RFR: 8300208: Optimize Adler32 stub for AVX-512 targets. [v2]

[Jatin Bhateja]

On Fri, 27 Jan 2023 01:34:02 GMT, Sandhya Viswanathan <sviswanathan at openjdk.org> wrote:

>> Jatin Bhateja has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   8300208: Review comments resolution.
>
> src/hotspot/cpu/x86/stubGenerator_x86_64_adler.cpp line 155:
> 
>> 153:       __ vpaddd(yb, yb, ya, Assembler::AVX_512bit);
>> 154:       __ addptr(data, CHUNKSIZE);
>> 155:       __ cmpptr(data, end);
> 
> This still processes 16 bytes worth of data in one loop iteration as the AVX2 loop. Have you given thoughts on processing double the size with AVX3?

If we double the size of inputs processed within the loop from 16 to 32 then subsequent ADLER_SCALE will also change from 0-31, given that we cannot accommodate more than 16 integer in a 512 bit vector hence it will not be possible to scale up the loop block size.

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PR: https://git.openjdk.org/jdk/pull/12045