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1998-07-16 10:23 Ulrich Drepper <drepper@cygnus.com> * argp/argp-fmtstream.c: Unify names of used global functions. * argp/argp-help.c: Likewise. * assert/assert-perr.c: Likewise * assert/assert.c: Likewise * dirent/scandir.c: Likewise * dirent/scandir64.c: Likewise * dirent/versionsort.c: Likewise * dirent/versionsort64.c: Likewise * gmon/bb_exit_func.c: Likewise. * gmon/gmon.c: Likewise. * grp/initgroups.c: Likewise. * iconv/gconv_conf.c: Likewise. * inet/getnameinfo.c: Likewise. * inet/getnetgrent_r.c: Likewise. * inet/inet_ntoa.c: Likewise. * inet/rcmd.c: Likewise. * inet/rexec.c: Likewise. * inet/ruserpass.c: Likewise. * io/fts.c: Likewise. * io/ftw.c: Likewise. * io/ftw64.c: Likewise. * io/getdirname.c: Likewise. * io/getwd.c: Likewise. * io/lockf.c: Likewise. * libio/iofdopen.c: Likewise. * libio/iopopen.c: Likewise. * login/utmp_daemon.c: Likewise. * malloc/mtrace.c: Likewise. * malloc/obstack.c * misc/daemon.c: Likewise. * misc/efgcvt_r.c: Likewise. * misc/err.c: Likewise. * misc/error.c: Likewise. * misc/fstab.c: Likewise. * misc/getpass.c: Likewise. * misc/getttyent.c: Likewise. * misc/mntent_r.c: Likewise. * misc/search.h: Likewise. * misc/syslog.c: Likewise. * nscd/nscd_getgr_r.c: Likewise. * nscd/nscd_getpw_r.c: Likewise. * posix/getpgrp.c: Likewise. * posix/wordexp.c: Likewise. * pwd/fgetpwent_r.c: Likewise. * pwd/getpw.c: Likewise. * resolv/herror.c: Likewise. * resolv/res_init.c: Likewise. * shadow/fgetspent_r.c: Likewise. * shadow/lckpwdf.c: Likewise. * signal/sigrelse.c: Likewise. * stdio-common/asprintf.c: Likewise. * stdio-common/dprintf.c: Likewise. * stdio-common/getw.c: Likewise. * stdio-common/putw.c: Likewise. * stdio-common/snprintf.c: Likewise. * stdio-common/sprintf.c: Likewise. * stdio-common/sscanf.c: Likewise. * stdlib/lrand48_r.c: Likewise. * stdlib/mrand48_r.c: Likewise. * string/argz-replace.c: Likewise. * string/envz.c: Likewise. * sunrpc/auth_des.c: Likewise. * sunrpc/auth_unix.c: Likewise. * sunrpc/bindrsvprt.c: Likewise. * sunrpc/clnt_gen.c: Likewise. * sunrpc/clnt_perr.c: Likewise. * sunrpc/clnt_simp.c: Likewise. * sunrpc/clnt_tcp.c: Likewise. * sunrpc/clnt_udp.c: Likewise. * sunrpc/get_myaddr.c: Likewise. * sunrpc/key_call.c: Likewise. * sunrpc/netname.c: Likewise. * sunrpc/openchild.c: Likewise. * sunrpc/pmap_rmt.c: Likewise. * sunrpc/rpc_dtable.c: Likewise. * sunrpc/rtime.c: Likewise. * sunrpc/svc_run.c: Likewise. * sunrpc/svc_simple.c: Likewise. * sunrpc/svc_tcp.c: Likewise. * sunrpc/svc_udp.c: Likewise. * sunrpc/svcauth_des.c: Likewise. * sunrpc/xdr_array.c: Likewise. * sunrpc/xdr_rec.c: Likewise. * sunrpc/xdr_ref.c: Likewise. * sunrpc/xdr_stdio.c: Likewise. * sysdeps/generic/abort.c: Likewise. * sysdeps/generic/dl-sysdep.c: Likewise. * sysdeps/generic/fstatfs64.c: Likewise. * sysdeps/generic/ftruncate64.c: Likewise. * sysdeps/generic/getrlimit64.c: Likewise. * sysdeps/generic/glob.c: Likewise. * sysdeps/generic/prof-freq.c: Likewise. * sysdeps/generic/putenv.c: Likewise. * sysdeps/generic/statfs64.c: Likewise. * sysdeps/generic/ttyname_r.c: Likewise. * sysdeps/generic/utmp_file.c: Likewise. * sysdeps/generic/vlimit.c: Likewise. * sysdeps/generic/vtimes.c: Likewise. * sysdeps/posix/cuserid.c: Likewise. * sysdeps/posix/euidaccess.c: Likewise. * sysdeps/posix/mkstemp.c: Likewise. * sysdeps/posix/mktemp.c: Likewise. * sysdeps/posix/pread.c: Likewise. * sysdeps/posix/pread64.c: Likewise. * sysdeps/posix/profil.c: Likewise. * sysdeps/posix/pwrite.c: Likewise. * sysdeps/posix/pwrite64.c: Likewise. * sysdeps/posix/sigblock.c: Likewise. * sysdeps/posix/sigpause.c: Likewise. * sysdeps/posix/ttyname.c: Likewise. * sysdeps/posix/ttyname_r.c: Likewise. * sysdeps/posix/waitid.c: Likewise. * sysdeps/unix/getlogin_r.c: Likewise. * sysdeps/unix/grantpt.c: Likewise. * sysdeps/unix/rewinddir.c: Likewise. * sysdeps/unix/sysv/linux/gethostid.c: Likewise. * sysdeps/unix/sysv/linux/getpt.c: Likewise. * sysdeps/unix/sysv/linux/if_index.c: Likewise. * sysdeps/unix/sysv/linux/ptsname.c: Likewise. * sysdeps/unix/sysv/linux/sendmsg.c: Likewise. * sysdeps/unix/sysv/linux/statvfs.c: Likewise. * sysdeps/unix/sysv/linux/ttyname.c: Likewise. * sysdeps/unix/sysv/linux/ttyname_r.c: Likewise. * sysdeps/unix/sysv/linux/ulimit.c: Likewise. * sysdeps/unix/sysv/linux/unlockpt.c: Likewise. * sysvipc/sys/shm.h: Likewise. * time/ctime_r.c: Likewise. * time/strptime.c: Likewise. * wcsmbs/mbrlen.c: Likewise. * wcsmbs/wcsdup.c: Likewise. * wcsmbs/wcsxfrm.c: Likewise. * wctype/wcfuncs.c: Likewise. * sysdeps/unix/sysv/linux/i386/socker.S: Change to honor NO_WEAK_ALIAS. * sysdeps/unix/sysv/linux/accept.S: Don't generate __ name. * sysdeps/unix/sysv/linux/bind.S: Likewise. * sysdeps/unix/sysv/linux/getsockname.S: Likewise. * sysdeps/unix/sysv/linux/listen.S: Likewise. * sysdeps/unix/sysv/linux/recvfrom.S: Likewise. * sysdeps/unix/sysv/linux/sendto.S: Likewise. * sysdeps/unix/sysv/linux/setsockopt.S: Likewise. * grp/fgetgrent_r.c: Use explicit locking of the stream. * elf/Makefile (rtld-routines): Add dl-environ. * sysdeps/generic/dl-environ.c: New file. * libio/Makefile [REENTRANT] (routines): Add iofputs_u. * libio/Versions: Add fputs_unlocked. * libio/iofputs_u.c: New file. * libio/stdio.h: Add prototype for fputs_unlocked. * sunrpc/rpc/auth.h: Use __PMT instead of __P in type definitions. * sunrpc/rpc/clnt.h: Likewise. * sunrpc/rpc/pmap_clnt.h: Likewise. * sunrpc/rpc/svc.h: Likewise. * sunrpc/rpc/xdr.h: Likewise. * sysdeps/i386/memchr.S: Correct for more strict gas. * sysdeps/i386/fpu/bits/mathinline.h: Likewise. * sysdeps/libm-i387/i686/s_fdim.S: Likewise. * sysdeps/libm-i387/i686/s_fdimf.S: Likewise. * sysdeps/libm-i387/i686/s_fdiml.S: Likewise. 1998-07-15 Andreas Jaeger <aj@arthur.rhein-neckar.de> * configure.in: Change message for binutils version from 2.8.1.0.17->2.8.1.0.23. 1998-07-15 Ulrich Drepper <drepper@cygnus.com> * sysdeps/unix/sysv/sysv4/solaris2/sparc/sysdep.h: Define LOC. Patch by John Tobey <jtobey@banta-im.com>.
317 lines
12 KiB
ArmAsm
317 lines
12 KiB
ArmAsm
/* memchr (str, ch, n) -- Return pointer to first occurrence of CH in STR less
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than N.
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For Intel 80x86, x>=3.
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Copyright (C) 1994, 1995, 1996, 1997, 1998 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Ulrich Drepper <drepper@gnu.ai.mit.edu>
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Optimised a little by Alan Modra <Alan@SPRI.Levels.UniSA.Edu.Au>
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This version is developed using the same algorithm as the fast C
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version which carries the following introduction:
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Based on strlen implementation by Torbjorn Granlund (tege@sics.se),
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with help from Dan Sahlin (dan@sics.se) and
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commentary by Jim Blandy (jimb@ai.mit.edu);
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adaptation to memchr suggested by Dick Karpinski (dick@cca.ucsf.edu),
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and implemented by Roland McGrath (roland@ai.mit.edu).
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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 Library General Public License as
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published by the Free Software Foundation; either version 2 of the
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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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Library General Public License for more details.
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You should have received a copy of the GNU Library General Public
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License along with the GNU C Library; see the file COPYING.LIB. If not,
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write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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Boston, MA 02111-1307, USA. */
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#include <sysdep.h>
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#include "asm-syntax.h"
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/*
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INPUT PARAMETERS:
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str (sp + 4)
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c (sp + 8)
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len (sp + 12)
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*/
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.text
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ENTRY (memchr)
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/* Save callee-safe registers used in this function. */
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pushl %esi
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pushl %edi
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/* Load parameters into registers. */
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movl 12(%esp), %eax /* str: pointer to memory block. */
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movl 16(%esp), %edx /* c: byte we are looking for. */
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movl 20(%esp), %esi /* len: length of memory block. */
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/* If my must not test more than three characters test
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them one by one. This is especially true for 0. */
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cmpl $4, %esi
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jb L(3)
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/* At the moment %edx contains C. What we need for the
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algorithm is C in all bytes of the dword. Avoid
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operations on 16 bit words because these require an
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prefix byte (and one more cycle). */
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movb %dl, %dh /* Now it is 0|0|c|c */
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movl %edx, %ecx
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shll $16, %edx /* Now c|c|0|0 */
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movw %cx, %dx /* And finally c|c|c|c */
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/* Better performance can be achieved if the word (32
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bit) memory access is aligned on a four-byte-boundary.
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So process first bytes one by one until boundary is
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reached. Don't use a loop for better performance. */
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testb $3, %al /* correctly aligned ? */
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je L(2) /* yes => begin loop */
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cmpb %dl, (%eax) /* compare byte */
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je L(9) /* target found => return */
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incl %eax /* increment source pointer */
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decl %esi /* decrement length counter */
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je L(4) /* len==0 => return NULL */
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testb $3, %al /* correctly aligned ? */
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je L(2) /* yes => begin loop */
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cmpb %dl, (%eax) /* compare byte */
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je L(9) /* target found => return */
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incl %eax /* increment source pointer */
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decl %esi /* decrement length counter */
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je L(4) /* len==0 => return NULL */
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testb $3, %al /* correctly aligned ? */
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je L(2) /* yes => begin loop */
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cmpb %dl, (%eax) /* compare byte */
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je L(9) /* target found => return */
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incl %eax /* increment source pointer */
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decl %esi /* decrement length counter */
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/* no test for len==0 here, because this is done in the
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loop head */
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jmp L(2)
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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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/* Each round the main loop processes 16 bytes. */
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ALIGN (4)
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L(1): movl (%eax), %ecx /* get word (= 4 bytes) in question */
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movl $0xfefefeff, %edi /* magic value */
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xorl %edx, %ecx /* XOR with word c|c|c|c => bytes of str == c
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are now 0 */
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addl %ecx, %edi /* add the magic value to the word. We get
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carry bits reported for each byte which
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is *not* 0 */
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/* According to the algorithm we had to reverse the effect of the
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XOR first and then test the overflow bits. But because the
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following XOR would destroy the carry flag and it would (in a
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representation with more than 32 bits) not alter then last
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overflow, we can now test this condition. If no carry is signaled
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no overflow must have occurred in the last byte => it was 0. */
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jnc L(8)
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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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xorl %ecx, %edi /* ((word^charmask)+magic)^(word^charmask) */
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/* Now test for the other three overflow bits. */
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orl $0xfefefeff, %edi /* set all non-carry bits */
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incl %edi /* add 1: if one carry bit was *not* set
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the addition will not result in 0. */
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/* If at least one byte of the word is C we don't get 0 in %edi. */
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jnz L(8) /* found it => return pointer */
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/* This process is unfolded four times for better performance.
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we don't increment the source pointer each time. Instead we
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use offsets and increment by 16 in each run of the loop. But
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before probing for the matching byte we need some extra code
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(following LL(13) below). Even the len can be compared with
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constants instead of decrementing each time. */
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movl 4(%eax), %ecx /* get word (= 4 bytes) in question */
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movl $0xfefefeff, %edi /* magic value */
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xorl %edx, %ecx /* XOR with word c|c|c|c => bytes of str == c
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are now 0 */
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addl %ecx, %edi /* add the magic value to the word. We get
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carry bits reported for each byte which
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is *not* 0 */
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jnc L(7) /* highest byte is C => return pointer */
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xorl %ecx, %edi /* ((word^charmask)+magic)^(word^charmask) */
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orl $0xfefefeff, %edi /* set all non-carry bits */
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incl %edi /* add 1: if one carry bit was *not* set
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the addition will not result in 0. */
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jnz L(7) /* found it => return pointer */
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movl 8(%eax), %ecx /* get word (= 4 bytes) in question */
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movl $0xfefefeff, %edi /* magic value */
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xorl %edx, %ecx /* XOR with word c|c|c|c => bytes of str == c
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are now 0 */
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addl %ecx, %edi /* add the magic value to the word. We get
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carry bits reported for each byte which
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is *not* 0 */
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jnc L(6) /* highest byte is C => return pointer */
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xorl %ecx, %edi /* ((word^charmask)+magic)^(word^charmask) */
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orl $0xfefefeff, %edi /* set all non-carry bits */
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incl %edi /* add 1: if one carry bit was *not* set
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the addition will not result in 0. */
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jnz L(6) /* found it => return pointer */
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movl 12(%eax), %ecx /* get word (= 4 bytes) in question */
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movl $0xfefefeff, %edi /* magic value */
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xorl %edx, %ecx /* XOR with word c|c|c|c => bytes of str == c
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are now 0 */
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addl %ecx, %edi /* add the magic value to the word. We get
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carry bits reported for each byte which
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is *not* 0 */
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jnc L(5) /* highest byte is C => return pointer */
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xorl %ecx, %edi /* ((word^charmask)+magic)^(word^charmask) */
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orl $0xfefefeff, %edi /* set all non-carry bits */
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incl %edi /* add 1: if one carry bit was *not* set
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the addition will not result in 0. */
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jnz L(5) /* found it => return pointer */
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/* Adjust both counters for a full round, i.e. 16 bytes. */
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addl $16, %eax
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L(2): subl $16, %esi
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jae L(1) /* Still more than 16 bytes remaining */
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/* Process remaining bytes separately. */
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cmpl $4-16, %esi /* rest < 4 bytes? */
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jb L(3) /* yes, than test byte by byte */
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movl (%eax), %ecx /* get word (= 4 bytes) in question */
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movl $0xfefefeff, %edi /* magic value */
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xorl %edx, %ecx /* XOR with word c|c|c|c => bytes of str == c
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are now 0 */
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addl %ecx, %edi /* add the magic value to the word. We get
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carry bits reported for each byte which
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is *not* 0 */
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jnc L(8) /* highest byte is C => return pointer */
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xorl %ecx, %edi /* ((word^charmask)+magic)^(word^charmask) */
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orl $0xfefefeff, %edi /* set all non-carry bits */
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incl %edi /* add 1: if one carry bit was *not* set
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the addition will not result in 0. */
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jne L(8) /* found it => return pointer */
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addl $4, %eax /* adjust source pointer */
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cmpl $8-16, %esi /* rest < 8 bytes? */
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jb L(3) /* yes, than test byte by byte */
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movl (%eax), %ecx /* get word (= 4 bytes) in question */
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movl $0xfefefeff, %edi /* magic value */
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xorl %edx, %ecx /* XOR with word c|c|c|c => bytes of str == c
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are now 0 */
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addl %ecx, %edi /* add the magic value to the word. We get
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carry bits reported for each byte which
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is *not* 0 */
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jnc L(8) /* highest byte is C => return pointer */
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xorl %ecx, %edi /* ((word^charmask)+magic)^(word^charmask) */
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orl $0xfefefeff, %edi /* set all non-carry bits */
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incl %edi /* add 1: if one carry bit was *not* set
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the addition will not result in 0. */
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jne L(8) /* found it => return pointer */
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addl $4, %eax /* adjust source pointer */
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cmpl $12-16, %esi /* rest < 12 bytes? */
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jb L(3) /* yes, than test byte by byte */
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movl (%eax), %ecx /* get word (= 4 bytes) in question */
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movl $0xfefefeff, %edi /* magic value */
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xorl %edx, %ecx /* XOR with word c|c|c|c => bytes of str == c
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are now 0 */
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addl %ecx, %edi /* add the magic value to the word. We get
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carry bits reported for each byte which
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is *not* 0 */
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jnc L(8) /* highest byte is C => return pointer */
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xorl %ecx, %edi /* ((word^charmask)+magic)^(word^charmask) */
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orl $0xfefefeff, %edi /* set all non-carry bits */
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incl %edi /* add 1: if one carry bit was *not* set
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the addition will not result in 0. */
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jne L(8) /* found it => return pointer */
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addl $4, %eax /* adjust source pointer */
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/* Check the remaining bytes one by one. */
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L(3): andl $3, %esi /* mask out uninteresting bytes */
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jz L(4) /* no remaining bytes => return NULL */
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cmpb %dl, (%eax) /* compare byte with C */
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je L(9) /* equal, than return pointer */
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incl %eax /* increment source pointer */
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decl %esi /* decrement length */
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jz L(4) /* no remaining bytes => return NULL */
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cmpb %dl, (%eax) /* compare byte with C */
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je L(9) /* equal, than return pointer */
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incl %eax /* increment source pointer */
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decl %esi /* decrement length */
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jz L(4) /* no remaining bytes => return NULL */
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cmpb %dl, (%eax) /* compare byte with C */
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je L(9) /* equal, than return pointer */
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L(4): /* no byte found => return NULL */
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xorl %eax, %eax
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jmp L(9)
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/* add missing source pointer increments */
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L(5): addl $4, %eax
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L(6): addl $4, %eax
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L(7): addl $4, %eax
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/* Test for the matching byte in the word. %ecx contains a NUL
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char in the byte which originally was the byte we are looking
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at. */
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L(8): testb %cl, %cl /* test first byte in dword */
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jz L(9) /* if zero => return pointer */
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incl %eax /* increment source pointer */
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testb %ch, %ch /* test second byte in dword */
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jz L(9) /* if zero => return pointer */
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incl %eax /* increment source pointer */
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|
|
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testl $0xff0000, %ecx /* test third byte in dword */
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jz L(9) /* if zero => return pointer */
|
|
incl %eax /* increment source pointer */
|
|
|
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/* No further test needed we we know it is one of the four bytes. */
|
|
|
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L(9): popl %edi /* pop saved registers */
|
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popl %esi
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|
|
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ret
|
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END (memchr)
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