pop and a discarded pop (the length - 1 store) branch on the array's
length and hole-free prefix bound. When the bound equals the length, the
last element is a present dense value: the emitted code clears its slot
and state, lowers the bound and the length, and moves the slot out (or
releases it for a discarded pop). An empty array answers undefined
without a call. Holes, present undefined and sparse storage keep the
runtime call.
Chris Tate
fc68a582d0