Better support for 'polymorphic' JS and external arrays

src/x64/macro-assembler-x64.cc

Index: src/x64/macro-assembler-x64.cc
diff --git a/src/x64/macro-assembler-x64.cc b/src/x64/macro-assembler-x64.cc
index eb3f7c19e3d00ae16c41a6a3576f1886cbf86480..1c16f8fa8b86b8fea5b2545c80ca5e333dcc3204 100644
--- a/src/x64/macro-assembler-x64.cc
+++ b/src/x64/macro-assembler-x64.cc
@@ -2570,6 +2570,21 @@ void MacroAssembler::CheckMap(Register obj,
 }
 
 
+void MacroAssembler::DispatchMap(Register obj,
+                                 Handle<Map> map,
+                                 Handle<Code> success,
+                                 bool is_heap_object) {
+  Label fail;
+  if (!is_heap_object) {
+    JumpIfSmi(obj, &fail);
+  }
+  Cmp(FieldOperand(obj, HeapObject::kMapOffset), map);
+  j(equal, success, RelocInfo::CODE_TARGET);
+
+  bind(&fail);
+}
+
+
 void MacroAssembler::AbortIfNotNumber(Register object) {
   Label ok;
   Condition is_smi = CheckSmi(object);