"use strict";

const {
    LUA_MULTRET,
    LUA_OPADD,
    LUA_OPBAND,
    LUA_OPBNOT,
    LUA_OPBOR,
    LUA_OPBXOR,
    LUA_OPDIV,
    LUA_OPIDIV,
    LUA_OPMOD,
    LUA_OPSHL,
    LUA_OPSHR,
    LUA_OPUNM,
    constant_types: {
        LUA_TBOOLEAN,
        LUA_TLIGHTUSERDATA,
        LUA_TLNGSTR,
        LUA_TNIL,
        LUA_TNUMFLT,
        LUA_TNUMINT,
        LUA_TTABLE
    },
    to_luastring
} = require('./defs.js');
const { lua_assert } = require("./llimits.js");
const llex     = require('./llex.js');
const lobject  = require('./lobject.js');
const lopcodes = require('./lopcodes.js');
const lparser  = require('./lparser.js');
const ltable   = require('./ltable.js');
const lvm      = require('./lvm.js');

const OpCodesI = lopcodes.OpCodesI;
const TValue   = lobject.TValue;

/* Maximum number of registers in a Lua function (must fit in 8 bits) */
const MAXREGS = 255;

/*
** Marks the end of a patch list. It is an invalid value both as an absolute
** address, and as a list link (would link an element to itself).
*/
const NO_JUMP = -1;

const BinOpr = {
    OPR_ADD:      0,
    OPR_SUB:      1,
    OPR_MUL:      2,
    OPR_MOD:      3,
    OPR_POW:      4,
    OPR_DIV:      5,
    OPR_IDIV:     6,
    OPR_BAND:     7,
    OPR_BOR:      8,
    OPR_BXOR:     9,
    OPR_SHL:      10,
    OPR_SHR:      11,
    OPR_CONCAT:   12,
    OPR_EQ:       13,
    OPR_LT:       14,
    OPR_LE:       15,
    OPR_NE:       16,
    OPR_GT:       17,
    OPR_GE:       18,
    OPR_AND:      19,
    OPR_OR:       20,
    OPR_NOBINOPR: 21
};

const UnOpr = {
    OPR_MINUS:    0,
    OPR_BNOT:     1,
    OPR_NOT:      2,
    OPR_LEN:      3,
    OPR_NOUNOPR:  4
};

const hasjumps = function(e) {
    return e.t !== e.f;
};

/*
** If expression is a numeric constant returns either true or a new TValue
** (depending on 'make_tvalue'). Otherwise, returns false.
*/
const tonumeral = function(e, make_tvalue) {
    let ek = lparser.expkind;
    if (hasjumps(e))
        return false;  /* not a numeral */
    switch (e.k) {
        case ek.VKINT:
            if (make_tvalue) {
                return new TValue(LUA_TNUMINT, e.u.ival);
            }
            return true;
        case ek.VKFLT:
            if (make_tvalue) {
                return new TValue(LUA_TNUMFLT, e.u.nval);
            }
            return true;
        default: return false;
    }
};

/*
** Create a OP_LOADNIL instruction, but try to optimize: if the previous
** instruction is also OP_LOADNIL and ranges are compatible, adjust
** range of previous instruction instead of emitting a new one. (For
** instance, 'local a; local b' will generate a single opcode.)
*/
const luaK_nil = function(fs, from, n) {
    let previous;
    let l = from + n - 1;  /* last register to set nil */
    if (fs.pc > fs.lasttarget) {  /* no jumps to current position? */
        previous = fs.f.code[fs.pc-1];
        if (previous.opcode === OpCodesI.OP_LOADNIL) {  /* previous is LOADNIL? */
            let pfrom = previous.A;  /* get previous range */
            let pl = pfrom + previous.B;
            if ((pfrom <= from && from <= pl + 1) ||
                    (from <= pfrom && pfrom <= l + 1)) {  /* can connect both? */
                if (pfrom < from) from = pfrom;  /* from = min(from, pfrom) */
                if (pl > l) l = pl;  /* l = max(l, pl) */
                lopcodes.SETARG_A(previous, from);
                lopcodes.SETARG_B(previous, l - from);
                return;
            }
        }  /* else go through */
    }
    luaK_codeABC(fs, OpCodesI.OP_LOADNIL, from, n - 1, 0);  /* else no optimization */
};

const getinstruction = function(fs, e) {
    return fs.f.code[e.u.info];
};

/*
** Gets the destination address of a jump instruction. Used to traverse
** a list of jumps.
*/
const getjump = function(fs, pc) {
    let offset = fs.f.code[pc].sBx;
    if (offset === NO_JUMP)  /* point to itself represents end of list */
        return NO_JUMP;  /* end of list */
    else
        return pc + 1 + offset;  /* turn offset into absolute position */
};

/*
** Fix jump instruction at position 'pc' to jump to 'dest'.
** (Jump addresses are relative in Lua)
*/
const fixjump = function(fs, pc, dest) {
    let jmp = fs.f.code[pc];
    let offset = dest - (pc + 1);
    lua_assert(dest !== NO_JUMP);
    if (Math.abs(offset) > lopcodes.MAXARG_sBx)
        llex.luaX_syntaxerror(fs.ls, to_luastring("control structure too long", true));
    lopcodes.SETARG_sBx(jmp, offset);
};

/*
** Concatenate jump-list 'l2' into jump-list 'l1'
*/
const luaK_concat = function(fs, l1, l2) {
    if (l2 === NO_JUMP) return l1;  /* nothing to concatenate? */
    else if (l1 === NO_JUMP)  /* no original list? */
        l1 = l2;
    else {
        let list = l1;
        let next = getjump(fs, list);
        while (next !== NO_JUMP) {  /* find last element */
            list = next;
            next = getjump(fs, list);
        }
        fixjump(fs, list, l2);
    }

    return l1;
};

/*
** Create a jump instruction and return its position, so its destination
** can be fixed later (with 'fixjump'). If there are jumps to
** this position (kept in 'jpc'), link them all together so that
** 'patchlistaux' will fix all them directly to the final destination.
*/
const luaK_jump = function (fs) {
    let jpc = fs.jpc;  /* save list of jumps to here */
    fs.jpc = NO_JUMP;  /* no more jumps to here */
    let j = luaK_codeAsBx(fs, OpCodesI.OP_JMP, 0, NO_JUMP);
    j = luaK_concat(fs, j, jpc);  /* keep them on hold */
    return j;
};

const luaK_jumpto = function(fs, t) {
    return luaK_patchlist(fs, luaK_jump(fs), t);
};

/*
** Code a 'return' instruction
*/
const luaK_ret = function(fs, first, nret) {
    luaK_codeABC(fs, OpCodesI.OP_RETURN, first, nret + 1, 0);
};

/*
** Code a "conditional jump", that is, a test or comparison opcode
** followed by a jump. Return jump position.
*/
const condjump = function(fs, op, A, B, C) {
    luaK_codeABC(fs, op, A, B, C);
    return luaK_jump(fs);
};

/*
** returns current 'pc' and marks it as a jump target (to avoid wrong
** optimizations with consecutive instructions not in the same basic block).
*/
const luaK_getlabel = function(fs) {
    fs.lasttarget = fs.pc;
    return fs.pc;
};

/*
** Returns the position of the instruction "controlling" a given
** jump (that is, its condition), or the jump itself if it is
** unconditional.
*/
const getjumpcontroloffset = function(fs, pc) {
    if (pc >= 1 && lopcodes.testTMode(fs.f.code[pc - 1].opcode))
        return pc - 1;
    else
        return pc;
};
const getjumpcontrol = function(fs, pc) {
    return fs.f.code[getjumpcontroloffset(fs, pc)];
};

/*
** Patch destination register for a TESTSET instruction.
** If instruction in position 'node' is not a TESTSET, return 0 ("fails").
** Otherwise, if 'reg' is not 'NO_REG', set it as the destination
** register. Otherwise, change instruction to a simple 'TEST' (produces
** no register value)
*/
const patchtestreg = function(fs, node, reg) {
    let pc = getjumpcontroloffset(fs, node);
    let i = fs.f.code[pc];
    if (i.opcode !== OpCodesI.OP_TESTSET)
        return false;  /* cannot patch other instructions */
    if (reg !== lopcodes.NO_REG && reg !== i.B)
        lopcodes.SETARG_A(i, reg);
    else {
        /* no register to put value or register already has the value;
           change instruction to simple test */
        fs.f.code[pc] = lopcodes.CREATE_ABC(OpCodesI.OP_TEST, i.B, 0, i.C);
    }
    return true;
};

/*
** Traverse a list of tests ensuring no one produces a value
*/
const removevalues = function(fs, list) {
    for (; list !== NO_JUMP; list = getjump(fs, list))
        patchtestreg(fs, list, lopcodes.NO_REG);
};

/*
** Traverse a list of tests, patching their destination address and
** registers: tests producing values jump to 'vtarget' (and put their
** values in 'reg'), other tests jump to 'dtarget'.
*/
const patchlistaux = function(fs, list, vtarget, reg, dtarget) {
    while (list !== NO_JUMP) {
        let next = getjump(fs, list);
        if (patchtestreg(fs, list, reg))
            fixjump(fs, list, vtarget);
        else
            fixjump(fs, list, dtarget);  /* jump to default target */
        list = next;
    }
};

/*
** Ensure all pending jumps to current position are fixed (jumping
** to current position with no values) and reset list of pending
** jumps
*/
const dischargejpc = function(fs) {
    patchlistaux(fs, fs.jpc, fs.pc, lopcodes.NO_REG, fs.pc);
    fs.jpc = NO_JUMP;
};

/*
** Add elements in 'list' to list of pending jumps to "here"
** (current position)
*/
const luaK_patchtohere = function(fs, list) {
    luaK_getlabel(fs);  /* mark "here" as a jump target */
    fs.jpc = luaK_concat(fs, fs.jpc, list);
};

/*
** Path all jumps in 'list' to jump to 'target'.
** (The assert means that we cannot fix a jump to a forward address
** because we only know addresses once code is generated.)
*/
const luaK_patchlist = function(fs, list, target) {
    if (target === fs.pc)  /* 'target' is current position? */
        luaK_patchtohere(fs, list);  /* add list to pending jumps */
    else {
        lua_assert(target < fs.pc);
        patchlistaux(fs, list, target, lopcodes.NO_REG, target);
    }
};

/*
** Path all jumps in 'list' to close upvalues up to given 'level'
** (The assertion checks that jumps either were closing nothing
** or were closing higher levels, from inner blocks.)
*/
const luaK_patchclose = function(fs, list, level) {
    level++;  /* argument is +1 to reserve 0 as non-op */
    for (; list !== NO_JUMP; list = getjump(fs, list)) {
        let ins = fs.f.code[list];
        lua_assert(ins.opcode === OpCodesI.OP_JMP && (ins.A === 0 || ins.A >= level));
        lopcodes.SETARG_A(ins, level);
    }
};

/*
** Emit instruction 'i', checking for array sizes and saving also its
** line information. Return 'i' position.
*/
const luaK_code = function(fs, i) {
    let f = fs.f;
    dischargejpc(fs);  /* 'pc' will change */
    /* put new instruction in code array */
    f.code[fs.pc] = i;
    f.lineinfo[fs.pc] = fs.ls.lastline;
    return fs.pc++;
};

/*
** Format and emit an 'iABC' instruction. (Assertions check consistency
** of parameters versus opcode.)
*/
const luaK_codeABC = function(fs, o, a, b, c) {
    lua_assert(lopcodes.getOpMode(o) === lopcodes.iABC);
    lua_assert(lopcodes.getBMode(o) !== lopcodes.OpArgN || b === 0);
    lua_assert(lopcodes.getCMode(o) !== lopcodes.OpArgN || c === 0);
    lua_assert(a <= lopcodes.MAXARG_A && b <= lopcodes.MAXARG_B && c <= lopcodes.MAXARG_C);
    return luaK_code(fs, lopcodes.CREATE_ABC(o, a, b, c));
};

/*
** Format and emit an 'iABx' instruction.
*/
const luaK_codeABx = function(fs, o, a, bc) {
    lua_assert(lopcodes.getOpMode(o) === lopcodes.iABx || lopcodes.getOpMode(o) === lopcodes.iAsBx);
    lua_assert(lopcodes.getCMode(o) === lopcodes.OpArgN);
    lua_assert(a <= lopcodes.MAXARG_A && bc <= lopcodes.MAXARG_Bx);
    return luaK_code(fs, lopcodes.CREATE_ABx(o, a, bc));
};

const luaK_codeAsBx = function(fs,o,A,sBx) {
    return luaK_codeABx(fs, o, A, (sBx) + lopcodes.MAXARG_sBx);
};

/*
** Emit an "extra argument" instruction (format 'iAx')
*/
const codeextraarg = function(fs, a) {
    lua_assert(a <= lopcodes.MAXARG_Ax);
    return luaK_code(fs, lopcodes.CREATE_Ax(OpCodesI.OP_EXTRAARG, a));
};

/*
** Emit a "load constant" instruction, using either 'OP_LOADK'
** (if constant index 'k' fits in 18 bits) or an 'OP_LOADKX'
** instruction with "extra argument".
*/
const luaK_codek = function(fs, reg, k) {
    if (k <= lopcodes.MAXARG_Bx)
        return luaK_codeABx(fs, OpCodesI.OP_LOADK, reg, k);
    else {
        let p = luaK_codeABx(fs, OpCodesI.OP_LOADKX, reg, 0);
        codeextraarg(fs, k);
        return p;
    }
};

/*
** Check register-stack level, keeping track of its maximum size
** in field 'maxstacksize'
*/
const luaK_checkstack = function(fs, n) {
    let newstack = fs.freereg + n;
    if (newstack > fs.f.maxstacksize) {
        if (newstack >= MAXREGS)
            llex.luaX_syntaxerror(fs.ls, to_luastring("function or expression needs too many registers", true));
        fs.f.maxstacksize = newstack;
    }
};

/*
** Reserve 'n' registers in register stack
*/
const luaK_reserveregs = function(fs, n) {
    luaK_checkstack(fs, n);
    fs.freereg += n;
};

/*
** Free register 'reg', if it is neither a constant index nor
** a local variable.
*/
const freereg = function(fs, reg) {
    if (!lopcodes.ISK(reg) && reg >= fs.nactvar) {
        fs.freereg--;
        lua_assert(reg === fs.freereg);
    }
};

/*
** Free register used by expression 'e' (if any)
*/
const freeexp = function(fs, e) {
    if (e.k === lparser.expkind.VNONRELOC)
        freereg(fs, e.u.info);
};

/*
** Free registers used by expressions 'e1' and 'e2' (if any) in proper
** order.
*/
const freeexps = function(fs, e1, e2) {
    let r1 = (e1.k === lparser.expkind.VNONRELOC) ? e1.u.info : -1;
    let r2 = (e2.k === lparser.expkind.VNONRELOC) ? e2.u.info : -1;
    if (r1 > r2) {
        freereg(fs, r1);
        freereg(fs, r2);
    }
    else {
        freereg(fs, r2);
        freereg(fs, r1);
    }
};


/*
** Add constant 'v' to prototype's list of constants (field 'k').
** Use scanner's table to cache position of constants in constant list
** and try to reuse constants. Because some values should not be used
** as keys (nil cannot be a key, integer keys can collapse with float
** keys), the caller must provide a useful 'key' for indexing the cache.
*/
const addk = function(fs, key, v) {
    let f = fs.f;
    let idx = ltable.luaH_set(fs.L, fs.ls.h, key);  /* index scanner table */
    if (idx.ttisinteger()) {  /* is there an index there? */
        let k = idx.value;
        /* correct value? (warning: must distinguish floats from integers!) */
        if (k < fs.nk && f.k[k].ttype() === v.ttype() && f.k[k].value === v.value)
            return k;  /* reuse index */
    }
    /* constant not found; create a new entry */
    let k = fs.nk;
    idx.setivalue(k);
    f.k[k] = v;
    fs.nk++;
    return k;
};

/*
** Add a string to list of constants and return its index.
*/
const luaK_stringK = function(fs, s) {
    let o = new TValue(LUA_TLNGSTR, s);
    return addk(fs, o, o);  /* use string itself as key */
};


/*
** Add an integer to list of constants and return its index.
** Integers use userdata as keys to avoid collision with floats with
** same value.
*/
const luaK_intK = function(fs, n) {
    let k = new TValue(LUA_TLIGHTUSERDATA, n);
    let o = new TValue(LUA_TNUMINT, n);
    return addk(fs, k, o);
};

/*
** Add a float to list of constants and return its index.
*/
const luaK_numberK = function(fs, r) {
    let o = new TValue(LUA_TNUMFLT, r);
    return addk(fs, o, o);  /* use number itself as key */
};


/*
** Add a boolean to list of constants and return its index.
*/
const boolK = function(fs, b) {
    let o = new TValue(LUA_TBOOLEAN, b);
    return addk(fs, o, o);  /* use boolean itself as key */
};


/*
** Add nil to list of constants and return its index.
*/
const nilK = function(fs) {
    let v = new TValue(LUA_TNIL, null);
    let k = new TValue(LUA_TTABLE, fs.ls.h);
    /* cannot use nil as key; instead use table itself to represent nil */
    return addk(fs, k, v);
};

/*
** Fix an expression to return the number of results 'nresults'.
** Either 'e' is a multi-ret expression (function call or vararg)
** or 'nresults' is LUA_MULTRET (as any expression can satisfy that).
*/
const luaK_setreturns = function(fs, e, nresults) {
    let ek = lparser.expkind;
    if (e.k === ek.VCALL) {  /* expression is an open function call? */
        lopcodes.SETARG_C(getinstruction(fs, e), nresults + 1);
    }
    else if (e.k === ek.VVARARG) {
        let pc = getinstruction(fs, e);
        lopcodes.SETARG_B(pc, nresults + 1);
        lopcodes.SETARG_A(pc, fs.freereg);
        luaK_reserveregs(fs, 1);
    }
    else lua_assert(nresults === LUA_MULTRET);
};

const luaK_setmultret = function(fs, e) {
    luaK_setreturns(fs, e, LUA_MULTRET);
};

/*
** Fix an expression to return one result.
** If expression is not a multi-ret expression (function call or
** vararg), it already returns one result, so nothing needs to be done.
** Function calls become VNONRELOC expressions (as its result comes
** fixed in the base register of the call), while vararg expressions
** become VRELOCABLE (as OP_VARARG puts its results where it wants).
** (Calls are created returning one result, so that does not need
** to be fixed.)
*/
const luaK_setoneret = function(fs, e) {
    let ek = lparser.expkind;
    if (e.k === ek.VCALL) {  /* expression is an open function call? */
        /* already returns 1 value */
        lua_assert(getinstruction(fs, e).C === 2);
        e.k = ek.VNONRELOC;  /* result has fixed position */
        e.u.info = getinstruction(fs, e).A;
    } else if (e.k === ek.VVARARG) {
        lopcodes.SETARG_B(getinstruction(fs, e), 2);
        e.k = ek.VRELOCABLE;  /* can relocate its simple result */
    }
};

/*
** Ensure that expression 'e' is not a variable.
*/
const luaK_dischargevars = function(fs, e) {
    let ek = lparser.expkind;

    switch (e.k) {
        case ek.VLOCAL: {  /* already in a register */
            e.k =  ek.VNONRELOC;  /* becomes a non-relocatable value */
            break;
        }
        case ek.VUPVAL: {  /* move value to some (pending) register */
            e.u.info = luaK_codeABC(fs, OpCodesI.OP_GETUPVAL, 0, e.u.info, 0);
            e.k = ek.VRELOCABLE;
            break;
        }
        case ek.VINDEXED: {
            let op;
            freereg(fs, e.u.ind.idx);
            if (e.u.ind.vt === ek.VLOCAL) {  /* is 't' in a register? */
                freereg(fs, e.u.ind.t);
                op = OpCodesI.OP_GETTABLE;
            } else {
                lua_assert(e.u.ind.vt === ek.VUPVAL);
                op = OpCodesI.OP_GETTABUP;  /* 't' is in an upvalue */
            }
            e.u.info = luaK_codeABC(fs, op, 0, e.u.ind.t, e.u.ind.idx);
            e.k = ek.VRELOCABLE;
            break;
        }
        case ek.VVARARG: case ek.VCALL: {
            luaK_setoneret(fs, e);
            break;
        }
        default: break;  /* there is one value available (somewhere) */
    }
};

const code_loadbool = function(fs, A, b, jump) {
    luaK_getlabel(fs);  /* those instructions may be jump targets */
    return luaK_codeABC(fs, OpCodesI.OP_LOADBOOL, A, b, jump);
};

/*
** Ensures expression value is in register 'reg' (and therefore
** 'e' will become a non-relocatable expression).
*/
const discharge2reg = function(fs, e, reg) {
    let ek = lparser.expkind;
    luaK_dischargevars(fs, e);
    switch (e.k) {
        case ek.VNIL: {
            luaK_nil(fs, reg, 1);
            break;
        }
        case ek.VFALSE: case ek.VTRUE: {
            luaK_codeABC(fs, OpCodesI.OP_LOADBOOL, reg, e.k === ek.VTRUE, 0);
            break;
        }
        case ek.VK: {
            luaK_codek(fs, reg, e.u.info);
            break;
        }
        case ek.VKFLT: {
            luaK_codek(fs, reg, luaK_numberK(fs, e.u.nval));
            break;
        }
        case ek.VKINT: {
            luaK_codek(fs, reg, luaK_intK(fs, e.u.ival));
            break;
        }
        case ek.VRELOCABLE: {
            let pc = getinstruction(fs, e);
            lopcodes.SETARG_A(pc, reg);  /* instruction will put result in 'reg' */
            break;
        }
        case ek.VNONRELOC: {
            if (reg !== e.u.info)
                luaK_codeABC(fs, OpCodesI.OP_MOVE, reg, e.u.info, 0);
            break;
        }
        default: {
            lua_assert(e.k === ek.VJMP);
            return;  /* nothing to do... */
        }
    }
    e.u.info = reg;
    e.k = ek.VNONRELOC;
};

/*
** Ensures expression value is in any register.
*/
const discharge2anyreg = function(fs, e) {
    if (e.k !== lparser.expkind.VNONRELOC) {  /* no fixed register yet? */
        luaK_reserveregs(fs, 1);  /* get a register */
        discharge2reg(fs, e, fs.freereg-1);  /* put value there */
    }
};

/*
** check whether list has any jump that do not produce a value
** or produce an inverted value
*/
const need_value = function(fs, list) {
    for (; list !== NO_JUMP; list = getjump(fs, list)) {
        let i = getjumpcontrol(fs, list);
        if (i.opcode !== OpCodesI.OP_TESTSET) return true;
    }
    return false;  /* not found */
};

/*
** Ensures final expression result (including results from its jump
** lists) is in register 'reg'.
** If expression has jumps, need to patch these jumps either to
** its final position or to "load" instructions (for those tests
** that do not produce values).
*/
const exp2reg = function(fs, e, reg) {
    let ek = lparser.expkind;
    discharge2reg(fs, e, reg);
    if (e.k === ek.VJMP)  /* expression itself is a test? */
        e.t = luaK_concat(fs, e.t, e.u.info);  /* put this jump in 't' list */
    if (hasjumps(e)) {
        let final;  /* position after whole expression */
        let p_f = NO_JUMP;  /* position of an eventual LOAD false */
        let p_t = NO_JUMP;  /* position of an eventual LOAD true */
        if (need_value(fs, e.t) || need_value(fs, e.f)) {
            let fj = (e.k === ek.VJMP) ? NO_JUMP : luaK_jump(fs);
            p_f = code_loadbool(fs, reg, 0, 1);
            p_t = code_loadbool(fs, reg, 1, 0);
            luaK_patchtohere(fs, fj);
        }
        final = luaK_getlabel(fs);
        patchlistaux(fs, e.f, final, reg, p_f);
        patchlistaux(fs, e.t, final, reg, p_t);
    }
    e.f = e.t = NO_JUMP;
    e.u.info = reg;
    e.k = ek.VNONRELOC;
};

/*
** Ensures final expression result (including results from its jump
** lists) is in next available register.
*/
const luaK_exp2nextreg = function(fs, e) {
    luaK_dischargevars(fs, e);
    freeexp(fs, e);
    luaK_reserveregs(fs, 1);
    exp2reg(fs, e, fs.freereg - 1);
};


/*
** Ensures final expression result (including results from its jump
** lists) is in some (any) register and return that register.
*/
const luaK_exp2anyreg = function(fs, e) {
    luaK_dischargevars(fs, e);
    if (e.k === lparser.expkind.VNONRELOC) {  /* expression already has a register? */
        if (!hasjumps(e))  /* no jumps? */
            return e.u.info;  /* result is already in a register */
        if (e.u.info >= fs.nactvar) {  /* reg. is not a local? */
            exp2reg(fs, e, e.u.info);  /* put final result in it */
            return e.u.info;
        }
    }
    luaK_exp2nextreg(fs, e);  /* otherwise, use next available register */
    return e.u.info;
};

/*
** Ensures final expression result is either in a register or in an
** upvalue.
*/
const luaK_exp2anyregup = function(fs, e) {
    if (e.k !== lparser.expkind.VUPVAL || hasjumps(e))
        luaK_exp2anyreg(fs, e);
};

/*
** Ensures final expression result is either in a register or it is
** a constant.
*/
const luaK_exp2val = function(fs, e) {
    if (hasjumps(e))
        luaK_exp2anyreg(fs, e);
    else
        luaK_dischargevars(fs, e);
};

/*
** Ensures final expression result is in a valid R/K index
** (that is, it is either in a register or in 'k' with an index
** in the range of R/K indices).
** Returns R/K index.
*/
const luaK_exp2RK = function(fs, e) {
    let ek = lparser.expkind;
    let vk = false;
    luaK_exp2val(fs, e);
    switch (e.k) {  /* move constants to 'k' */
        case ek.VTRUE: e.u.info = boolK(fs, true); vk = true; break;
        case ek.VFALSE: e.u.info = boolK(fs, false); vk = true; break;
        case ek.VNIL: e.u.info = nilK(fs); vk = true; break;
        case ek.VKINT: e.u.info = luaK_intK(fs, e.u.ival); vk = true; break;
        case ek.VKFLT: e.u.info = luaK_numberK(fs, e.u.nval); vk = true; break;
        case ek.VK: vk = true; break;
        default: break;
    }

    if (vk) {
        e.k = ek.VK;
        if (e.u.info <= lopcodes.MAXINDEXRK)  /* constant fits in 'argC'? */
            return lopcodes.RKASK(e.u.info);
    }

    /* not a constant in the right range: put it in a register */
    return luaK_exp2anyreg(fs, e);
};

/*
** Generate code to store result of expression 'ex' into variable 'var'.
*/
const luaK_storevar = function(fs, vr, ex) {
    let ek = lparser.expkind;
    switch (vr.k) {
        case ek.VLOCAL: {
            freeexp(fs, ex);
            exp2reg(fs, ex, vr.u.info);  /* compute 'ex' into proper place */
            return;
        }
        case ek.VUPVAL: {
            let e = luaK_exp2anyreg(fs, ex);
            luaK_codeABC(fs, OpCodesI.OP_SETUPVAL, e, vr.u.info, 0);
            break;
        }
        case ek.VINDEXED: {
            let op = (vr.u.ind.vt === ek.VLOCAL) ? OpCodesI.OP_SETTABLE : OpCodesI.OP_SETTABUP;
            let e = luaK_exp2RK(fs, ex);
            luaK_codeABC(fs, op, vr.u.ind.t, vr.u.ind.idx, e);
            break;
        }
    }
    freeexp(fs, ex);
};


/*
** Emit SELF instruction (convert expression 'e' into 'e:key(e,').
*/
const luaK_self = function(fs, e, key) {
    luaK_exp2anyreg(fs, e);
    let ereg = e.u.info;  /* register where 'e' was placed */
    freeexp(fs, e);
    e.u.info = fs.freereg;  /* base register for op_self */
    e.k = lparser.expkind.VNONRELOC;  /* self expression has a fixed register */
    luaK_reserveregs(fs, 2);  /* function and 'self' produced by op_self */
    luaK_codeABC(fs, OpCodesI.OP_SELF, e.u.info, ereg, luaK_exp2RK(fs, key));
    freeexp(fs, key);
};

/*
** Negate condition 'e' (where 'e' is a comparison).
*/
const negatecondition = function(fs, e) {
    let pc = getjumpcontrol(fs, e.u.info);
    lua_assert(lopcodes.testTMode(pc.opcode) && pc.opcode !== OpCodesI.OP_TESTSET && pc.opcode !== OpCodesI.OP_TEST);
    lopcodes.SETARG_A(pc, !(pc.A));
};

/*
** Emit instruction to jump if 'e' is 'cond' (that is, if 'cond'
** is true, code will jump if 'e' is true.) Return jump position.
** Optimize when 'e' is 'not' something, inverting the condition
** and removing the 'not'.
*/
const jumponcond = function(fs, e, cond) {
    if (e.k === lparser.expkind.VRELOCABLE) {
        let ie = getinstruction(fs, e);
        if (ie.opcode === OpCodesI.OP_NOT) {
            fs.pc--;  /* remove previous OP_NOT */
            return condjump(fs, OpCodesI.OP_TEST, ie.B, 0, !cond);
        }
        /* else go through */
    }
    discharge2anyreg(fs, e);
    freeexp(fs, e);
    return condjump(fs, OpCodesI.OP_TESTSET, lopcodes.NO_REG, e.u.info, cond);
};

/*
** Emit code to go through if 'e' is true, jump otherwise.
*/
const luaK_goiftrue = function(fs, e) {
    let ek = lparser.expkind;
    let pc;  /* pc of new jump */
    luaK_dischargevars(fs, e);
    switch (e.k) {
        case ek.VJMP: {  /* condition? */
            negatecondition(fs, e);  /* jump when it is false */
            pc = e.u.info;  /* save jump position */
            break;
        }
        case ek.VK: case ek.VKFLT: case ek.VKINT: case ek.VTRUE: {
            pc = NO_JUMP;  /* always true; do nothing */
            break;
        }
        default: {
            pc = jumponcond(fs, e, 0);  /* jump when false */
            break;
        }
    }
    e.f = luaK_concat(fs, e.f, pc);  /* insert new jump in false list */
    luaK_patchtohere(fs, e.t);  /* true list jumps to here (to go through) */
    e.t = NO_JUMP;
};

/*
** Emit code to go through if 'e' is false, jump otherwise.
*/
const luaK_goiffalse = function(fs, e) {
    let ek = lparser.expkind;
    let pc;  /* pc of new jump */
    luaK_dischargevars(fs, e);
    switch (e.k) {
        case ek.VJMP: {
            pc = e.u.info;  /* already jump if true */
            break;
        }
        case ek.VNIL: case ek.VFALSE: {
            pc = NO_JUMP;  /* always false; do nothing */
            break;
        }
        default: {
            pc = jumponcond(fs, e, 1);  /* jump if true */
            break;
        }
    }
    e.t = luaK_concat(fs, e.t, pc);  /* insert new jump in 't' list */
    luaK_patchtohere(fs, e.f);  /* false list jumps to here (to go through) */
    e.f = NO_JUMP;
};

/*
** Code 'not e', doing constant folding.
*/
const codenot = function(fs, e) {
    let ek = lparser.expkind;
    luaK_dischargevars(fs, e);
    switch (e.k) {
        case ek.VNIL: case ek.VFALSE: {
            e.k = ek.VTRUE;  /* true === not nil === not false */
            break;
        }
        case ek.VK: case ek.VKFLT: case ek.VKINT: case ek.VTRUE: {
            e.k = ek.VFALSE;  /* false === not "x" === not 0.5 === not 1 === not true */
            break;
        }
        case ek.VJMP: {
            negatecondition(fs, e);
            break;
        }
        case ek.VRELOCABLE:
        case ek.VNONRELOC: {
            discharge2anyreg(fs, e);
            freeexp(fs, e);
            e.u.info = luaK_codeABC(fs, OpCodesI.OP_NOT, 0, e.u.info, 0);
            e.k = ek.VRELOCABLE;
            break;
        }
    }
    /* interchange true and false lists */
    { let temp = e.f; e.f = e.t; e.t = temp; }
    removevalues(fs, e.f);  /* values are useless when negated */
    removevalues(fs, e.t);
};

/*
** Create expression 't[k]'. 't' must have its final result already in a
** register or upvalue.
*/
const luaK_indexed = function(fs, t, k) {
    let ek = lparser.expkind;
    lua_assert(!hasjumps(t) && (lparser.vkisinreg(t.k) || t.k === ek.VUPVAL));
    t.u.ind.t = t.u.info;  /* register or upvalue index */
    t.u.ind.idx = luaK_exp2RK(fs, k);  /* R/K index for key */
    t.u.ind.vt = (t.k === ek.VUPVAL) ? ek.VUPVAL : ek.VLOCAL;
    t.k = ek.VINDEXED;
};

/*
** Return false if folding can raise an error.
** Bitwise operations need operands convertible to integers; division
** operations cannot have 0 as divisor.
*/
const validop = function(op, v1, v2) {
    switch (op) {
        case LUA_OPBAND: case LUA_OPBOR: case LUA_OPBXOR:
        case LUA_OPSHL: case LUA_OPSHR: case LUA_OPBNOT: {  /* conversion errors */
            return (lvm.tointeger(v1) !== false && lvm.tointeger(v2) !== false);
        }
        case LUA_OPDIV: case LUA_OPIDIV: case LUA_OPMOD:  /* division by 0 */
            return (v2.value !== 0);
        default: return 1;  /* everything else is valid */
    }
};

/*
** Try to "constant-fold" an operation; return 1 iff successful.
** (In this case, 'e1' has the final result.)
*/
const constfolding = function(op, e1, e2) {
    let ek = lparser.expkind;
    let v1, v2;
    if (!(v1 = tonumeral(e1, true)) || !(v2 = tonumeral(e2, true)) || !validop(op, v1, v2))
        return 0;  /* non-numeric operands or not safe to fold */
    let res = new TValue(); /* FIXME */
    lobject.luaO_arith(null, op, v1, v2, res);  /* does operation */
    if (res.ttisinteger()) {
        e1.k = ek.VKINT;
        e1.u.ival = res.value;
    }
    else {  /* folds neither NaN nor 0.0 (to avoid problems with -0.0) */
        let n = res.value;
        if (isNaN(n) || n === 0)
            return false;
        e1.k = ek.VKFLT;
        e1.u.nval = n;
    }
    return true;
};

/*
** Emit code for unary expressions that "produce values"
** (everything but 'not').
** Expression to produce final result will be encoded in 'e'.
*/
const codeunexpval = function(fs, op, e, line) {
    let r = luaK_exp2anyreg(fs, e);  /* opcodes operate only on registers */
    freeexp(fs, e);
    e.u.info = luaK_codeABC(fs, op, 0, r, 0);  /* generate opcode */
    e.k = lparser.expkind.VRELOCABLE;  /* all those operations are relocatable */
    luaK_fixline(fs, line);
};

/*
** Emit code for binary expressions that "produce values"
** (everything but logical operators 'and'/'or' and comparison
** operators).
** Expression to produce final result will be encoded in 'e1'.
** Because 'luaK_exp2RK' can free registers, its calls must be
** in "stack order" (that is, first on 'e2', which may have more
** recent registers to be released).
*/
const codebinexpval = function(fs, op, e1, e2, line) {
    let rk2 = luaK_exp2RK(fs, e2);  /* both operands are "RK" */
    let rk1 = luaK_exp2RK(fs, e1);
    freeexps(fs, e1, e2);
    e1.u.info = luaK_codeABC(fs, op, 0, rk1, rk2);  /* generate opcode */
    e1.k = lparser.expkind.VRELOCABLE;  /* all those operations are relocatable */
    luaK_fixline(fs, line);
};


/*
** Emit code for comparisons.
** 'e1' was already put in R/K form by 'luaK_infix'.
*/
const codecomp = function(fs, opr, e1, e2) {
    let ek = lparser.expkind;

    let rk1;
    if (e1.k === ek.VK)
        rk1 = lopcodes.RKASK(e1.u.info);
    else {
        lua_assert(e1.k === ek.VNONRELOC);
        rk1 = e1.u.info;
    }

    let rk2 = luaK_exp2RK(fs, e2);
    freeexps(fs, e1, e2);
    switch (opr) {
        case BinOpr.OPR_NE: {  /* '(a ~= b)' ==> 'not (a === b)' */
            e1.u.info = condjump(fs, OpCodesI.OP_EQ, 0, rk1, rk2);
            break;
        }
        case BinOpr.OPR_GT: case BinOpr.OPR_GE: {
            /* '(a > b)' ==> '(b < a)';  '(a >= b)' ==> '(b <= a)' */
            let op = (opr - BinOpr.OPR_NE) + OpCodesI.OP_EQ;
            e1.u.info = condjump(fs, op, 1, rk2, rk1);  /* invert operands */
            break;
        }
        default: {  /* '==', '<', '<=' use their own opcodes */
            let op = (opr - BinOpr.OPR_EQ) + OpCodesI.OP_EQ;
            e1.u.info = condjump(fs, op, 1, rk1, rk2);
            break;
        }
    }
    e1.k = ek.VJMP;
};

/*
** Apply prefix operation 'op' to expression 'e'.
*/
const luaK_prefix = function(fs, op, e, line) {
    let ef = new lparser.expdesc();
    ef.k = lparser.expkind.VKINT;
    ef.u.ival = ef.u.nval = ef.u.info = 0;
    ef.t = NO_JUMP;
    ef.f = NO_JUMP;
    switch (op) {
        case UnOpr.OPR_MINUS: case UnOpr.OPR_BNOT:  /* use 'ef' as fake 2nd operand */
            if (constfolding(op + LUA_OPUNM, e, ef))
                break;
            /* FALLTHROUGH */
        case UnOpr.OPR_LEN:
            codeunexpval(fs, op + OpCodesI.OP_UNM, e, line);
            break;
        case UnOpr.OPR_NOT: codenot(fs, e); break;
    }
};

/*
** Process 1st operand 'v' of binary operation 'op' before reading
** 2nd operand.
*/
const luaK_infix = function(fs, op, v) {
    switch (op) {
        case BinOpr.OPR_AND: {
            luaK_goiftrue(fs, v);  /* go ahead only if 'v' is true */
            break;
        }
        case BinOpr.OPR_OR: {
            luaK_goiffalse(fs, v);  /* go ahead only if 'v' is false */
            break;
        }
        case BinOpr.OPR_CONCAT: {
            luaK_exp2nextreg(fs, v);  /* operand must be on the 'stack' */
            break;
        }
        case BinOpr.OPR_ADD: case BinOpr.OPR_SUB:
        case BinOpr.OPR_MUL: case BinOpr.OPR_DIV: case BinOpr.OPR_IDIV:
        case BinOpr.OPR_MOD: case BinOpr.OPR_POW:
        case BinOpr.OPR_BAND: case BinOpr.OPR_BOR: case BinOpr.OPR_BXOR:
        case BinOpr.OPR_SHL: case BinOpr.OPR_SHR: {
            if (!tonumeral(v, false))
                luaK_exp2RK(fs, v);
            /* else keep numeral, which may be folded with 2nd operand */
            break;
        }
        default: {
            luaK_exp2RK(fs, v);
            break;
        }
    }
};

/*
** Finalize code for binary operation, after reading 2nd operand.
** For '(a .. b .. c)' (which is '(a .. (b .. c))', because
** concatenation is right associative), merge second CONCAT into first
** one.
*/
const luaK_posfix = function(fs, op, e1, e2, line) {
    let ek = lparser.expkind;
    switch (op) {
        case BinOpr.OPR_AND: {
            lua_assert(e1.t === NO_JUMP);  /* list closed by 'luK_infix' */
            luaK_dischargevars(fs, e2);
            e2.f = luaK_concat(fs, e2.f, e1.f);
            e1.to(e2);
            break;
        }
        case BinOpr.OPR_OR: {
            lua_assert(e1.f === NO_JUMP);  /* list closed by 'luK_infix' */
            luaK_dischargevars(fs, e2);
            e2.t = luaK_concat(fs, e2.t, e1.t);
            e1.to(e2);
            break;
        }
        case BinOpr.OPR_CONCAT: {
            luaK_exp2val(fs, e2);
            let ins = getinstruction(fs, e2);
            if (e2.k === ek.VRELOCABLE && ins.opcode === OpCodesI.OP_CONCAT) {
                lua_assert(e1.u.info === ins.B - 1);
                freeexp(fs, e1);
                lopcodes.SETARG_B(ins, e1.u.info);
                e1.k = ek.VRELOCABLE; e1.u.info = e2.u.info;
            }
            else {
                luaK_exp2nextreg(fs, e2);  /* operand must be on the 'stack' */
                codebinexpval(fs, OpCodesI.OP_CONCAT, e1, e2, line);
            }
            break;
        }
        case BinOpr.OPR_ADD: case BinOpr.OPR_SUB: case BinOpr.OPR_MUL: case BinOpr.OPR_DIV:
        case BinOpr.OPR_IDIV: case BinOpr.OPR_MOD: case BinOpr.OPR_POW:
        case BinOpr.OPR_BAND: case BinOpr.OPR_BOR: case BinOpr.OPR_BXOR:
        case BinOpr.OPR_SHL: case BinOpr.OPR_SHR: {
            if (!constfolding(op + LUA_OPADD, e1, e2))
                codebinexpval(fs, op + OpCodesI.OP_ADD, e1, e2, line);
            break;
        }
        case BinOpr.OPR_EQ: case BinOpr.OPR_LT: case BinOpr.OPR_LE:
        case BinOpr.OPR_NE: case BinOpr.OPR_GT: case BinOpr.OPR_GE: {
            codecomp(fs, op, e1, e2);
            break;
        }
    }

    return e1;
};

/*
** Change line information associated with current position.
*/
const luaK_fixline = function(fs, line) {
    fs.f.lineinfo[fs.pc - 1] = line;
};

/*
** Emit a SETLIST instruction.
** 'base' is register that keeps table;
** 'nelems' is #table plus those to be stored now;
** 'tostore' is number of values (in registers 'base + 1',...) to add to
** table (or LUA_MULTRET to add up to stack top).
*/
const luaK_setlist = function(fs, base, nelems, tostore) {
    let c =  (nelems - 1)/lopcodes.LFIELDS_PER_FLUSH + 1;
    let b = (tostore === LUA_MULTRET) ? 0 : tostore;
    lua_assert(tostore !== 0 && tostore <= lopcodes.LFIELDS_PER_FLUSH);
    if (c <= lopcodes.MAXARG_C)
        luaK_codeABC(fs, OpCodesI.OP_SETLIST, base, b, c);
    else if (c <= lopcodes.MAXARG_Ax) {
        luaK_codeABC(fs, OpCodesI.OP_SETLIST, base, b, 0);
        codeextraarg(fs, c);
    }
    else
        llex.luaX_syntaxerror(fs.ls, to_luastring("constructor too long", true));
    fs.freereg = base + 1;  /* free registers with list values */
};


module.exports.BinOpr             = BinOpr;
module.exports.NO_JUMP            = NO_JUMP;
module.exports.UnOpr              = UnOpr;
module.exports.getinstruction     = getinstruction;
module.exports.luaK_checkstack    = luaK_checkstack;
module.exports.luaK_code          = luaK_code;
module.exports.luaK_codeABC       = luaK_codeABC;
module.exports.luaK_codeABx       = luaK_codeABx;
module.exports.luaK_codeAsBx      = luaK_codeAsBx;
module.exports.luaK_codek         = luaK_codek;
module.exports.luaK_concat        = luaK_concat;
module.exports.luaK_dischargevars = luaK_dischargevars;
module.exports.luaK_exp2RK        = luaK_exp2RK;
module.exports.luaK_exp2anyreg    = luaK_exp2anyreg;
module.exports.luaK_exp2anyregup  = luaK_exp2anyregup;
module.exports.luaK_exp2nextreg   = luaK_exp2nextreg;
module.exports.luaK_exp2val       = luaK_exp2val;
module.exports.luaK_fixline       = luaK_fixline;
module.exports.luaK_getlabel      = luaK_getlabel;
module.exports.luaK_goiffalse     = luaK_goiffalse;
module.exports.luaK_goiftrue      = luaK_goiftrue;
module.exports.luaK_indexed       = luaK_indexed;
module.exports.luaK_infix         = luaK_infix;
module.exports.luaK_intK          = luaK_intK;
module.exports.luaK_jump          = luaK_jump;
module.exports.luaK_jumpto        = luaK_jumpto;
module.exports.luaK_nil           = luaK_nil;
module.exports.luaK_numberK       = luaK_numberK;
module.exports.luaK_patchclose    = luaK_patchclose;
module.exports.luaK_patchlist     = luaK_patchlist;
module.exports.luaK_patchtohere   = luaK_patchtohere;
module.exports.luaK_posfix        = luaK_posfix;
module.exports.luaK_prefix        = luaK_prefix;
module.exports.luaK_reserveregs   = luaK_reserveregs;
module.exports.luaK_ret           = luaK_ret;
module.exports.luaK_self          = luaK_self;
module.exports.luaK_setlist       = luaK_setlist;
module.exports.luaK_setmultret    = luaK_setmultret;
module.exports.luaK_setoneret     = luaK_setoneret;
module.exports.luaK_setreturns    = luaK_setreturns;
module.exports.luaK_storevar      = luaK_storevar;
module.exports.luaK_stringK       = luaK_stringK;