[SwitchLowering] Handle multiple destinations on condensed case stmts
Switch cases statements with sequential values that branch to the same
destination BB may often be handled together in a single new source BB.
In this scenario we need to remove remaining incoming values from PHI
instructions in the destination BB, as to match the number of source
branches.
Differential Revision: http://reviews.llvm.org/D6415
rdar://problem/
19040894
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@222926
91177308-0d34-0410-b5e6-
96231b3b80d8