mirror of
https://sourceware.org/git/glibc.git
synced 2024-12-26 20:51:11 +00:00
258 lines
7.0 KiB
ArmAsm
258 lines
7.0 KiB
ArmAsm
/* strchr (str, ch) -- Return pointer to first occurrence of CH in STR.
|
|
For Motorola 68000.
|
|
Copyright (C) 1999 Free Software Foundation, Inc.
|
|
This file is part of the GNU C Library.
|
|
Contributed by Andreas Schwab <schwab@gnu.org>.
|
|
|
|
The GNU C Library is free software; you can redistribute it and/or
|
|
modify it under the terms of the GNU Library General Public License as
|
|
published by the Free Software Foundation; either version 2 of the
|
|
License, or (at your option) any later version.
|
|
|
|
The GNU C Library is distributed in the hope that it will be useful,
|
|
but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
|
Library General Public License for more details.
|
|
|
|
You should have received a copy of the GNU Library General Public
|
|
License along with the GNU C Library; see the file COPYING.LIB. If not,
|
|
write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
|
|
Boston, MA 02111-1307, USA. */
|
|
|
|
#include <sysdep.h>
|
|
#include "asm-syntax.h"
|
|
|
|
TEXT
|
|
ENTRY(strchr)
|
|
/* Save the callee-saved registers we use. */
|
|
movel R(d2),MEM_PREDEC(sp)
|
|
movel R(d3),MEM_PREDEC(sp)
|
|
|
|
/* Get string pointer and character. */
|
|
movel MEM_DISP(sp,12),R(a0)
|
|
moveb MEM_DISP(sp,19),R(d0)
|
|
|
|
/* Distribute the character to all bytes of a longword. */
|
|
movel R(d0),R(d1)
|
|
lsll #8,R(d1)
|
|
moveb R(d0),R(d1)
|
|
movel R(d1),R(d0)
|
|
swap R(d0)
|
|
movew R(d1),R(d0)
|
|
|
|
/* First search for the character one byte at a time until the
|
|
pointer is aligned to a longword boundary. */
|
|
movel R(a0),R(d1)
|
|
andw #3,R(d1)
|
|
beq L(L1)
|
|
moveb MEM(a0),R(d1)
|
|
cmpb R(d0),R(d1)
|
|
beq L(L9)
|
|
tstb R(d1)
|
|
beq L(L3)
|
|
addql #1,R(a0)
|
|
|
|
movel R(a0),R(d1)
|
|
andw #3,R(d1)
|
|
beq L(L1)
|
|
moveb MEM(a0),R(d1)
|
|
cmpb R(d0),R(d1)
|
|
beq L(L9)
|
|
tstb R(d1)
|
|
beq L(L3)
|
|
addql #1,R(a0)
|
|
|
|
movel R(a0),R(d1)
|
|
andw #3,R(d1)
|
|
beq L(L1)
|
|
moveb MEM(a0),R(d1)
|
|
cmpb R(d0),R(d1)
|
|
beq L(L9)
|
|
tstb R(d1)
|
|
beq L(L3)
|
|
addql #1,R(a0)
|
|
|
|
L(L1:)
|
|
/* Load the magic bits. Unlike the generic implementation we can
|
|
use the carry bit as the fourth hole. */
|
|
movel #0xfefefeff,R(d3)
|
|
|
|
/* We exit the loop if adding MAGIC_BITS to LONGWORD fails to
|
|
change any of the hole bits of LONGWORD.
|
|
|
|
1) Is this safe? Will it catch all the zero bytes?
|
|
Suppose there is a byte with all zeros. Any carry bits
|
|
propagating from its left will fall into the hole at its
|
|
least significant bit and stop. Since there will be no
|
|
carry from its most significant bit, the LSB of the
|
|
byte to the left will be unchanged, and the zero will be
|
|
detected.
|
|
|
|
2) Is this worthwhile? Will it ignore everything except
|
|
zero bytes? Suppose every byte of LONGWORD has a bit set
|
|
somewhere. There will be a carry into bit 8. If bit 8
|
|
is set, this will carry into bit 16. If bit 8 is clear,
|
|
one of bits 9-15 must be set, so there will be a carry
|
|
into bit 16. Similarly, there will be a carry into bit
|
|
24. If one of bits 24-31 is set, there will be a carry
|
|
into bit 32 (=carry flag), so all of the hole bits will
|
|
be changed.
|
|
|
|
3) But wait! Aren't we looking for C, not zero?
|
|
Good point. So what we do is XOR LONGWORD with a longword,
|
|
each of whose bytes is C. This turns each byte that is C
|
|
into a zero. */
|
|
|
|
L(L2:)
|
|
/* Get the longword in question. */
|
|
movel MEM_POSTINC(a0),R(d1)
|
|
/* XOR with the byte we search for. */
|
|
eorl R(d0),R(d1)
|
|
|
|
/* Add the magic value. We get carry bits reported for each byte
|
|
which is not C. */
|
|
movel R(d3),R(d2)
|
|
addl R(d1),R(d2)
|
|
|
|
/* Check the fourth carry bit before it is clobbered by the next
|
|
XOR. If it is not set we have a hit. */
|
|
bcc L(L8)
|
|
|
|
/* We are only interested in carry bits that change due to the
|
|
previous add, so remove original bits. */
|
|
eorl R(d1),R(d2)
|
|
|
|
/* Now test for the other three overflow bits.
|
|
Set all non-carry bits. */
|
|
orl R(d3),R(d2)
|
|
/* Add 1 to get zero if all carry bits were set. */
|
|
addql #1,R(d2)
|
|
|
|
/* If we don't get zero then at least one byte of the word equals
|
|
C. */
|
|
bne L(L8)
|
|
|
|
/* Next look for a NUL byte.
|
|
Restore original longword without reload. */
|
|
eorl R(d0),R(d1)
|
|
/* Add the magic value. We get carry bits reported for each byte
|
|
which is not NUL. */
|
|
movel R(d3),R(d2)
|
|
addl R(d1),R(d2)
|
|
|
|
/* Check the fourth carry bit before it is clobbered by the next
|
|
XOR. If it is not set we have a hit, and return NULL. */
|
|
bcc L(L3)
|
|
|
|
/* We are only interested in carry bits that change due to the
|
|
previous add, so remove original bits. */
|
|
eorl R(d1),R(d2)
|
|
|
|
/* Now test for the other three overflow bits.
|
|
Set all non-carry bits. */
|
|
orl R(d3),R(d2)
|
|
/* Add 1 to get zero if all carry bits were set. */
|
|
addql #1,R(d2)
|
|
|
|
/* If we don't get zero then at least one byte of the word was NUL
|
|
and we return NULL. Otherwise continue with the next longword. */
|
|
bne L(L3)
|
|
|
|
/* Get the longword in question. */
|
|
movel MEM_POSTINC(a0),R(d1)
|
|
/* XOR with the byte we search for. */
|
|
eorl R(d0),R(d1)
|
|
|
|
/* Add the magic value. We get carry bits reported for each byte
|
|
which is not C. */
|
|
movel R(d3),R(d2)
|
|
addl R(d1),R(d2)
|
|
|
|
/* Check the fourth carry bit before it is clobbered by the next
|
|
XOR. If it is not set we have a hit. */
|
|
bcc L(L8)
|
|
|
|
/* We are only interested in carry bits that change due to the
|
|
previous add, so remove original bits */
|
|
eorl R(d1),R(d2)
|
|
|
|
/* Now test for the other three overflow bits.
|
|
Set all non-carry bits. */
|
|
orl R(d3),R(d2)
|
|
/* Add 1 to get zero if all carry bits were set. */
|
|
addql #1,R(d2)
|
|
|
|
/* If we don't get zero then at least one byte of the word equals
|
|
C. */
|
|
bne L(L8)
|
|
|
|
/* Next look for a NUL byte.
|
|
Restore original longword without reload. */
|
|
eorl R(d0),R(d1)
|
|
/* Add the magic value. We get carry bits reported for each byte
|
|
which is not NUL. */
|
|
movel R(d3),R(d2)
|
|
addl R(d1),R(d2)
|
|
|
|
/* Check the fourth carry bit before it is clobbered by the next
|
|
XOR. If it is not set we have a hit, and return NULL. */
|
|
bcc L(L3)
|
|
|
|
/* We are only interested in carry bits that change due to the
|
|
previous add, so remove original bits */
|
|
eorl R(d1),R(d2)
|
|
|
|
/* Now test for the other three overflow bits.
|
|
Set all non-carry bits. */
|
|
orl R(d3),R(d2)
|
|
/* Add 1 to get zero if all carry bits were set. */
|
|
addql #1,R(d2)
|
|
|
|
/* If we don't get zero then at least one byte of the word was NUL
|
|
and we return NULL. Otherwise continue with the next longword. */
|
|
beq L(L2)
|
|
|
|
L(L3:)
|
|
/* Return NULL. */
|
|
clrl R(d0)
|
|
movel R(d0),R(a0)
|
|
movel MEM_POSTINC(sp),R(d3)
|
|
movel MEM_POSTINC(sp),R(d2)
|
|
rts
|
|
|
|
L(L8:)
|
|
/* We have a hit. Check to see which byte it was. First
|
|
compensate for the autoincrement in the loop. */
|
|
subql #4,R(a0)
|
|
|
|
moveb MEM(a0),R(d1)
|
|
cmpb R(d0),R(d1)
|
|
beq L(L9)
|
|
tstb R(d1)
|
|
beq L(L3)
|
|
addql #1,R(a0)
|
|
|
|
moveb MEM(a0),R(d1)
|
|
cmpb R(d0),R(d1)
|
|
beq L(L9)
|
|
tstb R(d1)
|
|
beq L(L3)
|
|
addql #1,R(a0)
|
|
|
|
moveb MEM(a0),R(d1)
|
|
cmpb R(d0),R(d1)
|
|
beq L(L9)
|
|
tstb R(d1)
|
|
beq L(L3)
|
|
addql #1,R(a0)
|
|
|
|
/* Otherwise the fourth byte must equal C. */
|
|
L(L9:)
|
|
movel R(a0),R(d0)
|
|
movel MEM_POSTINC(sp),R(d3)
|
|
movel MEM_POSTINC(sp),R(d2)
|
|
rts
|
|
END(strchr)
|
|
|
|
weak_alias (strchr, index)
|