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428 lines
8.6 KiB
ArmAsm
428 lines
8.6 KiB
ArmAsm
/* SPDX-License-Identifier: GPL-2.0+ */
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/*
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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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/*
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* Copyright 1995, 1996, 1998, 1999, 2000, 2003 Free Software Foundation, Inc.
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*/
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#include <linux/linkage.h>
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#include <asm/assembler.h>
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/*
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* U-Boot compatibility bit, define empty UNWIND() macro as, since we
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* do not support stack unwinding and define CONFIG_AEABI to make all
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* of the functions available without diverging from Linux code.
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*/
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#ifdef __UBOOT__
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#define UNWIND(x...)
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#define CONFIG_AEABI
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#endif
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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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.pushsection .text.__udivsi3, "ax"
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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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.popsection
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.pushsection .text.__umodsi3, "ax"
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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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.popsection
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.pushsection .text.__divsi3, "ax"
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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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.popsection
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.pushsection .text.__modsi3, "ax"
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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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.popsection
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#ifdef CONFIG_AEABI
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.pushsection .text.__aeabi_uidivmod, "ax"
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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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.popsection
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.pushsection .text.__aeabi_uidivmod, "ax"
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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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.popsection
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#endif
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.pushsection .text.Ldiv0, "ax"
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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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.popsection
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/* Thumb-1 specialities */
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#if CONFIG_IS_ENABLED(SYS_THUMB_BUILD) && !defined(CONFIG_HAS_THUMB2)
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.pushsection .text.__gnu_thumb1_case_sqi, "ax"
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ENTRY(__gnu_thumb1_case_sqi)
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push {r1}
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mov r1, lr
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lsrs r1, r1, #1
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lsls r1, r1, #1
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ldrsb r1, [r1, r0]
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lsls r1, r1, #1
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add lr, lr, r1
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pop {r1}
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bx lr
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ENDPROC(__gnu_thumb1_case_sqi)
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.popsection
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.pushsection .text.__gnu_thumb1_case_uqi, "ax"
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ENTRY(__gnu_thumb1_case_uqi)
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push {r1}
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mov r1, lr
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lsrs r1, r1, #1
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lsls r1, r1, #1
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ldrb r1, [r1, r0]
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lsls r1, r1, #1
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add lr, lr, r1
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pop {r1}
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bx lr
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ENDPROC(__gnu_thumb1_case_uqi)
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.popsection
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.pushsection .text.__gnu_thumb1_case_shi, "ax"
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ENTRY(__gnu_thumb1_case_shi)
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push {r0, r1}
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mov r1, lr
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lsrs r1, r1, #1
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lsls r0, r0, #1
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lsls r1, r1, #1
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ldrsh r1, [r1, r0]
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lsls r1, r1, #1
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add lr, lr, r1
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pop {r0, r1}
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bx lr
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ENDPROC(__gnu_thumb1_case_shi)
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.popsection
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.pushsection .text.__gnu_thumb1_case_uhi, "ax"
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ENTRY(__gnu_thumb1_case_uhi)
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push {r0, r1}
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mov r1, lr
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lsrs r1, r1, #1
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lsls r0, r0, #1
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lsls r1, r1, #1
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ldrh r1, [r1, r0]
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lsls r1, r1, #1
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add lr, lr, r1
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pop {r0, r1}
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bx lr
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ENDPROC(__gnu_thumb1_case_uhi)
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.popsection
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#endif
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