[jdk17u-dev] RFR: 8268276: Base64 Decoding optimization for x86 using AVX-512 [v2]

[Scott Gibbons]

On Wed, 26 Oct 2022 00:13:50 GMT, Scott Gibbons <duke at openjdk.org> wrote:

>> This is a backport of JDK-8268276: Base64 Decoding optimization for x86 using AVX-512.
>> 
>> We have had numerous customer requests for this functionality to be backported due to the ~19x performance improvement.
>>  
>> Original patch does not apply cleanly to 17u, because of a bug that was identified in the original commit, but not fixed until the later Base64 Encode acceleration enhancement was complete.  The fix is on line 6039 of src/hotspot/cpu/x86/stubGenerator_x86_64.cpp and has been included in this PR.  All four "translatedX" registers needed to be checked for illegal characters in the input stream.
>> 
>> Risk: I view the risk of this backport to be minimal.  This code has been in use for many months with no bugs reported.
>>  
>> Testing: x86_64 build, affected tests, tier1, tier2
>>  
>> Thanks,
>> --Scott
>
> Scott Gibbons has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Update .gitignore

src/hotspot/cpu/x86/stubGenerator_x86_64.cpp line 6039:

> 6037: 
> 6038:       __ vpternlogd(input3, 0xfe, translated0, translated1, Assembler::AVX_512bit);
> 6039:       __ vpternlogd(input0, 0xfe, translated2, translated3, Assembler::AVX_512bit);

This line (6039) was changed from

      __ vpternlogd(input0, 0xfe, translated1, translated2, Assembler::AVX_512bit);

It was changed to:

      __ vpternlogd(input0, 0xfe, translated2, translated3, Assembler::AVX_512bit);

-------------

PR: https://git.openjdk.org/jdk17u-dev/pull/840