1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
|
//===----- llvm/Analysis/CaptureTracking.h - Pointer capture ----*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file contains routines that help determine which pointers are captured.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_ANALYSIS_CAPTURETRACKING_H
#define LLVM_ANALYSIS_CAPTURETRACKING_H
namespace llvm {
class Value;
class Use;
class DataLayout;
class Instruction;
class DominatorTree;
class OrderedBasicBlock;
/// The default value for MaxUsesToExplore argument. It's relatively small to
/// keep the cost of analysis reasonable for clients like BasicAliasAnalysis,
/// where the results can't be cached.
/// TODO: we should probably introduce a caching CaptureTracking analysis and
/// use it where possible. The caching version can use much higher limit or
/// don't have this cap at all.
unsigned constexpr DefaultMaxUsesToExplore = 20;
/// PointerMayBeCaptured - Return true if this pointer value may be captured
/// by the enclosing function (which is required to exist). This routine can
/// be expensive, so consider caching the results. The boolean ReturnCaptures
/// specifies whether returning the value (or part of it) from the function
/// counts as capturing it or not. The boolean StoreCaptures specified
/// whether storing the value (or part of it) into memory anywhere
/// automatically counts as capturing it or not.
/// MaxUsesToExplore specifies how many uses should the analysis explore for
/// one value before giving up due too "too many uses".
bool PointerMayBeCaptured(const Value *V,
bool ReturnCaptures,
bool StoreCaptures,
unsigned MaxUsesToExplore = DefaultMaxUsesToExplore);
/// PointerMayBeCapturedBefore - Return true if this pointer value may be
/// captured by the enclosing function (which is required to exist). If a
/// DominatorTree is provided, only captures which happen before the given
/// instruction are considered. This routine can be expensive, so consider
/// caching the results. The boolean ReturnCaptures specifies whether
/// returning the value (or part of it) from the function counts as capturing
/// it or not. The boolean StoreCaptures specified whether storing the value
/// (or part of it) into memory anywhere automatically counts as capturing it
/// or not. Captures by the provided instruction are considered if the
/// final parameter is true. An ordered basic block in \p OBB could be used
/// to speed up capture-tracker queries.
/// MaxUsesToExplore specifies how many uses should the analysis explore for
/// one value before giving up due too "too many uses".
bool PointerMayBeCapturedBefore(const Value *V, bool ReturnCaptures,
bool StoreCaptures, const Instruction *I,
const DominatorTree *DT, bool IncludeI = false,
OrderedBasicBlock *OBB = nullptr,
unsigned MaxUsesToExplore = DefaultMaxUsesToExplore);
/// This callback is used in conjunction with PointerMayBeCaptured. In
/// addition to the interface here, you'll need to provide your own getters
/// to see whether anything was captured.
struct CaptureTracker {
virtual ~CaptureTracker();
/// tooManyUses - The depth of traversal has breached a limit. There may be
/// capturing instructions that will not be passed into captured().
virtual void tooManyUses() = 0;
/// shouldExplore - This is the use of a value derived from the pointer.
/// To prune the search (ie., assume that none of its users could possibly
/// capture) return false. To search it, return true.
///
/// U->getUser() is always an Instruction.
virtual bool shouldExplore(const Use *U);
/// captured - Information about the pointer was captured by the user of
/// use U. Return true to stop the traversal or false to continue looking
/// for more capturing instructions.
virtual bool captured(const Use *U) = 0;
/// isDereferenceableOrNull - Overload to allow clients with additional
/// knowledge about pointer dereferenceability to provide it and thereby
/// avoid conservative responses when a pointer is compared to null.
virtual bool isDereferenceableOrNull(Value *O, const DataLayout &DL);
};
/// PointerMayBeCaptured - Visit the value and the values derived from it and
/// find values which appear to be capturing the pointer value. This feeds
/// results into and is controlled by the CaptureTracker object.
/// MaxUsesToExplore specifies how many uses should the analysis explore for
/// one value before giving up due too "too many uses".
void PointerMayBeCaptured(const Value *V, CaptureTracker *Tracker,
unsigned MaxUsesToExplore = DefaultMaxUsesToExplore);
} // end namespace llvm
#endif
|
