* regcomp.c (setup_tree, onig_compile): optimize .* at last by

  converting into (?>.*), which does not backtrack.  [ruby-core:27791]

* test/ruby/test_regexp.rb: add a test for above.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@26701 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 18 insertions, 2 deletions

diff --git a/regcomp.c b/regcomp.c
index e1ac7ee85c..16c816b1f7 100644
--- a/regcomp.c
+++ b/regcomp.c
@@ -3643,6 +3643,7 @@ setup_comb_exp_check(Node* node, int state, ScanEnv* env)
 #define IN_NOT        (1<<1)
 #define IN_REPEAT     (1<<2)
 #define IN_VAR_REPEAT (1<<3)
+#define IN_LAST	      (1<<4)
 
 /* setup_tree does the following work.
  1. check empty loop. (set qn->target_empty_info)
@@ -3664,7 +3665,8 @@ setup_tree(Node* node, regex_t* reg, int state, ScanEnv* env)
     {
       Node* prev = NULL_NODE;
       do {
-	r = setup_tree(NCAR(node), reg, state, env);
+	int s = IS_NOT_NULL(NCDR(node)) ? (state & ~IN_LAST) : state;
+	r = setup_tree(NCAR(node), reg, s, env);
 	if (IS_NOT_NULL(prev) && r == 0) {
 	  r = next_setup(prev, NCAR(node), reg);
 	}
@@ -3795,6 +3797,20 @@ setup_tree(Node* node, regex_t* reg, int state, ScanEnv* env)
 	}
       }
 #endif
+
+      if ((state & IN_LAST) != 0 && qn->greedy && IS_REPEAT_INFINITE(qn->upper)) {
+	/* automatic posseivation a* (at last) ==> (?>a*) */
+	if (qn->lower <= 1) {
+	  int ttype = NTYPE(qn->target);
+	  if (IS_NODE_TYPE_SIMPLE(ttype)) {
+	    Node* en = onig_node_new_enclose(ENCLOSE_STOP_BACKTRACK);
+	    CHECK_NULL_RETURN_MEMERR(en);
+	    SET_ENCLOSE_STATUS(en, NST_STOP_BT_SIMPLE_REPEAT);
+	    swap_node(node, en);
+	    NENCLOSE(node)->target = en;
+	  }
+	}
+      }
     }
     break;
 
@@ -5423,7 +5439,7 @@ onig_compile(regex_t* reg, const UChar* pattern, const UChar* pattern_end,
     reg->num_call = 0;
 #endif
 
-  r = setup_tree(root, reg, 0, &scan_env);
+  r = setup_tree(root, reg, IN_LAST, &scan_env);
   if (r != 0) goto err_unset;
 
 #ifdef ONIG_DEBUG_PARSE_TREE