1 //===-- SaveAndRestore.h - Utility  -------------------------------*- 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 /// \file
10 /// This file provides utility classes that use RAII to save and restore
11 /// values.
12 ///
13 //===----------------------------------------------------------------------===//
14 
15 #ifndef LLVM_SUPPORT_SAVEANDRESTORE_H
16 #define LLVM_SUPPORT_SAVEANDRESTORE_H
17 
18 #include <utility>
19 
20 namespace llvm {
21 
22 /// A utility class that uses RAII to save and restore the value of a variable.
23 template <typename T> struct SaveAndRestore {
24   SaveAndRestore(T &X) : X(X), OldValue(X) {}
25   SaveAndRestore(T &X, const T &NewValue) : X(X), OldValue(X) { X = NewValue; }
26   SaveAndRestore(T &X, T &&NewValue) : X(X), OldValue(std::move(X)) {
27     X = std::move(NewValue);
28   }
29   ~SaveAndRestore() { X = std::move(OldValue); }
30   const T &get() { return OldValue; }
31 
32 private:
33   T &X;
34   T OldValue;
35 };
36 
37 // User-defined CTAD guides.
38 template <typename T> SaveAndRestore(T &) -> SaveAndRestore<T>;
39 template <typename T> SaveAndRestore(T &, const T &) -> SaveAndRestore<T>;
40 template <typename T> SaveAndRestore(T &, T &&) -> SaveAndRestore<T>;
41 
42 } // namespace llvm
43 
44 #endif
45