"Itanium C++ ABI" is a bit of a misnomer

"Itanium C++ ABI" is a bit of a misnomer

The "Itanium C++ ABI" doesn't actually have anything to do with the Itanium architecture. It's called that because GCC's Itanium back end was the first GCC back end to implement it, and it was written in collaboration with HP and Intel, with the goal that all C++ compilers for Itanium would be binary compatible. But it is a mostly architecture-independent description of how C++ features that need to be represented at the ABI level — name mangling, vtable layout, etc. — should be handled. Nowadays I believe GCC and LLVM both use it uniformly on all platforms except Windows (where there is an attempt to be MSVC-compatible instead).