Fold things like "phi [add (a,b), add(c,d)]" into two phi's and one add.

This triggers thousands of times on multisource.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@31341 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed