Index: fbcompose.c
===================================================================
RCS file: /cvsroot/mozilla/gfx/cairo/libpixman/src/fbcompose.c,v
retrieving revision 1.6
diff -u -8 -p -r1.6 fbcompose.c
--- fbcompose.c	11 Jan 2006 00:48:57 -0000	1.6
+++ fbcompose.c	8 Feb 2006 00:27:16 -0000
@@ -23,16 +23,17 @@
  * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
  * SOFTWARE.
  */
 #ifdef HAVE_CONFIG_H
 #include <config.h>
 #endif
 #include "pixman-xserver-compat.h"
 #include "fbpict.h"
+#include "fbmmx.h"
 
 #ifdef RENDER
 
 #include "pixregionint.h"
 
 #ifdef _MSC_VER
 #define _USE_MATH_DEFINES
 #endif
@@ -3756,16 +3757,34 @@ fbCompositeRect (const FbComposeData *da
 	data->mask->componentAlpha &&
 	PICT_FORMAT_RGB (data->mask->format_code))
     {
 	CARD32 *mask_buffer = dest_buffer + data->width;
 	CombineFuncC compose = composeFunctions.combineC[data->op];
 	if (!compose)
 	    return;
 
+	/* XXX: The non-MMX version of some of the fbCompose functions
+	 * overwrite the source or mask data (ones that use
+	 * fbCombineMaskC, fbCombineMaskAlphaC, or fbCombineMaskValueC
+	 * as helpers).  This causes problems with the optimization in
+	 * this function that only fetches the source or mask once if
+	 * possible.  If we're on a non-MMX machine, disable this
+	 * optimization as a bandaid fix.
+	 *
+	 * https://bugs.freedesktop.org/show_bug.cgi?id=5777
+	 */
+#ifdef USE_MMX
+	if (!fbHaveMMX())
+#endif
+	{
+	    srcClass = SourcePictClassUnknown;
+	    maskClass = SourcePictClassUnknown;
+	}
+
 	for (i = 0; i < data->height; ++i) {
 	    /* fill first half of scanline with source */
 	    if (fetchSrc)
 	    {
 		if (fetchMask)
 		{
 		    /* fetch mask before source so that fetching of
 		       source can be optimized */