Revert r319537: Bail out of a SimplifyCFG switch table opt at undef values.

Broke build bots so reverting.

llvm-svn: 319539

lib/Transforms/Utils/SimplifyCFG.cpp

@@ -5174,7 +5174,7 @@ static void reuseTableCompare(
   for (auto ValuePair : Values) {
     Constant *CaseConst = ConstantExpr::getICmp(CmpInst->getPredicate(),
                                                 ValuePair.second, CmpOp1, true);
-    if (!CaseConst || CaseConst == DefaultConst || isa<UndefValue>(CaseConst))
+    if (!CaseConst || CaseConst == DefaultConst)
       return;
     assert((CaseConst == TrueConst || CaseConst == FalseConst) &&
            "Expect true or false as compare result.");

test/Transforms/SimplifyCFG/switch_undef.ll

@@ -1,27 +0,0 @@
-; RUN: opt %s -keep-loops=false -switch-to-lookup=true -simplifycfg -S | FileCheck %s
-
-target triple = "x86_64-unknown-linux-gnu"
-
-define void @f6() #0 {
-; CHECK-LABEL: entry:
-; CHECK-NEXT:  br label %f1.exit.i
-; CHECK-LABEL: f1.exit.i:
-
-entry:
-  br label %for.cond.i
-
-for.cond.i:                                       ; preds = %f1.exit.i, %entry
-  switch i16 undef, label %f1.exit.i [
-    i16 -1, label %cond.false.i3.i
-    i16 1, label %cond.false.i3.i
-    i16 0, label %cond.false.i3.i
-  ]
-
-cond.false.i3.i:                                  ; preds = %for.cond.i, %for.cond.i, %for.cond.i
-  br label %f1.exit.i
-
-f1.exit.i:                                        ; preds = %cond.false.i3.i, %for.cond.i
-  %cond.i4.i = phi i16 [ undef, %cond.false.i3.i ], [ 1, %for.cond.i ]
-  %tobool7.i = icmp ne i16 %cond.i4.i, 0
-  br label %for.cond.i
-}