RFR: 8342095: Add autovectorizer support for subword vector casts [v3]

[Emanuel Peter]

On Sun, 9 Feb 2025 05:59:37 GMT, Jasmine Karthikeyan <jkarthikeyan at openjdk.org> wrote:

>> Jasmine Karthikeyan has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Fix some tests that now vectorize
>
> I also updated the benchmark, and got these results:
> 
>                                                   Baseline                    Patch
> Benchmark                  (SIZE)  Mode  Cnt    Score    Error  Units  Score    Error  Units  Improvement
> VectorSubword.byteToInt      1024  avgt   12  185.700 ± 0.798  ns/op   37.427 ± 0.276  ns/op  (4.96x)
> VectorSubword.byteToShort    1024  avgt   12  240.737 ± 1.087  ns/op   23.094 ± 0.502  ns/op  (10.42x)
> VectorSubword.intToByte      1024  avgt   12  181.680 ± 0.553  ns/op   49.873 ± 1.613  ns/op  (3.64x)
> VectorSubword.intToShort     1024  avgt   12  176.256 ± 1.414  ns/op   43.933 ± 4.310  ns/op  (4.01x)
> VectorSubword.shortToByte    1024  avgt   12  245.600 ± 6.217  ns/op   28.426 ± 0.649  ns/op  (8.64x)
> VectorSubword.shortToInt     1024  avgt   12  178.364 ± 2.921  ns/op   34.140 ± 0.229  ns/op  (5.22x)

@jaskarth just ping me whenever I should have a look again!

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

PR Comment: https://git.openjdk.org/jdk/pull/23413#issuecomment-2662917708