https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110554
--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
It is this one:
/* Handle cases of two conversions in a row. */
(for ocvt (convert float fix_trunc)
(for icvt (convert float)
(simplify
(ocvt (icvt@1 @0))
...
/* A truncation to an unsigned type (a zero-extension) should be
canonicalized as bitwise and of a mask. */
(if (GIMPLE /* PR70366: doing this in GENERIC breaks -Wconversion. */
&& final_int && inter_int && inside_int
&& final_prec == inside_prec
&& final_prec > inter_prec
&& inter_unsignedp)
(convert (bit_and @0 { wide_int_to_tree
(inside_type,
wi::mask (inter_prec, false,
TYPE_PRECISION (inside_type))); })))
