> I've realized that in Fedora Extras 4 the ocaml package contains the 
> following patch:
> -        : "+&r" (a), "+&r" (b), "+&rm" (blen), "+&r" (out)
> +        : "+&r" (a), "+&r" (b), "+m" (blen), "+&r" (out)
> Is this reasonable?

Yes, very much so.  You'll get better performance than with the
workaround I suggested (disabling inline asm).  I need to run a few
tests with gcc 4, but eventually will fix the problem along these lines.

> Also, 
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21291 suggests using -O0 
> (which seems to work as well).

That wil be costly in performance, especially if -O0 is applied to the
whole OCaml runtime system (not just otherlibs/num).

- Xavier Leroy