LiveVariables.h revision 9c378f705405d37f49795d5e915989de774fe11f 
1//===- LiveVariables.h - Live Variable Analysis for Source CFGs -*- 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 implements Live Variables analysis for source-level CFGs.
11//
12//===----------------------------------------------------------------------===//
13
14#ifndef LLVM_CLANG_LIVEVARIABLES_H
15#define LLVM_CLANG_LIVEVARIABLES_H
16
17#include "clang/AST/Decl.h"
18#include "llvm/ADT/DenseMap.h"
19#include "llvm/ADT/ImmutableSet.h"
20
21namespace clang {
22
23class CFG;
24class CFGBlock;
25class Stmt;
26class DeclRefExpr;
27class SourceManager;
28class AnalysisContext;
29
30class LiveVariables {
31public:
32  class LivenessValues {
33  public:
34
35    llvm::ImmutableSet<const Stmt *> liveStmts;
36    llvm::ImmutableSet<const VarDecl *> liveDecls;
37
38    bool equals(const LivenessValues &V) const;
39
40    LivenessValues()
41      : liveStmts(0), liveDecls(0) {}
42
43    LivenessValues(llvm::ImmutableSet<const Stmt *> LiveStmts,
44                   llvm::ImmutableSet<const VarDecl *> LiveDecls)
45      : liveStmts(LiveStmts), liveDecls(LiveDecls) {}
46
47    ~LivenessValues() {}
48
49    bool isLive(const Stmt *S) const;
50    bool isLive(const VarDecl *D) const;
51
52    friend class LiveVariables;
53  };
54
55  struct Observer {
56    virtual ~Observer() {}
57
58    /// A callback invoked right before invoking the
59    ///  liveness transfer function on the given statement.
60    virtual void observeStmt(const Stmt *S,
61                             const CFGBlock *currentBlock,
62                             const LivenessValues& V) {}
63
64    /// Called when the live variables analysis registers
65    /// that a variable is killed.
66    virtual void observerKill(const DeclRefExpr *DR) {}
67  };
68
69
70  ~LiveVariables();
71
72  /// Compute the liveness information for a given CFG.
73  static LiveVariables *computeLiveness(AnalysisContext &analysisContext,
74                                          bool killAtAssign = true);
75
76  /// Return true if a variable is live at the end of a
77  /// specified block.
78  bool isLive(const CFGBlock *B, const VarDecl *D);
79
80  /// Returns true if a variable is live at the beginning of the
81  ///  the statement.  This query only works if liveness information
82  ///  has been recorded at the statement level (see runOnAllBlocks), and
83  ///  only returns liveness information for block-level expressions.
84  bool isLive(const Stmt *S, const VarDecl *D);
85
86  /// Returns true the block-level expression "value" is live
87  ///  before the given block-level expression (see runOnAllBlocks).
88  bool isLive(const Stmt *Loc, const Stmt *StmtVal);
89
90  /// Print to stderr the liveness information associated with
91  /// each basic block.
92  void dumpBlockLiveness(const SourceManager& M);
93
94  void runOnAllBlocks(Observer &obs);
95
96private:
97  LiveVariables(void *impl);
98  void *impl;
99};
100
101} // end namespace clang
102
103#endif
104