| /* |
| * 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 |
