RFR: 8315750: Update subtype check profile collection on PPC following 8308869 [v4]

[Martin Doerr]

> Before this PR (measured on Power10):
> 
> Benchmark                                         (typePollution)   Mode  Cnt   Score   Error   Units
> RequireNonNullCheckcastScalability.isDuplicated1            false  thrpt   20  82,510 ± 0,366  ops/us
> RequireNonNullCheckcastScalability.isDuplicated1             true  thrpt   20  53,498 ± 0,112  ops/us
> 
> 
> With this PR:
> 
> Benchmark                                         (typePollution)   Mode  Cnt   Score   Error   Units
> RequireNonNullCheckcastScalability.isDuplicated1            false  thrpt   20  82,734 ± 0,129  ops/us
> RequireNonNullCheckcastScalability.isDuplicated1             true  thrpt   20  82,738 ± 0,039  ops/us
> 
> 
> See description in original PR: https://github.com/openjdk/jdk/pull/14375

Martin Doerr has updated the pull request incrementally with one additional commit since the last revision:

  Further simplification: Remove klass_RInfo preservation code which is no longer needed.

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/15685/files
  - new: https://git.openjdk.org/jdk/pull/15685/files/9f50e30a..8e2902bd

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=15685&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=15685&range=02-03

  Stats: 6 lines in 1 file changed: 0 ins; 5 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/15685.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15685/head:pull/15685

PR: https://git.openjdk.org/jdk/pull/15685