src/mips/regexp-macro-assembler-mips.cc

root/src/mips/regexp-macro-assembler-mips.cc

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DEFINITIONS

This source file includes following definitions.
internal_failure_label_
stack_limit_slack
AdvanceCurrentPosition
AdvanceRegister
Backtrack
Bind
CheckCharacter
CheckCharacterGT
CheckAtStart
CheckNotAtStart
CheckCharacterLT
CheckCharacters
CheckGreedyLoop
CheckNotBackReferenceIgnoreCase
CheckNotBackReference
CheckNotCharacter
CheckCharacterAfterAnd
CheckNotCharacterAfterAnd
CheckNotCharacterAfterMinusAnd
CheckCharacterInRange
CheckCharacterNotInRange
CheckBitInTable
CheckSpecialCharacterClass
Fail
GetCode
GoTo
IfRegisterGE
IfRegisterLT
IfRegisterEqPos
Implementation
LoadCurrentCharacter
PopCurrentPosition
PopRegister
PushBacktrack
PushCurrentPosition
PushRegister
ReadCurrentPositionFromRegister
ReadStackPointerFromRegister
SetCurrentPositionFromEnd
SetRegister
Succeed
WriteCurrentPositionToRegister
ClearRegisters
WriteStackPointerToRegister
CallCheckStackGuardState
frame_entry
CheckStackGuardState
register_location
CheckPosition
BranchOrBacktrack
SafeCall
SafeReturn
SafeCallTarget
Push
Pop
CheckPreemption
CheckStackLimit
CallCFunctionUsingStub
LoadCurrentCharacterUnchecked
Generate
// Copyright 2012 the V8 project authors. All rights reserved.
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
//       notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
//       copyright notice, this list of conditions and the following
//       disclaimer in the documentation and/or other materials provided
//       with the distribution.
//     * Neither the name of Google Inc. nor the names of its
//       contributors may be used to endorse or promote products derived
//       from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

#include "v8.h"

#if defined(V8_TARGET_ARCH_MIPS)

#include "unicode.h"
#include "log.h"
#include "code-stubs.h"
#include "regexp-stack.h"
#include "macro-assembler.h"
#include "regexp-macro-assembler.h"
#include "mips/regexp-macro-assembler-mips.h"

namespace v8 {
namespace internal {

#ifndef V8_INTERPRETED_REGEXP
/*
 * This assembler uses the following register assignment convention
 * - t7 : Temporarily stores the index of capture start after a matching pass
 *        for a global regexp.
 * - t1 : Pointer to current code object (Code*) including heap object tag.
 * - t2 : Current position in input, as negative offset from end of string.
 *        Please notice that this is the byte offset, not the character offset!
 * - t3 : Currently loaded character. Must be loaded using
 *        LoadCurrentCharacter before using any of the dispatch methods.
 * - t4 : Points to tip of backtrack stack
 * - t5 : Unused.
 * - t6 : End of input (points to byte after last character in input).
 * - fp : Frame pointer. Used to access arguments, local variables and
 *         RegExp registers.
 * - sp : Points to tip of C stack.
 *
 * The remaining registers are free for computations.
 * Each call to a public method should retain this convention.
 *
 * The stack will have the following structure:
 *
 *  - fp[64]  Isolate* isolate   (address of the current isolate)
 *  - fp[60]  direct_call  (if 1, direct call from JavaScript code,
 *                          if 0, call through the runtime system).
 *  - fp[56]  stack_area_base (High end of the memory area to use as
 *                             backtracking stack).
 *  - fp[52]  capture array size (may fit multiple sets of matches)
 *  - fp[48]  int* capture_array (int[num_saved_registers_], for output).
 *  - fp[44]  secondary link/return address used by native call.
 *  --- sp when called ---
 *  - fp[40]  return address      (lr).
 *  - fp[36]  old frame pointer   (r11).
 *  - fp[0..32]  backup of registers s0..s7.
 *  --- frame pointer ----
 *  - fp[-4]  end of input       (address of end of string).
 *  - fp[-8]  start of input     (address of first character in string).
 *  - fp[-12] start index        (character index of start).
 *  - fp[-16] void* input_string (location of a handle containing the string).
 *  - fp[-20] success counter    (only for global regexps to count matches).
 *  - fp[-24] Offset of location before start of input (effectively character
 *            position -1). Used to initialize capture registers to a
 *            non-position.
 *  - fp[-28] At start (if 1, we are starting at the start of the
 *    string, otherwise 0)
 *  - fp[-32] register 0         (Only positions must be stored in the first
 *  -         register 1          num_saved_registers_ registers)
 *  -         ...
 *  -         register num_registers-1
 *  --- sp ---
 *
 * The first num_saved_registers_ registers are initialized to point to
 * "character -1" in the string (i.e., char_size() bytes before the first
 * character of the string). The remaining registers start out as garbage.
 *
 * The data up to the return address must be placed there by the calling
 * code and the remaining arguments are passed in registers, e.g. by calling the
 * code entry as cast to a function with the signature:
 * int (*match)(String* input_string,
 *              int start_index,
 *              Address start,
 *              Address end,
 *              Address secondary_return_address,  // Only used by native call.
 *              int* capture_output_array,
 *              byte* stack_area_base,
 *              bool direct_call = false)
 * The call is performed by NativeRegExpMacroAssembler::Execute()
 * (in regexp-macro-assembler.cc) via the CALL_GENERATED_REGEXP_CODE macro
 * in mips/simulator-mips.h.
 * When calling as a non-direct call (i.e., from C++ code), the return address
 * area is overwritten with the ra register by the RegExp code. When doing a
 * direct call from generated code, the return address is placed there by
 * the calling code, as in a normal exit frame.
 */

#define __ ACCESS_MASM(masm_)

RegExpMacroAssemblerMIPS::RegExpMacroAssemblerMIPS(
    Mode mode,
    int registers_to_save,
    Zone* zone)
    : NativeRegExpMacroAssembler(zone),
      masm_(new MacroAssembler(Isolate::Current(), NULL, kRegExpCodeSize)),
      mode_(mode),
      num_registers_(registers_to_save),
      num_saved_registers_(registers_to_save),
      entry_label_(),
      start_label_(),
      success_label_(),
      backtrack_label_(),
      exit_label_(),
      internal_failure_label_() {
  ASSERT_EQ(0, registers_to_save % 2);
  __ jmp(&entry_label_);   // We'll write the entry code later.
  // If the code gets too big or corrupted, an internal exception will be
  // raised, and we will exit right away.
  __ bind(&internal_failure_label_);
  __ li(v0, Operand(FAILURE));
  __ Ret();
  __ bind(&start_label_);  // And then continue from here.
}


RegExpMacroAssemblerMIPS::~RegExpMacroAssemblerMIPS() {
  delete masm_;
  // Unuse labels in case we throw away the assembler without calling GetCode.
  entry_label_.Unuse();
  start_label_.Unuse();
  success_label_.Unuse();
  backtrack_label_.Unuse();
  exit_label_.Unuse();
  check_preempt_label_.Unuse();
  stack_overflow_label_.Unuse();
  internal_failure_label_.Unuse();
}


int RegExpMacroAssemblerMIPS::stack_limit_slack()  {
  return RegExpStack::kStackLimitSlack;
}


void RegExpMacroAssemblerMIPS::AdvanceCurrentPosition(int by) {
  if (by != 0) {
    __ Addu(current_input_offset(),
            current_input_offset(), Operand(by * char_size()));
  }
}


void RegExpMacroAssemblerMIPS::AdvanceRegister(int reg, int by) {
  ASSERT(reg >= 0);
  ASSERT(reg < num_registers_);
  if (by != 0) {
    __ lw(a0, register_location(reg));
    __ Addu(a0, a0, Operand(by));
    __ sw(a0, register_location(reg));
  }
}


void RegExpMacroAssemblerMIPS::Backtrack() {
  CheckPreemption();
  // Pop Code* offset from backtrack stack, add Code* and jump to location.
  Pop(a0);
  __ Addu(a0, a0, code_pointer());
  __ Jump(a0);
}


void RegExpMacroAssemblerMIPS::Bind(Label* label) {
  __ bind(label);
}


void RegExpMacroAssemblerMIPS::CheckCharacter(uint32_t c, Label* on_equal) {
  BranchOrBacktrack(on_equal, eq, current_character(), Operand(c));
}


void RegExpMacroAssemblerMIPS::CheckCharacterGT(uc16 limit, Label* on_greater) {
  BranchOrBacktrack(on_greater, gt, current_character(), Operand(limit));
}


void RegExpMacroAssemblerMIPS::CheckAtStart(Label* on_at_start) {
  Label not_at_start;
  // Did we start the match at the start of the string at all?
  __ lw(a0, MemOperand(frame_pointer(), kStartIndex));
  BranchOrBacktrack(&not_at_start, ne, a0, Operand(zero_reg));

  // If we did, are we still at the start of the input?
  __ lw(a1, MemOperand(frame_pointer(), kInputStart));
  __ Addu(a0, end_of_input_address(), Operand(current_input_offset()));
  BranchOrBacktrack(on_at_start, eq, a0, Operand(a1));
  __ bind(&not_at_start);
}


void RegExpMacroAssemblerMIPS::CheckNotAtStart(Label* on_not_at_start) {
  // Did we start the match at the start of the string at all?
  __ lw(a0, MemOperand(frame_pointer(), kStartIndex));
  BranchOrBacktrack(on_not_at_start, ne, a0, Operand(zero_reg));
  // If we did, are we still at the start of the input?
  __ lw(a1, MemOperand(frame_pointer(), kInputStart));
  __ Addu(a0, end_of_input_address(), Operand(current_input_offset()));
  BranchOrBacktrack(on_not_at_start, ne, a0, Operand(a1));
}


void RegExpMacroAssemblerMIPS::CheckCharacterLT(uc16 limit, Label* on_less) {
  BranchOrBacktrack(on_less, lt, current_character(), Operand(limit));
}


void RegExpMacroAssemblerMIPS::CheckCharacters(Vector<const uc16> str,
                                               int cp_offset,
                                               Label* on_failure,
                                               bool check_end_of_string) {
  if (on_failure == NULL) {
    // Instead of inlining a backtrack for each test, (re)use the global
    // backtrack target.
    on_failure = &backtrack_label_;
  }

  if (check_end_of_string) {
    // Is last character of required match inside string.
    CheckPosition(cp_offset + str.length() - 1, on_failure);
  }

  __ Addu(a0, end_of_input_address(), Operand(current_input_offset()));
  if (cp_offset != 0) {
    int byte_offset = cp_offset * char_size();
    __ Addu(a0, a0, Operand(byte_offset));
  }

  // a0 : Address of characters to match against str.
  int stored_high_byte = 0;
  for (int i = 0; i < str.length(); i++) {
    if (mode_ == ASCII) {
      __ lbu(a1, MemOperand(a0, 0));
      __ addiu(a0, a0, char_size());
      ASSERT(str[i] <= String::kMaxAsciiCharCode);
      BranchOrBacktrack(on_failure, ne, a1, Operand(str[i]));
    } else {
      __ lhu(a1, MemOperand(a0, 0));
      __ addiu(a0, a0, char_size());
      uc16 match_char = str[i];
      int match_high_byte = (match_char >> 8);
      if (match_high_byte == 0) {
        BranchOrBacktrack(on_failure, ne, a1, Operand(str[i]));
      } else {
        if (match_high_byte != stored_high_byte) {
          __ li(a2, Operand(match_high_byte));
          stored_high_byte = match_high_byte;
        }
        __ Addu(a3, a2, Operand(match_char & 0xff));
        BranchOrBacktrack(on_failure, ne, a1, Operand(a3));
      }
    }
  }
}


void RegExpMacroAssemblerMIPS::CheckGreedyLoop(Label* on_equal) {
  Label backtrack_non_equal;
  __ lw(a0, MemOperand(backtrack_stackpointer(), 0));
  __ Branch(&backtrack_non_equal, ne, current_input_offset(), Operand(a0));
  __ Addu(backtrack_stackpointer(),
          backtrack_stackpointer(),
          Operand(kPointerSize));
  __ bind(&backtrack_non_equal);
  BranchOrBacktrack(on_equal, eq, current_input_offset(), Operand(a0));
}


void RegExpMacroAssemblerMIPS::CheckNotBackReferenceIgnoreCase(
    int start_reg,
    Label* on_no_match) {
  Label fallthrough;
  __ lw(a0, register_location(start_reg));  // Index of start of capture.
  __ lw(a1, register_location(start_reg + 1));  // Index of end of capture.
  __ Subu(a1, a1, a0);  // Length of capture.

  // If length is zero, either the capture is empty or it is not participating.
  // In either case succeed immediately.
  __ Branch(&fallthrough, eq, a1, Operand(zero_reg));

  __ Addu(t5, a1, current_input_offset());
  // Check that there are enough characters left in the input.
  BranchOrBacktrack(on_no_match, gt, t5, Operand(zero_reg));

  if (mode_ == ASCII) {
    Label success;
    Label fail;
    Label loop_check;

    // a0 - offset of start of capture.
    // a1 - length of capture.
    __ Addu(a0, a0, Operand(end_of_input_address()));
    __ Addu(a2, end_of_input_address(), Operand(current_input_offset()));
    __ Addu(a1, a0, Operand(a1));

    // a0 - Address of start of capture.
    // a1 - Address of end of capture.
    // a2 - Address of current input position.

    Label loop;
    __ bind(&loop);
    __ lbu(a3, MemOperand(a0, 0));
    __ addiu(a0, a0, char_size());
    __ lbu(t0, MemOperand(a2, 0));
    __ addiu(a2, a2, char_size());

    __ Branch(&loop_check, eq, t0, Operand(a3));

    // Mismatch, try case-insensitive match (converting letters to lower-case).
    __ Or(a3, a3, Operand(0x20));  // Convert capture character to lower-case.
    __ Or(t0, t0, Operand(0x20));  // Also convert input character.
    __ Branch(&fail, ne, t0, Operand(a3));
    __ Subu(a3, a3, Operand('a'));
    __ Branch(&fail, hi, a3, Operand('z' - 'a'));  // Is a3 a lowercase letter?

    __ bind(&loop_check);
    __ Branch(&loop, lt, a0, Operand(a1));
    __ jmp(&success);

    __ bind(&fail);
    GoTo(on_no_match);

    __ bind(&success);
    // Compute new value of character position after the matched part.
    __ Subu(current_input_offset(), a2, end_of_input_address());
  } else {
    ASSERT(mode_ == UC16);
    // Put regexp engine registers on stack.
    RegList regexp_registers_to_retain = current_input_offset().bit() |
        current_character().bit() | backtrack_stackpointer().bit();
    __ MultiPush(regexp_registers_to_retain);

    int argument_count = 4;
    __ PrepareCallCFunction(argument_count, a2);

    // a0 - offset of start of capture.
    // a1 - length of capture.

    // Put arguments into arguments registers.
    // Parameters are
    //   a0: Address byte_offset1 - Address captured substring's start.
    //   a1: Address byte_offset2 - Address of current character position.
    //   a2: size_t byte_length - length of capture in bytes(!).
    //   a3: Isolate* isolate.

    // Address of start of capture.
    __ Addu(a0, a0, Operand(end_of_input_address()));
    // Length of capture.
    __ mov(a2, a1);
    // Save length in callee-save register for use on return.
    __ mov(s3, a1);
    // Address of current input position.
    __ Addu(a1, current_input_offset(), Operand(end_of_input_address()));
    // Isolate.
    __ li(a3, Operand(ExternalReference::isolate_address()));

    {
      AllowExternalCallThatCantCauseGC scope(masm_);
      ExternalReference function =
          ExternalReference::re_case_insensitive_compare_uc16(masm_->isolate());
      __ CallCFunction(function, argument_count);
    }

    // Restore regexp engine registers.
    __ MultiPop(regexp_registers_to_retain);
    __ li(code_pointer(), Operand(masm_->CodeObject()), CONSTANT_SIZE);
    __ lw(end_of_input_address(), MemOperand(frame_pointer(), kInputEnd));

    // Check if function returned non-zero for success or zero for failure.
    BranchOrBacktrack(on_no_match, eq, v0, Operand(zero_reg));
    // On success, increment position by length of capture.
    __ Addu(current_input_offset(), current_input_offset(), Operand(s3));
  }

  __ bind(&fallthrough);
}


void RegExpMacroAssemblerMIPS::CheckNotBackReference(
    int start_reg,
    Label* on_no_match) {
  Label fallthrough;
  Label success;

  // Find length of back-referenced capture.
  __ lw(a0, register_location(start_reg));
  __ lw(a1, register_location(start_reg + 1));
  __ Subu(a1, a1, a0);  // Length to check.
  // Succeed on empty capture (including no capture).
  __ Branch(&fallthrough, eq, a1, Operand(zero_reg));

  __ Addu(t5, a1, current_input_offset());
  // Check that there are enough characters left in the input.
  BranchOrBacktrack(on_no_match, gt, t5, Operand(zero_reg));

  // Compute pointers to match string and capture string.
  __ Addu(a0, a0, Operand(end_of_input_address()));
  __ Addu(a2, end_of_input_address(), Operand(current_input_offset()));
  __ Addu(a1, a1, Operand(a0));

  Label loop;
  __ bind(&loop);
  if (mode_ == ASCII) {
    __ lbu(a3, MemOperand(a0, 0));
    __ addiu(a0, a0, char_size());
    __ lbu(t0, MemOperand(a2, 0));
    __ addiu(a2, a2, char_size());
  } else {
    ASSERT(mode_ == UC16);
    __ lhu(a3, MemOperand(a0, 0));
    __ addiu(a0, a0, char_size());
    __ lhu(t0, MemOperand(a2, 0));
    __ addiu(a2, a2, char_size());
  }
  BranchOrBacktrack(on_no_match, ne, a3, Operand(t0));
  __ Branch(&loop, lt, a0, Operand(a1));

  // Move current character position to position after match.
  __ Subu(current_input_offset(), a2, end_of_input_address());
  __ bind(&fallthrough);
}


void RegExpMacroAssemblerMIPS::CheckNotCharacter(uint32_t c,
                                                 Label* on_not_equal) {
  BranchOrBacktrack(on_not_equal, ne, current_character(), Operand(c));
}


void RegExpMacroAssemblerMIPS::CheckCharacterAfterAnd(uint32_t c,
                                                      uint32_t mask,
                                                      Label* on_equal) {
  __ And(a0, current_character(), Operand(mask));
  Operand rhs = (c == 0) ? Operand(zero_reg) : Operand(c);
  BranchOrBacktrack(on_equal, eq, a0, rhs);
}


void RegExpMacroAssemblerMIPS::CheckNotCharacterAfterAnd(uint32_t c,
                                                         uint32_t mask,
                                                         Label* on_not_equal) {
  __ And(a0, current_character(), Operand(mask));
  Operand rhs = (c == 0) ? Operand(zero_reg) : Operand(c);
  BranchOrBacktrack(on_not_equal, ne, a0, rhs);
}


void RegExpMacroAssemblerMIPS::CheckNotCharacterAfterMinusAnd(
    uc16 c,
    uc16 minus,
    uc16 mask,
    Label* on_not_equal) {
  ASSERT(minus < String::kMaxUtf16CodeUnit);
  __ Subu(a0, current_character(), Operand(minus));
  __ And(a0, a0, Operand(mask));
  BranchOrBacktrack(on_not_equal, ne, a0, Operand(c));
}


void RegExpMacroAssemblerMIPS::CheckCharacterInRange(
    uc16 from,
    uc16 to,
    Label* on_in_range) {
  __ Subu(a0, current_character(), Operand(from));
  // Unsigned lower-or-same condition.
  BranchOrBacktrack(on_in_range, ls, a0, Operand(to - from));
}


void RegExpMacroAssemblerMIPS::CheckCharacterNotInRange(
    uc16 from,
    uc16 to,
    Label* on_not_in_range) {
  __ Subu(a0, current_character(), Operand(from));
  // Unsigned higher condition.
  BranchOrBacktrack(on_not_in_range, hi, a0, Operand(to - from));
}


void RegExpMacroAssemblerMIPS::CheckBitInTable(
    Handle<ByteArray> table,
    Label* on_bit_set) {
  __ li(a0, Operand(table));
  if (mode_ != ASCII || kTableMask != String::kMaxAsciiCharCode) {
    __ And(a1, current_character(), Operand(kTableSize - 1));
    __ Addu(a0, a0, a1);
  } else {
    __ Addu(a0, a0, current_character());
  }

  __ lbu(a0, FieldMemOperand(a0, ByteArray::kHeaderSize));
  BranchOrBacktrack(on_bit_set, ne, a0, Operand(zero_reg));
}


bool RegExpMacroAssemblerMIPS::CheckSpecialCharacterClass(uc16 type,
                                                          Label* on_no_match) {
  // Range checks (c in min..max) are generally implemented by an unsigned
  // (c - min) <= (max - min) check.
  switch (type) {
  case 's':
    // Match space-characters.
    if (mode_ == ASCII) {
      // ASCII space characters are '\t'..'\r' and ' '.
      Label success;
      __ Branch(&success, eq, current_character(), Operand(' '));
      // Check range 0x09..0x0d.
      __ Subu(a0, current_character(), Operand('\t'));
      BranchOrBacktrack(on_no_match, hi, a0, Operand('\r' - '\t'));
      __ bind(&success);
      return true;
    }
    return false;
  case 'S':
    // Match non-space characters.
    if (mode_ == ASCII) {
      // ASCII space characters are '\t'..'\r' and ' '.
      BranchOrBacktrack(on_no_match, eq, current_character(), Operand(' '));
      __ Subu(a0, current_character(), Operand('\t'));
      BranchOrBacktrack(on_no_match, ls, a0, Operand('\r' - '\t'));
      return true;
    }
    return false;
  case 'd':
    // Match ASCII digits ('0'..'9').
    __ Subu(a0, current_character(), Operand('0'));
    BranchOrBacktrack(on_no_match, hi, a0, Operand('9' - '0'));
    return true;
  case 'D':
    // Match non ASCII-digits.
    __ Subu(a0, current_character(), Operand('0'));
    BranchOrBacktrack(on_no_match, ls, a0, Operand('9' - '0'));
    return true;
  case '.': {
    // Match non-newlines (not 0x0a('\n'), 0x0d('\r'), 0x2028 and 0x2029).
    __ Xor(a0, current_character(), Operand(0x01));
    // See if current character is '\n'^1 or '\r'^1, i.e., 0x0b or 0x0c.
    __ Subu(a0, a0, Operand(0x0b));
    BranchOrBacktrack(on_no_match, ls, a0, Operand(0x0c - 0x0b));
    if (mode_ == UC16) {
      // Compare original value to 0x2028 and 0x2029, using the already
      // computed (current_char ^ 0x01 - 0x0b). I.e., check for
      // 0x201d (0x2028 - 0x0b) or 0x201e.
      __ Subu(a0, a0, Operand(0x2028 - 0x0b));
      BranchOrBacktrack(on_no_match, ls, a0, Operand(1));
    }
    return true;
  }
  case 'n': {
    // Match newlines (0x0a('\n'), 0x0d('\r'), 0x2028 and 0x2029).
    __ Xor(a0, current_character(), Operand(0x01));
    // See if current character is '\n'^1 or '\r'^1, i.e., 0x0b or 0x0c.
    __ Subu(a0, a0, Operand(0x0b));
    if (mode_ == ASCII) {
      BranchOrBacktrack(on_no_match, hi, a0, Operand(0x0c - 0x0b));
    } else {
      Label done;
      BranchOrBacktrack(&done, ls, a0, Operand(0x0c - 0x0b));
      // Compare original value to 0x2028 and 0x2029, using the already
      // computed (current_char ^ 0x01 - 0x0b). I.e., check for
      // 0x201d (0x2028 - 0x0b) or 0x201e.
      __ Subu(a0, a0, Operand(0x2028 - 0x0b));
      BranchOrBacktrack(on_no_match, hi, a0, Operand(1));
      __ bind(&done);
    }
    return true;
  }
  case 'w': {
    if (mode_ != ASCII) {
      // Table is 128 entries, so all ASCII characters can be tested.
      BranchOrBacktrack(on_no_match, hi, current_character(), Operand('z'));
    }
    ExternalReference map = ExternalReference::re_word_character_map();
    __ li(a0, Operand(map));
    __ Addu(a0, a0, current_character());
    __ lbu(a0, MemOperand(a0, 0));
    BranchOrBacktrack(on_no_match, eq, a0, Operand(zero_reg));
    return true;
  }
  case 'W': {
    Label done;
    if (mode_ != ASCII) {
      // Table is 128 entries, so all ASCII characters can be tested.
      __ Branch(&done, hi, current_character(), Operand('z'));
    }
    ExternalReference map = ExternalReference::re_word_character_map();
    __ li(a0, Operand(map));
    __ Addu(a0, a0, current_character());
    __ lbu(a0, MemOperand(a0, 0));
    BranchOrBacktrack(on_no_match, ne, a0, Operand(zero_reg));
    if (mode_ != ASCII) {
      __ bind(&done);
    }
    return true;
  }
  case '*':
    // Match any character.
    return true;
  // No custom implementation (yet): s(UC16), S(UC16).
  default:
    return false;
  }
}


void RegExpMacroAssemblerMIPS::Fail() {
  __ li(v0, Operand(FAILURE));
  __ jmp(&exit_label_);
}


Handle<HeapObject> RegExpMacroAssemblerMIPS::GetCode(Handle<String> source) {
  Label return_v0;
  if (masm_->has_exception()) {
    // If the code gets corrupted due to long regular expressions and lack of
    // space on trampolines, an internal exception flag is set. If this case
    // is detected, we will jump into exit sequence right away.
    __ bind_to(&entry_label_, internal_failure_label_.pos());
  } else {
    // Finalize code - write the entry point code now we know how many
    // registers we need.

    // Entry code:
    __ bind(&entry_label_);

    // Tell the system that we have a stack frame.  Because the type is MANUAL,
    // no is generated.
    FrameScope scope(masm_, StackFrame::MANUAL);

    // Actually emit code to start a new stack frame.
    // Push arguments
    // Save callee-save registers.
    // Start new stack frame.
    // Store link register in existing stack-cell.
    // Order here should correspond to order of offset constants in header file.
    RegList registers_to_retain = s0.bit() | s1.bit() | s2.bit() |
        s3.bit() | s4.bit() | s5.bit() | s6.bit() | s7.bit() | fp.bit();
    RegList argument_registers = a0.bit() | a1.bit() | a2.bit() | a3.bit();
    __ MultiPush(argument_registers | registers_to_retain | ra.bit());
    // Set frame pointer in space for it if this is not a direct call
    // from generated code.
    __ Addu(frame_pointer(), sp, Operand(4 * kPointerSize));
    __ mov(a0, zero_reg);
    __ push(a0);  // Make room for success counter and initialize it to 0.
    __ push(a0);  // Make room for "position - 1" constant (value irrelevant).

    // Check if we have space on the stack for registers.
    Label stack_limit_hit;
    Label stack_ok;

    ExternalReference stack_limit =
        ExternalReference::address_of_stack_limit(masm_->isolate());
    __ li(a0, Operand(stack_limit));
    __ lw(a0, MemOperand(a0));
    __ Subu(a0, sp, a0);
    // Handle it if the stack pointer is already below the stack limit.
    __ Branch(&stack_limit_hit, le, a0, Operand(zero_reg));
    // Check if there is room for the variable number of registers above
    // the stack limit.
    __ Branch(&stack_ok, hs, a0, Operand(num_registers_ * kPointerSize));
    // Exit with OutOfMemory exception. There is not enough space on the stack
    // for our working registers.
    __ li(v0, Operand(EXCEPTION));
    __ jmp(&return_v0);

    __ bind(&stack_limit_hit);
    CallCheckStackGuardState(a0);
    // If returned value is non-zero, we exit with the returned value as result.
    __ Branch(&return_v0, ne, v0, Operand(zero_reg));

    __ bind(&stack_ok);
    // Allocate space on stack for registers.
    __ Subu(sp, sp, Operand(num_registers_ * kPointerSize));
    // Load string end.
    __ lw(end_of_input_address(), MemOperand(frame_pointer(), kInputEnd));
    // Load input start.
    __ lw(a0, MemOperand(frame_pointer(), kInputStart));
    // Find negative length (offset of start relative to end).
    __ Subu(current_input_offset(), a0, end_of_input_address());
    // Set a0 to address of char before start of the input string
    // (effectively string position -1).
    __ lw(a1, MemOperand(frame_pointer(), kStartIndex));
    __ Subu(a0, current_input_offset(), Operand(char_size()));
    __ sll(t5, a1, (mode_ == UC16) ? 1 : 0);
    __ Subu(a0, a0, t5);
    // Store this value in a local variable, for use when clearing
    // position registers.
    __ sw(a0, MemOperand(frame_pointer(), kInputStartMinusOne));

    // Initialize code pointer register
    __ li(code_pointer(), Operand(masm_->CodeObject()), CONSTANT_SIZE);

    Label load_char_start_regexp, start_regexp;
    // Load newline if index is at start, previous character otherwise.
    __ Branch(&load_char_start_regexp, ne, a1, Operand(zero_reg));
    __ li(current_character(), Operand('\n'));
    __ jmp(&start_regexp);

    // Global regexp restarts matching here.
    __ bind(&load_char_start_regexp);
    // Load previous char as initial value of current character register.
    LoadCurrentCharacterUnchecked(-1, 1);
    __ bind(&start_regexp);

    // Initialize on-stack registers.
    if (num_saved_registers_ > 0) {  // Always is, if generated from a regexp.
      // Fill saved registers with initial value = start offset - 1.
      if (num_saved_registers_ > 8) {
        // Address of register 0.
        __ Addu(a1, frame_pointer(), Operand(kRegisterZero));
        __ li(a2, Operand(num_saved_registers_));
        Label init_loop;
        __ bind(&init_loop);
        __ sw(a0, MemOperand(a1));
        __ Addu(a1, a1, Operand(-kPointerSize));
        __ Subu(a2, a2, Operand(1));
        __ Branch(&init_loop, ne, a2, Operand(zero_reg));
      } else {
        for (int i = 0; i < num_saved_registers_; i++) {
          __ sw(a0, register_location(i));
        }
      }
    }

    // Initialize backtrack stack pointer.
    __ lw(backtrack_stackpointer(), MemOperand(frame_pointer(), kStackHighEnd));

    __ jmp(&start_label_);


    // Exit code:
    if (success_label_.is_linked()) {
      // Save captures when successful.
      __ bind(&success_label_);
      if (num_saved_registers_ > 0) {
        // Copy captures to output.
        __ lw(a1, MemOperand(frame_pointer(), kInputStart));
        __ lw(a0, MemOperand(frame_pointer(), kRegisterOutput));
        __ lw(a2, MemOperand(frame_pointer(), kStartIndex));
        __ Subu(a1, end_of_input_address(), a1);
        // a1 is length of input in bytes.
        if (mode_ == UC16) {
          __ srl(a1, a1, 1);
        }
        // a1 is length of input in characters.
        __ Addu(a1, a1, Operand(a2));
        // a1 is length of string in characters.

        ASSERT_EQ(0, num_saved_registers_ % 2);
        // Always an even number of capture registers. This allows us to
        // unroll the loop once to add an operation between a load of a register
        // and the following use of that register.
        for (int i = 0; i < num_saved_registers_; i += 2) {
          __ lw(a2, register_location(i));
          __ lw(a3, register_location(i + 1));
          if (i == 0 && global_with_zero_length_check()) {
            // Keep capture start in a4 for the zero-length check later.
            __ mov(t7, a2);
          }
          if (mode_ == UC16) {
            __ sra(a2, a2, 1);
            __ Addu(a2, a2, a1);
            __ sra(a3, a3, 1);
            __ Addu(a3, a3, a1);
          } else {
            __ Addu(a2, a1, Operand(a2));
            __ Addu(a3, a1, Operand(a3));
          }
          __ sw(a2, MemOperand(a0));
          __ Addu(a0, a0, kPointerSize);
          __ sw(a3, MemOperand(a0));
          __ Addu(a0, a0, kPointerSize);
        }
      }

      if (global()) {
        // Restart matching if the regular expression is flagged as global.
        __ lw(a0, MemOperand(frame_pointer(), kSuccessfulCaptures));
        __ lw(a1, MemOperand(frame_pointer(), kNumOutputRegisters));
        __ lw(a2, MemOperand(frame_pointer(), kRegisterOutput));
        // Increment success counter.
        __ Addu(a0, a0, 1);
        __ sw(a0, MemOperand(frame_pointer(), kSuccessfulCaptures));
        // Capture results have been stored, so the number of remaining global
        // output registers is reduced by the number of stored captures.
        __ Subu(a1, a1, num_saved_registers_);
        // Check whether we have enough room for another set of capture results.
        __ mov(v0, a0);
        __ Branch(&return_v0, lt, a1, Operand(num_saved_registers_));

        __ sw(a1, MemOperand(frame_pointer(), kNumOutputRegisters));
        // Advance the location for output.
        __ Addu(a2, a2, num_saved_registers_ * kPointerSize);
        __ sw(a2, MemOperand(frame_pointer(), kRegisterOutput));

        // Prepare a0 to initialize registers with its value in the next run.
        __ lw(a0, MemOperand(frame_pointer(), kInputStartMinusOne));

        if (global_with_zero_length_check()) {
          // Special case for zero-length matches.
          // t7: capture start index
          // Not a zero-length match, restart.
          __ Branch(
              &load_char_start_regexp, ne, current_input_offset(), Operand(t7));
          // Offset from the end is zero if we already reached the end.
          __ Branch(&exit_label_, eq, current_input_offset(),
                    Operand(zero_reg));
          // Advance current position after a zero-length match.
          __ Addu(current_input_offset(),
                  current_input_offset(),
                  Operand((mode_ == UC16) ? 2 : 1));
        }

        __ Branch(&load_char_start_regexp);
      } else {
        __ li(v0, Operand(SUCCESS));
      }
    }
    // Exit and return v0.
    __ bind(&exit_label_);
    if (global()) {
      __ lw(v0, MemOperand(frame_pointer(), kSuccessfulCaptures));
    }

    __ bind(&return_v0);
    // Skip sp past regexp registers and local variables..
    __ mov(sp, frame_pointer());
    // Restore registers s0..s7 and return (restoring ra to pc).
    __ MultiPop(registers_to_retain | ra.bit());
    __ Ret();

    // Backtrack code (branch target for conditional backtracks).
    if (backtrack_label_.is_linked()) {
      __ bind(&backtrack_label_);
      Backtrack();
    }

    Label exit_with_exception;

    // Preempt-code.
    if (check_preempt_label_.is_linked()) {
      SafeCallTarget(&check_preempt_label_);
      // Put regexp engine registers on stack.
      RegList regexp_registers_to_retain = current_input_offset().bit() |
          current_character().bit() | backtrack_stackpointer().bit();
      __ MultiPush(regexp_registers_to_retain);
      CallCheckStackGuardState(a0);
      __ MultiPop(regexp_registers_to_retain);
      // If returning non-zero, we should end execution with the given
      // result as return value.
      __ Branch(&return_v0, ne, v0, Operand(zero_reg));

      // String might have moved: Reload end of string from frame.
      __ lw(end_of_input_address(), MemOperand(frame_pointer(), kInputEnd));
      __ li(code_pointer(), Operand(masm_->CodeObject()), CONSTANT_SIZE);
      SafeReturn();
    }

    // Backtrack stack overflow code.
    if (stack_overflow_label_.is_linked()) {
      SafeCallTarget(&stack_overflow_label_);
      // Reached if the backtrack-stack limit has been hit.
      // Put regexp engine registers on stack first.
      RegList regexp_registers = current_input_offset().bit() |
          current_character().bit();
      __ MultiPush(regexp_registers);
      Label grow_failed;
      // Call GrowStack(backtrack_stackpointer(), &stack_base)
      static const int num_arguments = 3;
      __ PrepareCallCFunction(num_arguments, a0);
      __ mov(a0, backtrack_stackpointer());
      __ Addu(a1, frame_pointer(), Operand(kStackHighEnd));
      __ li(a2, Operand(ExternalReference::isolate_address()));
      ExternalReference grow_stack =
          ExternalReference::re_grow_stack(masm_->isolate());
      __ CallCFunction(grow_stack, num_arguments);
      // Restore regexp registers.
      __ MultiPop(regexp_registers);
      // If return NULL, we have failed to grow the stack, and
      // must exit with a stack-overflow exception.
      __ Branch(&exit_with_exception, eq, v0, Operand(zero_reg));
      // Otherwise use return value as new stack pointer.
      __ mov(backtrack_stackpointer(), v0);
      // Restore saved registers and continue.
      __ li(code_pointer(), Operand(masm_->CodeObject()), CONSTANT_SIZE);
      __ lw(end_of_input_address(), MemOperand(frame_pointer(), kInputEnd));
      SafeReturn();
    }

    if (exit_with_exception.is_linked()) {
      // If any of the code above needed to exit with an exception.
      __ bind(&exit_with_exception);
      // Exit with Result EXCEPTION(-1) to signal thrown exception.
      __ li(v0, Operand(EXCEPTION));
      __ jmp(&return_v0);
    }
  }

  CodeDesc code_desc;
  masm_->GetCode(&code_desc);
  Handle<Code> code = FACTORY->NewCode(code_desc,
                                       Code::ComputeFlags(Code::REGEXP),
                                       masm_->CodeObject());
  LOG(Isolate::Current(), RegExpCodeCreateEvent(*code, *source));
  return Handle<HeapObject>::cast(code);
}


void RegExpMacroAssemblerMIPS::GoTo(Label* to) {
  if (to == NULL) {
    Backtrack();
    return;
  }
  __ jmp(to);
  return;
}


void RegExpMacroAssemblerMIPS::IfRegisterGE(int reg,
                                            int comparand,
                                            Label* if_ge) {
  __ lw(a0, register_location(reg));
    BranchOrBacktrack(if_ge, ge, a0, Operand(comparand));
}


void RegExpMacroAssemblerMIPS::IfRegisterLT(int reg,
                                            int comparand,
                                            Label* if_lt) {
  __ lw(a0, register_location(reg));
  BranchOrBacktrack(if_lt, lt, a0, Operand(comparand));
}


void RegExpMacroAssemblerMIPS::IfRegisterEqPos(int reg,
                                               Label* if_eq) {
  __ lw(a0, register_location(reg));
  BranchOrBacktrack(if_eq, eq, a0, Operand(current_input_offset()));
}


RegExpMacroAssembler::IrregexpImplementation
    RegExpMacroAssemblerMIPS::Implementation() {
  return kMIPSImplementation;
}


void RegExpMacroAssemblerMIPS::LoadCurrentCharacter(int cp_offset,
                                                    Label* on_end_of_input,
                                                    bool check_bounds,
                                                    int characters) {
  ASSERT(cp_offset >= -1);      // ^ and \b can look behind one character.
  ASSERT(cp_offset < (1<<30));  // Be sane! (And ensure negation works).
  if (check_bounds) {
    CheckPosition(cp_offset + characters - 1, on_end_of_input);
  }
  LoadCurrentCharacterUnchecked(cp_offset, characters);
}


void RegExpMacroAssemblerMIPS::PopCurrentPosition() {
  Pop(current_input_offset());
}


void RegExpMacroAssemblerMIPS::PopRegister(int register_index) {
  Pop(a0);
  __ sw(a0, register_location(register_index));
}


void RegExpMacroAssemblerMIPS::PushBacktrack(Label* label) {
  if (label->is_bound()) {
    int target = label->pos();
    __ li(a0, Operand(target + Code::kHeaderSize - kHeapObjectTag));
  } else {
    Label after_constant;
    __ Branch(&after_constant);
    int offset = masm_->pc_offset();
    int cp_offset = offset + Code::kHeaderSize - kHeapObjectTag;
    __ emit(0);
    masm_->label_at_put(label, offset);
    __ bind(&after_constant);
    if (is_int16(cp_offset)) {
      __ lw(a0, MemOperand(code_pointer(), cp_offset));
    } else {
      __ Addu(a0, code_pointer(), cp_offset);
      __ lw(a0, MemOperand(a0, 0));
    }
  }
  Push(a0);
  CheckStackLimit();
}


void RegExpMacroAssemblerMIPS::PushCurrentPosition() {
  Push(current_input_offset());
}


void RegExpMacroAssemblerMIPS::PushRegister(int register_index,
                                            StackCheckFlag check_stack_limit) {
  __ lw(a0, register_location(register_index));
  Push(a0);
  if (check_stack_limit) CheckStackLimit();
}


void RegExpMacroAssemblerMIPS::ReadCurrentPositionFromRegister(int reg) {
  __ lw(current_input_offset(), register_location(reg));
}


void RegExpMacroAssemblerMIPS::ReadStackPointerFromRegister(int reg) {
  __ lw(backtrack_stackpointer(), register_location(reg));
  __ lw(a0, MemOperand(frame_pointer(), kStackHighEnd));
  __ Addu(backtrack_stackpointer(), backtrack_stackpointer(), Operand(a0));
}


void RegExpMacroAssemblerMIPS::SetCurrentPositionFromEnd(int by) {
  Label after_position;
  __ Branch(&after_position,
            ge,
            current_input_offset(),
            Operand(-by * char_size()));
  __ li(current_input_offset(), -by * char_size());
  // On RegExp code entry (where this operation is used), the character before
  // the current position is expected to be already loaded.
  // We have advanced the position, so it's safe to read backwards.
  LoadCurrentCharacterUnchecked(-1, 1);
  __ bind(&after_position);
}


void RegExpMacroAssemblerMIPS::SetRegister(int register_index, int to) {
  ASSERT(register_index >= num_saved_registers_);  // Reserved for positions!
  __ li(a0, Operand(to));
  __ sw(a0, register_location(register_index));
}


bool RegExpMacroAssemblerMIPS::Succeed() {
  __ jmp(&success_label_);
  return global();
}


void RegExpMacroAssemblerMIPS::WriteCurrentPositionToRegister(int reg,
                                                              int cp_offset) {
  if (cp_offset == 0) {
    __ sw(current_input_offset(), register_location(reg));
  } else {
    __ Addu(a0, current_input_offset(), Operand(cp_offset * char_size()));
    __ sw(a0, register_location(reg));
  }
}


void RegExpMacroAssemblerMIPS::ClearRegisters(int reg_from, int reg_to) {
  ASSERT(reg_from <= reg_to);
  __ lw(a0, MemOperand(frame_pointer(), kInputStartMinusOne));
  for (int reg = reg_from; reg <= reg_to; reg++) {
    __ sw(a0, register_location(reg));
  }
}


void RegExpMacroAssemblerMIPS::WriteStackPointerToRegister(int reg) {
  __ lw(a1, MemOperand(frame_pointer(), kStackHighEnd));
  __ Subu(a0, backtrack_stackpointer(), a1);
  __ sw(a0, register_location(reg));
}


// Private methods:

void RegExpMacroAssemblerMIPS::CallCheckStackGuardState(Register scratch) {
  static const int num_arguments = 3;
  __ PrepareCallCFunction(num_arguments, scratch);
  __ mov(a2, frame_pointer());
  // Code* of self.
  __ li(a1, Operand(masm_->CodeObject()), CONSTANT_SIZE);
  // a0 becomes return address pointer.
  ExternalReference stack_guard_check =
      ExternalReference::re_check_stack_guard_state(masm_->isolate());
  CallCFunctionUsingStub(stack_guard_check, num_arguments);
}


// Helper function for reading a value out of a stack frame.
template <typename T>
static T& frame_entry(Address re_frame, int frame_offset) {
  return reinterpret_cast<T&>(Memory::int32_at(re_frame + frame_offset));
}


int RegExpMacroAssemblerMIPS::CheckStackGuardState(Address* return_address,
                                                   Code* re_code,
                                                   Address re_frame) {
  Isolate* isolate = frame_entry<Isolate*>(re_frame, kIsolate);
  ASSERT(isolate == Isolate::Current());
  if (isolate->stack_guard()->IsStackOverflow()) {
    isolate->StackOverflow();
    return EXCEPTION;
  }

  // If not real stack overflow the stack guard was used to interrupt
  // execution for another purpose.

  // If this is a direct call from JavaScript retry the RegExp forcing the call
  // through the runtime system. Currently the direct call cannot handle a GC.
  if (frame_entry<int>(re_frame, kDirectCall) == 1) {
    return RETRY;
  }

  // Prepare for possible GC.
  HandleScope handles(isolate);
  Handle<Code> code_handle(re_code);

  Handle<String> subject(frame_entry<String*>(re_frame, kInputString));
  // Current string.
  bool is_ascii = subject->IsAsciiRepresentationUnderneath();

  ASSERT(re_code->instruction_start() <= *return_address);
  ASSERT(*return_address <=
      re_code->instruction_start() + re_code->instruction_size());

  MaybeObject* result = Execution::HandleStackGuardInterrupt(isolate);

  if (*code_handle != re_code) {  // Return address no longer valid.
    int delta = code_handle->address() - re_code->address();
    // Overwrite the return address on the stack.
    *return_address += delta;
  }

  if (result->IsException()) {
    return EXCEPTION;
  }

  Handle<String> subject_tmp = subject;
  int slice_offset = 0;

  // Extract the underlying string and the slice offset.
  if (StringShape(*subject_tmp).IsCons()) {
    subject_tmp = Handle<String>(ConsString::cast(*subject_tmp)->first());
  } else if (StringShape(*subject_tmp).IsSliced()) {
    SlicedString* slice = SlicedString::cast(*subject_tmp);
    subject_tmp = Handle<String>(slice->parent());
    slice_offset = slice->offset();
  }

  // String might have changed.
  if (subject_tmp->IsAsciiRepresentation() != is_ascii) {
    // If we changed between an ASCII and an UC16 string, the specialized
    // code cannot be used, and we need to restart regexp matching from
    // scratch (including, potentially, compiling a new version of the code).
    return RETRY;
  }

  // Otherwise, the content of the string might have moved. It must still
  // be a sequential or external string with the same content.
  // Update the start and end pointers in the stack frame to the current
  // location (whether it has actually moved or not).
  ASSERT(StringShape(*subject_tmp).IsSequential() ||
      StringShape(*subject_tmp).IsExternal());

  // The original start address of the characters to match.
  const byte* start_address = frame_entry<const byte*>(re_frame, kInputStart);

  // Find the current start address of the same character at the current string
  // position.
  int start_index = frame_entry<int>(re_frame, kStartIndex);
  const byte* new_address = StringCharacterPosition(*subject_tmp,
                                                    start_index + slice_offset);

  if (start_address != new_address) {
    // If there is a difference, update the object pointer and start and end
    // addresses in the RegExp stack frame to match the new value.
    const byte* end_address = frame_entry<const byte* >(re_frame, kInputEnd);
    int byte_length = static_cast<int>(end_address - start_address);
    frame_entry<const String*>(re_frame, kInputString) = *subject;
    frame_entry<const byte*>(re_frame, kInputStart) = new_address;
    frame_entry<const byte*>(re_frame, kInputEnd) = new_address + byte_length;
  } else if (frame_entry<const String*>(re_frame, kInputString) != *subject) {
    // Subject string might have been a ConsString that underwent
    // short-circuiting during GC. That will not change start_address but
    // will change pointer inside the subject handle.
    frame_entry<const String*>(re_frame, kInputString) = *subject;
  }

  return 0;
}


MemOperand RegExpMacroAssemblerMIPS::register_location(int register_index) {
  ASSERT(register_index < (1<<30));
  if (num_registers_ <= register_index) {
    num_registers_ = register_index + 1;
  }
  return MemOperand(frame_pointer(),
                    kRegisterZero - register_index * kPointerSize);
}


void RegExpMacroAssemblerMIPS::CheckPosition(int cp_offset,
                                             Label* on_outside_input) {
  BranchOrBacktrack(on_outside_input,
                    ge,
                    current_input_offset(),
                    Operand(-cp_offset * char_size()));
}


void RegExpMacroAssemblerMIPS::BranchOrBacktrack(Label* to,
                                                 Condition condition,
                                                 Register rs,
                                                 const Operand& rt) {
  if (condition == al) {  // Unconditional.
    if (to == NULL) {
      Backtrack();
      return;
    }
    __ jmp(to);
    return;
  }
  if (to == NULL) {
    __ Branch(&backtrack_label_, condition, rs, rt);
    return;
  }
  __ Branch(to, condition, rs, rt);
}


void RegExpMacroAssemblerMIPS::SafeCall(Label* to,
                                        Condition cond,
                                        Register rs,
                                        const Operand& rt) {
  __ BranchAndLink(to, cond, rs, rt);
}


void RegExpMacroAssemblerMIPS::SafeReturn() {
  __ pop(ra);
  __ Addu(t5, ra, Operand(masm_->CodeObject()));
  __ Jump(t5);
}


void RegExpMacroAssemblerMIPS::SafeCallTarget(Label* name) {
  __ bind(name);
  __ Subu(ra, ra, Operand(masm_->CodeObject()));
  __ push(ra);
}


void RegExpMacroAssemblerMIPS::Push(Register source) {
  ASSERT(!source.is(backtrack_stackpointer()));
  __ Addu(backtrack_stackpointer(),
          backtrack_stackpointer(),
          Operand(-kPointerSize));
  __ sw(source, MemOperand(backtrack_stackpointer()));
}


void RegExpMacroAssemblerMIPS::Pop(Register target) {
  ASSERT(!target.is(backtrack_stackpointer()));
  __ lw(target, MemOperand(backtrack_stackpointer()));
  __ Addu(backtrack_stackpointer(), backtrack_stackpointer(), kPointerSize);
}


void RegExpMacroAssemblerMIPS::CheckPreemption() {
  // Check for preemption.
  ExternalReference stack_limit =
      ExternalReference::address_of_stack_limit(masm_->isolate());
  __ li(a0, Operand(stack_limit));
  __ lw(a0, MemOperand(a0));
  SafeCall(&check_preempt_label_, ls, sp, Operand(a0));
}


void RegExpMacroAssemblerMIPS::CheckStackLimit() {
  ExternalReference stack_limit =
      ExternalReference::address_of_regexp_stack_limit(masm_->isolate());

  __ li(a0, Operand(stack_limit));
  __ lw(a0, MemOperand(a0));
  SafeCall(&stack_overflow_label_, ls, backtrack_stackpointer(), Operand(a0));
}


void RegExpMacroAssemblerMIPS::CallCFunctionUsingStub(
    ExternalReference function,
    int num_arguments) {
  // Must pass all arguments in registers. The stub pushes on the stack.
  ASSERT(num_arguments <= 4);
  __ li(code_pointer(), Operand(function));
  RegExpCEntryStub stub;
  __ CallStub(&stub);
  if (OS::ActivationFrameAlignment() != 0) {
    __ lw(sp, MemOperand(sp, 16));
  }
  __ li(code_pointer(), Operand(masm_->CodeObject()), CONSTANT_SIZE);
}


void RegExpMacroAssemblerMIPS::LoadCurrentCharacterUnchecked(int cp_offset,
                                                             int characters) {
  Register offset = current_input_offset();
  if (cp_offset != 0) {
    // t7 is not being used to store the capture start index at this point.
    __ Addu(t7, current_input_offset(), Operand(cp_offset * char_size()));
    offset = t7;
  }
  // We assume that we cannot do unaligned loads on MIPS, so this function
  // must only be used to load a single character at a time.
  ASSERT(characters == 1);
  __ Addu(t5, end_of_input_address(), Operand(offset));
  if (mode_ == ASCII) {
    __ lbu(current_character(), MemOperand(t5, 0));
  } else {
    ASSERT(mode_ == UC16);
    __ lhu(current_character(), MemOperand(t5, 0));
  }
}


void RegExpCEntryStub::Generate(MacroAssembler* masm_) {
  int stack_alignment = OS::ActivationFrameAlignment();
  if (stack_alignment < kPointerSize) stack_alignment = kPointerSize;
  // Stack is already aligned for call, so decrement by alignment
  // to make room for storing the return address.
  __ Subu(sp, sp, Operand(stack_alignment + kCArgsSlotsSize));
  const int return_address_offset = kCArgsSlotsSize;
  __ Addu(a0, sp, return_address_offset);
  __ sw(ra, MemOperand(a0, 0));
  __ mov(t9, t1);
  __ Call(t9);
  __ lw(ra, MemOperand(sp, return_address_offset));
  __ Addu(sp, sp, Operand(stack_alignment + kCArgsSlotsSize));
  __ Jump(ra);
}


#undef __

#endif  // V8_INTERPRETED_REGEXP

}}  // namespace v8::internal

#endif  // V8_TARGET_ARCH_MIPS
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