[Bug target/100648] New: Optimize away x<0 as mask argument of a blend for AVX512 mask

[crazylht at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100648

            Bug ID: 100648
           Summary: Optimize away x<0 as mask argument of a blend for
                    AVX512 mask
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: crazylht at gmail dot com
                CC: hjl.tools at gmail dot com
  Target Milestone: ---
              Host: x86_64-pc-linux-gnu
            Target: x86_64-*-* i?86-*-*

Similar to PR target/54700, but for AVX512 mask