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 Constant *SubInit = 0;
347 dyn_cast_or_null<ConstantExpr>(ConstantFoldInstruction(GEP));
348 if (Init && CE && CE->getOpcode() == Instruction::GetElementPtr)
349 SubInit = ConstantFoldLoadThroughGEPConstantExpr(Init, CE);
350 Changed |= CleanupConstantGlobalUsers(GEP, SubInit);
352 if (GEP->use_empty()) {
353 GEP->eraseFromParent();
356 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(U)) { // memset/cpy/mv
357 if (MI->getRawDest() == V) {
358 MI->eraseFromParent();
362 } else if (Constant *C = dyn_cast<Constant>(U)) {
363 // If we have a chain of dead constantexprs or other things dangling from
364 // us, and if they are all dead, nuke them without remorse.
365 if (ConstantIsDead(C)) {
366 C->destroyConstant();
367 // This could have invalidated UI, start over from scratch.
368 CleanupConstantGlobalUsers(V, Init);
376 /// SRAGlobal - Perform scalar replacement of aggregates on the specified global
377 /// variable. This opens the door for other optimizations by exposing the
378 /// behavior of the program in a more fine-grained way. We have determined that
379 /// this transformation is safe already. We return the first global variable we
380 /// insert so that the caller can reprocess it.
381 static GlobalVariable *SRAGlobal(GlobalVariable *GV) {
382 assert(GV->hasInternalLinkage() && !GV->isConstant());
383 Constant *Init = GV->getInitializer();
384 const Type *Ty = Init->getType();
386 std::vector<GlobalVariable*> NewGlobals;
387 Module::GlobalListType &Globals = GV->getParent()->getGlobalList();
389 if (const StructType *STy = dyn_cast<StructType>(Ty)) {
390 NewGlobals.reserve(STy->getNumElements());
391 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
392 Constant *In = getAggregateConstantElement(Init,
393 ConstantInt::get(Type::Int32Ty, i));
394 assert(In && "Couldn't get element of initializer?");
395 GlobalVariable *NGV = new GlobalVariable(STy->getElementType(i), false,
396 GlobalVariable::InternalLinkage,
397 In, GV->getName()+"."+utostr(i),
399 GV->isThreadLocal());
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 VectorType *PTy = dyn_cast<VectorType>(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 ConstantInt::get(Type::Int32Ty, 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),
424 GV->isThreadLocal());
425 Globals.insert(GV, NGV);
426 NewGlobals.push_back(NGV);
430 if (NewGlobals.empty())
433 DOUT << "PERFORMING GLOBAL SRA ON: " << *GV;
435 Constant *NullInt = Constant::getNullValue(Type::Int32Ty);
437 // Loop over all of the uses of the global, replacing the constantexpr geps,
438 // with smaller constantexpr geps or direct references.
439 while (!GV->use_empty()) {
440 User *GEP = GV->use_back();
441 assert(((isa<ConstantExpr>(GEP) &&
442 cast<ConstantExpr>(GEP)->getOpcode()==Instruction::GetElementPtr)||
443 isa<GetElementPtrInst>(GEP)) && "NonGEP CE's are not SRAable!");
445 // Ignore the 1th operand, which has to be zero or else the program is quite
446 // broken (undefined). Get the 2nd operand, which is the structure or array
448 unsigned Val = cast<ConstantInt>(GEP->getOperand(2))->getZExtValue();
449 if (Val >= NewGlobals.size()) Val = 0; // Out of bound array access.
451 Value *NewPtr = NewGlobals[Val];
453 // Form a shorter GEP if needed.
454 if (GEP->getNumOperands() > 3)
455 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GEP)) {
456 SmallVector<Constant*, 8> Idxs;
457 Idxs.push_back(NullInt);
458 for (unsigned i = 3, e = CE->getNumOperands(); i != e; ++i)
459 Idxs.push_back(CE->getOperand(i));
460 NewPtr = ConstantExpr::getGetElementPtr(cast<Constant>(NewPtr),
461 &Idxs[0], Idxs.size());
463 GetElementPtrInst *GEPI = cast<GetElementPtrInst>(GEP);
464 SmallVector<Value*, 8> Idxs;
465 Idxs.push_back(NullInt);
466 for (unsigned i = 3, e = GEPI->getNumOperands(); i != e; ++i)
467 Idxs.push_back(GEPI->getOperand(i));
468 NewPtr = new GetElementPtrInst(NewPtr, Idxs.begin(), Idxs.end(),
469 GEPI->getName()+"."+utostr(Val), GEPI);
471 GEP->replaceAllUsesWith(NewPtr);
473 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(GEP))
474 GEPI->eraseFromParent();
476 cast<ConstantExpr>(GEP)->destroyConstant();
479 // Delete the old global, now that it is dead.
483 // Loop over the new globals array deleting any globals that are obviously
484 // dead. This can arise due to scalarization of a structure or an array that
485 // has elements that are dead.
486 unsigned FirstGlobal = 0;
487 for (unsigned i = 0, e = NewGlobals.size(); i != e; ++i)
488 if (NewGlobals[i]->use_empty()) {
489 Globals.erase(NewGlobals[i]);
490 if (FirstGlobal == i) ++FirstGlobal;
493 return FirstGlobal != NewGlobals.size() ? NewGlobals[FirstGlobal] : 0;
496 /// AllUsesOfValueWillTrapIfNull - Return true if all users of the specified
497 /// value will trap if the value is dynamically null. PHIs keeps track of any
498 /// phi nodes we've seen to avoid reprocessing them.
499 static bool AllUsesOfValueWillTrapIfNull(Value *V,
500 SmallPtrSet<PHINode*, 8> &PHIs) {
501 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ++UI)
502 if (isa<LoadInst>(*UI)) {
504 } else if (StoreInst *SI = dyn_cast<StoreInst>(*UI)) {
505 if (SI->getOperand(0) == V) {
506 //cerr << "NONTRAPPING USE: " << **UI;
507 return false; // Storing the value.
509 } else if (CallInst *CI = dyn_cast<CallInst>(*UI)) {
510 if (CI->getOperand(0) != V) {
511 //cerr << "NONTRAPPING USE: " << **UI;
512 return false; // Not calling the ptr
514 } else if (InvokeInst *II = dyn_cast<InvokeInst>(*UI)) {
515 if (II->getOperand(0) != V) {
516 //cerr << "NONTRAPPING USE: " << **UI;
517 return false; // Not calling the ptr
519 } else if (BitCastInst *CI = dyn_cast<BitCastInst>(*UI)) {
520 if (!AllUsesOfValueWillTrapIfNull(CI, PHIs)) return false;
521 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(*UI)) {
522 if (!AllUsesOfValueWillTrapIfNull(GEPI, PHIs)) return false;
523 } else if (PHINode *PN = dyn_cast<PHINode>(*UI)) {
524 // If we've already seen this phi node, ignore it, it has already been
527 return AllUsesOfValueWillTrapIfNull(PN, PHIs);
528 } else if (isa<ICmpInst>(*UI) &&
529 isa<ConstantPointerNull>(UI->getOperand(1))) {
530 // Ignore setcc X, null
532 //cerr << "NONTRAPPING USE: " << **UI;
538 /// AllUsesOfLoadedValueWillTrapIfNull - Return true if all uses of any loads
539 /// from GV will trap if the loaded value is null. Note that this also permits
540 /// comparisons of the loaded value against null, as a special case.
541 static bool AllUsesOfLoadedValueWillTrapIfNull(GlobalVariable *GV) {
542 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); UI!=E; ++UI)
543 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
544 SmallPtrSet<PHINode*, 8> PHIs;
545 if (!AllUsesOfValueWillTrapIfNull(LI, PHIs))
547 } else if (isa<StoreInst>(*UI)) {
548 // Ignore stores to the global.
550 // We don't know or understand this user, bail out.
551 //cerr << "UNKNOWN USER OF GLOBAL!: " << **UI;
558 static bool OptimizeAwayTrappingUsesOfValue(Value *V, Constant *NewV) {
559 bool Changed = false;
560 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ) {
561 Instruction *I = cast<Instruction>(*UI++);
562 if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
563 LI->setOperand(0, NewV);
565 } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
566 if (SI->getOperand(1) == V) {
567 SI->setOperand(1, NewV);
570 } else if (isa<CallInst>(I) || isa<InvokeInst>(I)) {
571 if (I->getOperand(0) == V) {
572 // Calling through the pointer! Turn into a direct call, but be careful
573 // that the pointer is not also being passed as an argument.
574 I->setOperand(0, NewV);
576 bool PassedAsArg = false;
577 for (unsigned i = 1, e = I->getNumOperands(); i != e; ++i)
578 if (I->getOperand(i) == V) {
580 I->setOperand(i, NewV);
584 // Being passed as an argument also. Be careful to not invalidate UI!
588 } else if (CastInst *CI = dyn_cast<CastInst>(I)) {
589 Changed |= OptimizeAwayTrappingUsesOfValue(CI,
590 ConstantExpr::getCast(CI->getOpcode(),
591 NewV, CI->getType()));
592 if (CI->use_empty()) {
594 CI->eraseFromParent();
596 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I)) {
597 // Should handle GEP here.
598 SmallVector<Constant*, 8> Idxs;
599 Idxs.reserve(GEPI->getNumOperands()-1);
600 for (unsigned i = 1, e = GEPI->getNumOperands(); i != e; ++i)
601 if (Constant *C = dyn_cast<Constant>(GEPI->getOperand(i)))
605 if (Idxs.size() == GEPI->getNumOperands()-1)
606 Changed |= OptimizeAwayTrappingUsesOfValue(GEPI,
607 ConstantExpr::getGetElementPtr(NewV, &Idxs[0],
609 if (GEPI->use_empty()) {
611 GEPI->eraseFromParent();
620 /// OptimizeAwayTrappingUsesOfLoads - The specified global has only one non-null
621 /// value stored into it. If there are uses of the loaded value that would trap
622 /// if the loaded value is dynamically null, then we know that they cannot be
623 /// reachable with a null optimize away the load.
624 static bool OptimizeAwayTrappingUsesOfLoads(GlobalVariable *GV, Constant *LV) {
625 std::vector<LoadInst*> Loads;
626 bool Changed = false;
628 // Replace all uses of loads with uses of uses of the stored value.
629 for (Value::use_iterator GUI = GV->use_begin(), E = GV->use_end();
631 if (LoadInst *LI = dyn_cast<LoadInst>(*GUI)) {
633 Changed |= OptimizeAwayTrappingUsesOfValue(LI, LV);
635 // If we get here we could have stores, selects, or phi nodes whose values
637 assert((isa<StoreInst>(*GUI) || isa<PHINode>(*GUI) ||
638 isa<SelectInst>(*GUI)) &&
639 "Only expect load and stores!");
643 DOUT << "OPTIMIZED LOADS FROM STORED ONCE POINTER: " << *GV;
647 // Delete all of the loads we can, keeping track of whether we nuked them all!
648 bool AllLoadsGone = true;
649 while (!Loads.empty()) {
650 LoadInst *L = Loads.back();
651 if (L->use_empty()) {
652 L->eraseFromParent();
655 AllLoadsGone = false;
660 // If we nuked all of the loads, then none of the stores are needed either,
661 // nor is the global.
663 DOUT << " *** GLOBAL NOW DEAD!\n";
664 CleanupConstantGlobalUsers(GV, 0);
665 if (GV->use_empty()) {
666 GV->eraseFromParent();
674 /// ConstantPropUsersOf - Walk the use list of V, constant folding all of the
675 /// instructions that are foldable.
676 static void ConstantPropUsersOf(Value *V) {
677 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; )
678 if (Instruction *I = dyn_cast<Instruction>(*UI++))
679 if (Constant *NewC = ConstantFoldInstruction(I)) {
680 I->replaceAllUsesWith(NewC);
682 // Advance UI to the next non-I use to avoid invalidating it!
683 // Instructions could multiply use V.
684 while (UI != E && *UI == I)
686 I->eraseFromParent();
690 /// OptimizeGlobalAddressOfMalloc - This function takes the specified global
691 /// variable, and transforms the program as if it always contained the result of
692 /// the specified malloc. Because it is always the result of the specified
693 /// malloc, there is no reason to actually DO the malloc. Instead, turn the
694 /// malloc into a global, and any loads of GV as uses of the new global.
695 static GlobalVariable *OptimizeGlobalAddressOfMalloc(GlobalVariable *GV,
697 DOUT << "PROMOTING MALLOC GLOBAL: " << *GV << " MALLOC = " << *MI;
698 ConstantInt *NElements = cast<ConstantInt>(MI->getArraySize());
700 if (NElements->getZExtValue() != 1) {
701 // If we have an array allocation, transform it to a single element
702 // allocation to make the code below simpler.
703 Type *NewTy = ArrayType::get(MI->getAllocatedType(),
704 NElements->getZExtValue());
706 new MallocInst(NewTy, Constant::getNullValue(Type::Int32Ty),
707 MI->getAlignment(), MI->getName(), MI);
709 Indices[0] = Indices[1] = Constant::getNullValue(Type::Int32Ty);
710 Value *NewGEP = new GetElementPtrInst(NewMI, Indices, Indices + 2,
711 NewMI->getName()+".el0", MI);
712 MI->replaceAllUsesWith(NewGEP);
713 MI->eraseFromParent();
717 // Create the new global variable. The contents of the malloc'd memory is
718 // undefined, so initialize with an undef value.
719 Constant *Init = UndefValue::get(MI->getAllocatedType());
720 GlobalVariable *NewGV = new GlobalVariable(MI->getAllocatedType(), false,
721 GlobalValue::InternalLinkage, Init,
722 GV->getName()+".body",
724 GV->isThreadLocal());
725 GV->getParent()->getGlobalList().insert(GV, NewGV);
727 // Anything that used the malloc now uses the global directly.
728 MI->replaceAllUsesWith(NewGV);
730 Constant *RepValue = NewGV;
731 if (NewGV->getType() != GV->getType()->getElementType())
732 RepValue = ConstantExpr::getBitCast(RepValue,
733 GV->getType()->getElementType());
735 // If there is a comparison against null, we will insert a global bool to
736 // keep track of whether the global was initialized yet or not.
737 GlobalVariable *InitBool =
738 new GlobalVariable(Type::Int1Ty, false, GlobalValue::InternalLinkage,
739 ConstantInt::getFalse(), GV->getName()+".init",
740 (Module *)NULL, GV->isThreadLocal());
741 bool InitBoolUsed = false;
743 // Loop over all uses of GV, processing them in turn.
744 std::vector<StoreInst*> Stores;
745 while (!GV->use_empty())
746 if (LoadInst *LI = dyn_cast<LoadInst>(GV->use_back())) {
747 while (!LI->use_empty()) {
748 Use &LoadUse = LI->use_begin().getUse();
749 if (!isa<ICmpInst>(LoadUse.getUser()))
752 ICmpInst *CI = cast<ICmpInst>(LoadUse.getUser());
753 // Replace the cmp X, 0 with a use of the bool value.
754 Value *LV = new LoadInst(InitBool, InitBool->getName()+".val", CI);
756 switch (CI->getPredicate()) {
757 default: assert(0 && "Unknown ICmp Predicate!");
758 case ICmpInst::ICMP_ULT:
759 case ICmpInst::ICMP_SLT:
760 LV = ConstantInt::getFalse(); // X < null -> always false
762 case ICmpInst::ICMP_ULE:
763 case ICmpInst::ICMP_SLE:
764 case ICmpInst::ICMP_EQ:
765 LV = BinaryOperator::createNot(LV, "notinit", CI);
767 case ICmpInst::ICMP_NE:
768 case ICmpInst::ICMP_UGE:
769 case ICmpInst::ICMP_SGE:
770 case ICmpInst::ICMP_UGT:
771 case ICmpInst::ICMP_SGT:
774 CI->replaceAllUsesWith(LV);
775 CI->eraseFromParent();
778 LI->eraseFromParent();
780 StoreInst *SI = cast<StoreInst>(GV->use_back());
781 // The global is initialized when the store to it occurs.
782 new StoreInst(ConstantInt::getTrue(), InitBool, SI);
783 SI->eraseFromParent();
786 // If the initialization boolean was used, insert it, otherwise delete it.
788 while (!InitBool->use_empty()) // Delete initializations
789 cast<Instruction>(InitBool->use_back())->eraseFromParent();
792 GV->getParent()->getGlobalList().insert(GV, InitBool);
795 // Now the GV is dead, nuke it and the malloc.
796 GV->eraseFromParent();
797 MI->eraseFromParent();
799 // To further other optimizations, loop over all users of NewGV and try to
800 // constant prop them. This will promote GEP instructions with constant
801 // indices into GEP constant-exprs, which will allow global-opt to hack on it.
802 ConstantPropUsersOf(NewGV);
803 if (RepValue != NewGV)
804 ConstantPropUsersOf(RepValue);
809 /// ValueIsOnlyUsedLocallyOrStoredToOneGlobal - Scan the use-list of V checking
810 /// to make sure that there are no complex uses of V. We permit simple things
811 /// like dereferencing the pointer, but not storing through the address, unless
812 /// it is to the specified global.
813 static bool ValueIsOnlyUsedLocallyOrStoredToOneGlobal(Instruction *V,
815 SmallPtrSet<PHINode*, 8> &PHIs) {
816 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;++UI)
817 if (isa<LoadInst>(*UI) || isa<CmpInst>(*UI)) {
819 } else if (StoreInst *SI = dyn_cast<StoreInst>(*UI)) {
820 if (SI->getOperand(0) == V && SI->getOperand(1) != GV)
821 return false; // Storing the pointer itself... bad.
822 // Otherwise, storing through it, or storing into GV... fine.
823 } else if (isa<GetElementPtrInst>(*UI) || isa<SelectInst>(*UI) ||
824 isa<BitCastInst>(*UI)) {
825 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(cast<Instruction>(*UI),
828 } else if (PHINode *PN = dyn_cast<PHINode>(*UI)) {
829 // PHIs are ok if all uses are ok. Don't infinitely recurse through PHI
832 return ValueIsOnlyUsedLocallyOrStoredToOneGlobal(PN, GV, PHIs);
839 /// ReplaceUsesOfMallocWithGlobal - The Alloc pointer is stored into GV
840 /// somewhere. Transform all uses of the allocation into loads from the
841 /// global and uses of the resultant pointer. Further, delete the store into
842 /// GV. This assumes that these value pass the
843 /// 'ValueIsOnlyUsedLocallyOrStoredToOneGlobal' predicate.
844 static void ReplaceUsesOfMallocWithGlobal(Instruction *Alloc,
845 GlobalVariable *GV) {
846 while (!Alloc->use_empty()) {
847 Instruction *U = cast<Instruction>(*Alloc->use_begin());
848 Instruction *InsertPt = U;
849 if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
850 // If this is the store of the allocation into the global, remove it.
851 if (SI->getOperand(1) == GV) {
852 SI->eraseFromParent();
855 } else if (PHINode *PN = dyn_cast<PHINode>(U)) {
856 // Insert the load in the corresponding predecessor, not right before the
858 unsigned PredNo = Alloc->use_begin().getOperandNo()/2;
859 InsertPt = PN->getIncomingBlock(PredNo)->getTerminator();
862 // Insert a load from the global, and use it instead of the malloc.
863 Value *NL = new LoadInst(GV, GV->getName()+".val", InsertPt);
864 U->replaceUsesOfWith(Alloc, NL);
868 /// GlobalLoadUsesSimpleEnoughForHeapSRA - If all users of values loaded from
869 /// GV are simple enough to perform HeapSRA, return true.
870 static bool GlobalLoadUsesSimpleEnoughForHeapSRA(GlobalVariable *GV) {
871 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); UI != E;
873 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
874 // We permit two users of the load: setcc comparing against the null
875 // pointer, and a getelementptr of a specific form.
876 for (Value::use_iterator UI = LI->use_begin(), E = LI->use_end(); UI != E;
878 // Comparison against null is ok.
879 if (ICmpInst *ICI = dyn_cast<ICmpInst>(*UI)) {
880 if (!isa<ConstantPointerNull>(ICI->getOperand(1)))
885 // getelementptr is also ok, but only a simple form.
886 GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(*UI);
887 if (!GEPI) return false;
889 // Must index into the array and into the struct.
890 if (GEPI->getNumOperands() < 3)
893 // Otherwise the GEP is ok.
900 /// GetHeapSROALoad - Return the load for the specified field of the HeapSROA'd
901 /// value, lazily creating it on demand.
902 static Value *GetHeapSROALoad(LoadInst *Load, unsigned FieldNo,
903 const std::vector<GlobalVariable*> &FieldGlobals,
904 std::vector<Value *> &InsertedLoadsForPtr) {
905 if (InsertedLoadsForPtr.size() <= FieldNo)
906 InsertedLoadsForPtr.resize(FieldNo+1);
907 if (InsertedLoadsForPtr[FieldNo] == 0)
908 InsertedLoadsForPtr[FieldNo] = new LoadInst(FieldGlobals[FieldNo],
909 Load->getName()+".f" +
910 utostr(FieldNo), Load);
911 return InsertedLoadsForPtr[FieldNo];
914 /// RewriteHeapSROALoadUser - Given a load instruction and a value derived from
915 /// the load, rewrite the derived value to use the HeapSRoA'd load.
916 static void RewriteHeapSROALoadUser(LoadInst *Load, Instruction *LoadUser,
917 const std::vector<GlobalVariable*> &FieldGlobals,
918 std::vector<Value *> &InsertedLoadsForPtr) {
919 // If this is a comparison against null, handle it.
920 if (ICmpInst *SCI = dyn_cast<ICmpInst>(LoadUser)) {
921 assert(isa<ConstantPointerNull>(SCI->getOperand(1)));
922 // If we have a setcc of the loaded pointer, we can use a setcc of any
925 if (InsertedLoadsForPtr.empty()) {
926 NPtr = GetHeapSROALoad(Load, 0, FieldGlobals, InsertedLoadsForPtr);
928 NPtr = InsertedLoadsForPtr.back();
931 Value *New = new ICmpInst(SCI->getPredicate(), NPtr,
932 Constant::getNullValue(NPtr->getType()),
933 SCI->getName(), SCI);
934 SCI->replaceAllUsesWith(New);
935 SCI->eraseFromParent();
939 // Handle 'getelementptr Ptr, Idx, uint FieldNo ...'
940 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(LoadUser)) {
941 assert(GEPI->getNumOperands() >= 3 && isa<ConstantInt>(GEPI->getOperand(2))
942 && "Unexpected GEPI!");
944 // Load the pointer for this field.
945 unsigned FieldNo = cast<ConstantInt>(GEPI->getOperand(2))->getZExtValue();
946 Value *NewPtr = GetHeapSROALoad(Load, FieldNo,
947 FieldGlobals, InsertedLoadsForPtr);
949 // Create the new GEP idx vector.
950 SmallVector<Value*, 8> GEPIdx;
951 GEPIdx.push_back(GEPI->getOperand(1));
952 GEPIdx.append(GEPI->op_begin()+3, GEPI->op_end());
954 Value *NGEPI = new GetElementPtrInst(NewPtr, GEPIdx.begin(), GEPIdx.end(),
955 GEPI->getName(), GEPI);
956 GEPI->replaceAllUsesWith(NGEPI);
957 GEPI->eraseFromParent();
961 // Handle PHI nodes. All PHI nodes must be merging in the same values, so
962 // just treat them like a copy.
963 PHINode *PN = cast<PHINode>(LoadUser);
964 while (!PN->use_empty())
965 RewriteHeapSROALoadUser(Load, PN->use_back(),
966 FieldGlobals, InsertedLoadsForPtr);
967 PN->eraseFromParent();
970 /// RewriteUsesOfLoadForHeapSRoA - We are performing Heap SRoA on a global. Ptr
971 /// is a value loaded from the global. Eliminate all uses of Ptr, making them
972 /// use FieldGlobals instead. All uses of loaded values satisfy
973 /// GlobalLoadUsesSimpleEnoughForHeapSRA.
974 static void RewriteUsesOfLoadForHeapSRoA(LoadInst *Load,
975 const std::vector<GlobalVariable*> &FieldGlobals) {
976 std::vector<Value *> InsertedLoadsForPtr;
977 //InsertedLoadsForPtr.resize(FieldGlobals.size());
978 while (!Load->use_empty())
979 RewriteHeapSROALoadUser(Load, Load->use_back(),
980 FieldGlobals, InsertedLoadsForPtr);
983 /// PerformHeapAllocSRoA - MI is an allocation of an array of structures. Break
984 /// it up into multiple allocations of arrays of the fields.
985 static GlobalVariable *PerformHeapAllocSRoA(GlobalVariable *GV, MallocInst *MI){
986 DOUT << "SROA HEAP ALLOC: " << *GV << " MALLOC = " << *MI;
987 const StructType *STy = cast<StructType>(MI->getAllocatedType());
989 // There is guaranteed to be at least one use of the malloc (storing
990 // it into GV). If there are other uses, change them to be uses of
991 // the global to simplify later code. This also deletes the store
993 ReplaceUsesOfMallocWithGlobal(MI, GV);
995 // Okay, at this point, there are no users of the malloc. Insert N
996 // new mallocs at the same place as MI, and N globals.
997 std::vector<GlobalVariable*> FieldGlobals;
998 std::vector<MallocInst*> FieldMallocs;
1000 for (unsigned FieldNo = 0, e = STy->getNumElements(); FieldNo != e;++FieldNo){
1001 const Type *FieldTy = STy->getElementType(FieldNo);
1002 const Type *PFieldTy = PointerType::get(FieldTy);
1004 GlobalVariable *NGV =
1005 new GlobalVariable(PFieldTy, false, GlobalValue::InternalLinkage,
1006 Constant::getNullValue(PFieldTy),
1007 GV->getName() + ".f" + utostr(FieldNo), GV,
1008 GV->isThreadLocal());
1009 FieldGlobals.push_back(NGV);
1011 MallocInst *NMI = new MallocInst(FieldTy, MI->getArraySize(),
1012 MI->getName() + ".f" + utostr(FieldNo),MI);
1013 FieldMallocs.push_back(NMI);
1014 new StoreInst(NMI, NGV, MI);
1017 // The tricky aspect of this transformation is handling the case when malloc
1018 // fails. In the original code, malloc failing would set the result pointer
1019 // of malloc to null. In this case, some mallocs could succeed and others
1020 // could fail. As such, we emit code that looks like this:
1021 // F0 = malloc(field0)
1022 // F1 = malloc(field1)
1023 // F2 = malloc(field2)
1024 // if (F0 == 0 || F1 == 0 || F2 == 0) {
1025 // if (F0) { free(F0); F0 = 0; }
1026 // if (F1) { free(F1); F1 = 0; }
1027 // if (F2) { free(F2); F2 = 0; }
1029 Value *RunningOr = 0;
1030 for (unsigned i = 0, e = FieldMallocs.size(); i != e; ++i) {
1031 Value *Cond = new ICmpInst(ICmpInst::ICMP_EQ, FieldMallocs[i],
1032 Constant::getNullValue(FieldMallocs[i]->getType()),
1035 RunningOr = Cond; // First seteq
1037 RunningOr = BinaryOperator::createOr(RunningOr, Cond, "tmp", MI);
1040 // Split the basic block at the old malloc.
1041 BasicBlock *OrigBB = MI->getParent();
1042 BasicBlock *ContBB = OrigBB->splitBasicBlock(MI, "malloc_cont");
1044 // Create the block to check the first condition. Put all these blocks at the
1045 // end of the function as they are unlikely to be executed.
1046 BasicBlock *NullPtrBlock = new BasicBlock("malloc_ret_null",
1047 OrigBB->getParent());
1049 // Remove the uncond branch from OrigBB to ContBB, turning it into a cond
1050 // branch on RunningOr.
1051 OrigBB->getTerminator()->eraseFromParent();
1052 new BranchInst(NullPtrBlock, ContBB, RunningOr, OrigBB);
1054 // Within the NullPtrBlock, we need to emit a comparison and branch for each
1055 // pointer, because some may be null while others are not.
1056 for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) {
1057 Value *GVVal = new LoadInst(FieldGlobals[i], "tmp", NullPtrBlock);
1058 Value *Cmp = new ICmpInst(ICmpInst::ICMP_NE, GVVal,
1059 Constant::getNullValue(GVVal->getType()),
1060 "tmp", NullPtrBlock);
1061 BasicBlock *FreeBlock = new BasicBlock("free_it", OrigBB->getParent());
1062 BasicBlock *NextBlock = new BasicBlock("next", OrigBB->getParent());
1063 new BranchInst(FreeBlock, NextBlock, Cmp, NullPtrBlock);
1065 // Fill in FreeBlock.
1066 new FreeInst(GVVal, FreeBlock);
1067 new StoreInst(Constant::getNullValue(GVVal->getType()), FieldGlobals[i],
1069 new BranchInst(NextBlock, FreeBlock);
1071 NullPtrBlock = NextBlock;
1074 new BranchInst(ContBB, NullPtrBlock);
1077 // MI is no longer needed, remove it.
1078 MI->eraseFromParent();
1081 // Okay, the malloc site is completely handled. All of the uses of GV are now
1082 // loads, and all uses of those loads are simple. Rewrite them to use loads
1083 // of the per-field globals instead.
1084 while (!GV->use_empty()) {
1085 if (LoadInst *LI = dyn_cast<LoadInst>(GV->use_back())) {
1086 RewriteUsesOfLoadForHeapSRoA(LI, FieldGlobals);
1087 LI->eraseFromParent();
1089 // Must be a store of null.
1090 StoreInst *SI = cast<StoreInst>(GV->use_back());
1091 assert(isa<Constant>(SI->getOperand(0)) &&
1092 cast<Constant>(SI->getOperand(0))->isNullValue() &&
1093 "Unexpected heap-sra user!");
1095 // Insert a store of null into each global.
1096 for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) {
1098 Constant::getNullValue(FieldGlobals[i]->getType()->getElementType());
1099 new StoreInst(Null, FieldGlobals[i], SI);
1101 // Erase the original store.
1102 SI->eraseFromParent();
1106 // The old global is now dead, remove it.
1107 GV->eraseFromParent();
1110 return FieldGlobals[0];
1114 // OptimizeOnceStoredGlobal - Try to optimize globals based on the knowledge
1115 // that only one value (besides its initializer) is ever stored to the global.
1116 static bool OptimizeOnceStoredGlobal(GlobalVariable *GV, Value *StoredOnceVal,
1117 Module::global_iterator &GVI,
1119 if (CastInst *CI = dyn_cast<CastInst>(StoredOnceVal))
1120 StoredOnceVal = CI->getOperand(0);
1121 else if (GetElementPtrInst *GEPI =dyn_cast<GetElementPtrInst>(StoredOnceVal)){
1122 // "getelementptr Ptr, 0, 0, 0" is really just a cast.
1123 bool IsJustACast = true;
1124 for (unsigned i = 1, e = GEPI->getNumOperands(); i != e; ++i)
1125 if (!isa<Constant>(GEPI->getOperand(i)) ||
1126 !cast<Constant>(GEPI->getOperand(i))->isNullValue()) {
1127 IsJustACast = false;
1131 StoredOnceVal = GEPI->getOperand(0);
1134 // If we are dealing with a pointer global that is initialized to null and
1135 // only has one (non-null) value stored into it, then we can optimize any
1136 // users of the loaded value (often calls and loads) that would trap if the
1138 if (isa<PointerType>(GV->getInitializer()->getType()) &&
1139 GV->getInitializer()->isNullValue()) {
1140 if (Constant *SOVC = dyn_cast<Constant>(StoredOnceVal)) {
1141 if (GV->getInitializer()->getType() != SOVC->getType())
1142 SOVC = ConstantExpr::getBitCast(SOVC, GV->getInitializer()->getType());
1144 // Optimize away any trapping uses of the loaded value.
1145 if (OptimizeAwayTrappingUsesOfLoads(GV, SOVC))
1147 } else if (MallocInst *MI = dyn_cast<MallocInst>(StoredOnceVal)) {
1148 // If this is a malloc of an abstract type, don't touch it.
1149 if (!MI->getAllocatedType()->isSized())
1152 // We can't optimize this global unless all uses of it are *known* to be
1153 // of the malloc value, not of the null initializer value (consider a use
1154 // that compares the global's value against zero to see if the malloc has
1155 // been reached). To do this, we check to see if all uses of the global
1156 // would trap if the global were null: this proves that they must all
1157 // happen after the malloc.
1158 if (!AllUsesOfLoadedValueWillTrapIfNull(GV))
1161 // We can't optimize this if the malloc itself is used in a complex way,
1162 // for example, being stored into multiple globals. This allows the
1163 // malloc to be stored into the specified global, loaded setcc'd, and
1164 // GEP'd. These are all things we could transform to using the global
1167 SmallPtrSet<PHINode*, 8> PHIs;
1168 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(MI, GV, PHIs))
1173 // If we have a global that is only initialized with a fixed size malloc,
1174 // transform the program to use global memory instead of malloc'd memory.
1175 // This eliminates dynamic allocation, avoids an indirection accessing the
1176 // data, and exposes the resultant global to further GlobalOpt.
1177 if (ConstantInt *NElements = dyn_cast<ConstantInt>(MI->getArraySize())) {
1178 // Restrict this transformation to only working on small allocations
1179 // (2048 bytes currently), as we don't want to introduce a 16M global or
1181 if (NElements->getZExtValue()*
1182 TD.getTypeSize(MI->getAllocatedType()) < 2048) {
1183 GVI = OptimizeGlobalAddressOfMalloc(GV, MI);
1188 // If the allocation is an array of structures, consider transforming this
1189 // into multiple malloc'd arrays, one for each field. This is basically
1190 // SRoA for malloc'd memory.
1191 if (const StructType *AllocTy =
1192 dyn_cast<StructType>(MI->getAllocatedType())) {
1193 // This the structure has an unreasonable number of fields, leave it
1195 if (AllocTy->getNumElements() <= 16 && AllocTy->getNumElements() > 0 &&
1196 GlobalLoadUsesSimpleEnoughForHeapSRA(GV)) {
1197 GVI = PerformHeapAllocSRoA(GV, MI);
1207 /// ShrinkGlobalToBoolean - At this point, we have learned that the only two
1208 /// values ever stored into GV are its initializer and OtherVal.
1209 static void ShrinkGlobalToBoolean(GlobalVariable *GV, Constant *OtherVal) {
1210 // Create the new global, initializing it to false.
1211 GlobalVariable *NewGV = new GlobalVariable(Type::Int1Ty, false,
1212 GlobalValue::InternalLinkage, ConstantInt::getFalse(),
1215 GV->isThreadLocal());
1216 GV->getParent()->getGlobalList().insert(GV, NewGV);
1218 Constant *InitVal = GV->getInitializer();
1219 assert(InitVal->getType() != Type::Int1Ty && "No reason to shrink to bool!");
1221 // If initialized to zero and storing one into the global, we can use a cast
1222 // instead of a select to synthesize the desired value.
1223 bool IsOneZero = false;
1224 if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal))
1225 IsOneZero = InitVal->isNullValue() && CI->isOne();
1227 while (!GV->use_empty()) {
1228 Instruction *UI = cast<Instruction>(GV->use_back());
1229 if (StoreInst *SI = dyn_cast<StoreInst>(UI)) {
1230 // Change the store into a boolean store.
1231 bool StoringOther = SI->getOperand(0) == OtherVal;
1232 // Only do this if we weren't storing a loaded value.
1234 if (StoringOther || SI->getOperand(0) == InitVal)
1235 StoreVal = ConstantInt::get(Type::Int1Ty, StoringOther);
1237 // Otherwise, we are storing a previously loaded copy. To do this,
1238 // change the copy from copying the original value to just copying the
1240 Instruction *StoredVal = cast<Instruction>(SI->getOperand(0));
1242 // If we're already replaced the input, StoredVal will be a cast or
1243 // select instruction. If not, it will be a load of the original
1245 if (LoadInst *LI = dyn_cast<LoadInst>(StoredVal)) {
1246 assert(LI->getOperand(0) == GV && "Not a copy!");
1247 // Insert a new load, to preserve the saved value.
1248 StoreVal = new LoadInst(NewGV, LI->getName()+".b", LI);
1250 assert((isa<CastInst>(StoredVal) || isa<SelectInst>(StoredVal)) &&
1251 "This is not a form that we understand!");
1252 StoreVal = StoredVal->getOperand(0);
1253 assert(isa<LoadInst>(StoreVal) && "Not a load of NewGV!");
1256 new StoreInst(StoreVal, NewGV, SI);
1257 } else if (!UI->use_empty()) {
1258 // Change the load into a load of bool then a select.
1259 LoadInst *LI = cast<LoadInst>(UI);
1260 LoadInst *NLI = new LoadInst(NewGV, LI->getName()+".b", LI);
1263 NSI = new ZExtInst(NLI, LI->getType(), "", LI);
1265 NSI = new SelectInst(NLI, OtherVal, InitVal, "", LI);
1267 LI->replaceAllUsesWith(NSI);
1269 UI->eraseFromParent();
1272 GV->eraseFromParent();
1276 /// ProcessInternalGlobal - Analyze the specified global variable and optimize
1277 /// it if possible. If we make a change, return true.
1278 bool GlobalOpt::ProcessInternalGlobal(GlobalVariable *GV,
1279 Module::global_iterator &GVI) {
1280 std::set<PHINode*> PHIUsers;
1282 GV->removeDeadConstantUsers();
1284 if (GV->use_empty()) {
1285 DOUT << "GLOBAL DEAD: " << *GV;
1286 GV->eraseFromParent();
1291 if (!AnalyzeGlobal(GV, GS, PHIUsers)) {
1293 cerr << "Global: " << *GV;
1294 cerr << " isLoaded = " << GS.isLoaded << "\n";
1295 cerr << " StoredType = ";
1296 switch (GS.StoredType) {
1297 case GlobalStatus::NotStored: cerr << "NEVER STORED\n"; break;
1298 case GlobalStatus::isInitializerStored: cerr << "INIT STORED\n"; break;
1299 case GlobalStatus::isStoredOnce: cerr << "STORED ONCE\n"; break;
1300 case GlobalStatus::isStored: cerr << "stored\n"; break;
1302 if (GS.StoredType == GlobalStatus::isStoredOnce && GS.StoredOnceValue)
1303 cerr << " StoredOnceValue = " << *GS.StoredOnceValue << "\n";
1304 if (GS.AccessingFunction && !GS.HasMultipleAccessingFunctions)
1305 cerr << " AccessingFunction = " << GS.AccessingFunction->getName()
1307 cerr << " HasMultipleAccessingFunctions = "
1308 << GS.HasMultipleAccessingFunctions << "\n";
1309 cerr << " HasNonInstructionUser = " << GS.HasNonInstructionUser<<"\n";
1310 cerr << " isNotSuitableForSRA = " << GS.isNotSuitableForSRA << "\n";
1314 // If this is a first class global and has only one accessing function
1315 // and this function is main (which we know is not recursive we can make
1316 // this global a local variable) we replace the global with a local alloca
1317 // in this function.
1319 // NOTE: It doesn't make sense to promote non first class types since we
1320 // are just replacing static memory to stack memory.
1321 if (!GS.HasMultipleAccessingFunctions &&
1322 GS.AccessingFunction && !GS.HasNonInstructionUser &&
1323 GV->getType()->getElementType()->isFirstClassType() &&
1324 GS.AccessingFunction->getName() == "main" &&
1325 GS.AccessingFunction->hasExternalLinkage()) {
1326 DOUT << "LOCALIZING GLOBAL: " << *GV;
1327 Instruction* FirstI = GS.AccessingFunction->getEntryBlock().begin();
1328 const Type* ElemTy = GV->getType()->getElementType();
1329 // FIXME: Pass Global's alignment when globals have alignment
1330 AllocaInst* Alloca = new AllocaInst(ElemTy, NULL, GV->getName(), FirstI);
1331 if (!isa<UndefValue>(GV->getInitializer()))
1332 new StoreInst(GV->getInitializer(), Alloca, FirstI);
1334 GV->replaceAllUsesWith(Alloca);
1335 GV->eraseFromParent();
1340 // If the global is never loaded (but may be stored to), it is dead.
1343 DOUT << "GLOBAL NEVER LOADED: " << *GV;
1345 // Delete any stores we can find to the global. We may not be able to
1346 // make it completely dead though.
1347 bool Changed = CleanupConstantGlobalUsers(GV, GV->getInitializer());
1349 // If the global is dead now, delete it.
1350 if (GV->use_empty()) {
1351 GV->eraseFromParent();
1357 } else if (GS.StoredType <= GlobalStatus::isInitializerStored) {
1358 DOUT << "MARKING CONSTANT: " << *GV;
1359 GV->setConstant(true);
1361 // Clean up any obviously simplifiable users now.
1362 CleanupConstantGlobalUsers(GV, GV->getInitializer());
1364 // If the global is dead now, just nuke it.
1365 if (GV->use_empty()) {
1366 DOUT << " *** Marking constant allowed us to simplify "
1367 << "all users and delete global!\n";
1368 GV->eraseFromParent();
1374 } else if (!GS.isNotSuitableForSRA &&
1375 !GV->getInitializer()->getType()->isFirstClassType()) {
1376 if (GlobalVariable *FirstNewGV = SRAGlobal(GV)) {
1377 GVI = FirstNewGV; // Don't skip the newly produced globals!
1380 } else if (GS.StoredType == GlobalStatus::isStoredOnce) {
1381 // If the initial value for the global was an undef value, and if only
1382 // one other value was stored into it, we can just change the
1383 // initializer to be an undef value, then delete all stores to the
1384 // global. This allows us to mark it constant.
1385 if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue))
1386 if (isa<UndefValue>(GV->getInitializer())) {
1387 // Change the initial value here.
1388 GV->setInitializer(SOVConstant);
1390 // Clean up any obviously simplifiable users now.
1391 CleanupConstantGlobalUsers(GV, GV->getInitializer());
1393 if (GV->use_empty()) {
1394 DOUT << " *** Substituting initializer allowed us to "
1395 << "simplify all users and delete global!\n";
1396 GV->eraseFromParent();
1405 // Try to optimize globals based on the knowledge that only one value
1406 // (besides its initializer) is ever stored to the global.
1407 if (OptimizeOnceStoredGlobal(GV, GS.StoredOnceValue, GVI,
1408 getAnalysis<TargetData>()))
1411 // Otherwise, if the global was not a boolean, we can shrink it to be a
1413 if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue))
1414 if (GV->getType()->getElementType() != Type::Int1Ty &&
1415 !GV->getType()->getElementType()->isFloatingPoint() &&
1416 !isa<VectorType>(GV->getType()->getElementType()) &&
1417 !GS.HasPHIUser && !GS.isNotSuitableForSRA) {
1418 DOUT << " *** SHRINKING TO BOOL: " << *GV;
1419 ShrinkGlobalToBoolean(GV, SOVConstant);
1428 /// OnlyCalledDirectly - Return true if the specified function is only called
1429 /// directly. In other words, its address is never taken.
1430 static bool OnlyCalledDirectly(Function *F) {
1431 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){
1432 Instruction *User = dyn_cast<Instruction>(*UI);
1433 if (!User) return false;
1434 if (!isa<CallInst>(User) && !isa<InvokeInst>(User)) return false;
1436 // See if the function address is passed as an argument.
1437 for (unsigned i = 1, e = User->getNumOperands(); i != e; ++i)
1438 if (User->getOperand(i) == F) return false;
1443 /// ChangeCalleesToFastCall - Walk all of the direct calls of the specified
1444 /// function, changing them to FastCC.
1445 static void ChangeCalleesToFastCall(Function *F) {
1446 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){
1447 Instruction *User = cast<Instruction>(*UI);
1448 if (CallInst *CI = dyn_cast<CallInst>(User))
1449 CI->setCallingConv(CallingConv::Fast);
1451 cast<InvokeInst>(User)->setCallingConv(CallingConv::Fast);
1455 bool GlobalOpt::OptimizeFunctions(Module &M) {
1456 bool Changed = false;
1457 // Optimize functions.
1458 for (Module::iterator FI = M.begin(), E = M.end(); FI != E; ) {
1460 F->removeDeadConstantUsers();
1461 if (F->use_empty() && (F->hasInternalLinkage() ||
1462 F->hasLinkOnceLinkage())) {
1463 M.getFunctionList().erase(F);
1466 } else if (F->hasInternalLinkage() &&
1467 F->getCallingConv() == CallingConv::C && !F->isVarArg() &&
1468 OnlyCalledDirectly(F)) {
1469 // If this function has C calling conventions, is not a varargs
1470 // function, and is only called directly, promote it to use the Fast
1471 // calling convention.
1472 F->setCallingConv(CallingConv::Fast);
1473 ChangeCalleesToFastCall(F);
1481 bool GlobalOpt::OptimizeGlobalVars(Module &M) {
1482 bool Changed = false;
1483 for (Module::global_iterator GVI = M.global_begin(), E = M.global_end();
1485 GlobalVariable *GV = GVI++;
1486 if (!GV->isConstant() && GV->hasInternalLinkage() &&
1487 GV->hasInitializer())
1488 Changed |= ProcessInternalGlobal(GV, GVI);
1493 /// FindGlobalCtors - Find the llvm.globalctors list, verifying that all
1494 /// initializers have an init priority of 65535.
1495 GlobalVariable *GlobalOpt::FindGlobalCtors(Module &M) {
1496 for (Module::global_iterator I = M.global_begin(), E = M.global_end();
1498 if (I->getName() == "llvm.global_ctors") {
1499 // Found it, verify it's an array of { int, void()* }.
1500 const ArrayType *ATy =dyn_cast<ArrayType>(I->getType()->getElementType());
1502 const StructType *STy = dyn_cast<StructType>(ATy->getElementType());
1503 if (!STy || STy->getNumElements() != 2 ||
1504 STy->getElementType(0) != Type::Int32Ty) return 0;
1505 const PointerType *PFTy = dyn_cast<PointerType>(STy->getElementType(1));
1506 if (!PFTy) return 0;
1507 const FunctionType *FTy = dyn_cast<FunctionType>(PFTy->getElementType());
1508 if (!FTy || FTy->getReturnType() != Type::VoidTy || FTy->isVarArg() ||
1509 FTy->getNumParams() != 0)
1512 // Verify that the initializer is simple enough for us to handle.
1513 if (!I->hasInitializer()) return 0;
1514 ConstantArray *CA = dyn_cast<ConstantArray>(I->getInitializer());
1516 for (unsigned i = 0, e = CA->getNumOperands(); i != e; ++i)
1517 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(CA->getOperand(i))) {
1518 if (isa<ConstantPointerNull>(CS->getOperand(1)))
1521 // Must have a function or null ptr.
1522 if (!isa<Function>(CS->getOperand(1)))
1525 // Init priority must be standard.
1526 ConstantInt *CI = dyn_cast<ConstantInt>(CS->getOperand(0));
1527 if (!CI || CI->getZExtValue() != 65535)
1538 /// ParseGlobalCtors - Given a llvm.global_ctors list that we can understand,
1539 /// return a list of the functions and null terminator as a vector.
1540 static std::vector<Function*> ParseGlobalCtors(GlobalVariable *GV) {
1541 ConstantArray *CA = cast<ConstantArray>(GV->getInitializer());
1542 std::vector<Function*> Result;
1543 Result.reserve(CA->getNumOperands());
1544 for (unsigned i = 0, e = CA->getNumOperands(); i != e; ++i) {
1545 ConstantStruct *CS = cast<ConstantStruct>(CA->getOperand(i));
1546 Result.push_back(dyn_cast<Function>(CS->getOperand(1)));
1551 /// InstallGlobalCtors - Given a specified llvm.global_ctors list, install the
1552 /// specified array, returning the new global to use.
1553 static GlobalVariable *InstallGlobalCtors(GlobalVariable *GCL,
1554 const std::vector<Function*> &Ctors) {
1555 // If we made a change, reassemble the initializer list.
1556 std::vector<Constant*> CSVals;
1557 CSVals.push_back(ConstantInt::get(Type::Int32Ty, 65535));
1558 CSVals.push_back(0);
1560 // Create the new init list.
1561 std::vector<Constant*> CAList;
1562 for (unsigned i = 0, e = Ctors.size(); i != e; ++i) {
1564 CSVals[1] = Ctors[i];
1566 const Type *FTy = FunctionType::get(Type::VoidTy,
1567 std::vector<const Type*>(), false);
1568 const PointerType *PFTy = PointerType::get(FTy);
1569 CSVals[1] = Constant::getNullValue(PFTy);
1570 CSVals[0] = ConstantInt::get(Type::Int32Ty, 2147483647);
1572 CAList.push_back(ConstantStruct::get(CSVals));
1575 // Create the array initializer.
1576 const Type *StructTy =
1577 cast<ArrayType>(GCL->getType()->getElementType())->getElementType();
1578 Constant *CA = ConstantArray::get(ArrayType::get(StructTy, CAList.size()),
1581 // If we didn't change the number of elements, don't create a new GV.
1582 if (CA->getType() == GCL->getInitializer()->getType()) {
1583 GCL->setInitializer(CA);
1587 // Create the new global and insert it next to the existing list.
1588 GlobalVariable *NGV = new GlobalVariable(CA->getType(), GCL->isConstant(),
1589 GCL->getLinkage(), CA, "",
1591 GCL->isThreadLocal());
1592 GCL->getParent()->getGlobalList().insert(GCL, NGV);
1595 // Nuke the old list, replacing any uses with the new one.
1596 if (!GCL->use_empty()) {
1598 if (V->getType() != GCL->getType())
1599 V = ConstantExpr::getBitCast(V, GCL->getType());
1600 GCL->replaceAllUsesWith(V);
1602 GCL->eraseFromParent();
1611 static Constant *getVal(std::map<Value*, Constant*> &ComputedValues,
1613 if (Constant *CV = dyn_cast<Constant>(V)) return CV;
1614 Constant *R = ComputedValues[V];
1615 assert(R && "Reference to an uncomputed value!");
1619 /// isSimpleEnoughPointerToCommit - Return true if this constant is simple
1620 /// enough for us to understand. In particular, if it is a cast of something,
1621 /// we punt. We basically just support direct accesses to globals and GEP's of
1622 /// globals. This should be kept up to date with CommitValueTo.
1623 static bool isSimpleEnoughPointerToCommit(Constant *C) {
1624 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C)) {
1625 if (!GV->hasExternalLinkage() && !GV->hasInternalLinkage())
1626 return false; // do not allow weak/linkonce/dllimport/dllexport linkage.
1627 return !GV->isDeclaration(); // reject external globals.
1629 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
1630 // Handle a constantexpr gep.
1631 if (CE->getOpcode() == Instruction::GetElementPtr &&
1632 isa<GlobalVariable>(CE->getOperand(0))) {
1633 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
1634 if (!GV->hasExternalLinkage() && !GV->hasInternalLinkage())
1635 return false; // do not allow weak/linkonce/dllimport/dllexport linkage.
1636 return GV->hasInitializer() &&
1637 ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE);
1642 /// EvaluateStoreInto - Evaluate a piece of a constantexpr store into a global
1643 /// initializer. This returns 'Init' modified to reflect 'Val' stored into it.
1644 /// At this point, the GEP operands of Addr [0, OpNo) have been stepped into.
1645 static Constant *EvaluateStoreInto(Constant *Init, Constant *Val,
1646 ConstantExpr *Addr, unsigned OpNo) {
1647 // Base case of the recursion.
1648 if (OpNo == Addr->getNumOperands()) {
1649 assert(Val->getType() == Init->getType() && "Type mismatch!");
1653 if (const StructType *STy = dyn_cast<StructType>(Init->getType())) {
1654 std::vector<Constant*> Elts;
1656 // Break up the constant into its elements.
1657 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(Init)) {
1658 for (unsigned i = 0, e = CS->getNumOperands(); i != e; ++i)
1659 Elts.push_back(CS->getOperand(i));
1660 } else if (isa<ConstantAggregateZero>(Init)) {
1661 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
1662 Elts.push_back(Constant::getNullValue(STy->getElementType(i)));
1663 } else if (isa<UndefValue>(Init)) {
1664 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
1665 Elts.push_back(UndefValue::get(STy->getElementType(i)));
1667 assert(0 && "This code is out of sync with "
1668 " ConstantFoldLoadThroughGEPConstantExpr");
1671 // Replace the element that we are supposed to.
1672 ConstantInt *CU = cast<ConstantInt>(Addr->getOperand(OpNo));
1673 unsigned Idx = CU->getZExtValue();
1674 assert(Idx < STy->getNumElements() && "Struct index out of range!");
1675 Elts[Idx] = EvaluateStoreInto(Elts[Idx], Val, Addr, OpNo+1);
1677 // Return the modified struct.
1678 return ConstantStruct::get(&Elts[0], Elts.size(), STy->isPacked());
1680 ConstantInt *CI = cast<ConstantInt>(Addr->getOperand(OpNo));
1681 const ArrayType *ATy = cast<ArrayType>(Init->getType());
1683 // Break up the array into elements.
1684 std::vector<Constant*> Elts;
1685 if (ConstantArray *CA = dyn_cast<ConstantArray>(Init)) {
1686 for (unsigned i = 0, e = CA->getNumOperands(); i != e; ++i)
1687 Elts.push_back(CA->getOperand(i));
1688 } else if (isa<ConstantAggregateZero>(Init)) {
1689 Constant *Elt = Constant::getNullValue(ATy->getElementType());
1690 Elts.assign(ATy->getNumElements(), Elt);
1691 } else if (isa<UndefValue>(Init)) {
1692 Constant *Elt = UndefValue::get(ATy->getElementType());
1693 Elts.assign(ATy->getNumElements(), Elt);
1695 assert(0 && "This code is out of sync with "
1696 " ConstantFoldLoadThroughGEPConstantExpr");
1699 assert(CI->getZExtValue() < ATy->getNumElements());
1700 Elts[CI->getZExtValue()] =
1701 EvaluateStoreInto(Elts[CI->getZExtValue()], Val, Addr, OpNo+1);
1702 return ConstantArray::get(ATy, Elts);
1706 /// CommitValueTo - We have decided that Addr (which satisfies the predicate
1707 /// isSimpleEnoughPointerToCommit) should get Val as its value. Make it happen.
1708 static void CommitValueTo(Constant *Val, Constant *Addr) {
1709 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Addr)) {
1710 assert(GV->hasInitializer());
1711 GV->setInitializer(Val);
1715 ConstantExpr *CE = cast<ConstantExpr>(Addr);
1716 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
1718 Constant *Init = GV->getInitializer();
1719 Init = EvaluateStoreInto(Init, Val, CE, 2);
1720 GV->setInitializer(Init);
1723 /// ComputeLoadResult - Return the value that would be computed by a load from
1724 /// P after the stores reflected by 'memory' have been performed. If we can't
1725 /// decide, return null.
1726 static Constant *ComputeLoadResult(Constant *P,
1727 const std::map<Constant*, Constant*> &Memory) {
1728 // If this memory location has been recently stored, use the stored value: it
1729 // is the most up-to-date.
1730 std::map<Constant*, Constant*>::const_iterator I = Memory.find(P);
1731 if (I != Memory.end()) return I->second;
1734 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(P)) {
1735 if (GV->hasInitializer())
1736 return GV->getInitializer();
1740 // Handle a constantexpr getelementptr.
1741 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(P))
1742 if (CE->getOpcode() == Instruction::GetElementPtr &&
1743 isa<GlobalVariable>(CE->getOperand(0))) {
1744 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
1745 if (GV->hasInitializer())
1746 return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE);
1749 return 0; // don't know how to evaluate.
1752 /// EvaluateFunction - Evaluate a call to function F, returning true if
1753 /// successful, false if we can't evaluate it. ActualArgs contains the formal
1754 /// arguments for the function.
1755 static bool EvaluateFunction(Function *F, Constant *&RetVal,
1756 const std::vector<Constant*> &ActualArgs,
1757 std::vector<Function*> &CallStack,
1758 std::map<Constant*, Constant*> &MutatedMemory,
1759 std::vector<GlobalVariable*> &AllocaTmps) {
1760 // Check to see if this function is already executing (recursion). If so,
1761 // bail out. TODO: we might want to accept limited recursion.
1762 if (std::find(CallStack.begin(), CallStack.end(), F) != CallStack.end())
1765 CallStack.push_back(F);
1767 /// Values - As we compute SSA register values, we store their contents here.
1768 std::map<Value*, Constant*> Values;
1770 // Initialize arguments to the incoming values specified.
1772 for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end(); AI != E;
1774 Values[AI] = ActualArgs[ArgNo];
1776 /// ExecutedBlocks - We only handle non-looping, non-recursive code. As such,
1777 /// we can only evaluate any one basic block at most once. This set keeps
1778 /// track of what we have executed so we can detect recursive cases etc.
1779 std::set<BasicBlock*> ExecutedBlocks;
1781 // CurInst - The current instruction we're evaluating.
1782 BasicBlock::iterator CurInst = F->begin()->begin();
1784 // This is the main evaluation loop.
1786 Constant *InstResult = 0;
1788 if (StoreInst *SI = dyn_cast<StoreInst>(CurInst)) {
1789 if (SI->isVolatile()) return false; // no volatile accesses.
1790 Constant *Ptr = getVal(Values, SI->getOperand(1));
1791 if (!isSimpleEnoughPointerToCommit(Ptr))
1792 // If this is too complex for us to commit, reject it.
1794 Constant *Val = getVal(Values, SI->getOperand(0));
1795 MutatedMemory[Ptr] = Val;
1796 } else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(CurInst)) {
1797 InstResult = ConstantExpr::get(BO->getOpcode(),
1798 getVal(Values, BO->getOperand(0)),
1799 getVal(Values, BO->getOperand(1)));
1800 } else if (CmpInst *CI = dyn_cast<CmpInst>(CurInst)) {
1801 InstResult = ConstantExpr::getCompare(CI->getPredicate(),
1802 getVal(Values, CI->getOperand(0)),
1803 getVal(Values, CI->getOperand(1)));
1804 } else if (CastInst *CI = dyn_cast<CastInst>(CurInst)) {
1805 InstResult = ConstantExpr::getCast(CI->getOpcode(),
1806 getVal(Values, CI->getOperand(0)),
1808 } else if (SelectInst *SI = dyn_cast<SelectInst>(CurInst)) {
1809 InstResult = ConstantExpr::getSelect(getVal(Values, SI->getOperand(0)),
1810 getVal(Values, SI->getOperand(1)),
1811 getVal(Values, SI->getOperand(2)));
1812 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(CurInst)) {
1813 Constant *P = getVal(Values, GEP->getOperand(0));
1814 SmallVector<Constant*, 8> GEPOps;
1815 for (unsigned i = 1, e = GEP->getNumOperands(); i != e; ++i)
1816 GEPOps.push_back(getVal(Values, GEP->getOperand(i)));
1817 InstResult = ConstantExpr::getGetElementPtr(P, &GEPOps[0], GEPOps.size());
1818 } else if (LoadInst *LI = dyn_cast<LoadInst>(CurInst)) {
1819 if (LI->isVolatile()) return false; // no volatile accesses.
1820 InstResult = ComputeLoadResult(getVal(Values, LI->getOperand(0)),
1822 if (InstResult == 0) return false; // Could not evaluate load.
1823 } else if (AllocaInst *AI = dyn_cast<AllocaInst>(CurInst)) {
1824 if (AI->isArrayAllocation()) return false; // Cannot handle array allocs.
1825 const Type *Ty = AI->getType()->getElementType();
1826 AllocaTmps.push_back(new GlobalVariable(Ty, false,
1827 GlobalValue::InternalLinkage,
1828 UndefValue::get(Ty),
1830 InstResult = AllocaTmps.back();
1831 } else if (CallInst *CI = dyn_cast<CallInst>(CurInst)) {
1832 // Cannot handle inline asm.
1833 if (isa<InlineAsm>(CI->getOperand(0))) return false;
1835 // Resolve function pointers.
1836 Function *Callee = dyn_cast<Function>(getVal(Values, CI->getOperand(0)));
1837 if (!Callee) return false; // Cannot resolve.
1839 std::vector<Constant*> Formals;
1840 for (unsigned i = 1, e = CI->getNumOperands(); i != e; ++i)
1841 Formals.push_back(getVal(Values, CI->getOperand(i)));
1843 if (Callee->isDeclaration()) {
1844 // If this is a function we can constant fold, do it.
1845 if (Constant *C = ConstantFoldCall(Callee, &Formals[0],
1852 if (Callee->getFunctionType()->isVarArg())
1857 // Execute the call, if successful, use the return value.
1858 if (!EvaluateFunction(Callee, RetVal, Formals, CallStack,
1859 MutatedMemory, AllocaTmps))
1861 InstResult = RetVal;
1863 } else if (isa<TerminatorInst>(CurInst)) {
1864 BasicBlock *NewBB = 0;
1865 if (BranchInst *BI = dyn_cast<BranchInst>(CurInst)) {
1866 if (BI->isUnconditional()) {
1867 NewBB = BI->getSuccessor(0);
1870 dyn_cast<ConstantInt>(getVal(Values, BI->getCondition()));
1871 if (!Cond) return false; // Cannot determine.
1873 NewBB = BI->getSuccessor(!Cond->getZExtValue());
1875 } else if (SwitchInst *SI = dyn_cast<SwitchInst>(CurInst)) {
1877 dyn_cast<ConstantInt>(getVal(Values, SI->getCondition()));
1878 if (!Val) return false; // Cannot determine.
1879 NewBB = SI->getSuccessor(SI->findCaseValue(Val));
1880 } else if (ReturnInst *RI = dyn_cast<ReturnInst>(CurInst)) {
1881 if (RI->getNumOperands())
1882 RetVal = getVal(Values, RI->getOperand(0));
1884 CallStack.pop_back(); // return from fn.
1885 return true; // We succeeded at evaluating this ctor!
1887 // invoke, unwind, unreachable.
1888 return false; // Cannot handle this terminator.
1891 // Okay, we succeeded in evaluating this control flow. See if we have
1892 // executed the new block before. If so, we have a looping function,
1893 // which we cannot evaluate in reasonable time.
1894 if (!ExecutedBlocks.insert(NewBB).second)
1895 return false; // looped!
1897 // Okay, we have never been in this block before. Check to see if there
1898 // are any PHI nodes. If so, evaluate them with information about where
1900 BasicBlock *OldBB = CurInst->getParent();
1901 CurInst = NewBB->begin();
1903 for (; (PN = dyn_cast<PHINode>(CurInst)); ++CurInst)
1904 Values[PN] = getVal(Values, PN->getIncomingValueForBlock(OldBB));
1906 // Do NOT increment CurInst. We know that the terminator had no value.
1909 // Did not know how to evaluate this!
1913 if (!CurInst->use_empty())
1914 Values[CurInst] = InstResult;
1916 // Advance program counter.
1921 /// EvaluateStaticConstructor - Evaluate static constructors in the function, if
1922 /// we can. Return true if we can, false otherwise.
1923 static bool EvaluateStaticConstructor(Function *F) {
1924 /// MutatedMemory - For each store we execute, we update this map. Loads
1925 /// check this to get the most up-to-date value. If evaluation is successful,
1926 /// this state is committed to the process.
1927 std::map<Constant*, Constant*> MutatedMemory;
1929 /// AllocaTmps - To 'execute' an alloca, we create a temporary global variable
1930 /// to represent its body. This vector is needed so we can delete the
1931 /// temporary globals when we are done.
1932 std::vector<GlobalVariable*> AllocaTmps;
1934 /// CallStack - This is used to detect recursion. In pathological situations
1935 /// we could hit exponential behavior, but at least there is nothing
1937 std::vector<Function*> CallStack;
1939 // Call the function.
1940 Constant *RetValDummy;
1941 bool EvalSuccess = EvaluateFunction(F, RetValDummy, std::vector<Constant*>(),
1942 CallStack, MutatedMemory, AllocaTmps);
1944 // We succeeded at evaluation: commit the result.
1945 DOUT << "FULLY EVALUATED GLOBAL CTOR FUNCTION '"
1946 << F->getName() << "' to " << MutatedMemory.size()
1948 for (std::map<Constant*, Constant*>::iterator I = MutatedMemory.begin(),
1949 E = MutatedMemory.end(); I != E; ++I)
1950 CommitValueTo(I->second, I->first);
1953 // At this point, we are done interpreting. If we created any 'alloca'
1954 // temporaries, release them now.
1955 while (!AllocaTmps.empty()) {
1956 GlobalVariable *Tmp = AllocaTmps.back();
1957 AllocaTmps.pop_back();
1959 // If there are still users of the alloca, the program is doing something
1960 // silly, e.g. storing the address of the alloca somewhere and using it
1961 // later. Since this is undefined, we'll just make it be null.
1962 if (!Tmp->use_empty())
1963 Tmp->replaceAllUsesWith(Constant::getNullValue(Tmp->getType()));
1972 /// OptimizeGlobalCtorsList - Simplify and evaluation global ctors if possible.
1973 /// Return true if anything changed.
1974 bool GlobalOpt::OptimizeGlobalCtorsList(GlobalVariable *&GCL) {
1975 std::vector<Function*> Ctors = ParseGlobalCtors(GCL);
1976 bool MadeChange = false;
1977 if (Ctors.empty()) return false;
1979 // Loop over global ctors, optimizing them when we can.
1980 for (unsigned i = 0; i != Ctors.size(); ++i) {
1981 Function *F = Ctors[i];
1982 // Found a null terminator in the middle of the list, prune off the rest of
1985 if (i != Ctors.size()-1) {
1992 // We cannot simplify external ctor functions.
1993 if (F->empty()) continue;
1995 // If we can evaluate the ctor at compile time, do.
1996 if (EvaluateStaticConstructor(F)) {
1997 Ctors.erase(Ctors.begin()+i);
2000 ++NumCtorsEvaluated;
2005 if (!MadeChange) return false;
2007 GCL = InstallGlobalCtors(GCL, Ctors);
2012 bool GlobalOpt::runOnModule(Module &M) {
2013 bool Changed = false;
2015 // Try to find the llvm.globalctors list.
2016 GlobalVariable *GlobalCtors = FindGlobalCtors(M);
2018 bool LocalChange = true;
2019 while (LocalChange) {
2020 LocalChange = false;
2022 // Delete functions that are trivially dead, ccc -> fastcc
2023 LocalChange |= OptimizeFunctions(M);
2025 // Optimize global_ctors list.
2027 LocalChange |= OptimizeGlobalCtorsList(GlobalCtors);
2029 // Optimize non-address-taken globals.
2030 LocalChange |= OptimizeGlobalVars(M);
2031 Changed |= LocalChange;
2034 // TODO: Move all global ctors functions to the end of the module for code