114 lines
4.4 KiB
ArmAsm
114 lines
4.4 KiB
ArmAsm
/* $NetBSD: fpesub.S,v 1.2 1996/03/18 19:58:18 mark Exp $ */
|
|
|
|
/*
|
|
* Copyright (c) 1995 Mark Brinicombe.
|
|
* Copyright (c) 1995 Neil Carson.
|
|
* All rights reserved.
|
|
*
|
|
* Redistribution and use in source and binary forms, with or without
|
|
* modification, are permitted provided that the following conditions
|
|
* are met:
|
|
* 1. Redistributions of source code must retain the above copyright
|
|
* notice, this list of conditions and the following disclaimer.
|
|
* 2. Redistributions in binary form must reproduce the above copyright
|
|
* notice, this list of conditions and the following disclaimer in the
|
|
* documentation and/or other materials provided with the distribution.
|
|
* 3. All advertising materials mentioning features or use of this software
|
|
* must display the following acknowledgement:
|
|
* This product includes software developed by the RiscBSD kernel team.
|
|
* 4. The name of the company nor the name of the author may be used to
|
|
* endorse or promote products derived from this software without specific
|
|
* prior written permission.
|
|
*
|
|
* THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR IMPLIED
|
|
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
|
|
* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
|
|
* IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
|
|
* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
|
|
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
|
|
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
|
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
* SUCH DAMAGE.
|
|
*
|
|
* RiscBSD kernel project
|
|
*
|
|
* fpesub.S
|
|
*
|
|
* FP subtract
|
|
*
|
|
* Created : 11/02/95
|
|
*/
|
|
|
|
.global _nc_fp_sub
|
|
|
|
pc .req r15
|
|
|
|
mant1 .req r2
|
|
xp1 .req r3
|
|
mant2 .req r4
|
|
xp2 .req r5
|
|
wrk1 .req r14
|
|
|
|
_nc_fp_sub:
|
|
stmfd r13!,{r2-r5,r14}
|
|
mov xp1,r0,lsr #23 /* get exponent+sign */
|
|
bic mant1,r0,xp1,lsl #23 /* get mantissa */
|
|
cmp r0,#0
|
|
orrne mant1,mant1,#1<<23 /* set on bit to left of point */
|
|
and xp1,xp1,#255 /* remove sign */
|
|
|
|
mov xp2,r1,lsr #23 /* get exponent+sign */
|
|
bic mant2,r1,xp2,lsl #23 /* get mantissa */
|
|
cmp r1,#0
|
|
orrne mant2,mant2,#1<<23 /* set on bit to left of point */
|
|
and xp2,xp2,#255 /* remove sign */
|
|
|
|
eors wrk1,r0,r1 /* both +ve/-ve? */
|
|
bmi fp_sub_unequal /* no - special case */
|
|
|
|
subs wrk1,xp1,xp2 /* exp. difference */
|
|
subpl mant1,mant1,mant2,lsr wrk1 /* exp1>exp2, round mant2 & subtract */
|
|
rsbmi wrk1,wrk1,#0 /* as +ve difference */
|
|
rsbmi mant1,mant2,mant1,lsr wrk1 /* exp1<exp2, round mant1 & subtract */
|
|
movmi xp1,xp2 /* exponent of result */
|
|
and r0,r0,#1<<31 /* default sign of result */
|
|
cmp mant1,#0 /* flip sign? */
|
|
rsbmi mant1,mant1,#0 /* yes - flip mantissa */
|
|
eormi r0,r0,#1<<31 /* and final sign */
|
|
/* normalise result - adjust mantissa & exponent */
|
|
cmp mant1,#0 /* check for 0 - special case */
|
|
moveq r0,#0
|
|
beq fp_sub_exit
|
|
fp_sub_roundup:
|
|
tst mant1,#1<<23
|
|
bne fp_sub_normexit
|
|
sub xp1,xp1,#1
|
|
mov mant1,mant1,lsl #1
|
|
b fp_sub_roundup
|
|
|
|
/* r0 & r1 have different signs - add */
|
|
fp_sub_unequal:
|
|
subs wrk1,xp1,xp2 /* exp. difference */
|
|
addpl mant1,mant1,mant2,lsr wrk1 /* exp1>exp2, round mant2 & add */
|
|
rsbmi wrk1,wrk1,#0 /* as +ve difference */
|
|
addmi mant1,mant2,mant1,lsr wrk1 /* exp1<exp2, round mant1 & add */
|
|
movmi xp1,xp2 /* exponent of result */
|
|
and r0,r0,#1<<31 /* sign of result */
|
|
/* normalise result - adjust mantissa & exponent */
|
|
fp_sub_rounddown:
|
|
cmp mant1,#1<<24
|
|
blt fp_sub_normexit
|
|
add xp1,xp1,#1
|
|
mov mant1,mant1,lsr #1
|
|
b fp_sub_rounddown
|
|
/* combine result */
|
|
fp_sub_normexit:
|
|
orr r0,r0,xp1,lsl #23 /* set exponent */
|
|
bic mant1,mant1,#1<<23 /* clear hi-order */
|
|
orr r0,r0,mant1 /* full result */
|
|
fp_sub_exit:
|
|
ldmfd r13!,{r2-r5,pc}
|
|
|