VarBypassDetector.h revision 311143 
1//===--- VarBypassDetector.cpp - Bypass jumps detector ------------*- 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 contains VarBypassDetector class, which is used to detect
11// local variable declarations which can be bypassed by jumps.
12//
13//===----------------------------------------------------------------------===//
14
15#ifndef LLVM_CLANG_LIB_CODEGEN_VARBYPASSDETECTOR_H
16#define LLVM_CLANG_LIB_CODEGEN_VARBYPASSDETECTOR_H
17
18#include "llvm/ADT/DenseMap.h"
19#include "llvm/ADT/DenseSet.h"
20#include "llvm/ADT/SmallVector.h"
21
22namespace clang {
23
24class Decl;
25class Stmt;
26class VarDecl;
27
28namespace CodeGen {
29
30/// The class detects jumps which bypass local variables declaration:
31///    goto L;
32///    int a;
33///  L:
34///
35/// This is simplified version of JumpScopeChecker. Primary differences:
36///  * Detects only jumps into the scope local variables.
37///  * Does not detect jumps out of the scope of local variables.
38///  * Not limited to variables with initializers, JumpScopeChecker is limited.
39class VarBypassDetector {
40  // Scope information. Contains a parent scope and related variable
41  // declaration.
42  llvm::SmallVector<std::pair<unsigned, const VarDecl *>, 48> Scopes;
43  // List of jumps with scopes.
44  llvm::SmallVector<std::pair<const Stmt *, unsigned>, 16> FromScopes;
45  // Lookup map to find scope for destinations.
46  llvm::DenseMap<const Stmt *, unsigned> ToScopes;
47  // Set of variables which were bypassed by some jump.
48  llvm::DenseSet<const VarDecl *> Bypasses;
49  // If true assume that all variables are being bypassed.
50  bool AlwaysBypassed = false;
51
52public:
53  void Init(const Stmt *Body);
54
55  /// Returns true if the variable declaration was by bypassed by any goto or
56  /// switch statement.
57  bool IsBypassed(const VarDecl *D) const {
58    return AlwaysBypassed || Bypasses.find(D) != Bypasses.end();
59  }
60
61private:
62  bool BuildScopeInformation(const Decl *D, unsigned &ParentScope);
63  bool BuildScopeInformation(const Stmt *S, unsigned &origParentScope);
64  void Detect();
65  void Detect(unsigned From, unsigned To);
66};
67}
68}
69
70#endif
71