Optimize|libdeng2|Lockable: Use automatic storage with Lockable

Lockable, as used by Guard, should not use the current pimpl idiom
implementation as this allocates storage for the private instance
from the heap.

The multithreaded logging system makes frequent use of Guards for
ensuring concurrency robustness. This inadvertently resulted in a
significant and unnecessary perf bottleneck.

doomsday/libdeng2/include/de/concurrency/lockable.h

@@ -1,7 +1,8 @@
 /*
  * The Doomsday Engine Project -- libdeng2
  *
- * Copyright © 2004-2013 Jaakko Keränen <jaakko.keranen@iki.fi>
+ * @authors Copyright © 2004-2014 Jaakko Keränen <jaakko.keranen@iki.fi>
+ * @authors Copyright © 2014 Daniel Swanson <danij@dengine.net>
  *
  * @par License
  * LGPL: http://www.gnu.org/licenses/lgpl.html
@@ -50,7 +51,10 @@ class DENG2_PUBLIC Lockable
     bool isLocked() const;
 
 private:
-    DENG2_PRIVATE(d)
+    mutable QMutex _mutex;
+
+    mutable int _lockCount;
+    mutable QMutex _countMutex;
 };
 
 } // namespace de

doomsday/libdeng2/src/concurrency/lockable.cpp

@@ -1,7 +1,8 @@
 /*
  * The Doomsday Engine Project -- libdeng2
  *
- * Copyright © 2004-2013 Jaakko Keränen <jaakko.keranen@iki.fi>
+ * @authors Copyright © 2004-2014 Jaakko Keränen <jaakko.keranen@iki.fi>
+ * @authors Copyright © 2014 Daniel Swanson <danij@dengine.net>
  *
  * @par License
  * LGPL: http://www.gnu.org/licenses/lgpl.html
@@ -22,18 +23,9 @@
 
 namespace de {
 
-DENG2_PIMPL_NOREF(Lockable)
-{
-    mutable QMutex mutex;
-
-    mutable int lockCount;
-    mutable QMutex countMutex;
-
-    Instance() : mutex(QMutex::Recursive), lockCount(0)
-    {}
-};
-
-Lockable::Lockable() : d(new Instance)
+Lockable::Lockable()
+    : _mutex(QMutex::Recursive)
+    , _lockCount(0)
 {}
 
 Lockable::~Lockable()
@@ -46,31 +38,31 @@ Lockable::~Lockable()
 
 void Lockable::lock() const
 {
-    d->countMutex.lock();
-    d->lockCount++;
-    d->countMutex.unlock();
+    _countMutex.lock();
+    _lockCount++;
+    _countMutex.unlock();
 
-    d->mutex.lock();
+    _mutex.lock();
 }
 
 void Lockable::unlock() const
 {
     // Release the lock.
-    d->mutex.unlock();
+    _mutex.unlock();
 
-    d->countMutex.lock();
-    d->lockCount--;
-    d->countMutex.unlock();
+    _countMutex.lock();
+    _lockCount--;
+    _countMutex.unlock();
 
-    DENG2_ASSERT(d->lockCount >= 0);
+    DENG2_ASSERT(_lockCount >= 0);
 }
 
 bool Lockable::isLocked() const
 {
     bool result;
-    d->countMutex.lock();
-    result = (d->lockCount > 0);
-    d->countMutex.unlock();
+    _countMutex.lock();
+    result = (_lockCount > 0);
+    _countMutex.unlock();
     return result;
 }