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diff --git a/lib/ReaderWriter/MachO/ExecutableAtoms.hpp b/lib/ReaderWriter/MachO/ExecutableAtoms.hpp
new file mode 100644
index 0000000000000..cd562de216d9e
--- /dev/null
+++ b/lib/ReaderWriter/MachO/ExecutableAtoms.hpp
@@ -0,0 +1,136 @@
+//===- lib/ReaderWriter/MachO/ExecutableAtoms.hpp -------------------------===//
+//
+//                             The LLVM Linker
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLD_READER_WRITER_MACHO_EXECUTABLE_ATOMS_H
+#define LLD_READER_WRITER_MACHO_EXECUTABLE_ATOMS_H
+
+#include "Atoms.h"
+
+#include "llvm/Support/MachO.h"
+
+#include "lld/Core/ArchiveLibraryFile.h"
+#include "lld/Core/DefinedAtom.h"
+#include "lld/Core/File.h"
+#include "lld/Core/LinkingContext.h"
+#include "lld/Core/Reference.h"
+#include "lld/Core/Simple.h"
+#include "lld/Core/UndefinedAtom.h"
+#include "lld/ReaderWriter/MachOLinkingContext.h"
+
+namespace lld {
+namespace mach_o {
+
+
+//
+// CEntryFile adds an UndefinedAtom for "_main" so that the Resolving
+// phase will fail if "_main" is undefined.
+//
+class CEntryFile : public SimpleFile {
+public:
+  CEntryFile(const MachOLinkingContext &context)
+      : SimpleFile("C entry"),
+       _undefMain(*this, context.entrySymbolName()) {
+    this->addAtom(_undefMain);
+  }
+
+private:
+  SimpleUndefinedAtom   _undefMain;
+};
+
+
+//
+// StubHelperFile adds an UndefinedAtom for "dyld_stub_binder" so that
+// the Resolveing phase will fail if "dyld_stub_binder" is undefined.
+//
+class StubHelperFile : public SimpleFile {
+public:
+  StubHelperFile(const MachOLinkingContext &context)
+      : SimpleFile("stub runtime"),
+        _undefBinder(*this, context.binderSymbolName()) {
+    this->addAtom(_undefBinder);
+  }
+
+private:
+  SimpleUndefinedAtom   _undefBinder;
+};
+
+
+//
+// MachHeaderAliasFile lazily instantiates the magic symbols that mark the start
+// of the mach_header for final linked images.
+//
+class MachHeaderAliasFile : public ArchiveLibraryFile {
+public:
+  MachHeaderAliasFile(const MachOLinkingContext &context)
+      : ArchiveLibraryFile("mach_header symbols") {
+      switch (context.outputMachOType()) {
+      case llvm::MachO::MH_EXECUTE:
+        _machHeaderSymbolName = "__mh_execute_header";
+        break;
+      case llvm::MachO::MH_DYLIB:
+        _machHeaderSymbolName = "__mh_dylib_header";
+        break;
+      case llvm::MachO::MH_BUNDLE:
+        _machHeaderSymbolName = "__mh_bundle_header";
+        break;
+      case llvm::MachO::MH_DYLINKER:
+        _machHeaderSymbolName = "__mh_dylinker_header";
+        break;
+      case llvm::MachO::MH_PRELOAD:
+        _machHeaderSymbolName = "__mh_preload_header";
+        break;
+      default:
+        llvm_unreachable("no mach_header symbol for file type");
+      }
+  }
+
+  std::error_code
+  parseAllMembers(std::vector<std::unique_ptr<File>> &result) override {
+    return std::error_code();
+  }
+
+  File *find(StringRef sym, bool dataSymbolOnly) override {
+    if (sym.equals("___dso_handle") || sym.equals(_machHeaderSymbolName)) {
+      _definedAtoms._atoms.push_back(new (allocator()) MachODefinedAtom(
+          *this, sym, DefinedAtom::scopeLinkageUnit,
+          DefinedAtom::typeMachHeader, DefinedAtom::mergeNo, false, false,
+          ArrayRef<uint8_t>(), DefinedAtom::Alignment(12,0)));
+      return this;
+    }
+    return nullptr;
+  }
+
+  const atom_collection<DefinedAtom> &defined() const override {
+    return _definedAtoms;
+  }
+  const atom_collection<UndefinedAtom> &undefined() const override {
+    return _undefinedAtoms;
+  }
+
+  const atom_collection<SharedLibraryAtom> &sharedLibrary() const override {
+    return _sharedLibraryAtoms;
+  }
+
+  const atom_collection<AbsoluteAtom> &absolute() const override {
+    return _absoluteAtoms;
+  }
+
+
+private:
+  mutable atom_collection_vector<DefinedAtom> _definedAtoms;
+  atom_collection_vector<UndefinedAtom> _undefinedAtoms;
+  atom_collection_vector<SharedLibraryAtom> _sharedLibraryAtoms;
+  atom_collection_vector<AbsoluteAtom> _absoluteAtoms;
+  StringRef _machHeaderSymbolName;
+};
+
+} // namespace mach_o
+} // namespace lld
+
+#endif // LLD_READER_WRITER_MACHO_EXECUTABLE_ATOMS_H