RFR: 8270519: Move several vector helper methods to shared header file

[Jie Fu]

On Mon, 19 Jul 2021 04:34:24 GMT, Xiaohong Gong <xgong at openjdk.org> wrote:

> Hi, could anyone please take a look at this simple patch?
> 
> This is a followed-up patch to [1] which added several arch independent vector methods (e.g. `vector_length/vector_element_basic_type`). Since these methods also exist in x86.ad and are widely used in their match rules, it's better to move the shared methods to a common shared place.
> 
> [1] https://bugs.openjdk.java.net/browse/JDK-8269725
> 
> Tested tier1 and jdk:tier3.

See no objection, so sponsor it.

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PR: https://git.openjdk.java.net/jdk/pull/4822