1 //===- GlobalOpt.cpp - Optimize Global Variables --------------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This pass transforms simple global variables that never have their address
11 // taken. If obviously true, it marks read/write globals as constant, deletes
12 // variables only stored to, etc.
14 //===----------------------------------------------------------------------===//
16 #define DEBUG_TYPE "globalopt"
17 #include "llvm/Transforms/IPO.h"
18 #include "llvm/CallingConv.h"
19 #include "llvm/Constants.h"
20 #include "llvm/DerivedTypes.h"
21 #include "llvm/Instructions.h"
22 #include "llvm/IntrinsicInst.h"
23 #include "llvm/Module.h"
24 #include "llvm/Pass.h"
25 #include "llvm/Analysis/ConstantFolding.h"
26 #include "llvm/Target/TargetData.h"
27 #include "llvm/Support/CallSite.h"
28 #include "llvm/Support/Compiler.h"
29 #include "llvm/Support/Debug.h"
30 #include "llvm/Support/GetElementPtrTypeIterator.h"
31 #include "llvm/Support/MathExtras.h"
32 #include "llvm/ADT/SmallPtrSet.h"
33 #include "llvm/ADT/SmallVector.h"
34 #include "llvm/ADT/Statistic.h"
35 #include "llvm/ADT/StringExtras.h"
41 STATISTIC(NumMarked , "Number of globals marked constant");
42 STATISTIC(NumSRA , "Number of aggregate globals broken into scalars");
43 STATISTIC(NumHeapSRA , "Number of heap objects SRA'd");
44 STATISTIC(NumSubstitute,"Number of globals with initializers stored into them");
45 STATISTIC(NumDeleted , "Number of globals deleted");
46 STATISTIC(NumFnDeleted , "Number of functions deleted");
47 STATISTIC(NumGlobUses , "Number of global uses devirtualized");
48 STATISTIC(NumLocalized , "Number of globals localized");
49 STATISTIC(NumShrunkToBool , "Number of global vars shrunk to booleans");
50 STATISTIC(NumFastCallFns , "Number of functions converted to fastcc");
51 STATISTIC(NumCtorsEvaluated, "Number of static ctors evaluated");
52 STATISTIC(NumNestRemoved , "Number of nest attributes removed");
55 struct VISIBILITY_HIDDEN GlobalOpt : public ModulePass {
56 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
57 AU.addRequired<TargetData>();
59 static char ID; // Pass identification, replacement for typeid
60 GlobalOpt() : ModulePass((intptr_t)&ID) {}
62 bool runOnModule(Module &M);
65 GlobalVariable *FindGlobalCtors(Module &M);
66 bool OptimizeFunctions(Module &M);
67 bool OptimizeGlobalVars(Module &M);
68 bool OptimizeGlobalCtorsList(GlobalVariable *&GCL);
69 bool ProcessInternalGlobal(GlobalVariable *GV,Module::global_iterator &GVI);
73 char GlobalOpt::ID = 0;
74 static RegisterPass<GlobalOpt> X("globalopt", "Global Variable Optimizer");
76 ModulePass *llvm::createGlobalOptimizerPass() { return new GlobalOpt(); }
80 /// GlobalStatus - As we analyze each global, keep track of some information
81 /// about it. If we find out that the address of the global is taken, none of
82 /// this info will be accurate.
83 struct VISIBILITY_HIDDEN GlobalStatus {
84 /// isLoaded - True if the global is ever loaded. If the global isn't ever
85 /// loaded it can be deleted.
88 /// StoredType - Keep track of what stores to the global look like.
91 /// NotStored - There is no store to this global. It can thus be marked
95 /// isInitializerStored - This global is stored to, but the only thing
96 /// stored is the constant it was initialized with. This is only tracked
97 /// for scalar globals.
100 /// isStoredOnce - This global is stored to, but only its initializer and
101 /// one other value is ever stored to it. If this global isStoredOnce, we
102 /// track the value stored to it in StoredOnceValue below. This is only
103 /// tracked for scalar globals.
106 /// isStored - This global is stored to by multiple values or something else
107 /// that we cannot track.
111 /// StoredOnceValue - If only one value (besides the initializer constant) is
112 /// ever stored to this global, keep track of what value it is.
113 Value *StoredOnceValue;
115 /// AccessingFunction/HasMultipleAccessingFunctions - These start out
116 /// null/false. When the first accessing function is noticed, it is recorded.
117 /// When a second different accessing function is noticed,
118 /// HasMultipleAccessingFunctions is set to true.
119 Function *AccessingFunction;
120 bool HasMultipleAccessingFunctions;
122 /// HasNonInstructionUser - Set to true if this global has a user that is not
123 /// an instruction (e.g. a constant expr or GV initializer).
124 bool HasNonInstructionUser;
126 /// HasPHIUser - Set to true if this global has a user that is a PHI node.
129 GlobalStatus() : isLoaded(false), StoredType(NotStored), StoredOnceValue(0),
130 AccessingFunction(0), HasMultipleAccessingFunctions(false),
131 HasNonInstructionUser(false), HasPHIUser(false) {}
136 /// ConstantIsDead - Return true if the specified constant is (transitively)
137 /// dead. The constant may be used by other constants (e.g. constant arrays and
138 /// constant exprs) as long as they are dead, but it cannot be used by anything
140 static bool ConstantIsDead(Constant *C) {
141 if (isa<GlobalValue>(C)) return false;
143 for (Value::use_iterator UI = C->use_begin(), E = C->use_end(); UI != E; ++UI)
144 if (Constant *CU = dyn_cast<Constant>(*UI)) {
145 if (!ConstantIsDead(CU)) return false;
152 /// AnalyzeGlobal - Look at all uses of the global and fill in the GlobalStatus
153 /// structure. If the global has its address taken, return true to indicate we
154 /// can't do anything with it.
156 static bool AnalyzeGlobal(Value *V, GlobalStatus &GS,
157 std::set<PHINode*> &PHIUsers) {
158 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ++UI)
159 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(*UI)) {
160 GS.HasNonInstructionUser = true;
162 if (AnalyzeGlobal(CE, GS, PHIUsers)) return true;
164 } else if (Instruction *I = dyn_cast<Instruction>(*UI)) {
165 if (!GS.HasMultipleAccessingFunctions) {
166 Function *F = I->getParent()->getParent();
167 if (GS.AccessingFunction == 0)
168 GS.AccessingFunction = F;
169 else if (GS.AccessingFunction != F)
170 GS.HasMultipleAccessingFunctions = true;
172 if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
174 if (LI->isVolatile()) return true; // Don't hack on volatile loads.
175 } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
176 // Don't allow a store OF the address, only stores TO the address.
177 if (SI->getOperand(0) == V) return true;
179 if (SI->isVolatile()) return true; // Don't hack on volatile stores.
181 // If this is a direct store to the global (i.e., the global is a scalar
182 // value, not an aggregate), keep more specific information about
184 if (GS.StoredType != GlobalStatus::isStored) {
185 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(SI->getOperand(1))){
186 Value *StoredVal = SI->getOperand(0);
187 if (StoredVal == GV->getInitializer()) {
188 if (GS.StoredType < GlobalStatus::isInitializerStored)
189 GS.StoredType = GlobalStatus::isInitializerStored;
190 } else if (isa<LoadInst>(StoredVal) &&
191 cast<LoadInst>(StoredVal)->getOperand(0) == GV) {
193 if (GS.StoredType < GlobalStatus::isInitializerStored)
194 GS.StoredType = GlobalStatus::isInitializerStored;
195 } else if (GS.StoredType < GlobalStatus::isStoredOnce) {
196 GS.StoredType = GlobalStatus::isStoredOnce;
197 GS.StoredOnceValue = StoredVal;
198 } else if (GS.StoredType == GlobalStatus::isStoredOnce &&
199 GS.StoredOnceValue == StoredVal) {
202 GS.StoredType = GlobalStatus::isStored;
205 GS.StoredType = GlobalStatus::isStored;
208 } else if (isa<GetElementPtrInst>(I)) {
209 if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
210 } else if (isa<SelectInst>(I)) {
211 if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
212 } else if (PHINode *PN = dyn_cast<PHINode>(I)) {
213 // PHI nodes we can check just like select or GEP instructions, but we
214 // have to be careful about infinite recursion.
215 if (PHIUsers.insert(PN).second) // Not already visited.
216 if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
217 GS.HasPHIUser = true;
218 } else if (isa<CmpInst>(I)) {
219 } else if (isa<MemCpyInst>(I) || isa<MemMoveInst>(I)) {
220 if (I->getOperand(1) == V)
221 GS.StoredType = GlobalStatus::isStored;
222 if (I->getOperand(2) == V)
224 } else if (isa<MemSetInst>(I)) {
225 assert(I->getOperand(1) == V && "Memset only takes one pointer!");
226 GS.StoredType = GlobalStatus::isStored;
228 return true; // Any other non-load instruction might take address!
230 } else if (Constant *C = dyn_cast<Constant>(*UI)) {
231 GS.HasNonInstructionUser = true;
232 // We might have a dead and dangling constant hanging off of here.
233 if (!ConstantIsDead(C))
236 GS.HasNonInstructionUser = true;
237 // Otherwise must be some other user.
244 static Constant *getAggregateConstantElement(Constant *Agg, Constant *Idx) {
245 ConstantInt *CI = dyn_cast<ConstantInt>(Idx);
247 unsigned IdxV = CI->getZExtValue();
249 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(Agg)) {
250 if (IdxV < CS->getNumOperands()) return CS->getOperand(IdxV);
251 } else if (ConstantArray *CA = dyn_cast<ConstantArray>(Agg)) {
252 if (IdxV < CA->getNumOperands()) return CA->getOperand(IdxV);
253 } else if (ConstantVector *CP = dyn_cast<ConstantVector>(Agg)) {
254 if (IdxV < CP->getNumOperands()) return CP->getOperand(IdxV);
255 } else if (isa<ConstantAggregateZero>(Agg)) {
256 if (const StructType *STy = dyn_cast<StructType>(Agg->getType())) {
257 if (IdxV < STy->getNumElements())
258 return Constant::getNullValue(STy->getElementType(IdxV));
259 } else if (const SequentialType *STy =
260 dyn_cast<SequentialType>(Agg->getType())) {
261 return Constant::getNullValue(STy->getElementType());
263 } else if (isa<UndefValue>(Agg)) {
264 if (const StructType *STy = dyn_cast<StructType>(Agg->getType())) {
265 if (IdxV < STy->getNumElements())
266 return UndefValue::get(STy->getElementType(IdxV));
267 } else if (const SequentialType *STy =
268 dyn_cast<SequentialType>(Agg->getType())) {
269 return UndefValue::get(STy->getElementType());
276 /// CleanupConstantGlobalUsers - We just marked GV constant. Loop over all
277 /// users of the global, cleaning up the obvious ones. This is largely just a
278 /// quick scan over the use list to clean up the easy and obvious cruft. This
279 /// returns true if it made a change.
280 static bool CleanupConstantGlobalUsers(Value *V, Constant *Init) {
281 bool Changed = false;
282 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;) {
285 if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
287 // Replace the load with the initializer.
288 LI->replaceAllUsesWith(Init);
289 LI->eraseFromParent();
292 } else if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
293 // Store must be unreachable or storing Init into the global.
294 SI->eraseFromParent();
296 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U)) {
297 if (CE->getOpcode() == Instruction::GetElementPtr) {
298 Constant *SubInit = 0;
300 SubInit = ConstantFoldLoadThroughGEPConstantExpr(Init, CE);
301 Changed |= CleanupConstantGlobalUsers(CE, SubInit);
302 } else if (CE->getOpcode() == Instruction::BitCast &&
303 isa<PointerType>(CE->getType())) {
304 // Pointer cast, delete any stores and memsets to the global.
305 Changed |= CleanupConstantGlobalUsers(CE, 0);
308 if (CE->use_empty()) {
309 CE->destroyConstant();
312 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) {
313 // Do not transform "gepinst (gep constexpr (GV))" here, because forming
314 // "gepconstexpr (gep constexpr (GV))" will cause the two gep's to fold
315 // and will invalidate our notion of what Init is.
316 Constant *SubInit = 0;
317 if (!isa<ConstantExpr>(GEP->getOperand(0))) {
319 dyn_cast_or_null<ConstantExpr>(ConstantFoldInstruction(GEP));
320 if (Init && CE && CE->getOpcode() == Instruction::GetElementPtr)
321 SubInit = ConstantFoldLoadThroughGEPConstantExpr(Init, CE);
323 Changed |= CleanupConstantGlobalUsers(GEP, SubInit);
325 if (GEP->use_empty()) {
326 GEP->eraseFromParent();
329 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(U)) { // memset/cpy/mv
330 if (MI->getRawDest() == V) {
331 MI->eraseFromParent();
335 } else if (Constant *C = dyn_cast<Constant>(U)) {
336 // If we have a chain of dead constantexprs or other things dangling from
337 // us, and if they are all dead, nuke them without remorse.
338 if (ConstantIsDead(C)) {
339 C->destroyConstant();
340 // This could have invalidated UI, start over from scratch.
341 CleanupConstantGlobalUsers(V, Init);
349 /// isSafeSROAElementUse - Return true if the specified instruction is a safe
350 /// user of a derived expression from a global that we want to SROA.
351 static bool isSafeSROAElementUse(Value *V) {
352 // We might have a dead and dangling constant hanging off of here.
353 if (Constant *C = dyn_cast<Constant>(V))
354 return ConstantIsDead(C);
356 Instruction *I = dyn_cast<Instruction>(V);
357 if (!I) return false;
360 if (isa<LoadInst>(I)) return true;
362 // Stores *to* the pointer are ok.
363 if (StoreInst *SI = dyn_cast<StoreInst>(I))
364 return SI->getOperand(0) != V;
366 // Otherwise, it must be a GEP.
367 GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I);
368 if (GEPI == 0) return false;
370 if (GEPI->getNumOperands() < 3 || !isa<Constant>(GEPI->getOperand(1)) ||
371 !cast<Constant>(GEPI->getOperand(1))->isNullValue())
374 for (Value::use_iterator I = GEPI->use_begin(), E = GEPI->use_end();
376 if (!isSafeSROAElementUse(*I))
382 /// IsUserOfGlobalSafeForSRA - U is a direct user of the specified global value.
383 /// Look at it and its uses and decide whether it is safe to SROA this global.
385 static bool IsUserOfGlobalSafeForSRA(User *U, GlobalValue *GV) {
386 // The user of the global must be a GEP Inst or a ConstantExpr GEP.
387 if (!isa<GetElementPtrInst>(U) &&
388 (!isa<ConstantExpr>(U) ||
389 cast<ConstantExpr>(U)->getOpcode() != Instruction::GetElementPtr))
392 // Check to see if this ConstantExpr GEP is SRA'able. In particular, we
393 // don't like < 3 operand CE's, and we don't like non-constant integer
394 // indices. This enforces that all uses are 'gep GV, 0, C, ...' for some
396 if (U->getNumOperands() < 3 || !isa<Constant>(U->getOperand(1)) ||
397 !cast<Constant>(U->getOperand(1))->isNullValue() ||
398 !isa<ConstantInt>(U->getOperand(2)))
401 gep_type_iterator GEPI = gep_type_begin(U), E = gep_type_end(U);
402 ++GEPI; // Skip over the pointer index.
404 // If this is a use of an array allocation, do a bit more checking for sanity.
405 if (const ArrayType *AT = dyn_cast<ArrayType>(*GEPI)) {
406 uint64_t NumElements = AT->getNumElements();
407 ConstantInt *Idx = cast<ConstantInt>(U->getOperand(2));
409 // Check to make sure that index falls within the array. If not,
410 // something funny is going on, so we won't do the optimization.
412 if (Idx->getZExtValue() >= NumElements)
415 // We cannot scalar repl this level of the array unless any array
416 // sub-indices are in-range constants. In particular, consider:
417 // A[0][i]. We cannot know that the user isn't doing invalid things like
418 // allowing i to index an out-of-range subscript that accesses A[1].
420 // Scalar replacing *just* the outer index of the array is probably not
421 // going to be a win anyway, so just give up.
422 for (++GEPI; // Skip array index.
423 GEPI != E && (isa<ArrayType>(*GEPI) || isa<VectorType>(*GEPI));
425 uint64_t NumElements;
426 if (const ArrayType *SubArrayTy = dyn_cast<ArrayType>(*GEPI))
427 NumElements = SubArrayTy->getNumElements();
429 NumElements = cast<VectorType>(*GEPI)->getNumElements();
431 ConstantInt *IdxVal = dyn_cast<ConstantInt>(GEPI.getOperand());
432 if (!IdxVal || IdxVal->getZExtValue() >= NumElements)
437 for (Value::use_iterator I = U->use_begin(), E = U->use_end(); I != E; ++I)
438 if (!isSafeSROAElementUse(*I))
443 /// GlobalUsersSafeToSRA - Look at all uses of the global and decide whether it
444 /// is safe for us to perform this transformation.
446 static bool GlobalUsersSafeToSRA(GlobalValue *GV) {
447 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end();
449 if (!IsUserOfGlobalSafeForSRA(*UI, GV))
456 /// SRAGlobal - Perform scalar replacement of aggregates on the specified global
457 /// variable. This opens the door for other optimizations by exposing the
458 /// behavior of the program in a more fine-grained way. We have determined that
459 /// this transformation is safe already. We return the first global variable we
460 /// insert so that the caller can reprocess it.
461 static GlobalVariable *SRAGlobal(GlobalVariable *GV, const TargetData &TD) {
462 // Make sure this global only has simple uses that we can SRA.
463 if (!GlobalUsersSafeToSRA(GV))
466 assert(GV->hasInternalLinkage() && !GV->isConstant());
467 Constant *Init = GV->getInitializer();
468 const Type *Ty = Init->getType();
470 std::vector<GlobalVariable*> NewGlobals;
471 Module::GlobalListType &Globals = GV->getParent()->getGlobalList();
473 // Get the alignment of the global, either explicit or target-specific.
474 unsigned StartAlignment = GV->getAlignment();
475 if (StartAlignment == 0)
476 StartAlignment = TD.getABITypeAlignment(GV->getType());
478 if (const StructType *STy = dyn_cast<StructType>(Ty)) {
479 NewGlobals.reserve(STy->getNumElements());
480 const StructLayout &Layout = *TD.getStructLayout(STy);
481 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
482 Constant *In = getAggregateConstantElement(Init,
483 ConstantInt::get(Type::Int32Ty, i));
484 assert(In && "Couldn't get element of initializer?");
485 GlobalVariable *NGV = new GlobalVariable(STy->getElementType(i), false,
486 GlobalVariable::InternalLinkage,
487 In, GV->getName()+"."+utostr(i),
489 GV->isThreadLocal());
490 Globals.insert(GV, NGV);
491 NewGlobals.push_back(NGV);
493 // Calculate the known alignment of the field. If the original aggregate
494 // had 256 byte alignment for example, something might depend on that:
495 // propagate info to each field.
496 uint64_t FieldOffset = Layout.getElementOffset(i);
497 unsigned NewAlign = (unsigned)MinAlign(StartAlignment, FieldOffset);
498 if (NewAlign > TD.getABITypeAlignment(STy->getElementType(i)))
499 NGV->setAlignment(NewAlign);
501 } else if (const SequentialType *STy = dyn_cast<SequentialType>(Ty)) {
502 unsigned NumElements = 0;
503 if (const ArrayType *ATy = dyn_cast<ArrayType>(STy))
504 NumElements = ATy->getNumElements();
506 NumElements = cast<VectorType>(STy)->getNumElements();
508 if (NumElements > 16 && GV->hasNUsesOrMore(16))
509 return 0; // It's not worth it.
510 NewGlobals.reserve(NumElements);
512 uint64_t EltSize = TD.getABITypeSize(STy->getElementType());
513 unsigned EltAlign = TD.getABITypeAlignment(STy->getElementType());
514 for (unsigned i = 0, e = NumElements; i != e; ++i) {
515 Constant *In = getAggregateConstantElement(Init,
516 ConstantInt::get(Type::Int32Ty, i));
517 assert(In && "Couldn't get element of initializer?");
519 GlobalVariable *NGV = new GlobalVariable(STy->getElementType(), false,
520 GlobalVariable::InternalLinkage,
521 In, GV->getName()+"."+utostr(i),
523 GV->isThreadLocal());
524 Globals.insert(GV, NGV);
525 NewGlobals.push_back(NGV);
527 // Calculate the known alignment of the field. If the original aggregate
528 // had 256 byte alignment for example, something might depend on that:
529 // propagate info to each field.
530 unsigned NewAlign = (unsigned)MinAlign(StartAlignment, EltSize*i);
531 if (NewAlign > EltAlign)
532 NGV->setAlignment(NewAlign);
536 if (NewGlobals.empty())
539 DOUT << "PERFORMING GLOBAL SRA ON: " << *GV;
541 Constant *NullInt = Constant::getNullValue(Type::Int32Ty);
543 // Loop over all of the uses of the global, replacing the constantexpr geps,
544 // with smaller constantexpr geps or direct references.
545 while (!GV->use_empty()) {
546 User *GEP = GV->use_back();
547 assert(((isa<ConstantExpr>(GEP) &&
548 cast<ConstantExpr>(GEP)->getOpcode()==Instruction::GetElementPtr)||
549 isa<GetElementPtrInst>(GEP)) && "NonGEP CE's are not SRAable!");
551 // Ignore the 1th operand, which has to be zero or else the program is quite
552 // broken (undefined). Get the 2nd operand, which is the structure or array
554 unsigned Val = cast<ConstantInt>(GEP->getOperand(2))->getZExtValue();
555 if (Val >= NewGlobals.size()) Val = 0; // Out of bound array access.
557 Value *NewPtr = NewGlobals[Val];
559 // Form a shorter GEP if needed.
560 if (GEP->getNumOperands() > 3) {
561 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GEP)) {
562 SmallVector<Constant*, 8> Idxs;
563 Idxs.push_back(NullInt);
564 for (unsigned i = 3, e = CE->getNumOperands(); i != e; ++i)
565 Idxs.push_back(CE->getOperand(i));
566 NewPtr = ConstantExpr::getGetElementPtr(cast<Constant>(NewPtr),
567 &Idxs[0], Idxs.size());
569 GetElementPtrInst *GEPI = cast<GetElementPtrInst>(GEP);
570 SmallVector<Value*, 8> Idxs;
571 Idxs.push_back(NullInt);
572 for (unsigned i = 3, e = GEPI->getNumOperands(); i != e; ++i)
573 Idxs.push_back(GEPI->getOperand(i));
574 NewPtr = GetElementPtrInst::Create(NewPtr, Idxs.begin(), Idxs.end(),
575 GEPI->getName()+"."+utostr(Val), GEPI);
578 GEP->replaceAllUsesWith(NewPtr);
580 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(GEP))
581 GEPI->eraseFromParent();
583 cast<ConstantExpr>(GEP)->destroyConstant();
586 // Delete the old global, now that it is dead.
590 // Loop over the new globals array deleting any globals that are obviously
591 // dead. This can arise due to scalarization of a structure or an array that
592 // has elements that are dead.
593 unsigned FirstGlobal = 0;
594 for (unsigned i = 0, e = NewGlobals.size(); i != e; ++i)
595 if (NewGlobals[i]->use_empty()) {
596 Globals.erase(NewGlobals[i]);
597 if (FirstGlobal == i) ++FirstGlobal;
600 return FirstGlobal != NewGlobals.size() ? NewGlobals[FirstGlobal] : 0;
603 /// AllUsesOfValueWillTrapIfNull - Return true if all users of the specified
604 /// value will trap if the value is dynamically null. PHIs keeps track of any
605 /// phi nodes we've seen to avoid reprocessing them.
606 static bool AllUsesOfValueWillTrapIfNull(Value *V,
607 SmallPtrSet<PHINode*, 8> &PHIs) {
608 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ++UI)
609 if (isa<LoadInst>(*UI)) {
611 } else if (StoreInst *SI = dyn_cast<StoreInst>(*UI)) {
612 if (SI->getOperand(0) == V) {
613 //cerr << "NONTRAPPING USE: " << **UI;
614 return false; // Storing the value.
616 } else if (CallInst *CI = dyn_cast<CallInst>(*UI)) {
617 if (CI->getOperand(0) != V) {
618 //cerr << "NONTRAPPING USE: " << **UI;
619 return false; // Not calling the ptr
621 } else if (InvokeInst *II = dyn_cast<InvokeInst>(*UI)) {
622 if (II->getOperand(0) != V) {
623 //cerr << "NONTRAPPING USE: " << **UI;
624 return false; // Not calling the ptr
626 } else if (BitCastInst *CI = dyn_cast<BitCastInst>(*UI)) {
627 if (!AllUsesOfValueWillTrapIfNull(CI, PHIs)) return false;
628 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(*UI)) {
629 if (!AllUsesOfValueWillTrapIfNull(GEPI, PHIs)) return false;
630 } else if (PHINode *PN = dyn_cast<PHINode>(*UI)) {
631 // If we've already seen this phi node, ignore it, it has already been
634 return AllUsesOfValueWillTrapIfNull(PN, PHIs);
635 } else if (isa<ICmpInst>(*UI) &&
636 isa<ConstantPointerNull>(UI->getOperand(1))) {
637 // Ignore setcc X, null
639 //cerr << "NONTRAPPING USE: " << **UI;
645 /// AllUsesOfLoadedValueWillTrapIfNull - Return true if all uses of any loads
646 /// from GV will trap if the loaded value is null. Note that this also permits
647 /// comparisons of the loaded value against null, as a special case.
648 static bool AllUsesOfLoadedValueWillTrapIfNull(GlobalVariable *GV) {
649 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); UI!=E; ++UI)
650 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
651 SmallPtrSet<PHINode*, 8> PHIs;
652 if (!AllUsesOfValueWillTrapIfNull(LI, PHIs))
654 } else if (isa<StoreInst>(*UI)) {
655 // Ignore stores to the global.
657 // We don't know or understand this user, bail out.
658 //cerr << "UNKNOWN USER OF GLOBAL!: " << **UI;
665 static bool OptimizeAwayTrappingUsesOfValue(Value *V, Constant *NewV) {
666 bool Changed = false;
667 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ) {
668 Instruction *I = cast<Instruction>(*UI++);
669 if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
670 LI->setOperand(0, NewV);
672 } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
673 if (SI->getOperand(1) == V) {
674 SI->setOperand(1, NewV);
677 } else if (isa<CallInst>(I) || isa<InvokeInst>(I)) {
678 if (I->getOperand(0) == V) {
679 // Calling through the pointer! Turn into a direct call, but be careful
680 // that the pointer is not also being passed as an argument.
681 I->setOperand(0, NewV);
683 bool PassedAsArg = false;
684 for (unsigned i = 1, e = I->getNumOperands(); i != e; ++i)
685 if (I->getOperand(i) == V) {
687 I->setOperand(i, NewV);
691 // Being passed as an argument also. Be careful to not invalidate UI!
695 } else if (CastInst *CI = dyn_cast<CastInst>(I)) {
696 Changed |= OptimizeAwayTrappingUsesOfValue(CI,
697 ConstantExpr::getCast(CI->getOpcode(),
698 NewV, CI->getType()));
699 if (CI->use_empty()) {
701 CI->eraseFromParent();
703 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I)) {
704 // Should handle GEP here.
705 SmallVector<Constant*, 8> Idxs;
706 Idxs.reserve(GEPI->getNumOperands()-1);
707 for (unsigned i = 1, e = GEPI->getNumOperands(); i != e; ++i)
708 if (Constant *C = dyn_cast<Constant>(GEPI->getOperand(i)))
712 if (Idxs.size() == GEPI->getNumOperands()-1)
713 Changed |= OptimizeAwayTrappingUsesOfValue(GEPI,
714 ConstantExpr::getGetElementPtr(NewV, &Idxs[0],
716 if (GEPI->use_empty()) {
718 GEPI->eraseFromParent();
727 /// OptimizeAwayTrappingUsesOfLoads - The specified global has only one non-null
728 /// value stored into it. If there are uses of the loaded value that would trap
729 /// if the loaded value is dynamically null, then we know that they cannot be
730 /// reachable with a null optimize away the load.
731 static bool OptimizeAwayTrappingUsesOfLoads(GlobalVariable *GV, Constant *LV) {
732 std::vector<LoadInst*> Loads;
733 bool Changed = false;
735 // Replace all uses of loads with uses of uses of the stored value.
736 for (Value::use_iterator GUI = GV->use_begin(), E = GV->use_end();
738 if (LoadInst *LI = dyn_cast<LoadInst>(*GUI)) {
740 Changed |= OptimizeAwayTrappingUsesOfValue(LI, LV);
742 // If we get here we could have stores, selects, or phi nodes whose values
744 assert((isa<StoreInst>(*GUI) || isa<PHINode>(*GUI) ||
745 isa<SelectInst>(*GUI) || isa<ConstantExpr>(*GUI)) &&
746 "Only expect load and stores!");
750 DOUT << "OPTIMIZED LOADS FROM STORED ONCE POINTER: " << *GV;
754 // Delete all of the loads we can, keeping track of whether we nuked them all!
755 bool AllLoadsGone = true;
756 while (!Loads.empty()) {
757 LoadInst *L = Loads.back();
758 if (L->use_empty()) {
759 L->eraseFromParent();
762 AllLoadsGone = false;
767 // If we nuked all of the loads, then none of the stores are needed either,
768 // nor is the global.
770 DOUT << " *** GLOBAL NOW DEAD!\n";
771 CleanupConstantGlobalUsers(GV, 0);
772 if (GV->use_empty()) {
773 GV->eraseFromParent();
781 /// ConstantPropUsersOf - Walk the use list of V, constant folding all of the
782 /// instructions that are foldable.
783 static void ConstantPropUsersOf(Value *V) {
784 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; )
785 if (Instruction *I = dyn_cast<Instruction>(*UI++))
786 if (Constant *NewC = ConstantFoldInstruction(I)) {
787 I->replaceAllUsesWith(NewC);
789 // Advance UI to the next non-I use to avoid invalidating it!
790 // Instructions could multiply use V.
791 while (UI != E && *UI == I)
793 I->eraseFromParent();
797 /// OptimizeGlobalAddressOfMalloc - This function takes the specified global
798 /// variable, and transforms the program as if it always contained the result of
799 /// the specified malloc. Because it is always the result of the specified
800 /// malloc, there is no reason to actually DO the malloc. Instead, turn the
801 /// malloc into a global, and any loads of GV as uses of the new global.
802 static GlobalVariable *OptimizeGlobalAddressOfMalloc(GlobalVariable *GV,
804 DOUT << "PROMOTING MALLOC GLOBAL: " << *GV << " MALLOC = " << *MI;
805 ConstantInt *NElements = cast<ConstantInt>(MI->getArraySize());
807 if (NElements->getZExtValue() != 1) {
808 // If we have an array allocation, transform it to a single element
809 // allocation to make the code below simpler.
810 Type *NewTy = ArrayType::get(MI->getAllocatedType(),
811 NElements->getZExtValue());
813 new MallocInst(NewTy, Constant::getNullValue(Type::Int32Ty),
814 MI->getAlignment(), MI->getName(), MI);
816 Indices[0] = Indices[1] = Constant::getNullValue(Type::Int32Ty);
817 Value *NewGEP = GetElementPtrInst::Create(NewMI, Indices, Indices + 2,
818 NewMI->getName()+".el0", MI);
819 MI->replaceAllUsesWith(NewGEP);
820 MI->eraseFromParent();
824 // Create the new global variable. The contents of the malloc'd memory is
825 // undefined, so initialize with an undef value.
826 Constant *Init = UndefValue::get(MI->getAllocatedType());
827 GlobalVariable *NewGV = new GlobalVariable(MI->getAllocatedType(), false,
828 GlobalValue::InternalLinkage, Init,
829 GV->getName()+".body",
831 GV->isThreadLocal());
832 // FIXME: This new global should have the alignment returned by malloc. Code
833 // could depend on malloc returning large alignment (on the mac, 16 bytes) but
834 // this would only guarantee some lower alignment.
835 GV->getParent()->getGlobalList().insert(GV, NewGV);
837 // Anything that used the malloc now uses the global directly.
838 MI->replaceAllUsesWith(NewGV);
840 Constant *RepValue = NewGV;
841 if (NewGV->getType() != GV->getType()->getElementType())
842 RepValue = ConstantExpr::getBitCast(RepValue,
843 GV->getType()->getElementType());
845 // If there is a comparison against null, we will insert a global bool to
846 // keep track of whether the global was initialized yet or not.
847 GlobalVariable *InitBool =
848 new GlobalVariable(Type::Int1Ty, false, GlobalValue::InternalLinkage,
849 ConstantInt::getFalse(), GV->getName()+".init",
850 (Module *)NULL, GV->isThreadLocal());
851 bool InitBoolUsed = false;
853 // Loop over all uses of GV, processing them in turn.
854 std::vector<StoreInst*> Stores;
855 while (!GV->use_empty())
856 if (LoadInst *LI = dyn_cast<LoadInst>(GV->use_back())) {
857 while (!LI->use_empty()) {
858 Use &LoadUse = LI->use_begin().getUse();
859 if (!isa<ICmpInst>(LoadUse.getUser()))
862 ICmpInst *CI = cast<ICmpInst>(LoadUse.getUser());
863 // Replace the cmp X, 0 with a use of the bool value.
864 Value *LV = new LoadInst(InitBool, InitBool->getName()+".val", CI);
866 switch (CI->getPredicate()) {
867 default: assert(0 && "Unknown ICmp Predicate!");
868 case ICmpInst::ICMP_ULT:
869 case ICmpInst::ICMP_SLT:
870 LV = ConstantInt::getFalse(); // X < null -> always false
872 case ICmpInst::ICMP_ULE:
873 case ICmpInst::ICMP_SLE:
874 case ICmpInst::ICMP_EQ:
875 LV = BinaryOperator::CreateNot(LV, "notinit", CI);
877 case ICmpInst::ICMP_NE:
878 case ICmpInst::ICMP_UGE:
879 case ICmpInst::ICMP_SGE:
880 case ICmpInst::ICMP_UGT:
881 case ICmpInst::ICMP_SGT:
884 CI->replaceAllUsesWith(LV);
885 CI->eraseFromParent();
888 LI->eraseFromParent();
890 StoreInst *SI = cast<StoreInst>(GV->use_back());
891 // The global is initialized when the store to it occurs.
892 new StoreInst(ConstantInt::getTrue(), InitBool, SI);
893 SI->eraseFromParent();
896 // If the initialization boolean was used, insert it, otherwise delete it.
898 while (!InitBool->use_empty()) // Delete initializations
899 cast<Instruction>(InitBool->use_back())->eraseFromParent();
902 GV->getParent()->getGlobalList().insert(GV, InitBool);
905 // Now the GV is dead, nuke it and the malloc.
906 GV->eraseFromParent();
907 MI->eraseFromParent();
909 // To further other optimizations, loop over all users of NewGV and try to
910 // constant prop them. This will promote GEP instructions with constant
911 // indices into GEP constant-exprs, which will allow global-opt to hack on it.
912 ConstantPropUsersOf(NewGV);
913 if (RepValue != NewGV)
914 ConstantPropUsersOf(RepValue);
919 /// ValueIsOnlyUsedLocallyOrStoredToOneGlobal - Scan the use-list of V checking
920 /// to make sure that there are no complex uses of V. We permit simple things
921 /// like dereferencing the pointer, but not storing through the address, unless
922 /// it is to the specified global.
923 static bool ValueIsOnlyUsedLocallyOrStoredToOneGlobal(Instruction *V,
925 SmallPtrSet<PHINode*, 8> &PHIs) {
926 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ++UI)
927 if (isa<LoadInst>(*UI) || isa<CmpInst>(*UI)) {
929 } else if (StoreInst *SI = dyn_cast<StoreInst>(*UI)) {
930 if (SI->getOperand(0) == V && SI->getOperand(1) != GV)
931 return false; // Storing the pointer itself... bad.
932 // Otherwise, storing through it, or storing into GV... fine.
933 } else if (isa<GetElementPtrInst>(*UI)) {
934 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(cast<Instruction>(*UI),
937 } else if (PHINode *PN = dyn_cast<PHINode>(*UI)) {
938 // PHIs are ok if all uses are ok. Don't infinitely recurse through PHI
941 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(PN, GV, PHIs))
949 /// ReplaceUsesOfMallocWithGlobal - The Alloc pointer is stored into GV
950 /// somewhere. Transform all uses of the allocation into loads from the
951 /// global and uses of the resultant pointer. Further, delete the store into
952 /// GV. This assumes that these value pass the
953 /// 'ValueIsOnlyUsedLocallyOrStoredToOneGlobal' predicate.
954 static void ReplaceUsesOfMallocWithGlobal(Instruction *Alloc,
955 GlobalVariable *GV) {
956 while (!Alloc->use_empty()) {
957 Instruction *U = cast<Instruction>(*Alloc->use_begin());
958 Instruction *InsertPt = U;
959 if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
960 // If this is the store of the allocation into the global, remove it.
961 if (SI->getOperand(1) == GV) {
962 SI->eraseFromParent();
965 } else if (PHINode *PN = dyn_cast<PHINode>(U)) {
966 // Insert the load in the corresponding predecessor, not right before the
968 unsigned PredNo = Alloc->use_begin().getOperandNo()/2;
969 InsertPt = PN->getIncomingBlock(PredNo)->getTerminator();
972 // Insert a load from the global, and use it instead of the malloc.
973 Value *NL = new LoadInst(GV, GV->getName()+".val", InsertPt);
974 U->replaceUsesOfWith(Alloc, NL);
978 /// GlobalLoadUsesSimpleEnoughForHeapSRA - If all users of values loaded from
979 /// GV are simple enough to perform HeapSRA, return true.
980 static bool GlobalLoadUsesSimpleEnoughForHeapSRA(GlobalVariable *GV,
982 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); UI != E;
984 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
985 // We permit two users of the load: setcc comparing against the null
986 // pointer, and a getelementptr of a specific form.
987 for (Value::use_iterator UI = LI->use_begin(), E = LI->use_end(); UI != E;
989 // Comparison against null is ok.
990 if (ICmpInst *ICI = dyn_cast<ICmpInst>(*UI)) {
991 if (!isa<ConstantPointerNull>(ICI->getOperand(1)))
996 // getelementptr is also ok, but only a simple form.
997 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(*UI)) {
998 // Must index into the array and into the struct.
999 if (GEPI->getNumOperands() < 3)
1002 // Otherwise the GEP is ok.
1006 if (PHINode *PN = dyn_cast<PHINode>(*UI)) {
1007 // We have a phi of a load from the global. We can only handle this
1008 // if the other PHI'd values are actually the same. In this case,
1009 // the rewriter will just drop the phi entirely.
1010 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
1011 Value *IV = PN->getIncomingValue(i);
1012 if (IV == LI) continue; // Trivial the same.
1014 // If the phi'd value is from the malloc that initializes the value,
1016 if (IV == MI) continue;
1018 // Otherwise, we don't know what it is.
1024 // Otherwise we don't know what this is, not ok.
1031 /// GetHeapSROALoad - Return the load for the specified field of the HeapSROA'd
1032 /// value, lazily creating it on demand.
1033 static Value *GetHeapSROALoad(Instruction *Load, unsigned FieldNo,
1034 const std::vector<GlobalVariable*> &FieldGlobals,
1035 std::vector<Value *> &InsertedLoadsForPtr) {
1036 if (InsertedLoadsForPtr.size() <= FieldNo)
1037 InsertedLoadsForPtr.resize(FieldNo+1);
1038 if (InsertedLoadsForPtr[FieldNo] == 0)
1039 InsertedLoadsForPtr[FieldNo] = new LoadInst(FieldGlobals[FieldNo],
1040 Load->getName()+".f" +
1041 utostr(FieldNo), Load);
1042 return InsertedLoadsForPtr[FieldNo];
1045 /// RewriteHeapSROALoadUser - Given a load instruction and a value derived from
1046 /// the load, rewrite the derived value to use the HeapSRoA'd load.
1047 static void RewriteHeapSROALoadUser(LoadInst *Load, Instruction *LoadUser,
1048 const std::vector<GlobalVariable*> &FieldGlobals,
1049 std::vector<Value *> &InsertedLoadsForPtr) {
1050 // If this is a comparison against null, handle it.
1051 if (ICmpInst *SCI = dyn_cast<ICmpInst>(LoadUser)) {
1052 assert(isa<ConstantPointerNull>(SCI->getOperand(1)));
1053 // If we have a setcc of the loaded pointer, we can use a setcc of any
1056 if (InsertedLoadsForPtr.empty()) {
1057 NPtr = GetHeapSROALoad(Load, 0, FieldGlobals, InsertedLoadsForPtr);
1059 NPtr = InsertedLoadsForPtr.back();
1062 Value *New = new ICmpInst(SCI->getPredicate(), NPtr,
1063 Constant::getNullValue(NPtr->getType()),
1064 SCI->getName(), SCI);
1065 SCI->replaceAllUsesWith(New);
1066 SCI->eraseFromParent();
1070 // Handle 'getelementptr Ptr, Idx, uint FieldNo ...'
1071 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(LoadUser)) {
1072 assert(GEPI->getNumOperands() >= 3 && isa<ConstantInt>(GEPI->getOperand(2))
1073 && "Unexpected GEPI!");
1075 // Load the pointer for this field.
1076 unsigned FieldNo = cast<ConstantInt>(GEPI->getOperand(2))->getZExtValue();
1077 Value *NewPtr = GetHeapSROALoad(Load, FieldNo,
1078 FieldGlobals, InsertedLoadsForPtr);
1080 // Create the new GEP idx vector.
1081 SmallVector<Value*, 8> GEPIdx;
1082 GEPIdx.push_back(GEPI->getOperand(1));
1083 GEPIdx.append(GEPI->op_begin()+3, GEPI->op_end());
1085 Value *NGEPI = GetElementPtrInst::Create(NewPtr,
1086 GEPIdx.begin(), GEPIdx.end(),
1087 GEPI->getName(), GEPI);
1088 GEPI->replaceAllUsesWith(NGEPI);
1089 GEPI->eraseFromParent();
1093 // Handle PHI nodes. PHI nodes must be merging in the same values, plus
1094 // potentially the original malloc. Insert phi nodes for each field, then
1095 // process uses of the PHI.
1096 PHINode *PN = cast<PHINode>(LoadUser);
1097 std::vector<Value *> PHIsForField;
1098 PHIsForField.resize(FieldGlobals.size());
1099 for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) {
1100 Value *LoadV = GetHeapSROALoad(Load, i, FieldGlobals, InsertedLoadsForPtr);
1102 PHINode *FieldPN = PHINode::Create(LoadV->getType(),
1103 PN->getName()+"."+utostr(i), PN);
1104 // Fill in the predecessor values.
1105 for (unsigned pred = 0, e = PN->getNumIncomingValues(); pred != e; ++pred) {
1106 // Each predecessor either uses the load or the original malloc.
1107 Value *InVal = PN->getIncomingValue(pred);
1108 BasicBlock *BB = PN->getIncomingBlock(pred);
1110 if (isa<MallocInst>(InVal)) {
1111 // Insert a reload from the global in the predecessor.
1112 NewVal = GetHeapSROALoad(BB->getTerminator(), i, FieldGlobals,
1115 NewVal = InsertedLoadsForPtr[i];
1117 FieldPN->addIncoming(NewVal, BB);
1119 PHIsForField[i] = FieldPN;
1122 // Since PHIsForField specifies a phi for every input value, the lazy inserter
1123 // will never insert a load.
1124 while (!PN->use_empty())
1125 RewriteHeapSROALoadUser(Load, PN->use_back(), FieldGlobals, PHIsForField);
1126 PN->eraseFromParent();
1129 /// RewriteUsesOfLoadForHeapSRoA - We are performing Heap SRoA on a global. Ptr
1130 /// is a value loaded from the global. Eliminate all uses of Ptr, making them
1131 /// use FieldGlobals instead. All uses of loaded values satisfy
1132 /// GlobalLoadUsesSimpleEnoughForHeapSRA.
1133 static void RewriteUsesOfLoadForHeapSRoA(LoadInst *Load,
1134 const std::vector<GlobalVariable*> &FieldGlobals) {
1135 std::vector<Value *> InsertedLoadsForPtr;
1136 //InsertedLoadsForPtr.resize(FieldGlobals.size());
1137 while (!Load->use_empty())
1138 RewriteHeapSROALoadUser(Load, Load->use_back(),
1139 FieldGlobals, InsertedLoadsForPtr);
1142 /// PerformHeapAllocSRoA - MI is an allocation of an array of structures. Break
1143 /// it up into multiple allocations of arrays of the fields.
1144 static GlobalVariable *PerformHeapAllocSRoA(GlobalVariable *GV, MallocInst *MI){
1145 DOUT << "SROA HEAP ALLOC: " << *GV << " MALLOC = " << *MI;
1146 const StructType *STy = cast<StructType>(MI->getAllocatedType());
1148 // There is guaranteed to be at least one use of the malloc (storing
1149 // it into GV). If there are other uses, change them to be uses of
1150 // the global to simplify later code. This also deletes the store
1152 ReplaceUsesOfMallocWithGlobal(MI, GV);
1154 // Okay, at this point, there are no users of the malloc. Insert N
1155 // new mallocs at the same place as MI, and N globals.
1156 std::vector<GlobalVariable*> FieldGlobals;
1157 std::vector<MallocInst*> FieldMallocs;
1159 for (unsigned FieldNo = 0, e = STy->getNumElements(); FieldNo != e;++FieldNo){
1160 const Type *FieldTy = STy->getElementType(FieldNo);
1161 const Type *PFieldTy = PointerType::getUnqual(FieldTy);
1163 GlobalVariable *NGV =
1164 new GlobalVariable(PFieldTy, false, GlobalValue::InternalLinkage,
1165 Constant::getNullValue(PFieldTy),
1166 GV->getName() + ".f" + utostr(FieldNo), GV,
1167 GV->isThreadLocal());
1168 FieldGlobals.push_back(NGV);
1170 MallocInst *NMI = new MallocInst(FieldTy, MI->getArraySize(),
1171 MI->getName() + ".f" + utostr(FieldNo),MI);
1172 FieldMallocs.push_back(NMI);
1173 new StoreInst(NMI, NGV, MI);
1176 // The tricky aspect of this transformation is handling the case when malloc
1177 // fails. In the original code, malloc failing would set the result pointer
1178 // of malloc to null. In this case, some mallocs could succeed and others
1179 // could fail. As such, we emit code that looks like this:
1180 // F0 = malloc(field0)
1181 // F1 = malloc(field1)
1182 // F2 = malloc(field2)
1183 // if (F0 == 0 || F1 == 0 || F2 == 0) {
1184 // if (F0) { free(F0); F0 = 0; }
1185 // if (F1) { free(F1); F1 = 0; }
1186 // if (F2) { free(F2); F2 = 0; }
1188 Value *RunningOr = 0;
1189 for (unsigned i = 0, e = FieldMallocs.size(); i != e; ++i) {
1190 Value *Cond = new ICmpInst(ICmpInst::ICMP_EQ, FieldMallocs[i],
1191 Constant::getNullValue(FieldMallocs[i]->getType()),
1194 RunningOr = Cond; // First seteq
1196 RunningOr = BinaryOperator::CreateOr(RunningOr, Cond, "tmp", MI);
1199 // Split the basic block at the old malloc.
1200 BasicBlock *OrigBB = MI->getParent();
1201 BasicBlock *ContBB = OrigBB->splitBasicBlock(MI, "malloc_cont");
1203 // Create the block to check the first condition. Put all these blocks at the
1204 // end of the function as they are unlikely to be executed.
1205 BasicBlock *NullPtrBlock = BasicBlock::Create("malloc_ret_null",
1206 OrigBB->getParent());
1208 // Remove the uncond branch from OrigBB to ContBB, turning it into a cond
1209 // branch on RunningOr.
1210 OrigBB->getTerminator()->eraseFromParent();
1211 BranchInst::Create(NullPtrBlock, ContBB, RunningOr, OrigBB);
1213 // Within the NullPtrBlock, we need to emit a comparison and branch for each
1214 // pointer, because some may be null while others are not.
1215 for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) {
1216 Value *GVVal = new LoadInst(FieldGlobals[i], "tmp", NullPtrBlock);
1217 Value *Cmp = new ICmpInst(ICmpInst::ICMP_NE, GVVal,
1218 Constant::getNullValue(GVVal->getType()),
1219 "tmp", NullPtrBlock);
1220 BasicBlock *FreeBlock = BasicBlock::Create("free_it", OrigBB->getParent());
1221 BasicBlock *NextBlock = BasicBlock::Create("next", OrigBB->getParent());
1222 BranchInst::Create(FreeBlock, NextBlock, Cmp, NullPtrBlock);
1224 // Fill in FreeBlock.
1225 new FreeInst(GVVal, FreeBlock);
1226 new StoreInst(Constant::getNullValue(GVVal->getType()), FieldGlobals[i],
1228 BranchInst::Create(NextBlock, FreeBlock);
1230 NullPtrBlock = NextBlock;
1233 BranchInst::Create(ContBB, NullPtrBlock);
1235 // MI is no longer needed, remove it.
1236 MI->eraseFromParent();
1239 // Okay, the malloc site is completely handled. All of the uses of GV are now
1240 // loads, and all uses of those loads are simple. Rewrite them to use loads
1241 // of the per-field globals instead.
1242 while (!GV->use_empty()) {
1243 if (LoadInst *LI = dyn_cast<LoadInst>(GV->use_back())) {
1244 RewriteUsesOfLoadForHeapSRoA(LI, FieldGlobals);
1245 LI->eraseFromParent();
1247 // Must be a store of null.
1248 StoreInst *SI = cast<StoreInst>(GV->use_back());
1249 assert(isa<Constant>(SI->getOperand(0)) &&
1250 cast<Constant>(SI->getOperand(0))->isNullValue() &&
1251 "Unexpected heap-sra user!");
1253 // Insert a store of null into each global.
1254 for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) {
1256 Constant::getNullValue(FieldGlobals[i]->getType()->getElementType());
1257 new StoreInst(Null, FieldGlobals[i], SI);
1259 // Erase the original store.
1260 SI->eraseFromParent();
1264 // The old global is now dead, remove it.
1265 GV->eraseFromParent();
1268 return FieldGlobals[0];
1272 // OptimizeOnceStoredGlobal - Try to optimize globals based on the knowledge
1273 // that only one value (besides its initializer) is ever stored to the global.
1274 static bool OptimizeOnceStoredGlobal(GlobalVariable *GV, Value *StoredOnceVal,
1275 Module::global_iterator &GVI,
1277 if (CastInst *CI = dyn_cast<CastInst>(StoredOnceVal))
1278 StoredOnceVal = CI->getOperand(0);
1279 else if (GetElementPtrInst *GEPI =dyn_cast<GetElementPtrInst>(StoredOnceVal)){
1280 // "getelementptr Ptr, 0, 0, 0" is really just a cast.
1281 bool IsJustACast = true;
1282 for (unsigned i = 1, e = GEPI->getNumOperands(); i != e; ++i)
1283 if (!isa<Constant>(GEPI->getOperand(i)) ||
1284 !cast<Constant>(GEPI->getOperand(i))->isNullValue()) {
1285 IsJustACast = false;
1289 StoredOnceVal = GEPI->getOperand(0);
1292 // If we are dealing with a pointer global that is initialized to null and
1293 // only has one (non-null) value stored into it, then we can optimize any
1294 // users of the loaded value (often calls and loads) that would trap if the
1296 if (isa<PointerType>(GV->getInitializer()->getType()) &&
1297 GV->getInitializer()->isNullValue()) {
1298 if (Constant *SOVC = dyn_cast<Constant>(StoredOnceVal)) {
1299 if (GV->getInitializer()->getType() != SOVC->getType())
1300 SOVC = ConstantExpr::getBitCast(SOVC, GV->getInitializer()->getType());
1302 // Optimize away any trapping uses of the loaded value.
1303 if (OptimizeAwayTrappingUsesOfLoads(GV, SOVC))
1305 } else if (MallocInst *MI = dyn_cast<MallocInst>(StoredOnceVal)) {
1306 // If this is a malloc of an abstract type, don't touch it.
1307 if (!MI->getAllocatedType()->isSized())
1310 // We can't optimize this global unless all uses of it are *known* to be
1311 // of the malloc value, not of the null initializer value (consider a use
1312 // that compares the global's value against zero to see if the malloc has
1313 // been reached). To do this, we check to see if all uses of the global
1314 // would trap if the global were null: this proves that they must all
1315 // happen after the malloc.
1316 if (!AllUsesOfLoadedValueWillTrapIfNull(GV))
1319 // We can't optimize this if the malloc itself is used in a complex way,
1320 // for example, being stored into multiple globals. This allows the
1321 // malloc to be stored into the specified global, loaded setcc'd, and
1322 // GEP'd. These are all things we could transform to using the global
1325 SmallPtrSet<PHINode*, 8> PHIs;
1326 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(MI, GV, PHIs))
1331 // If we have a global that is only initialized with a fixed size malloc,
1332 // transform the program to use global memory instead of malloc'd memory.
1333 // This eliminates dynamic allocation, avoids an indirection accessing the
1334 // data, and exposes the resultant global to further GlobalOpt.
1335 if (ConstantInt *NElements = dyn_cast<ConstantInt>(MI->getArraySize())) {
1336 // Restrict this transformation to only working on small allocations
1337 // (2048 bytes currently), as we don't want to introduce a 16M global or
1339 if (NElements->getZExtValue()*
1340 TD.getABITypeSize(MI->getAllocatedType()) < 2048) {
1341 GVI = OptimizeGlobalAddressOfMalloc(GV, MI);
1346 // If the allocation is an array of structures, consider transforming this
1347 // into multiple malloc'd arrays, one for each field. This is basically
1348 // SRoA for malloc'd memory.
1349 if (const StructType *AllocTy =
1350 dyn_cast<StructType>(MI->getAllocatedType())) {
1351 // This the structure has an unreasonable number of fields, leave it
1353 if (AllocTy->getNumElements() <= 16 && AllocTy->getNumElements() > 0 &&
1354 GlobalLoadUsesSimpleEnoughForHeapSRA(GV, MI)) {
1355 GVI = PerformHeapAllocSRoA(GV, MI);
1365 /// TryToShrinkGlobalToBoolean - At this point, we have learned that the only
1366 /// two values ever stored into GV are its initializer and OtherVal. See if we
1367 /// can shrink the global into a boolean and select between the two values
1368 /// whenever it is used. This exposes the values to other scalar optimizations.
1369 static bool TryToShrinkGlobalToBoolean(GlobalVariable *GV, Constant *OtherVal) {
1370 const Type *GVElType = GV->getType()->getElementType();
1372 // If GVElType is already i1, it is already shrunk. If the type of the GV is
1373 // an FP value or vector, don't do this optimization because a select between
1374 // them is very expensive and unlikely to lead to later simplification.
1375 if (GVElType == Type::Int1Ty || GVElType->isFloatingPoint() ||
1376 isa<VectorType>(GVElType))
1379 // Walk the use list of the global seeing if all the uses are load or store.
1380 // If there is anything else, bail out.
1381 for (Value::use_iterator I = GV->use_begin(), E = GV->use_end(); I != E; ++I)
1382 if (!isa<LoadInst>(I) && !isa<StoreInst>(I))
1385 DOUT << " *** SHRINKING TO BOOL: " << *GV;
1387 // Create the new global, initializing it to false.
1388 GlobalVariable *NewGV = new GlobalVariable(Type::Int1Ty, false,
1389 GlobalValue::InternalLinkage, ConstantInt::getFalse(),
1392 GV->isThreadLocal());
1393 GV->getParent()->getGlobalList().insert(GV, NewGV);
1395 Constant *InitVal = GV->getInitializer();
1396 assert(InitVal->getType() != Type::Int1Ty && "No reason to shrink to bool!");
1398 // If initialized to zero and storing one into the global, we can use a cast
1399 // instead of a select to synthesize the desired value.
1400 bool IsOneZero = false;
1401 if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal))
1402 IsOneZero = InitVal->isNullValue() && CI->isOne();
1404 while (!GV->use_empty()) {
1405 Instruction *UI = cast<Instruction>(GV->use_back());
1406 if (StoreInst *SI = dyn_cast<StoreInst>(UI)) {
1407 // Change the store into a boolean store.
1408 bool StoringOther = SI->getOperand(0) == OtherVal;
1409 // Only do this if we weren't storing a loaded value.
1411 if (StoringOther || SI->getOperand(0) == InitVal)
1412 StoreVal = ConstantInt::get(Type::Int1Ty, StoringOther);
1414 // Otherwise, we are storing a previously loaded copy. To do this,
1415 // change the copy from copying the original value to just copying the
1417 Instruction *StoredVal = cast<Instruction>(SI->getOperand(0));
1419 // If we're already replaced the input, StoredVal will be a cast or
1420 // select instruction. If not, it will be a load of the original
1422 if (LoadInst *LI = dyn_cast<LoadInst>(StoredVal)) {
1423 assert(LI->getOperand(0) == GV && "Not a copy!");
1424 // Insert a new load, to preserve the saved value.
1425 StoreVal = new LoadInst(NewGV, LI->getName()+".b", LI);
1427 assert((isa<CastInst>(StoredVal) || isa<SelectInst>(StoredVal)) &&
1428 "This is not a form that we understand!");
1429 StoreVal = StoredVal->getOperand(0);
1430 assert(isa<LoadInst>(StoreVal) && "Not a load of NewGV!");
1433 new StoreInst(StoreVal, NewGV, SI);
1435 // Change the load into a load of bool then a select.
1436 LoadInst *LI = cast<LoadInst>(UI);
1437 LoadInst *NLI = new LoadInst(NewGV, LI->getName()+".b", LI);
1440 NSI = new ZExtInst(NLI, LI->getType(), "", LI);
1442 NSI = SelectInst::Create(NLI, OtherVal, InitVal, "", LI);
1444 LI->replaceAllUsesWith(NSI);
1446 UI->eraseFromParent();
1449 GV->eraseFromParent();
1454 /// ProcessInternalGlobal - Analyze the specified global variable and optimize
1455 /// it if possible. If we make a change, return true.
1456 bool GlobalOpt::ProcessInternalGlobal(GlobalVariable *GV,
1457 Module::global_iterator &GVI) {
1458 std::set<PHINode*> PHIUsers;
1460 GV->removeDeadConstantUsers();
1462 if (GV->use_empty()) {
1463 DOUT << "GLOBAL DEAD: " << *GV;
1464 GV->eraseFromParent();
1469 if (!AnalyzeGlobal(GV, GS, PHIUsers)) {
1471 cerr << "Global: " << *GV;
1472 cerr << " isLoaded = " << GS.isLoaded << "\n";
1473 cerr << " StoredType = ";
1474 switch (GS.StoredType) {
1475 case GlobalStatus::NotStored: cerr << "NEVER STORED\n"; break;
1476 case GlobalStatus::isInitializerStored: cerr << "INIT STORED\n"; break;
1477 case GlobalStatus::isStoredOnce: cerr << "STORED ONCE\n"; break;
1478 case GlobalStatus::isStored: cerr << "stored\n"; break;
1480 if (GS.StoredType == GlobalStatus::isStoredOnce && GS.StoredOnceValue)
1481 cerr << " StoredOnceValue = " << *GS.StoredOnceValue << "\n";
1482 if (GS.AccessingFunction && !GS.HasMultipleAccessingFunctions)
1483 cerr << " AccessingFunction = " << GS.AccessingFunction->getName()
1485 cerr << " HasMultipleAccessingFunctions = "
1486 << GS.HasMultipleAccessingFunctions << "\n";
1487 cerr << " HasNonInstructionUser = " << GS.HasNonInstructionUser<<"\n";
1491 // If this is a first class global and has only one accessing function
1492 // and this function is main (which we know is not recursive we can make
1493 // this global a local variable) we replace the global with a local alloca
1494 // in this function.
1496 // NOTE: It doesn't make sense to promote non single-value types since we
1497 // are just replacing static memory to stack memory.
1498 if (!GS.HasMultipleAccessingFunctions &&
1499 GS.AccessingFunction && !GS.HasNonInstructionUser &&
1500 GV->getType()->getElementType()->isSingleValueType() &&
1501 GS.AccessingFunction->getName() == "main" &&
1502 GS.AccessingFunction->hasExternalLinkage()) {
1503 DOUT << "LOCALIZING GLOBAL: " << *GV;
1504 Instruction* FirstI = GS.AccessingFunction->getEntryBlock().begin();
1505 const Type* ElemTy = GV->getType()->getElementType();
1506 // FIXME: Pass Global's alignment when globals have alignment
1507 AllocaInst* Alloca = new AllocaInst(ElemTy, NULL, GV->getName(), FirstI);
1508 if (!isa<UndefValue>(GV->getInitializer()))
1509 new StoreInst(GV->getInitializer(), Alloca, FirstI);
1511 GV->replaceAllUsesWith(Alloca);
1512 GV->eraseFromParent();
1517 // If the global is never loaded (but may be stored to), it is dead.
1520 DOUT << "GLOBAL NEVER LOADED: " << *GV;
1522 // Delete any stores we can find to the global. We may not be able to
1523 // make it completely dead though.
1524 bool Changed = CleanupConstantGlobalUsers(GV, GV->getInitializer());
1526 // If the global is dead now, delete it.
1527 if (GV->use_empty()) {
1528 GV->eraseFromParent();
1534 } else if (GS.StoredType <= GlobalStatus::isInitializerStored) {
1535 DOUT << "MARKING CONSTANT: " << *GV;
1536 GV->setConstant(true);
1538 // Clean up any obviously simplifiable users now.
1539 CleanupConstantGlobalUsers(GV, GV->getInitializer());
1541 // If the global is dead now, just nuke it.
1542 if (GV->use_empty()) {
1543 DOUT << " *** Marking constant allowed us to simplify "
1544 << "all users and delete global!\n";
1545 GV->eraseFromParent();
1551 } else if (!GV->getInitializer()->getType()->isSingleValueType()) {
1552 if (GlobalVariable *FirstNewGV = SRAGlobal(GV,
1553 getAnalysis<TargetData>())) {
1554 GVI = FirstNewGV; // Don't skip the newly produced globals!
1557 } else if (GS.StoredType == GlobalStatus::isStoredOnce) {
1558 // If the initial value for the global was an undef value, and if only
1559 // one other value was stored into it, we can just change the
1560 // initializer to be an undef value, then delete all stores to the
1561 // global. This allows us to mark it constant.
1562 if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue))
1563 if (isa<UndefValue>(GV->getInitializer())) {
1564 // Change the initial value here.
1565 GV->setInitializer(SOVConstant);
1567 // Clean up any obviously simplifiable users now.
1568 CleanupConstantGlobalUsers(GV, GV->getInitializer());
1570 if (GV->use_empty()) {
1571 DOUT << " *** Substituting initializer allowed us to "
1572 << "simplify all users and delete global!\n";
1573 GV->eraseFromParent();
1582 // Try to optimize globals based on the knowledge that only one value
1583 // (besides its initializer) is ever stored to the global.
1584 if (OptimizeOnceStoredGlobal(GV, GS.StoredOnceValue, GVI,
1585 getAnalysis<TargetData>()))
1588 // Otherwise, if the global was not a boolean, we can shrink it to be a
1590 if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue))
1591 if (TryToShrinkGlobalToBoolean(GV, SOVConstant)) {
1600 /// OnlyCalledDirectly - Return true if the specified function is only called
1601 /// directly. In other words, its address is never taken.
1602 static bool OnlyCalledDirectly(Function *F) {
1603 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){
1604 Instruction *User = dyn_cast<Instruction>(*UI);
1605 if (!User) return false;
1606 if (!isa<CallInst>(User) && !isa<InvokeInst>(User)) return false;
1608 // See if the function address is passed as an argument.
1609 for (unsigned i = 1, e = User->getNumOperands(); i != e; ++i)
1610 if (User->getOperand(i) == F) return false;
1615 /// ChangeCalleesToFastCall - Walk all of the direct calls of the specified
1616 /// function, changing them to FastCC.
1617 static void ChangeCalleesToFastCall(Function *F) {
1618 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){
1619 CallSite User(cast<Instruction>(*UI));
1620 User.setCallingConv(CallingConv::Fast);
1624 static PAListPtr StripNest(const PAListPtr &Attrs) {
1625 for (unsigned i = 0, e = Attrs.getNumSlots(); i != e; ++i) {
1626 if ((Attrs.getSlot(i).Attrs & ParamAttr::Nest) == 0)
1629 // There can be only one.
1630 return Attrs.removeAttr(Attrs.getSlot(i).Index, ParamAttr::Nest);
1636 static void RemoveNestAttribute(Function *F) {
1637 F->setParamAttrs(StripNest(F->getParamAttrs()));
1638 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){
1639 CallSite User(cast<Instruction>(*UI));
1640 User.setParamAttrs(StripNest(User.getParamAttrs()));
1644 bool GlobalOpt::OptimizeFunctions(Module &M) {
1645 bool Changed = false;
1646 // Optimize functions.
1647 for (Module::iterator FI = M.begin(), E = M.end(); FI != E; ) {
1649 F->removeDeadConstantUsers();
1650 if (F->use_empty() && (F->hasInternalLinkage() ||
1651 F->hasLinkOnceLinkage())) {
1652 M.getFunctionList().erase(F);
1655 } else if (F->hasInternalLinkage()) {
1656 if (F->getCallingConv() == CallingConv::C && !F->isVarArg() &&
1657 OnlyCalledDirectly(F)) {
1658 // If this function has C calling conventions, is not a varargs
1659 // function, and is only called directly, promote it to use the Fast
1660 // calling convention.
1661 F->setCallingConv(CallingConv::Fast);
1662 ChangeCalleesToFastCall(F);
1667 if (F->getParamAttrs().hasAttrSomewhere(ParamAttr::Nest) &&
1668 OnlyCalledDirectly(F)) {
1669 // The function is not used by a trampoline intrinsic, so it is safe
1670 // to remove the 'nest' attribute.
1671 RemoveNestAttribute(F);
1680 bool GlobalOpt::OptimizeGlobalVars(Module &M) {
1681 bool Changed = false;
1682 for (Module::global_iterator GVI = M.global_begin(), E = M.global_end();
1684 GlobalVariable *GV = GVI++;
1685 if (!GV->isConstant() && GV->hasInternalLinkage() &&
1686 GV->hasInitializer())
1687 Changed |= ProcessInternalGlobal(GV, GVI);
1692 /// FindGlobalCtors - Find the llvm.globalctors list, verifying that all
1693 /// initializers have an init priority of 65535.
1694 GlobalVariable *GlobalOpt::FindGlobalCtors(Module &M) {
1695 for (Module::global_iterator I = M.global_begin(), E = M.global_end();
1697 if (I->getName() == "llvm.global_ctors") {
1698 // Found it, verify it's an array of { int, void()* }.
1699 const ArrayType *ATy =dyn_cast<ArrayType>(I->getType()->getElementType());
1701 const StructType *STy = dyn_cast<StructType>(ATy->getElementType());
1702 if (!STy || STy->getNumElements() != 2 ||
1703 STy->getElementType(0) != Type::Int32Ty) return 0;
1704 const PointerType *PFTy = dyn_cast<PointerType>(STy->getElementType(1));
1705 if (!PFTy) return 0;
1706 const FunctionType *FTy = dyn_cast<FunctionType>(PFTy->getElementType());
1707 if (!FTy || FTy->getReturnType() != Type::VoidTy || FTy->isVarArg() ||
1708 FTy->getNumParams() != 0)
1711 // Verify that the initializer is simple enough for us to handle.
1712 if (!I->hasInitializer()) return 0;
1713 ConstantArray *CA = dyn_cast<ConstantArray>(I->getInitializer());
1715 for (unsigned i = 0, e = CA->getNumOperands(); i != e; ++i)
1716 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(CA->getOperand(i))) {
1717 if (isa<ConstantPointerNull>(CS->getOperand(1)))
1720 // Must have a function or null ptr.
1721 if (!isa<Function>(CS->getOperand(1)))
1724 // Init priority must be standard.
1725 ConstantInt *CI = dyn_cast<ConstantInt>(CS->getOperand(0));
1726 if (!CI || CI->getZExtValue() != 65535)
1737 /// ParseGlobalCtors - Given a llvm.global_ctors list that we can understand,
1738 /// return a list of the functions and null terminator as a vector.
1739 static std::vector<Function*> ParseGlobalCtors(GlobalVariable *GV) {
1740 ConstantArray *CA = cast<ConstantArray>(GV->getInitializer());
1741 std::vector<Function*> Result;
1742 Result.reserve(CA->getNumOperands());
1743 for (unsigned i = 0, e = CA->getNumOperands(); i != e; ++i) {
1744 ConstantStruct *CS = cast<ConstantStruct>(CA->getOperand(i));
1745 Result.push_back(dyn_cast<Function>(CS->getOperand(1)));
1750 /// InstallGlobalCtors - Given a specified llvm.global_ctors list, install the
1751 /// specified array, returning the new global to use.
1752 static GlobalVariable *InstallGlobalCtors(GlobalVariable *GCL,
1753 const std::vector<Function*> &Ctors) {
1754 // If we made a change, reassemble the initializer list.
1755 std::vector<Constant*> CSVals;
1756 CSVals.push_back(ConstantInt::get(Type::Int32Ty, 65535));
1757 CSVals.push_back(0);
1759 // Create the new init list.
1760 std::vector<Constant*> CAList;
1761 for (unsigned i = 0, e = Ctors.size(); i != e; ++i) {
1763 CSVals[1] = Ctors[i];
1765 const Type *FTy = FunctionType::get(Type::VoidTy,
1766 std::vector<const Type*>(), false);
1767 const PointerType *PFTy = PointerType::getUnqual(FTy);
1768 CSVals[1] = Constant::getNullValue(PFTy);
1769 CSVals[0] = ConstantInt::get(Type::Int32Ty, 2147483647);
1771 CAList.push_back(ConstantStruct::get(CSVals));
1774 // Create the array initializer.
1775 const Type *StructTy =
1776 cast<ArrayType>(GCL->getType()->getElementType())->getElementType();
1777 Constant *CA = ConstantArray::get(ArrayType::get(StructTy, CAList.size()),
1780 // If we didn't change the number of elements, don't create a new GV.
1781 if (CA->getType() == GCL->getInitializer()->getType()) {
1782 GCL->setInitializer(CA);
1786 // Create the new global and insert it next to the existing list.
1787 GlobalVariable *NGV = new GlobalVariable(CA->getType(), GCL->isConstant(),
1788 GCL->getLinkage(), CA, "",
1790 GCL->isThreadLocal());
1791 GCL->getParent()->getGlobalList().insert(GCL, NGV);
1794 // Nuke the old list, replacing any uses with the new one.
1795 if (!GCL->use_empty()) {
1797 if (V->getType() != GCL->getType())
1798 V = ConstantExpr::getBitCast(V, GCL->getType());
1799 GCL->replaceAllUsesWith(V);
1801 GCL->eraseFromParent();
1810 static Constant *getVal(std::map<Value*, Constant*> &ComputedValues,
1812 if (Constant *CV = dyn_cast<Constant>(V)) return CV;
1813 Constant *R = ComputedValues[V];
1814 assert(R && "Reference to an uncomputed value!");
1818 /// isSimpleEnoughPointerToCommit - Return true if this constant is simple
1819 /// enough for us to understand. In particular, if it is a cast of something,
1820 /// we punt. We basically just support direct accesses to globals and GEP's of
1821 /// globals. This should be kept up to date with CommitValueTo.
1822 static bool isSimpleEnoughPointerToCommit(Constant *C) {
1823 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C)) {
1824 if (!GV->hasExternalLinkage() && !GV->hasInternalLinkage())
1825 return false; // do not allow weak/linkonce/dllimport/dllexport linkage.
1826 return !GV->isDeclaration(); // reject external globals.
1828 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
1829 // Handle a constantexpr gep.
1830 if (CE->getOpcode() == Instruction::GetElementPtr &&
1831 isa<GlobalVariable>(CE->getOperand(0))) {
1832 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
1833 if (!GV->hasExternalLinkage() && !GV->hasInternalLinkage())
1834 return false; // do not allow weak/linkonce/dllimport/dllexport linkage.
1835 return GV->hasInitializer() &&
1836 ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE);
1841 /// EvaluateStoreInto - Evaluate a piece of a constantexpr store into a global
1842 /// initializer. This returns 'Init' modified to reflect 'Val' stored into it.
1843 /// At this point, the GEP operands of Addr [0, OpNo) have been stepped into.
1844 static Constant *EvaluateStoreInto(Constant *Init, Constant *Val,
1845 ConstantExpr *Addr, unsigned OpNo) {
1846 // Base case of the recursion.
1847 if (OpNo == Addr->getNumOperands()) {
1848 assert(Val->getType() == Init->getType() && "Type mismatch!");
1852 if (const StructType *STy = dyn_cast<StructType>(Init->getType())) {
1853 std::vector<Constant*> Elts;
1855 // Break up the constant into its elements.
1856 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(Init)) {
1857 for (unsigned i = 0, e = CS->getNumOperands(); i != e; ++i)
1858 Elts.push_back(CS->getOperand(i));
1859 } else if (isa<ConstantAggregateZero>(Init)) {
1860 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
1861 Elts.push_back(Constant::getNullValue(STy->getElementType(i)));
1862 } else if (isa<UndefValue>(Init)) {
1863 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
1864 Elts.push_back(UndefValue::get(STy->getElementType(i)));
1866 assert(0 && "This code is out of sync with "
1867 " ConstantFoldLoadThroughGEPConstantExpr");
1870 // Replace the element that we are supposed to.
1871 ConstantInt *CU = cast<ConstantInt>(Addr->getOperand(OpNo));
1872 unsigned Idx = CU->getZExtValue();
1873 assert(Idx < STy->getNumElements() && "Struct index out of range!");
1874 Elts[Idx] = EvaluateStoreInto(Elts[Idx], Val, Addr, OpNo+1);
1876 // Return the modified struct.
1877 return ConstantStruct::get(&Elts[0], Elts.size(), STy->isPacked());
1879 ConstantInt *CI = cast<ConstantInt>(Addr->getOperand(OpNo));
1880 const ArrayType *ATy = cast<ArrayType>(Init->getType());
1882 // Break up the array into elements.
1883 std::vector<Constant*> Elts;
1884 if (ConstantArray *CA = dyn_cast<ConstantArray>(Init)) {
1885 for (unsigned i = 0, e = CA->getNumOperands(); i != e; ++i)
1886 Elts.push_back(CA->getOperand(i));
1887 } else if (isa<ConstantAggregateZero>(Init)) {
1888 Constant *Elt = Constant::getNullValue(ATy->getElementType());
1889 Elts.assign(ATy->getNumElements(), Elt);
1890 } else if (isa<UndefValue>(Init)) {
1891 Constant *Elt = UndefValue::get(ATy->getElementType());
1892 Elts.assign(ATy->getNumElements(), Elt);
1894 assert(0 && "This code is out of sync with "
1895 " ConstantFoldLoadThroughGEPConstantExpr");
1898 assert(CI->getZExtValue() < ATy->getNumElements());
1899 Elts[CI->getZExtValue()] =
1900 EvaluateStoreInto(Elts[CI->getZExtValue()], Val, Addr, OpNo+1);
1901 return ConstantArray::get(ATy, Elts);
1905 /// CommitValueTo - We have decided that Addr (which satisfies the predicate
1906 /// isSimpleEnoughPointerToCommit) should get Val as its value. Make it happen.
1907 static void CommitValueTo(Constant *Val, Constant *Addr) {
1908 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Addr)) {
1909 assert(GV->hasInitializer());
1910 GV->setInitializer(Val);
1914 ConstantExpr *CE = cast<ConstantExpr>(Addr);
1915 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
1917 Constant *Init = GV->getInitializer();
1918 Init = EvaluateStoreInto(Init, Val, CE, 2);
1919 GV->setInitializer(Init);
1922 /// ComputeLoadResult - Return the value that would be computed by a load from
1923 /// P after the stores reflected by 'memory' have been performed. If we can't
1924 /// decide, return null.
1925 static Constant *ComputeLoadResult(Constant *P,
1926 const std::map<Constant*, Constant*> &Memory) {
1927 // If this memory location has been recently stored, use the stored value: it
1928 // is the most up-to-date.
1929 std::map<Constant*, Constant*>::const_iterator I = Memory.find(P);
1930 if (I != Memory.end()) return I->second;
1933 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(P)) {
1934 if (GV->hasInitializer())
1935 return GV->getInitializer();
1939 // Handle a constantexpr getelementptr.
1940 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(P))
1941 if (CE->getOpcode() == Instruction::GetElementPtr &&
1942 isa<GlobalVariable>(CE->getOperand(0))) {
1943 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
1944 if (GV->hasInitializer())
1945 return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE);
1948 return 0; // don't know how to evaluate.
1951 /// EvaluateFunction - Evaluate a call to function F, returning true if
1952 /// successful, false if we can't evaluate it. ActualArgs contains the formal
1953 /// arguments for the function.
1954 static bool EvaluateFunction(Function *F, Constant *&RetVal,
1955 const std::vector<Constant*> &ActualArgs,
1956 std::vector<Function*> &CallStack,
1957 std::map<Constant*, Constant*> &MutatedMemory,
1958 std::vector<GlobalVariable*> &AllocaTmps) {
1959 // Check to see if this function is already executing (recursion). If so,
1960 // bail out. TODO: we might want to accept limited recursion.
1961 if (std::find(CallStack.begin(), CallStack.end(), F) != CallStack.end())
1964 CallStack.push_back(F);
1966 /// Values - As we compute SSA register values, we store their contents here.
1967 std::map<Value*, Constant*> Values;
1969 // Initialize arguments to the incoming values specified.
1971 for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end(); AI != E;
1973 Values[AI] = ActualArgs[ArgNo];
1975 /// ExecutedBlocks - We only handle non-looping, non-recursive code. As such,
1976 /// we can only evaluate any one basic block at most once. This set keeps
1977 /// track of what we have executed so we can detect recursive cases etc.
1978 std::set<BasicBlock*> ExecutedBlocks;
1980 // CurInst - The current instruction we're evaluating.
1981 BasicBlock::iterator CurInst = F->begin()->begin();
1983 // This is the main evaluation loop.
1985 Constant *InstResult = 0;
1987 if (StoreInst *SI = dyn_cast<StoreInst>(CurInst)) {
1988 if (SI->isVolatile()) return false; // no volatile accesses.
1989 Constant *Ptr = getVal(Values, SI->getOperand(1));
1990 if (!isSimpleEnoughPointerToCommit(Ptr))
1991 // If this is too complex for us to commit, reject it.
1993 Constant *Val = getVal(Values, SI->getOperand(0));
1994 MutatedMemory[Ptr] = Val;
1995 } else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(CurInst)) {
1996 InstResult = ConstantExpr::get(BO->getOpcode(),
1997 getVal(Values, BO->getOperand(0)),
1998 getVal(Values, BO->getOperand(1)));
1999 } else if (CmpInst *CI = dyn_cast<CmpInst>(CurInst)) {
2000 InstResult = ConstantExpr::getCompare(CI->getPredicate(),
2001 getVal(Values, CI->getOperand(0)),
2002 getVal(Values, CI->getOperand(1)));
2003 } else if (CastInst *CI = dyn_cast<CastInst>(CurInst)) {
2004 InstResult = ConstantExpr::getCast(CI->getOpcode(),
2005 getVal(Values, CI->getOperand(0)),
2007 } else if (SelectInst *SI = dyn_cast<SelectInst>(CurInst)) {
2008 InstResult = ConstantExpr::getSelect(getVal(Values, SI->getOperand(0)),
2009 getVal(Values, SI->getOperand(1)),
2010 getVal(Values, SI->getOperand(2)));
2011 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(CurInst)) {
2012 Constant *P = getVal(Values, GEP->getOperand(0));
2013 SmallVector<Constant*, 8> GEPOps;
2014 for (unsigned i = 1, e = GEP->getNumOperands(); i != e; ++i)
2015 GEPOps.push_back(getVal(Values, GEP->getOperand(i)));
2016 InstResult = ConstantExpr::getGetElementPtr(P, &GEPOps[0], GEPOps.size());
2017 } else if (LoadInst *LI = dyn_cast<LoadInst>(CurInst)) {
2018 if (LI->isVolatile()) return false; // no volatile accesses.
2019 InstResult = ComputeLoadResult(getVal(Values, LI->getOperand(0)),
2021 if (InstResult == 0) return false; // Could not evaluate load.
2022 } else if (AllocaInst *AI = dyn_cast<AllocaInst>(CurInst)) {
2023 if (AI->isArrayAllocation()) return false; // Cannot handle array allocs.
2024 const Type *Ty = AI->getType()->getElementType();
2025 AllocaTmps.push_back(new GlobalVariable(Ty, false,
2026 GlobalValue::InternalLinkage,
2027 UndefValue::get(Ty),
2029 InstResult = AllocaTmps.back();
2030 } else if (CallInst *CI = dyn_cast<CallInst>(CurInst)) {
2031 // Cannot handle inline asm.
2032 if (isa<InlineAsm>(CI->getOperand(0))) return false;
2034 // Resolve function pointers.
2035 Function *Callee = dyn_cast<Function>(getVal(Values, CI->getOperand(0)));
2036 if (!Callee) return false; // Cannot resolve.
2038 std::vector<Constant*> Formals;
2039 for (unsigned i = 1, e = CI->getNumOperands(); i != e; ++i)
2040 Formals.push_back(getVal(Values, CI->getOperand(i)));
2042 if (Callee->isDeclaration()) {
2043 // If this is a function we can constant fold, do it.
2044 if (Constant *C = ConstantFoldCall(Callee, &Formals[0],
2051 if (Callee->getFunctionType()->isVarArg())
2056 // Execute the call, if successful, use the return value.
2057 if (!EvaluateFunction(Callee, RetVal, Formals, CallStack,
2058 MutatedMemory, AllocaTmps))
2060 InstResult = RetVal;
2062 } else if (isa<TerminatorInst>(CurInst)) {
2063 BasicBlock *NewBB = 0;
2064 if (BranchInst *BI = dyn_cast<BranchInst>(CurInst)) {
2065 if (BI->isUnconditional()) {
2066 NewBB = BI->getSuccessor(0);
2069 dyn_cast<ConstantInt>(getVal(Values, BI->getCondition()));
2070 if (!Cond) return false; // Cannot determine.
2072 NewBB = BI->getSuccessor(!Cond->getZExtValue());
2074 } else if (SwitchInst *SI = dyn_cast<SwitchInst>(CurInst)) {
2076 dyn_cast<ConstantInt>(getVal(Values, SI->getCondition()));
2077 if (!Val) return false; // Cannot determine.
2078 NewBB = SI->getSuccessor(SI->findCaseValue(Val));
2079 } else if (ReturnInst *RI = dyn_cast<ReturnInst>(CurInst)) {
2080 if (RI->getNumOperands())
2081 RetVal = getVal(Values, RI->getOperand(0));
2083 CallStack.pop_back(); // return from fn.
2084 return true; // We succeeded at evaluating this ctor!
2086 // invoke, unwind, unreachable.
2087 return false; // Cannot handle this terminator.
2090 // Okay, we succeeded in evaluating this control flow. See if we have
2091 // executed the new block before. If so, we have a looping function,
2092 // which we cannot evaluate in reasonable time.
2093 if (!ExecutedBlocks.insert(NewBB).second)
2094 return false; // looped!
2096 // Okay, we have never been in this block before. Check to see if there
2097 // are any PHI nodes. If so, evaluate them with information about where
2099 BasicBlock *OldBB = CurInst->getParent();
2100 CurInst = NewBB->begin();
2102 for (; (PN = dyn_cast<PHINode>(CurInst)); ++CurInst)
2103 Values[PN] = getVal(Values, PN->getIncomingValueForBlock(OldBB));
2105 // Do NOT increment CurInst. We know that the terminator had no value.
2108 // Did not know how to evaluate this!
2112 if (!CurInst->use_empty())
2113 Values[CurInst] = InstResult;
2115 // Advance program counter.
2120 /// EvaluateStaticConstructor - Evaluate static constructors in the function, if
2121 /// we can. Return true if we can, false otherwise.
2122 static bool EvaluateStaticConstructor(Function *F) {
2123 /// MutatedMemory - For each store we execute, we update this map. Loads
2124 /// check this to get the most up-to-date value. If evaluation is successful,
2125 /// this state is committed to the process.
2126 std::map<Constant*, Constant*> MutatedMemory;
2128 /// AllocaTmps - To 'execute' an alloca, we create a temporary global variable
2129 /// to represent its body. This vector is needed so we can delete the
2130 /// temporary globals when we are done.
2131 std::vector<GlobalVariable*> AllocaTmps;
2133 /// CallStack - This is used to detect recursion. In pathological situations
2134 /// we could hit exponential behavior, but at least there is nothing
2136 std::vector<Function*> CallStack;
2138 // Call the function.
2139 Constant *RetValDummy;
2140 bool EvalSuccess = EvaluateFunction(F, RetValDummy, std::vector<Constant*>(),
2141 CallStack, MutatedMemory, AllocaTmps);
2143 // We succeeded at evaluation: commit the result.
2144 DOUT << "FULLY EVALUATED GLOBAL CTOR FUNCTION '"
2145 << F->getName() << "' to " << MutatedMemory.size()
2147 for (std::map<Constant*, Constant*>::iterator I = MutatedMemory.begin(),
2148 E = MutatedMemory.end(); I != E; ++I)
2149 CommitValueTo(I->second, I->first);
2152 // At this point, we are done interpreting. If we created any 'alloca'
2153 // temporaries, release them now.
2154 while (!AllocaTmps.empty()) {
2155 GlobalVariable *Tmp = AllocaTmps.back();
2156 AllocaTmps.pop_back();
2158 // If there are still users of the alloca, the program is doing something
2159 // silly, e.g. storing the address of the alloca somewhere and using it
2160 // later. Since this is undefined, we'll just make it be null.
2161 if (!Tmp->use_empty())
2162 Tmp->replaceAllUsesWith(Constant::getNullValue(Tmp->getType()));
2171 /// OptimizeGlobalCtorsList - Simplify and evaluation global ctors if possible.
2172 /// Return true if anything changed.
2173 bool GlobalOpt::OptimizeGlobalCtorsList(GlobalVariable *&GCL) {
2174 std::vector<Function*> Ctors = ParseGlobalCtors(GCL);
2175 bool MadeChange = false;
2176 if (Ctors.empty()) return false;
2178 // Loop over global ctors, optimizing them when we can.
2179 for (unsigned i = 0; i != Ctors.size(); ++i) {
2180 Function *F = Ctors[i];
2181 // Found a null terminator in the middle of the list, prune off the rest of
2184 if (i != Ctors.size()-1) {
2191 // We cannot simplify external ctor functions.
2192 if (F->empty()) continue;
2194 // If we can evaluate the ctor at compile time, do.
2195 if (EvaluateStaticConstructor(F)) {
2196 Ctors.erase(Ctors.begin()+i);
2199 ++NumCtorsEvaluated;
2204 if (!MadeChange) return false;
2206 GCL = InstallGlobalCtors(GCL, Ctors);
2211 bool GlobalOpt::runOnModule(Module &M) {
2212 bool Changed = false;
2214 // Try to find the llvm.globalctors list.
2215 GlobalVariable *GlobalCtors = FindGlobalCtors(M);
2217 bool LocalChange = true;
2218 while (LocalChange) {
2219 LocalChange = false;
2221 // Delete functions that are trivially dead, ccc -> fastcc
2222 LocalChange |= OptimizeFunctions(M);
2224 // Optimize global_ctors list.
2226 LocalChange |= OptimizeGlobalCtorsList(GlobalCtors);
2228 // Optimize non-address-taken globals.
2229 LocalChange |= OptimizeGlobalVars(M);
2230 Changed |= LocalChange;
2233 // TODO: Move all global ctors functions to the end of the module for code