Index: lld/MachO/DriverUtils.cpp
===================================================================
--- lld/MachO/DriverUtils.cpp
+++ lld/MachO/DriverUtils.cpp
@@ -201,10 +201,11 @@
                                        DylibFile *umbrella,
                                        bool isBundleLoader) {
   CachedHashStringRef path(mbref.getBufferIdentifier());
-  DylibFile *file = loadedDylibs[path];
+  DylibFile *&file = loadedDylibs[path];
   if (file)
     return file;
 
+  DylibFile *newFile;
   file_magic magic = identify_magic(mbref.getBuffer());
   if (magic == file_magic::tapi_file) {
     Expected<std::unique_ptr<InterfaceFile>> result = TextAPIReader::get(mbref);
@@ -214,19 +215,27 @@
       return {};
     }
     file = make<DylibFile>(**result, umbrella, isBundleLoader);
+
+    // parseReexports() can recursively call loadDylib(). That's fine since
+    // we wrote DylibFile we just loaded to the loadDylib cache via the `file`
+    // reference. But the recursive load can grow loadDylibs, so the `file`
+    // reference might become invalid after parseReexports() -- so copy the
+    // pointer it refers to before going on.
+    newFile = file;
+    newFile->parseReexports(**result, umbrella);
   } else {
     assert(magic == file_magic::macho_dynamically_linked_shared_lib ||
            magic == file_magic::macho_dynamically_linked_shared_lib_stub ||
            magic == file_magic::macho_executable ||
            magic == file_magic::macho_bundle);
     file = make<DylibFile>(mbref, umbrella, isBundleLoader);
+
+    // parseLoadCommands() can also recursively call loadDylib(). See comment
+    // in previous block for why this means we must copy `file` here.
+    newFile = file;
+    newFile->parseLoadCommands(mbref, umbrella);
   }
-  // Note that DylibFile's ctor may recursively invoke loadDylib(), which can
-  // cause loadedDylibs to get resized and its iterators invalidated. As such,
-  // we redo the key lookup here instead of caching an iterator from our earlier
-  // lookup at the start of the function.
-  loadedDylibs[path] = file;
-  return file;
+  return newFile;
 }
 
 Optional<StringRef>
Index: lld/MachO/InputFiles.h
===================================================================
--- lld/MachO/InputFiles.h
+++ lld/MachO/InputFiles.h
@@ -130,6 +130,13 @@
 // .dylib file
 class DylibFile : public InputFile {
 public:
+  explicit DylibFile(MemoryBufferRef mb, DylibFile *umbrella,
+                     bool isBundleLoader = false);
+
+  explicit DylibFile(const llvm::MachO::InterfaceFile &interface,
+                     DylibFile *umbrella = nullptr,
+                     bool isBundleLoader = false);
+
   // Mach-O dylibs can re-export other dylibs as sub-libraries, meaning that the
   // symbols in those sub-libraries will be available under the umbrella
   // library's namespace. Those sub-libraries can also have their own
@@ -137,16 +144,14 @@
   // the root dylib to ensure symbols in the child library are correctly bound
   // to the root. On the other hand, if a dylib is being directly loaded
   // (through an -lfoo flag), then `umbrella` should be a nullptr.
-  explicit DylibFile(MemoryBufferRef mb, DylibFile *umbrella,
-                     bool isBundleLoader = false);
-
-  explicit DylibFile(const llvm::MachO::InterfaceFile &interface,
-                     DylibFile *umbrella = nullptr,
-                     bool isBundleLoader = false);
+  void parseLoadCommands(MemoryBufferRef mb, DylibFile *umbrella);
+  void parseReexports(const llvm::MachO::InterfaceFile &interface,
+                      DylibFile *umbrella);
 
   static bool classof(const InputFile *f) { return f->kind() == DylibKind; }
 
   StringRef dylibName;
+  DylibFile *exportingFile;
   uint32_t compatibilityVersion = 0;
   uint32_t currentVersion = 0;
   int64_t ordinal = 0; // Ordinal numbering starts from 1, so 0 is a sentinel
Index: lld/MachO/InputFiles.cpp
===================================================================
--- lld/MachO/InputFiles.cpp
+++ lld/MachO/InputFiles.cpp
@@ -832,7 +832,7 @@
     return;
 
   // Initialize symbols.
-  DylibFile *exportingFile = isImplicitlyLinked(dylibName) ? this : umbrella;
+  exportingFile = isImplicitlyLinked(dylibName) ? this : umbrella;
   if (const load_command *cmd = findCommand(hdr, LC_DYLD_INFO_ONLY)) {
     auto *c = reinterpret_cast<const dyld_info_command *>(cmd);
     parseTrie(buf + c->export_off, c->export_size,
@@ -847,8 +847,12 @@
     return;
   }
 
-  const uint8_t *p =
-      reinterpret_cast<const uint8_t *>(hdr) + target->headerSize;
+}
+
+void DylibFile::parseLoadCommands(MemoryBufferRef mb, DylibFile *umbrella) {
+  auto *hdr = reinterpret_cast<const mach_header *>(mb.getBufferStart());
+  const uint8_t *p = reinterpret_cast<const uint8_t *>(mb.getBufferStart()) +
+                     target->headerSize;
   for (uint32_t i = 0, n = hdr->ncmds; i < n; ++i) {
     auto *cmd = reinterpret_cast<const load_command *>(p);
     p += cmd->cmdsize;
@@ -877,6 +881,13 @@
   }
 }
 
+// Some versions of XCode ship with .tbd files that don't have the right
+// platform settings.
+static constexpr std::array<StringRef, 3> skipPlatformChecks{
+    "/usr/lib/system/libsystem_kernel.dylib",
+    "/usr/lib/system/libsystem_platform.dylib",
+    "/usr/lib/system/libsystem_pthread.dylib"};
+
 DylibFile::DylibFile(const InterfaceFile &interface, DylibFile *umbrella,
                      bool isBundleLoader)
     : InputFile(DylibKind, interface), refState(RefState::Unreferenced),
@@ -890,13 +901,6 @@
   compatibilityVersion = interface.getCompatibilityVersion().rawValue();
   currentVersion = interface.getCurrentVersion().rawValue();
 
-  // Some versions of XCode ship with .tbd files that don't have the right
-  // platform settings.
-  static constexpr std::array<StringRef, 3> skipPlatformChecks{
-      "/usr/lib/system/libsystem_kernel.dylib",
-      "/usr/lib/system/libsystem_platform.dylib",
-      "/usr/lib/system/libsystem_pthread.dylib"};
-
   if (!is_contained(skipPlatformChecks, dylibName) &&
       !is_contained(interface.targets(), config->platformInfo.target)) {
     error(toString(this) + " is incompatible with " +
@@ -904,7 +908,7 @@
     return;
   }
 
-  DylibFile *exportingFile = isImplicitlyLinked(dylibName) ? this : umbrella;
+  exportingFile = isImplicitlyLinked(dylibName) ? this : umbrella;
   auto addSymbol = [&](const Twine &name) -> void {
     symbols.push_back(symtab->addDylib(saver.save(name), exportingFile,
                                        /*isWeakDef=*/false,
@@ -934,10 +938,12 @@
       break;
     }
   }
+}
 
+void DylibFile::parseReexports(const llvm::MachO::InterfaceFile &interface,
+                               DylibFile *umbrella) {
   const InterfaceFile *topLevel =
       interface.getParent() == nullptr ? &interface : interface.getParent();
-
   for (InterfaceFileRef intfRef : interface.reexportedLibraries()) {
     InterfaceFile::const_target_range targets = intfRef.targets();
     if (is_contained(skipPlatformChecks, intfRef.getInstallName()) ||