unidasm: Add disassembler for DEC VAX architecture

scripts/src/cpu.lua

@@ -3251,6 +3251,16 @@ if opt_tool(CPUS, "DSP56000") then
 	table.insert(disasm_files , MAME_DIR .. "src/devices/cpu/dsp56000/dsp56000d.h")
 end
 
+--------------------------------------------------
+-- DEC VAX, disassembler only
+--@src/devices/cpu/vax/vax.h,CPUS["VAX"] = true
+--------------------------------------------------
+
+if opt_tool(CPUS, "VAX") then
+	table.insert(disasm_files , MAME_DIR .. "src/devices/cpu/vax/vaxdasm.cpp")
+	table.insert(disasm_files , MAME_DIR .. "src/devices/cpu/vax/vaxdasm.h")
+end
+
 --------------------------------------------------
 -- DEC VT50/VT52
 --@src/devices/cpu/vt50/vt50.h,CPUS["VT50"] = true

src/devices/cpu/vax/vaxdasm.h

@@ -0,0 +1,38 @@
+// license:BSD-3-Clause
+// copyright-holders:AJR
+
+#ifndef MAME_CPU_VAX_VAXDASM_H
+#define MAME_CPU_VAX_VAXDASM_H
+
+#pragma once
+
+class vax_disassembler : public util::disasm_interface
+{
+public:
+	enum class mode : u8;
+
+	struct opdef
+	{
+		std::string_view mnemonic;
+		mode operand[6];
+		u32 flags;
+	};
+
+	// construction/destruction
+	vax_disassembler();
+
+protected:
+	// disassembler overrides
+	virtual u32 opcode_alignment() const override;
+	virtual offs_t disassemble(std::ostream &stream, offs_t pc, const data_buffer &opcodes, const data_buffer &params) override;
+
+private:
+	// internal helpers
+	void format_immediate(std::ostream &stream, u32 i) const;
+	void format_signed(std::ostream &stream, s32 value) const;
+	void format_relative(std::ostream &stream, u32 pc, s32 displ) const;
+	void format_register_mask(std::ostream &stream, u16 mask) const;
+	offs_t disassemble_inst(std::ostream &stream, const opdef &inst, offs_t &pc, offs_t ppc, const data_buffer &opcodes) const;
+};
+
+#endif // MAME_CPU_VAX_VAXDASM_H

src/tools/unidasm.cpp

@@ -185,6 +185,7 @@ using util::BIT;
 #include "cpu/v60/v60d.h"
 #include "cpu/v810/v810dasm.h"
 #include "cpu/v850/v850dasm.h"
+#include "cpu/vax/vaxdasm.h"
 #include "cpu/vt50/vt50dasm.h"
 #include "cpu/vt61/vt61dasm.h"
 #include "cpu/we32000/we32100d.h"
@@ -638,6 +639,7 @@ static const dasm_table_entry dasm_table[] =
 	{ "v850",            le,  0, []() -> util::disasm_interface * { return new v850_disassembler; } },
 	{ "v850es",          le,  0, []() -> util::disasm_interface * { return new v850es_disassembler; } },
 	{ "v850e2",          le,  0, []() -> util::disasm_interface * { return new v850e2_disassembler; } },
+	{ "vax",             le,  0, []() -> util::disasm_interface * { return new vax_disassembler; } },
 	{ "vt50",            le,  0, []() -> util::disasm_interface * { return new vt50_disassembler; } },
 	{ "vt52",            le,  0, []() -> util::disasm_interface * { return new vt52_disassembler; } },
 	{ "vt61",            le, -1, []() -> util::disasm_interface * { return new vt61_disassembler; } },