diff --git a/llvm/include/llvm/MC/MCWinEH.h b/llvm/include/llvm/MC/MCWinEH.h
--- a/llvm/include/llvm/MC/MCWinEH.h
+++ b/llvm/include/llvm/MC/MCWinEH.h
@@ -26,6 +26,14 @@
 
   Instruction(unsigned Op, MCSymbol *L, unsigned Reg, unsigned Off)
     : Label(L), Offset(Off), Register(Reg), Operation(Op) {}
+
+  bool operator==(const Instruction &I) const {
+    // Check whether two instructions refer to the same operation
+    // applied at a different spot (i.e. pointing at a different label).
+    return Offset == I.Offset && Register == I.Register &&
+           Operation == I.Operation;
+  }
+  bool operator!=(const Instruction &I) const { return !(*this == I); }
 };
 
 struct FrameInfo {
diff --git a/llvm/lib/MC/MCWin64EH.cpp b/llvm/lib/MC/MCWin64EH.cpp
--- a/llvm/lib/MC/MCWin64EH.cpp
+++ b/llvm/lib/MC/MCWin64EH.cpp
@@ -264,8 +264,7 @@
   return value;
 }
 
-static uint32_t
-ARM64CountOfUnwindCodes(const std::vector<WinEH::Instruction> &Insns) {
+static uint32_t ARM64CountOfUnwindCodes(ArrayRef<WinEH::Instruction> Insns) {
   uint32_t Count = 0;
   for (const auto &I : Insns) {
     switch (static_cast<Win64EH::UnwindOpcodes>(I.Operation)) {
@@ -553,18 +552,23 @@
     // Convert 2-byte opcodes into equivalent 1-byte ones.
     if (Inst.Operation == Win64EH::UOP_SaveRegP && Inst.Register == 29) {
       Inst.Operation = Win64EH::UOP_SaveFPLR;
+      Inst.Register = -1;
     } else if (Inst.Operation == Win64EH::UOP_SaveRegPX &&
                Inst.Register == 29) {
       Inst.Operation = Win64EH::UOP_SaveFPLRX;
+      Inst.Register = -1;
     } else if (Inst.Operation == Win64EH::UOP_SaveRegPX &&
                Inst.Register == 19 && Inst.Offset <= 248) {
       Inst.Operation = Win64EH::UOP_SaveR19R20X;
+      Inst.Register = -1;
     } else if (Inst.Operation == Win64EH::UOP_AddFP && Inst.Offset == 0) {
       Inst.Operation = Win64EH::UOP_SetFP;
     } else if (Inst.Operation == Win64EH::UOP_SaveRegP &&
                Inst.Register == PrevRegister + 2 &&
                Inst.Offset == PrevOffset + 16) {
       Inst.Operation = Win64EH::UOP_SaveNext;
+      Inst.Register = -1;
+      Inst.Offset = 0;
       // Intentionally not creating UOP_SaveNext for float register pairs,
       // as current versions of Windows (up to at least 20.04) is buggy
       // regarding SaveNext for float pairs.
@@ -601,6 +605,47 @@
   }
 }
 
+static int checkPackedEpilog(MCStreamer &streamer, WinEH::FrameInfo *info,
+                             int PrologCodeBytes) {
+  // Can only pack if there's one single epilog
+  if (info->EpilogMap.size() != 1)
+    return -1;
+
+  const std::vector<WinEH::Instruction> &Epilog =
+      info->EpilogMap.begin()->second;
+
+  // Can pack if the epilog is a subset of the prolog but not vice versa
+  if (Epilog.size() > info->Instructions.size())
+    return -1;
+
+  // Check that the epilog actually is a perfect match for the end (backwrds)
+  // of the prolog.
+  for (int I = Epilog.size() - 1; I >= 0; I--) {
+    if (info->Instructions[I] != Epilog[Epilog.size() - 1 - I])
+      return -1;
+  }
+
+  // Check that the epilog actually is at the very end of the function,
+  // otherwise it can't be packed.
+  uint32_t DistanceFromEnd = (uint32_t)GetAbsDifference(
+      streamer, info->FuncletOrFuncEnd, info->EpilogMap.begin()->first);
+  if (DistanceFromEnd / 4 != Epilog.size())
+    return -1;
+
+  int Offset = ARM64CountOfUnwindCodes(
+      ArrayRef<WinEH::Instruction>(&info->Instructions[Epilog.size()],
+                                   info->Instructions.size() - Epilog.size()));
+
+  // Check that the offset and prolog size fits in the first word; it's
+  // unclear whether the epilog count in the extension word can be taken
+  // as packed epilog offset.
+  if (Offset > 31 || PrologCodeBytes > 124)
+    return -1;
+
+  info->EpilogMap.clear();
+  return Offset;
+}
+
 // Populate the .xdata section.  The format of .xdata on ARM64 is documented at
 // https://docs.microsoft.com/en-us/cpp/build/arm64-exception-handling
 static void ARM64EmitUnwindInfo(MCStreamer &streamer, WinEH::FrameInfo *info) {
@@ -679,6 +724,8 @@
   uint32_t PrologCodeBytes = ARM64CountOfUnwindCodes(info->Instructions);
   uint32_t TotalCodeBytes = PrologCodeBytes;
 
+  int PackedEpilogOffset = checkPackedEpilog(streamer, info, PrologCodeBytes);
+
   // Process epilogs.
   MapVector<MCSymbol *, uint32_t> EpilogInfo;
   // Epilogs processed so far.
@@ -711,15 +758,17 @@
   uint32_t CodeWordsMod = TotalCodeBytes % 4;
   if (CodeWordsMod)
     CodeWords++;
-  uint32_t EpilogCount = info->EpilogMap.size();
+  uint32_t EpilogCount =
+      PackedEpilogOffset >= 0 ? PackedEpilogOffset : info->EpilogMap.size();
   bool ExtensionWord = EpilogCount > 31 || TotalCodeBytes > 124;
   if (!ExtensionWord) {
     row1 |= (EpilogCount & 0x1F) << 22;
     row1 |= (CodeWords & 0x1F) << 27;
   }
-  // E is always 0 right now, TODO: packed epilog setup
   if (info->HandlesExceptions) // X
     row1 |= 1 << 20;
+  if (PackedEpilogOffset >= 0) // E
+    row1 |= 1 << 21;
   row1 |= FuncLength & 0x3FFFF;
   streamer.emitInt32(row1);
 
diff --git a/llvm/test/CodeGen/AArch64/wineh3.mir b/llvm/test/CodeGen/AArch64/wineh3.mir
--- a/llvm/test/CodeGen/AArch64/wineh3.mir
+++ b/llvm/test/CodeGen/AArch64/wineh3.mir
@@ -8,9 +8,9 @@
 # CHECK-NEXT:      FunctionLength: 124
 # CHECK-NEXT:      Version: 0
 # CHECK-NEXT:      ExceptionData: No
-# CHECK-NEXT:      EpiloguePacked: No
-# CHECK-NEXT:      EpilogueScopes: 1
-# CHECK-NEXT:      ByteCodeLength: 32
+# CHECK-NEXT:      EpiloguePacked: Yes
+# CHECK-NEXT:      EpilogueOffset: 0
+# CHECK-NEXT:      ByteCodeLength: 16
 # CHECK-NEXT:      Prologue [
 # CHECK-NEXT:        0xc80c              ; stp x19, x20, [sp, #96]
 # CHECK-NEXT:        0xc88a              ; stp x21, x22, [sp, #80]
@@ -21,22 +21,6 @@
 # CHECK-NEXT:        0xda8d              ; stp d10, d11, [sp, #-112]!
 # CHECK-NEXT:        0xe4                ; end
 # CHECK-NEXT:      ]
-# CHECK-NEXT:      EpilogueScopes [
-# CHECK-NEXT:        EpilogueScope {
-# CHECK-NEXT:          StartOffset: 23
-# CHECK-NEXT:          EpilogueStartIndex: 15
-# CHECK-NEXT:          Opcodes [
-# CHECK-NEXT:            0xc80c              ; ldp x19, x20, [sp, #96]
-# CHECK-NEXT:            0xc88a              ; ldp x21, x22, [sp, #80]
-# CHECK-NEXT:            0xc908              ; ldp x23, x24, [sp, #64]
-# CHECK-NEXT:            0xc986              ; ldp x25, x26, [sp, #48]
-# CHECK-NEXT:            0xca04              ; ldp x27, x28, [sp, #32]
-# CHECK-NEXT:            0xd802              ; ldp d8, d9, [sp, #16]
-# CHECK-NEXT:            0xda8d              ; ldp d10, d11, [sp], #112
-# CHECK-NEXT:            0xe4                ; end
-# CHECK-NEXT:          ]
-# CHECK-NEXT:        }
-# CHECK-NEXT:      ]
 # CHECK-NEXT:    }
 ...
 ---
diff --git a/llvm/test/CodeGen/AArch64/wineh6.mir b/llvm/test/CodeGen/AArch64/wineh6.mir
--- a/llvm/test/CodeGen/AArch64/wineh6.mir
+++ b/llvm/test/CodeGen/AArch64/wineh6.mir
@@ -6,25 +6,19 @@
 # CHECK-NEXT:      FunctionLength: 92
 # CHECK-NEXT:      Version: 0
 # CHECK-NEXT:      ExceptionData: No
-# CHECK-NEXT:      EpiloguePacked: No
-# CHECK-NEXT:      EpilogueScopes: 1
-# CHECK-NEXT:      ByteCodeLength: 8
+# CHECK-NEXT:      EpiloguePacked: Yes
+# CHECK-NEXT:      EpilogueOffset: 1
+# CHECK-NEXT:      ByteCodeLength: 4
 # CHECK-NEXT:      Prologue [
 # CHECK-NEXT:        0x02                ; sub sp, #32
 # CHECK-NEXT:        0xe1                ; mov fp, sp
 # CHECK-NEXT:        0x81                ; stp x29, x30, [sp, #-16]!
 # CHECK-NEXT:        0xe4                ; end
 # CHECK-NEXT:      ]
-# CHECK-NEXT:      EpilogueScopes [
-# CHECK-NEXT:        EpilogueScope {
-# CHECK-NEXT:          StartOffset: 20
-# CHECK-NEXT:          EpilogueStartIndex: 4
-# CHECK-NEXT:          Opcodes [
-# CHECK-NEXT:            0xe1                ; mov sp, fp
-# CHECK-NEXT:            0x81                ; ldp x29, x30, [sp], #16
-# CHECK-NEXT:            0xe4                ; end
-# CHECK-NEXT:          ]
-# CHECK-NEXT:        }
+# CHECK-NEXT:      Epilogue [
+# CHECK-NEXT:        0xe1                ; mov sp, fp
+# CHECK-NEXT:        0x81                ; ldp x29, x30, [sp], #16
+# CHECK-NEXT:        0xe4                ; end
 # CHECK-NEXT:      ]
 # CHECK-NEXT:    }
 ...
diff --git a/llvm/test/CodeGen/AArch64/wineh7.mir b/llvm/test/CodeGen/AArch64/wineh7.mir
--- a/llvm/test/CodeGen/AArch64/wineh7.mir
+++ b/llvm/test/CodeGen/AArch64/wineh7.mir
@@ -6,9 +6,9 @@
 # CHECK-NEXT:      FunctionLength: 72
 # CHECK-NEXT:      Version: 0
 # CHECK-NEXT:      ExceptionData: No
-# CHECK-NEXT:      EpiloguePacked: No
-# CHECK-NEXT:      EpilogueScopes: 1
-# CHECK-NEXT:      ByteCodeLength: 16
+# CHECK-NEXT:      EpiloguePacked: Yes
+# CHECK-NEXT:      EpilogueOffset: 0
+# CHECK-NEXT:      ByteCodeLength: 8
 # CHECK-NEXT:      Prologue [
 # CHECK-NEXT:        0xe204              ; add fp, sp, #32
 # CHECK-NEXT:        0x44                ; stp x29, x30, [sp, #32]
@@ -16,19 +16,6 @@
 # CHECK-NEXT:        0xcc85              ; stp x21, x22, [sp, #-48]!
 # CHECK-NEXT:        0xe4                ; end
 # CHECK-NEXT:      ]
-# CHECK-NEXT:      EpilogueScopes [
-# CHECK-NEXT:        EpilogueScope {
-# CHECK-NEXT:          StartOffset: 13
-# CHECK-NEXT:          EpilogueStartIndex: 8
-# CHECK-NEXT:          Opcodes [
-# CHECK-NEXT:            0xe204              ; sub sp, fp, #32
-# CHECK-NEXT:            0x44                ; ldp x29, x30, [sp, #32]
-# CHECK-NEXT:            0xc802              ; ldp x19, x20, [sp, #16]
-# CHECK-NEXT:            0xcc85              ; ldp x21, x22, [sp], #48
-# CHECK-NEXT:            0xe4                ; end
-# CHECK-NEXT:          ]
-# CHECK-NEXT:        }
-# CHECK-NEXT:      ]
 # CHECK-NEXT:    }
 # CHECK-NEXT:  }
 
diff --git a/llvm/test/MC/AArch64/seh-packed-epilog.s b/llvm/test/MC/AArch64/seh-packed-epilog.s
new file mode 100644
--- /dev/null
+++ b/llvm/test/MC/AArch64/seh-packed-epilog.s
@@ -0,0 +1,187 @@
+// This test checks that the epilogue is packed where possible.
+
+// RUN: llvm-mc -triple aarch64-pc-win32 -filetype=obj %s -o %t.o
+// RUN: llvm-readobj -u %t.o | FileCheck %s
+
+// CHECK:      UnwindInformation [
+// CHECK-NEXT:   RuntimeFunction {
+// CHECK-NEXT:     Function: func
+// CHECK-NEXT:     ExceptionRecord: .xdata
+// CHECK-NEXT:     ExceptionData {
+// CHECK-NEXT:       FunctionLength:
+// CHECK-NEXT:       Version:
+// CHECK-NEXT:       ExceptionData:
+// CHECK-NEXT:       EpiloguePacked: Yes
+// CHECK-NEXT:       EpilogueOffset: 2
+// CHECK-NEXT:       ByteCodeLength:
+// CHECK-NEXT:       Prologue [
+// CHECK-NEXT:         0xdc04              ; str d8, [sp, #32]
+// CHECK-NEXT:         0xe1                ; mov fp, sp
+// CHECK-NEXT:         0x42                ; stp x29, x30, [sp, #16]
+// CHECK-NEXT:         0x85                ; stp x29, x30, [sp, #-48]!
+// CHECK-NEXT:         0xe6                ; save next
+// CHECK-NEXT:         0x24                ; stp x19, x20, [sp, #-32]!
+// CHECK-NEXT:         0xc842              ; stp x20, x21, [sp, #16]
+// CHECK-NEXT:         0x03                ; sub sp, #48
+// CHECK-NEXT:         0xe4                ; end
+// CHECK-NEXT:       ]
+// CHECK-NEXT:       Epilogue [
+// CHECK-NEXT:         0xe1                ; mov sp, fp
+// CHECK-NEXT:         0x42                ; ldp x29, x30, [sp, #16]
+// CHECK-NEXT:         0x85                ; ldp x29, x30, [sp], #48
+// CHECK-NEXT:         0xe6                ; restore next
+// CHECK-NEXT:         0x24                ; ldp x19, x20, [sp], #32
+// CHECK-NEXT:         0xc842              ; ldp x20, x21, [sp, #16]
+// CHECK-NEXT:         0x03                ; add sp, #48
+// CHECK-NEXT:         0xe4                ; end
+// CHECK-NEXT:       ]
+// CHECK-NEXT:     }
+// CHECK-NEXT:   }
+// CHECK:        RuntimeFunction {
+// CHECK-NEXT:     Function: packed2
+// CHECK-NEXT:     ExceptionRecord:
+// CHECK-NEXT:     ExceptionData {
+// CHECK:            ExceptionData:
+// CHECK-NEXT:       EpiloguePacked: Yes
+// CHECK:        RuntimeFunction {
+// CHECK-NEXT:     Function: nonpacked1
+// CHECK-NEXT:     ExceptionRecord:
+// CHECK-NEXT:     ExceptionData {
+// CHECK:            ExceptionData:
+// CHECK-NEXT:       EpiloguePacked: No
+// CHECK:        RuntimeFunction {
+// CHECK-NEXT:     Function: nonpacked2
+// CHECK-NEXT:     ExceptionRecord:
+// CHECK-NEXT:     ExceptionData {
+// CHECK:            ExceptionData:
+// CHECK-NEXT:       EpiloguePacked: No
+// CHECK:        RuntimeFunction {
+// CHECK-NEXT:     Function: nonpacked3
+// CHECK-NEXT:     ExceptionRecord:
+// CHECK-NEXT:     ExceptionData {
+// CHECK:            ExceptionData:
+// CHECK-NEXT:       EpiloguePacked: No
+
+    .text
+    .globl func
+    .seh_proc func
+func:
+    sub sp, sp, #48
+    .seh_stackalloc 48
+    // Check that canonical opcode forms (r19r20_x, fplr, fplr_x, save_next,
+    // set_fp) are treated as a match even if one (in prologue or epilogue)
+    // was simplified from the more generic opcodes.
+    stp x20, x21, [sp, #16]
+    .seh_save_regp x20, 16
+    stp x19, x20, [sp, #-32]!
+    .seh_save_r19r20_x 32
+    stp x21, x22, [sp, #16]
+    .seh_save_regp x21, 16
+    stp x29, x30, [sp, #-48]!
+    .seh_save_regp_x x29, 48
+    stp x29, x30, [sp, #16]
+    .seh_save_regp x29, 16
+    add x29, sp, #0
+    .seh_add_fp 0
+    str d8, [sp, #32]
+    .seh_save_freg d8, 32
+    .seh_endprologue
+
+    nop
+
+    .seh_startepilogue
+    mov sp, x29
+    .seh_set_fp
+    ldp x29, x30, [sp, #16]
+    .seh_save_fplr 16
+    ldp x29, x30, [sp, #-48]!
+    .seh_save_fplr_x 48
+    ldp x21, x22, [sp, #16]
+    .seh_save_next
+    ldp x19, x20, [sp], #32
+    .seh_save_regp_x x19, 32
+    ldp x20, x21, [sp, #16]
+    .seh_save_regp x20, 16
+    add sp, sp, #48
+    .seh_stackalloc 48
+    .seh_endepilogue
+    ret
+    .seh_endproc
+
+
+    // Test a perfectly matching epilog with no offset.
+    .seh_proc packed2
+packed2:
+    sub sp, sp, #48
+    .seh_stackalloc 48
+    stp x29, lr, [sp, #-32]!
+    .seh_save_fplr_x 32
+    .seh_endprologue
+    nop
+    .seh_startepilogue
+    ldp x29, lr, [sp], #32
+    .seh_save_fplr_x 32
+    add sp, sp, #48
+    .seh_stackalloc 48
+    .seh_endepilogue
+    ret
+    .seh_endproc
+
+
+    .seh_proc nonpacked1
+nonpacked1:
+    sub sp, sp, #48
+    .seh_stackalloc 48
+    .seh_endprologue
+
+    nop
+    .seh_startepilogue
+    add sp, sp, #48
+    .seh_stackalloc 48
+    .seh_endepilogue
+    // This epilogue isn't packed with the prologue, as it doesn't align with
+    // the end of the function (one extra nop before the ret).
+    nop
+    ret
+    .seh_endproc
+
+
+    .seh_proc nonpacked2
+nonpacked2:
+    sub sp, sp, #48
+    .seh_stackalloc 48
+    sub sp, sp, #32
+    .seh_stackalloc 32
+    .seh_endprologue
+
+    nop
+    .seh_startepilogue
+    // Not packed; the epilogue mismatches at the second opcode.
+    add sp, sp, #16
+    .seh_stackalloc 16
+    add sp, sp, #48
+    .seh_stackalloc 48
+    .seh_endepilogue
+    ret
+    .seh_endproc
+
+    .seh_proc nonpacked3
+nonpacked3:
+    sub sp, sp, #48
+    .seh_stackalloc 48
+    sub sp, sp, #32
+    .seh_stackalloc 32
+    .seh_endprologue
+
+    nop
+    .seh_startepilogue
+    // Not packed; the epilogue is longer than the prologue.
+    mov sp, x29
+    .seh_set_fp
+    add sp, sp, #32
+    .seh_stackalloc 32
+    add sp, sp, #48
+    .seh_stackalloc 48
+    .seh_endepilogue
+    ret
+    .seh_endproc
diff --git a/llvm/test/MC/AArch64/seh.s b/llvm/test/MC/AArch64/seh.s
--- a/llvm/test/MC/AArch64/seh.s
+++ b/llvm/test/MC/AArch64/seh.s
@@ -20,7 +20,7 @@
 // CHECK-NEXT:   }
 // CHECK:        Section {
 // CHECK:          Name: .xdata
-// CHECK:          RawDataSize: 56
+// CHECK:          RawDataSize: 52
 // CHECK:          RelocationCount: 1
 // CHECK:          Characteristics [
 // CHECK-NEXT:       ALIGN_4BYTES
@@ -41,7 +41,7 @@
 
 // CHECK-NEXT: Relocations [
 // CHECK-NEXT:   Section (4) .xdata {
-// CHECK-NEXT:     0x2C IMAGE_REL_ARM64_ADDR32NB __C_specific_handler
+// CHECK-NEXT:     0x28 IMAGE_REL_ARM64_ADDR32NB __C_specific_handler
 // CHECK-NEXT:   }
 // CHECK-NEXT:   Section (5) .pdata {
 // CHECK-NEXT:     0x0 IMAGE_REL_ARM64_ADDR32NB func
@@ -80,15 +80,9 @@
 // CHECK-NEXT:         0x01                ; sub sp, #16
 // CHECK-NEXT:         0xe4                ; end
 // CHECK-NEXT:       ]
-// CHECK-NEXT:       EpilogueScopes [
-// CHECK-NEXT:         EpilogueScope {
-// CHECK-NEXT:           StartOffset: 23
-// CHECK-NEXT:           EpilogueStartIndex: 33
-// CHECK-NEXT:           Opcodes [
-// CHECK-NEXT:             0x01                ; add sp, #16
-// CHECK-NEXT:             0xe4                ; end
-// CHECK-NEXT:           ]
-// CHECK-NEXT:         }
+// CHECK-NEXT:       Epilogue [
+// CHECK-NEXT:         0x01                ; add sp, #16
+// CHECK-NEXT:         0xe4                ; end
 // CHECK-NEXT:       ]
 // CHECK-NEXT:       ExceptionHandler [
 // CHECK-NEXT:         Routine: __C_specific_handler (0x0)