| /* |
| * 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> |
| #include <machine/cpu-features.h> |
| |
| size_t strlen(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" |
| "it eq \n" |
| "ldreq %[v], [%[s]], #4 \n" |
| #if !defined(__OPTIMIZE_SIZE__) |
| "bne 1f \n" |
| "sub %[t], %[v], %[mask], lsr #7\n" |
| "and %[t], %[t], %[mask] \n" |
| "bics %[t], %[t], %[v] \n" |
| "it eq \n" |
| "ldreq %[v], [%[s]], #4 \n" |
| "bne 1f \n" |
| "sub %[t], %[v], %[mask], lsr #7\n" |
| "and %[t], %[t], %[mask] \n" |
| "bics %[t], %[t], %[v] \n" |
| "it eq \n" |
| "ldreq %[v], [%[s]], #4 \n" |
| "bne 1f \n" |
| "sub %[t], %[v], %[mask], lsr #7\n" |
| "and %[t], %[t], %[mask] \n" |
| "bics %[t], %[t], %[v] \n" |
| "it eq \n" |
| "ldreq %[v], [%[s]], #4 \n" |
| "bne 1f \n" |
| "sub %[t], %[v], %[mask], lsr #7\n" |
| "and %[t], %[t], %[mask] \n" |
| "bics %[t], %[t], %[v] \n" |
| "it eq \n" |
| "ldreq %[v], [%[s]], #4 \n" |
| "bne 1f \n" |
| "sub %[t], %[v], %[mask], lsr #7\n" |
| "and %[t], %[t], %[mask] \n" |
| "bics %[t], %[t], %[v] \n" |
| "it eq \n" |
| "ldreq %[v], [%[s]], #4 \n" |
| "bne 1f \n" |
| "sub %[t], %[v], %[mask], lsr #7\n" |
| "and %[t], %[t], %[mask] \n" |
| "bics %[t], %[t], %[v] \n" |
| "it eq \n" |
| "ldreq %[v], [%[s]], #4 \n" |
| "bne 1f \n" |
| "sub %[t], %[v], %[mask], lsr #7\n" |
| "and %[t], %[t], %[mask] \n" |
| "bics %[t], %[t], %[v] \n" |
| "it eq \n" |
| "ldreq %[v], [%[s]], #4 \n" |
| #endif |
| "beq 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; |
| } |