Summary:
There is a reserved range of type indexes for built-in types (like integers).
This will create a symbol for a built-in type if the caller askes for one by
type index. This is also plumbing for being able to recall symbols by type
index in general, but user-defined types will come in subsequent patches.
Reviewers: rnk, zturner
Subscribers: mgorny, hiraditya, llvm-commits
Differential Revision: https://reviews.llvm.org/D35163
llvm-svn: 307834