llvm/lib/Transforms/ObjCARC/DependencyAnalysis.h

   1 //===- DependencyAnalysis.h - ObjC ARC Optimization ---*- C++ -*-----------===//
   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 ///
  10 /// This file declares special dependency analysis routines used in Objective C
  11 /// ARC Optimizations.
  12 ///
  13 /// WARNING: This file knows about certain library functions. It recognizes them
  14 /// by name, and hardwires knowledge of their semantics.
  15 ///
  16 /// WARNING: This file knows about how certain Objective-C library functions are
  17 /// used. Naive LLVM IR transformations which would otherwise be
  18 /// behavior-preserving may break these assumptions.
  19 ///
  20 //===----------------------------------------------------------------------===//
  21
  22 #ifndef LLVM_LIB_TRANSFORMS_OBJCARC_DEPENDENCYANALYSIS_H
  23 #define LLVM_LIB_TRANSFORMS_OBJCARC_DEPENDENCYANALYSIS_H
  24
  25 #include "llvm/ADT/SmallPtrSet.h"
  26 #include "llvm/Analysis/ObjCARCInstKind.h"
  27
  28 namespace llvm {
  29   class BasicBlock;
  30   class Instruction;
  31   class Value;
  32 }
  33
  34 namespace llvm {
  35 namespace objcarc {
  36
  37 class ProvenanceAnalysis;
  38
  39 /// \enum DependenceKind
  40 /// Defines different dependence kinds among various ARC constructs.
  41 ///
  42 /// There are several kinds of dependence-like concepts in use here.
  43 ///
  44 enum DependenceKind {
  45   NeedsPositiveRetainCount,
  46   AutoreleasePoolBoundary,
  47   CanChangeRetainCount,
  48   RetainAutoreleaseDep,       ///< Blocks objc_retainAutorelease.
  49   RetainAutoreleaseRVDep      ///< Blocks objc_retainAutoreleaseReturnValue.
  50 };
  51
  52 /// Find dependent instructions. If there is exactly one dependent instruction,
  53 /// return it. Otherwise, return null.
  54 llvm::Instruction *findSingleDependency(DependenceKind Flavor, const Value *Arg,
  55                                         BasicBlock *StartBB,
  56                                         Instruction *StartInst,
  57                                         ProvenanceAnalysis &PA);
  58
  59 bool
  60 Depends(DependenceKind Flavor, Instruction *Inst, const Value *Arg,
  61         ProvenanceAnalysis &PA);
  62
  63 /// Test whether the given instruction can "use" the given pointer's object in a
  64 /// way that requires the reference count to be positive.
  65 bool CanUse(const Instruction *Inst, const Value *Ptr, ProvenanceAnalysis &PA,
  66             ARCInstKind Class);
  67
  68 /// Test whether the given instruction can result in a reference count
  69 /// modification (positive or negative) for the pointer's object.
  70 bool CanAlterRefCount(const Instruction *Inst, const Value *Ptr,
  71                       ProvenanceAnalysis &PA, ARCInstKind Class);
  72
  73 /// Returns true if we can not conservatively prove that Inst can not decrement
  74 /// the reference count of Ptr. Returns false if we can.
  75 bool CanDecrementRefCount(const Instruction *Inst, const Value *Ptr,
  76                           ProvenanceAnalysis &PA, ARCInstKind Class);
  77
  78 static inline bool CanDecrementRefCount(const Instruction *Inst,
  79                                         const Value *Ptr,
  80                                         ProvenanceAnalysis &PA) {
  81   return CanDecrementRefCount(Inst, Ptr, PA, GetARCInstKind(Inst));
  82 }
  83
  84 } // namespace objcarc
  85 } // namespace llvm
  86
  87 #endif