rustc_metadata: use configurable AtomicBool for privateness flag

This switches to using a `Cell` for single-threaded rustc.

1 files changed, 14 insertions, 0 deletions

diff --git a/compiler/rustc_data_structures/src/sync.rs b/compiler/rustc_data_structures/src/sync.rs
index 6c3197d8ec2..df8285cc729 100644
--- a/compiler/rustc_data_structures/src/sync.rs
+++ b/compiler/rustc_data_structures/src/sync.rs
@@ -143,6 +143,20 @@ cfg_if! {
                 self.0.set(val);
                 result
             }
+            pub fn fetch_update(
+                &self,
+                _order_set: Ordering,
+                _order_get: Ordering,
+                mut f: impl FnMut(bool) -> Option<bool>,
+            ) -> Result<bool, bool> {
+                let prev = self.0.get();
+                if let Some(next) = f(prev) {
+                    self.0.set(next);
+                    Ok(prev)
+                } else {
+                    Err(prev)
+                }
+            }
         }
 
         impl<T: Copy + PartialEq> Atomic<T> {