[Bug target/106545] New: peephole.md seems like it should not exist

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106545

            Bug ID: 106545
           Summary: peephole.md seems like it should not exist
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pinskia at gcc dot gnu.org
  Target Milestone: ---
            Target: riscv

There is one peephole2 in there for:
Simplify (unsigned long)(unsigned int)a << const

But that should really be handled in generic code in simplify-rtx/combine
already.
If it is not, then it should be added.