QtWidgets: use Q_UNLIKELY for every qWarning() (1)

If, after checking a condition, we issue a qWarning(),
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.

This change contains the changes to the util/,
dialogs/ and widgets/ subdirs.

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 QSystemTrayIcon::setVisible(), as a drive-by, I
swapped the evaluation order of an &&-expression
(newly wrapped in Q_UNLIKELY) to be more readable
and more efficient (cheaper check first) at the same
time.

Change-Id: I3564c5a5deacba49d67d3989fb0b53e680c57fcb
Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com>

1 files changed, 5 insertions, 5 deletions

diff --git a/src/widgets/dialogs/qprogressdialog.cpp b/src/widgets/dialogs/qprogressdialog.cpp
index bbb251c8b2..619d0051ea 100644
--- a/src/widgets/dialogs/qprogressdialog.cpp
+++ b/src/widgets/dialogs/qprogressdialog.cpp
@@ -353,7 +353,7 @@ void QProgressDialog::setLabel(QLabel *label)
 {
     Q_D(QProgressDialog);
     if (label == d->label) {
-        if (label)
+        if (Q_UNLIKELY(label))
             qWarning("QProgressDialog::setLabel: Attempt to set the same label again");
         return;
     }
@@ -402,7 +402,7 @@ void QProgressDialog::setCancelButton(QPushButton *cancelButton)
 {
     Q_D(QProgressDialog);
     if (d->cancel == cancelButton) {
-        if (cancelButton)
+        if (Q_UNLIKELY(cancelButton))
             qWarning("QProgressDialog::setCancelButton: Attempt to set the same button again");
         return;
     }
@@ -465,16 +465,16 @@ void QProgressDialogPrivate::setCancelButtonText(const QString &cancelButtonText
 void QProgressDialog::setBar(QProgressBar *bar)
 {
     Q_D(QProgressDialog);
-    if (!bar) {
+    if (Q_UNLIKELY(!bar)) {
         qWarning("QProgressDialog::setBar: Cannot set a null progress bar");
         return;
     }
 #ifndef QT_NO_DEBUG
-    if (value() > 0)
+    if (Q_UNLIKELY(value() > 0))
         qWarning("QProgressDialog::setBar: Cannot set a new progress bar "
                   "while the old one is active");
 #endif
-    if (bar == d->bar) {
+    if (Q_UNLIKELY(bar == d->bar)) {
         qWarning("QProgressDialog::setBar: Attempt to set the same progress bar again");
         return;
     }