QMimeTypeParser: plaster error paths with Q_UNLIKELY

... when more than a return would be executed, to
prompt the compiler to move it out of the way of
the normal execution path.

Unexpectedly costs ~200b in text size on optimized
GCC 5.3 Linux AMD64 builds.

Change-Id: I0ebfb56af7c2262f64271a1b0ec46533e6000bc9
Reviewed-by: Konstantin Ritt <ritt.ks@gmail.com>

2 files changed, 7 insertions, 7 deletions

diff --git a/src/corelib/mimetypes/qmimemagicrule.cpp b/src/corelib/mimetypes/qmimemagicrule.cpp
index 528dca3ff5..a4ba93192c 100644
--- a/src/corelib/mimetypes/qmimemagicrule.cpp
+++ b/src/corelib/mimetypes/qmimemagicrule.cpp
@@ -233,7 +233,7 @@ QMimeMagicRule::QMimeMagicRule(const QString &type,
       m_mask(mask),
       m_matchFunction(nullptr)
 {
-    if (m_type == Invalid)
+    if (Q_UNLIKELY(m_type == Invalid))
         *errorString = QLatin1String("Type ") + type + QLatin1String(" is not supported");
 
     // Parse for offset as "1" or "1:10"
@@ -246,7 +246,7 @@ QMimeMagicRule::QMimeMagicRule(const QString &type,
         return;
     }
 
-    if (m_value.isEmpty()) {
+    if (Q_UNLIKELY(m_value.isEmpty())) {
         m_type = Invalid;
         if (errorString)
             *errorString = QStringLiteral("Invalid empty magic rule value");
@@ -256,7 +256,7 @@ QMimeMagicRule::QMimeMagicRule(const QString &type,
     if (m_type >= Host16 && m_type <= Byte) {
         bool ok;
         m_number = m_value.toUInt(&ok, 0); // autodetect base
-        if (!ok) {
+        if (Q_UNLIKELY(!ok)) {
             m_type = Invalid;
             if (errorString)
                 *errorString = QLatin1String("Invalid magic rule value \"") + QLatin1String(m_value) + QLatin1Char('"');
@@ -270,7 +270,7 @@ QMimeMagicRule::QMimeMagicRule(const QString &type,
         m_pattern = makePattern(m_value);
         m_pattern.squeeze();
         if (!m_mask.isEmpty()) {
-            if (m_mask.size() < 4 || !m_mask.startsWith("0x")) {
+            if (Q_UNLIKELY(m_mask.size() < 4 || !m_mask.startsWith("0x"))) {
                 m_type = Invalid;
                 if (errorString)
                     *errorString = QLatin1String("Invalid magic rule mask \"") + QLatin1String(m_mask) + QLatin1Char('"');
@@ -278,7 +278,7 @@ QMimeMagicRule::QMimeMagicRule(const QString &type,
             }
             const QByteArray &tempMask = QByteArray::fromHex(QByteArray::fromRawData(
                                                      m_mask.constData() + 2, m_mask.size() - 2));
-            if (tempMask.size() != m_pattern.size()) {
+            if (Q_UNLIKELY(tempMask.size() != m_pattern.size())) {
                 m_type = Invalid;
                 if (errorString)
                     *errorString = QLatin1String("Invalid magic rule mask size \"") + QLatin1String(m_mask) + QLatin1Char('"');
diff --git a/src/corelib/mimetypes/qmimetypeparser.cpp b/src/corelib/mimetypes/qmimetypeparser.cpp
index 9ed345d37e..63e8f14018 100644
--- a/src/corelib/mimetypes/qmimetypeparser.cpp
+++ b/src/corelib/mimetypes/qmimetypeparser.cpp
@@ -164,7 +164,7 @@ bool QMimeTypeParserBase::parseNumber(const QStringRef &n, int *target, QString
 {
     bool ok;
     *target = n.toInt(&ok);
-    if (!ok) {
+    if (Q_UNLIKELY(!ok)) {
         *errorMessage = QLatin1String("Not a number '") + n + QLatin1String("'.");
         return false;
     }
@@ -325,7 +325,7 @@ bool QMimeTypeParserBase::parse(QIODevice *dev, const QString &fileName, QString
         }
     }
 
-    if (reader.hasError()) {
+    if (Q_UNLIKELY(reader.hasError())) {
         if (errorMessage)
             *errorMessage = QString::fromLatin1("An error has been encountered at line %1 of %2: %3:").arg(reader.lineNumber()).arg(fileName, reader.errorString());
         return false;