Currently, we have some confusion in the codebase regarding the meaning of LocationSize::unknown(): Some parts (including most of BasicAA) assume that LocationSize::unknown() only allows accesses after the base pointer. Some parts (various callers of AA) assume that LocationSize::unknown() allows accesses both before and after the base pointer (but within the underlying object).
This patch splits up LocationSize::unknown() into LocationSize::afterPointer() and LocationSize::beforeOrAfterPointer() to make this completely unambiguous. I tried my best to determine which one is appropriate for all the existing uses.
The test changes in cs-cs.ll in particular illustrate a previously clearly incorrect AA result: We were effectively assuming that argmemonly functions were only allowed to access their arguments after the passed pointer, but not before it. I'm pretty sure that this was not intentional, and it's certainly not specified by LangRef that way.