This is part of a patch series working towards the ability to make
SourceLocation into a 64-bit type to handle larger translation units.
Unconditionally expanding the serialized encoding to 64 bits is the
simplest way to ensure that it will be big enough to handle an
As I understand it, PCH files are already automatically versioned with
the exact revision of the compiler that built them, so this shouldn't
introduce any compatibility problem, because clang will already refuse
to load any PCH from a different version of itself.
Patch based on previous work by Mikhail Maltsev.