RFR: 8256056: Deoptimization stub doesn't save vector registers on x86

Mon Nov 9 21:24:55 UTC 2020

On Mon, 9 Nov 2020 20:00:20 GMT, Sandhya Viswanathan <sviswanathan at openjdk.org> wrote:

> If possible, it will be good to do this optionally.
As I mentioned earlier, it's possible, but requires 2 variants of deopt stub and dispatching logic to choose proper one depeding on the location it is patched with. 

Deoptimization process is already expensive and execution ends up in interpreter anyway. 

Is the frequency drop such a problem in case of deopt stub to justify the increase in complexity?
Also, I'd like to point out that on older CPUs with AVX512 supported (like Skylake) AVX=3 is turned off by default to avoid generating EVEX-encoded instructions on CPUs which have frequency scaling issues. So, if AVX=3 is specified, there are already many places (which are more performance sensitive IMO) with EVEX-encoded instructions.

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PR: https://git.openjdk.java.net/jdk/pull/1134