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 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-

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 #include "yarr/YarrJIT.h"

 #include "assembler/assembler/LinkBuffer.h"

 #include "yarr/Yarr.h"

 #include "yarr/YarrCanonicalizeUCS2.h"

 #if ENABLE_YARR_JIT

 using namespace WTF;

 namespace JSC { namespace Yarr {

 template<YarrJITCompileMode compileMode>

 class YarrGenerator : private MacroAssembler {

     friend void jitCompile(JSGlobalData*, YarrCodeBlock& jitObject, const String& pattern, unsigned& numSubpatterns, const char*& error, bool ignoreCase, bool multiline);

 #if WTF_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;

     static const RegisterID returnRegister2 = ARMRegisters::r1;

 #elif WTF_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;

     static const RegisterID returnRegister2 = MIPSRegisters::v1;

 #elif WTF_CPU_SH4

     static const RegisterID input = SH4Registers::r4;

     static const RegisterID index = SH4Registers::r5;

     static const RegisterID length = SH4Registers::r6;

     static const RegisterID output = SH4Registers::r7;

     static const RegisterID regT0 = SH4Registers::r0;

     static const RegisterID regT1 = SH4Registers::r1;

     static const RegisterID returnRegister = SH4Registers::r0;

     static const RegisterID returnRegister2 = SH4Registers::r1;

 #elif WTF_CPU_SPARC

     static const RegisterID input = SparcRegisters::i0;

     static const RegisterID index = SparcRegisters::i1;

     static const RegisterID length = SparcRegisters::i2;

     static const RegisterID output = SparcRegisters::i3;

     static const RegisterID regT0 = SparcRegisters::i4;

     static const RegisterID regT1 = SparcRegisters::i5;

     static const RegisterID returnRegister = SparcRegisters::i0;

 #elif WTF_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;

     static const RegisterID returnRegister2 = X86Registers::edx;

 #elif WTF_CPU_X86_64

 # if WTF_PLATFORM_WIN

     static const RegisterID input = X86Registers::ecx;

     static const RegisterID index = X86Registers::edx;

     static const RegisterID length = X86Registers::r8;

     static const RegisterID output = X86Registers::r9;

 # else

     static const RegisterID input = X86Registers::edi;

     static const RegisterID index = X86Registers::esi;

     static const RegisterID length = X86Registers::edx;

     static const RegisterID output = X86Registers::ecx;

 # endif

     static const RegisterID regT0 = X86Registers::eax;

     static const RegisterID regT1 = X86Registers::ebx;

     static const RegisterID returnRegister = X86Registers::eax;

 # if !WTF_PLATFORM_WIN

     // no way to use int128_t as return value on Win64 ABI

     static const RegisterID returnRegister2 = X86Registers::edx;

 # endif

 #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));

             matchDest.append(branchTest8(charClass->m_tableInverted ? Zero : NonZero, tableEntry));

             return;

         }

         Jump unicodeFail;

         if (charClass->m_matchesUnicode.size() || charClass->m_rangesUnicode.size()) {

             Jump isAscii = branch32(LessThanOrEqual, character, TrustedImm32(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(TrustedImm32(32), character);

                 for (unsigned i = 0; i < countAZaz; ++i)

                     matchDest.append(branch32(Equal, character, TrustedImm32(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 = 0)

     {

         if (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 jumpIfCharNotEquals(UChar ch, int inputPosition, RegisterID character)

     {

         readCharacter(inputPosition, character);

         // For case-insesitive compares, non-ascii characters that have different

         // upper & lower case representations are converted to a character class.

         ASSERT(!m_pattern.m_ignoreCase || isASCIIAlpha(ch) || isCanonicallyUnique(ch));

         if (m_pattern.m_ignoreCase && isASCIIAlpha(ch)) {

             or32(TrustedImm32(0x20), character);

             ch |= 0x20;

         }

         return branch32(NotEqual, character, Imm32(ch));

     }

     void readCharacter(int inputPosition, RegisterID reg)

     {

         if (m_charSize == Char8)

             load8(BaseIndex(input, index, TimesOne, inputPosition * sizeof(char)), reg);

         else

             load16(BaseIndex(input, index, TimesTwo, inputPosition * sizeof(UChar)), reg);

     }

     void storeToFrame(RegisterID reg, unsigned frameLocation)

     {

         poke(reg, frameLocation);

     }

     void storeToFrame(TrustedImm32 imm, unsigned frameLocation)

     {

         poke(imm, frameLocation);

     }

     DataLabelPtr storeToFrameWithPatch(unsigned frameLocation)

     {

         return storePtrWithPatch(TrustedImmPtr(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*)));

     }

     void initCallFrame()

     {

         unsigned callFrameSize = m_pattern.m_body->m_callFrameSize;

         if (callFrameSize)

             subPtr(Imm32(callFrameSize * sizeof(void*)), stackPointerRegister);

     }

     void removeCallFrame()

     {

         unsigned callFrameSize = m_pattern.m_body->m_callFrameSize;

         if (callFrameSize)

             addPtr(Imm32(callFrameSize * sizeof(void*)), stackPointerRegister);

     }

     // Used to record subpatters, should only be called if compileMode is IncludeSubpatterns.

     void setSubpatternStart(RegisterID reg, unsigned subpattern)

     {

         ASSERT(subpattern);

         // FIXME: should be able to ASSERT(compileMode == IncludeSubpatterns), but then this function is conditionally NORETURN. :-(

         store32(reg, Address(output, (subpattern << 1) * sizeof(int)));

     }

     void setSubpatternEnd(RegisterID reg, unsigned subpattern)

     {

         ASSERT(subpattern);

         // FIXME: should be able to ASSERT(compileMode == IncludeSubpatterns), but then this function is conditionally NORETURN. :-(

         store32(reg, Address(output, ((subpattern << 1) + 1) * sizeof(int)));

     }

     void clearSubpatternStart(unsigned subpattern)

     {

         ASSERT(subpattern);

         // FIXME: should be able to ASSERT(compileMode == IncludeSubpatterns), but then this function is conditionally NORETURN. :-(

         store32(TrustedImm32(-1), Address(output, (subpattern << 1) * sizeof(int)));

     }

     // We use one of three different strategies to track the start of the current match,

     // while matching.

     // 1) If the pattern has a fixed size, do nothing! - we calculate the value lazily

     //    at the end of matching. This is irrespective of compileMode, and in this case

     //    these methods should never be called.

     // 2) If we're compiling IncludeSubpatterns, 'output' contains a pointer to an output

     //    vector, store the match start in the output vector.

     // 3) If we're compiling MatchOnly, 'output' is unused, store the match start directly

     //    in this register.

     void setMatchStart(RegisterID reg)

     {

         ASSERT(!m_pattern.m_body->m_hasFixedSize);

         if (compileMode == IncludeSubpatterns)

             store32(reg, output);

         else

             move(reg, output);

     }

     void getMatchStart(RegisterID reg)

     {

         ASSERT(!m_pattern.m_body->m_hasFixedSize);

         if (compileMode == IncludeSubpatterns)

             load32(output, reg);

         else

             move(output, reg);

     }

     enum YarrOpCode {

         // These nodes wrap body alternatives - those in the main disjunction,

         // rather than subpatterns or assertions. These are chained together in

         // a doubly linked list, with a 'begin' node for the first alternative,

         // a 'next' node for each subsequent alternative, and an 'end' node at

         // the end. In the case of repeating alternatives, the 'end' node also

         // has a reference back to 'begin'.

         OpBodyAlternativeBegin,

         OpBodyAlternativeNext,

         OpBodyAlternativeEnd,

         // Similar to the body alternatives, but used for subpatterns with two

         // or more alternatives.

         OpNestedAlternativeBegin,

         OpNestedAlternativeNext,

         OpNestedAlternativeEnd,

         // Used for alternatives in subpatterns where there is only a single

         // alternative (backtrackingis easier in these cases), or for alternatives

         // which never need to be backtracked (those in parenthetical assertions,

         // terminal subpatterns).

         OpSimpleNestedAlternativeBegin,

         OpSimpleNestedAlternativeNext,

         OpSimpleNestedAlternativeEnd,

         // Used to wrap 'Once' subpattern matches (quantityCount == 1).

         OpParenthesesSubpatternOnceBegin,

         OpParenthesesSubpatternOnceEnd,

         // Used to wrap 'Terminal' subpattern matches (at the end of the regexp).

         OpParenthesesSubpatternTerminalBegin,

         OpParenthesesSubpatternTerminalEnd,

         // Used to wrap parenthetical assertions.

         OpParentheticalAssertionBegin,

         OpParentheticalAssertionEnd,

         // Wraps all simple terms (pattern characters, character classes).

         OpTerm,

         // Where an expression contains only 'once through' body alternatives

         // and no repeating ones, this op is used to return match failure.

         OpMatchFailed

     };

     // This structure is used to hold the compiled opcode information,

     // including reference back to the original PatternTerm/PatternAlternatives,

     // and JIT compilation data structures.

     struct YarrOp {

         explicit YarrOp(PatternTerm* term)

             : m_op(OpTerm)

             , m_term(term)

             , m_isDeadCode(false)

         {

         }

         explicit YarrOp(YarrOpCode op)

             : m_op(op)

             , m_isDeadCode(false)

         {

         }

         // The operation, as a YarrOpCode, and also a reference to the PatternTerm.

         YarrOpCode m_op;

         PatternTerm* m_term;

         // For alternatives, this holds the PatternAlternative and doubly linked

         // references to this alternative's siblings. In the case of the

         // OpBodyAlternativeEnd node at the end of a section of repeating nodes,

         // m_nextOp will reference the OpBodyAlternativeBegin node of the first

         // repeating alternative.

         PatternAlternative* m_alternative;

         size_t m_previousOp;

         size_t m_nextOp;

         // Used to record a set of Jumps out of the generated code, typically

         // used for jumps out to backtracking code, and a single reentry back

         // into the code for a node (likely where a backtrack will trigger

         // rematching).

         Label m_reentry;

         JumpList m_jumps;

         // Used for backtracking when the prior alternative did not consume any

         // characters but matched.

         Jump m_zeroLengthMatch;

         // This flag is used to null out the second pattern character, when

         // two are fused to match a pair together.

         bool m_isDeadCode;

         // Currently used in the case of some of the more complex management of

         // 'm_checked', to cache the offset used in this alternative, to avoid

         // recalculating it.

         int m_checkAdjust;

         // Used by OpNestedAlternativeNext/End to hold the pointer to the

         // value that will be pushed into the pattern's frame to return to,

         // upon backtracking back into the disjunction.

         DataLabelPtr m_returnAddress;

     };

     // BacktrackingState

     // This class encapsulates information about the state of code generation

     // whilst generating the code for backtracking, when a term fails to match.

     // Upon entry to code generation of the backtracking code for a given node,

     // the Backtracking state will hold references to all control flow sources

     // that are outputs in need of further backtracking from the prior node

     // generated (which is the subsequent operation in the regular expression,

     // and in the m_ops Vector, since we generated backtracking backwards).

     // These references to control flow take the form of:

     //  - A jump list of jumps, to be linked to code that will backtrack them

     //    further.

     //  - A set of DataLabelPtr values, to be populated with values to be

     //    treated effectively as return addresses backtracking into complex

     //    subpatterns.

     //  - A flag indicating that the current sequence of generated code up to

     //    this point requires backtracking.

     class BacktrackingState {

     public:

         BacktrackingState()

             : m_pendingFallthrough(false)

         {

         }

         // Add a jump or jumps, a return address, or set the flag indicating

         // that the current 'fallthrough' control flow requires backtracking.

         void append(const Jump& jump)

         {

             m_laterFailures.append(jump);

         }

         void append(JumpList& jumpList)

         {

             m_laterFailures.append(jumpList);

         }

         void append(const DataLabelPtr& returnAddress)

         {

             m_pendingReturns.append(returnAddress);

         }

         void fallthrough()

         {

             ASSERT(!m_pendingFallthrough);

             m_pendingFallthrough = true;

         }

         // These methods clear the backtracking state, either linking to the

         // current location, a provided label, or copying the backtracking out

         // to a JumpList. All actions may require code generation to take place,

         // and as such are passed a pointer to the assembler.

         void link(MacroAssembler* assembler)

         {

             if (m_pendingReturns.size()) {

                 Label here(assembler);

                 for (unsigned i = 0; i < m_pendingReturns.size(); ++i)

                     m_backtrackRecords.append(ReturnAddressRecord(m_pendingReturns[i], here));

                 m_pendingReturns.clear();

             }

             m_laterFailures.link(assembler);

             m_laterFailures.clear();

             m_pendingFallthrough = false;

         }

         void linkTo(Label label, MacroAssembler* assembler)

         {

             if (m_pendingReturns.size()) {

                 for (unsigned i = 0; i < m_pendingReturns.size(); ++i)

                     m_backtrackRecords.append(ReturnAddressRecord(m_pendingReturns[i], label));

                 m_pendingReturns.clear();

             }

             if (m_pendingFallthrough)

                 assembler->jump(label);

             m_laterFailures.linkTo(label, assembler);

             m_laterFailures.clear();

             m_pendingFallthrough = false;

         }

         void takeBacktracksToJumpList(JumpList& jumpList, MacroAssembler* assembler)

         {

             if (m_pendingReturns.size()) {

                 Label here(assembler);

                 for (unsigned i = 0; i < m_pendingReturns.size(); ++i)

                     m_backtrackRecords.append(ReturnAddressRecord(m_pendingReturns[i], here));

                 m_pendingReturns.clear();

                 m_pendingFallthrough = true;

             }

             if (m_pendingFallthrough)

                 jumpList.append(assembler->jump());

             jumpList.append(m_laterFailures);

             m_laterFailures.clear();

             m_pendingFallthrough = false;

         }

         bool isEmpty()

         {

             return m_laterFailures.empty() && m_pendingReturns.isEmpty() && !m_pendingFallthrough;

         }

         // Called at the end of code generation to link all return addresses.

         void linkDataLabels(LinkBuffer& linkBuffer)

         {

             ASSERT(isEmpty());

             for (unsigned i = 0; i < m_backtrackRecords.size(); ++i)

                 linkBuffer.patch(m_backtrackRecords[i].m_dataLabel, linkBuffer.locationOf(m_backtrackRecords[i].m_backtrackLocation));

         }

     private:

         struct ReturnAddressRecord {

             ReturnAddressRecord(DataLabelPtr dataLabel, Label backtrackLocation)

                 : m_dataLabel(dataLabel)

                 , m_backtrackLocation(backtrackLocation)

             {

             }

             DataLabelPtr m_dataLabel;

             Label m_backtrackLocation;

         };

         JumpList m_laterFailures;

         bool m_pendingFallthrough;

         Vector<DataLabelPtr, 4> m_pendingReturns;

         Vector<ReturnAddressRecord, 4> m_backtrackRecords;

     };

     // Generation methods:

     // ===================

     // This method provides a default implementation of backtracking common

     // to many terms; terms commonly jump out of the forwards  matching path

     // on any failed conditions, and add these jumps to the m_jumps list. If

     // no special handling is required we can often just backtrack to m_jumps.

     bool backtrackTermDefault(size_t opIndex)

     {

         YarrOp& op = m_ops[opIndex];

         m_backtrackingState.append(op.m_jumps);

         return true;

     }

     bool generateAssertionBOL(size_t opIndex)

     {

         YarrOp& op = m_ops[opIndex];

         PatternTerm* term = op.m_term;

         if (m_pattern.m_multiline) {

             const RegisterID character = regT0;

             JumpList matchDest;

             if (!term->inputPosition)

                 matchDest.append(branch32(Equal, index, Imm32(m_checked)));

             readCharacter((term->inputPosition - m_checked) - 1, character);

             matchCharacterClass(character, matchDest, m_pattern.newlineCharacterClass());

             op.m_jumps.append(jump());

             matchDest.link(this);

         } else {

             // Erk, really should poison out these alternatives early. :-/

             if (term->inputPosition)

                 op.m_jumps.append(jump());

             else

                 op.m_jumps.append(branch32(NotEqual, index, Imm32(m_checked)));

         }

         return true;

     }

     bool backtrackAssertionBOL(size_t opIndex)

     {

         return backtrackTermDefault(opIndex);

     }

     bool generateAssertionEOL(size_t opIndex)

     {

         YarrOp& op = m_ops[opIndex];

         PatternTerm* term = op.m_term;

         if (m_pattern.m_multiline) {

             const RegisterID character = regT0;

             JumpList matchDest;

             if (term->inputPosition == m_checked)

                 matchDest.append(atEndOfInput());

             readCharacter(term->inputPosition - m_checked, character);

             matchCharacterClass(character, matchDest, m_pattern.newlineCharacterClass());

             op.m_jumps.append(jump());

             matchDest.link(this);

         } else {

             if (term->inputPosition == m_checked)

                 op.m_jumps.append(notAtEndOfInput());

             // Erk, really should poison out these alternatives early. :-/

             else

                 op.m_jumps.append(jump());

         }

         return true;

     }

     bool backtrackAssertionEOL(size_t opIndex)

     {

         return backtrackTermDefault(opIndex);

     }

     // Also falls though on nextIsNotWordChar.

     void matchAssertionWordchar(size_t opIndex, JumpList& nextIsWordChar, JumpList& nextIsNotWordChar)

     {

         YarrOp& op = m_ops[opIndex];

         PatternTerm* term = op.m_term;

         const RegisterID character = regT0;

         if (term->inputPosition == m_checked)

             nextIsNotWordChar.append(atEndOfInput());

         readCharacter((term->inputPosition - m_checked), character);

         matchCharacterClass(character, nextIsWordChar, m_pattern.wordcharCharacterClass());

     }

     bool generateAssertionWordBoundary(size_t opIndex)

     {

         YarrOp& op = m_ops[opIndex];

         PatternTerm* term = op.m_term;

         const RegisterID character = regT0;

         Jump atBegin;

         JumpList matchDest;

         if (!term->inputPosition)

             atBegin = branch32(Equal, index, Imm32(m_checked));

         readCharacter((term->inputPosition - m_checked) - 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->invert()) {

             matchAssertionWordchar(opIndex, nonWordCharThenNonWordChar, nonWordCharThenWordChar);

             nonWordCharThenWordChar.append(jump());

         } else {

             matchAssertionWordchar(opIndex, nonWordCharThenWordChar, nonWordCharThenNonWordChar);

             nonWordCharThenNonWordChar.append(jump());

         }

         op.m_jumps.append(nonWordCharThenNonWordChar);

         // We jump here if the last character was a wordchar.

         matchDest.link(this);

         JumpList wordCharThenWordChar;

         JumpList wordCharThenNonWordChar;

         if (term->invert()) {

             matchAssertionWordchar(opIndex, wordCharThenNonWordChar, wordCharThenWordChar);

             wordCharThenWordChar.append(jump());

         } else {

             matchAssertionWordchar(opIndex, wordCharThenWordChar, wordCharThenNonWordChar);

             // This can fall-though!

         }

         op.m_jumps.append(wordCharThenWordChar);

         nonWordCharThenWordChar.link(this);

         wordCharThenNonWordChar.link(this);

         return true;

     }

     bool backtrackAssertionWordBoundary(size_t opIndex)

     {

         return backtrackTermDefault(opIndex);

     }

     bool generatePatternCharacterOnce(size_t opIndex)

     {

         YarrOp& op = m_ops[opIndex];

         if (op.m_isDeadCode)

             return true;

         // m_ops always ends with a OpBodyAlternativeEnd or OpMatchFailed

         // node, so there must always be at least one more node.

         ASSERT(opIndex + 1 < m_ops.size());

         YarrOp* nextOp = &m_ops[opIndex + 1];

         PatternTerm* term = op.m_term;

         UChar ch = term->patternCharacter;

         if ((ch > 0xff) && (m_charSize == Char8)) {

             // Have a 16 bit pattern character and an 8 bit string - short circuit

             op.m_jumps.append(jump());

             return true;

         }

         const RegisterID character = regT0;

         int maxCharactersAtOnce = m_charSize == Char8 ? 4 : 2;

         unsigned ignoreCaseMask = 0;

 #if CPU(BIG_ENDIAN)

         int allCharacters = ch << (m_charSize == Char8 ? 24 : 16);

 #else

         int allCharacters = ch;

 #endif

         int numberCharacters;

         int startTermPosition = term->inputPosition;

         // For case-insesitive compares, non-ascii characters that have different

         // upper & lower case representations are converted to a character class.

         ASSERT(!m_pattern.m_ignoreCase || isASCIIAlpha(ch) || isCanonicallyUnique(ch));

         if (m_pattern.m_ignoreCase && isASCIIAlpha(ch))

 #if CPU(BIG_ENDIAN)

             ignoreCaseMask |= 32 << (m_charSize == Char8 ? 24 : 16);

 #else

             ignoreCaseMask |= 32;

 #endif

         for (numberCharacters = 1; numberCharacters < maxCharactersAtOnce && nextOp->m_op == OpTerm; ++numberCharacters, nextOp = &m_ops[opIndex + numberCharacters]) {

             PatternTerm* nextTerm = nextOp->m_term;

             if (nextTerm->type != PatternTerm::TypePatternCharacter

                 || nextTerm->quantityType != QuantifierFixedCount

                 || nextTerm->quantityCount != 1

                 || nextTerm->inputPosition != (startTermPosition + numberCharacters))

                 break;

             nextOp->m_isDeadCode = true;

 #if CPU(BIG_ENDIAN)

             int shiftAmount = (m_charSize == Char8 ? 24 : 16) - ((m_charSize == Char8 ? 8 : 16) * numberCharacters);

 #else

             int shiftAmount = (m_charSize == Char8 ? 8 : 16) * numberCharacters;

 #endif

             UChar currentCharacter = nextTerm->patternCharacter;

             if ((currentCharacter > 0xff) && (m_charSize == Char8)) {

                 // Have a 16 bit pattern character and an 8 bit string - short circuit

                 op.m_jumps.append(jump());

                 return true;

             }

             // For case-insesitive compares, non-ascii characters that have different

             // upper & lower case representations are converted to a character class.

             ASSERT(!m_pattern.m_ignoreCase || isASCIIAlpha(currentCharacter) || isCanonicallyUnique(currentCharacter));

             allCharacters |= (currentCharacter << shiftAmount);

             if ((m_pattern.m_ignoreCase) && (isASCIIAlpha(currentCharacter)))

                 ignoreCaseMask |= 32 << shiftAmount;

         }

         if (m_charSize == Char8) {

             switch (numberCharacters) {

             case 1:

                 op.m_jumps.append(jumpIfCharNotEquals(ch, startTermPosition - m_checked, character));

                 return true;

             case 2: {

                 BaseIndex address(input, index, TimesOne, (startTermPosition - m_checked) * sizeof(LChar));

                 load16Unaligned(address, character);

                 break;

             }

             case 3: {

                 BaseIndex highAddress(input, index, TimesOne, (startTermPosition - m_checked) * sizeof(LChar));

                 load16Unaligned(highAddress, character);

                 if (ignoreCaseMask)

                     or32(Imm32(ignoreCaseMask), character);

                 op.m_jumps.append(branch32(NotEqual, character, Imm32((allCharacters & 0xffff) | ignoreCaseMask)));

                 op.m_jumps.append(jumpIfCharNotEquals(allCharacters >> 16, startTermPosition + 2 - m_checked, character));

                 return true;

             }

             case 4: {

                 BaseIndex address(input, index, TimesOne, (startTermPosition - m_checked) * sizeof(LChar));

                 load32WithUnalignedHalfWords(address, character);

                 break;

             }

             }

         } else {

             switch (numberCharacters) {

             case 1:

                 op.m_jumps.append(jumpIfCharNotEquals(ch, term->inputPosition - m_checked, character));

                 return true;

             case 2:

                 BaseIndex address(input, index, TimesTwo, (term->inputPosition - m_checked) * sizeof(UChar));

                 load32WithUnalignedHalfWords(address, character);

                 break;

             }

         }

         if (ignoreCaseMask)

             or32(Imm32(ignoreCaseMask), character);

         op.m_jumps.append(branch32(NotEqual, character, Imm32(allCharacters | ignoreCaseMask)));

         return true;

     }

     bool backtrackPatternCharacterOnce(size_t opIndex)

     {

         return backtrackTermDefault(opIndex);

     }

     bool generatePatternCharacterFixed(size_t opIndex)

     {

         YarrOp& op = m_ops[opIndex];

         PatternTerm* term = op.m_term;

         UChar ch = term->patternCharacter;

         const RegisterID character = regT0;

         const RegisterID countRegister = regT1;

         move(index, countRegister);

         if (term->quantityCount.hasOverflowed())

             return false;

         sub32(Imm32(term->quantityCount.unsafeGet()), countRegister);

         Label loop(this);

         int offset;

         if ((Checked<int>(term->inputPosition - m_checked + Checked<int64_t>(term->quantityCount)) * static_cast<int>(m_charSize == Char8 ? sizeof(char) : sizeof(UChar))).safeGet(offset))

             return false;

         BaseIndex address(input, countRegister, m_charScale, offset);

         if (m_charSize == Char8)

             load8(address, character);

         else

             load16(address, character);

         // For case-insesitive compares, non-ascii characters that have different

         // upper & lower case representations are converted to a character class.

         ASSERT(!m_pattern.m_ignoreCase || isASCIIAlpha(ch) || isCanonicallyUnique(ch));

         if (m_pattern.m_ignoreCase && isASCIIAlpha(ch)) {

             or32(TrustedImm32(0x20), character);

             ch |= 0x20;

         }

         op.m_jumps.append(branch32(NotEqual, character, Imm32(ch)));

         add32(TrustedImm32(1), countRegister);

         branch32(NotEqual, countRegister, index).linkTo(loop, this);

         return true;

     }

     bool backtrackPatternCharacterFixed(size_t opIndex)

     {

         return backtrackTermDefault(opIndex);

     }

     bool generatePatternCharacterGreedy(size_t opIndex)

     {

         YarrOp& op = m_ops[opIndex];

         PatternTerm* term = op.m_term;

         UChar ch = term->patternCharacter;

         const RegisterID character = regT0;

         const RegisterID countRegister = regT1;

         move(TrustedImm32(0), countRegister);

         // Unless have a 16 bit pattern character and an 8 bit string - short circuit

         if (!((ch > 0xff) && (m_charSize == Char8))) {

             JumpList failures;

             Label loop(this);

             failures.append(atEndOfInput());

             failures.append(jumpIfCharNotEquals(ch, term->inputPosition - m_checked, character));

             add32(TrustedImm32(1), countRegister);

             add32(TrustedImm32(1), index);

             if (term->quantityCount == quantifyInfinite) {

                 jump(loop);

             } else {

                 if (term->quantityCount.hasOverflowed())

                     return false;

                 branch32(NotEqual, countRegister, Imm32(term->quantityCount.unsafeGet())).linkTo(loop, this);

             }

             failures.link(this);

         }

         op.m_reentry = label();

         storeToFrame(countRegister, term->frameLocation);

         return true;

     }

     bool backtrackPatternCharacterGreedy(size_t opIndex)

     {

         YarrOp& op = m_ops[opIndex];

         PatternTerm* term = op.m_term;

         const RegisterID countRegister = regT1;

         m_backtrackingState.link(this);

         loadFromFrame(term->frameLocation, countRegister);

         m_backtrackingState.append(branchTest32(Zero, countRegister));

         sub32(TrustedImm32(1), countRegister);

         sub32(TrustedImm32(1), index);

         jump(op.m_reentry);

         return true;

     }

     bool generatePatternCharacterNonGreedy(size_t opIndex)

     {

         YarrOp& op = m_ops[opIndex];

         PatternTerm* term = op.m_term;

         const RegisterID countRegister = regT1;

         move(TrustedImm32(0), countRegister);

         op.m_reentry = label();

         storeToFrame(countRegister, term->frameLocation);

         return true;

     }

     bool backtrackPatternCharacterNonGreedy(size_t opIndex)

     {

         YarrOp& op = m_ops[opIndex];

         PatternTerm* term = op.m_term;

         UChar ch = term->patternCharacter;

         const RegisterID character = regT0;

         const RegisterID countRegister = regT1;

         m_backtrackingState.link(this);

         loadFromFrame(term->frameLocation, countRegister);

         // Unless have a 16 bit pattern character and an 8 bit string - short circuit

         if (!((ch > 0xff) && (m_charSize == Char8))) {

             JumpList nonGreedyFailures;

             nonGreedyFailures.append(atEndOfInput());

             if (term->quantityCount != quantifyInfinite) {

                 if (term->quantityCount.hasOverflowed())

                     return false;

                 nonGreedyFailures.append(branch32(Equal, countRegister, Imm32(term->quantityCount.unsafeGet())));

             }

             nonGreedyFailures.append(jumpIfCharNotEquals(ch, term->inputPosition - m_checked, character));

             add32(TrustedImm32(1), countRegister);

             add32(TrustedImm32(1), index);

             jump(op.m_reentry);

             nonGreedyFailures.link(this);

         }

         sub32(countRegister, index);

         m_backtrackingState.fallthrough();

         return true;

     }

     bool generateCharacterClassOnce(size_t opIndex)

     {

         YarrOp& op = m_ops[opIndex];

         PatternTerm* term = op.m_term;

         const RegisterID character = regT0;

         JumpList matchDest;

         readCharacter(term->inputPosition - m_checked, character);

         matchCharacterClass(character, matchDest, term->characterClass);

         if (term->invert())

             op.m_jumps.append(matchDest);

         else {

             op.m_jumps.append(jump());

             matchDest.link(this);

         }

         return true;

     }

     bool backtrackCharacterClassOnce(size_t opIndex)

     {

         return backtrackTermDefault(opIndex);

     }

     bool generateCharacterClassFixed(size_t opIndex)

     {

         YarrOp& op = m_ops[opIndex];

         PatternTerm* term = op.m_term;

         const RegisterID character = regT0;

         const RegisterID countRegister = regT1;

         move(index, countRegister);

         if (term->quantityCount.hasOverflowed())

             return false;

         sub32(Imm32(term->quantityCount.unsafeGet()), countRegister);

         Label loop(this);

         JumpList matchDest;

         int offset;

         Checked<int64_t> checkedOffset(term->inputPosition - m_checked + Checked<int64_t>(term->quantityCount));

         if (m_charSize == Char8) {

             if ((Checked<int>(checkedOffset) * static_cast<int>(sizeof(char))).safeGet(offset))

                 return false;

             load8(BaseIndex(input, countRegister, TimesOne, offset), character);

         } else {

             if ((Checked<int>(checkedOffset) * static_cast<int>(sizeof(UChar))).safeGet(offset))

                 return false;

             load16(BaseIndex(input, countRegister, TimesTwo, offset), character);

         }

         matchCharacterClass(character, matchDest, term->characterClass);

         if (term->invert())

             op.m_jumps.append(matchDest);

         else {

             op.m_jumps.append(jump());

             matchDest.link(this);

         }

         add32(TrustedImm32(1), countRegister);

         branch32(NotEqual, countRegister, index).linkTo(loop, this);

         return true;

     }

     bool backtrackCharacterClassFixed(size_t opIndex)

     {

         return backtrackTermDefault(opIndex);

     }

     bool generateCharacterClassGreedy(size_t opIndex)

     {

         YarrOp& op = m_ops[opIndex];

         PatternTerm* term = op.m_term;

         const RegisterID character = regT0;

         const RegisterID countRegister = regT1;

         move(TrustedImm32(0), countRegister);

         JumpList failures;

         Label loop(this);

         failures.append(atEndOfInput());

         if (term->invert()) {

             readCharacter(term->inputPosition - m_checked, character);

             matchCharacterClass(character, failures, term->characterClass);

         } else {

             JumpList matchDest;

             readCharacter(term->inputPosition - m_checked, character);

             matchCharacterClass(character, matchDest, term->characterClass);

             failures.append(jump());

             matchDest.link(this);

         }

         add32(TrustedImm32(1), countRegister);

         add32(TrustedImm32(1), index);

         if (term->quantityCount != quantifyInfinite) {

             unsigned quantityCount;

             if (term->quantityCount.safeGet(quantityCount))

                 return false;

             branch32(NotEqual, countRegister, Imm32(quantityCount)).linkTo(loop, this);

             failures.append(jump());

         } else

             jump(loop);

         failures.link(this);

         op.m_reentry = label();

         storeToFrame(countRegister, term->frameLocation);

         return true;

     }

     bool backtrackCharacterClassGreedy(size_t opIndex)

     {

         YarrOp& op = m_ops[opIndex];

         PatternTerm* term = op.m_term;

         const RegisterID countRegister = regT1;

         m_backtrackingState.link(this);

         loadFromFrame(term->frameLocation, countRegister);

         m_backtrackingState.append(branchTest32(Zero, countRegister));

         sub32(TrustedImm32(1), countRegister);

         sub32(TrustedImm32(1), index);

         jump(op.m_reentry);

         return true;

     }

     bool generateCharacterClassNonGreedy(size_t opIndex)

     {

         YarrOp& op = m_ops[opIndex];

         PatternTerm* term = op.m_term;

         const RegisterID countRegister = regT1;

         move(TrustedImm32(0), countRegister);

         op.m_reentry = label();

         storeToFrame(countRegister, term->frameLocation);

         return true;

     }

     bool backtrackCharacterClassNonGreedy(size_t opIndex)

     {

         YarrOp& op = m_ops[opIndex];

         PatternTerm* term = op.m_term;

         const RegisterID character = regT0;

         const RegisterID countRegister = regT1;

         JumpList nonGreedyFailures;

         m_backtrackingState.link(this);

         loadFromFrame(term->frameLocation, countRegister);

         nonGreedyFailures.append(atEndOfInput());

         if (term->quantityCount.hasOverflowed())

             return false;

         nonGreedyFailures.append(branch32(Equal, countRegister, Imm32(term->quantityCount.unsafeGet())));

         JumpList matchDest;

         readCharacter(term->inputPosition - m_checked, character);

         matchCharacterClass(character, matchDest, term->characterClass);

         if (term->invert())

             nonGreedyFailures.append(matchDest);

         else {

             nonGreedyFailures.append(jump());

             matchDest.link(this);

         }

         add32(TrustedImm32(1), countRegister);

         add32(TrustedImm32(1), index);

         jump(op.m_reentry);

         nonGreedyFailures.link(this);

         sub32(countRegister, index);

         m_backtrackingState.fallthrough();

         return true;

     }

     bool generateDotStarEnclosure(size_t opIndex)

     {

         YarrOp& op = m_ops[opIndex];

         PatternTerm* term = op.m_term;

         const RegisterID character = regT0;

         const RegisterID matchPos = regT1;

         JumpList foundBeginningNewLine;

         JumpList saveStartIndex;

         JumpList foundEndingNewLine;

         ASSERT(!m_pattern.m_body->m_hasFixedSize);

         getMatchStart(matchPos);

         saveStartIndex.append(branchTest32(Zero, matchPos));

         Label findBOLLoop(this);

         sub32(TrustedImm32(1), matchPos);

         if (m_charSize == Char8)

             load8(BaseIndex(input, matchPos, TimesOne, 0), character);

         else

             load16(BaseIndex(input, matchPos, TimesTwo, 0), character);

         matchCharacterClass(character, foundBeginningNewLine, m_pattern.newlineCharacterClass());

         branchTest32(NonZero, matchPos).linkTo(findBOLLoop, this);

         saveStartIndex.append(jump());

         foundBeginningNewLine.link(this);

         add32(TrustedImm32(1), matchPos); // Advance past newline

         saveStartIndex.link(this);

         if (!m_pattern.m_multiline && term->anchors.bolAnchor)

             op.m_jumps.append(branchTest32(NonZero, matchPos));

         ASSERT(!m_pattern.m_body->m_hasFixedSize);

         setMatchStart(matchPos);

         move(index, matchPos);

         Label findEOLLoop(this);

         foundEndingNewLine.append(branch32(Equal, matchPos, length));

         if (m_charSize == Char8)

             load8(BaseIndex(input, matchPos, TimesOne, 0), character);

         else

             load16(BaseIndex(input, matchPos, TimesTwo, 0), character);

         matchCharacterClass(character, foundEndingNewLine, m_pattern.newlineCharacterClass());

         add32(TrustedImm32(1), matchPos);

         jump(findEOLLoop);

         foundEndingNewLine.link(this);

         if (!m_pattern.m_multiline && term->anchors.eolAnchor)

             op.m_jumps.append(branch32(NotEqual, matchPos, length));

         move(matchPos, index);

         return true;

     }

     bool backtrackDotStarEnclosure(size_t opIndex)

     {

         return backtrackTermDefault(opIndex);

     }

     // Code generation/backtracking for simple terms

     // (pattern characters, character classes, and assertions).

     // These methods farm out work to the set of functions above.

     bool generateTerm(size_t opIndex)

     {

         YarrOp& op = m_ops[opIndex];

         PatternTerm* term = op.m_term;

         switch (term->type) {

         case PatternTerm::TypePatternCharacter:

             switch (term->quantityType) {

             case QuantifierFixedCount:

                 if (term->quantityCount == 1)

                     return generatePatternCharacterOnce(opIndex);

                 else

                     return generatePatternCharacterFixed(opIndex);

                 break;

             case QuantifierGreedy:

                 return generatePatternCharacterGreedy(opIndex);

             case QuantifierNonGreedy:

                 return generatePatternCharacterNonGreedy(opIndex);

             }

             break;

         case PatternTerm::TypeCharacterClass:

             switch (term->quantityType) {

             case QuantifierFixedCount:

                 if (term->quantityCount == 1)

                     return generateCharacterClassOnce(opIndex);

                 else

                     return generateCharacterClassFixed(opIndex);

                 break;

             case QuantifierGreedy:

                 return generateCharacterClassGreedy(opIndex);

             case QuantifierNonGreedy:

                 return generateCharacterClassNonGreedy(opIndex);

             }

             break;

         case PatternTerm::TypeAssertionBOL:

             return generateAssertionBOL(opIndex);

         case PatternTerm::TypeAssertionEOL:

             return generateAssertionEOL(opIndex);

         case PatternTerm::TypeAssertionWordBoundary:

             return generateAssertionWordBoundary(opIndex);

         case PatternTerm::TypeForwardReference:

             return true;

         case PatternTerm::TypeParenthesesSubpattern:

         case PatternTerm::TypeParentheticalAssertion:

             ASSERT_NOT_REACHED();

             return false;

         case PatternTerm::TypeBackReference:

             return false;

         case PatternTerm::TypeDotStarEnclosure:

             return generateDotStarEnclosure(opIndex);

         }

         return false;

     }

     bool backtrackTerm(size_t opIndex)

     {

         YarrOp& op = m_ops[opIndex];

         PatternTerm* term = op.m_term;

         switch (term->type) {

         case PatternTerm::TypePatternCharacter:

             switch (term->quantityType) {

             case QuantifierFixedCount:

                 if (term->quantityCount == 1)

                     return backtrackPatternCharacterOnce(opIndex);

                 else

                     return backtrackPatternCharacterFixed(opIndex);

             case QuantifierGreedy:

                 return backtrackPatternCharacterGreedy(opIndex);

             case QuantifierNonGreedy:

                 return backtrackPatternCharacterNonGreedy(opIndex);

             }

             break;

         case PatternTerm::TypeCharacterClass:

             switch (term->quantityType) {

             case QuantifierFixedCount:

                 if (term->quantityCount == 1)

                     return backtrackCharacterClassOnce(opIndex);

                 else

                     return backtrackCharacterClassFixed(opIndex);

             case QuantifierGreedy:

                 return backtrackCharacterClassGreedy(opIndex);

             case QuantifierNonGreedy:

                 return backtrackCharacterClassNonGreedy(opIndex);

             }

             break;

         case PatternTerm::TypeAssertionBOL:

             return backtrackAssertionBOL(opIndex);

         case PatternTerm::TypeAssertionEOL:

             return backtrackAssertionEOL(opIndex);

         case PatternTerm::TypeAssertionWordBoundary:

             return backtrackAssertionWordBoundary(opIndex);

         case PatternTerm::TypeForwardReference:

             return true;

         case PatternTerm::TypeParenthesesSubpattern:

         case PatternTerm::TypeParentheticalAssertion:

             ASSERT_NOT_REACHED();

             return false;

         case PatternTerm::TypeDotStarEnclosure:

             return backtrackDotStarEnclosure(opIndex);

         case PatternTerm::TypeBackReference:

             return false;

         }

         return true;

     }

     bool generate()

     {

         // Forwards generate the matching code.

         ASSERT(m_ops.size());

         size_t opIndex = 0;

         do {

             YarrOp& op = m_ops[opIndex];

             switch (op.m_op) {

             case OpTerm:

                 if (!generateTerm(opIndex))

                     return false;

                 break;

             // OpBodyAlternativeBegin/Next/End

             //

             // These nodes wrap the set of alternatives in the body of the regular expression.

             // There may be either one or two chains of OpBodyAlternative nodes, one representing

             // the 'once through' sequence of alternatives (if any exist), and one representing

             // the repeating alternatives (again, if any exist).

             //

             // Upon normal entry to the Begin alternative, we will check that input is available.

             // Reentry to the Begin alternative will take place after the check has taken place,

             // and will assume that the input position has already been progressed as appropriate.

             //

             // Entry to subsequent Next/End alternatives occurs when the prior alternative has

             // successfully completed a match - return a success state from JIT code.

             //

             // Next alternatives allow for reentry optimized to suit backtracking from its

             // preceding alternative. It expects the input position to still be set to a position

             // appropriate to its predecessor, and it will only perform an input check if the

             // predecessor had a minimum size less than its own.

             //

             // In the case 'once through' expressions, the End node will also have a reentry

             // point to jump to when the last alternative fails. Again, this expects the input

             // position to still reflect that expected by the prior alternative.

             case OpBodyAlternativeBegin: {

                 PatternAlternative* alternative = op.m_alternative;

                 // Upon entry at the head of the set of alternatives, check if input is available

                 // to run the first alternative. (This progresses the input position).

                 op.m_jumps.append(jumpIfNoAvailableInput(alternative->m_minimumSize));

                 // We will reenter after the check, and assume the input position to have been

                 // set as appropriate to this alternative.

                 op.m_reentry = label();

                 if (alternative->m_minimumSize > INT_MAX)

                     return false;

                 m_checked = alternative->m_minimumSize;

                 break;

             }

             case OpBodyAlternativeNext:

             case OpBodyAlternativeEnd: {

                 PatternAlternative* priorAlternative = m_ops[op.m_previousOp].m_alternative;

                 PatternAlternative* alternative = op.m_alternative;

                 // If we get here, the prior alternative matched - return success.

                 // Adjust the stack pointer to remove the pattern's frame.

 #if !WTF_CPU_SPARC

                 removeCallFrame();

 #endif

                 // Load appropriate values into the return register and the first output

                 // slot, and return. In the case of pattern with a fixed size, we will

                 // not have yet set the value in the first

                 ASSERT(index != returnRegister);

                 if (m_pattern.m_body->m_hasFixedSize) {

                     move(index, returnRegister);

                     if (priorAlternative->m_minimumSize)

                         sub32(Imm32(priorAlternative->m_minimumSize), returnRegister);

                     if (compileMode == IncludeSubpatterns)

                         store32(returnRegister, output);

                 } else

                     getMatchStart(returnRegister);

                 if (compileMode == IncludeSubpatterns)

                     store32(index, Address(output, 4));

 #if WTF_CPU_X86_64

                 // upper 32bit to 0

                 move32(returnRegister, returnRegister);

                 lshiftPtr(Imm32(32), index);

                 orPtr(index, returnRegister);

 #else

                 move(index, returnRegister2);

 #endif

                 generateReturn();

                 // This is the divide between the tail of the prior alternative, above, and

                 // the head of the subsequent alternative, below.

                 if (op.m_op == OpBodyAlternativeNext) {

                     // This is the reentry point for the Next alternative. We expect any code

                     // that jumps here to do so with the input position matching that of the

                     // PRIOR alteranative, and we will only check input availability if we

                     // need to progress it forwards.

                     op.m_reentry = label();

                     if (alternative->m_minimumSize > priorAlternative->m_minimumSize) {

                         add32(Imm32(alternative->m_minimumSize - priorAlternative->m_minimumSize), index);

                         op.m_jumps.append(jumpIfNoAvailableInput());

                     } else if (priorAlternative->m_minimumSize > alternative->m_minimumSize)

                         sub32(Imm32(priorAlternative->m_minimumSize - alternative->m_minimumSize), index);

                 } else if (op.m_nextOp == notFound) {

                     // This is the reentry point for the End of 'once through' alternatives,

                     // jumped to when the last alternative fails to match.

                     op.m_reentry = label();

                     sub32(Imm32(priorAlternative->m_minimumSize), index);

                 }

                 if (op.m_op == OpBodyAlternativeNext)

                     m_checked += alternative->m_minimumSize;

                 m_checked -= priorAlternative->m_minimumSize;

                 break;

             }

             // OpSimpleNestedAlternativeBegin/Next/End

             // OpNestedAlternativeBegin/Next/End

             //

             // These nodes are used to handle sets of alternatives that are nested within

             // subpatterns and parenthetical assertions. The 'simple' forms are used where

             // we do not need to be able to backtrack back into any alternative other than

             // the last, the normal forms allow backtracking into any alternative.

             //

             // Each Begin/Next node is responsible for planting an input check to ensure

             // sufficient input is available on entry. Next nodes additionally need to

             // jump to the end - Next nodes use the End node's m_jumps list to hold this

             // set of jumps.

             //

             // In the non-simple forms, successful alternative matches must store a

             // 'return address' using a DataLabelPtr, used to store the address to jump

             // to when backtracking, to get to the code for the appropriate alternative.

             case OpSimpleNestedAlternativeBegin:

             case OpNestedAlternativeBegin: {

                 PatternTerm* term = op.m_term;

                 PatternAlternative* alternative = op.m_alternative;

                 PatternDisjunction* disjunction = term->parentheses.disjunction;

                 // Calculate how much input we need to check for, and if non-zero check.

                 op.m_checkAdjust = alternative->m_minimumSize;

                 if ((term->quantityType == QuantifierFixedCount) && (term->type != PatternTerm::TypeParentheticalAssertion))

                     op.m_checkAdjust -= disjunction->m_minimumSize;

                 if (op.m_checkAdjust)

                     op.m_jumps.append(jumpIfNoAvailableInput(op.m_checkAdjust));

                 m_checked += op.m_checkAdjust;

                 break;

             }

             case OpSimpleNestedAlternativeNext:

             case OpNestedAlternativeNext: {

                 PatternTerm* term = op.m_term;

                 PatternAlternative* alternative = op.m_alternative;

                 PatternDisjunction* disjunction = term->parentheses.disjunction;

                 // In the non-simple case, store a 'return address' so we can backtrack correctly.

                 if (op.m_op == OpNestedAlternativeNext) {

                     unsigned parenthesesFrameLocation = term->frameLocation;

                     unsigned alternativeFrameLocation = parenthesesFrameLocation;

                     if (term->quantityType != QuantifierFixedCount)

                         alternativeFrameLocation += YarrStackSpaceForBackTrackInfoParenthesesOnce;

                     op.m_returnAddress = storeToFrameWithPatch(alternativeFrameLocation);

                 }

                 if (term->quantityType != QuantifierFixedCount && !m_ops[op.m_previousOp].m_alternative->m_minimumSize) {

                     // If the previous alternative matched without consuming characters then

                     // backtrack to try to match while consumming some input.

                     op.m_zeroLengthMatch = branch32(Equal, index, Address(stackPointerRegister, term->frameLocation * sizeof(void*)));

                 }

                 // If we reach here then the last alternative has matched - jump to the

                 // End node, to skip over any further alternatives.

                 //

                 // FIXME: this is logically O(N^2) (though N can be expected to be very

                 // small). We could avoid this either by adding an extra jump to the JIT

                 // data structures, or by making backtracking code that jumps to Next

                 // alternatives are responsible for checking that input is available (if

                 // we didn't need to plant the input checks, then m_jumps would be free).

                 YarrOp* endOp = &m_ops[op.m_nextOp];

                 while (endOp->m_nextOp != notFound) {

                     ASSERT(endOp->m_op == OpSimpleNestedAlternativeNext || endOp->m_op == OpNestedAlternativeNext);

                     endOp = &m_ops[endOp->m_nextOp];

                 }

                 ASSERT(endOp->m_op == OpSimpleNestedAlternativeEnd || endOp->m_op == OpNestedAlternativeEnd);

                 endOp->m_jumps.append(jump());

                 // This is the entry point for the next alternative.

                 op.m_reentry = label();

                 // Calculate how much input we need to check for, and if non-zero check.

                 op.m_checkAdjust = alternative->m_minimumSize;

                 if ((term->quantityType == QuantifierFixedCount) && (term->type != PatternTerm::TypeParentheticalAssertion))

                     op.m_checkAdjust -= disjunction->m_minimumSize;

                 if (op.m_checkAdjust)

                     op.m_jumps.append(jumpIfNoAvailableInput(op.m_checkAdjust));

                 YarrOp& lastOp = m_ops[op.m_previousOp];

                 m_checked -= lastOp.m_checkAdjust;

                 m_checked += op.m_checkAdjust;

                 break;

             }

             case OpSimpleNestedAlternativeEnd:

             case OpNestedAlternativeEnd: {

                 PatternTerm* term = op.m_term;

                 // In the non-simple case, store a 'return address' so we can backtrack correctly.

                 if (op.m_op == OpNestedAlternativeEnd) {

                     unsigned parenthesesFrameLocation = term->frameLocation;

                     unsigned alternativeFrameLocation = parenthesesFrameLocation;

                     if (term->quantityType != QuantifierFixedCount)

                         alternativeFrameLocation += YarrStackSpaceForBackTrackInfoParenthesesOnce;

                     op.m_returnAddress = storeToFrameWithPatch(alternativeFrameLocation);

                 }

                 if (term->quantityType != QuantifierFixedCount && !m_ops[op.m_previousOp].m_alternative->m_minimumSize) {

                     // If the previous alternative matched without consuming characters then

                     // backtrack to try to match while consumming some input.

                     op.m_zeroLengthMatch = branch32(Equal, index, Address(stackPointerRegister, term->frameLocation * sizeof(void*)));

                 }

                 // If this set of alternatives contains more than one alternative,

                 // then the Next nodes will have planted jumps to the End, and added

                 // them to this node's m_jumps list.

                 op.m_jumps.link(this);

                 op.m_jumps.clear();

                 YarrOp& lastOp = m_ops[op.m_previousOp];

                 m_checked -= lastOp.m_checkAdjust;

                 break;

             }

             // OpParenthesesSubpatternOnceBegin/End

             //

             // These nodes support (optionally) capturing subpatterns, that have a

             // quantity count of 1 (this covers fixed once, and ?/?? quantifiers).

             case OpParenthesesSubpatternOnceBegin: {

                 PatternTerm* term = op.m_term;

                 unsigned parenthesesFrameLocation = term->frameLocation;

                 const RegisterID indexTemporary = regT0;

                 ASSERT(term->quantityCount == 1);

                 // Upon entry to a Greedy quantified set of parenthese store the index.

                 // We'll use this for two purposes:

                 //  - To indicate which iteration we are on of mathing the remainder of

                 //    the expression after the parentheses - the first, including the

                 //    match within the parentheses, or the second having skipped over them.

                 //  - To check for empty matches, which must be rejected.

                 //

                 // At the head of a NonGreedy set of parentheses we'll immediately set the

                 // value on the stack to -1 (indicating a match skipping the subpattern),

                 // and plant a jump to the end. We'll also plant a label to backtrack to

                 // to reenter the subpattern later, with a store to set up index on the

                 // second iteration.

                 //

                 // FIXME: for capturing parens, could use the index in the capture array?

                 if (term->quantityType == QuantifierGreedy)

                     storeToFrame(index, parenthesesFrameLocation);

                 else if (term->quantityType == QuantifierNonGreedy) {

                     storeToFrame(TrustedImm32(-1), parenthesesFrameLocation);

                     op.m_jumps.append(jump());

                     op.m_reentry = label();

                     storeToFrame(index, parenthesesFrameLocation);

                 }

                 // If the parenthese are capturing, store the starting index value to the

                 // captures array, offsetting as necessary.

                 //

                 // FIXME: could avoid offsetting this value in JIT code, apply

                 // offsets only afterwards, at the point the results array is

                 // being accessed.

                 if (term->capture() && compileMode == IncludeSubpatterns) {

                     int inputOffset = term->inputPosition - m_checked;

                     if (term->quantityType == QuantifierFixedCount)

                         inputOffset -= term->parentheses.disjunction->m_minimumSize;

                     if (inputOffset) {

                         move(index, indexTemporary);

                         add32(Imm32(inputOffset), indexTemporary);

                         setSubpatternStart(indexTemporary, term->parentheses.subpatternId);

                     } else

                         setSubpatternStart(index, term->parentheses.subpatternId);

                 }

                 break;

             }

             case OpParenthesesSubpatternOnceEnd: {

                 PatternTerm* term = op.m_term;

                 const RegisterID indexTemporary = regT0;

                 ASSERT(term->quantityCount == 1);

 #ifndef NDEBUG

                 // Runtime ASSERT to make sure that the nested alternative handled the

                 // "no input consumed" check.

                 if (term->quantityType != QuantifierFixedCount && !term->parentheses.disjunction->m_minimumSize) {

                     Jump pastBreakpoint;

                     pastBreakpoint = branch32(NotEqual, index, Address(stackPointerRegister, term->frameLocation * sizeof(void*)));

                     breakpoint();

                     pastBreakpoint.link(this);

                 }

 #endif

                 // If the parenthese are capturing, store the ending index value to the

                 // captures array, offsetting as necessary.

                 //

                 // FIXME: could avoid offsetting this value in JIT code, apply

                 // offsets only afterwards, at the point the results array is

                 // being accessed.

                 if (term->capture() && compileMode == IncludeSubpatterns) {

                     int inputOffset = term->inputPosition - m_checked;

                     if (inputOffset) {

                         move(index, indexTemporary);

                         add32(Imm32(inputOffset), indexTemporary);

                         setSubpatternEnd(indexTemporary, term->parentheses.subpatternId);

                     } else

                         setSubpatternEnd(index, term->parentheses.subpatternId);

                 }

                 // If the parentheses are quantified Greedy then add a label to jump back

                 // to if get a failed match from after the parentheses. For NonGreedy

                 // parentheses, link the jump from before the subpattern to here.

                 if (term->quantityType == QuantifierGreedy)

                     op.m_reentry = label();

                 else if (term->quantityType == QuantifierNonGreedy) {

                     YarrOp& beginOp = m_ops[op.m_previousOp];

                     beginOp.m_jumps.link(this);

                 }

                 break;

             }

             // OpParenthesesSubpatternTerminalBegin/End

             case OpParenthesesSubpatternTerminalBegin: {

                 PatternTerm* term = op.m_term;

                 ASSERT(term->quantityType == QuantifierGreedy);

                 ASSERT(term->quantityCount == quantifyInfinite);

                 ASSERT(!term->capture());

                 // Upon entry set a label to loop back to.

                 op.m_reentry = label();

                 // Store the start index of the current match; we need to reject zero

                 // length matches.

                 storeToFrame(index, term->frameLocation);

                 break;

             }

             case OpParenthesesSubpatternTerminalEnd: {

                 YarrOp& beginOp = m_ops[op.m_previousOp];

 #ifndef NDEBUG

                 PatternTerm* term = op.m_term;

                 // Runtime ASSERT to make sure that the nested alternative handled the

                 // "no input consumed" check.

                 Jump pastBreakpoint;

                 pastBreakpoint = branch32(NotEqual, index, Address(stackPointerRegister, term->frameLocation * sizeof(void*)));

                 breakpoint();

                 pastBreakpoint.link(this);

 #endif

                 // We know that the match is non-zero, we can accept it  and

                 // loop back up to the head of the subpattern.

                 jump(beginOp.m_reentry);

                 // This is the entry point to jump to when we stop matching - we will

                 // do so once the subpattern cannot match any more.

                 op.m_reentry = label();

                 break;

             }

             // OpParentheticalAssertionBegin/End

             case OpParentheticalAssertionBegin: {

                 PatternTerm* term = op.m_term;

                 // Store the current index - assertions should not update index, so

                 // we will need to restore it upon a successful match.

                 unsigned parenthesesFrameLocation = term->frameLocation;

                 storeToFrame(index, parenthesesFrameLocation);

                 // Check

                 op.m_checkAdjust = m_checked - term->inputPosition;

                 if (op.m_checkAdjust)

                     sub32(Imm32(op.m_checkAdjust), index);

                 m_checked -= op.m_checkAdjust;

                 break;

             }

             case OpParentheticalAssertionEnd: {

                 PatternTerm* term = op.m_term;

                 // Restore the input index value.

                 unsigned parenthesesFrameLocation = term->frameLocation;

                 loadFromFrame(parenthesesFrameLocation, index);

                 // If inverted, a successful match of the assertion must be treated

                 // as a failure, so jump to backtracking.

                 if (term->invert()) {

                     op.m_jumps.append(jump());

                     op.m_reentry = label();

                 }

                 YarrOp& lastOp = m_ops[op.m_previousOp];

                 m_checked += lastOp.m_checkAdjust;

                 break;

             }

             case OpMatchFailed:

 #if !WTF_CPU_SPARC

                 removeCallFrame();

 #endif

 #if WTF_CPU_X86_64

                 move(TrustedImm32(int(WTF::notFound)), returnRegister);

 #else

                 move(TrustedImmPtr((void*)WTF::notFound), returnRegister);

                 move(TrustedImm32(0), returnRegister2);

 #endif

                 generateReturn();

                 break;

             }

             ++opIndex;

         } while (opIndex < m_ops.size());

         return true;

     }

     bool backtrack()

     {

         // Backwards generate the backtracking code.

         size_t opIndex = m_ops.size();

         ASSERT(opIndex);

         do {

             --opIndex;

             YarrOp& op = m_ops[opIndex];

             switch (op.m_op) {

             case OpTerm:

                 if (!backtrackTerm(opIndex))

                     return false;

                 break;

             // OpBodyAlternativeBegin/Next/End

             //

             // For each Begin/Next node representing an alternative, we need to decide what to do

             // in two circumstances:

             //  - If we backtrack back into this node, from within the alternative.

             //  - If the input check at the head of the alternative fails (if this exists).

             //

             // We treat these two cases differently since in the former case we have slightly

             // more information - since we are backtracking out of a prior alternative we know

             // that at least enough input was available to run it. For example, given the regular

             // expression /a|b/, if we backtrack out of the first alternative (a failed pattern

             // character match of 'a'), then we need not perform an additional input availability

             // check before running the second alternative.

             //

             // Backtracking required differs for the last alternative, which in the case of the

             // repeating set of alternatives must loop. The code generated for the last alternative

             // will also be used to handle all input check failures from any prior alternatives -

             // these require similar functionality, in seeking the next available alternative for

             // which there is sufficient input.

             //

             // Since backtracking of all other alternatives simply requires us to link backtracks

             // to the reentry point for the subsequent alternative, we will only be generating any

             // code when backtracking the last alternative.

             case OpBodyAlternativeBegin:

             case OpBodyAlternativeNext: {

                 PatternAlternative* alternative = op.m_alternative;

                 if (op.m_op == OpBodyAlternativeNext) {

                     PatternAlternative* priorAlternative = m_ops[op.m_previousOp].m_alternative;

                     m_checked += priorAlternative->m_minimumSize;

                 }

                 m_checked -= alternative->m_minimumSize;

                 // Is this the last alternative? If not, then if we backtrack to this point we just

                 // need to jump to try to match the next alternative.

                 if (m_ops[op.m_nextOp].m_op != OpBodyAlternativeEnd) {

                     m_backtrackingState.linkTo(m_ops[op.m_nextOp].m_reentry, this);

                     break;

                 }

                 YarrOp& endOp = m_ops[op.m_nextOp];

                 YarrOp* beginOp = &op;

                 while (beginOp->m_op != OpBodyAlternativeBegin) {

                     ASSERT(beginOp->m_op == OpBodyAlternativeNext);

                     beginOp = &m_ops[beginOp->m_previousOp];

                 }

                 bool onceThrough = endOp.m_nextOp == notFound;

                 // First, generate code to handle cases where we backtrack out of an attempted match

                 // of the last alternative. If this is a 'once through' set of alternatives then we

                 // have nothing to do - link this straight through to the End.

                 if (onceThrough)

                     m_backtrackingState.linkTo(endOp.m_reentry, this);

                 else {

                     // If we don't need to move the input poistion, and the pattern has a fixed size

                     // (in which case we omit the store of the start index until the pattern has matched)

                     // then we can just link the backtrack out of the last alternative straight to the

                     // head of the first alternative.

                     if (m_pattern.m_body->m_hasFixedSize

                         && (alternative->m_minimumSize > beginOp->m_alternative->m_minimumSize)

                         && (alternative->m_minimumSize - beginOp->m_alternative->m_minimumSize == 1))

                         m_backtrackingState.linkTo(beginOp->m_reentry, this);

                     else {

                         // We need to generate a trampoline of code to execute before looping back

                         // around to the first alternative.

                         m_backtrackingState.link(this);

                         // If the pattern size is not fixed, then store the start index, for use if we match.

                         if (!m_pattern.m_body->m_hasFixedSize) {

                             if (alternative->m_minimumSize == 1)

                                 setMatchStart(index);

                             else {

                                 move(index, regT0);

                                 if (alternative->m_minimumSize)

                                     sub32(Imm32(alternative->m_minimumSize - 1), regT0);

                                 else

                                     add32(TrustedImm32(1), regT0);

                                 setMatchStart(regT0);

                             }

                         }

                         // Generate code to loop. Check whether the last alternative is longer than the

                         // first (e.g. /a|xy/ or /a|xyz/).

                         if (alternative->m_minimumSize > beginOp->m_alternative->m_minimumSize) {

                             // We want to loop, and increment input position. If the delta is 1, it is

                             // already correctly incremented, if more than one then decrement as appropriate.

                             unsigned delta = alternative->m_minimumSize - beginOp->m_alternative->m_minimumSize;

                             ASSERT(delta);

                             if (delta != 1)

                                 sub32(Imm32(delta - 1), index);

                             jump(beginOp->m_reentry);

                         } else {

                             // If the first alternative has minimum size 0xFFFFFFFFu, then there cannot

                             // be sufficent input available to handle this, so just fall through.

                             unsigned delta = beginOp->m_alternative->m_minimumSize - alternative->m_minimumSize;

                             if (delta != 0xFFFFFFFFu) {

                                 // We need to check input because we are incrementing the input.

                                 add32(Imm32(delta + 1), index);

                                 checkInput().linkTo(beginOp->m_reentry, this);

                             }

                         }

                     }

                 }

                 // We can reach this point in the code in two ways:

                 //  - Fallthrough from the code above (a repeating alternative backtracked out of its

                 //    last alternative, and did not have sufficent input to run the first).

                 //  - We will loop back up to the following label when a releating alternative loops,

                 //    following a failed input check.

                 //

                 // Either way, we have just failed the input check for the first alternative.

                 Label firstInputCheckFailed(this);

                 // Generate code to handle input check failures from alternatives except the last.

                 // prevOp is the alternative we're handling a bail out from (initially Begin), and

                 // nextOp is the alternative we will be attempting to reenter into.

                 //

                 // We will link input check failures from the forwards matching path back to the code

                 // that can handle them.

                 YarrOp* prevOp = beginOp;

                 YarrOp* nextOp = &m_ops[beginOp->m_nextOp];

                 while (nextOp->m_op != OpBodyAlternativeEnd) {

                     prevOp->m_jumps.link(this);

                     // We only get here if an input check fails, it is only worth checking again

                     // if the next alternative has a minimum size less than the last.

                     if (prevOp->m_alternative->m_minimumSize > nextOp->m_alternative->m_minimumSize) {

                         // FIXME: if we added an extra label to YarrOp, we could avoid needing to

                         // subtract delta back out, and reduce this code. Should performance test

                         // the benefit of this.

                         unsigned delta = prevOp->m_alternative->m_minimumSize - nextOp->m_alternative->m_minimumSize;

                         sub32(Imm32(delta), index);

                         Jump fail = jumpIfNoAvailableInput();

                         add32(Imm32(delta), index);

                         jump(nextOp->m_reentry);

                         fail.link(this);

                     } else if (prevOp->m_alternative->m_minimumSize < nextOp->m_alternative->m_minimumSize)

                         add32(Imm32(nextOp->m_alternative->m_minimumSize - prevOp->m_alternative->m_minimumSize), index);

                     prevOp = nextOp;

                     nextOp = &m_ops[nextOp->m_nextOp];

                 }

                 // We fall through to here if there is insufficient input to run the last alternative.

                 // If there is insufficient input to run the last alternative, then for 'once through'

                 // alternatives we are done - just jump back up into the forwards matching path at the End.

                 if (onceThrough) {

                     op.m_jumps.linkTo(endOp.m_reentry, this);

                     jump(endOp.m_reentry);

                     break;

                 }

                 // For repeating alternatives, link any input check failure from the last alternative to

                 // this point.

                 op.m_jumps.link(this);

                 bool needsToUpdateMatchStart = !m_pattern.m_body->m_hasFixedSize;

                 // Check for cases where input position is already incremented by 1 for the last

                 // alternative (this is particularly useful where the minimum size of the body

                 // disjunction is 0, e.g. /a*|b/).

                 if (needsToUpdateMatchStart && alternative->m_minimumSize == 1) {

                     // index is already incremented by 1, so just store it now!

                     setMatchStart(index);

                     needsToUpdateMatchStart = false;

                 }

                 // Check whether there is sufficient input to loop. Increment the input position by

                 // one, and check. Also add in the minimum disjunction size before checking - there

                 // is no point in looping if we're just going to fail all the input checks around

                 // the next iteration.

                 ASSERT(alternative->m_minimumSize >= m_pattern.m_body->m_minimumSize);

                 if (alternative->m_minimumSize == m_pattern.m_body->m_minimumSize) {

                     // If the last alternative had the same minimum size as the disjunction,

                     // just simply increment input pos by 1, no adjustment based on minimum size.

                     add32(TrustedImm32(1), index);

                 } else {

                     // If the minumum for the last alternative was one greater than than that

                     // for the disjunction, we're already progressed by 1, nothing to do!

                     unsigned delta = (alternative->m_minimumSize - m_pattern.m_body->m_minimumSize) - 1;

                     if (delta)

                         sub32(Imm32(delta), index);

                 }

                 Jump matchFailed = jumpIfNoAvailableInput();

                 if (needsToUpdateMatchStart) {

                     if (!m_pattern.m_body->m_minimumSize)

                         setMatchStart(index);

                     else {

                         move(index, regT0);

                         sub32(Imm32(m_pattern.m_body->m_minimumSize), regT0);

                         setMatchStart(regT0);

                     }

                 }

                 // Calculate how much more input the first alternative requires than the minimum

                 // for the body as a whole. If no more is needed then we dont need an additional

                 // input check here - jump straight back up to the start of the first alternative.

                 if (beginOp->m_alternative->m_minimumSize == m_pattern.m_body->m_minimumSize)

                     jump(beginOp->m_reentry);

                 else {

                     if (beginOp->m_alternative->m_minimumSize > m_pattern.m_body->m_minimumSize)

                         add32(Imm32(beginOp->m_alternative->m_minimumSize - m_pattern.m_body->m_minimumSize), index);

                     else

                         sub32(Imm32(m_pattern.m_body->m_minimumSize - beginOp->m_alternative->m_minimumSize), index);

                     checkInput().linkTo(beginOp->m_reentry, this);

                     jump(firstInputCheckFailed);

                 }

                 // We jump to here if we iterate to the point that there is insufficient input to

                 // run any matches, and need to return a failure state from JIT code.

                 matchFailed.link(this);

 #if !WTF_CPU_SPARC

                 removeCallFrame();

 #endif

 #if WTF_CPU_X86_64

                 move(TrustedImm32(int(WTF::notFound)), returnRegister);

 #else

                 move(TrustedImmPtr((void*)WTF::notFound), returnRegister);

                 move(TrustedImm32(0), returnRegister2);

 #endif

                 generateReturn();

                 break;

             }

             case OpBodyAlternativeEnd: {

                 // We should never backtrack back into a body disjunction.

                 ASSERT(m_backtrackingState.isEmpty());

                 PatternAlternative* priorAlternative = m_ops[op.m_previousOp].m_alternative;

                 m_checked += priorAlternative->m_minimumSize;

                 break;

             }

             // OpSimpleNestedAlternativeBegin/Next/End

             // OpNestedAlternativeBegin/Next/End

             //

             // Generate code for when we backtrack back out of an alternative into

             // a Begin or Next node, or when the entry input count check fails. If

             // there are more alternatives we need to jump to the next alternative,

             // if not we backtrack back out of the current set of parentheses.

             //

             // In the case of non-simple nested assertions we need to also link the

             // 'return address' appropriately to backtrack back out into the correct

             // alternative.

             case OpSimpleNestedAlternativeBegin:

             case OpSimpleNestedAlternativeNext:

             case OpNestedAlternativeBegin:

             case OpNestedAlternativeNext: {

                 YarrOp& nextOp = m_ops[op.m_nextOp];

                 bool isBegin = op.m_previousOp == notFound;

                 bool isLastAlternative = nextOp.m_nextOp == notFound;

                 ASSERT(isBegin == (op.m_op == OpSimpleNestedAlternativeBegin || op.m_op == OpNestedAlternativeBegin));

                 ASSERT(isLastAlternative == (nextOp.m_op == OpSimpleNestedAlternativeEnd || nextOp.m_op == OpNestedAlternativeEnd));

                 // Treat an input check failure the same as a failed match.

                 m_backtrackingState.append(op.m_jumps);

                 // Set the backtracks to jump to the appropriate place. We may need

                 // to link the backtracks in one of three different way depending on

                 // the type of alternative we are dealing with:

                 //  - A single alternative, with no simplings.

                 //  - The last alternative of a set of two or more.

                 //  - An alternative other than the last of a set of two or more.

                 //

                 // In the case of a single alternative on its own, we don't need to

                 // jump anywhere - if the alternative fails to match we can just

                 // continue to backtrack out of the parentheses without jumping.

                 //

                 // In the case of the last alternative in a set of more than one, we

                 // need to jump to return back out to the beginning. We'll do so by

                 // adding a jump to the End node's m_jumps list, and linking this

                 // when we come to generate the Begin node. For alternatives other

                 // than the last, we need to jump to the next alternative.

                 //

                 // If the alternative had adjusted the input position we must link

                 // backtracking to here, correct, and then jump on. If not we can

                 // link the backtracks directly to their destination.

                 if (op.m_checkAdjust) {

                     // Handle the cases where we need to link the backtracks here.

                     m_backtrackingState.link(this);

                     sub32(Imm32(op.m_checkAdjust), index);

                     if (!isLastAlternative) {

                         // An alternative that is not the last should jump to its successor.

                         jump(nextOp.m_reentry);

                     } else if (!isBegin) {

                         // The last of more than one alternatives must jump back to the beginning.

                         nextOp.m_jumps.append(jump());

                     } else {

                         // A single alternative on its own can fall through.

                         m_backtrackingState.fallthrough();

                     }

                 } else {

                     // Handle the cases where we can link the backtracks directly to their destinations.

                     if (!isLastAlternative) {

                         // An alternative that is not the last should jump to its successor.

                         m_backtrackingState.linkTo(nextOp.m_reentry, this);

                     } else if (!isBegin) {

                         // The last of more than one alternatives must jump back to the beginning.

                         m_backtrackingState.takeBacktracksToJumpList(nextOp.m_jumps, this);

                     }

                     // In the case of a single alternative on its own do nothing - it can fall through.

                 }

                 // If there is a backtrack jump from a zero length match link it here.

                 if (op.m_zeroLengthMatch.isSet())

                     m_backtrackingState.append(op.m_zeroLengthMatch);

                 // At this point we've handled the backtracking back into this node.

                 // Now link any backtracks that need to jump to here.

                 // For non-simple alternatives, link the alternative's 'return address'

                 // so that we backtrack back out into the previous alternative.

                 if (op.m_op == OpNestedAlternativeNext)

                     m_backtrackingState.append(op.m_returnAddress);

                 // If there is more than one alternative, then the last alternative will

                 // have planted a jump to be linked to the end. This jump was added to the

                 // End node's m_jumps list. If we are back at the beginning, link it here.

                 if (isBegin) {

                     YarrOp* endOp = &m_ops[op.m_nextOp];

                     while (endOp->m_nextOp != notFound) {

                         ASSERT(endOp->m_op == OpSimpleNestedAlternativeNext || endOp->m_op == OpNestedAlternativeNext);

                         endOp = &m_ops[endOp->m_nextOp];

                     }

                     ASSERT(endOp->m_op == OpSimpleNestedAlternativeEnd || endOp->m_op == OpNestedAlternativeEnd);

                     m_backtrackingState.append(endOp->m_jumps);

                 }

                 if (!isBegin) {

                     YarrOp& lastOp = m_ops[op.m_previousOp];

                     m_checked += lastOp.m_checkAdjust;

                 }

                 m_checked -= op.m_checkAdjust;

                 break;

             }

             case OpSimpleNestedAlternativeEnd:

             case OpNestedAlternativeEnd: {

                 PatternTerm* term = op.m_term;

                 // If there is a backtrack jump from a zero length match link it here.

                 if (op.m_zeroLengthMatch.isSet())

                     m_backtrackingState.append(op.m_zeroLengthMatch);

                 // If we backtrack into the end of a simple subpattern do nothing;

                 // just continue through into the last alternative. If we backtrack

                 // into the end of a non-simple set of alterntives we need to jump

                 // to the backtracking return address set up during generation.

                 if (op.m_op == OpNestedAlternativeEnd) {

                     m_backtrackingState.link(this);

                     // Plant a jump to the return address.

                     unsigned parenthesesFrameLocation = term->frameLocation;

                     unsigned alternativeFrameLocation = parenthesesFrameLocation;

                     if (term->quantityType != QuantifierFixedCount)

                         alternativeFrameLocation += YarrStackSpaceForBackTrackInfoParenthesesOnce;

                     loadFromFrameAndJump(alternativeFrameLocation);

                     // Link the DataLabelPtr associated with the end of the last

                     // alternative to this point.

                     m_backtrackingState.append(op.m_returnAddress);

                 }

                 YarrOp& lastOp = m_ops[op.m_previousOp];

                 m_checked += lastOp.m_checkAdjust;

                 break;

             }

             // OpParenthesesSubpatternOnceBegin/End

             //

             // When we are backtracking back out of a capturing subpattern we need

             // to clear the start index in the matches output array, to record that

             // this subpattern has not been captured.

             //

             // When backtracking back out of a Greedy quantified subpattern we need

             // to catch this, and try running the remainder of the alternative after

             // the subpattern again, skipping the parentheses.

             //

             // Upon backtracking back into a quantified set of parentheses we need to

             // check whether we were currently skipping the subpattern. If not, we

             // can backtrack into them, if we were we need to either backtrack back

             // out of the start of the parentheses, or jump back to the forwards

             // matching start, depending of whether the match is Greedy or NonGreedy.

             case OpParenthesesSubpatternOnceBegin: {

                 PatternTerm* term = op.m_term;

                 ASSERT(term->quantityCount == 1);

                 // We only need to backtrack to thispoint if capturing or greedy.

                 if ((term->capture() && compileMode == IncludeSubpatterns) || term->quantityType == QuantifierGreedy) {

                     m_backtrackingState.link(this);

                     // If capturing, clear the capture (we only need to reset start).

                     if (term->capture() && compileMode == IncludeSubpatterns)

                         clearSubpatternStart(term->parentheses.subpatternId);

                     // If Greedy, jump to the end.

                     if (term->quantityType == QuantifierGreedy) {

                         // Clear the flag in the stackframe indicating we ran through the subpattern.

                         unsigned parenthesesFrameLocation = term->frameLocation;

                         storeToFrame(TrustedImm32(-1), parenthesesFrameLocation);

                         // Jump to after the parentheses, skipping the subpattern.

                         jump(m_ops[op.m_nextOp].m_reentry);

                         // A backtrack from after the parentheses, when skipping the subpattern,

                         // will jump back to here.

                         op.m_jumps.link(this);

                     }

                     m_backtrackingState.fallthrough();

                 }

                 break;

             }

             case OpParenthesesSubpatternOnceEnd: {

                 PatternTerm* term = op.m_term;

                 if (term->quantityType != QuantifierFixedCount) {

                     m_backtrackingState.link(this);

                     // Check whether we should backtrack back into the parentheses, or if we

                     // are currently in a state where we had skipped over the subpattern

                     // (in which case the flag value on the stack will be -1).

                     unsigned parenthesesFrameLocation = term->frameLocation;

                     Jump hadSkipped = branch32(Equal, Address(stackPointerRegister, parenthesesFrameLocation * sizeof(void*)), TrustedImm32(-1));

                     if (term->quantityType == QuantifierGreedy) {

                         // For Greedy parentheses, we skip after having already tried going

                         // through the subpattern, so if we get here we're done.

                         YarrOp& beginOp = m_ops[op.m_previousOp];

                         beginOp.m_jumps.append(hadSkipped);

                     } else {

                         // For NonGreedy parentheses, we try skipping the subpattern first,

                         // so if we get here we need to try running through the subpattern

                         // next. Jump back to the start of the parentheses in the forwards

                         // matching path.

                         ASSERT(term->quantityType == QuantifierNonGreedy);

                         YarrOp& beginOp = m_ops[op.m_previousOp];

                         hadSkipped.linkTo(beginOp.m_reentry, this);

                     }

                     m_backtrackingState.fallthrough();

                 }

                 m_backtrackingState.append(op.m_jumps);

                 break;

             }

             // OpParenthesesSubpatternTerminalBegin/End

             //

             // Terminal subpatterns will always match - there is nothing after them to

             // force a backtrack, and they have a minimum count of 0, and as such will

             // always produce an acceptable result.

             case OpParenthesesSubpatternTerminalBegin: {

                 // We will backtrack to this point once the subpattern cannot match any

                 // more. Since no match is accepted as a successful match (we are Greedy

                 // quantified with a minimum of zero) jump back to the forwards matching

                 // path at the end.

                 YarrOp& endOp = m_ops[op.m_nextOp];

                 m_backtrackingState.linkTo(endOp.m_reentry, this);

                 break;

             }

             case OpParenthesesSubpatternTerminalEnd:

                 // We should never be backtracking to here (hence the 'terminal' in the name).

                 ASSERT(m_backtrackingState.isEmpty());

                 m_backtrackingState.append(op.m_jumps);

                 break;

             // OpParentheticalAssertionBegin/End

             case OpParentheticalAssertionBegin: {

                 PatternTerm* term = op.m_term;

                 YarrOp& endOp = m_ops[op.m_nextOp];

                 // We need to handle the backtracks upon backtracking back out

                 // of a parenthetical assertion if either we need to correct

                 // the input index, or the assertion was inverted.

                 if (op.m_checkAdjust || term->invert()) {

                      m_backtrackingState.link(this);

                     if (op.m_checkAdjust)

                         add32(Imm32(op.m_checkAdjust), index);

                     // In an inverted assertion failure to match the subpattern

                     // is treated as a successful match - jump to the end of the

                     // subpattern. We already have adjusted the input position

                     // back to that before the assertion, which is correct.

                     if (term->invert())

                         jump(endOp.m_reentry);

                     m_backtrackingState.fallthrough();

                 }

                 // The End node's jump list will contain any backtracks into

                 // the end of the assertion. Also, if inverted, we will have

                 // added the failure caused by a successful match to this.

                 m_backtrackingState.append(endOp.m_jumps);

                 m_checked += op.m_checkAdjust;

                 break;

             }

             case OpParentheticalAssertionEnd: {

                 // FIXME: We should really be clearing any nested subpattern

                 // matches on bailing out from after the pattern. Firefox has

                 // this bug too (presumably because they use YARR!)

                 // Never backtrack into an assertion; later failures bail to before the begin.

                 m_backtrackingState.takeBacktracksToJumpList(op.m_jumps, this);

                 YarrOp& lastOp = m_ops[op.m_previousOp];

                 m_checked -= lastOp.m_checkAdjust;

                 break;

             }

             case OpMatchFailed:

                 break;

             }

         } while (opIndex);

         return true;

     }

     // Compilation methods:

     // ====================

     // opCompileParenthesesSubpattern

     // Emits ops for a subpattern (set of parentheses). These consist

     // of a set of alternatives wrapped in an outer set of nodes for

     // the parentheses.

     // Supported types of parentheses are 'Once' (quantityCount == 1)

     // and 'Terminal' (non-capturing parentheses quantified as greedy

     // and infinite).

     // Alternatives will use the 'Simple' set of ops if either the

     // subpattern is terminal (in which case we will never need to

     // backtrack), or if the subpattern only contains one alternative.

     void opCompileParenthesesSubpattern(PatternTerm* term)

     {

         YarrOpCode parenthesesBeginOpCode;

         YarrOpCode parenthesesEndOpCode;

         YarrOpCode alternativeBeginOpCode = OpSimpleNestedAlternativeBegin;

         YarrOpCode alternativeNextOpCode = OpSimpleNestedAlternativeNext;

         YarrOpCode alternativeEndOpCode = OpSimpleNestedAlternativeEnd;

         // We can currently only compile quantity 1 subpatterns that are

         // not copies. We generate a copy in the case of a range quantifier,

         // e.g. /(?:x){3,9}/, or /(?:x)+/ (These are effectively expanded to

         // /(?:x){3,3}(?:x){0,6}/ and /(?:x)(?:x)*/ repectively). The problem

         // comes where the subpattern is capturing, in which case we would

         // need to restore the capture from the first subpattern upon a

         // failure in the second.

         if (term->quantityCount == 1 && !term->parentheses.isCopy) {

             // Select the 'Once' nodes.

             parenthesesBeginOpCode = OpParenthesesSubpatternOnceBegin;

             parenthesesEndOpCode = OpParenthesesSubpatternOnceEnd;

             // If there is more than one alternative we cannot use the 'simple' nodes.

             if (term->parentheses.disjunction->m_alternatives.size() != 1) {

                 alternativeBeginOpCode = OpNestedAlternativeBegin;

                 alternativeNextOpCode = OpNestedAlternativeNext;

                 alternativeEndOpCode = OpNestedAlternativeEnd;

             }

         } else if (term->parentheses.isTerminal) {

             // Terminal groups are optimized on the assumption that matching will never

             // backtrack into the terminal group. But this is false if there is more

             // than one alternative and one of the alternatives can match empty. In that

             // case, the empty match is counted as a failure, so we would need to backtrack.

             // The backtracking code doesn't handle this case correctly, so we fall back

             // to the interpreter.

             Vector<PatternAlternative*>& alternatives = term->parentheses.disjunction->m_alternatives;

             if (alternatives.size() != 1) {

                 for (unsigned i = 0; i < alternatives.size(); ++i) {

                     if (alternatives[i]->m_minimumSize == 0) {

                         m_shouldFallBack = true;

                         return;

                     }

                 }

             }

             // Select the 'Terminal' nodes.

             parenthesesBeginOpCode = OpParenthesesSubpatternTerminalBegin;

             parenthesesEndOpCode = OpParenthesesSubpatternTerminalEnd;

         } else {

             // This subpattern is not supported by the JIT.

             m_shouldFallBack = true;

             return;

         }

         size_t parenBegin = m_ops.size();

         m_ops.append(parenthesesBeginOpCode);

         m_ops.append(alternativeBeginOpCode);

         m_ops.last().m_previousOp = notFound;

         m_ops.last().m_term = term;

         Vector<PatternAlternative*>& alternatives =  term->parentheses.disjunction->m_alternatives;

         for (unsigned i = 0; i < alternatives.size(); ++i) {

             size_t lastOpIndex = m_ops.size() - 1;

             PatternAlternative* nestedAlternative = alternatives[i];

             opCompileAlternative(nestedAlternative);

             size_t thisOpIndex = m_ops.size();

             m_ops.append(YarrOp(alternativeNextOpCode));

             YarrOp& lastOp = m_ops[lastOpIndex];

             YarrOp& thisOp = m_ops[thisOpIndex];

             lastOp.m_alternative = nestedAlternative;

             lastOp.m_nextOp = thisOpIndex;

             thisOp.m_previousOp = lastOpIndex;

             thisOp.m_term = term;

         }

         YarrOp& lastOp = m_ops.last();

         ASSERT(lastOp.m_op == alternativeNextOpCode);

         lastOp.m_op = alternativeEndOpCode;

         lastOp.m_alternative = 0;

         lastOp.m_nextOp = notFound;

         size_t parenEnd = m_ops.size();

         m_ops.append(parenthesesEndOpCode);

         m_ops[parenBegin].m_term = term;

         m_ops[parenBegin].m_previousOp = notFound;

         m_ops[parenBegin].m_nextOp = parenEnd;

         m_ops[parenEnd].m_term = term;

         m_ops[parenEnd].m_previousOp = parenBegin;

         m_ops[parenEnd].m_nextOp = notFound;

     }

     // opCompileParentheticalAssertion

     // Emits ops for a parenthetical assertion. These consist of an

     // OpSimpleNestedAlternativeBegin/Next/End set of nodes wrapping

     // the alternatives, with these wrapped by an outer pair of

     // OpParentheticalAssertionBegin/End nodes.

     // We can always use the OpSimpleNestedAlternative nodes in the

     // case of parenthetical assertions since these only ever match

     // once, and will never backtrack back into the assertion.

     void opCompileParentheticalAssertion(PatternTerm* term)

     {

         size_t parenBegin = m_ops.size();

         m_ops.append(OpParentheticalAssertionBegin);

         m_ops.append(OpSimpleNestedAlternativeBegin);

         m_ops.last().m_previousOp = notFound;

         m_ops.last().m_term = term;

         Vector<PatternAlternative*>& alternatives =  term->parentheses.disjunction->m_alternatives;

         for (unsigned i = 0; i < alternatives.size(); ++i) {

             size_t lastOpIndex = m_ops.size() - 1;

             PatternAlternative* nestedAlternative = alternatives[i];

             opCompileAlternative(nestedAlternative);

             size_t thisOpIndex = m_ops.size();

             m_ops.append(YarrOp(OpSimpleNestedAlternativeNext));

             YarrOp& lastOp = m_ops[lastOpIndex];

             YarrOp& thisOp = m_ops[thisOpIndex];

             lastOp.m_alternative = nestedAlternative;

             lastOp.m_nextOp = thisOpIndex;

             thisOp.m_previousOp = lastOpIndex;

             thisOp.m_term = term;

         }

         YarrOp& lastOp = m_ops.last();

         ASSERT(lastOp.m_op == OpSimpleNestedAlternativeNext);

         lastOp.m_op = OpSimpleNestedAlternativeEnd;

         lastOp.m_alternative = 0;

         lastOp.m_nextOp = notFound;

         size_t parenEnd = m_ops.size();

         m_ops.append(OpParentheticalAssertionEnd);

         m_ops[parenBegin].m_term = term;

         m_ops[parenBegin].m_previousOp = notFound;

         m_ops[parenBegin].m_nextOp = parenEnd;

         m_ops[parenEnd].m_term = term;

         m_ops[parenEnd].m_previousOp = parenBegin;

         m_ops[parenEnd].m_nextOp = notFound;

     }

     // opCompileAlternative

     // Called to emit nodes for all terms in an alternative.

     void opCompileAlternative(PatternAlternative* alternative)

     {

         optimizeAlternative(alternative);

         for (unsigned i = 0; i < alternative->m_terms.size(); ++i) {

             PatternTerm* term = &alternative->m_terms[i];

             switch (term->type) {

             case PatternTerm::TypeParenthesesSubpattern:

                 opCompileParenthesesSubpattern(term);

                 break;

             case PatternTerm::TypeParentheticalAssertion:

                 opCompileParentheticalAssertion(term);

                 break;

             default:

                 m_ops.append(term);

             }

         }

     }

     // opCompileBody

     // This method compiles the body disjunction of the regular expression.

     // The body consists of two sets of alternatives - zero or more 'once

     // through' (BOL anchored) alternatives, followed by zero or more

     // repeated alternatives.

     // For each of these two sets of alteratives, if not empty they will be

     // wrapped in a set of OpBodyAlternativeBegin/Next/End nodes (with the

     // 'begin' node referencing the first alternative, and 'next' nodes

     // referencing any further alternatives. The begin/next/end nodes are

     // linked together in a doubly linked list. In the case of repeating

     // alternatives, the end node is also linked back to the beginning.

     // If no repeating alternatives exist, then a OpMatchFailed node exists

     // to return the failing result.

     void opCompileBody(PatternDisjunction* disjunction)

     {

         Vector<PatternAlternative*>& alternatives =  disjunction->m_alternatives;

         size_t currentAlternativeIndex = 0;

         // Emit the 'once through' alternatives.

         if (alternatives.size() && alternatives[0]->onceThrough()) {

             m_ops.append(YarrOp(OpBodyAlternativeBegin));

             m_ops.last().m_previousOp = notFound;

             do {

                 size_t lastOpIndex = m_ops.size() - 1;

                 PatternAlternative* alternative = alternatives[currentAlternativeIndex];

                 opCompileAlternative(alternative);

                 size_t thisOpIndex = m_ops.size();

                 m_ops.append(YarrOp(OpBodyAlternativeNext));

                 YarrOp& lastOp = m_ops[lastOpIndex];

                 YarrOp& thisOp = m_ops[thisOpIndex];

                 lastOp.m_alternative = alternative;

                 lastOp.m_nextOp = thisOpIndex;

                 thisOp.m_previousOp = lastOpIndex;

                 ++currentAlternativeIndex;

             } while (currentAlternativeIndex < alternatives.size() && alternatives[currentAlternativeIndex]->onceThrough());

             YarrOp& lastOp = m_ops.last();

             ASSERT(lastOp.m_op == OpBodyAlternativeNext);

             lastOp.m_op = OpBodyAlternativeEnd;

             lastOp.m_alternative = 0;

             lastOp.m_nextOp = notFound;

         }

         if (currentAlternativeIndex == alternatives.size()) {

             m_ops.append(YarrOp(OpMatchFailed));

             return;

         }

         // Emit the repeated alternatives.

         size_t repeatLoop = m_ops.size();

         m_ops.append(YarrOp(OpBodyAlternativeBegin));

         m_ops.last().m_previousOp = notFound;

         do {

             size_t lastOpIndex = m_ops.size() - 1;

             PatternAlternative* alternative = alternatives[currentAlternativeIndex];

             ASSERT(!alternative->onceThrough());

             opCompileAlternative(alternative);

             size_t thisOpIndex = m_ops.size();

             m_ops.append(YarrOp(OpBodyAlternativeNext));

             YarrOp& lastOp = m_ops[lastOpIndex];

             YarrOp& thisOp = m_ops[thisOpIndex];

             lastOp.m_alternative = alternative;

             lastOp.m_nextOp = thisOpIndex;

             thisOp.m_previousOp = lastOpIndex;

             ++currentAlternativeIndex;

         } while (currentAlternativeIndex < alternatives.size());

         YarrOp& lastOp = m_ops.last();

         ASSERT(lastOp.m_op == OpBodyAlternativeNext);

         lastOp.m_op = OpBodyAlternativeEnd;

         lastOp.m_alternative = 0;

         lastOp.m_nextOp = repeatLoop;

     }

     void generateEnter()

     {

 #if WTF_CPU_X86_64

         push(X86Registers::ebp);

         move(stackPointerRegister, X86Registers::ebp);

         push(X86Registers::ebx);

         // The ABI doesn't guarantee the upper bits are zero on unsigned arguments, so clear them ourselves.

         zeroExtend32ToPtr(index, index);

         zeroExtend32ToPtr(length, length);

 #elif WTF_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 WTF_COMPILER_MSVC || WTF_COMPILER_SUNCC

         loadPtr(Address(X86Registers::ebp, 2 * sizeof(void*)), input);

         loadPtr(Address(X86Registers::ebp, 3 * sizeof(void*)), index);

         loadPtr(Address(X86Registers::ebp, 4 * sizeof(void*)), length);

         if (compileMode == IncludeSubpatterns)

             loadPtr(Address(X86Registers::ebp, 5 * sizeof(void*)), output);

 # else

         if (compileMode == IncludeSubpatterns)

             loadPtr(Address(X86Registers::ebp, 2 * sizeof(void*)), output);

 # endif

 #elif WTF_CPU_ARM

         push(ARMRegisters::r4);

         push(ARMRegisters::r5);

         push(ARMRegisters::r6);

 # if WTF_CPU_ARM_TRADITIONAL

         push(ARMRegisters::r8); // scratch register

 # endif

         if (compileMode == IncludeSubpatterns)

             move(ARMRegisters::r3, output);

 #elif WTF_CPU_SH4

         push(SH4Registers::r11);

         push(SH4Registers::r13);