RFR: JDK-8300808: Accelerate Base64 on x86 for AVX2 [v7]

[Claes Redestad]

On Wed, 1 Feb 2023 18:28:25 GMT, Scott Gibbons <duke at openjdk.org> wrote:

>> Added code for Base64 acceleration (encode and decode) which will accelerate ~4x for AVX2 platforms.
>> 
>> Encode performance:
>> **Old:**
>> 
>> Benchmark                      (maxNumBytes)   Mode  Cnt     Score   Error   Units
>> Base64Encode.testBase64Encode           1024  thrpt    3  4309.439 ± 2.632  ops/ms
>> 
>> 
>> **New:**
>> 
>> Benchmark                      (maxNumBytes)   Mode  Cnt      Score     Error   Units
>> Base64Encode.testBase64Encode           1024  thrpt    3  24211.397 ± 102.026  ops/ms
>> 
>> 
>> Decode performance:
>> **Old:**
>> 
>> Benchmark                      (errorIndex)  (lineSize)  (maxNumBytes)   Mode  Cnt     Score    Error   Units
>> Base64Decode.testBase64Decode           144           4           1024  thrpt    3  3961.768 ± 93.409  ops/ms
>> 
>> **New:**
>> Benchmark                      (errorIndex)  (lineSize)  (maxNumBytes)   Mode  Cnt      Score    Error   Units
>> Base64Decode.testBase64Decode           144           4           1024  thrpt    3  14738.051 ± 24.383  ops/ms
>
> Scott Gibbons has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Handle AVX2 URL; address review comments

src/hotspot/cpu/x86/stubGenerator_x86_64.cpp line 2202:

> 2200: }
> 2201: 
> 2202: address StubGenerator::base64_AVX2_decode_URL_tables_addr() {

Shouldn't this be `decode_lut_tables`? As it's used for URL and non-URL decoding alike.

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PR: https://git.openjdk.org/jdk/pull/12126