RFR: 8291600: [vectorapi] vector cast op check is not always needed for vector mask cast [v3]

[Quan Anh Mai]

On Thu, 25 Aug 2022 07:03:23 GMT, Xiaohong Gong <xgong at openjdk.org> wrote:

>> src/hotspot/cpu/x86/x86.ad line 8452:
>> 
>>> 8450:   predicate(Matcher::vector_length(n) == Matcher::vector_length(n->in(1)) &&
>>> 8451:             Matcher::vector_length_in_bytes(n) > Matcher::vector_length_in_bytes(n->in(1)) &&
>>> 8452:             UseAVX == 1 &&
>> 
>> Since most x86 would be avx > 1, I would suggest testing `UseAVX == 1` first and then others.
>
> Will fix this in a separate patch, thanks!

I think the general cases should come before the particular ones. These 2 rules are for a corner case where float or double masks with 256-bit width are involved. Thanks.

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PR: https://git.openjdk.org/jdk/pull/9737