diff --git a/llvm/tools/llvm-objcopy/MachO/MachOLayoutBuilder.cpp b/llvm/tools/llvm-objcopy/MachO/MachOLayoutBuilder.cpp
new file mode 100644
index 0000000..b06a622
--- /dev/null
+++ b/llvm/tools/llvm-objcopy/MachO/MachOLayoutBuilder.cpp
@@ -0,0 +1,322 @@
+//===- MachOLayoutBuilder.cpp -----------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "MachOLayoutBuilder.h"
+#include "llvm/Support/Errc.h"
+#include "llvm/Support/ErrorHandling.h"
+
+namespace llvm {
+namespace objcopy {
+namespace macho {
+
+uint32_t MachOLayoutBuilder::computeSizeOfCmds() const {
+  uint32_t Size = 0;
+  for (const auto &LC : O.LoadCommands) {
+    auto &MLC = LC.MachOLoadCommand;
+    auto cmd = MLC.load_command_data.cmd;
+    switch (cmd) {
+    case MachO::LC_SEGMENT:
+      Size += sizeof(MachO::segment_command) +
+              sizeof(MachO::section) * LC.Sections.size();
+      continue;
+    case MachO::LC_SEGMENT_64:
+      Size += sizeof(MachO::segment_command_64) +
+              sizeof(MachO::section_64) * LC.Sections.size();
+      continue;
+    }
+
+    switch (cmd) {
+#define HANDLE_LOAD_COMMAND(LCName, LCValue, LCStruct)                         \
+  case MachO::LCName:                                                          \
+    Size += sizeof(MachO::LCStruct) + LC.Payload.size();                       \
+    break;
+#include "llvm/BinaryFormat/MachO.def"
+#undef HANDLE_LOAD_COMMAND
+    }
+  }
+
+  return Size;
+}
+
+void MachOLayoutBuilder::constructStringTable() {
+  for (std::unique_ptr<SymbolEntry> &Sym : O.SymTable.Symbols)
+    StrTableBuilder.add(Sym->Name);
+  StrTableBuilder.finalize();
+}
+
+void MachOLayoutBuilder::updateSymbolIndexes() {
+  uint32_t Index = 0;
+  for (auto &Symbol : O.SymTable.Symbols)
+    Symbol->Index = Index++;
+}
+
+// Updates the index and the number of local/external/undefined symbols.
+void MachOLayoutBuilder::updateDySymTab(MachO::macho_load_command &MLC) {
+  assert(MLC.load_command_data.cmd == MachO::LC_DYSYMTAB);
+  // Make sure that nlist entries in the symbol table are sorted by the those
+  // types. The order is: local < defined external < undefined external.
+  assert(std::is_sorted(O.SymTable.Symbols.begin(), O.SymTable.Symbols.end(),
+                        [](const std::unique_ptr<SymbolEntry> &A,
+                           const std::unique_ptr<SymbolEntry> &B) {
+                          return (A->isLocalSymbol() && !B->isLocalSymbol()) ||
+                                 (!A->isUndefinedSymbol() &&
+                                  B->isUndefinedSymbol());
+                        }) &&
+         "Symbols are not sorted by their types.");
+
+  uint32_t NumLocalSymbols = 0;
+  auto Iter = O.SymTable.Symbols.begin();
+  auto End = O.SymTable.Symbols.end();
+  for (; Iter != End; ++Iter) {
+    if ((*Iter)->isExternalSymbol())
+      break;
+
+    ++NumLocalSymbols;
+  }
+
+  uint32_t NumExtDefSymbols = 0;
+  for (; Iter != End; ++Iter) {
+    if ((*Iter)->isUndefinedSymbol())
+      break;
+
+    ++NumExtDefSymbols;
+  }
+
+  MLC.dysymtab_command_data.ilocalsym = 0;
+  MLC.dysymtab_command_data.nlocalsym = NumLocalSymbols;
+  MLC.dysymtab_command_data.iextdefsym = NumLocalSymbols;
+  MLC.dysymtab_command_data.nextdefsym = NumExtDefSymbols;
+  MLC.dysymtab_command_data.iundefsym = NumLocalSymbols + NumExtDefSymbols;
+  MLC.dysymtab_command_data.nundefsym =
+      O.SymTable.Symbols.size() - (NumLocalSymbols + NumExtDefSymbols);
+}
+
+// Recomputes and updates offset and size fields in load commands and sections
+// since they could be modified.
+uint64_t MachOLayoutBuilder::layoutSegments() {
+  auto HeaderSize =
+      Is64Bit ? sizeof(MachO::mach_header_64) : sizeof(MachO::mach_header);
+  auto Offset = HeaderSize + O.Header.SizeOfCmds;
+
+  // Lay out sections.
+  for (auto &LC : O.LoadCommands) {
+    uint64_t FileOff = Offset;
+    auto &MLC = LC.MachOLoadCommand;
+    StringRef Segname;
+    switch (MLC.load_command_data.cmd) {
+    case MachO::LC_SEGMENT:
+      Segname = StringRef(MLC.segment_command_data.segname,
+                          strnlen(MLC.segment_command_data.segname,
+                                  sizeof(MLC.segment_command_data.segname)));
+      break;
+    case MachO::LC_SEGMENT_64:
+      Segname = StringRef(MLC.segment_command_64_data.segname,
+                          strnlen(MLC.segment_command_64_data.segname,
+                                  sizeof(MLC.segment_command_64_data.segname)));
+      break;
+    default:
+      continue;
+    }
+
+    if (Segname == "__LINKEDIT") {
+      // We update the __LINKEDIT segment later (in layoutTail).
+      assert(LC.Sections.empty() && "__LINKEDIT segment has sections");
+      LinkEditLoadCommand = &MLC;
+      continue;
+    }
+
+    // Update file offsets and sizes of sections.
+    uint64_t VMSize = 0;
+    uint64_t FileOffsetInSegment = 0;
+    for (auto &Sec : LC.Sections) {
+      if (!Sec.isVirtualSection()) {
+        auto FilePaddingSize =
+            OffsetToAlignment(FileOffsetInSegment, 1ull << Sec.Align);
+        Sec.Offset = Offset + FileOffsetInSegment + FilePaddingSize;
+        Sec.Size = Sec.Content.size();
+        FileOffsetInSegment += FilePaddingSize + Sec.Size;
+      }
+
+      VMSize = std::max(VMSize, Sec.Addr + Sec.Size);
+    }
+
+    // TODO: Handle the __PAGEZERO segment.
+    switch (MLC.load_command_data.cmd) {
+    case MachO::LC_SEGMENT:
+      MLC.segment_command_data.cmdsize =
+          sizeof(MachO::segment_command) +
+          sizeof(MachO::section) * LC.Sections.size();
+      MLC.segment_command_data.nsects = LC.Sections.size();
+      MLC.segment_command_data.fileoff = FileOff;
+      MLC.segment_command_data.vmsize = VMSize;
+      MLC.segment_command_data.filesize = FileOffsetInSegment;
+      break;
+    case MachO::LC_SEGMENT_64:
+      MLC.segment_command_64_data.cmdsize =
+          sizeof(MachO::segment_command_64) +
+          sizeof(MachO::section_64) * LC.Sections.size();
+      MLC.segment_command_64_data.nsects = LC.Sections.size();
+      MLC.segment_command_64_data.fileoff = FileOff;
+      MLC.segment_command_64_data.vmsize = VMSize;
+      MLC.segment_command_64_data.filesize = FileOffsetInSegment;
+      break;
+    }
+
+    Offset += FileOffsetInSegment;
+  }
+
+  return Offset;
+}
+
+uint64_t MachOLayoutBuilder::layoutRelocations(uint64_t Offset) {
+  for (auto &LC : O.LoadCommands)
+    for (auto &Sec : LC.Sections) {
+      Sec.RelOff = Sec.Relocations.empty() ? 0 : Offset;
+      Sec.NReloc = Sec.Relocations.size();
+      Offset += sizeof(MachO::any_relocation_info) * Sec.NReloc;
+    }
+
+  return Offset;
+}
+
+Error MachOLayoutBuilder::layoutTail(uint64_t Offset) {
+  // The order of LINKEDIT elements is as follows:
+  // rebase info, binding info, weak binding info, lazy binding info, export
+  // trie, data-in-code, symbol table, indirect symbol table, symbol table
+  // strings.
+  uint64_t NListSize = Is64Bit ? sizeof(MachO::nlist_64) : sizeof(MachO::nlist);
+  uint64_t StartOfLinkEdit = Offset;
+  uint64_t StartOfRebaseInfo = StartOfLinkEdit;
+  uint64_t StartOfBindingInfo = StartOfRebaseInfo + O.Rebases.Opcodes.size();
+  uint64_t StartOfWeakBindingInfo = StartOfBindingInfo + O.Binds.Opcodes.size();
+  uint64_t StartOfLazyBindingInfo =
+      StartOfWeakBindingInfo + O.WeakBinds.Opcodes.size();
+  uint64_t StartOfExportTrie =
+      StartOfLazyBindingInfo + O.LazyBinds.Opcodes.size();
+  uint64_t StartOfFunctionStarts = StartOfExportTrie + O.Exports.Trie.size();
+  uint64_t StartOfDataInCode =
+      StartOfFunctionStarts + O.FunctionStarts.Data.size();
+  uint64_t StartOfSymbols = StartOfDataInCode + O.DataInCode.Data.size();
+  uint64_t StartOfIndirectSymbols =
+      StartOfSymbols + NListSize * O.SymTable.Symbols.size();
+  uint64_t StartOfSymbolStrings =
+      StartOfIndirectSymbols +
+      sizeof(uint32_t) * O.IndirectSymTable.Symbols.size();
+  uint64_t LinkEditSize =
+      (StartOfSymbolStrings + StrTableBuilder.getSize()) - StartOfLinkEdit;
+
+  // Now we have determined the layout of the contents of the __LINKEDIT
+  // segment. Update its load command.
+  if (LinkEditLoadCommand) {
+    MachO::macho_load_command *MLC = LinkEditLoadCommand;
+    switch (LinkEditLoadCommand->load_command_data.cmd) {
+    case MachO::LC_SEGMENT:
+      MLC->segment_command_data.cmdsize = sizeof(MachO::segment_command);
+      MLC->segment_command_data.fileoff = StartOfLinkEdit;
+      MLC->segment_command_data.vmsize = alignTo(LinkEditSize, PageSize);
+      MLC->segment_command_data.filesize = LinkEditSize;
+      break;
+    case MachO::LC_SEGMENT_64:
+      MLC->segment_command_64_data.cmdsize = sizeof(MachO::segment_command_64);
+      MLC->segment_command_64_data.fileoff = StartOfLinkEdit;
+      MLC->segment_command_64_data.vmsize = alignTo(LinkEditSize, PageSize);
+      MLC->segment_command_64_data.filesize = LinkEditSize;
+      break;
+    }
+  }
+
+  for (auto &LC : O.LoadCommands) {
+    auto &MLC = LC.MachOLoadCommand;
+    auto cmd = MLC.load_command_data.cmd;
+    switch (cmd) {
+    case MachO::LC_SYMTAB:
+      MLC.symtab_command_data.symoff = StartOfSymbols;
+      MLC.symtab_command_data.nsyms = O.SymTable.Symbols.size();
+      MLC.symtab_command_data.stroff = StartOfSymbolStrings;
+      MLC.symtab_command_data.strsize = StrTableBuilder.getSize();
+      break;
+    case MachO::LC_DYSYMTAB: {
+      if (MLC.dysymtab_command_data.ntoc != 0 ||
+          MLC.dysymtab_command_data.nmodtab != 0 ||
+          MLC.dysymtab_command_data.nextrefsyms != 0 ||
+          MLC.dysymtab_command_data.nlocrel != 0 ||
+          MLC.dysymtab_command_data.nextrel != 0)
+        return createStringError(llvm::errc::not_supported,
+                                 "shared library is not yet supported");
+
+      if (!O.IndirectSymTable.Symbols.empty()) {
+        MLC.dysymtab_command_data.indirectsymoff = StartOfIndirectSymbols;
+        MLC.dysymtab_command_data.nindirectsyms =
+            O.IndirectSymTable.Symbols.size();
+      }
+
+      updateDySymTab(MLC);
+      break;
+    }
+    case MachO::LC_DATA_IN_CODE:
+      MLC.linkedit_data_command_data.dataoff = StartOfDataInCode;
+      MLC.linkedit_data_command_data.datasize = O.DataInCode.Data.size();
+      break;
+    case MachO::LC_FUNCTION_STARTS:
+      MLC.linkedit_data_command_data.dataoff = StartOfFunctionStarts;
+      MLC.linkedit_data_command_data.datasize = O.FunctionStarts.Data.size();
+      break;
+    case MachO::LC_DYLD_INFO:
+    case MachO::LC_DYLD_INFO_ONLY:
+      MLC.dyld_info_command_data.rebase_off =
+          O.Rebases.Opcodes.empty() ? 0 : StartOfRebaseInfo;
+      MLC.dyld_info_command_data.rebase_size = O.Rebases.Opcodes.size();
+      MLC.dyld_info_command_data.bind_off =
+          O.Binds.Opcodes.empty() ? 0 : StartOfBindingInfo;
+      MLC.dyld_info_command_data.bind_size = O.Binds.Opcodes.size();
+      MLC.dyld_info_command_data.weak_bind_off =
+          O.WeakBinds.Opcodes.empty() ? 0 : StartOfWeakBindingInfo;
+      MLC.dyld_info_command_data.weak_bind_size = O.WeakBinds.Opcodes.size();
+      MLC.dyld_info_command_data.lazy_bind_off =
+          O.LazyBinds.Opcodes.empty() ? 0 : StartOfLazyBindingInfo;
+      MLC.dyld_info_command_data.lazy_bind_size = O.LazyBinds.Opcodes.size();
+      MLC.dyld_info_command_data.export_off =
+          O.Exports.Trie.empty() ? 0 : StartOfExportTrie;
+      MLC.dyld_info_command_data.export_size = O.Exports.Trie.size();
+      break;
+    case MachO::LC_LOAD_DYLINKER:
+    case MachO::LC_MAIN:
+    case MachO::LC_RPATH:
+    case MachO::LC_SEGMENT:
+    case MachO::LC_SEGMENT_64:
+    case MachO::LC_VERSION_MIN_MACOSX:
+    case MachO::LC_BUILD_VERSION:
+    case MachO::LC_ID_DYLIB:
+    case MachO::LC_LOAD_DYLIB:
+    case MachO::LC_UUID:
+    case MachO::LC_SOURCE_VERSION:
+      // Nothing to update.
+      break;
+    default:
+      // Abort if it's unsupported in order to prevent corrupting the object.
+      return createStringError(llvm::errc::not_supported,
+                               "unsupported load command (cmd=0x%x)", cmd);
+    }
+  }
+
+  return Error::success();
+}
+
+Error MachOLayoutBuilder::layout() {
+  O.Header.NCmds = O.LoadCommands.size();
+  O.Header.SizeOfCmds = computeSizeOfCmds();
+  constructStringTable();
+  updateSymbolIndexes();
+  uint64_t Offset = layoutSegments();
+  Offset = layoutRelocations(Offset);
+  return layoutTail(Offset);
+}
+
+} // end namespace macho
+} // end namespace objcopy
+} // end namespace llvm