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)) {
824 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(cast<Instruction>(*UI),
827 } else if (PHINode *PN = dyn_cast<PHINode>(*UI)) {
828 // PHIs are ok if all uses are ok. Don't infinitely recurse through PHI
831 if (!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,
872 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); UI != E;
874 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
875 // We permit two users of the load: setcc comparing against the null
876 // pointer, and a getelementptr of a specific form.
877 for (Value::use_iterator UI = LI->use_begin(), E = LI->use_end(); UI != E;
879 // Comparison against null is ok.
880 if (ICmpInst *ICI = dyn_cast<ICmpInst>(*UI)) {
881 if (!isa<ConstantPointerNull>(ICI->getOperand(1)))
886 // getelementptr is also ok, but only a simple form.
887 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(*UI)) {
888 // Must index into the array and into the struct.
889 if (GEPI->getNumOperands() < 3)
892 // Otherwise the GEP is ok.
896 if (PHINode *PN = dyn_cast<PHINode>(*UI)) {
897 // We have a phi of a load from the global. We can only handle this
898 // if the other PHI'd values are actually the same. In this case,
899 // the rewriter will just drop the phi entirely.
900 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
901 Value *IV = PN->getIncomingValue(i);
902 if (IV == LI) continue; // Trivial the same.
904 // If the phi'd value is from the malloc that initializes the value,
906 if (IV == MI) continue;
908 // Otherwise, we don't know what it is.
914 // Otherwise we don't know what this is, not ok.
921 /// GetHeapSROALoad - Return the load for the specified field of the HeapSROA'd
922 /// value, lazily creating it on demand.
923 static Value *GetHeapSROALoad(Instruction *Load, unsigned FieldNo,
924 const std::vector<GlobalVariable*> &FieldGlobals,
925 std::vector<Value *> &InsertedLoadsForPtr) {
926 if (InsertedLoadsForPtr.size() <= FieldNo)
927 InsertedLoadsForPtr.resize(FieldNo+1);
928 if (InsertedLoadsForPtr[FieldNo] == 0)
929 InsertedLoadsForPtr[FieldNo] = new LoadInst(FieldGlobals[FieldNo],
930 Load->getName()+".f" +
931 utostr(FieldNo), Load);
932 return InsertedLoadsForPtr[FieldNo];
935 /// RewriteHeapSROALoadUser - Given a load instruction and a value derived from
936 /// the load, rewrite the derived value to use the HeapSRoA'd load.
937 static void RewriteHeapSROALoadUser(LoadInst *Load, Instruction *LoadUser,
938 const std::vector<GlobalVariable*> &FieldGlobals,
939 std::vector<Value *> &InsertedLoadsForPtr) {
940 // If this is a comparison against null, handle it.
941 if (ICmpInst *SCI = dyn_cast<ICmpInst>(LoadUser)) {
942 assert(isa<ConstantPointerNull>(SCI->getOperand(1)));
943 // If we have a setcc of the loaded pointer, we can use a setcc of any
946 if (InsertedLoadsForPtr.empty()) {
947 NPtr = GetHeapSROALoad(Load, 0, FieldGlobals, InsertedLoadsForPtr);
949 NPtr = InsertedLoadsForPtr.back();
952 Value *New = new ICmpInst(SCI->getPredicate(), NPtr,
953 Constant::getNullValue(NPtr->getType()),
954 SCI->getName(), SCI);
955 SCI->replaceAllUsesWith(New);
956 SCI->eraseFromParent();
960 // Handle 'getelementptr Ptr, Idx, uint FieldNo ...'
961 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(LoadUser)) {
962 assert(GEPI->getNumOperands() >= 3 && isa<ConstantInt>(GEPI->getOperand(2))
963 && "Unexpected GEPI!");
965 // Load the pointer for this field.
966 unsigned FieldNo = cast<ConstantInt>(GEPI->getOperand(2))->getZExtValue();
967 Value *NewPtr = GetHeapSROALoad(Load, FieldNo,
968 FieldGlobals, InsertedLoadsForPtr);
970 // Create the new GEP idx vector.
971 SmallVector<Value*, 8> GEPIdx;
972 GEPIdx.push_back(GEPI->getOperand(1));
973 GEPIdx.append(GEPI->op_begin()+3, GEPI->op_end());
975 Value *NGEPI = new GetElementPtrInst(NewPtr, GEPIdx.begin(), GEPIdx.end(),
976 GEPI->getName(), GEPI);
977 GEPI->replaceAllUsesWith(NGEPI);
978 GEPI->eraseFromParent();
982 // Handle PHI nodes. PHI nodes must be merging in the same values, plus
983 // potentially the original malloc. Insert phi nodes for each field, then
984 // process uses of the PHI.
985 PHINode *PN = cast<PHINode>(LoadUser);
986 std::vector<Value *> PHIsForField;
987 PHIsForField.resize(FieldGlobals.size());
988 for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) {
989 Value *LoadV = GetHeapSROALoad(Load, i, FieldGlobals, InsertedLoadsForPtr);
991 PHINode *FieldPN = new PHINode(LoadV->getType(),
992 PN->getName()+"."+utostr(i), PN);
993 // Fill in the predecessor values.
994 for (unsigned pred = 0, e = PN->getNumIncomingValues(); pred != e; ++pred) {
995 // Each predecessor either uses the load or the original malloc.
996 Value *InVal = PN->getIncomingValue(pred);
997 BasicBlock *BB = PN->getIncomingBlock(pred);
999 if (isa<MallocInst>(InVal)) {
1000 // Insert a reload from the global in the predecessor.
1001 NewVal = GetHeapSROALoad(BB->getTerminator(), i, FieldGlobals,
1004 NewVal = InsertedLoadsForPtr[i];
1006 FieldPN->addIncoming(NewVal, BB);
1008 PHIsForField[i] = FieldPN;
1011 // Since PHIsForField specifies a phi for every input value, the lazy inserter
1012 // will never insert a load.
1013 while (!PN->use_empty())
1014 RewriteHeapSROALoadUser(Load, PN->use_back(), FieldGlobals, PHIsForField);
1015 PN->eraseFromParent();
1018 /// RewriteUsesOfLoadForHeapSRoA - We are performing Heap SRoA on a global. Ptr
1019 /// is a value loaded from the global. Eliminate all uses of Ptr, making them
1020 /// use FieldGlobals instead. All uses of loaded values satisfy
1021 /// GlobalLoadUsesSimpleEnoughForHeapSRA.
1022 static void RewriteUsesOfLoadForHeapSRoA(LoadInst *Load,
1023 const std::vector<GlobalVariable*> &FieldGlobals) {
1024 std::vector<Value *> InsertedLoadsForPtr;
1025 //InsertedLoadsForPtr.resize(FieldGlobals.size());
1026 while (!Load->use_empty())
1027 RewriteHeapSROALoadUser(Load, Load->use_back(),
1028 FieldGlobals, InsertedLoadsForPtr);
1031 /// PerformHeapAllocSRoA - MI is an allocation of an array of structures. Break
1032 /// it up into multiple allocations of arrays of the fields.
1033 static GlobalVariable *PerformHeapAllocSRoA(GlobalVariable *GV, MallocInst *MI){
1034 DOUT << "SROA HEAP ALLOC: " << *GV << " MALLOC = " << *MI;
1035 const StructType *STy = cast<StructType>(MI->getAllocatedType());
1037 // There is guaranteed to be at least one use of the malloc (storing
1038 // it into GV). If there are other uses, change them to be uses of
1039 // the global to simplify later code. This also deletes the store
1041 ReplaceUsesOfMallocWithGlobal(MI, GV);
1043 // Okay, at this point, there are no users of the malloc. Insert N
1044 // new mallocs at the same place as MI, and N globals.
1045 std::vector<GlobalVariable*> FieldGlobals;
1046 std::vector<MallocInst*> FieldMallocs;
1048 for (unsigned FieldNo = 0, e = STy->getNumElements(); FieldNo != e;++FieldNo){
1049 const Type *FieldTy = STy->getElementType(FieldNo);
1050 const Type *PFieldTy = PointerType::get(FieldTy);
1052 GlobalVariable *NGV =
1053 new GlobalVariable(PFieldTy, false, GlobalValue::InternalLinkage,
1054 Constant::getNullValue(PFieldTy),
1055 GV->getName() + ".f" + utostr(FieldNo), GV,
1056 GV->isThreadLocal());
1057 FieldGlobals.push_back(NGV);
1059 MallocInst *NMI = new MallocInst(FieldTy, MI->getArraySize(),
1060 MI->getName() + ".f" + utostr(FieldNo),MI);
1061 FieldMallocs.push_back(NMI);
1062 new StoreInst(NMI, NGV, MI);
1065 // The tricky aspect of this transformation is handling the case when malloc
1066 // fails. In the original code, malloc failing would set the result pointer
1067 // of malloc to null. In this case, some mallocs could succeed and others
1068 // could fail. As such, we emit code that looks like this:
1069 // F0 = malloc(field0)
1070 // F1 = malloc(field1)
1071 // F2 = malloc(field2)
1072 // if (F0 == 0 || F1 == 0 || F2 == 0) {
1073 // if (F0) { free(F0); F0 = 0; }
1074 // if (F1) { free(F1); F1 = 0; }
1075 // if (F2) { free(F2); F2 = 0; }
1077 Value *RunningOr = 0;
1078 for (unsigned i = 0, e = FieldMallocs.size(); i != e; ++i) {
1079 Value *Cond = new ICmpInst(ICmpInst::ICMP_EQ, FieldMallocs[i],
1080 Constant::getNullValue(FieldMallocs[i]->getType()),
1083 RunningOr = Cond; // First seteq
1085 RunningOr = BinaryOperator::createOr(RunningOr, Cond, "tmp", MI);
1088 // Split the basic block at the old malloc.
1089 BasicBlock *OrigBB = MI->getParent();
1090 BasicBlock *ContBB = OrigBB->splitBasicBlock(MI, "malloc_cont");
1092 // Create the block to check the first condition. Put all these blocks at the
1093 // end of the function as they are unlikely to be executed.
1094 BasicBlock *NullPtrBlock = new BasicBlock("malloc_ret_null",
1095 OrigBB->getParent());
1097 // Remove the uncond branch from OrigBB to ContBB, turning it into a cond
1098 // branch on RunningOr.
1099 OrigBB->getTerminator()->eraseFromParent();
1100 new BranchInst(NullPtrBlock, ContBB, RunningOr, OrigBB);
1102 // Within the NullPtrBlock, we need to emit a comparison and branch for each
1103 // pointer, because some may be null while others are not.
1104 for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) {
1105 Value *GVVal = new LoadInst(FieldGlobals[i], "tmp", NullPtrBlock);
1106 Value *Cmp = new ICmpInst(ICmpInst::ICMP_NE, GVVal,
1107 Constant::getNullValue(GVVal->getType()),
1108 "tmp", NullPtrBlock);
1109 BasicBlock *FreeBlock = new BasicBlock("free_it", OrigBB->getParent());
1110 BasicBlock *NextBlock = new BasicBlock("next", OrigBB->getParent());
1111 new BranchInst(FreeBlock, NextBlock, Cmp, NullPtrBlock);
1113 // Fill in FreeBlock.
1114 new FreeInst(GVVal, FreeBlock);
1115 new StoreInst(Constant::getNullValue(GVVal->getType()), FieldGlobals[i],
1117 new BranchInst(NextBlock, FreeBlock);
1119 NullPtrBlock = NextBlock;
1122 new BranchInst(ContBB, NullPtrBlock);
1125 // MI is no longer needed, remove it.
1126 MI->eraseFromParent();
1129 // Okay, the malloc site is completely handled. All of the uses of GV are now
1130 // loads, and all uses of those loads are simple. Rewrite them to use loads
1131 // of the per-field globals instead.
1132 while (!GV->use_empty()) {
1133 if (LoadInst *LI = dyn_cast<LoadInst>(GV->use_back())) {
1134 RewriteUsesOfLoadForHeapSRoA(LI, FieldGlobals);
1135 LI->eraseFromParent();
1137 // Must be a store of null.
1138 StoreInst *SI = cast<StoreInst>(GV->use_back());
1139 assert(isa<Constant>(SI->getOperand(0)) &&
1140 cast<Constant>(SI->getOperand(0))->isNullValue() &&
1141 "Unexpected heap-sra user!");
1143 // Insert a store of null into each global.
1144 for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) {
1146 Constant::getNullValue(FieldGlobals[i]->getType()->getElementType());
1147 new StoreInst(Null, FieldGlobals[i], SI);
1149 // Erase the original store.
1150 SI->eraseFromParent();
1154 // The old global is now dead, remove it.
1155 GV->eraseFromParent();
1158 return FieldGlobals[0];
1162 // OptimizeOnceStoredGlobal - Try to optimize globals based on the knowledge
1163 // that only one value (besides its initializer) is ever stored to the global.
1164 static bool OptimizeOnceStoredGlobal(GlobalVariable *GV, Value *StoredOnceVal,
1165 Module::global_iterator &GVI,
1167 if (CastInst *CI = dyn_cast<CastInst>(StoredOnceVal))
1168 StoredOnceVal = CI->getOperand(0);
1169 else if (GetElementPtrInst *GEPI =dyn_cast<GetElementPtrInst>(StoredOnceVal)){
1170 // "getelementptr Ptr, 0, 0, 0" is really just a cast.
1171 bool IsJustACast = true;
1172 for (unsigned i = 1, e = GEPI->getNumOperands(); i != e; ++i)
1173 if (!isa<Constant>(GEPI->getOperand(i)) ||
1174 !cast<Constant>(GEPI->getOperand(i))->isNullValue()) {
1175 IsJustACast = false;
1179 StoredOnceVal = GEPI->getOperand(0);
1182 // If we are dealing with a pointer global that is initialized to null and
1183 // only has one (non-null) value stored into it, then we can optimize any
1184 // users of the loaded value (often calls and loads) that would trap if the
1186 if (isa<PointerType>(GV->getInitializer()->getType()) &&
1187 GV->getInitializer()->isNullValue()) {
1188 if (Constant *SOVC = dyn_cast<Constant>(StoredOnceVal)) {
1189 if (GV->getInitializer()->getType() != SOVC->getType())
1190 SOVC = ConstantExpr::getBitCast(SOVC, GV->getInitializer()->getType());
1192 // Optimize away any trapping uses of the loaded value.
1193 if (OptimizeAwayTrappingUsesOfLoads(GV, SOVC))
1195 } else if (MallocInst *MI = dyn_cast<MallocInst>(StoredOnceVal)) {
1196 // If this is a malloc of an abstract type, don't touch it.
1197 if (!MI->getAllocatedType()->isSized())
1200 // We can't optimize this global unless all uses of it are *known* to be
1201 // of the malloc value, not of the null initializer value (consider a use
1202 // that compares the global's value against zero to see if the malloc has
1203 // been reached). To do this, we check to see if all uses of the global
1204 // would trap if the global were null: this proves that they must all
1205 // happen after the malloc.
1206 if (!AllUsesOfLoadedValueWillTrapIfNull(GV))
1209 // We can't optimize this if the malloc itself is used in a complex way,
1210 // for example, being stored into multiple globals. This allows the
1211 // malloc to be stored into the specified global, loaded setcc'd, and
1212 // GEP'd. These are all things we could transform to using the global
1215 SmallPtrSet<PHINode*, 8> PHIs;
1216 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(MI, GV, PHIs))
1221 // If we have a global that is only initialized with a fixed size malloc,
1222 // transform the program to use global memory instead of malloc'd memory.
1223 // This eliminates dynamic allocation, avoids an indirection accessing the
1224 // data, and exposes the resultant global to further GlobalOpt.
1225 if (ConstantInt *NElements = dyn_cast<ConstantInt>(MI->getArraySize())) {
1226 // Restrict this transformation to only working on small allocations
1227 // (2048 bytes currently), as we don't want to introduce a 16M global or
1229 if (NElements->getZExtValue()*
1230 TD.getTypeSize(MI->getAllocatedType()) < 2048) {
1231 GVI = OptimizeGlobalAddressOfMalloc(GV, MI);
1236 // If the allocation is an array of structures, consider transforming this
1237 // into multiple malloc'd arrays, one for each field. This is basically
1238 // SRoA for malloc'd memory.
1239 if (const StructType *AllocTy =
1240 dyn_cast<StructType>(MI->getAllocatedType())) {
1241 // This the structure has an unreasonable number of fields, leave it
1243 if (AllocTy->getNumElements() <= 16 && AllocTy->getNumElements() > 0 &&
1244 GlobalLoadUsesSimpleEnoughForHeapSRA(GV, MI)) {
1245 GVI = PerformHeapAllocSRoA(GV, MI);
1255 /// ShrinkGlobalToBoolean - At this point, we have learned that the only two
1256 /// values ever stored into GV are its initializer and OtherVal.
1257 static void ShrinkGlobalToBoolean(GlobalVariable *GV, Constant *OtherVal) {
1258 // Create the new global, initializing it to false.
1259 GlobalVariable *NewGV = new GlobalVariable(Type::Int1Ty, false,
1260 GlobalValue::InternalLinkage, ConstantInt::getFalse(),
1263 GV->isThreadLocal());
1264 GV->getParent()->getGlobalList().insert(GV, NewGV);
1266 Constant *InitVal = GV->getInitializer();
1267 assert(InitVal->getType() != Type::Int1Ty && "No reason to shrink to bool!");
1269 // If initialized to zero and storing one into the global, we can use a cast
1270 // instead of a select to synthesize the desired value.
1271 bool IsOneZero = false;
1272 if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal))
1273 IsOneZero = InitVal->isNullValue() && CI->isOne();
1275 while (!GV->use_empty()) {
1276 Instruction *UI = cast<Instruction>(GV->use_back());
1277 if (StoreInst *SI = dyn_cast<StoreInst>(UI)) {
1278 // Change the store into a boolean store.
1279 bool StoringOther = SI->getOperand(0) == OtherVal;
1280 // Only do this if we weren't storing a loaded value.
1282 if (StoringOther || SI->getOperand(0) == InitVal)
1283 StoreVal = ConstantInt::get(Type::Int1Ty, StoringOther);
1285 // Otherwise, we are storing a previously loaded copy. To do this,
1286 // change the copy from copying the original value to just copying the
1288 Instruction *StoredVal = cast<Instruction>(SI->getOperand(0));
1290 // If we're already replaced the input, StoredVal will be a cast or
1291 // select instruction. If not, it will be a load of the original
1293 if (LoadInst *LI = dyn_cast<LoadInst>(StoredVal)) {
1294 assert(LI->getOperand(0) == GV && "Not a copy!");
1295 // Insert a new load, to preserve the saved value.
1296 StoreVal = new LoadInst(NewGV, LI->getName()+".b", LI);
1298 assert((isa<CastInst>(StoredVal) || isa<SelectInst>(StoredVal)) &&
1299 "This is not a form that we understand!");
1300 StoreVal = StoredVal->getOperand(0);
1301 assert(isa<LoadInst>(StoreVal) && "Not a load of NewGV!");
1304 new StoreInst(StoreVal, NewGV, SI);
1305 } else if (!UI->use_empty()) {
1306 // Change the load into a load of bool then a select.
1307 LoadInst *LI = cast<LoadInst>(UI);
1308 LoadInst *NLI = new LoadInst(NewGV, LI->getName()+".b", LI);
1311 NSI = new ZExtInst(NLI, LI->getType(), "", LI);
1313 NSI = new SelectInst(NLI, OtherVal, InitVal, "", LI);
1315 LI->replaceAllUsesWith(NSI);
1317 UI->eraseFromParent();
1320 GV->eraseFromParent();
1324 /// ProcessInternalGlobal - Analyze the specified global variable and optimize
1325 /// it if possible. If we make a change, return true.
1326 bool GlobalOpt::ProcessInternalGlobal(GlobalVariable *GV,
1327 Module::global_iterator &GVI) {
1328 std::set<PHINode*> PHIUsers;
1330 GV->removeDeadConstantUsers();
1332 if (GV->use_empty()) {
1333 DOUT << "GLOBAL DEAD: " << *GV;
1334 GV->eraseFromParent();
1339 if (!AnalyzeGlobal(GV, GS, PHIUsers)) {
1341 cerr << "Global: " << *GV;
1342 cerr << " isLoaded = " << GS.isLoaded << "\n";
1343 cerr << " StoredType = ";
1344 switch (GS.StoredType) {
1345 case GlobalStatus::NotStored: cerr << "NEVER STORED\n"; break;
1346 case GlobalStatus::isInitializerStored: cerr << "INIT STORED\n"; break;
1347 case GlobalStatus::isStoredOnce: cerr << "STORED ONCE\n"; break;
1348 case GlobalStatus::isStored: cerr << "stored\n"; break;
1350 if (GS.StoredType == GlobalStatus::isStoredOnce && GS.StoredOnceValue)
1351 cerr << " StoredOnceValue = " << *GS.StoredOnceValue << "\n";
1352 if (GS.AccessingFunction && !GS.HasMultipleAccessingFunctions)
1353 cerr << " AccessingFunction = " << GS.AccessingFunction->getName()
1355 cerr << " HasMultipleAccessingFunctions = "
1356 << GS.HasMultipleAccessingFunctions << "\n";
1357 cerr << " HasNonInstructionUser = " << GS.HasNonInstructionUser<<"\n";
1358 cerr << " isNotSuitableForSRA = " << GS.isNotSuitableForSRA << "\n";
1362 // If this is a first class global and has only one accessing function
1363 // and this function is main (which we know is not recursive we can make
1364 // this global a local variable) we replace the global with a local alloca
1365 // in this function.
1367 // NOTE: It doesn't make sense to promote non first class types since we
1368 // are just replacing static memory to stack memory.
1369 if (!GS.HasMultipleAccessingFunctions &&
1370 GS.AccessingFunction && !GS.HasNonInstructionUser &&
1371 GV->getType()->getElementType()->isFirstClassType() &&
1372 GS.AccessingFunction->getName() == "main" &&
1373 GS.AccessingFunction->hasExternalLinkage()) {
1374 DOUT << "LOCALIZING GLOBAL: " << *GV;
1375 Instruction* FirstI = GS.AccessingFunction->getEntryBlock().begin();
1376 const Type* ElemTy = GV->getType()->getElementType();
1377 // FIXME: Pass Global's alignment when globals have alignment
1378 AllocaInst* Alloca = new AllocaInst(ElemTy, NULL, GV->getName(), FirstI);
1379 if (!isa<UndefValue>(GV->getInitializer()))
1380 new StoreInst(GV->getInitializer(), Alloca, FirstI);
1382 GV->replaceAllUsesWith(Alloca);
1383 GV->eraseFromParent();
1388 // If the global is never loaded (but may be stored to), it is dead.
1391 DOUT << "GLOBAL NEVER LOADED: " << *GV;
1393 // Delete any stores we can find to the global. We may not be able to
1394 // make it completely dead though.
1395 bool Changed = CleanupConstantGlobalUsers(GV, GV->getInitializer());
1397 // If the global is dead now, delete it.
1398 if (GV->use_empty()) {
1399 GV->eraseFromParent();
1405 } else if (GS.StoredType <= GlobalStatus::isInitializerStored) {
1406 DOUT << "MARKING CONSTANT: " << *GV;
1407 GV->setConstant(true);
1409 // Clean up any obviously simplifiable users now.
1410 CleanupConstantGlobalUsers(GV, GV->getInitializer());
1412 // If the global is dead now, just nuke it.
1413 if (GV->use_empty()) {
1414 DOUT << " *** Marking constant allowed us to simplify "
1415 << "all users and delete global!\n";
1416 GV->eraseFromParent();
1422 } else if (!GS.isNotSuitableForSRA &&
1423 !GV->getInitializer()->getType()->isFirstClassType()) {
1424 if (GlobalVariable *FirstNewGV = SRAGlobal(GV)) {
1425 GVI = FirstNewGV; // Don't skip the newly produced globals!
1428 } else if (GS.StoredType == GlobalStatus::isStoredOnce) {
1429 // If the initial value for the global was an undef value, and if only
1430 // one other value was stored into it, we can just change the
1431 // initializer to be an undef value, then delete all stores to the
1432 // global. This allows us to mark it constant.
1433 if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue))
1434 if (isa<UndefValue>(GV->getInitializer())) {
1435 // Change the initial value here.
1436 GV->setInitializer(SOVConstant);
1438 // Clean up any obviously simplifiable users now.
1439 CleanupConstantGlobalUsers(GV, GV->getInitializer());
1441 if (GV->use_empty()) {
1442 DOUT << " *** Substituting initializer allowed us to "
1443 << "simplify all users and delete global!\n";
1444 GV->eraseFromParent();
1453 // Try to optimize globals based on the knowledge that only one value
1454 // (besides its initializer) is ever stored to the global.
1455 if (OptimizeOnceStoredGlobal(GV, GS.StoredOnceValue, GVI,
1456 getAnalysis<TargetData>()))
1459 // Otherwise, if the global was not a boolean, we can shrink it to be a
1461 if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue))
1462 if (GV->getType()->getElementType() != Type::Int1Ty &&
1463 !GV->getType()->getElementType()->isFloatingPoint() &&
1464 !isa<VectorType>(GV->getType()->getElementType()) &&
1465 !GS.HasPHIUser && !GS.isNotSuitableForSRA) {
1466 DOUT << " *** SHRINKING TO BOOL: " << *GV;
1467 ShrinkGlobalToBoolean(GV, SOVConstant);
1476 /// OnlyCalledDirectly - Return true if the specified function is only called
1477 /// directly. In other words, its address is never taken.
1478 static bool OnlyCalledDirectly(Function *F) {
1479 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){
1480 Instruction *User = dyn_cast<Instruction>(*UI);
1481 if (!User) return false;
1482 if (!isa<CallInst>(User) && !isa<InvokeInst>(User)) return false;
1484 // See if the function address is passed as an argument.
1485 for (unsigned i = 1, e = User->getNumOperands(); i != e; ++i)
1486 if (User->getOperand(i) == F) return false;
1491 /// ChangeCalleesToFastCall - Walk all of the direct calls of the specified
1492 /// function, changing them to FastCC.
1493 static void ChangeCalleesToFastCall(Function *F) {
1494 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){
1495 Instruction *User = cast<Instruction>(*UI);
1496 if (CallInst *CI = dyn_cast<CallInst>(User))
1497 CI->setCallingConv(CallingConv::Fast);
1499 cast<InvokeInst>(User)->setCallingConv(CallingConv::Fast);
1503 bool GlobalOpt::OptimizeFunctions(Module &M) {
1504 bool Changed = false;
1505 // Optimize functions.
1506 for (Module::iterator FI = M.begin(), E = M.end(); FI != E; ) {
1508 F->removeDeadConstantUsers();
1509 if (F->use_empty() && (F->hasInternalLinkage() ||
1510 F->hasLinkOnceLinkage())) {
1511 M.getFunctionList().erase(F);
1514 } else if (F->hasInternalLinkage() &&
1515 F->getCallingConv() == CallingConv::C && !F->isVarArg() &&
1516 OnlyCalledDirectly(F)) {
1517 // If this function has C calling conventions, is not a varargs
1518 // function, and is only called directly, promote it to use the Fast
1519 // calling convention.
1520 F->setCallingConv(CallingConv::Fast);
1521 ChangeCalleesToFastCall(F);
1529 bool GlobalOpt::OptimizeGlobalVars(Module &M) {
1530 bool Changed = false;
1531 for (Module::global_iterator GVI = M.global_begin(), E = M.global_end();
1533 GlobalVariable *GV = GVI++;
1534 if (!GV->isConstant() && GV->hasInternalLinkage() &&
1535 GV->hasInitializer())
1536 Changed |= ProcessInternalGlobal(GV, GVI);
1541 /// FindGlobalCtors - Find the llvm.globalctors list, verifying that all
1542 /// initializers have an init priority of 65535.
1543 GlobalVariable *GlobalOpt::FindGlobalCtors(Module &M) {
1544 for (Module::global_iterator I = M.global_begin(), E = M.global_end();
1546 if (I->getName() == "llvm.global_ctors") {
1547 // Found it, verify it's an array of { int, void()* }.
1548 const ArrayType *ATy =dyn_cast<ArrayType>(I->getType()->getElementType());
1550 const StructType *STy = dyn_cast<StructType>(ATy->getElementType());
1551 if (!STy || STy->getNumElements() != 2 ||
1552 STy->getElementType(0) != Type::Int32Ty) return 0;
1553 const PointerType *PFTy = dyn_cast<PointerType>(STy->getElementType(1));
1554 if (!PFTy) return 0;
1555 const FunctionType *FTy = dyn_cast<FunctionType>(PFTy->getElementType());
1556 if (!FTy || FTy->getReturnType() != Type::VoidTy || FTy->isVarArg() ||
1557 FTy->getNumParams() != 0)
1560 // Verify that the initializer is simple enough for us to handle.
1561 if (!I->hasInitializer()) return 0;
1562 ConstantArray *CA = dyn_cast<ConstantArray>(I->getInitializer());
1564 for (unsigned i = 0, e = CA->getNumOperands(); i != e; ++i)
1565 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(CA->getOperand(i))) {
1566 if (isa<ConstantPointerNull>(CS->getOperand(1)))
1569 // Must have a function or null ptr.
1570 if (!isa<Function>(CS->getOperand(1)))
1573 // Init priority must be standard.
1574 ConstantInt *CI = dyn_cast<ConstantInt>(CS->getOperand(0));
1575 if (!CI || CI->getZExtValue() != 65535)
1586 /// ParseGlobalCtors - Given a llvm.global_ctors list that we can understand,
1587 /// return a list of the functions and null terminator as a vector.
1588 static std::vector<Function*> ParseGlobalCtors(GlobalVariable *GV) {
1589 ConstantArray *CA = cast<ConstantArray>(GV->getInitializer());
1590 std::vector<Function*> Result;
1591 Result.reserve(CA->getNumOperands());
1592 for (unsigned i = 0, e = CA->getNumOperands(); i != e; ++i) {
1593 ConstantStruct *CS = cast<ConstantStruct>(CA->getOperand(i));
1594 Result.push_back(dyn_cast<Function>(CS->getOperand(1)));
1599 /// InstallGlobalCtors - Given a specified llvm.global_ctors list, install the
1600 /// specified array, returning the new global to use.
1601 static GlobalVariable *InstallGlobalCtors(GlobalVariable *GCL,
1602 const std::vector<Function*> &Ctors) {
1603 // If we made a change, reassemble the initializer list.
1604 std::vector<Constant*> CSVals;
1605 CSVals.push_back(ConstantInt::get(Type::Int32Ty, 65535));
1606 CSVals.push_back(0);
1608 // Create the new init list.
1609 std::vector<Constant*> CAList;
1610 for (unsigned i = 0, e = Ctors.size(); i != e; ++i) {
1612 CSVals[1] = Ctors[i];
1614 const Type *FTy = FunctionType::get(Type::VoidTy,
1615 std::vector<const Type*>(), false);
1616 const PointerType *PFTy = PointerType::get(FTy);
1617 CSVals[1] = Constant::getNullValue(PFTy);
1618 CSVals[0] = ConstantInt::get(Type::Int32Ty, 2147483647);
1620 CAList.push_back(ConstantStruct::get(CSVals));
1623 // Create the array initializer.
1624 const Type *StructTy =
1625 cast<ArrayType>(GCL->getType()->getElementType())->getElementType();
1626 Constant *CA = ConstantArray::get(ArrayType::get(StructTy, CAList.size()),
1629 // If we didn't change the number of elements, don't create a new GV.
1630 if (CA->getType() == GCL->getInitializer()->getType()) {
1631 GCL->setInitializer(CA);
1635 // Create the new global and insert it next to the existing list.
1636 GlobalVariable *NGV = new GlobalVariable(CA->getType(), GCL->isConstant(),
1637 GCL->getLinkage(), CA, "",
1639 GCL->isThreadLocal());
1640 GCL->getParent()->getGlobalList().insert(GCL, NGV);
1643 // Nuke the old list, replacing any uses with the new one.
1644 if (!GCL->use_empty()) {
1646 if (V->getType() != GCL->getType())
1647 V = ConstantExpr::getBitCast(V, GCL->getType());
1648 GCL->replaceAllUsesWith(V);
1650 GCL->eraseFromParent();
1659 static Constant *getVal(std::map<Value*, Constant*> &ComputedValues,
1661 if (Constant *CV = dyn_cast<Constant>(V)) return CV;
1662 Constant *R = ComputedValues[V];
1663 assert(R && "Reference to an uncomputed value!");
1667 /// isSimpleEnoughPointerToCommit - Return true if this constant is simple
1668 /// enough for us to understand. In particular, if it is a cast of something,
1669 /// we punt. We basically just support direct accesses to globals and GEP's of
1670 /// globals. This should be kept up to date with CommitValueTo.
1671 static bool isSimpleEnoughPointerToCommit(Constant *C) {
1672 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C)) {
1673 if (!GV->hasExternalLinkage() && !GV->hasInternalLinkage())
1674 return false; // do not allow weak/linkonce/dllimport/dllexport linkage.
1675 return !GV->isDeclaration(); // reject external globals.
1677 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
1678 // Handle a constantexpr gep.
1679 if (CE->getOpcode() == Instruction::GetElementPtr &&
1680 isa<GlobalVariable>(CE->getOperand(0))) {
1681 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
1682 if (!GV->hasExternalLinkage() && !GV->hasInternalLinkage())
1683 return false; // do not allow weak/linkonce/dllimport/dllexport linkage.
1684 return GV->hasInitializer() &&
1685 ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE);
1690 /// EvaluateStoreInto - Evaluate a piece of a constantexpr store into a global
1691 /// initializer. This returns 'Init' modified to reflect 'Val' stored into it.
1692 /// At this point, the GEP operands of Addr [0, OpNo) have been stepped into.
1693 static Constant *EvaluateStoreInto(Constant *Init, Constant *Val,
1694 ConstantExpr *Addr, unsigned OpNo) {
1695 // Base case of the recursion.
1696 if (OpNo == Addr->getNumOperands()) {
1697 assert(Val->getType() == Init->getType() && "Type mismatch!");
1701 if (const StructType *STy = dyn_cast<StructType>(Init->getType())) {
1702 std::vector<Constant*> Elts;
1704 // Break up the constant into its elements.
1705 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(Init)) {
1706 for (unsigned i = 0, e = CS->getNumOperands(); i != e; ++i)
1707 Elts.push_back(CS->getOperand(i));
1708 } else if (isa<ConstantAggregateZero>(Init)) {
1709 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
1710 Elts.push_back(Constant::getNullValue(STy->getElementType(i)));
1711 } else if (isa<UndefValue>(Init)) {
1712 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
1713 Elts.push_back(UndefValue::get(STy->getElementType(i)));
1715 assert(0 && "This code is out of sync with "
1716 " ConstantFoldLoadThroughGEPConstantExpr");
1719 // Replace the element that we are supposed to.
1720 ConstantInt *CU = cast<ConstantInt>(Addr->getOperand(OpNo));
1721 unsigned Idx = CU->getZExtValue();
1722 assert(Idx < STy->getNumElements() && "Struct index out of range!");
1723 Elts[Idx] = EvaluateStoreInto(Elts[Idx], Val, Addr, OpNo+1);
1725 // Return the modified struct.
1726 return ConstantStruct::get(&Elts[0], Elts.size(), STy->isPacked());
1728 ConstantInt *CI = cast<ConstantInt>(Addr->getOperand(OpNo));
1729 const ArrayType *ATy = cast<ArrayType>(Init->getType());
1731 // Break up the array into elements.
1732 std::vector<Constant*> Elts;
1733 if (ConstantArray *CA = dyn_cast<ConstantArray>(Init)) {
1734 for (unsigned i = 0, e = CA->getNumOperands(); i != e; ++i)
1735 Elts.push_back(CA->getOperand(i));
1736 } else if (isa<ConstantAggregateZero>(Init)) {
1737 Constant *Elt = Constant::getNullValue(ATy->getElementType());
1738 Elts.assign(ATy->getNumElements(), Elt);
1739 } else if (isa<UndefValue>(Init)) {
1740 Constant *Elt = UndefValue::get(ATy->getElementType());
1741 Elts.assign(ATy->getNumElements(), Elt);
1743 assert(0 && "This code is out of sync with "
1744 " ConstantFoldLoadThroughGEPConstantExpr");
1747 assert(CI->getZExtValue() < ATy->getNumElements());
1748 Elts[CI->getZExtValue()] =
1749 EvaluateStoreInto(Elts[CI->getZExtValue()], Val, Addr, OpNo+1);
1750 return ConstantArray::get(ATy, Elts);
1754 /// CommitValueTo - We have decided that Addr (which satisfies the predicate
1755 /// isSimpleEnoughPointerToCommit) should get Val as its value. Make it happen.
1756 static void CommitValueTo(Constant *Val, Constant *Addr) {
1757 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Addr)) {
1758 assert(GV->hasInitializer());
1759 GV->setInitializer(Val);
1763 ConstantExpr *CE = cast<ConstantExpr>(Addr);
1764 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
1766 Constant *Init = GV->getInitializer();
1767 Init = EvaluateStoreInto(Init, Val, CE, 2);
1768 GV->setInitializer(Init);
1771 /// ComputeLoadResult - Return the value that would be computed by a load from
1772 /// P after the stores reflected by 'memory' have been performed. If we can't
1773 /// decide, return null.
1774 static Constant *ComputeLoadResult(Constant *P,
1775 const std::map<Constant*, Constant*> &Memory) {
1776 // If this memory location has been recently stored, use the stored value: it
1777 // is the most up-to-date.
1778 std::map<Constant*, Constant*>::const_iterator I = Memory.find(P);
1779 if (I != Memory.end()) return I->second;
1782 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(P)) {
1783 if (GV->hasInitializer())
1784 return GV->getInitializer();
1788 // Handle a constantexpr getelementptr.
1789 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(P))
1790 if (CE->getOpcode() == Instruction::GetElementPtr &&
1791 isa<GlobalVariable>(CE->getOperand(0))) {
1792 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
1793 if (GV->hasInitializer())
1794 return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE);
1797 return 0; // don't know how to evaluate.
1800 /// EvaluateFunction - Evaluate a call to function F, returning true if
1801 /// successful, false if we can't evaluate it. ActualArgs contains the formal
1802 /// arguments for the function.
1803 static bool EvaluateFunction(Function *F, Constant *&RetVal,
1804 const std::vector<Constant*> &ActualArgs,
1805 std::vector<Function*> &CallStack,
1806 std::map<Constant*, Constant*> &MutatedMemory,
1807 std::vector<GlobalVariable*> &AllocaTmps) {
1808 // Check to see if this function is already executing (recursion). If so,
1809 // bail out. TODO: we might want to accept limited recursion.
1810 if (std::find(CallStack.begin(), CallStack.end(), F) != CallStack.end())
1813 CallStack.push_back(F);
1815 /// Values - As we compute SSA register values, we store their contents here.
1816 std::map<Value*, Constant*> Values;
1818 // Initialize arguments to the incoming values specified.
1820 for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end(); AI != E;
1822 Values[AI] = ActualArgs[ArgNo];
1824 /// ExecutedBlocks - We only handle non-looping, non-recursive code. As such,
1825 /// we can only evaluate any one basic block at most once. This set keeps
1826 /// track of what we have executed so we can detect recursive cases etc.
1827 std::set<BasicBlock*> ExecutedBlocks;
1829 // CurInst - The current instruction we're evaluating.
1830 BasicBlock::iterator CurInst = F->begin()->begin();
1832 // This is the main evaluation loop.
1834 Constant *InstResult = 0;
1836 if (StoreInst *SI = dyn_cast<StoreInst>(CurInst)) {
1837 if (SI->isVolatile()) return false; // no volatile accesses.
1838 Constant *Ptr = getVal(Values, SI->getOperand(1));
1839 if (!isSimpleEnoughPointerToCommit(Ptr))
1840 // If this is too complex for us to commit, reject it.
1842 Constant *Val = getVal(Values, SI->getOperand(0));
1843 MutatedMemory[Ptr] = Val;
1844 } else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(CurInst)) {
1845 InstResult = ConstantExpr::get(BO->getOpcode(),
1846 getVal(Values, BO->getOperand(0)),
1847 getVal(Values, BO->getOperand(1)));
1848 } else if (CmpInst *CI = dyn_cast<CmpInst>(CurInst)) {
1849 InstResult = ConstantExpr::getCompare(CI->getPredicate(),
1850 getVal(Values, CI->getOperand(0)),
1851 getVal(Values, CI->getOperand(1)));
1852 } else if (CastInst *CI = dyn_cast<CastInst>(CurInst)) {
1853 InstResult = ConstantExpr::getCast(CI->getOpcode(),
1854 getVal(Values, CI->getOperand(0)),
1856 } else if (SelectInst *SI = dyn_cast<SelectInst>(CurInst)) {
1857 InstResult = ConstantExpr::getSelect(getVal(Values, SI->getOperand(0)),
1858 getVal(Values, SI->getOperand(1)),
1859 getVal(Values, SI->getOperand(2)));
1860 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(CurInst)) {
1861 Constant *P = getVal(Values, GEP->getOperand(0));
1862 SmallVector<Constant*, 8> GEPOps;
1863 for (unsigned i = 1, e = GEP->getNumOperands(); i != e; ++i)
1864 GEPOps.push_back(getVal(Values, GEP->getOperand(i)));
1865 InstResult = ConstantExpr::getGetElementPtr(P, &GEPOps[0], GEPOps.size());
1866 } else if (LoadInst *LI = dyn_cast<LoadInst>(CurInst)) {
1867 if (LI->isVolatile()) return false; // no volatile accesses.
1868 InstResult = ComputeLoadResult(getVal(Values, LI->getOperand(0)),
1870 if (InstResult == 0) return false; // Could not evaluate load.
1871 } else if (AllocaInst *AI = dyn_cast<AllocaInst>(CurInst)) {
1872 if (AI->isArrayAllocation()) return false; // Cannot handle array allocs.
1873 const Type *Ty = AI->getType()->getElementType();
1874 AllocaTmps.push_back(new GlobalVariable(Ty, false,
1875 GlobalValue::InternalLinkage,
1876 UndefValue::get(Ty),
1878 InstResult = AllocaTmps.back();
1879 } else if (CallInst *CI = dyn_cast<CallInst>(CurInst)) {
1880 // Cannot handle inline asm.
1881 if (isa<InlineAsm>(CI->getOperand(0))) return false;
1883 // Resolve function pointers.
1884 Function *Callee = dyn_cast<Function>(getVal(Values, CI->getOperand(0)));
1885 if (!Callee) return false; // Cannot resolve.
1887 std::vector<Constant*> Formals;
1888 for (unsigned i = 1, e = CI->getNumOperands(); i != e; ++i)
1889 Formals.push_back(getVal(Values, CI->getOperand(i)));
1891 if (Callee->isDeclaration()) {
1892 // If this is a function we can constant fold, do it.
1893 if (Constant *C = ConstantFoldCall(Callee, &Formals[0],
1900 if (Callee->getFunctionType()->isVarArg())
1905 // Execute the call, if successful, use the return value.
1906 if (!EvaluateFunction(Callee, RetVal, Formals, CallStack,
1907 MutatedMemory, AllocaTmps))
1909 InstResult = RetVal;
1911 } else if (isa<TerminatorInst>(CurInst)) {
1912 BasicBlock *NewBB = 0;
1913 if (BranchInst *BI = dyn_cast<BranchInst>(CurInst)) {
1914 if (BI->isUnconditional()) {
1915 NewBB = BI->getSuccessor(0);
1918 dyn_cast<ConstantInt>(getVal(Values, BI->getCondition()));
1919 if (!Cond) return false; // Cannot determine.
1921 NewBB = BI->getSuccessor(!Cond->getZExtValue());
1923 } else if (SwitchInst *SI = dyn_cast<SwitchInst>(CurInst)) {
1925 dyn_cast<ConstantInt>(getVal(Values, SI->getCondition()));
1926 if (!Val) return false; // Cannot determine.
1927 NewBB = SI->getSuccessor(SI->findCaseValue(Val));
1928 } else if (ReturnInst *RI = dyn_cast<ReturnInst>(CurInst)) {
1929 if (RI->getNumOperands())
1930 RetVal = getVal(Values, RI->getOperand(0));
1932 CallStack.pop_back(); // return from fn.
1933 return true; // We succeeded at evaluating this ctor!
1935 // invoke, unwind, unreachable.
1936 return false; // Cannot handle this terminator.
1939 // Okay, we succeeded in evaluating this control flow. See if we have
1940 // executed the new block before. If so, we have a looping function,
1941 // which we cannot evaluate in reasonable time.
1942 if (!ExecutedBlocks.insert(NewBB).second)
1943 return false; // looped!
1945 // Okay, we have never been in this block before. Check to see if there
1946 // are any PHI nodes. If so, evaluate them with information about where
1948 BasicBlock *OldBB = CurInst->getParent();
1949 CurInst = NewBB->begin();
1951 for (; (PN = dyn_cast<PHINode>(CurInst)); ++CurInst)
1952 Values[PN] = getVal(Values, PN->getIncomingValueForBlock(OldBB));
1954 // Do NOT increment CurInst. We know that the terminator had no value.
1957 // Did not know how to evaluate this!
1961 if (!CurInst->use_empty())
1962 Values[CurInst] = InstResult;
1964 // Advance program counter.
1969 /// EvaluateStaticConstructor - Evaluate static constructors in the function, if
1970 /// we can. Return true if we can, false otherwise.
1971 static bool EvaluateStaticConstructor(Function *F) {
1972 /// MutatedMemory - For each store we execute, we update this map. Loads
1973 /// check this to get the most up-to-date value. If evaluation is successful,
1974 /// this state is committed to the process.
1975 std::map<Constant*, Constant*> MutatedMemory;
1977 /// AllocaTmps - To 'execute' an alloca, we create a temporary global variable
1978 /// to represent its body. This vector is needed so we can delete the
1979 /// temporary globals when we are done.
1980 std::vector<GlobalVariable*> AllocaTmps;
1982 /// CallStack - This is used to detect recursion. In pathological situations
1983 /// we could hit exponential behavior, but at least there is nothing
1985 std::vector<Function*> CallStack;
1987 // Call the function.
1988 Constant *RetValDummy;
1989 bool EvalSuccess = EvaluateFunction(F, RetValDummy, std::vector<Constant*>(),
1990 CallStack, MutatedMemory, AllocaTmps);
1992 // We succeeded at evaluation: commit the result.
1993 DOUT << "FULLY EVALUATED GLOBAL CTOR FUNCTION '"
1994 << F->getName() << "' to " << MutatedMemory.size()
1996 for (std::map<Constant*, Constant*>::iterator I = MutatedMemory.begin(),
1997 E = MutatedMemory.end(); I != E; ++I)
1998 CommitValueTo(I->second, I->first);
2001 // At this point, we are done interpreting. If we created any 'alloca'
2002 // temporaries, release them now.
2003 while (!AllocaTmps.empty()) {
2004 GlobalVariable *Tmp = AllocaTmps.back();
2005 AllocaTmps.pop_back();
2007 // If there are still users of the alloca, the program is doing something
2008 // silly, e.g. storing the address of the alloca somewhere and using it
2009 // later. Since this is undefined, we'll just make it be null.
2010 if (!Tmp->use_empty())
2011 Tmp->replaceAllUsesWith(Constant::getNullValue(Tmp->getType()));
2020 /// OptimizeGlobalCtorsList - Simplify and evaluation global ctors if possible.
2021 /// Return true if anything changed.
2022 bool GlobalOpt::OptimizeGlobalCtorsList(GlobalVariable *&GCL) {
2023 std::vector<Function*> Ctors = ParseGlobalCtors(GCL);
2024 bool MadeChange = false;
2025 if (Ctors.empty()) return false;
2027 // Loop over global ctors, optimizing them when we can.
2028 for (unsigned i = 0; i != Ctors.size(); ++i) {
2029 Function *F = Ctors[i];
2030 // Found a null terminator in the middle of the list, prune off the rest of
2033 if (i != Ctors.size()-1) {
2040 // We cannot simplify external ctor functions.
2041 if (F->empty()) continue;
2043 // If we can evaluate the ctor at compile time, do.
2044 if (EvaluateStaticConstructor(F)) {
2045 Ctors.erase(Ctors.begin()+i);
2048 ++NumCtorsEvaluated;
2053 if (!MadeChange) return false;
2055 GCL = InstallGlobalCtors(GCL, Ctors);
2060 bool GlobalOpt::runOnModule(Module &M) {
2061 bool Changed = false;
2063 // Try to find the llvm.globalctors list.
2064 GlobalVariable *GlobalCtors = FindGlobalCtors(M);
2066 bool LocalChange = true;
2067 while (LocalChange) {
2068 LocalChange = false;
2070 // Delete functions that are trivially dead, ccc -> fastcc
2071 LocalChange |= OptimizeFunctions(M);
2073 // Optimize global_ctors list.
2075 LocalChange |= OptimizeGlobalCtorsList(GlobalCtors);
2077 // Optimize non-address-taken globals.
2078 LocalChange |= OptimizeGlobalVars(M);
2079 Changed |= LocalChange;
2082 // TODO: Move all global ctors functions to the end of the module for code