diff options
Diffstat (limited to 'libc/string/i386/memmove.c')
| -rw-r--r-- | libc/string/i386/memmove.c | 52 |
1 files changed, 32 insertions, 20 deletions
diff --git a/libc/string/i386/memmove.c b/libc/string/i386/memmove.c index a924efcbc..cd746e804 100644 --- a/libc/string/i386/memmove.c +++ b/libc/string/i386/memmove.c @@ -32,28 +32,40 @@ #include <string.h> -/* Experimentally off - libc_hidden_proto(memmove) */ +#undef memmove +//#define memmove TESTING void *memmove(void *dest, const void *src, size_t n) { - int d0, d1, d2; - if (dest<src) + int eax, ecx, esi, edi; __asm__ __volatile__( - "rep\n\t" - "movsb" - : "=&c" (d0), "=&S" (d1), "=&D" (d2) - :"0" (n),"1" (src),"2" (dest) - : "memory"); - else - __asm__ __volatile__( - "std\n\t" - "rep\n\t" - "movsb\n\t" - "cld" - : "=&c" (d0), "=&S" (d1), "=&D" (d2) - :"0" (n), - "1" (n-1+(const char *)src), - "2" (n-1+(char *)dest) - :"memory"); - return dest; + " movl %%eax, %%edi\n" + " cmpl %%esi, %%eax\n" + " je 2f\n" /* (optional) src == dest -> NOP */ + " jb 1f\n" /* src > dest -> simple copy */ + " leal -1(%%esi,%%ecx), %%esi\n" + " leal -1(%%eax,%%ecx), %%edi\n" + " std\n" + "1: rep; movsb\n" + " cld\n" + "2:\n" + : "=&c" (ecx), "=&S" (esi), "=&a" (eax), "=&D" (edi) + : "0" (n), "1" (src), "2" (dest) + : "memory" + ); + return (void*)eax; } +#ifndef memmove libc_hidden_def(memmove) +#else +/* Uncomment TESTING, gcc -D__USE_GNU -m32 -Os memmove.c -o memmove + * and run ./memmove + */ +int main() +{ + static char str[] = "abcdef.123"; + memmove(str + 1, str, 5); + printf(strcmp(str, "aabcde.123") == 0 ? "ok\n" : "BAD!\n"); + memmove(str, str + 1, 5); + printf(strcmp(str, "abcdee.123") == 0 ? "ok\n" : "BAD!\n"); +} +#endif |