// Author: simon
// Author: ynwdlxm@163.com
// Date: 2024/4/13 22:53
// Desc: 操作码 每条指令占4 个字节（32 比特），其中 6 比特用于操作码（Opcode），26 比特用于操作数（Operand）
// * iABC 模式指令可以携带 A、B、C 三个操作数，分别占用 8、9、9 个比特
// * iABx 模式指令可以携带 A 和 Bx 两个操作数，分别占用 8 和 18 个比特
// * iAsBx 模式的指令可以携带 A 和 sBx 两个操作数，分别占用 8 和 18 个比特
// * iAx 模式的指令中携带一个操作数，占用全部 26 比特
// * 在 四种模式中，只用 iAsBx 模式下的 sBx 操作数会被解释成有符号整数，其他情况下操作数均被解释成无符号整数

package vm

// op MODE
const (
    IABC = iota
    IABx
    IAsBx
    IAx
)

// Lua 5.3 共定义了 47 条指令，按照作用，
// 可大致分为 常量加载指令、运算符相关指令、循环和跳转指令、函数调用相关指令、表操作指令以及 Upvalue 操作指令
const (
    MOVE = iota
    LOADK
    LOADKX

    LOADBOOL
    LOADNIL
    GETUPVAL
    GETTABUP
    GETTABLE
    SETTABUP
    SETUPVAL
    SETTABLE
    NEWTABLE
    SELF
    ADD
    SUB
    MUL
    MOD
    POW
    DIV
    IDIV
    BAND
    BOR
    BXOR
    SHL
    SHR
    UNM
    BNOT
    NOT
    LEN
    CONCAT
    JMP
    EQ
    LT
    LE
    TEST
    TESTSET
    CALL
    TALLCALL
    RETURN
    FORLOOP
    FORPREP
    TFORCALL
    TFORLOOP
    SETLIST
    CLOSURE
    VARARG
    EXTRAARG
)

// 操作数
const (
    OpArgN = iota // argument is not used
    OpArgU        // argument is used
    OpArgR        // argument is a register or a jump offset
    OpArgK        // argument is a constant or register/constant
)

type opcode struct {
    testFlag byte // operator is a test (next instruction must be a jump)
    setAFlag byte // instruction set register A
    argBMode byte // B arg mode
    argCMode byte // C arg mode
    opMode   byte // op mode
    name     string
}

var opcodes = []opcode{
    /*testFlag     setAFlag     argBMode          argCMode           opMode        name        */
    {0, 1, OpArgR, OpArgN, IABC, "MOVE     "},
    {0, 1, OpArgK, OpArgN, IABx, "LOADK    "},
    {0, 1, OpArgN, OpArgN, IABx, "LOADKX   "},
    {0, 1, OpArgU, OpArgU, IABC, "LOADBOOL "},
    {0, 1, OpArgU, OpArgN, IABC, "LOADNIl  "},
    {0, 1, OpArgU, OpArgN, IABC, "GETUPVAL "},
    {0, 1, OpArgU, OpArgK, IABC, "GETTABUP "},
    {0, 1, OpArgR, OpArgK, IABC, "GETTABLE "},
    {0, 0, OpArgK, OpArgK, IABC, "GETTABUP "},
    {0, 0, OpArgU, OpArgN, IABC, "SETUPVAL "},
    {0, 0, OpArgK, OpArgK, IABC, "SETTABLE "},
    {0, 1, OpArgU, OpArgU, IABC, "NEWTABLE "},
    {0, 1, OpArgR, OpArgK, IABC, "SELF     "},
    {0, 1, OpArgK, OpArgK, IABC, "ADD      "},
    {0, 1, OpArgK, OpArgK, IABC, "SUB      "},
    {0, 1, OpArgK, OpArgK, IABC, "MUL      "},
    {0, 1, OpArgK, OpArgK, IABC, "MOD      "},
    {0, 1, OpArgK, OpArgK, IABC, "POW      "},
    {0, 1, OpArgK, OpArgK, IABC, "DIV      "},
    {0, 1, OpArgK, OpArgK, IABC, "IDIV     "},
    {0, 1, OpArgK, OpArgK, IABC, "BAND     "},
    {0, 1, OpArgK, OpArgK, IABC, "BOR      "},
    {0, 1, OpArgK, OpArgK, IABC, "BXOR     "},
    {0, 1, OpArgK, OpArgK, IABC, "SHL      "},
    {0, 1, OpArgK, OpArgK, IABC, "SHR      "},
    {0, 1, OpArgR, OpArgN, IABC, "UNM      "},
    {0, 1, OpArgR, OpArgN, IABC, "BNOT     "},
    {0, 1, OpArgR, OpArgN, IABC, "NOT      "},
    {0, 1, OpArgR, OpArgN, IABC, "LEN      "},
    {0, 1, OpArgR, OpArgR, IABC, "CONCAT   "},
    {0, 0, OpArgR, OpArgN, IAsBx, "JMP     "},
    {1, 0, OpArgK, OpArgK, IABC, "EQ       "},
    {1, 0, OpArgK, OpArgK, IABC, "LT       "},
    {1, 0, OpArgK, OpArgK, IABC, "LE       "},
    {1, 0, OpArgN, OpArgU, IABC, "TEST     "},
    {1, 1, OpArgR, OpArgU, IABC, "TESTSET  "},
    {0, 1, OpArgU, OpArgU, IABC, "CALL     "},
    {0, 1, OpArgU, OpArgU, IABC, "TALLCALL "},
    {0, 0, OpArgU, OpArgN, IABC, "RETURN   "},
    {0, 1, OpArgR, OpArgN, IAsBx, "FORLOOP "},
    {0, 1, OpArgR, OpArgN, IAsBx, "FORREEP "},
    {0, 0, OpArgU, OpArgU, IABC, "SETLIST  "},
    {0, 1, OpArgU, OpArgN, IABx, "CLOSURE  "},
    {0, 1, OpArgU, OpArgN, IABC, "VARARG   "},
    {0, 0, OpArgU, OpArgU, IAx, "EXTRAARG  "},
}