[Bug tree-optimization/72785] [7 Regression] kernel build error since r236831

[dhowells at redhat dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=72785

--- Comment #17 from dhowells at redhat dot com <dhowells at redhat dot com> ---
(In reply to dhowells@redhat.com from comment #16)
> ...
> 0000000000000027 <clz_ilog2>:
>   27:   0f bd c7                bsr    %edi,%eax
>   2a:   83 f0 1f                xor    $0x1f,%eax
>   2d:   c3                      retq   
> 
> though the XOR is superfluous - for any valid input to ilog2(), I think the
> output is always in the range 0-31.

Ah - it's not actually an AND, so the XOR isn't necessarily superfluous.