[PATCH] D139627: clang/X86: Don't emit "min-legal-vector-width"="0"

[Matt Arsenault via Phabricator via cfe-commits]

arsenm added a comment.

In D139627#3983718 <https://reviews.llvm.org/D139627#3983718>, @pengfei wrote:

>> It also doesn't mean that, because the IR doesn't have to be consistent with the attribute. The IR exists independent of the attribute, and the attribute can only provide performance hints.
>
> I don't agree. There are attributes like `zeroext`, `byref` are ABI related see https://llvm.org/docs/LangRef.html#parameter-attributes. I'd take `min-legal-vector-width` as a similar one.

This is not an ABI attribute, it's an optimization hint. If it were an ABI attribute, inferring and propagating it like is done would not be correct. If you treat it like an optimization hint, you only have to consider this one place instead of everywhere the IR may change


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