[Bug target/100867] New: z13: Inefficient code for vec_revb(vector unsigned short)

[jens.seifert at de dot ibm.com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100867

            Bug ID: 100867
           Summary: z13: Inefficient code for vec_revb(vector unsigned
                    short)
           Product: gcc
           Version: 10.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jens.seifert at de dot ibm.com
  Target Milestone: ---

Input:

vector unsigned short revb(vector unsigned short a)
{
   return vec_revb(a);
}

Creates:

_Z4revbDv4_j:
.LFB1:
        .cfi_startproc
        larl    %r5,.L4
        vl      %v0,.L5-.L4(%r5),3
        vperm   %v24,%v24,%v24,%v0
        br      %r14

Optimal code sequence:

vector unsigned short revb_z13(vector unsigned short a)
{
   return vec_rli(a, 8);
}

Creates:
_Z8revb_z13Dv8_t:
.LFB5:
        .cfi_startproc
        verllh  %v24,%v24,8
        br      %r14
        .cfi_endproc