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 { SaveAndRestoreSaveAndRestore24 SaveAndRestore(T &X) : X(X), OldValue(X) {} SaveAndRestoreSaveAndRestore25 SaveAndRestore(T &X, const T &NewValue) : X(X), OldValue(X) { X = NewValue; } SaveAndRestoreSaveAndRestore26 SaveAndRestore(T &X, T &&NewValue) : X(X), OldValue(std::move(X)) { 27 X = std::move(NewValue); 28 } ~SaveAndRestoreSaveAndRestore29 ~SaveAndRestore() { X = std::move(OldValue); } getSaveAndRestore30 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