RFR: 8320347: Emulate vblendvp[sd] on ECore [v5]

[Volodymyr Paprotski]

On Sat, 25 Nov 2023 00:36:59 GMT, Jatin Bhateja <jbhateja at openjdk.org> wrote:

>> Hmm. Good catch!
>> 
>> Thinking about AVX1 case some more.. Platforms where this `vpblendvp*` emulation is needed have AVX2 at least, otherwise vpblendvp is faster. I think its better to disable this optimization entirely if AVX1 is required to be used. 
>> 
>> I would go even further and disable `EnableX86ECoreOpts` if `UseAVX==1`. Preference?
>
> vpblendps/pd are supported for AVX1 targets, Since the patch is about emulating floating point variable blends using alternate sequence I think we should remove any impediment which prohibit its usage over E-core at AVX1 level.

Decided to go with the smaller solution and disable just for the cases where the code generated is illegal. I still think the bigger solution of forcing `EnableX86ECoreOpts` to be off if `UseAVX==1`] is cleaner, but I suppose we can come back to that.

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PR Review Comment: https://git.openjdk.org/jdk/pull/16716#discussion_r1405454571