RFR: 8265491: Math Signum optimization for x86 [v9]

[Marcus G K Williams]

On Tue, 27 Apr 2021 21:40:24 GMT, Marcus G K Williams <github.com+168222+mgkwill at openjdk.org> wrote:

>> Marcus G K Williams has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   sviswa7 review
>>   
>>   Signed-off-by: Marcus G K Williams <marcus.williams at intel.com>
>
> Thanks for the review @sviswa7. 
> 
> I've updated to `StubRoutines::x86::float_sign_flip()` & `StubRoutines::x86::double_sign_flip()` as I was using when the code was in the src/hotspot/cpu/x86/x86.ad. If I understood your comment correctly this should use 128 bit aligned.
> 
> I've added comments as suggested.

> @mgkwill I was wrong. It looks like the CodeEntryAlignment is set to 16 bytes i.e. 128 bits as minimum (globals_x86.hpp). So please continue to use the vector_float_sign_flip and vector_double_sign_flip masks. Xorps and xorpd are vector instructions and we should use the vector masks here.

Thanks @sviswa7. I've reverted to `StubRoutines::x86::vector_float_sign_flip(`) `StubRoutines::x86::vector_double_sign_flip()`

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PR: https://git.openjdk.java.net/jdk/pull/3581