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"
44 STATISTIC(NumMarked , "Number of globals marked constant");
45 STATISTIC(NumUnnamed , "Number of globals marked unnamed_addr");
46 STATISTIC(NumSRA , "Number of aggregate globals broken into scalars");
47 STATISTIC(NumHeapSRA , "Number of heap objects SRA'd");
48 STATISTIC(NumSubstitute,"Number of globals with initializers stored into them");
49 STATISTIC(NumDeleted , "Number of globals deleted");
50 STATISTIC(NumFnDeleted , "Number of functions deleted");
51 STATISTIC(NumGlobUses , "Number of global uses devirtualized");
52 STATISTIC(NumLocalized , "Number of globals localized");
53 STATISTIC(NumShrunkToBool , "Number of global vars shrunk to booleans");
54 STATISTIC(NumFastCallFns , "Number of functions converted to fastcc");
55 STATISTIC(NumCtorsEvaluated, "Number of static ctors evaluated");
56 STATISTIC(NumNestRemoved , "Number of nest attributes removed");
57 STATISTIC(NumAliasesResolved, "Number of global aliases resolved");
58 STATISTIC(NumAliasesRemoved, "Number of global aliases eliminated");
59 STATISTIC(NumCXXDtorsRemoved, "Number of global C++ destructors removed");
63 struct GlobalOpt : public ModulePass {
64 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
65 AU.addRequired<TargetLibraryInfo>();
67 static char ID; // Pass identification, replacement for typeid
68 GlobalOpt() : ModulePass(ID) {
69 initializeGlobalOptPass(*PassRegistry::getPassRegistry());
72 bool runOnModule(Module &M);
75 GlobalVariable *FindGlobalCtors(Module &M);
76 bool OptimizeFunctions(Module &M);
77 bool OptimizeGlobalVars(Module &M);
78 bool OptimizeGlobalAliases(Module &M);
79 bool OptimizeGlobalCtorsList(GlobalVariable *&GCL);
80 bool ProcessGlobal(GlobalVariable *GV,Module::global_iterator &GVI);
81 bool ProcessInternalGlobal(GlobalVariable *GV,Module::global_iterator &GVI,
82 const SmallPtrSet<const PHINode*, 16> &PHIUsers,
83 const GlobalStatus &GS);
84 bool OptimizeEmptyGlobalCXXDtors(Function *CXAAtExitFn);
87 TargetLibraryInfo *TLI;
91 char GlobalOpt::ID = 0;
92 INITIALIZE_PASS_BEGIN(GlobalOpt, "globalopt",
93 "Global Variable Optimizer", false, false)
94 INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfo)
95 INITIALIZE_PASS_END(GlobalOpt, "globalopt",
96 "Global Variable Optimizer", false, false)
98 ModulePass *llvm::createGlobalOptimizerPass() { return new GlobalOpt(); }
102 /// GlobalStatus - As we analyze each global, keep track of some information
103 /// about it. If we find out that the address of the global is taken, none of
104 /// this info will be accurate.
105 struct GlobalStatus {
106 /// isCompared - True if the global's address is used in a comparison.
109 /// isLoaded - True if the global is ever loaded. If the global isn't ever
110 /// loaded it can be deleted.
113 /// StoredType - Keep track of what stores to the global look like.
116 /// NotStored - There is no store to this global. It can thus be marked
120 /// isInitializerStored - This global is stored to, but the only thing
121 /// stored is the constant it was initialized with. This is only tracked
122 /// for scalar globals.
125 /// isStoredOnce - This global is stored to, but only its initializer and
126 /// one other value is ever stored to it. If this global isStoredOnce, we
127 /// track the value stored to it in StoredOnceValue below. This is only
128 /// tracked for scalar globals.
131 /// isStored - This global is stored to by multiple values or something else
132 /// that we cannot track.
136 /// StoredOnceValue - If only one value (besides the initializer constant) is
137 /// ever stored to this global, keep track of what value it is.
138 Value *StoredOnceValue;
140 /// AccessingFunction/HasMultipleAccessingFunctions - These start out
141 /// null/false. When the first accessing function is noticed, it is recorded.
142 /// When a second different accessing function is noticed,
143 /// HasMultipleAccessingFunctions is set to true.
144 const Function *AccessingFunction;
145 bool HasMultipleAccessingFunctions;
147 /// HasNonInstructionUser - Set to true if this global has a user that is not
148 /// an instruction (e.g. a constant expr or GV initializer).
149 bool HasNonInstructionUser;
151 /// AtomicOrdering - Set to the strongest atomic ordering requirement.
152 AtomicOrdering Ordering;
154 GlobalStatus() : isCompared(false), isLoaded(false), StoredType(NotStored),
155 StoredOnceValue(0), AccessingFunction(0),
156 HasMultipleAccessingFunctions(false),
157 HasNonInstructionUser(false), Ordering(NotAtomic) {}
162 /// StrongerOrdering - Return the stronger of the two ordering. If the two
163 /// orderings are acquire and release, then return AcquireRelease.
165 static AtomicOrdering StrongerOrdering(AtomicOrdering X, AtomicOrdering Y) {
166 if (X == Acquire && Y == Release) return AcquireRelease;
167 if (Y == Acquire && X == Release) return AcquireRelease;
168 return (AtomicOrdering)std::max(X, Y);
171 /// SafeToDestroyConstant - It is safe to destroy a constant iff it is only used
172 /// by constants itself. Note that constants cannot be cyclic, so this test is
173 /// pretty easy to implement recursively.
175 static bool SafeToDestroyConstant(const Constant *C) {
176 if (isa<GlobalValue>(C)) return false;
178 for (Value::const_use_iterator UI = C->use_begin(), E = C->use_end(); UI != E;
180 if (const Constant *CU = dyn_cast<Constant>(*UI)) {
181 if (!SafeToDestroyConstant(CU)) return false;
188 /// AnalyzeGlobal - Look at all uses of the global and fill in the GlobalStatus
189 /// structure. If the global has its address taken, return true to indicate we
190 /// can't do anything with it.
192 static bool AnalyzeGlobal(const Value *V, GlobalStatus &GS,
193 SmallPtrSet<const PHINode*, 16> &PHIUsers) {
194 for (Value::const_use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;
197 if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(U)) {
198 GS.HasNonInstructionUser = true;
200 // If the result of the constantexpr isn't pointer type, then we won't
201 // know to expect it in various places. Just reject early.
202 if (!isa<PointerType>(CE->getType())) return true;
204 if (AnalyzeGlobal(CE, GS, PHIUsers)) return true;
205 } else if (const Instruction *I = dyn_cast<Instruction>(U)) {
206 if (!GS.HasMultipleAccessingFunctions) {
207 const Function *F = I->getParent()->getParent();
208 if (GS.AccessingFunction == 0)
209 GS.AccessingFunction = F;
210 else if (GS.AccessingFunction != F)
211 GS.HasMultipleAccessingFunctions = true;
213 if (const LoadInst *LI = dyn_cast<LoadInst>(I)) {
215 // Don't hack on volatile loads.
216 if (LI->isVolatile()) return true;
217 GS.Ordering = StrongerOrdering(GS.Ordering, LI->getOrdering());
218 } else if (const StoreInst *SI = dyn_cast<StoreInst>(I)) {
219 // Don't allow a store OF the address, only stores TO the address.
220 if (SI->getOperand(0) == V) return true;
222 // Don't hack on volatile stores.
223 if (SI->isVolatile()) return true;
225 GS.Ordering = StrongerOrdering(GS.Ordering, SI->getOrdering());
227 // If this is a direct store to the global (i.e., the global is a scalar
228 // value, not an aggregate), keep more specific information about
230 if (GS.StoredType != GlobalStatus::isStored) {
231 if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(
232 SI->getOperand(1))) {
233 Value *StoredVal = SI->getOperand(0);
235 if (Constant *C = dyn_cast<Constant>(StoredVal)) {
236 if (C->isThreadDependent()) {
237 // The stored value changes between threads; don't track it.
242 if (StoredVal == GV->getInitializer()) {
243 if (GS.StoredType < GlobalStatus::isInitializerStored)
244 GS.StoredType = GlobalStatus::isInitializerStored;
245 } else if (isa<LoadInst>(StoredVal) &&
246 cast<LoadInst>(StoredVal)->getOperand(0) == GV) {
247 if (GS.StoredType < GlobalStatus::isInitializerStored)
248 GS.StoredType = GlobalStatus::isInitializerStored;
249 } else if (GS.StoredType < GlobalStatus::isStoredOnce) {
250 GS.StoredType = GlobalStatus::isStoredOnce;
251 GS.StoredOnceValue = StoredVal;
252 } else if (GS.StoredType == GlobalStatus::isStoredOnce &&
253 GS.StoredOnceValue == StoredVal) {
256 GS.StoredType = GlobalStatus::isStored;
259 GS.StoredType = GlobalStatus::isStored;
262 } else if (isa<BitCastInst>(I)) {
263 if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
264 } else if (isa<GetElementPtrInst>(I)) {
265 if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
266 } else if (isa<SelectInst>(I)) {
267 if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
268 } else if (const PHINode *PN = dyn_cast<PHINode>(I)) {
269 // PHI nodes we can check just like select or GEP instructions, but we
270 // have to be careful about infinite recursion.
271 if (PHIUsers.insert(PN)) // Not already visited.
272 if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
273 } else if (isa<CmpInst>(I)) {
274 GS.isCompared = true;
275 } else if (const MemTransferInst *MTI = dyn_cast<MemTransferInst>(I)) {
276 if (MTI->isVolatile()) return true;
277 if (MTI->getArgOperand(0) == V)
278 GS.StoredType = GlobalStatus::isStored;
279 if (MTI->getArgOperand(1) == V)
281 } else if (const MemSetInst *MSI = dyn_cast<MemSetInst>(I)) {
282 assert(MSI->getArgOperand(0) == V && "Memset only takes one pointer!");
283 if (MSI->isVolatile()) return true;
284 GS.StoredType = GlobalStatus::isStored;
286 return true; // Any other non-load instruction might take address!
288 } else if (const Constant *C = dyn_cast<Constant>(U)) {
289 GS.HasNonInstructionUser = true;
290 // We might have a dead and dangling constant hanging off of here.
291 if (!SafeToDestroyConstant(C))
294 GS.HasNonInstructionUser = true;
295 // Otherwise must be some other user.
303 /// isLeakCheckerRoot - Is this global variable possibly used by a leak checker
304 /// as a root? If so, we might not really want to eliminate the stores to it.
305 static bool isLeakCheckerRoot(GlobalVariable *GV) {
306 // A global variable is a root if it is a pointer, or could plausibly contain
307 // a pointer. There are two challenges; one is that we could have a struct
308 // the has an inner member which is a pointer. We recurse through the type to
309 // detect these (up to a point). The other is that we may actually be a union
310 // of a pointer and another type, and so our LLVM type is an integer which
311 // gets converted into a pointer, or our type is an [i8 x #] with a pointer
312 // potentially contained here.
314 if (GV->hasPrivateLinkage())
317 SmallVector<Type *, 4> Types;
318 Types.push_back(cast<PointerType>(GV->getType())->getElementType());
322 Type *Ty = Types.pop_back_val();
323 switch (Ty->getTypeID()) {
325 case Type::PointerTyID: return true;
326 case Type::ArrayTyID:
327 case Type::VectorTyID: {
328 SequentialType *STy = cast<SequentialType>(Ty);
329 Types.push_back(STy->getElementType());
332 case Type::StructTyID: {
333 StructType *STy = cast<StructType>(Ty);
334 if (STy->isOpaque()) return true;
335 for (StructType::element_iterator I = STy->element_begin(),
336 E = STy->element_end(); I != E; ++I) {
338 if (isa<PointerType>(InnerTy)) return true;
339 if (isa<CompositeType>(InnerTy))
340 Types.push_back(InnerTy);
345 if (--Limit == 0) return true;
346 } while (!Types.empty());
350 /// Given a value that is stored to a global but never read, determine whether
351 /// it's safe to remove the store and the chain of computation that feeds the
353 static bool IsSafeComputationToRemove(Value *V, const TargetLibraryInfo *TLI) {
355 if (isa<Constant>(V))
359 if (isa<LoadInst>(V) || isa<InvokeInst>(V) || isa<Argument>(V) ||
362 if (isAllocationFn(V, TLI))
365 Instruction *I = cast<Instruction>(V);
366 if (I->mayHaveSideEffects())
368 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(I)) {
369 if (!GEP->hasAllConstantIndices())
371 } else if (I->getNumOperands() != 1) {
375 V = I->getOperand(0);
379 /// CleanupPointerRootUsers - This GV is a pointer root. Loop over all users
380 /// of the global and clean up any that obviously don't assign the global a
381 /// value that isn't dynamically allocated.
383 static bool CleanupPointerRootUsers(GlobalVariable *GV,
384 const TargetLibraryInfo *TLI) {
385 // A brief explanation of leak checkers. The goal is to find bugs where
386 // pointers are forgotten, causing an accumulating growth in memory
387 // usage over time. The common strategy for leak checkers is to whitelist the
388 // memory pointed to by globals at exit. This is popular because it also
389 // solves another problem where the main thread of a C++ program may shut down
390 // before other threads that are still expecting to use those globals. To
391 // handle that case, we expect the program may create a singleton and never
394 bool Changed = false;
396 // If Dead[n].first is the only use of a malloc result, we can delete its
397 // chain of computation and the store to the global in Dead[n].second.
398 SmallVector<std::pair<Instruction *, Instruction *>, 32> Dead;
400 // Constants can't be pointers to dynamically allocated memory.
401 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end();
404 if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
405 Value *V = SI->getValueOperand();
406 if (isa<Constant>(V)) {
408 SI->eraseFromParent();
409 } else if (Instruction *I = dyn_cast<Instruction>(V)) {
411 Dead.push_back(std::make_pair(I, SI));
413 } else if (MemSetInst *MSI = dyn_cast<MemSetInst>(U)) {
414 if (isa<Constant>(MSI->getValue())) {
416 MSI->eraseFromParent();
417 } else if (Instruction *I = dyn_cast<Instruction>(MSI->getValue())) {
419 Dead.push_back(std::make_pair(I, MSI));
421 } else if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(U)) {
422 GlobalVariable *MemSrc = dyn_cast<GlobalVariable>(MTI->getSource());
423 if (MemSrc && MemSrc->isConstant()) {
425 MTI->eraseFromParent();
426 } else if (Instruction *I = dyn_cast<Instruction>(MemSrc)) {
428 Dead.push_back(std::make_pair(I, MTI));
430 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U)) {
431 if (CE->use_empty()) {
432 CE->destroyConstant();
435 } else if (Constant *C = dyn_cast<Constant>(U)) {
436 if (SafeToDestroyConstant(C)) {
437 C->destroyConstant();
438 // This could have invalidated UI, start over from scratch.
440 CleanupPointerRootUsers(GV, TLI);
446 for (int i = 0, e = Dead.size(); i != e; ++i) {
447 if (IsSafeComputationToRemove(Dead[i].first, TLI)) {
448 Dead[i].second->eraseFromParent();
449 Instruction *I = Dead[i].first;
451 if (isAllocationFn(I, TLI))
453 Instruction *J = dyn_cast<Instruction>(I->getOperand(0));
456 I->eraseFromParent();
459 I->eraseFromParent();
466 /// CleanupConstantGlobalUsers - We just marked GV constant. Loop over all
467 /// users of the global, cleaning up the obvious ones. This is largely just a
468 /// quick scan over the use list to clean up the easy and obvious cruft. This
469 /// returns true if it made a change.
470 static bool CleanupConstantGlobalUsers(Value *V, Constant *Init,
471 DataLayout *TD, TargetLibraryInfo *TLI) {
472 bool Changed = false;
473 SmallVector<User*, 8> WorkList(V->use_begin(), V->use_end());
474 while (!WorkList.empty()) {
475 User *U = WorkList.pop_back_val();
477 if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
479 // Replace the load with the initializer.
480 LI->replaceAllUsesWith(Init);
481 LI->eraseFromParent();
484 } else if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
485 // Store must be unreachable or storing Init into the global.
486 SI->eraseFromParent();
488 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U)) {
489 if (CE->getOpcode() == Instruction::GetElementPtr) {
490 Constant *SubInit = 0;
492 SubInit = ConstantFoldLoadThroughGEPConstantExpr(Init, CE);
493 Changed |= CleanupConstantGlobalUsers(CE, SubInit, TD, TLI);
494 } else if (CE->getOpcode() == Instruction::BitCast &&
495 CE->getType()->isPointerTy()) {
496 // Pointer cast, delete any stores and memsets to the global.
497 Changed |= CleanupConstantGlobalUsers(CE, 0, TD, TLI);
500 if (CE->use_empty()) {
501 CE->destroyConstant();
504 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) {
505 // Do not transform "gepinst (gep constexpr (GV))" here, because forming
506 // "gepconstexpr (gep constexpr (GV))" will cause the two gep's to fold
507 // and will invalidate our notion of what Init is.
508 Constant *SubInit = 0;
509 if (!isa<ConstantExpr>(GEP->getOperand(0))) {
511 dyn_cast_or_null<ConstantExpr>(ConstantFoldInstruction(GEP, TD, TLI));
512 if (Init && CE && CE->getOpcode() == Instruction::GetElementPtr)
513 SubInit = ConstantFoldLoadThroughGEPConstantExpr(Init, CE);
515 // If the initializer is an all-null value and we have an inbounds GEP,
516 // we already know what the result of any load from that GEP is.
517 // TODO: Handle splats.
518 if (Init && isa<ConstantAggregateZero>(Init) && GEP->isInBounds())
519 SubInit = Constant::getNullValue(GEP->getType()->getElementType());
521 Changed |= CleanupConstantGlobalUsers(GEP, SubInit, TD, TLI);
523 if (GEP->use_empty()) {
524 GEP->eraseFromParent();
527 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(U)) { // memset/cpy/mv
528 if (MI->getRawDest() == V) {
529 MI->eraseFromParent();
533 } else if (Constant *C = dyn_cast<Constant>(U)) {
534 // If we have a chain of dead constantexprs or other things dangling from
535 // us, and if they are all dead, nuke them without remorse.
536 if (SafeToDestroyConstant(C)) {
537 C->destroyConstant();
538 CleanupConstantGlobalUsers(V, Init, TD, TLI);
546 /// isSafeSROAElementUse - Return true if the specified instruction is a safe
547 /// user of a derived expression from a global that we want to SROA.
548 static bool isSafeSROAElementUse(Value *V) {
549 // We might have a dead and dangling constant hanging off of here.
550 if (Constant *C = dyn_cast<Constant>(V))
551 return SafeToDestroyConstant(C);
553 Instruction *I = dyn_cast<Instruction>(V);
554 if (!I) return false;
557 if (isa<LoadInst>(I)) return true;
559 // Stores *to* the pointer are ok.
560 if (StoreInst *SI = dyn_cast<StoreInst>(I))
561 return SI->getOperand(0) != V;
563 // Otherwise, it must be a GEP.
564 GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I);
565 if (GEPI == 0) return false;
567 if (GEPI->getNumOperands() < 3 || !isa<Constant>(GEPI->getOperand(1)) ||
568 !cast<Constant>(GEPI->getOperand(1))->isNullValue())
571 for (Value::use_iterator I = GEPI->use_begin(), E = GEPI->use_end();
573 if (!isSafeSROAElementUse(*I))
579 /// IsUserOfGlobalSafeForSRA - U is a direct user of the specified global value.
580 /// Look at it and its uses and decide whether it is safe to SROA this global.
582 static bool IsUserOfGlobalSafeForSRA(User *U, GlobalValue *GV) {
583 // The user of the global must be a GEP Inst or a ConstantExpr GEP.
584 if (!isa<GetElementPtrInst>(U) &&
585 (!isa<ConstantExpr>(U) ||
586 cast<ConstantExpr>(U)->getOpcode() != Instruction::GetElementPtr))
589 // Check to see if this ConstantExpr GEP is SRA'able. In particular, we
590 // don't like < 3 operand CE's, and we don't like non-constant integer
591 // indices. This enforces that all uses are 'gep GV, 0, C, ...' for some
593 if (U->getNumOperands() < 3 || !isa<Constant>(U->getOperand(1)) ||
594 !cast<Constant>(U->getOperand(1))->isNullValue() ||
595 !isa<ConstantInt>(U->getOperand(2)))
598 gep_type_iterator GEPI = gep_type_begin(U), E = gep_type_end(U);
599 ++GEPI; // Skip over the pointer index.
601 // If this is a use of an array allocation, do a bit more checking for sanity.
602 if (ArrayType *AT = dyn_cast<ArrayType>(*GEPI)) {
603 uint64_t NumElements = AT->getNumElements();
604 ConstantInt *Idx = cast<ConstantInt>(U->getOperand(2));
606 // Check to make sure that index falls within the array. If not,
607 // something funny is going on, so we won't do the optimization.
609 if (Idx->getZExtValue() >= NumElements)
612 // We cannot scalar repl this level of the array unless any array
613 // sub-indices are in-range constants. In particular, consider:
614 // A[0][i]. We cannot know that the user isn't doing invalid things like
615 // allowing i to index an out-of-range subscript that accesses A[1].
617 // Scalar replacing *just* the outer index of the array is probably not
618 // going to be a win anyway, so just give up.
619 for (++GEPI; // Skip array index.
622 uint64_t NumElements;
623 if (ArrayType *SubArrayTy = dyn_cast<ArrayType>(*GEPI))
624 NumElements = SubArrayTy->getNumElements();
625 else if (VectorType *SubVectorTy = dyn_cast<VectorType>(*GEPI))
626 NumElements = SubVectorTy->getNumElements();
628 assert((*GEPI)->isStructTy() &&
629 "Indexed GEP type is not array, vector, or struct!");
633 ConstantInt *IdxVal = dyn_cast<ConstantInt>(GEPI.getOperand());
634 if (!IdxVal || IdxVal->getZExtValue() >= NumElements)
639 for (Value::use_iterator I = U->use_begin(), E = U->use_end(); I != E; ++I)
640 if (!isSafeSROAElementUse(*I))
645 /// GlobalUsersSafeToSRA - Look at all uses of the global and decide whether it
646 /// is safe for us to perform this transformation.
648 static bool GlobalUsersSafeToSRA(GlobalValue *GV) {
649 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end();
651 if (!IsUserOfGlobalSafeForSRA(*UI, GV))
658 /// SRAGlobal - Perform scalar replacement of aggregates on the specified global
659 /// variable. This opens the door for other optimizations by exposing the
660 /// behavior of the program in a more fine-grained way. We have determined that
661 /// this transformation is safe already. We return the first global variable we
662 /// insert so that the caller can reprocess it.
663 static GlobalVariable *SRAGlobal(GlobalVariable *GV, const DataLayout &TD) {
664 // Make sure this global only has simple uses that we can SRA.
665 if (!GlobalUsersSafeToSRA(GV))
668 assert(GV->hasLocalLinkage() && !GV->isConstant());
669 Constant *Init = GV->getInitializer();
670 Type *Ty = Init->getType();
672 std::vector<GlobalVariable*> NewGlobals;
673 Module::GlobalListType &Globals = GV->getParent()->getGlobalList();
675 // Get the alignment of the global, either explicit or target-specific.
676 unsigned StartAlignment = GV->getAlignment();
677 if (StartAlignment == 0)
678 StartAlignment = TD.getABITypeAlignment(GV->getType());
680 if (StructType *STy = dyn_cast<StructType>(Ty)) {
681 NewGlobals.reserve(STy->getNumElements());
682 const StructLayout &Layout = *TD.getStructLayout(STy);
683 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
684 Constant *In = Init->getAggregateElement(i);
685 assert(In && "Couldn't get element of initializer?");
686 GlobalVariable *NGV = new GlobalVariable(STy->getElementType(i), false,
687 GlobalVariable::InternalLinkage,
688 In, GV->getName()+"."+Twine(i),
689 GV->getThreadLocalMode(),
690 GV->getType()->getAddressSpace());
691 Globals.insert(GV, NGV);
692 NewGlobals.push_back(NGV);
694 // Calculate the known alignment of the field. If the original aggregate
695 // had 256 byte alignment for example, something might depend on that:
696 // propagate info to each field.
697 uint64_t FieldOffset = Layout.getElementOffset(i);
698 unsigned NewAlign = (unsigned)MinAlign(StartAlignment, FieldOffset);
699 if (NewAlign > TD.getABITypeAlignment(STy->getElementType(i)))
700 NGV->setAlignment(NewAlign);
702 } else if (SequentialType *STy = dyn_cast<SequentialType>(Ty)) {
703 unsigned NumElements = 0;
704 if (ArrayType *ATy = dyn_cast<ArrayType>(STy))
705 NumElements = ATy->getNumElements();
707 NumElements = cast<VectorType>(STy)->getNumElements();
709 if (NumElements > 16 && GV->hasNUsesOrMore(16))
710 return 0; // It's not worth it.
711 NewGlobals.reserve(NumElements);
713 uint64_t EltSize = TD.getTypeAllocSize(STy->getElementType());
714 unsigned EltAlign = TD.getABITypeAlignment(STy->getElementType());
715 for (unsigned i = 0, e = NumElements; i != e; ++i) {
716 Constant *In = Init->getAggregateElement(i);
717 assert(In && "Couldn't get element of initializer?");
719 GlobalVariable *NGV = new GlobalVariable(STy->getElementType(), false,
720 GlobalVariable::InternalLinkage,
721 In, GV->getName()+"."+Twine(i),
722 GV->getThreadLocalMode(),
723 GV->getType()->getAddressSpace());
724 Globals.insert(GV, NGV);
725 NewGlobals.push_back(NGV);
727 // Calculate the known alignment of the field. If the original aggregate
728 // had 256 byte alignment for example, something might depend on that:
729 // propagate info to each field.
730 unsigned NewAlign = (unsigned)MinAlign(StartAlignment, EltSize*i);
731 if (NewAlign > EltAlign)
732 NGV->setAlignment(NewAlign);
736 if (NewGlobals.empty())
739 DEBUG(dbgs() << "PERFORMING GLOBAL SRA ON: " << *GV);
741 Constant *NullInt =Constant::getNullValue(Type::getInt32Ty(GV->getContext()));
743 // Loop over all of the uses of the global, replacing the constantexpr geps,
744 // with smaller constantexpr geps or direct references.
745 while (!GV->use_empty()) {
746 User *GEP = GV->use_back();
747 assert(((isa<ConstantExpr>(GEP) &&
748 cast<ConstantExpr>(GEP)->getOpcode()==Instruction::GetElementPtr)||
749 isa<GetElementPtrInst>(GEP)) && "NonGEP CE's are not SRAable!");
751 // Ignore the 1th operand, which has to be zero or else the program is quite
752 // broken (undefined). Get the 2nd operand, which is the structure or array
754 unsigned Val = cast<ConstantInt>(GEP->getOperand(2))->getZExtValue();
755 if (Val >= NewGlobals.size()) Val = 0; // Out of bound array access.
757 Value *NewPtr = NewGlobals[Val];
759 // Form a shorter GEP if needed.
760 if (GEP->getNumOperands() > 3) {
761 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GEP)) {
762 SmallVector<Constant*, 8> Idxs;
763 Idxs.push_back(NullInt);
764 for (unsigned i = 3, e = CE->getNumOperands(); i != e; ++i)
765 Idxs.push_back(CE->getOperand(i));
766 NewPtr = ConstantExpr::getGetElementPtr(cast<Constant>(NewPtr), Idxs);
768 GetElementPtrInst *GEPI = cast<GetElementPtrInst>(GEP);
769 SmallVector<Value*, 8> Idxs;
770 Idxs.push_back(NullInt);
771 for (unsigned i = 3, e = GEPI->getNumOperands(); i != e; ++i)
772 Idxs.push_back(GEPI->getOperand(i));
773 NewPtr = GetElementPtrInst::Create(NewPtr, Idxs,
774 GEPI->getName()+"."+Twine(Val),GEPI);
777 GEP->replaceAllUsesWith(NewPtr);
779 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(GEP))
780 GEPI->eraseFromParent();
782 cast<ConstantExpr>(GEP)->destroyConstant();
785 // Delete the old global, now that it is dead.
789 // Loop over the new globals array deleting any globals that are obviously
790 // dead. This can arise due to scalarization of a structure or an array that
791 // has elements that are dead.
792 unsigned FirstGlobal = 0;
793 for (unsigned i = 0, e = NewGlobals.size(); i != e; ++i)
794 if (NewGlobals[i]->use_empty()) {
795 Globals.erase(NewGlobals[i]);
796 if (FirstGlobal == i) ++FirstGlobal;
799 return FirstGlobal != NewGlobals.size() ? NewGlobals[FirstGlobal] : 0;
802 /// AllUsesOfValueWillTrapIfNull - Return true if all users of the specified
803 /// value will trap if the value is dynamically null. PHIs keeps track of any
804 /// phi nodes we've seen to avoid reprocessing them.
805 static bool AllUsesOfValueWillTrapIfNull(const Value *V,
806 SmallPtrSet<const PHINode*, 8> &PHIs) {
807 for (Value::const_use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;
811 if (isa<LoadInst>(U)) {
813 } else if (const StoreInst *SI = dyn_cast<StoreInst>(U)) {
814 if (SI->getOperand(0) == V) {
815 //cerr << "NONTRAPPING USE: " << *U;
816 return false; // Storing the value.
818 } else if (const CallInst *CI = dyn_cast<CallInst>(U)) {
819 if (CI->getCalledValue() != V) {
820 //cerr << "NONTRAPPING USE: " << *U;
821 return false; // Not calling the ptr
823 } else if (const InvokeInst *II = dyn_cast<InvokeInst>(U)) {
824 if (II->getCalledValue() != V) {
825 //cerr << "NONTRAPPING USE: " << *U;
826 return false; // Not calling the ptr
828 } else if (const BitCastInst *CI = dyn_cast<BitCastInst>(U)) {
829 if (!AllUsesOfValueWillTrapIfNull(CI, PHIs)) return false;
830 } else if (const GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(U)) {
831 if (!AllUsesOfValueWillTrapIfNull(GEPI, PHIs)) return false;
832 } else if (const PHINode *PN = dyn_cast<PHINode>(U)) {
833 // If we've already seen this phi node, ignore it, it has already been
835 if (PHIs.insert(PN) && !AllUsesOfValueWillTrapIfNull(PN, PHIs))
837 } else if (isa<ICmpInst>(U) &&
838 isa<ConstantPointerNull>(UI->getOperand(1))) {
839 // Ignore icmp X, null
841 //cerr << "NONTRAPPING USE: " << *U;
848 /// AllUsesOfLoadedValueWillTrapIfNull - Return true if all uses of any loads
849 /// from GV will trap if the loaded value is null. Note that this also permits
850 /// comparisons of the loaded value against null, as a special case.
851 static bool AllUsesOfLoadedValueWillTrapIfNull(const GlobalVariable *GV) {
852 for (Value::const_use_iterator UI = GV->use_begin(), E = GV->use_end();
856 if (const LoadInst *LI = dyn_cast<LoadInst>(U)) {
857 SmallPtrSet<const PHINode*, 8> PHIs;
858 if (!AllUsesOfValueWillTrapIfNull(LI, PHIs))
860 } else if (isa<StoreInst>(U)) {
861 // Ignore stores to the global.
863 // We don't know or understand this user, bail out.
864 //cerr << "UNKNOWN USER OF GLOBAL!: " << *U;
871 static bool OptimizeAwayTrappingUsesOfValue(Value *V, Constant *NewV) {
872 bool Changed = false;
873 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ) {
874 Instruction *I = cast<Instruction>(*UI++);
875 if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
876 LI->setOperand(0, NewV);
878 } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
879 if (SI->getOperand(1) == V) {
880 SI->setOperand(1, NewV);
883 } else if (isa<CallInst>(I) || isa<InvokeInst>(I)) {
885 if (CS.getCalledValue() == V) {
886 // Calling through the pointer! Turn into a direct call, but be careful
887 // that the pointer is not also being passed as an argument.
888 CS.setCalledFunction(NewV);
890 bool PassedAsArg = false;
891 for (unsigned i = 0, e = CS.arg_size(); i != e; ++i)
892 if (CS.getArgument(i) == V) {
894 CS.setArgument(i, NewV);
898 // Being passed as an argument also. Be careful to not invalidate UI!
902 } else if (CastInst *CI = dyn_cast<CastInst>(I)) {
903 Changed |= OptimizeAwayTrappingUsesOfValue(CI,
904 ConstantExpr::getCast(CI->getOpcode(),
905 NewV, CI->getType()));
906 if (CI->use_empty()) {
908 CI->eraseFromParent();
910 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I)) {
911 // Should handle GEP here.
912 SmallVector<Constant*, 8> Idxs;
913 Idxs.reserve(GEPI->getNumOperands()-1);
914 for (User::op_iterator i = GEPI->op_begin() + 1, e = GEPI->op_end();
916 if (Constant *C = dyn_cast<Constant>(*i))
920 if (Idxs.size() == GEPI->getNumOperands()-1)
921 Changed |= OptimizeAwayTrappingUsesOfValue(GEPI,
922 ConstantExpr::getGetElementPtr(NewV, Idxs));
923 if (GEPI->use_empty()) {
925 GEPI->eraseFromParent();
934 /// OptimizeAwayTrappingUsesOfLoads - The specified global has only one non-null
935 /// value stored into it. If there are uses of the loaded value that would trap
936 /// if the loaded value is dynamically null, then we know that they cannot be
937 /// reachable with a null optimize away the load.
938 static bool OptimizeAwayTrappingUsesOfLoads(GlobalVariable *GV, Constant *LV,
940 TargetLibraryInfo *TLI) {
941 bool Changed = false;
943 // Keep track of whether we are able to remove all the uses of the global
944 // other than the store that defines it.
945 bool AllNonStoreUsesGone = true;
947 // Replace all uses of loads with uses of uses of the stored value.
948 for (Value::use_iterator GUI = GV->use_begin(), E = GV->use_end(); GUI != E;){
949 User *GlobalUser = *GUI++;
950 if (LoadInst *LI = dyn_cast<LoadInst>(GlobalUser)) {
951 Changed |= OptimizeAwayTrappingUsesOfValue(LI, LV);
952 // If we were able to delete all uses of the loads
953 if (LI->use_empty()) {
954 LI->eraseFromParent();
957 AllNonStoreUsesGone = false;
959 } else if (isa<StoreInst>(GlobalUser)) {
960 // Ignore the store that stores "LV" to the global.
961 assert(GlobalUser->getOperand(1) == GV &&
962 "Must be storing *to* the global");
964 AllNonStoreUsesGone = false;
966 // If we get here we could have other crazy uses that are transitively
968 assert((isa<PHINode>(GlobalUser) || isa<SelectInst>(GlobalUser) ||
969 isa<ConstantExpr>(GlobalUser) || isa<CmpInst>(GlobalUser) ||
970 isa<BitCastInst>(GlobalUser) ||
971 isa<GetElementPtrInst>(GlobalUser)) &&
972 "Only expect load and stores!");
977 DEBUG(dbgs() << "OPTIMIZED LOADS FROM STORED ONCE POINTER: " << *GV);
981 // If we nuked all of the loads, then none of the stores are needed either,
982 // nor is the global.
983 if (AllNonStoreUsesGone) {
984 if (isLeakCheckerRoot(GV)) {
985 Changed |= CleanupPointerRootUsers(GV, TLI);
988 CleanupConstantGlobalUsers(GV, 0, TD, TLI);
990 if (GV->use_empty()) {
991 DEBUG(dbgs() << " *** GLOBAL NOW DEAD!\n");
993 GV->eraseFromParent();
1000 /// ConstantPropUsersOf - Walk the use list of V, constant folding all of the
1001 /// instructions that are foldable.
1002 static void ConstantPropUsersOf(Value *V,
1003 DataLayout *TD, TargetLibraryInfo *TLI) {
1004 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; )
1005 if (Instruction *I = dyn_cast<Instruction>(*UI++))
1006 if (Constant *NewC = ConstantFoldInstruction(I, TD, TLI)) {
1007 I->replaceAllUsesWith(NewC);
1009 // Advance UI to the next non-I use to avoid invalidating it!
1010 // Instructions could multiply use V.
1011 while (UI != E && *UI == I)
1013 I->eraseFromParent();
1017 /// OptimizeGlobalAddressOfMalloc - This function takes the specified global
1018 /// variable, and transforms the program as if it always contained the result of
1019 /// the specified malloc. Because it is always the result of the specified
1020 /// malloc, there is no reason to actually DO the malloc. Instead, turn the
1021 /// malloc into a global, and any loads of GV as uses of the new global.
1022 static GlobalVariable *OptimizeGlobalAddressOfMalloc(GlobalVariable *GV,
1025 ConstantInt *NElements,
1027 TargetLibraryInfo *TLI) {
1028 DEBUG(errs() << "PROMOTING GLOBAL: " << *GV << " CALL = " << *CI << '\n');
1031 if (NElements->getZExtValue() == 1)
1032 GlobalType = AllocTy;
1034 // If we have an array allocation, the global variable is of an array.
1035 GlobalType = ArrayType::get(AllocTy, NElements->getZExtValue());
1037 // Create the new global variable. The contents of the malloc'd memory is
1038 // undefined, so initialize with an undef value.
1039 GlobalVariable *NewGV = new GlobalVariable(*GV->getParent(),
1041 GlobalValue::InternalLinkage,
1042 UndefValue::get(GlobalType),
1043 GV->getName()+".body",
1045 GV->getThreadLocalMode());
1047 // If there are bitcast users of the malloc (which is typical, usually we have
1048 // a malloc + bitcast) then replace them with uses of the new global. Update
1049 // other users to use the global as well.
1050 BitCastInst *TheBC = 0;
1051 while (!CI->use_empty()) {
1052 Instruction *User = cast<Instruction>(CI->use_back());
1053 if (BitCastInst *BCI = dyn_cast<BitCastInst>(User)) {
1054 if (BCI->getType() == NewGV->getType()) {
1055 BCI->replaceAllUsesWith(NewGV);
1056 BCI->eraseFromParent();
1058 BCI->setOperand(0, NewGV);
1062 TheBC = new BitCastInst(NewGV, CI->getType(), "newgv", CI);
1063 User->replaceUsesOfWith(CI, TheBC);
1067 Constant *RepValue = NewGV;
1068 if (NewGV->getType() != GV->getType()->getElementType())
1069 RepValue = ConstantExpr::getBitCast(RepValue,
1070 GV->getType()->getElementType());
1072 // If there is a comparison against null, we will insert a global bool to
1073 // keep track of whether the global was initialized yet or not.
1074 GlobalVariable *InitBool =
1075 new GlobalVariable(Type::getInt1Ty(GV->getContext()), false,
1076 GlobalValue::InternalLinkage,
1077 ConstantInt::getFalse(GV->getContext()),
1078 GV->getName()+".init", GV->getThreadLocalMode());
1079 bool InitBoolUsed = false;
1081 // Loop over all uses of GV, processing them in turn.
1082 while (!GV->use_empty()) {
1083 if (StoreInst *SI = dyn_cast<StoreInst>(GV->use_back())) {
1084 // The global is initialized when the store to it occurs.
1085 new StoreInst(ConstantInt::getTrue(GV->getContext()), InitBool, false, 0,
1086 SI->getOrdering(), SI->getSynchScope(), SI);
1087 SI->eraseFromParent();
1091 LoadInst *LI = cast<LoadInst>(GV->use_back());
1092 while (!LI->use_empty()) {
1093 Use &LoadUse = LI->use_begin().getUse();
1094 if (!isa<ICmpInst>(LoadUse.getUser())) {
1099 ICmpInst *ICI = cast<ICmpInst>(LoadUse.getUser());
1100 // Replace the cmp X, 0 with a use of the bool value.
1101 // Sink the load to where the compare was, if atomic rules allow us to.
1102 Value *LV = new LoadInst(InitBool, InitBool->getName()+".val", false, 0,
1103 LI->getOrdering(), LI->getSynchScope(),
1104 LI->isUnordered() ? (Instruction*)ICI : LI);
1105 InitBoolUsed = true;
1106 switch (ICI->getPredicate()) {
1107 default: llvm_unreachable("Unknown ICmp Predicate!");
1108 case ICmpInst::ICMP_ULT:
1109 case ICmpInst::ICMP_SLT: // X < null -> always false
1110 LV = ConstantInt::getFalse(GV->getContext());
1112 case ICmpInst::ICMP_ULE:
1113 case ICmpInst::ICMP_SLE:
1114 case ICmpInst::ICMP_EQ:
1115 LV = BinaryOperator::CreateNot(LV, "notinit", ICI);
1117 case ICmpInst::ICMP_NE:
1118 case ICmpInst::ICMP_UGE:
1119 case ICmpInst::ICMP_SGE:
1120 case ICmpInst::ICMP_UGT:
1121 case ICmpInst::ICMP_SGT:
1122 break; // no change.
1124 ICI->replaceAllUsesWith(LV);
1125 ICI->eraseFromParent();
1127 LI->eraseFromParent();
1130 // If the initialization boolean was used, insert it, otherwise delete it.
1131 if (!InitBoolUsed) {
1132 while (!InitBool->use_empty()) // Delete initializations
1133 cast<StoreInst>(InitBool->use_back())->eraseFromParent();
1136 GV->getParent()->getGlobalList().insert(GV, InitBool);
1138 // Now the GV is dead, nuke it and the malloc..
1139 GV->eraseFromParent();
1140 CI->eraseFromParent();
1142 // To further other optimizations, loop over all users of NewGV and try to
1143 // constant prop them. This will promote GEP instructions with constant
1144 // indices into GEP constant-exprs, which will allow global-opt to hack on it.
1145 ConstantPropUsersOf(NewGV, TD, TLI);
1146 if (RepValue != NewGV)
1147 ConstantPropUsersOf(RepValue, TD, TLI);
1152 /// ValueIsOnlyUsedLocallyOrStoredToOneGlobal - Scan the use-list of V checking
1153 /// to make sure that there are no complex uses of V. We permit simple things
1154 /// like dereferencing the pointer, but not storing through the address, unless
1155 /// it is to the specified global.
1156 static bool ValueIsOnlyUsedLocallyOrStoredToOneGlobal(const Instruction *V,
1157 const GlobalVariable *GV,
1158 SmallPtrSet<const PHINode*, 8> &PHIs) {
1159 for (Value::const_use_iterator UI = V->use_begin(), E = V->use_end();
1161 const Instruction *Inst = cast<Instruction>(*UI);
1163 if (isa<LoadInst>(Inst) || isa<CmpInst>(Inst)) {
1164 continue; // Fine, ignore.
1167 if (const StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
1168 if (SI->getOperand(0) == V && SI->getOperand(1) != GV)
1169 return false; // Storing the pointer itself... bad.
1170 continue; // Otherwise, storing through it, or storing into GV... fine.
1173 // Must index into the array and into the struct.
1174 if (isa<GetElementPtrInst>(Inst) && Inst->getNumOperands() >= 3) {
1175 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(Inst, GV, PHIs))
1180 if (const PHINode *PN = dyn_cast<PHINode>(Inst)) {
1181 // PHIs are ok if all uses are ok. Don't infinitely recurse through PHI
1183 if (PHIs.insert(PN))
1184 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(PN, GV, PHIs))
1189 if (const BitCastInst *BCI = dyn_cast<BitCastInst>(Inst)) {
1190 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(BCI, GV, PHIs))
1200 /// ReplaceUsesOfMallocWithGlobal - The Alloc pointer is stored into GV
1201 /// somewhere. Transform all uses of the allocation into loads from the
1202 /// global and uses of the resultant pointer. Further, delete the store into
1203 /// GV. This assumes that these value pass the
1204 /// 'ValueIsOnlyUsedLocallyOrStoredToOneGlobal' predicate.
1205 static void ReplaceUsesOfMallocWithGlobal(Instruction *Alloc,
1206 GlobalVariable *GV) {
1207 while (!Alloc->use_empty()) {
1208 Instruction *U = cast<Instruction>(*Alloc->use_begin());
1209 Instruction *InsertPt = U;
1210 if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
1211 // If this is the store of the allocation into the global, remove it.
1212 if (SI->getOperand(1) == GV) {
1213 SI->eraseFromParent();
1216 } else if (PHINode *PN = dyn_cast<PHINode>(U)) {
1217 // Insert the load in the corresponding predecessor, not right before the
1219 InsertPt = PN->getIncomingBlock(Alloc->use_begin())->getTerminator();
1220 } else if (isa<BitCastInst>(U)) {
1221 // Must be bitcast between the malloc and store to initialize the global.
1222 ReplaceUsesOfMallocWithGlobal(U, GV);
1223 U->eraseFromParent();
1225 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(U)) {
1226 // If this is a "GEP bitcast" and the user is a store to the global, then
1227 // just process it as a bitcast.
1228 if (GEPI->hasAllZeroIndices() && GEPI->hasOneUse())
1229 if (StoreInst *SI = dyn_cast<StoreInst>(GEPI->use_back()))
1230 if (SI->getOperand(1) == GV) {
1231 // Must be bitcast GEP between the malloc and store to initialize
1233 ReplaceUsesOfMallocWithGlobal(GEPI, GV);
1234 GEPI->eraseFromParent();
1239 // Insert a load from the global, and use it instead of the malloc.
1240 Value *NL = new LoadInst(GV, GV->getName()+".val", InsertPt);
1241 U->replaceUsesOfWith(Alloc, NL);
1245 /// LoadUsesSimpleEnoughForHeapSRA - Verify that all uses of V (a load, or a phi
1246 /// of a load) are simple enough to perform heap SRA on. This permits GEP's
1247 /// that index through the array and struct field, icmps of null, and PHIs.
1248 static bool LoadUsesSimpleEnoughForHeapSRA(const Value *V,
1249 SmallPtrSet<const PHINode*, 32> &LoadUsingPHIs,
1250 SmallPtrSet<const PHINode*, 32> &LoadUsingPHIsPerLoad) {
1251 // We permit two users of the load: setcc comparing against the null
1252 // pointer, and a getelementptr of a specific form.
1253 for (Value::const_use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;
1255 const Instruction *User = cast<Instruction>(*UI);
1257 // Comparison against null is ok.
1258 if (const ICmpInst *ICI = dyn_cast<ICmpInst>(User)) {
1259 if (!isa<ConstantPointerNull>(ICI->getOperand(1)))
1264 // getelementptr is also ok, but only a simple form.
1265 if (const GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
1266 // Must index into the array and into the struct.
1267 if (GEPI->getNumOperands() < 3)
1270 // Otherwise the GEP is ok.
1274 if (const PHINode *PN = dyn_cast<PHINode>(User)) {
1275 if (!LoadUsingPHIsPerLoad.insert(PN))
1276 // This means some phi nodes are dependent on each other.
1277 // Avoid infinite looping!
1279 if (!LoadUsingPHIs.insert(PN))
1280 // If we have already analyzed this PHI, then it is safe.
1283 // Make sure all uses of the PHI are simple enough to transform.
1284 if (!LoadUsesSimpleEnoughForHeapSRA(PN,
1285 LoadUsingPHIs, LoadUsingPHIsPerLoad))
1291 // Otherwise we don't know what this is, not ok.
1299 /// AllGlobalLoadUsesSimpleEnoughForHeapSRA - If all users of values loaded from
1300 /// GV are simple enough to perform HeapSRA, return true.
1301 static bool AllGlobalLoadUsesSimpleEnoughForHeapSRA(const GlobalVariable *GV,
1302 Instruction *StoredVal) {
1303 SmallPtrSet<const PHINode*, 32> LoadUsingPHIs;
1304 SmallPtrSet<const PHINode*, 32> LoadUsingPHIsPerLoad;
1305 for (Value::const_use_iterator UI = GV->use_begin(), E = GV->use_end();
1307 if (const LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
1308 if (!LoadUsesSimpleEnoughForHeapSRA(LI, LoadUsingPHIs,
1309 LoadUsingPHIsPerLoad))
1311 LoadUsingPHIsPerLoad.clear();
1314 // If we reach here, we know that all uses of the loads and transitive uses
1315 // (through PHI nodes) are simple enough to transform. However, we don't know
1316 // that all inputs the to the PHI nodes are in the same equivalence sets.
1317 // Check to verify that all operands of the PHIs are either PHIS that can be
1318 // transformed, loads from GV, or MI itself.
1319 for (SmallPtrSet<const PHINode*, 32>::const_iterator I = LoadUsingPHIs.begin()
1320 , E = LoadUsingPHIs.end(); I != E; ++I) {
1321 const PHINode *PN = *I;
1322 for (unsigned op = 0, e = PN->getNumIncomingValues(); op != e; ++op) {
1323 Value *InVal = PN->getIncomingValue(op);
1325 // PHI of the stored value itself is ok.
1326 if (InVal == StoredVal) continue;
1328 if (const PHINode *InPN = dyn_cast<PHINode>(InVal)) {
1329 // One of the PHIs in our set is (optimistically) ok.
1330 if (LoadUsingPHIs.count(InPN))
1335 // Load from GV is ok.
1336 if (const LoadInst *LI = dyn_cast<LoadInst>(InVal))
1337 if (LI->getOperand(0) == GV)
1342 // Anything else is rejected.
1350 static Value *GetHeapSROAValue(Value *V, unsigned FieldNo,
1351 DenseMap<Value*, std::vector<Value*> > &InsertedScalarizedValues,
1352 std::vector<std::pair<PHINode*, unsigned> > &PHIsToRewrite) {
1353 std::vector<Value*> &FieldVals = InsertedScalarizedValues[V];
1355 if (FieldNo >= FieldVals.size())
1356 FieldVals.resize(FieldNo+1);
1358 // If we already have this value, just reuse the previously scalarized
1360 if (Value *FieldVal = FieldVals[FieldNo])
1363 // Depending on what instruction this is, we have several cases.
1365 if (LoadInst *LI = dyn_cast<LoadInst>(V)) {
1366 // This is a scalarized version of the load from the global. Just create
1367 // a new Load of the scalarized global.
1368 Result = new LoadInst(GetHeapSROAValue(LI->getOperand(0), FieldNo,
1369 InsertedScalarizedValues,
1371 LI->getName()+".f"+Twine(FieldNo), LI);
1372 } else if (PHINode *PN = dyn_cast<PHINode>(V)) {
1373 // PN's type is pointer to struct. Make a new PHI of pointer to struct
1376 cast<StructType>(cast<PointerType>(PN->getType())->getElementType());
1379 PHINode::Create(PointerType::getUnqual(ST->getElementType(FieldNo)),
1380 PN->getNumIncomingValues(),
1381 PN->getName()+".f"+Twine(FieldNo), PN);
1383 PHIsToRewrite.push_back(std::make_pair(PN, FieldNo));
1385 llvm_unreachable("Unknown usable value");
1388 return FieldVals[FieldNo] = Result;
1391 /// RewriteHeapSROALoadUser - Given a load instruction and a value derived from
1392 /// the load, rewrite the derived value to use the HeapSRoA'd load.
1393 static void RewriteHeapSROALoadUser(Instruction *LoadUser,
1394 DenseMap<Value*, std::vector<Value*> > &InsertedScalarizedValues,
1395 std::vector<std::pair<PHINode*, unsigned> > &PHIsToRewrite) {
1396 // If this is a comparison against null, handle it.
1397 if (ICmpInst *SCI = dyn_cast<ICmpInst>(LoadUser)) {
1398 assert(isa<ConstantPointerNull>(SCI->getOperand(1)));
1399 // If we have a setcc of the loaded pointer, we can use a setcc of any
1401 Value *NPtr = GetHeapSROAValue(SCI->getOperand(0), 0,
1402 InsertedScalarizedValues, PHIsToRewrite);
1404 Value *New = new ICmpInst(SCI, SCI->getPredicate(), NPtr,
1405 Constant::getNullValue(NPtr->getType()),
1407 SCI->replaceAllUsesWith(New);
1408 SCI->eraseFromParent();
1412 // Handle 'getelementptr Ptr, Idx, i32 FieldNo ...'
1413 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(LoadUser)) {
1414 assert(GEPI->getNumOperands() >= 3 && isa<ConstantInt>(GEPI->getOperand(2))
1415 && "Unexpected GEPI!");
1417 // Load the pointer for this field.
1418 unsigned FieldNo = cast<ConstantInt>(GEPI->getOperand(2))->getZExtValue();
1419 Value *NewPtr = GetHeapSROAValue(GEPI->getOperand(0), FieldNo,
1420 InsertedScalarizedValues, PHIsToRewrite);
1422 // Create the new GEP idx vector.
1423 SmallVector<Value*, 8> GEPIdx;
1424 GEPIdx.push_back(GEPI->getOperand(1));
1425 GEPIdx.append(GEPI->op_begin()+3, GEPI->op_end());
1427 Value *NGEPI = GetElementPtrInst::Create(NewPtr, GEPIdx,
1428 GEPI->getName(), GEPI);
1429 GEPI->replaceAllUsesWith(NGEPI);
1430 GEPI->eraseFromParent();
1434 // Recursively transform the users of PHI nodes. This will lazily create the
1435 // PHIs that are needed for individual elements. Keep track of what PHIs we
1436 // see in InsertedScalarizedValues so that we don't get infinite loops (very
1437 // antisocial). If the PHI is already in InsertedScalarizedValues, it has
1438 // already been seen first by another load, so its uses have already been
1440 PHINode *PN = cast<PHINode>(LoadUser);
1441 if (!InsertedScalarizedValues.insert(std::make_pair(PN,
1442 std::vector<Value*>())).second)
1445 // If this is the first time we've seen this PHI, recursively process all
1447 for (Value::use_iterator UI = PN->use_begin(), E = PN->use_end(); UI != E; ) {
1448 Instruction *User = cast<Instruction>(*UI++);
1449 RewriteHeapSROALoadUser(User, InsertedScalarizedValues, PHIsToRewrite);
1453 /// RewriteUsesOfLoadForHeapSRoA - We are performing Heap SRoA on a global. Ptr
1454 /// is a value loaded from the global. Eliminate all uses of Ptr, making them
1455 /// use FieldGlobals instead. All uses of loaded values satisfy
1456 /// AllGlobalLoadUsesSimpleEnoughForHeapSRA.
1457 static void RewriteUsesOfLoadForHeapSRoA(LoadInst *Load,
1458 DenseMap<Value*, std::vector<Value*> > &InsertedScalarizedValues,
1459 std::vector<std::pair<PHINode*, unsigned> > &PHIsToRewrite) {
1460 for (Value::use_iterator UI = Load->use_begin(), E = Load->use_end();
1462 Instruction *User = cast<Instruction>(*UI++);
1463 RewriteHeapSROALoadUser(User, InsertedScalarizedValues, PHIsToRewrite);
1466 if (Load->use_empty()) {
1467 Load->eraseFromParent();
1468 InsertedScalarizedValues.erase(Load);
1472 /// PerformHeapAllocSRoA - CI is an allocation of an array of structures. Break
1473 /// it up into multiple allocations of arrays of the fields.
1474 static GlobalVariable *PerformHeapAllocSRoA(GlobalVariable *GV, CallInst *CI,
1475 Value *NElems, DataLayout *TD,
1476 const TargetLibraryInfo *TLI) {
1477 DEBUG(dbgs() << "SROA HEAP ALLOC: " << *GV << " MALLOC = " << *CI << '\n');
1478 Type *MAT = getMallocAllocatedType(CI, TLI);
1479 StructType *STy = cast<StructType>(MAT);
1481 // There is guaranteed to be at least one use of the malloc (storing
1482 // it into GV). If there are other uses, change them to be uses of
1483 // the global to simplify later code. This also deletes the store
1485 ReplaceUsesOfMallocWithGlobal(CI, GV);
1487 // Okay, at this point, there are no users of the malloc. Insert N
1488 // new mallocs at the same place as CI, and N globals.
1489 std::vector<Value*> FieldGlobals;
1490 std::vector<Value*> FieldMallocs;
1492 for (unsigned FieldNo = 0, e = STy->getNumElements(); FieldNo != e;++FieldNo){
1493 Type *FieldTy = STy->getElementType(FieldNo);
1494 PointerType *PFieldTy = PointerType::getUnqual(FieldTy);
1496 GlobalVariable *NGV =
1497 new GlobalVariable(*GV->getParent(),
1498 PFieldTy, false, GlobalValue::InternalLinkage,
1499 Constant::getNullValue(PFieldTy),
1500 GV->getName() + ".f" + Twine(FieldNo), GV,
1501 GV->getThreadLocalMode());
1502 FieldGlobals.push_back(NGV);
1504 unsigned TypeSize = TD->getTypeAllocSize(FieldTy);
1505 if (StructType *ST = dyn_cast<StructType>(FieldTy))
1506 TypeSize = TD->getStructLayout(ST)->getSizeInBytes();
1507 Type *IntPtrTy = TD->getIntPtrType(CI->getContext());
1508 Value *NMI = CallInst::CreateMalloc(CI, IntPtrTy, FieldTy,
1509 ConstantInt::get(IntPtrTy, TypeSize),
1511 CI->getName() + ".f" + Twine(FieldNo));
1512 FieldMallocs.push_back(NMI);
1513 new StoreInst(NMI, NGV, CI);
1516 // The tricky aspect of this transformation is handling the case when malloc
1517 // fails. In the original code, malloc failing would set the result pointer
1518 // of malloc to null. In this case, some mallocs could succeed and others
1519 // could fail. As such, we emit code that looks like this:
1520 // F0 = malloc(field0)
1521 // F1 = malloc(field1)
1522 // F2 = malloc(field2)
1523 // if (F0 == 0 || F1 == 0 || F2 == 0) {
1524 // if (F0) { free(F0); F0 = 0; }
1525 // if (F1) { free(F1); F1 = 0; }
1526 // if (F2) { free(F2); F2 = 0; }
1528 // The malloc can also fail if its argument is too large.
1529 Constant *ConstantZero = ConstantInt::get(CI->getArgOperand(0)->getType(), 0);
1530 Value *RunningOr = new ICmpInst(CI, ICmpInst::ICMP_SLT, CI->getArgOperand(0),
1531 ConstantZero, "isneg");
1532 for (unsigned i = 0, e = FieldMallocs.size(); i != e; ++i) {
1533 Value *Cond = new ICmpInst(CI, ICmpInst::ICMP_EQ, FieldMallocs[i],
1534 Constant::getNullValue(FieldMallocs[i]->getType()),
1536 RunningOr = BinaryOperator::CreateOr(RunningOr, Cond, "tmp", CI);
1539 // Split the basic block at the old malloc.
1540 BasicBlock *OrigBB = CI->getParent();
1541 BasicBlock *ContBB = OrigBB->splitBasicBlock(CI, "malloc_cont");
1543 // Create the block to check the first condition. Put all these blocks at the
1544 // end of the function as they are unlikely to be executed.
1545 BasicBlock *NullPtrBlock = BasicBlock::Create(OrigBB->getContext(),
1547 OrigBB->getParent());
1549 // Remove the uncond branch from OrigBB to ContBB, turning it into a cond
1550 // branch on RunningOr.
1551 OrigBB->getTerminator()->eraseFromParent();
1552 BranchInst::Create(NullPtrBlock, ContBB, RunningOr, OrigBB);
1554 // Within the NullPtrBlock, we need to emit a comparison and branch for each
1555 // pointer, because some may be null while others are not.
1556 for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) {
1557 Value *GVVal = new LoadInst(FieldGlobals[i], "tmp", NullPtrBlock);
1558 Value *Cmp = new ICmpInst(*NullPtrBlock, ICmpInst::ICMP_NE, GVVal,
1559 Constant::getNullValue(GVVal->getType()));
1560 BasicBlock *FreeBlock = BasicBlock::Create(Cmp->getContext(), "free_it",
1561 OrigBB->getParent());
1562 BasicBlock *NextBlock = BasicBlock::Create(Cmp->getContext(), "next",
1563 OrigBB->getParent());
1564 Instruction *BI = BranchInst::Create(FreeBlock, NextBlock,
1567 // Fill in FreeBlock.
1568 CallInst::CreateFree(GVVal, BI);
1569 new StoreInst(Constant::getNullValue(GVVal->getType()), FieldGlobals[i],
1571 BranchInst::Create(NextBlock, FreeBlock);
1573 NullPtrBlock = NextBlock;
1576 BranchInst::Create(ContBB, NullPtrBlock);
1578 // CI is no longer needed, remove it.
1579 CI->eraseFromParent();
1581 /// InsertedScalarizedLoads - As we process loads, if we can't immediately
1582 /// update all uses of the load, keep track of what scalarized loads are
1583 /// inserted for a given load.
1584 DenseMap<Value*, std::vector<Value*> > InsertedScalarizedValues;
1585 InsertedScalarizedValues[GV] = FieldGlobals;
1587 std::vector<std::pair<PHINode*, unsigned> > PHIsToRewrite;
1589 // Okay, the malloc site is completely handled. All of the uses of GV are now
1590 // loads, and all uses of those loads are simple. Rewrite them to use loads
1591 // of the per-field globals instead.
1592 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); UI != E;) {
1593 Instruction *User = cast<Instruction>(*UI++);
1595 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1596 RewriteUsesOfLoadForHeapSRoA(LI, InsertedScalarizedValues, PHIsToRewrite);
1600 // Must be a store of null.
1601 StoreInst *SI = cast<StoreInst>(User);
1602 assert(isa<ConstantPointerNull>(SI->getOperand(0)) &&
1603 "Unexpected heap-sra user!");
1605 // Insert a store of null into each global.
1606 for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) {
1607 PointerType *PT = cast<PointerType>(FieldGlobals[i]->getType());
1608 Constant *Null = Constant::getNullValue(PT->getElementType());
1609 new StoreInst(Null, FieldGlobals[i], SI);
1611 // Erase the original store.
1612 SI->eraseFromParent();
1615 // While we have PHIs that are interesting to rewrite, do it.
1616 while (!PHIsToRewrite.empty()) {
1617 PHINode *PN = PHIsToRewrite.back().first;
1618 unsigned FieldNo = PHIsToRewrite.back().second;
1619 PHIsToRewrite.pop_back();
1620 PHINode *FieldPN = cast<PHINode>(InsertedScalarizedValues[PN][FieldNo]);
1621 assert(FieldPN->getNumIncomingValues() == 0 &&"Already processed this phi");
1623 // Add all the incoming values. This can materialize more phis.
1624 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
1625 Value *InVal = PN->getIncomingValue(i);
1626 InVal = GetHeapSROAValue(InVal, FieldNo, InsertedScalarizedValues,
1628 FieldPN->addIncoming(InVal, PN->getIncomingBlock(i));
1632 // Drop all inter-phi links and any loads that made it this far.
1633 for (DenseMap<Value*, std::vector<Value*> >::iterator
1634 I = InsertedScalarizedValues.begin(), E = InsertedScalarizedValues.end();
1636 if (PHINode *PN = dyn_cast<PHINode>(I->first))
1637 PN->dropAllReferences();
1638 else if (LoadInst *LI = dyn_cast<LoadInst>(I->first))
1639 LI->dropAllReferences();
1642 // Delete all the phis and loads now that inter-references are dead.
1643 for (DenseMap<Value*, std::vector<Value*> >::iterator
1644 I = InsertedScalarizedValues.begin(), E = InsertedScalarizedValues.end();
1646 if (PHINode *PN = dyn_cast<PHINode>(I->first))
1647 PN->eraseFromParent();
1648 else if (LoadInst *LI = dyn_cast<LoadInst>(I->first))
1649 LI->eraseFromParent();
1652 // The old global is now dead, remove it.
1653 GV->eraseFromParent();
1656 return cast<GlobalVariable>(FieldGlobals[0]);
1659 /// TryToOptimizeStoreOfMallocToGlobal - This function is called when we see a
1660 /// pointer global variable with a single value stored it that is a malloc or
1662 static bool TryToOptimizeStoreOfMallocToGlobal(GlobalVariable *GV,
1665 AtomicOrdering Ordering,
1666 Module::global_iterator &GVI,
1668 TargetLibraryInfo *TLI) {
1672 // If this is a malloc of an abstract type, don't touch it.
1673 if (!AllocTy->isSized())
1676 // We can't optimize this global unless all uses of it are *known* to be
1677 // of the malloc value, not of the null initializer value (consider a use
1678 // that compares the global's value against zero to see if the malloc has
1679 // been reached). To do this, we check to see if all uses of the global
1680 // would trap if the global were null: this proves that they must all
1681 // happen after the malloc.
1682 if (!AllUsesOfLoadedValueWillTrapIfNull(GV))
1685 // We can't optimize this if the malloc itself is used in a complex way,
1686 // for example, being stored into multiple globals. This allows the
1687 // malloc to be stored into the specified global, loaded icmp'd, and
1688 // GEP'd. These are all things we could transform to using the global
1690 SmallPtrSet<const PHINode*, 8> PHIs;
1691 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(CI, GV, PHIs))
1694 // If we have a global that is only initialized with a fixed size malloc,
1695 // transform the program to use global memory instead of malloc'd memory.
1696 // This eliminates dynamic allocation, avoids an indirection accessing the
1697 // data, and exposes the resultant global to further GlobalOpt.
1698 // We cannot optimize the malloc if we cannot determine malloc array size.
1699 Value *NElems = getMallocArraySize(CI, TD, TLI, true);
1703 if (ConstantInt *NElements = dyn_cast<ConstantInt>(NElems))
1704 // Restrict this transformation to only working on small allocations
1705 // (2048 bytes currently), as we don't want to introduce a 16M global or
1707 if (NElements->getZExtValue() * TD->getTypeAllocSize(AllocTy) < 2048) {
1708 GVI = OptimizeGlobalAddressOfMalloc(GV, CI, AllocTy, NElements, TD, TLI);
1712 // If the allocation is an array of structures, consider transforming this
1713 // into multiple malloc'd arrays, one for each field. This is basically
1714 // SRoA for malloc'd memory.
1716 if (Ordering != NotAtomic)
1719 // If this is an allocation of a fixed size array of structs, analyze as a
1720 // variable size array. malloc [100 x struct],1 -> malloc struct, 100
1721 if (NElems == ConstantInt::get(CI->getArgOperand(0)->getType(), 1))
1722 if (ArrayType *AT = dyn_cast<ArrayType>(AllocTy))
1723 AllocTy = AT->getElementType();
1725 StructType *AllocSTy = dyn_cast<StructType>(AllocTy);
1729 // This the structure has an unreasonable number of fields, leave it
1731 if (AllocSTy->getNumElements() <= 16 && AllocSTy->getNumElements() != 0 &&
1732 AllGlobalLoadUsesSimpleEnoughForHeapSRA(GV, CI)) {
1734 // If this is a fixed size array, transform the Malloc to be an alloc of
1735 // structs. malloc [100 x struct],1 -> malloc struct, 100
1736 if (ArrayType *AT = dyn_cast<ArrayType>(getMallocAllocatedType(CI, TLI))) {
1737 Type *IntPtrTy = TD->getIntPtrType(CI->getContext());
1738 unsigned TypeSize = TD->getStructLayout(AllocSTy)->getSizeInBytes();
1739 Value *AllocSize = ConstantInt::get(IntPtrTy, TypeSize);
1740 Value *NumElements = ConstantInt::get(IntPtrTy, AT->getNumElements());
1741 Instruction *Malloc = CallInst::CreateMalloc(CI, IntPtrTy, AllocSTy,
1742 AllocSize, NumElements,
1744 Instruction *Cast = new BitCastInst(Malloc, CI->getType(), "tmp", CI);
1745 CI->replaceAllUsesWith(Cast);
1746 CI->eraseFromParent();
1747 if (BitCastInst *BCI = dyn_cast<BitCastInst>(Malloc))
1748 CI = cast<CallInst>(BCI->getOperand(0));
1750 CI = cast<CallInst>(Malloc);
1753 GVI = PerformHeapAllocSRoA(GV, CI, getMallocArraySize(CI, TD, TLI, true),
1761 // OptimizeOnceStoredGlobal - Try to optimize globals based on the knowledge
1762 // that only one value (besides its initializer) is ever stored to the global.
1763 static bool OptimizeOnceStoredGlobal(GlobalVariable *GV, Value *StoredOnceVal,
1764 AtomicOrdering Ordering,
1765 Module::global_iterator &GVI,
1766 DataLayout *TD, TargetLibraryInfo *TLI) {
1767 // Ignore no-op GEPs and bitcasts.
1768 StoredOnceVal = StoredOnceVal->stripPointerCasts();
1770 // If we are dealing with a pointer global that is initialized to null and
1771 // only has one (non-null) value stored into it, then we can optimize any
1772 // users of the loaded value (often calls and loads) that would trap if the
1774 if (GV->getInitializer()->getType()->isPointerTy() &&
1775 GV->getInitializer()->isNullValue()) {
1776 if (Constant *SOVC = dyn_cast<Constant>(StoredOnceVal)) {
1777 if (GV->getInitializer()->getType() != SOVC->getType())
1778 SOVC = ConstantExpr::getBitCast(SOVC, GV->getInitializer()->getType());
1780 // Optimize away any trapping uses of the loaded value.
1781 if (OptimizeAwayTrappingUsesOfLoads(GV, SOVC, TD, TLI))
1783 } else if (CallInst *CI = extractMallocCall(StoredOnceVal, TLI)) {
1784 Type *MallocType = getMallocAllocatedType(CI, TLI);
1786 TryToOptimizeStoreOfMallocToGlobal(GV, CI, MallocType, Ordering, GVI,
1795 /// TryToShrinkGlobalToBoolean - At this point, we have learned that the only
1796 /// two values ever stored into GV are its initializer and OtherVal. See if we
1797 /// can shrink the global into a boolean and select between the two values
1798 /// whenever it is used. This exposes the values to other scalar optimizations.
1799 static bool TryToShrinkGlobalToBoolean(GlobalVariable *GV, Constant *OtherVal) {
1800 Type *GVElType = GV->getType()->getElementType();
1802 // If GVElType is already i1, it is already shrunk. If the type of the GV is
1803 // an FP value, pointer or vector, don't do this optimization because a select
1804 // between them is very expensive and unlikely to lead to later
1805 // simplification. In these cases, we typically end up with "cond ? v1 : v2"
1806 // where v1 and v2 both require constant pool loads, a big loss.
1807 if (GVElType == Type::getInt1Ty(GV->getContext()) ||
1808 GVElType->isFloatingPointTy() ||
1809 GVElType->isPointerTy() || GVElType->isVectorTy())
1812 // Walk the use list of the global seeing if all the uses are load or store.
1813 // If there is anything else, bail out.
1814 for (Value::use_iterator I = GV->use_begin(), E = GV->use_end(); I != E; ++I){
1816 if (!isa<LoadInst>(U) && !isa<StoreInst>(U))
1820 DEBUG(dbgs() << " *** SHRINKING TO BOOL: " << *GV);
1822 // Create the new global, initializing it to false.
1823 GlobalVariable *NewGV = new GlobalVariable(Type::getInt1Ty(GV->getContext()),
1825 GlobalValue::InternalLinkage,
1826 ConstantInt::getFalse(GV->getContext()),
1828 GV->getThreadLocalMode(),
1829 GV->getType()->getAddressSpace());
1830 GV->getParent()->getGlobalList().insert(GV, NewGV);
1832 Constant *InitVal = GV->getInitializer();
1833 assert(InitVal->getType() != Type::getInt1Ty(GV->getContext()) &&
1834 "No reason to shrink to bool!");
1836 // If initialized to zero and storing one into the global, we can use a cast
1837 // instead of a select to synthesize the desired value.
1838 bool IsOneZero = false;
1839 if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal))
1840 IsOneZero = InitVal->isNullValue() && CI->isOne();
1842 while (!GV->use_empty()) {
1843 Instruction *UI = cast<Instruction>(GV->use_back());
1844 if (StoreInst *SI = dyn_cast<StoreInst>(UI)) {
1845 // Change the store into a boolean store.
1846 bool StoringOther = SI->getOperand(0) == OtherVal;
1847 // Only do this if we weren't storing a loaded value.
1849 if (StoringOther || SI->getOperand(0) == InitVal) {
1850 StoreVal = ConstantInt::get(Type::getInt1Ty(GV->getContext()),
1853 // Otherwise, we are storing a previously loaded copy. To do this,
1854 // change the copy from copying the original value to just copying the
1856 Instruction *StoredVal = cast<Instruction>(SI->getOperand(0));
1858 // If we've already replaced the input, StoredVal will be a cast or
1859 // select instruction. If not, it will be a load of the original
1861 if (LoadInst *LI = dyn_cast<LoadInst>(StoredVal)) {
1862 assert(LI->getOperand(0) == GV && "Not a copy!");
1863 // Insert a new load, to preserve the saved value.
1864 StoreVal = new LoadInst(NewGV, LI->getName()+".b", false, 0,
1865 LI->getOrdering(), LI->getSynchScope(), LI);
1867 assert((isa<CastInst>(StoredVal) || isa<SelectInst>(StoredVal)) &&
1868 "This is not a form that we understand!");
1869 StoreVal = StoredVal->getOperand(0);
1870 assert(isa<LoadInst>(StoreVal) && "Not a load of NewGV!");
1873 new StoreInst(StoreVal, NewGV, false, 0,
1874 SI->getOrdering(), SI->getSynchScope(), SI);
1876 // Change the load into a load of bool then a select.
1877 LoadInst *LI = cast<LoadInst>(UI);
1878 LoadInst *NLI = new LoadInst(NewGV, LI->getName()+".b", false, 0,
1879 LI->getOrdering(), LI->getSynchScope(), LI);
1882 NSI = new ZExtInst(NLI, LI->getType(), "", LI);
1884 NSI = SelectInst::Create(NLI, OtherVal, InitVal, "", LI);
1886 LI->replaceAllUsesWith(NSI);
1888 UI->eraseFromParent();
1891 // Retain the name of the old global variable. People who are debugging their
1892 // programs may expect these variables to be named the same.
1893 NewGV->takeName(GV);
1894 GV->eraseFromParent();
1899 /// ProcessGlobal - Analyze the specified global variable and optimize it if
1900 /// possible. If we make a change, return true.
1901 bool GlobalOpt::ProcessGlobal(GlobalVariable *GV,
1902 Module::global_iterator &GVI) {
1903 if (!GV->isDiscardableIfUnused())
1906 // Do more involved optimizations if the global is internal.
1907 GV->removeDeadConstantUsers();
1909 if (GV->use_empty()) {
1910 DEBUG(dbgs() << "GLOBAL DEAD: " << *GV);
1911 GV->eraseFromParent();
1916 if (!GV->hasLocalLinkage())
1919 SmallPtrSet<const PHINode*, 16> PHIUsers;
1922 if (AnalyzeGlobal(GV, GS, PHIUsers))
1925 if (!GS.isCompared && !GV->hasUnnamedAddr()) {
1926 GV->setUnnamedAddr(true);
1930 if (GV->isConstant() || !GV->hasInitializer())
1933 return ProcessInternalGlobal(GV, GVI, PHIUsers, GS);
1936 /// ProcessInternalGlobal - Analyze the specified global variable and optimize
1937 /// it if possible. If we make a change, return true.
1938 bool GlobalOpt::ProcessInternalGlobal(GlobalVariable *GV,
1939 Module::global_iterator &GVI,
1940 const SmallPtrSet<const PHINode*, 16> &PHIUsers,
1941 const GlobalStatus &GS) {
1942 // If this is a first class global and has only one accessing function
1943 // and this function is main (which we know is not recursive), we replace
1944 // the global with a local alloca in this function.
1946 // NOTE: It doesn't make sense to promote non single-value types since we
1947 // are just replacing static memory to stack memory.
1949 // If the global is in different address space, don't bring it to stack.
1950 if (!GS.HasMultipleAccessingFunctions &&
1951 GS.AccessingFunction && !GS.HasNonInstructionUser &&
1952 GV->getType()->getElementType()->isSingleValueType() &&
1953 GS.AccessingFunction->getName() == "main" &&
1954 GS.AccessingFunction->hasExternalLinkage() &&
1955 GV->getType()->getAddressSpace() == 0) {
1956 DEBUG(dbgs() << "LOCALIZING GLOBAL: " << *GV);
1957 Instruction &FirstI = const_cast<Instruction&>(*GS.AccessingFunction
1958 ->getEntryBlock().begin());
1959 Type *ElemTy = GV->getType()->getElementType();
1960 // FIXME: Pass Global's alignment when globals have alignment
1961 AllocaInst *Alloca = new AllocaInst(ElemTy, NULL, GV->getName(), &FirstI);
1962 if (!isa<UndefValue>(GV->getInitializer()))
1963 new StoreInst(GV->getInitializer(), Alloca, &FirstI);
1965 GV->replaceAllUsesWith(Alloca);
1966 GV->eraseFromParent();
1971 // If the global is never loaded (but may be stored to), it is dead.
1974 DEBUG(dbgs() << "GLOBAL NEVER LOADED: " << *GV);
1977 if (isLeakCheckerRoot(GV)) {
1978 // Delete any constant stores to the global.
1979 Changed = CleanupPointerRootUsers(GV, TLI);
1981 // Delete any stores we can find to the global. We may not be able to
1982 // make it completely dead though.
1983 Changed = CleanupConstantGlobalUsers(GV, GV->getInitializer(), TD, TLI);
1986 // If the global is dead now, delete it.
1987 if (GV->use_empty()) {
1988 GV->eraseFromParent();
1994 } else if (GS.StoredType <= GlobalStatus::isInitializerStored) {
1995 DEBUG(dbgs() << "MARKING CONSTANT: " << *GV << "\n");
1996 GV->setConstant(true);
1998 // Clean up any obviously simplifiable users now.
1999 CleanupConstantGlobalUsers(GV, GV->getInitializer(), TD, TLI);
2001 // If the global is dead now, just nuke it.
2002 if (GV->use_empty()) {
2003 DEBUG(dbgs() << " *** Marking constant allowed us to simplify "
2004 << "all users and delete global!\n");
2005 GV->eraseFromParent();
2011 } else if (!GV->getInitializer()->getType()->isSingleValueType()) {
2012 if (DataLayout *TD = getAnalysisIfAvailable<DataLayout>())
2013 if (GlobalVariable *FirstNewGV = SRAGlobal(GV, *TD)) {
2014 GVI = FirstNewGV; // Don't skip the newly produced globals!
2017 } else if (GS.StoredType == GlobalStatus::isStoredOnce) {
2018 // If the initial value for the global was an undef value, and if only
2019 // one other value was stored into it, we can just change the
2020 // initializer to be the stored value, then delete all stores to the
2021 // global. This allows us to mark it constant.
2022 if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue))
2023 if (isa<UndefValue>(GV->getInitializer())) {
2024 // Change the initial value here.
2025 GV->setInitializer(SOVConstant);
2027 // Clean up any obviously simplifiable users now.
2028 CleanupConstantGlobalUsers(GV, GV->getInitializer(), TD, TLI);
2030 if (GV->use_empty()) {
2031 DEBUG(dbgs() << " *** Substituting initializer allowed us to "
2032 << "simplify all users and delete global!\n");
2033 GV->eraseFromParent();
2042 // Try to optimize globals based on the knowledge that only one value
2043 // (besides its initializer) is ever stored to the global.
2044 if (OptimizeOnceStoredGlobal(GV, GS.StoredOnceValue, GS.Ordering, GVI,
2048 // Otherwise, if the global was not a boolean, we can shrink it to be a
2050 if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue))
2051 if (TryToShrinkGlobalToBoolean(GV, SOVConstant)) {
2060 /// ChangeCalleesToFastCall - Walk all of the direct calls of the specified
2061 /// function, changing them to FastCC.
2062 static void ChangeCalleesToFastCall(Function *F) {
2063 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){
2064 if (isa<BlockAddress>(*UI))
2066 CallSite User(cast<Instruction>(*UI));
2067 User.setCallingConv(CallingConv::Fast);
2071 static AttributeSet StripNest(LLVMContext &C, const AttributeSet &Attrs) {
2072 for (unsigned i = 0, e = Attrs.getNumSlots(); i != e; ++i) {
2073 unsigned Index = Attrs.getSlotIndex(i);
2074 if (!Attrs.getSlotAttributes(i).hasAttribute(Index, Attribute::Nest))
2077 // There can be only one.
2078 return Attrs.removeAttribute(C, Index, Attribute::Nest);
2084 static void RemoveNestAttribute(Function *F) {
2085 F->setAttributes(StripNest(F->getContext(), F->getAttributes()));
2086 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){
2087 if (isa<BlockAddress>(*UI))
2089 CallSite User(cast<Instruction>(*UI));
2090 User.setAttributes(StripNest(F->getContext(), User.getAttributes()));
2094 bool GlobalOpt::OptimizeFunctions(Module &M) {
2095 bool Changed = false;
2096 // Optimize functions.
2097 for (Module::iterator FI = M.begin(), E = M.end(); FI != E; ) {
2099 // Functions without names cannot be referenced outside this module.
2100 if (!F->hasName() && !F->isDeclaration())
2101 F->setLinkage(GlobalValue::InternalLinkage);
2102 F->removeDeadConstantUsers();
2103 if (F->isDefTriviallyDead()) {
2104 F->eraseFromParent();
2107 } else if (F->hasLocalLinkage()) {
2108 if (F->getCallingConv() == CallingConv::C && !F->isVarArg() &&
2109 !F->hasAddressTaken()) {
2110 // If this function has C calling conventions, is not a varargs
2111 // function, and is only called directly, promote it to use the Fast
2112 // calling convention.
2113 F->setCallingConv(CallingConv::Fast);
2114 ChangeCalleesToFastCall(F);
2119 if (F->getAttributes().hasAttrSomewhere(Attribute::Nest) &&
2120 !F->hasAddressTaken()) {
2121 // The function is not used by a trampoline intrinsic, so it is safe
2122 // to remove the 'nest' attribute.
2123 RemoveNestAttribute(F);
2132 bool GlobalOpt::OptimizeGlobalVars(Module &M) {
2133 bool Changed = false;
2134 for (Module::global_iterator GVI = M.global_begin(), E = M.global_end();
2136 GlobalVariable *GV = GVI++;
2137 // Global variables without names cannot be referenced outside this module.
2138 if (!GV->hasName() && !GV->isDeclaration())
2139 GV->setLinkage(GlobalValue::InternalLinkage);
2140 // Simplify the initializer.
2141 if (GV->hasInitializer())
2142 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GV->getInitializer())) {
2143 Constant *New = ConstantFoldConstantExpression(CE, TD, TLI);
2144 if (New && New != CE)
2145 GV->setInitializer(New);
2148 Changed |= ProcessGlobal(GV, GVI);
2153 /// FindGlobalCtors - Find the llvm.global_ctors list, verifying that all
2154 /// initializers have an init priority of 65535.
2155 GlobalVariable *GlobalOpt::FindGlobalCtors(Module &M) {
2156 GlobalVariable *GV = M.getGlobalVariable("llvm.global_ctors");
2157 if (GV == 0) return 0;
2159 // Verify that the initializer is simple enough for us to handle. We are
2160 // only allowed to optimize the initializer if it is unique.
2161 if (!GV->hasUniqueInitializer()) return 0;
2163 if (isa<ConstantAggregateZero>(GV->getInitializer()))
2165 ConstantArray *CA = cast<ConstantArray>(GV->getInitializer());
2167 for (User::op_iterator i = CA->op_begin(), e = CA->op_end(); i != e; ++i) {
2168 if (isa<ConstantAggregateZero>(*i))
2170 ConstantStruct *CS = cast<ConstantStruct>(*i);
2171 if (isa<ConstantPointerNull>(CS->getOperand(1)))
2174 // Must have a function or null ptr.
2175 if (!isa<Function>(CS->getOperand(1)))
2178 // Init priority must be standard.
2179 ConstantInt *CI = cast<ConstantInt>(CS->getOperand(0));
2180 if (CI->getZExtValue() != 65535)
2187 /// ParseGlobalCtors - Given a llvm.global_ctors list that we can understand,
2188 /// return a list of the functions and null terminator as a vector.
2189 static std::vector<Function*> ParseGlobalCtors(GlobalVariable *GV) {
2190 if (GV->getInitializer()->isNullValue())
2191 return std::vector<Function*>();
2192 ConstantArray *CA = cast<ConstantArray>(GV->getInitializer());
2193 std::vector<Function*> Result;
2194 Result.reserve(CA->getNumOperands());
2195 for (User::op_iterator i = CA->op_begin(), e = CA->op_end(); i != e; ++i) {
2196 ConstantStruct *CS = cast<ConstantStruct>(*i);
2197 Result.push_back(dyn_cast<Function>(CS->getOperand(1)));
2202 /// InstallGlobalCtors - Given a specified llvm.global_ctors list, install the
2203 /// specified array, returning the new global to use.
2204 static GlobalVariable *InstallGlobalCtors(GlobalVariable *GCL,
2205 const std::vector<Function*> &Ctors) {
2206 // If we made a change, reassemble the initializer list.
2207 Constant *CSVals[2];
2208 CSVals[0] = ConstantInt::get(Type::getInt32Ty(GCL->getContext()), 65535);
2211 StructType *StructTy =
2213 cast<ArrayType>(GCL->getType()->getElementType())->getElementType());
2215 // Create the new init list.
2216 std::vector<Constant*> CAList;
2217 for (unsigned i = 0, e = Ctors.size(); i != e; ++i) {
2219 CSVals[1] = Ctors[i];
2221 Type *FTy = FunctionType::get(Type::getVoidTy(GCL->getContext()),
2223 PointerType *PFTy = PointerType::getUnqual(FTy);
2224 CSVals[1] = Constant::getNullValue(PFTy);
2225 CSVals[0] = ConstantInt::get(Type::getInt32Ty(GCL->getContext()),
2228 CAList.push_back(ConstantStruct::get(StructTy, CSVals));
2231 // Create the array initializer.
2232 Constant *CA = ConstantArray::get(ArrayType::get(StructTy,
2233 CAList.size()), CAList);
2235 // If we didn't change the number of elements, don't create a new GV.
2236 if (CA->getType() == GCL->getInitializer()->getType()) {
2237 GCL->setInitializer(CA);
2241 // Create the new global and insert it next to the existing list.
2242 GlobalVariable *NGV = new GlobalVariable(CA->getType(), GCL->isConstant(),
2243 GCL->getLinkage(), CA, "",
2244 GCL->getThreadLocalMode());
2245 GCL->getParent()->getGlobalList().insert(GCL, NGV);
2248 // Nuke the old list, replacing any uses with the new one.
2249 if (!GCL->use_empty()) {
2251 if (V->getType() != GCL->getType())
2252 V = ConstantExpr::getBitCast(V, GCL->getType());
2253 GCL->replaceAllUsesWith(V);
2255 GCL->eraseFromParent();
2265 isSimpleEnoughValueToCommit(Constant *C,
2266 SmallPtrSet<Constant*, 8> &SimpleConstants,
2267 const DataLayout *TD);
2270 /// isSimpleEnoughValueToCommit - Return true if the specified constant can be
2271 /// handled by the code generator. We don't want to generate something like:
2272 /// void *X = &X/42;
2273 /// because the code generator doesn't have a relocation that can handle that.
2275 /// This function should be called if C was not found (but just got inserted)
2276 /// in SimpleConstants to avoid having to rescan the same constants all the
2278 static bool isSimpleEnoughValueToCommitHelper(Constant *C,
2279 SmallPtrSet<Constant*, 8> &SimpleConstants,
2280 const DataLayout *TD) {
2281 // Simple integer, undef, constant aggregate zero, global addresses, etc are
2283 if (C->getNumOperands() == 0 || isa<BlockAddress>(C) ||
2284 isa<GlobalValue>(C))
2287 // Aggregate values are safe if all their elements are.
2288 if (isa<ConstantArray>(C) || isa<ConstantStruct>(C) ||
2289 isa<ConstantVector>(C)) {
2290 for (unsigned i = 0, e = C->getNumOperands(); i != e; ++i) {
2291 Constant *Op = cast<Constant>(C->getOperand(i));
2292 if (!isSimpleEnoughValueToCommit(Op, SimpleConstants, TD))
2298 // We don't know exactly what relocations are allowed in constant expressions,
2299 // so we allow &global+constantoffset, which is safe and uniformly supported
2301 ConstantExpr *CE = cast<ConstantExpr>(C);
2302 switch (CE->getOpcode()) {
2303 case Instruction::BitCast:
2304 // Bitcast is fine if the casted value is fine.
2305 return isSimpleEnoughValueToCommit(CE->getOperand(0), SimpleConstants, TD);
2307 case Instruction::IntToPtr:
2308 case Instruction::PtrToInt:
2309 // int <=> ptr is fine if the int type is the same size as the
2311 if (!TD || TD->getTypeSizeInBits(CE->getType()) !=
2312 TD->getTypeSizeInBits(CE->getOperand(0)->getType()))
2314 return isSimpleEnoughValueToCommit(CE->getOperand(0), SimpleConstants, TD);
2316 // GEP is fine if it is simple + constant offset.
2317 case Instruction::GetElementPtr:
2318 for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i)
2319 if (!isa<ConstantInt>(CE->getOperand(i)))
2321 return isSimpleEnoughValueToCommit(CE->getOperand(0), SimpleConstants, TD);
2323 case Instruction::Add:
2324 // We allow simple+cst.
2325 if (!isa<ConstantInt>(CE->getOperand(1)))
2327 return isSimpleEnoughValueToCommit(CE->getOperand(0), SimpleConstants, TD);
2333 isSimpleEnoughValueToCommit(Constant *C,
2334 SmallPtrSet<Constant*, 8> &SimpleConstants,
2335 const DataLayout *TD) {
2336 // If we already checked this constant, we win.
2337 if (!SimpleConstants.insert(C)) return true;
2338 // Check the constant.
2339 return isSimpleEnoughValueToCommitHelper(C, SimpleConstants, TD);
2343 /// isSimpleEnoughPointerToCommit - Return true if this constant is simple
2344 /// enough for us to understand. In particular, if it is a cast to anything
2345 /// other than from one pointer type to another pointer type, we punt.
2346 /// We basically just support direct accesses to globals and GEP's of
2347 /// globals. This should be kept up to date with CommitValueTo.
2348 static bool isSimpleEnoughPointerToCommit(Constant *C) {
2349 // Conservatively, avoid aggregate types. This is because we don't
2350 // want to worry about them partially overlapping other stores.
2351 if (!cast<PointerType>(C->getType())->getElementType()->isSingleValueType())
2354 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C))
2355 // Do not allow weak/*_odr/linkonce/dllimport/dllexport linkage or
2356 // external globals.
2357 return GV->hasUniqueInitializer();
2359 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) {
2360 // Handle a constantexpr gep.
2361 if (CE->getOpcode() == Instruction::GetElementPtr &&
2362 isa<GlobalVariable>(CE->getOperand(0)) &&
2363 cast<GEPOperator>(CE)->isInBounds()) {
2364 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
2365 // Do not allow weak/*_odr/linkonce/dllimport/dllexport linkage or
2366 // external globals.
2367 if (!GV->hasUniqueInitializer())
2370 // The first index must be zero.
2371 ConstantInt *CI = dyn_cast<ConstantInt>(*llvm::next(CE->op_begin()));
2372 if (!CI || !CI->isZero()) return false;
2374 // The remaining indices must be compile-time known integers within the
2375 // notional bounds of the corresponding static array types.
2376 if (!CE->isGEPWithNoNotionalOverIndexing())
2379 return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE);
2381 // A constantexpr bitcast from a pointer to another pointer is a no-op,
2382 // and we know how to evaluate it by moving the bitcast from the pointer
2383 // operand to the value operand.
2384 } else if (CE->getOpcode() == Instruction::BitCast &&
2385 isa<GlobalVariable>(CE->getOperand(0))) {
2386 // Do not allow weak/*_odr/linkonce/dllimport/dllexport linkage or
2387 // external globals.
2388 return cast<GlobalVariable>(CE->getOperand(0))->hasUniqueInitializer();
2395 /// EvaluateStoreInto - Evaluate a piece of a constantexpr store into a global
2396 /// initializer. This returns 'Init' modified to reflect 'Val' stored into it.
2397 /// At this point, the GEP operands of Addr [0, OpNo) have been stepped into.
2398 static Constant *EvaluateStoreInto(Constant *Init, Constant *Val,
2399 ConstantExpr *Addr, unsigned OpNo) {
2400 // Base case of the recursion.
2401 if (OpNo == Addr->getNumOperands()) {
2402 assert(Val->getType() == Init->getType() && "Type mismatch!");
2406 SmallVector<Constant*, 32> Elts;
2407 if (StructType *STy = dyn_cast<StructType>(Init->getType())) {
2408 // Break up the constant into its elements.
2409 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
2410 Elts.push_back(Init->getAggregateElement(i));
2412 // Replace the element that we are supposed to.
2413 ConstantInt *CU = cast<ConstantInt>(Addr->getOperand(OpNo));
2414 unsigned Idx = CU->getZExtValue();
2415 assert(Idx < STy->getNumElements() && "Struct index out of range!");
2416 Elts[Idx] = EvaluateStoreInto(Elts[Idx], Val, Addr, OpNo+1);
2418 // Return the modified struct.
2419 return ConstantStruct::get(STy, Elts);
2422 ConstantInt *CI = cast<ConstantInt>(Addr->getOperand(OpNo));
2423 SequentialType *InitTy = cast<SequentialType>(Init->getType());
2426 if (ArrayType *ATy = dyn_cast<ArrayType>(InitTy))
2427 NumElts = ATy->getNumElements();
2429 NumElts = InitTy->getVectorNumElements();
2431 // Break up the array into elements.
2432 for (uint64_t i = 0, e = NumElts; i != e; ++i)
2433 Elts.push_back(Init->getAggregateElement(i));
2435 assert(CI->getZExtValue() < NumElts);
2436 Elts[CI->getZExtValue()] =
2437 EvaluateStoreInto(Elts[CI->getZExtValue()], Val, Addr, OpNo+1);
2439 if (Init->getType()->isArrayTy())
2440 return ConstantArray::get(cast<ArrayType>(InitTy), Elts);
2441 return ConstantVector::get(Elts);
2444 /// CommitValueTo - We have decided that Addr (which satisfies the predicate
2445 /// isSimpleEnoughPointerToCommit) should get Val as its value. Make it happen.
2446 static void CommitValueTo(Constant *Val, Constant *Addr) {
2447 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Addr)) {
2448 assert(GV->hasInitializer());
2449 GV->setInitializer(Val);
2453 ConstantExpr *CE = cast<ConstantExpr>(Addr);
2454 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
2455 GV->setInitializer(EvaluateStoreInto(GV->getInitializer(), Val, CE, 2));
2460 /// Evaluator - This class evaluates LLVM IR, producing the Constant
2461 /// representing each SSA instruction. Changes to global variables are stored
2462 /// in a mapping that can be iterated over after the evaluation is complete.
2463 /// Once an evaluation call fails, the evaluation object should not be reused.
2466 Evaluator(const DataLayout *TD, const TargetLibraryInfo *TLI)
2467 : TD(TD), TLI(TLI) {
2468 ValueStack.push_back(new DenseMap<Value*, Constant*>);
2472 DeleteContainerPointers(ValueStack);
2473 while (!AllocaTmps.empty()) {
2474 GlobalVariable *Tmp = AllocaTmps.back();
2475 AllocaTmps.pop_back();
2477 // If there are still users of the alloca, the program is doing something
2478 // silly, e.g. storing the address of the alloca somewhere and using it
2479 // later. Since this is undefined, we'll just make it be null.
2480 if (!Tmp->use_empty())
2481 Tmp->replaceAllUsesWith(Constant::getNullValue(Tmp->getType()));
2486 /// EvaluateFunction - Evaluate a call to function F, returning true if
2487 /// successful, false if we can't evaluate it. ActualArgs contains the formal
2488 /// arguments for the function.
2489 bool EvaluateFunction(Function *F, Constant *&RetVal,
2490 const SmallVectorImpl<Constant*> &ActualArgs);
2492 /// EvaluateBlock - Evaluate all instructions in block BB, returning true if
2493 /// successful, false if we can't evaluate it. NewBB returns the next BB that
2494 /// control flows into, or null upon return.
2495 bool EvaluateBlock(BasicBlock::iterator CurInst, BasicBlock *&NextBB);
2497 Constant *getVal(Value *V) {
2498 if (Constant *CV = dyn_cast<Constant>(V)) return CV;
2499 Constant *R = ValueStack.back()->lookup(V);
2500 assert(R && "Reference to an uncomputed value!");
2504 void setVal(Value *V, Constant *C) {
2505 ValueStack.back()->operator[](V) = C;
2508 const DenseMap<Constant*, Constant*> &getMutatedMemory() const {
2509 return MutatedMemory;
2512 const SmallPtrSet<GlobalVariable*, 8> &getInvariants() const {
2517 Constant *ComputeLoadResult(Constant *P);
2519 /// ValueStack - As we compute SSA register values, we store their contents
2520 /// here. The back of the vector contains the current function and the stack
2521 /// contains the values in the calling frames.
2522 SmallVector<DenseMap<Value*, Constant*>*, 4> ValueStack;
2524 /// CallStack - This is used to detect recursion. In pathological situations
2525 /// we could hit exponential behavior, but at least there is nothing
2527 SmallVector<Function*, 4> CallStack;
2529 /// MutatedMemory - For each store we execute, we update this map. Loads
2530 /// check this to get the most up-to-date value. If evaluation is successful,
2531 /// this state is committed to the process.
2532 DenseMap<Constant*, Constant*> MutatedMemory;
2534 /// AllocaTmps - To 'execute' an alloca, we create a temporary global variable
2535 /// to represent its body. This vector is needed so we can delete the
2536 /// temporary globals when we are done.
2537 SmallVector<GlobalVariable*, 32> AllocaTmps;
2539 /// Invariants - These global variables have been marked invariant by the
2540 /// static constructor.
2541 SmallPtrSet<GlobalVariable*, 8> Invariants;
2543 /// SimpleConstants - These are constants we have checked and know to be
2544 /// simple enough to live in a static initializer of a global.
2545 SmallPtrSet<Constant*, 8> SimpleConstants;
2547 const DataLayout *TD;
2548 const TargetLibraryInfo *TLI;
2551 } // anonymous namespace
2553 /// ComputeLoadResult - Return the value that would be computed by a load from
2554 /// P after the stores reflected by 'memory' have been performed. If we can't
2555 /// decide, return null.
2556 Constant *Evaluator::ComputeLoadResult(Constant *P) {
2557 // If this memory location has been recently stored, use the stored value: it
2558 // is the most up-to-date.
2559 DenseMap<Constant*, Constant*>::const_iterator I = MutatedMemory.find(P);
2560 if (I != MutatedMemory.end()) return I->second;
2563 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(P)) {
2564 if (GV->hasDefinitiveInitializer())
2565 return GV->getInitializer();
2569 // Handle a constantexpr getelementptr.
2570 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(P))
2571 if (CE->getOpcode() == Instruction::GetElementPtr &&
2572 isa<GlobalVariable>(CE->getOperand(0))) {
2573 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
2574 if (GV->hasDefinitiveInitializer())
2575 return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE);
2578 return 0; // don't know how to evaluate.
2581 /// EvaluateBlock - Evaluate all instructions in block BB, returning true if
2582 /// successful, false if we can't evaluate it. NewBB returns the next BB that
2583 /// control flows into, or null upon return.
2584 bool Evaluator::EvaluateBlock(BasicBlock::iterator CurInst,
2585 BasicBlock *&NextBB) {
2586 // This is the main evaluation loop.
2588 Constant *InstResult = 0;
2590 DEBUG(dbgs() << "Evaluating Instruction: " << *CurInst << "\n");
2592 if (StoreInst *SI = dyn_cast<StoreInst>(CurInst)) {
2593 if (!SI->isSimple()) {
2594 DEBUG(dbgs() << "Store is not simple! Can not evaluate.\n");
2595 return false; // no volatile/atomic accesses.
2597 Constant *Ptr = getVal(SI->getOperand(1));
2598 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr)) {
2599 DEBUG(dbgs() << "Folding constant ptr expression: " << *Ptr);
2600 Ptr = ConstantFoldConstantExpression(CE, TD, TLI);
2601 DEBUG(dbgs() << "; To: " << *Ptr << "\n");
2603 if (!isSimpleEnoughPointerToCommit(Ptr)) {
2604 // If this is too complex for us to commit, reject it.
2605 DEBUG(dbgs() << "Pointer is too complex for us to evaluate store.");
2609 Constant *Val = getVal(SI->getOperand(0));
2611 // If this might be too difficult for the backend to handle (e.g. the addr
2612 // of one global variable divided by another) then we can't commit it.
2613 if (!isSimpleEnoughValueToCommit(Val, SimpleConstants, TD)) {
2614 DEBUG(dbgs() << "Store value is too complex to evaluate store. " << *Val
2619 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr)) {
2620 if (CE->getOpcode() == Instruction::BitCast) {
2621 DEBUG(dbgs() << "Attempting to resolve bitcast on constant ptr.\n");
2622 // If we're evaluating a store through a bitcast, then we need
2623 // to pull the bitcast off the pointer type and push it onto the
2625 Ptr = CE->getOperand(0);
2627 Type *NewTy = cast<PointerType>(Ptr->getType())->getElementType();
2629 // In order to push the bitcast onto the stored value, a bitcast
2630 // from NewTy to Val's type must be legal. If it's not, we can try
2631 // introspecting NewTy to find a legal conversion.
2632 while (!Val->getType()->canLosslesslyBitCastTo(NewTy)) {
2633 // If NewTy is a struct, we can convert the pointer to the struct
2634 // into a pointer to its first member.
2635 // FIXME: This could be extended to support arrays as well.
2636 if (StructType *STy = dyn_cast<StructType>(NewTy)) {
2637 NewTy = STy->getTypeAtIndex(0U);
2639 IntegerType *IdxTy = IntegerType::get(NewTy->getContext(), 32);
2640 Constant *IdxZero = ConstantInt::get(IdxTy, 0, false);
2641 Constant * const IdxList[] = {IdxZero, IdxZero};
2643 Ptr = ConstantExpr::getGetElementPtr(Ptr, IdxList);
2644 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr))
2645 Ptr = ConstantFoldConstantExpression(CE, TD, TLI);
2647 // If we can't improve the situation by introspecting NewTy,
2648 // we have to give up.
2650 DEBUG(dbgs() << "Failed to bitcast constant ptr, can not "
2656 // If we found compatible types, go ahead and push the bitcast
2657 // onto the stored value.
2658 Val = ConstantExpr::getBitCast(Val, NewTy);
2660 DEBUG(dbgs() << "Evaluated bitcast: " << *Val << "\n");
2664 MutatedMemory[Ptr] = Val;
2665 } else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(CurInst)) {
2666 InstResult = ConstantExpr::get(BO->getOpcode(),
2667 getVal(BO->getOperand(0)),
2668 getVal(BO->getOperand(1)));
2669 DEBUG(dbgs() << "Found a BinaryOperator! Simplifying: " << *InstResult
2671 } else if (CmpInst *CI = dyn_cast<CmpInst>(CurInst)) {
2672 InstResult = ConstantExpr::getCompare(CI->getPredicate(),
2673 getVal(CI->getOperand(0)),
2674 getVal(CI->getOperand(1)));
2675 DEBUG(dbgs() << "Found a CmpInst! Simplifying: " << *InstResult
2677 } else if (CastInst *CI = dyn_cast<CastInst>(CurInst)) {
2678 InstResult = ConstantExpr::getCast(CI->getOpcode(),
2679 getVal(CI->getOperand(0)),
2681 DEBUG(dbgs() << "Found a Cast! Simplifying: " << *InstResult
2683 } else if (SelectInst *SI = dyn_cast<SelectInst>(CurInst)) {
2684 InstResult = ConstantExpr::getSelect(getVal(SI->getOperand(0)),
2685 getVal(SI->getOperand(1)),
2686 getVal(SI->getOperand(2)));
2687 DEBUG(dbgs() << "Found a Select! Simplifying: " << *InstResult
2689 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(CurInst)) {
2690 Constant *P = getVal(GEP->getOperand(0));
2691 SmallVector<Constant*, 8> GEPOps;
2692 for (User::op_iterator i = GEP->op_begin() + 1, e = GEP->op_end();
2694 GEPOps.push_back(getVal(*i));
2696 ConstantExpr::getGetElementPtr(P, GEPOps,
2697 cast<GEPOperator>(GEP)->isInBounds());
2698 DEBUG(dbgs() << "Found a GEP! Simplifying: " << *InstResult
2700 } else if (LoadInst *LI = dyn_cast<LoadInst>(CurInst)) {
2702 if (!LI->isSimple()) {
2703 DEBUG(dbgs() << "Found a Load! Not a simple load, can not evaluate.\n");
2704 return false; // no volatile/atomic accesses.
2707 Constant *Ptr = getVal(LI->getOperand(0));
2708 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr)) {
2709 Ptr = ConstantFoldConstantExpression(CE, TD, TLI);
2710 DEBUG(dbgs() << "Found a constant pointer expression, constant "
2711 "folding: " << *Ptr << "\n");
2713 InstResult = ComputeLoadResult(Ptr);
2714 if (InstResult == 0) {
2715 DEBUG(dbgs() << "Failed to compute load result. Can not evaluate load."
2717 return false; // Could not evaluate load.
2720 DEBUG(dbgs() << "Evaluated load: " << *InstResult << "\n");
2721 } else if (AllocaInst *AI = dyn_cast<AllocaInst>(CurInst)) {
2722 if (AI->isArrayAllocation()) {
2723 DEBUG(dbgs() << "Found an array alloca. Can not evaluate.\n");
2724 return false; // Cannot handle array allocs.
2726 Type *Ty = AI->getType()->getElementType();
2727 AllocaTmps.push_back(new GlobalVariable(Ty, false,
2728 GlobalValue::InternalLinkage,
2729 UndefValue::get(Ty),
2731 InstResult = AllocaTmps.back();
2732 DEBUG(dbgs() << "Found an alloca. Result: " << *InstResult << "\n");
2733 } else if (isa<CallInst>(CurInst) || isa<InvokeInst>(CurInst)) {
2734 CallSite CS(CurInst);
2736 // Debug info can safely be ignored here.
2737 if (isa<DbgInfoIntrinsic>(CS.getInstruction())) {
2738 DEBUG(dbgs() << "Ignoring debug info.\n");
2743 // Cannot handle inline asm.
2744 if (isa<InlineAsm>(CS.getCalledValue())) {
2745 DEBUG(dbgs() << "Found inline asm, can not evaluate.\n");
2749 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(CS.getInstruction())) {
2750 if (MemSetInst *MSI = dyn_cast<MemSetInst>(II)) {
2751 if (MSI->isVolatile()) {
2752 DEBUG(dbgs() << "Can not optimize a volatile memset " <<
2756 Constant *Ptr = getVal(MSI->getDest());
2757 Constant *Val = getVal(MSI->getValue());
2758 Constant *DestVal = ComputeLoadResult(getVal(Ptr));
2759 if (Val->isNullValue() && DestVal && DestVal->isNullValue()) {
2760 // This memset is a no-op.
2761 DEBUG(dbgs() << "Ignoring no-op memset.\n");
2767 if (II->getIntrinsicID() == Intrinsic::lifetime_start ||
2768 II->getIntrinsicID() == Intrinsic::lifetime_end) {
2769 DEBUG(dbgs() << "Ignoring lifetime intrinsic.\n");
2774 if (II->getIntrinsicID() == Intrinsic::invariant_start) {
2775 // We don't insert an entry into Values, as it doesn't have a
2776 // meaningful return value.
2777 if (!II->use_empty()) {
2778 DEBUG(dbgs() << "Found unused invariant_start. Cant evaluate.\n");
2781 ConstantInt *Size = cast<ConstantInt>(II->getArgOperand(0));
2782 Value *PtrArg = getVal(II->getArgOperand(1));
2783 Value *Ptr = PtrArg->stripPointerCasts();
2784 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Ptr)) {
2785 Type *ElemTy = cast<PointerType>(GV->getType())->getElementType();
2786 if (!Size->isAllOnesValue() &&
2787 Size->getValue().getLimitedValue() >=
2788 TD->getTypeStoreSize(ElemTy)) {
2789 Invariants.insert(GV);
2790 DEBUG(dbgs() << "Found a global var that is an invariant: " << *GV
2793 DEBUG(dbgs() << "Found a global var, but can not treat it as an "
2797 // Continue even if we do nothing.
2802 DEBUG(dbgs() << "Unknown intrinsic. Can not evaluate.\n");
2806 // Resolve function pointers.
2807 Function *Callee = dyn_cast<Function>(getVal(CS.getCalledValue()));
2808 if (!Callee || Callee->mayBeOverridden()) {
2809 DEBUG(dbgs() << "Can not resolve function pointer.\n");
2810 return false; // Cannot resolve.
2813 SmallVector<Constant*, 8> Formals;
2814 for (User::op_iterator i = CS.arg_begin(), e = CS.arg_end(); i != e; ++i)
2815 Formals.push_back(getVal(*i));
2817 if (Callee->isDeclaration()) {
2818 // If this is a function we can constant fold, do it.
2819 if (Constant *C = ConstantFoldCall(Callee, Formals, TLI)) {
2821 DEBUG(dbgs() << "Constant folded function call. Result: " <<
2822 *InstResult << "\n");
2824 DEBUG(dbgs() << "Can not constant fold function call.\n");
2828 if (Callee->getFunctionType()->isVarArg()) {
2829 DEBUG(dbgs() << "Can not constant fold vararg function call.\n");
2833 Constant *RetVal = 0;
2834 // Execute the call, if successful, use the return value.
2835 ValueStack.push_back(new DenseMap<Value*, Constant*>);
2836 if (!EvaluateFunction(Callee, RetVal, Formals)) {
2837 DEBUG(dbgs() << "Failed to evaluate function.\n");
2840 delete ValueStack.pop_back_val();
2841 InstResult = RetVal;
2843 if (InstResult != NULL) {
2844 DEBUG(dbgs() << "Successfully evaluated function. Result: " <<
2845 InstResult << "\n\n");
2847 DEBUG(dbgs() << "Successfully evaluated function. Result: 0\n\n");
2850 } else if (isa<TerminatorInst>(CurInst)) {
2851 DEBUG(dbgs() << "Found a terminator instruction.\n");
2853 if (BranchInst *BI = dyn_cast<BranchInst>(CurInst)) {
2854 if (BI->isUnconditional()) {
2855 NextBB = BI->getSuccessor(0);
2858 dyn_cast<ConstantInt>(getVal(BI->getCondition()));
2859 if (!Cond) return false; // Cannot determine.
2861 NextBB = BI->getSuccessor(!Cond->getZExtValue());
2863 } else if (SwitchInst *SI = dyn_cast<SwitchInst>(CurInst)) {
2865 dyn_cast<ConstantInt>(getVal(SI->getCondition()));
2866 if (!Val) return false; // Cannot determine.
2867 NextBB = SI->findCaseValue(Val).getCaseSuccessor();
2868 } else if (IndirectBrInst *IBI = dyn_cast<IndirectBrInst>(CurInst)) {
2869 Value *Val = getVal(IBI->getAddress())->stripPointerCasts();
2870 if (BlockAddress *BA = dyn_cast<BlockAddress>(Val))
2871 NextBB = BA->getBasicBlock();
2873 return false; // Cannot determine.
2874 } else if (isa<ReturnInst>(CurInst)) {
2877 // invoke, unwind, resume, unreachable.
2878 DEBUG(dbgs() << "Can not handle terminator.");
2879 return false; // Cannot handle this terminator.
2882 // We succeeded at evaluating this block!
2883 DEBUG(dbgs() << "Successfully evaluated block.\n");
2886 // Did not know how to evaluate this!
2887 DEBUG(dbgs() << "Failed to evaluate block due to unhandled instruction."
2892 if (!CurInst->use_empty()) {
2893 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(InstResult))
2894 InstResult = ConstantFoldConstantExpression(CE, TD, TLI);
2896 setVal(CurInst, InstResult);
2899 // If we just processed an invoke, we finished evaluating the block.
2900 if (InvokeInst *II = dyn_cast<InvokeInst>(CurInst)) {
2901 NextBB = II->getNormalDest();
2902 DEBUG(dbgs() << "Found an invoke instruction. Finished Block.\n\n");
2906 // Advance program counter.
2911 /// EvaluateFunction - Evaluate a call to function F, returning true if
2912 /// successful, false if we can't evaluate it. ActualArgs contains the formal
2913 /// arguments for the function.
2914 bool Evaluator::EvaluateFunction(Function *F, Constant *&RetVal,
2915 const SmallVectorImpl<Constant*> &ActualArgs) {
2916 // Check to see if this function is already executing (recursion). If so,
2917 // bail out. TODO: we might want to accept limited recursion.
2918 if (std::find(CallStack.begin(), CallStack.end(), F) != CallStack.end())
2921 CallStack.push_back(F);
2923 // Initialize arguments to the incoming values specified.
2925 for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end(); AI != E;
2927 setVal(AI, ActualArgs[ArgNo]);
2929 // ExecutedBlocks - We only handle non-looping, non-recursive code. As such,
2930 // we can only evaluate any one basic block at most once. This set keeps
2931 // track of what we have executed so we can detect recursive cases etc.
2932 SmallPtrSet<BasicBlock*, 32> ExecutedBlocks;
2934 // CurBB - The current basic block we're evaluating.
2935 BasicBlock *CurBB = F->begin();
2937 BasicBlock::iterator CurInst = CurBB->begin();
2940 BasicBlock *NextBB = 0; // Initialized to avoid compiler warnings.
2941 DEBUG(dbgs() << "Trying to evaluate BB: " << *CurBB << "\n");
2943 if (!EvaluateBlock(CurInst, NextBB))
2947 // Successfully running until there's no next block means that we found
2948 // the return. Fill it the return value and pop the call stack.
2949 ReturnInst *RI = cast<ReturnInst>(CurBB->getTerminator());
2950 if (RI->getNumOperands())
2951 RetVal = getVal(RI->getOperand(0));
2952 CallStack.pop_back();
2956 // Okay, we succeeded in evaluating this control flow. See if we have
2957 // executed the new block before. If so, we have a looping function,
2958 // which we cannot evaluate in reasonable time.
2959 if (!ExecutedBlocks.insert(NextBB))
2960 return false; // looped!
2962 // Okay, we have never been in this block before. Check to see if there
2963 // are any PHI nodes. If so, evaluate them with information about where
2966 for (CurInst = NextBB->begin();
2967 (PN = dyn_cast<PHINode>(CurInst)); ++CurInst)
2968 setVal(PN, getVal(PN->getIncomingValueForBlock(CurBB)));
2970 // Advance to the next block.
2975 /// EvaluateStaticConstructor - Evaluate static constructors in the function, if
2976 /// we can. Return true if we can, false otherwise.
2977 static bool EvaluateStaticConstructor(Function *F, const DataLayout *TD,
2978 const TargetLibraryInfo *TLI) {
2979 // Call the function.
2980 Evaluator Eval(TD, TLI);
2981 Constant *RetValDummy;
2982 bool EvalSuccess = Eval.EvaluateFunction(F, RetValDummy,
2983 SmallVector<Constant*, 0>());
2986 // We succeeded at evaluation: commit the result.
2987 DEBUG(dbgs() << "FULLY EVALUATED GLOBAL CTOR FUNCTION '"
2988 << F->getName() << "' to " << Eval.getMutatedMemory().size()
2990 for (DenseMap<Constant*, Constant*>::const_iterator I =
2991 Eval.getMutatedMemory().begin(), E = Eval.getMutatedMemory().end();
2993 CommitValueTo(I->second, I->first);
2994 for (SmallPtrSet<GlobalVariable*, 8>::const_iterator I =
2995 Eval.getInvariants().begin(), E = Eval.getInvariants().end();
2997 (*I)->setConstant(true);
3003 /// OptimizeGlobalCtorsList - Simplify and evaluation global ctors if possible.
3004 /// Return true if anything changed.
3005 bool GlobalOpt::OptimizeGlobalCtorsList(GlobalVariable *&GCL) {
3006 std::vector<Function*> Ctors = ParseGlobalCtors(GCL);
3007 bool MadeChange = false;
3008 if (Ctors.empty()) return false;
3010 // Loop over global ctors, optimizing them when we can.
3011 for (unsigned i = 0; i != Ctors.size(); ++i) {
3012 Function *F = Ctors[i];
3013 // Found a null terminator in the middle of the list, prune off the rest of
3016 if (i != Ctors.size()-1) {
3022 DEBUG(dbgs() << "Optimizing Global Constructor: " << *F << "\n");
3024 // We cannot simplify external ctor functions.
3025 if (F->empty()) continue;
3027 // If we can evaluate the ctor at compile time, do.
3028 if (EvaluateStaticConstructor(F, TD, TLI)) {
3029 Ctors.erase(Ctors.begin()+i);
3032 ++NumCtorsEvaluated;
3037 if (!MadeChange) return false;
3039 GCL = InstallGlobalCtors(GCL, Ctors);
3043 /// \brief Given "llvm.used" or "llvm.compiler_used" as a global name, collect
3044 /// the initializer elements of that global in Set and return the global itself.
3045 static GlobalVariable *
3046 collectUsedGlobalVariables(const Module &M, const char *Name,
3047 SmallPtrSet<GlobalValue *, 8> &Set) {
3048 GlobalVariable *GV = M.getGlobalVariable(Name);
3049 if (!GV || !GV->hasInitializer())
3052 const ConstantArray *Init = cast<ConstantArray>(GV->getInitializer());
3053 for (unsigned I = 0, E = Init->getNumOperands(); I != E; ++I) {
3054 Value *Op = Init->getOperand(I);
3055 GlobalValue *G = cast<GlobalValue>(Op->stripPointerCastsNoFollowAliases());
3061 static int compareNames(const void *A, const void *B) {
3062 const GlobalValue *VA = *reinterpret_cast<GlobalValue* const*>(A);
3063 const GlobalValue *VB = *reinterpret_cast<GlobalValue* const*>(B);
3064 if (VA->getName() < VB->getName())
3066 if (VB->getName() < VA->getName())
3071 static void setUsedInitializer(GlobalVariable &V,
3072 SmallPtrSet<GlobalValue *, 8> Init) {
3073 SmallVector<llvm::Constant *, 8> UsedArray;
3074 PointerType *Int8PtrTy = Type::getInt8PtrTy(V.getContext());
3076 for (SmallPtrSet<GlobalValue *, 8>::iterator I = Init.begin(), E = Init.end();
3078 Constant *Cast = llvm::ConstantExpr::getBitCast(*I, Int8PtrTy);
3079 UsedArray.push_back(Cast);
3081 // Sort to get deterministic order.
3082 array_pod_sort(UsedArray.begin(), UsedArray.end(), compareNames);
3083 ArrayType *ATy = ArrayType::get(Int8PtrTy, UsedArray.size());
3085 Module *M = V.getParent();
3086 V.removeFromParent();
3087 GlobalVariable *NV =
3088 new GlobalVariable(*M, ATy, false, llvm::GlobalValue::AppendingLinkage,
3089 llvm::ConstantArray::get(ATy, UsedArray), "");
3091 NV->setSection("llvm.metadata");
3096 /// \brief An easy to access representation of llvm.used and llvm.compiler_used.
3098 SmallPtrSet<GlobalValue *, 8> Used;
3099 SmallPtrSet<GlobalValue *, 8> CompilerUsed;
3100 GlobalVariable *UsedV;
3101 GlobalVariable *CompilerUsedV;
3104 LLVMUsed(const Module &M) {
3105 UsedV = collectUsedGlobalVariables(M, "llvm.used", Used);
3107 collectUsedGlobalVariables(M, "llvm.compiler_used", CompilerUsed);
3109 typedef SmallPtrSet<GlobalValue *, 8>::iterator iterator;
3110 iterator usedBegin() { return Used.begin(); }
3111 iterator usedEnd() { return Used.end(); }
3112 iterator compilerUsedBegin() { return CompilerUsed.begin(); }
3113 iterator compilerUsedEnd() { return CompilerUsed.end(); }
3114 bool usedCount(GlobalValue *GV) const { return Used.count(GV); }
3115 bool compilerUsedCount(GlobalValue *GV) const {
3116 return CompilerUsed.count(GV);
3118 bool usedErase(GlobalValue *GV) { return Used.erase(GV); }
3119 bool compilerUsedErase(GlobalValue *GV) { return CompilerUsed.erase(GV); }
3120 bool usedInsert(GlobalValue *GV) { return Used.insert(GV); }
3121 bool compilerUsedInsert(GlobalValue *GV) { return CompilerUsed.insert(GV); }
3123 void syncVariablesAndSets() {
3125 setUsedInitializer(*UsedV, Used);
3127 setUsedInitializer(*CompilerUsedV, CompilerUsed);
3132 static bool hasUseOtherThanLLVMUsed(GlobalAlias &GA, const LLVMUsed &U) {
3133 if (GA.use_empty()) // No use at all.
3136 assert((!U.usedCount(&GA) || !U.compilerUsedCount(&GA)) &&
3137 "We should have removed the duplicated "
3138 "element from llvm.compiler_used");
3139 if (!GA.hasOneUse())
3140 // Strictly more than one use. So at least one is not in llvm.used and
3141 // llvm.compiler_used.
3144 // Exactly one use. Check if it is in llvm.used or llvm.compiler_used.
3145 return !U.usedCount(&GA) && !U.compilerUsedCount(&GA);
3148 static bool hasMoreThanOneUseOtherThanLLVMUsed(GlobalValue &V,
3149 const LLVMUsed &U) {
3151 assert((!U.usedCount(&V) || !U.compilerUsedCount(&V)) &&
3152 "We should have removed the duplicated "
3153 "element from llvm.compiler_used");
3154 if (U.usedCount(&V) || U.compilerUsedCount(&V))
3156 return V.hasNUsesOrMore(N);
3159 static bool mayHaveOtherReferences(GlobalAlias &GA, const LLVMUsed &U) {
3160 if (!GA.hasLocalLinkage())
3163 return U.usedCount(&GA) || U.compilerUsedCount(&GA);
3166 static bool hasUsesToReplace(GlobalAlias &GA, LLVMUsed &U, bool &RenameTarget) {
3167 RenameTarget = false;
3169 if (hasUseOtherThanLLVMUsed(GA, U))
3172 // If the alias is externally visible, we may still be able to simplify it.
3173 if (!mayHaveOtherReferences(GA, U))
3176 // If the aliasee has internal linkage, give it the name and linkage
3177 // of the alias, and delete the alias. This turns:
3178 // define internal ... @f(...)
3179 // @a = alias ... @f
3181 // define ... @a(...)
3182 Constant *Aliasee = GA.getAliasee();
3183 GlobalValue *Target = cast<GlobalValue>(Aliasee->stripPointerCasts());
3184 if (!Target->hasLocalLinkage())
3187 // Do not perform the transform if multiple aliases potentially target the
3188 // aliasee. This check also ensures that it is safe to replace the section
3189 // and other attributes of the aliasee with those of the alias.
3190 if (hasMoreThanOneUseOtherThanLLVMUsed(*Target, U))
3193 RenameTarget = true;
3197 bool GlobalOpt::OptimizeGlobalAliases(Module &M) {
3198 bool Changed = false;
3201 for (SmallPtrSet<GlobalValue *, 8>::iterator I = Used.usedBegin(),
3204 Used.compilerUsedErase(*I);
3206 for (Module::alias_iterator I = M.alias_begin(), E = M.alias_end();
3208 Module::alias_iterator J = I++;
3209 // Aliases without names cannot be referenced outside this module.
3210 if (!J->hasName() && !J->isDeclaration())
3211 J->setLinkage(GlobalValue::InternalLinkage);
3212 // If the aliasee may change at link time, nothing can be done - bail out.
3213 if (J->mayBeOverridden())
3216 Constant *Aliasee = J->getAliasee();
3217 GlobalValue *Target = cast<GlobalValue>(Aliasee->stripPointerCasts());
3218 Target->removeDeadConstantUsers();
3220 // Make all users of the alias use the aliasee instead.
3222 if (!hasUsesToReplace(*J, Used, RenameTarget))
3225 J->replaceAllUsesWith(Aliasee);
3226 ++NumAliasesResolved;
3230 // Give the aliasee the name, linkage and other attributes of the alias.
3231 Target->takeName(J);
3232 Target->setLinkage(J->getLinkage());
3233 Target->GlobalValue::copyAttributesFrom(J);
3235 if (Used.usedErase(J))
3236 Used.usedInsert(Target);
3238 if (Used.compilerUsedErase(J))
3239 Used.compilerUsedInsert(Target);
3240 } else if (mayHaveOtherReferences(*J, Used))
3243 // Delete the alias.
3244 M.getAliasList().erase(J);
3245 ++NumAliasesRemoved;
3249 Used.syncVariablesAndSets();
3254 static Function *FindCXAAtExit(Module &M, TargetLibraryInfo *TLI) {
3255 if (!TLI->has(LibFunc::cxa_atexit))
3258 Function *Fn = M.getFunction(TLI->getName(LibFunc::cxa_atexit));
3263 FunctionType *FTy = Fn->getFunctionType();
3265 // Checking that the function has the right return type, the right number of
3266 // parameters and that they all have pointer types should be enough.
3267 if (!FTy->getReturnType()->isIntegerTy() ||
3268 FTy->getNumParams() != 3 ||
3269 !FTy->getParamType(0)->isPointerTy() ||
3270 !FTy->getParamType(1)->isPointerTy() ||
3271 !FTy->getParamType(2)->isPointerTy())
3277 /// cxxDtorIsEmpty - Returns whether the given function is an empty C++
3278 /// destructor and can therefore be eliminated.
3279 /// Note that we assume that other optimization passes have already simplified
3280 /// the code so we only look for a function with a single basic block, where
3281 /// the only allowed instructions are 'ret', 'call' to an empty C++ dtor and
3282 /// other side-effect free instructions.
3283 static bool cxxDtorIsEmpty(const Function &Fn,
3284 SmallPtrSet<const Function *, 8> &CalledFunctions) {
3285 // FIXME: We could eliminate C++ destructors if they're readonly/readnone and
3286 // nounwind, but that doesn't seem worth doing.
3287 if (Fn.isDeclaration())
3290 if (++Fn.begin() != Fn.end())
3293 const BasicBlock &EntryBlock = Fn.getEntryBlock();
3294 for (BasicBlock::const_iterator I = EntryBlock.begin(), E = EntryBlock.end();
3296 if (const CallInst *CI = dyn_cast<CallInst>(I)) {
3297 // Ignore debug intrinsics.
3298 if (isa<DbgInfoIntrinsic>(CI))
3301 const Function *CalledFn = CI->getCalledFunction();
3306 SmallPtrSet<const Function *, 8> NewCalledFunctions(CalledFunctions);
3308 // Don't treat recursive functions as empty.
3309 if (!NewCalledFunctions.insert(CalledFn))
3312 if (!cxxDtorIsEmpty(*CalledFn, NewCalledFunctions))
3314 } else if (isa<ReturnInst>(*I))
3315 return true; // We're done.
3316 else if (I->mayHaveSideEffects())
3317 return false; // Destructor with side effects, bail.
3323 bool GlobalOpt::OptimizeEmptyGlobalCXXDtors(Function *CXAAtExitFn) {
3324 /// Itanium C++ ABI p3.3.5:
3326 /// After constructing a global (or local static) object, that will require
3327 /// destruction on exit, a termination function is registered as follows:
3329 /// extern "C" int __cxa_atexit ( void (*f)(void *), void *p, void *d );
3331 /// This registration, e.g. __cxa_atexit(f,p,d), is intended to cause the
3332 /// call f(p) when DSO d is unloaded, before all such termination calls
3333 /// registered before this one. It returns zero if registration is
3334 /// successful, nonzero on failure.
3336 // This pass will look for calls to __cxa_atexit where the function is trivial
3338 bool Changed = false;
3340 for (Function::use_iterator I = CXAAtExitFn->use_begin(),
3341 E = CXAAtExitFn->use_end(); I != E;) {
3342 // We're only interested in calls. Theoretically, we could handle invoke
3343 // instructions as well, but neither llvm-gcc nor clang generate invokes
3345 CallInst *CI = dyn_cast<CallInst>(*I++);
3350 dyn_cast<Function>(CI->getArgOperand(0)->stripPointerCasts());
3354 SmallPtrSet<const Function *, 8> CalledFunctions;
3355 if (!cxxDtorIsEmpty(*DtorFn, CalledFunctions))
3358 // Just remove the call.
3359 CI->replaceAllUsesWith(Constant::getNullValue(CI->getType()));
3360 CI->eraseFromParent();
3362 ++NumCXXDtorsRemoved;
3370 bool GlobalOpt::runOnModule(Module &M) {
3371 bool Changed = false;
3373 TD = getAnalysisIfAvailable<DataLayout>();
3374 TLI = &getAnalysis<TargetLibraryInfo>();
3376 // Try to find the llvm.globalctors list.
3377 GlobalVariable *GlobalCtors = FindGlobalCtors(M);
3379 bool LocalChange = true;
3380 while (LocalChange) {
3381 LocalChange = false;
3383 // Delete functions that are trivially dead, ccc -> fastcc
3384 LocalChange |= OptimizeFunctions(M);
3386 // Optimize global_ctors list.
3388 LocalChange |= OptimizeGlobalCtorsList(GlobalCtors);
3390 // Optimize non-address-taken globals.
3391 LocalChange |= OptimizeGlobalVars(M);
3393 // Resolve aliases, when possible.
3394 LocalChange |= OptimizeGlobalAliases(M);
3396 // Try to remove trivial global destructors if they are not removed
3398 Function *CXAAtExitFn = FindCXAAtExit(M, TLI);
3400 LocalChange |= OptimizeEmptyGlobalCXXDtors(CXAAtExitFn);
3402 Changed |= LocalChange;
3405 // TODO: Move all global ctors functions to the end of the module for code