glibc/sysdeps/arm/strlen.S

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/* Copyright (C) 1998-2024 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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
License as published by the Free Software Foundation; either
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,
but WITHOUT ANY WARRANTY; without even the implied warranty of
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
Prefer https to http for gnu.org and fsf.org URLs Also, change sources.redhat.com to sourceware.org. This patch was automatically generated by running the following shell script, which uses GNU sed, and which avoids modifying files imported from upstream: sed -ri ' s,(http|ftp)(://(.*\.)?(gnu|fsf|sourceware)\.org($|[^.]|\.[^a-z])),https\2,g s,(http|ftp)(://(.*\.)?)sources\.redhat\.com($|[^.]|\.[^a-z]),https\2sourceware.org\4,g ' \ $(find $(git ls-files) -prune -type f \ ! -name '*.po' \ ! -name 'ChangeLog*' \ ! -path COPYING ! -path COPYING.LIB \ ! -path manual/fdl-1.3.texi ! -path manual/lgpl-2.1.texi \ ! -path manual/texinfo.tex ! -path scripts/config.guess \ ! -path scripts/config.sub ! -path scripts/install-sh \ ! -path scripts/mkinstalldirs ! -path scripts/move-if-change \ ! -path INSTALL ! -path locale/programs/charmap-kw.h \ ! -path po/libc.pot ! -path sysdeps/gnu/errlist.c \ ! '(' -name configure \ -execdir test -f configure.ac -o -f configure.in ';' ')' \ ! '(' -name preconfigure \ -execdir test -f preconfigure.ac ';' ')' \ -print) and then by running 'make dist-prepare' to regenerate files built from the altered files, and then executing the following to cleanup: chmod a+x sysdeps/unix/sysv/linux/riscv/configure # Omit irrelevant whitespace and comment-only changes, # perhaps from a slightly-different Autoconf version. git checkout -f \ sysdeps/csky/configure \ sysdeps/hppa/configure \ sysdeps/riscv/configure \ sysdeps/unix/sysv/linux/csky/configure # Omit changes that caused a pre-commit check to fail like this: # remote: *** error: sysdeps/powerpc/powerpc64/ppc-mcount.S: trailing lines git checkout -f \ sysdeps/powerpc/powerpc64/ppc-mcount.S \ sysdeps/unix/sysv/linux/s390/s390-64/syscall.S # Omit change that caused a pre-commit check to fail like this: # remote: *** error: sysdeps/sparc/sparc64/multiarch/memcpy-ultra3.S: last line does not end in newline git checkout -f sysdeps/sparc/sparc64/multiarch/memcpy-ultra3.S
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<https://www.gnu.org/licenses/>. */
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/* Thumb requires excessive IT insns here. */
#define NO_THUMB
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#include <sysdep.h>
/* size_t strlen(const char *S)
* entry: r0 -> string
* exit: r0 = len
*/
.syntax unified
.text
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ENTRY(strlen)
bic r1, r0, $3 @ addr of word containing first byte
ldr r2, [r1], $4 @ get the first word
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ands r3, r0, $3 @ how many bytes are duff?
rsb r0, r3, $0 @ get - that number into counter.
beq Laligned @ skip into main check routine if no
@ more
#ifdef __ARMEB__
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orr r2, r2, $0xff000000 @ set this byte to non-zero
subs r3, r3, $1 @ any more to do?
orrgt r2, r2, $0x00ff0000 @ if so, set this byte
subs r3, r3, $1 @ more?
orrgt r2, r2, $0x0000ff00 @ then set.
#else
orr r2, r2, $0x000000ff @ set this byte to non-zero
subs r3, r3, $1 @ any more to do?
orrgt r2, r2, $0x0000ff00 @ if so, set this byte
subs r3, r3, $1 @ more?
orrgt r2, r2, $0x00ff0000 @ then set.
#endif
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Laligned: @ here, we have a word in r2. Does it
tst r2, $0x000000ff @ contain any zeroes?
tstne r2, $0x0000ff00 @
tstne r2, $0x00ff0000 @
tstne r2, $0xff000000 @
addne r0, r0, $4 @ if not, the string is 4 bytes longer
ldrne r2, [r1], $4 @ and we continue to the next word
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bne Laligned @
Llastword: @ drop through to here once we find a
#ifdef __ARMEB__
tst r2, $0xff000000 @ word that has a zero byte in it
addne r0, r0, $1 @
tstne r2, $0x00ff0000 @ and add up to 3 bytes on to it
addne r0, r0, $1 @
tstne r2, $0x0000ff00 @ (if first three all non-zero, 4th
addne r0, r0, $1 @ must be zero)
#else
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tst r2, $0x000000ff @ word that has a zero byte in it
addne r0, r0, $1 @
tstne r2, $0x0000ff00 @ and add up to 3 bytes on to it
addne r0, r0, $1 @
tstne r2, $0x00ff0000 @ (if first three all non-zero, 4th
addne r0, r0, $1 @ must be zero)
#endif
DO_RET(lr)
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END(strlen)
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libc_hidden_builtin_def (strlen)