Centralize use of __attribute__((noinline))

There are currently only two users, but I have patches in
the pipeline which mark some other function noinline, so
proavtively centralize the ifdef'ery involved.

Change-Id: I1f02351fdc903d4e026089e12b8a976ed6a8d603
Reviewed-by: Kai Koehne <kai.koehne@theqtcompany.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/global/qglobal.h

@@ -485,6 +485,14 @@ typedef qptrdiff qintptr;
 #  define Q_ATTRIBUTE_FORMAT_PRINTF(A, B)
 #endif
 
+#ifdef Q_CC_MSVC
+#  define Q_NEVER_INLINE __declspec(noinline)
+#elif defined(Q_CC_GNU)
+#  define Q_NEVER_INLINE __attribute__((noinline))
+#else
+#  define Q_NEVER_INLINE
+#endif
+
 //defines the type for the WNDPROC on windows
 //the alignment needs to be forced for sse2 to not crash with mingw
 #if defined(Q_OS_WIN)

src/corelib/tools/qbytearray.cpp

@@ -2761,15 +2761,11 @@ QByteArray QByteArray::mid(int pos, int len) const
     \sa toUpper(), {8-bit Character Comparisons}
 */
 
-// noinline so that the compiler won't inline the function in each of
+// prevent the compiler from inlining the function in each of
 // toLower and toUpper when the only difference is the table being used
 // (even with constant propagation, there's no gain in performance).
 template <typename T>
-#ifdef Q_CC_MSVC
-__declspec(noinline)
-#elif defined(Q_CC_GNU)
-__attribute__((noinline))
-#endif
+Q_NEVER_INLINE
 static QByteArray toCase_template(T &input, const uchar * table)
 {
     // find the first bad character in input

src/corelib/tools/qstring.cpp

@@ -5559,11 +5559,7 @@ struct CasefoldTraits
 };
 
 template <typename Traits, typename T>
-#ifdef Q_CC_MSVC
-__declspec(noinline)
-#elif defined(Q_CC_GNU)
-__attribute__((noinline))
-#endif
+Q_NEVER_INLINE
 static QString detachAndConvertCase(T &str, QStringIterator it)
 {
     QString s = qMove(str);             // will copy if T is const QString