lua/lvm.c

/*
** $Id: lvm.c,v 2.217 2014/06/30 19:48:08 roberto Exp roberto $
** Lua virtual machine
** See Copyright Notice in lua.h
*/


#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define lvm_c
#define LUA_CORE

#include "lua.h"

#include "ldebug.h"
#include "ldo.h"
#include "lfunc.h"
#include "lgc.h"
#include "lobject.h"
#include "lopcodes.h"
#include "lstate.h"
#include "lstring.h"
#include "ltable.h"
#include "ltm.h"
#include "lvm.h"



/* limit for table tag-method chains (to avoid loops) */
#define MAXTAGLOOP	2000


/* maximum length of the conversion of a number to a string */
#define MAXNUMBER2STR	50


/*
** Similar to 'tonumber', but does not attempt to convert strings and
** ensure correct precision (no extra bits). Used in comparisons.
*/
static int tofloat (const TValue *obj, lua_Number *n) {
  if (ttisfloat(obj)) *n = fltvalue(obj);
  else if (ttisinteger(obj)) {
    volatile lua_Number x = cast_num(ivalue(obj));  /* avoid extra precision */
    *n = x;
  }
  else {
    *n = 0;  /* to avoid warnings */
    return 0;
  }
  return 1;
}


/*
** Try to convert a value to a float. Check 'isinteger' first, because
** in general the float case is already handled by the macro 'tonumber'.
*/
int luaV_tonumber_ (const TValue *obj, lua_Number *n) {
  TValue v;
 again:
  if (ttisinteger(obj)) {
    *n = cast_num(ivalue(obj));
    return 1;
  }
  else if (ttisfloat(obj)) {
    *n = fltvalue(obj);
    return 1;
  }
  else if (ttisstring(obj) &&  /* string convertible to number? */
            luaO_str2num(svalue(obj), &v) == tsvalue(obj)->len + 1) {
    obj = &v;
    goto again;  /* convert result from 'luaO_str2num' to a float */
  }
  return 0;  /* conversion failed */
}


/*
** try to convert a value to an integer, rounding according to 'mode':
** mode == 0: accepts only integral values
** mode < 0: takes the floor of the number
** mode > 0: takes the ceil of the number
*/
static int tointeger_aux (const TValue *obj, lua_Integer *p, int mode) {
  TValue v;
 again:
  if (ttisfloat(obj)) {
    lua_Number n = fltvalue(obj);
    lua_Number f = l_floor(n);
    if (n != f) {  /* not an integral value? */
      if (mode == 0) return 0;  /* fails if mode demands integral value */
      else if (mode > 0)  /* needs ceil? */
        f += 1;  /* convert floor to ceil (remember: n != f) */
    }
    return lua_numtointeger(f, p);
  }
  else if (ttisinteger(obj)) {
    *p = ivalue(obj);
    return 1;
  }
  else if (ttisstring(obj) &&
            luaO_str2num(svalue(obj), &v) == tsvalue(obj)->len + 1) {
    obj = &v;
    goto again;  /* convert result from 'luaO_str2num' to an integer */
  }
  return 0;  /* conversion failed */
}


/*
** try to convert a value to an integer
*/
int luaV_tointeger_ (const TValue *obj, lua_Integer *p) {
  return tointeger_aux(obj, p, 0);
}


/*
** Convert a number object to a string
*/
int luaV_tostring (lua_State *L, StkId obj) {
  if (!ttisnumber(obj))
    return 0;
  else {
    char buff[MAXNUMBER2STR];
    size_t len;
    if (ttisinteger(obj))
      len = lua_integer2str(buff, ivalue(obj));
    else {
      len = lua_number2str(buff, fltvalue(obj));
#if !defined(LUA_COMPAT_FLOATSTRING)
      if (buff[strspn(buff, "-0123456789")] == '\0') {  /* looks like an int? */
        buff[len++] = '.';
        buff[len++] = '0';  /* adds '.0' to result */
      }
#endif
    }
    setsvalue2s(L, obj, luaS_newlstr(L, buff, len));
    return 1;
  }
}


/*
** Try to convert a 'for' limit to an integer, preserving the
** semantics of the loop.
** (The following explanation assumes a non-negative step; it is valid
** for negative steps mutatis mutandis.)
** If the limit can be converted to an integer, rounding down, that is
** it.
** Otherwise, check whether the limit can be converted to a number.  If
** the number is too large, it is OK to set the limit as LUA_MAXINTEGER,
** which means no limit.  If the number is too negative, the loop
** should not run, because any initial integer value is larger than the
** limit. So, it sets the limit to LUA_MININTEGER. 'stopnow' corrects
** the extreme case when the initial value is LUA_MININTEGER, in which
** case the LUA_MININTEGER limit would still run the loop once.
*/
static int forlimit (const TValue *obj, lua_Integer *p, lua_Integer step,
                     int *stopnow) {
  *stopnow = 0;  /* usually, let loops run */
  if (!tointeger_aux(obj, p, (step < 0 ? 1 : -1))) {  /* not fit in integer? */
    lua_Number n;  /* try to convert to float */
    if (!tonumber(obj, &n)) /* cannot convert to float? */
      return 0;  /* not a number */
    if (n > 0) {  /* if true, float is larger than max integer */
      *p = LUA_MAXINTEGER;
      if (step < 0) *stopnow = 1;
    }
    else {  /* float is smaller than min integer */
      *p = LUA_MININTEGER;
      if (step >= 0) *stopnow = 1;
    }
  }
  return 1;
}


/*
** Main function for table access (invoking metamethods if needed).
** Compute 'val = t[key]'
*/
void luaV_gettable (lua_State *L, const TValue *t, TValue *key, StkId val) {
  int loop;  /* counter to avoid infinite loops */
  for (loop = 0; loop < MAXTAGLOOP; loop++) {
    const TValue *tm;
    if (ttistable(t)) {  /* `t' is a table? */
      Table *h = hvalue(t);
      const TValue *res = luaH_get(h, key); /* do a primitive get */
      if (!ttisnil(res) ||  /* result is not nil? */
          (tm = fasttm(L, h->metatable, TM_INDEX)) == NULL) { /* or no TM? */
        setobj2s(L, val, res);  /* result is the raw get */
        return;
      }
      /* else will try metamethod */
    }
    else if (ttisnil(tm = luaT_gettmbyobj(L, t, TM_INDEX)))
      luaG_typeerror(L, t, "index");  /* no metamethod */
    if (ttisfunction(tm)) {  /* metamethod is a function */
      luaT_callTM(L, tm, t, key, val, 1);
      return;
    }
    t = tm;  /* else repeat access over 'tm' */
  }
  luaG_runerror(L, "gettable chain too long; possible loop");
}


/*
** Main function for table assignment (invoking metamethods if needed).
** Compute 't[key] = val'
*/
void luaV_settable (lua_State *L, const TValue *t, TValue *key, StkId val) {
  int loop;  /* counter to avoid infinite loops */
  for (loop = 0; loop < MAXTAGLOOP; loop++) {
    const TValue *tm;
    if (ttistable(t)) {  /* `t' is a table? */
      Table *h = hvalue(t);
      TValue *oldval = cast(TValue *, luaH_get(h, key));
      /* if previous value is not nil, there must be a previous entry
         in the table; a metamethod has no relevance */
      if (!ttisnil(oldval) ||
         /* previous value is nil; must check the metamethod */
         ((tm = fasttm(L, h->metatable, TM_NEWINDEX)) == NULL &&
         /* no metamethod; is there a previous entry in the table? */
         (oldval != luaO_nilobject ||
         /* no previous entry; must create one. (The next test is
            always true; we only need the assignment.) */
         (oldval = luaH_newkey(L, h, key), 1)))) {
        /* no metamethod and (now) there is an entry with given key */
        setobj2t(L, oldval, val);  /* assign new value to that entry */
        invalidateTMcache(h);
        luaC_barrierback(L, h, val);
        return;
      }
      /* else will try the metamethod */
    }
    else  /* not a table; check metamethod */
      if (ttisnil(tm = luaT_gettmbyobj(L, t, TM_NEWINDEX)))
        luaG_typeerror(L, t, "index");
    /* try the metamethod */
    if (ttisfunction(tm)) {
      luaT_callTM(L, tm, t, key, val, 0);
      return;
    }
    t = tm;  /* else repeat assignment over 'tm' */
  }
  luaG_runerror(L, "settable chain too long; possible loop");
}


/*
** Compare two strings 'ls' x 'rs', returning an integer smaller-equal-
** -larger than zero if 'ls' is smaller-equal-larger than 'rs'.
** The code is a little tricky because it allows '\0' in the strings
** and it uses 'strcoll' (to respect locales) for each segments
** of the strings.
*/
static int l_strcmp (const TString *ls, const TString *rs) {
  const char *l = getstr(ls);
  size_t ll = ls->tsv.len;
  const char *r = getstr(rs);
  size_t lr = rs->tsv.len;
  for (;;) {  /* for each segment */
    int temp = strcoll(l, r);
    if (temp != 0)  /* not equal? */
      return temp;  /* done */
    else {  /* strings are equal up to a '\0' */
      size_t len = strlen(l);  /* index of first `\0' in both strings */
      if (len == lr)  /* 'rs' is finished? */
        return (len == ll) ? 0 : 1;  /* check 'ls' */
      else if (len == ll)  /* 'ls' is finished? */
        return -1;  /* 'ls' is smaller than 'rs' ('rs' is not finished) */
      /* both strings longer than `len'; go on comparing after the '\0' */
      len++;
      l += len; ll -= len; r += len; lr -= len;
    }
  }
}


/*
** Main operation less than; return 'l < r'.
*/
int luaV_lessthan (lua_State *L, const TValue *l, const TValue *r) {
  int res;
  lua_Number nl, nr;
  if (ttisinteger(l) && ttisinteger(r))  /* both operands are integers? */
    return (ivalue(l) < ivalue(r));
  else if (tofloat(l, &nl) && tofloat(r, &nr))  /* both are numbers? */
    return luai_numlt(nl, nr);
  else if (ttisstring(l) && ttisstring(r))  /* both are strings? */
    return l_strcmp(rawtsvalue(l), rawtsvalue(r)) < 0;
  else if ((res = luaT_callorderTM(L, l, r, TM_LT)) < 0)  /* no metamethod? */
    luaG_ordererror(L, l, r);  /* error */
  return res;
}


/*
** Main operation less than or equal to; return 'l <= r'.
*/
int luaV_lessequal (lua_State *L, const TValue *l, const TValue *r) {
  int res;
  lua_Number nl, nr;
  if (ttisinteger(l) && ttisinteger(r))  /* both operands are integers? */
    return (ivalue(l) <= ivalue(r));
  else if (tofloat(l, &nl) && tofloat(r, &nr))  /* both are numbers? */
    return luai_numle(nl, nr);
  else if (ttisstring(l) && ttisstring(r))  /* both are strings? */
    return l_strcmp(rawtsvalue(l), rawtsvalue(r)) <= 0;
  else if ((res = luaT_callorderTM(L, l, r, TM_LE)) >= 0)  /* first try `le' */
    return res;
  else if ((res = luaT_callorderTM(L, r, l, TM_LT)) < 0)  /* else try `lt' */
    luaG_ordererror(L, l, r);
  return !res;
}


/*
** Main operation for equality of Lua values; return 't1 == t2'. 
** L == NULL means raw equality (no metamethods)
*/
int luaV_equalobj (lua_State *L, const TValue *t1, const TValue *t2) {
  const TValue *tm;
  if (ttype(t1) != ttype(t2)) {  /* not the same variant? */
    if (ttnov(t1) != ttnov(t2) || ttnov(t1) != LUA_TNUMBER)
      return 0;  /* only numbers can be equal with different variants */
    else {  /* two numbers with different variants */
      lua_Number n1, n2;  /* compare them as floats */
      lua_assert(ttisnumber(t1) && ttisnumber(t2));
      cast_void(tofloat(t1, &n1)); cast_void(tofloat(t2, &n2));
      return luai_numeq(n1, n2);
    }
  }
  /* values have same type and same variant */
  switch (ttype(t1)) {
    case LUA_TNIL: return 1;
    case LUA_TNUMINT: return (ivalue(t1) == ivalue(t2));
    case LUA_TNUMFLT: return luai_numeq(fltvalue(t1), fltvalue(t2));
    case LUA_TBOOLEAN: return bvalue(t1) == bvalue(t2);  /* true must be 1 !! */
    case LUA_TLIGHTUSERDATA: return pvalue(t1) == pvalue(t2);
    case LUA_TLCF: return fvalue(t1) == fvalue(t2);
    case LUA_TSHRSTR: return eqshrstr(rawtsvalue(t1), rawtsvalue(t2));
    case LUA_TLNGSTR: return luaS_eqlngstr(rawtsvalue(t1), rawtsvalue(t2));
    case LUA_TUSERDATA: {
      if (uvalue(t1) == uvalue(t2)) return 1;
      else if (L == NULL) return 0;
      tm = fasttm(L, uvalue(t1)->metatable, TM_EQ);
      if (tm == NULL)
        tm = fasttm(L, uvalue(t2)->metatable, TM_EQ);
      break;  /* will try TM */
    }
    case LUA_TTABLE: {
      if (hvalue(t1) == hvalue(t2)) return 1;
      else if (L == NULL) return 0;
      tm = fasttm(L, hvalue(t1)->metatable, TM_EQ);
      if (tm == NULL)
        tm = fasttm(L, hvalue(t2)->metatable, TM_EQ);
      break;  /* will try TM */
    }
    default:
      return gcvalue(t1) == gcvalue(t2);
  }
  if (tm == NULL)  /* no TM? */
    return 0;  /* objects are different */
  luaT_callTM(L, tm, t1, t2, L->top, 1);  /* call TM */
  return !l_isfalse(L->top);
}


/* macro used by 'luaV_concat' to ensure that element at 'o' is a string */
#define tostring(L,o) (ttisstring(o) || (luaV_tostring(L, o)))

/*
** Main operation for concatenation: concat 'total' values in the stack,
** from 'L->top - total' up to 'L->top - 1'.
*/
void luaV_concat (lua_State *L, int total) {
  lua_assert(total >= 2);
  do {
    StkId top = L->top;
    int n = 2;  /* number of elements handled in this pass (at least 2) */
    if (!(ttisstring(top-2) || ttisnumber(top-2)) || !tostring(L, top-1))
      luaT_trybinTM(L, top-2, top-1, top-2, TM_CONCAT);
    else if (tsvalue(top-1)->len == 0)  /* second operand is empty? */
      cast_void(tostring(L, top - 2));  /* result is first operand */
    else if (ttisstring(top-2) && tsvalue(top-2)->len == 0) {
      setobjs2s(L, top - 2, top - 1);  /* result is second op. */
    }
    else {
      /* at least two non-empty string values; get as many as possible */
      size_t tl = tsvalue(top-1)->len;
      char *buffer;
      int i;
      /* collect total length */
      for (i = 1; i < total && tostring(L, top-i-1); i++) {
        size_t l = tsvalue(top-i-1)->len;
        if (l >= (MAX_SIZE/sizeof(char)) - tl)
          luaG_runerror(L, "string length overflow");
        tl += l;
      }
      buffer = luaZ_openspace(L, &G(L)->buff, tl);
      tl = 0;
      n = i;
      do {  /* copy all strings to buffer */
        size_t l = tsvalue(top-i)->len;
        memcpy(buffer+tl, svalue(top-i), l * sizeof(char));
        tl += l;
      } while (--i > 0);
      setsvalue2s(L, top-n, luaS_newlstr(L, buffer, tl));  /* create result */
    }
    total -= n-1;  /* got 'n' strings to create 1 new */
    L->top -= n-1;  /* popped 'n' strings and pushed one */
  } while (total > 1);  /* repeat until only 1 result left */
}


/*
** Main operation 'ra' = #rb'.
*/
void luaV_objlen (lua_State *L, StkId ra, const TValue *rb) {
  const TValue *tm;
  switch (ttnov(rb)) {
    case LUA_TTABLE: {
      Table *h = hvalue(rb);
      tm = fasttm(L, h->metatable, TM_LEN);
      if (tm) break;  /* metamethod? break switch to call it */
      setivalue(ra, luaH_getn(h));  /* else primitive len */
      return;
    }
    case LUA_TSTRING: {
      setivalue(ra, tsvalue(rb)->len);
      return;
    }
    default: {  /* try metamethod */
      tm = luaT_gettmbyobj(L, rb, TM_LEN);
      if (ttisnil(tm))  /* no metamethod? */
        luaG_typeerror(L, rb, "get length of");
      break;
    }
  }
  luaT_callTM(L, tm, rb, rb, ra, 1);
}


/*
** Integer division; return 'm // n'. (Assume that C division with
** negative operands follows C99 behavior.)
*/
lua_Integer luaV_div (lua_State *L, lua_Integer m, lua_Integer n) {
  if (l_castS2U(n) + 1u <= 1u) {  /* special cases: -1 or 0 */
    if (n == 0)
      luaG_runerror(L, "attempt to divide by zero");
    return intop(-, 0, m);   /* n==-1; avoid overflow with 0x80000...//-1 */
  }
  else {
    lua_Integer d = m / n;  /* perform division */
    if ((m ^ n) >= 0 || m % n == 0)   /* same signal or no rest? */
      return d;
    else
      return d - 1;  /* correct 'div' for negative case */
  }
}


/*
** Integer modulus; return 'm % n'. (Assume that C '%' with 
** negative operands follows C99 behavior.)
*/
lua_Integer luaV_mod (lua_State *L, lua_Integer m, lua_Integer n) {
  if (l_castS2U(n) + 1u <= 1u) {  /* special cases: -1 or 0 */
    if (n == 0)
      luaG_runerror(L, "attempt to perform 'n%%0'");
    return 0;   /* m % -1 == 0; avoid overflow with 0x80000...%-1 */
  }
  else {
    lua_Integer r = m % n;
    if (r == 0 || (m ^ n) >= 0)  /* no rest or same signal? */
      return r;
    else
      return r + n;  /* correct 'mod' for negative case */
  }
}


/* number of bits in an integer */
#define NBITS	cast_int(sizeof(lua_Integer) * CHAR_BIT)

/*
** Shift left operation. (Shift right just negates 'y'.)
*/
lua_Integer luaV_shiftl (lua_Integer x, lua_Integer y) {
  if (y < 0) {  /* shift right? */
    if (y <= -NBITS) return 0;
    else return intop(>>, x, -y);
  }
  else {  /* shift left */
    if (y >= NBITS) return 0;
    else return intop(<<, x, y);
  }
}


/*
** check whether cached closure in prototype 'p' may be reused, that is,
** whether there is a cached closure with the same upvalues needed by
** new closure to be created.
*/
static LClosure *getcached (Proto *p, UpVal **encup, StkId base) {
  LClosure *c = p->cache;
  if (c != NULL) {  /* is there a cached closure? */
    int nup = p->sizeupvalues;
    Upvaldesc *uv = p->upvalues;
    int i;
    for (i = 0; i < nup; i++) {  /* check whether it has right upvalues */
      TValue *v = uv[i].instack ? base + uv[i].idx : encup[uv[i].idx]->v;
      if (c->upvals[i]->v != v)
        return NULL;  /* wrong upvalue; cannot reuse closure */
    }
  }
  return c;  /* return cached closure (or NULL if no cached closure) */
}


/*
** create a new Lua closure, push it in the stack, and initialize
** its upvalues. Note that the closure is not cached if prototype is
** already black (which means that 'cache' was already cleared by the
** GC).
*/
static void pushclosure (lua_State *L, Proto *p, UpVal **encup, StkId base,
                         StkId ra) {
  int nup = p->sizeupvalues;
  Upvaldesc *uv = p->upvalues;
  int i;
  LClosure *ncl = luaF_newLclosure(L, nup);
  ncl->p = p;
  setclLvalue(L, ra, ncl);  /* anchor new closure in stack */
  for (i = 0; i < nup; i++) {  /* fill in its upvalues */
    if (uv[i].instack)  /* upvalue refers to local variable? */
      ncl->upvals[i] = luaF_findupval(L, base + uv[i].idx);
    else  /* get upvalue from enclosing function */
      ncl->upvals[i] = encup[uv[i].idx];
    ncl->upvals[i]->refcount++;
    /* new closure is white, so we do not need a barrier here */
  }
  if (!isblack(obj2gco(p)))  /* cache will not break GC invariant? */
    p->cache = ncl;  /* save it on cache for reuse */
}


/*
** finish execution of an opcode interrupted by an yield
*/
void luaV_finishOp (lua_State *L) {
  CallInfo *ci = L->ci;
  StkId base = ci->u.l.base;
  Instruction inst = *(ci->u.l.savedpc - 1);  /* interrupted instruction */
  OpCode op = GET_OPCODE(inst);
  switch (op) {  /* finish its execution */
    case OP_ADD: case OP_SUB: case OP_MUL: case OP_DIV: case OP_IDIV:
    case OP_BAND: case OP_BOR: case OP_BXOR: case OP_SHL: case OP_SHR:
    case OP_MOD: case OP_POW:
    case OP_UNM: case OP_BNOT: case OP_LEN:
    case OP_GETTABUP: case OP_GETTABLE: case OP_SELF: {
      setobjs2s(L, base + GETARG_A(inst), --L->top);
      break;
    }
    case OP_LE: case OP_LT: case OP_EQ: {
      int res = !l_isfalse(L->top - 1);
      L->top--;
      /* metamethod should not be called when operand is K */
      lua_assert(!ISK(GETARG_B(inst)));
      if (op == OP_LE &&  /* "<=" using "<" instead? */
          ttisnil(luaT_gettmbyobj(L, base + GETARG_B(inst), TM_LE)))
        res = !res;  /* invert result */
      lua_assert(GET_OPCODE(*ci->u.l.savedpc) == OP_JMP);
      if (res != GETARG_A(inst))  /* condition failed? */
        ci->u.l.savedpc++;  /* skip jump instruction */
      break;
    }
    case OP_CONCAT: {
      StkId top = L->top - 1;  /* top when 'luaT_trybinTM' was called */
      int b = GETARG_B(inst);      /* first element to concatenate */
      int total = cast_int(top - 1 - (base + b));  /* yet to concatenate */
      setobj2s(L, top - 2, top);  /* put TM result in proper position */
      if (total > 1) {  /* are there elements to concat? */
        L->top = top - 1;  /* top is one after last element (at top-2) */
        luaV_concat(L, total);  /* concat them (may yield again) */
      }
      /* move final result to final position */
      setobj2s(L, ci->u.l.base + GETARG_A(inst), L->top - 1);
      L->top = ci->top;  /* restore top */
      break;
    }
    case OP_TFORCALL: {
      lua_assert(GET_OPCODE(*ci->u.l.savedpc) == OP_TFORLOOP);
      L->top = ci->top;  /* correct top */
      break;
    }
    case OP_CALL: {
      if (GETARG_C(inst) - 1 >= 0)  /* nresults >= 0? */
        L->top = ci->top;  /* adjust results */
      break;
    }
    case OP_TAILCALL: case OP_SETTABUP: case OP_SETTABLE:
      break;
    default: lua_assert(0);
  }
}




/*
** {==================================================================
** Function 'luaV_execute': main interpreter loop
** ===================================================================
*/


/*
** some macros for common tasks in `luaV_execute'
*/

#if !defined luai_runtimecheck
#define luai_runtimecheck(L, c)		/* void */
#endif


#define RA(i)	(base+GETARG_A(i))
/* to be used after possible stack reallocation */
#define RB(i)	check_exp(getBMode(GET_OPCODE(i)) == OpArgR, base+GETARG_B(i))
#define RC(i)	check_exp(getCMode(GET_OPCODE(i)) == OpArgR, base+GETARG_C(i))
#define RKB(i)	check_exp(getBMode(GET_OPCODE(i)) == OpArgK, \
	ISK(GETARG_B(i)) ? k+INDEXK(GETARG_B(i)) : base+GETARG_B(i))
#define RKC(i)	check_exp(getCMode(GET_OPCODE(i)) == OpArgK, \
	ISK(GETARG_C(i)) ? k+INDEXK(GETARG_C(i)) : base+GETARG_C(i))
#define KBx(i)  \
  (k + (GETARG_Bx(i) != 0 ? GETARG_Bx(i) - 1 : GETARG_Ax(*ci->u.l.savedpc++)))


/* execute a jump instruction */
#define dojump(ci,i,e) \
  { int a = GETARG_A(i); \
    if (a > 0) luaF_close(L, ci->u.l.base + a - 1); \
    ci->u.l.savedpc += GETARG_sBx(i) + e; }

/* for test instructions, execute the jump instruction that follows it */
#define donextjump(ci)	{ i = *ci->u.l.savedpc; dojump(ci, i, 1); }


#define Protect(x)	{ {x;}; base = ci->u.l.base; }

#define checkGC(L,c)  \
  Protect( luaC_condGC(L,{L->top = (c);  /* limit of live values */ \
                          luaC_step(L); \
                          L->top = ci->top;})  /* restore top */ \
           luai_threadyield(L); )


#define vmdispatch(o)	switch(o)
#define vmcase(l,b)	case l: {b}  break;
#define vmcasenb(l,b)	case l: {b}		/* nb = no break */

void luaV_execute (lua_State *L) {
  CallInfo *ci = L->ci;
  LClosure *cl;
  TValue *k;
  StkId base;
 newframe:  /* reentry point when frame changes (call/return) */
  lua_assert(ci == L->ci);
  cl = clLvalue(ci->func);
  k = cl->p->k;
  base = ci->u.l.base;
  /* main loop of interpreter */
  for (;;) {
    Instruction i = *(ci->u.l.savedpc++);
    StkId ra;
    if ((L->hookmask & (LUA_MASKLINE | LUA_MASKCOUNT)) &&
        (--L->hookcount == 0 || L->hookmask & LUA_MASKLINE)) {
      Protect(luaG_traceexec(L));
    }
    /* WARNING: several calls may realloc the stack and invalidate `ra' */
    ra = RA(i);
    lua_assert(base == ci->u.l.base);
    lua_assert(base <= L->top && L->top < L->stack + L->stacksize);
    vmdispatch (GET_OPCODE(i)) {
      vmcase(OP_MOVE,
        setobjs2s(L, ra, RB(i));
      )
      vmcase(OP_LOADK,
        TValue *rb = k + GETARG_Bx(i);
        setobj2s(L, ra, rb);
      )
      vmcase(OP_LOADKX,
        TValue *rb;
        lua_assert(GET_OPCODE(*ci->u.l.savedpc) == OP_EXTRAARG);
        rb = k + GETARG_Ax(*ci->u.l.savedpc++);
        setobj2s(L, ra, rb);
      )
      vmcase(OP_LOADBOOL,
        setbvalue(ra, GETARG_B(i));
        if (GETARG_C(i)) ci->u.l.savedpc++;  /* skip next instruction (if C) */
      )
      vmcase(OP_LOADNIL,
        int b = GETARG_B(i);
        do {
          setnilvalue(ra++);
        } while (b--);
      )
      vmcase(OP_GETUPVAL,
        int b = GETARG_B(i);
        setobj2s(L, ra, cl->upvals[b]->v);
      )
      vmcase(OP_GETTABUP,
        int b = GETARG_B(i);
        Protect(luaV_gettable(L, cl->upvals[b]->v, RKC(i), ra));
      )
      vmcase(OP_GETTABLE,
        Protect(luaV_gettable(L, RB(i), RKC(i), ra));
      )
      vmcase(OP_SETTABUP,
        int a = GETARG_A(i);
        Protect(luaV_settable(L, cl->upvals[a]->v, RKB(i), RKC(i)));
      )
      vmcase(OP_SETUPVAL,
        UpVal *uv = cl->upvals[GETARG_B(i)];
        setobj(L, uv->v, ra);
        luaC_upvalbarrier(L, uv);
      )
      vmcase(OP_SETTABLE,
        Protect(luaV_settable(L, ra, RKB(i), RKC(i)));
      )
      vmcase(OP_NEWTABLE,
        int b = GETARG_B(i);
        int c = GETARG_C(i);
        Table *t = luaH_new(L);
        sethvalue(L, ra, t);
        if (b != 0 || c != 0)
          luaH_resize(L, t, luaO_fb2int(b), luaO_fb2int(c));
        checkGC(L, ra + 1);
      )
      vmcase(OP_SELF,
        StkId rb = RB(i);
        setobjs2s(L, ra+1, rb);
        Protect(luaV_gettable(L, rb, RKC(i), ra));
      )
      vmcase(OP_ADD, 
        TValue *rb = RKB(i);
        TValue *rc = RKC(i);
        lua_Number nb; lua_Number nc;
        if (ttisinteger(rb) && ttisinteger(rc)) {
          lua_Integer ib = ivalue(rb); lua_Integer ic = ivalue(rc);
          setivalue(ra, intop(+, ib, ic));
        }
        else if (tonumber(rb, &nb) && tonumber(rc, &nc)) {
          setfltvalue(ra, luai_numadd(L, nb, nc));
        }
        else { Protect(luaT_trybinTM(L, rb, rc, ra, TM_ADD)); }
      )
      vmcase(OP_SUB,
        TValue *rb = RKB(i);
        TValue *rc = RKC(i);
        lua_Number nb; lua_Number nc;
        if (ttisinteger(rb) && ttisinteger(rc)) {
          lua_Integer ib = ivalue(rb); lua_Integer ic = ivalue(rc);
          setivalue(ra, intop(-, ib, ic));
        }
        else if (tonumber(rb, &nb) && tonumber(rc, &nc)) {
          setfltvalue(ra, luai_numsub(L, nb, nc));
        }
        else { Protect(luaT_trybinTM(L, rb, rc, ra, TM_SUB)); }
      )
      vmcase(OP_MUL,
        TValue *rb = RKB(i);
        TValue *rc = RKC(i);
        lua_Number nb; lua_Number nc;
        if (ttisinteger(rb) && ttisinteger(rc)) {
          lua_Integer ib = ivalue(rb); lua_Integer ic = ivalue(rc);
          setivalue(ra, intop(*, ib, ic));
        }
        else if (tonumber(rb, &nb) && tonumber(rc, &nc)) {
          setfltvalue(ra, luai_nummul(L, nb, nc));
        }
        else { Protect(luaT_trybinTM(L, rb, rc, ra, TM_MUL)); }
      )
      vmcase(OP_DIV,  /* float division (always with floats) */
        TValue *rb = RKB(i);
        TValue *rc = RKC(i);
        lua_Number nb; lua_Number nc;
        if (tonumber(rb, &nb) && tonumber(rc, &nc)) {
          setfltvalue(ra, luai_numdiv(L, nb, nc));
        }
        else { Protect(luaT_trybinTM(L, rb, rc, ra, TM_DIV)); }
      )
      vmcase(OP_IDIV,  /* integer division */
        TValue *rb = RKB(i);
        TValue *rc = RKC(i);
        lua_Integer ib; lua_Integer ic;
        if (tointeger(rb, &ib) && tointeger(rc, &ic)) {
          setivalue(ra, luaV_div(L, ib, ic));
        }
        else { Protect(luaT_trybinTM(L, rb, rc, ra, TM_IDIV)); }
      )
      vmcase(OP_BAND,
        TValue *rb = RKB(i);
        TValue *rc = RKC(i);
        lua_Integer ib; lua_Integer ic;
        if (tointeger(rb, &ib) && tointeger(rc, &ic)) {
          setivalue(ra, intop(&, ib, ic));
        }
        else { Protect(luaT_trybinTM(L, rb, rc, ra, TM_BAND)); }
      )
      vmcase(OP_BOR,
        TValue *rb = RKB(i);
        TValue *rc = RKC(i);
        lua_Integer ib; lua_Integer ic;
        if (tointeger(rb, &ib) && tointeger(rc, &ic)) {
          setivalue(ra, intop(|, ib, ic));
        }
        else { Protect(luaT_trybinTM(L, rb, rc, ra, TM_BOR)); }
      )
      vmcase(OP_BXOR,
        TValue *rb = RKB(i);
        TValue *rc = RKC(i);
        lua_Integer ib; lua_Integer ic;
        if (tointeger(rb, &ib) && tointeger(rc, &ic)) {
          setivalue(ra, intop(^, ib, ic));
        }
        else { Protect(luaT_trybinTM(L, rb, rc, ra, TM_BXOR)); }
      )
      vmcase(OP_SHL,
        TValue *rb = RKB(i);
        TValue *rc = RKC(i);
        lua_Integer ib; lua_Integer ic;
        if (tointeger(rb, &ib) && tointeger(rc, &ic)) {
          setivalue(ra, luaV_shiftl(ib, ic));
        }
        else { Protect(luaT_trybinTM(L, rb, rc, ra, TM_SHL)); }
      )
      vmcase(OP_SHR,
        TValue *rb = RKB(i);
        TValue *rc = RKC(i);
        lua_Integer ib; lua_Integer ic;
        if (tointeger(rb, &ib) && tointeger(rc, &ic)) {
          setivalue(ra, luaV_shiftl(ib, -ic));
        }
        else { Protect(luaT_trybinTM(L, rb, rc, ra, TM_SHR)); }
      )
      vmcase(OP_MOD,
        TValue *rb = RKB(i);
        TValue *rc = RKC(i);
        lua_Number nb; lua_Number nc;
        if (ttisinteger(rb) && ttisinteger(rc)) {
          lua_Integer ib = ivalue(rb); lua_Integer ic = ivalue(rc);
          setivalue(ra, luaV_mod(L, ib, ic));
        }
        else if (tonumber(rb, &nb) && tonumber(rc, &nc)) {
          lua_Number m;
          luai_nummod(L, nb, nc, m);
          setfltvalue(ra, m);
        }
        else { Protect(luaT_trybinTM(L, rb, rc, ra, TM_MOD)); }
      )
      vmcase(OP_POW,
        TValue *rb = RKB(i);
        TValue *rc = RKC(i);
        lua_Number nb; lua_Number nc;
        if (tonumber(rb, &nb) && tonumber(rc, &nc)) {
          setfltvalue(ra, luai_numpow(L, nb, nc));
        }
        else { Protect(luaT_trybinTM(L, rb, rc, ra, TM_POW)); }
      )
      vmcase(OP_UNM,
        TValue *rb = RB(i);
        lua_Number nb;
        if (ttisinteger(rb)) {
          lua_Integer ib = ivalue(rb);
          setivalue(ra, intop(-, 0, ib));
        }
        else if (tonumber(rb, &nb)) {
          setfltvalue(ra, luai_numunm(L, nb));
        }
        else {
          Protect(luaT_trybinTM(L, rb, rb, ra, TM_UNM));
        }
      )
      vmcase(OP_BNOT,
        TValue *rb = RB(i);
        lua_Integer ib;
        if (tointeger(rb, &ib)) {
          setivalue(ra, intop(^, ~l_castS2U(0), ib));
        }
        else {
          Protect(luaT_trybinTM(L, rb, rb, ra, TM_BNOT));
        }
      )
      vmcase(OP_NOT,
        TValue *rb = RB(i);
        int res = l_isfalse(rb);  /* next assignment may change this value */
        setbvalue(ra, res);
      )
      vmcase(OP_LEN,
        Protect(luaV_objlen(L, ra, RB(i)));
      )
      vmcase(OP_CONCAT,
        int b = GETARG_B(i);
        int c = GETARG_C(i);
        StkId rb;
        L->top = base + c + 1;  /* mark the end of concat operands */
        Protect(luaV_concat(L, c - b + 1));
        ra = RA(i);  /* 'luav_concat' may invoke TMs and move the stack */
        rb = b + base;
        setobjs2s(L, ra, rb);
        checkGC(L, (ra >= rb ? ra + 1 : rb));
        L->top = ci->top;  /* restore top */
      )
      vmcase(OP_JMP,
        dojump(ci, i, 0);
      )
      vmcase(OP_EQ,
        TValue *rb = RKB(i);
        TValue *rc = RKC(i);
        Protect(
          if (cast_int(luaV_equalobj(L, rb, rc)) != GETARG_A(i))
            ci->u.l.savedpc++;
          else
            donextjump(ci);
        )
      )
      vmcase(OP_LT,
        Protect(
          if (luaV_lessthan(L, RKB(i), RKC(i)) != GETARG_A(i))
            ci->u.l.savedpc++;
          else
            donextjump(ci);
        )
      )
      vmcase(OP_LE,
        Protect(
          if (luaV_lessequal(L, RKB(i), RKC(i)) != GETARG_A(i))
            ci->u.l.savedpc++;
          else
            donextjump(ci);
        )
      )
      vmcase(OP_TEST,
        if (GETARG_C(i) ? l_isfalse(ra) : !l_isfalse(ra))
            ci->u.l.savedpc++;
          else
          donextjump(ci);
      )
      vmcase(OP_TESTSET,
        TValue *rb = RB(i);
        if (GETARG_C(i) ? l_isfalse(rb) : !l_isfalse(rb))
          ci->u.l.savedpc++;
        else {
          setobjs2s(L, ra, rb);
          donextjump(ci);
        }
      )
      vmcase(OP_CALL,
        int b = GETARG_B(i);
        int nresults = GETARG_C(i) - 1;
        if (b != 0) L->top = ra+b;  /* else previous instruction set top */
        if (luaD_precall(L, ra, nresults)) {  /* C function? */
          if (nresults >= 0) L->top = ci->top;  /* adjust results */
          base = ci->u.l.base;
        }
        else {  /* Lua function */
          ci = L->ci;
          ci->callstatus |= CIST_REENTRY;
          goto newframe;  /* restart luaV_execute over new Lua function */
        }
      )
      vmcase(OP_TAILCALL,
        int b = GETARG_B(i);
        if (b != 0) L->top = ra+b;  /* else previous instruction set top */
        lua_assert(GETARG_C(i) - 1 == LUA_MULTRET);
        if (luaD_precall(L, ra, LUA_MULTRET))  /* C function? */
          base = ci->u.l.base;
        else {
          /* tail call: put called frame (n) in place of caller one (o) */
          CallInfo *nci = L->ci;  /* called frame */
          CallInfo *oci = nci->previous;  /* caller frame */
          StkId nfunc = nci->func;  /* called function */
          StkId ofunc = oci->func;  /* caller function */
          /* last stack slot filled by 'precall' */
          StkId lim = nci->u.l.base + getproto(nfunc)->numparams;
          int aux;
          /* close all upvalues from previous call */
          if (cl->p->sizep > 0) luaF_close(L, oci->u.l.base);
          /* move new frame into old one */
          for (aux = 0; nfunc + aux < lim; aux++)
            setobjs2s(L, ofunc + aux, nfunc + aux);
          oci->u.l.base = ofunc + (nci->u.l.base - nfunc);  /* correct base */
          oci->top = L->top = ofunc + (L->top - nfunc);  /* correct top */
          oci->u.l.savedpc = nci->u.l.savedpc;
          oci->callstatus |= CIST_TAIL;  /* function was tail called */
          ci = L->ci = oci;  /* remove new frame */
          lua_assert(L->top == oci->u.l.base + getproto(ofunc)->maxstacksize);
          goto newframe;  /* restart luaV_execute over new Lua function */
        }
      )
      vmcasenb(OP_RETURN,
        int b = GETARG_B(i);
        if (b != 0) L->top = ra+b-1;
        if (cl->p->sizep > 0) luaF_close(L, base);
        b = luaD_poscall(L, ra);
        if (!(ci->callstatus & CIST_REENTRY))  /* 'ci' still the called one */
          return;  /* external invocation: return */
        else {  /* invocation via reentry: continue execution */
          ci = L->ci;
          if (b) L->top = ci->top;
          lua_assert(isLua(ci));
          lua_assert(GET_OPCODE(*((ci)->u.l.savedpc - 1)) == OP_CALL);
          goto newframe;  /* restart luaV_execute over new Lua function */
        }
      )
      vmcase(OP_FORLOOP,
        if (ttisinteger(ra)) {  /* integer loop? */
          lua_Integer step = ivalue(ra + 2);
          lua_Integer idx = ivalue(ra) + step; /* increment index */
          lua_Integer limit = ivalue(ra + 1);
          if ((0 < step) ? (idx <= limit) : (limit <= idx)) {
            ci->u.l.savedpc += GETARG_sBx(i);  /* jump back */
            setivalue(ra, idx);  /* update internal index... */
            setivalue(ra + 3, idx);  /* ...and external index */
          }
        }
        else {  /* floating loop */
          lua_Number step = fltvalue(ra + 2);
          lua_Number idx = luai_numadd(L, fltvalue(ra), step); /* inc. index */
          lua_Number limit = fltvalue(ra + 1);
          if (luai_numlt(0, step) ? luai_numle(idx, limit)
                                  : luai_numle(limit, idx)) {
            ci->u.l.savedpc += GETARG_sBx(i);  /* jump back */
            setfltvalue(ra, idx);  /* update internal index... */
            setfltvalue(ra + 3, idx);  /* ...and external index */
          }
        }
      )
      vmcase(OP_FORPREP,
        TValue *init = ra;
        TValue *plimit = ra + 1;
        TValue *pstep = ra + 2;
        lua_Integer ilimit;
        int stopnow;
        if (ttisinteger(init) && ttisinteger(pstep) &&
            forlimit(plimit, &ilimit, ivalue(pstep), &stopnow)) {
          /* all values are integer */
          lua_Integer initv = (stopnow ? 0 : ivalue(init));
          setivalue(plimit, ilimit);
          setivalue(init, initv - ivalue(pstep));
        }
        else {  /* try making all values floats */
          lua_Number ninit; lua_Number nlimit; lua_Number nstep;
          if (!tonumber(plimit, &nlimit))
            luaG_runerror(L, LUA_QL("for") " limit must be a number");
          setfltvalue(plimit, nlimit);
          if (!tonumber(pstep, &nstep))
            luaG_runerror(L, LUA_QL("for") " step must be a number");
          setfltvalue(pstep, nstep);
          if (!tonumber(init, &ninit))
            luaG_runerror(L, LUA_QL("for") " initial value must be a number");
          setfltvalue(init, luai_numsub(L, ninit, nstep));
        }
        ci->u.l.savedpc += GETARG_sBx(i);
      )
      vmcasenb(OP_TFORCALL,
        StkId cb = ra + 3;  /* call base */
        setobjs2s(L, cb+2, ra+2);
        setobjs2s(L, cb+1, ra+1);
        setobjs2s(L, cb, ra);
        L->top = cb + 3;  /* func. + 2 args (state and index) */
        Protect(luaD_call(L, cb, GETARG_C(i), 1));
        L->top = ci->top;
        i = *(ci->u.l.savedpc++);  /* go to next instruction */
        ra = RA(i);
        lua_assert(GET_OPCODE(i) == OP_TFORLOOP);
        goto l_tforloop;
      )
      vmcase(OP_TFORLOOP,
        l_tforloop:
        if (!ttisnil(ra + 1)) {  /* continue loop? */
          setobjs2s(L, ra, ra + 1);  /* save control variable */
           ci->u.l.savedpc += GETARG_sBx(i);  /* jump back */
        }
      )
      vmcase(OP_SETLIST,
        int n = GETARG_B(i);
        int c = GETARG_C(i);
        int last;
        Table *h;
        if (n == 0) n = cast_int(L->top - ra) - 1;
        if (c == 0) {
          lua_assert(GET_OPCODE(*ci->u.l.savedpc) == OP_EXTRAARG);
          c = GETARG_Ax(*ci->u.l.savedpc++);
        }
        luai_runtimecheck(L, ttistable(ra));
        h = hvalue(ra);
        last = ((c-1)*LFIELDS_PER_FLUSH) + n;
        if (last > h->sizearray)  /* needs more space? */
          luaH_resizearray(L, h, last);  /* pre-allocate it at once */
        for (; n > 0; n--) {
          TValue *val = ra+n;
          luaH_setint(L, h, last--, val);
          luaC_barrierback(L, h, val);
        }
        L->top = ci->top;  /* correct top (in case of previous open call) */
      )
      vmcase(OP_CLOSURE,
        Proto *p = cl->p->p[GETARG_Bx(i)];
        LClosure *ncl = getcached(p, cl->upvals, base);  /* cached closure */
        if (ncl == NULL)  /* no match? */
          pushclosure(L, p, cl->upvals, base, ra);  /* create a new one */
        else
          setclLvalue(L, ra, ncl);  /* push cashed closure */
        checkGC(L, ra + 1);
      )
      vmcase(OP_VARARG,
        int b = GETARG_B(i) - 1;
        int j;
        int n = cast_int(base - ci->func) - cl->p->numparams - 1;
        if (b < 0) {  /* B == 0? */
          b = n;  /* get all var. arguments */
          Protect(luaD_checkstack(L, n));
          ra = RA(i);  /* previous call may change the stack */
          L->top = ra + n;
        }
        for (j = 0; j < b; j++) {
          if (j < n) {
            setobjs2s(L, ra + j, base - n + j);
          }
          else {
            setnilvalue(ra + j);
          }
        }
      )
      vmcase(OP_EXTRAARG,
        lua_assert(0);
      )
    }
  }
}

/* }================================================================== */