[IPSCCP] Restore the old behaviour (pre r293799).

It's not clear the change I made a good idea, and it definitely needs
further discussion. Thanks to Eli for pointing out.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@293846 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed