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/*
* Copyright (c) 2008 ARM Ltd
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. The name of the company may not be used to endorse or promote
* products derived from this software without specific prior written
* permission.
*
* THIS SOFTWARE IS PROVIDED BY ARM LTD ``AS IS'' AND ANY EXPRESS OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL ARM LTD BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
* TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "arm_asm.h"
#include <_ansi.h>
#include <string.h>
#include <limits.h>
#if defined (__OPTIMIZE_SIZE__) || defined (PREFER_SIZE_OVER_SPEED) || \
(defined (__thumb__) && !defined (__thumb2__))
# if !defined (PREFER_SIZE_OVER_SPEED) && !defined (__OPTIMIZE_SIZE__)
/* Thumb1 only variant.
If speed is preferred, the strlen() function in ../../string/strlen.c
will be used.
Leave this field blank. So the strlen() is not defined, and this will
automatically pull in the default C definition of strlen() from
../../string/strlen.c. No need to include this file explicitely.
The lib_a-strlen.o will not be generated, so it won't replace the default
lib_a-strlen.o which is generated by ../../string/strlen.c. See the
commands in configure.in and Makefile.am for more details.
However, if we need to rewrite this function to be more efficient,
we can add the corresponding assembly code into this field and change
the commands in configure.in and Makefile.am to allow the corresponding
lib_a-strlen.o to be generated.
*/
# else
size_t
strlen (const char* str)
{
int scratch;
#if defined (__thumb__) && !defined (__thumb2__)
size_t len;
asm ("mov %0, #0\n"
"1:\n\t"
"ldrb %1, [%2, %0]\n\t"
"add %0, %0, #1\n\t"
"cmp %1, #0\n\t"
"bne 1b"
: "=&r" (len), "=&r" (scratch) : "r" (str) : "memory", "cc");
return len - 1;
#else
const char* end;
asm ("1:\n\t"
"ldrb %1, [%0], #1\n\t"
"cmp %1, #0\n\t"
"bne 1b"
: "=&r" (end), "=&r" (scratch) : "0" (str) : "memory", "cc");
return end - str - 1;
#endif
}
#endif
#else
#if !(defined(_ISA_ARM_7) || defined(__ARM_ARCH_6T2__))
size_t __attribute__((naked))
strlen (const char* str)
{
asm ("len .req r0\n\t"
"data .req r3\n\t"
"addr .req r1\n\t"
"optpld r0\n\t"
/* Word-align address */
"bic addr, r0, #3\n\t"
/* Get adjustment for start ... */
"ands len, r0, #3\n\t"
"neg len, len\n\t"
/* First word of data */
"ldr data, [addr], #4\n\t"
/* Ensure bytes preceeding start ... */
"add ip, len, #4\n\t"
"mov ip, ip, asl #3\n\t"
"mvn r2, #0\n\t"
/* ... are masked out */
#ifdef __thumb__
"itt ne\n\t"
# ifdef __ARMEB__
"lslne r2, ip\n\t"
# else
"lsrne r2, ip\n\t"
# endif
"orrne data, data, r2\n\t"
#else
"it ne\n\t"
# ifdef __ARMEB__
"orrne data, data, r2, lsl ip\n\t"
# else
"orrne data, data, r2, lsr ip\n\t"
# endif
#endif
/* Magic const 0x01010101 */
#ifdef _ISA_ARM_7
"movw ip, #0x101\n\t"
#else
"mov ip, #0x1\n\t"
"orr ip, ip, ip, lsl #8\n\t"
#endif
"orr ip, ip, ip, lsl #16\n"
/* This is the main loop. We subtract one from each byte in
the word: the sign bit changes iff the byte was zero or
0x80 -- we eliminate the latter case by anding the result
with the 1-s complement of the data. */
"1:\n\t"
/* test (data - 0x01010101) */
"sub r2, data, ip\n\t"
/* ... & ~data */
"bic r2, r2, data\n\t"
/* ... & 0x80808080 == 0? */
"ands r2, r2, ip, lsl #7\n\t"
#ifdef _ISA_ARM_7
/* yes, get more data... */
"itt eq\n\t"
"ldreq data, [addr], #4\n\t"
/* and 4 more bytes */
"addeq len, len, #4\n\t"
/* If we have PLD, then unroll the loop a bit. */
"optpld addr, #8\n\t"
/* test (data - 0x01010101) */
"ittt eq\n\t"
"subeq r2, data, ip\n\t"
/* ... & ~data */
"biceq r2, r2, data\n\t"
/* ... & 0x80808080 == 0? */
"andeqs r2, r2, ip, lsl #7\n\t"
#endif
"itt eq\n\t"
/* yes, get more data... */
"ldreq data, [addr], #4\n\t"
/* and 4 more bytes */
"addeq len, len, #4\n\t"
"beq 1b\n\t"
#ifdef __ARMEB__
"tst data, #0xff000000\n\t"
"itttt ne\n\t"
"addne len, len, #1\n\t"
"tstne data, #0xff0000\n\t"
"addne len, len, #1\n\t"
"tstne data, #0xff00\n\t"
"it ne\n\t"
"addne len, len, #1\n\t"
#else
# ifdef _ISA_ARM_5
/* R2 is the residual sign bits from the above test. All we
need to do now is establish the position of the first zero
byte... */
/* Little-endian is harder, we need the number of trailing
zeros / 8 */
# ifdef _ISA_ARM_7
"rbit r2, r2\n\t"
"clz r2, r2\n\t"
# else
"rsb r1, r2, #0\n\t"
"and r2, r2, r1\n\t"
"clz r2, r2\n\t"
"rsb r2, r2, #31\n\t"
# endif
"add len, len, r2, lsr #3\n\t"
# else /* No CLZ instruction */
"tst data, #0xff\n\t"
"itttt ne\n\t"
"addne len, len, #1\n\t"
"tstne data, #0xff00\n\t"
"addne len, len, #1\n\t"
"tstne data, #0xff0000\n\t"
"it ne\n\t"
"addne len, len, #1\n\t"
# endif
#endif
"RETURN");
}
#endif
#endif
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