gdi32: Add assembly helpers for filling solid rectangles.

dlls/gdi32/dibdrv/primitives.c

@@ -258,12 +258,26 @@ static inline void do_rop_codes_line_rev_1(BYTE *dst, int dst_x, const BYTE *src
 
 static inline void memset_32( DWORD *start, DWORD val, DWORD size )
 {
+#if defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))
+    DWORD dummy;
+    __asm__ __volatile__( "cld; rep; stosl"
+                          : "=c" (dummy), "=D" (dummy)
+                          : "a" (val), "0" (size), "1" (start) );
+#else
     while (size--) *start++ = val;
+#endif
 }
 
 static inline void memset_16( WORD *start, WORD val, DWORD size )
 {
+#if defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))
+    DWORD dummy;
+    __asm__ __volatile__( "cld; rep; stosw"
+                          : "=c" (dummy), "=D" (dummy)
+                          : "a" (val), "0" (size), "1" (start) );
+#else
     while (size--) *start++ = val;
+#endif
 }
 
 static void solid_rects_32(const dib_info *dib, int num, const RECT *rc, DWORD and, DWORD xor)