[AArch64][Windows] Add MC support for save_any_reg.

[efriedma]

Summary

Representing this as 12 separate operations is a bit ugly, but trying to represent the different modes using a bitfield seemed worse.

[mstorsjo]

Representing this as 12 separate operations is a bit ugly, but trying to represent the different modes using a bitfield seemed worse.

Yup, and there's a fairly limited amount of info you can store in the WinEH::Instruction class today, so I guess this looks reasonable.

Technically there's no need to have the assembly level directives mirror exactly the same 12 separate opcodes - we could consider e.g. checking whether the provided register name is in the range of x0-x30, d0-d31 or q0-q31 and pick the right opcode based on that - that would reduce the number of assembly directives down to 4 instead of 12. (That's the only aspect of this which is a public interface.) What do you think of that? Internally throughout the rest of the interfaces (AArch64TargetStreamer) it's probably easiest to keep all 12 separate entrypoints in any case.

llvm/lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp

6104

Nit: Missing space after ==

[efriedma]

That would be four directives, "seh_save_any_reg", seh_save_any_reg_p", "seh_save_any_reg_x", and "seh_save_any_reg_px"? I guess that works, although I'll have to reimplement the parseRegisterInRange() logic.

[mstorsjo]

In D135417#3843903, @efriedma wrote:

That would be four directives, "seh_save_any_reg", seh_save_any_reg_p", "seh_save_any_reg_x", and "seh_save_any_reg_px"? I guess that works, although I'll have to reimplement the parseRegisterInRange() logic.

Exactly.

I'm not entirely dead set on it, but I think it could be a nicer experience for the assembly directives and at least worth evaluating.

[efriedma]

Reduce to 4 user-visible asm directives. (Still 12 operations internally.)

[mstorsjo]

LGTM, thanks! This does look nicer to me in the end.

BTW, the process for contributing to the public docs on the unwind info format went really smoothly for me this time, so getting this opcode documented should hopefully go well too.

llvm/include/llvm/Support/Win64EH.h

enum UnwindOpcodes {
   UOP_AddFP,
   UOP_Nop,
   UOP_End,
   UOP_SaveNext,
   UOP_TrapFrame,
   UOP_Context,
   UOP_ClearUnwoundToCall,
   UOP_PACSignLR,
+  UOP_SaveAnyRegI,
+  UOP_SaveAnyRegIP,
+  UOP_SaveAnyRegD,
+  UOP_SaveAnyRegDP,
+  UOP_SaveAnyRegQ,
+  UOP_SaveAnyRegQP,
+  UOP_SaveAnyRegIX,
+  UOP_SaveAnyRegIPX,
+  UOP_SaveAnyRegDX,
+  UOP_SaveAnyRegDPX,
+  UOP_SaveAnyRegQX,
+  UOP_SaveAnyRegQPX,
+
   // The following set of unwind opcodes is for ARM.  They are documented at
   // https://docs.microsoft.com/en-us/cpp/build/arm-exception-handling
 
   // Stack allocations use UOP_AllocSmall, UOP_AllocLarge from above, plus
   // the following. AllocSmall, AllocLarge and AllocHuge represent a 16 bit
   // instruction, while the WideAlloc* opcodes represent a 32 bit instruction.
   // Small can represent a stack offset of 0x7f*4 (252) bytes, Medium can
   // represent up to 0x3ff*4 (4092) bytes, Large up to 0xffff*4 (262140) bytes,

llvm/lib/MC/MCWin64EH.cpp

case Win64EH::UOP_Context:
       Count += 1;
       break;
     case Win64EH::UOP_ClearUnwoundToCall:
       Count += 1;
       break;
     case Win64EH::UOP_PACSignLR:
       Count += 1;
       break;
+    case Win64EH::UOP_SaveAnyRegI:
+    case Win64EH::UOP_SaveAnyRegIP:
+    case Win64EH::UOP_SaveAnyRegD:
+    case Win64EH::UOP_SaveAnyRegDP:
+    case Win64EH::UOP_SaveAnyRegQ:
+    case Win64EH::UOP_SaveAnyRegQP:
+    case Win64EH::UOP_SaveAnyRegIX:
+    case Win64EH::UOP_SaveAnyRegIPX:
+    case Win64EH::UOP_SaveAnyRegDX:
+    case Win64EH::UOP_SaveAnyRegDPX:
+    case Win64EH::UOP_SaveAnyRegQX:
+    case Win64EH::UOP_SaveAnyRegQPX:
+      Count += 3;
+      break;
     }
   }
   return Count;
 }
 
 // Unwind opcode encodings and restrictions are documented at
 // https://docs.microsoft.com/en-us/cpp/build/arm64-exception-handling
 static void ARM64EmitUnwindCode(MCStreamer &streamer,
static void ARM64EmitUnwindCode(MCStreamer &streamer,
   case Win64EH::UOP_ClearUnwoundToCall:
     b = 0xEC;
     streamer.emitInt8(b);
     break;
   case Win64EH::UOP_PACSignLR:
     b = 0xFC;
     streamer.emitInt8(b);
     break;
+  case Win64EH::UOP_SaveAnyRegI:
+  case Win64EH::UOP_SaveAnyRegIP:
+  case Win64EH::UOP_SaveAnyRegD:
+  case Win64EH::UOP_SaveAnyRegDP:
+  case Win64EH::UOP_SaveAnyRegQ:
+  case Win64EH::UOP_SaveAnyRegQP:
+  case Win64EH::UOP_SaveAnyRegIX:
+  case Win64EH::UOP_SaveAnyRegIPX:
+  case Win64EH::UOP_SaveAnyRegDX:
+  case Win64EH::UOP_SaveAnyRegDPX:
+  case Win64EH::UOP_SaveAnyRegQX:
+  case Win64EH::UOP_SaveAnyRegQPX: {
+    // This assumes the opcodes are listed in the enum in a particular order.
+    int Op = inst.Operation - Win64EH::UOP_SaveAnyRegI;
+    int Writeback = Op / 6;
+    int Paired = Op % 2;
+    int Mode = (Op / 2) % 3;
+    int Offset = inst.Offset >> 3;
+    if (Writeback || Paired || Mode == 2)
+      Offset >>= 1;
+    if (Writeback)
+      --Offset;
+    b = 0xE7;
+    streamer.emitInt8(b);
+    assert(inst.Register < 32);
+    b = inst.Register | (Writeback << 5) | (Paired << 6);
+    streamer.emitInt8(b);
+    b = Offset | (Mode << 6);
+    streamer.emitInt8(b);
+    break;
+  }
   }
 }
 
 // Returns the epilog symbol of an epilog with the exact same unwind code
 // sequence, if it exists.  Otherwise, returns nullptr.
 // EpilogInstrs - Unwind codes for the current epilog.
 // Epilogs - Epilogs that potentialy match the current epilog.
 static MCSymbol*

llvm/lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp

private:
   bool parseDirectiveSEHSaveNext(SMLoc L);
   bool parseDirectiveSEHEpilogStart(SMLoc L);
   bool parseDirectiveSEHEpilogEnd(SMLoc L);
   bool parseDirectiveSEHTrapFrame(SMLoc L);
   bool parseDirectiveSEHMachineFrame(SMLoc L);
   bool parseDirectiveSEHContext(SMLoc L);
   bool parseDirectiveSEHClearUnwoundToCall(SMLoc L);
   bool parseDirectiveSEHPACSignLR(SMLoc L);
+  bool parseDirectiveSEHSaveAnyReg(SMLoc L, bool Paired, bool Writeback);
 
   bool validateInstruction(MCInst &Inst, SMLoc &IDLoc,
                            SmallVectorImpl<SMLoc> &Loc);
   bool MatchAndEmitInstruction(SMLoc IDLoc, unsigned &Opcode,
                                OperandVector &Operands, MCStreamer &Out,
                                uint64_t &ErrorInfo,
                                bool MatchingInlineAsm) override;
 /// @name Auto-generated Match Functions
else if (IsMachO) {
     else if (IDVal == ".seh_trap_frame")
       parseDirectiveSEHTrapFrame(Loc);
     else if (IDVal == ".seh_pushframe")
       parseDirectiveSEHMachineFrame(Loc);
     else if (IDVal == ".seh_context")
       parseDirectiveSEHContext(Loc);
     else if (IDVal == ".seh_clear_unwound_to_call")
       parseDirectiveSEHClearUnwoundToCall(Loc);
     else if (IDVal == ".seh_pac_sign_lr")
       parseDirectiveSEHPACSignLR(Loc);
+    else if (IDVal == ".seh_save_any_reg")
+      parseDirectiveSEHSaveAnyReg(Loc, false, false);
+    else if (IDVal == ".seh_save_any_reg_p")
+      parseDirectiveSEHSaveAnyReg(Loc, true, false);
+    else if (IDVal == ".seh_save_any_reg_x")
+      parseDirectiveSEHSaveAnyReg(Loc, false, true);
+    else if (IDVal == ".seh_save_any_reg_px")
+      parseDirectiveSEHSaveAnyReg(Loc, true, true);
     else
       return true;
   } else
     return true;
   return false;
 }
 
 static void ExpandCryptoAEK(AArch64::ArchKind ArchKind,

 
 /// parseDirectiveSEHPACSignLR
 /// ::= .seh_pac_sign_lr
 bool AArch64AsmParser::parseDirectiveSEHPACSignLR(SMLoc L) {
   getTargetStreamer().emitARM64WinCFIPACSignLR();
   return false;
 }
 
+/// parseDirectiveSEHSaveAnyReg
+/// ::= .seh_save_any_reg
+/// ::= .seh_save_any_reg_p
+/// ::= .seh_save_any_reg_x
+/// ::= .seh_save_any_reg_px
+bool AArch64AsmParser::parseDirectiveSEHSaveAnyReg(SMLoc L, bool Paired,
+                                                   bool Writeback) {
+  unsigned Reg;
+  SMLoc Start, End;
+  int64_t Offset;
+  if (check(ParseRegister(Reg, Start, End), getLoc(), "expected register") ||
+      parseComma() || parseImmExpr(Offset))
+    return true;
+
+  if (Reg == AArch64::FP || Reg == AArch64::LR ||
+      (Reg >= AArch64::X0 && Reg <= AArch64::X28)) {
+    if (Offset < 0 || Offset % (Paired || Writeback ? 16 : 8))
+      return Error(L, "invalid save_any_reg offset");
+    unsigned EncodedReg;
+    if (Reg == AArch64::FP)
+      EncodedReg = 29;
+    else if (Reg == AArch64::LR)
+      EncodedReg = 30;
+    else
+      EncodedReg = Reg - AArch64::X0;
+    if (Paired) {
+      if (Reg == AArch64::LR)
+        return Error(Start, "lr cannot be paired with another register");
+      if (Writeback)
+        getTargetStreamer().emitARM64WinCFISaveAnyRegIPX(EncodedReg, Offset);
+      else
+        getTargetStreamer().emitARM64WinCFISaveAnyRegIP(EncodedReg, Offset);
+    } else {
+      if (Writeback)
+        getTargetStreamer().emitARM64WinCFISaveAnyRegIX(EncodedReg, Offset);
+      else
+        getTargetStreamer().emitARM64WinCFISaveAnyRegI(EncodedReg, Offset);
+    }
+  } else if (Reg >= AArch64::D0 && Reg <= AArch64::D31) {
+    unsigned EncodedReg = Reg - AArch64::D0;
+    if (Offset < 0 || Offset % (Paired || Writeback ? 16 : 8))
+      return Error(L, "invalid save_any_reg offset");
+    if (Paired) {
+      if (Reg == AArch64::D31)
+        return Error(Start, "d31 cannot be paired with another register");
+      if (Writeback)
+        getTargetStreamer().emitARM64WinCFISaveAnyRegDPX(EncodedReg, Offset);
+      else
+        getTargetStreamer().emitARM64WinCFISaveAnyRegDP(EncodedReg, Offset);
+    } else {
+      if (Writeback)
+        getTargetStreamer().emitARM64WinCFISaveAnyRegDX(EncodedReg, Offset);
+      else
+        getTargetStreamer().emitARM64WinCFISaveAnyRegD(EncodedReg, Offset);
+    }
+  } else if (Reg >= AArch64::Q0 && Reg <= AArch64::Q31) {
+    unsigned EncodedReg = Reg - AArch64::Q0;
+    if (Offset < 0 || Offset % 16)
+      return Error(L, "invalid save_any_reg offset");
+    if (Paired) {
+      if (Reg == AArch64::Q31)
+        return Error(Start, "q31 cannot be paired with another register");
+      if (Writeback)
+        getTargetStreamer().emitARM64WinCFISaveAnyRegQPX(EncodedReg, Offset);
+      else
+        getTargetStreamer().emitARM64WinCFISaveAnyRegQP(EncodedReg, Offset);
+    } else {
+      if (Writeback)
+        getTargetStreamer().emitARM64WinCFISaveAnyRegQX(EncodedReg, Offset);
+      else
+        getTargetStreamer().emitARM64WinCFISaveAnyRegQ(EncodedReg, Offset);
+    }
+  } else {
+    return Error(Start, "save_any_reg register must be x, q or d register");
+  }
+  return false;
+}
+
 bool
 AArch64AsmParser::classifySymbolRef(const MCExpr *Expr,
                                     AArch64MCExpr::VariantKind &ELFRefKind,
                                     MCSymbolRefExpr::VariantKind &DarwinRefKind,
                                     int64_t &Addend) {
   ELFRefKind = AArch64MCExpr::VK_INVALID;
   DarwinRefKind = MCSymbolRefExpr::VK_None;
   Addend = 0;

llvm/lib/Target/AArch64/MCTargetDesc/AArch64ELFStreamer.cpp

class AArch64TargetAsmStreamer : public AArch64TargetStreamer {
   void emitARM64WinCFIContext() override { OS << "\t.seh_context\n"; }
   void emitARM64WinCFIClearUnwoundToCall() override {
     OS << "\t.seh_clear_unwound_to_call\n";
   }
   void emitARM64WinCFIPACSignLR() override {
     OS << "\t.seh_pac_sign_lr\n";
   }
 
+  void emitARM64WinCFISaveAnyRegI(unsigned Reg, int Offset) override {
+    OS << "\t.seh_save_any_reg\tx" << Reg << ", " << Offset << "\n";
+  }
+  void emitARM64WinCFISaveAnyRegIP(unsigned Reg, int Offset) override {
+    OS << "\t.seh_save_any_reg_p\tx" << Reg << ", " << Offset << "\n";
+  }
+  void emitARM64WinCFISaveAnyRegD(unsigned Reg, int Offset) override {
+    OS << "\t.seh_save_any_reg\td" << Reg << ", " << Offset << "\n";
+  }
+  void emitARM64WinCFISaveAnyRegDP(unsigned Reg, int Offset) override {
+    OS << "\t.seh_save_any_reg_p\td" << Reg << ", " << Offset << "\n";
+  }
+  void emitARM64WinCFISaveAnyRegQ(unsigned Reg, int Offset) override {
+    OS << "\t.seh_save_any_reg\tq" << Reg << ", " << Offset << "\n";
+  }
+  void emitARM64WinCFISaveAnyRegQP(unsigned Reg, int Offset) override {
+    OS << "\t.seh_save_any_reg_p\tq" << Reg << ", " << Offset << "\n";
+  }
+  void emitARM64WinCFISaveAnyRegIX(unsigned Reg, int Offset) override {
+    OS << "\t.seh_save_any_reg_x\tx" << Reg << ", " << Offset << "\n";
+  }
+  void emitARM64WinCFISaveAnyRegIPX(unsigned Reg, int Offset) override {
+    OS << "\t.seh_save_any_reg_px\tx" << Reg << ", " << Offset << "\n";
+  }
+  void emitARM64WinCFISaveAnyRegDX(unsigned Reg, int Offset) override {
+    OS << "\t.seh_save_any_reg_x\td" << Reg << ", " << Offset << "\n";
+  }
+  void emitARM64WinCFISaveAnyRegDPX(unsigned Reg, int Offset) override {
+    OS << "\t.seh_save_any_reg_px\td" << Reg << ", " << Offset << "\n";
+  }
+  void emitARM64WinCFISaveAnyRegQX(unsigned Reg, int Offset) override {
+    OS << "\t.seh_save_any_reg_x\tq" << Reg << ", " << Offset << "\n";
+  }
+  void emitARM64WinCFISaveAnyRegQPX(unsigned Reg, int Offset) override {
+    OS << "\t.seh_save_any_reg_px\tq" << Reg << ", " << Offset << "\n";
+  }
+
 public:
   AArch64TargetAsmStreamer(MCStreamer &S, formatted_raw_ostream &OS);
 };
 
 AArch64TargetAsmStreamer::AArch64TargetAsmStreamer(MCStreamer &S,
                                                    formatted_raw_ostream &OS)
   : AArch64TargetStreamer(S), OS(OS) {}
 

llvm/lib/Target/AArch64/MCTargetDesc/AArch64TargetStreamer.h

public:
   virtual void emitARM64WinCFIPrologEnd() {}
   virtual void emitARM64WinCFIEpilogStart() {}
   virtual void emitARM64WinCFIEpilogEnd() {}
   virtual void emitARM64WinCFITrapFrame() {}
   virtual void emitARM64WinCFIMachineFrame() {}
   virtual void emitARM64WinCFIContext() {}
   virtual void emitARM64WinCFIClearUnwoundToCall() {}
   virtual void emitARM64WinCFIPACSignLR() {}
+  virtual void emitARM64WinCFISaveAnyRegI(unsigned Reg, int Offset) {}
+  virtual void emitARM64WinCFISaveAnyRegIP(unsigned Reg, int Offset) {}
+  virtual void emitARM64WinCFISaveAnyRegD(unsigned Reg, int Offset) {}
+  virtual void emitARM64WinCFISaveAnyRegDP(unsigned Reg, int Offset) {}
+  virtual void emitARM64WinCFISaveAnyRegQ(unsigned Reg, int Offset) {}
+  virtual void emitARM64WinCFISaveAnyRegQP(unsigned Reg, int Offset) {}
+  virtual void emitARM64WinCFISaveAnyRegIX(unsigned Reg, int Offset) {}
+  virtual void emitARM64WinCFISaveAnyRegIPX(unsigned Reg, int Offset) {}
+  virtual void emitARM64WinCFISaveAnyRegDX(unsigned Reg, int Offset) {}
+  virtual void emitARM64WinCFISaveAnyRegDPX(unsigned Reg, int Offset) {}
+  virtual void emitARM64WinCFISaveAnyRegQX(unsigned Reg, int Offset) {}
+  virtual void emitARM64WinCFISaveAnyRegQPX(unsigned Reg, int Offset) {}
 
 private:
   std::unique_ptr<AssemblerConstantPools> ConstantPools;
 };
 
 class AArch64TargetELFStreamer : public AArch64TargetStreamer {
 private:
   AArch64ELFStreamer &getStreamer();
public:
   void emitARM64WinCFIPrologEnd() override;
   void emitARM64WinCFIEpilogStart() override;
   void emitARM64WinCFIEpilogEnd() override;
   void emitARM64WinCFITrapFrame() override;
   void emitARM64WinCFIMachineFrame() override;
   void emitARM64WinCFIContext() override;
   void emitARM64WinCFIClearUnwoundToCall() override;
   void emitARM64WinCFIPACSignLR() override;
+  void emitARM64WinCFISaveAnyRegI(unsigned Reg, int Offset) override;
+  void emitARM64WinCFISaveAnyRegIP(unsigned Reg, int Offset) override;
+  void emitARM64WinCFISaveAnyRegD(unsigned Reg, int Offset) override;
+  void emitARM64WinCFISaveAnyRegDP(unsigned Reg, int Offset) override;
+  void emitARM64WinCFISaveAnyRegQ(unsigned Reg, int Offset) override;
+  void emitARM64WinCFISaveAnyRegQP(unsigned Reg, int Offset) override;
+  void emitARM64WinCFISaveAnyRegIX(unsigned Reg, int Offset) override;
+  void emitARM64WinCFISaveAnyRegIPX(unsigned Reg, int Offset) override;
+  void emitARM64WinCFISaveAnyRegDX(unsigned Reg, int Offset) override;
+  void emitARM64WinCFISaveAnyRegDPX(unsigned Reg, int Offset) override;
+  void emitARM64WinCFISaveAnyRegQX(unsigned Reg, int Offset) override;
+  void emitARM64WinCFISaveAnyRegQPX(unsigned Reg, int Offset) override;
 
 private:
   void emitARM64WinUnwindCode(unsigned UnwindCode, int Reg, int Offset);
 };
 
 MCTargetStreamer *
 createAArch64ObjectTargetStreamer(MCStreamer &S, const MCSubtargetInfo &STI);
 
 } // end namespace llvm
 
 #endif

llvm/lib/Target/AArch64/MCTargetDesc/AArch64WinCOFFStreamer.cpp

 void AArch64TargetWinCOFFStreamer::emitARM64WinCFIClearUnwoundToCall() {
   emitARM64WinUnwindCode(Win64EH::UOP_ClearUnwoundToCall, -1, 0);
 }
 
 void AArch64TargetWinCOFFStreamer::emitARM64WinCFIPACSignLR() {
   emitARM64WinUnwindCode(Win64EH::UOP_PACSignLR, -1, 0);
 }
 
+void AArch64TargetWinCOFFStreamer::emitARM64WinCFISaveAnyRegI(unsigned Reg,
+                                                              int Offset) {
+  emitARM64WinUnwindCode(Win64EH::UOP_SaveAnyRegI, Reg, Offset);
+}
+
+void AArch64TargetWinCOFFStreamer::emitARM64WinCFISaveAnyRegIP(unsigned Reg,
+                                                               int Offset) {
+  emitARM64WinUnwindCode(Win64EH::UOP_SaveAnyRegIP, Reg, Offset);
+}
+
+void AArch64TargetWinCOFFStreamer::emitARM64WinCFISaveAnyRegD(unsigned Reg,
+                                                              int Offset) {
+  emitARM64WinUnwindCode(Win64EH::UOP_SaveAnyRegD, Reg, Offset);
+}
+
+void AArch64TargetWinCOFFStreamer::emitARM64WinCFISaveAnyRegDP(unsigned Reg,
+                                                               int Offset) {
+  emitARM64WinUnwindCode(Win64EH::UOP_SaveAnyRegDP, Reg, Offset);
+}
+
+void AArch64TargetWinCOFFStreamer::emitARM64WinCFISaveAnyRegQ(unsigned Reg,
+                                                              int Offset) {
+  emitARM64WinUnwindCode(Win64EH::UOP_SaveAnyRegQ, Reg, Offset);
+}
+
+void AArch64TargetWinCOFFStreamer::emitARM64WinCFISaveAnyRegQP(unsigned Reg,
+                                                               int Offset) {
+  emitARM64WinUnwindCode(Win64EH::UOP_SaveAnyRegQP, Reg, Offset);
+}
+
+void AArch64TargetWinCOFFStreamer::emitARM64WinCFISaveAnyRegIX(unsigned Reg,
+                                                               int Offset) {
+  emitARM64WinUnwindCode(Win64EH::UOP_SaveAnyRegIX, Reg, Offset);
+}
+
+void AArch64TargetWinCOFFStreamer::emitARM64WinCFISaveAnyRegIPX(unsigned Reg,
+                                                                int Offset) {
+  emitARM64WinUnwindCode(Win64EH::UOP_SaveAnyRegIPX, Reg, Offset);
+}
+
+void AArch64TargetWinCOFFStreamer::emitARM64WinCFISaveAnyRegDX(unsigned Reg,
+                                                               int Offset) {
+  emitARM64WinUnwindCode(Win64EH::UOP_SaveAnyRegDX, Reg, Offset);
+}
+
+void AArch64TargetWinCOFFStreamer::emitARM64WinCFISaveAnyRegDPX(unsigned Reg,
+                                                                int Offset) {
+  emitARM64WinUnwindCode(Win64EH::UOP_SaveAnyRegDPX, Reg, Offset);
+}
+
+void AArch64TargetWinCOFFStreamer::emitARM64WinCFISaveAnyRegQX(unsigned Reg,
+                                                               int Offset) {
+  emitARM64WinUnwindCode(Win64EH::UOP_SaveAnyRegQX, Reg, Offset);
+}
+
+void AArch64TargetWinCOFFStreamer::emitARM64WinCFISaveAnyRegQPX(unsigned Reg,
+                                                                int Offset) {
+  emitARM64WinUnwindCode(Win64EH::UOP_SaveAnyRegQPX, Reg, Offset);
+}
+
 MCWinCOFFStreamer *llvm::createAArch64WinCOFFStreamer(
     MCContext &Context, std::unique_ptr<MCAsmBackend> MAB,
     std::unique_ptr<MCObjectWriter> OW, std::unique_ptr<MCCodeEmitter> Emitter,
     bool RelaxAll, bool IncrementalLinkerCompatible) {
   auto *S = new AArch64WinCOFFStreamer(Context, std::move(MAB),
                                        std::move(Emitter), std::move(OW));
   S->getAssembler().setIncrementalLinkerCompatible(IncrementalLinkerCompatible);
   return S;
 }

llvm/test/MC/AArch64/seh.s

 // CHECK-NEXT:       ALIGN_4BYTES
 // CHECK-NEXT:       CNT_CODE
 // CHECK-NEXT:       MEM_EXECUTE
 // CHECK-NEXT:       MEM_READ
 // CHECK-NEXT:     ]
 // CHECK-NEXT:   }
 // CHECK:        Section {
 // CHECK:          Name: .xdata
-// CHECK:          RawDataSize: 56
+// CHECK:          RawDataSize: 92
 // CHECK:          RelocationCount: 1
 // CHECK:          Characteristics [
 // CHECK-NEXT:       ALIGN_4BYTES
 // CHECK-NEXT:       CNT_INITIALIZED_DATA
 // CHECK-NEXT:       MEM_READ
 // CHECK-NEXT:     ]
 // CHECK-NEXT:   }
 // CHECK:        Section {
 // CHECK:          Name: .pdata
 // CHECK:          RelocationCount: 2
 // CHECK:          Characteristics [
 // CHECK-NEXT:       ALIGN_4BYTES
 // CHECK-NEXT:       CNT_INITIALIZED_DATA
 // CHECK-NEXT:       MEM_READ
 // CHECK-NEXT:     ]
 // CHECK-NEXT:   }
 // CHECK-NEXT: ]
 
 // CHECK-NEXT: Relocations [
 // CHECK-NEXT:   Section (4) .xdata {
-// CHECK-NEXT:     0x2C IMAGE_REL_ARM64_ADDR32NB __C_specific_handler
+// CHECK-NEXT:     0x50 IMAGE_REL_ARM64_ADDR32NB __C_specific_handler
 // CHECK-NEXT:   }
 // CHECK-NEXT:   Section (5) .pdata {
 // CHECK-NEXT:     0x0 IMAGE_REL_ARM64_ADDR32NB .text
 // CHECK-NEXT:     0x4 IMAGE_REL_ARM64_ADDR32NB .xdata
 // CHECK-NEXT:   }
 // CHECK-NEXT: ]
 
 // CHECK-NEXT: UnwindInformation [
 // CHECK-NEXT:   RuntimeFunction {
 // CHECK-NEXT:     Function: func
 // CHECK-NEXT:     ExceptionRecord: .xdata
 // CHECK-NEXT:     ExceptionData {
-// CHECK-NEXT:       FunctionLength: 104
+// CHECK-NEXT:       FunctionLength: 152
 // CHECK:            Prologue [
+// CHECK-NEXT:         0xe76983            ; stp q9, q10, [sp, #-64]!
+// CHECK-NEXT:         0xe73d83            ; str q29, [sp, #-64]!
+// CHECK-NEXT:         0xe76243            ; stp d2, d3, [sp, #-64]!
+// CHECK-NEXT:         0xe73f43            ; str d31, [sp, #-64]!
+// CHECK-NEXT:         0xe77d03            ; stp x29, x30, [sp, #-64]!
+// CHECK-NEXT:         0xe73e03            ; str x30, [sp, #-64]!
+// CHECK-NEXT:         0xe74384            ; stp q3, q4, [sp, #64]
+// CHECK-NEXT:         0xe71e84            ; str q30, [sp, #64]
+// CHECK-NEXT:         0xe74444            ; stp d4, d5, [sp, #64]
+// CHECK-NEXT:         0xe71d48            ; str d29, [sp, #64]
+// CHECK-NEXT:         0xe74104            ; stp x1, x2, [sp, #64]
+// CHECK-NEXT:         0xe70008            ; str x0, [sp, #64]
 // CHECK-NEXT:         0xfc                ; pacibsp
 // CHECK-NEXT:         0xec                ; clear unwound to call
 // CHECK-NEXT:         0xea                ; context
 // CHECK-NEXT:         0xe9                ; machine frame
 // CHECK-NEXT:         0xe8                ; trap frame
 // CHECK-NEXT:         0xe3                ; nop
 // CHECK-NEXT:         0xe202              ; add fp, sp, #16
 // CHECK-NEXT:         0xdd41              ; str d13, [sp, #8]

 // CHECK-NEXT:         0xcc83              ; stp x21, x22, [sp, #-32]!
 // CHECK-NEXT:         0x83                ; stp x29, x30, [sp, #-32]!
 // CHECK-NEXT:         0xe1                ; mov fp, sp
 // CHECK-NEXT:         0x01                ; sub sp, #16
 // CHECK-NEXT:         0xe4                ; end
 // CHECK-NEXT:       ]
 // CHECK-NEXT:       EpilogueScopes [
 // CHECK-NEXT:         EpilogueScope {
-// CHECK-NEXT:           StartOffset: 24
-// CHECK-NEXT:           EpilogueStartIndex: 32
+// CHECK-NEXT:           StartOffset: 36
+// CHECK-NEXT:           EpilogueStartIndex: 68
 // CHECK-NEXT:           Opcodes [
 // CHECK-NEXT:             0x01                ; add sp, #16
 // CHECK-NEXT:             0xe4                ; end
 // CHECK-NEXT:           ]
 // CHECK-NEXT:         }
 // CHECK-NEXT:       ]
 // CHECK-NEXT:       ExceptionHandler [
 // CHECK-NEXT:         Routine: __C_specific_handler (0x0)
func:
     nop
     .seh_pushframe
     nop
     .seh_context
     nop
     .seh_clear_unwound_to_call
     pacibsp
     .seh_pac_sign_lr
+    nop
+    .seh_save_any_reg x0, 64
+    nop
+    .seh_save_any_reg_p x1, 64
+    nop
+    .seh_save_any_reg d29, 64
+    nop
+    .seh_save_any_reg_p d4, 64
+    nop
+    .seh_save_any_reg q30, 64
+    nop
+    .seh_save_any_reg_p q3, 64
+    nop
+    .seh_save_any_reg_x lr, 64
+    nop
+    .seh_save_any_reg_px fp, 64
+    nop
+    .seh_save_any_reg_x d31, 64
+    nop
+    .seh_save_any_reg_px d2, 64
+    nop
+    .seh_save_any_reg_x q29, 64
+    nop
+    .seh_save_any_reg_px q9, 64
     .seh_endprologue
     nop
     .seh_startepilogue
     add sp, sp, #24
     .seh_stackalloc 24
     .seh_endepilogue
     ret
     .seh_handler __C_specific_handler, @except