RFR: 8347422: Crash during safepoint handler execution with -XX:+UseAPX

[Jatin Bhateja]

This bug fix patch fixes an internal error seen during safepoint handler execution.
The problem occurs due to missing handling for REX2 prefixed polling test instruction.

Manually verified the patch with the -XX:+SafepointALot runtime flag.

Best Regards,
Jatin
PS: Patch will be opened for review after some validation.

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Commit messages:
 - 8347422: Crash during safepoint handler execution

Changes: https://git.openjdk.org/jdk/pull/23035/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23035&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8347422
  Stats: 23 lines in 1 file changed: 20 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/23035.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23035/head:pull/23035

PR: https://git.openjdk.org/jdk/pull/23035