Improve polymorphic loads on single slots.

src/hydrogen-instructions.cc

Index: src/hydrogen-instructions.cc
diff --git a/src/hydrogen-instructions.cc b/src/hydrogen-instructions.cc
index 1069684dbf3a972ed6cbc60e238531458aa3d0a1..9af466d951912ea8c9409a97f578ce4ec1714b3f 100644
--- a/src/hydrogen-instructions.cc
+++ b/src/hydrogen-instructions.cc
@@ -969,6 +969,16 @@ void HCheckMap::PrintDataTo(StringStream* stream) {
 }
 
 
+void HCheckMapSet::PrintDataTo(StringStream* stream) {
+  value()->PrintNameTo(stream);
+  stream->Add(" [%p", *map_set()->first());
+  for (int i = 1; i < map_set()->length(); ++i) {
+    stream->Add(",%p", *map_set()->at(i));
+  }
+  stream->Add("]");
+}
+
+
 void HCheckFunction::PrintDataTo(StringStream* stream) {
   value()->PrintNameTo(stream);
   stream->Add(" %p", *target());