[llvm-lipo] Add support for archives

[alexander-shaposhnikov]

Summary

Add support for creating universal binaries which can contain an archive.

Test plan: make check-all

[compnerd]

tools/llvm-lipo/llvm-lipo.cpp

217

Can we use the calculateAlignment here rather than hardcoding this? Also, I know its not part of your change, but, could you name Alginment as P2Alignment to make it clear that this is a power-of-two alignment and not byte alignment.

220

Please name this setP2Alignment.

228

Can we just make CPUType, CPUSubType, Alignment` const members and make them public? We can set them properly during the constructor and avoid the unnecessary accessors.

246

There are a couple of $ introduced in the comment.

251

Trailing $ in the comment?

[alexander-shaposhnikov]

tools/llvm-lipo/llvm-lipo.cpp

228

the thing is that archives those fields should be calculated first (extracted from the members of the archive), thus they can't be const, exposing them as a non-const public doesn't look good to me.

[alexander-shaposhnikov]

Address review comments

[smeenai]

LGTM

tools/llvm-lipo/llvm-lipo.cpp

161

"to stores" -> "to store"

246

Still have an $ here.

[alexander-shaposhnikov]

fix minor issues

[mtrent]

Logic looks fine. I have some concerns around alignment terminology that I suggest you address before committing.

tools/llvm-lipo/llvm-lipo.cpp

105

A segment alignment has no strong correlation to the section alignment, and the notion that the segment alignment is the maximum alignment of its sections is not true. Maybe the simplest way to say this is:

"For compatibility with cctools lipo, a file's alignment is calculated as the minimum aligment of all segments. For object files, the file's alignment is the maximum alignment of its sections."

Part of the problem is that the method here is named "calculateSegmentAlignment" but that 1) doesn't accurately describe how lipo is using that value, and 2) also doesn't completely describe what the function is doing. But cctools also has both these problems :) You have an opportunity to call this function something like "calculateSliceAlignment" or "calculateFileAlignment" which may be objectively better ...

Be aware the segment computation is merely a guess, and it may not be exactly correct. But it's correct enough for lipo.

And be aware the behavior for object files may change in future versions of cctools.

[alexander-shaposhnikov]

tools/llvm-lipo/llvm-lipo.cpp

105

You are right.
Thanks, will change it.

test/tools/llvm-lipo/create-archive-input.test

+# RUN: yaml2obj %p/Inputs/i386-slice.yaml > %t-i386.o
+# RUN: yaml2obj %p/Inputs/x86_64-slice.yaml > %t-x86_64.o
+# RUN: yaml2obj %p/Inputs/i386-x86_64-universal.yaml > %t-universal.o
+
+# RUN: llvm-ar cr %t.empty.a
+# RUN: not llvm-lipo %t.empty.a -create -output /dev/null 2>&1 | FileCheck --check-prefix=EMPTY-ARCHIVE %s
+
+# RUN: llvm-ar cr %t.different_architectures.a %t-i386.o %t-x86_64.o
+# RUN: not llvm-lipo %t.different_architectures.a -create -output /dev/null 2>&1 | FileCheck --check-prefix=ARCHIVE-WITH-DIFFERENT-ARCHS %s
+
+# RUN: llvm-ar cr %t.contains_fat_binary.a %t-universal.o 
+# RUN: not llvm-lipo %t.contains_fat_binary.a -create -output /dev/null 2>&1 | FileCheck --check-prefix=ARCHIVE-WITH-FAT-BINARY %s
+
+# RUN: llvm-ar cr %t-i386-lib.a %t-i386.o
+# RUN: llvm-lipo %t-i386-lib.a %t-x86_64.o -create -output %t-i386-x86_64-universal.o
+# RUN: llvm-lipo %t-i386-x86_64-universal.o -info | FileCheck --check-prefix=INFO-i386-x86_64 %s
+# RUN: llvm-lipo %t-i386-x86_64-universal.o -thin i386 -output %t-extracted-i386-lib.a
+# RUN: cmp %t-extracted-i386-lib.a %t-i386-lib.a
+# RUN: llvm-lipo %t-i386-x86_64-universal.o -thin x86_64 -output %t-extracted-x86_64.o
+# RUN: cmp %t-extracted-x86_64.o %t-x86_64.o
+#
+# EMPTY-ARCHIVE: empty archive
+# ARCHIVE-WITH-DIFFERENT-ARCHS: all members must match
+# ARCHIVE-WITH-FAT-BINARY: fat file (not allowed in an archive)
+#
+# INFO-i386-x86_64: i386 x86_64

tools/llvm-lipo/llvm-lipo.cpp

struct Config {
   SmallVector<std::string, 1> VerifyArchList;
   SmallVector<Replacement, 1> Replacements;
   StringMap<const uint32_t> SegmentAlignments;
   std::string ThinArchType;
   std::string OutputFile;
   LipoAction ActionToPerform;
 };
 
-struct Slice {
-  const MachOObjectFile *ObjectFile;
-  // Requires Alignment field to store slice alignment values from universal
-  // binaries. Also needed to order the slices using compareSlices, so the total
+// For compatibility with cctools lipo, alignment is calculated as the minimum
+// aligment of all segments. Each segments's alignment is the maximum alignment
+// from its sections
+static uint32_t calculateSegmentAlignment(const MachOObjectFile &O) {
+  uint32_t P2CurrentAlignment;
+  uint32_t P2MinAlignment = MachOUniversalBinary::MaxSectionAlignment;
+  const bool Is64Bit = O.is64Bit();
+
+  for (const auto &LC : O.load_commands()) {
+    if (LC.C.cmd != (Is64Bit ? MachO::LC_SEGMENT_64 : MachO::LC_SEGMENT))
+      continue;
+    if (O.getHeader().filetype == MachO::MH_OBJECT) {
+      unsigned NumberOfSections =
+          (Is64Bit ? O.getSegment64LoadCommand(LC).nsects
+                   : O.getSegmentLoadCommand(LC).nsects);
+      P2CurrentAlignment = NumberOfSections ? 2 : P2MinAlignment;
+      for (unsigned SI = 0; SI < NumberOfSections; ++SI) {
+        P2CurrentAlignment = std::max(P2CurrentAlignment,
+                                      (Is64Bit ? O.getSection64(LC, SI).align
+                                               : O.getSection(LC, SI).align));
+      }
+    } else {
+      P2CurrentAlignment =
+          countTrailingZeros(Is64Bit ? O.getSegment64LoadCommand(LC).vmaddr
+                                     : O.getSegmentLoadCommand(LC).vmaddr);
+    }
+    P2MinAlignment = std::min(P2MinAlignment, P2CurrentAlignment);
+  }
+  // return a value >= 4 byte aligned, and less than MachO MaxSectionAlignment
+  return std::max(
+      static_cast<uint32_t>(2),
+      std::min(P2MinAlignment, static_cast<uint32_t>(
+                                   MachOUniversalBinary::MaxSectionAlignment)));
+}
+
+static uint32_t calculateAlignment(const MachOObjectFile *ObjectFile) {
+  switch (ObjectFile->getHeader().cputype) {
+  case MachO::CPU_TYPE_I386:
+  case MachO::CPU_TYPE_X86_64:
+  case MachO::CPU_TYPE_POWERPC:
+  case MachO::CPU_TYPE_POWERPC64:
+    return 12; // log2 value of page size(4k) for x86 and PPC
+  case MachO::CPU_TYPE_ARM:
+  case MachO::CPU_TYPE_ARM64:
+  case MachO::CPU_TYPE_ARM64_32:
+    return 14; // log2 value of page size(16k) for Darwin ARM
+  default:
+    return calculateSegmentAlignment(*ObjectFile);
+  }
+}
+
+class Slice {
+  const Binary *B;
+  uint32_t CPUType;
+  uint32_t CPUSubType;
+  std::string ArchName;
+
+  // P2Alignment field stores slice alignment values from universal
+  // binaries. This is also needed to order the slices so the total
   // file size can be calculated before creating the output buffer.
-  uint32_t Alignment;
+  uint32_t P2Alignment;
+
+public:
+  Slice(const MachOObjectFile *O, uint32_t Align)
+      : B(O), CPUType(O->getHeader().cputype),
+        CPUSubType(O->getHeader().cpusubtype),
+        ArchName(O->getArchTriple().getArchName()), P2Alignment(Align) {}
+
+  explicit Slice(const MachOObjectFile *O) : Slice(O, calculateAlignment(O)){};
+
+  explicit Slice(const Archive *A) : B(A) {
+    Error Err = Error::success();
+    std::unique_ptr<MachOObjectFile> FO = nullptr;
+    for (const Archive::Child &Child : A->children(Err)) {
+      Expected<std::unique_ptr<Binary>> ChildOrErr = Child.getAsBinary();
+      if (!ChildOrErr)
+        reportError(A->getFileName(), ChildOrErr.takeError());
+      Binary *Bin = ChildOrErr.get().get();
+      if (Bin->isMachOUniversalBinary())
+        reportError(("archive member " + Bin->getFileName() +
+                     " is a fat file (not allowed in an archive)")
+                        .str());
+      if (!Bin->isMachO())
+        reportError(("archive member " + Bin->getFileName() +
+                     " is not a MachO file (not allowed in an archive)"));
+      MachOObjectFile *O = cast<MachOObjectFile>(Bin);
+      if (FO &&
+          std::tie(FO->getHeader().cputype, FO->getHeader().cpusubtype) !=
+              std::tie(O->getHeader().cputype, O->getHeader().cpusubtype)) {
+        reportError(("archive member " + O->getFileName() + " cputype (" +
+                     Twine(O->getHeader().cputype) + ") and cpusubtype(" +
+                     Twine(O->getHeader().cpusubtype) +
+                     ") does not match previous archive members cputype (" +
+                     Twine(FO->getHeader().cputype) + ") and cpusubtype(" +
+                     Twine(FO->getHeader().cpusubtype) +
+                     ") (all members must match) " + FO->getFileName())
+                        .str());
+      }
+      if (!FO) {
+        ChildOrErr.get().release();
+        FO.reset(O);
+      }
+    }
+    if (Err)
+      reportError(A->getFileName(), std::move(Err));
+    if (!FO)
+      reportError(("empty archive with no architecture specification: " +
+                   A->getFileName() + " (can't determine architecture for it)")
+                      .str());
+    CPUType = FO->getHeader().cputype;
+    CPUSubType = FO->getHeader().cpusubtype;
+    ArchName = FO->getArchTriple().getArchName();
+    // Replicate the behavior of cctools lipo.
+    P2Alignment = FO->is64Bit() ? 3 : 2;
+  }
+
+  void setP2Alignment(uint32_t Align) { P2Alignment = Align; }
+
+  const Binary *getBinary() const { return B; }
+
+  uint32_t getCPUType() const { return CPUType; }
+
+  uint32_t getCPUSubType() const { return CPUSubType; }
+
+  uint32_t getP2Alignment() const { return P2Alignment; }
+
+  uint64_t getCPUID() const {
+    return static_cast<uint64_t>(CPUType) << 32 | CPUSubType;
+  }
+
+  std::string getArchString() const {
+    if (!ArchName.empty())
+      return ArchName;
+    return ("unknown(" + Twine(CPUType) + "," +
+            Twine(CPUSubType & ~MachO::CPU_SUBTYPE_MASK) + ")")
+        .str();
+  }
+
+  friend bool operator<(const Slice &Lhs, const Slice &Rhs) {
+    if (Lhs.CPUType == Rhs.CPUType)
+      return Lhs.CPUSubType < Rhs.CPUSubType;
+    // force arm64-family to follow after all other slices for
+    // compatibility with cctools lipo
+    if (Lhs.CPUType == MachO::CPU_TYPE_ARM64)
+      return false;
+    if (Rhs.CPUType == MachO::CPU_TYPE_ARM64)
+      return true;
+    // Sort by alignment to minimize file size
+    return Lhs.P2Alignment < Rhs.P2Alignment;
+  }
 };
 
 } // end namespace
 
 static void validateArchitectureName(StringRef ArchitectureName) {
   if (!MachOObjectFile::isValidArch(ArchitectureName)) {
     std::string Buf;
     raw_string_ostream OS(Buf);

 
 static SmallVector<OwningBinary<Binary>, 1>
 readInputBinaries(ArrayRef<std::string> InputFiles) {
   SmallVector<OwningBinary<Binary>, 1> InputBinaries;
   for (StringRef InputFile : InputFiles) {
     Expected<OwningBinary<Binary>> BinaryOrErr = createBinary(InputFile);
     if (!BinaryOrErr)
       reportError(InputFile, BinaryOrErr.takeError());
-    // TODO: Add compatibility for archive files
-    if (BinaryOrErr->getBinary()->isArchive())
-      reportError("File " + InputFile +
-                  " is an archive file and is not yet supported.");
-    if (!BinaryOrErr->getBinary()->isMachO() &&
+    if (!BinaryOrErr->getBinary()->isArchive() &&
+        !BinaryOrErr->getBinary()->isMachO() &&
         !BinaryOrErr->getBinary()->isMachOUniversalBinary())
       reportError("File " + InputFile + " has unsupported binary format");
     InputBinaries.push_back(std::move(*BinaryOrErr));
   }
   return InputBinaries;
 }
 
 LLVM_ATTRIBUTE_NORETURN
 static void verifyArch(ArrayRef<OwningBinary<Binary>> InputBinaries,
                        ArrayRef<std::string> VerifyArchList) {
   assert(!VerifyArchList.empty() &&
          "The list of architectures should be non-empty");
   assert(InputBinaries.size() == 1 && "Incorrect number of input binaries");
 
   for (StringRef Arch : VerifyArchList)
     validateArchitectureName(Arch);
 
   if (auto UO =
           dyn_cast<MachOUniversalBinary>(InputBinaries.front().getBinary())) {
     for (StringRef Arch : VerifyArchList) {
-      auto ObjForArch = UO->getObjectForArch(Arch);
-      if (!ObjForArch)
+      Expected<MachOUniversalBinary::ObjectForArch> Obj =
+          UO->getObjectForArch(Arch);
+      if (!Obj)
         exit(EXIT_FAILURE);
     }
   } else if (auto O =
                  dyn_cast<MachOObjectFile>(InputBinaries.front().getBinary())) {
     const Triple::ArchType ObjectArch = O->getArch();
     for (StringRef Arch : VerifyArchList)
       if (ObjectArch != Triple(Arch).getArch())
         exit(EXIT_FAILURE);
   } else {
     llvm_unreachable("Unexpected binary format");
   }
   exit(EXIT_SUCCESS);
 }
 
-// Returns a string of the given Object file's architecture type
-// Unknown architectures formatted unknown(CPUType,CPUSubType) for compatibility
-// with cctools lipo
-static std::string getArchString(const MachOObjectFile &ObjectFile) {
-  const Triple T = ObjectFile.getArchTriple();
-  const StringRef ObjectArch = T.getArchName();
-  if (!ObjectArch.empty())
-    return ObjectArch;
-  return ("unknown(" + Twine(ObjectFile.getHeader().cputype) + "," +
-          Twine(ObjectFile.getHeader().cpusubtype & ~MachO::CPU_SUBTYPE_MASK) +
-          ")")
-      .str();
-}
-
 static void printBinaryArchs(const Binary *Binary, raw_ostream &OS) {
   // Prints trailing space for compatibility with cctools lipo.
   if (auto UO = dyn_cast<MachOUniversalBinary>(Binary)) {
     for (const auto &O : UO->objects()) {
-      Expected<std::unique_ptr<MachOObjectFile>> BinaryOrError =
+      Expected<std::unique_ptr<MachOObjectFile>> MachOObjOrError =
           O.getAsObjectFile();
-      if (!BinaryOrError)
-        reportError(Binary->getFileName(), BinaryOrError.takeError());
-      OS << getArchString(*BinaryOrError.get().get()) << " ";
+      if (MachOObjOrError) {
+        OS << Slice(MachOObjOrError->get()).getArchString() << " ";
+        continue;
+      }
+      Expected<std::unique_ptr<Archive>> ArchiveOrError = 
+          O.getAsArchive();
+      if (ArchiveOrError) {
+        consumeError(MachOObjOrError.takeError());
+        OS << Slice(ArchiveOrError->get()).getArchString() << " ";
+        continue;
+      }
+      consumeError(ArchiveOrError.takeError());  
+      reportError(Binary->getFileName(), MachOObjOrError.takeError());
     }
     OS << "\n";
     return;
   }
-  OS << getArchString(*cast<MachOObjectFile>(Binary)) << " \n";
+  OS << Slice(cast<MachOObjectFile>(Binary)).getArchString() << " \n";
 }
 
 LLVM_ATTRIBUTE_NORETURN
 static void printArchs(ArrayRef<OwningBinary<Binary>> InputBinaries) {
   assert(InputBinaries.size() == 1 && "Incorrect number of input binaries");
   printBinaryArchs(InputBinaries.front().getBinary(), outs());
   exit(EXIT_SUCCESS);
 }
reportError("input file " +
                 InputBinaries.front().getBinary()->getFileName() +
                 " must be a fat file when the -thin option is specified");
     exit(EXIT_FAILURE);
   }
 
   auto *UO = cast<MachOUniversalBinary>(InputBinaries.front().getBinary());
   Expected<std::unique_ptr<MachOObjectFile>> Obj =
       UO->getMachOObjectForArch(ThinArchType);
-  if (!Obj)
+  Expected<std::unique_ptr<Archive>> Ar = UO->getArchiveForArch(ThinArchType);
+  if (!Obj && !Ar)
     reportError("fat input file " + UO->getFileName() +
                 " does not contain the specified architecture " + ThinArchType +
                 " to thin it to");
-
+  Binary *B = Obj ? static_cast<Binary *>(Obj->get())
+                  : static_cast<Binary *>(Ar->get());
   Expected<std::unique_ptr<FileOutputBuffer>> OutFileOrError =
       FileOutputBuffer::create(OutputFileName,
-                               Obj.get()->getMemoryBufferRef().getBufferSize(),
+                               B->getMemoryBufferRef().getBufferSize(),
                                sys::fs::can_execute(UO->getFileName())
                                    ? FileOutputBuffer::F_executable
                                    : 0);
   if (!OutFileOrError)
     reportError(OutputFileName, OutFileOrError.takeError());
-  std::copy(Obj.get()->getMemoryBufferRef().getBufferStart(),
-            Obj.get()->getMemoryBufferRef().getBufferEnd(),
+  std::copy(B->getMemoryBufferRef().getBufferStart(),
+            B->getMemoryBufferRef().getBufferEnd(),
             OutFileOrError.get()->getBufferStart());
   if (Error E = OutFileOrError.get()->commit())
     reportError(OutputFileName, std::move(E));
   exit(EXIT_SUCCESS);
 }
 
 static void checkArchDuplicates(const ArrayRef<Slice> &Slices) {
-  DenseMap<uint64_t, const MachOObjectFile *> CPUIds;
-  auto CPUIDForSlice = [](const Slice &S) {
-    return static_cast<uint64_t>(S.ObjectFile->getHeader().cputype) << 32 |
-           S.ObjectFile->getHeader().cpusubtype;
-  };
+  DenseMap<uint64_t, const Binary *> CPUIds;
   for (const auto &S : Slices) {
-    auto Entry = CPUIds.try_emplace(CPUIDForSlice(S), S.ObjectFile);
+    auto Entry = CPUIds.try_emplace(S.getCPUID(), S.getBinary());
     if (!Entry.second)
       reportError(Entry.first->second->getFileName() + " and " +
-                  S.ObjectFile->getFileName() + " have the same architecture " +
-                  getArchString(*S.ObjectFile) +
+                  S.getBinary()->getFileName() +
+                  " have the same architecture " + S.getArchString() +
                   " and therefore cannot be in the same universal binary");
   }
 }
 
-// For compatibility with cctools lipo, alignment is calculated as the minimum
-// aligment of all segments. Each segments's alignment is the maximum alignment
-// from its sections
-static uint32_t calculateSegmentAlignment(const MachOObjectFile &O) {
-  uint32_t P2CurrentAlignment;
-  uint32_t P2MinAlignment = MachOUniversalBinary::MaxSectionAlignment;
-  const bool Is64Bit = O.is64Bit();
-
-  for (const auto &LC : O.load_commands()) {
-    if (LC.C.cmd != (Is64Bit ? MachO::LC_SEGMENT_64 : MachO::LC_SEGMENT))
-      continue;
-    if (O.getHeader().filetype == MachO::MH_OBJECT) {
-      unsigned NumberOfSections =
-          (Is64Bit ? O.getSegment64LoadCommand(LC).nsects
-                   : O.getSegmentLoadCommand(LC).nsects);
-      P2CurrentAlignment = NumberOfSections ? 2 : P2MinAlignment;
-      for (unsigned SI = 0; SI < NumberOfSections; ++SI) {
-        P2CurrentAlignment = std::max(P2CurrentAlignment,
-                                      (Is64Bit ? O.getSection64(LC, SI).align
-                                               : O.getSection(LC, SI).align));
-      }
-    } else {
-      P2CurrentAlignment =
-          countTrailingZeros(Is64Bit ? O.getSegment64LoadCommand(LC).vmaddr
-                                     : O.getSegmentLoadCommand(LC).vmaddr);
-    }
-    P2MinAlignment = std::min(P2MinAlignment, P2CurrentAlignment);
-  }
-  // return a value >= 4 byte aligned, and less than MachO MaxSectionAlignment
-  return std::max(
-      static_cast<uint32_t>(2),
-      std::min(P2MinAlignment, static_cast<uint32_t>(
-                                   MachOUniversalBinary::MaxSectionAlignment)));
-}
-
-static uint32_t calculateAlignment(const MachOObjectFile *ObjectFile) {
-  switch (ObjectFile->getHeader().cputype) {
-  case MachO::CPU_TYPE_I386:
-  case MachO::CPU_TYPE_X86_64:
-  case MachO::CPU_TYPE_POWERPC:
-  case MachO::CPU_TYPE_POWERPC64:
-    return 12; // log2 value of page size(4k) for x86 and PPC
-  case MachO::CPU_TYPE_ARM:
-  case MachO::CPU_TYPE_ARM64:
-  case MachO::CPU_TYPE_ARM64_32:
-    return 14; // log2 value of page size(16k) for Darwin ARM
-  default:
-    return calculateSegmentAlignment(*ObjectFile);
-  }
-}
-
-// This function replicates ordering from cctools lipo for consistency
-static bool compareSlices(const Slice &Lhs, const Slice &Rhs) {
-  if (Lhs.ObjectFile->getHeader().cputype ==
-      Rhs.ObjectFile->getHeader().cputype)
-    return Lhs.ObjectFile->getHeader().cpusubtype <
-           Rhs.ObjectFile->getHeader().cpusubtype;
-
-  // force arm64-family to follow after all other slices for compatibility
-  // with cctools lipo
-  if (Lhs.ObjectFile->getHeader().cputype == MachO::CPU_TYPE_ARM64)
-    return false;
-  if (Rhs.ObjectFile->getHeader().cputype == MachO::CPU_TYPE_ARM64)
-    return true;
-
-  // Sort by alignment to minimize file size
-  return Lhs.Alignment < Rhs.Alignment;
-}
-
 template <typename Range>
-static void
-updateSegmentAlignments(Range &Slices,
+static void updateAlignments(Range &Slices,
                              const StringMap<const uint32_t> &Alignments) {
   for (auto &Slice : Slices) {
-    auto Alignment = Alignments.find(getArchString(*Slice.ObjectFile));
+    auto Alignment = Alignments.find(Slice.getArchString());
     if (Alignment != Alignments.end())
-      Slice.Alignment = Alignment->second;
+      Slice.setP2Alignment(Alignment->second);
   }
 }
 
 static void checkUnusedAlignments(ArrayRef<Slice> Slices,
                                   const StringMap<const uint32_t> &Alignments) {
   auto HasArch = [&](StringRef Arch) {
     return llvm::find_if(Slices, [Arch](Slice S) {
-             return getArchString(*S.ObjectFile) == Arch;
+             return S.getArchString() == Arch;
            }) != Slices.end();
   };
   for (StringRef Arch : Alignments.keys())
     if (!HasArch(Arch))
       reportError("-segalign " + Arch +
                   " <value> specified but resulting fat file does not contain "
                   "that architecture ");
 }
for (auto &IB : InputBinaries) {
     const Binary *InputBinary = IB.getBinary();
     if (auto UO = dyn_cast<MachOUniversalBinary>(InputBinary)) {
       for (const auto &O : UO->objects()) {
         Expected<std::unique_ptr<MachOObjectFile>> BinaryOrError =
             O.getAsObjectFile();
         if (!BinaryOrError)
           reportError(InputBinary->getFileName(), BinaryOrError.takeError());
         ExtractedObjects.push_back(std::move(BinaryOrError.get()));
-        Slices.push_back(Slice{ExtractedObjects.back().get(), O.getAlign()});
+        Slices.emplace_back(ExtractedObjects.back().get(), O.getAlign());
       }
     } else if (auto O = dyn_cast<MachOObjectFile>(InputBinary)) {
-      Slices.push_back(Slice{O, calculateAlignment(O)});
+      Slices.emplace_back(O);
+    } else if (auto A = dyn_cast<Archive>(InputBinary)) {
+      Slices.emplace_back(A);
     } else {
       llvm_unreachable("Unexpected binary format");
     }
   }
-  updateSegmentAlignments(Slices, Alignments);
+  updateAlignments(Slices, Alignments);
   return Slices;
 }
 
 static SmallVector<MachO::fat_arch, 2>
 buildFatArchList(ArrayRef<Slice> Slices) {
   SmallVector<MachO::fat_arch, 2> FatArchList;
   uint64_t Offset =
       sizeof(MachO::fat_header) + Slices.size() * sizeof(MachO::fat_arch);
 
-  for (size_t Index = 0, Size = Slices.size(); Index < Size; ++Index) {
-    Offset = alignTo(Offset, 1ull << Slices[Index].Alignment);
-    const MachOObjectFile *ObjectFile = Slices[Index].ObjectFile;
+  for (const auto &S : Slices) {
+    Offset = alignTo(Offset, 1ull << S.getP2Alignment());
     if (Offset > UINT32_MAX)
       reportError("fat file too large to be created because the offset "
                   "field in struct fat_arch is only 32-bits and the offset " +
-                  Twine(Offset) + " for " + ObjectFile->getFileName() +
-                  " for architecture " + getArchString(*ObjectFile) +
-                  "exceeds that.");
+                  Twine(Offset) + " for " + S.getBinary()->getFileName() +
+                  " for architecture " + S.getArchString() + "exceeds that.");
 
     MachO::fat_arch FatArch;
-    FatArch.cputype = ObjectFile->getHeader().cputype;
-    FatArch.cpusubtype = ObjectFile->getHeader().cpusubtype;
+    FatArch.cputype = S.getCPUType();
+    FatArch.cpusubtype = S.getCPUSubType();
     FatArch.offset = Offset;
-    FatArch.size = ObjectFile->getMemoryBufferRef().getBufferSize();
-    FatArch.align = Slices[Index].Alignment;
+    FatArch.size = S.getBinary()->getMemoryBufferRef().getBufferSize();
+    FatArch.align = S.getP2Alignment();
     Offset += FatArch.size;
     FatArchList.push_back(FatArch);
   }
   return FatArchList;
 }
 
 static void createUniversalBinary(SmallVectorImpl<Slice> &Slices,
                                   StringRef OutputFileName) {
   MachO::fat_header FatHeader;
   FatHeader.magic = MachO::FAT_MAGIC;
   FatHeader.nfat_arch = Slices.size();
 
-  stable_sort(Slices, compareSlices);
+  stable_sort(Slices);
   SmallVector<MachO::fat_arch, 2> FatArchList = buildFatArchList(Slices);
 
   const bool IsExecutable = any_of(Slices, [](Slice S) {
-    return sys::fs::can_execute(S.ObjectFile->getFileName());
+    return sys::fs::can_execute(S.getBinary()->getFileName());
   });
   const uint64_t OutputFileSize =
       FatArchList.back().offset + FatArchList.back().size;
   Expected<std::unique_ptr<FileOutputBuffer>> OutFileOrError =
       FileOutputBuffer::create(OutputFileName, OutputFileSize,
                                IsExecutable ? FileOutputBuffer::F_executable
                                             : 0);
   if (!OutFileOrError)
     reportError(OutputFileName, OutFileOrError.takeError());
   std::unique_ptr<FileOutputBuffer> OutFile = std::move(OutFileOrError.get());
   std::memset(OutFile->getBufferStart(), 0, OutputFileSize);
 
   if (sys::IsLittleEndianHost)
     MachO::swapStruct(FatHeader);
   std::memcpy(OutFile->getBufferStart(), &FatHeader, sizeof(MachO::fat_header));
 
   for (size_t Index = 0, Size = Slices.size(); Index < Size; ++Index) {
-    MemoryBufferRef BufferRef = Slices[Index].ObjectFile->getMemoryBufferRef();
+    MemoryBufferRef BufferRef = Slices[Index].getBinary()->getMemoryBufferRef();
     std::copy(BufferRef.getBufferStart(), BufferRef.getBufferEnd(),
               OutFile->getBufferStart() + FatArchList[Index].offset);
   }
 
   // FatArchs written after Slices in order to reduce the number of swaps for
   // the LittleEndian case
   if (sys::IsLittleEndianHost)
     for (MachO::fat_arch &FA : FatArchList)
if (!O)
       reportError("replacement file: " + ReplacementBinary->getFileName() +
                   " is a fat file (must be a thin file)");
 
     if (O->getArch() != Triple(ReplacementArch).getArch())
       reportError("specified architecture: " + ReplacementArch +
                   " for replacement file: " + ReplacementBinary->getFileName() +
                   " does not match the file's architecture");
 
-    auto Entry =
-        Slices.try_emplace(ReplacementArch, Slice{O, calculateAlignment(O)});
+    auto Entry = Slices.try_emplace(ReplacementArch, Slice(O));
     if (!Entry.second)
       reportError("-replace " + ReplacementArch +
                   " <file_name> specified multiple times: " +
-                  Entry.first->second.ObjectFile->getFileName() + ", " +
+                  Entry.first->second.getBinary()->getFileName() + ", " +
                   O->getFileName());
   }
   auto SlicesMapRange = map_range(
       Slices, [](StringMapEntry<Slice> &E) -> Slice & { return E.getValue(); });
-  updateSegmentAlignments(SlicesMapRange, Alignments);
+  updateAlignments(SlicesMapRange, Alignments);
   return Slices;
 }
 
 LLVM_ATTRIBUTE_NORETURN
 static void replaceSlices(ArrayRef<OwningBinary<Binary>> InputBinaries,
                           const StringMap<const uint32_t> &Alignments,
                           StringRef OutputFileName,
                           ArrayRef<Replacement> Replacements) {
static void replaceSlices(ArrayRef<OwningBinary<Binary>> InputBinaries,
 
   StringMap<Slice> ReplacementSlices =
       buildReplacementSlices(ReplacementBinaries, Alignments, Replacements);
   SmallVector<std::unique_ptr<MachOObjectFile>, 2> ExtractedObjects;
   SmallVector<Slice, 2> Slices =
       buildSlices(InputBinaries, Alignments, ExtractedObjects);
 
   for (auto &Slice : Slices) {
-    auto It = ReplacementSlices.find(getArchString(*Slice.ObjectFile));
+    auto It = ReplacementSlices.find(Slice.getArchString());
     if (It != ReplacementSlices.end()) {
       Slice = It->second;
       ReplacementSlices.erase(It); // only keep remaining replacing arch_types
     }
   }
 
   if (!ReplacementSlices.empty())
     reportError("-replace " + ReplacementSlices.begin()->first() +