RFR: 8313779: RISC-V: use andn / orn in the MD5 instrinsic [v3]

[Antonios Printezis]

On Mon, 7 Aug 2023 13:50:48 GMT, Antonios Printezis <tonyp at openjdk.org> wrote:

>> Small improvement of the MD5 intrinsic when the Zbb extension is available. Performance comparison (with thanks again to @robehn for this!):
>> 
>> before:
>> 
>> 
>> MessageDigests.digest                   md5        64     DEFAULT  avgt    6    1835.246 ±  252.071  ns/op
>> MessageDigests.digest                   md5     16384     DEFAULT  avgt    6  145386.522 ±  444.446  ns/op
>> MessageDigests.getAndDigest             md5        64     DEFAULT  avgt    6    2555.515 ±  639.491  ns/op
>> MessageDigests.getAndDigest             md5     16384     DEFAULT  avgt    6  149045.631 ± 6658.545  ns/op
>> 
>> 
>> after:
>> 
>> 
>> MessageDigests.digest                   md5        64     DEFAULT  avgt    6    1779.637 ±  207.869  ns/op
>> MessageDigests.digest                   md5     16384     DEFAULT  avgt    6  137147.179 ±  706.396  ns/op
>> MessageDigests.getAndDigest             md5        64     DEFAULT  avgt    6    2645.354 ± 1245.318  ns/op
>> MessageDigests.getAndDigest             md5     16384     DEFAULT  avgt    6  141306.966 ± 7000.576  ns/op
>> 
>> 
>> (only line 3 is not an improvement, but it has higher variation)
>> 
>> It seems to save around 5% of executed instructions.
>
> Antonios Printezis has updated the pull request incrementally with one additional commit since the last revision:
> 
>   replaced li with mv

Tests pass (with both `-UseZbb` and `+UseZbb`) with the `li` -> `mv` change. I also confirmed that the generated code is the same.

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PR Comment: https://git.openjdk.org/jdk/pull/15156#issuecomment-1667943172