EMILE/libunix/udivsi3.S

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2005-11-08 02:04:54 +00:00
/*
*
* (c) 2004,2005 Laurent Vivier <LaurentVivier@wanadoo.fr>
*
* Some parts from libgcc routines for 68000 w/o floating-point hardware.
* Copyright (C) 1994, 1996, 1997, 1998 Free Software Foundation, Inc.
*
*/
.chip 68000
.align 2
.globl __udivsi3
__udivsi3:
movel %d2, %sp@-
movel %sp@(12), %d1 /* %d1 = divisor */
movel %sp@(8), %d0 /* %d0 = dividend */
cmpl #0x10000, %d1 /* divisor >= 2 ^ 16 ? */
jcc __udivsi3L3 /* then try next algorithm */
movel %d0, %d2
clrw %d2
swap %d2
divu %d1, %d2 /* high quotient in lower word */
movew %d2, %d0 /* save high quotient */
swap %d0
movew %sp@(10), %d2 /* get low dividend + high rest */
divu %d1, %d2 /* low quotient */
movew %d2, %d0
jra __udivsi3L6
__udivsi3L3: movel %d1, %d2 /* use %d2 as divisor backup */
__udivsi3L4: lsrl #1, %d1 /* shift divisor */
lsrl #1, %d0 /* shift dividend */
cmpl #0x10000, %d1 /* still divisor >= 2 ^ 16 ? */
jcc __udivsi3L4
divu %d1, %d0 /* now we have 16-bit divisor */
andl #0xffff, %d0 /* mask out divisor, ignore remainder */
/* Multiply the 16-bit tentative quotient with the 32-bit divisor. Because of
the operand ranges, this might give a 33-bit product. If this product is
greater than the dividend, the tentative quotient was too large. */
movel %d2, %d1
mulu %d0, %d1 /* low part, 32 bits */
swap %d2
mulu %d0, %d2 /* high part, at most 17 bits */
swap %d2 /* align high part with low part */
tstw %d2 /* high part 17 bits? */
jne __udivsi3L5 /* if 17 bits, quotient was too large */
addl %d2, %d1 /* add parts */
jcs __udivsi3L5 /* if sum is 33 bits, quotient was too large */
cmpl %sp@(8), %d1 /* compare the sum with the dividend */
jls __udivsi3L6 /* if sum > dividend, quotient was too large */
__udivsi3L5: subql #1, %d0 /* adjust quotient */
__udivsi3L6: movel %sp@+, %d2
rts