RFR: 8351994: Enable Extended EVEX to REX2/REX demotion when src and dst are the same

Fri Apr 4 01:21:34 UTC 2025

The current scheme for Intel APX NDD code generation favors the emission of NDD instruction on APX-enabled targets, even if destination and source registers are the same. To prevent this, this PR extends the assembler layer to demote EEVEX to REX encoding if dst matches with source operands.

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Commit messages:
 - 8351994: Enable Extended EVEX to REX2/REX demotion when src and dst are the same

Changes: https://git.openjdk.org/jdk/pull/24431/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=24431&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8351994
  Stats: 3561 lines in 4 files changed: 1376 ins; 298 del; 1887 mod
  Patch: https://git.openjdk.org/jdk/pull/24431.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24431/head:pull/24431

PR: https://git.openjdk.org/jdk/pull/24431