From 698f8c2f01ea549d77d7dc3338a12e04c11057b9 Mon Sep 17 00:00:00 2001
From: Daniel Baumann <daniel.baumann@progress-linux.org>
Date: Wed, 17 Apr 2024 14:02:58 +0200
Subject: Adding upstream version 1.64.0+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
---
 compiler/rustc_data_structures/src/atomic_ref.rs | 26 ++++++++++++++++++++++++
 1 file changed, 26 insertions(+)
 create mode 100644 compiler/rustc_data_structures/src/atomic_ref.rs

(limited to 'compiler/rustc_data_structures/src/atomic_ref.rs')

diff --git a/compiler/rustc_data_structures/src/atomic_ref.rs b/compiler/rustc_data_structures/src/atomic_ref.rs
new file mode 100644
index 000000000..eeb1b3092
--- /dev/null
+++ b/compiler/rustc_data_structures/src/atomic_ref.rs
@@ -0,0 +1,26 @@
+use std::marker::PhantomData;
+use std::sync::atomic::{AtomicPtr, Ordering};
+
+/// This is essentially an `AtomicPtr` but is guaranteed to always be valid
+pub struct AtomicRef<T: 'static>(AtomicPtr<T>, PhantomData<&'static T>);
+
+impl<T: 'static> AtomicRef<T> {
+    pub const fn new(initial: &'static T) -> AtomicRef<T> {
+        AtomicRef(AtomicPtr::new(initial as *const T as *mut T), PhantomData)
+    }
+
+    pub fn swap(&self, new: &'static T) -> &'static T {
+        // We never allow storing anything but a `'static` reference so it's safe to
+        // return it for the same.
+        unsafe { &*self.0.swap(new as *const T as *mut T, Ordering::SeqCst) }
+    }
+}
+
+impl<T: 'static> std::ops::Deref for AtomicRef<T> {
+    type Target = T;
+    fn deref(&self) -> &Self::Target {
+        // We never allow storing anything but a `'static` reference so it's safe to lend
+        // it out for any amount of time.
+        unsafe { &*self.0.load(Ordering::SeqCst) }
+    }
+}
-- 
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