RFR: 8283091: Support type conversion between different data sizes in SLP [v3]

[Vladimir Kozlov]

On Wed, 25 May 2022 01:13:36 GMT, Fei Gao <fgao at openjdk.org> wrote:

>> @fg1417  Thank you for suggesting this optimization. I see that it was not updated for some time. Do you still intend to work on it?
>> 
>> Please update to latest JDK (Loom was integrated) and run performance again. Also include % of changes.
>> 
>> I have the same concern as @DamonFool about regression when vectorizing some conversions. May be we should have additional `Matcher` property we could consult when trying to **auto-vectorize**. I understand that we need `vcvt2Dto2I` when VectorAPI specifically asking to generate it but we should not enforce auto-generation.
>
>> Please update to latest JDK (Loom was integrated) and run performance again. Also include % of changes.
>> 
>> I have the same concern as @DamonFool about regression when vectorizing some conversions. May be we should have additional `Matcher` property we could consult when trying to **auto-vectorize**. I understand that we need `vcvt2Dto2I` when VectorAPI specifically asking to generate it but we should not enforce auto-generation.
> 
> @vnkozlov thanks for your review and kind suggestion! I'll update the patch to resolve the potential performance regression.

@fg1417  I don't see new update in this PR.  Please also show performance numbers with new changes

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

PR: https://git.openjdk.java.net/jdk/pull/7806