Two changes:

Two changes:
  1. Chain to the parent implementation of M/R analysis if we can't find
     any information.  It has some heuristics that often do well.
  2. Do not clear all flags, this can make invalid nodes by turning nodes
     that used to be collapsed into non-collapsed nodes (fixing crashes)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@20659 91177308-0d34-0410-b5e6-96231b3b80d8