Move code flushing support into shared visitor.

src/objects-visiting-inl.h

 // 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 120 matching lines @@
 
   table_.Register(kVisitOddball,
                   &FixedBodyVisitor<StaticVisitor,
                   Oddball::BodyDescriptor,
                   void>::Visit);
 
   table_.Register(kVisitMap, &VisitMap);
 
   table_.Register(kVisitCode, &VisitCode);
 
-  // Registration for kVisitSharedFunctionInfo is done by StaticVisitor.
+  table_.Register(kVisitSharedFunctionInfo, &VisitSharedFunctionInfo);
 
-  // Registration for kVisitJSFunction is done by StaticVisitor.
+  table_.Register(kVisitJSFunction, &VisitJSFunction);
 
   // Registration for kVisitJSRegExp is done by StaticVisitor.
 
   table_.Register(kVisitPropertyCell,
                   &FixedBodyVisitor<StaticVisitor,
                   JSGlobalPropertyCell::BodyDescriptor,
                   void>::Visit);
 
   table_.template RegisterSpecializations<DataObjectVisitor,
                                           kVisitDataObject,
@@ skipping 123 matching lines @@
   Heap* heap = map->GetHeap();
   Code* code = Code::cast(object);
   if (FLAG_cleanup_code_caches_at_gc) {
     code->ClearTypeFeedbackCells(heap);
   }
   code->CodeIterateBody<StaticVisitor>(heap);
 }
 
 
 template<typename StaticVisitor>
+void StaticMarkingVisitor<StaticVisitor>::VisitSharedFunctionInfo(
+    Map* map, HeapObject* object) {
+  Heap* heap = map->GetHeap();
+  SharedFunctionInfo* shared = SharedFunctionInfo::cast(object);
+  if (shared->ic_age() != heap->global_ic_age()) {
+    shared->ResetForNewContext(heap->global_ic_age());
+  }
+  MarkCompactCollector* collector = heap->mark_compact_collector();
+  if (collector->is_code_flushing_enabled()) {
+    if (IsFlushable(heap, shared)) {
+      // This function's code looks flushable. But we have to postpone
+      // the decision until we see all functions that point to the same
+      // SharedFunctionInfo because some of them might be optimized.
+      // That would also make the non-optimized version of the code
+      // non-flushable, because it is required for bailing out from
+      // optimized code.
+      collector->code_flusher()->AddCandidate(shared);
+      // Treat the reference to the code object weakly.
+      VisitSharedFunctionInfoWeakCode(heap, object);
+      return;
+    }
+  }
+  VisitSharedFunctionInfoStrongCode(heap, object);
+}
+
+
+template<typename StaticVisitor>
+void StaticMarkingVisitor<StaticVisitor>::VisitJSFunction(
+    Map* map, HeapObject* object) {
+  Heap* heap = map->GetHeap();
+  JSFunction* function = JSFunction::cast(object);
+  MarkCompactCollector* collector = heap->mark_compact_collector();
+  if (collector->is_code_flushing_enabled()) {
+    if (IsFlushable(heap, function)) {
+      // This function's code looks flushable. But we have to postpone
+      // the decision until we see all functions that point to the same
+      // SharedFunctionInfo because some of them might be optimized.
+      // That would also make the non-optimized version of the code
+      // non-flushable, because it is required for bailing out from
+      // optimized code.
+      collector->code_flusher()->AddCandidate(function);
+      // Visit shared function info immediately to avoid double checking
+      // of its flushability later. This is just an optimization because
+      // the shared function info would eventually be visited.
+      SharedFunctionInfo* shared = function->unchecked_shared();
+      if (StaticVisitor::MarkObjectWithoutPush(heap, shared)) {
+        StaticVisitor::MarkObject(heap, shared->map());
+        VisitSharedFunctionInfoWeakCode(heap, shared);
+      }
+      // Treat the reference to the code object weakly.
+      VisitJSFunctionWeakCode(heap, object);
+      return;
+    } else {
+      // Visit all unoptimized code objects to prevent flushing them.
+      StaticVisitor::MarkObject(heap, function->shared()->code());
+      if (function->code()->kind() == Code::OPTIMIZED_FUNCTION) {
+        MarkInlinedFunctionsCode(heap, function->code());
+      }
+    }
+  }
+  VisitJSFunctionStrongCode(heap, object);
+}
+
+
+template<typename StaticVisitor>
 void StaticMarkingVisitor<StaticVisitor>::VisitJSRegExp(
     Map* map, HeapObject* object) {
   int last_property_offset =
       JSRegExp::kSize + kPointerSize * map->inobject_properties();
   Object** start_slot =
       HeapObject::RawField(object, JSRegExp::kPropertiesOffset);
   Object** end_slot =
       HeapObject::RawField(object, last_property_offset);
   StaticVisitor::VisitPointers(
       map->GetHeap(), start_slot, start_slot, end_slot);
@@ skipping 51 matching lines @@
     HeapObject* obj = HeapObject::cast(*slot);
     heap->mark_compact_collector()->RecordSlot(slot, slot, obj);
     StaticVisitor::MarkObjectWithoutPush(heap, obj);
   }
 
   for (int i = 0; i < transitions->number_of_transitions(); ++i) {
     StaticVisitor::VisitPointer(heap, transitions->GetKeySlot(i));
   }
 }
 
+template<typename StaticVisitor>
+void StaticMarkingVisitor<StaticVisitor>::MarkInlinedFunctionsCode(
+    Heap* heap, Code* code) {
+  // For optimized functions we should retain both non-optimized version
+  // of its code and non-optimized version of all inlined functions.
+  // This is required to support bailing out from inlined code.
+  DeoptimizationInputData* data =
+      DeoptimizationInputData::cast(code->deoptimization_data());
+  FixedArray* literals = data->LiteralArray();
+  for (int i = 0, count = data->InlinedFunctionCount()->value();
+       i < count;
+       i++) {
+    JSFunction* inlined = JSFunction::cast(literals->get(i));
+    StaticVisitor::MarkObject(heap, inlined->shared()->code());
+  }
+}
+
+
+inline static bool IsValidNonBuiltinContext(Object* context) {
+  return context->IsContext() &&
+      !Context::cast(context)->global_object()->IsJSBuiltinsObject();
+}
+
+
+inline static bool HasSourceCode(Heap* heap, SharedFunctionInfo* info) {
+  Object* undefined = heap->undefined_value();
+  return (info->script() != undefined) &&
+      (reinterpret_cast<Script*>(info->script())->source() != undefined);
+}
+
+
+template<typename StaticVisitor>
+bool StaticMarkingVisitor<StaticVisitor>::IsFlushable(
+    Heap* heap, JSFunction* function) {
+  SharedFunctionInfo* shared_info = function->unchecked_shared();
+
+  // Code is either on stack, in compilation cache or referenced
+  // by optimized version of function.
+  MarkBit code_mark = Marking::MarkBitFrom(function->code());
+  if (code_mark.Get()) {
+    if (!Marking::MarkBitFrom(shared_info).Get()) {
+      shared_info->set_code_age(0);
+    }
+    return false;
+  }
+
+  // The function must have a valid context and not be a builtin.
+  if (!IsValidNonBuiltinContext(function->unchecked_context())) {
+    return false;
+  }
+
+  // We do not flush code for optimized functions.
+  if (function->code() != shared_info->code()) {
+    return false;
+  }
+
+  return IsFlushable(heap, shared_info);
+}
+
+
+template<typename StaticVisitor>
+bool StaticMarkingVisitor<StaticVisitor>::IsFlushable(
+    Heap* heap, SharedFunctionInfo* shared_info) {
+  // Code is either on stack, in compilation cache or referenced
+  // by optimized version of function.
+  MarkBit code_mark = Marking::MarkBitFrom(shared_info->code());
+  if (code_mark.Get()) {
+    return false;
+  }
+
+  // The function must be compiled and have the source code available,
+  // to be able to recompile it in case we need the function again.
+  if (!(shared_info->is_compiled() && HasSourceCode(heap, shared_info))) {
+    return false;
+  }
+
+  // We never flush code for API functions.
+  Object* function_data = shared_info->function_data();
+  if (function_data->IsFunctionTemplateInfo()) {
+    return false;
+  }
+
+  // Only flush code for functions.
+  if (shared_info->code()->kind() != Code::FUNCTION) {
+    return false;
+  }
+
+  // Function must be lazy compilable.
+  if (!shared_info->allows_lazy_compilation()) {
+    return false;
+  }
+
+  // If this is a full script wrapped in a function we do no flush the code.
+  if (shared_info->is_toplevel()) {
+    return false;
+  }
+
+  // TODO(mstarzinger): The following will soon be replaced by a new way of
+  // aging code, that is based on an aging stub in the function prologue.
+
+  // How many collections newly compiled code object will survive before being
+  // flushed.
+  static const int kCodeAgeThreshold = 5;
+
+  // Age this shared function info.
+  if (shared_info->code_age() < kCodeAgeThreshold) {
+    shared_info->set_code_age(shared_info->code_age() + 1);
+    return false;
+  }
+
+  return true;
+}
+
+
+template<typename StaticVisitor>
+void StaticMarkingVisitor<StaticVisitor>::VisitSharedFunctionInfoStrongCode(
+    Heap* heap, HeapObject* object) {
+  StaticVisitor::BeforeVisitingSharedFunctionInfo(object);
+  Object** start_slot =
+      HeapObject::RawField(object,
+                           SharedFunctionInfo::BodyDescriptor::kStartOffset);
+  Object** end_slot =
+      HeapObject::RawField(object,
+                           SharedFunctionInfo::BodyDescriptor::kEndOffset);
+  StaticVisitor::VisitPointers(heap, start_slot, start_slot, end_slot);
+}
+
+
+template<typename StaticVisitor>
+void StaticMarkingVisitor<StaticVisitor>::VisitSharedFunctionInfoWeakCode(
+    Heap* heap, HeapObject* object) {
+  StaticVisitor::BeforeVisitingSharedFunctionInfo(object);
+  Object** name_slot =
+      HeapObject::RawField(object, SharedFunctionInfo::kNameOffset);
+  StaticVisitor::VisitPointer(heap, name_slot);
+
+  // Skip visiting kCodeOffset as it is treated weakly here.

[ulan, 2012/10/12 11:48:32]

Maybe add static asserts that kNameOffset + kPointerSize == kCodeOffset and
kCodeOffset + kPointerSize == kOptimizesCodeMapOffset?

[Michael Starzinger, 2012/10/12 12:16:37]

Done.

+
+  Object** start_slot =
+      HeapObject::RawField(object,
+                           SharedFunctionInfo::kOptimizedCodeMapOffset);
+  Object** end_slot =
+      HeapObject::RawField(object,
+                           SharedFunctionInfo::BodyDescriptor::kEndOffset);
+  StaticVisitor::VisitPointers(heap, start_slot, start_slot, end_slot);
+}
+
+
+template<typename StaticVisitor>
+void StaticMarkingVisitor<StaticVisitor>::VisitJSFunctionStrongCode(
+    Heap* heap, HeapObject* object) {
+  Object** start_slot =
+      HeapObject::RawField(object, JSFunction::kPropertiesOffset);
+  Object** end_slot =
+      HeapObject::RawField(object, JSFunction::kCodeEntryOffset);
+  StaticVisitor::VisitPointers(heap, start_slot, start_slot, end_slot);
+
+  VisitCodeEntry(heap, object->address() + JSFunction::kCodeEntryOffset);

[Michael Starzinger, 2012/10/12 12:16:37]

As discussed offline, I also added the static assert here.

+
+  start_slot =
+      HeapObject::RawField(object, JSFunction::kPrototypeOrInitialMapOffset);
+  end_slot =
+      HeapObject::RawField(object, JSFunction::kNonWeakFieldsEndOffset);
+  StaticVisitor::VisitPointers(heap, start_slot, start_slot, end_slot);
+}
+
+
+template<typename StaticVisitor>
+void StaticMarkingVisitor<StaticVisitor>::VisitJSFunctionWeakCode(
+    Heap* heap, HeapObject* object) {
+  Object** start_slot =
+      HeapObject::RawField(object, JSFunction::kPropertiesOffset);
+  Object** end_slot =
+      HeapObject::RawField(object, JSFunction::kCodeEntryOffset);
+  StaticVisitor::VisitPointers(heap, start_slot, start_slot, end_slot);
+
+  // Skip visiting kCodeEntryOffset as it is treated weakly here.

[ulan, 2012/10/12 11:48:32]

Maybe add static asserts as in the comment above?

[Michael Starzinger, 2012/10/12 12:16:37]

Done.

+
+  start_slot =
+      HeapObject::RawField(object, JSFunction::kPrototypeOrInitialMapOffset);
+  end_slot =
+      HeapObject::RawField(object, JSFunction::kNonWeakFieldsEndOffset);
+  StaticVisitor::VisitPointers(heap, start_slot, start_slot, end_slot);
+}
+
 
 void Code::CodeIterateBody(ObjectVisitor* v) {
   int mode_mask = RelocInfo::kCodeTargetMask |
                   RelocInfo::ModeMask(RelocInfo::EMBEDDED_OBJECT) |
                   RelocInfo::ModeMask(RelocInfo::GLOBAL_PROPERTY_CELL) |
                   RelocInfo::ModeMask(RelocInfo::EXTERNAL_REFERENCE) |
                   RelocInfo::ModeMask(RelocInfo::JS_RETURN) |
                   RelocInfo::ModeMask(RelocInfo::DEBUG_BREAK_SLOT) |
                   RelocInfo::ModeMask(RelocInfo::RUNTIME_ENTRY);
 
@@ skipping 39 matching lines @@
   RelocIterator it(this, mode_mask);
   for (; !it.done(); it.next()) {
     it.rinfo()->template Visit<StaticVisitor>(heap);
   }
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_VISITING_INL_H_