RFR: 8365570: C2 fails assert(false) failed: Unexpected node in SuperWord truncation: CastII

[Jasmine Karthikeyan]

Hi all,
This is a quick patch for the assert failure in superword truncation with CastII. I've added a check for all constraint cast nodes, and attached a reduced version of the fuzzer test. Thanks!

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Commit messages:
 - Fix truncation assert for constraint casts

Changes: https://git.openjdk.org/jdk/pull/26827/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=26827&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8365570
  Stats: 28 lines in 2 files changed: 26 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/26827.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26827/head:pull/26827

PR: https://git.openjdk.org/jdk/pull/26827