[heap] Use store buffer for writes coming from mutator.

src/heap/store-buffer.cc

Index: src/heap/store-buffer.cc
diff --git a/src/heap/store-buffer.cc b/src/heap/store-buffer.cc
index 45fc7a22f639c4ff18ad378259150b60c66538f5..abf6da409e1906cb5b95ef902678b5ffdcf27611 100644
--- a/src/heap/store-buffer.cc
+++ b/src/heap/store-buffer.cc
@@ -138,14 +138,28 @@ void StoreBuffer::ConcurrentlyProcessStoreBuffer() {
 }
 
 void StoreBuffer::DeleteEntry(Address start, Address end) {
-  if (top_ + sizeof(Address) * 2 > limit_[current_]) {
-    StoreBufferOverflow(heap_->isolate());
+  // 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.
+  if (heap_->gc_state() == Heap::NOT_IN_GC) {
+    if (top_ + sizeof(Address) * 2 > limit_[current_]) {
+      StoreBufferOverflow(heap_->isolate());
+    }
+    *top_ = MarkDeletionAddress(start);
+    top_++;
+    *top_ = end;
+    top_++;
+  } else {
+    // In GC the store buffer has to be empty at any time.
+    DCHECK(Empty());
+    Page* page = Page::FromAddress(start);
+    if (end) {
+      RememberedSet<OLD_TO_NEW>::RemoveRange(page, start, end,
+                                             SlotSet::PREFREE_EMPTY_BUCKETS);
+    } else {
+      RememberedSet<OLD_TO_NEW>::Remove(page, start);
+    }
   }
-  *top_ = MarkDeletionAddress(start);
-  top_++;
-  *top_ = end;
-  top_++;
 }
-
 }  // namespace internal
 }  // namespace v8