For gcc source (gcc-4.1.0.tar.gz) see:
http://gcc.gnu.org/gcc-4.1
gcc 4.1.0 introduces support for IBM System z9 and support for long
double 128-bit IEEE floating point, as well as other enhancements.
For details see: http://gcc.gnu.org/gcc-4.1/changes.html section "S/390, zSeries and System z9".