[modules] Introduce new VariableLocation for module imports/exports.

src/full-codegen/s390/full-codegen-s390.cc

Index: src/full-codegen/s390/full-codegen-s390.cc
diff --git a/src/full-codegen/s390/full-codegen-s390.cc b/src/full-codegen/s390/full-codegen-s390.cc
index 8c5971d26b6e5a3560058273cb1f984fd90d306a..99bbc011fdf0d068a2cc032005c8c4666935ee67 100644
--- a/src/full-codegen/s390/full-codegen-s390.cc
+++ b/src/full-codegen/s390/full-codegen-s390.cc
@@ -749,6 +749,9 @@ void FullCodeGenerator::VisitVariableDeclaration(
       PrepareForBailoutForId(proxy->id(), BailoutState::NO_REGISTERS);
       break;
     }
+
+    case VariableLocation::MODULE:
+      UNREACHABLE();
   }
 }
 
@@ -802,6 +805,9 @@ void FullCodeGenerator::VisitFunctionDeclaration(
       PrepareForBailoutForId(proxy->id(), BailoutState::NO_REGISTERS);
       break;
     }
+
+    case VariableLocation::MODULE:
+      UNREACHABLE();
   }
 }
 
@@ -1286,7 +1292,11 @@ void FullCodeGenerator::EmitVariableLoad(VariableProxy* proxy,
       __ CallRuntime(function_id);
       __ bind(&done);
       context()->Plug(r2);
+      break;
     }
+
+    case VariableLocation::MODULE:
+      UNREACHABLE();
   }
 }