RFR: 8284563: AArch64: bitperm feature detection for SVE2 on Linux

[Andrew Haley]

On Mon, 18 Apr 2022 06:32:06 GMT, Ningsheng Jian <njian at openjdk.org> wrote:

>> Yeah, I was thinking this before. Indeed, A53MAC and  STXR_PREFETCH are not CPU feature. Considering that some codes depend on that, it's acceptable to me leaving them here at this moment.
>
> OK. Then could you also update the usages of these two `features` with your new functions?

`STXR_PREFETCH` is usually done unconditionally in non-JVM code. Does it ever hurt performance? If not, let's get rid of `STXR_PREFETCH` and do prefetching unconditionally.

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PR: https://git.openjdk.java.net/jdk/pull/8258