LiveVariables.h revision e0dbda136444b2f3550a421f4436d438230c732f 
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;
26
27struct LiveVariables_ValueTypes {
28
29  struct ObserverTy;
30
31  // We keep dataflow state for declarations and block-level expressions;
32  typedef StmtDeclBitVector_Types::ValTy ValTy;
33
34  // We need to keep track of both declarations and CFGBlock-level expressions,
35  // (so that we don't explore such expressions twice).  We also want
36  // to compute liveness information for block-level expressions, since these
37  // act as "temporary" values.
38
39  struct AnalysisDataTy : public StmtDeclBitVector_Types::AnalysisDataTy {
40    ObserverTy* Observer;
41    ValTy AlwaysLive;
42
43    AnalysisDataTy() : Observer(NULL) {}
44  };
45
46  //===-----------------------------------------------------===//
47  // ObserverTy - Observer for uninitialized values queries.
48  //===-----------------------------------------------------===//
49
50  struct ObserverTy {
51    virtual ~ObserverTy() {}
52
53    /// ObserveStmt - A callback invoked right before invoking the
54    ///  liveness transfer function on the given statement.
55    virtual void ObserveStmt(Stmt* S, const AnalysisDataTy& AD,
56                             const ValTy& V) {}
57
58    virtual void ObserverKill(DeclRefExpr* DR) {}
59  };
60};
61
62class LiveVariables : public DataflowValues<LiveVariables_ValueTypes,
63                                            dataflow::backward_analysis_tag> {
64
65
66public:
67  typedef LiveVariables_ValueTypes::ObserverTy ObserverTy;
68
69  LiveVariables(ASTContext& Ctx, CFG& cfg);
70
71  /// IsLive - Return true if a variable is live at beginning of a
72  /// specified block.
73  bool isLive(const CFGBlock* B, const VarDecl* D) const;
74
75  /// IsLive - Returns true if a variable is live at the beginning of the
76  ///  the statement.  This query only works if liveness information
77  ///  has been recorded at the statement level (see runOnAllBlocks), and
78  ///  only returns liveness information for block-level expressions.
79  bool isLive(const Stmt* S, const VarDecl* D) const;
80
81  /// IsLive - Returns true the block-level expression "value" is live
82  ///  before the given block-level expression (see runOnAllBlocks).
83  bool isLive(const Stmt* Loc, const Stmt* StmtVal) const;
84
85  /// IsLive - Return true if a variable is live according to the
86  ///  provided livness bitvector.
87  bool isLive(const ValTy& V, const VarDecl* D) const;
88
89  /// dumpLiveness - Print to stderr the liveness information encoded
90  ///  by a specified bitvector.
91  void dumpLiveness(const ValTy& V, SourceManager& M) const;
92
93  /// dumpBlockLiveness - Print to stderr the liveness information
94  ///  associated with each basic block.
95  void dumpBlockLiveness(SourceManager& M) const;
96
97  /// getNumDecls - Return the number of variables (declarations) that
98  ///  whose liveness status is being tracked by the dataflow
99  ///  analysis.
100  unsigned getNumDecls() const { return getAnalysisData().getNumDecls(); }
101
102  /// IntializeValues - This routine can perform extra initialization, but
103  ///  for LiveVariables this does nothing since all that logic is in
104  ///  the constructor.
105  void InitializeValues(const CFG& cfg) {}
106
107  void runOnCFG(CFG& cfg);
108
109  /// runOnAllBlocks - Propagate the dataflow values once for each block,
110  ///  starting from the current dataflow values.  'recordStmtValues' indicates
111  ///  whether the method should store dataflow values per each individual
112  ///  block-level expression.
113  void runOnAllBlocks(const CFG& cfg, ObserverTy* Obs,
114                      bool recordStmtValues=false);
115};
116
117} // end namespace clang
118
119#endif
120