Index: test/tools/llvm-objcopy/ELF/binary-input-with-arch.test
===================================================================
--- /dev/null
+++ test/tools/llvm-objcopy/ELF/binary-input-with-arch.test
@@ -0,0 +1,36 @@
+# RUN: echo -n abcd > %t.x-txt
+# Preserve input to verify it is not modified
+# RUN: cp %t.x-txt %t-copy.txt
+# RUN: llvm-objcopy -I binary -B i386 -O elf64-x86-64 %t.x-txt %t.o
+# RUN: llvm-readobj -file-headers %t.o | FileCheck %s
+# RUN: cmp %t.x-txt %t-copy.txt
+
+# CHECK:      Format: ELF64-x86-64
+# CHECK-NEXT: Arch: x86_64
+# CHECK-NEXT: AddressSize: 64bit
+# CHECK-NEXT: LoadName:
+# CHECK-NEXT: ElfHeader {
+# CHECK-NEXT:   Ident {
+# CHECK-NEXT:     Magic: (7F 45 4C 46)
+# CHECK-NEXT:     Class: 64-bit (0x2)
+# CHECK-NEXT:     DataEncoding: LittleEndian (0x1)
+# CHECK-NEXT:     FileVersion: 1
+# CHECK-NEXT:     OS/ABI: SystemV (0x0)
+# CHECK-NEXT:     ABIVersion: 0
+# CHECK-NEXT:     Unused: (00 00 00 00 00 00 00)
+# CHECK-NEXT:   }
+# CHECK-NEXT:   Type: Relocatable (0x1)
+# CHECK-NEXT:   Machine: EM_X86_64 (0x3E)
+# CHECK-NEXT:   Version: 1
+# CHECK-NEXT:   Entry:
+# CHECK-NEXT:   ProgramHeaderOffset:
+# CHECK-NEXT:   SectionHeaderOffset:
+# CHECK-NEXT:   Flags [ (0x0)
+# CHECK-NEXT:   ]
+# CHECK-NEXT:   HeaderSize:
+# CHECK-NEXT:   ProgramHeaderEntrySize:
+# CHECK-NEXT:   ProgramHeaderCount:
+# CHECK-NEXT:   SectionHeaderEntrySize: 64
+# CHECK-NEXT:   SectionHeaderCount:
+# CHECK-NEXT:   StringTableSectionIndex:
+# CHECK-NEXT: }
Index: test/tools/llvm-objcopy/ELF/cross-arch-bad-format.test
===================================================================
--- /dev/null
+++ test/tools/llvm-objcopy/ELF/cross-arch-bad-format.test
@@ -0,0 +1,13 @@
+# RUN: yaml2obj %s > %t.o
+
+# RUN: not llvm-objcopy -O xyz %t.o %t.2.o 2>&1 \
+# RUN:   | FileCheck %s --check-prefix=BAD-OUTPUT-FORMAT
+
+!ELF
+FileHeader:
+  Class:           ELFCLASS32
+  Data:            ELFDATA2LSB
+  Type:            ET_EXEC
+  Machine:         EM_386
+
+# BAD-OUTPUT-FORMAT: Invalid format: 'xyz'.
Index: test/tools/llvm-objcopy/ELF/cross-arch-headers.test
===================================================================
--- /dev/null
+++ test/tools/llvm-objcopy/ELF/cross-arch-headers.test
@@ -0,0 +1,89 @@
+# RUN: yaml2obj %s > %t.o
+
+# RUN: llvm-objcopy %t.o -Oelf32-i386 %t.elf32_i386.o
+# RUN: llvm-readobj -file-headers %t.elf32_i386.o | FileCheck %s --check-prefixes=CHECK,I386,32
+
+# RUN: llvm-objcopy %t.o -Oelf32-powerpcle %t.elf32_ppcle.o
+# RUN: llvm-readobj -file-headers %t.elf32_ppcle.o | FileCheck %s --check-prefixes=CHECK,PPC,32
+
+# RUN: llvm-objcopy %t.o -Oelf32-x86-64 %t.elf32_x86_64.o
+# RUN: llvm-readobj -file-headers %t.elf32_x86_64.o | FileCheck %s --check-prefixes=CHECK,X86-64,32
+
+# RUN: llvm-objcopy %t.o -Oelf64-powerpcle %t.elf64_ppcle.o
+# RUN: llvm-readobj -file-headers %t.elf64_ppcle.o | FileCheck %s --check-prefixes=CHECK,PPC64,64
+
+# RUN: llvm-objcopy %t.o -Oelf64-x86-64 %t.elf64_x86_64.o
+# RUN: llvm-readobj -file-headers %t.elf64_x86_64.o | FileCheck %s --check-prefixes=CHECK,X86-64,64
+
+!ELF
+FileHeader:
+  Class:           ELFCLASS32
+  Data:            ELFDATA2LSB
+  Type:            ET_EXEC
+  Machine:         EM_386
+Sections:
+  - Name:            .text
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC, SHF_EXECINSTR ]
+  - Name:            .data
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC ]
+Symbols:
+  Global:
+    - Name:     foo
+      Type:     STT_FUNC
+      Section:  .text
+      Value:    0x1234
+    - Name:     bar
+      Type:     STT_OBJECT
+      Section:  .data
+      Value:    0xabcd
+
+# CHECK: Format:
+# 32-SAME:      ELF32-
+# 64-SAME:      ELF64-
+# I386-SAME:    i386
+# PPC-SAME:     ppc
+# PPC64-SAME:   ppc64
+# X86-64-SAME:  x86-64
+
+# I386-NEXT:    Arch: i386
+# PPC-NEXT:     Arch: powerpc
+# PPC64-NEXT:   Arch: powerpc64le
+# X86-64-NEXT:  Arch: x86_64
+
+# 32-NEXT:      AddressSize: 32bit
+# 64-NEXT:      AddressSize: 64bit
+
+# CHECK:        ElfHeader {
+# CHECK-NEXT:     Ident {
+# CHECK-NEXT:       Magic: (7F 45 4C 46)
+# 32-NEXT:          Class: 32-bit (0x1)
+# 64-NEXT:          Class: 64-bit (0x2)
+# CHECK-NEXT:       DataEncoding: LittleEndian (0x1)
+# CHECK-NEXT:       FileVersion: 1
+# CHECK-NEXT:       OS/ABI: SystemV (0x0)
+# CHECK-NEXT:       ABIVersion: 0
+# CHECK-NEXT:       Unused: (00 00 00 00 00 00 00)
+# CHECK-NEXT:     }
+# CHECK-NEXT:     Type: Executable (0x2)
+# I386-NEXT:      Machine: EM_386 (0x3)
+# PPC-NEXT:       Machine: EM_PPC (0x14)
+# PPC64-NEXT:     Machine: EM_PPC64 (0x15)
+# X86-64-NEXT:    Machine: EM_X86_64 (0x3E)
+# CHECK-NEXT:     Version: 1
+# CHECK-NEXT:     Entry: 0x0
+# CHECK-NEXT:     ProgramHeaderOffset:
+# CHECK-NEXT:     SectionHeaderOffset:
+# CHECK-NEXT:     Flags [ (0x0)
+# CHECK-NEXT:     ]
+# 32-NEXT:        HeaderSize: 52
+# 64-NEXT:        HeaderSize: 64
+# 32-NEXT:        ProgramHeaderEntrySize: 0
+# 64-NEXT:        ProgramHeaderEntrySize: 0
+# CHECK-NEXT:     ProgramHeaderCount: 0
+# 32-NEXT:        SectionHeaderEntrySize: 40
+# 64-NEXT:        SectionHeaderEntrySize: 64
+# CHECK-NEXT:     SectionHeaderCount: 6
+# CHECK-NEXT:     StringTableSectionIndex:
+# CHECK-NEXT:   }
Index: test/tools/llvm-objcopy/ELF/cross-arch-sections-symbols.test
===================================================================
--- /dev/null
+++ test/tools/llvm-objcopy/ELF/cross-arch-sections-symbols.test
@@ -0,0 +1,149 @@
+# RUN: yaml2obj %s > %t.o
+# Preserve input to verify it is not modified
+# RUN: cp %t.o %t-copy.o
+# RUN: llvm-objcopy %t.o -Oelf64-x86-64 %t.2.o
+# RUN: llvm-readobj -sections -symbols %t.2.o | FileCheck %s
+# RUN: cmp %t.o %t-copy.o
+
+!ELF
+FileHeader:
+  Class:           ELFCLASS32
+  Data:            ELFDATA2LSB
+  Type:            ET_EXEC
+  Machine:         EM_386
+Sections:
+  - Name:            .text
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC, SHF_EXECINSTR ]
+  - Name:            .data
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC ]
+Symbols:
+  Global:
+    - Name:     foo
+      Type:     STT_FUNC
+      Section:  .text
+      Value:    0x1234
+    - Name:     bar
+      Type:     STT_OBJECT
+      Section:  .data
+      Value:    0xabcd
+
+# CHECK:      Sections [
+# CHECK-NEXT:   Section {
+# CHECK-NEXT:     Index: 0
+# CHECK-NEXT:     Name:  (0)
+# CHECK-NEXT:     Type: SHT_NULL (0x0)
+# CHECK-NEXT:     Flags [ (0x0)
+# CHECK-NEXT:     ]
+# CHECK-NEXT:     Address:
+# CHECK-NEXT:     Offset:
+# CHECK-NEXT:     Size: 0
+# CHECK-NEXT:     Link: 0
+# CHECK-NEXT:     Info: 0
+# CHECK-NEXT:     AddressAlignment: 0
+# CHECK-NEXT:     EntrySize: 0
+# CHECK-NEXT:   }
+# CHECK-NEXT:   Section {
+# CHECK-NEXT:     Index: 1
+# CHECK-NEXT:     Name: .text
+# CHECK-NEXT:     Type: SHT_PROGBITS (0x1)
+# CHECK-NEXT:     Flags [ (0x6)
+# CHECK-NEXT:       SHF_ALLOC (0x2)
+# CHECK-NEXT:       SHF_EXECINSTR (0x4)
+# CHECK-NEXT:     ]
+# CHECK-NEXT:     Address:
+# CHECK-NEXT:     Offset:
+# CHECK-NEXT:     Size: 0
+# CHECK-NEXT:     Link: 0
+# CHECK-NEXT:     Info: 0
+# CHECK-NEXT:     AddressAlignment: 0
+# CHECK-NEXT:     EntrySize: 0
+# CHECK-NEXT:   }
+# CHECK-NEXT:   Section {
+# CHECK-NEXT:     Index: 2
+# CHECK-NEXT:     Name: .data
+# CHECK-NEXT:     Type: SHT_PROGBITS (0x1)
+# CHECK-NEXT:     Flags [ (0x2)
+# CHECK-NEXT:       SHF_ALLOC (0x2)
+# CHECK-NEXT:     ]
+# CHECK-NEXT:     Address:
+# CHECK-NEXT:     Offset:
+# CHECK-NEXT:     Size: 0
+# CHECK-NEXT:     Link: 0
+# CHECK-NEXT:     Info: 0
+# CHECK-NEXT:     AddressAlignment: 0
+# CHECK-NEXT:     EntrySize: 0
+# CHECK-NEXT:   }
+# CHECK-NEXT:   Section {
+# CHECK-NEXT:     Index: 3
+# CHECK-NEXT:     Name: .symtab
+# CHECK-NEXT:     Type: SHT_SYMTAB (0x2)
+# CHECK-NEXT:     Flags [ (0x0)
+# CHECK-NEXT:     ]
+# CHECK-NEXT:     Address:
+# CHECK-NEXT:     Offset:
+# CHECK-NEXT:     Size: 72
+# CHECK-NEXT:     Link: 4
+# CHECK-NEXT:     Info: 1
+# CHECK-NEXT:     AddressAlignment: 8
+# CHECK-NEXT:     EntrySize: 24
+# CHECK-NEXT:   }
+# CHECK-NEXT:   Section {
+# CHECK-NEXT:     Index: 4
+# CHECK-NEXT:     Name: .strtab
+# CHECK-NEXT:     Type: SHT_STRTAB (0x3)
+# CHECK-NEXT:     Flags [ (0x0)
+# CHECK-NEXT:     ]
+# CHECK-NEXT:     Address:
+# CHECK-NEXT:     Offset:
+# CHECK-NEXT:     Size: 10
+# CHECK-NEXT:     Link: 0
+# CHECK-NEXT:     Info: 0
+# CHECK-NEXT:     AddressAlignment: 1
+# CHECK-NEXT:     EntrySize: 0
+# CHECK-NEXT:   }
+# CHECK-NEXT:   Section {
+# CHECK-NEXT:     Index: 5
+# CHECK-NEXT:     Name: .shstrtab
+# CHECK-NEXT:     Type: SHT_STRTAB (0x3)
+# CHECK-NEXT:     Flags [ (0x0)
+# CHECK-NEXT:     ]
+# CHECK-NEXT:     Address:
+# CHECK-NEXT:     Offset:
+# CHECK-NEXT:     Size: 39
+# CHECK-NEXT:     Link: 0
+# CHECK-NEXT:     Info: 0
+# CHECK-NEXT:     AddressAlignment: 1
+# CHECK-NEXT:     EntrySize: 0
+# CHECK-NEXT:   }
+# CHECK-NEXT: ]
+# CHECK-NEXT: Symbols [
+# CHECK-NEXT:   Symbol {
+# CHECK-NEXT:     Name:
+# CHECK-NEXT:     Value: 0x0
+# CHECK-NEXT:     Size: 0
+# CHECK-NEXT:     Binding: Local (0x0)
+# CHECK-NEXT:     Type: None (0x0)
+# CHECK-NEXT:     Other: 0
+# CHECK-NEXT:     Section: Undefined
+# CHECK-NEXT:   }
+# CHECK-NEXT:   Symbol {
+# CHECK-NEXT:     Name: foo
+# CHECK-NEXT:     Value: 0x1234
+# CHECK-NEXT:     Size: 0
+# CHECK-NEXT:     Binding: Global (0x1)
+# CHECK-NEXT:     Type: Function (0x2)
+# CHECK-NEXT:     Other: 0
+# CHECK-NEXT:     Section: .text
+# CHECK-NEXT:   }
+# CHECK-NEXT:   Symbol {
+# CHECK-NEXT:     Name: bar
+# CHECK-NEXT:     Value: 0xABCD
+# CHECK-NEXT:     Size: 0
+# CHECK-NEXT:     Binding: Global (0x1)
+# CHECK-NEXT:     Type: Object (0x1)
+# CHECK-NEXT:     Other: 0
+# CHECK-NEXT:     Section: .data
+# CHECK-NEXT:   }
+# CHECK-NEXT: ]
Index: tools/llvm-objcopy/CopyConfig.h
===================================================================
--- tools/llvm-objcopy/CopyConfig.h
+++ tools/llvm-objcopy/CopyConfig.h
@@ -48,6 +48,8 @@
 
   // Only applicable for --input-format=Binary
   MachineInfo BinaryArch;
+  // Only applicable when --output-format != Binary (e.g. elf64-x86-64).
+  Optional<MachineInfo> OutputArch;
 
   // Advanced options
   StringRef AddGnuDebugLink;
Index: tools/llvm-objcopy/CopyConfig.cpp
===================================================================
--- tools/llvm-objcopy/CopyConfig.cpp
+++ tools/llvm-objcopy/CopyConfig.cpp
@@ -189,6 +189,22 @@
   return Iter->getValue();
 }
 
+static const StringMap<MachineInfo> FormatMap{
+    // Name, {EMachine, 64bit, LittleEndian}
+    {"elf32-i386", {ELF::EM_386, false, true}},
+    {"elf32-powerpcle", {ELF::EM_PPC, false, true}},
+    {"elf32-x86-64", {ELF::EM_X86_64, false, true}},
+    {"elf64-powerpcle", {ELF::EM_PPC64, true, true}},
+    {"elf64-x86-64", {ELF::EM_X86_64, true, true}},
+};
+
+static const MachineInfo &getFormatMachineInfo(StringRef Format) {
+  auto Iter = FormatMap.find(Format);
+  if (Iter == std::end(FormatMap))
+    error("Invalid format: '" + Format + "'");
+  return Iter->getValue();
+}
+
 static void addGlobalSymbolsFromFile(std::vector<std::string> &Symbols,
                                      StringRef Filename) {
   SmallVector<StringRef, 16> Lines;
@@ -266,6 +282,8 @@
       error("Specified binary input without specifiying an architecture");
     Config.BinaryArch = getMachineInfo(BinaryArch);
   }
+  if (!Config.OutputFormat.empty() && Config.OutputFormat != "binary")
+    Config.OutputArch = getFormatMachineInfo(Config.OutputFormat);
 
   if (auto Arg = InputArgs.getLastArg(OBJCOPY_compress_debug_sections,
                                       OBJCOPY_compress_debug_sections_eq)) {
Index: tools/llvm-objcopy/ELF/ELFObjcopy.cpp
===================================================================
--- tools/llvm-objcopy/ELF/ELFObjcopy.cpp
+++ tools/llvm-objcopy/ELF/ELFObjcopy.cpp
@@ -173,6 +173,8 @@
   auto DWOFile = Reader.create();
   DWOFile->removeSections(
       [&](const SectionBase &Sec) { return onlyKeepDWOPred(*DWOFile, Sec); });
+  if (Config.OutputArch)
+    DWOFile->Machine = Config.OutputArch.getValue().EMachine;
   FileBuffer FB(File);
   auto Writer = createWriter(Config, *DWOFile, FB, OutputElfType);
   Writer->finalize();
@@ -261,6 +263,8 @@
   if (!Config.SplitDWO.empty()) {
     splitDWOToFile(Config, Reader, Config.SplitDWO, OutputElfType);
   }
+  if (Config.OutputArch)
+    Obj.Machine = Config.OutputArch.getValue().EMachine;
 
   // TODO: update or remove symbols only if there is an option that affects
   // them.
@@ -528,7 +532,10 @@
   BinaryReader Reader(Config.BinaryArch, &In);
   std::unique_ptr<Object> Obj = Reader.create();
 
-  const ElfType OutputElfType = getOutputElfType(Config.BinaryArch);
+  // Prefer OutputArch (-O<format>) if set, otherwise fallback to BinaryArch
+  // (-B<arch>).
+  const ElfType OutputElfType = getOutputElfType(
+      Config.OutputArch ? Config.OutputArch.getValue() : Config.BinaryArch);
   handleArgs(Config, *Obj, Reader, OutputElfType);
   std::unique_ptr<Writer> Writer =
       createWriter(Config, *Obj, Out, OutputElfType);
@@ -540,7 +547,10 @@
                             object::ELFObjectFileBase &In, Buffer &Out) {
   ELFReader Reader(&In);
   std::unique_ptr<Object> Obj = Reader.create();
-  const ElfType OutputElfType = getOutputElfType(In);
+  // Prefer OutputArch (-O<format>) if set, otherwise infer if from the input.
+  const ElfType OutputElfType =
+      Config.OutputArch ? getOutputElfType(Config.OutputArch.getValue())
+                        : getOutputElfType(In);
   ArrayRef<uint8_t> BuildIdBytes;
 
   if (!Config.BuildIdLinkDir.empty()) {