RFR: 8341141: Optimize DirectCodeBuilder [v16]

[Shaojin Wen]

> Some DirectCodeBuilder related optimizations to improve startup and running performance:
> 1. Merge calls, merge writeU1 and writeU2 into writeU3
> 2. Merge calls, merge writeU1 and writeIndex operations
> 3. Directly use writeU1 instead of writeBytecode
> 4. Rewrite the implementation of load and store

Shaojin Wen has updated the pull request incrementally with one additional commit since the last revision:

  optimization for powerOctal

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/21243/files
  - new: https://git.openjdk.org/jdk/pull/21243/files/36c81ec1..e7b32d43

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=21243&range=15
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=21243&range=14-15

  Stats: 3 lines in 2 files changed: 1 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/21243.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21243/head:pull/21243

PR: https://git.openjdk.org/jdk/pull/21243