https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119509
--- Comment #7 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Nick Hudson from comment #4)
> (In reply to Andrew Pinski from comment #2)
> > _5 = val_2(D) & 0xffff00;
> > _1 = _5 > 0xff;
> >
> > Confirmed.
> >
> > GCC does handle:
> > ```
> > unsigned
> > foo0(unsigned val)
> > {
> > return (val & (~0xff000000)) > 0xff;
> > }
> > ```
> >
> > Correctly.
>
> where does this happen?
>
> I've tried to find it in gcc/match.pd, but failed.
```
(for cmp (le gt)
eqcmp (eq ne)
(simplify
(cmp (bit_and@0 @1 INTEGER_CST@2) INTEGER_CST@3)
(if (INTEGRAL_TYPE_P (TREE_TYPE (@0)))
(with
{
tree ty = TREE_TYPE (@0);
unsigned prec = TYPE_PRECISION (ty);
wide_int mask = wi::to_wide (@2, prec);
wide_int rhs = wi::to_wide (@3, prec);
signop sgn = TYPE_SIGN (ty);
}
(if ((mask & (mask + 1)) == 0 && wi::gt_p (rhs, 0, sgn)
&& (rhs & (rhs + 1)) == 0 && wi::ge_p (mask, rhs, sgn))
(eqcmp (bit_and @1 { wide_int_to_tree (ty, mask - rhs); })
{ build_zero_cst (ty); }))))))
```
You can find out via -fdump-tree-original-folding:
Applying pattern match.pd:7941, generic-match-3.cc:3327
