RFR: 8293488: Add EOR3 backend rule for aarch64 SHA3 extension [v3]

[Bhavana Kilambi]

On Wed, 19 Oct 2022 14:27:34 GMT, Bhavana Kilambi <bkilambi at openjdk.org> wrote:

>> Arm ISA v8.2A and v9.0A include SHA3 feature extensions and one of those SHA3 instructions - "eor3" performs an exclusive OR of three vectors. This is helpful in applications that have multiple, consecutive "eor" operations which can be reduced by clubbing them into fewer operations using the "eor3" instruction. For example -
>> 
>> eor a, a, b
>> eor a, a, c
>> 
>> can be optimized to single instruction - `eor3 a, b, c`
>> 
>> This patch adds backend rules for Neon and SVE2 "eor3" instructions and a micro benchmark to assess the performance gains with this patch. Following are the results of the included micro benchmark on a 128-bit aarch64 machine that supports Neon, SVE2 and SHA3 features -
>> 
>> 
>> Benchmark               gain
>> TestEor3.test1Int       10.87%
>> TestEor3.test1Long      8.84%
>> TestEor3.test2Int       21.68%
>> TestEor3.test2Long      21.04%
>> 
>> 
>> The numbers shown are performance gains with using Neon eor3 instruction over the master branch that uses multiple "eor" instructions instead. Similar gains can be observed with the SVE2 "eor3" version as well since the "eor3" instruction is unpredicated and the machine under test uses a maximum vector width of 128 bits which makes the SVE2 code generation very similar to the one with Neon.
>
> Bhavana Kilambi has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Changed the modifier order preference in JTREG test

The new patch removes the svesha3 feature check for eor3 instruction. Eor3 instruction is part of the SHA3 feature but it is present by default in SVE2 and is not part of the SVESHA3 feature. Please review. Thank you ..

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PR: https://git.openjdk.org/jdk/pull/10407