[COFF, ARM64] Add support for Windows ARM64 COFF format

Summary:
This is the llvm part of the initial implementation to support Windows ARM64 COFF format.
I will gradually add more functionality in subsequent patches.

Reviewers: ruiu, rnk, t.p.northover, compnerd

Reviewed By: ruiu, compnerd

Subscribers: aemerson, mgorny, javed.absar, llvm-commits, kristof.beyls

Differential Revision: https://reviews.llvm.org/D34705

llvm-svn: 306490
diff --git a/llvm/lib/Target/AArch64/AArch64MCInstLower.h b/llvm/lib/Target/AArch64/AArch64MCInstLower.h
index 1e29b80..aa30fe1 100644
--- a/llvm/lib/Target/AArch64/AArch64MCInstLower.h
+++ b/llvm/lib/Target/AArch64/AArch64MCInstLower.h
@@ -42,6 +42,8 @@
                                      MCSymbol *Sym) const;
   MCOperand lowerSymbolOperandELF(const MachineOperand &MO,
                                   MCSymbol *Sym) const;
+  MCOperand lowerSymbolOperandCOFF(const MachineOperand &MO,
+                                   MCSymbol *Sym) const;
   MCOperand LowerSymbolOperand(const MachineOperand &MO, MCSymbol *Sym) const;
 
   MCSymbol *GetGlobalAddressSymbol(const MachineOperand &MO) const;