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6c4009 |
/* strchr (str, ch) -- Return pointer to first occurrence of CH in STR.
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Packit |
6c4009 |
For Motorola 68000.
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6c4009 |
Copyright (C) 1999-2018 Free Software Foundation, Inc.
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6c4009 |
This file is part of the GNU C Library.
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6c4009 |
Contributed by Andreas Schwab <schwab@gnu.org>.
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6c4009 |
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6c4009 |
The GNU C Library is free software; you can redistribute it and/or
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6c4009 |
modify it under the terms of the GNU Lesser General Public
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Packit |
6c4009 |
License as published by the Free Software Foundation; either
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Packit |
6c4009 |
version 2.1 of the License, or (at your option) any later version.
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6c4009 |
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Packit |
6c4009 |
The GNU C Library is distributed in the hope that it will be useful,
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6c4009 |
but WITHOUT ANY WARRANTY; without even the implied warranty of
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6c4009 |
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Packit |
6c4009 |
Lesser General Public License for more details.
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Packit |
6c4009 |
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Packit |
6c4009 |
You should have received a copy of the GNU Lesser General Public
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Packit |
6c4009 |
License along with the GNU C Library. If not, see
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Packit |
6c4009 |
<http://www.gnu.org/licenses/>. */
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6c4009 |
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6c4009 |
#include <sysdep.h>
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6c4009 |
#include "asm-syntax.h"
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6c4009 |
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6c4009 |
TEXT
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Packit |
6c4009 |
ENTRY(strchr)
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6c4009 |
/* Save the callee-saved registers we use. */
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Packit |
6c4009 |
movel R(d2),MEM_PREDEC(sp)
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Packit |
6c4009 |
cfi_adjust_cfa_offset (4)
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Packit |
6c4009 |
movel R(d3),MEM_PREDEC(sp)
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Packit |
6c4009 |
cfi_adjust_cfa_offset (4)
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Packit |
6c4009 |
cfi_rel_offset (R(d2),4)
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Packit |
6c4009 |
cfi_rel_offset (R(d3),0)
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Packit |
6c4009 |
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Packit |
6c4009 |
/* Get string pointer and character. */
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Packit |
6c4009 |
movel MEM_DISP(sp,12),R(a0)
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Packit |
6c4009 |
moveb MEM_DISP(sp,19),R(d0)
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Packit |
6c4009 |
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Packit |
6c4009 |
/* Distribute the character to all bytes of a longword. */
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Packit |
6c4009 |
movel R(d0),R(d1)
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Packit |
6c4009 |
lsll #8,R(d1)
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Packit |
6c4009 |
moveb R(d0),R(d1)
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Packit |
6c4009 |
movel R(d1),R(d0)
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Packit |
6c4009 |
swap R(d0)
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Packit |
6c4009 |
movew R(d1),R(d0)
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Packit |
6c4009 |
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6c4009 |
/* First search for the character one byte at a time until the
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Packit |
6c4009 |
pointer is aligned to a longword boundary. */
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Packit |
6c4009 |
movel R(a0),R(d1)
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6c4009 |
#ifdef __mcoldfire__
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6c4009 |
andl #3,R(d1)
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6c4009 |
#else
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Packit |
6c4009 |
andw #3,R(d1)
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6c4009 |
#endif
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6c4009 |
beq L(L1)
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Packit |
6c4009 |
moveb MEM(a0),R(d2)
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6c4009 |
cmpb R(d0),R(d2)
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6c4009 |
beq L(L9)
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6c4009 |
tstb R(d2)
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6c4009 |
beq L(L3)
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Packit |
6c4009 |
addql #1,R(a0)
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Packit |
6c4009 |
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Packit |
6c4009 |
#ifdef __mcoldfire__
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6c4009 |
subql #3,R(d1)
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6c4009 |
#else
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Packit |
6c4009 |
subqw #3,R(d1)
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Packit |
6c4009 |
#endif
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6c4009 |
beq L(L1)
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Packit |
6c4009 |
moveb MEM(a0),R(d2)
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Packit |
6c4009 |
cmpb R(d0),R(d2)
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6c4009 |
beq L(L9)
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6c4009 |
tstb R(d2)
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Packit |
6c4009 |
beq L(L3)
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Packit |
6c4009 |
addql #1,R(a0)
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Packit |
6c4009 |
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Packit |
6c4009 |
#ifdef __mcoldfire__
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6c4009 |
addql #1,R(d1)
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Packit |
6c4009 |
#else
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Packit |
6c4009 |
addqw #1,R(d1)
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Packit |
6c4009 |
#endif
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Packit |
6c4009 |
beq L(L1)
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Packit |
6c4009 |
moveb MEM(a0),R(d2)
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6c4009 |
cmpb R(d0),R(d2)
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Packit |
6c4009 |
beq L(L9)
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Packit |
6c4009 |
tstb R(d2)
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Packit |
6c4009 |
beq L(L3)
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Packit |
6c4009 |
addql #1,R(a0)
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Packit |
6c4009 |
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Packit |
6c4009 |
L(L1:)
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6c4009 |
/* Load the magic bits. Unlike the generic implementation we can
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6c4009 |
use the carry bit as the fourth hole. */
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Packit |
6c4009 |
movel #0xfefefeff,R(d3)
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Packit |
6c4009 |
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Packit |
6c4009 |
/* We exit the loop if adding MAGIC_BITS to LONGWORD fails to
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6c4009 |
change any of the hole bits of LONGWORD.
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6c4009 |
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6c4009 |
1) Is this safe? Will it catch all the zero bytes?
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6c4009 |
Suppose there is a byte with all zeros. Any carry bits
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6c4009 |
propagating from its left will fall into the hole at its
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6c4009 |
least significant bit and stop. Since there will be no
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6c4009 |
carry from its most significant bit, the LSB of the
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6c4009 |
byte to the left will be unchanged, and the zero will be
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6c4009 |
detected.
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6c4009 |
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6c4009 |
2) Is this worthwhile? Will it ignore everything except
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6c4009 |
zero bytes? Suppose every byte of LONGWORD has a bit set
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Packit |
6c4009 |
somewhere. There will be a carry into bit 8. If bit 8
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Packit |
6c4009 |
is set, this will carry into bit 16. If bit 8 is clear,
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6c4009 |
one of bits 9-15 must be set, so there will be a carry
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6c4009 |
into bit 16. Similarly, there will be a carry into bit
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6c4009 |
24. If one of bits 24-31 is set, there will be a carry
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Packit |
6c4009 |
into bit 32 (=carry flag), so all of the hole bits will
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Packit |
6c4009 |
be changed.
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Packit |
6c4009 |
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Packit |
6c4009 |
3) But wait! Aren't we looking for C, not zero?
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6c4009 |
Good point. So what we do is XOR LONGWORD with a longword,
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Packit |
6c4009 |
each of whose bytes is C. This turns each byte that is C
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Packit |
6c4009 |
into a zero. */
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Packit |
6c4009 |
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Packit |
6c4009 |
L(L2:)
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Packit |
6c4009 |
/* Get the longword in question. */
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Packit |
6c4009 |
movel MEM_POSTINC(a0),R(d1)
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Packit |
6c4009 |
/* XOR with the byte we search for. */
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Packit |
6c4009 |
eorl R(d0),R(d1)
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Packit |
6c4009 |
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Packit |
6c4009 |
/* Add the magic value. We get carry bits reported for each byte
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Packit |
6c4009 |
which is not C. */
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Packit |
6c4009 |
movel R(d3),R(d2)
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Packit |
6c4009 |
addl R(d1),R(d2)
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Packit |
6c4009 |
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Packit |
6c4009 |
/* Check the fourth carry bit before it is clobbered by the next
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Packit |
6c4009 |
XOR. If it is not set we have a hit. */
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Packit |
6c4009 |
bcc L(L8)
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Packit |
6c4009 |
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Packit |
6c4009 |
/* We are only interested in carry bits that change due to the
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Packit |
6c4009 |
previous add, so remove original bits. */
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Packit |
6c4009 |
eorl R(d1),R(d2)
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Packit |
6c4009 |
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Packit |
6c4009 |
/* Now test for the other three overflow bits.
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Packit |
6c4009 |
Set all non-carry bits. */
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Packit |
6c4009 |
orl R(d3),R(d2)
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Packit |
6c4009 |
/* Add 1 to get zero if all carry bits were set. */
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Packit |
6c4009 |
addql #1,R(d2)
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Packit |
6c4009 |
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Packit |
6c4009 |
/* If we don't get zero then at least one byte of the word equals
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Packit |
6c4009 |
C. */
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Packit |
6c4009 |
bne L(L8)
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Packit |
6c4009 |
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Packit |
6c4009 |
/* Next look for a NUL byte.
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Packit |
6c4009 |
Restore original longword without reload. */
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Packit |
6c4009 |
eorl R(d0),R(d1)
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Packit |
6c4009 |
/* Add the magic value. We get carry bits reported for each byte
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Packit |
6c4009 |
which is not NUL. */
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Packit |
6c4009 |
movel R(d3),R(d2)
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Packit |
6c4009 |
addl R(d1),R(d2)
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Packit |
6c4009 |
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Packit |
6c4009 |
/* Check the fourth carry bit before it is clobbered by the next
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Packit |
6c4009 |
XOR. If it is not set we have a hit, and return NULL. */
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Packit |
6c4009 |
bcc L(L3)
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Packit |
6c4009 |
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Packit |
6c4009 |
/* We are only interested in carry bits that change due to the
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|
Packit |
6c4009 |
previous add, so remove original bits. */
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Packit |
6c4009 |
eorl R(d1),R(d2)
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Packit |
6c4009 |
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Packit |
6c4009 |
/* Now test for the other three overflow bits.
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Packit |
6c4009 |
Set all non-carry bits. */
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Packit |
6c4009 |
orl R(d3),R(d2)
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Packit |
6c4009 |
/* Add 1 to get zero if all carry bits were set. */
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Packit |
6c4009 |
addql #1,R(d2)
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Packit |
6c4009 |
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|
Packit |
6c4009 |
/* If we don't get zero then at least one byte of the word was NUL
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|
Packit |
6c4009 |
and we return NULL. Otherwise continue with the next longword. */
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Packit |
6c4009 |
bne L(L3)
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Packit |
6c4009 |
|
|
Packit |
6c4009 |
/* Get the longword in question. */
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|
Packit |
6c4009 |
movel MEM_POSTINC(a0),R(d1)
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|
Packit |
6c4009 |
/* XOR with the byte we search for. */
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|
Packit |
6c4009 |
eorl R(d0),R(d1)
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|
Packit |
6c4009 |
|
|
Packit |
6c4009 |
/* Add the magic value. We get carry bits reported for each byte
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|
Packit |
6c4009 |
which is not C. */
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|
Packit |
6c4009 |
movel R(d3),R(d2)
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|
Packit |
6c4009 |
addl R(d1),R(d2)
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|
Packit |
6c4009 |
|
|
Packit |
6c4009 |
/* Check the fourth carry bit before it is clobbered by the next
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|
Packit |
6c4009 |
XOR. If it is not set we have a hit. */
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Packit |
6c4009 |
bcc L(L8)
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|
Packit |
6c4009 |
|
|
Packit |
6c4009 |
/* We are only interested in carry bits that change due to the
|
|
Packit |
6c4009 |
previous add, so remove original bits */
|
|
Packit |
6c4009 |
eorl R(d1),R(d2)
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|
Packit |
6c4009 |
|
|
Packit |
6c4009 |
/* Now test for the other three overflow bits.
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|
Packit |
6c4009 |
Set all non-carry bits. */
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|
Packit |
6c4009 |
orl R(d3),R(d2)
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|
Packit |
6c4009 |
/* Add 1 to get zero if all carry bits were set. */
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|
Packit |
6c4009 |
addql #1,R(d2)
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|
Packit |
6c4009 |
|
|
Packit |
6c4009 |
/* If we don't get zero then at least one byte of the word equals
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|
Packit |
6c4009 |
C. */
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|
Packit |
6c4009 |
bne L(L8)
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|
Packit |
6c4009 |
|
|
Packit |
6c4009 |
/* Next look for a NUL byte.
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|
Packit |
6c4009 |
Restore original longword without reload. */
|
|
Packit |
6c4009 |
eorl R(d0),R(d1)
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|
Packit |
6c4009 |
/* Add the magic value. We get carry bits reported for each byte
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|
Packit |
6c4009 |
which is not NUL. */
|
|
Packit |
6c4009 |
movel R(d3),R(d2)
|
|
Packit |
6c4009 |
addl R(d1),R(d2)
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|
Packit |
6c4009 |
|
|
Packit |
6c4009 |
/* Check the fourth carry bit before it is clobbered by the next
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|
Packit |
6c4009 |
XOR. If it is not set we have a hit, and return NULL. */
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|
Packit |
6c4009 |
bcc L(L3)
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|
Packit |
6c4009 |
|
|
Packit |
6c4009 |
/* We are only interested in carry bits that change due to the
|
|
Packit |
6c4009 |
previous add, so remove original bits */
|
|
Packit |
6c4009 |
eorl R(d1),R(d2)
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|
Packit |
6c4009 |
|
|
Packit |
6c4009 |
/* Now test for the other three overflow bits.
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|
Packit |
6c4009 |
Set all non-carry bits. */
|
|
Packit |
6c4009 |
orl R(d3),R(d2)
|
|
Packit |
6c4009 |
/* Add 1 to get zero if all carry bits were set. */
|
|
Packit |
6c4009 |
addql #1,R(d2)
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|
Packit |
6c4009 |
|
|
Packit |
6c4009 |
/* If we don't get zero then at least one byte of the word was NUL
|
|
Packit |
6c4009 |
and we return NULL. Otherwise continue with the next longword. */
|
|
Packit |
6c4009 |
beq L(L2)
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|
Packit |
6c4009 |
|
|
Packit |
6c4009 |
L(L3:)
|
|
Packit |
6c4009 |
/* Return NULL. */
|
|
Packit |
6c4009 |
clrl R(d0)
|
|
Packit |
6c4009 |
movel R(d0),R(a0)
|
|
Packit |
6c4009 |
movel MEM_POSTINC(sp),R(d3)
|
|
Packit |
6c4009 |
cfi_remember_state
|
|
Packit |
6c4009 |
cfi_adjust_cfa_offset (-4)
|
|
Packit |
6c4009 |
cfi_restore (R(d3))
|
|
Packit |
6c4009 |
movel MEM_POSTINC(sp),R(d2)
|
|
Packit |
6c4009 |
cfi_adjust_cfa_offset (-4)
|
|
Packit |
6c4009 |
cfi_restore (R(d2))
|
|
Packit |
6c4009 |
rts
|
|
Packit |
6c4009 |
|
|
Packit |
6c4009 |
cfi_restore_state
|
|
Packit |
6c4009 |
L(L8:)
|
|
Packit |
6c4009 |
/* We have a hit. Check to see which byte it was. First
|
|
Packit |
6c4009 |
compensate for the autoincrement in the loop. */
|
|
Packit |
6c4009 |
subql #4,R(a0)
|
|
Packit |
6c4009 |
|
|
Packit |
6c4009 |
moveb MEM(a0),R(d1)
|
|
Packit |
6c4009 |
cmpb R(d0),R(d1)
|
|
Packit |
6c4009 |
beq L(L9)
|
|
Packit |
6c4009 |
tstb R(d1)
|
|
Packit |
6c4009 |
beq L(L3)
|
|
Packit |
6c4009 |
addql #1,R(a0)
|
|
Packit |
6c4009 |
|
|
Packit |
6c4009 |
moveb MEM(a0),R(d1)
|
|
Packit |
6c4009 |
cmpb R(d0),R(d1)
|
|
Packit |
6c4009 |
beq L(L9)
|
|
Packit |
6c4009 |
tstb R(d1)
|
|
Packit |
6c4009 |
beq L(L3)
|
|
Packit |
6c4009 |
addql #1,R(a0)
|
|
Packit |
6c4009 |
|
|
Packit |
6c4009 |
moveb MEM(a0),R(d1)
|
|
Packit |
6c4009 |
cmpb R(d0),R(d1)
|
|
Packit |
6c4009 |
beq L(L9)
|
|
Packit |
6c4009 |
tstb R(d1)
|
|
Packit |
6c4009 |
beq L(L3)
|
|
Packit |
6c4009 |
addql #1,R(a0)
|
|
Packit |
6c4009 |
|
|
Packit |
6c4009 |
/* Otherwise the fourth byte must equal C. */
|
|
Packit |
6c4009 |
L(L9:)
|
|
Packit |
6c4009 |
movel R(a0),R(d0)
|
|
Packit |
6c4009 |
movel MEM_POSTINC(sp),R(d3)
|
|
Packit |
6c4009 |
cfi_adjust_cfa_offset (-4)
|
|
Packit |
6c4009 |
cfi_restore (R(d3))
|
|
Packit |
6c4009 |
movel MEM_POSTINC(sp),R(d2)
|
|
Packit |
6c4009 |
cfi_adjust_cfa_offset (-4)
|
|
Packit |
6c4009 |
cfi_restore (R(d2))
|
|
Packit |
6c4009 |
rts
|
|
Packit |
6c4009 |
END(strchr)
|
|
Packit |
6c4009 |
|
|
Packit |
6c4009 |
weak_alias (strchr, index)
|
|
Packit |
6c4009 |
libc_hidden_builtin_def (strchr)
|