Lua2RTT/lua-5.3.4/lcode.c

/*
** $Id: lcode.c,v 2.112 2016/12/22 13:08:50 roberto Exp $
** Code generator for Lua
** See Copyright Notice in lua.h
*/

#define lcode_c
#define LUA_CORE

#include "lprefix.h"


#include <math.h>
#include <stdlib.h>

#include "lua.h"

#include "lcode.h"
#include "ldebug.h"
#include "ldo.h"
#include "lgc.h"
#include "llex.h"
#include "lmem.h"
#include "lobject.h"
#include "lopcodes.h"
#include "lparser.h"
#include "lstring.h"
#include "ltable.h"
#include "lvm.h"


/* Maximum number of registers in a Lua function (must fit in 8 bits) */
#define MAXREGS     255


#define hasjumps(e) ((e)->t != (e)->f)


/*
** If expression is a numeric constant, fills 'v' with its value
** and returns 1. Otherwise, returns 0.
*/
static int tonumeral(const expdesc *e, TValue *v)
{
    if (hasjumps(e))
        return 0;  /* not a numeral */
    switch (e->k)
    {
    case VKINT:
        if (v) setivalue(v, e->u.ival);
        return 1;
    case VKFLT:
        if (v) setfltvalue(v, e->u.nval);
        return 1;
    default:
        return 0;
    }
}


/*
** 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.)
*/
void luaK_nil(FuncState *fs, int from, int n)
{
    Instruction *previous;
    int 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 (GET_OPCODE(*previous) == OP_LOADNIL)    /* previous is LOADNIL? */
        {
            int pfrom = GETARG_A(*previous);  /* get previous range */
            int pl = pfrom + GETARG_B(*previous);
            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) */
                SETARG_A(*previous, from);
                SETARG_B(*previous, l - from);
                return;
            }
        }  /* else go through */
    }
    luaK_codeABC(fs, OP_LOADNIL, from, n - 1, 0);  /* else no optimization */
}


/*
** Gets the destination address of a jump instruction. Used to traverse
** a list of jumps.
*/
static int getjump(FuncState *fs, int pc)
{
    int offset = GETARG_sBx(fs->f->code[pc]);
    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)
*/
static void fixjump(FuncState *fs, int pc, int dest)
{
    Instruction *jmp = &fs->f->code[pc];
    int offset = dest - (pc + 1);
    lua_assert(dest != NO_JUMP);
    if (abs(offset) > MAXARG_sBx)
        luaX_syntaxerror(fs->ls, "control structure too long");
    SETARG_sBx(*jmp, offset);
}


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


/*
** 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.
*/
int luaK_jump(FuncState *fs)
{
    int jpc = fs->jpc;  /* save list of jumps to here */
    int j;
    fs->jpc = NO_JUMP;  /* no more jumps to here */
    j = luaK_codeAsBx(fs, OP_JMP, 0, NO_JUMP);
    luaK_concat(fs, &j, jpc);  /* keep them on hold */
    return j;
}


/*
** Code a 'return' instruction
*/
void luaK_ret(FuncState *fs, int first, int nret)
{
    luaK_codeABC(fs, OP_RETURN, first, nret + 1, 0);
}


/*
** Code a "conditional jump", that is, a test or comparison opcode
** followed by a jump. Return jump position.
*/
static int condjump(FuncState *fs, OpCode op, int A, int B, int 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).
*/
int luaK_getlabel(FuncState *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.
*/
static Instruction *getjumpcontrol(FuncState *fs, int pc)
{
    Instruction *pi = &fs->f->code[pc];
    if (pc >= 1 && testTMode(GET_OPCODE(*(pi - 1))))
        return pi - 1;
    else
        return pi;
}


/*
** 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)
*/
static int patchtestreg(FuncState *fs, int node, int reg)
{
    Instruction *i = getjumpcontrol(fs, node);
    if (GET_OPCODE(*i) != OP_TESTSET)
        return 0;  /* cannot patch other instructions */
    if (reg != NO_REG && reg != GETARG_B(*i))
        SETARG_A(*i, reg);
    else
    {
        /* no register to put value or register already has the value;
           change instruction to simple test */
        *i = CREATE_ABC(OP_TEST, GETARG_B(*i), 0, GETARG_C(*i));
    }
    return 1;
}


/*
** Traverse a list of tests ensuring no one produces a value
*/
static void removevalues(FuncState *fs, int list)
{
    for (; list != NO_JUMP; list = getjump(fs, list))
        patchtestreg(fs, list, 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'.
*/
static void patchlistaux(FuncState *fs, int list, int vtarget, int reg,
                         int dtarget)
{
    while (list != NO_JUMP)
    {
        int 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
*/
static void dischargejpc(FuncState *fs)
{
    patchlistaux(fs, fs->jpc, fs->pc, NO_REG, fs->pc);
    fs->jpc = NO_JUMP;
}


/*
** Add elements in 'list' to list of pending jumps to "here"
** (current position)
*/
void luaK_patchtohere(FuncState *fs, int list)
{
    luaK_getlabel(fs);  /* mark "here" as a jump target */
    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.)
*/
void luaK_patchlist(FuncState *fs, int list, int 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, 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.)
*/
void luaK_patchclose(FuncState *fs, int list, int level)
{
    level++;  /* argument is +1 to reserve 0 as non-op */
    for (; list != NO_JUMP; list = getjump(fs, list))
    {
        lua_assert(GET_OPCODE(fs->f->code[list]) == OP_JMP &&
                   (GETARG_A(fs->f->code[list]) == 0 ||
                    GETARG_A(fs->f->code[list]) >= level));
        SETARG_A(fs->f->code[list], level);
    }
}


/*
** Emit instruction 'i', checking for array sizes and saving also its
** line information. Return 'i' position.
*/
static int luaK_code(FuncState *fs, Instruction i)
{
    Proto *f = fs->f;
    dischargejpc(fs);  /* 'pc' will change */
    /* put new instruction in code array */
    luaM_growvector(fs->ls->L, f->code, fs->pc, f->sizecode, Instruction,
                    MAX_INT, "opcodes");
    f->code[fs->pc] = i;
    /* save corresponding line information */
    luaM_growvector(fs->ls->L, f->lineinfo, fs->pc, f->sizelineinfo, int,
                    MAX_INT, "opcodes");
    f->lineinfo[fs->pc] = fs->ls->lastline;
    return fs->pc++;
}


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


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


/*
** Emit an "extra argument" instruction (format 'iAx')
*/
static int codeextraarg(FuncState *fs, int a)
{
    lua_assert(a <= MAXARG_Ax);
    return luaK_code(fs, CREATE_Ax(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".
*/
int luaK_codek(FuncState *fs, int reg, int k)
{
    if (k <= MAXARG_Bx)
        return luaK_codeABx(fs, OP_LOADK, reg, k);
    else
    {
        int p = luaK_codeABx(fs, OP_LOADKX, reg, 0);
        codeextraarg(fs, k);
        return p;
    }
}


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


/*
** Reserve 'n' registers in register stack
*/
void luaK_reserveregs(FuncState *fs, int n)
{
    luaK_checkstack(fs, n);
    fs->freereg += n;
}


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


/*
** Free register used by expression 'e' (if any)
*/
static void freeexp(FuncState *fs, expdesc *e)
{
    if (e->k == VNONRELOC)
        freereg(fs, e->u.info);
}


/*
** Free registers used by expressions 'e1' and 'e2' (if any) in proper
** order.
*/
static void freeexps(FuncState *fs, expdesc *e1, expdesc *e2)
{
    int r1 = (e1->k == VNONRELOC) ? e1->u.info : -1;
    int r2 = (e2->k == 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.
*/
static int addk(FuncState *fs, TValue *key, TValue *v)
{
    lua_State *L = fs->ls->L;
    Proto *f = fs->f;
    TValue *idx = luaH_set(L, fs->ls->h, key);  /* index scanner table */
    int k, oldsize;
    if (ttisinteger(idx))    /* is there an index there? */
    {
        k = cast_int(ivalue(idx));
        /* correct value? (warning: must distinguish floats from integers!) */
        if (k < fs->nk && ttype(&f->k[k]) == ttype(v) &&
                luaV_rawequalobj(&f->k[k], v))
            return k;  /* reuse index */
    }
    /* constant not found; create a new entry */
    oldsize = f->sizek;
    k = fs->nk;
    /* numerical value does not need GC barrier;
       table has no metatable, so it does not need to invalidate cache */
    setivalue(idx, k);
    luaM_growvector(L, f->k, k, f->sizek, TValue, MAXARG_Ax, "constants");
    while (oldsize < f->sizek) setnilvalue(&f->k[oldsize++]);
    setobj(L, &f->k[k], v);
    fs->nk++;
    luaC_barrier(L, f, v);
    return k;
}


/*
** Add a string to list of constants and return its index.
*/
int luaK_stringK(FuncState *fs, TString *s)
{
    TValue o;
    setsvalue(fs->ls->L, &o, 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; conversion to 'void*' is used only for hashing, so there
** are no "precision" problems.
*/
int luaK_intK(FuncState *fs, lua_Integer n)
{
    TValue k, o;
    setpvalue(&k, cast(void *, cast(size_t, n)));
    setivalue(&o, n);
    return addk(fs, &k, &o);
}

/*
** Add a float to list of constants and return its index.
*/
static int luaK_numberK(FuncState *fs, lua_Number r)
{
    TValue o;
    setfltvalue(&o, r);
    return addk(fs, &o, &o);  /* use number itself as key */
}


/*
** Add a boolean to list of constants and return its index.
*/
static int boolK(FuncState *fs, int b)
{
    TValue o;
    setbvalue(&o, b);
    return addk(fs, &o, &o);  /* use boolean itself as key */
}


/*
** Add nil to list of constants and return its index.
*/
static int nilK(FuncState *fs)
{
    TValue k, v;
    setnilvalue(&v);
    /* cannot use nil as key; instead use table itself to represent nil */
    sethvalue(fs->ls->L, &k, fs->ls->h);
    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).
*/
void luaK_setreturns(FuncState *fs, expdesc *e, int nresults)
{
    if (e->k == VCALL)    /* expression is an open function call? */
    {
        SETARG_C(getinstruction(fs, e), nresults + 1);
    }
    else if (e->k == VVARARG)
    {
        Instruction *pc = &getinstruction(fs, e);
        SETARG_B(*pc, nresults + 1);
        SETARG_A(*pc, fs->freereg);
        luaK_reserveregs(fs, 1);
    }
    else lua_assert(nresults == 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.)
*/
void luaK_setoneret(FuncState *fs, expdesc *e)
{
    if (e->k == VCALL)    /* expression is an open function call? */
    {
        /* already returns 1 value */
        lua_assert(GETARG_C(getinstruction(fs, e)) == 2);
        e->k = VNONRELOC;  /* result has fixed position */
        e->u.info = GETARG_A(getinstruction(fs, e));
    }
    else if (e->k == VVARARG)
    {
        SETARG_B(getinstruction(fs, e), 2);
        e->k = VRELOCABLE;  /* can relocate its simple result */
    }
}


/*
** Ensure that expression 'e' is not a variable.
*/
void luaK_dischargevars(FuncState *fs, expdesc *e)
{
    switch (e->k)
    {
    case VLOCAL:    /* already in a register */
    {
        e->k = VNONRELOC;  /* becomes a non-relocatable value */
        break;
    }
    case VUPVAL:    /* move value to some (pending) register */
    {
        e->u.info = luaK_codeABC(fs, OP_GETUPVAL, 0, e->u.info, 0);
        e->k = VRELOCABLE;
        break;
    }
    case VINDEXED:
    {
        OpCode op;
        freereg(fs, e->u.ind.idx);
        if (e->u.ind.vt == VLOCAL)    /* is 't' in a register? */
        {
            freereg(fs, e->u.ind.t);
            op = OP_GETTABLE;
        }
        else
        {
            lua_assert(e->u.ind.vt == VUPVAL);
            op = 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 = VRELOCABLE;
        break;
    }
    case VVARARG:
    case VCALL:
    {
        luaK_setoneret(fs, e);
        break;
    }
    default:
        break;  /* there is one value available (somewhere) */
    }
}


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


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


static int code_loadbool(FuncState *fs, int A, int b, int jump)
{
    luaK_getlabel(fs);  /* those instructions may be jump targets */
    return luaK_codeABC(fs, OP_LOADBOOL, A, b, jump);
}


/*
** check whether list has any jump that do not produce a value
** or produce an inverted value
*/
static int need_value(FuncState *fs, int list)
{
    for (; list != NO_JUMP; list = getjump(fs, list))
    {
        Instruction i = *getjumpcontrol(fs, list);
        if (GET_OPCODE(i) != OP_TESTSET) return 1;
    }
    return 0;  /* 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).
*/
static void exp2reg(FuncState *fs, expdesc *e, int reg)
{
    discharge2reg(fs, e, reg);
    if (e->k == VJMP)  /* expression itself is a test? */
        luaK_concat(fs, &e->t, e->u.info);  /* put this jump in 't' list */
    if (hasjumps(e))
    {
        int final;  /* position after whole expression */
        int p_f = NO_JUMP;  /* position of an eventual LOAD false */
        int p_t = NO_JUMP;  /* position of an eventual LOAD true */
        if (need_value(fs, e->t) || need_value(fs, e->f))
        {
            int fj = (e->k == 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 = VNONRELOC;
}


/*
** Ensures final expression result (including results from its jump
** lists) is in next available register.
*/
void luaK_exp2nextreg(FuncState *fs, expdesc *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.
*/
int luaK_exp2anyreg(FuncState *fs, expdesc *e)
{
    luaK_dischargevars(fs, e);
    if (e->k == 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.
*/
void luaK_exp2anyregup(FuncState *fs, expdesc *e)
{
    if (e->k != VUPVAL || hasjumps(e))
        luaK_exp2anyreg(fs, e);
}


/*
** Ensures final expression result is either in a register or it is
** a constant.
*/
void luaK_exp2val(FuncState *fs, expdesc *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.
*/
int luaK_exp2RK(FuncState *fs, expdesc *e)
{
    luaK_exp2val(fs, e);
    switch (e->k)    /* move constants to 'k' */
    {
    case VTRUE:
        e->u.info = boolK(fs, 1);
        goto vk;
    case VFALSE:
        e->u.info = boolK(fs, 0);
        goto vk;
    case VNIL:
        e->u.info = nilK(fs);
        goto vk;
    case VKINT:
        e->u.info = luaK_intK(fs, e->u.ival);
        goto vk;
    case VKFLT:
        e->u.info = luaK_numberK(fs, e->u.nval);
        goto vk;
    case VK:
vk:
        e->k = VK;
        if (e->u.info <= MAXINDEXRK)  /* constant fits in 'argC'? */
            return RKASK(e->u.info);
        else break;
    default:
        break;
    }
    /* 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'.
*/
void luaK_storevar(FuncState *fs, expdesc *var, expdesc *ex)
{
    switch (var->k)
    {
    case VLOCAL:
    {
        freeexp(fs, ex);
        exp2reg(fs, ex, var->u.info);  /* compute 'ex' into proper place */
        return;
    }
    case VUPVAL:
    {
        int e = luaK_exp2anyreg(fs, ex);
        luaK_codeABC(fs, OP_SETUPVAL, e, var->u.info, 0);
        break;
    }
    case VINDEXED:
    {
        OpCode op = (var->u.ind.vt == VLOCAL) ? OP_SETTABLE : OP_SETTABUP;
        int e = luaK_exp2RK(fs, ex);
        luaK_codeABC(fs, op, var->u.ind.t, var->u.ind.idx, e);
        break;
    }
    default:
        lua_assert(0);  /* invalid var kind to store */
    }
    freeexp(fs, ex);
}


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


/*
** Negate condition 'e' (where 'e' is a comparison).
*/
static void negatecondition(FuncState *fs, expdesc *e)
{
    Instruction *pc = getjumpcontrol(fs, e->u.info);
    lua_assert(testTMode(GET_OPCODE(*pc)) && GET_OPCODE(*pc) != OP_TESTSET &&
               GET_OPCODE(*pc) != OP_TEST);
    SETARG_A(*pc, !(GETARG_A(*pc)));
}


/*
** 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'.
*/
static int jumponcond(FuncState *fs, expdesc *e, int cond)
{
    if (e->k == VRELOCABLE)
    {
        Instruction ie = getinstruction(fs, e);
        if (GET_OPCODE(ie) == OP_NOT)
        {
            fs->pc--;  /* remove previous OP_NOT */
            return condjump(fs, OP_TEST, GETARG_B(ie), 0, !cond);
        }
        /* else go through */
    }
    discharge2anyreg(fs, e);
    freeexp(fs, e);
    return condjump(fs, OP_TESTSET, NO_REG, e->u.info, cond);
}


/*
** Emit code to go through if 'e' is true, jump otherwise.
*/
void luaK_goiftrue(FuncState *fs, expdesc *e)
{
    int pc;  /* pc of new jump */
    luaK_dischargevars(fs, e);
    switch (e->k)
    {
    case VJMP:    /* condition? */
    {
        negatecondition(fs, e);  /* jump when it is false */
        pc = e->u.info;  /* save jump position */
        break;
    }
    case VK:
    case VKFLT:
    case VKINT:
    case VTRUE:
    {
        pc = NO_JUMP;  /* always true; do nothing */
        break;
    }
    default:
    {
        pc = jumponcond(fs, e, 0);  /* jump when false */
        break;
    }
    }
    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.
*/
void luaK_goiffalse(FuncState *fs, expdesc *e)
{
    int pc;  /* pc of new jump */
    luaK_dischargevars(fs, e);
    switch (e->k)
    {
    case VJMP:
    {
        pc = e->u.info;  /* already jump if true */
        break;
    }
    case VNIL:
    case VFALSE:
    {
        pc = NO_JUMP;  /* always false; do nothing */
        break;
    }
    default:
    {
        pc = jumponcond(fs, e, 1);  /* jump if true */
        break;
    }
    }
    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.
*/
static void codenot(FuncState *fs, expdesc *e)
{
    luaK_dischargevars(fs, e);
    switch (e->k)
    {
    case VNIL:
    case VFALSE:
    {
        e->k = VTRUE;  /* true == not nil == not false */
        break;
    }
    case VK:
    case VKFLT:
    case VKINT:
    case VTRUE:
    {
        e->k = VFALSE;  /* false == not "x" == not 0.5 == not 1 == not true */
        break;
    }
    case VJMP:
    {
        negatecondition(fs, e);
        break;
    }
    case VRELOCABLE:
    case VNONRELOC:
    {
        discharge2anyreg(fs, e);
        freeexp(fs, e);
        e->u.info = luaK_codeABC(fs, OP_NOT, 0, e->u.info, 0);
        e->k = VRELOCABLE;
        break;
    }
    default:
        lua_assert(0);  /* cannot happen */
    }
    /* interchange true and false lists */
    {
        int 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.
*/
void luaK_indexed(FuncState *fs, expdesc *t, expdesc *k)
{
    lua_assert(!hasjumps(t) && (vkisinreg(t->k) || t->k == 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 == VUPVAL) ? VUPVAL : VLOCAL;
    t->k = VINDEXED;
}


/*
** Return false if folding can raise an error.
** Bitwise operations need operands convertible to integers; division
** operations cannot have 0 as divisor.
*/
static int validop(int op, TValue *v1, TValue *v2)
{
    switch (op)
    {
    case LUA_OPBAND:
    case LUA_OPBOR:
    case LUA_OPBXOR:
    case LUA_OPSHL:
    case LUA_OPSHR:
    case LUA_OPBNOT:    /* conversion errors */
    {
        lua_Integer i;
        return (tointeger(v1, &i) && tointeger(v2, &i));
    }
    case LUA_OPDIV:
    case LUA_OPIDIV:
    case LUA_OPMOD:  /* division by 0 */
        return (nvalue(v2) != 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.)
*/
static int constfolding(FuncState *fs, int op, expdesc *e1,
                        const expdesc *e2)
{
    TValue v1, v2, res;
    if (!tonumeral(e1, &v1) || !tonumeral(e2, &v2) || !validop(op, &v1, &v2))
        return 0;  /* non-numeric operands or not safe to fold */
    luaO_arith(fs->ls->L, op, &v1, &v2, &res);  /* does operation */
    if (ttisinteger(&res))
    {
        e1->k = VKINT;
        e1->u.ival = ivalue(&res);
    }
    else    /* folds neither NaN nor 0.0 (to avoid problems with -0.0) */
    {
        lua_Number n = fltvalue(&res);
        if (luai_numisnan(n) || n == 0)
            return 0;
        e1->k = VKFLT;
        e1->u.nval = n;
    }
    return 1;
}


/*
** Emit code for unary expressions that "produce values"
** (everything but 'not').
** Expression to produce final result will be encoded in 'e'.
*/
static void codeunexpval(FuncState *fs, OpCode op, expdesc *e, int line)
{
    int 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 = 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).
*/
static void codebinexpval(FuncState *fs, OpCode op,
                          expdesc *e1, expdesc *e2, int line)
{
    int rk2 = luaK_exp2RK(fs, e2);  /* both operands are "RK" */
    int rk1 = luaK_exp2RK(fs, e1);
    freeexps(fs, e1, e2);
    e1->u.info = luaK_codeABC(fs, op, 0, rk1, rk2);  /* generate opcode */
    e1->k = 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'.
*/
static void codecomp(FuncState *fs, BinOpr opr, expdesc *e1, expdesc *e2)
{
    int rk1 = (e1->k == VK) ? RKASK(e1->u.info)
              : check_exp(e1->k == VNONRELOC, e1->u.info);
    int rk2 = luaK_exp2RK(fs, e2);
    freeexps(fs, e1, e2);
    switch (opr)
    {
    case OPR_NE:    /* '(a ~= b)' ==> 'not (a == b)' */
    {
        e1->u.info = condjump(fs, OP_EQ, 0, rk1, rk2);
        break;
    }
    case OPR_GT:
    case OPR_GE:
    {
        /* '(a > b)' ==> '(b < a)';  '(a >= b)' ==> '(b <= a)' */
        OpCode op = cast(OpCode, (opr - OPR_NE) + OP_EQ);
        e1->u.info = condjump(fs, op, 1, rk2, rk1);  /* invert operands */
        break;
    }
    default:    /* '==', '<', '<=' use their own opcodes */
    {
        OpCode op = cast(OpCode, (opr - OPR_EQ) + OP_EQ);
        e1->u.info = condjump(fs, op, 1, rk1, rk2);
        break;
    }
    }
    e1->k = VJMP;
}


/*
** Aplly prefix operation 'op' to expression 'e'.
*/
void luaK_prefix(FuncState *fs, UnOpr op, expdesc *e, int line)
{
    static const expdesc ef = {VKINT, {0}, NO_JUMP, NO_JUMP};
    switch (op)
    {
    case OPR_MINUS:
    case OPR_BNOT:  /* use 'ef' as fake 2nd operand */
        if (constfolding(fs, op + LUA_OPUNM, e, &ef))
            break;
        /* FALLTHROUGH */
    case OPR_LEN:
        codeunexpval(fs, cast(OpCode, op + OP_UNM), e, line);
        break;
    case OPR_NOT:
        codenot(fs, e);
        break;
    default:
        lua_assert(0);
    }
}


/*
** Process 1st operand 'v' of binary operation 'op' before reading
** 2nd operand.
*/
void luaK_infix(FuncState *fs, BinOpr op, expdesc *v)
{
    switch (op)
    {
    case OPR_AND:
    {
        luaK_goiftrue(fs, v);  /* go ahead only if 'v' is true */
        break;
    }
    case OPR_OR:
    {
        luaK_goiffalse(fs, v);  /* go ahead only if 'v' is false */
        break;
    }
    case OPR_CONCAT:
    {
        luaK_exp2nextreg(fs, v);  /* operand must be on the 'stack' */
        break;
    }
    case OPR_ADD:
    case OPR_SUB:
    case OPR_MUL:
    case OPR_DIV:
    case OPR_IDIV:
    case OPR_MOD:
    case OPR_POW:
    case OPR_BAND:
    case OPR_BOR:
    case OPR_BXOR:
    case OPR_SHL:
    case OPR_SHR:
    {
        if (!tonumeral(v, NULL))
            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.
*/
void luaK_posfix(FuncState *fs, BinOpr op,
                 expdesc *e1, expdesc *e2, int line)
{
    switch (op)
    {
    case OPR_AND:
    {
        lua_assert(e1->t == NO_JUMP);  /* list closed by 'luK_infix' */
        luaK_dischargevars(fs, e2);
        luaK_concat(fs, &e2->f, e1->f);
        *e1 = *e2;
        break;
    }
    case OPR_OR:
    {
        lua_assert(e1->f == NO_JUMP);  /* list closed by 'luK_infix' */
        luaK_dischargevars(fs, e2);
        luaK_concat(fs, &e2->t, e1->t);
        *e1 = *e2;
        break;
    }
    case OPR_CONCAT:
    {
        luaK_exp2val(fs, e2);
        if (e2->k == VRELOCABLE &&
                GET_OPCODE(getinstruction(fs, e2)) == OP_CONCAT)
        {
            lua_assert(e1->u.info == GETARG_B(getinstruction(fs, e2)) - 1);
            freeexp(fs, e1);
            SETARG_B(getinstruction(fs, e2), e1->u.info);
            e1->k = VRELOCABLE;
            e1->u.info = e2->u.info;
        }
        else
        {
            luaK_exp2nextreg(fs, e2);  /* operand must be on the 'stack' */
            codebinexpval(fs, OP_CONCAT, e1, e2, line);
        }
        break;
    }
    case OPR_ADD:
    case OPR_SUB:
    case OPR_MUL:
    case OPR_DIV:
    case OPR_IDIV:
    case OPR_MOD:
    case OPR_POW:
    case OPR_BAND:
    case OPR_BOR:
    case OPR_BXOR:
    case OPR_SHL:
    case OPR_SHR:
    {
        if (!constfolding(fs, op + LUA_OPADD, e1, e2))
            codebinexpval(fs, cast(OpCode, op + OP_ADD), e1, e2, line);
        break;
    }
    case OPR_EQ:
    case OPR_LT:
    case OPR_LE:
    case OPR_NE:
    case OPR_GT:
    case OPR_GE:
    {
        codecomp(fs, op, e1, e2);
        break;
    }
    default:
        lua_assert(0);
    }
}


/*
** Change line information associated with current position.
*/
void luaK_fixline(FuncState *fs, int 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).
*/
void luaK_setlist(FuncState *fs, int base, int nelems, int tostore)
{
    int c = (nelems - 1) / LFIELDS_PER_FLUSH + 1;
    int b = (tostore == LUA_MULTRET) ? 0 : tostore;
    lua_assert(tostore != 0 && tostore <= LFIELDS_PER_FLUSH);
    if (c <= MAXARG_C)
        luaK_codeABC(fs, OP_SETLIST, base, b, c);
    else if (c <= MAXARG_Ax)
    {
        luaK_codeABC(fs, OP_SETLIST, base, b, 0);
        codeextraarg(fs, c);
    }
    else
        luaX_syntaxerror(fs->ls, "constructor too long");
    fs->freereg = base + 1;  /* free registers with list values */
}