[Bug target/114514] v16qi >> 7 can be optimized with vpcmpgtb

["pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114514

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |enhancement
   Last reconfirmed|                            |2024-03-28
                 CC|                            |pinskia at gcc dot gnu.org
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |NEW

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Confirmed.

Note non sign bit can be improved too:
```
#define vector __attribute__((vector_size(16)))

typedef vector signed char v16qi;
typedef vector unsigned char v16uqi;

v16qi
foo2 (v16qi a, v16qi b)
{
    return a >> 6;
}
v16uqi
foo1 (v16uqi a, v16uqi b)
{
    return a >> 6;
}
```

clang produces:
```
_Z4foo2Dv16_aS_:
        psrlw   $6, %xmm0
        pand    .LCPI0_0(%rip), %xmm0 #{3,3,3,...}
        movdqa  .LCPI0_1(%rip), %xmm1 #{2,2,2,...}
        pxor    %xmm1, %xmm0
        psubb   %xmm1, %xmm0
        retq
_Z4foo1Dv16_hS_:
        psrlw   $6, %xmm0
        pand    .LCPI1_0(%rip), %xmm0 #{3,3,3,...}
        retq
```