Reland of "[heap] Fine-grained JSArrayBuffer tracking"

src/heap/array-buffer-tracker-inl.h

+// Copyright 2016 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "src/heap/array-buffer-tracker.h"
+#include "src/heap/heap.h"
+#include "src/heap/mark-compact.h"
+#include "src/isolate.h"
+
+namespace v8 {
+namespace internal {
+
+template <typename Callback>
+void LocalArrayBufferTracker::Process(Callback callback) {
+  JSArrayBuffer* new_buffer = nullptr;
+  size_t freed_memory = 0;
+  for (TrackingMap::iterator it = live_.begin(); it != live_.end();) {
+    switch (callback(it->first, &new_buffer)) {
+      case kKeepEntry:
+        it++;
+        break;
+      case kKeepAndUpdateEntry:
+        DCHECK_NOT_NULL(new_buffer);
+        Page::FromAddress(new_buffer->address())
+            ->local_tracker<Page::kCreateIfNotPresent>()
+            ->AddLive(new_buffer, it->second);
+        live_.erase(it++);
+        break;
+      case kRemoveEntry:
+        heap_->isolate()->array_buffer_allocator()->Free(it->second.first,
+                                                         it->second.second);
+        freed_memory += it->second.second;
+        live_.erase(it++);
+        break;
+      default:
+        UNREACHABLE();
+    }
+  }
+  if (freed_memory > 0) {
+    heap_->update_amount_of_external_allocated_freed_memory(
+        static_cast<intptr_t>(freed_memory));
+  }
+  not_yet_discovered_.clear();
+  started_ = false;
+}
+
+template <LocalArrayBufferTracker::LivenessIndicator liveness_indicator>
+void LocalArrayBufferTracker::ScanAndFreeDead() {
+  switch (liveness_indicator) {
+    case kForwardingPointer:
+      Process([](JSArrayBuffer* old_buffer, JSArrayBuffer** new_buffer) {
+        MapWord map_word = old_buffer->map_word();
+        if (map_word.IsForwardingAddress()) {
+          *new_buffer = JSArrayBuffer::cast(map_word.ToForwardingAddress());
+          return LocalArrayBufferTracker::kKeepAndUpdateEntry;
+        }
+        return LocalArrayBufferTracker::kRemoveEntry;
+      });
+      break;
+    case kMarkBit:
+      Process([](JSArrayBuffer* old_buffer, JSArrayBuffer**) {
+        if (Marking::IsBlackOrGrey(Marking::MarkBitFrom(old_buffer))) {
+          return LocalArrayBufferTracker::kKeepEntry;
+        }
+        return LocalArrayBufferTracker::kRemoveEntry;
+      });
+      break;
+    default:
+      UNREACHABLE();
+  }
+}
+
+}  // namespace internal
+}  // namespace v8