RFR: 8283307: Vectorize unsigned shift right on signed subword types [v3]

[Jie Fu]

On Fri, 3 Jun 2022 10:02:48 GMT, Fei Gao <fgao at openjdk.org> wrote:

> 
> @DamonFool , no `RShiftB` nodes are generated with `-XX:UseAVX=0 -XX:UseSSE=2` on x86. The test passed because when adding VM options `-XX:UseAVX=0 -XX:UseSSE=2` externally, the IR framework won't do the IR check and just run the java code, I verified and made the guess. But I'm not clear whether all external VM options would stop the IR framework to do the IR check.

Thanks for the verification.
Then, I think the test is fine.

What do you think? @vnkozlov

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PR: https://git.openjdk.java.net/jdk/pull/7979