AOT Brainfuck compiler to bytecode for Lua 5.1

bfcompile.lua

--[[
    registers: 0 = data table, 1 = data pointer, 2 = function temp, 3 = current data (4 total)
    expects `get(): number` and `put(n: number)` global functions

    init code
    GETGLOBAL   R(0), K("setmetatable")
    NEWTABLE    R(1), 0, 0
    NEWTABLE    R(2), 0, 1
    CLOSURE     R(3), KP(0)
    SETTABLE    R(2), K("__index"), R(3)
    CALL        R(0), 3, 2
    LOADK       R(1), K(0)
    LOADK       R(3), K(0)

    >, increment data pointer
    SETTABLE    R(0), R(1), R(3)
    ADD         R(1), R(1), K(1)
    GETTABLE    R(3), R(0), R(1)

    <, decrement data pointer
    SETTABLE    R(0), R(1), R(3)
    SUB         R(1), R(1), K(1)
    GETTABLE    R(3), R(0), R(1)

    +, increment data
    ADD         R(3), R(3), K(1)

    -, decrement data
    SUB         R(3), R(3), K(1)

    ., output byte
    GETGLOBAL   R(2), K("put")
    CALL        R(2), 2, 1

    ,, input byte
    GETGLOBAL   R(3), K("get")
    CALL        R(3), 1, 2

    [, jump forward if zero
    EQ          1, R(3), K(0)
    JMP         $displacement*3

    ], jump backward if not zero
    EQ          0, R(3), K(0)
    JMP         $displacement*-3
]]

assert(_VERSION == "Lua 5.1")

local header = string.dump(function() end):sub(1, 12)
local ENDIAN = header:byte(7) == 0 and ">" or "<"
local INT = "i" .. header:byte(8)
local STRING = "s" .. header:byte(9)
local INSTRUCTION = "I" .. header:byte(10)
local NUMBER = (header:byte(12) == 0 and (header:byte(11) == 4 and "f" or "d") or ("i" .. header:byte(11)))
local HEADER = ENDIAN .. STRING .. INT .. INT .. "BBBB"
local FOOTER = (ENDIAN .. INT .. "B" .. NUMBER .. "B" .. NUMBER .. "B" .. STRING .. "B" .. STRING .. "B" .. STRING .. "B" .. STRING .. INT .. STRING .. INT .. INT .. "BBBB" .. INT .. INSTRUCTION:rep(2) .. INT .. "B" .. NUMBER .. INT:rep(7)):pack(6, 3, 0, 3, 1, 4, "put\0", 4, "get\0", 4, "setmetatable\0", 4, "__index\0", 1, "\0", 0, 0, 0, 0, 0, 1, 2, 0x00000001, 0x0100001E, 1, 3, 0, 0, 0, 0, 0, 0, 0, 0)
local function encode(c) return (INT .. INSTRUCTION:rep(#c)):pack(#c, table.unpack(c)) end
local instructions = {
    [">"] = {
        0x0080C009,
        0x00C0404C,
        0x000040C6
    },
    ["<"] = {
        0x0080C009,
        0x00C0404D,
        0x000040C6
    },
    ["+"] = {
        0x01C040CC
    },
    ["-"] = {
        0x01C040CD
    },
    ["."] = {
        0x00008085,
        0x0100409C
    },
    [","] = {
        0x0000C0C5,
        0x008080DC
    },
    ["["] = {
        0x01C00057,
        0x00000016
    },
    ["]"] = {
        0x01C00017,
        0x00000016
    }
}

local function bfcompile(src)
    local insts, stack = {
        0x00010005,
        0x0000004A,
        0x0000408A,
        0x000000E4,
        0x8280C089,
        0x0180801C,
        0x00000041,
        0x000000C1
    }, {}
    for c in src:gmatch "[<>%+%-%.,%[%]]" do
        local i = instructions[c]
        insts[#insts+1] = i[1]
        insts[#insts+1] = i[2]
        insts[#insts+1] = i[3]
        if c == "[" then stack[#stack+1] = #insts
        elseif c == "]" then
            local p = stack[#stack]
            local d = #insts - p
            stack[#stack] = nil
            insts[p] = 0x16 + (d + 0x1FFFF) * 0x4000
            insts[#insts] = 0x16 + (0x1FFFF - d) * 0x4000
        end
    end
    insts[#insts+1] = 0x0080001E -- RETURN 0, 1
    local chunk = header .. HEADER:pack(src .. "\0", 0, 0, 0, 0, 0, 4) .. encode(insts) .. FOOTER
    --[[print(chunk:gsub(".", function(c) return ("%02X "):format(c:byte()) end))
    local file = fs.open("bfcompile.tmp", "wb")
    file.write(chunk)
    file.close()]]
    return load(chunk, src, "b", _ENV)
end

function get() return select(2, os.pullEvent("char")):byte() end
function put(c) write(string.char(c)) end
assert(bfcompile(read()))()