overflow check insns also in 6502 (bvs), x86 (into), m68k (trapv) - the gp was after something that wouldn't need to be checked every time, if interpreted as "n

overflow check insns also in 6502 (bvs), x86 (into), m68k (trapv) - the gp was after something that wouldn't need to be checked every time, if interpreted as "no extra instructions" then that's a tall order. But the checks are practically free in modern big core CPUs since we have so much spare capacity in issue width in 99% of workloads.