RFR: 8269476: Skip nmethod entry barrier if there is no oops in the jit code [v2]

[王超]

On Mon, 28 Jun 2021 13:42:03 GMT, Andrew Haley <aph at openjdk.org> wrote:

> This `membar` is evil, and it would be very nice to be rid of it. If we have a `nop` before the guard load, we can patch it to jump around the whole sequence, so that would be my preferred thing to do.

thanks for your suggestion, I'll try to implement the `nop` version on aarch64 architecture.

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PR: https://git.openjdk.java.net/jdk/pull/4610