toolchain/gcc/newlib/libc/machine/m68k/strlen.c

   1 /*
   2  *  C library strlen routine
   3  *
   4  *  This routine has been optimized for the CPU32+.
   5  *  It should run on all 68k machines.
   6  *
   7  *  W. Eric Norum
   8  *  Saskatchewan Accelerator Laboratory
   9  *  University of Saskatchewan
  10  *  Saskatoon, Saskatchewan, CANADA
  11  *  eric@skatter.usask.ca
  12  */
  13
  14 #include <string.h>
  15
  16 /*
  17  * Test bytes using CPU32+ loop mode if possible.
  18  */
  19 size_t
  20 strlen (const char *str)
  21 {
  22         unsigned int n = ~0;
  23         const char *cp = str;
  24
  25         asm volatile ("1:\n"
  26              "\ttst.b (%0)+\n"
  27 #if defined(__mcpu32__)
  28              "\tdbeq %1,1b\n"
  29 #endif
  30              "\tbne.b 1b\n" :
  31                 "=a" (cp), "=d" (n) :
  32                  "0" (cp),  "1" (n) :
  33                  "cc");
  34         return (cp - str) - 1;
  35 }