| //===- ObjCARCExpand.cpp - ObjC ARC Optimization --------------------------===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| /// \file |
| /// This file defines ObjC ARC optimizations. ARC stands for Automatic |
| /// Reference Counting and is a system for managing reference counts for objects |
| /// in Objective C. |
| /// |
| /// This specific file deals with early optimizations which perform certain |
| /// cleanup operations. |
| /// |
| /// WARNING: This file knows about certain library functions. It recognizes them |
| /// by name, and hardwires knowledge of their semantics. |
| /// |
| /// WARNING: This file knows about how certain Objective-C library functions are |
| /// used. Naive LLVM IR transformations which would otherwise be |
| /// behavior-preserving may break these assumptions. |
| /// |
| //===----------------------------------------------------------------------===// |
| |
| #include "ObjCARC.h" |
| #include "llvm/IR/Function.h" |
| #include "llvm/IR/InstIterator.h" |
| #include "llvm/IR/Instruction.h" |
| #include "llvm/IR/Instructions.h" |
| #include "llvm/IR/PassManager.h" |
| #include "llvm/IR/Value.h" |
| #include "llvm/InitializePasses.h" |
| #include "llvm/Pass.h" |
| #include "llvm/PassRegistry.h" |
| #include "llvm/Support/Casting.h" |
| #include "llvm/Support/Debug.h" |
| #include "llvm/Support/raw_ostream.h" |
| #include "llvm/Transforms/ObjCARC.h" |
| |
| #define DEBUG_TYPE "objc-arc-expand" |
| |
| using namespace llvm; |
| using namespace llvm::objcarc; |
| |
| namespace { |
| static bool runImpl(Function &F) { |
| if (!EnableARCOpts) |
| return false; |
| |
| // If nothing in the Module uses ARC, don't do anything. |
| if (!ModuleHasARC(*F.getParent())) |
| return false; |
| |
| bool Changed = false; |
| |
| LLVM_DEBUG(dbgs() << "ObjCARCExpand: Visiting Function: " << F.getName() |
| << "\n"); |
| |
| for (Instruction &Inst : instructions(&F)) { |
| LLVM_DEBUG(dbgs() << "ObjCARCExpand: Visiting: " << Inst << "\n"); |
| |
| switch (GetBasicARCInstKind(&Inst)) { |
| case ARCInstKind::Retain: |
| case ARCInstKind::RetainRV: |
| case ARCInstKind::Autorelease: |
| case ARCInstKind::AutoreleaseRV: |
| case ARCInstKind::FusedRetainAutorelease: |
| case ARCInstKind::FusedRetainAutoreleaseRV: { |
| // These calls return their argument verbatim, as a low-level |
| // optimization. However, this makes high-level optimizations |
| // harder. Undo any uses of this optimization that the front-end |
| // emitted here. We'll redo them in the contract pass. |
| Changed = true; |
| Value *Value = cast<CallInst>(&Inst)->getArgOperand(0); |
| LLVM_DEBUG(dbgs() << "ObjCARCExpand: Old = " << Inst |
| << "\n" |
| " New = " |
| << *Value << "\n"); |
| Inst.replaceAllUsesWith(Value); |
| break; |
| } |
| default: |
| break; |
| } |
| } |
| |
| LLVM_DEBUG(dbgs() << "ObjCARCExpand: Finished List.\n\n"); |
| |
| return Changed; |
| } |
| |
| /// Early ARC transformations. |
| class ObjCARCExpand : public FunctionPass { |
| void getAnalysisUsage(AnalysisUsage &AU) const override; |
| bool runOnFunction(Function &F) override; |
| |
| public: |
| static char ID; |
| ObjCARCExpand() : FunctionPass(ID) { |
| initializeObjCARCExpandPass(*PassRegistry::getPassRegistry()); |
| } |
| }; |
| } // namespace |
| |
| char ObjCARCExpand::ID = 0; |
| INITIALIZE_PASS(ObjCARCExpand, "objc-arc-expand", "ObjC ARC expansion", false, |
| false) |
| |
| Pass *llvm::createObjCARCExpandPass() { return new ObjCARCExpand(); } |
| |
| void ObjCARCExpand::getAnalysisUsage(AnalysisUsage &AU) const { |
| AU.setPreservesCFG(); |
| } |
| |
| bool ObjCARCExpand::runOnFunction(Function &F) { return runImpl(F); } |
| |
| PreservedAnalyses ObjCARCExpandPass::run(Function &F, |
| FunctionAnalysisManager &AM) { |
| if (!runImpl(F)) |
| return PreservedAnalyses::all(); |
| PreservedAnalyses PA; |
| PA.preserveSet<CFGAnalyses>(); |
| return PA; |
| } |