> I think there's a mulhi instruction in newer ARMs; gcc could certainly abuse
> that to optimise division by a constant. (It does so on m68020-040).

I think you mean smul and umul (mulhi is a conditionally executed 32-bit 
multiply).  Yes, -march=armv3m (or armv4) causes the compiler to use these 
for division by a constant.

R.