updated for version 7.4.349
Problem:    When there are matches to highlight the whole window is redrawn,
            which is slow.
Solution:   Only redraw everything when lines were inserted or deleted.
            Reset b_mod_xlines when needed.  (Alexey Radkov)
diff --git a/src/screen.c b/src/screen.c
index 8e61691..65aadc4 100644
--- a/src/screen.c
+++ b/src/screen.c
@@ -1769,8 +1769,10 @@
 					syntax_check_changed(lnum)))
 #endif
 #ifdef FEAT_SEARCH_EXTRA
-				/* match in fixed position might need redraw */
-				||  wp->w_match_head != NULL
+				/* match in fixed position might need redraw
+				 * if lines were inserted or deleted */
+				|| (wp->w_match_head != NULL
+						    && buf->b_mod_xlines != 0)
 #endif
 				)))))
 	{