Optimize for horizontal writing mode

Source/core/dom/Document.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
@@ skipping 764 matching lines @@
     // have been calculated on the fly (without associating it with the actual element) somewhere.
     Element* viewportDefiningElement(RenderStyle* rootStyle = 0) const;
 
     DocumentMarkerController& markers() const { return *m_markers; }
 
     bool directionSetOnDocumentElement() const { return m_directionSetOnDocumentElement; }
     bool writingModeSetOnDocumentElement() const { return m_writingModeSetOnDocumentElement; }
     void setDirectionSetOnDocumentElement(bool b) { m_directionSetOnDocumentElement = b; }
     void setWritingModeSetOnDocumentElement(bool b) { m_writingModeSetOnDocumentElement = b; }
 
+    bool hasVerticalWritingMode() const { return m_hasVerticalWritingMode; }

[pdr., 2014/10/21 22:11:26]

Would we still see the perf benefit if we moved the unlikely in here? This would
be a bit cleaner and I think it'll all inline.

Bikeshed: I can see someone not realizing that this is for the entire document.
What do you think about containsAnyVerticalWritingModes or similar?

[eae, 2014/10/21 22:21:46]

The effect of the UNLIKELY macro is minimal, it didn't show a statistically
significant improvement on any of the tests. I'm guessing it adds 0.1-0.5% by
priming the branch predictor. The macro only works for conditions (afaik) so I'm
not sure how it could be used here.
That is a much better name, thanks!

+    void setHasVerticalWritingMode(bool b) { m_hasVerticalWritingMode = b; }
+
     bool execCommand(const String& command, bool userInterface = false, const String& value = String());
     bool queryCommandEnabled(const String& command);
     bool queryCommandIndeterm(const String& command);
     bool queryCommandState(const String& command);
     bool queryCommandSupported(const String& command);
     String queryCommandValue(const String& command);
 
     KURL openSearchDescriptionURL();
 
     // designMode support
@@ skipping 529 matching lines @@
 
     ViewportDescription m_viewportDescription;
     ViewportDescription m_legacyViewportDescription;
     Length m_viewportDefaultMinWidth;
 
     bool m_didSetReferrerPolicy;
     ReferrerPolicy m_referrerPolicy;
 
     bool m_directionSetOnDocumentElement;
     bool m_writingModeSetOnDocumentElement;
+    bool m_hasVerticalWritingMode;
     DocumentTiming m_documentTiming;
     RefPtrWillBeMember<MediaQueryMatcher> m_mediaQueryMatcher;
     bool m_writeRecursionIsTooDeep;
     unsigned m_writeRecursionDepth;
 
     RefPtrWillBeMember<ScriptedAnimationController> m_scriptedAnimationController;
     OwnPtr<MainThreadTaskRunner> m_taskRunner;
     OwnPtrWillBeMember<TextAutosizer> m_textAutosizer;
 
     RefPtrWillBeMember<CustomElementRegistrationContext> m_registrationContext;
@@ skipping 67 matching lines @@
 Node* eventTargetNodeForDocument(Document*);
 
 } // namespace blink
 
 #ifndef NDEBUG
 // Outside the WebCore namespace for ease of invocation from gdb.
 void showLiveDocumentInstances();
 #endif
 
 #endif // Document_h