RFR: 8288445: AArch64: C2 compilation fails with guarantee(!true || (true && (shift != 0))) failed: impossible encoding

[Dean Long]

The range for aarch64 vector right-shift is 1 to the element width.  This issue fixes the problem in the back-end.  There is a separate problem in the front-end that shift by 0 is not always optimized out.

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Commit messages:
 - fix comment
 - remove -XX:+PrintOptoAssembly left over from testing
 - Avoid "impossible encoding" for right-shift by 0

Changes: https://git.openjdk.org/jdk19/pull/40/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk19&pr=40&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8288445
  Stats: 115 lines in 4 files changed: 83 ins; 0 del; 32 mod
  Patch: https://git.openjdk.org/jdk19/pull/40.diff
  Fetch: git fetch https://git.openjdk.org/jdk19 pull/40/head:pull/40

PR: https://git.openjdk.org/jdk19/pull/40