Summary: Proposal: Backward-edge CFI for return statements (RCFI)

Reviewers: pcc, eugenis, krasin

Reviewed By: eugenis

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D31112

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@298303 91177308-0d34-0410-b5e6-96231b3b80d8