LLVM already supports completely arbitrary integer sizes up to 2^23-1 in its IR (https://llvm.org/docs/LangRef.html#integer-type https://llvm.org/docs/LangRef.h

LLVM already supports completely arbitrary integer sizes up to 2^23-1 in its IR (https://llvm.org/docs/LangRef.html#integer-type https://llvm.org/docs/LangRef.html#integer-type), and I think it can “lower” any integer size to fit what the hardware actually supports. So if Clang doesn't add an artificial constraint on top, in theory you could use a one million-bit integer size if you wanted to?