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| /*
| * linux/arch/arm/lib/lib1funcs.S: Optimized ARM division routines
| *
| * Author: Nicolas Pitre <nico@fluxnic.net>
| * - 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>
| #include <asm/unwind.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?
| movsne \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 subtractions 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
| subsge \order, \order, #4
| bge 1b
|
| tst \order, #3
| teqne \dividend, #0
| beq 5f
|
| @ Either 1, 2 or 3 comparison/subtractions 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
|
|
| #ifdef CONFIG_ARM_PATCH_IDIV
| .align 3
| #endif
|
| ENTRY(__udivsi3)
| ENTRY(__aeabi_uidiv)
| UNWIND(.fnstart)
|
| subs r2, r1, #1
| reteq lr
| bcc Ldiv0
| cmp r0, r1
| bls 11f
| tst r1, r2
| beq 12f
|
| ARM_DIV_BODY r0, r1, r2, r3
|
| mov r0, r2
| ret lr
|
| 11: moveq r0, #1
| movne r0, #0
| ret lr
|
| 12: ARM_DIV2_ORDER r1, r2
|
| mov r0, r0, lsr r2
| ret lr
|
| UNWIND(.fnend)
| ENDPROC(__udivsi3)
| ENDPROC(__aeabi_uidiv)
|
| ENTRY(__umodsi3)
| UNWIND(.fnstart)
|
| 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
| retls lr
|
| ARM_MOD_BODY r0, r1, r2, r3
|
| ret lr
|
| UNWIND(.fnend)
| ENDPROC(__umodsi3)
|
| #ifdef CONFIG_ARM_PATCH_IDIV
| .align 3
| #endif
|
| ENTRY(__divsi3)
| ENTRY(__aeabi_idiv)
| UNWIND(.fnstart)
|
| 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
| ret lr
|
| 10: teq ip, r0 @ same sign ?
| rsbmi r0, r0, #0
| ret lr
|
| 11: movlo r0, #0
| moveq r0, ip, asr #31
| orreq r0, r0, #1
| ret lr
|
| 12: ARM_DIV2_ORDER r1, r2
|
| cmp ip, #0
| mov r0, r3, lsr r2
| rsbmi r0, r0, #0
| ret lr
|
| UNWIND(.fnend)
| ENDPROC(__divsi3)
| ENDPROC(__aeabi_idiv)
|
| ENTRY(__modsi3)
| UNWIND(.fnstart)
|
| 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
| ret lr
|
| UNWIND(.fnend)
| ENDPROC(__modsi3)
|
| #ifdef CONFIG_AEABI
|
| ENTRY(__aeabi_uidivmod)
| UNWIND(.fnstart)
| UNWIND(.save {r0, r1, ip, lr} )
|
| stmfd sp!, {r0, r1, ip, lr}
| bl __aeabi_uidiv
| ldmfd sp!, {r1, r2, ip, lr}
| mul r3, r0, r2
| sub r1, r1, r3
| ret lr
|
| UNWIND(.fnend)
| ENDPROC(__aeabi_uidivmod)
|
| ENTRY(__aeabi_idivmod)
| UNWIND(.fnstart)
| UNWIND(.save {r0, r1, ip, lr} )
| stmfd sp!, {r0, r1, ip, lr}
| bl __aeabi_idiv
| ldmfd sp!, {r1, r2, ip, lr}
| mul r3, r0, r2
| sub r1, r1, r3
| ret lr
|
| UNWIND(.fnend)
| ENDPROC(__aeabi_idivmod)
|
| #endif
|
| Ldiv0:
| UNWIND(.fnstart)
| UNWIND(.pad #4)
| UNWIND(.save {lr})
| str lr, [sp, #-8]!
| bl __div0
| mov r0, #0 @ About as wrong as it could be.
| ldr pc, [sp], #8
| UNWIND(.fnend)
| ENDPROC(Ldiv0)
|
|
