Index: include/llvm/CodeGen/GlobalISel/LegalizerInfo.h
===================================================================
--- include/llvm/CodeGen/GlobalISel/LegalizerInfo.h
+++ include/llvm/CodeGen/GlobalISel/LegalizerInfo.h
@@ -153,8 +153,12 @@
     do {
       Ty = NextType(Ty);
       auto ActionIt = Map.find(Ty);
-      if (ActionIt == Map.end())
-        Action = DefaultActions.find(Aspect.Opcode)->second;
+      if (ActionIt == Map.end()) {
+        auto DefaultIt = DefaultActions.find(Aspect.Opcode);
+        if (DefaultIt == DefaultActions.end())
+          return LLT();
+        Action = DefaultIt->second;
+      }
       else
         Action = ActionIt->second;
     } while(Action != Legal);