LiveVariables.h revision b1a7b65231e86f7da6aacbf00bcdc16c56350e65 
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 "clang/Analysis/Support/BlkExprDeclBitVector.h"
19#include "clang/Analysis/FlowSensitive/DataflowValues.h"
20
21namespace clang {
22
23class Stmt;
24class DeclRefExpr;
25class SourceManager;
26class AnalysisContext;
27
28struct LiveVariables_ValueTypes {
29
30  struct ObserverTy;
31
32  // We keep dataflow state for declarations and block-level expressions;
33  typedef StmtDeclBitVector_Types::ValTy ValTy;
34
35  // We need to keep track of both declarations and CFGBlock-level expressions,
36  // (so that we don't explore such expressions twice).  We also want
37  // to compute liveness information for block-level expressions, since these
38  // act as "temporary" values.
39
40  struct AnalysisDataTy : public StmtDeclBitVector_Types::AnalysisDataTy {
41    ObserverTy* Observer;
42    ValTy AlwaysLive;
43    AnalysisContext *AC;
44
45    AnalysisDataTy() : Observer(NULL), AC(NULL) {}
46  };
47
48  //===-----------------------------------------------------===//
49  // ObserverTy - Observer for uninitialized values queries.
50  //===-----------------------------------------------------===//
51
52  struct ObserverTy {
53    virtual ~ObserverTy() {}
54
55    /// ObserveStmt - A callback invoked right before invoking the
56    ///  liveness transfer function on the given statement.
57    virtual void ObserveStmt(Stmt* S, const AnalysisDataTy& AD,
58                             const ValTy& V) {}
59
60    virtual void ObserverKill(DeclRefExpr* DR) {}
61  };
62};
63
64class LiveVariables : public DataflowValues<LiveVariables_ValueTypes,
65                                            dataflow::backward_analysis_tag> {
66
67
68public:
69  typedef LiveVariables_ValueTypes::ObserverTy ObserverTy;
70
71  LiveVariables(AnalysisContext &AC);
72
73  /// IsLive - Return true if a variable is live at beginning of a
74  /// specified block.
75  bool isLive(const CFGBlock* B, const VarDecl* D) const;
76
77  /// IsLive - Returns true if a variable is live at the beginning of the
78  ///  the statement.  This query only works if liveness information
79  ///  has been recorded at the statement level (see runOnAllBlocks), and
80  ///  only returns liveness information for block-level expressions.
81  bool isLive(const Stmt* S, const VarDecl* D) const;
82
83  /// IsLive - Returns true the block-level expression "value" is live
84  ///  before the given block-level expression (see runOnAllBlocks).
85  bool isLive(const Stmt* Loc, const Stmt* StmtVal) const;
86
87  /// IsLive - Return true if a variable is live according to the
88  ///  provided livness bitvector.
89  bool isLive(const ValTy& V, const VarDecl* D) const;
90
91  /// dumpLiveness - Print to stderr the liveness information encoded
92  ///  by a specified bitvector.
93  void dumpLiveness(const ValTy& V, const SourceManager& M) const;
94
95  /// dumpBlockLiveness - Print to stderr the liveness information
96  ///  associated with each basic block.
97  void dumpBlockLiveness(const SourceManager& M) const;
98
99  /// getNumDecls - Return the number of variables (declarations) that
100  ///  whose liveness status is being tracked by the dataflow
101  ///  analysis.
102  unsigned getNumDecls() const { return getAnalysisData().getNumDecls(); }
103
104  /// IntializeValues - This routine can perform extra initialization, but
105  ///  for LiveVariables this does nothing since all that logic is in
106  ///  the constructor.
107  void InitializeValues(const CFG& cfg) {}
108
109  void runOnCFG(CFG& cfg);
110
111  /// runOnAllBlocks - Propagate the dataflow values once for each block,
112  ///  starting from the current dataflow values.  'recordStmtValues' indicates
113  ///  whether the method should store dataflow values per each individual
114  ///  block-level expression.
115  void runOnAllBlocks(const CFG& cfg, ObserverTy* Obs,
116                      bool recordStmtValues=false);
117};
118
119} // end namespace clang
120
121#endif
122