[heap] Remove deletion entries from store buffer

Get rid of deletion entries in the store buffer. Clearing a slot now
first empties the store buffer and then directly deletes the slot
from the remembered set.

Bug: v8:9454
Change-Id: I656db593a0478db3fa63324d7f3c6862b4b5e776
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1766130Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#63359}

src/heap/heap.cc

@@ -5527,7 +5527,8 @@ void Heap::ClearRecordedSlot(HeapObject object, ObjectSlot slot) {
   Page* page = Page::FromAddress(slot.address());
   if (!page->InYoungGeneration()) {
     DCHECK_EQ(page->owner_identity(), OLD_SPACE);
-    store_buffer()->DeleteEntry(slot.address());
+    store_buffer()->MoveAllEntriesToRememberedSet();
+    RememberedSet<OLD_TO_NEW>::Remove(page, slot.address());
   }
 }
 
@@ -5550,7 +5551,9 @@ void Heap::ClearRecordedSlotRange(Address start, Address end) {
   DCHECK(!page->IsLargePage());
   if (!page->InYoungGeneration()) {
     DCHECK_EQ(page->owner_identity(), OLD_SPACE);
-    store_buffer()->DeleteEntry(start, end);
+    store_buffer()->MoveAllEntriesToRememberedSet();
+    RememberedSet<OLD_TO_NEW>::RemoveRange(page, start, end,
+                                           SlotSet::KEEP_EMPTY_BUCKETS);
   }
 }
 

src/heap/store-buffer-inl.h

@@ -12,16 +12,6 @@
 namespace v8 {
 namespace internal {
 
-void StoreBuffer::InsertDeletionIntoStoreBuffer(Address start, Address end) {
-  if (top_ + sizeof(Address) * 2 > limit_[current_]) {
-    StoreBufferOverflow(heap_->isolate());
-  }
-  *top_ = MarkDeletionAddress(start);
-  top_++;
-  *top_ = end;
-  top_++;
-}
-
 void StoreBuffer::InsertIntoStoreBuffer(Address slot) {
   if (top_ + sizeof(Address) > limit_[current_]) {
     StoreBufferOverflow(heap_->isolate());

src/heap/store-buffer.cc

@@ -28,7 +28,6 @@ StoreBuffer::StoreBuffer(Heap* heap)
   }
   task_running_ = false;
   insertion_callback = &InsertDuringRuntime;
-  deletion_callback = &DeleteDuringRuntime;
 }
 
 void StoreBuffer::SetUp() {
@@ -91,22 +90,11 @@ void StoreBuffer::TearDown() {
   }
 }
 
-void StoreBuffer::DeleteDuringRuntime(StoreBuffer* store_buffer, Address start,
-                                      Address end) {
-  DCHECK(store_buffer->mode() == StoreBuffer::NOT_IN_GC);
-  store_buffer->InsertDeletionIntoStoreBuffer(start, end);
-}
-
 void StoreBuffer::InsertDuringRuntime(StoreBuffer* store_buffer, Address slot) {
   DCHECK(store_buffer->mode() == StoreBuffer::NOT_IN_GC);
   store_buffer->InsertIntoStoreBuffer(slot);
 }
 
-void StoreBuffer::DeleteDuringGarbageCollection(StoreBuffer* store_buffer,
-                                                Address start, Address end) {
-  UNREACHABLE();
-}
-
 void StoreBuffer::InsertDuringGarbageCollection(StoreBuffer* store_buffer,
                                                 Address slot) {
   DCHECK(store_buffer->mode() != StoreBuffer::NOT_IN_GC);
@@ -117,10 +105,8 @@ void StoreBuffer::SetMode(StoreBufferMode mode) {
   mode_ = mode;
   if (mode == NOT_IN_GC) {
     insertion_callback = &InsertDuringRuntime;
-    deletion_callback = &DeleteDuringRuntime;
   } else {
     insertion_callback = &InsertDuringGarbageCollection;
-    deletion_callback = &DeleteDuringGarbageCollection;
   }
 }
 
@@ -160,24 +146,9 @@ void StoreBuffer::MoveEntriesToRememberedSet(int index) {
         MemoryChunk::BaseAddress(addr) != chunk->address()) {
       chunk = MemoryChunk::FromAnyPointerAddress(addr);
     }
-    if (IsDeletionAddress(addr)) {
-      last_inserted_addr = kNullAddress;
-      current++;
-      Address end = *current;
-      DCHECK(!IsDeletionAddress(end));
-      addr = UnmarkDeletionAddress(addr);
-      if (end) {
-        RememberedSet<OLD_TO_NEW>::RemoveRange(chunk, addr, end,
-                                               SlotSet::PREFREE_EMPTY_BUCKETS);
-      } else {
-        RememberedSet<OLD_TO_NEW>::Remove(chunk, addr);
-      }
-    } else {
-      DCHECK(!IsDeletionAddress(addr));
-      if (addr != last_inserted_addr) {
-        RememberedSet<OLD_TO_NEW>::Insert(chunk, addr);
-        last_inserted_addr = addr;
-      }
+    if (addr != last_inserted_addr) {
+      RememberedSet<OLD_TO_NEW>::Insert(chunk, addr);
+      last_inserted_addr = addr;
     }
   }
   lazy_top_[index] = nullptr;

src/heap/store-buffer.h

@@ -33,17 +33,11 @@ class StoreBuffer {
       Max(static_cast<int>(kMinExpectedOSPageSize / kStoreBuffers),
           1 << (11 + kSystemPointerSizeLog2));
   static const int kStoreBufferMask = kStoreBufferSize - 1;
-  static const intptr_t kDeletionTag = 1;
 
   V8_EXPORT_PRIVATE static int StoreBufferOverflow(Isolate* isolate);
 
-  static void DeleteDuringGarbageCollection(StoreBuffer* store_buffer,
-                                            Address start, Address end);
   static void InsertDuringGarbageCollection(StoreBuffer* store_buffer,
                                             Address slot);
-
-  static void DeleteDuringRuntime(StoreBuffer* store_buffer, Address start,
-                                  Address end);
   static void InsertDuringRuntime(StoreBuffer* store_buffer, Address slot);
 
   explicit StoreBuffer(Heap* heap);
@@ -61,19 +55,6 @@ class StoreBuffer {
   // the remembered set.
   void MoveAllEntriesToRememberedSet();
 
-  inline bool IsDeletionAddress(Address address) const {
-    return address & kDeletionTag;
-  }
-
-  inline Address MarkDeletionAddress(Address address) {
-    return address | kDeletionTag;
-  }
-
-  inline Address UnmarkDeletionAddress(Address address) {
-    return address & ~kDeletionTag;
-  }
-
-  inline void InsertDeletionIntoStoreBuffer(Address start, Address end);
   inline void InsertIntoStoreBuffer(Address slot);
 
   void InsertEntry(Address slot) {
@@ -83,16 +64,6 @@ class StoreBuffer {
     insertion_callback(this, slot);
   }
 
-  // If we only want to delete a single slot, end should be set to null which
-  // will be written into the second field. When processing the store buffer
-  // the more efficient Remove method will be called in this case.
-  void DeleteEntry(Address start, Address end = kNullAddress) {
-    // Deletions coming from the GC are directly deleted from the remembered
-    // set. Deletions coming from the runtime are added to the store buffer
-    // to allow concurrent processing.
-    deletion_callback(this, start, end);
-  }
-
   void SetMode(StoreBufferMode mode);
 
   // Used by the concurrent processing thread to transfer entries from the
@@ -174,7 +145,6 @@ class StoreBuffer {
   // Callbacks are more efficient than reading out the gc state for every
   // store buffer operation.
   void (*insertion_callback)(StoreBuffer*, Address);
-  void (*deletion_callback)(StoreBuffer*, Address, Address);
 };
 
 }  // namespace internal