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Stabilize cmpxchg16b instrinsic (#1358)

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Resolves https://github.com/rust-lang/stdarch/issues/827
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Nugine 2023-01-06 01:52:56 +08:00 • committed by GitHub
parent 755a95168f
commit ee060659d9
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1 changed files with 10 additions and 6 deletions
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16
library/stdarch/crates/core_arch/src/x86_64/cmpxchg16b.rs
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@ -37,11 +37,12 @@ use stdarch_test::assert_instr;
/// The failure ordering must be [`Ordering::SeqCst`], [`Ordering::Acquire`] or
/// [`Ordering::Relaxed`], or this function call is undefined. See the `Atomic*`
/// documentation's `compare_exchange` function for more information. When
/// `compare_exchange` panics, this is undefined behavior. Currently this
/// function aborts the process with an undefined instruction.
/// `compare_exchange` panics, this is undefined behavior.
#[inline]
#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
#[cfg_attr(test, assert_instr(cmpxchg16b, success = Ordering::SeqCst, failure = Ordering::SeqCst))]
#[target_feature(enable = "cmpxchg16b")]
#[stable(feature = "cmpxchg16b_instrinsic", since = "1.67.0")]
pub unsafe fn cmpxchg16b(
dst: *mut u128,
old: u128,
@ -53,6 +54,8 @@ pub unsafe fn cmpxchg16b(
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),
@ -69,11 +72,12 @@ pub unsafe fn cmpxchg16b(
(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"),
// The above block is all copied from libcore, and this statement is
// also copied from libcore except that it's a panic in libcore and we
// have a little bit more of a lightweight panic here.
_ => crate::core_arch::x86::ud2(),
// `atomic::Ordering` is non_exhaustive. It warns when `core_arch` is built as a part of `core`.
#[allow(unreachable_patterns)]
(_, _) => unreachable!(),
};
val
}