1//===- GlobalOpt.cpp - Optimize Global Variables --------------------------===//
2//
3// The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
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.
13//
14//===----------------------------------------------------------------------===//
15
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/DenseMap.h"
33#include "llvm/ADT/SmallPtrSet.h"
34#include "llvm/ADT/SmallVector.h"
35#include "llvm/ADT/Statistic.h"
36#include "llvm/ADT/StringExtras.h"
37#include "llvm/ADT/STLExtras.h"
38#include <algorithm>
39using namespace llvm;
40
41STATISTIC(NumMarked , "Number of globals marked constant");
42STATISTIC(NumSRA , "Number of aggregate globals broken into scalars");
43STATISTIC(NumHeapSRA , "Number of heap objects SRA'd");
44STATISTIC(NumSubstitute,"Number of globals with initializers stored into them");
45STATISTIC(NumDeleted , "Number of globals deleted");
46STATISTIC(NumFnDeleted , "Number of functions deleted");
47STATISTIC(NumGlobUses , "Number of global uses devirtualized");
48STATISTIC(NumLocalized , "Number of globals localized");
49STATISTIC(NumShrunkToBool , "Number of global vars shrunk to booleans");
50STATISTIC(NumFastCallFns , "Number of functions converted to fastcc");
51STATISTIC(NumCtorsEvaluated, "Number of static ctors evaluated");
52STATISTIC(NumNestRemoved , "Number of nest attributes removed");
53STATISTIC(NumAliasesResolved, "Number of global aliases resolved");
54STATISTIC(NumAliasesRemoved, "Number of global aliases eliminated");
55
56namespace {
57 struct VISIBILITY_HIDDEN GlobalOpt : public ModulePass {
58 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
59 AU.addRequired<TargetData>();
60 }
61 static char ID; // Pass identification, replacement for typeid
62 GlobalOpt() : ModulePass(&ID) {}
63
64 bool runOnModule(Module &M);
65
66 private:
67 GlobalVariable *FindGlobalCtors(Module &M);
68 bool OptimizeFunctions(Module &M);
69 bool OptimizeGlobalVars(Module &M);
70 bool OptimizeGlobalAliases(Module &M);
71 bool OptimizeGlobalCtorsList(GlobalVariable *&GCL);
72 bool ProcessInternalGlobal(GlobalVariable *GV,Module::global_iterator &GVI);
73 };
74}
75
76char GlobalOpt::ID = 0;
77static RegisterPass<GlobalOpt> X("globalopt", "Global Variable Optimizer");
78
79ModulePass *llvm::createGlobalOptimizerPass() { return new GlobalOpt(); }
80
81namespace {
82
83/// GlobalStatus - As we analyze each global, keep track of some information
84/// about it. If we find out that the address of the global is taken, none of
85/// this info will be accurate.
86struct VISIBILITY_HIDDEN GlobalStatus {
87 /// isLoaded - True if the global is ever loaded. If the global isn't ever
88 /// loaded it can be deleted.
89 bool isLoaded;
90
91 /// StoredType - Keep track of what stores to the global look like.
92 ///
93 enum StoredType {
94 /// NotStored - There is no store to this global. It can thus be marked
95 /// constant.
96 NotStored,
97
98 /// isInitializerStored - This global is stored to, but the only thing
99 /// stored is the constant it was initialized with. This is only tracked
100 /// for scalar globals.
101 isInitializerStored,
102
103 /// isStoredOnce - This global is stored to, but only its initializer and
104 /// one other value is ever stored to it. If this global isStoredOnce, we
105 /// track the value stored to it in StoredOnceValue below. This is only
106 /// tracked for scalar globals.
107 isStoredOnce,
108
109 /// isStored - This global is stored to by multiple values or something else
110 /// that we cannot track.
111 isStored
112 } StoredType;
113
114 /// StoredOnceValue - If only one value (besides the initializer constant) is
115 /// ever stored to this global, keep track of what value it is.
116 Value *StoredOnceValue;
117
118 /// AccessingFunction/HasMultipleAccessingFunctions - These start out
119 /// null/false. When the first accessing function is noticed, it is recorded.
120 /// When a second different accessing function is noticed,
121 /// HasMultipleAccessingFunctions is set to true.
122 Function *AccessingFunction;
123 bool HasMultipleAccessingFunctions;
124
125 /// HasNonInstructionUser - Set to true if this global has a user that is not
126 /// an instruction (e.g. a constant expr or GV initializer).
127 bool HasNonInstructionUser;
128
129 /// HasPHIUser - Set to true if this global has a user that is a PHI node.
130 bool HasPHIUser;
131
132 GlobalStatus() : isLoaded(false), StoredType(NotStored), StoredOnceValue(0),
133 AccessingFunction(0), HasMultipleAccessingFunctions(false),
134 HasNonInstructionUser(false), HasPHIUser(false) {}
135};
136
137}
138
139/// ConstantIsDead - Return true if the specified constant is (transitively)
140/// dead. The constant may be used by other constants (e.g. constant arrays and
141/// constant exprs) as long as they are dead, but it cannot be used by anything
142/// else.
143static bool ConstantIsDead(Constant *C) {
144 if (isa<GlobalValue>(C)) return false;
145
146 for (Value::use_iterator UI = C->use_begin(), E = C->use_end(); UI != E; ++UI)
147 if (Constant *CU = dyn_cast<Constant>(*UI)) {
148 if (!ConstantIsDead(CU)) return false;
149 } else
150 return false;
151 return true;
152}
153
154
155/// AnalyzeGlobal - Look at all uses of the global and fill in the GlobalStatus
156/// structure. If the global has its address taken, return true to indicate we
157/// can't do anything with it.
158///
159static bool AnalyzeGlobal(Value *V, GlobalStatus &GS,
160 SmallPtrSet<PHINode*, 16> &PHIUsers) {
161 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ++UI)
162 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(*UI)) {
163 GS.HasNonInstructionUser = true;
164
165 if (AnalyzeGlobal(CE, GS, PHIUsers)) return true;
166
167 } else if (Instruction *I = dyn_cast<Instruction>(*UI)) {
168 if (!GS.HasMultipleAccessingFunctions) {
169 Function *F = I->getParent()->getParent();
170 if (GS.AccessingFunction == 0)
171 GS.AccessingFunction = F;
172 else if (GS.AccessingFunction != F)
173 GS.HasMultipleAccessingFunctions = true;
174 }
175 if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
176 GS.isLoaded = true;
177 if (LI->isVolatile()) return true; // Don't hack on volatile loads.
178 } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
179 // Don't allow a store OF the address, only stores TO the address.
180 if (SI->getOperand(0) == V) return true;
181
182 if (SI->isVolatile()) return true; // Don't hack on volatile stores.
183
184 // If this is a direct store to the global (i.e., the global is a scalar
185 // value, not an aggregate), keep more specific information about
186 // stores.
187 if (GS.StoredType != GlobalStatus::isStored) {
188 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(SI->getOperand(1))){
189 Value *StoredVal = SI->getOperand(0);
190 if (StoredVal == GV->getInitializer()) {
191 if (GS.StoredType < GlobalStatus::isInitializerStored)
192 GS.StoredType = GlobalStatus::isInitializerStored;
193 } else if (isa<LoadInst>(StoredVal) &&
194 cast<LoadInst>(StoredVal)->getOperand(0) == GV) {
195 // G = G
196 if (GS.StoredType < GlobalStatus::isInitializerStored)
197 GS.StoredType = GlobalStatus::isInitializerStored;
198 } else if (GS.StoredType < GlobalStatus::isStoredOnce) {
199 GS.StoredType = GlobalStatus::isStoredOnce;
200 GS.StoredOnceValue = StoredVal;
201 } else if (GS.StoredType == GlobalStatus::isStoredOnce &&
202 GS.StoredOnceValue == StoredVal) {
203 // noop.
204 } else {
205 GS.StoredType = GlobalStatus::isStored;
206 }
207 } else {
208 GS.StoredType = GlobalStatus::isStored;
209 }
210 }
211 } else if (isa<GetElementPtrInst>(I)) {
212 if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
213 } else if (isa<SelectInst>(I)) {
214 if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
215 } else if (PHINode *PN = dyn_cast<PHINode>(I)) {
216 // PHI nodes we can check just like select or GEP instructions, but we
217 // have to be careful about infinite recursion.
218 if (PHIUsers.insert(PN)) // Not already visited.
219 if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
220 GS.HasPHIUser = true;
221 } else if (isa<CmpInst>(I)) {
222 } else if (isa<MemTransferInst>(I)) {
223 if (I->getOperand(1) == V)
224 GS.StoredType = GlobalStatus::isStored;
225 if (I->getOperand(2) == V)
226 GS.isLoaded = true;
227 } else if (isa<MemSetInst>(I)) {
228 assert(I->getOperand(1) == V && "Memset only takes one pointer!");
229 GS.StoredType = GlobalStatus::isStored;
230 } else {
231 return true; // Any other non-load instruction might take address!
232 }
233 } else if (Constant *C = dyn_cast<Constant>(*UI)) {
234 GS.HasNonInstructionUser = true;
235 // We might have a dead and dangling constant hanging off of here.
236 if (!ConstantIsDead(C))
237 return true;
238 } else {
239 GS.HasNonInstructionUser = true;
240 // Otherwise must be some other user.
241 return true;
242 }
243
244 return false;
245}
246
247static Constant *getAggregateConstantElement(Constant *Agg, Constant *Idx) {
248 ConstantInt *CI = dyn_cast<ConstantInt>(Idx);
249 if (!CI) return 0;
250 unsigned IdxV = CI->getZExtValue();
251
252 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(Agg)) {
253 if (IdxV < CS->getNumOperands()) return CS->getOperand(IdxV);
254 } else if (ConstantArray *CA = dyn_cast<ConstantArray>(Agg)) {
255 if (IdxV < CA->getNumOperands()) return CA->getOperand(IdxV);
256 } else if (ConstantVector *CP = dyn_cast<ConstantVector>(Agg)) {
257 if (IdxV < CP->getNumOperands()) return CP->getOperand(IdxV);
258 } else if (isa<ConstantAggregateZero>(Agg)) {
259 if (const StructType *STy = dyn_cast<StructType>(Agg->getType())) {
260 if (IdxV < STy->getNumElements())
261 return Constant::getNullValue(STy->getElementType(IdxV));
262 } else if (const SequentialType *STy =
263 dyn_cast<SequentialType>(Agg->getType())) {
264 return Constant::getNullValue(STy->getElementType());
265 }
266 } else if (isa<UndefValue>(Agg)) {
267 if (const StructType *STy = dyn_cast<StructType>(Agg->getType())) {
268 if (IdxV < STy->getNumElements())
269 return UndefValue::get(STy->getElementType(IdxV));
270 } else if (const SequentialType *STy =
271 dyn_cast<SequentialType>(Agg->getType())) {
272 return UndefValue::get(STy->getElementType());
273 }
274 }
275 return 0;
276}
277
278
279/// CleanupConstantGlobalUsers - We just marked GV constant. Loop over all
280/// users of the global, cleaning up the obvious ones. This is largely just a
281/// quick scan over the use list to clean up the easy and obvious cruft. This
282/// returns true if it made a change.
283static bool CleanupConstantGlobalUsers(Value *V, Constant *Init) {
284 bool Changed = false;
285 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;) {
286 User *U = *UI++;
287
288 if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
289 if (Init) {
290 // Replace the load with the initializer.
291 LI->replaceAllUsesWith(Init);
292 LI->eraseFromParent();
293 Changed = true;
294 }
295 } else if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
296 // Store must be unreachable or storing Init into the global.
297 SI->eraseFromParent();
298 Changed = true;
299 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U)) {
300 if (CE->getOpcode() == Instruction::GetElementPtr) {
301 Constant *SubInit = 0;
302 if (Init)
303 SubInit = ConstantFoldLoadThroughGEPConstantExpr(Init, CE);
304 Changed |= CleanupConstantGlobalUsers(CE, SubInit);
305 } else if (CE->getOpcode() == Instruction::BitCast &&
306 isa<PointerType>(CE->getType())) {
307 // Pointer cast, delete any stores and memsets to the global.
308 Changed |= CleanupConstantGlobalUsers(CE, 0);
309 }
310
311 if (CE->use_empty()) {
312 CE->destroyConstant();
313 Changed = true;
314 }
315 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) {
316 // Do not transform "gepinst (gep constexpr (GV))" here, because forming
317 // "gepconstexpr (gep constexpr (GV))" will cause the two gep's to fold
318 // and will invalidate our notion of what Init is.
319 Constant *SubInit = 0;
320 if (!isa<ConstantExpr>(GEP->getOperand(0))) {
321 ConstantExpr *CE =
322 dyn_cast_or_null<ConstantExpr>(ConstantFoldInstruction(GEP));
323 if (Init && CE && CE->getOpcode() == Instruction::GetElementPtr)
324 SubInit = ConstantFoldLoadThroughGEPConstantExpr(Init, CE);
325 }
326 Changed |= CleanupConstantGlobalUsers(GEP, SubInit);
327
328 if (GEP->use_empty()) {
329 GEP->eraseFromParent();
330 Changed = true;
331 }
332 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(U)) { // memset/cpy/mv
333 if (MI->getRawDest() == V) {
334 MI->eraseFromParent();
335 Changed = true;
336 }
337
338 } else if (Constant *C = dyn_cast<Constant>(U)) {
339 // If we have a chain of dead constantexprs or other things dangling from
340 // us, and if they are all dead, nuke them without remorse.
341 if (ConstantIsDead(C)) {
342 C->destroyConstant();
343 // This could have invalidated UI, start over from scratch.
344 CleanupConstantGlobalUsers(V, Init);
345 return true;
346 }
347 }
348 }
349 return Changed;
350}
351
352/// isSafeSROAElementUse - Return true if the specified instruction is a safe
353/// user of a derived expression from a global that we want to SROA.
354static bool isSafeSROAElementUse(Value *V) {
355 // We might have a dead and dangling constant hanging off of here.
356 if (Constant *C = dyn_cast<Constant>(V))
357 return ConstantIsDead(C);
358
359 Instruction *I = dyn_cast<Instruction>(V);
360 if (!I) return false;
361
362 // Loads are ok.
363 if (isa<LoadInst>(I)) return true;
364
365 // Stores *to* the pointer are ok.
366 if (StoreInst *SI = dyn_cast<StoreInst>(I))
367 return SI->getOperand(0) != V;
368
369 // Otherwise, it must be a GEP.
370 GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I);
371 if (GEPI == 0) return false;
372
373 if (GEPI->getNumOperands() < 3 || !isa<Constant>(GEPI->getOperand(1)) ||
374 !cast<Constant>(GEPI->getOperand(1))->isNullValue())
375 return false;
376
377 for (Value::use_iterator I = GEPI->use_begin(), E = GEPI->use_end();
378 I != E; ++I)
379 if (!isSafeSROAElementUse(*I))
380 return false;
381 return true;
382}
383
384
385/// IsUserOfGlobalSafeForSRA - U is a direct user of the specified global value.
386/// Look at it and its uses and decide whether it is safe to SROA this global.
387///
388static bool IsUserOfGlobalSafeForSRA(User *U, GlobalValue *GV) {
389 // The user of the global must be a GEP Inst or a ConstantExpr GEP.
390 if (!isa<GetElementPtrInst>(U) &&
391 (!isa<ConstantExpr>(U) ||
392 cast<ConstantExpr>(U)->getOpcode() != Instruction::GetElementPtr))
393 return false;
394
395 // Check to see if this ConstantExpr GEP is SRA'able. In particular, we
396 // don't like < 3 operand CE's, and we don't like non-constant integer
397 // indices. This enforces that all uses are 'gep GV, 0, C, ...' for some
398 // value of C.
399 if (U->getNumOperands() < 3 || !isa<Constant>(U->getOperand(1)) ||
400 !cast<Constant>(U->getOperand(1))->isNullValue() ||
401 !isa<ConstantInt>(U->getOperand(2)))
402 return false;
403
404 gep_type_iterator GEPI = gep_type_begin(U), E = gep_type_end(U);
405 ++GEPI; // Skip over the pointer index.
406
407 // If this is a use of an array allocation, do a bit more checking for sanity.
408 if (const ArrayType *AT = dyn_cast<ArrayType>(*GEPI)) {
409 uint64_t NumElements = AT->getNumElements();
410 ConstantInt *Idx = cast<ConstantInt>(U->getOperand(2));
411
412 // Check to make sure that index falls within the array. If not,
413 // something funny is going on, so we won't do the optimization.
414 //
415 if (Idx->getZExtValue() >= NumElements)
416 return false;
417
418 // We cannot scalar repl this level of the array unless any array
419 // sub-indices are in-range constants. In particular, consider:
420 // A[0][i]. We cannot know that the user isn't doing invalid things like
421 // allowing i to index an out-of-range subscript that accesses A[1].
422 //
423 // Scalar replacing *just* the outer index of the array is probably not
424 // going to be a win anyway, so just give up.
425 for (++GEPI; // Skip array index.
426 GEPI != E && (isa<ArrayType>(*GEPI) || isa<VectorType>(*GEPI));
427 ++GEPI) {
428 uint64_t NumElements;
429 if (const ArrayType *SubArrayTy = dyn_cast<ArrayType>(*GEPI))
430 NumElements = SubArrayTy->getNumElements();
431 else
432 NumElements = cast<VectorType>(*GEPI)->getNumElements();
433
434 ConstantInt *IdxVal = dyn_cast<ConstantInt>(GEPI.getOperand());
435 if (!IdxVal || IdxVal->getZExtValue() >= NumElements)
436 return false;
437 }
438 }
439
440 for (Value::use_iterator I = U->use_begin(), E = U->use_end(); I != E; ++I)
441 if (!isSafeSROAElementUse(*I))
442 return false;
443 return true;
444}
445
446/// GlobalUsersSafeToSRA - Look at all uses of the global and decide whether it
447/// is safe for us to perform this transformation.
448///
449static bool GlobalUsersSafeToSRA(GlobalValue *GV) {
450 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end();
451 UI != E; ++UI) {
452 if (!IsUserOfGlobalSafeForSRA(*UI, GV))
453 return false;
454 }
455 return true;
456}
457
458
459/// SRAGlobal - Perform scalar replacement of aggregates on the specified global
460/// variable. This opens the door for other optimizations by exposing the
461/// behavior of the program in a more fine-grained way. We have determined that
462/// this transformation is safe already. We return the first global variable we
463/// insert so that the caller can reprocess it.
464static GlobalVariable *SRAGlobal(GlobalVariable *GV, const TargetData &TD) {
465 // Make sure this global only has simple uses that we can SRA.
466 if (!GlobalUsersSafeToSRA(GV))
467 return 0;
468
469 assert(GV->hasLocalLinkage() && !GV->isConstant());
470 Constant *Init = GV->getInitializer();
471 const Type *Ty = Init->getType();
472
473 std::vector<GlobalVariable*> NewGlobals;
474 Module::GlobalListType &Globals = GV->getParent()->getGlobalList();
475
476 // Get the alignment of the global, either explicit or target-specific.
477 unsigned StartAlignment = GV->getAlignment();
478 if (StartAlignment == 0)
479 StartAlignment = TD.getABITypeAlignment(GV->getType());
480
481 if (const StructType *STy = dyn_cast<StructType>(Ty)) {
482 NewGlobals.reserve(STy->getNumElements());
483 const StructLayout &Layout = *TD.getStructLayout(STy);
484 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
485 Constant *In = getAggregateConstantElement(Init,
486 ConstantInt::get(Type::Int32Ty, i));
487 assert(In && "Couldn't get element of initializer?");
488 GlobalVariable *NGV = new GlobalVariable(STy->getElementType(i), false,
489 GlobalVariable::InternalLinkage,
490 In, GV->getName()+"."+utostr(i),
491 (Module *)NULL,
492 GV->isThreadLocal(),
493 GV->getType()->getAddressSpace());
494 Globals.insert(GV, NGV);
495 NewGlobals.push_back(NGV);
496
497 // Calculate the known alignment of the field. If the original aggregate
498 // had 256 byte alignment for example, something might depend on that:
499 // propagate info to each field.
500 uint64_t FieldOffset = Layout.getElementOffset(i);
501 unsigned NewAlign = (unsigned)MinAlign(StartAlignment, FieldOffset);
502 if (NewAlign > TD.getABITypeAlignment(STy->getElementType(i)))
503 NGV->setAlignment(NewAlign);
504 }
505 } else if (const SequentialType *STy = dyn_cast<SequentialType>(Ty)) {
506 unsigned NumElements = 0;
507 if (const ArrayType *ATy = dyn_cast<ArrayType>(STy))
508 NumElements = ATy->getNumElements();
509 else
510 NumElements = cast<VectorType>(STy)->getNumElements();
511
512 if (NumElements > 16 && GV->hasNUsesOrMore(16))
513 return 0; // It's not worth it.
514 NewGlobals.reserve(NumElements);
515
516 uint64_t EltSize = TD.getTypeAllocSize(STy->getElementType());
517 unsigned EltAlign = TD.getABITypeAlignment(STy->getElementType());
518 for (unsigned i = 0, e = NumElements; i != e; ++i) {
519 Constant *In = getAggregateConstantElement(Init,
520 ConstantInt::get(Type::Int32Ty, i));
521 assert(In && "Couldn't get element of initializer?");
522
523 GlobalVariable *NGV = new GlobalVariable(STy->getElementType(), false,
524 GlobalVariable::InternalLinkage,
525 In, GV->getName()+"."+utostr(i),
526 (Module *)NULL,
527 GV->isThreadLocal(),
528 GV->getType()->getAddressSpace());
529 Globals.insert(GV, NGV);
530 NewGlobals.push_back(NGV);
531
532 // Calculate the known alignment of the field. If the original aggregate
533 // had 256 byte alignment for example, something might depend on that:
534 // propagate info to each field.
535 unsigned NewAlign = (unsigned)MinAlign(StartAlignment, EltSize*i);
536 if (NewAlign > EltAlign)
537 NGV->setAlignment(NewAlign);
538 }
539 }
540
541 if (NewGlobals.empty())
542 return 0;
543
544 DOUT << "PERFORMING GLOBAL SRA ON: " << *GV;
545
546 Constant *NullInt = Constant::getNullValue(Type::Int32Ty);
547
548 // Loop over all of the uses of the global, replacing the constantexpr geps,
549 // with smaller constantexpr geps or direct references.
550 while (!GV->use_empty()) {
551 User *GEP = GV->use_back();
552 assert(((isa<ConstantExpr>(GEP) &&
553 cast<ConstantExpr>(GEP)->getOpcode()==Instruction::GetElementPtr)||
554 isa<GetElementPtrInst>(GEP)) && "NonGEP CE's are not SRAable!");
555
556 // Ignore the 1th operand, which has to be zero or else the program is quite
557 // broken (undefined). Get the 2nd operand, which is the structure or array
558 // index.
559 unsigned Val = cast<ConstantInt>(GEP->getOperand(2))->getZExtValue();
560 if (Val >= NewGlobals.size()) Val = 0; // Out of bound array access.
561
562 Value *NewPtr = NewGlobals[Val];
563
564 // Form a shorter GEP if needed.
565 if (GEP->getNumOperands() > 3) {
566 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GEP)) {
567 SmallVector<Constant*, 8> Idxs;
568 Idxs.push_back(NullInt);
569 for (unsigned i = 3, e = CE->getNumOperands(); i != e; ++i)
570 Idxs.push_back(CE->getOperand(i));
571 NewPtr = ConstantExpr::getGetElementPtr(cast<Constant>(NewPtr),
572 &Idxs[0], Idxs.size());
573 } else {
574 GetElementPtrInst *GEPI = cast<GetElementPtrInst>(GEP);
575 SmallVector<Value*, 8> Idxs;
576 Idxs.push_back(NullInt);
577 for (unsigned i = 3, e = GEPI->getNumOperands(); i != e; ++i)
578 Idxs.push_back(GEPI->getOperand(i));
579 NewPtr = GetElementPtrInst::Create(NewPtr, Idxs.begin(), Idxs.end(),
580 GEPI->getName()+"."+utostr(Val), GEPI);
581 }
582 }
583 GEP->replaceAllUsesWith(NewPtr);
584
585 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(GEP))
586 GEPI->eraseFromParent();
587 else
588 cast<ConstantExpr>(GEP)->destroyConstant();
589 }
590
591 // Delete the old global, now that it is dead.
592 Globals.erase(GV);
593 ++NumSRA;
594
595 // Loop over the new globals array deleting any globals that are obviously
596 // dead. This can arise due to scalarization of a structure or an array that
597 // has elements that are dead.
598 unsigned FirstGlobal = 0;
599 for (unsigned i = 0, e = NewGlobals.size(); i != e; ++i)
600 if (NewGlobals[i]->use_empty()) {
601 Globals.erase(NewGlobals[i]);
602 if (FirstGlobal == i) ++FirstGlobal;
603 }
604
605 return FirstGlobal != NewGlobals.size() ? NewGlobals[FirstGlobal] : 0;
606}
607
608/// AllUsesOfValueWillTrapIfNull - Return true if all users of the specified
609/// value will trap if the value is dynamically null. PHIs keeps track of any
610/// phi nodes we've seen to avoid reprocessing them.
611static bool AllUsesOfValueWillTrapIfNull(Value *V,
612 SmallPtrSet<PHINode*, 8> &PHIs) {
613 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ++UI)
614 if (isa<LoadInst>(*UI)) {
615 // Will trap.
616 } else if (StoreInst *SI = dyn_cast<StoreInst>(*UI)) {
617 if (SI->getOperand(0) == V) {
618 //cerr << "NONTRAPPING USE: " << **UI;
619 return false; // Storing the value.
620 }
621 } else if (CallInst *CI = dyn_cast<CallInst>(*UI)) {
622 if (CI->getOperand(0) != V) {
623 //cerr << "NONTRAPPING USE: " << **UI;
624 return false; // Not calling the ptr
625 }
626 } else if (InvokeInst *II = dyn_cast<InvokeInst>(*UI)) {
627 if (II->getOperand(0) != V) {
628 //cerr << "NONTRAPPING USE: " << **UI;
629 return false; // Not calling the ptr
630 }
631 } else if (BitCastInst *CI = dyn_cast<BitCastInst>(*UI)) {
632 if (!AllUsesOfValueWillTrapIfNull(CI, PHIs)) return false;
633 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(*UI)) {
634 if (!AllUsesOfValueWillTrapIfNull(GEPI, PHIs)) return false;
635 } else if (PHINode *PN = dyn_cast<PHINode>(*UI)) {
636 // If we've already seen this phi node, ignore it, it has already been
637 // checked.
638 if (PHIs.insert(PN))
639 return AllUsesOfValueWillTrapIfNull(PN, PHIs);
640 } else if (isa<ICmpInst>(*UI) &&
641 isa<ConstantPointerNull>(UI->getOperand(1))) {
642 // Ignore setcc X, null
643 } else {
644 //cerr << "NONTRAPPING USE: " << **UI;
645 return false;
646 }
647 return true;
648}
649
650/// AllUsesOfLoadedValueWillTrapIfNull - Return true if all uses of any loads
651/// from GV will trap if the loaded value is null. Note that this also permits
652/// comparisons of the loaded value against null, as a special case.
653static bool AllUsesOfLoadedValueWillTrapIfNull(GlobalVariable *GV) {
654 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); UI!=E; ++UI)
655 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
656 SmallPtrSet<PHINode*, 8> PHIs;
657 if (!AllUsesOfValueWillTrapIfNull(LI, PHIs))
658 return false;
659 } else if (isa<StoreInst>(*UI)) {
660 // Ignore stores to the global.
661 } else {
662 // We don't know or understand this user, bail out.
663 //cerr << "UNKNOWN USER OF GLOBAL!: " << **UI;
664 return false;
665 }
666
667 return true;
668}
669
670static bool OptimizeAwayTrappingUsesOfValue(Value *V, Constant *NewV) {
671 bool Changed = false;
672 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ) {
673 Instruction *I = cast<Instruction>(*UI++);
674 if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
675 LI->setOperand(0, NewV);
676 Changed = true;
677 } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
678 if (SI->getOperand(1) == V) {
679 SI->setOperand(1, NewV);
680 Changed = true;
681 }
682 } else if (isa<CallInst>(I) || isa<InvokeInst>(I)) {
683 if (I->getOperand(0) == V) {
684 // Calling through the pointer! Turn into a direct call, but be careful
685 // that the pointer is not also being passed as an argument.
686 I->setOperand(0, NewV);
687 Changed = true;
688 bool PassedAsArg = false;
689 for (unsigned i = 1, e = I->getNumOperands(); i != e; ++i)
690 if (I->getOperand(i) == V) {
691 PassedAsArg = true;
692 I->setOperand(i, NewV);
693 }
694
695 if (PassedAsArg) {
696 // Being passed as an argument also. Be careful to not invalidate UI!
697 UI = V->use_begin();
698 }
699 }
700 } else if (CastInst *CI = dyn_cast<CastInst>(I)) {
701 Changed |= OptimizeAwayTrappingUsesOfValue(CI,
702 ConstantExpr::getCast(CI->getOpcode(),
703 NewV, CI->getType()));
704 if (CI->use_empty()) {
705 Changed = true;
706 CI->eraseFromParent();
707 }
708 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I)) {
709 // Should handle GEP here.
710 SmallVector<Constant*, 8> Idxs;
711 Idxs.reserve(GEPI->getNumOperands()-1);
712 for (User::op_iterator i = GEPI->op_begin() + 1, e = GEPI->op_end();
713 i != e; ++i)
714 if (Constant *C = dyn_cast<Constant>(*i))
715 Idxs.push_back(C);
716 else
717 break;
718 if (Idxs.size() == GEPI->getNumOperands()-1)
719 Changed |= OptimizeAwayTrappingUsesOfValue(GEPI,
720 ConstantExpr::getGetElementPtr(NewV, &Idxs[0],
721 Idxs.size()));
722 if (GEPI->use_empty()) {
723 Changed = true;
724 GEPI->eraseFromParent();
725 }
726 }
727 }
728
729 return Changed;
730}
731
732
733/// OptimizeAwayTrappingUsesOfLoads - The specified global has only one non-null
734/// value stored into it. If there are uses of the loaded value that would trap
735/// if the loaded value is dynamically null, then we know that they cannot be
736/// reachable with a null optimize away the load.
737static bool OptimizeAwayTrappingUsesOfLoads(GlobalVariable *GV, Constant *LV) {
738 bool Changed = false;
739
740 // Keep track of whether we are able to remove all the uses of the global
741 // other than the store that defines it.
742 bool AllNonStoreUsesGone = true;
743
744 // Replace all uses of loads with uses of uses of the stored value.
745 for (Value::use_iterator GUI = GV->use_begin(), E = GV->use_end(); GUI != E;){
746 User *GlobalUser = *GUI++;
747 if (LoadInst *LI = dyn_cast<LoadInst>(GlobalUser)) {
748 Changed |= OptimizeAwayTrappingUsesOfValue(LI, LV);
749 // If we were able to delete all uses of the loads
750 if (LI->use_empty()) {
751 LI->eraseFromParent();
752 Changed = true;
753 } else {
754 AllNonStoreUsesGone = false;
755 }
756 } else if (isa<StoreInst>(GlobalUser)) {
757 // Ignore the store that stores "LV" to the global.
758 assert(GlobalUser->getOperand(1) == GV &&
759 "Must be storing *to* the global");
760 } else {
761 AllNonStoreUsesGone = false;
762
763 // If we get here we could have other crazy uses that are transitively
764 // loaded.
765 assert((isa<PHINode>(GlobalUser) || isa<SelectInst>(GlobalUser) ||
766 isa<ConstantExpr>(GlobalUser)) && "Only expect load and stores!");
767 }
768 }
769
770 if (Changed) {
771 DOUT << "OPTIMIZED LOADS FROM STORED ONCE POINTER: " << *GV;
772 ++NumGlobUses;
773 }
774
775 // If we nuked all of the loads, then none of the stores are needed either,
776 // nor is the global.
777 if (AllNonStoreUsesGone) {
778 DOUT << " *** GLOBAL NOW DEAD!\n";
779 CleanupConstantGlobalUsers(GV, 0);
780 if (GV->use_empty()) {
781 GV->eraseFromParent();
782 ++NumDeleted;
783 }
784 Changed = true;
785 }
786 return Changed;
787}
788
789/// ConstantPropUsersOf - Walk the use list of V, constant folding all of the
790/// instructions that are foldable.
791static void ConstantPropUsersOf(Value *V) {
792 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; )
793 if (Instruction *I = dyn_cast<Instruction>(*UI++))
794 if (Constant *NewC = ConstantFoldInstruction(I)) {
795 I->replaceAllUsesWith(NewC);
796
797 // Advance UI to the next non-I use to avoid invalidating it!
798 // Instructions could multiply use V.
799 while (UI != E && *UI == I)
800 ++UI;
801 I->eraseFromParent();
802 }
803}
804
805/// OptimizeGlobalAddressOfMalloc - This function takes the specified global
806/// variable, and transforms the program as if it always contained the result of
807/// the specified malloc. Because it is always the result of the specified
808/// malloc, there is no reason to actually DO the malloc. Instead, turn the
809/// malloc into a global, and any loads of GV as uses of the new global.
810static GlobalVariable *OptimizeGlobalAddressOfMalloc(GlobalVariable *GV,
811 MallocInst *MI) {
812 DOUT << "PROMOTING MALLOC GLOBAL: " << *GV << " MALLOC = " << *MI;
813 ConstantInt *NElements = cast<ConstantInt>(MI->getArraySize());
814
815 if (NElements->getZExtValue() != 1) {
816 // If we have an array allocation, transform it to a single element
817 // allocation to make the code below simpler.
818 Type *NewTy = ArrayType::get(MI->getAllocatedType(),
819 NElements->getZExtValue());
820 MallocInst *NewMI =
821 new MallocInst(NewTy, Constant::getNullValue(Type::Int32Ty),
822 MI->getAlignment(), MI->getName(), MI);
823 Value* Indices[2];
824 Indices[0] = Indices[1] = Constant::getNullValue(Type::Int32Ty);
825 Value *NewGEP = GetElementPtrInst::Create(NewMI, Indices, Indices + 2,
826 NewMI->getName()+".el0", MI);
827 MI->replaceAllUsesWith(NewGEP);
828 MI->eraseFromParent();
829 MI = NewMI;
830 }
831
832 // Create the new global variable. The contents of the malloc'd memory is
833 // undefined, so initialize with an undef value.
834 Constant *Init = UndefValue::get(MI->getAllocatedType());
835 GlobalVariable *NewGV = new GlobalVariable(MI->getAllocatedType(), false,
836 GlobalValue::InternalLinkage, Init,
837 GV->getName()+".body",
838 (Module *)NULL,
839 GV->isThreadLocal());
840 // FIXME: This new global should have the alignment returned by malloc. Code
841 // could depend on malloc returning large alignment (on the mac, 16 bytes) but
842 // this would only guarantee some lower alignment.
843 GV->getParent()->getGlobalList().insert(GV, NewGV);
844
845 // Anything that used the malloc now uses the global directly.
846 MI->replaceAllUsesWith(NewGV);
847
848 Constant *RepValue = NewGV;
849 if (NewGV->getType() != GV->getType()->getElementType())
850 RepValue = ConstantExpr::getBitCast(RepValue,
851 GV->getType()->getElementType());
852
853 // If there is a comparison against null, we will insert a global bool to
854 // keep track of whether the global was initialized yet or not.
855 GlobalVariable *InitBool =
856 new GlobalVariable(Type::Int1Ty, false, GlobalValue::InternalLinkage,
857 ConstantInt::getFalse(), GV->getName()+".init",
858 (Module *)NULL, GV->isThreadLocal());
859 bool InitBoolUsed = false;
860
861 // Loop over all uses of GV, processing them in turn.
862 std::vector<StoreInst*> Stores;
863 while (!GV->use_empty())
864 if (LoadInst *LI = dyn_cast<LoadInst>(GV->use_back())) {
865 while (!LI->use_empty()) {
866 Use &LoadUse = LI->use_begin().getUse();
867 if (!isa<ICmpInst>(LoadUse.getUser()))
868 LoadUse = RepValue;
869 else {
870 ICmpInst *CI = cast<ICmpInst>(LoadUse.getUser());
871 // Replace the cmp X, 0 with a use of the bool value.
872 Value *LV = new LoadInst(InitBool, InitBool->getName()+".val", CI);
873 InitBoolUsed = true;
874 switch (CI->getPredicate()) {
875 default: assert(0 && "Unknown ICmp Predicate!");
876 case ICmpInst::ICMP_ULT:
877 case ICmpInst::ICMP_SLT:
878 LV = ConstantInt::getFalse(); // X < null -> always false
879 break;
880 case ICmpInst::ICMP_ULE:
881 case ICmpInst::ICMP_SLE:
882 case ICmpInst::ICMP_EQ:
883 LV = BinaryOperator::CreateNot(LV, "notinit", CI);
884 break;
885 case ICmpInst::ICMP_NE:
886 case ICmpInst::ICMP_UGE:
887 case ICmpInst::ICMP_SGE:
888 case ICmpInst::ICMP_UGT:
889 case ICmpInst::ICMP_SGT:
890 break; // no change.
891 }
892 CI->replaceAllUsesWith(LV);
893 CI->eraseFromParent();
894 }
895 }
896 LI->eraseFromParent();
897 } else {
898 StoreInst *SI = cast<StoreInst>(GV->use_back());
899 // The global is initialized when the store to it occurs.
900 new StoreInst(ConstantInt::getTrue(), InitBool, SI);
901 SI->eraseFromParent();
902 }
903
904 // If the initialization boolean was used, insert it, otherwise delete it.
905 if (!InitBoolUsed) {
906 while (!InitBool->use_empty()) // Delete initializations
907 cast<Instruction>(InitBool->use_back())->eraseFromParent();
908 delete InitBool;
909 } else
910 GV->getParent()->getGlobalList().insert(GV, InitBool);
911
912
913 // Now the GV is dead, nuke it and the malloc.
914 GV->eraseFromParent();
915 MI->eraseFromParent();
916
917 // To further other optimizations, loop over all users of NewGV and try to
918 // constant prop them. This will promote GEP instructions with constant
919 // indices into GEP constant-exprs, which will allow global-opt to hack on it.
920 ConstantPropUsersOf(NewGV);
921 if (RepValue != NewGV)
922 ConstantPropUsersOf(RepValue);
923
924 return NewGV;
925}
926
927/// ValueIsOnlyUsedLocallyOrStoredToOneGlobal - Scan the use-list of V checking
928/// to make sure that there are no complex uses of V. We permit simple things
929/// like dereferencing the pointer, but not storing through the address, unless
930/// it is to the specified global.
931static bool ValueIsOnlyUsedLocallyOrStoredToOneGlobal(Instruction *V,
932 GlobalVariable *GV,
933 SmallPtrSet<PHINode*, 8> &PHIs) {
934 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;++UI){
| 1//===- GlobalOpt.cpp - Optimize Global Variables --------------------------===//
2//
3// The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
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.
13//
14//===----------------------------------------------------------------------===//
15
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/DenseMap.h"
33#include "llvm/ADT/SmallPtrSet.h"
34#include "llvm/ADT/SmallVector.h"
35#include "llvm/ADT/Statistic.h"
36#include "llvm/ADT/StringExtras.h"
37#include "llvm/ADT/STLExtras.h"
38#include <algorithm>
39using namespace llvm;
40
41STATISTIC(NumMarked , "Number of globals marked constant");
42STATISTIC(NumSRA , "Number of aggregate globals broken into scalars");
43STATISTIC(NumHeapSRA , "Number of heap objects SRA'd");
44STATISTIC(NumSubstitute,"Number of globals with initializers stored into them");
45STATISTIC(NumDeleted , "Number of globals deleted");
46STATISTIC(NumFnDeleted , "Number of functions deleted");
47STATISTIC(NumGlobUses , "Number of global uses devirtualized");
48STATISTIC(NumLocalized , "Number of globals localized");
49STATISTIC(NumShrunkToBool , "Number of global vars shrunk to booleans");
50STATISTIC(NumFastCallFns , "Number of functions converted to fastcc");
51STATISTIC(NumCtorsEvaluated, "Number of static ctors evaluated");
52STATISTIC(NumNestRemoved , "Number of nest attributes removed");
53STATISTIC(NumAliasesResolved, "Number of global aliases resolved");
54STATISTIC(NumAliasesRemoved, "Number of global aliases eliminated");
55
56namespace {
57 struct VISIBILITY_HIDDEN GlobalOpt : public ModulePass {
58 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
59 AU.addRequired<TargetData>();
60 }
61 static char ID; // Pass identification, replacement for typeid
62 GlobalOpt() : ModulePass(&ID) {}
63
64 bool runOnModule(Module &M);
65
66 private:
67 GlobalVariable *FindGlobalCtors(Module &M);
68 bool OptimizeFunctions(Module &M);
69 bool OptimizeGlobalVars(Module &M);
70 bool OptimizeGlobalAliases(Module &M);
71 bool OptimizeGlobalCtorsList(GlobalVariable *&GCL);
72 bool ProcessInternalGlobal(GlobalVariable *GV,Module::global_iterator &GVI);
73 };
74}
75
76char GlobalOpt::ID = 0;
77static RegisterPass<GlobalOpt> X("globalopt", "Global Variable Optimizer");
78
79ModulePass *llvm::createGlobalOptimizerPass() { return new GlobalOpt(); }
80
81namespace {
82
83/// GlobalStatus - As we analyze each global, keep track of some information
84/// about it. If we find out that the address of the global is taken, none of
85/// this info will be accurate.
86struct VISIBILITY_HIDDEN GlobalStatus {
87 /// isLoaded - True if the global is ever loaded. If the global isn't ever
88 /// loaded it can be deleted.
89 bool isLoaded;
90
91 /// StoredType - Keep track of what stores to the global look like.
92 ///
93 enum StoredType {
94 /// NotStored - There is no store to this global. It can thus be marked
95 /// constant.
96 NotStored,
97
98 /// isInitializerStored - This global is stored to, but the only thing
99 /// stored is the constant it was initialized with. This is only tracked
100 /// for scalar globals.
101 isInitializerStored,
102
103 /// isStoredOnce - This global is stored to, but only its initializer and
104 /// one other value is ever stored to it. If this global isStoredOnce, we
105 /// track the value stored to it in StoredOnceValue below. This is only
106 /// tracked for scalar globals.
107 isStoredOnce,
108
109 /// isStored - This global is stored to by multiple values or something else
110 /// that we cannot track.
111 isStored
112 } StoredType;
113
114 /// StoredOnceValue - If only one value (besides the initializer constant) is
115 /// ever stored to this global, keep track of what value it is.
116 Value *StoredOnceValue;
117
118 /// AccessingFunction/HasMultipleAccessingFunctions - These start out
119 /// null/false. When the first accessing function is noticed, it is recorded.
120 /// When a second different accessing function is noticed,
121 /// HasMultipleAccessingFunctions is set to true.
122 Function *AccessingFunction;
123 bool HasMultipleAccessingFunctions;
124
125 /// HasNonInstructionUser - Set to true if this global has a user that is not
126 /// an instruction (e.g. a constant expr or GV initializer).
127 bool HasNonInstructionUser;
128
129 /// HasPHIUser - Set to true if this global has a user that is a PHI node.
130 bool HasPHIUser;
131
132 GlobalStatus() : isLoaded(false), StoredType(NotStored), StoredOnceValue(0),
133 AccessingFunction(0), HasMultipleAccessingFunctions(false),
134 HasNonInstructionUser(false), HasPHIUser(false) {}
135};
136
137}
138
139/// ConstantIsDead - Return true if the specified constant is (transitively)
140/// dead. The constant may be used by other constants (e.g. constant arrays and
141/// constant exprs) as long as they are dead, but it cannot be used by anything
142/// else.
143static bool ConstantIsDead(Constant *C) {
144 if (isa<GlobalValue>(C)) return false;
145
146 for (Value::use_iterator UI = C->use_begin(), E = C->use_end(); UI != E; ++UI)
147 if (Constant *CU = dyn_cast<Constant>(*UI)) {
148 if (!ConstantIsDead(CU)) return false;
149 } else
150 return false;
151 return true;
152}
153
154
155/// AnalyzeGlobal - Look at all uses of the global and fill in the GlobalStatus
156/// structure. If the global has its address taken, return true to indicate we
157/// can't do anything with it.
158///
159static bool AnalyzeGlobal(Value *V, GlobalStatus &GS,
160 SmallPtrSet<PHINode*, 16> &PHIUsers) {
161 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ++UI)
162 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(*UI)) {
163 GS.HasNonInstructionUser = true;
164
165 if (AnalyzeGlobal(CE, GS, PHIUsers)) return true;
166
167 } else if (Instruction *I = dyn_cast<Instruction>(*UI)) {
168 if (!GS.HasMultipleAccessingFunctions) {
169 Function *F = I->getParent()->getParent();
170 if (GS.AccessingFunction == 0)
171 GS.AccessingFunction = F;
172 else if (GS.AccessingFunction != F)
173 GS.HasMultipleAccessingFunctions = true;
174 }
175 if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
176 GS.isLoaded = true;
177 if (LI->isVolatile()) return true; // Don't hack on volatile loads.
178 } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
179 // Don't allow a store OF the address, only stores TO the address.
180 if (SI->getOperand(0) == V) return true;
181
182 if (SI->isVolatile()) return true; // Don't hack on volatile stores.
183
184 // If this is a direct store to the global (i.e., the global is a scalar
185 // value, not an aggregate), keep more specific information about
186 // stores.
187 if (GS.StoredType != GlobalStatus::isStored) {
188 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(SI->getOperand(1))){
189 Value *StoredVal = SI->getOperand(0);
190 if (StoredVal == GV->getInitializer()) {
191 if (GS.StoredType < GlobalStatus::isInitializerStored)
192 GS.StoredType = GlobalStatus::isInitializerStored;
193 } else if (isa<LoadInst>(StoredVal) &&
194 cast<LoadInst>(StoredVal)->getOperand(0) == GV) {
195 // G = G
196 if (GS.StoredType < GlobalStatus::isInitializerStored)
197 GS.StoredType = GlobalStatus::isInitializerStored;
198 } else if (GS.StoredType < GlobalStatus::isStoredOnce) {
199 GS.StoredType = GlobalStatus::isStoredOnce;
200 GS.StoredOnceValue = StoredVal;
201 } else if (GS.StoredType == GlobalStatus::isStoredOnce &&
202 GS.StoredOnceValue == StoredVal) {
203 // noop.
204 } else {
205 GS.StoredType = GlobalStatus::isStored;
206 }
207 } else {
208 GS.StoredType = GlobalStatus::isStored;
209 }
210 }
211 } else if (isa<GetElementPtrInst>(I)) {
212 if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
213 } else if (isa<SelectInst>(I)) {
214 if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
215 } else if (PHINode *PN = dyn_cast<PHINode>(I)) {
216 // PHI nodes we can check just like select or GEP instructions, but we
217 // have to be careful about infinite recursion.
218 if (PHIUsers.insert(PN)) // Not already visited.
219 if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
220 GS.HasPHIUser = true;
221 } else if (isa<CmpInst>(I)) {
222 } else if (isa<MemTransferInst>(I)) {
223 if (I->getOperand(1) == V)
224 GS.StoredType = GlobalStatus::isStored;
225 if (I->getOperand(2) == V)
226 GS.isLoaded = true;
227 } else if (isa<MemSetInst>(I)) {
228 assert(I->getOperand(1) == V && "Memset only takes one pointer!");
229 GS.StoredType = GlobalStatus::isStored;
230 } else {
231 return true; // Any other non-load instruction might take address!
232 }
233 } else if (Constant *C = dyn_cast<Constant>(*UI)) {
234 GS.HasNonInstructionUser = true;
235 // We might have a dead and dangling constant hanging off of here.
236 if (!ConstantIsDead(C))
237 return true;
238 } else {
239 GS.HasNonInstructionUser = true;
240 // Otherwise must be some other user.
241 return true;
242 }
243
244 return false;
245}
246
247static Constant *getAggregateConstantElement(Constant *Agg, Constant *Idx) {
248 ConstantInt *CI = dyn_cast<ConstantInt>(Idx);
249 if (!CI) return 0;
250 unsigned IdxV = CI->getZExtValue();
251
252 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(Agg)) {
253 if (IdxV < CS->getNumOperands()) return CS->getOperand(IdxV);
254 } else if (ConstantArray *CA = dyn_cast<ConstantArray>(Agg)) {
255 if (IdxV < CA->getNumOperands()) return CA->getOperand(IdxV);
256 } else if (ConstantVector *CP = dyn_cast<ConstantVector>(Agg)) {
257 if (IdxV < CP->getNumOperands()) return CP->getOperand(IdxV);
258 } else if (isa<ConstantAggregateZero>(Agg)) {
259 if (const StructType *STy = dyn_cast<StructType>(Agg->getType())) {
260 if (IdxV < STy->getNumElements())
261 return Constant::getNullValue(STy->getElementType(IdxV));
262 } else if (const SequentialType *STy =
263 dyn_cast<SequentialType>(Agg->getType())) {
264 return Constant::getNullValue(STy->getElementType());
265 }
266 } else if (isa<UndefValue>(Agg)) {
267 if (const StructType *STy = dyn_cast<StructType>(Agg->getType())) {
268 if (IdxV < STy->getNumElements())
269 return UndefValue::get(STy->getElementType(IdxV));
270 } else if (const SequentialType *STy =
271 dyn_cast<SequentialType>(Agg->getType())) {
272 return UndefValue::get(STy->getElementType());
273 }
274 }
275 return 0;
276}
277
278
279/// CleanupConstantGlobalUsers - We just marked GV constant. Loop over all
280/// users of the global, cleaning up the obvious ones. This is largely just a
281/// quick scan over the use list to clean up the easy and obvious cruft. This
282/// returns true if it made a change.
283static bool CleanupConstantGlobalUsers(Value *V, Constant *Init) {
284 bool Changed = false;
285 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;) {
286 User *U = *UI++;
287
288 if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
289 if (Init) {
290 // Replace the load with the initializer.
291 LI->replaceAllUsesWith(Init);
292 LI->eraseFromParent();
293 Changed = true;
294 }
295 } else if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
296 // Store must be unreachable or storing Init into the global.
297 SI->eraseFromParent();
298 Changed = true;
299 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U)) {
300 if (CE->getOpcode() == Instruction::GetElementPtr) {
301 Constant *SubInit = 0;
302 if (Init)
303 SubInit = ConstantFoldLoadThroughGEPConstantExpr(Init, CE);
304 Changed |= CleanupConstantGlobalUsers(CE, SubInit);
305 } else if (CE->getOpcode() == Instruction::BitCast &&
306 isa<PointerType>(CE->getType())) {
307 // Pointer cast, delete any stores and memsets to the global.
308 Changed |= CleanupConstantGlobalUsers(CE, 0);
309 }
310
311 if (CE->use_empty()) {
312 CE->destroyConstant();
313 Changed = true;
314 }
315 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) {
316 // Do not transform "gepinst (gep constexpr (GV))" here, because forming
317 // "gepconstexpr (gep constexpr (GV))" will cause the two gep's to fold
318 // and will invalidate our notion of what Init is.
319 Constant *SubInit = 0;
320 if (!isa<ConstantExpr>(GEP->getOperand(0))) {
321 ConstantExpr *CE =
322 dyn_cast_or_null<ConstantExpr>(ConstantFoldInstruction(GEP));
323 if (Init && CE && CE->getOpcode() == Instruction::GetElementPtr)
324 SubInit = ConstantFoldLoadThroughGEPConstantExpr(Init, CE);
325 }
326 Changed |= CleanupConstantGlobalUsers(GEP, SubInit);
327
328 if (GEP->use_empty()) {
329 GEP->eraseFromParent();
330 Changed = true;
331 }
332 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(U)) { // memset/cpy/mv
333 if (MI->getRawDest() == V) {
334 MI->eraseFromParent();
335 Changed = true;
336 }
337
338 } else if (Constant *C = dyn_cast<Constant>(U)) {
339 // If we have a chain of dead constantexprs or other things dangling from
340 // us, and if they are all dead, nuke them without remorse.
341 if (ConstantIsDead(C)) {
342 C->destroyConstant();
343 // This could have invalidated UI, start over from scratch.
344 CleanupConstantGlobalUsers(V, Init);
345 return true;
346 }
347 }
348 }
349 return Changed;
350}
351
352/// isSafeSROAElementUse - Return true if the specified instruction is a safe
353/// user of a derived expression from a global that we want to SROA.
354static bool isSafeSROAElementUse(Value *V) {
355 // We might have a dead and dangling constant hanging off of here.
356 if (Constant *C = dyn_cast<Constant>(V))
357 return ConstantIsDead(C);
358
359 Instruction *I = dyn_cast<Instruction>(V);
360 if (!I) return false;
361
362 // Loads are ok.
363 if (isa<LoadInst>(I)) return true;
364
365 // Stores *to* the pointer are ok.
366 if (StoreInst *SI = dyn_cast<StoreInst>(I))
367 return SI->getOperand(0) != V;
368
369 // Otherwise, it must be a GEP.
370 GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I);
371 if (GEPI == 0) return false;
372
373 if (GEPI->getNumOperands() < 3 || !isa<Constant>(GEPI->getOperand(1)) ||
374 !cast<Constant>(GEPI->getOperand(1))->isNullValue())
375 return false;
376
377 for (Value::use_iterator I = GEPI->use_begin(), E = GEPI->use_end();
378 I != E; ++I)
379 if (!isSafeSROAElementUse(*I))
380 return false;
381 return true;
382}
383
384
385/// IsUserOfGlobalSafeForSRA - U is a direct user of the specified global value.
386/// Look at it and its uses and decide whether it is safe to SROA this global.
387///
388static bool IsUserOfGlobalSafeForSRA(User *U, GlobalValue *GV) {
389 // The user of the global must be a GEP Inst or a ConstantExpr GEP.
390 if (!isa<GetElementPtrInst>(U) &&
391 (!isa<ConstantExpr>(U) ||
392 cast<ConstantExpr>(U)->getOpcode() != Instruction::GetElementPtr))
393 return false;
394
395 // Check to see if this ConstantExpr GEP is SRA'able. In particular, we
396 // don't like < 3 operand CE's, and we don't like non-constant integer
397 // indices. This enforces that all uses are 'gep GV, 0, C, ...' for some
398 // value of C.
399 if (U->getNumOperands() < 3 || !isa<Constant>(U->getOperand(1)) ||
400 !cast<Constant>(U->getOperand(1))->isNullValue() ||
401 !isa<ConstantInt>(U->getOperand(2)))
402 return false;
403
404 gep_type_iterator GEPI = gep_type_begin(U), E = gep_type_end(U);
405 ++GEPI; // Skip over the pointer index.
406
407 // If this is a use of an array allocation, do a bit more checking for sanity.
408 if (const ArrayType *AT = dyn_cast<ArrayType>(*GEPI)) {
409 uint64_t NumElements = AT->getNumElements();
410 ConstantInt *Idx = cast<ConstantInt>(U->getOperand(2));
411
412 // Check to make sure that index falls within the array. If not,
413 // something funny is going on, so we won't do the optimization.
414 //
415 if (Idx->getZExtValue() >= NumElements)
416 return false;
417
418 // We cannot scalar repl this level of the array unless any array
419 // sub-indices are in-range constants. In particular, consider:
420 // A[0][i]. We cannot know that the user isn't doing invalid things like
421 // allowing i to index an out-of-range subscript that accesses A[1].
422 //
423 // Scalar replacing *just* the outer index of the array is probably not
424 // going to be a win anyway, so just give up.
425 for (++GEPI; // Skip array index.
426 GEPI != E && (isa<ArrayType>(*GEPI) || isa<VectorType>(*GEPI));
427 ++GEPI) {
428 uint64_t NumElements;
429 if (const ArrayType *SubArrayTy = dyn_cast<ArrayType>(*GEPI))
430 NumElements = SubArrayTy->getNumElements();
431 else
432 NumElements = cast<VectorType>(*GEPI)->getNumElements();
433
434 ConstantInt *IdxVal = dyn_cast<ConstantInt>(GEPI.getOperand());
435 if (!IdxVal || IdxVal->getZExtValue() >= NumElements)
436 return false;
437 }
438 }
439
440 for (Value::use_iterator I = U->use_begin(), E = U->use_end(); I != E; ++I)
441 if (!isSafeSROAElementUse(*I))
442 return false;
443 return true;
444}
445
446/// GlobalUsersSafeToSRA - Look at all uses of the global and decide whether it
447/// is safe for us to perform this transformation.
448///
449static bool GlobalUsersSafeToSRA(GlobalValue *GV) {
450 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end();
451 UI != E; ++UI) {
452 if (!IsUserOfGlobalSafeForSRA(*UI, GV))
453 return false;
454 }
455 return true;
456}
457
458
459/// SRAGlobal - Perform scalar replacement of aggregates on the specified global
460/// variable. This opens the door for other optimizations by exposing the
461/// behavior of the program in a more fine-grained way. We have determined that
462/// this transformation is safe already. We return the first global variable we
463/// insert so that the caller can reprocess it.
464static GlobalVariable *SRAGlobal(GlobalVariable *GV, const TargetData &TD) {
465 // Make sure this global only has simple uses that we can SRA.
466 if (!GlobalUsersSafeToSRA(GV))
467 return 0;
468
469 assert(GV->hasLocalLinkage() && !GV->isConstant());
470 Constant *Init = GV->getInitializer();
471 const Type *Ty = Init->getType();
472
473 std::vector<GlobalVariable*> NewGlobals;
474 Module::GlobalListType &Globals = GV->getParent()->getGlobalList();
475
476 // Get the alignment of the global, either explicit or target-specific.
477 unsigned StartAlignment = GV->getAlignment();
478 if (StartAlignment == 0)
479 StartAlignment = TD.getABITypeAlignment(GV->getType());
480
481 if (const StructType *STy = dyn_cast<StructType>(Ty)) {
482 NewGlobals.reserve(STy->getNumElements());
483 const StructLayout &Layout = *TD.getStructLayout(STy);
484 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
485 Constant *In = getAggregateConstantElement(Init,
486 ConstantInt::get(Type::Int32Ty, i));
487 assert(In && "Couldn't get element of initializer?");
488 GlobalVariable *NGV = new GlobalVariable(STy->getElementType(i), false,
489 GlobalVariable::InternalLinkage,
490 In, GV->getName()+"."+utostr(i),
491 (Module *)NULL,
492 GV->isThreadLocal(),
493 GV->getType()->getAddressSpace());
494 Globals.insert(GV, NGV);
495 NewGlobals.push_back(NGV);
496
497 // Calculate the known alignment of the field. If the original aggregate
498 // had 256 byte alignment for example, something might depend on that:
499 // propagate info to each field.
500 uint64_t FieldOffset = Layout.getElementOffset(i);
501 unsigned NewAlign = (unsigned)MinAlign(StartAlignment, FieldOffset);
502 if (NewAlign > TD.getABITypeAlignment(STy->getElementType(i)))
503 NGV->setAlignment(NewAlign);
504 }
505 } else if (const SequentialType *STy = dyn_cast<SequentialType>(Ty)) {
506 unsigned NumElements = 0;
507 if (const ArrayType *ATy = dyn_cast<ArrayType>(STy))
508 NumElements = ATy->getNumElements();
509 else
510 NumElements = cast<VectorType>(STy)->getNumElements();
511
512 if (NumElements > 16 && GV->hasNUsesOrMore(16))
513 return 0; // It's not worth it.
514 NewGlobals.reserve(NumElements);
515
516 uint64_t EltSize = TD.getTypeAllocSize(STy->getElementType());
517 unsigned EltAlign = TD.getABITypeAlignment(STy->getElementType());
518 for (unsigned i = 0, e = NumElements; i != e; ++i) {
519 Constant *In = getAggregateConstantElement(Init,
520 ConstantInt::get(Type::Int32Ty, i));
521 assert(In && "Couldn't get element of initializer?");
522
523 GlobalVariable *NGV = new GlobalVariable(STy->getElementType(), false,
524 GlobalVariable::InternalLinkage,
525 In, GV->getName()+"."+utostr(i),
526 (Module *)NULL,
527 GV->isThreadLocal(),
528 GV->getType()->getAddressSpace());
529 Globals.insert(GV, NGV);
530 NewGlobals.push_back(NGV);
531
532 // Calculate the known alignment of the field. If the original aggregate
533 // had 256 byte alignment for example, something might depend on that:
534 // propagate info to each field.
535 unsigned NewAlign = (unsigned)MinAlign(StartAlignment, EltSize*i);
536 if (NewAlign > EltAlign)
537 NGV->setAlignment(NewAlign);
538 }
539 }
540
541 if (NewGlobals.empty())
542 return 0;
543
544 DOUT << "PERFORMING GLOBAL SRA ON: " << *GV;
545
546 Constant *NullInt = Constant::getNullValue(Type::Int32Ty);
547
548 // Loop over all of the uses of the global, replacing the constantexpr geps,
549 // with smaller constantexpr geps or direct references.
550 while (!GV->use_empty()) {
551 User *GEP = GV->use_back();
552 assert(((isa<ConstantExpr>(GEP) &&
553 cast<ConstantExpr>(GEP)->getOpcode()==Instruction::GetElementPtr)||
554 isa<GetElementPtrInst>(GEP)) && "NonGEP CE's are not SRAable!");
555
556 // Ignore the 1th operand, which has to be zero or else the program is quite
557 // broken (undefined). Get the 2nd operand, which is the structure or array
558 // index.
559 unsigned Val = cast<ConstantInt>(GEP->getOperand(2))->getZExtValue();
560 if (Val >= NewGlobals.size()) Val = 0; // Out of bound array access.
561
562 Value *NewPtr = NewGlobals[Val];
563
564 // Form a shorter GEP if needed.
565 if (GEP->getNumOperands() > 3) {
566 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GEP)) {
567 SmallVector<Constant*, 8> Idxs;
568 Idxs.push_back(NullInt);
569 for (unsigned i = 3, e = CE->getNumOperands(); i != e; ++i)
570 Idxs.push_back(CE->getOperand(i));
571 NewPtr = ConstantExpr::getGetElementPtr(cast<Constant>(NewPtr),
572 &Idxs[0], Idxs.size());
573 } else {
574 GetElementPtrInst *GEPI = cast<GetElementPtrInst>(GEP);
575 SmallVector<Value*, 8> Idxs;
576 Idxs.push_back(NullInt);
577 for (unsigned i = 3, e = GEPI->getNumOperands(); i != e; ++i)
578 Idxs.push_back(GEPI->getOperand(i));
579 NewPtr = GetElementPtrInst::Create(NewPtr, Idxs.begin(), Idxs.end(),
580 GEPI->getName()+"."+utostr(Val), GEPI);
581 }
582 }
583 GEP->replaceAllUsesWith(NewPtr);
584
585 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(GEP))
586 GEPI->eraseFromParent();
587 else
588 cast<ConstantExpr>(GEP)->destroyConstant();
589 }
590
591 // Delete the old global, now that it is dead.
592 Globals.erase(GV);
593 ++NumSRA;
594
595 // Loop over the new globals array deleting any globals that are obviously
596 // dead. This can arise due to scalarization of a structure or an array that
597 // has elements that are dead.
598 unsigned FirstGlobal = 0;
599 for (unsigned i = 0, e = NewGlobals.size(); i != e; ++i)
600 if (NewGlobals[i]->use_empty()) {
601 Globals.erase(NewGlobals[i]);
602 if (FirstGlobal == i) ++FirstGlobal;
603 }
604
605 return FirstGlobal != NewGlobals.size() ? NewGlobals[FirstGlobal] : 0;
606}
607
608/// AllUsesOfValueWillTrapIfNull - Return true if all users of the specified
609/// value will trap if the value is dynamically null. PHIs keeps track of any
610/// phi nodes we've seen to avoid reprocessing them.
611static bool AllUsesOfValueWillTrapIfNull(Value *V,
612 SmallPtrSet<PHINode*, 8> &PHIs) {
613 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ++UI)
614 if (isa<LoadInst>(*UI)) {
615 // Will trap.
616 } else if (StoreInst *SI = dyn_cast<StoreInst>(*UI)) {
617 if (SI->getOperand(0) == V) {
618 //cerr << "NONTRAPPING USE: " << **UI;
619 return false; // Storing the value.
620 }
621 } else if (CallInst *CI = dyn_cast<CallInst>(*UI)) {
622 if (CI->getOperand(0) != V) {
623 //cerr << "NONTRAPPING USE: " << **UI;
624 return false; // Not calling the ptr
625 }
626 } else if (InvokeInst *II = dyn_cast<InvokeInst>(*UI)) {
627 if (II->getOperand(0) != V) {
628 //cerr << "NONTRAPPING USE: " << **UI;
629 return false; // Not calling the ptr
630 }
631 } else if (BitCastInst *CI = dyn_cast<BitCastInst>(*UI)) {
632 if (!AllUsesOfValueWillTrapIfNull(CI, PHIs)) return false;
633 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(*UI)) {
634 if (!AllUsesOfValueWillTrapIfNull(GEPI, PHIs)) return false;
635 } else if (PHINode *PN = dyn_cast<PHINode>(*UI)) {
636 // If we've already seen this phi node, ignore it, it has already been
637 // checked.
638 if (PHIs.insert(PN))
639 return AllUsesOfValueWillTrapIfNull(PN, PHIs);
640 } else if (isa<ICmpInst>(*UI) &&
641 isa<ConstantPointerNull>(UI->getOperand(1))) {
642 // Ignore setcc X, null
643 } else {
644 //cerr << "NONTRAPPING USE: " << **UI;
645 return false;
646 }
647 return true;
648}
649
650/// AllUsesOfLoadedValueWillTrapIfNull - Return true if all uses of any loads
651/// from GV will trap if the loaded value is null. Note that this also permits
652/// comparisons of the loaded value against null, as a special case.
653static bool AllUsesOfLoadedValueWillTrapIfNull(GlobalVariable *GV) {
654 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); UI!=E; ++UI)
655 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
656 SmallPtrSet<PHINode*, 8> PHIs;
657 if (!AllUsesOfValueWillTrapIfNull(LI, PHIs))
658 return false;
659 } else if (isa<StoreInst>(*UI)) {
660 // Ignore stores to the global.
661 } else {
662 // We don't know or understand this user, bail out.
663 //cerr << "UNKNOWN USER OF GLOBAL!: " << **UI;
664 return false;
665 }
666
667 return true;
668}
669
670static bool OptimizeAwayTrappingUsesOfValue(Value *V, Constant *NewV) {
671 bool Changed = false;
672 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ) {
673 Instruction *I = cast<Instruction>(*UI++);
674 if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
675 LI->setOperand(0, NewV);
676 Changed = true;
677 } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
678 if (SI->getOperand(1) == V) {
679 SI->setOperand(1, NewV);
680 Changed = true;
681 }
682 } else if (isa<CallInst>(I) || isa<InvokeInst>(I)) {
683 if (I->getOperand(0) == V) {
684 // Calling through the pointer! Turn into a direct call, but be careful
685 // that the pointer is not also being passed as an argument.
686 I->setOperand(0, NewV);
687 Changed = true;
688 bool PassedAsArg = false;
689 for (unsigned i = 1, e = I->getNumOperands(); i != e; ++i)
690 if (I->getOperand(i) == V) {
691 PassedAsArg = true;
692 I->setOperand(i, NewV);
693 }
694
695 if (PassedAsArg) {
696 // Being passed as an argument also. Be careful to not invalidate UI!
697 UI = V->use_begin();
698 }
699 }
700 } else if (CastInst *CI = dyn_cast<CastInst>(I)) {
701 Changed |= OptimizeAwayTrappingUsesOfValue(CI,
702 ConstantExpr::getCast(CI->getOpcode(),
703 NewV, CI->getType()));
704 if (CI->use_empty()) {
705 Changed = true;
706 CI->eraseFromParent();
707 }
708 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I)) {
709 // Should handle GEP here.
710 SmallVector<Constant*, 8> Idxs;
711 Idxs.reserve(GEPI->getNumOperands()-1);
712 for (User::op_iterator i = GEPI->op_begin() + 1, e = GEPI->op_end();
713 i != e; ++i)
714 if (Constant *C = dyn_cast<Constant>(*i))
715 Idxs.push_back(C);
716 else
717 break;
718 if (Idxs.size() == GEPI->getNumOperands()-1)
719 Changed |= OptimizeAwayTrappingUsesOfValue(GEPI,
720 ConstantExpr::getGetElementPtr(NewV, &Idxs[0],
721 Idxs.size()));
722 if (GEPI->use_empty()) {
723 Changed = true;
724 GEPI->eraseFromParent();
725 }
726 }
727 }
728
729 return Changed;
730}
731
732
733/// OptimizeAwayTrappingUsesOfLoads - The specified global has only one non-null
734/// value stored into it. If there are uses of the loaded value that would trap
735/// if the loaded value is dynamically null, then we know that they cannot be
736/// reachable with a null optimize away the load.
737static bool OptimizeAwayTrappingUsesOfLoads(GlobalVariable *GV, Constant *LV) {
738 bool Changed = false;
739
740 // Keep track of whether we are able to remove all the uses of the global
741 // other than the store that defines it.
742 bool AllNonStoreUsesGone = true;
743
744 // Replace all uses of loads with uses of uses of the stored value.
745 for (Value::use_iterator GUI = GV->use_begin(), E = GV->use_end(); GUI != E;){
746 User *GlobalUser = *GUI++;
747 if (LoadInst *LI = dyn_cast<LoadInst>(GlobalUser)) {
748 Changed |= OptimizeAwayTrappingUsesOfValue(LI, LV);
749 // If we were able to delete all uses of the loads
750 if (LI->use_empty()) {
751 LI->eraseFromParent();
752 Changed = true;
753 } else {
754 AllNonStoreUsesGone = false;
755 }
756 } else if (isa<StoreInst>(GlobalUser)) {
757 // Ignore the store that stores "LV" to the global.
758 assert(GlobalUser->getOperand(1) == GV &&
759 "Must be storing *to* the global");
760 } else {
761 AllNonStoreUsesGone = false;
762
763 // If we get here we could have other crazy uses that are transitively
764 // loaded.
765 assert((isa<PHINode>(GlobalUser) || isa<SelectInst>(GlobalUser) ||
766 isa<ConstantExpr>(GlobalUser)) && "Only expect load and stores!");
767 }
768 }
769
770 if (Changed) {
771 DOUT << "OPTIMIZED LOADS FROM STORED ONCE POINTER: " << *GV;
772 ++NumGlobUses;
773 }
774
775 // If we nuked all of the loads, then none of the stores are needed either,
776 // nor is the global.
777 if (AllNonStoreUsesGone) {
778 DOUT << " *** GLOBAL NOW DEAD!\n";
779 CleanupConstantGlobalUsers(GV, 0);
780 if (GV->use_empty()) {
781 GV->eraseFromParent();
782 ++NumDeleted;
783 }
784 Changed = true;
785 }
786 return Changed;
787}
788
789/// ConstantPropUsersOf - Walk the use list of V, constant folding all of the
790/// instructions that are foldable.
791static void ConstantPropUsersOf(Value *V) {
792 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; )
793 if (Instruction *I = dyn_cast<Instruction>(*UI++))
794 if (Constant *NewC = ConstantFoldInstruction(I)) {
795 I->replaceAllUsesWith(NewC);
796
797 // Advance UI to the next non-I use to avoid invalidating it!
798 // Instructions could multiply use V.
799 while (UI != E && *UI == I)
800 ++UI;
801 I->eraseFromParent();
802 }
803}
804
805/// OptimizeGlobalAddressOfMalloc - This function takes the specified global
806/// variable, and transforms the program as if it always contained the result of
807/// the specified malloc. Because it is always the result of the specified
808/// malloc, there is no reason to actually DO the malloc. Instead, turn the
809/// malloc into a global, and any loads of GV as uses of the new global.
810static GlobalVariable *OptimizeGlobalAddressOfMalloc(GlobalVariable *GV,
811 MallocInst *MI) {
812 DOUT << "PROMOTING MALLOC GLOBAL: " << *GV << " MALLOC = " << *MI;
813 ConstantInt *NElements = cast<ConstantInt>(MI->getArraySize());
814
815 if (NElements->getZExtValue() != 1) {
816 // If we have an array allocation, transform it to a single element
817 // allocation to make the code below simpler.
818 Type *NewTy = ArrayType::get(MI->getAllocatedType(),
819 NElements->getZExtValue());
820 MallocInst *NewMI =
821 new MallocInst(NewTy, Constant::getNullValue(Type::Int32Ty),
822 MI->getAlignment(), MI->getName(), MI);
823 Value* Indices[2];
824 Indices[0] = Indices[1] = Constant::getNullValue(Type::Int32Ty);
825 Value *NewGEP = GetElementPtrInst::Create(NewMI, Indices, Indices + 2,
826 NewMI->getName()+".el0", MI);
827 MI->replaceAllUsesWith(NewGEP);
828 MI->eraseFromParent();
829 MI = NewMI;
830 }
831
832 // Create the new global variable. The contents of the malloc'd memory is
833 // undefined, so initialize with an undef value.
834 Constant *Init = UndefValue::get(MI->getAllocatedType());
835 GlobalVariable *NewGV = new GlobalVariable(MI->getAllocatedType(), false,
836 GlobalValue::InternalLinkage, Init,
837 GV->getName()+".body",
838 (Module *)NULL,
839 GV->isThreadLocal());
840 // FIXME: This new global should have the alignment returned by malloc. Code
841 // could depend on malloc returning large alignment (on the mac, 16 bytes) but
842 // this would only guarantee some lower alignment.
843 GV->getParent()->getGlobalList().insert(GV, NewGV);
844
845 // Anything that used the malloc now uses the global directly.
846 MI->replaceAllUsesWith(NewGV);
847
848 Constant *RepValue = NewGV;
849 if (NewGV->getType() != GV->getType()->getElementType())
850 RepValue = ConstantExpr::getBitCast(RepValue,
851 GV->getType()->getElementType());
852
853 // If there is a comparison against null, we will insert a global bool to
854 // keep track of whether the global was initialized yet or not.
855 GlobalVariable *InitBool =
856 new GlobalVariable(Type::Int1Ty, false, GlobalValue::InternalLinkage,
857 ConstantInt::getFalse(), GV->getName()+".init",
858 (Module *)NULL, GV->isThreadLocal());
859 bool InitBoolUsed = false;
860
861 // Loop over all uses of GV, processing them in turn.
862 std::vector<StoreInst*> Stores;
863 while (!GV->use_empty())
864 if (LoadInst *LI = dyn_cast<LoadInst>(GV->use_back())) {
865 while (!LI->use_empty()) {
866 Use &LoadUse = LI->use_begin().getUse();
867 if (!isa<ICmpInst>(LoadUse.getUser()))
868 LoadUse = RepValue;
869 else {
870 ICmpInst *CI = cast<ICmpInst>(LoadUse.getUser());
871 // Replace the cmp X, 0 with a use of the bool value.
872 Value *LV = new LoadInst(InitBool, InitBool->getName()+".val", CI);
873 InitBoolUsed = true;
874 switch (CI->getPredicate()) {
875 default: assert(0 && "Unknown ICmp Predicate!");
876 case ICmpInst::ICMP_ULT:
877 case ICmpInst::ICMP_SLT:
878 LV = ConstantInt::getFalse(); // X < null -> always false
879 break;
880 case ICmpInst::ICMP_ULE:
881 case ICmpInst::ICMP_SLE:
882 case ICmpInst::ICMP_EQ:
883 LV = BinaryOperator::CreateNot(LV, "notinit", CI);
884 break;
885 case ICmpInst::ICMP_NE:
886 case ICmpInst::ICMP_UGE:
887 case ICmpInst::ICMP_SGE:
888 case ICmpInst::ICMP_UGT:
889 case ICmpInst::ICMP_SGT:
890 break; // no change.
891 }
892 CI->replaceAllUsesWith(LV);
893 CI->eraseFromParent();
894 }
895 }
896 LI->eraseFromParent();
897 } else {
898 StoreInst *SI = cast<StoreInst>(GV->use_back());
899 // The global is initialized when the store to it occurs.
900 new StoreInst(ConstantInt::getTrue(), InitBool, SI);
901 SI->eraseFromParent();
902 }
903
904 // If the initialization boolean was used, insert it, otherwise delete it.
905 if (!InitBoolUsed) {
906 while (!InitBool->use_empty()) // Delete initializations
907 cast<Instruction>(InitBool->use_back())->eraseFromParent();
908 delete InitBool;
909 } else
910 GV->getParent()->getGlobalList().insert(GV, InitBool);
911
912
913 // Now the GV is dead, nuke it and the malloc.
914 GV->eraseFromParent();
915 MI->eraseFromParent();
916
917 // To further other optimizations, loop over all users of NewGV and try to
918 // constant prop them. This will promote GEP instructions with constant
919 // indices into GEP constant-exprs, which will allow global-opt to hack on it.
920 ConstantPropUsersOf(NewGV);
921 if (RepValue != NewGV)
922 ConstantPropUsersOf(RepValue);
923
924 return NewGV;
925}
926
927/// ValueIsOnlyUsedLocallyOrStoredToOneGlobal - Scan the use-list of V checking
928/// to make sure that there are no complex uses of V. We permit simple things
929/// like dereferencing the pointer, but not storing through the address, unless
930/// it is to the specified global.
931static bool ValueIsOnlyUsedLocallyOrStoredToOneGlobal(Instruction *V,
932 GlobalVariable *GV,
933 SmallPtrSet<PHINode*, 8> &PHIs) {
934 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;++UI){
|
937
938 if (isa<LoadInst>(Inst) || isa<CmpInst>(Inst)) {
939 continue; // Fine, ignore.
940 }
941
942 if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
943 if (SI->getOperand(0) == V && SI->getOperand(1) != GV)
944 return false; // Storing the pointer itself... bad.
945 continue; // Otherwise, storing through it, or storing into GV... fine.
946 }
947
948 if (isa<GetElementPtrInst>(Inst)) {
949 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(Inst, GV, PHIs))
950 return false;
951 continue;
952 }
953
954 if (PHINode *PN = dyn_cast<PHINode>(Inst)) {
955 // PHIs are ok if all uses are ok. Don't infinitely recurse through PHI
956 // cycles.
957 if (PHIs.insert(PN))
958 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(PN, GV, PHIs))
959 return false;
960 continue;
961 }
962
963 if (BitCastInst *BCI = dyn_cast<BitCastInst>(Inst)) {
964 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(BCI, GV, PHIs))
965 return false;
966 continue;
967 }
968
969 return false;
970 }
971 return true;
972}
973
974/// ReplaceUsesOfMallocWithGlobal - The Alloc pointer is stored into GV
975/// somewhere. Transform all uses of the allocation into loads from the
976/// global and uses of the resultant pointer. Further, delete the store into
977/// GV. This assumes that these value pass the
978/// 'ValueIsOnlyUsedLocallyOrStoredToOneGlobal' predicate.
979static void ReplaceUsesOfMallocWithGlobal(Instruction *Alloc,
980 GlobalVariable *GV) {
981 while (!Alloc->use_empty()) {
982 Instruction *U = cast<Instruction>(*Alloc->use_begin());
983 Instruction *InsertPt = U;
984 if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
985 // If this is the store of the allocation into the global, remove it.
986 if (SI->getOperand(1) == GV) {
987 SI->eraseFromParent();
988 continue;
989 }
990 } else if (PHINode *PN = dyn_cast<PHINode>(U)) {
991 // Insert the load in the corresponding predecessor, not right before the
992 // PHI.
993 InsertPt = PN->getIncomingBlock(Alloc->use_begin())->getTerminator();
994 } else if (isa<BitCastInst>(U)) {
995 // Must be bitcast between the malloc and store to initialize the global.
996 ReplaceUsesOfMallocWithGlobal(U, GV);
997 U->eraseFromParent();
998 continue;
999 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(U)) {
1000 // If this is a "GEP bitcast" and the user is a store to the global, then
1001 // just process it as a bitcast.
1002 if (GEPI->hasAllZeroIndices() && GEPI->hasOneUse())
1003 if (StoreInst *SI = dyn_cast<StoreInst>(GEPI->use_back()))
1004 if (SI->getOperand(1) == GV) {
1005 // Must be bitcast GEP between the malloc and store to initialize
1006 // the global.
1007 ReplaceUsesOfMallocWithGlobal(GEPI, GV);
1008 GEPI->eraseFromParent();
1009 continue;
1010 }
1011 }
1012
1013 // Insert a load from the global, and use it instead of the malloc.
1014 Value *NL = new LoadInst(GV, GV->getName()+".val", InsertPt);
1015 U->replaceUsesOfWith(Alloc, NL);
1016 }
1017}
1018
1019/// LoadUsesSimpleEnoughForHeapSRA - Verify that all uses of V (a load, or a phi
1020/// of a load) are simple enough to perform heap SRA on. This permits GEP's
1021/// that index through the array and struct field, icmps of null, and PHIs.
1022static bool LoadUsesSimpleEnoughForHeapSRA(Value *V,
1023 SmallPtrSet<PHINode*, 32> &LoadUsingPHIs,
1024 SmallPtrSet<PHINode*, 32> &LoadUsingPHIsPerLoad) {
1025 // We permit two users of the load: setcc comparing against the null
1026 // pointer, and a getelementptr of a specific form.
1027 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;++UI){
1028 Instruction *User = cast<Instruction>(*UI);
1029
1030 // Comparison against null is ok.
1031 if (ICmpInst *ICI = dyn_cast<ICmpInst>(User)) {
1032 if (!isa<ConstantPointerNull>(ICI->getOperand(1)))
1033 return false;
1034 continue;
1035 }
1036
1037 // getelementptr is also ok, but only a simple form.
1038 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
1039 // Must index into the array and into the struct.
1040 if (GEPI->getNumOperands() < 3)
1041 return false;
1042
1043 // Otherwise the GEP is ok.
1044 continue;
1045 }
1046
1047 if (PHINode *PN = dyn_cast<PHINode>(User)) {
1048 if (!LoadUsingPHIsPerLoad.insert(PN))
1049 // This means some phi nodes are dependent on each other.
1050 // Avoid infinite looping!
1051 return false;
1052 if (!LoadUsingPHIs.insert(PN))
1053 // If we have already analyzed this PHI, then it is safe.
1054 continue;
1055
1056 // Make sure all uses of the PHI are simple enough to transform.
1057 if (!LoadUsesSimpleEnoughForHeapSRA(PN,
1058 LoadUsingPHIs, LoadUsingPHIsPerLoad))
1059 return false;
1060
1061 continue;
1062 }
1063
1064 // Otherwise we don't know what this is, not ok.
1065 return false;
1066 }
1067
1068 return true;
1069}
1070
1071
1072/// AllGlobalLoadUsesSimpleEnoughForHeapSRA - If all users of values loaded from
1073/// GV are simple enough to perform HeapSRA, return true.
1074static bool AllGlobalLoadUsesSimpleEnoughForHeapSRA(GlobalVariable *GV,
1075 MallocInst *MI) {
1076 SmallPtrSet<PHINode*, 32> LoadUsingPHIs;
1077 SmallPtrSet<PHINode*, 32> LoadUsingPHIsPerLoad;
1078 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); UI != E;
1079 ++UI)
1080 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
1081 if (!LoadUsesSimpleEnoughForHeapSRA(LI, LoadUsingPHIs,
1082 LoadUsingPHIsPerLoad))
1083 return false;
1084 LoadUsingPHIsPerLoad.clear();
1085 }
1086
1087 // If we reach here, we know that all uses of the loads and transitive uses
1088 // (through PHI nodes) are simple enough to transform. However, we don't know
1089 // that all inputs the to the PHI nodes are in the same equivalence sets.
1090 // Check to verify that all operands of the PHIs are either PHIS that can be
1091 // transformed, loads from GV, or MI itself.
1092 for (SmallPtrSet<PHINode*, 32>::iterator I = LoadUsingPHIs.begin(),
1093 E = LoadUsingPHIs.end(); I != E; ++I) {
1094 PHINode *PN = *I;
1095 for (unsigned op = 0, e = PN->getNumIncomingValues(); op != e; ++op) {
1096 Value *InVal = PN->getIncomingValue(op);
1097
1098 // PHI of the stored value itself is ok.
1099 if (InVal == MI) continue;
1100
1101 if (PHINode *InPN = dyn_cast<PHINode>(InVal)) {
1102 // One of the PHIs in our set is (optimistically) ok.
1103 if (LoadUsingPHIs.count(InPN))
1104 continue;
1105 return false;
1106 }
1107
1108 // Load from GV is ok.
1109 if (LoadInst *LI = dyn_cast<LoadInst>(InVal))
1110 if (LI->getOperand(0) == GV)
1111 continue;
1112
1113 // UNDEF? NULL?
1114
1115 // Anything else is rejected.
1116 return false;
1117 }
1118 }
1119
1120 return true;
1121}
1122
1123static Value *GetHeapSROAValue(Value *V, unsigned FieldNo,
1124 DenseMap<Value*, std::vector<Value*> > &InsertedScalarizedValues,
1125 std::vector<std::pair<PHINode*, unsigned> > &PHIsToRewrite) {
1126 std::vector<Value*> &FieldVals = InsertedScalarizedValues[V];
1127
1128 if (FieldNo >= FieldVals.size())
1129 FieldVals.resize(FieldNo+1);
1130
1131 // If we already have this value, just reuse the previously scalarized
1132 // version.
1133 if (Value *FieldVal = FieldVals[FieldNo])
1134 return FieldVal;
1135
1136 // Depending on what instruction this is, we have several cases.
1137 Value *Result;
1138 if (LoadInst *LI = dyn_cast<LoadInst>(V)) {
1139 // This is a scalarized version of the load from the global. Just create
1140 // a new Load of the scalarized global.
1141 Result = new LoadInst(GetHeapSROAValue(LI->getOperand(0), FieldNo,
1142 InsertedScalarizedValues,
1143 PHIsToRewrite),
1144 LI->getName()+".f" + utostr(FieldNo), LI);
1145 } else if (PHINode *PN = dyn_cast<PHINode>(V)) {
1146 // PN's type is pointer to struct. Make a new PHI of pointer to struct
1147 // field.
1148 const StructType *ST =
1149 cast<StructType>(cast<PointerType>(PN->getType())->getElementType());
1150
1151 Result =PHINode::Create(PointerType::getUnqual(ST->getElementType(FieldNo)),
1152 PN->getName()+".f"+utostr(FieldNo), PN);
1153 PHIsToRewrite.push_back(std::make_pair(PN, FieldNo));
1154 } else {
1155 assert(0 && "Unknown usable value");
1156 Result = 0;
1157 }
1158
1159 return FieldVals[FieldNo] = Result;
1160}
1161
1162/// RewriteHeapSROALoadUser - Given a load instruction and a value derived from
1163/// the load, rewrite the derived value to use the HeapSRoA'd load.
1164static void RewriteHeapSROALoadUser(Instruction *LoadUser,
1165 DenseMap<Value*, std::vector<Value*> > &InsertedScalarizedValues,
1166 std::vector<std::pair<PHINode*, unsigned> > &PHIsToRewrite) {
1167 // If this is a comparison against null, handle it.
1168 if (ICmpInst *SCI = dyn_cast<ICmpInst>(LoadUser)) {
1169 assert(isa<ConstantPointerNull>(SCI->getOperand(1)));
1170 // If we have a setcc of the loaded pointer, we can use a setcc of any
1171 // field.
1172 Value *NPtr = GetHeapSROAValue(SCI->getOperand(0), 0,
1173 InsertedScalarizedValues, PHIsToRewrite);
1174
1175 Value *New = new ICmpInst(SCI->getPredicate(), NPtr,
1176 Constant::getNullValue(NPtr->getType()),
1177 SCI->getName(), SCI);
1178 SCI->replaceAllUsesWith(New);
1179 SCI->eraseFromParent();
1180 return;
1181 }
1182
1183 // Handle 'getelementptr Ptr, Idx, i32 FieldNo ...'
1184 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(LoadUser)) {
1185 assert(GEPI->getNumOperands() >= 3 && isa<ConstantInt>(GEPI->getOperand(2))
1186 && "Unexpected GEPI!");
1187
1188 // Load the pointer for this field.
1189 unsigned FieldNo = cast<ConstantInt>(GEPI->getOperand(2))->getZExtValue();
1190 Value *NewPtr = GetHeapSROAValue(GEPI->getOperand(0), FieldNo,
1191 InsertedScalarizedValues, PHIsToRewrite);
1192
1193 // Create the new GEP idx vector.
1194 SmallVector<Value*, 8> GEPIdx;
1195 GEPIdx.push_back(GEPI->getOperand(1));
1196 GEPIdx.append(GEPI->op_begin()+3, GEPI->op_end());
1197
1198 Value *NGEPI = GetElementPtrInst::Create(NewPtr,
1199 GEPIdx.begin(), GEPIdx.end(),
1200 GEPI->getName(), GEPI);
1201 GEPI->replaceAllUsesWith(NGEPI);
1202 GEPI->eraseFromParent();
1203 return;
1204 }
1205
1206 // Recursively transform the users of PHI nodes. This will lazily create the
1207 // PHIs that are needed for individual elements. Keep track of what PHIs we
1208 // see in InsertedScalarizedValues so that we don't get infinite loops (very
1209 // antisocial). If the PHI is already in InsertedScalarizedValues, it has
1210 // already been seen first by another load, so its uses have already been
1211 // processed.
1212 PHINode *PN = cast<PHINode>(LoadUser);
1213 bool Inserted;
1214 DenseMap<Value*, std::vector<Value*> >::iterator InsertPos;
1215 tie(InsertPos, Inserted) =
1216 InsertedScalarizedValues.insert(std::make_pair(PN, std::vector<Value*>()));
1217 if (!Inserted) return;
1218
1219 // If this is the first time we've seen this PHI, recursively process all
1220 // users.
1221 for (Value::use_iterator UI = PN->use_begin(), E = PN->use_end(); UI != E; ) {
1222 Instruction *User = cast<Instruction>(*UI++);
1223 RewriteHeapSROALoadUser(User, InsertedScalarizedValues, PHIsToRewrite);
1224 }
1225}
1226
1227/// RewriteUsesOfLoadForHeapSRoA - We are performing Heap SRoA on a global. Ptr
1228/// is a value loaded from the global. Eliminate all uses of Ptr, making them
1229/// use FieldGlobals instead. All uses of loaded values satisfy
1230/// AllGlobalLoadUsesSimpleEnoughForHeapSRA.
1231static void RewriteUsesOfLoadForHeapSRoA(LoadInst *Load,
1232 DenseMap<Value*, std::vector<Value*> > &InsertedScalarizedValues,
1233 std::vector<std::pair<PHINode*, unsigned> > &PHIsToRewrite) {
1234 for (Value::use_iterator UI = Load->use_begin(), E = Load->use_end();
1235 UI != E; ) {
1236 Instruction *User = cast<Instruction>(*UI++);
1237 RewriteHeapSROALoadUser(User, InsertedScalarizedValues, PHIsToRewrite);
1238 }
1239
1240 if (Load->use_empty()) {
1241 Load->eraseFromParent();
1242 InsertedScalarizedValues.erase(Load);
1243 }
1244}
1245
1246/// PerformHeapAllocSRoA - MI is an allocation of an array of structures. Break
1247/// it up into multiple allocations of arrays of the fields.
1248static GlobalVariable *PerformHeapAllocSRoA(GlobalVariable *GV, MallocInst *MI){
1249 DOUT << "SROA HEAP ALLOC: " << *GV << " MALLOC = " << *MI;
1250 const StructType *STy = cast<StructType>(MI->getAllocatedType());
1251
1252 // There is guaranteed to be at least one use of the malloc (storing
1253 // it into GV). If there are other uses, change them to be uses of
1254 // the global to simplify later code. This also deletes the store
1255 // into GV.
1256 ReplaceUsesOfMallocWithGlobal(MI, GV);
1257
1258 // Okay, at this point, there are no users of the malloc. Insert N
1259 // new mallocs at the same place as MI, and N globals.
1260 std::vector<Value*> FieldGlobals;
1261 std::vector<MallocInst*> FieldMallocs;
1262
1263 for (unsigned FieldNo = 0, e = STy->getNumElements(); FieldNo != e;++FieldNo){
1264 const Type *FieldTy = STy->getElementType(FieldNo);
1265 const Type *PFieldTy = PointerType::getUnqual(FieldTy);
1266
1267 GlobalVariable *NGV =
1268 new GlobalVariable(PFieldTy, false, GlobalValue::InternalLinkage,
1269 Constant::getNullValue(PFieldTy),
1270 GV->getName() + ".f" + utostr(FieldNo), GV,
1271 GV->isThreadLocal());
1272 FieldGlobals.push_back(NGV);
1273
1274 MallocInst *NMI = new MallocInst(FieldTy, MI->getArraySize(),
1275 MI->getName() + ".f" + utostr(FieldNo),MI);
1276 FieldMallocs.push_back(NMI);
1277 new StoreInst(NMI, NGV, MI);
1278 }
1279
1280 // The tricky aspect of this transformation is handling the case when malloc
1281 // fails. In the original code, malloc failing would set the result pointer
1282 // of malloc to null. In this case, some mallocs could succeed and others
1283 // could fail. As such, we emit code that looks like this:
1284 // F0 = malloc(field0)
1285 // F1 = malloc(field1)
1286 // F2 = malloc(field2)
1287 // if (F0 == 0 || F1 == 0 || F2 == 0) {
1288 // if (F0) { free(F0); F0 = 0; }
1289 // if (F1) { free(F1); F1 = 0; }
1290 // if (F2) { free(F2); F2 = 0; }
1291 // }
1292 Value *RunningOr = 0;
1293 for (unsigned i = 0, e = FieldMallocs.size(); i != e; ++i) {
1294 Value *Cond = new ICmpInst(ICmpInst::ICMP_EQ, FieldMallocs[i],
1295 Constant::getNullValue(FieldMallocs[i]->getType()),
1296 "isnull", MI);
1297 if (!RunningOr)
1298 RunningOr = Cond; // First seteq
1299 else
1300 RunningOr = BinaryOperator::CreateOr(RunningOr, Cond, "tmp", MI);
1301 }
1302
1303 // Split the basic block at the old malloc.
1304 BasicBlock *OrigBB = MI->getParent();
1305 BasicBlock *ContBB = OrigBB->splitBasicBlock(MI, "malloc_cont");
1306
1307 // Create the block to check the first condition. Put all these blocks at the
1308 // end of the function as they are unlikely to be executed.
1309 BasicBlock *NullPtrBlock = BasicBlock::Create("malloc_ret_null",
1310 OrigBB->getParent());
1311
1312 // Remove the uncond branch from OrigBB to ContBB, turning it into a cond
1313 // branch on RunningOr.
1314 OrigBB->getTerminator()->eraseFromParent();
1315 BranchInst::Create(NullPtrBlock, ContBB, RunningOr, OrigBB);
1316
1317 // Within the NullPtrBlock, we need to emit a comparison and branch for each
1318 // pointer, because some may be null while others are not.
1319 for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) {
1320 Value *GVVal = new LoadInst(FieldGlobals[i], "tmp", NullPtrBlock);
1321 Value *Cmp = new ICmpInst(ICmpInst::ICMP_NE, GVVal,
1322 Constant::getNullValue(GVVal->getType()),
1323 "tmp", NullPtrBlock);
1324 BasicBlock *FreeBlock = BasicBlock::Create("free_it", OrigBB->getParent());
1325 BasicBlock *NextBlock = BasicBlock::Create("next", OrigBB->getParent());
1326 BranchInst::Create(FreeBlock, NextBlock, Cmp, NullPtrBlock);
1327
1328 // Fill in FreeBlock.
1329 new FreeInst(GVVal, FreeBlock);
1330 new StoreInst(Constant::getNullValue(GVVal->getType()), FieldGlobals[i],
1331 FreeBlock);
1332 BranchInst::Create(NextBlock, FreeBlock);
1333
1334 NullPtrBlock = NextBlock;
1335 }
1336
1337 BranchInst::Create(ContBB, NullPtrBlock);
1338
1339 // MI is no longer needed, remove it.
1340 MI->eraseFromParent();
1341
1342 /// InsertedScalarizedLoads - As we process loads, if we can't immediately
1343 /// update all uses of the load, keep track of what scalarized loads are
1344 /// inserted for a given load.
1345 DenseMap<Value*, std::vector<Value*> > InsertedScalarizedValues;
1346 InsertedScalarizedValues[GV] = FieldGlobals;
1347
1348 std::vector<std::pair<PHINode*, unsigned> > PHIsToRewrite;
1349
1350 // Okay, the malloc site is completely handled. All of the uses of GV are now
1351 // loads, and all uses of those loads are simple. Rewrite them to use loads
1352 // of the per-field globals instead.
1353 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); UI != E;) {
1354 Instruction *User = cast<Instruction>(*UI++);
1355
1356 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1357 RewriteUsesOfLoadForHeapSRoA(LI, InsertedScalarizedValues, PHIsToRewrite);
1358 continue;
1359 }
1360
1361 // Must be a store of null.
1362 StoreInst *SI = cast<StoreInst>(User);
1363 assert(isa<ConstantPointerNull>(SI->getOperand(0)) &&
1364 "Unexpected heap-sra user!");
1365
1366 // Insert a store of null into each global.
1367 for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) {
1368 const PointerType *PT = cast<PointerType>(FieldGlobals[i]->getType());
1369 Constant *Null = Constant::getNullValue(PT->getElementType());
1370 new StoreInst(Null, FieldGlobals[i], SI);
1371 }
1372 // Erase the original store.
1373 SI->eraseFromParent();
1374 }
1375
1376 // While we have PHIs that are interesting to rewrite, do it.
1377 while (!PHIsToRewrite.empty()) {
1378 PHINode *PN = PHIsToRewrite.back().first;
1379 unsigned FieldNo = PHIsToRewrite.back().second;
1380 PHIsToRewrite.pop_back();
1381 PHINode *FieldPN = cast<PHINode>(InsertedScalarizedValues[PN][FieldNo]);
1382 assert(FieldPN->getNumIncomingValues() == 0 &&"Already processed this phi");
1383
1384 // Add all the incoming values. This can materialize more phis.
1385 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
1386 Value *InVal = PN->getIncomingValue(i);
1387 InVal = GetHeapSROAValue(InVal, FieldNo, InsertedScalarizedValues,
1388 PHIsToRewrite);
1389 FieldPN->addIncoming(InVal, PN->getIncomingBlock(i));
1390 }
1391 }
1392
1393 // Drop all inter-phi links and any loads that made it this far.
1394 for (DenseMap<Value*, std::vector<Value*> >::iterator
1395 I = InsertedScalarizedValues.begin(), E = InsertedScalarizedValues.end();
1396 I != E; ++I) {
1397 if (PHINode *PN = dyn_cast<PHINode>(I->first))
1398 PN->dropAllReferences();
1399 else if (LoadInst *LI = dyn_cast<LoadInst>(I->first))
1400 LI->dropAllReferences();
1401 }
1402
1403 // Delete all the phis and loads now that inter-references are dead.
1404 for (DenseMap<Value*, std::vector<Value*> >::iterator
1405 I = InsertedScalarizedValues.begin(), E = InsertedScalarizedValues.end();
1406 I != E; ++I) {
1407 if (PHINode *PN = dyn_cast<PHINode>(I->first))
1408 PN->eraseFromParent();
1409 else if (LoadInst *LI = dyn_cast<LoadInst>(I->first))
1410 LI->eraseFromParent();
1411 }
1412
1413 // The old global is now dead, remove it.
1414 GV->eraseFromParent();
1415
1416 ++NumHeapSRA;
1417 return cast<GlobalVariable>(FieldGlobals[0]);
1418}
1419
1420/// TryToOptimizeStoreOfMallocToGlobal - This function is called when we see a
1421/// pointer global variable with a single value stored it that is a malloc or
1422/// cast of malloc.
1423static bool TryToOptimizeStoreOfMallocToGlobal(GlobalVariable *GV,
1424 MallocInst *MI,
1425 Module::global_iterator &GVI,
1426 TargetData &TD) {
1427 // If this is a malloc of an abstract type, don't touch it.
1428 if (!MI->getAllocatedType()->isSized())
1429 return false;
1430
1431 // We can't optimize this global unless all uses of it are *known* to be
1432 // of the malloc value, not of the null initializer value (consider a use
1433 // that compares the global's value against zero to see if the malloc has
1434 // been reached). To do this, we check to see if all uses of the global
1435 // would trap if the global were null: this proves that they must all
1436 // happen after the malloc.
1437 if (!AllUsesOfLoadedValueWillTrapIfNull(GV))
1438 return false;
1439
1440 // We can't optimize this if the malloc itself is used in a complex way,
1441 // for example, being stored into multiple globals. This allows the
1442 // malloc to be stored into the specified global, loaded setcc'd, and
1443 // GEP'd. These are all things we could transform to using the global
1444 // for.
1445 {
1446 SmallPtrSet<PHINode*, 8> PHIs;
1447 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(MI, GV, PHIs))
1448 return false;
1449 }
1450
1451
1452 // If we have a global that is only initialized with a fixed size malloc,
1453 // transform the program to use global memory instead of malloc'd memory.
1454 // This eliminates dynamic allocation, avoids an indirection accessing the
1455 // data, and exposes the resultant global to further GlobalOpt.
1456 if (ConstantInt *NElements = dyn_cast<ConstantInt>(MI->getArraySize())) {
1457 // Restrict this transformation to only working on small allocations
1458 // (2048 bytes currently), as we don't want to introduce a 16M global or
1459 // something.
1460 if (NElements->getZExtValue()*
1461 TD.getTypeAllocSize(MI->getAllocatedType()) < 2048) {
1462 GVI = OptimizeGlobalAddressOfMalloc(GV, MI);
1463 return true;
1464 }
1465 }
1466
1467 // If the allocation is an array of structures, consider transforming this
1468 // into multiple malloc'd arrays, one for each field. This is basically
1469 // SRoA for malloc'd memory.
1470 const Type *AllocTy = MI->getAllocatedType();
1471
1472 // If this is an allocation of a fixed size array of structs, analyze as a
1473 // variable size array. malloc [100 x struct],1 -> malloc struct, 100
1474 if (!MI->isArrayAllocation())
1475 if (const ArrayType *AT = dyn_cast<ArrayType>(AllocTy))
1476 AllocTy = AT->getElementType();
1477
1478 if (const StructType *AllocSTy = dyn_cast<StructType>(AllocTy)) {
1479 // This the structure has an unreasonable number of fields, leave it
1480 // alone.
1481 if (AllocSTy->getNumElements() <= 16 && AllocSTy->getNumElements() != 0 &&
1482 AllGlobalLoadUsesSimpleEnoughForHeapSRA(GV, MI)) {
1483
1484 // If this is a fixed size array, transform the Malloc to be an alloc of
1485 // structs. malloc [100 x struct],1 -> malloc struct, 100
1486 if (const ArrayType *AT = dyn_cast<ArrayType>(MI->getAllocatedType())) {
1487 MallocInst *NewMI =
1488 new MallocInst(AllocSTy,
1489 ConstantInt::get(Type::Int32Ty, AT->getNumElements()),
1490 "", MI);
1491 NewMI->takeName(MI);
1492 Value *Cast = new BitCastInst(NewMI, MI->getType(), "tmp", MI);
1493 MI->replaceAllUsesWith(Cast);
1494 MI->eraseFromParent();
1495 MI = NewMI;
1496 }
1497
1498 GVI = PerformHeapAllocSRoA(GV, MI);
1499 return true;
1500 }
1501 }
1502
1503 return false;
1504}
1505
1506// OptimizeOnceStoredGlobal - Try to optimize globals based on the knowledge
1507// that only one value (besides its initializer) is ever stored to the global.
1508static bool OptimizeOnceStoredGlobal(GlobalVariable *GV, Value *StoredOnceVal,
1509 Module::global_iterator &GVI,
1510 TargetData &TD) {
1511 // Ignore no-op GEPs and bitcasts.
1512 StoredOnceVal = StoredOnceVal->stripPointerCasts();
1513
1514 // If we are dealing with a pointer global that is initialized to null and
1515 // only has one (non-null) value stored into it, then we can optimize any
1516 // users of the loaded value (often calls and loads) that would trap if the
1517 // value was null.
1518 if (isa<PointerType>(GV->getInitializer()->getType()) &&
1519 GV->getInitializer()->isNullValue()) {
1520 if (Constant *SOVC = dyn_cast<Constant>(StoredOnceVal)) {
1521 if (GV->getInitializer()->getType() != SOVC->getType())
1522 SOVC = ConstantExpr::getBitCast(SOVC, GV->getInitializer()->getType());
1523
1524 // Optimize away any trapping uses of the loaded value.
1525 if (OptimizeAwayTrappingUsesOfLoads(GV, SOVC))
1526 return true;
1527 } else if (MallocInst *MI = dyn_cast<MallocInst>(StoredOnceVal)) {
1528 if (TryToOptimizeStoreOfMallocToGlobal(GV, MI, GVI, TD))
1529 return true;
1530 }
1531 }
1532
1533 return false;
1534}
1535
1536/// TryToShrinkGlobalToBoolean - At this point, we have learned that the only
1537/// two values ever stored into GV are its initializer and OtherVal. See if we
1538/// can shrink the global into a boolean and select between the two values
1539/// whenever it is used. This exposes the values to other scalar optimizations.
1540static bool TryToShrinkGlobalToBoolean(GlobalVariable *GV, Constant *OtherVal) {
1541 const Type *GVElType = GV->getType()->getElementType();
1542
1543 // If GVElType is already i1, it is already shrunk. If the type of the GV is
1544 // an FP value, pointer or vector, don't do this optimization because a select
1545 // between them is very expensive and unlikely to lead to later
1546 // simplification. In these cases, we typically end up with "cond ? v1 : v2"
1547 // where v1 and v2 both require constant pool loads, a big loss.
1548 if (GVElType == Type::Int1Ty || GVElType->isFloatingPoint() ||
1549 isa<PointerType>(GVElType) || isa<VectorType>(GVElType))
1550 return false;
1551
1552 // Walk the use list of the global seeing if all the uses are load or store.
1553 // If there is anything else, bail out.
1554 for (Value::use_iterator I = GV->use_begin(), E = GV->use_end(); I != E; ++I)
1555 if (!isa<LoadInst>(I) && !isa<StoreInst>(I))
1556 return false;
1557
1558 DOUT << " *** SHRINKING TO BOOL: " << *GV;
1559
1560 // Create the new global, initializing it to false.
1561 GlobalVariable *NewGV = new GlobalVariable(Type::Int1Ty, false,
1562 GlobalValue::InternalLinkage, ConstantInt::getFalse(),
1563 GV->getName()+".b",
1564 (Module *)NULL,
1565 GV->isThreadLocal());
1566 GV->getParent()->getGlobalList().insert(GV, NewGV);
1567
1568 Constant *InitVal = GV->getInitializer();
1569 assert(InitVal->getType() != Type::Int1Ty && "No reason to shrink to bool!");
1570
1571 // If initialized to zero and storing one into the global, we can use a cast
1572 // instead of a select to synthesize the desired value.
1573 bool IsOneZero = false;
1574 if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal))
1575 IsOneZero = InitVal->isNullValue() && CI->isOne();
1576
1577 while (!GV->use_empty()) {
1578 Instruction *UI = cast<Instruction>(GV->use_back());
1579 if (StoreInst *SI = dyn_cast<StoreInst>(UI)) {
1580 // Change the store into a boolean store.
1581 bool StoringOther = SI->getOperand(0) == OtherVal;
1582 // Only do this if we weren't storing a loaded value.
1583 Value *StoreVal;
1584 if (StoringOther || SI->getOperand(0) == InitVal)
1585 StoreVal = ConstantInt::get(Type::Int1Ty, StoringOther);
1586 else {
1587 // Otherwise, we are storing a previously loaded copy. To do this,
1588 // change the copy from copying the original value to just copying the
1589 // bool.
1590 Instruction *StoredVal = cast<Instruction>(SI->getOperand(0));
1591
1592 // If we're already replaced the input, StoredVal will be a cast or
1593 // select instruction. If not, it will be a load of the original
1594 // global.
1595 if (LoadInst *LI = dyn_cast<LoadInst>(StoredVal)) {
1596 assert(LI->getOperand(0) == GV && "Not a copy!");
1597 // Insert a new load, to preserve the saved value.
1598 StoreVal = new LoadInst(NewGV, LI->getName()+".b", LI);
1599 } else {
1600 assert((isa<CastInst>(StoredVal) || isa<SelectInst>(StoredVal)) &&
1601 "This is not a form that we understand!");
1602 StoreVal = StoredVal->getOperand(0);
1603 assert(isa<LoadInst>(StoreVal) && "Not a load of NewGV!");
1604 }
1605 }
1606 new StoreInst(StoreVal, NewGV, SI);
1607 } else {
1608 // Change the load into a load of bool then a select.
1609 LoadInst *LI = cast<LoadInst>(UI);
1610 LoadInst *NLI = new LoadInst(NewGV, LI->getName()+".b", LI);
1611 Value *NSI;
1612 if (IsOneZero)
1613 NSI = new ZExtInst(NLI, LI->getType(), "", LI);
1614 else
1615 NSI = SelectInst::Create(NLI, OtherVal, InitVal, "", LI);
1616 NSI->takeName(LI);
1617 LI->replaceAllUsesWith(NSI);
1618 }
1619 UI->eraseFromParent();
1620 }
1621
1622 GV->eraseFromParent();
1623 return true;
1624}
1625
1626
1627/// ProcessInternalGlobal - Analyze the specified global variable and optimize
1628/// it if possible. If we make a change, return true.
1629bool GlobalOpt::ProcessInternalGlobal(GlobalVariable *GV,
1630 Module::global_iterator &GVI) {
1631 SmallPtrSet<PHINode*, 16> PHIUsers;
1632 GlobalStatus GS;
1633 GV->removeDeadConstantUsers();
1634
1635 if (GV->use_empty()) {
1636 DOUT << "GLOBAL DEAD: " << *GV;
1637 GV->eraseFromParent();
1638 ++NumDeleted;
1639 return true;
1640 }
1641
1642 if (!AnalyzeGlobal(GV, GS, PHIUsers)) {
1643#if 0
1644 cerr << "Global: " << *GV;
1645 cerr << " isLoaded = " << GS.isLoaded << "\n";
1646 cerr << " StoredType = ";
1647 switch (GS.StoredType) {
1648 case GlobalStatus::NotStored: cerr << "NEVER STORED\n"; break;
1649 case GlobalStatus::isInitializerStored: cerr << "INIT STORED\n"; break;
1650 case GlobalStatus::isStoredOnce: cerr << "STORED ONCE\n"; break;
1651 case GlobalStatus::isStored: cerr << "stored\n"; break;
1652 }
1653 if (GS.StoredType == GlobalStatus::isStoredOnce && GS.StoredOnceValue)
1654 cerr << " StoredOnceValue = " << *GS.StoredOnceValue << "\n";
1655 if (GS.AccessingFunction && !GS.HasMultipleAccessingFunctions)
1656 cerr << " AccessingFunction = " << GS.AccessingFunction->getName()
1657 << "\n";
1658 cerr << " HasMultipleAccessingFunctions = "
1659 << GS.HasMultipleAccessingFunctions << "\n";
1660 cerr << " HasNonInstructionUser = " << GS.HasNonInstructionUser<<"\n";
1661 cerr << "\n";
1662#endif
1663
1664 // If this is a first class global and has only one accessing function
1665 // and this function is main (which we know is not recursive we can make
1666 // this global a local variable) we replace the global with a local alloca
1667 // in this function.
1668 //
1669 // NOTE: It doesn't make sense to promote non single-value types since we
1670 // are just replacing static memory to stack memory.
1671 if (!GS.HasMultipleAccessingFunctions &&
1672 GS.AccessingFunction && !GS.HasNonInstructionUser &&
1673 GV->getType()->getElementType()->isSingleValueType() &&
1674 GS.AccessingFunction->getName() == "main" &&
1675 GS.AccessingFunction->hasExternalLinkage()) {
1676 DOUT << "LOCALIZING GLOBAL: " << *GV;
1677 Instruction* FirstI = GS.AccessingFunction->getEntryBlock().begin();
1678 const Type* ElemTy = GV->getType()->getElementType();
1679 // FIXME: Pass Global's alignment when globals have alignment
1680 AllocaInst* Alloca = new AllocaInst(ElemTy, NULL, GV->getName(), FirstI);
1681 if (!isa<UndefValue>(GV->getInitializer()))
1682 new StoreInst(GV->getInitializer(), Alloca, FirstI);
1683
1684 GV->replaceAllUsesWith(Alloca);
1685 GV->eraseFromParent();
1686 ++NumLocalized;
1687 return true;
1688 }
1689
1690 // If the global is never loaded (but may be stored to), it is dead.
1691 // Delete it now.
1692 if (!GS.isLoaded) {
1693 DOUT << "GLOBAL NEVER LOADED: " << *GV;
1694
1695 // Delete any stores we can find to the global. We may not be able to
1696 // make it completely dead though.
1697 bool Changed = CleanupConstantGlobalUsers(GV, GV->getInitializer());
1698
1699 // If the global is dead now, delete it.
1700 if (GV->use_empty()) {
1701 GV->eraseFromParent();
1702 ++NumDeleted;
1703 Changed = true;
1704 }
1705 return Changed;
1706
1707 } else if (GS.StoredType <= GlobalStatus::isInitializerStored) {
1708 DOUT << "MARKING CONSTANT: " << *GV;
1709 GV->setConstant(true);
1710
1711 // Clean up any obviously simplifiable users now.
1712 CleanupConstantGlobalUsers(GV, GV->getInitializer());
1713
1714 // If the global is dead now, just nuke it.
1715 if (GV->use_empty()) {
1716 DOUT << " *** Marking constant allowed us to simplify "
1717 << "all users and delete global!\n";
1718 GV->eraseFromParent();
1719 ++NumDeleted;
1720 }
1721
1722 ++NumMarked;
1723 return true;
1724 } else if (!GV->getInitializer()->getType()->isSingleValueType()) {
1725 if (GlobalVariable *FirstNewGV = SRAGlobal(GV,
1726 getAnalysis<TargetData>())) {
1727 GVI = FirstNewGV; // Don't skip the newly produced globals!
1728 return true;
1729 }
1730 } else if (GS.StoredType == GlobalStatus::isStoredOnce) {
1731 // If the initial value for the global was an undef value, and if only
1732 // one other value was stored into it, we can just change the
1733 // initializer to be the stored value, then delete all stores to the
1734 // global. This allows us to mark it constant.
1735 if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue))
1736 if (isa<UndefValue>(GV->getInitializer())) {
1737 // Change the initial value here.
1738 GV->setInitializer(SOVConstant);
1739
1740 // Clean up any obviously simplifiable users now.
1741 CleanupConstantGlobalUsers(GV, GV->getInitializer());
1742
1743 if (GV->use_empty()) {
1744 DOUT << " *** Substituting initializer allowed us to "
1745 << "simplify all users and delete global!\n";
1746 GV->eraseFromParent();
1747 ++NumDeleted;
1748 } else {
1749 GVI = GV;
1750 }
1751 ++NumSubstitute;
1752 return true;
1753 }
1754
1755 // Try to optimize globals based on the knowledge that only one value
1756 // (besides its initializer) is ever stored to the global.
1757 if (OptimizeOnceStoredGlobal(GV, GS.StoredOnceValue, GVI,
1758 getAnalysis<TargetData>()))
1759 return true;
1760
1761 // Otherwise, if the global was not a boolean, we can shrink it to be a
1762 // boolean.
1763 if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue))
1764 if (TryToShrinkGlobalToBoolean(GV, SOVConstant)) {
1765 ++NumShrunkToBool;
1766 return true;
1767 }
1768 }
1769 }
1770 return false;
1771}
1772
1773/// OnlyCalledDirectly - Return true if the specified function is only called
1774/// directly. In other words, its address is never taken.
1775static bool OnlyCalledDirectly(Function *F) {
1776 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){
1777 Instruction *User = dyn_cast<Instruction>(*UI);
1778 if (!User) return false;
1779 if (!isa<CallInst>(User) && !isa<InvokeInst>(User)) return false;
1780
1781 // See if the function address is passed as an argument.
1782 for (User::op_iterator i = User->op_begin() + 1, e = User->op_end();
1783 i != e; ++i)
1784 if (*i == F) return false;
1785 }
1786 return true;
1787}
1788
1789/// ChangeCalleesToFastCall - Walk all of the direct calls of the specified
1790/// function, changing them to FastCC.
1791static void ChangeCalleesToFastCall(Function *F) {
1792 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){
1793 CallSite User(cast<Instruction>(*UI));
1794 User.setCallingConv(CallingConv::Fast);
1795 }
1796}
1797
1798static AttrListPtr StripNest(const AttrListPtr &Attrs) {
1799 for (unsigned i = 0, e = Attrs.getNumSlots(); i != e; ++i) {
1800 if ((Attrs.getSlot(i).Attrs & Attribute::Nest) == 0)
1801 continue;
1802
1803 // There can be only one.
1804 return Attrs.removeAttr(Attrs.getSlot(i).Index, Attribute::Nest);
1805 }
1806
1807 return Attrs;
1808}
1809
1810static void RemoveNestAttribute(Function *F) {
1811 F->setAttributes(StripNest(F->getAttributes()));
1812 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){
1813 CallSite User(cast<Instruction>(*UI));
1814 User.setAttributes(StripNest(User.getAttributes()));
1815 }
1816}
1817
1818bool GlobalOpt::OptimizeFunctions(Module &M) {
1819 bool Changed = false;
1820 // Optimize functions.
1821 for (Module::iterator FI = M.begin(), E = M.end(); FI != E; ) {
1822 Function *F = FI++;
1823 // Functions without names cannot be referenced outside this module.
1824 if (!F->hasName() && !F->isDeclaration())
1825 F->setLinkage(GlobalValue::InternalLinkage);
1826 F->removeDeadConstantUsers();
1827 if (F->use_empty() && (F->hasLocalLinkage() ||
1828 F->hasLinkOnceLinkage())) {
1829 M.getFunctionList().erase(F);
1830 Changed = true;
1831 ++NumFnDeleted;
1832 } else if (F->hasLocalLinkage()) {
1833 if (F->getCallingConv() == CallingConv::C && !F->isVarArg() &&
1834 OnlyCalledDirectly(F)) {
1835 // If this function has C calling conventions, is not a varargs
1836 // function, and is only called directly, promote it to use the Fast
1837 // calling convention.
1838 F->setCallingConv(CallingConv::Fast);
1839 ChangeCalleesToFastCall(F);
1840 ++NumFastCallFns;
1841 Changed = true;
1842 }
1843
1844 if (F->getAttributes().hasAttrSomewhere(Attribute::Nest) &&
1845 OnlyCalledDirectly(F)) {
1846 // The function is not used by a trampoline intrinsic, so it is safe
1847 // to remove the 'nest' attribute.
1848 RemoveNestAttribute(F);
1849 ++NumNestRemoved;
1850 Changed = true;
1851 }
1852 }
1853 }
1854 return Changed;
1855}
1856
1857bool GlobalOpt::OptimizeGlobalVars(Module &M) {
1858 bool Changed = false;
1859 for (Module::global_iterator GVI = M.global_begin(), E = M.global_end();
1860 GVI != E; ) {
1861 GlobalVariable *GV = GVI++;
1862 // Global variables without names cannot be referenced outside this module.
1863 if (!GV->hasName() && !GV->isDeclaration())
1864 GV->setLinkage(GlobalValue::InternalLinkage);
1865 if (!GV->isConstant() && GV->hasLocalLinkage() &&
1866 GV->hasInitializer())
1867 Changed |= ProcessInternalGlobal(GV, GVI);
1868 }
1869 return Changed;
1870}
1871
1872/// FindGlobalCtors - Find the llvm.globalctors list, verifying that all
1873/// initializers have an init priority of 65535.
1874GlobalVariable *GlobalOpt::FindGlobalCtors(Module &M) {
1875 for (Module::global_iterator I = M.global_begin(), E = M.global_end();
1876 I != E; ++I)
1877 if (I->getName() == "llvm.global_ctors") {
1878 // Found it, verify it's an array of { int, void()* }.
1879 const ArrayType *ATy =dyn_cast<ArrayType>(I->getType()->getElementType());
1880 if (!ATy) return 0;
1881 const StructType *STy = dyn_cast<StructType>(ATy->getElementType());
1882 if (!STy || STy->getNumElements() != 2 ||
1883 STy->getElementType(0) != Type::Int32Ty) return 0;
1884 const PointerType *PFTy = dyn_cast<PointerType>(STy->getElementType(1));
1885 if (!PFTy) return 0;
1886 const FunctionType *FTy = dyn_cast<FunctionType>(PFTy->getElementType());
1887 if (!FTy || FTy->getReturnType() != Type::VoidTy || FTy->isVarArg() ||
1888 FTy->getNumParams() != 0)
1889 return 0;
1890
1891 // Verify that the initializer is simple enough for us to handle.
1892 if (!I->hasInitializer()) return 0;
1893 ConstantArray *CA = dyn_cast<ConstantArray>(I->getInitializer());
1894 if (!CA) return 0;
1895 for (User::op_iterator i = CA->op_begin(), e = CA->op_end(); i != e; ++i)
1896 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(*i)) {
1897 if (isa<ConstantPointerNull>(CS->getOperand(1)))
1898 continue;
1899
1900 // Must have a function or null ptr.
1901 if (!isa<Function>(CS->getOperand(1)))
1902 return 0;
1903
1904 // Init priority must be standard.
1905 ConstantInt *CI = dyn_cast<ConstantInt>(CS->getOperand(0));
1906 if (!CI || CI->getZExtValue() != 65535)
1907 return 0;
1908 } else {
1909 return 0;
1910 }
1911
1912 return I;
1913 }
1914 return 0;
1915}
1916
1917/// ParseGlobalCtors - Given a llvm.global_ctors list that we can understand,
1918/// return a list of the functions and null terminator as a vector.
1919static std::vector<Function*> ParseGlobalCtors(GlobalVariable *GV) {
1920 ConstantArray *CA = cast<ConstantArray>(GV->getInitializer());
1921 std::vector<Function*> Result;
1922 Result.reserve(CA->getNumOperands());
1923 for (User::op_iterator i = CA->op_begin(), e = CA->op_end(); i != e; ++i) {
1924 ConstantStruct *CS = cast<ConstantStruct>(*i);
1925 Result.push_back(dyn_cast<Function>(CS->getOperand(1)));
1926 }
1927 return Result;
1928}
1929
1930/// InstallGlobalCtors - Given a specified llvm.global_ctors list, install the
1931/// specified array, returning the new global to use.
1932static GlobalVariable *InstallGlobalCtors(GlobalVariable *GCL,
1933 const std::vector<Function*> &Ctors) {
1934 // If we made a change, reassemble the initializer list.
1935 std::vector<Constant*> CSVals;
1936 CSVals.push_back(ConstantInt::get(Type::Int32Ty, 65535));
1937 CSVals.push_back(0);
1938
1939 // Create the new init list.
1940 std::vector<Constant*> CAList;
1941 for (unsigned i = 0, e = Ctors.size(); i != e; ++i) {
1942 if (Ctors[i]) {
1943 CSVals[1] = Ctors[i];
1944 } else {
1945 const Type *FTy = FunctionType::get(Type::VoidTy,
1946 std::vector<const Type*>(), false);
1947 const PointerType *PFTy = PointerType::getUnqual(FTy);
1948 CSVals[1] = Constant::getNullValue(PFTy);
1949 CSVals[0] = ConstantInt::get(Type::Int32Ty, 2147483647);
1950 }
1951 CAList.push_back(ConstantStruct::get(CSVals));
1952 }
1953
1954 // Create the array initializer.
1955 const Type *StructTy =
1956 cast<ArrayType>(GCL->getType()->getElementType())->getElementType();
1957 Constant *CA = ConstantArray::get(ArrayType::get(StructTy, CAList.size()),
1958 CAList);
1959
1960 // If we didn't change the number of elements, don't create a new GV.
1961 if (CA->getType() == GCL->getInitializer()->getType()) {
1962 GCL->setInitializer(CA);
1963 return GCL;
1964 }
1965
1966 // Create the new global and insert it next to the existing list.
1967 GlobalVariable *NGV = new GlobalVariable(CA->getType(), GCL->isConstant(),
1968 GCL->getLinkage(), CA, "",
1969 (Module *)NULL,
1970 GCL->isThreadLocal());
1971 GCL->getParent()->getGlobalList().insert(GCL, NGV);
1972 NGV->takeName(GCL);
1973
1974 // Nuke the old list, replacing any uses with the new one.
1975 if (!GCL->use_empty()) {
1976 Constant *V = NGV;
1977 if (V->getType() != GCL->getType())
1978 V = ConstantExpr::getBitCast(V, GCL->getType());
1979 GCL->replaceAllUsesWith(V);
1980 }
1981 GCL->eraseFromParent();
1982
1983 if (Ctors.size())
1984 return NGV;
1985 else
1986 return 0;
1987}
1988
1989
1990static Constant *getVal(DenseMap<Value*, Constant*> &ComputedValues,
1991 Value *V) {
1992 if (Constant *CV = dyn_cast<Constant>(V)) return CV;
1993 Constant *R = ComputedValues[V];
1994 assert(R && "Reference to an uncomputed value!");
1995 return R;
1996}
1997
1998/// isSimpleEnoughPointerToCommit - Return true if this constant is simple
1999/// enough for us to understand. In particular, if it is a cast of something,
2000/// we punt. We basically just support direct accesses to globals and GEP's of
2001/// globals. This should be kept up to date with CommitValueTo.
2002static bool isSimpleEnoughPointerToCommit(Constant *C) {
2003 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C)) {
2004 if (!GV->hasExternalLinkage() && !GV->hasLocalLinkage())
2005 return false; // do not allow weak/linkonce/dllimport/dllexport linkage.
2006 return !GV->isDeclaration(); // reject external globals.
2007 }
2008 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
2009 // Handle a constantexpr gep.
2010 if (CE->getOpcode() == Instruction::GetElementPtr &&
2011 isa<GlobalVariable>(CE->getOperand(0))) {
2012 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
2013 if (!GV->hasExternalLinkage() && !GV->hasLocalLinkage())
2014 return false; // do not allow weak/linkonce/dllimport/dllexport linkage.
2015 return GV->hasInitializer() &&
2016 ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE);
2017 }
2018 return false;
2019}
2020
2021/// EvaluateStoreInto - Evaluate a piece of a constantexpr store into a global
2022/// initializer. This returns 'Init' modified to reflect 'Val' stored into it.
2023/// At this point, the GEP operands of Addr [0, OpNo) have been stepped into.
2024static Constant *EvaluateStoreInto(Constant *Init, Constant *Val,
2025 ConstantExpr *Addr, unsigned OpNo) {
2026 // Base case of the recursion.
2027 if (OpNo == Addr->getNumOperands()) {
2028 assert(Val->getType() == Init->getType() && "Type mismatch!");
2029 return Val;
2030 }
2031
2032 if (const StructType *STy = dyn_cast<StructType>(Init->getType())) {
2033 std::vector<Constant*> Elts;
2034
2035 // Break up the constant into its elements.
2036 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(Init)) {
2037 for (User::op_iterator i = CS->op_begin(), e = CS->op_end(); i != e; ++i)
2038 Elts.push_back(cast<Constant>(*i));
2039 } else if (isa<ConstantAggregateZero>(Init)) {
2040 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
2041 Elts.push_back(Constant::getNullValue(STy->getElementType(i)));
2042 } else if (isa<UndefValue>(Init)) {
2043 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
2044 Elts.push_back(UndefValue::get(STy->getElementType(i)));
2045 } else {
2046 assert(0 && "This code is out of sync with "
2047 " ConstantFoldLoadThroughGEPConstantExpr");
2048 }
2049
2050 // Replace the element that we are supposed to.
2051 ConstantInt *CU = cast<ConstantInt>(Addr->getOperand(OpNo));
2052 unsigned Idx = CU->getZExtValue();
2053 assert(Idx < STy->getNumElements() && "Struct index out of range!");
2054 Elts[Idx] = EvaluateStoreInto(Elts[Idx], Val, Addr, OpNo+1);
2055
2056 // Return the modified struct.
2057 return ConstantStruct::get(&Elts[0], Elts.size(), STy->isPacked());
2058 } else {
2059 ConstantInt *CI = cast<ConstantInt>(Addr->getOperand(OpNo));
2060 const ArrayType *ATy = cast<ArrayType>(Init->getType());
2061
2062 // Break up the array into elements.
2063 std::vector<Constant*> Elts;
2064 if (ConstantArray *CA = dyn_cast<ConstantArray>(Init)) {
2065 for (User::op_iterator i = CA->op_begin(), e = CA->op_end(); i != e; ++i)
2066 Elts.push_back(cast<Constant>(*i));
2067 } else if (isa<ConstantAggregateZero>(Init)) {
2068 Constant *Elt = Constant::getNullValue(ATy->getElementType());
2069 Elts.assign(ATy->getNumElements(), Elt);
2070 } else if (isa<UndefValue>(Init)) {
2071 Constant *Elt = UndefValue::get(ATy->getElementType());
2072 Elts.assign(ATy->getNumElements(), Elt);
2073 } else {
2074 assert(0 && "This code is out of sync with "
2075 " ConstantFoldLoadThroughGEPConstantExpr");
2076 }
2077
2078 assert(CI->getZExtValue() < ATy->getNumElements());
2079 Elts[CI->getZExtValue()] =
2080 EvaluateStoreInto(Elts[CI->getZExtValue()], Val, Addr, OpNo+1);
2081 return ConstantArray::get(ATy, Elts);
2082 }
2083}
2084
2085/// CommitValueTo - We have decided that Addr (which satisfies the predicate
2086/// isSimpleEnoughPointerToCommit) should get Val as its value. Make it happen.
2087static void CommitValueTo(Constant *Val, Constant *Addr) {
2088 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Addr)) {
2089 assert(GV->hasInitializer());
2090 GV->setInitializer(Val);
2091 return;
2092 }
2093
2094 ConstantExpr *CE = cast<ConstantExpr>(Addr);
2095 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
2096
2097 Constant *Init = GV->getInitializer();
2098 Init = EvaluateStoreInto(Init, Val, CE, 2);
2099 GV->setInitializer(Init);
2100}
2101
2102/// ComputeLoadResult - Return the value that would be computed by a load from
2103/// P after the stores reflected by 'memory' have been performed. If we can't
2104/// decide, return null.
2105static Constant *ComputeLoadResult(Constant *P,
2106 const DenseMap<Constant*, Constant*> &Memory) {
2107 // If this memory location has been recently stored, use the stored value: it
2108 // is the most up-to-date.
2109 DenseMap<Constant*, Constant*>::const_iterator I = Memory.find(P);
2110 if (I != Memory.end()) return I->second;
2111
2112 // Access it.
2113 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(P)) {
2114 if (GV->hasInitializer())
2115 return GV->getInitializer();
2116 return 0;
2117 }
2118
2119 // Handle a constantexpr getelementptr.
2120 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(P))
2121 if (CE->getOpcode() == Instruction::GetElementPtr &&
2122 isa<GlobalVariable>(CE->getOperand(0))) {
2123 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
2124 if (GV->hasInitializer())
2125 return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE);
2126 }
2127
2128 return 0; // don't know how to evaluate.
2129}
2130
2131/// EvaluateFunction - Evaluate a call to function F, returning true if
2132/// successful, false if we can't evaluate it. ActualArgs contains the formal
2133/// arguments for the function.
2134static bool EvaluateFunction(Function *F, Constant *&RetVal,
2135 const std::vector<Constant*> &ActualArgs,
2136 std::vector<Function*> &CallStack,
2137 DenseMap<Constant*, Constant*> &MutatedMemory,
2138 std::vector<GlobalVariable*> &AllocaTmps) {
2139 // Check to see if this function is already executing (recursion). If so,
2140 // bail out. TODO: we might want to accept limited recursion.
2141 if (std::find(CallStack.begin(), CallStack.end(), F) != CallStack.end())
2142 return false;
2143
2144 CallStack.push_back(F);
2145
2146 /// Values - As we compute SSA register values, we store their contents here.
2147 DenseMap<Value*, Constant*> Values;
2148
2149 // Initialize arguments to the incoming values specified.
2150 unsigned ArgNo = 0;
2151 for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end(); AI != E;
2152 ++AI, ++ArgNo)
2153 Values[AI] = ActualArgs[ArgNo];
2154
2155 /// ExecutedBlocks - We only handle non-looping, non-recursive code. As such,
2156 /// we can only evaluate any one basic block at most once. This set keeps
2157 /// track of what we have executed so we can detect recursive cases etc.
2158 SmallPtrSet<BasicBlock*, 32> ExecutedBlocks;
2159
2160 // CurInst - The current instruction we're evaluating.
2161 BasicBlock::iterator CurInst = F->begin()->begin();
2162
2163 // This is the main evaluation loop.
2164 while (1) {
2165 Constant *InstResult = 0;
2166
2167 if (StoreInst *SI = dyn_cast<StoreInst>(CurInst)) {
2168 if (SI->isVolatile()) return false; // no volatile accesses.
2169 Constant *Ptr = getVal(Values, SI->getOperand(1));
2170 if (!isSimpleEnoughPointerToCommit(Ptr))
2171 // If this is too complex for us to commit, reject it.
2172 return false;
2173 Constant *Val = getVal(Values, SI->getOperand(0));
2174 MutatedMemory[Ptr] = Val;
2175 } else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(CurInst)) {
2176 InstResult = ConstantExpr::get(BO->getOpcode(),
2177 getVal(Values, BO->getOperand(0)),
2178 getVal(Values, BO->getOperand(1)));
2179 } else if (CmpInst *CI = dyn_cast<CmpInst>(CurInst)) {
2180 InstResult = ConstantExpr::getCompare(CI->getPredicate(),
2181 getVal(Values, CI->getOperand(0)),
2182 getVal(Values, CI->getOperand(1)));
2183 } else if (CastInst *CI = dyn_cast<CastInst>(CurInst)) {
2184 InstResult = ConstantExpr::getCast(CI->getOpcode(),
2185 getVal(Values, CI->getOperand(0)),
2186 CI->getType());
2187 } else if (SelectInst *SI = dyn_cast<SelectInst>(CurInst)) {
2188 InstResult = ConstantExpr::getSelect(getVal(Values, SI->getOperand(0)),
2189 getVal(Values, SI->getOperand(1)),
2190 getVal(Values, SI->getOperand(2)));
2191 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(CurInst)) {
2192 Constant *P = getVal(Values, GEP->getOperand(0));
2193 SmallVector<Constant*, 8> GEPOps;
2194 for (User::op_iterator i = GEP->op_begin() + 1, e = GEP->op_end();
2195 i != e; ++i)
2196 GEPOps.push_back(getVal(Values, *i));
2197 InstResult = ConstantExpr::getGetElementPtr(P, &GEPOps[0], GEPOps.size());
2198 } else if (LoadInst *LI = dyn_cast<LoadInst>(CurInst)) {
2199 if (LI->isVolatile()) return false; // no volatile accesses.
2200 InstResult = ComputeLoadResult(getVal(Values, LI->getOperand(0)),
2201 MutatedMemory);
2202 if (InstResult == 0) return false; // Could not evaluate load.
2203 } else if (AllocaInst *AI = dyn_cast<AllocaInst>(CurInst)) {
2204 if (AI->isArrayAllocation()) return false; // Cannot handle array allocs.
2205 const Type *Ty = AI->getType()->getElementType();
2206 AllocaTmps.push_back(new GlobalVariable(Ty, false,
2207 GlobalValue::InternalLinkage,
2208 UndefValue::get(Ty),
2209 AI->getName()));
2210 InstResult = AllocaTmps.back();
2211 } else if (CallInst *CI = dyn_cast<CallInst>(CurInst)) {
2212
2213 // Debug info can safely be ignored here.
2214 if (isa<DbgInfoIntrinsic>(CI)) {
2215 ++CurInst;
2216 continue;
2217 }
2218
2219 // Cannot handle inline asm.
2220 if (isa<InlineAsm>(CI->getOperand(0))) return false;
2221
2222 // Resolve function pointers.
2223 Function *Callee = dyn_cast<Function>(getVal(Values, CI->getOperand(0)));
2224 if (!Callee) return false; // Cannot resolve.
2225
2226 std::vector<Constant*> Formals;
2227 for (User::op_iterator i = CI->op_begin() + 1, e = CI->op_end();
2228 i != e; ++i)
2229 Formals.push_back(getVal(Values, *i));
2230
2231 if (Callee->isDeclaration()) {
2232 // If this is a function we can constant fold, do it.
2233 if (Constant *C = ConstantFoldCall(Callee, &Formals[0],
2234 Formals.size())) {
2235 InstResult = C;
2236 } else {
2237 return false;
2238 }
2239 } else {
2240 if (Callee->getFunctionType()->isVarArg())
2241 return false;
2242
2243 Constant *RetVal;
2244 // Execute the call, if successful, use the return value.
2245 if (!EvaluateFunction(Callee, RetVal, Formals, CallStack,
2246 MutatedMemory, AllocaTmps))
2247 return false;
2248 InstResult = RetVal;
2249 }
2250 } else if (isa<TerminatorInst>(CurInst)) {
2251 BasicBlock *NewBB = 0;
2252 if (BranchInst *BI = dyn_cast<BranchInst>(CurInst)) {
2253 if (BI->isUnconditional()) {
2254 NewBB = BI->getSuccessor(0);
2255 } else {
2256 ConstantInt *Cond =
2257 dyn_cast<ConstantInt>(getVal(Values, BI->getCondition()));
2258 if (!Cond) return false; // Cannot determine.
2259
2260 NewBB = BI->getSuccessor(!Cond->getZExtValue());
2261 }
2262 } else if (SwitchInst *SI = dyn_cast<SwitchInst>(CurInst)) {
2263 ConstantInt *Val =
2264 dyn_cast<ConstantInt>(getVal(Values, SI->getCondition()));
2265 if (!Val) return false; // Cannot determine.
2266 NewBB = SI->getSuccessor(SI->findCaseValue(Val));
2267 } else if (ReturnInst *RI = dyn_cast<ReturnInst>(CurInst)) {
2268 if (RI->getNumOperands())
2269 RetVal = getVal(Values, RI->getOperand(0));
2270
2271 CallStack.pop_back(); // return from fn.
2272 return true; // We succeeded at evaluating this ctor!
2273 } else {
2274 // invoke, unwind, unreachable.
2275 return false; // Cannot handle this terminator.
2276 }
2277
2278 // Okay, we succeeded in evaluating this control flow. See if we have
2279 // executed the new block before. If so, we have a looping function,
2280 // which we cannot evaluate in reasonable time.
2281 if (!ExecutedBlocks.insert(NewBB))
2282 return false; // looped!
2283
2284 // Okay, we have never been in this block before. Check to see if there
2285 // are any PHI nodes. If so, evaluate them with information about where
2286 // we came from.
2287 BasicBlock *OldBB = CurInst->getParent();
2288 CurInst = NewBB->begin();
2289 PHINode *PN;
2290 for (; (PN = dyn_cast<PHINode>(CurInst)); ++CurInst)
2291 Values[PN] = getVal(Values, PN->getIncomingValueForBlock(OldBB));
2292
2293 // Do NOT increment CurInst. We know that the terminator had no value.
2294 continue;
2295 } else {
2296 // Did not know how to evaluate this!
2297 return false;
2298 }
2299
2300 if (!CurInst->use_empty())
2301 Values[CurInst] = InstResult;
2302
2303 // Advance program counter.
2304 ++CurInst;
2305 }
2306}
2307
2308/// EvaluateStaticConstructor - Evaluate static constructors in the function, if
2309/// we can. Return true if we can, false otherwise.
2310static bool EvaluateStaticConstructor(Function *F) {
2311 /// MutatedMemory - For each store we execute, we update this map. Loads
2312 /// check this to get the most up-to-date value. If evaluation is successful,
2313 /// this state is committed to the process.
2314 DenseMap<Constant*, Constant*> MutatedMemory;
2315
2316 /// AllocaTmps - To 'execute' an alloca, we create a temporary global variable
2317 /// to represent its body. This vector is needed so we can delete the
2318 /// temporary globals when we are done.
2319 std::vector<GlobalVariable*> AllocaTmps;
2320
2321 /// CallStack - This is used to detect recursion. In pathological situations
2322 /// we could hit exponential behavior, but at least there is nothing
2323 /// unbounded.
2324 std::vector<Function*> CallStack;
2325
2326 // Call the function.
2327 Constant *RetValDummy;
2328 bool EvalSuccess = EvaluateFunction(F, RetValDummy, std::vector<Constant*>(),
2329 CallStack, MutatedMemory, AllocaTmps);
2330 if (EvalSuccess) {
2331 // We succeeded at evaluation: commit the result.
2332 DOUT << "FULLY EVALUATED GLOBAL CTOR FUNCTION '"
2333 << F->getName() << "' to " << MutatedMemory.size()
2334 << " stores.\n";
2335 for (DenseMap<Constant*, Constant*>::iterator I = MutatedMemory.begin(),
2336 E = MutatedMemory.end(); I != E; ++I)
2337 CommitValueTo(I->second, I->first);
2338 }
2339
2340 // At this point, we are done interpreting. If we created any 'alloca'
2341 // temporaries, release them now.
2342 while (!AllocaTmps.empty()) {
2343 GlobalVariable *Tmp = AllocaTmps.back();
2344 AllocaTmps.pop_back();
2345
2346 // If there are still users of the alloca, the program is doing something
2347 // silly, e.g. storing the address of the alloca somewhere and using it
2348 // later. Since this is undefined, we'll just make it be null.
2349 if (!Tmp->use_empty())
2350 Tmp->replaceAllUsesWith(Constant::getNullValue(Tmp->getType()));
2351 delete Tmp;
2352 }
2353
2354 return EvalSuccess;
2355}
2356
2357
2358
2359/// OptimizeGlobalCtorsList - Simplify and evaluation global ctors if possible.
2360/// Return true if anything changed.
2361bool GlobalOpt::OptimizeGlobalCtorsList(GlobalVariable *&GCL) {
2362 std::vector<Function*> Ctors = ParseGlobalCtors(GCL);
2363 bool MadeChange = false;
2364 if (Ctors.empty()) return false;
2365
2366 // Loop over global ctors, optimizing them when we can.
2367 for (unsigned i = 0; i != Ctors.size(); ++i) {
2368 Function *F = Ctors[i];
2369 // Found a null terminator in the middle of the list, prune off the rest of
2370 // the list.
2371 if (F == 0) {
2372 if (i != Ctors.size()-1) {
2373 Ctors.resize(i+1);
2374 MadeChange = true;
2375 }
2376 break;
2377 }
2378
2379 // We cannot simplify external ctor functions.
2380 if (F->empty()) continue;
2381
2382 // If we can evaluate the ctor at compile time, do.
2383 if (EvaluateStaticConstructor(F)) {
2384 Ctors.erase(Ctors.begin()+i);
2385 MadeChange = true;
2386 --i;
2387 ++NumCtorsEvaluated;
2388 continue;
2389 }
2390 }
2391
2392 if (!MadeChange) return false;
2393
2394 GCL = InstallGlobalCtors(GCL, Ctors);
2395 return true;
2396}
2397
2398bool GlobalOpt::OptimizeGlobalAliases(Module &M) {
2399 bool Changed = false;
2400
2401 for (Module::alias_iterator I = M.alias_begin(), E = M.alias_end();
2402 I != E;) {
2403 Module::alias_iterator J = I++;
2404 // Aliases without names cannot be referenced outside this module.
2405 if (!J->hasName() && !J->isDeclaration())
2406 J->setLinkage(GlobalValue::InternalLinkage);
2407 // If the aliasee may change at link time, nothing can be done - bail out.
2408 if (J->mayBeOverridden())
2409 continue;
2410
2411 Constant *Aliasee = J->getAliasee();
2412 GlobalValue *Target = cast<GlobalValue>(Aliasee->stripPointerCasts());
2413 Target->removeDeadConstantUsers();
2414 bool hasOneUse = Target->hasOneUse() && Aliasee->hasOneUse();
2415
2416 // Make all users of the alias use the aliasee instead.
2417 if (!J->use_empty()) {
2418 J->replaceAllUsesWith(Aliasee);
2419 ++NumAliasesResolved;
2420 Changed = true;
2421 }
2422
2423 // If the aliasee has internal linkage, give it the name and linkage
2424 // of the alias, and delete the alias. This turns:
2425 // define internal ... @f(...)
2426 // @a = alias ... @f
2427 // into:
2428 // define ... @a(...)
2429 if (!Target->hasLocalLinkage())
2430 continue;
2431
2432 // The transform is only useful if the alias does not have internal linkage.
2433 if (J->hasLocalLinkage())
2434 continue;
2435
2436 // Do not perform the transform if multiple aliases potentially target the
2437 // aliasee. This check also ensures that it is safe to replace the section
2438 // and other attributes of the aliasee with those of the alias.
2439 if (!hasOneUse)
2440 continue;
2441
2442 // Give the aliasee the name, linkage and other attributes of the alias.
2443 Target->takeName(J);
2444 Target->setLinkage(J->getLinkage());
2445 Target->GlobalValue::copyAttributesFrom(J);
2446
2447 // Delete the alias.
2448 M.getAliasList().erase(J);
2449 ++NumAliasesRemoved;
2450 Changed = true;
2451 }
2452
2453 return Changed;
2454}
2455
2456bool GlobalOpt::runOnModule(Module &M) {
2457 bool Changed = false;
2458
2459 // Try to find the llvm.globalctors list.
2460 GlobalVariable *GlobalCtors = FindGlobalCtors(M);
2461
2462 bool LocalChange = true;
2463 while (LocalChange) {
2464 LocalChange = false;
2465
2466 // Delete functions that are trivially dead, ccc -> fastcc
2467 LocalChange |= OptimizeFunctions(M);
2468
2469 // Optimize global_ctors list.
2470 if (GlobalCtors)
2471 LocalChange |= OptimizeGlobalCtorsList(GlobalCtors);
2472
2473 // Optimize non-address-taken globals.
2474 LocalChange |= OptimizeGlobalVars(M);
2475
2476 // Resolve aliases, when possible.
2477 LocalChange |= OptimizeGlobalAliases(M);
2478 Changed |= LocalChange;
2479 }
2480
2481 // TODO: Move all global ctors functions to the end of the module for code
2482 // layout.
2483
2484 return Changed;
2485}
| 936
937 if (isa<LoadInst>(Inst) || isa<CmpInst>(Inst)) {
938 continue; // Fine, ignore.
939 }
940
941 if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
942 if (SI->getOperand(0) == V && SI->getOperand(1) != GV)
943 return false; // Storing the pointer itself... bad.
944 continue; // Otherwise, storing through it, or storing into GV... fine.
945 }
946
947 if (isa<GetElementPtrInst>(Inst)) {
948 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(Inst, GV, PHIs))
949 return false;
950 continue;
951 }
952
953 if (PHINode *PN = dyn_cast<PHINode>(Inst)) {
954 // PHIs are ok if all uses are ok. Don't infinitely recurse through PHI
955 // cycles.
956 if (PHIs.insert(PN))
957 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(PN, GV, PHIs))
958 return false;
959 continue;
960 }
961
962 if (BitCastInst *BCI = dyn_cast<BitCastInst>(Inst)) {
963 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(BCI, GV, PHIs))
964 return false;
965 continue;
966 }
967
968 return false;
969 }
970 return true;
971}
972
973/// ReplaceUsesOfMallocWithGlobal - The Alloc pointer is stored into GV
974/// somewhere. Transform all uses of the allocation into loads from the
975/// global and uses of the resultant pointer. Further, delete the store into
976/// GV. This assumes that these value pass the
977/// 'ValueIsOnlyUsedLocallyOrStoredToOneGlobal' predicate.
978static void ReplaceUsesOfMallocWithGlobal(Instruction *Alloc,
979 GlobalVariable *GV) {
980 while (!Alloc->use_empty()) {
981 Instruction *U = cast<Instruction>(*Alloc->use_begin());
982 Instruction *InsertPt = U;
983 if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
984 // If this is the store of the allocation into the global, remove it.
985 if (SI->getOperand(1) == GV) {
986 SI->eraseFromParent();
987 continue;
988 }
989 } else if (PHINode *PN = dyn_cast<PHINode>(U)) {
990 // Insert the load in the corresponding predecessor, not right before the
991 // PHI.
992 InsertPt = PN->getIncomingBlock(Alloc->use_begin())->getTerminator();
993 } else if (isa<BitCastInst>(U)) {
994 // Must be bitcast between the malloc and store to initialize the global.
995 ReplaceUsesOfMallocWithGlobal(U, GV);
996 U->eraseFromParent();
997 continue;
998 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(U)) {
999 // If this is a "GEP bitcast" and the user is a store to the global, then
1000 // just process it as a bitcast.
1001 if (GEPI->hasAllZeroIndices() && GEPI->hasOneUse())
1002 if (StoreInst *SI = dyn_cast<StoreInst>(GEPI->use_back()))
1003 if (SI->getOperand(1) == GV) {
1004 // Must be bitcast GEP between the malloc and store to initialize
1005 // the global.
1006 ReplaceUsesOfMallocWithGlobal(GEPI, GV);
1007 GEPI->eraseFromParent();
1008 continue;
1009 }
1010 }
1011
1012 // Insert a load from the global, and use it instead of the malloc.
1013 Value *NL = new LoadInst(GV, GV->getName()+".val", InsertPt);
1014 U->replaceUsesOfWith(Alloc, NL);
1015 }
1016}
1017
1018/// LoadUsesSimpleEnoughForHeapSRA - Verify that all uses of V (a load, or a phi
1019/// of a load) are simple enough to perform heap SRA on. This permits GEP's
1020/// that index through the array and struct field, icmps of null, and PHIs.
1021static bool LoadUsesSimpleEnoughForHeapSRA(Value *V,
1022 SmallPtrSet<PHINode*, 32> &LoadUsingPHIs,
1023 SmallPtrSet<PHINode*, 32> &LoadUsingPHIsPerLoad) {
1024 // We permit two users of the load: setcc comparing against the null
1025 // pointer, and a getelementptr of a specific form.
1026 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;++UI){
1027 Instruction *User = cast<Instruction>(*UI);
1028
1029 // Comparison against null is ok.
1030 if (ICmpInst *ICI = dyn_cast<ICmpInst>(User)) {
1031 if (!isa<ConstantPointerNull>(ICI->getOperand(1)))
1032 return false;
1033 continue;
1034 }
1035
1036 // getelementptr is also ok, but only a simple form.
1037 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
1038 // Must index into the array and into the struct.
1039 if (GEPI->getNumOperands() < 3)
1040 return false;
1041
1042 // Otherwise the GEP is ok.
1043 continue;
1044 }
1045
1046 if (PHINode *PN = dyn_cast<PHINode>(User)) {
1047 if (!LoadUsingPHIsPerLoad.insert(PN))
1048 // This means some phi nodes are dependent on each other.
1049 // Avoid infinite looping!
1050 return false;
1051 if (!LoadUsingPHIs.insert(PN))
1052 // If we have already analyzed this PHI, then it is safe.
1053 continue;
1054
1055 // Make sure all uses of the PHI are simple enough to transform.
1056 if (!LoadUsesSimpleEnoughForHeapSRA(PN,
1057 LoadUsingPHIs, LoadUsingPHIsPerLoad))
1058 return false;
1059
1060 continue;
1061 }
1062
1063 // Otherwise we don't know what this is, not ok.
1064 return false;
1065 }
1066
1067 return true;
1068}
1069
1070
1071/// AllGlobalLoadUsesSimpleEnoughForHeapSRA - If all users of values loaded from
1072/// GV are simple enough to perform HeapSRA, return true.
1073static bool AllGlobalLoadUsesSimpleEnoughForHeapSRA(GlobalVariable *GV,
1074 MallocInst *MI) {
1075 SmallPtrSet<PHINode*, 32> LoadUsingPHIs;
1076 SmallPtrSet<PHINode*, 32> LoadUsingPHIsPerLoad;
1077 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); UI != E;
1078 ++UI)
1079 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
1080 if (!LoadUsesSimpleEnoughForHeapSRA(LI, LoadUsingPHIs,
1081 LoadUsingPHIsPerLoad))
1082 return false;
1083 LoadUsingPHIsPerLoad.clear();
1084 }
1085
1086 // If we reach here, we know that all uses of the loads and transitive uses
1087 // (through PHI nodes) are simple enough to transform. However, we don't know
1088 // that all inputs the to the PHI nodes are in the same equivalence sets.
1089 // Check to verify that all operands of the PHIs are either PHIS that can be
1090 // transformed, loads from GV, or MI itself.
1091 for (SmallPtrSet<PHINode*, 32>::iterator I = LoadUsingPHIs.begin(),
1092 E = LoadUsingPHIs.end(); I != E; ++I) {
1093 PHINode *PN = *I;
1094 for (unsigned op = 0, e = PN->getNumIncomingValues(); op != e; ++op) {
1095 Value *InVal = PN->getIncomingValue(op);
1096
1097 // PHI of the stored value itself is ok.
1098 if (InVal == MI) continue;
1099
1100 if (PHINode *InPN = dyn_cast<PHINode>(InVal)) {
1101 // One of the PHIs in our set is (optimistically) ok.
1102 if (LoadUsingPHIs.count(InPN))
1103 continue;
1104 return false;
1105 }
1106
1107 // Load from GV is ok.
1108 if (LoadInst *LI = dyn_cast<LoadInst>(InVal))
1109 if (LI->getOperand(0) == GV)
1110 continue;
1111
1112 // UNDEF? NULL?
1113
1114 // Anything else is rejected.
1115 return false;
1116 }
1117 }
1118
1119 return true;
1120}
1121
1122static Value *GetHeapSROAValue(Value *V, unsigned FieldNo,
1123 DenseMap<Value*, std::vector<Value*> > &InsertedScalarizedValues,
1124 std::vector<std::pair<PHINode*, unsigned> > &PHIsToRewrite) {
1125 std::vector<Value*> &FieldVals = InsertedScalarizedValues[V];
1126
1127 if (FieldNo >= FieldVals.size())
1128 FieldVals.resize(FieldNo+1);
1129
1130 // If we already have this value, just reuse the previously scalarized
1131 // version.
1132 if (Value *FieldVal = FieldVals[FieldNo])
1133 return FieldVal;
1134
1135 // Depending on what instruction this is, we have several cases.
1136 Value *Result;
1137 if (LoadInst *LI = dyn_cast<LoadInst>(V)) {
1138 // This is a scalarized version of the load from the global. Just create
1139 // a new Load of the scalarized global.
1140 Result = new LoadInst(GetHeapSROAValue(LI->getOperand(0), FieldNo,
1141 InsertedScalarizedValues,
1142 PHIsToRewrite),
1143 LI->getName()+".f" + utostr(FieldNo), LI);
1144 } else if (PHINode *PN = dyn_cast<PHINode>(V)) {
1145 // PN's type is pointer to struct. Make a new PHI of pointer to struct
1146 // field.
1147 const StructType *ST =
1148 cast<StructType>(cast<PointerType>(PN->getType())->getElementType());
1149
1150 Result =PHINode::Create(PointerType::getUnqual(ST->getElementType(FieldNo)),
1151 PN->getName()+".f"+utostr(FieldNo), PN);
1152 PHIsToRewrite.push_back(std::make_pair(PN, FieldNo));
1153 } else {
1154 assert(0 && "Unknown usable value");
1155 Result = 0;
1156 }
1157
1158 return FieldVals[FieldNo] = Result;
1159}
1160
1161/// RewriteHeapSROALoadUser - Given a load instruction and a value derived from
1162/// the load, rewrite the derived value to use the HeapSRoA'd load.
1163static void RewriteHeapSROALoadUser(Instruction *LoadUser,
1164 DenseMap<Value*, std::vector<Value*> > &InsertedScalarizedValues,
1165 std::vector<std::pair<PHINode*, unsigned> > &PHIsToRewrite) {
1166 // If this is a comparison against null, handle it.
1167 if (ICmpInst *SCI = dyn_cast<ICmpInst>(LoadUser)) {
1168 assert(isa<ConstantPointerNull>(SCI->getOperand(1)));
1169 // If we have a setcc of the loaded pointer, we can use a setcc of any
1170 // field.
1171 Value *NPtr = GetHeapSROAValue(SCI->getOperand(0), 0,
1172 InsertedScalarizedValues, PHIsToRewrite);
1173
1174 Value *New = new ICmpInst(SCI->getPredicate(), NPtr,
1175 Constant::getNullValue(NPtr->getType()),
1176 SCI->getName(), SCI);
1177 SCI->replaceAllUsesWith(New);
1178 SCI->eraseFromParent();
1179 return;
1180 }
1181
1182 // Handle 'getelementptr Ptr, Idx, i32 FieldNo ...'
1183 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(LoadUser)) {
1184 assert(GEPI->getNumOperands() >= 3 && isa<ConstantInt>(GEPI->getOperand(2))
1185 && "Unexpected GEPI!");
1186
1187 // Load the pointer for this field.
1188 unsigned FieldNo = cast<ConstantInt>(GEPI->getOperand(2))->getZExtValue();
1189 Value *NewPtr = GetHeapSROAValue(GEPI->getOperand(0), FieldNo,
1190 InsertedScalarizedValues, PHIsToRewrite);
1191
1192 // Create the new GEP idx vector.
1193 SmallVector<Value*, 8> GEPIdx;
1194 GEPIdx.push_back(GEPI->getOperand(1));
1195 GEPIdx.append(GEPI->op_begin()+3, GEPI->op_end());
1196
1197 Value *NGEPI = GetElementPtrInst::Create(NewPtr,
1198 GEPIdx.begin(), GEPIdx.end(),
1199 GEPI->getName(), GEPI);
1200 GEPI->replaceAllUsesWith(NGEPI);
1201 GEPI->eraseFromParent();
1202 return;
1203 }
1204
1205 // Recursively transform the users of PHI nodes. This will lazily create the
1206 // PHIs that are needed for individual elements. Keep track of what PHIs we
1207 // see in InsertedScalarizedValues so that we don't get infinite loops (very
1208 // antisocial). If the PHI is already in InsertedScalarizedValues, it has
1209 // already been seen first by another load, so its uses have already been
1210 // processed.
1211 PHINode *PN = cast<PHINode>(LoadUser);
1212 bool Inserted;
1213 DenseMap<Value*, std::vector<Value*> >::iterator InsertPos;
1214 tie(InsertPos, Inserted) =
1215 InsertedScalarizedValues.insert(std::make_pair(PN, std::vector<Value*>()));
1216 if (!Inserted) return;
1217
1218 // If this is the first time we've seen this PHI, recursively process all
1219 // users.
1220 for (Value::use_iterator UI = PN->use_begin(), E = PN->use_end(); UI != E; ) {
1221 Instruction *User = cast<Instruction>(*UI++);
1222 RewriteHeapSROALoadUser(User, InsertedScalarizedValues, PHIsToRewrite);
1223 }
1224}
1225
1226/// RewriteUsesOfLoadForHeapSRoA - We are performing Heap SRoA on a global. Ptr
1227/// is a value loaded from the global. Eliminate all uses of Ptr, making them
1228/// use FieldGlobals instead. All uses of loaded values satisfy
1229/// AllGlobalLoadUsesSimpleEnoughForHeapSRA.
1230static void RewriteUsesOfLoadForHeapSRoA(LoadInst *Load,
1231 DenseMap<Value*, std::vector<Value*> > &InsertedScalarizedValues,
1232 std::vector<std::pair<PHINode*, unsigned> > &PHIsToRewrite) {
1233 for (Value::use_iterator UI = Load->use_begin(), E = Load->use_end();
1234 UI != E; ) {
1235 Instruction *User = cast<Instruction>(*UI++);
1236 RewriteHeapSROALoadUser(User, InsertedScalarizedValues, PHIsToRewrite);
1237 }
1238
1239 if (Load->use_empty()) {
1240 Load->eraseFromParent();
1241 InsertedScalarizedValues.erase(Load);
1242 }
1243}
1244
1245/// PerformHeapAllocSRoA - MI is an allocation of an array of structures. Break
1246/// it up into multiple allocations of arrays of the fields.
1247static GlobalVariable *PerformHeapAllocSRoA(GlobalVariable *GV, MallocInst *MI){
1248 DOUT << "SROA HEAP ALLOC: " << *GV << " MALLOC = " << *MI;
1249 const StructType *STy = cast<StructType>(MI->getAllocatedType());
1250
1251 // There is guaranteed to be at least one use of the malloc (storing
1252 // it into GV). If there are other uses, change them to be uses of
1253 // the global to simplify later code. This also deletes the store
1254 // into GV.
1255 ReplaceUsesOfMallocWithGlobal(MI, GV);
1256
1257 // Okay, at this point, there are no users of the malloc. Insert N
1258 // new mallocs at the same place as MI, and N globals.
1259 std::vector<Value*> FieldGlobals;
1260 std::vector<MallocInst*> FieldMallocs;
1261
1262 for (unsigned FieldNo = 0, e = STy->getNumElements(); FieldNo != e;++FieldNo){
1263 const Type *FieldTy = STy->getElementType(FieldNo);
1264 const Type *PFieldTy = PointerType::getUnqual(FieldTy);
1265
1266 GlobalVariable *NGV =
1267 new GlobalVariable(PFieldTy, false, GlobalValue::InternalLinkage,
1268 Constant::getNullValue(PFieldTy),
1269 GV->getName() + ".f" + utostr(FieldNo), GV,
1270 GV->isThreadLocal());
1271 FieldGlobals.push_back(NGV);
1272
1273 MallocInst *NMI = new MallocInst(FieldTy, MI->getArraySize(),
1274 MI->getName() + ".f" + utostr(FieldNo),MI);
1275 FieldMallocs.push_back(NMI);
1276 new StoreInst(NMI, NGV, MI);
1277 }
1278
1279 // The tricky aspect of this transformation is handling the case when malloc
1280 // fails. In the original code, malloc failing would set the result pointer
1281 // of malloc to null. In this case, some mallocs could succeed and others
1282 // could fail. As such, we emit code that looks like this:
1283 // F0 = malloc(field0)
1284 // F1 = malloc(field1)
1285 // F2 = malloc(field2)
1286 // if (F0 == 0 || F1 == 0 || F2 == 0) {
1287 // if (F0) { free(F0); F0 = 0; }
1288 // if (F1) { free(F1); F1 = 0; }
1289 // if (F2) { free(F2); F2 = 0; }
1290 // }
1291 Value *RunningOr = 0;
1292 for (unsigned i = 0, e = FieldMallocs.size(); i != e; ++i) {
1293 Value *Cond = new ICmpInst(ICmpInst::ICMP_EQ, FieldMallocs[i],
1294 Constant::getNullValue(FieldMallocs[i]->getType()),
1295 "isnull", MI);
1296 if (!RunningOr)
1297 RunningOr = Cond; // First seteq
1298 else
1299 RunningOr = BinaryOperator::CreateOr(RunningOr, Cond, "tmp", MI);
1300 }
1301
1302 // Split the basic block at the old malloc.
1303 BasicBlock *OrigBB = MI->getParent();
1304 BasicBlock *ContBB = OrigBB->splitBasicBlock(MI, "malloc_cont");
1305
1306 // Create the block to check the first condition. Put all these blocks at the
1307 // end of the function as they are unlikely to be executed.
1308 BasicBlock *NullPtrBlock = BasicBlock::Create("malloc_ret_null",
1309 OrigBB->getParent());
1310
1311 // Remove the uncond branch from OrigBB to ContBB, turning it into a cond
1312 // branch on RunningOr.
1313 OrigBB->getTerminator()->eraseFromParent();
1314 BranchInst::Create(NullPtrBlock, ContBB, RunningOr, OrigBB);
1315
1316 // Within the NullPtrBlock, we need to emit a comparison and branch for each
1317 // pointer, because some may be null while others are not.
1318 for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) {
1319 Value *GVVal = new LoadInst(FieldGlobals[i], "tmp", NullPtrBlock);
1320 Value *Cmp = new ICmpInst(ICmpInst::ICMP_NE, GVVal,
1321 Constant::getNullValue(GVVal->getType()),
1322 "tmp", NullPtrBlock);
1323 BasicBlock *FreeBlock = BasicBlock::Create("free_it", OrigBB->getParent());
1324 BasicBlock *NextBlock = BasicBlock::Create("next", OrigBB->getParent());
1325 BranchInst::Create(FreeBlock, NextBlock, Cmp, NullPtrBlock);
1326
1327 // Fill in FreeBlock.
1328 new FreeInst(GVVal, FreeBlock);
1329 new StoreInst(Constant::getNullValue(GVVal->getType()), FieldGlobals[i],
1330 FreeBlock);
1331 BranchInst::Create(NextBlock, FreeBlock);
1332
1333 NullPtrBlock = NextBlock;
1334 }
1335
1336 BranchInst::Create(ContBB, NullPtrBlock);
1337
1338 // MI is no longer needed, remove it.
1339 MI->eraseFromParent();
1340
1341 /// InsertedScalarizedLoads - As we process loads, if we can't immediately
1342 /// update all uses of the load, keep track of what scalarized loads are
1343 /// inserted for a given load.
1344 DenseMap<Value*, std::vector<Value*> > InsertedScalarizedValues;
1345 InsertedScalarizedValues[GV] = FieldGlobals;
1346
1347 std::vector<std::pair<PHINode*, unsigned> > PHIsToRewrite;
1348
1349 // Okay, the malloc site is completely handled. All of the uses of GV are now
1350 // loads, and all uses of those loads are simple. Rewrite them to use loads
1351 // of the per-field globals instead.
1352 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); UI != E;) {
1353 Instruction *User = cast<Instruction>(*UI++);
1354
1355 if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1356 RewriteUsesOfLoadForHeapSRoA(LI, InsertedScalarizedValues, PHIsToRewrite);
1357 continue;
1358 }
1359
1360 // Must be a store of null.
1361 StoreInst *SI = cast<StoreInst>(User);
1362 assert(isa<ConstantPointerNull>(SI->getOperand(0)) &&
1363 "Unexpected heap-sra user!");
1364
1365 // Insert a store of null into each global.
1366 for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) {
1367 const PointerType *PT = cast<PointerType>(FieldGlobals[i]->getType());
1368 Constant *Null = Constant::getNullValue(PT->getElementType());
1369 new StoreInst(Null, FieldGlobals[i], SI);
1370 }
1371 // Erase the original store.
1372 SI->eraseFromParent();
1373 }
1374
1375 // While we have PHIs that are interesting to rewrite, do it.
1376 while (!PHIsToRewrite.empty()) {
1377 PHINode *PN = PHIsToRewrite.back().first;
1378 unsigned FieldNo = PHIsToRewrite.back().second;
1379 PHIsToRewrite.pop_back();
1380 PHINode *FieldPN = cast<PHINode>(InsertedScalarizedValues[PN][FieldNo]);
1381 assert(FieldPN->getNumIncomingValues() == 0 &&"Already processed this phi");
1382
1383 // Add all the incoming values. This can materialize more phis.
1384 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
1385 Value *InVal = PN->getIncomingValue(i);
1386 InVal = GetHeapSROAValue(InVal, FieldNo, InsertedScalarizedValues,
1387 PHIsToRewrite);
1388 FieldPN->addIncoming(InVal, PN->getIncomingBlock(i));
1389 }
1390 }
1391
1392 // Drop all inter-phi links and any loads that made it this far.
1393 for (DenseMap<Value*, std::vector<Value*> >::iterator
1394 I = InsertedScalarizedValues.begin(), E = InsertedScalarizedValues.end();
1395 I != E; ++I) {
1396 if (PHINode *PN = dyn_cast<PHINode>(I->first))
1397 PN->dropAllReferences();
1398 else if (LoadInst *LI = dyn_cast<LoadInst>(I->first))
1399 LI->dropAllReferences();
1400 }
1401
1402 // Delete all the phis and loads now that inter-references are dead.
1403 for (DenseMap<Value*, std::vector<Value*> >::iterator
1404 I = InsertedScalarizedValues.begin(), E = InsertedScalarizedValues.end();
1405 I != E; ++I) {
1406 if (PHINode *PN = dyn_cast<PHINode>(I->first))
1407 PN->eraseFromParent();
1408 else if (LoadInst *LI = dyn_cast<LoadInst>(I->first))
1409 LI->eraseFromParent();
1410 }
1411
1412 // The old global is now dead, remove it.
1413 GV->eraseFromParent();
1414
1415 ++NumHeapSRA;
1416 return cast<GlobalVariable>(FieldGlobals[0]);
1417}
1418
1419/// TryToOptimizeStoreOfMallocToGlobal - This function is called when we see a
1420/// pointer global variable with a single value stored it that is a malloc or
1421/// cast of malloc.
1422static bool TryToOptimizeStoreOfMallocToGlobal(GlobalVariable *GV,
1423 MallocInst *MI,
1424 Module::global_iterator &GVI,
1425 TargetData &TD) {
1426 // If this is a malloc of an abstract type, don't touch it.
1427 if (!MI->getAllocatedType()->isSized())
1428 return false;
1429
1430 // We can't optimize this global unless all uses of it are *known* to be
1431 // of the malloc value, not of the null initializer value (consider a use
1432 // that compares the global's value against zero to see if the malloc has
1433 // been reached). To do this, we check to see if all uses of the global
1434 // would trap if the global were null: this proves that they must all
1435 // happen after the malloc.
1436 if (!AllUsesOfLoadedValueWillTrapIfNull(GV))
1437 return false;
1438
1439 // We can't optimize this if the malloc itself is used in a complex way,
1440 // for example, being stored into multiple globals. This allows the
1441 // malloc to be stored into the specified global, loaded setcc'd, and
1442 // GEP'd. These are all things we could transform to using the global
1443 // for.
1444 {
1445 SmallPtrSet<PHINode*, 8> PHIs;
1446 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(MI, GV, PHIs))
1447 return false;
1448 }
1449
1450
1451 // If we have a global that is only initialized with a fixed size malloc,
1452 // transform the program to use global memory instead of malloc'd memory.
1453 // This eliminates dynamic allocation, avoids an indirection accessing the
1454 // data, and exposes the resultant global to further GlobalOpt.
1455 if (ConstantInt *NElements = dyn_cast<ConstantInt>(MI->getArraySize())) {
1456 // Restrict this transformation to only working on small allocations
1457 // (2048 bytes currently), as we don't want to introduce a 16M global or
1458 // something.
1459 if (NElements->getZExtValue()*
1460 TD.getTypeAllocSize(MI->getAllocatedType()) < 2048) {
1461 GVI = OptimizeGlobalAddressOfMalloc(GV, MI);
1462 return true;
1463 }
1464 }
1465
1466 // If the allocation is an array of structures, consider transforming this
1467 // into multiple malloc'd arrays, one for each field. This is basically
1468 // SRoA for malloc'd memory.
1469 const Type *AllocTy = MI->getAllocatedType();
1470
1471 // If this is an allocation of a fixed size array of structs, analyze as a
1472 // variable size array. malloc [100 x struct],1 -> malloc struct, 100
1473 if (!MI->isArrayAllocation())
1474 if (const ArrayType *AT = dyn_cast<ArrayType>(AllocTy))
1475 AllocTy = AT->getElementType();
1476
1477 if (const StructType *AllocSTy = dyn_cast<StructType>(AllocTy)) {
1478 // This the structure has an unreasonable number of fields, leave it
1479 // alone.
1480 if (AllocSTy->getNumElements() <= 16 && AllocSTy->getNumElements() != 0 &&
1481 AllGlobalLoadUsesSimpleEnoughForHeapSRA(GV, MI)) {
1482
1483 // If this is a fixed size array, transform the Malloc to be an alloc of
1484 // structs. malloc [100 x struct],1 -> malloc struct, 100
1485 if (const ArrayType *AT = dyn_cast<ArrayType>(MI->getAllocatedType())) {
1486 MallocInst *NewMI =
1487 new MallocInst(AllocSTy,
1488 ConstantInt::get(Type::Int32Ty, AT->getNumElements()),
1489 "", MI);
1490 NewMI->takeName(MI);
1491 Value *Cast = new BitCastInst(NewMI, MI->getType(), "tmp", MI);
1492 MI->replaceAllUsesWith(Cast);
1493 MI->eraseFromParent();
1494 MI = NewMI;
1495 }
1496
1497 GVI = PerformHeapAllocSRoA(GV, MI);
1498 return true;
1499 }
1500 }
1501
1502 return false;
1503}
1504
1505// OptimizeOnceStoredGlobal - Try to optimize globals based on the knowledge
1506// that only one value (besides its initializer) is ever stored to the global.
1507static bool OptimizeOnceStoredGlobal(GlobalVariable *GV, Value *StoredOnceVal,
1508 Module::global_iterator &GVI,
1509 TargetData &TD) {
1510 // Ignore no-op GEPs and bitcasts.
1511 StoredOnceVal = StoredOnceVal->stripPointerCasts();
1512
1513 // If we are dealing with a pointer global that is initialized to null and
1514 // only has one (non-null) value stored into it, then we can optimize any
1515 // users of the loaded value (often calls and loads) that would trap if the
1516 // value was null.
1517 if (isa<PointerType>(GV->getInitializer()->getType()) &&
1518 GV->getInitializer()->isNullValue()) {
1519 if (Constant *SOVC = dyn_cast<Constant>(StoredOnceVal)) {
1520 if (GV->getInitializer()->getType() != SOVC->getType())
1521 SOVC = ConstantExpr::getBitCast(SOVC, GV->getInitializer()->getType());
1522
1523 // Optimize away any trapping uses of the loaded value.
1524 if (OptimizeAwayTrappingUsesOfLoads(GV, SOVC))
1525 return true;
1526 } else if (MallocInst *MI = dyn_cast<MallocInst>(StoredOnceVal)) {
1527 if (TryToOptimizeStoreOfMallocToGlobal(GV, MI, GVI, TD))
1528 return true;
1529 }
1530 }
1531
1532 return false;
1533}
1534
1535/// TryToShrinkGlobalToBoolean - At this point, we have learned that the only
1536/// two values ever stored into GV are its initializer and OtherVal. See if we
1537/// can shrink the global into a boolean and select between the two values
1538/// whenever it is used. This exposes the values to other scalar optimizations.
1539static bool TryToShrinkGlobalToBoolean(GlobalVariable *GV, Constant *OtherVal) {
1540 const Type *GVElType = GV->getType()->getElementType();
1541
1542 // If GVElType is already i1, it is already shrunk. If the type of the GV is
1543 // an FP value, pointer or vector, don't do this optimization because a select
1544 // between them is very expensive and unlikely to lead to later
1545 // simplification. In these cases, we typically end up with "cond ? v1 : v2"
1546 // where v1 and v2 both require constant pool loads, a big loss.
1547 if (GVElType == Type::Int1Ty || GVElType->isFloatingPoint() ||
1548 isa<PointerType>(GVElType) || isa<VectorType>(GVElType))
1549 return false;
1550
1551 // Walk the use list of the global seeing if all the uses are load or store.
1552 // If there is anything else, bail out.
1553 for (Value::use_iterator I = GV->use_begin(), E = GV->use_end(); I != E; ++I)
1554 if (!isa<LoadInst>(I) && !isa<StoreInst>(I))
1555 return false;
1556
1557 DOUT << " *** SHRINKING TO BOOL: " << *GV;
1558
1559 // Create the new global, initializing it to false.
1560 GlobalVariable *NewGV = new GlobalVariable(Type::Int1Ty, false,
1561 GlobalValue::InternalLinkage, ConstantInt::getFalse(),
1562 GV->getName()+".b",
1563 (Module *)NULL,
1564 GV->isThreadLocal());
1565 GV->getParent()->getGlobalList().insert(GV, NewGV);
1566
1567 Constant *InitVal = GV->getInitializer();
1568 assert(InitVal->getType() != Type::Int1Ty && "No reason to shrink to bool!");
1569
1570 // If initialized to zero and storing one into the global, we can use a cast
1571 // instead of a select to synthesize the desired value.
1572 bool IsOneZero = false;
1573 if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal))
1574 IsOneZero = InitVal->isNullValue() && CI->isOne();
1575
1576 while (!GV->use_empty()) {
1577 Instruction *UI = cast<Instruction>(GV->use_back());
1578 if (StoreInst *SI = dyn_cast<StoreInst>(UI)) {
1579 // Change the store into a boolean store.
1580 bool StoringOther = SI->getOperand(0) == OtherVal;
1581 // Only do this if we weren't storing a loaded value.
1582 Value *StoreVal;
1583 if (StoringOther || SI->getOperand(0) == InitVal)
1584 StoreVal = ConstantInt::get(Type::Int1Ty, StoringOther);
1585 else {
1586 // Otherwise, we are storing a previously loaded copy. To do this,
1587 // change the copy from copying the original value to just copying the
1588 // bool.
1589 Instruction *StoredVal = cast<Instruction>(SI->getOperand(0));
1590
1591 // If we're already replaced the input, StoredVal will be a cast or
1592 // select instruction. If not, it will be a load of the original
1593 // global.
1594 if (LoadInst *LI = dyn_cast<LoadInst>(StoredVal)) {
1595 assert(LI->getOperand(0) == GV && "Not a copy!");
1596 // Insert a new load, to preserve the saved value.
1597 StoreVal = new LoadInst(NewGV, LI->getName()+".b", LI);
1598 } else {
1599 assert((isa<CastInst>(StoredVal) || isa<SelectInst>(StoredVal)) &&
1600 "This is not a form that we understand!");
1601 StoreVal = StoredVal->getOperand(0);
1602 assert(isa<LoadInst>(StoreVal) && "Not a load of NewGV!");
1603 }
1604 }
1605 new StoreInst(StoreVal, NewGV, SI);
1606 } else {
1607 // Change the load into a load of bool then a select.
1608 LoadInst *LI = cast<LoadInst>(UI);
1609 LoadInst *NLI = new LoadInst(NewGV, LI->getName()+".b", LI);
1610 Value *NSI;
1611 if (IsOneZero)
1612 NSI = new ZExtInst(NLI, LI->getType(), "", LI);
1613 else
1614 NSI = SelectInst::Create(NLI, OtherVal, InitVal, "", LI);
1615 NSI->takeName(LI);
1616 LI->replaceAllUsesWith(NSI);
1617 }
1618 UI->eraseFromParent();
1619 }
1620
1621 GV->eraseFromParent();
1622 return true;
1623}
1624
1625
1626/// ProcessInternalGlobal - Analyze the specified global variable and optimize
1627/// it if possible. If we make a change, return true.
1628bool GlobalOpt::ProcessInternalGlobal(GlobalVariable *GV,
1629 Module::global_iterator &GVI) {
1630 SmallPtrSet<PHINode*, 16> PHIUsers;
1631 GlobalStatus GS;
1632 GV->removeDeadConstantUsers();
1633
1634 if (GV->use_empty()) {
1635 DOUT << "GLOBAL DEAD: " << *GV;
1636 GV->eraseFromParent();
1637 ++NumDeleted;
1638 return true;
1639 }
1640
1641 if (!AnalyzeGlobal(GV, GS, PHIUsers)) {
1642#if 0
1643 cerr << "Global: " << *GV;
1644 cerr << " isLoaded = " << GS.isLoaded << "\n";
1645 cerr << " StoredType = ";
1646 switch (GS.StoredType) {
1647 case GlobalStatus::NotStored: cerr << "NEVER STORED\n"; break;
1648 case GlobalStatus::isInitializerStored: cerr << "INIT STORED\n"; break;
1649 case GlobalStatus::isStoredOnce: cerr << "STORED ONCE\n"; break;
1650 case GlobalStatus::isStored: cerr << "stored\n"; break;
1651 }
1652 if (GS.StoredType == GlobalStatus::isStoredOnce && GS.StoredOnceValue)
1653 cerr << " StoredOnceValue = " << *GS.StoredOnceValue << "\n";
1654 if (GS.AccessingFunction && !GS.HasMultipleAccessingFunctions)
1655 cerr << " AccessingFunction = " << GS.AccessingFunction->getName()
1656 << "\n";
1657 cerr << " HasMultipleAccessingFunctions = "
1658 << GS.HasMultipleAccessingFunctions << "\n";
1659 cerr << " HasNonInstructionUser = " << GS.HasNonInstructionUser<<"\n";
1660 cerr << "\n";
1661#endif
1662
1663 // If this is a first class global and has only one accessing function
1664 // and this function is main (which we know is not recursive we can make
1665 // this global a local variable) we replace the global with a local alloca
1666 // in this function.
1667 //
1668 // NOTE: It doesn't make sense to promote non single-value types since we
1669 // are just replacing static memory to stack memory.
1670 if (!GS.HasMultipleAccessingFunctions &&
1671 GS.AccessingFunction && !GS.HasNonInstructionUser &&
1672 GV->getType()->getElementType()->isSingleValueType() &&
1673 GS.AccessingFunction->getName() == "main" &&
1674 GS.AccessingFunction->hasExternalLinkage()) {
1675 DOUT << "LOCALIZING GLOBAL: " << *GV;
1676 Instruction* FirstI = GS.AccessingFunction->getEntryBlock().begin();
1677 const Type* ElemTy = GV->getType()->getElementType();
1678 // FIXME: Pass Global's alignment when globals have alignment
1679 AllocaInst* Alloca = new AllocaInst(ElemTy, NULL, GV->getName(), FirstI);
1680 if (!isa<UndefValue>(GV->getInitializer()))
1681 new StoreInst(GV->getInitializer(), Alloca, FirstI);
1682
1683 GV->replaceAllUsesWith(Alloca);
1684 GV->eraseFromParent();
1685 ++NumLocalized;
1686 return true;
1687 }
1688
1689 // If the global is never loaded (but may be stored to), it is dead.
1690 // Delete it now.
1691 if (!GS.isLoaded) {
1692 DOUT << "GLOBAL NEVER LOADED: " << *GV;
1693
1694 // Delete any stores we can find to the global. We may not be able to
1695 // make it completely dead though.
1696 bool Changed = CleanupConstantGlobalUsers(GV, GV->getInitializer());
1697
1698 // If the global is dead now, delete it.
1699 if (GV->use_empty()) {
1700 GV->eraseFromParent();
1701 ++NumDeleted;
1702 Changed = true;
1703 }
1704 return Changed;
1705
1706 } else if (GS.StoredType <= GlobalStatus::isInitializerStored) {
1707 DOUT << "MARKING CONSTANT: " << *GV;
1708 GV->setConstant(true);
1709
1710 // Clean up any obviously simplifiable users now.
1711 CleanupConstantGlobalUsers(GV, GV->getInitializer());
1712
1713 // If the global is dead now, just nuke it.
1714 if (GV->use_empty()) {
1715 DOUT << " *** Marking constant allowed us to simplify "
1716 << "all users and delete global!\n";
1717 GV->eraseFromParent();
1718 ++NumDeleted;
1719 }
1720
1721 ++NumMarked;
1722 return true;
1723 } else if (!GV->getInitializer()->getType()->isSingleValueType()) {
1724 if (GlobalVariable *FirstNewGV = SRAGlobal(GV,
1725 getAnalysis<TargetData>())) {
1726 GVI = FirstNewGV; // Don't skip the newly produced globals!
1727 return true;
1728 }
1729 } else if (GS.StoredType == GlobalStatus::isStoredOnce) {
1730 // If the initial value for the global was an undef value, and if only
1731 // one other value was stored into it, we can just change the
1732 // initializer to be the stored value, then delete all stores to the
1733 // global. This allows us to mark it constant.
1734 if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue))
1735 if (isa<UndefValue>(GV->getInitializer())) {
1736 // Change the initial value here.
1737 GV->setInitializer(SOVConstant);
1738
1739 // Clean up any obviously simplifiable users now.
1740 CleanupConstantGlobalUsers(GV, GV->getInitializer());
1741
1742 if (GV->use_empty()) {
1743 DOUT << " *** Substituting initializer allowed us to "
1744 << "simplify all users and delete global!\n";
1745 GV->eraseFromParent();
1746 ++NumDeleted;
1747 } else {
1748 GVI = GV;
1749 }
1750 ++NumSubstitute;
1751 return true;
1752 }
1753
1754 // Try to optimize globals based on the knowledge that only one value
1755 // (besides its initializer) is ever stored to the global.
1756 if (OptimizeOnceStoredGlobal(GV, GS.StoredOnceValue, GVI,
1757 getAnalysis<TargetData>()))
1758 return true;
1759
1760 // Otherwise, if the global was not a boolean, we can shrink it to be a
1761 // boolean.
1762 if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue))
1763 if (TryToShrinkGlobalToBoolean(GV, SOVConstant)) {
1764 ++NumShrunkToBool;
1765 return true;
1766 }
1767 }
1768 }
1769 return false;
1770}
1771
1772/// OnlyCalledDirectly - Return true if the specified function is only called
1773/// directly. In other words, its address is never taken.
1774static bool OnlyCalledDirectly(Function *F) {
1775 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){
1776 Instruction *User = dyn_cast<Instruction>(*UI);
1777 if (!User) return false;
1778 if (!isa<CallInst>(User) && !isa<InvokeInst>(User)) return false;
1779
1780 // See if the function address is passed as an argument.
1781 for (User::op_iterator i = User->op_begin() + 1, e = User->op_end();
1782 i != e; ++i)
1783 if (*i == F) return false;
1784 }
1785 return true;
1786}
1787
1788/// ChangeCalleesToFastCall - Walk all of the direct calls of the specified
1789/// function, changing them to FastCC.
1790static void ChangeCalleesToFastCall(Function *F) {
1791 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){
1792 CallSite User(cast<Instruction>(*UI));
1793 User.setCallingConv(CallingConv::Fast);
1794 }
1795}
1796
1797static AttrListPtr StripNest(const AttrListPtr &Attrs) {
1798 for (unsigned i = 0, e = Attrs.getNumSlots(); i != e; ++i) {
1799 if ((Attrs.getSlot(i).Attrs & Attribute::Nest) == 0)
1800 continue;
1801
1802 // There can be only one.
1803 return Attrs.removeAttr(Attrs.getSlot(i).Index, Attribute::Nest);
1804 }
1805
1806 return Attrs;
1807}
1808
1809static void RemoveNestAttribute(Function *F) {
1810 F->setAttributes(StripNest(F->getAttributes()));
1811 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){
1812 CallSite User(cast<Instruction>(*UI));
1813 User.setAttributes(StripNest(User.getAttributes()));
1814 }
1815}
1816
1817bool GlobalOpt::OptimizeFunctions(Module &M) {
1818 bool Changed = false;
1819 // Optimize functions.
1820 for (Module::iterator FI = M.begin(), E = M.end(); FI != E; ) {
1821 Function *F = FI++;
1822 // Functions without names cannot be referenced outside this module.
1823 if (!F->hasName() && !F->isDeclaration())
1824 F->setLinkage(GlobalValue::InternalLinkage);
1825 F->removeDeadConstantUsers();
1826 if (F->use_empty() && (F->hasLocalLinkage() ||
1827 F->hasLinkOnceLinkage())) {
1828 M.getFunctionList().erase(F);
1829 Changed = true;
1830 ++NumFnDeleted;
1831 } else if (F->hasLocalLinkage()) {
1832 if (F->getCallingConv() == CallingConv::C && !F->isVarArg() &&
1833 OnlyCalledDirectly(F)) {
1834 // If this function has C calling conventions, is not a varargs
1835 // function, and is only called directly, promote it to use the Fast
1836 // calling convention.
1837 F->setCallingConv(CallingConv::Fast);
1838 ChangeCalleesToFastCall(F);
1839 ++NumFastCallFns;
1840 Changed = true;
1841 }
1842
1843 if (F->getAttributes().hasAttrSomewhere(Attribute::Nest) &&
1844 OnlyCalledDirectly(F)) {
1845 // The function is not used by a trampoline intrinsic, so it is safe
1846 // to remove the 'nest' attribute.
1847 RemoveNestAttribute(F);
1848 ++NumNestRemoved;
1849 Changed = true;
1850 }
1851 }
1852 }
1853 return Changed;
1854}
1855
1856bool GlobalOpt::OptimizeGlobalVars(Module &M) {
1857 bool Changed = false;
1858 for (Module::global_iterator GVI = M.global_begin(), E = M.global_end();
1859 GVI != E; ) {
1860 GlobalVariable *GV = GVI++;
1861 // Global variables without names cannot be referenced outside this module.
1862 if (!GV->hasName() && !GV->isDeclaration())
1863 GV->setLinkage(GlobalValue::InternalLinkage);
1864 if (!GV->isConstant() && GV->hasLocalLinkage() &&
1865 GV->hasInitializer())
1866 Changed |= ProcessInternalGlobal(GV, GVI);
1867 }
1868 return Changed;
1869}
1870
1871/// FindGlobalCtors - Find the llvm.globalctors list, verifying that all
1872/// initializers have an init priority of 65535.
1873GlobalVariable *GlobalOpt::FindGlobalCtors(Module &M) {
1874 for (Module::global_iterator I = M.global_begin(), E = M.global_end();
1875 I != E; ++I)
1876 if (I->getName() == "llvm.global_ctors") {
1877 // Found it, verify it's an array of { int, void()* }.
1878 const ArrayType *ATy =dyn_cast<ArrayType>(I->getType()->getElementType());
1879 if (!ATy) return 0;
1880 const StructType *STy = dyn_cast<StructType>(ATy->getElementType());
1881 if (!STy || STy->getNumElements() != 2 ||
1882 STy->getElementType(0) != Type::Int32Ty) return 0;
1883 const PointerType *PFTy = dyn_cast<PointerType>(STy->getElementType(1));
1884 if (!PFTy) return 0;
1885 const FunctionType *FTy = dyn_cast<FunctionType>(PFTy->getElementType());
1886 if (!FTy || FTy->getReturnType() != Type::VoidTy || FTy->isVarArg() ||
1887 FTy->getNumParams() != 0)
1888 return 0;
1889
1890 // Verify that the initializer is simple enough for us to handle.
1891 if (!I->hasInitializer()) return 0;
1892 ConstantArray *CA = dyn_cast<ConstantArray>(I->getInitializer());
1893 if (!CA) return 0;
1894 for (User::op_iterator i = CA->op_begin(), e = CA->op_end(); i != e; ++i)
1895 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(*i)) {
1896 if (isa<ConstantPointerNull>(CS->getOperand(1)))
1897 continue;
1898
1899 // Must have a function or null ptr.
1900 if (!isa<Function>(CS->getOperand(1)))
1901 return 0;
1902
1903 // Init priority must be standard.
1904 ConstantInt *CI = dyn_cast<ConstantInt>(CS->getOperand(0));
1905 if (!CI || CI->getZExtValue() != 65535)
1906 return 0;
1907 } else {
1908 return 0;
1909 }
1910
1911 return I;
1912 }
1913 return 0;
1914}
1915
1916/// ParseGlobalCtors - Given a llvm.global_ctors list that we can understand,
1917/// return a list of the functions and null terminator as a vector.
1918static std::vector<Function*> ParseGlobalCtors(GlobalVariable *GV) {
1919 ConstantArray *CA = cast<ConstantArray>(GV->getInitializer());
1920 std::vector<Function*> Result;
1921 Result.reserve(CA->getNumOperands());
1922 for (User::op_iterator i = CA->op_begin(), e = CA->op_end(); i != e; ++i) {
1923 ConstantStruct *CS = cast<ConstantStruct>(*i);
1924 Result.push_back(dyn_cast<Function>(CS->getOperand(1)));
1925 }
1926 return Result;
1927}
1928
1929/// InstallGlobalCtors - Given a specified llvm.global_ctors list, install the
1930/// specified array, returning the new global to use.
1931static GlobalVariable *InstallGlobalCtors(GlobalVariable *GCL,
1932 const std::vector<Function*> &Ctors) {
1933 // If we made a change, reassemble the initializer list.
1934 std::vector<Constant*> CSVals;
1935 CSVals.push_back(ConstantInt::get(Type::Int32Ty, 65535));
1936 CSVals.push_back(0);
1937
1938 // Create the new init list.
1939 std::vector<Constant*> CAList;
1940 for (unsigned i = 0, e = Ctors.size(); i != e; ++i) {
1941 if (Ctors[i]) {
1942 CSVals[1] = Ctors[i];
1943 } else {
1944 const Type *FTy = FunctionType::get(Type::VoidTy,
1945 std::vector<const Type*>(), false);
1946 const PointerType *PFTy = PointerType::getUnqual(FTy);
1947 CSVals[1] = Constant::getNullValue(PFTy);
1948 CSVals[0] = ConstantInt::get(Type::Int32Ty, 2147483647);
1949 }
1950 CAList.push_back(ConstantStruct::get(CSVals));
1951 }
1952
1953 // Create the array initializer.
1954 const Type *StructTy =
1955 cast<ArrayType>(GCL->getType()->getElementType())->getElementType();
1956 Constant *CA = ConstantArray::get(ArrayType::get(StructTy, CAList.size()),
1957 CAList);
1958
1959 // If we didn't change the number of elements, don't create a new GV.
1960 if (CA->getType() == GCL->getInitializer()->getType()) {
1961 GCL->setInitializer(CA);
1962 return GCL;
1963 }
1964
1965 // Create the new global and insert it next to the existing list.
1966 GlobalVariable *NGV = new GlobalVariable(CA->getType(), GCL->isConstant(),
1967 GCL->getLinkage(), CA, "",
1968 (Module *)NULL,
1969 GCL->isThreadLocal());
1970 GCL->getParent()->getGlobalList().insert(GCL, NGV);
1971 NGV->takeName(GCL);
1972
1973 // Nuke the old list, replacing any uses with the new one.
1974 if (!GCL->use_empty()) {
1975 Constant *V = NGV;
1976 if (V->getType() != GCL->getType())
1977 V = ConstantExpr::getBitCast(V, GCL->getType());
1978 GCL->replaceAllUsesWith(V);
1979 }
1980 GCL->eraseFromParent();
1981
1982 if (Ctors.size())
1983 return NGV;
1984 else
1985 return 0;
1986}
1987
1988
1989static Constant *getVal(DenseMap<Value*, Constant*> &ComputedValues,
1990 Value *V) {
1991 if (Constant *CV = dyn_cast<Constant>(V)) return CV;
1992 Constant *R = ComputedValues[V];
1993 assert(R && "Reference to an uncomputed value!");
1994 return R;
1995}
1996
1997/// isSimpleEnoughPointerToCommit - Return true if this constant is simple
1998/// enough for us to understand. In particular, if it is a cast of something,
1999/// we punt. We basically just support direct accesses to globals and GEP's of
2000/// globals. This should be kept up to date with CommitValueTo.
2001static bool isSimpleEnoughPointerToCommit(Constant *C) {
2002 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C)) {
2003 if (!GV->hasExternalLinkage() && !GV->hasLocalLinkage())
2004 return false; // do not allow weak/linkonce/dllimport/dllexport linkage.
2005 return !GV->isDeclaration(); // reject external globals.
2006 }
2007 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
2008 // Handle a constantexpr gep.
2009 if (CE->getOpcode() == Instruction::GetElementPtr &&
2010 isa<GlobalVariable>(CE->getOperand(0))) {
2011 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
2012 if (!GV->hasExternalLinkage() && !GV->hasLocalLinkage())
2013 return false; // do not allow weak/linkonce/dllimport/dllexport linkage.
2014 return GV->hasInitializer() &&
2015 ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE);
2016 }
2017 return false;
2018}
2019
2020/// EvaluateStoreInto - Evaluate a piece of a constantexpr store into a global
2021/// initializer. This returns 'Init' modified to reflect 'Val' stored into it.
2022/// At this point, the GEP operands of Addr [0, OpNo) have been stepped into.
2023static Constant *EvaluateStoreInto(Constant *Init, Constant *Val,
2024 ConstantExpr *Addr, unsigned OpNo) {
2025 // Base case of the recursion.
2026 if (OpNo == Addr->getNumOperands()) {
2027 assert(Val->getType() == Init->getType() && "Type mismatch!");
2028 return Val;
2029 }
2030
2031 if (const StructType *STy = dyn_cast<StructType>(Init->getType())) {
2032 std::vector<Constant*> Elts;
2033
2034 // Break up the constant into its elements.
2035 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(Init)) {
2036 for (User::op_iterator i = CS->op_begin(), e = CS->op_end(); i != e; ++i)
2037 Elts.push_back(cast<Constant>(*i));
2038 } else if (isa<ConstantAggregateZero>(Init)) {
2039 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
2040 Elts.push_back(Constant::getNullValue(STy->getElementType(i)));
2041 } else if (isa<UndefValue>(Init)) {
2042 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
2043 Elts.push_back(UndefValue::get(STy->getElementType(i)));
2044 } else {
2045 assert(0 && "This code is out of sync with "
2046 " ConstantFoldLoadThroughGEPConstantExpr");
2047 }
2048
2049 // Replace the element that we are supposed to.
2050 ConstantInt *CU = cast<ConstantInt>(Addr->getOperand(OpNo));
2051 unsigned Idx = CU->getZExtValue();
2052 assert(Idx < STy->getNumElements() && "Struct index out of range!");
2053 Elts[Idx] = EvaluateStoreInto(Elts[Idx], Val, Addr, OpNo+1);
2054
2055 // Return the modified struct.
2056 return ConstantStruct::get(&Elts[0], Elts.size(), STy->isPacked());
2057 } else {
2058 ConstantInt *CI = cast<ConstantInt>(Addr->getOperand(OpNo));
2059 const ArrayType *ATy = cast<ArrayType>(Init->getType());
2060
2061 // Break up the array into elements.
2062 std::vector<Constant*> Elts;
2063 if (ConstantArray *CA = dyn_cast<ConstantArray>(Init)) {
2064 for (User::op_iterator i = CA->op_begin(), e = CA->op_end(); i != e; ++i)
2065 Elts.push_back(cast<Constant>(*i));
2066 } else if (isa<ConstantAggregateZero>(Init)) {
2067 Constant *Elt = Constant::getNullValue(ATy->getElementType());
2068 Elts.assign(ATy->getNumElements(), Elt);
2069 } else if (isa<UndefValue>(Init)) {
2070 Constant *Elt = UndefValue::get(ATy->getElementType());
2071 Elts.assign(ATy->getNumElements(), Elt);
2072 } else {
2073 assert(0 && "This code is out of sync with "
2074 " ConstantFoldLoadThroughGEPConstantExpr");
2075 }
2076
2077 assert(CI->getZExtValue() < ATy->getNumElements());
2078 Elts[CI->getZExtValue()] =
2079 EvaluateStoreInto(Elts[CI->getZExtValue()], Val, Addr, OpNo+1);
2080 return ConstantArray::get(ATy, Elts);
2081 }
2082}
2083
2084/// CommitValueTo - We have decided that Addr (which satisfies the predicate
2085/// isSimpleEnoughPointerToCommit) should get Val as its value. Make it happen.
2086static void CommitValueTo(Constant *Val, Constant *Addr) {
2087 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Addr)) {
2088 assert(GV->hasInitializer());
2089 GV->setInitializer(Val);
2090 return;
2091 }
2092
2093 ConstantExpr *CE = cast<ConstantExpr>(Addr);
2094 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
2095
2096 Constant *Init = GV->getInitializer();
2097 Init = EvaluateStoreInto(Init, Val, CE, 2);
2098 GV->setInitializer(Init);
2099}
2100
2101/// ComputeLoadResult - Return the value that would be computed by a load from
2102/// P after the stores reflected by 'memory' have been performed. If we can't
2103/// decide, return null.
2104static Constant *ComputeLoadResult(Constant *P,
2105 const DenseMap<Constant*, Constant*> &Memory) {
2106 // If this memory location has been recently stored, use the stored value: it
2107 // is the most up-to-date.
2108 DenseMap<Constant*, Constant*>::const_iterator I = Memory.find(P);
2109 if (I != Memory.end()) return I->second;
2110
2111 // Access it.
2112 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(P)) {
2113 if (GV->hasInitializer())
2114 return GV->getInitializer();
2115 return 0;
2116 }
2117
2118 // Handle a constantexpr getelementptr.
2119 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(P))
2120 if (CE->getOpcode() == Instruction::GetElementPtr &&
2121 isa<GlobalVariable>(CE->getOperand(0))) {
2122 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
2123 if (GV->hasInitializer())
2124 return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE);
2125 }
2126
2127 return 0; // don't know how to evaluate.
2128}
2129
2130/// EvaluateFunction - Evaluate a call to function F, returning true if
2131/// successful, false if we can't evaluate it. ActualArgs contains the formal
2132/// arguments for the function.
2133static bool EvaluateFunction(Function *F, Constant *&RetVal,
2134 const std::vector<Constant*> &ActualArgs,
2135 std::vector<Function*> &CallStack,
2136 DenseMap<Constant*, Constant*> &MutatedMemory,
2137 std::vector<GlobalVariable*> &AllocaTmps) {
2138 // Check to see if this function is already executing (recursion). If so,
2139 // bail out. TODO: we might want to accept limited recursion.
2140 if (std::find(CallStack.begin(), CallStack.end(), F) != CallStack.end())
2141 return false;
2142
2143 CallStack.push_back(F);
2144
2145 /// Values - As we compute SSA register values, we store their contents here.
2146 DenseMap<Value*, Constant*> Values;
2147
2148 // Initialize arguments to the incoming values specified.
2149 unsigned ArgNo = 0;
2150 for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end(); AI != E;
2151 ++AI, ++ArgNo)
2152 Values[AI] = ActualArgs[ArgNo];
2153
2154 /// ExecutedBlocks - We only handle non-looping, non-recursive code. As such,
2155 /// we can only evaluate any one basic block at most once. This set keeps
2156 /// track of what we have executed so we can detect recursive cases etc.
2157 SmallPtrSet<BasicBlock*, 32> ExecutedBlocks;
2158
2159 // CurInst - The current instruction we're evaluating.
2160 BasicBlock::iterator CurInst = F->begin()->begin();
2161
2162 // This is the main evaluation loop.
2163 while (1) {
2164 Constant *InstResult = 0;
2165
2166 if (StoreInst *SI = dyn_cast<StoreInst>(CurInst)) {
2167 if (SI->isVolatile()) return false; // no volatile accesses.
2168 Constant *Ptr = getVal(Values, SI->getOperand(1));
2169 if (!isSimpleEnoughPointerToCommit(Ptr))
2170 // If this is too complex for us to commit, reject it.
2171 return false;
2172 Constant *Val = getVal(Values, SI->getOperand(0));
2173 MutatedMemory[Ptr] = Val;
2174 } else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(CurInst)) {
2175 InstResult = ConstantExpr::get(BO->getOpcode(),
2176 getVal(Values, BO->getOperand(0)),
2177 getVal(Values, BO->getOperand(1)));
2178 } else if (CmpInst *CI = dyn_cast<CmpInst>(CurInst)) {
2179 InstResult = ConstantExpr::getCompare(CI->getPredicate(),
2180 getVal(Values, CI->getOperand(0)),
2181 getVal(Values, CI->getOperand(1)));
2182 } else if (CastInst *CI = dyn_cast<CastInst>(CurInst)) {
2183 InstResult = ConstantExpr::getCast(CI->getOpcode(),
2184 getVal(Values, CI->getOperand(0)),
2185 CI->getType());
2186 } else if (SelectInst *SI = dyn_cast<SelectInst>(CurInst)) {
2187 InstResult = ConstantExpr::getSelect(getVal(Values, SI->getOperand(0)),
2188 getVal(Values, SI->getOperand(1)),
2189 getVal(Values, SI->getOperand(2)));
2190 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(CurInst)) {
2191 Constant *P = getVal(Values, GEP->getOperand(0));
2192 SmallVector<Constant*, 8> GEPOps;
2193 for (User::op_iterator i = GEP->op_begin() + 1, e = GEP->op_end();
2194 i != e; ++i)
2195 GEPOps.push_back(getVal(Values, *i));
2196 InstResult = ConstantExpr::getGetElementPtr(P, &GEPOps[0], GEPOps.size());
2197 } else if (LoadInst *LI = dyn_cast<LoadInst>(CurInst)) {
2198 if (LI->isVolatile()) return false; // no volatile accesses.
2199 InstResult = ComputeLoadResult(getVal(Values, LI->getOperand(0)),
2200 MutatedMemory);
2201 if (InstResult == 0) return false; // Could not evaluate load.
2202 } else if (AllocaInst *AI = dyn_cast<AllocaInst>(CurInst)) {
2203 if (AI->isArrayAllocation()) return false; // Cannot handle array allocs.
2204 const Type *Ty = AI->getType()->getElementType();
2205 AllocaTmps.push_back(new GlobalVariable(Ty, false,
2206 GlobalValue::InternalLinkage,
2207 UndefValue::get(Ty),
2208 AI->getName()));
2209 InstResult = AllocaTmps.back();
2210 } else if (CallInst *CI = dyn_cast<CallInst>(CurInst)) {
2211
2212 // Debug info can safely be ignored here.
2213 if (isa<DbgInfoIntrinsic>(CI)) {
2214 ++CurInst;
2215 continue;
2216 }
2217
2218 // Cannot handle inline asm.
2219 if (isa<InlineAsm>(CI->getOperand(0))) return false;
2220
2221 // Resolve function pointers.
2222 Function *Callee = dyn_cast<Function>(getVal(Values, CI->getOperand(0)));
2223 if (!Callee) return false; // Cannot resolve.
2224
2225 std::vector<Constant*> Formals;
2226 for (User::op_iterator i = CI->op_begin() + 1, e = CI->op_end();
2227 i != e; ++i)
2228 Formals.push_back(getVal(Values, *i));
2229
2230 if (Callee->isDeclaration()) {
2231 // If this is a function we can constant fold, do it.
2232 if (Constant *C = ConstantFoldCall(Callee, &Formals[0],
2233 Formals.size())) {
2234 InstResult = C;
2235 } else {
2236 return false;
2237 }
2238 } else {
2239 if (Callee->getFunctionType()->isVarArg())
2240 return false;
2241
2242 Constant *RetVal;
2243 // Execute the call, if successful, use the return value.
2244 if (!EvaluateFunction(Callee, RetVal, Formals, CallStack,
2245 MutatedMemory, AllocaTmps))
2246 return false;
2247 InstResult = RetVal;
2248 }
2249 } else if (isa<TerminatorInst>(CurInst)) {
2250 BasicBlock *NewBB = 0;
2251 if (BranchInst *BI = dyn_cast<BranchInst>(CurInst)) {
2252 if (BI->isUnconditional()) {
2253 NewBB = BI->getSuccessor(0);
2254 } else {
2255 ConstantInt *Cond =
2256 dyn_cast<ConstantInt>(getVal(Values, BI->getCondition()));
2257 if (!Cond) return false; // Cannot determine.
2258
2259 NewBB = BI->getSuccessor(!Cond->getZExtValue());
2260 }
2261 } else if (SwitchInst *SI = dyn_cast<SwitchInst>(CurInst)) {
2262 ConstantInt *Val =
2263 dyn_cast<ConstantInt>(getVal(Values, SI->getCondition()));
2264 if (!Val) return false; // Cannot determine.
2265 NewBB = SI->getSuccessor(SI->findCaseValue(Val));
2266 } else if (ReturnInst *RI = dyn_cast<ReturnInst>(CurInst)) {
2267 if (RI->getNumOperands())
2268 RetVal = getVal(Values, RI->getOperand(0));
2269
2270 CallStack.pop_back(); // return from fn.
2271 return true; // We succeeded at evaluating this ctor!
2272 } else {
2273 // invoke, unwind, unreachable.
2274 return false; // Cannot handle this terminator.
2275 }
2276
2277 // Okay, we succeeded in evaluating this control flow. See if we have
2278 // executed the new block before. If so, we have a looping function,
2279 // which we cannot evaluate in reasonable time.
2280 if (!ExecutedBlocks.insert(NewBB))
2281 return false; // looped!
2282
2283 // Okay, we have never been in this block before. Check to see if there
2284 // are any PHI nodes. If so, evaluate them with information about where
2285 // we came from.
2286 BasicBlock *OldBB = CurInst->getParent();
2287 CurInst = NewBB->begin();
2288 PHINode *PN;
2289 for (; (PN = dyn_cast<PHINode>(CurInst)); ++CurInst)
2290 Values[PN] = getVal(Values, PN->getIncomingValueForBlock(OldBB));
2291
2292 // Do NOT increment CurInst. We know that the terminator had no value.
2293 continue;
2294 } else {
2295 // Did not know how to evaluate this!
2296 return false;
2297 }
2298
2299 if (!CurInst->use_empty())
2300 Values[CurInst] = InstResult;
2301
2302 // Advance program counter.
2303 ++CurInst;
2304 }
2305}
2306
2307/// EvaluateStaticConstructor - Evaluate static constructors in the function, if
2308/// we can. Return true if we can, false otherwise.
2309static bool EvaluateStaticConstructor(Function *F) {
2310 /// MutatedMemory - For each store we execute, we update this map. Loads
2311 /// check this to get the most up-to-date value. If evaluation is successful,
2312 /// this state is committed to the process.
2313 DenseMap<Constant*, Constant*> MutatedMemory;
2314
2315 /// AllocaTmps - To 'execute' an alloca, we create a temporary global variable
2316 /// to represent its body. This vector is needed so we can delete the
2317 /// temporary globals when we are done.
2318 std::vector<GlobalVariable*> AllocaTmps;
2319
2320 /// CallStack - This is used to detect recursion. In pathological situations
2321 /// we could hit exponential behavior, but at least there is nothing
2322 /// unbounded.
2323 std::vector<Function*> CallStack;
2324
2325 // Call the function.
2326 Constant *RetValDummy;
2327 bool EvalSuccess = EvaluateFunction(F, RetValDummy, std::vector<Constant*>(),
2328 CallStack, MutatedMemory, AllocaTmps);
2329 if (EvalSuccess) {
2330 // We succeeded at evaluation: commit the result.
2331 DOUT << "FULLY EVALUATED GLOBAL CTOR FUNCTION '"
2332 << F->getName() << "' to " << MutatedMemory.size()
2333 << " stores.\n";
2334 for (DenseMap<Constant*, Constant*>::iterator I = MutatedMemory.begin(),
2335 E = MutatedMemory.end(); I != E; ++I)
2336 CommitValueTo(I->second, I->first);
2337 }
2338
2339 // At this point, we are done interpreting. If we created any 'alloca'
2340 // temporaries, release them now.
2341 while (!AllocaTmps.empty()) {
2342 GlobalVariable *Tmp = AllocaTmps.back();
2343 AllocaTmps.pop_back();
2344
2345 // If there are still users of the alloca, the program is doing something
2346 // silly, e.g. storing the address of the alloca somewhere and using it
2347 // later. Since this is undefined, we'll just make it be null.
2348 if (!Tmp->use_empty())
2349 Tmp->replaceAllUsesWith(Constant::getNullValue(Tmp->getType()));
2350 delete Tmp;
2351 }
2352
2353 return EvalSuccess;
2354}
2355
2356
2357
2358/// OptimizeGlobalCtorsList - Simplify and evaluation global ctors if possible.
2359/// Return true if anything changed.
2360bool GlobalOpt::OptimizeGlobalCtorsList(GlobalVariable *&GCL) {
2361 std::vector<Function*> Ctors = ParseGlobalCtors(GCL);
2362 bool MadeChange = false;
2363 if (Ctors.empty()) return false;
2364
2365 // Loop over global ctors, optimizing them when we can.
2366 for (unsigned i = 0; i != Ctors.size(); ++i) {
2367 Function *F = Ctors[i];
2368 // Found a null terminator in the middle of the list, prune off the rest of
2369 // the list.
2370 if (F == 0) {
2371 if (i != Ctors.size()-1) {
2372 Ctors.resize(i+1);
2373 MadeChange = true;
2374 }
2375 break;
2376 }
2377
2378 // We cannot simplify external ctor functions.
2379 if (F->empty()) continue;
2380
2381 // If we can evaluate the ctor at compile time, do.
2382 if (EvaluateStaticConstructor(F)) {
2383 Ctors.erase(Ctors.begin()+i);
2384 MadeChange = true;
2385 --i;
2386 ++NumCtorsEvaluated;
2387 continue;
2388 }
2389 }
2390
2391 if (!MadeChange) return false;
2392
2393 GCL = InstallGlobalCtors(GCL, Ctors);
2394 return true;
2395}
2396
2397bool GlobalOpt::OptimizeGlobalAliases(Module &M) {
2398 bool Changed = false;
2399
2400 for (Module::alias_iterator I = M.alias_begin(), E = M.alias_end();
2401 I != E;) {
2402 Module::alias_iterator J = I++;
2403 // Aliases without names cannot be referenced outside this module.
2404 if (!J->hasName() && !J->isDeclaration())
2405 J->setLinkage(GlobalValue::InternalLinkage);
2406 // If the aliasee may change at link time, nothing can be done - bail out.
2407 if (J->mayBeOverridden())
2408 continue;
2409
2410 Constant *Aliasee = J->getAliasee();
2411 GlobalValue *Target = cast<GlobalValue>(Aliasee->stripPointerCasts());
2412 Target->removeDeadConstantUsers();
2413 bool hasOneUse = Target->hasOneUse() && Aliasee->hasOneUse();
2414
2415 // Make all users of the alias use the aliasee instead.
2416 if (!J->use_empty()) {
2417 J->replaceAllUsesWith(Aliasee);
2418 ++NumAliasesResolved;
2419 Changed = true;
2420 }
2421
2422 // If the aliasee has internal linkage, give it the name and linkage
2423 // of the alias, and delete the alias. This turns:
2424 // define internal ... @f(...)
2425 // @a = alias ... @f
2426 // into:
2427 // define ... @a(...)
2428 if (!Target->hasLocalLinkage())
2429 continue;
2430
2431 // The transform is only useful if the alias does not have internal linkage.
2432 if (J->hasLocalLinkage())
2433 continue;
2434
2435 // Do not perform the transform if multiple aliases potentially target the
2436 // aliasee. This check also ensures that it is safe to replace the section
2437 // and other attributes of the aliasee with those of the alias.
2438 if (!hasOneUse)
2439 continue;
2440
2441 // Give the aliasee the name, linkage and other attributes of the alias.
2442 Target->takeName(J);
2443 Target->setLinkage(J->getLinkage());
2444 Target->GlobalValue::copyAttributesFrom(J);
2445
2446 // Delete the alias.
2447 M.getAliasList().erase(J);
2448 ++NumAliasesRemoved;
2449 Changed = true;
2450 }
2451
2452 return Changed;
2453}
2454
2455bool GlobalOpt::runOnModule(Module &M) {
2456 bool Changed = false;
2457
2458 // Try to find the llvm.globalctors list.
2459 GlobalVariable *GlobalCtors = FindGlobalCtors(M);
2460
2461 bool LocalChange = true;
2462 while (LocalChange) {
2463 LocalChange = false;
2464
2465 // Delete functions that are trivially dead, ccc -> fastcc
2466 LocalChange |= OptimizeFunctions(M);
2467
2468 // Optimize global_ctors list.
2469 if (GlobalCtors)
2470 LocalChange |= OptimizeGlobalCtorsList(GlobalCtors);
2471
2472 // Optimize non-address-taken globals.
2473 LocalChange |= OptimizeGlobalVars(M);
2474
2475 // Resolve aliases, when possible.
2476 LocalChange |= OptimizeGlobalAliases(M);
2477 Changed |= LocalChange;
2478 }
2479
2480 // TODO: Move all global ctors functions to the end of the module for code
2481 // layout.
2482
2483 return Changed;
2484}
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