RFR: 8287325: AArch64: fix virtual threads with -XX:UseBranchProtection=pac-ret

[Andrew Haley]

On Tue, 7 Jun 2022 20:04:40 GMT, Ron Pressler <rpressler at openjdk.org> wrote:

> If this feature requires re-signing every frame, then PAC-RET should be reconsidered for Java frames (though not native frames). In that case, the right fix for JDK 19 would be to disable this mode when preview is enabled. BTW, +PreserveFramePointer also causes a huge slowdown for virtual threads as it requires the slow path to be taken on every thaw.

I agree. For the preview, I think we can do without  -XX:UseBranchProtection=pac-ret. We should take some time to think about the best way to approach pac-ret with virtual threads.

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PR: https://git.openjdk.java.net/jdk/pull/9067