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 Stmt *> liveStmts;
34 llvm::ImmutableSet<const VarDecl *> liveDecls;
35 llvm::ImmutableSet<const BindingDecl *> liveBindings;
36
37 bool equals(const LivenessValues &V) const;
38
39 LivenessValues()
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
106private:
107 LiveVariables(void *impl);
108 void *impl;
109};
110
111class RelaxedLiveVariables : public LiveVariables {
112public:
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
123