Availability of compilers supporting 128-bit arithmetic?

[Will Galway]

My apologies for posing a question which is only peripherally related to 
GMP, but I expect that the community that reads this list is well placed 
to answer my question.

Much my research involves arithmetic modulo 64-bit numbers, which means 
that 128-bit arithmetic is the "sweet spot" for computing products, 
remainders, etc.  I understand that recent versions of the Gnu C 
Compiler (gcc) support 128-bit integers, declared as__int128, although 
I'm puzzled to read at

   http://gcc.gnu.org/onlinedocs/gcc/_005f_005fint128.html

that "There is no support in GCC to express an integer constant of type 
__int128 for targets having long long integer with less then 128 bit 
width."  (In which case, why not just declare 128-bit integers to be 
type long long int?)

I'm currently using an Intel Core i3-540 running Ubuntu Linux with the 
default gcc:"(Ubuntu/Linaro 4.4.4-14ubuntu5) 4.4.5."  Would anyone know 
if the Core i3-540 (etc.) has hardware support for 128-bit arithmetic, 
and if so what I'd need to do to get compiler support for it?  If the 
Core i3-540 does NOT support 128-bit arithmetic, could someone point me 
to a list of architectures that do?

-- Regards, Will