careful when folding "c ? load p : load q" that C doesn't reach either load.
If so, folding this into load (c ? p : q) will induce a cycle in the graph.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@33251 91177308-0d34-0410-b5e6-96231b3b80d8