LiveVariables.h source code [clang_source_code/include/clang/Analysis/Analyses/LiveVariables.h]

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
20	namespace clang {
21
22	class CFG;
23	class CFGBlock;
24	class Stmt;
25	class DeclRefExpr;
26	class SourceManager;
27
28	class LiveVariables : public ManagedAnalysis {
29	public:
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
106	private:
107	LiveVariables(void *impl);
108	void *impl;
109	};
110
111	class RelaxedLiveVariables : public LiveVariables {
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
123