RFR: 8284563: AArch64: bitperm feature detection for SVE2 on Linux [v2]

[Vladimir Kozlov]

On Mon, 18 Apr 2022 10:58:39 GMT, Eric Liu <eliu at openjdk.org> wrote:

>> This patch adds BITPERM feature detection for SVE2 on Linux. BITPERM is
>> an optional feature in SVE2 [1]. It enables 3 SVE2 instructions (BEXT,
>> BDEP, BGRP). BEXT and BDEP map efficiently to some vector operations,
>> e.g., the compress and expand functionalities [2] which are proposed in
>> VectorAPI's 4th incubation [3]. Besides, to generate specific code based
>> on different architecture features like x86, this patch exports
>> VM_Version::supports_XXX() for all CPU features.  E.g.,
>> VM_Version::supports_svebitperm() for easy use.
>> 
>> This patch also fixes a trivial bug, that sets UseSVE back to 1 if it's
>> 2 in SVE1 system.
>> 
>> [1] https://developer.arm.com/documentation/ddi0601/2022-03/AArch64-Registers/ID-AA64ZFR0-EL1--SVE-Feature-ID-register-0
>> [2] https://bugs.openjdk.java.net/browse/JDK-8283893
>> [3] https://bugs.openjdk.java.net/browse/JDK-8280173
>
> Eric Liu has updated the pull request incrementally with one additional commit since the last revision:
> 
>   small fix
>   
>   Change-Id: Ida979f925055761ad73e50655d0584dcee24aea4

I am testing the fix: rename `sha2` back to `sha256`.

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