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>

72 files changed, 204 insertions, 209 deletions

diff --git a/src/corelib/io/qprocess_unix.cpp b/src/corelib/io/qprocess_unix.cpp
index 472d8699a2..9a25f56c5f 100644
--- a/src/corelib/io/qprocess_unix.cpp
+++ b/src/corelib/io/qprocess_unix.cpp
@@ -560,7 +560,7 @@ static int doSpawn(pid_t *ppid, const posix_spawn_file_actions_t *file_actions,
             qWarning("ThreadCtl(): failed to chdir to %s", oldWorkingDir);
 
 #  ifdef Q_OS_QNX
-        if (ThreadCtl(_NTO_TCTL_THREADS_CONT, 0) == -1)
+        if (Q_UNLIKELY(ThreadCtl(_NTO_TCTL_THREADS_CONT, 0) == -1))
             qFatal("ThreadCtl(): cannot resume threads: %s", qPrintable(qt_error_string(errno)));
 #  endif
     }
diff --git a/src/corelib/kernel/qcoreapplication.cpp b/src/corelib/kernel/qcoreapplication.cpp
index 5fe0ea3559..8d9b923e61 100644
--- a/src/corelib/kernel/qcoreapplication.cpp
+++ b/src/corelib/kernel/qcoreapplication.cpp
@@ -417,7 +417,7 @@ QCoreApplicationPrivate::QCoreApplicationPrivate(int &aargc, char **aargv, uint
     QCoreApplicationPrivate::is_app_closing = false;
 
 #  if defined(Q_OS_UNIX)
-    if (!setuidAllowed && (geteuid() != getuid()))
+    if (Q_UNLIKELY(!setuidAllowed && (geteuid() != getuid())))
         qFatal("FATAL: The application binary appears to be running setuid, this is a security hole.");
 #  endif // Q_OS_UNIX
 
diff --git a/src/corelib/kernel/qeventdispatcher_unix.cpp b/src/corelib/kernel/qeventdispatcher_unix.cpp
index 30122e809b..d45ea30a45 100644
--- a/src/corelib/kernel/qeventdispatcher_unix.cpp
+++ b/src/corelib/kernel/qeventdispatcher_unix.cpp
@@ -135,7 +135,7 @@ QEventDispatcherUNIXPrivate::QEventDispatcherUNIXPrivate()
     }
 #endif
 
-    if (pipefail)
+    if (Q_UNLIKELY(pipefail))
         qFatal("QEventDispatcherUNIXPrivate(): Can not continue without a thread pipe");
 
     sn_highest = -1;
diff --git a/src/corelib/kernel/qeventdispatcher_win.cpp b/src/corelib/kernel/qeventdispatcher_win.cpp
index ecaa78cbbc..47b869f62a 100644
--- a/src/corelib/kernel/qeventdispatcher_win.cpp
+++ b/src/corelib/kernel/qeventdispatcher_win.cpp
@@ -667,7 +667,7 @@ void QEventDispatcherWin32::installMessageHook()
 #ifndef Q_OS_WINCE
     // setup GetMessage hook needed to drive our posted events
     d->getMessageHook = SetWindowsHookEx(WH_GETMESSAGE, (HOOKPROC) qt_GetMessageHook, NULL, GetCurrentThreadId());
-    if (!d->getMessageHook) {
+    if (Q_UNLIKELY(!d->getMessageHook)) {
         int errorCode = GetLastError();
         qFatal("Qt: INTERNAL ERROR: failed to install GetMessage hook: %d, %s",
                errorCode, qPrintable(qt_error_string(errorCode)));
diff --git a/src/corelib/kernel/qmetatype.cpp b/src/corelib/kernel/qmetatype.cpp
index e6d745bb74..c0caa3cca5 100644
--- a/src/corelib/kernel/qmetatype.cpp
+++ b/src/corelib/kernel/qmetatype.cpp
@@ -1074,7 +1074,7 @@ int QMetaType::registerNormalizedType(const NS(QByteArray) &normalizedTypeName,
         previousFlags = QMetaType::typeFlags(idx);
     }
 
-    if (previousSize != size) {
+    if (Q_UNLIKELY(previousSize != size)) {
         qFatal("QMetaType::registerType: Binary compatibility break "
             "-- Size mismatch for type '%s' [%i]. Previously registered "
             "size %i, now registering size %i.",
@@ -1084,7 +1084,7 @@ int QMetaType::registerNormalizedType(const NS(QByteArray) &normalizedTypeName,
     // these flags cannot change in a binary compatible way:
     const int binaryCompatibilityFlag = PointerToQObject | IsEnumeration | SharedPointerToQObject
                                                 | WeakPointerToQObject | TrackingPointerToQObject;
-    if ((previousFlags ^ flags) & binaryCompatibilityFlag) {
+    if (Q_UNLIKELY((previousFlags ^ flags) & binaryCompatibilityFlag)) {
 
         const char *msg = "QMetaType::registerType: Binary compatibility break. "
                 "\nType flags for type '%s' [%i] don't match. Previously "
diff --git a/src/corelib/kernel/qobject.cpp b/src/corelib/kernel/qobject.cpp
index c9884cd76c..4717cfbf3c 100644
--- a/src/corelib/kernel/qobject.cpp
+++ b/src/corelib/kernel/qobject.cpp
@@ -203,7 +203,7 @@ QObjectPrivate::QObjectPrivate(int version)
     // This allows incompatible versions to be loaded, possibly for testing.
     Q_UNUSED(version);
 #else
-    if (version != QObjectPrivateVersion)
+    if (Q_UNLIKELY(version != QObjectPrivateVersion))
         qFatal("Cannot mix incompatible Qt library (version 0x%x) with this library (version 0x%x)",
                 version, QObjectPrivateVersion);
 #endif
diff --git a/src/corelib/tools/qhash.cpp b/src/corelib/tools/qhash.cpp
index b334a697a9..7724516a5d 100644
--- a/src/corelib/tools/qhash.cpp
+++ b/src/corelib/tools/qhash.cpp
@@ -682,17 +682,17 @@ void QHashData::dump()
 
 void QHashData::checkSanity()
 {
-    if (fakeNext)
+    if (Q_UNLIKELY(fakeNext))
         qFatal("Fake next isn't 0");
 
     for (int i = 0; i < numBuckets; ++i) {
         Node *n = buckets[i];
         Node *p = n;
-        if (!n)
+        if (Q_UNLIKELY(!n))
             qFatal("%d: Bucket entry is 0", i);
         if (n != reinterpret_cast<Node *>(this)) {
             while (n != reinterpret_cast<Node *>(this)) {
-                if (!n->next)
+                if (Q_UNLIKELY(!n->next))
                     qFatal("%d: Next of %p is 0, should be %p", i, n, this);
                 n = n->next;
             }
diff --git a/src/corelib/tools/qsharedpointer.cpp b/src/corelib/tools/qsharedpointer.cpp
index 4d30396cb6..b5e27cc720 100644
--- a/src/corelib/tools/qsharedpointer.cpp
+++ b/src/corelib/tools/qsharedpointer.cpp
@@ -1508,7 +1508,7 @@ void QtSharedPointer::internalSafetyCheckAdd(const void *d_ptr, const volatile v
     //qDebug("Adding d=%p value=%p", d_ptr, ptr);
 
     const void *other_d_ptr = kp->dataPointers.value(ptr, 0);
-    if (other_d_ptr) {
+    if (Q_UNLIKELY(other_d_ptr)) {
 #  ifdef BACKTRACE_SUPPORTED
         printBacktrace(knownPointers()->dPointers.value(other_d_ptr).backtrace);
 #  endif
@@ -1539,7 +1539,7 @@ void QtSharedPointer::internalSafetyCheckRemove(const void *d_ptr)
     QMutexLocker lock(&kp->mutex);
 
     QHash<const void *, Data>::iterator it = kp->dPointers.find(d_ptr);
-    if (it == kp->dPointers.end()) {
+    if (Q_UNLIKELY(it == kp->dPointers.end())) {
         qFatal("QSharedPointer: internal self-check inconsistency: pointer %p was not tracked. "
                "To use QT_SHAREDPOINTER_TRACK_POINTERS, you have to enable it throughout "
                "in your code.", d_ptr);
@@ -1566,10 +1566,10 @@ void QtSharedPointer::internalSafetyCheckCleanCheck()
     KnownPointers *const kp = knownPointers();
     Q_ASSERT_X(kp, "internalSafetyCheckSelfCheck()", "Called after global statics deletion!");
 
-    if (kp->dPointers.size() != kp->dataPointers.size())
+    if (Q_UNLIKELY(kp->dPointers.size() != kp->dataPointers.size()))
         qFatal("Internal consistency error: the number of pointers is not equal!");
 
-    if (!kp->dPointers.isEmpty())
+    if (Q_UNLIKELY(!kp->dPointers.isEmpty()))
         qFatal("Pointer cleaning failed: %d entries remaining", kp->dPointers.size());
 #  endif
 }
diff --git a/src/corelib/tools/qsimd.cpp b/src/corelib/tools/qsimd.cpp
index 3e4fdfaaf1..0b3b84a302 100644
--- a/src/corelib/tools/qsimd.cpp
+++ b/src/corelib/tools/qsimd.cpp
@@ -685,7 +685,7 @@ void qDetectCpuFeatures()
 #else
     bool runningOnValgrind = false;
 #endif
-    if (!runningOnValgrind && (minFeature != 0 && (f & minFeature) != minFeature)) {
+    if (Q_UNLIKELY(!runningOnValgrind && minFeature != 0 && (f & minFeature) != minFeature)) {
         quint64 missing = minFeature & ~f;
         fprintf(stderr, "Incompatible processor. This Qt build requires the following features:\n   ");
         for (int i = 0; i < features_count; ++i) {
diff --git a/src/dbus/qdbus_symbols.cpp b/src/dbus/qdbus_symbols.cpp
index 395a436869..3f5df41582 100644
--- a/src/dbus/qdbus_symbols.cpp
+++ b/src/dbus/qdbus_symbols.cpp
@@ -130,11 +130,11 @@ void (*qdbus_resolve_conditionally(const char *name))()
 void (*qdbus_resolve_me(const char *name))()
 {
 #ifndef QT_NO_LIBRARY
-    if (!qdbus_loadLibDBus())
+    if (Q_UNLIKELY(!qdbus_loadLibDBus()))
         qFatal("Cannot find libdbus-1 in your system to resolve symbol '%s'.", name);
 
     QFunctionPointer ptr = qdbus_libdbus->resolve(name);
-    if (!ptr)
+    if (Q_UNLIKELY(!ptr))
         qFatal("Cannot resolve '%s' in your libdbus-1.", name);
 
     return ptr;
diff --git a/src/dbus/qdbusintegrator.cpp b/src/dbus/qdbusintegrator.cpp
index d3f899676b..1aac16119b 100644
--- a/src/dbus/qdbusintegrator.cpp
+++ b/src/dbus/qdbusintegrator.cpp
@@ -868,7 +868,7 @@ void QDBusConnectionPrivate::deliverCall(QObject *object, int /*flags*/, const Q
                 *reinterpret_cast<const QDBusArgument *>(arg.constData());
             QVariant &out = auxParameters[auxParameters.count() - 1];
 
-            if (!QDBusMetaType::demarshall(in, out.userType(), out.data()))
+            if (Q_UNLIKELY(!QDBusMetaType::demarshall(in, out.userType(), out.data())))
                 qFatal("Internal error: demarshalling function for type '%s' (%d) failed!",
                        out.typeName(), out.userType());
 
diff --git a/src/dbus/qdbuspendingcall.cpp b/src/dbus/qdbuspendingcall.cpp
index c93d6acf84..c20b56f973 100644
--- a/src/dbus/qdbuspendingcall.cpp
+++ b/src/dbus/qdbuspendingcall.cpp
@@ -190,7 +190,7 @@ void QDBusPendingCallPrivate::setMetaTypes(int count, const int *types)
     sig.reserve(count + count / 2);
     for (int i = 0; i < count; ++i) {
         const char *typeSig = QDBusMetaType::typeToSignature(types[i]);
-        if (!typeSig) {
+        if (Q_UNLIKELY(!typeSig)) {
             qFatal("QDBusPendingReply: type %s is not registered with QtDBus",
                    QMetaType::typeName(types[i]));
         }
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());
diff --git a/src/network/access/qhttpnetworkconnection.cpp b/src/network/access/qhttpnetworkconnection.cpp
index c4cb8e65c0..bb1580044f 100644
--- a/src/network/access/qhttpnetworkconnection.cpp
+++ b/src/network/access/qhttpnetworkconnection.cpp
@@ -263,7 +263,7 @@ void QHttpNetworkConnectionPrivate::prepareRequest(HttpMessagePair &messagePair)
             request.setContentLength(uploadByteDevice->size());
         } else if (request.contentLength() != -1 && uploadByteDevice->size() == -1) {
             // everything OK, the user supplied us the contentLength
-        } else if (request.contentLength() == -1 && uploadByteDevice->size() == -1) {
+        } else if (Q_UNLIKELY(request.contentLength() == -1 && uploadByteDevice->size() == -1)) {
             qFatal("QHttpNetworkConnectionPrivate: Neither content-length nor upload device size were given");
         }
     }
diff --git a/src/network/access/qnetworkreplyhttpimpl.cpp b/src/network/access/qnetworkreplyhttpimpl.cpp
index 2c31afc225..05457decc4 100644
--- a/src/network/access/qnetworkreplyhttpimpl.cpp
+++ b/src/network/access/qnetworkreplyhttpimpl.cpp
@@ -993,7 +993,7 @@ void QNetworkReplyHttpImplPrivate::initCacheSaveDevice()
         q->connect(cacheSaveDevice, SIGNAL(aboutToClose()), SLOT(_q_cacheSaveDeviceAboutToClose()));
 
     if (!cacheSaveDevice || (cacheSaveDevice && !cacheSaveDevice->isOpen())) {
-        if (cacheSaveDevice && !cacheSaveDevice->isOpen())
+        if (Q_UNLIKELY(cacheSaveDevice && !cacheSaveDevice->isOpen()))
             qCritical("QNetworkReplyImpl: network cache returned a device that is not open -- "
                   "class %s probably needs to be fixed",
                   managerPrivate->networkCache->metaObject()->className());
@@ -2216,7 +2216,7 @@ void QNetworkReplyHttpImplPrivate::setCachingEnabled(bool enable)
         return;                 // nothing to do either!
 
     if (enable) {
-        if (bytesDownloaded) {
+        if (Q_UNLIKELY(bytesDownloaded)) {
             qDebug() << "setCachingEnabled: " << bytesDownloaded << " bytesDownloaded";
             // refuse to enable in this case
             qCritical("QNetworkReplyImpl: backend error: caching was enabled after some bytes had been written");
diff --git a/src/network/access/qnetworkreplyimpl.cpp b/src/network/access/qnetworkreplyimpl.cpp
index 3df39c9bdc..12ecad5ff7 100644
--- a/src/network/access/qnetworkreplyimpl.cpp
+++ b/src/network/access/qnetworkreplyimpl.cpp
@@ -515,7 +515,7 @@ void QNetworkReplyImplPrivate::setCachingEnabled(bool enable)
         return;                 // nothing to do either!
 
     if (enable) {
-        if (bytesDownloaded) {
+        if (Q_UNLIKELY(bytesDownloaded)) {
             // refuse to enable in this case
             qCritical("QNetworkReplyImpl: backend error: caching was enabled after some bytes had been written");
             return;
@@ -604,7 +604,7 @@ void QNetworkReplyImplPrivate::initCacheSaveDevice()
     cacheSaveDevice = networkCache()->prepare(metaData);
 
     if (!cacheSaveDevice || (cacheSaveDevice && !cacheSaveDevice->isOpen())) {
-        if (cacheSaveDevice && !cacheSaveDevice->isOpen())
+        if (Q_UNLIKELY(cacheSaveDevice && !cacheSaveDevice->isOpen()))
             qCritical("QNetworkReplyImpl: network cache returned a device that is not open -- "
                   "class %s probably needs to be fixed",
                   networkCache()->metaObject()->className());
@@ -678,7 +678,7 @@ void QNetworkReplyImplPrivate::appendDownstreamData(QIODevice *data)
         return;
 
     // read until EOF from data
-    if (copyDevice) {
+    if (Q_UNLIKELY(copyDevice)) {
         qCritical("QNetworkReplyImpl: copy from QIODevice already in progress -- "
                   "backend probly needs to be fixed");
         return;
diff --git a/src/opengl/gl2paintengineex/qglengineshadermanager.cpp b/src/opengl/gl2paintengineex/qglengineshadermanager.cpp
index 903f34f939..984590435d 100644
--- a/src/opengl/gl2paintengineex/qglengineshadermanager.cpp
+++ b/src/opengl/gl2paintengineex/qglengineshadermanager.cpp
@@ -188,7 +188,7 @@ QGLEngineSharedShaders::QGLEngineSharedShaders(const QGLContext* 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);
             }
@@ -237,11 +237,11 @@ QGLEngineSharedShaders::QGLEngineSharedShaders(const QGLContext* 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:
@@ -278,11 +278,11 @@ QGLEngineSharedShaders::QGLEngineSharedShaders(const QGLContext* 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/platformsupport/input/libinput/qlibinputhandler.cpp b/src/platformsupport/input/libinput/qlibinputhandler.cpp
index 5aa66a4eaf..58fbaacd2b 100644
--- a/src/platformsupport/input/libinput/qlibinputhandler.cpp
+++ b/src/platformsupport/input/libinput/qlibinputhandler.cpp
@@ -85,18 +85,18 @@ QLibInputHandler::QLibInputHandler(const QString &key, const QString &spec)
     Q_UNUSED(spec);
 
     m_udev = udev_new();
-    if (!m_udev)
+    if (Q_UNLIKELY(!m_udev))
         qFatal("Failed to get udev context for libinput");
 
     m_li = libinput_udev_create_context(&liInterface, Q_NULLPTR, m_udev);
-    if (!m_li)
+    if (Q_UNLIKELY(!m_li))
         qFatal("Failed to get libinput context");
 
     libinput_log_set_handler(m_li, liLogHandler);
     if (qLcLibInput().isDebugEnabled())
         libinput_log_set_priority(m_li, LIBINPUT_LOG_PRIORITY_DEBUG);
 
-    if (libinput_udev_assign_seat(m_li, "seat0"))
+    if (Q_UNLIKELY(libinput_udev_assign_seat(m_li, "seat0")))
         qFatal("Failed to assign seat");
 
     m_liFd = libinput_get_fd(m_li);
diff --git a/src/plugins/platforms/android/androidjnimain.cpp b/src/plugins/platforms/android/androidjnimain.cpp
index d419e42cd5..9a96534c38 100644
--- a/src/plugins/platforms/android/androidjnimain.cpp
+++ b/src/plugins/platforms/android/androidjnimain.cpp
@@ -487,7 +487,7 @@ static jboolean startQtApplication(JNIEnv *env, jobject /*object*/, jstring para
         // Obtain a handle to the main library (the library that contains the main() function).
         // This library should already be loaded, and calling dlopen() will just return a reference to it.
         m_mainLibraryHnd = dlopen(m_applicationParams.first().data(), 0);
-        if (m_mainLibraryHnd == nullptr) {
+        if (Q_UNLIKELY(!m_mainLibraryHnd)) {
             qCritical() << "dlopen failed:" << dlerror();
             return false;
         }
@@ -497,7 +497,7 @@ static jboolean startQtApplication(JNIEnv *env, jobject /*object*/, jstring para
         m_main = (Main)dlsym(RTLD_DEFAULT, "main");
     }
 
-    if (!m_main) {
+    if (Q_UNLIKELY(!m_main)) {
         qCritical() << "dlsym failed:" << dlerror();
         qCritical() << "Could not find main method";
         return false;
diff --git a/src/plugins/platforms/android/qandroidinputcontext.cpp b/src/plugins/platforms/android/qandroidinputcontext.cpp
index e3ea048e84..92c0c2cf0f 100644
--- a/src/plugins/platforms/android/qandroidinputcontext.cpp
+++ b/src/plugins/platforms/android/qandroidinputcontext.cpp
@@ -339,7 +339,7 @@ QAndroidInputContext::QAndroidInputContext()
     : QPlatformInputContext(), m_composingTextStart(-1), m_blockUpdateSelection(false),  m_batchEditNestingLevel(0), m_focusObject(0)
 {
     jclass clazz = QJNIEnvironmentPrivate::findClass(QtNativeInputConnectionClassName);
-    if (clazz == NULL) {
+    if (Q_UNLIKELY(!clazz)) {
         qCritical() << "Native registration unable to find class '"
                     << QtNativeInputConnectionClassName
                     << '\'';
@@ -347,7 +347,7 @@ QAndroidInputContext::QAndroidInputContext()
     }
 
     QJNIEnvironmentPrivate env;
-    if (env->RegisterNatives(clazz, methods, sizeof(methods) / sizeof(methods[0])) < 0) {
+    if (Q_UNLIKELY(env->RegisterNatives(clazz, methods, sizeof(methods) / sizeof(methods[0])) < 0)) {
         qCritical() << "RegisterNatives failed for '"
                     << QtNativeInputConnectionClassName
                     << '\'';
@@ -355,7 +355,7 @@ QAndroidInputContext::QAndroidInputContext()
     }
 
     clazz = QJNIEnvironmentPrivate::findClass(QtExtractedTextClassName);
-    if (clazz == NULL) {
+    if (Q_UNLIKELY(!clazz)) {
         qCritical() << "Native registration unable to find class '"
                     << QtExtractedTextClassName
                     << '\'';
@@ -364,43 +364,43 @@ QAndroidInputContext::QAndroidInputContext()
 
     m_extractedTextClass = static_cast<jclass>(env->NewGlobalRef(clazz));
     m_classConstructorMethodID = env->GetMethodID(m_extractedTextClass, "<init>", "()V");
-    if (m_classConstructorMethodID == NULL) {
+    if (Q_UNLIKELY(!m_classConstructorMethodID)) {
         qCritical() << "GetMethodID failed";
         return;
     }
 
     m_partialEndOffsetFieldID = env->GetFieldID(m_extractedTextClass, "partialEndOffset", "I");
-    if (m_partialEndOffsetFieldID == NULL) {
+    if (Q_UNLIKELY(!m_partialEndOffsetFieldID)) {
         qCritical() << "Can't find field partialEndOffset";
         return;
     }
 
     m_partialStartOffsetFieldID = env->GetFieldID(m_extractedTextClass, "partialStartOffset", "I");
-    if (m_partialStartOffsetFieldID == NULL) {
+    if (Q_UNLIKELY(!m_partialStartOffsetFieldID)) {
         qCritical() << "Can't find field partialStartOffset";
         return;
     }
 
     m_selectionEndFieldID = env->GetFieldID(m_extractedTextClass, "selectionEnd", "I");
-    if (m_selectionEndFieldID == NULL) {
+    if (Q_UNLIKELY(!m_selectionEndFieldID)) {
         qCritical() << "Can't find field selectionEnd";
         return;
     }
 
     m_selectionStartFieldID = env->GetFieldID(m_extractedTextClass, "selectionStart", "I");
-    if (m_selectionStartFieldID == NULL) {
+    if (Q_UNLIKELY(!m_selectionStartFieldID)) {
         qCritical() << "Can't find field selectionStart";
         return;
     }
 
     m_startOffsetFieldID = env->GetFieldID(m_extractedTextClass, "startOffset", "I");
-    if (m_startOffsetFieldID == NULL) {
+    if (Q_UNLIKELY(!m_startOffsetFieldID)) {
         qCritical() << "Can't find field startOffset";
         return;
     }
 
     m_textFieldID = env->GetFieldID(m_extractedTextClass, "text", "Ljava/lang/String;");
-    if (m_textFieldID == NULL) {
+    if (Q_UNLIKELY(!m_textFieldID)) {
         qCritical() << "Can't find field text";
         return;
     }
diff --git a/src/plugins/platforms/android/qandroidplatformfontdatabase.cpp b/src/plugins/platforms/android/qandroidplatformfontdatabase.cpp
index a8bbec9400..835ca8a10a 100644
--- a/src/plugins/platforms/android/qandroidplatformfontdatabase.cpp
+++ b/src/plugins/platforms/android/qandroidplatformfontdatabase.cpp
@@ -47,7 +47,7 @@ void QAndroidPlatformFontDatabase::populateFontDatabase()
     QString fontpath = fontDir();
     QDir dir(fontpath);
 
-    if (!dir.exists()) {
+    if (Q_UNLIKELY(!dir.exists())) {
         qFatal("QFontDatabase: Cannot find font directory %s - is Qt installed correctly?",
                qPrintable(fontpath));
     }
diff --git a/src/plugins/platforms/android/qandroidplatformintegration.cpp b/src/plugins/platforms/android/qandroidplatformintegration.cpp
index 2a127f5c3c..23d242a95f 100644
--- a/src/plugins/platforms/android/qandroidplatformintegration.cpp
+++ b/src/plugins/platforms/android/qandroidplatformintegration.cpp
@@ -120,14 +120,14 @@ QAndroidPlatformIntegration::QAndroidPlatformIntegration(const QStringList &para
     m_androidPlatformNativeInterface = new QAndroidPlatformNativeInterface();
 
     m_eglDisplay = eglGetDisplay(EGL_DEFAULT_DISPLAY);
-    if (m_eglDisplay == EGL_NO_DISPLAY)
+    if (Q_UNLIKELY(m_eglDisplay == EGL_NO_DISPLAY))
         qFatal("Could not open egl display");
 
     EGLint major, minor;
-    if (!eglInitialize(m_eglDisplay, &major, &minor))
+    if (Q_UNLIKELY(!eglInitialize(m_eglDisplay, &major, &minor)))
         qFatal("Could not initialize egl display");
 
-    if (!eglBindAPI(EGL_OPENGL_ES_API))
+    if (Q_UNLIKELY(!eglBindAPI(EGL_OPENGL_ES_API)))
         qFatal("Could not bind GL_ES API");
 
     m_primaryScreen = new QAndroidPlatformScreen();
diff --git a/src/plugins/platforms/android/qandroidplatformopenglwindow.cpp b/src/plugins/platforms/android/qandroidplatformopenglwindow.cpp
index 57d3bfaf22..85f51d7d29 100644
--- a/src/plugins/platforms/android/qandroidplatformopenglwindow.cpp
+++ b/src/plugins/platforms/android/qandroidplatformopenglwindow.cpp
@@ -175,7 +175,7 @@ void QAndroidPlatformOpenGLWindow::createEgl(EGLConfig config)
     m_androidSurfaceObject = QJNIObjectPrivate();
     m_eglSurface = eglCreateWindowSurface(m_eglDisplay, config, m_nativeWindow, NULL);
     m_format = q_glFormatFromConfig(m_eglDisplay, config, window()->requestedFormat());
-    if (m_eglSurface == EGL_NO_SURFACE) {
+    if (Q_UNLIKELY(m_eglSurface == EGL_NO_SURFACE)) {
         EGLint error = eglGetError();
         eglTerminate(m_eglDisplay);
         qFatal("EGL Error : Could not create the egl surface: error = 0x%x\n", error);
diff --git a/src/plugins/platforms/android/qandroidplatformtheme.cpp b/src/plugins/platforms/android/qandroidplatformtheme.cpp
index 55bef1a1e8..949d31740a 100644
--- a/src/plugins/platforms/android/qandroidplatformtheme.cpp
+++ b/src/plugins/platforms/android/qandroidplatformtheme.cpp
@@ -203,12 +203,12 @@ QJsonObject AndroidStyle::loadStyleData()
 
     QJsonParseError error;
     QJsonDocument document = QJsonDocument::fromJson(f.readAll(), &error);
-    if (document.isNull()) {
+    if (Q_UNLIKELY(document.isNull())) {
         qCritical() << error.errorString();
         return QJsonObject();
     }
 
-    if (!document.isObject()) {
+    if (Q_UNLIKELY(!document.isObject())) {
         qCritical() << "Style.json does not contain a valid style.";
         return QJsonObject();
     }
diff --git a/src/plugins/platforms/direct2d/qwindowsdirect2ddevicecontext.cpp b/src/plugins/platforms/direct2d/qwindowsdirect2ddevicecontext.cpp
index 154023fb11..418c2e3745 100644
--- a/src/plugins/platforms/direct2d/qwindowsdirect2ddevicecontext.cpp
+++ b/src/plugins/platforms/direct2d/qwindowsdirect2ddevicecontext.cpp
@@ -51,7 +51,7 @@ public:
             HRESULT hr = QWindowsDirect2DContext::instance()->d2dDevice()->CreateDeviceContext(
                         D2D1_DEVICE_CONTEXT_OPTIONS_NONE,
                         &deviceContext);
-            if (FAILED(hr))
+            if (Q_UNLIKELY(FAILED(hr)))
                 qFatal("%s: Couldn't create Direct2D Device Context: %#x", __FUNCTION__, hr);
         }
 
diff --git a/src/plugins/platforms/eglfs/deviceintegration/eglfs_kms/qeglfskmsintegration.cpp b/src/plugins/platforms/eglfs/deviceintegration/eglfs_kms/qeglfskmsintegration.cpp
index d1814fb85d..789f2fa86f 100644
--- a/src/plugins/platforms/eglfs/deviceintegration/eglfs_kms/qeglfskmsintegration.cpp
+++ b/src/plugins/platforms/eglfs/deviceintegration/eglfs_kms/qeglfskmsintegration.cpp
@@ -77,7 +77,7 @@ void QEglFSKmsIntegration::platformInit()
         qCDebug(qLcEglfsKmsDebug) << "Found the following video devices:" << devices;
         d->deleteLater();
 
-        if (devices.isEmpty())
+        if (Q_UNLIKELY(devices.isEmpty()))
             qFatal("Could not find DRM device!");
 
         m_devicePath = devices.first();
@@ -85,7 +85,7 @@ void QEglFSKmsIntegration::platformInit()
     }
 
     m_device = new QEglFSKmsDevice(this, m_devicePath);
-    if (!m_device->open())
+    if (Q_UNLIKELY(!m_device->open()))
         qFatal("Could not open device %s - aborting!", qPrintable(m_devicePath));
 }
 
diff --git a/src/plugins/platforms/eglfs/deviceintegration/eglfs_kms_egldevice/qeglfskmsegldeviceintegration.cpp b/src/plugins/platforms/eglfs/deviceintegration/eglfs_kms_egldevice/qeglfskmsegldeviceintegration.cpp
index 1ddcb3b862..b364056b91 100644
--- a/src/plugins/platforms/eglfs/deviceintegration/eglfs_kms_egldevice/qeglfskmsegldeviceintegration.cpp
+++ b/src/plugins/platforms/eglfs/deviceintegration/eglfs_kms_egldevice/qeglfskmsegldeviceintegration.cpp
@@ -52,20 +52,20 @@ QEglFSKmsEglDeviceIntegration::QEglFSKmsEglDeviceIntegration()
 
 void QEglFSKmsEglDeviceIntegration::platformInit()
 {
-    if (!query_egl_device())
+    if (Q_UNLIKELY(!query_egl_device()))
         qFatal("Could not set up EGL device!");
 
     const char *deviceName = m_funcs->query_device_string(m_egl_device, EGL_DRM_DEVICE_FILE_EXT);
-    if (!deviceName)
+    if (Q_UNLIKELY(!deviceName))
         qFatal("Failed to query device name from EGLDevice");
 
     qCDebug(qLcEglfsKmsDebug, "Opening %s", deviceName);
 
     m_dri_fd = drmOpen(deviceName, Q_NULLPTR);
-    if (m_dri_fd < 0)
+    if (Q_UNLIKELY(m_dri_fd < 0))
         qFatal("Could not open DRM device");
 
-    if (!setup_kms())
+    if (Q_UNLIKELY(!setup_kms()))
         qFatal("Could not set up KMS on device %s!", m_device.constData());
 
     qCDebug(qLcEglfsKmsDebug, "DRM/KMS initialized");
@@ -100,14 +100,14 @@ EGLDisplay QEglFSKmsEglDeviceIntegration::createDisplay(EGLNativeDisplayType nat
         display = eglGetDisplay(nativeDisplay);
     }
 
-    if (display == EGL_NO_DISPLAY)
+    if (Q_UNLIKELY(display == EGL_NO_DISPLAY))
         qFatal("Could not get EGL display");
 
     EGLint major, minor;
-    if (!eglInitialize(display, &major, &minor))
+    if (Q_UNLIKELY(!eglInitialize(display, &major, &minor)))
         qFatal("Could not initialize egl display");
 
-    if (!eglBindAPI(EGL_OPENGL_ES_API))
+    if (Q_UNLIKELY(!eglBindAPI(EGL_OPENGL_ES_API)))
         qFatal("Failed to bind EGL_OPENGL_ES_API\n");
 
     return display;
@@ -255,8 +255,8 @@ QEglFSWindow *QEglFSKmsEglDeviceIntegration::createWindow(QWindow *window) const
     QEglJetsonTK1Window *eglWindow = new QEglJetsonTK1Window(window, this);
 
     m_funcs->initialize(eglWindow->screen()->display());
-    if (!(m_funcs->has_egl_output_base && m_funcs->has_egl_output_drm && m_funcs->has_egl_stream
-          && m_funcs->has_egl_stream_producer_eglsurface && m_funcs->has_egl_stream_consumer_egloutput))
+    if (Q_UNLIKELY(!(m_funcs->has_egl_output_base && m_funcs->has_egl_output_drm && m_funcs->has_egl_stream &&
+                     m_funcs->has_egl_stream_producer_eglsurface && m_funcs->has_egl_stream_consumer_egloutput)))
         qFatal("Required extensions missing!");
 
     return eglWindow;
@@ -298,7 +298,7 @@ void QEglFSKmsEglDeviceIntegration::waitForVSync(QPlatformSurface *) const
                                  -1, 0, 0,
                                  &m_drm_connector->connector_id, 1,
                                  const_cast<const drmModeModeInfoPtr>(&m_drm_mode));
-        if (ret)
+        if (Q_UNLIKELY(ret))
             qFatal("drmModeSetCrtc failed");
     }
 }
@@ -367,7 +367,7 @@ bool QEglFSKmsEglDeviceIntegration::setup_kms()
         }
     }
 
-    if (crtc == 0)
+    if (Q_UNLIKELY(crtc == 0))
         qFatal("No suitable CRTC available");
 
     m_drm_connector = connector;
@@ -387,7 +387,7 @@ bool QEglFSKmsEglDeviceIntegration::setup_kms()
 bool QEglFSKmsEglDeviceIntegration::query_egl_device()
 {
     m_funcs = new QEGLStreamConvenience;
-    if (!m_funcs->has_egl_device_base)
+    if (Q_UNLIKELY(!m_funcs->has_egl_device_base))
         qFatal("EGL_EXT_device_base missing");
 
     EGLint num_devices = 0;
diff --git a/src/plugins/platforms/eglfs/deviceintegration/eglfs_x11/qeglfsx11integration.cpp b/src/plugins/platforms/eglfs/deviceintegration/eglfs_x11/qeglfsx11integration.cpp
index 4d29b96608..ef586622e2 100644
--- a/src/plugins/platforms/eglfs/deviceintegration/eglfs_x11/qeglfsx11integration.cpp
+++ b/src/plugins/platforms/eglfs/deviceintegration/eglfs_x11/qeglfsx11integration.cpp
@@ -172,7 +172,7 @@ void QEglFSX11Integration::sendConnectionEvent(xcb_atom_t a)
 void QEglFSX11Integration::platformInit()
 {
     m_display = XOpenDisplay(0);
-    if (!m_display)
+    if (Q_UNLIKELY(!m_display))
         qFatal("Could not open display");
 
     XSetEventQueueOwner(DISPLAY, XCBOwnsEventQueue);
diff --git a/src/plugins/platforms/eglfs/qeglfsdeviceintegration.cpp b/src/plugins/platforms/eglfs/qeglfsdeviceintegration.cpp
index 064b9f6306..e55a17585e 100644
--- a/src/plugins/platforms/eglfs/qeglfsdeviceintegration.cpp
+++ b/src/plugins/platforms/eglfs/qeglfsdeviceintegration.cpp
@@ -155,7 +155,7 @@ void QEGLDeviceIntegration::platformInit()
 
     framebuffer = qt_safe_open(fbDev, O_RDONLY);
 
-    if (framebuffer == -1) {
+    if (Q_UNLIKELY(framebuffer == -1)) {
         qWarning("EGLFS: Failed to open %s", fbDev.constData());
         qFatal("EGLFS: Can't continue without a display");
     }
diff --git a/src/plugins/platforms/eglfs/qeglfsintegration.cpp b/src/plugins/platforms/eglfs/qeglfsintegration.cpp
index 2086ce56e2..001dd76803 100644
--- a/src/plugins/platforms/eglfs/qeglfsintegration.cpp
+++ b/src/plugins/platforms/eglfs/qeglfsintegration.cpp
@@ -118,11 +118,11 @@ void QEglFSIntegration::initialize()
     qt_egl_device_integration()->platformInit();
 
     m_display = qt_egl_device_integration()->createDisplay(nativeDisplay());
-    if (m_display == EGL_NO_DISPLAY)
+    if (Q_UNLIKELY(m_display == EGL_NO_DISPLAY))
         qFatal("Could not open egl display");
 
     EGLint major, minor;
-    if (!eglInitialize(m_display, &major, &minor))
+    if (Q_UNLIKELY(!eglInitialize(m_display, &major, &minor)))
         qFatal("Could not initialize egl display");
 
     m_inputContext = QPlatformInputContextFactory::create();
diff --git a/src/plugins/platforms/eglfs/qeglfswindow.cpp b/src/plugins/platforms/eglfs/qeglfswindow.cpp
index 8301be8c17..b29981bc98 100644
--- a/src/plugins/platforms/eglfs/qeglfswindow.cpp
+++ b/src/plugins/platforms/eglfs/qeglfswindow.cpp
@@ -102,17 +102,15 @@ void QEglFSWindow::create()
     QEglFSScreen *screen = this->screen();
     QOpenGLCompositor *compositor = QOpenGLCompositor::instance();
     if (screen->primarySurface() != EGL_NO_SURFACE) {
-        if (isRaster() && compositor->targetWindow()) {
-            m_format = compositor->targetWindow()->format();
-            return;
-        }
-
+        if (Q_UNLIKELY(!isRaster() || !compositor->targetWindow())) {
 #if !defined(Q_OS_ANDROID) || defined(Q_OS_ANDROID_NO_SDK)
-        // We can have either a single OpenGL window or multiple raster windows.
-        // Other combinations cannot work.
-        qFatal("EGLFS: OpenGL windows cannot be mixed with others.");
+            // We can have either a single OpenGL window or multiple raster windows.
+            // Other combinations cannot work.
+            qFatal("EGLFS: OpenGL windows cannot be mixed with others.");
 #endif
-
+            return;
+        }
+        m_format = compositor->targetWindow()->format();
         return;
     }
 
@@ -122,7 +120,7 @@ void QEglFSWindow::create()
 
     resetSurface();
 
-    if (m_surface == EGL_NO_SURFACE) {
+    if (Q_UNLIKELY(m_surface == EGL_NO_SURFACE)) {
         EGLint error = eglGetError();
         eglTerminate(screen->display());
         qFatal("EGL Error : Could not create the egl surface: error = 0x%x\n", error);
@@ -135,7 +133,7 @@ void QEglFSWindow::create()
         context->setShareContext(qt_gl_global_share_context());
         context->setFormat(m_format);
         context->setScreen(window()->screen());
-        if (!context->create())
+        if (Q_UNLIKELY(!context->create()))
             qFatal("EGLFS: Failed to create compositing context");
         compositor->setTarget(context, window());
     }
diff --git a/src/plugins/platforms/haiku/qhaikuwindow.cpp b/src/plugins/platforms/haiku/qhaikuwindow.cpp
index 9622d12111..1576e7c04e 100644
--- a/src/plugins/platforms/haiku/qhaikuwindow.cpp
+++ b/src/plugins/platforms/haiku/qhaikuwindow.cpp
@@ -127,7 +127,7 @@ QHaikuWindow::QHaikuWindow(QWindow *window)
 
     m_window = haikuWindow;
 
-    if (!m_window)
+    if (Q_UNLIKELY(!m_window))
         qFatal("QHaikuWindow: failed to create window");
 
     setGeometry(rect);
diff --git a/src/plugins/platforms/ios/qioseventdispatcher.mm b/src/plugins/platforms/ios/qioseventdispatcher.mm
index 0e9f176487..e1c6071c38 100644
--- a/src/plugins/platforms/ios/qioseventdispatcher.mm
+++ b/src/plugins/platforms/ios/qioseventdispatcher.mm
@@ -129,7 +129,7 @@ namespace
 
             // Which we verify, just in case
             struct rlimit stackLimit = {0, 0};
-            if (getrlimit(RLIMIT_STACK, &stackLimit) == 0 && stackSize > stackLimit.rlim_cur)
+            if (Q_UNLIKELY(getrlimit(RLIMIT_STACK, &stackLimit) == 0 && stackSize > stackLimit.rlim_cur))
                 qFatal("Unexpectedly exceeded stack limit");
 
             return stackSize;
@@ -250,7 +250,7 @@ static void __attribute__((noinline, noreturn)) user_main_trampoline()
         unsigned int bufferSize = [arg lengthOfBytesUsingEncoding:cStringEncoding] + 1;
         argv[i] = reinterpret_cast<char *>(malloc(bufferSize));
 
-        if (![arg getCString:argv[i] maxLength:bufferSize encoding:cStringEncoding])
+        if (Q_UNLIKELY(![arg getCString:argv[i] maxLength:bufferSize encoding:cStringEncoding]))
             qFatal("Could not convert argv[%d] to C string", i);
     }
 
diff --git a/src/plugins/platforms/ios/qiosintegration.mm b/src/plugins/platforms/ios/qiosintegration.mm
index 0e3da8dce8..72c9286f86 100644
--- a/src/plugins/platforms/ios/qiosintegration.mm
+++ b/src/plugins/platforms/ios/qiosintegration.mm
@@ -70,7 +70,7 @@ QIOSIntegration::QIOSIntegration()
     , m_accessibility(0)
     , m_debugWindowManagement(false)
 {
-    if (![UIApplication sharedApplication]) {
+    if (Q_UNLIKELY(![UIApplication sharedApplication])) {
         qFatal("Error: You are creating QApplication before calling UIApplicationMain.\n" \
                "If you are writing a native iOS application, and only want to use Qt for\n" \
                "parts of the application, a good place to create QApplication is from within\n" \
diff --git a/src/plugins/platforms/minimalegl/qminimaleglscreen.cpp b/src/plugins/platforms/minimalegl/qminimaleglscreen.cpp
index 59062338cb..093a1c689c 100644
--- a/src/plugins/platforms/minimalegl/qminimaleglscreen.cpp
+++ b/src/plugins/platforms/minimalegl/qminimaleglscreen.cpp
@@ -74,19 +74,19 @@ QMinimalEglScreen::QMinimalEglScreen(EGLNativeDisplayType display)
 
     EGLint major, minor;
 
-    if (!eglBindAPI(EGL_OPENGL_ES_API)) {
+    if (Q_UNLIKELY(!eglBindAPI(EGL_OPENGL_ES_API))) {
         qWarning("Could not bind GL_ES API\n");
         qFatal("EGL error");
     }
 
     m_dpy = eglGetDisplay(display);
-    if (m_dpy == EGL_NO_DISPLAY) {
+    if (Q_UNLIKELY(m_dpy == EGL_NO_DISPLAY)) {
         qWarning("Could not open egl display\n");
         qFatal("EGL error");
     }
     qWarning("Opened display %p\n", m_dpy);
 
-    if (!eglInitialize(m_dpy, &major, &minor)) {
+    if (Q_UNLIKELY(!eglInitialize(m_dpy, &major, &minor))) {
         qWarning("Could not initialize egl display\n");
         qFatal("EGL error");
     }
@@ -135,9 +135,9 @@ void QMinimalEglScreen::createAndSetPlatformContext()
 
     EGLNativeWindowType eglWindow = 0;
 #ifdef Q_OPENKODE
-    if (kdInitializeNV() == KD_ENOTINITIALIZED) {
+    if (Q_UNLIKELY(kdInitializeNV() == KD_ENOTINITIALIZED))
         qFatal("Did not manage to initialize openkode");
-    }
+
     KDWindow *window = kdCreateWindow(m_dpy,config,0);
 
     kdRealizeWindow(window,&eglWindow);
@@ -148,7 +148,7 @@ void QMinimalEglScreen::createAndSetPlatformContext()
 #endif
 
     m_surface = eglCreateWindowSurface(m_dpy, config, eglWindow, NULL);
-    if (m_surface == EGL_NO_SURFACE) {
+    if (Q_UNLIKELY(m_surface == EGL_NO_SURFACE)) {
         qWarning("Could not create the egl surface: error = 0x%x\n", eglGetError());
         eglTerminate(m_dpy);
         qFatal("EGL error");
diff --git a/src/plugins/platforms/mirclient/qmirclientclipboard.cpp b/src/plugins/platforms/mirclient/qmirclientclipboard.cpp
index aa2ddf2103..4494847b54 100644
--- a/src/plugins/platforms/mirclient/qmirclientclipboard.cpp
+++ b/src/plugins/platforms/mirclient/qmirclientclipboard.cpp
@@ -100,7 +100,7 @@ void QMirClientClipboard::onDBusClipboardGetContentsFinished(QDBusPendingCallWat
     Q_ASSERT(call == mPendingGetContentsCall.data());
 
     QDBusPendingReply<QByteArray> reply = *call;
-    if (reply.isError()) {
+    if (Q_UNLIKELY(reply.isError())) {
         qCritical("QMirClientClipboard - Failed to get system clipboard contents via D-Bus. %s, %s",
                 qPrintable(reply.error().name()), qPrintable(reply.error().message()));
         // TODO: Might try again later a number of times...
@@ -114,7 +114,7 @@ void QMirClientClipboard::onDBusClipboardGetContentsFinished(QDBusPendingCallWat
 void QMirClientClipboard::onDBusClipboardSetContentsFinished(QDBusPendingCallWatcher *call)
 {
     QDBusPendingReply<void> reply = *call;
-    if (reply.isError()) {
+    if (Q_UNLIKELY(reply.isError())) {
         qCritical("QMirClientClipboard - Failed to set the system clipboard contents via D-Bus. %s, %s",
                 qPrintable(reply.error().name()), qPrintable(reply.error().message()));
         // TODO: Might try again later a number of times...
@@ -148,9 +148,8 @@ void QMirClientClipboard::setupDBus()
             "com.canonical.QtMir.Clipboard",
             "ContentsChanged",
             this, SLOT(updateMimeData(QByteArray)));
-    if (!ok) {
+    if (Q_UNLIKELY(!ok))
         qCritical("QMirClientClipboard - Failed to connect to ContentsChanged signal form the D-Bus system clipboard.");
-    }
 
     mDBusClipboard = new QDBusInterface("com.canonical.QtMir",
             "/com/canonical/QtMir/Clipboard",
diff --git a/src/plugins/platforms/mirclient/qmirclientintegration.cpp b/src/plugins/platforms/mirclient/qmirclientintegration.cpp
index a234f4eac6..87d2002c56 100644
--- a/src/plugins/platforms/mirclient/qmirclientintegration.cpp
+++ b/src/plugins/platforms/mirclient/qmirclientintegration.cpp
@@ -95,7 +95,7 @@ QMirClientClientIntegration::QMirClientClientIntegration()
     // Create new application instance
     mInstance = u_application_instance_new_from_description_with_options(mDesc, mOptions);
 
-    if (mInstance == nullptr)
+    if (Q_UNLIKELY(!mInstance))
         qFatal("QMirClientClientIntegration: connection to Mir server failed. Check that a Mir server is\n"
                "running, and the correct socket is being used and is accessible. The shell may have\n"
                "rejected the incoming connection, so check its log file");
diff --git a/src/plugins/platforms/offscreen/qoffscreenintegration_x11.cpp b/src/plugins/platforms/offscreen/qoffscreenintegration_x11.cpp
index eb704f2dfa..dfaaa43c1d 100644
--- a/src/plugins/platforms/offscreen/qoffscreenintegration_x11.cpp
+++ b/src/plugins/platforms/offscreen/qoffscreenintegration_x11.cpp
@@ -143,7 +143,7 @@ static Window createDummyWindow(QOffscreenX11Info *x11, XVisualInfo *visualInfo)
 static Window createDummyWindow(QOffscreenX11Info *x11, GLXFBConfig config)
 {
     XVisualInfo *visualInfo = glXGetVisualFromFBConfig(x11->display(), config);
-    if (!visualInfo)
+    if (Q_UNLIKELY(!visualInfo))
         qFatal("Could not initialize GLX");
     Window window = createDummyWindow(x11, visualInfo);
     XFree(visualInfo);
@@ -177,7 +177,7 @@ QOffscreenX11GLXContext::QOffscreenX11GLXContext(QOffscreenX11Info *x11, QOpenGL
         d->window = createDummyWindow(x11, config);
     } else {
         XVisualInfo *visualInfo = qglx_findVisualInfo(x11->display(), 0, &d->format);
-        if (!visualInfo)
+        if (Q_UNLIKELY(!visualInfo))
             qFatal("Could not initialize GLX");
         d->context = glXCreateContext(x11->display(), visualInfo, d->shareContext, true);
         if (!d->context && d->shareContext) {
diff --git a/src/plugins/platforms/openwfd/qopenwfdport.cpp b/src/plugins/platforms/openwfd/qopenwfdport.cpp
index 8da1e9bd34..c1646fbdf9 100644
--- a/src/plugins/platforms/openwfd/qopenwfdport.cpp
+++ b/src/plugins/platforms/openwfd/qopenwfdport.cpp
@@ -96,9 +96,8 @@ void QOpenWFDPort::attach()
     mPhysicalSize = QSizeF(physicalWFDSize[0],physicalWFDSize[1]);
 
     WFDint numAvailablePipelines = wfdGetPortAttribi(mDevice->handle(),mPort,WFD_PORT_PIPELINE_ID_COUNT);
-    if (!numAvailablePipelines) {
+    if (Q_UNLIKELY(!numAvailablePipelines))
         qFatal("Not possible to make screen that is not possible to create WFPort with no pipline");
-    }
 
     WFDint pipeIds[numAvailablePipelines];
     wfdGetPortAttribiv(mDevice->handle(),mPort,WFD_PORT_BINDABLE_PIPELINE_IDS,numAvailablePipelines,pipeIds);
@@ -109,9 +108,9 @@ void QOpenWFDPort::attach()
             mDevice-> addToUsedPipelineSet(mPipelineId,this);
 
             mPipeline = wfdCreatePipeline(mDevice->handle(),mPipelineId,WFD_NONE);
-            if (mPipeline == WFD_INVALID_HANDLE) {
+            if (Q_UNLIKELY(mPipeline == WFD_INVALID_HANDLE))
                 qFatal("Failed to create pipeline for port %p", this);
-            }
+
             break;
         }
     }
diff --git a/src/plugins/platforms/qnx/qqnxbuffer.cpp b/src/plugins/platforms/qnx/qqnxbuffer.cpp
index 2c3a42ac7c..8589775fdf 100644
--- a/src/plugins/platforms/qnx/qqnxbuffer.cpp
+++ b/src/plugins/platforms/qnx/qqnxbuffer.cpp
@@ -76,7 +76,7 @@ QQnxBuffer::QQnxBuffer(screen_buffer_t buffer)
             screen_get_buffer_property_pv(buffer, SCREEN_PROPERTY_POINTER, (void **)&dataPtr),
             "Failed to query buffer pointer");
 
-    if (dataPtr == 0)
+    if (Q_UNLIKELY(!dataPtr))
         qFatal("QQNX: buffer pointer is NULL, errno=%d", errno);
 
     // Get format of buffer
@@ -131,13 +131,13 @@ void QQnxBuffer::invalidateInCache()
     qBufferDebug() << Q_FUNC_INFO;
 
     // Verify native buffer exists
-    if (m_buffer == 0)
+    if (Q_UNLIKELY(!m_buffer))
         qFatal("QQNX: can't invalidate cache for null buffer");
 
     // Evict buffer's data from cache
     errno = 0;
     int result = msync(m_image.bits(), m_image.height() * m_image.bytesPerLine(), MS_INVALIDATE | MS_CACHE_ONLY);
-    if (result != 0)
+    if (Q_UNLIKELY(result != 0))
         qFatal("QQNX: failed to invalidate cache, errno=%d", errno);
 }
 
diff --git a/src/plugins/platforms/qnx/qqnxeglwindow.cpp b/src/plugins/platforms/qnx/qqnxeglwindow.cpp
index 77630018e9..8faa474718 100644
--- a/src/plugins/platforms/qnx/qqnxeglwindow.cpp
+++ b/src/plugins/platforms/qnx/qqnxeglwindow.cpp
@@ -59,7 +59,7 @@ QQnxEglWindow::QQnxEglWindow(QWindow *window, screen_context_t context, bool nee
     // Set window usage
     const int val = SCREEN_USAGE_OPENGL_ES2;
     const int result = screen_set_window_property_iv(nativeHandle(), SCREEN_PROPERTY_USAGE, &val);
-    if (result != 0)
+    if (Q_UNLIKELY(result != 0))
         qFatal("QQnxEglWindow: failed to set window alpha usage, errno=%d", errno);
 
     m_requestedBufferSize = shouldMakeFullScreen() ? screen()->geometry().size() : window->geometry().size();
@@ -106,7 +106,7 @@ void QQnxEglWindow::destroyEGLSurface()
     // Destroy EGL surface if it exists
     if (m_eglSurface != EGL_NO_SURFACE) {
         EGLBoolean eglResult = eglDestroySurface(platformOpenGLContext()->getEglDisplay(), m_eglSurface);
-        if (eglResult != EGL_TRUE)
+        if (Q_UNLIKELY(eglResult != EGL_TRUE))
             qFatal("QQNX: failed to destroy EGL surface, err=%d", eglGetError());
     }
 
@@ -118,12 +118,12 @@ void QQnxEglWindow::swapEGLBuffers()
     qEglWindowDebug() << Q_FUNC_INFO;
     // Set current rendering API
     EGLBoolean eglResult = eglBindAPI(EGL_OPENGL_ES_API);
-    if (eglResult != EGL_TRUE)
+    if (Q_UNLIKELY(eglResult != EGL_TRUE))
         qFatal("QQNX: failed to set EGL API, err=%d", eglGetError());
 
     // Post EGL surface to window
     eglResult = eglSwapBuffers(m_platformOpenGLContext->getEglDisplay(), m_eglSurface);
-    if (eglResult != EGL_TRUE)
+    if (Q_UNLIKELY(eglResult != EGL_TRUE))
         qFatal("QQNX: failed to swap EGL buffers, err=%d", eglGetError());
 
     windowPosted();
@@ -178,15 +178,15 @@ int QQnxEglWindow::pixelFormat() const
     const QSurfaceFormat format = m_platformOpenGLContext->format();
     // Extract size of color channels from window format
     const int redSize = format.redBufferSize();
-    if (redSize == -1)
+    if (Q_UNLIKELY(redSize == -1))
         qFatal("QQnxWindow: red size not defined");
 
     const int greenSize = format.greenBufferSize();
-    if (greenSize == -1)
+    if (Q_UNLIKELY(greenSize == -1))
         qFatal("QQnxWindow: green size not defined");
 
     const int blueSize = format.blueBufferSize();
-    if (blueSize == -1)
+    if (Q_UNLIKELY(blueSize == -1))
         qFatal("QQnxWindow: blue size not defined");
 
     // select matching native format
diff --git a/src/plugins/platforms/qnx/qqnxglcontext.cpp b/src/plugins/platforms/qnx/qqnxglcontext.cpp
index deac419a36..266de22205 100644
--- a/src/plugins/platforms/qnx/qqnxglcontext.cpp
+++ b/src/plugins/platforms/qnx/qqnxglcontext.cpp
@@ -61,7 +61,7 @@ QQnxGLContext::QQnxGLContext(QOpenGLContext *glContext)
 
     // Set current rendering API
     EGLBoolean eglResult = eglBindAPI(EGL_OPENGL_ES_API);
-    if (eglResult != EGL_TRUE)
+    if (Q_UNLIKELY(eglResult != EGL_TRUE))
         qFatal("QQNX: failed to set EGL API, err=%d", eglGetError());
 
     // Get colour channel sizes from window format
@@ -113,7 +113,7 @@ QQnxGLContext::QQnxGLContext(QOpenGLContext *glContext)
 
     // Select EGL config based on requested window format
     m_eglConfig = q_configFromGLFormat(ms_eglDisplay, format);
-    if (m_eglConfig == 0)
+    if (Q_UNLIKELY(m_eglConfig == 0))
         qFatal("QQnxGLContext: failed to find EGL config");
 
     QQnxGLContext *glShareContext = static_cast<QQnxGLContext*>(m_glContext->shareHandle());
@@ -121,7 +121,7 @@ QQnxGLContext::QQnxGLContext(QOpenGLContext *glContext)
 
     m_eglContext = eglCreateContext(ms_eglDisplay, m_eglConfig, m_eglShareContext,
                                     contextAttrs(format));
-    if (m_eglContext == EGL_NO_CONTEXT) {
+    if (Q_UNLIKELY(m_eglContext == EGL_NO_CONTEXT)) {
         checkEGLError("eglCreateContext");
         qFatal("QQnxGLContext: failed to create EGL context, err=%d", eglGetError());
     }
@@ -170,13 +170,13 @@ void QQnxGLContext::initializeContext()
 
     // Initialize connection to EGL
     ms_eglDisplay = eglGetDisplay(EGL_DEFAULT_DISPLAY);
-    if (ms_eglDisplay == EGL_NO_DISPLAY) {
+    if (Q_UNLIKELY(ms_eglDisplay == EGL_NO_DISPLAY)) {
         checkEGLError("eglGetDisplay");
         qFatal("QQnxGLContext: failed to obtain EGL display");
     }
 
     EGLBoolean eglResult = eglInitialize(ms_eglDisplay, 0, 0);
-    if (eglResult != EGL_TRUE) {
+    if (Q_UNLIKELY(eglResult != EGL_TRUE)) {
         checkEGLError("eglInitialize");
         qFatal("QQnxGLContext: failed to initialize EGL display, err=%d", eglGetError());
     }
@@ -198,7 +198,7 @@ bool QQnxGLContext::makeCurrent(QPlatformSurface *surface)
 
     // Set current rendering API
     EGLBoolean eglResult = eglBindAPI(EGL_OPENGL_ES_API);
-    if (eglResult != EGL_TRUE)
+    if (Q_UNLIKELY(eglResult != EGL_TRUE))
         qFatal("QQnxGLContext: failed to set EGL API, err=%d", eglGetError());
 
     QQnxEglWindow *platformWindow = dynamic_cast<QQnxEglWindow*>(surface);
@@ -227,12 +227,12 @@ void QQnxGLContext::doneCurrent()
 
     // set current rendering API
     EGLBoolean eglResult = eglBindAPI(EGL_OPENGL_ES_API);
-    if (eglResult != EGL_TRUE)
+    if (Q_UNLIKELY(eglResult != EGL_TRUE))
         qFatal("QQNX: failed to set EGL API, err=%d", eglGetError());
 
     // clear curent EGL context and unbind EGL surface
     eglResult = eglMakeCurrent(ms_eglDisplay, EGL_NO_SURFACE, EGL_NO_SURFACE, EGL_NO_CONTEXT);
-    if (eglResult != EGL_TRUE)
+    if (Q_UNLIKELY(eglResult != EGL_TRUE))
         qFatal("QQNX: failed to clear current EGL context, err=%d", eglGetError());
 }
 
@@ -252,7 +252,7 @@ QFunctionPointer QQnxGLContext::getProcAddress(const QByteArray &procName)
 
     // Set current rendering API
     EGLBoolean eglResult = eglBindAPI(EGL_OPENGL_ES_API);
-    if (eglResult != EGL_TRUE)
+    if (Q_UNLIKELY(eglResult != EGL_TRUE))
         qFatal("QQNX: failed to set EGL API, err=%d", eglGetError());
 
     // Lookup EGL extension function pointer
diff --git a/src/plugins/platforms/qnx/qqnxglobal.cpp b/src/plugins/platforms/qnx/qqnxglobal.cpp
index 01e7675839..4d2599746e 100644
--- a/src/plugins/platforms/qnx/qqnxglobal.cpp
+++ b/src/plugins/platforms/qnx/qqnxglobal.cpp
@@ -44,8 +44,8 @@ void qScreenCheckError(int rc, const char *funcInfo, const char *message, bool c
         rc = screen_flush_context(QQnxIntegration::screenContext(), 0);
     }
 
-    if (rc) {
-        if (critical)
+    if (Q_UNLIKELY(rc)) {
+        if (Q_UNLIKELY(critical))
             qCritical("%s - Screen: %s - Error: %s (%i)", funcInfo, message, strerror(errno), errno);
         else
             qWarning("%s - Screen: %s - Error: %s (%i)", funcInfo, message, strerror(errno), errno);
diff --git a/src/plugins/platforms/qnx/qqnxinputcontext_imf.cpp b/src/plugins/platforms/qnx/qqnxinputcontext_imf.cpp
index ed0db82685..603ddc5c2b 100644
--- a/src/plugins/platforms/qnx/qqnxinputcontext_imf.cpp
+++ b/src/plugins/platforms/qnx/qqnxinputcontext_imf.cpp
@@ -530,29 +530,28 @@ static bool imfAvailable()
 
     if ( p_imf_client_init == 0 ) {
         void *handle = dlopen("libinput_client.so.1", 0);
-        if ( handle ) {
-            p_imf_client_init = (int32_t (*)()) dlsym(handle, "imf_client_init");
-            p_imf_client_disconnect = (void (*)()) dlsym(handle, "imf_client_disconnect");
-            p_ictrl_open_session = (const input_session_t *(*)(connection_interface_t *))dlsym(handle, "ictrl_open_session");
-            p_ictrl_close_session = (void (*)(input_session_t *))dlsym(handle, "ictrl_close_session");
-            p_ictrl_dispatch_event = (int32_t (*)(event_t *))dlsym(handle, "ictrl_dispatch_event");
-            p_vkb_init_selection_service = (int32_t (*)())dlsym(handle, "vkb_init_selection_service");
-            p_ictrl_get_num_active_sessions = (int32_t (*)())dlsym(handle, "ictrl_get_num_active_sessions");
-        } else {
+        if (Q_UNLIKELY(!handle)) {
             qCritical() << Q_FUNC_INFO << "libinput_client.so.1 is not present - IMF services are disabled.";
             s_imfDisabled = true;
             return false;
         }
-
-        if ( p_imf_client_init && p_ictrl_open_session && p_ictrl_dispatch_event ) {
-            s_imfReady = true;
-        } else {
+        p_imf_client_init = (int32_t (*)()) dlsym(handle, "imf_client_init");
+        p_imf_client_disconnect = (void (*)()) dlsym(handle, "imf_client_disconnect");
+        p_ictrl_open_session = (const input_session_t *(*)(connection_interface_t *))dlsym(handle, "ictrl_open_session");
+        p_ictrl_close_session = (void (*)(input_session_t *))dlsym(handle, "ictrl_close_session");
+        p_ictrl_dispatch_event = (int32_t (*)(event_t *))dlsym(handle, "ictrl_dispatch_event");
+        p_vkb_init_selection_service = (int32_t (*)())dlsym(handle, "vkb_init_selection_service");
+        p_ictrl_get_num_active_sessions = (int32_t (*)())dlsym(handle, "ictrl_get_num_active_sessions");
+
+        if (Q_UNLIKELY(!p_imf_client_init || !p_ictrl_open_session || !p_ictrl_dispatch_event)) {
             p_ictrl_open_session = 0;
             p_ictrl_dispatch_event = 0;
             s_imfDisabled = true;
             qCritical() << Q_FUNC_INFO << "libinput_client.so.1 did not contain the correct symbols, library mismatch? IMF services are disabled.";
             return false;
         }
+
+        s_imfReady = true;
     }
 
     return s_imfReady;
@@ -581,7 +580,7 @@ QQnxInputContext::QQnxInputContext(QQnxIntegration *integration, QQnxAbstractVir
     Q_ASSERT(sInputContextInstance == 0);
     sInputContextInstance = this;
 
-    if (p_imf_client_init() != 0) {
+    if (Q_UNLIKELY(p_imf_client_init() != 0)) {
         s_imfInitFailed = true;
         qCritical("imf_client_init failed - IMF services will be unavailable");
     }
diff --git a/src/plugins/platforms/qnx/qqnxintegration.cpp b/src/plugins/platforms/qnx/qqnxintegration.cpp
index 57f8213a4e..36d59ef134 100644
--- a/src/plugins/platforms/qnx/qqnxintegration.cpp
+++ b/src/plugins/platforms/qnx/qqnxintegration.cpp
@@ -425,7 +425,7 @@ void QQnxIntegration::createDisplays()
                                                 &displayCount);
     Q_SCREEN_CRITICALERROR(result, "Failed to query display count");
 
-    if (displayCount < 1) {
+    if (Q_UNLIKELY(displayCount < 1)) {
         // Never happens, even if there's no display, libscreen returns 1
         qFatal("QQnxIntegration: displayCount=%d", displayCount);
     }
diff --git a/src/plugins/platforms/qnx/qqnxnavigatoreventnotifier.cpp b/src/plugins/platforms/qnx/qqnxnavigatoreventnotifier.cpp
index aa47b5409b..d7221a9185 100644
--- a/src/plugins/platforms/qnx/qqnxnavigatoreventnotifier.cpp
+++ b/src/plugins/platforms/qnx/qqnxnavigatoreventnotifier.cpp
@@ -102,7 +102,7 @@ void QQnxNavigatorEventNotifier::parsePPS(const QByteArray &ppsData, QByteArray
     QList<QByteArray> lines = ppsData.split('\n');
 
     // validate pps object
-    if (lines.size() == 0 || lines.at(0) != "@control")
+    if (Q_UNLIKELY(lines.empty() || lines.at(0) != "@control"))
         qFatal("QQNX: unrecognized pps object, data=%s", ppsData.constData());
 
     // parse pps object attributes and extract values
@@ -160,7 +160,7 @@ void QQnxNavigatorEventNotifier::replyPPS(const QByteArray &res, const QByteArra
     // send pps message to navigator
     errno = 0;
     int bytes = write(m_fd, ppsData.constData(), ppsData.size());
-    if (bytes == -1)
+    if (Q_UNLIKELY(bytes == -1))
         qFatal("QQNX: failed to write navigator pps, errno=%d", errno);
 }
 
@@ -198,7 +198,7 @@ void QQnxNavigatorEventNotifier::readData()
     // attempt to read pps data
     errno = 0;
     int bytes = qt_safe_read(m_fd, buffer, ppsBufferSize - 1);
-    if (bytes == -1)
+    if (Q_UNLIKELY(bytes == -1))
         qFatal("QQNX: failed to read navigator pps, errno=%d", errno);
 
     // check if pps data was received
diff --git a/src/plugins/platforms/qnx/qqnxnavigatorpps.cpp b/src/plugins/platforms/qnx/qqnxnavigatorpps.cpp
index c3b088ae5f..d5bdbb3ec6 100644
--- a/src/plugins/platforms/qnx/qqnxnavigatorpps.cpp
+++ b/src/plugins/platforms/qnx/qqnxnavigatorpps.cpp
@@ -100,7 +100,7 @@ bool QQnxNavigatorPps::sendPpsMessage(const QByteArray &message, const QByteArra
     // send pps message to navigator
     errno = 0;
     int bytes = qt_safe_write(m_fd, ppsMessage.constData(), ppsMessage.size());
-    if (bytes == -1)
+    if (Q_UNLIKELY(bytes == -1))
         qFatal("QQNX: failed to write navigator pps, errno=%d", errno);
 
     // allocate buffer for pps data
@@ -110,7 +110,7 @@ bool QQnxNavigatorPps::sendPpsMessage(const QByteArray &message, const QByteArra
     do {
         errno = 0;
         bytes = qt_safe_read(m_fd, buffer, ppsBufferSize - 1);
-        if (bytes == -1)
+        if (Q_UNLIKELY(bytes == -1))
             qFatal("QQNX: failed to read navigator pps, errno=%d", errno);
     } while (bytes == 0);
 
@@ -125,7 +125,7 @@ bool QQnxNavigatorPps::sendPpsMessage(const QByteArray &message, const QByteArra
     parsePPS(ppsData, responseFields);
 
     if (responseFields.contains("res") && responseFields.value("res") == message) {
-        if (responseFields.contains("err")) {
+        if (Q_UNLIKELY(responseFields.contains("err"))) {
             qCritical() << "navigator responded with error: " << responseFields.value("err");
             return false;
         }
@@ -142,7 +142,7 @@ void QQnxNavigatorPps::parsePPS(const QByteArray &ppsData, QHash<QByteArray, QBy
     QList<QByteArray> lines = ppsData.split('\n');
 
     // validate pps object
-    if (lines.size() == 0 || lines.at(0) != "@control")
+    if (Q_UNLIKELY(lines.empty() || lines.at(0) != "@control"))
         qFatal("QQNX: unrecognized pps object, data=%s", ppsData.constData());
 
     // parse pps object attributes and extract values
diff --git a/src/plugins/platforms/qnx/qqnxrasterwindow.cpp b/src/plugins/platforms/qnx/qqnxrasterwindow.cpp
index 6a346e2bb4..30103b4b9a 100644
--- a/src/plugins/platforms/qnx/qqnxrasterwindow.cpp
+++ b/src/plugins/platforms/qnx/qqnxrasterwindow.cpp
@@ -61,7 +61,7 @@ QQnxRasterWindow::QQnxRasterWindow(QWindow *window, screen_context_t context, bo
 
     const int val = SCREEN_USAGE_NATIVE | SCREEN_USAGE_READ | SCREEN_USAGE_WRITE;
     const int result = screen_set_window_property_iv(nativeHandle(), SCREEN_PROPERTY_USAGE, &val);
-    if (result != 0)
+    if (Q_UNLIKELY(result != 0))
         qFatal("QQnxRasterWindow: failed to set window alpha usage, errno=%d", errno);
 }
 
diff --git a/src/plugins/platforms/qnx/qqnxscreeneventhandler.cpp b/src/plugins/platforms/qnx/qqnxscreeneventhandler.cpp
index 4baabbb4fa..01a54a8a5e 100644
--- a/src/plugins/platforms/qnx/qqnxscreeneventhandler.cpp
+++ b/src/plugins/platforms/qnx/qqnxscreeneventhandler.cpp
@@ -579,12 +579,12 @@ void QQnxScreenEventHandler::handlePropertyEvent(screen_event_t event)
 
     errno = 0;
     screen_window_t window = 0;
-    if (screen_get_event_property_pv(event, SCREEN_PROPERTY_WINDOW, (void**)&window) != 0)
+    if (Q_UNLIKELY(screen_get_event_property_pv(event, SCREEN_PROPERTY_WINDOW, (void**)&window) != 0))
         qFatal("QQnx: failed to query window property, errno=%d", errno);
 
     errno = 0;
     int property;
-    if (screen_get_event_property_iv(event, SCREEN_PROPERTY_NAME, &property) != 0)
+    if (Q_UNLIKELY(screen_get_event_property_iv(event, SCREEN_PROPERTY_NAME, &property) != 0))
         qFatal("QQnx: failed to query window property, errno=%d", errno);
 
     switch (property) {
@@ -601,7 +601,7 @@ void QQnxScreenEventHandler::handleKeyboardFocusPropertyEvent(screen_window_t wi
 {
     errno = 0;
     int focus = 0;
-    if (window && screen_get_window_property_iv(window, SCREEN_PROPERTY_KEYBOARD_FOCUS, &focus) != 0)
+    if (Q_UNLIKELY(window && screen_get_window_property_iv(window, SCREEN_PROPERTY_KEYBOARD_FOCUS, &focus) != 0))
         qFatal("QQnx: failed to query keyboard focus property, errno=%d", errno);
 
     QWindow *focusWindow = QQnxIntegration::window(window);
diff --git a/src/plugins/platforms/qnx/qqnxvirtualkeyboardpps.cpp b/src/plugins/platforms/qnx/qqnxvirtualkeyboardpps.cpp
index 2c7a28e835..33e5cf2947 100644
--- a/src/plugins/platforms/qnx/qqnxvirtualkeyboardpps.cpp
+++ b/src/plugins/platforms/qnx/qqnxvirtualkeyboardpps.cpp
@@ -127,7 +127,7 @@ bool QQnxVirtualKeyboardPps::connect()
     }
 
     m_buffer = new char[ms_bufferSize];
-    if (!m_buffer) {
+    if (Q_UNLIKELY(!m_buffer)) {
         qCritical("QQnxVirtualKeyboard: Unable to allocate buffer of %d bytes. "
                   "Size is unavailable.",  ms_bufferSize);
         return false;
@@ -170,7 +170,7 @@ void QQnxVirtualKeyboardPps::ppsDataReady()
         return;
 
     // nread is the real space necessary, not the amount read.
-    if (static_cast<size_t>(nread) > ms_bufferSize - 1) {
+    if (Q_UNLIKELY(static_cast<size_t>(nread) > ms_bufferSize - 1)) {
         qCritical("QQnxVirtualKeyboard: Keyboard buffer size too short; need %u.", nread + 1);
         connect(); // reconnect
         return;
@@ -184,7 +184,7 @@ void QQnxVirtualKeyboardPps::ppsDataReady()
 #endif
 
     const char *value;
-    if (pps_decoder_get_string(m_decoder, "error", &value) == PPS_DECODER_OK) {
+    if (Q_UNLIKELY(pps_decoder_get_string(m_decoder, "error", &value) == PPS_DECODER_OK)) {
         qCritical("QQnxVirtualKeyboard: Keyboard PPS decoder error: %s", value ? value : "[null]");
         return;
     }
@@ -214,11 +214,11 @@ void QQnxVirtualKeyboardPps::handleKeyboardInfoMessage()
 {
     int newHeight = 0;
 
-    if (pps_decoder_push(m_decoder, "dat") != PPS_DECODER_OK) {
+    if (Q_UNLIKELY(pps_decoder_push(m_decoder, "dat") != PPS_DECODER_OK)) {
         qCritical("QQnxVirtualKeyboard: Keyboard PPS dat object not found");
         return;
     }
-    if (pps_decoder_get_int(m_decoder, "size", &newHeight) != PPS_DECODER_OK) {
+    if (Q_UNLIKELY(pps_decoder_get_int(m_decoder, "size", &newHeight) != PPS_DECODER_OK)) {
         qCritical("QQnxVirtualKeyboard: Keyboard PPS size field not found");
         return;
     }
diff --git a/src/plugins/platforms/qnx/qqnxwindow.cpp b/src/plugins/platforms/qnx/qqnxwindow.cpp
index c081aa6d28..6adc352e2d 100644
--- a/src/plugins/platforms/qnx/qqnxwindow.cpp
+++ b/src/plugins/platforms/qnx/qqnxwindow.cpp
@@ -372,7 +372,7 @@ void QQnxWindow::setBufferSize(const QSize &size)
         screen_get_window_property_iv(m_window, SCREEN_PROPERTY_RENDER_BUFFER_COUNT, &bufferCount),
         "Failed to query render buffer count");
 
-    if (bufferCount != MAX_BUFFER_COUNT) {
+    if (Q_UNLIKELY(bufferCount != MAX_BUFFER_COUNT)) {
         qFatal("QQnxWindow: invalid buffer count. Expected = %d, got = %d.",
                 MAX_BUFFER_COUNT, bufferCount);
     }
@@ -450,10 +450,10 @@ void QQnxWindow::removeFromParent()
     qWindowDebug() << Q_FUNC_INFO << "window =" << window();
     // Remove from old Hierarchy position
     if (m_parentWindow) {
-        if (m_parentWindow->m_childWindows.removeAll(this))
-            m_parentWindow = 0;
-        else
+        if (Q_UNLIKELY(!m_parentWindow->m_childWindows.removeAll(this)))
             qFatal("QQnxWindow: Window Hierarchy broken; window has parent, but parent hasn't got child.");
+        else
+            m_parentWindow = 0;
     } else if (m_screen) {
         m_screen->removeWindow(this);
     }
diff --git a/src/plugins/platforms/windows/qwindowscontext.cpp b/src/plugins/platforms/windows/qwindowscontext.cpp
index 5cda6379de..82cc1deb23 100644
--- a/src/plugins/platforms/windows/qwindowscontext.cpp
+++ b/src/plugins/platforms/windows/qwindowscontext.cpp
@@ -187,7 +187,7 @@ void QWindowsUser32DLL::init()
     // MinGW (g++ 3.4.5) accepts only C casts.
     setLayeredWindowAttributes = (SetLayeredWindowAttributes)(library.resolve("SetLayeredWindowAttributes"));
     updateLayeredWindow = (UpdateLayeredWindow)(library.resolve("UpdateLayeredWindow"));
-    if (!setLayeredWindowAttributes || !updateLayeredWindow)
+    if (Q_UNLIKELY(!setLayeredWindowAttributes || !updateLayeredWindow))
         qFatal("This version of Windows is not supported (User32.dll is missing the symbols 'SetLayeredWindowAttributes', 'UpdateLayeredWindow').");
 
     updateLayeredWindowIndirect = (UpdateLayeredWindowIndirect)(library.resolve("UpdateLayeredWindowIndirect"));
diff --git a/src/plugins/platforms/windows/qwindowsfontdatabase.cpp b/src/plugins/platforms/windows/qwindowsfontdatabase.cpp
index a30e545807..bb7d0fd8d7 100644
--- a/src/plugins/platforms/windows/qwindowsfontdatabase.cpp
+++ b/src/plugins/platforms/windows/qwindowsfontdatabase.cpp
@@ -1582,7 +1582,7 @@ LOGFONT QWindowsFontDatabase::fontDefToLOGFONT(const QFontDef &request)
     lf.lfPitchAndFamily = DEFAULT_PITCH | hint;
 
     QString fam = request.family;
-    if (fam.size() >= LF_FACESIZE) {
+    if (Q_UNLIKELY(fam.size() >= LF_FACESIZE)) {
         qCritical("%s: Family name '%s' is too long.", __FUNCTION__, qPrintable(fam));
         fam.truncate(LF_FACESIZE - 1);
     }
diff --git a/src/plugins/platforms/windows/qwindowsnativeimage.cpp b/src/plugins/platforms/windows/qwindowsnativeimage.cpp
index 66e64e64b4..56e18e20d7 100644
--- a/src/plugins/platforms/windows/qwindowsnativeimage.cpp
+++ b/src/plugins/platforms/windows/qwindowsnativeimage.cpp
@@ -96,7 +96,7 @@ static inline HBITMAP createDIB(HDC hdc, int width, int height,
     void *bits = 0;
     HBITMAP bitmap = CreateDIBSection(hdc, reinterpret_cast<BITMAPINFO *>(&bmi),
                                       DIB_RGB_COLORS, &bits, 0, 0);
-    if (!bitmap || !bits)
+    if (Q_UNLIKELY(!bitmap || !bits))
         qFatal("%s: CreateDIBSection failed.", __FUNCTION__);
 
     *bitsIn = (uchar*)bits;
diff --git a/src/plugins/platforms/winrt/qwinrteglcontext.cpp b/src/plugins/platforms/winrt/qwinrteglcontext.cpp
index 3fd0278360..1008e1c5e8 100644
--- a/src/plugins/platforms/winrt/qwinrteglcontext.cpp
+++ b/src/plugins/platforms/winrt/qwinrteglcontext.cpp
@@ -55,7 +55,7 @@ struct WinRTEGLDisplay
 {
     WinRTEGLDisplay() {
         eglDisplay = eglGetDisplay(EGL_DEFAULT_DISPLAY);
-        if (eglDisplay == EGL_NO_DISPLAY)
+        if (Q_UNLIKELY(eglDisplay == EGL_NO_DISPLAY))
             qCritical("Failed to initialize EGL display: 0x%x", eglGetError());
     }
     ~WinRTEGLDisplay() {
@@ -114,10 +114,10 @@ void QWinRTEGLContext::initialize()
         EGL_NONE,
     };
     g->eglDisplay = eglGetPlatformDisplayEXT(EGL_PLATFORM_ANGLE_ANGLE, EGL_DEFAULT_DISPLAY, displayAttributes);
-    if (g->eglDisplay == EGL_NO_DISPLAY)
+    if (Q_UNLIKELY(g->eglDisplay == EGL_NO_DISPLAY))
         qCritical("Failed to initialize EGL display: 0x%x", eglGetError());
 
-    if (!eglInitialize(g->eglDisplay, nullptr, nullptr))
+    if (Q_UNLIKELY(!eglInitialize(g->eglDisplay, nullptr, nullptr)))
         qCritical("Failed to initialize EGL: 0x%x", eglGetError());
 
     d->eglConfig = q_configFromGLFormat(g->eglDisplay, d->format);
diff --git a/src/plugins/platforms/winrt/qwinrtwindow.cpp b/src/plugins/platforms/winrt/qwinrtwindow.cpp
index bec94c1e51..8a53047d1e 100644
--- a/src/plugins/platforms/winrt/qwinrtwindow.cpp
+++ b/src/plugins/platforms/winrt/qwinrtwindow.cpp
@@ -180,7 +180,7 @@ QWinRTWindow::~QWinRTWindow()
 
     EGLBoolean value = eglDestroySurface(d->display, d->surface);
     d->surface = EGL_NO_SURFACE;
-    if (value == EGL_FALSE)
+    if (Q_UNLIKELY(value == EGL_FALSE))
         qCritical("Failed to destroy EGL window surface: 0x%x", eglGetError());
 }
 
@@ -321,7 +321,7 @@ void QWinRTWindow::createEglSurface(EGLDisplay display, EGLConfig config)
             d->surface = eglCreateWindowSurface(display, config,
                                                 reinterpret_cast<EGLNativeWindowType>(winId()),
                                                 nullptr);
-            if (d->surface == EGL_NO_SURFACE)
+            if (Q_UNLIKELY(d->surface == EGL_NO_SURFACE))
                 qCritical("Failed to create EGL window surface: 0x%x", eglGetError());
             return S_OK;
         });
diff --git a/src/plugins/platforms/xcb/gl_integrations/xcb_glx/qglxintegration.cpp b/src/plugins/platforms/xcb/gl_integrations/xcb_glx/qglxintegration.cpp
index 37f01d4eed..e1fb63fbc4 100644
--- a/src/plugins/platforms/xcb/gl_integrations/xcb_glx/qglxintegration.cpp
+++ b/src/plugins/platforms/xcb/gl_integrations/xcb_glx/qglxintegration.cpp
@@ -99,7 +99,7 @@ static Window createDummyWindow(Display *dpy, XVisualInfo *visualInfo, int scree
 static Window createDummyWindow(Display *dpy, GLXFBConfig config, int screenNumber, Window rootWin)
 {
     XVisualInfo *visualInfo = glXGetVisualFromFBConfig(dpy, config);
-    if (!visualInfo)
+    if (Q_UNLIKELY(!visualInfo))
         qFatal("Could not initialize GLX");
     Window window = createDummyWindow(dpy, visualInfo, screenNumber, rootWin);
     XFree(visualInfo);
@@ -301,7 +301,7 @@ void QGLXContext::init(QXcbScreen *screen, QPlatformOpenGLContext *share)
 
         // Note that m_format gets updated with the used surface format
         visualInfo = qglx_findVisualInfo(m_display, screen->screenNumber(), &m_format);
-        if (!visualInfo)
+        if (Q_UNLIKELY(!visualInfo))
             qFatal("Could not initialize GLX");
         m_context = glXCreateContext(m_display, visualInfo, m_shareContext, true);
         if (!m_context && m_shareContext) {
diff --git a/src/plugins/platforms/xcb/qxcbconnection.cpp b/src/plugins/platforms/xcb/qxcbconnection.cpp
index 50d49ca798..ff39b24e93 100644
--- a/src/plugins/platforms/xcb/qxcbconnection.cpp
+++ b/src/plugins/platforms/xcb/qxcbconnection.cpp
@@ -521,7 +521,7 @@ QXcbConnection::QXcbConnection(QXcbNativeInterface *nativeInterface, bool canGra
     m_connection = xcb_connect(m_displayName.constData(), &m_primaryScreenNumber);
 #endif //XCB_USE_XLIB
 
-    if (!m_connection || xcb_connection_has_error(m_connection))
+    if (Q_UNLIKELY(!m_connection || xcb_connection_has_error(m_connection)))
         qFatal("QXcbConnection: Could not connect to display %s", m_displayName.constData());
 
 
@@ -553,7 +553,7 @@ QXcbConnection::QXcbConnection(QXcbNativeInterface *nativeInterface, bool canGra
     initializeXFixes();
     initializeScreens();
 
-    if (m_screens.isEmpty())
+    if (Q_UNLIKELY(m_screens.isEmpty()))
         qFatal("QXcbConnection: no screens available");
 
     initializeXRender();
diff --git a/src/plugins/platforms/xcb/qxcbwindow.cpp b/src/plugins/platforms/xcb/qxcbwindow.cpp
index 4bd4639833..3e01a90402 100644
--- a/src/plugins/platforms/xcb/qxcbwindow.cpp
+++ b/src/plugins/platforms/xcb/qxcbwindow.cpp
@@ -395,7 +395,7 @@ void QXcbWindow::create()
         if (!visualInfo)
             visualInfo = static_cast<XVisualInfo *>(createVisual());
 
-        if (!visualInfo && window()->surfaceType() == QSurface::OpenGLSurface)
+        if (Q_UNLIKELY(!visualInfo && window()->surfaceType() == QSurface::OpenGLSurface))
             qFatal("Could not initialize OpenGL");
 
         if (!visualInfo && window()->surfaceType() == QSurface::RasterGLSurface) {
diff --git a/src/printsupport/kernel/qprinter.cpp b/src/printsupport/kernel/qprinter.cpp
index 2cecf61573..734691d504 100644
--- a/src/printsupport/kernel/qprinter.cpp
+++ b/src/printsupport/kernel/qprinter.cpp
@@ -695,7 +695,7 @@ QPrinter::QPrinter(const QPrinterInfo& printer, PrinterMode mode)
 
 void QPrinterPrivate::init(const QPrinterInfo &printer, QPrinter::PrinterMode mode)
 {
-    if (!QCoreApplication::instance()) {
+    if (Q_UNLIKELY(!QCoreApplication::instance())) {
         qFatal("QPrinter: Must construct a QCoreApplication before a QPrinter");
         return;
     }
diff --git a/src/sql/drivers/ibase/qsql_ibase.cpp b/src/sql/drivers/ibase/qsql_ibase.cpp
index b15ba4462d..975c92a116 100644
--- a/src/sql/drivers/ibase/qsql_ibase.cpp
+++ b/src/sql/drivers/ibase/qsql_ibase.cpp
@@ -1910,7 +1910,7 @@ void QIBaseDriver::qHandleEventNotification(void *updatedResultBuffer)
                                     (isc_callback)qEventCallback,
 #endif
                                    eBuffer->resultBuffer);
-            if (status[0] == 1 && status[1]) {
+            if (Q_UNLIKELY(status[0] == 1 && status[1])) {
                 qCritical("QIBaseDriver::qHandleEventNotification: could not resubscribe to '%s'",
                     qPrintable(i.key()));
             }
diff --git a/src/testlib/qbenchmarkvalgrind.cpp b/src/testlib/qbenchmarkvalgrind.cpp
index ada3cfc768..7cb5eef30c 100644
--- a/src/testlib/qbenchmarkvalgrind.cpp
+++ b/src/testlib/qbenchmarkvalgrind.cpp
@@ -96,7 +96,7 @@ qint64 QBenchmarkValgrindUtils::extractResult(const QString &fileName)
             break;
         }
     }
-    if (!valSeen)
+    if (Q_UNLIKELY(!valSeen))
         qFatal("Failed to extract result");
     return val;
 }
diff --git a/src/testlib/qtestcase.cpp b/src/testlib/qtestcase.cpp
index 0847d639fd..f5f399978e 100644
--- a/src/testlib/qtestcase.cpp
+++ b/src/testlib/qtestcase.cpp
@@ -2132,7 +2132,7 @@ public:
             int t = timeout.load();
             if (!t)
                 break;
-            if (!waitCondition.wait(&mutex, t)) {
+            if (Q_UNLIKELY(!waitCondition.wait(&mutex, t))) {
                 stackTrace();
                 qFatal("Test function timed out");
             }
@@ -2256,12 +2256,12 @@ void *fetchData(QTestData *data, const char *tagName, int typeId)
 
     int idx = data->parent()->indexOf(tagName);
 
-    if (idx == -1 || idx >= data->dataCount()) {
+    if (Q_UNLIKELY(idx == -1 || idx >= data->dataCount())) {
         qFatal("QFETCH: Requested testdata '%s' not available, check your _data function.",
                 tagName);
     }
 
-    if (typeId != data->parent()->elementTypeId(idx)) {
+    if (Q_UNLIKELY(typeId != data->parent()->elementTypeId(idx))) {
         qFatal("Requested type '%s' does not match available type '%s'.",
                QMetaType::typeName(typeId),
                QMetaType::typeName(data->parent()->elementTypeId(idx)));
@@ -2940,7 +2940,7 @@ int QTest::qExec(QObject *testObject, int argc, char **argv)
 
 #ifdef QTESTLIB_USE_VALGRIND
     if (QBenchmarkGlobalData::current->mode() == QBenchmarkGlobalData::CallgrindParentProcess) {
-        if (!qApp)
+        if (Q_UNLIKELY(!qApp))
             qFatal("QtTest: -callgrind option is not available with QTEST_APPLESS_MAIN");
 
         const QStringList origAppArgs(QCoreApplication::arguments());
diff --git a/src/testlib/qxctestlogger.mm b/src/testlib/qxctestlogger.mm
index 34116a2670..1e9119c9c0 100644
--- a/src/testlib/qxctestlogger.mm
+++ b/src/testlib/qxctestlogger.mm
@@ -124,7 +124,7 @@ private:
     if (![XCTestProbe isTesting])
         return;
 
-    if (!([NSDate timeIntervalSinceReferenceDate] > 0))
+    if (Q_UNLIKELY(!([NSDate timeIntervalSinceReferenceDate] > 0)))
         qFatal("error: Device date '%s' is bad, likely set to update automatically. Please correct.",
             [[NSDate date] description].UTF8String);
 
diff --git a/src/tools/rcc/main.cpp b/src/tools/rcc/main.cpp
index d8d5728414..1405f19a3a 100644
--- a/src/tools/rcc/main.cpp
+++ b/src/tools/rcc/main.cpp
@@ -304,7 +304,7 @@ int main(int argc, char *argv[])
 {
     // rcc uses a QHash to store files in the resource system.
     // we must force a certain hash order when testing or tst_rcc will fail, see QTBUG-25078
-    if (!qEnvironmentVariableIsEmpty("QT_RCC_TEST") && !qt_qhash_seed.testAndSetRelaxed(-1, 0))
+    if (Q_UNLIKELY(!qEnvironmentVariableIsEmpty("QT_RCC_TEST") && !qt_qhash_seed.testAndSetRelaxed(-1, 0)))
         qFatal("Cannot force QHash seed for testing as requested");
 
     return QT_PREPEND_NAMESPACE(runRcc)(argc, argv);
diff --git a/src/widgets/kernel/qwidget.cpp b/src/widgets/kernel/qwidget.cpp
index 308403175a..fbaa14a2b2 100644
--- a/src/widgets/kernel/qwidget.cpp
+++ b/src/widgets/kernel/qwidget.cpp
@@ -289,7 +289,7 @@ QWidgetPrivate::QWidgetPrivate(int version)
       , qd_hd(0)
 #endif
 {
-    if (!qApp) {
+    if (Q_UNLIKELY(!qApp)) {
         qFatal("QWidget: Must construct a QApplication before a QWidget");
         return;
     }
@@ -299,7 +299,7 @@ QWidgetPrivate::QWidgetPrivate(int version)
     // This allows incompatible versions to be loaded, possibly for testing.
     Q_UNUSED(version);
 #else
-    if (version != QObjectPrivateVersion)
+    if (Q_UNLIKELY(version != QObjectPrivateVersion))
         qFatal("Cannot mix incompatible Qt library (version 0x%x) with this library (version 0x%x)",
                 version, QObjectPrivateVersion);
 #endif
@@ -1116,7 +1116,7 @@ void QWidgetPrivate::adjustFlags(Qt::WindowFlags &flags, QWidget *w)
 void QWidgetPrivate::init(QWidget *parentWidget, Qt::WindowFlags f)
 {
     Q_Q(QWidget);
-    if (!qobject_cast<QApplication *>(QCoreApplication::instance()))
+    if (Q_UNLIKELY(!qobject_cast<QApplication *>(QCoreApplication::instance())))
         qFatal("QWidget: Cannot create a QWidget without QApplication");
 
     Q_ASSERT(allWidgets);