Limit how many places we generate code to flush the same actions. This gives...

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 1158 matching lines @@
   };
 
   Trace()
       : cp_offset_(0),
         actions_(NULL),
         backtrack_(NULL),
         stop_node_(NULL),
         loop_label_(NULL),
         characters_preloaded_(0),
         bound_checked_up_to_(0),
+        flush_budget_(100),

[Lasse Reichstein, 2009/02/18 15:29:05]

Have other initial values of flush_budget been tried? 
How would lowering it to, say, 10 affect performance.

         at_start_(UNKNOWN) { }
 
   // End the trace.  This involves flushing the deferred actions in the trace
   // and pushing a backtrack location onto the backtrack stack.  Once this is
   // done we can start a new trace or go to one that has already been
   // generated.
   void Flush(RegExpCompiler* compiler, RegExpNode* successor);
   int cp_offset() { return cp_offset_; }
   DeferredAction* actions() { return actions_; }
   // A trivial trace is one that has no deferred actions or other state that
@@ skipping 15 matching lines @@
            quick_check_performed_.characters() == 0 &&
            at_start_ == UNKNOWN;
   }
   TriBool at_start() { return at_start_; }
   void set_at_start(bool at_start) { at_start_ = at_start ? TRUE : FALSE; }
   Label* backtrack() { return backtrack_; }
   Label* loop_label() { return loop_label_; }
   RegExpNode* stop_node() { return stop_node_; }
   int characters_preloaded() { return characters_preloaded_; }
   int bound_checked_up_to() { return bound_checked_up_to_; }
+  int flush_budget() { return flush_budget_; }
   QuickCheckDetails* quick_check_performed() { return &quick_check_performed_; }
   bool mentions_reg(int reg);
   // Returns true if a deferred position store exists to the specified
   // register and stores the offset in the out-parameter.  Otherwise
   // returns false.
   bool GetStoredPosition(int reg, int* cp_offset);
   // These set methods and AdvanceCurrentPositionInTrace should be used only on
   // new traces - the intention is that traces are immutable after creation.
   void add_action(DeferredAction* new_action) {
     ASSERT(new_action->next_ == NULL);
     new_action->next_ = actions_;
     actions_ = new_action;
   }
   void set_backtrack(Label* backtrack) { backtrack_ = backtrack; }
   void set_stop_node(RegExpNode* node) { stop_node_ = node; }
   void set_loop_label(Label* label) { loop_label_ = label; }
   void set_characters_preloaded(int cpre) { characters_preloaded_ = cpre; }
   void set_bound_checked_up_to(int to) { bound_checked_up_to_ = to; }
+  void set_flush_budget(int to) { flush_budget_ = to; }
   void set_quick_check_performed(QuickCheckDetails* d) {
     quick_check_performed_ = *d;
   }
   void InvalidateCurrentCharacter();
   void AdvanceCurrentPositionInTrace(int by, RegExpCompiler* compiler);
  private:
   int FindAffectedRegisters(OutSet* affected_registers);
   void PerformDeferredActions(RegExpMacroAssembler* macro,
                                int max_register,
                                OutSet& affected_registers,
                                OutSet* registers_to_pop,
                                OutSet* registers_to_clear);
   void RestoreAffectedRegisters(RegExpMacroAssembler* macro,
                                 int max_register,
                                 OutSet& registers_to_pop,
                                 OutSet& registers_to_clear);
   int cp_offset_;
   DeferredAction* actions_;
   Label* backtrack_;
   RegExpNode* stop_node_;
   Label* loop_label_;
   int characters_preloaded_;
   int bound_checked_up_to_;
   QuickCheckDetails quick_check_performed_;
+  int flush_budget_;
   TriBool at_start_;
 };
 
 
 class NodeVisitor {
  public:
   virtual ~NodeVisitor() { }
 #define DECLARE_VISIT(Type)                                          \
   virtual void Visit##Type(Type##Node* that) = 0;
 FOR_EACH_NODE_TYPE(DECLARE_VISIT)
@@ skipping 89 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_