Coverage Report

Created: 2019-07-24 05:18

/Users/buildslave/jenkins/workspace/clang-stage2-coverage-R/llvm/lib/Transforms/ObjCARC/ObjCARCExpand.cpp
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//===- 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/Value.h"
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#include "llvm/Pass.h"
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#include "llvm/PassAnalysisSupport.h"
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#include "llvm/PassRegistry.h"
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#include "llvm/PassSupport.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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#define DEBUG_TYPE "objc-arc-expand"
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namespace llvm {
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  class Module;
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}
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using namespace llvm;
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using namespace llvm::objcarc;
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namespace {
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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 doInitialization(Module &M) override;
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    bool runOnFunction(Function &F) override;
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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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  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; 
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) {
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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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}