[jdk21u-dev] RFR: 8375530: PPC64: incorrect quick verify_method_data_pointer check causes poor performance in debug build

[David Briemann]

This pull request contains a backport of commit [30f39d88](https://github.com/openjdk/jdk/commit/30f39d88e5af36bb6db458c03215e9fa6a31d6f3) from the [openjdk/jdk](https://git.openjdk.org/jdk) repository.

The commit being backported was authored by David Briemann on 19 Jan 2026 and was reviewed by Martin Doerr and Aleksey Shipilev.

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Commit messages:
 - Backport 30f39d88e5af36bb6db458c03215e9fa6a31d6f3

Changes: https://git.openjdk.org/jdk21u-dev/pull/2556/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=2556&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8375530
  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/2556.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/2556/head:pull/2556

PR: https://git.openjdk.org/jdk21u-dev/pull/2556