4.3BSD - /usr/src/sys/vax/udiv.s

   1: /*
   2:  *	@(#)udiv.s	7.1 (Berkeley) 6/5/86
   3:  *
   4:  *	udiv - unsigned division for vax-11
   5:  *
   6:  *	arguments: dividend, divisor.
   7:  *	result: quotient.
   8:  *	uses r0-r2
   9:  *
  10:  *	If 1 < divisor <= 2147483647, zero-extend the dividend
  11:  *	to 64 bits and let ediv do the work.  If the divisor is 1,
  12:  *	ediv will overflow if bit 31 of the dividend is on, so
  13:  *	just return the dividend unchanged.  If the divisor is 0,
  14:  *	do the ediv also, so it will generate the proper exception.
  15:  *	All other values of the divisor have bit 31 on: in this case
  16:  *	the quotient must be 0 if divisor > dividend, and 1 otherwise,
  17:  *	provided that the comparison is made as unsigned.
  18:  */
  19:         .text
  20:         .align  1
  21:         .globl  udiv
  22: udiv:   .word   0x0000
  23: #ifdef GPROF
  24:         jsb     mcount
  25: #endif GPROF
  26:         movl    4(ap),r0        # Dividend
  27:         movl    8(ap),r2        # Divisor
  28:         jeql    div             # If divisor=0, force exception
  29:         cmpl    r2,$1           # If divisor <= 1 (signed),
  30:         jleq    nodiv           #  no division is necessary
  31: div:    clrl    r1              # Zero-extend the dividend
  32:         ediv    r2,r0,r0,r2     # Divide.  q->r0, r->r2 (discarded)
  33:         ret
  34: nodiv:  jeql    retn            # If divisor=1, return dividend
  35:         cmpl    r0,r2           # Unsigned comparison between
  36:         jgequ   one             #  dividend and divisor
  37:         clrl    r0              # Dividend < divisor, return 0
  38:         ret
  39: one:    movl    $1,r0           # Dividend >= divisor, return 1
  40: retn:   ret

Defined functions