RFR: 8269598: Regressions up to 5% on aarch64 seems due to JDK-8268858

[Joshua Zhu]

On Thu, 15 Jul 2021 20:39:18 GMT, Dean Long <dlong at openjdk.org> wrote:

>> Thanks @vnkozlov @dean-long for your review.
>
> @JoshuaZhuwj Please try SPECjvm2008 compress on x86/x64 with -XX:+PreserveFramePointer.  We are seeing a regression after JDK-8268858.

@dean-long Thanks for your information. Previously I already found performance degradation with -XX:+PreserveFramePointer in Alibaba Flink Nexmark benchmark. It's caused by inefficient codes generated by RA. That's why I begin working on register pressure. I already created JDK-8270808 [1] to track it. Meanwhile I will also track your mentioned regression issue together with it. Hope they're caused by the same reason.

[1] https://bugs.openjdk.java.net/browse/JDK-8270808

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PR: https://git.openjdk.java.net/jdk/pull/4766