can be used to improve the locations when generating remarks for loops.

Depends on the companion LLVM change r286227.

Patch by Florian Hahn.

Differential Revision: https://reviews.llvm.org/D25764



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@286456 91177308-0d34-0410-b5e6-96231b3b80d8