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[unix-history] / usr / src / sys / vax / vax / udiv.s
/*
* @(#)udiv.s 6.3 (Berkeley) %G%
*
* udiv - unsigned division for vax-11
*
* arguments: dividend, divisor.
* result: quotient.
* uses r0-r2
*
* If 1 < divisor <= 2147483647, zero-extend the dividend
* to 64 bits and let ediv do the work. If the divisor is 1,
* ediv will overflow if bit 31 of the dividend is on, so
* just return the dividend unchanged. If the divisor is 0,
* do the ediv also, so it will generate the proper exception.
* All other values of the divisor have bit 31 on: in this case
* the quotient must be 0 if divisor > dividend, and 1 otherwise,
* provided that the comparison is made as unsigned.
*/
.text
.align 1
.globl udiv
udiv: .word 0x0000
#ifdef GPROF
jsb mcount
#endif GPROF
movl 4(ap),r0 # Dividend
movl 8(ap),r2 # Divisor
jeql div # If divisor=0, force exception
cmpl r2,$1 # If divisor <= 1 (signed),
jleq nodiv # no division is necessary
div: clrl r1 # Zero-extend the dividend
ediv r2,r0,r0,r2 # Divide. q->r0, r->r2 (discarded)
ret
nodiv: jeql retn # If divisor=1, return dividend
cmpl r0,r2 # Unsigned comparison between
jgequ one # dividend and divisor
clrl r0 # Dividend < divisor, return 0
ret
one: movl $1,r0 # Dividend >= divisor, return 1
retn: ret