gdk: select pixelops sources by target architecture

configure.ac

@@ -117,6 +117,20 @@ AC_DEFINE_UNQUOTED(GETTEXT_PACKAGE, "$GETTEXT_PACKAGE",
 
 AC_CANONICAL_HOST
 
+gdk_pixelops_i386=no
+
+case "$host_cpu" in
+  i?86)
+    gdk_pixelops_i386=yes
+    AC_DEFINE([HAVE_GDK_PIXELOPS_INIT], [1],
+              [Define if GDK pixel operations require runtime dispatch initialization])
+    ;;
+esac
+
+AM_CONDITIONAL(GDK_PIXELOPS_I386,
+               test "$gdk_pixelops_i386" = yes)
+
+
 MATH_LIB=-lm
 AC_MSG_CHECKING([for native Win32])
 LIB_EXE_MACHINE_FLAG=X86

gdk/Makefile.am

@@ -119,8 +119,15 @@ gdk_private_headers =   \
     gdkpoly-generic.h	\
 	gdkregion-generic.h
 
+gdk_pixelops_arch_sources =
+
+if GDK_PIXELOPS_I386
+gdk_pixelops_arch_sources += gdkpixelops-x86.c
+endif
+
 gdk_pixelops_private_sources = \
-        gdkpixelops-generic.c
+        gdkpixelops-generic.c \
+        $(gdk_pixelops_arch_sources)
 
 gdk_c_sources =                 \
 	$(medialib_sources)     \

gdk/gdkpixelops-x86.c

@@ -0,0 +1,13 @@
+/* GDK - The GIMP Drawing Kit
+ *
+ * x86 pixel operation backend.
+ *
+ * This file is selected at build time only for x86 targets.
+ */
+
+#include "config.h"
+
+#if !defined(__i386__) && !defined(__x86_64__) && \
+    !defined(_M_IX86) && !defined(_M_X64)
+#error "gdkpixelops-x86.c must only be built for an x86 target"
+#endif

gdk/makefile.msc

@@ -74,6 +74,7 @@ gdk_OBJECTS = \
 	gdkdraw.obj \
 	gdkpixelops.obj \
 	gdkpixelops-generic.obj \
+	gdkpixelops-x86.obj \
 	gdkenumtypes.obj \
 	gdkevents.obj \
 	gdkfont.obj \