- Fixed performance regression caused by ComputeContextSlotReceiver.

- Eliminated a few write barriers.

Review URL: http://codereview.chromium.org/8103

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@573 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/heap.cc

@@ -1378,12 +1378,11 @@ Object* Heap::AllocateConsString(String* first, String* second) {
 
   Object* result = Allocate(map, NEW_SPACE);
   if (result->IsFailure()) return result;
-
+  ASSERT(InNewSpace(result));
   ConsString* cons_string = ConsString::cast(result);
-  cons_string->set_first(first);
-  cons_string->set_second(second);
+  cons_string->set_first(first, SKIP_WRITE_BARRIER);
+  cons_string->set_second(second, SKIP_WRITE_BARRIER);
   cons_string->set_length(length);
-
   return result;
 }
 
@@ -1615,7 +1614,7 @@ Object* Heap::InitializeFunction(JSFunction* function,
   function->set_shared(shared);
   function->set_prototype_or_initial_map(prototype);
   function->set_context(undefined_value());
-  function->set_literals(empty_fixed_array());
+  function->set_literals(empty_fixed_array(), SKIP_WRITE_BARRIER);
   return function;
 }
 
@@ -1676,14 +1675,6 @@ Object* Heap::AllocateArgumentsObject(Object* callee, int length) {
                                                 Smi::FromInt(length),
                                                 SKIP_WRITE_BARRIER);
 
-  // Allocate the elements if needed.
-  if (length > 0) {
-    // Allocate the fixed array.
-    Object* obj = Heap::AllocateFixedArray(length);
-    if (obj->IsFailure()) return obj;
-    JSObject::cast(result)->set_elements(FixedArray::cast(obj));
-  }
-
   // Check the state of the object
   ASSERT(JSObject::cast(result)->HasFastProperties());
   ASSERT(JSObject::cast(result)->HasFastElements());

src/heap.h

@@ -741,6 +741,9 @@ class Heap : public AllStatic {
     return amount_of_external_allocated_memory_;
   }
 
+  // Allocate unitialized fixed array (pretenure == NON_TENURE).
+  static Object* AllocateRawFixedArray(int length);
+
  private:
   static int semispace_size_;
   static int initial_semispace_size_;
@@ -835,9 +838,6 @@ class Heap : public AllStatic {
   // (since both AllocateRaw and AllocateRawMap are inlined).
   static inline Object* AllocateRawMap(int size_in_bytes);
 
-  // Allocate unitialized fixed array (pretenure == NON_TENURE).
-  static Object* AllocateRawFixedArray(int length);
-
   // Initializes a JSObject based on its map.
   static void InitializeJSObjectFromMap(JSObject* obj,
                                         FixedArray* properties,

src/objects-inl.h

@@ -510,7 +510,7 @@ Object* Object::GetProperty(String* key, PropertyAttributes* attributes) {
 #define WRITE_BARRIER(object, offset) \
   Heap::RecordWrite(object->address(), offset);
 
-// CONITIONAL_WRITE_BARRIER must be issued after the actual
+// CONDITIONAL_WRITE_BARRIER must be issued after the actual
 // write due to the assert validating the written value.
 #define CONDITIONAL_WRITE_BARRIER(object, offset, mode) \
   if (mode == UPDATE_WRITE_BARRIER) { \
@@ -1534,9 +1534,9 @@ Object* ConsString::first() {
 }
 
 
-void ConsString::set_first(Object* value) {
+void ConsString::set_first(Object* value, WriteBarrierMode mode) {
   WRITE_FIELD(this, kFirstOffset, value);
-  WRITE_BARRIER(this, kFirstOffset);
+  CONDITIONAL_WRITE_BARRIER(this, kFirstOffset, mode);
 }
 
 
@@ -1545,9 +1545,9 @@ Object* ConsString::second() {
 }
 
 
-void ConsString::set_second(Object* value) {
+void ConsString::set_second(Object* value, WriteBarrierMode mode) {
   WRITE_FIELD(this, kSecondOffset, value);
-  WRITE_BARRIER(this, kSecondOffset);
+  CONDITIONAL_WRITE_BARRIER(this, kSecondOffset, mode);
 }
 
 
@@ -2071,6 +2071,11 @@ bool JSFunction::is_compiled() {
 }
 
 
+int JSFunction::NumberOfLiterals() {
+  return literals()->length();
+}
+
+
 Object* JSBuiltinsObject::javascript_builtin(Builtins::JavaScript id) {
   ASSERT(0 <= id && id < kJSBuiltinsCount);
   return READ_FIELD(this, kJSBuiltinsOffset + (id * kPointerSize));
@@ -2351,7 +2356,7 @@ void Map::ClearCodeCache() {
 
 
 void JSArray::SetContent(FixedArray* storage) {
-  set_length(Smi::FromInt(storage->length()));
+  set_length(Smi::FromInt(storage->length()), SKIP_WRITE_BARRIER);
   set_elements(storage);
 }
 

src/objects.cc

@@ -2580,14 +2580,15 @@ Object* FixedArray::UnionOfKeys(FixedArray* other) {
   if (obj->IsFailure()) return obj;
   // Fill in the content
   FixedArray* result = FixedArray::cast(obj);
+  WriteBarrierMode mode = result->GetWriteBarrierMode();
   for (int i = 0; i < len0; i++) {
-    result->set(i, get(i));
+    result->set(i, get(i), mode);
   }
   // Fill in the extra keys.
   int index = 0;
   for (int y = 0; y < len1; y++) {
     if (!HasKey(this, other->get(y))) {
-      result->set(len0 + index, other->get(y));
+      result->set(len0 + index, other->get(y), mode);
       index++;
     }
   }
@@ -2601,14 +2602,14 @@ Object* FixedArray::CopySize(int new_length) {
   Object* obj = Heap::AllocateFixedArray(new_length);
   if (obj->IsFailure()) return obj;
   FixedArray* result = FixedArray::cast(obj);
-  WriteBarrierMode mode = result->GetWriteBarrierMode();
   // Copy the content
   int len = length();
   if (new_length < len) len = new_length;
+  result->set_map(map());
+  WriteBarrierMode mode = result->GetWriteBarrierMode();
   for (int i = 0; i < len; i++) {
     result->set(i, get(i), mode);
   }
-  result->set_map(map());
   return result;
 }
 
@@ -4047,11 +4048,6 @@ void Map::MapIterateBody(ObjectVisitor* v) {
 }
 
 
-int JSFunction::NumberOfLiterals() {
-  return literals()->length();
-}
-
-
 Object* JSFunction::SetInstancePrototype(Object* value) {
   ASSERT(value->IsJSObject());
 
@@ -5974,7 +5970,7 @@ Object* LookupCache::Put(Map* map, String* name, int value) {
   int entry = cache->FindInsertionEntry(k, key.Hash());
   int index = EntryToIndex(entry);
   cache->set(index, k);
-  cache->set(index + 1, Smi::FromInt(value));
+  cache->set(index + 1, Smi::FromInt(value), SKIP_WRITE_BARRIER);
   cache->ElementAdded();
   return cache;
 }

src/objects.h

@@ -1601,7 +1601,6 @@ class DescriptorArray: public FixedArray {
   inline void Get(int descriptor_number, Descriptor* desc);
   inline void Set(int descriptor_number, Descriptor* desc);
 
-
   // Copy the descriptor array, insert a new descriptor and optionally
   // remove map transitions.  If the descriptor is already present, it is
   // replaced.  If a replaced descriptor is a real property (not a transition
@@ -2750,7 +2749,7 @@ class JSFunction: public JSObject {
 #endif
 
   // Returns the number of allocated literals.
-  int NumberOfLiterals();
+  inline int NumberOfLiterals();
 
   // Retrieve the global context from a function's literal array.
   static Context* GlobalContextFromLiterals(FixedArray* literals);
@@ -3347,11 +3346,13 @@ class ConsString: public String {
  public:
   // First object of the cons cell.
   inline Object* first();
-  inline void set_first(Object* first);
+  inline void set_first(Object* first,
+                        WriteBarrierMode mode = UPDATE_WRITE_BARRIER);
 
   // Second object of the cons cell.
   inline Object* second();
-  inline void set_second(Object* second);
+  inline void set_second(Object* second,
+                         WriteBarrierMode mode = UPDATE_WRITE_BARRIER);
 
   // Dispatched behavior.
   uint16_t ConsStringGet(int index);

src/runtime.cc

@@ -928,7 +928,7 @@ static Object* Runtime_SetCode(Arguments args) {
       literals->set(JSFunction::kLiteralGlobalContextIndex,
                     context->global_context());
     }
-    target->set_literals(*literals);
+    target->set_literals(*literals, SKIP_WRITE_BARRIER);
   }
 
   target->set_context(*context);
@@ -3134,11 +3134,16 @@ static Object* Runtime_NewArguments(Arguments args) {
   const int length = frame->GetProvidedParametersCount();
   Object* result = Heap::AllocateArgumentsObject(callee, length);
   if (result->IsFailure()) return result;
-  FixedArray* array = FixedArray::cast(JSObject::cast(result)->elements());
-  ASSERT(array->length() == length);
-  WriteBarrierMode mode = array->GetWriteBarrierMode();
-  for (int i = 0; i < length; i++) {
-    array->set(i, frame->GetParameter(i), mode);
+  if (length > 0) {
+    Object* obj =  Heap::AllocateFixedArray(length);
+    if (obj->IsFailure()) return obj;
+    FixedArray* array = FixedArray::cast(obj);
+    ASSERT(array->length() == length);
+    WriteBarrierMode mode = array->GetWriteBarrierMode();
+    for (int i = 0; i < length; i++) {
+      array->set(i, frame->GetParameter(i), mode);
+    }
+    JSObject::cast(result)->set_elements(array);
   }
   return result;
 }
@@ -3154,11 +3159,22 @@ static Object* Runtime_NewArgumentsFast(Arguments args) {
 
   Object* result = Heap::AllocateArgumentsObject(callee, length);
   if (result->IsFailure()) return result;
-  FixedArray* array = FixedArray::cast(JSObject::cast(result)->elements());
-  ASSERT(array->length() == length);
-  WriteBarrierMode mode = array->GetWriteBarrierMode();
-  for (int i = 0; i < length; i++) {
-    array->set(i, *--parameters, mode);
+  ASSERT(Heap::InNewSpace(result));
+
+  // Allocate the elements if needed.
+  if (length > 0) {
+    // Allocate the fixed array.
+    Object* obj = Heap::AllocateRawFixedArray(length);
+    if (obj->IsFailure()) return obj;
+    reinterpret_cast<Array*>(obj)->set_map(Heap::fixed_array_map());
+    FixedArray* array = FixedArray::cast(obj);
+    array->set_length(length);
+    WriteBarrierMode mode = array->GetWriteBarrierMode();
+    for (int i = 0; i < length; i++) {
+      array->set(i, *--parameters, mode);
+    }
+    JSObject::cast(result)->set_elements(FixedArray::cast(obj),
+                                         SKIP_WRITE_BARRIER);
   }
   return result;
 }
@@ -3366,10 +3382,17 @@ static Object* ComputeContextSlotReceiver(Object* holder) {
   // If the "property" we were looking for is a local variable or an
   // argument in a context, the receiver is the global object; see
   // ECMA-262, 3rd., 10.1.6 and 10.2.3.
-  HeapObject* object = HeapObject::cast(holder);
-  Context* top = Top::context();
-  if (holder->IsContext()) return top->global()->global_receiver();
+  // Contexts and global objects are most common.
+  if (holder->IsContext()) {
+    return Context::cast(holder)->global()->global_receiver();
+  }
+  if (holder->IsGlobalObject()) {
+    // If the holder is a global object, we have to be careful to wrap
+    // it in its proxy if necessary.
+    return GlobalObject::cast(holder)->global_receiver();
+  }
 
+  Context* top = Top::context();
   // TODO(125): Find a better - and faster way - of checking for
   // arguments and context extension objects. This kinda sucks.
   JSFunction* context_extension_function =
@@ -3386,13 +3409,7 @@ static Object* ComputeContextSlotReceiver(Object* holder) {
     return Top::context()->global()->global_receiver();
   }
 
-  // If the holder is a global object, we have to be careful to wrap
-  // it in its proxy if necessary.
-  if (object->IsGlobalObject()) {
-    return GlobalObject::cast(object)->global_receiver();
-  } else {
-    return object;
-  }
+  return holder;
 }
 
 
@@ -4900,13 +4917,13 @@ static Handle<Object> GetArgumentsObject(JavaScriptFrame* frame,
   }
 
   const int length = frame->GetProvidedParametersCount();
-  Handle<Object> arguments = Factory::NewArgumentsObject(function, length);
-  FixedArray* array = FixedArray::cast(JSObject::cast(*arguments)->elements());
-  ASSERT(array->length() == length);
+  Handle<JSObject> arguments = Factory::NewArgumentsObject(function, length);
+  Handle<FixedArray> array = Factory::NewFixedArray(length);
   WriteBarrierMode mode = array->GetWriteBarrierMode();
   for (int i = 0; i < length; i++) {
     array->set(i, frame->GetParameter(i), mode);
   }
+  arguments->set_elements(*array);
   return arguments;
 }