[jdk21u-dev] RFR: 8341893: AArch64: Micro-optimize compressed ptr decoding

[Dmitry Chuyko]

This is a small clean backport to fix compressed ptr decoding inefficiency. 

Testing: tier 1,2 on linux-aarch64.

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Commit messages:
 - Backport e3f650393744790e24820b2d6d99dd1da1a44de6

Changes: https://git.openjdk.org/jdk21u-dev/pull/1551/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=1551&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8341893
  Stats: 3 lines in 1 file changed: 2 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/1551.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/1551/head:pull/1551

PR: https://git.openjdk.org/jdk21u-dev/pull/1551