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

[Fei Gao]

On Tue, 24 May 2022 16:02:54 GMT, Vladimir Kozlov <kvn at openjdk.org> wrote:

> 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.

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