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