Index: lib/Analysis/InstructionSimplify.cpp
===================================================================
--- lib/Analysis/InstructionSimplify.cpp
+++ lib/Analysis/InstructionSimplify.cpp
@@ -3754,9 +3754,9 @@
     return TrueVal;
 
   if (isa<UndefValue>(CondVal)) {  // select undef, X, Y -> X or Y
-    if (isa<Constant>(TrueVal))
-      return TrueVal;
-    return FalseVal;
+    if (isa<Constant>(FalseVal))
+      return FalseVal;
+    return TrueVal;
   }
   if (isa<UndefValue>(TrueVal))   // select C, undef, X -> X
     return FalseVal;