RFR: 8375010: C2 VectorAPI: assert(vbox->is_CheckCastPP()) failed: should be expanded [v4]

[Kerem Kat]

> The check `vect->is_Vector() || vect->is_LoadVector()` doesn't handle `Proj` nodes that resolve to vector types, causing an assertion failure when such nodes flow through a `Phi` into `VectorBox`.

Kerem Kat 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 five additional commits since the last revision:

 - Merge branch 'master' into fix-c2-checkCastPP
 - Merge branch 'master' into fix-c2-checkCastPP
 - 8374903: C2 VectorAPI: assert(vbox->as_Phi()->region() == vect->as_Phi()->region()) failed
 - Simplify expand_vbox_node_helper by merging VectorBox Phi handling
 - 8375010: C2 VectorAPI: assert(vbox->is_CheckCastPP()) failed: should be expanded

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/29200/files
  - new: https://git.openjdk.org/jdk/pull/29200/files/6b3695cc..9670be04

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=29200&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=29200&range=02-03

  Stats: 12402 lines in 338 files changed: 7735 ins; 1772 del; 2895 mod
  Patch: https://git.openjdk.org/jdk/pull/29200.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29200/head:pull/29200

PR: https://git.openjdk.org/jdk/pull/29200