[ic] Simplify handling of primitive maps.

src/ic/x64/handler-compiler-x64.cc

Index: src/ic/x64/handler-compiler-x64.cc
diff --git a/src/ic/x64/handler-compiler-x64.cc b/src/ic/x64/handler-compiler-x64.cc
index 0139ad97f1fa833d294dcd1d849819f369711672..57208f988db81f73a0651e8f621dffda927b91e0 100644
--- a/src/ic/x64/handler-compiler-x64.cc
+++ b/src/ic/x64/handler-compiler-x64.cc
@@ -401,10 +401,9 @@ void NamedStoreHandlerCompiler::GenerateFieldTypeChecks(FieldType* field_type,
   }
 }
 
-
 Register PropertyHandlerCompiler::CheckPrototypes(
     Register object_reg, Register holder_reg, Register scratch1,
-    Register scratch2, Handle<Name> name, Label* miss, PrototypeCheckType check,
+    Register scratch2, Handle<Name> name, Label* miss,
     ReturnHolder return_what) {
   Handle<Map> receiver_map = map();
 
@@ -424,17 +423,6 @@ Register PropertyHandlerCompiler::CheckPrototypes(
     __ j(not_equal, miss);
   }
 
-  // The prototype chain of primitives (and their JSValue wrappers) depends
-  // on the native context, which can't be guarded by validity cells.
-  // |object_reg| holds the native context specific prototype in this case;
-  // we need to check its map.
-  if (check == CHECK_ALL_MAPS) {
-    __ movp(scratch1, FieldOperand(object_reg, HeapObject::kMapOffset));
-    Handle<WeakCell> cell = Map::WeakCellForMap(receiver_map);
-    __ CmpWeakValue(scratch1, cell, scratch2);
-    __ j(not_equal, miss);
-  }
-
   // Keep track of the current object in register reg.  On the first
   // iteration, reg is an alias for object_reg, on later iterations,
   // it is an alias for holder_reg.
@@ -446,15 +434,14 @@ Register PropertyHandlerCompiler::CheckPrototypes(
     current = isolate()->global_object();
   }
 
-  Handle<JSObject> prototype = Handle<JSObject>::null();
-  Handle<Map> current_map = receiver_map;
+  Handle<Map> current_map(receiver_map->GetPrototypeChainRootMap(isolate()),
+                          isolate());
   Handle<Map> holder_map(holder()->map());
   // Traverse the prototype chain and check the maps in the prototype chain for
   // fast and global objects or do negative lookup for normal objects.
   while (!current_map.is_identical_to(holder_map)) {
     ++depth;
 
-    prototype = handle(JSObject::cast(current_map->prototype()));
     if (current_map->IsJSGlobalObjectMap()) {
       GenerateCheckPropertyCell(masm(), Handle<JSGlobalObject>::cast(current),
                                 name, scratch2, miss);
@@ -476,7 +463,7 @@ Register PropertyHandlerCompiler::CheckPrototypes(
 
     reg = holder_reg;  // From now on the object will be in holder_reg.
     // Go to the next object in the prototype chain.
-    current = prototype;
+    current = handle(JSObject::cast(current_map->prototype()));
     current_map = handle(current->map());
   }