(:temporary (:scs (non-descriptor-reg)) count)
(:generator 1
(let ((offset
- (- (* (+ index vector-data-offset) word-bytes) other-pointer-lowtag)))
+ (- (* (+ index vector-data-offset) n-word-bytes)
+ other-pointer-lowtag)))
(inst ldl count offset count-vector)
(inst addq count 1 count)
(inst stl count offset count-vector))))