Re: Add memory clobber for i486 string inlines

[Andreas Jaeger <aj at suse dot de>]

Richard Henderson <rth@redhat.com> writes:

> On Tue, Mar 12, 2002 at 08:38:51PM +0100, Andreas Jaeger wrote:
>> As Richard Henderson mentioned on the gcc list (see:
>> http://gcc.gnu.org/ml/gcc-patches/2002-03/msg00534.html), we need to
>> add a memory clobber even for reading memory.
>
> Err, no, I said you should describe the read from memory.
> For memcmp you have the length of the access; for the others
> you can just use an array size of 0xffffffff or something.

A length of 0xffffffff does not work, it gives:
str.c:56: size of array `__x' is too large
I used one f less.

But the following two examples compile.  Are these ok?

void *
memcpy_g (void *__dest, __const void *__src, size_t __n)
{
  register unsigned long int __d0, __d1, __d2;
  register void *__tmp = __dest;

  __asm__ __volatile__
    ("cld\n\t"
     "shrl	$1,%%ecx\n\t"
     "jnc	1f\n\t"
     "movsb\n"
     "1:\n\t"
     "shrl	$1,%%ecx\n\t"
     "jnc	2f\n\t"
     "movsw\n"
     "2:\n\t"
     "rep; movsl"
     : "=&c" (__d0), "=&D" (__d1), "=&S" (__d2),
       "=m" ( *(struct { char __x[__n]; } *)__dest)
     : "0" (__n), "1" (__tmp), "2" (__src),
       "m" ( *(struct { char __x[__n]; } *)__src)
     : "cc");
  return __dest;
}

char *
__strpbrk_g (__const char *__s, __const char *__accept)
{
  register unsigned long int __d0, __d1, __d2, __d3;
  register char *__res;
  
  __asm__ __volatile__
    ("movl	%%ebx,%%edi\n\t"
     "cld\n\t"
     "repne; scasb\n\t"
     "notl	%%ecx\n\t"
     "leal	-1(%%ecx),%%edx\n"
     "1:\n\t"
     "lodsb\n\t"
     "testb	%%al,%%al\n\t"
     "je	2f\n\t"
     "movl	%%ebx,%%edi\n\t"
     "movl	%%edx,%%ecx\n\t"
     "repne; scasb\n\t"
     "jne	1b\n\t"
     "decl	%0\n\t"
     "jmp	3f\n"
     "2:\n\t"
     "xorl	%0,%0\n"
     "3:"
     : "=S" (__res), "=&a" (__d0), "=&c" (__d1), "=&d" (__d2), "=&D" (__d3)
     : "0" (__s), "1" (0), "2" (0xffffffff), "b" (__accept),
     "m" ( *(struct { char __x[0xfffffff]; } *)__s),
       "m" ( *(struct { char __x[0xfffffff]; } *)__accept)
     : "cc");
  return __res;
}

Andreas
-- 
 Andreas Jaeger
  SuSE Labs aj@suse.de
   private aj@arthur.inka.de
    http://www.suse.de/~aj