The ia64-hpux version of GCC supports several options that don't appear to be documented. I see at least the following:
-milp32 -mlp64 -mt -- Summary: undocumented ia64-hpux options Product: gcc Version: 3.4.1 Status: UNCONFIRMED Severity: minor Priority: P2 Component: c AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: jweening at ccrwest dot org CC: gcc-bugs at gcc dot gnu dot org GCC build triplet: ia64-hp-hpux11.23 GCC host triplet: ia64-hp-hpux11.23 GCC target triplet: ia64-hp-hpux11.23 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18027