Changeset 36663 in webkit for trunk/JavaScriptCore/wtf/RefCounted.h

Timestamp:

Sep 19, 2008, 1:50:13 AM (17 years ago)

Author:

[email protected]

Message:

2008-09-19 Julien Chaffraix <​[email protected]>

Reviewed by Alexey Proskuryakov.

Use the template hoisting technique on the RefCounted class. This reduces the code bloat due to
non-template methods' code been copied for each instance of the template.
The patch splits RefCounted between a base class that holds non-template methods and attributes
and the template RefCounted class that keeps the same functionnality.

On my Linux with gcc 4.3 for the Gtk port, this is:

• a ~600KB save on libwebkit.so in release.
• a ~1.6MB save on libwebkit.so in debug.

It is a wash on Sunspider and a small win on Dromaeo (not sure it is relevant).
On the whole, it should be a small win as we reduce the compiled code size and the only
new function call should be inlined by the compiler.

• wtf/RefCounted.h: (WTF::RefCountedBase::ref): Copied from RefCounted. (WTF::RefCountedBase::hasOneRef): Ditto. (WTF::RefCountedBase::refCount): Ditto. (WTF::RefCountedBase::RefCountedBase): Ditto. (WTF::RefCountedBase::~RefCountedBase): Ditto. (WTF::RefCountedBase::derefBase): Tweaked from the RefCounted version to remove template section. (WTF::RefCounted::RefCounted): (WTF::RefCounted::deref): Small wrapper around RefCountedBase::derefBase(). (WTF::RefCounted::~RefCounted): Keep private destructor.

File:

• trunk/JavaScriptCore/wtf/RefCounted.h (modified) (3 diffs)

trunk/JavaScriptCore/wtf/RefCounted.h

@@ -27 +27 @@
 namespace WTF {
 
-template<class T> class RefCounted : Noncopyable {
+// This base class holds the non-template methods and attributes.
+// The RefCounted class inherits from it reducing the template bloat
+// generated by the compiler (technique called template hoisting).
+class RefCountedBase : Noncopyable {
 public:
-    RefCounted(int initialRefCount = 1)
-        : m_refCount(initialRefCount)
-#ifndef NDEBUG
-        , m_deletionHasBegun(false)
-#endif
-    {
-    }
-
     void ref()
     {
         ASSERT(!m_deletionHasBegun);
         ++m_refCount;
-    }
-
-    void deref()
-    {
-        ASSERT(!m_deletionHasBegun);
-        ASSERT(m_refCount > 0);
-        if (m_refCount == 1) {
-#ifndef NDEBUG
-            m_deletionHasBegun = true;
-#endif
-            delete static_cast<T*>(this);
-        } else 
-            --m_refCount;
     }
 
@@ -68 +50 @@
 
 protected:
-    ~RefCounted() {}
+    RefCountedBase(int initialRefCount)
+        : m_refCount(initialRefCount)
+#ifndef NDEBUG
+        , m_deletionHasBegun(false)
+#endif
+    {
+    }
+
+    ~RefCountedBase() {}
+
+    // Returns whether the pointer should be freed or not.
+    bool derefBase()
+    {
+        ASSERT(!m_deletionHasBegun);
+        ASSERT(m_refCount > 0);
+        if (m_refCount == 1) {
+#ifndef NDEBUG
+            m_deletionHasBegun = true;
+#endif
+            return true;
+        }
+
+        --m_refCount;
+        return false;
+    }
 
 private:
@@ -77 +83 @@
 };
 
+
+template<class T> class RefCounted : public RefCountedBase {
+public:
+    RefCounted(int initialRefCount = 1)
+        : RefCountedBase(initialRefCount)
+    {
+    }
+
+    void deref()
+    {
+        if (derefBase())
+            delete static_cast<T*>(this);
+    }
+
+protected:
+    ~RefCounted() {}
+};
+
 } // namespace WTF