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 "clang/AST/Decl.h"
19 #include "llvm/ADT/DenseMap.h"
20 #include "llvm/ADT/DenseSet.h"
21 #include "llvm/ADT/SmallVector.h"
22 
23 namespace clang {
24 
25 class Decl;
26 class Stmt;
27 class VarDecl;
28 
29 namespace CodeGen {
30 
31 /// The class detects jumps which bypass local variables declaration:
32 ///    goto L;
33 ///    int a;
34 ///  L:
35 ///
36 /// This is simplified version of JumpScopeChecker. Primary differences:
37 ///  * Detects only jumps into the scope local variables.
38 ///  * Does not detect jumps out of the scope of local variables.
39 ///  * Not limited to variables with initializers, JumpScopeChecker is limited.
40 class VarBypassDetector {
41   // Scope information. Contains a parent scope and related variable
42   // declaration.
43   llvm::SmallVector<std::pair<unsigned, const VarDecl *>, 48> Scopes;
44   // List of jumps with scopes.
45   llvm::SmallVector<std::pair<const Stmt *, unsigned>, 16> FromScopes;
46   // Lookup map to find scope for destinations.
47   llvm::DenseMap<const Stmt *, unsigned> ToScopes;
48   // Set of variables which were bypassed by some jump.
49   llvm::DenseSet<const VarDecl *> Bypasses;
50   // If true assume that all variables are being bypassed.
51   bool AlwaysBypassed = false;
52 
53 public:
54   void Init(const Stmt *Body);
55 
56   /// Returns true if the variable declaration was by bypassed by any goto or
57   /// switch statement.
58   bool IsBypassed(const VarDecl *D) const {
59     return AlwaysBypassed || Bypasses.find(D) != Bypasses.end();
60   }
61 
62 private:
63   bool BuildScopeInformation(const Decl *D, unsigned &ParentScope);
64   bool BuildScopeInformation(const Stmt *S, unsigned &origParentScope);
65   void Detect();
66   void Detect(unsigned From, unsigned To);
67 };
68 }
69 }
70 
71 #endif
72