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(NumLocalized , "Number of globals localized");
54 STATISTIC(NumShrunkToBool , "Number of global vars shrunk to booleans");
55 STATISTIC(NumFastCallFns , "Number of functions converted to fastcc");
56 STATISTIC(NumCtorsEvaluated, "Number of static ctors evaluated");
57 STATISTIC(NumNestRemoved , "Number of nest attributes removed");
58 STATISTIC(NumAliasesResolved, "Number of global aliases resolved");
59 STATISTIC(NumAliasesRemoved, "Number of global aliases eliminated");
60 STATISTIC(NumCXXDtorsRemoved, "Number of global C++ destructors removed");
64 struct GlobalOpt : public ModulePass {
65 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
66 AU.addRequired<TargetLibraryInfo>();
68 static char ID; // Pass identification, replacement for typeid
69 GlobalOpt() : ModulePass(ID) {
70 initializeGlobalOptPass(*PassRegistry::getPassRegistry());
73 bool runOnModule(Module &M);
76 GlobalVariable *FindGlobalCtors(Module &M);
77 bool OptimizeFunctions(Module &M);
78 bool OptimizeGlobalVars(Module &M);
79 bool OptimizeGlobalAliases(Module &M);
80 bool OptimizeGlobalCtorsList(GlobalVariable *&GCL);
81 bool ProcessGlobal(GlobalVariable *GV,Module::global_iterator &GVI);
82 bool ProcessInternalGlobal(GlobalVariable *GV,Module::global_iterator &GVI,
83 const SmallPtrSet<const PHINode*, 16> &PHIUsers,
84 const GlobalStatus &GS);
85 bool OptimizeEmptyGlobalCXXDtors(Function *CXAAtExitFn);
88 TargetLibraryInfo *TLI;
92 char GlobalOpt::ID = 0;
93 INITIALIZE_PASS_BEGIN(GlobalOpt, "globalopt",
94 "Global Variable Optimizer", false, false)
95 INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfo)
96 INITIALIZE_PASS_END(GlobalOpt, "globalopt",
97 "Global Variable Optimizer", false, false)
99 ModulePass *llvm::createGlobalOptimizerPass() { return new GlobalOpt(); }
103 /// GlobalStatus - As we analyze each global, keep track of some information
104 /// about it. If we find out that the address of the global is taken, none of
105 /// this info will be accurate.
106 struct GlobalStatus {
107 /// isCompared - True if the global's address is used in a comparison.
110 /// isLoaded - True if the global is ever loaded. If the global isn't ever
111 /// loaded it can be deleted.
114 /// StoredType - Keep track of what stores to the global look like.
117 /// NotStored - There is no store to this global. It can thus be marked
121 /// isInitializerStored - This global is stored to, but the only thing
122 /// stored is the constant it was initialized with. This is only tracked
123 /// for scalar globals.
126 /// isStoredOnce - This global is stored to, but only its initializer and
127 /// one other value is ever stored to it. If this global isStoredOnce, we
128 /// track the value stored to it in StoredOnceValue below. This is only
129 /// tracked for scalar globals.
132 /// isStored - This global is stored to by multiple values or something else
133 /// that we cannot track.
137 /// StoredOnceValue - If only one value (besides the initializer constant) is
138 /// ever stored to this global, keep track of what value it is.
139 Value *StoredOnceValue;
141 /// AccessingFunction/HasMultipleAccessingFunctions - These start out
142 /// null/false. When the first accessing function is noticed, it is recorded.
143 /// When a second different accessing function is noticed,
144 /// HasMultipleAccessingFunctions is set to true.
145 const Function *AccessingFunction;
146 bool HasMultipleAccessingFunctions;
148 /// HasNonInstructionUser - Set to true if this global has a user that is not
149 /// an instruction (e.g. a constant expr or GV initializer).
150 bool HasNonInstructionUser;
152 /// AtomicOrdering - Set to the strongest atomic ordering requirement.
153 AtomicOrdering Ordering;
155 GlobalStatus() : isCompared(false), isLoaded(false), StoredType(NotStored),
156 StoredOnceValue(0), AccessingFunction(0),
157 HasMultipleAccessingFunctions(false),
158 HasNonInstructionUser(false), Ordering(NotAtomic) {}
163 /// StrongerOrdering - Return the stronger of the two ordering. If the two
164 /// orderings are acquire and release, then return AcquireRelease.
166 static AtomicOrdering StrongerOrdering(AtomicOrdering X, AtomicOrdering Y) {
167 if (X == Acquire && Y == Release) return AcquireRelease;
168 if (Y == Acquire && X == Release) return AcquireRelease;
169 return (AtomicOrdering)std::max(X, Y);
172 /// SafeToDestroyConstant - It is safe to destroy a constant iff it is only used
173 /// by constants itself. Note that constants cannot be cyclic, so this test is
174 /// pretty easy to implement recursively.
176 static bool SafeToDestroyConstant(const Constant *C) {
177 if (isa<GlobalValue>(C)) return false;
179 for (Value::const_use_iterator UI = C->use_begin(), E = C->use_end(); UI != E;
181 if (const Constant *CU = dyn_cast<Constant>(*UI)) {
182 if (!SafeToDestroyConstant(CU)) return false;
189 /// AnalyzeGlobal - Look at all uses of the global and fill in the GlobalStatus
190 /// structure. If the global has its address taken, return true to indicate we
191 /// can't do anything with it.
193 static bool AnalyzeGlobal(const Value *V, GlobalStatus &GS,
194 SmallPtrSet<const PHINode*, 16> &PHIUsers) {
195 for (Value::const_use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;
198 if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(U)) {
199 GS.HasNonInstructionUser = true;
201 // If the result of the constantexpr isn't pointer type, then we won't
202 // know to expect it in various places. Just reject early.
203 if (!isa<PointerType>(CE->getType())) return true;
205 if (AnalyzeGlobal(CE, GS, PHIUsers)) return true;
206 } else if (const Instruction *I = dyn_cast<Instruction>(U)) {
207 if (!GS.HasMultipleAccessingFunctions) {
208 const Function *F = I->getParent()->getParent();
209 if (GS.AccessingFunction == 0)
210 GS.AccessingFunction = F;
211 else if (GS.AccessingFunction != F)
212 GS.HasMultipleAccessingFunctions = true;
214 if (const LoadInst *LI = dyn_cast<LoadInst>(I)) {
216 // Don't hack on volatile loads.
217 if (LI->isVolatile()) return true;
218 GS.Ordering = StrongerOrdering(GS.Ordering, LI->getOrdering());
219 } else if (const StoreInst *SI = dyn_cast<StoreInst>(I)) {
220 // Don't allow a store OF the address, only stores TO the address.
221 if (SI->getOperand(0) == V) return true;
223 // Don't hack on volatile stores.
224 if (SI->isVolatile()) return true;
226 GS.Ordering = StrongerOrdering(GS.Ordering, SI->getOrdering());
228 // If this is a direct store to the global (i.e., the global is a scalar
229 // value, not an aggregate), keep more specific information about
231 if (GS.StoredType != GlobalStatus::isStored) {
232 if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(
233 SI->getOperand(1))) {
234 Value *StoredVal = SI->getOperand(0);
236 if (Constant *C = dyn_cast<Constant>(StoredVal)) {
237 if (C->isThreadDependent()) {
238 // The stored value changes between threads; don't track it.
243 if (StoredVal == GV->getInitializer()) {
244 if (GS.StoredType < GlobalStatus::isInitializerStored)
245 GS.StoredType = GlobalStatus::isInitializerStored;
246 } else if (isa<LoadInst>(StoredVal) &&
247 cast<LoadInst>(StoredVal)->getOperand(0) == GV) {
248 if (GS.StoredType < GlobalStatus::isInitializerStored)
249 GS.StoredType = GlobalStatus::isInitializerStored;
250 } else if (GS.StoredType < GlobalStatus::isStoredOnce) {
251 GS.StoredType = GlobalStatus::isStoredOnce;
252 GS.StoredOnceValue = StoredVal;
253 } else if (GS.StoredType == GlobalStatus::isStoredOnce &&
254 GS.StoredOnceValue == StoredVal) {
257 GS.StoredType = GlobalStatus::isStored;
260 GS.StoredType = GlobalStatus::isStored;
263 } else if (isa<BitCastInst>(I)) {
264 if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
265 } else if (isa<GetElementPtrInst>(I)) {
266 if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
267 } else if (isa<SelectInst>(I)) {
268 if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
269 } else if (const PHINode *PN = dyn_cast<PHINode>(I)) {
270 // PHI nodes we can check just like select or GEP instructions, but we
271 // have to be careful about infinite recursion.
272 if (PHIUsers.insert(PN)) // Not already visited.
273 if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
274 } else if (isa<CmpInst>(I)) {
275 GS.isCompared = true;
276 } else if (const MemTransferInst *MTI = dyn_cast<MemTransferInst>(I)) {
277 if (MTI->isVolatile()) return true;
278 if (MTI->getArgOperand(0) == V)
279 GS.StoredType = GlobalStatus::isStored;
280 if (MTI->getArgOperand(1) == V)
282 } else if (const MemSetInst *MSI = dyn_cast<MemSetInst>(I)) {
283 assert(MSI->getArgOperand(0) == V && "Memset only takes one pointer!");
284 if (MSI->isVolatile()) return true;
285 GS.StoredType = GlobalStatus::isStored;
287 return true; // Any other non-load instruction might take address!
289 } else if (const Constant *C = dyn_cast<Constant>(U)) {
290 GS.HasNonInstructionUser = true;
291 // We might have a dead and dangling constant hanging off of here.
292 if (!SafeToDestroyConstant(C))
295 GS.HasNonInstructionUser = true;
296 // Otherwise must be some other user.
304 /// isLeakCheckerRoot - Is this global variable possibly used by a leak checker
305 /// as a root? If so, we might not really want to eliminate the stores to it.
306 static bool isLeakCheckerRoot(GlobalVariable *GV) {
307 // A global variable is a root if it is a pointer, or could plausibly contain
308 // a pointer. There are two challenges; one is that we could have a struct
309 // the has an inner member which is a pointer. We recurse through the type to
310 // detect these (up to a point). The other is that we may actually be a union
311 // of a pointer and another type, and so our LLVM type is an integer which
312 // gets converted into a pointer, or our type is an [i8 x #] with a pointer
313 // potentially contained here.
315 if (GV->hasPrivateLinkage())
318 SmallVector<Type *, 4> Types;
319 Types.push_back(cast<PointerType>(GV->getType())->getElementType());
323 Type *Ty = Types.pop_back_val();
324 switch (Ty->getTypeID()) {
326 case Type::PointerTyID: return true;
327 case Type::ArrayTyID:
328 case Type::VectorTyID: {
329 SequentialType *STy = cast<SequentialType>(Ty);
330 Types.push_back(STy->getElementType());
333 case Type::StructTyID: {
334 StructType *STy = cast<StructType>(Ty);
335 if (STy->isOpaque()) return true;
336 for (StructType::element_iterator I = STy->element_begin(),
337 E = STy->element_end(); I != E; ++I) {
339 if (isa<PointerType>(InnerTy)) return true;
340 if (isa<CompositeType>(InnerTy))
341 Types.push_back(InnerTy);
346 if (--Limit == 0) return true;
347 } while (!Types.empty());
351 /// Given a value that is stored to a global but never read, determine whether
352 /// it's safe to remove the store and the chain of computation that feeds the
354 static bool IsSafeComputationToRemove(Value *V, const TargetLibraryInfo *TLI) {
356 if (isa<Constant>(V))
360 if (isa<LoadInst>(V) || isa<InvokeInst>(V) || isa<Argument>(V) ||
363 if (isAllocationFn(V, TLI))
366 Instruction *I = cast<Instruction>(V);
367 if (I->mayHaveSideEffects())
369 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(I)) {
370 if (!GEP->hasAllConstantIndices())
372 } else if (I->getNumOperands() != 1) {
376 V = I->getOperand(0);
380 /// CleanupPointerRootUsers - This GV is a pointer root. Loop over all users
381 /// of the global and clean up any that obviously don't assign the global a
382 /// value that isn't dynamically allocated.
384 static bool CleanupPointerRootUsers(GlobalVariable *GV,
385 const TargetLibraryInfo *TLI) {
386 // A brief explanation of leak checkers. The goal is to find bugs where
387 // pointers are forgotten, causing an accumulating growth in memory
388 // usage over time. The common strategy for leak checkers is to whitelist the
389 // memory pointed to by globals at exit. This is popular because it also
390 // solves another problem where the main thread of a C++ program may shut down
391 // before other threads that are still expecting to use those globals. To
392 // handle that case, we expect the program may create a singleton and never
395 bool Changed = false;
397 // If Dead[n].first is the only use of a malloc result, we can delete its
398 // chain of computation and the store to the global in Dead[n].second.
399 SmallVector<std::pair<Instruction *, Instruction *>, 32> Dead;
401 // Constants can't be pointers to dynamically allocated memory.
402 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end();
405 if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
406 Value *V = SI->getValueOperand();
407 if (isa<Constant>(V)) {
409 SI->eraseFromParent();
410 } else if (Instruction *I = dyn_cast<Instruction>(V)) {
412 Dead.push_back(std::make_pair(I, SI));
414 } else if (MemSetInst *MSI = dyn_cast<MemSetInst>(U)) {
415 if (isa<Constant>(MSI->getValue())) {
417 MSI->eraseFromParent();
418 } else if (Instruction *I = dyn_cast<Instruction>(MSI->getValue())) {
420 Dead.push_back(std::make_pair(I, MSI));
422 } else if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(U)) {
423 GlobalVariable *MemSrc = dyn_cast<GlobalVariable>(MTI->getSource());
424 if (MemSrc && MemSrc->isConstant()) {
426 MTI->eraseFromParent();
427 } else if (Instruction *I = dyn_cast<Instruction>(MemSrc)) {
429 Dead.push_back(std::make_pair(I, MTI));
431 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U)) {
432 if (CE->use_empty()) {
433 CE->destroyConstant();
436 } else if (Constant *C = dyn_cast<Constant>(U)) {
437 if (SafeToDestroyConstant(C)) {
438 C->destroyConstant();
439 // This could have invalidated UI, start over from scratch.
441 CleanupPointerRootUsers(GV, TLI);
447 for (int i = 0, e = Dead.size(); i != e; ++i) {
448 if (IsSafeComputationToRemove(Dead[i].first, TLI)) {
449 Dead[i].second->eraseFromParent();
450 Instruction *I = Dead[i].first;
452 if (isAllocationFn(I, TLI))
454 Instruction *J = dyn_cast<Instruction>(I->getOperand(0));
457 I->eraseFromParent();
460 I->eraseFromParent();
467 /// CleanupConstantGlobalUsers - We just marked GV constant. Loop over all
468 /// users of the global, cleaning up the obvious ones. This is largely just a
469 /// quick scan over the use list to clean up the easy and obvious cruft. This
470 /// returns true if it made a change.
471 static bool CleanupConstantGlobalUsers(Value *V, Constant *Init,
472 DataLayout *TD, TargetLibraryInfo *TLI) {
473 bool Changed = false;
474 SmallVector<User*, 8> WorkList(V->use_begin(), V->use_end());
475 while (!WorkList.empty()) {
476 User *U = WorkList.pop_back_val();
478 if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
480 // Replace the load with the initializer.
481 LI->replaceAllUsesWith(Init);
482 LI->eraseFromParent();
485 } else if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
486 // Store must be unreachable or storing Init into the global.
487 SI->eraseFromParent();
489 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U)) {
490 if (CE->getOpcode() == Instruction::GetElementPtr) {
491 Constant *SubInit = 0;
493 SubInit = ConstantFoldLoadThroughGEPConstantExpr(Init, CE);
494 Changed |= CleanupConstantGlobalUsers(CE, SubInit, TD, TLI);
495 } else if (CE->getOpcode() == Instruction::BitCast &&
496 CE->getType()->isPointerTy()) {
497 // Pointer cast, delete any stores and memsets to the global.
498 Changed |= CleanupConstantGlobalUsers(CE, 0, TD, TLI);
501 if (CE->use_empty()) {
502 CE->destroyConstant();
505 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) {
506 // Do not transform "gepinst (gep constexpr (GV))" here, because forming
507 // "gepconstexpr (gep constexpr (GV))" will cause the two gep's to fold
508 // and will invalidate our notion of what Init is.
509 Constant *SubInit = 0;
510 if (!isa<ConstantExpr>(GEP->getOperand(0))) {
512 dyn_cast_or_null<ConstantExpr>(ConstantFoldInstruction(GEP, TD, TLI));
513 if (Init && CE && CE->getOpcode() == Instruction::GetElementPtr)
514 SubInit = ConstantFoldLoadThroughGEPConstantExpr(Init, CE);
516 // If the initializer is an all-null value and we have an inbounds GEP,
517 // we already know what the result of any load from that GEP is.
518 // TODO: Handle splats.
519 if (Init && isa<ConstantAggregateZero>(Init) && GEP->isInBounds())
520 SubInit = Constant::getNullValue(GEP->getType()->getElementType());
522 Changed |= CleanupConstantGlobalUsers(GEP, SubInit, TD, TLI);
524 if (GEP->use_empty()) {
525 GEP->eraseFromParent();
528 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(U)) { // memset/cpy/mv
529 if (MI->getRawDest() == V) {
530 MI->eraseFromParent();
534 } else if (Constant *C = dyn_cast<Constant>(U)) {
535 // If we have a chain of dead constantexprs or other things dangling from
536 // us, and if they are all dead, nuke them without remorse.
537 if (SafeToDestroyConstant(C)) {
538 C->destroyConstant();
539 CleanupConstantGlobalUsers(V, Init, TD, TLI);
547 /// isSafeSROAElementUse - Return true if the specified instruction is a safe
548 /// user of a derived expression from a global that we want to SROA.
549 static bool isSafeSROAElementUse(Value *V) {
550 // We might have a dead and dangling constant hanging off of here.
551 if (Constant *C = dyn_cast<Constant>(V))
552 return SafeToDestroyConstant(C);
554 Instruction *I = dyn_cast<Instruction>(V);
555 if (!I) return false;
558 if (isa<LoadInst>(I)) return true;
560 // Stores *to* the pointer are ok.
561 if (StoreInst *SI = dyn_cast<StoreInst>(I))
562 return SI->getOperand(0) != V;
564 // Otherwise, it must be a GEP.
565 GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I);
566 if (GEPI == 0) return false;
568 if (GEPI->getNumOperands() < 3 || !isa<Constant>(GEPI->getOperand(1)) ||
569 !cast<Constant>(GEPI->getOperand(1))->isNullValue())
572 for (Value::use_iterator I = GEPI->use_begin(), E = GEPI->use_end();
574 if (!isSafeSROAElementUse(*I))
580 /// IsUserOfGlobalSafeForSRA - U is a direct user of the specified global value.
581 /// Look at it and its uses and decide whether it is safe to SROA this global.
583 static bool IsUserOfGlobalSafeForSRA(User *U, GlobalValue *GV) {
584 // The user of the global must be a GEP Inst or a ConstantExpr GEP.
585 if (!isa<GetElementPtrInst>(U) &&
586 (!isa<ConstantExpr>(U) ||
587 cast<ConstantExpr>(U)->getOpcode() != Instruction::GetElementPtr))
590 // Check to see if this ConstantExpr GEP is SRA'able. In particular, we
591 // don't like < 3 operand CE's, and we don't like non-constant integer
592 // indices. This enforces that all uses are 'gep GV, 0, C, ...' for some
594 if (U->getNumOperands() < 3 || !isa<Constant>(U->getOperand(1)) ||
595 !cast<Constant>(U->getOperand(1))->isNullValue() ||
596 !isa<ConstantInt>(U->getOperand(2)))
599 gep_type_iterator GEPI = gep_type_begin(U), E = gep_type_end(U);
600 ++GEPI; // Skip over the pointer index.
602 // If this is a use of an array allocation, do a bit more checking for sanity.
603 if (ArrayType *AT = dyn_cast<ArrayType>(*GEPI)) {
604 uint64_t NumElements = AT->getNumElements();
605 ConstantInt *Idx = cast<ConstantInt>(U->getOperand(2));
607 // Check to make sure that index falls within the array. If not,
608 // something funny is going on, so we won't do the optimization.
610 if (Idx->getZExtValue() >= NumElements)
613 // We cannot scalar repl this level of the array unless any array
614 // sub-indices are in-range constants. In particular, consider:
615 // A[0][i]. We cannot know that the user isn't doing invalid things like
616 // allowing i to index an out-of-range subscript that accesses A[1].
618 // Scalar replacing *just* the outer index of the array is probably not
619 // going to be a win anyway, so just give up.
620 for (++GEPI; // Skip array index.
623 uint64_t NumElements;
624 if (ArrayType *SubArrayTy = dyn_cast<ArrayType>(*GEPI))
625 NumElements = SubArrayTy->getNumElements();
626 else if (VectorType *SubVectorTy = dyn_cast<VectorType>(*GEPI))
627 NumElements = SubVectorTy->getNumElements();
629 assert((*GEPI)->isStructTy() &&
630 "Indexed GEP type is not array, vector, or struct!");
634 ConstantInt *IdxVal = dyn_cast<ConstantInt>(GEPI.getOperand());
635 if (!IdxVal || IdxVal->getZExtValue() >= NumElements)
640 for (Value::use_iterator I = U->use_begin(), E = U->use_end(); I != E; ++I)
641 if (!isSafeSROAElementUse(*I))
646 /// GlobalUsersSafeToSRA - Look at all uses of the global and decide whether it
647 /// is safe for us to perform this transformation.
649 static bool GlobalUsersSafeToSRA(GlobalValue *GV) {
650 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end();
652 if (!IsUserOfGlobalSafeForSRA(*UI, GV))
659 /// SRAGlobal - Perform scalar replacement of aggregates on the specified global
660 /// variable. This opens the door for other optimizations by exposing the
661 /// behavior of the program in a more fine-grained way. We have determined that
662 /// this transformation is safe already. We return the first global variable we
663 /// insert so that the caller can reprocess it.
664 static GlobalVariable *SRAGlobal(GlobalVariable *GV, const DataLayout &TD) {
665 // Make sure this global only has simple uses that we can SRA.
666 if (!GlobalUsersSafeToSRA(GV))
669 assert(GV->hasLocalLinkage() && !GV->isConstant());
670 Constant *Init = GV->getInitializer();
671 Type *Ty = Init->getType();
673 std::vector<GlobalVariable*> NewGlobals;
674 Module::GlobalListType &Globals = GV->getParent()->getGlobalList();
676 // Get the alignment of the global, either explicit or target-specific.
677 unsigned StartAlignment = GV->getAlignment();
678 if (StartAlignment == 0)
679 StartAlignment = TD.getABITypeAlignment(GV->getType());
681 if (StructType *STy = dyn_cast<StructType>(Ty)) {
682 NewGlobals.reserve(STy->getNumElements());
683 const StructLayout &Layout = *TD.getStructLayout(STy);
684 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
685 Constant *In = Init->getAggregateElement(i);
686 assert(In && "Couldn't get element of initializer?");
687 GlobalVariable *NGV = new GlobalVariable(STy->getElementType(i), false,
688 GlobalVariable::InternalLinkage,
689 In, GV->getName()+"."+Twine(i),
690 GV->getThreadLocalMode(),
691 GV->getType()->getAddressSpace());
692 Globals.insert(GV, NGV);
693 NewGlobals.push_back(NGV);
695 // Calculate the known alignment of the field. If the original aggregate
696 // had 256 byte alignment for example, something might depend on that:
697 // propagate info to each field.
698 uint64_t FieldOffset = Layout.getElementOffset(i);
699 unsigned NewAlign = (unsigned)MinAlign(StartAlignment, FieldOffset);
700 if (NewAlign > TD.getABITypeAlignment(STy->getElementType(i)))
701 NGV->setAlignment(NewAlign);
703 } else if (SequentialType *STy = dyn_cast<SequentialType>(Ty)) {
704 unsigned NumElements = 0;
705 if (ArrayType *ATy = dyn_cast<ArrayType>(STy))
706 NumElements = ATy->getNumElements();
708 NumElements = cast<VectorType>(STy)->getNumElements();
710 if (NumElements > 16 && GV->hasNUsesOrMore(16))
711 return 0; // It's not worth it.
712 NewGlobals.reserve(NumElements);
714 uint64_t EltSize = TD.getTypeAllocSize(STy->getElementType());
715 unsigned EltAlign = TD.getABITypeAlignment(STy->getElementType());
716 for (unsigned i = 0, e = NumElements; i != e; ++i) {
717 Constant *In = Init->getAggregateElement(i);
718 assert(In && "Couldn't get element of initializer?");
720 GlobalVariable *NGV = new GlobalVariable(STy->getElementType(), false,
721 GlobalVariable::InternalLinkage,
722 In, GV->getName()+"."+Twine(i),
723 GV->getThreadLocalMode(),
724 GV->getType()->getAddressSpace());
725 Globals.insert(GV, NGV);
726 NewGlobals.push_back(NGV);
728 // Calculate the known alignment of the field. If the original aggregate
729 // had 256 byte alignment for example, something might depend on that:
730 // propagate info to each field.
731 unsigned NewAlign = (unsigned)MinAlign(StartAlignment, EltSize*i);
732 if (NewAlign > EltAlign)
733 NGV->setAlignment(NewAlign);
737 if (NewGlobals.empty())
740 DEBUG(dbgs() << "PERFORMING GLOBAL SRA ON: " << *GV);
742 Constant *NullInt =Constant::getNullValue(Type::getInt32Ty(GV->getContext()));
744 // Loop over all of the uses of the global, replacing the constantexpr geps,
745 // with smaller constantexpr geps or direct references.
746 while (!GV->use_empty()) {
747 User *GEP = GV->use_back();
748 assert(((isa<ConstantExpr>(GEP) &&
749 cast<ConstantExpr>(GEP)->getOpcode()==Instruction::GetElementPtr)||
750 isa<GetElementPtrInst>(GEP)) && "NonGEP CE's are not SRAable!");
752 // Ignore the 1th operand, which has to be zero or else the program is quite
753 // broken (undefined). Get the 2nd operand, which is the structure or array
755 unsigned Val = cast<ConstantInt>(GEP->getOperand(2))->getZExtValue();
756 if (Val >= NewGlobals.size()) Val = 0; // Out of bound array access.
758 Value *NewPtr = NewGlobals[Val];
760 // Form a shorter GEP if needed.
761 if (GEP->getNumOperands() > 3) {
762 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GEP)) {
763 SmallVector<Constant*, 8> Idxs;
764 Idxs.push_back(NullInt);
765 for (unsigned i = 3, e = CE->getNumOperands(); i != e; ++i)
766 Idxs.push_back(CE->getOperand(i));
767 NewPtr = ConstantExpr::getGetElementPtr(cast<Constant>(NewPtr), Idxs);
769 GetElementPtrInst *GEPI = cast<GetElementPtrInst>(GEP);
770 SmallVector<Value*, 8> Idxs;
771 Idxs.push_back(NullInt);
772 for (unsigned i = 3, e = GEPI->getNumOperands(); i != e; ++i)
773 Idxs.push_back(GEPI->getOperand(i));
774 NewPtr = GetElementPtrInst::Create(NewPtr, Idxs,
775 GEPI->getName()+"."+Twine(Val),GEPI);
778 GEP->replaceAllUsesWith(NewPtr);
780 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(GEP))
781 GEPI->eraseFromParent();
783 cast<ConstantExpr>(GEP)->destroyConstant();
786 // Delete the old global, now that it is dead.
790 // Loop over the new globals array deleting any globals that are obviously
791 // dead. This can arise due to scalarization of a structure or an array that
792 // has elements that are dead.
793 unsigned FirstGlobal = 0;
794 for (unsigned i = 0, e = NewGlobals.size(); i != e; ++i)
795 if (NewGlobals[i]->use_empty()) {
796 Globals.erase(NewGlobals[i]);
797 if (FirstGlobal == i) ++FirstGlobal;
800 return FirstGlobal != NewGlobals.size() ? NewGlobals[FirstGlobal] : 0;
803 /// AllUsesOfValueWillTrapIfNull - Return true if all users of the specified
804 /// value will trap if the value is dynamically null. PHIs keeps track of any
805 /// phi nodes we've seen to avoid reprocessing them.
806 static bool AllUsesOfValueWillTrapIfNull(const Value *V,
807 SmallPtrSet<const PHINode*, 8> &PHIs) {
808 for (Value::const_use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;
812 if (isa<LoadInst>(U)) {
814 } else if (const StoreInst *SI = dyn_cast<StoreInst>(U)) {
815 if (SI->getOperand(0) == V) {
816 //cerr << "NONTRAPPING USE: " << *U;
817 return false; // Storing the value.
819 } else if (const CallInst *CI = dyn_cast<CallInst>(U)) {
820 if (CI->getCalledValue() != V) {
821 //cerr << "NONTRAPPING USE: " << *U;
822 return false; // Not calling the ptr
824 } else if (const InvokeInst *II = dyn_cast<InvokeInst>(U)) {
825 if (II->getCalledValue() != V) {
826 //cerr << "NONTRAPPING USE: " << *U;
827 return false; // Not calling the ptr
829 } else if (const BitCastInst *CI = dyn_cast<BitCastInst>(U)) {
830 if (!AllUsesOfValueWillTrapIfNull(CI, PHIs)) return false;
831 } else if (const GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(U)) {
832 if (!AllUsesOfValueWillTrapIfNull(GEPI, PHIs)) return false;
833 } else if (const PHINode *PN = dyn_cast<PHINode>(U)) {
834 // If we've already seen this phi node, ignore it, it has already been
836 if (PHIs.insert(PN) && !AllUsesOfValueWillTrapIfNull(PN, PHIs))
838 } else if (isa<ICmpInst>(U) &&
839 isa<ConstantPointerNull>(UI->getOperand(1))) {
840 // Ignore icmp X, null
842 //cerr << "NONTRAPPING USE: " << *U;
849 /// AllUsesOfLoadedValueWillTrapIfNull - Return true if all uses of any loads
850 /// from GV will trap if the loaded value is null. Note that this also permits
851 /// comparisons of the loaded value against null, as a special case.
852 static bool AllUsesOfLoadedValueWillTrapIfNull(const GlobalVariable *GV) {
853 for (Value::const_use_iterator UI = GV->use_begin(), E = GV->use_end();
857 if (const LoadInst *LI = dyn_cast<LoadInst>(U)) {
858 SmallPtrSet<const PHINode*, 8> PHIs;
859 if (!AllUsesOfValueWillTrapIfNull(LI, PHIs))
861 } else if (isa<StoreInst>(U)) {
862 // Ignore stores to the global.
864 // We don't know or understand this user, bail out.
865 //cerr << "UNKNOWN USER OF GLOBAL!: " << *U;
872 static bool OptimizeAwayTrappingUsesOfValue(Value *V, Constant *NewV) {
873 bool Changed = false;
874 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ) {
875 Instruction *I = cast<Instruction>(*UI++);
876 if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
877 LI->setOperand(0, NewV);
879 } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
880 if (SI->getOperand(1) == V) {
881 SI->setOperand(1, NewV);
884 } else if (isa<CallInst>(I) || isa<InvokeInst>(I)) {
886 if (CS.getCalledValue() == V) {
887 // Calling through the pointer! Turn into a direct call, but be careful
888 // that the pointer is not also being passed as an argument.
889 CS.setCalledFunction(NewV);
891 bool PassedAsArg = false;
892 for (unsigned i = 0, e = CS.arg_size(); i != e; ++i)
893 if (CS.getArgument(i) == V) {
895 CS.setArgument(i, NewV);
899 // Being passed as an argument also. Be careful to not invalidate UI!
903 } else if (CastInst *CI = dyn_cast<CastInst>(I)) {
904 Changed |= OptimizeAwayTrappingUsesOfValue(CI,
905 ConstantExpr::getCast(CI->getOpcode(),
906 NewV, CI->getType()));
907 if (CI->use_empty()) {
909 CI->eraseFromParent();
911 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I)) {
912 // Should handle GEP here.
913 SmallVector<Constant*, 8> Idxs;
914 Idxs.reserve(GEPI->getNumOperands()-1);
915 for (User::op_iterator i = GEPI->op_begin() + 1, e = GEPI->op_end();
917 if (Constant *C = dyn_cast<Constant>(*i))
921 if (Idxs.size() == GEPI->getNumOperands()-1)
922 Changed |= OptimizeAwayTrappingUsesOfValue(GEPI,
923 ConstantExpr::getGetElementPtr(NewV, Idxs));
924 if (GEPI->use_empty()) {
926 GEPI->eraseFromParent();
935 /// OptimizeAwayTrappingUsesOfLoads - The specified global has only one non-null
936 /// value stored into it. If there are uses of the loaded value that would trap
937 /// if the loaded value is dynamically null, then we know that they cannot be
938 /// reachable with a null optimize away the load.
939 static bool OptimizeAwayTrappingUsesOfLoads(GlobalVariable *GV, Constant *LV,
941 TargetLibraryInfo *TLI) {
942 bool Changed = false;
944 // Keep track of whether we are able to remove all the uses of the global
945 // other than the store that defines it.
946 bool AllNonStoreUsesGone = true;
948 // Replace all uses of loads with uses of uses of the stored value.
949 for (Value::use_iterator GUI = GV->use_begin(), E = GV->use_end(); GUI != E;){
950 User *GlobalUser = *GUI++;
951 if (LoadInst *LI = dyn_cast<LoadInst>(GlobalUser)) {
952 Changed |= OptimizeAwayTrappingUsesOfValue(LI, LV);
953 // If we were able to delete all uses of the loads
954 if (LI->use_empty()) {
955 LI->eraseFromParent();
958 AllNonStoreUsesGone = false;
960 } else if (isa<StoreInst>(GlobalUser)) {
961 // Ignore the store that stores "LV" to the global.
962 assert(GlobalUser->getOperand(1) == GV &&
963 "Must be storing *to* the global");
965 AllNonStoreUsesGone = false;
967 // If we get here we could have other crazy uses that are transitively
969 assert((isa<PHINode>(GlobalUser) || isa<SelectInst>(GlobalUser) ||
970 isa<ConstantExpr>(GlobalUser) || isa<CmpInst>(GlobalUser) ||
971 isa<BitCastInst>(GlobalUser) ||
972 isa<GetElementPtrInst>(GlobalUser)) &&
973 "Only expect load and stores!");
978 DEBUG(dbgs() << "OPTIMIZED LOADS FROM STORED ONCE POINTER: " << *GV);
982 // If we nuked all of the loads, then none of the stores are needed either,
983 // nor is the global.
984 if (AllNonStoreUsesGone) {
985 if (isLeakCheckerRoot(GV)) {
986 Changed |= CleanupPointerRootUsers(GV, TLI);
989 CleanupConstantGlobalUsers(GV, 0, TD, TLI);
991 if (GV->use_empty()) {
992 DEBUG(dbgs() << " *** GLOBAL NOW DEAD!\n");
994 GV->eraseFromParent();
1001 /// ConstantPropUsersOf - Walk the use list of V, constant folding all of the
1002 /// instructions that are foldable.
1003 static void ConstantPropUsersOf(Value *V,
1004 DataLayout *TD, TargetLibraryInfo *TLI) {
1005 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; )
1006 if (Instruction *I = dyn_cast<Instruction>(*UI++))
1007 if (Constant *NewC = ConstantFoldInstruction(I, TD, TLI)) {
1008 I->replaceAllUsesWith(NewC);
1010 // Advance UI to the next non-I use to avoid invalidating it!
1011 // Instructions could multiply use V.
1012 while (UI != E && *UI == I)
1014 I->eraseFromParent();
1018 /// OptimizeGlobalAddressOfMalloc - This function takes the specified global
1019 /// variable, and transforms the program as if it always contained the result of
1020 /// the specified malloc. Because it is always the result of the specified
1021 /// malloc, there is no reason to actually DO the malloc. Instead, turn the
1022 /// malloc into a global, and any loads of GV as uses of the new global.
1023 static GlobalVariable *OptimizeGlobalAddressOfMalloc(GlobalVariable *GV,
1026 ConstantInt *NElements,
1028 TargetLibraryInfo *TLI) {
1029 DEBUG(errs() << "PROMOTING GLOBAL: " << *GV << " CALL = " << *CI << '\n');
1032 if (NElements->getZExtValue() == 1)
1033 GlobalType = AllocTy;
1035 // If we have an array allocation, the global variable is of an array.
1036 GlobalType = ArrayType::get(AllocTy, NElements->getZExtValue());
1038 // Create the new global variable. The contents of the malloc'd memory is
1039 // undefined, so initialize with an undef value.
1040 GlobalVariable *NewGV = new GlobalVariable(*GV->getParent(),
1042 GlobalValue::InternalLinkage,
1043 UndefValue::get(GlobalType),
1044 GV->getName()+".body",
1046 GV->getThreadLocalMode());
1048 // If there are bitcast users of the malloc (which is typical, usually we have
1049 // a malloc + bitcast) then replace them with uses of the new global. Update
1050 // other users to use the global as well.
1051 BitCastInst *TheBC = 0;
1052 while (!CI->use_empty()) {
1053 Instruction *User = cast<Instruction>(CI->use_back());
1054 if (BitCastInst *BCI = dyn_cast<BitCastInst>(User)) {
1055 if (BCI->getType() == NewGV->getType()) {
1056 BCI->replaceAllUsesWith(NewGV);
1057 BCI->eraseFromParent();
1059 BCI->setOperand(0, NewGV);
1063 TheBC = new BitCastInst(NewGV, CI->getType(), "newgv", CI);
1064 User->replaceUsesOfWith(CI, TheBC);
1068 Constant *RepValue = NewGV;
1069 if (NewGV->getType() != GV->getType()->getElementType())
1070 RepValue = ConstantExpr::getBitCast(RepValue,
1071 GV->getType()->getElementType());
1073 // If there is a comparison against null, we will insert a global bool to
1074 // keep track of whether the global was initialized yet or not.
1075 GlobalVariable *InitBool =
1076 new GlobalVariable(Type::getInt1Ty(GV->getContext()), false,
1077 GlobalValue::InternalLinkage,
1078 ConstantInt::getFalse(GV->getContext()),
1079 GV->getName()+".init", GV->getThreadLocalMode());
1080 bool InitBoolUsed = false;
1082 // Loop over all uses of GV, processing them in turn.
1083 while (!GV->use_empty()) {
1084 if (StoreInst *SI = dyn_cast<StoreInst>(GV->use_back())) {
1085 // The global is initialized when the store to it occurs.
1086 new StoreInst(ConstantInt::getTrue(GV->getContext()), InitBool, false, 0,
1087 SI->getOrdering(), SI->getSynchScope(), SI);
1088 SI->eraseFromParent();
1092 LoadInst *LI = cast<LoadInst>(GV->use_back());
1093 while (!LI->use_empty()) {
1094 Use &LoadUse = LI->use_begin().getUse();
1095 if (!isa<ICmpInst>(LoadUse.getUser())) {
1100 ICmpInst *ICI = cast<ICmpInst>(LoadUse.getUser());
1101 // Replace the cmp X, 0 with a use of the bool value.
1102 // Sink the load to where the compare was, if atomic rules allow us to.
1103 Value *LV = new LoadInst(InitBool, InitBool->getName()+".val", false, 0,
1104 LI->getOrdering(), LI->getSynchScope(),
1105 LI->isUnordered() ? (Instruction*)ICI : LI);
1106 InitBoolUsed = true;
1107 switch (ICI->getPredicate()) {
1108 default: llvm_unreachable("Unknown ICmp Predicate!");
1109 case ICmpInst::ICMP_ULT:
1110 case ICmpInst::ICMP_SLT: // X < null -> always false
1111 LV = ConstantInt::getFalse(GV->getContext());
1113 case ICmpInst::ICMP_ULE:
1114 case ICmpInst::ICMP_SLE:
1115 case ICmpInst::ICMP_EQ:
1116 LV = BinaryOperator::CreateNot(LV, "notinit", ICI);
1118 case ICmpInst::ICMP_NE:
1119 case ICmpInst::ICMP_UGE:
1120 case ICmpInst::ICMP_SGE:
1121 case ICmpInst::ICMP_UGT:
1122 case ICmpInst::ICMP_SGT:
1123 break; // no change.
1125 ICI->replaceAllUsesWith(LV);
1126 ICI->eraseFromParent();
1128 LI->eraseFromParent();
1131 // If the initialization boolean was used, insert it, otherwise delete it.
1132 if (!InitBoolUsed) {
1133 while (!InitBool->use_empty()) // Delete initializations
1134 cast<StoreInst>(InitBool->use_back())->eraseFromParent();
1137 GV->getParent()->getGlobalList().insert(GV, InitBool);
1139 // Now the GV is dead, nuke it and the malloc..
1140 GV->eraseFromParent();
1141 CI->eraseFromParent();
1143 // To further other optimizations, loop over all users of NewGV and try to
1144 // constant prop them. This will promote GEP instructions with constant
1145 // indices into GEP constant-exprs, which will allow global-opt to hack on it.
1146 ConstantPropUsersOf(NewGV, TD, TLI);
1147 if (RepValue != NewGV)
1148 ConstantPropUsersOf(RepValue, TD, TLI);
1153 /// ValueIsOnlyUsedLocallyOrStoredToOneGlobal - Scan the use-list of V checking
1154 /// to make sure that there are no complex uses of V. We permit simple things
1155 /// like dereferencing the pointer, but not storing through the address, unless
1156 /// it is to the specified global.
1157 static bool ValueIsOnlyUsedLocallyOrStoredToOneGlobal(const Instruction *V,
1158 const GlobalVariable *GV,
1159 SmallPtrSet<const PHINode*, 8> &PHIs) {
1160 for (Value::const_use_iterator UI = V->use_begin(), E = V->use_end();
1162 const Instruction *Inst = cast<Instruction>(*UI);
1164 if (isa<LoadInst>(Inst) || isa<CmpInst>(Inst)) {
1165 continue; // Fine, ignore.
1168 if (const StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
1169 if (SI->getOperand(0) == V && SI->getOperand(1) != GV)
1170 return false; // Storing the pointer itself... bad.
1171 continue; // Otherwise, storing through it, or storing into GV... fine.
1174 // Must index into the array and into the struct.
1175 if (isa<GetElementPtrInst>(Inst) && Inst->getNumOperands() >= 3) {
1176 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(Inst, GV, PHIs))
1181 if (const PHINode *PN = dyn_cast<PHINode>(Inst)) {
1182 // PHIs are ok if all uses are ok. Don't infinitely recurse through PHI
1184 if (PHIs.insert(PN))
1185 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(PN, GV, PHIs))
1190 if (const BitCastInst *BCI = dyn_cast<BitCastInst>(Inst)) {
1191 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(BCI, GV, PHIs))
1201 /// ReplaceUsesOfMallocWithGlobal - The Alloc pointer is stored into GV
1202 /// somewhere. Transform all uses of the allocation into loads from the
1203 /// global and uses of the resultant pointer. Further, delete the store into
1204 /// GV. This assumes that these value pass the
1205 /// 'ValueIsOnlyUsedLocallyOrStoredToOneGlobal' predicate.
1206 static void ReplaceUsesOfMallocWithGlobal(Instruction *Alloc,
1207 GlobalVariable *GV) {
1208 while (!Alloc->use_empty()) {
1209 Instruction *U = cast<Instruction>(*Alloc->use_begin());
1210 Instruction *InsertPt = U;
1211 if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
1212 // If this is the store of the allocation into the global, remove it.
1213 if (SI->getOperand(1) == GV) {
1214 SI->eraseFromParent();
1217 } else if (PHINode *PN = dyn_cast<PHINode>(U)) {
1218 // Insert the load in the corresponding predecessor, not right before the
1220 InsertPt = PN->getIncomingBlock(Alloc->use_begin())->getTerminator();
1221 } else if (isa<BitCastInst>(U)) {
1222 // Must be bitcast between the malloc and store to initialize the global.
1223 ReplaceUsesOfMallocWithGlobal(U, GV);
1224 U->eraseFromParent();
1226 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(U)) {
1227 // If this is a "GEP bitcast" and the user is a store to the global, then
1228 // just process it as a bitcast.
1229 if (GEPI->hasAllZeroIndices() && GEPI->hasOneUse())
1230 if (StoreInst *SI = dyn_cast<StoreInst>(GEPI->use_back()))
1231 if (SI->getOperand(1) == GV) {
1232 // Must be bitcast GEP between the malloc and store to initialize
1234 ReplaceUsesOfMallocWithGlobal(GEPI, GV);
1235 GEPI->eraseFromParent();
1240 // Insert a load from the global, and use it instead of the malloc.
1241 Value *NL = new LoadInst(GV, GV->getName()+".val", InsertPt);
1242 U->replaceUsesOfWith(Alloc, NL);
1246 /// LoadUsesSimpleEnoughForHeapSRA - Verify that all uses of V (a load, or a phi
1247 /// of a load) are simple enough to perform heap SRA on. This permits GEP's
1248 /// that index through the array and struct field, icmps of null, and PHIs.
1249 static bool LoadUsesSimpleEnoughForHeapSRA(const Value *V,
1250 SmallPtrSet<const PHINode*, 32> &LoadUsingPHIs,
1251 SmallPtrSet<const PHINode*, 32> &LoadUsingPHIsPerLoad) {
1252 // We permit two users of the load: setcc comparing against the null
1253 // pointer, and a getelementptr of a specific form.
1254 for (Value::const_use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;
1256 const Instruction *User = cast<Instruction>(*UI);
1258 // Comparison against null is ok.
1259 if (const ICmpInst *ICI = dyn_cast<ICmpInst>(User)) {
1260 if (!isa<ConstantPointerNull>(ICI->getOperand(1)))
1265 // getelementptr is also ok, but only a simple form.
1266 if (const GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
1267 // Must index into the array and into the struct.
1268 if (GEPI->getNumOperands() < 3)
1271 // Otherwise the GEP is ok.
1275 if (const PHINode *PN = dyn_cast<PHINode>(User)) {
1276 if (!LoadUsingPHIsPerLoad.insert(PN))
1277 // This means some phi nodes are dependent on each other.
1278 // Avoid infinite looping!
1280 if (!LoadUsingPHIs.insert(PN))
1281 // If we have already analyzed this PHI, then it is safe.
1284 // Make sure all uses of the PHI are simple enough to transform.
1285 if (!LoadUsesSimpleEnoughForHeapSRA(PN,
1286 LoadUsingPHIs, LoadUsingPHIsPerLoad))
1292 // Otherwise we don't know what this is, not ok.
1300 /// AllGlobalLoadUsesSimpleEnoughForHeapSRA - If all users of values loaded from
1301 /// GV are simple enough to perform HeapSRA, return true.
1302 static bool AllGlobalLoadUsesSimpleEnoughForHeapSRA(const GlobalVariable *GV,
1303 Instruction *StoredVal) {
1304 SmallPtrSet<const PHINode*, 32> LoadUsingPHIs;
1305 SmallPtrSet<const PHINode*, 32> LoadUsingPHIsPerLoad;
1306 for (Value::const_use_iterator UI = GV->use_begin(), E = GV->use_end();
1308 if (const LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
1309 if (!LoadUsesSimpleEnoughForHeapSRA(LI, LoadUsingPHIs,
1310 LoadUsingPHIsPerLoad))
1312 LoadUsingPHIsPerLoad.clear();
1315 // If we reach here, we know that all uses of the loads and transitive uses
1316 // (through PHI nodes) are simple enough to transform. However, we don't know
1317 // that all inputs the to the PHI nodes are in the same equivalence sets.
1318 // Check to verify that all operands of the PHIs are either PHIS that can be
1319 // transformed, loads from GV, or MI itself.
1320 for (SmallPtrSet<const PHINode*, 32>::const_iterator I = LoadUsingPHIs.begin()
1321 , E = LoadUsingPHIs.end(); I != E; ++I) {
1322 const PHINode *PN = *I;
1323 for (unsigned op = 0, e = PN->getNumIncomingValues(); op != e; ++op) {
1324 Value *InVal = PN->getIncomingValue(op);
1326 // PHI of the stored value itself is ok.
1327 if (InVal == StoredVal) continue;
1329 if (const PHINode *InPN = dyn_cast<PHINode>(InVal)) {
1330 // One of the PHIs in our set is (optimistically) ok.
1331 if (LoadUsingPHIs.count(InPN))
1336 // Load from GV is ok.
1337 if (const LoadInst *LI = dyn_cast<LoadInst>(InVal))
1338 if (LI->getOperand(0) == GV)
1343 // Anything else is rejected.
1351 static Value *GetHeapSROAValue(Value *V, unsigned FieldNo,
1352 DenseMap<Value*, std::vector<Value*> > &InsertedScalarizedValues,
1353 std::vector<std::pair<PHINode*, unsigned> > &PHIsToRewrite) {
1354 std::vector<Value*> &FieldVals = InsertedScalarizedValues[V];
1356 if (FieldNo >= FieldVals.size())
1357 FieldVals.resize(FieldNo+1);
1359 // If we already have this value, just reuse the previously scalarized
1361 if (Value *FieldVal = FieldVals[FieldNo])
1364 // Depending on what instruction this is, we have several cases.
1366 if (LoadInst *LI = dyn_cast<LoadInst>(V)) {
1367 // This is a scalarized version of the load from the global. Just create
1368 // a new Load of the scalarized global.
1369 Result = new LoadInst(GetHeapSROAValue(LI->getOperand(0), FieldNo,
1370 InsertedScalarizedValues,
1372 LI->getName()+".f"+Twine(FieldNo), LI);
1373 } else if (PHINode *PN = dyn_cast<PHINode>(V)) {
1374 // PN's type is pointer to struct. Make a new PHI of pointer to struct
1377 cast<StructType>(cast<PointerType>(PN->getType())->getElementType());
1380 PHINode::Create(PointerType::getUnqual(ST->getElementType(FieldNo)),
1381 PN->getNumIncomingValues(),
1382 PN->getName()+".f"+Twine(FieldNo), PN);
1384 PHIsToRewrite.push_back(std::make_pair(PN, FieldNo));
1386 llvm_unreachable("Unknown usable value");
1389 return FieldVals[FieldNo] = Result;
1392 /// RewriteHeapSROALoadUser - Given a load instruction and a value derived from
1393 /// the load, rewrite the derived value to use the HeapSRoA'd load.
1394 static void RewriteHeapSROALoadUser(Instruction *LoadUser,
1395 DenseMap<Value*, std::vector<Value*> > &InsertedScalarizedValues,
1396 std::vector<std::pair<PHINode*, unsigned> > &PHIsToRewrite) {
1397 // If this is a comparison against null, handle it.
1398 if (ICmpInst *SCI = dyn_cast<ICmpInst>(LoadUser)) {
1399 assert(isa<ConstantPointerNull>(SCI->getOperand(1)));
1400 // If we have a setcc of the loaded pointer, we can use a setcc of any
1402 Value *NPtr = GetHeapSROAValue(SCI->getOperand(0), 0,
1403 InsertedScalarizedValues, PHIsToRewrite);
1405 Value *New = new ICmpInst(SCI, SCI->getPredicate(), NPtr,
1406 Constant::getNullValue(NPtr->getType()),
1408 SCI->replaceAllUsesWith(New);
1409 SCI->eraseFromParent();
1413 // Handle 'getelementptr Ptr, Idx, i32 FieldNo ...'
1414 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(LoadUser)) {
1415 assert(GEPI->getNumOperands() >= 3 && isa<ConstantInt>(GEPI->getOperand(2))
1416 && "Unexpected GEPI!");
1418 // Load the pointer for this field.
1419 unsigned FieldNo = cast<ConstantInt>(GEPI->getOperand(2))->getZExtValue();
1420 Value *NewPtr = GetHeapSROAValue(GEPI->getOperand(0), FieldNo,
1421 InsertedScalarizedValues, PHIsToRewrite);
1423 // Create the new GEP idx vector.
1424 SmallVector<Value*, 8> GEPIdx;
1425 GEPIdx.push_back(GEPI->getOperand(1));
1426 GEPIdx.append(GEPI->op_begin()+3, GEPI->op_end());
1428 Value *NGEPI = GetElementPtrInst::Create(NewPtr, GEPIdx,
1429 GEPI->getName(), GEPI);
1430 GEPI->replaceAllUsesWith(NGEPI);
1431 GEPI->eraseFromParent();
1435 // Recursively transform the users of PHI nodes. This will lazily create the
1436 // PHIs that are needed for individual elements. Keep track of what PHIs we
1437 // see in InsertedScalarizedValues so that we don't get infinite loops (very
1438 // antisocial). If the PHI is already in InsertedScalarizedValues, it has
1439 // already been seen first by another load, so its uses have already been
1441 PHINode *PN = cast<PHINode>(LoadUser);
1442 if (!InsertedScalarizedValues.insert(std::make_pair(PN,
1443 std::vector<Value*>())).second)
1446 // If this is the first time we've seen this PHI, recursively process all
1448 for (Value::use_iterator UI = PN->use_begin(), E = PN->use_end(); UI != E; ) {
1449 Instruction *User = cast<Instruction>(*UI++);
1450 RewriteHeapSROALoadUser(User, InsertedScalarizedValues, PHIsToRewrite);
1454 /// RewriteUsesOfLoadForHeapSRoA - We are performing Heap SRoA on a global. Ptr
1455 /// is a value loaded from the global. Eliminate all uses of Ptr, making them
1456 /// use FieldGlobals instead. All uses of loaded values satisfy
1457 /// AllGlobalLoadUsesSimpleEnoughForHeapSRA.
1458 static void RewriteUsesOfLoadForHeapSRoA(LoadInst *Load,
1459 DenseMap<Value*, std::vector<Value*> > &InsertedScalarizedValues,
1460 std::vector<std::pair<PHINode*, unsigned> > &PHIsToRewrite) {
1461 for (Value::use_iterator UI = Load->use_begin(), E = Load->use_end();
1463 Instruction *User = cast<Instruction>(*UI++);
1464 RewriteHeapSROALoadUser(User, InsertedScalarizedValues, PHIsToRewrite);
1467 if (Load->use_empty()) {
1468 Load->eraseFromParent();
1469 InsertedScalarizedValues.erase(Load);
1473 /// PerformHeapAllocSRoA - CI is an allocation of an array of structures. Break
1474 /// it up into multiple allocations of arrays of the fields.
1475 static GlobalVariable *PerformHeapAllocSRoA(GlobalVariable *GV, CallInst *CI,
1476 Value *NElems, DataLayout *TD,
1477 const TargetLibraryInfo *TLI) {
1478 DEBUG(dbgs() << "SROA HEAP ALLOC: " << *GV << " MALLOC = " << *CI << '\n');
1479 Type *MAT = getMallocAllocatedType(CI, TLI);
1480 StructType *STy = cast<StructType>(MAT);
1482 // There is guaranteed to be at least one use of the malloc (storing
1483 // it into GV). If there are other uses, change them to be uses of
1484 // the global to simplify later code. This also deletes the store
1486 ReplaceUsesOfMallocWithGlobal(CI, GV);
1488 // Okay, at this point, there are no users of the malloc. Insert N
1489 // new mallocs at the same place as CI, and N globals.
1490 std::vector<Value*> FieldGlobals;
1491 std::vector<Value*> FieldMallocs;
1493 for (unsigned FieldNo = 0, e = STy->getNumElements(); FieldNo != e;++FieldNo){
1494 Type *FieldTy = STy->getElementType(FieldNo);
1495 PointerType *PFieldTy = PointerType::getUnqual(FieldTy);
1497 GlobalVariable *NGV =
1498 new GlobalVariable(*GV->getParent(),
1499 PFieldTy, false, GlobalValue::InternalLinkage,
1500 Constant::getNullValue(PFieldTy),
1501 GV->getName() + ".f" + Twine(FieldNo), GV,
1502 GV->getThreadLocalMode());
1503 FieldGlobals.push_back(NGV);
1505 unsigned TypeSize = TD->getTypeAllocSize(FieldTy);
1506 if (StructType *ST = dyn_cast<StructType>(FieldTy))
1507 TypeSize = TD->getStructLayout(ST)->getSizeInBytes();
1508 Type *IntPtrTy = TD->getIntPtrType(CI->getContext());
1509 Value *NMI = CallInst::CreateMalloc(CI, IntPtrTy, FieldTy,
1510 ConstantInt::get(IntPtrTy, TypeSize),
1512 CI->getName() + ".f" + Twine(FieldNo));
1513 FieldMallocs.push_back(NMI);
1514 new StoreInst(NMI, NGV, CI);
1517 // The tricky aspect of this transformation is handling the case when malloc
1518 // fails. In the original code, malloc failing would set the result pointer
1519 // of malloc to null. In this case, some mallocs could succeed and others
1520 // could fail. As such, we emit code that looks like this:
1521 // F0 = malloc(field0)
1522 // F1 = malloc(field1)
1523 // F2 = malloc(field2)
1524 // if (F0 == 0 || F1 == 0 || F2 == 0) {
1525 // if (F0) { free(F0); F0 = 0; }
1526 // if (F1) { free(F1); F1 = 0; }
1527 // if (F2) { free(F2); F2 = 0; }
1529 // The malloc can also fail if its argument is too large.
1530 Constant *ConstantZero = ConstantInt::get(CI->getArgOperand(0)->getType(), 0);
1531 Value *RunningOr = new ICmpInst(CI, ICmpInst::ICMP_SLT, CI->getArgOperand(0),
1532 ConstantZero, "isneg");
1533 for (unsigned i = 0, e = FieldMallocs.size(); i != e; ++i) {
1534 Value *Cond = new ICmpInst(CI, ICmpInst::ICMP_EQ, FieldMallocs[i],
1535 Constant::getNullValue(FieldMallocs[i]->getType()),
1537 RunningOr = BinaryOperator::CreateOr(RunningOr, Cond, "tmp", CI);
1540 // Split the basic block at the old malloc.
1541 BasicBlock *OrigBB = CI->getParent();
1542 BasicBlock *ContBB = OrigBB->splitBasicBlock(CI, "malloc_cont");
1544 // Create the block to check the first condition. Put all these blocks at the
1545 // end of the function as they are unlikely to be executed.
1546 BasicBlock *NullPtrBlock = BasicBlock::Create(OrigBB->getContext(),
1548 OrigBB->getParent());
1550 // Remove the uncond branch from OrigBB to ContBB, turning it into a cond
1551 // branch on RunningOr.
1552 OrigBB->getTerminator()->eraseFromParent();
1553 BranchInst::Create(NullPtrBlock, ContBB, RunningOr, OrigBB);
1555 // Within the NullPtrBlock, we need to emit a comparison and branch for each
1556 // pointer, because some may be null while others are not.
1557 for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) {
1558 Value *GVVal = new LoadInst(FieldGlobals[i], "tmp", NullPtrBlock);
1559 Value *Cmp = new ICmpInst(*NullPtrBlock, ICmpInst::ICMP_NE, GVVal,
1560 Constant::getNullValue(GVVal->getType()));
1561 BasicBlock *FreeBlock = BasicBlock::Create(Cmp->getContext(), "free_it",
1562 OrigBB->getParent());
1563 BasicBlock *NextBlock = BasicBlock::Create(Cmp->getContext(), "next",
1564 OrigBB->getParent());
1565 Instruction *BI = BranchInst::Create(FreeBlock, NextBlock,
1568 // Fill in FreeBlock.
1569 CallInst::CreateFree(GVVal, BI);
1570 new StoreInst(Constant::getNullValue(GVVal->getType()), FieldGlobals[i],
1572 BranchInst::Create(NextBlock, FreeBlock);
1574 NullPtrBlock = NextBlock;
1577 BranchInst::Create(ContBB, NullPtrBlock);
1579 // CI is no longer needed, remove it.
1580 CI->eraseFromParent();
1582 /// InsertedScalarizedLoads - As we process loads, if we can't immediately
1583 /// update all uses of the load, keep track of what scalarized loads are
1584 /// inserted for a given load.
1585 DenseMap<Value*, std::vector<Value*> > InsertedScalarizedValues;
1586 InsertedScalarizedValues[GV] = FieldGlobals;
1588 std::vector<std::pair<PHINode*, unsigned> > PHIsToRewrite;
1590 // Okay, the malloc site is completely handled. All of the uses of GV are now
1591 // loads, and all uses of those loads are simple. Rewrite them to use loads
1592 // of the per-field globals instead.
1593 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); UI != E;) {
1594 Instruction *User = cast<Instruction>(*UI++);
1596 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1597 RewriteUsesOfLoadForHeapSRoA(LI, InsertedScalarizedValues, PHIsToRewrite);
1601 // Must be a store of null.
1602 StoreInst *SI = cast<StoreInst>(User);
1603 assert(isa<ConstantPointerNull>(SI->getOperand(0)) &&
1604 "Unexpected heap-sra user!");
1606 // Insert a store of null into each global.
1607 for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) {
1608 PointerType *PT = cast<PointerType>(FieldGlobals[i]->getType());
1609 Constant *Null = Constant::getNullValue(PT->getElementType());
1610 new StoreInst(Null, FieldGlobals[i], SI);
1612 // Erase the original store.
1613 SI->eraseFromParent();
1616 // While we have PHIs that are interesting to rewrite, do it.
1617 while (!PHIsToRewrite.empty()) {
1618 PHINode *PN = PHIsToRewrite.back().first;
1619 unsigned FieldNo = PHIsToRewrite.back().second;
1620 PHIsToRewrite.pop_back();
1621 PHINode *FieldPN = cast<PHINode>(InsertedScalarizedValues[PN][FieldNo]);
1622 assert(FieldPN->getNumIncomingValues() == 0 &&"Already processed this phi");
1624 // Add all the incoming values. This can materialize more phis.
1625 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
1626 Value *InVal = PN->getIncomingValue(i);
1627 InVal = GetHeapSROAValue(InVal, FieldNo, InsertedScalarizedValues,
1629 FieldPN->addIncoming(InVal, PN->getIncomingBlock(i));
1633 // Drop all inter-phi links and any loads that made it this far.
1634 for (DenseMap<Value*, std::vector<Value*> >::iterator
1635 I = InsertedScalarizedValues.begin(), E = InsertedScalarizedValues.end();
1637 if (PHINode *PN = dyn_cast<PHINode>(I->first))
1638 PN->dropAllReferences();
1639 else if (LoadInst *LI = dyn_cast<LoadInst>(I->first))
1640 LI->dropAllReferences();
1643 // Delete all the phis and loads now that inter-references are dead.
1644 for (DenseMap<Value*, std::vector<Value*> >::iterator
1645 I = InsertedScalarizedValues.begin(), E = InsertedScalarizedValues.end();
1647 if (PHINode *PN = dyn_cast<PHINode>(I->first))
1648 PN->eraseFromParent();
1649 else if (LoadInst *LI = dyn_cast<LoadInst>(I->first))
1650 LI->eraseFromParent();
1653 // The old global is now dead, remove it.
1654 GV->eraseFromParent();
1657 return cast<GlobalVariable>(FieldGlobals[0]);
1660 /// TryToOptimizeStoreOfMallocToGlobal - This function is called when we see a
1661 /// pointer global variable with a single value stored it that is a malloc or
1663 static bool TryToOptimizeStoreOfMallocToGlobal(GlobalVariable *GV,
1666 AtomicOrdering Ordering,
1667 Module::global_iterator &GVI,
1669 TargetLibraryInfo *TLI) {
1673 // If this is a malloc of an abstract type, don't touch it.
1674 if (!AllocTy->isSized())
1677 // We can't optimize this global unless all uses of it are *known* to be
1678 // of the malloc value, not of the null initializer value (consider a use
1679 // that compares the global's value against zero to see if the malloc has
1680 // been reached). To do this, we check to see if all uses of the global
1681 // would trap if the global were null: this proves that they must all
1682 // happen after the malloc.
1683 if (!AllUsesOfLoadedValueWillTrapIfNull(GV))
1686 // We can't optimize this if the malloc itself is used in a complex way,
1687 // for example, being stored into multiple globals. This allows the
1688 // malloc to be stored into the specified global, loaded icmp'd, and
1689 // GEP'd. These are all things we could transform to using the global
1691 SmallPtrSet<const PHINode*, 8> PHIs;
1692 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(CI, GV, PHIs))
1695 // If we have a global that is only initialized with a fixed size malloc,
1696 // transform the program to use global memory instead of malloc'd memory.
1697 // This eliminates dynamic allocation, avoids an indirection accessing the
1698 // data, and exposes the resultant global to further GlobalOpt.
1699 // We cannot optimize the malloc if we cannot determine malloc array size.
1700 Value *NElems = getMallocArraySize(CI, TD, TLI, true);
1704 if (ConstantInt *NElements = dyn_cast<ConstantInt>(NElems))
1705 // Restrict this transformation to only working on small allocations
1706 // (2048 bytes currently), as we don't want to introduce a 16M global or
1708 if (NElements->getZExtValue() * TD->getTypeAllocSize(AllocTy) < 2048) {
1709 GVI = OptimizeGlobalAddressOfMalloc(GV, CI, AllocTy, NElements, TD, TLI);
1713 // If the allocation is an array of structures, consider transforming this
1714 // into multiple malloc'd arrays, one for each field. This is basically
1715 // SRoA for malloc'd memory.
1717 if (Ordering != NotAtomic)
1720 // If this is an allocation of a fixed size array of structs, analyze as a
1721 // variable size array. malloc [100 x struct],1 -> malloc struct, 100
1722 if (NElems == ConstantInt::get(CI->getArgOperand(0)->getType(), 1))
1723 if (ArrayType *AT = dyn_cast<ArrayType>(AllocTy))
1724 AllocTy = AT->getElementType();
1726 StructType *AllocSTy = dyn_cast<StructType>(AllocTy);
1730 // This the structure has an unreasonable number of fields, leave it
1732 if (AllocSTy->getNumElements() <= 16 && AllocSTy->getNumElements() != 0 &&
1733 AllGlobalLoadUsesSimpleEnoughForHeapSRA(GV, CI)) {
1735 // If this is a fixed size array, transform the Malloc to be an alloc of
1736 // structs. malloc [100 x struct],1 -> malloc struct, 100
1737 if (ArrayType *AT = dyn_cast<ArrayType>(getMallocAllocatedType(CI, TLI))) {
1738 Type *IntPtrTy = TD->getIntPtrType(CI->getContext());
1739 unsigned TypeSize = TD->getStructLayout(AllocSTy)->getSizeInBytes();
1740 Value *AllocSize = ConstantInt::get(IntPtrTy, TypeSize);
1741 Value *NumElements = ConstantInt::get(IntPtrTy, AT->getNumElements());
1742 Instruction *Malloc = CallInst::CreateMalloc(CI, IntPtrTy, AllocSTy,
1743 AllocSize, NumElements,
1745 Instruction *Cast = new BitCastInst(Malloc, CI->getType(), "tmp", CI);
1746 CI->replaceAllUsesWith(Cast);
1747 CI->eraseFromParent();
1748 if (BitCastInst *BCI = dyn_cast<BitCastInst>(Malloc))
1749 CI = cast<CallInst>(BCI->getOperand(0));
1751 CI = cast<CallInst>(Malloc);
1754 GVI = PerformHeapAllocSRoA(GV, CI, getMallocArraySize(CI, TD, TLI, true),
1762 // OptimizeOnceStoredGlobal - Try to optimize globals based on the knowledge
1763 // that only one value (besides its initializer) is ever stored to the global.
1764 static bool OptimizeOnceStoredGlobal(GlobalVariable *GV, Value *StoredOnceVal,
1765 AtomicOrdering Ordering,
1766 Module::global_iterator &GVI,
1767 DataLayout *TD, TargetLibraryInfo *TLI) {
1768 // Ignore no-op GEPs and bitcasts.
1769 StoredOnceVal = StoredOnceVal->stripPointerCasts();
1771 // If we are dealing with a pointer global that is initialized to null and
1772 // only has one (non-null) value stored into it, then we can optimize any
1773 // users of the loaded value (often calls and loads) that would trap if the
1775 if (GV->getInitializer()->getType()->isPointerTy() &&
1776 GV->getInitializer()->isNullValue()) {
1777 if (Constant *SOVC = dyn_cast<Constant>(StoredOnceVal)) {
1778 if (GV->getInitializer()->getType() != SOVC->getType())
1779 SOVC = ConstantExpr::getBitCast(SOVC, GV->getInitializer()->getType());
1781 // Optimize away any trapping uses of the loaded value.
1782 if (OptimizeAwayTrappingUsesOfLoads(GV, SOVC, TD, TLI))
1784 } else if (CallInst *CI = extractMallocCall(StoredOnceVal, TLI)) {
1785 Type *MallocType = getMallocAllocatedType(CI, TLI);
1787 TryToOptimizeStoreOfMallocToGlobal(GV, CI, MallocType, Ordering, GVI,
1796 /// TryToShrinkGlobalToBoolean - At this point, we have learned that the only
1797 /// two values ever stored into GV are its initializer and OtherVal. See if we
1798 /// can shrink the global into a boolean and select between the two values
1799 /// whenever it is used. This exposes the values to other scalar optimizations.
1800 static bool TryToShrinkGlobalToBoolean(GlobalVariable *GV, Constant *OtherVal) {
1801 Type *GVElType = GV->getType()->getElementType();
1803 // If GVElType is already i1, it is already shrunk. If the type of the GV is
1804 // an FP value, pointer or vector, don't do this optimization because a select
1805 // between them is very expensive and unlikely to lead to later
1806 // simplification. In these cases, we typically end up with "cond ? v1 : v2"
1807 // where v1 and v2 both require constant pool loads, a big loss.
1808 if (GVElType == Type::getInt1Ty(GV->getContext()) ||
1809 GVElType->isFloatingPointTy() ||
1810 GVElType->isPointerTy() || GVElType->isVectorTy())
1813 // Walk the use list of the global seeing if all the uses are load or store.
1814 // If there is anything else, bail out.
1815 for (Value::use_iterator I = GV->use_begin(), E = GV->use_end(); I != E; ++I){
1817 if (!isa<LoadInst>(U) && !isa<StoreInst>(U))
1821 DEBUG(dbgs() << " *** SHRINKING TO BOOL: " << *GV);
1823 // Create the new global, initializing it to false.
1824 GlobalVariable *NewGV = new GlobalVariable(Type::getInt1Ty(GV->getContext()),
1826 GlobalValue::InternalLinkage,
1827 ConstantInt::getFalse(GV->getContext()),
1829 GV->getThreadLocalMode(),
1830 GV->getType()->getAddressSpace());
1831 GV->getParent()->getGlobalList().insert(GV, NewGV);
1833 Constant *InitVal = GV->getInitializer();
1834 assert(InitVal->getType() != Type::getInt1Ty(GV->getContext()) &&
1835 "No reason to shrink to bool!");
1837 // If initialized to zero and storing one into the global, we can use a cast
1838 // instead of a select to synthesize the desired value.
1839 bool IsOneZero = false;
1840 if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal))
1841 IsOneZero = InitVal->isNullValue() && CI->isOne();
1843 while (!GV->use_empty()) {
1844 Instruction *UI = cast<Instruction>(GV->use_back());
1845 if (StoreInst *SI = dyn_cast<StoreInst>(UI)) {
1846 // Change the store into a boolean store.
1847 bool StoringOther = SI->getOperand(0) == OtherVal;
1848 // Only do this if we weren't storing a loaded value.
1850 if (StoringOther || SI->getOperand(0) == InitVal) {
1851 StoreVal = ConstantInt::get(Type::getInt1Ty(GV->getContext()),
1854 // Otherwise, we are storing a previously loaded copy. To do this,
1855 // change the copy from copying the original value to just copying the
1857 Instruction *StoredVal = cast<Instruction>(SI->getOperand(0));
1859 // If we've already replaced the input, StoredVal will be a cast or
1860 // select instruction. If not, it will be a load of the original
1862 if (LoadInst *LI = dyn_cast<LoadInst>(StoredVal)) {
1863 assert(LI->getOperand(0) == GV && "Not a copy!");
1864 // Insert a new load, to preserve the saved value.
1865 StoreVal = new LoadInst(NewGV, LI->getName()+".b", false, 0,
1866 LI->getOrdering(), LI->getSynchScope(), LI);
1868 assert((isa<CastInst>(StoredVal) || isa<SelectInst>(StoredVal)) &&
1869 "This is not a form that we understand!");
1870 StoreVal = StoredVal->getOperand(0);
1871 assert(isa<LoadInst>(StoreVal) && "Not a load of NewGV!");
1874 new StoreInst(StoreVal, NewGV, false, 0,
1875 SI->getOrdering(), SI->getSynchScope(), SI);
1877 // Change the load into a load of bool then a select.
1878 LoadInst *LI = cast<LoadInst>(UI);
1879 LoadInst *NLI = new LoadInst(NewGV, LI->getName()+".b", false, 0,
1880 LI->getOrdering(), LI->getSynchScope(), LI);
1883 NSI = new ZExtInst(NLI, LI->getType(), "", LI);
1885 NSI = SelectInst::Create(NLI, OtherVal, InitVal, "", LI);
1887 LI->replaceAllUsesWith(NSI);
1889 UI->eraseFromParent();
1892 // Retain the name of the old global variable. People who are debugging their
1893 // programs may expect these variables to be named the same.
1894 NewGV->takeName(GV);
1895 GV->eraseFromParent();
1900 /// ProcessGlobal - Analyze the specified global variable and optimize it if
1901 /// possible. If we make a change, return true.
1902 bool GlobalOpt::ProcessGlobal(GlobalVariable *GV,
1903 Module::global_iterator &GVI) {
1904 if (!GV->isDiscardableIfUnused())
1907 // Do more involved optimizations if the global is internal.
1908 GV->removeDeadConstantUsers();
1910 if (GV->use_empty()) {
1911 DEBUG(dbgs() << "GLOBAL DEAD: " << *GV);
1912 GV->eraseFromParent();
1917 if (!GV->hasLocalLinkage())
1920 SmallPtrSet<const PHINode*, 16> PHIUsers;
1923 if (AnalyzeGlobal(GV, GS, PHIUsers))
1926 if (!GS.isCompared && !GV->hasUnnamedAddr()) {
1927 GV->setUnnamedAddr(true);
1931 if (GV->isConstant() || !GV->hasInitializer())
1934 return ProcessInternalGlobal(GV, GVI, PHIUsers, GS);
1937 /// ProcessInternalGlobal - Analyze the specified global variable and optimize
1938 /// it if possible. If we make a change, return true.
1939 bool GlobalOpt::ProcessInternalGlobal(GlobalVariable *GV,
1940 Module::global_iterator &GVI,
1941 const SmallPtrSet<const PHINode*, 16> &PHIUsers,
1942 const GlobalStatus &GS) {
1943 // If this is a first class global and has only one accessing function
1944 // and this function is main (which we know is not recursive), we replace
1945 // the global with a local alloca in this function.
1947 // NOTE: It doesn't make sense to promote non single-value types since we
1948 // are just replacing static memory to stack memory.
1950 // If the global is in different address space, don't bring it to stack.
1951 if (!GS.HasMultipleAccessingFunctions &&
1952 GS.AccessingFunction && !GS.HasNonInstructionUser &&
1953 GV->getType()->getElementType()->isSingleValueType() &&
1954 GS.AccessingFunction->getName() == "main" &&
1955 GS.AccessingFunction->hasExternalLinkage() &&
1956 GV->getType()->getAddressSpace() == 0) {
1957 DEBUG(dbgs() << "LOCALIZING GLOBAL: " << *GV);
1958 Instruction &FirstI = const_cast<Instruction&>(*GS.AccessingFunction
1959 ->getEntryBlock().begin());
1960 Type *ElemTy = GV->getType()->getElementType();
1961 // FIXME: Pass Global's alignment when globals have alignment
1962 AllocaInst *Alloca = new AllocaInst(ElemTy, NULL, GV->getName(), &FirstI);
1963 if (!isa<UndefValue>(GV->getInitializer()))
1964 new StoreInst(GV->getInitializer(), Alloca, &FirstI);
1966 GV->replaceAllUsesWith(Alloca);
1967 GV->eraseFromParent();
1972 // If the global is never loaded (but may be stored to), it is dead.
1975 DEBUG(dbgs() << "GLOBAL NEVER LOADED: " << *GV);
1978 if (isLeakCheckerRoot(GV)) {
1979 // Delete any constant stores to the global.
1980 Changed = CleanupPointerRootUsers(GV, TLI);
1982 // Delete any stores we can find to the global. We may not be able to
1983 // make it completely dead though.
1984 Changed = CleanupConstantGlobalUsers(GV, GV->getInitializer(), TD, TLI);
1987 // If the global is dead now, delete it.
1988 if (GV->use_empty()) {
1989 GV->eraseFromParent();
1995 } else if (GS.StoredType <= GlobalStatus::isInitializerStored) {
1996 DEBUG(dbgs() << "MARKING CONSTANT: " << *GV << "\n");
1997 GV->setConstant(true);
1999 // Clean up any obviously simplifiable users now.
2000 CleanupConstantGlobalUsers(GV, GV->getInitializer(), TD, TLI);
2002 // If the global is dead now, just nuke it.
2003 if (GV->use_empty()) {
2004 DEBUG(dbgs() << " *** Marking constant allowed us to simplify "
2005 << "all users and delete global!\n");
2006 GV->eraseFromParent();
2012 } else if (!GV->getInitializer()->getType()->isSingleValueType()) {
2013 if (DataLayout *TD = getAnalysisIfAvailable<DataLayout>())
2014 if (GlobalVariable *FirstNewGV = SRAGlobal(GV, *TD)) {
2015 GVI = FirstNewGV; // Don't skip the newly produced globals!
2018 } else if (GS.StoredType == GlobalStatus::isStoredOnce) {
2019 // If the initial value for the global was an undef value, and if only
2020 // one other value was stored into it, we can just change the
2021 // initializer to be the stored value, then delete all stores to the
2022 // global. This allows us to mark it constant.
2023 if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue))
2024 if (isa<UndefValue>(GV->getInitializer())) {
2025 // Change the initial value here.
2026 GV->setInitializer(SOVConstant);
2028 // Clean up any obviously simplifiable users now.
2029 CleanupConstantGlobalUsers(GV, GV->getInitializer(), TD, TLI);
2031 if (GV->use_empty()) {
2032 DEBUG(dbgs() << " *** Substituting initializer allowed us to "
2033 << "simplify all users and delete global!\n");
2034 GV->eraseFromParent();
2043 // Try to optimize globals based on the knowledge that only one value
2044 // (besides its initializer) is ever stored to the global.
2045 if (OptimizeOnceStoredGlobal(GV, GS.StoredOnceValue, GS.Ordering, GVI,
2049 // Otherwise, if the global was not a boolean, we can shrink it to be a
2051 if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue))
2052 if (TryToShrinkGlobalToBoolean(GV, SOVConstant)) {
2061 /// ChangeCalleesToFastCall - Walk all of the direct calls of the specified
2062 /// function, changing them to FastCC.
2063 static void ChangeCalleesToFastCall(Function *F) {
2064 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){
2065 if (isa<BlockAddress>(*UI))
2067 CallSite User(cast<Instruction>(*UI));
2068 User.setCallingConv(CallingConv::Fast);
2072 static AttributeSet StripNest(LLVMContext &C, const AttributeSet &Attrs) {
2073 for (unsigned i = 0, e = Attrs.getNumSlots(); i != e; ++i) {
2074 unsigned Index = Attrs.getSlotIndex(i);
2075 if (!Attrs.getSlotAttributes(i).hasAttribute(Index, Attribute::Nest))
2078 // There can be only one.
2079 return Attrs.removeAttribute(C, Index, Attribute::Nest);
2085 static void RemoveNestAttribute(Function *F) {
2086 F->setAttributes(StripNest(F->getContext(), F->getAttributes()));
2087 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){
2088 if (isa<BlockAddress>(*UI))
2090 CallSite User(cast<Instruction>(*UI));
2091 User.setAttributes(StripNest(F->getContext(), User.getAttributes()));
2095 bool GlobalOpt::OptimizeFunctions(Module &M) {
2096 bool Changed = false;
2097 // Optimize functions.
2098 for (Module::iterator FI = M.begin(), E = M.end(); FI != E; ) {
2100 // Functions without names cannot be referenced outside this module.
2101 if (!F->hasName() && !F->isDeclaration())
2102 F->setLinkage(GlobalValue::InternalLinkage);
2103 F->removeDeadConstantUsers();
2104 if (F->isDefTriviallyDead()) {
2105 F->eraseFromParent();
2108 } else if (F->hasLocalLinkage()) {
2109 if (F->getCallingConv() == CallingConv::C && !F->isVarArg() &&
2110 !F->hasAddressTaken()) {
2111 // If this function has C calling conventions, is not a varargs
2112 // function, and is only called directly, promote it to use the Fast
2113 // calling convention.
2114 F->setCallingConv(CallingConv::Fast);
2115 ChangeCalleesToFastCall(F);
2120 if (F->getAttributes().hasAttrSomewhere(Attribute::Nest) &&
2121 !F->hasAddressTaken()) {
2122 // The function is not used by a trampoline intrinsic, so it is safe
2123 // to remove the 'nest' attribute.
2124 RemoveNestAttribute(F);
2133 bool GlobalOpt::OptimizeGlobalVars(Module &M) {
2134 bool Changed = false;
2135 for (Module::global_iterator GVI = M.global_begin(), E = M.global_end();
2137 GlobalVariable *GV = GVI++;
2138 // Global variables without names cannot be referenced outside this module.
2139 if (!GV->hasName() && !GV->isDeclaration())
2140 GV->setLinkage(GlobalValue::InternalLinkage);
2141 // Simplify the initializer.
2142 if (GV->hasInitializer())
2143 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GV->getInitializer())) {
2144 Constant *New = ConstantFoldConstantExpression(CE, TD, TLI);
2145 if (New && New != CE)
2146 GV->setInitializer(New);
2149 Changed |= ProcessGlobal(GV, GVI);
2154 /// FindGlobalCtors - Find the llvm.global_ctors list, verifying that all
2155 /// initializers have an init priority of 65535.
2156 GlobalVariable *GlobalOpt::FindGlobalCtors(Module &M) {
2157 GlobalVariable *GV = M.getGlobalVariable("llvm.global_ctors");
2158 if (GV == 0) return 0;
2160 // Verify that the initializer is simple enough for us to handle. We are
2161 // only allowed to optimize the initializer if it is unique.
2162 if (!GV->hasUniqueInitializer()) return 0;
2164 if (isa<ConstantAggregateZero>(GV->getInitializer()))
2166 ConstantArray *CA = cast<ConstantArray>(GV->getInitializer());
2168 for (User::op_iterator i = CA->op_begin(), e = CA->op_end(); i != e; ++i) {
2169 if (isa<ConstantAggregateZero>(*i))
2171 ConstantStruct *CS = cast<ConstantStruct>(*i);
2172 if (isa<ConstantPointerNull>(CS->getOperand(1)))
2175 // Must have a function or null ptr.
2176 if (!isa<Function>(CS->getOperand(1)))
2179 // Init priority must be standard.
2180 ConstantInt *CI = cast<ConstantInt>(CS->getOperand(0));
2181 if (CI->getZExtValue() != 65535)
2188 /// ParseGlobalCtors - Given a llvm.global_ctors list that we can understand,
2189 /// return a list of the functions and null terminator as a vector.
2190 static std::vector<Function*> ParseGlobalCtors(GlobalVariable *GV) {
2191 if (GV->getInitializer()->isNullValue())
2192 return std::vector<Function*>();
2193 ConstantArray *CA = cast<ConstantArray>(GV->getInitializer());
2194 std::vector<Function*> Result;
2195 Result.reserve(CA->getNumOperands());
2196 for (User::op_iterator i = CA->op_begin(), e = CA->op_end(); i != e; ++i) {
2197 ConstantStruct *CS = cast<ConstantStruct>(*i);
2198 Result.push_back(dyn_cast<Function>(CS->getOperand(1)));
2203 /// InstallGlobalCtors - Given a specified llvm.global_ctors list, install the
2204 /// specified array, returning the new global to use.
2205 static GlobalVariable *InstallGlobalCtors(GlobalVariable *GCL,
2206 const std::vector<Function*> &Ctors) {
2207 // If we made a change, reassemble the initializer list.
2208 Constant *CSVals[2];
2209 CSVals[0] = ConstantInt::get(Type::getInt32Ty(GCL->getContext()), 65535);
2212 StructType *StructTy =
2214 cast<ArrayType>(GCL->getType()->getElementType())->getElementType());
2216 // Create the new init list.
2217 std::vector<Constant*> CAList;
2218 for (unsigned i = 0, e = Ctors.size(); i != e; ++i) {
2220 CSVals[1] = Ctors[i];
2222 Type *FTy = FunctionType::get(Type::getVoidTy(GCL->getContext()),
2224 PointerType *PFTy = PointerType::getUnqual(FTy);
2225 CSVals[1] = Constant::getNullValue(PFTy);
2226 CSVals[0] = ConstantInt::get(Type::getInt32Ty(GCL->getContext()),
2229 CAList.push_back(ConstantStruct::get(StructTy, CSVals));
2232 // Create the array initializer.
2233 Constant *CA = ConstantArray::get(ArrayType::get(StructTy,
2234 CAList.size()), CAList);
2236 // If we didn't change the number of elements, don't create a new GV.
2237 if (CA->getType() == GCL->getInitializer()->getType()) {
2238 GCL->setInitializer(CA);
2242 // Create the new global and insert it next to the existing list.
2243 GlobalVariable *NGV = new GlobalVariable(CA->getType(), GCL->isConstant(),
2244 GCL->getLinkage(), CA, "",
2245 GCL->getThreadLocalMode());
2246 GCL->getParent()->getGlobalList().insert(GCL, NGV);
2249 // Nuke the old list, replacing any uses with the new one.
2250 if (!GCL->use_empty()) {
2252 if (V->getType() != GCL->getType())
2253 V = ConstantExpr::getBitCast(V, GCL->getType());
2254 GCL->replaceAllUsesWith(V);
2256 GCL->eraseFromParent();
2266 isSimpleEnoughValueToCommit(Constant *C,
2267 SmallPtrSet<Constant*, 8> &SimpleConstants,
2268 const DataLayout *TD);
2271 /// isSimpleEnoughValueToCommit - Return true if the specified constant can be
2272 /// handled by the code generator. We don't want to generate something like:
2273 /// void *X = &X/42;
2274 /// because the code generator doesn't have a relocation that can handle that.
2276 /// This function should be called if C was not found (but just got inserted)
2277 /// in SimpleConstants to avoid having to rescan the same constants all the
2279 static bool isSimpleEnoughValueToCommitHelper(Constant *C,
2280 SmallPtrSet<Constant*, 8> &SimpleConstants,
2281 const DataLayout *TD) {
2282 // Simple integer, undef, constant aggregate zero, global addresses, etc are
2284 if (C->getNumOperands() == 0 || isa<BlockAddress>(C) ||
2285 isa<GlobalValue>(C))
2288 // Aggregate values are safe if all their elements are.
2289 if (isa<ConstantArray>(C) || isa<ConstantStruct>(C) ||
2290 isa<ConstantVector>(C)) {
2291 for (unsigned i = 0, e = C->getNumOperands(); i != e; ++i) {
2292 Constant *Op = cast<Constant>(C->getOperand(i));
2293 if (!isSimpleEnoughValueToCommit(Op, SimpleConstants, TD))
2299 // We don't know exactly what relocations are allowed in constant expressions,
2300 // so we allow &global+constantoffset, which is safe and uniformly supported
2302 ConstantExpr *CE = cast<ConstantExpr>(C);
2303 switch (CE->getOpcode()) {
2304 case Instruction::BitCast:
2305 // Bitcast is fine if the casted value is fine.
2306 return isSimpleEnoughValueToCommit(CE->getOperand(0), SimpleConstants, TD);
2308 case Instruction::IntToPtr:
2309 case Instruction::PtrToInt:
2310 // int <=> ptr is fine if the int type is the same size as the
2312 if (!TD || TD->getTypeSizeInBits(CE->getType()) !=
2313 TD->getTypeSizeInBits(CE->getOperand(0)->getType()))
2315 return isSimpleEnoughValueToCommit(CE->getOperand(0), SimpleConstants, TD);
2317 // GEP is fine if it is simple + constant offset.
2318 case Instruction::GetElementPtr:
2319 for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i)
2320 if (!isa<ConstantInt>(CE->getOperand(i)))
2322 return isSimpleEnoughValueToCommit(CE->getOperand(0), SimpleConstants, TD);
2324 case Instruction::Add:
2325 // We allow simple+cst.
2326 if (!isa<ConstantInt>(CE->getOperand(1)))
2328 return isSimpleEnoughValueToCommit(CE->getOperand(0), SimpleConstants, TD);
2334 isSimpleEnoughValueToCommit(Constant *C,
2335 SmallPtrSet<Constant*, 8> &SimpleConstants,
2336 const DataLayout *TD) {
2337 // If we already checked this constant, we win.
2338 if (!SimpleConstants.insert(C)) return true;
2339 // Check the constant.
2340 return isSimpleEnoughValueToCommitHelper(C, SimpleConstants, TD);
2344 /// isSimpleEnoughPointerToCommit - Return true if this constant is simple
2345 /// enough for us to understand. In particular, if it is a cast to anything
2346 /// other than from one pointer type to another pointer type, we punt.
2347 /// We basically just support direct accesses to globals and GEP's of
2348 /// globals. This should be kept up to date with CommitValueTo.
2349 static bool isSimpleEnoughPointerToCommit(Constant *C) {
2350 // Conservatively, avoid aggregate types. This is because we don't
2351 // want to worry about them partially overlapping other stores.
2352 if (!cast<PointerType>(C->getType())->getElementType()->isSingleValueType())
2355 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C))
2356 // Do not allow weak/*_odr/linkonce/dllimport/dllexport linkage or
2357 // external globals.
2358 return GV->hasUniqueInitializer();
2360 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) {
2361 // Handle a constantexpr gep.
2362 if (CE->getOpcode() == Instruction::GetElementPtr &&
2363 isa<GlobalVariable>(CE->getOperand(0)) &&
2364 cast<GEPOperator>(CE)->isInBounds()) {
2365 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
2366 // Do not allow weak/*_odr/linkonce/dllimport/dllexport linkage or
2367 // external globals.
2368 if (!GV->hasUniqueInitializer())
2371 // The first index must be zero.
2372 ConstantInt *CI = dyn_cast<ConstantInt>(*llvm::next(CE->op_begin()));
2373 if (!CI || !CI->isZero()) return false;
2375 // The remaining indices must be compile-time known integers within the
2376 // notional bounds of the corresponding static array types.
2377 if (!CE->isGEPWithNoNotionalOverIndexing())
2380 return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE);
2382 // A constantexpr bitcast from a pointer to another pointer is a no-op,
2383 // and we know how to evaluate it by moving the bitcast from the pointer
2384 // operand to the value operand.
2385 } else if (CE->getOpcode() == Instruction::BitCast &&
2386 isa<GlobalVariable>(CE->getOperand(0))) {
2387 // Do not allow weak/*_odr/linkonce/dllimport/dllexport linkage or
2388 // external globals.
2389 return cast<GlobalVariable>(CE->getOperand(0))->hasUniqueInitializer();
2396 /// EvaluateStoreInto - Evaluate a piece of a constantexpr store into a global
2397 /// initializer. This returns 'Init' modified to reflect 'Val' stored into it.
2398 /// At this point, the GEP operands of Addr [0, OpNo) have been stepped into.
2399 static Constant *EvaluateStoreInto(Constant *Init, Constant *Val,
2400 ConstantExpr *Addr, unsigned OpNo) {
2401 // Base case of the recursion.
2402 if (OpNo == Addr->getNumOperands()) {
2403 assert(Val->getType() == Init->getType() && "Type mismatch!");
2407 SmallVector<Constant*, 32> Elts;
2408 if (StructType *STy = dyn_cast<StructType>(Init->getType())) {
2409 // Break up the constant into its elements.
2410 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
2411 Elts.push_back(Init->getAggregateElement(i));
2413 // Replace the element that we are supposed to.
2414 ConstantInt *CU = cast<ConstantInt>(Addr->getOperand(OpNo));
2415 unsigned Idx = CU->getZExtValue();
2416 assert(Idx < STy->getNumElements() && "Struct index out of range!");
2417 Elts[Idx] = EvaluateStoreInto(Elts[Idx], Val, Addr, OpNo+1);
2419 // Return the modified struct.
2420 return ConstantStruct::get(STy, Elts);
2423 ConstantInt *CI = cast<ConstantInt>(Addr->getOperand(OpNo));
2424 SequentialType *InitTy = cast<SequentialType>(Init->getType());
2427 if (ArrayType *ATy = dyn_cast<ArrayType>(InitTy))
2428 NumElts = ATy->getNumElements();
2430 NumElts = InitTy->getVectorNumElements();
2432 // Break up the array into elements.
2433 for (uint64_t i = 0, e = NumElts; i != e; ++i)
2434 Elts.push_back(Init->getAggregateElement(i));
2436 assert(CI->getZExtValue() < NumElts);
2437 Elts[CI->getZExtValue()] =
2438 EvaluateStoreInto(Elts[CI->getZExtValue()], Val, Addr, OpNo+1);
2440 if (Init->getType()->isArrayTy())
2441 return ConstantArray::get(cast<ArrayType>(InitTy), Elts);
2442 return ConstantVector::get(Elts);
2445 /// CommitValueTo - We have decided that Addr (which satisfies the predicate
2446 /// isSimpleEnoughPointerToCommit) should get Val as its value. Make it happen.
2447 static void CommitValueTo(Constant *Val, Constant *Addr) {
2448 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Addr)) {
2449 assert(GV->hasInitializer());
2450 GV->setInitializer(Val);
2454 ConstantExpr *CE = cast<ConstantExpr>(Addr);
2455 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
2456 GV->setInitializer(EvaluateStoreInto(GV->getInitializer(), Val, CE, 2));
2461 /// Evaluator - This class evaluates LLVM IR, producing the Constant
2462 /// representing each SSA instruction. Changes to global variables are stored
2463 /// in a mapping that can be iterated over after the evaluation is complete.
2464 /// Once an evaluation call fails, the evaluation object should not be reused.
2467 Evaluator(const DataLayout *TD, const TargetLibraryInfo *TLI)
2468 : TD(TD), TLI(TLI) {
2469 ValueStack.push_back(new DenseMap<Value*, Constant*>);
2473 DeleteContainerPointers(ValueStack);
2474 while (!AllocaTmps.empty()) {
2475 GlobalVariable *Tmp = AllocaTmps.back();
2476 AllocaTmps.pop_back();
2478 // If there are still users of the alloca, the program is doing something
2479 // silly, e.g. storing the address of the alloca somewhere and using it
2480 // later. Since this is undefined, we'll just make it be null.
2481 if (!Tmp->use_empty())
2482 Tmp->replaceAllUsesWith(Constant::getNullValue(Tmp->getType()));
2487 /// EvaluateFunction - Evaluate a call to function F, returning true if
2488 /// successful, false if we can't evaluate it. ActualArgs contains the formal
2489 /// arguments for the function.
2490 bool EvaluateFunction(Function *F, Constant *&RetVal,
2491 const SmallVectorImpl<Constant*> &ActualArgs);
2493 /// EvaluateBlock - Evaluate all instructions in block BB, returning true if
2494 /// successful, false if we can't evaluate it. NewBB returns the next BB that
2495 /// control flows into, or null upon return.
2496 bool EvaluateBlock(BasicBlock::iterator CurInst, BasicBlock *&NextBB);
2498 Constant *getVal(Value *V) {
2499 if (Constant *CV = dyn_cast<Constant>(V)) return CV;
2500 Constant *R = ValueStack.back()->lookup(V);
2501 assert(R && "Reference to an uncomputed value!");
2505 void setVal(Value *V, Constant *C) {
2506 ValueStack.back()->operator[](V) = C;
2509 const DenseMap<Constant*, Constant*> &getMutatedMemory() const {
2510 return MutatedMemory;
2513 const SmallPtrSet<GlobalVariable*, 8> &getInvariants() const {
2518 Constant *ComputeLoadResult(Constant *P);
2520 /// ValueStack - As we compute SSA register values, we store their contents
2521 /// here. The back of the vector contains the current function and the stack
2522 /// contains the values in the calling frames.
2523 SmallVector<DenseMap<Value*, Constant*>*, 4> ValueStack;
2525 /// CallStack - This is used to detect recursion. In pathological situations
2526 /// we could hit exponential behavior, but at least there is nothing
2528 SmallVector<Function*, 4> CallStack;
2530 /// MutatedMemory - For each store we execute, we update this map. Loads
2531 /// check this to get the most up-to-date value. If evaluation is successful,
2532 /// this state is committed to the process.
2533 DenseMap<Constant*, Constant*> MutatedMemory;
2535 /// AllocaTmps - To 'execute' an alloca, we create a temporary global variable
2536 /// to represent its body. This vector is needed so we can delete the
2537 /// temporary globals when we are done.
2538 SmallVector<GlobalVariable*, 32> AllocaTmps;
2540 /// Invariants - These global variables have been marked invariant by the
2541 /// static constructor.
2542 SmallPtrSet<GlobalVariable*, 8> Invariants;
2544 /// SimpleConstants - These are constants we have checked and know to be
2545 /// simple enough to live in a static initializer of a global.
2546 SmallPtrSet<Constant*, 8> SimpleConstants;
2548 const DataLayout *TD;
2549 const TargetLibraryInfo *TLI;
2552 } // anonymous namespace
2554 /// ComputeLoadResult - Return the value that would be computed by a load from
2555 /// P after the stores reflected by 'memory' have been performed. If we can't
2556 /// decide, return null.
2557 Constant *Evaluator::ComputeLoadResult(Constant *P) {
2558 // If this memory location has been recently stored, use the stored value: it
2559 // is the most up-to-date.
2560 DenseMap<Constant*, Constant*>::const_iterator I = MutatedMemory.find(P);
2561 if (I != MutatedMemory.end()) return I->second;
2564 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(P)) {
2565 if (GV->hasDefinitiveInitializer())
2566 return GV->getInitializer();
2570 // Handle a constantexpr getelementptr.
2571 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(P))
2572 if (CE->getOpcode() == Instruction::GetElementPtr &&
2573 isa<GlobalVariable>(CE->getOperand(0))) {
2574 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
2575 if (GV->hasDefinitiveInitializer())
2576 return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE);
2579 return 0; // don't know how to evaluate.
2582 /// EvaluateBlock - Evaluate all instructions in block BB, returning true if
2583 /// successful, false if we can't evaluate it. NewBB returns the next BB that
2584 /// control flows into, or null upon return.
2585 bool Evaluator::EvaluateBlock(BasicBlock::iterator CurInst,
2586 BasicBlock *&NextBB) {
2587 // This is the main evaluation loop.
2589 Constant *InstResult = 0;
2591 DEBUG(dbgs() << "Evaluating Instruction: " << *CurInst << "\n");
2593 if (StoreInst *SI = dyn_cast<StoreInst>(CurInst)) {
2594 if (!SI->isSimple()) {
2595 DEBUG(dbgs() << "Store is not simple! Can not evaluate.\n");
2596 return false; // no volatile/atomic accesses.
2598 Constant *Ptr = getVal(SI->getOperand(1));
2599 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr)) {
2600 DEBUG(dbgs() << "Folding constant ptr expression: " << *Ptr);
2601 Ptr = ConstantFoldConstantExpression(CE, TD, TLI);
2602 DEBUG(dbgs() << "; To: " << *Ptr << "\n");
2604 if (!isSimpleEnoughPointerToCommit(Ptr)) {
2605 // If this is too complex for us to commit, reject it.
2606 DEBUG(dbgs() << "Pointer is too complex for us to evaluate store.");
2610 Constant *Val = getVal(SI->getOperand(0));
2612 // If this might be too difficult for the backend to handle (e.g. the addr
2613 // of one global variable divided by another) then we can't commit it.
2614 if (!isSimpleEnoughValueToCommit(Val, SimpleConstants, TD)) {
2615 DEBUG(dbgs() << "Store value is too complex to evaluate store. " << *Val
2620 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr)) {
2621 if (CE->getOpcode() == Instruction::BitCast) {
2622 DEBUG(dbgs() << "Attempting to resolve bitcast on constant ptr.\n");
2623 // If we're evaluating a store through a bitcast, then we need
2624 // to pull the bitcast off the pointer type and push it onto the
2626 Ptr = CE->getOperand(0);
2628 Type *NewTy = cast<PointerType>(Ptr->getType())->getElementType();
2630 // In order to push the bitcast onto the stored value, a bitcast
2631 // from NewTy to Val's type must be legal. If it's not, we can try
2632 // introspecting NewTy to find a legal conversion.
2633 while (!Val->getType()->canLosslesslyBitCastTo(NewTy)) {
2634 // If NewTy is a struct, we can convert the pointer to the struct
2635 // into a pointer to its first member.
2636 // FIXME: This could be extended to support arrays as well.
2637 if (StructType *STy = dyn_cast<StructType>(NewTy)) {
2638 NewTy = STy->getTypeAtIndex(0U);
2640 IntegerType *IdxTy = IntegerType::get(NewTy->getContext(), 32);
2641 Constant *IdxZero = ConstantInt::get(IdxTy, 0, false);
2642 Constant * const IdxList[] = {IdxZero, IdxZero};
2644 Ptr = ConstantExpr::getGetElementPtr(Ptr, IdxList);
2645 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr))
2646 Ptr = ConstantFoldConstantExpression(CE, TD, TLI);
2648 // If we can't improve the situation by introspecting NewTy,
2649 // we have to give up.
2651 DEBUG(dbgs() << "Failed to bitcast constant ptr, can not "
2657 // If we found compatible types, go ahead and push the bitcast
2658 // onto the stored value.
2659 Val = ConstantExpr::getBitCast(Val, NewTy);
2661 DEBUG(dbgs() << "Evaluated bitcast: " << *Val << "\n");
2665 MutatedMemory[Ptr] = Val;
2666 } else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(CurInst)) {
2667 InstResult = ConstantExpr::get(BO->getOpcode(),
2668 getVal(BO->getOperand(0)),
2669 getVal(BO->getOperand(1)));
2670 DEBUG(dbgs() << "Found a BinaryOperator! Simplifying: " << *InstResult
2672 } else if (CmpInst *CI = dyn_cast<CmpInst>(CurInst)) {
2673 InstResult = ConstantExpr::getCompare(CI->getPredicate(),
2674 getVal(CI->getOperand(0)),
2675 getVal(CI->getOperand(1)));
2676 DEBUG(dbgs() << "Found a CmpInst! Simplifying: " << *InstResult
2678 } else if (CastInst *CI = dyn_cast<CastInst>(CurInst)) {
2679 InstResult = ConstantExpr::getCast(CI->getOpcode(),
2680 getVal(CI->getOperand(0)),
2682 DEBUG(dbgs() << "Found a Cast! Simplifying: " << *InstResult
2684 } else if (SelectInst *SI = dyn_cast<SelectInst>(CurInst)) {
2685 InstResult = ConstantExpr::getSelect(getVal(SI->getOperand(0)),
2686 getVal(SI->getOperand(1)),
2687 getVal(SI->getOperand(2)));
2688 DEBUG(dbgs() << "Found a Select! Simplifying: " << *InstResult
2690 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(CurInst)) {
2691 Constant *P = getVal(GEP->getOperand(0));
2692 SmallVector<Constant*, 8> GEPOps;
2693 for (User::op_iterator i = GEP->op_begin() + 1, e = GEP->op_end();
2695 GEPOps.push_back(getVal(*i));
2697 ConstantExpr::getGetElementPtr(P, GEPOps,
2698 cast<GEPOperator>(GEP)->isInBounds());
2699 DEBUG(dbgs() << "Found a GEP! Simplifying: " << *InstResult
2701 } else if (LoadInst *LI = dyn_cast<LoadInst>(CurInst)) {
2703 if (!LI->isSimple()) {
2704 DEBUG(dbgs() << "Found a Load! Not a simple load, can not evaluate.\n");
2705 return false; // no volatile/atomic accesses.
2708 Constant *Ptr = getVal(LI->getOperand(0));
2709 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr)) {
2710 Ptr = ConstantFoldConstantExpression(CE, TD, TLI);
2711 DEBUG(dbgs() << "Found a constant pointer expression, constant "
2712 "folding: " << *Ptr << "\n");
2714 InstResult = ComputeLoadResult(Ptr);
2715 if (InstResult == 0) {
2716 DEBUG(dbgs() << "Failed to compute load result. Can not evaluate load."
2718 return false; // Could not evaluate load.
2721 DEBUG(dbgs() << "Evaluated load: " << *InstResult << "\n");
2722 } else if (AllocaInst *AI = dyn_cast<AllocaInst>(CurInst)) {
2723 if (AI->isArrayAllocation()) {
2724 DEBUG(dbgs() << "Found an array alloca. Can not evaluate.\n");
2725 return false; // Cannot handle array allocs.
2727 Type *Ty = AI->getType()->getElementType();
2728 AllocaTmps.push_back(new GlobalVariable(Ty, false,
2729 GlobalValue::InternalLinkage,
2730 UndefValue::get(Ty),
2732 InstResult = AllocaTmps.back();
2733 DEBUG(dbgs() << "Found an alloca. Result: " << *InstResult << "\n");
2734 } else if (isa<CallInst>(CurInst) || isa<InvokeInst>(CurInst)) {
2735 CallSite CS(CurInst);
2737 // Debug info can safely be ignored here.
2738 if (isa<DbgInfoIntrinsic>(CS.getInstruction())) {
2739 DEBUG(dbgs() << "Ignoring debug info.\n");
2744 // Cannot handle inline asm.
2745 if (isa<InlineAsm>(CS.getCalledValue())) {
2746 DEBUG(dbgs() << "Found inline asm, can not evaluate.\n");
2750 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(CS.getInstruction())) {
2751 if (MemSetInst *MSI = dyn_cast<MemSetInst>(II)) {
2752 if (MSI->isVolatile()) {
2753 DEBUG(dbgs() << "Can not optimize a volatile memset " <<
2757 Constant *Ptr = getVal(MSI->getDest());
2758 Constant *Val = getVal(MSI->getValue());
2759 Constant *DestVal = ComputeLoadResult(getVal(Ptr));
2760 if (Val->isNullValue() && DestVal && DestVal->isNullValue()) {
2761 // This memset is a no-op.
2762 DEBUG(dbgs() << "Ignoring no-op memset.\n");
2768 if (II->getIntrinsicID() == Intrinsic::lifetime_start ||
2769 II->getIntrinsicID() == Intrinsic::lifetime_end) {
2770 DEBUG(dbgs() << "Ignoring lifetime intrinsic.\n");
2775 if (II->getIntrinsicID() == Intrinsic::invariant_start) {
2776 // We don't insert an entry into Values, as it doesn't have a
2777 // meaningful return value.
2778 if (!II->use_empty()) {
2779 DEBUG(dbgs() << "Found unused invariant_start. Cant evaluate.\n");
2782 ConstantInt *Size = cast<ConstantInt>(II->getArgOperand(0));
2783 Value *PtrArg = getVal(II->getArgOperand(1));
2784 Value *Ptr = PtrArg->stripPointerCasts();
2785 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Ptr)) {
2786 Type *ElemTy = cast<PointerType>(GV->getType())->getElementType();
2787 if (TD && !Size->isAllOnesValue() &&
2788 Size->getValue().getLimitedValue() >=
2789 TD->getTypeStoreSize(ElemTy)) {
2790 Invariants.insert(GV);
2791 DEBUG(dbgs() << "Found a global var that is an invariant: " << *GV
2794 DEBUG(dbgs() << "Found a global var, but can not treat it as an "
2798 // Continue even if we do nothing.
2803 DEBUG(dbgs() << "Unknown intrinsic. Can not evaluate.\n");
2807 // Resolve function pointers.
2808 Function *Callee = dyn_cast<Function>(getVal(CS.getCalledValue()));
2809 if (!Callee || Callee->mayBeOverridden()) {
2810 DEBUG(dbgs() << "Can not resolve function pointer.\n");
2811 return false; // Cannot resolve.
2814 SmallVector<Constant*, 8> Formals;
2815 for (User::op_iterator i = CS.arg_begin(), e = CS.arg_end(); i != e; ++i)
2816 Formals.push_back(getVal(*i));
2818 if (Callee->isDeclaration()) {
2819 // If this is a function we can constant fold, do it.
2820 if (Constant *C = ConstantFoldCall(Callee, Formals, TLI)) {
2822 DEBUG(dbgs() << "Constant folded function call. Result: " <<
2823 *InstResult << "\n");
2825 DEBUG(dbgs() << "Can not constant fold function call.\n");
2829 if (Callee->getFunctionType()->isVarArg()) {
2830 DEBUG(dbgs() << "Can not constant fold vararg function call.\n");
2834 Constant *RetVal = 0;
2835 // Execute the call, if successful, use the return value.
2836 ValueStack.push_back(new DenseMap<Value*, Constant*>);
2837 if (!EvaluateFunction(Callee, RetVal, Formals)) {
2838 DEBUG(dbgs() << "Failed to evaluate function.\n");
2841 delete ValueStack.pop_back_val();
2842 InstResult = RetVal;
2844 if (InstResult != NULL) {
2845 DEBUG(dbgs() << "Successfully evaluated function. Result: " <<
2846 InstResult << "\n\n");
2848 DEBUG(dbgs() << "Successfully evaluated function. Result: 0\n\n");
2851 } else if (isa<TerminatorInst>(CurInst)) {
2852 DEBUG(dbgs() << "Found a terminator instruction.\n");
2854 if (BranchInst *BI = dyn_cast<BranchInst>(CurInst)) {
2855 if (BI->isUnconditional()) {
2856 NextBB = BI->getSuccessor(0);
2859 dyn_cast<ConstantInt>(getVal(BI->getCondition()));
2860 if (!Cond) return false; // Cannot determine.
2862 NextBB = BI->getSuccessor(!Cond->getZExtValue());
2864 } else if (SwitchInst *SI = dyn_cast<SwitchInst>(CurInst)) {
2866 dyn_cast<ConstantInt>(getVal(SI->getCondition()));
2867 if (!Val) return false; // Cannot determine.
2868 NextBB = SI->findCaseValue(Val).getCaseSuccessor();
2869 } else if (IndirectBrInst *IBI = dyn_cast<IndirectBrInst>(CurInst)) {
2870 Value *Val = getVal(IBI->getAddress())->stripPointerCasts();
2871 if (BlockAddress *BA = dyn_cast<BlockAddress>(Val))
2872 NextBB = BA->getBasicBlock();
2874 return false; // Cannot determine.
2875 } else if (isa<ReturnInst>(CurInst)) {
2878 // invoke, unwind, resume, unreachable.
2879 DEBUG(dbgs() << "Can not handle terminator.");
2880 return false; // Cannot handle this terminator.
2883 // We succeeded at evaluating this block!
2884 DEBUG(dbgs() << "Successfully evaluated block.\n");
2887 // Did not know how to evaluate this!
2888 DEBUG(dbgs() << "Failed to evaluate block due to unhandled instruction."
2893 if (!CurInst->use_empty()) {
2894 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(InstResult))
2895 InstResult = ConstantFoldConstantExpression(CE, TD, TLI);
2897 setVal(CurInst, InstResult);
2900 // If we just processed an invoke, we finished evaluating the block.
2901 if (InvokeInst *II = dyn_cast<InvokeInst>(CurInst)) {
2902 NextBB = II->getNormalDest();
2903 DEBUG(dbgs() << "Found an invoke instruction. Finished Block.\n\n");
2907 // Advance program counter.
2912 /// EvaluateFunction - Evaluate a call to function F, returning true if
2913 /// successful, false if we can't evaluate it. ActualArgs contains the formal
2914 /// arguments for the function.
2915 bool Evaluator::EvaluateFunction(Function *F, Constant *&RetVal,
2916 const SmallVectorImpl<Constant*> &ActualArgs) {
2917 // Check to see if this function is already executing (recursion). If so,
2918 // bail out. TODO: we might want to accept limited recursion.
2919 if (std::find(CallStack.begin(), CallStack.end(), F) != CallStack.end())
2922 CallStack.push_back(F);
2924 // Initialize arguments to the incoming values specified.
2926 for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end(); AI != E;
2928 setVal(AI, ActualArgs[ArgNo]);
2930 // ExecutedBlocks - We only handle non-looping, non-recursive code. As such,
2931 // we can only evaluate any one basic block at most once. This set keeps
2932 // track of what we have executed so we can detect recursive cases etc.
2933 SmallPtrSet<BasicBlock*, 32> ExecutedBlocks;
2935 // CurBB - The current basic block we're evaluating.
2936 BasicBlock *CurBB = F->begin();
2938 BasicBlock::iterator CurInst = CurBB->begin();
2941 BasicBlock *NextBB = 0; // Initialized to avoid compiler warnings.
2942 DEBUG(dbgs() << "Trying to evaluate BB: " << *CurBB << "\n");
2944 if (!EvaluateBlock(CurInst, NextBB))
2948 // Successfully running until there's no next block means that we found
2949 // the return. Fill it the return value and pop the call stack.
2950 ReturnInst *RI = cast<ReturnInst>(CurBB->getTerminator());
2951 if (RI->getNumOperands())
2952 RetVal = getVal(RI->getOperand(0));
2953 CallStack.pop_back();
2957 // Okay, we succeeded in evaluating this control flow. See if we have
2958 // executed the new block before. If so, we have a looping function,
2959 // which we cannot evaluate in reasonable time.
2960 if (!ExecutedBlocks.insert(NextBB))
2961 return false; // looped!
2963 // Okay, we have never been in this block before. Check to see if there
2964 // are any PHI nodes. If so, evaluate them with information about where
2967 for (CurInst = NextBB->begin();
2968 (PN = dyn_cast<PHINode>(CurInst)); ++CurInst)
2969 setVal(PN, getVal(PN->getIncomingValueForBlock(CurBB)));
2971 // Advance to the next block.
2976 /// EvaluateStaticConstructor - Evaluate static constructors in the function, if
2977 /// we can. Return true if we can, false otherwise.
2978 static bool EvaluateStaticConstructor(Function *F, const DataLayout *TD,
2979 const TargetLibraryInfo *TLI) {
2980 // Call the function.
2981 Evaluator Eval(TD, TLI);
2982 Constant *RetValDummy;
2983 bool EvalSuccess = Eval.EvaluateFunction(F, RetValDummy,
2984 SmallVector<Constant*, 0>());
2987 // We succeeded at evaluation: commit the result.
2988 DEBUG(dbgs() << "FULLY EVALUATED GLOBAL CTOR FUNCTION '"
2989 << F->getName() << "' to " << Eval.getMutatedMemory().size()
2991 for (DenseMap<Constant*, Constant*>::const_iterator I =
2992 Eval.getMutatedMemory().begin(), E = Eval.getMutatedMemory().end();
2994 CommitValueTo(I->second, I->first);
2995 for (SmallPtrSet<GlobalVariable*, 8>::const_iterator I =
2996 Eval.getInvariants().begin(), E = Eval.getInvariants().end();
2998 (*I)->setConstant(true);
3004 /// OptimizeGlobalCtorsList - Simplify and evaluation global ctors if possible.
3005 /// Return true if anything changed.
3006 bool GlobalOpt::OptimizeGlobalCtorsList(GlobalVariable *&GCL) {
3007 std::vector<Function*> Ctors = ParseGlobalCtors(GCL);
3008 bool MadeChange = false;
3009 if (Ctors.empty()) return false;
3011 // Loop over global ctors, optimizing them when we can.
3012 for (unsigned i = 0; i != Ctors.size(); ++i) {
3013 Function *F = Ctors[i];
3014 // Found a null terminator in the middle of the list, prune off the rest of
3017 if (i != Ctors.size()-1) {
3023 DEBUG(dbgs() << "Optimizing Global Constructor: " << *F << "\n");
3025 // We cannot simplify external ctor functions.
3026 if (F->empty()) continue;
3028 // If we can evaluate the ctor at compile time, do.
3029 if (EvaluateStaticConstructor(F, TD, TLI)) {
3030 Ctors.erase(Ctors.begin()+i);
3033 ++NumCtorsEvaluated;
3038 if (!MadeChange) return false;
3040 GCL = InstallGlobalCtors(GCL, Ctors);
3044 static int compareNames(const void *A, const void *B) {
3045 const GlobalValue *VA = *reinterpret_cast<GlobalValue* const*>(A);
3046 const GlobalValue *VB = *reinterpret_cast<GlobalValue* const*>(B);
3047 if (VA->getName() < VB->getName())
3049 if (VB->getName() < VA->getName())
3054 static void setUsedInitializer(GlobalVariable &V,
3055 SmallPtrSet<GlobalValue *, 8> Init) {
3057 V.eraseFromParent();
3061 SmallVector<llvm::Constant *, 8> UsedArray;
3062 PointerType *Int8PtrTy = Type::getInt8PtrTy(V.getContext());
3064 for (SmallPtrSet<GlobalValue *, 8>::iterator I = Init.begin(), E = Init.end();
3066 Constant *Cast = llvm::ConstantExpr::getBitCast(*I, Int8PtrTy);
3067 UsedArray.push_back(Cast);
3069 // Sort to get deterministic order.
3070 array_pod_sort(UsedArray.begin(), UsedArray.end(), compareNames);
3071 ArrayType *ATy = ArrayType::get(Int8PtrTy, UsedArray.size());
3073 Module *M = V.getParent();
3074 V.removeFromParent();
3075 GlobalVariable *NV =
3076 new GlobalVariable(*M, ATy, false, llvm::GlobalValue::AppendingLinkage,
3077 llvm::ConstantArray::get(ATy, UsedArray), "");
3079 NV->setSection("llvm.metadata");
3084 /// \brief An easy to access representation of llvm.used and llvm.compiler.used.
3086 SmallPtrSet<GlobalValue *, 8> Used;
3087 SmallPtrSet<GlobalValue *, 8> CompilerUsed;
3088 GlobalVariable *UsedV;
3089 GlobalVariable *CompilerUsedV;
3092 LLVMUsed(Module &M) {
3093 UsedV = collectUsedGlobalVariables(M, Used, false);
3094 CompilerUsedV = collectUsedGlobalVariables(M, CompilerUsed, true);
3096 typedef SmallPtrSet<GlobalValue *, 8>::iterator iterator;
3097 iterator usedBegin() { return Used.begin(); }
3098 iterator usedEnd() { return Used.end(); }
3099 iterator compilerUsedBegin() { return CompilerUsed.begin(); }
3100 iterator compilerUsedEnd() { return CompilerUsed.end(); }
3101 bool usedCount(GlobalValue *GV) const { return Used.count(GV); }
3102 bool compilerUsedCount(GlobalValue *GV) const {
3103 return CompilerUsed.count(GV);
3105 bool usedErase(GlobalValue *GV) { return Used.erase(GV); }
3106 bool compilerUsedErase(GlobalValue *GV) { return CompilerUsed.erase(GV); }
3107 bool usedInsert(GlobalValue *GV) { return Used.insert(GV); }
3108 bool compilerUsedInsert(GlobalValue *GV) { return CompilerUsed.insert(GV); }
3110 void syncVariablesAndSets() {
3112 setUsedInitializer(*UsedV, Used);
3114 setUsedInitializer(*CompilerUsedV, CompilerUsed);
3119 static bool hasUseOtherThanLLVMUsed(GlobalAlias &GA, const LLVMUsed &U) {
3120 if (GA.use_empty()) // No use at all.
3123 assert((!U.usedCount(&GA) || !U.compilerUsedCount(&GA)) &&
3124 "We should have removed the duplicated "
3125 "element from llvm.compiler.used");
3126 if (!GA.hasOneUse())
3127 // Strictly more than one use. So at least one is not in llvm.used and
3128 // llvm.compiler.used.
3131 // Exactly one use. Check if it is in llvm.used or llvm.compiler.used.
3132 return !U.usedCount(&GA) && !U.compilerUsedCount(&GA);
3135 static bool hasMoreThanOneUseOtherThanLLVMUsed(GlobalValue &V,
3136 const LLVMUsed &U) {
3138 assert((!U.usedCount(&V) || !U.compilerUsedCount(&V)) &&
3139 "We should have removed the duplicated "
3140 "element from llvm.compiler.used");
3141 if (U.usedCount(&V) || U.compilerUsedCount(&V))
3143 return V.hasNUsesOrMore(N);
3146 static bool mayHaveOtherReferences(GlobalAlias &GA, const LLVMUsed &U) {
3147 if (!GA.hasLocalLinkage())
3150 return U.usedCount(&GA) || U.compilerUsedCount(&GA);
3153 static bool hasUsesToReplace(GlobalAlias &GA, LLVMUsed &U, bool &RenameTarget) {
3154 RenameTarget = false;
3156 if (hasUseOtherThanLLVMUsed(GA, U))
3159 // If the alias is externally visible, we may still be able to simplify it.
3160 if (!mayHaveOtherReferences(GA, U))
3163 // If the aliasee has internal linkage, give it the name and linkage
3164 // of the alias, and delete the alias. This turns:
3165 // define internal ... @f(...)
3166 // @a = alias ... @f
3168 // define ... @a(...)
3169 Constant *Aliasee = GA.getAliasee();
3170 GlobalValue *Target = cast<GlobalValue>(Aliasee->stripPointerCasts());
3171 if (!Target->hasLocalLinkage())
3174 // Do not perform the transform if multiple aliases potentially target the
3175 // aliasee. This check also ensures that it is safe to replace the section
3176 // and other attributes of the aliasee with those of the alias.
3177 if (hasMoreThanOneUseOtherThanLLVMUsed(*Target, U))
3180 RenameTarget = true;
3184 bool GlobalOpt::OptimizeGlobalAliases(Module &M) {
3185 bool Changed = false;
3188 for (SmallPtrSet<GlobalValue *, 8>::iterator I = Used.usedBegin(),
3191 Used.compilerUsedErase(*I);
3193 for (Module::alias_iterator I = M.alias_begin(), E = M.alias_end();
3195 Module::alias_iterator J = I++;
3196 // Aliases without names cannot be referenced outside this module.
3197 if (!J->hasName() && !J->isDeclaration())
3198 J->setLinkage(GlobalValue::InternalLinkage);
3199 // If the aliasee may change at link time, nothing can be done - bail out.
3200 if (J->mayBeOverridden())
3203 Constant *Aliasee = J->getAliasee();
3204 GlobalValue *Target = cast<GlobalValue>(Aliasee->stripPointerCasts());
3205 Target->removeDeadConstantUsers();
3207 // Make all users of the alias use the aliasee instead.
3209 if (!hasUsesToReplace(*J, Used, RenameTarget))
3212 J->replaceAllUsesWith(Aliasee);
3213 ++NumAliasesResolved;
3217 // Give the aliasee the name, linkage and other attributes of the alias.
3218 Target->takeName(J);
3219 Target->setLinkage(J->getLinkage());
3220 Target->GlobalValue::copyAttributesFrom(J);
3222 if (Used.usedErase(J))
3223 Used.usedInsert(Target);
3225 if (Used.compilerUsedErase(J))
3226 Used.compilerUsedInsert(Target);
3227 } else if (mayHaveOtherReferences(*J, Used))
3230 // Delete the alias.
3231 M.getAliasList().erase(J);
3232 ++NumAliasesRemoved;
3236 Used.syncVariablesAndSets();
3241 static Function *FindCXAAtExit(Module &M, TargetLibraryInfo *TLI) {
3242 if (!TLI->has(LibFunc::cxa_atexit))
3245 Function *Fn = M.getFunction(TLI->getName(LibFunc::cxa_atexit));
3250 FunctionType *FTy = Fn->getFunctionType();
3252 // Checking that the function has the right return type, the right number of
3253 // parameters and that they all have pointer types should be enough.
3254 if (!FTy->getReturnType()->isIntegerTy() ||
3255 FTy->getNumParams() != 3 ||
3256 !FTy->getParamType(0)->isPointerTy() ||
3257 !FTy->getParamType(1)->isPointerTy() ||
3258 !FTy->getParamType(2)->isPointerTy())
3264 /// cxxDtorIsEmpty - Returns whether the given function is an empty C++
3265 /// destructor and can therefore be eliminated.
3266 /// Note that we assume that other optimization passes have already simplified
3267 /// the code so we only look for a function with a single basic block, where
3268 /// the only allowed instructions are 'ret', 'call' to an empty C++ dtor and
3269 /// other side-effect free instructions.
3270 static bool cxxDtorIsEmpty(const Function &Fn,
3271 SmallPtrSet<const Function *, 8> &CalledFunctions) {
3272 // FIXME: We could eliminate C++ destructors if they're readonly/readnone and
3273 // nounwind, but that doesn't seem worth doing.
3274 if (Fn.isDeclaration())
3277 if (++Fn.begin() != Fn.end())
3280 const BasicBlock &EntryBlock = Fn.getEntryBlock();
3281 for (BasicBlock::const_iterator I = EntryBlock.begin(), E = EntryBlock.end();
3283 if (const CallInst *CI = dyn_cast<CallInst>(I)) {
3284 // Ignore debug intrinsics.
3285 if (isa<DbgInfoIntrinsic>(CI))
3288 const Function *CalledFn = CI->getCalledFunction();
3293 SmallPtrSet<const Function *, 8> NewCalledFunctions(CalledFunctions);
3295 // Don't treat recursive functions as empty.
3296 if (!NewCalledFunctions.insert(CalledFn))
3299 if (!cxxDtorIsEmpty(*CalledFn, NewCalledFunctions))
3301 } else if (isa<ReturnInst>(*I))
3302 return true; // We're done.
3303 else if (I->mayHaveSideEffects())
3304 return false; // Destructor with side effects, bail.
3310 bool GlobalOpt::OptimizeEmptyGlobalCXXDtors(Function *CXAAtExitFn) {
3311 /// Itanium C++ ABI p3.3.5:
3313 /// After constructing a global (or local static) object, that will require
3314 /// destruction on exit, a termination function is registered as follows:
3316 /// extern "C" int __cxa_atexit ( void (*f)(void *), void *p, void *d );
3318 /// This registration, e.g. __cxa_atexit(f,p,d), is intended to cause the
3319 /// call f(p) when DSO d is unloaded, before all such termination calls
3320 /// registered before this one. It returns zero if registration is
3321 /// successful, nonzero on failure.
3323 // This pass will look for calls to __cxa_atexit where the function is trivial
3325 bool Changed = false;
3327 for (Function::use_iterator I = CXAAtExitFn->use_begin(),
3328 E = CXAAtExitFn->use_end(); I != E;) {
3329 // We're only interested in calls. Theoretically, we could handle invoke
3330 // instructions as well, but neither llvm-gcc nor clang generate invokes
3332 CallInst *CI = dyn_cast<CallInst>(*I++);
3337 dyn_cast<Function>(CI->getArgOperand(0)->stripPointerCasts());
3341 SmallPtrSet<const Function *, 8> CalledFunctions;
3342 if (!cxxDtorIsEmpty(*DtorFn, CalledFunctions))
3345 // Just remove the call.
3346 CI->replaceAllUsesWith(Constant::getNullValue(CI->getType()));
3347 CI->eraseFromParent();
3349 ++NumCXXDtorsRemoved;
3357 bool GlobalOpt::runOnModule(Module &M) {
3358 bool Changed = false;
3360 TD = getAnalysisIfAvailable<DataLayout>();
3361 TLI = &getAnalysis<TargetLibraryInfo>();
3363 // Try to find the llvm.globalctors list.
3364 GlobalVariable *GlobalCtors = FindGlobalCtors(M);
3366 bool LocalChange = true;
3367 while (LocalChange) {
3368 LocalChange = false;
3370 // Delete functions that are trivially dead, ccc -> fastcc
3371 LocalChange |= OptimizeFunctions(M);
3373 // Optimize global_ctors list.
3375 LocalChange |= OptimizeGlobalCtorsList(GlobalCtors);
3377 // Optimize non-address-taken globals.
3378 LocalChange |= OptimizeGlobalVars(M);
3380 // Resolve aliases, when possible.
3381 LocalChange |= OptimizeGlobalAliases(M);
3383 // Try to remove trivial global destructors if they are not removed
3385 Function *CXAAtExitFn = FindCXAAtExit(M, TLI);
3387 LocalChange |= OptimizeEmptyGlobalCXXDtors(CXAAtExitFn);
3389 Changed |= LocalChange;
3392 // TODO: Move all global ctors functions to the end of the module for code