# HG changeset patch
# User Norihiro Tanaka <noritnk@kcn.ne.jp>
# Date 1537371349 25200
# Node ID ad0f0ab5d3d72b60396413af35245bdbff151a8c
# Parent  313e63262f55516f6a507d7ebfdff402356c48ab
dfa: optimization for state merge

* lib/dfa.c (merge2): New function.
(merge_nfa_state): Use it.

diff -r 313e63262f55 -r ad0f0ab5d3d7 ChangeLog
--- a/ChangeLog	Tue Sep 18 21:26:01 2018 -0700
+++ b/ChangeLog	Wed Sep 19 08:35:49 2018 -0700
@@ -1,3 +1,9 @@
+2018-09-19  Norihiro Tanaka  <noritnk@kcn.ne.jp>
+
+	dfa: optimization for state merge
+	* lib/dfa.c (merge2): New function.
+	(merge_nfa_state): Use it.
+
 2018-09-18  Jim Meyering  <meyering@fb.com>
 
 	dfa: trivial comment fix: s/is/if/
diff -r 313e63262f55 -r ad0f0ab5d3d7 lib/dfa.c
--- a/lib/dfa.c	Tue Sep 18 21:26:01 2018 -0700
+++ b/lib/dfa.c	Wed Sep 19 08:35:49 2018 -0700
@@ -2102,6 +2102,21 @@
   merge_constrained (s1, s2, -1, m);
 }
 
+static void
+merge2 (position_set *dst, position_set const *src, position_set *m)
+{
+  if (src->nelem < 4)
+    {
+      for (ptrdiff_t i = 0; i < src->nelem; ++i)
+        insert (src->elems[i], dst);
+    }
+   else
+    {
+      merge (src, dst, m);
+      copy (m, dst);
+    }
+}
+
 /* Delete a position from a set.  Return the nonzero constraint of the
    deleted position, or zero if there was no such position.  */
 static unsigned int
@@ -2388,8 +2403,7 @@
           if (flags[sindex] & OPT_REPEAT)
             delete (sindex, &follows[sindex]);
 
-          merge (&follows[dindex], &follows[sindex], merged);
-          copy (merged, &follows[dindex]);
+          merge2 (&follows[dindex], &follows[sindex], merged);
 
           /* Mark it as pruned in future.  */
           follows[tindex].elems[j].constraint = 0;