[TypeFeedbackVector] Root feedback vectors at function literal site.

src/debug/liveedit.cc

Index: src/debug/liveedit.cc
diff --git a/src/debug/liveedit.cc b/src/debug/liveedit.cc
index fe0d0c5a3976a4be6b2aa02c1f85ca07b9c3b7fc..7d33ab165991e8b8e424cd263abb202281f6fe4e 100644
--- a/src/debug/liveedit.cc
+++ b/src/debug/liveedit.cc
@@ -742,27 +742,24 @@ static void ReplaceCodeObject(Handle<Code> original,
   }
 }
 
-
-// Patch function literals.
-// Name 'literals' is a misnomer. Rather it's a cache for complex object
-// boilerplates and for a native context. We must clean cached values.
-// Additionally we may need to allocate a new array if number of literals
-// changed.
-class LiteralFixer {
+// Patch function feedback vector.
+// The feedback vector is a cache for complex object boilerplates and for a
+// native context. We must clean cached values, or if the structure of the
+// vector itself changes we need to allocate a new one.
+class FeedbackVectorFixer {
  public:
-  static void PatchLiterals(FunctionInfoWrapper* compile_info_wrapper,
-                            Handle<SharedFunctionInfo> shared_info,
-                            bool feedback_metadata_changed, Isolate* isolate) {
+  static void PatchFeedbackVector(FunctionInfoWrapper* compile_info_wrapper,
+                                  Handle<SharedFunctionInfo> shared_info,
+                                  bool feedback_metadata_changed,
+                                  Isolate* isolate) {
     int new_literal_count = compile_info_wrapper->GetLiteralCount();
-    int old_literal_count = shared_info->num_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.
+    if (!feedback_metadata_changed) {
+      // It's enough to clear the feedback vector in this case.
       ClearValuesVisitor visitor;
       IterateJSFunctions(shared_info, &visitor);
     } else {
-      // When literal count changes, we have to create new array instances.
+      // When feedback metadata 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 =
@@ -774,11 +771,11 @@ class LiteralFixer {
         Handle<JSFunction> fun(JSFunction::cast(function_instances->get(i)));
         Handle<TypeFeedbackVector> vector =
             TypeFeedbackVector::New(isolate, feedback_metadata);
-        fun->set_feedback_vector(*vector);
+        fun->feedback_vector_cell()->set_value(*vector);
       }
-
-      shared_info->set_num_literals(new_literal_count);
     }
+
+    shared_info->set_num_literals(new_literal_count);
   }
 
  private:
@@ -799,6 +796,18 @@ class LiteralFixer {
     }
   }
 
+  template <typename Visitor>
+  static void IterateAllJSFunctions(Heap* heap, Visitor* visitor) {

[mvstanton, 2017/02/03 12:16:37]

dead code, remove.

+    HeapIterator iterator(heap);
+    for (HeapObject* obj = iterator.next(); obj != NULL;
+         obj = iterator.next()) {
+      if (obj->IsJSFunction()) {
+        JSFunction* function = JSFunction::cast(obj);
+        visitor->visit(function);
+      }
+    }
+  }
+
   // Finds all instances of JSFunction that refers to the provided shared_info
   // and returns array with them.
   static Handle<FixedArray> CollectJSFunctions(
@@ -819,8 +828,10 @@ class LiteralFixer {
   class ClearValuesVisitor {
    public:
     void visit(JSFunction* fun) {
-      TypeFeedbackVector* vector = fun->feedback_vector();
-      vector->ClearSlots(fun->shared());
+      if (fun->feedback_vector_cell()->value()->IsTypeFeedbackVector()) {
+        TypeFeedbackVector* vector = fun->feedback_vector();
+        vector->ClearSlots(fun->shared());
+      }
     }
   };
 
@@ -944,7 +955,8 @@ void LiveEdit::ReplaceFunctionCode(
     Handle<TypeFeedbackMetadata> new_feedback_metadata(
         new_shared_info->feedback_metadata());
     feedback_metadata_changed =
-        new_feedback_metadata->DiffersFrom(shared_info->feedback_metadata());
+        new_feedback_metadata->DiffersFrom(shared_info->feedback_metadata()) ||
+        new_feedback_metadata->HasFunctionLiteralSlots();
     shared_info->set_feedback_metadata(*new_feedback_metadata);
   }
 
@@ -953,8 +965,8 @@ void LiveEdit::ReplaceFunctionCode(
   shared_info->set_start_position(start_position);
   shared_info->set_end_position(end_position);
 
-  LiteralFixer::PatchLiterals(&compile_info_wrapper, shared_info,
-                              feedback_metadata_changed, isolate);
+  FeedbackVectorFixer::PatchFeedbackVector(&compile_info_wrapper, shared_info,
+                                           feedback_metadata_changed, isolate);
 
   DeoptimizeDependentFunctions(*shared_info);
   isolate->compilation_cache()->Remove(shared_info);