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30891f35fa
We stopped adding "Contributed by" or similar lines in sources in 2012 in favour of git logs and keeping the Contributors section of the glibc manual up to date. Removing these lines makes the license header a bit more consistent across files and also removes the possibility of error in attribution when license blocks or files are copied across since the contributed-by lines don't actually reflect reality in those cases. Move all "Contributed by" and similar lines (Written by, Test by, etc.) into a new file CONTRIBUTED-BY to retain record of these contributions. These contributors are also mentioned in manual/contrib.texi, so we just maintain this additional record as a courtesy to the earlier developers. The following scripts were used to filter a list of files to edit in place and to clean up the CONTRIBUTED-BY file respectively. These were not added to the glibc sources because they're not expected to be of any use in future given that this is a one time task: https://gist.github.com/siddhesh/b5ecac94eabfd72ed2916d6d8157e7dc https://gist.github.com/siddhesh/15ea1f5e435ace9774f485030695ee02 Reviewed-by: Carlos O'Donell <carlos@redhat.com>
281 lines
7.3 KiB
ArmAsm
281 lines
7.3 KiB
ArmAsm
/* strchr (str, ch) -- Return pointer to first occurrence of CH in STR.
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For Motorola 68000.
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Copyright (C) 1999-2021 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but 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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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library. If not, see
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<https://www.gnu.org/licenses/>. */
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#include <sysdep.h>
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#include "asm-syntax.h"
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TEXT
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ENTRY(strchr)
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/* Save the callee-saved registers we use. */
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movel R(d2),MEM_PREDEC(sp)
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cfi_adjust_cfa_offset (4)
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movel R(d3),MEM_PREDEC(sp)
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cfi_adjust_cfa_offset (4)
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cfi_rel_offset (R(d2),4)
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cfi_rel_offset (R(d3),0)
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/* Get string pointer and character. */
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movel MEM_DISP(sp,12),R(a0)
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moveb MEM_DISP(sp,19),R(d0)
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/* Distribute the character to all bytes of a longword. */
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movel R(d0),R(d1)
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lsll #8,R(d1)
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moveb R(d0),R(d1)
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movel R(d1),R(d0)
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swap R(d0)
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movew R(d1),R(d0)
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/* First search for the character one byte at a time until the
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pointer is aligned to a longword boundary. */
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movel R(a0),R(d1)
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#ifdef __mcoldfire__
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andl #3,R(d1)
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#else
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andw #3,R(d1)
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#endif
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beq L(L1)
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moveb MEM(a0),R(d2)
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cmpb R(d0),R(d2)
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beq L(L9)
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tstb R(d2)
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beq L(L3)
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addql #1,R(a0)
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#ifdef __mcoldfire__
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subql #3,R(d1)
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#else
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subqw #3,R(d1)
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#endif
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beq L(L1)
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moveb MEM(a0),R(d2)
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cmpb R(d0),R(d2)
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beq L(L9)
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tstb R(d2)
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beq L(L3)
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addql #1,R(a0)
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#ifdef __mcoldfire__
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addql #1,R(d1)
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#else
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addqw #1,R(d1)
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#endif
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beq L(L1)
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moveb MEM(a0),R(d2)
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cmpb R(d0),R(d2)
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beq L(L9)
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tstb R(d2)
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beq L(L3)
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addql #1,R(a0)
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L(L1:)
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/* Load the magic bits. Unlike the generic implementation we can
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use the carry bit as the fourth hole. */
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movel #0xfefefeff,R(d3)
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/* We exit the loop if adding MAGIC_BITS to LONGWORD fails to
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change any of the hole bits of LONGWORD.
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1) Is this safe? Will it catch all the zero bytes?
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Suppose there is a byte with all zeros. Any carry bits
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propagating from its left will fall into the hole at its
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least significant bit and stop. Since there will be no
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carry from its most significant bit, the LSB of the
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byte to the left will be unchanged, and the zero will be
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detected.
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2) Is this worthwhile? Will it ignore everything except
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zero bytes? Suppose every byte of LONGWORD has a bit set
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somewhere. There will be a carry into bit 8. If bit 8
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is set, this will carry into bit 16. If bit 8 is clear,
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one of bits 9-15 must be set, so there will be a carry
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into bit 16. Similarly, there will be a carry into bit
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24. If one of bits 24-31 is set, there will be a carry
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into bit 32 (=carry flag), so all of the hole bits will
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be changed.
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3) But wait! Aren't we looking for C, not zero?
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Good point. So what we do is XOR LONGWORD with a longword,
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each of whose bytes is C. This turns each byte that is C
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into a zero. */
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L(L2:)
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/* Get the longword in question. */
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movel MEM_POSTINC(a0),R(d1)
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/* XOR with the byte we search for. */
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eorl R(d0),R(d1)
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/* Add the magic value. We get carry bits reported for each byte
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which is not C. */
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movel R(d3),R(d2)
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addl R(d1),R(d2)
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/* Check the fourth carry bit before it is clobbered by the next
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XOR. If it is not set we have a hit. */
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bcc L(L8)
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/* We are only interested in carry bits that change due to the
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previous add, so remove original bits. */
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eorl R(d1),R(d2)
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/* Now test for the other three overflow bits.
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Set all non-carry bits. */
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orl R(d3),R(d2)
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/* Add 1 to get zero if all carry bits were set. */
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addql #1,R(d2)
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/* If we don't get zero then at least one byte of the word equals
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C. */
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bne L(L8)
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/* Next look for a NUL byte.
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Restore original longword without reload. */
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eorl R(d0),R(d1)
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/* Add the magic value. We get carry bits reported for each byte
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which is not NUL. */
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movel R(d3),R(d2)
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addl R(d1),R(d2)
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/* Check the fourth carry bit before it is clobbered by the next
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XOR. If it is not set we have a hit, and return NULL. */
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bcc L(L3)
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/* We are only interested in carry bits that change due to the
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previous add, so remove original bits. */
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eorl R(d1),R(d2)
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/* Now test for the other three overflow bits.
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Set all non-carry bits. */
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orl R(d3),R(d2)
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/* Add 1 to get zero if all carry bits were set. */
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addql #1,R(d2)
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/* If we don't get zero then at least one byte of the word was NUL
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and we return NULL. Otherwise continue with the next longword. */
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bne L(L3)
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/* Get the longword in question. */
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movel MEM_POSTINC(a0),R(d1)
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/* XOR with the byte we search for. */
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eorl R(d0),R(d1)
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/* Add the magic value. We get carry bits reported for each byte
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which is not C. */
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movel R(d3),R(d2)
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addl R(d1),R(d2)
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/* Check the fourth carry bit before it is clobbered by the next
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XOR. If it is not set we have a hit. */
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bcc L(L8)
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/* We are only interested in carry bits that change due to the
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previous add, so remove original bits */
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eorl R(d1),R(d2)
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/* Now test for the other three overflow bits.
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Set all non-carry bits. */
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orl R(d3),R(d2)
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/* Add 1 to get zero if all carry bits were set. */
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addql #1,R(d2)
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/* If we don't get zero then at least one byte of the word equals
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C. */
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bne L(L8)
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/* Next look for a NUL byte.
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Restore original longword without reload. */
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eorl R(d0),R(d1)
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/* Add the magic value. We get carry bits reported for each byte
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which is not NUL. */
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movel R(d3),R(d2)
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addl R(d1),R(d2)
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/* Check the fourth carry bit before it is clobbered by the next
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XOR. If it is not set we have a hit, and return NULL. */
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bcc L(L3)
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/* We are only interested in carry bits that change due to the
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previous add, so remove original bits */
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eorl R(d1),R(d2)
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/* Now test for the other three overflow bits.
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Set all non-carry bits. */
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orl R(d3),R(d2)
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/* Add 1 to get zero if all carry bits were set. */
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addql #1,R(d2)
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/* If we don't get zero then at least one byte of the word was NUL
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and we return NULL. Otherwise continue with the next longword. */
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beq L(L2)
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L(L3:)
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/* Return NULL. */
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clrl R(d0)
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movel R(d0),R(a0)
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movel MEM_POSTINC(sp),R(d3)
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cfi_remember_state
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cfi_adjust_cfa_offset (-4)
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cfi_restore (R(d3))
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movel MEM_POSTINC(sp),R(d2)
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cfi_adjust_cfa_offset (-4)
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cfi_restore (R(d2))
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rts
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cfi_restore_state
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L(L8:)
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/* We have a hit. Check to see which byte it was. First
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compensate for the autoincrement in the loop. */
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subql #4,R(a0)
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moveb MEM(a0),R(d1)
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cmpb R(d0),R(d1)
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beq L(L9)
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tstb R(d1)
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beq L(L3)
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addql #1,R(a0)
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moveb MEM(a0),R(d1)
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cmpb R(d0),R(d1)
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beq L(L9)
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tstb R(d1)
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beq L(L3)
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addql #1,R(a0)
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moveb MEM(a0),R(d1)
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cmpb R(d0),R(d1)
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beq L(L9)
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tstb R(d1)
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beq L(L3)
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addql #1,R(a0)
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/* Otherwise the fourth byte must equal C. */
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L(L9:)
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movel R(a0),R(d0)
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movel MEM_POSTINC(sp),R(d3)
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cfi_adjust_cfa_offset (-4)
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cfi_restore (R(d3))
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movel MEM_POSTINC(sp),R(d2)
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cfi_adjust_cfa_offset (-4)
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cfi_restore (R(d2))
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rts
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END(strchr)
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weak_alias (strchr, index)
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libc_hidden_builtin_def (strchr)
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