Introduce basic type feedback for for-in statements to avoid deopts.

src/type-info.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 136 matching lines @@
   return value->IsMap() || value->IsSmi() || value->IsJSFunction();
 }
 
 
 bool TypeFeedbackOracle::CallNewIsMonomorphic(CallNew* expr) {
   Handle<Object> value = GetInfo(expr->id());
   return value->IsJSFunction();
 }
 
 
+bool TypeFeedbackOracle::IsForInFastCase(ForInStatement* stmt) {
+  Handle<Object> value = GetInfo(stmt->PrepareId());
+  return value->IsSmi() &&
+      Smi::cast(*value)->value() == TypeFeedbackCells::kForInFastCaseMarker;
+}
+
+
 Handle<Map> TypeFeedbackOracle::LoadMonomorphicReceiverType(Property* expr) {
   ASSERT(LoadIsMonomorphicNormal(expr));
   Handle<Object> map_or_code = GetInfo(expr->id());
   if (map_or_code->IsCode()) {
     Handle<Code> code = Handle<Code>::cast(map_or_code);
     Map* first_map = code->FindFirstMap();
     ASSERT(first_map != NULL);
     return CanRetainOtherContext(first_map, *global_context_)
         ? Handle<Map>::null()
         : Handle<Map>(first_map);
@@ skipping 485 matching lines @@
 
 
 void TypeFeedbackOracle::ProcessTypeFeedbackCells(Handle<Code> code) {
   Object* raw_info = code->type_feedback_info();
   if (!raw_info->IsTypeFeedbackInfo()) return;
   Handle<TypeFeedbackCells> cache(
       TypeFeedbackInfo::cast(raw_info)->type_feedback_cells());
   for (int i = 0; i < cache->CellCount(); i++) {
     unsigned ast_id = cache->AstId(i)->value();
     Object* value = cache->Cell(i)->value();
-    if (value->IsJSFunction() &&
-        !CanRetainOtherContext(JSFunction::cast(value),
-                               *global_context_)) {
+    if (value->IsSmi() ||
+        (value->IsJSFunction() &&
+         !CanRetainOtherContext(JSFunction::cast(value),
+                                *global_context_))) {
       SetInfo(ast_id, value);
     }
   }
 }
 
 
 void TypeFeedbackOracle::SetInfo(unsigned ast_id, Object* target) {
   ASSERT(dictionary_->FindEntry(ast_id) == UnseededNumberDictionary::kNotFound);
   MaybeObject* maybe_result = dictionary_->AtNumberPut(ast_id, target);
   USE(maybe_result);
 #ifdef DEBUG
   Object* result = NULL;
   // Dictionary has been allocated with sufficient size for all elements.
   ASSERT(maybe_result->ToObject(&result));
   ASSERT(*dictionary_ == result);
 #endif
 }
 
 } }  // namespace v8::internal