LLVM  6.0.0svn
CaptureTracking.h
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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 
17 namespace 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
virtual void tooManyUses()=0
tooManyUses - The depth of traversal has breached a limit.
This callback is used in conjunction with PointerMayBeCaptured.
Compute iterated dominance frontiers using a linear time algorithm.
Definition: AllocatorList.h:24
virtual bool shouldExplore(const Use *U)
shouldExplore - This is the use of a value derived from the pointer.
A Use represents the edge between a Value definition and its users.
Definition: Use.h:56
virtual bool captured(const Use *U)=0
captured - Information about the pointer was captured by the user of use U.
bool PointerMayBeCaptured(const Value *V, bool ReturnCaptures, bool StoreCaptures)
PointerMayBeCaptured - Return true if this pointer value may be captured by the enclosing function (w...
#define I(x, y, z)
Definition: MD5.cpp:58
bool PointerMayBeCapturedBefore(const Value *V, bool ReturnCaptures, bool StoreCaptures, const Instruction *I, DominatorTree *DT, bool IncludeI=false, OrderedBasicBlock *OBB=nullptr)
PointerMayBeCapturedBefore - Return true if this pointer value may be captured by the enclosing funct...
LLVM Value Representation.
Definition: Value.h:73