clang  9.0.0svn
LiveVariables.h
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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"
18 #include "llvm/ADT/ImmutableSet.h"
19 
20 namespace clang {
21 
22 class CFG;
23 class CFGBlock;
24 class Stmt;
25 class DeclRefExpr;
26 class SourceManager;
27 
29 public:
31  public:
32 
33  llvm::ImmutableSet<const Stmt *> liveStmts;
34  llvm::ImmutableSet<const VarDecl *> liveDecls;
35  llvm::ImmutableSet<const BindingDecl *> liveBindings;
36 
37  bool equals(const LivenessValues &V) const;
38 
40  : liveStmts(nullptr), liveDecls(nullptr), liveBindings(nullptr) {}
41 
42  LivenessValues(llvm::ImmutableSet<const Stmt *> LiveStmts,
43  llvm::ImmutableSet<const VarDecl *> LiveDecls,
44  llvm::ImmutableSet<const BindingDecl *> LiveBindings)
45  : liveStmts(LiveStmts), liveDecls(LiveDecls),
46  liveBindings(LiveBindings) {}
47 
48  bool isLive(const Stmt *S) 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 LiveVariables *computeLiveness(AnalysisDeclContext &analysisContext,
74  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 Stmt *StmtVal);
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 statement liveness information associated with
95  /// each basic block.
96  void dumpStmtLiveness(const SourceManager &M);
97 
98  void runOnAllBlocks(Observer &obs);
99 
100  static LiveVariables *create(AnalysisDeclContext &analysisContext) {
101  return computeLiveness(analysisContext, true);
102  }
103 
104  static const void *getTag();
105 
106 private:
107  LiveVariables(void *impl);
108  void *impl;
109 };
110 
112 public:
113  static LiveVariables *create(AnalysisDeclContext &analysisContext) {
114  return computeLiveness(analysisContext, false);
115  }
116 
117  static const void *getTag();
118 };
119 
120 } // end namespace clang
121 
122 #endif
The base class of a hierarchy of objects representing analyses tied to AnalysisDeclContext.
static LiveVariables * computeLiveness(AnalysisDeclContext &analysisContext, bool killAtAssign)
Compute the liveness information for a given CFG.
Stmt - This represents one statement.
Definition: Stmt.h:66
Represents a variable declaration or definition.
Definition: Decl.h:812
llvm::ImmutableSet< const BindingDecl * > liveBindings
Definition: LiveVariables.h:35
bool equals(const LivenessValues &V) const
AnalysisDeclContext contains the context data for the function or method under analysis.
void runOnAllBlocks(Observer &obs)
static const void * getTag()
Represents a single basic block in a source-level CFG.
Definition: CFG.h:570
#define V(N, I)
Definition: ASTContext.h:2912
virtual void observerKill(const DeclRefExpr *DR)
Called when the live variables analysis registers that a variable is killed.
Definition: LiveVariables.h:67
void dumpBlockLiveness(const SourceManager &M)
Print to stderr the variable liveness information associated with each basic block.
llvm::ImmutableSet< const VarDecl * > liveDecls
Definition: LiveVariables.h:34
Dataflow Directional Tag Classes.
bool isLive(const Stmt *S) const
static LiveVariables * create(AnalysisDeclContext &analysisContext)
llvm::ImmutableSet< const Stmt * > liveStmts
Definition: LiveVariables.h:33
virtual void observeStmt(const Stmt *S, const CFGBlock *currentBlock, const LivenessValues &V)
A callback invoked right before invoking the liveness transfer function on the given statement...
Definition: LiveVariables.h:61
static LiveVariables * create(AnalysisDeclContext &analysisContext)
void dumpStmtLiveness(const SourceManager &M)
Print to stderr the statement liveness information associated with each basic block.
A reference to a declared variable, function, enum, etc.
Definition: Expr.h:1143
This class handles loading and caching of source files into memory.
LivenessValues(llvm::ImmutableSet< const Stmt *> LiveStmts, llvm::ImmutableSet< const VarDecl *> LiveDecls, llvm::ImmutableSet< const BindingDecl *> LiveBindings)
Definition: LiveVariables.h:42