RFR: 8269404: Base64 Encoding optimization enhancements for x86 using AVX-512 [v2]

[Vladimir Kozlov]

On Sat, 26 Jun 2021 18:26:24 GMT, Scott Gibbons <github.com+6704669+asgibbons at openjdk.org> wrote:

>> Enhance the Base64 Encode intrinsic for x86 using AVX-512 to get better performance. Also allow for performance improvement on non-AVX-512 enabled platforms.
>> 
>> Added AVX-512 code for encoding Base64 blocks, including slight improvements for non-AVX-512 x86 platforms.
>> 
>> Running the Base64Decode benchmark, this change increases decode performance by an average of 2.6x with a maximum 9.7x for buffers > ~20k.  The numbers are given in the table below.
>> 
>> **Base Score** is without intrinsic support, **Optimized Score** is using this intrinsic, and **Gain** is **Base** / **Optimized**.
>> 
>> Benchmark Name | Base Score | Optimized Score | Gain
>> -- | -- | -- | --
>> testBase64Encode size 1 | 8.10 | 8.04 | 1.01
>> testBase64Encode size 2 | 8.51 | 8.43 | 1.01
>> testBase64Encode size 3 | 11.08 | 10.72 | 1.03
>> testBase64Encode size 6 | 13.98 | 13.12 | 1.07
>> testBase64Encode size 7 | 14.44 | 13.38 | 1.08
>> testBase64Encode size 9 | 15.44 | 14.37 | 1.07
>> testBase64Encode size 10 | 16.13 | 14.97 | 1.08
>> testBase64Encode size 48 | 27.14 | 23.23 | 1.17
>> testBase64Encode size 512 | 123.86 | 30.75 | 4.03
>> testBase64Encode size 1000 | 224.42 | 37.71 | 5.95
>> testBase64Encode size 20000 | 4202.11 | 430.16 | 9.77
>
> Scott Gibbons has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Format warning removal.

compiler/intrinsics/base64/TestBase64.java failed with wrong result on Windows (avx512):

----------System.out:(1/17)----------
5000 iterations
----------System.err:(17/1502)----------
java.lang.RuntimeException: Assertion failed! The result is not same as expected
 result: ICAgICAgICAxNiBRICAgICAgICAgICAgsTsA6igAoigAoigAoigAoj0QIHk= expected: ICAgICAgICAxNiBRICAgICAgICAgICAgMzMgaCAgICAgICAgICAgIDUwIHk=
	at compiler.intrinsics.base64.TestBase64.assertEqual(TestBase64.java:238)
	at compiler.intrinsics.base64.TestBase64.test0(TestBase64.java:151)
	at compiler.intrinsics.base64.TestBase64.main(TestBase64.java:72)

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

PR: https://git.openjdk.java.net/jdk/pull/4601