RFR: 8353345: C2 asserts because maskShiftAmount modifies node without deleting the hash [v3]

[Marc Chevalier]

> First delete the hash, then `set_req`. This way, we avoid changing the node (a non-`this` node) without deleting the hash. This wrong ordering is not new from [JDK-8347459](https://bugs.openjdk.org/browse/JDK-8347459), but before that, only `this` was going through this function, so it was ok. But since, it is used with other nodes, hence the need to remove the hash.
> 
> Also, not do any of that outside IGVN, but requires to register nested shifts for IGVN in parsing not to miss them later.
> 
> Thanks,
> Marc

Marc Chevalier has updated the pull request incrementally with one additional commit since the last revision:

  address review comments

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/24355/files
  - new: https://git.openjdk.org/jdk/pull/24355/files/d84b3d6d..7c9ec24a

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=24355&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=24355&range=01-02

  Stats: 25 lines in 1 file changed: 0 ins; 2 del; 23 mod
  Patch: https://git.openjdk.org/jdk/pull/24355.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24355/head:pull/24355

PR: https://git.openjdk.org/jdk/pull/24355