Simplify prefinalizer processing.

third_party/WebKit/Source/platform/heap/ThreadState.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 1320 matching lines @@
 void ThreadState::unlockThreadAttachMutex()
 {
     threadAttachMutex().unlock();
 }
 
 void ThreadState::invokePreFinalizers()
 {
     ASSERT(checkThread());
     ASSERT(!sweepForbidden());
     TRACE_EVENT0("blink_gc", "ThreadState::invokePreFinalizers");
+
     double startTime = WTF::currentTimeMS();
+    if (!m_orderedPreFinalizers.isEmpty()) {
+        SweepForbiddenScope forbiddenScope(this);
+        if (isMainThread())
+            ScriptForbiddenScope::enter();
 
-    if (isMainThread())
-        ScriptForbiddenScope::enter();
+        // Call the prefinalizers in the opposite order to their registration.
+        //
+        // The prefinalizer callback wrapper returns |true| when its associated
+        // object is unreachable garbage and the prefinalizer callback has run.
+        // The registered prefinalizer entry must then be removed and deleted.
+        //
+        auto it = --m_orderedPreFinalizers.end();
+        bool done;
+        do {
+            auto entry = it;
+            done = it == m_orderedPreFinalizers.begin();
+            if (!done)
+                --it;
+            if ((entry->second)(entry->first))
+                m_orderedPreFinalizers.remove(entry);
+        } while (!done);
 
-    SweepForbiddenScope forbiddenScope(this);
-    Vector<PreFinalizer> deadPreFinalizers;
-    // Call the pre-finalizers in the reverse order in which they
-    // are registered.
-    for (auto it = m_orderedPreFinalizers.rbegin(); it != m_orderedPreFinalizers.rend(); ++it) {
-        if (!(it->second)(it->first))
-            continue;
-        deadPreFinalizers.append(*it);
+        if (isMainThread())
+            ScriptForbiddenScope::exit();
     }
-    // FIXME: removeAll is inefficient.  It can shrink repeatedly.
-    m_orderedPreFinalizers.removeAll(deadPreFinalizers);
-
     if (isMainThread()) {
-        ScriptForbiddenScope::exit();
         double timeForInvokingPreFinalizers = WTF::currentTimeMS() - startTime;
         Platform::current()->histogramCustomCounts("BlinkGC.TimeForInvokingPreFinalizers", timeForInvokingPreFinalizers, 1, 10 * 1000, 50);
     }
 }
 
 void ThreadState::clearHeapAges()
 {
     memset(m_heapAges, 0, sizeof(size_t) * BlinkGC::NumberOfHeaps);
     memset(m_likelyToBePromptlyFreed.get(), 0, sizeof(int) * likelyToBePromptlyFreedArraySize);
     m_currentHeapAges = 0;
@@ skipping 113 matching lines @@
     threadDump->addScalar("dead_count", "objects", totalDeadCount);
     threadDump->addScalar("live_size", "bytes", totalLiveSize);
     threadDump->addScalar("dead_size", "bytes", totalDeadSize);
 
     WebMemoryAllocatorDump* heapsDump = BlinkGCMemoryDumpProvider::instance()->createMemoryAllocatorDumpForCurrentGC(heapsDumpName);
     WebMemoryAllocatorDump* classesDump = BlinkGCMemoryDumpProvider::instance()->createMemoryAllocatorDumpForCurrentGC(classesDumpName);
     BlinkGCMemoryDumpProvider::instance()->currentProcessMemoryDump()->addOwnershipEdge(classesDump->guid(), heapsDump->guid());
 }
 
 } // namespace blink