RFR: 8374518: C1: Remove dead LinearScanStatistic::Counter::counter_fpu_stack

[Martin Doerr]

On Mon, 5 Jan 2026 13:28:41 GMT, Christian Hagedorn <chagedorn at openjdk.org> wrote:

> The usages of `LinearScanStatistic::Counter::counter_fpu_stack` were removed with [JDK-8351156](https://bugs.openjdk.org/browse/JDK-8351156) when the FPU stack support was removed. But the definition in the `Counter` enum was missed to clean up. When now printing the counters with `-XX:+CountLinearScan -XX:+CITime`, we reach a `ShouldNotReach` in `LinearScanStatistic::counter_name()` for `Counter::counter_fpu_stack` because there is no longer an entry there - it's dead.
> 
> I added a simple hello world sanity test that runs with `-XX:+CountLinearScan -XX:+CITime`.
> 
> Thanks,
> Christian

LGTM.

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Marked as reviewed by mdoerr (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/29037#pullrequestreview-3626894269