Layout descriptor must be trimmed when corresponding descriptors array is trimmed to stay in sync.

src/layout-descriptor-inl.h

Index: src/layout-descriptor-inl.h
diff --git a/src/layout-descriptor-inl.h b/src/layout-descriptor-inl.h
index ceee09a8105603102d201b8d812cc7f0ec194325..248bd00f2fe93ee19477ae90b37cd7b9d0b13344 100644
--- a/src/layout-descriptor-inl.h
+++ b/src/layout-descriptor-inl.h
@@ -154,6 +154,61 @@ LayoutDescriptor* LayoutDescriptor::cast_gc_safe(Object* object) {
 }
 
 
+int LayoutDescriptor::CalculateCapacity(Map* map, DescriptorArray* descriptors,
+                                        int num_descriptors) {
+  int inobject_properties = map->inobject_properties();
+  if (inobject_properties == 0) return 0;
+
+  DCHECK(num_descriptors <= descriptors->number_of_descriptors());

[Toon Verwaest, 2015/03/30 11:42:25]

_LE

[Igor Sheludko, 2015/03/30 16:01:29]

Done.

+
+  int layout_descriptor_length;
+  const int kMaxWordsPerField = kDoubleSize / kPointerSize;
+
+  if (num_descriptors <= kSmiValueSize / kMaxWordsPerField) {
+    // Even in the "worst" case (all fields are doubles) it would fit into
+    // a Smi, so no need to calculate length.
+    layout_descriptor_length = kSmiValueSize;
+
+  } else {
+    layout_descriptor_length = 0;
+
+    for (int i = 0; i < num_descriptors; i++) {
+      PropertyDetails details = descriptors->GetDetails(i);
+      if (!InobjectUnboxedField(inobject_properties, details)) continue;
+      int field_index = details.field_index();
+      int field_width_in_words = details.field_width_in_words();
+      layout_descriptor_length =
+          Max(layout_descriptor_length, field_index + field_width_in_words);
+    }
+  }
+  layout_descriptor_length = Min(layout_descriptor_length, inobject_properties);
+  return layout_descriptor_length;
+}
+
+
+LayoutDescriptor* LayoutDescriptor::Initialize(
+    LayoutDescriptor* layout_descriptor, Map* map, DescriptorArray* descriptors,
+    int num_descriptors) {
+  DisallowHeapAllocation no_allocation;
+  int inobject_properties = map->inobject_properties();
+
+  for (int i = 0; i < num_descriptors; i++) {
+    PropertyDetails details = descriptors->GetDetails(i);
+    if (!InobjectUnboxedField(inobject_properties, details)) {
+      DCHECK(details.location() != kField ||
+             layout_descriptor->IsTagged(details.field_index()));
+      continue;
+    }
+    int field_index = details.field_index();
+    layout_descriptor = layout_descriptor->SetRawData(field_index);
+    if (details.field_width_in_words() > 1) {
+      layout_descriptor = layout_descriptor->SetRawData(field_index + 1);
+    }
+  }
+  return layout_descriptor;
+}
+
+
 // InobjectPropertiesHelper is a helper class for querying whether inobject
 // property at offset is Double or not.
 LayoutDescriptorHelper::LayoutDescriptorHelper(Map* map)