Reviewers: Michael Starzinger,
Message:
The added patch fixes the iteration bug introduced in the second patch of
the
original issue. Now seems to run stable. Please verify.
Description:
TraversableMap only dependent on DescriptorArray
This is the first step towards merging the ContentArray into the
DescriptorArray, (hence reclaiming 3 words per descriptor array).
Please review this at https://chromiumcodereview.appspot.com/10455005/
SVN Base: https://v8.googlecode.com/svn/branches/bleeding_edge
Affected files:
M src/objects.h
M src/objects.cc
Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index
a8970584d8b3e206d6dc0abc89084d8046b5887e..46eb2be34b0a383645e9f91c1dac53cbfb9b8d97
100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -5088,39 +5088,46 @@ class IntrusiveMapTransitionIterator {
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;
+ int num = descriptor_array_->number_of_descriptors();
+ while (index < num) {
+ 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;
+ if ((raw_index & 1) == 0) {
+ accessor = accessors->getter();
+ } else {
+ ++index;
+ accessor = accessors->setter();
+ }
+ ++raw_index;
if (accessor->IsMap()) {
- *ContentHeader() = Smi::FromInt(index);
+ *DescriptorArrayHeader() = Smi::FromInt(raw_index);
return static_cast<Map*>(accessor);
}
break;
@@ -5132,28 +5139,42 @@ class IntrusiveMapTransitionIterator {
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;
+ }
+
+ Object** DescriptorArrayHeader() {
+ return HeapObject::RawField(descriptor_array_,
DescriptorArray::kMapOffset);
+ }
+
+ FixedArray* RawGetContentArray() {
+ Object* array =
+ descriptor_array_->get(DescriptorArray::kContentArrayIndex);
+ return static_cast<FixedArray*>(array);
}
- FixedArray* ContentArray() {
- Object* array =
descriptor_array_->get(DescriptorArray::kContentArrayIndex);
- return static_cast<FixedArray*>(array);
+ Object* RawGetValue(int descriptor_number) {
+ return RawGetContentArray()->get(
+ DescriptorArray::ToValueIndex(descriptor_number));
}
- Object** ContentHeader() {
- return HeapObject::RawField(ContentArray(),
DescriptorArray::kMapOffset);
+ PropertyDetails RawGetDetails(int descriptor_number) {
+ Object* details = RawGetContentArray()->get(
+ DescriptorArray::ToDetailsIndex(descriptor_number));
+ return PropertyDetails(Smi::cast(details));
}
+
DescriptorArray* descriptor_array_;
};
@@ -5252,6 +5273,22 @@ class TraversableMap : public 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);
+ ASSERT((*HeapObject::RawField(descriptor_array,
+
DescriptorArray::kMapOffset))->IsSmi());
+ return descriptor_array;
+ }
+ }
+
// Start iterating over this map's children, possibly destroying a
FixedArray
// map (see explanation above).
void ChildIteratorStart() {
@@ -5263,7 +5300,8 @@ class TraversableMap : public Map {
// 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());
+ IntrusiveMapTransitionIterator
+ descriptor_iterator(MutatedInstanceDescriptors());
if (descriptor_iterator.IsIterating()) {
Map* next = descriptor_iterator.Next();
if (next != NULL) return static_cast<TraversableMap*>(next);
Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index
e9dfe6ca55b94b8a923137b3cdfbcd47355ae79e..b6462dd78770e318d70c97187ea0ce97a914961d
100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -2588,6 +2588,8 @@ class DescriptorArray: public FixedArray {
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 @@ class DescriptorArray: public FixedArray {
FixedArray* GetContentArray() {
return FixedArray::cast(get(kContentArrayIndex));
}
+
DISALLOW_IMPLICIT_CONSTRUCTORS(DescriptorArray);
};
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