Initial import.

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diff --git a/chromium/v8/src/jsregexp.cc b/chromium/v8/src/jsregexp.cc
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+// Copyright 2012 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include "v8.h"
+
+#include "ast.h"
+#include "compiler.h"
+#include "execution.h"
+#include "factory.h"
+#include "jsregexp.h"
+#include "jsregexp-inl.h"
+#include "platform.h"
+#include "string-search.h"
+#include "runtime.h"
+#include "compilation-cache.h"
+#include "string-stream.h"
+#include "parser.h"
+#include "regexp-macro-assembler.h"
+#include "regexp-macro-assembler-tracer.h"
+#include "regexp-macro-assembler-irregexp.h"
+#include "regexp-stack.h"
+
+#ifndef V8_INTERPRETED_REGEXP
+#if V8_TARGET_ARCH_IA32
+#include "ia32/regexp-macro-assembler-ia32.h"
+#elif V8_TARGET_ARCH_X64
+#include "x64/regexp-macro-assembler-x64.h"
+#elif V8_TARGET_ARCH_ARM
+#include "arm/regexp-macro-assembler-arm.h"
+#elif V8_TARGET_ARCH_MIPS
+#include "mips/regexp-macro-assembler-mips.h"
+#else
+#error Unsupported target architecture.
+#endif
+#endif
+
+#include "interpreter-irregexp.h"
+
+
+namespace v8 {
+namespace internal {
+
+Handle<Object> RegExpImpl::CreateRegExpLiteral(Handle<JSFunction> constructor,
+                                               Handle<String> pattern,
+                                               Handle<String> flags,
+                                               bool* has_pending_exception) {
+  // Call the construct code with 2 arguments.
+  Handle<Object> argv[] = { pattern, flags };
+  return Execution::New(constructor, ARRAY_SIZE(argv), argv,
+                        has_pending_exception);
+}
+
+
+static JSRegExp::Flags RegExpFlagsFromString(Handle<String> str) {
+  int flags = JSRegExp::NONE;
+  for (int i = 0; i < str->length(); i++) {
+    switch (str->Get(i)) {
+      case 'i':
+        flags |= JSRegExp::IGNORE_CASE;
+        break;
+      case 'g':
+        flags |= JSRegExp::GLOBAL;
+        break;
+      case 'm':
+        flags |= JSRegExp::MULTILINE;
+        break;
+    }
+  }
+  return JSRegExp::Flags(flags);
+}
+
+
+static inline void ThrowRegExpException(Handle<JSRegExp> re,
+                                        Handle<String> pattern,
+                                        Handle<String> error_text,
+                                        const char* message) {
+  Isolate* isolate = re->GetIsolate();
+  Factory* factory = isolate->factory();
+  Handle<FixedArray> elements = factory->NewFixedArray(2);
+  elements->set(0, *pattern);
+  elements->set(1, *error_text);
+  Handle<JSArray> array = factory->NewJSArrayWithElements(elements);
+  Handle<Object> regexp_err = factory->NewSyntaxError(message, array);
+  isolate->Throw(*regexp_err);
+}
+
+
+ContainedInLattice AddRange(ContainedInLattice containment,
+                            const int* ranges,
+                            int ranges_length,
+                            Interval new_range) {
+  ASSERT((ranges_length & 1) == 1);
+  ASSERT(ranges[ranges_length - 1] == String::kMaxUtf16CodeUnit + 1);
+  if (containment == kLatticeUnknown) return containment;
+  bool inside = false;
+  int last = 0;
+  for (int 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;
+}
+
+
+// More makes code generation slower, less makes V8 benchmark score lower.
+const int kMaxLookaheadForBoyerMoore = 8;
+// In a 3-character pattern you can maximally step forwards 3 characters
+// at a time, which is not always enough to pay for the extra logic.
+const int kPatternTooShortForBoyerMoore = 2;
+
+
+// Identifies the sort of regexps where the regexp engine is faster
+// than the code used for atom matches.
+static bool HasFewDifferentCharacters(Handle<String> pattern) {
+  int length = Min(kMaxLookaheadForBoyerMoore, pattern->length());
+  if (length <= kPatternTooShortForBoyerMoore) return false;
+  const int kMod = 128;
+  bool character_found[kMod];
+  int different = 0;
+  memset(&character_found[0], 0, sizeof(character_found));
+  for (int i = 0; i < length; i++) {
+    int ch = (pattern->Get(i) & (kMod - 1));
+    if (!character_found[ch]) {
+      character_found[ch] = true;
+      different++;
+      // We declare a regexp low-alphabet if it has at least 3 times as many
+      // characters as it has different characters.
+      if (different * 3 > length) return false;
+    }
+  }
+  return true;
+}
+
+
+// Generic RegExp methods. Dispatches to implementation specific methods.
+
+
+Handle<Object> RegExpImpl::Compile(Handle<JSRegExp> re,
+                                   Handle<String> pattern,
+                                   Handle<String> flag_str) {
+  Isolate* isolate = re->GetIsolate();
+  Zone zone(isolate);
+  JSRegExp::Flags flags = RegExpFlagsFromString(flag_str);
+  CompilationCache* compilation_cache = isolate->compilation_cache();
+  Handle<FixedArray> cached = compilation_cache->LookupRegExp(pattern, flags);
+  bool in_cache = !cached.is_null();
+  LOG(isolate, RegExpCompileEvent(re, in_cache));
+
+  Handle<Object> result;
+  if (in_cache) {
+    re->set_data(*cached);
+    return re;
+  }
+  pattern = FlattenGetString(pattern);
+  PostponeInterruptsScope postpone(isolate);
+  RegExpCompileData parse_result;
+  FlatStringReader reader(isolate, pattern);
+  if (!RegExpParser::ParseRegExp(&reader, flags.is_multiline(),
+                                 &parse_result, &zone)) {
+    // Throw an exception if we fail to parse the pattern.
+    ThrowRegExpException(re,
+                         pattern,
+                         parse_result.error,
+                         "malformed_regexp");
+    return Handle<Object>::null();
+  }
+
+  bool has_been_compiled = false;
+
+  if (parse_result.simple &&
+      !flags.is_ignore_case() &&
+      !HasFewDifferentCharacters(pattern)) {
+    // Parse-tree is a single atom that is equal to the pattern.
+    AtomCompile(re, pattern, flags, pattern);
+    has_been_compiled = true;
+  } else if (parse_result.tree->IsAtom() &&
+      !flags.is_ignore_case() &&
+      parse_result.capture_count == 0) {
+    RegExpAtom* atom = parse_result.tree->AsAtom();
+    Vector<const uc16> atom_pattern = atom->data();
+    Handle<String> atom_string =
+        isolate->factory()->NewStringFromTwoByte(atom_pattern);
+    if (!HasFewDifferentCharacters(atom_string)) {
+      AtomCompile(re, pattern, flags, atom_string);
+      has_been_compiled = true;
+    }
+  }
+  if (!has_been_compiled) {
+    IrregexpInitialize(re, pattern, flags, parse_result.capture_count);
+  }
+  ASSERT(re->data()->IsFixedArray());
+  // Compilation succeeded so the data is set on the regexp
+  // and we can store it in the cache.
+  Handle<FixedArray> data(FixedArray::cast(re->data()));
+  compilation_cache->PutRegExp(pattern, flags, data);
+
+  return re;
+}
+
+
+Handle<Object> RegExpImpl::Exec(Handle<JSRegExp> regexp,
+                                Handle<String> subject,
+                                int index,
+                                Handle<JSArray> last_match_info) {
+  switch (regexp->TypeTag()) {
+    case JSRegExp::ATOM:
+      return AtomExec(regexp, subject, index, last_match_info);
+    case JSRegExp::IRREGEXP: {
+      Handle<Object> result =
+          IrregexpExec(regexp, subject, index, last_match_info);
+      ASSERT(!result.is_null() ||
+             regexp->GetIsolate()->has_pending_exception());
+      return result;
+    }
+    default:
+      UNREACHABLE();
+      return Handle<Object>::null();
+  }
+}
+
+
+// RegExp Atom implementation: Simple string search using indexOf.
+
+
+void RegExpImpl::AtomCompile(Handle<JSRegExp> re,
+                             Handle<String> pattern,
+                             JSRegExp::Flags flags,
+                             Handle<String> match_pattern) {
+  re->GetIsolate()->factory()->SetRegExpAtomData(re,
+                                                 JSRegExp::ATOM,
+                                                 pattern,
+                                                 flags,
+                                                 match_pattern);
+}
+
+
+static void SetAtomLastCapture(FixedArray* array,
+                               String* subject,
+                               int from,
+                               int to) {
+  SealHandleScope shs(array->GetIsolate());
+  RegExpImpl::SetLastCaptureCount(array, 2);
+  RegExpImpl::SetLastSubject(array, subject);
+  RegExpImpl::SetLastInput(array, subject);
+  RegExpImpl::SetCapture(array, 0, from);
+  RegExpImpl::SetCapture(array, 1, to);
+}
+
+
+int RegExpImpl::AtomExecRaw(Handle<JSRegExp> regexp,
+                            Handle<String> subject,
+                            int index,
+                            int32_t* output,
+                            int output_size) {
+  Isolate* isolate = regexp->GetIsolate();
+
+  ASSERT(0 <= index);
+  ASSERT(index <= subject->length());
+
+  if (!subject->IsFlat()) FlattenString(subject);
+  DisallowHeapAllocation no_gc;  // ensure vectors stay valid
+
+  String* needle = String::cast(regexp->DataAt(JSRegExp::kAtomPatternIndex));
+  int needle_len = needle->length();
+  ASSERT(needle->IsFlat());
+  ASSERT_LT(0, needle_len);
+
+  if (index + needle_len > subject->length()) {
+    return RegExpImpl::RE_FAILURE;
+  }
+
+  for (int i = 0; i < output_size; i += 2) {
+    String::FlatContent needle_content = needle->GetFlatContent();
+    String::FlatContent subject_content = subject->GetFlatContent();
+    ASSERT(needle_content.IsFlat());
+    ASSERT(subject_content.IsFlat());
+    // dispatch on type of strings
+    index = (needle_content.IsAscii()
+             ? (subject_content.IsAscii()
+                ? SearchString(isolate,
+                               subject_content.ToOneByteVector(),
+                               needle_content.ToOneByteVector(),
+                               index)
+                : SearchString(isolate,
+                               subject_content.ToUC16Vector(),
+                               needle_content.ToOneByteVector(),
+                               index))
+             : (subject_content.IsAscii()
+                ? SearchString(isolate,
+                               subject_content.ToOneByteVector(),
+                               needle_content.ToUC16Vector(),
+                               index)
+                : SearchString(isolate,
+                               subject_content.ToUC16Vector(),
+                               needle_content.ToUC16Vector(),
+                               index)));
+    if (index == -1) {
+      return i / 2;  // Return number of matches.
+    } else {
+      output[i] = index;
+      output[i+1] = index + needle_len;
+      index += needle_len;
+    }
+  }
+  return output_size / 2;
+}
+
+
+Handle<Object> RegExpImpl::AtomExec(Handle<JSRegExp> re,
+                                    Handle<String> subject,
+                                    int index,
+                                    Handle<JSArray> last_match_info) {
+  Isolate* isolate = re->GetIsolate();
+
+  static const int kNumRegisters = 2;
+  STATIC_ASSERT(kNumRegisters <= Isolate::kJSRegexpStaticOffsetsVectorSize);
+  int32_t* output_registers = isolate->jsregexp_static_offsets_vector();
+
+  int res = AtomExecRaw(re, subject, index, output_registers, kNumRegisters);
+
+  if (res == RegExpImpl::RE_FAILURE) return isolate->factory()->null_value();
+
+  ASSERT_EQ(res, RegExpImpl::RE_SUCCESS);
+  SealHandleScope shs(isolate);
+  FixedArray* array = FixedArray::cast(last_match_info->elements());
+  SetAtomLastCapture(array, *subject, output_registers[0], output_registers[1]);
+  return last_match_info;
+}
+
+
+// Irregexp implementation.
+
+// Ensures that the regexp object contains a compiled version of the
+// source for either ASCII or non-ASCII strings.
+// If the compiled version doesn't already exist, it is compiled
+// from the source pattern.
+// If compilation fails, an exception is thrown and this function
+// returns false.
+bool RegExpImpl::EnsureCompiledIrregexp(
+    Handle<JSRegExp> re, Handle<String> sample_subject, bool is_ascii) {
+  Object* compiled_code = re->DataAt(JSRegExp::code_index(is_ascii));
+#ifdef V8_INTERPRETED_REGEXP
+  if (compiled_code->IsByteArray()) return true;
+#else  // V8_INTERPRETED_REGEXP (RegExp native code)
+  if (compiled_code->IsCode()) return true;
+#endif
+  // We could potentially have marked this as flushable, but have kept
+  // a saved version if we did not flush it yet.
+  Object* saved_code = re->DataAt(JSRegExp::saved_code_index(is_ascii));
+  if (saved_code->IsCode()) {
+    // Reinstate the code in the original place.
+    re->SetDataAt(JSRegExp::code_index(is_ascii), saved_code);
+    ASSERT(compiled_code->IsSmi());
+    return true;
+  }
+  return CompileIrregexp(re, sample_subject, is_ascii);
+}
+
+
+static bool CreateRegExpErrorObjectAndThrow(Handle<JSRegExp> re,
+                                            bool is_ascii,
+                                            Handle<String> error_message,
+                                            Isolate* isolate) {
+  Factory* factory = isolate->factory();
+  Handle<FixedArray> elements = factory->NewFixedArray(2);
+  elements->set(0, re->Pattern());
+  elements->set(1, *error_message);
+  Handle<JSArray> array = factory->NewJSArrayWithElements(elements);
+  Handle<Object> regexp_err =
+      factory->NewSyntaxError("malformed_regexp", array);
+  isolate->Throw(*regexp_err);
+  return false;
+}
+
+
+bool RegExpImpl::CompileIrregexp(Handle<JSRegExp> re,
+                                 Handle<String> sample_subject,
+                                 bool is_ascii) {
+  // Compile the RegExp.
+  Isolate* isolate = re->GetIsolate();
+  Zone zone(isolate);
+  PostponeInterruptsScope postpone(isolate);
+  // If we had a compilation error the last time this is saved at the
+  // saved code index.
+  Object* entry = re->DataAt(JSRegExp::code_index(is_ascii));
+  // When arriving here entry can only be a smi, either representing an
+  // uncompiled regexp, a previous compilation error, or code that has
+  // been flushed.
+  ASSERT(entry->IsSmi());
+  int entry_value = Smi::cast(entry)->value();
+  ASSERT(entry_value == JSRegExp::kUninitializedValue ||
+         entry_value == JSRegExp::kCompilationErrorValue ||
+         (entry_value < JSRegExp::kCodeAgeMask && entry_value >= 0));
+
+  if (entry_value == JSRegExp::kCompilationErrorValue) {
+    // A previous compilation failed and threw an error which we store in
+    // the saved code index (we store the error message, not the actual
+    // error). Recreate the error object and throw it.
+    Object* error_string = re->DataAt(JSRegExp::saved_code_index(is_ascii));
+    ASSERT(error_string->IsString());
+    Handle<String> error_message(String::cast(error_string));
+    CreateRegExpErrorObjectAndThrow(re, is_ascii, error_message, isolate);
+    return false;
+  }
+
+  JSRegExp::Flags flags = re->GetFlags();
+
+  Handle<String> pattern(re->Pattern());
+  if (!pattern->IsFlat()) FlattenString(pattern);
+  RegExpCompileData compile_data;
+  FlatStringReader reader(isolate, pattern);
+  if (!RegExpParser::ParseRegExp(&reader, flags.is_multiline(),
+                                 &compile_data,
+                                 &zone)) {
+    // Throw an exception if we fail to parse the pattern.
+    // THIS SHOULD NOT HAPPEN. We already pre-parsed it successfully once.
+    ThrowRegExpException(re,
+                         pattern,
+                         compile_data.error,
+                         "malformed_regexp");
+    return false;
+  }
+  RegExpEngine::CompilationResult result =
+      RegExpEngine::Compile(&compile_data,
+                            flags.is_ignore_case(),
+                            flags.is_global(),
+                            flags.is_multiline(),
+                            pattern,
+                            sample_subject,
+                            is_ascii,
+                            &zone);
+  if (result.error_message != NULL) {
+    // Unable to compile regexp.
+    Handle<String> error_message =
+        isolate->factory()->NewStringFromUtf8(CStrVector(result.error_message));
+    CreateRegExpErrorObjectAndThrow(re, is_ascii, error_message, isolate);
+    return false;
+  }
+
+  Handle<FixedArray> data = Handle<FixedArray>(FixedArray::cast(re->data()));
+  data->set(JSRegExp::code_index(is_ascii), result.code);
+  int register_max = IrregexpMaxRegisterCount(*data);
+  if (result.num_registers > register_max) {
+    SetIrregexpMaxRegisterCount(*data, result.num_registers);
+  }
+
+  return true;
+}
+
+
+int RegExpImpl::IrregexpMaxRegisterCount(FixedArray* re) {
+  return Smi::cast(
+      re->get(JSRegExp::kIrregexpMaxRegisterCountIndex))->value();
+}
+
+
+void RegExpImpl::SetIrregexpMaxRegisterCount(FixedArray* re, int value) {
+  re->set(JSRegExp::kIrregexpMaxRegisterCountIndex, Smi::FromInt(value));
+}
+
+
+int RegExpImpl::IrregexpNumberOfCaptures(FixedArray* re) {
+  return Smi::cast(re->get(JSRegExp::kIrregexpCaptureCountIndex))->value();
+}
+
+
+int RegExpImpl::IrregexpNumberOfRegisters(FixedArray* re) {
+  return Smi::cast(re->get(JSRegExp::kIrregexpMaxRegisterCountIndex))->value();
+}
+
+
+ByteArray* RegExpImpl::IrregexpByteCode(FixedArray* re, bool is_ascii) {
+  return ByteArray::cast(re->get(JSRegExp::code_index(is_ascii)));
+}
+
+
+Code* RegExpImpl::IrregexpNativeCode(FixedArray* re, bool is_ascii) {
+  return Code::cast(re->get(JSRegExp::code_index(is_ascii)));
+}
+
+
+void RegExpImpl::IrregexpInitialize(Handle<JSRegExp> re,
+                                    Handle<String> pattern,
+                                    JSRegExp::Flags flags,
+                                    int capture_count) {
+  // Initialize compiled code entries to null.
+  re->GetIsolate()->factory()->SetRegExpIrregexpData(re,
+                                                     JSRegExp::IRREGEXP,
+                                                     pattern,
+                                                     flags,
+                                                     capture_count);
+}
+
+
+int RegExpImpl::IrregexpPrepare(Handle<JSRegExp> regexp,
+                                Handle<String> subject) {
+  if (!subject->IsFlat()) FlattenString(subject);
+
+  // Check the asciiness of the underlying storage.
+  bool is_ascii = subject->IsOneByteRepresentationUnderneath();
+  if (!EnsureCompiledIrregexp(regexp, subject, is_ascii)) return -1;
+
+#ifdef V8_INTERPRETED_REGEXP
+  // Byte-code regexp needs space allocated for all its registers.
+  // The result captures are copied to the start of the registers array
+  // if the match succeeds.  This way those registers are not clobbered
+  // when we set the last match info from last successful match.
+  return IrregexpNumberOfRegisters(FixedArray::cast(regexp->data())) +
+         (IrregexpNumberOfCaptures(FixedArray::cast(regexp->data())) + 1) * 2;
+#else  // V8_INTERPRETED_REGEXP
+  // Native regexp only needs room to output captures. Registers are handled
+  // internally.
+  return (IrregexpNumberOfCaptures(FixedArray::cast(regexp->data())) + 1) * 2;
+#endif  // V8_INTERPRETED_REGEXP
+}
+
+
+int RegExpImpl::IrregexpExecRaw(Handle<JSRegExp> regexp,
+                                Handle<String> subject,
+                                int index,
+                                int32_t* output,
+                                int output_size) {
+  Isolate* isolate = regexp->GetIsolate();
+
+  Handle<FixedArray> irregexp(FixedArray::cast(regexp->data()), isolate);
+
+  ASSERT(index >= 0);
+  ASSERT(index <= subject->length());
+  ASSERT(subject->IsFlat());
+
+  bool is_ascii = subject->IsOneByteRepresentationUnderneath();
+
+#ifndef V8_INTERPRETED_REGEXP
+  ASSERT(output_size >= (IrregexpNumberOfCaptures(*irregexp) + 1) * 2);
+  do {
+    EnsureCompiledIrregexp(regexp, subject, is_ascii);
+    Handle<Code> code(IrregexpNativeCode(*irregexp, is_ascii), isolate);
+    // The stack is used to allocate registers for the compiled regexp code.
+    // This means that in case of failure, the output registers array is left
+    // untouched and contains the capture results from the previous successful
+    // match.  We can use that to set the last match info lazily.
+    NativeRegExpMacroAssembler::Result res =
+        NativeRegExpMacroAssembler::Match(code,
+                                          subject,
+                                          output,
+                                          output_size,
+                                          index,
+                                          isolate);
+    if (res != NativeRegExpMacroAssembler::RETRY) {
+      ASSERT(res != NativeRegExpMacroAssembler::EXCEPTION ||
+             isolate->has_pending_exception());
+      STATIC_ASSERT(
+          static_cast<int>(NativeRegExpMacroAssembler::SUCCESS) == RE_SUCCESS);
+      STATIC_ASSERT(
+          static_cast<int>(NativeRegExpMacroAssembler::FAILURE) == RE_FAILURE);
+      STATIC_ASSERT(static_cast<int>(NativeRegExpMacroAssembler::EXCEPTION)
+                    == RE_EXCEPTION);
+      return static_cast<IrregexpResult>(res);
+    }
+    // If result is RETRY, the string has changed representation, and we
+    // must restart from scratch.
+    // In this case, it means we must make sure we are prepared to handle
+    // the, potentially, different subject (the string can switch between
+    // being internal and external, and even between being ASCII and UC16,
+    // but the characters are always the same).
+    IrregexpPrepare(regexp, subject);
+    is_ascii = subject->IsOneByteRepresentationUnderneath();
+  } while (true);
+  UNREACHABLE();
+  return RE_EXCEPTION;
+#else  // V8_INTERPRETED_REGEXP
+
+  ASSERT(output_size >= IrregexpNumberOfRegisters(*irregexp));
+  // We must have done EnsureCompiledIrregexp, so we can get the number of
+  // registers.
+  int number_of_capture_registers =
+      (IrregexpNumberOfCaptures(*irregexp) + 1) * 2;
+  int32_t* raw_output = &output[number_of_capture_registers];
+  // We do not touch the actual capture result registers until we know there
+  // has been a match so that we can use those capture results to set the
+  // last match info.
+  for (int i = number_of_capture_registers - 1; i >= 0; i--) {
+    raw_output[i] = -1;
+  }
+  Handle<ByteArray> byte_codes(IrregexpByteCode(*irregexp, is_ascii), isolate);
+
+  IrregexpResult result = IrregexpInterpreter::Match(isolate,
+                                                     byte_codes,
+                                                     subject,
+                                                     raw_output,
+                                                     index);
+  if (result == RE_SUCCESS) {
+    // Copy capture results to the start of the registers array.
+    OS::MemCopy(
+        output, raw_output, number_of_capture_registers * sizeof(int32_t));
+  }
+  if (result == RE_EXCEPTION) {
+    ASSERT(!isolate->has_pending_exception());
+    isolate->StackOverflow();
+  }
+  return result;
+#endif  // V8_INTERPRETED_REGEXP
+}
+
+
+Handle<Object> RegExpImpl::IrregexpExec(Handle<JSRegExp> regexp,
+                                        Handle<String> subject,
+                                        int previous_index,
+                                        Handle<JSArray> last_match_info) {
+  Isolate* isolate = regexp->GetIsolate();
+  ASSERT_EQ(regexp->TypeTag(), JSRegExp::IRREGEXP);
+
+  // Prepare space for the return values.
+#if defined(V8_INTERPRETED_REGEXP) && defined(DEBUG)
+  if (FLAG_trace_regexp_bytecodes) {
+    String* pattern = regexp->Pattern();
+    PrintF("\n\nRegexp match:   /%s/\n\n", *(pattern->ToCString()));
+    PrintF("\n\nSubject string: '%s'\n\n", *(subject->ToCString()));
+  }
+#endif
+  int required_registers = RegExpImpl::IrregexpPrepare(regexp, subject);
+  if (required_registers < 0) {
+    // Compiling failed with an exception.
+    ASSERT(isolate->has_pending_exception());
+    return Handle<Object>::null();
+  }
+
+  int32_t* output_registers = NULL;
+  if (required_registers > Isolate::kJSRegexpStaticOffsetsVectorSize) {
+    output_registers = NewArray<int32_t>(required_registers);
+  }
+  SmartArrayPointer<int32_t> auto_release(output_registers);
+  if (output_registers == NULL) {
+    output_registers = isolate->jsregexp_static_offsets_vector();
+  }
+
+  int res = RegExpImpl::IrregexpExecRaw(
+      regexp, subject, previous_index, output_registers, required_registers);
+  if (res == RE_SUCCESS) {
+    int capture_count =
+        IrregexpNumberOfCaptures(FixedArray::cast(regexp->data()));
+    return SetLastMatchInfo(
+        last_match_info, subject, capture_count, output_registers);
+  }
+  if (res == RE_EXCEPTION) {
+    ASSERT(isolate->has_pending_exception());
+    return Handle<Object>::null();
+  }
+  ASSERT(res == RE_FAILURE);
+  return isolate->factory()->null_value();
+}
+
+
+Handle<JSArray> RegExpImpl::SetLastMatchInfo(Handle<JSArray> last_match_info,
+                                             Handle<String> subject,
+                                             int capture_count,
+                                             int32_t* match) {
+  ASSERT(last_match_info->HasFastObjectElements());
+  int capture_register_count = (capture_count + 1) * 2;
+  last_match_info->EnsureSize(capture_register_count + kLastMatchOverhead);
+  DisallowHeapAllocation no_allocation;
+  FixedArray* array = FixedArray::cast(last_match_info->elements());
+  if (match != NULL) {
+    for (int i = 0; i < capture_register_count; i += 2) {
+      SetCapture(array, i, match[i]);
+      SetCapture(array, i + 1, match[i + 1]);
+    }
+  }
+  SetLastCaptureCount(array, capture_register_count);
+  SetLastSubject(array, *subject);
+  SetLastInput(array, *subject);
+  return last_match_info;
+}
+
+
+RegExpImpl::GlobalCache::GlobalCache(Handle<JSRegExp> regexp,
+                                     Handle<String> subject,
+                                     bool is_global,
+                                     Isolate* isolate)
+  : register_array_(NULL),
+    register_array_size_(0),
+    regexp_(regexp),
+    subject_(subject) {
+#ifdef V8_INTERPRETED_REGEXP
+  bool interpreted = true;
+#else
+  bool interpreted = false;
+#endif  // V8_INTERPRETED_REGEXP
+
+  if (regexp_->TypeTag() == JSRegExp::ATOM) {
+    static const int kAtomRegistersPerMatch = 2;
+    registers_per_match_ = kAtomRegistersPerMatch;
+    // There is no distinction between interpreted and native for atom regexps.
+    interpreted = false;
+  } else {
+    registers_per_match_ = RegExpImpl::IrregexpPrepare(regexp_, subject_);
+    if (registers_per_match_ < 0) {
+      num_matches_ = -1;  // Signal exception.
+      return;
+    }
+  }
+
+  if (is_global && !interpreted) {
+    register_array_size_ =
+        Max(registers_per_match_, Isolate::kJSRegexpStaticOffsetsVectorSize);
+    max_matches_ = register_array_size_ / registers_per_match_;
+  } else {
+    // Global loop in interpreted regexp is not implemented.  We choose
+    // the size of the offsets vector so that it can only store one match.
+    register_array_size_ = registers_per_match_;
+    max_matches_ = 1;
+  }
+
+  if (register_array_size_ > Isolate::kJSRegexpStaticOffsetsVectorSize) {
+    register_array_ = NewArray<int32_t>(register_array_size_);
+  } else {
+    register_array_ = isolate->jsregexp_static_offsets_vector();
+  }
+
+  // Set state so that fetching the results the first time triggers a call
+  // to the compiled regexp.
+  current_match_index_ = max_matches_ - 1;
+  num_matches_ = max_matches_;
+  ASSERT(registers_per_match_ >= 2);  // Each match has at least one capture.
+  ASSERT_GE(register_array_size_, registers_per_match_);
+  int32_t* last_match =
+      &register_array_[current_match_index_ * registers_per_match_];
+  last_match[0] = -1;
+  last_match[1] = 0;
+}
+
+
+// -------------------------------------------------------------------
+// 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 either
+// bytecodes or native code.
+
+//   The Irregexp regexp engine is structured in three steps.
+//   1) The parser generates an abstract syntax tree.  See 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 either byte codes or native code
+//      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 (whether as byte codes or native code) 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, Zone* zone) {
+  UNREACHABLE();
+}
+
+
+void RegExpAtom::AppendToText(RegExpText* text, Zone* zone) {
+  text->AddElement(TextElement::Atom(this), zone);
+}
+
+
+void RegExpCharacterClass::AppendToText(RegExpText* text, Zone* zone) {
+  text->AddElement(TextElement::CharClass(this), zone);
+}
+
+
+void RegExpText::AppendToText(RegExpText* text, Zone* zone) {
+  for (int i = 0; i < elements()->length(); i++)
+    text->AddElement(elements()->at(i), zone);
+}
+
+
+TextElement TextElement::Atom(RegExpAtom* atom) {
+  TextElement result = TextElement(ATOM);
+  result.data.u_atom = atom;
+  return result;
+}
+
+
+TextElement TextElement::CharClass(
+      RegExpCharacterClass* char_class) {
+  TextElement result = TextElement(CHAR_CLASS);
+  result.data.u_char_class = char_class;
+  return result;
+}
+
+
+int TextElement::length() {
+  if (text_type == ATOM) {
+    return data.u_atom->length();
+  } else {
+    ASSERT(text_type == CHAR_CLASS);
+    return 1;
+  }
+}
+
+
+DispatchTable* ChoiceNode::GetTable(bool ignore_case) {
+  if (table_ == NULL) {
+    table_ = new(zone()) DispatchTable(zone());
+    DispatchTableConstructor cons(table_, ignore_case, zone());
+    cons.BuildTable(this);
+  }
+  return table_;
+}
+
+
+class FrequencyCollator {
+ public:
+  FrequencyCollator() : total_samples_(0) {
+    for (int i = 0; i < RegExpMacroAssembler::kTableSize; i++) {
+      frequencies_[i] = CharacterFrequency(i);
+    }
+  }
+
+  void CountCharacter(int character) {
+    int 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).
+  int Frequency(int in_character) {
+    ASSERT((in_character & RegExpMacroAssembler::kTableMask) == in_character);
+    if (total_samples_ < 1) return 1;  // Division by zero.
+    int 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(int character)
+        : counter_(0), character_(character) { }
+
+    void Increment() { counter_++; }
+    int counter() { return counter_; }
+    int character() { return character_; }
+
+   private:
+    int counter_;
+    int character_;
+  };
+
+
+ private:
+  CharacterFrequency frequencies_[RegExpMacroAssembler::kTableSize];
+  int total_samples_;
+};
+
+
+class RegExpCompiler {
+ public:
+  RegExpCompiler(int capture_count, bool ignore_case, bool is_ascii,
+                 Zone* zone);
+
+  int AllocateRegister() {
+    if (next_register_ >= RegExpMacroAssembler::kMaxRegister) {
+      reg_exp_too_big_ = true;
+      return next_register_;
+    }
+    return next_register_++;
+  }
+
+  RegExpEngine::CompilationResult Assemble(RegExpMacroAssembler* assembler,
+                                           RegExpNode* start,
+                                           int capture_count,
+                                           Handle<String> pattern);
+
+  inline void AddWork(RegExpNode* node) { work_list_->Add(node); }
+
+  static const int kImplementationOffset = 0;
+  static const int kNumberOfRegistersOffset = 0;
+  static const int kCodeOffset = 1;
+
+  RegExpMacroAssembler* macro_assembler() { return macro_assembler_; }
+  EndNode* accept() { return accept_; }
+
+  static const int kMaxRecursion = 100;
+  inline int 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 ascii() { return ascii_; }
+  FrequencyCollator* frequency_collator() { return &frequency_collator_; }
+
+  int current_expansion_factor() { return current_expansion_factor_; }
+  void set_current_expansion_factor(int value) {
+    current_expansion_factor_ = value;
+  }
+
+  Zone* zone() const { return zone_; }
+
+  static const int kNoRegister = -1;
+
+ private:
+  EndNode* accept_;
+  int next_register_;
+  List<RegExpNode*>* work_list_;
+  int recursion_depth_;
+  RegExpMacroAssembler* macro_assembler_;
+  bool ignore_case_;
+  bool ascii_;
+  bool reg_exp_too_big_;
+  int current_expansion_factor_;
+  FrequencyCollator frequency_collator_;
+  Zone* zone_;
+};
+
+
+class RecursionCheck {
+ 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(int capture_count, bool ignore_case, bool ascii,
+                               Zone* zone)
+    : next_register_(2 * (capture_count + 1)),
+      work_list_(NULL),
+      recursion_depth_(0),
+      ignore_case_(ignore_case),
+      ascii_(ascii),
+      reg_exp_too_big_(false),
+      current_expansion_factor_(1),
+      frequency_collator_(),
+      zone_(zone) {
+  accept_ = new(zone) EndNode(EndNode::ACCEPT, zone);
+  ASSERT(next_register_ - 1 <= RegExpMacroAssembler::kMaxRegister);
+}
+
+
+RegExpEngine::CompilationResult RegExpCompiler::Assemble(
+    RegExpMacroAssembler* macro_assembler,
+    RegExpNode* start,
+    int capture_count,
+    Handle<String> pattern) {
+  Heap* heap = pattern->GetHeap();
+
+  bool use_slow_safe_regexp_compiler = false;
+  if (heap->total_regexp_code_generated() >
+          RegExpImpl::kRegWxpCompiledLimit &&
+      heap->isolate()->memory_allocator()->SizeExecutable() >
+          RegExpImpl::kRegExpExecutableMemoryLimit) {
+    use_slow_safe_regexp_compiler = true;
+  }
+
+  macro_assembler->set_slow_safe(use_slow_safe_regexp_compiler);
+
+#ifdef DEBUG
+  if (FLAG_trace_regexp_assembler)
+    macro_assembler_ = new RegExpMacroAssemblerTracer(macro_assembler);
+  else
+#endif
+    macro_assembler_ = macro_assembler;
+
+  List <RegExpNode*> work_list(0);
+  work_list_ = &work_list;
+  Label fail;
+  macro_assembler_->PushBacktrack(&fail);
+  Trace new_trace;
+  start->Emit(this, &new_trace);
+  macro_assembler_->Bind(&fail);
+  macro_assembler_->Fail();
+  while (!work_list.is_empty()) {
+    work_list.RemoveLast()->Emit(this, &new_trace);
+  }
+  if (reg_exp_too_big_) return IrregexpRegExpTooBig();
+
+  Handle<HeapObject> code = macro_assembler_->GetCode(pattern);
+  heap->IncreaseTotalRegexpCodeGenerated(code->Size());
+  work_list_ = NULL;
+#ifdef DEBUG
+  if (FLAG_print_code) {
+    Handle<Code>::cast(code)->Disassemble(*pattern->ToCString());
+  }
+  if (FLAG_trace_regexp_assembler) {
+    delete macro_assembler_;
+  }
+#endif
+  return RegExpEngine::CompilationResult(*code, next_register_);
+}
+
+
+bool Trace::DeferredAction::Mentions(int 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(int reg) {
+  for (DeferredAction* action = actions_;
+       action != NULL;
+       action = action->next()) {
+    if (action->Mentions(reg))
+      return true;
+  }
+  return false;
+}
+
+
+bool Trace::GetStoredPosition(int reg, int* cp_offset) {
+  ASSERT_EQ(0, *cp_offset);
+  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;
+}
+
+
+int Trace::FindAffectedRegisters(OutSet* affected_registers,
+                                 Zone* zone) {
+  int 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 (int i = range.from(); i <= range.to(); i++)
+        affected_registers->Set(i, zone);
+      if (range.to() > max_register) max_register = range.to();
+    } else {
+      affected_registers->Set(action->reg(), zone);
+      if (action->reg() > max_register) max_register = action->reg();
+    }
+  }
+  return max_register;
+}
+
+
+void Trace::RestoreAffectedRegisters(RegExpMacroAssembler* assembler,
+                                     int max_register,
+                                     OutSet& registers_to_pop,
+                                     OutSet& registers_to_clear) {
+  for (int reg = max_register; reg >= 0; reg--) {
+    if (registers_to_pop.Get(reg)) assembler->PopRegister(reg);
+    else if (registers_to_clear.Get(reg)) {
+      int clear_to = reg;
+      while (reg > 0 && registers_to_clear.Get(reg - 1)) {
+        reg--;
+      }
+      assembler->ClearRegisters(reg, clear_to);
+    }
+  }
+}
+
+
+void Trace::PerformDeferredActions(RegExpMacroAssembler* assembler,
+                                   int max_register,
+                                   OutSet& affected_registers,
+                                   OutSet* registers_to_pop,
+                                   OutSet* registers_to_clear,
+                                   Zone* zone) {
+  // The "+1" is to avoid a push_limit of zero if stack_limit_slack() is 1.
+  const int push_limit = (assembler->stack_limit_slack() + 1) / 2;
+
+  // Count pushes performed to force a stack limit check occasionally.
+  int pushes = 0;
+
+  for (int 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;
+
+    int value = 0;
+    bool absolute = false;
+    bool clear = false;
+    int 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_EQ(store_position, -1);
+            ASSERT(!clear);
+            break;
+          }
+          case ActionNode::INCREMENT_REGISTER:
+            if (!absolute) {
+              value++;
+            }
+            ASSERT_EQ(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_EQ(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_EQ(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) {
+      pushes++;
+      RegExpMacroAssembler::StackCheckFlag stack_check =
+          RegExpMacroAssembler::kNoStackLimitCheck;
+      if (pushes == push_limit) {
+        stack_check = RegExpMacroAssembler::kCheckStackLimit;
+        pushes = 0;
+      }
+
+      assembler->PushRegister(reg, stack_check);
+      registers_to_pop->Set(reg, zone);
+    } else if (undo_action == CLEAR) {
+      registers_to_clear->Set(reg, zone);
+    }
+    // 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();
+  }
+
+  int max_register = FindAffectedRegisters(&affected_registers,
+                                           compiler->zone());
+  OutSet registers_to_pop;
+  OutSet registers_to_clear;
+  PerformDeferredActions(assembler,
+                         max_register,
+                         affected_registers,
+                         &registers_to_pop,
+                         &registers_to_clear,
+                         compiler->zone());
+  if (cp_offset_ != 0) {
+    assembler->AdvanceCurrentPosition(cp_offset_);
+  }
+
+  // Create a new trivial state and generate the node with that.
+  Label undo;
+  assembler->PushBacktrack(&undo);
+  Trace new_state;
+  successor->Emit(compiler, &new_state);
+
+  // On backtrack we need to restore state.
+  assembler->Bind(&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()->is_bound()) {
+    // We are completely independent of the trace, since we ignore it,
+    // so this code can be used as the generic version.
+    assembler->Bind(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()->is_bound()) {
+    assembler->Bind(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, Zone* zone) {
+  if (guards_ == NULL)
+    guards_ = new(zone) ZoneList<Guard*>(1, zone);
+  guards_->Add(guard, zone);
+}
+
+
+ActionNode* ActionNode::SetRegister(int reg,
+                                    int val,
+                                    RegExpNode* on_success) {
+  ActionNode* result =
+      new(on_success->zone()) ActionNode(SET_REGISTER, on_success);
+  result->data_.u_store_register.reg = reg;
+  result->data_.u_store_register.value = val;
+  return result;
+}
+
+
+ActionNode* ActionNode::IncrementRegister(int reg, RegExpNode* on_success) {
+  ActionNode* result =
+      new(on_success->zone()) ActionNode(INCREMENT_REGISTER, on_success);
+  result->data_.u_increment_register.reg = reg;
+  return result;
+}
+
+
+ActionNode* ActionNode::StorePosition(int reg,
+                                      bool is_capture,
+                                      RegExpNode* on_success) {
+  ActionNode* result =
+      new(on_success->zone()) 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->zone()) 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(int stack_reg,
+                                      int position_reg,
+                                      RegExpNode* on_success) {
+  ActionNode* result =
+      new(on_success->zone()) 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(int stack_reg,
+                                                int position_reg,
+                                                int clear_register_count,
+                                                int clear_register_from,
+                                                RegExpNode* on_success) {
+  ActionNode* result =
+      new(on_success->zone()) 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(int start_register,
+                                        int repetition_register,
+                                        int repetition_limit,
+                                        RegExpNode* on_success) {
+  ActionNode* result =
+      new(on_success->zone()) 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 int GetCaseIndependentLetters(Isolate* isolate,
+                                     uc16 character,
+                                     bool ascii_subject,
+                                     unibrow::uchar* letters) {
+  int length =
+      isolate->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 (!ascii_subject || character <= String::kMaxOneByteCharCode) {
+    return length;
+  }
+  // The standard requires that non-ASCII characters cannot have ASCII
+  // character codes in their equivalence class.
+  return 0;
+}
+
+
+static inline bool EmitSimpleCharacter(Isolate* isolate,
+                                       RegExpCompiler* compiler,
+                                       uc16 c,
+                                       Label* on_failure,
+                                       int 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,
+                                     uc16 c,
+                                     Label* on_failure,
+                                     int cp_offset,
+                                     bool check,
+                                     bool preloaded) {
+  RegExpMacroAssembler* macro_assembler = compiler->macro_assembler();
+  bool ascii = compiler->ascii();
+  unibrow::uchar chars[unibrow::Ecma262UnCanonicalize::kMaxWidth];
+  int length = GetCaseIndependentLetters(isolate, c, ascii, chars);
+  if (length < 1) {
+    // This can't match.  Must be an ASCII subject and a non-ASCII character.
+    // We do not need to do anything since the ASCII 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 (ascii && c > String::kMaxOneByteCharCodeU) {
+      // 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 ascii,
+                                      uc16 c1,
+                                      uc16 c2,
+                                      Label* on_failure) {
+  uc16 char_mask;
+  if (ascii) {
+    char_mask = String::kMaxOneByteCharCode;
+  } else {
+    char_mask = String::kMaxUtf16CodeUnit;
+  }
+  uc16 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);
+    uc16 mask = char_mask ^ exor;
+    macro_assembler->CheckNotCharacterAfterAnd(c1, mask, on_failure);
+    return true;
+  }
+  ASSERT(c2 > c1);
+  uc16 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.
+    uc16 mask = char_mask ^ diff;
+    macro_assembler->CheckNotCharacterAfterMinusAnd(c1 - diff,
+                                                    diff,
+                                                    mask,
+                                                    on_failure);
+    return true;
+  }
+  return false;
+}
+
+
+typedef bool EmitCharacterFunction(Isolate* isolate,
+                                   RegExpCompiler* compiler,
+                                   uc16 c,
+                                   Label* on_failure,
+                                   int 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,
+                                  uc16 c,
+                                  Label* on_failure,
+                                  int cp_offset,
+                                  bool check,
+                                  bool preloaded) {
+  RegExpMacroAssembler* macro_assembler = compiler->macro_assembler();
+  bool ascii = compiler->ascii();
+  unibrow::uchar chars[unibrow::Ecma262UnCanonicalize::kMaxWidth];
+  int length = GetCaseIndependentLetters(isolate, c, ascii, 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);
+  }
+  Label ok;
+  ASSERT(unibrow::Ecma262UnCanonicalize::kMaxWidth == 4);
+  switch (length) {
+    case 2: {
+      if (ShortCutEmitCharacterPair(macro_assembler,
+                                    ascii,
+                                    chars[0],
+                                    chars[1],
+                                    on_failure)) {
+      } else {
+        macro_assembler->CheckCharacter(chars[0], &ok);
+        macro_assembler->CheckNotCharacter(chars[1], on_failure);
+        macro_assembler->Bind(&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->Bind(&ok);
+      break;
+    default:
+      UNREACHABLE();
+      break;
+  }
+  return true;
+}
+
+
+static void EmitBoundaryTest(RegExpMacroAssembler* masm,
+                             int border,
+                             Label* fall_through,
+                             Label* above_or_equal,
+                             Label* 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,
+                                   int first,
+                                   int last,
+                                   Label* fall_through,
+                                   Label* in_range,
+                                   Label* 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,
+    ZoneList<int>* ranges,
+    int start_index,
+    int end_index,
+    int min_char,
+    Label* fall_through,
+    Label* even_label,
+    Label* odd_label) {
+  static const int kSize = RegExpMacroAssembler::kTableSize;
+  static const int kMask = RegExpMacroAssembler::kTableMask;
+
+  int base = (min_char & ~kMask);
+  USE(base);
+
+  // Assert that everything is on one kTableSize page.
+  for (int i = start_index; i <= end_index; i++) {
+    ASSERT_EQ(ranges->at(i) & ~kMask, base);
+  }
+  ASSERT(start_index == 0 || (ranges->at(start_index - 1) & ~kMask) <= base);
+
+  char templ[kSize];
+  Label* on_bit_set;
+  Label* on_bit_clear;
+  int 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 (int i = 0; i < (ranges->at(start_index) & kMask) && i < kSize; i++) {
+    templ[i] = bit;
+  }
+  int j = 0;
+  bit ^= 1;
+  for (int 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 (int i = j; i < kSize; i++) {
+    templ[i] = bit;
+  }
+  Factory* factory = Isolate::Current()->factory();
+  // TODO(erikcorry): Cache these.
+  Handle<ByteArray> ba = factory->NewByteArray(kSize, TENURED);
+  for (int i = 0; i < kSize; i++) {
+    ba->set(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,
+                        ZoneList<int>* ranges,
+                        int start_index,
+                        int end_index,
+                        int cut_index,
+                        Label* even_label,
+                        Label* odd_label) {
+  bool odd = (((cut_index - start_index) & 1) == 1);
+  Label* in_range_label = odd ? odd_label : even_label;
+  Label dummy;
+  EmitDoubleBoundaryTest(masm,
+                         ranges->at(cut_index),
+                         ranges->at(cut_index + 1) - 1,
+                         &dummy,
+                         in_range_label,
+                         &dummy);
+  ASSERT(!dummy.is_linked());
+  // 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 (int j = cut_index; j > start_index; j--) {
+    ranges->at(j) = ranges->at(j - 1);
+  }
+  for (int j = cut_index + 1; j < end_index; j++) {
+    ranges->at(j) = ranges->at(j + 1);
+  }
+}
+
+
+// Unicode case.  Split the search space into kSize spaces that are handled
+// with recursion.
+static void SplitSearchSpace(ZoneList<int>* ranges,
+                             int start_index,
+                             int end_index,
+                             int* new_start_index,
+                             int* new_end_index,
+                             int* border) {
+  static const int kSize = RegExpMacroAssembler::kTableSize;
+  static const int kMask = RegExpMacroAssembler::kTableMask;
+
+  int first = ranges->at(start_index);
+  int 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-ASCII
+  // 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).
+  int binary_chop_index = (end_index + start_index) / 2;
+  // The first test ensures that we get to the code that handles the ASCII
+  // range with a single not-taken branch, speeding up this important
+  // character range (even non-ASCII charset-based text has spaces and
+  // punctuation).
+  if (*border - 1 > String::kMaxOneByteCharCode &&  // ASCII 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) {
+    int scan_forward_for_section_border = binary_chop_index;;
+    int 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,
+                             ZoneList<int>* ranges,
+                             int start_index,
+                             int end_index,
+                             uc16 min_char,
+                             uc16 max_char,
+                             Label* fall_through,
+                             Label* even_label,
+                             Label* odd_label) {
+  int first = ranges->at(start_index);
+  int last = ranges->at(end_index) - 1;
+
+  ASSERT_LT(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 int kNoCutIndex = -1;
+    int cut = kNoCutIndex;
+    for (int 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_GE(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 int 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;
+  }
+
+  int new_start_index = 0;
+  int new_end_index = 0;
+  int border = 0;
+
+  SplitSearchSpace(ranges,
+                   start_index,
+                   end_index,
+                   &new_start_index,
+                   &new_end_index,
+                   &border);
+
+  Label handle_rest;
+  Label* 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_LE(start_index, new_end_index);
+  ASSERT_LE(new_start_index, end_index);
+  ASSERT_LT(start_index, new_start_index);
+  ASSERT_LT(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_LT(min_char, border - 1);
+  ASSERT_LT(border, max_char);
+  ASSERT_LT(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);
+  Label dummy;
+  GenerateBranches(masm,
+                   ranges,
+                   start_index,
+                   new_end_index,
+                   min_char,
+                   border - 1,
+                   &dummy,
+                   even_label,
+                   odd_label);
+  if (handle_rest.is_linked()) {
+    masm->Bind(&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 ascii,
+                          Label* on_failure,
+                          int cp_offset,
+                          bool check_offset,
+                          bool preloaded,
+                          Zone* zone) {
+  ZoneList<CharacterRange>* ranges = cc->ranges(zone);
+  if (!CharacterRange::IsCanonical(ranges)) {
+    CharacterRange::Canonicalize(ranges);
+  }
+
+  int max_char;
+  if (ascii) {
+    max_char = String::kMaxOneByteCharCode;
+  } else {
+    max_char = String::kMaxUtf16CodeUnit;
+  }
+
+  int range_count = ranges->length();
+
+  int last_valid_range = range_count - 1;
+  while (last_valid_range >= 0) {
+    CharacterRange& range = ranges->at(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(zone) &&
+        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).
+  ZoneList<int>* range_boundaries =
+      new(zone) ZoneList<int>(last_valid_range, zone);
+
+  bool zeroth_entry_is_failure = !cc->is_negated();
+
+  for (int i = 0; i <= last_valid_range; i++) {
+    CharacterRange& range = ranges->at(i);
+    if (range.from() == 0) {
+      ASSERT_EQ(i, 0);
+      zeroth_entry_is_failure = !zeroth_entry_is_failure;
+    } else {
+      range_boundaries->Add(range.from(), zone);
+    }
+    range_boundaries->Add(range.to() + 1, zone);
+  }
+  int end_index = range_boundaries->length() - 1;
+  if (range_boundaries->at(end_index) > max_char) {
+    end_index--;
+  }
+
+  Label 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->Bind(&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_.is_bound()) {
+      // 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->Bind(&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 (FLAG_regexp_optimization &&
+      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;
+}
+
+
+int ActionNode::EatsAtLeast(int still_to_find,
+                            int 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(int offset,
+                              int 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);
+}
+
+
+int AssertionNode::EatsAtLeast(int still_to_find,
+                               int 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(int offset,
+                                 int 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);
+}
+
+
+int BackReferenceNode::EatsAtLeast(int still_to_find,
+                                   int budget,
+                                   bool not_at_start) {
+  if (budget <= 0) return 0;
+  return on_success()->EatsAtLeast(still_to_find,
+                                   budget - 1,
+                                   not_at_start);
+}
+
+
+int TextNode::EatsAtLeast(int still_to_find,
+                          int budget,
+                          bool not_at_start) {
+  int 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);
+}
+
+
+int NegativeLookaheadChoiceNode::EatsAtLeast(int still_to_find,
+                                             int 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_->at(1).node();
+  return node->EatsAtLeast(still_to_find, budget - 1, not_at_start);
+}
+
+
+void NegativeLookaheadChoiceNode::GetQuickCheckDetails(
+    QuickCheckDetails* details,
+    RegExpCompiler* compiler,
+    int filled_in,
+    bool not_at_start) {
+  // Alternative 0 is the negative lookahead, alternative 1 is what comes
+  // afterwards.
+  RegExpNode* node = alternatives_->at(1).node();
+  return node->GetQuickCheckDetails(details, compiler, filled_in, not_at_start);
+}
+
+
+int ChoiceNode::EatsAtLeastHelper(int still_to_find,
+                                  int budget,
+                                  RegExpNode* ignore_this_node,
+                                  bool not_at_start) {
+  if (budget <= 0) return 0;
+  int min = 100;
+  int choice_count = alternatives_->length();
+  budget = (budget - 1) / choice_count;
+  for (int i = 0; i < choice_count; i++) {
+    RegExpNode* node = alternatives_->at(i).node();
+    if (node == ignore_this_node) continue;
+    int 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;
+}
+
+
+int LoopChoiceNode::EatsAtLeast(int still_to_find,
+                                int budget,
+                                bool not_at_start) {
+  return EatsAtLeastHelper(still_to_find,
+                           budget - 1,
+                           loop_node_,
+                           not_at_start);
+}
+
+
+int ChoiceNode::EatsAtLeast(int still_to_find,
+                            int 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 = String::kMaxOneByteCharCode;
+  } else {
+    char_mask = String::kMaxUtf16CodeUnit;
+  }
+  mask_ = 0;
+  value_ = 0;
+  int char_shift = 0;
+  for (int i = 0; i < characters_; i++) {
+    Position* pos = &positions_[i];
+    if ((pos->mask & String::kMaxOneByteCharCode) != 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* trace,
+                                bool preload_has_checked_bounds,
+                                Label* 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->ascii())) 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()) {
+    assembler->LoadCurrentCharacter(trace->cp_offset(),
+                                    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->ascii()) {
+      char_mask = String::kMaxOneByteCharCode;
+    } else {
+      char_mask = String::kMaxUtf16CodeUnit;
+    }
+    if ((mask & char_mask) == char_mask) need_mask = false;
+    mask &= char_mask;
+  } else {
+    // For 2-character preloads in ASCII mode or 1-character preloads in
+    // TWO_BYTE mode we also use a 16 bit load with zero extend.
+    if (details->characters() == 2 && compiler->ascii()) {
+      if ((mask & 0xffff) == 0xffff) need_mask = false;
+    } else if (details->characters() == 1 && !compiler->ascii()) {
+      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,
+                                    int characters_filled_in,
+                                    bool not_at_start) {
+  Isolate* isolate = Isolate::Current();
+  ASSERT(characters_filled_in < details->characters());
+  int characters = details->characters();
+  int char_mask;
+  if (compiler->ascii()) {
+    char_mask = String::kMaxOneByteCharCode;
+  } else {
+    char_mask = String::kMaxUtf16CodeUnit;
+  }
+  for (int k = 0; k < elms_->length(); k++) {
+    TextElement elm = elms_->at(k);
+    if (elm.text_type == TextElement::ATOM) {
+      Vector<const uc16> quarks = elm.data.u_atom->data();
+      for (int i = 0; i < characters && i < quarks.length(); i++) {
+        QuickCheckDetails::Position* pos =
+            details->positions(characters_filled_in);
+        uc16 c = quarks[i];
+        if (c > char_mask) {
+          // If we expect a non-ASCII character from an ASCII string,
+          // there is no way we can match. Not even case independent
+          // matching can turn an ASCII character into non-ASCII or
+          // vice versa.
+          details->set_cannot_match();
+          pos->determines_perfectly = false;
+          return;
+        }
+        if (compiler->ignore_case()) {
+          unibrow::uchar chars[unibrow::Ecma262UnCanonicalize::kMaxWidth];
+          int length = GetCaseIndependentLetters(isolate, c, compiler->ascii(),
+                                                 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 (int 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.data.u_char_class;
+      ZoneList<CharacterRange>* ranges = tree->ranges(zone());
+      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 {
+        int 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);
+        uc16 from = range.from();
+        uc16 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 (int i = first_range + 1; i < ranges->length(); i++) {
+          CharacterRange range = ranges->at(i);
+          uc16 from = range.from();
+          uc16 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(int by, bool ascii) {
+  ASSERT(by >= 0);
+  if (by >= characters_) {
+    Clear();
+    return;
+  }
+  for (int i = 0; i < characters_ - by; i++) {
+    positions_[i] = positions_[by + i];
+  }
+  for (int 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, int from_index) {
+  ASSERT(characters_ == other->characters_);
+  if (other->cannot_match_) {
+    return;
+  }
+  if (cannot_match_) {
+    *this = *other;
+    return;
+  }
+  for (int 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;
+    uc16 differing_bits = (pos->value ^ other_pos->value);
+    pos->mask &= ~differing_bits;
+    pos->value &= pos->mask;
+  }
+}
+
+
+class VisitMarker {
+ public:
+  explicit VisitMarker(NodeInfo* info) : info_(info) {
+    ASSERT(!info->visited);
+    info->visited = true;
+  }
+  ~VisitMarker() {
+    info_->visited = false;
+  }
+ private:
+  NodeInfo* info_;
+};
+
+
+RegExpNode* SeqRegExpNode::FilterASCII(int 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(int depth, bool ignore_case) {
+  RegExpNode* next = on_success_->FilterASCII(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(ZoneList<CharacterRange>* ranges) {
+  for (int i = 0; i < ranges->length(); i++) {
+    // TODO(dcarney): this could be a lot more efficient.
+    if (RangeContainsLatin1Equivalents(ranges->at(i))) return true;
+  }
+  return false;
+}
+
+
+RegExpNode* TextNode::FilterASCII(int depth, bool ignore_case) {
+  if (info()->replacement_calculated) return replacement();
+  if (depth < 0) return this;
+  ASSERT(!info()->visited);
+  VisitMarker marker(info());
+  int element_count = elms_->length();
+  for (int i = 0; i < element_count; i++) {
+    TextElement elm = elms_->at(i);
+    if (elm.text_type == TextElement::ATOM) {
+      Vector<const uc16> quarks = elm.data.u_atom->data();
+      for (int j = 0; j < quarks.length(); j++) {
+        uint16_t c = quarks[j];
+        if (c <= String::kMaxOneByteCharCode) 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 = unibrow::Latin1::ConvertNonLatin1ToLatin1(c);
+        // Character is outside Latin-1 completely
+        if (converted == 0) return set_replacement(NULL);
+        // Convert quark to Latin-1 in place.
+        uint16_t* copy = const_cast<uint16_t*>(quarks.start());
+        copy[j] = converted;
+      }
+    } else {
+      ASSERT(elm.text_type == TextElement::CHAR_CLASS);
+      RegExpCharacterClass* cc = elm.data.u_char_class;
+      ZoneList<CharacterRange>* ranges = cc->ranges(zone());
+      if (!CharacterRange::IsCanonical(ranges)) {
+        CharacterRange::Canonicalize(ranges);
+      }
+      // Now they are in order so we only need to look at the first.
+      int range_count = ranges->length();
+      if (cc->is_negated()) {
+        if (range_count != 0 &&
+            ranges->at(0).from() == 0 &&
+            ranges->at(0).to() >= String::kMaxOneByteCharCode) {
+          // 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() > String::kMaxOneByteCharCode) {
+          // 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::FilterASCII(int 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_->FilterASCII(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::FilterASCII(depth - 1, ignore_case);
+}
+
+
+RegExpNode* ChoiceNode::FilterASCII(int depth, bool ignore_case) {
+  if (info()->replacement_calculated) return replacement();
+  if (depth < 0) return this;
+  if (info()->visited) return this;
+  VisitMarker marker(info());
+  int choice_count = alternatives_->length();
+
+  for (int i = 0; i < choice_count; i++) {
+    GuardedAlternative alternative = alternatives_->at(i);
+    if (alternative.guards() != NULL && alternative.guards()->length() != 0) {
+      set_replacement(this);
+      return this;
+    }
+  }
+
+  int surviving = 0;
+  RegExpNode* survivor = NULL;
+  for (int i = 0; i < choice_count; i++) {
+    GuardedAlternative alternative = alternatives_->at(i);
+    RegExpNode* replacement =
+        alternative.node()->FilterASCII(depth - 1, ignore_case);
+    ASSERT(replacement != this);  // No missing EMPTY_MATCH_CHECK.
+    if (replacement != NULL) {
+      alternatives_->at(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.
+  ZoneList<GuardedAlternative>* new_alternatives =
+      new(zone()) ZoneList<GuardedAlternative>(surviving, zone());
+  for (int i = 0; i < choice_count; i++) {
+    RegExpNode* replacement =
+        alternatives_->at(i).node()->FilterASCII(depth - 1, ignore_case);
+    if (replacement != NULL) {
+      alternatives_->at(i).set_node(replacement);
+      new_alternatives->Add(alternatives_->at(i), zone());
+    }
+  }
+  alternatives_ = new_alternatives;
+  return this;
+}
+
+
+RegExpNode* NegativeLookaheadChoiceNode::FilterASCII(int 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_->at(1).node();
+  RegExpNode* replacement = node->FilterASCII(depth - 1, ignore_case);
+  if (replacement == NULL) return set_replacement(NULL);
+  alternatives_->at(1).set_node(replacement);
+
+  RegExpNode* neg_node = alternatives_->at(0).node();
+  RegExpNode* neg_replacement = neg_node->FilterASCII(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_->at(0).set_node(neg_replacement);
+  return set_replacement(this);
+}
+
+
+void LoopChoiceNode::GetQuickCheckDetails(QuickCheckDetails* details,
+                                          RegExpCompiler* compiler,
+                                          int 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(int offset,
+                                  int 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,
+                                      int characters_filled_in,
+                                      bool not_at_start) {
+  not_at_start = (not_at_start || not_at_start_);
+  int choice_count = alternatives_->length();
+  ASSERT(choice_count > 0);
+  alternatives_->at(0).node()->GetQuickCheckDetails(details,
+                                                    compiler,
+                                                    characters_filled_in,
+                                                    not_at_start);
+  for (int i = 1; i < choice_count; i++) {
+    QuickCheckDetails new_details(details->characters());
+    RegExpNode* node = alternatives_->at(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,
+                          Label* word,
+                          Label* 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();
+
+  Label 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->ascii()) {
+      assembler->CheckCharacterAfterAnd(0x2028, 0xfffe, &ok);
+    }
+    assembler->CheckCharacter('\n', &ok);
+    assembler->CheckNotCharacter('\r', new_trace.backtrack());
+  }
+  assembler->Bind(&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) {
+    int eats_at_least =
+        Min(kMaxLookaheadForBoyerMoore, EatsAtLeast(kMaxLookaheadForBoyerMoore,
+                                                    kRecursionBudget,
+                                                    not_at_start));
+    if (eats_at_least >= 1) {
+      BoyerMooreLookahead* bm =
+          new(zone()) BoyerMooreLookahead(eats_at_least, compiler, zone());
+      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) {
+    Label before_non_word;
+    Label 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->Bind(&before_non_word);
+    Label ok;
+    BacktrackIfPrevious(compiler, trace, at_boundary ? kIsNonWord : kIsWord);
+    assembler->GoTo(&ok);
+
+    assembler->Bind(&before_word);
+    BacktrackIfPrevious(compiler, trace, at_boundary ? kIsWord : kIsNonWord);
+    assembler->Bind(&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();
+
+  Label fall_through, dummy;
+
+  Label* non_word = backtrack_if_previous == kIsNonWord ?
+                    new_trace.backtrack() :
+                    &fall_through;
+  Label* 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->Bind(&fall_through);
+  on_success()->Emit(compiler, &new_trace);
+}
+
+
+void AssertionNode::GetQuickCheckDetails(QuickCheckDetails* details,
+                                         RegExpCompiler* compiler,
+                                         int 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: {
+      Label ok;
+      assembler->CheckPosition(trace->cp_offset(), &ok);
+      assembler->GoTo(trace->backtrack());
+      assembler->Bind(&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, int offset) {
+  if (quick_check == NULL) return false;
+  if (offset >= quick_check->characters()) return false;
+  return quick_check->positions(offset)->determines_perfectly;
+}
+
+
+static void UpdateBoundsCheck(int index, int* 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,
+                            int* checked_up_to) {
+  Isolate* isolate = Isolate::Current();
+  RegExpMacroAssembler* assembler = compiler->macro_assembler();
+  bool ascii = compiler->ascii();
+  Label* backtrack = trace->backtrack();
+  QuickCheckDetails* quick_check = trace->quick_check_performed();
+  int element_count = elms_->length();
+  for (int i = preloaded ? 0 : element_count - 1; i >= 0; i--) {
+    TextElement elm = elms_->at(i);
+    int cp_offset = trace->cp_offset() + elm.cp_offset;
+    if (elm.text_type == TextElement::ATOM) {
+      Vector<const uc16> quarks = elm.data.u_atom->data();
+      for (int 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_ASCII_MATCH:
+            ASSERT(ascii);
+            if (quarks[j] > String::kMaxOneByteCharCode) {
+              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(isolate,
+                                             compiler,
+                                             quarks[j],
+                                             backtrack,
+                                             cp_offset + j,
+                                             *checked_up_to < cp_offset + j,
+                                             preloaded);
+          if (bound_checked) UpdateBoundsCheck(cp_offset + j, checked_up_to);
+        }
+      }
+    } else {
+      ASSERT_EQ(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.data.u_char_class;
+        EmitCharClass(assembler,
+                      cc,
+                      ascii,
+                      backtrack,
+                      cp_offset,
+                      *checked_up_to < cp_offset,
+                      preloaded,
+                      zone());
+        UpdateBoundsCheck(cp_offset, checked_up_to);
+      }
+    }
+  }
+}
+
+
+int TextNode::Length() {
+  TextElement elm = elms_->last();
+  ASSERT(elm.cp_offset >= 0);
+  if (elm.text_type == TextElement::ATOM) {
+    return elm.cp_offset + elm.data.u_atom->data().length();
+  } else {
+    return elm.cp_offset + 1;
+  }
+}
+
+
+bool TextNode::SkipPass(int int_pass, bool ignore_case) {
+  TextEmitPassType pass = static_cast<TextEmitPassType>(int_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->ascii()) {
+    int dummy = 0;
+    TextEmitPass(compiler, NON_ASCII_MATCH, false, trace, false, &dummy);
+  }
+
+  bool first_elt_done = false;
+  int 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 (int 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 (int 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(int 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->ascii());
+  cp_offset_ += by;
+  if (cp_offset_ > RegExpMacroAssembler::kMaxCPOffset) {
+    compiler->SetRegExpTooBig();
+    cp_offset_ = 0;
+  }
+  bound_checked_up_to_ = Max(0, bound_checked_up_to_ - by);
+}
+
+
+void TextNode::MakeCaseIndependent(bool is_ascii) {
+  int element_count = elms_->length();
+  for (int i = 0; i < element_count; i++) {
+    TextElement elm = elms_->at(i);
+    if (elm.text_type == TextElement::CHAR_CLASS) {
+      RegExpCharacterClass* cc = elm.data.u_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(zone())) continue;
+      ZoneList<CharacterRange>* ranges = cc->ranges(zone());
+      int range_count = ranges->length();
+      for (int j = 0; j < range_count; j++) {
+        ranges->at(j).AddCaseEquivalents(ranges, is_ascii, zone());
+      }
+    }
+  }
+}
+
+
+int TextNode::GreedyLoopTextLength() {
+  TextElement elm = elms_->at(elms_->length() - 1);
+  if (elm.text_type == TextElement::CHAR_CLASS) {
+    return elm.cp_offset + 1;
+  } else {
+    return elm.cp_offset + elm.data.u_atom->data().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.data.u_char_class;
+  ZoneList<CharacterRange>* ranges = node->ranges(zone());
+  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->ascii()) {
+    max_char = String::kMaxOneByteCharCode;
+  } else {
+    max_char = String::kMaxUtf16CodeUnit;
+  }
+  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.
+int ChoiceNode::GreedyLoopTextLengthForAlternative(
+    GuardedAlternative* alternative) {
+  int 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.
+  int recursion_depth = 0;
+  while (node != this) {
+    if (recursion_depth++ > RegExpCompiler::kMaxRecursion) {
+      return kNodeIsTooComplexForGreedyLoops;
+    }
+    int 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_EQ(loop_node_, NULL);
+  AddAlternative(alt);
+  loop_node_ = alt.node();
+}
+
+
+void LoopChoiceNode::AddContinueAlternative(GuardedAlternative alt) {
+  ASSERT_EQ(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) {
+    int text_length =
+        GreedyLoopTextLengthForAlternative(&(alternatives_->at(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);
+}
+
+
+int ChoiceNode::CalculatePreloadCharacters(RegExpCompiler* compiler,
+                                           int eats_at_least) {
+  int preload_characters = Min(4, eats_at_least);
+  if (compiler->macro_assembler()->CanReadUnaligned()) {
+    bool ascii = compiler->ascii();
+    if (ascii) {
+      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 class is used when generating the alternatives in a choice node.  It
+// records the way the alternative is being code generated.
+class AlternativeGeneration: public Malloced {
+ public:
+  AlternativeGeneration()
+      : possible_success(),
+        expects_preload(false),
+        after(),
+        quick_check_details() { }
+  Label possible_success;
+  bool expects_preload;
+  Label 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:
+  AlternativeGenerationList(int count, Zone* zone)
+      : alt_gens_(count, zone) {
+    for (int i = 0; i < count && i < kAFew; i++) {
+      alt_gens_.Add(a_few_alt_gens_ + i, zone);
+    }
+    for (int i = kAFew; i < count; i++) {
+      alt_gens_.Add(new AlternativeGeneration(), zone);
+    }
+  }
+  ~AlternativeGenerationList() {
+    for (int i = kAFew; i < alt_gens_.length(); i++) {
+      delete alt_gens_[i];
+      alt_gens_[i] = NULL;
+    }
+  }
+
+  AlternativeGeneration* at(int i) {
+    return alt_gens_[i];
+  }
+
+ private:
+  static const int kAFew = 10;
+  ZoneList<AlternativeGeneration*> alt_gens_;
+  AlternativeGeneration a_few_alt_gens_[kAFew];
+};
+
+
+// The '2' variant is has inclusive from and exclusive to.
+static const int 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 int kSpaceRangeCount = ARRAY_SIZE(kSpaceRanges);
+
+static const int kWordRanges[] = {
+    '0', '9' + 1, 'A', 'Z' + 1, '_', '_' + 1, 'a', 'z' + 1, 0x10000 };
+static const int kWordRangeCount = ARRAY_SIZE(kWordRanges);
+static const int kDigitRanges[] = { '0', '9' + 1, 0x10000 };
+static const int kDigitRangeCount = ARRAY_SIZE(kDigitRanges);
+static const int kSurrogateRanges[] = { 0xd800, 0xe000, 0x10000 };
+static const int kSurrogateRangeCount = ARRAY_SIZE(kSurrogateRanges);
+static const int kLineTerminatorRanges[] = { 0x000A, 0x000B, 0x000D, 0x000E,
+    0x2028, 0x202A, 0x10000 };
+static const int kLineTerminatorRangeCount = ARRAY_SIZE(kLineTerminatorRanges);
+
+
+void BoyerMoorePositionInfo::Set(int 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 (int i = 0; i < kMapSize; i++) map_->at(i) = true;
+    }
+    return;
+  }
+  for (int i = interval.from(); i <= interval.to(); i++) {
+    int mod_character = (i & kMask);
+    if (!map_->at(mod_character)) {
+      map_count_++;
+      map_->at(mod_character) = true;
+    }
+    if (map_count_ == kMapSize) return;
+  }
+}
+
+
+void BoyerMoorePositionInfo::SetAll() {
+  s_ = w_ = d_ = kLatticeUnknown;
+  if (map_count_ != kMapSize) {
+    map_count_ = kMapSize;
+    for (int i = 0; i < kMapSize; i++) map_->at(i) = true;
+  }
+}
+
+
+BoyerMooreLookahead::BoyerMooreLookahead(
+    int length, RegExpCompiler* compiler, Zone* zone)
+    : length_(length),
+      compiler_(compiler) {
+  if (compiler->ascii()) {
+    max_char_ = String::kMaxOneByteCharCode;
+  } else {
+    max_char_ = String::kMaxUtf16CodeUnit;
+  }
+  bitmaps_ = new(zone) ZoneList<BoyerMoorePositionInfo*>(length, zone);
+  for (int i = 0; i < length; i++) {
+    bitmaps_->Add(new(zone) BoyerMoorePositionInfo(zone), zone);
+  }
+}
+
+
+// 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(int* from, int* to) {
+  int 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 int kMaxMax = 32;
+  for (int 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.
+int BoyerMooreLookahead::FindBestInterval(
+    int max_number_of_chars, int old_biggest_points, int* from, int* to) {
+  int biggest_points = old_biggest_points;
+  static const int kSize = RegExpMacroAssembler::kTableSize;
+  for (int i = 0; i < length_; ) {
+    while (i < length_ && Count(i) > max_number_of_chars) i++;
+    if (i == length_) break;
+    int remembered_from = i;
+    bool union_map[kSize];
+    for (int j = 0; j < kSize; j++) union_map[j] = false;
+    while (i < length_ && Count(i) <= max_number_of_chars) {
+      BoyerMoorePositionInfo* map = bitmaps_->at(i);
+      for (int j = 0; j < kSize; j++) union_map[j] |= map->at(j);
+      i++;
+    }
+    int frequency = 0;
+    for (int 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_->ascii() ? remembered_from <= 4 : remembered_from <= 2));
+    // Called 'probability' but it is only a rough estimate and can actually
+    // be outside the 0-kSize range.
+    int probability = (in_quickcheck_range ? kSize / 2 : kSize) - frequency;
+    int 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.
+int BoyerMooreLookahead::GetSkipTable(int min_lookahead,
+                                      int max_lookahead,
+                                      Handle<ByteArray> boolean_skip_table) {
+  const int kSize = RegExpMacroAssembler::kTableSize;
+
+  const int kSkipArrayEntry = 0;
+  const int kDontSkipArrayEntry = 1;
+
+  for (int i = 0; i < kSize; i++) {
+    boolean_skip_table->set(i, kSkipArrayEntry);
+  }
+  int skip = max_lookahead + 1 - min_lookahead;
+
+  for (int i = max_lookahead; i >= min_lookahead; i--) {
+    BoyerMoorePositionInfo* map = bitmaps_->at(i);
+    for (int j = 0; j < kSize; j++) {
+      if (map->at(j)) {
+        boolean_skip_table->set(j, kDontSkipArrayEntry);
+      }
+    }
+  }
+
+  return skip;
+}
+
+
+// See comment above on the implementation of GetSkipTable.
+bool BoyerMooreLookahead::EmitSkipInstructions(RegExpMacroAssembler* masm) {
+  const int kSize = RegExpMacroAssembler::kTableSize;
+
+  int min_lookahead = 0;
+  int max_lookahead = 0;
+
+  if (!FindWorthwhileInterval(&min_lookahead, &max_lookahead)) return false;
+
+  bool found_single_character = false;
+  int single_character = 0;
+  for (int 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 (int j = 0; j < kSize; j++) {
+      if (map->at(j)) {
+        found_single_character = true;
+        single_character = j;
+        break;
+      }
+    }
+  }
+
+  int 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 false;
+  }
+
+  if (found_single_character) {
+    Label cont, again;
+    masm->Bind(&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->Bind(&cont);
+    return true;
+  }
+
+  Factory* factory = Isolate::Current()->factory();
+  Handle<ByteArray> boolean_skip_table = factory->NewByteArray(kSize, TENURED);
+  int skip_distance = GetSkipTable(
+      min_lookahead, max_lookahead, boolean_skip_table);
+  ASSERT(skip_distance != 0);
+
+  Label cont, again;
+  masm->Bind(&again);
+  masm->LoadCurrentCharacter(max_lookahead, &cont, true);
+  masm->CheckBitInTable(boolean_skip_table, &cont);
+  masm->AdvanceCurrentPosition(skip_distance);
+  masm->GoTo(&again);
+  masm->Bind(&cont);
+
+  return true;
+}
+
+
+/* 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 reverse our expectation and expect to match rather
+ * than fail. Therefore we want the loop code to look like this (U is the
+ * unwind code that steps back in the greedy loop).  The following alternatives
+ * look the same as above.
+ *              _____
+ *             /     \
+ *             V     |
+ * ----------> S1    |
+ *            /|     |
+ *           / |S    |
+ *         F/  \_____/
+ *         /
+ *        |<-----------
+ *        |            \
+ *        V             \
+ *        Q2 ---> S2     \
+ *        |  S   /       |
+ *       F|     /        |
+ *        |   F/         |
+ *        |   /          |
+ *        |  R           |
+ *        | /            |
+ *   F    VL             |
+ * <------U              |
+ * back   |S             |
+ *        \______________/
+ */
+
+void ChoiceNode::Emit(RegExpCompiler* compiler, Trace* trace) {
+  RegExpMacroAssembler* macro_assembler = compiler->macro_assembler();
+  int choice_count = alternatives_->length();
+#ifdef DEBUG
+  for (int i = 0; i < choice_count - 1; i++) {
+    GuardedAlternative alternative = alternatives_->at(i);
+    ZoneList<Guard*>* guards = alternative.guards();
+    int guard_count = (guards == NULL) ? 0 : guards->length();
+    for (int j = 0; j < guard_count; j++) {
+      ASSERT(!trace->mentions_reg(guards->at(j)->reg()));
+    }
+  }
+#endif
+
+  LimitResult limit_result = LimitVersions(compiler, trace);
+  if (limit_result == DONE) return;
+  ASSERT(limit_result == CONTINUE);
+
+  int new_flush_budget = trace->flush_budget() / choice_count;
+  if (trace->flush_budget() == 0 && trace->actions() != NULL) {
+    trace->Flush(compiler, this);
+    return;
+  }
+
+  RecursionCheck rc(compiler);
+
+  Trace* current_trace = trace;
+
+  int text_length = GreedyLoopTextLengthForAlternative(&(alternatives_->at(0)));
+  bool greedy_loop = false;
+  Label greedy_loop_label;
+  Trace counter_backtrack_trace;
+  counter_backtrack_trace.set_backtrack(&greedy_loop_label);
+  if (not_at_start()) counter_backtrack_trace.set_at_start(false);
+
+  if (choice_count > 1 && text_length != kNodeIsTooComplexForGreedyLoops) {
+    // 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.
+    greedy_loop = true;
+    ASSERT(trace->stop_node() == NULL);
+    macro_assembler->PushCurrentPosition();
+    current_trace = &counter_backtrack_trace;
+    Label 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);
+    Label loop_label;
+    macro_assembler->Bind(&loop_label);
+    greedy_match_trace.set_stop_node(this);
+    greedy_match_trace.set_loop_label(&loop_label);
+    alternatives_->at(0).node()->Emit(compiler, &greedy_match_trace);
+    macro_assembler->Bind(&greedy_match_failed);
+  }
+
+  Label second_choice;  // For use in greedy matches.
+  macro_assembler->Bind(&second_choice);
+
+  int first_normal_choice = greedy_loop ? 1 : 0;
+
+  bool not_at_start = current_trace->at_start() == Trace::FALSE_VALUE;
+  const int kEatsAtLeastNotYetInitialized = -1;
+  int eats_at_least = kEatsAtLeastNotYetInitialized;
+
+  bool skip_was_emitted = false;
+
+  if (!greedy_loop && choice_count == 2) {
+    GuardedAlternative alt1 = alternatives_->at(1);
+    if (alt1.guards() == NULL || alt1.guards()->length() == 0) {
+      RegExpNode* eats_anything_node = alt1.node();
+      if (eats_anything_node->GetSuccessorOfOmnivorousTextNode(compiler) ==
+          this) {
+        // 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.
+        ASSERT(trace->is_trivial());  // This is the case on LoopChoiceNodes.
+        BoyerMooreLookahead* lookahead = bm_info(not_at_start);
+        if (lookahead == NULL) {
+          eats_at_least = Min(kMaxLookaheadForBoyerMoore,
+                              EatsAtLeast(kMaxLookaheadForBoyerMoore,
+                                          kRecursionBudget,
+                                          not_at_start));
+          if (eats_at_least >= 1) {
+            BoyerMooreLookahead* bm =
+                new(zone()) BoyerMooreLookahead(eats_at_least,
+                                                compiler,
+                                                zone());
+            GuardedAlternative alt0 = alternatives_->at(0);
+            alt0.node()->FillInBMInfo(0, kRecursionBudget, bm, not_at_start);
+            skip_was_emitted = bm->EmitSkipInstructions(macro_assembler);
+          }
+        } else {
+          skip_was_emitted = lookahead->EmitSkipInstructions(macro_assembler);
+        }
+      }
+    }
+  }
+
+  if (eats_at_least == kEatsAtLeastNotYetInitialized) {
+    // Save some time by looking at most one machine word ahead.
+    eats_at_least =
+        EatsAtLeast(compiler->ascii() ? 4 : 2, kRecursionBudget, not_at_start);
+  }
+  int preload_characters = CalculatePreloadCharacters(compiler, eats_at_least);
+
+  bool preload_is_current = !skip_was_emitted &&
+      (current_trace->characters_preloaded() == preload_characters);
+  bool preload_has_checked_bounds = preload_is_current;
+
+  AlternativeGenerationList alt_gens(choice_count, zone());
+
+  // 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.
+  for (int i = first_normal_choice; i < choice_count; i++) {
+    GuardedAlternative alternative = alternatives_->at(i);
+    AlternativeGeneration* alt_gen = alt_gens.at(i);
+    alt_gen->quick_check_details.set_characters(preload_characters);
+    ZoneList<Guard*>* guards = alternative.guards();
+    int guard_count = (guards == NULL) ? 0 : guards->length();
+    Trace new_trace(*current_trace);
+    new_trace.set_characters_preloaded(preload_is_current ?
+                                         preload_characters :
+                                         0);
+    if (preload_has_checked_bounds) {
+      new_trace.set_bound_checked_up_to(preload_characters);
+    }
+    new_trace.quick_check_performed()->Clear();
+    if (not_at_start_) new_trace.set_at_start(Trace::FALSE_VALUE);
+    alt_gen->expects_preload = preload_is_current;
+    bool generate_full_check_inline = false;
+    if (FLAG_regexp_optimization &&
+        try_to_emit_quick_check_for_alternative(i) &&
+        alternative.node()->EmitQuickCheck(compiler,
+                                           &new_trace,
+                                           preload_has_checked_bounds,
+                                           &alt_gen->possible_success,
+                                           &alt_gen->quick_check_details,
+                                           i < choice_count - 1)) {
+      // Quick check was generated for this choice.
+      preload_is_current = true;
+      preload_has_checked_bounds = true;
+      // On the last choice in the ChoiceNode we generated the quick
+      // check to fall through on possible success.  So now we need to
+      // generate the full check inline.
+      if (i == choice_count - 1) {
+        macro_assembler->Bind(&alt_gen->possible_success);
+        new_trace.set_quick_check_performed(&alt_gen->quick_check_details);
+        new_trace.set_characters_preloaded(preload_characters);
+        new_trace.set_bound_checked_up_to(preload_characters);
+        generate_full_check_inline = true;
+      }
+    } else if (alt_gen->quick_check_details.cannot_match()) {
+      if (i == choice_count - 1 && !greedy_loop) {
+        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_normal_choice) {
+        alt_gen->expects_preload = false;
+        new_trace.InvalidateCurrentCharacter();
+      }
+      if (i < choice_count - 1) {
+        new_trace.set_backtrack(&alt_gen->after);
+      }
+      generate_full_check_inline = true;
+    }
+    if (generate_full_check_inline) {
+      if (new_trace.actions() != NULL) {
+        new_trace.set_flush_budget(new_flush_budget);
+      }
+      for (int j = 0; j < guard_count; j++) {
+        GenerateGuard(macro_assembler, guards->at(j), &new_trace);
+      }
+      alternative.node()->Emit(compiler, &new_trace);
+      preload_is_current = false;
+    }
+    macro_assembler->Bind(&alt_gen->after);
+  }
+  if (greedy_loop) {
+    macro_assembler->Bind(&greedy_loop_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);
+  }
+
+  // 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.
+  for (int i = first_normal_choice; i < choice_count - 1; i++) {
+    AlternativeGeneration* alt_gen = alt_gens.at(i);
+    Trace new_trace(*current_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);
+    }
+    EmitOutOfLineContinuation(compiler,
+                              &new_trace,
+                              alternatives_->at(i),
+                              alt_gen,
+                              preload_characters,
+                              alt_gens.at(i + 1)->expects_preload);
+  }
+}
+
+
+void ChoiceNode::EmitOutOfLineContinuation(RegExpCompiler* compiler,
+                                           Trace* trace,
+                                           GuardedAlternative alternative,
+                                           AlternativeGeneration* alt_gen,
+                                           int preload_characters,
+                                           bool next_expects_preload) {
+  if (!alt_gen->possible_success.is_linked()) return;
+
+  RegExpMacroAssembler* macro_assembler = compiler->macro_assembler();
+  macro_assembler->Bind(&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);
+  ZoneList<Guard*>* guards = alternative.guards();
+  int guard_count = (guards == NULL) ? 0 : guards->length();
+  if (next_expects_preload) {
+    Label reload_current_char;
+    out_of_line_trace.set_backtrack(&reload_current_char);
+    for (int 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->Bind(&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 (int 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: {
+      int start_pos_reg = data_.u_empty_match_check.start_register;
+      int stored_pos = 0;
+      int 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 {
+        Label 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) {
+          int 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->Bind(&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);
+      int clear_register_count = data_.u_submatch.clear_register_count;
+      if (clear_register_count == 0) {
+        on_success()->Emit(compiler, trace);
+        return;
+      }
+      int clear_registers_from = data_.u_submatch.clear_register_from;
+      Label clear_registers_backtrack;
+      Trace new_trace = *trace;
+      new_trace.set_backtrack(&clear_registers_backtrack);
+      on_success()->Emit(compiler, &new_trace);
+
+      assembler->Bind(&clear_registers_backtrack);
+      int 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_EQ(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),
+        stream_(&alloc_) { }
+  void PrintNode(const char* label, RegExpNode* node);
+  void Visit(RegExpNode* node);
+  void PrintAttributes(RegExpNode* from);
+  StringStream* stream() { return &stream_; }
+  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_;
+  HeapStringAllocator alloc_;
+  StringStream stream_;
+};
+
+
+void DotPrinter::PrintNode(const char* label, RegExpNode* node) {
+  stream()->Add("digraph G {\n  graph [label=\"");
+  for (int i = 0; label[i]; i++) {
+    switch (label[i]) {
+      case '\\':
+        stream()->Add("\\\\");
+        break;
+      case '"':
+        stream()->Add("\"");
+        break;
+      default:
+        stream()->Put(label[i]);
+        break;
+    }
+  }
+  stream()->Add("\"];\n");
+  Visit(node);
+  stream()->Add("}\n");
+  printf("%s", *(stream()->ToCString()));
+}
+
+
+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) {
+  stream()->Add("  n%p -> n%p [style=dotted];\n", from, on_failure);
+  Visit(on_failure);
+}
+
+
+class TableEntryBodyPrinter {
+ public:
+  TableEntryBodyPrinter(StringStream* stream, ChoiceNode* choice)
+      : stream_(stream), choice_(choice) { }
+  void Call(uc16 from, DispatchTable::Entry entry) {
+    OutSet* out_set = entry.out_set();
+    for (unsigned i = 0; i < OutSet::kFirstLimit; i++) {
+      if (out_set->Get(i)) {
+        stream()->Add("    n%p:s%io%i -> n%p;\n",
+                      choice(),
+                      from,
+                      i,
+                      choice()->alternatives()->at(i).node());
+      }
+    }
+  }
+ private:
+  StringStream* stream() { return stream_; }
+  ChoiceNode* choice() { return choice_; }
+  StringStream* stream_;
+  ChoiceNode* choice_;
+};
+
+
+class TableEntryHeaderPrinter {
+ public:
+  explicit TableEntryHeaderPrinter(StringStream* stream)
+      : first_(true), stream_(stream) { }
+  void Call(uc16 from, DispatchTable::Entry entry) {
+    if (first_) {
+      first_ = false;
+    } else {
+      stream()->Add("|");
+    }
+    stream()->Add("{\\%k-\\%k|{", from, entry.to());
+    OutSet* out_set = entry.out_set();
+    int priority = 0;
+    for (unsigned i = 0; i < OutSet::kFirstLimit; i++) {
+      if (out_set->Get(i)) {
+        if (priority > 0) stream()->Add("|");
+        stream()->Add("<s%io%i> %i", from, i, priority);
+        priority++;
+      }
+    }
+    stream()->Add("}}");
+  }
+
+ private:
+  bool first_;
+  StringStream* stream() { return stream_; }
+  StringStream* stream_;
+};
+
+
+class AttributePrinter {
+ public:
+  explicit AttributePrinter(DotPrinter* out)
+      : out_(out), first_(true) { }
+  void PrintSeparator() {
+    if (first_) {
+      first_ = false;
+    } else {
+      out_->stream()->Add("|");
+    }
+  }
+  void PrintBit(const char* name, bool value) {
+    if (!value) return;
+    PrintSeparator();
+    out_->stream()->Add("{%s}", name);
+  }
+  void PrintPositive(const char* name, int value) {
+    if (value < 0) return;
+    PrintSeparator();
+    out_->stream()->Add("{%s|%x}", name, value);
+  }
+ private:
+  DotPrinter* out_;
+  bool first_;
+};
+
+
+void DotPrinter::PrintAttributes(RegExpNode* that) {
+  stream()->Add("  a%p [shape=Mrecord, color=grey, fontcolor=grey, "
+                "margin=0.1, fontsize=10, label=\"{",
+                that);
+  AttributePrinter printer(this);
+  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);
+  Label* label = that->label();
+  if (label->is_bound())
+    printer.PrintPositive("@", label->pos());
+  stream()->Add("}\"];\n");
+  stream()->Add("  a%p -> n%p [style=dashed, color=grey, "
+                "arrowhead=none];\n", that, that);
+}
+
+
+static const bool kPrintDispatchTable = false;
+void DotPrinter::VisitChoice(ChoiceNode* that) {
+  if (kPrintDispatchTable) {
+    stream()->Add("  n%p [shape=Mrecord, label=\"", that);
+    TableEntryHeaderPrinter header_printer(stream());
+    that->GetTable(ignore_case_)->ForEach(&header_printer);
+    stream()->Add("\"]\n", that);
+    PrintAttributes(that);
+    TableEntryBodyPrinter body_printer(stream(), that);
+    that->GetTable(ignore_case_)->ForEach(&body_printer);
+  } else {
+    stream()->Add("  n%p [shape=Mrecord, label=\"?\"];\n", that);
+    for (int i = 0; i < that->alternatives()->length(); i++) {
+      GuardedAlternative alt = that->alternatives()->at(i);
+      stream()->Add("  n%p -> n%p;\n", that, alt.node());
+    }
+  }
+  for (int i = 0; i < that->alternatives()->length(); i++) {
+    GuardedAlternative alt = that->alternatives()->at(i);
+    alt.node()->Accept(this);
+  }
+}
+
+
+void DotPrinter::VisitText(TextNode* that) {
+  Zone* zone = that->zone();
+  stream()->Add("  n%p [label=\"", that);
+  for (int i = 0; i < that->elements()->length(); i++) {
+    if (i > 0) stream()->Add(" ");
+    TextElement elm = that->elements()->at(i);
+    switch (elm.text_type) {
+      case TextElement::ATOM: {
+        stream()->Add("'%w'", elm.data.u_atom->data());
+        break;
+      }
+      case TextElement::CHAR_CLASS: {
+        RegExpCharacterClass* node = elm.data.u_char_class;
+        stream()->Add("[");
+        if (node->is_negated())
+          stream()->Add("^");
+        for (int j = 0; j < node->ranges(zone)->length(); j++) {
+          CharacterRange range = node->ranges(zone)->at(j);
+          stream()->Add("%k-%k", range.from(), range.to());
+        }
+        stream()->Add("]");
+        break;
+      }
+      default:
+        UNREACHABLE();
+    }
+  }
+  stream()->Add("\", shape=box, peripheries=2];\n");
+  PrintAttributes(that);
+  stream()->Add("  n%p -> n%p;\n", that, that->on_success());
+  Visit(that->on_success());
+}
+
+
+void DotPrinter::VisitBackReference(BackReferenceNode* that) {
+  stream()->Add("  n%p [label=\"$%i..$%i\", shape=doubleoctagon];\n",
+                that,
+                that->start_register(),
+                that->end_register());
+  PrintAttributes(that);
+  stream()->Add("  n%p -> n%p;\n", that, that->on_success());
+  Visit(that->on_success());
+}
+
+
+void DotPrinter::VisitEnd(EndNode* that) {
+  stream()->Add("  n%p [style=bold, shape=point];\n", that);
+  PrintAttributes(that);
+}
+
+
+void DotPrinter::VisitAssertion(AssertionNode* that) {
+  stream()->Add("  n%p [", that);
+  switch (that->assertion_type()) {
+    case AssertionNode::AT_END:
+      stream()->Add("label=\"$\", shape=septagon");
+      break;
+    case AssertionNode::AT_START:
+      stream()->Add("label=\"^\", shape=septagon");
+      break;
+    case AssertionNode::AT_BOUNDARY:
+      stream()->Add("label=\"\\b\", shape=septagon");
+      break;
+    case AssertionNode::AT_NON_BOUNDARY:
+      stream()->Add("label=\"\\B\", shape=septagon");
+      break;
+    case AssertionNode::AFTER_NEWLINE:
+      stream()->Add("label=\"(?<=\\n)\", shape=septagon");
+      break;
+  }
+  stream()->Add("];\n");
+  PrintAttributes(that);
+  RegExpNode* successor = that->on_success();
+  stream()->Add("  n%p -> n%p;\n", that, successor);
+  Visit(successor);
+}
+
+
+void DotPrinter::VisitAction(ActionNode* that) {
+  stream()->Add("  n%p [", that);
+  switch (that->action_type_) {
+    case ActionNode::SET_REGISTER:
+      stream()->Add("label=\"$%i:=%i\", shape=octagon",
+                    that->data_.u_store_register.reg,
+                    that->data_.u_store_register.value);
+      break;
+    case ActionNode::INCREMENT_REGISTER:
+      stream()->Add("label=\"$%i++\", shape=octagon",
+                    that->data_.u_increment_register.reg);
+      break;
+    case ActionNode::STORE_POSITION:
+      stream()->Add("label=\"$%i:=$pos\", shape=octagon",
+                    that->data_.u_position_register.reg);
+      break;
+    case ActionNode::BEGIN_SUBMATCH:
+      stream()->Add("label=\"$%i:=$pos,begin\", shape=septagon",
+                    that->data_.u_submatch.current_position_register);
+      break;
+    case ActionNode::POSITIVE_SUBMATCH_SUCCESS:
+      stream()->Add("label=\"escape\", shape=septagon");
+      break;
+    case ActionNode::EMPTY_MATCH_CHECK:
+      stream()->Add("label=\"$%i=$pos?,$%i<%i?\", 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: {
+      stream()->Add("label=\"clear $%i to $%i\", shape=septagon",
+                    that->data_.u_clear_captures.range_from,
+                    that->data_.u_clear_captures.range_to);
+      break;
+    }
+  }
+  stream()->Add("];\n");
+  PrintAttributes(that);
+  RegExpNode* successor = that->on_success();
+  stream()->Add("  n%p -> n%p;\n", that, successor);
+  Visit(successor);
+}
+
+
+class DispatchTableDumper {
+ public:
+  explicit DispatchTableDumper(StringStream* stream) : stream_(stream) { }
+  void Call(uc16 key, DispatchTable::Entry entry);
+  StringStream* stream() { return stream_; }
+ private:
+  StringStream* stream_;
+};
+
+
+void DispatchTableDumper::Call(uc16 key, DispatchTable::Entry entry) {
+  stream()->Add("[%k-%k]: {", key, entry.to());
+  OutSet* set = entry.out_set();
+  bool first = true;
+  for (unsigned i = 0; i < OutSet::kFirstLimit; i++) {
+    if (set->Get(i)) {
+      if (first) {
+        first = false;
+      } else {
+        stream()->Add(", ");
+      }
+      stream()->Add("%i", i);
+    }
+  }
+  stream()->Add("}\n");
+}
+
+
+void DispatchTable::Dump() {
+  HeapStringAllocator alloc;
+  StringStream stream(&alloc);
+  DispatchTableDumper dumper(&stream);
+  tree()->ForEach(&dumper);
+  OS::PrintError("%s", *stream.ToCString());
+}
+
+
+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) {
+  ZoneList<TextElement>* elms =
+      new(compiler->zone()) ZoneList<TextElement>(1, compiler->zone());
+  elms->Add(TextElement::Atom(this), compiler->zone());
+  return new(compiler->zone()) TextNode(elms, on_success);
+}
+
+
+RegExpNode* RegExpText::ToNode(RegExpCompiler* compiler,
+                               RegExpNode* on_success) {
+  return new(compiler->zone()) TextNode(elements(), on_success);
+}
+
+
+static bool CompareInverseRanges(ZoneList<CharacterRange>* ranges,
+                                 const int* special_class,
+                                 int 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 (int 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(ZoneList<CharacterRange>* ranges,
+                          const int* special_class,
+                          int length) {
+  length--;  // Remove final 0x10000.
+  ASSERT(special_class[length] == 0x10000);
+  if (ranges->length() * 2 != length) {
+    return false;
+  }
+  for (int 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(Zone* zone) {
+  // 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(zone), kSpaceRanges, kSpaceRangeCount)) {
+    set_.set_standard_set_type('s');
+    return true;
+  }
+  if (CompareInverseRanges(set_.ranges(zone), kSpaceRanges, kSpaceRangeCount)) {
+    set_.set_standard_set_type('S');
+    return true;
+  }
+  if (CompareInverseRanges(set_.ranges(zone),
+                           kLineTerminatorRanges,
+                           kLineTerminatorRangeCount)) {
+    set_.set_standard_set_type('.');
+    return true;
+  }
+  if (CompareRanges(set_.ranges(zone),
+                    kLineTerminatorRanges,
+                    kLineTerminatorRangeCount)) {
+    set_.set_standard_set_type('n');
+    return true;
+  }
+  if (CompareRanges(set_.ranges(zone), kWordRanges, kWordRangeCount)) {
+    set_.set_standard_set_type('w');
+    return true;
+  }
+  if (CompareInverseRanges(set_.ranges(zone), kWordRanges, kWordRangeCount)) {
+    set_.set_standard_set_type('W');
+    return true;
+  }
+  return false;
+}
+
+
+RegExpNode* RegExpCharacterClass::ToNode(RegExpCompiler* compiler,
+                                         RegExpNode* on_success) {
+  return new(compiler->zone()) TextNode(this, on_success);
+}
+
+
+RegExpNode* RegExpDisjunction::ToNode(RegExpCompiler* compiler,
+                                      RegExpNode* on_success) {
+  ZoneList<RegExpTree*>* alternatives = this->alternatives();
+  int length = alternatives->length();
+  ChoiceNode* result =
+      new(compiler->zone()) ChoiceNode(length, compiler->zone());
+  for (int 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:
+  static const int kMaxExpansionFactor = 6;
+  RegExpExpansionLimiter(RegExpCompiler* compiler, int 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 {
+        int 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_;
+  int saved_expansion_factor_;
+  bool ok_to_expand_;
+
+  DISALLOW_IMPLICIT_CONSTRUCTORS(RegExpExpansionLimiter);
+};
+
+
+RegExpNode* RegExpQuantifier::ToNode(int min,
+                                     int 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.
+  static const int kMaxUnrolledMinMatches = 3;  // Unroll (foo)+ and (foo){3,}
+  static const int kMaxUnrolledMaxMatches = 3;  // Unroll (foo)? and (foo){x,3}
+  if (max == 0) return on_success;  // This can happen due to recursion.
+  bool body_can_be_empty = (body->min_match() == 0);
+  int body_start_reg = RegExpCompiler::kNoRegister;
+  Interval capture_registers = body->CaptureRegisters();
+  bool needs_capture_clearing = !capture_registers.is_empty();
+  Zone* zone = compiler->zone();
+
+  if (body_can_be_empty) {
+    body_start_reg = compiler->AllocateRegister();
+  } else if (FLAG_regexp_optimization && !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()) {
+        int 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 (int 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 (int i = 0; i < max; i++) {
+          ChoiceNode* alternation = new(zone) ChoiceNode(2, zone);
+          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;
+  int reg_ctr = needs_counter
+      ? compiler->AllocateRegister()
+      : RegExpCompiler::kNoRegister;
+  LoopChoiceNode* center = new(zone) LoopChoiceNode(body->min_match() == 0,
+                                                    zone);
+  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(zone) Guard(reg_ctr, Guard::LT, max);
+    body_alt.AddGuard(body_guard, zone);
+  }
+  GuardedAlternative rest_alt(on_success);
+  if (has_min) {
+    Guard* rest_guard = new(compiler->zone()) Guard(reg_ctr, Guard::GEQ, min);
+    rest_alt.AddGuard(rest_guard, zone);
+  }
+  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) {
+  NodeInfo info;
+  Zone* zone = compiler->zone();
+
+  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.
+      int stack_pointer_register = compiler->AllocateRegister();
+      int position_register = compiler->AllocateRegister();
+      // The ChoiceNode to distinguish between a newline and end-of-input.
+      ChoiceNode* result = new(zone) ChoiceNode(2, zone);
+      // Create a newline atom.
+      ZoneList<CharacterRange>* newline_ranges =
+          new(zone) ZoneList<CharacterRange>(3, zone);
+      CharacterRange::AddClassEscape('n', newline_ranges, zone);
+      RegExpCharacterClass* newline_atom = new(zone) RegExpCharacterClass('n');
+      TextNode* newline_matcher = new(zone) 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(compiler->zone())
+      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) {
+  int stack_pointer_register = compiler->AllocateRegister();
+  int position_register = compiler->AllocateRegister();
+
+  const int registers_per_capture = 2;
+  const int register_of_first_capture = 2;
+  int register_count = capture_count_ * registers_per_capture;
+  int 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.
+    Zone* zone = compiler->zone();
+
+    GuardedAlternative body_alt(
+        body()->ToNode(
+            compiler,
+            success = new(zone) NegativeSubmatchSuccess(stack_pointer_register,
+                                                        position_register,
+                                                        register_count,
+                                                        register_start,
+                                                        zone)));
+    ChoiceNode* choice_node =
+        new(zone) NegativeLookaheadChoiceNode(body_alt,
+                                              GuardedAlternative(on_success),
+                                              zone);
+    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,
+                                  int index,
+                                  RegExpCompiler* compiler,
+                                  RegExpNode* on_success) {
+  int start_reg = RegExpCapture::StartRegister(index);
+  int 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) {
+  ZoneList<RegExpTree*>* children = nodes();
+  RegExpNode* current = on_success;
+  for (int i = children->length() - 1; i >= 0; i--) {
+    current = children->at(i)->ToNode(compiler, current);
+  }
+  return current;
+}
+
+
+static void AddClass(const int* elmv,
+                     int elmc,
+                     ZoneList<CharacterRange>* ranges,
+                     Zone* zone) {
+  elmc--;
+  ASSERT(elmv[elmc] == 0x10000);
+  for (int i = 0; i < elmc; i += 2) {
+    ASSERT(elmv[i] < elmv[i + 1]);
+    ranges->Add(CharacterRange(elmv[i], elmv[i + 1] - 1), zone);
+  }
+}
+
+
+static void AddClassNegated(const int *elmv,
+                            int elmc,
+                            ZoneList<CharacterRange>* ranges,
+                            Zone* zone) {
+  elmc--;
+  ASSERT(elmv[elmc] == 0x10000);
+  ASSERT(elmv[0] != 0x0000);
+  ASSERT(elmv[elmc-1] != String::kMaxUtf16CodeUnit);
+  uc16 last = 0x0000;
+  for (int i = 0; i < elmc; i += 2) {
+    ASSERT(last <= elmv[i] - 1);
+    ASSERT(elmv[i] < elmv[i + 1]);
+    ranges->Add(CharacterRange(last, elmv[i] - 1), zone);
+    last = elmv[i + 1];
+  }
+  ranges->Add(CharacterRange(last, String::kMaxUtf16CodeUnit), zone);
+}
+
+
+void CharacterRange::AddClassEscape(uc16 type,
+                                    ZoneList<CharacterRange>* ranges,
+                                    Zone* zone) {
+  switch (type) {
+    case 's':
+      AddClass(kSpaceRanges, kSpaceRangeCount, ranges, zone);
+      break;
+    case 'S':
+      AddClassNegated(kSpaceRanges, kSpaceRangeCount, ranges, zone);
+      break;
+    case 'w':
+      AddClass(kWordRanges, kWordRangeCount, ranges, zone);
+      break;
+    case 'W':
+      AddClassNegated(kWordRanges, kWordRangeCount, ranges, zone);
+      break;
+    case 'd':
+      AddClass(kDigitRanges, kDigitRangeCount, ranges, zone);
+      break;
+    case 'D':
+      AddClassNegated(kDigitRanges, kDigitRangeCount, ranges, zone);
+      break;
+    case '.':
+      AddClassNegated(kLineTerminatorRanges,
+                      kLineTerminatorRangeCount,
+                      ranges,
+                      zone);
+      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(), zone);
+      break;
+    // This is the set of characters matched by the $ and ^ symbols
+    // in multiline mode.
+    case 'n':
+      AddClass(kLineTerminatorRanges,
+               kLineTerminatorRangeCount,
+               ranges,
+               zone);
+      break;
+    default:
+      UNREACHABLE();
+  }
+}
+
+
+Vector<const int> CharacterRange::GetWordBounds() {
+  return Vector<const int>(kWordRanges, kWordRangeCount - 1);
+}
+
+
+class CharacterRangeSplitter {
+ public:
+  CharacterRangeSplitter(ZoneList<CharacterRange>** included,
+                         ZoneList<CharacterRange>** excluded,
+                         Zone* zone)
+      : included_(included),
+        excluded_(excluded),
+        zone_(zone) { }
+  void Call(uc16 from, DispatchTable::Entry entry);
+
+  static const int kInBase = 0;
+  static const int kInOverlay = 1;
+
+ private:
+  ZoneList<CharacterRange>** included_;
+  ZoneList<CharacterRange>** excluded_;
+  Zone* zone_;
+};
+
+
+void CharacterRangeSplitter::Call(uc16 from, DispatchTable::Entry entry) {
+  if (!entry.out_set()->Get(kInBase)) return;
+  ZoneList<CharacterRange>** target = entry.out_set()->Get(kInOverlay)
+    ? included_
+    : excluded_;
+  if (*target == NULL) *target = new(zone_) ZoneList<CharacterRange>(2, zone_);
+  (*target)->Add(CharacterRange(entry.from(), entry.to()), zone_);
+}
+
+
+void CharacterRange::Split(ZoneList<CharacterRange>* base,
+                           Vector<const int> overlay,
+                           ZoneList<CharacterRange>** included,
+                           ZoneList<CharacterRange>** excluded,
+                           Zone* zone) {
+  ASSERT_EQ(NULL, *included);
+  ASSERT_EQ(NULL, *excluded);
+  DispatchTable table(zone);
+  for (int i = 0; i < base->length(); i++)
+    table.AddRange(base->at(i), CharacterRangeSplitter::kInBase, zone);
+  for (int i = 0; i < overlay.length(); i += 2) {
+    table.AddRange(CharacterRange(overlay[i], overlay[i + 1] - 1),
+                   CharacterRangeSplitter::kInOverlay, zone);
+  }
+  CharacterRangeSplitter callback(included, excluded, zone);
+  table.ForEach(&callback);
+}
+
+
+void CharacterRange::AddCaseEquivalents(ZoneList<CharacterRange>* ranges,
+                                        bool is_ascii,
+                                        Zone* zone) {
+  Isolate* isolate = Isolate::Current();
+  uc16 bottom = from();
+  uc16 top = to();
+  if (is_ascii && !RangeContainsLatin1Equivalents(*this)) {
+    if (bottom > String::kMaxOneByteCharCode) return;
+    if (top > String::kMaxOneByteCharCode) top = String::kMaxOneByteCharCode;
+  }
+  unibrow::uchar chars[unibrow::Ecma262UnCanonicalize::kMaxWidth];
+  if (top == bottom) {
+    // If this is a singleton we just expand the one character.
+    int length = isolate->jsregexp_uncanonicalize()->get(bottom, '\0', chars);
+    for (int i = 0; i < length; i++) {
+      uc32 chr = chars[i];
+      if (chr != bottom) {
+        ranges->Add(CharacterRange::Singleton(chars[i]), zone);
+      }
+    }
+  } 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").
+    unibrow::uchar range[unibrow::Ecma262UnCanonicalize::kMaxWidth];
+    int pos = bottom;
+    while (pos <= top) {
+      int length = isolate->jsregexp_canonrange()->get(pos, '\0', range);
+      uc16 block_end;
+      if (length == 0) {
+        block_end = pos;
+      } else {
+        ASSERT_EQ(1, length);
+        block_end = range[0];
+      }
+      int end = (block_end > top) ? top : block_end;
+      length = isolate->jsregexp_uncanonicalize()->get(block_end, '\0', range);
+      for (int i = 0; i < length; i++) {
+        uc32 c = range[i];
+        uc16 range_from = c - (block_end - pos);
+        uc16 range_to = c - (block_end - end);
+        if (!(bottom <= range_from && range_to <= top)) {
+          ranges->Add(CharacterRange(range_from, range_to), zone);
+        }
+      }
+      pos = end + 1;
+    }
+  }
+}
+
+
+bool CharacterRange::IsCanonical(ZoneList<CharacterRange>* ranges) {
+  ASSERT_NOT_NULL(ranges);
+  int n = ranges->length();
+  if (n <= 1) return true;
+  int max = ranges->at(0).to();
+  for (int 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;
+}
+
+
+ZoneList<CharacterRange>* CharacterSet::ranges(Zone* zone) {
+  if (ranges_ == NULL) {
+    ranges_ = new(zone) ZoneList<CharacterRange>(2, zone);
+    CharacterRange::AddClassEscape(standard_set_type_, ranges_, zone);
+  }
+  return ranges_;
+}
+
+
+// Move a number of elements in a zonelist to another position
+// in the same list. Handles overlapping source and target areas.
+static void MoveRanges(ZoneList<CharacterRange>* list,
+                       int from,
+                       int to,
+                       int count) {
+  // Ranges are potentially overlapping.
+  if (from < to) {
+    for (int i = count - 1; i >= 0; i--) {
+      list->at(to + i) = list->at(from + i);
+    }
+  } else {
+    for (int i = 0; i < count; i++) {
+      list->at(to + i) = list->at(from + i);
+    }
+  }
+}
+
+
+static int InsertRangeInCanonicalList(ZoneList<CharacterRange>* list,
+                                      int 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.
+  uc16 from = insert.from();
+  uc16 to = insert.to();
+  int start_pos = 0;
+  int end_pos = count;
+  for (int 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->at(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);
+    int new_from = Min(to_replace.from(), from);
+    int new_to = Max(to_replace.to(), to);
+    list->at(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.
+
+  int new_from = Min(list->at(start_pos).from(), from);
+  int new_to = Max(list->at(end_pos - 1).to(), to);
+  if (end_pos < count) {
+    MoveRanges(list, end_pos, start_pos + 1, count - end_pos);
+  }
+  list->at(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(ZoneList<CharacterRange>* character_ranges) {
+  if (character_ranges->length() <= 1) return;
+  // Check whether ranges are already canonical (increasing, non-overlapping,
+  // non-adjacent).
+  int n = character_ranges->length();
+  int max = character_ranges->at(0).to();
+  int 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.
+  int read = i;  // Range to insert.
+  int 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->Rewind(num_canonical);
+
+  ASSERT(CharacterRange::IsCanonical(character_ranges));
+}
+
+
+void CharacterRange::Negate(ZoneList<CharacterRange>* ranges,
+                            ZoneList<CharacterRange>* negated_ranges,
+                            Zone* zone) {
+  ASSERT(CharacterRange::IsCanonical(ranges));
+  ASSERT_EQ(0, negated_ranges->length());
+  int range_count = ranges->length();
+  uc16 from = 0;
+  int 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), zone);
+    from = range.to();
+    i++;
+  }
+  if (from < String::kMaxUtf16CodeUnit) {
+    negated_ranges->Add(CharacterRange(from + 1, String::kMaxUtf16CodeUnit),
+                        zone);
+  }
+}
+
+
+// -------------------------------------------------------------------
+// Splay tree
+
+
+OutSet* OutSet::Extend(unsigned value, Zone* zone) {
+  if (Get(value))
+    return this;
+  if (successors(zone) != NULL) {
+    for (int i = 0; i < successors(zone)->length(); i++) {
+      OutSet* successor = successors(zone)->at(i);
+      if (successor->Get(value))
+        return successor;
+    }
+  } else {
+    successors_ = new(zone) ZoneList<OutSet*>(2, zone);
+  }
+  OutSet* result = new(zone) OutSet(first_, remaining_);
+  result->Set(value, zone);
+  successors(zone)->Add(result, zone);
+  return result;
+}
+
+
+void OutSet::Set(unsigned value, Zone *zone) {
+  if (value < kFirstLimit) {
+    first_ |= (1 << value);
+  } else {
+    if (remaining_ == NULL)
+      remaining_ = new(zone) ZoneList<unsigned>(1, zone);
+    if (remaining_->is_empty() || !remaining_->Contains(value))
+      remaining_->Add(value, zone);
+  }
+}
+
+
+bool OutSet::Get(unsigned value) {
+  if (value < kFirstLimit) {
+    return (first_ & (1 << value)) != 0;
+  } else if (remaining_ == NULL) {
+    return false;
+  } else {
+    return remaining_->Contains(value);
+  }
+}
+
+
+const uc16 DispatchTable::Config::kNoKey = unibrow::Utf8::kBadChar;
+
+
+void DispatchTable::AddRange(CharacterRange full_range, int value,
+                             Zone* zone) {
+  CharacterRange current = full_range;
+  if (tree()->is_empty()) {
+    // If this is the first range we just insert into the table.
+    ZoneSplayTree<Config>::Locator loc;
+    ASSERT_RESULT(tree()->Insert(current.from(), &loc));
+    loc.set_value(Entry(current.from(), current.to(),
+                        empty()->Extend(value, zone)));
+    return;
+  }
+  // First see if there is a range to the left of this one that
+  // overlaps.
+  ZoneSplayTree<Config>::Locator loc;
+  if (tree()->FindGreatestLessThan(current.from(), &loc)) {
+    Entry* entry = &loc.value();
+    // If we've found a range that overlaps with this one, and it
+    // starts strictly to the left of this one, we have to fix it
+    // because the following code only handles ranges that start on
+    // or after the start point of the range we're adding.
+    if (entry->from() < current.from() && entry->to() >= current.from()) {
+      // Snap the overlapping range in half around the start point of
+      // the range we're adding.
+      CharacterRange left(entry->from(), current.from() - 1);
+      CharacterRange right(current.from(), entry->to());
+      // The left part of the overlapping range doesn't overlap.
+      // Truncate the whole entry to be just the left part.
+      entry->set_to(left.to());
+      // The right part is the one that overlaps.  We add this part
+      // to the map and let the next step deal with merging it with
+      // the range we're adding.
+      ZoneSplayTree<Config>::Locator loc;
+      ASSERT_RESULT(tree()->Insert(right.from(), &loc));
+      loc.set_value(Entry(right.from(),
+                          right.to(),
+                          entry->out_set()));
+    }
+  }
+  while (current.is_valid()) {
+    if (tree()->FindLeastGreaterThan(current.from(), &loc) &&
+        (loc.value().from() <= current.to()) &&
+        (loc.value().to() >= current.from())) {
+      Entry* entry = &loc.value();
+      // We have overlap.  If there is space between the start point of
+      // the range we're adding and where the overlapping range starts
+      // then we have to add a range covering just that space.
+      if (current.from() < entry->from()) {
+        ZoneSplayTree<Config>::Locator ins;
+        ASSERT_RESULT(tree()->Insert(current.from(), &ins));
+        ins.set_value(Entry(current.from(),
+                            entry->from() - 1,
+                            empty()->Extend(value, zone)));
+        current.set_from(entry->from());
+      }
+      ASSERT_EQ(current.from(), entry->from());
+      // If the overlapping range extends beyond the one we want to add
+      // we have to snap the right part off and add it separately.
+      if (entry->to() > current.to()) {
+        ZoneSplayTree<Config>::Locator ins;
+        ASSERT_RESULT(tree()->Insert(current.to() + 1, &ins));
+        ins.set_value(Entry(current.to() + 1,
+                            entry->to(),
+                            entry->out_set()));
+        entry->set_to(current.to());
+      }
+      ASSERT(entry->to() <= current.to());
+      // The overlapping range is now completely contained by the range
+      // we're adding so we can just update it and move the start point
+      // of the range we're adding just past it.
+      entry->AddValue(value, zone);
+      // Bail out if the last interval ended at 0xFFFF since otherwise
+      // adding 1 will wrap around to 0.
+      if (entry->to() == String::kMaxUtf16CodeUnit)
+        break;
+      ASSERT(entry->to() + 1 > current.from());
+      current.set_from(entry->to() + 1);
+    } else {
+      // There is no overlap so we can just add the range
+      ZoneSplayTree<Config>::Locator ins;
+      ASSERT_RESULT(tree()->Insert(current.from(), &ins));
+      ins.set_value(Entry(current.from(),
+                          current.to(),
+                          empty()->Extend(value, zone)));
+      break;
+    }
+  }
+}
+
+
+OutSet* DispatchTable::Get(uc16 value) {
+  ZoneSplayTree<Config>::Locator loc;
+  if (!tree()->FindGreatestLessThan(value, &loc))
+    return empty();
+  Entry* entry = &loc.value();
+  if (value <= entry->to())
+    return entry->out_set();
+  else
+    return empty();
+}
+
+
+// -------------------------------------------------------------------
+// Analysis
+
+
+void Analysis::EnsureAnalyzed(RegExpNode* that) {
+  StackLimitCheck check(Isolate::Current());
+  if (check.HasOverflowed()) {
+    fail("Stack overflow");
+    return;
+  }
+  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() {
+  int 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.
+  int cp_offset = 0;
+  for (int i = 0; i < element_count; i++) {
+    TextElement& elm = elements()->at(i);
+    elm.cp_offset = cp_offset;
+    if (elm.text_type == TextElement::ATOM) {
+      cp_offset += elm.data.u_atom->data().length();
+    } else {
+      cp_offset++;
+    }
+  }
+}
+
+
+void Analysis::VisitText(TextNode* that) {
+  if (ignore_case_) {
+    that->MakeCaseIndependent(is_ascii_);
+  }
+  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 (int i = 0; i < that->alternatives()->length(); i++) {
+    RegExpNode* node = that->alternatives()->at(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 (int i = 0; i < that->alternatives()->length(); i++) {
+    RegExpNode* node = that->alternatives()->at(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(int offset,
+                                     int 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);
+}
+
+
+STATIC_ASSERT(BoyerMoorePositionInfo::kMapSize ==
+              RegExpMacroAssembler::kTableSize);
+
+
+void ChoiceNode::FillInBMInfo(int offset,
+                              int budget,
+                              BoyerMooreLookahead* bm,
+                              bool not_at_start) {
+  ZoneList<GuardedAlternative>* alts = alternatives();
+  budget = (budget - 1) / alts->length();
+  for (int i = 0; i < alts->length(); i++) {
+    GuardedAlternative& alt = alts->at(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(int initial_offset,
+                            int budget,
+                            BoyerMooreLookahead* bm,
+                            bool not_at_start) {
+  if (initial_offset >= bm->length()) return;
+  int offset = initial_offset;
+  int max_char = bm->max_char();
+  for (int 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.data.u_atom;
+      for (int j = 0; j < atom->length(); j++, offset++) {
+        if (offset >= bm->length()) {
+          if (initial_offset == 0) set_bm_info(not_at_start, bm);
+          return;
+        }
+        uc16 character = atom->data()[j];
+        if (bm->compiler()->ignore_case()) {
+          unibrow::uchar chars[unibrow::Ecma262UnCanonicalize::kMaxWidth];
+          int length = GetCaseIndependentLetters(
+              ISOLATE,
+              character,
+              bm->max_char() == String::kMaxOneByteCharCode,
+              chars);
+          for (int 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.data.u_char_class;
+      ZoneList<CharacterRange>* ranges = char_class->ranges(zone());
+      if (char_class->is_negated()) {
+        bm->SetAll(offset);
+      } else {
+        for (int k = 0; k < ranges->length(); k++) {
+          CharacterRange& range = ranges->at(k);
+          if (range.from() > max_char) continue;
+          int to = Min(max_char, static_cast<int>(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);
+}
+
+
+// -------------------------------------------------------------------
+// Dispatch table construction
+
+
+void DispatchTableConstructor::VisitEnd(EndNode* that) {
+  AddRange(CharacterRange::Everything());
+}
+
+
+void DispatchTableConstructor::BuildTable(ChoiceNode* node) {
+  node->set_being_calculated(true);
+  ZoneList<GuardedAlternative>* alternatives = node->alternatives();
+  for (int i = 0; i < alternatives->length(); i++) {
+    set_choice_index(i);
+    alternatives->at(i).node()->Accept(this);
+  }
+  node->set_being_calculated(false);
+}
+
+
+class AddDispatchRange {
+ public:
+  explicit AddDispatchRange(DispatchTableConstructor* constructor)
+    : constructor_(constructor) { }
+  void Call(uc32 from, DispatchTable::Entry entry);
+ private:
+  DispatchTableConstructor* constructor_;
+};
+
+
+void AddDispatchRange::Call(uc32 from, DispatchTable::Entry entry) {
+  CharacterRange range(from, entry.to());
+  constructor_->AddRange(range);
+}
+
+
+void DispatchTableConstructor::VisitChoice(ChoiceNode* node) {
+  if (node->being_calculated())
+    return;
+  DispatchTable* table = node->GetTable(ignore_case_);
+  AddDispatchRange adder(this);
+  table->ForEach(&adder);
+}
+
+
+void DispatchTableConstructor::VisitBackReference(BackReferenceNode* that) {
+  // TODO(160): Find the node that we refer back to and propagate its start
+  // set back to here.  For now we just accept anything.
+  AddRange(CharacterRange::Everything());
+}
+
+
+void DispatchTableConstructor::VisitAssertion(AssertionNode* that) {
+  RegExpNode* target = that->on_success();
+  target->Accept(this);
+}
+
+
+static int CompareRangeByFrom(const CharacterRange* a,
+                              const CharacterRange* b) {
+  return Compare<uc16>(a->from(), b->from());
+}
+
+
+void DispatchTableConstructor::AddInverse(ZoneList<CharacterRange>* ranges) {
+  ranges->Sort(CompareRangeByFrom);
+  uc16 last = 0;
+  for (int i = 0; i < ranges->length(); i++) {
+    CharacterRange range = ranges->at(i);
+    if (last < range.from())
+      AddRange(CharacterRange(last, range.from() - 1));
+    if (range.to() >= last) {
+      if (range.to() == String::kMaxUtf16CodeUnit) {
+        return;
+      } else {
+        last = range.to() + 1;
+      }
+    }
+  }
+  AddRange(CharacterRange(last, String::kMaxUtf16CodeUnit));
+}
+
+
+void DispatchTableConstructor::VisitText(TextNode* that) {
+  TextElement elm = that->elements()->at(0);
+  switch (elm.text_type) {
+    case TextElement::ATOM: {
+      uc16 c = elm.data.u_atom->data()[0];
+      AddRange(CharacterRange(c, c));
+      break;
+    }
+    case TextElement::CHAR_CLASS: {
+      RegExpCharacterClass* tree = elm.data.u_char_class;
+      ZoneList<CharacterRange>* ranges = tree->ranges(that->zone());
+      if (tree->is_negated()) {
+        AddInverse(ranges);
+      } else {
+        for (int i = 0; i < ranges->length(); i++)
+          AddRange(ranges->at(i));
+      }
+      break;
+    }
+    default: {
+      UNIMPLEMENTED();
+    }
+  }
+}
+
+
+void DispatchTableConstructor::VisitAction(ActionNode* that) {
+  RegExpNode* target = that->on_success();
+  target->Accept(this);
+}
+
+
+RegExpEngine::CompilationResult RegExpEngine::Compile(
+    RegExpCompileData* data,
+    bool ignore_case,
+    bool is_global,
+    bool is_multiline,
+    Handle<String> pattern,
+    Handle<String> sample_subject,
+    bool is_ascii,
+    Zone* zone) {
+  if ((data->capture_count + 1) * 2 - 1 > RegExpMacroAssembler::kMaxRegister) {
+    return IrregexpRegExpTooBig();
+  }
+  RegExpCompiler compiler(data->capture_count, ignore_case, is_ascii, zone);
+
+  // Sample some characters from the middle of the string.
+  static const int kSampleSize = 128;
+
+  FlattenString(sample_subject);
+  int chars_sampled = 0;
+  int half_way = (sample_subject->length() - kSampleSize) / 2;
+  for (int i = Max(0, half_way);
+       i < sample_subject->length() && chars_sampled < kSampleSize;
+       i++, chars_sampled++) {
+    compiler.frequency_collator()->CountCharacter(sample_subject->Get(i));
+  }
+
+  // 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();
+  int 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(zone) 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(zone) ChoiceNode(2, zone);
+      first_step_node->AddAlternative(GuardedAlternative(captured_body));
+      first_step_node->AddAlternative(GuardedAlternative(
+          new(zone) TextNode(new(zone) RegExpCharacterClass('*'), loop_node)));
+      node = first_step_node;
+    } else {
+      node = loop_node;
+    }
+  }
+  if (is_ascii) {
+    node = node->FilterASCII(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->FilterASCII(RegExpCompiler::kMaxRecursion, ignore_case);
+    }
+  }
+
+  if (node == NULL) node = new(zone) EndNode(EndNode::BACKTRACK, zone);
+  data->node = node;
+  Analysis analysis(ignore_case, is_ascii);
+  analysis.EnsureAnalyzed(node);
+  if (analysis.has_failed()) {
+    const char* error_message = analysis.error_message();
+    return CompilationResult(error_message);
+  }
+
+  // Create the correct assembler for the architecture.
+#ifndef V8_INTERPRETED_REGEXP
+  // Native regexp implementation.
+
+  NativeRegExpMacroAssembler::Mode mode =
+      is_ascii ? NativeRegExpMacroAssembler::ASCII
+               : NativeRegExpMacroAssembler::UC16;
+
+#if V8_TARGET_ARCH_IA32
+  RegExpMacroAssemblerIA32 macro_assembler(mode, (data->capture_count + 1) * 2,
+                                           zone);
+#elif V8_TARGET_ARCH_X64
+  RegExpMacroAssemblerX64 macro_assembler(mode, (data->capture_count + 1) * 2,
+                                          zone);
+#elif V8_TARGET_ARCH_ARM
+  RegExpMacroAssemblerARM macro_assembler(mode, (data->capture_count + 1) * 2,
+                                          zone);
+#elif V8_TARGET_ARCH_MIPS
+  RegExpMacroAssemblerMIPS macro_assembler(mode, (data->capture_count + 1) * 2,
+                                           zone);
+#endif
+
+#else  // V8_INTERPRETED_REGEXP
+  // Interpreted regexp implementation.
+  EmbeddedVector<byte, 1024> codes;
+  RegExpMacroAssemblerIrregexp macro_assembler(codes, zone);
+#endif  // V8_INTERPRETED_REGEXP
+
+  // Inserted here, instead of in Assembler, because it depends on information
+  // in the AST that isn't replicated in the Node structure.
+  static const int 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);
+  }
+
+  return compiler.Assemble(&macro_assembler,
+                           node,
+                           data->capture_count,
+                           pattern);
+}
+
+
+}}  // namespace v8::internal