RFR: 8363910: Avoid tuning for Power10 CPUs on Linux ppc64le when gcc < 10 is used

[Matthias Baesken]

On Thu, 24 Jul 2025 16:30:08 GMT, Lutz Schmidt <lucy at openjdk.org> wrote:

> Just for my understanding: If `-mtune=power10` is already in the arguments, nothing is changed/added. In any other case (e.g. `-mtune=power11`), the string `-mtune=power8` is added. Is that intended?

We do not set '-mtune=power11'   , just power10 (default for recent gcc versions) and for old ones where it is not supported (like gcc8) now with this change power8.
In case the user brings in own `-mtune=power<x> ` settings via  additional c/cxx flags , it is up to the user to set them at the right place to overwrite the default .

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PR Comment: https://git.openjdk.org/jdk/pull/26442#issuecomment-3116679724