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 aa090560e5a8f7eeb45b45424aedf715a7516f7b..f2e27b5fd34efda422537c70e72bb84bb232f6ba 100644
--- a/src/x64/macro-assembler-x64.cc
+++ b/src/x64/macro-assembler-x64.cc
@@ -1897,6 +1897,21 @@ 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);