[Bug target/115176] New: rbit pattern should use bitreverse rtl now

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115176

            Bug ID: 115176
           Summary: rbit pattern should use bitreverse rtl now
           Product: gcc
           Version: 15.0
            Status: UNCONFIRMED
          Keywords: internal-improvement
          Severity: enhancement
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pinskia at gcc dot gnu.org
  Target Milestone: ---

While looking at some code I noticed that it uses clang's __builtin_bitreverse8
builtin and looking at the aarch64 backend, I noticed the rbit patterns don't
use bitreverse but still an UNSPEC.

We should be able to change the pattern to use the rtl now.