RFR: 8315750: Update subtype check profile collection on PPC following 8308869 [v3]

[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:

  Minor simplification of slow path in emit_typecheck_helper.

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/15685/files
  - new: https://git.openjdk.org/jdk/pull/15685/files/327a1783..9f50e30a

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=15685&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=15685&range=01-02

  Stats: 8 lines in 1 file changed: 0 ins; 5 del; 3 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