Indeed, and for good spilling decisions, you'll want to have next-use distance information for values. While a stack machine gives you an approximation of this

Indeed, and for good spilling decisions, you'll want to have next-use distance information for values. While a stack machine gives you an approximation of this (deeper in the stack is farther in the future), for best results I imagine you'll want to do two passes anyway, so locals are no worse for this, other than at block boundaries, if you lack liveness you have to spill them.