Intel Is Trying To Support The x32 ABI For LLVM/Clang
The Linux x32 ABI about allowing programs to take advantage of x86_64 features (and being dependent upon x86 64-bit CPUs) while using 32-bit memory pointers. The x32 ABI support is currently found within the GCC compiler and then within the Linux kernel, Glibc, Binutils, etc. Work was underway a few years ago to support x32 within LLVM/Clang, but that work went abandoned until now when Intel developers are restoring work on the compiler ABI support.
Pavel Chupin of Intel shared the LLVM/Clang x32 plans via this mailing list post and they intend to get out fresh patches in the near future.