When we have an annotated local variable after a function returns, we
generate IR that fails verification with the error
> Instruction referencing instruction not embedded in a basic block!
And it means that bitcast referencing alloca doesn't have a parent basic
block.
Fix by checking if we are at an unreachable point and skip emitting
annotations. This approach is similar to the way we emit variable
initializer and debug info.
rdar://problem/46200420
Reviewers: rjmccall
Reviewed By: rjmccall
Subscribers: aprantl, jkorous, dexonsmith, cfe-commits
Differential Revision: https://reviews.llvm.org/D58147
llvm-svn: 355166