RFR: 8270446: Remove the MemBarNode that has been optimized from the current block

[Andrew Haley]

On Thu, 15 Jul 2021 08:13:31 GMT, SUN Guoyun <github.com+40024232+sunny868 at openjdk.org> wrote:

> For continuous and same type membar, like"membar_release membar_release"，maybe http://hg.openjdk.java.net/jdk9/jdk9/hotspot/rev/93ae449c9b52 was also only a workround. I`ll try to fix it in share/opto.

It was actually fixed by this:
http://hg.openjdk.java.net/jdk/hs/rev/8f1bc5a0d16d

And no, I agree with Vladimir. There's nothing to fix. OptoAssembly isn't supposed to be the exact instructions we generate: PrintAssembly does that.

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PR: https://git.openjdk.java.net/jdk/pull/4774