1//===- LiveVariables.h - Live Variable Analysis for Source CFGs -*- C++ --*-//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file implements Live Variables analysis for source-level CFGs.
10//
11//===----------------------------------------------------------------------===//
12
13#ifndef LLVM_CLANG_ANALYSIS_ANALYSES_LIVEVARIABLES_H
14#define LLVM_CLANG_ANALYSIS_ANALYSES_LIVEVARIABLES_H
15
16#include "clang/AST/Decl.h"
17#include "clang/Analysis/AnalysisDeclContext.h"
18#include "llvm/ADT/ImmutableSet.h"
19
20namespace clang {
21
22class CFG;
23class CFGBlock;
24class Stmt;
25class DeclRefExpr;
26class SourceManager;
27
28class LiveVariables : public ManagedAnalysis {
29public:
30  class LivenessValues {
31  public:
32
33    llvm::ImmutableSet<const Expr *> liveExprs;
34    llvm::ImmutableSet<const VarDecl *> liveDecls;
35    llvm::ImmutableSet<const BindingDecl *> liveBindings;
36
37    bool equals(const LivenessValues &V) const;
38
39    LivenessValues()
40      : liveExprs(nullptr), liveDecls(nullptr), liveBindings(nullptr) {}
41
42    LivenessValues(llvm::ImmutableSet<const Expr *> liveExprs,
43                   llvm::ImmutableSet<const VarDecl *> LiveDecls,
44                   llvm::ImmutableSet<const BindingDecl *> LiveBindings)
45        : liveExprs(liveExprs), liveDecls(LiveDecls),
46          liveBindings(LiveBindings) {}
47
48    bool isLive(const Expr *E) const;
49    bool isLive(const VarDecl *D) const;
50
51    friend class LiveVariables;
52  };
53
54  class Observer {
55    virtual void anchor();
56  public:
57    virtual ~Observer() {}
58
59    /// A callback invoked right before invoking the
60    ///  liveness transfer function on the given statement.
61    virtual void observeStmt(const Stmt *S,
62                             const CFGBlock *currentBlock,
63                             const LivenessValues& V) {}
64
65    /// Called when the live variables analysis registers
66    /// that a variable is killed.
67    virtual void observerKill(const DeclRefExpr *DR) {}
68  };
69
70  ~LiveVariables() override;
71
72  /// Compute the liveness information for a given CFG.
73  static std::unique_ptr<LiveVariables>
74  computeLiveness(AnalysisDeclContext &analysisContext, bool killAtAssign);
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 Expr *Val);
89
90  /// Print to stderr the variable liveness information associated with
91  /// each basic block.
92  void dumpBlockLiveness(const SourceManager &M);
93
94  /// Print to stderr the expression liveness information associated with
95  /// each basic block.
96  void dumpExprLiveness(const SourceManager &M);
97
98  void runOnAllBlocks(Observer &obs);
99
100  static std::unique_ptr<LiveVariables>
101  create(AnalysisDeclContext &analysisContext) {
102    return computeLiveness(analysisContext, true);
103  }
104
105  static const void *getTag();
106
107private:
108  LiveVariables(void *impl);
109  void *impl;
110};
111
112class RelaxedLiveVariables : public LiveVariables {
113public:
114  static std::unique_ptr<LiveVariables>
115  create(AnalysisDeclContext &analysisContext) {
116    return computeLiveness(analysisContext, false);
117  }
118
119  static const void *getTag();
120};
121
122} // end namespace clang
123
124#endif
125