1//===--- VarBypassDetector.h - Bypass jumps detector --------------*- 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 contains VarBypassDetector class, which is used to detect
10// local variable declarations which can be bypassed by jumps.
11//
12//===----------------------------------------------------------------------===//
13
14#ifndef LLVM_CLANG_LIB_CODEGEN_VARBYPASSDETECTOR_H
15#define LLVM_CLANG_LIB_CODEGEN_VARBYPASSDETECTOR_H
16
17#include "clang/AST/Decl.h"
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