[jdk21u-dev] RFR: 8328938: C2 SuperWord: disable vectorization for large stride and scale [v2]

[Volker Simonis]

On Wed, 17 Apr 2024 09:42:33 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> Unclean backport to prevent accidents in C2 loop optimizations. The patch is unclean, because JDK 21u misses major SuperWord refactorings. I applied the hunk by hand in the similar place, and also used `slp->iv_stride()` in one place to get this thing to work.
>> 
>> @eme64, if you want to take a look at this?
>> 
>> Additional testing:
>>  - [x] New regression test fails without the patch, passes with it
>>  - [x] Linux x86_64 server fastdebug, `all`
>>  - [x] Linux x86_64 server fastdebug, 100K Fuzzer tests
>>  - [x] Linux x86_64 server fastdebug, Maven CTW
>
> Aleksey Shipilev has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Check if stride is actually con before touching iv_stride

Looks good to me.

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Marked as reviewed by simonis (Reviewer).

PR Review: https://git.openjdk.org/jdk21u-dev/pull/495#pullrequestreview-2009119940