RFR: 8325083: jdk/incubator/vector/Double512VectorTests.java crashes in Assembler::vex_prefix_and_encode

[Jatin Bhateja]

This bugfix patch limits the register class for operands of byte to double cast pattern to prevent reported assertion failure on Knights family CPUs.

Kindly review and share your feedback.

Best Regards,
Jatin

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Commit messages:
 - 8325083: jdk/incubator/vector/Double512VectorTests.java crashes in Assembler::vex_prefix_and_encode

Changes: https://git.openjdk.org/jdk/pull/19407/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=19407&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8325083
  Stats: 14 lines in 1 file changed: 13 ins; 1 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/19407.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19407/head:pull/19407

PR: https://git.openjdk.org/jdk/pull/19407