regex_automaton.h (_NFA<>::_M_insert_repeat): Add _S_opcode_repeat support to…

regex_automaton.h (_NFA<>::_M_insert_repeat): Add _S_opcode_repeat support to distingush a loop from _S_opcode_alternative.

2014-04-27  Tim Shen  <timshen91@gmail.com>

	* include/bits/regex_automaton.h (_NFA<>::_M_insert_repeat):
	Add _S_opcode_repeat support to distingush a loop from
	_S_opcode_alternative.
	* include/bits/regex_automaton.tcc (_State_base::_M_print,
	_State_base::_M_dot, _NFA<>::_M_eliminate_dummy,
	_StateSeq<>::_M_clone): Likewise.
	* include/bits/regex_compiler.tcc (_Compiler<>::_M_quantifier):
	Likewise.
	* include/bits/regex_executor.tcc (_Executor<>::_M_dfs): Likewise.
	* include/bits/regex_scanner.tcc (_Scanner<>::_M_eat_escape_ecma):
	Uglify local variable __i.
	* include/bits/regex_compiler.h (_BracketMatcher<>::_M_make_cache):
	Use size_t instead of int to compare with vector::size().

2014-04-27  Tim Shen  <timshen91@gmail.com>

	* include/bits/regex_executor.h: Add _M_rep_count to track how
	many times this repeat node are visited.
	* include/bits/regex_executor.tcc (_Executor<>::_M_rep_once_more,
	_Executor<>::_M_dfs): Use _M_rep_count to prevent entering
	infinite loop.

2014-04-27  Tim Shen  <timshen91@gmail.com>

	* include/bits/regex.tcc (__regex_algo_impl<>): Remove
	_GLIBCXX_REGEX_DFS_QUANTIFIERS_LIMIT and use
	_GLIBCXX_REGEX_USE_THOMPSON_NFA instead.
	* include/bits/regex_automaton.h: Remove quantifier counting variable.
	* include/bits/regex_automaton.tcc (_State_base::_M_dot):
	Adjust debug NFA dump.

From-SVN: r209844

libstdc++-v3/ChangeLog

+2014-04-27  Tim Shen  <timshen91@gmail.com>
+
+	* include/bits/regex_automaton.h (_NFA<>::_M_insert_repeat):
+	Add _S_opcode_repeat support to distingush a loop from
+	_S_opcode_alternative.
+	* include/bits/regex_automaton.tcc (_State_base::_M_print,
+	_State_base::_M_dot, _NFA<>::_M_eliminate_dummy,
+	_StateSeq<>::_M_clone): Likewise.
+	* include/bits/regex_compiler.tcc (_Compiler<>::_M_quantifier):
+	Likewise.
+	* include/bits/regex_executor.tcc (_Executor<>::_M_dfs): Likewise.
+	* include/bits/regex_scanner.tcc (_Scanner<>::_M_eat_escape_ecma):
+	Uglify local variable __i.
+	* include/bits/regex_compiler.h (_BracketMatcher<>::_M_make_cache):
+	Use size_t instead of int to compare with vector::size().
+
+2014-04-27  Tim Shen  <timshen91@gmail.com>
+
+	* include/bits/regex_executor.h: Add _M_rep_count to track how
+	many times this repeat node are visited.
+	* include/bits/regex_executor.tcc (_Executor<>::_M_rep_once_more,
+	_Executor<>::_M_dfs): Use _M_rep_count to prevent entering
+	infinite loop.
+
+2014-04-27  Tim Shen  <timshen91@gmail.com>
+
+	* include/bits/regex.tcc (__regex_algo_impl<>): Remove
+	_GLIBCXX_REGEX_DFS_QUANTIFIERS_LIMIT and use
+	_GLIBCXX_REGEX_USE_THOMPSON_NFA instead.
+	* include/bits/regex_automaton.h: Remove quantifier counting variable.
+	* include/bits/regex_automaton.tcc (_State_base::_M_dot):
+	Adjust debug NFA dump.
+
 2014-04-25  Lars Gullik Bjønnes  <larsbj@gullik.org>
 
 	PR libstdc++/60710

libstdc++-v3/include/bits/regex.tcc

@@ -28,12 +28,12 @@
  *  Do not attempt to use it directly. @headername{regex}
  */
 
-// See below __regex_algo_impl to get what this is talking about. The default
-// value 1 indicated a conservative optimization without giving up worst case
-// performance.
-#ifndef _GLIBCXX_REGEX_DFS_QUANTIFIERS_LIMIT
-#define _GLIBCXX_REGEX_DFS_QUANTIFIERS_LIMIT 1
-#endif
+// A non-standard switch to let the user pick the matching algorithm.
+// If _GLIBCXX_REGEX_USE_THOMPSON_NFA is defined, the thompson NFA
+// algorithm will be used. This algorithm is not enabled by default,
+// and cannot be used if the regex contains back-references, but has better
+// (polynomial instead of exponential) worst case performace.
+// See __regex_algo_impl below.
 
 namespace std _GLIBCXX_VISIBILITY(default)
 {
@@ -66,24 +66,15 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       for (auto& __it : __res)
 	__it.matched = false;
 
-      // This function decide which executor to use under given circumstances.
-      // The _S_auto policy now is the following: if a NFA has no
-      // back-references and has more than _GLIBCXX_REGEX_DFS_QUANTIFIERS_LIMIT
-      // quantifiers (*, +, ?), the BFS executor will be used, other wise
-      // DFS executor. This is because DFS executor has a exponential upper
-      // bound, but better best-case performace. Meanwhile, BFS executor can
-      // effectively prevent from exponential-long time matching (which must
-      // contains many quantifiers), but it's slower in average.
-      //
-      // For simple regex, BFS executor could be 2 or more times slower than
-      // DFS executor.
-      //
-      // Of course, BFS executor cannot handle back-references.
+      // __policy is used by testsuites so that they can use Thompson NFA
+      // without defining a macro. Users should define
+      // _GLIBCXX_REGEX_USE_THOMPSON_NFA if they need to use this approach.
       bool __ret;
       if (!__re._M_automaton->_M_has_backref
-	  && (__policy == _RegexExecutorPolicy::_S_alternate
-	      || __re._M_automaton->_M_quant_count
-		> _GLIBCXX_REGEX_DFS_QUANTIFIERS_LIMIT))
+#ifndef _GLIBCXX_REGEX_USE_THOMPSON_NFA
+	  && __policy == _RegexExecutorPolicy::_S_alternate
+#endif
+	  )
 	{
 	  _Executor<_BiIter, _Alloc, _TraitsT, false>
 	    __executor(__s, __e, __m, __re, __flags);

libstdc++-v3/include/bits/regex_automaton.h

@@ -52,6 +52,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   {
       _S_opcode_unknown,
       _S_opcode_alternative,
+      _S_opcode_repeat,
       _S_opcode_backref,
       _S_opcode_line_begin_assertion,
       _S_opcode_line_end_assertion,
@@ -74,9 +75,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       size_t _M_backref_index;  // for _S_opcode_backref
       struct
       {
-	// for _S_opcode_alternative.
-	_StateIdT  _M_quant_index;
-	// for _S_opcode_alternative or _S_opcode_subexpr_lookahead
+	// for _S_opcode_alternative, _S_opcode_repeat and
+	// _S_opcode_subexpr_lookahead
 	_StateIdT  _M_alt;
 	// for _S_opcode_word_boundary or _S_opcode_subexpr_lookahead or
 	// quantifiers (ungreedy if set true)
@@ -120,7 +120,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     explicit
     _NFA_base(_FlagT __f)
     : _M_flags(__f), _M_start_state(0), _M_subexpr_count(0),
-    _M_quant_count(0), _M_has_backref(false)
+    _M_has_backref(false)
     { }
 
     _NFA_base(_NFA_base&&) = default;
@@ -145,7 +145,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     _FlagT                    _M_flags;
     _StateIdT                 _M_start_state;
     _SizeT                    _M_subexpr_count;
-    _SizeT                    _M_quant_count;
     bool                      _M_has_backref;
   };
 
@@ -175,7 +174,17 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	_StateT __tmp(_S_opcode_alternative);
 	// It labels every quantifier to make greedy comparison easier in BFS
 	// approach.
-	__tmp._M_quant_index = this->_M_quant_count++;
+	__tmp._M_next = __next;
+	__tmp._M_alt = __alt;
+	return _M_insert_state(std::move(__tmp));
+      }
+
+      _StateIdT
+      _M_insert_repeat(_StateIdT __next, _StateIdT __alt, bool __neg)
+      {
+	_StateT __tmp(_S_opcode_repeat);
+	// It labels every quantifier to make greedy comparison easier in BFS
+	// approach.
 	__tmp._M_next = __next;
 	__tmp._M_alt = __alt;
 	__tmp._M_neg = __neg;

libstdc++-v3/include/bits/regex_automaton.tcc

@@ -41,6 +41,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     switch (_M_opcode)
     {
       case _S_opcode_alternative:
+      case _S_opcode_repeat:
 	ostr << "alt next=" << _M_next << " alt=" << _M_alt;
 	break;
       case _S_opcode_subexpr_begin:
@@ -72,11 +73,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     switch (_M_opcode)
     {
       case _S_opcode_alternative:
+      case _S_opcode_repeat:
 	__ostr << __id << " [label=\"" << __id << "\\nALT\"];\n"
 	       << __id << " -> " << _M_next
-	       << " [label=\"epsilon\", tailport=\"s\"];\n"
+	       << " [label=\"next\", tailport=\"s\"];\n"
 	       << __id << " -> " << _M_alt
-	       << " [label=\"epsilon\", tailport=\"n\"];\n";
+	       << " [label=\"alt\", tailport=\"n\"];\n";
 	break;
       case _S_opcode_backref:
 	__ostr << __id << " [label=\"" << __id << "\\nBACKREF "
@@ -174,6 +176,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 		 == _S_opcode_dummy)
 	    __it._M_next = (*this)[__it._M_next]._M_next;
 	  if (__it._M_opcode == _S_opcode_alternative
+	      || __it._M_opcode == _S_opcode_repeat
 	      || __it._M_opcode == _S_opcode_subexpr_lookahead)
 	    while (__it._M_alt >= 0 && (*this)[__it._M_alt]._M_opcode
 		   == _S_opcode_dummy)
@@ -198,6 +201,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	  auto __id = _M_nfa._M_insert_state(__dup);
 	  __m[__u] = __id;
 	  if (__dup._M_opcode == _S_opcode_alternative
+	      || __dup._M_opcode == _S_opcode_repeat
 	      || __dup._M_opcode == _S_opcode_subexpr_lookahead)
 	    if (__dup._M_alt != _S_invalid_state_id && __m[__dup._M_alt] == -1)
 	      __stack.push(__dup._M_alt);
@@ -217,6 +221,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	      __ref._M_next = __m[__ref._M_next];
 	    }
 	  if (__ref._M_opcode == _S_opcode_alternative
+	      || __ref._M_opcode == _S_opcode_repeat
 	      || __ref._M_opcode == _S_opcode_subexpr_lookahead)
 	    if (__ref._M_alt != _S_invalid_state_id)
 	      {

libstdc++-v3/include/bits/regex_compiler.h

@@ -421,7 +421,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       void
       _M_make_cache(true_type)
       {
-	for (int __i = 0; __i < _M_cache.size(); __i++)
+	for (size_t __i = 0; __i < _M_cache.size(); __i++)
 	  _M_cache[static_cast<_UnsignedCharT>(__i)] =
 	    _M_apply(__i, false_type());
       }

libstdc++-v3/include/bits/regex_compiler.tcc

@@ -188,8 +188,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	{
 	  __init();
 	  auto __e = _M_pop();
-	  _StateSeqT __r(_M_nfa, _M_nfa._M_insert_alt(_S_invalid_state_id,
-						      __e._M_start, __neg));
+	  _StateSeqT __r(_M_nfa, _M_nfa._M_insert_repeat(_S_invalid_state_id,
+							 __e._M_start, __neg));
 	  __e._M_append(__r);
 	  _M_stack.push(__r);
 	}
@@ -197,8 +197,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	{
 	  __init();
 	  auto __e = _M_pop();
-	  __e._M_append(_M_nfa._M_insert_alt(_S_invalid_state_id, __e._M_start,
-					     __neg));
+	  __e._M_append(_M_nfa._M_insert_repeat(_S_invalid_state_id,
+						__e._M_start, __neg));
 	  _M_stack.push(__e);
 	}
       else if (_M_match_token(_ScannerT::_S_token_opt))
@@ -206,8 +206,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	  __init();
 	  auto __e = _M_pop();
 	  auto __end = _M_nfa._M_insert_dummy();
-	  _StateSeqT __r(_M_nfa, _M_nfa._M_insert_alt(_S_invalid_state_id,
-						      __e._M_start, __neg));
+	  _StateSeqT __r(_M_nfa, _M_nfa._M_insert_repeat(_S_invalid_state_id,
+							 __e._M_start, __neg));
 	  __e._M_append(__end);
 	  __r._M_append(__end);
 	  _M_stack.push(__r);
@@ -244,8 +244,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	    {
 	      auto __tmp = __r._M_clone();
 	      _StateSeqT __s(_M_nfa,
-			     _M_nfa._M_insert_alt(_S_invalid_state_id,
-						  __tmp._M_start, __neg));
+			     _M_nfa._M_insert_repeat(_S_invalid_state_id,
+						     __tmp._M_start, __neg));
 	      __tmp._M_append(__s);
 	      __e._M_append(__s);
 	    }
@@ -261,8 +261,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	      for (long __i = 0; __i < __n; ++__i)
 		{
 		  auto __tmp = __r._M_clone();
-		  auto __alt = _M_nfa._M_insert_alt(__tmp._M_start,
-						    __end, __neg);
+		  auto __alt = _M_nfa._M_insert_repeat(__tmp._M_start,
+						       __end, __neg);
 		  __stack.push(__alt);
 		  __e._M_append(_StateSeqT(_M_nfa, __alt, __tmp._M_end));
 		}

libstdc++-v3/include/bits/regex_executor.h

@@ -73,6 +73,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       _M_results(__results),
       _M_match_queue(__dfs_mode ? nullptr
 		     : new vector<pair<_StateIdT, _ResultsVec>>()),
+      _M_rep_count(_M_nfa.size()),
       _M_visited(__dfs_mode ? nullptr : new vector<bool>(_M_nfa.size())),
       _M_flags((__flags & regex_constants::match_prev_avail)
 	       ? (__flags
@@ -104,6 +105,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     private:
       template<bool __match_mode>
 	void
+	_M_rep_once_more(_StateIdT);
+
+      template<bool __match_mode>
+	void
 	_M_dfs(_StateIdT __start);
 
       template<bool __match_mode>
@@ -149,9 +154,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       _ResultsVec&                                          _M_results;
       // Used in BFS, saving states that need to be considered for the next
       // character.
-      std::unique_ptr<vector<pair<_StateIdT, _ResultsVec>>> _M_match_queue;
+      unique_ptr<vector<pair<_StateIdT, _ResultsVec>>>      _M_match_queue;
       // Used in BFS, indicating that which state is already visited.
-      std::unique_ptr<vector<bool>>                         _M_visited;
+      vector<pair<_BiIter, int>>                            _M_rep_count;
+      unique_ptr<vector<bool>>                              _M_visited;
       _FlagT                                                _M_flags;
       // To record current solution.
       _StateIdT                                             _M_start_state;

libstdc++-v3/include/bits/regex_executor.tcc

@@ -161,7 +161,39 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       return false;
     }
 
-  // TODO: Use a function vector to dispatch, instead of using switch-case.
+  // __rep_count records how many times (__rep_count.second)
+  // this node is visited under certain input iterator
+  // (__rep_count.first). This prevent the executor from entering
+  // infinite loop by refusing to continue when it's already been
+  // visited more than twice. It's `twice` instead of `once` because
+  // we need to spare one more time for potential group capture.
+  template<typename _BiIter, typename _Alloc, typename _TraitsT,
+    bool __dfs_mode>
+  template<bool __match_mode>
+    void _Executor<_BiIter, _Alloc, _TraitsT, __dfs_mode>::
+    _M_rep_once_more(_StateIdT __i)
+    {
+      const auto& __state = _M_nfa[__i];
+      auto& __rep_count = _M_rep_count[__i];
+      if (__rep_count.second == 0 || __rep_count.first != _M_current)
+	{
+	  auto __back = __rep_count;
+	  __rep_count.first = _M_current;
+	  __rep_count.second = 1;
+	  _M_dfs<__match_mode>(__state._M_alt);
+	  __rep_count = __back;
+	}
+      else
+	{
+	  if (__rep_count.second < 2)
+	    {
+	      __rep_count.second++;
+	      _M_dfs<__match_mode>(__state._M_alt);
+	      __rep_count.second--;
+	    }
+	}
+    };
+
   template<typename _BiIter, typename _Alloc, typename _TraitsT,
     bool __dfs_mode>
   template<bool __match_mode>
@@ -184,69 +216,61 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	// of this quantifier". Executing _M_next first or _M_alt first don't
 	// mean the same thing, and we need to choose the correct order under
 	// given greedy mode.
-	case _S_opcode_alternative:
-	  // Greedy.
-	  if (!__state._M_neg)
-	    {
-	      // "Once more" is preferred in greedy mode.
-	      _M_dfs<__match_mode>(__state._M_alt);
-	      // If it's DFS executor and already accepted, we're done.
-	      if (!__dfs_mode || !_M_has_sol)
-		_M_dfs<__match_mode>(__state._M_next);
-	    }
-	  else // Non-greedy mode
-	    {
-	      if (__dfs_mode)
-		{
-		  // vice-versa.
+	case _S_opcode_repeat:
+	  {
+	    // Greedy.
+	    if (!__state._M_neg)
+	      {
+		_M_rep_once_more<__match_mode>(__i);
+		// If it's DFS executor and already accepted, we're done.
+		if (!__dfs_mode || !_M_has_sol)
 		  _M_dfs<__match_mode>(__state._M_next);
-		  if (!_M_has_sol)
-		    _M_dfs<__match_mode>(__state._M_alt);
-		}
-	      else
-		{
-		  // DON'T attempt anything, because there's already another
-		  // state with higher priority accepted. This state cannot be
-		  // better by attempting its next node.
-		  if (!_M_has_sol)
-		    {
-		      _M_dfs<__match_mode>(__state._M_next);
-		      // DON'T attempt anything if it's already accepted. An
-		      // accepted state *must* be better than a solution that
-		      // matches a non-greedy quantifier one more time.
-		      if (!_M_has_sol)
-			_M_dfs<__match_mode>(__state._M_alt);
-		    }
-		}
+	      }
+	    else // Non-greedy mode
+	      {
+		if (__dfs_mode)
+		  {
+		    // vice-versa.
+		    _M_dfs<__match_mode>(__state._M_next);
+		    if (!_M_has_sol)
+		      _M_rep_once_more<__match_mode>(__i);
+		  }
+		else
+		  {
+		    // DON'T attempt anything, because there's already another
+		    // state with higher priority accepted. This state cannot be
+		    // better by attempting its next node.
+		    if (!_M_has_sol)
+		      {
+			_M_dfs<__match_mode>(__state._M_next);
+			// DON'T attempt anything if it's already accepted. An
+			// accepted state *must* be better than a solution that
+			// matches a non-greedy quantifier one more time.
+			if (!_M_has_sol)
+			  _M_rep_once_more<__match_mode>(__i);
+		      }
+		  }
+	      }
 	    }
 	  break;
 	case _S_opcode_subexpr_begin:
-	  // If there's nothing changed since last visit, do NOT continue.
-	  // This prevents the executor from get into infinite loop when using
-	  // "()*" to match "".
-	  if (!_M_cur_results[__state._M_subexpr].matched
-	      || _M_cur_results[__state._M_subexpr].first != _M_current)
-	    {
-	      auto& __res = _M_cur_results[__state._M_subexpr];
-	      auto __back = __res.first;
-	      __res.first = _M_current;
-	      _M_dfs<__match_mode>(__state._M_next);
-	      __res.first = __back;
-	    }
+	  {
+	    auto& __res = _M_cur_results[__state._M_subexpr];
+	    auto __back = __res.first;
+	    __res.first = _M_current;
+	    _M_dfs<__match_mode>(__state._M_next);
+	    __res.first = __back;
+	  }
 	  break;
 	case _S_opcode_subexpr_end:
-	  if (_M_cur_results[__state._M_subexpr].second != _M_current
-	      || _M_cur_results[__state._M_subexpr].matched != true)
-	    {
-	      auto& __res = _M_cur_results[__state._M_subexpr];
-	      auto __back = __res;
-	      __res.second = _M_current;
-	      __res.matched = true;
-	      _M_dfs<__match_mode>(__state._M_next);
-	      __res = __back;
-	    }
-	  else
+	  {
+	    auto& __res = _M_cur_results[__state._M_subexpr];
+	    auto __back = __res;
+	    __res.second = _M_current;
+	    __res.matched = true;
 	    _M_dfs<__match_mode>(__state._M_next);
+	    __res = __back;
+	  }
 	  break;
 	case _S_opcode_line_begin_assertion:
 	  if (_M_at_begin())
@@ -339,6 +363,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 		  }
 	    }
 	  break;
+	case _S_opcode_alternative:
+	  _M_dfs<__match_mode>(__state._M_alt);
+	  if (!__dfs_mode || !_M_has_sol)
+	    _M_dfs<__match_mode>(__state._M_next);
+	  break;
 	default:
 	  _GLIBCXX_DEBUG_ASSERT(false);
 	}

libstdc++-v3/include/bits/regex_scanner.tcc

@@ -335,7 +335,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       else if (__c == 'x' || __c == 'u')
 	{
 	  _M_value.erase();
-	  for (int i = 0; i < (__c == 'x' ? 2 : 4); i++)
+	  for (int __i = 0; __i < (__c == 'x' ? 2 : 4); __i++)
 	    {
 	      if (_M_current == _M_end
 		  || !_M_ctype.is(_CtypeT::xdigit, *_M_current))

libstdc++-v3/testsuite/28_regex/algorithms/regex_match/ecma/char/emptygroup.cc

@@ -50,6 +50,7 @@ test01()
     const char s[] = "";
     VERIFY( regex_match_debug(s, m, re) );
   }
+  VERIFY(regex_match_debug("", regex("(?:)*")));
 }
 
 int