/*
** Lua parser (source code -> bytecode).
** Copyright (C) 2005-2014 Mike Pall. See Copyright Notice in luajit.h
**
** Major portions taken verbatim or adapted from the Lua interpreter.
** Copyright (C) 1994-2008 Lua.org, PUC-Rio. See Copyright Notice in lua.h
*/

#define lj_parse_c
#define LUA_CORE

#include "lj_obj.h"
#include "lj_gc.h"
#include "lj_err.h"
#include "lj_debug.h"
#include "lj_str.h"
#include "lj_tab.h"
#include "lj_func.h"
#include "lj_state.h"
#include "lj_bc.h"
#if LJ_HASFFI
    #include "lj_ctype.h"
#endif
#include "lj_lex.h"
#include "lj_parse.h"
#include "lj_vm.h"
#include "lj_vmevent.h"

/* -- Parser structures and definitions ----------------------------------- */

/* Expression kinds. */
typedef enum {
    /* Constant expressions must be first and in this order: */
    VKNIL,
    VKFALSE,
    VKTRUE,
    VKSTR, /* sval = string value */
    VKNUM, /* nval = number value */
    VKLAST = VKNUM,
    VKCDATA, /* nval = cdata value, not treated as a constant expression */
    /* Non-constant expressions follow: */
    VLOCAL,     /* info = local register, aux = vstack index */
    VUPVAL,     /* info = upvalue index, aux = vstack index */
    VGLOBAL,    /* sval = string value */
    VINDEXED,   /* info = table register, aux = index reg/byte/string const */
    VJMP,       /* info = instruction PC */
    VRELOCABLE, /* info = instruction PC */
    VNONRELOC,  /* info = result register */
    VCALL,      /* info = instruction PC, aux = base */
    VVOID
} ExpKind;

/* Expression descriptor. */
typedef struct ExpDesc {
    union {
        struct {
            uint32_t info; /* Primary info. */
            uint32_t aux;  /* Secondary info. */
        } s;
        TValue nval; /* Number value. */
        GCstr *sval; /* String value. */
    } u;
    ExpKind k;
    BCPos t; /* True condition jump list. */
    BCPos f; /* False condition jump list. */
} ExpDesc;

/* Macros for expressions. */
#define expr_hasjump(e) ((e)->t != (e)->f)

#define expr_isk(e) ((e)->k <= VKLAST)
#define expr_isk_nojump(e) (expr_isk(e) && !expr_hasjump(e))
#define expr_isnumk(e) ((e)->k == VKNUM)
#define expr_isnumk_nojump(e) (expr_isnumk(e) && !expr_hasjump(e))
#define expr_isstrk(e) ((e)->k == VKSTR)

#define expr_numtv(e) check_exp(expr_isnumk((e)), &(e)->u.nval)
#define expr_numberV(e) numberVnum(expr_numtv((e)))

/* Initialize expression. */
static LJ_AINLINE void expr_init(ExpDesc *e, ExpKind k, uint32_t info)
{
    e->k = k;
    e->u.s.info = info;
    e->f = e->t = NO_JMP;
}

/* Check number constant for +-0. */
static int expr_numiszero(ExpDesc *e)
{
    TValue *o = expr_numtv(e);
    return tvisint(o) ? (intV(o) == 0) : tviszero(o);
}

/* Per-function linked list of scope blocks. */
typedef struct FuncScope {
    struct FuncScope *prev; /* Link to outer scope. */
    MSize vstart;           /* Start of block-local variables. */
    uint8_t nactvar;        /* Number of active vars outside the scope. */
    uint8_t flags;          /* Scope flags. */
} FuncScope;

#define FSCOPE_LOOP 0x01    /* Scope is a (breakable) loop. */
#define FSCOPE_BREAK 0x02   /* Break used in scope. */
#define FSCOPE_GOLA 0x04    /* Goto or label used in scope. */
#define FSCOPE_UPVAL 0x08   /* Upvalue in scope. */
#define FSCOPE_NOCLOSE 0x10 /* Do not close upvalues. */

#define NAME_BREAK ((GCstr *)(uintptr_t)1)

/* Index into variable stack. */
typedef uint16_t VarIndex;
#define LJ_MAX_VSTACK (65536 - LJ_MAX_UPVAL)

/* Variable/goto/label info. */
#define VSTACK_VAR_RW 0x01 /* R/W variable. */
#define VSTACK_GOTO 0x02   /* Pending goto. */
#define VSTACK_LABEL 0x04  /* Label. */

/* Per-function state. */
typedef struct FuncState {
    GCtab *kt;              /* Hash table for constants. */
    LexState *ls;           /* Lexer state. */
    lua_State *L;           /* Lua state. */
    FuncScope *bl;          /* Current scope. */
    struct FuncState *prev; /* Enclosing function. */
    BCPos pc;               /* Next bytecode position. */
    BCPos lasttarget;       /* Bytecode position of last jump target. */
    BCPos jpc;              /* Pending jump list to next bytecode. */
    BCReg freereg;          /* First free register. */
    BCReg nactvar;          /* Number of active local variables. */
    BCReg nkn, nkgc;        /* Number of lua_Number/GCobj constants */
    BCLine linedefined;     /* First line of the function definition. */
    BCInsLine *bcbase;      /* Base of bytecode stack. */
    BCPos bclim;            /* Limit of bytecode stack. */
    MSize vbase;            /* Base of variable stack for this function. */
    uint8_t flags;          /* Prototype flags. */
    uint8_t numparams;      /* Number of parameters. */
    uint8_t framesize;      /* Fixed frame size. */
    uint8_t nuv;            /* Number of upvalues */
    VarIndex varmap[LJ_MAX_LOCVAR]; /* Map from register to variable idx. */
    VarIndex uvmap[LJ_MAX_UPVAL];   /* Map from upvalue to variable idx. */
    VarIndex uvtmp[LJ_MAX_UPVAL];   /* Temporary upvalue map. */
} FuncState;

/* Binary and unary operators. ORDER OPR */
typedef enum BinOpr {
    OPR_ADD,
    OPR_SUB,
    OPR_MUL,
    OPR_DIV,
    OPR_MOD,
    OPR_POW, /* ORDER ARITH */
    OPR_CONCAT,
    OPR_NE,
    OPR_EQ,
    OPR_LT,
    OPR_GE,
    OPR_LE,
    OPR_GT,
    OPR_AND,
    OPR_OR,
    OPR_NOBINOPR
} BinOpr;

LJ_STATIC_ASSERT((int)BC_ISGE - (int)BC_ISLT == (int)OPR_GE - (int)OPR_LT);
LJ_STATIC_ASSERT((int)BC_ISLE - (int)BC_ISLT == (int)OPR_LE - (int)OPR_LT);
LJ_STATIC_ASSERT((int)BC_ISGT - (int)BC_ISLT == (int)OPR_GT - (int)OPR_LT);
LJ_STATIC_ASSERT((int)BC_SUBVV - (int)BC_ADDVV == (int)OPR_SUB - (int)OPR_ADD);
LJ_STATIC_ASSERT((int)BC_MULVV - (int)BC_ADDVV == (int)OPR_MUL - (int)OPR_ADD);
LJ_STATIC_ASSERT((int)BC_DIVVV - (int)BC_ADDVV == (int)OPR_DIV - (int)OPR_ADD);
LJ_STATIC_ASSERT((int)BC_MODVV - (int)BC_ADDVV == (int)OPR_MOD - (int)OPR_ADD);

/* -- Error handling ------------------------------------------------------ */

LJ_NORET LJ_NOINLINE static void err_syntax(LexState *ls, ErrMsg em)
{
    lj_lex_error(ls, ls->token, em);
}

LJ_NORET LJ_NOINLINE static void err_token(LexState *ls, LexToken token)
{
    lj_lex_error(ls, ls->token, LJ_ERR_XTOKEN, lj_lex_token2str(ls, token));
}

LJ_NORET static void err_limit(FuncState *fs, uint32_t limit, const char *what)
{
    if (fs->linedefined == 0)
        lj_lex_error(fs->ls, 0, LJ_ERR_XLIMM, limit, what);
    else
        lj_lex_error(fs->ls, 0, LJ_ERR_XLIMF, fs->linedefined, limit, what);
}

#define checklimit(fs, v, l, m)                                                \
    if ((v) >= (l))                                                            \
    err_limit(fs, l, m)
#define checklimitgt(fs, v, l, m)                                              \
    if ((v) > (l))                                                             \
    err_limit(fs, l, m)
#define checkcond(ls, c, em)                                                   \
    {                                                                          \
        if (!(c))                                                              \
            err_syntax(ls, em);                                                \
    }

/* -- Management of constants --------------------------------------------- */

/* Return bytecode encoding for primitive constant. */
#define const_pri(e) check_exp((e)->k <= VKTRUE, (e)->k)

#define tvhaskslot(o) ((o)->u32.hi == 0)
#define tvkslot(o) ((o)->u32.lo)

/* Add a number constant. */
static BCReg const_num(FuncState *fs, ExpDesc *e)
{
    lua_State *L = fs->L;
    TValue *o;
    lua_assert(expr_isnumk(e));
    o = lj_tab_set(L, fs->kt, &e->u.nval);
    if (tvhaskslot(o))
        return tvkslot(o);
    o->u64 = fs->nkn;
    return fs->nkn++;
}

/* Add a GC object constant. */
static BCReg const_gc(FuncState *fs, GCobj *gc, uint32_t itype)
{
    lua_State *L = fs->L;
    TValue key, *o;
    setgcV(L, &key, gc, itype);
    /* NOBARRIER: the key is new or kept alive. */
    o = lj_tab_set(L, fs->kt, &key);
    if (tvhaskslot(o))
        return tvkslot(o);
    o->u64 = fs->nkgc;
    return fs->nkgc++;
}

/* Add a string constant. */
static BCReg const_str(FuncState *fs, ExpDesc *e)
{
    lua_assert(expr_isstrk(e) || e->k == VGLOBAL);
    return const_gc(fs, obj2gco(e->u.sval), LJ_TSTR);
}

/* Anchor string constant to avoid GC. */
GCstr *lj_parse_keepstr(LexState *ls, const char *str, size_t len)
{
    /* NOBARRIER: the key is new or kept alive. */
    lua_State *L = ls->L;
    GCstr *s = lj_str_new(L, str, len);
    TValue *tv = lj_tab_setstr(L, ls->fs->kt, s);
    if (tvisnil(tv))
        setboolV(tv, 1);
    lj_gc_check(L);
    return s;
}

#if LJ_HASFFI
/* Anchor cdata to avoid GC. */
void lj_parse_keepcdata(LexState *ls, TValue *tv, GCcdata *cd)
{
    /* NOBARRIER: the key is new or kept alive. */
    lua_State *L = ls->L;
    setcdataV(L, tv, cd);
    setboolV(lj_tab_set(L, ls->fs->kt, tv), 1);
}
#endif

/* -- Jump list handling -------------------------------------------------- */

/* Get next element in jump list. */
static BCPos jmp_next(FuncState *fs, BCPos pc)
{
    ptrdiff_t delta = bc_j(fs->bcbase[pc].ins);
    if ((BCPos)delta == NO_JMP)
        return NO_JMP;
    else
        return (BCPos)(((ptrdiff_t)pc + 1) + delta);
}

/* Check if any of the instructions on the jump list produce no value. */
static int jmp_novalue(FuncState *fs, BCPos list)
{
    for (; list != NO_JMP; list = jmp_next(fs, list)) {
        BCIns p = fs->bcbase[list >= 1 ? list - 1 : list].ins;
        if (!(bc_op(p) == BC_ISTC || bc_op(p) == BC_ISFC || bc_a(p) == NO_REG))
            return 1;
    }
    return 0;
}

/* Patch register of test instructions. */
static int jmp_patchtestreg(FuncState *fs, BCPos pc, BCReg reg)
{
    BCInsLine *ilp = &fs->bcbase[pc >= 1 ? pc - 1 : pc];
    BCOp op = bc_op(ilp->ins);
    if (op == BC_ISTC || op == BC_ISFC) {
        if (reg != NO_REG && reg != bc_d(ilp->ins)) {
            setbc_a(&ilp->ins, reg);
        }
        else { /* Nothing to store or already in the right register. */
            setbc_op(&ilp->ins, op + (BC_IST - BC_ISTC));
            setbc_a(&ilp->ins, 0);
        }
    }
    else if (bc_a(ilp->ins) == NO_REG) {
        if (reg == NO_REG) {
            ilp->ins = BCINS_AJ(BC_JMP, bc_a(fs->bcbase[pc].ins), 0);
        }
        else {
            setbc_a(&ilp->ins, reg);
            if (reg >= bc_a(ilp[1].ins))
                setbc_a(&ilp[1].ins, reg + 1);
        }
    }
    else {
        return 0; /* Cannot patch other instructions. */
    }
    return 1;
}

/* Drop values for all instructions on jump list. */
static void jmp_dropval(FuncState *fs, BCPos list)
{
    for (; list != NO_JMP; list = jmp_next(fs, list))
        jmp_patchtestreg(fs, list, NO_REG);
}

/* Patch jump instruction to target. */
static void jmp_patchins(FuncState *fs, BCPos pc, BCPos dest)
{
    BCIns *jmp = &fs->bcbase[pc].ins;
    BCPos offset = dest - (pc + 1) + BCBIAS_J;
    lua_assert(dest != NO_JMP);
    if (offset > BCMAX_D)
        err_syntax(fs->ls, LJ_ERR_XJUMP);
    setbc_d(jmp, offset);
}

/* Append to jump list. */
static void jmp_append(FuncState *fs, BCPos *l1, BCPos l2)
{
    if (l2 == NO_JMP) {
        return;
    }
    else if (*l1 == NO_JMP) {
        *l1 = l2;
    }
    else {
        BCPos list = *l1;
        BCPos next;
        while ((next = jmp_next(fs, list)) != NO_JMP) /* Find last element. */
            list = next;
        jmp_patchins(fs, list, l2);
    }
}

/* Patch jump list and preserve produced values. */
static void jmp_patchval(FuncState *fs, BCPos list, BCPos vtarget, BCReg reg,
                         BCPos dtarget)
{
    while (list != NO_JMP) {
        BCPos next = jmp_next(fs, list);
        if (jmp_patchtestreg(fs, list, reg))
            jmp_patchins(fs, list, vtarget); /* Jump to target with value. */
        else
            jmp_patchins(fs, list, dtarget); /* Jump to default target. */
        list = next;
    }
}

/* Jump to following instruction. Append to list of pending jumps. */
static void jmp_tohere(FuncState *fs, BCPos list)
{
    fs->lasttarget = fs->pc;
    jmp_append(fs, &fs->jpc, list);
}

/* Patch jump list to target. */
static void jmp_patch(FuncState *fs, BCPos list, BCPos target)
{
    if (target == fs->pc) {
        jmp_tohere(fs, list);
    }
    else {
        lua_assert(target < fs->pc);
        jmp_patchval(fs, list, target, NO_REG, target);
    }
}

/* -- Bytecode register allocator ----------------------------------------- */

/* Bump frame size. */
static void bcreg_bump(FuncState *fs, BCReg n)
{
    BCReg sz = fs->freereg + n;
    if (sz > fs->framesize) {
        if (sz >= LJ_MAX_SLOTS)
            err_syntax(fs->ls, LJ_ERR_XSLOTS);
        fs->framesize = (uint8_t)sz;
    }
}

/* Reserve registers. */
static void bcreg_reserve(FuncState *fs, BCReg n)
{
    bcreg_bump(fs, n);
    fs->freereg += n;
}

/* Free register. */
static void bcreg_free(FuncState *fs, BCReg reg)
{
    if (reg >= fs->nactvar) {
        fs->freereg--;
        lua_assert(reg == fs->freereg);
    }
}

/* Free register for expression. */
static void expr_free(FuncState *fs, ExpDesc *e)
{
    if (e->k == VNONRELOC)
        bcreg_free(fs, e->u.s.info);
}

/* -- Bytecode emitter ---------------------------------------------------- */

/* Emit bytecode instruction. */
static BCPos bcemit_INS(FuncState *fs, BCIns ins)
{
    BCPos pc = fs->pc;
    LexState *ls = fs->ls;
    jmp_patchval(fs, fs->jpc, pc, NO_REG, pc);
    fs->jpc = NO_JMP;
    if (LJ_UNLIKELY(pc >= fs->bclim)) {
        ptrdiff_t base = fs->bcbase - ls->bcstack;
        checklimit(fs, ls->sizebcstack, LJ_MAX_BCINS, "bytecode instructions");
        lj_mem_growvec(fs->L, ls->bcstack, ls->sizebcstack, LJ_MAX_BCINS,
                       BCInsLine);
        fs->bclim = (BCPos)(ls->sizebcstack - base);
        fs->bcbase = ls->bcstack + base;
    }
    fs->bcbase[pc].ins = ins;
    fs->bcbase[pc].line = ls->lastline;
    fs->pc = pc + 1;
    return pc;
}

#define bcemit_ABC(fs, o, a, b, c) bcemit_INS(fs, BCINS_ABC(o, a, b, c))
#define bcemit_AD(fs, o, a, d) bcemit_INS(fs, BCINS_AD(o, a, d))
#define bcemit_AJ(fs, o, a, j) bcemit_INS(fs, BCINS_AJ(o, a, j))

#define bcptr(fs, e) (&(fs)->bcbase[(e)->u.s.info].ins)

/* -- Bytecode emitter for expressions ------------------------------------ */

/* Discharge non-constant expression to any register. */
static void expr_discharge(FuncState *fs, ExpDesc *e)
{
    BCIns ins;
    if (e->k == VUPVAL) {
        ins = BCINS_AD(BC_UGET, 0, e->u.s.info);
    }
    else if (e->k == VGLOBAL) {
        ins = BCINS_AD(BC_GGET, 0, const_str(fs, e));
    }
    else if (e->k == VINDEXED) {
        BCReg rc = e->u.s.aux;
        if ((int32_t)rc < 0) {
            ins = BCINS_ABC(BC_TGETS, 0, e->u.s.info, ~rc);
        }
        else if (rc > BCMAX_C) {
            ins = BCINS_ABC(BC_TGETB, 0, e->u.s.info, rc - (BCMAX_C + 1));
        }
        else {
            bcreg_free(fs, rc);
            ins = BCINS_ABC(BC_TGETV, 0, e->u.s.info, rc);
        }
        bcreg_free(fs, e->u.s.info);
    }
    else if (e->k == VCALL) {
        e->u.s.info = e->u.s.aux;
        e->k = VNONRELOC;
        return;
    }
    else if (e->k == VLOCAL) {
        e->k = VNONRELOC;
        return;
    }
    else {
        return;
    }
    e->u.s.info = bcemit_INS(fs, ins);
    e->k = VRELOCABLE;
}

/* Emit bytecode to set a range of registers to nil. */
static void bcemit_nil(FuncState *fs, BCReg from, BCReg n)
{
    if (fs->pc > fs->lasttarget) { /* No jumps to current position? */
        BCIns *ip = &fs->bcbase[fs->pc - 1].ins;
        BCReg pto, pfrom = bc_a(*ip);
        switch (bc_op(*ip)) { /* Try to merge with the previous instruction. */
        case BC_KPRI:
            if (bc_d(*ip) != ~LJ_TNIL)
                break;
            if (from == pfrom) {
                if (n == 1)
                    return;
            }
            else if (from == pfrom + 1) {
                from = pfrom;
                n++;
            }
            else {
                break;
            }
            *ip = BCINS_AD(BC_KNIL, from, from + n - 1); /* Replace KPRI. */
            return;
        case BC_KNIL:
            pto = bc_d(*ip);
            if (pfrom <= from &&
                from <= pto + 1) { /* Can we connect both ranges? */
                if (from + n - 1 > pto)
                    setbc_d(ip, from + n -
                                    1); /* Patch previous instruction range. */
                return;
            }
            break;
        default:
            break;
        }
    }
    /* Emit new instruction or replace old instruction. */
    bcemit_INS(fs, n == 1 ? BCINS_AD(BC_KPRI, from, VKNIL)
                          : BCINS_AD(BC_KNIL, from, from + n - 1));
}

/* Discharge an expression to a specific register. Ignore branches. */
static void expr_toreg_nobranch(FuncState *fs, ExpDesc *e, BCReg reg)
{
    BCIns ins;
    expr_discharge(fs, e);
    if (e->k == VKSTR) {
        ins = BCINS_AD(BC_KSTR, reg, const_str(fs, e));
    }
    else if (e->k == VKNUM) {
#if LJ_DUALNUM
        cTValue *tv = expr_numtv(e);
        if (tvisint(tv) && checki16(intV(tv)))
            ins = BCINS_AD(BC_KSHORT, reg, (BCReg)(uint16_t)intV(tv));
        else
#else
        lua_Number n = expr_numberV(e);
        int32_t k = lj_num2int(n);
        if (checki16(k) && n == (lua_Number)k)
            ins = BCINS_AD(BC_KSHORT, reg, (BCReg)(uint16_t)k);
        else
#endif
            ins = BCINS_AD(BC_KNUM, reg, const_num(fs, e));
#if LJ_HASFFI
    }
    else if (e->k == VKCDATA) {
        fs->flags |= PROTO_FFI;
        ins = BCINS_AD(BC_KCDATA, reg,
                       const_gc(fs, obj2gco(cdataV(&e->u.nval)), LJ_TCDATA));
#endif
    }
    else if (e->k == VRELOCABLE) {
        setbc_a(bcptr(fs, e), reg);
        goto noins;
    }
    else if (e->k == VNONRELOC) {
        if (reg == e->u.s.info)
            goto noins;
        ins = BCINS_AD(BC_MOV, reg, e->u.s.info);
    }
    else if (e->k == VKNIL) {
        bcemit_nil(fs, reg, 1);
        goto noins;
    }
    else if (e->k <= VKTRUE) {
        ins = BCINS_AD(BC_KPRI, reg, const_pri(e));
    }
    else {
        lua_assert(e->k == VVOID || e->k == VJMP);
        return;
    }
    bcemit_INS(fs, ins);
noins:
    e->u.s.info = reg;
    e->k = VNONRELOC;
}

/* Forward declaration. */
static BCPos bcemit_jmp(FuncState *fs);

/* Discharge an expression to a specific register. */
static void expr_toreg(FuncState *fs, ExpDesc *e, BCReg reg)
{
    expr_toreg_nobranch(fs, e, reg);
    if (e->k == VJMP)
        jmp_append(fs, &e->t, e->u.s.info); /* Add it to the true jump list. */
    if (expr_hasjump(e)) { /* Discharge expression with branches. */
        BCPos jend, jfalse = NO_JMP, jtrue = NO_JMP;
        if (jmp_novalue(fs, e->t) || jmp_novalue(fs, e->f)) {
            BCPos jval = (e->k == VJMP) ? NO_JMP : bcemit_jmp(fs);
            jfalse = bcemit_AD(fs, BC_KPRI, reg, VKFALSE);
            bcemit_AJ(fs, BC_JMP, fs->freereg, 1);
            jtrue = bcemit_AD(fs, BC_KPRI, reg, VKTRUE);
            jmp_tohere(fs, jval);
        }
        jend = fs->pc;
        fs->lasttarget = jend;
        jmp_patchval(fs, e->f, jend, reg, jfalse);
        jmp_patchval(fs, e->t, jend, reg, jtrue);
    }
    e->f = e->t = NO_JMP;
    e->u.s.info = reg;
    e->k = VNONRELOC;
}

/* Discharge an expression to the next free register. */
static void expr_tonextreg(FuncState *fs, ExpDesc *e)
{
    expr_discharge(fs, e);
    expr_free(fs, e);
    bcreg_reserve(fs, 1);
    expr_toreg(fs, e, fs->freereg - 1);
}

/* Discharge an expression to any register. */
static BCReg expr_toanyreg(FuncState *fs, ExpDesc *e)
{
    expr_discharge(fs, e);
    if (e->k == VNONRELOC) {
        if (!expr_hasjump(e))
            return e->u.s.info; /* Already in a register. */
        if (e->u.s.info >= fs->nactvar) {
            expr_toreg(fs, e, e->u.s.info); /* Discharge to temp. register. */
            return e->u.s.info;
        }
    }
    expr_tonextreg(fs, e); /* Discharge to next register. */
    return e->u.s.info;
}

/* Partially discharge expression to a value. */
static void expr_toval(FuncState *fs, ExpDesc *e)
{
    if (expr_hasjump(e))
        expr_toanyreg(fs, e);
    else
        expr_discharge(fs, e);
}

/* Emit store for LHS expression. */
static void bcemit_store(FuncState *fs, ExpDesc *var, ExpDesc *e)
{
    BCIns ins;
    if (var->k == VLOCAL) {
        fs->ls->vstack[var->u.s.aux].info |= VSTACK_VAR_RW;
        expr_free(fs, e);
        expr_toreg(fs, e, var->u.s.info);
        return;
    }
    else if (var->k == VUPVAL) {
        fs->ls->vstack[var->u.s.aux].info |= VSTACK_VAR_RW;
        expr_toval(fs, e);
        if (e->k <= VKTRUE)
            ins = BCINS_AD(BC_USETP, var->u.s.info, const_pri(e));
        else if (e->k == VKSTR)
            ins = BCINS_AD(BC_USETS, var->u.s.info, const_str(fs, e));
        else if (e->k == VKNUM)
            ins = BCINS_AD(BC_USETN, var->u.s.info, const_num(fs, e));
        else
            ins = BCINS_AD(BC_USETV, var->u.s.info, expr_toanyreg(fs, e));
    }
    else if (var->k == VGLOBAL) {
        BCReg ra = expr_toanyreg(fs, e);
        ins = BCINS_AD(BC_GSET, ra, const_str(fs, var));
    }
    else {
        BCReg ra, rc;
        lua_assert(var->k == VINDEXED);
        ra = expr_toanyreg(fs, e);
        rc = var->u.s.aux;
        if ((int32_t)rc < 0) {
            ins = BCINS_ABC(BC_TSETS, ra, var->u.s.info, ~rc);
        }
        else if (rc > BCMAX_C) {
            ins = BCINS_ABC(BC_TSETB, ra, var->u.s.info, rc - (BCMAX_C + 1));
        }
        else {
            /* Free late alloced key reg to avoid assert on free of value reg. */
            /* This can only happen when called from expr_table(). */
            lua_assert(e->k != VNONRELOC || ra < fs->nactvar || rc < ra ||
                       (bcreg_free(fs, rc), 1));
            ins = BCINS_ABC(BC_TSETV, ra, var->u.s.info, rc);
        }
    }
    bcemit_INS(fs, ins);
    expr_free(fs, e);
}

/* Emit method lookup expression. */
static void bcemit_method(FuncState *fs, ExpDesc *e, ExpDesc *key)
{
    BCReg idx, func, obj = expr_toanyreg(fs, e);
    expr_free(fs, e);
    func = fs->freereg;
    bcemit_AD(fs, BC_MOV, func + 1, obj); /* Copy object to first argument. */
    lua_assert(expr_isstrk(key));
    idx = const_str(fs, key);
    if (idx <= BCMAX_C) {
        bcreg_reserve(fs, 2);
        bcemit_ABC(fs, BC_TGETS, func, obj, idx);
    }
    else {
        bcreg_reserve(fs, 3);
        bcemit_AD(fs, BC_KSTR, func + 2, idx);
        bcemit_ABC(fs, BC_TGETV, func, obj, func + 2);
        fs->freereg--;
    }
    e->u.s.info = func;
    e->k = VNONRELOC;
}

/* -- Bytecode emitter for branches --------------------------------------- */

/* Emit unconditional branch. */
static BCPos bcemit_jmp(FuncState *fs)
{
    BCPos jpc = fs->jpc;
    BCPos j = fs->pc - 1;
    BCIns *ip = &fs->bcbase[j].ins;
    fs->jpc = NO_JMP;
    if ((int32_t)j >= (int32_t)fs->lasttarget && bc_op(*ip) == BC_UCLO)
        setbc_j(ip, NO_JMP);
    else
        j = bcemit_AJ(fs, BC_JMP, fs->freereg, NO_JMP);
    jmp_append(fs, &j, jpc);
    return j;
}

/* Invert branch condition of bytecode instruction. */
static void invertcond(FuncState *fs, ExpDesc *e)
{
    BCIns *ip = &fs->bcbase[e->u.s.info - 1].ins;
    setbc_op(ip, bc_op(*ip) ^ 1);
}

/* Emit conditional branch. */
static BCPos bcemit_branch(FuncState *fs, ExpDesc *e, int cond)
{
    BCPos pc;
    if (e->k == VRELOCABLE) {
        BCIns *ip = bcptr(fs, e);
        if (bc_op(*ip) == BC_NOT) {
            *ip = BCINS_AD(cond ? BC_ISF : BC_IST, 0, bc_d(*ip));
            return bcemit_jmp(fs);
        }
    }
    if (e->k != VNONRELOC) {
        bcreg_reserve(fs, 1);
        expr_toreg_nobranch(fs, e, fs->freereg - 1);
    }
    bcemit_AD(fs, cond ? BC_ISTC : BC_ISFC, NO_REG, e->u.s.info);
    pc = bcemit_jmp(fs);
    expr_free(fs, e);
    return pc;
}

/* Emit branch on true condition. */
static void bcemit_branch_t(FuncState *fs, ExpDesc *e)
{
    BCPos pc;
    expr_discharge(fs, e);
    if (e->k == VKSTR || e->k == VKNUM || e->k == VKTRUE)
        pc = NO_JMP; /* Never jump. */
    else if (e->k == VJMP)
        invertcond(fs, e), pc = e->u.s.info;
    else if (e->k == VKFALSE || e->k == VKNIL)
        expr_toreg_nobranch(fs, e, NO_REG), pc = bcemit_jmp(fs);
    else
        pc = bcemit_branch(fs, e, 0);
    jmp_append(fs, &e->f, pc);
    jmp_tohere(fs, e->t);
    e->t = NO_JMP;
}

/* Emit branch on false condition. */
static void bcemit_branch_f(FuncState *fs, ExpDesc *e)
{
    BCPos pc;
    expr_discharge(fs, e);
    if (e->k == VKNIL || e->k == VKFALSE)
        pc = NO_JMP; /* Never jump. */
    else if (e->k == VJMP)
        pc = e->u.s.info;
    else if (e->k == VKSTR || e->k == VKNUM || e->k == VKTRUE)
        expr_toreg_nobranch(fs, e, NO_REG), pc = bcemit_jmp(fs);
    else
        pc = bcemit_branch(fs, e, 1);
    jmp_append(fs, &e->t, pc);
    jmp_tohere(fs, e->f);
    e->f = NO_JMP;
}

/* -- Bytecode emitter for operators -------------------------------------- */

/* Try constant-folding of arithmetic operators. */
static int foldarith(BinOpr opr, ExpDesc *e1, ExpDesc *e2)
{
    TValue o;
    lua_Number n;
    if (!expr_isnumk_nojump(e1) || !expr_isnumk_nojump(e2))
        return 0;
    n = lj_vm_foldarith(expr_numberV(e1), expr_numberV(e2), (int)opr - OPR_ADD);
    setnumV(&o, n);
    if (tvisnan(&o) || tvismzero(&o))
        return 0; /* Avoid NaN and -0 as consts. */
    if (LJ_DUALNUM) {
        int32_t k = lj_num2int(n);
        if ((lua_Number)k == n) {
            setintV(&e1->u.nval, k);
            return 1;
        }
    }
    setnumV(&e1->u.nval, n);
    return 1;
}

/* Emit arithmetic operator. */
static void bcemit_arith(FuncState *fs, BinOpr opr, ExpDesc *e1, ExpDesc *e2)
{
    BCReg rb, rc, t;
    uint32_t op;
    if (foldarith(opr, e1, e2))
        return;
    if (opr == OPR_POW) {
        op = BC_POW;
        rc = expr_toanyreg(fs, e2);
        rb = expr_toanyreg(fs, e1);
    }
    else {
        op = opr - OPR_ADD + BC_ADDVV;
        /* Must discharge 2nd operand first since VINDEXED might free regs. */
        expr_toval(fs, e2);
        if (expr_isnumk(e2) && (rc = const_num(fs, e2)) <= BCMAX_C)
            op -= BC_ADDVV - BC_ADDVN;
        else
            rc = expr_toanyreg(fs, e2);
        /* 1st operand discharged by bcemit_binop_left, but need KNUM/KSHORT. */
        lua_assert(expr_isnumk(e1) || e1->k == VNONRELOC);
        expr_toval(fs, e1);
        /* Avoid two consts to satisfy bytecode constraints. */
        if (expr_isnumk(e1) && !expr_isnumk(e2) &&
            (t = const_num(fs, e1)) <= BCMAX_B) {
            rb = rc;
            rc = t;
            op -= BC_ADDVV - BC_ADDNV;
        }
        else {
            rb = expr_toanyreg(fs, e1);
        }
    }
    /* Using expr_free might cause asserts if the order is wrong. */
    if (e1->k == VNONRELOC && e1->u.s.info >= fs->nactvar)
        fs->freereg--;
    if (e2->k == VNONRELOC && e2->u.s.info >= fs->nactvar)
        fs->freereg--;
    e1->u.s.info = bcemit_ABC(fs, op, 0, rb, rc);
    e1->k = VRELOCABLE;
}

/* Emit comparison operator. */
static void bcemit_comp(FuncState *fs, BinOpr opr, ExpDesc *e1, ExpDesc *e2)
{
    ExpDesc *eret = e1;
    BCIns ins;
    expr_toval(fs, e1);
    if (opr == OPR_EQ || opr == OPR_NE) {
        BCOp op = opr == OPR_EQ ? BC_ISEQV : BC_ISNEV;
        BCReg ra;
        if (expr_isk(e1)) {
            e1 = e2;
            e2 = eret;
        }                           /* Need constant in 2nd arg. */
        ra = expr_toanyreg(fs, e1); /* First arg must be in a reg. */
        expr_toval(fs, e2);
        switch (e2->k) {
        case VKNIL:
        case VKFALSE:
        case VKTRUE:
            ins = BCINS_AD(op + (BC_ISEQP - BC_ISEQV), ra, const_pri(e2));
            break;
        case VKSTR:
            ins = BCINS_AD(op + (BC_ISEQS - BC_ISEQV), ra, const_str(fs, e2));
            break;
        case VKNUM:
            ins = BCINS_AD(op + (BC_ISEQN - BC_ISEQV), ra, const_num(fs, e2));
            break;
        default:
            ins = BCINS_AD(op, ra, expr_toanyreg(fs, e2));
            break;
        }
    }
    else {
        uint32_t op = opr - OPR_LT + BC_ISLT;
        BCReg ra, rd;
        if ((op - BC_ISLT) & 1) { /* GT -> LT, GE -> LE */
            e1 = e2;
            e2 = eret; /* Swap operands. */
            op = ((op - BC_ISLT) ^ 3) + BC_ISLT;
            expr_toval(fs, e1);
        }
        rd = expr_toanyreg(fs, e2);
        ra = expr_toanyreg(fs, e1);
        ins = BCINS_AD(op, ra, rd);
    }
    /* Using expr_free might cause asserts if the order is wrong. */
    if (e1->k == VNONRELOC && e1->u.s.info >= fs->nactvar)
        fs->freereg--;
    if (e2->k == VNONRELOC && e2->u.s.info >= fs->nactvar)
        fs->freereg--;
    bcemit_INS(fs, ins);
    eret->u.s.info = bcemit_jmp(fs);
    eret->k = VJMP;
}

/* Fixup left side of binary operator. */
static void bcemit_binop_left(FuncState *fs, BinOpr op, ExpDesc *e)
{
    if (op == OPR_AND) {
        bcemit_branch_t(fs, e);
    }
    else if (op == OPR_OR) {
        bcemit_branch_f(fs, e);
    }
    else if (op == OPR_CONCAT) {
        expr_tonextreg(fs, e);
    }
    else if (op == OPR_EQ || op == OPR_NE) {
        if (!expr_isk_nojump(e))
            expr_toanyreg(fs, e);
    }
    else {
        if (!expr_isnumk_nojump(e))
            expr_toanyreg(fs, e);
    }
}

/* Emit binary operator. */
static void bcemit_binop(FuncState *fs, BinOpr op, ExpDesc *e1, ExpDesc *e2)
{
    if (op <= OPR_POW) {
        bcemit_arith(fs, op, e1, e2);
    }
    else if (op == OPR_AND) {
        lua_assert(e1->t == NO_JMP); /* List must be closed. */
        expr_discharge(fs, e2);
        jmp_append(fs, &e2->f, e1->f);
        *e1 = *e2;
    }
    else if (op == OPR_OR) {
        lua_assert(e1->f == NO_JMP); /* List must be closed. */
        expr_discharge(fs, e2);
        jmp_append(fs, &e2->t, e1->t);
        *e1 = *e2;
    }
    else if (op == OPR_CONCAT) {
        expr_toval(fs, e2);
        if (e2->k == VRELOCABLE && bc_op(*bcptr(fs, e2)) == BC_CAT) {
            lua_assert(e1->u.s.info == bc_b(*bcptr(fs, e2)) - 1);
            expr_free(fs, e1);
            setbc_b(bcptr(fs, e2), e1->u.s.info);
            e1->u.s.info = e2->u.s.info;
        }
        else {
            expr_tonextreg(fs, e2);
            expr_free(fs, e2);
            expr_free(fs, e1);
            e1->u.s.info =
                bcemit_ABC(fs, BC_CAT, 0, e1->u.s.info, e2->u.s.info);
        }
        e1->k = VRELOCABLE;
    }
    else {
        lua_assert(op == OPR_NE || op == OPR_EQ || op == OPR_LT ||
                   op == OPR_GE || op == OPR_LE || op == OPR_GT);
        bcemit_comp(fs, op, e1, e2);
    }
}

/* Emit unary operator. */
static void bcemit_unop(FuncState *fs, BCOp op, ExpDesc *e)
{
    if (op == BC_NOT) {
        /* Swap true and false lists. */
        {
            BCPos temp = e->f;
            e->f = e->t;
            e->t = temp;
        }
        jmp_dropval(fs, e->f);
        jmp_dropval(fs, e->t);
        expr_discharge(fs, e);
        if (e->k == VKNIL || e->k == VKFALSE) {
            e->k = VKTRUE;
            return;
        }
        else if (expr_isk(e) || (LJ_HASFFI && e->k == VKCDATA)) {
            e->k = VKFALSE;
            return;
        }
        else if (e->k == VJMP) {
            invertcond(fs, e);
            return;
        }
        else if (e->k == VRELOCABLE) {
            bcreg_reserve(fs, 1);
            setbc_a(bcptr(fs, e), fs->freereg - 1);
            e->u.s.info = fs->freereg - 1;
            e->k = VNONRELOC;
        }
        else {
            lua_assert(e->k == VNONRELOC);
        }
    }
    else {
        lua_assert(op == BC_UNM || op == BC_LEN);
        if (op == BC_UNM && !expr_hasjump(e)) { /* Constant-fold negations. */
#if LJ_HASFFI
            if (e->k ==
                VKCDATA) { /* Fold in-place since cdata is not interned. */
                GCcdata *cd = cdataV(&e->u.nval);
                int64_t *p = (int64_t *)cdataptr(cd);
                if (cd->ctypeid == CTID_COMPLEX_DOUBLE)
                    p[1] ^= (int64_t)U64x(80000000, 00000000);
                else
                    *p = -*p;
                return;
            }
            else
#endif
                if (expr_isnumk(e) &&
                    !expr_numiszero(e)) { /* Avoid folding to -0. */
                TValue *o = expr_numtv(e);
                if (tvisint(o)) {
                    int32_t k = intV(o);
                    if (k == -k)
                        setnumV(o, -(lua_Number)k);
                    else
                        setintV(o, -k);
                    return;
                }
                else {
                    o->u64 ^= U64x(80000000, 00000000);
                    return;
                }
            }
        }
        expr_toanyreg(fs, e);
    }
    expr_free(fs, e);
    e->u.s.info = bcemit_AD(fs, op, 0, e->u.s.info);
    e->k = VRELOCABLE;
}

/* -- Lexer support ------------------------------------------------------- */

/* Check and consume optional token. */
static int lex_opt(LexState *ls, LexToken tok)
{
    if (ls->token == tok) {
        lj_lex_next(ls);
        return 1;
    }
    return 0;
}

/* Check and consume token. */
static void lex_check(LexState *ls, LexToken tok)
{
    if (ls->token != tok)
        err_token(ls, tok);
    lj_lex_next(ls);
}

/* Check for matching token. */
static void lex_match(LexState *ls, LexToken what, LexToken who, BCLine line)
{
    if (!lex_opt(ls, what)) {
        if (line == ls->linenumber) {
            err_token(ls, what);
        }
        else {
            const char *swhat = lj_lex_token2str(ls, what);
            const char *swho = lj_lex_token2str(ls, who);
            lj_lex_error(ls, ls->token, LJ_ERR_XMATCH, swhat, swho, line);
        }
    }
}

/* Check for string token. */
static GCstr *lex_str(LexState *ls)
{
    GCstr *s;
    if (ls->token != TK_name && (LJ_52 || ls->token != TK_goto))
        err_token(ls, TK_name);
    s = strV(&ls->tokenval);
    lj_lex_next(ls);
    return s;
}

/* -- Variable handling --------------------------------------------------- */

#define var_get(ls, fs, i) ((ls)->vstack[(fs)->varmap[(i)]])

/* Define a new local variable. */
static void var_new(LexState *ls, BCReg n, GCstr *name)
{
    FuncState *fs = ls->fs;
    MSize vtop = ls->vtop;
    checklimit(fs, fs->nactvar + n, LJ_MAX_LOCVAR, "local variables");
    if (LJ_UNLIKELY(vtop >= ls->sizevstack)) {
        if (ls->sizevstack >= LJ_MAX_VSTACK)
            lj_lex_error(ls, 0, LJ_ERR_XLIMC, LJ_MAX_VSTACK);
        lj_mem_growvec(ls->L, ls->vstack, ls->sizevstack, LJ_MAX_VSTACK,
                       VarInfo);
    }
    lua_assert((uintptr_t)name < VARNAME__MAX ||
               lj_tab_getstr(fs->kt, name) != NULL);
    /* NOBARRIER: name is anchored in fs->kt and ls->vstack is not a GCobj. */
    setgcref(ls->vstack[vtop].name, obj2gco(name));
    fs->varmap[fs->nactvar + n] = (uint16_t)vtop;
    ls->vtop = vtop + 1;
}

#define var_new_lit(ls, n, v)                                                  \
    var_new(ls, (n), lj_parse_keepstr(ls, "" v, sizeof(v) - 1))

#define var_new_fixed(ls, n, vn) var_new(ls, (n), (GCstr *)(uintptr_t)(vn))

/* Add local variables. */
static void var_add(LexState *ls, BCReg nvars)
{
    FuncState *fs = ls->fs;
    BCReg nactvar = fs->nactvar;
    while (nvars--) {
        VarInfo *v = &var_get(ls, fs, nactvar);
        v->startpc = fs->pc;
        v->slot = nactvar++;
        v->info = 0;
    }
    fs->nactvar = nactvar;
}

/* Remove local variables. */
static void var_remove(LexState *ls, BCReg tolevel)
{
    FuncState *fs = ls->fs;
    while (fs->nactvar > tolevel)
        var_get(ls, fs, --fs->nactvar).endpc = fs->pc;
}

/* Lookup local variable name. */
static BCReg var_lookup_local(FuncState *fs, GCstr *n)
{
    int i;
    for (i = fs->nactvar - 1; i >= 0; i--) {
        if (n == strref(var_get(fs->ls, fs, i).name))
            return (BCReg)i;
    }
    return (BCReg)-1; /* Not found. */
}

/* Lookup or add upvalue index. */
static MSize var_lookup_uv(FuncState *fs, MSize vidx, ExpDesc *e)
{
    MSize i, n = fs->nuv;
    for (i = 0; i < n; i++)
        if (fs->uvmap[i] == vidx)
            return i; /* Already exists. */
    /* Otherwise create a new one. */
    checklimit(fs, fs->nuv, LJ_MAX_UPVAL, "upvalues");
    lua_assert(e->k == VLOCAL || e->k == VUPVAL);
    fs->uvmap[n] = (uint16_t)vidx;
    fs->uvtmp[n] =
        (uint16_t)(e->k == VLOCAL ? vidx : LJ_MAX_VSTACK + e->u.s.info);
    fs->nuv = n + 1;
    return n;
}

/* Forward declaration. */
static void fscope_uvmark(FuncState *fs, BCReg level);

/* Recursively lookup variables in enclosing functions. */
static MSize var_lookup_(FuncState *fs, GCstr *name, ExpDesc *e, int first)
{
    if (fs) {
        BCReg reg = var_lookup_local(fs, name);
        if ((int32_t)reg >= 0) { /* Local in this function? */
            expr_init(e, VLOCAL, reg);
            if (!first)
                fscope_uvmark(fs, reg); /* Scope now has an upvalue. */
            return (MSize)(e->u.s.aux = (uint32_t)fs->varmap[reg]);
        }
        else {
            MSize vidx =
                var_lookup_(fs->prev, name, e, 0); /* Var in outer func? */
            if ((int32_t)vidx >= 0) { /* Yes, make it an upvalue here. */
                e->u.s.info = (uint8_t)var_lookup_uv(fs, vidx, e);
                e->k = VUPVAL;
                return vidx;
            }
        }
    }
    else { /* Not found in any function, must be a global. */
        expr_init(e, VGLOBAL, 0);
        e->u.sval = name;
    }
    return (MSize)-1; /* Global. */
}

/* Lookup variable name. */
#define var_lookup(ls, e) var_lookup_((ls)->fs, lex_str(ls), (e), 1)

/* -- Goto an label handling ---------------------------------------------- */

/* Add a new goto or label. */
static MSize gola_new(LexState *ls, GCstr *name, uint8_t info, BCPos pc)
{
    FuncState *fs = ls->fs;
    MSize vtop = ls->vtop;
    if (LJ_UNLIKELY(vtop >= ls->sizevstack)) {
        if (ls->sizevstack >= LJ_MAX_VSTACK)
            lj_lex_error(ls, 0, LJ_ERR_XLIMC, LJ_MAX_VSTACK);
        lj_mem_growvec(ls->L, ls->vstack, ls->sizevstack, LJ_MAX_VSTACK,
                       VarInfo);
    }
    lua_assert(name == NAME_BREAK || lj_tab_getstr(fs->kt, name) != NULL);
    /* NOBARRIER: name is anchored in fs->kt and ls->vstack is not a GCobj. */
    setgcref(ls->vstack[vtop].name, obj2gco(name));
    ls->vstack[vtop].startpc = pc;
    ls->vstack[vtop].slot = (uint8_t)fs->nactvar;
    ls->vstack[vtop].info = info;
    ls->vtop = vtop + 1;
    return vtop;
}

#define gola_isgoto(v) ((v)->info & VSTACK_GOTO)
#define gola_islabel(v) ((v)->info & VSTACK_LABEL)
#define gola_isgotolabel(v) ((v)->info & (VSTACK_GOTO | VSTACK_LABEL))

/* Patch goto to jump to label. */
static void gola_patch(LexState *ls, VarInfo *vg, VarInfo *vl)
{
    FuncState *fs = ls->fs;
    BCPos pc = vg->startpc;
    setgcrefnull(vg->name); /* Invalidate pending goto. */
    setbc_a(&fs->bcbase[pc].ins, vl->slot);
    jmp_patch(fs, pc, vl->startpc);
}

/* Patch goto to close upvalues. */
static void gola_close(LexState *ls, VarInfo *vg)
{
    FuncState *fs = ls->fs;
    BCPos pc = vg->startpc;
    BCIns *ip = &fs->bcbase[pc].ins;
    lua_assert(gola_isgoto(vg));
    lua_assert(bc_op(*ip) == BC_JMP || bc_op(*ip) == BC_UCLO);
    setbc_a(ip, vg->slot);
    if (bc_op(*ip) == BC_JMP) {
        BCPos next = jmp_next(fs, pc);
        if (next != NO_JMP)
            jmp_patch(fs, next, pc); /* Jump to UCLO. */
        setbc_op(ip, BC_UCLO);       /* Turn into UCLO. */
        setbc_j(ip, NO_JMP);
    }
}

/* Resolve pending forward gotos for label. */
static void gola_resolve(LexState *ls, FuncScope *bl, MSize idx)
{
    VarInfo *vg = ls->vstack + bl->vstart;
    VarInfo *vl = ls->vstack + idx;
    for (; vg < vl; vg++)
        if (gcrefeq(vg->name, vl->name) && gola_isgoto(vg)) {
            if (vg->slot < vl->slot) {
                GCstr *name = strref(var_get(ls, ls->fs, vg->slot).name);
                lua_assert((uintptr_t)name >= VARNAME__MAX);
                ls->linenumber = ls->fs->bcbase[vg->startpc].line;
                lua_assert(strref(vg->name) != NAME_BREAK);
                lj_lex_error(ls, 0, LJ_ERR_XGSCOPE, strdata(strref(vg->name)),
                             strdata(name));
            }
            gola_patch(ls, vg, vl);
        }
}

/* Fixup remaining gotos and labels for scope. */
static void gola_fixup(LexState *ls, FuncScope *bl)
{
    VarInfo *v = ls->vstack + bl->vstart;
    VarInfo *ve = ls->vstack + ls->vtop;
    for (; v < ve; v++) {
        GCstr *name = strref(v->name);
        if (name != NULL) { /* Only consider remaining valid gotos/labels. */
            if (gola_islabel(v)) {
                VarInfo *vg;
                setgcrefnull(
                    v->name); /* Invalidate label that goes out of scope. */
                for (vg = v + 1; vg < ve;
                     vg++) /* Resolve pending backward gotos. */
                    if (strref(vg->name) == name && gola_isgoto(vg)) {
                        if ((bl->flags & FSCOPE_UPVAL) && vg->slot > v->slot)
                            gola_close(ls, vg);
                        gola_patch(ls, vg, v);
                    }
            }
            else if (gola_isgoto(v)) {
                if (bl->prev) { /* Propagate goto or break to outer scope. */
                    bl->prev->flags |=
                        name == NAME_BREAK ? FSCOPE_BREAK : FSCOPE_GOLA;
                    v->slot = bl->nactvar;
                    if ((bl->flags & FSCOPE_UPVAL))
                        gola_close(ls, v);
                }
                else { /* No outer scope: undefined goto label or no loop. */
                    ls->linenumber = ls->fs->bcbase[v->startpc].line;
                    if (name == NAME_BREAK)
                        lj_lex_error(ls, 0, LJ_ERR_XBREAK);
                    else
                        lj_lex_error(ls, 0, LJ_ERR_XLUNDEF, strdata(name));
                }
            }
        }
    }
}

/* Find existing label. */
static VarInfo *gola_findlabel(LexState *ls, GCstr *name)
{
    VarInfo *v = ls->vstack + ls->fs->bl->vstart;
    VarInfo *ve = ls->vstack + ls->vtop;
    for (; v < ve; v++)
        if (strref(v->name) == name && gola_islabel(v))
            return v;
    return NULL;
}

/* -- Scope handling ------------------------------------------------------ */

/* Begin a scope. */
static void fscope_begin(FuncState *fs, FuncScope *bl, int flags)
{
    bl->nactvar = (uint8_t)fs->nactvar;
    bl->flags = flags;
    bl->vstart = fs->ls->vtop;
    bl->prev = fs->bl;
    fs->bl = bl;
    lua_assert(fs->freereg == fs->nactvar);
}

/* End a scope. */
static void fscope_end(FuncState *fs)
{
    FuncScope *bl = fs->bl;
    LexState *ls = fs->ls;
    fs->bl = bl->prev;
    var_remove(ls, bl->nactvar);
    fs->freereg = fs->nactvar;
    lua_assert(bl->nactvar == fs->nactvar);
    if ((bl->flags & (FSCOPE_UPVAL | FSCOPE_NOCLOSE)) == FSCOPE_UPVAL)
        bcemit_AJ(fs, BC_UCLO, bl->nactvar, 0);
    if ((bl->flags & FSCOPE_BREAK)) {
        if ((bl->flags & FSCOPE_LOOP)) {
            MSize idx = gola_new(ls, NAME_BREAK, VSTACK_LABEL, fs->pc);
            ls->vtop = idx; /* Drop break label immediately. */
            gola_resolve(ls, bl, idx);
            return;
        } /* else: need the fixup step to propagate the breaks. */
    }
    else if (!(bl->flags & FSCOPE_GOLA)) {
        return;
    }
    gola_fixup(ls, bl);
}

/* Mark scope as having an upvalue. */
static void fscope_uvmark(FuncState *fs, BCReg level)
{
    FuncScope *bl;
    for (bl = fs->bl; bl && bl->nactvar > level; bl = bl->prev)
        ;
    if (bl)
        bl->flags |= FSCOPE_UPVAL;
}

/* -- Function state management ------------------------------------------- */

/* Fixup bytecode for prototype. */
static void fs_fixup_bc(FuncState *fs, GCproto *pt, BCIns *bc, MSize n)
{
    BCInsLine *base = fs->bcbase;
    MSize i;
    pt->sizebc = n;
    bc[0] = BCINS_AD((fs->flags & PROTO_VARARG) ? BC_FUNCV : BC_FUNCF,
                     fs->framesize, 0);
    for (i = 1; i < n; i++)
        bc[i] = base[i].ins;
}

/* Fixup upvalues for child prototype, step #2. */
static void fs_fixup_uv2(FuncState *fs, GCproto *pt)
{
    VarInfo *vstack = fs->ls->vstack;
    uint16_t *uv = proto_uv(pt);
    MSize i, n = pt->sizeuv;
    for (i = 0; i < n; i++) {
        VarIndex vidx = uv[i];
        if (vidx >= LJ_MAX_VSTACK)
            uv[i] = vidx - LJ_MAX_VSTACK;
        else if ((vstack[vidx].info & VSTACK_VAR_RW))
            uv[i] = vstack[vidx].slot | PROTO_UV_LOCAL;
        else
            uv[i] = vstack[vidx].slot | PROTO_UV_LOCAL | PROTO_UV_IMMUTABLE;
    }
}

/* Fixup constants for prototype. */
static void fs_fixup_k(FuncState *fs, GCproto *pt, void *kptr)
{
    GCtab *kt;
    TValue *array;
    Node *node;
    MSize i, hmask;
    checklimitgt(fs, fs->nkn, BCMAX_D + 1, "constants");
    checklimitgt(fs, fs->nkgc, BCMAX_D + 1, "constants");
    setmref(pt->k, kptr);
    pt->sizekn = fs->nkn;
    pt->sizekgc = fs->nkgc;
    kt = fs->kt;
    array = tvref(kt->array);
    for (i = 0; i < kt->asize; i++)
        if (tvhaskslot(&array[i])) {
            TValue *tv = &((TValue *)kptr)[tvkslot(&array[i])];
            if (LJ_DUALNUM)
                setintV(tv, (int32_t)i);
            else
                setnumV(tv, (lua_Number)i);
        }
    node = noderef(kt->node);
    hmask = kt->hmask;
    for (i = 0; i <= hmask; i++) {
        Node *n = &node[i];
        if (tvhaskslot(&n->val)) {
            ptrdiff_t kidx = (ptrdiff_t)tvkslot(&n->val);
            lua_assert(!tvisint(&n->key));
            if (tvisnum(&n->key)) {
                TValue *tv = &((TValue *)kptr)[kidx];
                if (LJ_DUALNUM) {
                    lua_Number nn = numV(&n->key);
                    int32_t k = lj_num2int(nn);
                    lua_assert(!tvismzero(&n->key));
                    if ((lua_Number)k == nn)
                        setintV(tv, k);
                    else
                        *tv = n->key;
                }
                else {
                    *tv = n->key;
                }
            }
            else {
                GCobj *o = gcV(&n->key);
                setgcref(((GCRef *)kptr)[~kidx], o);
                lj_gc_objbarrier(fs->L, pt, o);
                if (tvisproto(&n->key))
                    fs_fixup_uv2(fs, gco2pt(o));
            }
        }
    }
}

/* Fixup upvalues for prototype, step #1. */
static void fs_fixup_uv1(FuncState *fs, GCproto *pt, uint16_t *uv)
{
    setmref(pt->uv, uv);
    pt->sizeuv = fs->nuv;
    memcpy(uv, fs->uvtmp, fs->nuv * sizeof(VarIndex));
}

#ifndef LUAJIT_DISABLE_DEBUGINFO
/* Prepare lineinfo for prototype. */
static size_t fs_prep_line(FuncState *fs, BCLine numline)
{
    return (fs->pc - 1) << (numline < 256 ? 0 : numline < 65536 ? 1 : 2);
}

/* Fixup lineinfo for prototype. */
static void fs_fixup_line(FuncState *fs, GCproto *pt, void *lineinfo,
                          BCLine numline)
{
    BCInsLine *base = fs->bcbase + 1;
    BCLine first = fs->linedefined;
    MSize i = 0, n = fs->pc - 1;
    pt->firstline = fs->linedefined;
    pt->numline = numline;
    setmref(pt->lineinfo, lineinfo);
    if (LJ_LIKELY(numline < 256)) {
        uint8_t *li = (uint8_t *)lineinfo;
        do {
            BCLine delta = base[i].line - first;
            lua_assert(delta >= 0 && delta < 256);
            li[i] = (uint8_t)delta;
        } while (++i < n);
    }
    else if (LJ_LIKELY(numline < 65536)) {
        uint16_t *li = (uint16_t *)lineinfo;
        do {
            BCLine delta = base[i].line - first;
            lua_assert(delta >= 0 && delta < 65536);
            li[i] = (uint16_t)delta;
        } while (++i < n);
    }
    else {
        uint32_t *li = (uint32_t *)lineinfo;
        do {
            BCLine delta = base[i].line - first;
            lua_assert(delta >= 0);
            li[i] = (uint32_t)delta;
        } while (++i < n);
    }
}

/* Resize buffer if needed. */
static LJ_NOINLINE void fs_buf_resize(LexState *ls, MSize len)
{
    MSize sz = ls->sb.sz * 2;
    while (ls->sb.n + len > sz)
        sz = sz * 2;
    lj_str_resizebuf(ls->L, &ls->sb, sz);
}

static LJ_AINLINE void fs_buf_need(LexState *ls, MSize len)
{
    if (LJ_UNLIKELY(ls->sb.n + len > ls->sb.sz))
        fs_buf_resize(ls, len);
}

/* Add string to buffer. */
static void fs_buf_str(LexState *ls, const char *str, MSize len)
{
    char *p = ls->sb.buf + ls->sb.n;
    MSize i;
    ls->sb.n += len;
    for (i = 0; i < len; i++)
        p[i] = str[i];
}

/* Add ULEB128 value to buffer. */
static void fs_buf_uleb128(LexState *ls, uint32_t v)
{
    MSize n = ls->sb.n;
    uint8_t *p = (uint8_t *)ls->sb.buf;
    for (; v >= 0x80; v >>= 7)
        p[n++] = (uint8_t)((v & 0x7f) | 0x80);
    p[n++] = (uint8_t)v;
    ls->sb.n = n;
}

/* Prepare variable info for prototype. */
static size_t fs_prep_var(LexState *ls, FuncState *fs, size_t *ofsvar)
{
    VarInfo *vs = ls->vstack, *ve;
    MSize i, n;
    BCPos lastpc;
    lj_str_resetbuf(&ls->sb); /* Copy to temp. string buffer. */
    /* Store upvalue names. */
    for (i = 0, n = fs->nuv; i < n; i++) {
        GCstr *s = strref(vs[fs->uvmap[i]].name);
        MSize len = s->len + 1;
        fs_buf_need(ls, len);
        fs_buf_str(ls, strdata(s), len);
    }
    *ofsvar = ls->sb.n;
    lastpc = 0;
    /* Store local variable names and compressed ranges. */
    for (ve = vs + ls->vtop, vs += fs->vbase; vs < ve; vs++) {
        if (!gola_isgotolabel(vs)) {
            GCstr *s = strref(vs->name);
            BCPos startpc;
            if ((uintptr_t)s < VARNAME__MAX) {
                fs_buf_need(ls, 1 + 2 * 5);
                ls->sb.buf[ls->sb.n++] = (uint8_t)(uintptr_t)s;
            }
            else {
                MSize len = s->len + 1;
                fs_buf_need(ls, len + 2 * 5);
                fs_buf_str(ls, strdata(s), len);
            }
            startpc = vs->startpc;
            fs_buf_uleb128(ls, startpc - lastpc);
            fs_buf_uleb128(ls, vs->endpc - startpc);
            lastpc = startpc;
        }
    }
    fs_buf_need(ls, 1);
    ls->sb.buf[ls->sb.n++] = '\0'; /* Terminator for varinfo. */
    return ls->sb.n;
}

/* Fixup variable info for prototype. */
static void fs_fixup_var(LexState *ls, GCproto *pt, uint8_t *p, size_t ofsvar)
{
    setmref(pt->uvinfo, p);
    setmref(pt->varinfo, (char *)p + ofsvar);
    memcpy(p, ls->sb.buf, ls->sb.n); /* Copy from temp. string buffer. */
}
#else

    /* Initialize with empty debug info, if disabled. */
    #define fs_prep_line(fs, numline) (UNUSED(numline), 0)
    #define fs_fixup_line(fs, pt, li, numline)                                 \
        pt->firstline = pt->numline = 0, setmref((pt)->lineinfo, NULL)
    #define fs_prep_var(ls, fs, ofsvar) (UNUSED(ofsvar), 0)
    #define fs_fixup_var(ls, pt, p, ofsvar)                                    \
        setmref((pt)->uvinfo, NULL), setmref((pt)->varinfo, NULL)

#endif

/* Check if bytecode op returns. */
static int bcopisret(BCOp op)
{
    switch (op) {
    case BC_CALLMT:
    case BC_CALLT:
    case BC_RETM:
    case BC_RET:
    case BC_RET0:
    case BC_RET1:
        return 1;
    default:
        return 0;
    }
}

/* Fixup return instruction for prototype. */
static void fs_fixup_ret(FuncState *fs)
{
    BCPos lastpc = fs->pc;
    if (lastpc <= fs->lasttarget ||
        !bcopisret(bc_op(fs->bcbase[lastpc - 1].ins))) {
        if ((fs->bl->flags & FSCOPE_UPVAL))
            bcemit_AJ(fs, BC_UCLO, 0, 0);
        bcemit_AD(fs, BC_RET0, 0, 1); /* Need final return. */
    }
    fs->bl->flags |= FSCOPE_NOCLOSE; /* Handled above. */
    fscope_end(fs);
    lua_assert(fs->bl == NULL);
    /* May need to fixup returns encoded before first function was created. */
    if (fs->flags & PROTO_FIXUP_RETURN) {
        BCPos pc;
        for (pc = 1; pc < lastpc; pc++) {
            BCIns ins = fs->bcbase[pc].ins;
            BCPos offset;
            switch (bc_op(ins)) {
            case BC_CALLMT:
            case BC_CALLT:
            case BC_RETM:
            case BC_RET:
            case BC_RET0:
            case BC_RET1:
                offset = bcemit_INS(fs, ins); /* Copy original instruction. */
                fs->bcbase[offset].line = fs->bcbase[pc].line;
                offset = offset - (pc + 1) + BCBIAS_J;
                if (offset > BCMAX_D)
                    err_syntax(fs->ls, LJ_ERR_XFIXUP);
                /* Replace with UCLO plus branch. */
                fs->bcbase[pc].ins = BCINS_AD(BC_UCLO, 0, offset);
                break;
            case BC_UCLO:
                return; /* We're done. */
            default:
                break;
            }
        }
    }
}

/* Finish a FuncState and return the new prototype. */
static GCproto *fs_finish(LexState *ls, BCLine line)
{
    lua_State *L = ls->L;
    FuncState *fs = ls->fs;
    BCLine numline = line - fs->linedefined;
    size_t sizept, ofsk, ofsuv, ofsli, ofsdbg, ofsvar;
    GCproto *pt;

    /* Apply final fixups. */
    fs_fixup_ret(fs);

    /* Calculate total size of prototype including all colocated arrays. */
    sizept =
        sizeof(GCproto) + fs->pc * sizeof(BCIns) + fs->nkgc * sizeof(GCRef);
    sizept = (sizept + sizeof(TValue) - 1) & ~(sizeof(TValue) - 1);
    ofsk = sizept;
    sizept += fs->nkn * sizeof(TValue);
    ofsuv = sizept;
    sizept += ((fs->nuv + 1) & ~1) * 2;
    ofsli = sizept;
    sizept += fs_prep_line(fs, numline);
    ofsdbg = sizept;
    sizept += fs_prep_var(ls, fs, &ofsvar);

    /* Allocate prototype and initialize its fields. */
    pt = (GCproto *)lj_mem_newgco(L, (MSize)sizept);
    pt->gct = ~LJ_TPROTO;
    pt->sizept = (MSize)sizept;
    pt->trace = 0;
    pt->flags = (uint8_t)(fs->flags & ~(PROTO_HAS_RETURN | PROTO_FIXUP_RETURN));
    pt->numparams = fs->numparams;
    pt->framesize = fs->framesize;
    setgcref(pt->chunkname, obj2gco(ls->chunkname));

    /* Close potentially uninitialized gap between bc and kgc. */
    *(uint32_t *)((char *)pt + ofsk - sizeof(GCRef) * (fs->nkgc + 1)) = 0;
    fs_fixup_bc(fs, pt, (BCIns *)((char *)pt + sizeof(GCproto)), fs->pc);
    fs_fixup_k(fs, pt, (void *)((char *)pt + ofsk));
    fs_fixup_uv1(fs, pt, (uint16_t *)((char *)pt + ofsuv));
    fs_fixup_line(fs, pt, (void *)((char *)pt + ofsli), numline);
    fs_fixup_var(ls, pt, (uint8_t *)((char *)pt + ofsdbg), ofsvar);

    lj_vmevent_send(L, BC, setprotoV(L, L->top++, pt););

    L->top--;             /* Pop table of constants. */
    ls->vtop = fs->vbase; /* Reset variable stack. */
    ls->fs = fs->prev;
    lua_assert(ls->fs != NULL || ls->token == TK_eof);
    return pt;
}

/* Initialize a new FuncState. */
static void fs_init(LexState *ls, FuncState *fs)
{
    lua_State *L = ls->L;
    fs->prev = ls->fs;
    ls->fs = fs; /* Append to list. */
    fs->ls = ls;
    fs->vbase = ls->vtop;
    fs->L = L;
    fs->pc = 0;
    fs->lasttarget = 0;
    fs->jpc = NO_JMP;
    fs->freereg = 0;
    fs->nkgc = 0;
    fs->nkn = 0;
    fs->nactvar = 0;
    fs->nuv = 0;
    fs->bl = NULL;
    fs->flags = 0;
    fs->framesize = 1; /* Minimum frame size. */
    fs->kt = lj_tab_new(L, 0, 0);
    /* Anchor table of constants in stack to avoid being collected. */
    settabV(L, L->top, fs->kt);
    incr_top(L);
}

/* -- Expressions --------------------------------------------------------- */

/* Forward declaration. */
static void expr(LexState *ls, ExpDesc *v);

/* Return string expression. */
static void expr_str(LexState *ls, ExpDesc *e)
{
    expr_init(e, VKSTR, 0);
    e->u.sval = lex_str(ls);
}

/* Return index expression. */
static void expr_index(FuncState *fs, ExpDesc *t, ExpDesc *e)
{
    /* Already called: expr_toval(fs, e). */
    t->k = VINDEXED;
    if (expr_isnumk(e)) {
#if LJ_DUALNUM
        if (tvisint(expr_numtv(e))) {
            int32_t k = intV(expr_numtv(e));
            if (checku8(k)) {
                t->u.s.aux =
                    BCMAX_C + 1 + (uint32_t)k; /* 256..511: const byte key */
                return;
            }
        }
#else
        lua_Number n = expr_numberV(e);
        int32_t k = lj_num2int(n);
        if (checku8(k) && n == (lua_Number)k) {
            t->u.s.aux =
                BCMAX_C + 1 + (uint32_t)k; /* 256..511: const byte key */
            return;
        }
#endif
    }
    else if (expr_isstrk(e)) {
        BCReg idx = const_str(fs, e);
        if (idx <= BCMAX_C) {
            t->u.s.aux = ~idx; /* -256..-1: const string key */
            return;
        }
    }
    t->u.s.aux = expr_toanyreg(fs, e); /* 0..255: register */
}

/* Parse index expression with named field. */
static void expr_field(LexState *ls, ExpDesc *v)
{
    FuncState *fs = ls->fs;
    ExpDesc key;
    expr_toanyreg(fs, v);
    lj_lex_next(ls); /* Skip dot or colon. */
    expr_str(ls, &key);
    expr_index(fs, v, &key);
}

/* Parse index expression with brackets. */
static void expr_bracket(LexState *ls, ExpDesc *v)
{
    lj_lex_next(ls); /* Skip '['. */
    expr(ls, v);
    expr_toval(ls->fs, v);
    lex_check(ls, ']');
}

/* Get value of constant expression. */
static void expr_kvalue(TValue *v, ExpDesc *e)
{
    if (e->k <= VKTRUE) {
        setitype(v, ~(uint32_t)e->k);
    }
    else if (e->k == VKSTR) {
        setgcref(v->gcr, obj2gco(e->u.sval));
        setitype(v, LJ_TSTR);
    }
    else {
        lua_assert(tvisnumber(expr_numtv(e)));
        *v = *expr_numtv(e);
    }
}

/* Parse table constructor expression. */
static void expr_table(LexState *ls, ExpDesc *e)
{
    FuncState *fs = ls->fs;
    BCLine line = ls->linenumber;
    GCtab *t = NULL;
    int vcall = 0, needarr = 0, fixt = 0;
    uint32_t narr = 1;  /* First array index. */
    uint32_t nhash = 0; /* Number of hash entries. */
    BCReg freg = fs->freereg;
    BCPos pc = bcemit_AD(fs, BC_TNEW, freg, 0);
    expr_init(e, VNONRELOC, freg);
    bcreg_reserve(fs, 1);
    freg++;
    lex_check(ls, '{');
    while (ls->token != '}') {
        ExpDesc key, val;
        vcall = 0;
        if (ls->token == '[') {
            expr_bracket(ls, &key); /* Already calls expr_toval. */
            if (!expr_isk(&key))
                expr_index(fs, e, &key);
            if (expr_isnumk(&key) && expr_numiszero(&key))
                needarr = 1;
            else
                nhash++;
            lex_check(ls, '=');
        }
        else if ((ls->token == TK_name || (!LJ_52 && ls->token == TK_goto)) &&
                 lj_lex_lookahead(ls) == '=') {
            expr_str(ls, &key);
            lex_check(ls, '=');
            nhash++;
        }
        else {
            expr_init(&key, VKNUM, 0);
            setintV(&key.u.nval, (int)narr);
            narr++;
            needarr = vcall = 1;
        }
        expr(ls, &val);
        if (expr_isk(&key) && key.k != VKNIL &&
            (key.k == VKSTR || expr_isk_nojump(&val))) {
            TValue k, *v;
            if (!t) { /* Create template table on demand. */
                BCReg kidx;
                t = lj_tab_new(fs->L, needarr ? narr : 0, hsize2hbits(nhash));
                kidx = const_gc(fs, obj2gco(t), LJ_TTAB);
                fs->bcbase[pc].ins = BCINS_AD(BC_TDUP, freg - 1, kidx);
            }
            vcall = 0;
            expr_kvalue(&k, &key);
            v = lj_tab_set(fs->L, t, &k);
            lj_gc_anybarriert(fs->L, t);
            if (expr_isk_nojump(
                    &val)) { /* Add const key/value to template table. */
                expr_kvalue(v, &val);
            }
            else { /* Otherwise create dummy string key (avoids lj_tab_newkey). */
                settabV(fs->L, v,
                        t); /* Preserve key with table itself as value. */
                fixt = 1;   /* Fix this later, after all resizes. */
                goto nonconst;
            }
        }
        else {
        nonconst:
            if (val.k != VCALL) {
                expr_toanyreg(fs, &val);
                vcall = 0;
            }
            if (expr_isk(&key))
                expr_index(fs, e, &key);
            bcemit_store(fs, e, &val);
        }
        fs->freereg = freg;
        if (!lex_opt(ls, ',') && !lex_opt(ls, ';'))
            break;
    }
    lex_match(ls, '}', '{', line);
    if (vcall) {
        BCInsLine *ilp = &fs->bcbase[fs->pc - 1];
        ExpDesc en;
        lua_assert(bc_a(ilp->ins) == freg &&
                   bc_op(ilp->ins) == (narr > 256 ? BC_TSETV : BC_TSETB));
        expr_init(&en, VKNUM, 0);
        en.u.nval.u32.lo = narr - 1;
        en.u.nval.u32.hi = 0x43300000; /* Biased integer to avoid denormals. */
        if (narr > 256) {
            fs->pc--;
            ilp--;
        }
        ilp->ins = BCINS_AD(BC_TSETM, freg, const_num(fs, &en));
        setbc_b(&ilp[-1].ins, 0);
    }
    if (pc == fs->pc - 1) { /* Make expr relocable if possible. */
        e->u.s.info = pc;
        fs->freereg--;
        e->k = VRELOCABLE;
    }
    else {
        e->k = VNONRELOC; /* May have been changed by expr_index. */
    }
    if (!t) { /* Construct TNEW RD: hhhhhaaaaaaaaaaa. */
        BCIns *ip = &fs->bcbase[pc].ins;
        if (!needarr)
            narr = 0;
        else if (narr < 3)
            narr = 3;
        else if (narr > 0x7ff)
            narr = 0x7ff;
        setbc_d(ip, narr | (hsize2hbits(nhash) << 11));
    }
    else {
        if (needarr && t->asize < narr)
            lj_tab_reasize(fs->L, t, narr - 1);
        if (fixt) { /* Fix value for dummy keys in template table. */
            Node *node = noderef(t->node);
            uint32_t i, hmask = t->hmask;
            for (i = 0; i <= hmask; i++) {
                Node *n = &node[i];
                if (tvistab(&n->val)) {
                    lua_assert(tabV(&n->val) == t);
                    setnilV(&n->val); /* Turn value into nil. */
                }
            }
        }
        lj_gc_check(fs->L);
    }
}

/* Parse function parameters. */
static BCReg parse_params(LexState *ls, int needself)
{
    FuncState *fs = ls->fs;
    BCReg nparams = 0;
    lex_check(ls, '(');
    if (needself)
        var_new_lit(ls, nparams++, "self");
    if (ls->token != ')') {
        do {
            if (ls->token == TK_name || (!LJ_52 && ls->token == TK_goto)) {
                var_new(ls, nparams++, lex_str(ls));
            }
            else if (ls->token == TK_dots) {
                lj_lex_next(ls);
                fs->flags |= PROTO_VARARG;
                break;
            }
            else {
                err_syntax(ls, LJ_ERR_XPARAM);
            }
        } while (lex_opt(ls, ','));
    }
    var_add(ls, nparams);
    lua_assert(fs->nactvar == nparams);
    bcreg_reserve(fs, nparams);
    lex_check(ls, ')');
    return nparams;
}

/* Forward declaration. */
static void parse_chunk(LexState *ls);

/* Parse body of a function. */
static void parse_body(LexState *ls, ExpDesc *e, int needself, BCLine line)
{
    FuncState fs, *pfs = ls->fs;
    FuncScope bl;
    GCproto *pt;
    ptrdiff_t oldbase = pfs->bcbase - ls->bcstack;
    fs_init(ls, &fs);
    fscope_begin(&fs, &bl, 0);
    fs.linedefined = line;
    fs.numparams = (uint8_t)parse_params(ls, needself);
    fs.bcbase = pfs->bcbase + pfs->pc;
    fs.bclim = pfs->bclim - pfs->pc;
    bcemit_AD(&fs, BC_FUNCF, 0, 0); /* Placeholder. */
    parse_chunk(ls);
    if (ls->token != TK_end)
        lex_match(ls, TK_end, TK_function, line);
    pt = fs_finish(ls, (ls->lastline = ls->linenumber));
    pfs->bcbase = ls->bcstack + oldbase; /* May have been reallocated. */
    pfs->bclim = (BCPos)(ls->sizebcstack - oldbase);
    /* Store new prototype in the constant array of the parent. */
    expr_init(
        e, VRELOCABLE,
        bcemit_AD(pfs, BC_FNEW, 0, const_gc(pfs, obj2gco(pt), LJ_TPROTO)));
#if LJ_HASFFI
    pfs->flags |= (fs.flags & PROTO_FFI);
#endif
    if (!(pfs->flags & PROTO_CHILD)) {
        if (pfs->flags & PROTO_HAS_RETURN)
            pfs->flags |= PROTO_FIXUP_RETURN;
        pfs->flags |= PROTO_CHILD;
    }
    lj_lex_next(ls);
}

/* Parse expression list. Last expression is left open. */
static BCReg expr_list(LexState *ls, ExpDesc *v)
{
    BCReg n = 1;
    expr(ls, v);
    while (lex_opt(ls, ',')) {
        expr_tonextreg(ls->fs, v);
        expr(ls, v);
        n++;
    }
    return n;
}

/* Parse function argument list. */
static void parse_args(LexState *ls, ExpDesc *e)
{
    FuncState *fs = ls->fs;
    ExpDesc args;
    BCIns ins;
    BCReg base;
    BCLine line = ls->linenumber;
    if (ls->token == '(') {
#if !LJ_52
        if (line != ls->lastline)
            err_syntax(ls, LJ_ERR_XAMBIG);
#endif
        lj_lex_next(ls);
        if (ls->token == ')') { /* f(). */
            args.k = VVOID;
        }
        else {
            expr_list(ls, &args);
            if (args.k == VCALL) /* f(a, b, g()) or f(a, b, ...). */
                setbc_b(bcptr(fs, &args), 0); /* Pass on multiple results. */
        }
        lex_match(ls, ')', '(', line);
    }
    else if (ls->token == '{') {
        expr_table(ls, &args);
    }
    else if (ls->token == TK_string) {
        expr_init(&args, VKSTR, 0);
        args.u.sval = strV(&ls->tokenval);
        lj_lex_next(ls);
    }
    else {
        err_syntax(ls, LJ_ERR_XFUNARG);
        return; /* Silence compiler. */
    }
    lua_assert(e->k == VNONRELOC);
    base = e->u.s.info; /* Base register for call. */
    if (args.k == VCALL) {
        ins = BCINS_ABC(BC_CALLM, base, 2, args.u.s.aux - base - 1);
    }
    else {
        if (args.k != VVOID)
            expr_tonextreg(fs, &args);
        ins = BCINS_ABC(BC_CALL, base, 2, fs->freereg - base);
    }
    expr_init(e, VCALL, bcemit_INS(fs, ins));
    e->u.s.aux = base;
    fs->bcbase[fs->pc - 1].line = line;
    fs->freereg = base + 1; /* Leave one result by default. */
}

/* Parse primary expression. */
static void expr_primary(LexState *ls, ExpDesc *v)
{
    FuncState *fs = ls->fs;
    /* Parse prefix expression. */
    if (ls->token == '(') {
        BCLine line = ls->linenumber;
        lj_lex_next(ls);
        expr(ls, v);
        lex_match(ls, ')', '(', line);
        expr_discharge(ls->fs, v);
    }
    else if (ls->token == TK_name || (!LJ_52 && ls->token == TK_goto)) {
        var_lookup(ls, v);
    }
    else {
        err_syntax(ls, LJ_ERR_XSYMBOL);
    }
    for (;;) { /* Parse multiple expression suffixes. */
        if (ls->token == '.') {
            expr_field(ls, v);
        }
        else if (ls->token == '[') {
            ExpDesc key;
            expr_toanyreg(fs, v);
            expr_bracket(ls, &key);
            expr_index(fs, v, &key);
        }
        else if (ls->token == ':') {
            ExpDesc key;
            lj_lex_next(ls);
            expr_str(ls, &key);
            bcemit_method(fs, v, &key);
            parse_args(ls, v);
        }
        else if (ls->token == '(' || ls->token == TK_string ||
                 ls->token == '{') {
            expr_tonextreg(fs, v);
            parse_args(ls, v);
        }
        else {
            break;
        }
    }
}

/* Parse simple expression. */
static void expr_simple(LexState *ls, ExpDesc *v)
{
    switch (ls->token) {
    case TK_number:
        expr_init(v, (LJ_HASFFI && tviscdata(&ls->tokenval)) ? VKCDATA : VKNUM,
                  0);
        copyTV(ls->L, &v->u.nval, &ls->tokenval);
        break;
    case TK_string:
        expr_init(v, VKSTR, 0);
        v->u.sval = strV(&ls->tokenval);
        break;
    case TK_nil:
        expr_init(v, VKNIL, 0);
        break;
    case TK_true:
        expr_init(v, VKTRUE, 0);
        break;
    case TK_false:
        expr_init(v, VKFALSE, 0);
        break;
    case TK_dots: { /* Vararg. */
        FuncState *fs = ls->fs;
        BCReg base;
        checkcond(ls, fs->flags & PROTO_VARARG, LJ_ERR_XDOTS);
        bcreg_reserve(fs, 1);
        base = fs->freereg - 1;
        expr_init(v, VCALL, bcemit_ABC(fs, BC_VARG, base, 2, fs->numparams));
        v->u.s.aux = base;
        break;
    }
    case '{': /* Table constructor. */
        expr_table(ls, v);
        return;
    case TK_function:
        lj_lex_next(ls);
        parse_body(ls, v, 0, ls->linenumber);
        return;
    default:
        expr_primary(ls, v);
        return;
    }
    lj_lex_next(ls);
}

/* Manage syntactic levels to avoid blowing up the stack. */
static void synlevel_begin(LexState *ls)
{
    if (++ls->level >= LJ_MAX_XLEVEL)
        lj_lex_error(ls, 0, LJ_ERR_XLEVELS);
}

#define synlevel_end(ls) ((ls)->level--)

/* Convert token to binary operator. */
static BinOpr token2binop(LexToken tok)
{
    switch (tok) {
    case '+':
        return OPR_ADD;
    case '-':
        return OPR_SUB;
    case '*':
        return OPR_MUL;
    case '/':
        return OPR_DIV;
    case '%':
        return OPR_MOD;
    case '^':
        return OPR_POW;
    case TK_concat:
        return OPR_CONCAT;
    case TK_ne:
        return OPR_NE;
    case TK_eq:
        return OPR_EQ;
    case '<':
        return OPR_LT;
    case TK_le:
        return OPR_LE;
    case '>':
        return OPR_GT;
    case TK_ge:
        return OPR_GE;
    case TK_and:
        return OPR_AND;
    case TK_or:
        return OPR_OR;
    default:
        return OPR_NOBINOPR;
    }
}

/* Priorities for each binary operator. ORDER OPR. */
static const struct {
    uint8_t left;  /* Left priority. */
    uint8_t right; /* Right priority. */
} priority[] = {
    {6, 6},  {6, 6}, {7, 7}, {7, 7}, {7, 7}, /* ADD SUB MUL DIV MOD */
    {10, 9}, {5, 4},                 /* POW CONCAT (right associative) */
    {3, 3},  {3, 3},                 /* EQ NE */
    {3, 3},  {3, 3}, {3, 3}, {3, 3}, /* LT GE GT LE */
    {2, 2},  {1, 1}                  /* AND OR */
};

#define UNARY_PRIORITY 8 /* Priority for unary operators. */

/* Forward declaration. */
static BinOpr expr_binop(LexState *ls, ExpDesc *v, uint32_t limit);

/* Parse unary expression. */
static void expr_unop(LexState *ls, ExpDesc *v)
{
    BCOp op;
    if (ls->token == TK_not) {
        op = BC_NOT;
    }
    else if (ls->token == '-') {
        op = BC_UNM;
    }
    else if (ls->token == '#') {
        op = BC_LEN;
    }
    else {
        expr_simple(ls, v);
        return;
    }
    lj_lex_next(ls);
    expr_binop(ls, v, UNARY_PRIORITY);
    bcemit_unop(ls->fs, op, v);
}

/* Parse binary expressions with priority higher than the limit. */
static BinOpr expr_binop(LexState *ls, ExpDesc *v, uint32_t limit)
{
    BinOpr op;
    synlevel_begin(ls);
    expr_unop(ls, v);
    op = token2binop(ls->token);
    while (op != OPR_NOBINOPR && priority[op].left > limit) {
        ExpDesc v2;
        BinOpr nextop;
        lj_lex_next(ls);
        bcemit_binop_left(ls->fs, op, v);
        /* Parse binary expression with higher priority. */
        nextop = expr_binop(ls, &v2, priority[op].right);
        bcemit_binop(ls->fs, op, v, &v2);
        op = nextop;
    }
    synlevel_end(ls);
    return op; /* Return unconsumed binary operator (if any). */
}

/* Parse expression. */
static void expr(LexState *ls, ExpDesc *v)
{
    expr_binop(ls, v, 0); /* Priority 0: parse whole expression. */
}

/* Assign expression to the next register. */
static void expr_next(LexState *ls)
{
    ExpDesc e;
    expr(ls, &e);
    expr_tonextreg(ls->fs, &e);
}

/* Parse conditional expression. */
static BCPos expr_cond(LexState *ls)
{
    ExpDesc v;
    expr(ls, &v);
    if (v.k == VKNIL)
        v.k = VKFALSE;
    bcemit_branch_t(ls->fs, &v);
    return v.f;
}

/* -- Assignments --------------------------------------------------------- */

/* List of LHS variables. */
typedef struct LHSVarList {
    ExpDesc v;               /* LHS variable. */
    struct LHSVarList *prev; /* Link to previous LHS variable. */
} LHSVarList;

/* Eliminate write-after-read hazards for local variable assignment. */
static void assign_hazard(LexState *ls, LHSVarList *lh, const ExpDesc *v)
{
    FuncState *fs = ls->fs;
    BCReg reg = v->u.s.info; /* Check against this variable. */
    BCReg tmp = fs->freereg; /* Rename to this temp. register (if needed). */
    int hazard = 0;
    for (; lh; lh = lh->prev) {
        if (lh->v.k == VINDEXED) {
            if (lh->v.u.s.info == reg) { /* t[i], t = 1, 2 */
                hazard = 1;
                lh->v.u.s.info = tmp;
            }
            if (lh->v.u.s.aux == reg) { /* t[i], i = 1, 2 */
                hazard = 1;
                lh->v.u.s.aux = tmp;
            }
        }
    }
    if (hazard) {
        bcemit_AD(fs, BC_MOV, tmp, reg); /* Rename conflicting variable. */
        bcreg_reserve(fs, 1);
    }
}

/* Adjust LHS/RHS of an assignment. */
static void assign_adjust(LexState *ls, BCReg nvars, BCReg nexps, ExpDesc *e)
{
    FuncState *fs = ls->fs;
    int32_t extra = (int32_t)nvars - (int32_t)nexps;
    if (e->k == VCALL) {
        extra++; /* Compensate for the VCALL itself. */
        if (extra < 0)
            extra = 0;
        setbc_b(bcptr(fs, e), extra + 1); /* Fixup call results. */
        if (extra > 1)
            bcreg_reserve(fs, (BCReg)extra - 1);
    }
    else {
        if (e->k != VVOID)
            expr_tonextreg(fs, e); /* Close last expression. */
        if (extra > 0) {           /* Leftover LHS are set to nil. */
            BCReg reg = fs->freereg;
            bcreg_reserve(fs, (BCReg)extra);
            bcemit_nil(fs, reg, (BCReg)extra);
        }
    }
}

/* Recursively parse assignment statement. */
static void parse_assignment(LexState *ls, LHSVarList *lh, BCReg nvars)
{
    ExpDesc e;
    checkcond(ls, VLOCAL <= lh->v.k && lh->v.k <= VINDEXED, LJ_ERR_XSYNTAX);
    if (lex_opt(ls, ',')) { /* Collect LHS list and recurse upwards. */
        LHSVarList vl;
        vl.prev = lh;
        expr_primary(ls, &vl.v);
        if (vl.v.k == VLOCAL)
            assign_hazard(ls, lh, &vl.v);
        checklimit(ls->fs, ls->level + nvars, LJ_MAX_XLEVEL, "variable names");
        parse_assignment(ls, &vl, nvars + 1);
    }
    else { /* Parse RHS. */
        BCReg nexps;
        lex_check(ls, '=');
        nexps = expr_list(ls, &e);
        if (nexps == nvars) {
            if (e.k == VCALL) {
                if (bc_op(*bcptr(ls->fs, &e)) ==
                    BC_VARG) { /* Vararg assignment. */
                    ls->fs->freereg--;
                    e.k = VRELOCABLE;
                }
                else { /* Multiple call results. */
                    e.u.s.info =
                        e.u.s.aux; /* Base of call is not relocatable. */
                    e.k = VNONRELOC;
                }
            }
            bcemit_store(ls->fs, &lh->v, &e);
            return;
        }
        assign_adjust(ls, nvars, nexps, &e);
        if (nexps > nvars)
            ls->fs->freereg -= nexps - nvars; /* Drop leftover regs. */
    }
    /* Assign RHS to LHS and recurse downwards. */
    expr_init(&e, VNONRELOC, ls->fs->freereg - 1);
    bcemit_store(ls->fs, &lh->v, &e);
}

/* Parse call statement or assignment. */
static void parse_call_assign(LexState *ls)
{
    FuncState *fs = ls->fs;
    LHSVarList vl;
    expr_primary(ls, &vl.v);
    if (vl.v.k == VCALL) {            /* Function call statement. */
        setbc_b(bcptr(fs, &vl.v), 1); /* No results. */
    }
    else { /* Start of an assignment. */
        vl.prev = NULL;
        parse_assignment(ls, &vl, 1);
    }
}

/* Parse 'local' statement. */
static void parse_local(LexState *ls)
{
    if (lex_opt(ls, TK_function)) { /* Local function declaration. */
        ExpDesc v, b;
        FuncState *fs = ls->fs;
        var_new(ls, 0, lex_str(ls));
        expr_init(&v, VLOCAL, fs->freereg);
        v.u.s.aux = fs->varmap[fs->freereg];
        bcreg_reserve(fs, 1);
        var_add(ls, 1);
        parse_body(ls, &b, 0, ls->linenumber);
        /* bcemit_store(fs, &v, &b) without setting VSTACK_VAR_RW. */
        expr_free(fs, &b);
        expr_toreg(fs, &b, v.u.s.info);
        /* The upvalue is in scope, but the local is only valid after the store. */
        var_get(ls, fs, fs->nactvar - 1).startpc = fs->pc;
    }
    else { /* Local variable declaration. */
        ExpDesc e;
        BCReg nexps, nvars = 0;
        do { /* Collect LHS. */
            var_new(ls, nvars++, lex_str(ls));
        } while (lex_opt(ls, ','));
        if (lex_opt(ls, '=')) { /* Optional RHS. */
            nexps = expr_list(ls, &e);
        }
        else { /* Or implicitly set to nil. */
            e.k = VVOID;
            nexps = 0;
        }
        assign_adjust(ls, nvars, nexps, &e);
        var_add(ls, nvars);
    }
}

/* Parse 'function' statement. */
static void parse_func(LexState *ls, BCLine line)
{
    FuncState *fs;
    ExpDesc v, b;
    int needself = 0;
    lj_lex_next(ls); /* Skip 'function'. */
    /* Parse function name. */
    var_lookup(ls, &v);
    while (ls->token == '.') /* Multiple dot-separated fields. */
        expr_field(ls, &v);
    if (ls->token == ':') { /* Optional colon to signify method call. */
        needself = 1;
        expr_field(ls, &v);
    }
    parse_body(ls, &b, needself, line);
    fs = ls->fs;
    bcemit_store(fs, &v, &b);
    fs->bcbase[fs->pc - 1].line = line; /* Set line for the store. */
}

/* -- Control transfer statements ----------------------------------------- */

/* Check for end of block. */
static int endofblock(LexToken token)
{
    switch (token) {
    case TK_else:
    case TK_elseif:
    case TK_end:
    case TK_until:
    case TK_eof:
        return 1;
    default:
        return 0;
    }
}

/* Parse 'return' statement. */
static void parse_return(LexState *ls)
{
    BCIns ins;
    FuncState *fs = ls->fs;
    lj_lex_next(ls); /* Skip 'return'. */
    fs->flags |= PROTO_HAS_RETURN;
    if (endofblock(ls->token) || ls->token == ';') { /* Bare return. */
        ins = BCINS_AD(BC_RET0, 0, 1);
    }
    else {         /* Return with one or more values. */
        ExpDesc e; /* Receives the _last_ expression in the list. */
        BCReg nret = expr_list(ls, &e);
        if (nret == 1) {        /* Return one result. */
            if (e.k == VCALL) { /* Check for tail call. */
                BCIns *ip = bcptr(fs, &e);
                /* It doesn't pay off to add BC_VARGT just for 'return ...'. */
                if (bc_op(*ip) == BC_VARG)
                    goto notailcall;
                fs->pc--;
                ins = BCINS_AD(bc_op(*ip) - BC_CALL + BC_CALLT, bc_a(*ip),
                               bc_c(*ip));
            }
            else { /* Can return the result from any register. */
                ins = BCINS_AD(BC_RET1, expr_toanyreg(fs, &e), 2);
            }
        }
        else {
            if (e.k == VCALL) { /* Append all results from a call. */
            notailcall:
                setbc_b(bcptr(fs, &e), 0);
                ins = BCINS_AD(BC_RETM, fs->nactvar, e.u.s.aux - fs->nactvar);
            }
            else {
                expr_tonextreg(fs, &e); /* Force contiguous registers. */
                ins = BCINS_AD(BC_RET, fs->nactvar, nret + 1);
            }
        }
    }
    if (fs->flags & PROTO_CHILD)
        bcemit_AJ(fs, BC_UCLO, 0, 0); /* May need to close upvalues first. */
    bcemit_INS(fs, ins);
}

/* Parse 'break' statement. */
static void parse_break(LexState *ls)
{
    ls->fs->bl->flags |= FSCOPE_BREAK;
    gola_new(ls, NAME_BREAK, VSTACK_GOTO, bcemit_jmp(ls->fs));
}

/* Parse 'goto' statement. */
static void parse_goto(LexState *ls)
{
    FuncState *fs = ls->fs;
    GCstr *name = lex_str(ls);
    VarInfo *vl = gola_findlabel(ls, name);
    if (vl) /* Treat backwards goto within same scope like a loop. */
        bcemit_AJ(fs, BC_LOOP, vl->slot, -1); /* No BC range check. */
    fs->bl->flags |= FSCOPE_GOLA;
    gola_new(ls, name, VSTACK_GOTO, bcemit_jmp(fs));
}

/* Parse label. */
static void parse_label(LexState *ls)
{
    FuncState *fs = ls->fs;
    GCstr *name;
    MSize idx;
    fs->lasttarget = fs->pc;
    fs->bl->flags |= FSCOPE_GOLA;
    lj_lex_next(ls); /* Skip '::'. */
    name = lex_str(ls);
    if (gola_findlabel(ls, name))
        lj_lex_error(ls, 0, LJ_ERR_XLDUP, strdata(name));
    idx = gola_new(ls, name, VSTACK_LABEL, fs->pc);
    lex_check(ls, TK_label);
    /* Recursively parse trailing statements: labels and ';' (Lua 5.2 only). */
    for (;;) {
        if (ls->token == TK_label) {
            synlevel_begin(ls);
            parse_label(ls);
            synlevel_end(ls);
        }
        else if (LJ_52 && ls->token == ';') {
            lj_lex_next(ls);
        }
        else {
            break;
        }
    }
    /* Trailing label is considered to be outside of scope. */
    if (endofblock(ls->token) && ls->token != TK_until)
        ls->vstack[idx].slot = fs->bl->nactvar;
    gola_resolve(ls, fs->bl, idx);
}

/* -- Blocks, loops and conditional statements ---------------------------- */

/* Parse a block. */
static void parse_block(LexState *ls)
{
    FuncState *fs = ls->fs;
    FuncScope bl;
    fscope_begin(fs, &bl, 0);
    parse_chunk(ls);
    fscope_end(fs);
}

/* Parse 'while' statement. */
static void parse_while(LexState *ls, BCLine line)
{
    FuncState *fs = ls->fs;
    BCPos start, loop, condexit;
    FuncScope bl;
    lj_lex_next(ls); /* Skip 'while'. */
    start = fs->lasttarget = fs->pc;
    condexit = expr_cond(ls);
    fscope_begin(fs, &bl, FSCOPE_LOOP);
    lex_check(ls, TK_do);
    loop = bcemit_AD(fs, BC_LOOP, fs->nactvar, 0);
    parse_block(ls);
    jmp_patch(fs, bcemit_jmp(fs), start);
    lex_match(ls, TK_end, TK_while, line);
    fscope_end(fs);
    jmp_tohere(fs, condexit);
    jmp_patchins(fs, loop, fs->pc);
}

/* Parse 'repeat' statement. */
static void parse_repeat(LexState *ls, BCLine line)
{
    FuncState *fs = ls->fs;
    BCPos loop = fs->lasttarget = fs->pc;
    BCPos condexit;
    FuncScope bl1, bl2;
    fscope_begin(fs, &bl1, FSCOPE_LOOP); /* Breakable loop scope. */
    fscope_begin(fs, &bl2, 0);           /* Inner scope. */
    lj_lex_next(ls);                     /* Skip 'repeat'. */
    bcemit_AD(fs, BC_LOOP, fs->nactvar, 0);
    parse_chunk(ls);
    lex_match(ls, TK_until, TK_repeat, line);
    condexit = expr_cond(ls); /* Parse condition (still inside inner scope). */
    if (!(bl2.flags & FSCOPE_UPVAL)) { /* No upvalues? Just end inner scope. */
        fscope_end(fs);
    }
    else { /* Otherwise generate: cond: UCLO+JMP out, !cond: UCLO+JMP loop. */
        parse_break(ls); /* Break from loop and close upvalues. */
        jmp_tohere(fs, condexit);
        fscope_end(fs); /* End inner scope and close upvalues. */
        condexit = bcemit_jmp(fs);
    }
    jmp_patch(fs, condexit, loop); /* Jump backwards if !cond. */
    jmp_patchins(fs, loop, fs->pc);
    fscope_end(fs); /* End loop scope. */
}

/* Parse numeric 'for'. */
static void parse_for_num(LexState *ls, GCstr *varname, BCLine line)
{
    FuncState *fs = ls->fs;
    BCReg base = fs->freereg;
    FuncScope bl;
    BCPos loop, loopend;
    /* Hidden control variables. */
    var_new_fixed(ls, FORL_IDX, VARNAME_FOR_IDX);
    var_new_fixed(ls, FORL_STOP, VARNAME_FOR_STOP);
    var_new_fixed(ls, FORL_STEP, VARNAME_FOR_STEP);
    /* Visible copy of index variable. */
    var_new(ls, FORL_EXT, varname);
    lex_check(ls, '=');
    expr_next(ls);
    lex_check(ls, ',');
    expr_next(ls);
    if (lex_opt(ls, ',')) {
        expr_next(ls);
    }
    else {
        bcemit_AD(fs, BC_KSHORT, fs->freereg, 1); /* Default step is 1. */
        bcreg_reserve(fs, 1);
    }
    var_add(ls, 3); /* Hidden control variables. */
    lex_check(ls, TK_do);
    loop = bcemit_AJ(fs, BC_FORI, base, NO_JMP);
    fscope_begin(fs, &bl, 0); /* Scope for visible variables. */
    var_add(ls, 1);
    bcreg_reserve(fs, 1);
    parse_block(ls);
    fscope_end(fs);
    /* Perform loop inversion. Loop control instructions are at the end. */
    loopend = bcemit_AJ(fs, BC_FORL, base, NO_JMP);
    fs->bcbase[loopend].line = line; /* Fix line for control ins. */
    jmp_patchins(fs, loopend, loop + 1);
    jmp_patchins(fs, loop, fs->pc);
}

/* Try to predict whether the iterator is next() and specialize the bytecode.
** Detecting next() and pairs() by name is simplistic, but quite effective.
** The interpreter backs off if the check for the closure fails at runtime.
*/
static int predict_next(LexState *ls, FuncState *fs, BCPos pc)
{
    BCIns ins = fs->bcbase[pc].ins;
    GCstr *name;
    cTValue *o;
    switch (bc_op(ins)) {
    case BC_MOV:
        name = gco2str(gcref(var_get(ls, fs, bc_d(ins)).name));
        break;
    case BC_UGET:
        name = gco2str(gcref(ls->vstack[fs->uvmap[bc_d(ins)]].name));
        break;
    case BC_GGET:
        /* There's no inverse index (yet), so lookup the strings. */
        o = lj_tab_getstr(fs->kt, lj_str_newlit(ls->L, "pairs"));
        if (o && tvhaskslot(o) && tvkslot(o) == bc_d(ins))
            return 1;
        o = lj_tab_getstr(fs->kt, lj_str_newlit(ls->L, "next"));
        if (o && tvhaskslot(o) && tvkslot(o) == bc_d(ins))
            return 1;
        return 0;
    default:
        return 0;
    }
    return (name->len == 5 && !strcmp(strdata(name), "pairs")) ||
           (name->len == 4 && !strcmp(strdata(name), "next"));
}

/* Parse 'for' iterator. */
static void parse_for_iter(LexState *ls, GCstr *indexname)
{
    FuncState *fs = ls->fs;
    ExpDesc e;
    BCReg nvars = 0;
    BCLine line;
    BCReg base = fs->freereg + 3;
    BCPos loop, loopend, exprpc = fs->pc;
    FuncScope bl;
    int isnext;
    /* Hidden control variables. */
    var_new_fixed(ls, nvars++, VARNAME_FOR_GEN);
    var_new_fixed(ls, nvars++, VARNAME_FOR_STATE);
    var_new_fixed(ls, nvars++, VARNAME_FOR_CTL);
    /* Visible variables returned from iterator. */
    var_new(ls, nvars++, indexname);
    while (lex_opt(ls, ','))
        var_new(ls, nvars++, lex_str(ls));
    lex_check(ls, TK_in);
    line = ls->linenumber;
    assign_adjust(ls, 3, expr_list(ls, &e), &e);
    bcreg_bump(fs, 3); /* The iterator needs another 3 slots (func + 2 args). */
    isnext = (nvars <= 5 && predict_next(ls, fs, exprpc));
    var_add(ls, 3); /* Hidden control variables. */
    lex_check(ls, TK_do);
    loop = bcemit_AJ(fs, isnext ? BC_ISNEXT : BC_JMP, base, NO_JMP);
    fscope_begin(fs, &bl, 0); /* Scope for visible variables. */
    var_add(ls, nvars - 3);
    bcreg_reserve(fs, nvars - 3);
    parse_block(ls);
    fscope_end(fs);
    /* Perform loop inversion. Loop control instructions are at the end. */
    jmp_patchins(fs, loop, fs->pc);
    bcemit_ABC(fs, isnext ? BC_ITERN : BC_ITERC, base, nvars - 3 + 1, 2 + 1);
    loopend = bcemit_AJ(fs, BC_ITERL, base, NO_JMP);
    fs->bcbase[loopend - 1].line = line; /* Fix line for control ins. */
    fs->bcbase[loopend].line = line;
    jmp_patchins(fs, loopend, loop + 1);
}

/* Parse 'for' statement. */
static void parse_for(LexState *ls, BCLine line)
{
    FuncState *fs = ls->fs;
    GCstr *varname;
    FuncScope bl;
    fscope_begin(fs, &bl, FSCOPE_LOOP);
    lj_lex_next(ls);       /* Skip 'for'. */
    varname = lex_str(ls); /* Get first variable name. */
    if (ls->token == '=')
        parse_for_num(ls, varname, line);
    else if (ls->token == ',' || ls->token == TK_in)
        parse_for_iter(ls, varname);
    else
        err_syntax(ls, LJ_ERR_XFOR);
    lex_match(ls, TK_end, TK_for, line);
    fscope_end(fs); /* Resolve break list. */
}

/* Parse condition and 'then' block. */
static BCPos parse_then(LexState *ls)
{
    BCPos condexit;
    lj_lex_next(ls); /* Skip 'if' or 'elseif'. */
    condexit = expr_cond(ls);
    lex_check(ls, TK_then);
    parse_block(ls);
    return condexit;
}

/* Parse 'if' statement. */
static void parse_if(LexState *ls, BCLine line)
{
    FuncState *fs = ls->fs;
    BCPos flist;
    BCPos escapelist = NO_JMP;
    flist = parse_then(ls);
    while (ls->token == TK_elseif) { /* Parse multiple 'elseif' blocks. */
        jmp_append(fs, &escapelist, bcemit_jmp(fs));
        jmp_tohere(fs, flist);
        flist = parse_then(ls);
    }
    if (ls->token == TK_else) { /* Parse optional 'else' block. */
        jmp_append(fs, &escapelist, bcemit_jmp(fs));
        jmp_tohere(fs, flist);
        lj_lex_next(ls); /* Skip 'else'. */
        parse_block(ls);
    }
    else {
        jmp_append(fs, &escapelist, flist);
    }
    jmp_tohere(fs, escapelist);
    lex_match(ls, TK_end, TK_if, line);
}

/* -- Parse statements ---------------------------------------------------- */

/* Parse a statement. Returns 1 if it must be the last one in a chunk. */
static int parse_stmt(LexState *ls)
{
    BCLine line = ls->linenumber;
    switch (ls->token) {
    case TK_if:
        parse_if(ls, line);
        break;
    case TK_while:
        parse_while(ls, line);
        break;
    case TK_do:
        lj_lex_next(ls);
        parse_block(ls);
        lex_match(ls, TK_end, TK_do, line);
        break;
    case TK_for:
        parse_for(ls, line);
        break;
    case TK_repeat:
        parse_repeat(ls, line);
        break;
    case TK_function:
        parse_func(ls, line);
        break;
    case TK_local:
        lj_lex_next(ls);
        parse_local(ls);
        break;
    case TK_return:
        parse_return(ls);
        return 1; /* Must be last. */
    case TK_break:
        lj_lex_next(ls);
        parse_break(ls);
        return !LJ_52; /* Must be last in Lua 5.1. */
#if LJ_52
    case ';':
        lj_lex_next(ls);
        break;
#endif
    case TK_label:
        parse_label(ls);
        break;
    case TK_goto:
        if (LJ_52 || lj_lex_lookahead(ls) == TK_name) {
            lj_lex_next(ls);
            parse_goto(ls);
            break;
        } /* else: fallthrough */
    default:
        parse_call_assign(ls);
        break;
    }
    return 0;
}

/* A chunk is a list of statements optionally separated by semicolons. */
static void parse_chunk(LexState *ls)
{
    int islast = 0;
    synlevel_begin(ls);
    while (!islast && !endofblock(ls->token)) {
        islast = parse_stmt(ls);
        lex_opt(ls, ';');
        lua_assert(ls->fs->framesize >= ls->fs->freereg &&
                   ls->fs->freereg >= ls->fs->nactvar);
        ls->fs->freereg = ls->fs->nactvar; /* Free registers after each stmt. */
    }
    synlevel_end(ls);
}

/* Entry point of bytecode parser. */
GCproto *lj_parse(LexState *ls)
{
    FuncState fs;
    FuncScope bl;
    GCproto *pt;
    lua_State *L = ls->L;
#ifdef LUAJIT_DISABLE_DEBUGINFO
    ls->chunkname = lj_str_newlit(L, "=");
#else
    ls->chunkname = lj_str_newz(L, ls->chunkarg);
#endif
    setstrV(L, L->top, ls->chunkname); /* Anchor chunkname string. */
    incr_top(L);
    ls->level = 0;
    fs_init(ls, &fs);
    fs.linedefined = 0;
    fs.numparams = 0;
    fs.bcbase = NULL;
    fs.bclim = 0;
    fs.flags |= PROTO_VARARG; /* Main chunk is always a vararg func. */
    fscope_begin(&fs, &bl, 0);
    bcemit_AD(&fs, BC_FUNCV, 0, 0); /* Placeholder. */
    lj_lex_next(ls);                /* Read-ahead first token. */
    parse_chunk(ls);
    if (ls->token != TK_eof)
        err_token(ls, TK_eof);
    pt = fs_finish(ls, ls->linenumber);
    L->top--; /* Drop chunkname. */
    lua_assert(fs.prev == NULL);
    lua_assert(ls->fs == NULL);
    lua_assert(pt->sizeuv == 0);
    return pt;
}
