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ObjCARCContract.cpp
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1 //===- ObjCARCContract.cpp - ObjC ARC Optimization ------------------------===//
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 /// \file
10 /// This file defines late ObjC ARC optimizations. ARC stands for Automatic
11 /// Reference Counting and is a system for managing reference counts for objects
12 /// in Objective C.
13 ///
14 /// This specific file mainly deals with ``contracting'' multiple lower level
15 /// operations into singular higher level operations through pattern matching.
16 ///
17 /// WARNING: This file knows about certain library functions. It recognizes them
18 /// by name, and hardwires knowledge of their semantics.
19 ///
20 /// WARNING: This file knows about how certain Objective-C library functions are
21 /// used. Naive LLVM IR transformations which would otherwise be
22 /// behavior-preserving may break these assumptions.
23 ///
24 //===----------------------------------------------------------------------===//
25 
26 // TODO: ObjCARCContract could insert PHI nodes when uses aren't
27 // dominated by single calls.
28 
29 #include "ARCRuntimeEntryPoints.h"
30 #include "DependencyAnalysis.h"
31 #include "ObjCARC.h"
32 #include "ProvenanceAnalysis.h"
33 #include "llvm/ADT/Statistic.h"
34 #include "llvm/IR/Dominators.h"
35 #include "llvm/IR/InlineAsm.h"
36 #include "llvm/IR/Operator.h"
37 #include "llvm/Support/Debug.h"
39 
40 using namespace llvm;
41 using namespace llvm::objcarc;
42 
43 #define DEBUG_TYPE "objc-arc-contract"
44 
45 STATISTIC(NumPeeps, "Number of calls peephole-optimized");
46 STATISTIC(NumStoreStrongs, "Number objc_storeStrong calls formed");
47 
48 //===----------------------------------------------------------------------===//
49 // Declarations
50 //===----------------------------------------------------------------------===//
51 
52 namespace {
53  /// \brief Late ARC optimizations
54  ///
55  /// These change the IR in a way that makes it difficult to be analyzed by
56  /// ObjCARCOpt, so it's run late.
57  class ObjCARCContract : public FunctionPass {
58  bool Changed;
59  AliasAnalysis *AA;
60  DominatorTree *DT;
63 
64  /// A flag indicating whether this optimization pass should run.
65  bool Run;
66 
67  /// The inline asm string to insert between calls and RetainRV calls to make
68  /// the optimization work on targets which need it.
69  const MDString *RVInstMarker;
70 
71  /// The set of inserted objc_storeStrong calls. If at the end of walking the
72  /// function we have found no alloca instructions, these calls can be marked
73  /// "tail".
74  SmallPtrSet<CallInst *, 8> StoreStrongCalls;
75 
76  /// Returns true if we eliminated Inst.
77  bool tryToPeepholeInstruction(Function &F, Instruction *Inst,
78  inst_iterator &Iter,
81  bool &TailOkForStoreStrong);
82 
83  bool optimizeRetainCall(Function &F, Instruction *Retain);
84 
85  bool
86  contractAutorelease(Function &F, Instruction *Autorelease,
87  ARCInstKind Class,
88  SmallPtrSetImpl<Instruction *> &DependingInstructions,
90 
91  void tryToContractReleaseIntoStoreStrong(Instruction *Release,
92  inst_iterator &Iter);
93 
94  void getAnalysisUsage(AnalysisUsage &AU) const override;
95  bool doInitialization(Module &M) override;
96  bool runOnFunction(Function &F) override;
97 
98  public:
99  static char ID;
100  ObjCARCContract() : FunctionPass(ID) {
102  }
103  };
104 }
105 
106 //===----------------------------------------------------------------------===//
107 // Implementation
108 //===----------------------------------------------------------------------===//
109 
110 /// Turn objc_retain into objc_retainAutoreleasedReturnValue if the operand is a
111 /// return value. We do this late so we do not disrupt the dataflow analysis in
112 /// ObjCARCOpt.
113 bool ObjCARCContract::optimizeRetainCall(Function &F, Instruction *Retain) {
115  const Instruction *Call = CS.getInstruction();
116  if (!Call)
117  return false;
118  if (Call->getParent() != Retain->getParent())
119  return false;
120 
121  // Check that the call is next to the retain.
123  while (IsNoopInstruction(&*I))
124  ++I;
125  if (&*I != Retain)
126  return false;
127 
128  // Turn it to an objc_retainAutoreleasedReturnValue.
129  Changed = true;
130  ++NumPeeps;
131 
132  DEBUG(dbgs() << "Transforming objc_retain => "
133  "objc_retainAutoreleasedReturnValue since the operand is a "
134  "return value.\nOld: "<< *Retain << "\n");
135 
136  // We do not have to worry about tail calls/does not throw since
137  // retain/retainRV have the same properties.
139  cast<CallInst>(Retain)->setCalledFunction(Decl);
140 
141  DEBUG(dbgs() << "New: " << *Retain << "\n");
142  return true;
143 }
144 
145 /// Merge an autorelease with a retain into a fused call.
146 bool ObjCARCContract::contractAutorelease(
148  SmallPtrSetImpl<Instruction *> &DependingInstructions,
150  const Value *Arg = GetArgRCIdentityRoot(Autorelease);
151 
152  // Check that there are no instructions between the retain and the autorelease
153  // (such as an autorelease_pop) which may change the count.
154  CallInst *Retain = nullptr;
155  if (Class == ARCInstKind::AutoreleaseRV)
157  Autorelease->getParent(), Autorelease,
158  DependingInstructions, Visited, PA);
159  else
161  Autorelease->getParent(), Autorelease,
162  DependingInstructions, Visited, PA);
163 
164  Visited.clear();
165  if (DependingInstructions.size() != 1) {
166  DependingInstructions.clear();
167  return false;
168  }
169 
170  Retain = dyn_cast_or_null<CallInst>(*DependingInstructions.begin());
171  DependingInstructions.clear();
172 
173  if (!Retain || GetBasicARCInstKind(Retain) != ARCInstKind::Retain ||
174  GetArgRCIdentityRoot(Retain) != Arg)
175  return false;
176 
177  Changed = true;
178  ++NumPeeps;
179 
180  DEBUG(dbgs() << " Fusing retain/autorelease!\n"
181  " Autorelease:" << *Autorelease << "\n"
182  " Retain: " << *Retain << "\n");
183 
184  Constant *Decl = EP.get(Class == ARCInstKind::AutoreleaseRV
187  Retain->setCalledFunction(Decl);
188 
189  DEBUG(dbgs() << " New RetainAutorelease: " << *Retain << "\n");
190 
191  EraseInstruction(Autorelease);
192  return true;
193 }
194 
197  ProvenanceAnalysis &PA,
198  AliasAnalysis *AA) {
199  StoreInst *Store = nullptr;
200  bool SawRelease = false;
201 
202  // Get the location associated with Load.
204  auto *LocPtr = Loc.Ptr->stripPointerCasts();
205 
206  // Walk down to find the store and the release, which may be in either order.
207  for (auto I = std::next(BasicBlock::iterator(Load)),
208  E = Load->getParent()->end();
209  I != E; ++I) {
210  // If we found the store we were looking for and saw the release,
211  // break. There is no more work to be done.
212  if (Store && SawRelease)
213  break;
214 
215  // Now we know that we have not seen either the store or the release. If I
216  // is the release, mark that we saw the release and continue.
217  Instruction *Inst = &*I;
218  if (Inst == Release) {
219  SawRelease = true;
220  continue;
221  }
222 
223  // Otherwise, we check if Inst is a "good" store. Grab the instruction class
224  // of Inst.
225  ARCInstKind Class = GetBasicARCInstKind(Inst);
226 
227  // If Inst is an unrelated retain, we don't care about it.
228  //
229  // TODO: This is one area where the optimization could be made more
230  // aggressive.
231  if (IsRetain(Class))
232  continue;
233 
234  // If we have seen the store, but not the release...
235  if (Store) {
236  // We need to make sure that it is safe to move the release from its
237  // current position to the store. This implies proving that any
238  // instruction in between Store and the Release conservatively can not use
239  // the RCIdentityRoot of Release. If we can prove we can ignore Inst, so
240  // continue...
241  if (!CanUse(Inst, Load, PA, Class)) {
242  continue;
243  }
244 
245  // Otherwise, be conservative and return nullptr.
246  return nullptr;
247  }
248 
249  // Ok, now we know we have not seen a store yet. See if Inst can write to
250  // our load location, if it can not, just ignore the instruction.
251  if (!(AA->getModRefInfo(Inst, Loc) & MRI_Mod))
252  continue;
253 
254  Store = dyn_cast<StoreInst>(Inst);
255 
256  // If Inst can, then check if Inst is a simple store. If Inst is not a
257  // store or a store that is not simple, then we have some we do not
258  // understand writing to this memory implying we can not move the load
259  // over the write to any subsequent store that we may find.
260  if (!Store || !Store->isSimple())
261  return nullptr;
262 
263  // Then make sure that the pointer we are storing to is Ptr. If so, we
264  // found our Store!
265  if (Store->getPointerOperand()->stripPointerCasts() == LocPtr)
266  continue;
267 
268  // Otherwise, we have an unknown store to some other ptr that clobbers
269  // Loc.Ptr. Bail!
270  return nullptr;
271  }
272 
273  // If we did not find the store or did not see the release, fail.
274  if (!Store || !SawRelease)
275  return nullptr;
276 
277  // We succeeded!
278  return Store;
279 }
280 
281 static Instruction *
284  ProvenanceAnalysis &PA) {
285  // Walk up from the Store to find the retain.
286  BasicBlock::iterator I = Store->getIterator();
287  BasicBlock::iterator Begin = Store->getParent()->begin();
288  while (I != Begin && GetBasicARCInstKind(&*I) != ARCInstKind::Retain) {
289  Instruction *Inst = &*I;
290 
291  // It is only safe to move the retain to the store if we can prove
292  // conservatively that nothing besides the release can decrement reference
293  // counts in between the retain and the store.
294  if (CanDecrementRefCount(Inst, New, PA) && Inst != Release)
295  return nullptr;
296  --I;
297  }
298  Instruction *Retain = &*I;
300  return nullptr;
301  if (GetArgRCIdentityRoot(Retain) != New)
302  return nullptr;
303  return Retain;
304 }
305 
306 /// Attempt to merge an objc_release with a store, load, and objc_retain to form
307 /// an objc_storeStrong. An objc_storeStrong:
308 ///
309 /// objc_storeStrong(i8** %old_ptr, i8* new_value)
310 ///
311 /// is equivalent to the following IR sequence:
312 ///
313 /// ; Load old value.
314 /// %old_value = load i8** %old_ptr (1)
315 ///
316 /// ; Increment the new value and then release the old value. This must occur
317 /// ; in order in case old_value releases new_value in its destructor causing
318 /// ; us to potentially have a dangling ptr.
319 /// tail call i8* @objc_retain(i8* %new_value) (2)
320 /// tail call void @objc_release(i8* %old_value) (3)
321 ///
322 /// ; Store the new_value into old_ptr
323 /// store i8* %new_value, i8** %old_ptr (4)
324 ///
325 /// The safety of this optimization is based around the following
326 /// considerations:
327 ///
328 /// 1. We are forming the store strong at the store. Thus to perform this
329 /// optimization it must be safe to move the retain, load, and release to
330 /// (4).
331 /// 2. We need to make sure that any re-orderings of (1), (2), (3), (4) are
332 /// safe.
333 void ObjCARCContract::tryToContractReleaseIntoStoreStrong(Instruction *Release,
334  inst_iterator &Iter) {
335  // See if we are releasing something that we just loaded.
336  auto *Load = dyn_cast<LoadInst>(GetArgRCIdentityRoot(Release));
337  if (!Load || !Load->isSimple())
338  return;
339 
340  // For now, require everything to be in one basic block.
341  BasicBlock *BB = Release->getParent();
342  if (Load->getParent() != BB)
343  return;
344 
345  // First scan down the BB from Load, looking for a store of the RCIdentityRoot
346  // of Load's
347  StoreInst *Store =
349  // If we fail, bail.
350  if (!Store)
351  return;
352 
353  // Then find what new_value's RCIdentity Root is.
354  Value *New = GetRCIdentityRoot(Store->getValueOperand());
355 
356  // Then walk up the BB and look for a retain on New without any intervening
357  // instructions which conservatively might decrement ref counts.
358  Instruction *Retain =
359  findRetainForStoreStrongContraction(New, Store, Release, PA);
360 
361  // If we fail, bail.
362  if (!Retain)
363  return;
364 
365  Changed = true;
366  ++NumStoreStrongs;
367 
368  DEBUG(
369  llvm::dbgs() << " Contracting retain, release into objc_storeStrong.\n"
370  << " Old:\n"
371  << " Store: " << *Store << "\n"
372  << " Release: " << *Release << "\n"
373  << " Retain: " << *Retain << "\n"
374  << " Load: " << *Load << "\n");
375 
376  LLVMContext &C = Release->getContext();
378  Type *I8XX = PointerType::getUnqual(I8X);
379 
380  Value *Args[] = { Load->getPointerOperand(), New };
381  if (Args[0]->getType() != I8XX)
382  Args[0] = new BitCastInst(Args[0], I8XX, "", Store);
383  if (Args[1]->getType() != I8X)
384  Args[1] = new BitCastInst(Args[1], I8X, "", Store);
386  CallInst *StoreStrong = CallInst::Create(Decl, Args, "", Store);
387  StoreStrong->setDoesNotThrow();
388  StoreStrong->setDebugLoc(Store->getDebugLoc());
389 
390  // We can't set the tail flag yet, because we haven't yet determined
391  // whether there are any escaping allocas. Remember this call, so that
392  // we can set the tail flag once we know it's safe.
393  StoreStrongCalls.insert(StoreStrong);
394 
395  DEBUG(llvm::dbgs() << " New Store Strong: " << *StoreStrong << "\n");
396 
397  if (&*Iter == Retain) ++Iter;
398  if (&*Iter == Store) ++Iter;
399  Store->eraseFromParent();
400  Release->eraseFromParent();
401  EraseInstruction(Retain);
402  if (Load->use_empty())
403  Load->eraseFromParent();
404 }
405 
406 bool ObjCARCContract::tryToPeepholeInstruction(
407  Function &F, Instruction *Inst, inst_iterator &Iter,
408  SmallPtrSetImpl<Instruction *> &DependingInsts,
410  bool &TailOkForStoreStrongs) {
411  // Only these library routines return their argument. In particular,
412  // objc_retainBlock does not necessarily return its argument.
413  ARCInstKind Class = GetBasicARCInstKind(Inst);
414  switch (Class) {
417  return false;
420  return contractAutorelease(F, Inst, Class, DependingInsts, Visited);
421  case ARCInstKind::Retain:
422  // Attempt to convert retains to retainrvs if they are next to function
423  // calls.
424  if (!optimizeRetainCall(F, Inst))
425  return false;
426  // If we succeed in our optimization, fall through.
429  case ARCInstKind::ClaimRV: {
430  // If we're compiling for a target which needs a special inline-asm
431  // marker to do the return value optimization, insert it now.
432  if (!RVInstMarker)
433  return false;
434  BasicBlock::iterator BBI = Inst->getIterator();
435  BasicBlock *InstParent = Inst->getParent();
436 
437  // Step up to see if the call immediately precedes the RV call.
438  // If it's an invoke, we have to cross a block boundary. And we have
439  // to carefully dodge no-op instructions.
440  do {
441  if (BBI == InstParent->begin()) {
442  BasicBlock *Pred = InstParent->getSinglePredecessor();
443  if (!Pred)
444  goto decline_rv_optimization;
445  BBI = Pred->getTerminator()->getIterator();
446  break;
447  }
448  --BBI;
449  } while (IsNoopInstruction(&*BBI));
450 
451  if (&*BBI == GetArgRCIdentityRoot(Inst)) {
452  DEBUG(dbgs() << "Adding inline asm marker for the return value "
453  "optimization.\n");
454  Changed = true;
457  /*isVarArg=*/false),
458  RVInstMarker->getString(),
459  /*Constraints=*/"", /*hasSideEffects=*/true);
460  CallInst::Create(IA, "", Inst);
461  }
462  decline_rv_optimization:
463  return false;
464  }
465  case ARCInstKind::InitWeak: {
466  // objc_initWeak(p, null) => *p = null
467  CallInst *CI = cast<CallInst>(Inst);
468  if (IsNullOrUndef(CI->getArgOperand(1))) {
469  Value *Null =
470  ConstantPointerNull::get(cast<PointerType>(CI->getType()));
471  Changed = true;
472  new StoreInst(Null, CI->getArgOperand(0), CI);
473 
474  DEBUG(dbgs() << "OBJCARCContract: Old = " << *CI << "\n"
475  << " New = " << *Null << "\n");
476 
477  CI->replaceAllUsesWith(Null);
478  CI->eraseFromParent();
479  }
480  return true;
481  }
483  // Try to form an objc store strong from our release. If we fail, there is
484  // nothing further to do below, so continue.
485  tryToContractReleaseIntoStoreStrong(Inst, Iter);
486  return true;
487  case ARCInstKind::User:
488  // Be conservative if the function has any alloca instructions.
489  // Technically we only care about escaping alloca instructions,
490  // but this is sufficient to handle some interesting cases.
491  if (isa<AllocaInst>(Inst))
492  TailOkForStoreStrongs = false;
493  return true;
495  // Remove calls to @clang.arc.use(...).
496  Inst->eraseFromParent();
497  return true;
498  default:
499  return true;
500  }
501 }
502 
503 //===----------------------------------------------------------------------===//
504 // Top Level Driver
505 //===----------------------------------------------------------------------===//
506 
508  if (!EnableARCOpts)
509  return false;
510 
511  // If nothing in the Module uses ARC, don't do anything.
512  if (!Run)
513  return false;
514 
515  Changed = false;
516  AA = &getAnalysis<AAResultsWrapperPass>().getAAResults();
517  DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
518 
519  PA.setAA(&getAnalysis<AAResultsWrapperPass>().getAAResults());
520 
521  DEBUG(llvm::dbgs() << "**** ObjCARC Contract ****\n");
522 
523  // Track whether it's ok to mark objc_storeStrong calls with the "tail"
524  // keyword. Be conservative if the function has variadic arguments.
525  // It seems that functions which "return twice" are also unsafe for the
526  // "tail" argument, because they are setjmp, which could need to
527  // return to an earlier stack state.
528  bool TailOkForStoreStrongs =
530 
531  // For ObjC library calls which return their argument, replace uses of the
532  // argument with uses of the call return value, if it dominates the use. This
533  // reduces register pressure.
534  SmallPtrSet<Instruction *, 4> DependingInstructions;
536  for (inst_iterator I = inst_begin(&F), E = inst_end(&F); I != E;) {
537  Instruction *Inst = &*I++;
538 
539  DEBUG(dbgs() << "Visiting: " << *Inst << "\n");
540 
541  // First try to peephole Inst. If there is nothing further we can do in
542  // terms of undoing objc-arc-expand, process the next inst.
543  if (tryToPeepholeInstruction(F, Inst, I, DependingInstructions, Visited,
544  TailOkForStoreStrongs))
545  continue;
546 
547  // Otherwise, try to undo objc-arc-expand.
548 
549  // Don't use GetArgRCIdentityRoot because we don't want to look through bitcasts
550  // and such; to do the replacement, the argument must have type i8*.
551 
552  // Function for replacing uses of Arg dominated by Inst.
553  auto ReplaceArgUses = [Inst, this](Value *Arg) {
554  // If we're compiling bugpointed code, don't get in trouble.
555  if (!isa<Instruction>(Arg) && !isa<Argument>(Arg))
556  return;
557 
558  // Look through the uses of the pointer.
559  for (Value::use_iterator UI = Arg->use_begin(), UE = Arg->use_end();
560  UI != UE; ) {
561  // Increment UI now, because we may unlink its element.
562  Use &U = *UI++;
563  unsigned OperandNo = U.getOperandNo();
564 
565  // If the call's return value dominates a use of the call's argument
566  // value, rewrite the use to use the return value. We check for
567  // reachability here because an unreachable call is considered to
568  // trivially dominate itself, which would lead us to rewriting its
569  // argument in terms of its return value, which would lead to
570  // infinite loops in GetArgRCIdentityRoot.
571  if (DT->isReachableFromEntry(U) && DT->dominates(Inst, U)) {
572  Changed = true;
573  Instruction *Replacement = Inst;
574  Type *UseTy = U.get()->getType();
575  if (PHINode *PHI = dyn_cast<PHINode>(U.getUser())) {
576  // For PHI nodes, insert the bitcast in the predecessor block.
577  unsigned ValNo = PHINode::getIncomingValueNumForOperand(OperandNo);
578  BasicBlock *BB = PHI->getIncomingBlock(ValNo);
579  if (Replacement->getType() != UseTy)
580  Replacement = new BitCastInst(Replacement, UseTy, "",
581  &BB->back());
582  // While we're here, rewrite all edges for this PHI, rather
583  // than just one use at a time, to minimize the number of
584  // bitcasts we emit.
585  for (unsigned i = 0, e = PHI->getNumIncomingValues(); i != e; ++i)
586  if (PHI->getIncomingBlock(i) == BB) {
587  // Keep the UI iterator valid.
588  if (UI != UE &&
589  &PHI->getOperandUse(
591  ++UI;
592  PHI->setIncomingValue(i, Replacement);
593  }
594  } else {
595  if (Replacement->getType() != UseTy)
596  Replacement = new BitCastInst(Replacement, UseTy, "",
597  cast<Instruction>(U.getUser()));
598  U.set(Replacement);
599  }
600  }
601  }
602  };
603 
604 
605  Value *Arg = cast<CallInst>(Inst)->getArgOperand(0);
606  Value *OrigArg = Arg;
607 
608  // TODO: Change this to a do-while.
609  for (;;) {
610  ReplaceArgUses(Arg);
611 
612  // If Arg is a no-op casted pointer, strip one level of casts and iterate.
613  if (const BitCastInst *BI = dyn_cast<BitCastInst>(Arg))
614  Arg = BI->getOperand(0);
615  else if (isa<GEPOperator>(Arg) &&
616  cast<GEPOperator>(Arg)->hasAllZeroIndices())
617  Arg = cast<GEPOperator>(Arg)->getPointerOperand();
618  else if (isa<GlobalAlias>(Arg) &&
619  !cast<GlobalAlias>(Arg)->isInterposable())
620  Arg = cast<GlobalAlias>(Arg)->getAliasee();
621  else
622  break;
623  }
624 
625  // Replace bitcast users of Arg that are dominated by Inst.
626  SmallVector<BitCastInst *, 2> BitCastUsers;
627 
628  // Add all bitcast users of the function argument first.
629  for (User *U : OrigArg->users())
630  if (auto *BC = dyn_cast<BitCastInst>(U))
631  BitCastUsers.push_back(BC);
632 
633  // Replace the bitcasts with the call return. Iterate until list is empty.
634  while (!BitCastUsers.empty()) {
635  auto *BC = BitCastUsers.pop_back_val();
636  for (User *U : BC->users())
637  if (auto *B = dyn_cast<BitCastInst>(U))
638  BitCastUsers.push_back(B);
639 
640  ReplaceArgUses(BC);
641  }
642  }
643 
644  // If this function has no escaping allocas or suspicious vararg usage,
645  // objc_storeStrong calls can be marked with the "tail" keyword.
646  if (TailOkForStoreStrongs)
647  for (CallInst *CI : StoreStrongCalls)
648  CI->setTailCall();
649  StoreStrongCalls.clear();
650 
651  return Changed;
652 }
653 
654 //===----------------------------------------------------------------------===//
655 // Misc Pass Manager
656 //===----------------------------------------------------------------------===//
657 
658 char ObjCARCContract::ID = 0;
659 INITIALIZE_PASS_BEGIN(ObjCARCContract, "objc-arc-contract",
660  "ObjC ARC contraction", false, false)
663 INITIALIZE_PASS_END(ObjCARCContract, "objc-arc-contract",
664  "ObjC ARC contraction", false, false)
665 
666 void ObjCARCContract::getAnalysisUsage(AnalysisUsage &AU) const {
667  AU.addRequired<AAResultsWrapperPass>();
668  AU.addRequired<DominatorTreeWrapperPass>();
669  AU.setPreservesCFG();
670 }
671 
672 Pass *llvm::createObjCARCContractPass() { return new ObjCARCContract(); }
673 
674 bool ObjCARCContract::doInitialization(Module &M) {
675  // If nothing in the Module uses ARC, don't do anything.
676  Run = ModuleHasARC(M);
677  if (!Run)
678  return false;
679 
680  EP.init(&M);
681 
682  // Initialize RVInstMarker.
683  RVInstMarker = nullptr;
684  if (NamedMDNode *NMD =
685  M.getNamedMetadata("clang.arc.retainAutoreleasedReturnValueMarker"))
686  if (NMD->getNumOperands() == 1) {
687  const MDNode *N = NMD->getOperand(0);
688  if (N->getNumOperands() == 1)
689  if (const MDString *S = dyn_cast<MDString>(N->getOperand(0)))
690  RVInstMarker = S;
691  }
692 
693  return false;
694 }
Pass interface - Implemented by all &#39;passes&#39;.
Definition: Pass.h:81
bool isVarArg() const
isVarArg - Return true if this function takes a variable number of arguments.
Definition: Function.h:158
objc arc contract
uint64_t CallInst * C
Value * getValueOperand()
Definition: Instructions.h:395
SymbolTableList< Instruction >::iterator eraseFromParent()
This method unlinks &#39;this&#39; from the containing basic block and deletes it.
Definition: Instruction.cpp:69
use_iterator use_end()
Definition: Value.h:348
This file declares special dependency analysis routines used in Objective C ARC Optimizations.
void setDoesNotThrow()
static PassRegistry * getPassRegistry()
getPassRegistry - Access the global registry object, which is automatically initialized at applicatio...
This file contains a class ARCRuntimeEntryPoints for use in creating/managing references to entry poi...
Compute iterated dominance frontiers using a linear time algorithm.
Definition: AllocatorList.h:24
A Module instance is used to store all the information related to an LLVM module. ...
Definition: Module.h:63
bool CanUse(const Instruction *Inst, const Value *Ptr, ProvenanceAnalysis &PA, ARCInstKind Class)
Test whether the given instruction can "use" the given pointer&#39;s object in a way that requires the re...
Blocks objc_retainAutorelease.
This class represents a function call, abstracting a target machine&#39;s calling convention.
Value * GetArgRCIdentityRoot(Value *Inst)
Assuming the given instruction is one of the special calls such as objc_retain or objc_release...
LLVMContext & getContext() const
All values hold a context through their type.
Definition: Value.cpp:728
STATISTIC(NumFunctions, "Total number of functions")
Metadata node.
Definition: Metadata.h:862
F(f)
static CallInst * Create(Value *Func, ArrayRef< Value *> Args, ArrayRef< OperandBundleDef > Bundles=None, const Twine &NameStr="", Instruction *InsertBefore=nullptr)
could call objc_release
const MDOperand & getOperand(unsigned I) const
Definition: Metadata.h:1067
An instruction for reading from memory.
Definition: Instructions.h:164
The access modifies the value stored in memory.
Value * get() const
Definition: Use.h:108
iterator begin()
Instruction iterator methods.
Definition: BasicBlock.h:252
static unsigned getOperandNumForIncomingValue(unsigned i)
#define INITIALIZE_PASS_DEPENDENCY(depName)
Definition: PassSupport.h:51
A tuple of MDNodes.
Definition: Metadata.h:1323
objc_autoreleaseReturnValue
static Value * getPointerOperand(Instruction &Inst)
inst_iterator inst_begin(Function *F)
Definition: InstIterator.h:132
A Use represents the edge between a Value definition and its users.
Definition: Use.h:56
void initializeObjCARCContractPass(PassRegistry &)
bool IsNullOrUndef(const Value *V)
This file defines common definitions/declarations used by the ObjC ARC Optimizer. ...
objc_retainAutoreleasedReturnValue
User * getUser() const LLVM_READONLY
Returns the User that contains this Use.
Definition: Use.cpp:41
Type * getType() const
All values are typed, get the type of this value.
Definition: Value.h:245
Pass * createObjCARCContractPass()
bool EnableARCOpts
A handy option to enable/disable all ARC Optimizations.
NamedMDNode * getNamedMetadata(const Twine &Name) const
Return the first NamedMDNode in the module with the specified name.
Definition: Module.cpp:242
This class represents a no-op cast from one type to another.
An instruction for storing to memory.
Definition: Instructions.h:306
void replaceAllUsesWith(Value *V)
Change all uses of this to point to a new Value.
Definition: Value.cpp:430
unsigned getOperandNo() const
Return the operand # of this use in its User.
Definition: Use.cpp:48
INITIALIZE_PASS_BEGIN(ObjCARCContract, "objc-arc-contract", "ObjC ARC contraction", false, false) INITIALIZE_PASS_END(ObjCARCContract
Concrete subclass of DominatorTreeBase that is used to compute a normal dominator tree...
Definition: Dominators.h:140
bool ModuleHasARC(const Module &M)
Test if the given module looks interesting to run ARC optimization on.
use_iterator_impl< Use > use_iterator
Definition: Value.h:333
static bool runOnFunction(Function &F, bool PostInlining)
static MemoryLocation get(const LoadInst *LI)
Return a location with information about the memory reference by the given instruction.
static GCRegistry::Add< OcamlGC > B("ocaml", "ocaml 3.10-compatible GC")
static StoreInst * findSafeStoreForStoreStrongContraction(LoadInst *Load, Instruction *Release, ProvenanceAnalysis &PA, AliasAnalysis *AA)
void setDebugLoc(DebugLoc Loc)
Set the debug location information for this instruction.
Definition: Instruction.h:281
static ConstantPointerNull * get(PointerType *T)
Static factory methods - Return objects of the specified value.
Definition: Constants.cpp:1306
const BasicBlock * getSinglePredecessor() const
Return the predecessor of this block if it has a single predecessor block.
Definition: BasicBlock.cpp:217
void set(Value *Val)
Definition: Value.h:677
LLVM Basic Block Representation.
Definition: BasicBlock.h:59
The instances of the Type class are immutable: once they are created, they are never changed...
Definition: Type.h:46
This is an important class for using LLVM in a threaded context.
Definition: LLVMContext.h:69
static GCRegistry::Add< CoreCLRGC > E("coreclr", "CoreCLR-compatible GC")
This is an important base class in LLVM.
Definition: Constant.h:42
objc_initWeak (derived)
Represent the analysis usage information of a pass.
static Type * getVoidTy(LLVMContext &C)
Definition: Type.cpp:161
const Instruction & back() const
Definition: BasicBlock.h:266
FunctionPass class - This class is used to implement most global optimizations.
Definition: Pass.h:285
static FunctionType * get(Type *Result, ArrayRef< Type *> Params, bool isVarArg)
This static method is the primary way of constructing a FunctionType.
Definition: Type.cpp:297
self_iterator getIterator()
Definition: ilist_node.h:82
static Instruction * findRetainForStoreStrongContraction(Value *New, StoreInst *Store, Instruction *Release, ProvenanceAnalysis &PA)
const Value * stripPointerCasts() const
Strip off pointer casts, all-zero GEPs, and aliases.
Definition: Value.cpp:558
static unsigned getIncomingValueNumForOperand(unsigned i)
static wasm::ValType getType(const TargetRegisterClass *RC)
INITIALIZE_PASS_END(RegBankSelect, DEBUG_TYPE, "Assign register bank of generic virtual registers", false, false) RegBankSelect
ARCInstKind GetBasicARCInstKind(const Value *V)
Determine which objc runtime call instruction class V belongs to.
bool CanDecrementRefCount(ARCInstKind Kind)
Returns false if conservatively we can prove that any instruction mapped to this kind can not decreme...
const Value * Ptr
The address of the start of the location.
Representation for a specific memory location.
static void EraseInstruction(Instruction *CI)
Erase the given instruction.
Definition: ObjCARC.h:52
objc arc ObjC ARC contraction
Iterator for intrusive lists based on ilist_node.
SmallPtrSet - This class implements a set which is optimized for holding SmallSize or less elements...
Definition: SmallPtrSet.h:418
static PointerType * getUnqual(Type *ElementType)
This constructs a pointer to an object of the specified type in the generic address space (address sp...
Definition: DerivedTypes.h:482
iterator end()
Definition: BasicBlock.h:254
This file declares a special form of Alias Analysis called ``Provenance Analysis&#39;&#39;.
This is a &#39;vector&#39; (really, a variable-sized array), optimized for the case when the array is small...
Definition: SmallVector.h:864
ARCInstKind
Equivalence classes of instructions in the ARC Model.
objc_unsafeClaimAutoreleasedReturnValue
LLVM_NODISCARD T pop_back_val()
Definition: SmallVector.h:385
raw_ostream & dbgs()
dbgs() - This returns a reference to a raw_ostream for debugging messages.
Definition: Debug.cpp:132
ModRefInfo getModRefInfo(ImmutableCallSite CS, const MemoryLocation &Loc)
getModRefInfo (for call sites) - Return information about whether a particular call site modifies or ...
void FindDependencies(DependenceKind Flavor, const Value *Arg, BasicBlock *StartBB, Instruction *StartInst, SmallPtrSetImpl< Instruction *> &DependingInstructions, SmallPtrSetImpl< const BasicBlock *> &Visited, ProvenanceAnalysis &PA)
Walk up the CFG from StartPos (which is in StartBB) and find local and non-local dependencies on Arg...
iterator_range< user_iterator > users()
Definition: Value.h:401
objc arc
objc_storeStrong (derived)
amdgpu Simplify well known AMD library false Value Value * Arg
could "use" a pointer
bool IsRetain(ARCInstKind Class)
Test if the given class is objc_retain or equivalent.
use_iterator use_begin()
Definition: Value.h:340
void setCalledFunction(Value *Fn)
Set the function called.
const DebugLoc & getDebugLoc() const
Return the debug location for this node as a DebugLoc.
Definition: Instruction.h:284
LLVM_NODISCARD bool empty() const
Definition: SmallVector.h:61
Value * getArgOperand(unsigned i) const
getArgOperand/setArgOperand - Return/set the i-th call argument.
Establish a view to a call site for examination.
Definition: CallSite.h:713
Blocks objc_retainAutoreleaseReturnValue.
#define I(x, y, z)
Definition: MD5.cpp:58
#define N
LLVM_NODISCARD std::enable_if<!is_simple_type< Y >::value, typename cast_retty< X, const Y >::ret_type >::type dyn_cast(const Y &Val)
Definition: Casting.h:323
Declarations for ObjC runtime functions and constants.
static InlineAsm * get(FunctionType *Ty, StringRef AsmString, StringRef Constraints, bool hasSideEffects, bool isAlignStack=false, AsmDialect asmDialect=AD_ATT)
InlineAsm::get - Return the specified uniqued inline asm string.
Definition: InlineAsm.cpp:43
bool callsFunctionThatReturnsTwice() const
callsFunctionThatReturnsTwice - Return true if the function has a call to setjmp or other function th...
Definition: Function.cpp:1249
LLVM Value Representation.
Definition: Value.h:73
#define LLVM_FALLTHROUGH
LLVM_FALLTHROUGH - Mark fallthrough cases in switch statements.
Definition: Compiler.h:235
#define DEBUG(X)
Definition: Debug.h:118
This is similar to BasicAliasAnalysis, and it uses many of the same techniques, except it uses specia...
const Value * GetRCIdentityRoot(const Value *V)
The RCIdentity root of a value V is a dominating value U for which retaining or releasing U is equiva...
inst_iterator inst_end(Function *F)
Definition: InstIterator.h:133
A single uniqued string.
Definition: Metadata.h:602
Legacy analysis pass which computes a DominatorTree.
Definition: Dominators.h:267
A wrapper pass to provide the legacy pass manager access to a suitably prepared AAResults object...
bool isSimple() const
Definition: Instructions.h:387
const TerminatorInst * getTerminator() const LLVM_READONLY
Returns the terminator instruction if the block is well formed or null if the block is not well forme...
Definition: BasicBlock.cpp:120
unsigned getNumOperands() const
Return number of MDNode operands.
Definition: Metadata.h:1073
Value * getPointerOperand()
Definition: Instructions.h:398
static IntegerType * getInt8Ty(LLVMContext &C)
Definition: Type.cpp:174
constexpr char Args[]
Key for Kernel::Metadata::mArgs.
bool IsNoopInstruction(const Instruction *I)
const BasicBlock * getParent() const
Definition: Instruction.h:66