RFR: 8278525: Additional -Wnonnull errors happen with GCC 11

[Dan Lutker]

8271515 introduced more issues with xmm0

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

Commit messages:
 - 8278525: Additional -Wnonnull errors happen with GCC 11.

Changes: https://git.openjdk.java.net/jdk/pull/6788/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6788&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8278525
  Stats: 5 lines in 1 file changed: 5 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6788.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6788/head:pull/6788

PR: https://git.openjdk.java.net/jdk/pull/6788