RFR: 8343068: C2: CastX2P Ideal transformation not always applied [v2]

[Roland Westrelin]

> The transformation:
> 
> 
> (CastX2P (AddL base i)) -> (AddP (CastX2P base) i) 
> 
> 
> when i fits in an int is not always applied: when the type of `i` is
> narrowed so it fits in an int, the `CastX2P` is not enqueued for
> igvn. This can get in the way of vectorization as shown by test case
> `test2`.

Roland Westrelin has updated the pull request incrementally with one additional commit since the last revision:

  fix test

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/21714/files
  - new: https://git.openjdk.org/jdk/pull/21714/files/19fd4179..12a471f0

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=21714&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=21714&range=00-01

  Stats: 3 lines in 1 file changed: 2 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/21714.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21714/head:pull/21714

PR: https://git.openjdk.org/jdk/pull/21714