Oops ;-) resending, as I forgot to sign last version:

Unlike x86, x86_64 already passes arguments in registers. The use of
regparm attribute makes no difference in produced code, and the use of
fastcall just bloats the code.

Signed-off-by: Glauber de Oliveira Costa <gcosta@redhat.com>

-- 
Glauber de Oliveira Costa
Red Hat Inc.
"Free as in Freedom"