Performance: reduce TLS overhead of QGLContext::currentContext()

The handling for the current QGLContext was looking up the same
TLS data several times per call (hasLocalData() and localData()
calls particularly).

This change also refactors the code a little so that the
setting of the QGLContext within makeCurrent() and doneCurrent()
is in one location in the code instead of six (one per platform).

Reviewed-by: Michael Brasser
Reviewed-by: Sarah Smith

8 files changed, 42 insertions, 64 deletions

diff --git a/src/opengl/qgl.cpp b/src/opengl/qgl.cpp
index c2b747a..1a0957c 100644
--- a/src/opengl/qgl.cpp
+++ b/src/opengl/qgl.cpp
@@ -103,7 +103,11 @@ QT_BEGIN_NAMESPACE
 QGLExtensionFuncs QGLContextPrivate::qt_extensionFuncs;
 #endif
 
-QThreadStorage<QGLThreadContext *> qgl_context_storage;
+struct QGLThreadContext {
+    QGLContext *context;
+};
+
+static QThreadStorage<QGLThreadContext *> qgl_context_storage;
 
 Q_GLOBAL_STATIC(QGLFormat, qgl_default_format)
 
@@ -2939,11 +2943,28 @@ void QGLContext::setInitialized(bool on)
 
 const QGLContext* QGLContext::currentContext()
 {
-    if (qgl_context_storage.hasLocalData())
-        return qgl_context_storage.localData()->context;
+    QGLThreadContext *threadContext = qgl_context_storage.localData();
+    if (threadContext)
+        return threadContext->context;
     return 0;
 }
 
+void QGLContextPrivate::setCurrentContext(QGLContext *context)
+{
+    QGLThreadContext *threadContext = qgl_context_storage.localData();
+    if (!threadContext) {
+        if (!QThread::currentThread()) {
+            // We don't have a current QThread, so just set the static.
+            QGLContext::currentCtx = context;
+            return;
+        }
+        threadContext = new QGLThreadContext;
+        qgl_context_storage.setLocalData(threadContext);
+    }
+    threadContext->context = context;
+    QGLContext::currentCtx = context; // XXX: backwards-compat, not thread-safe
+}
+
 /*!
     \fn bool QGLContext::chooseContext(const QGLContext* shareContext = 0)
 
diff --git a/src/opengl/qgl_mac.mm b/src/opengl/qgl_mac.mm
index dd9d9ff..063082b 100644
--- a/src/opengl/qgl_mac.mm
+++ b/src/opengl/qgl_mac.mm
@@ -493,11 +493,7 @@ void QGLContext::makeCurrent()
 #else
     [static_cast<NSOpenGLContext *>(d->cx) makeCurrentContext];
 #endif
-    currentCtx = this;
-    if (!qgl_context_storage.hasLocalData() && QThread::currentThread())
-        qgl_context_storage.setLocalData(new QGLThreadContext);
-    if (qgl_context_storage.hasLocalData())
-        qgl_context_storage.localData()->context = this;
+    QGLContextPrivate::setCurrentContext(this);
 }
 
 #ifndef QT_MAC_USE_COCOA
@@ -656,9 +652,7 @@ void QGLContext::doneCurrent()
        )
         return;
 
-    currentCtx = 0;
-    if (qgl_context_storage.hasLocalData())
-        qgl_context_storage.localData()->context = 0;
+    QGLContextPrivate::setCurrentContext(0);
 #ifndef QT_MAC_USE_COCOA
     aglSetCurrentContext(0);
 #else
diff --git a/src/opengl/qgl_p.h b/src/opengl/qgl_p.h
index 57b40fb..2b74e69 100644
--- a/src/opengl/qgl_p.h
+++ b/src/opengl/qgl_p.h
@@ -351,6 +351,8 @@ public:
     static inline QGLExtensionFuncs& extensionFuncs(QGLContextGroup *) { return qt_extensionFuncs; }
 #endif
 
+    static void setCurrentContext(QGLContext *context);
+
     QPixmapFilter *createPixmapFilter(int type) const;
 };
 
@@ -398,11 +400,6 @@ public:
 Q_DECLARE_OPERATORS_FOR_FLAGS(QGLExtensions::Extensions)
 
 
-struct QGLThreadContext {
-    QGLContext *context;
-};
-extern QThreadStorage<QGLThreadContext *> qgl_context_storage;
-
 class QGLShareRegister
 {
 public:
diff --git a/src/opengl/qgl_qws.cpp b/src/opengl/qgl_qws.cpp
index 759f9de..7197776 100644
--- a/src/opengl/qgl_qws.cpp
+++ b/src/opengl/qgl_qws.cpp
@@ -260,13 +260,8 @@ void QGLContext::makeCurrent()
         return;
     }
 
-    if (d->eglContext->makeCurrent()) {
-        if (!qgl_context_storage.hasLocalData() && QThread::currentThread())
-            qgl_context_storage.setLocalData(new QGLThreadContext);
-        if (qgl_context_storage.hasLocalData())
-            qgl_context_storage.localData()->context = this;
-        currentCtx = this;
-    }
+    if (d->eglContext->makeCurrent())
+        QGLContextPrivate::setCurrentContext(this);
 }
 
 void QGLContext::doneCurrent()
@@ -275,9 +270,7 @@ void QGLContext::doneCurrent()
     if (d->eglContext)
         d->eglContext->doneCurrent();
 
-    if (qgl_context_storage.hasLocalData())
-        qgl_context_storage.localData()->context = 0;
-    currentCtx = 0;
+    QGLContextPrivate::setCurrentContext(0);
 }
 
 
diff --git a/src/opengl/qgl_win.cpp b/src/opengl/qgl_win.cpp
index 78dad80..2f9e225 100644
--- a/src/opengl/qgl_win.cpp
+++ b/src/opengl/qgl_win.cpp
@@ -1173,11 +1173,7 @@ void QGLContext::makeCurrent()
     }
 
     if (wglMakeCurrent(d->dc, d->rc)) {
-        if (!qgl_context_storage.hasLocalData() && QThread::currentThread())
-            qgl_context_storage.setLocalData(new QGLThreadContext);
-        if (qgl_context_storage.hasLocalData())
-            qgl_context_storage.localData()->context = this;
-        currentCtx = this;
+        QGLContextPrivate::setCurrentContext(this);
     } else {
         qwglError("QGLContext::makeCurrent()", "wglMakeCurrent");
     }
@@ -1187,10 +1183,8 @@ void QGLContext::makeCurrent()
 void QGLContext::doneCurrent()
 {
     Q_D(QGLContext);
-    currentCtx = 0;
     wglMakeCurrent(0, 0);
-    if (qgl_context_storage.hasLocalData())
-        qgl_context_storage.localData()->context = 0;
+    QGLContextPrivate::setCurrentContext(0);
     if (deviceIsPixmap() && d->hbitmap) {
         QPixmap *pm = static_cast<QPixmap *>(d->paintDevice);
         *pm = QPixmap::fromWinHBITMAP(d->hbitmap);
diff --git a/src/opengl/qgl_wince.cpp b/src/opengl/qgl_wince.cpp
index 83efca8..4e655f1 100644
--- a/src/opengl/qgl_wince.cpp
+++ b/src/opengl/qgl_wince.cpp
@@ -450,13 +450,8 @@ void QGLContext::makeCurrent()
         return;
     }
 
-    if (d->eglContext->makeCurrent()) {
-        if (!qgl_context_storage.hasLocalData() && QThread::currentThread())
-            qgl_context_storage.setLocalData(new QGLThreadContext);
-        if (qgl_context_storage.hasLocalData())
-            qgl_context_storage.localData()->context = this;
-        currentCtx = this;
-    }
+    if (d->eglContext->makeCurrent())
+        QGLContextPrivate::setCurrentContext(this);
 }
 
 
@@ -467,9 +462,7 @@ void QGLContext::doneCurrent()
     if (d->eglContext)
         d->eglContext->doneCurrent();
 
-    if (qgl_context_storage.hasLocalData())
-        qgl_context_storage.localData()->context = 0;
-    currentCtx = 0;
+    QGLContextPrivate::setCurrentContext(0);
 }
 
 void QGLContext::swapBuffers() const
diff --git a/src/opengl/qgl_x11.cpp b/src/opengl/qgl_x11.cpp
index cb1da18..da7972d 100644
--- a/src/opengl/qgl_x11.cpp
+++ b/src/opengl/qgl_x11.cpp
@@ -791,22 +791,15 @@ void QGLContext::makeCurrent()
     if (!ok)
         qWarning("QGLContext::makeCurrent(): Failed.");
 
-    if (ok) {
-        if (!qgl_context_storage.hasLocalData() && QThread::currentThread())
-            qgl_context_storage.setLocalData(new QGLThreadContext);
-        if (qgl_context_storage.hasLocalData())
-            qgl_context_storage.localData()->context = this;
-        currentCtx = this;
-    }
+    if (ok)
+        QGLContextPrivate::setCurrentContext(this);
 }
 
 void QGLContext::doneCurrent()
 {
     Q_D(QGLContext);
     glXMakeCurrent(qt_x11Info(d->paintDevice)->display(), 0, 0);
-    if (qgl_context_storage.hasLocalData())
-        qgl_context_storage.localData()->context = 0;
-    currentCtx = 0;
+    QGLContextPrivate::setCurrentContext(0);
 }
 
 
diff --git a/src/opengl/qgl_x11egl.cpp b/src/opengl/qgl_x11egl.cpp
index c54315f..7dfd642 100644
--- a/src/opengl/qgl_x11egl.cpp
+++ b/src/opengl/qgl_x11egl.cpp
@@ -146,13 +146,8 @@ void QGLContext::makeCurrent()
         return;
     }
 
-    if (d->eglContext->makeCurrent()) {
-        if (!qgl_context_storage.hasLocalData() && QThread::currentThread())
-            qgl_context_storage.setLocalData(new QGLThreadContext);
-        if (qgl_context_storage.hasLocalData())
-            qgl_context_storage.localData()->context = this;
-        currentCtx = this;
-    }
+    if (d->eglContext->makeCurrent())
+        QGLContextPrivate::setCurrentContext(this);
 }
 
 void QGLContext::doneCurrent()
@@ -161,9 +156,7 @@ void QGLContext::doneCurrent()
     if (d->eglContext)
         d->eglContext->doneCurrent();
 
-    if (qgl_context_storage.hasLocalData())
-        qgl_context_storage.localData()->context = 0;
-    currentCtx = 0;
+    QGLContextPrivate::setCurrentContext(0);
 }