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1 //===-- SaveAndRestore.h - Utility  -------------------------------*- 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 /// \file
11 /// This file provides utility classes that use RAII to save and restore
12 /// values.
13 ///
14 //===----------------------------------------------------------------------===//
15 
16 #ifndef LLVM_SUPPORT_SAVEANDRESTORE_H
17 #define LLVM_SUPPORT_SAVEANDRESTORE_H
18 
19 namespace llvm {
20 
21 /// A utility class that uses RAII to save and restore the value of a variable.
22 template <typename T> struct SaveAndRestore {
SaveAndRestoreSaveAndRestore23   SaveAndRestore(T &X) : X(X), OldValue(X) {}
SaveAndRestoreSaveAndRestore24   SaveAndRestore(T &X, const T &NewValue) : X(X), OldValue(X) {
25     X = NewValue;
26   }
~SaveAndRestoreSaveAndRestore27   ~SaveAndRestore() { X = OldValue; }
getSaveAndRestore28   T get() { return OldValue; }
29 
30 private:
31   T &X;
32   T OldValue;
33 };
34 
35 /// Similar to \c SaveAndRestore.  Operates only on bools; the old value of a
36 /// variable is saved, and during the dstor the old value is or'ed with the new
37 /// value.
38 struct SaveOr {
SaveOrSaveOr39   SaveOr(bool &X) : X(X), OldValue(X) { X = false; }
~SaveOrSaveOr40   ~SaveOr() { X |= OldValue; }
41 
42 private:
43   bool &X;
44   const bool OldValue;
45 };
46 
47 } // namespace llvm
48 
49 #endif
50