LLVM  6.0.0svn
ObjCARC.h
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1 //===- ObjCARC.h - ObjC ARC Optimization --------------*- C++ -*-----------===//
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 common definitions/declarations used by the ObjC ARC
11 /// Optimizer. ARC stands for Automatic Reference Counting and is a system for
12 /// managing reference counts for objects in Objective C.
13 ///
14 /// WARNING: This file knows about certain library functions. It recognizes them
15 /// by name, and hardwires knowledge of their semantics.
16 ///
17 /// WARNING: This file knows about how certain Objective-C library functions are
18 /// used. Naive LLVM IR transformations which would otherwise be
19 /// behavior-preserving may break these assumptions.
20 ///
21 //===----------------------------------------------------------------------===//
22 
23 #ifndef LLVM_LIB_TRANSFORMS_OBJCARC_OBJCARC_H
24 #define LLVM_LIB_TRANSFORMS_OBJCARC_OBJCARC_H
25 
26 #include "llvm/ADT/StringSwitch.h"
30 #include "llvm/Analysis/Passes.h"
32 #include "llvm/IR/CallSite.h"
33 #include "llvm/IR/InstIterator.h"
34 #include "llvm/IR/Module.h"
35 #include "llvm/Pass.h"
38 
39 namespace llvm {
40 class raw_ostream;
41 }
42 
43 namespace llvm {
44 namespace objcarc {
45 
46 /// \brief Erase the given instruction.
47 ///
48 /// Many ObjC calls return their argument verbatim,
49 /// so if it's such a call and the return value has users, replace them with the
50 /// argument value.
51 ///
52 static inline void EraseInstruction(Instruction *CI) {
53  Value *OldArg = cast<CallInst>(CI)->getArgOperand(0);
54 
55  bool Unused = CI->use_empty();
56 
57  if (!Unused) {
58  // Replace the return value with the argument.
61  isa<ConstantPointerNull>(OldArg))) &&
62  "Can't delete non-forwarding instruction with users!");
63  CI->replaceAllUsesWith(OldArg);
64  }
65 
66  CI->eraseFromParent();
67 
68  if (Unused)
70 }
71 
72 /// If Inst is a ReturnRV and its operand is a call or invoke, return the
73 /// operand. Otherwise return null.
74 static inline const Instruction *getreturnRVOperand(const Instruction &Inst,
75  ARCInstKind Class) {
76  if (Class != ARCInstKind::RetainRV)
77  return nullptr;
78 
79  const auto *Opnd = Inst.getOperand(0)->stripPointerCasts();
80  if (const auto *C = dyn_cast<CallInst>(Opnd))
81  return C;
82  return dyn_cast<InvokeInst>(Opnd);
83 }
84 
85 } // end namespace objcarc
86 } // end namespace llvm
87 
88 #endif
uint64_t CallInst * C
SymbolTableList< Instruction >::iterator eraseFromParent()
This method unlinks &#39;this&#39; from the containing basic block and deletes it.
Definition: Instruction.cpp:69
Compute iterated dominance frontiers using a linear time algorithm.
Definition: AllocatorList.h:24
bool IsNoopOnNull(ARCInstKind Class)
Test if the given class represents instructions which do nothing if passed a null pointer...
bool IsForwarding(ARCInstKind Class)
Test if the given class represents instructions which return their argument verbatim.
objc_retainAutoreleasedReturnValue
void replaceAllUsesWith(Value *V)
Change all uses of this to point to a new Value.
Definition: Value.cpp:430
Value * getOperand(unsigned i) const
Definition: User.h:154
bool RecursivelyDeleteTriviallyDeadInstructions(Value *V, const TargetLibraryInfo *TLI=nullptr)
If the specified value is a trivially dead instruction, delete it.
Definition: Local.cpp:401
const Value * stripPointerCasts() const
Strip off pointer casts, all-zero GEPs, and aliases.
Definition: Value.cpp:558
This file defines common analysis utilities used by the ObjC ARC Optimizer.
ARCInstKind GetBasicARCInstKind(const Value *V)
Determine which objc runtime call instruction class V belongs to.
static void EraseInstruction(Instruction *CI)
Erase the given instruction.
Definition: ObjCARC.h:52
static const Instruction * getreturnRVOperand(const Instruction &Inst, ARCInstKind Class)
If Inst is a ReturnRV and its operand is a call or invoke, return the operand.
Definition: ObjCARC.h:74
ARCInstKind
Equivalence classes of instructions in the ARC Model.
Module.h This file contains the declarations for the Module class.
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
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
LLVM Value Representation.
Definition: Value.h:73
Invoke instruction.
bool use_empty() const
Definition: Value.h:328