[Triple] Add triple for UEFI

[Prabhuk]

Summary

Target triple to support "x86_64-unknown-uefi"

[phosek]

clang/lib/Basic/Targets.cpp

579

What does this comment refer to?

clang/lib/Basic/Targets/OSTargets.h

945

I'd start with only necessary minimum and add more later if needed. Initially we probably only need a define to identify this target, likely __UEFI__.

[Prabhuk]

Added changes to the Driver.cpp.
This version uses underlying MSVC toolchain to compile UEFI target introduced here.

[Prabhuk]

Introducing UEFIX86_64TargetInfo.

[Prabhuk]

Add UEFI macro.

[phosek]

clang/lib/Basic/Targets/X86.h

812–828

According to https://wiki.osdev.org/UEFI#Calling_Conventions, only cdecl, Microsoft's 64-bit calling convention and ARM SMC are supported for UEFI. This would translate to CC_C and CC_Win64 (I'm not sure if SMC is supported by Clang, it doesn't appear to be).

[Prabhuk]

Introducing a new toolchain for UEFI COFF.

[Prabhuk]

Added tests to the new UEFI target.

[phosek]

clang/lib/Driver/ToolChains/UEFI.cpp

42–46

I'd hardcode and inline this for simplicity, this toolchain is only used for x86_64 and arm64 right now so now need to duplicate that here.

49–50

I'd hardcode and inline this for simplicity, this toolchain is only used for x86_64 and arm64 right now so now need to duplicate that here.

53

I'd inline this.

56–57

I'd hardcode and inline this for simplicity, this toolchain is only used for x86_64 and arm64 right now so now need to duplicate that here.

60

I'd inline this.

clang/lib/Driver/ToolChains/UEFI.h

23

You also need HasNativeLLVMSupport, see https://github.com/llvm/llvm-project/blob/46dee4a3a3dfb372a0eaa0b4490c80be2f421f29/clang/lib/Driver/ToolChains/Fuchsia.h#L43

29

You'll also need to override buildLinker since the default implementation doesn't do anything, see https://github.com/llvm/llvm-project/blob/46dee4a3a3dfb372a0eaa0b4490c80be2f421f29/clang/lib/Driver/ToolChain.cpp#L319

I'd hardcode it to use lld-link for simplicty. You can use Fuchsia's implementation for inspiration (although the flags are going to be different since Fuchsia uses ld.lld, not lld-link):

https://github.com/llvm/llvm-project/blob/main/clang/lib/Driver/ToolChains/Fuchsia.h#L17-L34
https://github.com/llvm/llvm-project/blob/609b789170625277f631139c790c22d527ff1eed/clang/lib/Driver/ToolChains/Fuchsia.cpp#L31-L191

[Prabhuk]

Added UEFI toolchain. Constructing linker and started a WIP UEFI toolchain to break away from MSVC toolchain.

[Prabhuk]

Not ready for review yet. Updating build files and tests.
Fixed a compile time error.

[Prabhuk]

Use make_unique instead of new for UEFI TargetInfo.

[Prabhuk]

Addressing Petr's comments. Adding buildLinker initial draft for UEFI.

[Prabhuk]

Simplifying the patch to include just the scaffolding for X86_64 platform.
Removing the predefines to be added as a separate patch.

[phosek]

I'd split the llvm/ changes into a separate change.

clang/lib/Driver/ToolChains/UEFI.cpp

59–60

I don't think these should be needed for UEFI targets.

llvm/test/ExecutionEngine/RuntimeDyld/X86/coff-alignment.ll

4 ↗

(On Diff #528064)

Should this be uefi?

llvm/test/Instrumentation/InstrProfiling/profiling.ll

10 ↗

(On Diff #528064)

Should this be uefi?

llvm/test/Transforms/PGOProfile/comdat_rename.ll

3 ↗

(On Diff #528064)

Should this be uefi?

[phosek]

I'd omit the lit test cases for now since they're not necessary. There should be a test case in https://github.com/llvm/llvm-project/blob/86b6ac5d54d7fe5cd21beff64b5c2194b1368bdf/llvm/unittests/TargetParser/TripleTest.cpp though.

[Prabhuk]

Update the test. Remove unnecessary items in UEFI toolchain.

[Prabhuk]

Updated commit message.

[phosek]

Can you also provide description for this change (this should be the same you'll use for the Git message).

llvm/include/llvm/MC/TargetRegistry.h

558

Nit: phrasing.

llvm/lib/MC/MCContext.cpp

96

Nit: update the error message.

llvm/lib/Target/X86/MCTargetDesc/X86AsmBackend.cpp

1554

Nit: consistent case in assert messages.

clang/lib/Basic/Targets.cpp

case llvm::Triple::x86_64:
     case llvm::Triple::FreeBSD:
       return new FreeBSDTargetInfo<X86_64TargetInfo>(Triple, Opts);
     case llvm::Triple::Fuchsia:
       return new FuchsiaTargetInfo<X86_64TargetInfo>(Triple, Opts);
     case llvm::Triple::KFreeBSD:
       return new KFreeBSDTargetInfo<X86_64TargetInfo>(Triple, Opts);
     case llvm::Triple::Solaris:
       return new SolarisTargetInfo<X86_64TargetInfo>(Triple, Opts);
+    case llvm::Triple::UEFI:
+      return new UEFIX86_64TargetInfo(Triple, Opts);
     case llvm::Triple::Win32: {
       switch (Triple.getEnvironment()) {
       case llvm::Triple::Cygnus:
         return new CygwinX86_64TargetInfo(Triple, Opts);
       case llvm::Triple::GNU:
         return new MinGWX86_64TargetInfo(Triple, Opts);
       case llvm::Triple::MSVC:
       default: // Assume MSVC for unknown environments

clang/lib/Basic/Targets/OSTargets.h

ZOSTargetInfo(const llvm::Triple &Triple, const TargetOptions &Opts)
     this->MaxAlignedAttribute = 128;
     this->UseBitFieldTypeAlignment = false;
     this->UseZeroLengthBitfieldAlignment = true;
     this->UseLeadingZeroLengthBitfield = false;
     this->ZeroLengthBitfieldBoundary = 32;
   }
 };
 
+// UEFI target
+template <typename Target>
+class LLVM_LIBRARY_VISIBILITY UEFITargetInfo : public OSTargetInfo<Target> {
+protected:
+  void getOSDefines(const LangOptions &Opts, const llvm::Triple &Triple,
+                    MacroBuilder &Builder) const override {
+    Builder.defineMacro("__UEFI__");
+  }
+
+public:
+  UEFITargetInfo(const llvm::Triple &Triple, const TargetOptions &Opts)
+      : OSTargetInfo<Target>(Triple, Opts) {
+    this->WCharType = TargetInfo::UnsignedShort;
+    this->WIntType = TargetInfo::UnsignedShort;
+  }
+};
+
 void addWindowsDefines(const llvm::Triple &Triple, const LangOptions &Opts,
                        MacroBuilder &Builder);
 
 // Windows target
 template <typename Target>
 class LLVM_LIBRARY_VISIBILITY WindowsTargetInfo : public OSTargetInfo<Target> {
 protected:
   void getOSDefines(const LangOptions &Opts, const llvm::Triple &Triple,

 };
 
 // Fuchsia Target
 template <typename Target>
 class LLVM_LIBRARY_VISIBILITY FuchsiaTargetInfo : public OSTargetInfo<Target> {
 protected:
   void getOSDefines(const LangOptions &Opts, const llvm::Triple &Triple,
                     MacroBuilder &Builder) const override {
     Builder.defineMacro("__Fuchsia__");
     Builder.defineMacro("__ELF__");
     if (Opts.POSIXThreads)
       Builder.defineMacro("_REENTRANT");
     // Required by the libc++ locale support.
     if (Opts.CPlusPlus)
       Builder.defineMacro("_GNU_SOURCE");
     Builder.defineMacro("__Fuchsia_API_level__", Twine(Opts.FuchsiaAPILevel));
     this->PlatformName = "fuchsia";

clang/lib/Basic/Targets/X86.h

if (hasFeature("cx16"))
       MaxAtomicInlineWidth = 128;
   }
 
   ArrayRef<Builtin::Info> getTargetBuiltins() const override;
 
   bool hasBitIntType() const override { return true; }
 };
 
+// x86-64 UEFI target
+class LLVM_LIBRARY_VISIBILITY UEFIX86_64TargetInfo
+    : public UEFITargetInfo<X86_64TargetInfo> {
+public:
+  UEFIX86_64TargetInfo(const llvm::Triple &Triple, const TargetOptions &Opts)
+      : UEFITargetInfo<X86_64TargetInfo>(Triple, Opts) {
+    LongWidth = LongAlign = 32;
+    DoubleAlign = LongLongAlign = 64;
+    IntMaxType = SignedLongLong;
+    Int64Type = SignedLongLong;
+    SizeType = UnsignedLongLong;
+    PtrDiffType = SignedLongLong;
+    IntPtrType = SignedLongLong;
+    LongDoubleWidth = LongDoubleAlign = 64;
+    LongDoubleFormat = &llvm::APFloat::IEEEdouble();
+  }
+
+  void getTargetDefines(const LangOptions &Opts,
+                        MacroBuilder &Builder) const override {
+    Builder.defineMacro("_M_X64", "100");
+    Builder.defineMacro("_M_AMD64", "100");
+    getOSDefines(Opts, X86TargetInfo::getTriple(), Builder);
+  }
+
+  BuiltinVaListKind getBuiltinVaListKind() const override {
+    return TargetInfo::CharPtrBuiltinVaList;
+  }
+
+  CallingConvCheckResult checkCallingConvention(CallingConv CC) const override {
+    switch (CC) {
+    case CC_X86StdCall:
+    case CC_X86ThisCall:
+    case CC_X86FastCall:
+      return CCCR_Ignore;
+    case CC_C:
+    case CC_X86VectorCall:
+    case CC_IntelOclBicc:
+    case CC_PreserveMost:
+    case CC_PreserveAll:
+    case CC_X86_64SysV:
+    case CC_Swift:
+    case CC_SwiftAsync:
+    case CC_X86RegCall:
+    case CC_OpenCLKernel:
+      return CCCR_OK;
+    default:
+      return CCCR_Warning;
+    }
+  }
+
+  TargetInfo::CallingConvKind
+  getCallingConvKind(bool ClangABICompat4) const override {
+    return CCK_MicrosoftWin64;
+  }
+};
+
 // x86-64 Windows target
 class LLVM_LIBRARY_VISIBILITY WindowsX86_64TargetInfo
     : public WindowsTargetInfo<X86_64TargetInfo> {
 public:
   WindowsX86_64TargetInfo(const llvm::Triple &Triple, const TargetOptions &Opts)
       : WindowsTargetInfo<X86_64TargetInfo>(Triple, Opts) {
     LongWidth = LongAlign = 32;
     DoubleAlign = LongLongAlign = 64;

clang/lib/Driver/CMakeLists.txt

add_clang_library(clangDriver
   ToolChains/NaCl.cpp
   ToolChains/NetBSD.cpp
   ToolChains/OpenBSD.cpp
   ToolChains/PS4CPU.cpp
   ToolChains/RISCVToolchain.cpp
   ToolChains/Solaris.cpp
   ToolChains/SPIRV.cpp
   ToolChains/TCE.cpp
+  ToolChains/UEFI.cpp
   ToolChains/VEToolchain.cpp
   ToolChains/WebAssembly.cpp
   ToolChains/XCore.cpp
   ToolChains/PPCLinux.cpp
   ToolChains/PPCFreeBSD.cpp
   ToolChains/InterfaceStubs.cpp
   ToolChains/ZOS.cpp
   Types.cpp

clang/lib/Driver/Driver.cpp

 #include "ToolChains/OpenBSD.h"
 #include "ToolChains/PPCFreeBSD.h"
 #include "ToolChains/PPCLinux.h"
 #include "ToolChains/PS4CPU.h"
 #include "ToolChains/RISCVToolchain.h"
 #include "ToolChains/SPIRV.h"
 #include "ToolChains/Solaris.h"
 #include "ToolChains/TCE.h"
+#include "ToolChains/UEFI.h"
 #include "ToolChains/VEToolchain.h"
 #include "ToolChains/WebAssembly.h"
 #include "ToolChains/XCore.h"
 #include "ToolChains/ZOS.h"
 #include "clang/Basic/TargetID.h"
 #include "clang/Basic/Version.h"
 #include "clang/Config/config.h"
 #include "clang/Driver/Action.h"
static llvm::Triple computeTargetTriple(const Driver &D,
   if (A && Target.isRISCV()) {
     StringRef ArchName = A->getValue();
     if (ArchName.startswith_insensitive("rv32"))
       Target.setArch(llvm::Triple::riscv32);
     else if (ArchName.startswith_insensitive("rv64"))
       Target.setArch(llvm::Triple::riscv64);
   }
 
+  // If target is UEFI set default object format
+  if (Target.isUEFI()) {
+    Target.setObjectFormat(llvm::Triple::COFF);
+  }
+
   return Target;
 }
 
 // Parse the LTO options and record the type of LTO compilation
 // based on which -f(no-)?lto(=.*)? or -f(no-)?offload-lto(=.*)?
 // option occurs last.
 static driver::LTOKind parseLTOMode(Driver &D, const llvm::opt::ArgList &Args,
                                     OptSpecifier OptEq, OptSpecifier OptNeg) {
case llvm::Triple::Solaris:
       break;
     case llvm::Triple::AMDHSA:
       TC = std::make_unique<toolchains::ROCMToolChain>(*this, Target, Args);
       break;
     case llvm::Triple::AMDPAL:
     case llvm::Triple::Mesa3D:
       TC = std::make_unique<toolchains::AMDGPUToolChain>(*this, Target, Args);
       break;
+    case llvm::Triple::UEFI:
+      TC = std::make_unique<toolchains::UEFI>(*this, Target, Args);
+      break;
     case llvm::Triple::Win32:
       switch (Target.getEnvironment()) {
       default:
         if (Target.isOSBinFormatELF())
           TC = std::make_unique<toolchains::Generic_ELF>(*this, Target, Args);
         else if (Target.isOSBinFormatMachO())
           TC = std::make_unique<toolchains::MachO>(*this, Target, Args);
         else

clang/lib/Driver/ToolChains/UEFI.h

+//===--- UEFI.h - UEFI ToolChain Implementations ----------*- 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_LIB_DRIVER_TOOLCHAINS_UEFI_H
+#define LLVM_CLANG_LIB_DRIVER_TOOLCHAINS_UEFI_H
+#include "clang/Driver/ToolChain.h"
+
+namespace clang {
+namespace driver {
+
+namespace toolchains {
+
+class LLVM_LIBRARY_VISIBILITY UEFI : public ToolChain {
+public:
+  UEFI(const Driver &D, const llvm::Triple &Triple,
+       const llvm::opt::ArgList &Args);
+
+  bool IsIntegratedAssemblerDefault() const override;
+  bool IsUnwindTablesDefault(const llvm::opt::ArgList &Args) const override;
+  bool isPICDefault() const override;
+  bool isPIEDefault(const llvm::opt::ArgList &Args) const override;
+  bool isPICDefaultForced() const override;
+};
+} // namespace toolchains
+} // namespace driver
+} // namespace clang
+#endif // LLVM_CLANG_LIB_DRIVER_TOOLCHAINS_UEFI_H

clang/lib/Driver/ToolChains/UEFI.cpp

+//===--- UEFI.h - UEFI ToolChain Implementations ----------*- 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 "UEFI.h"
+#include "CommonArgs.h"
+#include "Darwin.h"
+#include "clang/Basic/CharInfo.h"
+#include "clang/Basic/Version.h"
+#include "clang/Config/config.h"
+#include "clang/Driver/Compilation.h"
+#include "clang/Driver/Driver.h"
+#include "clang/Driver/Options.h"
+#include "clang/Driver/SanitizerArgs.h"
+#include "llvm/ADT/StringExtras.h"
+#include "llvm/ADT/StringSwitch.h"
+#include "llvm/Option/Arg.h"
+#include "llvm/Option/ArgList.h"
+#include "llvm/Support/FileSystem.h"
+#include "llvm/Support/Host.h"
+#include "llvm/Support/MemoryBuffer.h"
+#include "llvm/Support/Process.h"
+#include "llvm/Support/VirtualFileSystem.h"
+
+using namespace clang::driver;
+using namespace clang::driver::toolchains;
+using namespace clang;
+using namespace llvm::opt;
+
+UEFI::UEFI(const Driver &D, const llvm::Triple &Triple, const ArgList &Args)
+    : ToolChain(D, Triple, Args) {
+  getProgramPaths().push_back(getDriver().getInstalledDir());
+  if (getDriver().getInstalledDir() != getDriver().Dir)
+    getProgramPaths().push_back(getDriver().Dir);
+}
+
+bool UEFI::IsUnwindTablesDefault(const ArgList &Args) const {
+  // TODO(prabhukr):: What about x86_32?
+  return getArch() == llvm::Triple::x86_64 || getArch() == llvm::Triple::arm ||
+         getArch() == llvm::Triple::thumb || getArch() == llvm::Triple::aarch64;
+}
+
+bool UEFI::isPICDefault() const {
+  return getArch() == llvm::Triple::x86_64 ||
+         getArch() == llvm::Triple::aarch64;
+}
+
+bool UEFI::isPIEDefault(const llvm::opt::ArgList &Args) const { return false; }
+
+bool UEFI::isPICDefaultForced() const {
+  return getArch() == llvm::Triple::x86_64 ||
+         getArch() == llvm::Triple::aarch64;
+}
+
+bool UEFI::IsIntegratedAssemblerDefault() const { return true; }
 No newline at end of file

llvm/include/llvm/ADT/Triple.h

enum OSType {
     IOS,
     KFreeBSD,
     Linux,
     Lv2,        // PS3
     MacOSX,
     NetBSD,
     OpenBSD,
     Solaris,
+    UEFI,
     Win32,
     ZOS,
     Haiku,
     Minix,
     RTEMS,
     NaCl,       // Native Client
     AIX,
     CUDA,       // NVIDIA CUDA
bool isOSContiki() const {
     return getOS() == Triple::Contiki;
   }
 
   /// Tests whether the OS is Haiku.
   bool isOSHaiku() const {
     return getOS() == Triple::Haiku;
   }
 
+  /// Tests whether the OS is UEFI.
+  bool isUEFI() const {
+    return getOS() == Triple::UEFI;
+  }
+
   /// Tests whether the OS is Windows.
   bool isOSWindows() const {
     return getOS() == Triple::Win32;
   }
 
   /// Checks if the environment is MSVC.
   bool isKnownWindowsMSVCEnvironment() const {
     return isOSWindows() && getEnvironment() == Triple::MSVC;

llvm/include/llvm/MC/TargetRegistry.h

MCStreamer *createMCObjectStreamer(const Triple &T, MCContext &Ctx,
                                      const MCSubtargetInfo &STI, bool RelaxAll,
                                      bool IncrementalLinkerCompatible,
                                      bool DWARFMustBeAtTheEnd) const {
     MCStreamer *S = nullptr;
     switch (T.getObjectFormat()) {
     case Triple::UnknownObjectFormat:
       llvm_unreachable("Unknown object format");
     case Triple::COFF:
-      assert(T.isOSWindows() && "only Windows COFF is supported");
+      assert((T.isOSWindows() || T.isUEFI()) &&
+             "only Windows and UEFI COFF are supported");
       S = COFFStreamerCtorFn(Ctx, std::move(TAB), std::move(OW),
                              std::move(Emitter), RelaxAll,
                              IncrementalLinkerCompatible);
       break;
     case Triple::MachO:
       if (MachOStreamerCtorFn)
         S = MachOStreamerCtorFn(Ctx, std::move(TAB), std::move(OW),
                                 std::move(Emitter), RelaxAll,

llvm/lib/MC/MCContext.cpp

if (SrcMgr && SrcMgr->getNumBuffers())
     MainFileName = std::string(SrcMgr->getMemoryBuffer(SrcMgr->getMainFileID())
                                    ->getBufferIdentifier());
 
   switch (TheTriple.getObjectFormat()) {
   case Triple::MachO:
     Env = IsMachO;
     break;
   case Triple::COFF:
-    if (!TheTriple.isOSWindows())
+    if (!TheTriple.isOSWindows() && !TheTriple.isUEFI())
       report_fatal_error(
           "Cannot initialize MC for non-Windows COFF object files.");
 
     Env = IsCOFF;
     break;
   case Triple::ELF:
     Env = IsELF;
     break;
   case Triple::Wasm:
     Env = IsWasm;

llvm/lib/Support/Triple.cpp

StringRef Triple::getOSTypeName(OSType Kind) {
   case NaCl: return "nacl";
   case NetBSD: return "netbsd";
   case OpenBSD: return "openbsd";
   case PS4: return "ps4";
   case PS5: return "ps5";
   case RTEMS: return "rtems";
   case Solaris: return "solaris";
   case TvOS: return "tvos";
+  case UEFI: return "uefi";
   case WASI: return "wasi";
   case WatchOS: return "watchos";
   case Win32: return "windows";
   case ZOS: return "zos";
   case ShaderModel: return "shadermodel";
   }
 
   llvm_unreachable("Invalid OSType");
return StringSwitch<Triple::OSType>(OSName)
     .StartsWith("ios", Triple::IOS)
     .StartsWith("kfreebsd", Triple::KFreeBSD)
     .StartsWith("linux", Triple::Linux)
     .StartsWith("lv2", Triple::Lv2)
     .StartsWith("macos", Triple::MacOSX)
     .StartsWith("netbsd", Triple::NetBSD)
     .StartsWith("openbsd", Triple::OpenBSD)
     .StartsWith("solaris", Triple::Solaris)
+    .StartsWith("uefi", Triple::UEFI)
     .StartsWith("win32", Triple::Win32)
     .StartsWith("windows", Triple::Win32)
     .StartsWith("zos", Triple::ZOS)
     .StartsWith("haiku", Triple::Haiku)
     .StartsWith("minix", Triple::Minix)
     .StartsWith("rtems", Triple::RTEMS)
     .StartsWith("nacl", Triple::NaCl)
     .StartsWith("aix", Triple::AIX)

llvm/lib/Target/X86/MCTargetDesc/X86AsmBackend.cpp

MCAsmBackend *llvm::createX86_32AsmBackend(const Target &T,
                                            const MCTargetOptions &Options) {
   const Triple &TheTriple = STI.getTargetTriple();
   if (TheTriple.isOSBinFormatMachO())
     return new DarwinX86AsmBackend(T, MRI, STI);
 
   if (TheTriple.isOSWindows() && TheTriple.isOSBinFormatCOFF())
     return new WindowsX86AsmBackend(T, false, STI);
 
+  if (TheTriple.isUEFI()) {
+    assert(TheTriple.isOSBinFormatCOFF() &&
+         "Only COFF format is supported in UEFI environment.");
+    // $TODO(prabhukr): Create a new UEFIX86AsmBackend
+    return new WindowsX86AsmBackend(T, false, STI);
+  }
+
   uint8_t OSABI = MCELFObjectTargetWriter::getOSABI(TheTriple.getOS());
 
   if (TheTriple.isOSIAMCU())
     return new ELFX86_IAMCUAsmBackend(T, OSABI, STI);
 
   return new ELFX86_32AsmBackend(T, OSABI, STI);
 }
 
 MCAsmBackend *llvm::createX86_64AsmBackend(const Target &T,
                                            const MCSubtargetInfo &STI,
                                            const MCRegisterInfo &MRI,
                                            const MCTargetOptions &Options) {
   const Triple &TheTriple = STI.getTargetTriple();
   if (TheTriple.isOSBinFormatMachO())
     return new DarwinX86AsmBackend(T, MRI, STI);
 
   if (TheTriple.isOSWindows() && TheTriple.isOSBinFormatCOFF())
     return new WindowsX86AsmBackend(T, true, STI);
 
+  if (TheTriple.isUEFI()) {
+    assert(TheTriple.isOSBinFormatCOFF() &&
+         "Only COFF format is supported in UEFI environment.");
+    // $TODO(prabhukr): Create a new UEFIX86AsmBackend
+    return new WindowsX86AsmBackend(T, true, STI);
+  }
+
   uint8_t OSABI = MCELFObjectTargetWriter::getOSABI(TheTriple.getOS());
 
   if (TheTriple.isX32())
     return new ELFX86_X32AsmBackend(T, OSABI, STI);
   return new ELFX86_64AsmBackend(T, OSABI, STI);
 }

llvm/lib/Target/X86/MCTargetDesc/X86MCAsmInfo.cpp

X86MCAsmInfoMicrosoftMASM::X86MCAsmInfoMicrosoftMASM(const Triple &Triple)
   AllowQuestionAtStartOfIdentifier = true;
   AllowDollarAtStartOfIdentifier = true;
   AllowAtAtStartOfIdentifier = true;
 }
 
 void X86MCAsmInfoGNUCOFF::anchor() { }
 
 X86MCAsmInfoGNUCOFF::X86MCAsmInfoGNUCOFF(const Triple &Triple) {
-  assert(Triple.isOSWindows() && "Windows is the only supported COFF target");
+  assert((Triple.isOSWindows() || Triple.isUEFI()) &&
+         "Windows and UEFI are the only supported COFF targets");
   if (Triple.getArch() == Triple::x86_64) {
     PrivateGlobalPrefix = ".L";
     PrivateLabelPrefix = ".L";
     CodePointerSize = 8;
     WinEHEncodingType = WinEH::EncodingType::Itanium;
     ExceptionsType = ExceptionHandling::WinEH;
   } else {
     ExceptionsType = ExceptionHandling::DwarfCFI;
   }
 
   AssemblerDialect = AsmWriterFlavor;
 
   TextAlignFillValue = 0x90;
 
   AllowAtInName = true;
 }

llvm/lib/Target/X86/MCTargetDesc/X86MCTargetDesc.cpp

MAI = new X86ELFMCAsmInfo(TheTriple);
              TheTriple.isWindowsCoreCLREnvironment()) {
     if (Options.getAssemblyLanguage().equals_insensitive("masm"))
       MAI = new X86MCAsmInfoMicrosoftMASM(TheTriple);
     else
       MAI = new X86MCAsmInfoMicrosoft(TheTriple);
   } else if (TheTriple.isOSCygMing() ||
              TheTriple.isWindowsItaniumEnvironment()) {
     MAI = new X86MCAsmInfoGNUCOFF(TheTriple);
+  } else if (TheTriple.isUEFI()) {
+    MAI = new X86MCAsmInfoGNUCOFF(TheTriple);
   } else {
     // The default is ELF.
     MAI = new X86ELFMCAsmInfo(TheTriple);
   }
 
   // Initialize initial frame state.
   // Calculate amount of bytes used for return address storing
   int stackGrowth = is64Bit ? -8 : -4;

llvm/lib/Target/X86/X86MCInstLower.cpp

if (isa<UndefValue>(COp)) {
     printConstant(CF->getValueAPF(), CS);
   } else {
     CS << "?";
   }
 }
 
 void X86AsmPrinter::EmitSEHInstruction(const MachineInstr *MI) {
   assert(MF->hasWinCFI() && "SEH_ instruction in function without WinCFI?");
-  assert(getSubtarget().isOSWindows() && "SEH_ instruction Windows only");
+  assert((getSubtarget().isOSWindows() || TM.getTargetTriple().isUEFI()) &&
+         "SEH_ instruction Windows and UEFI only");
 
   // Use the .cv_fpo directives if we're emitting CodeView on 32-bit x86.
   if (EmitFPOData) {
     X86TargetStreamer *XTS =
         static_cast<X86TargetStreamer *>(OutStreamer->getTargetStreamer());
     switch (MI->getOpcode()) {
     case X86::SEH_PushReg:
       XTS->emitFPOPushReg(MI->getOperand(0).getImm());