1 //===- GlobalOpt.cpp - Optimize Global Variables --------------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This pass transforms simple global variables that never have their address
11 // taken. If obviously true, it marks read/write globals as constant, deletes
12 // variables only stored to, etc.
14 //===----------------------------------------------------------------------===//
16 #define DEBUG_TYPE "globalopt"
17 #include "llvm/Transforms/IPO.h"
18 #include "llvm/CallingConv.h"
19 #include "llvm/Constants.h"
20 #include "llvm/DerivedTypes.h"
21 #include "llvm/Instructions.h"
22 #include "llvm/IntrinsicInst.h"
23 #include "llvm/LLVMContext.h"
24 #include "llvm/Module.h"
25 #include "llvm/Pass.h"
26 #include "llvm/Analysis/ConstantFolding.h"
27 #include "llvm/Target/TargetData.h"
28 #include "llvm/Support/CallSite.h"
29 #include "llvm/Support/Compiler.h"
30 #include "llvm/Support/Debug.h"
31 #include "llvm/Support/ErrorHandling.h"
32 #include "llvm/Support/GetElementPtrTypeIterator.h"
33 #include "llvm/Support/MathExtras.h"
34 #include "llvm/Support/raw_ostream.h"
35 #include "llvm/ADT/DenseMap.h"
36 #include "llvm/ADT/SmallPtrSet.h"
37 #include "llvm/ADT/SmallVector.h"
38 #include "llvm/ADT/Statistic.h"
39 #include "llvm/ADT/StringExtras.h"
40 #include "llvm/ADT/STLExtras.h"
44 STATISTIC(NumMarked , "Number of globals marked constant");
45 STATISTIC(NumSRA , "Number of aggregate globals broken into scalars");
46 STATISTIC(NumHeapSRA , "Number of heap objects SRA'd");
47 STATISTIC(NumSubstitute,"Number of globals with initializers stored into them");
48 STATISTIC(NumDeleted , "Number of globals deleted");
49 STATISTIC(NumFnDeleted , "Number of functions deleted");
50 STATISTIC(NumGlobUses , "Number of global uses devirtualized");
51 STATISTIC(NumLocalized , "Number of globals localized");
52 STATISTIC(NumShrunkToBool , "Number of global vars shrunk to booleans");
53 STATISTIC(NumFastCallFns , "Number of functions converted to fastcc");
54 STATISTIC(NumCtorsEvaluated, "Number of static ctors evaluated");
55 STATISTIC(NumNestRemoved , "Number of nest attributes removed");
56 STATISTIC(NumAliasesResolved, "Number of global aliases resolved");
57 STATISTIC(NumAliasesRemoved, "Number of global aliases eliminated");
60 struct VISIBILITY_HIDDEN GlobalOpt : public ModulePass {
61 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
62 AU.addRequired<TargetData>();
64 static char ID; // Pass identification, replacement for typeid
65 GlobalOpt() : ModulePass(&ID) {}
67 bool runOnModule(Module &M);
70 GlobalVariable *FindGlobalCtors(Module &M);
71 bool OptimizeFunctions(Module &M);
72 bool OptimizeGlobalVars(Module &M);
73 bool OptimizeGlobalAliases(Module &M);
74 bool OptimizeGlobalCtorsList(GlobalVariable *&GCL);
75 bool ProcessInternalGlobal(GlobalVariable *GV,Module::global_iterator &GVI);
79 char GlobalOpt::ID = 0;
80 static RegisterPass<GlobalOpt> X("globalopt", "Global Variable Optimizer");
82 ModulePass *llvm::createGlobalOptimizerPass() { return new GlobalOpt(); }
86 /// GlobalStatus - As we analyze each global, keep track of some information
87 /// about it. If we find out that the address of the global is taken, none of
88 /// this info will be accurate.
89 struct VISIBILITY_HIDDEN GlobalStatus {
90 /// isLoaded - True if the global is ever loaded. If the global isn't ever
91 /// loaded it can be deleted.
94 /// StoredType - Keep track of what stores to the global look like.
97 /// NotStored - There is no store to this global. It can thus be marked
101 /// isInitializerStored - This global is stored to, but the only thing
102 /// stored is the constant it was initialized with. This is only tracked
103 /// for scalar globals.
106 /// isStoredOnce - This global is stored to, but only its initializer and
107 /// one other value is ever stored to it. If this global isStoredOnce, we
108 /// track the value stored to it in StoredOnceValue below. This is only
109 /// tracked for scalar globals.
112 /// isStored - This global is stored to by multiple values or something else
113 /// that we cannot track.
117 /// StoredOnceValue - If only one value (besides the initializer constant) is
118 /// ever stored to this global, keep track of what value it is.
119 Value *StoredOnceValue;
121 /// AccessingFunction/HasMultipleAccessingFunctions - These start out
122 /// null/false. When the first accessing function is noticed, it is recorded.
123 /// When a second different accessing function is noticed,
124 /// HasMultipleAccessingFunctions is set to true.
125 Function *AccessingFunction;
126 bool HasMultipleAccessingFunctions;
128 /// HasNonInstructionUser - Set to true if this global has a user that is not
129 /// an instruction (e.g. a constant expr or GV initializer).
130 bool HasNonInstructionUser;
132 /// HasPHIUser - Set to true if this global has a user that is a PHI node.
135 GlobalStatus() : isLoaded(false), StoredType(NotStored), StoredOnceValue(0),
136 AccessingFunction(0), HasMultipleAccessingFunctions(false),
137 HasNonInstructionUser(false), HasPHIUser(false) {}
142 // SafeToDestroyConstant - It is safe to destroy a constant iff it is only used
143 // by constants itself. Note that constants cannot be cyclic, so this test is
144 // pretty easy to implement recursively.
146 static bool SafeToDestroyConstant(Constant *C) {
147 if (isa<GlobalValue>(C)) return false;
149 for (Value::use_iterator UI = C->use_begin(), E = C->use_end(); UI != E; ++UI)
150 if (Constant *CU = dyn_cast<Constant>(*UI)) {
151 if (!SafeToDestroyConstant(CU)) return false;
158 /// AnalyzeGlobal - Look at all uses of the global and fill in the GlobalStatus
159 /// structure. If the global has its address taken, return true to indicate we
160 /// can't do anything with it.
162 static bool AnalyzeGlobal(Value *V, GlobalStatus &GS,
163 SmallPtrSet<PHINode*, 16> &PHIUsers) {
164 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ++UI)
165 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(*UI)) {
166 GS.HasNonInstructionUser = true;
168 if (AnalyzeGlobal(CE, GS, PHIUsers)) return true;
170 } else if (Instruction *I = dyn_cast<Instruction>(*UI)) {
171 if (!GS.HasMultipleAccessingFunctions) {
172 Function *F = I->getParent()->getParent();
173 if (GS.AccessingFunction == 0)
174 GS.AccessingFunction = F;
175 else if (GS.AccessingFunction != F)
176 GS.HasMultipleAccessingFunctions = true;
178 if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
180 if (LI->isVolatile()) return true; // Don't hack on volatile loads.
181 } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
182 // Don't allow a store OF the address, only stores TO the address.
183 if (SI->getOperand(0) == V) return true;
185 if (SI->isVolatile()) return true; // Don't hack on volatile stores.
187 // If this is a direct store to the global (i.e., the global is a scalar
188 // value, not an aggregate), keep more specific information about
190 if (GS.StoredType != GlobalStatus::isStored) {
191 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(SI->getOperand(1))){
192 Value *StoredVal = SI->getOperand(0);
193 if (StoredVal == GV->getInitializer()) {
194 if (GS.StoredType < GlobalStatus::isInitializerStored)
195 GS.StoredType = GlobalStatus::isInitializerStored;
196 } else if (isa<LoadInst>(StoredVal) &&
197 cast<LoadInst>(StoredVal)->getOperand(0) == GV) {
199 if (GS.StoredType < GlobalStatus::isInitializerStored)
200 GS.StoredType = GlobalStatus::isInitializerStored;
201 } else if (GS.StoredType < GlobalStatus::isStoredOnce) {
202 GS.StoredType = GlobalStatus::isStoredOnce;
203 GS.StoredOnceValue = StoredVal;
204 } else if (GS.StoredType == GlobalStatus::isStoredOnce &&
205 GS.StoredOnceValue == StoredVal) {
208 GS.StoredType = GlobalStatus::isStored;
211 GS.StoredType = GlobalStatus::isStored;
214 } else if (isa<GetElementPtrInst>(I)) {
215 if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
216 } else if (isa<SelectInst>(I)) {
217 if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
218 } else if (PHINode *PN = dyn_cast<PHINode>(I)) {
219 // PHI nodes we can check just like select or GEP instructions, but we
220 // have to be careful about infinite recursion.
221 if (PHIUsers.insert(PN)) // Not already visited.
222 if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
223 GS.HasPHIUser = true;
224 } else if (isa<CmpInst>(I)) {
225 } else if (isa<MemTransferInst>(I)) {
226 if (I->getOperand(1) == V)
227 GS.StoredType = GlobalStatus::isStored;
228 if (I->getOperand(2) == V)
230 } else if (isa<MemSetInst>(I)) {
231 assert(I->getOperand(1) == V && "Memset only takes one pointer!");
232 GS.StoredType = GlobalStatus::isStored;
234 return true; // Any other non-load instruction might take address!
236 } else if (Constant *C = dyn_cast<Constant>(*UI)) {
237 GS.HasNonInstructionUser = true;
238 // We might have a dead and dangling constant hanging off of here.
239 if (!SafeToDestroyConstant(C))
242 GS.HasNonInstructionUser = true;
243 // Otherwise must be some other user.
250 static Constant *getAggregateConstantElement(Constant *Agg, Constant *Idx,
251 LLVMContext &Context) {
252 ConstantInt *CI = dyn_cast<ConstantInt>(Idx);
254 unsigned IdxV = CI->getZExtValue();
256 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(Agg)) {
257 if (IdxV < CS->getNumOperands()) return CS->getOperand(IdxV);
258 } else if (ConstantArray *CA = dyn_cast<ConstantArray>(Agg)) {
259 if (IdxV < CA->getNumOperands()) return CA->getOperand(IdxV);
260 } else if (ConstantVector *CP = dyn_cast<ConstantVector>(Agg)) {
261 if (IdxV < CP->getNumOperands()) return CP->getOperand(IdxV);
262 } else if (isa<ConstantAggregateZero>(Agg)) {
263 if (const StructType *STy = dyn_cast<StructType>(Agg->getType())) {
264 if (IdxV < STy->getNumElements())
265 return Context.getNullValue(STy->getElementType(IdxV));
266 } else if (const SequentialType *STy =
267 dyn_cast<SequentialType>(Agg->getType())) {
268 return Context.getNullValue(STy->getElementType());
270 } else if (isa<UndefValue>(Agg)) {
271 if (const StructType *STy = dyn_cast<StructType>(Agg->getType())) {
272 if (IdxV < STy->getNumElements())
273 return Context.getUndef(STy->getElementType(IdxV));
274 } else if (const SequentialType *STy =
275 dyn_cast<SequentialType>(Agg->getType())) {
276 return Context.getUndef(STy->getElementType());
283 /// CleanupConstantGlobalUsers - We just marked GV constant. Loop over all
284 /// users of the global, cleaning up the obvious ones. This is largely just a
285 /// quick scan over the use list to clean up the easy and obvious cruft. This
286 /// returns true if it made a change.
287 static bool CleanupConstantGlobalUsers(Value *V, Constant *Init,
288 LLVMContext &Context) {
289 bool Changed = false;
290 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;) {
293 if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
295 // Replace the load with the initializer.
296 LI->replaceAllUsesWith(Init);
297 LI->eraseFromParent();
300 } else if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
301 // Store must be unreachable or storing Init into the global.
302 SI->eraseFromParent();
304 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U)) {
305 if (CE->getOpcode() == Instruction::GetElementPtr) {
306 Constant *SubInit = 0;
308 SubInit = ConstantFoldLoadThroughGEPConstantExpr(Init, CE, Context);
309 Changed |= CleanupConstantGlobalUsers(CE, SubInit, Context);
310 } else if (CE->getOpcode() == Instruction::BitCast &&
311 isa<PointerType>(CE->getType())) {
312 // Pointer cast, delete any stores and memsets to the global.
313 Changed |= CleanupConstantGlobalUsers(CE, 0, Context);
316 if (CE->use_empty()) {
317 CE->destroyConstant();
320 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) {
321 // Do not transform "gepinst (gep constexpr (GV))" here, because forming
322 // "gepconstexpr (gep constexpr (GV))" will cause the two gep's to fold
323 // and will invalidate our notion of what Init is.
324 Constant *SubInit = 0;
325 if (!isa<ConstantExpr>(GEP->getOperand(0))) {
327 dyn_cast_or_null<ConstantExpr>(ConstantFoldInstruction(GEP, Context));
328 if (Init && CE && CE->getOpcode() == Instruction::GetElementPtr)
329 SubInit = ConstantFoldLoadThroughGEPConstantExpr(Init, CE, Context);
331 Changed |= CleanupConstantGlobalUsers(GEP, SubInit, Context);
333 if (GEP->use_empty()) {
334 GEP->eraseFromParent();
337 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(U)) { // memset/cpy/mv
338 if (MI->getRawDest() == V) {
339 MI->eraseFromParent();
343 } else if (Constant *C = dyn_cast<Constant>(U)) {
344 // If we have a chain of dead constantexprs or other things dangling from
345 // us, and if they are all dead, nuke them without remorse.
346 if (SafeToDestroyConstant(C)) {
347 C->destroyConstant();
348 // This could have invalidated UI, start over from scratch.
349 CleanupConstantGlobalUsers(V, Init, Context);
357 /// isSafeSROAElementUse - Return true if the specified instruction is a safe
358 /// user of a derived expression from a global that we want to SROA.
359 static bool isSafeSROAElementUse(Value *V) {
360 // We might have a dead and dangling constant hanging off of here.
361 if (Constant *C = dyn_cast<Constant>(V))
362 return SafeToDestroyConstant(C);
364 Instruction *I = dyn_cast<Instruction>(V);
365 if (!I) return false;
368 if (isa<LoadInst>(I)) return true;
370 // Stores *to* the pointer are ok.
371 if (StoreInst *SI = dyn_cast<StoreInst>(I))
372 return SI->getOperand(0) != V;
374 // Otherwise, it must be a GEP.
375 GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I);
376 if (GEPI == 0) return false;
378 if (GEPI->getNumOperands() < 3 || !isa<Constant>(GEPI->getOperand(1)) ||
379 !cast<Constant>(GEPI->getOperand(1))->isNullValue())
382 for (Value::use_iterator I = GEPI->use_begin(), E = GEPI->use_end();
384 if (!isSafeSROAElementUse(*I))
390 /// IsUserOfGlobalSafeForSRA - U is a direct user of the specified global value.
391 /// Look at it and its uses and decide whether it is safe to SROA this global.
393 static bool IsUserOfGlobalSafeForSRA(User *U, GlobalValue *GV) {
394 // The user of the global must be a GEP Inst or a ConstantExpr GEP.
395 if (!isa<GetElementPtrInst>(U) &&
396 (!isa<ConstantExpr>(U) ||
397 cast<ConstantExpr>(U)->getOpcode() != Instruction::GetElementPtr))
400 // Check to see if this ConstantExpr GEP is SRA'able. In particular, we
401 // don't like < 3 operand CE's, and we don't like non-constant integer
402 // indices. This enforces that all uses are 'gep GV, 0, C, ...' for some
404 if (U->getNumOperands() < 3 || !isa<Constant>(U->getOperand(1)) ||
405 !cast<Constant>(U->getOperand(1))->isNullValue() ||
406 !isa<ConstantInt>(U->getOperand(2)))
409 gep_type_iterator GEPI = gep_type_begin(U), E = gep_type_end(U);
410 ++GEPI; // Skip over the pointer index.
412 // If this is a use of an array allocation, do a bit more checking for sanity.
413 if (const ArrayType *AT = dyn_cast<ArrayType>(*GEPI)) {
414 uint64_t NumElements = AT->getNumElements();
415 ConstantInt *Idx = cast<ConstantInt>(U->getOperand(2));
417 // Check to make sure that index falls within the array. If not,
418 // something funny is going on, so we won't do the optimization.
420 if (Idx->getZExtValue() >= NumElements)
423 // We cannot scalar repl this level of the array unless any array
424 // sub-indices are in-range constants. In particular, consider:
425 // A[0][i]. We cannot know that the user isn't doing invalid things like
426 // allowing i to index an out-of-range subscript that accesses A[1].
428 // Scalar replacing *just* the outer index of the array is probably not
429 // going to be a win anyway, so just give up.
430 for (++GEPI; // Skip array index.
431 GEPI != E && (isa<ArrayType>(*GEPI) || isa<VectorType>(*GEPI));
433 uint64_t NumElements;
434 if (const ArrayType *SubArrayTy = dyn_cast<ArrayType>(*GEPI))
435 NumElements = SubArrayTy->getNumElements();
437 NumElements = cast<VectorType>(*GEPI)->getNumElements();
439 ConstantInt *IdxVal = dyn_cast<ConstantInt>(GEPI.getOperand());
440 if (!IdxVal || IdxVal->getZExtValue() >= NumElements)
445 for (Value::use_iterator I = U->use_begin(), E = U->use_end(); I != E; ++I)
446 if (!isSafeSROAElementUse(*I))
451 /// GlobalUsersSafeToSRA - Look at all uses of the global and decide whether it
452 /// is safe for us to perform this transformation.
454 static bool GlobalUsersSafeToSRA(GlobalValue *GV) {
455 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end();
457 if (!IsUserOfGlobalSafeForSRA(*UI, GV))
464 /// SRAGlobal - Perform scalar replacement of aggregates on the specified global
465 /// variable. This opens the door for other optimizations by exposing the
466 /// behavior of the program in a more fine-grained way. We have determined that
467 /// this transformation is safe already. We return the first global variable we
468 /// insert so that the caller can reprocess it.
469 static GlobalVariable *SRAGlobal(GlobalVariable *GV, const TargetData &TD,
470 LLVMContext &Context) {
471 // Make sure this global only has simple uses that we can SRA.
472 if (!GlobalUsersSafeToSRA(GV))
475 assert(GV->hasLocalLinkage() && !GV->isConstant());
476 Constant *Init = GV->getInitializer();
477 const Type *Ty = Init->getType();
479 std::vector<GlobalVariable*> NewGlobals;
480 Module::GlobalListType &Globals = GV->getParent()->getGlobalList();
482 // Get the alignment of the global, either explicit or target-specific.
483 unsigned StartAlignment = GV->getAlignment();
484 if (StartAlignment == 0)
485 StartAlignment = TD.getABITypeAlignment(GV->getType());
487 if (const StructType *STy = dyn_cast<StructType>(Ty)) {
488 NewGlobals.reserve(STy->getNumElements());
489 const StructLayout &Layout = *TD.getStructLayout(STy);
490 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
491 Constant *In = getAggregateConstantElement(Init,
492 ConstantInt::get(Type::Int32Ty, i),
494 assert(In && "Couldn't get element of initializer?");
495 GlobalVariable *NGV = new GlobalVariable(Context,
496 STy->getElementType(i), false,
497 GlobalVariable::InternalLinkage,
498 In, GV->getName()+"."+utostr(i),
500 GV->getType()->getAddressSpace());
501 Globals.insert(GV, NGV);
502 NewGlobals.push_back(NGV);
504 // Calculate the known alignment of the field. If the original aggregate
505 // had 256 byte alignment for example, something might depend on that:
506 // propagate info to each field.
507 uint64_t FieldOffset = Layout.getElementOffset(i);
508 unsigned NewAlign = (unsigned)MinAlign(StartAlignment, FieldOffset);
509 if (NewAlign > TD.getABITypeAlignment(STy->getElementType(i)))
510 NGV->setAlignment(NewAlign);
512 } else if (const SequentialType *STy = dyn_cast<SequentialType>(Ty)) {
513 unsigned NumElements = 0;
514 if (const ArrayType *ATy = dyn_cast<ArrayType>(STy))
515 NumElements = ATy->getNumElements();
517 NumElements = cast<VectorType>(STy)->getNumElements();
519 if (NumElements > 16 && GV->hasNUsesOrMore(16))
520 return 0; // It's not worth it.
521 NewGlobals.reserve(NumElements);
523 uint64_t EltSize = TD.getTypeAllocSize(STy->getElementType());
524 unsigned EltAlign = TD.getABITypeAlignment(STy->getElementType());
525 for (unsigned i = 0, e = NumElements; i != e; ++i) {
526 Constant *In = getAggregateConstantElement(Init,
527 ConstantInt::get(Type::Int32Ty, i),
529 assert(In && "Couldn't get element of initializer?");
531 GlobalVariable *NGV = new GlobalVariable(Context,
532 STy->getElementType(), false,
533 GlobalVariable::InternalLinkage,
534 In, GV->getName()+"."+utostr(i),
536 GV->getType()->getAddressSpace());
537 Globals.insert(GV, NGV);
538 NewGlobals.push_back(NGV);
540 // Calculate the known alignment of the field. If the original aggregate
541 // had 256 byte alignment for example, something might depend on that:
542 // propagate info to each field.
543 unsigned NewAlign = (unsigned)MinAlign(StartAlignment, EltSize*i);
544 if (NewAlign > EltAlign)
545 NGV->setAlignment(NewAlign);
549 if (NewGlobals.empty())
552 DOUT << "PERFORMING GLOBAL SRA ON: " << *GV;
554 Constant *NullInt = Context.getNullValue(Type::Int32Ty);
556 // Loop over all of the uses of the global, replacing the constantexpr geps,
557 // with smaller constantexpr geps or direct references.
558 while (!GV->use_empty()) {
559 User *GEP = GV->use_back();
560 assert(((isa<ConstantExpr>(GEP) &&
561 cast<ConstantExpr>(GEP)->getOpcode()==Instruction::GetElementPtr)||
562 isa<GetElementPtrInst>(GEP)) && "NonGEP CE's are not SRAable!");
564 // Ignore the 1th operand, which has to be zero or else the program is quite
565 // broken (undefined). Get the 2nd operand, which is the structure or array
567 unsigned Val = cast<ConstantInt>(GEP->getOperand(2))->getZExtValue();
568 if (Val >= NewGlobals.size()) Val = 0; // Out of bound array access.
570 Value *NewPtr = NewGlobals[Val];
572 // Form a shorter GEP if needed.
573 if (GEP->getNumOperands() > 3) {
574 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GEP)) {
575 SmallVector<Constant*, 8> Idxs;
576 Idxs.push_back(NullInt);
577 for (unsigned i = 3, e = CE->getNumOperands(); i != e; ++i)
578 Idxs.push_back(CE->getOperand(i));
579 NewPtr = Context.getConstantExprGetElementPtr(cast<Constant>(NewPtr),
580 &Idxs[0], Idxs.size());
582 GetElementPtrInst *GEPI = cast<GetElementPtrInst>(GEP);
583 SmallVector<Value*, 8> Idxs;
584 Idxs.push_back(NullInt);
585 for (unsigned i = 3, e = GEPI->getNumOperands(); i != e; ++i)
586 Idxs.push_back(GEPI->getOperand(i));
587 NewPtr = GetElementPtrInst::Create(NewPtr, Idxs.begin(), Idxs.end(),
588 GEPI->getName()+"."+utostr(Val), GEPI);
591 GEP->replaceAllUsesWith(NewPtr);
593 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(GEP))
594 GEPI->eraseFromParent();
596 cast<ConstantExpr>(GEP)->destroyConstant();
599 // Delete the old global, now that it is dead.
603 // Loop over the new globals array deleting any globals that are obviously
604 // dead. This can arise due to scalarization of a structure or an array that
605 // has elements that are dead.
606 unsigned FirstGlobal = 0;
607 for (unsigned i = 0, e = NewGlobals.size(); i != e; ++i)
608 if (NewGlobals[i]->use_empty()) {
609 Globals.erase(NewGlobals[i]);
610 if (FirstGlobal == i) ++FirstGlobal;
613 return FirstGlobal != NewGlobals.size() ? NewGlobals[FirstGlobal] : 0;
616 /// AllUsesOfValueWillTrapIfNull - Return true if all users of the specified
617 /// value will trap if the value is dynamically null. PHIs keeps track of any
618 /// phi nodes we've seen to avoid reprocessing them.
619 static bool AllUsesOfValueWillTrapIfNull(Value *V,
620 SmallPtrSet<PHINode*, 8> &PHIs) {
621 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ++UI)
622 if (isa<LoadInst>(*UI)) {
624 } else if (StoreInst *SI = dyn_cast<StoreInst>(*UI)) {
625 if (SI->getOperand(0) == V) {
626 //cerr << "NONTRAPPING USE: " << **UI;
627 return false; // Storing the value.
629 } else if (CallInst *CI = dyn_cast<CallInst>(*UI)) {
630 if (CI->getOperand(0) != V) {
631 //cerr << "NONTRAPPING USE: " << **UI;
632 return false; // Not calling the ptr
634 } else if (InvokeInst *II = dyn_cast<InvokeInst>(*UI)) {
635 if (II->getOperand(0) != V) {
636 //cerr << "NONTRAPPING USE: " << **UI;
637 return false; // Not calling the ptr
639 } else if (BitCastInst *CI = dyn_cast<BitCastInst>(*UI)) {
640 if (!AllUsesOfValueWillTrapIfNull(CI, PHIs)) return false;
641 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(*UI)) {
642 if (!AllUsesOfValueWillTrapIfNull(GEPI, PHIs)) return false;
643 } else if (PHINode *PN = dyn_cast<PHINode>(*UI)) {
644 // If we've already seen this phi node, ignore it, it has already been
647 return AllUsesOfValueWillTrapIfNull(PN, PHIs);
648 } else if (isa<ICmpInst>(*UI) &&
649 isa<ConstantPointerNull>(UI->getOperand(1))) {
650 // Ignore setcc X, null
652 //cerr << "NONTRAPPING USE: " << **UI;
658 /// AllUsesOfLoadedValueWillTrapIfNull - Return true if all uses of any loads
659 /// from GV will trap if the loaded value is null. Note that this also permits
660 /// comparisons of the loaded value against null, as a special case.
661 static bool AllUsesOfLoadedValueWillTrapIfNull(GlobalVariable *GV) {
662 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); UI!=E; ++UI)
663 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
664 SmallPtrSet<PHINode*, 8> PHIs;
665 if (!AllUsesOfValueWillTrapIfNull(LI, PHIs))
667 } else if (isa<StoreInst>(*UI)) {
668 // Ignore stores to the global.
670 // We don't know or understand this user, bail out.
671 //cerr << "UNKNOWN USER OF GLOBAL!: " << **UI;
678 static bool OptimizeAwayTrappingUsesOfValue(Value *V, Constant *NewV,
679 LLVMContext &Context) {
680 bool Changed = false;
681 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ) {
682 Instruction *I = cast<Instruction>(*UI++);
683 if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
684 LI->setOperand(0, NewV);
686 } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
687 if (SI->getOperand(1) == V) {
688 SI->setOperand(1, NewV);
691 } else if (isa<CallInst>(I) || isa<InvokeInst>(I)) {
692 if (I->getOperand(0) == V) {
693 // Calling through the pointer! Turn into a direct call, but be careful
694 // that the pointer is not also being passed as an argument.
695 I->setOperand(0, NewV);
697 bool PassedAsArg = false;
698 for (unsigned i = 1, e = I->getNumOperands(); i != e; ++i)
699 if (I->getOperand(i) == V) {
701 I->setOperand(i, NewV);
705 // Being passed as an argument also. Be careful to not invalidate UI!
709 } else if (CastInst *CI = dyn_cast<CastInst>(I)) {
710 Changed |= OptimizeAwayTrappingUsesOfValue(CI,
711 Context.getConstantExprCast(CI->getOpcode(),
712 NewV, CI->getType()), Context);
713 if (CI->use_empty()) {
715 CI->eraseFromParent();
717 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I)) {
718 // Should handle GEP here.
719 SmallVector<Constant*, 8> Idxs;
720 Idxs.reserve(GEPI->getNumOperands()-1);
721 for (User::op_iterator i = GEPI->op_begin() + 1, e = GEPI->op_end();
723 if (Constant *C = dyn_cast<Constant>(*i))
727 if (Idxs.size() == GEPI->getNumOperands()-1)
728 Changed |= OptimizeAwayTrappingUsesOfValue(GEPI,
729 Context.getConstantExprGetElementPtr(NewV, &Idxs[0],
730 Idxs.size()), Context);
731 if (GEPI->use_empty()) {
733 GEPI->eraseFromParent();
742 /// OptimizeAwayTrappingUsesOfLoads - The specified global has only one non-null
743 /// value stored into it. If there are uses of the loaded value that would trap
744 /// if the loaded value is dynamically null, then we know that they cannot be
745 /// reachable with a null optimize away the load.
746 static bool OptimizeAwayTrappingUsesOfLoads(GlobalVariable *GV, Constant *LV,
747 LLVMContext &Context) {
748 bool Changed = false;
750 // Keep track of whether we are able to remove all the uses of the global
751 // other than the store that defines it.
752 bool AllNonStoreUsesGone = true;
754 // Replace all uses of loads with uses of uses of the stored value.
755 for (Value::use_iterator GUI = GV->use_begin(), E = GV->use_end(); GUI != E;){
756 User *GlobalUser = *GUI++;
757 if (LoadInst *LI = dyn_cast<LoadInst>(GlobalUser)) {
758 Changed |= OptimizeAwayTrappingUsesOfValue(LI, LV, Context);
759 // If we were able to delete all uses of the loads
760 if (LI->use_empty()) {
761 LI->eraseFromParent();
764 AllNonStoreUsesGone = false;
766 } else if (isa<StoreInst>(GlobalUser)) {
767 // Ignore the store that stores "LV" to the global.
768 assert(GlobalUser->getOperand(1) == GV &&
769 "Must be storing *to* the global");
771 AllNonStoreUsesGone = false;
773 // If we get here we could have other crazy uses that are transitively
775 assert((isa<PHINode>(GlobalUser) || isa<SelectInst>(GlobalUser) ||
776 isa<ConstantExpr>(GlobalUser)) && "Only expect load and stores!");
781 DOUT << "OPTIMIZED LOADS FROM STORED ONCE POINTER: " << *GV;
785 // If we nuked all of the loads, then none of the stores are needed either,
786 // nor is the global.
787 if (AllNonStoreUsesGone) {
788 DOUT << " *** GLOBAL NOW DEAD!\n";
789 CleanupConstantGlobalUsers(GV, 0, Context);
790 if (GV->use_empty()) {
791 GV->eraseFromParent();
799 /// ConstantPropUsersOf - Walk the use list of V, constant folding all of the
800 /// instructions that are foldable.
801 static void ConstantPropUsersOf(Value *V, LLVMContext &Context) {
802 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; )
803 if (Instruction *I = dyn_cast<Instruction>(*UI++))
804 if (Constant *NewC = ConstantFoldInstruction(I, Context)) {
805 I->replaceAllUsesWith(NewC);
807 // Advance UI to the next non-I use to avoid invalidating it!
808 // Instructions could multiply use V.
809 while (UI != E && *UI == I)
811 I->eraseFromParent();
815 /// OptimizeGlobalAddressOfMalloc - This function takes the specified global
816 /// variable, and transforms the program as if it always contained the result of
817 /// the specified malloc. Because it is always the result of the specified
818 /// malloc, there is no reason to actually DO the malloc. Instead, turn the
819 /// malloc into a global, and any loads of GV as uses of the new global.
820 static GlobalVariable *OptimizeGlobalAddressOfMalloc(GlobalVariable *GV,
822 LLVMContext &Context) {
823 DOUT << "PROMOTING MALLOC GLOBAL: " << *GV << " MALLOC = " << *MI;
824 ConstantInt *NElements = cast<ConstantInt>(MI->getArraySize());
826 if (NElements->getZExtValue() != 1) {
827 // If we have an array allocation, transform it to a single element
828 // allocation to make the code below simpler.
829 Type *NewTy = Context.getArrayType(MI->getAllocatedType(),
830 NElements->getZExtValue());
832 new MallocInst(NewTy, Context.getNullValue(Type::Int32Ty),
833 MI->getAlignment(), MI->getName(), MI);
835 Indices[0] = Indices[1] = Context.getNullValue(Type::Int32Ty);
836 Value *NewGEP = GetElementPtrInst::Create(NewMI, Indices, Indices + 2,
837 NewMI->getName()+".el0", MI);
838 MI->replaceAllUsesWith(NewGEP);
839 MI->eraseFromParent();
843 // Create the new global variable. The contents of the malloc'd memory is
844 // undefined, so initialize with an undef value.
845 // FIXME: This new global should have the alignment returned by malloc. Code
846 // could depend on malloc returning large alignment (on the mac, 16 bytes) but
847 // this would only guarantee some lower alignment.
848 Constant *Init = Context.getUndef(MI->getAllocatedType());
849 GlobalVariable *NewGV = new GlobalVariable(*GV->getParent(),
850 MI->getAllocatedType(), false,
851 GlobalValue::InternalLinkage, Init,
852 GV->getName()+".body",
854 GV->isThreadLocal());
856 // Anything that used the malloc now uses the global directly.
857 MI->replaceAllUsesWith(NewGV);
859 Constant *RepValue = NewGV;
860 if (NewGV->getType() != GV->getType()->getElementType())
861 RepValue = Context.getConstantExprBitCast(RepValue,
862 GV->getType()->getElementType());
864 // If there is a comparison against null, we will insert a global bool to
865 // keep track of whether the global was initialized yet or not.
866 GlobalVariable *InitBool =
867 new GlobalVariable(Context, Type::Int1Ty, false,
868 GlobalValue::InternalLinkage,
869 Context.getFalse(), GV->getName()+".init",
870 GV->isThreadLocal());
871 bool InitBoolUsed = false;
873 // Loop over all uses of GV, processing them in turn.
874 std::vector<StoreInst*> Stores;
875 while (!GV->use_empty())
876 if (LoadInst *LI = dyn_cast<LoadInst>(GV->use_back())) {
877 while (!LI->use_empty()) {
878 Use &LoadUse = LI->use_begin().getUse();
879 if (!isa<ICmpInst>(LoadUse.getUser()))
882 ICmpInst *CI = cast<ICmpInst>(LoadUse.getUser());
883 // Replace the cmp X, 0 with a use of the bool value.
884 Value *LV = new LoadInst(InitBool, InitBool->getName()+".val", CI);
886 switch (CI->getPredicate()) {
887 default: llvm_unreachable("Unknown ICmp Predicate!");
888 case ICmpInst::ICMP_ULT:
889 case ICmpInst::ICMP_SLT:
890 LV = Context.getFalse(); // X < null -> always false
892 case ICmpInst::ICMP_ULE:
893 case ICmpInst::ICMP_SLE:
894 case ICmpInst::ICMP_EQ:
895 LV = BinaryOperator::CreateNot(Context, LV, "notinit", CI);
897 case ICmpInst::ICMP_NE:
898 case ICmpInst::ICMP_UGE:
899 case ICmpInst::ICMP_SGE:
900 case ICmpInst::ICMP_UGT:
901 case ICmpInst::ICMP_SGT:
904 CI->replaceAllUsesWith(LV);
905 CI->eraseFromParent();
908 LI->eraseFromParent();
910 StoreInst *SI = cast<StoreInst>(GV->use_back());
911 // The global is initialized when the store to it occurs.
912 new StoreInst(Context.getTrue(), InitBool, SI);
913 SI->eraseFromParent();
916 // If the initialization boolean was used, insert it, otherwise delete it.
918 while (!InitBool->use_empty()) // Delete initializations
919 cast<Instruction>(InitBool->use_back())->eraseFromParent();
922 GV->getParent()->getGlobalList().insert(GV, InitBool);
925 // Now the GV is dead, nuke it and the malloc.
926 GV->eraseFromParent();
927 MI->eraseFromParent();
929 // To further other optimizations, loop over all users of NewGV and try to
930 // constant prop them. This will promote GEP instructions with constant
931 // indices into GEP constant-exprs, which will allow global-opt to hack on it.
932 ConstantPropUsersOf(NewGV, Context);
933 if (RepValue != NewGV)
934 ConstantPropUsersOf(RepValue, Context);
939 /// ValueIsOnlyUsedLocallyOrStoredToOneGlobal - Scan the use-list of V checking
940 /// to make sure that there are no complex uses of V. We permit simple things
941 /// like dereferencing the pointer, but not storing through the address, unless
942 /// it is to the specified global.
943 static bool ValueIsOnlyUsedLocallyOrStoredToOneGlobal(Instruction *V,
945 SmallPtrSet<PHINode*, 8> &PHIs) {
946 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;++UI){
947 Instruction *Inst = cast<Instruction>(*UI);
949 if (isa<LoadInst>(Inst) || isa<CmpInst>(Inst)) {
950 continue; // Fine, ignore.
953 if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
954 if (SI->getOperand(0) == V && SI->getOperand(1) != GV)
955 return false; // Storing the pointer itself... bad.
956 continue; // Otherwise, storing through it, or storing into GV... fine.
959 if (isa<GetElementPtrInst>(Inst)) {
960 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(Inst, GV, PHIs))
965 if (PHINode *PN = dyn_cast<PHINode>(Inst)) {
966 // PHIs are ok if all uses are ok. Don't infinitely recurse through PHI
969 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(PN, GV, PHIs))
974 if (BitCastInst *BCI = dyn_cast<BitCastInst>(Inst)) {
975 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(BCI, GV, PHIs))
985 /// ReplaceUsesOfMallocWithGlobal - The Alloc pointer is stored into GV
986 /// somewhere. Transform all uses of the allocation into loads from the
987 /// global and uses of the resultant pointer. Further, delete the store into
988 /// GV. This assumes that these value pass the
989 /// 'ValueIsOnlyUsedLocallyOrStoredToOneGlobal' predicate.
990 static void ReplaceUsesOfMallocWithGlobal(Instruction *Alloc,
991 GlobalVariable *GV) {
992 while (!Alloc->use_empty()) {
993 Instruction *U = cast<Instruction>(*Alloc->use_begin());
994 Instruction *InsertPt = U;
995 if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
996 // If this is the store of the allocation into the global, remove it.
997 if (SI->getOperand(1) == GV) {
998 SI->eraseFromParent();
1001 } else if (PHINode *PN = dyn_cast<PHINode>(U)) {
1002 // Insert the load in the corresponding predecessor, not right before the
1004 InsertPt = PN->getIncomingBlock(Alloc->use_begin())->getTerminator();
1005 } else if (isa<BitCastInst>(U)) {
1006 // Must be bitcast between the malloc and store to initialize the global.
1007 ReplaceUsesOfMallocWithGlobal(U, GV);
1008 U->eraseFromParent();
1010 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(U)) {
1011 // If this is a "GEP bitcast" and the user is a store to the global, then
1012 // just process it as a bitcast.
1013 if (GEPI->hasAllZeroIndices() && GEPI->hasOneUse())
1014 if (StoreInst *SI = dyn_cast<StoreInst>(GEPI->use_back()))
1015 if (SI->getOperand(1) == GV) {
1016 // Must be bitcast GEP between the malloc and store to initialize
1018 ReplaceUsesOfMallocWithGlobal(GEPI, GV);
1019 GEPI->eraseFromParent();
1024 // Insert a load from the global, and use it instead of the malloc.
1025 Value *NL = new LoadInst(GV, GV->getName()+".val", InsertPt);
1026 U->replaceUsesOfWith(Alloc, NL);
1030 /// LoadUsesSimpleEnoughForHeapSRA - Verify that all uses of V (a load, or a phi
1031 /// of a load) are simple enough to perform heap SRA on. This permits GEP's
1032 /// that index through the array and struct field, icmps of null, and PHIs.
1033 static bool LoadUsesSimpleEnoughForHeapSRA(Value *V,
1034 SmallPtrSet<PHINode*, 32> &LoadUsingPHIs,
1035 SmallPtrSet<PHINode*, 32> &LoadUsingPHIsPerLoad) {
1036 // We permit two users of the load: setcc comparing against the null
1037 // pointer, and a getelementptr of a specific form.
1038 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;++UI){
1039 Instruction *User = cast<Instruction>(*UI);
1041 // Comparison against null is ok.
1042 if (ICmpInst *ICI = dyn_cast<ICmpInst>(User)) {
1043 if (!isa<ConstantPointerNull>(ICI->getOperand(1)))
1048 // getelementptr is also ok, but only a simple form.
1049 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
1050 // Must index into the array and into the struct.
1051 if (GEPI->getNumOperands() < 3)
1054 // Otherwise the GEP is ok.
1058 if (PHINode *PN = dyn_cast<PHINode>(User)) {
1059 if (!LoadUsingPHIsPerLoad.insert(PN))
1060 // This means some phi nodes are dependent on each other.
1061 // Avoid infinite looping!
1063 if (!LoadUsingPHIs.insert(PN))
1064 // If we have already analyzed this PHI, then it is safe.
1067 // Make sure all uses of the PHI are simple enough to transform.
1068 if (!LoadUsesSimpleEnoughForHeapSRA(PN,
1069 LoadUsingPHIs, LoadUsingPHIsPerLoad))
1075 // Otherwise we don't know what this is, not ok.
1083 /// AllGlobalLoadUsesSimpleEnoughForHeapSRA - If all users of values loaded from
1084 /// GV are simple enough to perform HeapSRA, return true.
1085 static bool AllGlobalLoadUsesSimpleEnoughForHeapSRA(GlobalVariable *GV,
1087 SmallPtrSet<PHINode*, 32> LoadUsingPHIs;
1088 SmallPtrSet<PHINode*, 32> LoadUsingPHIsPerLoad;
1089 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); UI != E;
1091 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
1092 if (!LoadUsesSimpleEnoughForHeapSRA(LI, LoadUsingPHIs,
1093 LoadUsingPHIsPerLoad))
1095 LoadUsingPHIsPerLoad.clear();
1098 // If we reach here, we know that all uses of the loads and transitive uses
1099 // (through PHI nodes) are simple enough to transform. However, we don't know
1100 // that all inputs the to the PHI nodes are in the same equivalence sets.
1101 // Check to verify that all operands of the PHIs are either PHIS that can be
1102 // transformed, loads from GV, or MI itself.
1103 for (SmallPtrSet<PHINode*, 32>::iterator I = LoadUsingPHIs.begin(),
1104 E = LoadUsingPHIs.end(); I != E; ++I) {
1106 for (unsigned op = 0, e = PN->getNumIncomingValues(); op != e; ++op) {
1107 Value *InVal = PN->getIncomingValue(op);
1109 // PHI of the stored value itself is ok.
1110 if (InVal == MI) continue;
1112 if (PHINode *InPN = dyn_cast<PHINode>(InVal)) {
1113 // One of the PHIs in our set is (optimistically) ok.
1114 if (LoadUsingPHIs.count(InPN))
1119 // Load from GV is ok.
1120 if (LoadInst *LI = dyn_cast<LoadInst>(InVal))
1121 if (LI->getOperand(0) == GV)
1126 // Anything else is rejected.
1134 static Value *GetHeapSROAValue(Value *V, unsigned FieldNo,
1135 DenseMap<Value*, std::vector<Value*> > &InsertedScalarizedValues,
1136 std::vector<std::pair<PHINode*, unsigned> > &PHIsToRewrite,
1137 LLVMContext &Context) {
1138 std::vector<Value*> &FieldVals = InsertedScalarizedValues[V];
1140 if (FieldNo >= FieldVals.size())
1141 FieldVals.resize(FieldNo+1);
1143 // If we already have this value, just reuse the previously scalarized
1145 if (Value *FieldVal = FieldVals[FieldNo])
1148 // Depending on what instruction this is, we have several cases.
1150 if (LoadInst *LI = dyn_cast<LoadInst>(V)) {
1151 // This is a scalarized version of the load from the global. Just create
1152 // a new Load of the scalarized global.
1153 Result = new LoadInst(GetHeapSROAValue(LI->getOperand(0), FieldNo,
1154 InsertedScalarizedValues,
1155 PHIsToRewrite, Context),
1156 LI->getName()+".f" + utostr(FieldNo), LI);
1157 } else if (PHINode *PN = dyn_cast<PHINode>(V)) {
1158 // PN's type is pointer to struct. Make a new PHI of pointer to struct
1160 const StructType *ST =
1161 cast<StructType>(cast<PointerType>(PN->getType())->getElementType());
1164 PHINode::Create(Context.getPointerTypeUnqual(ST->getElementType(FieldNo)),
1165 PN->getName()+".f"+utostr(FieldNo), PN);
1166 PHIsToRewrite.push_back(std::make_pair(PN, FieldNo));
1168 llvm_unreachable("Unknown usable value");
1172 return FieldVals[FieldNo] = Result;
1175 /// RewriteHeapSROALoadUser - Given a load instruction and a value derived from
1176 /// the load, rewrite the derived value to use the HeapSRoA'd load.
1177 static void RewriteHeapSROALoadUser(Instruction *LoadUser,
1178 DenseMap<Value*, std::vector<Value*> > &InsertedScalarizedValues,
1179 std::vector<std::pair<PHINode*, unsigned> > &PHIsToRewrite,
1180 LLVMContext &Context) {
1181 // If this is a comparison against null, handle it.
1182 if (ICmpInst *SCI = dyn_cast<ICmpInst>(LoadUser)) {
1183 assert(isa<ConstantPointerNull>(SCI->getOperand(1)));
1184 // If we have a setcc of the loaded pointer, we can use a setcc of any
1186 Value *NPtr = GetHeapSROAValue(SCI->getOperand(0), 0,
1187 InsertedScalarizedValues, PHIsToRewrite,
1190 Value *New = new ICmpInst(SCI, SCI->getPredicate(), NPtr,
1191 Context.getNullValue(NPtr->getType()),
1193 SCI->replaceAllUsesWith(New);
1194 SCI->eraseFromParent();
1198 // Handle 'getelementptr Ptr, Idx, i32 FieldNo ...'
1199 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(LoadUser)) {
1200 assert(GEPI->getNumOperands() >= 3 && isa<ConstantInt>(GEPI->getOperand(2))
1201 && "Unexpected GEPI!");
1203 // Load the pointer for this field.
1204 unsigned FieldNo = cast<ConstantInt>(GEPI->getOperand(2))->getZExtValue();
1205 Value *NewPtr = GetHeapSROAValue(GEPI->getOperand(0), FieldNo,
1206 InsertedScalarizedValues, PHIsToRewrite,
1209 // Create the new GEP idx vector.
1210 SmallVector<Value*, 8> GEPIdx;
1211 GEPIdx.push_back(GEPI->getOperand(1));
1212 GEPIdx.append(GEPI->op_begin()+3, GEPI->op_end());
1214 Value *NGEPI = GetElementPtrInst::Create(NewPtr,
1215 GEPIdx.begin(), GEPIdx.end(),
1216 GEPI->getName(), GEPI);
1217 GEPI->replaceAllUsesWith(NGEPI);
1218 GEPI->eraseFromParent();
1222 // Recursively transform the users of PHI nodes. This will lazily create the
1223 // PHIs that are needed for individual elements. Keep track of what PHIs we
1224 // see in InsertedScalarizedValues so that we don't get infinite loops (very
1225 // antisocial). If the PHI is already in InsertedScalarizedValues, it has
1226 // already been seen first by another load, so its uses have already been
1228 PHINode *PN = cast<PHINode>(LoadUser);
1230 DenseMap<Value*, std::vector<Value*> >::iterator InsertPos;
1231 tie(InsertPos, Inserted) =
1232 InsertedScalarizedValues.insert(std::make_pair(PN, std::vector<Value*>()));
1233 if (!Inserted) return;
1235 // If this is the first time we've seen this PHI, recursively process all
1237 for (Value::use_iterator UI = PN->use_begin(), E = PN->use_end(); UI != E; ) {
1238 Instruction *User = cast<Instruction>(*UI++);
1239 RewriteHeapSROALoadUser(User, InsertedScalarizedValues, PHIsToRewrite,
1244 /// RewriteUsesOfLoadForHeapSRoA - We are performing Heap SRoA on a global. Ptr
1245 /// is a value loaded from the global. Eliminate all uses of Ptr, making them
1246 /// use FieldGlobals instead. All uses of loaded values satisfy
1247 /// AllGlobalLoadUsesSimpleEnoughForHeapSRA.
1248 static void RewriteUsesOfLoadForHeapSRoA(LoadInst *Load,
1249 DenseMap<Value*, std::vector<Value*> > &InsertedScalarizedValues,
1250 std::vector<std::pair<PHINode*, unsigned> > &PHIsToRewrite,
1251 LLVMContext &Context) {
1252 for (Value::use_iterator UI = Load->use_begin(), E = Load->use_end();
1254 Instruction *User = cast<Instruction>(*UI++);
1255 RewriteHeapSROALoadUser(User, InsertedScalarizedValues, PHIsToRewrite,
1259 if (Load->use_empty()) {
1260 Load->eraseFromParent();
1261 InsertedScalarizedValues.erase(Load);
1265 /// PerformHeapAllocSRoA - MI is an allocation of an array of structures. Break
1266 /// it up into multiple allocations of arrays of the fields.
1267 static GlobalVariable *PerformHeapAllocSRoA(GlobalVariable *GV, MallocInst *MI,
1268 LLVMContext &Context){
1269 DOUT << "SROA HEAP ALLOC: " << *GV << " MALLOC = " << *MI;
1270 const StructType *STy = cast<StructType>(MI->getAllocatedType());
1272 // There is guaranteed to be at least one use of the malloc (storing
1273 // it into GV). If there are other uses, change them to be uses of
1274 // the global to simplify later code. This also deletes the store
1276 ReplaceUsesOfMallocWithGlobal(MI, GV);
1278 // Okay, at this point, there are no users of the malloc. Insert N
1279 // new mallocs at the same place as MI, and N globals.
1280 std::vector<Value*> FieldGlobals;
1281 std::vector<MallocInst*> FieldMallocs;
1283 for (unsigned FieldNo = 0, e = STy->getNumElements(); FieldNo != e;++FieldNo){
1284 const Type *FieldTy = STy->getElementType(FieldNo);
1285 const Type *PFieldTy = Context.getPointerTypeUnqual(FieldTy);
1287 GlobalVariable *NGV =
1288 new GlobalVariable(*GV->getParent(),
1289 PFieldTy, false, GlobalValue::InternalLinkage,
1290 Context.getNullValue(PFieldTy),
1291 GV->getName() + ".f" + utostr(FieldNo), GV,
1292 GV->isThreadLocal());
1293 FieldGlobals.push_back(NGV);
1295 MallocInst *NMI = new MallocInst(FieldTy, MI->getArraySize(),
1296 MI->getName() + ".f" + utostr(FieldNo),MI);
1297 FieldMallocs.push_back(NMI);
1298 new StoreInst(NMI, NGV, MI);
1301 // The tricky aspect of this transformation is handling the case when malloc
1302 // fails. In the original code, malloc failing would set the result pointer
1303 // of malloc to null. In this case, some mallocs could succeed and others
1304 // could fail. As such, we emit code that looks like this:
1305 // F0 = malloc(field0)
1306 // F1 = malloc(field1)
1307 // F2 = malloc(field2)
1308 // if (F0 == 0 || F1 == 0 || F2 == 0) {
1309 // if (F0) { free(F0); F0 = 0; }
1310 // if (F1) { free(F1); F1 = 0; }
1311 // if (F2) { free(F2); F2 = 0; }
1313 Value *RunningOr = 0;
1314 for (unsigned i = 0, e = FieldMallocs.size(); i != e; ++i) {
1315 Value *Cond = new ICmpInst(MI, ICmpInst::ICMP_EQ, FieldMallocs[i],
1316 Context.getNullValue(FieldMallocs[i]->getType()),
1319 RunningOr = Cond; // First seteq
1321 RunningOr = BinaryOperator::CreateOr(RunningOr, Cond, "tmp", MI);
1324 // Split the basic block at the old malloc.
1325 BasicBlock *OrigBB = MI->getParent();
1326 BasicBlock *ContBB = OrigBB->splitBasicBlock(MI, "malloc_cont");
1328 // Create the block to check the first condition. Put all these blocks at the
1329 // end of the function as they are unlikely to be executed.
1330 BasicBlock *NullPtrBlock = BasicBlock::Create("malloc_ret_null",
1331 OrigBB->getParent());
1333 // Remove the uncond branch from OrigBB to ContBB, turning it into a cond
1334 // branch on RunningOr.
1335 OrigBB->getTerminator()->eraseFromParent();
1336 BranchInst::Create(NullPtrBlock, ContBB, RunningOr, OrigBB);
1338 // Within the NullPtrBlock, we need to emit a comparison and branch for each
1339 // pointer, because some may be null while others are not.
1340 for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) {
1341 Value *GVVal = new LoadInst(FieldGlobals[i], "tmp", NullPtrBlock);
1342 Value *Cmp = new ICmpInst(*NullPtrBlock, ICmpInst::ICMP_NE, GVVal,
1343 Context.getNullValue(GVVal->getType()),
1345 BasicBlock *FreeBlock = BasicBlock::Create("free_it", OrigBB->getParent());
1346 BasicBlock *NextBlock = BasicBlock::Create("next", OrigBB->getParent());
1347 BranchInst::Create(FreeBlock, NextBlock, Cmp, NullPtrBlock);
1349 // Fill in FreeBlock.
1350 new FreeInst(GVVal, FreeBlock);
1351 new StoreInst(Context.getNullValue(GVVal->getType()), FieldGlobals[i],
1353 BranchInst::Create(NextBlock, FreeBlock);
1355 NullPtrBlock = NextBlock;
1358 BranchInst::Create(ContBB, NullPtrBlock);
1360 // MI is no longer needed, remove it.
1361 MI->eraseFromParent();
1363 /// InsertedScalarizedLoads - As we process loads, if we can't immediately
1364 /// update all uses of the load, keep track of what scalarized loads are
1365 /// inserted for a given load.
1366 DenseMap<Value*, std::vector<Value*> > InsertedScalarizedValues;
1367 InsertedScalarizedValues[GV] = FieldGlobals;
1369 std::vector<std::pair<PHINode*, unsigned> > PHIsToRewrite;
1371 // Okay, the malloc site is completely handled. All of the uses of GV are now
1372 // loads, and all uses of those loads are simple. Rewrite them to use loads
1373 // of the per-field globals instead.
1374 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); UI != E;) {
1375 Instruction *User = cast<Instruction>(*UI++);
1377 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1378 RewriteUsesOfLoadForHeapSRoA(LI, InsertedScalarizedValues, PHIsToRewrite,
1383 // Must be a store of null.
1384 StoreInst *SI = cast<StoreInst>(User);
1385 assert(isa<ConstantPointerNull>(SI->getOperand(0)) &&
1386 "Unexpected heap-sra user!");
1388 // Insert a store of null into each global.
1389 for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) {
1390 const PointerType *PT = cast<PointerType>(FieldGlobals[i]->getType());
1391 Constant *Null = Context.getNullValue(PT->getElementType());
1392 new StoreInst(Null, FieldGlobals[i], SI);
1394 // Erase the original store.
1395 SI->eraseFromParent();
1398 // While we have PHIs that are interesting to rewrite, do it.
1399 while (!PHIsToRewrite.empty()) {
1400 PHINode *PN = PHIsToRewrite.back().first;
1401 unsigned FieldNo = PHIsToRewrite.back().second;
1402 PHIsToRewrite.pop_back();
1403 PHINode *FieldPN = cast<PHINode>(InsertedScalarizedValues[PN][FieldNo]);
1404 assert(FieldPN->getNumIncomingValues() == 0 &&"Already processed this phi");
1406 // Add all the incoming values. This can materialize more phis.
1407 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
1408 Value *InVal = PN->getIncomingValue(i);
1409 InVal = GetHeapSROAValue(InVal, FieldNo, InsertedScalarizedValues,
1410 PHIsToRewrite, Context);
1411 FieldPN->addIncoming(InVal, PN->getIncomingBlock(i));
1415 // Drop all inter-phi links and any loads that made it this far.
1416 for (DenseMap<Value*, std::vector<Value*> >::iterator
1417 I = InsertedScalarizedValues.begin(), E = InsertedScalarizedValues.end();
1419 if (PHINode *PN = dyn_cast<PHINode>(I->first))
1420 PN->dropAllReferences();
1421 else if (LoadInst *LI = dyn_cast<LoadInst>(I->first))
1422 LI->dropAllReferences();
1425 // Delete all the phis and loads now that inter-references are dead.
1426 for (DenseMap<Value*, std::vector<Value*> >::iterator
1427 I = InsertedScalarizedValues.begin(), E = InsertedScalarizedValues.end();
1429 if (PHINode *PN = dyn_cast<PHINode>(I->first))
1430 PN->eraseFromParent();
1431 else if (LoadInst *LI = dyn_cast<LoadInst>(I->first))
1432 LI->eraseFromParent();
1435 // The old global is now dead, remove it.
1436 GV->eraseFromParent();
1439 return cast<GlobalVariable>(FieldGlobals[0]);
1442 /// TryToOptimizeStoreOfMallocToGlobal - This function is called when we see a
1443 /// pointer global variable with a single value stored it that is a malloc or
1445 static bool TryToOptimizeStoreOfMallocToGlobal(GlobalVariable *GV,
1447 Module::global_iterator &GVI,
1449 LLVMContext &Context) {
1450 // If this is a malloc of an abstract type, don't touch it.
1451 if (!MI->getAllocatedType()->isSized())
1454 // We can't optimize this global unless all uses of it are *known* to be
1455 // of the malloc value, not of the null initializer value (consider a use
1456 // that compares the global's value against zero to see if the malloc has
1457 // been reached). To do this, we check to see if all uses of the global
1458 // would trap if the global were null: this proves that they must all
1459 // happen after the malloc.
1460 if (!AllUsesOfLoadedValueWillTrapIfNull(GV))
1463 // We can't optimize this if the malloc itself is used in a complex way,
1464 // for example, being stored into multiple globals. This allows the
1465 // malloc to be stored into the specified global, loaded setcc'd, and
1466 // GEP'd. These are all things we could transform to using the global
1469 SmallPtrSet<PHINode*, 8> PHIs;
1470 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(MI, GV, PHIs))
1475 // If we have a global that is only initialized with a fixed size malloc,
1476 // transform the program to use global memory instead of malloc'd memory.
1477 // This eliminates dynamic allocation, avoids an indirection accessing the
1478 // data, and exposes the resultant global to further GlobalOpt.
1479 if (ConstantInt *NElements = dyn_cast<ConstantInt>(MI->getArraySize())) {
1480 // Restrict this transformation to only working on small allocations
1481 // (2048 bytes currently), as we don't want to introduce a 16M global or
1483 if (NElements->getZExtValue()*
1484 TD.getTypeAllocSize(MI->getAllocatedType()) < 2048) {
1485 GVI = OptimizeGlobalAddressOfMalloc(GV, MI, Context);
1490 // If the allocation is an array of structures, consider transforming this
1491 // into multiple malloc'd arrays, one for each field. This is basically
1492 // SRoA for malloc'd memory.
1493 const Type *AllocTy = MI->getAllocatedType();
1495 // If this is an allocation of a fixed size array of structs, analyze as a
1496 // variable size array. malloc [100 x struct],1 -> malloc struct, 100
1497 if (!MI->isArrayAllocation())
1498 if (const ArrayType *AT = dyn_cast<ArrayType>(AllocTy))
1499 AllocTy = AT->getElementType();
1501 if (const StructType *AllocSTy = dyn_cast<StructType>(AllocTy)) {
1502 // This the structure has an unreasonable number of fields, leave it
1504 if (AllocSTy->getNumElements() <= 16 && AllocSTy->getNumElements() != 0 &&
1505 AllGlobalLoadUsesSimpleEnoughForHeapSRA(GV, MI)) {
1507 // If this is a fixed size array, transform the Malloc to be an alloc of
1508 // structs. malloc [100 x struct],1 -> malloc struct, 100
1509 if (const ArrayType *AT = dyn_cast<ArrayType>(MI->getAllocatedType())) {
1511 new MallocInst(AllocSTy,
1512 ConstantInt::get(Type::Int32Ty, AT->getNumElements()),
1514 NewMI->takeName(MI);
1515 Value *Cast = new BitCastInst(NewMI, MI->getType(), "tmp", MI);
1516 MI->replaceAllUsesWith(Cast);
1517 MI->eraseFromParent();
1521 GVI = PerformHeapAllocSRoA(GV, MI, Context);
1529 // OptimizeOnceStoredGlobal - Try to optimize globals based on the knowledge
1530 // that only one value (besides its initializer) is ever stored to the global.
1531 static bool OptimizeOnceStoredGlobal(GlobalVariable *GV, Value *StoredOnceVal,
1532 Module::global_iterator &GVI,
1533 TargetData &TD, LLVMContext &Context) {
1534 // Ignore no-op GEPs and bitcasts.
1535 StoredOnceVal = StoredOnceVal->stripPointerCasts();
1537 // If we are dealing with a pointer global that is initialized to null and
1538 // only has one (non-null) value stored into it, then we can optimize any
1539 // users of the loaded value (often calls and loads) that would trap if the
1541 if (isa<PointerType>(GV->getInitializer()->getType()) &&
1542 GV->getInitializer()->isNullValue()) {
1543 if (Constant *SOVC = dyn_cast<Constant>(StoredOnceVal)) {
1544 if (GV->getInitializer()->getType() != SOVC->getType())
1546 Context.getConstantExprBitCast(SOVC, GV->getInitializer()->getType());
1548 // Optimize away any trapping uses of the loaded value.
1549 if (OptimizeAwayTrappingUsesOfLoads(GV, SOVC, Context))
1551 } else if (MallocInst *MI = dyn_cast<MallocInst>(StoredOnceVal)) {
1552 if (TryToOptimizeStoreOfMallocToGlobal(GV, MI, GVI, TD, Context))
1560 /// TryToShrinkGlobalToBoolean - At this point, we have learned that the only
1561 /// two values ever stored into GV are its initializer and OtherVal. See if we
1562 /// can shrink the global into a boolean and select between the two values
1563 /// whenever it is used. This exposes the values to other scalar optimizations.
1564 static bool TryToShrinkGlobalToBoolean(GlobalVariable *GV, Constant *OtherVal,
1565 LLVMContext &Context) {
1566 const Type *GVElType = GV->getType()->getElementType();
1568 // If GVElType is already i1, it is already shrunk. If the type of the GV is
1569 // an FP value, pointer or vector, don't do this optimization because a select
1570 // between them is very expensive and unlikely to lead to later
1571 // simplification. In these cases, we typically end up with "cond ? v1 : v2"
1572 // where v1 and v2 both require constant pool loads, a big loss.
1573 if (GVElType == Type::Int1Ty || GVElType->isFloatingPoint() ||
1574 isa<PointerType>(GVElType) || isa<VectorType>(GVElType))
1577 // Walk the use list of the global seeing if all the uses are load or store.
1578 // If there is anything else, bail out.
1579 for (Value::use_iterator I = GV->use_begin(), E = GV->use_end(); I != E; ++I)
1580 if (!isa<LoadInst>(I) && !isa<StoreInst>(I))
1583 DOUT << " *** SHRINKING TO BOOL: " << *GV;
1585 // Create the new global, initializing it to false.
1586 GlobalVariable *NewGV = new GlobalVariable(Context, Type::Int1Ty, false,
1587 GlobalValue::InternalLinkage, Context.getFalse(),
1589 GV->isThreadLocal());
1590 GV->getParent()->getGlobalList().insert(GV, NewGV);
1592 Constant *InitVal = GV->getInitializer();
1593 assert(InitVal->getType() != Type::Int1Ty && "No reason to shrink to bool!");
1595 // If initialized to zero and storing one into the global, we can use a cast
1596 // instead of a select to synthesize the desired value.
1597 bool IsOneZero = false;
1598 if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal))
1599 IsOneZero = InitVal->isNullValue() && CI->isOne();
1601 while (!GV->use_empty()) {
1602 Instruction *UI = cast<Instruction>(GV->use_back());
1603 if (StoreInst *SI = dyn_cast<StoreInst>(UI)) {
1604 // Change the store into a boolean store.
1605 bool StoringOther = SI->getOperand(0) == OtherVal;
1606 // Only do this if we weren't storing a loaded value.
1608 if (StoringOther || SI->getOperand(0) == InitVal)
1609 StoreVal = ConstantInt::get(Type::Int1Ty, StoringOther);
1611 // Otherwise, we are storing a previously loaded copy. To do this,
1612 // change the copy from copying the original value to just copying the
1614 Instruction *StoredVal = cast<Instruction>(SI->getOperand(0));
1616 // If we're already replaced the input, StoredVal will be a cast or
1617 // select instruction. If not, it will be a load of the original
1619 if (LoadInst *LI = dyn_cast<LoadInst>(StoredVal)) {
1620 assert(LI->getOperand(0) == GV && "Not a copy!");
1621 // Insert a new load, to preserve the saved value.
1622 StoreVal = new LoadInst(NewGV, LI->getName()+".b", LI);
1624 assert((isa<CastInst>(StoredVal) || isa<SelectInst>(StoredVal)) &&
1625 "This is not a form that we understand!");
1626 StoreVal = StoredVal->getOperand(0);
1627 assert(isa<LoadInst>(StoreVal) && "Not a load of NewGV!");
1630 new StoreInst(StoreVal, NewGV, SI);
1632 // Change the load into a load of bool then a select.
1633 LoadInst *LI = cast<LoadInst>(UI);
1634 LoadInst *NLI = new LoadInst(NewGV, LI->getName()+".b", LI);
1637 NSI = new ZExtInst(NLI, LI->getType(), "", LI);
1639 NSI = SelectInst::Create(NLI, OtherVal, InitVal, "", LI);
1641 LI->replaceAllUsesWith(NSI);
1643 UI->eraseFromParent();
1646 GV->eraseFromParent();
1651 /// ProcessInternalGlobal - Analyze the specified global variable and optimize
1652 /// it if possible. If we make a change, return true.
1653 bool GlobalOpt::ProcessInternalGlobal(GlobalVariable *GV,
1654 Module::global_iterator &GVI) {
1655 SmallPtrSet<PHINode*, 16> PHIUsers;
1657 GV->removeDeadConstantUsers();
1659 if (GV->use_empty()) {
1660 DOUT << "GLOBAL DEAD: " << *GV;
1661 GV->eraseFromParent();
1666 if (!AnalyzeGlobal(GV, GS, PHIUsers)) {
1668 cerr << "Global: " << *GV;
1669 cerr << " isLoaded = " << GS.isLoaded << "\n";
1670 cerr << " StoredType = ";
1671 switch (GS.StoredType) {
1672 case GlobalStatus::NotStored: cerr << "NEVER STORED\n"; break;
1673 case GlobalStatus::isInitializerStored: cerr << "INIT STORED\n"; break;
1674 case GlobalStatus::isStoredOnce: cerr << "STORED ONCE\n"; break;
1675 case GlobalStatus::isStored: cerr << "stored\n"; break;
1677 if (GS.StoredType == GlobalStatus::isStoredOnce && GS.StoredOnceValue)
1678 cerr << " StoredOnceValue = " << *GS.StoredOnceValue << "\n";
1679 if (GS.AccessingFunction && !GS.HasMultipleAccessingFunctions)
1680 cerr << " AccessingFunction = " << GS.AccessingFunction->getName()
1682 cerr << " HasMultipleAccessingFunctions = "
1683 << GS.HasMultipleAccessingFunctions << "\n";
1684 cerr << " HasNonInstructionUser = " << GS.HasNonInstructionUser<<"\n";
1688 // If this is a first class global and has only one accessing function
1689 // and this function is main (which we know is not recursive we can make
1690 // this global a local variable) we replace the global with a local alloca
1691 // in this function.
1693 // NOTE: It doesn't make sense to promote non single-value types since we
1694 // are just replacing static memory to stack memory.
1696 // If the global is in different address space, don't bring it to stack.
1697 if (!GS.HasMultipleAccessingFunctions &&
1698 GS.AccessingFunction && !GS.HasNonInstructionUser &&
1699 GV->getType()->getElementType()->isSingleValueType() &&
1700 GS.AccessingFunction->getName() == "main" &&
1701 GS.AccessingFunction->hasExternalLinkage() &&
1702 GV->getType()->getAddressSpace() == 0) {
1703 DOUT << "LOCALIZING GLOBAL: " << *GV;
1704 Instruction* FirstI = GS.AccessingFunction->getEntryBlock().begin();
1705 const Type* ElemTy = GV->getType()->getElementType();
1706 // FIXME: Pass Global's alignment when globals have alignment
1707 AllocaInst* Alloca = new AllocaInst(ElemTy, NULL, GV->getName(), FirstI);
1708 if (!isa<UndefValue>(GV->getInitializer()))
1709 new StoreInst(GV->getInitializer(), Alloca, FirstI);
1711 GV->replaceAllUsesWith(Alloca);
1712 GV->eraseFromParent();
1717 // If the global is never loaded (but may be stored to), it is dead.
1720 DOUT << "GLOBAL NEVER LOADED: " << *GV;
1722 // Delete any stores we can find to the global. We may not be able to
1723 // make it completely dead though.
1724 bool Changed = CleanupConstantGlobalUsers(GV, GV->getInitializer(),
1727 // If the global is dead now, delete it.
1728 if (GV->use_empty()) {
1729 GV->eraseFromParent();
1735 } else if (GS.StoredType <= GlobalStatus::isInitializerStored) {
1736 DOUT << "MARKING CONSTANT: " << *GV;
1737 GV->setConstant(true);
1739 // Clean up any obviously simplifiable users now.
1740 CleanupConstantGlobalUsers(GV, GV->getInitializer(), GV->getContext());
1742 // If the global is dead now, just nuke it.
1743 if (GV->use_empty()) {
1744 DOUT << " *** Marking constant allowed us to simplify "
1745 << "all users and delete global!\n";
1746 GV->eraseFromParent();
1752 } else if (!GV->getInitializer()->getType()->isSingleValueType()) {
1753 if (GlobalVariable *FirstNewGV = SRAGlobal(GV,
1754 getAnalysis<TargetData>(),
1755 GV->getContext())) {
1756 GVI = FirstNewGV; // Don't skip the newly produced globals!
1759 } else if (GS.StoredType == GlobalStatus::isStoredOnce) {
1760 // If the initial value for the global was an undef value, and if only
1761 // one other value was stored into it, we can just change the
1762 // initializer to be the stored value, then delete all stores to the
1763 // global. This allows us to mark it constant.
1764 if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue))
1765 if (isa<UndefValue>(GV->getInitializer())) {
1766 // Change the initial value here.
1767 GV->setInitializer(SOVConstant);
1769 // Clean up any obviously simplifiable users now.
1770 CleanupConstantGlobalUsers(GV, GV->getInitializer(),
1773 if (GV->use_empty()) {
1774 DOUT << " *** Substituting initializer allowed us to "
1775 << "simplify all users and delete global!\n";
1776 GV->eraseFromParent();
1785 // Try to optimize globals based on the knowledge that only one value
1786 // (besides its initializer) is ever stored to the global.
1787 if (OptimizeOnceStoredGlobal(GV, GS.StoredOnceValue, GVI,
1788 getAnalysis<TargetData>(), GV->getContext()))
1791 // Otherwise, if the global was not a boolean, we can shrink it to be a
1793 if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue))
1794 if (TryToShrinkGlobalToBoolean(GV, SOVConstant, GV->getContext())) {
1803 /// ChangeCalleesToFastCall - Walk all of the direct calls of the specified
1804 /// function, changing them to FastCC.
1805 static void ChangeCalleesToFastCall(Function *F) {
1806 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){
1807 CallSite User(cast<Instruction>(*UI));
1808 User.setCallingConv(CallingConv::Fast);
1812 static AttrListPtr StripNest(const AttrListPtr &Attrs) {
1813 for (unsigned i = 0, e = Attrs.getNumSlots(); i != e; ++i) {
1814 if ((Attrs.getSlot(i).Attrs & Attribute::Nest) == 0)
1817 // There can be only one.
1818 return Attrs.removeAttr(Attrs.getSlot(i).Index, Attribute::Nest);
1824 static void RemoveNestAttribute(Function *F) {
1825 F->setAttributes(StripNest(F->getAttributes()));
1826 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){
1827 CallSite User(cast<Instruction>(*UI));
1828 User.setAttributes(StripNest(User.getAttributes()));
1832 bool GlobalOpt::OptimizeFunctions(Module &M) {
1833 bool Changed = false;
1834 // Optimize functions.
1835 for (Module::iterator FI = M.begin(), E = M.end(); FI != E; ) {
1837 // Functions without names cannot be referenced outside this module.
1838 if (!F->hasName() && !F->isDeclaration())
1839 F->setLinkage(GlobalValue::InternalLinkage);
1840 F->removeDeadConstantUsers();
1841 if (F->use_empty() && (F->hasLocalLinkage() ||
1842 F->hasLinkOnceLinkage())) {
1843 M.getFunctionList().erase(F);
1846 } else if (F->hasLocalLinkage()) {
1847 if (F->getCallingConv() == CallingConv::C && !F->isVarArg() &&
1848 !F->hasAddressTaken()) {
1849 // If this function has C calling conventions, is not a varargs
1850 // function, and is only called directly, promote it to use the Fast
1851 // calling convention.
1852 F->setCallingConv(CallingConv::Fast);
1853 ChangeCalleesToFastCall(F);
1858 if (F->getAttributes().hasAttrSomewhere(Attribute::Nest) &&
1859 !F->hasAddressTaken()) {
1860 // The function is not used by a trampoline intrinsic, so it is safe
1861 // to remove the 'nest' attribute.
1862 RemoveNestAttribute(F);
1871 bool GlobalOpt::OptimizeGlobalVars(Module &M) {
1872 bool Changed = false;
1873 for (Module::global_iterator GVI = M.global_begin(), E = M.global_end();
1875 GlobalVariable *GV = GVI++;
1876 // Global variables without names cannot be referenced outside this module.
1877 if (!GV->hasName() && !GV->isDeclaration())
1878 GV->setLinkage(GlobalValue::InternalLinkage);
1879 if (!GV->isConstant() && GV->hasLocalLinkage() &&
1880 GV->hasInitializer())
1881 Changed |= ProcessInternalGlobal(GV, GVI);
1886 /// FindGlobalCtors - Find the llvm.globalctors list, verifying that all
1887 /// initializers have an init priority of 65535.
1888 GlobalVariable *GlobalOpt::FindGlobalCtors(Module &M) {
1889 for (Module::global_iterator I = M.global_begin(), E = M.global_end();
1891 if (I->getName() == "llvm.global_ctors") {
1892 // Found it, verify it's an array of { int, void()* }.
1893 const ArrayType *ATy =dyn_cast<ArrayType>(I->getType()->getElementType());
1895 const StructType *STy = dyn_cast<StructType>(ATy->getElementType());
1896 if (!STy || STy->getNumElements() != 2 ||
1897 STy->getElementType(0) != Type::Int32Ty) return 0;
1898 const PointerType *PFTy = dyn_cast<PointerType>(STy->getElementType(1));
1899 if (!PFTy) return 0;
1900 const FunctionType *FTy = dyn_cast<FunctionType>(PFTy->getElementType());
1901 if (!FTy || FTy->getReturnType() != Type::VoidTy || FTy->isVarArg() ||
1902 FTy->getNumParams() != 0)
1905 // Verify that the initializer is simple enough for us to handle.
1906 if (!I->hasInitializer()) return 0;
1907 ConstantArray *CA = dyn_cast<ConstantArray>(I->getInitializer());
1909 for (User::op_iterator i = CA->op_begin(), e = CA->op_end(); i != e; ++i)
1910 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(*i)) {
1911 if (isa<ConstantPointerNull>(CS->getOperand(1)))
1914 // Must have a function or null ptr.
1915 if (!isa<Function>(CS->getOperand(1)))
1918 // Init priority must be standard.
1919 ConstantInt *CI = dyn_cast<ConstantInt>(CS->getOperand(0));
1920 if (!CI || CI->getZExtValue() != 65535)
1931 /// ParseGlobalCtors - Given a llvm.global_ctors list that we can understand,
1932 /// return a list of the functions and null terminator as a vector.
1933 static std::vector<Function*> ParseGlobalCtors(GlobalVariable *GV) {
1934 ConstantArray *CA = cast<ConstantArray>(GV->getInitializer());
1935 std::vector<Function*> Result;
1936 Result.reserve(CA->getNumOperands());
1937 for (User::op_iterator i = CA->op_begin(), e = CA->op_end(); i != e; ++i) {
1938 ConstantStruct *CS = cast<ConstantStruct>(*i);
1939 Result.push_back(dyn_cast<Function>(CS->getOperand(1)));
1944 /// InstallGlobalCtors - Given a specified llvm.global_ctors list, install the
1945 /// specified array, returning the new global to use.
1946 static GlobalVariable *InstallGlobalCtors(GlobalVariable *GCL,
1947 const std::vector<Function*> &Ctors,
1948 LLVMContext &Context) {
1949 // If we made a change, reassemble the initializer list.
1950 std::vector<Constant*> CSVals;
1951 CSVals.push_back(ConstantInt::get(Type::Int32Ty, 65535));
1952 CSVals.push_back(0);
1954 // Create the new init list.
1955 std::vector<Constant*> CAList;
1956 for (unsigned i = 0, e = Ctors.size(); i != e; ++i) {
1958 CSVals[1] = Ctors[i];
1960 const Type *FTy = Context.getFunctionType(Type::VoidTy, false);
1961 const PointerType *PFTy = Context.getPointerTypeUnqual(FTy);
1962 CSVals[1] = Context.getNullValue(PFTy);
1963 CSVals[0] = ConstantInt::get(Type::Int32Ty, 2147483647);
1965 CAList.push_back(ConstantStruct::get(CSVals));
1968 // Create the array initializer.
1969 const Type *StructTy =
1970 cast<ArrayType>(GCL->getType()->getElementType())->getElementType();
1971 Constant *CA = ConstantArray::get(ArrayType::get(StructTy,
1972 CAList.size()), CAList);
1974 // If we didn't change the number of elements, don't create a new GV.
1975 if (CA->getType() == GCL->getInitializer()->getType()) {
1976 GCL->setInitializer(CA);
1980 // Create the new global and insert it next to the existing list.
1981 GlobalVariable *NGV = new GlobalVariable(Context, CA->getType(),
1983 GCL->getLinkage(), CA, "",
1984 GCL->isThreadLocal());
1985 GCL->getParent()->getGlobalList().insert(GCL, NGV);
1988 // Nuke the old list, replacing any uses with the new one.
1989 if (!GCL->use_empty()) {
1991 if (V->getType() != GCL->getType())
1992 V = Context.getConstantExprBitCast(V, GCL->getType());
1993 GCL->replaceAllUsesWith(V);
1995 GCL->eraseFromParent();
2004 static Constant *getVal(DenseMap<Value*, Constant*> &ComputedValues,
2006 if (Constant *CV = dyn_cast<Constant>(V)) return CV;
2007 Constant *R = ComputedValues[V];
2008 assert(R && "Reference to an uncomputed value!");
2012 /// isSimpleEnoughPointerToCommit - Return true if this constant is simple
2013 /// enough for us to understand. In particular, if it is a cast of something,
2014 /// we punt. We basically just support direct accesses to globals and GEP's of
2015 /// globals. This should be kept up to date with CommitValueTo.
2016 static bool isSimpleEnoughPointerToCommit(Constant *C, LLVMContext &Context) {
2017 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C)) {
2018 if (!GV->hasExternalLinkage() && !GV->hasLocalLinkage())
2019 return false; // do not allow weak/linkonce/dllimport/dllexport linkage.
2020 return !GV->isDeclaration(); // reject external globals.
2022 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
2023 // Handle a constantexpr gep.
2024 if (CE->getOpcode() == Instruction::GetElementPtr &&
2025 isa<GlobalVariable>(CE->getOperand(0))) {
2026 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
2027 if (!GV->hasExternalLinkage() && !GV->hasLocalLinkage())
2028 return false; // do not allow weak/linkonce/dllimport/dllexport linkage.
2029 return GV->hasInitializer() &&
2030 ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE,
2036 /// EvaluateStoreInto - Evaluate a piece of a constantexpr store into a global
2037 /// initializer. This returns 'Init' modified to reflect 'Val' stored into it.
2038 /// At this point, the GEP operands of Addr [0, OpNo) have been stepped into.
2039 static Constant *EvaluateStoreInto(Constant *Init, Constant *Val,
2040 ConstantExpr *Addr, unsigned OpNo,
2041 LLVMContext &Context) {
2042 // Base case of the recursion.
2043 if (OpNo == Addr->getNumOperands()) {
2044 assert(Val->getType() == Init->getType() && "Type mismatch!");
2048 if (const StructType *STy = dyn_cast<StructType>(Init->getType())) {
2049 std::vector<Constant*> Elts;
2051 // Break up the constant into its elements.
2052 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(Init)) {
2053 for (User::op_iterator i = CS->op_begin(), e = CS->op_end(); i != e; ++i)
2054 Elts.push_back(cast<Constant>(*i));
2055 } else if (isa<ConstantAggregateZero>(Init)) {
2056 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
2057 Elts.push_back(Context.getNullValue(STy->getElementType(i)));
2058 } else if (isa<UndefValue>(Init)) {
2059 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
2060 Elts.push_back(Context.getUndef(STy->getElementType(i)));
2062 llvm_unreachable("This code is out of sync with "
2063 " ConstantFoldLoadThroughGEPConstantExpr");
2066 // Replace the element that we are supposed to.
2067 ConstantInt *CU = cast<ConstantInt>(Addr->getOperand(OpNo));
2068 unsigned Idx = CU->getZExtValue();
2069 assert(Idx < STy->getNumElements() && "Struct index out of range!");
2070 Elts[Idx] = EvaluateStoreInto(Elts[Idx], Val, Addr, OpNo+1, Context);
2072 // Return the modified struct.
2073 return ConstantStruct::get(&Elts[0], Elts.size(), STy->isPacked());
2075 ConstantInt *CI = cast<ConstantInt>(Addr->getOperand(OpNo));
2076 const ArrayType *ATy = cast<ArrayType>(Init->getType());
2078 // Break up the array into elements.
2079 std::vector<Constant*> Elts;
2080 if (ConstantArray *CA = dyn_cast<ConstantArray>(Init)) {
2081 for (User::op_iterator i = CA->op_begin(), e = CA->op_end(); i != e; ++i)
2082 Elts.push_back(cast<Constant>(*i));
2083 } else if (isa<ConstantAggregateZero>(Init)) {
2084 Constant *Elt = Context.getNullValue(ATy->getElementType());
2085 Elts.assign(ATy->getNumElements(), Elt);
2086 } else if (isa<UndefValue>(Init)) {
2087 Constant *Elt = Context.getUndef(ATy->getElementType());
2088 Elts.assign(ATy->getNumElements(), Elt);
2090 llvm_unreachable("This code is out of sync with "
2091 " ConstantFoldLoadThroughGEPConstantExpr");
2094 assert(CI->getZExtValue() < ATy->getNumElements());
2095 Elts[CI->getZExtValue()] =
2096 EvaluateStoreInto(Elts[CI->getZExtValue()], Val, Addr, OpNo+1, Context);
2097 return ConstantArray::get(ATy, Elts);
2101 /// CommitValueTo - We have decided that Addr (which satisfies the predicate
2102 /// isSimpleEnoughPointerToCommit) should get Val as its value. Make it happen.
2103 static void CommitValueTo(Constant *Val, Constant *Addr,
2104 LLVMContext &Context) {
2105 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Addr)) {
2106 assert(GV->hasInitializer());
2107 GV->setInitializer(Val);
2111 ConstantExpr *CE = cast<ConstantExpr>(Addr);
2112 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
2114 Constant *Init = GV->getInitializer();
2115 Init = EvaluateStoreInto(Init, Val, CE, 2, Context);
2116 GV->setInitializer(Init);
2119 /// ComputeLoadResult - Return the value that would be computed by a load from
2120 /// P after the stores reflected by 'memory' have been performed. If we can't
2121 /// decide, return null.
2122 static Constant *ComputeLoadResult(Constant *P,
2123 const DenseMap<Constant*, Constant*> &Memory,
2124 LLVMContext &Context) {
2125 // If this memory location has been recently stored, use the stored value: it
2126 // is the most up-to-date.
2127 DenseMap<Constant*, Constant*>::const_iterator I = Memory.find(P);
2128 if (I != Memory.end()) return I->second;
2131 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(P)) {
2132 if (GV->hasInitializer())
2133 return GV->getInitializer();
2137 // Handle a constantexpr getelementptr.
2138 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(P))
2139 if (CE->getOpcode() == Instruction::GetElementPtr &&
2140 isa<GlobalVariable>(CE->getOperand(0))) {
2141 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
2142 if (GV->hasInitializer())
2143 return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE,
2147 return 0; // don't know how to evaluate.
2150 /// EvaluateFunction - Evaluate a call to function F, returning true if
2151 /// successful, false if we can't evaluate it. ActualArgs contains the formal
2152 /// arguments for the function.
2153 static bool EvaluateFunction(Function *F, Constant *&RetVal,
2154 const std::vector<Constant*> &ActualArgs,
2155 std::vector<Function*> &CallStack,
2156 DenseMap<Constant*, Constant*> &MutatedMemory,
2157 std::vector<GlobalVariable*> &AllocaTmps) {
2158 // Check to see if this function is already executing (recursion). If so,
2159 // bail out. TODO: we might want to accept limited recursion.
2160 if (std::find(CallStack.begin(), CallStack.end(), F) != CallStack.end())
2163 LLVMContext &Context = F->getContext();
2165 CallStack.push_back(F);
2167 /// Values - As we compute SSA register values, we store their contents here.
2168 DenseMap<Value*, Constant*> Values;
2170 // Initialize arguments to the incoming values specified.
2172 for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end(); AI != E;
2174 Values[AI] = ActualArgs[ArgNo];
2176 /// ExecutedBlocks - We only handle non-looping, non-recursive code. As such,
2177 /// we can only evaluate any one basic block at most once. This set keeps
2178 /// track of what we have executed so we can detect recursive cases etc.
2179 SmallPtrSet<BasicBlock*, 32> ExecutedBlocks;
2181 // CurInst - The current instruction we're evaluating.
2182 BasicBlock::iterator CurInst = F->begin()->begin();
2184 // This is the main evaluation loop.
2186 Constant *InstResult = 0;
2188 if (StoreInst *SI = dyn_cast<StoreInst>(CurInst)) {
2189 if (SI->isVolatile()) return false; // no volatile accesses.
2190 Constant *Ptr = getVal(Values, SI->getOperand(1));
2191 if (!isSimpleEnoughPointerToCommit(Ptr, Context))
2192 // If this is too complex for us to commit, reject it.
2194 Constant *Val = getVal(Values, SI->getOperand(0));
2195 MutatedMemory[Ptr] = Val;
2196 } else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(CurInst)) {
2197 InstResult = Context.getConstantExpr(BO->getOpcode(),
2198 getVal(Values, BO->getOperand(0)),
2199 getVal(Values, BO->getOperand(1)));
2200 } else if (CmpInst *CI = dyn_cast<CmpInst>(CurInst)) {
2201 InstResult = Context.getConstantExprCompare(CI->getPredicate(),
2202 getVal(Values, CI->getOperand(0)),
2203 getVal(Values, CI->getOperand(1)));
2204 } else if (CastInst *CI = dyn_cast<CastInst>(CurInst)) {
2205 InstResult = Context.getConstantExprCast(CI->getOpcode(),
2206 getVal(Values, CI->getOperand(0)),
2208 } else if (SelectInst *SI = dyn_cast<SelectInst>(CurInst)) {
2210 Context.getConstantExprSelect(getVal(Values, SI->getOperand(0)),
2211 getVal(Values, SI->getOperand(1)),
2212 getVal(Values, SI->getOperand(2)));
2213 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(CurInst)) {
2214 Constant *P = getVal(Values, GEP->getOperand(0));
2215 SmallVector<Constant*, 8> GEPOps;
2216 for (User::op_iterator i = GEP->op_begin() + 1, e = GEP->op_end();
2218 GEPOps.push_back(getVal(Values, *i));
2220 Context.getConstantExprGetElementPtr(P, &GEPOps[0], GEPOps.size());
2221 } else if (LoadInst *LI = dyn_cast<LoadInst>(CurInst)) {
2222 if (LI->isVolatile()) return false; // no volatile accesses.
2223 InstResult = ComputeLoadResult(getVal(Values, LI->getOperand(0)),
2224 MutatedMemory, Context);
2225 if (InstResult == 0) return false; // Could not evaluate load.
2226 } else if (AllocaInst *AI = dyn_cast<AllocaInst>(CurInst)) {
2227 if (AI->isArrayAllocation()) return false; // Cannot handle array allocs.
2228 const Type *Ty = AI->getType()->getElementType();
2229 AllocaTmps.push_back(new GlobalVariable(Context, Ty, false,
2230 GlobalValue::InternalLinkage,
2231 Context.getUndef(Ty),
2233 InstResult = AllocaTmps.back();
2234 } else if (CallInst *CI = dyn_cast<CallInst>(CurInst)) {
2236 // Debug info can safely be ignored here.
2237 if (isa<DbgInfoIntrinsic>(CI)) {
2242 // Cannot handle inline asm.
2243 if (isa<InlineAsm>(CI->getOperand(0))) return false;
2245 // Resolve function pointers.
2246 Function *Callee = dyn_cast<Function>(getVal(Values, CI->getOperand(0)));
2247 if (!Callee) return false; // Cannot resolve.
2249 std::vector<Constant*> Formals;
2250 for (User::op_iterator i = CI->op_begin() + 1, e = CI->op_end();
2252 Formals.push_back(getVal(Values, *i));
2254 if (Callee->isDeclaration()) {
2255 // If this is a function we can constant fold, do it.
2256 if (Constant *C = ConstantFoldCall(Callee, &Formals[0],
2263 if (Callee->getFunctionType()->isVarArg())
2267 // Execute the call, if successful, use the return value.
2268 if (!EvaluateFunction(Callee, RetVal, Formals, CallStack,
2269 MutatedMemory, AllocaTmps))
2271 InstResult = RetVal;
2273 } else if (isa<TerminatorInst>(CurInst)) {
2274 BasicBlock *NewBB = 0;
2275 if (BranchInst *BI = dyn_cast<BranchInst>(CurInst)) {
2276 if (BI->isUnconditional()) {
2277 NewBB = BI->getSuccessor(0);
2280 dyn_cast<ConstantInt>(getVal(Values, BI->getCondition()));
2281 if (!Cond) return false; // Cannot determine.
2283 NewBB = BI->getSuccessor(!Cond->getZExtValue());
2285 } else if (SwitchInst *SI = dyn_cast<SwitchInst>(CurInst)) {
2287 dyn_cast<ConstantInt>(getVal(Values, SI->getCondition()));
2288 if (!Val) return false; // Cannot determine.
2289 NewBB = SI->getSuccessor(SI->findCaseValue(Val));
2290 } else if (ReturnInst *RI = dyn_cast<ReturnInst>(CurInst)) {
2291 if (RI->getNumOperands())
2292 RetVal = getVal(Values, RI->getOperand(0));
2294 CallStack.pop_back(); // return from fn.
2295 return true; // We succeeded at evaluating this ctor!
2297 // invoke, unwind, unreachable.
2298 return false; // Cannot handle this terminator.
2301 // Okay, we succeeded in evaluating this control flow. See if we have
2302 // executed the new block before. If so, we have a looping function,
2303 // which we cannot evaluate in reasonable time.
2304 if (!ExecutedBlocks.insert(NewBB))
2305 return false; // looped!
2307 // Okay, we have never been in this block before. Check to see if there
2308 // are any PHI nodes. If so, evaluate them with information about where
2310 BasicBlock *OldBB = CurInst->getParent();
2311 CurInst = NewBB->begin();
2313 for (; (PN = dyn_cast<PHINode>(CurInst)); ++CurInst)
2314 Values[PN] = getVal(Values, PN->getIncomingValueForBlock(OldBB));
2316 // Do NOT increment CurInst. We know that the terminator had no value.
2319 // Did not know how to evaluate this!
2323 if (!CurInst->use_empty())
2324 Values[CurInst] = InstResult;
2326 // Advance program counter.
2331 /// EvaluateStaticConstructor - Evaluate static constructors in the function, if
2332 /// we can. Return true if we can, false otherwise.
2333 static bool EvaluateStaticConstructor(Function *F) {
2334 /// MutatedMemory - For each store we execute, we update this map. Loads
2335 /// check this to get the most up-to-date value. If evaluation is successful,
2336 /// this state is committed to the process.
2337 DenseMap<Constant*, Constant*> MutatedMemory;
2339 /// AllocaTmps - To 'execute' an alloca, we create a temporary global variable
2340 /// to represent its body. This vector is needed so we can delete the
2341 /// temporary globals when we are done.
2342 std::vector<GlobalVariable*> AllocaTmps;
2344 /// CallStack - This is used to detect recursion. In pathological situations
2345 /// we could hit exponential behavior, but at least there is nothing
2347 std::vector<Function*> CallStack;
2349 // Call the function.
2350 Constant *RetValDummy;
2351 bool EvalSuccess = EvaluateFunction(F, RetValDummy, std::vector<Constant*>(),
2352 CallStack, MutatedMemory, AllocaTmps);
2354 // We succeeded at evaluation: commit the result.
2355 DEBUG(errs() << "FULLY EVALUATED GLOBAL CTOR FUNCTION '"
2356 << F->getName() << "' to " << MutatedMemory.size()
2358 for (DenseMap<Constant*, Constant*>::iterator I = MutatedMemory.begin(),
2359 E = MutatedMemory.end(); I != E; ++I)
2360 CommitValueTo(I->second, I->first, F->getContext());
2363 // At this point, we are done interpreting. If we created any 'alloca'
2364 // temporaries, release them now.
2365 while (!AllocaTmps.empty()) {
2366 GlobalVariable *Tmp = AllocaTmps.back();
2367 AllocaTmps.pop_back();
2369 // If there are still users of the alloca, the program is doing something
2370 // silly, e.g. storing the address of the alloca somewhere and using it
2371 // later. Since this is undefined, we'll just make it be null.
2372 if (!Tmp->use_empty())
2373 Tmp->replaceAllUsesWith(F->getContext().getNullValue(Tmp->getType()));
2382 /// OptimizeGlobalCtorsList - Simplify and evaluation global ctors if possible.
2383 /// Return true if anything changed.
2384 bool GlobalOpt::OptimizeGlobalCtorsList(GlobalVariable *&GCL) {
2385 std::vector<Function*> Ctors = ParseGlobalCtors(GCL);
2386 bool MadeChange = false;
2387 if (Ctors.empty()) return false;
2389 // Loop over global ctors, optimizing them when we can.
2390 for (unsigned i = 0; i != Ctors.size(); ++i) {
2391 Function *F = Ctors[i];
2392 // Found a null terminator in the middle of the list, prune off the rest of
2395 if (i != Ctors.size()-1) {
2402 // We cannot simplify external ctor functions.
2403 if (F->empty()) continue;
2405 // If we can evaluate the ctor at compile time, do.
2406 if (EvaluateStaticConstructor(F)) {
2407 Ctors.erase(Ctors.begin()+i);
2410 ++NumCtorsEvaluated;
2415 if (!MadeChange) return false;
2417 GCL = InstallGlobalCtors(GCL, Ctors, GCL->getContext());
2421 bool GlobalOpt::OptimizeGlobalAliases(Module &M) {
2422 bool Changed = false;
2424 for (Module::alias_iterator I = M.alias_begin(), E = M.alias_end();
2426 Module::alias_iterator J = I++;
2427 // Aliases without names cannot be referenced outside this module.
2428 if (!J->hasName() && !J->isDeclaration())
2429 J->setLinkage(GlobalValue::InternalLinkage);
2430 // If the aliasee may change at link time, nothing can be done - bail out.
2431 if (J->mayBeOverridden())
2434 Constant *Aliasee = J->getAliasee();
2435 GlobalValue *Target = cast<GlobalValue>(Aliasee->stripPointerCasts());
2436 Target->removeDeadConstantUsers();
2437 bool hasOneUse = Target->hasOneUse() && Aliasee->hasOneUse();
2439 // Make all users of the alias use the aliasee instead.
2440 if (!J->use_empty()) {
2441 J->replaceAllUsesWith(Aliasee);
2442 ++NumAliasesResolved;
2446 // If the aliasee has internal linkage, give it the name and linkage
2447 // of the alias, and delete the alias. This turns:
2448 // define internal ... @f(...)
2449 // @a = alias ... @f
2451 // define ... @a(...)
2452 if (!Target->hasLocalLinkage())
2455 // The transform is only useful if the alias does not have internal linkage.
2456 if (J->hasLocalLinkage())
2459 // Do not perform the transform if multiple aliases potentially target the
2460 // aliasee. This check also ensures that it is safe to replace the section
2461 // and other attributes of the aliasee with those of the alias.
2465 // Give the aliasee the name, linkage and other attributes of the alias.
2466 Target->takeName(J);
2467 Target->setLinkage(J->getLinkage());
2468 Target->GlobalValue::copyAttributesFrom(J);
2470 // Delete the alias.
2471 M.getAliasList().erase(J);
2472 ++NumAliasesRemoved;
2479 bool GlobalOpt::runOnModule(Module &M) {
2480 bool Changed = false;
2482 // Try to find the llvm.globalctors list.
2483 GlobalVariable *GlobalCtors = FindGlobalCtors(M);
2485 bool LocalChange = true;
2486 while (LocalChange) {
2487 LocalChange = false;
2489 // Delete functions that are trivially dead, ccc -> fastcc
2490 LocalChange |= OptimizeFunctions(M);
2492 // Optimize global_ctors list.
2494 LocalChange |= OptimizeGlobalCtorsList(GlobalCtors);
2496 // Optimize non-address-taken globals.
2497 LocalChange |= OptimizeGlobalVars(M);
2499 // Resolve aliases, when possible.
2500 LocalChange |= OptimizeGlobalAliases(M);
2501 Changed |= LocalChange;
2504 // TODO: Move all global ctors functions to the end of the module for code