https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97459
--- Comment #10 from Thomas Koenig <tkoenig at gcc dot gnu.org> ---
There are a couple of more constants for this could be tried.
Base 7:
static unsigned
rem_7_v2 (mytype n)
{
unsigned long a, b, c, d;
a = n & MASK_48;
b = (n >> 48) & MASK_48;
c = n >> 96;
return (a+b+c) % 7;
}
gives the reminder with respect to 7.
The reason is that 2^48-1 = 3*3*5*7*13*17*97*241*257*673, so a shift
of 48 bits works for any combination of these factors. However, for 15,
I would have to check if it would be better to use the 64-bit shift.
For 19, it's a shift of 56 that would work.
I think I'd better make a table.
