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Rollup merge of #72324 - Amanieu:atomic_minmax, r=dtolnay

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Stabilize AtomicN::fetch_min and AtomicN::fetch_max

Some architectures (ARMv8.1 LSE and RISC-V) have specific instructions for atomic min/max which the compiler can only generate through explicit instrinsics.
This commit is contained in:
Yuki Okushi
2020-05-29 15:06:57 +09:00
committed by GitHub
parent d472f8e462 1d7a731f3d
commit 986c60c78b
1 changed files with 2 additions and 10 deletions
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12
src/libcore/sync/atomic.rs
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@@ -1878,7 +1878,6 @@ using [`Release`] makes the load part [`Relaxed`].
# Examples # Examples
``` ```
#![feature(atomic_min_max)]
", $extra_feature, "use std::sync::atomic::{", stringify!($atomic_type), ", Ordering}; ", $extra_feature, "use std::sync::atomic::{", stringify!($atomic_type), ", Ordering};
let foo = ", stringify!($atomic_type), "::new(23); let foo = ", stringify!($atomic_type), "::new(23);
@@ -1889,7 +1888,6 @@ assert_eq!(foo.load(Ordering::SeqCst), 42);
If you want to obtain the maximum value in one step, you can use the following: If you want to obtain the maximum value in one step, you can use the following:
``` ```
#![feature(atomic_min_max)]
", $extra_feature, "use std::sync::atomic::{", stringify!($atomic_type), ", Ordering}; ", $extra_feature, "use std::sync::atomic::{", stringify!($atomic_type), ", Ordering};
let foo = ", stringify!($atomic_type), "::new(23); let foo = ", stringify!($atomic_type), "::new(23);
@@ -1898,9 +1896,7 @@ let max_foo = foo.fetch_max(bar, Ordering::SeqCst).max(bar);
assert!(max_foo == 42); assert!(max_foo == 42);
```"), ```"),
#[inline] #[inline]
#[unstable(feature = "atomic_min_max", #[stable(feature = "atomic_min_max", since = "1.45.0")]
reason = "easier and faster min/max than writing manual CAS loop",
issue = "48655")]
#[$cfg_cas] #[$cfg_cas]
pub fn fetch_max(&self, val: $int_type, order: Ordering) -> $int_type { pub fn fetch_max(&self, val: $int_type, order: Ordering) -> $int_type {
// SAFETY: data races are prevented by atomic intrinsics. // SAFETY: data races are prevented by atomic intrinsics.
@@ -1929,7 +1925,6 @@ using [`Release`] makes the load part [`Relaxed`].
# Examples # Examples
``` ```
#![feature(atomic_min_max)]
", $extra_feature, "use std::sync::atomic::{", stringify!($atomic_type), ", Ordering}; ", $extra_feature, "use std::sync::atomic::{", stringify!($atomic_type), ", Ordering};
let foo = ", stringify!($atomic_type), "::new(23); let foo = ", stringify!($atomic_type), "::new(23);
@@ -1942,7 +1937,6 @@ assert_eq!(foo.load(Ordering::Relaxed), 22);
If you want to obtain the minimum value in one step, you can use the following: If you want to obtain the minimum value in one step, you can use the following:
``` ```
#![feature(atomic_min_max)]
", $extra_feature, "use std::sync::atomic::{", stringify!($atomic_type), ", Ordering}; ", $extra_feature, "use std::sync::atomic::{", stringify!($atomic_type), ", Ordering};
let foo = ", stringify!($atomic_type), "::new(23); let foo = ", stringify!($atomic_type), "::new(23);
@@ -1951,9 +1945,7 @@ let min_foo = foo.fetch_min(bar, Ordering::SeqCst).min(bar);
assert_eq!(min_foo, 12); assert_eq!(min_foo, 12);
```"), ```"),
#[inline] #[inline]
#[unstable(feature = "atomic_min_max", #[stable(feature = "atomic_min_max", since = "1.45.0")]
reason = "easier and faster min/max than writing manual CAS loop",
issue = "48655")]
#[$cfg_cas] #[$cfg_cas]
pub fn fetch_min(&self, val: $int_type, order: Ordering) -> $int_type { pub fn fetch_min(&self, val: $int_type, order: Ordering) -> $int_type {
// SAFETY: data races are prevented by atomic intrinsics. // SAFETY: data races are prevented by atomic intrinsics.