forked from OSchip/llvm-project
112 lines
3.3 KiB
C++
112 lines
3.3 KiB
C++
//===- ObjCARCExpand.cpp - ObjC ARC Optimization --------------------------===//
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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 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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#define DEBUG_TYPE "objc-arc-expand"
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#include "ObjCARC.h"
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using namespace llvm;
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using namespace llvm::objcarc;
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namespace {
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/// \brief Early ARC transformations.
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class ObjCARCExpand : public FunctionPass {
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virtual void getAnalysisUsage(AnalysisUsage &AU) const;
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virtual bool doInitialization(Module &M);
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virtual bool runOnFunction(Function &F);
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/// A flag indicating whether this optimization pass should run.
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bool Run;
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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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}
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char ObjCARCExpand::ID = 0;
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INITIALIZE_PASS(ObjCARCExpand,
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"objc-arc-expand", "ObjC ARC expansion", false, false)
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Pass *llvm::createObjCARCExpandPass() {
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return new ObjCARCExpand();
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}
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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::doInitialization(Module &M) {
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Run = ModuleHasARC(M);
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return false;
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}
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bool ObjCARCExpand::runOnFunction(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 (!Run)
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return false;
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bool Changed = false;
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DEBUG(dbgs() << "ObjCARCExpand: Visiting Function: " << F.getName() << "\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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DEBUG(dbgs() << "ObjCARCExpand: Visiting: " << *Inst << "\n");
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switch (GetBasicInstructionClass(Inst)) {
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case IC_Retain:
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case IC_RetainRV:
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case IC_Autorelease:
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case IC_AutoreleaseRV:
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case IC_FusedRetainAutorelease:
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case IC_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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DEBUG(dbgs() << "ObjCARCExpand: Old = " << *Inst << "\n"
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" New = " << *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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DEBUG(dbgs() << "ObjCARCExpand: Finished List.\n\n");
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return Changed;
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}
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