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xtensa: add helpers for division, remainder and shifts
Don't rely on libgcc presence, build own versions of the helpers with correct ABI. Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
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‎arch/xtensa/include/asm/asmmacro.h‎

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#endif
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.endm
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.macro do_nsau cnt, val, tmp, a
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#if XCHAL_HAVE_NSA
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nsau \cnt, \val
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#else
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mov \a, \val
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movi \cnt, 0
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extui \tmp, \a, 16, 16
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bnez \tmp, 0f
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movi \cnt, 16
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slli \a, \a, 16
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0:
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extui \tmp, \a, 24, 8
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bnez \tmp, 1f
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addi \cnt, \cnt, 8
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slli \a, \a, 8
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1:
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movi \tmp, __nsau_data
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extui \a, \a, 24, 8
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add \tmp, \tmp, \a
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l8ui \tmp, \tmp, 0
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add \cnt, \cnt, \tmp
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#endif /* !XCHAL_HAVE_NSA */
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.endm
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.macro do_abs dst, src, tmp
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#if XCHAL_HAVE_ABS
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abs \dst, \src
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#else
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neg \tmp, \src
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movgez \tmp, \src, \src
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mov \dst, \tmp
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#endif
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.endm
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#define XTENSA_STACK_ALIGNMENT 16
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#if defined(__XTENSA_WINDOWED_ABI__)

‎arch/xtensa/lib/Makefile‎

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#
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lib-y += memcopy.o memset.o checksum.o \
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ashldi3.o ashrdi3.o lshrdi3.o \
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divsi3.o udivsi3.o modsi3.o umodsi3.o mulsi3.o \
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usercopy.o strncpy_user.o strnlen_user.o
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lib-$(CONFIG_PCI) += pci-auto.o

‎arch/xtensa/lib/ashldi3.S‎

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/* SPDX-License-Identifier: GPL-2.0-or-later WITH GCC-exception-2.0 */
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#include <linux/linkage.h>
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#include <asm/asmmacro.h>
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#include <asm/core.h>
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#ifdef __XTENSA_EB__
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#define uh a2
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#define ul a3
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#else
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#define uh a3
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#define ul a2
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#endif /* __XTENSA_EB__ */
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ENTRY(__ashldi3)
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abi_entry_default
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ssl a4
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bgei a4, 32, .Llow_only
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src uh, uh, ul
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sll ul, ul
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abi_ret_default
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.Llow_only:
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sll uh, ul
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movi ul, 0
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abi_ret_default
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ENDPROC(__ashldi3)

‎arch/xtensa/lib/ashrdi3.S‎

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/* SPDX-License-Identifier: GPL-2.0-or-later WITH GCC-exception-2.0 */
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#include <linux/linkage.h>
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#include <asm/asmmacro.h>
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#include <asm/core.h>
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#ifdef __XTENSA_EB__
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#define uh a2
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#define ul a3
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#else
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#define uh a3
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#define ul a2
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#endif /* __XTENSA_EB__ */
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ENTRY(__ashrdi3)
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abi_entry_default
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ssr a4
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bgei a4, 32, .Lhigh_only
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src ul, uh, ul
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sra uh, uh
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abi_ret_default
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.Lhigh_only:
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sra ul, uh
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srai uh, uh, 31
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abi_ret_default
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ENDPROC(__ashrdi3)

‎arch/xtensa/lib/divsi3.S‎

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/* SPDX-License-Identifier: GPL-2.0-or-later WITH GCC-exception-2.0 */
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#include <linux/linkage.h>
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#include <asm/asmmacro.h>
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#include <asm/core.h>
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ENTRY(__divsi3)
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abi_entry_default
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#if XCHAL_HAVE_DIV32
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quos a2, a2, a3
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#else
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xor a7, a2, a3 /* sign = dividend ^ divisor */
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do_abs a6, a2, a4 /* udividend = abs (dividend) */
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do_abs a3, a3, a4 /* udivisor = abs (divisor) */
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bltui a3, 2, .Lle_one /* check if udivisor <= 1 */
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do_nsau a5, a6, a2, a8 /* udividend_shift = nsau (udividend) */
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do_nsau a4, a3, a2, a8 /* udivisor_shift = nsau (udivisor) */
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bgeu a5, a4, .Lspecial
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sub a4, a4, a5 /* count = udivisor_shift - udividend_shift */
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ssl a4
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sll a3, a3 /* udivisor <<= count */
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movi a2, 0 /* quotient = 0 */
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/* test-subtract-and-shift loop; one quotient bit on each iteration */
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#if XCHAL_HAVE_LOOPS
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loopnez a4, .Lloopend
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#endif /* XCHAL_HAVE_LOOPS */
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.Lloop:
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bltu a6, a3, .Lzerobit
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sub a6, a6, a3
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addi a2, a2, 1
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.Lzerobit:
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slli a2, a2, 1
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srli a3, a3, 1
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#if !XCHAL_HAVE_LOOPS
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addi a4, a4, -1
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bnez a4, .Lloop
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#endif /* !XCHAL_HAVE_LOOPS */
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.Lloopend:
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bltu a6, a3, .Lreturn
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addi a2, a2, 1 /* increment if udividend >= udivisor */
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.Lreturn:
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neg a5, a2
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movltz a2, a5, a7 /* return (sign < 0) ? -quotient : quotient */
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abi_ret_default
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.Lle_one:
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beqz a3, .Lerror
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neg a2, a6 /* if udivisor == 1, then return... */
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movgez a2, a6, a7 /* (sign < 0) ? -udividend : udividend */
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abi_ret_default
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.Lspecial:
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bltu a6, a3, .Lreturn0 /* if dividend < divisor, return 0 */
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movi a2, 1
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movi a4, -1
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movltz a2, a4, a7 /* else return (sign < 0) ? -1 : 1 */
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abi_ret_default
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.Lerror:
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/* Divide by zero: Use an illegal instruction to force an exception.
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The subsequent "DIV0" string can be recognized by the exception
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handler to identify the real cause of the exception. */
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ill
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.ascii "DIV0"
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.Lreturn0:
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movi a2, 0
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#endif /* XCHAL_HAVE_DIV32 */
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abi_ret_default
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ENDPROC(__divsi3)

‎arch/xtensa/lib/lshrdi3.S‎

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/* SPDX-License-Identifier: GPL-2.0-or-later WITH GCC-exception-2.0 */
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#include <linux/linkage.h>
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#include <asm/asmmacro.h>
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#include <asm/core.h>
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#ifdef __XTENSA_EB__
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#define uh a2
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#define ul a3
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#else
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#define uh a3
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#define ul a2
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#endif /* __XTENSA_EB__ */
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ENTRY(__lshrdi3)
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abi_entry_default
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ssr a4
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bgei a4, 32, .Lhigh_only
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src ul, uh, ul
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srl uh, uh
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abi_ret_default
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.Lhigh_only:
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srl ul, uh
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movi uh, 0
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abi_ret_default
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ENDPROC(__lshrdi3)

‎arch/xtensa/lib/modsi3.S‎

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/* SPDX-License-Identifier: GPL-2.0-or-later WITH GCC-exception-2.0 */
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#include <linux/linkage.h>
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#include <asm/asmmacro.h>
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#include <asm/core.h>
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ENTRY(__modsi3)
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abi_entry_default
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#if XCHAL_HAVE_DIV32
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rems a2, a2, a3
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#else
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mov a7, a2 /* save original (signed) dividend */
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do_abs a2, a2, a4 /* udividend = abs (dividend) */
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do_abs a3, a3, a4 /* udivisor = abs (divisor) */
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bltui a3, 2, .Lle_one /* check if udivisor <= 1 */
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do_nsau a5, a2, a6, a8 /* udividend_shift = nsau (udividend) */
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do_nsau a4, a3, a6, a8 /* udivisor_shift = nsau (udivisor) */
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bgeu a5, a4, .Lspecial
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sub a4, a4, a5 /* count = udivisor_shift - udividend_shift */
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ssl a4
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sll a3, a3 /* udivisor <<= count */
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/* test-subtract-and-shift loop */
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#if XCHAL_HAVE_LOOPS
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loopnez a4, .Lloopend
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#endif /* XCHAL_HAVE_LOOPS */
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.Lloop:
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bltu a2, a3, .Lzerobit
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sub a2, a2, a3
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.Lzerobit:
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srli a3, a3, 1
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#if !XCHAL_HAVE_LOOPS
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addi a4, a4, -1
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bnez a4, .Lloop
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#endif /* !XCHAL_HAVE_LOOPS */
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.Lloopend:
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.Lspecial:
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bltu a2, a3, .Lreturn
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sub a2, a2, a3 /* subtract again if udividend >= udivisor */
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.Lreturn:
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bgez a7, .Lpositive
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neg a2, a2 /* if (dividend < 0), return -udividend */
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.Lpositive:
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abi_ret_default
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.Lle_one:
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bnez a3, .Lreturn0
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/* Divide by zero: Use an illegal instruction to force an exception.
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The subsequent "DIV0" string can be recognized by the exception
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handler to identify the real cause of the exception. */
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ill
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.ascii "DIV0"
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.Lreturn0:
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movi a2, 0
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#endif /* XCHAL_HAVE_DIV32 */
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abi_ret_default
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ENDPROC(__modsi3)
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#if !XCHAL_HAVE_NSA
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.section .rodata
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.align 4
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.global __nsau_data
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.type __nsau_data, @object
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__nsau_data:
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.byte 8, 7, 6, 6, 5, 5, 5, 5, 4, 4, 4, 4, 4, 4, 4, 4
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.byte 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3
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.byte 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2
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.byte 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2
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.byte 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1
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.byte 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1
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.byte 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1
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.byte 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1
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.byte 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
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.byte 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
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.byte 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
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.byte 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
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.byte 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
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.byte 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
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.byte 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
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.byte 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
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.size __nsau_data, . - __nsau_data
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#endif /* !XCHAL_HAVE_NSA */

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