[Bug target/84431] Suboptimal code for masked shifts (x86/x86-64)

[nruslan_devel at yahoo dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84431

--- Comment #4 from Ruslan Nikolaev <nruslan_devel at yahoo dot com> ---
(In reply to Uroš Bizjak from comment #3)
> Created attachment 43471 [details]
> Prototype patch
> 
> Prototype patch, compiles the testcase to:
> 
>         movl    4(%esp), %eax
>         movl    12(%esp), %ecx
>         movl    8(%esp), %edx
>         shldl   %eax, %edx
>         sall    %cl, %eax
>         ret
> 
> The patch also handles right shifts and cases where mask is less than 31
> bits.

Thanks! I was wondering if the patch also fixes the same thing for x86-64
(i.e., -m64); in which case we would have something like this:

__uint128_t func(__uint128_t a, unsigned shift)
{
   return a << (shift & 63);
}