Limit EatAtLeast recursion by a budget.

src/jsregexp.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 564 matching lines @@
   virtual void Accept(NodeVisitor* visitor) = 0;
   // Generates a goto to this node or actually generates the code at this point.
   virtual void Emit(RegExpCompiler* compiler, Trace* trace) = 0;
   // How many characters must this node consume at a minimum in order to
   // succeed.  If we have found at least 'still_to_find' characters that
   // must be consumed there is no need to ask any following nodes whether
   // they are sure to eat any more characters.  The not_at_start argument is
   // used to indicate that we know we are not at the start of the input.  In
   // this case anchored branches will always fail and can be ignored when
   // determining how many characters are consumed on success.
-  virtual int EatsAtLeast(int still_to_find,
-                          int recursion_depth,
-                          bool not_at_start) = 0;
+  virtual int EatsAtLeast(int still_to_find, int budget, bool not_at_start) = 0;
   // Emits some quick code that checks whether the preloaded characters match.
   // Falls through on certain failure, jumps to the label on possible success.
   // If the node cannot make a quick check it does nothing and returns false.
   bool EmitQuickCheck(RegExpCompiler* compiler,
                       Trace* trace,
                       bool preload_has_checked_bounds,
                       Label* on_possible_success,
                       QuickCheckDetails* details_return,
                       bool fall_through_on_failure);
   // For a given number of characters this returns a mask and a value.  The
@@ skipping 11 matching lines @@
   virtual RegExpNode* GetSuccessorOfOmnivorousTextNode(
       RegExpCompiler* compiler) {
     return NULL;
   }
 
   // Collects information on the possible code units (mod 128) that can match if
   // we look forward.  This is used for a Boyer-Moore-like string searching
   // implementation.  TODO(erikcorry):  This should share more code with
   // EatsAtLeast, GetQuickCheckDetails.  The budget argument is used to limit
   // the number of nodes we are willing to look at in order to create this data.
   static const int kFillInBMBudget = 200;

[erikcorry, 2013/03/01 09:15:53]

This seems misnamed now.  How about kRecursionBudget or kAnalysisBudget?

   virtual void FillInBMInfo(int offset,
-                            int recursion_depth,
                             int budget,
                             BoyerMooreLookahead* bm,
                             bool not_at_start) {
     UNREACHABLE();
   }
 
   // If we know that the input is ASCII then there are some nodes that can
   // never match.  This method returns a node that can be substituted for
   // itself, or NULL if the node can never match.
   virtual RegExpNode* FilterASCII(int depth, bool ignore_case) { return this; }
@@ skipping 86 matching lines @@
 
 
 class SeqRegExpNode: public RegExpNode {
  public:
   explicit SeqRegExpNode(RegExpNode* on_success)
       : RegExpNode(on_success->zone()), on_success_(on_success) { }
   RegExpNode* on_success() { return on_success_; }
   void set_on_success(RegExpNode* node) { on_success_ = node; }
   virtual RegExpNode* FilterASCII(int depth, bool ignore_case);
   virtual void FillInBMInfo(int offset,
-                            int recursion_depth,
                             int budget,
                             BoyerMooreLookahead* bm,
                             bool not_at_start) {
-    on_success_->FillInBMInfo(
-        offset, recursion_depth + 1, budget - 1, bm, not_at_start);
+    on_success_->FillInBMInfo(offset, budget - 1, bm, not_at_start);
     if (offset == 0) set_bm_info(not_at_start, bm);
   }
 
  protected:
   RegExpNode* FilterSuccessor(int depth, bool ignore_case);
 
  private:
   RegExpNode* on_success_;
 };
 
@@ skipping 22 matching lines @@
                                              int restore_reg,
                                              int clear_capture_count,
                                              int clear_capture_from,
                                              RegExpNode* on_success);
   static ActionNode* EmptyMatchCheck(int start_register,
                                      int repetition_register,
                                      int repetition_limit,
                                      RegExpNode* on_success);
   virtual void Accept(NodeVisitor* visitor);
   virtual void Emit(RegExpCompiler* compiler, Trace* trace);
-  virtual int EatsAtLeast(int still_to_find,
-                          int recursion_depth,
-                          bool not_at_start);
+  virtual int EatsAtLeast(int still_to_find, int budget, bool not_at_start);
   virtual void GetQuickCheckDetails(QuickCheckDetails* details,
                                     RegExpCompiler* compiler,
                                     int filled_in,
                                     bool not_at_start) {
     return on_success()->GetQuickCheckDetails(
         details, compiler, filled_in, not_at_start);
   }
   virtual void FillInBMInfo(int offset,
-                            int recursion_depth,
                             int budget,
                             BoyerMooreLookahead* bm,
                             bool not_at_start);
   Type type() { return type_; }
   // TODO(erikcorry): We should allow some action nodes in greedy loops.
   virtual int GreedyLoopTextLength() { return kNodeIsTooComplexForGreedyLoops; }
 
  private:
   union {
     struct {
@@ skipping 38 matching lines @@
       : SeqRegExpNode(on_success),
         elms_(elms) { }
   TextNode(RegExpCharacterClass* that,
            RegExpNode* on_success)
       : SeqRegExpNode(on_success),
         elms_(new(zone()) ZoneList<TextElement>(1, zone())) {
     elms_->Add(TextElement::CharClass(that), zone());
   }
   virtual void Accept(NodeVisitor* visitor);
   virtual void Emit(RegExpCompiler* compiler, Trace* trace);
-  virtual int EatsAtLeast(int still_to_find,
-                          int recursion_depth,
-                          bool not_at_start);
+  virtual int EatsAtLeast(int still_to_find, int budget, bool not_at_start);
   virtual void GetQuickCheckDetails(QuickCheckDetails* details,
                                     RegExpCompiler* compiler,
                                     int characters_filled_in,
                                     bool not_at_start);
   ZoneList<TextElement>* elements() { return elms_; }
   void MakeCaseIndependent(bool is_ascii);
   virtual int GreedyLoopTextLength();
   virtual RegExpNode* GetSuccessorOfOmnivorousTextNode(
       RegExpCompiler* compiler);
   virtual void FillInBMInfo(int offset,
-                            int recursion_depth,
                             int budget,
                             BoyerMooreLookahead* bm,
                             bool not_at_start);
   void CalculateOffsets();
   virtual RegExpNode* FilterASCII(int depth, bool ignore_case);
 
  private:
   enum TextEmitPassType {
     NON_ASCII_MATCH,             // Check for characters that can't match.
     SIMPLE_CHARACTER_MATCH,      // Case-dependent single character check.
@@ skipping 34 matching lines @@
     return new(on_success->zone()) AssertionNode(AT_BOUNDARY, on_success);
   }
   static AssertionNode* AtNonBoundary(RegExpNode* on_success) {
     return new(on_success->zone()) AssertionNode(AT_NON_BOUNDARY, on_success);
   }
   static AssertionNode* AfterNewline(RegExpNode* on_success) {
     return new(on_success->zone()) AssertionNode(AFTER_NEWLINE, on_success);
   }
   virtual void Accept(NodeVisitor* visitor);
   virtual void Emit(RegExpCompiler* compiler, Trace* trace);
-  virtual int EatsAtLeast(int still_to_find,
-                          int recursion_depth,
-                          bool not_at_start);
+  virtual int EatsAtLeast(int still_to_find, int budget, bool not_at_start);
   virtual void GetQuickCheckDetails(QuickCheckDetails* details,
                                     RegExpCompiler* compiler,
                                     int filled_in,
                                     bool not_at_start);
   virtual void FillInBMInfo(int offset,
-                            int recursion_depth,
                             int budget,
                             BoyerMooreLookahead* bm,
                             bool not_at_start);
   AssertionNodeType type() { return type_; }
   void set_type(AssertionNodeType type) { type_ = type; }
 
  private:
   void EmitBoundaryCheck(RegExpCompiler* compiler, Trace* trace);
   enum IfPrevious { kIsNonWord, kIsWord };
   void BacktrackIfPrevious(RegExpCompiler* compiler,
@@ skipping 20 matching lines @@
   virtual int EatsAtLeast(int still_to_find,
                           int recursion_depth,
                           bool not_at_start);
   virtual void GetQuickCheckDetails(QuickCheckDetails* details,
                                     RegExpCompiler* compiler,
                                     int characters_filled_in,
                                     bool not_at_start) {
     return;
   }
   virtual void FillInBMInfo(int offset,
-                            int recursion_depth,
                             int budget,
                             BoyerMooreLookahead* bm,
                             bool not_at_start);
 
  private:
   int start_reg_;
   int end_reg_;
 };
 
 
 class EndNode: public RegExpNode {
  public:
   enum Action { ACCEPT, BACKTRACK, NEGATIVE_SUBMATCH_SUCCESS };
   explicit EndNode(Action action, Zone* zone)
       : RegExpNode(zone), action_(action) { }
   virtual void Accept(NodeVisitor* visitor);
   virtual void Emit(RegExpCompiler* compiler, Trace* trace);
   virtual int EatsAtLeast(int still_to_find,
                           int recursion_depth,
                           bool not_at_start) { return 0; }
   virtual void GetQuickCheckDetails(QuickCheckDetails* details,
                                     RegExpCompiler* compiler,
                                     int characters_filled_in,
                                     bool not_at_start) {
     // Returning 0 from EatsAtLeast should ensure we never get here.
     UNREACHABLE();
   }
   virtual void FillInBMInfo(int offset,
-                            int recursion_depth,
                             int budget,
                             BoyerMooreLookahead* bm,
                             bool not_at_start) {
     // Returning 0 from EatsAtLeast should ensure we never get here.
     UNREACHABLE();
   }
 
  private:
   Action action_;
 };
@@ skipping 65 matching lines @@
         table_(NULL),
         not_at_start_(false),
         being_calculated_(false) { }
   virtual void Accept(NodeVisitor* visitor);
   void AddAlternative(GuardedAlternative node) {
     alternatives()->Add(node, zone());
   }
   ZoneList<GuardedAlternative>* alternatives() { return alternatives_; }
   DispatchTable* GetTable(bool ignore_case);
   virtual void Emit(RegExpCompiler* compiler, Trace* trace);
-  virtual int EatsAtLeast(int still_to_find,
-                          int recursion_depth,
-                          bool not_at_start);
+  virtual int EatsAtLeast(int still_to_find, int budget, bool not_at_start);
   int EatsAtLeastHelper(int still_to_find,
-                        int recursion_depth,
+                        int budget,
                         RegExpNode* ignore_this_node,
                         bool not_at_start);
   virtual void GetQuickCheckDetails(QuickCheckDetails* details,
                                     RegExpCompiler* compiler,
                                     int characters_filled_in,
                                     bool not_at_start);
   virtual void FillInBMInfo(int offset,
-                            int recursion_depth,
                             int budget,
                             BoyerMooreLookahead* bm,
                             bool not_at_start);
 
   bool being_calculated() { return being_calculated_; }
   bool not_at_start() { return not_at_start_; }
   void set_not_at_start() { not_at_start_ = true; }
   void set_being_calculated(bool b) { being_calculated_ = b; }
   virtual bool try_to_emit_quick_check_for_alternative(int i) { return true; }
   virtual RegExpNode* FilterASCII(int depth, bool ignore_case);
@@ skipping 25 matching lines @@
 
 class NegativeLookaheadChoiceNode: public ChoiceNode {
  public:
   explicit NegativeLookaheadChoiceNode(GuardedAlternative this_must_fail,
                                        GuardedAlternative then_do_this,
                                        Zone* zone)
       : ChoiceNode(2, zone) {
     AddAlternative(this_must_fail);
     AddAlternative(then_do_this);
   }
-  virtual int EatsAtLeast(int still_to_find,
-                          int recursion_depth,
-                          bool not_at_start);
+  virtual int EatsAtLeast(int still_to_find, int budget, bool not_at_start);
   virtual void GetQuickCheckDetails(QuickCheckDetails* details,
                                     RegExpCompiler* compiler,
                                     int characters_filled_in,
                                     bool not_at_start);
   virtual void FillInBMInfo(int offset,
-                            int recursion_depth,
                             int budget,
                             BoyerMooreLookahead* bm,
                             bool not_at_start) {
     alternatives_->at(1).node()->FillInBMInfo(
-        offset, recursion_depth + 1, budget - 1, bm, not_at_start);
+        offset, budget - 1, bm, not_at_start);
     if (offset == 0) set_bm_info(not_at_start, bm);
   }
   // For a negative lookahead we don't emit the quick check for the
   // alternative that is expected to fail.  This is because quick check code
   // starts by loading enough characters for the alternative that takes fewest
   // characters, but on a negative lookahead the negative branch did not take
   // part in that calculation (EatsAtLeast) so the assumptions don't hold.
   virtual bool try_to_emit_quick_check_for_alternative(int i) { return i != 0; }
   virtual RegExpNode* FilterASCII(int depth, bool ignore_case);
 };
 
 
 class LoopChoiceNode: public ChoiceNode {
  public:
   explicit LoopChoiceNode(bool body_can_be_zero_length, Zone* zone)
       : ChoiceNode(2, zone),
         loop_node_(NULL),
         continue_node_(NULL),
         body_can_be_zero_length_(body_can_be_zero_length) { }
   void AddLoopAlternative(GuardedAlternative alt);
   void AddContinueAlternative(GuardedAlternative alt);
   virtual void Emit(RegExpCompiler* compiler, Trace* trace);
-  virtual int EatsAtLeast(int still_to_find,
-                          int recursion_depth,
-                          bool not_at_start);
+  virtual int EatsAtLeast(int still_to_find,  int budget, bool not_at_start);
   virtual void GetQuickCheckDetails(QuickCheckDetails* details,
                                     RegExpCompiler* compiler,
                                     int characters_filled_in,
                                     bool not_at_start);
   virtual void FillInBMInfo(int offset,
-                            int recursion_depth,
                             int budget,
                             BoyerMooreLookahead* bm,
                             bool not_at_start);
   RegExpNode* loop_node() { return loop_node_; }
   RegExpNode* continue_node() { return continue_node_; }
   bool body_can_be_zero_length() { return body_can_be_zero_length_; }
   virtual void Accept(NodeVisitor* visitor);
   virtual RegExpNode* FilterASCII(int depth, bool ignore_case);
 
  private:
@@ skipping 449 matching lines @@
                                    Handle<String> sample_subject,
                                    bool is_ascii, Zone* zone);
 
   static void DotPrint(const char* label, RegExpNode* node, bool ignore_case);
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_JSREGEXP_H_