[LLDB][RISCV] Add DWARF Registers

[Emmmer]

Summary

According to RISC-V DWARF Specification add RISCV DWARF Registers.

Don't worry about the difference between riscv32 and riscv64, they just have different bytes of registers.

[DavidSpickett]

I couldn't find a definition for Alternate Frame Return Column. Perhaps it's this "alternate link register" I see elsewhere that's used for calling compressed code functions? Seems like a thing you could easily add later if needed.

LGTM.

[Emmmer]

Add missing Alternate Frame Return Column.

It is used for storing the address where the signal handler will return, so we might need it.

lldb/source/Utility/RISCV_DWARF_Registers.h

+//===-- RISCV_DWARF_Registers.h ---------------------------------*- 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 LLDB_SOURCE_UTILITY_RISCV_DWARF_REGISTERS_H
+#define LLDB_SOURCE_UTILITY_RISCV_DWARF_REGISTERS_H
+
+#include "lldb/lldb-private.h"
+
+namespace riscv_dwarf {
+
+enum {
+  dwarf_gpr_x0 = 0,
+  dwarf_gpr_x1,
+  dwarf_gpr_x2,
+  dwarf_gpr_x3,
+  dwarf_gpr_x4,
+  dwarf_gpr_x5,
+  dwarf_gpr_x6,
+  dwarf_gpr_x7,
+  dwarf_gpr_x8,
+  dwarf_gpr_x9,
+  dwarf_gpr_x10,
+  dwarf_gpr_x11,
+  dwarf_gpr_x12,
+  dwarf_gpr_x13,
+  dwarf_gpr_x14,
+  dwarf_gpr_x15,
+  dwarf_gpr_x16,
+  dwarf_gpr_x17,
+  dwarf_gpr_x18,
+  dwarf_gpr_x19,
+  dwarf_gpr_x20,
+  dwarf_gpr_x21,
+  dwarf_gpr_x22,
+  dwarf_gpr_x23,
+  dwarf_gpr_x24,
+  dwarf_gpr_x25,
+  dwarf_gpr_x26,
+  dwarf_gpr_x27,
+  dwarf_gpr_x28,
+  dwarf_gpr_x29,
+  dwarf_gpr_x30,
+  dwarf_gpr_x31 = 31,
+
+  dwarf_fpr_f0 = 32,
+  dwarf_fpr_f1,
+  dwarf_fpr_f2,
+  dwarf_fpr_f3,
+  dwarf_fpr_f4,
+  dwarf_fpr_f5,
+  dwarf_fpr_f6,
+  dwarf_fpr_f7,
+  dwarf_fpr_f8,
+  dwarf_fpr_f9,
+  dwarf_fpr_f10,
+  dwarf_fpr_f11,
+  dwarf_fpr_f12,
+  dwarf_fpr_f13,
+  dwarf_fpr_f14,
+  dwarf_fpr_f15,
+  dwarf_fpr_f16,
+  dwarf_fpr_f17,
+  dwarf_fpr_f18,
+  dwarf_fpr_f19,
+  dwarf_fpr_f20,
+  dwarf_fpr_f21,
+  dwarf_fpr_f22,
+  dwarf_fpr_f23,
+  dwarf_fpr_f24,
+  dwarf_fpr_f25,
+  dwarf_fpr_f26,
+  dwarf_fpr_f27,
+  dwarf_fpr_f28,
+  dwarf_fpr_f29,
+  dwarf_fpr_f30,
+  dwarf_fpr_f31 = 63,
+
+  // alternate frame return column
+  dwarf_alt_fr_col = 64,
+
+  dwarf_v0 = 96,
+  dwarf_v1,
+  dwarf_v2,
+  dwarf_v3,
+  dwarf_v4,
+  dwarf_v5,
+  dwarf_v6,
+  dwarf_v7,
+  dwarf_v8,
+  dwarf_v9,
+  dwarf_v10,
+  dwarf_v11,
+  dwarf_v12,
+  dwarf_v13,
+  dwarf_v14,
+  dwarf_v15,
+  dwarf_v16,
+  dwarf_v17,
+  dwarf_v18,
+  dwarf_v19,
+  dwarf_v20,
+  dwarf_v21,
+  dwarf_v22,
+  dwarf_v23,
+  dwarf_v24,
+  dwarf_v25,
+  dwarf_v26,
+  dwarf_v27,
+  dwarf_v28,
+  dwarf_v29,
+  dwarf_v30,
+  dwarf_v31 = 127,
+  dwarf_first_csr = 4096,
+  dwarf_last_csr = 8191,
+
+  // register name alias
+  dwarf_gpr_ra = dwarf_gpr_x1,
+  dwarf_gpr_sp = dwarf_gpr_x2,
+  dwarf_gpr_fp = dwarf_gpr_x8,
+
+  // mock pc regnum
+  dwarf_gpr_pc = UINT32_MAX,
+};
+
+} // namespace riscv_dwarf
+
+#endif // LLDB_SOURCE_UTILITY_RISCV_DWARF_REGISTERS_H