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Diffstat (limited to 'sysdeps/m68k/strchr.S')
| -rw-r--r-- | sysdeps/m68k/strchr.S | 258 |
1 files changed, 0 insertions, 258 deletions
diff --git a/sysdeps/m68k/strchr.S b/sysdeps/m68k/strchr.S deleted file mode 100644 index 04626ff..0000000 --- a/sysdeps/m68k/strchr.S +++ /dev/null @@ -1,258 +0,0 @@ -/* strchr (str, ch) -- Return pointer to first occurrence of CH in STR. - For Motorola 68000. - Copyright (C) 1999, 2003 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 Lesser General Public - License as published by the Free Software Foundation; either - version 2.1 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 - Lesser General Public License for more details. - - You should have received a copy of the GNU Lesser General Public - License along with the GNU C Library; 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) -libc_hidden_builtin_def (strchr) |