Copy irregexp related code from V8.

runtime/vm/regexp.h

+// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+#ifndef VM_REGEXP_H_
+#define VM_REGEXP_H_
+
+// SNIP
+
+namespace dart {
+
+class NodeVisitor;
+class RegExpCompiler;
+class RegExpMacroAssembler;
+class RegExpNode;
+class RegExpTree;
+class BoyerMooreLookahead;
+
+// Represents the location of one element relative to the intersection of
+// two sets. Corresponds to the four areas of a Venn diagram.
+enum ElementInSetsRelation {
+  kInsideNone = 0,
+  kInsideFirst = 1,
+  kInsideSecond = 2,
+  kInsideBoth = 3
+};
+
+
+// Represents code units in the range from from_ to to_, both ends are
+// inclusive.
+class CharacterRange {
+ public:
+  CharacterRange() : from_(0), to_(0) { }
+  // For compatibility with the CHECK_OK macro
+  CharacterRange(void* null) { DCHECK_EQ(NULL, null); }  //NOLINT
+  CharacterRange(uc16 from, uc16 to) : from_(from), to_(to) { }
+  static void AddClassEscape(uc16 type, ZoneList<CharacterRange>* ranges,
+                             Zone* zone);
+  static Vector<const int> GetWordBounds();
+  static inline CharacterRange Singleton(uc16 value) {
+    return CharacterRange(value, value);
+  }
+  static inline CharacterRange Range(uc16 from, uc16 to) {
+    DCHECK(from <= to);
+    return CharacterRange(from, to);
+  }
+  static inline CharacterRange Everything() {
+    return CharacterRange(0, 0xFFFF);
+  }
+  bool Contains(uc16 i) { return from_ <= i && i <= to_; }
+  uc16 from() const { return from_; }
+  void set_from(uc16 value) { from_ = value; }
+  uc16 to() const { return to_; }
+  void set_to(uc16 value) { to_ = value; }
+  bool is_valid() { return from_ <= to_; }
+  bool IsEverything(uc16 max) { return from_ == 0 && to_ >= max; }
+  bool IsSingleton() { return (from_ == to_); }
+  void AddCaseEquivalents(ZoneList<CharacterRange>* ranges, bool is_one_byte,
+                          Zone* zone);
+  static void Split(ZoneList<CharacterRange>* base,
+                    Vector<const int> overlay,
+                    ZoneList<CharacterRange>** included,
+                    ZoneList<CharacterRange>** excluded,
+                    Zone* zone);
+  // Whether a range list is in canonical form: Ranges ordered by from value,
+  // and ranges non-overlapping and non-adjacent.
+  static bool IsCanonical(ZoneList<CharacterRange>* ranges);
+  // Convert range list to canonical form. The characters covered by the ranges
+  // will still be the same, but no character is in more than one range, and
+  // adjacent ranges are merged. The resulting list may be shorter than the
+  // original, but cannot be longer.
+  static void Canonicalize(ZoneList<CharacterRange>* ranges);
+  // Negate the contents of a character range in canonical form.
+  static void Negate(ZoneList<CharacterRange>* src,
+                     ZoneList<CharacterRange>* dst,
+                     Zone* zone);
+  static const int kStartMarker = (1 << 24);
+  static const int kPayloadMask = (1 << 24) - 1;
+
+ private:
+  uc16 from_;
+  uc16 to_;
+};
+
+
+// A set of unsigned integers that behaves especially well on small
+// integers (< 32).  May do zone-allocation.
+class OutSet: public ZoneObject {
+ public:
+  OutSet() : first_(0), remaining_(NULL), successors_(NULL) { }
+  OutSet* Extend(unsigned value, Zone* zone);
+  bool Get(unsigned value) const;
+  static const unsigned kFirstLimit = 32;
+
+ private:
+  // Destructively set a value in this set.  In most cases you want
+  // to use Extend instead to ensure that only one instance exists
+  // that contains the same values.
+  void Set(unsigned value, Zone* zone);
+
+  // The successors are a list of sets that contain the same values
+  // as this set and the one more value that is not present in this
+  // set.
+  ZoneList<OutSet*>* successors(Zone* zone) { return successors_; }
+
+  OutSet(uint32_t first, ZoneList<unsigned>* remaining)
+      : first_(first), remaining_(remaining), successors_(NULL) { }
+  uint32_t first_;
+  ZoneList<unsigned>* remaining_;
+  ZoneList<OutSet*>* successors_;
+  friend class Trace;
+};
+
+
+// A mapping from integers, specified as ranges, to a set of integers.
+// Used for mapping character ranges to choices.
+class DispatchTable : public ZoneObject {
+ public:
+  explicit DispatchTable(Zone* zone) : tree_(zone) { }
+
+  class Entry {
+   public:
+    Entry() : from_(0), to_(0), out_set_(NULL) { }
+    Entry(uc16 from, uc16 to, OutSet* out_set)
+        : from_(from), to_(to), out_set_(out_set) { }
+    uc16 from() { return from_; }
+    uc16 to() { return to_; }
+    void set_to(uc16 value) { to_ = value; }
+    void AddValue(int value, Zone* zone) {
+      out_set_ = out_set_->Extend(value, zone);
+    }
+    OutSet* out_set() { return out_set_; }
+   private:
+    uc16 from_;
+    uc16 to_;
+    OutSet* out_set_;
+  };
+
+  class Config {
+   public:
+    typedef uc16 Key;
+    typedef Entry Value;
+    static const uc16 kNoKey;
+    static const Entry NoValue() { return Value(); }
+    static inline int Compare(uc16 a, uc16 b) {
+      if (a == b)
+        return 0;
+      else if (a < b)
+        return -1;
+      else
+        return 1;
+    }
+  };
+
+  void AddRange(CharacterRange range, int value, Zone* zone);
+  OutSet* Get(uc16 value);
+  void Dump();
+
+  template <typename Callback>
+  void ForEach(Callback* callback) {
+    return tree()->ForEach(callback);
+  }
+
+ private:
+  // There can't be a static empty set since it allocates its
+  // successors in a zone and caches them.
+  OutSet* empty() { return &empty_; }
+  OutSet empty_;
+  ZoneSplayTree<Config>* tree() { return &tree_; }
+  ZoneSplayTree<Config> tree_;
+};
+
+
+#define FOR_EACH_NODE_TYPE(VISIT)                                    \
+  VISIT(End)                                                         \
+  VISIT(Action)                                                      \
+  VISIT(Choice)                                                      \
+  VISIT(BackReference)                                               \
+  VISIT(Assertion)                                                   \
+  VISIT(Text)
+
+
+#define FOR_EACH_REG_EXP_TREE_TYPE(VISIT)                            \
+  VISIT(Disjunction)                                                 \
+  VISIT(Alternative)                                                 \
+  VISIT(Assertion)                                                   \
+  VISIT(CharacterClass)                                              \
+  VISIT(Atom)                                                        \
+  VISIT(Quantifier)                                                  \
+  VISIT(Capture)                                                     \
+  VISIT(Lookahead)                                                   \
+  VISIT(BackReference)                                               \
+  VISIT(Empty)                                                       \
+  VISIT(Text)
+
+
+#define FORWARD_DECLARE(Name) class RegExp##Name;
+FOR_EACH_REG_EXP_TREE_TYPE(FORWARD_DECLARE)
+#undef FORWARD_DECLARE
+
+
+class TextElement FINAL BASE_EMBEDDED {
+ public:
+  enum TextType {
+    ATOM,
+    CHAR_CLASS
+  };
+
+  static TextElement Atom(RegExpAtom* atom);
+  static TextElement CharClass(RegExpCharacterClass* char_class);
+
+  int cp_offset() const { return cp_offset_; }
+  void set_cp_offset(int cp_offset) { cp_offset_ = cp_offset; }
+  int length() const;
+
+  TextType text_type() const { return text_type_; }
+
+  RegExpTree* tree() const { return tree_; }
+
+  RegExpAtom* atom() const {
+    DCHECK(text_type() == ATOM);
+    return reinterpret_cast<RegExpAtom*>(tree());
+  }
+
+  RegExpCharacterClass* char_class() const {
+    DCHECK(text_type() == CHAR_CLASS);
+    return reinterpret_cast<RegExpCharacterClass*>(tree());
+  }
+
+ private:
+  TextElement(TextType text_type, RegExpTree* tree)
+      : cp_offset_(-1), text_type_(text_type), tree_(tree) {}
+
+  int cp_offset_;
+  TextType text_type_;
+  RegExpTree* tree_;
+};
+
+
+class Trace;
+struct PreloadState;
+class GreedyLoopState;
+class AlternativeGenerationList;
+
+struct NodeInfo {
+  NodeInfo()
+      : being_analyzed(false),
+        been_analyzed(false),
+        follows_word_interest(false),
+        follows_newline_interest(false),
+        follows_start_interest(false),
+        at_end(false),
+        visited(false),
+        replacement_calculated(false) { }
+
+  // Returns true if the interests and assumptions of this node
+  // matches the given one.
+  bool Matches(NodeInfo* that) {
+    return (at_end == that->at_end) &&
+           (follows_word_interest == that->follows_word_interest) &&
+           (follows_newline_interest == that->follows_newline_interest) &&
+           (follows_start_interest == that->follows_start_interest);
+  }
+
+  // Updates the interests of this node given the interests of the
+  // node preceding it.
+  void AddFromPreceding(NodeInfo* that) {
+    at_end |= that->at_end;
+    follows_word_interest |= that->follows_word_interest;
+    follows_newline_interest |= that->follows_newline_interest;
+    follows_start_interest |= that->follows_start_interest;
+  }
+
+  bool HasLookbehind() {
+    return follows_word_interest ||
+           follows_newline_interest ||
+           follows_start_interest;
+  }
+
+  // Sets the interests of this node to include the interests of the
+  // following node.
+  void AddFromFollowing(NodeInfo* that) {
+    follows_word_interest |= that->follows_word_interest;
+    follows_newline_interest |= that->follows_newline_interest;
+    follows_start_interest |= that->follows_start_interest;
+  }
+
+  void ResetCompilationState() {
+    being_analyzed = false;
+    been_analyzed = false;
+  }
+
+  bool being_analyzed: 1;
+  bool been_analyzed: 1;
+
+  // These bits are set of this node has to know what the preceding
+  // character was.
+  bool follows_word_interest: 1;
+  bool follows_newline_interest: 1;
+  bool follows_start_interest: 1;
+
+  bool at_end: 1;
+  bool visited: 1;
+  bool replacement_calculated: 1;
+};
+
+
+// Details of a quick mask-compare check that can look ahead in the
+// input stream.
+class QuickCheckDetails {
+ public:
+  QuickCheckDetails()
+      : characters_(0),
+        mask_(0),
+        value_(0),
+        cannot_match_(false) { }
+  explicit QuickCheckDetails(int characters)
+      : characters_(characters),
+        mask_(0),
+        value_(0),
+        cannot_match_(false) { }
+  bool Rationalize(bool one_byte);
+  // Merge in the information from another branch of an alternation.
+  void Merge(QuickCheckDetails* other, int from_index);
+  // Advance the current position by some amount.
+  void Advance(int by, bool one_byte);
+  void Clear();
+  bool cannot_match() { return cannot_match_; }
+  void set_cannot_match() { cannot_match_ = true; }
+  struct Position {
+    Position() : mask(0), value(0), determines_perfectly(false) { }
+    uc16 mask;
+    uc16 value;
+    bool determines_perfectly;
+  };
+  int characters() { return characters_; }
+  void set_characters(int characters) { characters_ = characters; }
+  Position* positions(int index) {
+    DCHECK(index >= 0);
+    DCHECK(index < characters_);
+    return positions_ + index;
+  }
+  uint32_t mask() { return mask_; }
+  uint32_t value() { return value_; }
+
+ private:
+  // How many characters do we have quick check information from.  This is
+  // the same for all branches of a choice node.
+  int characters_;
+  Position positions_[4];
+  // These values are the condensate of the above array after Rationalize().
+  uint32_t mask_;
+  uint32_t value_;
+  // If set to true, there is no way this quick check can match at all.
+  // E.g., if it requires to be at the start of the input, and isn't.
+  bool cannot_match_;
+};
+
+
+extern int kUninitializedRegExpNodePlaceHolder;
+
+
+class RegExpNode: public ZoneObject {
+ public:
+  explicit RegExpNode(Zone* zone)
+  : replacement_(NULL), trace_count_(0), zone_(zone) {
+    bm_info_[0] = bm_info_[1] = NULL;
+  }
+  virtual ~RegExpNode();
+  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 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* bounds_check_trace,
+                      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
+  // next n characters are anded with the mask and compared with the value.
+  // A comparison failure indicates the node cannot match the next n characters.
+  // A comparison success indicates the node may match.
+  virtual void GetQuickCheckDetails(QuickCheckDetails* details,
+                                    RegExpCompiler* compiler,
+                                    int characters_filled_in,
+                                    bool not_at_start) = 0;
+  static const int kNodeIsTooComplexForGreedyLoops = -1;
+  virtual int GreedyLoopTextLength() { return kNodeIsTooComplexForGreedyLoops; }
+  // Only returns the successor for a text node of length 1 that matches any
+  // character and that has no guards on it.
+  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 kRecursionBudget = 200;
+  virtual void FillInBMInfo(int offset,
+                            int budget,
+                            BoyerMooreLookahead* bm,
+                            bool not_at_start) {
+    UNREACHABLE();
+  }
+
+  // If we know that the input is one-byte 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* FilterOneByte(int depth, bool ignore_case) {
+    return this;
+  }
+  // Helper for FilterOneByte.
+  RegExpNode* replacement() {
+    DCHECK(info()->replacement_calculated);
+    return replacement_;
+  }
+  RegExpNode* set_replacement(RegExpNode* replacement) {
+    info()->replacement_calculated = true;
+    replacement_ =  replacement;
+    return replacement;  // For convenience.
+  }
+
+  // We want to avoid recalculating the lookahead info, so we store it on the
+  // node.  Only info that is for this node is stored.  We can tell that the
+  // info is for this node when offset == 0, so the information is calculated
+  // relative to this node.
+  void SaveBMInfo(BoyerMooreLookahead* bm, bool not_at_start, int offset) {
+    if (offset == 0) set_bm_info(not_at_start, bm);
+  }
+
+  Label* label() { return &label_; }
+  // If non-generic code is generated for a node (i.e. the node is not at the
+  // start of the trace) then it cannot be reused.  This variable sets a limit
+  // on how often we allow that to happen before we insist on starting a new
+  // trace and generating generic code for a node that can be reused by flushing
+  // the deferred actions in the current trace and generating a goto.
+  static const int kMaxCopiesCodeGenerated = 10;
+
+  NodeInfo* info() { return &info_; }
+
+  BoyerMooreLookahead* bm_info(bool not_at_start) {
+    return bm_info_[not_at_start ? 1 : 0];
+  }
+
+  Zone* zone() const { return zone_; }
+
+ protected:
+  enum LimitResult { DONE, CONTINUE };
+  RegExpNode* replacement_;
+
+  LimitResult LimitVersions(RegExpCompiler* compiler, Trace* trace);
+
+  void set_bm_info(bool not_at_start, BoyerMooreLookahead* bm) {
+    bm_info_[not_at_start ? 1 : 0] = bm;
+  }
+
+ private:
+  static const int kFirstCharBudget = 10;
+  Label label_;
+  NodeInfo info_;
+  // This variable keeps track of how many times code has been generated for
+  // this node (in different traces).  We don't keep track of where the
+  // generated code is located unless the code is generated at the start of
+  // a trace, in which case it is generic and can be reused by flushing the
+  // deferred operations in the current trace and generating a goto.
+  int trace_count_;
+  BoyerMooreLookahead* bm_info_[2];
+
+  Zone* zone_;
+};
+
+
+// A simple closed interval.
+class Interval {
+ public:
+  Interval() : from_(kNone), to_(kNone) { }
+  Interval(int from, int to) : from_(from), to_(to) { }
+  Interval Union(Interval that) {
+    if (that.from_ == kNone)
+      return *this;
+    else if (from_ == kNone)
+      return that;
+    else
+      return Interval(Min(from_, that.from_), Max(to_, that.to_));
+  }
+  bool Contains(int value) {
+    return (from_ <= value) && (value <= to_);
+  }
+  bool is_empty() { return from_ == kNone; }
+  int from() const { return from_; }
+  int to() const { return to_; }
+  static Interval Empty() { return Interval(); }
+  static const int kNone = -1;
+ private:
+  int from_;
+  int to_;
+};
+
+
+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* FilterOneByte(int depth, bool ignore_case);
+  virtual void FillInBMInfo(int offset,
+                            int budget,
+                            BoyerMooreLookahead* bm,
+                            bool 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_;
+};
+
+
+class ActionNode: public SeqRegExpNode {
+ public:
+  enum ActionType {
+    SET_REGISTER,
+    INCREMENT_REGISTER,
+    STORE_POSITION,
+    BEGIN_SUBMATCH,
+    POSITIVE_SUBMATCH_SUCCESS,
+    EMPTY_MATCH_CHECK,
+    CLEAR_CAPTURES
+  };
+  static ActionNode* SetRegister(int reg, int val, RegExpNode* on_success);
+  static ActionNode* IncrementRegister(int reg, RegExpNode* on_success);
+  static ActionNode* StorePosition(int reg,
+                                   bool is_capture,
+                                   RegExpNode* on_success);
+  static ActionNode* ClearCaptures(Interval range, RegExpNode* on_success);
+  static ActionNode* BeginSubmatch(int stack_pointer_reg,
+                                   int position_reg,
+                                   RegExpNode* on_success);
+  static ActionNode* PositiveSubmatchSuccess(int stack_pointer_reg,
+                                             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 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 budget,
+                            BoyerMooreLookahead* bm,
+                            bool not_at_start);
+  ActionType action_type() { return action_type_; }
+  // TODO(erikcorry): We should allow some action nodes in greedy loops.
+  virtual int GreedyLoopTextLength() { return kNodeIsTooComplexForGreedyLoops; }
+
+ private:
+  union {
+    struct {
+      int reg;
+      int value;
+    } u_store_register;
+    struct {
+      int reg;
+    } u_increment_register;
+    struct {
+      int reg;
+      bool is_capture;
+    } u_position_register;
+    struct {
+      int stack_pointer_register;
+      int current_position_register;
+      int clear_register_count;
+      int clear_register_from;
+    } u_submatch;
+    struct {
+      int start_register;
+      int repetition_register;
+      int repetition_limit;
+    } u_empty_match_check;
+    struct {
+      int range_from;
+      int range_to;
+    } u_clear_captures;
+  } data_;
+  ActionNode(ActionType action_type, RegExpNode* on_success)
+      : SeqRegExpNode(on_success),
+        action_type_(action_type) { }
+  ActionType action_type_;
+  friend class DotPrinter;
+};
+
+
+class TextNode: public SeqRegExpNode {
+ public:
+  TextNode(ZoneList<TextElement>* elms,
+           RegExpNode* on_success)
+      : 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 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_one_byte);
+  virtual int GreedyLoopTextLength();
+  virtual RegExpNode* GetSuccessorOfOmnivorousTextNode(
+      RegExpCompiler* compiler);
+  virtual void FillInBMInfo(int offset,
+                            int budget,
+                            BoyerMooreLookahead* bm,
+                            bool not_at_start);
+  void CalculateOffsets();
+  virtual RegExpNode* FilterOneByte(int depth, bool ignore_case);
+
+ private:
+  enum TextEmitPassType {
+    NON_LATIN1_MATCH,            // Check for characters that can't match.
+    SIMPLE_CHARACTER_MATCH,      // Case-dependent single character check.
+    NON_LETTER_CHARACTER_MATCH,  // Check characters that have no case equivs.
+    CASE_CHARACTER_MATCH,        // Case-independent single character check.
+    CHARACTER_CLASS_MATCH        // Character class.
+  };
+  static bool SkipPass(int pass, bool ignore_case);
+  static const int kFirstRealPass = SIMPLE_CHARACTER_MATCH;
+  static const int kLastPass = CHARACTER_CLASS_MATCH;
+  void TextEmitPass(RegExpCompiler* compiler,
+                    TextEmitPassType pass,
+                    bool preloaded,
+                    Trace* trace,
+                    bool first_element_checked,
+                    int* checked_up_to);
+  int Length();
+  ZoneList<TextElement>* elms_;
+};
+
+
+class AssertionNode: public SeqRegExpNode {
+ public:
+  enum AssertionType {
+    AT_END,
+    AT_START,
+    AT_BOUNDARY,
+    AT_NON_BOUNDARY,
+    AFTER_NEWLINE
+  };
+  static AssertionNode* AtEnd(RegExpNode* on_success) {
+    return new(on_success->zone()) AssertionNode(AT_END, on_success);
+  }
+  static AssertionNode* AtStart(RegExpNode* on_success) {
+    return new(on_success->zone()) AssertionNode(AT_START, on_success);
+  }
+  static AssertionNode* AtBoundary(RegExpNode* on_success) {
+    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 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 budget,
+                            BoyerMooreLookahead* bm,
+                            bool not_at_start);
+  AssertionType assertion_type() { return assertion_type_; }
+
+ private:
+  void EmitBoundaryCheck(RegExpCompiler* compiler, Trace* trace);
+  enum IfPrevious { kIsNonWord, kIsWord };
+  void BacktrackIfPrevious(RegExpCompiler* compiler,
+                           Trace* trace,
+                           IfPrevious backtrack_if_previous);
+  AssertionNode(AssertionType t, RegExpNode* on_success)
+      : SeqRegExpNode(on_success), assertion_type_(t) { }
+  AssertionType assertion_type_;
+};
+
+
+class BackReferenceNode: public SeqRegExpNode {
+ public:
+  BackReferenceNode(int start_reg,
+                    int end_reg,
+                    RegExpNode* on_success)
+      : SeqRegExpNode(on_success),
+        start_reg_(start_reg),
+        end_reg_(end_reg) { }
+  virtual void Accept(NodeVisitor* visitor);
+  int start_register() { return start_reg_; }
+  int end_register() { return end_reg_; }
+  virtual void Emit(RegExpCompiler* compiler, Trace* trace);
+  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 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 budget,
+                            BoyerMooreLookahead* bm,
+                            bool not_at_start) {
+    // Returning 0 from EatsAtLeast should ensure we never get here.
+    UNREACHABLE();
+  }
+
+ private:
+  Action action_;
+};
+
+
+class NegativeSubmatchSuccess: public EndNode {
+ public:
+  NegativeSubmatchSuccess(int stack_pointer_reg,
+                          int position_reg,
+                          int clear_capture_count,
+                          int clear_capture_start,
+                          Zone* zone)
+      : EndNode(NEGATIVE_SUBMATCH_SUCCESS, zone),
+        stack_pointer_register_(stack_pointer_reg),
+        current_position_register_(position_reg),
+        clear_capture_count_(clear_capture_count),
+        clear_capture_start_(clear_capture_start) { }
+  virtual void Emit(RegExpCompiler* compiler, Trace* trace);
+
+ private:
+  int stack_pointer_register_;
+  int current_position_register_;
+  int clear_capture_count_;
+  int clear_capture_start_;
+};
+
+
+class Guard: public ZoneObject {
+ public:
+  enum Relation { LT, GEQ };
+  Guard(int reg, Relation op, int value)
+      : reg_(reg),
+        op_(op),
+        value_(value) { }
+  int reg() { return reg_; }
+  Relation op() { return op_; }
+  int value() { return value_; }
+
+ private:
+  int reg_;
+  Relation op_;
+  int value_;
+};
+
+
+class GuardedAlternative {
+ public:
+  explicit GuardedAlternative(RegExpNode* node) : node_(node), guards_(NULL) { }
+  void AddGuard(Guard* guard, Zone* zone);
+  RegExpNode* node() { return node_; }
+  void set_node(RegExpNode* node) { node_ = node; }
+  ZoneList<Guard*>* guards() { return guards_; }
+
+ private:
+  RegExpNode* node_;
+  ZoneList<Guard*>* guards_;
+};
+
+
+class AlternativeGeneration;
+
+
+class ChoiceNode: public RegExpNode {
+ public:
+  explicit ChoiceNode(int expected_size, Zone* zone)
+      : RegExpNode(zone),
+        alternatives_(new(zone)
+                      ZoneList<GuardedAlternative>(expected_size, zone)),
+        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 budget, bool not_at_start);
+  int EatsAtLeastHelper(int still_to_find,
+                        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 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(bool is_first) {
+    return true;
+  }
+  virtual RegExpNode* FilterOneByte(int depth, bool ignore_case);
+
+ protected:
+  int GreedyLoopTextLengthForAlternative(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, int eats_at_least);
+  void EmitOutOfLineContinuation(RegExpCompiler* compiler,
+                                 Trace* trace,
+                                 GuardedAlternative alternative,
+                                 AlternativeGeneration* alt_gen,
+                                 int preload_characters,
+                                 bool next_expects_preload);
+  void SetUpPreLoad(RegExpCompiler* compiler,
+                    Trace* current_trace,
+                    PreloadState* preloads);
+  void AssertGuardsMentionRegisters(Trace* trace);
+  int EmitOptimizedUnanchoredSearch(RegExpCompiler* compiler, Trace* trace);
+  Trace* EmitGreedyLoop(RegExpCompiler* compiler,
+                        Trace* trace,
+                        AlternativeGenerationList* alt_gens,
+                        PreloadState* preloads,
+                        GreedyLoopState* greedy_loop_state,
+                        int text_length);
+  void EmitChoices(RegExpCompiler* compiler,
+                   AlternativeGenerationList* alt_gens,
+                   int first_choice,
+                   Trace* trace,
+                   PreloadState* preloads);
+  DispatchTable* table_;
+  // If true, this node is never checked at the start of the input.
+  // Allows a new trace to start with at_start() set to false.
+  bool not_at_start_;
+  bool being_calculated_;
+};
+
+
+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 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 budget,
+                            BoyerMooreLookahead* bm,
+                            bool not_at_start) {
+    alternatives_->at(1).node()->FillInBMInfo(
+        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(bool is_first) {
+    return !is_first;
+  }
+  virtual RegExpNode* FilterOneByte(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 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 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* FilterOneByte(int depth, bool ignore_case);
+
+ private:
+  // AddAlternative is made private for loop nodes because alternatives
+  // should not be added freely, we need to keep track of which node
+  // goes back to the node itself.
+  void AddAlternative(GuardedAlternative node) {
+    ChoiceNode::AddAlternative(node);
+  }
+
+  RegExpNode* loop_node_;
+  RegExpNode* continue_node_;
+  bool body_can_be_zero_length_;
+};
+
+
+// Improve the speed that we scan for an initial point where a non-anchored
+// regexp can match by using a Boyer-Moore-like table. This is done by
+// identifying non-greedy non-capturing loops in the nodes that eat any
+// character one at a time.  For example in the middle of the regexp
+// /foo[\s\S]*?bar/ we find such a loop.  There is also such a loop implicitly
+// inserted at the start of any non-anchored regexp.
+//
+// When we have found such a loop we look ahead in the nodes to find the set of
+// characters that can come at given distances. For example for the regexp
+// /.?foo/ we know that there are at least 3 characters ahead of us, and the
+// sets of characters that can occur are [any, [f, o], [o]]. We find a range in
+// the lookahead info where the set of characters is reasonably constrained. In
+// our example this is from index 1 to 2 (0 is not constrained). We can now
+// look 3 characters ahead and if we don't find one of [f, o] (the union of
+// [f, o] and [o]) then we can skip forwards by the range size (in this case 2).
+//
+// For Unicode input strings we do the same, but modulo 128.
+//
+// We also look at the first string fed to the regexp and use that to get a hint
+// of the character frequencies in the inputs. This affects the assessment of
+// whether the set of characters is 'reasonably constrained'.
+//
+// We also have another lookahead mechanism (called quick check in the code),
+// which uses a wide load of multiple characters followed by a mask and compare
+// to determine whether a match is possible at this point.
+enum ContainedInLattice {
+  kNotYet = 0,
+  kLatticeIn = 1,
+  kLatticeOut = 2,
+  kLatticeUnknown = 3  // Can also mean both in and out.
+};
+
+
+inline ContainedInLattice Combine(ContainedInLattice a, ContainedInLattice b) {
+  return static_cast<ContainedInLattice>(a | b);
+}
+
+
+ContainedInLattice AddRange(ContainedInLattice a,
+                            const int* ranges,
+                            int ranges_size,
+                            Interval new_range);
+
+
+class BoyerMoorePositionInfo : public ZoneObject {
+ public:
+  explicit BoyerMoorePositionInfo(Zone* zone)
+      : map_(new(zone) ZoneList<bool>(kMapSize, zone)),
+        map_count_(0),
+        w_(kNotYet),
+        s_(kNotYet),
+        d_(kNotYet),
+        surrogate_(kNotYet) {
+     for (int i = 0; i < kMapSize; i++) {
+       map_->Add(false, zone);
+     }
+  }
+
+  bool& at(int i) { return map_->at(i); }
+
+  static const int kMapSize = 128;
+  static const int kMask = kMapSize - 1;
+
+  int map_count() const { return map_count_; }
+
+  void Set(int character);
+  void SetInterval(const Interval& interval);
+  void SetAll();
+  bool is_non_word() { return w_ == kLatticeOut; }
+  bool is_word() { return w_ == kLatticeIn; }
+
+ private:
+  ZoneList<bool>* map_;
+  int map_count_;  // Number of set bits in the map.
+  ContainedInLattice w_;  // The \w character class.
+  ContainedInLattice s_;  // The \s character class.
+  ContainedInLattice d_;  // The \d character class.
+  ContainedInLattice surrogate_;  // Surrogate UTF-16 code units.
+};
+
+
+class BoyerMooreLookahead : public ZoneObject {
+ public:
+  BoyerMooreLookahead(int length, RegExpCompiler* compiler, Zone* zone);
+
+  int length() { return length_; }
+  int max_char() { return max_char_; }
+  RegExpCompiler* compiler() { return compiler_; }
+
+  int Count(int map_number) {
+    return bitmaps_->at(map_number)->map_count();
+  }
+
+  BoyerMoorePositionInfo* at(int i) { return bitmaps_->at(i); }
+
+  void Set(int map_number, int character) {
+    if (character > max_char_) return;
+    BoyerMoorePositionInfo* info = bitmaps_->at(map_number);
+    info->Set(character);
+  }
+
+  void SetInterval(int map_number, const Interval& interval) {
+    if (interval.from() > max_char_) return;
+    BoyerMoorePositionInfo* info = bitmaps_->at(map_number);
+    if (interval.to() > max_char_) {
+      info->SetInterval(Interval(interval.from(), max_char_));
+    } else {
+      info->SetInterval(interval);
+    }
+  }
+
+  void SetAll(int map_number) {
+    bitmaps_->at(map_number)->SetAll();
+  }
+
+  void SetRest(int from_map) {
+    for (int i = from_map; i < length_; i++) SetAll(i);
+  }
+  void EmitSkipInstructions(RegExpMacroAssembler* masm);
+
+ private:
+  // This is the value obtained by EatsAtLeast.  If we do not have at least this
+  // many characters left in the sample string then the match is bound to fail.
+  // Therefore it is OK to read a character this far ahead of the current match
+  // point.
+  int length_;
+  RegExpCompiler* compiler_;
+  // 0xff for Latin1, 0xffff for UTF-16.
+  int max_char_;
+  ZoneList<BoyerMoorePositionInfo*>* bitmaps_;
+
+  int GetSkipTable(int min_lookahead,
+                   int max_lookahead,
+                   Handle<ByteArray> boolean_skip_table);
+  bool FindWorthwhileInterval(int* from, int* to);
+  int FindBestInterval(
+    int max_number_of_chars, int old_biggest_points, int* from, int* to);
+};
+
+
+// There are many ways to generate code for a node.  This class encapsulates
+// the current way we should be generating.  In other words it encapsulates
+// the current state of the code generator.  The effect of this is that we
+// generate code for paths that the matcher can take through the regular
+// expression.  A given node in the regexp can be code-generated several times
+// as it can be part of several traces.  For example for the regexp:
+// /foo(bar|ip)baz/ the code to match baz will be generated twice, once as part
+// of the foo-bar-baz trace and once as part of the foo-ip-baz trace.  The code
+// to match foo is generated only once (the traces have a common prefix).  The
+// code to store the capture is deferred and generated (twice) after the places
+// where baz has been matched.
+class Trace {
+ public:
+  // A value for a property that is either known to be true, know to be false,
+  // or not known.
+  enum TriBool {
+    UNKNOWN = -1, FALSE_VALUE = 0, TRUE_VALUE = 1
+  };
+
+  class DeferredAction {
+   public:
+    DeferredAction(ActionNode::ActionType action_type, int reg)
+        : action_type_(action_type), reg_(reg), next_(NULL) { }
+    DeferredAction* next() { return next_; }
+    bool Mentions(int reg);
+    int reg() { return reg_; }
+    ActionNode::ActionType action_type() { return action_type_; }
+   private:
+    ActionNode::ActionType action_type_;
+    int reg_;
+    DeferredAction* next_;
+    friend class Trace;
+  };
+
+  class DeferredCapture : public DeferredAction {
+   public:
+    DeferredCapture(int reg, bool is_capture, Trace* trace)
+        : DeferredAction(ActionNode::STORE_POSITION, reg),
+          cp_offset_(trace->cp_offset()),
+          is_capture_(is_capture) { }
+    int cp_offset() { return cp_offset_; }
+    bool is_capture() { return is_capture_; }
+   private:
+    int cp_offset_;
+    bool is_capture_;
+    void set_cp_offset(int cp_offset) { cp_offset_ = cp_offset; }
+  };
+
+  class DeferredSetRegister : public DeferredAction {
+   public:
+    DeferredSetRegister(int reg, int value)
+        : DeferredAction(ActionNode::SET_REGISTER, reg),
+          value_(value) { }
+    int value() { return value_; }
+   private:
+    int value_;
+  };
+
+  class DeferredClearCaptures : public DeferredAction {
+   public:
+    explicit DeferredClearCaptures(Interval range)
+        : DeferredAction(ActionNode::CLEAR_CAPTURES, -1),
+          range_(range) { }
+    Interval range() { return range_; }
+   private:
+    Interval range_;
+  };
+
+  class DeferredIncrementRegister : public DeferredAction {
+   public:
+    explicit DeferredIncrementRegister(int reg)
+        : DeferredAction(ActionNode::INCREMENT_REGISTER, reg) { }
+  };
+
+  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),
+        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
+  // affects the assumptions used when generating code.  There is no recorded
+  // backtrack location in a trivial trace, so with a trivial trace we will
+  // generate code that, on a failure to match, gets the backtrack location
+  // from the backtrack stack rather than using a direct jump instruction.  We
+  // always start code generation with a trivial trace and non-trivial traces
+  // are created as we emit code for nodes or add to the list of deferred
+  // actions in the trace.  The location of the code generated for a node using
+  // a trivial trace is recorded in a label in the node so that gotos can be
+  // generated to that code.
+  bool is_trivial() {
+    return backtrack_ == NULL &&
+           actions_ == NULL &&
+           cp_offset_ == 0 &&
+           characters_preloaded_ == 0 &&
+           bound_checked_up_to_ == 0 &&
+           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_VALUE : FALSE_VALUE;
+  }
+  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) {
+    DCHECK(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 count) { characters_preloaded_ = count; }
+  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, Zone* zone);
+  void PerformDeferredActions(RegExpMacroAssembler* macro,
+                              int max_register,
+                              const OutSet& affected_registers,
+                              OutSet* registers_to_pop,
+                              OutSet* registers_to_clear,
+                              Zone* zone);
+  void RestoreAffectedRegisters(RegExpMacroAssembler* macro,
+                                int max_register,
+                                const OutSet& registers_to_pop,
+                                const 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 GreedyLoopState {
+ public:
+  explicit GreedyLoopState(bool not_at_start);
+
+  Label* label() { return &label_; }
+  Trace* counter_backtrack_trace() { return &counter_backtrack_trace_; }
+
+ private:
+  Label label_;
+  Trace counter_backtrack_trace_;
+};
+
+
+struct PreloadState {
+  static const int kEatsAtLeastNotYetInitialized = -1;
+  bool preload_is_current_;
+  bool preload_has_checked_bounds_;
+  int preload_characters_;
+  int eats_at_least_;
+  void init() {
+    eats_at_least_ = kEatsAtLeastNotYetInitialized;
+  }
+};
+
+
+class NodeVisitor {
+ public:
+  virtual ~NodeVisitor() { }
+#define DECLARE_VISIT(Type)                                          \
+  virtual void Visit##Type(Type##Node* that) = 0;
+FOR_EACH_NODE_TYPE(DECLARE_VISIT)
+#undef DECLARE_VISIT
+  virtual void VisitLoopChoice(LoopChoiceNode* that) { VisitChoice(that); }
+};
+
+
+// Node visitor used to add the start set of the alternatives to the
+// dispatch table of a choice node.
+class DispatchTableConstructor: public NodeVisitor {
+ public:
+  DispatchTableConstructor(DispatchTable* table, bool ignore_case,
+                           Zone* zone)
+      : table_(table),
+        choice_index_(-1),
+        ignore_case_(ignore_case),
+        zone_(zone) { }
+
+  void BuildTable(ChoiceNode* node);
+
+  void AddRange(CharacterRange range) {
+    table()->AddRange(range, choice_index_, zone_);
+  }
+
+  void AddInverse(ZoneList<CharacterRange>* ranges);
+
+#define DECLARE_VISIT(Type)                                          \
+  virtual void Visit##Type(Type##Node* that);
+FOR_EACH_NODE_TYPE(DECLARE_VISIT)
+#undef DECLARE_VISIT
+
+  DispatchTable* table() { return table_; }
+  void set_choice_index(int value) { choice_index_ = value; }
+
+ protected:
+  DispatchTable* table_;
+  int choice_index_;
+  bool ignore_case_;
+  Zone* zone_;
+};
+
+
+// Assertion propagation moves information about assertions such as
+// \b to the affected nodes.  For instance, in /.\b./ information must
+// be propagated to the first '.' that whatever follows needs to know
+// if it matched a word or a non-word, and to the second '.' that it
+// has to check if it succeeds a word or non-word.  In this case the
+// result will be something like:
+//
+//   +-------+        +------------+
+//   |   .   |        |      .     |
+//   +-------+  --->  +------------+
+//   | word? |        | check word |
+//   +-------+        +------------+
+class Analysis: public NodeVisitor {
+ public:
+  Analysis(bool ignore_case, bool is_one_byte)
+      : ignore_case_(ignore_case),
+        is_one_byte_(is_one_byte),
+        error_message_(NULL) {}
+  void EnsureAnalyzed(RegExpNode* node);
+
+#define DECLARE_VISIT(Type)                                          \
+  virtual void Visit##Type(Type##Node* that);
+FOR_EACH_NODE_TYPE(DECLARE_VISIT)
+#undef DECLARE_VISIT
+  virtual void VisitLoopChoice(LoopChoiceNode* that);
+
+  bool has_failed() { return error_message_ != NULL; }
+  const char* error_message() {
+    DCHECK(error_message_ != NULL);
+    return error_message_;
+  }
+  void fail(const char* error_message) {
+    error_message_ = error_message;
+  }
+
+ private:
+  bool ignore_case_;
+  bool is_one_byte_;
+  const char* error_message_;
+
+  DISALLOW_IMPLICIT_CONSTRUCTORS(Analysis);
+};
+
+
+struct RegExpCompileData {
+  RegExpCompileData()
+    : tree(NULL),
+      node(NULL),
+      simple(true),
+      contains_anchor(false),
+      capture_count(0) { }
+  RegExpTree* tree;
+  RegExpNode* node;
+  bool simple;
+  bool contains_anchor;
+  Handle<String> error;
+  int capture_count;
+};
+
+
+class RegExpEngine: public AllStatic {
+ public:
+  struct CompilationResult {
+    CompilationResult(Isolate* isolate, const char* error_message)
+        : error_message(error_message),
+          code(isolate->heap()->the_hole_value()),
+          num_registers(0) {}
+    CompilationResult(Object* code, int registers)
+      : error_message(NULL),
+        code(code),
+        num_registers(registers) {}
+    const char* error_message;
+    Object* code;
+    int num_registers;
+  };
+
+  static CompilationResult Compile(RegExpCompileData* input, bool ignore_case,
+                                   bool global, bool multiline, bool sticky,
+                                   Handle<String> pattern,
+                                   Handle<String> sample_subject,
+                                   bool is_one_byte, Zone* zone);
+
+  static void DotPrint(const char* label, RegExpNode* node, bool ignore_case);
+};
+
+}  // namespace dart
+
+#endif  // VM_REGEXP_H_