clang/lib/CodeGen/VarBypassDetector.h

   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
  22 namespace clang {
  23
  24 class Decl;
  25 class Stmt;
  26 class VarDecl;
  27
  28 namespace 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.
  39 class 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
  52 public:
  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.contains(D);
  59   }
  60
  61 private:
  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