https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109476
--- Comment #1 from Wilhelm M <klaus.doldinger64 at googlemail dot com> ---
Inetristingly changing the function to
uint16_t mul(const uint8_t a, const uint16_t b) {
return static_cast<uint8_t>((b >> 8) + 1) * a ;
}
produces optimal
mul(unsigned char, unsigned int):
subi r23,lo8(-(1))
mul r23,r24
movw r24,r0
clr __zero_reg__
ret
