diff --git a/src/objects.h b/src/objects.h
index 9427227ac3..891d667bce 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -8880,6 +8880,7 @@ class String: public Name {
   static const uint32_t kMaxOneByteCharCodeU = unibrow::Latin1::kMaxChar;
   static const int kMaxUtf16CodeUnit = 0xffff;
   static const uint32_t kMaxUtf16CodeUnitU = kMaxUtf16CodeUnit;
+  static const uc32 kMaxCodePoint = 0x10ffff;
 
   // Value of hash field containing computed hash equal to zero.
   static const int kEmptyStringHash = kIsNotArrayIndexMask;
diff --git a/src/ostreams.cc b/src/ostreams.cc
index a7a67f5d2f..120db257cd 100644
--- a/src/ostreams.cc
+++ b/src/ostreams.cc
@@ -3,6 +3,7 @@
 // found in the LICENSE file.
 
 #include "src/ostreams.h"
+#include "src/objects.h"
 
 #if V8_OS_WIN
 #if _MSC_VER < 1900
@@ -60,6 +61,16 @@ std::ostream& PrintUC16(std::ostream& os, uint16_t c, bool (*pred)(uint16_t)) {
   return os << buf;
 }
 
+
+std::ostream& PrintUC32(std::ostream& os, int32_t c, bool (*pred)(uint16_t)) {
+  if (c <= String::kMaxUtf16CodeUnit) {
+    return PrintUC16(os, static_cast<uint16_t>(c), pred);
+  }
+  char buf[13];
+  snprintf(buf, sizeof(buf), "\\u{%06x}", c);
+  return os << buf;
+}
+
 }  // namespace
 
 
@@ -81,5 +92,10 @@ std::ostream& operator<<(std::ostream& os, const AsUC16& c) {
   return PrintUC16(os, c.value, IsPrint);
 }
 
+
+std::ostream& operator<<(std::ostream& os, const AsUC32& c) {
+  return PrintUC32(os, c.value, IsPrint);
+}
+
 }  // namespace internal
 }  // namespace v8
diff --git a/src/ostreams.h b/src/ostreams.h
index 56f4aa7e45..1c2f38a153 100644
--- a/src/ostreams.h
+++ b/src/ostreams.h
@@ -50,6 +50,12 @@ struct AsUC16 {
 };
 
 
+struct AsUC32 {
+  explicit AsUC32(int32_t v) : value(v) {}
+  int32_t value;
+};
+
+
 struct AsReversiblyEscapedUC16 {
   explicit AsReversiblyEscapedUC16(uint16_t v) : value(v) {}
   uint16_t value;
@@ -73,6 +79,10 @@ std::ostream& operator<<(std::ostream& os, const AsEscapedUC16ForJSON& c);
 // of printable ASCII range.
 std::ostream& operator<<(std::ostream& os, const AsUC16& c);
 
+// Writes the given character to the output escaping everything outside
+// of printable ASCII range.
+std::ostream& operator<<(std::ostream& os, const AsUC32& c);
+
 }  // namespace internal
 }  // namespace v8
 
diff --git a/src/regexp/jsregexp.cc b/src/regexp/jsregexp.cc
index 34d20fe781..3559bcd111 100644
--- a/src/regexp/jsregexp.cc
+++ b/src/regexp/jsregexp.cc
@@ -72,7 +72,7 @@ ContainedInLattice AddRange(ContainedInLattice containment,
                             int ranges_length,
                             Interval new_range) {
   DCHECK((ranges_length & 1) == 1);
-  DCHECK(ranges[ranges_length - 1] == String::kMaxUtf16CodeUnit + 1);
+  DCHECK(ranges[ranges_length - 1] == String::kMaxCodePoint + 1);
   if (containment == kLatticeUnknown) return containment;
   bool inside = false;
   int last = 0;
@@ -145,9 +145,8 @@ MaybeHandle<Object> RegExpImpl::Compile(Handle<JSRegExp> re,
   PostponeInterruptsScope postpone(isolate);
   RegExpCompileData parse_result;
   FlatStringReader reader(isolate, pattern);
-  if (!RegExpParser::ParseRegExp(re->GetIsolate(), &zone, &reader,
-                                 flags & JSRegExp::kMultiline,
-                                 flags & JSRegExp::kUnicode, &parse_result)) {
+  if (!RegExpParser::ParseRegExp(re->GetIsolate(), &zone, &reader, flags,
+                                 &parse_result)) {
     // Throw an exception if we fail to parse the pattern.
     return ThrowRegExpException(re, pattern, parse_result.error);
   }
@@ -371,18 +370,16 @@ bool RegExpImpl::CompileIrregexp(Handle<JSRegExp> re,
   pattern = String::Flatten(pattern);
   RegExpCompileData compile_data;
   FlatStringReader reader(isolate, pattern);
-  if (!RegExpParser::ParseRegExp(isolate, &zone, &reader,
-                                 flags & JSRegExp::kMultiline,
-                                 flags & JSRegExp::kUnicode, &compile_data)) {
+  if (!RegExpParser::ParseRegExp(isolate, &zone, &reader, flags,
+                                 &compile_data)) {
     // Throw an exception if we fail to parse the pattern.
     // THIS SHOULD NOT HAPPEN. We already pre-parsed it successfully once.
     USE(ThrowRegExpException(re, pattern, compile_data.error));
     return false;
   }
-  RegExpEngine::CompilationResult result = RegExpEngine::Compile(
-      isolate, &zone, &compile_data, flags & JSRegExp::kIgnoreCase,
-      flags & JSRegExp::kGlobal, flags & JSRegExp::kMultiline,
-      flags & JSRegExp::kSticky, pattern, sample_subject, is_one_byte);
+  RegExpEngine::CompilationResult result =
+      RegExpEngine::Compile(isolate, &zone, &compile_data, flags, pattern,
+                            sample_subject, is_one_byte);
   if (result.error_message != NULL) {
     // Unable to compile regexp.
     Handle<String> error_message = isolate->factory()->NewStringFromUtf8(
@@ -945,7 +942,7 @@ class FrequencyCollator {
 class RegExpCompiler {
  public:
   RegExpCompiler(Isolate* isolate, Zone* zone, int capture_count,
-                 bool ignore_case, bool is_one_byte);
+                 JSRegExp::Flags flags, bool is_one_byte);
 
   int AllocateRegister() {
     if (next_register_ >= RegExpMacroAssembler::kMaxRegister) {
@@ -955,6 +952,22 @@ class RegExpCompiler {
     return next_register_++;
   }
 
+  // Lookarounds to match lone surrogates for unicode character class matches
+  // are never nested. We can therefore reuse registers.
+  int UnicodeLookaroundStackRegister() {
+    if (unicode_lookaround_stack_register_ == kNoRegister) {
+      unicode_lookaround_stack_register_ = AllocateRegister();
+    }
+    return unicode_lookaround_stack_register_;
+  }
+
+  int UnicodeLookaroundPositionRegister() {
+    if (unicode_lookaround_position_register_ == kNoRegister) {
+      unicode_lookaround_position_register_ = AllocateRegister();
+    }
+    return unicode_lookaround_position_register_;
+  }
+
   RegExpEngine::CompilationResult Assemble(RegExpMacroAssembler* assembler,
                                            RegExpNode* start,
                                            int capture_count,
@@ -981,7 +994,8 @@ class RegExpCompiler {
 
   void SetRegExpTooBig() { reg_exp_too_big_ = true; }
 
-  inline bool ignore_case() { return ignore_case_; }
+  inline bool ignore_case() { return (flags_ & JSRegExp::kIgnoreCase) != 0; }
+  inline bool unicode() { return (flags_ & JSRegExp::kUnicode) != 0; }
   inline bool one_byte() { return one_byte_; }
   inline bool optimize() { return optimize_; }
   inline void set_optimize(bool value) { optimize_ = value; }
@@ -1006,10 +1020,12 @@ class RegExpCompiler {
  private:
   EndNode* accept_;
   int next_register_;
+  int unicode_lookaround_stack_register_;
+  int unicode_lookaround_position_register_;
   List<RegExpNode*>* work_list_;
   int recursion_depth_;
   RegExpMacroAssembler* macro_assembler_;
-  bool ignore_case_;
+  JSRegExp::Flags flags_;
   bool one_byte_;
   bool reg_exp_too_big_;
   bool limiting_recursion_;
@@ -1041,11 +1057,13 @@ static RegExpEngine::CompilationResult IrregexpRegExpTooBig(Isolate* isolate) {
 // 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(Isolate* isolate, Zone* zone, int capture_count,
-                               bool ignore_case, bool one_byte)
+                               JSRegExp::Flags flags, bool one_byte)
     : next_register_(2 * (capture_count + 1)),
+      unicode_lookaround_stack_register_(kNoRegister),
+      unicode_lookaround_position_register_(kNoRegister),
       work_list_(NULL),
       recursion_depth_(0),
-      ignore_case_(ignore_case),
+      flags_(flags),
       one_byte_(one_byte),
       reg_exp_too_big_(false),
       limiting_recursion_(false),
@@ -2098,9 +2116,7 @@ static void EmitCharClass(RegExpMacroAssembler* macro_assembler,
                           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);
-  }
+  CharacterRange::Canonicalize(ranges);
 
   int max_char;
   if (one_byte) {
@@ -2142,23 +2158,14 @@ static void EmitCharClass(RegExpMacroAssembler* macro_assembler,
     }
     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)) {
+      macro_assembler->CheckSpecialCharacterClass(cc->standard_type(),
+                                                  on_failure)) {
       return;
   }
 
@@ -2798,9 +2805,7 @@ RegExpNode* TextNode::FilterOneByte(int depth, bool ignore_case) {
       DCHECK(elm.text_type() == TextElement::CHAR_CLASS);
       RegExpCharacterClass* cc = elm.char_class();
       ZoneList<CharacterRange>* ranges = cc->ranges(zone());
-      if (!CharacterRange::IsCanonical(ranges)) {
-        CharacterRange::Canonicalize(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()) {
@@ -3289,6 +3294,36 @@ bool TextNode::SkipPass(int int_pass, bool ignore_case) {
 }
 
 
+TextNode* TextNode::CreateForCharacterRanges(Zone* zone,
+                                             ZoneList<CharacterRange>* ranges,
+                                             bool read_backward,
+                                             RegExpNode* on_success) {
+  DCHECK_NOT_NULL(ranges);
+  ZoneList<TextElement>* elms = new (zone) ZoneList<TextElement>(1, zone);
+  elms->Add(
+      TextElement::CharClass(new (zone) RegExpCharacterClass(ranges, false)),
+      zone);
+  return new (zone) TextNode(elms, read_backward, on_success);
+}
+
+
+TextNode* TextNode::CreateForSurrogatePair(Zone* zone, CharacterRange lead,
+                                           CharacterRange trail,
+                                           bool read_backward,
+                                           RegExpNode* on_success) {
+  ZoneList<CharacterRange>* lead_ranges = CharacterRange::List(zone, lead);
+  ZoneList<CharacterRange>* trail_ranges = CharacterRange::List(zone, trail);
+  ZoneList<TextElement>* elms = new (zone) ZoneList<TextElement>(2, zone);
+  elms->Add(TextElement::CharClass(
+                new (zone) RegExpCharacterClass(lead_ranges, false)),
+            zone);
+  elms->Add(TextElement::CharClass(
+                new (zone) RegExpCharacterClass(trail_ranges, false)),
+            zone);
+  return new (zone) TextNode(elms, read_backward, on_success);
+}
+
+
 // 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
@@ -3405,9 +3440,7 @@ RegExpNode* TextNode::GetSuccessorOfOmnivorousTextNode(
   if (elm.text_type() != TextElement::CHAR_CLASS) return NULL;
   RegExpCharacterClass* node = elm.char_class();
   ZoneList<CharacterRange>* ranges = node->ranges(zone());
-  if (!CharacterRange::IsCanonical(ranges)) {
-    CharacterRange::Canonicalize(ranges);
-  }
+  CharacterRange::Canonicalize(ranges);
   if (node->is_negated()) {
     return ranges->length() == 0 ? on_success() : NULL;
   }
@@ -3554,27 +3587,35 @@ class AlternativeGenerationList {
 };
 
 
+static const uc32 kLeadSurrogateStart = 0xd800;
+static const uc32 kLeadSurrogateEnd = 0xdbff;
+static const uc32 kTrailSurrogateStart = 0xdc00;
+static const uc32 kTrailSurrogateEnd = 0xdfff;
+static const uc32 kNonBmpStart = 0x10000;
+static const uc32 kNonBmpEnd = 0x10ffff;
+static const uc32 kRangeEndMarker = 0x110000;
+
 // The '2' variant is has inclusive from and exclusive to.
 // This covers \s as defined in ECMA-262 5.1, 15.10.2.12,
 // which include WhiteSpace (7.2) or LineTerminator (7.3) values.
-static const 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 kSpaceRanges[] = {
+    '\t',   '\r' + 1, ' ',    ' ' + 1, 0x00A0, 0x00A1, 0x1680,         0x1681,
+    0x180E, 0x180F,   0x2000, 0x200B,  0x2028, 0x202A, 0x202F,         0x2030,
+    0x205F, 0x2060,   0x3000, 0x3001,  0xFEFF, 0xFF00, kRangeEndMarker};
 static const int kSpaceRangeCount = arraysize(kSpaceRanges);
 
 static const int kWordRanges[] = {
-    '0', '9' + 1, 'A', 'Z' + 1, '_', '_' + 1, 'a', 'z' + 1, 0x10000 };
+    '0', '9' + 1, 'A', 'Z' + 1, '_', '_' + 1, 'a', 'z' + 1, kRangeEndMarker};
 static const int kWordRangeCount = arraysize(kWordRanges);
-static const int kDigitRanges[] = { '0', '9' + 1, 0x10000 };
+static const int kDigitRanges[] = {'0', '9' + 1, kRangeEndMarker};
 static const int kDigitRangeCount = arraysize(kDigitRanges);
-static const int kSurrogateRanges[] = { 0xd800, 0xe000, 0x10000 };
+static const int kSurrogateRanges[] = {
+    kLeadSurrogateStart, kLeadSurrogateStart + 1, kRangeEndMarker};
 static const int kSurrogateRangeCount = arraysize(kSurrogateRanges);
-static const int kLineTerminatorRanges[] = { 0x000A, 0x000B, 0x000D, 0x000E,
-    0x2028, 0x202A, 0x10000 };
+static const int kLineTerminatorRanges[] = {
+    0x000A, 0x000B, 0x000D, 0x000E, 0x2028, 0x202A, kRangeEndMarker};
 static const int kLineTerminatorRangeCount = arraysize(kLineTerminatorRanges);
 
-
 void BoyerMoorePositionInfo::Set(int character) {
   SetInterval(Interval(character, character));
 }
@@ -4732,8 +4773,8 @@ RegExpNode* RegExpText::ToNode(RegExpCompiler* compiler,
 static bool CompareInverseRanges(ZoneList<CharacterRange>* ranges,
                                  const int* special_class,
                                  int length) {
-  length--;  // Remove final 0x10000.
-  DCHECK(special_class[length] == 0x10000);
+  length--;  // Remove final marker.
+  DCHECK(special_class[length] == kRangeEndMarker);
   DCHECK(ranges->length() != 0);
   DCHECK(length != 0);
   DCHECK(special_class[0] != 0);
@@ -4763,8 +4804,8 @@ static bool CompareInverseRanges(ZoneList<CharacterRange>* ranges,
 static bool CompareRanges(ZoneList<CharacterRange>* ranges,
                           const int* special_class,
                           int length) {
-  length--;  // Remove final 0x10000.
-  DCHECK(special_class[length] == 0x10000);
+  length--;  // Remove final marker.
+  DCHECK(special_class[length] == kRangeEndMarker);
   if (ranges->length() * 2 != length) {
     return false;
   }
@@ -4820,10 +4861,257 @@ bool RegExpCharacterClass::is_standard(Zone* zone) {
 }
 
 
+bool RegExpCharacterClass::NeedsDesugaringForUnicode(Zone* zone) {
+  ZoneList<CharacterRange>* ranges = this->ranges(zone);
+  CharacterRange::Canonicalize(ranges);
+  for (int i = ranges->length() - 1; i >= 0; i--) {
+    uc32 from = ranges->at(i).from();
+    uc32 to = ranges->at(i).to();
+    // Check for non-BMP characters.
+    if (to >= kNonBmpStart) return true;
+    // Check for lone surrogates.
+    if (from <= kTrailSurrogateEnd && to >= kLeadSurrogateStart) return true;
+  }
+  return false;
+}
+
+
+UnicodeRangeSplitter::UnicodeRangeSplitter(Zone* zone,
+                                           ZoneList<CharacterRange>* base)
+    : zone_(zone),
+      table_(zone),
+      bmp_(nullptr),
+      lead_surrogates_(nullptr),
+      trail_surrogates_(nullptr),
+      non_bmp_(nullptr) {
+  // The unicode range splitter categorizes given character ranges into:
+  // - Code points from the BMP representable by one code unit.
+  // - Code points outside the BMP that need to be split into surrogate pairs.
+  // - Lone lead surrogates.
+  // - Lone trail surrogates.
+  // Lone surrogates are valid code points, even though no actual characters.
+  // They require special matching to make sure we do not split surrogate pairs.
+  // We use the dispatch table to accomplish this. The base range is split up
+  // by the table by the overlay ranges, and the Call callback is used to
+  // filter and collect ranges for each category.
+  for (int i = 0; i < base->length(); i++) {
+    table_.AddRange(base->at(i), kBase, zone_);
+  }
+  // Add overlay ranges.
+  table_.AddRange(CharacterRange(0, kLeadSurrogateStart - 1), kBmpCodePoints,
+                  zone_);
+  table_.AddRange(CharacterRange(kLeadSurrogateStart, kLeadSurrogateEnd),
+                  kLeadSurrogates, zone_);
+  table_.AddRange(CharacterRange(kTrailSurrogateStart, kTrailSurrogateEnd),
+                  kTrailSurrogates, zone_);
+  table_.AddRange(CharacterRange(kTrailSurrogateEnd, kNonBmpStart - 1),
+                  kBmpCodePoints, zone_);
+  table_.AddRange(CharacterRange(kNonBmpStart, kNonBmpEnd), kNonBmpCodePoints,
+                  zone_);
+  table_.ForEach(this);
+}
+
+
+void UnicodeRangeSplitter::Call(uc32 from, DispatchTable::Entry entry) {
+  OutSet* outset = entry.out_set();
+  if (!outset->Get(kBase)) return;
+  ZoneList<CharacterRange>** target = NULL;
+  if (outset->Get(kBmpCodePoints)) {
+    target = &bmp_;
+  } else if (outset->Get(kLeadSurrogates)) {
+    target = &lead_surrogates_;
+  } else if (outset->Get(kTrailSurrogates)) {
+    target = &trail_surrogates_;
+  } else {
+    DCHECK(outset->Get(kNonBmpCodePoints));
+    target = &non_bmp_;
+  }
+  if (*target == NULL) *target = new (zone_) ZoneList<CharacterRange>(2, zone_);
+  (*target)->Add(CharacterRange::Range(entry.from(), entry.to()), zone_);
+}
+
+
+void AddBmpCharacters(RegExpCompiler* compiler, ChoiceNode* result,
+                      RegExpNode* on_success, UnicodeRangeSplitter* splitter) {
+  ZoneList<CharacterRange>* bmp = splitter->bmp();
+  if (bmp == nullptr) return;
+  result->AddAlternative(GuardedAlternative(TextNode::CreateForCharacterRanges(
+      compiler->zone(), bmp, compiler->read_backward(), on_success)));
+}
+
+
+void AddNonBmpSurrogatePairs(RegExpCompiler* compiler, ChoiceNode* result,
+                             RegExpNode* on_success,
+                             UnicodeRangeSplitter* splitter) {
+  ZoneList<CharacterRange>* non_bmp = splitter->non_bmp();
+  if (non_bmp == nullptr) return;
+  DCHECK(compiler->unicode());
+  DCHECK(!compiler->one_byte());
+  Zone* zone = compiler->zone();
+  CharacterRange::Canonicalize(non_bmp);
+  for (int i = 0; i < non_bmp->length(); i++) {
+    // Match surrogate pair.
+    // E.g. [\u10005-\u11005] becomes
+    //      \ud800[\udc05-\udfff]|
+    //      [\ud801-\ud803][\udc00-\udfff]|
+    //      \ud804[\udc00-\udc05]
+    uc32 from = non_bmp->at(i).from();
+    uc32 to = non_bmp->at(i).to();
+    uc16 from_l = unibrow::Utf16::LeadSurrogate(from);
+    uc16 from_t = unibrow::Utf16::TrailSurrogate(from);
+    uc16 to_l = unibrow::Utf16::LeadSurrogate(to);
+    uc16 to_t = unibrow::Utf16::TrailSurrogate(to);
+    if (from_l == to_l) {
+      // The lead surrogate is the same.
+      result->AddAlternative(
+          GuardedAlternative(TextNode::CreateForSurrogatePair(
+              zone, CharacterRange::Singleton(from_l),
+              CharacterRange::Range(from_t, to_t), compiler->read_backward(),
+              on_success)));
+    } else {
+      if (from_t != kTrailSurrogateStart) {
+        // Add [from_l][from_t-\udfff]
+        result->AddAlternative(
+            GuardedAlternative(TextNode::CreateForSurrogatePair(
+                zone, CharacterRange::Singleton(from_l),
+                CharacterRange::Range(from_t, kTrailSurrogateEnd),
+                compiler->read_backward(), on_success)));
+        from_l++;
+      }
+      if (to_t != kTrailSurrogateEnd) {
+        // Add [to_l][\udc00-to_t]
+        result->AddAlternative(
+            GuardedAlternative(TextNode::CreateForSurrogatePair(
+                zone, CharacterRange::Singleton(to_l),
+                CharacterRange::Range(kTrailSurrogateStart, to_t),
+                compiler->read_backward(), on_success)));
+        to_l--;
+      }
+      if (from_l <= to_l) {
+        // Add [from_l-to_l][\udc00-\udfff]
+        result->AddAlternative(
+            GuardedAlternative(TextNode::CreateForSurrogatePair(
+                zone, CharacterRange::Range(from_l, to_l),
+                CharacterRange::Range(kTrailSurrogateStart, kTrailSurrogateEnd),
+                compiler->read_backward(), on_success)));
+      }
+    }
+  }
+}
+
+
+RegExpNode* NegativeLookaroundAgainstReadDirectionAndMatch(
+    RegExpCompiler* compiler, ZoneList<CharacterRange>* lookbehind,
+    ZoneList<CharacterRange>* match, RegExpNode* on_success,
+    bool read_backward) {
+  Zone* zone = compiler->zone();
+  RegExpNode* match_node = TextNode::CreateForCharacterRanges(
+      zone, match, read_backward, on_success);
+  int stack_register = compiler->UnicodeLookaroundStackRegister();
+  int position_register = compiler->UnicodeLookaroundPositionRegister();
+  RegExpLookaround::Builder lookaround(false, match_node, stack_register,
+                                       position_register);
+  RegExpNode* negative_match = TextNode::CreateForCharacterRanges(
+      zone, lookbehind, !read_backward, lookaround.on_match_success());
+  return lookaround.ForMatch(negative_match);
+}
+
+
+RegExpNode* MatchAndNegativeLookaroundInReadDirection(
+    RegExpCompiler* compiler, ZoneList<CharacterRange>* match,
+    ZoneList<CharacterRange>* lookahead, RegExpNode* on_success,
+    bool read_backward) {
+  Zone* zone = compiler->zone();
+  int stack_register = compiler->UnicodeLookaroundStackRegister();
+  int position_register = compiler->UnicodeLookaroundPositionRegister();
+  RegExpLookaround::Builder lookaround(false, on_success, stack_register,
+                                       position_register);
+  RegExpNode* negative_match = TextNode::CreateForCharacterRanges(
+      zone, lookahead, read_backward, lookaround.on_match_success());
+  return TextNode::CreateForCharacterRanges(
+      zone, match, read_backward, lookaround.ForMatch(negative_match));
+}
+
+
+void AddLoneLeadSurrogates(RegExpCompiler* compiler, ChoiceNode* result,
+                           RegExpNode* on_success,
+                           UnicodeRangeSplitter* splitter) {
+  ZoneList<CharacterRange>* lead_surrogates = splitter->lead_surrogates();
+  if (lead_surrogates == nullptr) return;
+  Zone* zone = compiler->zone();
+  // E.g. \ud801 becomes \ud801(?![\udc00-\udfff]).
+  ZoneList<CharacterRange>* trail_surrogates =
+      new (zone) ZoneList<CharacterRange>(1, zone);
+  trail_surrogates->Add(
+      CharacterRange::Range(kTrailSurrogateStart, kTrailSurrogateEnd), zone);
+
+  RegExpNode* match =
+      compiler->read_backward()
+          // Reading backward. Assert that reading forward, there is no trail
+          // surrogate, and then backward match the lead surrogate.
+          ? NegativeLookaroundAgainstReadDirectionAndMatch(
+                compiler, trail_surrogates, lead_surrogates, on_success, true)
+          // Reading forward. Forwrad match the lead surrogate and assert that
+          // no
+          // trail surrogate follows.
+          : MatchAndNegativeLookaroundInReadDirection(
+                compiler, lead_surrogates, trail_surrogates, on_success, false);
+  result->AddAlternative(GuardedAlternative(match));
+}
+
+
+void AddLoneTrailSurrogates(RegExpCompiler* compiler, ChoiceNode* result,
+                            RegExpNode* on_success,
+                            UnicodeRangeSplitter* splitter) {
+  ZoneList<CharacterRange>* trail_surrogates = splitter->trail_surrogates();
+  if (trail_surrogates == nullptr) return;
+  Zone* zone = compiler->zone();
+  // E.g. \udc01 becomes (?<![\ud800-\udbff])\udc01
+  ZoneList<CharacterRange>* lead_surrogates =
+      new (zone) ZoneList<CharacterRange>(1, zone);
+  lead_surrogates->Add(
+      CharacterRange::Range(kLeadSurrogateStart, kLeadSurrogateEnd), zone);
+
+  RegExpNode* match =
+      compiler->read_backward()
+          // Reading backward. Backward match the trail surrogate and assert
+          // that no lead surrogate precedes it.
+          ? MatchAndNegativeLookaroundInReadDirection(
+                compiler, trail_surrogates, lead_surrogates, on_success, true)
+          // Reading forward. Assert that reading backward, there is no lead
+          // surrogate, and then forward match the trail surrogate.
+          : NegativeLookaroundAgainstReadDirectionAndMatch(
+                compiler, lead_surrogates, trail_surrogates, on_success, false);
+  result->AddAlternative(GuardedAlternative(match));
+}
+
+
 RegExpNode* RegExpCharacterClass::ToNode(RegExpCompiler* compiler,
                                          RegExpNode* on_success) {
-  return new (compiler->zone())
-      TextNode(this, compiler->read_backward(), on_success);
+  set_.Canonicalize();
+  Zone* zone = compiler->zone();
+  ZoneList<CharacterRange>* ranges = this->ranges(zone);
+  if (compiler->unicode() && !compiler->one_byte()) {
+    if (is_negated()) {
+      ZoneList<CharacterRange>* negated =
+          new (zone) ZoneList<CharacterRange>(2, zone);
+      CharacterRange::Negate(ranges, negated, zone);
+      ranges = negated;
+    }
+    if (ranges->length() == 0) {
+      // No matches possible.
+      return new (zone) EndNode(EndNode::BACKTRACK, zone);
+    }
+    UnicodeRangeSplitter splitter(zone, ranges);
+    ChoiceNode* result = new (compiler->zone()) ChoiceNode(2, compiler->zone());
+    AddBmpCharacters(compiler, result, on_success, &splitter);
+    AddNonBmpSurrogatePairs(compiler, result, on_success, &splitter);
+    AddLoneLeadSurrogates(compiler, result, on_success, &splitter);
+    AddLoneTrailSurrogates(compiler, result, on_success, &splitter);
+    return result;
+  } else {
+    return new (zone) TextNode(this, compiler->read_backward(), on_success);
+  }
 }
 
 
@@ -5338,6 +5626,47 @@ RegExpNode* RegExpEmpty::ToNode(RegExpCompiler* compiler,
 }
 
 
+RegExpLookaround::Builder::Builder(bool is_positive, RegExpNode* on_success,
+                                   int stack_pointer_register,
+                                   int position_register,
+                                   int capture_register_count,
+                                   int capture_register_start)
+    : is_positive_(is_positive),
+      on_success_(on_success),
+      stack_pointer_register_(stack_pointer_register),
+      position_register_(position_register) {
+  if (is_positive_) {
+    on_match_success_ = ActionNode::PositiveSubmatchSuccess(
+        stack_pointer_register, position_register, capture_register_count,
+        capture_register_start, on_success_);
+  } else {
+    Zone* zone = on_success_->zone();
+    on_match_success_ = new (zone) NegativeSubmatchSuccess(
+        stack_pointer_register, position_register, capture_register_count,
+        capture_register_start, zone);
+  }
+}
+
+
+RegExpNode* RegExpLookaround::Builder::ForMatch(RegExpNode* match) {
+  if (is_positive_) {
+    return ActionNode::BeginSubmatch(stack_pointer_register_,
+                                     position_register_, match);
+  } else {
+    Zone* zone = on_success_->zone();
+    // We use a ChoiceNode to represent the negative lookaround. The first
+    // alternative is the negative match. On success, the end node backtracks.
+    // On failure, the second alternative is tried and leads to success.
+    // NegativeLookaheadChoiceNode is a special ChoiceNode that ignores the
+    // first exit when calculating quick checks.
+    ChoiceNode* choice_node = new (zone) NegativeLookaroundChoiceNode(
+        GuardedAlternative(match), GuardedAlternative(on_success_), zone);
+    return ActionNode::BeginSubmatch(stack_pointer_register_,
+                                     position_register_, choice_node);
+  }
+}
+
+
 RegExpNode* RegExpLookaround::ToNode(RegExpCompiler* compiler,
                                      RegExpNode* on_success) {
   int stack_pointer_register = compiler->AllocateRegister();
@@ -5352,35 +5681,10 @@ RegExpNode* RegExpLookaround::ToNode(RegExpCompiler* compiler,
   RegExpNode* result;
   bool was_reading_backward = compiler->read_backward();
   compiler->set_read_backward(type() == LOOKBEHIND);
-  if (is_positive()) {
-    result = ActionNode::BeginSubmatch(
-        stack_pointer_register, position_register,
-        body()->ToNode(compiler,
-                       ActionNode::PositiveSubmatchSuccess(
-                           stack_pointer_register, position_register,
-                           register_count, register_start, on_success)));
-  } 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, new (zone) NegativeSubmatchSuccess(
-                                     stack_pointer_register, position_register,
-                                     register_count, register_start, zone)));
-    ChoiceNode* choice_node = new (zone) NegativeLookaroundChoiceNode(
-        body_alt, GuardedAlternative(on_success), zone);
-    result = ActionNode::BeginSubmatch(stack_pointer_register,
-                                       position_register, choice_node);
-  }
+  Builder builder(is_positive(), on_success, stack_pointer_register,
+                  position_register, register_count, register_start);
+  RegExpNode* match = body_->ToNode(compiler, builder.on_match_success());
+  result = builder.ForMatch(match);
   compiler->set_read_backward(was_reading_backward);
   return result;
 }
@@ -5428,7 +5732,7 @@ static void AddClass(const int* elmv,
                      ZoneList<CharacterRange>* ranges,
                      Zone* zone) {
   elmc--;
-  DCHECK(elmv[elmc] == 0x10000);
+  DCHECK(elmv[elmc] == kRangeEndMarker);
   for (int i = 0; i < elmc; i += 2) {
     DCHECK(elmv[i] < elmv[i + 1]);
     ranges->Add(CharacterRange(elmv[i], elmv[i + 1] - 1), zone);
@@ -5441,9 +5745,9 @@ static void AddClassNegated(const int *elmv,
                             ZoneList<CharacterRange>* ranges,
                             Zone* zone) {
   elmc--;
-  DCHECK(elmv[elmc] == 0x10000);
+  DCHECK(elmv[elmc] == kRangeEndMarker);
   DCHECK(elmv[0] != 0x0000);
-  DCHECK(elmv[elmc-1] != String::kMaxUtf16CodeUnit);
+  DCHECK(elmv[elmc - 1] != String::kMaxCodePoint);
   uc16 last = 0x0000;
   for (int i = 0; i < elmc; i += 2) {
     DCHECK(last <= elmv[i] - 1);
@@ -5451,7 +5755,7 @@ static void AddClassNegated(const int *elmv,
     ranges->Add(CharacterRange(last, elmv[i] - 1), zone);
     last = elmv[i + 1];
   }
-  ranges->Add(CharacterRange(last, String::kMaxUtf16CodeUnit), zone);
+  ranges->Add(CharacterRange(last, String::kMaxCodePoint), zone);
 }
 
 
@@ -5508,60 +5812,13 @@ Vector<const int> CharacterRange::GetWordBounds() {
 }
 
 
-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) {
-  DCHECK_NULL(*included);
-  DCHECK_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(Isolate* isolate, Zone* zone,
                                         ZoneList<CharacterRange>* ranges,
                                         bool is_one_byte) {
-  uc16 bottom = from();
-  uc16 top = to();
+  uc32 bottom = from();
+  uc32 top = to();
+  // Nothing to be done for surrogates.
+  if (bottom >= kLeadSurrogateStart && top <= kTrailSurrogateEnd) return;
   if (is_one_byte && !RangeContainsLatin1Equivalents(*this)) {
     if (bottom > String::kMaxOneByteCharCode) return;
     if (top > String::kMaxOneByteCharCode) top = String::kMaxOneByteCharCode;
@@ -5599,7 +5856,7 @@ void CharacterRange::AddCaseEquivalents(Isolate* isolate, Zone* zone,
     int pos = bottom;
     while (pos <= top) {
       int length = isolate->jsregexp_canonrange()->get(pos, '\0', range);
-      uc16 block_end;
+      uc32 block_end;
       if (length == 0) {
         block_end = pos;
       } else {
@@ -5610,8 +5867,8 @@ void CharacterRange::AddCaseEquivalents(Isolate* isolate, Zone* zone,
       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);
+        uc32 range_from = c - (block_end - pos);
+        uc32 range_to = c - (block_end - end);
         if (!(bottom <= range_from && range_to <= top)) {
           ranges->Add(CharacterRange(range_from, range_to), zone);
         }
@@ -5672,8 +5929,8 @@ static int InsertRangeInCanonicalList(ZoneList<CharacterRange>* list,
   // 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();
+  uc32 from = insert.from();
+  uc32 to = insert.to();
   int start_pos = 0;
   int end_pos = count;
   for (int i = count - 1; i >= 0; i--) {
@@ -5773,7 +6030,7 @@ void CharacterRange::Negate(ZoneList<CharacterRange>* ranges,
   DCHECK(CharacterRange::IsCanonical(ranges));
   DCHECK_EQ(0, negated_ranges->length());
   int range_count = ranges->length();
-  uc16 from = 0;
+  uc32 from = 0;
   int i = 0;
   if (range_count > 0 && ranges->at(0).from() == 0) {
     from = ranges->at(0).to();
@@ -5785,9 +6042,8 @@ void CharacterRange::Negate(ZoneList<CharacterRange>* ranges,
     from = range.to();
     i++;
   }
-  if (from < String::kMaxUtf16CodeUnit) {
-    negated_ranges->Add(CharacterRange(from + 1, String::kMaxUtf16CodeUnit),
-                        zone);
+  if (from < String::kMaxCodePoint) {
+    negated_ranges->Add(CharacterRange(from + 1, String::kMaxCodePoint), zone);
   }
 }
 
@@ -5838,7 +6094,7 @@ bool OutSet::Get(unsigned value) const {
 }
 
 
-const uc16 DispatchTable::Config::kNoKey = unibrow::Utf8::kBadChar;
+const uc32 DispatchTable::Config::kNoKey = unibrow::Utf8::kBadChar;
 
 
 void DispatchTable::AddRange(CharacterRange full_range, int value,
@@ -5940,7 +6196,7 @@ void DispatchTable::AddRange(CharacterRange full_range, int value,
 }
 
 
-OutSet* DispatchTable::Get(uc16 value) {
+OutSet* DispatchTable::Get(uc32 value) {
   ZoneSplayTree<Config>::Locator loc;
   if (!tree()->FindGreatestLessThan(value, &loc))
     return empty();
@@ -6258,13 +6514,16 @@ void DispatchTableConstructor::VisitAction(ActionNode* that) {
 
 
 RegExpEngine::CompilationResult RegExpEngine::Compile(
-    Isolate* isolate, Zone* zone, RegExpCompileData* data, bool ignore_case,
-    bool is_global, bool is_multiline, bool is_sticky, Handle<String> pattern,
+    Isolate* isolate, Zone* zone, RegExpCompileData* data,
+    JSRegExp::Flags flags, Handle<String> pattern,
     Handle<String> sample_subject, bool is_one_byte) {
   if ((data->capture_count + 1) * 2 - 1 > RegExpMacroAssembler::kMaxRegister) {
     return IrregexpRegExpTooBig(isolate);
   }
-  RegExpCompiler compiler(isolate, zone, data->capture_count, ignore_case,
+  bool ignore_case = flags & JSRegExp::kIgnoreCase;
+  bool is_sticky = flags & JSRegExp::kSticky;
+  bool is_global = flags & JSRegExp::kGlobal;
+  RegExpCompiler compiler(isolate, zone, data->capture_count, flags,
                           is_one_byte);
 
   if (compiler.optimize()) compiler.set_optimize(!TooMuchRegExpCode(pattern));
diff --git a/src/regexp/jsregexp.h b/src/regexp/jsregexp.h
index 0ad4b79c87..f4051fdf43 100644
--- a/src/regexp/jsregexp.h
+++ b/src/regexp/jsregexp.h
@@ -265,28 +265,28 @@ class DispatchTable : public ZoneObject {
   class Entry {
    public:
     Entry() : from_(0), to_(0), out_set_(NULL) { }
-    Entry(uc16 from, uc16 to, OutSet* out_set)
-        : from_(from), to_(to), out_set_(out_set) { }
-    uc16 from() { return from_; }
-    uc16 to() { return to_; }
-    void set_to(uc16 value) { to_ = value; }
+    Entry(uc32 from, uc32 to, OutSet* out_set)
+        : from_(from), to_(to), out_set_(out_set) {}
+    uc32 from() { return from_; }
+    uc32 to() { return to_; }
+    void set_to(uc32 value) { to_ = value; }
     void AddValue(int value, Zone* zone) {
       out_set_ = out_set_->Extend(value, zone);
     }
     OutSet* out_set() { return out_set_; }
    private:
-    uc16 from_;
-    uc16 to_;
+    uc32 from_;
+    uc32 to_;
     OutSet* out_set_;
   };
 
   class Config {
    public:
-    typedef uc16 Key;
+    typedef uc32 Key;
     typedef Entry Value;
-    static const uc16 kNoKey;
+    static const uc32 kNoKey;
     static const Entry NoValue() { return Value(); }
-    static inline int Compare(uc16 a, uc16 b) {
+    static inline int Compare(uc32 a, uc32 b) {
       if (a == b)
         return 0;
       else if (a < b)
@@ -297,7 +297,7 @@ class DispatchTable : public ZoneObject {
   };
 
   void AddRange(CharacterRange range, int value, Zone* zone);
-  OutSet* Get(uc16 value);
+  OutSet* Get(uc32 value);
   void Dump();
 
   template <typename Callback>
@@ -315,6 +315,34 @@ class DispatchTable : public ZoneObject {
 };
 
 
+// Categorizes character ranges into BMP, non-BMP, lead, and trail surrogates.
+class UnicodeRangeSplitter {
+ public:
+  UnicodeRangeSplitter(Zone* zone, ZoneList<CharacterRange>* base);
+  void Call(uc32 from, DispatchTable::Entry entry);
+
+  ZoneList<CharacterRange>* bmp() { return bmp_; }
+  ZoneList<CharacterRange>* lead_surrogates() { return lead_surrogates_; }
+  ZoneList<CharacterRange>* trail_surrogates() { return trail_surrogates_; }
+  ZoneList<CharacterRange>* non_bmp() const { return non_bmp_; }
+
+ private:
+  static const int kBase = 0;
+  // Separate ranges into
+  static const int kBmpCodePoints = 1;
+  static const int kLeadSurrogates = 2;
+  static const int kTrailSurrogates = 3;
+  static const int kNonBmpCodePoints = 4;
+
+  Zone* zone_;
+  DispatchTable table_;
+  ZoneList<CharacterRange>* bmp_;
+  ZoneList<CharacterRange>* lead_surrogates_;
+  ZoneList<CharacterRange>* trail_surrogates_;
+  ZoneList<CharacterRange>* non_bmp_;
+};
+
+
 #define FOR_EACH_NODE_TYPE(VISIT)                                    \
   VISIT(End)                                                         \
   VISIT(Action)                                                      \
@@ -690,6 +718,17 @@ class TextNode: public SeqRegExpNode {
         read_backward_(read_backward) {
     elms_->Add(TextElement::CharClass(that), zone());
   }
+  // Create TextNode for a single character class for the given ranges.
+  static TextNode* CreateForCharacterRanges(Zone* zone,
+                                            ZoneList<CharacterRange>* ranges,
+                                            bool read_backward,
+                                            RegExpNode* on_success);
+  // Create TextNode for a surrogate pair with a range given for the
+  // lead and the trail surrogate each.
+  static TextNode* CreateForSurrogatePair(Zone* zone, CharacterRange lead,
+                                          CharacterRange trail,
+                                          bool read_backward,
+                                          RegExpNode* on_success);
   virtual void Accept(NodeVisitor* visitor);
   virtual void Emit(RegExpCompiler* compiler, Trace* trace);
   virtual int EatsAtLeast(int still_to_find, int budget, bool not_at_start);
@@ -813,8 +852,7 @@ class BackReferenceNode: public SeqRegExpNode {
 class EndNode: public RegExpNode {
  public:
   enum Action { ACCEPT, BACKTRACK, NEGATIVE_SUBMATCH_SUCCESS };
-  explicit EndNode(Action action, Zone* zone)
-      : RegExpNode(zone), action_(action) { }
+  EndNode(Action action, Zone* zone) : RegExpNode(zone), action_(action) {}
   virtual void Accept(NodeVisitor* visitor);
   virtual void Emit(RegExpCompiler* compiler, Trace* trace);
   virtual int EatsAtLeast(int still_to_find,
@@ -1505,8 +1543,8 @@ class RegExpEngine: public AllStatic {
   };
 
   static CompilationResult Compile(Isolate* isolate, Zone* zone,
-                                   RegExpCompileData* input, bool ignore_case,
-                                   bool global, bool multiline, bool sticky,
+                                   RegExpCompileData* input,
+                                   JSRegExp::Flags flags,
                                    Handle<String> pattern,
                                    Handle<String> sample_subject,
                                    bool is_one_byte);
diff --git a/src/regexp/regexp-ast.cc b/src/regexp/regexp-ast.cc
index 31c93b114f..b5c2bb6d91 100644
--- a/src/regexp/regexp-ast.cc
+++ b/src/regexp/regexp-ast.cc
@@ -172,9 +172,9 @@ void* RegExpUnparser::VisitAlternative(RegExpAlternative* that, void* data) {
 
 
 void RegExpUnparser::VisitCharacterRange(CharacterRange that) {
-  os_ << AsUC16(that.from());
+  os_ << AsUC32(that.from());
   if (!that.IsSingleton()) {
-    os_ << "-" << AsUC16(that.to());
+    os_ << "-" << AsUC32(that.to());
   }
 }
 
diff --git a/src/regexp/regexp-ast.h b/src/regexp/regexp-ast.h
index f87778596a..ed91a82d49 100644
--- a/src/regexp/regexp-ast.h
+++ b/src/regexp/regexp-ast.h
@@ -5,6 +5,7 @@
 #ifndef V8_REGEXP_REGEXP_AST_H_
 #define V8_REGEXP_REGEXP_AST_H_
 
+#include "src/objects.h"
 #include "src/utils.h"
 #include "src/zone.h"
 
@@ -77,33 +78,38 @@ class CharacterRange {
   CharacterRange() : from_(0), to_(0) {}
   // For compatibility with the CHECK_OK macro
   CharacterRange(void* null) { DCHECK_NULL(null); }  // NOLINT
-  CharacterRange(uc16 from, uc16 to) : from_(from), to_(to) {}
+  CharacterRange(uc32 from, uc32 to) : from_(from), to_(to) {}
   static void AddClassEscape(uc16 type, ZoneList<CharacterRange>* ranges,
                              Zone* zone);
   static Vector<const int> GetWordBounds();
-  static inline CharacterRange Singleton(uc16 value) {
+  static inline CharacterRange Singleton(uc32 value) {
     return CharacterRange(value, value);
   }
-  static inline CharacterRange Range(uc16 from, uc16 to) {
-    DCHECK(from <= to);
+  static inline CharacterRange Range(uc32 from, uc32 to) {
+    DCHECK(0 <= from && to <= String::kMaxCodePoint);
+    DCHECK(static_cast<uint32_t>(from) <= static_cast<uint32_t>(to));
     return CharacterRange(from, to);
   }
   static inline CharacterRange Everything() {
-    return CharacterRange(0, 0xFFFF);
+    return CharacterRange(0, String::kMaxCodePoint);
   }
-  bool Contains(uc16 i) { return from_ <= i && i <= to_; }
-  uc16 from() const { return from_; }
-  void set_from(uc16 value) { from_ = value; }
-  uc16 to() const { return to_; }
-  void set_to(uc16 value) { to_ = value; }
+  static inline ZoneList<CharacterRange>* List(Zone* zone,
+                                               CharacterRange range) {
+    ZoneList<CharacterRange>* list =
+        new (zone) ZoneList<CharacterRange>(1, zone);
+    list->Add(range, zone);
+    return list;
+  }
+  bool Contains(uc32 i) { return from_ <= i && i <= to_; }
+  uc32 from() const { return from_; }
+  void set_from(uc32 value) { from_ = value; }
+  uc32 to() const { return to_; }
+  void set_to(uc32 value) { to_ = value; }
   bool is_valid() { return from_ <= to_; }
   bool IsEverything(uc16 max) { return from_ == 0 && to_ >= max; }
   bool IsSingleton() { return (from_ == to_); }
   void AddCaseEquivalents(Isolate* isolate, Zone* zone,
                           ZoneList<CharacterRange>* ranges, bool is_one_byte);
-  static void Split(ZoneList<CharacterRange>* base, Vector<const int> overlay,
-                    ZoneList<CharacterRange>** included,
-                    ZoneList<CharacterRange>** excluded, Zone* zone);
   // Whether a range list is in canonical form: Ranges ordered by from value,
   // and ranges non-overlapping and non-adjacent.
   static bool IsCanonical(ZoneList<CharacterRange>* ranges);
@@ -119,8 +125,8 @@ class CharacterRange {
   static const int kPayloadMask = (1 << 24) - 1;
 
  private:
-  uc16 from_;
-  uc16 to_;
+  uc32 from_;
+  uc32 to_;
 };
 
 
@@ -287,6 +293,7 @@ class RegExpCharacterClass final : public RegExpTree {
   RegExpCharacterClass* AsCharacterClass() override;
   bool IsCharacterClass() override;
   bool IsTextElement() override { return true; }
+  bool NeedsDesugaringForUnicode(Zone* zone);
   int min_match() override { return 1; }
   int max_match() override { return 1; }
   void AppendToText(RegExpText* text, Zone* zone) override;
@@ -451,6 +458,22 @@ class RegExpLookaround final : public RegExpTree {
   int capture_from() { return capture_from_; }
   Type type() { return type_; }
 
+  class Builder {
+   public:
+    Builder(bool is_positive, RegExpNode* on_success,
+            int stack_pointer_register, int position_register,
+            int capture_register_count = 0, int capture_register_start = 0);
+    RegExpNode* on_match_success() { return on_match_success_; }
+    RegExpNode* ForMatch(RegExpNode* match);
+
+   private:
+    bool is_positive_;
+    RegExpNode* on_match_success_;
+    RegExpNode* on_success_;
+    int stack_pointer_register_;
+    int position_register_;
+  };
+
  private:
   RegExpTree* body_;
   bool is_positive_;
diff --git a/src/regexp/regexp-parser.cc b/src/regexp/regexp-parser.cc
index fa8900342c..07d5779675 100644
--- a/src/regexp/regexp-parser.cc
+++ b/src/regexp/regexp-parser.cc
@@ -15,20 +15,18 @@ namespace v8 {
 namespace internal {
 
 RegExpParser::RegExpParser(FlatStringReader* in, Handle<String>* error,
-                           bool multiline, bool unicode, Isolate* isolate,
-                           Zone* zone)
+                           JSRegExp::Flags flags, Isolate* isolate, Zone* zone)
     : isolate_(isolate),
       zone_(zone),
       error_(error),
       captures_(NULL),
       in_(in),
       current_(kEndMarker),
+      flags_(flags),
       next_pos_(0),
       captures_started_(0),
       capture_count_(0),
       has_more_(true),
-      multiline_(multiline),
-      unicode_(unicode),
       simple_(false),
       contains_anchor_(false),
       is_scanned_for_captures_(false),
@@ -37,9 +35,28 @@ RegExpParser::RegExpParser(FlatStringReader* in, Handle<String>* error,
 }
 
 
+template <bool update_position>
+uc32 RegExpParser::ReadNext() {
+  int position = next_pos_;
+  uc32 c0 = in()->Get(position);
+  position++;
+  // Read the whole surrogate pair in case of unicode flag, if possible.
+  if (unicode() && position < in()->length() &&
+      unibrow::Utf16::IsLeadSurrogate(static_cast<uc16>(c0))) {
+    uc16 c1 = in()->Get(position);
+    if (unibrow::Utf16::IsTrailSurrogate(c1)) {
+      c0 = unibrow::Utf16::CombineSurrogatePair(static_cast<uc16>(c0), c1);
+      position++;
+    }
+  }
+  if (update_position) next_pos_ = position;
+  return c0;
+}
+
+
 uc32 RegExpParser::Next() {
   if (has_next()) {
-    return in()->Get(next_pos_);
+    return ReadNext<false>();
   } else {
     return kEndMarker;
   }
@@ -47,25 +64,14 @@ uc32 RegExpParser::Next() {
 
 
 void RegExpParser::Advance() {
-  if (next_pos_ < in()->length()) {
+  if (has_next()) {
     StackLimitCheck check(isolate());
     if (check.HasOverflowed()) {
       ReportError(CStrVector(Isolate::kStackOverflowMessage));
     } else if (zone()->excess_allocation()) {
       ReportError(CStrVector("Regular expression too large"));
     } else {
-      current_ = in()->Get(next_pos_);
-      next_pos_++;
-      // Read the whole surrogate pair in case of unicode flag, if possible.
-      if (unicode_ && next_pos_ < in()->length() &&
-          unibrow::Utf16::IsLeadSurrogate(static_cast<uc16>(current_))) {
-        uc16 trail = in()->Get(next_pos_);
-        if (unibrow::Utf16::IsTrailSurrogate(trail)) {
-          current_ = unibrow::Utf16::CombineSurrogatePair(
-              static_cast<uc16>(current_), trail);
-          next_pos_++;
-        }
-      }
+      current_ = ReadNext<true>();
     }
   } else {
     current_ = kEndMarker;
@@ -142,7 +148,7 @@ RegExpTree* RegExpParser::ParsePattern() {
 RegExpTree* RegExpParser::ParseDisjunction() {
   // Used to store current state while parsing subexpressions.
   RegExpParserState initial_state(NULL, INITIAL, RegExpLookaround::LOOKAHEAD, 0,
-                                  zone());
+                                  flags_, zone());
   RegExpParserState* state = &initial_state;
   // Cache the builder in a local variable for quick access.
   RegExpBuilder* builder = initial_state.builder();
@@ -206,7 +212,7 @@ RegExpTree* RegExpParser::ParseDisjunction() {
         return ReportError(CStrVector("Nothing to repeat"));
       case '^': {
         Advance();
-        if (multiline_) {
+        if (multiline()) {
           builder->AddAssertion(
               new (zone()) RegExpAssertion(RegExpAssertion::START_OF_LINE));
         } else {
@@ -219,8 +225,8 @@ RegExpTree* RegExpParser::ParseDisjunction() {
       case '$': {
         Advance();
         RegExpAssertion::AssertionType assertion_type =
-            multiline_ ? RegExpAssertion::END_OF_LINE
-                       : RegExpAssertion::END_OF_INPUT;
+            multiline() ? RegExpAssertion::END_OF_LINE
+                        : RegExpAssertion::END_OF_INPUT;
         builder->AddAssertion(new (zone()) RegExpAssertion(assertion_type));
         continue;
       }
@@ -230,8 +236,9 @@ RegExpTree* RegExpParser::ParseDisjunction() {
         ZoneList<CharacterRange>* ranges =
             new (zone()) ZoneList<CharacterRange>(2, zone());
         CharacterRange::AddClassEscape('.', ranges, zone());
-        RegExpTree* atom = new (zone()) RegExpCharacterClass(ranges, false);
-        builder->AddAtom(atom);
+        RegExpCharacterClass* cc =
+            new (zone()) RegExpCharacterClass(ranges, false);
+        builder->AddCharacterClass(cc);
         break;
       }
       case '(': {
@@ -276,14 +283,15 @@ RegExpTree* RegExpParser::ParseDisjunction() {
           captures_started_++;
         }
         // Store current state and begin new disjunction parsing.
-        state = new (zone()) RegExpParserState(
-            state, subexpr_type, lookaround_type, captures_started_, zone());
+        state =
+            new (zone()) RegExpParserState(state, subexpr_type, lookaround_type,
+                                           captures_started_, flags_, zone());
         builder = state->builder();
         continue;
       }
       case '[': {
-        RegExpTree* atom = ParseCharacterClass(CHECK_FAILED);
-        builder->AddAtom(atom);
+        RegExpTree* cc = ParseCharacterClass(CHECK_FAILED);
+        builder->AddCharacterClass(cc->AsCharacterClass());
         break;
       }
       // Atom ::
@@ -318,8 +326,9 @@ RegExpTree* RegExpParser::ParseDisjunction() {
             ZoneList<CharacterRange>* ranges =
                 new (zone()) ZoneList<CharacterRange>(2, zone());
             CharacterRange::AddClassEscape(c, ranges, zone());
-            RegExpTree* atom = new (zone()) RegExpCharacterClass(ranges, false);
-            builder->AddAtom(atom);
+            RegExpCharacterClass* cc =
+                new (zone()) RegExpCharacterClass(ranges, false);
+            builder->AddCharacterClass(cc);
             break;
           }
           case '1':
@@ -353,7 +362,7 @@ RegExpTree* RegExpParser::ParseDisjunction() {
               // escaped,
               // no other identity escapes are allowed. If the 'u' flag is not
               // present, all identity escapes are allowed.
-              if (!unicode_) {
+              if (!unicode()) {
                 builder->AddCharacter(first_digit);
                 Advance(2);
               } else {
@@ -414,7 +423,7 @@ RegExpTree* RegExpParser::ParseDisjunction() {
             uc32 value;
             if (ParseHexEscape(2, &value)) {
               builder->AddCharacter(value);
-            } else if (!unicode_) {
+            } else if (!unicode()) {
               builder->AddCharacter('x');
             } else {
               // If the 'u' flag is present, invalid escapes are not treated as
@@ -428,7 +437,7 @@ RegExpTree* RegExpParser::ParseDisjunction() {
             uc32 value;
             if (ParseUnicodeEscape(&value)) {
               builder->AddUnicodeCharacter(value);
-            } else if (!unicode_) {
+            } else if (!unicode()) {
               builder->AddCharacter('u');
             } else {
               // If the 'u' flag is present, invalid escapes are not treated as
@@ -444,7 +453,7 @@ RegExpTree* RegExpParser::ParseDisjunction() {
             // other identity escapes are allowed. If the 'u' flag is not
             // present,
             // all identity escapes are allowed.
-            if (!unicode_ || IsSyntaxCharacter(current())) {
+            if (!unicode() || IsSyntaxCharacter(current())) {
               builder->AddCharacter(current());
               Advance();
             } else {
@@ -745,7 +754,7 @@ bool RegExpParser::ParseUnicodeEscape(uc32* value) {
   // Accept both \uxxxx and \u{xxxxxx} (if harmony unicode escapes are
   // allowed). In the latter case, the number of hex digits between { } is
   // arbitrary. \ and u have already been read.
-  if (current() == '{' && unicode_) {
+  if (current() == '{' && unicode()) {
     int start = position();
     Advance();
     if (ParseUnlimitedLengthHexNumber(0x10ffff, value)) {
@@ -840,7 +849,7 @@ uc32 RegExpParser::ParseClassCharacterEscape() {
       if (ParseHexEscape(2, &value)) {
         return value;
       }
-      if (!unicode_) {
+      if (!unicode()) {
         // If \x is not followed by a two-digit hexadecimal, treat it
         // as an identity escape.
         return 'x';
@@ -856,7 +865,7 @@ uc32 RegExpParser::ParseClassCharacterEscape() {
       if (ParseUnicodeEscape(&value)) {
         return value;
       }
-      if (!unicode_) {
+      if (!unicode()) {
         return 'u';
       }
       // If the 'u' flag is present, invalid escapes are not treated as
@@ -869,7 +878,7 @@ uc32 RegExpParser::ParseClassCharacterEscape() {
       // If the 'u' flag is present, only syntax characters can be escaped, no
       // other identity escapes are allowed. If the 'u' flag is not present, all
       // identity escapes are allowed.
-      if (!unicode_ || IsSyntaxCharacter(result)) {
+      if (!unicode() || IsSyntaxCharacter(result)) {
         Advance();
         return result;
       }
@@ -899,13 +908,29 @@ CharacterRange RegExpParser::ParseClassAtom(uc16* char_class) {
       case kEndMarker:
         return ReportError(CStrVector("\\ at end of pattern"));
       default:
-        uc32 c = ParseClassCharacterEscape(CHECK_FAILED);
-        return CharacterRange::Singleton(c);
+        first = ParseClassCharacterEscape(CHECK_FAILED);
     }
   } else {
     Advance();
-    return CharacterRange::Singleton(first);
   }
+
+  if (unicode() && unibrow::Utf16::IsLeadSurrogate(first)) {
+    // Combine with possibly following trail surrogate.
+    int start = position();
+    uc32 second = current();
+    if (second == '\\') {
+      second = ParseClassCharacterEscape(CHECK_FAILED);
+    } else {
+      Advance();
+    }
+    if (unibrow::Utf16::IsTrailSurrogate(second)) {
+      first = unibrow::Utf16::CombineSurrogatePair(first, second);
+    } else {
+      Reset(start);
+    }
+  }
+
+  return CharacterRange::Singleton(first);
 }
 
 
@@ -985,10 +1010,10 @@ RegExpTree* RegExpParser::ParseCharacterClass() {
 
 
 bool RegExpParser::ParseRegExp(Isolate* isolate, Zone* zone,
-                               FlatStringReader* input, bool multiline,
-                               bool unicode, RegExpCompileData* result) {
+                               FlatStringReader* input, JSRegExp::Flags flags,
+                               RegExpCompileData* result) {
   DCHECK(result != NULL);
-  RegExpParser parser(input, &result->error, multiline, unicode, isolate, zone);
+  RegExpParser parser(input, &result->error, flags, isolate, zone);
   RegExpTree* tree = parser.ParsePattern();
   if (parser.failed()) {
     DCHECK(tree == NULL);
@@ -1011,10 +1036,12 @@ bool RegExpParser::ParseRegExp(Isolate* isolate, Zone* zone,
 }
 
 
-RegExpBuilder::RegExpBuilder(Zone* zone)
+RegExpBuilder::RegExpBuilder(Zone* zone, JSRegExp::Flags flags)
     : zone_(zone),
       pending_empty_(false),
+      flags_(flags),
       characters_(NULL),
+      pending_surrogate_(kNoPendingSurrogate),
       terms_(),
       alternatives_()
 #ifdef DEBUG
@@ -1025,7 +1052,48 @@ RegExpBuilder::RegExpBuilder(Zone* zone)
 }
 
 
+void RegExpBuilder::AddLeadSurrogate(uc16 lead_surrogate) {
+  DCHECK(unibrow::Utf16::IsLeadSurrogate(lead_surrogate));
+  FlushPendingSurrogate();
+  // Hold onto the lead surrogate, waiting for a trail surrogate to follow.
+  pending_surrogate_ = lead_surrogate;
+}
+
+
+void RegExpBuilder::AddTrailSurrogate(uc16 trail_surrogate) {
+  DCHECK(unibrow::Utf16::IsTrailSurrogate(trail_surrogate));
+  if (pending_surrogate_ != kNoPendingSurrogate) {
+    uc16 lead_surrogate = pending_surrogate_;
+    DCHECK(unibrow::Utf16::IsLeadSurrogate(lead_surrogate));
+    ZoneList<uc16> surrogate_pair(2, zone());
+    surrogate_pair.Add(lead_surrogate, zone());
+    surrogate_pair.Add(trail_surrogate, zone());
+    RegExpAtom* atom = new (zone()) RegExpAtom(surrogate_pair.ToConstVector());
+    pending_surrogate_ = kNoPendingSurrogate;
+    AddAtom(atom);
+  } else {
+    pending_surrogate_ = trail_surrogate;
+    FlushPendingSurrogate();
+  }
+}
+
+
+void RegExpBuilder::FlushPendingSurrogate() {
+  if (pending_surrogate_ != kNoPendingSurrogate) {
+    // Use character class to desugar lone surrogate matching.
+    RegExpCharacterClass* cc = new (zone()) RegExpCharacterClass(
+        CharacterRange::List(zone(),
+                             CharacterRange::Singleton(pending_surrogate_)),
+        false);
+    pending_surrogate_ = kNoPendingSurrogate;
+    DCHECK(unicode());
+    AddCharacterClass(cc);
+  }
+}
+
+
 void RegExpBuilder::FlushCharacters() {
+  FlushPendingSurrogate();
   pending_empty_ = false;
   if (characters_ != NULL) {
     RegExpTree* atom = new (zone()) RegExpAtom(characters_->ToConstVector());
@@ -1053,6 +1121,7 @@ void RegExpBuilder::FlushText() {
 
 
 void RegExpBuilder::AddCharacter(uc16 c) {
+  FlushPendingSurrogate();
   pending_empty_ = false;
   if (characters_ == NULL) {
     characters_ = new (zone()) ZoneList<uc16>(4, zone());
@@ -1064,11 +1133,13 @@ void RegExpBuilder::AddCharacter(uc16 c) {
 
 void RegExpBuilder::AddUnicodeCharacter(uc32 c) {
   if (c > unibrow::Utf16::kMaxNonSurrogateCharCode) {
-    ZoneList<uc16> surrogate_pair(2, zone());
-    surrogate_pair.Add(unibrow::Utf16::LeadSurrogate(c), zone());
-    surrogate_pair.Add(unibrow::Utf16::TrailSurrogate(c), zone());
-    RegExpAtom* atom = new (zone()) RegExpAtom(surrogate_pair.ToConstVector());
-    AddAtom(atom);
+    DCHECK(unicode());
+    AddLeadSurrogate(unibrow::Utf16::LeadSurrogate(c));
+    AddTrailSurrogate(unibrow::Utf16::TrailSurrogate(c));
+  } else if (unicode() && unibrow::Utf16::IsLeadSurrogate(c)) {
+    AddLeadSurrogate(c);
+  } else if (unicode() && unibrow::Utf16::IsTrailSurrogate(c)) {
+    AddTrailSurrogate(c);
   } else {
     AddCharacter(static_cast<uc16>(c));
   }
@@ -1078,6 +1149,17 @@ void RegExpBuilder::AddUnicodeCharacter(uc32 c) {
 void RegExpBuilder::AddEmpty() { pending_empty_ = true; }
 
 
+void RegExpBuilder::AddCharacterClass(RegExpCharacterClass* cc) {
+  if (unicode() && cc->NeedsDesugaringForUnicode(zone())) {
+    // In unicode mode, character class needs to be desugared, so it
+    // must be a standalone term instead of being part of a RegExpText.
+    AddTerm(cc);
+  } else {
+    AddAtom(cc);
+  }
+}
+
+
 void RegExpBuilder::AddAtom(RegExpTree* term) {
   if (term->IsEmpty()) {
     AddEmpty();
@@ -1094,6 +1176,13 @@ void RegExpBuilder::AddAtom(RegExpTree* term) {
 }
 
 
+void RegExpBuilder::AddTerm(RegExpTree* term) {
+  FlushText();
+  terms_.Add(term, zone());
+  LAST(ADD_ATOM);
+}
+
+
 void RegExpBuilder::AddAssertion(RegExpTree* assert) {
   FlushText();
   terms_.Add(assert, zone());
@@ -1132,6 +1221,7 @@ RegExpTree* RegExpBuilder::ToRegExp() {
 
 void RegExpBuilder::AddQuantifierToAtom(
     int min, int max, RegExpQuantifier::QuantifierType quantifier_type) {
+  FlushPendingSurrogate();
   if (pending_empty_) {
     pending_empty_ = false;
     return;
diff --git a/src/regexp/regexp-parser.h b/src/regexp/regexp-parser.h
index af9b765fba..dc0d943f86 100644
--- a/src/regexp/regexp-parser.h
+++ b/src/regexp/regexp-parser.h
@@ -99,13 +99,15 @@ class BufferedZoneList {
 // Accumulates RegExp atoms and assertions into lists of terms and alternatives.
 class RegExpBuilder : public ZoneObject {
  public:
-  explicit RegExpBuilder(Zone* zone);
+  RegExpBuilder(Zone* zone, JSRegExp::Flags flags);
   void AddCharacter(uc16 character);
   void AddUnicodeCharacter(uc32 character);
   // "Adds" an empty expression. Does nothing except consume a
   // following quantifier
   void AddEmpty();
+  void AddCharacterClass(RegExpCharacterClass* cc);
   void AddAtom(RegExpTree* tree);
+  void AddTerm(RegExpTree* tree);
   void AddAssertion(RegExpTree* tree);
   void NewAlternative();  // '|'
   void AddQuantifierToAtom(int min, int max,
@@ -113,14 +115,21 @@ class RegExpBuilder : public ZoneObject {
   RegExpTree* ToRegExp();
 
  private:
+  static const uc16 kNoPendingSurrogate = 0;
+  void AddLeadSurrogate(uc16 lead_surrogate);
+  void AddTrailSurrogate(uc16 trail_surrogate);
+  void FlushPendingSurrogate();
   void FlushCharacters();
   void FlushText();
   void FlushTerms();
   Zone* zone() const { return zone_; }
+  bool unicode() const { return (flags_ & JSRegExp::kUnicode) != 0; }
 
   Zone* zone_;
   bool pending_empty_;
+  JSRegExp::Flags flags_;
   ZoneList<uc16>* characters_;
+  uc16 pending_surrogate_;
   BufferedZoneList<RegExpTree, 2> terms_;
   BufferedZoneList<RegExpTree, 2> text_;
   BufferedZoneList<RegExpTree, 2> alternatives_;
@@ -135,12 +144,11 @@ class RegExpBuilder : public ZoneObject {
 
 class RegExpParser BASE_EMBEDDED {
  public:
-  RegExpParser(FlatStringReader* in, Handle<String>* error, bool multiline_mode,
-               bool unicode, Isolate* isolate, Zone* zone);
+  RegExpParser(FlatStringReader* in, Handle<String>* error,
+               JSRegExp::Flags flags, Isolate* isolate, Zone* zone);
 
   static bool ParseRegExp(Isolate* isolate, Zone* zone, FlatStringReader* input,
-                          bool multiline, bool unicode,
-                          RegExpCompileData* result);
+                          JSRegExp::Flags flags, RegExpCompileData* result);
 
   RegExpTree* ParsePattern();
   RegExpTree* ParseDisjunction();
@@ -183,6 +191,8 @@ class RegExpParser BASE_EMBEDDED {
   int captures_started() { return captures_started_; }
   int position() { return next_pos_ - 1; }
   bool failed() { return failed_; }
+  bool unicode() const { return (flags_ & JSRegExp::kUnicode) != 0; }
+  bool multiline() const { return (flags_ & JSRegExp::kMultiline) != 0; }
 
   static bool IsSyntaxCharacter(uc32 c);
 
@@ -203,9 +213,10 @@ class RegExpParser BASE_EMBEDDED {
     RegExpParserState(RegExpParserState* previous_state,
                       SubexpressionType group_type,
                       RegExpLookaround::Type lookaround_type,
-                      int disjunction_capture_index, Zone* zone)
+                      int disjunction_capture_index, JSRegExp::Flags flags,
+                      Zone* zone)
         : previous_state_(previous_state),
-          builder_(new (zone) RegExpBuilder(zone)),
+          builder_(new (zone) RegExpBuilder(zone, flags)),
           group_type_(group_type),
           lookaround_type_(lookaround_type),
           disjunction_capture_index_(disjunction_capture_index) {}
@@ -249,6 +260,8 @@ class RegExpParser BASE_EMBEDDED {
   bool has_more() { return has_more_; }
   bool has_next() { return next_pos_ < in()->length(); }
   uc32 Next();
+  template <bool update_position>
+  uc32 ReadNext();
   FlatStringReader* in() { return in_; }
   void ScanForCaptures();
 
@@ -258,13 +271,12 @@ class RegExpParser BASE_EMBEDDED {
   ZoneList<RegExpCapture*>* captures_;
   FlatStringReader* in_;
   uc32 current_;
+  JSRegExp::Flags flags_;
   int next_pos_;
   int captures_started_;
   // The capture count is only valid after we have scanned for captures.
   int capture_count_;
   bool has_more_;
-  bool multiline_;
-  bool unicode_;
   bool simple_;
   bool contains_anchor_;
   bool is_scanned_for_captures_;
diff --git a/test/cctest/test-regexp.cc b/test/cctest/test-regexp.cc
index a91058cc24..85616c45b8 100644
--- a/test/cctest/test-regexp.cc
+++ b/test/cctest/test-regexp.cc
@@ -96,7 +96,7 @@ static bool CheckParse(const char* input) {
   FlatStringReader reader(CcTest::i_isolate(), CStrVector(input));
   RegExpCompileData result;
   return v8::internal::RegExpParser::ParseRegExp(
-      CcTest::i_isolate(), &zone, &reader, false, false, &result);
+      CcTest::i_isolate(), &zone, &reader, JSRegExp::kNone, &result);
 }
 
 
@@ -106,8 +106,10 @@ static void CheckParseEq(const char* input, const char* expected,
   Zone zone;
   FlatStringReader reader(CcTest::i_isolate(), CStrVector(input));
   RegExpCompileData result;
-  CHECK(v8::internal::RegExpParser::ParseRegExp(
-      CcTest::i_isolate(), &zone, &reader, false, unicode, &result));
+  JSRegExp::Flags flags = JSRegExp::kNone;
+  if (unicode) flags |= JSRegExp::kUnicode;
+  CHECK(v8::internal::RegExpParser::ParseRegExp(CcTest::i_isolate(), &zone,
+                                                &reader, flags, &result));
   CHECK(result.tree != NULL);
   CHECK(result.error.is_null());
   std::ostringstream os;
@@ -125,7 +127,7 @@ static bool CheckSimple(const char* input) {
   FlatStringReader reader(CcTest::i_isolate(), CStrVector(input));
   RegExpCompileData result;
   CHECK(v8::internal::RegExpParser::ParseRegExp(
-      CcTest::i_isolate(), &zone, &reader, false, false, &result));
+      CcTest::i_isolate(), &zone, &reader, JSRegExp::kNone, &result));
   CHECK(result.tree != NULL);
   CHECK(result.error.is_null());
   return result.simple;
@@ -143,7 +145,7 @@ static MinMaxPair CheckMinMaxMatch(const char* input) {
   FlatStringReader reader(CcTest::i_isolate(), CStrVector(input));
   RegExpCompileData result;
   CHECK(v8::internal::RegExpParser::ParseRegExp(
-      CcTest::i_isolate(), &zone, &reader, false, false, &result));
+      CcTest::i_isolate(), &zone, &reader, JSRegExp::kNone, &result));
   CHECK(result.tree != NULL);
   CHECK(result.error.is_null());
   int min_match = result.tree->min_match();
@@ -206,8 +208,8 @@ void TestRegExpParser(bool lookbehind) {
   }
   CheckParseEq("()", "(^ %)");
   CheckParseEq("(?=)", "(-> + %)");
-  CheckParseEq("[]", "^[\\x00-\\uffff]");  // Doesn't compile on windows
-  CheckParseEq("[^]", "[\\x00-\\uffff]");  // \uffff isn't in codepage 1252
+  CheckParseEq("[]", "^[\\x00-\\u{10ffff}]");  // Doesn't compile on windows
+  CheckParseEq("[^]", "[\\x00-\\u{10ffff}]");  // \uffff isn't in codepage 1252
   CheckParseEq("[x]", "[x]");
   CheckParseEq("[xyz]", "[x y z]");
   CheckParseEq("[a-zA-Z0-9]", "[a-z A-Z 0-9]");
@@ -316,6 +318,10 @@ void TestRegExpParser(bool lookbehind) {
   CheckParseEq("\\u{12345}{3}", "(# 3 3 g '\\ud808\\udf45')", true);
   CheckParseEq("\\u{12345}*", "(# 0 - g '\\ud808\\udf45')", true);
 
+  CheckParseEq("\\ud808\\udf45*", "(# 0 - g '\\ud808\\udf45')", true);
+  CheckParseEq("[\\ud808\\udf45-\\ud809\\udccc]", "[\\u{012345}-\\u{0124cc}]",
+               true);
+
   CHECK_SIMPLE("", false);
   CHECK_SIMPLE("a", true);
   CHECK_SIMPLE("a|b", false);
@@ -454,7 +460,7 @@ static void ExpectError(const char* input,
   FlatStringReader reader(CcTest::i_isolate(), CStrVector(input));
   RegExpCompileData result;
   CHECK(!v8::internal::RegExpParser::ParseRegExp(
-            CcTest::i_isolate(), &zone, &reader, false, false, &result));
+      CcTest::i_isolate(), &zone, &reader, JSRegExp::kNone, &result));
   CHECK(result.tree == NULL);
   CHECK(!result.error.is_null());
   v8::base::SmartArrayPointer<char> str = result.error->ToCString(ALLOW_NULLS);
@@ -523,7 +529,7 @@ static void TestCharacterClassEscapes(uc16 c, bool (pred)(uc16 c)) {
   ZoneList<CharacterRange>* ranges =
       new(&zone) ZoneList<CharacterRange>(2, &zone);
   CharacterRange::AddClassEscape(c, ranges, &zone);
-  for (unsigned i = 0; i < (1 << 16); i++) {
+  for (uc32 i = 0; i < (1 << 16); i++) {
     bool in_class = false;
     for (int j = 0; !in_class && j < ranges->length(); j++) {
       CharacterRange& range = ranges->at(j);
@@ -550,17 +556,19 @@ static RegExpNode* Compile(const char* input, bool multiline, bool unicode,
   Isolate* isolate = CcTest::i_isolate();
   FlatStringReader reader(isolate, CStrVector(input));
   RegExpCompileData compile_data;
+  JSRegExp::Flags flags = JSRegExp::kNone;
+  if (multiline) flags = JSRegExp::kMultiline;
+  if (unicode) flags = JSRegExp::kUnicode;
   if (!v8::internal::RegExpParser::ParseRegExp(CcTest::i_isolate(), zone,
-                                               &reader, multiline, unicode,
-                                               &compile_data))
+                                               &reader, flags, &compile_data))
     return NULL;
   Handle<String> pattern = isolate->factory()
                                ->NewStringFromUtf8(CStrVector(input))
                                .ToHandleChecked();
   Handle<String> sample_subject =
       isolate->factory()->NewStringFromUtf8(CStrVector("")).ToHandleChecked();
-  RegExpEngine::Compile(isolate, zone, &compile_data, false, false, multiline,
-                        false, pattern, sample_subject, is_one_byte);
+  RegExpEngine::Compile(isolate, zone, &compile_data, flags, pattern,
+                        sample_subject, is_one_byte);
   return compile_data.node;
 }
 
@@ -1669,7 +1677,7 @@ TEST(CharacterRangeCaseIndependence) {
 }
 
 
-static bool InClass(uc16 c, ZoneList<CharacterRange>* ranges) {
+static bool InClass(uc32 c, ZoneList<CharacterRange>* ranges) {
   if (ranges == NULL)
     return false;
   for (int i = 0; i < ranges->length(); i++) {
@@ -1681,29 +1689,46 @@ static bool InClass(uc16 c, ZoneList<CharacterRange>* ranges) {
 }
 
 
-TEST(CharClassDifference) {
+TEST(UnicodeRangeSplitter) {
   Zone zone;
   ZoneList<CharacterRange>* base =
       new(&zone) ZoneList<CharacterRange>(1, &zone);
   base->Add(CharacterRange::Everything(), &zone);
-  Vector<const int> overlay = CharacterRange::GetWordBounds();
-  ZoneList<CharacterRange>* included = NULL;
-  ZoneList<CharacterRange>* excluded = NULL;
-  CharacterRange::Split(base, overlay, &included, &excluded, &zone);
-  for (int i = 0; i < (1 << 16); i++) {
-    bool in_base = InClass(i, base);
-    if (in_base) {
-      bool in_overlay = false;
-      for (int j = 0; !in_overlay && j < overlay.length(); j += 2) {
-        if (overlay[j] <= i && i < overlay[j+1])
-          in_overlay = true;
-      }
-      CHECK_EQ(in_overlay, InClass(i, included));
-      CHECK_EQ(!in_overlay, InClass(i, excluded));
-    } else {
-      CHECK(!InClass(i, included));
-      CHECK(!InClass(i, excluded));
-    }
+  UnicodeRangeSplitter splitter(&zone, base);
+  // BMP
+  for (uc32 c = 0; c < 0xd800; c++) {
+    CHECK(InClass(c, splitter.bmp()));
+    CHECK(!InClass(c, splitter.lead_surrogates()));
+    CHECK(!InClass(c, splitter.trail_surrogates()));
+    CHECK(!InClass(c, splitter.non_bmp()));
+  }
+  // Lead surrogates
+  for (uc32 c = 0xd800; c < 0xdbff; c++) {
+    CHECK(!InClass(c, splitter.bmp()));
+    CHECK(InClass(c, splitter.lead_surrogates()));
+    CHECK(!InClass(c, splitter.trail_surrogates()));
+    CHECK(!InClass(c, splitter.non_bmp()));
+  }
+  // Trail surrogates
+  for (uc32 c = 0xdc00; c < 0xdfff; c++) {
+    CHECK(!InClass(c, splitter.bmp()));
+    CHECK(!InClass(c, splitter.lead_surrogates()));
+    CHECK(InClass(c, splitter.trail_surrogates()));
+    CHECK(!InClass(c, splitter.non_bmp()));
+  }
+  // BMP
+  for (uc32 c = 0xe000; c < 0xffff; c++) {
+    CHECK(InClass(c, splitter.bmp()));
+    CHECK(!InClass(c, splitter.lead_surrogates()));
+    CHECK(!InClass(c, splitter.trail_surrogates()));
+    CHECK(!InClass(c, splitter.non_bmp()));
+  }
+  // Non-BMP
+  for (uc32 c = 0x10000; c < 0x10ffff; c++) {
+    CHECK(!InClass(c, splitter.bmp()));
+    CHECK(!InClass(c, splitter.lead_surrogates()));
+    CHECK(!InClass(c, splitter.trail_surrogates()));
+    CHECK(InClass(c, splitter.non_bmp()));
   }
 }
 
diff --git a/test/mjsunit/harmony/unicode-character-ranges.js b/test/mjsunit/harmony/unicode-character-ranges.js
new file mode 100644
index 0000000000..75a592f334
--- /dev/null
+++ b/test/mjsunit/harmony/unicode-character-ranges.js
@@ -0,0 +1,156 @@
+// Copyright 2016 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --harmony-unicode-regexps --harmony-regexp-lookbehind
+
+function execl(expectation, regexp, subject) {
+  if (regexp instanceof String) regexp = new RegExp(regexp, "u");
+  assertEquals(expectation, regexp.exec(subject));
+}
+
+function execs(expectation, regexp_source, subject) {
+  execl(expectation, new RegExp(regexp_source, "u"), subject);
+}
+
+// Character ranges.
+execl(["A"], /[A-D]/u, "A");
+execs(["A"], "[A-D]", "A");
+execl(["ABCD"], /[A-D]+/u, "ZABCDEF");
+execs(["ABCD"], "[A-D]+", "ZABCDEF");
+
+execl(["\u{12345}"], /[\u1234-\u{12345}]/u, "\u{12345}");
+execs(["\u{12345}"], "[\u1234-\u{12345}]", "\u{12345}");
+execl(null, /[^\u1234-\u{12345}]/u, "\u{12345}");
+execs(null, "[^\u1234-\u{12345}]", "\u{12345}");
+
+execl(["\u{1234}"], /[\u1234-\u{12345}]/u, "\u{1234}");
+execs(["\u{1234}"], "[\u1234-\u{12345}]", "\u{1234}");
+execl(null, /[^\u1234-\u{12345}]/u, "\u{1234}");
+execs(null, "[^\u1234-\u{12345}]", "\u{1234}");
+
+execl(null, /[\u1234-\u{12345}]/u, "\u{1233}");
+execs(null, "[\u1234-\u{12345}]", "\u{1233}");
+execl(["\u{1233}"], /[^\u1234-\u{12345}]/u, "\u{1233}");
+execs(["\u{1233}"], "[^\u1234-\u{12345}]", "\u{1233}");
+
+execl(["\u{12346}"], /[^\u1234-\u{12345}]/u, "\u{12346}");
+execs(["\u{12346}"], "[^\u1234-\u{12345}]", "\u{12346}");
+execl(null, /[\u1234-\u{12345}]/u, "\u{12346}");
+execs(null, "[\u1234-\u{12345}]", "\u{12346}");
+
+execl(["\u{12342}"], /[\u{12340}-\u{12345}]/u, "\u{12342}");
+execs(["\u{12342}"], "[\u{12340}-\u{12345}]", "\u{12342}");
+execl(["\u{12342}"], /[\ud808\udf40-\ud808\udf45]/u, "\u{12342}");
+execs(["\u{12342}"], "[\ud808\udf40-\ud808\udf45]", "\u{12342}");
+execl(null, /[^\u{12340}-\u{12345}]/u, "\u{12342}");
+execs(null, "[^\u{12340}-\u{12345}]", "\u{12342}");
+execl(null, /[^\ud808\udf40-\ud808\udf45]/u, "\u{12342}");
+execs(null, "[^\ud808\udf40-\ud808\udf45]", "\u{12342}");
+
+execl(["\u{ffff}"], /[\u{ff80}-\u{12345}]/u, "\u{ffff}");
+execs(["\u{ffff}"], "[\u{ff80}-\u{12345}]", "\u{ffff}");
+execl(["\u{ffff}"], /[\u{ff80}-\ud808\udf45]/u, "\u{ffff}");
+execs(["\u{ffff}"], "[\u{ff80}-\ud808\udf45]", "\u{ffff}");
+execl(null, /[^\u{ff80}-\u{12345}]/u, "\u{ffff}");
+execs(null, "[^\u{ff80}-\u{12345}]", "\u{ffff}");
+execl(null, /[^\u{ff80}-\ud808\udf45]/u, "\u{ffff}");
+execs(null, "[^\u{ff80}-\ud808\udf45]", "\u{ffff}");
+
+// Lone surrogate
+execl(["\ud800"], /[^\u{ff80}-\u{12345}]/u, "\uff99\u{d800}A");
+execs(["\udc00"], "[^\u{ff80}-\u{12345}]", "\uff99\u{dc00}A");
+execl(["\udc01"], /[\u0100-\u{10ffff}]/u, "A\udc01");
+execl(["\udc03"], /[\udc01-\udc03]/u, "\ud801\udc02\udc03");
+execl(["\ud801"], /[\ud801-\ud803]/u, "\ud802\udc01\ud801");
+
+// Paired sorrogate.
+execl(null, /[^\u{ff80}-\u{12345}]/u, "\u{d800}\u{dc00}");
+execs(null, "[^\u{ff80}-\u{12345}]", "\u{d800}\u{dc00}");
+execl(["\ud800\udc00"], /[\u{ff80}-\u{12345}]/u, "\u{d800}\u{dc00}");
+execs(["\ud800\udc00"], "[\u{ff80}-\u{12345}]", "\u{d800}\u{dc00}");
+execl(["foo\u{10e6d}bar"], /foo\ud803\ude6dbar/u, "foo\u{10e6d}bar");
+
+// Lone surrogates
+execl(["\ud801\ud801"], /\ud801+/u, "\ud801\udc01\ud801\ud801");
+execl(["\udc01\udc01"], /\udc01+/u, "\ud801\ud801\udc01\udc01\udc01");
+
+execl(["\udc02\udc03A"], /\W\WA/u, "\ud801\udc01A\udc02\udc03A");
+execl(["\ud801\ud802"], /\ud801./u, "\ud801\udc01\ud801\ud802");
+execl(["\udc02\udc03A"], /[\ud800-\udfff][\ud800-\udfff]A/u,
+      "\ud801\udc01A\udc02\udc03A");
+
+// Character classes
+execl(null, /\w/u, "\ud801\udc01");
+execl(["\ud801"], /[^\w]/, "\ud801\udc01");
+execl(["\ud801\udc01"], /[^\w]/u, "\ud801\udc01");
+execl(["\ud801"], /\W/, "\ud801\udc01");
+execl(["\ud801\udc01"], /\W/u, "\ud801\udc01");
+
+execl(["\ud800X"], /.X/u, "\ud800XaX");
+execl(["aX"], /.(?<!\ud800)X/u, "\ud800XaX");
+execl(["aX"], /.(?<![\ud800-\ud900])X/u, "\ud800XaX");
+
+execl(null, /[]/u, "\u1234");
+execl(["0abc"], /[^]abc/u, "0abc");
+execl(["\u1234abc"], /[^]abc/u, "\u1234abc");
+execl(["\u{12345}abc"], /[^]abc/u, "\u{12345}abc");
+
+// Backward matches of lone surrogates.
+execl(["B", "\ud803A"], /(?<=([\ud800-\ud900]A))B/u,
+      "\ud801\udc00AB\udc00AB\ud802\ud803AB");
+execl(["B", "\udc00A"], /(?<=([\ud800-\u{10300}]A))B/u,
+       "\ud801\udc00AB\udc00AB\ud802\ud803AB");
+execl(["B", "\udc11A"], /(?<=([\udc00-\udd00]A))B/u,
+      "\ud801\udc00AB\udc11AB\ud802\ud803AB");
+execl(["X", "\ud800C"], /(?<=(\ud800\w))X/u,
+      "\ud800\udc00AX\udc11BX\ud800\ud800CX");
+execl(["C", "\ud800\ud800"], /(?<=(\ud800.))\w/u,
+      "\ud800\udc00AX\udc11BX\ud800\ud800CX");
+execl(["X", "\udc01C"], /(?<=(\udc01\w))X/u,
+      "\ud800\udc01AX\udc11BX\udc01\udc01CX");
+execl(["C", "\udc01\udc01"], /(?<=(\udc01.))./u,
+      "\ud800\udc01AX\udc11BX\udc01\udc01CX");
+
+var L = "\ud800";
+var T = "\udc00";
+var X = "X";
+
+// Test string contains only match.
+function testw(expect, src, subject) {
+  var re = new RegExp("^" + src + "$", "u");
+  assertEquals(expect, re.test(subject));
+}
+
+// Test string starts with match.
+function tests(expect, src, subject) {
+  var re = new RegExp("^" + src, "u");
+  assertEquals(expect, re.test(subject));
+}
+
+testw(true, X, X);
+testw(true, L, L);
+testw(true, T, T);
+testw(true, L + T, L + T);
+testw(true, T + L, T + L);
+testw(false, T, L + T);
+testw(false, L, L + T);
+testw(true, ".(?<=" + L + ")", L);
+testw(true, ".(?<=" + T + ")", T);
+testw(true, ".(?<=" + L + T + ")", L + T);
+testw(true, ".(?<=" + L + T + ")", L + T);
+tests(true, ".(?<=" + T + ")", T + L);
+tests(false, ".(?<=" + L + ")", L + T);
+tests(false, ".(?<=" + T + ")", L + T);
+tests(true, "..(?<=" + T + ")", T + T + L);
+tests(true, "..(?<=" + T + ")", X + T + L);
+tests(true, "...(?<=" + L + ")", X + T + L);
+tests(false, "...(?<=" + T + ")", X + L + T)
+tests(true, "..(?<=" + L + T + ")", X + L + T)
+tests(true, "..(?<=" + L + T + "(?<=" + L + T + "))", X + L + T);
+tests(false, "..(?<=" + L + "(" + T + "))", X + L + T);
+tests(false, ".*" + L, X + L + T);
+tests(true, ".*" + L, X + L + L + T);
+tests(false, ".*" + L, X + L + T + L + T);
+tests(false, ".*" + T, X + L + T + L + T);
+tests(true, ".*" + T, X + L + T + T + L + T);
diff --git a/test/mjsunit/harmony/unicode-escapes-in-regexps.js b/test/mjsunit/harmony/unicode-escapes-in-regexps.js
index f591dac930..10187412aa 100644
--- a/test/mjsunit/harmony/unicode-escapes-in-regexps.js
+++ b/test/mjsunit/harmony/unicode-escapes-in-regexps.js
@@ -252,6 +252,30 @@ assertFalse(/(\u{12345}|\u{23456}).\1/u.test("\u{12345}b\u{23456}"));
 assertTrue(new RegExp("\u{12345}{3}", "u").test("\u{12345}\u{12345}\u{12345}"));
 assertTrue(/\u{12345}{3}/u.test("\u{12345}\u{12345}\u{12345}"));
 assertTrue(new RegExp("\u{12345}{3}").test("\u{12345}\udf45\udf45"));
-assertTrue(/\ud808\udf45{3}/u.test("\u{12345}\udf45\udf45"));
+assertFalse(/\ud808\udf45{3}/u.test("\u{12345}\udf45\udf45"));
+assertTrue(/\ud808\udf45{3}/u.test("\u{12345}\u{12345}\u{12345}"));
 assertFalse(new RegExp("\u{12345}{3}", "u").test("\u{12345}\udf45\udf45"));
 assertFalse(/\u{12345}{3}/u.test("\u{12345}\udf45\udf45"));
+
+// Mixed escapes and literal surrogates.
+assertEquals(["\u{10000}\u{10000}"],
+             new RegExp("\ud800\udc00+", "u").exec("\u{10000}\u{10000}"));
+assertEquals(["\u{10000}\u{10000}"],
+             new RegExp("\\ud800\\udc00+", "u").exec("\u{10000}\u{10000}"));
+assertEquals(["\u{10000}\u{10000}"],
+             new RegExp("\\ud800\udc00+", "u").exec("\u{10000}\u{10000}"));
+assertEquals(["\u{10000}\u{10000}"],
+             new RegExp("\ud800\\udc00+", "u").exec("\u{10000}\u{10000}"));
+
+assertEquals(["\u{10003}\u{50001}"],
+             new RegExp("[\\ud800\\udc03-\\ud900\\udc01\]+", "u").exec(
+                 "\u{10003}\u{50001}"));
+assertEquals(["\u{10003}\u{50001}"],
+             new RegExp("[\\ud800\udc03-\ud900\\udc01\]+", "u").exec(
+                 "\u{10003}\u{50001}"));
+assertEquals(["\u{50001}"],
+             new RegExp("[\\ud800\udc03-\ud900\\udc01\]+", "u").exec(
+                 "\u{10002}\u{50001}"));
+assertEquals(["\u{10003}\u{50001}"],
+             new RegExp("[\ud800\udc03-\u{50001}\]+", "u").exec(
+                 "\u{10003}\u{50001}"));