Push/pop.b lifted incorrectly

[jrozner]

Push/Pop operations always decrement/increment the stack pointer by 2, presumably to keep the stack aligned, whether using word or byte operand width. It doesn't look like there is a way to using BNIL to correctly represent the behavior explained below while using push/pop instructions.

push

push.b should push the low byte of the operand onto the stack while leaving the high byte unchanged and decrement the stack pointer by 2.

pop

pop.b should move the stack pointer down by 2 and pop the top value, with the high byte zeroed out, into the register specified.