When emitting a label for a PostCall safe point, the machine

When emitting a label for a PostCall safe point, the machine
instruction to insert before can be end(). getDebugLoc on
end() returns an invalid value, therefore use the debug
loc of the call instruction, and give it to InsertLabel.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@81207 91177308-0d34-0410-b5e6-96231b3b80d8