.entry binary_search, ^m<R3, R4, R5>
	clrl R3          ; top index
	movl 8(AP), R4   ; bottom index
	movl 4(AP), R0   ; key
	moval 12(AP), R6 ; &x[0]

next_element:
	subl3 R3, R4, R5 ; offset
	blss not_found
	divl #2, R5
	tstl R5
	addl R3, R5      ; middle index
	cmpl (R6)[R5], R0
	beql found
	blss overshot
	addl3 #1, R5, R3
	brb next_element
overshot:
	subl3 #1, R5, R4
	brb next_element
not_found:
	movl #-1, R0
	brb end
found:
	movl R5, R0
end:
	ret
.end