src/regexp/regexp.cc

// Copyright 2012 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.

#include "src/regexp/regexp.h"

#include "src/codegen/compilation-cache.h"
#include "src/diagnostics/code-tracer.h"
#include "src/heap/heap-inl.h"
#include "src/objects/js-regexp-inl.h"
#include "src/regexp/experimental/experimental.h"
#include "src/regexp/regexp-bytecode-generator.h"
#include "src/regexp/regexp-bytecodes.h"
#include "src/regexp/regexp-compiler.h"
#include "src/regexp/regexp-dotprinter.h"
#include "src/regexp/regexp-interpreter.h"
#include "src/regexp/regexp-macro-assembler-arch.h"
#include "src/regexp/regexp-macro-assembler-tracer.h"
#include "src/regexp/regexp-parser.h"
#include "src/regexp/regexp-utils.h"
#include "src/strings/string-search.h"
#include "src/utils/ostreams.h"

namespace v8 {
namespace internal {

using namespace regexp_compiler_constants;  // NOLINT(build/namespaces)

class RegExpImpl final : public AllStatic {
 public:
  // Returns a string representation of a regular expression.
  // Implements RegExp.prototype.toString, see ECMA-262 section 15.10.6.4.
  // This function calls the garbage collector if necessary.
  static Handle<String> ToString(Handle<Object> value);

  // Prepares a JSRegExp object with Irregexp-specific data.
  static void IrregexpInitialize(Isolate* isolate, Handle<JSRegExp> re,
                                 Handle<String> pattern, JSRegExp::Flags flags,
                                 int capture_count, uint32_t backtrack_limit);

  // Prepare a RegExp for being executed one or more times (using
  // IrregexpExecOnce) on the subject.
  // This ensures that the regexp is compiled for the subject, and that
  // the subject is flat.
  // Returns the number of integer spaces required by IrregexpExecOnce
  // as its "registers" argument.  If the regexp cannot be compiled,
  // an exception is set as pending, and this function returns negative.
  static int IrregexpPrepare(Isolate* isolate, Handle<JSRegExp> regexp,
                             Handle<String> subject);

  static void AtomCompile(Isolate* isolate, Handle<JSRegExp> re,
                          Handle<String> pattern, JSRegExp::Flags flags,
                          Handle<String> match_pattern);

  static int AtomExecRaw(Isolate* isolate, Handle<JSRegExp> regexp,
                         Handle<String> subject, int index, int32_t* output,
                         int output_size);

  static Handle<Object> AtomExec(Isolate* isolate, Handle<JSRegExp> regexp,
                                 Handle<String> subject, int index,
                                 Handle<RegExpMatchInfo> last_match_info);

  // Execute a regular expression on the subject, starting from index.
  // If matching succeeds, return the number of matches.  This can be larger
  // than one in the case of global regular expressions.
  // The captures and subcaptures are stored into the registers vector.
  // If matching fails, returns RE_FAILURE.
  // If execution fails, sets a pending exception and returns RE_EXCEPTION.
  static int IrregexpExecRaw(Isolate* isolate, Handle<JSRegExp> regexp,
                             Handle<String> subject, int index, int32_t* output,
                             int output_size);

  // Execute an Irregexp bytecode pattern.
  // On a successful match, the result is a JSArray containing
  // captured positions.  On a failure, the result is the null value.
  // Returns an empty handle in case of an exception.
  V8_WARN_UNUSED_RESULT static MaybeHandle<Object> IrregexpExec(
      Isolate* isolate, Handle<JSRegExp> regexp, Handle<String> subject,
      int index, Handle<RegExpMatchInfo> last_match_info);

  static bool CompileIrregexp(Isolate* isolate, Handle<JSRegExp> re,
                              Handle<String> sample_subject, bool is_one_byte);
  static inline bool EnsureCompiledIrregexp(Isolate* isolate,
                                            Handle<JSRegExp> re,
                                            Handle<String> sample_subject,
                                            bool is_one_byte);

  // Returns true on success, false on failure.
  static bool Compile(Isolate* isolate, Zone* zone, RegExpCompileData* input,
                      JSRegExp::Flags flags, Handle<String> pattern,
                      Handle<String> sample_subject, bool is_one_byte,
                      uint32_t& backtrack_limit);

  // For acting on the JSRegExp data FixedArray.
  static int IrregexpMaxRegisterCount(FixedArray re);
  static void SetIrregexpMaxRegisterCount(FixedArray re, int value);
  static int IrregexpNumberOfCaptures(FixedArray re);
  static ByteArray IrregexpByteCode(FixedArray re, bool is_one_byte);
  static Code IrregexpNativeCode(FixedArray re, bool is_one_byte);
};

MaybeHandle<Object> RegExp::ThrowRegExpException(Isolate* isolate,
                                                 Handle<JSRegExp> re,
                                                 Handle<String> pattern,
                                                 RegExpError error) {
  Vector<const char> error_data = CStrVector(RegExpErrorString(error));
  Handle<String> error_text =
      isolate->factory()
          ->NewStringFromOneByte(Vector<const uint8_t>::cast(error_data))
          .ToHandleChecked();
  THROW_NEW_ERROR(
      isolate,
      NewSyntaxError(MessageTemplate::kMalformedRegExp, pattern, error_text),
      Object);
}

void RegExp::ThrowRegExpException(Isolate* isolate, Handle<JSRegExp> re,
                                  RegExpError error_text) {
  USE(ThrowRegExpException(isolate, re, Handle<String>(re->Pattern(), isolate),
                           error_text));
}

bool RegExp::IsUnmodifiedRegExp(Isolate* isolate, Handle<JSRegExp> regexp) {
  return RegExpUtils::IsUnmodifiedRegExp(isolate, regexp);
}

// 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.

// static
MaybeHandle<Object> RegExp::Compile(Isolate* isolate, Handle<JSRegExp> re,
                                    Handle<String> pattern,
                                    JSRegExp::Flags flags,
                                    uint32_t backtrack_limit) {
  DCHECK(pattern->IsFlat());

  // Caching is based only on the pattern and flags, but code also differs when
  // a backtrack limit is set. A present backtrack limit is very much *not* the
  // common case, so just skip the cache for these.
  const bool is_compilation_cache_enabled =
      (backtrack_limit == JSRegExp::kNoBacktrackLimit);

  Zone zone(isolate->allocator(), ZONE_NAME);
  CompilationCache* compilation_cache = nullptr;
  if (is_compilation_cache_enabled) {
    compilation_cache = isolate->compilation_cache();
    MaybeHandle<FixedArray> maybe_cached =
        compilation_cache->LookupRegExp(pattern, flags);
    Handle<FixedArray> cached;
    if (maybe_cached.ToHandle(&cached)) {
      re->set_data(*cached);
      return re;
    }
  }

  PostponeInterruptsScope postpone(isolate);
  RegExpCompileData parse_result;
  FlatStringReader reader(isolate, pattern);
  DCHECK(!isolate->has_pending_exception());
  if (!RegExpParser::ParseRegExp(isolate, &zone, &reader, flags,
                                 &parse_result)) {
    // Throw an exception if we fail to parse the pattern.
    return RegExp::ThrowRegExpException(isolate, re, pattern,
                                        parse_result.error);
  }

  bool has_been_compiled = false;

  if (FLAG_default_to_experimental_regexp_engine &&
      ExperimentalRegExp::CanBeHandled(parse_result.tree, flags,
                                       parse_result.capture_count)) {
    DCHECK(FLAG_enable_experimental_regexp_engine);
    ExperimentalRegExp::Initialize(isolate, re, pattern, flags,
                                   parse_result.capture_count);
    has_been_compiled = true;
  } else if (flags & JSRegExp::kLinear) {
    DCHECK(FLAG_enable_experimental_regexp_engine);
    if (!ExperimentalRegExp::CanBeHandled(parse_result.tree, flags,
                                          parse_result.capture_count)) {
      // TODO(mbid): The error could provide a reason for why the regexp can't
      // be executed in linear time (e.g. due to back references).
      return RegExp::ThrowRegExpException(isolate, re, pattern,
                                          RegExpError::kNotLinear);
    }
    ExperimentalRegExp::Initialize(isolate, re, pattern, flags,
                                   parse_result.capture_count);
    has_been_compiled = true;
  } else if (parse_result.simple && !IgnoreCase(flags) && !IsSticky(flags) &&
             !HasFewDifferentCharacters(pattern)) {
    // Parse-tree is a single atom that is equal to the pattern.
    RegExpImpl::AtomCompile(isolate, re, pattern, flags, pattern);
    has_been_compiled = true;
  } else if (parse_result.tree->IsAtom() && !IsSticky(flags) &&
             parse_result.capture_count == 0) {
    RegExpAtom* atom = parse_result.tree->AsAtom();
    // The pattern source might (?) contain escape sequences, but they're
    // resolved in atom_string.
    Vector<const uc16> atom_pattern = atom->data();
    Handle<String> atom_string;
    ASSIGN_RETURN_ON_EXCEPTION(
        isolate, atom_string,
        isolate->factory()->NewStringFromTwoByte(atom_pattern), Object);
    if (!IgnoreCase(atom->flags()) && !HasFewDifferentCharacters(atom_string)) {
      RegExpImpl::AtomCompile(isolate, re, pattern, flags, atom_string);
      has_been_compiled = true;
    }
  }
  if (!has_been_compiled) {
    RegExpImpl::IrregexpInitialize(isolate, re, pattern, flags,
                                   parse_result.capture_count, backtrack_limit);
  }
  DCHECK(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()), isolate);
  if (is_compilation_cache_enabled) {
    compilation_cache->PutRegExp(pattern, flags, data);
  }

  return re;
}

// static
bool RegExp::EnsureFullyCompiled(Isolate* isolate, Handle<JSRegExp> re,
                                 Handle<String> subject) {
  switch (re->TypeTag()) {
    case JSRegExp::NOT_COMPILED:
      UNREACHABLE();
    case JSRegExp::ATOM:
      return true;
    case JSRegExp::IRREGEXP:
      if (RegExpImpl::IrregexpPrepare(isolate, re, subject) == -1) {
        DCHECK(isolate->has_pending_exception());
        return false;
      }
      return true;
    case JSRegExp::EXPERIMENTAL:
      if (!ExperimentalRegExp::IsCompiled(re, isolate) &&
          !ExperimentalRegExp::Compile(isolate, re)) {
        DCHECK(isolate->has_pending_exception());
        return false;
      }
      return true;
  }
}

// static
MaybeHandle<Object> RegExp::ExperimentalOneshotExec(
    Isolate* isolate, Handle<JSRegExp> regexp, Handle<String> subject,
    int index, Handle<RegExpMatchInfo> last_match_info) {
  return ExperimentalRegExp::OneshotExec(isolate, regexp, subject, index,
                                         last_match_info);
}

// static
MaybeHandle<Object> RegExp::Exec(Isolate* isolate, Handle<JSRegExp> regexp,
                                 Handle<String> subject, int index,
                                 Handle<RegExpMatchInfo> last_match_info) {
  switch (regexp->TypeTag()) {
    case JSRegExp::NOT_COMPILED:
      UNREACHABLE();
    case JSRegExp::ATOM:
      return RegExpImpl::AtomExec(isolate, regexp, subject, index,
                                  last_match_info);
    case JSRegExp::IRREGEXP:
      return RegExpImpl::IrregexpExec(isolate, regexp, subject, index,
                                      last_match_info);
    case JSRegExp::EXPERIMENTAL:
      return ExperimentalRegExp::Exec(isolate, regexp, subject, index,
                                      last_match_info);
  }
}

// RegExp Atom implementation: Simple string search using indexOf.

void RegExpImpl::AtomCompile(Isolate* isolate, Handle<JSRegExp> re,
                             Handle<String> pattern, JSRegExp::Flags flags,
                             Handle<String> match_pattern) {
  isolate->factory()->SetRegExpAtomData(re, pattern, flags, match_pattern);
}

static void SetAtomLastCapture(Isolate* isolate,
                               Handle<RegExpMatchInfo> last_match_info,
                               String subject, int from, int to) {
  SealHandleScope shs(isolate);
  last_match_info->SetNumberOfCaptureRegisters(2);
  last_match_info->SetLastSubject(subject);
  last_match_info->SetLastInput(subject);
  last_match_info->SetCapture(0, from);
  last_match_info->SetCapture(1, to);
}

int RegExpImpl::AtomExecRaw(Isolate* isolate, Handle<JSRegExp> regexp,
                            Handle<String> subject, int index, int32_t* output,
                            int output_size) {
  DCHECK_LE(0, index);
  DCHECK_LE(index, subject->length());

  subject = String::Flatten(isolate, subject);
  DisallowHeapAllocation no_gc;  // ensure vectors stay valid

  String needle = String::cast(regexp->DataAt(JSRegExp::kAtomPatternIndex));
  int needle_len = needle.length();
  DCHECK(needle.IsFlat());
  DCHECK_LT(0, needle_len);

  if (index + needle_len > subject->length()) {
    return RegExp::RE_FAILURE;
  }

  for (int i = 0; i < output_size; i += 2) {
    String::FlatContent needle_content = needle.GetFlatContent(no_gc);
    String::FlatContent subject_content = subject->GetFlatContent(no_gc);
    DCHECK(needle_content.IsFlat());
    DCHECK(subject_content.IsFlat());
    // dispatch on type of strings
    index =
        (needle_content.IsOneByte()
             ? (subject_content.IsOneByte()
                    ? SearchString(isolate, subject_content.ToOneByteVector(),
                                   needle_content.ToOneByteVector(), index)
                    : SearchString(isolate, subject_content.ToUC16Vector(),
                                   needle_content.ToOneByteVector(), index))
             : (subject_content.IsOneByte()
                    ? 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(Isolate* isolate, Handle<JSRegExp> re,
                                    Handle<String> subject, int index,
                                    Handle<RegExpMatchInfo> last_match_info) {
  static const int kNumRegisters = 2;
  STATIC_ASSERT(kNumRegisters <= Isolate::kJSRegexpStaticOffsetsVectorSize);
  int32_t* output_registers = isolate->jsregexp_static_offsets_vector();

  int res =
      AtomExecRaw(isolate, re, subject, index, output_registers, kNumRegisters);

  if (res == RegExp::RE_FAILURE) return isolate->factory()->null_value();

  DCHECK_EQ(res, RegExp::RE_SUCCESS);
  SealHandleScope shs(isolate);
  SetAtomLastCapture(isolate, last_match_info, *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 one-byte or two-byte subject 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(Isolate* isolate, Handle<JSRegExp> re,
                                        Handle<String> sample_subject,
                                        bool is_one_byte) {
  Object compiled_code = re->Code(is_one_byte);
  Object bytecode = re->Bytecode(is_one_byte);
  bool needs_initial_compilation =
      compiled_code == Smi::FromInt(JSRegExp::kUninitializedValue);
  // Recompile is needed when we're dealing with the first execution of the
  // regexp after the decision to tier up has been made. If the tiering up
  // strategy is not in use, this value is always false.
  bool needs_tier_up_compilation =
      re->MarkedForTierUp() && bytecode.IsByteArray();

  if (FLAG_trace_regexp_tier_up && needs_tier_up_compilation) {
    PrintF("JSRegExp object %p needs tier-up compilation\n",
           reinterpret_cast<void*>(re->ptr()));
  }

  if (!needs_initial_compilation && !needs_tier_up_compilation) {
    DCHECK(compiled_code.IsCode());
    DCHECK_IMPLIES(FLAG_regexp_interpret_all, bytecode.IsByteArray());
    return true;
  }

  DCHECK_IMPLIES(needs_tier_up_compilation, bytecode.IsByteArray());

  return CompileIrregexp(isolate, re, sample_subject, is_one_byte);
}

#ifdef DEBUG
namespace {

bool RegExpCodeIsValidForPreCompilation(Handle<JSRegExp> re, bool is_one_byte) {
  Object entry = re->Code(is_one_byte);
  Object bytecode = re->Bytecode(is_one_byte);
  // If we're not using the tier-up strategy, entry can only be a smi
  // representing an uncompiled regexp here. If we're using the tier-up
  // strategy, entry can still be a smi representing an uncompiled regexp, when
  // compiling the regexp before the tier-up, or it can contain a trampoline to
  // the regexp interpreter, in which case the bytecode field contains compiled
  // bytecode, when recompiling the regexp after the tier-up. If the
  // tier-up was forced, which happens for global replaces, entry is a smi
  // representing an uncompiled regexp, even though we're "recompiling" after
  // the tier-up.
  if (re->ShouldProduceBytecode()) {
    DCHECK(entry.IsSmi());
    DCHECK(bytecode.IsSmi());
    int entry_value = Smi::ToInt(entry);
    int bytecode_value = Smi::ToInt(bytecode);
    DCHECK_EQ(JSRegExp::kUninitializedValue, entry_value);
    DCHECK_EQ(JSRegExp::kUninitializedValue, bytecode_value);
  } else {
    DCHECK(entry.IsSmi() || (entry.IsCode() && bytecode.IsByteArray()));
  }

  return true;
}

}  // namespace
#endif

bool RegExpImpl::CompileIrregexp(Isolate* isolate, Handle<JSRegExp> re,
                                 Handle<String> sample_subject,
                                 bool is_one_byte) {
  // Compile the RegExp.
  Zone zone(isolate->allocator(), ZONE_NAME);
  PostponeInterruptsScope postpone(isolate);

  DCHECK(RegExpCodeIsValidForPreCompilation(re, is_one_byte));

  JSRegExp::Flags flags = re->GetFlags();

  Handle<String> pattern(re->Pattern(), isolate);
  pattern = String::Flatten(isolate, pattern);
  RegExpCompileData compile_data;
  FlatStringReader reader(isolate, pattern);
  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(RegExp::ThrowRegExpException(isolate, re, pattern, compile_data.error));
    return false;
  }
  // The compilation target is a kBytecode if we're interpreting all regexp
  // objects, or if we're using the tier-up strategy but the tier-up hasn't
  // happened yet. The compilation target is a kNative if we're using the
  // tier-up strategy and we need to recompile to tier-up, or if we're producing
  // native code for all regexp objects.
  compile_data.compilation_target = re->ShouldProduceBytecode()
                                        ? RegExpCompilationTarget::kBytecode
                                        : RegExpCompilationTarget::kNative;
  uint32_t backtrack_limit = re->BacktrackLimit();
  const bool compilation_succeeded =
      Compile(isolate, &zone, &compile_data, flags, pattern, sample_subject,
              is_one_byte, backtrack_limit);
  if (!compilation_succeeded) {
    DCHECK(compile_data.error != RegExpError::kNone);
    RegExp::ThrowRegExpException(isolate, re, compile_data.error);
    return false;
  }

  Handle<FixedArray> data =
      Handle<FixedArray>(FixedArray::cast(re->data()), isolate);
  if (compile_data.compilation_target == RegExpCompilationTarget::kNative) {
    data->set(JSRegExp::code_index(is_one_byte), *compile_data.code);
    // Reset bytecode to uninitialized. In case we use tier-up we know that
    // tier-up has happened this way.
    data->set(JSRegExp::bytecode_index(is_one_byte),
              Smi::FromInt(JSRegExp::kUninitializedValue));
  } else {
    DCHECK_EQ(compile_data.compilation_target,
              RegExpCompilationTarget::kBytecode);
    // Store code generated by compiler in bytecode and trampoline to
    // interpreter in code.
    data->set(JSRegExp::bytecode_index(is_one_byte), *compile_data.code);
    Handle<Code> trampoline =
        BUILTIN_CODE(isolate, RegExpInterpreterTrampoline);
    data->set(JSRegExp::code_index(is_one_byte), *trampoline);
  }
  re->SetCaptureNameMap(compile_data.capture_name_map);
  int register_max = IrregexpMaxRegisterCount(*data);
  if (compile_data.register_count > register_max) {
    SetIrregexpMaxRegisterCount(*data, compile_data.register_count);
  }
  data->set(JSRegExp::kIrregexpBacktrackLimit, Smi::FromInt(backtrack_limit));

  if (FLAG_trace_regexp_tier_up) {
    PrintF("JSRegExp object %p %s size: %d\n",
           reinterpret_cast<void*>(re->ptr()),
           re->ShouldProduceBytecode() ? "bytecode" : "native code",
           re->ShouldProduceBytecode()
               ? IrregexpByteCode(*data, is_one_byte).Size()
               : IrregexpNativeCode(*data, is_one_byte).Size());
  }

  return true;
}

int RegExpImpl::IrregexpMaxRegisterCount(FixedArray re) {
  return Smi::ToInt(re.get(JSRegExp::kIrregexpMaxRegisterCountIndex));
}

void RegExpImpl::SetIrregexpMaxRegisterCount(FixedArray re, int value) {
  re.set(JSRegExp::kIrregexpMaxRegisterCountIndex, Smi::FromInt(value));
}

int RegExpImpl::IrregexpNumberOfCaptures(FixedArray re) {
  return Smi::ToInt(re.get(JSRegExp::kIrregexpCaptureCountIndex));
}

ByteArray RegExpImpl::IrregexpByteCode(FixedArray re, bool is_one_byte) {
  return ByteArray::cast(re.get(JSRegExp::bytecode_index(is_one_byte)));
}

Code RegExpImpl::IrregexpNativeCode(FixedArray re, bool is_one_byte) {
  return Code::cast(re.get(JSRegExp::code_index(is_one_byte)));
}

void RegExpImpl::IrregexpInitialize(Isolate* isolate, Handle<JSRegExp> re,
                                    Handle<String> pattern,
                                    JSRegExp::Flags flags, int capture_count,
                                    uint32_t backtrack_limit) {
  // Initialize compiled code entries to null.
  isolate->factory()->SetRegExpIrregexpData(re, pattern, flags, capture_count,
                                            backtrack_limit);
}

// static
int RegExpImpl::IrregexpPrepare(Isolate* isolate, Handle<JSRegExp> regexp,
                                Handle<String> subject) {
  DCHECK(subject->IsFlat());

  // Check representation of the underlying storage.
  bool is_one_byte = String::IsOneByteRepresentationUnderneath(*subject);
  if (!RegExpImpl::EnsureCompiledIrregexp(isolate, regexp, subject,
                                          is_one_byte)) {
    return -1;
  }

  // Only reserve room for output captures. Internal registers are allocated by
  // the engine.
  return JSRegExp::RegistersForCaptureCount(regexp->CaptureCount());
}

int RegExpImpl::IrregexpExecRaw(Isolate* isolate, Handle<JSRegExp> regexp,
                                Handle<String> subject, int index,
                                int32_t* output, int output_size) {
  DCHECK_LE(0, index);
  DCHECK_LE(index, subject->length());
  DCHECK(subject->IsFlat());
  DCHECK_GE(output_size,
            JSRegExp::RegistersForCaptureCount(regexp->CaptureCount()));

  bool is_one_byte = String::IsOneByteRepresentationUnderneath(*subject);

  if (!regexp->ShouldProduceBytecode()) {
    do {
      EnsureCompiledIrregexp(isolate, regexp, subject, is_one_byte);
      // 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.
      int res = NativeRegExpMacroAssembler::Match(regexp, subject, output,
                                                  output_size, index, isolate);
      if (res != NativeRegExpMacroAssembler::RETRY) {
        DCHECK(res != NativeRegExpMacroAssembler::EXCEPTION ||
               isolate->has_pending_exception());
        STATIC_ASSERT(static_cast<int>(NativeRegExpMacroAssembler::SUCCESS) ==
                      RegExp::RE_SUCCESS);
        STATIC_ASSERT(static_cast<int>(NativeRegExpMacroAssembler::FAILURE) ==
                      RegExp::RE_FAILURE);
        STATIC_ASSERT(static_cast<int>(NativeRegExpMacroAssembler::EXCEPTION) ==
                      RegExp::RE_EXCEPTION);
        return 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 Latin1 and UC16,
      // but the characters are always the same).
      is_one_byte = String::IsOneByteRepresentationUnderneath(*subject);
    } while (true);
    UNREACHABLE();
  } else {
    DCHECK(regexp->ShouldProduceBytecode());

    do {
      IrregexpInterpreter::Result result =
          IrregexpInterpreter::MatchForCallFromRuntime(
              isolate, regexp, subject, output, output_size, index);
      DCHECK_IMPLIES(result == IrregexpInterpreter::EXCEPTION,
                     isolate->has_pending_exception());

      switch (result) {
        case IrregexpInterpreter::SUCCESS:
        case IrregexpInterpreter::EXCEPTION:
        case IrregexpInterpreter::FAILURE:
        case IrregexpInterpreter::FALLBACK_TO_EXPERIMENTAL:
          return result;
        case IrregexpInterpreter::RETRY:
          // The string has changed representation, and we must restart the
          // match.
          // We need to reset the tier up to start over with compilation.
          if (FLAG_regexp_tier_up) regexp->ResetLastTierUpTick();
          is_one_byte = String::IsOneByteRepresentationUnderneath(*subject);
          EnsureCompiledIrregexp(isolate, regexp, subject, is_one_byte);
          break;
      }
    } while (true);
    UNREACHABLE();
  }
}

MaybeHandle<Object> RegExpImpl::IrregexpExec(
    Isolate* isolate, Handle<JSRegExp> regexp, Handle<String> subject,
    int previous_index, Handle<RegExpMatchInfo> last_match_info) {
  DCHECK_EQ(regexp->TypeTag(), JSRegExp::IRREGEXP);

  subject = String::Flatten(isolate, subject);

#ifdef DEBUG
  if (FLAG_trace_regexp_bytecodes && regexp->ShouldProduceBytecode()) {
    String pattern = regexp->Pattern();
    PrintF("\n\nRegexp match:   /%s/\n\n", pattern.ToCString().get());
    PrintF("\n\nSubject string: '%s'\n\n", subject->ToCString().get());
  }
#endif

  // For very long subject strings, the regexp interpreter is currently much
  // slower than the jitted code execution. If the tier-up strategy is turned
  // on, we want to avoid this performance penalty so we eagerly tier-up if the
  // subject string length is equal or greater than the given heuristic value.
  if (FLAG_regexp_tier_up &&
      subject->length() >= JSRegExp::kTierUpForSubjectLengthValue) {
    regexp->MarkTierUpForNextExec();
    if (FLAG_trace_regexp_tier_up) {
      PrintF(
          "Forcing tier-up for very long strings in "
          "RegExpImpl::IrregexpExec\n");
    }
  }

  // Prepare space for the return values.
  int required_registers =
      RegExpImpl::IrregexpPrepare(isolate, regexp, subject);
  if (required_registers < 0) {
    // Compiling failed with an exception.
    DCHECK(isolate->has_pending_exception());
    return MaybeHandle<Object>();
  }

  int32_t* output_registers = nullptr;
  if (required_registers > Isolate::kJSRegexpStaticOffsetsVectorSize) {
    output_registers = NewArray<int32_t>(required_registers);
  }
  std::unique_ptr<int32_t[]> auto_release(output_registers);
  if (output_registers == nullptr) {
    output_registers = isolate->jsregexp_static_offsets_vector();
  }

  int res =
      RegExpImpl::IrregexpExecRaw(isolate, regexp, subject, previous_index,
                                  output_registers, required_registers);

  if (res == RegExp::RE_SUCCESS) {
    int capture_count = regexp->CaptureCount();
    return RegExp::SetLastMatchInfo(isolate, last_match_info, subject,
                                    capture_count, output_registers);
  } else if (res == RegExp::RE_FALLBACK_TO_EXPERIMENTAL) {
    return ExperimentalRegExp::OneshotExec(isolate, regexp, subject,
                                           previous_index, last_match_info);
  } else if (res == RegExp::RE_EXCEPTION) {
    DCHECK(isolate->has_pending_exception());
    return MaybeHandle<Object>();
  } else {
    DCHECK(res == RegExp::RE_FAILURE);
    return isolate->factory()->null_value();
  }
}

// static
Handle<RegExpMatchInfo> RegExp::SetLastMatchInfo(
    Isolate* isolate, Handle<RegExpMatchInfo> last_match_info,
    Handle<String> subject, int capture_count, int32_t* match) {
  // This is the only place where match infos can grow. If, after executing the
  // regexp, RegExpExecStub finds that the match info is too small, it restarts
  // execution in RegExpImpl::Exec, which finally grows the match info right
  // here.
  Handle<RegExpMatchInfo> result =
      RegExpMatchInfo::ReserveCaptures(isolate, last_match_info, capture_count);
  if (*result != *last_match_info) {
    if (*last_match_info == *isolate->regexp_last_match_info()) {
      // This inner condition is only needed for special situations like the
      // regexp fuzzer, where we pass our own custom RegExpMatchInfo to
      // RegExpImpl::Exec; there actually want to bypass the Isolate's match
      // info and execute the regexp without side effects.
      isolate->native_context()->set_regexp_last_match_info(*result);
    }
  }

  int capture_register_count =
      JSRegExp::RegistersForCaptureCount(capture_count);
  DisallowHeapAllocation no_allocation;
  if (match != nullptr) {
    for (int i = 0; i < capture_register_count; i += 2) {
      result->SetCapture(i, match[i]);
      result->SetCapture(i + 1, match[i + 1]);
    }
  }
  result->SetLastSubject(*subject);
  result->SetLastInput(*subject);
  return result;
}

// static
void RegExp::DotPrintForTesting(const char* label, RegExpNode* node) {
  DotPrinter::DotPrint(label, node);
}

namespace {

// Returns true if we've either generated too much irregex code within this
// isolate, or the pattern string is too long.
bool TooMuchRegExpCode(Isolate* isolate, Handle<String> pattern) {
  // Limit the space regexps take up on the heap.  In order to limit this we
  // would like to keep track of the amount of regexp code on the heap.  This
  // is not tracked, however.  As a conservative approximation we track the
  // total regexp code compiled including code that has subsequently been freed
  // and the total executable memory at any point.
  static constexpr size_t kRegExpExecutableMemoryLimit = 16 * MB;
  static constexpr size_t kRegExpCompiledLimit = 1 * MB;

  Heap* heap = isolate->heap();
  if (pattern->length() > RegExp::kRegExpTooLargeToOptimize) return true;
  return (isolate->total_regexp_code_generated() > kRegExpCompiledLimit &&
          heap->CommittedMemoryExecutable() > kRegExpExecutableMemoryLimit);
}

}  // namespace

// static
bool RegExp::CompileForTesting(Isolate* isolate, Zone* zone,
                               RegExpCompileData* data, JSRegExp::Flags flags,
                               Handle<String> pattern,
                               Handle<String> sample_subject,
                               bool is_one_byte) {
  uint32_t backtrack_limit = JSRegExp::kNoBacktrackLimit;
  return RegExpImpl::Compile(isolate, zone, data, flags, pattern,
                             sample_subject, is_one_byte, backtrack_limit);
}

bool RegExpImpl::Compile(Isolate* isolate, Zone* zone, RegExpCompileData* data,
                         JSRegExp::Flags flags, Handle<String> pattern,
                         Handle<String> sample_subject, bool is_one_byte,
                         uint32_t& backtrack_limit) {
  if (JSRegExp::RegistersForCaptureCount(data->capture_count) >
      RegExpMacroAssembler::kMaxRegisterCount) {
    data->error = RegExpError::kTooLarge;
    return false;
  }

  RegExpCompiler compiler(isolate, zone, data->capture_count, is_one_byte);

  if (compiler.optimize()) {
    compiler.set_optimize(!TooMuchRegExpCode(isolate, pattern));
  }

  // Sample some characters from the middle of the string.
  static const int kSampleSize = 128;

  sample_subject = String::Flatten(isolate, 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));
  }

  data->node = compiler.PreprocessRegExp(data, flags, is_one_byte);
  data->error = AnalyzeRegExp(isolate, is_one_byte, data->node);
  if (data->error != RegExpError::kNone) {
    return false;
  }

  // Create the correct assembler for the architecture.
  std::unique_ptr<RegExpMacroAssembler> macro_assembler;
  if (data->compilation_target == RegExpCompilationTarget::kNative) {
    // Native regexp implementation.
    DCHECK(!FLAG_jitless);

    NativeRegExpMacroAssembler::Mode mode =
        is_one_byte ? NativeRegExpMacroAssembler::LATIN1
                    : NativeRegExpMacroAssembler::UC16;

    const int output_register_count =
        JSRegExp::RegistersForCaptureCount(data->capture_count);
#if V8_TARGET_ARCH_IA32
    macro_assembler.reset(new RegExpMacroAssemblerIA32(isolate, zone, mode,
                                                       output_register_count));
#elif V8_TARGET_ARCH_X64
    macro_assembler.reset(new RegExpMacroAssemblerX64(isolate, zone, mode,
                                                      output_register_count));
#elif V8_TARGET_ARCH_ARM
    macro_assembler.reset(new RegExpMacroAssemblerARM(isolate, zone, mode,
                                                      output_register_count));
#elif V8_TARGET_ARCH_ARM64
    macro_assembler.reset(new RegExpMacroAssemblerARM64(isolate, zone, mode,
                                                        output_register_count));
#elif V8_TARGET_ARCH_S390
    macro_assembler.reset(new RegExpMacroAssemblerS390(isolate, zone, mode,
                                                       output_register_count));
#elif V8_TARGET_ARCH_PPC || V8_TARGET_ARCH_PPC64
    macro_assembler.reset(new RegExpMacroAssemblerPPC(isolate, zone, mode,
                                                      output_register_count));
#elif V8_TARGET_ARCH_MIPS
    macro_assembler.reset(new RegExpMacroAssemblerMIPS(isolate, zone, mode,
                                                       output_register_count));
#elif V8_TARGET_ARCH_MIPS64
    macro_assembler.reset(new RegExpMacroAssemblerMIPS(isolate, zone, mode,
                                                       output_register_count));
#else
#error "Unsupported architecture"
#endif
  } else {
    DCHECK_EQ(data->compilation_target, RegExpCompilationTarget::kBytecode);
    // Interpreted regexp implementation.
    macro_assembler.reset(new RegExpBytecodeGenerator(isolate, zone));
  }

  macro_assembler->set_slow_safe(TooMuchRegExpCode(isolate, pattern));
  if (FLAG_enable_experimental_regexp_engine_on_excessive_backtracks &&
      ExperimentalRegExp::CanBeHandled(data->tree, flags,
                                       data->capture_count)) {
    if (backtrack_limit == JSRegExp::kNoBacktrackLimit) {
      backtrack_limit = FLAG_regexp_backtracks_before_fallback;
    } else {
      backtrack_limit =
          std::min(backtrack_limit, FLAG_regexp_backtracks_before_fallback);
    }
    macro_assembler->set_backtrack_limit(backtrack_limit);
    macro_assembler->set_can_fallback(true);
  } else {
    macro_assembler->set_backtrack_limit(backtrack_limit);
    macro_assembler->set_can_fallback(false);
  }

  // Inserted here, instead of in Assembler, because it depends on information
  // in the AST that isn't replicated in the Node structure.
  bool is_end_anchored = data->tree->IsAnchoredAtEnd();
  bool is_start_anchored = data->tree->IsAnchoredAtStart();
  int max_length = data->tree->max_match();
  static const int kMaxBacksearchLimit = 1024;
  if (is_end_anchored && !is_start_anchored && !IsSticky(flags) &&
      max_length < kMaxBacksearchLimit) {
    macro_assembler->SetCurrentPositionFromEnd(max_length);
  }

  if (IsGlobal(flags)) {
    RegExpMacroAssembler::GlobalMode mode = RegExpMacroAssembler::GLOBAL;
    if (data->tree->min_match() > 0) {
      mode = RegExpMacroAssembler::GLOBAL_NO_ZERO_LENGTH_CHECK;
    } else if (IsUnicode(flags)) {
      mode = RegExpMacroAssembler::GLOBAL_UNICODE;
    }
    macro_assembler->set_global_mode(mode);
  }

  RegExpMacroAssembler* macro_assembler_ptr = macro_assembler.get();
#ifdef DEBUG
  std::unique_ptr<RegExpMacroAssembler> tracer_macro_assembler;
  if (FLAG_trace_regexp_assembler) {
    tracer_macro_assembler.reset(
        new RegExpMacroAssemblerTracer(isolate, macro_assembler_ptr));
    macro_assembler_ptr = tracer_macro_assembler.get();
  }
#endif

  RegExpCompiler::CompilationResult result = compiler.Assemble(
      isolate, macro_assembler_ptr, data->node, data->capture_count, pattern);

  // Code / bytecode printing.
  {
#ifdef ENABLE_DISASSEMBLER
    if (FLAG_print_regexp_code &&
        data->compilation_target == RegExpCompilationTarget::kNative) {
      CodeTracer::Scope trace_scope(isolate->GetCodeTracer());
      OFStream os(trace_scope.file());
      Handle<Code> c = Handle<Code>::cast(result.code);
      auto pattern_cstring = pattern->ToCString();
      c->Disassemble(pattern_cstring.get(), os, isolate);
    }
#endif
    if (FLAG_print_regexp_bytecode &&
        data->compilation_target == RegExpCompilationTarget::kBytecode) {
      Handle<ByteArray> bytecode = Handle<ByteArray>::cast(result.code);
      auto pattern_cstring = pattern->ToCString();
      RegExpBytecodeDisassemble(bytecode->GetDataStartAddress(),
                                bytecode->length(), pattern_cstring.get());
    }
  }

  if (result.error != RegExpError::kNone) {
    if (FLAG_correctness_fuzzer_suppressions &&
        result.error == RegExpError::kStackOverflow) {
      FATAL("Aborting on stack overflow");
    }
    data->error = result.error;
  }

  data->code = result.code;
  data->register_count = result.num_registers;

  return result.Succeeded();
}

RegExpGlobalCache::RegExpGlobalCache(Handle<JSRegExp> regexp,
                                     Handle<String> subject, Isolate* isolate)
    : register_array_(nullptr),
      register_array_size_(0),
      regexp_(regexp),
      subject_(subject),
      isolate_(isolate) {
  DCHECK(IsGlobal(regexp->GetFlags()));

  switch (regexp_->TypeTag()) {
    case JSRegExp::NOT_COMPILED:
      UNREACHABLE();
    case JSRegExp::ATOM: {
      // ATOM regexps do not have a global loop, so we search for one match at
      // a time.
      static const int kAtomRegistersPerMatch = 2;
      registers_per_match_ = kAtomRegistersPerMatch;
      register_array_size_ = registers_per_match_;
      break;
    }
    case JSRegExp::IRREGEXP: {
      registers_per_match_ =
          RegExpImpl::IrregexpPrepare(isolate_, regexp_, subject_);
      if (registers_per_match_ < 0) {
        num_matches_ = -1;  // Signal exception.
        return;
      }
      if (regexp->ShouldProduceBytecode()) {
        // 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;
      } else {
        register_array_size_ = Max(registers_per_match_,
                                   Isolate::kJSRegexpStaticOffsetsVectorSize);
      }
      break;
    }
    case JSRegExp::EXPERIMENTAL: {
      if (!ExperimentalRegExp::IsCompiled(regexp, isolate_) &&
          !ExperimentalRegExp::Compile(isolate_, regexp)) {
        DCHECK(isolate->has_pending_exception());
        num_matches_ = -1;  // Signal exception.
        return;
      }
      registers_per_match_ =
          JSRegExp::RegistersForCaptureCount(regexp->CaptureCount());
      register_array_size_ =
          Max(registers_per_match_, Isolate::kJSRegexpStaticOffsetsVectorSize);
      break;
    }
  }

  max_matches_ = register_array_size_ / registers_per_match_;

  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_;
  DCHECK_LE(2, registers_per_match_);  // Each match has at least one capture.
  DCHECK_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;
}

RegExpGlobalCache::~RegExpGlobalCache() {
  // Deallocate the register array if we allocated it in the constructor
  // (as opposed to using the existing jsregexp_static_offsets_vector).
  if (register_array_size_ > Isolate::kJSRegexpStaticOffsetsVectorSize) {
    DeleteArray(register_array_);
  }
}

int RegExpGlobalCache::AdvanceZeroLength(int last_index) {
  if (IsUnicode(regexp_->GetFlags()) && last_index + 1 < subject_->length() &&
      unibrow::Utf16::IsLeadSurrogate(subject_->Get(last_index)) &&
      unibrow::Utf16::IsTrailSurrogate(subject_->Get(last_index + 1))) {
    // Advance over the surrogate pair.
    return last_index + 2;
  }
  return last_index + 1;
}

int32_t* RegExpGlobalCache::FetchNext() {
  current_match_index_++;

  if (current_match_index_ >= num_matches_) {
    // Current batch of results exhausted.
    // Fail if last batch was not even fully filled.
    if (num_matches_ < max_matches_) {
      num_matches_ = 0;  // Signal failed match.
      return nullptr;
    }

    int32_t* last_match =
        &register_array_[(current_match_index_ - 1) * registers_per_match_];
    int last_end_index = last_match[1];

    switch (regexp_->TypeTag()) {
      case JSRegExp::NOT_COMPILED:
        UNREACHABLE();
      case JSRegExp::ATOM:
        num_matches_ =
            RegExpImpl::AtomExecRaw(isolate_, regexp_, subject_, last_end_index,
                                    register_array_, register_array_size_);
        break;
      case JSRegExp::EXPERIMENTAL: {
        DCHECK(ExperimentalRegExp::IsCompiled(regexp_, isolate_));
        DisallowHeapAllocation no_gc;
        num_matches_ = ExperimentalRegExp::ExecRaw(
            isolate_, RegExp::kFromRuntime, *regexp_, *subject_,
            register_array_, register_array_size_, last_end_index);
        break;
      }
      case JSRegExp::IRREGEXP: {
        int last_start_index = last_match[0];
        if (last_start_index == last_end_index) {
          // Zero-length match. Advance by one code point.
          last_end_index = AdvanceZeroLength(last_end_index);
        }
        if (last_end_index > subject_->length()) {
          num_matches_ = 0;  // Signal failed match.
          return nullptr;
        }
        num_matches_ = RegExpImpl::IrregexpExecRaw(
            isolate_, regexp_, subject_, last_end_index, register_array_,
            register_array_size_);
        break;
      }
    }

    // Fall back to experimental engine if needed and possible.
    if (num_matches_ == RegExp::kInternalRegExpFallbackToExperimental) {
      num_matches_ = ExperimentalRegExp::OneshotExecRaw(
          isolate_, regexp_, subject_, register_array_, register_array_size_,
          last_end_index);
    }

    if (num_matches_ <= 0) {
      return nullptr;
    }
    current_match_index_ = 0;
    return register_array_;
  } else {
    return &register_array_[current_match_index_ * registers_per_match_];
  }
}

int32_t* RegExpGlobalCache::LastSuccessfulMatch() {
  int index = current_match_index_ * registers_per_match_;
  if (num_matches_ == 0) {
    // After a failed match we shift back by one result.
    index -= registers_per_match_;
  }
  return &register_array_[index];
}

Object RegExpResultsCache::Lookup(Heap* heap, String key_string,
                                  Object key_pattern,
                                  FixedArray* last_match_cache,
                                  ResultsCacheType type) {
  FixedArray cache;
  if (!key_string.IsInternalizedString()) return Smi::zero();
  if (type == STRING_SPLIT_SUBSTRINGS) {
    DCHECK(key_pattern.IsString());
    if (!key_pattern.IsInternalizedString()) return Smi::zero();
    cache = heap->string_split_cache();
  } else {
    DCHECK(type == REGEXP_MULTIPLE_INDICES);
    DCHECK(key_pattern.IsFixedArray());
    cache = heap->regexp_multiple_cache();
  }

  uint32_t hash = key_string.Hash();
  uint32_t index = ((hash & (kRegExpResultsCacheSize - 1)) &
                    ~(kArrayEntriesPerCacheEntry - 1));
  if (cache.get(index + kStringOffset) != key_string ||
      cache.get(index + kPatternOffset) != key_pattern) {
    index =
        ((index + kArrayEntriesPerCacheEntry) & (kRegExpResultsCacheSize - 1));
    if (cache.get(index + kStringOffset) != key_string ||
        cache.get(index + kPatternOffset) != key_pattern) {
      return Smi::zero();
    }
  }

  *last_match_cache = FixedArray::cast(cache.get(index + kLastMatchOffset));
  return cache.get(index + kArrayOffset);
}

void RegExpResultsCache::Enter(Isolate* isolate, Handle<String> key_string,
                               Handle<Object> key_pattern,
                               Handle<FixedArray> value_array,
                               Handle<FixedArray> last_match_cache,
                               ResultsCacheType type) {
  Factory* factory = isolate->factory();
  Handle<FixedArray> cache;
  if (!key_string->IsInternalizedString()) return;
  if (type == STRING_SPLIT_SUBSTRINGS) {
    DCHECK(key_pattern->IsString());
    if (!key_pattern->IsInternalizedString()) return;
    cache = factory->string_split_cache();
  } else {
    DCHECK(type == REGEXP_MULTIPLE_INDICES);
    DCHECK(key_pattern->IsFixedArray());
    cache = factory->regexp_multiple_cache();
  }

  uint32_t hash = key_string->Hash();
  uint32_t index = ((hash & (kRegExpResultsCacheSize - 1)) &
                    ~(kArrayEntriesPerCacheEntry - 1));
  if (cache->get(index + kStringOffset) == Smi::zero()) {
    cache->set(index + kStringOffset, *key_string);
    cache->set(index + kPatternOffset, *key_pattern);
    cache->set(index + kArrayOffset, *value_array);
    cache->set(index + kLastMatchOffset, *last_match_cache);
  } else {
    uint32_t index2 =
        ((index + kArrayEntriesPerCacheEntry) & (kRegExpResultsCacheSize - 1));
    if (cache->get(index2 + kStringOffset) == Smi::zero()) {
      cache->set(index2 + kStringOffset, *key_string);
      cache->set(index2 + kPatternOffset, *key_pattern);
      cache->set(index2 + kArrayOffset, *value_array);
      cache->set(index2 + kLastMatchOffset, *last_match_cache);
    } else {
      cache->set(index2 + kStringOffset, Smi::zero());
      cache->set(index2 + kPatternOffset, Smi::zero());
      cache->set(index2 + kArrayOffset, Smi::zero());
      cache->set(index2 + kLastMatchOffset, Smi::zero());
      cache->set(index + kStringOffset, *key_string);
      cache->set(index + kPatternOffset, *key_pattern);
      cache->set(index + kArrayOffset, *value_array);
      cache->set(index + kLastMatchOffset, *last_match_cache);
    }
  }
  // If the array is a reasonably short list of substrings, convert it into a
  // list of internalized strings.
  if (type == STRING_SPLIT_SUBSTRINGS && value_array->length() < 100) {
    for (int i = 0; i < value_array->length(); i++) {
      Handle<String> str(String::cast(value_array->get(i)), isolate);
      Handle<String> internalized_str = factory->InternalizeString(str);
      value_array->set(i, *internalized_str);
    }
  }
  // Convert backing store to a copy-on-write array.
  value_array->set_map_no_write_barrier(
      ReadOnlyRoots(isolate).fixed_cow_array_map());
}

void RegExpResultsCache::Clear(FixedArray cache) {
  for (int i = 0; i < kRegExpResultsCacheSize; i++) {
    cache.set(i, Smi::zero());
  }
}

}  // namespace internal
}  // namespace v8