mvm.lua

local MEM = {}
local PC = 0
local registers = {
	A = 0,
	B = 0,
	C = 0,
	D = 0
}

local fetch = function()
	PC = PC + 1
	return MEM[PC]
end

local operands = {
	["0x00"] = "A",
	["0x01"] = "B",
	["0x02"] = "C",
	["0x03"] = "D",
}

local opcodes = {
	["0x00"] = function() -- NOP
	end,
	["0x01"] = function() -- MOV R, c
		local A = operands[fetch()]
		local c = fetch()
		registers[A] = tonumber(c)
	end,
	["0x02"] = function() -- ADD R, r
		local R = operands[fetch()]
		local r = operands[fetch()]
		registers[R] = registers[R] + registers[r]
	end,
	["0x03"] = function() -- SUB R, r
		local R = operands[fetch()]
		local r = operands[fetch()]
		registers[R] = registers[R] - registers[r]
	end,
	["0x04"] = function() -- JMP addr
		local addr = fetch()
		PC = tonumber(addr)
	end,
	["0x05"] = function() -- IFE R, r
		local R = registers[operands[fetch()]]
		local r = registers[operands[fetch()]]
		PC = (R == r) and PC + 3 or PC
	end
}

local FDX = function()
	print("PC", "IR", "A", "B")
	while PC < #MEM do
		local IR = fetch()
		opcodes[IR]()
		print(PC, IR, registers.A, registers.B, registers.C)
	end
end


-- TEST machine

MEM = {
	"0x00", -- NOP
	"0x01", "0x01", "0x05", -- MOV B, 5
	"0x01", "0x02", "0x01", -- MOV C, 1
	"0x02", "0x00", "0x02", -- ADD A, C
	"0x05", "0x00", "0x01", -- IFE A, B
	"0x04", "0x7", -- JMP 1
	"0x00",
	"0x00"
}

FDX()