On Monday 27 June 2005 21:43, Paolo Ornati wrote:
> PS: I've readded LKML to CC, since I think that this is a problem with the
> ASM template
Yes, you are right, it is not a compiler bug.
My apologies to the GCC team, in case anyone has read it.
[...]
> A little better workaround would be to add "memory" to clobbered registers
> in the asm template:
>
> static inline int strcmp(const char * cs,const char * ct)
> {
> int d0, d1;
> register int __res;
> __asm__ __volatile__(
> "1:\tlodsb\n\t"
> "scasb\n\t"
> "jne 2f\n\t"
> "testb %%al,%%al\n\t"
> "jne 1b\n\t"
> "xorl %%eax,%%eax\n\t"
> "jmp 3f\n"
> "2:\tsbbl %%eax,%%eax\n\t"
> "orb $1,%%al\n"
> "3:"
>
> :"=a" (__res), "=&S" (d0), "=&D" (d1)
> :
> :"1" (cs),"2" (ct)
> : "memory"); // <--- workaround
>
> return __res;
> }
>
>
> In this way GCC puts everything is cached in register back to memory when
> you call strcmp()... but you can argue that this isn't optimal.
Indeed the compiler has to assume that any memory location has changed.
> I don't know if there is a better way... basically you need to tell GCC to
> NOT cache these values.
There is one, it says that cs and ct address structures with 4 gigabyte size.
This is anyway not 64 bit clean.
static inline int strcmp(const char * cs,const char * ct)
{
int d0, d1;
register int __res;
__asm__ __volatile__(
"1:\tlodsb\n\t"
"scasb\n\t"
"jne 2f\n\t"
"testb %%al,%%al\n\t"
"jne 1b\n\t"
"xorl %%eax,%%eax\n\t"
"jmp 3f\n"
"2:\tsbbl %%eax,%%eax\n\t"
"orb $1,%%al\n"
"3:"
:"=a" (__res), "=&S" (d0), "=&D" (d1)
:"1" (cs),"2" (ct),
"m" ( *(struct { char __x[0xfffffff]; } *)cs),
"m" ( *(struct { char __x[0xfffffff]; } *)ct));
return __res;
}
Now, how do i formally submit this as a bug report ?
Andreas.
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