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cmpxchg16b: use atomic_compare_exchange from libcore #1811

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Merged
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May 30, 2025
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cmpxchg16b: use atomic_compare_exchange from libcore #1811

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30 changes: 2 additions & 28 deletions crates/core_arch/src/x86_64/cmpxchg16b.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -48,34 +48,8 @@ pub unsafe fn cmpxchg16b(
success: Ordering,
failure: Ordering,
) -> u128 {
use crate::{intrinsics, sync::atomic::Ordering::*};

debug_assert!(dst as usize % 16 == 0);

// Copied from `atomic_compare_exchange` in `core`.
// https://github.com/rust-lang/rust/blob/f8a2e49/library/core/src/sync/atomic.rs#L3046-L3079
let (val, _ok) = match (success, failure) {
(Relaxed, Relaxed) => intrinsics::atomic_cxchg_relaxed_relaxed(dst, old, new),
(Relaxed, Acquire) => intrinsics::atomic_cxchg_relaxed_acquire(dst, old, new),
(Relaxed, SeqCst) => intrinsics::atomic_cxchg_relaxed_seqcst(dst, old, new),
(Acquire, Relaxed) => intrinsics::atomic_cxchg_acquire_relaxed(dst, old, new),
(Acquire, Acquire) => intrinsics::atomic_cxchg_acquire_acquire(dst, old, new),
(Acquire, SeqCst) => intrinsics::atomic_cxchg_acquire_seqcst(dst, old, new),
(Release, Relaxed) => intrinsics::atomic_cxchg_release_relaxed(dst, old, new),
(Release, Acquire) => intrinsics::atomic_cxchg_release_acquire(dst, old, new),
(Release, SeqCst) => intrinsics::atomic_cxchg_release_seqcst(dst, old, new),
(AcqRel, Relaxed) => intrinsics::atomic_cxchg_acqrel_relaxed(dst, old, new),
(AcqRel, Acquire) => intrinsics::atomic_cxchg_acqrel_acquire(dst, old, new),
(AcqRel, SeqCst) => intrinsics::atomic_cxchg_acqrel_seqcst(dst, old, new),
(SeqCst, Relaxed) => intrinsics::atomic_cxchg_seqcst_relaxed(dst, old, new),
(SeqCst, Acquire) => intrinsics::atomic_cxchg_seqcst_acquire(dst, old, new),
(SeqCst, SeqCst) => intrinsics::atomic_cxchg_seqcst_seqcst(dst, old, new),
(_, AcqRel) => panic!("there is no such thing as an acquire-release failure ordering"),
(_, Release) => panic!("there is no such thing as a release failure ordering"),

// `atomic::Ordering` is non_exhaustive. It warns when `core_arch` is built as a part of `core`.
#[allow(unreachable_patterns)]
(_, _) => unreachable!(),
};
val
let res = crate::sync::atomic::atomic_compare_exchange(dst, old, new, success, failure);
res.unwrap_or_else(|x| x)
}