1 //===- GlobalOpt.cpp - Optimize Global Variables --------------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This pass transforms simple global variables that never have their address
11 // taken. If obviously true, it marks read/write globals as constant, deletes
12 // variables only stored to, etc.
14 //===----------------------------------------------------------------------===//
16 #define DEBUG_TYPE "globalopt"
17 #include "llvm/Transforms/IPO.h"
18 #include "llvm/CallingConv.h"
19 #include "llvm/Constants.h"
20 #include "llvm/DerivedTypes.h"
21 #include "llvm/Instructions.h"
22 #include "llvm/IntrinsicInst.h"
23 #include "llvm/Module.h"
24 #include "llvm/Pass.h"
25 #include "llvm/Analysis/ConstantFolding.h"
26 #include "llvm/Target/TargetData.h"
27 #include "llvm/Support/Compiler.h"
28 #include "llvm/Support/Debug.h"
29 #include "llvm/Support/GetElementPtrTypeIterator.h"
30 #include "llvm/ADT/SmallPtrSet.h"
31 #include "llvm/ADT/SmallVector.h"
32 #include "llvm/ADT/Statistic.h"
33 #include "llvm/ADT/StringExtras.h"
38 STATISTIC(NumMarked , "Number of globals marked constant");
39 STATISTIC(NumSRA , "Number of aggregate globals broken into scalars");
40 STATISTIC(NumHeapSRA , "Number of heap objects SRA'd");
41 STATISTIC(NumSubstitute,"Number of globals with initializers stored into them");
42 STATISTIC(NumDeleted , "Number of globals deleted");
43 STATISTIC(NumFnDeleted , "Number of functions deleted");
44 STATISTIC(NumGlobUses , "Number of global uses devirtualized");
45 STATISTIC(NumLocalized , "Number of globals localized");
46 STATISTIC(NumShrunkToBool , "Number of global vars shrunk to booleans");
47 STATISTIC(NumFastCallFns , "Number of functions converted to fastcc");
48 STATISTIC(NumCtorsEvaluated, "Number of static ctors evaluated");
51 struct VISIBILITY_HIDDEN GlobalOpt : public ModulePass {
52 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
53 AU.addRequired<TargetData>();
55 static char ID; // Pass identification, replacement for typeid
56 GlobalOpt() : ModulePass((intptr_t)&ID) {}
58 bool runOnModule(Module &M);
61 GlobalVariable *FindGlobalCtors(Module &M);
62 bool OptimizeFunctions(Module &M);
63 bool OptimizeGlobalVars(Module &M);
64 bool OptimizeGlobalCtorsList(GlobalVariable *&GCL);
65 bool ProcessInternalGlobal(GlobalVariable *GV,Module::global_iterator &GVI);
68 char GlobalOpt::ID = 0;
69 RegisterPass<GlobalOpt> X("globalopt", "Global Variable Optimizer");
72 ModulePass *llvm::createGlobalOptimizerPass() { return new GlobalOpt(); }
74 /// GlobalStatus - As we analyze each global, keep track of some information
75 /// about it. If we find out that the address of the global is taken, none of
76 /// this info will be accurate.
77 struct VISIBILITY_HIDDEN GlobalStatus {
78 /// isLoaded - True if the global is ever loaded. If the global isn't ever
79 /// loaded it can be deleted.
82 /// StoredType - Keep track of what stores to the global look like.
85 /// NotStored - There is no store to this global. It can thus be marked
89 /// isInitializerStored - This global is stored to, but the only thing
90 /// stored is the constant it was initialized with. This is only tracked
91 /// for scalar globals.
94 /// isStoredOnce - This global is stored to, but only its initializer and
95 /// one other value is ever stored to it. If this global isStoredOnce, we
96 /// track the value stored to it in StoredOnceValue below. This is only
97 /// tracked for scalar globals.
100 /// isStored - This global is stored to by multiple values or something else
101 /// that we cannot track.
105 /// StoredOnceValue - If only one value (besides the initializer constant) is
106 /// ever stored to this global, keep track of what value it is.
107 Value *StoredOnceValue;
109 /// AccessingFunction/HasMultipleAccessingFunctions - These start out
110 /// null/false. When the first accessing function is noticed, it is recorded.
111 /// When a second different accessing function is noticed,
112 /// HasMultipleAccessingFunctions is set to true.
113 Function *AccessingFunction;
114 bool HasMultipleAccessingFunctions;
116 /// HasNonInstructionUser - Set to true if this global has a user that is not
117 /// an instruction (e.g. a constant expr or GV initializer).
118 bool HasNonInstructionUser;
120 /// HasPHIUser - Set to true if this global has a user that is a PHI node.
123 GlobalStatus() : isLoaded(false), StoredType(NotStored), StoredOnceValue(0),
124 AccessingFunction(0), HasMultipleAccessingFunctions(false),
125 HasNonInstructionUser(false), HasPHIUser(false) {}
130 /// ConstantIsDead - Return true if the specified constant is (transitively)
131 /// dead. The constant may be used by other constants (e.g. constant arrays and
132 /// constant exprs) as long as they are dead, but it cannot be used by anything
134 static bool ConstantIsDead(Constant *C) {
135 if (isa<GlobalValue>(C)) return false;
137 for (Value::use_iterator UI = C->use_begin(), E = C->use_end(); UI != E; ++UI)
138 if (Constant *CU = dyn_cast<Constant>(*UI)) {
139 if (!ConstantIsDead(CU)) return false;
146 /// AnalyzeGlobal - Look at all uses of the global and fill in the GlobalStatus
147 /// structure. If the global has its address taken, return true to indicate we
148 /// can't do anything with it.
150 static bool AnalyzeGlobal(Value *V, GlobalStatus &GS,
151 std::set<PHINode*> &PHIUsers) {
152 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ++UI)
153 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(*UI)) {
154 GS.HasNonInstructionUser = true;
156 if (AnalyzeGlobal(CE, GS, PHIUsers)) return true;
158 } else if (Instruction *I = dyn_cast<Instruction>(*UI)) {
159 if (!GS.HasMultipleAccessingFunctions) {
160 Function *F = I->getParent()->getParent();
161 if (GS.AccessingFunction == 0)
162 GS.AccessingFunction = F;
163 else if (GS.AccessingFunction != F)
164 GS.HasMultipleAccessingFunctions = true;
166 if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
168 if (LI->isVolatile()) return true; // Don't hack on volatile loads.
169 } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
170 // Don't allow a store OF the address, only stores TO the address.
171 if (SI->getOperand(0) == V) return true;
173 if (SI->isVolatile()) return true; // Don't hack on volatile stores.
175 // If this is a direct store to the global (i.e., the global is a scalar
176 // value, not an aggregate), keep more specific information about
178 if (GS.StoredType != GlobalStatus::isStored)
179 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(SI->getOperand(1))){
180 Value *StoredVal = SI->getOperand(0);
181 if (StoredVal == GV->getInitializer()) {
182 if (GS.StoredType < GlobalStatus::isInitializerStored)
183 GS.StoredType = GlobalStatus::isInitializerStored;
184 } else if (isa<LoadInst>(StoredVal) &&
185 cast<LoadInst>(StoredVal)->getOperand(0) == GV) {
187 if (GS.StoredType < GlobalStatus::isInitializerStored)
188 GS.StoredType = GlobalStatus::isInitializerStored;
189 } else if (GS.StoredType < GlobalStatus::isStoredOnce) {
190 GS.StoredType = GlobalStatus::isStoredOnce;
191 GS.StoredOnceValue = StoredVal;
192 } else if (GS.StoredType == GlobalStatus::isStoredOnce &&
193 GS.StoredOnceValue == StoredVal) {
196 GS.StoredType = GlobalStatus::isStored;
199 GS.StoredType = GlobalStatus::isStored;
201 } else if (isa<GetElementPtrInst>(I)) {
202 if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
203 } else if (isa<SelectInst>(I)) {
204 if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
205 } else if (PHINode *PN = dyn_cast<PHINode>(I)) {
206 // PHI nodes we can check just like select or GEP instructions, but we
207 // have to be careful about infinite recursion.
208 if (PHIUsers.insert(PN).second) // Not already visited.
209 if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
210 GS.HasPHIUser = true;
211 } else if (isa<CmpInst>(I)) {
212 } else if (isa<MemCpyInst>(I) || isa<MemMoveInst>(I)) {
213 if (I->getOperand(1) == V)
214 GS.StoredType = GlobalStatus::isStored;
215 if (I->getOperand(2) == V)
217 } else if (isa<MemSetInst>(I)) {
218 assert(I->getOperand(1) == V && "Memset only takes one pointer!");
219 GS.StoredType = GlobalStatus::isStored;
221 return true; // Any other non-load instruction might take address!
223 } else if (Constant *C = dyn_cast<Constant>(*UI)) {
224 GS.HasNonInstructionUser = true;
225 // We might have a dead and dangling constant hanging off of here.
226 if (!ConstantIsDead(C))
229 GS.HasNonInstructionUser = true;
230 // Otherwise must be some other user.
237 static Constant *getAggregateConstantElement(Constant *Agg, Constant *Idx) {
238 ConstantInt *CI = dyn_cast<ConstantInt>(Idx);
240 unsigned IdxV = CI->getZExtValue();
242 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(Agg)) {
243 if (IdxV < CS->getNumOperands()) return CS->getOperand(IdxV);
244 } else if (ConstantArray *CA = dyn_cast<ConstantArray>(Agg)) {
245 if (IdxV < CA->getNumOperands()) return CA->getOperand(IdxV);
246 } else if (ConstantVector *CP = dyn_cast<ConstantVector>(Agg)) {
247 if (IdxV < CP->getNumOperands()) return CP->getOperand(IdxV);
248 } else if (isa<ConstantAggregateZero>(Agg)) {
249 if (const StructType *STy = dyn_cast<StructType>(Agg->getType())) {
250 if (IdxV < STy->getNumElements())
251 return Constant::getNullValue(STy->getElementType(IdxV));
252 } else if (const SequentialType *STy =
253 dyn_cast<SequentialType>(Agg->getType())) {
254 return Constant::getNullValue(STy->getElementType());
256 } else if (isa<UndefValue>(Agg)) {
257 if (const StructType *STy = dyn_cast<StructType>(Agg->getType())) {
258 if (IdxV < STy->getNumElements())
259 return UndefValue::get(STy->getElementType(IdxV));
260 } else if (const SequentialType *STy =
261 dyn_cast<SequentialType>(Agg->getType())) {
262 return UndefValue::get(STy->getElementType());
269 /// CleanupConstantGlobalUsers - We just marked GV constant. Loop over all
270 /// users of the global, cleaning up the obvious ones. This is largely just a
271 /// quick scan over the use list to clean up the easy and obvious cruft. This
272 /// returns true if it made a change.
273 static bool CleanupConstantGlobalUsers(Value *V, Constant *Init) {
274 bool Changed = false;
275 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;) {
278 if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
280 // Replace the load with the initializer.
281 LI->replaceAllUsesWith(Init);
282 LI->eraseFromParent();
285 } else if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
286 // Store must be unreachable or storing Init into the global.
287 SI->eraseFromParent();
289 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U)) {
290 if (CE->getOpcode() == Instruction::GetElementPtr) {
291 Constant *SubInit = 0;
293 SubInit = ConstantFoldLoadThroughGEPConstantExpr(Init, CE);
294 Changed |= CleanupConstantGlobalUsers(CE, SubInit);
295 } else if (CE->getOpcode() == Instruction::BitCast &&
296 isa<PointerType>(CE->getType())) {
297 // Pointer cast, delete any stores and memsets to the global.
298 Changed |= CleanupConstantGlobalUsers(CE, 0);
301 if (CE->use_empty()) {
302 CE->destroyConstant();
305 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) {
306 // Do not transform "gepinst (gep constexpr (GV))" here, because forming
307 // "gepconstexpr (gep constexpr (GV))" will cause the two gep's to fold
308 // and will invalidate our notion of what Init is.
309 Constant *SubInit = 0;
310 if (!isa<ConstantExpr>(GEP->getOperand(0))) {
312 dyn_cast_or_null<ConstantExpr>(ConstantFoldInstruction(GEP));
313 if (Init && CE && CE->getOpcode() == Instruction::GetElementPtr)
314 SubInit = ConstantFoldLoadThroughGEPConstantExpr(Init, CE);
316 Changed |= CleanupConstantGlobalUsers(GEP, SubInit);
318 if (GEP->use_empty()) {
319 GEP->eraseFromParent();
322 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(U)) { // memset/cpy/mv
323 if (MI->getRawDest() == V) {
324 MI->eraseFromParent();
328 } else if (Constant *C = dyn_cast<Constant>(U)) {
329 // If we have a chain of dead constantexprs or other things dangling from
330 // us, and if they are all dead, nuke them without remorse.
331 if (ConstantIsDead(C)) {
332 C->destroyConstant();
333 // This could have invalidated UI, start over from scratch.
334 CleanupConstantGlobalUsers(V, Init);
342 /// isSafeSROAElementUse - Return true if the specified instruction is a safe
343 /// user of a derived expression from a global that we want to SROA.
344 static bool isSafeSROAElementUse(Value *V) {
345 // We might have a dead and dangling constant hanging off of here.
346 if (Constant *C = dyn_cast<Constant>(V))
347 return ConstantIsDead(C);
349 Instruction *I = dyn_cast<Instruction>(V);
350 if (!I) return false;
353 if (isa<LoadInst>(I)) return true;
355 // Stores *to* the pointer are ok.
356 if (StoreInst *SI = dyn_cast<StoreInst>(I))
357 return SI->getOperand(0) != V;
359 // Otherwise, it must be a GEP.
360 GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I);
361 if (GEPI == 0) return false;
363 if (GEPI->getNumOperands() < 3 || !isa<Constant>(GEPI->getOperand(1)) ||
364 !cast<Constant>(GEPI->getOperand(1))->isNullValue())
367 for (Value::use_iterator I = GEPI->use_begin(), E = GEPI->use_end();
369 if (!isSafeSROAElementUse(*I))
375 /// IsUserOfGlobalSafeForSRA - U is a direct user of the specified global value.
376 /// Look at it and its uses and decide whether it is safe to SROA this global.
378 static bool IsUserOfGlobalSafeForSRA(User *U, GlobalValue *GV) {
379 // The user of the global must be a GEP Inst or a ConstantExpr GEP.
380 if (!isa<GetElementPtrInst>(U) &&
381 (!isa<ConstantExpr>(U) ||
382 cast<ConstantExpr>(U)->getOpcode() != Instruction::GetElementPtr))
385 // Check to see if this ConstantExpr GEP is SRA'able. In particular, we
386 // don't like < 3 operand CE's, and we don't like non-constant integer
387 // indices. This enforces that all uses are 'gep GV, 0, C, ...' for some
389 if (U->getNumOperands() < 3 || !isa<Constant>(U->getOperand(1)) ||
390 !cast<Constant>(U->getOperand(1))->isNullValue() ||
391 !isa<ConstantInt>(U->getOperand(2)))
394 gep_type_iterator GEPI = gep_type_begin(U), E = gep_type_end(U);
395 ++GEPI; // Skip over the pointer index.
397 // If this is a use of an array allocation, do a bit more checking for sanity.
398 if (const ArrayType *AT = dyn_cast<ArrayType>(*GEPI)) {
399 uint64_t NumElements = AT->getNumElements();
400 ConstantInt *Idx = cast<ConstantInt>(U->getOperand(2));
402 // Check to make sure that index falls within the array. If not,
403 // something funny is going on, so we won't do the optimization.
405 if (Idx->getZExtValue() >= NumElements)
408 // We cannot scalar repl this level of the array unless any array
409 // sub-indices are in-range constants. In particular, consider:
410 // A[0][i]. We cannot know that the user isn't doing invalid things like
411 // allowing i to index an out-of-range subscript that accesses A[1].
413 // Scalar replacing *just* the outer index of the array is probably not
414 // going to be a win anyway, so just give up.
415 for (++GEPI; // Skip array index.
416 GEPI != E && (isa<ArrayType>(*GEPI) || isa<VectorType>(*GEPI));
418 uint64_t NumElements;
419 if (const ArrayType *SubArrayTy = dyn_cast<ArrayType>(*GEPI))
420 NumElements = SubArrayTy->getNumElements();
422 NumElements = cast<VectorType>(*GEPI)->getNumElements();
424 ConstantInt *IdxVal = dyn_cast<ConstantInt>(GEPI.getOperand());
425 if (!IdxVal || IdxVal->getZExtValue() >= NumElements)
430 for (Value::use_iterator I = U->use_begin(), E = U->use_end(); I != E; ++I)
431 if (!isSafeSROAElementUse(*I))
436 /// GlobalUsersSafeToSRA - Look at all uses of the global and decide whether it
437 /// is safe for us to perform this transformation.
439 static bool GlobalUsersSafeToSRA(GlobalValue *GV) {
440 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end();
442 if (!IsUserOfGlobalSafeForSRA(*UI, GV))
449 /// SRAGlobal - Perform scalar replacement of aggregates on the specified global
450 /// variable. This opens the door for other optimizations by exposing the
451 /// behavior of the program in a more fine-grained way. We have determined that
452 /// this transformation is safe already. We return the first global variable we
453 /// insert so that the caller can reprocess it.
454 static GlobalVariable *SRAGlobal(GlobalVariable *GV) {
455 // Make sure this global only has simple uses that we can SRA.
456 if (!GlobalUsersSafeToSRA(GV))
459 assert(GV->hasInternalLinkage() && !GV->isConstant());
460 Constant *Init = GV->getInitializer();
461 const Type *Ty = Init->getType();
463 std::vector<GlobalVariable*> NewGlobals;
464 Module::GlobalListType &Globals = GV->getParent()->getGlobalList();
466 if (const StructType *STy = dyn_cast<StructType>(Ty)) {
467 NewGlobals.reserve(STy->getNumElements());
468 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
469 Constant *In = getAggregateConstantElement(Init,
470 ConstantInt::get(Type::Int32Ty, i));
471 assert(In && "Couldn't get element of initializer?");
472 GlobalVariable *NGV = new GlobalVariable(STy->getElementType(i), false,
473 GlobalVariable::InternalLinkage,
474 In, GV->getName()+"."+utostr(i),
476 GV->isThreadLocal());
477 Globals.insert(GV, NGV);
478 NewGlobals.push_back(NGV);
480 } else if (const SequentialType *STy = dyn_cast<SequentialType>(Ty)) {
481 unsigned NumElements = 0;
482 if (const ArrayType *ATy = dyn_cast<ArrayType>(STy))
483 NumElements = ATy->getNumElements();
484 else if (const VectorType *PTy = dyn_cast<VectorType>(STy))
485 NumElements = PTy->getNumElements();
487 assert(0 && "Unknown aggregate sequential type!");
489 if (NumElements > 16 && GV->hasNUsesOrMore(16))
490 return 0; // It's not worth it.
491 NewGlobals.reserve(NumElements);
492 for (unsigned i = 0, e = NumElements; i != e; ++i) {
493 Constant *In = getAggregateConstantElement(Init,
494 ConstantInt::get(Type::Int32Ty, i));
495 assert(In && "Couldn't get element of initializer?");
497 GlobalVariable *NGV = new GlobalVariable(STy->getElementType(), false,
498 GlobalVariable::InternalLinkage,
499 In, GV->getName()+"."+utostr(i),
501 GV->isThreadLocal());
502 Globals.insert(GV, NGV);
503 NewGlobals.push_back(NGV);
507 if (NewGlobals.empty())
510 DOUT << "PERFORMING GLOBAL SRA ON: " << *GV;
512 Constant *NullInt = Constant::getNullValue(Type::Int32Ty);
514 // Loop over all of the uses of the global, replacing the constantexpr geps,
515 // with smaller constantexpr geps or direct references.
516 while (!GV->use_empty()) {
517 User *GEP = GV->use_back();
518 assert(((isa<ConstantExpr>(GEP) &&
519 cast<ConstantExpr>(GEP)->getOpcode()==Instruction::GetElementPtr)||
520 isa<GetElementPtrInst>(GEP)) && "NonGEP CE's are not SRAable!");
522 // Ignore the 1th operand, which has to be zero or else the program is quite
523 // broken (undefined). Get the 2nd operand, which is the structure or array
525 unsigned Val = cast<ConstantInt>(GEP->getOperand(2))->getZExtValue();
526 if (Val >= NewGlobals.size()) Val = 0; // Out of bound array access.
528 Value *NewPtr = NewGlobals[Val];
530 // Form a shorter GEP if needed.
531 if (GEP->getNumOperands() > 3)
532 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GEP)) {
533 SmallVector<Constant*, 8> Idxs;
534 Idxs.push_back(NullInt);
535 for (unsigned i = 3, e = CE->getNumOperands(); i != e; ++i)
536 Idxs.push_back(CE->getOperand(i));
537 NewPtr = ConstantExpr::getGetElementPtr(cast<Constant>(NewPtr),
538 &Idxs[0], Idxs.size());
540 GetElementPtrInst *GEPI = cast<GetElementPtrInst>(GEP);
541 SmallVector<Value*, 8> Idxs;
542 Idxs.push_back(NullInt);
543 for (unsigned i = 3, e = GEPI->getNumOperands(); i != e; ++i)
544 Idxs.push_back(GEPI->getOperand(i));
545 NewPtr = new GetElementPtrInst(NewPtr, Idxs.begin(), Idxs.end(),
546 GEPI->getName()+"."+utostr(Val), GEPI);
548 GEP->replaceAllUsesWith(NewPtr);
550 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(GEP))
551 GEPI->eraseFromParent();
553 cast<ConstantExpr>(GEP)->destroyConstant();
556 // Delete the old global, now that it is dead.
560 // Loop over the new globals array deleting any globals that are obviously
561 // dead. This can arise due to scalarization of a structure or an array that
562 // has elements that are dead.
563 unsigned FirstGlobal = 0;
564 for (unsigned i = 0, e = NewGlobals.size(); i != e; ++i)
565 if (NewGlobals[i]->use_empty()) {
566 Globals.erase(NewGlobals[i]);
567 if (FirstGlobal == i) ++FirstGlobal;
570 return FirstGlobal != NewGlobals.size() ? NewGlobals[FirstGlobal] : 0;
573 /// AllUsesOfValueWillTrapIfNull - Return true if all users of the specified
574 /// value will trap if the value is dynamically null. PHIs keeps track of any
575 /// phi nodes we've seen to avoid reprocessing them.
576 static bool AllUsesOfValueWillTrapIfNull(Value *V,
577 SmallPtrSet<PHINode*, 8> &PHIs) {
578 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ++UI)
579 if (isa<LoadInst>(*UI)) {
581 } else if (StoreInst *SI = dyn_cast<StoreInst>(*UI)) {
582 if (SI->getOperand(0) == V) {
583 //cerr << "NONTRAPPING USE: " << **UI;
584 return false; // Storing the value.
586 } else if (CallInst *CI = dyn_cast<CallInst>(*UI)) {
587 if (CI->getOperand(0) != V) {
588 //cerr << "NONTRAPPING USE: " << **UI;
589 return false; // Not calling the ptr
591 } else if (InvokeInst *II = dyn_cast<InvokeInst>(*UI)) {
592 if (II->getOperand(0) != V) {
593 //cerr << "NONTRAPPING USE: " << **UI;
594 return false; // Not calling the ptr
596 } else if (BitCastInst *CI = dyn_cast<BitCastInst>(*UI)) {
597 if (!AllUsesOfValueWillTrapIfNull(CI, PHIs)) return false;
598 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(*UI)) {
599 if (!AllUsesOfValueWillTrapIfNull(GEPI, PHIs)) return false;
600 } else if (PHINode *PN = dyn_cast<PHINode>(*UI)) {
601 // If we've already seen this phi node, ignore it, it has already been
604 return AllUsesOfValueWillTrapIfNull(PN, PHIs);
605 } else if (isa<ICmpInst>(*UI) &&
606 isa<ConstantPointerNull>(UI->getOperand(1))) {
607 // Ignore setcc X, null
609 //cerr << "NONTRAPPING USE: " << **UI;
615 /// AllUsesOfLoadedValueWillTrapIfNull - Return true if all uses of any loads
616 /// from GV will trap if the loaded value is null. Note that this also permits
617 /// comparisons of the loaded value against null, as a special case.
618 static bool AllUsesOfLoadedValueWillTrapIfNull(GlobalVariable *GV) {
619 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); UI!=E; ++UI)
620 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
621 SmallPtrSet<PHINode*, 8> PHIs;
622 if (!AllUsesOfValueWillTrapIfNull(LI, PHIs))
624 } else if (isa<StoreInst>(*UI)) {
625 // Ignore stores to the global.
627 // We don't know or understand this user, bail out.
628 //cerr << "UNKNOWN USER OF GLOBAL!: " << **UI;
635 static bool OptimizeAwayTrappingUsesOfValue(Value *V, Constant *NewV) {
636 bool Changed = false;
637 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ) {
638 Instruction *I = cast<Instruction>(*UI++);
639 if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
640 LI->setOperand(0, NewV);
642 } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
643 if (SI->getOperand(1) == V) {
644 SI->setOperand(1, NewV);
647 } else if (isa<CallInst>(I) || isa<InvokeInst>(I)) {
648 if (I->getOperand(0) == V) {
649 // Calling through the pointer! Turn into a direct call, but be careful
650 // that the pointer is not also being passed as an argument.
651 I->setOperand(0, NewV);
653 bool PassedAsArg = false;
654 for (unsigned i = 1, e = I->getNumOperands(); i != e; ++i)
655 if (I->getOperand(i) == V) {
657 I->setOperand(i, NewV);
661 // Being passed as an argument also. Be careful to not invalidate UI!
665 } else if (CastInst *CI = dyn_cast<CastInst>(I)) {
666 Changed |= OptimizeAwayTrappingUsesOfValue(CI,
667 ConstantExpr::getCast(CI->getOpcode(),
668 NewV, CI->getType()));
669 if (CI->use_empty()) {
671 CI->eraseFromParent();
673 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I)) {
674 // Should handle GEP here.
675 SmallVector<Constant*, 8> Idxs;
676 Idxs.reserve(GEPI->getNumOperands()-1);
677 for (unsigned i = 1, e = GEPI->getNumOperands(); i != e; ++i)
678 if (Constant *C = dyn_cast<Constant>(GEPI->getOperand(i)))
682 if (Idxs.size() == GEPI->getNumOperands()-1)
683 Changed |= OptimizeAwayTrappingUsesOfValue(GEPI,
684 ConstantExpr::getGetElementPtr(NewV, &Idxs[0],
686 if (GEPI->use_empty()) {
688 GEPI->eraseFromParent();
697 /// OptimizeAwayTrappingUsesOfLoads - The specified global has only one non-null
698 /// value stored into it. If there are uses of the loaded value that would trap
699 /// if the loaded value is dynamically null, then we know that they cannot be
700 /// reachable with a null optimize away the load.
701 static bool OptimizeAwayTrappingUsesOfLoads(GlobalVariable *GV, Constant *LV) {
702 std::vector<LoadInst*> Loads;
703 bool Changed = false;
705 // Replace all uses of loads with uses of uses of the stored value.
706 for (Value::use_iterator GUI = GV->use_begin(), E = GV->use_end();
708 if (LoadInst *LI = dyn_cast<LoadInst>(*GUI)) {
710 Changed |= OptimizeAwayTrappingUsesOfValue(LI, LV);
712 // If we get here we could have stores, selects, or phi nodes whose values
714 assert((isa<StoreInst>(*GUI) || isa<PHINode>(*GUI) ||
715 isa<SelectInst>(*GUI) || isa<ConstantExpr>(*GUI)) &&
716 "Only expect load and stores!");
720 DOUT << "OPTIMIZED LOADS FROM STORED ONCE POINTER: " << *GV;
724 // Delete all of the loads we can, keeping track of whether we nuked them all!
725 bool AllLoadsGone = true;
726 while (!Loads.empty()) {
727 LoadInst *L = Loads.back();
728 if (L->use_empty()) {
729 L->eraseFromParent();
732 AllLoadsGone = false;
737 // If we nuked all of the loads, then none of the stores are needed either,
738 // nor is the global.
740 DOUT << " *** GLOBAL NOW DEAD!\n";
741 CleanupConstantGlobalUsers(GV, 0);
742 if (GV->use_empty()) {
743 GV->eraseFromParent();
751 /// ConstantPropUsersOf - Walk the use list of V, constant folding all of the
752 /// instructions that are foldable.
753 static void ConstantPropUsersOf(Value *V) {
754 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; )
755 if (Instruction *I = dyn_cast<Instruction>(*UI++))
756 if (Constant *NewC = ConstantFoldInstruction(I)) {
757 I->replaceAllUsesWith(NewC);
759 // Advance UI to the next non-I use to avoid invalidating it!
760 // Instructions could multiply use V.
761 while (UI != E && *UI == I)
763 I->eraseFromParent();
767 /// OptimizeGlobalAddressOfMalloc - This function takes the specified global
768 /// variable, and transforms the program as if it always contained the result of
769 /// the specified malloc. Because it is always the result of the specified
770 /// malloc, there is no reason to actually DO the malloc. Instead, turn the
771 /// malloc into a global, and any loads of GV as uses of the new global.
772 static GlobalVariable *OptimizeGlobalAddressOfMalloc(GlobalVariable *GV,
774 DOUT << "PROMOTING MALLOC GLOBAL: " << *GV << " MALLOC = " << *MI;
775 ConstantInt *NElements = cast<ConstantInt>(MI->getArraySize());
777 if (NElements->getZExtValue() != 1) {
778 // If we have an array allocation, transform it to a single element
779 // allocation to make the code below simpler.
780 Type *NewTy = ArrayType::get(MI->getAllocatedType(),
781 NElements->getZExtValue());
783 new MallocInst(NewTy, Constant::getNullValue(Type::Int32Ty),
784 MI->getAlignment(), MI->getName(), MI);
786 Indices[0] = Indices[1] = Constant::getNullValue(Type::Int32Ty);
787 Value *NewGEP = new GetElementPtrInst(NewMI, Indices, Indices + 2,
788 NewMI->getName()+".el0", MI);
789 MI->replaceAllUsesWith(NewGEP);
790 MI->eraseFromParent();
794 // Create the new global variable. The contents of the malloc'd memory is
795 // undefined, so initialize with an undef value.
796 Constant *Init = UndefValue::get(MI->getAllocatedType());
797 GlobalVariable *NewGV = new GlobalVariable(MI->getAllocatedType(), false,
798 GlobalValue::InternalLinkage, Init,
799 GV->getName()+".body",
801 GV->isThreadLocal());
802 GV->getParent()->getGlobalList().insert(GV, NewGV);
804 // Anything that used the malloc now uses the global directly.
805 MI->replaceAllUsesWith(NewGV);
807 Constant *RepValue = NewGV;
808 if (NewGV->getType() != GV->getType()->getElementType())
809 RepValue = ConstantExpr::getBitCast(RepValue,
810 GV->getType()->getElementType());
812 // If there is a comparison against null, we will insert a global bool to
813 // keep track of whether the global was initialized yet or not.
814 GlobalVariable *InitBool =
815 new GlobalVariable(Type::Int1Ty, false, GlobalValue::InternalLinkage,
816 ConstantInt::getFalse(), GV->getName()+".init",
817 (Module *)NULL, GV->isThreadLocal());
818 bool InitBoolUsed = false;
820 // Loop over all uses of GV, processing them in turn.
821 std::vector<StoreInst*> Stores;
822 while (!GV->use_empty())
823 if (LoadInst *LI = dyn_cast<LoadInst>(GV->use_back())) {
824 while (!LI->use_empty()) {
825 Use &LoadUse = LI->use_begin().getUse();
826 if (!isa<ICmpInst>(LoadUse.getUser()))
829 ICmpInst *CI = cast<ICmpInst>(LoadUse.getUser());
830 // Replace the cmp X, 0 with a use of the bool value.
831 Value *LV = new LoadInst(InitBool, InitBool->getName()+".val", CI);
833 switch (CI->getPredicate()) {
834 default: assert(0 && "Unknown ICmp Predicate!");
835 case ICmpInst::ICMP_ULT:
836 case ICmpInst::ICMP_SLT:
837 LV = ConstantInt::getFalse(); // X < null -> always false
839 case ICmpInst::ICMP_ULE:
840 case ICmpInst::ICMP_SLE:
841 case ICmpInst::ICMP_EQ:
842 LV = BinaryOperator::createNot(LV, "notinit", CI);
844 case ICmpInst::ICMP_NE:
845 case ICmpInst::ICMP_UGE:
846 case ICmpInst::ICMP_SGE:
847 case ICmpInst::ICMP_UGT:
848 case ICmpInst::ICMP_SGT:
851 CI->replaceAllUsesWith(LV);
852 CI->eraseFromParent();
855 LI->eraseFromParent();
857 StoreInst *SI = cast<StoreInst>(GV->use_back());
858 // The global is initialized when the store to it occurs.
859 new StoreInst(ConstantInt::getTrue(), InitBool, SI);
860 SI->eraseFromParent();
863 // If the initialization boolean was used, insert it, otherwise delete it.
865 while (!InitBool->use_empty()) // Delete initializations
866 cast<Instruction>(InitBool->use_back())->eraseFromParent();
869 GV->getParent()->getGlobalList().insert(GV, InitBool);
872 // Now the GV is dead, nuke it and the malloc.
873 GV->eraseFromParent();
874 MI->eraseFromParent();
876 // To further other optimizations, loop over all users of NewGV and try to
877 // constant prop them. This will promote GEP instructions with constant
878 // indices into GEP constant-exprs, which will allow global-opt to hack on it.
879 ConstantPropUsersOf(NewGV);
880 if (RepValue != NewGV)
881 ConstantPropUsersOf(RepValue);
886 /// ValueIsOnlyUsedLocallyOrStoredToOneGlobal - Scan the use-list of V checking
887 /// to make sure that there are no complex uses of V. We permit simple things
888 /// like dereferencing the pointer, but not storing through the address, unless
889 /// it is to the specified global.
890 static bool ValueIsOnlyUsedLocallyOrStoredToOneGlobal(Instruction *V,
892 SmallPtrSet<PHINode*, 8> &PHIs) {
893 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ++UI)
894 if (isa<LoadInst>(*UI) || isa<CmpInst>(*UI)) {
896 } else if (StoreInst *SI = dyn_cast<StoreInst>(*UI)) {
897 if (SI->getOperand(0) == V && SI->getOperand(1) != GV)
898 return false; // Storing the pointer itself... bad.
899 // Otherwise, storing through it, or storing into GV... fine.
900 } else if (isa<GetElementPtrInst>(*UI)) {
901 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(cast<Instruction>(*UI),
904 } else if (PHINode *PN = dyn_cast<PHINode>(*UI)) {
905 // PHIs are ok if all uses are ok. Don't infinitely recurse through PHI
908 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(PN, GV, PHIs))
916 /// ReplaceUsesOfMallocWithGlobal - The Alloc pointer is stored into GV
917 /// somewhere. Transform all uses of the allocation into loads from the
918 /// global and uses of the resultant pointer. Further, delete the store into
919 /// GV. This assumes that these value pass the
920 /// 'ValueIsOnlyUsedLocallyOrStoredToOneGlobal' predicate.
921 static void ReplaceUsesOfMallocWithGlobal(Instruction *Alloc,
922 GlobalVariable *GV) {
923 while (!Alloc->use_empty()) {
924 Instruction *U = cast<Instruction>(*Alloc->use_begin());
925 Instruction *InsertPt = U;
926 if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
927 // If this is the store of the allocation into the global, remove it.
928 if (SI->getOperand(1) == GV) {
929 SI->eraseFromParent();
932 } else if (PHINode *PN = dyn_cast<PHINode>(U)) {
933 // Insert the load in the corresponding predecessor, not right before the
935 unsigned PredNo = Alloc->use_begin().getOperandNo()/2;
936 InsertPt = PN->getIncomingBlock(PredNo)->getTerminator();
939 // Insert a load from the global, and use it instead of the malloc.
940 Value *NL = new LoadInst(GV, GV->getName()+".val", InsertPt);
941 U->replaceUsesOfWith(Alloc, NL);
945 /// GlobalLoadUsesSimpleEnoughForHeapSRA - If all users of values loaded from
946 /// GV are simple enough to perform HeapSRA, return true.
947 static bool GlobalLoadUsesSimpleEnoughForHeapSRA(GlobalVariable *GV,
949 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); UI != E;
951 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
952 // We permit two users of the load: setcc comparing against the null
953 // pointer, and a getelementptr of a specific form.
954 for (Value::use_iterator UI = LI->use_begin(), E = LI->use_end(); UI != E;
956 // Comparison against null is ok.
957 if (ICmpInst *ICI = dyn_cast<ICmpInst>(*UI)) {
958 if (!isa<ConstantPointerNull>(ICI->getOperand(1)))
963 // getelementptr is also ok, but only a simple form.
964 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(*UI)) {
965 // Must index into the array and into the struct.
966 if (GEPI->getNumOperands() < 3)
969 // Otherwise the GEP is ok.
973 if (PHINode *PN = dyn_cast<PHINode>(*UI)) {
974 // We have a phi of a load from the global. We can only handle this
975 // if the other PHI'd values are actually the same. In this case,
976 // the rewriter will just drop the phi entirely.
977 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
978 Value *IV = PN->getIncomingValue(i);
979 if (IV == LI) continue; // Trivial the same.
981 // If the phi'd value is from the malloc that initializes the value,
983 if (IV == MI) continue;
985 // Otherwise, we don't know what it is.
991 // Otherwise we don't know what this is, not ok.
998 /// GetHeapSROALoad - Return the load for the specified field of the HeapSROA'd
999 /// value, lazily creating it on demand.
1000 static Value *GetHeapSROALoad(Instruction *Load, unsigned FieldNo,
1001 const std::vector<GlobalVariable*> &FieldGlobals,
1002 std::vector<Value *> &InsertedLoadsForPtr) {
1003 if (InsertedLoadsForPtr.size() <= FieldNo)
1004 InsertedLoadsForPtr.resize(FieldNo+1);
1005 if (InsertedLoadsForPtr[FieldNo] == 0)
1006 InsertedLoadsForPtr[FieldNo] = new LoadInst(FieldGlobals[FieldNo],
1007 Load->getName()+".f" +
1008 utostr(FieldNo), Load);
1009 return InsertedLoadsForPtr[FieldNo];
1012 /// RewriteHeapSROALoadUser - Given a load instruction and a value derived from
1013 /// the load, rewrite the derived value to use the HeapSRoA'd load.
1014 static void RewriteHeapSROALoadUser(LoadInst *Load, Instruction *LoadUser,
1015 const std::vector<GlobalVariable*> &FieldGlobals,
1016 std::vector<Value *> &InsertedLoadsForPtr) {
1017 // If this is a comparison against null, handle it.
1018 if (ICmpInst *SCI = dyn_cast<ICmpInst>(LoadUser)) {
1019 assert(isa<ConstantPointerNull>(SCI->getOperand(1)));
1020 // If we have a setcc of the loaded pointer, we can use a setcc of any
1023 if (InsertedLoadsForPtr.empty()) {
1024 NPtr = GetHeapSROALoad(Load, 0, FieldGlobals, InsertedLoadsForPtr);
1026 NPtr = InsertedLoadsForPtr.back();
1029 Value *New = new ICmpInst(SCI->getPredicate(), NPtr,
1030 Constant::getNullValue(NPtr->getType()),
1031 SCI->getName(), SCI);
1032 SCI->replaceAllUsesWith(New);
1033 SCI->eraseFromParent();
1037 // Handle 'getelementptr Ptr, Idx, uint FieldNo ...'
1038 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(LoadUser)) {
1039 assert(GEPI->getNumOperands() >= 3 && isa<ConstantInt>(GEPI->getOperand(2))
1040 && "Unexpected GEPI!");
1042 // Load the pointer for this field.
1043 unsigned FieldNo = cast<ConstantInt>(GEPI->getOperand(2))->getZExtValue();
1044 Value *NewPtr = GetHeapSROALoad(Load, FieldNo,
1045 FieldGlobals, InsertedLoadsForPtr);
1047 // Create the new GEP idx vector.
1048 SmallVector<Value*, 8> GEPIdx;
1049 GEPIdx.push_back(GEPI->getOperand(1));
1050 GEPIdx.append(GEPI->op_begin()+3, GEPI->op_end());
1052 Value *NGEPI = new GetElementPtrInst(NewPtr, GEPIdx.begin(), GEPIdx.end(),
1053 GEPI->getName(), GEPI);
1054 GEPI->replaceAllUsesWith(NGEPI);
1055 GEPI->eraseFromParent();
1059 // Handle PHI nodes. PHI nodes must be merging in the same values, plus
1060 // potentially the original malloc. Insert phi nodes for each field, then
1061 // process uses of the PHI.
1062 PHINode *PN = cast<PHINode>(LoadUser);
1063 std::vector<Value *> PHIsForField;
1064 PHIsForField.resize(FieldGlobals.size());
1065 for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) {
1066 Value *LoadV = GetHeapSROALoad(Load, i, FieldGlobals, InsertedLoadsForPtr);
1068 PHINode *FieldPN = new PHINode(LoadV->getType(),
1069 PN->getName()+"."+utostr(i), PN);
1070 // Fill in the predecessor values.
1071 for (unsigned pred = 0, e = PN->getNumIncomingValues(); pred != e; ++pred) {
1072 // Each predecessor either uses the load or the original malloc.
1073 Value *InVal = PN->getIncomingValue(pred);
1074 BasicBlock *BB = PN->getIncomingBlock(pred);
1076 if (isa<MallocInst>(InVal)) {
1077 // Insert a reload from the global in the predecessor.
1078 NewVal = GetHeapSROALoad(BB->getTerminator(), i, FieldGlobals,
1081 NewVal = InsertedLoadsForPtr[i];
1083 FieldPN->addIncoming(NewVal, BB);
1085 PHIsForField[i] = FieldPN;
1088 // Since PHIsForField specifies a phi for every input value, the lazy inserter
1089 // will never insert a load.
1090 while (!PN->use_empty())
1091 RewriteHeapSROALoadUser(Load, PN->use_back(), FieldGlobals, PHIsForField);
1092 PN->eraseFromParent();
1095 /// RewriteUsesOfLoadForHeapSRoA - We are performing Heap SRoA on a global. Ptr
1096 /// is a value loaded from the global. Eliminate all uses of Ptr, making them
1097 /// use FieldGlobals instead. All uses of loaded values satisfy
1098 /// GlobalLoadUsesSimpleEnoughForHeapSRA.
1099 static void RewriteUsesOfLoadForHeapSRoA(LoadInst *Load,
1100 const std::vector<GlobalVariable*> &FieldGlobals) {
1101 std::vector<Value *> InsertedLoadsForPtr;
1102 //InsertedLoadsForPtr.resize(FieldGlobals.size());
1103 while (!Load->use_empty())
1104 RewriteHeapSROALoadUser(Load, Load->use_back(),
1105 FieldGlobals, InsertedLoadsForPtr);
1108 /// PerformHeapAllocSRoA - MI is an allocation of an array of structures. Break
1109 /// it up into multiple allocations of arrays of the fields.
1110 static GlobalVariable *PerformHeapAllocSRoA(GlobalVariable *GV, MallocInst *MI){
1111 DOUT << "SROA HEAP ALLOC: " << *GV << " MALLOC = " << *MI;
1112 const StructType *STy = cast<StructType>(MI->getAllocatedType());
1114 // There is guaranteed to be at least one use of the malloc (storing
1115 // it into GV). If there are other uses, change them to be uses of
1116 // the global to simplify later code. This also deletes the store
1118 ReplaceUsesOfMallocWithGlobal(MI, GV);
1120 // Okay, at this point, there are no users of the malloc. Insert N
1121 // new mallocs at the same place as MI, and N globals.
1122 std::vector<GlobalVariable*> FieldGlobals;
1123 std::vector<MallocInst*> FieldMallocs;
1125 for (unsigned FieldNo = 0, e = STy->getNumElements(); FieldNo != e;++FieldNo){
1126 const Type *FieldTy = STy->getElementType(FieldNo);
1127 const Type *PFieldTy = PointerType::getUnqual(FieldTy);
1129 GlobalVariable *NGV =
1130 new GlobalVariable(PFieldTy, false, GlobalValue::InternalLinkage,
1131 Constant::getNullValue(PFieldTy),
1132 GV->getName() + ".f" + utostr(FieldNo), GV,
1133 GV->isThreadLocal());
1134 FieldGlobals.push_back(NGV);
1136 MallocInst *NMI = new MallocInst(FieldTy, MI->getArraySize(),
1137 MI->getName() + ".f" + utostr(FieldNo),MI);
1138 FieldMallocs.push_back(NMI);
1139 new StoreInst(NMI, NGV, MI);
1142 // The tricky aspect of this transformation is handling the case when malloc
1143 // fails. In the original code, malloc failing would set the result pointer
1144 // of malloc to null. In this case, some mallocs could succeed and others
1145 // could fail. As such, we emit code that looks like this:
1146 // F0 = malloc(field0)
1147 // F1 = malloc(field1)
1148 // F2 = malloc(field2)
1149 // if (F0 == 0 || F1 == 0 || F2 == 0) {
1150 // if (F0) { free(F0); F0 = 0; }
1151 // if (F1) { free(F1); F1 = 0; }
1152 // if (F2) { free(F2); F2 = 0; }
1154 Value *RunningOr = 0;
1155 for (unsigned i = 0, e = FieldMallocs.size(); i != e; ++i) {
1156 Value *Cond = new ICmpInst(ICmpInst::ICMP_EQ, FieldMallocs[i],
1157 Constant::getNullValue(FieldMallocs[i]->getType()),
1160 RunningOr = Cond; // First seteq
1162 RunningOr = BinaryOperator::createOr(RunningOr, Cond, "tmp", MI);
1165 // Split the basic block at the old malloc.
1166 BasicBlock *OrigBB = MI->getParent();
1167 BasicBlock *ContBB = OrigBB->splitBasicBlock(MI, "malloc_cont");
1169 // Create the block to check the first condition. Put all these blocks at the
1170 // end of the function as they are unlikely to be executed.
1171 BasicBlock *NullPtrBlock = new BasicBlock("malloc_ret_null",
1172 OrigBB->getParent());
1174 // Remove the uncond branch from OrigBB to ContBB, turning it into a cond
1175 // branch on RunningOr.
1176 OrigBB->getTerminator()->eraseFromParent();
1177 new BranchInst(NullPtrBlock, ContBB, RunningOr, OrigBB);
1179 // Within the NullPtrBlock, we need to emit a comparison and branch for each
1180 // pointer, because some may be null while others are not.
1181 for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) {
1182 Value *GVVal = new LoadInst(FieldGlobals[i], "tmp", NullPtrBlock);
1183 Value *Cmp = new ICmpInst(ICmpInst::ICMP_NE, GVVal,
1184 Constant::getNullValue(GVVal->getType()),
1185 "tmp", NullPtrBlock);
1186 BasicBlock *FreeBlock = new BasicBlock("free_it", OrigBB->getParent());
1187 BasicBlock *NextBlock = new BasicBlock("next", OrigBB->getParent());
1188 new BranchInst(FreeBlock, NextBlock, Cmp, NullPtrBlock);
1190 // Fill in FreeBlock.
1191 new FreeInst(GVVal, FreeBlock);
1192 new StoreInst(Constant::getNullValue(GVVal->getType()), FieldGlobals[i],
1194 new BranchInst(NextBlock, FreeBlock);
1196 NullPtrBlock = NextBlock;
1199 new BranchInst(ContBB, NullPtrBlock);
1202 // MI is no longer needed, remove it.
1203 MI->eraseFromParent();
1206 // Okay, the malloc site is completely handled. All of the uses of GV are now
1207 // loads, and all uses of those loads are simple. Rewrite them to use loads
1208 // of the per-field globals instead.
1209 while (!GV->use_empty()) {
1210 if (LoadInst *LI = dyn_cast<LoadInst>(GV->use_back())) {
1211 RewriteUsesOfLoadForHeapSRoA(LI, FieldGlobals);
1212 LI->eraseFromParent();
1214 // Must be a store of null.
1215 StoreInst *SI = cast<StoreInst>(GV->use_back());
1216 assert(isa<Constant>(SI->getOperand(0)) &&
1217 cast<Constant>(SI->getOperand(0))->isNullValue() &&
1218 "Unexpected heap-sra user!");
1220 // Insert a store of null into each global.
1221 for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) {
1223 Constant::getNullValue(FieldGlobals[i]->getType()->getElementType());
1224 new StoreInst(Null, FieldGlobals[i], SI);
1226 // Erase the original store.
1227 SI->eraseFromParent();
1231 // The old global is now dead, remove it.
1232 GV->eraseFromParent();
1235 return FieldGlobals[0];
1239 // OptimizeOnceStoredGlobal - Try to optimize globals based on the knowledge
1240 // that only one value (besides its initializer) is ever stored to the global.
1241 static bool OptimizeOnceStoredGlobal(GlobalVariable *GV, Value *StoredOnceVal,
1242 Module::global_iterator &GVI,
1244 if (CastInst *CI = dyn_cast<CastInst>(StoredOnceVal))
1245 StoredOnceVal = CI->getOperand(0);
1246 else if (GetElementPtrInst *GEPI =dyn_cast<GetElementPtrInst>(StoredOnceVal)){
1247 // "getelementptr Ptr, 0, 0, 0" is really just a cast.
1248 bool IsJustACast = true;
1249 for (unsigned i = 1, e = GEPI->getNumOperands(); i != e; ++i)
1250 if (!isa<Constant>(GEPI->getOperand(i)) ||
1251 !cast<Constant>(GEPI->getOperand(i))->isNullValue()) {
1252 IsJustACast = false;
1256 StoredOnceVal = GEPI->getOperand(0);
1259 // If we are dealing with a pointer global that is initialized to null and
1260 // only has one (non-null) value stored into it, then we can optimize any
1261 // users of the loaded value (often calls and loads) that would trap if the
1263 if (isa<PointerType>(GV->getInitializer()->getType()) &&
1264 GV->getInitializer()->isNullValue()) {
1265 if (Constant *SOVC = dyn_cast<Constant>(StoredOnceVal)) {
1266 if (GV->getInitializer()->getType() != SOVC->getType())
1267 SOVC = ConstantExpr::getBitCast(SOVC, GV->getInitializer()->getType());
1269 // Optimize away any trapping uses of the loaded value.
1270 if (OptimizeAwayTrappingUsesOfLoads(GV, SOVC))
1272 } else if (MallocInst *MI = dyn_cast<MallocInst>(StoredOnceVal)) {
1273 // If this is a malloc of an abstract type, don't touch it.
1274 if (!MI->getAllocatedType()->isSized())
1277 // We can't optimize this global unless all uses of it are *known* to be
1278 // of the malloc value, not of the null initializer value (consider a use
1279 // that compares the global's value against zero to see if the malloc has
1280 // been reached). To do this, we check to see if all uses of the global
1281 // would trap if the global were null: this proves that they must all
1282 // happen after the malloc.
1283 if (!AllUsesOfLoadedValueWillTrapIfNull(GV))
1286 // We can't optimize this if the malloc itself is used in a complex way,
1287 // for example, being stored into multiple globals. This allows the
1288 // malloc to be stored into the specified global, loaded setcc'd, and
1289 // GEP'd. These are all things we could transform to using the global
1292 SmallPtrSet<PHINode*, 8> PHIs;
1293 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(MI, GV, PHIs))
1298 // If we have a global that is only initialized with a fixed size malloc,
1299 // transform the program to use global memory instead of malloc'd memory.
1300 // This eliminates dynamic allocation, avoids an indirection accessing the
1301 // data, and exposes the resultant global to further GlobalOpt.
1302 if (ConstantInt *NElements = dyn_cast<ConstantInt>(MI->getArraySize())) {
1303 // Restrict this transformation to only working on small allocations
1304 // (2048 bytes currently), as we don't want to introduce a 16M global or
1306 if (NElements->getZExtValue()*
1307 TD.getABITypeSize(MI->getAllocatedType()) < 2048) {
1308 GVI = OptimizeGlobalAddressOfMalloc(GV, MI);
1313 // If the allocation is an array of structures, consider transforming this
1314 // into multiple malloc'd arrays, one for each field. This is basically
1315 // SRoA for malloc'd memory.
1316 if (const StructType *AllocTy =
1317 dyn_cast<StructType>(MI->getAllocatedType())) {
1318 // This the structure has an unreasonable number of fields, leave it
1320 if (AllocTy->getNumElements() <= 16 && AllocTy->getNumElements() > 0 &&
1321 GlobalLoadUsesSimpleEnoughForHeapSRA(GV, MI)) {
1322 GVI = PerformHeapAllocSRoA(GV, MI);
1332 /// TryToShrinkGlobalToBoolean - At this point, we have learned that the only
1333 /// two values ever stored into GV are its initializer and OtherVal. See if we
1334 /// can shrink the global into a boolean and select between the two values
1335 /// whenever it is used. This exposes the values to other scalar optimizations.
1336 static bool TryToShrinkGlobalToBoolean(GlobalVariable *GV, Constant *OtherVal) {
1337 const Type *GVElType = GV->getType()->getElementType();
1339 // If GVElType is already i1, it is already shrunk. If the type of the GV is
1340 // an FP value or vector, don't do this optimization because a select between
1341 // them is very expensive and unlikely to lead to later simplification.
1342 if (GVElType == Type::Int1Ty || GVElType->isFloatingPoint() ||
1343 isa<VectorType>(GVElType))
1346 // Walk the use list of the global seeing if all the uses are load or store.
1347 // If there is anything else, bail out.
1348 for (Value::use_iterator I = GV->use_begin(), E = GV->use_end(); I != E; ++I)
1349 if (!isa<LoadInst>(I) && !isa<StoreInst>(I))
1352 DOUT << " *** SHRINKING TO BOOL: " << *GV;
1354 // Create the new global, initializing it to false.
1355 GlobalVariable *NewGV = new GlobalVariable(Type::Int1Ty, false,
1356 GlobalValue::InternalLinkage, ConstantInt::getFalse(),
1359 GV->isThreadLocal());
1360 GV->getParent()->getGlobalList().insert(GV, NewGV);
1362 Constant *InitVal = GV->getInitializer();
1363 assert(InitVal->getType() != Type::Int1Ty && "No reason to shrink to bool!");
1365 // If initialized to zero and storing one into the global, we can use a cast
1366 // instead of a select to synthesize the desired value.
1367 bool IsOneZero = false;
1368 if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal))
1369 IsOneZero = InitVal->isNullValue() && CI->isOne();
1371 while (!GV->use_empty()) {
1372 Instruction *UI = cast<Instruction>(GV->use_back());
1373 if (StoreInst *SI = dyn_cast<StoreInst>(UI)) {
1374 // Change the store into a boolean store.
1375 bool StoringOther = SI->getOperand(0) == OtherVal;
1376 // Only do this if we weren't storing a loaded value.
1378 if (StoringOther || SI->getOperand(0) == InitVal)
1379 StoreVal = ConstantInt::get(Type::Int1Ty, StoringOther);
1381 // Otherwise, we are storing a previously loaded copy. To do this,
1382 // change the copy from copying the original value to just copying the
1384 Instruction *StoredVal = cast<Instruction>(SI->getOperand(0));
1386 // If we're already replaced the input, StoredVal will be a cast or
1387 // select instruction. If not, it will be a load of the original
1389 if (LoadInst *LI = dyn_cast<LoadInst>(StoredVal)) {
1390 assert(LI->getOperand(0) == GV && "Not a copy!");
1391 // Insert a new load, to preserve the saved value.
1392 StoreVal = new LoadInst(NewGV, LI->getName()+".b", LI);
1394 assert((isa<CastInst>(StoredVal) || isa<SelectInst>(StoredVal)) &&
1395 "This is not a form that we understand!");
1396 StoreVal = StoredVal->getOperand(0);
1397 assert(isa<LoadInst>(StoreVal) && "Not a load of NewGV!");
1400 new StoreInst(StoreVal, NewGV, SI);
1402 // Change the load into a load of bool then a select.
1403 LoadInst *LI = cast<LoadInst>(UI);
1404 LoadInst *NLI = new LoadInst(NewGV, LI->getName()+".b", LI);
1407 NSI = new ZExtInst(NLI, LI->getType(), "", LI);
1409 NSI = new SelectInst(NLI, OtherVal, InitVal, "", LI);
1411 LI->replaceAllUsesWith(NSI);
1413 UI->eraseFromParent();
1416 GV->eraseFromParent();
1421 /// ProcessInternalGlobal - Analyze the specified global variable and optimize
1422 /// it if possible. If we make a change, return true.
1423 bool GlobalOpt::ProcessInternalGlobal(GlobalVariable *GV,
1424 Module::global_iterator &GVI) {
1425 std::set<PHINode*> PHIUsers;
1427 GV->removeDeadConstantUsers();
1429 if (GV->use_empty()) {
1430 DOUT << "GLOBAL DEAD: " << *GV;
1431 GV->eraseFromParent();
1436 if (!AnalyzeGlobal(GV, GS, PHIUsers)) {
1438 cerr << "Global: " << *GV;
1439 cerr << " isLoaded = " << GS.isLoaded << "\n";
1440 cerr << " StoredType = ";
1441 switch (GS.StoredType) {
1442 case GlobalStatus::NotStored: cerr << "NEVER STORED\n"; break;
1443 case GlobalStatus::isInitializerStored: cerr << "INIT STORED\n"; break;
1444 case GlobalStatus::isStoredOnce: cerr << "STORED ONCE\n"; break;
1445 case GlobalStatus::isStored: cerr << "stored\n"; break;
1447 if (GS.StoredType == GlobalStatus::isStoredOnce && GS.StoredOnceValue)
1448 cerr << " StoredOnceValue = " << *GS.StoredOnceValue << "\n";
1449 if (GS.AccessingFunction && !GS.HasMultipleAccessingFunctions)
1450 cerr << " AccessingFunction = " << GS.AccessingFunction->getName()
1452 cerr << " HasMultipleAccessingFunctions = "
1453 << GS.HasMultipleAccessingFunctions << "\n";
1454 cerr << " HasNonInstructionUser = " << GS.HasNonInstructionUser<<"\n";
1458 // If this is a first class global and has only one accessing function
1459 // and this function is main (which we know is not recursive we can make
1460 // this global a local variable) we replace the global with a local alloca
1461 // in this function.
1463 // NOTE: It doesn't make sense to promote non first class types since we
1464 // are just replacing static memory to stack memory.
1465 if (!GS.HasMultipleAccessingFunctions &&
1466 GS.AccessingFunction && !GS.HasNonInstructionUser &&
1467 GV->getType()->getElementType()->isFirstClassType() &&
1468 GS.AccessingFunction->getName() == "main" &&
1469 GS.AccessingFunction->hasExternalLinkage()) {
1470 DOUT << "LOCALIZING GLOBAL: " << *GV;
1471 Instruction* FirstI = GS.AccessingFunction->getEntryBlock().begin();
1472 const Type* ElemTy = GV->getType()->getElementType();
1473 // FIXME: Pass Global's alignment when globals have alignment
1474 AllocaInst* Alloca = new AllocaInst(ElemTy, NULL, GV->getName(), FirstI);
1475 if (!isa<UndefValue>(GV->getInitializer()))
1476 new StoreInst(GV->getInitializer(), Alloca, FirstI);
1478 GV->replaceAllUsesWith(Alloca);
1479 GV->eraseFromParent();
1484 // If the global is never loaded (but may be stored to), it is dead.
1487 DOUT << "GLOBAL NEVER LOADED: " << *GV;
1489 // Delete any stores we can find to the global. We may not be able to
1490 // make it completely dead though.
1491 bool Changed = CleanupConstantGlobalUsers(GV, GV->getInitializer());
1493 // If the global is dead now, delete it.
1494 if (GV->use_empty()) {
1495 GV->eraseFromParent();
1501 } else if (GS.StoredType <= GlobalStatus::isInitializerStored) {
1502 DOUT << "MARKING CONSTANT: " << *GV;
1503 GV->setConstant(true);
1505 // Clean up any obviously simplifiable users now.
1506 CleanupConstantGlobalUsers(GV, GV->getInitializer());
1508 // If the global is dead now, just nuke it.
1509 if (GV->use_empty()) {
1510 DOUT << " *** Marking constant allowed us to simplify "
1511 << "all users and delete global!\n";
1512 GV->eraseFromParent();
1518 } else if (!GV->getInitializer()->getType()->isFirstClassType()) {
1519 if (GlobalVariable *FirstNewGV = SRAGlobal(GV)) {
1520 GVI = FirstNewGV; // Don't skip the newly produced globals!
1523 } else if (GS.StoredType == GlobalStatus::isStoredOnce) {
1524 // If the initial value for the global was an undef value, and if only
1525 // one other value was stored into it, we can just change the
1526 // initializer to be an undef value, then delete all stores to the
1527 // global. This allows us to mark it constant.
1528 if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue))
1529 if (isa<UndefValue>(GV->getInitializer())) {
1530 // Change the initial value here.
1531 GV->setInitializer(SOVConstant);
1533 // Clean up any obviously simplifiable users now.
1534 CleanupConstantGlobalUsers(GV, GV->getInitializer());
1536 if (GV->use_empty()) {
1537 DOUT << " *** Substituting initializer allowed us to "
1538 << "simplify all users and delete global!\n";
1539 GV->eraseFromParent();
1548 // Try to optimize globals based on the knowledge that only one value
1549 // (besides its initializer) is ever stored to the global.
1550 if (OptimizeOnceStoredGlobal(GV, GS.StoredOnceValue, GVI,
1551 getAnalysis<TargetData>()))
1554 // Otherwise, if the global was not a boolean, we can shrink it to be a
1556 if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue))
1557 if (TryToShrinkGlobalToBoolean(GV, SOVConstant)) {
1566 /// OnlyCalledDirectly - Return true if the specified function is only called
1567 /// directly. In other words, its address is never taken.
1568 static bool OnlyCalledDirectly(Function *F) {
1569 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){
1570 Instruction *User = dyn_cast<Instruction>(*UI);
1571 if (!User) return false;
1572 if (!isa<CallInst>(User) && !isa<InvokeInst>(User)) return false;
1574 // See if the function address is passed as an argument.
1575 for (unsigned i = 1, e = User->getNumOperands(); i != e; ++i)
1576 if (User->getOperand(i) == F) return false;
1581 /// ChangeCalleesToFastCall - Walk all of the direct calls of the specified
1582 /// function, changing them to FastCC.
1583 static void ChangeCalleesToFastCall(Function *F) {
1584 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){
1585 Instruction *User = cast<Instruction>(*UI);
1586 if (CallInst *CI = dyn_cast<CallInst>(User))
1587 CI->setCallingConv(CallingConv::Fast);
1589 cast<InvokeInst>(User)->setCallingConv(CallingConv::Fast);
1593 bool GlobalOpt::OptimizeFunctions(Module &M) {
1594 bool Changed = false;
1595 // Optimize functions.
1596 for (Module::iterator FI = M.begin(), E = M.end(); FI != E; ) {
1598 F->removeDeadConstantUsers();
1599 if (F->use_empty() && (F->hasInternalLinkage() ||
1600 F->hasLinkOnceLinkage())) {
1601 M.getFunctionList().erase(F);
1604 } else if (F->hasInternalLinkage() &&
1605 F->getCallingConv() == CallingConv::C && !F->isVarArg() &&
1606 OnlyCalledDirectly(F)) {
1607 // If this function has C calling conventions, is not a varargs
1608 // function, and is only called directly, promote it to use the Fast
1609 // calling convention.
1610 F->setCallingConv(CallingConv::Fast);
1611 ChangeCalleesToFastCall(F);
1619 bool GlobalOpt::OptimizeGlobalVars(Module &M) {
1620 bool Changed = false;
1621 for (Module::global_iterator GVI = M.global_begin(), E = M.global_end();
1623 GlobalVariable *GV = GVI++;
1624 if (!GV->isConstant() && GV->hasInternalLinkage() &&
1625 GV->hasInitializer())
1626 Changed |= ProcessInternalGlobal(GV, GVI);
1631 /// FindGlobalCtors - Find the llvm.globalctors list, verifying that all
1632 /// initializers have an init priority of 65535.
1633 GlobalVariable *GlobalOpt::FindGlobalCtors(Module &M) {
1634 for (Module::global_iterator I = M.global_begin(), E = M.global_end();
1636 if (I->getName() == "llvm.global_ctors") {
1637 // Found it, verify it's an array of { int, void()* }.
1638 const ArrayType *ATy =dyn_cast<ArrayType>(I->getType()->getElementType());
1640 const StructType *STy = dyn_cast<StructType>(ATy->getElementType());
1641 if (!STy || STy->getNumElements() != 2 ||
1642 STy->getElementType(0) != Type::Int32Ty) return 0;
1643 const PointerType *PFTy = dyn_cast<PointerType>(STy->getElementType(1));
1644 if (!PFTy) return 0;
1645 const FunctionType *FTy = dyn_cast<FunctionType>(PFTy->getElementType());
1646 if (!FTy || FTy->getReturnType() != Type::VoidTy || FTy->isVarArg() ||
1647 FTy->getNumParams() != 0)
1650 // Verify that the initializer is simple enough for us to handle.
1651 if (!I->hasInitializer()) return 0;
1652 ConstantArray *CA = dyn_cast<ConstantArray>(I->getInitializer());
1654 for (unsigned i = 0, e = CA->getNumOperands(); i != e; ++i)
1655 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(CA->getOperand(i))) {
1656 if (isa<ConstantPointerNull>(CS->getOperand(1)))
1659 // Must have a function or null ptr.
1660 if (!isa<Function>(CS->getOperand(1)))
1663 // Init priority must be standard.
1664 ConstantInt *CI = dyn_cast<ConstantInt>(CS->getOperand(0));
1665 if (!CI || CI->getZExtValue() != 65535)
1676 /// ParseGlobalCtors - Given a llvm.global_ctors list that we can understand,
1677 /// return a list of the functions and null terminator as a vector.
1678 static std::vector<Function*> ParseGlobalCtors(GlobalVariable *GV) {
1679 ConstantArray *CA = cast<ConstantArray>(GV->getInitializer());
1680 std::vector<Function*> Result;
1681 Result.reserve(CA->getNumOperands());
1682 for (unsigned i = 0, e = CA->getNumOperands(); i != e; ++i) {
1683 ConstantStruct *CS = cast<ConstantStruct>(CA->getOperand(i));
1684 Result.push_back(dyn_cast<Function>(CS->getOperand(1)));
1689 /// InstallGlobalCtors - Given a specified llvm.global_ctors list, install the
1690 /// specified array, returning the new global to use.
1691 static GlobalVariable *InstallGlobalCtors(GlobalVariable *GCL,
1692 const std::vector<Function*> &Ctors) {
1693 // If we made a change, reassemble the initializer list.
1694 std::vector<Constant*> CSVals;
1695 CSVals.push_back(ConstantInt::get(Type::Int32Ty, 65535));
1696 CSVals.push_back(0);
1698 // Create the new init list.
1699 std::vector<Constant*> CAList;
1700 for (unsigned i = 0, e = Ctors.size(); i != e; ++i) {
1702 CSVals[1] = Ctors[i];
1704 const Type *FTy = FunctionType::get(Type::VoidTy,
1705 std::vector<const Type*>(), false);
1706 const PointerType *PFTy = PointerType::getUnqual(FTy);
1707 CSVals[1] = Constant::getNullValue(PFTy);
1708 CSVals[0] = ConstantInt::get(Type::Int32Ty, 2147483647);
1710 CAList.push_back(ConstantStruct::get(CSVals));
1713 // Create the array initializer.
1714 const Type *StructTy =
1715 cast<ArrayType>(GCL->getType()->getElementType())->getElementType();
1716 Constant *CA = ConstantArray::get(ArrayType::get(StructTy, CAList.size()),
1719 // If we didn't change the number of elements, don't create a new GV.
1720 if (CA->getType() == GCL->getInitializer()->getType()) {
1721 GCL->setInitializer(CA);
1725 // Create the new global and insert it next to the existing list.
1726 GlobalVariable *NGV = new GlobalVariable(CA->getType(), GCL->isConstant(),
1727 GCL->getLinkage(), CA, "",
1729 GCL->isThreadLocal());
1730 GCL->getParent()->getGlobalList().insert(GCL, NGV);
1733 // Nuke the old list, replacing any uses with the new one.
1734 if (!GCL->use_empty()) {
1736 if (V->getType() != GCL->getType())
1737 V = ConstantExpr::getBitCast(V, GCL->getType());
1738 GCL->replaceAllUsesWith(V);
1740 GCL->eraseFromParent();
1749 static Constant *getVal(std::map<Value*, Constant*> &ComputedValues,
1751 if (Constant *CV = dyn_cast<Constant>(V)) return CV;
1752 Constant *R = ComputedValues[V];
1753 assert(R && "Reference to an uncomputed value!");
1757 /// isSimpleEnoughPointerToCommit - Return true if this constant is simple
1758 /// enough for us to understand. In particular, if it is a cast of something,
1759 /// we punt. We basically just support direct accesses to globals and GEP's of
1760 /// globals. This should be kept up to date with CommitValueTo.
1761 static bool isSimpleEnoughPointerToCommit(Constant *C) {
1762 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C)) {
1763 if (!GV->hasExternalLinkage() && !GV->hasInternalLinkage())
1764 return false; // do not allow weak/linkonce/dllimport/dllexport linkage.
1765 return !GV->isDeclaration(); // reject external globals.
1767 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
1768 // Handle a constantexpr gep.
1769 if (CE->getOpcode() == Instruction::GetElementPtr &&
1770 isa<GlobalVariable>(CE->getOperand(0))) {
1771 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
1772 if (!GV->hasExternalLinkage() && !GV->hasInternalLinkage())
1773 return false; // do not allow weak/linkonce/dllimport/dllexport linkage.
1774 return GV->hasInitializer() &&
1775 ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE);
1780 /// EvaluateStoreInto - Evaluate a piece of a constantexpr store into a global
1781 /// initializer. This returns 'Init' modified to reflect 'Val' stored into it.
1782 /// At this point, the GEP operands of Addr [0, OpNo) have been stepped into.
1783 static Constant *EvaluateStoreInto(Constant *Init, Constant *Val,
1784 ConstantExpr *Addr, unsigned OpNo) {
1785 // Base case of the recursion.
1786 if (OpNo == Addr->getNumOperands()) {
1787 assert(Val->getType() == Init->getType() && "Type mismatch!");
1791 if (const StructType *STy = dyn_cast<StructType>(Init->getType())) {
1792 std::vector<Constant*> Elts;
1794 // Break up the constant into its elements.
1795 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(Init)) {
1796 for (unsigned i = 0, e = CS->getNumOperands(); i != e; ++i)
1797 Elts.push_back(CS->getOperand(i));
1798 } else if (isa<ConstantAggregateZero>(Init)) {
1799 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
1800 Elts.push_back(Constant::getNullValue(STy->getElementType(i)));
1801 } else if (isa<UndefValue>(Init)) {
1802 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
1803 Elts.push_back(UndefValue::get(STy->getElementType(i)));
1805 assert(0 && "This code is out of sync with "
1806 " ConstantFoldLoadThroughGEPConstantExpr");
1809 // Replace the element that we are supposed to.
1810 ConstantInt *CU = cast<ConstantInt>(Addr->getOperand(OpNo));
1811 unsigned Idx = CU->getZExtValue();
1812 assert(Idx < STy->getNumElements() && "Struct index out of range!");
1813 Elts[Idx] = EvaluateStoreInto(Elts[Idx], Val, Addr, OpNo+1);
1815 // Return the modified struct.
1816 return ConstantStruct::get(&Elts[0], Elts.size(), STy->isPacked());
1818 ConstantInt *CI = cast<ConstantInt>(Addr->getOperand(OpNo));
1819 const ArrayType *ATy = cast<ArrayType>(Init->getType());
1821 // Break up the array into elements.
1822 std::vector<Constant*> Elts;
1823 if (ConstantArray *CA = dyn_cast<ConstantArray>(Init)) {
1824 for (unsigned i = 0, e = CA->getNumOperands(); i != e; ++i)
1825 Elts.push_back(CA->getOperand(i));
1826 } else if (isa<ConstantAggregateZero>(Init)) {
1827 Constant *Elt = Constant::getNullValue(ATy->getElementType());
1828 Elts.assign(ATy->getNumElements(), Elt);
1829 } else if (isa<UndefValue>(Init)) {
1830 Constant *Elt = UndefValue::get(ATy->getElementType());
1831 Elts.assign(ATy->getNumElements(), Elt);
1833 assert(0 && "This code is out of sync with "
1834 " ConstantFoldLoadThroughGEPConstantExpr");
1837 assert(CI->getZExtValue() < ATy->getNumElements());
1838 Elts[CI->getZExtValue()] =
1839 EvaluateStoreInto(Elts[CI->getZExtValue()], Val, Addr, OpNo+1);
1840 return ConstantArray::get(ATy, Elts);
1844 /// CommitValueTo - We have decided that Addr (which satisfies the predicate
1845 /// isSimpleEnoughPointerToCommit) should get Val as its value. Make it happen.
1846 static void CommitValueTo(Constant *Val, Constant *Addr) {
1847 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Addr)) {
1848 assert(GV->hasInitializer());
1849 GV->setInitializer(Val);
1853 ConstantExpr *CE = cast<ConstantExpr>(Addr);
1854 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
1856 Constant *Init = GV->getInitializer();
1857 Init = EvaluateStoreInto(Init, Val, CE, 2);
1858 GV->setInitializer(Init);
1861 /// ComputeLoadResult - Return the value that would be computed by a load from
1862 /// P after the stores reflected by 'memory' have been performed. If we can't
1863 /// decide, return null.
1864 static Constant *ComputeLoadResult(Constant *P,
1865 const std::map<Constant*, Constant*> &Memory) {
1866 // If this memory location has been recently stored, use the stored value: it
1867 // is the most up-to-date.
1868 std::map<Constant*, Constant*>::const_iterator I = Memory.find(P);
1869 if (I != Memory.end()) return I->second;
1872 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(P)) {
1873 if (GV->hasInitializer())
1874 return GV->getInitializer();
1878 // Handle a constantexpr getelementptr.
1879 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(P))
1880 if (CE->getOpcode() == Instruction::GetElementPtr &&
1881 isa<GlobalVariable>(CE->getOperand(0))) {
1882 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
1883 if (GV->hasInitializer())
1884 return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE);
1887 return 0; // don't know how to evaluate.
1890 /// EvaluateFunction - Evaluate a call to function F, returning true if
1891 /// successful, false if we can't evaluate it. ActualArgs contains the formal
1892 /// arguments for the function.
1893 static bool EvaluateFunction(Function *F, Constant *&RetVal,
1894 const std::vector<Constant*> &ActualArgs,
1895 std::vector<Function*> &CallStack,
1896 std::map<Constant*, Constant*> &MutatedMemory,
1897 std::vector<GlobalVariable*> &AllocaTmps) {
1898 // Check to see if this function is already executing (recursion). If so,
1899 // bail out. TODO: we might want to accept limited recursion.
1900 if (std::find(CallStack.begin(), CallStack.end(), F) != CallStack.end())
1903 CallStack.push_back(F);
1905 /// Values - As we compute SSA register values, we store their contents here.
1906 std::map<Value*, Constant*> Values;
1908 // Initialize arguments to the incoming values specified.
1910 for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end(); AI != E;
1912 Values[AI] = ActualArgs[ArgNo];
1914 /// ExecutedBlocks - We only handle non-looping, non-recursive code. As such,
1915 /// we can only evaluate any one basic block at most once. This set keeps
1916 /// track of what we have executed so we can detect recursive cases etc.
1917 std::set<BasicBlock*> ExecutedBlocks;
1919 // CurInst - The current instruction we're evaluating.
1920 BasicBlock::iterator CurInst = F->begin()->begin();
1922 // This is the main evaluation loop.
1924 Constant *InstResult = 0;
1926 if (StoreInst *SI = dyn_cast<StoreInst>(CurInst)) {
1927 if (SI->isVolatile()) return false; // no volatile accesses.
1928 Constant *Ptr = getVal(Values, SI->getOperand(1));
1929 if (!isSimpleEnoughPointerToCommit(Ptr))
1930 // If this is too complex for us to commit, reject it.
1932 Constant *Val = getVal(Values, SI->getOperand(0));
1933 MutatedMemory[Ptr] = Val;
1934 } else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(CurInst)) {
1935 InstResult = ConstantExpr::get(BO->getOpcode(),
1936 getVal(Values, BO->getOperand(0)),
1937 getVal(Values, BO->getOperand(1)));
1938 } else if (CmpInst *CI = dyn_cast<CmpInst>(CurInst)) {
1939 InstResult = ConstantExpr::getCompare(CI->getPredicate(),
1940 getVal(Values, CI->getOperand(0)),
1941 getVal(Values, CI->getOperand(1)));
1942 } else if (CastInst *CI = dyn_cast<CastInst>(CurInst)) {
1943 InstResult = ConstantExpr::getCast(CI->getOpcode(),
1944 getVal(Values, CI->getOperand(0)),
1946 } else if (SelectInst *SI = dyn_cast<SelectInst>(CurInst)) {
1947 InstResult = ConstantExpr::getSelect(getVal(Values, SI->getOperand(0)),
1948 getVal(Values, SI->getOperand(1)),
1949 getVal(Values, SI->getOperand(2)));
1950 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(CurInst)) {
1951 Constant *P = getVal(Values, GEP->getOperand(0));
1952 SmallVector<Constant*, 8> GEPOps;
1953 for (unsigned i = 1, e = GEP->getNumOperands(); i != e; ++i)
1954 GEPOps.push_back(getVal(Values, GEP->getOperand(i)));
1955 InstResult = ConstantExpr::getGetElementPtr(P, &GEPOps[0], GEPOps.size());
1956 } else if (LoadInst *LI = dyn_cast<LoadInst>(CurInst)) {
1957 if (LI->isVolatile()) return false; // no volatile accesses.
1958 InstResult = ComputeLoadResult(getVal(Values, LI->getOperand(0)),
1960 if (InstResult == 0) return false; // Could not evaluate load.
1961 } else if (AllocaInst *AI = dyn_cast<AllocaInst>(CurInst)) {
1962 if (AI->isArrayAllocation()) return false; // Cannot handle array allocs.
1963 const Type *Ty = AI->getType()->getElementType();
1964 AllocaTmps.push_back(new GlobalVariable(Ty, false,
1965 GlobalValue::InternalLinkage,
1966 UndefValue::get(Ty),
1968 InstResult = AllocaTmps.back();
1969 } else if (CallInst *CI = dyn_cast<CallInst>(CurInst)) {
1970 // Cannot handle inline asm.
1971 if (isa<InlineAsm>(CI->getOperand(0))) return false;
1973 // Resolve function pointers.
1974 Function *Callee = dyn_cast<Function>(getVal(Values, CI->getOperand(0)));
1975 if (!Callee) return false; // Cannot resolve.
1977 std::vector<Constant*> Formals;
1978 for (unsigned i = 1, e = CI->getNumOperands(); i != e; ++i)
1979 Formals.push_back(getVal(Values, CI->getOperand(i)));
1981 if (Callee->isDeclaration()) {
1982 // If this is a function we can constant fold, do it.
1983 if (Constant *C = ConstantFoldCall(Callee, &Formals[0],
1990 if (Callee->getFunctionType()->isVarArg())
1995 // Execute the call, if successful, use the return value.
1996 if (!EvaluateFunction(Callee, RetVal, Formals, CallStack,
1997 MutatedMemory, AllocaTmps))
1999 InstResult = RetVal;
2001 } else if (isa<TerminatorInst>(CurInst)) {
2002 BasicBlock *NewBB = 0;
2003 if (BranchInst *BI = dyn_cast<BranchInst>(CurInst)) {
2004 if (BI->isUnconditional()) {
2005 NewBB = BI->getSuccessor(0);
2008 dyn_cast<ConstantInt>(getVal(Values, BI->getCondition()));
2009 if (!Cond) return false; // Cannot determine.
2011 NewBB = BI->getSuccessor(!Cond->getZExtValue());
2013 } else if (SwitchInst *SI = dyn_cast<SwitchInst>(CurInst)) {
2015 dyn_cast<ConstantInt>(getVal(Values, SI->getCondition()));
2016 if (!Val) return false; // Cannot determine.
2017 NewBB = SI->getSuccessor(SI->findCaseValue(Val));
2018 } else if (ReturnInst *RI = dyn_cast<ReturnInst>(CurInst)) {
2019 if (RI->getNumOperands())
2020 RetVal = getVal(Values, RI->getOperand(0));
2022 CallStack.pop_back(); // return from fn.
2023 return true; // We succeeded at evaluating this ctor!
2025 // invoke, unwind, unreachable.
2026 return false; // Cannot handle this terminator.
2029 // Okay, we succeeded in evaluating this control flow. See if we have
2030 // executed the new block before. If so, we have a looping function,
2031 // which we cannot evaluate in reasonable time.
2032 if (!ExecutedBlocks.insert(NewBB).second)
2033 return false; // looped!
2035 // Okay, we have never been in this block before. Check to see if there
2036 // are any PHI nodes. If so, evaluate them with information about where
2038 BasicBlock *OldBB = CurInst->getParent();
2039 CurInst = NewBB->begin();
2041 for (; (PN = dyn_cast<PHINode>(CurInst)); ++CurInst)
2042 Values[PN] = getVal(Values, PN->getIncomingValueForBlock(OldBB));
2044 // Do NOT increment CurInst. We know that the terminator had no value.
2047 // Did not know how to evaluate this!
2051 if (!CurInst->use_empty())
2052 Values[CurInst] = InstResult;
2054 // Advance program counter.
2059 /// EvaluateStaticConstructor - Evaluate static constructors in the function, if
2060 /// we can. Return true if we can, false otherwise.
2061 static bool EvaluateStaticConstructor(Function *F) {
2062 /// MutatedMemory - For each store we execute, we update this map. Loads
2063 /// check this to get the most up-to-date value. If evaluation is successful,
2064 /// this state is committed to the process.
2065 std::map<Constant*, Constant*> MutatedMemory;
2067 /// AllocaTmps - To 'execute' an alloca, we create a temporary global variable
2068 /// to represent its body. This vector is needed so we can delete the
2069 /// temporary globals when we are done.
2070 std::vector<GlobalVariable*> AllocaTmps;
2072 /// CallStack - This is used to detect recursion. In pathological situations
2073 /// we could hit exponential behavior, but at least there is nothing
2075 std::vector<Function*> CallStack;
2077 // Call the function.
2078 Constant *RetValDummy;
2079 bool EvalSuccess = EvaluateFunction(F, RetValDummy, std::vector<Constant*>(),
2080 CallStack, MutatedMemory, AllocaTmps);
2082 // We succeeded at evaluation: commit the result.
2083 DOUT << "FULLY EVALUATED GLOBAL CTOR FUNCTION '"
2084 << F->getName() << "' to " << MutatedMemory.size()
2086 for (std::map<Constant*, Constant*>::iterator I = MutatedMemory.begin(),
2087 E = MutatedMemory.end(); I != E; ++I)
2088 CommitValueTo(I->second, I->first);
2091 // At this point, we are done interpreting. If we created any 'alloca'
2092 // temporaries, release them now.
2093 while (!AllocaTmps.empty()) {
2094 GlobalVariable *Tmp = AllocaTmps.back();
2095 AllocaTmps.pop_back();
2097 // If there are still users of the alloca, the program is doing something
2098 // silly, e.g. storing the address of the alloca somewhere and using it
2099 // later. Since this is undefined, we'll just make it be null.
2100 if (!Tmp->use_empty())
2101 Tmp->replaceAllUsesWith(Constant::getNullValue(Tmp->getType()));
2110 /// OptimizeGlobalCtorsList - Simplify and evaluation global ctors if possible.
2111 /// Return true if anything changed.
2112 bool GlobalOpt::OptimizeGlobalCtorsList(GlobalVariable *&GCL) {
2113 std::vector<Function*> Ctors = ParseGlobalCtors(GCL);
2114 bool MadeChange = false;
2115 if (Ctors.empty()) return false;
2117 // Loop over global ctors, optimizing them when we can.
2118 for (unsigned i = 0; i != Ctors.size(); ++i) {
2119 Function *F = Ctors[i];
2120 // Found a null terminator in the middle of the list, prune off the rest of
2123 if (i != Ctors.size()-1) {
2130 // We cannot simplify external ctor functions.
2131 if (F->empty()) continue;
2133 // If we can evaluate the ctor at compile time, do.
2134 if (EvaluateStaticConstructor(F)) {
2135 Ctors.erase(Ctors.begin()+i);
2138 ++NumCtorsEvaluated;
2143 if (!MadeChange) return false;
2145 GCL = InstallGlobalCtors(GCL, Ctors);
2150 bool GlobalOpt::runOnModule(Module &M) {
2151 bool Changed = false;
2153 // Try to find the llvm.globalctors list.
2154 GlobalVariable *GlobalCtors = FindGlobalCtors(M);
2156 bool LocalChange = true;
2157 while (LocalChange) {
2158 LocalChange = false;
2160 // Delete functions that are trivially dead, ccc -> fastcc
2161 LocalChange |= OptimizeFunctions(M);
2163 // Optimize global_ctors list.
2165 LocalChange |= OptimizeGlobalCtorsList(GlobalCtors);
2167 // Optimize non-address-taken globals.
2168 LocalChange |= OptimizeGlobalVars(M);
2169 Changed |= LocalChange;
2172 // TODO: Move all global ctors functions to the end of the module for code