5f44c653cf
Add a MIR pass to lower 128-bit operators to lang item calls Runs only with `-Z lower_128bit_ops` since it's not hooked into targets yet. This isn't really useful on its own, but the declarations for the lang items need to be in the compiler before compiler-builtins can be updated to define them, so this is part 1 of at least 3. cc https://github.com/rust-lang/rust/issues/45676 @est31 @nagisa