[Bug target/81357] New: Extra mov for zero extend of add

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81357

            Bug ID: 81357
           Summary: Extra mov for zero extend of add
           Product: gcc
           Version: 8.0
            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: aarch64-linux-gnu

Take:
unsigned long long d;
unsigned int test1(unsigned int fParm)
{
  d = fParm + 1;
  return fParm + 1;
}

--- CUT ---
Currently this produces:
test1:
        add     w2, w0, 1
        adrp    x1, d
        str     x2, [x1, #:lo12:d]
        mov     x0, x2
        ret

But w0 is dead after the add, so why not use w0 instead of x2.  This should
allow the removal of the mov at the end of the function.

This looks like it only shows up with function returns.