1 //===----- llvm/Analysis/CaptureTracking.h - Pointer capture ----*- C++ -*-===//
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
7 //===----------------------------------------------------------------------===//
9 // This file contains routines that help determine which pointers are captured.
11 //===----------------------------------------------------------------------===//
13 #ifndef LLVM_ANALYSIS_CAPTURETRACKING_H
14 #define LLVM_ANALYSIS_CAPTURETRACKING_H
24 /// getDefaultMaxUsesToExploreForCaptureTracking - Return default value of
25 /// the maximal number of uses to explore before giving up. It is used by
26 /// PointerMayBeCaptured family analysis.
27 unsigned getDefaultMaxUsesToExploreForCaptureTracking();
29 /// PointerMayBeCaptured - Return true if this pointer value may be captured
30 /// by the enclosing function (which is required to exist). This routine can
31 /// be expensive, so consider caching the results. The boolean ReturnCaptures
32 /// specifies whether returning the value (or part of it) from the function
33 /// counts as capturing it or not. The boolean StoreCaptures specified
34 /// whether storing the value (or part of it) into memory anywhere
35 /// automatically counts as capturing it or not.
36 /// MaxUsesToExplore specifies how many uses the analysis should explore for
37 /// one value before giving up due too "too many uses". If MaxUsesToExplore
38 /// is zero, a default value is assumed.
39 bool PointerMayBeCaptured(const Value *V, bool ReturnCaptures,
41 unsigned MaxUsesToExplore = 0);
43 /// PointerMayBeCapturedBefore - Return true if this pointer value may be
44 /// captured by the enclosing function (which is required to exist). If a
45 /// DominatorTree is provided, only captures which happen before the given
46 /// instruction are considered. This routine can be expensive, so consider
47 /// caching the results. The boolean ReturnCaptures specifies whether
48 /// returning the value (or part of it) from the function counts as capturing
49 /// it or not. The boolean StoreCaptures specified whether storing the value
50 /// (or part of it) into memory anywhere automatically counts as capturing it
51 /// or not. Captures by the provided instruction are considered if the
52 /// final parameter is true.
53 /// MaxUsesToExplore specifies how many uses the analysis should explore for
54 /// one value before giving up due too "too many uses". If MaxUsesToExplore
55 /// is zero, a default value is assumed.
56 bool PointerMayBeCapturedBefore(
57 const Value *V, bool ReturnCaptures, bool StoreCaptures,
58 const Instruction *I, const DominatorTree *DT, bool IncludeI = false,
59 unsigned MaxUsesToExplore = 0);
61 /// This callback is used in conjunction with PointerMayBeCaptured. In
62 /// addition to the interface here, you'll need to provide your own getters
63 /// to see whether anything was captured.
64 struct CaptureTracker {
65 virtual ~CaptureTracker();
67 /// tooManyUses - The depth of traversal has breached a limit. There may be
68 /// capturing instructions that will not be passed into captured().
69 virtual void tooManyUses() = 0;
71 /// shouldExplore - This is the use of a value derived from the pointer.
72 /// To prune the search (ie., assume that none of its users could possibly
73 /// capture) return false. To search it, return true.
75 /// U->getUser() is always an Instruction.
76 virtual bool shouldExplore(const Use *U);
78 /// captured - Information about the pointer was captured by the user of
79 /// use U. Return true to stop the traversal or false to continue looking
80 /// for more capturing instructions.
81 virtual bool captured(const Use *U) = 0;
83 /// isDereferenceableOrNull - Overload to allow clients with additional
84 /// knowledge about pointer dereferenceability to provide it and thereby
85 /// avoid conservative responses when a pointer is compared to null.
86 virtual bool isDereferenceableOrNull(Value *O, const DataLayout &DL);
89 /// PointerMayBeCaptured - Visit the value and the values derived from it and
90 /// find values which appear to be capturing the pointer value. This feeds
91 /// results into and is controlled by the CaptureTracker object.
92 /// MaxUsesToExplore specifies how many uses the analysis should explore for
93 /// one value before giving up due too "too many uses". If MaxUsesToExplore
94 /// is zero, a default value is assumed.
95 void PointerMayBeCaptured(const Value *V, CaptureTracker *Tracker,
96 unsigned MaxUsesToExplore = 0);
97 } // end namespace llvm