RFR: 8351994: Enable Extended EVEX to REX2/REX demotion when src and dst are the same [v17]

[Srinivas Vamsi Parasa]

> 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:

  more clarifying comments next to boolean literals

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Changes:
  - all: https://git.openjdk.org/jdk/pull/24431/files
  - new: https://git.openjdk.org/jdk/pull/24431/files/386ebe41..d1c1b077

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=24431&range=16
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=24431&range=15-16

  Stats: 5 lines in 1 file changed: 0 ins; 0 del; 5 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