toolchain/gcc/newlib/libc/machine/mips/strcmp.c

   1 /*
   2  * strcmp.c -- strcmp function.  On at least some MIPS chips, a strcmp that is
   3  * unrolled twice is faster than the 'optimized' C version in newlib.
   4  *
   5  * Copyright (c) 2001 Red Hat, Inc.
   6  *
   7  * The authors hereby grant permission to use, copy, modify, distribute,
   8  * and license this software and its documentation for any purpose, provided
   9  * that existing copyright notices are retained in all copies and that this
  10  * notice is included verbatim in any distributions. No written agreement,
  11  * license, or royalty fee is required for any of the authorized uses.
  12  * Modifications to this software may be copyrighted by their authors
  13  * and need not follow the licensing terms described here, provided that
  14  * the new terms are clearly indicated on the first page of each file where
  15  * they apply.  */
  16
  17 #include <stddef.h>
  18 #include <string.h>
  19 #include <stdlib.h>
  20
  21 int
  22 strcmp (const char *s1, const char *s2)
  23 {
  24   unsigned const char *us1 = (unsigned const char *)s1;
  25   unsigned const char *us2 = (unsigned const char *)s2;
  26   int c1a, c1b;
  27   int c2a, c2b;
  28
  29   /* If the pointers aren't both aligned to a 16-byte boundary, do the
  30      comparison byte by byte, so that we don't get an invalid page fault if we
  31      are comparing a string whose null byte is at the last byte on the last
  32      valid page.  */
  33   if (((((long)us1) | ((long)us2)) & 1) == 0)
  34     {
  35       c1a = *us1;
  36       for (;;)
  37         {
  38           c1b = *us2;
  39           us1 += 2;
  40           if (c1a == '\0')
  41             goto ret1;
  42
  43           c2a = us1[-1];
  44           if (c1a != c1b)
  45             goto ret1;
  46
  47           c2b = us2[1];
  48           us2 += 2;
  49           if (c2a == '\0')
  50             break;
  51
  52           c1a = *us1;
  53           if (c2a != c2b)
  54             break;
  55         }
  56
  57       return c2a - c2b;
  58     }
  59   else
  60     {
  61       do
  62         {
  63           c1a = *us1++;
  64           c1b = *us2++;
  65         }
  66       while (c1a != '\0' && c1a == c1b);
  67     }
  68
  69  ret1:
  70   return c1a - c1b;
  71 }