RFR: 8351994: Enable Extended EVEX to REX2/REX demotion when src and dst are the same [v4]

Wed Apr 16 22:55:01 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.

Srinivas Vamsi Parasa has updated the pull request incrementally with one additional commit since the last revision:

  refactor RRM instructions to avoid explicit demotion

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Changes:
  - all: https://git.openjdk.org/jdk/pull/24431/files
  - new: https://git.openjdk.org/jdk/pull/24431/files/09d3c3a8..bc69f323

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=24431&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=24431&range=02-03

  Stats: 132 lines in 2 files changed: 36 ins; 84 del; 12 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