Revision: 11665
Author: [email protected]
Date: Fri May 25 06:03:34 2012
Log: TraversableMap only dependent on DescriptorArray
This is the first step towards merging the ContentArray into the
DescriptorArray, (hence reclaiming 3 words per descriptor array).
Review URL: https://chromiumcodereview.appspot.com/10411067
http://code.google.com/p/v8/source/detail?r=11665
Modified:
/branches/bleeding_edge/src/objects.cc
/branches/bleeding_edge/src/objects.h
=======================================
--- /branches/bleeding_edge/src/objects.cc Fri May 25 05:32:02 2012
+++ /branches/bleeding_edge/src/objects.cc Fri May 25 06:03:34 2012
@@ -5088,39 +5088,40 @@
void Start() {
ASSERT(!IsIterating());
- if (HasContentArray()) *ContentHeader() = Smi::FromInt(0);
+ if (HasDescriptors()) *DescriptorArrayHeader() = Smi::FromInt(0);
}
bool IsIterating() {
- return HasContentArray() && (*ContentHeader())->IsSmi();
+ return HasDescriptors() && (*DescriptorArrayHeader())->IsSmi();
}
Map* Next() {
ASSERT(IsIterating());
- FixedArray* contents = ContentArray();
- // Attention, tricky index manipulation ahead: Every entry in the
contents
- // array consists of a value/details pair, so the index is typically
even.
- // An exception is made for CALLBACKS entries: An even index means we
look
- // at its getter, and an odd index means we look at its setter.
- int index = Smi::cast(*ContentHeader())->value();
- while (index < contents->length()) {
- PropertyDetails details(Smi::cast(contents->get(index | 1)));
+ // Attention, tricky index manipulation ahead: Two consecutive indices
are
+ // assigned to each descriptor. Most descriptors directly advance to
the
+ // next descriptor by adding 2 to the index. The exceptions are the
+ // CALLBACKS entries: An even index means we look at its getter, and
an odd
+ // index means we look at its setter.
+ int raw_index = Smi::cast(*DescriptorArrayHeader())->value();
+ int index = raw_index / 2;
+ while (index < descriptor_array_->number_of_descriptors()) {
+ PropertyDetails details(RawGetDetails(index));
switch (details.type()) {
case MAP_TRANSITION:
case CONSTANT_TRANSITION:
case ELEMENTS_TRANSITION:
// We definitely have a map transition.
- *ContentHeader() = Smi::FromInt(index + 2);
- return static_cast<Map*>(contents->get(index));
+ *DescriptorArrayHeader() = Smi::FromInt(raw_index + 2);
+ return static_cast<Map*>(RawGetValue(index));
case CALLBACKS: {
// We might have a map transition in a getter or in a setter.
AccessorPair* accessors =
- static_cast<AccessorPair*>(contents->get(index & ~1));
- Object* accessor =
- ((index & 1) == 0) ? accessors->getter() :
accessors->setter();
- index++;
+ static_cast<AccessorPair*>(RawGetValue(index));
+ Object* accessor = ((raw_index & 1) == 0)
+ ? accessors->getter()
+ : accessors->setter();
if (accessor->IsMap()) {
- *ContentHeader() = Smi::FromInt(index);
+ *DescriptorArrayHeader() = Smi::FromInt(raw_index + 1);
return static_cast<Map*>(accessor);
}
break;
@@ -5132,28 +5133,42 @@
case INTERCEPTOR:
case NULL_DESCRIPTOR:
// We definitely have no map transition.
- index += 2;
+ raw_index += 2;
+ ++index;
break;
}
}
- *ContentHeader() = descriptor_array_->GetHeap()->fixed_array_map();
+ *DescriptorArrayHeader() =
descriptor_array_->GetHeap()->fixed_array_map();
return NULL;
}
private:
- bool HasContentArray() {
- return descriptor_array_-> length() >
DescriptorArray::kContentArrayIndex;
+ bool HasDescriptors() {
+ return descriptor_array_-> length() > DescriptorArray::kFirstIndex;
}
- FixedArray* ContentArray() {
- Object* array =
descriptor_array_->get(DescriptorArray::kContentArrayIndex);
- return static_cast<FixedArray*>(array);
+ Object** DescriptorArrayHeader() {
+ return HeapObject::RawField(descriptor_array_,
DescriptorArray::kMapOffset);
}
- Object** ContentHeader() {
- return HeapObject::RawField(ContentArray(),
DescriptorArray::kMapOffset);
+ FixedArray* RawGetContentArray() {
+ Object* array =
+ descriptor_array_->get(DescriptorArray::kContentArrayIndex);
+ return static_cast<FixedArray*>(array);
}
+ Object* RawGetValue(int descriptor_number) {
+ return RawGetContentArray()->get(
+ DescriptorArray::ToValueIndex(descriptor_number));
+ }
+
+ PropertyDetails RawGetDetails(int descriptor_number) {
+ Object* details = RawGetContentArray()->get(
+ DescriptorArray::ToDetailsIndex(descriptor_number));
+ return PropertyDetails(Smi::cast(details));
+ }
+
+
DescriptorArray* descriptor_array_;
};
@@ -5251,6 +5266,23 @@
set_map_no_write_barrier(GetHeap()->meta_map());
return old_parent;
}
+
+ // Can either be Smi (no instance descriptors), or a descriptor array
with the
+ // header overwritten as a Smi (thus iterating).
+ DescriptorArray* MutatedInstanceDescriptors() {
+ Object* object =
+ *HeapObject::RawField(this, kInstanceDescriptorsOrBitField3Offset);
+ if (object->IsSmi()) {
+ return GetHeap()->empty_descriptor_array();
+ } else {
+ DescriptorArray* descriptor_array =
+ static_cast<DescriptorArray*>(object);
+ Object* map =
+ *HeapObject::RawField(descriptor_array,
DescriptorArray::kMapOffset);
+ ASSERT(map->IsSmi());
+ return descriptor_array;
+ }
+ }
// Start iterating over this map's children, possibly destroying a
FixedArray
// map (see explanation above).
@@ -5263,17 +5295,18 @@
// If we have an unvisited child map, return that one and advance. If we
have
// none, return NULL and reset any destroyed FixedArray maps.
TraversableMap* ChildIteratorNext() {
- IntrusiveMapTransitionIterator
descriptor_iterator(instance_descriptors());
- if (descriptor_iterator.IsIterating()) {
- Map* next = descriptor_iterator.Next();
- if (next != NULL) return static_cast<TraversableMap*>(next);
- }
IntrusivePrototypeTransitionIterator
proto_iterator(unchecked_prototype_transitions());
if (proto_iterator.IsIterating()) {
Map* next = proto_iterator.Next();
if (next != NULL) return static_cast<TraversableMap*>(next);
}
+ IntrusiveMapTransitionIterator
+ descriptor_iterator(MutatedInstanceDescriptors());
+ if (descriptor_iterator.IsIterating()) {
+ Map* next = descriptor_iterator.Next();
+ if (next != NULL) return static_cast<TraversableMap*>(next);
+ }
return NULL;
}
};
=======================================
--- /branches/bleeding_edge/src/objects.h Thu May 24 03:40:24 2012
+++ /branches/bleeding_edge/src/objects.h Fri May 25 06:03:34 2012
@@ -2588,6 +2588,8 @@
static const int kMaxNumberOfDescriptors = 1024 + 512;
private:
+ friend class IntrusiveMapTransitionIterator;
+
// An entry in a DescriptorArray, represented as an (array, index) pair.
class Entry {
public:
@@ -2626,6 +2628,7 @@
FixedArray* GetContentArray() {
return FixedArray::cast(get(kContentArrayIndex));
}
+
DISALLOW_IMPLICIT_CONSTRUCTORS(DescriptorArray);
};
--
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