BLEN = 20

.entry int_to_string, ^m<R2, R3, R4, R5, R6, R7>
    clrl  R3             ; ediv's divisor is a quad word
    movl  4(AP), R2      ; incoming number
    movl  8(AP), R4
    addl3 R4, #BLEN,  R5 ; end of output string
    incl R4              ; beginning of outgoing string
    clrl R6              ; count of string length
    clrb @8(AP)

    tstl R2
    bgeq next_digit
    movb #^A/-/, (R4)+
    mnegl R2, R2
    movb #1, @8(AP)

  next_digit:
    ediv #10, R2, R2, R7
    movl R7, R7
    addb3 #^A/0/, R7, -(R5)
    incl R6
    tstl R2
    bleq number_finished
    brb next_digit

  number_finished:
    addb R6, @8(AP)

  shift:
    movb (R5)+, (R4)+
    sobgtr R6, shift
    movb #0, (R4)+
    ret
.end