1//===----- llvm/Analysis/CaptureTracking.h - Pointer capture ----*- C++ -*-===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file contains routines that help determine which pointers are captured.
11//
12//===----------------------------------------------------------------------===//
13
14#ifndef LLVM_ANALYSIS_CAPTURETRACKING_H
15#define LLVM_ANALYSIS_CAPTURETRACKING_H
16
17namespace llvm {
18
19  class Value;
20  class Use;
21  class Instruction;
22  class DominatorTree;
23  class OrderedBasicBlock;
24
25  /// PointerMayBeCaptured - Return true if this pointer value may be captured
26  /// by the enclosing function (which is required to exist).  This routine can
27  /// be expensive, so consider caching the results.  The boolean ReturnCaptures
28  /// specifies whether returning the value (or part of it) from the function
29  /// counts as capturing it or not.  The boolean StoreCaptures specified
30  /// whether storing the value (or part of it) into memory anywhere
31  /// automatically counts as capturing it or not.
32  bool PointerMayBeCaptured(const Value *V,
33                            bool ReturnCaptures,
34                            bool StoreCaptures);
35
36  /// PointerMayBeCapturedBefore - Return true if this pointer value may be
37  /// captured by the enclosing function (which is required to exist). If a
38  /// DominatorTree is provided, only captures which happen before the given
39  /// instruction are considered. This routine can be expensive, so consider
40  /// caching the results.  The boolean ReturnCaptures specifies whether
41  /// returning the value (or part of it) from the function counts as capturing
42  /// it or not.  The boolean StoreCaptures specified whether storing the value
43  /// (or part of it) into memory anywhere automatically counts as capturing it
44  /// or not. Captures by the provided instruction are considered if the
45  /// final parameter is true. An ordered basic block in \p OBB could be used
46  /// to speed up capture-tracker queries.
47  bool PointerMayBeCapturedBefore(const Value *V, bool ReturnCaptures,
48                                  bool StoreCaptures, const Instruction *I,
49                                  DominatorTree *DT, bool IncludeI = false,
50                                  OrderedBasicBlock *OBB = nullptr);
51
52  /// This callback is used in conjunction with PointerMayBeCaptured. In
53  /// addition to the interface here, you'll need to provide your own getters
54  /// to see whether anything was captured.
55  struct CaptureTracker {
56    virtual ~CaptureTracker();
57
58    /// tooManyUses - The depth of traversal has breached a limit. There may be
59    /// capturing instructions that will not be passed into captured().
60    virtual void tooManyUses() = 0;
61
62    /// shouldExplore - This is the use of a value derived from the pointer.
63    /// To prune the search (ie., assume that none of its users could possibly
64    /// capture) return false. To search it, return true.
65    ///
66    /// U->getUser() is always an Instruction.
67    virtual bool shouldExplore(const Use *U);
68
69    /// captured - Information about the pointer was captured by the user of
70    /// use U. Return true to stop the traversal or false to continue looking
71    /// for more capturing instructions.
72    virtual bool captured(const Use *U) = 0;
73  };
74
75  /// PointerMayBeCaptured - Visit the value and the values derived from it and
76  /// find values which appear to be capturing the pointer value. This feeds
77  /// results into and is controlled by the CaptureTracker object.
78  void PointerMayBeCaptured(const Value *V, CaptureTracker *Tracker);
79} // end namespace llvm
80
81#endif
82