Index: llvm/lib/Analysis/InstructionSimplify.cpp
===================================================================
--- llvm/lib/Analysis/InstructionSimplify.cpp
+++ llvm/lib/Analysis/InstructionSimplify.cpp
@@ -4117,11 +4117,6 @@
   if (TrueVal == FalseVal)
     return TrueVal;
 
-  if (isa<UndefValue>(TrueVal))   // select ?, undef, X -> X
-    return FalseVal;
-  if (isa<UndefValue>(FalseVal))   // select ?, X, undef -> X
-    return TrueVal;
-
   // Deal with partial undef vector constants: select ?, VecC, VecC' --> VecC''
   Constant *TrueC, *FalseC;
   if (TrueVal->getType()->isVectorTy() && match(TrueVal, m_Constant(TrueC)) &&