LLVM  14.0.0git
CaptureTracking.h
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1 //===----- llvm/Analysis/CaptureTracking.h - Pointer capture ----*- 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 //
9 // This file contains routines that help determine which pointers are captured.
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #ifndef LLVM_ANALYSIS_CAPTURETRACKING_H
14 #define LLVM_ANALYSIS_CAPTURETRACKING_H
15 
16 #include "llvm/ADT/DenseMap.h"
17 
18 namespace llvm {
19 
20  class Value;
21  class Use;
22  class DataLayout;
23  class Instruction;
24  class DominatorTree;
25  class LoopInfo;
26  class Function;
27 
28  /// getDefaultMaxUsesToExploreForCaptureTracking - Return default value of
29  /// the maximal number of uses to explore before giving up. It is used by
30  /// PointerMayBeCaptured family analysis.
32 
33  /// PointerMayBeCaptured - Return true if this pointer value may be captured
34  /// by the enclosing function (which is required to exist). This routine can
35  /// be expensive, so consider caching the results. The boolean ReturnCaptures
36  /// specifies whether returning the value (or part of it) from the function
37  /// counts as capturing it or not. The boolean StoreCaptures specified
38  /// whether storing the value (or part of it) into memory anywhere
39  /// automatically counts as capturing it or not.
40  /// MaxUsesToExplore specifies how many uses the analysis should explore for
41  /// one value before giving up due too "too many uses". If MaxUsesToExplore
42  /// is zero, a default value is assumed.
43  bool PointerMayBeCaptured(const Value *V, bool ReturnCaptures,
44  bool StoreCaptures,
45  unsigned MaxUsesToExplore = 0);
46 
47  /// PointerMayBeCapturedBefore - Return true if this pointer value may be
48  /// captured by the enclosing function (which is required to exist). If a
49  /// DominatorTree is provided, only captures which happen before the given
50  /// instruction are considered. This routine can be expensive, so consider
51  /// caching the results. The boolean ReturnCaptures specifies whether
52  /// returning the value (or part of it) from the function counts as capturing
53  /// it or not. The boolean StoreCaptures specified whether storing the value
54  /// (or part of it) into memory anywhere automatically counts as capturing it
55  /// or not. Captures by the provided instruction are considered if the
56  /// final parameter is true.
57  /// MaxUsesToExplore specifies how many uses the analysis should explore for
58  /// one value before giving up due too "too many uses". If MaxUsesToExplore
59  /// is zero, a default value is assumed.
60  bool PointerMayBeCapturedBefore(const Value *V, bool ReturnCaptures,
61  bool StoreCaptures, const Instruction *I,
62  const DominatorTree *DT,
63  bool IncludeI = false,
64  unsigned MaxUsesToExplore = 0,
65  const LoopInfo *LI = nullptr);
66 
67  // Returns the 'earliest' instruction that captures \p V in \F. An instruction
68  // A is considered earlier than instruction B, if A dominates B. If 2 escapes
69  // do not dominate each other, the terminator of the common dominator is
70  // chosen. If not all uses can be analyzed, the earliest escape is set to
71  // the first instruction in the function entry block. If \p V does not escape,
72  // nullptr is returned. Note that the caller of the function has to ensure
73  // that the instruction the result value is compared against is not in a
74  // cycle.
75  Instruction *FindEarliestCapture(const Value *V, Function &F,
76  bool ReturnCaptures, bool StoreCaptures,
77  const DominatorTree &DT,
78  unsigned MaxUsesToExplore = 0);
79 
80  /// This callback is used in conjunction with PointerMayBeCaptured. In
81  /// addition to the interface here, you'll need to provide your own getters
82  /// to see whether anything was captured.
83  struct CaptureTracker {
84  virtual ~CaptureTracker();
85 
86  /// tooManyUses - The depth of traversal has breached a limit. There may be
87  /// capturing instructions that will not be passed into captured().
88  virtual void tooManyUses() = 0;
89 
90  /// shouldExplore - This is the use of a value derived from the pointer.
91  /// To prune the search (ie., assume that none of its users could possibly
92  /// capture) return false. To search it, return true.
93  ///
94  /// U->getUser() is always an Instruction.
95  virtual bool shouldExplore(const Use *U);
96 
97  /// captured - Information about the pointer was captured by the user of
98  /// use U. Return true to stop the traversal or false to continue looking
99  /// for more capturing instructions.
100  virtual bool captured(const Use *U) = 0;
101 
102  /// isDereferenceableOrNull - Overload to allow clients with additional
103  /// knowledge about pointer dereferenceability to provide it and thereby
104  /// avoid conservative responses when a pointer is compared to null.
105  virtual bool isDereferenceableOrNull(Value *O, const DataLayout &DL);
106  };
107 
108  /// PointerMayBeCaptured - Visit the value and the values derived from it and
109  /// find values which appear to be capturing the pointer value. This feeds
110  /// results into and is controlled by the CaptureTracker object.
111  /// MaxUsesToExplore specifies how many uses the analysis should explore for
112  /// one value before giving up due too "too many uses". If MaxUsesToExplore
113  /// is zero, a default value is assumed.
114  void PointerMayBeCaptured(const Value *V, CaptureTracker *Tracker,
115  unsigned MaxUsesToExplore = 0);
116 
117  /// Returns true if the pointer is to a function-local object that never
118  /// escapes from the function.
120  const Value *V,
121  SmallDenseMap<const Value *, bool, 8> *IsCapturedCache = nullptr);
122 } // end namespace llvm
123 
124 #endif
llvm
This file implements support for optimizing divisions by a constant.
Definition: AllocatorList.h:23
llvm::FindEarliestCapture
Instruction * FindEarliestCapture(const Value *V, Function &F, bool ReturnCaptures, bool StoreCaptures, const DominatorTree &DT, unsigned MaxUsesToExplore=0)
Definition: CaptureTracking.cpp:269
llvm::getDefaultMaxUsesToExploreForCaptureTracking
unsigned getDefaultMaxUsesToExploreForCaptureTracking()
getDefaultMaxUsesToExploreForCaptureTracking - Return default value of the maximal number of uses to ...
Definition: CaptureTracking.cpp:51
llvm::DataLayout
A parsed version of the target data layout string in and methods for querying it.
Definition: DataLayout.h:113
llvm::isNonEscapingLocalObject
bool isNonEscapingLocalObject(const Value *V, SmallDenseMap< const Value *, bool, 8 > *IsCapturedCache=nullptr)
Returns true if the pointer is to a function-local object that never escapes from the function.
Definition: CaptureTracking.cpp:456
llvm::CaptureTracker
This callback is used in conjunction with PointerMayBeCaptured.
Definition: CaptureTracking.h:83
llvm::CaptureTracker::captured
virtual bool captured(const Use *U)=0
captured - Information about the pointer was captured by the user of use U.
llvm::SmallDenseMap
Definition: DenseMap.h:880
DenseMap.h
F
#define F(x, y, z)
Definition: MD5.cpp:56
llvm::CaptureTracker::~CaptureTracker
virtual ~CaptureTracker()
Definition: CaptureTracking.cpp:55
llvm::CaptureTracker::shouldExplore
virtual bool shouldExplore(const Use *U)
shouldExplore - This is the use of a value derived from the pointer.
Definition: CaptureTracking.cpp:57
llvm::CaptureTracker::isDereferenceableOrNull
virtual bool isDereferenceableOrNull(Value *O, const DataLayout &DL)
isDereferenceableOrNull - Overload to allow clients with additional knowledge about pointer dereferen...
Definition: CaptureTracking.cpp:59
llvm::RISCVFenceField::O
@ O
Definition: RISCVBaseInfo.h:197
I
#define I(x, y, z)
Definition: MD5.cpp:59
llvm::PointerMayBeCaptured
bool PointerMayBeCaptured(const Value *V, bool ReturnCaptures, bool StoreCaptures, unsigned MaxUsesToExplore=0)
PointerMayBeCaptured - Return true if this pointer value may be captured by the enclosing function (w...
Definition: CaptureTracking.cpp:215
DL
MachineBasicBlock MachineBasicBlock::iterator DebugLoc DL
Definition: AArch64SLSHardening.cpp:76
llvm::TargetStackID::Value
Value
Definition: TargetFrameLowering.h:27
llvm::CaptureTracker::tooManyUses
virtual void tooManyUses()=0
tooManyUses - The depth of traversal has breached a limit.
llvm::PointerMayBeCapturedBefore
bool PointerMayBeCapturedBefore(const Value *V, bool ReturnCaptures, bool StoreCaptures, const Instruction *I, const DominatorTree *DT, bool IncludeI=false, unsigned MaxUsesToExplore=0, const LoopInfo *LI=nullptr)
PointerMayBeCapturedBefore - Return true if this pointer value may be captured by the enclosing funct...
Definition: CaptureTracking.cpp:245
llvm::Value
LLVM Value Representation.
Definition: Value.h:75
llvm::codeview::PublicSymFlags::Function
@ Function
llvm::Use
A Use represents the edge between a Value definition and its users.
Definition: Use.h:44