diff -r 41300fa6a67c -r 2f34d5167611 src/gui/painting/qdrawhelper_mmx_p.h
--- a/src/gui/painting/qdrawhelper_mmx_p.h	Tue Feb 02 00:43:10 2010 +0200
+++ b/src/gui/painting/qdrawhelper_mmx_p.h	Fri Apr 16 15:50:13 2010 +0300
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
+** Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies).
 ** All rights reserved.
 ** Contact: Nokia Corporation (qt-info@nokia.com)
 **
@@ -146,36 +146,30 @@
   result = 0
   d = d * cia
 */
+#define comp_func_Clear_impl(dest, length, const_alpha)\
+{\
+    if (const_alpha == 255) {\
+        qt_memfill(static_cast<quint32*>(dest), quint32(0), length);\
+    } else {\
+        C_FF; C_80; C_00;\
+        m64 ia = MM::negate(MM::load_alpha(const_alpha));\
+        for (int i = 0; i < length; ++i) {\
+            dest[i] = MM::store(MM::byte_mul(MM::load(dest[i]), ia));\
+        }\
+        MM::end();\
+    }\
+}
+
 template <class MM>
 static void QT_FASTCALL comp_func_solid_Clear(uint *dest, int length, uint, uint const_alpha)
 {
-    if (!length)
-        return;
-
-    if (const_alpha == 255) {
-        qt_memfill(static_cast<quint32*>(dest), quint32(0), length);
-    } else {
-        C_FF; C_80; C_00;
-        m64 ia = MM::negate(MM::load_alpha(const_alpha));
-        for (int i = 0; i < length; ++i) {
-            dest[i] = MM::store(MM::byte_mul(MM::load(dest[i]), ia));
-        }
-    }
-    MM::end();
+    comp_func_Clear_impl(dest, length, const_alpha);
 }
 
 template <class MM>
 static void QT_FASTCALL comp_func_Clear(uint *dest, const uint *, int length, uint const_alpha)
 {
-    if (const_alpha == 255) {
-        qt_memfill(static_cast<quint32*>(dest), quint32(0), length);
-    } else {
-        C_FF; C_80; C_00;
-        m64 ia = MM::negate(MM::load_alpha(const_alpha));
-        for (int i = 0; i < length; ++i)
-            dest[i] = MM::store(MM::byte_mul(MM::load(dest[i]), ia));
-    }
-    MM::end();
+    comp_func_Clear_impl(dest, length, const_alpha);
 }
 
 /*
@@ -246,7 +240,10 @@
     C_FF; C_80; C_00;
     if (const_alpha == 255) {
         for (int i = 0; i < length; ++i) {
-            if ((0xff000000 & src[i]) == 0xff000000) {
+            const uint alphaMaskedSource = 0xff000000 & src[i];
+            if (alphaMaskedSource == 0)
+                continue;
+            if (alphaMaskedSource == 0xff000000) {
                 dest[i] = src[i];
             } else {
                 m64 s = MM::load(src[i]);
@@ -257,6 +254,8 @@
     } else {
         m64 ca = MM::load_alpha(const_alpha);
         for (int i = 0; i < length; ++i) {
+            if ((0xff000000 & src[i]) == 0)
+                continue;
             m64 s = MM::byte_mul(MM::load(src[i]), ca);
             m64 ia = MM::negate(MM::alpha(s));
             dest[i] = MM::store(MM::add(s, MM::byte_mul(MM::load(dest[i]), ia)));