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