[InstCombine] allow icmp (and X, C2), C1 folds for splat constant vectors

This is a revert of r280676 which was a revert of r280637;
ie, this is r280637 again. It was speculatively reverted to
help debug buildbot failures.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@280861 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed