[jdk21u] RFR: 8313262: C2: Sinking node may cause required cast to be dropped [v2]

[Aleksey Shipilev]

> Clean backport to fix recent JDK 21 backport regression.
> 
> Additional testing:
>  - [x] New test fails without the fix, passes with it
>  - [ ] Linux x86_64 fastdebug `tier1 tier2 tier3`

Aleksey Shipilev has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains two additional commits since the last revision:

 - Merge branch 'master' into JDK-8313262-c2-sinking-node-cast
 - Backport 1cee3b9fd9720e7938029a6992460b9053e65e57

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

Changes:
  - all: https://git.openjdk.org/jdk21u/pull/99/files
  - new: https://git.openjdk.org/jdk21u/pull/99/files/40877111..6f95682e

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk21u&pr=99&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk21u&pr=99&range=00-01

  Stats: 328 lines in 24 files changed: 260 ins; 1 del; 67 mod
  Patch: https://git.openjdk.org/jdk21u/pull/99.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u.git pull/99/head:pull/99

PR: https://git.openjdk.org/jdk21u/pull/99