Revision: 8516 Author: [email protected] Date: Fri Jul 1 06:18:42 2011 Log: Do a backing store sparseness check on fast element delete.
[email protected] Review URL: http://codereview.chromium.org/7298004 http://code.google.com/p/v8/source/detail?r=8516 Modified: /branches/bleeding_edge/src/objects.cc ======================================= --- /branches/bleeding_edge/src/objects.cc Wed Jun 29 07:56:08 2011 +++ /branches/bleeding_edge/src/objects.cc Fri Jul 1 06:18:42 2011 @@ -3031,11 +3031,33 @@ if (!maybe->ToObject(&writable)) return maybe; backing_store = FixedArray::cast(writable); } - int length = IsJSArray() + uint32_t length = static_cast<uint32_t>( + IsJSArray() ? Smi::cast(JSArray::cast(this)->length())->value() - : backing_store->length(); - if (index < static_cast<uint32_t>(length)) { + : backing_store->length()); + if (index < length) { backing_store->set_the_hole(index); + // If an old space backing store is larger than a certain size and + // has too few used values, normalize it. + // To avoid doing the check on every delete we require at least + // one adjacent hole to the value being deleted. + Object* hole = heap->the_hole_value(); + const int kMinLengthForSparsenessCheck = 64; + if (backing_store->length() >= kMinLengthForSparsenessCheck && + !heap->InNewSpace(backing_store) && + ((index > 0 && backing_store->get(index - 1) == hole) || + (index + 1 < length && backing_store->get(index + 1) == hole))) { + int num_used = 0; + for (int i = 0; i < backing_store->length(); ++i) { + if (backing_store->get(i) != hole) ++num_used; + // Bail out early if more than 1/4 is used. + if (4 * num_used > backing_store->length()) break; + } + if (4 * num_used <= backing_store->length()) { + MaybeObject* result = NormalizeElements(); + if (result->IsFailure()) return result; + } + } } return heap->true_value(); } -- v8-dev mailing list [email protected] http://groups.google.com/group/v8-dev
