re-stabilize the AVX-512 features that were stabilized in Rust 1.27.0 #842
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rust-lang#739 added per-feature stabilization of runtime CPU feature detection. In so doing, it de-stabilized some detection features that had been stable since Rust 1.27.0, breaking some published crates (on nightly). This commit re-stabilizes the subset of AVX-512 detection features that were included in 1.27.0 (that is, the pre-Ice-Lake subset). Other instruction sets (MMX in particular) remain de-stabilized, pending a decision about whether should ever stabilize them. See rust-lang/rust#68905.
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(CI failure appears unrelated.) |
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Could you add a comment saying that the AVX512 intrinsics are not stable yet, only the feature check. And that these were stabilized to avoid breaking code that was already relying on it. Add a reference to rust-lang/rust#68905. This doesn't have to be a doc comment, just a small note in the code for the next person who stumbles across this code wondering why these are stable while the intrinsics aren't. |
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In light of rust-lang/rust#68905 (comment), should we expand this PR to stabilize the entire set of AVX-512 features, and also mmx/sse4a/tbm? I don't know whether detection for those things actually works. |
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👍 |
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Also "cmpxchg16b" and "rtm"? I haven't seen those discussed yet. If someone who knows what they're doing would like to land this PR, and then make follow-up changes on top of it, that might be a better option :) I don't have any expertise in this area, and I'm worried about breaking things. |
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This PR is now up to speed with rust-lang/rust#68905 (comment) and is potentially ready to merge. I've sanity checked it locally by building the |
Update stdarch submodule This only includes one commit: - rust-lang/stdarch@abe96ca (rust-lang/stdarch#842) Fixes rust-lang#68905
#739 added per-feature
stabilization of runtime CPU feature detection. In so doing, it
de-stabilized some detection features that had been stable since Rust
1.27.0, breaking some published crates (on nightly). This commit
re-stabilizes the subset of AVX-512 detection features that were
included in 1.27.0 (that is, the pre-Ice-Lake subset). Other instruction
sets (MMX in particular) remain de-stabilized, pending a decision about
whether should ever stabilize them.
See rust-lang/rust#68905.