Re: [PATCH] gcc-3.1 ffs problem, kernel 2.4.18

[Richard Henderson]

On Tue, Apr 02, 2002 at 01:48:48PM +0200, Michal Moskal wrote:
> Could you please check if it compiles for you?

Ah, I see the bug.  I was looking at ffz (which is correct),
not ffs (which isn't).

> 	__asm__("bsfl %1,%0\n\t"
> 		"jnz 1f\n\t"
> 		"movl $-1,%0\n"
> 		"1:" : "=r" (r) : "g" (x));

The problem is                    ^^^

That sez any of register, memory, or immediate is ok.
It should be "r" instead, just like in ffz.

That said, we should probably be using __builtin_ffs
instead.  The compiler knows how to do bsfl plus the
adjustment.  Plus, it knows how to evaluate it at
compile-time for constants.

r~