Integrate the Irregexp Regular Expression Engine.

runtime/vm/regexp.cc

+// 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.
+
+#include "vm/regexp.h"
+
+#include "vm/dart_entry.h"
+#include "vm/regexp_assembler.h"
+#include "vm/regexp_ast.h"
+#include "vm/unibrow-inl.h"
+#include "vm/unicode.h"
+#include "vm/symbols.h"
+
+#define I (isolate())
+#define CI (compiler->isolate())
+
+namespace dart {
+
+DECLARE_FLAG(bool, trace_irregexp);
+
+// Default to generating optimized regexp code.
+static const bool kRegexpOptimization = true;
+
+// More makes code generation slower, less makes V8 benchmark score lower.
+static const intptr_t kMaxLookaheadForBoyerMoore = 8;
+
+ContainedInLattice AddRange(ContainedInLattice containment,
+                            const intptr_t* ranges,
+                            intptr_t ranges_length,
+                            Interval new_range) {
+  ASSERT((ranges_length & 1) == 1);
+  ASSERT(ranges[ranges_length - 1] == Utf16::kMaxCodeUnit + 1);
+  if (containment == kLatticeUnknown) return containment;
+  bool inside = false;
+  intptr_t last = 0;
+  for (intptr_t i = 0; i < ranges_length;
+       inside = !inside, last = ranges[i], i++) {
+    // Consider the range from last to ranges[i].
+    // We haven't got to the new range yet.
+    if (ranges[i] <= new_range.from()) continue;
+    // New range is wholly inside last-ranges[i].  Note that new_range.to() is
+    // inclusive, but the values in ranges are not.
+    if (last <= new_range.from() && new_range.to() < ranges[i]) {
+      return Combine(containment, inside ? kLatticeIn : kLatticeOut);
+    }
+    return kLatticeUnknown;
+  }
+  return containment;
+}
+
+// -------------------------------------------------------------------
+// Implementation of the Irregexp regular expression engine.
+//
+// The Irregexp regular expression engine is intended to be a complete
+// implementation of ECMAScript regular expressions.  It generates
+// IR code that is subsequently compiled to native code.
+
+//   The Irregexp regexp engine is structured in three steps.
+//   1) The parser generates an abstract syntax tree.  See regexp_ast.cc.
+//   2) From the AST a node network is created.  The nodes are all
+//      subclasses of RegExpNode.  The nodes represent states when
+//      executing a regular expression.  Several optimizations are
+//      performed on the node network.
+//   3) From the nodes we generate IR instructions that can actually
+//      execute the regular expression (perform the search).  The
+//      code generation step is described in more detail below.
+
+// Code generation.
+//
+//   The nodes are divided into four main categories.
+//   * Choice nodes
+//        These represent places where the regular expression can
+//        match in more than one way.  For example on entry to an
+//        alternation (foo|bar) or a repetition (*, +, ? or {}).
+//   * Action nodes
+//        These represent places where some action should be
+//        performed.  Examples include recording the current position
+//        in the input string to a register (in order to implement
+//        captures) or other actions on register for example in order
+//        to implement the counters needed for {} repetitions.
+//   * Matching nodes
+//        These attempt to match some element part of the input string.
+//        Examples of elements include character classes, plain strings
+//        or back references.
+//   * End nodes
+//        These are used to implement the actions required on finding
+//        a successful match or failing to find a match.
+//
+//   The code generated maintains some state as it runs.  This consists of the
+//   following elements:
+//
+//   * The capture registers.  Used for string captures.
+//   * Other registers.  Used for counters etc.
+//   * The current position.
+//   * The stack of backtracking information.  Used when a matching node
+//     fails to find a match and needs to try an alternative.
+//
+// Conceptual regular expression execution model:
+//
+//   There is a simple conceptual model of regular expression execution
+//   which will be presented first.  The actual code generated is a more
+//   efficient simulation of the simple conceptual model:
+//
+//   * Choice nodes are implemented as follows:
+//     For each choice except the last {
+//       push current position
+//       push backtrack code location
+//       <generate code to test for choice>
+//       backtrack code location:
+//       pop current position
+//     }
+//     <generate code to test for last choice>
+//
+//   * Actions nodes are generated as follows
+//     <push affected registers on backtrack stack>
+//     <generate code to perform action>
+//     push backtrack code location
+//     <generate code to test for following nodes>
+//     backtrack code location:
+//     <pop affected registers to restore their state>
+//     <pop backtrack location from stack and go to it>
+//
+//   * Matching nodes are generated as follows:
+//     if input string matches at current position
+//       update current position
+//       <generate code to test for following nodes>
+//     else
+//       <pop backtrack location from stack and go to it>
+//
+//   Thus it can be seen that the current position is saved and restored
+//   by the choice nodes, whereas the registers are saved and restored by
+//   by the action nodes that manipulate them.
+//
+//   The other interesting aspect of this model is that nodes are generated
+//   at the point where they are needed by a recursive call to Emit().  If
+//   the node has already been code generated then the Emit() call will
+//   generate a jump to the previously generated code instead.  In order to
+//   limit recursion it is possible for the Emit() function to put the node
+//   on a work list for later generation and instead generate a jump.  The
+//   destination of the jump is resolved later when the code is generated.
+//
+// Actual regular expression code generation.
+//
+//   Code generation is actually more complicated than the above.  In order
+//   to improve the efficiency of the generated code some optimizations are
+//   performed
+//
+//   * Choice nodes have 1-character lookahead.
+//     A choice node looks at the following character and eliminates some of
+//     the choices immediately based on that character.  This is not yet
+//     implemented.
+//   * Simple greedy loops store reduced backtracking information.
+//     A quantifier like /.*foo/m will greedily match the whole input.  It will
+//     then need to backtrack to a point where it can match "foo".  The naive
+//     implementation of this would push each character position onto the
+//     backtracking stack, then pop them off one by one.  This would use space
+//     proportional to the length of the input string.  However since the "."
+//     can only match in one way and always has a constant length (in this case
+//     of 1) it suffices to store the current position on the top of the stack
+//     once.  Matching now becomes merely incrementing the current position and
+//     backtracking becomes decrementing the current position and checking the
+//     result against the stored current position.  This is faster and saves
+//     space.
+//   * The current state is virtualized.
+//     This is used to defer expensive operations until it is clear that they
+//     are needed and to generate code for a node more than once, allowing
+//     specialized an efficient versions of the code to be created. This is
+//     explained in the section below.
+//
+// Execution state virtualization.
+//
+//   Instead of emitting code, nodes that manipulate the state can record their
+//   manipulation in an object called the Trace.  The Trace object can record a
+//   current position offset, an optional backtrack code location on the top of
+//   the virtualized backtrack stack and some register changes.  When a node is
+//   to be emitted it can flush the Trace or update it.  Flushing the Trace
+//   will emit code to bring the actual state into line with the virtual state.
+//   Avoiding flushing the state can postpone some work (e.g. updates of capture
+//   registers).  Postponing work can save time when executing the regular
+//   expression since it may be found that the work never has to be done as a
+//   failure to match can occur.  In addition it is much faster to jump to a
+//   known backtrack code location than it is to pop an unknown backtrack
+//   location from the stack and jump there.
+//
+//   The virtual state found in the Trace affects code generation.  For example
+//   the virtual state contains the difference between the actual current
+//   position and the virtual current position, and matching code needs to use
+//   this offset to attempt a match in the correct location of the input
+//   string.  Therefore code generated for a non-trivial trace is specialized
+//   to that trace.  The code generator therefore has the ability to generate
+//   code for each node several times.  In order to limit the size of the
+//   generated code there is an arbitrary limit on how many specialized sets of
+//   code may be generated for a given node.  If the limit is reached, the
+//   trace is flushed and a generic version of the code for a node is emitted.
+//   This is subsequently used for that node.  The code emitted for non-generic
+//   trace is not recorded in the node and so it cannot currently be reused in
+//   the event that code generation is requested for an identical trace.
+
+
+void RegExpTree::AppendToText(RegExpText* text) {
+  UNREACHABLE();
+}
+
+
+void RegExpAtom::AppendToText(RegExpText* text) {
+  text->AddElement(TextElement::Atom(this));
+}
+
+
+void RegExpCharacterClass::AppendToText(RegExpText* text) {
+  text->AddElement(TextElement::CharClass(this));
+}
+
+
+void RegExpText::AppendToText(RegExpText* text) {
+  for (intptr_t i = 0; i < elements()->length(); i++)
+    text->AddElement((*elements())[i]);
+}
+
+
+TextElement TextElement::Atom(RegExpAtom* atom) {
+  return TextElement(ATOM, atom);
+}
+
+
+TextElement TextElement::CharClass(RegExpCharacterClass* char_class) {
+  return TextElement(CHAR_CLASS, char_class);
+}
+
+
+intptr_t TextElement::length() const {
+  switch (text_type()) {
+    case ATOM:
+      return atom()->length();
+
+    case CHAR_CLASS:
+      return 1;
+  }
+  UNREACHABLE();
+  return 0;
+}
+
+
+class FrequencyCollator : public ValueObject {
+ public:
+  FrequencyCollator() : total_samples_(0) {
+    for (intptr_t i = 0; i < RegExpMacroAssembler::kTableSize; i++) {
+      frequencies_[i] = CharacterFrequency(i);
+    }
+  }
+
+  void CountCharacter(intptr_t character) {
+    intptr_t index = (character & RegExpMacroAssembler::kTableMask);
+    frequencies_[index].Increment();
+    total_samples_++;
+  }
+
+  // Does not measure in percent, but rather per-128 (the table size from the
+  // regexp macro assembler).
+  intptr_t Frequency(intptr_t in_character) {
+    ASSERT((in_character & RegExpMacroAssembler::kTableMask) == in_character);
+    if (total_samples_ < 1) return 1;  // Division by zero.
+    intptr_t freq_in_per128 =
+        (frequencies_[in_character].counter() * 128) / total_samples_;
+    return freq_in_per128;
+  }
+
+ private:
+  class CharacterFrequency {
+   public:
+    CharacterFrequency() : counter_(0), character_(-1) { }
+    explicit CharacterFrequency(intptr_t character)
+        : counter_(0), character_(character) { }
+
+    void Increment() { counter_++; }
+    intptr_t counter() { return counter_; }
+    intptr_t character() { return character_; }
+
+   private:
+    intptr_t counter_;
+    intptr_t character_;
+
+    DISALLOW_ALLOCATION();
+  };
+
+
+ private:
+  CharacterFrequency frequencies_[RegExpMacroAssembler::kTableSize];
+  intptr_t total_samples_;
+};
+
+
+class RegExpCompiler : public ValueObject {
+ public:
+  RegExpCompiler(intptr_t capture_count,
+                 bool ignore_case,
+                 intptr_t specialization_cid);
+
+  intptr_t AllocateRegister() {
+    return next_register_++;
+  }
+
+  RegExpEngine::CompilationResult Assemble(IRRegExpMacroAssembler* assembler,
+                                           RegExpNode* start,
+                                           intptr_t capture_count,
+                                           const String& pattern);
+
+  inline void AddWork(RegExpNode* node) { work_list_->Add(node); }
+
+  static const intptr_t kImplementationOffset = 0;
+  static const intptr_t kNumberOfRegistersOffset = 0;
+  static const intptr_t kCodeOffset = 1;
+
+  IRRegExpMacroAssembler* macro_assembler() { return macro_assembler_; }
+  EndNode* accept() { return accept_; }
+
+  static const intptr_t kMaxRecursion = 100;
+  inline intptr_t recursion_depth() { return recursion_depth_; }
+  inline void IncrementRecursionDepth() { recursion_depth_++; }
+  inline void DecrementRecursionDepth() { recursion_depth_--; }
+
+  void SetRegExpTooBig() { reg_exp_too_big_ = true; }
+
+  inline bool ignore_case() { return ignore_case_; }
+  inline bool one_byte() const {
+    return (specialization_cid_ == kOneByteStringCid ||
+            specialization_cid_ == kExternalOneByteStringCid);
+  }
+  inline intptr_t specialization_cid() { return specialization_cid_; }
+  FrequencyCollator* frequency_collator() { return &frequency_collator_; }
+
+  intptr_t current_expansion_factor() { return current_expansion_factor_; }
+  void set_current_expansion_factor(intptr_t value) {
+    current_expansion_factor_ = value;
+  }
+
+  Isolate* isolate() const { return isolate_; }
+
+  static const intptr_t kNoRegister = -1;
+
+ private:
+  EndNode* accept_;
+  intptr_t next_register_;
+  ZoneGrowableArray<RegExpNode*>* work_list_;
+  intptr_t recursion_depth_;
+  IRRegExpMacroAssembler* macro_assembler_;
+  bool ignore_case_;
+  intptr_t specialization_cid_;
+  bool reg_exp_too_big_;
+  intptr_t current_expansion_factor_;
+  FrequencyCollator frequency_collator_;
+  Isolate* isolate_;
+};
+
+
+class RecursionCheck : public ValueObject {
+ public:
+  explicit RecursionCheck(RegExpCompiler* compiler) : compiler_(compiler) {
+    compiler->IncrementRecursionDepth();
+  }
+  ~RecursionCheck() { compiler_->DecrementRecursionDepth(); }
+ private:
+  RegExpCompiler* compiler_;
+};
+
+
+static RegExpEngine::CompilationResult IrregexpRegExpTooBig() {
+  return RegExpEngine::CompilationResult("RegExp too big");
+}
+
+
+// Attempts to compile the regexp using an Irregexp code generator.  Returns
+// a fixed array or a null handle depending on whether it succeeded.
+RegExpCompiler::RegExpCompiler(intptr_t capture_count, bool ignore_case,
+                               intptr_t specialization_cid)
+    : next_register_(2 * (capture_count + 1)),
+      work_list_(NULL),
+      recursion_depth_(0),
+      ignore_case_(ignore_case),
+      specialization_cid_(specialization_cid),
+      reg_exp_too_big_(false),
+      current_expansion_factor_(1),
+      isolate_(Isolate::Current()) {
+  accept_ = new(I) EndNode(EndNode::ACCEPT, I);
+}
+
+
+RegExpEngine::CompilationResult RegExpCompiler::Assemble(
+    IRRegExpMacroAssembler* macro_assembler,
+    RegExpNode* start,
+    intptr_t capture_count,
+    const String& pattern) {
+  static const bool use_slow_safe_regexp_compiler = false;
+
+  macro_assembler->set_slow_safe(use_slow_safe_regexp_compiler);
+  macro_assembler_ = macro_assembler;
+
+  ZoneGrowableArray<RegExpNode*> work_list(0);
+  work_list_ = &work_list;
+  BlockLabel fail;
+  macro_assembler_->PushBacktrack(&fail);
+  Trace new_trace;
+  start->Emit(this, &new_trace);
+  macro_assembler_->BindBlock(&fail);
+  macro_assembler_->Fail();
+  while (!work_list.is_empty()) {
+    work_list.RemoveLast()->Emit(this, &new_trace);
+  }
+  if (reg_exp_too_big_) return IrregexpRegExpTooBig();
+
+  macro_assembler->FinalizeIndirectGotos();
+
+  return RegExpEngine::CompilationResult(macro_assembler,
+                                         macro_assembler->graph_entry(),
+                                         macro_assembler->num_blocks(),
+                                         macro_assembler->num_stack_locals());
+}
+
+
+bool Trace::DeferredAction::Mentions(intptr_t that) {
+  if (action_type() == ActionNode::CLEAR_CAPTURES) {
+    Interval range = static_cast<DeferredClearCaptures*>(this)->range();
+    return range.Contains(that);
+  } else {
+    return reg() == that;
+  }
+}
+
+
+bool Trace::mentions_reg(intptr_t reg) {
+  for (DeferredAction* action = actions_;
+       action != NULL;
+       action = action->next()) {
+    if (action->Mentions(reg))
+      return true;
+  }
+  return false;
+}
+
+
+bool Trace::GetStoredPosition(intptr_t reg, intptr_t* cp_offset) {
+  ASSERT(*cp_offset == 0);
+  for (DeferredAction* action = actions_;
+       action != NULL;
+       action = action->next()) {
+    if (action->Mentions(reg)) {
+      if (action->action_type() == ActionNode::STORE_POSITION) {
+        *cp_offset = static_cast<DeferredCapture*>(action)->cp_offset();
+        return true;
+      } else {
+        return false;
+      }
+    }
+  }
+  return false;
+}
+
+
+// This is called as we come into a loop choice node and some other tricky
+// nodes.  It normalizes the state of the code generator to ensure we can
+// generate generic code.
+intptr_t Trace::FindAffectedRegisters(OutSet* affected_registers,
+                                      Isolate* isolate) {
+  intptr_t max_register = RegExpCompiler::kNoRegister;
+  for (DeferredAction* action = actions_;
+       action != NULL;
+       action = action->next()) {
+    if (action->action_type() == ActionNode::CLEAR_CAPTURES) {
+      Interval range = static_cast<DeferredClearCaptures*>(action)->range();
+      for (intptr_t i = range.from(); i <= range.to(); i++)
+        affected_registers->Set(i, isolate);
+      if (range.to() > max_register) max_register = range.to();
+    } else {
+      affected_registers->Set(action->reg(), isolate);
+      if (action->reg() > max_register) max_register = action->reg();
+    }
+  }
+  return max_register;
+}
+
+
+void Trace::RestoreAffectedRegisters(RegExpMacroAssembler* assembler,
+                                     intptr_t max_register,
+                                     const OutSet& registers_to_pop,
+                                     const OutSet& registers_to_clear) {
+  for (intptr_t reg = max_register; reg >= 0; reg--) {
+    if (registers_to_pop.Get(reg)) {
+      assembler->PopRegister(reg);
+    } else if (registers_to_clear.Get(reg)) {
+      intptr_t clear_to = reg;
+      while (reg > 0 && registers_to_clear.Get(reg - 1)) {
+        reg--;
+      }
+      assembler->ClearRegisters(reg, clear_to);
+    }
+  }
+}
+
+
+void Trace::PerformDeferredActions(RegExpMacroAssembler* assembler,
+                                   intptr_t max_register,
+                                   const OutSet& affected_registers,
+                                   OutSet* registers_to_pop,
+                                   OutSet* registers_to_clear,
+                                   Isolate* isolate) {
+  for (intptr_t reg = 0; reg <= max_register; reg++) {
+    if (!affected_registers.Get(reg)) {
+      continue;
+    }
+
+    // The chronologically first deferred action in the trace
+    // is used to infer the action needed to restore a register
+    // to its previous state (or not, if it's safe to ignore it).
+    enum DeferredActionUndoType { IGNORE, RESTORE, CLEAR };
+    DeferredActionUndoType undo_action = IGNORE;
+
+    intptr_t value = 0;
+    bool absolute = false;
+    bool clear = false;
+    intptr_t store_position = -1;
+    // This is a little tricky because we are scanning the actions in reverse
+    // historical order (newest first).
+    for (DeferredAction* action = actions_;
+         action != NULL;
+         action = action->next()) {
+      if (action->Mentions(reg)) {
+        switch (action->action_type()) {
+          case ActionNode::SET_REGISTER: {
+            Trace::DeferredSetRegister* psr =
+                static_cast<Trace::DeferredSetRegister*>(action);
+            if (!absolute) {
+              value += psr->value();
+              absolute = true;
+            }
+            // SET_REGISTER is currently only used for newly introduced loop
+            // counters. They can have a significant previous value if they
+            // occour in a loop. TODO(lrn): Propagate this information, so
+            // we can set undo_action to IGNORE if we know there is no value to
+            // restore.
+            undo_action = RESTORE;
+            ASSERT(store_position == -1);
+            ASSERT(!clear);
+            break;
+          }
+          case ActionNode::INCREMENT_REGISTER:
+            if (!absolute) {
+              value++;
+            }
+            ASSERT(store_position == -1);
+            ASSERT(!clear);
+            undo_action = RESTORE;
+            break;
+          case ActionNode::STORE_POSITION: {
+            Trace::DeferredCapture* pc =
+                static_cast<Trace::DeferredCapture*>(action);
+            if (!clear && store_position == -1) {
+              store_position = pc->cp_offset();
+            }
+
+            // For captures we know that stores and clears alternate.
+            // Other register, are never cleared, and if the occur
+            // inside a loop, they might be assigned more than once.
+            if (reg <= 1) {
+              // Registers zero and one, aka "capture zero", is
+              // always set correctly if we succeed. There is no
+              // need to undo a setting on backtrack, because we
+              // will set it again or fail.
+              undo_action = IGNORE;
+            } else {
+              undo_action = pc->is_capture() ? CLEAR : RESTORE;
+            }
+            ASSERT(!absolute);
+            ASSERT(value == 0);
+            break;
+          }
+          case ActionNode::CLEAR_CAPTURES: {
+            // Since we're scanning in reverse order, if we've already
+            // set the position we have to ignore historically earlier
+            // clearing operations.
+            if (store_position == -1) {
+              clear = true;
+            }
+            undo_action = RESTORE;
+            ASSERT(!absolute);
+            ASSERT(value == 0);
+            break;
+          }
+          default:
+            UNREACHABLE();
+            break;
+        }
+      }
+    }
+    // Prepare for the undo-action (e.g., push if it's going to be popped).
+    if (undo_action == RESTORE) {
+      assembler->PushRegister(reg);
+      registers_to_pop->Set(reg, isolate);
+    } else if (undo_action == CLEAR) {
+      registers_to_clear->Set(reg, isolate);
+    }
+    // Perform the chronologically last action (or accumulated increment)
+    // for the register.
+    if (store_position != -1) {
+      assembler->WriteCurrentPositionToRegister(reg, store_position);
+    } else if (clear) {
+      assembler->ClearRegisters(reg, reg);
+    } else if (absolute) {
+      assembler->SetRegister(reg, value);
+    } else if (value != 0) {
+      assembler->AdvanceRegister(reg, value);
+    }
+  }
+}
+
+
+// This is called as we come into a loop choice node and some other tricky
+// nodes.  It normalizes the state of the code generator to ensure we can
+// generate generic code.
+void Trace::Flush(RegExpCompiler* compiler, RegExpNode* successor) {
+  RegExpMacroAssembler* assembler = compiler->macro_assembler();
+
+  ASSERT(!is_trivial());
+
+  if (actions_ == NULL && backtrack() == NULL) {
+    // Here we just have some deferred cp advances to fix and we are back to
+    // a normal situation.  We may also have to forget some information gained
+    // through a quick check that was already performed.
+    if (cp_offset_ != 0) assembler->AdvanceCurrentPosition(cp_offset_);
+    // Create a new trivial state and generate the node with that.
+    Trace new_state;
+    successor->Emit(compiler, &new_state);
+    return;
+  }
+
+  // Generate deferred actions here along with code to undo them again.
+  OutSet affected_registers;
+
+  if (backtrack() != NULL) {
+    // Here we have a concrete backtrack location.  These are set up by choice
+    // nodes and so they indicate that we have a deferred save of the current
+    // position which we may need to emit here.
+    assembler->PushCurrentPosition();
+  }
+
+  intptr_t max_register = FindAffectedRegisters(&affected_registers, CI);
+  OutSet registers_to_pop;
+  OutSet registers_to_clear;
+  PerformDeferredActions(assembler,
+                         max_register,
+                         affected_registers,
+                         &registers_to_pop,
+                         &registers_to_clear,
+                         CI);
+  if (cp_offset_ != 0) {
+    assembler->AdvanceCurrentPosition(cp_offset_);
+  }
+
+  // Create a new trivial state and generate the node with that.
+  BlockLabel undo;
+  assembler->PushBacktrack(&undo);
+  Trace new_state;
+  successor->Emit(compiler, &new_state);
+
+  // On backtrack we need to restore state.
+  assembler->BindBlock(&undo);
+  RestoreAffectedRegisters(assembler,
+                           max_register,
+                           registers_to_pop,
+                           registers_to_clear);
+  if (backtrack() == NULL) {
+    assembler->Backtrack();
+  } else {
+    assembler->PopCurrentPosition();
+    assembler->GoTo(backtrack());
+  }
+}
+
+
+void NegativeSubmatchSuccess::Emit(RegExpCompiler* compiler, Trace* trace) {
+  RegExpMacroAssembler* assembler = compiler->macro_assembler();
+
+  // Omit flushing the trace. We discard the entire stack frame anyway.
+
+  if (!label()->IsBound()) {
+    // We are completely independent of the trace, since we ignore it,
+    // so this code can be used as the generic version.
+    assembler->BindBlock(label());
+  }
+
+  // Throw away everything on the backtrack stack since the start
+  // of the negative submatch and restore the character position.
+  assembler->ReadCurrentPositionFromRegister(current_position_register_);
+  assembler->ReadStackPointerFromRegister(stack_pointer_register_);
+  if (clear_capture_count_ > 0) {
+    // Clear any captures that might have been performed during the success
+    // of the body of the negative look-ahead.
+    int clear_capture_end = clear_capture_start_ + clear_capture_count_ - 1;
+    assembler->ClearRegisters(clear_capture_start_, clear_capture_end);
+  }
+  // Now that we have unwound the stack we find at the top of the stack the
+  // backtrack that the BeginSubmatch node got.
+  assembler->Backtrack();
+}
+
+
+void EndNode::Emit(RegExpCompiler* compiler, Trace* trace) {
+  if (!trace->is_trivial()) {
+    trace->Flush(compiler, this);
+    return;
+  }
+  RegExpMacroAssembler* assembler = compiler->macro_assembler();
+  if (!label()->IsBound()) {
+    assembler->BindBlock(label());
+  }
+  switch (action_) {
+    case ACCEPT:
+      assembler->Succeed();
+      return;
+    case BACKTRACK:
+      assembler->GoTo(trace->backtrack());
+      return;
+    case NEGATIVE_SUBMATCH_SUCCESS:
+      // This case is handled in a different virtual method.
+      UNREACHABLE();
+  }
+  UNIMPLEMENTED();
+}
+
+
+void GuardedAlternative::AddGuard(Guard* guard, Isolate* isolate) {
+  if (guards_ == NULL)
+    guards_ = new(isolate) ZoneGrowableArray<Guard*>(1);
+  guards_->Add(guard);
+}
+
+
+ActionNode* ActionNode::SetRegister(intptr_t reg,
+                                    intptr_t val,
+                                    RegExpNode* on_success) {
+  ActionNode* result =
+      new(on_success->isolate()) ActionNode(SET_REGISTER, on_success);
+  result->data_.u_store_register.reg = reg;
+  result->data_.u_store_register.value = val;
+  return result;
+}
+
+
+ActionNode* ActionNode::IncrementRegister(intptr_t reg,
+                                          RegExpNode* on_success) {
+  ActionNode* result =
+      new(on_success->isolate()) ActionNode(INCREMENT_REGISTER, on_success);
+  result->data_.u_increment_register.reg = reg;
+  return result;
+}
+
+
+ActionNode* ActionNode::StorePosition(intptr_t reg,
+                                      bool is_capture,
+                                      RegExpNode* on_success) {
+  ActionNode* result =
+      new(on_success->isolate()) ActionNode(STORE_POSITION, on_success);
+  result->data_.u_position_register.reg = reg;
+  result->data_.u_position_register.is_capture = is_capture;
+  return result;
+}
+
+
+ActionNode* ActionNode::ClearCaptures(Interval range,
+                                      RegExpNode* on_success) {
+  ActionNode* result =
+      new(on_success->isolate()) ActionNode(CLEAR_CAPTURES, on_success);
+  result->data_.u_clear_captures.range_from = range.from();
+  result->data_.u_clear_captures.range_to = range.to();
+  return result;
+}
+
+
+ActionNode* ActionNode::BeginSubmatch(intptr_t stack_reg,
+                                      intptr_t position_reg,
+                                      RegExpNode* on_success) {
+  ActionNode* result =
+      new(on_success->isolate()) ActionNode(BEGIN_SUBMATCH, on_success);
+  result->data_.u_submatch.stack_pointer_register = stack_reg;
+  result->data_.u_submatch.current_position_register = position_reg;
+  return result;
+}
+
+
+ActionNode* ActionNode::PositiveSubmatchSuccess(intptr_t stack_reg,
+                                                intptr_t position_reg,
+                                                intptr_t clear_register_count,
+                                                intptr_t clear_register_from,
+                                                RegExpNode* on_success) {
+  ActionNode* result =
+      new(on_success->isolate()) ActionNode(POSITIVE_SUBMATCH_SUCCESS,
+                                            on_success);
+  result->data_.u_submatch.stack_pointer_register = stack_reg;
+  result->data_.u_submatch.current_position_register = position_reg;
+  result->data_.u_submatch.clear_register_count = clear_register_count;
+  result->data_.u_submatch.clear_register_from = clear_register_from;
+  return result;
+}
+
+
+ActionNode* ActionNode::EmptyMatchCheck(intptr_t start_register,
+                                        intptr_t repetition_register,
+                                        intptr_t repetition_limit,
+                                        RegExpNode* on_success) {
+  ActionNode* result =
+      new(on_success->isolate()) ActionNode(EMPTY_MATCH_CHECK, on_success);
+  result->data_.u_empty_match_check.start_register = start_register;
+  result->data_.u_empty_match_check.repetition_register = repetition_register;
+  result->data_.u_empty_match_check.repetition_limit = repetition_limit;
+  return result;
+}
+
+
+#define DEFINE_ACCEPT(Type)                                          \
+  void Type##Node::Accept(NodeVisitor* visitor) {                    \
+    visitor->Visit##Type(this);                                      \
+  }
+FOR_EACH_NODE_TYPE(DEFINE_ACCEPT)
+#undef DEFINE_ACCEPT
+
+
+void LoopChoiceNode::Accept(NodeVisitor* visitor) {
+  visitor->VisitLoopChoice(this);
+}
+
+
+// -------------------------------------------------------------------
+// Emit code.
+
+
+void ChoiceNode::GenerateGuard(RegExpMacroAssembler* macro_assembler,
+                               Guard* guard,
+                               Trace* trace) {
+  switch (guard->op()) {
+    case Guard::LT:
+      ASSERT(!trace->mentions_reg(guard->reg()));
+      macro_assembler->IfRegisterGE(guard->reg(),
+                                    guard->value(),
+                                    trace->backtrack());
+      break;
+    case Guard::GEQ:
+      ASSERT(!trace->mentions_reg(guard->reg()));
+      macro_assembler->IfRegisterLT(guard->reg(),
+                                    guard->value(),
+                                    trace->backtrack());
+      break;
+  }
+}
+
+
+// Returns the number of characters in the equivalence class, omitting those
+// that cannot occur in the source string because it is ASCII.
+static intptr_t GetCaseIndependentLetters(uint16_t character,
+                                          bool one_byte_subject,
+                                          int32_t* letters) {
+  unibrow::Mapping<unibrow::Ecma262UnCanonicalize> jsregexp_uncanonicalize;
+  intptr_t length = jsregexp_uncanonicalize.get(character, '\0', letters);
+  // Unibrow returns 0 or 1 for characters where case independence is
+  // trivial.
+  if (length == 0) {
+    letters[0] = character;
+    length = 1;
+  }
+  if (!one_byte_subject || character <= Symbols::kMaxOneCharCodeSymbol) {
+    return length;
+  }
+
+  // The standard requires that non-ASCII characters cannot have ASCII
+  // character codes in their equivalence class.
+  // TODO(dcarney): issue 3550 this is not actually true for Latin1 anymore,
+  // is it?  For example, \u00C5 is equivalent to \u212B.
+  return 0;
+}
+
+
+static inline bool EmitSimpleCharacter(Isolate* isolate,
+                                       RegExpCompiler* compiler,
+                                       uint16_t c,
+                                       BlockLabel* on_failure,
+                                       intptr_t cp_offset,
+                                       bool check,
+                                       bool preloaded) {
+  RegExpMacroAssembler* assembler = compiler->macro_assembler();
+  bool bound_checked = false;
+  if (!preloaded) {
+    assembler->LoadCurrentCharacter(
+        cp_offset,
+        on_failure,
+        check);
+    bound_checked = true;
+  }
+  assembler->CheckNotCharacter(c, on_failure);
+  return bound_checked;
+}
+
+
+// Only emits non-letters (things that don't have case).  Only used for case
+// independent matches.
+static inline bool EmitAtomNonLetter(Isolate* isolate,
+                                     RegExpCompiler* compiler,
+                                     uint16_t c,
+                                     BlockLabel* on_failure,
+                                     intptr_t cp_offset,
+                                     bool check,
+                                     bool preloaded) {
+  RegExpMacroAssembler* macro_assembler = compiler->macro_assembler();
+  bool one_byte = compiler->one_byte();
+  int32_t chars[unibrow::Ecma262UnCanonicalize::kMaxWidth];
+  intptr_t length = GetCaseIndependentLetters(c, one_byte, chars);
+  if (length < 1) {
+    // This can't match.  Must be an one-byte subject and a non-one-byte
+    // character.  We do not need to do anything since the one-byte pass
+    // already handled this.
+    return false;  // Bounds not checked.
+  }
+  bool checked = false;
+  // We handle the length > 1 case in a later pass.
+  if (length == 1) {
+    if (one_byte && c > Symbols::kMaxOneCharCodeSymbol) {
+      // Can't match - see above.
+      return false;  // Bounds not checked.
+    }
+    if (!preloaded) {
+      macro_assembler->LoadCurrentCharacter(cp_offset, on_failure, check);
+      checked = check;
+    }
+    macro_assembler->CheckNotCharacter(c, on_failure);
+  }
+  return checked;
+}
+
+
+static bool ShortCutEmitCharacterPair(RegExpMacroAssembler* macro_assembler,
+                                      bool one_byte,
+                                      uint16_t c1,
+                                      uint16_t c2,
+                                      BlockLabel* on_failure) {
+  uint16_t char_mask;
+  if (one_byte) {
+    char_mask = Symbols::kMaxOneCharCodeSymbol;
+  } else {
+    char_mask = Utf16::kMaxCodeUnit;
+  }
+  uint16_t exor = c1 ^ c2;
+  // Check whether exor has only one bit set.
+  if (((exor - 1) & exor) == 0) {
+    // If c1 and c2 differ only by one bit.
+    // Ecma262UnCanonicalize always gives the highest number last.
+    ASSERT(c2 > c1);
+    uint16_t mask = char_mask ^ exor;
+    macro_assembler->CheckNotCharacterAfterAnd(c1, mask, on_failure);
+    return true;
+  }
+  ASSERT(c2 > c1);
+  uint16_t diff = c2 - c1;
+  if (((diff - 1) & diff) == 0 && c1 >= diff) {
+    // If the characters differ by 2^n but don't differ by one bit then
+    // subtract the difference from the found character, then do the or
+    // trick.  We avoid the theoretical case where negative numbers are
+    // involved in order to simplify code generation.
+    uint16_t mask = char_mask ^ diff;
+    macro_assembler->CheckNotCharacterAfterMinusAnd(c1 - diff,
+                                                    diff,
+                                                    mask,
+                                                    on_failure);
+    return true;
+  }
+  return false;
+}
+
+
+typedef bool EmitCharacterFunction(Isolate* isolate,
+                                   RegExpCompiler* compiler,
+                                   uint16_t c,
+                                   BlockLabel* on_failure,
+                                   intptr_t cp_offset,
+                                   bool check,
+                                   bool preloaded);
+
+// Only emits letters (things that have case).  Only used for case independent
+// matches.
+static inline bool EmitAtomLetter(Isolate* isolate,
+                                  RegExpCompiler* compiler,
+                                  uint16_t c,
+                                  BlockLabel* on_failure,
+                                  intptr_t cp_offset,
+                                  bool check,
+                                  bool preloaded) {
+  RegExpMacroAssembler* macro_assembler = compiler->macro_assembler();
+  bool one_byte = compiler->one_byte();
+  int32_t chars[unibrow::Ecma262UnCanonicalize::kMaxWidth];
+  intptr_t length = GetCaseIndependentLetters(c, one_byte, chars);
+  if (length <= 1) return false;
+  // We may not need to check against the end of the input string
+  // if this character lies before a character that matched.
+  if (!preloaded) {
+    macro_assembler->LoadCurrentCharacter(cp_offset, on_failure, check);
+  }
+  BlockLabel ok;
+  ASSERT(unibrow::Ecma262UnCanonicalize::kMaxWidth == 4);
+  switch (length) {
+    case 2: {
+      if (ShortCutEmitCharacterPair(macro_assembler,
+                                    one_byte,
+                                    chars[0],
+                                    chars[1],
+                                    on_failure)) {
+      } else {
+        macro_assembler->CheckCharacter(chars[0], &ok);
+        macro_assembler->CheckNotCharacter(chars[1], on_failure);
+        macro_assembler->BindBlock(&ok);
+      }
+      break;
+    }
+    case 4:
+      macro_assembler->CheckCharacter(chars[3], &ok);
+      // Fall through!
+    case 3:
+      macro_assembler->CheckCharacter(chars[0], &ok);
+      macro_assembler->CheckCharacter(chars[1], &ok);
+      macro_assembler->CheckNotCharacter(chars[2], on_failure);
+      macro_assembler->BindBlock(&ok);
+      break;
+    default:
+      UNREACHABLE();
+      break;
+  }
+  return true;
+}
+
+
+static void EmitBoundaryTest(RegExpMacroAssembler* masm,
+                             intptr_t border,
+                             BlockLabel* fall_through,
+                             BlockLabel* above_or_equal,
+                             BlockLabel* below) {
+  if (below != fall_through) {
+    masm->CheckCharacterLT(border, below);
+    if (above_or_equal != fall_through) masm->GoTo(above_or_equal);
+  } else {
+    masm->CheckCharacterGT(border - 1, above_or_equal);
+  }
+}
+
+
+static void EmitDoubleBoundaryTest(RegExpMacroAssembler* masm,
+                                   intptr_t first,
+                                   intptr_t last,
+                                   BlockLabel* fall_through,
+                                   BlockLabel* in_range,
+                                   BlockLabel* out_of_range) {
+  if (in_range == fall_through) {
+    if (first == last) {
+      masm->CheckNotCharacter(first, out_of_range);
+    } else {
+      masm->CheckCharacterNotInRange(first, last, out_of_range);
+    }
+  } else {
+    if (first == last) {
+      masm->CheckCharacter(first, in_range);
+    } else {
+      masm->CheckCharacterInRange(first, last, in_range);
+    }
+    if (out_of_range != fall_through) masm->GoTo(out_of_range);
+  }
+}
+
+
+// even_label is for ranges[i] to ranges[i + 1] where i - start_index is even.
+// odd_label is for ranges[i] to ranges[i + 1] where i - start_index is odd.
+static void EmitUseLookupTable(
+    RegExpMacroAssembler* masm,
+    ZoneGrowableArray<int>* ranges,
+    intptr_t start_index,
+    intptr_t end_index,
+    intptr_t min_char,
+    BlockLabel* fall_through,
+    BlockLabel* even_label,
+    BlockLabel* odd_label) {
+  static const intptr_t kSize = RegExpMacroAssembler::kTableSize;
+  static const intptr_t kMask = RegExpMacroAssembler::kTableMask;
+
+  intptr_t base = (min_char & ~kMask);
+
+  // Assert that everything is on one kTableSize page.
+  for (intptr_t i = start_index; i <= end_index; i++) {
+    ASSERT((ranges->At(i) & ~kMask) == base);
+  }
+  ASSERT(start_index == 0 || (ranges->At(start_index - 1) & ~kMask) <= base);
+
+  char templ[kSize];
+  BlockLabel* on_bit_set;
+  BlockLabel* on_bit_clear;
+  intptr_t bit;
+  if (even_label == fall_through) {
+    on_bit_set = odd_label;
+    on_bit_clear = even_label;
+    bit = 1;
+  } else {
+    on_bit_set = even_label;
+    on_bit_clear = odd_label;
+    bit = 0;
+  }
+  for (intptr_t i = 0; i < (ranges->At(start_index) & kMask) && i < kSize;
+       i++) {
+    templ[i] = bit;
+  }
+  intptr_t j = 0;
+  bit ^= 1;
+  for (intptr_t i = start_index; i < end_index; i++) {
+    for (j = (ranges->At(i) & kMask); j < (ranges->At(i + 1) & kMask); j++) {
+      templ[j] = bit;
+    }
+    bit ^= 1;
+  }
+  for (intptr_t i = j; i < kSize; i++) {
+    templ[i] = bit;
+  }
+  // TODO(erikcorry): Cache these.
+  const TypedData& ba = TypedData::ZoneHandle(
+        masm->isolate(),
+        TypedData::New(kTypedDataUint8ArrayCid, kSize, Heap::kOld));
+  for (intptr_t i = 0; i < kSize; i++) {
+    ba.SetUint8(i, templ[i]);
+  }
+  masm->CheckBitInTable(ba, on_bit_set);
+  if (on_bit_clear != fall_through) masm->GoTo(on_bit_clear);
+}
+
+
+static void CutOutRange(RegExpMacroAssembler* masm,
+                        ZoneGrowableArray<int>* ranges,
+                        intptr_t start_index,
+                        intptr_t end_index,
+                        intptr_t cut_index,
+                        BlockLabel* even_label,
+                        BlockLabel* odd_label) {
+  bool odd = (((cut_index - start_index) & 1) == 1);
+  BlockLabel* in_range_label = odd ? odd_label : even_label;
+  BlockLabel dummy;
+  EmitDoubleBoundaryTest(masm,
+                         ranges->At(cut_index),
+                         ranges->At(cut_index + 1) - 1,
+                         &dummy,
+                         in_range_label,
+                         &dummy);
+  ASSERT(!dummy.IsLinked());
+  // Cut out the single range by rewriting the array.  This creates a new
+  // range that is a merger of the two ranges on either side of the one we
+  // are cutting out.  The oddity of the labels is preserved.
+  for (intptr_t j = cut_index; j > start_index; j--) {
+    (*ranges)[j] = ranges->At(j - 1);
+  }
+  for (intptr_t j = cut_index + 1; j < end_index; j++) {
+    (*ranges)[j] = ranges->At(j + 1);
+  }
+}
+
+
+// Unicode case.  Split the search space into kSize spaces that are handled
+// with recursion.
+static void SplitSearchSpace(ZoneGrowableArray<int>* ranges,
+                             intptr_t start_index,
+                             intptr_t end_index,
+                             intptr_t* new_start_index,
+                             intptr_t* new_end_index,
+                             intptr_t* border) {
+  static const intptr_t kSize = RegExpMacroAssembler::kTableSize;
+  static const intptr_t kMask = RegExpMacroAssembler::kTableMask;
+
+  intptr_t first = ranges->At(start_index);
+  intptr_t last = ranges->At(end_index) - 1;
+
+  *new_start_index = start_index;
+  *border = (ranges->At(start_index) & ~kMask) + kSize;
+  while (*new_start_index < end_index) {
+    if (ranges->At(*new_start_index) > *border) break;
+    (*new_start_index)++;
+  }
+  // new_start_index is the index of the first edge that is beyond the
+  // current kSize space.
+
+  // For very large search spaces we do a binary chop search of the non-Latin1
+  // space instead of just going to the end of the current kSize space.  The
+  // heuristics are complicated a little by the fact that any 128-character
+  // encoding space can be quickly tested with a table lookup, so we don't
+  // wish to do binary chop search at a smaller granularity than that.  A
+  // 128-character space can take up a lot of space in the ranges array if,
+  // for example, we only want to match every second character (eg. the lower
+  // case characters on some Unicode pages).
+  intptr_t binary_chop_index = (end_index + start_index) / 2;
+  // The first test ensures that we get to the code that handles the Latin1
+  // range with a single not-taken branch, speeding up this important
+  // character range (even non-Latin1 charset-based text has spaces and
+  // punctuation).
+  if (*border - 1 > Symbols::kMaxOneCharCodeSymbol &&  // Latin1 case.
+      end_index - start_index > (*new_start_index - start_index) * 2 &&
+      last - first > kSize * 2 &&
+      binary_chop_index > *new_start_index &&
+      ranges->At(binary_chop_index) >= first + 2 * kSize) {
+    intptr_t scan_forward_for_section_border = binary_chop_index;;
+    intptr_t new_border = (ranges->At(binary_chop_index) | kMask) + 1;
+
+    while (scan_forward_for_section_border < end_index) {
+      if (ranges->At(scan_forward_for_section_border) > new_border) {
+        *new_start_index = scan_forward_for_section_border;
+        *border = new_border;
+        break;
+      }
+      scan_forward_for_section_border++;
+    }
+  }
+
+  ASSERT(*new_start_index > start_index);
+  *new_end_index = *new_start_index - 1;
+  if (ranges->At(*new_end_index) == *border) {
+    (*new_end_index)--;
+  }
+  if (*border >= ranges->At(end_index)) {
+    *border = ranges->At(end_index);
+    *new_start_index = end_index;  // Won't be used.
+    *new_end_index = end_index - 1;
+  }
+}
+
+
+// Gets a series of segment boundaries representing a character class.  If the
+// character is in the range between an even and an odd boundary (counting from
+// start_index) then go to even_label, otherwise go to odd_label.  We already
+// know that the character is in the range of min_char to max_char inclusive.
+// Either label can be NULL indicating backtracking.  Either label can also be
+// equal to the fall_through label.
+static void GenerateBranches(RegExpMacroAssembler* masm,
+                             ZoneGrowableArray<int>* ranges,
+                             intptr_t start_index,
+                             intptr_t end_index,
+                             uint16_t min_char,
+                             uint16_t max_char,
+                             BlockLabel* fall_through,
+                             BlockLabel* even_label,
+                             BlockLabel* odd_label) {
+  intptr_t first = ranges->At(start_index);
+  intptr_t last = ranges->At(end_index) - 1;
+
+  ASSERT(min_char < first);
+
+  // Just need to test if the character is before or on-or-after
+  // a particular character.
+  if (start_index == end_index) {
+    EmitBoundaryTest(masm, first, fall_through, even_label, odd_label);
+    return;
+  }
+
+  // Another almost trivial case:  There is one interval in the middle that is
+  // different from the end intervals.
+  if (start_index + 1 == end_index) {
+    EmitDoubleBoundaryTest(
+        masm, first, last, fall_through, even_label, odd_label);
+    return;
+  }
+
+  // It's not worth using table lookup if there are very few intervals in the
+  // character class.
+  if (end_index - start_index <= 6) {
+    // It is faster to test for individual characters, so we look for those
+    // first, then try arbitrary ranges in the second round.
+    static intptr_t kNoCutIndex = -1;
+    intptr_t cut = kNoCutIndex;
+    for (intptr_t i = start_index; i < end_index; i++) {
+      if (ranges->At(i) == ranges->At(i + 1) - 1) {
+        cut = i;
+        break;
+      }
+    }
+    if (cut == kNoCutIndex) cut = start_index;
+    CutOutRange(
+        masm, ranges, start_index, end_index, cut, even_label, odd_label);
+    ASSERT(end_index - start_index >= 2);
+    GenerateBranches(masm,
+                     ranges,
+                     start_index + 1,
+                     end_index - 1,
+                     min_char,
+                     max_char,
+                     fall_through,
+                     even_label,
+                     odd_label);
+    return;
+  }
+
+  // If there are a lot of intervals in the regexp, then we will use tables to
+  // determine whether the character is inside or outside the character class.
+  static const intptr_t kBits = RegExpMacroAssembler::kTableSizeBits;
+
+  if ((max_char >> kBits) == (min_char >> kBits)) {
+    EmitUseLookupTable(masm,
+                       ranges,
+                       start_index,
+                       end_index,
+                       min_char,
+                       fall_through,
+                       even_label,
+                       odd_label);
+    return;
+  }
+
+  if ((min_char >> kBits) != (first >> kBits)) {
+    masm->CheckCharacterLT(first, odd_label);
+    GenerateBranches(masm,
+                     ranges,
+                     start_index + 1,
+                     end_index,
+                     first,
+                     max_char,
+                     fall_through,
+                     odd_label,
+                     even_label);
+    return;
+  }
+
+  intptr_t new_start_index = 0;
+  intptr_t new_end_index = 0;
+  intptr_t border = 0;
+
+  SplitSearchSpace(ranges,
+                   start_index,
+                   end_index,
+                   &new_start_index,
+                   &new_end_index,
+                   &border);
+
+  BlockLabel handle_rest;
+  BlockLabel* above = &handle_rest;
+  if (border == last + 1) {
+    // We didn't find any section that started after the limit, so everything
+    // above the border is one of the terminal labels.
+    above = (end_index & 1) != (start_index & 1) ? odd_label : even_label;
+    ASSERT(new_end_index == end_index - 1);
+  }
+
+  ASSERT(start_index <= new_end_index);
+  ASSERT(new_start_index <= end_index);
+  ASSERT(start_index < new_start_index);
+  ASSERT(new_end_index < end_index);
+  ASSERT(new_end_index + 1 == new_start_index ||
+         (new_end_index + 2 == new_start_index &&
+          border == ranges->At(new_end_index + 1)));
+  ASSERT(min_char < border - 1);
+  ASSERT(border < max_char);
+  ASSERT(ranges->At(new_end_index) < border);
+  ASSERT(border < ranges->At(new_start_index) ||
+         (border == ranges->At(new_start_index) &&
+          new_start_index == end_index &&
+          new_end_index == end_index - 1 &&
+          border == last + 1));
+  ASSERT(new_start_index == 0 || border >= ranges->At(new_start_index - 1));
+
+  masm->CheckCharacterGT(border - 1, above);
+  BlockLabel dummy;
+  GenerateBranches(masm,
+                   ranges,
+                   start_index,
+                   new_end_index,
+                   min_char,
+                   border - 1,
+                   &dummy,
+                   even_label,
+                   odd_label);
+
+  if (handle_rest.IsLinked()) {
+    masm->BindBlock(&handle_rest);
+    bool flip = (new_start_index & 1) != (start_index & 1);
+    GenerateBranches(masm,
+                     ranges,
+                     new_start_index,
+                     end_index,
+                     border,
+                     max_char,
+                     &dummy,
+                     flip ? odd_label : even_label,
+                     flip ? even_label : odd_label);
+  }
+}
+
+
+static void EmitCharClass(RegExpMacroAssembler* macro_assembler,
+                          RegExpCharacterClass* cc,
+                          bool one_byte,
+                          BlockLabel* on_failure,
+                          intptr_t cp_offset,
+                          bool check_offset,
+                          bool preloaded,
+                          Isolate* isolate) {
+  ZoneGrowableArray<CharacterRange>* ranges = cc->ranges();
+  if (!CharacterRange::IsCanonical(ranges)) {
+    CharacterRange::Canonicalize(ranges);
+  }
+
+  intptr_t max_char;
+  if (one_byte) {
+    max_char = Symbols::kMaxOneCharCodeSymbol;
+  } else {
+    max_char = Utf16::kMaxCodeUnit;
+  }
+
+  intptr_t range_count = ranges->length();
+
+  intptr_t last_valid_range = range_count - 1;
+  while (last_valid_range >= 0) {
+    CharacterRange& range = (*ranges)[last_valid_range];
+    if (range.from() <= max_char) {
+      break;
+    }
+    last_valid_range--;
+  }
+
+  if (last_valid_range < 0) {
+    if (!cc->is_negated()) {
+      macro_assembler->GoTo(on_failure);
+    }
+    if (check_offset) {
+      macro_assembler->CheckPosition(cp_offset, on_failure);
+    }
+    return;
+  }
+
+  if (last_valid_range == 0 &&
+      ranges->At(0).IsEverything(max_char)) {
+    if (cc->is_negated()) {
+      macro_assembler->GoTo(on_failure);
+    } else {
+      // This is a common case hit by non-anchored expressions.
+      if (check_offset) {
+        macro_assembler->CheckPosition(cp_offset, on_failure);
+      }
+    }
+    return;
+  }
+  if (last_valid_range == 0 &&
+      !cc->is_negated() &&
+      ranges->At(0).IsEverything(max_char)) {
+    // This is a common case hit by non-anchored expressions.
+    if (check_offset) {
+      macro_assembler->CheckPosition(cp_offset, on_failure);
+    }
+    return;
+  }
+
+  if (!preloaded) {
+    macro_assembler->LoadCurrentCharacter(cp_offset, on_failure, check_offset);
+  }
+
+  if (cc->is_standard() &&
+        macro_assembler->CheckSpecialCharacterClass(cc->standard_type(),
+                                                    on_failure)) {
+      return;
+  }
+
+
+  // A new list with ascending entries.  Each entry is a code unit
+  // where there is a boundary between code units that are part of
+  // the class and code units that are not.  Normally we insert an
+  // entry at zero which goes to the failure label, but if there
+  // was already one there we fall through for success on that entry.
+  // Subsequent entries have alternating meaning (success/failure).
+  ZoneGrowableArray<int>* range_boundaries =
+      new(isolate) ZoneGrowableArray<int>(last_valid_range);
+
+  bool zeroth_entry_is_failure = !cc->is_negated();
+
+  for (intptr_t i = 0; i <= last_valid_range; i++) {
+    CharacterRange& range = (*ranges)[i];
+    if (range.from() == 0) {
+      ASSERT(i == 0);
+      zeroth_entry_is_failure = !zeroth_entry_is_failure;
+    } else {
+      range_boundaries->Add(range.from());
+    }
+    range_boundaries->Add(range.to() + 1);
+  }
+  intptr_t end_index = range_boundaries->length() - 1;
+  if (range_boundaries->At(end_index) > max_char) {
+    end_index--;
+  }
+
+  BlockLabel fall_through;
+  GenerateBranches(macro_assembler,
+                   range_boundaries,
+                   0,  // start_index.
+                   end_index,
+                   0,  // min_char.
+                   max_char,
+                   &fall_through,
+                   zeroth_entry_is_failure ? &fall_through : on_failure,
+                   zeroth_entry_is_failure ? on_failure : &fall_through);
+  macro_assembler->BindBlock(&fall_through);
+}
+
+
+RegExpNode::~RegExpNode() {
+}
+
+
+RegExpNode::LimitResult RegExpNode::LimitVersions(RegExpCompiler* compiler,
+                                                  Trace* trace) {
+  // If we are generating a greedy loop then don't stop and don't reuse code.
+  if (trace->stop_node() != NULL) {
+    return CONTINUE;
+  }
+
+  RegExpMacroAssembler* macro_assembler = compiler->macro_assembler();
+  if (trace->is_trivial()) {
+    if (label_.IsBound()) {
+      // We are being asked to generate a generic version, but that's already
+      // been done so just go to it.
+      macro_assembler->GoTo(&label_);
+      return DONE;
+    }
+    if (compiler->recursion_depth() >= RegExpCompiler::kMaxRecursion) {
+      // To avoid too deep recursion we push the node to the work queue and just
+      // generate a goto here.
+      compiler->AddWork(this);
+      macro_assembler->GoTo(&label_);
+      return DONE;
+    }
+    // Generate generic version of the node and bind the label for later use.
+    macro_assembler->BindBlock(&label_);
+    return CONTINUE;
+  }
+
+  // We are being asked to make a non-generic version.  Keep track of how many
+  // non-generic versions we generate so as not to overdo it.
+  trace_count_++;
+  if (kRegexpOptimization &&
+      trace_count_ < kMaxCopiesCodeGenerated &&
+      compiler->recursion_depth() <= RegExpCompiler::kMaxRecursion) {
+    return CONTINUE;
+  }
+
+  // If we get here code has been generated for this node too many times or
+  // recursion is too deep.  Time to switch to a generic version.  The code for
+  // generic versions above can handle deep recursion properly.
+  trace->Flush(compiler, this);
+  return DONE;
+}
+
+
+intptr_t ActionNode::EatsAtLeast(intptr_t still_to_find,
+                                 intptr_t budget,
+                                 bool not_at_start) {
+  if (budget <= 0) return 0;
+  if (action_type_ == POSITIVE_SUBMATCH_SUCCESS) return 0;  // Rewinds input!
+  return on_success()->EatsAtLeast(still_to_find,
+                                   budget - 1,
+                                   not_at_start);
+}
+
+
+void ActionNode::FillInBMInfo(intptr_t offset,
+                              intptr_t budget,
+                              BoyerMooreLookahead* bm,
+                              bool not_at_start) {
+  if (action_type_ == BEGIN_SUBMATCH) {
+    bm->SetRest(offset);
+  } else if (action_type_ != POSITIVE_SUBMATCH_SUCCESS) {
+    on_success()->FillInBMInfo(offset, budget - 1, bm, not_at_start);
+  }
+  SaveBMInfo(bm, not_at_start, offset);
+}
+
+
+intptr_t AssertionNode::EatsAtLeast(intptr_t still_to_find,
+                                    intptr_t budget,
+                                    bool not_at_start) {
+  if (budget <= 0) return 0;
+  // If we know we are not at the start and we are asked "how many characters
+  // will you match if you succeed?" then we can answer anything since false
+  // implies false.  So lets just return the max answer (still_to_find) since
+  // that won't prevent us from preloading a lot of characters for the other
+  // branches in the node graph.
+  if (assertion_type() == AT_START && not_at_start) return still_to_find;
+  return on_success()->EatsAtLeast(still_to_find,
+                                   budget - 1,
+                                   not_at_start);
+}
+
+
+void AssertionNode::FillInBMInfo(intptr_t offset,
+                                 intptr_t budget,
+                                 BoyerMooreLookahead* bm,
+                                 bool not_at_start) {
+  // Match the behaviour of EatsAtLeast on this node.
+  if (assertion_type() == AT_START && not_at_start) return;
+  on_success()->FillInBMInfo(offset, budget - 1, bm, not_at_start);
+  SaveBMInfo(bm, not_at_start, offset);
+}
+
+
+intptr_t BackReferenceNode::EatsAtLeast(intptr_t still_to_find,
+                                        intptr_t budget,
+                                        bool not_at_start) {
+  if (budget <= 0) return 0;
+  return on_success()->EatsAtLeast(still_to_find,
+                                   budget - 1,
+                                   not_at_start);
+}
+
+
+intptr_t TextNode::EatsAtLeast(intptr_t still_to_find,
+                               intptr_t budget,
+                               bool not_at_start) {
+  intptr_t answer = Length();
+  if (answer >= still_to_find) return answer;
+  if (budget <= 0) return answer;
+  // We are not at start after this node so we set the last argument to 'true'.
+  return answer + on_success()->EatsAtLeast(still_to_find - answer,
+                                            budget - 1,
+                                            true);
+}
+
+
+intptr_t NegativeLookaheadChoiceNode::EatsAtLeast(intptr_t still_to_find,
+                                                  intptr_t budget,
+                                                  bool not_at_start) {
+  if (budget <= 0) return 0;
+  // Alternative 0 is the negative lookahead, alternative 1 is what comes
+  // afterwards.
+  RegExpNode* node = (*alternatives_)[1].node();
+  return node->EatsAtLeast(still_to_find, budget - 1, not_at_start);
+}
+
+
+void NegativeLookaheadChoiceNode::GetQuickCheckDetails(
+    QuickCheckDetails* details,
+    RegExpCompiler* compiler,
+    intptr_t filled_in,
+    bool not_at_start) {
+  // Alternative 0 is the negative lookahead, alternative 1 is what comes
+  // afterwards.
+  RegExpNode* node = (*alternatives_)[1].node();
+  return node->GetQuickCheckDetails(details, compiler, filled_in, not_at_start);
+}
+
+
+intptr_t ChoiceNode::EatsAtLeastHelper(intptr_t still_to_find,
+                                       intptr_t budget,
+                                       RegExpNode* ignore_this_node,
+                                       bool not_at_start) {
+  if (budget <= 0) return 0;
+  intptr_t min = 100;
+  intptr_t choice_count = alternatives_->length();
+  budget = (budget - 1) / choice_count;
+  for (intptr_t i = 0; i < choice_count; i++) {
+    RegExpNode* node = (*alternatives_)[i].node();
+    if (node == ignore_this_node) continue;
+    intptr_t node_eats_at_least =
+        node->EatsAtLeast(still_to_find, budget, not_at_start);
+    if (node_eats_at_least < min) min = node_eats_at_least;
+    if (min == 0) return 0;
+  }
+  return min;
+}
+
+
+intptr_t LoopChoiceNode::EatsAtLeast(intptr_t still_to_find,
+                                     intptr_t budget,
+                                     bool not_at_start) {
+  return EatsAtLeastHelper(still_to_find,
+                           budget - 1,
+                           loop_node_,
+                           not_at_start);
+}
+
+
+intptr_t ChoiceNode::EatsAtLeast(intptr_t still_to_find,
+                                 intptr_t budget,
+                                 bool not_at_start) {
+  return EatsAtLeastHelper(still_to_find,
+                           budget,
+                           NULL,
+                           not_at_start);
+}
+
+
+// Takes the left-most 1-bit and smears it out, setting all bits to its right.
+static inline uint32_t SmearBitsRight(uint32_t v) {
+  v |= v >> 1;
+  v |= v >> 2;
+  v |= v >> 4;
+  v |= v >> 8;
+  v |= v >> 16;
+  return v;
+}
+
+
+bool QuickCheckDetails::Rationalize(bool asc) {
+  bool found_useful_op = false;
+  uint32_t char_mask;
+  if (asc) {
+    char_mask = Symbols::kMaxOneCharCodeSymbol;
+  } else {
+    char_mask = Utf16::kMaxCodeUnit;
+  }
+  mask_ = 0;
+  value_ = 0;
+  intptr_t char_shift = 0;
+  for (intptr_t i = 0; i < characters_; i++) {
+    Position* pos = &positions_[i];
+    if ((pos->mask & Symbols::kMaxOneCharCodeSymbol) != 0) {
+      found_useful_op = true;
+    }
+    mask_ |= (pos->mask & char_mask) << char_shift;
+    value_ |= (pos->value & char_mask) << char_shift;
+    char_shift += asc ? 8 : 16;
+  }
+  return found_useful_op;
+}
+
+
+bool RegExpNode::EmitQuickCheck(RegExpCompiler* compiler,
+                                Trace* bounds_check_trace,
+                                Trace* trace,
+                                bool preload_has_checked_bounds,
+                                BlockLabel* on_possible_success,
+                                QuickCheckDetails* details,
+                                bool fall_through_on_failure) {
+  if (details->characters() == 0) return false;
+  GetQuickCheckDetails(
+      details, compiler, 0, trace->at_start() == Trace::FALSE_VALUE);
+  if (details->cannot_match()) return false;
+  if (!details->Rationalize(compiler->one_byte())) return false;
+  ASSERT(details->characters() == 1 ||
+         compiler->macro_assembler()->CanReadUnaligned());
+  uint32_t mask = details->mask();
+  uint32_t value = details->value();
+
+  RegExpMacroAssembler* assembler = compiler->macro_assembler();
+
+  if (trace->characters_preloaded() != details->characters()) {
+    ASSERT(trace->cp_offset() == bounds_check_trace->cp_offset());
+    // We are attempting to preload the minimum number of characters
+    // any choice would eat, so if the bounds check fails, then none of the
+    // choices can succeed, so we can just immediately backtrack, rather
+    // than go to the next choice.
+    assembler->LoadCurrentCharacter(trace->cp_offset(),
+                                    bounds_check_trace->backtrack(),
+                                    !preload_has_checked_bounds,
+                                    details->characters());
+  }
+
+
+  bool need_mask = true;
+
+  if (details->characters() == 1) {
+    // If number of characters preloaded is 1 then we used a byte or 16 bit
+    // load so the value is already masked down.
+    uint32_t char_mask;
+    if (compiler->one_byte()) {
+      char_mask = Symbols::kMaxOneCharCodeSymbol;
+    } else {
+      char_mask = Utf16::kMaxCodeUnit;
+    }
+    if ((mask & char_mask) == char_mask) need_mask = false;
+    mask &= char_mask;
+  } else {
+    // For 2-character preloads in one-byte mode or 1-character preloads in
+    // two-byte mode we also use a 16 bit load with zero extend.
+    if (details->characters() == 2 && compiler->one_byte()) {
+      if ((mask & 0xffff) == 0xffff) need_mask = false;
+    } else if (details->characters() == 1 && !compiler->one_byte()) {
+      if ((mask & 0xffff) == 0xffff) need_mask = false;
+    } else {
+      if (mask == 0xffffffff) need_mask = false;
+    }
+  }
+
+  if (fall_through_on_failure) {
+    if (need_mask) {
+      assembler->CheckCharacterAfterAnd(value, mask, on_possible_success);
+    } else {
+      assembler->CheckCharacter(value, on_possible_success);
+    }
+  } else {
+    if (need_mask) {
+      assembler->CheckNotCharacterAfterAnd(value, mask, trace->backtrack());
+    } else {
+      assembler->CheckNotCharacter(value, trace->backtrack());
+    }
+  }
+  return true;
+}
+
+
+// Here is the meat of GetQuickCheckDetails (see also the comment on the
+// super-class in the .h file).
+//
+// We iterate along the text object, building up for each character a
+// mask and value that can be used to test for a quick failure to match.
+// The masks and values for the positions will be combined into a single
+// machine word for the current character width in order to be used in
+// generating a quick check.
+void TextNode::GetQuickCheckDetails(QuickCheckDetails* details,
+                                    RegExpCompiler* compiler,
+                                    intptr_t characters_filled_in,
+                                    bool not_at_start) {
+  ASSERT(characters_filled_in < details->characters());
+  intptr_t characters = details->characters();
+  intptr_t char_mask;
+  if (compiler->one_byte()) {
+    char_mask = Symbols::kMaxOneCharCodeSymbol;
+  } else {
+    char_mask = Utf16::kMaxCodeUnit;
+  }
+  for (intptr_t k = 0; k < elms_->length(); k++) {
+    TextElement elm = elms_->At(k);
+    if (elm.text_type() == TextElement::ATOM) {
+      ZoneGrowableArray<uint16_t>* quarks = elm.atom()->data();
+      for (intptr_t i = 0; i < characters && i < quarks->length(); i++) {
+        QuickCheckDetails::Position* pos =
+            details->positions(characters_filled_in);
+        uint16_t c = quarks->At(i);
+        if (c > char_mask) {
+          // If we expect a non-Latin1 character from an one-byte string,
+          // there is no way we can match. Not even case independent
+          // matching can turn an Latin1 character into non-Latin1 or
+          // vice versa.
+          // TODO(dcarney): issue 3550.  Verify that this works as expected.
+          // For example, \u0178 is uppercase of \u00ff (y-umlaut).
+          details->set_cannot_match();
+          pos->determines_perfectly = false;
+          return;
+        }
+        if (compiler->ignore_case()) {
+          int32_t chars[unibrow::Ecma262UnCanonicalize::kMaxWidth];
+          intptr_t length =
+              GetCaseIndependentLetters(c, compiler->one_byte(), chars);
+          ASSERT(length != 0);  // Can only happen if c > char_mask (see above).
+          if (length == 1) {
+            // This letter has no case equivalents, so it's nice and simple
+            // and the mask-compare will determine definitely whether we have
+            // a match at this character position.
+            pos->mask = char_mask;
+            pos->value = c;
+            pos->determines_perfectly = true;
+          } else {
+            uint32_t common_bits = char_mask;
+            uint32_t bits = chars[0];
+            for (intptr_t j = 1; j < length; j++) {
+              uint32_t differing_bits = ((chars[j] & common_bits) ^ bits);
+              common_bits ^= differing_bits;
+              bits &= common_bits;
+            }
+            // If length is 2 and common bits has only one zero in it then
+            // our mask and compare instruction will determine definitely
+            // whether we have a match at this character position.  Otherwise
+            // it can only be an approximate check.
+            uint32_t one_zero = (common_bits | ~char_mask);
+            if (length == 2 && ((~one_zero) & ((~one_zero) - 1)) == 0) {
+              pos->determines_perfectly = true;
+            }
+            pos->mask = common_bits;
+            pos->value = bits;
+          }
+        } else {
+          // Don't ignore case.  Nice simple case where the mask-compare will
+          // determine definitely whether we have a match at this character
+          // position.
+          pos->mask = char_mask;
+          pos->value = c;
+          pos->determines_perfectly = true;
+        }
+        characters_filled_in++;
+        ASSERT(characters_filled_in <= details->characters());
+        if (characters_filled_in == details->characters()) {
+          return;
+        }
+      }
+    } else {
+      QuickCheckDetails::Position* pos =
+          details->positions(characters_filled_in);
+      RegExpCharacterClass* tree = elm.char_class();
+      ZoneGrowableArray<CharacterRange>* ranges = tree->ranges();
+      if (tree->is_negated()) {
+        // A quick check uses multi-character mask and compare.  There is no
+        // useful way to incorporate a negative char class into this scheme
+        // so we just conservatively create a mask and value that will always
+        // succeed.
+        pos->mask = 0;
+        pos->value = 0;
+      } else {
+        intptr_t first_range = 0;
+        while (ranges->At(first_range).from() > char_mask) {
+          first_range++;
+          if (first_range == ranges->length()) {
+            details->set_cannot_match();
+            pos->determines_perfectly = false;
+            return;
+          }
+        }
+        CharacterRange range = ranges->At(first_range);
+        uint16_t from = range.from();
+        uint16_t to = range.to();
+        if (to > char_mask) {
+          to = char_mask;
+        }
+        uint32_t differing_bits = (from ^ to);
+        // A mask and compare is only perfect if the differing bits form a
+        // number like 00011111 with one single block of trailing 1s.
+        if ((differing_bits & (differing_bits + 1)) == 0 &&
+             from + differing_bits == to) {
+          pos->determines_perfectly = true;
+        }
+        uint32_t common_bits = ~SmearBitsRight(differing_bits);
+        uint32_t bits = (from & common_bits);
+        for (intptr_t i = first_range + 1; i < ranges->length(); i++) {
+          CharacterRange range = ranges->At(i);
+          uint16_t from = range.from();
+          uint16_t to = range.to();
+          if (from > char_mask) continue;
+          if (to > char_mask) to = char_mask;
+          // Here we are combining more ranges into the mask and compare
+          // value.  With each new range the mask becomes more sparse and
+          // so the chances of a false positive rise.  A character class
+          // with multiple ranges is assumed never to be equivalent to a
+          // mask and compare operation.
+          pos->determines_perfectly = false;
+          uint32_t new_common_bits = (from ^ to);
+          new_common_bits = ~SmearBitsRight(new_common_bits);
+          common_bits &= new_common_bits;
+          bits &= new_common_bits;
+          uint32_t differing_bits = (from & common_bits) ^ bits;
+          common_bits ^= differing_bits;
+          bits &= common_bits;
+        }
+        pos->mask = common_bits;
+        pos->value = bits;
+      }
+      characters_filled_in++;
+      ASSERT(characters_filled_in <= details->characters());
+      if (characters_filled_in == details->characters()) {
+        return;
+      }
+    }
+  }
+  ASSERT(characters_filled_in != details->characters());
+  if (!details->cannot_match()) {
+    on_success()-> GetQuickCheckDetails(details,
+                                        compiler,
+                                        characters_filled_in,
+                                        true);
+  }
+}
+
+
+void QuickCheckDetails::Clear() {
+  for (int i = 0; i < characters_; i++) {
+    positions_[i].mask = 0;
+    positions_[i].value = 0;
+    positions_[i].determines_perfectly = false;
+  }
+  characters_ = 0;
+}
+
+
+void QuickCheckDetails::Advance(intptr_t by, bool one_byte) {
+  ASSERT(by >= 0);
+  if (by >= characters_) {
+    Clear();
+    return;
+  }
+  for (intptr_t i = 0; i < characters_ - by; i++) {
+    positions_[i] = positions_[by + i];
+  }
+  for (intptr_t i = characters_ - by; i < characters_; i++) {
+    positions_[i].mask = 0;
+    positions_[i].value = 0;
+    positions_[i].determines_perfectly = false;
+  }
+  characters_ -= by;
+  // We could change mask_ and value_ here but we would never advance unless
+  // they had already been used in a check and they won't be used again because
+  // it would gain us nothing.  So there's no point.
+}
+
+
+void QuickCheckDetails::Merge(QuickCheckDetails* other, intptr_t from_index) {
+  ASSERT(characters_ == other->characters_);
+  if (other->cannot_match_) {
+    return;
+  }
+  if (cannot_match_) {
+    *this = *other;
+    return;
+  }
+  for (intptr_t i = from_index; i < characters_; i++) {
+    QuickCheckDetails::Position* pos = positions(i);
+    QuickCheckDetails::Position* other_pos = other->positions(i);
+    if (pos->mask != other_pos->mask ||
+        pos->value != other_pos->value ||
+        !other_pos->determines_perfectly) {
+      // Our mask-compare operation will be approximate unless we have the
+      // exact same operation on both sides of the alternation.
+      pos->determines_perfectly = false;
+    }
+    pos->mask &= other_pos->mask;
+    pos->value &= pos->mask;
+    other_pos->value &= pos->mask;
+    uint16_t differing_bits = (pos->value ^ other_pos->value);
+    pos->mask &= ~differing_bits;
+    pos->value &= pos->mask;
+  }
+}
+
+
+class VisitMarker : public ValueObject {
+ public:
+  explicit VisitMarker(NodeInfo* info) : info_(info) {
+    ASSERT(!info->visited);
+    info->visited = true;
+  }
+  ~VisitMarker() {
+    info_->visited = false;
+  }
+ private:
+  NodeInfo* info_;
+};
+
+
+RegExpNode* SeqRegExpNode::FilterOneByte(intptr_t depth, bool ignore_case) {
+  if (info()->replacement_calculated) return replacement();
+  if (depth < 0) return this;
+  ASSERT(!info()->visited);
+  VisitMarker marker(info());
+  return FilterSuccessor(depth - 1, ignore_case);
+}
+
+
+RegExpNode* SeqRegExpNode::FilterSuccessor(intptr_t depth, bool ignore_case) {
+  RegExpNode* next = on_success_->FilterOneByte(depth - 1, ignore_case);
+  if (next == NULL) return set_replacement(NULL);
+  on_success_ = next;
+  return set_replacement(this);
+}
+
+
+// We need to check for the following characters: 0x39c 0x3bc 0x178.
+static inline bool RangeContainsLatin1Equivalents(CharacterRange range) {
+  // TODO(dcarney): this could be a lot more efficient.
+  return range.Contains(0x39c) ||
+      range.Contains(0x3bc) || range.Contains(0x178);
+}
+
+
+static bool RangesContainLatin1Equivalents(
+    ZoneGrowableArray<CharacterRange>* ranges) {
+  for (intptr_t i = 0; i < ranges->length(); i++) {
+    // TODO(dcarney): this could be a lot more efficient.
+    if (RangeContainsLatin1Equivalents(ranges->At(i))) return true;
+  }
+  return false;
+}
+
+
+static uint16_t ConvertNonLatin1ToLatin1(uint16_t c) {
+  ASSERT(c > Symbols::kMaxOneCharCodeSymbol);
+  switch (c) {
+    // This are equivalent characters in unicode.
+    case 0x39c:
+    case 0x3bc:
+      return 0xb5;
+    // This is an uppercase of a Latin-1 character
+    // outside of Latin-1.
+    case 0x178:
+      return 0xff;
+  }
+  return 0;
+}
+
+
+RegExpNode* TextNode::FilterOneByte(intptr_t depth, bool ignore_case) {
+  if (info()->replacement_calculated) return replacement();
+  if (depth < 0) return this;
+  ASSERT(!info()->visited);
+  VisitMarker marker(info());
+  intptr_t element_count = elms_->length();
+  for (intptr_t i = 0; i < element_count; i++) {
+    TextElement elm = elms_->At(i);
+    if (elm.text_type() == TextElement::ATOM) {
+      ZoneGrowableArray<uint16_t>* quarks = elm.atom()->data();
+      for (intptr_t j = 0; j < quarks->length(); j++) {
+        uint16_t c = quarks->At(j);
+        if (c <= Symbols::kMaxOneCharCodeSymbol) continue;
+        if (!ignore_case) return set_replacement(NULL);
+        // Here, we need to check for characters whose upper and lower cases
+        // are outside the Latin-1 range.
+        uint16_t converted = ConvertNonLatin1ToLatin1(c);
+        // Character is outside Latin-1 completely
+        if (converted == 0) return set_replacement(NULL);
+        // Convert quark to Latin-1 in place.
+        (*quarks)[0] = converted;
+      }
+    } else {
+      ASSERT(elm.text_type() == TextElement::CHAR_CLASS);
+      RegExpCharacterClass* cc = elm.char_class();
+      ZoneGrowableArray<CharacterRange>* ranges = cc->ranges();
+      if (!CharacterRange::IsCanonical(ranges)) {
+        CharacterRange::Canonicalize(ranges);
+      }
+      // Now they are in order so we only need to look at the first.
+      intptr_t range_count = ranges->length();
+      if (cc->is_negated()) {
+        if (range_count != 0 &&
+            ranges->At(0).from() == 0 &&
+            ranges->At(0).to() >= Symbols::kMaxOneCharCodeSymbol) {
+          // This will be handled in a later filter.
+          if (ignore_case && RangesContainLatin1Equivalents(ranges)) continue;
+          return set_replacement(NULL);
+        }
+      } else {
+        if (range_count == 0 ||
+            ranges->At(0).from() > Symbols::kMaxOneCharCodeSymbol) {
+          // This will be handled in a later filter.
+          if (ignore_case && RangesContainLatin1Equivalents(ranges)) continue;
+          return set_replacement(NULL);
+        }
+      }
+    }
+  }
+  return FilterSuccessor(depth - 1, ignore_case);
+}
+
+
+RegExpNode* LoopChoiceNode::FilterOneByte(intptr_t depth, bool ignore_case) {
+  if (info()->replacement_calculated) return replacement();
+  if (depth < 0) return this;
+  if (info()->visited) return this;
+  {
+    VisitMarker marker(info());
+
+    RegExpNode* continue_replacement =
+        continue_node_->FilterOneByte(depth - 1, ignore_case);
+    // If we can't continue after the loop then there is no sense in doing the
+    // loop.
+    if (continue_replacement == NULL) return set_replacement(NULL);
+  }
+
+  return ChoiceNode::FilterOneByte(depth - 1, ignore_case);
+}
+
+
+RegExpNode* ChoiceNode::FilterOneByte(intptr_t depth, bool ignore_case) {
+  if (info()->replacement_calculated) return replacement();
+  if (depth < 0) return this;
+  if (info()->visited) return this;
+  VisitMarker marker(info());
+  intptr_t choice_count = alternatives_->length();
+
+  for (intptr_t i = 0; i < choice_count; i++) {
+    GuardedAlternative alternative = alternatives_->At(i);
+    if (alternative.guards() != NULL && alternative.guards()->length() != 0) {
+      set_replacement(this);
+      return this;
+    }
+  }
+
+  intptr_t surviving = 0;
+  RegExpNode* survivor = NULL;
+  for (intptr_t i = 0; i < choice_count; i++) {
+    GuardedAlternative alternative = alternatives_->At(i);
+    RegExpNode* replacement =
+        alternative.node()->FilterOneByte(depth - 1, ignore_case);
+    ASSERT(replacement != this);  // No missing EMPTY_MATCH_CHECK.
+    if (replacement != NULL) {
+      (*alternatives_)[i].set_node(replacement);
+      surviving++;
+      survivor = replacement;
+    }
+  }
+  if (surviving < 2) return set_replacement(survivor);
+
+  set_replacement(this);
+  if (surviving == choice_count) {
+    return this;
+  }
+  // Only some of the nodes survived the filtering.  We need to rebuild the
+  // alternatives list.
+  ZoneGrowableArray<GuardedAlternative>* new_alternatives =
+      new(I) ZoneGrowableArray<GuardedAlternative>(surviving);
+  for (intptr_t i = 0; i < choice_count; i++) {
+    RegExpNode* replacement =
+        (*alternatives_)[i].node()->FilterOneByte(depth - 1, ignore_case);
+    if (replacement != NULL) {
+      (*alternatives_)[i].set_node(replacement);
+      new_alternatives->Add((*alternatives_)[i]);
+    }
+  }
+  alternatives_ = new_alternatives;
+  return this;
+}
+
+
+RegExpNode* NegativeLookaheadChoiceNode::FilterOneByte(intptr_t depth,
+                                                       bool ignore_case) {
+  if (info()->replacement_calculated) return replacement();
+  if (depth < 0) return this;
+  if (info()->visited) return this;
+  VisitMarker marker(info());
+  // Alternative 0 is the negative lookahead, alternative 1 is what comes
+  // afterwards.
+  RegExpNode* node = (*alternatives_)[1].node();
+  RegExpNode* replacement = node->FilterOneByte(depth - 1, ignore_case);
+  if (replacement == NULL) return set_replacement(NULL);
+  (*alternatives_)[1].set_node(replacement);
+
+  RegExpNode* neg_node = (*alternatives_)[0].node();
+  RegExpNode* neg_replacement = neg_node->FilterOneByte(depth - 1, ignore_case);
+  // If the negative lookahead is always going to fail then
+  // we don't need to check it.
+  if (neg_replacement == NULL) return set_replacement(replacement);
+  (*alternatives_)[0].set_node(neg_replacement);
+  return set_replacement(this);
+}
+
+
+void LoopChoiceNode::GetQuickCheckDetails(QuickCheckDetails* details,
+                                          RegExpCompiler* compiler,
+                                          intptr_t characters_filled_in,
+                                          bool not_at_start) {
+  if (body_can_be_zero_length_ || info()->visited) return;
+  VisitMarker marker(info());
+  return ChoiceNode::GetQuickCheckDetails(details,
+                                          compiler,
+                                          characters_filled_in,
+                                          not_at_start);
+}
+
+
+void LoopChoiceNode::FillInBMInfo(intptr_t offset,
+                                  intptr_t budget,
+                                  BoyerMooreLookahead* bm,
+                                  bool not_at_start) {
+  if (body_can_be_zero_length_ || budget <= 0) {
+    bm->SetRest(offset);
+    SaveBMInfo(bm, not_at_start, offset);
+    return;
+  }
+  ChoiceNode::FillInBMInfo(offset, budget - 1, bm, not_at_start);
+  SaveBMInfo(bm, not_at_start, offset);
+}
+
+
+void ChoiceNode::GetQuickCheckDetails(QuickCheckDetails* details,
+                                      RegExpCompiler* compiler,
+                                      intptr_t characters_filled_in,
+                                      bool not_at_start) {
+  not_at_start = (not_at_start || not_at_start_);
+  intptr_t choice_count = alternatives_->length();
+  ASSERT(choice_count > 0);
+  (*alternatives_)[0].node()->GetQuickCheckDetails(details,
+                                                    compiler,
+                                                    characters_filled_in,
+                                                    not_at_start);
+  for (intptr_t i = 1; i < choice_count; i++) {
+    QuickCheckDetails new_details(details->characters());
+    RegExpNode* node = (*alternatives_)[i].node();
+    node->GetQuickCheckDetails(&new_details, compiler,
+                               characters_filled_in,
+                               not_at_start);
+    // Here we merge the quick match details of the two branches.
+    details->Merge(&new_details, characters_filled_in);
+  }
+}
+
+
+// Check for [0-9A-Z_a-z].
+static void EmitWordCheck(RegExpMacroAssembler* assembler,
+                          BlockLabel* word,
+                          BlockLabel* non_word,
+                          bool fall_through_on_word) {
+  if (assembler->CheckSpecialCharacterClass(
+          fall_through_on_word ? 'w' : 'W',
+          fall_through_on_word ? non_word : word)) {
+    // Optimized implementation available.
+    return;
+  }
+  assembler->CheckCharacterGT('z', non_word);
+  assembler->CheckCharacterLT('0', non_word);
+  assembler->CheckCharacterGT('a' - 1, word);
+  assembler->CheckCharacterLT('9' + 1, word);
+  assembler->CheckCharacterLT('A', non_word);
+  assembler->CheckCharacterLT('Z' + 1, word);
+  if (fall_through_on_word) {
+    assembler->CheckNotCharacter('_', non_word);
+  } else {
+    assembler->CheckCharacter('_', word);
+  }
+}
+
+
+// Emit the code to check for a ^ in multiline mode (1-character lookbehind
+// that matches newline or the start of input).
+static void EmitHat(RegExpCompiler* compiler,
+                    RegExpNode* on_success,
+                    Trace* trace) {
+  RegExpMacroAssembler* assembler = compiler->macro_assembler();
+  // We will be loading the previous character into the current character
+  // register.
+  Trace new_trace(*trace);
+  new_trace.InvalidateCurrentCharacter();
+
+  BlockLabel ok;
+  if (new_trace.cp_offset() == 0) {
+    // The start of input counts as a newline in this context, so skip to
+    // ok if we are at the start.
+    assembler->CheckAtStart(&ok);
+  }
+  // We already checked that we are not at the start of input so it must be
+  // OK to load the previous character.
+  assembler->LoadCurrentCharacter(new_trace.cp_offset() -1,
+                                  new_trace.backtrack(),
+                                  false);
+  if (!assembler->CheckSpecialCharacterClass('n',
+                                             new_trace.backtrack())) {
+    // Newline means \n, \r, 0x2028 or 0x2029.
+    if (!compiler->one_byte()) {
+      assembler->CheckCharacterAfterAnd(0x2028, 0xfffe, &ok);
+    }
+    assembler->CheckCharacter('\n', &ok);
+    assembler->CheckNotCharacter('\r', new_trace.backtrack());
+  }
+  assembler->BindBlock(&ok);
+  on_success->Emit(compiler, &new_trace);
+}
+
+
+// Emit the code to handle \b and \B (word-boundary or non-word-boundary).
+void AssertionNode::EmitBoundaryCheck(RegExpCompiler* compiler, Trace* trace) {
+  RegExpMacroAssembler* assembler = compiler->macro_assembler();
+  Trace::TriBool next_is_word_character = Trace::UNKNOWN;
+  bool not_at_start = (trace->at_start() == Trace::FALSE_VALUE);
+  BoyerMooreLookahead* lookahead = bm_info(not_at_start);
+  if (lookahead == NULL) {
+    intptr_t eats_at_least =
+        Utils::Minimum(kMaxLookaheadForBoyerMoore,
+                       EatsAtLeast(kMaxLookaheadForBoyerMoore,
+                                   kRecursionBudget,
+                                   not_at_start));
+    if (eats_at_least >= 1) {
+      BoyerMooreLookahead* bm =
+          new(I) BoyerMooreLookahead(eats_at_least, compiler, I);
+      FillInBMInfo(0, kRecursionBudget, bm, not_at_start);
+      if (bm->at(0)->is_non_word())
+        next_is_word_character = Trace::FALSE_VALUE;
+      if (bm->at(0)->is_word()) next_is_word_character = Trace::TRUE_VALUE;
+    }
+  } else {
+    if (lookahead->at(0)->is_non_word())
+      next_is_word_character = Trace::FALSE_VALUE;
+    if (lookahead->at(0)->is_word())
+      next_is_word_character = Trace::TRUE_VALUE;
+  }
+  bool at_boundary = (assertion_type_ == AssertionNode::AT_BOUNDARY);
+  if (next_is_word_character == Trace::UNKNOWN) {
+    BlockLabel before_non_word;
+    BlockLabel before_word;
+    if (trace->characters_preloaded() != 1) {
+      assembler->LoadCurrentCharacter(trace->cp_offset(), &before_non_word);
+    }
+    // Fall through on non-word.
+    EmitWordCheck(assembler, &before_word, &before_non_word, false);
+    // Next character is not a word character.
+    assembler->BindBlock(&before_non_word);
+    BlockLabel ok;
+    // Backtrack on \B (non-boundary check) if previous is a word,
+    // since we know next *is not* a word and this would be a boundary.
+    BacktrackIfPrevious(compiler, trace, at_boundary ? kIsNonWord : kIsWord);
+
+    if (!assembler->IsClosed()) {
+      assembler->GoTo(&ok);
+    }
+
+    assembler->BindBlock(&before_word);
+    BacktrackIfPrevious(compiler, trace, at_boundary ? kIsWord : kIsNonWord);
+    assembler->BindBlock(&ok);
+  } else if (next_is_word_character == Trace::TRUE_VALUE) {
+    BacktrackIfPrevious(compiler, trace, at_boundary ? kIsWord : kIsNonWord);
+  } else {
+    ASSERT(next_is_word_character == Trace::FALSE_VALUE);
+    BacktrackIfPrevious(compiler, trace, at_boundary ? kIsNonWord : kIsWord);
+  }
+}
+
+
+void AssertionNode::BacktrackIfPrevious(
+    RegExpCompiler* compiler,
+    Trace* trace,
+    AssertionNode::IfPrevious backtrack_if_previous) {
+  RegExpMacroAssembler* assembler = compiler->macro_assembler();
+  Trace new_trace(*trace);
+  new_trace.InvalidateCurrentCharacter();
+
+  BlockLabel fall_through, dummy;
+
+  BlockLabel* non_word = backtrack_if_previous == kIsNonWord ?
+                         new_trace.backtrack() :
+                         &fall_through;
+  BlockLabel* word = backtrack_if_previous == kIsNonWord ?
+                     &fall_through :
+                     new_trace.backtrack();
+
+  if (new_trace.cp_offset() == 0) {
+    // The start of input counts as a non-word character, so the question is
+    // decided if we are at the start.
+    assembler->CheckAtStart(non_word);
+  }
+  // We already checked that we are not at the start of input so it must be
+  // OK to load the previous character.
+  assembler->LoadCurrentCharacter(new_trace.cp_offset() - 1, &dummy, false);
+  EmitWordCheck(assembler, word, non_word, backtrack_if_previous == kIsNonWord);
+
+  assembler->BindBlock(&fall_through);
+  on_success()->Emit(compiler, &new_trace);
+}
+
+
+void AssertionNode::GetQuickCheckDetails(QuickCheckDetails* details,
+                                         RegExpCompiler* compiler,
+                                         intptr_t filled_in,
+                                         bool not_at_start) {
+  if (assertion_type_ == AT_START && not_at_start) {
+    details->set_cannot_match();
+    return;
+  }
+  return on_success()->GetQuickCheckDetails(details,
+                                            compiler,
+                                            filled_in,
+                                            not_at_start);
+}
+
+
+void AssertionNode::Emit(RegExpCompiler* compiler, Trace* trace) {
+  RegExpMacroAssembler* assembler = compiler->macro_assembler();
+  switch (assertion_type_) {
+    case AT_END: {
+      BlockLabel ok;
+      assembler->CheckPosition(trace->cp_offset(), &ok);
+      assembler->GoTo(trace->backtrack());
+      assembler->BindBlock(&ok);
+      break;
+    }
+    case AT_START: {
+      if (trace->at_start() == Trace::FALSE_VALUE) {
+        assembler->GoTo(trace->backtrack());
+        return;
+      }
+      if (trace->at_start() == Trace::UNKNOWN) {
+        assembler->CheckNotAtStart(trace->backtrack());
+        Trace at_start_trace = *trace;
+        at_start_trace.set_at_start(true);
+        on_success()->Emit(compiler, &at_start_trace);
+        return;
+      }
+    }
+    break;
+    case AFTER_NEWLINE:
+      EmitHat(compiler, on_success(), trace);
+      return;
+    case AT_BOUNDARY:
+    case AT_NON_BOUNDARY: {
+      EmitBoundaryCheck(compiler, trace);
+      return;
+    }
+  }
+  on_success()->Emit(compiler, trace);
+}
+
+
+static bool DeterminedAlready(QuickCheckDetails* quick_check, intptr_t offset) {
+  if (quick_check == NULL) return false;
+  if (offset >= quick_check->characters()) return false;
+  return quick_check->positions(offset)->determines_perfectly;
+}
+
+
+static void UpdateBoundsCheck(intptr_t index, intptr_t* checked_up_to) {
+  if (index > *checked_up_to) {
+    *checked_up_to = index;
+  }
+}
+
+
+// We call this repeatedly to generate code for each pass over the text node.
+// The passes are in increasing order of difficulty because we hope one
+// of the first passes will fail in which case we are saved the work of the
+// later passes.  for example for the case independent regexp /%[asdfghjkl]a/
+// we will check the '%' in the first pass, the case independent 'a' in the
+// second pass and the character class in the last pass.
+//
+// The passes are done from right to left, so for example to test for /bar/
+// we will first test for an 'r' with offset 2, then an 'a' with offset 1
+// and then a 'b' with offset 0.  This means we can avoid the end-of-input
+// bounds check most of the time.  In the example we only need to check for
+// end-of-input when loading the putative 'r'.
+//
+// A slight complication involves the fact that the first character may already
+// be fetched into a register by the previous node.  In this case we want to
+// do the test for that character first.  We do this in separate passes.  The
+// 'preloaded' argument indicates that we are doing such a 'pass'.  If such a
+// pass has been performed then subsequent passes will have true in
+// first_element_checked to indicate that that character does not need to be
+// checked again.
+//
+// In addition to all this we are passed a Trace, which can
+// contain an AlternativeGeneration object.  In this AlternativeGeneration
+// object we can see details of any quick check that was already passed in
+// order to get to the code we are now generating.  The quick check can involve
+// loading characters, which means we do not need to recheck the bounds
+// up to the limit the quick check already checked.  In addition the quick
+// check can have involved a mask and compare operation which may simplify
+// or obviate the need for further checks at some character positions.
+void TextNode::TextEmitPass(RegExpCompiler* compiler,
+                            TextEmitPassType pass,
+                            bool preloaded,
+                            Trace* trace,
+                            bool first_element_checked,
+                            intptr_t* checked_up_to) {
+  RegExpMacroAssembler* assembler = compiler->macro_assembler();
+  bool one_byte = compiler->one_byte();
+  BlockLabel* backtrack = trace->backtrack();
+  QuickCheckDetails* quick_check = trace->quick_check_performed();
+  intptr_t element_count = elms_->length();
+  for (intptr_t i = preloaded ? 0 : element_count - 1; i >= 0; i--) {
+    TextElement elm = elms_->At(i);
+    intptr_t cp_offset = trace->cp_offset() + elm.cp_offset();
+    if (elm.text_type() == TextElement::ATOM) {
+      ZoneGrowableArray<uint16_t>* quarks = elm.atom()->data();
+      for (intptr_t j = preloaded ? 0 : quarks->length() - 1; j >= 0; j--) {
+        if (first_element_checked && i == 0 && j == 0) continue;
+        if (DeterminedAlready(quick_check, elm.cp_offset() + j)) continue;
+        EmitCharacterFunction* emit_function = NULL;
+        switch (pass) {
+          case NON_LATIN1_MATCH:
+            ASSERT(one_byte);
+            if (quarks->At(j) > Symbols::kMaxOneCharCodeSymbol) {
+              assembler->GoTo(backtrack);
+              return;
+            }
+            break;
+          case NON_LETTER_CHARACTER_MATCH:
+            emit_function = &EmitAtomNonLetter;
+            break;
+          case SIMPLE_CHARACTER_MATCH:
+            emit_function = &EmitSimpleCharacter;
+            break;
+          case CASE_CHARACTER_MATCH:
+            emit_function = &EmitAtomLetter;
+            break;
+          default:
+            break;
+        }
+        if (emit_function != NULL) {
+          bool bound_checked = emit_function(I,
+                                             compiler,
+                                             quarks->At(j),
+                                             backtrack,
+                                             cp_offset + j,
+                                             *checked_up_to < cp_offset + j,
+                                             preloaded);
+          if (bound_checked) UpdateBoundsCheck(cp_offset + j, checked_up_to);
+        }
+      }
+    } else {
+      ASSERT(elm.text_type() == TextElement::CHAR_CLASS);
+      if (pass == CHARACTER_CLASS_MATCH) {
+        if (first_element_checked && i == 0) continue;
+        if (DeterminedAlready(quick_check, elm.cp_offset())) continue;
+        RegExpCharacterClass* cc = elm.char_class();
+        EmitCharClass(assembler,
+                      cc,
+                      one_byte,
+                      backtrack,
+                      cp_offset,
+                      *checked_up_to < cp_offset,
+                      preloaded,
+                      I);
+        UpdateBoundsCheck(cp_offset, checked_up_to);
+      }
+    }
+  }
+}
+
+
+intptr_t TextNode::Length() {
+  TextElement elm = elms_->Last();
+  ASSERT(elm.cp_offset() >= 0);
+  return elm.cp_offset() + elm.length();
+}
+
+
+bool TextNode::SkipPass(intptr_t intptr_t_pass, bool ignore_case) {
+  TextEmitPassType pass = static_cast<TextEmitPassType>(intptr_t_pass);
+  if (ignore_case) {
+    return pass == SIMPLE_CHARACTER_MATCH;
+  } else {
+    return pass == NON_LETTER_CHARACTER_MATCH || pass == CASE_CHARACTER_MATCH;
+  }
+}
+
+
+// This generates the code to match a text node.  A text node can contain
+// straight character sequences (possibly to be matched in a case-independent
+// way) and character classes.  For efficiency we do not do this in a single
+// pass from left to right.  Instead we pass over the text node several times,
+// emitting code for some character positions every time.  See the comment on
+// TextEmitPass for details.
+void TextNode::Emit(RegExpCompiler* compiler, Trace* trace) {
+  LimitResult limit_result = LimitVersions(compiler, trace);
+  if (limit_result == DONE) return;
+  ASSERT(limit_result == CONTINUE);
+
+  if (trace->cp_offset() + Length() > RegExpMacroAssembler::kMaxCPOffset) {
+    compiler->SetRegExpTooBig();
+    return;
+  }
+
+  if (compiler->one_byte()) {
+    intptr_t dummy = 0;
+    TextEmitPass(compiler, NON_LATIN1_MATCH, false, trace, false, &dummy);
+  }
+
+  bool first_elt_done = false;
+  intptr_t bound_checked_to = trace->cp_offset() - 1;
+  bound_checked_to += trace->bound_checked_up_to();
+
+  // If a character is preloaded into the current character register then
+  // check that now.
+  if (trace->characters_preloaded() == 1) {
+    for (intptr_t pass = kFirstRealPass; pass <= kLastPass; pass++) {
+      if (!SkipPass(pass, compiler->ignore_case())) {
+        TextEmitPass(compiler,
+                     static_cast<TextEmitPassType>(pass),
+                     true,
+                     trace,
+                     false,
+                     &bound_checked_to);
+      }
+    }
+    first_elt_done = true;
+  }
+
+  for (intptr_t pass = kFirstRealPass; pass <= kLastPass; pass++) {
+    if (!SkipPass(pass, compiler->ignore_case())) {
+      TextEmitPass(compiler,
+                   static_cast<TextEmitPassType>(pass),
+                   false,
+                   trace,
+                   first_elt_done,
+                   &bound_checked_to);
+    }
+  }
+
+  Trace successor_trace(*trace);
+  successor_trace.set_at_start(false);
+  successor_trace.AdvanceCurrentPositionInTrace(Length(), compiler);
+  RecursionCheck rc(compiler);
+  on_success()->Emit(compiler, &successor_trace);
+}
+
+
+void Trace::InvalidateCurrentCharacter() {
+  characters_preloaded_ = 0;
+}
+
+
+void Trace::AdvanceCurrentPositionInTrace(intptr_t by,
+                                          RegExpCompiler* compiler) {
+  ASSERT(by > 0);
+  // We don't have an instruction for shifting the current character register
+  // down or for using a shifted value for anything so lets just forget that
+  // we preloaded any characters into it.
+  characters_preloaded_ = 0;
+  // Adjust the offsets of the quick check performed information.  This
+  // information is used to find out what we already determined about the
+  // characters by means of mask and compare.
+  quick_check_performed_.Advance(by, compiler->one_byte());
+  cp_offset_ += by;
+  if (cp_offset_ > RegExpMacroAssembler::kMaxCPOffset) {
+    compiler->SetRegExpTooBig();
+    cp_offset_ = 0;
+  }
+  bound_checked_up_to_ = Utils::Maximum(static_cast<intptr_t>(0),
+                                        bound_checked_up_to_ - by);
+}
+
+
+void TextNode::MakeCaseIndependent(bool is_one_byte) {
+  intptr_t element_count = elms_->length();
+  for (intptr_t i = 0; i < element_count; i++) {
+    TextElement elm = elms_->At(i);
+    if (elm.text_type() == TextElement::CHAR_CLASS) {
+      RegExpCharacterClass* cc = elm.char_class();
+      // None of the standard character classes is different in the case
+      // independent case and it slows us down if we don't know that.
+      if (cc->is_standard()) continue;
+      ZoneGrowableArray<CharacterRange>* ranges = cc->ranges();
+      intptr_t range_count = ranges->length();
+      for (intptr_t j = 0; j < range_count; j++) {
+        (*ranges)[j].AddCaseEquivalents(ranges, is_one_byte, I);
+      }
+    }
+  }
+}
+
+
+intptr_t TextNode::GreedyLoopTextLength() {
+  TextElement elm = elms_->At(elms_->length() - 1);
+  return elm.cp_offset() + elm.length();
+}
+
+
+RegExpNode* TextNode::GetSuccessorOfOmnivorousTextNode(
+    RegExpCompiler* compiler) {
+  if (elms_->length() != 1) return NULL;
+  TextElement elm = elms_->At(0);
+  if (elm.text_type() != TextElement::CHAR_CLASS) return NULL;
+  RegExpCharacterClass* node = elm.char_class();
+  ZoneGrowableArray<CharacterRange>* ranges = node->ranges();
+  if (!CharacterRange::IsCanonical(ranges)) {
+    CharacterRange::Canonicalize(ranges);
+  }
+  if (node->is_negated()) {
+    return ranges->length() == 0 ? on_success() : NULL;
+  }
+  if (ranges->length() != 1) return NULL;
+  uint32_t max_char;
+  if (compiler->one_byte()) {
+    max_char = Symbols::kMaxOneCharCodeSymbol;
+  } else {
+    max_char = Utf16::kMaxCodeUnit;
+  }
+  return ranges->At(0).IsEverything(max_char) ? on_success() : NULL;
+}
+
+
+// Finds the fixed match length of a sequence of nodes that goes from
+// this alternative and back to this choice node.  If there are variable
+// length nodes or other complications in the way then return a sentinel
+// value indicating that a greedy loop cannot be constructed.
+intptr_t ChoiceNode::GreedyLoopTextLengthForAlternative(
+    GuardedAlternative* alternative) {
+  intptr_t length = 0;
+  RegExpNode* node = alternative->node();
+  // Later we will generate code for all these text nodes using recursion
+  // so we have to limit the max number.
+  intptr_t recursion_depth = 0;
+  while (node != this) {
+    if (recursion_depth++ > RegExpCompiler::kMaxRecursion) {
+      return kNodeIsTooComplexForGreedyLoops;
+    }
+    intptr_t node_length = node->GreedyLoopTextLength();
+    if (node_length == kNodeIsTooComplexForGreedyLoops) {
+      return kNodeIsTooComplexForGreedyLoops;
+    }
+    length += node_length;
+    SeqRegExpNode* seq_node = static_cast<SeqRegExpNode*>(node);
+    node = seq_node->on_success();
+  }
+  return length;
+}
+
+
+void LoopChoiceNode::AddLoopAlternative(GuardedAlternative alt) {
+  ASSERT(loop_node_ == NULL);
+  AddAlternative(alt);
+  loop_node_ = alt.node();
+}
+
+
+void LoopChoiceNode::AddContinueAlternative(GuardedAlternative alt) {
+  ASSERT(continue_node_ == NULL);
+  AddAlternative(alt);
+  continue_node_ = alt.node();
+}
+
+
+void LoopChoiceNode::Emit(RegExpCompiler* compiler, Trace* trace) {
+  RegExpMacroAssembler* macro_assembler = compiler->macro_assembler();
+  if (trace->stop_node() == this) {
+    // Back edge of greedy optimized loop node graph.
+    intptr_t text_length =
+        GreedyLoopTextLengthForAlternative(&((*alternatives_)[0]));
+    ASSERT(text_length != kNodeIsTooComplexForGreedyLoops);
+    // Update the counter-based backtracking info on the stack.  This is an
+    // optimization for greedy loops (see below).
+    ASSERT(trace->cp_offset() == text_length);
+    macro_assembler->AdvanceCurrentPosition(text_length);
+    macro_assembler->GoTo(trace->loop_label());
+    return;
+  }
+  ASSERT(trace->stop_node() == NULL);
+  if (!trace->is_trivial()) {
+    trace->Flush(compiler, this);
+    return;
+  }
+  ChoiceNode::Emit(compiler, trace);
+}
+
+
+intptr_t ChoiceNode::CalculatePreloadCharacters(RegExpCompiler* compiler,
+                                                intptr_t eats_at_least) {
+  intptr_t preload_characters = Utils::Minimum(static_cast<intptr_t>(4),
+                                               eats_at_least);
+  if (compiler->macro_assembler()->CanReadUnaligned()) {
+    bool one_byte = compiler->one_byte();
+    if (one_byte) {
+      if (preload_characters > 4) preload_characters = 4;
+      // We can't preload 3 characters because there is no machine instruction
+      // to do that.  We can't just load 4 because we could be reading
+      // beyond the end of the string, which could cause a memory fault.
+      if (preload_characters == 3) preload_characters = 2;
+    } else {
+      if (preload_characters > 2) preload_characters = 2;
+    }
+  } else {
+    if (preload_characters > 1) preload_characters = 1;
+  }
+  return preload_characters;
+}
+
+
+// This structure is used when generating the alternatives in a choice node.  It
+// records the way the alternative is being code generated.
+struct AlternativeGeneration {
+  AlternativeGeneration()
+      : possible_success(),
+        expects_preload(false),
+        after(),
+        quick_check_details() { }
+  BlockLabel possible_success;
+  bool expects_preload;
+  BlockLabel after;
+  QuickCheckDetails quick_check_details;
+};
+
+
+// Creates a list of AlternativeGenerations.  If the list has a reasonable
+// size then it is on the stack, otherwise the excess is on the heap.
+class AlternativeGenerationList {
+ public:
+  explicit AlternativeGenerationList(intptr_t count)
+      : alt_gens_(count) {
+    for (intptr_t i = 0; i < count && i < kAFew; i++) {
+      alt_gens_.Add(a_few_alt_gens_ + i);
+    }
+    for (intptr_t i = kAFew; i < count; i++) {
+      alt_gens_.Add(new AlternativeGeneration());
+    }
+  }
+  ~AlternativeGenerationList() {
+    for (intptr_t i = kAFew; i < alt_gens_.length(); i++) {
+      delete alt_gens_[i];
+      alt_gens_[i] = NULL;
+    }
+  }
+
+  AlternativeGeneration* at(intptr_t i) {
+    return alt_gens_[i];
+  }
+
+ private:
+  static const intptr_t kAFew = 10;
+  GrowableArray<AlternativeGeneration*> alt_gens_;
+  AlternativeGeneration a_few_alt_gens_[kAFew];
+
+  DISALLOW_ALLOCATION();
+};
+
+
+// The '2' variant is inclusive from and exclusive to.
+// This covers \s as defined in ECMA-262 5.1, 15.10.2.12,
+// which include WhiteSpace (7.2) or LineTerminator (7.3) values.
+static const intptr_t kSpaceRanges[] = { '\t', '\r' + 1, ' ', ' ' + 1,
+    0x00A0, 0x00A1, 0x1680, 0x1681, 0x180E, 0x180F, 0x2000, 0x200B,
+    0x2028, 0x202A, 0x202F, 0x2030, 0x205F, 0x2060, 0x3000, 0x3001,
+    0xFEFF, 0xFF00, 0x10000 };
+static const intptr_t kSpaceRangeCount = ARRAY_SIZE(kSpaceRanges);
+static const intptr_t kWordRanges[] = {
+    '0', '9' + 1, 'A', 'Z' + 1, '_', '_' + 1, 'a', 'z' + 1, 0x10000 };
+static const intptr_t kWordRangeCount = ARRAY_SIZE(kWordRanges);
+static const intptr_t kDigitRanges[] = { '0', '9' + 1, 0x10000 };
+static const intptr_t kDigitRangeCount = ARRAY_SIZE(kDigitRanges);
+static const intptr_t kSurrogateRanges[] = { 0xd800, 0xe000, 0x10000 };
+static const intptr_t kSurrogateRangeCount = ARRAY_SIZE(kSurrogateRanges);
+static const intptr_t kLineTerminatorRanges[] = {
+    0x000A, 0x000B, 0x000D, 0x000E, 0x2028, 0x202A, 0x10000 };
+static const intptr_t kLineTerminatorRangeCount =
+    ARRAY_SIZE(kLineTerminatorRanges);
+
+
+void BoyerMoorePositionInfo::Set(intptr_t character) {
+  SetInterval(Interval(character, character));
+}
+
+
+void BoyerMoorePositionInfo::SetInterval(const Interval& interval) {
+  s_ = AddRange(s_, kSpaceRanges, kSpaceRangeCount, interval);
+  w_ = AddRange(w_, kWordRanges, kWordRangeCount, interval);
+  d_ = AddRange(d_, kDigitRanges, kDigitRangeCount, interval);
+  surrogate_ =
+      AddRange(surrogate_, kSurrogateRanges, kSurrogateRangeCount, interval);
+  if (interval.to() - interval.from() >= kMapSize - 1) {
+    if (map_count_ != kMapSize) {
+      map_count_ = kMapSize;
+      for (intptr_t i = 0; i < kMapSize; i++) (*map_)[i] = true;
+    }
+    return;
+  }
+  for (intptr_t i = interval.from(); i <= interval.to(); i++) {
+    intptr_t mod_character = (i & kMask);
+    if (!map_->At(mod_character)) {
+      map_count_++;
+      (*map_)[mod_character] = true;
+    }
+    if (map_count_ == kMapSize) return;
+  }
+}
+
+
+void BoyerMoorePositionInfo::SetAll() {
+  s_ = w_ = d_ = kLatticeUnknown;
+  if (map_count_ != kMapSize) {
+    map_count_ = kMapSize;
+    for (intptr_t i = 0; i < kMapSize; i++) (*map_)[i] = true;
+  }
+}
+
+
+BoyerMooreLookahead::BoyerMooreLookahead(
+    intptr_t length, RegExpCompiler* compiler, Isolate* isolate)
+    : length_(length),
+      compiler_(compiler) {
+  if (compiler->one_byte()) {
+    max_char_ = Symbols::kMaxOneCharCodeSymbol;
+  } else {
+    max_char_ = Utf16::kMaxCodeUnit;
+  }
+  bitmaps_ = new(isolate) ZoneGrowableArray<BoyerMoorePositionInfo*>(length);
+  for (intptr_t i = 0; i < length; i++) {
+    bitmaps_->Add(new(isolate) BoyerMoorePositionInfo(isolate));
+  }
+}
+
+
+// Find the longest range of lookahead that has the fewest number of different
+// characters that can occur at a given position.  Since we are optimizing two
+// different parameters at once this is a tradeoff.
+bool BoyerMooreLookahead::FindWorthwhileInterval(intptr_t* from, intptr_t* to) {
+  intptr_t biggest_points = 0;
+  // If more than 32 characters out of 128 can occur it is unlikely that we can
+  // be lucky enough to step forwards much of the time.
+  const intptr_t kMaxMax = 32;
+  for (intptr_t max_number_of_chars = 4;
+       max_number_of_chars < kMaxMax;
+       max_number_of_chars *= 2) {
+    biggest_points =
+        FindBestInterval(max_number_of_chars, biggest_points, from, to);
+  }
+  if (biggest_points == 0) return false;
+  return true;
+}
+
+
+// Find the highest-points range between 0 and length_ where the character
+// information is not too vague.  'Too vague' means that there are more than
+// max_number_of_chars that can occur at this position.  Calculates the number
+// of points as the product of width-of-the-range and
+// probability-of-finding-one-of-the-characters, where the probability is
+// calculated using the frequency distribution of the sample subject string.
+intptr_t BoyerMooreLookahead::FindBestInterval(
+    intptr_t max_number_of_chars,
+    intptr_t old_biggest_points,
+    intptr_t* from,
+    intptr_t* to) {
+  intptr_t biggest_points = old_biggest_points;
+  static const intptr_t kSize = RegExpMacroAssembler::kTableSize;
+  for (intptr_t i = 0; i < length_; ) {
+    while (i < length_ && Count(i) > max_number_of_chars) i++;
+    if (i == length_) break;
+    intptr_t remembered_from = i;
+    bool union_map[kSize];
+    for (intptr_t j = 0; j < kSize; j++) union_map[j] = false;
+    while (i < length_ && Count(i) <= max_number_of_chars) {
+      BoyerMoorePositionInfo* map = bitmaps_->At(i);
+      for (intptr_t j = 0; j < kSize; j++) union_map[j] |= map->at(j);
+      i++;
+    }
+    intptr_t frequency = 0;
+    for (intptr_t j = 0; j < kSize; j++) {
+      if (union_map[j]) {
+        // Add 1 to the frequency to give a small per-character boost for
+        // the cases where our sampling is not good enough and many
+        // characters have a frequency of zero.  This means the frequency
+        // can theoretically be up to 2*kSize though we treat it mostly as
+        // a fraction of kSize.
+        frequency += compiler_->frequency_collator()->Frequency(j) + 1;
+      }
+    }
+    // We use the probability of skipping times the distance we are skipping to
+    // judge the effectiveness of this.  Actually we have a cut-off:  By
+    // dividing by 2 we switch off the skipping if the probability of skipping
+    // is less than 50%.  This is because the multibyte mask-and-compare
+    // skipping in quickcheck is more likely to do well on this case.
+    bool in_quickcheck_range = ((i - remembered_from < 4) ||
+        (compiler_->one_byte() ? remembered_from <= 4 : remembered_from <= 2));
+    // Called 'probability' but it is only a rough estimate and can actually
+    // be outside the 0-kSize range.
+    intptr_t probability =
+        (in_quickcheck_range ? kSize / 2 : kSize) - frequency;
+    intptr_t points = (i - remembered_from) * probability;
+    if (points > biggest_points) {
+      *from = remembered_from;
+      *to = i - 1;
+      biggest_points = points;
+    }
+  }
+  return biggest_points;
+}
+
+
+// Take all the characters that will not prevent a successful match if they
+// occur in the subject string in the range between min_lookahead and
+// max_lookahead (inclusive) measured from the current position.  If the
+// character at max_lookahead offset is not one of these characters, then we
+// can safely skip forwards by the number of characters in the range.
+intptr_t BoyerMooreLookahead::GetSkipTable(
+    intptr_t min_lookahead,
+    intptr_t max_lookahead,
+    const TypedData& boolean_skip_table) {
+  const intptr_t kSize = RegExpMacroAssembler::kTableSize;
+
+  const intptr_t kSkipArrayEntry = 0;
+  const intptr_t kDontSkipArrayEntry = 1;
+
+  for (intptr_t i = 0; i < kSize; i++) {
+    boolean_skip_table.SetUint8(i, kSkipArrayEntry);
+  }
+  intptr_t skip = max_lookahead + 1 - min_lookahead;
+
+  for (intptr_t i = max_lookahead; i >= min_lookahead; i--) {
+    BoyerMoorePositionInfo* map = bitmaps_->At(i);
+    for (intptr_t j = 0; j < kSize; j++) {
+      if (map->at(j)) {
+        boolean_skip_table.SetUint8(j, kDontSkipArrayEntry);
+      }
+    }
+  }
+
+  return skip;
+}
+
+
+// See comment above on the implementation of GetSkipTable.
+void BoyerMooreLookahead::EmitSkipInstructions(RegExpMacroAssembler* masm) {
+  const intptr_t kSize = RegExpMacroAssembler::kTableSize;
+
+  intptr_t min_lookahead = 0;
+  intptr_t max_lookahead = 0;
+
+  if (!FindWorthwhileInterval(&min_lookahead, &max_lookahead)) return;
+
+  bool found_single_character = false;
+  intptr_t single_character = 0;
+  for (intptr_t i = max_lookahead; i >= min_lookahead; i--) {
+    BoyerMoorePositionInfo* map = bitmaps_->At(i);
+    if (map->map_count() > 1 ||
+        (found_single_character && map->map_count() != 0)) {
+      found_single_character = false;
+      break;
+    }
+    for (intptr_t j = 0; j < kSize; j++) {
+      if (map->at(j)) {
+        found_single_character = true;
+        single_character = j;
+        break;
+      }
+    }
+  }
+
+  intptr_t lookahead_width = max_lookahead + 1 - min_lookahead;
+
+  if (found_single_character && lookahead_width == 1 && max_lookahead < 3) {
+    // The mask-compare can probably handle this better.
+    return;
+  }
+
+  if (found_single_character) {
+    BlockLabel cont, again;
+    masm->BindBlock(&again);
+    masm->LoadCurrentCharacter(max_lookahead, &cont, true);
+    if (max_char_ > kSize) {
+      masm->CheckCharacterAfterAnd(single_character,
+                                   RegExpMacroAssembler::kTableMask,
+                                   &cont);
+    } else {
+      masm->CheckCharacter(single_character, &cont);
+    }
+    masm->AdvanceCurrentPosition(lookahead_width);
+    masm->GoTo(&again);
+    masm->BindBlock(&cont);
+    return;
+  }
+
+  const TypedData& boolean_skip_table = TypedData::ZoneHandle(
+        compiler_->isolate(),
+        TypedData::New(kTypedDataUint8ArrayCid, kSize, Heap::kOld));
+  intptr_t skip_distance = GetSkipTable(
+      min_lookahead, max_lookahead, boolean_skip_table);
+  ASSERT(skip_distance != 0);
+
+  BlockLabel cont, again;
+
+  masm->BindBlock(&again);
+  masm->LoadCurrentCharacter(max_lookahead, &cont, true);
+  masm->CheckBitInTable(boolean_skip_table, &cont);
+  masm->AdvanceCurrentPosition(skip_distance);
+  masm->GoTo(&again);
+  masm->BindBlock(&cont);
+
+  return;
+}
+
+
+/* Code generation for choice nodes.
+ *
+ * We generate quick checks that do a mask and compare to eliminate a
+ * choice.  If the quick check succeeds then it jumps to the continuation to
+ * do slow checks and check subsequent nodes.  If it fails (the common case)
+ * it falls through to the next choice.
+ *
+ * Here is the desired flow graph.  Nodes directly below each other imply
+ * fallthrough.  Alternatives 1 and 2 have quick checks.  Alternative
+ * 3 doesn't have a quick check so we have to call the slow check.
+ * Nodes are marked Qn for quick checks and Sn for slow checks.  The entire
+ * regexp continuation is generated directly after the Sn node, up to the
+ * next GoTo if we decide to reuse some already generated code.  Some
+ * nodes expect preload_characters to be preloaded into the current
+ * character register.  R nodes do this preloading.  Vertices are marked
+ * F for failures and S for success (possible success in the case of quick
+ * nodes).  L, V, < and > are used as arrow heads.
+ *
+ * ----------> R
+ *             |
+ *             V
+ *            Q1 -----> S1
+ *             |   S   /
+ *            F|      /
+ *             |    F/
+ *             |    /
+ *             |   R
+ *             |  /
+ *             V L
+ *            Q2 -----> S2
+ *             |   S   /
+ *            F|      /
+ *             |    F/
+ *             |    /
+ *             |   R
+ *             |  /
+ *             V L
+ *            S3
+ *             |
+ *            F|
+ *             |
+ *             R
+ *             |
+ * backtrack   V
+ * <----------Q4
+ *   \    F    |
+ *    \        |S
+ *     \   F   V
+ *      \-----S4
+ *
+ * For greedy loops we push the current position, then generate the code that
+ * eats the input specially in EmitGreedyLoop.  The other choice (the
+ * continuation) is generated by the normal code in EmitChoices, and steps back
+ * in the input to the starting position when it fails to match.  The loop code
+ * looks like this (U is the unwind code that steps back in the greedy loop).
+ *
+ *              _____
+ *             /     \
+ *             V     |
+ * ----------> S1    |
+ *            /|     |
+ *           / |S    |
+ *         F/  \_____/
+ *         /
+ *        |<-----
+ *        |      \
+ *        V       |S
+ *        Q2 ---> U----->backtrack
+ *        |  F   /
+ *       S|     /
+ *        V  F /
+ *        S2--/
+ */
+
+GreedyLoopState::GreedyLoopState(bool not_at_start) {
+  counter_backtrack_trace_.set_backtrack(&label_);
+  if (not_at_start) counter_backtrack_trace_.set_at_start(false);
+}
+
+
+void ChoiceNode::AssertGuardsMentionRegisters(Trace* trace) {
+#ifdef DEBUG
+  intptr_t choice_count = alternatives_->length();
+  for (intptr_t i = 0; i < choice_count - 1; i++) {
+    GuardedAlternative alternative = alternatives_->At(i);
+    ZoneGrowableArray<Guard*>* guards = alternative.guards();
+    intptr_t guard_count = (guards == NULL) ? 0 : guards->length();
+    for (intptr_t j = 0; j < guard_count; j++) {
+      ASSERT(!trace->mentions_reg(guards->At(j)->reg()));
+    }
+  }
+#endif
+}
+
+
+void ChoiceNode::SetUpPreLoad(RegExpCompiler* compiler,
+                              Trace* current_trace,
+                              PreloadState* state) {
+    if (state->eats_at_least_ == PreloadState::kEatsAtLeastNotYetInitialized) {
+      // Save some time by looking at most one machine word ahead.
+      state->eats_at_least_ =
+          EatsAtLeast(compiler->one_byte() ? 4 : 2, kRecursionBudget,
+                      current_trace->at_start() == Trace::FALSE_VALUE);
+    }
+    state->preload_characters_ =
+        CalculatePreloadCharacters(compiler, state->eats_at_least_);
+
+    state->preload_is_current_ =
+        (current_trace->characters_preloaded() == state->preload_characters_);
+    state->preload_has_checked_bounds_ = state->preload_is_current_;
+}
+
+
+void ChoiceNode::Emit(RegExpCompiler* compiler, Trace* trace) {
+  intptr_t choice_count = alternatives_->length();
+
+  AssertGuardsMentionRegisters(trace);
+
+  LimitResult limit_result = LimitVersions(compiler, trace);
+  if (limit_result == DONE) return;
+  ASSERT(limit_result == CONTINUE);
+
+  // For loop nodes we already flushed (see LoopChoiceNode::Emit), but for
+  // other choice nodes we only flush if we are out of code size budget.
+  if (trace->flush_budget() == 0 && trace->actions() != NULL) {
+    trace->Flush(compiler, this);
+    return;
+  }
+
+  RecursionCheck rc(compiler);
+
+  PreloadState preload;
+  preload.init();
+  GreedyLoopState greedy_loop_state(not_at_start());
+
+  intptr_t text_length =
+      GreedyLoopTextLengthForAlternative(&((*alternatives_)[0]));
+  AlternativeGenerationList alt_gens(choice_count);
+
+  if (choice_count > 1 && text_length != kNodeIsTooComplexForGreedyLoops) {
+    trace = EmitGreedyLoop(compiler,
+                           trace,
+                           &alt_gens,
+                           &preload,
+                           &greedy_loop_state,
+                           text_length);
+  } else {
+    // TODO(erikcorry): Delete this.  We don't need this label, but it makes us
+    // match the traces produced pre-cleanup.
+    BlockLabel second_choice;
+    compiler->macro_assembler()->BindBlock(&second_choice);
+
+    preload.eats_at_least_ = EmitOptimizedUnanchoredSearch(compiler, trace);
+
+    EmitChoices(compiler,
+                &alt_gens,
+                0,
+                trace,
+                &preload);
+  }
+
+  // At this point we need to generate slow checks for the alternatives where
+  // the quick check was inlined.  We can recognize these because the associated
+  // label was bound.
+  intptr_t new_flush_budget = trace->flush_budget() / choice_count;
+  for (intptr_t i = 0; i < choice_count; i++) {
+    AlternativeGeneration* alt_gen = alt_gens.at(i);
+    Trace new_trace(*trace);
+    // If there are actions to be flushed we have to limit how many times
+    // they are flushed.  Take the budget of the parent trace and distribute
+    // it fairly amongst the children.
+    if (new_trace.actions() != NULL) {
+      new_trace.set_flush_budget(new_flush_budget);
+    }
+    bool next_expects_preload =
+        i == choice_count - 1 ? false : alt_gens.at(i + 1)->expects_preload;
+    EmitOutOfLineContinuation(compiler,
+                              &new_trace,
+                              alternatives_->At(i),
+                              alt_gen,
+                              preload.preload_characters_,
+                              next_expects_preload);
+  }
+}
+
+Trace* ChoiceNode::EmitGreedyLoop(RegExpCompiler* compiler,
+                                  Trace* trace,
+                                  AlternativeGenerationList* alt_gens,
+                                  PreloadState* preload,
+                                  GreedyLoopState* greedy_loop_state,
+                                  intptr_t text_length) {
+  RegExpMacroAssembler* macro_assembler = compiler->macro_assembler();
+  // Here we have special handling for greedy loops containing only text nodes
+  // and other simple nodes.  These are handled by pushing the current
+  // position on the stack and then incrementing the current position each
+  // time around the switch.  On backtrack we decrement the current position
+  // and check it against the pushed value.  This avoids pushing backtrack
+  // information for each iteration of the loop, which could take up a lot of
+  // space.
+  ASSERT(trace->stop_node() == NULL);
+  macro_assembler->PushCurrentPosition();
+  BlockLabel greedy_match_failed;
+  Trace greedy_match_trace;
+  if (not_at_start()) greedy_match_trace.set_at_start(false);
+  greedy_match_trace.set_backtrack(&greedy_match_failed);
+  BlockLabel loop_label;
+  macro_assembler->BindBlock(&loop_label);
+  greedy_match_trace.set_stop_node(this);
+  greedy_match_trace.set_loop_label(&loop_label);
+  (*alternatives_)[0].node()->Emit(compiler, &greedy_match_trace);
+  macro_assembler->BindBlock(&greedy_match_failed);
+
+  BlockLabel second_choice;  // For use in greedy matches.
+  macro_assembler->BindBlock(&second_choice);
+
+  Trace* new_trace = greedy_loop_state->counter_backtrack_trace();
+
+  EmitChoices(compiler,
+              alt_gens,
+              1,
+              new_trace,
+              preload);
+
+  macro_assembler->BindBlock(greedy_loop_state->label());
+  // If we have unwound to the bottom then backtrack.
+  macro_assembler->CheckGreedyLoop(trace->backtrack());
+  // Otherwise try the second priority at an earlier position.
+  macro_assembler->AdvanceCurrentPosition(-text_length);
+  macro_assembler->GoTo(&second_choice);
+  return new_trace;
+}
+
+
+intptr_t ChoiceNode::EmitOptimizedUnanchoredSearch(RegExpCompiler* compiler,
+                                                   Trace* trace) {
+  intptr_t eats_at_least = PreloadState::kEatsAtLeastNotYetInitialized;
+  if (alternatives_->length() != 2) return eats_at_least;
+
+  GuardedAlternative alt1 = alternatives_->At(1);
+  if (alt1.guards() != NULL && alt1.guards()->length() != 0) {
+    return eats_at_least;
+  }
+  RegExpNode* eats_anything_node = alt1.node();
+  if (eats_anything_node->GetSuccessorOfOmnivorousTextNode(compiler) != this) {
+    return eats_at_least;
+  }
+
+  // Really we should be creating a new trace when we execute this function,
+  // but there is no need, because the code it generates cannot backtrack, and
+  // we always arrive here with a trivial trace (since it's the entry to a
+  // loop.  That also implies that there are no preloaded characters, which is
+  // good, because it means we won't be violating any assumptions by
+  // overwriting those characters with new load instructions.
+  ASSERT(trace->is_trivial());
+
+  RegExpMacroAssembler* macro_assembler = compiler->macro_assembler();
+  // At this point we know that we are at a non-greedy loop that will eat
+  // any character one at a time.  Any non-anchored regexp has such a
+  // loop prepended to it in order to find where it starts.  We look for
+  // a pattern of the form ...abc... where we can look 6 characters ahead
+  // and step forwards 3 if the character is not one of abc.  Abc need
+  // not be atoms, they can be any reasonably limited character class or
+  // small alternation.
+  BoyerMooreLookahead* bm = bm_info(false);
+  if (bm == NULL) {
+    eats_at_least = Utils::Minimum(kMaxLookaheadForBoyerMoore,
+                        EatsAtLeast(kMaxLookaheadForBoyerMoore,
+                                    kRecursionBudget,
+                                    false));
+    if (eats_at_least >= 1) {
+      bm = new(I) BoyerMooreLookahead(eats_at_least, compiler, I);
+      GuardedAlternative alt0 = alternatives_->At(0);
+      alt0.node()->FillInBMInfo(0, kRecursionBudget, bm, false);
+    }
+  }
+  if (bm != NULL) {
+    bm->EmitSkipInstructions(macro_assembler);
+  }
+  return eats_at_least;
+}
+
+
+void ChoiceNode::EmitChoices(RegExpCompiler* compiler,
+                             AlternativeGenerationList* alt_gens,
+                             intptr_t first_choice,
+                             Trace* trace,
+                             PreloadState* preload) {
+  RegExpMacroAssembler* macro_assembler = compiler->macro_assembler();
+  SetUpPreLoad(compiler, trace, preload);
+
+  // For now we just call all choices one after the other.  The idea ultimately
+  // is to use the Dispatch table to try only the relevant ones.
+  intptr_t choice_count = alternatives_->length();
+
+  intptr_t new_flush_budget = trace->flush_budget() / choice_count;
+
+  for (intptr_t i = first_choice; i < choice_count; i++) {
+    bool is_last = i == choice_count - 1;
+    bool fall_through_on_failure = !is_last;
+    GuardedAlternative alternative = alternatives_->At(i);
+    AlternativeGeneration* alt_gen = alt_gens->at(i);
+    alt_gen->quick_check_details.set_characters(preload->preload_characters_);
+    ZoneGrowableArray<Guard*>* guards = alternative.guards();
+    intptr_t guard_count = (guards == NULL) ? 0 : guards->length();
+    Trace new_trace(*trace);
+    new_trace.set_characters_preloaded(preload->preload_is_current_ ?
+                                         preload->preload_characters_ :
+                                         0);
+    if (preload->preload_has_checked_bounds_) {
+      new_trace.set_bound_checked_up_to(preload->preload_characters_);
+    }
+    new_trace.quick_check_performed()->Clear();
+    if (not_at_start_) new_trace.set_at_start(Trace::FALSE_VALUE);
+    if (!is_last) {
+      new_trace.set_backtrack(&alt_gen->after);
+    }
+    alt_gen->expects_preload = preload->preload_is_current_;
+    bool generate_full_check_inline = false;
+    if (kRegexpOptimization &&
+        try_to_emit_quick_check_for_alternative(i == 0) &&
+        alternative.node()->EmitQuickCheck(compiler,
+                                           trace,
+                                           &new_trace,
+                                           preload->preload_has_checked_bounds_,
+                                           &alt_gen->possible_success,
+                                           &alt_gen->quick_check_details,
+                                           fall_through_on_failure)) {
+      // Quick check was generated for this choice.
+      preload->preload_is_current_ = true;
+      preload->preload_has_checked_bounds_ = true;
+      // If we generated the quick check to fall through on possible success,
+      // we now need to generate the full check inline.
+      if (!fall_through_on_failure) {
+        macro_assembler->BindBlock(&alt_gen->possible_success);
+        new_trace.set_quick_check_performed(&alt_gen->quick_check_details);
+        new_trace.set_characters_preloaded(preload->preload_characters_);
+        new_trace.set_bound_checked_up_to(preload->preload_characters_);
+        generate_full_check_inline = true;
+      }
+    } else if (alt_gen->quick_check_details.cannot_match()) {
+      if (!fall_through_on_failure) {
+        macro_assembler->GoTo(trace->backtrack());
+      }
+      continue;
+    } else {
+      // No quick check was generated.  Put the full code here.
+      // If this is not the first choice then there could be slow checks from
+      // previous cases that go here when they fail.  There's no reason to
+      // insist that they preload characters since the slow check we are about
+      // to generate probably can't use it.
+      if (i != first_choice) {
+        alt_gen->expects_preload = false;
+        new_trace.InvalidateCurrentCharacter();
+      }
+      generate_full_check_inline = true;
+    }
+    if (generate_full_check_inline) {
+      if (new_trace.actions() != NULL) {
+        new_trace.set_flush_budget(new_flush_budget);
+      }
+      for (intptr_t j = 0; j < guard_count; j++) {
+        GenerateGuard(macro_assembler, guards->At(j), &new_trace);
+      }
+      alternative.node()->Emit(compiler, &new_trace);
+      preload->preload_is_current_ = false;
+    }
+    macro_assembler->BindBlock(&alt_gen->after);
+  }
+}
+
+
+void ChoiceNode::EmitOutOfLineContinuation(RegExpCompiler* compiler,
+                                           Trace* trace,
+                                           GuardedAlternative alternative,
+                                           AlternativeGeneration* alt_gen,
+                                           intptr_t preload_characters,
+                                           bool next_expects_preload) {
+  if (!alt_gen->possible_success.IsLinked()) return;
+
+  RegExpMacroAssembler* macro_assembler = compiler->macro_assembler();
+  macro_assembler->BindBlock(&alt_gen->possible_success);
+  Trace out_of_line_trace(*trace);
+  out_of_line_trace.set_characters_preloaded(preload_characters);
+  out_of_line_trace.set_quick_check_performed(&alt_gen->quick_check_details);
+  if (not_at_start_) out_of_line_trace.set_at_start(Trace::FALSE_VALUE);
+  ZoneGrowableArray<Guard*>* guards = alternative.guards();
+  intptr_t guard_count = (guards == NULL) ? 0 : guards->length();
+  if (next_expects_preload) {
+    BlockLabel reload_current_char;
+    out_of_line_trace.set_backtrack(&reload_current_char);
+    for (intptr_t j = 0; j < guard_count; j++) {
+      GenerateGuard(macro_assembler, guards->At(j), &out_of_line_trace);
+    }
+    alternative.node()->Emit(compiler, &out_of_line_trace);
+    macro_assembler->BindBlock(&reload_current_char);
+    // Reload the current character, since the next quick check expects that.
+    // We don't need to check bounds here because we only get into this
+    // code through a quick check which already did the checked load.
+    macro_assembler->LoadCurrentCharacter(trace->cp_offset(),
+                                          NULL,
+                                          false,
+                                          preload_characters);
+    macro_assembler->GoTo(&(alt_gen->after));
+  } else {
+    out_of_line_trace.set_backtrack(&(alt_gen->after));
+    for (intptr_t j = 0; j < guard_count; j++) {
+      GenerateGuard(macro_assembler, guards->At(j), &out_of_line_trace);
+    }
+    alternative.node()->Emit(compiler, &out_of_line_trace);
+  }
+}
+
+
+void ActionNode::Emit(RegExpCompiler* compiler, Trace* trace) {
+  RegExpMacroAssembler* assembler = compiler->macro_assembler();
+  LimitResult limit_result = LimitVersions(compiler, trace);
+  if (limit_result == DONE) return;
+  ASSERT(limit_result == CONTINUE);
+
+  RecursionCheck rc(compiler);
+
+  switch (action_type_) {
+    case STORE_POSITION: {
+      Trace::DeferredCapture
+          new_capture(data_.u_position_register.reg,
+                      data_.u_position_register.is_capture,
+                      trace);
+      Trace new_trace = *trace;
+      new_trace.add_action(&new_capture);
+      on_success()->Emit(compiler, &new_trace);
+      break;
+    }
+    case INCREMENT_REGISTER: {
+      Trace::DeferredIncrementRegister
+          new_increment(data_.u_increment_register.reg);
+      Trace new_trace = *trace;
+      new_trace.add_action(&new_increment);
+      on_success()->Emit(compiler, &new_trace);
+      break;
+    }
+    case SET_REGISTER: {
+      Trace::DeferredSetRegister
+          new_set(data_.u_store_register.reg, data_.u_store_register.value);
+      Trace new_trace = *trace;
+      new_trace.add_action(&new_set);
+      on_success()->Emit(compiler, &new_trace);
+      break;
+    }
+    case CLEAR_CAPTURES: {
+      Trace::DeferredClearCaptures
+        new_capture(Interval(data_.u_clear_captures.range_from,
+                             data_.u_clear_captures.range_to));
+      Trace new_trace = *trace;
+      new_trace.add_action(&new_capture);
+      on_success()->Emit(compiler, &new_trace);
+      break;
+    }
+    case BEGIN_SUBMATCH:
+      if (!trace->is_trivial()) {
+        trace->Flush(compiler, this);
+      } else {
+        assembler->WriteCurrentPositionToRegister(
+            data_.u_submatch.current_position_register, 0);
+        assembler->WriteStackPointerToRegister(
+            data_.u_submatch.stack_pointer_register);
+        on_success()->Emit(compiler, trace);
+      }
+      break;
+    case EMPTY_MATCH_CHECK: {
+      intptr_t start_pos_reg = data_.u_empty_match_check.start_register;
+      intptr_t stored_pos = 0;
+      intptr_t rep_reg = data_.u_empty_match_check.repetition_register;
+      bool has_minimum = (rep_reg != RegExpCompiler::kNoRegister);
+      bool know_dist = trace->GetStoredPosition(start_pos_reg, &stored_pos);
+      if (know_dist && !has_minimum && stored_pos == trace->cp_offset()) {
+        // If we know we haven't advanced and there is no minimum we
+        // can just backtrack immediately.
+        assembler->GoTo(trace->backtrack());
+      } else if (know_dist && stored_pos < trace->cp_offset()) {
+        // If we know we've advanced we can generate the continuation
+        // immediately.
+        on_success()->Emit(compiler, trace);
+      } else if (!trace->is_trivial()) {
+        trace->Flush(compiler, this);
+      } else {
+        BlockLabel skip_empty_check;
+        // If we have a minimum number of repetitions we check the current
+        // number first and skip the empty check if it's not enough.
+        if (has_minimum) {
+          intptr_t limit = data_.u_empty_match_check.repetition_limit;
+          assembler->IfRegisterLT(rep_reg, limit, &skip_empty_check);
+        }
+        // If the match is empty we bail out, otherwise we fall through
+        // to the on-success continuation.
+        assembler->IfRegisterEqPos(data_.u_empty_match_check.start_register,
+                                   trace->backtrack());
+        assembler->BindBlock(&skip_empty_check);
+        on_success()->Emit(compiler, trace);
+      }
+      break;
+    }
+    case POSITIVE_SUBMATCH_SUCCESS: {
+      if (!trace->is_trivial()) {
+        trace->Flush(compiler, this);
+        return;
+      }
+      assembler->ReadCurrentPositionFromRegister(
+          data_.u_submatch.current_position_register);
+      assembler->ReadStackPointerFromRegister(
+          data_.u_submatch.stack_pointer_register);
+      intptr_t clear_register_count = data_.u_submatch.clear_register_count;
+      if (clear_register_count == 0) {
+        on_success()->Emit(compiler, trace);
+        return;
+      }
+      intptr_t clear_registers_from = data_.u_submatch.clear_register_from;
+      BlockLabel clear_registers_backtrack;
+      Trace new_trace = *trace;
+      new_trace.set_backtrack(&clear_registers_backtrack);
+      on_success()->Emit(compiler, &new_trace);
+
+      assembler->BindBlock(&clear_registers_backtrack);
+      intptr_t clear_registers_to =
+          clear_registers_from + clear_register_count - 1;
+      assembler->ClearRegisters(clear_registers_from, clear_registers_to);
+
+      ASSERT(trace->backtrack() == NULL);
+      assembler->Backtrack();
+      return;
+    }
+    default:
+      UNREACHABLE();
+  }
+}
+
+
+void BackReferenceNode::Emit(RegExpCompiler* compiler, Trace* trace) {
+  RegExpMacroAssembler* assembler = compiler->macro_assembler();
+  if (!trace->is_trivial()) {
+    trace->Flush(compiler, this);
+    return;
+  }
+
+  LimitResult limit_result = LimitVersions(compiler, trace);
+  if (limit_result == DONE) return;
+  ASSERT(limit_result == CONTINUE);
+
+  RecursionCheck rc(compiler);
+
+  ASSERT(start_reg_ + 1 == end_reg_);
+  if (compiler->ignore_case()) {
+    assembler->CheckNotBackReferenceIgnoreCase(start_reg_,
+                                               trace->backtrack());
+  } else {
+    assembler->CheckNotBackReference(start_reg_, trace->backtrack());
+  }
+  on_success()->Emit(compiler, trace);
+}
+
+
+// -------------------------------------------------------------------
+// Dot/dotty output
+
+
+#ifdef DEBUG
+
+
+class DotPrinter: public NodeVisitor {
+ public:
+  explicit DotPrinter(bool ignore_case)
+      : ignore_case_(ignore_case) {}
+  void PrintNode(const char* label, RegExpNode* node);
+  void Visit(RegExpNode* node);
+  void PrintAttributes(RegExpNode* from);
+  void PrintOnFailure(RegExpNode* from, RegExpNode* to);
+#define DECLARE_VISIT(Type)                                          \
+  virtual void Visit##Type(Type##Node* that);
+FOR_EACH_NODE_TYPE(DECLARE_VISIT)
+#undef DECLARE_VISIT
+ private:
+  bool ignore_case_;
+};
+
+
+void DotPrinter::PrintNode(const char* label, RegExpNode* node) {
+  OS::Print("digraph G {\n  graph [label=\"");
+  for (intptr_t i = 0; label[i]; i++) {
+    switch (label[i]) {
+      case '\\':
+        OS::Print("\\\\");
+        break;
+      case '"':
+        OS::Print("\"");
+        break;
+      default:
+        OS::Print("%c", label[i]);
+        break;
+    }
+  }
+  OS::Print("\"];\n");
+  Visit(node);
+  OS::Print("}\n");
+}
+
+
+void DotPrinter::Visit(RegExpNode* node) {
+  if (node->info()->visited) return;
+  node->info()->visited = true;
+  node->Accept(this);
+}
+
+
+void DotPrinter::PrintOnFailure(RegExpNode* from, RegExpNode* on_failure) {
+  OS::Print("  n%p -> n%p [style=dotted];\n", from, on_failure);
+  Visit(on_failure);
+}
+
+
+class AttributePrinter : public ValueObject {
+ public:
+  AttributePrinter() : first_(true) {}
+  void PrintSeparator() {
+    if (first_) {
+      first_ = false;
+    } else {
+      OS::Print("|");
+    }
+  }
+  void PrintBit(const char* name, bool value) {
+    if (!value) return;
+    PrintSeparator();
+    OS::Print("{%s}", name);
+  }
+  void PrintPositive(const char* name, intptr_t value) {
+    if (value < 0) return;
+    PrintSeparator();
+    OS::Print("{%s|%" Pd "}", name, value);
+  }
+
+ private:
+  bool first_;
+};
+
+
+void DotPrinter::PrintAttributes(RegExpNode* that) {
+  OS::Print("  a%p [shape=Mrecord, color=grey, fontcolor=grey, "
+            "margin=0.1, fontsize=10, label=\"{", that);
+  AttributePrinter printer;
+  NodeInfo* info = that->info();
+  printer.PrintBit("NI", info->follows_newline_interest);
+  printer.PrintBit("WI", info->follows_word_interest);
+  printer.PrintBit("SI", info->follows_start_interest);
+  BlockLabel* label = that->label();
+  if (label->IsBound())
+    printer.PrintPositive("@", label->Position());
+  OS::Print("}\"];\n"
+            "  a%p -> n%p [style=dashed, color=grey, arrowhead=none];\n",
+            that, that);
+}
+
+
+void DotPrinter::VisitChoice(ChoiceNode* that) {
+  OS::Print("  n%p [shape=Mrecord, label=\"?\"];\n", that);
+  for (intptr_t i = 0; i < that->alternatives()->length(); i++) {
+    GuardedAlternative alt = that->alternatives()->At(i);
+    OS::Print("  n%p -> n%p", that, alt.node());
+  }
+  for (intptr_t i = 0; i < that->alternatives()->length(); i++) {
+    GuardedAlternative alt = that->alternatives()->At(i);
+    alt.node()->Accept(this);
+  }
+}
+
+
+void DotPrinter::VisitText(TextNode* that) {
+  OS::Print("  n%p [label=\"", that);
+  for (intptr_t i = 0; i < that->elements()->length(); i++) {
+    if (i > 0) OS::Print(" ");
+    TextElement elm = that->elements()->At(i);
+    switch (elm.text_type()) {
+      case TextElement::ATOM: {
+        ZoneGrowableArray<uint16_t>* data = elm.atom()->data();
+        for (intptr_t i = 0; i < data->length(); i++) {
+          OS::Print("%c", static_cast<char>(data->At(i)));
+        }
+        break;
+      }
+      case TextElement::CHAR_CLASS: {
+        RegExpCharacterClass* node = elm.char_class();
+        OS::Print("[");
+        if (node->is_negated()) OS::Print("^");
+        for (intptr_t j = 0; j < node->ranges()->length(); j++) {
+          CharacterRange range = node->ranges()->At(j);
+          PrintUtf16(range.from());
+          OS::Print("-");
+          PrintUtf16(range.to());
+        }
+        OS::Print("]");
+        break;
+      }
+      default:
+        UNREACHABLE();
+    }
+  }
+  OS::Print("\", shape=box, peripheries=2];\n");
+  PrintAttributes(that);
+  OS::Print("  n%p -> n%p;\n", that, that->on_success());
+  Visit(that->on_success());
+}
+
+
+void DotPrinter::VisitBackReference(BackReferenceNode* that) {
+  OS::Print("  n%p [label=\"$%" Pd "..$%" Pd "\", shape=doubleoctagon];\n",
+            that, that->start_register(), that->end_register());
+  PrintAttributes(that);
+  OS::Print("  n%p -> n%p;\n", that, that->on_success());
+  Visit(that->on_success());
+}
+
+
+void DotPrinter::VisitEnd(EndNode* that) {
+  OS::Print("  n%p [style=bold, shape=point];\n", that);
+  PrintAttributes(that);
+}
+
+
+void DotPrinter::VisitAssertion(AssertionNode* that) {
+  OS::Print("  n%p [", that);
+  switch (that->assertion_type()) {
+    case AssertionNode::AT_END:
+      OS::Print("label=\"$\", shape=septagon");
+      break;
+    case AssertionNode::AT_START:
+      OS::Print("label=\"^\", shape=septagon");
+      break;
+    case AssertionNode::AT_BOUNDARY:
+      OS::Print("label=\"\\b\", shape=septagon");
+      break;
+    case AssertionNode::AT_NON_BOUNDARY:
+      OS::Print("label=\"\\B\", shape=septagon");
+      break;
+    case AssertionNode::AFTER_NEWLINE:
+      OS::Print("label=\"(?<=\\n)\", shape=septagon");
+      break;
+  }
+  OS::Print("];\n");
+  PrintAttributes(that);
+  RegExpNode* successor = that->on_success();
+  OS::Print("  n%p -> n%p;\n", that, successor);
+  Visit(successor);
+}
+
+
+void DotPrinter::VisitAction(ActionNode* that) {
+  OS::Print("  n%p [", that);
+  switch (that->action_type_) {
+    case ActionNode::SET_REGISTER:
+      OS::Print("label=\"$%" Pd ":=%" Pd "\", shape=octagon",
+                that->data_.u_store_register.reg,
+                that->data_.u_store_register.value);
+      break;
+    case ActionNode::INCREMENT_REGISTER:
+      OS::Print("label=\"$%" Pd "++\", shape=octagon",
+                that->data_.u_increment_register.reg);
+      break;
+    case ActionNode::STORE_POSITION:
+      OS::Print("label=\"$%" Pd ":=$pos\", shape=octagon",
+                that->data_.u_position_register.reg);
+      break;
+    case ActionNode::BEGIN_SUBMATCH:
+      OS::Print("label=\"$%" Pd ":=$pos,begin\", shape=septagon",
+                that->data_.u_submatch.current_position_register);
+      break;
+    case ActionNode::POSITIVE_SUBMATCH_SUCCESS:
+      OS::Print("label=\"escape\", shape=septagon");
+      break;
+    case ActionNode::EMPTY_MATCH_CHECK:
+      OS::Print("label=\"$%" Pd "=$pos?,$%" Pd "<%" Pd "?\", shape=septagon",
+                that->data_.u_empty_match_check.start_register,
+                that->data_.u_empty_match_check.repetition_register,
+                that->data_.u_empty_match_check.repetition_limit);
+      break;
+    case ActionNode::CLEAR_CAPTURES: {
+      OS::Print("label=\"clear $%" Pd " to $%" Pd "\", shape=septagon",
+                that->data_.u_clear_captures.range_from,
+                that->data_.u_clear_captures.range_to);
+      break;
+    }
+  }
+  OS::Print("];\n");
+  PrintAttributes(that);
+  RegExpNode* successor = that->on_success();
+  OS::Print("  n%p -> n%p;\n", that, successor);
+  Visit(successor);
+}
+
+
+void RegExpEngine::DotPrint(const char* label,
+                            RegExpNode* node,
+                            bool ignore_case) {
+  DotPrinter printer(ignore_case);
+  printer.PrintNode(label, node);
+}
+
+
+#endif  // DEBUG
+
+
+// -------------------------------------------------------------------
+// Tree to graph conversion
+
+RegExpNode* RegExpAtom::ToNode(RegExpCompiler* compiler,
+                               RegExpNode* on_success) {
+  ZoneGrowableArray<TextElement>* elms =
+      new(CI) ZoneGrowableArray<TextElement>(1);
+  elms->Add(TextElement::Atom(this));
+  return new(CI) TextNode(elms, on_success);
+}
+
+
+RegExpNode* RegExpText::ToNode(RegExpCompiler* compiler,
+                               RegExpNode* on_success) {
+  ZoneGrowableArray<TextElement>* elms =
+      new(CI) ZoneGrowableArray<TextElement>(1);
+  for (intptr_t  i = 0; i < elements()->length(); i++) {
+    elms->Add(elements()->At(i));
+  }
+  return new(CI) TextNode(elms, on_success);
+}
+
+
+static bool CompareInverseRanges(ZoneGrowableArray<CharacterRange>* ranges,
+                                 const intptr_t* special_class,
+                                 intptr_t length) {
+  length--;  // Remove final 0x10000.
+  ASSERT(special_class[length] == 0x10000);
+  ASSERT(ranges->length() != 0);
+  ASSERT(length != 0);
+  ASSERT(special_class[0] != 0);
+  if (ranges->length() != (length >> 1) + 1) {
+    return false;
+  }
+  CharacterRange range = ranges->At(0);
+  if (range.from() != 0) {
+    return false;
+  }
+  for (intptr_t i = 0; i < length; i += 2) {
+    if (special_class[i] != (range.to() + 1)) {
+      return false;
+    }
+    range = ranges->At((i >> 1) + 1);
+    if (special_class[i+1] != range.from()) {
+      return false;
+    }
+  }
+  if (range.to() != 0xffff) {
+    return false;
+  }
+  return true;
+}
+
+
+static bool CompareRanges(ZoneGrowableArray<CharacterRange>* ranges,
+                          const intptr_t* special_class,
+                          intptr_t length) {
+  length--;  // Remove final 0x10000.
+  ASSERT(special_class[length] == 0x10000);
+  if (ranges->length() * 2 != length) {
+    return false;
+  }
+  for (intptr_t i = 0; i < length; i += 2) {
+    CharacterRange range = ranges->At(i >> 1);
+    if (range.from() != special_class[i] ||
+        range.to() != special_class[i + 1] - 1) {
+      return false;
+    }
+  }
+  return true;
+}
+
+
+bool RegExpCharacterClass::is_standard() {
+  // TODO(lrn): Remove need for this function, by not throwing away information
+  // along the way.
+  if (is_negated_) {
+    return false;
+  }
+  if (set_.is_standard()) {
+    return true;
+  }
+  if (CompareRanges(set_.ranges(), kSpaceRanges, kSpaceRangeCount)) {
+    set_.set_standard_set_type('s');
+    return true;
+  }
+  if (CompareInverseRanges(set_.ranges(), kSpaceRanges, kSpaceRangeCount)) {
+    set_.set_standard_set_type('S');
+    return true;
+  }
+  if (CompareInverseRanges(set_.ranges(),
+                           kLineTerminatorRanges,
+                           kLineTerminatorRangeCount)) {
+    set_.set_standard_set_type('.');
+    return true;
+  }
+  if (CompareRanges(set_.ranges(),
+                    kLineTerminatorRanges,
+                    kLineTerminatorRangeCount)) {
+    set_.set_standard_set_type('n');
+    return true;
+  }
+  if (CompareRanges(set_.ranges(), kWordRanges, kWordRangeCount)) {
+    set_.set_standard_set_type('w');
+    return true;
+  }
+  if (CompareInverseRanges(set_.ranges(), kWordRanges, kWordRangeCount)) {
+    set_.set_standard_set_type('W');
+    return true;
+  }
+  return false;
+}
+
+
+RegExpNode* RegExpCharacterClass::ToNode(RegExpCompiler* compiler,
+                                         RegExpNode* on_success) {
+  return new(CI) TextNode(this, on_success);
+}
+
+
+RegExpNode* RegExpDisjunction::ToNode(RegExpCompiler* compiler,
+                                      RegExpNode* on_success) {
+  ZoneGrowableArray<RegExpTree*>* alternatives = this->alternatives();
+  intptr_t length = alternatives->length();
+  ChoiceNode* result =
+      new(CI) ChoiceNode(length, CI);
+  for (intptr_t i = 0; i < length; i++) {
+    GuardedAlternative alternative(alternatives->At(i)->ToNode(compiler,
+                                                               on_success));
+    result->AddAlternative(alternative);
+  }
+  return result;
+}
+
+
+RegExpNode* RegExpQuantifier::ToNode(RegExpCompiler* compiler,
+                                     RegExpNode* on_success) {
+  return ToNode(min(),
+                max(),
+                is_greedy(),
+                body(),
+                compiler,
+                on_success);
+}
+
+
+// Scoped object to keep track of how much we unroll quantifier loops in the
+// regexp graph generator.
+class RegExpExpansionLimiter : public ValueObject {
+ public:
+  static const intptr_t kMaxExpansionFactor = 6;
+  RegExpExpansionLimiter(RegExpCompiler* compiler, intptr_t factor)
+      : compiler_(compiler),
+        saved_expansion_factor_(compiler->current_expansion_factor()),
+        ok_to_expand_(saved_expansion_factor_ <= kMaxExpansionFactor) {
+    ASSERT(factor > 0);
+    if (ok_to_expand_) {
+      if (factor > kMaxExpansionFactor) {
+        // Avoid integer overflow of the current expansion factor.
+        ok_to_expand_ = false;
+        compiler->set_current_expansion_factor(kMaxExpansionFactor + 1);
+      } else {
+        intptr_t new_factor = saved_expansion_factor_ * factor;
+        ok_to_expand_ = (new_factor <= kMaxExpansionFactor);
+        compiler->set_current_expansion_factor(new_factor);
+      }
+    }
+  }
+
+  ~RegExpExpansionLimiter() {
+    compiler_->set_current_expansion_factor(saved_expansion_factor_);
+  }
+
+  bool ok_to_expand() { return ok_to_expand_; }
+
+ private:
+  RegExpCompiler* compiler_;
+  intptr_t saved_expansion_factor_;
+  bool ok_to_expand_;
+
+  DISALLOW_IMPLICIT_CONSTRUCTORS(RegExpExpansionLimiter);
+};
+
+
+RegExpNode* RegExpQuantifier::ToNode(intptr_t min,
+                                     intptr_t max,
+                                     bool is_greedy,
+                                     RegExpTree* body,
+                                     RegExpCompiler* compiler,
+                                     RegExpNode* on_success,
+                                     bool not_at_start) {
+  // x{f, t} becomes this:
+  //
+  //             (r++)<-.
+  //               |     `
+  //               |     (x)
+  //               v     ^
+  //      (r=0)-->(?)---/ [if r < t]
+  //               |
+  //   [if r >= f] \----> ...
+  //
+
+  // 15.10.2.5 RepeatMatcher algorithm.
+  // The parser has already eliminated the case where max is 0.  In the case
+  // where max_match is zero the parser has removed the quantifier if min was
+  // > 0 and removed the atom if min was 0.  See AddQuantifierToAtom.
+
+  // If we know that we cannot match zero length then things are a little
+  // simpler since we don't need to make the special zero length match check
+  // from step 2.1.  If the min and max are small we can unroll a little in
+  // this case.
+  // Unroll (foo)+ and (foo){3,}
+  static const intptr_t kMaxUnrolledMinMatches = 3;
+  // Unroll (foo)? and (foo){x,3}
+  static const intptr_t kMaxUnrolledMaxMatches = 3;
+  if (max == 0) return on_success;  // This can happen due to recursion.
+  bool body_can_be_empty = (body->min_match() == 0);
+  intptr_t body_start_reg = RegExpCompiler::kNoRegister;
+  Interval capture_registers = body->CaptureRegisters();
+  bool needs_capture_clearing = !capture_registers.is_empty();
+  Isolate* isolate = compiler->isolate();
+
+  if (body_can_be_empty) {
+    body_start_reg = compiler->AllocateRegister();
+  } else if (kRegexpOptimization && !needs_capture_clearing) {
+    // Only unroll if there are no captures and the body can't be
+    // empty.
+    {
+      RegExpExpansionLimiter limiter(
+          compiler, min + ((max != min) ? 1 : 0));
+      if (min > 0 && min <= kMaxUnrolledMinMatches && limiter.ok_to_expand()) {
+        intptr_t new_max = (max == kInfinity) ? max : max - min;
+        // Recurse once to get the loop or optional matches after the fixed
+        // ones.
+        RegExpNode* answer = ToNode(
+            0, new_max, is_greedy, body, compiler, on_success, true);
+        // Unroll the forced matches from 0 to min.  This can cause chains of
+        // TextNodes (which the parser does not generate).  These should be
+        // combined if it turns out they hinder good code generation.
+        for (intptr_t i = 0; i < min; i++) {
+          answer = body->ToNode(compiler, answer);
+        }
+        return answer;
+      }
+    }
+    if (max <= kMaxUnrolledMaxMatches && min == 0) {
+      ASSERT(max > 0);  // Due to the 'if' above.
+      RegExpExpansionLimiter limiter(compiler, max);
+      if (limiter.ok_to_expand()) {
+        // Unroll the optional matches up to max.
+        RegExpNode* answer = on_success;
+        for (intptr_t i = 0; i < max; i++) {
+          ChoiceNode* alternation = new(isolate) ChoiceNode(2, isolate);
+          if (is_greedy) {
+            alternation->AddAlternative(
+                GuardedAlternative(body->ToNode(compiler, answer)));
+            alternation->AddAlternative(GuardedAlternative(on_success));
+          } else {
+            alternation->AddAlternative(GuardedAlternative(on_success));
+            alternation->AddAlternative(
+                GuardedAlternative(body->ToNode(compiler, answer)));
+          }
+          answer = alternation;
+          if (not_at_start) alternation->set_not_at_start();
+        }
+        return answer;
+      }
+    }
+  }
+  bool has_min = min > 0;
+  bool has_max = max < RegExpTree::kInfinity;
+  bool needs_counter = has_min || has_max;
+  intptr_t reg_ctr = needs_counter
+      ? compiler->AllocateRegister()
+      : RegExpCompiler::kNoRegister;
+  LoopChoiceNode* center = new(isolate) LoopChoiceNode(body->min_match() == 0,
+                                                       isolate);
+  if (not_at_start) center->set_not_at_start();
+  RegExpNode* loop_return = needs_counter
+      ? static_cast<RegExpNode*>(ActionNode::IncrementRegister(reg_ctr, center))
+      : static_cast<RegExpNode*>(center);
+  if (body_can_be_empty) {
+    // If the body can be empty we need to check if it was and then
+    // backtrack.
+    loop_return = ActionNode::EmptyMatchCheck(body_start_reg,
+                                              reg_ctr,
+                                              min,
+                                              loop_return);
+  }
+  RegExpNode* body_node = body->ToNode(compiler, loop_return);
+  if (body_can_be_empty) {
+    // If the body can be empty we need to store the start position
+    // so we can bail out if it was empty.
+    body_node = ActionNode::StorePosition(body_start_reg, false, body_node);
+  }
+  if (needs_capture_clearing) {
+    // Before entering the body of this loop we need to clear captures.
+    body_node = ActionNode::ClearCaptures(capture_registers, body_node);
+  }
+  GuardedAlternative body_alt(body_node);
+  if (has_max) {
+    Guard* body_guard =
+        new(isolate) Guard(reg_ctr, Guard::LT, max);
+    body_alt.AddGuard(body_guard, isolate);
+  }
+  GuardedAlternative rest_alt(on_success);
+  if (has_min) {
+    Guard* rest_guard = new(isolate) Guard(reg_ctr, Guard::GEQ, min);
+    rest_alt.AddGuard(rest_guard, isolate);
+  }
+  if (is_greedy) {
+    center->AddLoopAlternative(body_alt);
+    center->AddContinueAlternative(rest_alt);
+  } else {
+    center->AddContinueAlternative(rest_alt);
+    center->AddLoopAlternative(body_alt);
+  }
+  if (needs_counter) {
+    return ActionNode::SetRegister(reg_ctr, 0, center);
+  } else {
+    return center;
+  }
+}
+
+
+RegExpNode* RegExpAssertion::ToNode(RegExpCompiler* compiler,
+                                    RegExpNode* on_success) {
+  switch (assertion_type()) {
+    case START_OF_LINE:
+      return AssertionNode::AfterNewline(on_success);
+    case START_OF_INPUT:
+      return AssertionNode::AtStart(on_success);
+    case BOUNDARY:
+      return AssertionNode::AtBoundary(on_success);
+    case NON_BOUNDARY:
+      return AssertionNode::AtNonBoundary(on_success);
+    case END_OF_INPUT:
+      return AssertionNode::AtEnd(on_success);
+    case END_OF_LINE: {
+      // Compile $ in multiline regexps as an alternation with a positive
+      // lookahead in one side and an end-of-input on the other side.
+      // We need two registers for the lookahead.
+      intptr_t stack_pointer_register = compiler->AllocateRegister();
+      intptr_t position_register = compiler->AllocateRegister();
+      // The ChoiceNode to distinguish between a newline and end-of-input.
+      ChoiceNode* result = new ChoiceNode(2, on_success->isolate());
+      // Create a newline atom.
+      ZoneGrowableArray<CharacterRange>* newline_ranges =
+          new ZoneGrowableArray<CharacterRange>(3);
+      CharacterRange::AddClassEscape('n', newline_ranges);
+      RegExpCharacterClass* newline_atom = new RegExpCharacterClass('n');
+      TextNode* newline_matcher = new TextNode(
+         newline_atom,
+         ActionNode::PositiveSubmatchSuccess(stack_pointer_register,
+                                             position_register,
+                                             0,  // No captures inside.
+                                             -1,  // Ignored if no captures.
+                                             on_success));
+      // Create an end-of-input matcher.
+      RegExpNode* end_of_line = ActionNode::BeginSubmatch(
+          stack_pointer_register,
+          position_register,
+          newline_matcher);
+      // Add the two alternatives to the ChoiceNode.
+      GuardedAlternative eol_alternative(end_of_line);
+      result->AddAlternative(eol_alternative);
+      GuardedAlternative end_alternative(AssertionNode::AtEnd(on_success));
+      result->AddAlternative(end_alternative);
+      return result;
+    }
+    default:
+      UNREACHABLE();
+  }
+  return on_success;
+}
+
+
+RegExpNode* RegExpBackReference::ToNode(RegExpCompiler* compiler,
+                                        RegExpNode* on_success) {
+  return new(CI)
+      BackReferenceNode(RegExpCapture::StartRegister(index()),
+                        RegExpCapture::EndRegister(index()),
+                        on_success);
+}
+
+
+RegExpNode* RegExpEmpty::ToNode(RegExpCompiler* compiler,
+                                RegExpNode* on_success) {
+  return on_success;
+}
+
+
+RegExpNode* RegExpLookahead::ToNode(RegExpCompiler* compiler,
+                                    RegExpNode* on_success) {
+  intptr_t stack_pointer_register = compiler->AllocateRegister();
+  intptr_t position_register = compiler->AllocateRegister();
+
+  const intptr_t registers_per_capture = 2;
+  const intptr_t register_of_first_capture = 2;
+  intptr_t register_count = capture_count_ * registers_per_capture;
+  intptr_t register_start =
+    register_of_first_capture + capture_from_ * registers_per_capture;
+
+  RegExpNode* success;
+  if (is_positive()) {
+    RegExpNode* node = ActionNode::BeginSubmatch(
+        stack_pointer_register,
+        position_register,
+        body()->ToNode(
+            compiler,
+            ActionNode::PositiveSubmatchSuccess(stack_pointer_register,
+                                                position_register,
+                                                register_count,
+                                                register_start,
+                                                on_success)));
+    return node;
+  } else {
+    // We use a ChoiceNode for a negative lookahead because it has most of
+    // the characteristics we need.  It has the body of the lookahead as its
+    // first alternative and the expression after the lookahead of the second
+    // alternative.  If the first alternative succeeds then the
+    // NegativeSubmatchSuccess will unwind the stack including everything the
+    // choice node set up and backtrack.  If the first alternative fails then
+    // the second alternative is tried, which is exactly the desired result
+    // for a negative lookahead.  The NegativeLookaheadChoiceNode is a special
+    // ChoiceNode that knows to ignore the first exit when calculating quick
+    // checks.
+
+    GuardedAlternative body_alt(
+        body()->ToNode(
+            compiler,
+            success = new(CI) NegativeSubmatchSuccess(stack_pointer_register,
+                                                      position_register,
+                                                      register_count,
+                                                      register_start,
+                                                      CI)));
+    ChoiceNode* choice_node =
+        new(CI) NegativeLookaheadChoiceNode(body_alt,
+                                            GuardedAlternative(on_success),
+                                            CI);
+    return ActionNode::BeginSubmatch(stack_pointer_register,
+                                     position_register,
+                                     choice_node);
+  }
+}
+
+
+RegExpNode* RegExpCapture::ToNode(RegExpCompiler* compiler,
+                                  RegExpNode* on_success) {
+  return ToNode(body(), index(), compiler, on_success);
+}
+
+
+RegExpNode* RegExpCapture::ToNode(RegExpTree* body,
+                                  intptr_t index,
+                                  RegExpCompiler* compiler,
+                                  RegExpNode* on_success) {
+  intptr_t start_reg = RegExpCapture::StartRegister(index);
+  intptr_t end_reg = RegExpCapture::EndRegister(index);
+  RegExpNode* store_end = ActionNode::StorePosition(end_reg, true, on_success);
+  RegExpNode* body_node = body->ToNode(compiler, store_end);
+  return ActionNode::StorePosition(start_reg, true, body_node);
+}
+
+
+RegExpNode* RegExpAlternative::ToNode(RegExpCompiler* compiler,
+                                      RegExpNode* on_success) {
+  ZoneGrowableArray<RegExpTree*>* children = nodes();
+  RegExpNode* current = on_success;
+  for (intptr_t i = children->length() - 1; i >= 0; i--) {
+    current = children->At(i)->ToNode(compiler, current);
+  }
+  return current;
+}
+
+
+static void AddClass(const intptr_t* elmv,
+                     intptr_t elmc,
+                     ZoneGrowableArray<CharacterRange>* ranges) {
+  elmc--;
+  ASSERT(elmv[elmc] == 0x10000);
+  for (intptr_t i = 0; i < elmc; i += 2) {
+    ASSERT(elmv[i] < elmv[i + 1]);
+    ranges->Add(CharacterRange(elmv[i], elmv[i + 1] - 1));
+  }
+}
+
+
+static void AddClassNegated(const intptr_t *elmv,
+                            intptr_t elmc,
+                            ZoneGrowableArray<CharacterRange>* ranges) {
+  elmc--;
+  ASSERT(elmv[elmc] == 0x10000);
+  ASSERT(elmv[0] != 0x0000);
+  ASSERT(elmv[elmc-1] != Utf16::kMaxCodeUnit);
+  uint16_t last = 0x0000;
+  for (intptr_t i = 0; i < elmc; i += 2) {
+    ASSERT(last <= elmv[i] - 1);
+    ASSERT(elmv[i] < elmv[i + 1]);
+    ranges->Add(CharacterRange(last, elmv[i] - 1));
+    last = elmv[i + 1];
+  }
+  ranges->Add(CharacterRange(last, Utf16::kMaxCodeUnit));
+}
+
+
+void CharacterRange::AddClassEscape(uint16_t type,
+                                    ZoneGrowableArray<CharacterRange>* ranges) {
+  switch (type) {
+    case 's':
+      AddClass(kSpaceRanges, kSpaceRangeCount, ranges);
+      break;
+    case 'S':
+      AddClassNegated(kSpaceRanges, kSpaceRangeCount, ranges);
+      break;
+    case 'w':
+      AddClass(kWordRanges, kWordRangeCount, ranges);
+      break;
+    case 'W':
+      AddClassNegated(kWordRanges, kWordRangeCount, ranges);
+      break;
+    case 'd':
+      AddClass(kDigitRanges, kDigitRangeCount, ranges);
+      break;
+    case 'D':
+      AddClassNegated(kDigitRanges, kDigitRangeCount, ranges);
+      break;
+    case '.':
+      AddClassNegated(kLineTerminatorRanges,
+                      kLineTerminatorRangeCount,
+                      ranges);
+      break;
+    // This is not a character range as defined by the spec but a
+    // convenient shorthand for a character class that matches any
+    // character.
+    case '*':
+      ranges->Add(CharacterRange::Everything());
+      break;
+    // This is the set of characters matched by the $ and ^ symbols
+    // in multiline mode.
+    case 'n':
+      AddClass(kLineTerminatorRanges,
+               kLineTerminatorRangeCount,
+               ranges);
+      break;
+    default:
+      UNREACHABLE();
+  }
+}
+
+
+void CharacterRange::AddCaseEquivalents(
+                        ZoneGrowableArray<CharacterRange>* ranges,
+                        bool is_one_byte,
+                        Isolate* isolate) {
+  uint16_t bottom = from();
+  uint16_t top = to();
+  if (is_one_byte && !RangeContainsLatin1Equivalents(*this)) {
+    if (bottom > Symbols::kMaxOneCharCodeSymbol) return;
+    if (top > Symbols::kMaxOneCharCodeSymbol) {
+      top = Symbols::kMaxOneCharCodeSymbol;
+    }
+  }
+
+  unibrow::Mapping<unibrow::Ecma262UnCanonicalize> jsregexp_uncanonicalize;
+  unibrow::Mapping<unibrow::CanonicalizationRange> jsregexp_canonrange;
+  int32_t chars[unibrow::Ecma262UnCanonicalize::kMaxWidth];
+  if (top == bottom) {
+    // If this is a singleton we just expand the one character.
+    intptr_t length = jsregexp_uncanonicalize.get(bottom, '\0', chars); // NOLINT
+    for (intptr_t i = 0; i < length; i++) {
+      uint32_t chr = chars[i];
+      if (chr != bottom) {
+        ranges->Add(CharacterRange::Singleton(chars[i]));
+      }
+    }
+  } else {
+    // If this is a range we expand the characters block by block,
+    // expanding contiguous subranges (blocks) one at a time.
+    // The approach is as follows.  For a given start character we
+    // look up the remainder of the block that contains it (represented
+    // by the end point), for instance we find 'z' if the character
+    // is 'c'.  A block is characterized by the property
+    // that all characters uncanonicalize in the same way, except that
+    // each entry in the result is incremented by the distance from the first
+    // element.  So a-z is a block because 'a' uncanonicalizes to ['a', 'A'] and
+    // the k'th letter uncanonicalizes to ['a' + k, 'A' + k].
+    // Once we've found the end point we look up its uncanonicalization
+    // and produce a range for each element.  For instance for [c-f]
+    // we look up ['z', 'Z'] and produce [c-f] and [C-F].  We then only
+    // add a range if it is not already contained in the input, so [c-f]
+    // will be skipped but [C-F] will be added.  If this range is not
+    // completely contained in a block we do this for all the blocks
+    // covered by the range (handling characters that is not in a block
+    // as a "singleton block").
+    int32_t range[unibrow::Ecma262UnCanonicalize::kMaxWidth];
+    intptr_t pos = bottom;
+    while (pos <= top) {
+      intptr_t length = jsregexp_canonrange.get(pos, '\0', range);
+      uint16_t block_end;
+      if (length == 0) {
+        block_end = pos;
+      } else {
+        ASSERT(length == 1);
+        block_end = range[0];
+      }
+      intptr_t end = (block_end > top) ? top : block_end;
+      length = jsregexp_uncanonicalize.get(block_end, '\0', range); // NOLINT
+      for (intptr_t i = 0; i < length; i++) {
+        uint32_t c = range[i];
+        uint16_t range_from = c - (block_end - pos);
+        uint16_t range_to = c - (block_end - end);
+        if (!(bottom <= range_from && range_to <= top)) {
+          ranges->Add(CharacterRange(range_from, range_to));
+        }
+      }
+      pos = end + 1;
+    }
+  }
+}
+
+
+bool CharacterRange::IsCanonical(ZoneGrowableArray<CharacterRange>* ranges) {
+  ASSERT(ranges != NULL);
+  intptr_t n = ranges->length();
+  if (n <= 1) return true;
+  intptr_t max = ranges->At(0).to();
+  for (intptr_t i = 1; i < n; i++) {
+    CharacterRange next_range = ranges->At(i);
+    if (next_range.from() <= max + 1) return false;
+    max = next_range.to();
+  }
+  return true;
+}
+
+
+ZoneGrowableArray<CharacterRange>* CharacterSet::ranges() {
+  if (ranges_ == NULL) {
+    ranges_ = new ZoneGrowableArray<CharacterRange>(2);
+    CharacterRange::AddClassEscape(standard_set_type_, ranges_);
+  }
+  return ranges_;
+}
+
+
+// Move a number of elements in a zone array to another position
+// in the same array. Handles overlapping source and target areas.
+static void MoveRanges(ZoneGrowableArray<CharacterRange>* list,
+                       intptr_t from,
+                       intptr_t to,
+                       intptr_t count) {
+  // Ranges are potentially overlapping.
+  if (from < to) {
+    for (intptr_t i = count - 1; i >= 0; i--) {
+      (*list)[to + i] = list->At(from + i);
+    }
+  } else {
+    for (intptr_t i = 0; i < count; i++) {
+      (*list)[to + i] = list->At(from + i);
+    }
+  }
+}
+
+
+static intptr_t InsertRangeInCanonicalList(
+                    ZoneGrowableArray<CharacterRange>* list,
+                    intptr_t count,
+                    CharacterRange insert) {
+  // Inserts a range into list[0..count[, which must be sorted
+  // by from value and non-overlapping and non-adjacent, using at most
+  // list[0..count] for the result. Returns the number of resulting
+  // canonicalized ranges. Inserting a range may collapse existing ranges into
+  // fewer ranges, so the return value can be anything in the range 1..count+1.
+  uint16_t from = insert.from();
+  uint16_t to = insert.to();
+  intptr_t start_pos = 0;
+  intptr_t end_pos = count;
+  for (intptr_t i = count - 1; i >= 0; i--) {
+    CharacterRange current = list->At(i);
+    if (current.from() > to + 1) {
+      end_pos = i;
+    } else if (current.to() + 1 < from) {
+      start_pos = i + 1;
+      break;
+    }
+  }
+
+  // Inserted range overlaps, or is adjacent to, ranges at positions
+  // [start_pos..end_pos[. Ranges before start_pos or at or after end_pos are
+  // not affected by the insertion.
+  // If start_pos == end_pos, the range must be inserted before start_pos.
+  // if start_pos < end_pos, the entire range from start_pos to end_pos
+  // must be merged with the insert range.
+
+  if (start_pos == end_pos) {
+    // Insert between existing ranges at position start_pos.
+    if (start_pos < count) {
+      MoveRanges(list, start_pos, start_pos + 1, count - start_pos);
+    }
+    (*list)[start_pos] = insert;
+    return count + 1;
+  }
+  if (start_pos + 1 == end_pos) {
+    // Replace single existing range at position start_pos.
+    CharacterRange to_replace = list->At(start_pos);
+    intptr_t new_from = Utils::Minimum(to_replace.from(), from);
+    intptr_t new_to = Utils::Maximum(to_replace.to(), to);
+    (*list)[start_pos] = CharacterRange(new_from, new_to);
+    return count;
+  }
+  // Replace a number of existing ranges from start_pos to end_pos - 1.
+  // Move the remaining ranges down.
+
+  intptr_t new_from = Utils::Minimum(list->At(start_pos).from(), from);
+  intptr_t new_to = Utils::Maximum(list->At(end_pos - 1).to(), to);
+  if (end_pos < count) {
+    MoveRanges(list, end_pos, start_pos + 1, count - end_pos);
+  }
+  (*list)[start_pos] = CharacterRange(new_from, new_to);
+  return count - (end_pos - start_pos) + 1;
+}
+
+
+void CharacterSet::Canonicalize() {
+  // Special/default classes are always considered canonical. The result
+  // of calling ranges() will be sorted.
+  if (ranges_ == NULL) return;
+  CharacterRange::Canonicalize(ranges_);
+}
+
+
+void CharacterRange::Canonicalize(
+    ZoneGrowableArray<CharacterRange>* character_ranges) {
+  if (character_ranges->length() <= 1) return;
+  // Check whether ranges are already canonical (increasing, non-overlapping,
+  // non-adjacent).
+  intptr_t n = character_ranges->length();
+  intptr_t max = character_ranges->At(0).to();
+  intptr_t i = 1;
+  while (i < n) {
+    CharacterRange current = character_ranges->At(i);
+    if (current.from() <= max + 1) {
+      break;
+    }
+    max = current.to();
+    i++;
+  }
+  // Canonical until the i'th range. If that's all of them, we are done.
+  if (i == n) return;
+
+  // The ranges at index i and forward are not canonicalized. Make them so by
+  // doing the equivalent of insertion sort (inserting each into the previous
+  // list, in order).
+  // Notice that inserting a range can reduce the number of ranges in the
+  // result due to combining of adjacent and overlapping ranges.
+  intptr_t read = i;  // Range to insert.
+  intptr_t num_canonical = i;  // Length of canonicalized part of list.
+  do {
+    num_canonical = InsertRangeInCanonicalList(character_ranges,
+                                               num_canonical,
+                                               character_ranges->At(read));
+    read++;
+  } while (read < n);
+  character_ranges->TruncateTo(num_canonical);
+
+  ASSERT(CharacterRange::IsCanonical(character_ranges));
+}
+
+
+void CharacterRange::Negate(ZoneGrowableArray<CharacterRange>* ranges,
+                            ZoneGrowableArray<CharacterRange>* negated_ranges) {
+  ASSERT(CharacterRange::IsCanonical(ranges));
+  ASSERT(negated_ranges->length() == 0);
+  intptr_t range_count = ranges->length();
+  uint16_t from = 0;
+  intptr_t i = 0;
+  if (range_count > 0 && ranges->At(0).from() == 0) {
+    from = ranges->At(0).to();
+    i = 1;
+  }
+  while (i < range_count) {
+    CharacterRange range = ranges->At(i);
+    negated_ranges->Add(CharacterRange(from + 1, range.from() - 1));
+    from = range.to();
+    i++;
+  }
+  if (from < Utf16::kMaxCodeUnit) {
+    negated_ranges->Add(CharacterRange(from + 1, Utf16::kMaxCodeUnit));
+  }
+}
+
+
+// -------------------------------------------------------------------
+// Splay tree
+
+
+// Workaround for the fact that ZoneGrowableArray does not have contains().
+static bool ArrayContains(ZoneGrowableArray<unsigned>* array,
+                          unsigned value) {
+  for (intptr_t i = 0; i < array->length(); i++) {
+    if (array->At(i) == value) {
+      return true;
+    }
+  }
+  return false;
+}
+
+
+void OutSet::Set(unsigned value, Isolate* isolate) {
+  if (value < kFirstLimit) {
+    first_ |= (1 << value);
+  } else {
+    if (remaining_ == NULL)
+      remaining_ = new(isolate) ZoneGrowableArray<unsigned>(1);
+
+    bool remaining_contains_value = ArrayContains(remaining_, value);
+    if (remaining_->is_empty() || !remaining_contains_value) {
+      remaining_->Add(value);
+    }
+  }
+}
+
+
+bool OutSet::Get(unsigned value) const {
+  if (value < kFirstLimit) {
+    return (first_ & (1 << value)) != 0;
+  } else if (remaining_ == NULL) {
+    return false;
+  } else {
+    return ArrayContains(remaining_, value);
+  }
+}
+
+
+// -------------------------------------------------------------------
+// Analysis
+
+
+void Analysis::EnsureAnalyzed(RegExpNode* that) {
+  if (that->info()->been_analyzed || that->info()->being_analyzed)
+    return;
+  that->info()->being_analyzed = true;
+  that->Accept(this);
+  that->info()->being_analyzed = false;
+  that->info()->been_analyzed = true;
+}
+
+
+void Analysis::VisitEnd(EndNode* that) {
+  // nothing to do
+}
+
+
+void TextNode::CalculateOffsets() {
+  intptr_t element_count = elements()->length();
+  // Set up the offsets of the elements relative to the start.  This is a fixed
+  // quantity since a TextNode can only contain fixed-width things.
+  intptr_t cp_offset = 0;
+  for (intptr_t i = 0; i < element_count; i++) {
+    TextElement& elm = (*elements())[i];
+    elm.set_cp_offset(cp_offset);
+    cp_offset += elm.length();
+  }
+}
+
+
+void Analysis::VisitText(TextNode* that) {
+  if (ignore_case_) {
+    that->MakeCaseIndependent(is_one_byte_);
+  }
+  EnsureAnalyzed(that->on_success());
+  if (!has_failed()) {
+    that->CalculateOffsets();
+  }
+}
+
+
+void Analysis::VisitAction(ActionNode* that) {
+  RegExpNode* target = that->on_success();
+  EnsureAnalyzed(target);
+  if (!has_failed()) {
+    // If the next node is interested in what it follows then this node
+    // has to be interested too so it can pass the information on.
+    that->info()->AddFromFollowing(target->info());
+  }
+}
+
+
+void Analysis::VisitChoice(ChoiceNode* that) {
+  NodeInfo* info = that->info();
+  for (intptr_t i = 0; i < that->alternatives()->length(); i++) {
+    RegExpNode* node = (*that->alternatives())[i].node();
+    EnsureAnalyzed(node);
+    if (has_failed()) return;
+    // Anything the following nodes need to know has to be known by
+    // this node also, so it can pass it on.
+    info->AddFromFollowing(node->info());
+  }
+}
+
+
+void Analysis::VisitLoopChoice(LoopChoiceNode* that) {
+  NodeInfo* info = that->info();
+  for (intptr_t i = 0; i < that->alternatives()->length(); i++) {
+    RegExpNode* node = (*that->alternatives())[i].node();
+    if (node != that->loop_node()) {
+      EnsureAnalyzed(node);
+      if (has_failed()) return;
+      info->AddFromFollowing(node->info());
+    }
+  }
+  // Check the loop last since it may need the value of this node
+  // to get a correct result.
+  EnsureAnalyzed(that->loop_node());
+  if (!has_failed()) {
+    info->AddFromFollowing(that->loop_node()->info());
+  }
+}
+
+
+void Analysis::VisitBackReference(BackReferenceNode* that) {
+  EnsureAnalyzed(that->on_success());
+}
+
+
+void Analysis::VisitAssertion(AssertionNode* that) {
+  EnsureAnalyzed(that->on_success());
+}
+
+
+void BackReferenceNode::FillInBMInfo(intptr_t offset,
+                                     intptr_t budget,
+                                     BoyerMooreLookahead* bm,
+                                     bool not_at_start) {
+  // Working out the set of characters that a backreference can match is too
+  // hard, so we just say that any character can match.
+  bm->SetRest(offset);
+  SaveBMInfo(bm, not_at_start, offset);
+}
+
+
+COMPILE_ASSERT(BoyerMoorePositionInfo::kMapSize ==
+               RegExpMacroAssembler::kTableSize);
+
+
+void ChoiceNode::FillInBMInfo(intptr_t offset,
+                              intptr_t budget,
+                              BoyerMooreLookahead* bm,
+                              bool not_at_start) {
+  ZoneGrowableArray<GuardedAlternative>* alts = alternatives();
+  budget = (budget - 1) / alts->length();
+  for (intptr_t i = 0; i < alts->length(); i++) {
+    GuardedAlternative& alt = (*alts)[i];
+    if (alt.guards() != NULL && alt.guards()->length() != 0) {
+      bm->SetRest(offset);  // Give up trying to fill in info.
+      SaveBMInfo(bm, not_at_start, offset);
+      return;
+    }
+    alt.node()->FillInBMInfo(offset, budget, bm, not_at_start);
+  }
+  SaveBMInfo(bm, not_at_start, offset);
+}
+
+
+void TextNode::FillInBMInfo(intptr_t initial_offset,
+                            intptr_t budget,
+                            BoyerMooreLookahead* bm,
+                            bool not_at_start) {
+  if (initial_offset >= bm->length()) return;
+  intptr_t offset = initial_offset;
+  intptr_t max_char = bm->max_char();
+  for (intptr_t i = 0; i < elements()->length(); i++) {
+    if (offset >= bm->length()) {
+      if (initial_offset == 0) set_bm_info(not_at_start, bm);
+      return;
+    }
+    TextElement text = elements()->At(i);
+    if (text.text_type() == TextElement::ATOM) {
+      RegExpAtom* atom = text.atom();
+      for (intptr_t j = 0; j < atom->length(); j++, offset++) {
+        if (offset >= bm->length()) {
+          if (initial_offset == 0) set_bm_info(not_at_start, bm);
+          return;
+        }
+        uint16_t character = atom->data()->At(j);
+        if (bm->compiler()->ignore_case()) {
+          int32_t chars[unibrow::Ecma262UnCanonicalize::kMaxWidth];
+          intptr_t length = GetCaseIndependentLetters(
+              character,
+              bm->max_char() == Symbols::kMaxOneCharCodeSymbol,
+              chars);
+          for (intptr_t j = 0; j < length; j++) {
+            bm->Set(offset, chars[j]);
+          }
+        } else {
+          if (character <= max_char) bm->Set(offset, character);
+        }
+      }
+    } else {
+      ASSERT(text.text_type() == TextElement::CHAR_CLASS);
+      RegExpCharacterClass* char_class = text.char_class();
+      ZoneGrowableArray<CharacterRange>* ranges = char_class->ranges();
+      if (char_class->is_negated()) {
+        bm->SetAll(offset);
+      } else {
+        for (intptr_t k = 0; k < ranges->length(); k++) {
+          CharacterRange& range = (*ranges)[k];
+          if (range.from() > max_char) continue;
+          intptr_t to = Utils::Minimum(max_char,
+                                       static_cast<intptr_t>(range.to()));
+          bm->SetInterval(offset, Interval(range.from(), to));
+        }
+      }
+      offset++;
+    }
+  }
+  if (offset >= bm->length()) {
+    if (initial_offset == 0) set_bm_info(not_at_start, bm);
+    return;
+  }
+  on_success()->FillInBMInfo(offset,
+                             budget - 1,
+                             bm,
+                             true);  // Not at start after a text node.
+  if (initial_offset == 0) set_bm_info(not_at_start, bm);
+}
+
+
+RegExpEngine::CompilationResult RegExpEngine::Compile(
+    RegExpCompileData* data,
+    const ParsedFunction* parsed_function,
+    const ZoneGrowableArray<const ICData*>& ic_data_array) {
+  Isolate* isolate = Isolate::Current();
+
+  const Function& function = parsed_function->function();
+  const intptr_t specialization_cid = function.regexp_cid();
+  const bool is_one_byte = (specialization_cid == kOneByteStringCid ||
+                            specialization_cid == kExternalOneByteStringCid);
+  JSRegExp& regexp = JSRegExp::Handle(isolate, function.regexp());
+  const String& pattern = String::Handle(isolate, regexp.pattern());
+
+  ASSERT(!regexp.IsNull());
+  ASSERT(!pattern.IsNull());
+
+  const bool ignore_case = regexp.is_ignore_case();
+  const bool is_global = regexp.is_global();
+
+  RegExpCompiler compiler(data->capture_count, ignore_case, specialization_cid);
+
+  // TODO(zerny): Frequency sampling is currently disabled because of several
+  // issues. We do not want to store subject strings in the regexp object since
+  // they might be long and we should not prevent their garbage collection.
+  // Passing them to this function explicitly does not help, since we must
+  // generate exactly the same IR for both the unoptimizing and optimizing
+  // pipelines (otherwise it gets confused when i.e. deopt id's differ).
+  // An option would be to store sampling results in the regexp object, but
+  // I'm not sure the performance gains are relevant enough.
+
+  // Wrap the body of the regexp in capture #0.
+  RegExpNode* captured_body = RegExpCapture::ToNode(data->tree,
+                                                    0,
+                                                    &compiler,
+                                                    compiler.accept());
+
+  RegExpNode* node = captured_body;
+  bool is_end_anchored = data->tree->IsAnchoredAtEnd();
+  bool is_start_anchored = data->tree->IsAnchoredAtStart();
+  intptr_t max_length = data->tree->max_match();
+  if (!is_start_anchored) {
+    // Add a .*? at the beginning, outside the body capture, unless
+    // this expression is anchored at the beginning.
+    RegExpNode* loop_node =
+        RegExpQuantifier::ToNode(0,
+                                 RegExpTree::kInfinity,
+                                 false,
+                                 new(isolate) RegExpCharacterClass('*'),
+                                 &compiler,
+                                 captured_body,
+                                 data->contains_anchor);
+
+    if (data->contains_anchor) {
+      // Unroll loop once, to take care of the case that might start
+      // at the start of input.
+      ChoiceNode* first_step_node = new(isolate) ChoiceNode(2, isolate);
+      first_step_node->AddAlternative(GuardedAlternative(captured_body));
+      first_step_node->AddAlternative(GuardedAlternative(
+          new(isolate) TextNode(
+              new(isolate) RegExpCharacterClass('*'), loop_node)));
+      node = first_step_node;
+    } else {
+      node = loop_node;
+    }
+  }
+  if (is_one_byte) {
+    node = node->FilterOneByte(RegExpCompiler::kMaxRecursion, ignore_case);
+    // Do it again to propagate the new nodes to places where they were not
+    // put because they had not been calculated yet.
+    if (node != NULL) {
+      node = node->FilterOneByte(RegExpCompiler::kMaxRecursion, ignore_case);
+    }
+  }
+
+  if (node == NULL) node = new(isolate) EndNode(EndNode::BACKTRACK, isolate);
+  data->node = node;
+  Analysis analysis(ignore_case, is_one_byte);
+  analysis.EnsureAnalyzed(node);
+  if (analysis.has_failed()) {
+    const char* error_message = analysis.error_message();
+    return CompilationResult(error_message);
+  }
+
+  // Native regexp implementation.
+
+  IRRegExpMacroAssembler* macro_assembler =
+      new(isolate) IRRegExpMacroAssembler(specialization_cid,
+                                          data->capture_count,
+                                          parsed_function,
+                                          ic_data_array,
+                                          isolate);
+
+  // Inserted here, instead of in Assembler, because it depends on information
+  // in the AST that isn't replicated in the Node structure.
+  static const intptr_t kMaxBacksearchLimit = 1024;
+  if (is_end_anchored &&
+      !is_start_anchored &&
+      max_length < kMaxBacksearchLimit) {
+    macro_assembler->SetCurrentPositionFromEnd(max_length);
+  }
+
+  if (is_global) {
+    macro_assembler->set_global_mode(
+        (data->tree->min_match() > 0)
+            ? RegExpMacroAssembler::GLOBAL_NO_ZERO_LENGTH_CHECK
+            : RegExpMacroAssembler::GLOBAL);
+  }
+
+  RegExpEngine::CompilationResult result =
+      compiler.Assemble(macro_assembler,
+                        node,
+                        data->capture_count,
+                        pattern);
+
+  if (FLAG_trace_irregexp) {
+    macro_assembler->PrintBlocks();
+  }
+
+  return result;
+}
+
+
+static void CreateSpecializedFunction(Isolate* isolate,
+                                      const JSRegExp& regexp,
+                                      intptr_t specialization_cid,
+                                      const Object& owner) {
+  const intptr_t kParamCount = RegExpMacroAssembler::kParamCount;
+
+  Function& fn = Function::Handle(isolate,
+        Function::New(String::Handle(isolate, Symbols::New("RegExp")),
+                      RawFunction::kIrregexpFunction,
+                      true,   // Static.
+                      false,  // Not const.
+                      false,  // Not abstract.
+                      false,  // Not external.
+                      false,  // Not native.
+                      owner,
+                      0));  // Requires a non-negative token position.
+
+  // TODO(zerny): Share these arrays between all irregexp functions.
+  fn.set_num_fixed_parameters(kParamCount);
+  fn.set_parameter_types(Array::Handle(isolate, Array::New(kParamCount,
+                                                           Heap::kOld)));
+  fn.set_parameter_names(Array::Handle(isolate, Array::New(kParamCount,
+                                                           Heap::kOld)));
+  fn.SetParameterTypeAt(0, Type::Handle(isolate, Type::DynamicType()));
+  fn.SetParameterNameAt(0, Symbols::string_param_());
+  fn.SetParameterTypeAt(1, Type::Handle(isolate, Type::DynamicType()));
+  fn.SetParameterNameAt(1, Symbols::start_index_param_());
+  fn.set_result_type(Type::Handle(isolate, Type::ArrayType()));
+
+  // Cache the result.
+  regexp.set_function(specialization_cid, fn);
+
+  fn.set_regexp(regexp);
+  fn.set_regexp_cid(specialization_cid);
+
+  // The function is compiled lazily during the first call.
+}
+
+
+RawJSRegExp* RegExpEngine::CreateJSRegExp(Isolate* isolate,
+                                          const String& pattern,
+                                          bool multi_line,
+                                          bool ignore_case) {
+  const JSRegExp& regexp = JSRegExp::Handle(JSRegExp::New(0));
+
+  regexp.set_pattern(pattern);
+
+  if (multi_line) {
+    regexp.set_is_multi_line();
+  }
+  if (ignore_case) {
+    regexp.set_is_ignore_case();
+  }
+
+  // TODO(zerny): We might want to use normal string searching algorithms
+  // for simple patterns.
+  regexp.set_is_complex();
+  regexp.set_is_global();   // All dart regexps are global.
+
+  const Library& lib = Library::Handle(isolate, Library::CoreLibrary());
+  const Class& owner = Class::Handle(isolate,
+        lib.LookupClass(String::Handle(isolate, Symbols::New("RegExp"))));
+
+  CreateSpecializedFunction(isolate, regexp, kOneByteStringCid, owner);
+  CreateSpecializedFunction(isolate, regexp, kTwoByteStringCid, owner);
+  CreateSpecializedFunction(isolate, regexp, kExternalOneByteStringCid, owner);
+  CreateSpecializedFunction(isolate, regexp, kExternalTwoByteStringCid, owner);
+
+  return regexp.raw();
+}
+
+
+}  // namespace dart