RFR: 8302191: Performance degradation for float/double modulo on Linux [v9]

[Sandhya Viswanathan]

On Fri, 3 Mar 2023 13:45:11 GMT, Jan Kratochvil <duke at openjdk.org> wrote:

>> I have OCA already processed/approved. I am not Author but my Author request is being processed these days (sent to Rob McKenna).
>> I did regression test x86_64 OpenJDK-8. I will leave other regression testing on GHA.
>> The patch (and former GCC performance regression) affects only x86_64+i686.
>
> Jan Kratochvil has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains eight additional commits since the last revision:
> 
>  - Merge remote-tracking branch 'origin/master' into modulo
>  - Always include the _WIN64 workaround - a review by dholmes-ora.
>  - Remove comments to be moved to JBS (Bug System) - a review by jddarcy.
>  - Uppercase L - a review by turbanoff.
>  - Fix copyright author.
>  - Fix WIN32 vs. WIN64.
>  - Update according to the upstream review by David Holmes.
>  - 8302191: Performance degradation for float/double modulo on Linux

Very nice performance increase. The only concern I have is that the x87 fpu control (using fldcw instruction) is not set in 64 bit builds by the JVM anymore explicitly.  It is only set in the 32bit builds. Maybe @iwanowww or @shipilev have some thoughts on this.

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

PR: https://git.openjdk.org/jdk/pull/12508