Better framework for conditional cleanups;  untested as yet.
I'm separately committing this because it incidentally changes some
block orderings and minor IR issues, like using a phi instead of
an unnecessary alloca.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@124277 91177308-0d34-0410-b5e6-96231b3b80d8
9 files changed