1 //===----- llvm/Analysis/CaptureTracking.h - Pointer capture ----*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file contains routines that help determine which pointers are captured.
12 //===----------------------------------------------------------------------===//
14 #ifndef LLVM_ANALYSIS_CAPTURETRACKING_H
15 #define LLVM_ANALYSIS_CAPTURETRACKING_H
24 /// PointerMayBeCaptured - Return true if this pointer value may be captured
25 /// by the enclosing function (which is required to exist). This routine can
26 /// be expensive, so consider caching the results. The boolean ReturnCaptures
27 /// specifies whether returning the value (or part of it) from the function
28 /// counts as capturing it or not. The boolean StoreCaptures specified
29 /// whether storing the value (or part of it) into memory anywhere
30 /// automatically counts as capturing it or not.
31 bool PointerMayBeCaptured(const Value *V,
35 /// PointerMayBeCapturedBefore - Return true if this pointer value may be
36 /// captured by the enclosing function (which is required to exist). If a
37 /// DominatorTree is provided, only captures which happen before the given
38 /// instruction are considered. This routine can be expensive, so consider
39 /// caching the results. The boolean ReturnCaptures specifies whether
40 /// returning the value (or part of it) from the function counts as capturing
41 /// it or not. The boolean StoreCaptures specified whether storing the value
42 /// (or part of it) into memory anywhere automatically counts as capturing it
43 /// or not. Captures by the provided instruction are considered if the
44 /// final parameter is true.
45 bool PointerMayBeCapturedBefore(const Value *V, bool ReturnCaptures,
46 bool StoreCaptures, const Instruction *I,
47 DominatorTree *DT, bool IncludeI = false);
49 /// This callback is used in conjunction with PointerMayBeCaptured. In
50 /// addition to the interface here, you'll need to provide your own getters
51 /// to see whether anything was captured.
52 struct CaptureTracker {
53 virtual ~CaptureTracker();
55 /// tooManyUses - The depth of traversal has breached a limit. There may be
56 /// capturing instructions that will not be passed into captured().
57 virtual void tooManyUses() = 0;
59 /// shouldExplore - This is the use of a value derived from the pointer.
60 /// To prune the search (ie., assume that none of its users could possibly
61 /// capture) return false. To search it, return true.
63 /// U->getUser() is always an Instruction.
64 virtual bool shouldExplore(const Use *U);
66 /// captured - Information about the pointer was captured by the user of
67 /// use U. Return true to stop the traversal or false to continue looking
68 /// for more capturing instructions.
69 virtual bool captured(const Use *U) = 0;
72 /// PointerMayBeCaptured - Visit the value and the values derived from it and
73 /// find values which appear to be capturing the pointer value. This feeds
74 /// results into and is controlled by the CaptureTracker object.
75 void PointerMayBeCaptured(const Value *V, CaptureTracker *Tracker);
76 } // end namespace llvm