[crac] RFR: RFC: -XX:CPUFeatures=0xnumber for CPU migration [v2]

[Ashutosh Mehra]

On Fri, 10 Feb 2023 12:40:06 GMT, Anton Kozlov <akozlov at openjdk.org> wrote:

> so are you proposing -XX:+PortableCode to change default CPU features to some conservative set, that still can be extended by existing Hotpost options?

That's right.

> even for CPUFeatures we may want values like generic, native (again, in gcc terms)

Yes, something like CPUFeatures=generic would serve the same purpose as PortableCode.  IMO adding something like `-XX:CPUFeatures=[generic|native]` or `-XX:[+-]PortableCode` is more appropriate. To enable/disable extended instruction sets, hotspot already has options (like UseSSE). Combining those options with `CPUFeatures=[generic|native]` or `PortableCode` would provide an easier way for the user to control the cpu features that hotspot should use.

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PR: https://git.openjdk.org/crac/pull/41