Fix a bug in just submitted rL369789

Started implementing the vector case and realized the scalar case hadn't handled the GEP producing a different type than the base correctly.  It's entertaining seeing what slips through review when we're focused on the 'hard' parts.  :(

Also adding an extra vector test as it happened to be in workspace and wasn't worth separating.

llvm-svn: 369795
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
index 2bc2129..4e161d6 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -914,7 +914,10 @@
     // In general, we're allowed to make values less poison (i.e. remove
     //   sources of full UB), so in this case, we just select between the two
     //   non-poison cases (1 and 4 above).
-    return new ICmpInst(Cond, GEPLHS->getPointerOperand(), RHS);
+    auto *Base = GEPLHS->getPointerOperand();
+    return new ICmpInst(Cond, Base,
+                        ConstantExpr::getBitCast(cast<Constant>(RHS),
+                                                 Base->getType()));
   } else if (GEPOperator *GEPRHS = dyn_cast<GEPOperator>(RHS)) {
     // If the base pointers are different, but the indices are the same, just
     // compare the base pointer.