Tracking issue for integer_atomics (`AtomicU128`/`AtomicI128`)

[tamird]

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Tracking rust-lang/rfcs#1543.

• std::sync::atomic::AtomicI128
• std::sync::atomic::AtomicU128

Seems related to #56071. See also #57425 which stabilized other atomic integer widths.

Probably blocked by various LLVM issues:

• [AArch64]: 128-bit Sequentially Consistent load allows reordering before prior store when armv8 and armv8.4 implementations are Mixed llvm/llvm-project#81978
• LLVM fails to select cmpxchg16b for 128-bit atomics on x86_64 llvm/llvm-project#187503

[RalfJung]

It'd be good to list the APIs that are covered by this tracking issue, and copy any open questions that have been noted in the RFC of the previous tracking issue.

[kadiwa4]

The unstable ATOMIC_*_INIT constants can be removed, right? Or should they be stabilized for consistency with the stable ATOMIC_*_INIT constants? (All of them are deprecated.)

[eric-seppanen]

The standard library docs for AtomicU128, etc. still point to #32976 instead of here.

[kadiwa4]

What do you mean?

(rust 1.66.1)

Interestingly, in the online documentation the types don't show up at all, whereas they do show up in my local copy (rust-docs from rustup).

[eric-seppanen]

Apologies, I must have accidentally followed a link to somebody else's stale docs.