diff --git a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index 2e63cd9b4481c..e164a196ba72d 100644
--- a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -4096,7 +4096,8 @@ const MCExpr *AsmPrinter::lowerBlockAddressConstant(const BlockAddress &BA) {
 
 /// GetCPISymbol - Return the symbol for the specified constant pool entry.
 MCSymbol *AsmPrinter::GetCPISymbol(unsigned CPID) const {
-  if (getSubtargetInfo().getTargetTriple().isWindowsMSVCEnvironment()) {
+  if (getSubtargetInfo().getTargetTriple().isWindowsMSVCEnvironment() ||
+      getSubtargetInfo().getTargetTriple().isUEFI()) {
     const MachineConstantPoolEntry &CPE =
         MF->getConstantPool()->getConstants()[CPID];
     if (!CPE.isMachineConstantPoolEntry()) {
diff --git a/llvm/lib/IR/Mangler.cpp b/llvm/lib/IR/Mangler.cpp
index 3b9c00cf993f3..cba8ee8c707df 100644
--- a/llvm/lib/IR/Mangler.cpp
+++ b/llvm/lib/IR/Mangler.cpp
@@ -223,7 +223,8 @@ void llvm::emitLinkerFlagsForGlobalCOFF(raw_ostream &OS, const GlobalValue *GV,
     bool NeedQuotes = GV->hasName() && !canBeUnquotedInDirective(GV->getName());
     if (NeedQuotes)
       OS << "\"";
-    if (TT.isWindowsGNUEnvironment() || TT.isWindowsCygwinEnvironment()) {
+    if (TT.isWindowsGNUEnvironment() || TT.isWindowsCygwinEnvironment() ||
+        TT.isUEFI()) {
       std::string Flag;
       raw_string_ostream FlagOS(Flag);
       Mangler.getNameWithPrefix(FlagOS, GV, false);
@@ -249,7 +250,7 @@ void llvm::emitLinkerFlagsForGlobalCOFF(raw_ostream &OS, const GlobalValue *GV,
       OS << "\"";
 
     if (!GV->getValueType()->isFunctionTy()) {
-      if (TT.isWindowsMSVCEnvironment())
+      if (TT.isWindowsMSVCEnvironment() || TT.isUEFI())
         OS << ",DATA";
       else
         OS << ",data";
diff --git a/llvm/lib/Target/X86/MCTargetDesc/X86MCTargetDesc.cpp b/llvm/lib/Target/X86/MCTargetDesc/X86MCTargetDesc.cpp
index 1c4d68d5448d6..f552ca329a4af 100644
--- a/llvm/lib/Target/X86/MCTargetDesc/X86MCTargetDesc.cpp
+++ b/llvm/lib/Target/X86/MCTargetDesc/X86MCTargetDesc.cpp
@@ -444,7 +444,7 @@ static MCAsmInfo *createX86MCAsmInfo(const MCRegisterInfo &MRI,
     // Force the use of an ELF container.
     MAI = new X86ELFMCAsmInfo(TheTriple);
   } else if (TheTriple.isWindowsMSVCEnvironment() ||
-             TheTriple.isWindowsCoreCLREnvironment()) {
+             TheTriple.isWindowsCoreCLREnvironment() || TheTriple.isUEFI()) {
     if (Options.getAssemblyLanguage().equals_insensitive("masm"))
       MAI = new X86MCAsmInfoMicrosoftMASM(TheTriple);
     else
@@ -452,8 +452,6 @@ static MCAsmInfo *createX86MCAsmInfo(const MCRegisterInfo &MRI,
   } 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);
diff --git a/llvm/lib/Target/X86/X86CallingConv.td b/llvm/lib/Target/X86/X86CallingConv.td
index 0d087e057a2bd..82f6dfd5a3b07 100644
--- a/llvm/lib/Target/X86/X86CallingConv.td
+++ b/llvm/lib/Target/X86/X86CallingConv.td
@@ -284,7 +284,7 @@ def RetCC_X86Common : CallingConv<[
 
   // Long double types are always returned in FP0 (even with SSE),
   // except on Win64.
-  CCIfNotSubtarget<"isTargetWin64()", CCIfType<[f80], CCAssignToReg<[FP0, FP1]>>>
+  CCIfNotSubtarget<"isTargetWindowsOrUEFI64()", CCIfType<[f80], CCAssignToReg<[FP0, FP1]>>>
 ]>;
 
 // X86-32 C return-value convention.
@@ -495,6 +495,9 @@ def RetCC_X86_64 : CallingConv<[
   // Mingw64 and native Win64 use Win64 CC
   CCIfSubtarget<"isTargetWin64()", CCDelegateTo<RetCC_X86_Win64_C>>,
 
+  // UEFI64 uses Win64 CC
+  CCIfSubtarget<"isTargetUEFI64()", CCDelegateTo<RetCC_X86_Win64_C>>,
+
   // Otherwise, drop to normal X86-64 CC
   CCDelegateTo<RetCC_X86_64_C>
 ]>;
@@ -1084,6 +1087,8 @@ def CC_X86_64 : CallingConv<[
 
   // Mingw64 and native Win64 use Win64 CC
   CCIfSubtarget<"isTargetWin64()", CCDelegateTo<CC_X86_Win64_C>>,
+  // UEFI uses Win64 CC
+  CCIfSubtarget<"isTargetUEFI64()", CCDelegateTo<CC_X86_Win64_C>>,
 
   // Otherwise, drop to normal X86-64 CC
   CCDelegateTo<CC_X86_64_C>
diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index ee2c72bc9cced..e51ad7f48645b 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -585,6 +585,7 @@ X86TargetLowering::X86TargetLowering(const X86TargetMachine &TM,
   // FIXME - use subtarget debug flags
   if (!Subtarget.isTargetDarwin() && !Subtarget.isTargetELF() &&
       !Subtarget.isTargetCygMing() && !Subtarget.isTargetWin64() &&
+      !Subtarget.isTargetUEFI64() &&
       TM.Options.ExceptionModel != ExceptionHandling::SjLj) {
     setOperationAction(ISD::EH_LABEL, MVT::Other, Expand);
   }
@@ -28087,7 +28088,6 @@ Register X86TargetLowering::getRegisterByName(const char* RegName, LLT VT,
                      .Case("r14", X86::R14)
                      .Case("r15", X86::R15)
                      .Default(0);
-
   if (Reg == X86::EBP || Reg == X86::RBP) {
     if (!TFI.hasFP(MF))
       report_fatal_error("register " + StringRef(RegName) +
@@ -28131,7 +28131,7 @@ Register X86TargetLowering::getExceptionSelectorRegister(
 }
 
 bool X86TargetLowering::needsFixedCatchObjects() const {
-  return Subtarget.isTargetWin64();
+  return Subtarget.isTargetWin64() || Subtarget.isTargetUEFI64();
 }
 
 SDValue X86TargetLowering::LowerEH_RETURN(SDValue Op, SelectionDAG &DAG) const {
@@ -61613,8 +61613,8 @@ bool X86TargetLowering::hasStackProbeSymbol(const MachineFunction &MF) const {
 /// Returns true if stack probing through inline assembly is requested.
 bool X86TargetLowering::hasInlineStackProbe(const MachineFunction &MF) const {
 
-  // No inline stack probe for Windows, they have their own mechanism.
-  if (Subtarget.isOSWindows() ||
+  // No inline stack probe for Windows and UEFI, they have their own mechanism.
+  if (Subtarget.isOSWindowsOrUEFI() ||
       MF.getFunction().hasFnAttribute("no-stack-arg-probe"))
     return false;
 
@@ -61638,9 +61638,9 @@ X86TargetLowering::getStackProbeSymbolName(const MachineFunction &MF) const {
   if (MF.getFunction().hasFnAttribute("probe-stack"))
     return MF.getFunction().getFnAttribute("probe-stack").getValueAsString();
 
-  // Generally, if we aren't on Windows, the platform ABI does not include
-  // support for stack probes, so don't emit them.
-  if (!Subtarget.isOSWindows() || Subtarget.isTargetMachO() ||
+  // Generally, if we aren't on Windows or UEFI, the platform ABI does not
+  // include support for stack probes, so don't emit them.
+  if (!(Subtarget.isOSWindowsOrUEFI()) || Subtarget.isTargetMachO() ||
       MF.getFunction().hasFnAttribute("no-stack-arg-probe"))
     return "";
 
diff --git a/llvm/lib/Target/X86/X86RegisterInfo.cpp b/llvm/lib/Target/X86/X86RegisterInfo.cpp
index b59d980172458..9a2fcde7f766c 100644
--- a/llvm/lib/Target/X86/X86RegisterInfo.cpp
+++ b/llvm/lib/Target/X86/X86RegisterInfo.cpp
@@ -60,6 +60,7 @@ X86RegisterInfo::X86RegisterInfo(const Triple &TT)
   // Cache some information.
   Is64Bit = TT.isArch64Bit();
   IsWin64 = Is64Bit && TT.isOSWindows();
+  IsUEFI64 = Is64Bit && TT.isUEFI();
 
   // Use a callee-saved register as the base pointer.  These registers must
   // not conflict with any ABI requirements.  For example, in 32-bit mode PIC
@@ -227,7 +228,7 @@ X86RegisterInfo::getPointerRegClass(const MachineFunction &MF,
 const TargetRegisterClass *
 X86RegisterInfo::getGPRsForTailCall(const MachineFunction &MF) const {
   const Function &F = MF.getFunction();
-  if (IsWin64 || (F.getCallingConv() == CallingConv::Win64))
+  if (IsWin64 || IsUEFI64 || (F.getCallingConv() == CallingConv::Win64))
     return &X86::GR64_TCW64RegClass;
   else if (Is64Bit)
     return &X86::GR64_TCRegClass;
@@ -389,7 +390,7 @@ X86RegisterInfo::getCalleeSavedRegs(const MachineFunction *MF) const {
       return IsWin64 ? CSR_Win64_SwiftError_SaveList
                      : CSR_64_SwiftError_SaveList;
 
-    if (IsWin64)
+    if (IsWin64 || IsUEFI64)
       return HasSSE ? CSR_Win64_SaveList : CSR_Win64_NoSSE_SaveList;
     if (CallsEHReturn)
       return CSR_64EHRet_SaveList;
@@ -456,7 +457,7 @@ X86RegisterInfo::getCallPreservedMask(const MachineFunction &MF,
   }
   case CallingConv::X86_RegCall:
     if (Is64Bit) {
-      if (IsWin64) {
+      if (IsWin64 || IsUEFI64) {
         return (HasSSE ? CSR_Win64_RegCall_RegMask :
                          CSR_Win64_RegCall_NoSSE_RegMask);
       } else {
@@ -514,7 +515,7 @@ X86RegisterInfo::getCallPreservedMask(const MachineFunction &MF,
     if (IsSwiftCC)
       return IsWin64 ? CSR_Win64_SwiftError_RegMask : CSR_64_SwiftError_RegMask;
 
-    return IsWin64 ? CSR_Win64_RegMask : CSR_64_RegMask;
+    return (IsWin64 || IsUEFI64) ? CSR_Win64_RegMask : CSR_64_RegMask;
   }
 
   return CSR_32_RegMask;
diff --git a/llvm/lib/Target/X86/X86RegisterInfo.h b/llvm/lib/Target/X86/X86RegisterInfo.h
index 5b6ac3c5da019..0f3ec2f6a6a7e 100644
--- a/llvm/lib/Target/X86/X86RegisterInfo.h
+++ b/llvm/lib/Target/X86/X86RegisterInfo.h
@@ -27,10 +27,14 @@ class X86RegisterInfo final : public X86GenRegisterInfo {
   ///
   bool Is64Bit;
 
-  /// IsWin64 - Is the target on of win64 flavours
+  /// IsWin64 - Is the target one of win64 flavours
   ///
   bool IsWin64;
 
+  /// IsUEFI64 - Is this UEFI 64 bit target
+  ///
+  bool IsUEFI64;
+
   /// SlotSize - Stack slot size in bytes.
   ///
   unsigned SlotSize;
diff --git a/llvm/lib/Target/X86/X86Subtarget.h b/llvm/lib/Target/X86/X86Subtarget.h
index 8f2d326a69398..e68420e4a3cb3 100644
--- a/llvm/lib/Target/X86/X86Subtarget.h
+++ b/llvm/lib/Target/X86/X86Subtarget.h
@@ -327,11 +327,17 @@ class X86Subtarget final : public X86GenSubtargetInfo {
 
   bool isTargetCygMing() const { return TargetTriple.isOSCygMing(); }
 
+  bool isOSWindows() const { return TargetTriple.isOSWindows(); }
+
   bool isUEFI() const { return TargetTriple.isUEFI(); }
 
-  bool isOSWindows() const { return TargetTriple.isOSWindows(); }
+  bool isOSWindowsOrUEFI() const { return TargetTriple.isOSWindowsOrUEFI(); }
+
+  bool isTargetWindowsOrUEFI64() const {
+    return isTargetWin64() || isTargetUEFI64();
+  }
 
-  bool isOSWindowsOrUEFI() const { return isOSWindows() || isUEFI(); }
+  bool isTargetUEFI64() const { return Is64Bit && isUEFI(); }
 
   bool isTargetWin64() const { return Is64Bit && isOSWindows(); }
 
@@ -348,8 +354,10 @@ class X86Subtarget final : public X86GenSubtargetInfo {
 
   bool isCallingConvWin64(CallingConv::ID CC) const {
     switch (CC) {
-    // On Win64, all these conventions just use the default convention.
+    // On Win64 and UEFI64, all these conventions just use the default
+    // convention.
     case CallingConv::C:
+      return isTargetWin64() || isTargetUEFI64();
     case CallingConv::Fast:
     case CallingConv::Tail:
     case CallingConv::Swift:
diff --git a/llvm/test/CodeGen/X86/mangle-question-mark.ll b/llvm/test/CodeGen/X86/mangle-question-mark.ll
index fea62ecad97c9..15fdae34bc4c3 100644
--- a/llvm/test/CodeGen/X86/mangle-question-mark.ll
+++ b/llvm/test/CodeGen/X86/mangle-question-mark.ll
@@ -2,6 +2,7 @@
 
 ; RUN: llc -mtriple i686-pc-win32 < %s | FileCheck %s --check-prefix=COFF
 ; RUN: llc -mtriple x86_64-pc-win32 < %s | FileCheck %s --check-prefix=COFF64
+; RUN: llc -mtriple x86_64-unknown-uefi < %s | FileCheck %s --check-prefix=COFF64
 ; RUN: llc -mtriple i686-linux-gnu < %s | FileCheck %s --check-prefix=ELF
 ; RUN: llc -mtriple i686-apple-darwin < %s | FileCheck %s --check-prefix=MACHO
 
diff --git a/llvm/test/CodeGen/X86/win32-preemption.ll b/llvm/test/CodeGen/X86/win32-preemption.ll
index 77dcfa7280daf..139a1e514556e 100644
--- a/llvm/test/CodeGen/X86/win32-preemption.ll
+++ b/llvm/test/CodeGen/X86/win32-preemption.ll
@@ -4,6 +4,8 @@
 ; RUN:     -relocation-model=pic     < %s | FileCheck --check-prefix=COFF %s
 ; RUN: llc -mtriple x86_64-pc-win32 \
 ; RUN:  -relocation-model=dynamic-no-pic < %s | FileCheck --check-prefix=COFF %s
+; RUN: llc -mtriple x86_64-unknown-uefi \
+; RUN:  -relocation-model=dynamic-no-pic < %s | FileCheck --check-prefix=COFF %s
 
 
 ; 32 bits