Subversion Repositories or1k_soc_on_altera_embedded_dev_kit

/*
 * 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)
ENTRY(__aeabi_uidiv)

        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)
ENTRY(__aeabi_idiv)

        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

#ifdef CONFIG_AEABI

ENTRY(__aeabi_uidivmod)

        stmfd   sp!, {r0, r1, ip, lr}
        bl      __aeabi_uidiv
        ldmfd   sp!, {r1, r2, ip, lr}
        mul     r3, r0, r2
        sub     r1, r1, r3
        mov     pc, lr

ENTRY(__aeabi_idivmod)

        stmfd   sp!, {r0, r1, ip, lr}
        bl      __aeabi_idiv
        ldmfd   sp!, {r1, r2, ip, lr}
        mul     r3, r0, r2
        sub     r1, r1, r3
        mov     pc, lr

#endif

Ldiv0:

        str     lr, [sp, #-8]!
        bl      __div0
        mov     r0, #0                  @ About as wrong as it could be.
        ldr     pc, [sp], #8