RFR: 8283091: Support type conversion between different data sizes in SLP [v7]

[Fei Gao]

On Mon, 6 Jun 2022 19:38:14 GMT, Vladimir Kozlov <kvn at openjdk.org> wrote:

> May be we should rename it to `match_rule_supported_superword`. That is how we call auto-vectorizer in C2.

Done. 

And update after https://github.com/openjdk/jdk/pull/8877. Thanks.

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