operations (like findProperties) should be faster, at the expense of
unionSets being slower in cases that are rare in practise.
Don't erase a dead Instruction. This fixes a memory corruption issue.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@30235 91177308-0d34-0410-b5e6-96231b3b80d8
