CaptureTracking.h revision c92b8aa79f4a2cd16f7b674189e425c2c367e886 
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#include "llvm/Constants.h"
18#include "llvm/Instructions.h"
19#include "llvm/Analysis/AliasAnalysis.h"
20#include "llvm/Support/CallSite.h"
21
22namespace llvm {
23  /// PointerMayBeCaptured - Return true if this pointer value may be captured
24  /// by the enclosing function (which is required to exist).  This routine can
25  /// be expensive, so consider caching the results.  The boolean ReturnCaptures
26  /// specifies whether returning the value (or part of it) from the function
27  /// counts as capturing it or not.  The boolean StoreCaptures specified
28  /// whether storing the value (or part of it) into memory anywhere
29  /// automatically counts as capturing it or not.
30  bool PointerMayBeCaptured(const Value *V,
31                            bool ReturnCaptures,
32                            bool StoreCaptures);
33
34  /// This callback is used in conjunction with PointerMayBeCaptured. In
35  /// addition to the interface here, you'll need to provide your own getters
36  /// to see whether anything was captured.
37  struct CaptureTracker {
38    virtual ~CaptureTracker();
39
40    /// tooManyUses - The depth of traversal has breached a limit. There may be
41    /// capturing instructions that will not be passed into captured().
42    virtual void tooManyUses() = 0;
43
44    /// shouldExplore - This is the use of a value derived from the pointer.
45    /// To prune the search (ie., assume that none of its users could possibly
46    /// capture) return false. To search it, return true.
47    ///
48    /// U->getUser() is always an Instruction.
49    virtual bool shouldExplore(Use *U);
50
51    /// captured - Information about the pointer was captured by the user of
52    /// use U. Return true to stop the traversal or false to continue looking
53    /// for more capturing instructions.
54    virtual bool captured(Use *U) = 0;
55  };
56
57  /// PointerMayBeCaptured - Visit the value and the values derived from it and
58  /// find values which appear to be capturing the pointer value. This feeds
59  /// results into and is controlled by the CaptureTracker object.
60  void PointerMayBeCaptured(const Value *V, CaptureTracker *Tracker);
61} // end namespace llvm
62
63#endif
64