Add a kSimd128 machine type for Turbofan.

src/compiler/representation-change.cc

Index: src/compiler/representation-change.cc
diff --git a/src/compiler/representation-change.cc b/src/compiler/representation-change.cc
index 40580e86bffaf41d5290a090a57d286e5fc9d3ee..2f7720beb3705599929416c442e2f1ab910677dc 100644
--- a/src/compiler/representation-change.cc
+++ b/src/compiler/representation-change.cc
@@ -145,6 +145,9 @@ Node* RepresentationChanger::GetRepresentationFor(
       return GetWord32RepresentationFor(node, output_rep, output_type);
     case MachineRepresentation::kWord64:
       return GetWord64RepresentationFor(node, output_rep, output_type);
+    case MachineRepresentation::kSimd128:  // Fall through.
+      // TODO(bbudge) Handle conversions between tagged and untagged.
+      break;
     case MachineRepresentation::kNone:
       return node;
   }