RFR: 8335860: compiler/vectorization/TestFloat16VectorConvChain.java fails with non-standard AVX/SSE settings [v2]

[Jatin Bhateja]

On Tue, 16 Jul 2024 18:30:35 GMT, Sandhya Viswanathan <sviswanathan at openjdk.org> wrote:

>> Jatin Bhateja has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Review suggestions incorporated
>
> src/hotspot/cpu/x86/vm_version_x86.hpp line 838:
> 
>> 836: 
>> 837:   // For AVX CPUs only since it needs VEX encoding which is missing on SSE targets,
>> 838:   // thus f16c support is disabled if UseAVX == 0.
> 
> This comment is somewhat or vey confusing. The code for supports_float16() by itself is very clear. I am wondering why do we need this explanation in the comment at all? Let us remove it altogether.

Sure, FTR my comment was in relation to following check
https://github.com/openjdk/jdk/blob/master/src/hotspot/cpu/x86/vm_version_x86.cpp#L1056

 FP16-FP32 conversions are VEX encoded instructions and do not have SSE flavor. Thus, only works with UseAVX > 0.

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PR Review Comment: https://git.openjdk.org/jdk/pull/20160#discussion_r1680430908