LLVM 20.0.0git
ObjCARCExpand.cpp
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1//===- ObjCARCExpand.cpp - ObjC ARC Optimization --------------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8/// \file
9/// This file defines ObjC ARC optimizations. ARC stands for Automatic
10/// Reference Counting and is a system for managing reference counts for objects
11/// in Objective C.
12///
13/// This specific file deals with early optimizations which perform certain
14/// cleanup operations.
15///
16/// WARNING: This file knows about certain library functions. It recognizes them
17/// by name, and hardwires knowledge of their semantics.
18///
19/// WARNING: This file knows about how certain Objective-C library functions are
20/// used. Naive LLVM IR transformations which would otherwise be
21/// behavior-preserving may break these assumptions.
22///
23//===----------------------------------------------------------------------===//
24
26#include "llvm/IR/Function.h"
28#include "llvm/IR/Instruction.h"
30#include "llvm/IR/PassManager.h"
31#include "llvm/IR/Value.h"
33#include "llvm/Support/Debug.h"
36
37#define DEBUG_TYPE "objc-arc-expand"
38
39using namespace llvm;
40using namespace llvm::objcarc;
41
42namespace {
43static bool runImpl(Function &F) {
44 if (!EnableARCOpts)
45 return false;
46
47 // If nothing in the Module uses ARC, don't do anything.
48 if (!ModuleHasARC(*F.getParent()))
49 return false;
50
51 bool Changed = false;
52
53 LLVM_DEBUG(dbgs() << "ObjCARCExpand: Visiting Function: " << F.getName()
54 << "\n");
55
56 for (Instruction &Inst : instructions(&F)) {
57 LLVM_DEBUG(dbgs() << "ObjCARCExpand: Visiting: " << Inst << "\n");
58
59 switch (GetBasicARCInstKind(&Inst)) {
60 case ARCInstKind::Retain:
61 case ARCInstKind::RetainRV:
62 case ARCInstKind::Autorelease:
63 case ARCInstKind::AutoreleaseRV:
64 case ARCInstKind::FusedRetainAutorelease:
65 case ARCInstKind::FusedRetainAutoreleaseRV: {
66 // These calls return their argument verbatim, as a low-level
67 // optimization. However, this makes high-level optimizations
68 // harder. Undo any uses of this optimization that the front-end
69 // emitted here. We'll redo them in the contract pass.
70 Changed = true;
71 Value *Value = cast<CallInst>(&Inst)->getArgOperand(0);
72 LLVM_DEBUG(dbgs() << "ObjCARCExpand: Old = " << Inst
73 << "\n"
74 " New = "
75 << *Value << "\n");
76 Inst.replaceAllUsesWith(Value);
77 break;
78 }
79 default:
80 break;
81 }
82 }
83
84 LLVM_DEBUG(dbgs() << "ObjCARCExpand: Finished List.\n\n");
85
86 return Changed;
87}
88
89} // namespace
90
93 if (!runImpl(F))
97 return PA;
98}
Expand Atomic instructions
#define LLVM_DEBUG(...)
Definition: Debug.h:106
static bool runImpl(Function &F, const TargetLowering &TLI)
This header defines various interfaces for pass management in LLVM.
#define F(x, y, z)
Definition: MD5.cpp:55
This file defines common analysis utilities used by the ObjC ARC Optimizer.
A container for analyses that lazily runs them and caches their results.
Definition: PassManager.h:253
Represents analyses that only rely on functions' control flow.
Definition: Analysis.h:72
A set of analyses that are preserved following a run of a transformation pass.
Definition: Analysis.h:111
static PreservedAnalyses all()
Construct a special preserved set that preserves all passes.
Definition: Analysis.h:117
void preserveSet()
Mark an analysis set as preserved.
Definition: Analysis.h:146
LLVM Value Representation.
Definition: Value.h:74
bool ModuleHasARC(const Module &M)
Test if the given module looks interesting to run ARC optimization on.
bool EnableARCOpts
A handy option to enable/disable all ARC Optimizations.
ARCInstKind GetBasicARCInstKind(const Value *V)
Determine which objc runtime call instruction class V belongs to.
This is an optimization pass for GlobalISel generic memory operations.
Definition: AddressRanges.h:18
raw_ostream & dbgs()
dbgs() - This returns a reference to a raw_ostream for debugging messages.
Definition: Debug.cpp:163
PreservedAnalyses run(Function &M, FunctionAnalysisManager &AM)