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_ANALYSIS_ANALYSES_LIVEVARIABLES_H
15#define LLVM_CLANG_ANALYSIS_ANALYSES_LIVEVARIABLES_H
16
17#include "clang/AST/Decl.h"
18#include "clang/Analysis/AnalysisContext.h"
19#include "llvm/ADT/DenseMap.h"
20#include "llvm/ADT/ImmutableSet.h"
21
22namespace clang {
23
24class CFG;
25class CFGBlock;
26class Stmt;
27class DeclRefExpr;
28class SourceManager;
29
30class LiveVariables : public ManagedAnalysis {
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(nullptr), liveDecls(nullptr) {}
42
43    LivenessValues(llvm::ImmutableSet<const Stmt *> LiveStmts,
44                   llvm::ImmutableSet<const VarDecl *> LiveDecls)
45      : liveStmts(LiveStmts), liveDecls(LiveDecls) {}
46
47    bool isLive(const Stmt *S) const;
48    bool isLive(const VarDecl *D) const;
49
50    friend class LiveVariables;
51  };
52
53  class Observer {
54    virtual void anchor();
55  public:
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  ~LiveVariables() override;
70
71  /// Compute the liveness information for a given CFG.
72  static LiveVariables *computeLiveness(AnalysisDeclContext &analysisContext,
73                                        bool killAtAssign);
74
75  /// Return true if a variable is live at the end of a
76  /// specified block.
77  bool isLive(const CFGBlock *B, const VarDecl *D);
78
79  /// Returns true if a variable is live at the beginning of the
80  ///  the statement.  This query only works if liveness information
81  ///  has been recorded at the statement level (see runOnAllBlocks), and
82  ///  only returns liveness information for block-level expressions.
83  bool isLive(const Stmt *S, const VarDecl *D);
84
85  /// Returns true the block-level expression "value" is live
86  ///  before the given block-level expression (see runOnAllBlocks).
87  bool isLive(const Stmt *Loc, const Stmt *StmtVal);
88
89  /// Print to stderr the liveness information associated with
90  /// each basic block.
91  void dumpBlockLiveness(const SourceManager& M);
92
93  void runOnAllBlocks(Observer &obs);
94
95  static LiveVariables *create(AnalysisDeclContext &analysisContext) {
96    return computeLiveness(analysisContext, true);
97  }
98
99  static const void *getTag();
100
101private:
102  LiveVariables(void *impl);
103  void *impl;
104};
105
106class RelaxedLiveVariables : public LiveVariables {
107public:
108  static LiveVariables *create(AnalysisDeclContext &analysisContext) {
109    return computeLiveness(analysisContext, false);
110  }
111
112  static const void *getTag();
113};
114
115} // end namespace clang
116
117#endif
118