check to see if there
1951 // are any PHI nodes. If so, evaluate them with information about where
1953 BasicBlock *OldBB = CurInst->getParent();
1954 CurInst = NewBB->begin();
1956 for (; (PN = dyn_cast<PHINode>(CurInst)); ++CurInst)
1957 Values[PN] = getVal(Values, PN->getIncomingValueForBlock(OldBB));
1959 // Do NOT increment CurInst. We know that the terminator had no value.
1962 // Did not know how to evaluate this!
1966 if (!CurInst->use_empty())
1967 Values[CurInst] = InstResult;
1969 // Advance program counter.
1974 /// EvaluateStaticConstructor - Evaluate static constructors in the function, if
1975 /// we can. Return true if we can, false otherwise.
1976 static bool EvaluateStaticConstructor(Function *F) {
1977 /// MutatedMemory - For each store we execute, we update this map. Loads
1978 /// check this to get the most up-to-date value. If evaluation is successful,
1979 /// this state is committed to the process.
1980 std::map<Constant*, Constant*> MutatedMemory;
1982 /// AllocaTmps - To 'execute' an alloca, we create a temporary global variable
1983 /// to represent its body. This vector is needed so we can delete the
1984 /// temporary globals when we are done.
1985 std::vector<GlobalVariable*> AllocaTmps;
1987 /// CallStack - This is used to detect recursion. In pathological situations
1988 /// we could hit exponential behavior, but at least there is nothing
1990 std::vector<Function*> CallStack;
1992 // Call the function.
1993 Constant *RetValDummy;
1994 bool EvalSuccess = EvaluateFunction(F, RetValDummy, std::vector<Constant*>(),
1995 CallStack, MutatedMemory, AllocaTmps);
1997 // We succeeded at evaluation: commit the result.
1998 DOUT << "FULLY EVALUATED GLOBAL CTOR FUNCTION '"
1999 << F->getName() << "' to " << MutatedMemory.size()
2001 for (std::map<Constant*, Constant*>::iterator I = MutatedMemory.begin(),
2002 E = MutatedMemory.end(); I != E; ++I)
2003 CommitValueTo(I->second, I->first);
2006 // At this point, we are done interpreting. If we created any 'alloca'
2007 // temporaries, release them now.
2008 while (!AllocaTmps.empty()) {
2009 GlobalVariable *Tmp = AllocaTmps.back();
2010 AllocaTmps.pop_back();
2012 // If there are still users of the alloca, the program is doing something
2013 // silly, e.g. storing the address of the alloca somewhere and using it
2014 // later. Since this is undefined, we'll just make it be null.
2015 if (!Tmp->use_empty())
2016 Tmp->replaceAllUsesWith(Constant::getNullValue(Tmp->getType()));
2025 /// OptimizeGlobalCtorsList - Simplify and evaluation global ctors if possible.
2026 /// Return true if anything changed.
2027 bool GlobalOpt::OptimizeGlobalCtorsList(GlobalVariable *&GCL) {
2028 std::vector<Function*> Ctors = ParseGlobalCtors(GCL);
2029 bool MadeChange = false;
2030 if (Ctors.empty()) return false;
2032 // Loop over global ctors, optimizing them when we can.
2033 for (unsigned i = 0; i != Ctors.size(); ++i) {
2034 Function *F = Ctors[i];
2035 // Found a null terminator in the middle of the list, prune off the rest of
2038 if (i != Ctors.size()-1) {
2045 // We cannot simplify external ctor functions.
2046 if (F->empty()) continue;
2048 // If we can evaluate the ctor at compile time, do.
2049 if (EvaluateStaticConstructor(F)) {
2050 Ctors.erase(Ctors.begin()+i);
2053 ++NumCtorsEvaluated;
2058 if (!MadeChange) return false;
2060 GCL = InstallGlobalCtors(GCL, Ctors);
2065 bool GlobalOpt::runOnModule(Module &M) {
2066 bool Changed = false;
2068 // Try to find the llvm.globalctors list.
2069 GlobalVariable *GlobalCtors = FindGlobalCtors(M);
2071 bool LocalChange = true;
2072 while (LocalChange) {
2073 LocalChange = false;
2075 // Delete functions that are trivially dead, ccc -> fastcc
2076 LocalChange |= OptimizeFunctions(M);
2078 // Optimize global_ctors list.
2080 LocalChange |= OptimizeGlobalCtorsList(GlobalCtors);
2082 // Optimize non-address-taken globals.
2083 LocalChange |= OptimizeGlobalVars(M);
2084 Changed |= LocalChange;
2087 // TODO: Move all global ctors functions to the end of the module for code