RFR: 8364296: Set IntelJccErratumMitigation flag ergonomically

[Oli Gillespie]

On Thu, 31 Jul 2025 04:50:02 GMT, Jatin Bhateja <jbhateja at openjdk.org> wrote:

> Hi @olivergillespie , This change looks good to me, what about other flags in vm_version_x86.cpp https://github.com/openjdk/jdk/blob/master/src/hotspot/cpu/x86/vm_version_x86.cpp#L1198
> 
> JVM flag which is enabled through feature detection should have ERGONOMIC origin.

Thanks, good point, there are many more cases there. Looks like this is the only one where the actual value is out of sync with the flag, though, which is the most egregious part. The others all use FLAG_SET_DEFAULT or equivalent, so it's just the source of the updated value which is wrong. It actually seems like that's a pattern across the codebase - [this one](https://github.com/openjdk/jdk/blob/b9f7caed775e86e71f7d37789cb196fb1444ef12/src/hotspot/share/gc/shenandoah/heuristics/shenandoahHeuristics.hpp#L38-L39) literally points out that it's an ergonomic setting while using FLAG_SET_DEFAULT.

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PR Comment: https://git.openjdk.org/jdk/pull/26560#issuecomment-3139106672