Optimization: The quick check should ignore the negative lookahead instead of...

src/jsregexp.h

 // Copyright 2006-2008 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 962 matching lines @@
   virtual bool Emit(RegExpCompiler* compiler, Trace* trace);
   virtual int EatsAtLeast(int recursion_depth);
   int EatsAtLeastHelper(int recursion_depth, RegExpNode* ignore_this_node);
   virtual void GetQuickCheckDetails(QuickCheckDetails* details,
                                     RegExpCompiler* compiler,
                                     int characters_filled_in);
   virtual ChoiceNode* Clone() { return new ChoiceNode(*this); }
 
   bool being_calculated() { return being_calculated_; }
   void set_being_calculated(bool b) { being_calculated_ = b; }
+  virtual bool try_to_emit_quick_check_for_alternative(int i) { return true; }
 
  protected:
   int GreedyLoopTextLength(GuardedAlternative *alternative);
   ZoneList<GuardedAlternative>* alternatives_;
 
  private:
   friend class DispatchTableConstructor;
   friend class Analysis;
   void GenerateGuard(RegExpMacroAssembler* macro_assembler,
                      Guard *guard,
                      Trace* trace);
   int CalculatePreloadCharacters(RegExpCompiler* compiler);
   bool EmitOutOfLineContinuation(RegExpCompiler* compiler,
                                  Trace* trace,
                                  GuardedAlternative alternative,
                                  AlternativeGeneration* alt_gen,
                                  int preload_characters,
                                  bool next_expects_preload);
   DispatchTable* table_;
   bool being_calculated_;
 };
 
 
+class NegativeLookaheadChoiceNode: public ChoiceNode {
+ public:
+  explicit NegativeLookaheadChoiceNode(GuardedAlternative this_must_fail,
+                                       GuardedAlternative then_do_this)
+      : ChoiceNode(2) {
+    AddAlternative(this_must_fail);
+    AddAlternative(then_do_this);
+  }
+  virtual int EatsAtLeast(int recursion_depth);
+  virtual void GetQuickCheckDetails(QuickCheckDetails* details,
+                                    RegExpCompiler* compiler,
+                                    int characters_filled_in);
+  // 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; }
+};
+
+
 class LoopChoiceNode: public ChoiceNode {
  public:
   explicit LoopChoiceNode(bool body_can_be_zero_length)
       : ChoiceNode(2),
         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 bool Emit(RegExpCompiler* compiler, Trace* trace);
@@ skipping 265 matching lines @@
                                     Handle<String> pattern,
                                     bool is_ascii);
 
   static void DotPrint(const char* label, RegExpNode* node, bool ignore_case);
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_JSREGEXP_H_