RFR: 8369039: JDK-8348611 caused regression in Javac-Hot-Generate [v2]

[Archie Cobbs]

> The refactoring in [JDK-8348611](https://bugs.openjdk.org/browse/JDK-8348611) caused a regression in compiler performance. In the the refactoring there were a couple of simple optimizations that were missed. When put in place, these seem to (mostly) address the performance issue.

Archie Cobbs has updated the pull request incrementally with two additional commits since the last revision:

 - Unstream loops.
 - Put back the drive-by tweaks; they seem to matter.

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/27651/files
  - new: https://git.openjdk.org/jdk/pull/27651/files/02d2e73f..816162e0

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=27651&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=27651&range=00-01

  Stats: 21 lines in 1 file changed: 6 ins; 2 del; 13 mod
  Patch: https://git.openjdk.org/jdk/pull/27651.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27651/head:pull/27651

PR: https://git.openjdk.org/jdk/pull/27651