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/*
* linux/arch/arm/lib/lib1funcs.S: Optimized ARM division routines
*
* Author: Nicolas Pitre <nico@cam.org>
* - contributed to gcc-3.4 on Sep 30, 2003
* - adapted for the Linux kernel on Oct 2, 2003
*/
/* Copyright 1995, 1996, 1998, 1999, 2000, 2003 Free Software Foundation, Inc.
This file is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the
Free Software Foundation; either version 2, or (at your option) any
later version.
In addition to the permissions in the GNU General Public License, the
Free Software Foundation gives you unlimited permission to link the
compiled version of this file into combinations with other programs,
and to distribute those combinations without any restriction coming
from the use of this file. (The General Public License restrictions
do apply in other respects; for example, they cover modification of
the file, and distribution when not linked into a combine
executable.)
This file is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; see the file COPYING. If not, write to
the Free Software Foundation, 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA. */
#include <linux/linkage.h>
#include <asm/assembler.h>
.macro ARM_DIV_BODY dividend, divisor, result, curbit
#if __LINUX_ARM_ARCH__ >= 5
clz \curbit, \divisor
clz \result, \dividend
sub \result, \curbit, \result
mov \curbit, #1
mov \divisor, \divisor, lsl \result
mov \curbit, \curbit, lsl \result
mov \result, #0
#else
@ Initially shift the divisor left 3 bits if possible,
@ set curbit accordingly. This allows for curbit to be located
@ at the left end of each 4 bit nibbles in the division loop
@ to save one loop in most cases.
tst \divisor, #0xe0000000
moveq \divisor, \divisor, lsl #3
moveq \curbit, #8
movne \curbit, #1
@ Unless the divisor is very big, shift it up in multiples of
@ four bits, since this is the amount of unwinding in the main
@ division loop. Continue shifting until the divisor is
@ larger than the dividend.
1: cmp \divisor, #0x10000000
cmplo \divisor, \dividend
movlo \divisor, \divisor, lsl #4
movlo \curbit, \curbit, lsl #4
blo 1b
@ For very big divisors, we must shift it a bit at a time, or
@ we will be in danger of overflowing.
1: cmp \divisor, #0x80000000
cmplo \divisor, \dividend
movlo \divisor, \divisor, lsl #1
movlo \curbit, \curbit, lsl #1
blo 1b
mov \result, #0
#endif
@ Division loop
1: cmp \dividend, \divisor
subhs \dividend, \dividend, \divisor
orrhs \result, \result, \curbit
cmp \dividend, \divisor, lsr #1
subhs \dividend, \dividend, \divisor, lsr #1
orrhs \result, \result, \curbit, lsr #1
cmp \dividend, \divisor, lsr #2
subhs \dividend, \dividend, \divisor, lsr #2
orrhs \result, \result, \curbit, lsr #2
cmp \dividend, \divisor, lsr #3
subhs \dividend, \dividend, \divisor, lsr #3
orrhs \result, \result, \curbit, lsr #3
cmp \dividend, #0 @ Early termination?
movnes \curbit, \curbit, lsr #4 @ No, any more bits to do?
movne \divisor, \divisor, lsr #4
bne 1b
.endm
.macro ARM_DIV2_ORDER divisor, order
#if __LINUX_ARM_ARCH__ >= 5
clz \order, \divisor
rsb \order, \order, #31
#else
cmp \divisor, #(1 << 16)
movhs \divisor, \divisor, lsr #16
movhs \order, #16
movlo \order, #0
cmp \divisor, #(1 << 8)
movhs \divisor, \divisor, lsr #8
addhs \order, \order, #8
cmp \divisor, #(1 << 4)
movhs \divisor, \divisor, lsr #4
addhs \order, \order, #4
cmp \divisor, #(1 << 2)
addhi \order, \order, #3
addls \order, \order, \divisor, lsr #1
#endif
.endm
.macro ARM_MOD_BODY dividend, divisor, order, spare
#if __LINUX_ARM_ARCH__ >= 5
clz \order, \divisor
clz \spare, \dividend
sub \order, \order, \spare
mov \divisor, \divisor, lsl \order
#else
mov \order, #0
@ Unless the divisor is very big, shift it up in multiples of
@ four bits, since this is the amount of unwinding in the main
@ division loop. Continue shifting until the divisor is
@ larger than the dividend.
1: cmp \divisor, #0x10000000
cmplo \divisor, \dividend
movlo \divisor, \divisor, lsl #4
addlo \order, \order, #4
blo 1b
@ For very big divisors, we must shift it a bit at a time, or
@ we will be in danger of overflowing.
1: cmp \divisor, #0x80000000
cmplo \divisor, \dividend
movlo \divisor, \divisor, lsl #1
addlo \order, \order, #1
blo 1b
#endif
@ Perform all needed substractions to keep only the reminder.
@ Do comparisons in batch of 4 first.
subs \order, \order, #3 @ yes, 3 is intended here
blt 2f
1: cmp \dividend, \divisor
subhs \dividend, \dividend, \divisor
cmp \dividend, \divisor, lsr #1
subhs \dividend, \dividend, \divisor, lsr #1
cmp \dividend, \divisor, lsr #2
subhs \dividend, \dividend, \divisor, lsr #2
cmp \dividend, \divisor, lsr #3
subhs \dividend, \dividend, \divisor, lsr #3
cmp \dividend, #1
mov \divisor, \divisor, lsr #4
subges \order, \order, #4
bge 1b
tst \order, #3
teqne \dividend, #0
beq 5f
@ Either 1, 2 or 3 comparison/substractions are left.
2: cmn \order, #2
blt 4f
beq 3f
cmp \dividend, \divisor
subhs \dividend, \dividend, \divisor
mov \divisor, \divisor, lsr #1
3: cmp \dividend, \divisor
subhs \dividend, \dividend, \divisor
mov \divisor, \divisor, lsr #1
4: cmp \dividend, \divisor
subhs \dividend, \dividend, \divisor
5:
.endm
ENTRY(__udivsi3)
subs r2, r1, #1
moveq pc, lr
bcc Ldiv0
cmp r0, r1
bls 11f
tst r1, r2
beq 12f
ARM_DIV_BODY r0, r1, r2, r3
mov r0, r2
mov pc, lr
11: moveq r0, #1
movne r0, #0
mov pc, lr
12: ARM_DIV2_ORDER r1, r2
mov r0, r0, lsr r2
mov pc, lr
ENTRY(__umodsi3)
subs r2, r1, #1 @ compare divisor with 1
bcc Ldiv0
cmpne r0, r1 @ compare dividend with divisor
moveq r0, #0
tsthi r1, r2 @ see if divisor is power of 2
andeq r0, r0, r2
movls pc, lr
ARM_MOD_BODY r0, r1, r2, r3
mov pc, lr
ENTRY(__divsi3)
cmp r1, #0
eor ip, r0, r1 @ save the sign of the result.
beq Ldiv0
rsbmi r1, r1, #0 @ loops below use unsigned.
subs r2, r1, #1 @ division by 1 or -1 ?
beq 10f
movs r3, r0
rsbmi r3, r0, #0 @ positive dividend value
cmp r3, r1
bls 11f
tst r1, r2 @ divisor is power of 2 ?
beq 12f
ARM_DIV_BODY r3, r1, r0, r2
cmp ip, #0
rsbmi r0, r0, #0
mov pc, lr
10: teq ip, r0 @ same sign ?
rsbmi r0, r0, #0
mov pc, lr
11: movlo r0, #0
moveq r0, ip, asr #31
orreq r0, r0, #1
mov pc, lr
12: ARM_DIV2_ORDER r1, r2
cmp ip, #0
mov r0, r3, lsr r2
rsbmi r0, r0, #0
mov pc, lr
ENTRY(__modsi3)
cmp r1, #0
beq Ldiv0
rsbmi r1, r1, #0 @ loops below use unsigned.
movs ip, r0 @ preserve sign of dividend
rsbmi r0, r0, #0 @ if negative make positive
subs r2, r1, #1 @ compare divisor with 1
cmpne r0, r1 @ compare dividend with divisor
moveq r0, #0
tsthi r1, r2 @ see if divisor is power of 2
andeq r0, r0, r2
bls 10f
ARM_MOD_BODY r0, r1, r2, r3
10: cmp ip, #0
rsbmi r0, r0, #0
mov pc, lr
Ldiv0:
str lr, [sp, #-4]!
bl __div0
mov r0, #0 @ About as wrong as it could be.
ldr pc, [sp], #4
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