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/ADT/DenseMap.h"
19 #include "llvm/ADT/STLExtras.h"
20 #include "llvm/ADT/SmallPtrSet.h"
21 #include "llvm/ADT/SmallVector.h"
22 #include "llvm/ADT/Statistic.h"
23 #include "llvm/Analysis/ConstantFolding.h"
24 #include "llvm/Analysis/MemoryBuiltins.h"
25 #include "llvm/IR/CallingConv.h"
26 #include "llvm/IR/Constants.h"
27 #include "llvm/IR/DataLayout.h"
28 #include "llvm/IR/DerivedTypes.h"
29 #include "llvm/IR/Instructions.h"
30 #include "llvm/IR/IntrinsicInst.h"
31 #include "llvm/IR/Module.h"
32 #include "llvm/IR/Operator.h"
33 #include "llvm/Pass.h"
34 #include "llvm/Support/CallSite.h"
35 #include "llvm/Support/Debug.h"
36 #include "llvm/Support/ErrorHandling.h"
37 #include "llvm/Support/GetElementPtrTypeIterator.h"
38 #include "llvm/Support/MathExtras.h"
39 #include "llvm/Support/raw_ostream.h"
40 #include "llvm/Target/TargetLibraryInfo.h"
41 #include "llvm/Transforms/Utils/ModuleUtils.h"
45 STATISTIC(NumMarked , "Number of globals marked constant");
46 STATISTIC(NumUnnamed , "Number of globals marked unnamed_addr");
47 STATISTIC(NumSRA , "Number of aggregate globals broken into scalars");
48 STATISTIC(NumHeapSRA , "Number of heap objects SRA'd");
49 STATISTIC(NumSubstitute,"Number of globals with initializers stored into them");
50 STATISTIC(NumDeleted , "Number of globals deleted");
51 STATISTIC(NumFnDeleted , "Number of functions deleted");
52 STATISTIC(NumGlobUses , "Number of global uses devirtualized");
53 STATISTIC(NumShrunkToBool , "Number of global vars shrunk to booleans");
54 STATISTIC(NumFastCallFns , "Number of functions converted to fastcc");
55 STATISTIC(NumCtorsEvaluated, "Number of static ctors evaluated");
56 STATISTIC(NumNestRemoved , "Number of nest attributes removed");
57 STATISTIC(NumAliasesResolved, "Number of global aliases resolved");
58 STATISTIC(NumAliasesRemoved, "Number of global aliases eliminated");
59 STATISTIC(NumCXXDtorsRemoved, "Number of global C++ destructors removed");
63 struct GlobalOpt : public ModulePass {
64 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
65 AU.addRequired<TargetLibraryInfo>();
67 static char ID; // Pass identification, replacement for typeid
68 GlobalOpt() : ModulePass(ID) {
69 initializeGlobalOptPass(*PassRegistry::getPassRegistry());
72 bool runOnModule(Module &M);
75 GlobalVariable *FindGlobalCtors(Module &M);
76 bool OptimizeFunctions(Module &M);
77 bool OptimizeGlobalVars(Module &M);
78 bool OptimizeGlobalAliases(Module &M);
79 bool OptimizeGlobalCtorsList(GlobalVariable *&GCL);
80 bool ProcessGlobal(GlobalVariable *GV,Module::global_iterator &GVI);
81 bool ProcessInternalGlobal(GlobalVariable *GV,Module::global_iterator &GVI,
82 const GlobalStatus &GS);
83 bool OptimizeEmptyGlobalCXXDtors(Function *CXAAtExitFn);
86 TargetLibraryInfo *TLI;
90 char GlobalOpt::ID = 0;
91 INITIALIZE_PASS_BEGIN(GlobalOpt, "globalopt",
92 "Global Variable Optimizer", false, false)
93 INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfo)
94 INITIALIZE_PASS_END(GlobalOpt, "globalopt",
95 "Global Variable Optimizer", false, false)
97 ModulePass *llvm::createGlobalOptimizerPass() { return new GlobalOpt(); }
101 /// GlobalStatus - As we analyze each global, keep track of some information
102 /// about it. If we find out that the address of the global is taken, none of
103 /// this info will be accurate.
104 struct GlobalStatus {
105 /// isCompared - True if the global's address is used in a comparison.
108 /// isLoaded - True if the global is ever loaded. If the global isn't ever
109 /// loaded it can be deleted.
112 /// StoredType - Keep track of what stores to the global look like.
115 /// NotStored - There is no store to this global. It can thus be marked
119 /// isInitializerStored - This global is stored to, but the only thing
120 /// stored is the constant it was initialized with. This is only tracked
121 /// for scalar globals.
124 /// isStoredOnce - This global is stored to, but only its initializer and
125 /// one other value is ever stored to it. If this global isStoredOnce, we
126 /// track the value stored to it in StoredOnceValue below. This is only
127 /// tracked for scalar globals.
130 /// isStored - This global is stored to by multiple values or something else
131 /// that we cannot track.
135 /// StoredOnceValue - If only one value (besides the initializer constant) is
136 /// ever stored to this global, keep track of what value it is.
137 Value *StoredOnceValue;
139 /// AtomicOrdering - Set to the strongest atomic ordering requirement.
140 AtomicOrdering Ordering;
143 : isCompared(false), isLoaded(false), StoredType(NotStored),
144 StoredOnceValue(0), Ordering(NotAtomic) {}
149 /// StrongerOrdering - Return the stronger of the two ordering. If the two
150 /// orderings are acquire and release, then return AcquireRelease.
152 static AtomicOrdering StrongerOrdering(AtomicOrdering X, AtomicOrdering Y) {
153 if (X == Acquire && Y == Release) return AcquireRelease;
154 if (Y == Acquire && X == Release) return AcquireRelease;
155 return (AtomicOrdering)std::max(X, Y);
158 /// SafeToDestroyConstant - It is safe to destroy a constant iff it is only used
159 /// by constants itself. Note that constants cannot be cyclic, so this test is
160 /// pretty easy to implement recursively.
162 static bool SafeToDestroyConstant(const Constant *C) {
163 if (isa<GlobalValue>(C)) return false;
165 for (Value::const_use_iterator UI = C->use_begin(), E = C->use_end(); UI != E;
167 if (const Constant *CU = dyn_cast<Constant>(*UI)) {
168 if (!SafeToDestroyConstant(CU)) return false;
175 /// AnalyzeGlobal - Look at all uses of the global and fill in the GlobalStatus
176 /// structure. If the global has its address taken, return true to indicate we
177 /// can't do anything with it.
179 static bool AnalyzeGlobal(const Value *V, GlobalStatus &GS,
180 SmallPtrSet<const PHINode*, 16> &PHIUsers) {
181 for (Value::const_use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;
184 if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(U)) {
185 // If the result of the constantexpr isn't pointer type, then we won't
186 // know to expect it in various places. Just reject early.
187 if (!isa<PointerType>(CE->getType())) return true;
189 if (AnalyzeGlobal(CE, GS, PHIUsers)) return true;
190 } else if (const Instruction *I = dyn_cast<Instruction>(U)) {
191 if (const LoadInst *LI = dyn_cast<LoadInst>(I)) {
193 // Don't hack on volatile loads.
194 if (LI->isVolatile()) return true;
195 GS.Ordering = StrongerOrdering(GS.Ordering, LI->getOrdering());
196 } else if (const StoreInst *SI = dyn_cast<StoreInst>(I)) {
197 // Don't allow a store OF the address, only stores TO the address.
198 if (SI->getOperand(0) == V) return true;
200 // Don't hack on volatile stores.
201 if (SI->isVolatile()) return true;
203 GS.Ordering = StrongerOrdering(GS.Ordering, SI->getOrdering());
205 // If this is a direct store to the global (i.e., the global is a scalar
206 // value, not an aggregate), keep more specific information about
208 if (GS.StoredType != GlobalStatus::isStored) {
209 if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(
210 SI->getOperand(1))) {
211 Value *StoredVal = SI->getOperand(0);
213 if (Constant *C = dyn_cast<Constant>(StoredVal)) {
214 if (C->isThreadDependent()) {
215 // The stored value changes between threads; don't track it.
220 if (StoredVal == GV->getInitializer()) {
221 if (GS.StoredType < GlobalStatus::isInitializerStored)
222 GS.StoredType = GlobalStatus::isInitializerStored;
223 } else if (isa<LoadInst>(StoredVal) &&
224 cast<LoadInst>(StoredVal)->getOperand(0) == GV) {
225 if (GS.StoredType < GlobalStatus::isInitializerStored)
226 GS.StoredType = GlobalStatus::isInitializerStored;
227 } else if (GS.StoredType < GlobalStatus::isStoredOnce) {
228 GS.StoredType = GlobalStatus::isStoredOnce;
229 GS.StoredOnceValue = StoredVal;
230 } else if (GS.StoredType == GlobalStatus::isStoredOnce &&
231 GS.StoredOnceValue == StoredVal) {
234 GS.StoredType = GlobalStatus::isStored;
237 GS.StoredType = GlobalStatus::isStored;
240 } else if (isa<BitCastInst>(I)) {
241 if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
242 } else if (isa<GetElementPtrInst>(I)) {
243 if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
244 } else if (isa<SelectInst>(I)) {
245 if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
246 } else if (const PHINode *PN = dyn_cast<PHINode>(I)) {
247 // PHI nodes we can check just like select or GEP instructions, but we
248 // have to be careful about infinite recursion.
249 if (PHIUsers.insert(PN)) // Not already visited.
250 if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
251 } else if (isa<CmpInst>(I)) {
252 GS.isCompared = true;
253 } else if (const MemTransferInst *MTI = dyn_cast<MemTransferInst>(I)) {
254 if (MTI->isVolatile()) return true;
255 if (MTI->getArgOperand(0) == V)
256 GS.StoredType = GlobalStatus::isStored;
257 if (MTI->getArgOperand(1) == V)
259 } else if (const MemSetInst *MSI = dyn_cast<MemSetInst>(I)) {
260 assert(MSI->getArgOperand(0) == V && "Memset only takes one pointer!");
261 if (MSI->isVolatile()) return true;
262 GS.StoredType = GlobalStatus::isStored;
264 return true; // Any other non-load instruction might take address!
266 } else if (const Constant *C = dyn_cast<Constant>(U)) {
267 // We might have a dead and dangling constant hanging off of here.
268 if (!SafeToDestroyConstant(C))
271 // Otherwise must be some other user.
279 /// isLeakCheckerRoot - Is this global variable possibly used by a leak checker
280 /// as a root? If so, we might not really want to eliminate the stores to it.
281 static bool isLeakCheckerRoot(GlobalVariable *GV) {
282 // A global variable is a root if it is a pointer, or could plausibly contain
283 // a pointer. There are two challenges; one is that we could have a struct
284 // the has an inner member which is a pointer. We recurse through the type to
285 // detect these (up to a point). The other is that we may actually be a union
286 // of a pointer and another type, and so our LLVM type is an integer which
287 // gets converted into a pointer, or our type is an [i8 x #] with a pointer
288 // potentially contained here.
290 if (GV->hasPrivateLinkage())
293 SmallVector<Type *, 4> Types;
294 Types.push_back(cast<PointerType>(GV->getType())->getElementType());
298 Type *Ty = Types.pop_back_val();
299 switch (Ty->getTypeID()) {
301 case Type::PointerTyID: return true;
302 case Type::ArrayTyID:
303 case Type::VectorTyID: {
304 SequentialType *STy = cast<SequentialType>(Ty);
305 Types.push_back(STy->getElementType());
308 case Type::StructTyID: {
309 StructType *STy = cast<StructType>(Ty);
310 if (STy->isOpaque()) return true;
311 for (StructType::element_iterator I = STy->element_begin(),
312 E = STy->element_end(); I != E; ++I) {
314 if (isa<PointerType>(InnerTy)) return true;
315 if (isa<CompositeType>(InnerTy))
316 Types.push_back(InnerTy);
321 if (--Limit == 0) return true;
322 } while (!Types.empty());
326 /// Given a value that is stored to a global but never read, determine whether
327 /// it's safe to remove the store and the chain of computation that feeds the
329 static bool IsSafeComputationToRemove(Value *V, const TargetLibraryInfo *TLI) {
331 if (isa<Constant>(V))
335 if (isa<LoadInst>(V) || isa<InvokeInst>(V) || isa<Argument>(V) ||
338 if (isAllocationFn(V, TLI))
341 Instruction *I = cast<Instruction>(V);
342 if (I->mayHaveSideEffects())
344 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(I)) {
345 if (!GEP->hasAllConstantIndices())
347 } else if (I->getNumOperands() != 1) {
351 V = I->getOperand(0);
355 /// CleanupPointerRootUsers - This GV is a pointer root. Loop over all users
356 /// of the global and clean up any that obviously don't assign the global a
357 /// value that isn't dynamically allocated.
359 static bool CleanupPointerRootUsers(GlobalVariable *GV,
360 const TargetLibraryInfo *TLI) {
361 // A brief explanation of leak checkers. The goal is to find bugs where
362 // pointers are forgotten, causing an accumulating growth in memory
363 // usage over time. The common strategy for leak checkers is to whitelist the
364 // memory pointed to by globals at exit. This is popular because it also
365 // solves another problem where the main thread of a C++ program may shut down
366 // before other threads that are still expecting to use those globals. To
367 // handle that case, we expect the program may create a singleton and never
370 bool Changed = false;
372 // If Dead[n].first is the only use of a malloc result, we can delete its
373 // chain of computation and the store to the global in Dead[n].second.
374 SmallVector<std::pair<Instruction *, Instruction *>, 32> Dead;
376 // Constants can't be pointers to dynamically allocated memory.
377 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end();
380 if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
381 Value *V = SI->getValueOperand();
382 if (isa<Constant>(V)) {
384 SI->eraseFromParent();
385 } else if (Instruction *I = dyn_cast<Instruction>(V)) {
387 Dead.push_back(std::make_pair(I, SI));
389 } else if (MemSetInst *MSI = dyn_cast<MemSetInst>(U)) {
390 if (isa<Constant>(MSI->getValue())) {
392 MSI->eraseFromParent();
393 } else if (Instruction *I = dyn_cast<Instruction>(MSI->getValue())) {
395 Dead.push_back(std::make_pair(I, MSI));
397 } else if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(U)) {
398 GlobalVariable *MemSrc = dyn_cast<GlobalVariable>(MTI->getSource());
399 if (MemSrc && MemSrc->isConstant()) {
401 MTI->eraseFromParent();
402 } else if (Instruction *I = dyn_cast<Instruction>(MemSrc)) {
404 Dead.push_back(std::make_pair(I, MTI));
406 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U)) {
407 if (CE->use_empty()) {
408 CE->destroyConstant();
411 } else if (Constant *C = dyn_cast<Constant>(U)) {
412 if (SafeToDestroyConstant(C)) {
413 C->destroyConstant();
414 // This could have invalidated UI, start over from scratch.
416 CleanupPointerRootUsers(GV, TLI);
422 for (int i = 0, e = Dead.size(); i != e; ++i) {
423 if (IsSafeComputationToRemove(Dead[i].first, TLI)) {
424 Dead[i].second->eraseFromParent();
425 Instruction *I = Dead[i].first;
427 if (isAllocationFn(I, TLI))
429 Instruction *J = dyn_cast<Instruction>(I->getOperand(0));
432 I->eraseFromParent();
435 I->eraseFromParent();
442 /// CleanupConstantGlobalUsers - We just marked GV constant. Loop over all
443 /// users of the global, cleaning up the obvious ones. This is largely just a
444 /// quick scan over the use list to clean up the easy and obvious cruft. This
445 /// returns true if it made a change.
446 static bool CleanupConstantGlobalUsers(Value *V, Constant *Init,
447 DataLayout *TD, TargetLibraryInfo *TLI) {
448 bool Changed = false;
449 SmallVector<User*, 8> WorkList(V->use_begin(), V->use_end());
450 while (!WorkList.empty()) {
451 User *U = WorkList.pop_back_val();
453 if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
455 // Replace the load with the initializer.
456 LI->replaceAllUsesWith(Init);
457 LI->eraseFromParent();
460 } else if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
461 // Store must be unreachable or storing Init into the global.
462 SI->eraseFromParent();
464 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U)) {
465 if (CE->getOpcode() == Instruction::GetElementPtr) {
466 Constant *SubInit = 0;
468 SubInit = ConstantFoldLoadThroughGEPConstantExpr(Init, CE);
469 Changed |= CleanupConstantGlobalUsers(CE, SubInit, TD, TLI);
470 } else if (CE->getOpcode() == Instruction::BitCast &&
471 CE->getType()->isPointerTy()) {
472 // Pointer cast, delete any stores and memsets to the global.
473 Changed |= CleanupConstantGlobalUsers(CE, 0, TD, TLI);
476 if (CE->use_empty()) {
477 CE->destroyConstant();
480 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) {
481 // Do not transform "gepinst (gep constexpr (GV))" here, because forming
482 // "gepconstexpr (gep constexpr (GV))" will cause the two gep's to fold
483 // and will invalidate our notion of what Init is.
484 Constant *SubInit = 0;
485 if (!isa<ConstantExpr>(GEP->getOperand(0))) {
487 dyn_cast_or_null<ConstantExpr>(ConstantFoldInstruction(GEP, TD, TLI));
488 if (Init && CE && CE->getOpcode() == Instruction::GetElementPtr)
489 SubInit = ConstantFoldLoadThroughGEPConstantExpr(Init, CE);
491 // If the initializer is an all-null value and we have an inbounds GEP,
492 // we already know what the result of any load from that GEP is.
493 // TODO: Handle splats.
494 if (Init && isa<ConstantAggregateZero>(Init) && GEP->isInBounds())
495 SubInit = Constant::getNullValue(GEP->getType()->getElementType());
497 Changed |= CleanupConstantGlobalUsers(GEP, SubInit, TD, TLI);
499 if (GEP->use_empty()) {
500 GEP->eraseFromParent();
503 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(U)) { // memset/cpy/mv
504 if (MI->getRawDest() == V) {
505 MI->eraseFromParent();
509 } else if (Constant *C = dyn_cast<Constant>(U)) {
510 // If we have a chain of dead constantexprs or other things dangling from
511 // us, and if they are all dead, nuke them without remorse.
512 if (SafeToDestroyConstant(C)) {
513 C->destroyConstant();
514 CleanupConstantGlobalUsers(V, Init, TD, TLI);
522 /// isSafeSROAElementUse - Return true if the specified instruction is a safe
523 /// user of a derived expression from a global that we want to SROA.
524 static bool isSafeSROAElementUse(Value *V) {
525 // We might have a dead and dangling constant hanging off of here.
526 if (Constant *C = dyn_cast<Constant>(V))
527 return SafeToDestroyConstant(C);
529 Instruction *I = dyn_cast<Instruction>(V);
530 if (!I) return false;
533 if (isa<LoadInst>(I)) return true;
535 // Stores *to* the pointer are ok.
536 if (StoreInst *SI = dyn_cast<StoreInst>(I))
537 return SI->getOperand(0) != V;
539 // Otherwise, it must be a GEP.
540 GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I);
541 if (GEPI == 0) return false;
543 if (GEPI->getNumOperands() < 3 || !isa<Constant>(GEPI->getOperand(1)) ||
544 !cast<Constant>(GEPI->getOperand(1))->isNullValue())
547 for (Value::use_iterator I = GEPI->use_begin(), E = GEPI->use_end();
549 if (!isSafeSROAElementUse(*I))
555 /// IsUserOfGlobalSafeForSRA - U is a direct user of the specified global value.
556 /// Look at it and its uses and decide whether it is safe to SROA this global.
558 static bool IsUserOfGlobalSafeForSRA(User *U, GlobalValue *GV) {
559 // The user of the global must be a GEP Inst or a ConstantExpr GEP.
560 if (!isa<GetElementPtrInst>(U) &&
561 (!isa<ConstantExpr>(U) ||
562 cast<ConstantExpr>(U)->getOpcode() != Instruction::GetElementPtr))
565 // Check to see if this ConstantExpr GEP is SRA'able. In particular, we
566 // don't like < 3 operand CE's, and we don't like non-constant integer
567 // indices. This enforces that all uses are 'gep GV, 0, C, ...' for some
569 if (U->getNumOperands() < 3 || !isa<Constant>(U->getOperand(1)) ||
570 !cast<Constant>(U->getOperand(1))->isNullValue() ||
571 !isa<ConstantInt>(U->getOperand(2)))
574 gep_type_iterator GEPI = gep_type_begin(U), E = gep_type_end(U);
575 ++GEPI; // Skip over the pointer index.
577 // If this is a use of an array allocation, do a bit more checking for sanity.
578 if (ArrayType *AT = dyn_cast<ArrayType>(*GEPI)) {
579 uint64_t NumElements = AT->getNumElements();
580 ConstantInt *Idx = cast<ConstantInt>(U->getOperand(2));
582 // Check to make sure that index falls within the array. If not,
583 // something funny is going on, so we won't do the optimization.
585 if (Idx->getZExtValue() >= NumElements)
588 // We cannot scalar repl this level of the array unless any array
589 // sub-indices are in-range constants. In particular, consider:
590 // A[0][i]. We cannot know that the user isn't doing invalid things like
591 // allowing i to index an out-of-range subscript that accesses A[1].
593 // Scalar replacing *just* the outer index of the array is probably not
594 // going to be a win anyway, so just give up.
595 for (++GEPI; // Skip array index.
598 uint64_t NumElements;
599 if (ArrayType *SubArrayTy = dyn_cast<ArrayType>(*GEPI))
600 NumElements = SubArrayTy->getNumElements();
601 else if (VectorType *SubVectorTy = dyn_cast<VectorType>(*GEPI))
602 NumElements = SubVectorTy->getNumElements();
604 assert((*GEPI)->isStructTy() &&
605 "Indexed GEP type is not array, vector, or struct!");
609 ConstantInt *IdxVal = dyn_cast<ConstantInt>(GEPI.getOperand());
610 if (!IdxVal || IdxVal->getZExtValue() >= NumElements)
615 for (Value::use_iterator I = U->use_begin(), E = U->use_end(); I != E; ++I)
616 if (!isSafeSROAElementUse(*I))
621 /// GlobalUsersSafeToSRA - Look at all uses of the global and decide whether it
622 /// is safe for us to perform this transformation.
624 static bool GlobalUsersSafeToSRA(GlobalValue *GV) {
625 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end();
627 if (!IsUserOfGlobalSafeForSRA(*UI, GV))
634 /// SRAGlobal - Perform scalar replacement of aggregates on the specified global
635 /// variable. This opens the door for other optimizations by exposing the
636 /// behavior of the program in a more fine-grained way. We have determined that
637 /// this transformation is safe already. We return the first global variable we
638 /// insert so that the caller can reprocess it.
639 static GlobalVariable *SRAGlobal(GlobalVariable *GV, const DataLayout &TD) {
640 // Make sure this global only has simple uses that we can SRA.
641 if (!GlobalUsersSafeToSRA(GV))
644 assert(GV->hasLocalLinkage() && !GV->isConstant());
645 Constant *Init = GV->getInitializer();
646 Type *Ty = Init->getType();
648 std::vector<GlobalVariable*> NewGlobals;
649 Module::GlobalListType &Globals = GV->getParent()->getGlobalList();
651 // Get the alignment of the global, either explicit or target-specific.
652 unsigned StartAlignment = GV->getAlignment();
653 if (StartAlignment == 0)
654 StartAlignment = TD.getABITypeAlignment(GV->getType());
656 if (StructType *STy = dyn_cast<StructType>(Ty)) {
657 NewGlobals.reserve(STy->getNumElements());
658 const StructLayout &Layout = *TD.getStructLayout(STy);
659 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
660 Constant *In = Init->getAggregateElement(i);
661 assert(In && "Couldn't get element of initializer?");
662 GlobalVariable *NGV = new GlobalVariable(STy->getElementType(i), false,
663 GlobalVariable::InternalLinkage,
664 In, GV->getName()+"."+Twine(i),
665 GV->getThreadLocalMode(),
666 GV->getType()->getAddressSpace());
667 Globals.insert(GV, NGV);
668 NewGlobals.push_back(NGV);
670 // Calculate the known alignment of the field. If the original aggregate
671 // had 256 byte alignment for example, something might depend on that:
672 // propagate info to each field.
673 uint64_t FieldOffset = Layout.getElementOffset(i);
674 unsigned NewAlign = (unsigned)MinAlign(StartAlignment, FieldOffset);
675 if (NewAlign > TD.getABITypeAlignment(STy->getElementType(i)))
676 NGV->setAlignment(NewAlign);
678 } else if (SequentialType *STy = dyn_cast<SequentialType>(Ty)) {
679 unsigned NumElements = 0;
680 if (ArrayType *ATy = dyn_cast<ArrayType>(STy))
681 NumElements = ATy->getNumElements();
683 NumElements = cast<VectorType>(STy)->getNumElements();
685 if (NumElements > 16 && GV->hasNUsesOrMore(16))
686 return 0; // It's not worth it.
687 NewGlobals.reserve(NumElements);
689 uint64_t EltSize = TD.getTypeAllocSize(STy->getElementType());
690 unsigned EltAlign = TD.getABITypeAlignment(STy->getElementType());
691 for (unsigned i = 0, e = NumElements; i != e; ++i) {
692 Constant *In = Init->getAggregateElement(i);
693 assert(In && "Couldn't get element of initializer?");
695 GlobalVariable *NGV = new GlobalVariable(STy->getElementType(), false,
696 GlobalVariable::InternalLinkage,
697 In, GV->getName()+"."+Twine(i),
698 GV->getThreadLocalMode(),
699 GV->getType()->getAddressSpace());
700 Globals.insert(GV, NGV);
701 NewGlobals.push_back(NGV);
703 // Calculate the known alignment of the field. If the original aggregate
704 // had 256 byte alignment for example, something might depend on that:
705 // propagate info to each field.
706 unsigned NewAlign = (unsigned)MinAlign(StartAlignment, EltSize*i);
707 if (NewAlign > EltAlign)
708 NGV->setAlignment(NewAlign);
712 if (NewGlobals.empty())
715 DEBUG(dbgs() << "PERFORMING GLOBAL SRA ON: " << *GV);
717 Constant *NullInt =Constant::getNullValue(Type::getInt32Ty(GV->getContext()));
719 // Loop over all of the uses of the global, replacing the constantexpr geps,
720 // with smaller constantexpr geps or direct references.
721 while (!GV->use_empty()) {
722 User *GEP = GV->use_back();
723 assert(((isa<ConstantExpr>(GEP) &&
724 cast<ConstantExpr>(GEP)->getOpcode()==Instruction::GetElementPtr)||
725 isa<GetElementPtrInst>(GEP)) && "NonGEP CE's are not SRAable!");
727 // Ignore the 1th operand, which has to be zero or else the program is quite
728 // broken (undefined). Get the 2nd operand, which is the structure or array
730 unsigned Val = cast<ConstantInt>(GEP->getOperand(2))->getZExtValue();
731 if (Val >= NewGlobals.size()) Val = 0; // Out of bound array access.
733 Value *NewPtr = NewGlobals[Val];
735 // Form a shorter GEP if needed.
736 if (GEP->getNumOperands() > 3) {
737 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GEP)) {
738 SmallVector<Constant*, 8> Idxs;
739 Idxs.push_back(NullInt);
740 for (unsigned i = 3, e = CE->getNumOperands(); i != e; ++i)
741 Idxs.push_back(CE->getOperand(i));
742 NewPtr = ConstantExpr::getGetElementPtr(cast<Constant>(NewPtr), Idxs);
744 GetElementPtrInst *GEPI = cast<GetElementPtrInst>(GEP);
745 SmallVector<Value*, 8> Idxs;
746 Idxs.push_back(NullInt);
747 for (unsigned i = 3, e = GEPI->getNumOperands(); i != e; ++i)
748 Idxs.push_back(GEPI->getOperand(i));
749 NewPtr = GetElementPtrInst::Create(NewPtr, Idxs,
750 GEPI->getName()+"."+Twine(Val),GEPI);
753 GEP->replaceAllUsesWith(NewPtr);
755 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(GEP))
756 GEPI->eraseFromParent();
758 cast<ConstantExpr>(GEP)->destroyConstant();
761 // Delete the old global, now that it is dead.
765 // Loop over the new globals array deleting any globals that are obviously
766 // dead. This can arise due to scalarization of a structure or an array that
767 // has elements that are dead.
768 unsigned FirstGlobal = 0;
769 for (unsigned i = 0, e = NewGlobals.size(); i != e; ++i)
770 if (NewGlobals[i]->use_empty()) {
771 Globals.erase(NewGlobals[i]);
772 if (FirstGlobal == i) ++FirstGlobal;
775 return FirstGlobal != NewGlobals.size() ? NewGlobals[FirstGlobal] : 0;
778 /// AllUsesOfValueWillTrapIfNull - Return true if all users of the specified
779 /// value will trap if the value is dynamically null. PHIs keeps track of any
780 /// phi nodes we've seen to avoid reprocessing them.
781 static bool AllUsesOfValueWillTrapIfNull(const Value *V,
782 SmallPtrSet<const PHINode*, 8> &PHIs) {
783 for (Value::const_use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;
787 if (isa<LoadInst>(U)) {
789 } else if (const StoreInst *SI = dyn_cast<StoreInst>(U)) {
790 if (SI->getOperand(0) == V) {
791 //cerr << "NONTRAPPING USE: " << *U;
792 return false; // Storing the value.
794 } else if (const CallInst *CI = dyn_cast<CallInst>(U)) {
795 if (CI->getCalledValue() != V) {
796 //cerr << "NONTRAPPING USE: " << *U;
797 return false; // Not calling the ptr
799 } else if (const InvokeInst *II = dyn_cast<InvokeInst>(U)) {
800 if (II->getCalledValue() != V) {
801 //cerr << "NONTRAPPING USE: " << *U;
802 return false; // Not calling the ptr
804 } else if (const BitCastInst *CI = dyn_cast<BitCastInst>(U)) {
805 if (!AllUsesOfValueWillTrapIfNull(CI, PHIs)) return false;
806 } else if (const GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(U)) {
807 if (!AllUsesOfValueWillTrapIfNull(GEPI, PHIs)) return false;
808 } else if (const PHINode *PN = dyn_cast<PHINode>(U)) {
809 // If we've already seen this phi node, ignore it, it has already been
811 if (PHIs.insert(PN) && !AllUsesOfValueWillTrapIfNull(PN, PHIs))
813 } else if (isa<ICmpInst>(U) &&
814 isa<ConstantPointerNull>(UI->getOperand(1))) {
815 // Ignore icmp X, null
817 //cerr << "NONTRAPPING USE: " << *U;
824 /// AllUsesOfLoadedValueWillTrapIfNull - Return true if all uses of any loads
825 /// from GV will trap if the loaded value is null. Note that this also permits
826 /// comparisons of the loaded value against null, as a special case.
827 static bool AllUsesOfLoadedValueWillTrapIfNull(const GlobalVariable *GV) {
828 for (Value::const_use_iterator UI = GV->use_begin(), E = GV->use_end();
832 if (const LoadInst *LI = dyn_cast<LoadInst>(U)) {
833 SmallPtrSet<const PHINode*, 8> PHIs;
834 if (!AllUsesOfValueWillTrapIfNull(LI, PHIs))
836 } else if (isa<StoreInst>(U)) {
837 // Ignore stores to the global.
839 // We don't know or understand this user, bail out.
840 //cerr << "UNKNOWN USER OF GLOBAL!: " << *U;
847 static bool OptimizeAwayTrappingUsesOfValue(Value *V, Constant *NewV) {
848 bool Changed = false;
849 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ) {
850 Instruction *I = cast<Instruction>(*UI++);
851 if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
852 LI->setOperand(0, NewV);
854 } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
855 if (SI->getOperand(1) == V) {
856 SI->setOperand(1, NewV);
859 } else if (isa<CallInst>(I) || isa<InvokeInst>(I)) {
861 if (CS.getCalledValue() == V) {
862 // Calling through the pointer! Turn into a direct call, but be careful
863 // that the pointer is not also being passed as an argument.
864 CS.setCalledFunction(NewV);
866 bool PassedAsArg = false;
867 for (unsigned i = 0, e = CS.arg_size(); i != e; ++i)
868 if (CS.getArgument(i) == V) {
870 CS.setArgument(i, NewV);
874 // Being passed as an argument also. Be careful to not invalidate UI!
878 } else if (CastInst *CI = dyn_cast<CastInst>(I)) {
879 Changed |= OptimizeAwayTrappingUsesOfValue(CI,
880 ConstantExpr::getCast(CI->getOpcode(),
881 NewV, CI->getType()));
882 if (CI->use_empty()) {
884 CI->eraseFromParent();
886 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I)) {
887 // Should handle GEP here.
888 SmallVector<Constant*, 8> Idxs;
889 Idxs.reserve(GEPI->getNumOperands()-1);
890 for (User::op_iterator i = GEPI->op_begin() + 1, e = GEPI->op_end();
892 if (Constant *C = dyn_cast<Constant>(*i))
896 if (Idxs.size() == GEPI->getNumOperands()-1)
897 Changed |= OptimizeAwayTrappingUsesOfValue(GEPI,
898 ConstantExpr::getGetElementPtr(NewV, Idxs));
899 if (GEPI->use_empty()) {
901 GEPI->eraseFromParent();
910 /// OptimizeAwayTrappingUsesOfLoads - The specified global has only one non-null
911 /// value stored into it. If there are uses of the loaded value that would trap
912 /// if the loaded value is dynamically null, then we know that they cannot be
913 /// reachable with a null optimize away the load.
914 static bool OptimizeAwayTrappingUsesOfLoads(GlobalVariable *GV, Constant *LV,
916 TargetLibraryInfo *TLI) {
917 bool Changed = false;
919 // Keep track of whether we are able to remove all the uses of the global
920 // other than the store that defines it.
921 bool AllNonStoreUsesGone = true;
923 // Replace all uses of loads with uses of uses of the stored value.
924 for (Value::use_iterator GUI = GV->use_begin(), E = GV->use_end(); GUI != E;){
925 User *GlobalUser = *GUI++;
926 if (LoadInst *LI = dyn_cast<LoadInst>(GlobalUser)) {
927 Changed |= OptimizeAwayTrappingUsesOfValue(LI, LV);
928 // If we were able to delete all uses of the loads
929 if (LI->use_empty()) {
930 LI->eraseFromParent();
933 AllNonStoreUsesGone = false;
935 } else if (isa<StoreInst>(GlobalUser)) {
936 // Ignore the store that stores "LV" to the global.
937 assert(GlobalUser->getOperand(1) == GV &&
938 "Must be storing *to* the global");
940 AllNonStoreUsesGone = false;
942 // If we get here we could have other crazy uses that are transitively
944 assert((isa<PHINode>(GlobalUser) || isa<SelectInst>(GlobalUser) ||
945 isa<ConstantExpr>(GlobalUser) || isa<CmpInst>(GlobalUser) ||
946 isa<BitCastInst>(GlobalUser) ||
947 isa<GetElementPtrInst>(GlobalUser)) &&
948 "Only expect load and stores!");
953 DEBUG(dbgs() << "OPTIMIZED LOADS FROM STORED ONCE POINTER: " << *GV);
957 // If we nuked all of the loads, then none of the stores are needed either,
958 // nor is the global.
959 if (AllNonStoreUsesGone) {
960 if (isLeakCheckerRoot(GV)) {
961 Changed |= CleanupPointerRootUsers(GV, TLI);
964 CleanupConstantGlobalUsers(GV, 0, TD, TLI);
966 if (GV->use_empty()) {
967 DEBUG(dbgs() << " *** GLOBAL NOW DEAD!\n");
969 GV->eraseFromParent();
976 /// ConstantPropUsersOf - Walk the use list of V, constant folding all of the
977 /// instructions that are foldable.
978 static void ConstantPropUsersOf(Value *V,
979 DataLayout *TD, TargetLibraryInfo *TLI) {
980 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; )
981 if (Instruction *I = dyn_cast<Instruction>(*UI++))
982 if (Constant *NewC = ConstantFoldInstruction(I, TD, TLI)) {
983 I->replaceAllUsesWith(NewC);
985 // Advance UI to the next non-I use to avoid invalidating it!
986 // Instructions could multiply use V.
987 while (UI != E && *UI == I)
989 I->eraseFromParent();
993 /// OptimizeGlobalAddressOfMalloc - This function takes the specified global
994 /// variable, and transforms the program as if it always contained the result of
995 /// the specified malloc. Because it is always the result of the specified
996 /// malloc, there is no reason to actually DO the malloc. Instead, turn the
997 /// malloc into a global, and any loads of GV as uses of the new global.
998 static GlobalVariable *OptimizeGlobalAddressOfMalloc(GlobalVariable *GV,
1001 ConstantInt *NElements,
1003 TargetLibraryInfo *TLI) {
1004 DEBUG(errs() << "PROMOTING GLOBAL: " << *GV << " CALL = " << *CI << '\n');
1007 if (NElements->getZExtValue() == 1)
1008 GlobalType = AllocTy;
1010 // If we have an array allocation, the global variable is of an array.
1011 GlobalType = ArrayType::get(AllocTy, NElements->getZExtValue());
1013 // Create the new global variable. The contents of the malloc'd memory is
1014 // undefined, so initialize with an undef value.
1015 GlobalVariable *NewGV = new GlobalVariable(*GV->getParent(),
1017 GlobalValue::InternalLinkage,
1018 UndefValue::get(GlobalType),
1019 GV->getName()+".body",
1021 GV->getThreadLocalMode());
1023 // If there are bitcast users of the malloc (which is typical, usually we have
1024 // a malloc + bitcast) then replace them with uses of the new global. Update
1025 // other users to use the global as well.
1026 BitCastInst *TheBC = 0;
1027 while (!CI->use_empty()) {
1028 Instruction *User = cast<Instruction>(CI->use_back());
1029 if (BitCastInst *BCI = dyn_cast<BitCastInst>(User)) {
1030 if (BCI->getType() == NewGV->getType()) {
1031 BCI->replaceAllUsesWith(NewGV);
1032 BCI->eraseFromParent();
1034 BCI->setOperand(0, NewGV);
1038 TheBC = new BitCastInst(NewGV, CI->getType(), "newgv", CI);
1039 User->replaceUsesOfWith(CI, TheBC);
1043 Constant *RepValue = NewGV;
1044 if (NewGV->getType() != GV->getType()->getElementType())
1045 RepValue = ConstantExpr::getBitCast(RepValue,
1046 GV->getType()->getElementType());
1048 // If there is a comparison against null, we will insert a global bool to
1049 // keep track of whether the global was initialized yet or not.
1050 GlobalVariable *InitBool =
1051 new GlobalVariable(Type::getInt1Ty(GV->getContext()), false,
1052 GlobalValue::InternalLinkage,
1053 ConstantInt::getFalse(GV->getContext()),
1054 GV->getName()+".init", GV->getThreadLocalMode());
1055 bool InitBoolUsed = false;
1057 // Loop over all uses of GV, processing them in turn.
1058 while (!GV->use_empty()) {
1059 if (StoreInst *SI = dyn_cast<StoreInst>(GV->use_back())) {
1060 // The global is initialized when the store to it occurs.
1061 new StoreInst(ConstantInt::getTrue(GV->getContext()), InitBool, false, 0,
1062 SI->getOrdering(), SI->getSynchScope(), SI);
1063 SI->eraseFromParent();
1067 LoadInst *LI = cast<LoadInst>(GV->use_back());
1068 while (!LI->use_empty()) {
1069 Use &LoadUse = LI->use_begin().getUse();
1070 if (!isa<ICmpInst>(LoadUse.getUser())) {
1075 ICmpInst *ICI = cast<ICmpInst>(LoadUse.getUser());
1076 // Replace the cmp X, 0 with a use of the bool value.
1077 // Sink the load to where the compare was, if atomic rules allow us to.
1078 Value *LV = new LoadInst(InitBool, InitBool->getName()+".val", false, 0,
1079 LI->getOrdering(), LI->getSynchScope(),
1080 LI->isUnordered() ? (Instruction*)ICI : LI);
1081 InitBoolUsed = true;
1082 switch (ICI->getPredicate()) {
1083 default: llvm_unreachable("Unknown ICmp Predicate!");
1084 case ICmpInst::ICMP_ULT:
1085 case ICmpInst::ICMP_SLT: // X < null -> always false
1086 LV = ConstantInt::getFalse(GV->getContext());
1088 case ICmpInst::ICMP_ULE:
1089 case ICmpInst::ICMP_SLE:
1090 case ICmpInst::ICMP_EQ:
1091 LV = BinaryOperator::CreateNot(LV, "notinit", ICI);
1093 case ICmpInst::ICMP_NE:
1094 case ICmpInst::ICMP_UGE:
1095 case ICmpInst::ICMP_SGE:
1096 case ICmpInst::ICMP_UGT:
1097 case ICmpInst::ICMP_SGT:
1098 break; // no change.
1100 ICI->replaceAllUsesWith(LV);
1101 ICI->eraseFromParent();
1103 LI->eraseFromParent();
1106 // If the initialization boolean was used, insert it, otherwise delete it.
1107 if (!InitBoolUsed) {
1108 while (!InitBool->use_empty()) // Delete initializations
1109 cast<StoreInst>(InitBool->use_back())->eraseFromParent();
1112 GV->getParent()->getGlobalList().insert(GV, InitBool);
1114 // Now the GV is dead, nuke it and the malloc..
1115 GV->eraseFromParent();
1116 CI->eraseFromParent();
1118 // To further other optimizations, loop over all users of NewGV and try to
1119 // constant prop them. This will promote GEP instructions with constant
1120 // indices into GEP constant-exprs, which will allow global-opt to hack on it.
1121 ConstantPropUsersOf(NewGV, TD, TLI);
1122 if (RepValue != NewGV)
1123 ConstantPropUsersOf(RepValue, TD, TLI);
1128 /// ValueIsOnlyUsedLocallyOrStoredToOneGlobal - Scan the use-list of V checking
1129 /// to make sure that there are no complex uses of V. We permit simple things
1130 /// like dereferencing the pointer, but not storing through the address, unless
1131 /// it is to the specified global.
1132 static bool ValueIsOnlyUsedLocallyOrStoredToOneGlobal(const Instruction *V,
1133 const GlobalVariable *GV,
1134 SmallPtrSet<const PHINode*, 8> &PHIs) {
1135 for (Value::const_use_iterator UI = V->use_begin(), E = V->use_end();
1137 const Instruction *Inst = cast<Instruction>(*UI);
1139 if (isa<LoadInst>(Inst) || isa<CmpInst>(Inst)) {
1140 continue; // Fine, ignore.
1143 if (const StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
1144 if (SI->getOperand(0) == V && SI->getOperand(1) != GV)
1145 return false; // Storing the pointer itself... bad.
1146 continue; // Otherwise, storing through it, or storing into GV... fine.
1149 // Must index into the array and into the struct.
1150 if (isa<GetElementPtrInst>(Inst) && Inst->getNumOperands() >= 3) {
1151 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(Inst, GV, PHIs))
1156 if (const PHINode *PN = dyn_cast<PHINode>(Inst)) {
1157 // PHIs are ok if all uses are ok. Don't infinitely recurse through PHI
1159 if (PHIs.insert(PN))
1160 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(PN, GV, PHIs))
1165 if (const BitCastInst *BCI = dyn_cast<BitCastInst>(Inst)) {
1166 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(BCI, GV, PHIs))
1176 /// ReplaceUsesOfMallocWithGlobal - The Alloc pointer is stored into GV
1177 /// somewhere. Transform all uses of the allocation into loads from the
1178 /// global and uses of the resultant pointer. Further, delete the store into
1179 /// GV. This assumes that these value pass the
1180 /// 'ValueIsOnlyUsedLocallyOrStoredToOneGlobal' predicate.
1181 static void ReplaceUsesOfMallocWithGlobal(Instruction *Alloc,
1182 GlobalVariable *GV) {
1183 while (!Alloc->use_empty()) {
1184 Instruction *U = cast<Instruction>(*Alloc->use_begin());
1185 Instruction *InsertPt = U;
1186 if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
1187 // If this is the store of the allocation into the global, remove it.
1188 if (SI->getOperand(1) == GV) {
1189 SI->eraseFromParent();
1192 } else if (PHINode *PN = dyn_cast<PHINode>(U)) {
1193 // Insert the load in the corresponding predecessor, not right before the
1195 InsertPt = PN->getIncomingBlock(Alloc->use_begin())->getTerminator();
1196 } else if (isa<BitCastInst>(U)) {
1197 // Must be bitcast between the malloc and store to initialize the global.
1198 ReplaceUsesOfMallocWithGlobal(U, GV);
1199 U->eraseFromParent();
1201 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(U)) {
1202 // If this is a "GEP bitcast" and the user is a store to the global, then
1203 // just process it as a bitcast.
1204 if (GEPI->hasAllZeroIndices() && GEPI->hasOneUse())
1205 if (StoreInst *SI = dyn_cast<StoreInst>(GEPI->use_back()))
1206 if (SI->getOperand(1) == GV) {
1207 // Must be bitcast GEP between the malloc and store to initialize
1209 ReplaceUsesOfMallocWithGlobal(GEPI, GV);
1210 GEPI->eraseFromParent();
1215 // Insert a load from the global, and use it instead of the malloc.
1216 Value *NL = new LoadInst(GV, GV->getName()+".val", InsertPt);
1217 U->replaceUsesOfWith(Alloc, NL);
1221 /// LoadUsesSimpleEnoughForHeapSRA - Verify that all uses of V (a load, or a phi
1222 /// of a load) are simple enough to perform heap SRA on. This permits GEP's
1223 /// that index through the array and struct field, icmps of null, and PHIs.
1224 static bool LoadUsesSimpleEnoughForHeapSRA(const Value *V,
1225 SmallPtrSet<const PHINode*, 32> &LoadUsingPHIs,
1226 SmallPtrSet<const PHINode*, 32> &LoadUsingPHIsPerLoad) {
1227 // We permit two users of the load: setcc comparing against the null
1228 // pointer, and a getelementptr of a specific form.
1229 for (Value::const_use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;
1231 const Instruction *User = cast<Instruction>(*UI);
1233 // Comparison against null is ok.
1234 if (const ICmpInst *ICI = dyn_cast<ICmpInst>(User)) {
1235 if (!isa<ConstantPointerNull>(ICI->getOperand(1)))
1240 // getelementptr is also ok, but only a simple form.
1241 if (const GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
1242 // Must index into the array and into the struct.
1243 if (GEPI->getNumOperands() < 3)
1246 // Otherwise the GEP is ok.
1250 if (const PHINode *PN = dyn_cast<PHINode>(User)) {
1251 if (!LoadUsingPHIsPerLoad.insert(PN))
1252 // This means some phi nodes are dependent on each other.
1253 // Avoid infinite looping!
1255 if (!LoadUsingPHIs.insert(PN))
1256 // If we have already analyzed this PHI, then it is safe.
1259 // Make sure all uses of the PHI are simple enough to transform.
1260 if (!LoadUsesSimpleEnoughForHeapSRA(PN,
1261 LoadUsingPHIs, LoadUsingPHIsPerLoad))
1267 // Otherwise we don't know what this is, not ok.
1275 /// AllGlobalLoadUsesSimpleEnoughForHeapSRA - If all users of values loaded from
1276 /// GV are simple enough to perform HeapSRA, return true.
1277 static bool AllGlobalLoadUsesSimpleEnoughForHeapSRA(const GlobalVariable *GV,
1278 Instruction *StoredVal) {
1279 SmallPtrSet<const PHINode*, 32> LoadUsingPHIs;
1280 SmallPtrSet<const PHINode*, 32> LoadUsingPHIsPerLoad;
1281 for (Value::const_use_iterator UI = GV->use_begin(), E = GV->use_end();
1283 if (const LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
1284 if (!LoadUsesSimpleEnoughForHeapSRA(LI, LoadUsingPHIs,
1285 LoadUsingPHIsPerLoad))
1287 LoadUsingPHIsPerLoad.clear();
1290 // If we reach here, we know that all uses of the loads and transitive uses
1291 // (through PHI nodes) are simple enough to transform. However, we don't know
1292 // that all inputs the to the PHI nodes are in the same equivalence sets.
1293 // Check to verify that all operands of the PHIs are either PHIS that can be
1294 // transformed, loads from GV, or MI itself.
1295 for (SmallPtrSet<const PHINode*, 32>::const_iterator I = LoadUsingPHIs.begin()
1296 , E = LoadUsingPHIs.end(); I != E; ++I) {
1297 const PHINode *PN = *I;
1298 for (unsigned op = 0, e = PN->getNumIncomingValues(); op != e; ++op) {
1299 Value *InVal = PN->getIncomingValue(op);
1301 // PHI of the stored value itself is ok.
1302 if (InVal == StoredVal) continue;
1304 if (const PHINode *InPN = dyn_cast<PHINode>(InVal)) {
1305 // One of the PHIs in our set is (optimistically) ok.
1306 if (LoadUsingPHIs.count(InPN))
1311 // Load from GV is ok.
1312 if (const LoadInst *LI = dyn_cast<LoadInst>(InVal))
1313 if (LI->getOperand(0) == GV)
1318 // Anything else is rejected.
1326 static Value *GetHeapSROAValue(Value *V, unsigned FieldNo,
1327 DenseMap<Value*, std::vector<Value*> > &InsertedScalarizedValues,
1328 std::vector<std::pair<PHINode*, unsigned> > &PHIsToRewrite) {
1329 std::vector<Value*> &FieldVals = InsertedScalarizedValues[V];
1331 if (FieldNo >= FieldVals.size())
1332 FieldVals.resize(FieldNo+1);
1334 // If we already have this value, just reuse the previously scalarized
1336 if (Value *FieldVal = FieldVals[FieldNo])
1339 // Depending on what instruction this is, we have several cases.
1341 if (LoadInst *LI = dyn_cast<LoadInst>(V)) {
1342 // This is a scalarized version of the load from the global. Just create
1343 // a new Load of the scalarized global.
1344 Result = new LoadInst(GetHeapSROAValue(LI->getOperand(0), FieldNo,
1345 InsertedScalarizedValues,
1347 LI->getName()+".f"+Twine(FieldNo), LI);
1348 } else if (PHINode *PN = dyn_cast<PHINode>(V)) {
1349 // PN's type is pointer to struct. Make a new PHI of pointer to struct
1352 cast<StructType>(cast<PointerType>(PN->getType())->getElementType());
1355 PHINode::Create(PointerType::getUnqual(ST->getElementType(FieldNo)),
1356 PN->getNumIncomingValues(),
1357 PN->getName()+".f"+Twine(FieldNo), PN);
1359 PHIsToRewrite.push_back(std::make_pair(PN, FieldNo));
1361 llvm_unreachable("Unknown usable value");
1364 return FieldVals[FieldNo] = Result;
1367 /// RewriteHeapSROALoadUser - Given a load instruction and a value derived from
1368 /// the load, rewrite the derived value to use the HeapSRoA'd load.
1369 static void RewriteHeapSROALoadUser(Instruction *LoadUser,
1370 DenseMap<Value*, std::vector<Value*> > &InsertedScalarizedValues,
1371 std::vector<std::pair<PHINode*, unsigned> > &PHIsToRewrite) {
1372 // If this is a comparison against null, handle it.
1373 if (ICmpInst *SCI = dyn_cast<ICmpInst>(LoadUser)) {
1374 assert(isa<ConstantPointerNull>(SCI->getOperand(1)));
1375 // If we have a setcc of the loaded pointer, we can use a setcc of any
1377 Value *NPtr = GetHeapSROAValue(SCI->getOperand(0), 0,
1378 InsertedScalarizedValues, PHIsToRewrite);
1380 Value *New = new ICmpInst(SCI, SCI->getPredicate(), NPtr,
1381 Constant::getNullValue(NPtr->getType()),
1383 SCI->replaceAllUsesWith(New);
1384 SCI->eraseFromParent();
1388 // Handle 'getelementptr Ptr, Idx, i32 FieldNo ...'
1389 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(LoadUser)) {
1390 assert(GEPI->getNumOperands() >= 3 && isa<ConstantInt>(GEPI->getOperand(2))
1391 && "Unexpected GEPI!");
1393 // Load the pointer for this field.
1394 unsigned FieldNo = cast<ConstantInt>(GEPI->getOperand(2))->getZExtValue();
1395 Value *NewPtr = GetHeapSROAValue(GEPI->getOperand(0), FieldNo,
1396 InsertedScalarizedValues, PHIsToRewrite);
1398 // Create the new GEP idx vector.
1399 SmallVector<Value*, 8> GEPIdx;
1400 GEPIdx.push_back(GEPI->getOperand(1));
1401 GEPIdx.append(GEPI->op_begin()+3, GEPI->op_end());
1403 Value *NGEPI = GetElementPtrInst::Create(NewPtr, GEPIdx,
1404 GEPI->getName(), GEPI);
1405 GEPI->replaceAllUsesWith(NGEPI);
1406 GEPI->eraseFromParent();
1410 // Recursively transform the users of PHI nodes. This will lazily create the
1411 // PHIs that are needed for individual elements. Keep track of what PHIs we
1412 // see in InsertedScalarizedValues so that we don't get infinite loops (very
1413 // antisocial). If the PHI is already in InsertedScalarizedValues, it has
1414 // already been seen first by another load, so its uses have already been
1416 PHINode *PN = cast<PHINode>(LoadUser);
1417 if (!InsertedScalarizedValues.insert(std::make_pair(PN,
1418 std::vector<Value*>())).second)
1421 // If this is the first time we've seen this PHI, recursively process all
1423 for (Value::use_iterator UI = PN->use_begin(), E = PN->use_end(); UI != E; ) {
1424 Instruction *User = cast<Instruction>(*UI++);
1425 RewriteHeapSROALoadUser(User, InsertedScalarizedValues, PHIsToRewrite);
1429 /// RewriteUsesOfLoadForHeapSRoA - We are performing Heap SRoA on a global. Ptr
1430 /// is a value loaded from the global. Eliminate all uses of Ptr, making them
1431 /// use FieldGlobals instead. All uses of loaded values satisfy
1432 /// AllGlobalLoadUsesSimpleEnoughForHeapSRA.
1433 static void RewriteUsesOfLoadForHeapSRoA(LoadInst *Load,
1434 DenseMap<Value*, std::vector<Value*> > &InsertedScalarizedValues,
1435 std::vector<std::pair<PHINode*, unsigned> > &PHIsToRewrite) {
1436 for (Value::use_iterator UI = Load->use_begin(), E = Load->use_end();
1438 Instruction *User = cast<Instruction>(*UI++);
1439 RewriteHeapSROALoadUser(User, InsertedScalarizedValues, PHIsToRewrite);
1442 if (Load->use_empty()) {
1443 Load->eraseFromParent();
1444 InsertedScalarizedValues.erase(Load);
1448 /// PerformHeapAllocSRoA - CI is an allocation of an array of structures. Break
1449 /// it up into multiple allocations of arrays of the fields.
1450 static GlobalVariable *PerformHeapAllocSRoA(GlobalVariable *GV, CallInst *CI,
1451 Value *NElems, DataLayout *TD,
1452 const TargetLibraryInfo *TLI) {
1453 DEBUG(dbgs() << "SROA HEAP ALLOC: " << *GV << " MALLOC = " << *CI << '\n');
1454 Type *MAT = getMallocAllocatedType(CI, TLI);
1455 StructType *STy = cast<StructType>(MAT);
1457 // There is guaranteed to be at least one use of the malloc (storing
1458 // it into GV). If there are other uses, change them to be uses of
1459 // the global to simplify later code. This also deletes the store
1461 ReplaceUsesOfMallocWithGlobal(CI, GV);
1463 // Okay, at this point, there are no users of the malloc. Insert N
1464 // new mallocs at the same place as CI, and N globals.
1465 std::vector<Value*> FieldGlobals;
1466 std::vector<Value*> FieldMallocs;
1468 for (unsigned FieldNo = 0, e = STy->getNumElements(); FieldNo != e;++FieldNo){
1469 Type *FieldTy = STy->getElementType(FieldNo);
1470 PointerType *PFieldTy = PointerType::getUnqual(FieldTy);
1472 GlobalVariable *NGV =
1473 new GlobalVariable(*GV->getParent(),
1474 PFieldTy, false, GlobalValue::InternalLinkage,
1475 Constant::getNullValue(PFieldTy),
1476 GV->getName() + ".f" + Twine(FieldNo), GV,
1477 GV->getThreadLocalMode());
1478 FieldGlobals.push_back(NGV);
1480 unsigned TypeSize = TD->getTypeAllocSize(FieldTy);
1481 if (StructType *ST = dyn_cast<StructType>(FieldTy))
1482 TypeSize = TD->getStructLayout(ST)->getSizeInBytes();
1483 Type *IntPtrTy = TD->getIntPtrType(CI->getType());
1484 Value *NMI = CallInst::CreateMalloc(CI, IntPtrTy, FieldTy,
1485 ConstantInt::get(IntPtrTy, TypeSize),
1487 CI->getName() + ".f" + Twine(FieldNo));
1488 FieldMallocs.push_back(NMI);
1489 new StoreInst(NMI, NGV, CI);
1492 // The tricky aspect of this transformation is handling the case when malloc
1493 // fails. In the original code, malloc failing would set the result pointer
1494 // of malloc to null. In this case, some mallocs could succeed and others
1495 // could fail. As such, we emit code that looks like this:
1496 // F0 = malloc(field0)
1497 // F1 = malloc(field1)
1498 // F2 = malloc(field2)
1499 // if (F0 == 0 || F1 == 0 || F2 == 0) {
1500 // if (F0) { free(F0); F0 = 0; }
1501 // if (F1) { free(F1); F1 = 0; }
1502 // if (F2) { free(F2); F2 = 0; }
1504 // The malloc can also fail if its argument is too large.
1505 Constant *ConstantZero = ConstantInt::get(CI->getArgOperand(0)->getType(), 0);
1506 Value *RunningOr = new ICmpInst(CI, ICmpInst::ICMP_SLT, CI->getArgOperand(0),
1507 ConstantZero, "isneg");
1508 for (unsigned i = 0, e = FieldMallocs.size(); i != e; ++i) {
1509 Value *Cond = new ICmpInst(CI, ICmpInst::ICMP_EQ, FieldMallocs[i],
1510 Constant::getNullValue(FieldMallocs[i]->getType()),
1512 RunningOr = BinaryOperator::CreateOr(RunningOr, Cond, "tmp", CI);
1515 // Split the basic block at the old malloc.
1516 BasicBlock *OrigBB = CI->getParent();
1517 BasicBlock *ContBB = OrigBB->splitBasicBlock(CI, "malloc_cont");
1519 // Create the block to check the first condition. Put all these blocks at the
1520 // end of the function as they are unlikely to be executed.
1521 BasicBlock *NullPtrBlock = BasicBlock::Create(OrigBB->getContext(),
1523 OrigBB->getParent());
1525 // Remove the uncond branch from OrigBB to ContBB, turning it into a cond
1526 // branch on RunningOr.
1527 OrigBB->getTerminator()->eraseFromParent();
1528 BranchInst::Create(NullPtrBlock, ContBB, RunningOr, OrigBB);
1530 // Within the NullPtrBlock, we need to emit a comparison and branch for each
1531 // pointer, because some may be null while others are not.
1532 for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) {
1533 Value *GVVal = new LoadInst(FieldGlobals[i], "tmp", NullPtrBlock);
1534 Value *Cmp = new ICmpInst(*NullPtrBlock, ICmpInst::ICMP_NE, GVVal,
1535 Constant::getNullValue(GVVal->getType()));
1536 BasicBlock *FreeBlock = BasicBlock::Create(Cmp->getContext(), "free_it",
1537 OrigBB->getParent());
1538 BasicBlock *NextBlock = BasicBlock::Create(Cmp->getContext(), "next",
1539 OrigBB->getParent());
1540 Instruction *BI = BranchInst::Create(FreeBlock, NextBlock,
1543 // Fill in FreeBlock.
1544 CallInst::CreateFree(GVVal, BI);
1545 new StoreInst(Constant::getNullValue(GVVal->getType()), FieldGlobals[i],
1547 BranchInst::Create(NextBlock, FreeBlock);
1549 NullPtrBlock = NextBlock;
1552 BranchInst::Create(ContBB, NullPtrBlock);
1554 // CI is no longer needed, remove it.
1555 CI->eraseFromParent();
1557 /// InsertedScalarizedLoads - As we process loads, if we can't immediately
1558 /// update all uses of the load, keep track of what scalarized loads are
1559 /// inserted for a given load.
1560 DenseMap<Value*, std::vector<Value*> > InsertedScalarizedValues;
1561 InsertedScalarizedValues[GV] = FieldGlobals;
1563 std::vector<std::pair<PHINode*, unsigned> > PHIsToRewrite;
1565 // Okay, the malloc site is completely handled. All of the uses of GV are now
1566 // loads, and all uses of those loads are simple. Rewrite them to use loads
1567 // of the per-field globals instead.
1568 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); UI != E;) {
1569 Instruction *User = cast<Instruction>(*UI++);
1571 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1572 RewriteUsesOfLoadForHeapSRoA(LI, InsertedScalarizedValues, PHIsToRewrite);
1576 // Must be a store of null.
1577 StoreInst *SI = cast<StoreInst>(User);
1578 assert(isa<ConstantPointerNull>(SI->getOperand(0)) &&
1579 "Unexpected heap-sra user!");
1581 // Insert a store of null into each global.
1582 for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) {
1583 PointerType *PT = cast<PointerType>(FieldGlobals[i]->getType());
1584 Constant *Null = Constant::getNullValue(PT->getElementType());
1585 new StoreInst(Null, FieldGlobals[i], SI);
1587 // Erase the original store.
1588 SI->eraseFromParent();
1591 // While we have PHIs that are interesting to rewrite, do it.
1592 while (!PHIsToRewrite.empty()) {
1593 PHINode *PN = PHIsToRewrite.back().first;
1594 unsigned FieldNo = PHIsToRewrite.back().second;
1595 PHIsToRewrite.pop_back();
1596 PHINode *FieldPN = cast<PHINode>(InsertedScalarizedValues[PN][FieldNo]);
1597 assert(FieldPN->getNumIncomingValues() == 0 &&"Already processed this phi");
1599 // Add all the incoming values. This can materialize more phis.
1600 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
1601 Value *InVal = PN->getIncomingValue(i);
1602 InVal = GetHeapSROAValue(InVal, FieldNo, InsertedScalarizedValues,
1604 FieldPN->addIncoming(InVal, PN->getIncomingBlock(i));
1608 // Drop all inter-phi links and any loads that made it this far.
1609 for (DenseMap<Value*, std::vector<Value*> >::iterator
1610 I = InsertedScalarizedValues.begin(), E = InsertedScalarizedValues.end();
1612 if (PHINode *PN = dyn_cast<PHINode>(I->first))
1613 PN->dropAllReferences();
1614 else if (LoadInst *LI = dyn_cast<LoadInst>(I->first))
1615 LI->dropAllReferences();
1618 // Delete all the phis and loads now that inter-references are dead.
1619 for (DenseMap<Value*, std::vector<Value*> >::iterator
1620 I = InsertedScalarizedValues.begin(), E = InsertedScalarizedValues.end();
1622 if (PHINode *PN = dyn_cast<PHINode>(I->first))
1623 PN->eraseFromParent();
1624 else if (LoadInst *LI = dyn_cast<LoadInst>(I->first))
1625 LI->eraseFromParent();
1628 // The old global is now dead, remove it.
1629 GV->eraseFromParent();
1632 return cast<GlobalVariable>(FieldGlobals[0]);
1635 /// TryToOptimizeStoreOfMallocToGlobal - This function is called when we see a
1636 /// pointer global variable with a single value stored it that is a malloc or
1638 static bool TryToOptimizeStoreOfMallocToGlobal(GlobalVariable *GV,
1641 AtomicOrdering Ordering,
1642 Module::global_iterator &GVI,
1644 TargetLibraryInfo *TLI) {
1648 // If this is a malloc of an abstract type, don't touch it.
1649 if (!AllocTy->isSized())
1652 // We can't optimize this global unless all uses of it are *known* to be
1653 // of the malloc value, not of the null initializer value (consider a use
1654 // that compares the global's value against zero to see if the malloc has
1655 // been reached). To do this, we check to see if all uses of the global
1656 // would trap if the global were null: this proves that they must all
1657 // happen after the malloc.
1658 if (!AllUsesOfLoadedValueWillTrapIfNull(GV))
1661 // We can't optimize this if the malloc itself is used in a complex way,
1662 // for example, being stored into multiple globals. This allows the
1663 // malloc to be stored into the specified global, loaded icmp'd, and
1664 // GEP'd. These are all things we could transform to using the global
1666 SmallPtrSet<const PHINode*, 8> PHIs;
1667 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(CI, GV, PHIs))
1670 // If we have a global that is only initialized with a fixed size malloc,
1671 // transform the program to use global memory instead of malloc'd memory.
1672 // This eliminates dynamic allocation, avoids an indirection accessing the
1673 // data, and exposes the resultant global to further GlobalOpt.
1674 // We cannot optimize the malloc if we cannot determine malloc array size.
1675 Value *NElems = getMallocArraySize(CI, TD, TLI, true);
1679 if (ConstantInt *NElements = dyn_cast<ConstantInt>(NElems))
1680 // Restrict this transformation to only working on small allocations
1681 // (2048 bytes currently), as we don't want to introduce a 16M global or
1683 if (NElements->getZExtValue() * TD->getTypeAllocSize(AllocTy) < 2048) {
1684 GVI = OptimizeGlobalAddressOfMalloc(GV, CI, AllocTy, NElements, TD, TLI);
1688 // If the allocation is an array of structures, consider transforming this
1689 // into multiple malloc'd arrays, one for each field. This is basically
1690 // SRoA for malloc'd memory.
1692 if (Ordering != NotAtomic)
1695 // If this is an allocation of a fixed size array of structs, analyze as a
1696 // variable size array. malloc [100 x struct],1 -> malloc struct, 100
1697 if (NElems == ConstantInt::get(CI->getArgOperand(0)->getType(), 1))
1698 if (ArrayType *AT = dyn_cast<ArrayType>(AllocTy))
1699 AllocTy = AT->getElementType();
1701 StructType *AllocSTy = dyn_cast<StructType>(AllocTy);
1705 // This the structure has an unreasonable number of fields, leave it
1707 if (AllocSTy->getNumElements() <= 16 && AllocSTy->getNumElements() != 0 &&
1708 AllGlobalLoadUsesSimpleEnoughForHeapSRA(GV, CI)) {
1710 // If this is a fixed size array, transform the Malloc to be an alloc of
1711 // structs. malloc [100 x struct],1 -> malloc struct, 100
1712 if (ArrayType *AT = dyn_cast<ArrayType>(getMallocAllocatedType(CI, TLI))) {
1713 Type *IntPtrTy = TD->getIntPtrType(CI->getType());
1714 unsigned TypeSize = TD->getStructLayout(AllocSTy)->getSizeInBytes();
1715 Value *AllocSize = ConstantInt::get(IntPtrTy, TypeSize);
1716 Value *NumElements = ConstantInt::get(IntPtrTy, AT->getNumElements());
1717 Instruction *Malloc = CallInst::CreateMalloc(CI, IntPtrTy, AllocSTy,
1718 AllocSize, NumElements,
1720 Instruction *Cast = new BitCastInst(Malloc, CI->getType(), "tmp", CI);
1721 CI->replaceAllUsesWith(Cast);
1722 CI->eraseFromParent();
1723 if (BitCastInst *BCI = dyn_cast<BitCastInst>(Malloc))
1724 CI = cast<CallInst>(BCI->getOperand(0));
1726 CI = cast<CallInst>(Malloc);
1729 GVI = PerformHeapAllocSRoA(GV, CI, getMallocArraySize(CI, TD, TLI, true),
1737 // OptimizeOnceStoredGlobal - Try to optimize globals based on the knowledge
1738 // that only one value (besides its initializer) is ever stored to the global.
1739 static bool OptimizeOnceStoredGlobal(GlobalVariable *GV, Value *StoredOnceVal,
1740 AtomicOrdering Ordering,
1741 Module::global_iterator &GVI,
1742 DataLayout *TD, TargetLibraryInfo *TLI) {
1743 // Ignore no-op GEPs and bitcasts.
1744 StoredOnceVal = StoredOnceVal->stripPointerCasts();
1746 // If we are dealing with a pointer global that is initialized to null and
1747 // only has one (non-null) value stored into it, then we can optimize any
1748 // users of the loaded value (often calls and loads) that would trap if the
1750 if (GV->getInitializer()->getType()->isPointerTy() &&
1751 GV->getInitializer()->isNullValue()) {
1752 if (Constant *SOVC = dyn_cast<Constant>(StoredOnceVal)) {
1753 if (GV->getInitializer()->getType() != SOVC->getType())
1754 SOVC = ConstantExpr::getBitCast(SOVC, GV->getInitializer()->getType());
1756 // Optimize away any trapping uses of the loaded value.
1757 if (OptimizeAwayTrappingUsesOfLoads(GV, SOVC, TD, TLI))
1759 } else if (CallInst *CI = extractMallocCall(StoredOnceVal, TLI)) {
1760 Type *MallocType = getMallocAllocatedType(CI, TLI);
1762 TryToOptimizeStoreOfMallocToGlobal(GV, CI, MallocType, Ordering, GVI,
1771 /// TryToShrinkGlobalToBoolean - At this point, we have learned that the only
1772 /// two values ever stored into GV are its initializer and OtherVal. See if we
1773 /// can shrink the global into a boolean and select between the two values
1774 /// whenever it is used. This exposes the values to other scalar optimizations.
1775 static bool TryToShrinkGlobalToBoolean(GlobalVariable *GV, Constant *OtherVal) {
1776 Type *GVElType = GV->getType()->getElementType();
1778 // If GVElType is already i1, it is already shrunk. If the type of the GV is
1779 // an FP value, pointer or vector, don't do this optimization because a select
1780 // between them is very expensive and unlikely to lead to later
1781 // simplification. In these cases, we typically end up with "cond ? v1 : v2"
1782 // where v1 and v2 both require constant pool loads, a big loss.
1783 if (GVElType == Type::getInt1Ty(GV->getContext()) ||
1784 GVElType->isFloatingPointTy() ||
1785 GVElType->isPointerTy() || GVElType->isVectorTy())
1788 // Walk the use list of the global seeing if all the uses are load or store.
1789 // If there is anything else, bail out.
1790 for (Value::use_iterator I = GV->use_begin(), E = GV->use_end(); I != E; ++I){
1792 if (!isa<LoadInst>(U) && !isa<StoreInst>(U))
1796 DEBUG(dbgs() << " *** SHRINKING TO BOOL: " << *GV);
1798 // Create the new global, initializing it to false.
1799 GlobalVariable *NewGV = new GlobalVariable(Type::getInt1Ty(GV->getContext()),
1801 GlobalValue::InternalLinkage,
1802 ConstantInt::getFalse(GV->getContext()),
1804 GV->getThreadLocalMode(),
1805 GV->getType()->getAddressSpace());
1806 GV->getParent()->getGlobalList().insert(GV, NewGV);
1808 Constant *InitVal = GV->getInitializer();
1809 assert(InitVal->getType() != Type::getInt1Ty(GV->getContext()) &&
1810 "No reason to shrink to bool!");
1812 // If initialized to zero and storing one into the global, we can use a cast
1813 // instead of a select to synthesize the desired value.
1814 bool IsOneZero = false;
1815 if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal))
1816 IsOneZero = InitVal->isNullValue() && CI->isOne();
1818 while (!GV->use_empty()) {
1819 Instruction *UI = cast<Instruction>(GV->use_back());
1820 if (StoreInst *SI = dyn_cast<StoreInst>(UI)) {
1821 // Change the store into a boolean store.
1822 bool StoringOther = SI->getOperand(0) == OtherVal;
1823 // Only do this if we weren't storing a loaded value.
1825 if (StoringOther || SI->getOperand(0) == InitVal) {
1826 StoreVal = ConstantInt::get(Type::getInt1Ty(GV->getContext()),
1829 // Otherwise, we are storing a previously loaded copy. To do this,
1830 // change the copy from copying the original value to just copying the
1832 Instruction *StoredVal = cast<Instruction>(SI->getOperand(0));
1834 // If we've already replaced the input, StoredVal will be a cast or
1835 // select instruction. If not, it will be a load of the original
1837 if (LoadInst *LI = dyn_cast<LoadInst>(StoredVal)) {
1838 assert(LI->getOperand(0) == GV && "Not a copy!");
1839 // Insert a new load, to preserve the saved value.
1840 StoreVal = new LoadInst(NewGV, LI->getName()+".b", false, 0,
1841 LI->getOrdering(), LI->getSynchScope(), LI);
1843 assert((isa<CastInst>(StoredVal) || isa<SelectInst>(StoredVal)) &&
1844 "This is not a form that we understand!");
1845 StoreVal = StoredVal->getOperand(0);
1846 assert(isa<LoadInst>(StoreVal) && "Not a load of NewGV!");
1849 new StoreInst(StoreVal, NewGV, false, 0,
1850 SI->getOrdering(), SI->getSynchScope(), SI);
1852 // Change the load into a load of bool then a select.
1853 LoadInst *LI = cast<LoadInst>(UI);
1854 LoadInst *NLI = new LoadInst(NewGV, LI->getName()+".b", false, 0,
1855 LI->getOrdering(), LI->getSynchScope(), LI);
1858 NSI = new ZExtInst(NLI, LI->getType(), "", LI);
1860 NSI = SelectInst::Create(NLI, OtherVal, InitVal, "", LI);
1862 LI->replaceAllUsesWith(NSI);
1864 UI->eraseFromParent();
1867 // Retain the name of the old global variable. People who are debugging their
1868 // programs may expect these variables to be named the same.
1869 NewGV->takeName(GV);
1870 GV->eraseFromParent();
1875 /// ProcessGlobal - Analyze the specified global variable and optimize it if
1876 /// possible. If we make a change, return true.
1877 bool GlobalOpt::ProcessGlobal(GlobalVariable *GV,
1878 Module::global_iterator &GVI) {
1879 if (!GV->isDiscardableIfUnused())
1882 // Do more involved optimizations if the global is internal.
1883 GV->removeDeadConstantUsers();
1885 if (GV->use_empty()) {
1886 DEBUG(dbgs() << "GLOBAL DEAD: " << *GV);
1887 GV->eraseFromParent();
1892 if (!GV->hasLocalLinkage())
1895 SmallPtrSet<const PHINode*, 16> PHIUsers;
1898 if (AnalyzeGlobal(GV, GS, PHIUsers))
1901 if (!GS.isCompared && !GV->hasUnnamedAddr()) {
1902 GV->setUnnamedAddr(true);
1906 if (GV->isConstant() || !GV->hasInitializer())
1909 return ProcessInternalGlobal(GV, GVI, GS);
1912 /// ProcessInternalGlobal - Analyze the specified global variable and optimize
1913 /// it if possible. If we make a change, return true.
1914 bool GlobalOpt::ProcessInternalGlobal(GlobalVariable *GV,
1915 Module::global_iterator &GVI,
1916 const GlobalStatus &GS) {
1917 // If the global is never loaded (but may be stored to), it is dead.
1920 DEBUG(dbgs() << "GLOBAL NEVER LOADED: " << *GV);
1923 if (isLeakCheckerRoot(GV)) {
1924 // Delete any constant stores to the global.
1925 Changed = CleanupPointerRootUsers(GV, TLI);
1927 // Delete any stores we can find to the global. We may not be able to
1928 // make it completely dead though.
1929 Changed = CleanupConstantGlobalUsers(GV, GV->getInitializer(), TD, TLI);
1932 // If the global is dead now, delete it.
1933 if (GV->use_empty()) {
1934 GV->eraseFromParent();
1940 } else if (GS.StoredType <= GlobalStatus::isInitializerStored) {
1941 DEBUG(dbgs() << "MARKING CONSTANT: " << *GV << "\n");
1942 GV->setConstant(true);
1944 // Clean up any obviously simplifiable users now.
1945 CleanupConstantGlobalUsers(GV, GV->getInitializer(), TD, TLI);
1947 // If the global is dead now, just nuke it.
1948 if (GV->use_empty()) {
1949 DEBUG(dbgs() << " *** Marking constant allowed us to simplify "
1950 << "all users and delete global!\n");
1951 GV->eraseFromParent();
1957 } else if (!GV->getInitializer()->getType()->isSingleValueType()) {
1958 if (DataLayout *TD = getAnalysisIfAvailable<DataLayout>())
1959 if (GlobalVariable *FirstNewGV = SRAGlobal(GV, *TD)) {
1960 GVI = FirstNewGV; // Don't skip the newly produced globals!
1963 } else if (GS.StoredType == GlobalStatus::isStoredOnce) {
1964 // If the initial value for the global was an undef value, and if only
1965 // one other value was stored into it, we can just change the
1966 // initializer to be the stored value, then delete all stores to the
1967 // global. This allows us to mark it constant.
1968 if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue))
1969 if (isa<UndefValue>(GV->getInitializer())) {
1970 // Change the initial value here.
1971 GV->setInitializer(SOVConstant);
1973 // Clean up any obviously simplifiable users now.
1974 CleanupConstantGlobalUsers(GV, GV->getInitializer(), TD, TLI);
1976 if (GV->use_empty()) {
1977 DEBUG(dbgs() << " *** Substituting initializer allowed us to "
1978 << "simplify all users and delete global!\n");
1979 GV->eraseFromParent();
1988 // Try to optimize globals based on the knowledge that only one value
1989 // (besides its initializer) is ever stored to the global.
1990 if (OptimizeOnceStoredGlobal(GV, GS.StoredOnceValue, GS.Ordering, GVI,
1994 // Otherwise, if the global was not a boolean, we can shrink it to be a
1996 if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue)) {
1997 if (GS.Ordering == NotAtomic) {
1998 if (TryToShrinkGlobalToBoolean(GV, SOVConstant)) {
2009 /// ChangeCalleesToFastCall - Walk all of the direct calls of the specified
2010 /// function, changing them to FastCC.
2011 static void ChangeCalleesToFastCall(Function *F) {
2012 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){
2013 if (isa<BlockAddress>(*UI))
2015 CallSite User(cast<Instruction>(*UI));
2016 User.setCallingConv(CallingConv::Fast);
2020 static AttributeSet StripNest(LLVMContext &C, const AttributeSet &Attrs) {
2021 for (unsigned i = 0, e = Attrs.getNumSlots(); i != e; ++i) {
2022 unsigned Index = Attrs.getSlotIndex(i);
2023 if (!Attrs.getSlotAttributes(i).hasAttribute(Index, Attribute::Nest))
2026 // There can be only one.
2027 return Attrs.removeAttribute(C, Index, Attribute::Nest);
2033 static void RemoveNestAttribute(Function *F) {
2034 F->setAttributes(StripNest(F->getContext(), F->getAttributes()));
2035 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){
2036 if (isa<BlockAddress>(*UI))
2038 CallSite User(cast<Instruction>(*UI));
2039 User.setAttributes(StripNest(F->getContext(), User.getAttributes()));
2043 bool GlobalOpt::OptimizeFunctions(Module &M) {
2044 bool Changed = false;
2045 // Optimize functions.
2046 for (Module::iterator FI = M.begin(), E = M.end(); FI != E; ) {
2048 // Functions without names cannot be referenced outside this module.
2049 if (!F->hasName() && !F->isDeclaration())
2050 F->setLinkage(GlobalValue::InternalLinkage);
2051 F->removeDeadConstantUsers();
2052 if (F->isDefTriviallyDead()) {
2053 F->eraseFromParent();
2056 } else if (F->hasLocalLinkage()) {
2057 if (F->getCallingConv() == CallingConv::C && !F->isVarArg() &&
2058 !F->hasAddressTaken()) {
2059 // If this function has C calling conventions, is not a varargs
2060 // function, and is only called directly, promote it to use the Fast
2061 // calling convention.
2062 F->setCallingConv(CallingConv::Fast);
2063 ChangeCalleesToFastCall(F);
2068 if (F->getAttributes().hasAttrSomewhere(Attribute::Nest) &&
2069 !F->hasAddressTaken()) {
2070 // The function is not used by a trampoline intrinsic, so it is safe
2071 // to remove the 'nest' attribute.
2072 RemoveNestAttribute(F);
2081 bool GlobalOpt::OptimizeGlobalVars(Module &M) {
2082 bool Changed = false;
2083 for (Module::global_iterator GVI = M.global_begin(), E = M.global_end();
2085 GlobalVariable *GV = GVI++;
2086 // Global variables without names cannot be referenced outside this module.
2087 if (!GV->hasName() && !GV->isDeclaration())
2088 GV->setLinkage(GlobalValue::InternalLinkage);
2089 // Simplify the initializer.
2090 if (GV->hasInitializer())
2091 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GV->getInitializer())) {
2092 Constant *New = ConstantFoldConstantExpression(CE, TD, TLI);
2093 if (New && New != CE)
2094 GV->setInitializer(New);
2097 Changed |= ProcessGlobal(GV, GVI);
2102 /// FindGlobalCtors - Find the llvm.global_ctors list, verifying that all
2103 /// initializers have an init priority of 65535.
2104 GlobalVariable *GlobalOpt::FindGlobalCtors(Module &M) {
2105 GlobalVariable *GV = M.getGlobalVariable("llvm.global_ctors");
2106 if (GV == 0) return 0;
2108 // Verify that the initializer is simple enough for us to handle. We are
2109 // only allowed to optimize the initializer if it is unique.
2110 if (!GV->hasUniqueInitializer()) return 0;
2112 if (isa<ConstantAggregateZero>(GV->getInitializer()))
2114 ConstantArray *CA = cast<ConstantArray>(GV->getInitializer());
2116 for (User::op_iterator i = CA->op_begin(), e = CA->op_end(); i != e; ++i) {
2117 if (isa<ConstantAggregateZero>(*i))
2119 ConstantStruct *CS = cast<ConstantStruct>(*i);
2120 if (isa<ConstantPointerNull>(CS->getOperand(1)))
2123 // Must have a function or null ptr.
2124 if (!isa<Function>(CS->getOperand(1)))
2127 // Init priority must be standard.
2128 ConstantInt *CI = cast<ConstantInt>(CS->getOperand(0));
2129 if (CI->getZExtValue() != 65535)
2136 /// ParseGlobalCtors - Given a llvm.global_ctors list that we can understand,
2137 /// return a list of the functions and null terminator as a vector.
2138 static std::vector<Function*> ParseGlobalCtors(GlobalVariable *GV) {
2139 if (GV->getInitializer()->isNullValue())
2140 return std::vector<Function*>();
2141 ConstantArray *CA = cast<ConstantArray>(GV->getInitializer());
2142 std::vector<Function*> Result;
2143 Result.reserve(CA->getNumOperands());
2144 for (User::op_iterator i = CA->op_begin(), e = CA->op_end(); i != e; ++i) {
2145 ConstantStruct *CS = cast<ConstantStruct>(*i);
2146 Result.push_back(dyn_cast<Function>(CS->getOperand(1)));
2151 /// InstallGlobalCtors - Given a specified llvm.global_ctors list, install the
2152 /// specified array, returning the new global to use.
2153 static GlobalVariable *InstallGlobalCtors(GlobalVariable *GCL,
2154 const std::vector<Function*> &Ctors) {
2155 // If we made a change, reassemble the initializer list.
2156 Constant *CSVals[2];
2157 CSVals[0] = ConstantInt::get(Type::getInt32Ty(GCL->getContext()), 65535);
2160 StructType *StructTy =
2162 cast<ArrayType>(GCL->getType()->getElementType())->getElementType());
2164 // Create the new init list.
2165 std::vector<Constant*> CAList;
2166 for (unsigned i = 0, e = Ctors.size(); i != e; ++i) {
2168 CSVals[1] = Ctors[i];
2170 Type *FTy = FunctionType::get(Type::getVoidTy(GCL->getContext()),
2172 PointerType *PFTy = PointerType::getUnqual(FTy);
2173 CSVals[1] = Constant::getNullValue(PFTy);
2174 CSVals[0] = ConstantInt::get(Type::getInt32Ty(GCL->getContext()),
2177 CAList.push_back(ConstantStruct::get(StructTy, CSVals));
2180 // Create the array initializer.
2181 Constant *CA = ConstantArray::get(ArrayType::get(StructTy,
2182 CAList.size()), CAList);
2184 // If we didn't change the number of elements, don't create a new GV.
2185 if (CA->getType() == GCL->getInitializer()->getType()) {
2186 GCL->setInitializer(CA);
2190 // Create the new global and insert it next to the existing list.
2191 GlobalVariable *NGV = new GlobalVariable(CA->getType(), GCL->isConstant(),
2192 GCL->getLinkage(), CA, "",
2193 GCL->getThreadLocalMode());
2194 GCL->getParent()->getGlobalList().insert(GCL, NGV);
2197 // Nuke the old list, replacing any uses with the new one.
2198 if (!GCL->use_empty()) {
2200 if (V->getType() != GCL->getType())
2201 V = ConstantExpr::getBitCast(V, GCL->getType());
2202 GCL->replaceAllUsesWith(V);
2204 GCL->eraseFromParent();
2214 isSimpleEnoughValueToCommit(Constant *C,
2215 SmallPtrSet<Constant*, 8> &SimpleConstants,
2216 const DataLayout *TD);
2219 /// isSimpleEnoughValueToCommit - Return true if the specified constant can be
2220 /// handled by the code generator. We don't want to generate something like:
2221 /// void *X = &X/42;
2222 /// because the code generator doesn't have a relocation that can handle that.
2224 /// This function should be called if C was not found (but just got inserted)
2225 /// in SimpleConstants to avoid having to rescan the same constants all the
2227 static bool isSimpleEnoughValueToCommitHelper(Constant *C,
2228 SmallPtrSet<Constant*, 8> &SimpleConstants,
2229 const DataLayout *TD) {
2230 // Simple integer, undef, constant aggregate zero, global addresses, etc are
2232 if (C->getNumOperands() == 0 || isa<BlockAddress>(C) ||
2233 isa<GlobalValue>(C))
2236 // Aggregate values are safe if all their elements are.
2237 if (isa<ConstantArray>(C) || isa<ConstantStruct>(C) ||
2238 isa<ConstantVector>(C)) {
2239 for (unsigned i = 0, e = C->getNumOperands(); i != e; ++i) {
2240 Constant *Op = cast<Constant>(C->getOperand(i));
2241 if (!isSimpleEnoughValueToCommit(Op, SimpleConstants, TD))
2247 // We don't know exactly what relocations are allowed in constant expressions,
2248 // so we allow &global+constantoffset, which is safe and uniformly supported
2250 ConstantExpr *CE = cast<ConstantExpr>(C);
2251 switch (CE->getOpcode()) {
2252 case Instruction::BitCast:
2253 // Bitcast is fine if the casted value is fine.
2254 return isSimpleEnoughValueToCommit(CE->getOperand(0), SimpleConstants, TD);
2256 case Instruction::IntToPtr:
2257 case Instruction::PtrToInt:
2258 // int <=> ptr is fine if the int type is the same size as the
2260 if (!TD || TD->getTypeSizeInBits(CE->getType()) !=
2261 TD->getTypeSizeInBits(CE->getOperand(0)->getType()))
2263 return isSimpleEnoughValueToCommit(CE->getOperand(0), SimpleConstants, TD);
2265 // GEP is fine if it is simple + constant offset.
2266 case Instruction::GetElementPtr:
2267 for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i)
2268 if (!isa<ConstantInt>(CE->getOperand(i)))
2270 return isSimpleEnoughValueToCommit(CE->getOperand(0), SimpleConstants, TD);
2272 case Instruction::Add:
2273 // We allow simple+cst.
2274 if (!isa<ConstantInt>(CE->getOperand(1)))
2276 return isSimpleEnoughValueToCommit(CE->getOperand(0), SimpleConstants, TD);
2282 isSimpleEnoughValueToCommit(Constant *C,
2283 SmallPtrSet<Constant*, 8> &SimpleConstants,
2284 const DataLayout *TD) {
2285 // If we already checked this constant, we win.
2286 if (!SimpleConstants.insert(C)) return true;
2287 // Check the constant.
2288 return isSimpleEnoughValueToCommitHelper(C, SimpleConstants, TD);
2292 /// isSimpleEnoughPointerToCommit - Return true if this constant is simple
2293 /// enough for us to understand. In particular, if it is a cast to anything
2294 /// other than from one pointer type to another pointer type, we punt.
2295 /// We basically just support direct accesses to globals and GEP's of
2296 /// globals. This should be kept up to date with CommitValueTo.
2297 static bool isSimpleEnoughPointerToCommit(Constant *C) {
2298 // Conservatively, avoid aggregate types. This is because we don't
2299 // want to worry about them partially overlapping other stores.
2300 if (!cast<PointerType>(C->getType())->getElementType()->isSingleValueType())
2303 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C))
2304 // Do not allow weak/*_odr/linkonce/dllimport/dllexport linkage or
2305 // external globals.
2306 return GV->hasUniqueInitializer();
2308 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) {
2309 // Handle a constantexpr gep.
2310 if (CE->getOpcode() == Instruction::GetElementPtr &&
2311 isa<GlobalVariable>(CE->getOperand(0)) &&
2312 cast<GEPOperator>(CE)->isInBounds()) {
2313 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
2314 // Do not allow weak/*_odr/linkonce/dllimport/dllexport linkage or
2315 // external globals.
2316 if (!GV->hasUniqueInitializer())
2319 // The first index must be zero.
2320 ConstantInt *CI = dyn_cast<ConstantInt>(*llvm::next(CE->op_begin()));
2321 if (!CI || !CI->isZero()) return false;
2323 // The remaining indices must be compile-time known integers within the
2324 // notional bounds of the corresponding static array types.
2325 if (!CE->isGEPWithNoNotionalOverIndexing())
2328 return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE);
2330 // A constantexpr bitcast from a pointer to another pointer is a no-op,
2331 // and we know how to evaluate it by moving the bitcast from the pointer
2332 // operand to the value operand.
2333 } else if (CE->getOpcode() == Instruction::BitCast &&
2334 isa<GlobalVariable>(CE->getOperand(0))) {
2335 // Do not allow weak/*_odr/linkonce/dllimport/dllexport linkage or
2336 // external globals.
2337 return cast<GlobalVariable>(CE->getOperand(0))->hasUniqueInitializer();
2344 /// EvaluateStoreInto - Evaluate a piece of a constantexpr store into a global
2345 /// initializer. This returns 'Init' modified to reflect 'Val' stored into it.
2346 /// At this point, the GEP operands of Addr [0, OpNo) have been stepped into.
2347 static Constant *EvaluateStoreInto(Constant *Init, Constant *Val,
2348 ConstantExpr *Addr, unsigned OpNo) {
2349 // Base case of the recursion.
2350 if (OpNo == Addr->getNumOperands()) {
2351 assert(Val->getType() == Init->getType() && "Type mismatch!");
2355 SmallVector<Constant*, 32> Elts;
2356 if (StructType *STy = dyn_cast<StructType>(Init->getType())) {
2357 // Break up the constant into its elements.
2358 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
2359 Elts.push_back(Init->getAggregateElement(i));
2361 // Replace the element that we are supposed to.
2362 ConstantInt *CU = cast<ConstantInt>(Addr->getOperand(OpNo));
2363 unsigned Idx = CU->getZExtValue();
2364 assert(Idx < STy->getNumElements() && "Struct index out of range!");
2365 Elts[Idx] = EvaluateStoreInto(Elts[Idx], Val, Addr, OpNo+1);
2367 // Return the modified struct.
2368 return ConstantStruct::get(STy, Elts);
2371 ConstantInt *CI = cast<ConstantInt>(Addr->getOperand(OpNo));
2372 SequentialType *InitTy = cast<SequentialType>(Init->getType());
2375 if (ArrayType *ATy = dyn_cast<ArrayType>(InitTy))
2376 NumElts = ATy->getNumElements();
2378 NumElts = InitTy->getVectorNumElements();
2380 // Break up the array into elements.
2381 for (uint64_t i = 0, e = NumElts; i != e; ++i)
2382 Elts.push_back(Init->getAggregateElement(i));
2384 assert(CI->getZExtValue() < NumElts);
2385 Elts[CI->getZExtValue()] =
2386 EvaluateStoreInto(Elts[CI->getZExtValue()], Val, Addr, OpNo+1);
2388 if (Init->getType()->isArrayTy())
2389 return ConstantArray::get(cast<ArrayType>(InitTy), Elts);
2390 return ConstantVector::get(Elts);
2393 /// CommitValueTo - We have decided that Addr (which satisfies the predicate
2394 /// isSimpleEnoughPointerToCommit) should get Val as its value. Make it happen.
2395 static void CommitValueTo(Constant *Val, Constant *Addr) {
2396 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Addr)) {
2397 assert(GV->hasInitializer());
2398 GV->setInitializer(Val);
2402 ConstantExpr *CE = cast<ConstantExpr>(Addr);
2403 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
2404 GV->setInitializer(EvaluateStoreInto(GV->getInitializer(), Val, CE, 2));
2409 /// Evaluator - This class evaluates LLVM IR, producing the Constant
2410 /// representing each SSA instruction. Changes to global variables are stored
2411 /// in a mapping that can be iterated over after the evaluation is complete.
2412 /// Once an evaluation call fails, the evaluation object should not be reused.
2415 Evaluator(const DataLayout *TD, const TargetLibraryInfo *TLI)
2416 : TD(TD), TLI(TLI) {
2417 ValueStack.push_back(new DenseMap<Value*, Constant*>);
2421 DeleteContainerPointers(ValueStack);
2422 while (!AllocaTmps.empty()) {
2423 GlobalVariable *Tmp = AllocaTmps.back();
2424 AllocaTmps.pop_back();
2426 // If there are still users of the alloca, the program is doing something
2427 // silly, e.g. storing the address of the alloca somewhere and using it
2428 // later. Since this is undefined, we'll just make it be null.
2429 if (!Tmp->use_empty())
2430 Tmp->replaceAllUsesWith(Constant::getNullValue(Tmp->getType()));
2435 /// EvaluateFunction - Evaluate a call to function F, returning true if
2436 /// successful, false if we can't evaluate it. ActualArgs contains the formal
2437 /// arguments for the function.
2438 bool EvaluateFunction(Function *F, Constant *&RetVal,
2439 const SmallVectorImpl<Constant*> &ActualArgs);
2441 /// EvaluateBlock - Evaluate all instructions in block BB, returning true if
2442 /// successful, false if we can't evaluate it. NewBB returns the next BB that
2443 /// control flows into, or null upon return.
2444 bool EvaluateBlock(BasicBlock::iterator CurInst, BasicBlock *&NextBB);
2446 Constant *getVal(Value *V) {
2447 if (Constant *CV = dyn_cast<Constant>(V)) return CV;
2448 Constant *R = ValueStack.back()->lookup(V);
2449 assert(R && "Reference to an uncomputed value!");
2453 void setVal(Value *V, Constant *C) {
2454 ValueStack.back()->operator[](V) = C;
2457 const DenseMap<Constant*, Constant*> &getMutatedMemory() const {
2458 return MutatedMemory;
2461 const SmallPtrSet<GlobalVariable*, 8> &getInvariants() const {
2466 Constant *ComputeLoadResult(Constant *P);
2468 /// ValueStack - As we compute SSA register values, we store their contents
2469 /// here. The back of the vector contains the current function and the stack
2470 /// contains the values in the calling frames.
2471 SmallVector<DenseMap<Value*, Constant*>*, 4> ValueStack;
2473 /// CallStack - This is used to detect recursion. In pathological situations
2474 /// we could hit exponential behavior, but at least there is nothing
2476 SmallVector<Function*, 4> CallStack;
2478 /// MutatedMemory - For each store we execute, we update this map. Loads
2479 /// check this to get the most up-to-date value. If evaluation is successful,
2480 /// this state is committed to the process.
2481 DenseMap<Constant*, Constant*> MutatedMemory;
2483 /// AllocaTmps - To 'execute' an alloca, we create a temporary global variable
2484 /// to represent its body. This vector is needed so we can delete the
2485 /// temporary globals when we are done.
2486 SmallVector<GlobalVariable*, 32> AllocaTmps;
2488 /// Invariants - These global variables have been marked invariant by the
2489 /// static constructor.
2490 SmallPtrSet<GlobalVariable*, 8> Invariants;
2492 /// SimpleConstants - These are constants we have checked and know to be
2493 /// simple enough to live in a static initializer of a global.
2494 SmallPtrSet<Constant*, 8> SimpleConstants;
2496 const DataLayout *TD;
2497 const TargetLibraryInfo *TLI;
2500 } // anonymous namespace
2502 /// ComputeLoadResult - Return the value that would be computed by a load from
2503 /// P after the stores reflected by 'memory' have been performed. If we can't
2504 /// decide, return null.
2505 Constant *Evaluator::ComputeLoadResult(Constant *P) {
2506 // If this memory location has been recently stored, use the stored value: it
2507 // is the most up-to-date.
2508 DenseMap<Constant*, Constant*>::const_iterator I = MutatedMemory.find(P);
2509 if (I != MutatedMemory.end()) return I->second;
2512 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(P)) {
2513 if (GV->hasDefinitiveInitializer())
2514 return GV->getInitializer();
2518 // Handle a constantexpr getelementptr.
2519 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(P))
2520 if (CE->getOpcode() == Instruction::GetElementPtr &&
2521 isa<GlobalVariable>(CE->getOperand(0))) {
2522 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
2523 if (GV->hasDefinitiveInitializer())
2524 return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE);
2527 return 0; // don't know how to evaluate.
2530 /// EvaluateBlock - Evaluate all instructions in block BB, returning true if
2531 /// successful, false if we can't evaluate it. NewBB returns the next BB that
2532 /// control flows into, or null upon return.
2533 bool Evaluator::EvaluateBlock(BasicBlock::iterator CurInst,
2534 BasicBlock *&NextBB) {
2535 // This is the main evaluation loop.
2537 Constant *InstResult = 0;
2539 DEBUG(dbgs() << "Evaluating Instruction: " << *CurInst << "\n");
2541 if (StoreInst *SI = dyn_cast<StoreInst>(CurInst)) {
2542 if (!SI->isSimple()) {
2543 DEBUG(dbgs() << "Store is not simple! Can not evaluate.\n");
2544 return false; // no volatile/atomic accesses.
2546 Constant *Ptr = getVal(SI->getOperand(1));
2547 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr)) {
2548 DEBUG(dbgs() << "Folding constant ptr expression: " << *Ptr);
2549 Ptr = ConstantFoldConstantExpression(CE, TD, TLI);
2550 DEBUG(dbgs() << "; To: " << *Ptr << "\n");
2552 if (!isSimpleEnoughPointerToCommit(Ptr)) {
2553 // If this is too complex for us to commit, reject it.
2554 DEBUG(dbgs() << "Pointer is too complex for us to evaluate store.");
2558 Constant *Val = getVal(SI->getOperand(0));
2560 // If this might be too difficult for the backend to handle (e.g. the addr
2561 // of one global variable divided by another) then we can't commit it.
2562 if (!isSimpleEnoughValueToCommit(Val, SimpleConstants, TD)) {
2563 DEBUG(dbgs() << "Store value is too complex to evaluate store. " << *Val
2568 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr)) {
2569 if (CE->getOpcode() == Instruction::BitCast) {
2570 DEBUG(dbgs() << "Attempting to resolve bitcast on constant ptr.\n");
2571 // If we're evaluating a store through a bitcast, then we need
2572 // to pull the bitcast off the pointer type and push it onto the
2574 Ptr = CE->getOperand(0);
2576 Type *NewTy = cast<PointerType>(Ptr->getType())->getElementType();
2578 // In order to push the bitcast onto the stored value, a bitcast
2579 // from NewTy to Val's type must be legal. If it's not, we can try
2580 // introspecting NewTy to find a legal conversion.
2581 while (!Val->getType()->canLosslesslyBitCastTo(NewTy)) {
2582 // If NewTy is a struct, we can convert the pointer to the struct
2583 // into a pointer to its first member.
2584 // FIXME: This could be extended to support arrays as well.
2585 if (StructType *STy = dyn_cast<StructType>(NewTy)) {
2586 NewTy = STy->getTypeAtIndex(0U);
2588 IntegerType *IdxTy = IntegerType::get(NewTy->getContext(), 32);
2589 Constant *IdxZero = ConstantInt::get(IdxTy, 0, false);
2590 Constant * const IdxList[] = {IdxZero, IdxZero};
2592 Ptr = ConstantExpr::getGetElementPtr(Ptr, IdxList);
2593 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr))
2594 Ptr = ConstantFoldConstantExpression(CE, TD, TLI);
2596 // If we can't improve the situation by introspecting NewTy,
2597 // we have to give up.
2599 DEBUG(dbgs() << "Failed to bitcast constant ptr, can not "
2605 // If we found compatible types, go ahead and push the bitcast
2606 // onto the stored value.
2607 Val = ConstantExpr::getBitCast(Val, NewTy);
2609 DEBUG(dbgs() << "Evaluated bitcast: " << *Val << "\n");
2613 MutatedMemory[Ptr] = Val;
2614 } else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(CurInst)) {
2615 InstResult = ConstantExpr::get(BO->getOpcode(),
2616 getVal(BO->getOperand(0)),
2617 getVal(BO->getOperand(1)));
2618 DEBUG(dbgs() << "Found a BinaryOperator! Simplifying: " << *InstResult
2620 } else if (CmpInst *CI = dyn_cast<CmpInst>(CurInst)) {
2621 InstResult = ConstantExpr::getCompare(CI->getPredicate(),
2622 getVal(CI->getOperand(0)),
2623 getVal(CI->getOperand(1)));
2624 DEBUG(dbgs() << "Found a CmpInst! Simplifying: " << *InstResult
2626 } else if (CastInst *CI = dyn_cast<CastInst>(CurInst)) {
2627 InstResult = ConstantExpr::getCast(CI->getOpcode(),
2628 getVal(CI->getOperand(0)),
2630 DEBUG(dbgs() << "Found a Cast! Simplifying: " << *InstResult
2632 } else if (SelectInst *SI = dyn_cast<SelectInst>(CurInst)) {
2633 InstResult = ConstantExpr::getSelect(getVal(SI->getOperand(0)),
2634 getVal(SI->getOperand(1)),
2635 getVal(SI->getOperand(2)));
2636 DEBUG(dbgs() << "Found a Select! Simplifying: " << *InstResult
2638 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(CurInst)) {
2639 Constant *P = getVal(GEP->getOperand(0));
2640 SmallVector<Constant*, 8> GEPOps;
2641 for (User::op_iterator i = GEP->op_begin() + 1, e = GEP->op_end();
2643 GEPOps.push_back(getVal(*i));
2645 ConstantExpr::getGetElementPtr(P, GEPOps,
2646 cast<GEPOperator>(GEP)->isInBounds());
2647 DEBUG(dbgs() << "Found a GEP! Simplifying: " << *InstResult
2649 } else if (LoadInst *LI = dyn_cast<LoadInst>(CurInst)) {
2651 if (!LI->isSimple()) {
2652 DEBUG(dbgs() << "Found a Load! Not a simple load, can not evaluate.\n");
2653 return false; // no volatile/atomic accesses.
2656 Constant *Ptr = getVal(LI->getOperand(0));
2657 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr)) {
2658 Ptr = ConstantFoldConstantExpression(CE, TD, TLI);
2659 DEBUG(dbgs() << "Found a constant pointer expression, constant "
2660 "folding: " << *Ptr << "\n");
2662 InstResult = ComputeLoadResult(Ptr);
2663 if (InstResult == 0) {
2664 DEBUG(dbgs() << "Failed to compute load result. Can not evaluate load."
2666 return false; // Could not evaluate load.
2669 DEBUG(dbgs() << "Evaluated load: " << *InstResult << "\n");
2670 } else if (AllocaInst *AI = dyn_cast<AllocaInst>(CurInst)) {
2671 if (AI->isArrayAllocation()) {
2672 DEBUG(dbgs() << "Found an array alloca. Can not evaluate.\n");
2673 return false; // Cannot handle array allocs.
2675 Type *Ty = AI->getType()->getElementType();
2676 AllocaTmps.push_back(new GlobalVariable(Ty, false,
2677 GlobalValue::InternalLinkage,
2678 UndefValue::get(Ty),
2680 InstResult = AllocaTmps.back();
2681 DEBUG(dbgs() << "Found an alloca. Result: " << *InstResult << "\n");
2682 } else if (isa<CallInst>(CurInst) || isa<InvokeInst>(CurInst)) {
2683 CallSite CS(CurInst);
2685 // Debug info can safely be ignored here.
2686 if (isa<DbgInfoIntrinsic>(CS.getInstruction())) {
2687 DEBUG(dbgs() << "Ignoring debug info.\n");
2692 // Cannot handle inline asm.
2693 if (isa<InlineAsm>(CS.getCalledValue())) {
2694 DEBUG(dbgs() << "Found inline asm, can not evaluate.\n");
2698 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(CS.getInstruction())) {
2699 if (MemSetInst *MSI = dyn_cast<MemSetInst>(II)) {
2700 if (MSI->isVolatile()) {
2701 DEBUG(dbgs() << "Can not optimize a volatile memset " <<
2705 Constant *Ptr = getVal(MSI->getDest());
2706 Constant *Val = getVal(MSI->getValue());
2707 Constant *DestVal = ComputeLoadResult(getVal(Ptr));
2708 if (Val->isNullValue() && DestVal && DestVal->isNullValue()) {
2709 // This memset is a no-op.
2710 DEBUG(dbgs() << "Ignoring no-op memset.\n");
2716 if (II->getIntrinsicID() == Intrinsic::lifetime_start ||
2717 II->getIntrinsicID() == Intrinsic::lifetime_end) {
2718 DEBUG(dbgs() << "Ignoring lifetime intrinsic.\n");
2723 if (II->getIntrinsicID() == Intrinsic::invariant_start) {
2724 // We don't insert an entry into Values, as it doesn't have a
2725 // meaningful return value.
2726 if (!II->use_empty()) {
2727 DEBUG(dbgs() << "Found unused invariant_start. Cant evaluate.\n");
2730 ConstantInt *Size = cast<ConstantInt>(II->getArgOperand(0));
2731 Value *PtrArg = getVal(II->getArgOperand(1));
2732 Value *Ptr = PtrArg->stripPointerCasts();
2733 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Ptr)) {
2734 Type *ElemTy = cast<PointerType>(GV->getType())->getElementType();
2735 if (TD && !Size->isAllOnesValue() &&
2736 Size->getValue().getLimitedValue() >=
2737 TD->getTypeStoreSize(ElemTy)) {
2738 Invariants.insert(GV);
2739 DEBUG(dbgs() << "Found a global var that is an invariant: " << *GV
2742 DEBUG(dbgs() << "Found a global var, but can not treat it as an "
2746 // Continue even if we do nothing.
2751 DEBUG(dbgs() << "Unknown intrinsic. Can not evaluate.\n");
2755 // Resolve function pointers.
2756 Function *Callee = dyn_cast<Function>(getVal(CS.getCalledValue()));
2757 if (!Callee || Callee->mayBeOverridden()) {
2758 DEBUG(dbgs() << "Can not resolve function pointer.\n");
2759 return false; // Cannot resolve.
2762 SmallVector<Constant*, 8> Formals;
2763 for (User::op_iterator i = CS.arg_begin(), e = CS.arg_end(); i != e; ++i)
2764 Formals.push_back(getVal(*i));
2766 if (Callee->isDeclaration()) {
2767 // If this is a function we can constant fold, do it.
2768 if (Constant *C = ConstantFoldCall(Callee, Formals, TLI)) {
2770 DEBUG(dbgs() << "Constant folded function call. Result: " <<
2771 *InstResult << "\n");
2773 DEBUG(dbgs() << "Can not constant fold function call.\n");
2777 if (Callee->getFunctionType()->isVarArg()) {
2778 DEBUG(dbgs() << "Can not constant fold vararg function call.\n");
2782 Constant *RetVal = 0;
2783 // Execute the call, if successful, use the return value.
2784 ValueStack.push_back(new DenseMap<Value*, Constant*>);
2785 if (!EvaluateFunction(Callee, RetVal, Formals)) {
2786 DEBUG(dbgs() << "Failed to evaluate function.\n");
2789 delete ValueStack.pop_back_val();
2790 InstResult = RetVal;
2792 if (InstResult != NULL) {
2793 DEBUG(dbgs() << "Successfully evaluated function. Result: " <<
2794 InstResult << "\n\n");
2796 DEBUG(dbgs() << "Successfully evaluated function. Result: 0\n\n");
2799 } else if (isa<TerminatorInst>(CurInst)) {
2800 DEBUG(dbgs() << "Found a terminator instruction.\n");
2802 if (BranchInst *BI = dyn_cast<BranchInst>(CurInst)) {
2803 if (BI->isUnconditional()) {
2804 NextBB = BI->getSuccessor(0);
2807 dyn_cast<ConstantInt>(getVal(BI->getCondition()));
2808 if (!Cond) return false; // Cannot determine.
2810 NextBB = BI->getSuccessor(!Cond->getZExtValue());
2812 } else if (SwitchInst *SI = dyn_cast<SwitchInst>(CurInst)) {
2814 dyn_cast<ConstantInt>(getVal(SI->getCondition()));
2815 if (!Val) return false; // Cannot determine.
2816 NextBB = SI->findCaseValue(Val).getCaseSuccessor();
2817 } else if (IndirectBrInst *IBI = dyn_cast<IndirectBrInst>(CurInst)) {
2818 Value *Val = getVal(IBI->getAddress())->stripPointerCasts();
2819 if (BlockAddress *BA = dyn_cast<BlockAddress>(Val))
2820 NextBB = BA->getBasicBlock();
2822 return false; // Cannot determine.
2823 } else if (isa<ReturnInst>(CurInst)) {
2826 // invoke, unwind, resume, unreachable.
2827 DEBUG(dbgs() << "Can not handle terminator.");
2828 return false; // Cannot handle this terminator.
2831 // We succeeded at evaluating this block!
2832 DEBUG(dbgs() << "Successfully evaluated block.\n");
2835 // Did not know how to evaluate this!
2836 DEBUG(dbgs() << "Failed to evaluate block due to unhandled instruction."
2841 if (!CurInst->use_empty()) {
2842 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(InstResult))
2843 InstResult = ConstantFoldConstantExpression(CE, TD, TLI);
2845 setVal(CurInst, InstResult);
2848 // If we just processed an invoke, we finished evaluating the block.
2849 if (InvokeInst *II = dyn_cast<InvokeInst>(CurInst)) {
2850 NextBB = II->getNormalDest();
2851 DEBUG(dbgs() << "Found an invoke instruction. Finished Block.\n\n");
2855 // Advance program counter.
2860 /// EvaluateFunction - Evaluate a call to function F, returning true if
2861 /// successful, false if we can't evaluate it. ActualArgs contains the formal
2862 /// arguments for the function.
2863 bool Evaluator::EvaluateFunction(Function *F, Constant *&RetVal,
2864 const SmallVectorImpl<Constant*> &ActualArgs) {
2865 // Check to see if this function is already executing (recursion). If so,
2866 // bail out. TODO: we might want to accept limited recursion.
2867 if (std::find(CallStack.begin(), CallStack.end(), F) != CallStack.end())
2870 CallStack.push_back(F);
2872 // Initialize arguments to the incoming values specified.
2874 for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end(); AI != E;
2876 setVal(AI, ActualArgs[ArgNo]);
2878 // ExecutedBlocks - We only handle non-looping, non-recursive code. As such,
2879 // we can only evaluate any one basic block at most once. This set keeps
2880 // track of what we have executed so we can detect recursive cases etc.
2881 SmallPtrSet<BasicBlock*, 32> ExecutedBlocks;
2883 // CurBB - The current basic block we're evaluating.
2884 BasicBlock *CurBB = F->begin();
2886 BasicBlock::iterator CurInst = CurBB->begin();
2889 BasicBlock *NextBB = 0; // Initialized to avoid compiler warnings.
2890 DEBUG(dbgs() << "Trying to evaluate BB: " << *CurBB << "\n");
2892 if (!EvaluateBlock(CurInst, NextBB))
2896 // Successfully running until there's no next block means that we found
2897 // the return. Fill it the return value and pop the call stack.
2898 ReturnInst *RI = cast<ReturnInst>(CurBB->getTerminator());
2899 if (RI->getNumOperands())
2900 RetVal = getVal(RI->getOperand(0));
2901 CallStack.pop_back();
2905 // Okay, we succeeded in evaluating this control flow. See if we have
2906 // executed the new block before. If so, we have a looping function,
2907 // which we cannot evaluate in reasonable time.
2908 if (!ExecutedBlocks.insert(NextBB))
2909 return false; // looped!
2911 // Okay, we have never been in this block before. Check to see if there
2912 // are any PHI nodes. If so, evaluate them with information about where
2915 for (CurInst = NextBB->begin();
2916 (PN = dyn_cast<PHINode>(CurInst)); ++CurInst)
2917 setVal(PN, getVal(PN->getIncomingValueForBlock(CurBB)));
2919 // Advance to the next block.
2924 /// EvaluateStaticConstructor - Evaluate static constructors in the function, if
2925 /// we can. Return true if we can, false otherwise.
2926 static bool EvaluateStaticConstructor(Function *F, const DataLayout *TD,
2927 const TargetLibraryInfo *TLI) {
2928 // Call the function.
2929 Evaluator Eval(TD, TLI);
2930 Constant *RetValDummy;
2931 bool EvalSuccess = Eval.EvaluateFunction(F, RetValDummy,
2932 SmallVector<Constant*, 0>());
2935 // We succeeded at evaluation: commit the result.
2936 DEBUG(dbgs() << "FULLY EVALUATED GLOBAL CTOR FUNCTION '"
2937 << F->getName() << "' to " << Eval.getMutatedMemory().size()
2939 for (DenseMap<Constant*, Constant*>::const_iterator I =
2940 Eval.getMutatedMemory().begin(), E = Eval.getMutatedMemory().end();
2942 CommitValueTo(I->second, I->first);
2943 for (SmallPtrSet<GlobalVariable*, 8>::const_iterator I =
2944 Eval.getInvariants().begin(), E = Eval.getInvariants().end();
2946 (*I)->setConstant(true);
2952 /// OptimizeGlobalCtorsList - Simplify and evaluation global ctors if possible.
2953 /// Return true if anything changed.
2954 bool GlobalOpt::OptimizeGlobalCtorsList(GlobalVariable *&GCL) {
2955 std::vector<Function*> Ctors = ParseGlobalCtors(GCL);
2956 bool MadeChange = false;
2957 if (Ctors.empty()) return false;
2959 // Loop over global ctors, optimizing them when we can.
2960 for (unsigned i = 0; i != Ctors.size(); ++i) {
2961 Function *F = Ctors[i];
2962 // Found a null terminator in the middle of the list, prune off the rest of
2965 if (i != Ctors.size()-1) {
2971 DEBUG(dbgs() << "Optimizing Global Constructor: " << *F << "\n");
2973 // We cannot simplify external ctor functions.
2974 if (F->empty()) continue;
2976 // If we can evaluate the ctor at compile time, do.
2977 if (EvaluateStaticConstructor(F, TD, TLI)) {
2978 Ctors.erase(Ctors.begin()+i);
2981 ++NumCtorsEvaluated;
2986 if (!MadeChange) return false;
2988 GCL = InstallGlobalCtors(GCL, Ctors);
2992 static int compareNames(Constant *const *A, Constant *const *B) {
2993 return (*A)->getName().compare((*B)->getName());
2996 static void setUsedInitializer(GlobalVariable &V,
2997 SmallPtrSet<GlobalValue *, 8> Init) {
2999 V.eraseFromParent();
3003 SmallVector<llvm::Constant *, 8> UsedArray;
3004 PointerType *Int8PtrTy = Type::getInt8PtrTy(V.getContext());
3006 for (SmallPtrSet<GlobalValue *, 8>::iterator I = Init.begin(), E = Init.end();
3008 Constant *Cast = llvm::ConstantExpr::getBitCast(*I, Int8PtrTy);
3009 UsedArray.push_back(Cast);
3011 // Sort to get deterministic order.
3012 array_pod_sort(UsedArray.begin(), UsedArray.end(), compareNames);
3013 ArrayType *ATy = ArrayType::get(Int8PtrTy, UsedArray.size());
3015 Module *M = V.getParent();
3016 V.removeFromParent();
3017 GlobalVariable *NV =
3018 new GlobalVariable(*M, ATy, false, llvm::GlobalValue::AppendingLinkage,
3019 llvm::ConstantArray::get(ATy, UsedArray), "");
3021 NV->setSection("llvm.metadata");
3026 /// \brief An easy to access representation of llvm.used and llvm.compiler.used.
3028 SmallPtrSet<GlobalValue *, 8> Used;
3029 SmallPtrSet<GlobalValue *, 8> CompilerUsed;
3030 GlobalVariable *UsedV;
3031 GlobalVariable *CompilerUsedV;
3034 LLVMUsed(Module &M) {
3035 UsedV = collectUsedGlobalVariables(M, Used, false);
3036 CompilerUsedV = collectUsedGlobalVariables(M, CompilerUsed, true);
3038 typedef SmallPtrSet<GlobalValue *, 8>::iterator iterator;
3039 iterator usedBegin() { return Used.begin(); }
3040 iterator usedEnd() { return Used.end(); }
3041 iterator compilerUsedBegin() { return CompilerUsed.begin(); }
3042 iterator compilerUsedEnd() { return CompilerUsed.end(); }
3043 bool usedCount(GlobalValue *GV) const { return Used.count(GV); }
3044 bool compilerUsedCount(GlobalValue *GV) const {
3045 return CompilerUsed.count(GV);
3047 bool usedErase(GlobalValue *GV) { return Used.erase(GV); }
3048 bool compilerUsedErase(GlobalValue *GV) { return CompilerUsed.erase(GV); }
3049 bool usedInsert(GlobalValue *GV) { return Used.insert(GV); }
3050 bool compilerUsedInsert(GlobalValue *GV) { return CompilerUsed.insert(GV); }
3052 void syncVariablesAndSets() {
3054 setUsedInitializer(*UsedV, Used);
3056 setUsedInitializer(*CompilerUsedV, CompilerUsed);
3061 static bool hasUseOtherThanLLVMUsed(GlobalAlias &GA, const LLVMUsed &U) {
3062 if (GA.use_empty()) // No use at all.
3065 assert((!U.usedCount(&GA) || !U.compilerUsedCount(&GA)) &&
3066 "We should have removed the duplicated "
3067 "element from llvm.compiler.used");
3068 if (!GA.hasOneUse())
3069 // Strictly more than one use. So at least one is not in llvm.used and
3070 // llvm.compiler.used.
3073 // Exactly one use. Check if it is in llvm.used or llvm.compiler.used.
3074 return !U.usedCount(&GA) && !U.compilerUsedCount(&GA);
3077 static bool hasMoreThanOneUseOtherThanLLVMUsed(GlobalValue &V,
3078 const LLVMUsed &U) {
3080 assert((!U.usedCount(&V) || !U.compilerUsedCount(&V)) &&
3081 "We should have removed the duplicated "
3082 "element from llvm.compiler.used");
3083 if (U.usedCount(&V) || U.compilerUsedCount(&V))
3085 return V.hasNUsesOrMore(N);
3088 static bool mayHaveOtherReferences(GlobalAlias &GA, const LLVMUsed &U) {
3089 if (!GA.hasLocalLinkage())
3092 return U.usedCount(&GA) || U.compilerUsedCount(&GA);
3095 static bool hasUsesToReplace(GlobalAlias &GA, LLVMUsed &U, bool &RenameTarget) {
3096 RenameTarget = false;
3098 if (hasUseOtherThanLLVMUsed(GA, U))
3101 // If the alias is externally visible, we may still be able to simplify it.
3102 if (!mayHaveOtherReferences(GA, U))
3105 // If the aliasee has internal linkage, give it the name and linkage
3106 // of the alias, and delete the alias. This turns:
3107 // define internal ... @f(...)
3108 // @a = alias ... @f
3110 // define ... @a(...)
3111 Constant *Aliasee = GA.getAliasee();
3112 GlobalValue *Target = cast<GlobalValue>(Aliasee->stripPointerCasts());
3113 if (!Target->hasLocalLinkage())
3116 // Do not perform the transform if multiple aliases potentially target the
3117 // aliasee. This check also ensures that it is safe to replace the section
3118 // and other attributes of the aliasee with those of the alias.
3119 if (hasMoreThanOneUseOtherThanLLVMUsed(*Target, U))
3122 RenameTarget = true;
3126 bool GlobalOpt::OptimizeGlobalAliases(Module &M) {
3127 bool Changed = false;
3130 for (SmallPtrSet<GlobalValue *, 8>::iterator I = Used.usedBegin(),
3133 Used.compilerUsedErase(*I);
3135 for (Module::alias_iterator I = M.alias_begin(), E = M.alias_end();
3137 Module::alias_iterator J = I++;
3138 // Aliases without names cannot be referenced outside this module.
3139 if (!J->hasName() && !J->isDeclaration())
3140 J->setLinkage(GlobalValue::InternalLinkage);
3141 // If the aliasee may change at link time, nothing can be done - bail out.
3142 if (J->mayBeOverridden())
3145 Constant *Aliasee = J->getAliasee();
3146 GlobalValue *Target = cast<GlobalValue>(Aliasee->stripPointerCasts());
3147 Target->removeDeadConstantUsers();
3149 // Make all users of the alias use the aliasee instead.
3151 if (!hasUsesToReplace(*J, Used, RenameTarget))
3154 J->replaceAllUsesWith(Aliasee);
3155 ++NumAliasesResolved;
3159 // Give the aliasee the name, linkage and other attributes of the alias.
3160 Target->takeName(J);
3161 Target->setLinkage(J->getLinkage());
3162 Target->GlobalValue::copyAttributesFrom(J);
3164 if (Used.usedErase(J))
3165 Used.usedInsert(Target);
3167 if (Used.compilerUsedErase(J))
3168 Used.compilerUsedInsert(Target);
3169 } else if (mayHaveOtherReferences(*J, Used))
3172 // Delete the alias.
3173 M.getAliasList().erase(J);
3174 ++NumAliasesRemoved;
3178 Used.syncVariablesAndSets();
3183 static Function *FindCXAAtExit(Module &M, TargetLibraryInfo *TLI) {
3184 if (!TLI->has(LibFunc::cxa_atexit))
3187 Function *Fn = M.getFunction(TLI->getName(LibFunc::cxa_atexit));
3192 FunctionType *FTy = Fn->getFunctionType();
3194 // Checking that the function has the right return type, the right number of
3195 // parameters and that they all have pointer types should be enough.
3196 if (!FTy->getReturnType()->isIntegerTy() ||
3197 FTy->getNumParams() != 3 ||
3198 !FTy->getParamType(0)->isPointerTy() ||
3199 !FTy->getParamType(1)->isPointerTy() ||
3200 !FTy->getParamType(2)->isPointerTy())
3206 /// cxxDtorIsEmpty - Returns whether the given function is an empty C++
3207 /// destructor and can therefore be eliminated.
3208 /// Note that we assume that other optimization passes have already simplified
3209 /// the code so we only look for a function with a single basic block, where
3210 /// the only allowed instructions are 'ret', 'call' to an empty C++ dtor and
3211 /// other side-effect free instructions.
3212 static bool cxxDtorIsEmpty(const Function &Fn,
3213 SmallPtrSet<const Function *, 8> &CalledFunctions) {
3214 // FIXME: We could eliminate C++ destructors if they're readonly/readnone and
3215 // nounwind, but that doesn't seem worth doing.
3216 if (Fn.isDeclaration())
3219 if (++Fn.begin() != Fn.end())
3222 const BasicBlock &EntryBlock = Fn.getEntryBlock();
3223 for (BasicBlock::const_iterator I = EntryBlock.begin(), E = EntryBlock.end();
3225 if (const CallInst *CI = dyn_cast<CallInst>(I)) {
3226 // Ignore debug intrinsics.
3227 if (isa<DbgInfoIntrinsic>(CI))
3230 const Function *CalledFn = CI->getCalledFunction();
3235 SmallPtrSet<const Function *, 8> NewCalledFunctions(CalledFunctions);
3237 // Don't treat recursive functions as empty.
3238 if (!NewCalledFunctions.insert(CalledFn))
3241 if (!cxxDtorIsEmpty(*CalledFn, NewCalledFunctions))
3243 } else if (isa<ReturnInst>(*I))
3244 return true; // We're done.
3245 else if (I->mayHaveSideEffects())
3246 return false; // Destructor with side effects, bail.
3252 bool GlobalOpt::OptimizeEmptyGlobalCXXDtors(Function *CXAAtExitFn) {
3253 /// Itanium C++ ABI p3.3.5:
3255 /// After constructing a global (or local static) object, that will require
3256 /// destruction on exit, a termination function is registered as follows:
3258 /// extern "C" int __cxa_atexit ( void (*f)(void *), void *p, void *d );
3260 /// This registration, e.g. __cxa_atexit(f,p,d), is intended to cause the
3261 /// call f(p) when DSO d is unloaded, before all such termination calls
3262 /// registered before this one. It returns zero if registration is
3263 /// successful, nonzero on failure.
3265 // This pass will look for calls to __cxa_atexit where the function is trivial
3267 bool Changed = false;
3269 for (Function::use_iterator I = CXAAtExitFn->use_begin(),
3270 E = CXAAtExitFn->use_end(); I != E;) {
3271 // We're only interested in calls. Theoretically, we could handle invoke
3272 // instructions as well, but neither llvm-gcc nor clang generate invokes
3274 CallInst *CI = dyn_cast<CallInst>(*I++);
3279 dyn_cast<Function>(CI->getArgOperand(0)->stripPointerCasts());
3283 SmallPtrSet<const Function *, 8> CalledFunctions;
3284 if (!cxxDtorIsEmpty(*DtorFn, CalledFunctions))
3287 // Just remove the call.
3288 CI->replaceAllUsesWith(Constant::getNullValue(CI->getType()));
3289 CI->eraseFromParent();
3291 ++NumCXXDtorsRemoved;
3299 bool GlobalOpt::runOnModule(Module &M) {
3300 bool Changed = false;
3302 TD = getAnalysisIfAvailable<DataLayout>();
3303 TLI = &getAnalysis<TargetLibraryInfo>();
3305 // Try to find the llvm.globalctors list.
3306 GlobalVariable *GlobalCtors = FindGlobalCtors(M);
3308 bool LocalChange = true;
3309 while (LocalChange) {
3310 LocalChange = false;
3312 // Delete functions that are trivially dead, ccc -> fastcc
3313 LocalChange |= OptimizeFunctions(M);
3315 // Optimize global_ctors list.
3317 LocalChange |= OptimizeGlobalCtorsList(GlobalCtors);
3319 // Optimize non-address-taken globals.
3320 LocalChange |= OptimizeGlobalVars(M);
3322 // Resolve aliases, when possible.
3323 LocalChange |= OptimizeGlobalAliases(M);
3325 // Try to remove trivial global destructors if they are not removed
3327 Function *CXAAtExitFn = FindCXAAtExit(M, TLI);
3329 LocalChange |= OptimizeEmptyGlobalCXXDtors(CXAAtExitFn);
3331 Changed |= LocalChange;
3334 // TODO: Move all global ctors functions to the end of the module for code