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/*
* Copyright (C) 2008 The Android Open Source Project
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * 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.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "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 THE
* COPYRIGHT OWNER OR CONTRIBUTORS 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 <string.h>
#include <stdint.h>
size_t strlen_generic(const char *s)
{
__builtin_prefetch(s);
__builtin_prefetch(s+32);
union {
const char *b;
const uint32_t *w;
uintptr_t i;
} u;
// these are some scratch variables for the asm code below
uint32_t v, t;
// initialize the string length to zero
size_t l = 0;
// align the pointer to a 32-bit word boundary
u.b = s;
while (u.i & 0x3) {
if (__builtin_expect(*u.b++ == 0, 0)) {
goto done;
}
l++;
}
// loop for each word, testing if it contains a zero byte
// if so, exit the loop and update the length.
// We need to process 32 bytes per loop to schedule PLD properly
// and achieve the maximum bus speed.
asm(
"ldr %[v], [%[s]], #4 \n"
"sub %[l], %[l], %[s] \n"
"0: \n"
"pld [%[s], #64] \n"
"sub %[t], %[v], %[mask], lsr #7\n"
"and %[t], %[t], %[mask] \n"
"bics %[t], %[t], %[v] \n"
"bne 1f \n"
"ldr %[v], [%[s]], #4 \n"
#if !defined(__OPTIMIZE_SIZE__)
"sub %[t], %[v], %[mask], lsr #7\n"
"and %[t], %[t], %[mask] \n"
"bics %[t], %[t], %[v] \n"
"bne 1f \n"
"ldr %[v], [%[s]], #4 \n"
"sub %[t], %[v], %[mask], lsr #7\n"
"and %[t], %[t], %[mask] \n"
"bics %[t], %[t], %[v] \n"
"bne 1f \n"
"ldr %[v], [%[s]], #4 \n"
"sub %[t], %[v], %[mask], lsr #7\n"
"and %[t], %[t], %[mask] \n"
"bics %[t], %[t], %[v] \n"
"bne 1f \n"
"ldr %[v], [%[s]], #4 \n"
"sub %[t], %[v], %[mask], lsr #7\n"
"and %[t], %[t], %[mask] \n"
"bics %[t], %[t], %[v] \n"
"bne 1f \n"
"ldr %[v], [%[s]], #4 \n"
"sub %[t], %[v], %[mask], lsr #7\n"
"and %[t], %[t], %[mask] \n"
"bics %[t], %[t], %[v] \n"
"bne 1f \n"
"ldr %[v], [%[s]], #4 \n"
"sub %[t], %[v], %[mask], lsr #7\n"
"and %[t], %[t], %[mask] \n"
"bics %[t], %[t], %[v] \n"
"bne 1f \n"
"ldr %[v], [%[s]], #4 \n"
"sub %[t], %[v], %[mask], lsr #7\n"
"and %[t], %[t], %[mask] \n"
"bics %[t], %[t], %[v] \n"
"bne 1f \n"
"ldr %[v], [%[s]], #4 \n"
#endif
"b 0b \n"
"1: \n"
"add %[l], %[l], %[s] \n"
"tst %[v], #0xFF \n"
"beq 2f \n"
"add %[l], %[l], #1 \n"
"tst %[v], #0xFF00 \n"
"beq 2f \n"
"add %[l], %[l], #1 \n"
"tst %[v], #0xFF0000 \n"
"it ne \n"
"addne %[l], %[l], #1 \n"
"2: \n"
: [l]"=&r"(l), [v]"=&r"(v), [t]"=&r"(t), [s]"=&r"(u.b)
: "%[l]"(l), "%[s]"(u.b), [mask]"r"(0x80808080UL)
: "cc"
);
done:
return l;
}
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