In cases such as the attached test, where the case value for a switch
destination is used in a phi node that follows the destination, it
might be better to replace that value with the condition value of the
switch, so that more blocks can be folded away with
TryToSimplifyUncondBranchFromEmptyBlock because there are less
conflicts in the phi node.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@133344 91177308-0d34-0410-b5e6-96231b3b80d8
