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dyld3/shared-cache/OptimizerObjC.cpp dyld-733.8 dyld-655.1.1
--- dyld/dyld-733.8/dyld3/shared-cache/OptimizerObjC.cpp
+++ dyld/dyld-655.1.1/dyld3/shared-cache/OptimizerObjC.cpp
@@ -36,11 +36,6 @@
 #include "FileAbstraction.hpp"
 #include "MachOFileAbstraction.hpp"
 #include "MachOLoaded.h"
-#include "MachOAnalyzer.h"
-
-#ifndef MH_HAS_OBJC
-  #define MH_HAS_OBJC            0x40000000
-#endif
 
 // Scan a C++ or Swift length-mangled field.
 static bool scanMangledField(const char *&string, const char *end, 
@@ -129,13 +124,13 @@
     uint64_t vmAddrForOnDiskVMAddr(uint64_t vmaddr) {
         if ( _chainedFixups ) {
             dyld3::MachOLoaded::ChainedFixupPointerOnDisk ptr;
-            ptr.raw64 = vmaddr;
-            assert(ptr.arm64e.authRebase.bind == 0);
-            if ( ptr.arm64e.authRebase.auth ) {
-                vmaddr = _cacheUnslideAddr + ptr.arm64e.authRebase.target;
+            ptr.raw = vmaddr;
+            assert(ptr.authRebase.bind == 0);
+            if ( ptr.authRebase.auth ) {
+                vmaddr = _cacheUnslideAddr + ptr.authRebase.target;
             }
             else {
-                vmaddr = ptr.arm64e.unpackTarget();
+                vmaddr = ptr.plainRebase.signExtendedTarget();
             }
         }
         return vmaddr;
@@ -288,14 +283,6 @@
         return (pint_t)element->second;
     }
 
-    void visitCoalescedStrings(const CacheBuilder::CacheCoalescedText& coalescedText) {
-        const CacheBuilder::CacheCoalescedText::StringSection& methodNames = coalescedText.getSectionData("__objc_methname");
-        for (const auto& stringAndOffset : methodNames.stringsToOffsets) {
-            uint64_t vmAddr = methodNames.bufferVMAddr + stringAndOffset.second;
-            _selectorStrings[stringAndOffset.first.data()] = vmAddr;
-        }
-    }
-
     objc_opt::string_map& strings() { 
         return _selectorStrings;
     }
@@ -354,13 +341,11 @@
 private:
     typedef typename P::uint_t pint_t;
 
-    objc_opt::string_map                                _protocolNames;
-    objc_opt::legacy_protocol_map                       _protocols;
-    objc_opt::protocol_map                              _protocolsAndHeaders;
-    size_t                                              _protocolCount;
-    size_t                                              _protocolReferenceCount;
-    Diagnostics&                                        _diagnostics;
-    HeaderInfoOptimizer<P, objc_header_info_ro_t<P>>&   _hInfos;
+    objc_opt::string_map    _protocolNames;
+    objc_opt::protocol_map  _protocols;
+    size_t                  _protocolCount;
+    size_t                  _protocolReferenceCount;
+    Diagnostics&            _diagnostics;
 
     friend class ProtocolReferenceWalker<P, ProtocolOptimizer<P>>;
 
@@ -375,8 +360,8 @@
 
 public:
 
-    ProtocolOptimizer(Diagnostics& diag, HeaderInfoOptimizer<P, objc_header_info_ro_t<P>>& hinfos)
-        : _protocolCount(0), _protocolReferenceCount(0), _diagnostics(diag), _hInfos(hinfos) {
+    ProtocolOptimizer(Diagnostics& diag)
+        : _protocolCount(0), _protocolReferenceCount(0), _diagnostics(diag) {
     }
 
     void addProtocols(ContentAccessor* cache, const macho_header<P>* header)
@@ -393,17 +378,13 @@
                     _diagnostics.error("objc protocol is too big");
                     return;
                 }
+
                 uint64_t name_vmaddr = cache->vmAddrForContent((void*)name);
                 uint64_t proto_vmaddr = cache->vmAddrForContent(proto);
                 _protocolNames.insert(objc_opt::string_map::value_type(name, name_vmaddr));
-                _protocols.insert(objc_opt::legacy_protocol_map::value_type(name, proto_vmaddr));
+                _protocols.insert(objc_opt::protocol_map::value_type(name, proto_vmaddr));
                 _protocolCount++;
             }
-
-            // Note down which header this protocol came from.  We'll fill in the proto_vmaddr here later
-            // once we've chosen a single definition for the protocol with this name.
-            uint64_t hinfo_vmaddr = cache->vmAddrForContent(_hInfos.hinfoForHeader(cache, header));
-            _protocolsAndHeaders.insert(objc_opt::class_map::value_type(name, std::pair<uint64_t, uint64_t>(0, hinfo_vmaddr)));
         }
     }
 
@@ -424,7 +405,9 @@
             return "libobjc's read-write section is too small (metadata not optimized)";
         }
 
-        for (auto iter = _protocols.begin(); iter != _protocols.end(); ++iter)
+        for (objc_opt::protocol_map::iterator iter = _protocols.begin();
+             iter != _protocols.end();
+             ++iter)
         {
             objc_protocol_t<P>* oldProto = (objc_protocol_t<P>*)
                 cache->contentForVMAddr(iter->second);
@@ -467,19 +450,12 @@
                 proto->setDemangledName(cache, roName, _diagnostics);
             }
             proto->setFixedUp();
-            proto->setIsCanonical();
 
             // Redirect the protocol table at our new object.
             iter->second = cache->vmAddrForContent(proto);
 
             // Add new rebase entries.
             proto->addPointers(cache, aslrTracker);
-        }
-
-        // Now that we've chosen the canonical protocols, set the duplicate headers to
-        // point to their protocols.
-        for (auto iter = _protocolsAndHeaders.begin(); iter != _protocolsAndHeaders.end(); ++iter) {
-            iter->second.first = _protocols[iter->first];
         }
         
         return NULL;
@@ -491,17 +467,13 @@
         refs.walk(cache, header);
     }
 
-    objc_opt::string_map& protocolNames() {
+    objc_opt::string_map& protocolNames() { 
         return _protocolNames;
     }
 
-    objc_opt::legacy_protocol_map& protocols() {
+    objc_opt::protocol_map& protocols() { 
         return _protocols;
-    }
-
-    objc_opt::protocol_map& protocolsAndHeaders() {
-        return _protocolsAndHeaders;
-    }
+   }
 
     size_t protocolCount() const { return _protocolCount; }
     size_t protocolReferenceCount() const { return _protocolReferenceCount; }
@@ -515,87 +487,11 @@
         return 100;
 }
 
-template <typename P>
-void addObjcSegments(Diagnostics& diag, DyldSharedCache* cache, const mach_header* libobjcMH,
-                     uint8_t* objcReadOnlyBuffer, uint64_t objcReadOnlyBufferSizeAllocated,
-                     uint8_t* objcReadWriteBuffer, uint64_t objcReadWriteBufferSizeAllocated,
-                     uint32_t objcRwFileOffset)
-{
-    // validate there is enough free space to add the load commands
-    const dyld3::MachOAnalyzer* libobjcMA = ((dyld3::MachOAnalyzer*)libobjcMH);
-    uint32_t freeSpace = libobjcMA->loadCommandsFreeSpace();
-    const uint32_t segSize = sizeof(macho_segment_command<P>);
-    if ( freeSpace < 2*segSize ) {
-        diag.warning("not enough space in libojbc.dylib to add load commands for objc optimization regions");
-        return;
-    }
-
-    // find location of LINKEDIT LC_SEGMENT load command, we need to insert new segments before it
-    __block uint8_t* linkeditSeg = nullptr;
-    libobjcMA->forEachSegment(^(const dyld3::MachOFile::SegmentInfo& info, bool& stop) {
-        if ( strcmp(info.segName, "__LINKEDIT") == 0 )
-            linkeditSeg = (uint8_t*)libobjcMH + info.loadCommandOffset;
-    });
-    if ( linkeditSeg == nullptr ) {
-        diag.warning("__LINKEDIT not found in libojbc.dylib");
-        return;
-    }
-
-    // move load commands to make room to insert two new ones before LINKEDIT segment load command
-    uint8_t* endOfLoadCommands = (uint8_t*)libobjcMH + sizeof(macho_header<P>) + libobjcMH->sizeofcmds;
-    uint32_t remainingSize = (uint32_t)(endOfLoadCommands - linkeditSeg);
-    memmove(linkeditSeg+2*segSize, linkeditSeg, remainingSize);
-
-    // insert new segments
-    macho_segment_command<P>* roSeg = (macho_segment_command<P>*)(linkeditSeg);
-    macho_segment_command<P>* rwSeg = (macho_segment_command<P>*)(linkeditSeg+sizeof(macho_segment_command<P>));
-    roSeg->set_cmd(macho_segment_command<P>::CMD);
-    roSeg->set_cmdsize(segSize);
-    roSeg->set_segname("__OBJC_RO");
-    roSeg->set_vmaddr(cache->unslidLoadAddress() + objcReadOnlyBuffer - (uint8_t*)cache);
-    roSeg->set_vmsize(objcReadOnlyBufferSizeAllocated);
-    roSeg->set_fileoff(objcReadOnlyBuffer - (uint8_t*)cache);
-    roSeg->set_filesize(objcReadOnlyBufferSizeAllocated);
-    roSeg->set_maxprot(VM_PROT_READ);
-    roSeg->set_initprot(VM_PROT_READ);
-    roSeg->set_nsects(0);
-    roSeg->set_flags(0);
-    rwSeg->set_cmd(macho_segment_command<P>::CMD);
-    rwSeg->set_cmdsize(segSize);
-    rwSeg->set_segname("__OBJC_RW");
-    rwSeg->set_vmaddr(cache->unslidLoadAddress() + objcReadWriteBuffer - (uint8_t*)cache);
-    rwSeg->set_vmsize(objcReadWriteBufferSizeAllocated);
-    rwSeg->set_fileoff(objcRwFileOffset);
-    rwSeg->set_filesize(objcReadWriteBufferSizeAllocated);
-    rwSeg->set_maxprot(VM_PROT_WRITE|VM_PROT_READ);
-    rwSeg->set_initprot(VM_PROT_WRITE|VM_PROT_READ);
-    rwSeg->set_nsects(0);
-    rwSeg->set_flags(0);
-
-    // update mach_header to account for new load commands
-    macho_header<P>* mh = (macho_header<P>*)libobjcMH;
-    mh->set_sizeofcmds(mh->sizeofcmds() + 2*segSize);
-    mh->set_ncmds(mh->ncmds()+2);
-
-    // fix up table at start of dyld cache that has pointer into install name for libobjc
-    dyld_cache_image_info* images = (dyld_cache_image_info*)((uint8_t*)cache + cache->header.imagesOffset);
-    uint64_t libobjcUnslidAddress = cache->unslidLoadAddress() + ((uint8_t*)libobjcMH - (uint8_t*)cache);
-    for (uint32_t i=0; i < cache->header.imagesCount; ++i) {
-        if ( images[i].address == libobjcUnslidAddress ) {
-            images[i].pathFileOffset += (2*segSize);
-            break;
-        }
-    }
-}
-
 
 template <typename P>
 void doOptimizeObjC(DyldSharedCache* cache, bool forProduction, CacheBuilder::ASLR_Tracker& aslrTracker,
-                    CacheBuilder::LOH_Tracker& lohTracker, const CacheBuilder::CacheCoalescedText& coalescedText,
-                    const std::map<void*, std::string>& missingWeakImports, Diagnostics& diag,
-                    uint8_t* objcReadOnlyBuffer, uint64_t objcReadOnlyBufferSizeUsed, uint64_t objcReadOnlyBufferSizeAllocated,
-                    uint8_t* objcReadWriteBuffer, uint64_t objcReadWriteBufferSizeAllocated,
-                    uint32_t objcRwFileOffset)
+                    CacheBuilder::LOH_Tracker& lohTracker,
+                    const std::map<void*, std::string>& missingWeakImports, Diagnostics& diag)
 {
     typedef typename P::E           E;
     typedef typename P::uint_t      pint_t;
@@ -613,15 +509,15 @@
     //
     // Find libobjc's empty sections and build list of images with objc metadata
     //
-    __block const mach_header*      libobjcMH = nullptr;
     __block const macho_section<P> *optROSection = nullptr;
+    __block const macho_section<P> *optRWSection = nullptr;
     __block const macho_section<P> *optPointerListSection = nullptr;
     __block std::vector<const macho_header<P>*> objcDylibs;
     cache->forEachImage(^(const mach_header* machHeader, const char* installName) {
         const macho_header<P>* mh = (const macho_header<P>*)machHeader;
         if ( strstr(installName, "/libobjc.") != nullptr ) {
-            libobjcMH = (mach_header*)mh;
             optROSection = mh->getSection("__TEXT", "__objc_opt_ro");
+            optRWSection = mh->getSection("__DATA", "__objc_opt_rw");
             optPointerListSection = mh->getSection("__DATA", "__objc_opt_ptrs");
         }
         if ( mh->getSection("__DATA", "__objc_imageinfo") || mh->getSection("__OBJC", "__image_info") ) {
@@ -633,21 +529,23 @@
         diag.warning("libobjc's read-only section missing (metadata not optimized)");
         return;
     }
+    if ( optRWSection == nullptr ) {
+        diag.warning("libobjc's read/write section missing (metadata not optimized)");
+        return;
+    }
     if ( optPointerListSection == nullptr ) {
         diag.warning("libobjc's pointer list section missing (metadata not optimized)");
         return;
     }
-    // point optROData into space allocated in dyld cache
-    uint8_t* optROData = objcReadOnlyBuffer + objcReadOnlyBufferSizeUsed;
-    size_t optRORemaining = objcReadOnlyBufferSizeAllocated - objcReadOnlyBufferSizeUsed;
-    *((uint32_t*)optROData) = objc_opt::VERSION;
+
+    uint8_t* optROData = (uint8_t*)cacheAccessor.contentForVMAddr(optROSection->addr());
     if ( optROData == nullptr ) {
         diag.warning("libobjc's read-only section has bad content");
         return;
     }
-
-    uint8_t* optRWData = objcReadWriteBuffer;
-    size_t optRWRemaining = objcReadWriteBufferSizeAllocated;
+    size_t optRORemaining = optROSection->size();
+    uint8_t* optRWData = (uint8_t*)cacheAccessor.contentForVMAddr(optRWSection->addr());
+    size_t optRWRemaining = optRWSection->size();
     if (optRORemaining < headerSize) {
         diag.warning("libobjc's read-only section is too small (metadata not optimized)");
         return;
@@ -683,7 +581,7 @@
     //
     // First the RO header info
     // log("writing out %d RO dylibs at offset %d", (uint32_t)objcDylibs.size(), (uint32_t)(optROSection->size() - optRORemaining));
-    uint64_t hinfoROVMAddr = cacheAccessor.vmAddrForContent(optROData);
+    uint64_t hinfoROVMAddr = optROSection->addr() + optROSection->size() - optRORemaining;
     HeaderInfoOptimizer<P, objc_header_info_ro_t<P>> hinfoROOptimizer;
     const char* err = hinfoROOptimizer.init((uint32_t)objcDylibs.size(), optROData, optRORemaining);
     if (err) {
@@ -698,7 +596,7 @@
 
     // Then the RW header info
     // log("writing out %d RW dylibs at offset %d", (uint32_t)objcDylibs.size(), (uint32_t)(optRWSection->size() - optRWRemaining));
-    uint64_t hinfoRWVMAddr = cacheAccessor.vmAddrForContent(optRWData);
+    uint64_t hinfoRWVMAddr = (uint64_t)optRWSection->addr() + (uint64_t)optRWSection->size() - optRWRemaining;
     HeaderInfoOptimizer<P, objc_header_info_rw_t<P>> hinfoRWOptimizer;
     err = hinfoRWOptimizer.init((uint32_t)objcDylibs.size(), optRWData, optRWRemaining);
     if (err) {
@@ -723,39 +621,6 @@
     ObjCSelectorUniquer<P> uniq(&cacheAccessor);
     std::vector<const macho_header<P>*> sizeSortedDylibs = objcDylibs;
     std::sort(sizeSortedDylibs.begin(), sizeSortedDylibs.end(),  [](const macho_header<P>* lmh, const macho_header<P>* rmh) -> bool {
-        // Sort a select few heavy hitters first.
-        auto getPriority = [](const char* installName) -> int {
-            if (!strcmp(installName, "/usr/lib/libobjc.A.dylib"))
-                return 0;
-            if (!strcmp(installName, "/System/Library/Frameworks/Foundation.framework/Versions/C/Foundation") ||
-                !strcmp(installName, "/System/Library/Frameworks/Foundation.framework/Foundation"))
-                return 1;
-            if (!strcmp(installName, "/System/Library/Frameworks/CoreFoundation.framework/Versions/A/CoreFoundation") ||
-                !strcmp(installName, "/System/Library/Frameworks/CoreFoundation.framework/CoreFoundation"))
-                return 2;
-            // Note we don't sort iOSMac UIKitCore early as we want iOSMac after macOS.
-            if (!strcmp(installName, "/System/Library/PrivateFrameworks/UIKitCore.framework/UIKitCore"))
-                return 3;
-            if (!strcmp(installName, "/System/Library/Frameworks/AppKit.framework/Versions/C/AppKit"))
-                return 4;
-            if (!strcmp(installName, "/System/Library/Frameworks/CFNetwork.framework/Versions/A/CFNetwork") ||
-                !strcmp(installName, "/System/Library/Frameworks/CFNetwork.framework/CFNetwork"))
-                return 5;
-            return INT_MAX;
-        };
-
-        // Sort by priority first
-        int priorityA = getPriority(((const dyld3::MachOFile*)lmh)->installName());
-        int priorityB = getPriority(((const dyld3::MachOFile*)rmh)->installName());
-        if (priorityA != priorityB)
-            return priorityA < priorityB;
-
-        // Sort mac before iOSMac
-        bool isIOSMacA = strncmp(((const dyld3::MachOFile*)lmh)->installName(), "/System/iOSSupport/", 19) == 0;
-        bool isIOSMacB = strncmp(((const dyld3::MachOFile*)rmh)->installName(), "/System/iOSSupport/", 19) == 0;
-        if (isIOSMacA != isIOSMacB)
-            return !isIOSMacA;
-        
         const macho_section<P>* lSection = lmh->getSection("__TEXT", "__objc_methname");
         const macho_section<P>* rSection = rmh->getSection("__TEXT", "__objc_methname");
         uint64_t lSelectorSize = (lSection ? lSection->size() : 0);
@@ -763,12 +628,7 @@
         return lSelectorSize > rSelectorSize;
     });
 
-    auto alignPointer = [](uint8_t* ptr) -> uint8_t* {
-        return (uint8_t*)(((uintptr_t)ptr + 0x7) & ~0x7);
-    };
-
     SelectorOptimizer<P, ObjCSelectorUniquer<P> > selOptimizer(uniq);
-    selOptimizer.visitCoalescedStrings(coalescedText);
     for (const macho_header<P>* mh : sizeSortedDylibs) {
         LegacySelectorUpdater<P, ObjCSelectorUniquer<P>>::update(&cacheAccessor, mh, uniq);
         selOptimizer.optimize(&cacheAccessor, mh);
@@ -777,7 +637,7 @@
     diag.verbose("  uniqued  %6lu selectors\n", uniq.strings().size());
     diag.verbose("  updated  %6lu selector references\n", uniq.count());
 
-    uint64_t seloptVMAddr = cacheAccessor.vmAddrForContent(optROData);
+    uint64_t seloptVMAddr = optROSection->addr() + optROSection->size() - optRORemaining;
     objc_opt::objc_selopt_t *selopt = new(optROData) objc_opt::objc_selopt_t;
     err = selopt->write(seloptVMAddr, optRORemaining, uniq.strings());
     if (err) {
@@ -785,7 +645,6 @@
         return;
     }
     optROData += selopt->size();
-    optROData = alignPointer(optROData);
     optRORemaining -= selopt->size();
     uint32_t seloptCapacity = selopt->capacity;
     uint32_t seloptOccupied = selopt->occupied;
@@ -799,24 +658,20 @@
     // 
     // Detect classes that have missing weak-import superclasses.
     // 
-    // Production shared caches don't support roots so we can set this and know
-    // there will definitely not be missing weak superclasses at runtime.
-    // Development shared caches can set this bit as the objc runtime only trusts
-    // this bit if there are no roots at runtime.
+    // Production only. Development cache does not do this: a replacement 
+    // library could omit a class at runtime that was present during 
+    // cache construction.
     // 
     // This is SAFE: the binaries themselves are unmodified.
-    WeakClassDetector<P> weakopt;
-    bool noMissingWeakSuperclasses = weakopt.noMissingWeakSuperclasses(&cacheAccessor,
-                                                                       missingWeakImports,
-                                                                       sizeSortedDylibs);
-
+    bool noMissingWeakSuperclasses = false; // dev cache can't promise otherwise
     if (forProduction) {
-        // Shared cache does not currently support unbound weak references.
-        // Here we assert that there are none. If support is added later then
+        WeakClassDetector<P> weakopt;
+        noMissingWeakSuperclasses = 
+            weakopt.noMissingWeakSuperclasses(&cacheAccessor, missingWeakImports, sizeSortedDylibs);
+
+        // Shared cache does not currently support unbound weak references. 
+        // Here we assert that there are none. If support is added later then 
         // this assertion needs to be removed and this path needs to be tested.
-        // FIXME: The internal cache also isn't going to notice that an on-disk
-        // dylib could resolve a weak bind from the shared cache.  Should we just
-        // error on all caches, regardless of dev/customer?
         if (!noMissingWeakSuperclasses) {
             diag.error("Some Objective-C class has a superclass that is "
                        "weak-import and missing from the cache.");
@@ -836,7 +691,7 @@
 
     diag.verbose("  recorded % 6ld classes\n", classes.classNames().size());
 
-    uint64_t clsoptVMAddr = cacheAccessor.vmAddrForContent(optROData);
+    uint64_t clsoptVMAddr = optROSection->addr() + optROSection->size() - optRORemaining;
     objc_opt::objc_clsopt_t *clsopt = new(optROData) objc_opt::objc_clsopt_t;
     err = clsopt->write(clsoptVMAddr, optRORemaining, 
                         classes.classNames(), classes.classes(), false);
@@ -845,7 +700,6 @@
         return;
     }
     optROData += clsopt->size();
-    optROData = alignPointer(optROData);
     optRORemaining -= clsopt->size();
     size_t duplicateCount = clsopt->duplicateCount();
     uint32_t clsoptCapacity = clsopt->capacity;
@@ -878,7 +732,7 @@
     // This is SAFE: no protocol references are updated yet
     // This must be done AFTER updating method lists.
 
-    ProtocolOptimizer<P> protocolOptimizer(diag, hinfoROOptimizer);
+    ProtocolOptimizer<P> protocolOptimizer(diag);
     for (const macho_header<P>* mh : sizeSortedDylibs) {
         protocolOptimizer.addProtocols(&cacheAccessor, mh);
     }
@@ -896,29 +750,24 @@
         return;
     }
 
-    // Align the buffer again.  The new protocols may have added an odd number of name characters
-    optROData = alignPointer(optROData);
-
-    // New protocol table which tracks loaded images.
-    uint64_t protocoloptVMAddr = cacheAccessor.vmAddrForContent(optROData);
-    objc_opt::objc_protocolopt2_t *protocolopt = new (optROData) objc_opt::objc_protocolopt2_t;
-    err = protocolopt->write(protocoloptVMAddr, optRORemaining,
-                             protocolOptimizer.protocolNames(),
-                             protocolOptimizer.protocolsAndHeaders(), false);
+    uint64_t protocoloptVMAddr = optROSection->addr() + optROSection->size() - optRORemaining;
+    objc_opt::objc_protocolopt_t *protocolopt = new (optROData) objc_opt::objc_protocolopt_t;
+    err = protocolopt->write(protocoloptVMAddr, optRORemaining, 
+                             protocolOptimizer.protocolNames(), 
+                             protocolOptimizer.protocols(), true);
     if (err) {
         diag.warning("%s", err);
         return;
     }
     optROData += protocolopt->size();
-    optROData = alignPointer(optROData);
     optRORemaining -= protocolopt->size();
     uint32_t protocoloptCapacity = protocolopt->capacity;
     uint32_t protocoloptOccupied = protocolopt->occupied;
     protocolopt->byteswap(E::little_endian), protocolopt = NULL;
 
     diag.verbose("  protocol table occupancy %u/%u (%u%%)\n",
-                 protocoloptOccupied, protocoloptCapacity,
-                 (unsigned)(protocoloptOccupied/(double)protocoloptCapacity*100));
+               protocoloptOccupied, protocoloptCapacity, 
+               (unsigned)(protocoloptOccupied/(double)protocoloptCapacity*100));
 
 
     // Redirect protocol references to the uniqued protocols.
@@ -966,32 +815,25 @@
     }
 
 
-    // Success. Update __objc_opt_ro section in libobjc.dylib to contain offsets to generated optimization structures
-    objc_opt::objc_opt_t* libROHeader = (objc_opt::objc_opt_t *)cacheAccessor.contentForVMAddr(optROSection->addr());
-    E::set32(libROHeader->flags, headerFlags);
-    E::set32(libROHeader->selopt_offset, (uint32_t)(seloptVMAddr - optROSection->addr()));
-    E::set32(libROHeader->clsopt_offset, (uint32_t)(clsoptVMAddr - optROSection->addr()));
-    E::set32(libROHeader->unused_protocolopt_offset, 0);
-    E::set32(libROHeader->headeropt_ro_offset, (uint32_t)(hinfoROVMAddr - optROSection->addr()));
-    E::set32(libROHeader->headeropt_rw_offset, (uint32_t)(hinfoRWVMAddr - optROSection->addr()));
-    E::set32(libROHeader->protocolopt_offset, (uint32_t)(protocoloptVMAddr - optROSection->addr()));
+    // Success. Update RO header last.
+    E::set32(optROHeader->flags, headerFlags);
+    E::set32(optROHeader->selopt_offset, (uint32_t)(seloptVMAddr - optROSection->addr()));
+    E::set32(optROHeader->clsopt_offset, (uint32_t)(clsoptVMAddr - optROSection->addr()));
+    E::set32(optROHeader->protocolopt_offset, (uint32_t)(protocoloptVMAddr - optROSection->addr()));
+    E::set32(optROHeader->headeropt_ro_offset, (uint32_t)(hinfoROVMAddr - optROSection->addr()));
+    E::set32(optROHeader->headeropt_rw_offset, (uint32_t)(hinfoRWVMAddr - optROSection->addr()));
 
     // Log statistics.
-    size_t roSize = objcReadOnlyBufferSizeAllocated - optRORemaining;
-    size_t rwSize = objcReadWriteBufferSizeAllocated - optRWRemaining;
-    diag.verbose("  %lu/%llu bytes (%d%%) used in shared cache read-only optimization region\n",
-                  roSize, objcReadOnlyBufferSizeAllocated, percent(roSize, objcReadOnlyBufferSizeAllocated));
-    diag.verbose("  %lu/%llu bytes (%d%%) used in shared cache read/write optimization region\n",
-                  rwSize, objcReadWriteBufferSizeAllocated, percent(rwSize, objcReadWriteBufferSizeAllocated));
+    size_t roSize = optROSection->size() - optRORemaining;
+    size_t rwSize = optRWSection->size() - optRWRemaining;
+    diag.verbose("  %lu/%llu bytes (%d%%) used in libobjc read-only optimization section\n",
+                  roSize, optROSection->size(), percent(roSize, optROSection->size()));
+    diag.verbose("  %lu/%llu bytes (%d%%) used in libobjc read/write optimization section\n",
+                  rwSize, optRWSection->size(), percent(rwSize, optRWSection->size()));
     diag.verbose("  wrote objc metadata optimization version %d\n", objc_opt::VERSION);
-
-    // Add segments to libobjc.dylib that cover cache builder allocated r/o and r/w regions
-    addObjcSegments<P>(diag, cache, libobjcMH, objcReadOnlyBuffer, objcReadOnlyBufferSizeAllocated, objcReadWriteBuffer, objcReadWriteBufferSizeAllocated, objcRwFileOffset);
-
 
     // Now that objc has uniqued the selector references, we can apply the LOHs so that ADRP/LDR -> ADRP/ADD
     if (forProduction) {
-        const bool logSelectors = false;
         uint64_t lohADRPCount = 0;
         uint64_t lohLDRCount = 0;
 
@@ -1020,8 +862,7 @@
 
                         if (pass == 0) {
                             if ( (newPage21 > 2097151) || (newPage21 < -2097151) ) {
-                                if (logSelectors)
-                                    fprintf(stderr, "Out of bounds ADRP selector reference target\n");
+                                diag.verbose("Out of bounds ADRP selector reference target\n");
                                 instructions.clear();
                                 break;
                             }
@@ -1040,15 +881,13 @@
                         if (pass == 0) {
                             if ( (instruction & 0xC0C00000) != 0xC0400000 ) {
                                 // Not a load, or dest reg isn't xN, or uses sign extension
-                                if (logSelectors)
-                                    fprintf(stderr, "Bad LDR for selector reference optimisation\n");
+                                diag.verbose("Bad LDR for selector reference optimisation\n");
                                 instructions.clear();
                                 break;
                             }
                             if ( (instruction & 0x04000000) != 0 ) {
                                 // Loading a float
-                                if (logSelectors)
-                                    fprintf(stderr, "Bad LDR for selector reference optimisation\n");
+                                diag.verbose("Bad LDR for selector reference optimisation\n");
                                 instructions.clear();
                                 break;
                             }
@@ -1073,14 +912,12 @@
                     if ( (instruction & 0xFFC00000) == 0x91000000 ) {
                         // ADD imm12
                         // We don't support ADDs.
-                        if (logSelectors)
-                            fprintf(stderr, "Bad ADD for selector reference optimisation\n");
+                        diag.verbose("Bad ADD for selector reference optimisation\n");
                         instructions.clear();
                         break;
                     }
 
-                    if (logSelectors)
-                        fprintf(stderr, "Unknown instruction for selref optimisation\n");
+                    diag.verbose("Unknown instruction for selref optimisation\n");
                     instructions.clear();
                     break;
                 }
@@ -1104,36 +941,10 @@
 
 void CacheBuilder::optimizeObjC()
 {
-    uint32_t objcRwFileOffset = (uint32_t)((_objcReadWriteBuffer - _readWriteRegion.buffer) + _readWriteRegion.cacheFileOffset);
     if ( _archLayout->is64 )
-        doOptimizeObjC<Pointer64<LittleEndian>>((DyldSharedCache*)_readExecuteRegion.buffer, _options.optimizeStubs, _aslrTracker, _lohTracker,
-                                                _coalescedText, _missingWeakImports,
-                                                _diagnostics, _objcReadOnlyBuffer, _objcReadOnlyBufferSizeUsed, _objcReadOnlyBufferSizeAllocated,
-                                                _objcReadWriteBuffer, _objcReadWriteBufferSizeAllocated, objcRwFileOffset);
+        doOptimizeObjC<Pointer64<LittleEndian>>((DyldSharedCache*)_readExecuteRegion.buffer, _options.optimizeStubs, _aslrTracker, _lohTracker, _missingWeakImports, _diagnostics);
     else
-        doOptimizeObjC<Pointer32<LittleEndian>>((DyldSharedCache*)_readExecuteRegion.buffer, _options.optimizeStubs, _aslrTracker, _lohTracker,
-                                                _coalescedText, _missingWeakImports,
-                                                _diagnostics, _objcReadOnlyBuffer, _objcReadOnlyBufferSizeUsed, _objcReadOnlyBufferSizeAllocated,
-                                                _objcReadWriteBuffer, _objcReadWriteBufferSizeAllocated, objcRwFileOffset);
+        doOptimizeObjC<Pointer32<LittleEndian>>((DyldSharedCache*)_readExecuteRegion.buffer, _options.optimizeStubs, _aslrTracker, _lohTracker, _missingWeakImports, _diagnostics);
 }
 
-static uint32_t hashTableSize(uint32_t maxElements, uint32_t perElementData)
-{
-    uint32_t elementsWithPadding = maxElements*11/10; // if close to power of 2, perfect hash may fail, so don't get within 10% of that
-    uint32_t powTwoCapacity = 1 << (32 - __builtin_clz(elementsWithPadding - 1));
-    uint32_t headerSize = 4*(8+256);
-    return headerSize + powTwoCapacity/2 + powTwoCapacity + powTwoCapacity*perElementData;
-}
-
-// The goal here is to allocate space in the dyld shared cache (while it is being laid out) that will contain
-// the objc structures that previously were in the __objc_opt_ro section.
-uint32_t CacheBuilder::computeReadOnlyObjC(uint32_t selRefCount, uint32_t classDefCount, uint32_t protocolDefCount)
-{
-    return 0xA000 + hashTableSize(selRefCount, 5) + hashTableSize(classDefCount, 12) + hashTableSize(protocolDefCount, 8);
-}
-
-// Space to replace the __objc_opt_rw section.
-uint32_t CacheBuilder::computeReadWriteObjC(uint32_t imageCount, uint32_t protocolDefCount)
-{
-    return 8*imageCount + protocolDefCount*12*(_archLayout->is64 ? 8 : 4);
-}
+