Reland of Rehash and clear deleted entries in weak collections during GC

jeisinger · Commit bot · commit 09db5406d411 · 2016-04-15T14:41:06.000Z
BUG=v8:4909 R=hpayer@chromium.org,ulan@chromium.org LOG=n Review URL: https://codereview.chromium.org/1890123002 Cr-Commit-Position: refs/heads/master@{#35538}
diff --git a/src/objects.cc b/src/objects.cc
@@ -16867,6 +16867,16 @@ void HashTable<Derived, Shape, Key>::Rehash(Key key) {
       }
     }
   }
+  // Wipe deleted entries.
+  Heap* heap = GetHeap();
+  Object* the_hole = heap->the_hole_value();
+  Object* undefined = heap->undefined_value();
+  for (uint32_t current = 0; current < capacity; current++) {
+    if (get(EntryToIndex(current)) == the_hole) {
+      set(EntryToIndex(current), undefined);
+    }
+  }
+  SetNumberOfDeletedElements(0);
 }
 
 
@@ -18229,6 +18239,12 @@ Handle<ObjectHashTable> ObjectHashTable::Put(Handle<ObjectHashTable> table,
     return table;
   }
 
+  // Rehash if more than 25% of the entries are deleted entries.
+  // TODO(jochen): Consider to shrink the fixed array in place.
+  if ((table->NumberOfDeletedElements() << 1) > table->NumberOfElements()) {
+    table->Rehash(isolate->factory()->undefined_value());
+  }
+
   // Check whether the hash table should be extended.
   table = EnsureCapacity(table, 1, key);
   table->AddEntry(table->FindInsertionEntry(hash), *key, *value);

Original file line number	Diff line number	Diff line change
`@@ -16867,6 +16867,16 @@ void HashTable<Derived, Shape, Key>::Rehash(Key key) {`
`16867`	`16867`	`}`
`16868`	`16868`	`}`
`16869`	`16869`	`}`
	`16870`	`+ // Wipe deleted entries.`
	`16871`	`+ Heap* heap = GetHeap();`
	`16872`	`+ Object* the_hole = heap->the_hole_value();`
	`16873`	`+ Object* undefined = heap->undefined_value();`
	`16874`	`+ for (uint32_t current = 0; current < capacity; current++) {`
	`16875`	`+ if (get(EntryToIndex(current)) == the_hole) {`
	`16876`	`+ set(EntryToIndex(current), undefined);`
	`16877`	`+ }`
	`16878`	`+ }`
	`16879`	`+ SetNumberOfDeletedElements(0);`
`16870`	`16880`	`}`
`16871`	`16881`
`16872`	`16882`
`@@ -18229,6 +18239,12 @@ Handle<ObjectHashTable> ObjectHashTable::Put(Handle<ObjectHashTable> table,`
`18229`	`18239`	`return table;`
`18230`	`18240`	`}`
`18231`	`18241`
	`18242`	`+ // Rehash if more than 25% of the entries are deleted entries.`
	`18243`	`+ // TODO(jochen): Consider to shrink the fixed array in place.`
	`18244`	`+ if ((table->NumberOfDeletedElements() << 1) > table->NumberOfElements()) {`
	`18245`	`+ table->Rehash(isolate->factory()->undefined_value());`
	`18246`	`+ }`
	`18247`	`+`
`18232`	`18248`	`// Check whether the hash table should be extended.`
`18233`	`18249`	`table = EnsureCapacity(table, 1, key);`
`18234`	`18250`	`table->AddEntry(table->FindInsertionEntry(hash), key, value);`