Use Q_UNLIKELY for every qFatal()/qCritical()

If, after checking a condition, we issue a qFatal()
or a qCritical(), by definition that check is
unlikely to be true.

Tell the compiler so it can move the error handling
code out of the normal code path to increase the
effective icache size.

Moved conditional code around where possible so that
we could always use Q_UNLIKELY, instead of having to
revert to Q_LIKELY here and there.

In some cases, simplified the expressions newly wrapped
in Q_UNLIKELY as a drive-by.

Change-Id: I67537d62b04bc6977d69254690c5ebbdf98bfd6d
Reviewed-by: Konstantin Ritt <ritt.ks@gmail.com>
Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com>

7 files changed, 23 insertions, 23 deletions

diff --git a/src/gui/image/qpixmap.cpp b/src/gui/image/qpixmap.cpp
index e53af8038f..492268402d 100644
--- a/src/gui/image/qpixmap.cpp
+++ b/src/gui/image/qpixmap.cpp
@@ -64,7 +64,7 @@ QT_BEGIN_NAMESPACE
 
 static bool qt_pixmap_thread_test()
 {
-    if (!QCoreApplication::instance()) {
+    if (Q_UNLIKELY(!QCoreApplication::instance())) {
         qFatal("QPixmap: Must construct a QGuiApplication before a QPixmap");
         return false;
     }
diff --git a/src/gui/kernel/qguiapplication.cpp b/src/gui/kernel/qguiapplication.cpp
index 248a7d0d1d..f88f6dc01a 100644
--- a/src/gui/kernel/qguiapplication.cpp
+++ b/src/gui/kernel/qguiapplication.cpp
@@ -1065,9 +1065,7 @@ static void init_platform(const QString &pluginArgument, const QString &platform
 
    // Create the platform integration.
     QGuiApplicationPrivate::platform_integration = QPlatformIntegrationFactory::create(name, arguments, argc, argv, platformPluginPath);
-    if (QGuiApplicationPrivate::platform_integration) {
-        QGuiApplicationPrivate::platform_name = new QString(name);
-    } else {
+    if (Q_UNLIKELY(!QGuiApplicationPrivate::platform_integration)) {
         QStringList keys = QPlatformIntegrationFactory::keys(platformPluginPath);
 
         QString fatalMessage
@@ -1087,6 +1085,8 @@ static void init_platform(const QString &pluginArgument, const QString &platform
         return;
     }
 
+    QGuiApplicationPrivate::platform_name = new QString(name);
+
     // Many platforms have created QScreens at this point. Finish initializing
     // QHighDpiScaling to be prepared for early calls to qt_defaultDpi().
     if (QGuiApplication::primaryScreen()) {
@@ -1414,16 +1414,16 @@ void QGuiApplicationPrivate::init()
 
     if (loadTestability) {
         QLibrary testLib(QStringLiteral("qttestability"));
-        if (testLib.load()) {
+        if (Q_UNLIKELY(!testLib.load())) {
+            qCritical() << "Library qttestability load failed:" << testLib.errorString();
+        } else {
             typedef void (*TasInitialize)(void);
             TasInitialize initFunction = (TasInitialize)testLib.resolve("qt_testability_init");
-            if (initFunction) {
-                initFunction();
-            } else {
+            if (Q_UNLIKELY(!initFunction)) {
                 qCritical() << "Library qttestability resolve failed!";
+            } else {
+                initFunction();
             }
-        } else {
-            qCritical() << "Library qttestability load failed:" << testLib.errorString();
         }
     }
 #else
diff --git a/src/gui/kernel/qopenglcontext.cpp b/src/gui/kernel/qopenglcontext.cpp
index 85d05959de..3a51c2b7b2 100644
--- a/src/gui/kernel/qopenglcontext.cpp
+++ b/src/gui/kernel/qopenglcontext.cpp
@@ -948,7 +948,7 @@ bool QOpenGLContext::makeCurrent(QSurface *surface)
     if (!isValid())
         return false;
 
-    if (thread() != QThread::currentThread())
+    if (Q_UNLIKELY(thread() != QThread::currentThread()))
         qFatal("Cannot make QOpenGLContext current in a different thread");
 
     if (!surface) {
diff --git a/src/gui/kernel/qwindow.cpp b/src/gui/kernel/qwindow.cpp
index 2b9340c04d..95f0f1cc90 100644
--- a/src/gui/kernel/qwindow.cpp
+++ b/src/gui/kernel/qwindow.cpp
@@ -212,7 +212,7 @@ void QWindowPrivate::init()
 
     // If your application aborts here, you are probably creating a QWindow
     // before the screen list is populated.
-    if (!parentWindow && !topLevelScreen) {
+    if (Q_UNLIKELY(!parentWindow && !topLevelScreen)) {
         qFatal("Cannot create window: no screens available");
         exit(1);
     }
diff --git a/src/gui/opengl/qopenglengineshadermanager.cpp b/src/gui/opengl/qopenglengineshadermanager.cpp
index 40f4ce94c2..7bdd3cb1bb 100644
--- a/src/gui/opengl/qopenglengineshadermanager.cpp
+++ b/src/gui/opengl/qopenglengineshadermanager.cpp
@@ -191,7 +191,7 @@ QOpenGLEngineSharedShaders::QOpenGLEngineSharedShaders(QOpenGLContext* context)
 #if defined(QT_DEBUG)
         // Check that all the elements have been filled:
         for (int i = 0; i < TotalSnippetCount; ++i) {
-            if (qShaderSnippets[i] == 0) {
+            if (Q_UNLIKELY(!qShaderSnippets[i])) {
                 qFatal("Shader snippet for %s (#%d) is missing!",
                        snippetNameStr(SnippetName(i)).constData(), i);
             }
@@ -240,11 +240,11 @@ QOpenGLEngineSharedShaders::QOpenGLEngineSharedShaders(QOpenGLContext* context)
 
     simpleShaderProg->link();
 
-    if (simpleShaderProg->isLinked()) {
+    if (Q_UNLIKELY(!simpleShaderProg->isLinked())) {
+        qCritical("Errors linking simple shader: %s", qPrintable(simpleShaderProg->log()));
+    } else {
         if (!inCache)
             simpleShaderCache.store(simpleShaderProg, context);
-    } else {
-        qCritical("Errors linking simple shader: %s", qPrintable(simpleShaderProg->log()));
     }
 
     // Compile the blit shader:
@@ -281,11 +281,11 @@ QOpenGLEngineSharedShaders::QOpenGLEngineSharedShaders(QOpenGLContext* context)
     }
 
     blitShaderProg->link();
-    if (blitShaderProg->isLinked()) {
+    if (Q_UNLIKELY(!blitShaderProg->isLinked())) {
+        qCritical("Errors linking blit shader: %s", qPrintable(blitShaderProg->log()));
+    } else {
         if (!inCache)
             blitShaderCache.store(blitShaderProg, context);
-    } else {
-        qCritical("Errors linking blit shader: %s", qPrintable(blitShaderProg->log()));
     }
 
 #ifdef QT_GL_SHARED_SHADER_DEBUG
diff --git a/src/gui/opengl/qopenglfunctions.cpp b/src/gui/opengl/qopenglfunctions.cpp
index d614ad8401..bfd30735b2 100644
--- a/src/gui/opengl/qopenglfunctions.cpp
+++ b/src/gui/opengl/qopenglfunctions.cpp
@@ -5795,7 +5795,9 @@ QOpenGLES3Helper::QOpenGLES3Helper()
 {
     m_supportedVersion = qMakePair(2, 0);
 
-    if (init()) {
+    if (Q_UNLIKELY(!init())) {
+        qFatal("Failed to load libGLESv2");
+    } else {
         const QPair<int, int> contextVersion = QOpenGLContext::currentContext()->format().version();
 
         qCDebug(lcGLES3, "Resolving OpenGL ES 3.0 entry points");
@@ -5993,8 +5995,6 @@ QOpenGLES3Helper::QOpenGLES3Helper()
             }
             m_supportedVersion = qMakePair(3, 1);
         }
-    } else {
-        qFatal("Failed to load libGLESv2");
     }
 }
 
diff --git a/src/gui/text/qfontdatabase.cpp b/src/gui/text/qfontdatabase.cpp
index 80908122a8..8916705c0e 100644
--- a/src/gui/text/qfontdatabase.cpp
+++ b/src/gui/text/qfontdatabase.cpp
@@ -1339,7 +1339,7 @@ QString QFontDatabase::styleString(const QFontInfo &fontInfo)
 */
 QFontDatabase::QFontDatabase()
 {
-    if (!qApp || !QGuiApplicationPrivate::platformIntegration())
+    if (Q_UNLIKELY(!qApp || !QGuiApplicationPrivate::platformIntegration()))
         qFatal("QFontDatabase: Must construct a QGuiApplication before accessing QFontDatabase");
 
     QMutexLocker locker(fontDatabaseMutex());