[apple/ld64.git] / src / ld / passes / compact_unwind.cpp

/* -*- mode: C++; c-basic-offset: 4; tab-width: 4 -*-
 *
 * Copyright (c) 2009 Apple Inc. All rights reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 *
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this
 * file.
 *
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 *
 * @APPLE_LICENSE_HEADER_END@
 */


#include <stdint.h>
#include <math.h>
#include <unistd.h>
#include <dlfcn.h>
#include <mach/machine.h>
#include <mach-o/compact_unwind_encoding.h>

#include <vector>
#include <map>

#include "ld.hpp"
#include "compact_unwind.h"
#include "Architectures.hpp"
#include "MachOFileAbstraction.hpp"


namespace ld {
namespace passes {
namespace compact_unwind {


struct UnwindEntry { 
                                                UnwindEntry(const ld::Atom* f, uint64_t a, uint32_t o, const ld::Atom* d, 
                                                                                                                        const ld::Atom* l, const ld::Atom* p, uint32_t en)
                                                        : func(f), fde(d), lsda(l), personalityPointer(p), funcTentAddress(a), 
                                                                functionOffset(o), encoding(en) { }
        const ld::Atom*                         func; 
        const ld::Atom*                         fde; 
        const ld::Atom*                         lsda; 
        const ld::Atom*                         personalityPointer; 
        uint64_t                                        funcTentAddress;
        uint32_t                                        functionOffset;
        compact_unwind_encoding_t       encoding; 
};

struct LSDAEntry { 
        const ld::Atom*         func; 
        const ld::Atom*         lsda; 
};


template <typename A>
class UnwindInfoAtom : public ld::Atom {
public:
                                                                                        UnwindInfoAtom(const std::vector<UnwindEntry>& entries,uint64_t ehFrameSize);
                                                                                        ~UnwindInfoAtom();
                                                                                        
        virtual const ld::File*                                 file() const                                    { return NULL; }
        virtual const char*                                             name() const                                    { return "compact unwind info"; }
        virtual uint64_t                                                size() const                                    { return _headerSize+_pagesSize; }
        virtual uint64_t                                                objectAddress() const                   { return 0; }
        virtual void                                                    copyRawContent(uint8_t buffer[]) const;
        virtual void                                                    setScope(Scope)                                 { }
        virtual ld::Fixup::iterator                             fixupsBegin() const                             { return (ld::Fixup*)&_fixups[0]; }
        virtual ld::Fixup::iterator                             fixupsEnd()     const                           { return (ld::Fixup*)&_fixups[_fixups.size()]; }

private:
        typedef typename A::P                                           P;
        typedef typename A::P::E                                        E;
        typedef typename A::P::uint_t                           pint_t;

        typedef macho_unwind_info_compressed_second_level_page_header<P> CSLP;

        bool                                            encodingMeansUseDwarf(compact_unwind_encoding_t enc);
        void                                            compressDuplicates(const std::vector<UnwindEntry>& entries, 
                                                                                                        std::vector<UnwindEntry>& uniqueEntries);
        void                                            makePersonalityIndexes(std::vector<UnwindEntry>& entries, 
                                                                                                                std::map<const ld::Atom*, uint32_t>& personalityIndexMap);
        void                                            findCommonEncoding(const std::vector<UnwindEntry>& entries, 
                                                                                                        std::map<compact_unwind_encoding_t, unsigned int>& commonEncodings);
        void                                            makeLsdaIndex(const std::vector<UnwindEntry>& entries, std::vector<LSDAEntry>& lsdaIndex, 
                                                                                                                                std::map<const ld::Atom*, uint32_t>& lsdaIndexOffsetMap);
        unsigned int                            makeCompressedSecondLevelPage(const std::vector<UnwindEntry>& uniqueInfos,   
                                                                                                        const std::map<compact_unwind_encoding_t,unsigned int> commonEncodings,  
                                                                                                        uint32_t pageSize, unsigned int endIndex, uint8_t*& pageEnd);
        unsigned int                            makeRegularSecondLevelPage(const std::vector<UnwindEntry>& uniqueInfos, uint32_t pageSize,  
                                                                                                                        unsigned int endIndex, uint8_t*& pageEnd);
        void                                            addCompressedAddressOffsetFixup(uint32_t offset, const ld::Atom* func, const ld::Atom* fromFunc);
        void                                            addCompressedEncodingFixup(uint32_t offset, const ld::Atom* fde);
        void                                            addRegularAddressFixup(uint32_t offset, const ld::Atom* func);
        void                                            addRegularFDEOffsetFixup(uint32_t offset, const ld::Atom* fde);
        void                                            addImageOffsetFixup(uint32_t offset, const ld::Atom* targ);
        void                                            addImageOffsetFixupPlusAddend(uint32_t offset, const ld::Atom* targ, uint32_t addend);

        uint8_t*                                                                _pagesForDelete;
        uint8_t*                                                                _pageAlignedPages;
        uint8_t*                                                                _pages;
        uint64_t                                                                _pagesSize;
        uint8_t*                                                                _header;
        uint64_t                                                                _headerSize;
        std::vector<ld::Fixup>                                  _fixups;
        
        static bool                                                             _s_log;
        static ld::Section                                              _s_section;
};

template <typename A>
bool UnwindInfoAtom<A>::_s_log = false;

template <typename A>
ld::Section UnwindInfoAtom<A>::_s_section("__TEXT", "__unwind_info", ld::Section::typeUnwindInfo);


template <typename A>
UnwindInfoAtom<A>::UnwindInfoAtom(const std::vector<UnwindEntry>& entries, uint64_t ehFrameSize)
        : ld::Atom(_s_section, ld::Atom::definitionRegular, ld::Atom::combineNever,
                                ld::Atom::scopeLinkageUnit, ld::Atom::typeUnclassified, 
                                symbolTableNotIn, false, false, false, ld::Atom::Alignment(2)),
                _pagesForDelete(NULL), _pageAlignedPages(NULL), _pages(NULL), _pagesSize(0), _header(NULL), _headerSize(0)
{
        // build new compressed list by removing entries where next function has same encoding 
        std::vector<UnwindEntry> uniqueEntries;
        compressDuplicates(entries, uniqueEntries);

        // reserve room so _fixups vector is not reallocated a bunch of times
        _fixups.reserve(uniqueEntries.size()*3);

        // build personality index, update encodings with personality index
        std::map<const ld::Atom*, uint32_t>     personalityIndexMap;
        makePersonalityIndexes(uniqueEntries, personalityIndexMap);
        if ( personalityIndexMap.size() > 3 ) {
                throw "too many personality routines for compact unwind to encode";
        }

        // put the most common encodings into the common table, but at most 127 of them
        std::map<compact_unwind_encoding_t, unsigned int> commonEncodings;
        findCommonEncoding(uniqueEntries, commonEncodings);
        
        // build lsda index
        std::map<const ld::Atom*, uint32_t> lsdaIndexOffsetMap;
        std::vector<LSDAEntry>  lsdaIndex;
        makeLsdaIndex(uniqueEntries, lsdaIndex, lsdaIndexOffsetMap);
        
        // calculate worst case size for all unwind info pages when allocating buffer
        const unsigned int entriesPerRegularPage = (4096-sizeof(unwind_info_regular_second_level_page_header))/sizeof(unwind_info_regular_second_level_entry);
        assert(uniqueEntries.size() > 0);
        const unsigned int pageCount = ((uniqueEntries.size() - 1)/entriesPerRegularPage) + 2;
        _pagesForDelete = (uint8_t*)calloc(pageCount+1,4096);
        if ( _pagesForDelete == NULL ) {
                warning("could not allocate space for compact unwind info");
                return;
        }
        _pageAlignedPages = (uint8_t*)((((uintptr_t)_pagesForDelete) + 4095) & -4096);
        
        // make last second level page smaller so that all other second level pages can be page aligned
        uint32_t maxLastPageSize = 4096 - (ehFrameSize % 4096);
        uint32_t tailPad = 0;
        if ( maxLastPageSize < 128 ) {
                tailPad = maxLastPageSize;
                maxLastPageSize = 4096;
        }
        
        // fill in pages in reverse order
        const ld::Atom* secondLevelFirstFuncs[pageCount*3];
        uint8_t* secondLevelPagesStarts[pageCount*3];
        unsigned int endIndex = uniqueEntries.size();
        unsigned int secondLevelPageCount = 0;
        uint8_t* pageEnd = &_pageAlignedPages[pageCount*4096];
        uint32_t pageSize = maxLastPageSize;
        while ( endIndex > 0 ) {
                endIndex = makeCompressedSecondLevelPage(uniqueEntries, commonEncodings, pageSize, endIndex, pageEnd);
                secondLevelPagesStarts[secondLevelPageCount] = pageEnd;
                secondLevelFirstFuncs[secondLevelPageCount] = uniqueEntries[endIndex].func;
                ++secondLevelPageCount;
                // if this requires more than one page, align so that next starts on page boundary
                if ( (pageSize != 4096) && (endIndex > 0) ) {
                        pageEnd = (uint8_t*)((uintptr_t)(pageEnd) & -4096);
                        pageSize = 4096;  // last page can be odd size, make rest up to 4096 bytes in size
                }
        }
        _pages = pageEnd;
        _pagesSize = &_pageAlignedPages[pageCount*4096] - pageEnd;

        // calculate section layout
        const uint32_t commonEncodingsArraySectionOffset = sizeof(macho_unwind_info_section_header<P>);
        const uint32_t commonEncodingsArrayCount = commonEncodings.size();
        const uint32_t commonEncodingsArraySize = commonEncodingsArrayCount * sizeof(compact_unwind_encoding_t);
        const uint32_t personalityArraySectionOffset = commonEncodingsArraySectionOffset + commonEncodingsArraySize;
        const uint32_t personalityArrayCount = personalityIndexMap.size();
        const uint32_t personalityArraySize = personalityArrayCount * sizeof(uint32_t);
        const uint32_t indexSectionOffset = personalityArraySectionOffset + personalityArraySize;
        const uint32_t indexCount = secondLevelPageCount+1;
        const uint32_t indexSize = indexCount * sizeof(macho_unwind_info_section_header_index_entry<P>);
        const uint32_t lsdaIndexArraySectionOffset = indexSectionOffset + indexSize;
        const uint32_t lsdaIndexArrayCount = lsdaIndex.size();
        const uint32_t lsdaIndexArraySize = lsdaIndexArrayCount * sizeof(macho_unwind_info_section_header_lsda_index_entry<P>);
        const uint32_t headerEndSectionOffset = lsdaIndexArraySectionOffset + lsdaIndexArraySize;

        // now that we know the size of the header, slide all existing fixups on the pages
        const int32_t fixupSlide = headerEndSectionOffset + (_pageAlignedPages - _pages);
        for(std::vector<ld::Fixup>::iterator it = _fixups.begin(); it != _fixups.end(); ++it) {
                it->offsetInAtom += fixupSlide;
        }

        // allocate and fill in section header
        _headerSize = headerEndSectionOffset;
        _header = new uint8_t[_headerSize];
        bzero(_header, _headerSize);
        macho_unwind_info_section_header<P>* sectionHeader = (macho_unwind_info_section_header<P>*)_header;
        sectionHeader->set_version(UNWIND_SECTION_VERSION);
        sectionHeader->set_commonEncodingsArraySectionOffset(commonEncodingsArraySectionOffset);
        sectionHeader->set_commonEncodingsArrayCount(commonEncodingsArrayCount);
        sectionHeader->set_personalityArraySectionOffset(personalityArraySectionOffset);
        sectionHeader->set_personalityArrayCount(personalityArrayCount);
        sectionHeader->set_indexSectionOffset(indexSectionOffset);
        sectionHeader->set_indexCount(indexCount);
        
        // copy common encodings
        uint32_t* commonEncodingsTable = (uint32_t*)&_header[commonEncodingsArraySectionOffset];
        for (std::map<uint32_t, unsigned int>::iterator it=commonEncodings.begin(); it != commonEncodings.end(); ++it)
                E::set32(commonEncodingsTable[it->second], it->first);
                
        // make references for personality entries
        uint32_t* personalityArray = (uint32_t*)&_header[sectionHeader->personalityArraySectionOffset()];
        for (std::map<const ld::Atom*, unsigned int>::iterator it=personalityIndexMap.begin(); it != personalityIndexMap.end(); ++it) {
                uint32_t offset = (uint8_t*)&personalityArray[it->second-1] - _header;
                this->addImageOffsetFixup(offset, it->first);
        }

        // build first level index and references
        macho_unwind_info_section_header_index_entry<P>* indexTable = (macho_unwind_info_section_header_index_entry<P>*)&_header[indexSectionOffset];
        uint32_t refOffset;
        for (unsigned int i=0; i < secondLevelPageCount; ++i) {
                unsigned int reverseIndex = secondLevelPageCount - 1 - i;
                indexTable[i].set_functionOffset(0);
                indexTable[i].set_secondLevelPagesSectionOffset(secondLevelPagesStarts[reverseIndex]-_pages+headerEndSectionOffset);
                indexTable[i].set_lsdaIndexArraySectionOffset(lsdaIndexOffsetMap[secondLevelFirstFuncs[reverseIndex]]+lsdaIndexArraySectionOffset); 
                refOffset = (uint8_t*)&indexTable[i] - _header;
                this->addImageOffsetFixup(refOffset, secondLevelFirstFuncs[reverseIndex]);
        }
        indexTable[secondLevelPageCount].set_functionOffset(0);
        indexTable[secondLevelPageCount].set_secondLevelPagesSectionOffset(0);
        indexTable[secondLevelPageCount].set_lsdaIndexArraySectionOffset(lsdaIndexArraySectionOffset+lsdaIndexArraySize); 
        refOffset = (uint8_t*)&indexTable[secondLevelPageCount] - _header;
        this->addImageOffsetFixupPlusAddend(refOffset, entries.back().func, entries.back().func->size()+1);
        
        // build lsda references
        uint32_t lsdaEntrySectionOffset = lsdaIndexArraySectionOffset;
        for (std::vector<LSDAEntry>::iterator it = lsdaIndex.begin(); it != lsdaIndex.end(); ++it) {
                this->addImageOffsetFixup(lsdaEntrySectionOffset, it->func);
                this->addImageOffsetFixup(lsdaEntrySectionOffset+4, it->lsda);
                lsdaEntrySectionOffset += sizeof(unwind_info_section_header_lsda_index_entry);
        }
        
}

template <typename A>
UnwindInfoAtom<A>::~UnwindInfoAtom()
{
        free(_pagesForDelete);
        free(_header);
}

template <typename A>
void UnwindInfoAtom<A>::copyRawContent(uint8_t buffer[]) const
{
        // content is in two parts
        memcpy(buffer, _header, _headerSize);
        memcpy(&buffer[_headerSize], _pages, _pagesSize);
}


template <>
bool UnwindInfoAtom<x86>::encodingMeansUseDwarf(compact_unwind_encoding_t enc)
{
        return ((enc & UNWIND_X86_MODE_MASK) == UNWIND_X86_MODE_DWARF);
}

template <>
bool UnwindInfoAtom<x86_64>::encodingMeansUseDwarf(compact_unwind_encoding_t enc)
{
        return ((enc & UNWIND_X86_64_MODE_MASK) == UNWIND_X86_64_MODE_DWARF);
}

template <>
bool UnwindInfoAtom<arm64>::encodingMeansUseDwarf(compact_unwind_encoding_t enc)
{
        return ((enc & UNWIND_ARM64_MODE_MASK) == UNWIND_ARM64_MODE_DWARF);
}

template <>
bool UnwindInfoAtom<arm>::encodingMeansUseDwarf(compact_unwind_encoding_t enc)
{
        return ((enc & UNWIND_ARM_MODE_MASK) == UNWIND_ARM_MODE_DWARF);
}


template <typename A>
void UnwindInfoAtom<A>::compressDuplicates(const std::vector<UnwindEntry>& entries, std::vector<UnwindEntry>& uniqueEntries)
{
        // build new list removing entries where next function has same encoding 
        uniqueEntries.reserve(entries.size());
        UnwindEntry last(NULL, 0, 0, NULL, NULL, NULL, 0xFFFFFFFF);
        for(std::vector<UnwindEntry>::const_iterator it=entries.begin(); it != entries.end(); ++it) {
                const UnwindEntry& next = *it;
                bool newNeedsDwarf = encodingMeansUseDwarf(next.encoding);
                // remove entries which have same encoding and personalityPointer as last one
                if ( newNeedsDwarf || (next.encoding != last.encoding) || (next.personalityPointer != last.personalityPointer) 
                                                || (next.lsda != NULL) || (last.lsda != NULL) ) {
                        uniqueEntries.push_back(next);
                }
                last = next;
        }
        if (_s_log) fprintf(stderr, "compressDuplicates() entries.size()=%lu, uniqueEntries.size()=%lu\n", 
                                                                entries.size(), uniqueEntries.size());
}

template <typename A>
void UnwindInfoAtom<A>::makePersonalityIndexes(std::vector<UnwindEntry>& entries, std::map<const ld::Atom*, uint32_t>& personalityIndexMap)
{
        for(std::vector<UnwindEntry>::iterator it=entries.begin(); it != entries.end(); ++it) {
                if ( it->personalityPointer != NULL ) {
                        std::map<const ld::Atom*, uint32_t>::iterator pos = personalityIndexMap.find(it->personalityPointer);
                        if ( pos == personalityIndexMap.end() ) {
                                const uint32_t nextIndex = personalityIndexMap.size() + 1;
                                personalityIndexMap[it->personalityPointer] = nextIndex;
                        }
                        uint32_t personalityIndex = personalityIndexMap[it->personalityPointer];
                        it->encoding |= (personalityIndex << (__builtin_ctz(UNWIND_PERSONALITY_MASK)) );
                }
        }
        if (_s_log) fprintf(stderr, "makePersonalityIndexes() %lu personality routines used\n", personalityIndexMap.size()); 
}


template <typename A>
void UnwindInfoAtom<A>::findCommonEncoding(const std::vector<UnwindEntry>& entries, 
                                                                                        std::map<compact_unwind_encoding_t, unsigned int>& commonEncodings)
{
        // scan infos to get frequency counts for each encoding
        std::map<compact_unwind_encoding_t, unsigned int> encodingsUsed;
        unsigned int mostCommonEncodingUsageCount = 0;
        for(std::vector<UnwindEntry>::const_iterator it=entries.begin(); it != entries.end(); ++it) {
                // never put dwarf into common table
                if ( encodingMeansUseDwarf(it->encoding) )
                        continue;
                std::map<compact_unwind_encoding_t, unsigned int>::iterator pos = encodingsUsed.find(it->encoding);
                if ( pos == encodingsUsed.end() ) {
                        encodingsUsed[it->encoding] = 1;
                }
                else {
                        encodingsUsed[it->encoding] += 1;
                        if ( mostCommonEncodingUsageCount < encodingsUsed[it->encoding] )
                                mostCommonEncodingUsageCount = encodingsUsed[it->encoding];
                }
        }
        // put the most common encodings into the common table, but at most 127 of them
        for(unsigned int usages=mostCommonEncodingUsageCount; usages > 1; --usages) {
                for (std::map<compact_unwind_encoding_t, unsigned int>::iterator euit=encodingsUsed.begin(); euit != encodingsUsed.end(); ++euit) {
                        if ( euit->second == usages ) {
                                unsigned int sz = commonEncodings.size();
                                if ( sz < 127 ) {
                                        commonEncodings[euit->first] = sz;
                                }
                        }
                }
        }
        if (_s_log) fprintf(stderr, "findCommonEncoding() %lu common encodings found\n", commonEncodings.size()); 
}


template <typename A>
void UnwindInfoAtom<A>::makeLsdaIndex(const std::vector<UnwindEntry>& entries, std::vector<LSDAEntry>& lsdaIndex, std::map<const ld::Atom*, uint32_t>& lsdaIndexOffsetMap)
{
        for(std::vector<UnwindEntry>::const_iterator it=entries.begin(); it != entries.end(); ++it) {
                lsdaIndexOffsetMap[it->func] = lsdaIndex.size() * sizeof(unwind_info_section_header_lsda_index_entry);
                if ( it->lsda != NULL ) {
                        LSDAEntry entry;
                        entry.func = it->func;
                        entry.lsda = it->lsda;
                        lsdaIndex.push_back(entry);
                }
        }
        if (_s_log) fprintf(stderr, "makeLsdaIndex() %lu LSDAs found\n", lsdaIndex.size()); 
}


template <>
void UnwindInfoAtom<x86>::addCompressedAddressOffsetFixup(uint32_t offset, const ld::Atom* func, const ld::Atom* fromFunc)
{
        _fixups.push_back(ld::Fixup(offset, ld::Fixup::k1of3, ld::Fixup::kindSetTargetAddress, func));
        _fixups.push_back(ld::Fixup(offset, ld::Fixup::k2of3, ld::Fixup::kindSubtractTargetAddress, fromFunc));
        _fixups.push_back(ld::Fixup(offset, ld::Fixup::k3of3, ld::Fixup::kindStoreLittleEndianLow24of32));
}

template <>
void UnwindInfoAtom<x86_64>::addCompressedAddressOffsetFixup(uint32_t offset, const ld::Atom* func, const ld::Atom* fromFunc)
{
        _fixups.push_back(ld::Fixup(offset, ld::Fixup::k1of3, ld::Fixup::kindSetTargetAddress, func));
        _fixups.push_back(ld::Fixup(offset, ld::Fixup::k2of3, ld::Fixup::kindSubtractTargetAddress, fromFunc));
        _fixups.push_back(ld::Fixup(offset, ld::Fixup::k3of3, ld::Fixup::kindStoreLittleEndianLow24of32));
}

template <>
void UnwindInfoAtom<arm64>::addCompressedAddressOffsetFixup(uint32_t offset, const ld::Atom* func, const ld::Atom* fromFunc)
{
        _fixups.push_back(ld::Fixup(offset, ld::Fixup::k1of3, ld::Fixup::kindSetTargetAddress, func));
        _fixups.push_back(ld::Fixup(offset, ld::Fixup::k2of3, ld::Fixup::kindSubtractTargetAddress, fromFunc));
        _fixups.push_back(ld::Fixup(offset, ld::Fixup::k3of3, ld::Fixup::kindStoreLittleEndianLow24of32));
}

template <>
void UnwindInfoAtom<arm>::addCompressedAddressOffsetFixup(uint32_t offset, const ld::Atom* func, const ld::Atom* fromFunc)
{
        if ( fromFunc->isThumb() ) {
                _fixups.push_back(ld::Fixup(offset, ld::Fixup::k1of4, ld::Fixup::kindSetTargetAddress, func));
                _fixups.push_back(ld::Fixup(offset, ld::Fixup::k2of4, ld::Fixup::kindSubtractTargetAddress, fromFunc));
                _fixups.push_back(ld::Fixup(offset, ld::Fixup::k3of4, ld::Fixup::kindSubtractAddend, 1));
                _fixups.push_back(ld::Fixup(offset, ld::Fixup::k4of4, ld::Fixup::kindStoreLittleEndianLow24of32));
        }
        else {
                _fixups.push_back(ld::Fixup(offset, ld::Fixup::k1of3, ld::Fixup::kindSetTargetAddress, func));
                _fixups.push_back(ld::Fixup(offset, ld::Fixup::k2of3, ld::Fixup::kindSubtractTargetAddress, fromFunc));
                _fixups.push_back(ld::Fixup(offset, ld::Fixup::k3of3, ld::Fixup::kindStoreLittleEndianLow24of32));
        }
}

template <>
void UnwindInfoAtom<x86>::addCompressedEncodingFixup(uint32_t offset, const ld::Atom* fde)
{
        _fixups.push_back(ld::Fixup(offset, ld::Fixup::k1of2, ld::Fixup::kindSetTargetSectionOffset, fde));
        _fixups.push_back(ld::Fixup(offset, ld::Fixup::k2of2, ld::Fixup::kindStoreLittleEndianLow24of32));
}

template <>
void UnwindInfoAtom<x86_64>::addCompressedEncodingFixup(uint32_t offset, const ld::Atom* fde)
{
        _fixups.push_back(ld::Fixup(offset, ld::Fixup::k1of2, ld::Fixup::kindSetTargetSectionOffset, fde));
        _fixups.push_back(ld::Fixup(offset, ld::Fixup::k2of2, ld::Fixup::kindStoreLittleEndianLow24of32));
}

template <>
void UnwindInfoAtom<arm64>::addCompressedEncodingFixup(uint32_t offset, const ld::Atom* fde)
{
        _fixups.push_back(ld::Fixup(offset, ld::Fixup::k1of2, ld::Fixup::kindSetTargetSectionOffset, fde));
        _fixups.push_back(ld::Fixup(offset, ld::Fixup::k2of2, ld::Fixup::kindStoreLittleEndianLow24of32));
}

template <>
void UnwindInfoAtom<arm>::addCompressedEncodingFixup(uint32_t offset, const ld::Atom* fde)
{
        _fixups.push_back(ld::Fixup(offset, ld::Fixup::k1of2, ld::Fixup::kindSetTargetSectionOffset, fde));
        _fixups.push_back(ld::Fixup(offset, ld::Fixup::k2of2, ld::Fixup::kindStoreLittleEndianLow24of32));
}

template <>
void UnwindInfoAtom<x86>::addRegularAddressFixup(uint32_t offset, const ld::Atom* func)
{
        _fixups.push_back(ld::Fixup(offset, ld::Fixup::k1of2, ld::Fixup::kindSetTargetImageOffset, func));
        _fixups.push_back(ld::Fixup(offset, ld::Fixup::k2of2, ld::Fixup::kindStoreLittleEndian32));
}

template <>
void UnwindInfoAtom<x86_64>::addRegularAddressFixup(uint32_t offset, const ld::Atom* func)
{
        _fixups.push_back(ld::Fixup(offset, ld::Fixup::k1of2, ld::Fixup::kindSetTargetImageOffset, func));
        _fixups.push_back(ld::Fixup(offset, ld::Fixup::k2of2, ld::Fixup::kindStoreLittleEndian32));
}

template <>
void UnwindInfoAtom<arm64>::addRegularAddressFixup(uint32_t offset, const ld::Atom* func)
{
        _fixups.push_back(ld::Fixup(offset, ld::Fixup::k1of2, ld::Fixup::kindSetTargetImageOffset, func));
        _fixups.push_back(ld::Fixup(offset, ld::Fixup::k2of2, ld::Fixup::kindStoreLittleEndian32));
}

template <>
void UnwindInfoAtom<arm>::addRegularAddressFixup(uint32_t offset, const ld::Atom* func)
{
        _fixups.push_back(ld::Fixup(offset, ld::Fixup::k1of2, ld::Fixup::kindSetTargetImageOffset, func));
        _fixups.push_back(ld::Fixup(offset, ld::Fixup::k2of2, ld::Fixup::kindStoreLittleEndian32));
}

template <>
void UnwindInfoAtom<x86>::addRegularFDEOffsetFixup(uint32_t offset, const ld::Atom* fde)
{
        _fixups.push_back(ld::Fixup(offset+4, ld::Fixup::k1of2, ld::Fixup::kindSetTargetSectionOffset, fde));
        _fixups.push_back(ld::Fixup(offset+4, ld::Fixup::k2of2, ld::Fixup::kindStoreLittleEndianLow24of32));
}

template <>
void UnwindInfoAtom<x86_64>::addRegularFDEOffsetFixup(uint32_t offset, const ld::Atom* fde)
{
        _fixups.push_back(ld::Fixup(offset+4, ld::Fixup::k1of2, ld::Fixup::kindSetTargetSectionOffset, fde));
        _fixups.push_back(ld::Fixup(offset+4, ld::Fixup::k2of2, ld::Fixup::kindStoreLittleEndianLow24of32));
}

template <>
void UnwindInfoAtom<arm64>::addRegularFDEOffsetFixup(uint32_t offset, const ld::Atom* fde)
{
        _fixups.push_back(ld::Fixup(offset+4, ld::Fixup::k1of2, ld::Fixup::kindSetTargetSectionOffset, fde));
        _fixups.push_back(ld::Fixup(offset+4, ld::Fixup::k2of2, ld::Fixup::kindStoreLittleEndianLow24of32));
}

template <>
void UnwindInfoAtom<arm>::addRegularFDEOffsetFixup(uint32_t offset, const ld::Atom* fde)
{
        _fixups.push_back(ld::Fixup(offset+4, ld::Fixup::k1of2, ld::Fixup::kindSetTargetSectionOffset, fde));
        _fixups.push_back(ld::Fixup(offset+4, ld::Fixup::k2of2, ld::Fixup::kindStoreLittleEndianLow24of32));
}

template <>
void UnwindInfoAtom<x86>::addImageOffsetFixup(uint32_t offset, const ld::Atom* targ)
{
        _fixups.push_back(ld::Fixup(offset, ld::Fixup::k1of2, ld::Fixup::kindSetTargetImageOffset, targ));
        _fixups.push_back(ld::Fixup(offset, ld::Fixup::k2of2, ld::Fixup::kindStoreLittleEndian32));
}

template <>
void UnwindInfoAtom<x86_64>::addImageOffsetFixup(uint32_t offset, const ld::Atom* targ)
{
        _fixups.push_back(ld::Fixup(offset, ld::Fixup::k1of2, ld::Fixup::kindSetTargetImageOffset, targ));
        _fixups.push_back(ld::Fixup(offset, ld::Fixup::k2of2, ld::Fixup::kindStoreLittleEndian32));
}

template <>
void UnwindInfoAtom<arm64>::addImageOffsetFixup(uint32_t offset, const ld::Atom* targ)
{
        _fixups.push_back(ld::Fixup(offset, ld::Fixup::k1of2, ld::Fixup::kindSetTargetImageOffset, targ));
        _fixups.push_back(ld::Fixup(offset, ld::Fixup::k2of2, ld::Fixup::kindStoreLittleEndian32));
}

template <>
void UnwindInfoAtom<arm>::addImageOffsetFixup(uint32_t offset, const ld::Atom* targ)
{
        _fixups.push_back(ld::Fixup(offset, ld::Fixup::k1of2, ld::Fixup::kindSetTargetImageOffset, targ));
        _fixups.push_back(ld::Fixup(offset, ld::Fixup::k2of2, ld::Fixup::kindStoreLittleEndian32));
}

template <>
void UnwindInfoAtom<x86>::addImageOffsetFixupPlusAddend(uint32_t offset, const ld::Atom* targ, uint32_t addend)
{
        _fixups.push_back(ld::Fixup(offset, ld::Fixup::k1of3, ld::Fixup::kindSetTargetImageOffset, targ));
        _fixups.push_back(ld::Fixup(offset, ld::Fixup::k2of3, ld::Fixup::kindAddAddend, addend));
        _fixups.push_back(ld::Fixup(offset, ld::Fixup::k3of3, ld::Fixup::kindStoreLittleEndian32));
}

template <>
void UnwindInfoAtom<x86_64>::addImageOffsetFixupPlusAddend(uint32_t offset, const ld::Atom* targ, uint32_t addend)
{
        _fixups.push_back(ld::Fixup(offset, ld::Fixup::k1of3, ld::Fixup::kindSetTargetImageOffset, targ));
        _fixups.push_back(ld::Fixup(offset, ld::Fixup::k2of3, ld::Fixup::kindAddAddend, addend));
        _fixups.push_back(ld::Fixup(offset, ld::Fixup::k3of3, ld::Fixup::kindStoreLittleEndian32));
}

template <>
void UnwindInfoAtom<arm64>::addImageOffsetFixupPlusAddend(uint32_t offset, const ld::Atom* targ, uint32_t addend)
{
        _fixups.push_back(ld::Fixup(offset, ld::Fixup::k1of3, ld::Fixup::kindSetTargetImageOffset, targ));
        _fixups.push_back(ld::Fixup(offset, ld::Fixup::k2of3, ld::Fixup::kindAddAddend, addend));
        _fixups.push_back(ld::Fixup(offset, ld::Fixup::k3of3, ld::Fixup::kindStoreLittleEndian32));
}

template <>
void UnwindInfoAtom<arm>::addImageOffsetFixupPlusAddend(uint32_t offset, const ld::Atom* targ, uint32_t addend)
{
        _fixups.push_back(ld::Fixup(offset, ld::Fixup::k1of3, ld::Fixup::kindSetTargetImageOffset, targ));
        _fixups.push_back(ld::Fixup(offset, ld::Fixup::k2of3, ld::Fixup::kindAddAddend, addend));
        _fixups.push_back(ld::Fixup(offset, ld::Fixup::k3of3, ld::Fixup::kindStoreLittleEndian32));
}




template <typename A>
unsigned int UnwindInfoAtom<A>::makeRegularSecondLevelPage(const std::vector<UnwindEntry>& uniqueInfos, uint32_t pageSize,  
                                                                                                                        unsigned int endIndex, uint8_t*& pageEnd)
{
        const unsigned int maxEntriesPerPage = (pageSize - sizeof(unwind_info_regular_second_level_page_header))/sizeof(unwind_info_regular_second_level_entry);
        const unsigned int entriesToAdd = ((endIndex > maxEntriesPerPage) ? maxEntriesPerPage : endIndex);
        uint8_t* pageStart = pageEnd 
                                                - entriesToAdd*sizeof(unwind_info_regular_second_level_entry) 
                                                - sizeof(unwind_info_regular_second_level_page_header);
        macho_unwind_info_regular_second_level_page_header<P>* page = (macho_unwind_info_regular_second_level_page_header<P>*)pageStart;
        page->set_kind(UNWIND_SECOND_LEVEL_REGULAR);
        page->set_entryPageOffset(sizeof(macho_unwind_info_regular_second_level_page_header<P>));
        page->set_entryCount(entriesToAdd);
        macho_unwind_info_regular_second_level_entry<P>* entryTable = (macho_unwind_info_regular_second_level_entry<P>*)(pageStart + page->entryPageOffset());
        for (unsigned int i=0; i < entriesToAdd; ++i) {
                const UnwindEntry& info = uniqueInfos[endIndex-entriesToAdd+i];
                entryTable[i].set_functionOffset(0);
                entryTable[i].set_encoding(info.encoding);
                // add fixup for address part of entry
                uint32_t offset = (uint8_t*)(&entryTable[i]) - _pageAlignedPages;
                this->addRegularAddressFixup(offset, info.func);
                if ( encodingMeansUseDwarf(info.encoding) ) {
                        // add fixup for dwarf offset part of page specific encoding
                        uint32_t encOffset = (uint8_t*)(&entryTable[i]) - _pageAlignedPages;
                        this->addRegularFDEOffsetFixup(encOffset, info.fde);
                }
        }
        if (_s_log) fprintf(stderr, "regular page with %u entries\n", entriesToAdd);
        pageEnd = pageStart;
        return endIndex - entriesToAdd;
}


template <typename A>
unsigned int UnwindInfoAtom<A>::makeCompressedSecondLevelPage(const std::vector<UnwindEntry>& uniqueInfos,   
                                                                                                        const std::map<compact_unwind_encoding_t,unsigned int> commonEncodings,  
                                                                                                        uint32_t pageSize, unsigned int endIndex, uint8_t*& pageEnd)
{
        if (_s_log) fprintf(stderr, "makeCompressedSecondLevelPage(pageSize=%u, endIndex=%u)\n", pageSize, endIndex);
        // first pass calculates how many compressed entries we could fit in this sized page
        // keep adding entries to page until:
        //  1) encoding table plus entry table plus header exceed page size
        //  2) the file offset delta from the first to last function > 24 bits
        //  3) custom encoding index reaches 255
        //  4) run out of uniqueInfos to encode
        std::map<compact_unwind_encoding_t, unsigned int> pageSpecificEncodings;
        uint32_t space4 =  (pageSize - sizeof(unwind_info_compressed_second_level_page_header))/sizeof(uint32_t);
        int index = endIndex-1;
        int entryCount = 0;
        uint64_t lastEntryAddress = uniqueInfos[index].funcTentAddress;
        bool canDo = true;
        while ( canDo && (index >= 0) ) {
                const UnwindEntry& info = uniqueInfos[index--];
                // compute encoding index
                unsigned int encodingIndex;
                std::map<compact_unwind_encoding_t, unsigned int>::const_iterator pos = commonEncodings.find(info.encoding);
                if ( pos != commonEncodings.end() ) {
                        encodingIndex = pos->second;
                        if (_s_log) fprintf(stderr, "makeCompressedSecondLevelPage(): funcIndex=%d, re-use commonEncodings[%d]=0x%08X\n", index, encodingIndex, info.encoding);
                }
                else {
                        // no commmon entry, so add one on this page
                        uint32_t encoding = info.encoding;
                        if ( encodingMeansUseDwarf(encoding) ) {
                                // make unique pseudo encoding so this dwarf will gets is own encoding entry slot
                                encoding += (index+1);
                        }
                        std::map<compact_unwind_encoding_t, unsigned int>::iterator ppos = pageSpecificEncodings.find(encoding);
                        if ( ppos != pageSpecificEncodings.end() ) {
                                encodingIndex = pos->second;
                                if (_s_log) fprintf(stderr, "makeCompressedSecondLevelPage(): funcIndex=%d, re-use pageSpecificEncodings[%d]=0x%08X\n", index, encodingIndex, encoding);
                        }
                        else {
                                encodingIndex = commonEncodings.size() + pageSpecificEncodings.size();
                                if ( encodingIndex <= 255 ) {
                                        pageSpecificEncodings[encoding] = encodingIndex;
                                        if (_s_log) fprintf(stderr, "makeCompressedSecondLevelPage(): funcIndex=%d, pageSpecificEncodings[%d]=0x%08X\n", index, encodingIndex, encoding);
                                }
                                else {
                                        canDo = false; // case 3)
                                        if (_s_log) fprintf(stderr, "end of compressed page with %u entries, %lu custom encodings because too many custom encodings\n", 
                                                                                        entryCount, pageSpecificEncodings.size());
                                }
                        }
                }
                // compute function offset
                uint32_t funcOffsetWithInPage = lastEntryAddress - info.funcTentAddress;
                if ( funcOffsetWithInPage > 0x00FFFF00 ) {
                        // don't use 0x00FFFFFF because addresses may vary after atoms are laid out again
                        canDo = false; // case 2)
                        if (_s_log) fprintf(stderr, "can't use compressed page with %u entries because function offset too big\n", entryCount);
                }
                // check room for entry
                if ( (pageSpecificEncodings.size()+entryCount) > space4 ) {
                        canDo = false; // case 1)
                        --entryCount;
                        if (_s_log) fprintf(stderr, "end of compressed page with %u entries because full\n", entryCount);
                }
                //if (_s_log) fprintf(stderr, "space4=%d, pageSpecificEncodings.size()=%ld, entryCount=%d\n", space4, pageSpecificEncodings.size(), entryCount);
                if ( canDo ) {
                        ++entryCount;
                }
        }
        
        // check for cases where it would be better to use a regular (non-compressed) page
        const unsigned int compressPageUsed = sizeof(unwind_info_compressed_second_level_page_header) 
                                                                + pageSpecificEncodings.size()*sizeof(uint32_t)
                                                                + entryCount*sizeof(uint32_t);
        if ( (compressPageUsed < (pageSize-4) && (index >= 0) ) ) {
                const int regularEntriesPerPage = (pageSize - sizeof(unwind_info_regular_second_level_page_header))/sizeof(unwind_info_regular_second_level_entry);
                if ( entryCount < regularEntriesPerPage ) {
                        return makeRegularSecondLevelPage(uniqueInfos, pageSize, endIndex, pageEnd);
                }
        }
        
        // check if we need any padding because adding another entry would take 8 bytes but only have room for 4
        uint32_t pad = 0;
        if ( compressPageUsed == (pageSize-4) )
                pad = 4;

        // second pass fills in page 
        uint8_t* pageStart = pageEnd - compressPageUsed - pad;
        CSLP* page = (CSLP*)pageStart;
        page->set_kind(UNWIND_SECOND_LEVEL_COMPRESSED);
        page->set_entryPageOffset(sizeof(CSLP));
        page->set_entryCount(entryCount);
        page->set_encodingsPageOffset(page->entryPageOffset()+entryCount*sizeof(uint32_t));
        page->set_encodingsCount(pageSpecificEncodings.size());
        uint32_t* const encodingsArray = (uint32_t*)&pageStart[page->encodingsPageOffset()];
        // fill in entry table
        uint32_t* const entiresArray = (uint32_t*)&pageStart[page->entryPageOffset()];
        const ld::Atom* firstFunc = uniqueInfos[endIndex-entryCount].func;
        for(unsigned int i=endIndex-entryCount; i < endIndex; ++i) {
                const UnwindEntry& info = uniqueInfos[i];
                uint8_t encodingIndex;
                if ( encodingMeansUseDwarf(info.encoding) ) {
                        // dwarf entries are always in page specific encodings
                        assert(pageSpecificEncodings.find(info.encoding+i) != pageSpecificEncodings.end());
                        encodingIndex = pageSpecificEncodings[info.encoding+i];
                }
                else {
                        std::map<uint32_t, unsigned int>::const_iterator pos = commonEncodings.find(info.encoding);
                        if ( pos != commonEncodings.end() ) 
                                encodingIndex = pos->second;
                        else 
                                encodingIndex = pageSpecificEncodings[info.encoding];
                }
                uint32_t entryIndex = i - endIndex + entryCount;
                E::set32(entiresArray[entryIndex], encodingIndex << 24);
                // add fixup for address part of entry
                uint32_t offset = (uint8_t*)(&entiresArray[entryIndex]) - _pageAlignedPages;
                this->addCompressedAddressOffsetFixup(offset, info.func, firstFunc);
                if ( encodingMeansUseDwarf(info.encoding) ) {
                        // add fixup for dwarf offset part of page specific encoding
                        uint32_t encOffset = (uint8_t*)(&encodingsArray[encodingIndex-commonEncodings.size()]) - _pageAlignedPages;
                        this->addCompressedEncodingFixup(encOffset, info.fde);
                }
        }
        // fill in encodings table
        for(std::map<uint32_t, unsigned int>::const_iterator it = pageSpecificEncodings.begin(); it != pageSpecificEncodings.end(); ++it) {
                E::set32(encodingsArray[it->second-commonEncodings.size()], it->first);
        }
        
        if (_s_log) fprintf(stderr, "compressed page with %u entries, %lu custom encodings\n", entryCount, pageSpecificEncodings.size());
        
        // update pageEnd;
        pageEnd = pageStart;
        return endIndex-entryCount;  // endIndex for next page
}




static uint64_t calculateEHFrameSize(ld::Internal& state)
{
        bool allCIEs = true;
        uint64_t size = 0;
        for (ld::Internal::FinalSection* sect : state.sections) {
                if ( sect->type() == ld::Section::typeCFI ) {
                        for (const ld::Atom* atom : sect->atoms) {
                                size += atom->size();
                                if ( strcmp(atom->name(), "CIE") != 0 )
                                        allCIEs = false;
                        }
                        if ( allCIEs ) {
                                // <rdar://problem/21427393> Linker generates eh_frame data even when there's only an unused CIEs in it
                                sect->atoms.clear();
                                state.sections.erase(std::remove(state.sections.begin(), state.sections.end(), sect), state.sections.end());
                                return 0;
                        }
                }
        }
        return size;
}

static void getAllUnwindInfos(const ld::Internal& state, std::vector<UnwindEntry>& entries)
{
        uint64_t address = 0;
        for (std::vector<ld::Internal::FinalSection*>::const_iterator sit=state.sections.begin(); sit != state.sections.end(); ++sit) {
                ld::Internal::FinalSection* sect = *sit;
                for (std::vector<const ld::Atom*>::iterator ait=sect->atoms.begin(); ait != sect->atoms.end(); ++ait) {
                        const ld::Atom* atom = *ait;
                        // adjust address for atom alignment
                        uint64_t alignment = 1 << atom->alignment().powerOf2;
                        uint64_t currentModulus = (address % alignment);
                        uint64_t requiredModulus = atom->alignment().modulus;
                        if ( currentModulus != requiredModulus ) {
                                if ( requiredModulus > currentModulus )
                                        address += requiredModulus-currentModulus;
                                else
                                        address += requiredModulus+alignment-currentModulus;
                        }

                        if ( atom->beginUnwind() == atom->endUnwind() ) {
                                // be sure to mark that we have no unwind info for stuff in the TEXT segment without unwind info
                                if ( (atom->section().type() == ld::Section::typeCode) && (atom->size() !=0) ) {
                                        entries.push_back(UnwindEntry(atom, address, 0, NULL, NULL, NULL, 0));
                                }
                        }
                        else {
                                // atom has unwind info(s), add entry for each
                                const ld::Atom* fde = NULL;
                                const ld::Atom* lsda = NULL; 
                                const ld::Atom* personalityPointer = NULL; 
                                for (ld::Fixup::iterator fit = atom->fixupsBegin(), end=atom->fixupsEnd(); fit != end; ++fit) {
                                        switch ( fit->kind ) {
                                                case ld::Fixup::kindNoneGroupSubordinateFDE:
                                                        assert(fit->binding == ld::Fixup::bindingDirectlyBound);
                                                        fde = fit->u.target;
                                                        break;
                                                case ld::Fixup::kindNoneGroupSubordinateLSDA:
                                                        assert(fit->binding == ld::Fixup::bindingDirectlyBound);
                                                        lsda = fit->u.target;
                                                        break;
                                                case ld::Fixup::kindNoneGroupSubordinatePersonality:
                                                        assert(fit->binding == ld::Fixup::bindingDirectlyBound);
                                                        personalityPointer = fit->u.target;
                                                        assert(personalityPointer->section().type() == ld::Section::typeNonLazyPointer);
                                                        break;
                                                default:
                                                        break;
                                        }
                                }
                                if ( fde != NULL ) {
                                        // find CIE for this FDE
                                        const ld::Atom* cie = NULL;
                                        for (ld::Fixup::iterator fit = fde->fixupsBegin(), end=fde->fixupsEnd(); fit != end; ++fit) {
                                                if ( fit->kind != ld::Fixup::kindSubtractTargetAddress )
                                                        continue;
                                                if ( fit->binding != ld::Fixup::bindingDirectlyBound )
                                                        continue;
                                                cie = fit->u.target;
                                                // CIE is only direct subtracted target in FDE
                                                assert(cie->section().type() == ld::Section::typeCFI);
                                                break;
                                        }
                                        if ( cie != NULL ) {
                                                // if CIE can have just one fixup - to the personality pointer
                                                for (ld::Fixup::iterator fit = cie->fixupsBegin(), end=cie->fixupsEnd(); fit != end; ++fit) {
                                                        if ( fit->kind == ld::Fixup::kindSetTargetAddress ) {
                                                                switch ( fit->binding ) {
                                                                        case ld::Fixup::bindingsIndirectlyBound:
                                                                                personalityPointer = state.indirectBindingTable[fit->u.bindingIndex];
                                                                                assert(personalityPointer->section().type() == ld::Section::typeNonLazyPointer);
                                                                                break;
                                                                        case ld::Fixup::bindingDirectlyBound:
                                                                                personalityPointer = fit->u.target;
                                                                                assert(personalityPointer->section().type() == ld::Section::typeNonLazyPointer);
                                                                                break;
                                                                        default:
                                                                                break;
                                                                }
                                                        }
                                                }
                                        }
                                }
                                for ( ld::Atom::UnwindInfo::iterator uit = atom->beginUnwind(); uit != atom->endUnwind(); ++uit ) {
                                        entries.push_back(UnwindEntry(atom, address, uit->startOffset, fde, lsda, personalityPointer, uit->unwindInfo));
                                }
                        }
                        address += atom->size();
                }
        }
}


static void makeFinalLinkedImageCompactUnwindSection(const Options& opts, ld::Internal& state)
{
        // walk every atom and gets its unwind info
        std::vector<UnwindEntry> entries;
        entries.reserve(64);
        getAllUnwindInfos(state, entries);

        // don't generate an __unwind_info section if there is no code in this linkage unit
        if ( entries.size() == 0 )
                return;
                
        // calculate size of __eh_frame section, so __unwind_info can go before it and page align
        uint64_t ehFrameSize = calculateEHFrameSize(state);

        // create atom that contains the whole compact unwind table
        switch ( opts.architecture() ) {
#if SUPPORT_ARCH_x86_64
                case CPU_TYPE_X86_64:
                        state.addAtom(*new UnwindInfoAtom<x86_64>(entries, ehFrameSize));
                        break;
#endif
#if SUPPORT_ARCH_i386
                case CPU_TYPE_I386:
                        state.addAtom(*new UnwindInfoAtom<x86>(entries, ehFrameSize));
                        break;
#endif
#if SUPPORT_ARCH_arm64
                case CPU_TYPE_ARM64:
                        state.addAtom(*new UnwindInfoAtom<arm64>(entries, ehFrameSize));
                        break;
#endif
#if SUPPORT_ARCH_arm_any
                case CPU_TYPE_ARM:
                        if ( opts.armUsesZeroCostExceptions() )
                                state.addAtom(*new UnwindInfoAtom<arm>(entries, ehFrameSize));
                        break;
#endif
                default:
                        assert(0 && "no compact unwind for arch");
        }       
}



template <typename A>
class CompactUnwindAtom : public ld::Atom {
public:
                                                                                        CompactUnwindAtom(ld::Internal& state,const ld::Atom* funcAtom, 
                                                                                                                          uint32_t startOffset, uint32_t len, uint32_t cui);
                                                                                        ~CompactUnwindAtom() {}
                                                                                        
        virtual const ld::File*                                 file() const                                    { return NULL; }
        virtual const char*                                             name() const                                    { return "compact unwind info"; }
        virtual uint64_t                                                size() const                                    { return sizeof(macho_compact_unwind_entry<P>); }
        virtual uint64_t                                                objectAddress() const                   { return 0; }
        virtual void                                                    copyRawContent(uint8_t buffer[]) const;
        virtual void                                                    setScope(Scope)                                 { }
        virtual ld::Fixup::iterator                             fixupsBegin() const                             { return (ld::Fixup*)&_fixups[0]; }
        virtual ld::Fixup::iterator                             fixupsEnd()     const                           { return (ld::Fixup*)&_fixups[_fixups.size()]; }

private:
        typedef typename A::P                                           P;
        typedef typename A::P::E                                        E;
        typedef typename A::P::uint_t                           pint_t;
        

        const ld::Atom*                                                 _atom;
        const uint32_t                                                  _startOffset;
        const uint32_t                                                  _len;
        const uint32_t                                                  _compactUnwindInfo;
        std::vector<ld::Fixup>                                  _fixups;
        
        static ld::Fixup::Kind                                  _s_pointerKind;
        static ld::Fixup::Kind                                  _s_pointerStoreKind;
        static ld::Section                                              _s_section;
};


template <typename A>
ld::Section CompactUnwindAtom<A>::_s_section("__LD", "__compact_unwind", ld::Section::typeDebug);

template <> ld::Fixup::Kind CompactUnwindAtom<x86>::_s_pointerKind = ld::Fixup::kindStoreLittleEndian32;
template <> ld::Fixup::Kind CompactUnwindAtom<x86>::_s_pointerStoreKind = ld::Fixup::kindStoreTargetAddressLittleEndian32;
template <> ld::Fixup::Kind CompactUnwindAtom<x86_64>::_s_pointerKind = ld::Fixup::kindStoreLittleEndian64;
template <> ld::Fixup::Kind CompactUnwindAtom<x86_64>::_s_pointerStoreKind = ld::Fixup::kindStoreTargetAddressLittleEndian64;
#if SUPPORT_ARCH_arm64
template <> ld::Fixup::Kind CompactUnwindAtom<arm64>::_s_pointerKind = ld::Fixup::kindStoreLittleEndian64;
template <> ld::Fixup::Kind CompactUnwindAtom<arm64>::_s_pointerStoreKind = ld::Fixup::kindStoreTargetAddressLittleEndian64;
#endif
template <> ld::Fixup::Kind CompactUnwindAtom<arm>::_s_pointerKind = ld::Fixup::kindStoreLittleEndian32;
template <> ld::Fixup::Kind CompactUnwindAtom<arm>::_s_pointerStoreKind = ld::Fixup::kindStoreTargetAddressLittleEndian32;

template <typename A>
CompactUnwindAtom<A>::CompactUnwindAtom(ld::Internal& state,const ld::Atom* funcAtom, uint32_t startOffset,
                                                                                uint32_t len, uint32_t cui)
        : ld::Atom(_s_section, ld::Atom::definitionRegular, ld::Atom::combineNever,
                                ld::Atom::scopeTranslationUnit, ld::Atom::typeUnclassified, 
                                symbolTableNotIn, false, false, false, ld::Atom::Alignment(log2(sizeof(pint_t)))),
        _atom(funcAtom), _startOffset(startOffset), _len(len), _compactUnwindInfo(cui)
{
        _fixups.push_back(ld::Fixup(macho_compact_unwind_entry<P>::codeStartFieldOffset(), ld::Fixup::k1of3, ld::Fixup::kindSetTargetAddress, funcAtom));
        _fixups.push_back(ld::Fixup(macho_compact_unwind_entry<P>::codeStartFieldOffset(), ld::Fixup::k2of3, ld::Fixup::kindAddAddend, _startOffset));
        _fixups.push_back(ld::Fixup(macho_compact_unwind_entry<P>::codeStartFieldOffset(), ld::Fixup::k3of3, _s_pointerKind));
        // see if atom has subordinate personality function or lsda
        for (ld::Fixup::iterator fit = funcAtom->fixupsBegin(), end=funcAtom->fixupsEnd(); fit != end; ++fit) {
                switch ( fit->kind ) {
                        case ld::Fixup::kindNoneGroupSubordinatePersonality:
                                assert(fit->binding == ld::Fixup::bindingsIndirectlyBound);
                                _fixups.push_back(ld::Fixup(macho_compact_unwind_entry<P>::personalityFieldOffset(), ld::Fixup::k1of1, _s_pointerStoreKind, state.indirectBindingTable[fit->u.bindingIndex]));
                                break;
                        case ld::Fixup::kindNoneGroupSubordinateLSDA:
                                assert(fit->binding == ld::Fixup::bindingDirectlyBound);
                                _fixups.push_back(ld::Fixup(macho_compact_unwind_entry<P>::lsdaFieldOffset(), ld::Fixup::k1of1, _s_pointerStoreKind, fit->u.target));
                                break;
                        default:
                                break;
                }
        }

}

template <typename A>
void CompactUnwindAtom<A>::copyRawContent(uint8_t buffer[]) const
{
        macho_compact_unwind_entry<P>* buf = (macho_compact_unwind_entry<P>*)buffer;
        buf->set_codeStart(0);
        buf->set_codeLen(_len);
        buf->set_compactUnwindInfo(_compactUnwindInfo);
        buf->set_personality(0);
        buf->set_lsda(0);
}


static void makeCompactUnwindAtom(const Options& opts, ld::Internal& state, const ld::Atom* atom, 
                                                                                        uint32_t startOffset, uint32_t endOffset, uint32_t cui)
{
        switch ( opts.architecture() ) {
#if SUPPORT_ARCH_x86_64
                case CPU_TYPE_X86_64:
                        state.addAtom(*new CompactUnwindAtom<x86_64>(state, atom, startOffset, endOffset-startOffset, cui));
                        break;
#endif
#if SUPPORT_ARCH_i386
                case CPU_TYPE_I386:
                        state.addAtom(*new CompactUnwindAtom<x86>(state, atom, startOffset, endOffset-startOffset, cui));
                        break;
#endif
#if SUPPORT_ARCH_arm64
                case CPU_TYPE_ARM64:
                        state.addAtom(*new CompactUnwindAtom<arm64>(state, atom, startOffset, endOffset-startOffset, cui));
                        break;
#endif
                case CPU_TYPE_ARM:
                        state.addAtom(*new CompactUnwindAtom<arm>(state, atom, startOffset, endOffset-startOffset, cui));
                        break;
        }
}

static void makeRelocateableCompactUnwindSection(const Options& opts, ld::Internal& state)
{
        // can't add CompactUnwindAtom atoms will iterating, so pre-scan
        std::vector<const ld::Atom*> atomsWithUnwind;
        for (std::vector<ld::Internal::FinalSection*>::const_iterator sit=state.sections.begin(); sit != state.sections.end(); ++sit) {
                ld::Internal::FinalSection* sect = *sit;
                for (std::vector<const ld::Atom*>::iterator ait=sect->atoms.begin(); ait != sect->atoms.end(); ++ait) {
                        const ld::Atom* atom = *ait;
                        if ( atom->beginUnwind() != atom->endUnwind() ) 
                                atomsWithUnwind.push_back(atom);
                }
        }
        // make one CompactUnwindAtom for each compact unwind range in each atom
        for (std::vector<const ld::Atom*>::iterator it = atomsWithUnwind.begin(); it != atomsWithUnwind.end(); ++it) {
                const ld::Atom* atom = *it;
                uint32_t lastOffset = 0;
                uint32_t lastCUE = 0;
                bool first = true;
                for (ld::Atom::UnwindInfo::iterator uit=atom->beginUnwind(); uit != atom->endUnwind(); ++uit) {
                        if ( !first ) {
                                makeCompactUnwindAtom(opts, state, atom, lastOffset, uit->startOffset, lastCUE);
                        }
                        lastOffset = uit->startOffset;
                        lastCUE = uit->unwindInfo;
                        first = false;
                }
                makeCompactUnwindAtom(opts, state, atom, lastOffset, (uint32_t)atom->size(), lastCUE);
        }
}


void doPass(const Options& opts, ld::Internal& state)
{
        if ( opts.outputKind() == Options::kObjectFile )
                makeRelocateableCompactUnwindSection(opts, state);
                
        else if ( opts.needsUnwindInfoSection() ) 
                makeFinalLinkedImageCompactUnwindSection(opts, state);
}


} // namespace compact_unwind
} // namespace passes 
} // namespace ld