Revert [TypeFeedbackVector] Root literal arrays in function literal slots

src/debug/liveedit.cc

Index: src/debug/liveedit.cc
diff --git a/src/debug/liveedit.cc b/src/debug/liveedit.cc
index fea5d679a91cde427007519c11811ec2874db723..3ced3cc427405584f1dfed241f62d992a302cf87 100644
--- a/src/debug/liveedit.cc
+++ b/src/debug/liveedit.cc
@@ -823,33 +823,35 @@ class LiteralFixer {
  public:
   static void PatchLiterals(FunctionInfoWrapper* compile_info_wrapper,
                             Handle<SharedFunctionInfo> shared_info,
-                            Isolate* isolate) {
+                            bool feedback_metadata_changed, Isolate* isolate) {
     int new_literal_count = compile_info_wrapper->GetLiteralCount();
+    int old_literal_count = shared_info->num_literals();
 
-    // Recreate the literal array and type feedback vector.
-    // Since the feedback vector roots literal arrays for nested functions,
-    // we can't simply leave it in place because those nested literal
-    // array and feedback vectors may have changed structure.
-    Handle<FixedArray> function_instances =
-        CollectJSFunctions(shared_info, isolate);
-    Handle<TypeFeedbackMetadata> feedback_metadata(
-        shared_info->feedback_metadata());
-
-    for (int i = 0; i < function_instances->length(); i++) {
-      Handle<JSFunction> fun(JSFunction::cast(function_instances->get(i)));
-      Handle<TypeFeedbackVector> vector =
-          TypeFeedbackVector::New(isolate, feedback_metadata);
-      Handle<LiteralsArray> new_literals =
-          LiteralsArray::New(isolate, vector, new_literal_count);
-      Handle<LiteralsArray> old_literals(fun->literals(), isolate);
-      fun->set_literals(*new_literals);
-
-      // The literals are rooted in a containing feedback vector.
-      // Replace them there, so new closures have the correct literals.
-      ReplaceRoots(old_literals, new_literals);
-    }
+    if (old_literal_count == new_literal_count && !feedback_metadata_changed) {
+      // If literal count didn't change, simply go over all functions
+      // and clear literal arrays.
+      ClearValuesVisitor visitor;
+      IterateJSFunctions(shared_info, &visitor);
+    } else {
+      // When literal count changes, we have to create new array instances.
+      // Since we cannot create instances when iterating heap, we should first
+      // collect all functions and fix their literal arrays.
+      Handle<FixedArray> function_instances =
+          CollectJSFunctions(shared_info, isolate);
+      Handle<TypeFeedbackMetadata> feedback_metadata(
+          shared_info->feedback_metadata());
+
+      for (int i = 0; i < function_instances->length(); i++) {
+        Handle<JSFunction> fun(JSFunction::cast(function_instances->get(i)));
+        Handle<TypeFeedbackVector> vector =
+            TypeFeedbackVector::New(isolate, feedback_metadata);
+        Handle<LiteralsArray> new_literals =
+            LiteralsArray::New(isolate, vector, new_literal_count);
+        fun->set_literals(*new_literals);
+      }
 
-    shared_info->set_num_literals(new_literal_count);
+      shared_info->set_num_literals(new_literal_count);
+    }
   }
 
  private:
@@ -870,56 +872,6 @@ class LiteralFixer {
     }
   }
 
-  template <typename Visitor>
-  static void IterateAllJSFunctions(Heap* heap, Visitor* visitor) {
-    HeapIterator iterator(heap);
-    for (HeapObject* obj = iterator.next(); obj != NULL;
-         obj = iterator.next()) {
-      if (obj->IsJSFunction()) {
-        JSFunction* function = JSFunction::cast(obj);
-        visitor->visit(function);
-      }
-    }
-  }
-
-  class ReplaceRootsVisitor {
-   public:
-    ReplaceRootsVisitor(Handle<LiteralsArray> old_literals,
-                        Handle<LiteralsArray> new_literals)
-        : old_literals_(old_literals), new_literals_(new_literals) {}
-
-    void visit(JSFunction* fun) {
-      if (!fun->shared()->is_compiled()) return;
-
-      // Look in the type feedback vector for a copy of literals.
-      TypeFeedbackVector* vector = fun->feedback_vector();
-      // Note: it's important to get the feedback metadata from the
-      // type feedback vector, because there may be a new metadata
-      // object in the SharedFunctionInfo (with a different slot
-      // configuration).
-      TypeFeedbackMetadataIterator iter(vector->metadata());
-      while (iter.HasNext()) {
-        FeedbackVectorSlot slot = iter.Next();
-        FeedbackVectorSlotKind kind = iter.kind();
-        if (kind == FeedbackVectorSlotKind::CREATE_CLOSURE) {
-          Object* obj = vector->Get(slot);
-          if (obj == *old_literals_) {
-            vector->Set(slot, *new_literals_);
-          }
-        }
-      }
-    }
-
-    Handle<LiteralsArray> old_literals_;
-    Handle<LiteralsArray> new_literals_;
-  };
-
-  static void ReplaceRoots(Handle<LiteralsArray> old_literals,
-                           Handle<LiteralsArray> new_literals) {
-    ReplaceRootsVisitor replace_visitor(old_literals, new_literals);
-    IterateAllJSFunctions(old_literals->GetHeap(), &replace_visitor);
-  }
-
   // Finds all instances of JSFunction that refers to the provided shared_info
   // and returns array with them.
   static Handle<FixedArray> CollectJSFunctions(
@@ -1020,6 +972,7 @@ void LiveEdit::ReplaceFunctionCode(
   Handle<SharedFunctionInfo> shared_info = shared_info_wrapper.GetInfo();
   Handle<SharedFunctionInfo> new_shared_info =
       compile_info_wrapper.GetSharedFunctionInfo();
+  bool feedback_metadata_changed = false;
 
   if (shared_info->is_compiled()) {
     // Take whatever code we can get from the new shared function info. We
@@ -1066,6 +1019,8 @@ void LiveEdit::ReplaceFunctionCode(
     // Update the type feedback vector, if needed.
     Handle<TypeFeedbackMetadata> new_feedback_metadata(
         new_shared_info->feedback_metadata());
+    feedback_metadata_changed =
+        new_feedback_metadata->DiffersFrom(shared_info->feedback_metadata());
     shared_info->set_feedback_metadata(*new_feedback_metadata);
   }
 
@@ -1074,7 +1029,8 @@ void LiveEdit::ReplaceFunctionCode(
   shared_info->set_start_position(start_position);
   shared_info->set_end_position(end_position);
 
-  LiteralFixer::PatchLiterals(&compile_info_wrapper, shared_info, isolate);
+  LiteralFixer::PatchLiterals(&compile_info_wrapper, shared_info,
+                              feedback_metadata_changed, isolate);
 
   DeoptimizeDependentFunctions(*shared_info);
   isolate->compilation_cache()->Remove(shared_info);