text: 
  /*
  Copyright 2012 Aphid Mobile
  
  Licensed under the Apache License, Version 2.0 (the "License");
  you may not use this file except in compliance with the License.
  You may obtain a copy of the License at
   
     http://www.apache.org/licenses/LICENSE-2.0
  
  Unless required by applicable law or agreed to in writing, software
  distributed under the License is distributed on an "AS IS" BASIS,
  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  See the License for the specific language governing permissions and
  limitations under the License.
  
  */
  /*
   * Copyright (C) 2009 Apple Inc. All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   * 2. 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.
   *
   * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``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 APPLE INC. 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 "config.h"
  #include "RegexJIT.h"
  
  #include "ASCIICType.h"
  #include "AJGlobalData.h"
  #include "LinkBuffer.h"
  #include "MacroAssembler.h"
  #include "RegExpCache.h"
  #include "RegexCompiler.h"
  
  
  //#include "pcre.h"
  
  #if ENABLE(YARR_JIT)
  
  using namespace ATF;
  
  namespace AJ { namespace Yarr {
  
  class RegexGenerator : private MacroAssembler {
      friend void jitCompileRegex(AJGlobalData* globalData, RegexCodeBlock& jitObject, const UString& pattern, unsigned& numSubpatterns, const char*& error, bool ignoreCase, bool multiline);
  
  #if CPU(ARM)
      static const RegisterID input = ARMRegisters::r0;
      static const RegisterID index = ARMRegisters::r1;
      static const RegisterID length = ARMRegisters::r2;
      static const RegisterID output = ARMRegisters::r4;
  
      static const RegisterID regT0 = ARMRegisters::r5;
      static const RegisterID regT1 = ARMRegisters::r6;
  
      static const RegisterID returnRegister = ARMRegisters::r0;
  #elif CPU(MIPS)
      static const RegisterID input = MIPSRegisters::a0;
      static const RegisterID index = MIPSRegisters::a1;
      static const RegisterID length = MIPSRegisters::a2;
      static const RegisterID output = MIPSRegisters::a3;
  
      static const RegisterID regT0 = MIPSRegisters::t4;
      static const RegisterID regT1 = MIPSRegisters::t5;
  
      static const RegisterID returnRegister = MIPSRegisters::v0;
  #elif CPU(X86)
      static const RegisterID input = X86Registers::eax;
      static const RegisterID index = X86Registers::edx;
      static const RegisterID length = X86Registers::ecx;
      static const RegisterID output = X86Registers::edi;
  
      static const RegisterID regT0 = X86Registers::ebx;
      static const RegisterID regT1 = X86Registers::esi;
  
      static const RegisterID returnRegister = X86Registers::eax;
  #elif CPU(X86_64)
      static const RegisterID input = X86Registers::edi;
      static const RegisterID index = X86Registers::esi;
      static const RegisterID length = X86Registers::edx;
      static const RegisterID output = X86Registers::ecx;
  
      static const RegisterID regT0 = X86Registers::eax;
      static const RegisterID regT1 = X86Registers::ebx;
  
      static const RegisterID returnRegister = X86Registers::eax;
  #endif
  
      void optimizeAlternative(PatternAlternative* alternative)
      {
          if (!alternative->m_terms.size())
              return;
  
          for (unsigned i = 0; i < alternative->m_terms.size() - 1; ++i) {
              PatternTerm& term = alternative->m_terms[i];
              PatternTerm& nextTerm = alternative->m_terms[i + 1];
  
              if ((term.type == PatternTerm::TypeCharacterClass)
                  && (term.quantityType == QuantifierFixedCount)
                  && (nextTerm.type == PatternTerm::TypePatternCharacter)
                  && (nextTerm.quantityType == QuantifierFixedCount)) {
                  PatternTerm termCopy = term;
                  alternative->m_terms[i] = nextTerm;
                  alternative->m_terms[i + 1] = termCopy;
              }
          }
      }
  
      void matchCharacterClassRange(RegisterID character, JumpList& failures, JumpList& matchDest, const CharacterRange* ranges, unsigned count, unsigned* matchIndex, const UChar* matches, unsigned matchCount)
      {
          do {
              // pick which range we're going to generate
              int which = count >> 1;
              char lo = ranges[which].begin;
              char hi = ranges[which].end;
              
              // check if there are any ranges or matches below lo.  If not, just jl to failure -
              // if there is anything else to check, check that first, if it falls through jmp to failure.
              if ((*matchIndex < matchCount) && (matches[*matchIndex] < lo)) {
                  Jump loOrAbove = branch32(GreaterThanOrEqual, character, Imm32((unsigned short)lo));
                  
                  // generate code for all ranges before this one
                  if (which)
                      matchCharacterClassRange(character, failures, matchDest, ranges, which, matchIndex, matches, matchCount);
                  
                  while ((*matchIndex < matchCount) && (matches[*matchIndex] < lo)) {
                      matchDest.append(branch32(Equal, character, Imm32((unsigned short)matches[*matchIndex])));
                      ++*matchIndex;
                  }
                  failures.append(jump());
  
                  loOrAbove.link(this);
              } else if (which) {
                  Jump loOrAbove = branch32(GreaterThanOrEqual, character, Imm32((unsigned short)lo));
  
                  matchCharacterClassRange(character, failures, matchDest, ranges, which, matchIndex, matches, matchCount);
                  failures.append(jump());
  
                  loOrAbove.link(this);
              } else
                  failures.append(branch32(LessThan, character, Imm32((unsigned short)lo)));
  
              while ((*matchIndex < matchCount) && (matches[*matchIndex] <= hi))
                  ++*matchIndex;
  
              matchDest.append(branch32(LessThanOrEqual, character, Imm32((unsigned short)hi)));
              // fall through to here, the value is above hi.
  
              // shuffle along & loop around if there are any more matches to handle.
              unsigned next = which + 1;
              ranges += next;
              count -= next;
          } while (count);
      }
  
      void matchCharacterClass(RegisterID character, JumpList& matchDest, const CharacterClass* charClass)
      {
          if (charClass->m_table) {
              ExtendedAddress tableEntry(character, reinterpret_cast<intptr_t>(charClass->m_table->m_table));
              matchDest.append(branchTest8(charClass->m_table->m_inverted ? Zero : NonZero, tableEntry));   
              return;
          }
          Jump unicodeFail;
          if (charClass->m_matchesUnicode.size() || charClass->m_rangesUnicode.size()) {
              Jump isAscii = branch32(LessThanOrEqual, character, Imm32(0x7f));
          
              if (charClass->m_matchesUnicode.size()) {
                  for (unsigned i = 0; i < charClass->m_matchesUnicode.size(); ++i) {
                      UChar ch = charClass->m_matchesUnicode[i];
                      matchDest.append(branch32(Equal, character, Imm32(ch)));
                  }
              }
              
              if (charClass->m_rangesUnicode.size()) {
                  for (unsigned i = 0; i < charClass->m_rangesUnicode.size(); ++i) {
                      UChar lo = charClass->m_rangesUnicode[i].begin;
                      UChar hi = charClass->m_rangesUnicode[i].end;
                      
                      Jump below = branch32(LessThan, character, Imm32(lo));
                      matchDest.append(branch32(LessThanOrEqual, character, Imm32(hi)));
                      below.link(this);
                  }
              }
  
              unicodeFail = jump();
              isAscii.link(this);
          }
  
          if (charClass->m_ranges.size()) {
              unsigned matchIndex = 0;
              JumpList failures; 
              matchCharacterClassRange(character, failures, matchDest, charClass->m_ranges.begin(), charClass->m_ranges.size(), &matchIndex, charClass->m_matches.begin(), charClass->m_matches.size());
              while (matchIndex < charClass->m_matches.size())
                  matchDest.append(branch32(Equal, character, Imm32((unsigned short)charClass->m_matches[matchIndex++])));
  
              failures.link(this);
          } else if (charClass->m_matches.size()) {
              // optimization: gather 'a','A' etc back together, can mask & test once.
              Vector<char> matchesAZaz;
  
              for (unsigned i = 0; i < charClass->m_matches.size(); ++i) {
                  char ch = charClass->m_matches[i];
                  if (m_pattern.m_ignoreCase) {
                      if (isASCIILower(ch)) {
                          matchesAZaz.append(ch);
                          continue;
                      }
                      if (isASCIIUpper(ch))
                          continue;
                  }
                  matchDest.append(branch32(Equal, character, Imm32((unsigned short)ch)));
              }
  
              if (unsigned countAZaz = matchesAZaz.size()) {
                  or32(Imm32(32), character);
                  for (unsigned i = 0; i < countAZaz; ++i)
                      matchDest.append(branch32(Equal, character, Imm32(matchesAZaz[i])));
              }
          }
  
          if (charClass->m_matchesUnicode.size() || charClass->m_rangesUnicode.size())
              unicodeFail.link(this);
      }
  
      // Jumps if input not available; will have (incorrectly) incremented already!
      Jump jumpIfNoAvailableInput(unsigned countToCheck)
      {
          add32(Imm32(countToCheck), index);
          return branch32(Above, index, length);
      }
  
      Jump jumpIfAvailableInput(unsigned countToCheck)
      {
          add32(Imm32(countToCheck), index);
          return branch32(BelowOrEqual, index, length);
      }
  
      Jump checkInput()
      {
          return branch32(BelowOrEqual, index, length);
      }
  
      Jump atEndOfInput()
      {
          return branch32(Equal, index, length);
      }
  
      Jump notAtEndOfInput()
      {
          return branch32(NotEqual, index, length);
      }
  
      Jump jumpIfCharEquals(UChar ch, int inputPosition)
      {
          return branch16(Equal, BaseIndex(input, index, TimesTwo, inputPosition * sizeof(UChar)), Imm32(ch));
      }
  
      Jump jumpIfCharNotEquals(UChar ch, int inputPosition)
      {
          return branch16(NotEqual, BaseIndex(input, index, TimesTwo, inputPosition * sizeof(UChar)), Imm32(ch));
      }
  
      void readCharacter(int inputPosition, RegisterID reg)
      {
          load16(BaseIndex(input, index, TimesTwo, inputPosition * sizeof(UChar)), reg);
      }
  
      void storeToFrame(RegisterID reg, unsigned frameLocation)
      {
          poke(reg, frameLocation);
      }
  
      void storeToFrame(Imm32 imm, unsigned frameLocation)
      {
          poke(imm, frameLocation);
      }
  
      DataLabelPtr storeToFrameWithPatch(unsigned frameLocation)
      {
          return storePtrWithPatch(ImmPtr(0), Address(stackPointerRegister, frameLocation * sizeof(void*)));
      }
  
      void loadFromFrame(unsigned frameLocation, RegisterID reg)
      {
          peek(reg, frameLocation);
      }
  
      void loadFromFrameAndJump(unsigned frameLocation)
      {
          jump(Address(stackPointerRegister, frameLocation * sizeof(void*)));
      }
  
      struct AlternativeBacktrackRecord {
          DataLabelPtr dataLabel;
          Label backtrackLocation;
  
          AlternativeBacktrackRecord(DataLabelPtr dataLabel, Label backtrackLocation)
              : dataLabel(dataLabel)
              , backtrackLocation(backtrackLocation)
          {
          }
      };
  
      struct TermGenerationState {
          TermGenerationState(PatternDisjunction* disjunction, unsigned checkedTotal)
              : disjunction(disjunction)
              , checkedTotal(checkedTotal)
          {
          }
  
          void resetAlternative()
          {
              isBackTrackGenerated = false;
              alt = 0;
          }
          bool alternativeValid()
          {
              return alt < disjunction->m_alternatives.size();
          }
          void nextAlternative()
          {
              ++alt;
          }
          PatternAlternative* alternative()
          {
              return disjunction->m_alternatives[alt];
          }
  
          void resetTerm()
          {
              ASSERT(alternativeValid());
              t = 0;
          }
          bool termValid()
          {
              ASSERT(alternativeValid());
              return t < alternative()->m_terms.size();
          }
          void nextTerm()
          {
              ASSERT(alternativeValid());
              ++t;
          }
          PatternTerm& term()
          {
              ASSERT(alternativeValid());
              return alternative()->m_terms[t];
          }
  
          PatternTerm& lookaheadTerm()
          {
              ASSERT(alternativeValid());
              ASSERT((t + 1) < alternative()->m_terms.size());
              return alternative()->m_terms[t + 1];
          }
          bool isSinglePatternCharacterLookaheadTerm()
          {
              ASSERT(alternativeValid());
              return ((t + 1) < alternative()->m_terms.size())
                  && (lookaheadTerm().type == PatternTerm::TypePatternCharacter)
                  && (lookaheadTerm().quantityType == QuantifierFixedCount)
                  && (lookaheadTerm().quantityCount == 1);
          }
  
          int inputOffset()
          {
              return term().inputPosition - checkedTotal;
          }
  
          void jumpToBacktrack(Jump jump, MacroAssembler* masm)
          {
              if (isBackTrackGenerated)
                  jump.linkTo(backtrackLabel, masm);
              else
                  backTrackJumps.append(jump);
          }
          void jumpToBacktrack(JumpList& jumps, MacroAssembler* masm)
          {
              if (isBackTrackGenerated)
                  jumps.linkTo(backtrackLabel, masm);
              else
                  backTrackJumps.append(jumps);
          }
          bool plantJumpToBacktrackIfExists(MacroAssembler* masm)
          {
              if (isBackTrackGenerated) {
                  masm->jump(backtrackLabel);
                  return true;
              }
              return false;
          }
          void addBacktrackJump(Jump jump)
          {
              backTrackJumps.append(jump);
          }
          void setBacktrackGenerated(Label label)
          {
              isBackTrackGenerated = true;
              backtrackLabel = label;
          }
          void linkAlternativeBacktracks(MacroAssembler* masm)
          {
              isBackTrackGenerated = false;
              backTrackJumps.link(masm);
          }
          void linkAlternativeBacktracksTo(Label label, MacroAssembler* masm)
          {
              isBackTrackGenerated = false;
              backTrackJumps.linkTo(label, masm);
          }
          void propagateBacktrackingFrom(TermGenerationState& nestedParenthesesState, MacroAssembler* masm)
          {
              jumpToBacktrack(nestedParenthesesState.backTrackJumps, masm);
              if (nestedParenthesesState.isBackTrackGenerated)
                  setBacktrackGenerated(nestedParenthesesState.backtrackLabel);
          }
  
          PatternDisjunction* disjunction;
          int checkedTotal;
      private:
          unsigned alt;
          unsigned t;
          JumpList backTrackJumps;
          Label backtrackLabel;
          bool isBackTrackGenerated;
      };
  
      void generateAssertionBOL(TermGenerationState& state)
      {
          PatternTerm& term = state.term();
  
          if (m_pattern.m_multiline) {
              const RegisterID character = regT0;
  
              JumpList matchDest;
              if (!term.inputPosition)
                  matchDest.append(branch32(Equal, index, Imm32(state.checkedTotal)));
  
              readCharacter(state.inputOffset() - 1, character);
              matchCharacterClass(character, matchDest, m_pattern.newlineCharacterClass());
              state.jumpToBacktrack(jump(), this);
  
              matchDest.link(this);
          } else {
              // Erk, really should poison out these alternatives early. :-/
              if (term.inputPosition)
                  state.jumpToBacktrack(jump(), this);
              else
                  state.jumpToBacktrack(branch32(NotEqual, index, Imm32(state.checkedTotal)), this);
          }
      }
  
      void generateAssertionEOL(TermGenerationState& state)
      {
          PatternTerm& term = state.term();
  
          if (m_pattern.m_multiline) {
              const RegisterID character = regT0;
  
              JumpList matchDest;
              if (term.inputPosition == state.checkedTotal)
                  matchDest.append(atEndOfInput());
  
              readCharacter(state.inputOffset(), character);
              matchCharacterClass(character, matchDest, m_pattern.newlineCharacterClass());
              state.jumpToBacktrack(jump(), this);
  
              matchDest.link(this);
          } else {
              if (term.inputPosition == state.checkedTotal)
                  state.jumpToBacktrack(notAtEndOfInput(), this);
              // Erk, really should poison out these alternatives early. :-/
              else
                  state.jumpToBacktrack(jump(), this);
          }
      }
  
      // Also falls though on nextIsNotWordChar.
      void matchAssertionWordchar(TermGenerationState& state, JumpList& nextIsWordChar, JumpList& nextIsNotWordChar)
      {
          const RegisterID character = regT0;
          PatternTerm& term = state.term();
  
          if (term.inputPosition == state.checkedTotal)
              nextIsNotWordChar.append(atEndOfInput());
  
          readCharacter(state.inputOffset(), character);
          matchCharacterClass(character, nextIsWordChar, m_pattern.wordcharCharacterClass());
      }
  
      void generateAssertionWordBoundary(TermGenerationState& state)
      {
          const RegisterID character = regT0;
          PatternTerm& term = state.term();
  
          Jump atBegin;
          JumpList matchDest;
          if (!term.inputPosition)
              atBegin = branch32(Equal, index, Imm32(state.checkedTotal));
          readCharacter(state.inputOffset() - 1, character);
          matchCharacterClass(character, matchDest, m_pattern.wordcharCharacterClass());
          if (!term.inputPosition)
              atBegin.link(this);
  
          // We fall through to here if the last character was not a wordchar.
          JumpList nonWordCharThenWordChar;
          JumpList nonWordCharThenNonWordChar;
          if (term.invertOrCapture) {
              matchAssertionWordchar(state, nonWordCharThenNonWordChar, nonWordCharThenWordChar);
              nonWordCharThenWordChar.append(jump());
          } else {
              matchAssertionWordchar(state, nonWordCharThenWordChar, nonWordCharThenNonWordChar);
              nonWordCharThenNonWordChar.append(jump());
          }
          state.jumpToBacktrack(nonWordCharThenNonWordChar, this);
  
          // We jump here if the last character was a wordchar.
          matchDest.link(this);
          JumpList wordCharThenWordChar;
          JumpList wordCharThenNonWordChar;
          if (term.invertOrCapture) {
              matchAssertionWordchar(state, wordCharThenNonWordChar, wordCharThenWordChar);
              wordCharThenWordChar.append(jump());
          } else {
              matchAssertionWordchar(state, wordCharThenWordChar, wordCharThenNonWordChar);
              // This can fall-though!
          }
  
          state.jumpToBacktrack(wordCharThenWordChar, this);
          
          nonWordCharThenWordChar.link(this);
          wordCharThenNonWordChar.link(this);
      }
  
      void generatePatternCharacterSingle(TermGenerationState& state)
      {
          const RegisterID character = regT0;
          UChar ch = state.term().patternCharacter;
  
          if (m_pattern.m_ignoreCase && isASCIIAlpha(ch)) {
              readCharacter(state.inputOffset(), character);
              or32(Imm32(32), character);
  						//XXX:
              //state.jumpToBacktrack(branch32(NotEqual, character, Imm32(Unicode::toLower(ch))), this);
  						state.jumpToBacktrack(branch32(NotEqual, character, Imm32(ch | 32)), this);
          } else {
              ASSERT(!m_pattern.m_ignoreCase || (Unicode::toLower(ch) == Unicode::toUpper(ch)));
              state.jumpToBacktrack(jumpIfCharNotEquals(ch, state.inputOffset()), this);
          }
      }
  
      void generatePatternCharacterPair(TermGenerationState& state)
      {
          const RegisterID character = regT0;
          UChar ch1 = state.term().patternCharacter;
          UChar ch2 = state.lookaheadTerm().patternCharacter;
  
          int mask = 0;
          int chPair = ch1 | (ch2 << 16);
          
          if (m_pattern.m_ignoreCase) {
              if (isASCIIAlpha(ch1))
                  mask |= 32;
              if (isASCIIAlpha(ch2))
                  mask |= 32 << 16;
          }
  
          if (mask) {
              load32WithUnalignedHalfWords(BaseIndex(input, index, TimesTwo, state.inputOffset() * sizeof(UChar)), character);
              or32(Imm32(mask), character);
              state.jumpToBacktrack(branch32(NotEqual, character, Imm32(chPair | mask)), this);
          } else
              state.jumpToBacktrack(branch32WithUnalignedHalfWords(NotEqual, BaseIndex(input, index, TimesTwo, state.inputOffset() * sizeof(UChar)), Imm32(chPair)), this);
      }
  
      void generatePatternCharacterFixed(TermGenerationState& state)
      {
          const RegisterID character = regT0;
          const RegisterID countRegister = regT1;
          PatternTerm& term = state.term();
          UChar ch = term.patternCharacter;
  
          move(index, countRegister);
          sub32(Imm32(term.quantityCount), countRegister);
  
          Label loop(this);
          if (m_pattern.m_ignoreCase && isASCIIAlpha(ch)) {
              load16(BaseIndex(input, countRegister, TimesTwo, (state.inputOffset() + term.quantityCount) * sizeof(UChar)), character);
              or32(Imm32(32), character);
              state.jumpToBacktrack(branch32(NotEqual, character, Imm32(Unicode::toLower(ch))), this);
          } else {
              ASSERT(!m_pattern.m_ignoreCase || (Unicode::toLower(ch) == Unicode::toUpper(ch)));
              state.jumpToBacktrack(branch16(NotEqual, BaseIndex(input, countRegister, TimesTwo, (state.inputOffset() + term.quantityCount) * sizeof(UChar)), Imm32(ch)), this);
          }
          add32(Imm32(1), countRegister);
          branch32(NotEqual, countRegister, index).linkTo(loop, this);
      }
  
      void generatePatternCharacterGreedy(TermGenerationState& state)
      {
          const RegisterID character = regT0;
          const RegisterID countRegister = regT1;
          PatternTerm& term = state.term();
          UChar ch = term.patternCharacter;
      
          move(Imm32(0), countRegister);
  
          JumpList failures;
          Label loop(this);
          failures.append(atEndOfInput());
          if (m_pattern.m_ignoreCase && isASCIIAlpha(ch)) {
              readCharacter(state.inputOffset(), character);
              or32(Imm32(32), character);
              failures.append(branch32(NotEqual, character, Imm32(Unicode::toLower(ch))));
          } else {
              ASSERT(!m_pattern.m_ignoreCase || (Unicode::toLower(ch) == Unicode::toUpper(ch)));
              failures.append(jumpIfCharNotEquals(ch, state.inputOffset()));
          }
  
          add32(Imm32(1), countRegister);
          add32(Imm32(1), index);
          if (term.quantityCount != 0xffffffff)
              branch32(NotEqual, countRegister, Imm32(term.quantityCount)).linkTo(loop, this);
          else
              jump(loop);
  
          failures.append(jump());
  
          Label backtrackBegin(this);
          loadFromFrame(term.frameLocation, countRegister);
          state.jumpToBacktrack(branchTest32(Zero, countRegister), this);
          sub32(Imm32(1), countRegister);
          sub32(Imm32(1), index);
  
          failures.link(this);
  
          storeToFrame(countRegister, term.frameLocation);
  
          state.setBacktrackGenerated(backtrackBegin);
      }
  
      void generatePatternCharacterNonGreedy(TermGenerationState& state)
      {
          const RegisterID character = regT0;
          const RegisterID countRegister = regT1;
          PatternTerm& term = state.term();
          UChar ch = term.patternCharacter;
      
          move(Imm32(0), countRegister);
  
          Jump firstTimeDoNothing = jump();
  
          Label hardFail(this);
          sub32(countRegister, index);
          state.jumpToBacktrack(jump(), this);
  
          Label backtrackBegin(this);
          loadFromFrame(term.frameLocation, countRegister);
  
          atEndOfInput().linkTo(hardFail, this);
          if (term.quantityCount != 0xffffffff)
              branch32(Equal, countRegister, Imm32(term.quantityCount), hardFail);
          if (m_pattern.m_ignoreCase && isASCIIAlpha(ch)) {
              readCharacter(state.inputOffset(), character);
              or32(Imm32(32), character);
              branch32(NotEqual, character, Imm32(Unicode::toLower(ch))).linkTo(hardFail, this);
          } else {
              ASSERT(!m_pattern.m_ignoreCase || (Unicode::toLower(ch) == Unicode::toUpper(ch)));
              jumpIfCharNotEquals(ch, state.inputOffset()).linkTo(hardFail, this);
          }
  
          add32(Imm32(1), countRegister);
          add32(Imm32(1), index);
  
          firstTimeDoNothing.link(this);
          storeToFrame(countRegister, term.frameLocation);
  
          state.setBacktrackGenerated(backtrackBegin);
      }
  
      void generateCharacterClassSingle(TermGenerationState& state)
      {
          const RegisterID character = regT0;
          PatternTerm& term = state.term();
  
          JumpList matchDest;
          readCharacter(state.inputOffset(), character);
          matchCharacterClass(character, matchDest, term.characterClass);
  
          if (term.invertOrCapture)
              state.jumpToBacktrack(matchDest, this);
          else {
              state.jumpToBacktrack(jump(), this);
              matchDest.link(this);
          }
      }
  
      void generateCharacterClassFixed(TermGenerationState& state)
      {
          const RegisterID character = regT0;
          const RegisterID countRegister = regT1;
          PatternTerm& term = state.term();
  
          move(index, countRegister);
          sub32(Imm32(term.quantityCount), countRegister);
  
          Label loop(this);
          JumpList matchDest;
          load16(BaseIndex(input, countRegister, TimesTwo, (state.inputOffset() + term.quantityCount) * sizeof(UChar)), character);
          matchCharacterClass(character, matchDest, term.characterClass);
  
          if (term.invertOrCapture)
              state.jumpToBacktrack(matchDest, this);
          else {
              state.jumpToBacktrack(jump(), this);
              matchDest.link(this);
          }
  
          add32(Imm32(1), countRegister);
          branch32(NotEqual, countRegister, index).linkTo(loop, this);
      }
  
      void generateCharacterClassGreedy(TermGenerationState& state)
      {
          const RegisterID character = regT0;
          const RegisterID countRegister = regT1;
          PatternTerm& term = state.term();
      
          move(Imm32(0), countRegister);
  
          JumpList failures;
          Label loop(this);
          failures.append(atEndOfInput());
  
          if (term.invertOrCapture) {
              readCharacter(state.inputOffset(), character);
              matchCharacterClass(character, failures, term.characterClass);
          } else {
              JumpList matchDest;
              readCharacter(state.inputOffset(), character);
              matchCharacterClass(character, matchDest, term.characterClass);
              failures.append(jump());
              matchDest.link(this);
          }
  
          add32(Imm32(1), countRegister);
          add32(Imm32(1), index);
          if (term.quantityCount != 0xffffffff)
              branch32(NotEqual, countRegister, Imm32(term.quantityCount)).linkTo(loop, this);
          else
              jump(loop);
  
          failures.append(jump());
  
          Label backtrackBegin(this);
          loadFromFrame(term.frameLocation, countRegister);
          state.jumpToBacktrack(branchTest32(Zero, countRegister), this);
          sub32(Imm32(1), countRegister);
          sub32(Imm32(1), index);
  
          failures.link(this);
  
          storeToFrame(countRegister, term.frameLocation);
  
          state.setBacktrackGenerated(backtrackBegin);
      }
  
      void generateCharacterClassNonGreedy(TermGenerationState& state)
      {
          const RegisterID character = regT0;
          const RegisterID countRegister = regT1;
          PatternTerm& term = state.term();
      
          move(Imm32(0), countRegister);
  
          Jump firstTimeDoNothing = jump();
  
          Label hardFail(this);
          sub32(countRegister, index);
          state.jumpToBacktrack(jump(), this);
  
          Label backtrackBegin(this);
          loadFromFrame(term.frameLocation, countRegister);
  
          atEndOfInput().linkTo(hardFail, this);
          branch32(Equal, countRegister, Imm32(term.quantityCount), hardFail);
  
          JumpList matchDest;
          readCharacter(state.inputOffset(), character);
          matchCharacterClass(character, matchDest, term.characterClass);
  
          if (term.invertOrCapture)
              matchDest.linkTo(hardFail, this);
          else {
              jump(hardFail);
              matchDest.link(this);
          }
  
          add32(Imm32(1), countRegister);
          add32(Imm32(1), index);
  
          firstTimeDoNothing.link(this);
          storeToFrame(countRegister, term.frameLocation);
  
          state.setBacktrackGenerated(backtrackBegin);
      }
  
      void generateParenthesesDisjunction(PatternTerm& parenthesesTerm, TermGenerationState& state, unsigned alternativeFrameLocation)
      {
          ASSERT((parenthesesTerm.type == PatternTerm::TypeParenthesesSubpattern) || (parenthesesTerm.type == PatternTerm::TypeParentheticalAssertion));
          ASSERT(parenthesesTerm.quantityCount == 1);
      
          PatternDisjunction* disjunction = parenthesesTerm.parentheses.disjunction;
          unsigned preCheckedCount = ((parenthesesTerm.quantityType == QuantifierFixedCount) && (parenthesesTerm.type != PatternTerm::TypeParentheticalAssertion)) ? disjunction->m_minimumSize : 0;
  
          if (disjunction->m_alternatives.size() == 1) {
              state.resetAlternative();
              ASSERT(state.alternativeValid());
              PatternAlternative* alternative = state.alternative();
              optimizeAlternative(alternative);
  
              int countToCheck = alternative->m_minimumSize - preCheckedCount;
              if (countToCheck) {
                  ASSERT((parenthesesTerm.type == PatternTerm::TypeParentheticalAssertion) || (parenthesesTerm.quantityType != QuantifierFixedCount));
  
                  // FIXME: This is quite horrible.  The call to 'plantJumpToBacktrackIfExists'
                  // will be forced to always trampoline into here, just to decrement the index.
                  // Ick. 
                  Jump skip = jump();
  
                  Label backtrackBegin(this);
                  sub32(Imm32(countToCheck), index);
                  state.addBacktrackJump(jump());
                  
                  skip.link(this);
  
                  state.setBacktrackGenerated(backtrackBegin);
  
                  state.jumpToBacktrack(jumpIfNoAvailableInput(countToCheck), this);
                  state.checkedTotal += countToCheck;
              }
  
              for (state.resetTerm(); state.termValid(); state.nextTerm())
                  generateTerm(state);
  
              state.checkedTotal -= countToCheck;
          } else {
              JumpList successes;
  
              for (state.resetAlternative(); state.alternativeValid(); state.nextAlternative()) {
  
                  PatternAlternative* alternative = state.alternative();
                  optimizeAlternative(alternative);
  
                  ASSERT(alternative->m_minimumSize >= preCheckedCount);
                  int countToCheck = alternative->m_minimumSize - preCheckedCount;
                  if (countToCheck) {
                      state.addBacktrackJump(jumpIfNoAvailableInput(countToCheck));
                      state.checkedTotal += countToCheck;
                  }
  
                  for (state.resetTerm(); state.termValid(); state.nextTerm())
                      generateTerm(state);
  
                  // Matched an alternative.
                  DataLabelPtr dataLabel = storeToFrameWithPatch(alternativeFrameLocation);
                  successes.append(jump());
  
                  // Alternative did not match.
                  Label backtrackLocation(this);
                  
                  // Can we backtrack the alternative? - if so, do so.  If not, just fall through to the next one.
                  state.plantJumpToBacktrackIfExists(this);
                  
                  state.linkAlternativeBacktracks(this);
  
                  if (countToCheck) {
                      sub32(Imm32(countToCheck), index);
                      state.checkedTotal -= countToCheck;
                  }
  
                  m_backtrackRecords.append(AlternativeBacktrackRecord(dataLabel, backtrackLocation));
              }
              // We fall through to here when the last alternative fails.
              // Add a backtrack out of here for the parenthese handling code to link up.
              state.addBacktrackJump(jump());
  
              // Generate a trampoline for the parens code to backtrack to, to retry the
              // next alternative.
              state.setBacktrackGenerated(label());
              loadFromFrameAndJump(alternativeFrameLocation);
  
              // FIXME: both of the above hooks are a little inefficient, in that you
              // may end up trampolining here, just to trampoline back out to the
              // parentheses code, or vice versa.  We can probably eliminate a jump
              // by restructuring, but coding this way for now for simplicity during
              // development.
  
              successes.link(this);
          }
      }
  
      void generateParenthesesSingle(TermGenerationState& state)
      {
          const RegisterID indexTemporary = regT0;
          PatternTerm& term = state.term();
          PatternDisjunction* disjunction = term.parentheses.disjunction;
          ASSERT(term.quantityCount == 1);
  
          unsigned preCheckedCount = ((term.quantityCount == 1) && (term.quantityType == QuantifierFixedCount)) ? disjunction->m_minimumSize : 0;
  
          unsigned parenthesesFrameLocation = term.frameLocation;
          unsigned alternativeFrameLocation = parenthesesFrameLocation;
          if (term.quantityType != QuantifierFixedCount)
              alternativeFrameLocation += RegexStackSpaceForBackTrackInfoParenthesesOnce;
  
          // optimized case - no capture & no quantifier can be handled in a light-weight manner.
          if (!term.invertOrCapture && (term.quantityType == QuantifierFixedCount)) {
              TermGenerationState parenthesesState(disjunction, state.checkedTotal);
              generateParenthesesDisjunction(state.term(), parenthesesState, alternativeFrameLocation);
              // this expects that any backtracks back out of the parentheses will be in the
              // parenthesesState's backTrackJumps vector, and that if they need backtracking
              // they will have set an entry point on the parenthesesState's backtrackLabel.
              state.propagateBacktrackingFrom(parenthesesState, this);
          } else {
              Jump nonGreedySkipParentheses;
              Label nonGreedyTryParentheses;
              if (term.quantityType == QuantifierGreedy)
                  storeToFrame(Imm32(1), parenthesesFrameLocation);
              else if (term.quantityType == QuantifierNonGreedy) {
                  storeToFrame(Imm32(0), parenthesesFrameLocation);
                  nonGreedySkipParentheses = jump();
                  nonGreedyTryParentheses = label();
                  storeToFrame(Imm32(1), parenthesesFrameLocation);
              }
  
              // store the match start index
              if (term.invertOrCapture) {
                  int inputOffset = state.inputOffset() - preCheckedCount;
                  if (inputOffset) {
                      move(index, indexTemporary);
                      add32(Imm32(inputOffset), indexTemporary);
                      store32(indexTemporary, Address(output, (term.parentheses.subpatternId << 1) * sizeof(int)));
                  } else
                      store32(index, Address(output, (term.parentheses.subpatternId << 1) * sizeof(int)));
              }
  
              // generate the body of the parentheses
              TermGenerationState parenthesesState(disjunction, state.checkedTotal);
              generateParenthesesDisjunction(state.term(), parenthesesState, alternativeFrameLocation);
  
              // store the match end index
              if (term.invertOrCapture) {
                  int inputOffset = state.inputOffset();
                  if (inputOffset) {
                      move(index, indexTemporary);
                      add32(Imm32(state.inputOffset()), indexTemporary);
                      store32(indexTemporary, Address(output, ((term.parentheses.subpatternId << 1) + 1) * sizeof(int)));
                  } else
                      store32(index, Address(output, ((term.parentheses.subpatternId << 1) + 1) * sizeof(int)));
              }
              Jump success = jump();
  
              // A failure AFTER the parens jumps here
              Label backtrackFromAfterParens(this);
  
              if (term.quantityType == QuantifierGreedy) {
                  // If this is zero we have now tested with both with and without the parens.
                  loadFromFrame(parenthesesFrameLocation, indexTemporary);
                  state.jumpToBacktrack(branchTest32(Zero, indexTemporary), this);
              } else if (term.quantityType == QuantifierNonGreedy) {
                  // If this is zero we have now tested with both with and without the parens.
                  loadFromFrame(parenthesesFrameLocation, indexTemporary);
                  branchTest32(Zero, indexTemporary).linkTo(nonGreedyTryParentheses, this);
              }
  
              parenthesesState.plantJumpToBacktrackIfExists(this);
              // A failure WITHIN the parens jumps here
              parenthesesState.linkAlternativeBacktracks(this);
              if (term.invertOrCapture) {
                  store32(Imm32(-1), Address(output, (term.parentheses.subpatternId << 1) * sizeof(int)));
                  store32(Imm32(-1), Address(output, ((term.parentheses.subpatternId << 1) + 1) * sizeof(int)));
              }
  
              if (term.quantityType == QuantifierGreedy)
                  storeToFrame(Imm32(0), parenthesesFrameLocation);
              else
                  state.jumpToBacktrack(jump(), this);
  
              state.setBacktrackGenerated(backtrackFromAfterParens);
              if (term.quantityType == QuantifierNonGreedy)
                  nonGreedySkipParentheses.link(this);
              success.link(this);
          }
      }
  
      void generateParentheticalAssertion(TermGenerationState& state)
      {
          PatternTerm& term = state.term();
          PatternDisjunction* disjunction = term.parentheses.disjunction;
          ASSERT(term.quantityCount == 1);
          ASSERT(term.quantityType == QuantifierFixedCount);
  
          unsigned parenthesesFrameLocation = term.frameLocation;
          unsigned alternativeFrameLocation = parenthesesFrameLocation + RegexStackSpaceForBackTrackInfoParentheticalAssertion;
  
          int countCheckedAfterAssertion = state.checkedTotal - term.inputPosition;
  
          if (term.invertOrCapture) {
              // Inverted case
              storeToFrame(index, parenthesesFrameLocation);
  
              state.checkedTotal -= countCheckedAfterAssertion;
              if (countCheckedAfterAssertion)
                  sub32(Imm32(countCheckedAfterAssertion), index);
  
              TermGenerationState parenthesesState(disjunction, state.checkedTotal);
              generateParenthesesDisjunction(state.term(), parenthesesState, alternativeFrameLocation);
              // Success! - which means - Fail!
              loadFromFrame(parenthesesFrameLocation, index);
              state.jumpToBacktrack(jump(), this);
  
              // And fail means success.
              parenthesesState.linkAlternativeBacktracks(this);
              loadFromFrame(parenthesesFrameLocation, index);
  
              state.checkedTotal += countCheckedAfterAssertion;
          } else {
              // Normal case
              storeToFrame(index, parenthesesFrameLocation);
  
              state.checkedTotal -= countCheckedAfterAssertion;
              if (countCheckedAfterAssertion)
                  sub32(Imm32(countCheckedAfterAssertion), index);
  
              TermGenerationState parenthesesState(disjunction, state.checkedTotal);
              generateParenthesesDisjunction(state.term(), parenthesesState, alternativeFrameLocation);
              // Success! - which means - Success!
              loadFromFrame(parenthesesFrameLocation, index);
              Jump success = jump();
  
              parenthesesState.linkAlternativeBacktracks(this);
              loadFromFrame(parenthesesFrameLocation, index);
              state.jumpToBacktrack(jump(), this);
  
              success.link(this);
  
              state.checkedTotal += countCheckedAfterAssertion;
          }
      }
  
      void generateTerm(TermGenerationState& state)
      {
          PatternTerm& term = state.term();
  
          switch (term.type) {
          case PatternTerm::TypeAssertionBOL:
              generateAssertionBOL(state);
              break;
          
          case PatternTerm::TypeAssertionEOL:
              generateAssertionEOL(state);
              break;
          
          case PatternTerm::TypeAssertionWordBoundary:
              generateAssertionWordBoundary(state);
              break;
          
          case PatternTerm::TypePatternCharacter:
              switch (term.quantityType) {
              case QuantifierFixedCount:
                  if (term.quantityCount == 1) {
                      if (state.isSinglePatternCharacterLookaheadTerm() && (state.lookaheadTerm().inputPosition == (term.inputPosition + 1))) {
                          generatePatternCharacterPair(state);
                          state.nextTerm();
                      } else
                          generatePatternCharacterSingle(state);
                  } else
                      generatePatternCharacterFixed(state);
                  break;
              case QuantifierGreedy:
                  generatePatternCharacterGreedy(state);
                  break;
              case QuantifierNonGreedy:
                  generatePatternCharacterNonGreedy(state);
                  break;
              }
              break;
  
          case PatternTerm::TypeCharacterClass:
              switch (term.quantityType) {
              case QuantifierFixedCount:
                  if (term.quantityCount == 1)
                      generateCharacterClassSingle(state);
                  else
                      generateCharacterClassFixed(state);
                  break;
              case QuantifierGreedy:
                  generateCharacterClassGreedy(state);
                  break;
              case QuantifierNonGreedy:
                  generateCharacterClassNonGreedy(state);
                  break;
              }
              break;
  
          case PatternTerm::TypeBackReference:
              ASSERT_NOT_REACHED();
              break;
  
          case PatternTerm::TypeForwardReference:
              break;
  
          case PatternTerm::TypeParenthesesSubpattern:
              ASSERT((term.quantityCount == 1) && !term.parentheses.isCopy); // must fallback to pcre before this point
              generateParenthesesSingle(state);
              break;
  
          case PatternTerm::TypeParentheticalAssertion:
              generateParentheticalAssertion(state);
              break;
          }
      }
  
      void generateDisjunction(PatternDisjunction* disjunction)
      {
          TermGenerationState state(disjunction, 0);
          state.resetAlternative();
  
          // Plant a check to see if there is sufficient input available to run the first alternative.
          // Jumping back to the label 'firstAlternative' will get to this check, jumping to
          // 'firstAlternativeInputChecked' will jump directly to matching the alternative having
          // skipped this check.
  
          Label firstAlternative(this);
  
          // check availability for the next alternative
          int countCheckedForCurrentAlternative = 0;
          int countToCheckForFirstAlternative = 0;
          bool hasShorterAlternatives = false;
          JumpList notEnoughInputForPreviousAlternative;
  
          if (state.alternativeValid()) {
              PatternAlternative* alternative = state.alternative();
              countToCheckForFirstAlternative = alternative->m_minimumSize;
              state.checkedTotal += countToCheckForFirstAlternative;
              if (countToCheckForFirstAlternative)
                  notEnoughInputForPreviousAlternative.append(jumpIfNoAvailableInput(countToCheckForFirstAlternative));
              countCheckedForCurrentAlternative = countToCheckForFirstAlternative;
          }
  
          Label firstAlternativeInputChecked(this);
  
          while (state.alternativeValid()) {
              // Track whether any alternatives are shorter than the first one.
              hasShorterAlternatives = hasShorterAlternatives || (countCheckedForCurrentAlternative < countToCheckForFirstAlternative);
  
              PatternAlternative* alternative = state.alternative();
              optimizeAlternative(alternative);
  
              for (state.resetTerm(); state.termValid(); state.nextTerm())
                  generateTerm(state);
  
              // If we get here, the alternative matched.
              if (m_pattern.m_body->m_callFrameSize)
                  addPtr(Imm32(m_pattern.m_body->m_callFrameSize * sizeof(void*)), stackPointerRegister);
              
              ASSERT(index != returnRegister);
              if (m_pattern.m_body->m_hasFixedSize) {
                  move(index, returnRegister);
                  if (alternative->m_minimumSize)
                      sub32(Imm32(alternative->m_minimumSize), returnRegister);
              } else
                  pop(returnRegister);
              store32(index, Address(output, 4));
              store32(returnRegister, output);
  
              generateReturn();
  
              state.nextAlternative();
  
              // if there are any more alternatives, plant the check for input before looping.
              if (state.alternativeValid()) {
                  PatternAlternative* nextAlternative = state.alternative();
                  int countToCheckForNextAlternative = nextAlternative->m_minimumSize;
  
                  if (countCheckedForCurrentAlternative > countToCheckForNextAlternative) { // CASE 1: current alternative was longer than the next one.
                      // If we get here, there the last input checked failed.
                      notEnoughInputForPreviousAlternative.link(this);
  
                      // Check if sufficent input available to run the next alternative 
                      notEnoughInputForPreviousAlternative.append(jumpIfNoAvailableInput(countToCheckForNextAlternative - countCheckedForCurrentAlternative));
                      // We are now in the correct state to enter the next alternative; this add is only required
                      // to mirror and revert operation of the sub32, just below.
                      add32(Imm32(countCheckedForCurrentAlternative - countToCheckForNextAlternative), index);
  
                      // If we get here, there the last input checked passed.
                      state.linkAlternativeBacktracks(this);
                      // No need to check if we can run the next alternative, since it is shorter -
                      // just update index.
                      sub32(Imm32(countCheckedForCurrentAlternative - countToCheckForNextAlternative), index);
                  } else if (countCheckedForCurrentAlternative < countToCheckForNextAlternative) { // CASE 2: next alternative is longer than the current one.
                      // If we get here, there the last input checked failed.
                      // If there is insufficient input to run the current alternative, and the next alternative is longer,
                      // then there is definitely not enough input to run it - don't even check. Just adjust index, as if
                      // we had checked.
                      notEnoughInputForPreviousAlternative.link(this);
                      add32(Imm32(countToCheckForNextAlternative - countCheckedForCurrentAlternative), index);
                      notEnoughInputForPreviousAlternative.append(jump());
  
                      // The next alternative is longer than the current one; check the difference.
                      state.linkAlternativeBacktracks(this);
                      notEnoughInputForPreviousAlternative.append(jumpIfNoAvailableInput(countToCheckForNextAlternative - countCheckedForCurrentAlternative));
                  } else { // CASE 3: Both alternatives are the same length.
                      ASSERT(countCheckedForCurrentAlternative == countToCheckForNextAlternative);
  
                      // If the next alterative is the same length as this one, then no need to check the input -
                      // if there was sufficent input to run the current alternative then there is sufficient
                      // input to run the next one; if not, there isn't.
                      state.linkAlternativeBacktracks(this);
                  }
  
                  state.checkedTotal -= countCheckedForCurrentAlternative;
                  countCheckedForCurrentAlternative = countToCheckForNextAlternative;
                  state.checkedTotal += countCheckedForCurrentAlternative;
              }
          }
          
          // If we get here, all Alternatives failed...
  
          state.checkedTotal -= countCheckedForCurrentAlternative;
  
          // How much more input need there be to be able to retry from the first alternative?
          // examples:
          //   /yarr_jit/ or /wrec|pcre/
          //     In these examples we need check for one more input before looping.
          //   /yarr_jit|pcre/
          //     In this case we need check for 5 more input to loop (+4 to allow for the first alterative
          //     being four longer than the last alternative checked, and another +1 to effectively move
          //     the start position along by one).
          //   /yarr|rules/ or /wrec|notsomuch/
          //     In these examples, provided that there was sufficient input to have just been matching for
          //     the second alternative we can loop without checking for available input (since the second
          //     alternative is longer than the first).  In the latter example we need to decrement index
          //     (by 4) so the start position is only progressed by 1 from the last iteration.
          int incrementForNextIter = (countToCheckForFirstAlternative - countCheckedForCurrentAlternative) + 1;
  
          // First, deal with the cases where there was sufficient input to try the last alternative.
          if (incrementForNextIter > 0) // We need to check for more input anyway, fall through to the checking below.
              state.linkAlternativeBacktracks(this);
          else if (m_pattern.m_body->m_hasFixedSize && !incrementForNextIter) // No need to update anything, link these backtracks straight to the to pof the loop!
              state.linkAlternativeBacktracksTo(firstAlternativeInputChecked, this);
          else { // no need to check the input, but we do have some bookkeeping to do first.
              state.linkAlternativeBacktracks(this);
  
              // Where necessary update our preserved start position.
              if (!m_pattern.m_body->m_hasFixedSize) {
                  move(index, regT0);
                  sub32(Imm32(countCheckedForCurrentAlternative - 1), regT0);
                  poke(regT0, m_pattern.m_body->m_callFrameSize);
              }
  
              // Update index if necessary, and loop (without checking).
              if (incrementForNextIter)
                  add32(Imm32(incrementForNextIter), index);
              jump().linkTo(firstAlternativeInputChecked, this);
          }
  
          notEnoughInputForPreviousAlternative.link(this);
          // Update our idea of the start position, if we're tracking this.
          if (!m_pattern.m_body->m_hasFixedSize) {
              if (countCheckedForCurrentAlternative - 1) {
                  move(index, regT0);
                  sub32(Imm32(countCheckedForCurrentAlternative - 1), regT0);
                  poke(regT0, m_pattern.m_body->m_callFrameSize);
              } else
                  poke(index, m_pattern.m_body->m_callFrameSize);
          }
          // Check if there is sufficent input to run the first alternative again.
          jumpIfAvailableInput(incrementForNextIter).linkTo(firstAlternativeInputChecked, this);
          // No - insufficent input to run the first alteranative, are there any other alternatives we
          // might need to check?  If so, the last check will have left the index incremented by
          // (countToCheckForFirstAlternative + 1), so we need test whether countToCheckForFirstAlternative
          // LESS input is available, to have the effect of just progressing the start position by 1
          // from the last iteration.  If this check passes we can just jump up to the check associated
          // with the first alternative in the loop.  This is a bit sad, since we'll end up trying the
          // first alternative again, and this check will fail (otherwise the check planted just above
          // here would have passed).  This is a bit sad, however it saves trying to do something more
          // complex here in compilation, and in the common case we should end up coallescing the checks.
          //
          // FIXME: a nice improvement here may be to stop trying to match sooner, based on the least
          // of the minimum-alternative-lengths.  E.g. if I have two alternatives of length 200 and 150,
          // and a string of length 100, we'll end up looping index from 0 to 100, checking whether there
          // is sufficient input to run either alternative (constantly failing).  If there had been only
          // one alternative, or if the shorter alternative had come first, we would have terminated
          // immediately. :-/
          if (hasShorterAlternatives)
              jumpIfAvailableInput(-countToCheckForFirstAlternative).linkTo(firstAlternative, this);
          // index will now be a bit garbled (depending on whether 'hasShorterAlternatives' is true,
          // it has either been incremented by 1 or by (countToCheckForFirstAlternative + 1) ... 
          // but since we're about to return a failure this doesn't really matter!)
  
          unsigned frameSize = m_pattern.m_body->m_callFrameSize;
          if (!m_pattern.m_body->m_hasFixedSize)
              ++frameSize;
          if (frameSize)
              addPtr(Imm32(frameSize * sizeof(void*)), stackPointerRegister);
  
          move(Imm32(-1), returnRegister);
  
          generateReturn();
      }
  
      void generateEnter()
      {
  #if CPU(X86_64)
          push(X86Registers::ebp);
          move(stackPointerRegister, X86Registers::ebp);
          push(X86Registers::ebx);
  #elif CPU(X86)
          push(X86Registers::ebp);
          move(stackPointerRegister, X86Registers::ebp);
          // TODO: do we need spill registers to fill the output pointer if there are no sub captures?
          push(X86Registers::ebx);
          push(X86Registers::edi);
          push(X86Registers::esi);
          // load output into edi (2 = saved ebp + return address).
      #if COMPILER(MSVC)
          loadPtr(Address(X86Registers::ebp, 2 * sizeof(void*)), input);
          loadPtr(Address(X86Registers::ebp, 3 * sizeof(void*)), index);
          loadPtr(Address(X86Registers::ebp, 4 * sizeof(void*)), length);
          loadPtr(Address(X86Registers::ebp, 5 * sizeof(void*)), output);
      #else
          loadPtr(Address(X86Registers::ebp, 2 * sizeof(void*)), output);
      #endif
  #elif CPU(ARM)
          push(ARMRegisters::r4);
          push(ARMRegisters::r5);
          push(ARMRegisters::r6);
          move(ARMRegisters::r3, output);
  #elif CPU(MIPS)
          // Do nothing.
  #endif
      }
  
      void generateReturn()
      {
  #if CPU(X86_64)
          pop(X86Registers::ebx);
          pop(X86Registers::ebp);
  #elif CPU(X86)
          pop(X86Registers::esi);
          pop(X86Registers::edi);
          pop(X86Registers::ebx);
          pop(X86Registers::ebp);
  #elif CPU(ARM)
          pop(ARMRegisters::r6);
          pop(ARMRegisters::r5);
          pop(ARMRegisters::r4);
  #elif CPU(MIPS)
          // Do nothing
  #endif
          ret();
      }
  
  public:
      RegexGenerator(RegexPattern& pattern)
          : m_pattern(pattern)
      {
      }
  
      void generate()
      {
          generateEnter();
  
          // TODO: do I really want this on the stack?
          if (!m_pattern.m_body->m_hasFixedSize)
              push(index);
  
          if (m_pattern.m_body->m_callFrameSize)
              subPtr(Imm32(m_pattern.m_body->m_callFrameSize * sizeof(void*)), stackPointerRegister);
  
          generateDisjunction(m_pattern.m_body);
      }
  
      void compile(AJGlobalData* globalData, RegexCodeBlock& jitObject)
      {
          generate();
  
          LinkBuffer patchBuffer(this, globalData->regexAllocator.poolForSize(size()), 0);
  
          for (unsigned i = 0; i < m_backtrackRecords.size(); ++i)
              patchBuffer.patch(m_backtrackRecords[i].dataLabel, patchBuffer.locationOf(m_backtrackRecords[i].backtrackLocation));
  
          jitObject.set(patchBuffer.finalizeCode());
      }
  
  private:
      RegexPattern& m_pattern;
      Vector<AlternativeBacktrackRecord> m_backtrackRecords;
  };
  
  void jitCompileRegex(AJGlobalData* globalData, RegexCodeBlock& jitObject, const UString& patternString, unsigned& numSubpatterns, const char*& error, bool ignoreCase, bool multiline)
  {
      RegexPattern pattern(ignoreCase, multiline);
      if ((error = compileRegex(patternString, pattern)))
          return;
      numSubpatterns = pattern.m_numSubpatterns;
  
      if (!pattern.m_shouldFallBack && globalData->canUseJIT() && RegExpCache::isCacheable(patternString)) {
          RegexGenerator generator(pattern);
          generator.compile(globalData, jitObject);
          return;
      }
  
      JSRegExpIgnoreCaseOption ignoreCaseOption = ignoreCase ? JSRegExpIgnoreCase : JSRegExpDoNotIgnoreCase;
      JSRegExpMultilineOption multilineOption = multiline ? JSRegExpMultiline : JSRegExpSingleLine;
      jitObject.setFallback(jsRegExpCompile(reinterpret_cast<const UChar*>(patternString.data()), patternString.size(), ignoreCaseOption, multilineOption, &numSubpatterns, &error));
  }
  
  }}
  
  #endif
  
  
  
  
  
  