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>

3 files changed, 3 insertions, 3 deletions

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;