Fix double initialization of QRgba64 with C++14

Use constructors with C++11/C++14 where it is allowed to avoid hack
that caused double initialization and thereby performance regression
with C++14.

Change-Id: I7ae86df8aa34000b2c186e22bd9917303354b794
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

diff --git a/src/gui/painting/qrgba64.h b/src/gui/painting/qrgba64.h
index b701b224bee3ed73bc835023739774514275bf65..cca901995942d478f3d41ce3883d04523649eddb 100644 (file)
--- a/src/gui/painting/qrgba64.h
+++ b/src/gui/painting/qrgba64.h
@@ -58,33 +58,34 @@ class QRgba64 {
 #endif
     };
 
+    // No constructors are allowed in C++98, since this needs to be usable in a union.
+    // We however require one for constexprs in C++11/C++14
+#ifdef Q_COMPILER_CONSTEXPR
+    explicit Q_ALWAYS_INLINE Q_DECL_CONSTEXPR QRgba64(quint64 c) : rgba(c) { }
+#endif
 public:
-    // No constructors are allowed, since this needs to be usable in a union in no-c++11 mode.
-    // When c++11 is mandatory, we can add all but a copy constructor.
-    Q_DECL_RELAXED_CONSTEXPR static
-    QRgba64 fromRgba64(quint16 red, quint16 green, quint16 blue, quint16 alpha)
-    {
-        QRgba64 rgba64
-#ifdef Q_COMPILER_UNIFORM_INIT
-            = {}
+#ifdef Q_COMPILER_CONSTEXPR
+    Q_ALWAYS_INLINE Q_DECL_CONSTEXPR QRgba64() : rgba(0) { }
 #endif
-        ;
-        rgba64.rgba = quint64(red)   << RedShift
-                    | quint64(green) << GreenShift
-                    | quint64(blue)  << BlueShift
-                    | quint64(alpha) << AlphaShift;
-        return rgba64;
-    }
-    Q_DECL_RELAXED_CONSTEXPR static
+
+    Q_DECL_CONSTEXPR static
     QRgba64 fromRgba64(quint64 c)
     {
-        QRgba64 rgba64
-#ifdef Q_COMPILER_UNIFORM_INIT
-            = {}
-#endif
-        ;
+#ifdef Q_COMPILER_CONSTEXPR
+        return QRgba64(c);
+#else
+        QRgba64 rgba64;
         rgba64.rgba = c;
         return rgba64;
+#endif
+    }
+    Q_DECL_CONSTEXPR static
+    QRgba64 fromRgba64(quint16 red, quint16 green, quint16 blue, quint16 alpha)
+    {
+        return fromRgba64(quint64(red)   << RedShift
+                        | quint64(green) << GreenShift
+                        | quint64(blue)  << BlueShift
+                        | quint64(alpha) << AlphaShift);
     }
     Q_DECL_RELAXED_CONSTEXPR static QRgba64 fromRgba(quint8 red, quint8 green, quint8 blue, quint8 alpha)
     {
@@ -190,12 +191,12 @@ private:
 
 Q_DECLARE_TYPEINFO(QRgba64, Q_PRIMITIVE_TYPE);
 
-Q_DECL_RELAXED_CONSTEXPR inline QRgba64 qRgba64(quint16 r, quint16 g, quint16 b, quint16 a)
+Q_DECL_CONSTEXPR inline QRgba64 qRgba64(quint16 r, quint16 g, quint16 b, quint16 a)
 {
     return QRgba64::fromRgba64(r, g, b, a);
 }
 
-Q_DECL_RELAXED_CONSTEXPR inline QRgba64 qRgba64(quint64 c)
+Q_DECL_CONSTEXPR inline QRgba64 qRgba64(quint64 c)
 {
     return QRgba64::fromRgba64(c);
 }