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0e5c4f5246
retainAutoreleasedReturnValue that retains the returned value. This commit fixes a bug in ARC optimizer where it moves a release between a call and a retainAutoreleasedReturnValue, causing the returned object to be released before the retainAutoreleasedReturnValue can retain it. This commit accomplishes that by doing a lookahead and checking whether the call prevents the release from moving upwards. In the long term, we should treat the region between the retainAutoreleasedReturnValue and the call as a critical section and disallow moving anything there (possibly using operand bundles). rdar://problem/20449878 llvm-svn: 301724
89 lines
2.9 KiB
C++
89 lines
2.9 KiB
C++
//===- ObjCARC.h - ObjC ARC Optimization --------------*- C++ -*-----------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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/// \file
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/// This file defines common definitions/declarations used by the ObjC ARC
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/// Optimizer. ARC stands for Automatic Reference Counting and is a system for
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/// managing reference counts for objects in Objective C.
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///
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/// WARNING: This file knows about certain library functions. It recognizes them
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/// by name, and hardwires knowledge of their semantics.
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///
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/// WARNING: This file knows about how certain Objective-C library functions are
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/// used. Naive LLVM IR transformations which would otherwise be
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/// behavior-preserving may break these assumptions.
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///
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_LIB_TRANSFORMS_OBJCARC_OBJCARC_H
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#define LLVM_LIB_TRANSFORMS_OBJCARC_OBJCARC_H
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#include "llvm/ADT/StringSwitch.h"
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#include "llvm/Analysis/AliasAnalysis.h"
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#include "llvm/Analysis/ObjCARCAnalysisUtils.h"
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#include "llvm/Analysis/ObjCARCInstKind.h"
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#include "llvm/Analysis/Passes.h"
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#include "llvm/Analysis/ValueTracking.h"
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#include "llvm/IR/CallSite.h"
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#include "llvm/IR/InstIterator.h"
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#include "llvm/IR/Module.h"
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#include "llvm/Pass.h"
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#include "llvm/Transforms/ObjCARC.h"
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#include "llvm/Transforms/Utils/Local.h"
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namespace llvm {
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class raw_ostream;
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}
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namespace llvm {
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namespace objcarc {
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/// \brief Erase the given instruction.
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///
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/// Many ObjC calls return their argument verbatim,
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/// so if it's such a call and the return value has users, replace them with the
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/// argument value.
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///
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static inline void EraseInstruction(Instruction *CI) {
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Value *OldArg = cast<CallInst>(CI)->getArgOperand(0);
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bool Unused = CI->use_empty();
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if (!Unused) {
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// Replace the return value with the argument.
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assert((IsForwarding(GetBasicARCInstKind(CI)) ||
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(IsNoopOnNull(GetBasicARCInstKind(CI)) &&
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isa<ConstantPointerNull>(OldArg))) &&
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"Can't delete non-forwarding instruction with users!");
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CI->replaceAllUsesWith(OldArg);
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}
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CI->eraseFromParent();
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if (Unused)
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RecursivelyDeleteTriviallyDeadInstructions(OldArg);
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}
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/// If Inst is a ReturnRV and its operand is a call or invoke, return the
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/// operand. Otherwise return null.
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static inline const Instruction *getreturnRVOperand(const Instruction &Inst,
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ARCInstKind Class) {
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if (Class != ARCInstKind::RetainRV)
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return nullptr;
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const auto *Opnd = Inst.getOperand(0)->stripPointerCasts();
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if (const auto *C = dyn_cast<CallInst>(Opnd))
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return C;
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return dyn_cast<InvokeInst>(Opnd);
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}
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} // end namespace objcarc
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} // end namespace llvm
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#endif
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