RFR: 8343724: [PPC64] Disallow OptoScheduling

[Richard Reingruber]

On Wed, 6 Nov 2024 16:18:11 GMT, Martin Doerr <mdoerr at openjdk.org> wrote:

> Force off OptoScheduling for PPC64. It should be properly maintained before allowing users to switch it on. It's probably not important for this platform. Also see JBS issue for motivation.

src/hotspot/cpu/ppc/c2_init_ppc.cpp line 58:

> 56:     warning("OptoScheduling is not supported on this CPU.");
> 57:     FLAG_SET_DEFAULT(OptoScheduling, false);
> 58:   }

Makes sense but better do it in `VM_Version::initialize()` because `Compile::pd_compiler2_init()` is called after initialization of flags has been completed and the setting will not be shown with `PrintFlagsFinal`.
I'd even suggest to move the other flag settings there with this PR.

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PR Review Comment: https://git.openjdk.org/jdk/pull/21935#discussion_r1832283840