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@@ -1,335 +0,0 @@
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-From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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-From: Toon Verwaest <[email protected]>
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-Date: Thu, 11 Jan 2024 10:47:17 +0100
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-Subject: Drop fast last-property deletion
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-
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-This interacts badly with other optimizations and isn't particularly
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-common.
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-
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-Bug: chromium:1517354
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-Change-Id: I7adb51a8fc0ec47eaeb911ca2a4cbc517088e416
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-Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/5185340
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-Commit-Queue: Leszek Swirski <[email protected]>
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-Reviewed-by: Leszek Swirski <[email protected]>
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-Auto-Submit: Toon Verwaest <[email protected]>
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-Commit-Queue: Toon Verwaest <[email protected]>
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-Cr-Commit-Position: refs/heads/main@{#91782}
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-
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-diff --git a/src/runtime/runtime-object.cc b/src/runtime/runtime-object.cc
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-index 94af9625f372c09b6cf10aead05f71832c274a6b..87b20def865db3cd1f50e35c70f8aedf226bdede 100644
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---- a/src/runtime/runtime-object.cc
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-+++ b/src/runtime/runtime-object.cc
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-@@ -71,186 +71,10 @@ MaybeHandle<Object> Runtime::HasProperty(Isolate* isolate,
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- return ReadOnlyRoots(isolate).boolean_value_handle(maybe.FromJust());
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- }
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-
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--namespace {
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--
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--// This function sets the sentinel value in a deleted field. Thes sentinel has
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--// to look like a proper standalone object because the slack tracking may
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--// complete at any time. For this reason we use the filler map word.
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--// If V8_MAP_PACKING is enabled, then the filler map word is a packed filler
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--// map. Otherwise, the filler map word is the same as the filler map.
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--inline void ClearField(Isolate* isolate, Tagged<JSObject> object,
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-- FieldIndex index) {
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-- if (index.is_inobject()) {
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-- MapWord filler_map_word =
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-- ReadOnlyRoots(isolate).one_pointer_filler_map_word();
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--#ifndef V8_MAP_PACKING
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-- DCHECK_EQ(filler_map_word.ToMap(),
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-- ReadOnlyRoots(isolate).one_pointer_filler_map());
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--#endif
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-- int offset = index.offset();
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-- TaggedField<MapWord>::Release_Store(object, offset, filler_map_word);
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-- } else {
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-- object->property_array()->set(
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-- index.outobject_array_index(),
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-- ReadOnlyRoots(isolate).one_pointer_filler_map());
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-- }
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--}
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--
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--void GeneralizeAllTransitionsToFieldAsMutable(Isolate* isolate, Handle<Map> map,
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-- Handle<Name> name) {
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-- InternalIndex descriptor(map->NumberOfOwnDescriptors());
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--
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-- Handle<Map> target_maps[kPropertyAttributesCombinationsCount];
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-- int target_maps_count = 0;
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--
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-- // Collect all outgoing field transitions.
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-- {
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-- DisallowGarbageCollection no_gc;
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-- TransitionsAccessor transitions(isolate, *map);
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-- transitions.ForEachTransitionTo(
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-- *name,
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-- [&](Tagged<Map> target) {
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-- DCHECK_EQ(descriptor, target->LastAdded());
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-- DCHECK_EQ(*name, target->GetLastDescriptorName(isolate));
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-- PropertyDetails details = target->GetLastDescriptorDetails(isolate);
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-- // Currently, we track constness only for fields.
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-- if (details.kind() == PropertyKind::kData &&
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-- details.constness() == PropertyConstness::kConst) {
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-- target_maps[target_maps_count++] = handle(target, isolate);
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-- }
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-- DCHECK_IMPLIES(details.kind() == PropertyKind::kAccessor,
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-- details.constness() == PropertyConstness::kConst);
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-- },
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-- &no_gc);
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-- CHECK_LE(target_maps_count, kPropertyAttributesCombinationsCount);
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-- }
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--
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-- for (int i = 0; i < target_maps_count; i++) {
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-- Handle<Map> target = target_maps[i];
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-- PropertyDetails details =
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-- target->instance_descriptors(isolate)->GetDetails(descriptor);
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-- Handle<FieldType> field_type(
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-- target->instance_descriptors(isolate)->GetFieldType(descriptor),
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-- isolate);
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-- MapUpdater::GeneralizeField(isolate, target, descriptor,
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-- PropertyConstness::kMutable,
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-- details.representation(), field_type);
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-- DCHECK_EQ(PropertyConstness::kMutable, target->instance_descriptors(isolate)
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-- ->GetDetails(descriptor)
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-- .constness());
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-- }
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--}
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--
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--bool DeleteObjectPropertyFast(Isolate* isolate, Handle<JSReceiver> receiver,
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-- Handle<Object> raw_key) {
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-- // This implements a special case for fast property deletion: when the
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-- // last property in an object is deleted, then instead of normalizing
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-- // the properties, we can undo the last map transition, with a few
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-- // prerequisites:
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-- // (1) The receiver must be a regular object and the key a unique name.
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-- Handle<Map> receiver_map(receiver->map(), isolate);
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-- if (IsSpecialReceiverMap(*receiver_map)) return false;
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-- DCHECK(IsJSObjectMap(*receiver_map));
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--
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-- if (!IsUniqueName(*raw_key)) return false;
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-- Handle<Name> key = Handle<Name>::cast(raw_key);
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-- // (2) The property to be deleted must be the last property.
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-- int nof = receiver_map->NumberOfOwnDescriptors();
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-- if (nof == 0) return false;
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-- InternalIndex descriptor(nof - 1);
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-- Handle<DescriptorArray> descriptors(
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-- receiver_map->instance_descriptors(isolate), isolate);
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-- if (descriptors->GetKey(descriptor) != *key) return false;
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-- // (3) The property to be deleted must be deletable.
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-- PropertyDetails details = descriptors->GetDetails(descriptor);
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-- if (!details.IsConfigurable()) return false;
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-- // (4) The map must have a back pointer.
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-- Handle<Object> backpointer(receiver_map->GetBackPointer(), isolate);
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-- if (!IsMap(*backpointer)) return false;
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-- Handle<Map> parent_map = Handle<Map>::cast(backpointer);
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-- // (5) The last transition must have been caused by adding a property
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-- // (and not any kind of special transition).
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-- if (parent_map->NumberOfOwnDescriptors() != nof - 1) return false;
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--
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-- // Preconditions successful. No more bailouts after this point.
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--
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-- // Zap the property to avoid keeping objects alive. Zapping is not necessary
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-- // for properties stored in the descriptor array.
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-- if (details.location() == PropertyLocation::kField) {
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-- DisallowGarbageCollection no_gc;
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--
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-- // Invalidate slots manually later in case we delete an in-object tagged
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-- // property. In this case we might later store an untagged value in the
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-- // recorded slot.
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-- isolate->heap()->NotifyObjectLayoutChange(
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-- *receiver, no_gc, InvalidateRecordedSlots::kNo,
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-- InvalidateExternalPointerSlots::kNo);
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-- FieldIndex index =
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-- FieldIndex::ForPropertyIndex(*receiver_map, details.field_index());
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-- // Special case deleting the last out-of object property.
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-- if (!index.is_inobject() && index.outobject_array_index() == 0) {
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-- DCHECK(!parent_map->HasOutOfObjectProperties());
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-- // Clear out the properties backing store.
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-- receiver->SetProperties(ReadOnlyRoots(isolate).empty_fixed_array());
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-- } else {
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-- ClearField(isolate, JSObject::cast(*receiver), index);
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-- if (index.is_inobject()) {
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-- // We need to clear the recorded slot in this case because in-object
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-- // slack tracking might not be finished. This ensures that we don't
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-- // have recorded slots in free space.
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-- isolate->heap()->ClearRecordedSlot(*receiver,
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-- receiver->RawField(index.offset()));
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-- }
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-- }
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-- }
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-- // If the {receiver_map} was marked stable before, then there could be
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-- // optimized code that depends on the assumption that no object that
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-- // reached this {receiver_map} transitions away from it without triggering
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-- // the "deoptimize dependent code" mechanism.
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-- receiver_map->NotifyLeafMapLayoutChange(isolate);
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-- // Finally, perform the map rollback.
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-- receiver->set_map(*parent_map, kReleaseStore);
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--#if VERIFY_HEAP
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-- if (v8_flags.verify_heap) {
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-- receiver->HeapObjectVerify(isolate);
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-- receiver->property_array()->PropertyArrayVerify(isolate);
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-- }
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--#endif
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--
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-- // If the {descriptor} was "const" so far, we need to update the
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-- // {receiver_map} here, otherwise we could get the constants wrong, i.e.
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-- //
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-- // o.x = 1;
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-- // [change o.x's attributes or reconfigure property kind]
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-- // delete o.x;
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-- // o.x = 2;
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-- //
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-- // could trick V8 into thinking that `o.x` is still 1 even after the second
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-- // assignment.
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--
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-- // Step 1: Migrate object to an up-to-date shape.
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-- if (parent_map->is_deprecated()) {
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-- JSObject::MigrateInstance(isolate, Handle<JSObject>::cast(receiver));
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-- parent_map = handle(receiver->map(), isolate);
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-- }
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--
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-- // Step 2: Mark outgoing transitions from the up-to-date version of the
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-- // parent_map to same property name of any kind or attributes as mutable.
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-- // Also migrate object to the up-to-date map to make the object shapes
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-- // converge sooner.
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-- GeneralizeAllTransitionsToFieldAsMutable(isolate, parent_map, key);
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--
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-- return true;
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--}
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--
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--} // namespace
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--
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- Maybe<bool> Runtime::DeleteObjectProperty(Isolate* isolate,
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- Handle<JSReceiver> receiver,
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- Handle<Object> key,
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- LanguageMode language_mode) {
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-- if (DeleteObjectPropertyFast(isolate, receiver, key)) return Just(true);
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--
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- bool success = false;
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- PropertyKey lookup_key(isolate, key, &success);
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- if (!success) return Nothing<bool>();
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-diff --git a/test/cctest/test-field-type-tracking.cc b/test/cctest/test-field-type-tracking.cc
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-index 41500ea14a571d3a081c79ed10f0d37430df852c..65193aa2308764cdf64c1c75d5a8ada4e6315c30 100644
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---- a/test/cctest/test-field-type-tracking.cc
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-+++ b/test/cctest/test-field-type-tracking.cc
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-@@ -3030,122 +3030,6 @@ TEST(RepresentationPredicatesAreInSync) {
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- }
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- }
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-
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--TEST(DeletePropertyGeneralizesConstness) {
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-- CcTest::InitializeVM();
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-- v8::HandleScope scope(CcTest::isolate());
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-- Isolate* isolate = CcTest::i_isolate();
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-- Handle<FieldType> any_type = FieldType::Any(isolate);
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--
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-- // Create a map with some properties.
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-- Handle<Map> initial_map = Map::Create(isolate, kPropCount + 3);
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-- Handle<Map> map = initial_map;
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-- for (int i = 0; i < kPropCount; i++) {
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-- Handle<String> name = CcTest::MakeName("prop", i);
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-- map = Map::CopyWithField(isolate, map, name, any_type, NONE,
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-- PropertyConstness::kConst, Representation::Smi(),
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-- INSERT_TRANSITION)
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-- .ToHandleChecked();
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-- }
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-- Handle<Map> parent_map = map;
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-- CHECK(!map->is_deprecated());
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--
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-- Handle<String> name_x = CcTest::MakeString("x");
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-- Handle<String> name_y = CcTest::MakeString("y");
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--
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-- map = Map::CopyWithField(isolate, parent_map, name_x, any_type, NONE,
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-- PropertyConstness::kConst, Representation::Smi(),
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-- INSERT_TRANSITION)
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-- .ToHandleChecked();
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--
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-- // Create an object, initialize its properties and add a couple of clones.
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-- Handle<JSObject> object1 = isolate->factory()->NewJSObjectFromMap(map);
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-- for (int i = 0; i < kPropCount; i++) {
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-- FieldIndex index = FieldIndex::ForDescriptor(*map, InternalIndex(i));
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-- object1->FastPropertyAtPut(index, Smi::FromInt(i));
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-- }
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-- Handle<JSObject> object2 = isolate->factory()->CopyJSObject(object1);
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--
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-- CHECK(!map->is_deprecated());
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-- CHECK(!parent_map->is_deprecated());
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--
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-- // Transition to Double must deprecate m1.
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-- CHECK(!Representation::Smi().CanBeInPlaceChangedTo(Representation::Double()));
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--
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-- // Reconfigure one of the first properties to make the whole transition tree
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-- // deprecated (including |parent_map| and |map|).
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-- Handle<Map> new_map =
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-- ReconfigureProperty(isolate, map, InternalIndex(0), PropertyKind::kData,
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-- NONE, Representation::Double(), any_type);
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-- CHECK(map->is_deprecated());
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-- CHECK(parent_map->is_deprecated());
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-- CHECK(!new_map->is_deprecated());
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-- // The "x" property is still kConst.
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-- CHECK_EQ(new_map->GetLastDescriptorDetails(isolate).constness(),
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-- PropertyConstness::kConst);
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--
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-- Handle<Map> new_parent_map = Map::Update(isolate, parent_map);
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-- CHECK(!new_parent_map->is_deprecated());
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--
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-- // |new_parent_map| must have exactly one outgoing transition to |new_map|.
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-- {
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-- TransitionsAccessor ta(isolate, *new_parent_map);
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-- CHECK_EQ(ta.NumberOfTransitions(), 1);
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-- CHECK_EQ(ta.GetTarget(0), *new_map);
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-- }
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--
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-- // Deletion of the property from |object1| must migrate it to |new_parent_map|
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-- // which is an up-to-date version of the |parent_map|. The |new_map|'s "x"
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-- // property should be marked as mutable.
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-- CHECK_EQ(object1->map(isolate), *map);
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-- CHECK(Runtime::DeleteObjectProperty(isolate, object1, name_x,
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-- LanguageMode::kSloppy)
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-- .ToChecked());
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-- CHECK_EQ(object1->map(isolate), *new_parent_map);
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-- CHECK_EQ(new_map->GetLastDescriptorDetails(isolate).constness(),
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-- PropertyConstness::kMutable);
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--
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-- // Now add transitions to "x" and "y" properties from |new_parent_map|.
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-- std::vector<Handle<Map>> transitions;
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-- Handle<Object> value = handle(Smi::FromInt(0), isolate);
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-- for (int i = 0; i < kPropertyAttributesCombinationsCount; i++) {
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-- auto attributes = PropertyAttributesFromInt(i);
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--
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-- Handle<Map> tmp;
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-- // Add some transitions to "x" and "y".
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-- tmp = Map::TransitionToDataProperty(isolate, new_parent_map, name_x, value,
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-- attributes, PropertyConstness::kConst,
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-- StoreOrigin::kNamed);
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-- CHECK(!tmp->map(isolate)->is_dictionary_map());
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-- transitions.push_back(tmp);
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--
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-- tmp = Map::TransitionToDataProperty(isolate, new_parent_map, name_y, value,
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-- attributes, PropertyConstness::kConst,
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-- StoreOrigin::kNamed);
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-- CHECK(!tmp->map(isolate)->is_dictionary_map());
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-- transitions.push_back(tmp);
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-- }
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--
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-- // Deletion of the property from |object2| must migrate it to |new_parent_map|
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-- // which is an up-to-date version of the |parent_map|.
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-- // All outgoing transitions from |new_map| that add "x" must be marked as
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-- // mutable, transitions to other properties must remain const.
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-- CHECK_EQ(object2->map(isolate), *map);
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-- CHECK(Runtime::DeleteObjectProperty(isolate, object2, name_x,
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-- LanguageMode::kSloppy)
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-- .ToChecked());
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-- CHECK_EQ(object2->map(isolate), *new_parent_map);
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-- for (Handle<Map> m : transitions) {
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-- if (m->GetLastDescriptorName(isolate) == *name_x) {
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-- CHECK_EQ(m->GetLastDescriptorDetails(isolate).constness(),
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-- PropertyConstness::kMutable);
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--
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-- } else {
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-- CHECK_EQ(m->GetLastDescriptorDetails(isolate).constness(),
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-- PropertyConstness::kConst);
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-- }
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-- }
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--}
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--
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- #define CHECK_SAME(object, rep, expected) \
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- CHECK_EQ(Object::FitsRepresentation(*object, rep, true), \
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- Object::FitsRepresentation(*object, rep, false)); \
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