RFR: 8320448: Accelerate IndexOf using AVX2 [v33]

[Scott Gibbons]

On Fri, 24 May 2024 06:31:36 GMT, Daniel Jeliński <djelinski at openjdk.org> wrote:

>> Thanks for finding this.  It was ignorance on my part as I thought the xorq would have logic to not emit the REX prefix if not necessary, but it doesn't.  Fixed.
>
> Right, it seems to surprise people. There's a lot of preexisting uses of xorq / xorptr to zero a register. I think it would make sense to implement this logic in xorq. I can do this if others agree.

Good idea.  I vote yes.

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PR Review Comment: https://git.openjdk.org/jdk/pull/16753#discussion_r1613506958