30088298194

Committed 24 Jul 2026 11:03AM UTC coverage: 93.169% (-0.1%) from 93.267%

Build # 30088298194

Build Type

push

github

Committed by

Buristan

Commit Message

ARM: Make hard-float tobit conversions match JIT backend behavior.

Reported by Peter Cawley.

(cherry picked from commit 32a683d22)

On the ARM architecture, the `tobit()` function incorrectly truncates
instead of rounding to the nearest integer. This leads to inconsistency
between various VMs (comparing to x86/x64, for example) and between the
ARM VM and JIT.

This patch uses an addition of 2^52 + 2^51 constant to the given
argument to convert it to the nearest integer value. After reading the
lowest 32 bits of the register, we get the expected result.

The test is the same as for the previous commit.

Sergey Kaplun:
* added the description for the problem

Part of tarantool/tarantool#12880

Coverage Stats

5732 of 6058 branches covered (94.62%)

Branch coverage included in aggregate %.

21859 of 23556 relevant lines covered (92.8%)

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Source File
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96.66

/src/lj_record.c

/*
** Trace recorder (bytecode -> SSA IR).
** Copyright (C) 2005-2017 Mike Pall. See Copyright Notice in luajit.h
*/

#define lj_record_c
#define LUA_CORE

#include "lj_obj.h"

#if LJ_HASJIT

#include "lj_err.h"
#include "lj_str.h"
#include "lj_tab.h"
#include "lj_meta.h"
#include "lj_frame.h"
#if LJ_HASFFI
#include "lj_ctype.h"
#endif
#include "lj_bc.h"
#include "lj_ff.h"
#if LJ_HASPROFILE
#include "lj_debug.h"
#endif
#include "lj_ir.h"
#include "lj_jit.h"
#include "lj_ircall.h"
#include "lj_iropt.h"
#include "lj_trace.h"
#include "lj_record.h"
#include "lj_ffrecord.h"
#include "lj_snap.h"
#include "lj_dispatch.h"
#include "lj_vm.h"

/* Some local macros to save typing. Undef'd at the end. */
#define IR(ref)                        (&J->cur.ir[(ref)])

/* Pass IR on to next optimization in chain (FOLD). */
#define emitir(ot, a, b)        (lj_ir_set(J, (ot), (a), (b)), lj_opt_fold(J))

/* Emit raw IR without passing through optimizations. */
#define emitir_raw(ot, a, b)        (lj_ir_set(J, (ot), (a), (b)), lj_ir_emit(J))

/* -- Sanity checks ------------------------------------------------------- */

#ifdef LUA_USE_ASSERT
/* Sanity check the whole IR -- sloooow. */
static void rec_check_ir(jit_State *J)
{
  IRRef i, nins = J->cur.nins, nk = J->cur.nk;
  lj_assertJ(nk <= REF_BIAS && nins >= REF_BIAS && nins < 65536,
             "inconsistent IR layout");
  for (i = nk; i < nins; i++) {
    IRIns *ir = IR(i);
    uint32_t mode = lj_ir_mode[ir->o];
    IRRef op1 = ir->op1;
    IRRef op2 = ir->op2;
    const char *err = NULL;
    switch (irm_op1(mode)) {
    case IRMnone:
      if (op1 != 0) err = "IRMnone op1 used";
      break;
    case IRMref:
      if (op1 < nk || (i >= REF_BIAS ? op1 >= i : op1 <= i))
        err = "IRMref op1 out of range";
      break;
    case IRMlit: break;
    case IRMcst:
      if (i >= REF_BIAS) { err = "constant in IR range"; break; }
      if (irt_is64(ir->t) && ir->o != IR_KNULL)
        i++;
      continue;
    }
    switch (irm_op2(mode)) {
    case IRMnone:
      if (op2) err = "IRMnone op2 used";
      break;
    case IRMref:
      if (op2 < nk || (i >= REF_BIAS ? op2 >= i : op2 <= i))
        err = "IRMref op2 out of range";
      break;
    case IRMlit: break;
    case IRMcst: err = "IRMcst op2"; break;
    }
    if (!err && ir->prev) {
      if (ir->prev < nk || (i >= REF_BIAS ? ir->prev >= i : ir->prev <= i))
        err = "chain out of range";
      else if (ir->o != IR_NOP && IR(ir->prev)->o != ir->o)
        err = "chain to different op";
    }
    lj_assertJ(!err, "bad IR %04d op %d(%04d,%04d): %s",
               i-REF_BIAS,
               ir->o,
               irm_op1(mode) == IRMref ? op1-REF_BIAS : op1,
               irm_op2(mode) == IRMref ? op2-REF_BIAS : op2,
               err);
  }
}

/* Compare stack slots and frames of the recorder and the VM. */
static void rec_check_slots(jit_State *J)
{
  BCReg s, nslots = J->baseslot + J->maxslot;
  int32_t depth = 0;
  cTValue *base = J->L->base - J->baseslot;
  lj_assertJ(J->baseslot >= 1+LJ_FR2, "bad baseslot");
  lj_assertJ(J->baseslot == 1+LJ_FR2 || (J->slot[J->baseslot-1] & TREF_FRAME),
             "baseslot does not point to frame");
  lj_assertJ(nslots <= LJ_MAX_JSLOTS, "slot overflow");
  for (s = 0; s < nslots; s++) {
    TRef tr = J->slot[s];
    if (tr) {
      cTValue *tv = &base[s];
      IRRef ref = tref_ref(tr);
      IRIns *ir = NULL;  /* Silence compiler. */
      lj_assertJ(tv < J->L->top, "slot %d above top of Lua stack", s);
      if (!LJ_FR2 || ref || !(tr & (TREF_FRAME | TREF_CONT))) {
        lj_assertJ(ref >= J->cur.nk && ref < J->cur.nins,
                   "slot %d ref %04d out of range", s, ref - REF_BIAS);
        ir = IR(ref);
        lj_assertJ(irt_t(ir->t) == tref_t(tr), "slot %d IR type mismatch", s);
      }
      if (s == 0) {
        lj_assertJ(tref_isfunc(tr), "frame slot 0 is not a function");
#if LJ_FR2
      } else if (s == 1) {
        lj_assertJ((tr & ~TREF_FRAME) == 0, "bad frame slot 1");
#endif
      } else if ((tr & TREF_FRAME)) {
        GCfunc *fn = gco2func(frame_gc(tv));
        BCReg delta = (BCReg)(tv - frame_prev(tv));
#if LJ_FR2
        lj_assertJ(!ref || ir_knum(ir)->u64 == tv->u64,
                   "frame slot %d PC mismatch", s);
        tr = J->slot[s-1];
        ir = IR(tref_ref(tr));
#endif
        lj_assertJ(tref_isfunc(tr),
                   "frame slot %d is not a function", s-LJ_FR2);
        lj_assertJ(!tref_isk(tr) || fn == ir_kfunc(ir),
                   "frame slot %d function mismatch", s-LJ_FR2);
        lj_assertJ(s > delta + LJ_FR2 ? (J->slot[s-delta] & TREF_FRAME)
                                      : (s == delta + LJ_FR2),
                   "frame slot %d broken chain", s-LJ_FR2);
        depth++;
      } else if ((tr & TREF_CONT)) {
#if LJ_FR2
        lj_assertJ(!ref || ir_knum(ir)->u64 == tv->u64,
                   "cont slot %d continuation mismatch", s);
#else
        lj_assertJ(ir_kptr(ir) == gcrefp(tv->gcr, void),
                   "cont slot %d continuation mismatch", s);
#endif
        lj_assertJ((J->slot[s+1+LJ_FR2] & TREF_FRAME),
                   "cont slot %d not followed by frame", s);
        depth++;
      } else {
        /* Number repr. may differ, but other types must be the same. */
        lj_assertJ(tvisnumber(tv) ? tref_isnumber(tr) :
                                    itype2irt(tv) == tref_type(tr),
                   "slot %d type mismatch: stack type %d vs IR type %d",
                   s, itypemap(tv), tref_type(tr));
        if (tref_isk(tr)) {  /* Compare constants. */
          TValue tvk;
          lj_ir_kvalue(J->L, &tvk, ir);
          lj_assertJ((tvisnum(&tvk) && tvisnan(&tvk)) ?
                     (tvisnum(tv) && tvisnan(tv)) :
                     lj_obj_equal(tv, &tvk),
                     "slot %d const mismatch: stack %016llx vs IR %016llx",
                     s, tv->u64, tvk.u64);
        }
      }
    }
  }
  lj_assertJ(J->framedepth == depth,
             "frame depth mismatch %d vs %d", J->framedepth, depth);
}
#endif

/* -- Type handling and specialization ------------------------------------ */

/* Note: these functions return tagged references (TRef). */

/* Specialize a slot to a specific type. Note: slot can be negative! */
static TRef sloadt(jit_State *J, int32_t slot, IRType t, int mode)
{
  /* Caller may set IRT_GUARD in t. */
  TRef ref = emitir_raw(IRT(IR_SLOAD, t), (int32_t)J->baseslot+slot, mode);
  J->base[slot] = ref;
  return ref;
}

/* Specialize a slot to the runtime type. Note: slot can be negative! */
static TRef sload(jit_State *J, int32_t slot)
{
  IRType t = itype2irt(&J->L->base[slot]);
  TRef ref = emitir_raw(IRTG(IR_SLOAD, t), (int32_t)J->baseslot+slot,
                        IRSLOAD_TYPECHECK);
  if (irtype_ispri(t)) ref = TREF_PRI(t);  /* Canonicalize primitive refs. */
  J->base[slot] = ref;
  return ref;
}

/* Get TRef from slot. Load slot and specialize if not done already. */
#define getslot(J, s)        (J->base[(s)] ? J->base[(s)] : sload(J, (int32_t)(s)))

/* Get TRef for current function. */
static TRef getcurrf(jit_State *J)
{
  if (J->base[-1-LJ_FR2])
    return J->base[-1-LJ_FR2];
  /* Non-base frame functions ought to be loaded already. */
  lj_assertJ(J->baseslot == 1+LJ_FR2, "bad baseslot");
  return sloadt(J, -1-LJ_FR2, IRT_FUNC, IRSLOAD_READONLY);
}

/* Compare for raw object equality.
** Returns 0 if the objects are the same.
** Returns 1 if they are different, but the same type.
** Returns 2 for two different types.
** Comparisons between primitives always return 1 -- no caller cares about it.
*/
int lj_record_objcmp(jit_State *J, TRef a, TRef b, cTValue *av, cTValue *bv)
{
  int diff = !lj_obj_equal(av, bv);
  if (!tref_isk2(a, b)) {  /* Shortcut, also handles primitives. */
    IRType ta = tref_isinteger(a) ? IRT_INT : tref_type(a);
    IRType tb = tref_isinteger(b) ? IRT_INT : tref_type(b);
    if (ta != tb) {
      /* Widen mixed number/int comparisons to number/number comparison. */
      if (ta == IRT_INT && tb == IRT_NUM) {
        a = emitir(IRTN(IR_CONV), a, IRCONV_NUM_INT);
        ta = IRT_NUM;
      } else if (ta == IRT_NUM && tb == IRT_INT) {
        b = emitir(IRTN(IR_CONV), b, IRCONV_NUM_INT);
      } else {
        return 2;  /* Two different types are never equal. */
      }
    }
    emitir(IRTG(diff ? IR_NE : IR_EQ, ta), a, b);
  }
  return diff;
}

/* Constify a value. Returns 0 for non-representable object types. */
TRef lj_record_constify(jit_State *J, cTValue *o)
{
  if (tvisgcv(o))
    return lj_ir_kgc(J, gcV(o), itype2irt(o));
  else if (tvisint(o))
    return lj_ir_kint(J, intV(o));
  else if (tvisnum(o))
    return lj_ir_knumint(J, numV(o));
  else if (tvisbool(o))
    return TREF_PRI(itype2irt(o));
  else
    return 0;  /* Can't represent lightuserdata (pointless). */
}

/* -- Record loop ops ----------------------------------------------------- */

/* Loop event. */
typedef enum {
  LOOPEV_LEAVE,                /* Loop is left or not entered. */
  LOOPEV_ENTERLO,        /* Loop is entered with a low iteration count left. */
  LOOPEV_ENTER                /* Loop is entered. */
} LoopEvent;

/* Canonicalize slots: convert integers to numbers. */
static void canonicalize_slots(jit_State *J)
{
  BCReg s;
  if (LJ_DUALNUM) return;
  for (s = J->baseslot+J->maxslot-1; s >= 1; s--) {
    TRef tr = J->slot[s];
    if (tref_isinteger(tr)) {
      IRIns *ir = IR(tref_ref(tr));
      if (!(ir->o == IR_SLOAD && (ir->op2 & IRSLOAD_READONLY)))
        J->slot[s] = emitir(IRTN(IR_CONV), tr, IRCONV_NUM_INT);
    }
  }
}

/* Stop recording. */
void lj_record_stop(jit_State *J, TraceLink linktype, TraceNo lnk)
{
#ifdef LUAJIT_ENABLE_TABLE_BUMP
  if (J->retryrec)
    lj_trace_err(J, LJ_TRERR_RETRY);
#endif
  lj_trace_end(J);
  J->cur.linktype = (uint8_t)linktype;
  J->cur.link = (uint16_t)lnk;
  /* Looping back at the same stack level? */
  if (lnk == J->cur.traceno && J->framedepth + J->retdepth == 0) {
    if ((J->flags & JIT_F_OPT_LOOP))  /* Shall we try to create a loop? */
      goto nocanon;  /* Do not canonicalize or we lose the narrowing. */
    if (J->cur.root)  /* Otherwise ensure we always link to the root trace. */
      J->cur.link = J->cur.root;
  }
  canonicalize_slots(J);
nocanon:
  /* Note: all loop ops must set J->pc to the following instruction! */
  lj_snap_add(J);  /* Add loop snapshot. */
  J->needsnap = 0;
  J->mergesnap = 1;  /* In case recording continues. */
}

/* Search bytecode backwards for a int/num constant slot initializer. */
static TRef find_kinit(jit_State *J, const BCIns *endpc, BCReg slot, IRType t)
{
  /* This algorithm is rather simplistic and assumes quite a bit about
  ** how the bytecode is generated. It works fine for FORI initializers,
  ** but it won't necessarily work in other cases (e.g. iterator arguments).
  ** It doesn't do anything fancy, either (like backpropagating MOVs).
  */
  const BCIns *pc, *startpc = proto_bc(J->pt);
  for (pc = endpc-1; pc > startpc; pc--) {
    BCIns ins = *pc;
    BCOp op = bc_op(ins);
    /* First try to find the last instruction that stores to this slot. */
    if (bcmode_a(op) == BCMbase && bc_a(ins) <= slot) {
      return 0;  /* Multiple results, e.g. from a CALL or KNIL. */
    } else if (bcmode_a(op) == BCMdst && bc_a(ins) == slot) {
      if (op == BC_KSHORT || op == BC_KNUM) {  /* Found const. initializer. */
        /* Now try to verify there's no forward jump across it. */
        const BCIns *kpc = pc;
        for (; pc > startpc; pc--)
          if (bc_op(*pc) == BC_JMP) {
            const BCIns *target = pc+bc_j(*pc)+1;
            if (target > kpc && target <= endpc)
              return 0;  /* Conditional assignment. */
          }
        if (op == BC_KSHORT) {
          int32_t k = (int32_t)(int16_t)bc_d(ins);
          return t == IRT_INT ? lj_ir_kint(J, k) : lj_ir_knum(J, (lua_Number)k);
        } else {
          cTValue *tv = proto_knumtv(J->pt, bc_d(ins));
          if (t == IRT_INT) {
            int32_t k = numberVint(tv);
            if (tvisint(tv) || numV(tv) == (lua_Number)k)  /* -0 is ok here. */
              return lj_ir_kint(J, k);
            return 0;  /* Type mismatch. */
          } else {
            return lj_ir_knum(J, numberVnum(tv));
          }
        }
      }
      return 0;  /* Non-constant initializer. */
    }
  }
  return 0;  /* No assignment to this slot found? */
}

/* Load and optionally convert a FORI argument from a slot. */
static TRef fori_load(jit_State *J, BCReg slot, IRType t, int mode)
{
  int conv = (tvisint(&J->L->base[slot]) != (t==IRT_INT)) ? IRSLOAD_CONVERT : 0;
  return sloadt(J, (int32_t)slot,
                t + (((mode & IRSLOAD_TYPECHECK) ||
                      (conv && t == IRT_INT && !(mode >> 16))) ?
                     IRT_GUARD : 0),
                mode + conv);
}

/* Convert FORI argument to expected target type. */
static TRef fori_conv(jit_State *J, TRef tr, IRType t)
{
  if (t == IRT_INT) {
    if (!tref_isinteger(tr))
      return emitir(IRTGI(IR_CONV), tr, IRCONV_INT_NUM|IRCONV_CHECK);
  } else {
    if (!tref_isnum(tr))
      return emitir(IRTN(IR_CONV), tr, IRCONV_NUM_INT);
  }
  return tr;
}

/* Peek before FORI to find a const initializer. Otherwise load from slot. */
static TRef fori_arg(jit_State *J, const BCIns *fori, BCReg slot,
                     IRType t, int mode)
{
  TRef tr = J->base[slot];
  if (tr) {
    tr = fori_conv(J, tr, t);
  } else {
    tr = find_kinit(J, fori, slot, t);
    if (!tr)
      tr = fori_load(J, slot, t, mode);
  }
  return tr;
}

/* Return the direction of the FOR loop iterator.
** It's important to exactly reproduce the semantics of the interpreter.
*/
static int rec_for_direction(cTValue *o)
{
  return (tvisint(o) ? intV(o) : (int32_t)o->u32.hi) >= 0;
}

/* Simulate the runtime behavior of the FOR loop iterator. */
static LoopEvent rec_for_iter(IROp *op, cTValue *o, int isforl)
{
  lua_Number stopv = numberVnum(&o[FORL_STOP]);
  lua_Number idxv = numberVnum(&o[FORL_IDX]);
  lua_Number stepv = numberVnum(&o[FORL_STEP]);
  if (isforl)
    idxv += stepv;
  if (rec_for_direction(&o[FORL_STEP])) {
    if (idxv <= stopv) {
      *op = IR_LE;
      return idxv + 2*stepv > stopv ? LOOPEV_ENTERLO : LOOPEV_ENTER;
    }
    *op = IR_GT; return LOOPEV_LEAVE;
  } else {
    if (stopv <= idxv) {
      *op = IR_GE;
      return idxv + 2*stepv < stopv ? LOOPEV_ENTERLO : LOOPEV_ENTER;
    }
    *op = IR_LT; return LOOPEV_LEAVE;
  }
}

/* Record checks for FOR loop overflow and step direction. */
static void rec_for_check(jit_State *J, IRType t, int dir,
                          TRef stop, TRef step, int init)
{
  if (!tref_isk(step)) {
    /* Non-constant step: need a guard for the direction. */
    TRef zero = (t == IRT_INT) ? lj_ir_kint(J, 0) : lj_ir_knum_zero(J);
    emitir(IRTG(dir ? IR_GE : IR_LT, t), step, zero);
    /* Add hoistable overflow checks for a narrowed FORL index. */
    if (init && t == IRT_INT) {
      if (tref_isk(stop)) {
        /* Constant stop: optimize check away or to a range check for step. */
        int32_t k = IR(tref_ref(stop))->i;
        if (dir) {
          if (k > 0)
            emitir(IRTGI(IR_LE), step, lj_ir_kint(J, (int32_t)0x7fffffff-k));
        } else {
          if (k < 0)
            emitir(IRTGI(IR_GE), step, lj_ir_kint(J, (int32_t)0x80000000-k));
        }
      } else {
        /* Stop+step variable: need full overflow check. */
        TRef tr = emitir(IRTGI(IR_ADDOV), step, stop);
        emitir(IRTI(IR_USE), tr, 0);  /* ADDOV is weak. Avoid dead result. */
      }
    }
  } else if (init && t == IRT_INT && !tref_isk(stop)) {
    /* Constant step: optimize overflow check to a range check for stop. */
    int32_t k = IR(tref_ref(step))->i;
    k = (int32_t)(dir ? 0x7fffffff : 0x80000000) - k;
    emitir(IRTGI(dir ? IR_LE : IR_GE), stop, lj_ir_kint(J, k));
  }
}

/* Record a FORL instruction. */
static void rec_for_loop(jit_State *J, const BCIns *fori, ScEvEntry *scev,
                         int init)
{
  BCReg ra = bc_a(*fori);
  cTValue *tv = &J->L->base[ra];
  TRef idx = J->base[ra+FORL_IDX];
  IRType t = idx ? tref_type(idx) :
             (init || LJ_DUALNUM) ? lj_opt_narrow_forl(J, tv) : IRT_NUM;
  int mode = IRSLOAD_INHERIT +
    ((!LJ_DUALNUM || tvisint(tv) == (t == IRT_INT)) ? IRSLOAD_READONLY : 0);
  TRef stop = fori_arg(J, fori, ra+FORL_STOP, t, mode);
  TRef step = fori_arg(J, fori, ra+FORL_STEP, t, mode);
  int tc, dir = rec_for_direction(&tv[FORL_STEP]);
  lj_assertJ(bc_op(*fori) == BC_FORI || bc_op(*fori) == BC_JFORI,
             "bad bytecode %d instead of FORI/JFORI", bc_op(*fori));
  scev->t.irt = t;
  scev->dir = dir;
  scev->stop = tref_ref(stop);
  scev->step = tref_ref(step);
  rec_for_check(J, t, dir, stop, step, init);
  scev->start = tref_ref(find_kinit(J, fori, ra+FORL_IDX, IRT_INT));
  tc = (LJ_DUALNUM &&
        !(scev->start && irref_isk(scev->stop) && irref_isk(scev->step) &&
          tvisint(&tv[FORL_IDX]) == (t == IRT_INT))) ?
        IRSLOAD_TYPECHECK : 0;
  if (tc) {
    J->base[ra+FORL_STOP] = stop;
    J->base[ra+FORL_STEP] = step;
  }
  if (!idx)
    idx = fori_load(J, ra+FORL_IDX, t,
                    IRSLOAD_INHERIT + tc + (J->scev.start << 16));
  if (!init)
    J->base[ra+FORL_IDX] = idx = emitir(IRT(IR_ADD, t), idx, step);
  J->base[ra+FORL_EXT] = idx;
  scev->idx = tref_ref(idx);
  setmref(scev->pc, fori);
  J->maxslot = ra+FORL_EXT+1;
}

/* Record FORL/JFORL or FORI/JFORI. */
static LoopEvent rec_for(jit_State *J, const BCIns *fori, int isforl)
{
  BCReg ra = bc_a(*fori);
  TValue *tv = &J->L->base[ra];
  TRef *tr = &J->base[ra];
  IROp op;
  LoopEvent ev;
  TRef stop;
  IRType t;
  /* Avoid semantic mismatches and always failing guards. */
  if ((tvisnum(&tv[FORL_IDX]) && tvisnan(&tv[FORL_IDX])) ||
      (tvisnum(&tv[FORL_STOP]) && tvisnan(&tv[FORL_STOP])) ||
      (tvisnum(&tv[FORL_STEP]) && tvisnan(&tv[FORL_STEP])) ||
      tvismzero(&tv[FORL_STEP]))
    lj_trace_err(J, LJ_TRERR_GFAIL);
  if (isforl) {  /* Handle FORL/JFORL opcodes. */
    TRef idx = tr[FORL_IDX];
    if (mref(J->scev.pc, const BCIns) == fori && tref_ref(idx) == J->scev.idx) {
      t = J->scev.t.irt;
      stop = J->scev.stop;
      idx = emitir(IRT(IR_ADD, t), idx, J->scev.step);
      tr[FORL_EXT] = tr[FORL_IDX] = idx;
    } else {
      ScEvEntry scev;
      rec_for_loop(J, fori, &scev, 0);
      t = scev.t.irt;
      stop = scev.stop;
    }
  } else {  /* Handle FORI/JFORI opcodes. */
    BCReg i;
    lj_meta_for(J->L, tv);
    t = (LJ_DUALNUM || tref_isint(tr[FORL_IDX])) ? lj_opt_narrow_forl(J, tv) :
                                                   IRT_NUM;
    for (i = FORL_IDX; i <= FORL_STEP; i++) {
      if (!tr[i]) sload(J, ra+i);
      lj_assertJ(tref_isnumber_str(tr[i]), "bad FORI argument type");
      if (tref_isstr(tr[i]))
        tr[i] = emitir(IRTG(IR_STRTO, IRT_NUM), tr[i], 0);
      tr[i] = fori_conv(J, tr[i], t);
    }
    tr[FORL_EXT] = tr[FORL_IDX];
    stop = tr[FORL_STOP];
    rec_for_check(J, t, rec_for_direction(&tv[FORL_STEP]),
                  stop, tr[FORL_STEP], 1);
  }

  ev = rec_for_iter(&op, tv, isforl);
  if (ev == LOOPEV_LEAVE) {
    J->maxslot = ra+FORL_EXT+1;
    J->pc = fori+1;
  } else {
    J->maxslot = ra;
    J->pc = fori+bc_j(*fori)+1;
  }
  lj_snap_add(J);

  emitir(IRTG(op, t), tr[FORL_IDX], stop);

  if (ev == LOOPEV_LEAVE) {
    J->maxslot = ra;
    J->pc = fori+bc_j(*fori)+1;
  } else {
    J->maxslot = ra+FORL_EXT+1;
    J->pc = fori+1;
  }
  J->needsnap = 1;
  return ev;
}

/* Record ITERL/JITERL. */
static LoopEvent rec_iterl(jit_State *J, const BCIns iterins)
{
  BCReg ra = bc_a(iterins);
  if (!tref_isnil(getslot(J, ra))) {  /* Looping back? */
    J->base[ra-1] = J->base[ra];  /* Copy result of ITERC to control var. */
    J->maxslot = ra-1+bc_b(J->pc[-1]);
    J->pc += bc_j(iterins)+1;
    return LOOPEV_ENTER;
  } else {
    J->maxslot = ra-3;
    J->pc++;
    return LOOPEV_LEAVE;
  }
}

/* Record LOOP/JLOOP. Now, that was easy. */
static LoopEvent rec_loop(jit_State *J, BCReg ra, int skip)
{
  if (ra < J->maxslot) J->maxslot = ra;
  J->pc += skip;
  return LOOPEV_ENTER;
}

/* Check if a loop repeatedly failed to trace because it didn't loop back. */
static int innerloopleft(jit_State *J, const BCIns *pc)
{
  ptrdiff_t i;
  for (i = 0; i < PENALTY_SLOTS; i++)
    if (mref(J->penalty[i].pc, const BCIns) == pc) {
      if ((J->penalty[i].reason == LJ_TRERR_LLEAVE ||
           J->penalty[i].reason == LJ_TRERR_LINNER) &&
          J->penalty[i].val >= 2*PENALTY_MIN)
        return 1;
      break;
    }
  return 0;
}

/* Handle the case when an interpreted loop op is hit. */
static void rec_loop_interp(jit_State *J, const BCIns *pc, LoopEvent ev)
{
  if (J->parent == 0 && J->exitno == 0) {
    if (pc == J->startpc && J->framedepth + J->retdepth == 0) {
      /* Same loop? */
      if (ev == LOOPEV_LEAVE)  /* Must loop back to form a root trace. */
        lj_trace_err(J, LJ_TRERR_LLEAVE);
      lj_record_stop(J, LJ_TRLINK_LOOP, J->cur.traceno);  /* Looping trace. */
    } else if (ev != LOOPEV_LEAVE) {  /* Entering inner loop? */
      /* It's usually better to abort here and wait until the inner loop
      ** is traced. But if the inner loop repeatedly didn't loop back,
      ** this indicates a low trip count. In this case try unrolling
      ** an inner loop even in a root trace. But it's better to be a bit
      ** more conservative here and only do it for very short loops.
      */
      if (bc_j(*pc) != -1 && !innerloopleft(J, pc))
        lj_trace_err(J, LJ_TRERR_LINNER);  /* Root trace hit an inner loop. */
      if ((ev != LOOPEV_ENTERLO &&
           J->loopref && J->cur.nins - J->loopref > 24) || --J->loopunroll < 0)
        lj_trace_err(J, LJ_TRERR_LUNROLL);  /* Limit loop unrolling. */
      J->loopref = J->cur.nins;
    }
  } else if (ev != LOOPEV_LEAVE) {  /* Side trace enters an inner loop. */
    J->loopref = J->cur.nins;
    if (--J->loopunroll < 0)
      lj_trace_err(J, LJ_TRERR_LUNROLL);  /* Limit loop unrolling. */
  }  /* Side trace continues across a loop that's left or not entered. */
}

/* Handle the case when an already compiled loop op is hit. */
static void rec_loop_jit(jit_State *J, TraceNo lnk, LoopEvent ev)
{
  if (J->parent == 0 && J->exitno == 0) {  /* Root trace hit an inner loop. */
    /* Better let the inner loop spawn a side trace back here. */
    lj_trace_err(J, LJ_TRERR_LINNER);
  } else if (ev != LOOPEV_LEAVE) {  /* Side trace enters a compiled loop. */
    J->instunroll = 0;  /* Cannot continue across a compiled loop op. */
    if (J->pc == J->startpc && J->framedepth + J->retdepth == 0)
      lj_record_stop(J, LJ_TRLINK_LOOP, J->cur.traceno);  /* Form extra loop. */
    else
      lj_record_stop(J, LJ_TRLINK_ROOT, lnk);  /* Link to the loop. */
  }  /* Side trace continues across a loop that's left or not entered. */
}

/* -- Record profiler hook checks ----------------------------------------- */

#if LJ_HASPROFILE

/* Need to insert profiler hook check? */
static int rec_profile_need(jit_State *J, GCproto *pt, const BCIns *pc)
{
  GCproto *ppt;
  lj_assertJ(J->prof_mode == 'f' || J->prof_mode == 'l',
             "bad profiler mode %c", J->prof_mode);
  if (!pt)
    return 0;
  ppt = J->prev_pt;
  J->prev_pt = pt;
  if (pt != ppt && ppt) {
    J->prev_line = -1;
    return 1;
  }
  if (J->prof_mode == 'l') {
    BCLine line = lj_debug_line(pt, proto_bcpos(pt, pc));
    BCLine pline = J->prev_line;
    J->prev_line = line;
    if (pline != line)
      return 1;
  }
  return 0;
}

static void rec_profile_ins(jit_State *J, const BCIns *pc)
{
  if (J->prof_mode && rec_profile_need(J, J->pt, pc)) {
    emitir(IRTG(IR_PROF, IRT_NIL), 0, 0);
    lj_snap_add(J);
  }
}

static void rec_profile_ret(jit_State *J)
{
  if (J->prof_mode == 'f') {
    emitir(IRTG(IR_PROF, IRT_NIL), 0, 0);
    J->prev_pt = NULL;
    lj_snap_add(J);
  }
}

#endif

/* -- Record calls and returns -------------------------------------------- */

/* Specialize to the runtime value of the called function or its prototype. */
static TRef rec_call_specialize(jit_State *J, GCfunc *fn, TRef tr)
{
  TRef kfunc;
  if (isluafunc(fn)) {
    GCproto *pt = funcproto(fn);
    /* Too many closures created? Probably not a monomorphic function. */
    if (pt->flags >= PROTO_CLC_POLY) {  /* Specialize to prototype instead. */
      TRef trpt = emitir(IRT(IR_FLOAD, IRT_PGC), tr, IRFL_FUNC_PC);
      emitir(IRTG(IR_EQ, IRT_PGC), trpt, lj_ir_kptr(J, proto_bc(pt)));
      (void)lj_ir_kgc(J, obj2gco(pt), IRT_PROTO);  /* Prevent GC of proto. */
      return tr;
    }
  } else {
    /* Don't specialize to non-monomorphic builtins. */
    switch (fn->c.ffid) {
    case FF_coroutine_wrap_aux:
    case FF_string_gmatch_aux:
      /* NYI: io_file_iter doesn't have an ffid, yet. */
      {  /* Specialize to the ffid. */
        TRef trid = emitir(IRT(IR_FLOAD, IRT_U8), tr, IRFL_FUNC_FFID);
        emitir(IRTG(IR_EQ, IRT_INT), trid, lj_ir_kint(J, fn->c.ffid));
      }
      return tr;
    default:
      /* NYI: don't specialize to non-monomorphic C functions. */
      break;
    }
  }
  /* Otherwise specialize to the function (closure) value itself. */
  kfunc = lj_ir_kfunc(J, fn);
  emitir(IRTG(IR_EQ, IRT_FUNC), tr, kfunc);
  return kfunc;
}

/* Record call setup. */
static void rec_call_setup(jit_State *J, BCReg func, ptrdiff_t nargs)
{
  RecordIndex ix;
  TValue *functv = &J->L->base[func];
  TRef kfunc, *fbase = &J->base[func];
  ptrdiff_t i;
  (void)getslot(J, func); /* Ensure func has a reference. */
  for (i = 1; i <= nargs; i++)
    (void)getslot(J, func+LJ_FR2+i);  /* Ensure all args have a reference. */
  if (!tref_isfunc(fbase[0])) {  /* Resolve __call metamethod. */
    ix.tab = fbase[0];
    copyTV(J->L, &ix.tabv, functv);
    if (!lj_record_mm_lookup(J, &ix, MM_call) || !tref_isfunc(ix.mobj))
      lj_trace_err(J, LJ_TRERR_NOMM);
    for (i = ++nargs; i > LJ_FR2; i--)  /* Shift arguments up. */
      fbase[i+LJ_FR2] = fbase[i+LJ_FR2-1];
#if LJ_FR2
    fbase[2] = fbase[0];
#endif
    fbase[0] = ix.mobj;  /* Replace function. */
    functv = &ix.mobjv;
  }
  kfunc = rec_call_specialize(J, funcV(functv), fbase[0]);
#if LJ_FR2
  fbase[0] = kfunc;
  fbase[1] = TREF_FRAME;
#else
  fbase[0] = kfunc | TREF_FRAME;
#endif
  J->maxslot = (BCReg)nargs;
}

/* Record call. */
void lj_record_call(jit_State *J, BCReg func, ptrdiff_t nargs)
{
  rec_call_setup(J, func, nargs);
  /* Bump frame. */
  J->framedepth++;
  J->base += func+1+LJ_FR2;
  J->baseslot += func+1+LJ_FR2;
  if (J->baseslot + J->maxslot >= LJ_MAX_JSLOTS)
    lj_trace_err(J, LJ_TRERR_STACKOV);
}

/* Record tail call. */
void lj_record_tailcall(jit_State *J, BCReg func, ptrdiff_t nargs)
{
  rec_call_setup(J, func, nargs);
  if (frame_isvarg(J->L->base - 1)) {
    BCReg cbase = (BCReg)frame_delta(J->L->base - 1);
    if (--J->framedepth < 0)
      lj_trace_err(J, LJ_TRERR_NYIRETL);
    J->baseslot -= (BCReg)cbase;
    J->base -= cbase;
    func += cbase;
  }
  /* Move func + args down. */
  if (LJ_FR2 && J->baseslot == 2)
    J->base[func+1] = TREF_FRAME;
  memmove(&J->base[-1-LJ_FR2], &J->base[func], sizeof(TRef)*(J->maxslot+1+LJ_FR2));
  /* Note: the new TREF_FRAME is now at J->base[-1] (even for slot #0). */
  /* Tailcalls can form a loop, so count towards the loop unroll limit. */
  if (++J->tailcalled > J->loopunroll)
    lj_trace_err(J, LJ_TRERR_LUNROLL);
}

/* Check unroll limits for down-recursion. */
static int check_downrec_unroll(jit_State *J, GCproto *pt)
{
  IRRef ptref;
  for (ptref = J->chain[IR_KGC]; ptref; ptref = IR(ptref)->prev)
    if (ir_kgc(IR(ptref)) == obj2gco(pt)) {
      int count = 0;
      IRRef ref;
      for (ref = J->chain[IR_RETF]; ref; ref = IR(ref)->prev)
        if (IR(ref)->op1 == ptref)
          count++;
      if (count) {
        if (J->pc == J->startpc) {
          if (count + J->tailcalled > J->param[JIT_P_recunroll])
            return 1;
        } else {
          lj_trace_err(J, LJ_TRERR_DOWNREC);
        }
      }
    }
  return 0;
}

static TRef rec_cat(jit_State *J, BCReg baseslot, BCReg topslot);

/* Record return. */
void lj_record_ret(jit_State *J, BCReg rbase, ptrdiff_t gotresults)
{
  TValue *frame = J->L->base - 1;
  ptrdiff_t i;
  BCReg baseadj = 0;
  for (i = 0; i < gotresults; i++)
    (void)getslot(J, rbase+i);  /* Ensure all results have a reference. */
  while (frame_ispcall(frame)) {  /* Immediately resolve pcall() returns. */
    BCReg cbase = (BCReg)frame_delta(frame);
    if (--J->framedepth <= 0)
      lj_trace_err(J, LJ_TRERR_NYIRETL);
    lj_assertJ(J->baseslot > 1+LJ_FR2, "bad baseslot for return");
    gotresults++;
    baseadj += cbase;
    rbase += cbase;
    J->baseslot -= (BCReg)cbase;
    J->base -= cbase;
    J->base[--rbase] = TREF_TRUE;  /* Prepend true to results. */
    frame = frame_prevd(frame);
    J->needsnap = 1;  /* Stop catching on-trace errors. */
  }
  /* Return to lower frame via interpreter for unhandled cases. */
  if (J->framedepth == 0 && J->pt && bc_isret(bc_op(*J->pc)) &&
       (!frame_islua(frame) ||
        (J->parent == 0 && J->exitno == 0 &&
         !bc_isret(bc_op(J->cur.startins))))) {
    /* NYI: specialize to frame type and return directly, not via RET*. */
    for (i = 0; i < (ptrdiff_t)rbase; i++)
      J->base[i] = 0;  /* Purge dead slots. */
    J->maxslot = rbase + (BCReg)gotresults;
    lj_record_stop(J, LJ_TRLINK_RETURN, 0);  /* Return to interpreter. */
    return;
  }
  if (frame_isvarg(frame)) {
    BCReg cbase = (BCReg)frame_delta(frame);
    if (--J->framedepth < 0)  /* NYI: return of vararg func to lower frame. */
      lj_trace_err(J, LJ_TRERR_NYIRETL);
    lj_assertJ(J->baseslot > 1+LJ_FR2, "bad baseslot for return");
    baseadj += cbase;
    rbase += cbase;
    J->baseslot -= (BCReg)cbase;
    J->base -= cbase;
    frame = frame_prevd(frame);
  }
  if (frame_islua(frame)) {  /* Return to Lua frame. */
    BCIns callins = *(frame_pc(frame)-1);
    ptrdiff_t nresults = bc_b(callins) ? (ptrdiff_t)bc_b(callins)-1 :gotresults;
    BCReg cbase = bc_a(callins);
    GCproto *pt = funcproto(frame_func(frame - (cbase+1+LJ_FR2)));
    if ((pt->flags & PROTO_NOJIT))
      lj_trace_err(J, LJ_TRERR_CJITOFF);
    if (J->framedepth == 0 && J->pt && frame == J->L->base - 1) {
      if (!J->cur.root && check_downrec_unroll(J, pt)) {
        J->maxslot = (BCReg)(rbase + gotresults);
        lj_snap_purge(J);
        lj_record_stop(J, LJ_TRLINK_DOWNREC, J->cur.traceno);  /* Down-rec. */
        return;
      }
      lj_snap_add(J);
    }
    for (i = 0; i < nresults; i++)  /* Adjust results. */
      J->base[i-1-LJ_FR2] = i < gotresults ? J->base[rbase+i] : TREF_NIL;
    J->maxslot = cbase+(BCReg)nresults;
    if (J->framedepth > 0) {  /* Return to a frame that is part of the trace. */
      J->framedepth--;
      lj_assertJ(J->baseslot > cbase+1+LJ_FR2, "bad baseslot for return");
      J->baseslot -= cbase+1+LJ_FR2;
      J->base -= cbase+1+LJ_FR2;
    } else if (J->parent == 0 && J->exitno == 0 &&
               !bc_isret(bc_op(J->cur.startins))) {
      /* Return to lower frame would leave the loop in a root trace. */
      lj_trace_err(J, LJ_TRERR_LLEAVE);
    } else if (J->needsnap) {  /* Tailcalled to ff with side-effects. */
      lj_trace_err(J, LJ_TRERR_NYIRETL);  /* No way to insert snapshot here. */
    } else if (1 + pt->framesize >= LJ_MAX_JSLOTS ||
               J->baseslot + J->maxslot >= LJ_MAX_JSLOTS) {
      lj_trace_err(J, LJ_TRERR_STACKOV);
    } else {  /* Return to lower frame. Guard for the target we return to. */
      TRef trpt = lj_ir_kgc(J, obj2gco(pt), IRT_PROTO);
      TRef trpc = lj_ir_kptr(J, (void *)frame_pc(frame));
      emitir(IRTG(IR_RETF, IRT_PGC), trpt, trpc);
      J->retdepth++;
      J->needsnap = 1;
      J->scev.idx = REF_NIL;
      lj_assertJ(J->baseslot == 1+LJ_FR2, "bad baseslot for return");
      /* Shift result slots up and clear the slots of the new frame below. */
      memmove(J->base + cbase, J->base-1-LJ_FR2, sizeof(TRef)*nresults);
      memset(J->base-1-LJ_FR2, 0, sizeof(TRef)*(cbase+1+LJ_FR2));
    }
  } else if (frame_iscont(frame)) {  /* Return to continuation frame. */
    ASMFunction cont = frame_contf(frame);
    BCReg cbase = (BCReg)frame_delta(frame);
    if ((J->framedepth -= 2) < 0)
      lj_trace_err(J, LJ_TRERR_NYIRETL);
    J->baseslot -= (BCReg)cbase;
    J->base -= cbase;
    J->maxslot = cbase-(2<<LJ_FR2);
    if (cont == lj_cont_ra) {
      /* Copy result to destination slot. */
      BCReg dst = bc_a(*(frame_contpc(frame)-1));
      J->base[dst] = gotresults ? J->base[cbase+rbase] : TREF_NIL;
      if (dst >= J->maxslot) {
        J->maxslot = dst+1;
      }
    } else if (cont == lj_cont_nop) {
      /* Nothing to do here. */
    } else if (cont == lj_cont_cat) {
      BCReg bslot = bc_b(*(frame_contpc(frame)-1));
      TRef tr = gotresults ? J->base[cbase+rbase] : TREF_NIL;
      if (bslot != J->maxslot) {  /* Concatenate the remainder. */
        /* Simulate lower frame and result. */
        TValue *b = J->L->base - baseadj, save;
        /* Can't handle MM_concat + CALLT + fast func side-effects. */
        if (J->postproc != LJ_POST_NONE)
          lj_trace_err(J, LJ_TRERR_NYIRETL);
        J->base[J->maxslot] = tr;
        copyTV(J->L, &save, b-(2<<LJ_FR2));
        if (gotresults)
          copyTV(J->L, b-(2<<LJ_FR2), b+rbase);
        else
          setnilV(b-(2<<LJ_FR2));
        J->L->base = b - cbase;
        tr = rec_cat(J, bslot, cbase-(2<<LJ_FR2));
        b = J->L->base + cbase;  /* Undo. */
        J->L->base = b + baseadj;
        copyTV(J->L, b-(2<<LJ_FR2), &save);
      }
      if (tr >= 0xffffff00) {
        lj_err_throw(J->L, -(int32_t)tr);  /* Propagate errors. */
      } else if (tr) {  /* Store final result. */
        BCReg dst = bc_a(*(frame_contpc(frame)-1));
        J->base[dst] = tr;
        if (dst >= J->maxslot) {
          J->maxslot = dst+1;
        }
      }  /* Otherwise continue with another __concat call. */
    } else {
      /* Result type already specialized. */
      lj_assertJ(cont == lj_cont_condf || cont == lj_cont_condt,
                 "bad continuation type");
    }
  } else {
    lj_trace_err(J, LJ_TRERR_NYIRETL);  /* NYI: handle return to C frame. */
  }
  lj_assertJ(J->baseslot >= 1+LJ_FR2, "bad baseslot for return");
}

/* -- Metamethod handling ------------------------------------------------- */

/* Prepare to record call to metamethod. */
static BCReg rec_mm_prep(jit_State *J, ASMFunction cont)
{
  BCReg s, top = cont == lj_cont_cat ? J->maxslot : curr_proto(J->L)->framesize;
#if LJ_FR2
  J->base[top] = lj_ir_k64(J, IR_KNUM, u64ptr(contptr(cont)));
  J->base[top+1] = TREF_CONT;
#else
  J->base[top] = lj_ir_kptr(J, contptr(cont)) | TREF_CONT;
#endif
  J->framedepth++;
  for (s = J->maxslot; s < top; s++)
    J->base[s] = 0;  /* Clear frame gap to avoid resurrecting previous refs. */
  return top+1+LJ_FR2;
}

/* Record metamethod lookup. */
int lj_record_mm_lookup(jit_State *J, RecordIndex *ix, MMS mm)
{
  RecordIndex mix;
  GCtab *mt;
  if (tref_istab(ix->tab)) {
    mt = tabref(tabV(&ix->tabv)->metatable);
    mix.tab = emitir(IRT(IR_FLOAD, IRT_TAB), ix->tab, IRFL_TAB_META);
  } else if (tref_isudata(ix->tab)) {
    int udtype = udataV(&ix->tabv)->udtype;
    mt = tabref(udataV(&ix->tabv)->metatable);
    /* The metatables of special userdata objects are treated as immutable. */
    if (udtype > UDTYPE_IO_FILE) {
      cTValue *mo;
      if (LJ_HASFFI && udtype == UDTYPE_FFI_CLIB) {
        /* Specialize to the C library namespace object. */
        emitir(IRTG(IR_EQ, IRT_PGC), ix->tab, lj_ir_kptr(J, udataV(&ix->tabv)));
      } else {
        /* Specialize to the type of userdata. */
        TRef tr = emitir(IRT(IR_FLOAD, IRT_U8), ix->tab, IRFL_UDATA_UDTYPE);
        emitir(IRTGI(IR_EQ), tr, lj_ir_kint(J, udtype));
      }
  immutable_mt:
      mo = lj_tab_getstr(mt, mmname_str(J2G(J), mm));
      if (!mo || tvisnil(mo))
        return 0;  /* No metamethod. */
      /* Treat metamethod or index table as immutable, too. */
      if (!(tvisfunc(mo) || tvistab(mo)))
        lj_trace_err(J, LJ_TRERR_BADTYPE);
      copyTV(J->L, &ix->mobjv, mo);
      ix->mobj = lj_ir_kgc(J, gcV(mo), tvisfunc(mo) ? IRT_FUNC : IRT_TAB);
      ix->mtv = mt;
      ix->mt = TREF_NIL;  /* Dummy value for comparison semantics. */
      return 1;  /* Got metamethod or index table. */
    }
    mix.tab = emitir(IRT(IR_FLOAD, IRT_TAB), ix->tab, IRFL_UDATA_META);
  } else {
    /* Specialize to base metatable. Must flush mcode in lua_setmetatable(). */
    mt = tabref(basemt_obj(J2G(J), &ix->tabv));
    if (mt == NULL) {
      ix->mt = TREF_NIL;
      return 0;  /* No metamethod. */
    }
    /* The cdata metatable is treated as immutable. */
    if (LJ_HASFFI && tref_iscdata(ix->tab)) goto immutable_mt;
#if LJ_GC64
    /* TODO: fix ARM32 asm_fload(), so we can use this for all archs. */
    ix->mt = mix.tab = lj_ir_ggfload(J, IRT_TAB,
      GG_OFS(g.gcroot[GCROOT_BASEMT+itypemap(&ix->tabv)]));
#else
    ix->mt = mix.tab = lj_ir_ktab(J, mt);
#endif
    goto nocheck;
  }
  ix->mt = mt ? mix.tab : TREF_NIL;
  emitir(IRTG(mt ? IR_NE : IR_EQ, IRT_TAB), mix.tab, lj_ir_knull(J, IRT_TAB));
nocheck:
  if (mt) {
    GCstr *mmstr = mmname_str(J2G(J), mm);
    cTValue *mo = lj_tab_getstr(mt, mmstr);
    if (mo && !tvisnil(mo))
      copyTV(J->L, &ix->mobjv, mo);
    ix->mtv = mt;
    settabV(J->L, &mix.tabv, mt);
    setstrV(J->L, &mix.keyv, mmstr);
    mix.key = lj_ir_kstr(J, mmstr);
    mix.val = 0;
    mix.idxchain = 0;
    ix->mobj = lj_record_idx(J, &mix);
    return !tref_isnil(ix->mobj);  /* 1 if metamethod found, 0 if not. */
  }
  return 0;  /* No metamethod. */
}

/* Record call to arithmetic metamethod. */
static TRef rec_mm_arith(jit_State *J, RecordIndex *ix, MMS mm)
{
  /* Set up metamethod call first to save ix->tab and ix->tabv. */
  BCReg func = rec_mm_prep(J, mm == MM_concat ? lj_cont_cat : lj_cont_ra);
  TRef *base = J->base + func;
  TValue *basev = J->L->base + func;
  base[1+LJ_FR2] = ix->tab; base[2+LJ_FR2] = ix->key;
  copyTV(J->L, basev+1+LJ_FR2, &ix->tabv);
  copyTV(J->L, basev+2+LJ_FR2, &ix->keyv);
  if (!lj_record_mm_lookup(J, ix, mm)) {  /* Lookup mm on 1st operand. */
    if (mm != MM_unm) {
      ix->tab = ix->key;
      copyTV(J->L, &ix->tabv, &ix->keyv);
      if (lj_record_mm_lookup(J, ix, mm))  /* Lookup mm on 2nd operand. */
        goto ok;
    }
    lj_trace_err(J, LJ_TRERR_NOMM);
  }
ok:
  base[0] = ix->mobj;
#if LJ_FR2
  base[1] = 0;
#endif
  copyTV(J->L, basev+0, &ix->mobjv);
  lj_record_call(J, func, 2);
  return 0;  /* No result yet. */
}

/* Record call to __len metamethod. */
static TRef rec_mm_len(jit_State *J, TRef tr, TValue *tv)
{
  RecordIndex ix;
  ix.tab = tr;
  copyTV(J->L, &ix.tabv, tv);
  if (lj_record_mm_lookup(J, &ix, MM_len)) {
    BCReg func = rec_mm_prep(J, lj_cont_ra);
    TRef *base = J->base + func;
    TValue *basev = J->L->base + func;
    base[0] = ix.mobj; copyTV(J->L, basev+0, &ix.mobjv);
    base += LJ_FR2;
    basev += LJ_FR2;
    base[1] = tr; copyTV(J->L, basev+1, tv);
#if LJ_52
    base[2] = tr; copyTV(J->L, basev+2, tv);
#else
    base[2] = TREF_NIL; setnilV(basev+2);
#endif
    lj_record_call(J, func, 2);
  } else {
    if (LJ_52 && tref_istab(tr))
      return lj_ir_call(J, IRCALL_lj_tab_len, tr);
    lj_trace_err(J, LJ_TRERR_NOMM);
  }
  return 0;  /* No result yet. */
}

/* Call a comparison metamethod. */
static void rec_mm_callcomp(jit_State *J, RecordIndex *ix, int op)
{
  BCReg func = rec_mm_prep(J, (op&1) ? lj_cont_condf : lj_cont_condt);
  TRef *base = J->base + func + LJ_FR2;
  TValue *tv = J->L->base + func + LJ_FR2;
  base[-LJ_FR2] = ix->mobj; base[1] = ix->val; base[2] = ix->key;
  copyTV(J->L, tv-LJ_FR2, &ix->mobjv);
  copyTV(J->L, tv+1, &ix->valv);
  copyTV(J->L, tv+2, &ix->keyv);
  lj_record_call(J, func, 2);
}

/* Record call to equality comparison metamethod (for tab and udata only). */
static void rec_mm_equal(jit_State *J, RecordIndex *ix, int op)
{
  ix->tab = ix->val;
  copyTV(J->L, &ix->tabv, &ix->valv);
  if (lj_record_mm_lookup(J, ix, MM_eq)) {  /* Lookup mm on 1st operand. */
    cTValue *bv;
    TRef mo1 = ix->mobj;
    TValue mo1v;
    copyTV(J->L, &mo1v, &ix->mobjv);
    /* Avoid the 2nd lookup and the objcmp if the metatables are equal. */
    bv = &ix->keyv;
    if (tvistab(bv) && tabref(tabV(bv)->metatable) == ix->mtv) {
      TRef mt2 = emitir(IRT(IR_FLOAD, IRT_TAB), ix->key, IRFL_TAB_META);
      emitir(IRTG(IR_EQ, IRT_TAB), mt2, ix->mt);
    } else if (tvisudata(bv) && tabref(udataV(bv)->metatable) == ix->mtv) {
      TRef mt2 = emitir(IRT(IR_FLOAD, IRT_TAB), ix->key, IRFL_UDATA_META);
      emitir(IRTG(IR_EQ, IRT_TAB), mt2, ix->mt);
    } else {  /* Lookup metamethod on 2nd operand and compare both. */
      ix->tab = ix->key;
      copyTV(J->L, &ix->tabv, bv);
      if (!lj_record_mm_lookup(J, ix, MM_eq) ||
          lj_record_objcmp(J, mo1, ix->mobj, &mo1v, &ix->mobjv))
        return;
    }
    rec_mm_callcomp(J, ix, op);
  }
}

/* Record call to ordered comparison metamethods (for arbitrary objects). */
static void rec_mm_comp(jit_State *J, RecordIndex *ix, int op)
{
  ix->tab = ix->val;
  copyTV(J->L, &ix->tabv, &ix->valv);
  while (1) {
    MMS mm = (op & 2) ? MM_le : MM_lt;  /* Try __le + __lt or only __lt. */
#if LJ_52
    if (!lj_record_mm_lookup(J, ix, mm)) {  /* Lookup mm on 1st operand. */
      ix->tab = ix->key;
      copyTV(J->L, &ix->tabv, &ix->keyv);
      if (!lj_record_mm_lookup(J, ix, mm))  /* Lookup mm on 2nd operand. */
        goto nomatch;
    }
    rec_mm_callcomp(J, ix, op);
    return;
#else
    if (lj_record_mm_lookup(J, ix, mm)) {  /* Lookup mm on 1st operand. */
      cTValue *bv;
      TRef mo1 = ix->mobj;
      TValue mo1v;
      copyTV(J->L, &mo1v, &ix->mobjv);
      /* Avoid the 2nd lookup and the objcmp if the metatables are equal. */
      bv = &ix->keyv;
      if (tvistab(bv) && tabref(tabV(bv)->metatable) == ix->mtv) {
        TRef mt2 = emitir(IRT(IR_FLOAD, IRT_TAB), ix->key, IRFL_TAB_META);
        emitir(IRTG(IR_EQ, IRT_TAB), mt2, ix->mt);
      } else if (tvisudata(bv) && tabref(udataV(bv)->metatable) == ix->mtv) {
        TRef mt2 = emitir(IRT(IR_FLOAD, IRT_TAB), ix->key, IRFL_UDATA_META);
        emitir(IRTG(IR_EQ, IRT_TAB), mt2, ix->mt);
      } else {  /* Lookup metamethod on 2nd operand and compare both. */
        ix->tab = ix->key;
        copyTV(J->L, &ix->tabv, bv);
        if (!lj_record_mm_lookup(J, ix, mm) ||
            lj_record_objcmp(J, mo1, ix->mobj, &mo1v, &ix->mobjv))
          goto nomatch;
      }
      rec_mm_callcomp(J, ix, op);
      return;
    }
#endif
  nomatch:
    /* Lookup failed. Retry with  __lt and swapped operands. */
    if (!(op & 2)) break;  /* Already at __lt. Interpreter will throw. */
    ix->tab = ix->key; ix->key = ix->val; ix->val = ix->tab;
    copyTV(J->L, &ix->tabv, &ix->keyv);
    copyTV(J->L, &ix->keyv, &ix->valv);
    copyTV(J->L, &ix->valv, &ix->tabv);
    op ^= 3;
  }
}

#if LJ_HASFFI
/* Setup call to cdata comparison metamethod. */
static void rec_mm_comp_cdata(jit_State *J, RecordIndex *ix, int op, MMS mm)
{
  lj_snap_add(J);
  if (tref_iscdata(ix->val)) {
    ix->tab = ix->val;
    copyTV(J->L, &ix->tabv, &ix->valv);
  } else {
    lj_assertJ(tref_iscdata(ix->key), "cdata expected");
    ix->tab = ix->key;
    copyTV(J->L, &ix->tabv, &ix->keyv);
  }
  lj_record_mm_lookup(J, ix, mm);
  rec_mm_callcomp(J, ix, op);
}
#endif

/* -- Indexed access ------------------------------------------------------ */

#ifdef LUAJIT_ENABLE_TABLE_BUMP
/* Bump table allocations in bytecode when they grow during recording. */
static void rec_idx_bump(jit_State *J, RecordIndex *ix)
{
  RBCHashEntry *rbc = &J->rbchash[(ix->tab & (RBCHASH_SLOTS-1))];
  if (tref_ref(ix->tab) == rbc->ref) {
    const BCIns *pc = mref(rbc->pc, const BCIns);
    GCtab *tb = tabV(&ix->tabv);
    uint32_t nhbits;
    IRIns *ir;
    if (!tvisnil(&ix->keyv))
      (void)lj_tab_set(J->L, tb, &ix->keyv);  /* Grow table right now. */
    nhbits = tb->hmask > 0 ? lj_fls(tb->hmask)+1 : 0;
    ir = IR(tref_ref(ix->tab));
    if (ir->o == IR_TNEW) {
      uint32_t ah = bc_d(*pc);
      uint32_t asize = ah & 0x7ff, hbits = ah >> 11;
      if (nhbits > hbits) hbits = nhbits;
      if (tb->asize > asize) {
        asize = tb->asize <= 0x7ff ? tb->asize : 0x7ff;
      }
      if ((asize | (hbits<<11)) != ah) {  /* Has the size changed? */
        /* Patch bytecode, but continue recording (for more patching). */
        setbc_d(pc, (asize | (hbits<<11)));
        /* Patching TNEW operands is only safe if the trace is aborted. */
        ir->op1 = asize; ir->op2 = hbits;
        J->retryrec = 1;  /* Abort the trace at the end of recording. */
      }
    } else if (ir->o == IR_TDUP) {
      GCtab *tpl = gco2tab(proto_kgc(&gcref(rbc->pt)->pt, ~(ptrdiff_t)bc_d(*pc)));
      /* Grow template table, but preserve keys with nil values. */
      if ((tb->asize > tpl->asize && (1u << nhbits)-1 == tpl->hmask) ||
          (tb->asize == tpl->asize && (1u << nhbits)-1 > tpl->hmask)) {
        Node *node = noderef(tpl->node);
        uint32_t i, hmask = tpl->hmask, asize;
        TValue *array;
        for (i = 0; i <= hmask; i++) {
          if (!tvisnil(&node[i].key) && tvisnil(&node[i].val))
            settabV(J->L, &node[i].val, tpl);
        }
        if (!tvisnil(&ix->keyv) && tref_isk(ix->key)) {
          TValue *o = lj_tab_set(J->L, tpl, &ix->keyv);
          if (tvisnil(o)) settabV(J->L, o, tpl);
        }
        lj_tab_resize(J->L, tpl, tb->asize, nhbits);
        node = noderef(tpl->node);
        hmask = tpl->hmask;
        for (i = 0; i <= hmask; i++) {
          /* This is safe, since template tables only hold immutable values. */
          if (tvistab(&node[i].val))
            setnilV(&node[i].val);
        }
        /* The shape of the table may have changed. Clean up array part, too. */
        asize = tpl->asize;
        array = tvref(tpl->array);
        for (i = 0; i < asize; i++) {
          if (tvistab(&array[i]))
            setnilV(&array[i]);
        }
        J->retryrec = 1;  /* Abort the trace at the end of recording. */
      }
    }
  }
}
#endif

/* Record bounds-check. */
static void rec_idx_abc(jit_State *J, TRef asizeref, TRef ikey, uint32_t asize)
{
  /* Try to emit invariant bounds checks. */
  if ((J->flags & (JIT_F_OPT_LOOP|JIT_F_OPT_ABC)) ==
      (JIT_F_OPT_LOOP|JIT_F_OPT_ABC)) {
    IRRef ref = tref_ref(ikey);
    IRIns *ir = IR(ref);
    int32_t ofs = 0;
    IRRef ofsref = 0;
    /* Handle constant offsets. */
    if (ir->o == IR_ADD && irref_isk(ir->op2)) {
      ofsref = ir->op2;
      ofs = IR(ofsref)->i;
      ref = ir->op1;
      ir = IR(ref);
    }
    /* Got scalar evolution analysis results for this reference? */
    if (ref == J->scev.idx) {
      int32_t stop;
      lj_assertJ(irt_isint(J->scev.t) && ir->o == IR_SLOAD,
                 "only int SCEV supported");
      stop = numberVint(&(J->L->base - J->baseslot)[ir->op1 + FORL_STOP]);
      /* Runtime value for stop of loop is within bounds? */
      if ((uint64_t)stop + ofs < (uint64_t)asize) {
        /* Emit invariant bounds check for stop. */
        uint32_t abc = IRTG(IR_ABC, tref_isk(asizeref) ? IRT_U32 : IRT_P32);
        emitir(abc, asizeref, ofs == 0 ? J->scev.stop :
               emitir(IRTI(IR_ADD), J->scev.stop, ofsref));
        /* Emit invariant bounds check for start, if not const or negative. */
        if (!(J->scev.dir && J->scev.start &&
              (int64_t)IR(J->scev.start)->i + ofs >= 0))
          emitir(abc, asizeref, ikey);
        return;
      }
    }
  }
  emitir(IRTGI(IR_ABC), asizeref, ikey);  /* Emit regular bounds check. */
}

/* Record indexed key lookup. */
static TRef rec_idx_key(jit_State *J, RecordIndex *ix, IRRef *rbref,
                        IRType1 *rbguard)
{
  TRef key;
  GCtab *t = tabV(&ix->tabv);
  ix->oldv = lj_tab_get(J->L, t, &ix->keyv);  /* Lookup previous value. */
  *rbref = 0;
  rbguard->irt = 0;

  /* Integer keys are looked up in the array part first. */
  key = ix->key;
  if (tref_isnumber(key)) {
    int32_t k = numberVint(&ix->keyv);
    if (!tvisint(&ix->keyv) && numV(&ix->keyv) != (lua_Number)k)
      k = LJ_MAX_ASIZE;
    if ((MSize)k < LJ_MAX_ASIZE) {  /* Potential array key? */
      TRef ikey = lj_opt_narrow_index(J, key);
      TRef asizeref = emitir(IRTI(IR_FLOAD), ix->tab, IRFL_TAB_ASIZE);
      if ((MSize)k < t->asize) {  /* Currently an array key? */
        TRef arrayref;
        rec_idx_abc(J, asizeref, ikey, t->asize);
        arrayref = emitir(IRT(IR_FLOAD, IRT_PGC), ix->tab, IRFL_TAB_ARRAY);
        return emitir(IRT(IR_AREF, IRT_PGC), arrayref, ikey);
      } else {  /* Currently not in array (may be an array extension)? */
        emitir(IRTGI(IR_ULE), asizeref, ikey);  /* Inv. bounds check. */
        if (k == 0 && tref_isk(key))
          key = lj_ir_knum_zero(J);  /* Canonicalize 0 or +-0.0 to +0.0. */
        /* And continue with the hash lookup. */
      }
    } else if (!tref_isk(key)) {
      /* We can rule out const numbers which failed the integerness test
      ** above. But all other numbers are potential array keys.
      */
      if (t->asize == 0) {  /* True sparse tables have an empty array part. */
        /* Guard that the array part stays empty. */
        TRef tmp = emitir(IRTI(IR_FLOAD), ix->tab, IRFL_TAB_ASIZE);
        emitir(IRTGI(IR_EQ), tmp, lj_ir_kint(J, 0));
      } else {
        lj_trace_err(J, LJ_TRERR_NYITMIX);
      }
    }
  }

  /* Otherwise the key is located in the hash part. */
  if (t->hmask == 0) {  /* Shortcut for empty hash part. */
    /* Guard that the hash part stays empty. */
    TRef tmp = emitir(IRTI(IR_FLOAD), ix->tab, IRFL_TAB_HMASK);
    emitir(IRTGI(IR_EQ), tmp, lj_ir_kint(J, 0));
    return lj_ir_kkptr(J, niltvg(J2G(J)));
  }
  if (tref_isinteger(key))  /* Hash keys are based on numbers, not ints. */
    key = emitir(IRTN(IR_CONV), key, IRCONV_NUM_INT);
  if (tref_isk(key)) {
    /* Optimize lookup of constant hash keys. */
    GCSize hslot = (GCSize)((char *)ix->oldv-(char *)&noderef(t->node)[0].val);
    if (hslot <= t->hmask*(GCSize)sizeof(Node) &&
        hslot <= 65535*(GCSize)sizeof(Node)) {
      TRef node, kslot, hm;
      *rbref = J->cur.nins;  /* Mark possible rollback point. */
      *rbguard = J->guardemit;
      hm = emitir(IRTI(IR_FLOAD), ix->tab, IRFL_TAB_HMASK);
      emitir(IRTGI(IR_EQ), hm, lj_ir_kint(J, (int32_t)t->hmask));
      node = emitir(IRT(IR_FLOAD, IRT_PGC), ix->tab, IRFL_TAB_NODE);
      kslot = lj_ir_kslot(J, key, (IRRef)(hslot / sizeof(Node)));
      return emitir(IRTG(IR_HREFK, IRT_PGC), node, kslot);
    }
  }
  /* Fall back to a regular hash lookup. */
  return emitir(IRT(IR_HREF, IRT_PGC), ix->tab, key);
}

/* Determine whether a key is NOT one of the fast metamethod names. */
static int nommstr(jit_State *J, TRef key)
{
  if (tref_isstr(key)) {
    if (tref_isk(key)) {
      GCstr *str = ir_kstr(IR(tref_ref(key)));
      uint32_t mm;
      for (mm = 0; mm <= MM_FAST; mm++)
        if (mmname_str(J2G(J), mm) == str)
          return 0;  /* MUST be one the fast metamethod names. */
    } else {
      return 0;  /* Variable string key MAY be a metamethod name. */
    }
  }
  return 1;  /* CANNOT be a metamethod name. */
}

/* Record indexed load/store. */
TRef lj_record_idx(jit_State *J, RecordIndex *ix)
{
  TRef xref;
  IROp xrefop, loadop;
  IRRef rbref;
  IRType1 rbguard;
  cTValue *oldv;

  while (!tref_istab(ix->tab)) { /* Handle non-table lookup. */
    /* Never call raw lj_record_idx() on non-table. */
    lj_assertJ(ix->idxchain != 0, "bad usage");
    if (!lj_record_mm_lookup(J, ix, ix->val ? MM_newindex : MM_index))
      lj_trace_err(J, LJ_TRERR_NOMM);
  handlemm:
    if (tref_isfunc(ix->mobj)) {  /* Handle metamethod call. */
      BCReg func = rec_mm_prep(J, ix->val ? lj_cont_nop : lj_cont_ra);
      TRef *base = J->base + func + LJ_FR2;
      TValue *tv = J->L->base + func + LJ_FR2;
      base[-LJ_FR2] = ix->mobj; base[1] = ix->tab; base[2] = ix->key;
      setfuncV(J->L, tv-LJ_FR2, funcV(&ix->mobjv));
      copyTV(J->L, tv+1, &ix->tabv);
      copyTV(J->L, tv+2, &ix->keyv);
      if (ix->val) {
        base[3] = ix->val;
        copyTV(J->L, tv+3, &ix->valv);
        lj_record_call(J, func, 3);  /* mobj(tab, key, val) */
        return 0;
      } else {
        lj_record_call(J, func, 2);  /* res = mobj(tab, key) */
        return 0;  /* No result yet. */
      }
    }
    /* Otherwise retry lookup with metaobject. */
    ix->tab = ix->mobj;
    copyTV(J->L, &ix->tabv, &ix->mobjv);
    if (--ix->idxchain == 0)
      lj_trace_err(J, LJ_TRERR_IDXLOOP);
  }

  /* First catch nil and NaN keys for tables. */
  if (tvisnil(&ix->keyv) || (tvisnum(&ix->keyv) && tvisnan(&ix->keyv))) {
    if (ix->val)  /* Better fail early. */
      lj_trace_err(J, LJ_TRERR_STORENN);
    if (tref_isk(ix->key)) {
      if (ix->idxchain && lj_record_mm_lookup(J, ix, MM_index))
        goto handlemm;
      return TREF_NIL;
    }
  }

  /* Record the key lookup. */
  xref = rec_idx_key(J, ix, &rbref, &rbguard);
  xrefop = IR(tref_ref(xref))->o;
  loadop = xrefop == IR_AREF ? IR_ALOAD : IR_HLOAD;
  /* The lj_meta_tset() inconsistency is gone, but better play safe. */
  oldv = xrefop == IR_KKPTR ? (cTValue *)ir_kptr(IR(tref_ref(xref))) : ix->oldv;

  if (ix->val == 0) {  /* Indexed load */
    IRType t = itype2irt(oldv);
    TRef res;
    if (oldv == niltvg(J2G(J))) {
      emitir(IRTG(IR_EQ, IRT_PGC), xref, lj_ir_kkptr(J, niltvg(J2G(J))));
      res = TREF_NIL;
    } else {
      res = emitir(IRTG(loadop, t), xref, 0);
    }
    if (tref_ref(res) < rbref) {  /* HREFK + load forwarded? */
      lj_ir_rollback(J, rbref);  /* Rollback to eliminate hmask guard. */
      J->guardemit = rbguard;
    }
    if (t == IRT_NIL && ix->idxchain && lj_record_mm_lookup(J, ix, MM_index))
      goto handlemm;
    if (irtype_ispri(t)) res = TREF_PRI(t);  /* Canonicalize primitives. */
    return res;
  } else {  /* Indexed store. */
    GCtab *mt = tabref(tabV(&ix->tabv)->metatable);
    int keybarrier = tref_isgcv(ix->key) && !tref_isnil(ix->val);
    if (tref_ref(xref) < rbref) {  /* HREFK forwarded? */
      lj_ir_rollback(J, rbref);  /* Rollback to eliminate hmask guard. */
      J->guardemit = rbguard;
    }
    if (tvisnil(oldv)) {  /* Previous value was nil? */
      /* Need to duplicate the hasmm check for the early guards. */
      int hasmm = 0;
      if (ix->idxchain && mt) {
        cTValue *mo = lj_tab_getstr(mt, mmname_str(J2G(J), MM_newindex));
        hasmm = mo && !tvisnil(mo);
      }
      if (hasmm)
        emitir(IRTG(loadop, IRT_NIL), xref, 0);  /* Guard for nil value. */
      else if (xrefop == IR_HREF)
        emitir(IRTG(oldv == niltvg(J2G(J)) ? IR_EQ : IR_NE, IRT_PGC),
               xref, lj_ir_kkptr(J, niltvg(J2G(J))));
      if (ix->idxchain && lj_record_mm_lookup(J, ix, MM_newindex)) {
        lj_assertJ(hasmm, "inconsistent metamethod handling");
        goto handlemm;
      }
      lj_assertJ(!hasmm, "inconsistent metamethod handling");
      if (oldv == niltvg(J2G(J))) {  /* Need to insert a new key. */
        TRef key = ix->key;
        if (tref_isinteger(key)) {  /* NEWREF needs a TValue as a key. */
          key = emitir(IRTN(IR_CONV), key, IRCONV_NUM_INT);
        } else if (tref_isnum(key)) {
          if (tref_isk(key)) {
            if (tvismzero(&ix->keyv))
              key = lj_ir_knum_zero(J);  /* Canonicalize -0.0 to +0.0. */
          } else {
            emitir(IRTG(IR_EQ, IRT_NUM), key, key);  /* Check for !NaN. */
          }
        }
        xref = emitir(IRT(IR_NEWREF, IRT_PGC), ix->tab, key);
        keybarrier = 0;  /* NEWREF already takes care of the key barrier. */
#ifdef LUAJIT_ENABLE_TABLE_BUMP
        if ((J->flags & JIT_F_OPT_SINK))  /* Avoid a separate flag. */
          rec_idx_bump(J, ix);
#endif
      }
    } else if (!lj_opt_fwd_wasnonnil(J, loadop, tref_ref(xref))) {
      /* Cannot derive that the previous value was non-nil, must do checks. */
      if (xrefop == IR_HREF)  /* Guard against store to niltv. */
        emitir(IRTG(IR_NE, IRT_PGC), xref, lj_ir_kkptr(J, niltvg(J2G(J))));
      if (ix->idxchain) {  /* Metamethod lookup required? */
        /* A check for NULL metatable is cheaper (hoistable) than a load. */
        if (!mt) {
          TRef mtref = emitir(IRT(IR_FLOAD, IRT_TAB), ix->tab, IRFL_TAB_META);
          emitir(IRTG(IR_EQ, IRT_TAB), mtref, lj_ir_knull(J, IRT_TAB));
        } else {
          IRType t = itype2irt(oldv);
          emitir(IRTG(loadop, t), xref, 0);  /* Guard for non-nil value. */
        }
      }
    } else {
      keybarrier = 0;  /* Previous non-nil value kept the key alive. */
    }
    /* Convert int to number before storing. */
    if (!LJ_DUALNUM && tref_isinteger(ix->val))
      ix->val = emitir(IRTN(IR_CONV), ix->val, IRCONV_NUM_INT);
    emitir(IRT(loadop+IRDELTA_L2S, tref_type(ix->val)), xref, ix->val);
    if (keybarrier || tref_isgcv(ix->val))
      emitir(IRT(IR_TBAR, IRT_NIL), ix->tab, 0);
    /* Invalidate neg. metamethod cache for stores with certain string keys. */
    if (!nommstr(J, ix->key)) {
      TRef fref = emitir(IRT(IR_FREF, IRT_PGC), ix->tab, IRFL_TAB_NOMM);
      emitir(IRT(IR_FSTORE, IRT_U8), fref, lj_ir_kint(J, 0));
    }
    J->needsnap = 1;
    return 0;
  }
}

static void rec_tsetm(jit_State *J, BCReg ra, BCReg rn, int32_t i)
{
  RecordIndex ix;
  cTValue *basev = J->L->base;
  GCtab *t = tabV(&basev[ra-1]);
  settabV(J->L, &ix.tabv, t);
  ix.tab = getslot(J, ra-1);
  ix.idxchain = 0;
#ifdef LUAJIT_ENABLE_TABLE_BUMP
  if ((J->flags & JIT_F_OPT_SINK)) {
    if (t->asize < i+rn-ra)
      lj_tab_reasize(J->L, t, i+rn-ra);
    setnilV(&ix.keyv);
    rec_idx_bump(J, &ix);
  }
#endif
  for (; ra < rn; i++, ra++) {
    setintV(&ix.keyv, i);
    ix.key = lj_ir_kint(J, i);
    copyTV(J->L, &ix.valv, &basev[ra]);
    ix.val = getslot(J, ra);
    lj_record_idx(J, &ix);
  }
}

/* -- Upvalue access ------------------------------------------------------ */

/* Check whether upvalue is immutable and ok to constify. */
static int rec_upvalue_constify(jit_State *J, GCupval *uvp)
{
  if (uvp->immutable) {
    cTValue *o = uvval(uvp);
    /* Don't constify objects that may retain large amounts of memory. */
#if LJ_HASFFI
    if (tviscdata(o)) {
      GCcdata *cd = cdataV(o);
      if (!cdataisv(cd) && !(cd->marked & LJ_GC_CDATA_FIN)) {
        CType *ct = ctype_raw(ctype_ctsG(J2G(J)), cd->ctypeid);
        if (!ctype_hassize(ct->info) || ct->size <= 16)
          return 1;
      }
      return 0;
    }
#else
    UNUSED(J);
#endif
    if (!(tvistab(o) || tvisudata(o) || tvisthread(o)))
      return 1;
  }
  return 0;
}

/* Record upvalue load/store. */
static TRef rec_upvalue(jit_State *J, uint32_t uv, TRef val)
{
  GCupval *uvp = &gcref(J->fn->l.uvptr[uv])->uv;
  TRef fn = getcurrf(J);
  IRRef uref;
  int needbarrier = 0;
  if (rec_upvalue_constify(J, uvp)) {  /* Try to constify immutable upvalue. */
    TRef tr, kfunc;
    lj_assertJ(val == 0, "bad usage");
    if (!tref_isk(fn)) {  /* Late specialization of current function. */
      if (J->pt->flags >= PROTO_CLC_POLY)
        goto noconstify;
      kfunc = lj_ir_kfunc(J, J->fn);
      emitir(IRTG(IR_EQ, IRT_FUNC), fn, kfunc);
#if LJ_FR2
      J->base[-2] = kfunc;
#else
      J->base[-1] = kfunc | TREF_FRAME;
#endif
      fn = kfunc;
    }
    tr = lj_record_constify(J, uvval(uvp));
    if (tr)
      return tr;
  }
noconstify:
  /* Note: this effectively limits LJ_MAX_UPVAL to 127. */
  uv = (uv << 8) | (hashrot(uvp->dhash, uvp->dhash + HASH_BIAS) & 0xff);
  if (!uvp->closed) {
    uref = tref_ref(emitir(IRTG(IR_UREFO, IRT_PGC), fn, uv));
    /* In current stack? */
    if (uvval(uvp) >= tvref(J->L->stack) &&
        uvval(uvp) < tvref(J->L->maxstack)) {
      int32_t slot = (int32_t)(uvval(uvp) - (J->L->base - J->baseslot));
      if (slot >= 0) {  /* Aliases an SSA slot? */
        emitir(IRTG(IR_EQ, IRT_PGC),
               REF_BASE,
               emitir(IRT(IR_ADD, IRT_PGC), uref,
                      lj_ir_kint(J, (slot - 1 - LJ_FR2) * -8)));
        slot -= (int32_t)J->baseslot;  /* Note: slot number may be negative! */
        if (val == 0) {
          return getslot(J, slot);
        } else {
          J->base[slot] = val;
          if (slot >= (int32_t)J->maxslot) J->maxslot = (BCReg)(slot+1);
          return 0;
        }
      }
    }
    emitir(IRTG(IR_UGT, IRT_PGC),
           emitir(IRT(IR_SUB, IRT_PGC), uref, REF_BASE),
           lj_ir_kint(J, (J->baseslot + J->maxslot) * 8));
  } else {
    needbarrier = 1;
    uref = tref_ref(emitir(IRTG(IR_UREFC, IRT_PGC), fn, uv));
  }
  if (val == 0) {  /* Upvalue load */
    IRType t = itype2irt(uvval(uvp));
    TRef res = emitir(IRTG(IR_ULOAD, t), uref, 0);
    if (irtype_ispri(t)) res = TREF_PRI(t);  /* Canonicalize primitive refs. */
    return res;
  } else {  /* Upvalue store. */
    /* Convert int to number before storing. */
    if (!LJ_DUALNUM && tref_isinteger(val))
      val = emitir(IRTN(IR_CONV), val, IRCONV_NUM_INT);
    emitir(IRT(IR_USTORE, tref_type(val)), uref, val);
    if (needbarrier && tref_isgcv(val))
      emitir(IRT(IR_OBAR, IRT_NIL), uref, val);
    J->needsnap = 1;
    return 0;
  }
}

/* -- Record calls to Lua functions --------------------------------------- */

/* Check unroll limits for calls. */
static void check_call_unroll(jit_State *J, TraceNo lnk)
{
  cTValue *frame = J->L->base - 1;
  void *pc = mref(frame_func(frame)->l.pc, void);
  int32_t depth = J->framedepth;
  int32_t count = 0;
  if ((J->pt->flags & PROTO_VARARG)) depth--;  /* Vararg frame still missing. */
  for (; depth > 0; depth--) {  /* Count frames with same prototype. */
    if (frame_iscont(frame)) depth--;
    frame = frame_prev(frame);
    if (mref(frame_func(frame)->l.pc, void) == pc)
      count++;
  }
  if (J->pc == J->startpc) {
    if (count + J->tailcalled > J->param[JIT_P_recunroll]) {
      J->pc++;
      if (J->framedepth + J->retdepth == 0)
        lj_record_stop(J, LJ_TRLINK_TAILREC, J->cur.traceno);  /* Tail-rec. */
      else
        lj_record_stop(J, LJ_TRLINK_UPREC, J->cur.traceno);  /* Up-recursion. */
    }
  } else {
    if (count > J->param[JIT_P_callunroll]) {
      if (lnk) {  /* Possible tail- or up-recursion. */
        lj_trace_flush(J, lnk);  /* Flush trace that only returns. */
        /* Set a small, pseudo-random hotcount for a quick retry of JFUNC*. */
        hotcount_set(J2GG(J), J->pc+1, LJ_PRNG_BITS(J, 4));
      }
      lj_trace_err(J, LJ_TRERR_CUNROLL);
    }
  }
}

/* Record Lua function setup. */
static void rec_func_setup(jit_State *J)
{
  GCproto *pt = J->pt;
  BCReg s, numparams = pt->numparams;
  if ((pt->flags & PROTO_NOJIT))
    lj_trace_err(J, LJ_TRERR_CJITOFF);
  if (J->baseslot + pt->framesize >= LJ_MAX_JSLOTS)
    lj_trace_err(J, LJ_TRERR_STACKOV);
  /* Fill up missing parameters with nil. */
  for (s = J->maxslot; s < numparams; s++)
    J->base[s] = TREF_NIL;
  /* The remaining slots should never be read before they are written. */
  J->maxslot = numparams;
}

/* Record Lua vararg function setup. */
static void rec_func_vararg(jit_State *J)
{
  GCproto *pt = J->pt;
  BCReg s, fixargs, vframe = J->maxslot+1+LJ_FR2;
  lj_assertJ((pt->flags & PROTO_VARARG), "FUNCV in non-vararg function");
  if (J->baseslot + vframe + pt->framesize >= LJ_MAX_JSLOTS)
    lj_trace_err(J, LJ_TRERR_STACKOV);
  J->base[vframe-1-LJ_FR2] = J->base[-1-LJ_FR2];  /* Copy function up. */
#if LJ_FR2
  J->base[vframe-1] = TREF_FRAME;
#endif
  /* Copy fixarg slots up and set their original slots to nil. */
  fixargs = pt->numparams < J->maxslot ? pt->numparams : J->maxslot;
  for (s = 0; s < fixargs; s++) {
    J->base[vframe+s] = J->base[s];
    J->base[s] = TREF_NIL;
  }
  J->maxslot = fixargs;
  J->framedepth++;
  J->base += vframe;
  J->baseslot += vframe;
}

/* Record entry to a Lua function. */
static void rec_func_lua(jit_State *J)
{
  rec_func_setup(J);
  check_call_unroll(J, 0);
}

/* Record entry to an already compiled function. */
static void rec_func_jit(jit_State *J, TraceNo lnk)
{
  GCtrace *T;
  rec_func_setup(J);
  T = traceref(J, lnk);
  if (T->linktype == LJ_TRLINK_RETURN) {  /* Trace returns to interpreter? */
    check_call_unroll(J, lnk);
    /* Temporarily unpatch JFUNC* to continue recording across function. */
    J->patchins = *J->pc;
    J->patchpc = (BCIns *)J->pc;
    *J->patchpc = T->startins;
    return;
  }
  J->instunroll = 0;  /* Cannot continue across a compiled function. */
  if (J->pc == J->startpc && J->framedepth + J->retdepth == 0)
    lj_record_stop(J, LJ_TRLINK_TAILREC, J->cur.traceno);  /* Extra tail-rec. */
  else
    lj_record_stop(J, LJ_TRLINK_ROOT, lnk);  /* Link to the function. */
}

/* -- Vararg handling ----------------------------------------------------- */

/* Detect y = select(x, ...) idiom. */
static int select_detect(jit_State *J)
{
  BCIns ins = J->pc[1];
  if (bc_op(ins) == BC_CALLM && bc_b(ins) == 2 && bc_c(ins) == 1) {
    cTValue *func = &J->L->base[bc_a(ins)];
    if (tvisfunc(func) && funcV(func)->c.ffid == FF_select) {
      TRef kfunc = lj_ir_kfunc(J, funcV(func));
      emitir(IRTG(IR_EQ, IRT_FUNC), getslot(J, bc_a(ins)), kfunc);
      return 1;
    }
  }
  return 0;
}

/* Record vararg instruction. */
static void rec_varg(jit_State *J, BCReg dst, ptrdiff_t nresults)
{
  int32_t numparams = J->pt->numparams;
  ptrdiff_t nvararg = frame_delta(J->L->base-1) - numparams - 1 - LJ_FR2;
  lj_assertJ(frame_isvarg(J->L->base-1), "VARG in non-vararg frame");
  if (LJ_FR2 && dst > J->maxslot)
    J->base[dst-1] = 0;  /* Prevent resurrection of unrelated slot. */
  if (J->framedepth > 0) {  /* Simple case: varargs defined on-trace. */
    ptrdiff_t i;
    if (nvararg < 0) nvararg = 0;
    if (nresults != 1) {
      if (nresults == -1) nresults = nvararg;
      J->maxslot = dst + (BCReg)nresults;
    } else if (dst >= J->maxslot) {
      J->maxslot = dst + 1;
    }
    if (J->baseslot + J->maxslot >= LJ_MAX_JSLOTS)
      lj_trace_err(J, LJ_TRERR_STACKOV);
    for (i = 0; i < nresults; i++)
      J->base[dst+i] = i < nvararg ? getslot(J, i - nvararg - 1 - LJ_FR2) : TREF_NIL;
  } else {  /* Unknown number of varargs passed to trace. */
    TRef fr = emitir(IRTI(IR_SLOAD), LJ_FR2, IRSLOAD_READONLY|IRSLOAD_FRAME);
    int32_t frofs = 8*(1+LJ_FR2+numparams)+FRAME_VARG;
    if (nresults >= 0) {  /* Known fixed number of results. */
      ptrdiff_t i;
      if (nvararg > 0) {
        ptrdiff_t nload = nvararg >= nresults ? nresults : nvararg;
        TRef vbase;
        if (nvararg >= nresults)
          emitir(IRTGI(IR_GE), fr, lj_ir_kint(J, frofs+8*(int32_t)nresults));
        else
          emitir(IRTGI(IR_EQ), fr,
                 lj_ir_kint(J, (int32_t)frame_ftsz(J->L->base-1)));
        vbase = emitir(IRT(IR_SUB, IRT_IGC), REF_BASE, fr);
        vbase = emitir(IRT(IR_ADD, IRT_PGC), vbase, lj_ir_kint(J, frofs-8*(1+LJ_FR2)));
        for (i = 0; i < nload; i++) {
          IRType t = itype2irt(&J->L->base[i-1-LJ_FR2-nvararg]);
          TRef aref = emitir(IRT(IR_AREF, IRT_PGC),
                             vbase, lj_ir_kint(J, (int32_t)i));
          TRef tr = emitir(IRTG(IR_VLOAD, t), aref, 0);
          if (irtype_ispri(t)) tr = TREF_PRI(t);  /* Canonicalize primitives. */
          J->base[dst+i] = tr;
        }
      } else {
        emitir(IRTGI(IR_LE), fr, lj_ir_kint(J, frofs));
        nvararg = 0;
      }
      for (i = nvararg; i < nresults; i++)
        J->base[dst+i] = TREF_NIL;
      if (nresults != 1 || dst >= J->maxslot) {
        J->maxslot = dst + (BCReg)nresults;
      }
    } else if (select_detect(J)) {  /* y = select(x, ...) */
      TRef tridx = getslot(J, dst-1);
      TRef tr = TREF_NIL;
      ptrdiff_t idx = lj_ffrecord_select_mode(J, tridx, &J->L->base[dst-1]);
      if (idx < 0) goto nyivarg;
      if (idx != 0 && !tref_isinteger(tridx)) {
        if (tref_isstr(tridx))
          tridx = emitir(IRTG(IR_STRTO, IRT_NUM), tridx, 0);
        tridx = emitir(IRTGI(IR_CONV), tridx, IRCONV_INT_NUM|IRCONV_INDEX);
      }
      if (idx != 0 && tref_isk(tridx)) {
        emitir(IRTGI(idx <= nvararg ? IR_GE : IR_LT),
               fr, lj_ir_kint(J, frofs+8*(int32_t)idx));
        frofs -= 8;  /* Bias for 1-based index. */
      } else if (idx <= nvararg) {  /* Compute size. */
        TRef tmp = emitir(IRTI(IR_ADD), fr, lj_ir_kint(J, -frofs));
        if (numparams)
          emitir(IRTGI(IR_GE), tmp, lj_ir_kint(J, 0));
        tr = emitir(IRTI(IR_BSHR), tmp, lj_ir_kint(J, 3));
        if (idx != 0) {
          tridx = emitir(IRTI(IR_ADD), tridx, lj_ir_kint(J, -1));
          rec_idx_abc(J, tr, tridx, (uint32_t)nvararg);
        }
      } else {
        TRef tmp = lj_ir_kint(J, frofs);
        if (idx != 0) {
          TRef tmp2 = emitir(IRTI(IR_BSHL), tridx, lj_ir_kint(J, 3));
          tmp = emitir(IRTI(IR_ADD), tmp2, tmp);
        } else {
          tr = lj_ir_kint(J, 0);
        }
        emitir(IRTGI(IR_LT), fr, tmp);
      }
      if (idx != 0 && idx <= nvararg) {
        IRType t;
        TRef aref, vbase = emitir(IRT(IR_SUB, IRT_IGC), REF_BASE, fr);
        vbase = emitir(IRT(IR_ADD, IRT_PGC), vbase,
                       lj_ir_kint(J, frofs-(8<<LJ_FR2)));
        t = itype2irt(&J->L->base[idx-2-LJ_FR2-nvararg]);
        aref = emitir(IRT(IR_AREF, IRT_PGC), vbase, tridx);
        tr = emitir(IRTG(IR_VLOAD, t), aref, 0);
        if (irtype_ispri(t)) tr = TREF_PRI(t);  /* Canonicalize primitives. */
      }
      J->base[dst-2-LJ_FR2] = tr;
      J->maxslot = dst-1-LJ_FR2;
      J->bcskip = 2;  /* Skip CALLM + select. */
    } else {
    nyivarg:
      setintV(&J->errinfo, BC_VARG);
      lj_trace_err_info(J, LJ_TRERR_NYIBC);
    }
  }
}

/* -- Record allocations -------------------------------------------------- */

static TRef rec_tnew(jit_State *J, uint32_t ah)
{
  uint32_t asize = ah & 0x7ff;
  uint32_t hbits = ah >> 11;
  TRef tr;
  if (asize == 0x7ff) asize = 0x801;
  tr = emitir(IRTG(IR_TNEW, IRT_TAB), asize, hbits);
#ifdef LUAJIT_ENABLE_TABLE_BUMP
  J->rbchash[(tr & (RBCHASH_SLOTS-1))].ref = tref_ref(tr);
  setmref(J->rbchash[(tr & (RBCHASH_SLOTS-1))].pc, J->pc);
  setgcref(J->rbchash[(tr & (RBCHASH_SLOTS-1))].pt, obj2gco(J->pt));
#endif
  return tr;
}

/* -- Concatenation ------------------------------------------------------- */

typedef struct RecCatDataCP {
  TValue savetv[5+LJ_FR2];
  jit_State *J;
  BCReg baseslot, topslot;
  TRef tr;
} RecCatDataCP;

static TValue *rec_mm_concat_cp(lua_State *L, lua_CFunction dummy, void *ud)
{
  RecCatDataCP *rcd = (RecCatDataCP *)ud;
  jit_State *J = rcd->J;
  BCReg baseslot = rcd->baseslot, topslot = rcd->topslot;
  TRef *top = &J->base[topslot];
  BCReg s;
  RecordIndex ix;
  UNUSED(L); UNUSED(dummy);
  lj_assertJ(baseslot < topslot, "bad CAT arg");
  for (s = baseslot; s <= topslot; s++)
    (void)getslot(J, s);  /* Ensure all arguments have a reference. */
  if (tref_isnumber_str(top[0]) && tref_isnumber_str(top[-1])) {
    TRef tr, hdr, *trp, *xbase, *base = &J->base[baseslot];
    /* First convert numbers to strings. */
    for (trp = top; trp >= base; trp--) {
      if (tref_isnumber(*trp))
        *trp = emitir(IRT(IR_TOSTR, IRT_STR), *trp,
                      tref_isnum(*trp) ? IRTOSTR_NUM : IRTOSTR_INT);
      else if (!tref_isstr(*trp))
        break;
    }
    xbase = ++trp;
    tr = hdr = emitir(IRT(IR_BUFHDR, IRT_PGC),
                      lj_ir_kptr(J, &J2G(J)->tmpbuf), IRBUFHDR_RESET);
    do {
      tr = emitir(IRT(IR_BUFPUT, IRT_PGC), tr, *trp++);
    } while (trp <= top);
    tr = emitir(IRT(IR_BUFSTR, IRT_STR), tr, hdr);
    J->maxslot = (BCReg)(xbase - J->base);
    if (xbase == base) {
      rcd->tr = tr;  /* Return simple concatenation result. */
      return NULL;
    }
    /* Pass partial result. */
    rcd->topslot = topslot = J->maxslot--;
    /* Save updated range of slots. */
    memcpy(rcd->savetv, &L->base[topslot-1], sizeof(rcd->savetv));
    *xbase = tr;
    top = xbase;
    setstrV(J->L, &ix.keyv, &J2G(J)->strempty);  /* Simulate string result. */
  } else {
    J->maxslot = topslot-1;
    copyTV(J->L, &ix.keyv, &J->L->base[topslot]);
  }
  copyTV(J->L, &ix.tabv, &J->L->base[topslot-1]);
  ix.tab = top[-1];
  ix.key = top[0];
  rec_mm_arith(J, &ix, MM_concat);  /* Call __concat metamethod. */
  rcd->tr = 0;  /* No result yet. */
  return NULL;
}

static TRef rec_cat(jit_State *J, BCReg baseslot, BCReg topslot)
{
  lua_State *L = J->L;
  ptrdiff_t delta = L->top - L->base;
  TValue errobj;
  RecCatDataCP rcd;
  int errcode;
  rcd.J = J;
  rcd.baseslot = baseslot;
  rcd.topslot = topslot;
  /* Save slots. */
  memcpy(rcd.savetv, &L->base[topslot-1], sizeof(rcd.savetv));
  errcode = lj_vm_cpcall(L, NULL, &rcd, rec_mm_concat_cp);
  if (errcode) copyTV(L, &errobj, L->top-1);
  /* Restore slots. */
  memcpy(&L->base[rcd.topslot-1], rcd.savetv, sizeof(rcd.savetv));
  if (errcode) {
    L->top = L->base + delta;
    copyTV(L, L->top++, &errobj);
    return (TRef)(-errcode);
  }
  return rcd.tr;
}

/* -- Record bytecode ops ------------------------------------------------- */

/* Prepare for comparison. */
static void rec_comp_prep(jit_State *J)
{
  /* Prevent merging with snapshot #0 (GC exit) since we fixup the PC. */
  if (J->cur.nsnap == 1 && J->cur.snap[0].ref == J->cur.nins)
    emitir_raw(IRT(IR_NOP, IRT_NIL), 0, 0);
  lj_snap_add(J);
}

/* Fixup comparison. */
static void rec_comp_fixup(jit_State *J, const BCIns *pc, int cond)
{
  BCIns jmpins = pc[1];
  const BCIns *npc = pc + 2 + (cond ? bc_j(jmpins) : 0);
  SnapShot *snap = &J->cur.snap[J->cur.nsnap-1];
  /* Set PC to opposite target to avoid re-recording the comp. in side trace. */
#if LJ_FR2
  SnapEntry *flink = &J->cur.snapmap[snap->mapofs + snap->nent];
  uint64_t pcbase;
  memcpy(&pcbase, flink, sizeof(uint64_t));
  pcbase = (pcbase & 0xff) | (u64ptr(npc) << 8);
  memcpy(flink, &pcbase, sizeof(uint64_t));
#else
  J->cur.snapmap[snap->mapofs + snap->nent] = SNAP_MKPC(npc);
#endif
  J->needsnap = 1;
  if (bc_a(jmpins) < J->maxslot) J->maxslot = bc_a(jmpins);
  lj_snap_shrink(J);  /* Shrink last snapshot if possible. */
}

/* Record the next bytecode instruction (_before_ it's executed). */
void lj_record_ins(jit_State *J)
{
  cTValue *lbase;
  RecordIndex ix;
  const BCIns *pc;
  BCIns ins;
  BCOp op;
  TRef ra, rb, rc;

  /* Perform post-processing action before recording the next instruction. */
  if (LJ_UNLIKELY(J->postproc != LJ_POST_NONE)) {
    switch (J->postproc) {
    case LJ_POST_FIXCOMP:  /* Fixup comparison. */
      pc = (const BCIns *)(uintptr_t)J2G(J)->tmptv.u64;
      rec_comp_fixup(J, pc, (!tvistruecond(&J2G(J)->tmptv2) ^ (bc_op(*pc)&1)));
      /* fallthrough */
    case LJ_POST_FIXGUARD:  /* Fixup and emit pending guard. */
    case LJ_POST_FIXGUARDSNAP:  /* Fixup and emit pending guard and snapshot. */
      if (!tvistruecond(&J2G(J)->tmptv2)) {
        J->fold.ins.o ^= 1;  /* Flip guard to opposite. */
        if (J->postproc == LJ_POST_FIXGUARDSNAP) {
          SnapShot *snap = &J->cur.snap[J->cur.nsnap-1];
          J->cur.snapmap[snap->mapofs+snap->nent-1]--;  /* False -> true. */
        }
      }
      lj_opt_fold(J);  /* Emit pending guard. */
      /* fallthrough */
    case LJ_POST_FIXBOOL:
      if (!tvistruecond(&J2G(J)->tmptv2)) {
        BCReg s;
        TValue *tv = J->L->base;
        for (s = 0; s < J->maxslot; s++)  /* Fixup stack slot (if any). */
          if (J->base[s] == TREF_TRUE && tvisfalse(&tv[s])) {
            J->base[s] = TREF_FALSE;
            break;
          }
      }
      break;
    case LJ_POST_FIXCONST:
      {
        BCReg s;
        TValue *tv = J->L->base;
        for (s = 0; s < J->maxslot; s++)  /* Constify stack slots (if any). */
          if (J->base[s] == TREF_NIL && !tvisnil(&tv[s]))
            J->base[s] = lj_record_constify(J, &tv[s]);
      }
      break;
    case LJ_POST_FFRETRY:  /* Suppress recording of retried fast function. */
      if (bc_op(*J->pc) >= BC__MAX)
        return;
      break;
    default: lj_assertJ(0, "bad post-processing mode"); break;
    }
    J->postproc = LJ_POST_NONE;
  }

  /* Need snapshot before recording next bytecode (e.g. after a store). */
  if (J->needsnap) {
    J->needsnap = 0;
    if (J->pt && bc_op(*J->pc) < BC_FUNCF) lj_snap_purge(J);
    lj_snap_add(J);
    J->mergesnap = 1;
  }

  /* Skip some bytecodes. */
  if (LJ_UNLIKELY(J->bcskip > 0)) {
    J->bcskip--;
    return;
  }

  /* Record only closed loops for root traces. */
  pc = J->pc;
  if (J->framedepth == 0 &&
     (MSize)((char *)pc - (char *)J->bc_min) >= J->bc_extent)
    lj_trace_err(J, LJ_TRERR_LLEAVE);

#ifdef LUA_USE_ASSERT
  rec_check_slots(J);
  rec_check_ir(J);
#endif

#if LJ_HASPROFILE
  rec_profile_ins(J, pc);
#endif

  /* Keep a copy of the runtime values of var/num/str operands. */
#define rav        (&ix.valv)
#define rbv        (&ix.tabv)
#define rcv        (&ix.keyv)

  lbase = J->L->base;
  ins = *pc;
  op = bc_op(ins);
  ra = bc_a(ins);
  ix.val = 0;
  switch (bcmode_a(op)) {
  case BCMvar:
    copyTV(J->L, rav, &lbase[ra]); ix.val = ra = getslot(J, ra); break;
  default: break;  /* Handled later. */
  }
  rb = bc_b(ins);
  rc = bc_c(ins);
  switch (bcmode_b(op)) {
  case BCMnone: rb = 0; rc = bc_d(ins); break;  /* Upgrade rc to 'rd'. */
  case BCMvar:
    copyTV(J->L, rbv, &lbase[rb]); ix.tab = rb = getslot(J, rb); break;
  default: break;  /* Handled later. */
  }
  switch (bcmode_c(op)) {
  case BCMvar:
    copyTV(J->L, rcv, &lbase[rc]); ix.key = rc = getslot(J, rc); break;
  case BCMpri: setpriV(rcv, ~rc); ix.key = rc = TREF_PRI(IRT_NIL+rc); break;
  case BCMnum: { cTValue *tv = proto_knumtv(J->pt, rc);
    copyTV(J->L, rcv, tv); ix.key = rc = tvisint(tv) ? lj_ir_kint(J, intV(tv)) :
    lj_ir_knumint(J, numV(tv)); } break;
  case BCMstr: { GCstr *s = gco2str(proto_kgc(J->pt, ~(ptrdiff_t)rc));
    setstrV(J->L, rcv, s); ix.key = rc = lj_ir_kstr(J, s); } break;
  default: break;  /* Handled later. */
  }

  switch (op) {

  /* -- Comparison ops ---------------------------------------------------- */

  case BC_ISLT: case BC_ISGE: case BC_ISLE: case BC_ISGT:
#if LJ_HASFFI
    if (tref_iscdata(ra) || tref_iscdata(rc)) {
      rec_mm_comp_cdata(J, &ix, op, ((int)op & 2) ? MM_le : MM_lt);
      break;
    }
#endif
    /* Emit nothing for two numeric or string consts. */
    if (!(tref_isk2(ra,rc) && tref_isnumber_str(ra) && tref_isnumber_str(rc))) {
      IRType ta = tref_isinteger(ra) ? IRT_INT : tref_type(ra);
      IRType tc = tref_isinteger(rc) ? IRT_INT : tref_type(rc);
      int irop;
      if (ta != tc) {
        /* Widen mixed number/int comparisons to number/number comparison. */
        if (ta == IRT_INT && tc == IRT_NUM) {
          ra = emitir(IRTN(IR_CONV), ra, IRCONV_NUM_INT);
          ta = IRT_NUM;
        } else if (ta == IRT_NUM && tc == IRT_INT) {
          rc = emitir(IRTN(IR_CONV), rc, IRCONV_NUM_INT);
        } else if (LJ_52) {
          ta = IRT_NIL;  /* Force metamethod for different types. */
        } else if (!((ta == IRT_FALSE || ta == IRT_TRUE) &&
                     (tc == IRT_FALSE || tc == IRT_TRUE))) {
          break;  /* Interpreter will throw for two different types. */
        }
      }
      rec_comp_prep(J);
      irop = (int)op - (int)BC_ISLT + (int)IR_LT;
      if (ta == IRT_NUM) {
        if ((irop & 1)) irop ^= 4;  /* ISGE/ISGT are unordered. */
        if (!lj_ir_numcmp(numberVnum(rav), numberVnum(rcv), (IROp)irop))
          irop ^= 5;
      } else if (ta == IRT_INT) {
        if (!lj_ir_numcmp(numberVnum(rav), numberVnum(rcv), (IROp)irop))
          irop ^= 1;
      } else if (ta == IRT_STR) {
        if (!lj_ir_strcmp(strV(rav), strV(rcv), (IROp)irop)) irop ^= 1;
        ra = lj_ir_call(J, IRCALL_lj_str_cmp, ra, rc);
        rc = lj_ir_kint(J, 0);
        ta = IRT_INT;
      } else {
        rec_mm_comp(J, &ix, (int)op);
        break;
      }
      emitir(IRTG(irop, ta), ra, rc);
      rec_comp_fixup(J, J->pc, ((int)op ^ irop) & 1);
    }
    break;

  case BC_ISEQV: case BC_ISNEV:
  case BC_ISEQS: case BC_ISNES:
  case BC_ISEQN: case BC_ISNEN:
  case BC_ISEQP: case BC_ISNEP:
#if LJ_HASFFI
    if (tref_iscdata(ra) || tref_iscdata(rc)) {
      rec_mm_comp_cdata(J, &ix, op, MM_eq);
      break;
    }
#endif
    /* Emit nothing for two non-table, non-udata consts. */
    if (!(tref_isk2(ra, rc) && !(tref_istab(ra) || tref_isudata(ra)))) {
      int diff;
      rec_comp_prep(J);
      diff = lj_record_objcmp(J, ra, rc, rav, rcv);
      if (diff == 2 || !(tref_istab(ra) || tref_isudata(ra)))
        rec_comp_fixup(J, J->pc, ((int)op & 1) == !diff);
      else if (diff == 1)  /* Only check __eq if different, but same type. */
        rec_mm_equal(J, &ix, (int)op);
    }
    break;

  /* -- Unary test and copy ops ------------------------------------------- */

  case BC_ISTC: case BC_ISFC:
    if ((op & 1) == tref_istruecond(rc))
      rc = 0;  /* Don't store if condition is not true. */
    /* fallthrough */
  case BC_IST: case BC_ISF:  /* Type specialization suffices. */
    if (bc_a(pc[1]) < J->maxslot)
      J->maxslot = bc_a(pc[1]);  /* Shrink used slots. */
    break;

  case BC_ISTYPE: case BC_ISNUM:
    /* These coercions need to correspond with lj_meta_istype(). */
    if (LJ_DUALNUM && rc == ~LJ_TNUMX+1)
      ra = lj_opt_narrow_toint(J, ra);
    else if (rc == ~LJ_TNUMX+2)
      ra = lj_ir_tonum(J, ra);
    else if (rc == ~LJ_TSTR+1)
      ra = lj_ir_tostr(J, ra);
    /* else: type specialization suffices. */
    J->base[bc_a(ins)] = ra;
    break;

  /* -- Unary ops --------------------------------------------------------- */

  case BC_NOT:
    /* Type specialization already forces const result. */
    rc = tref_istruecond(rc) ? TREF_FALSE : TREF_TRUE;
    break;

  case BC_LEN:
    if (tref_isstr(rc))
      rc = emitir(IRTI(IR_FLOAD), rc, IRFL_STR_LEN);
    else if (!LJ_52 && tref_istab(rc))
      rc = lj_ir_call(J, IRCALL_lj_tab_len, rc);
    else
      rc = rec_mm_len(J, rc, rcv);
    break;

  /* -- Arithmetic ops ---------------------------------------------------- */

  case BC_UNM:
    if (tref_isnumber_str(rc)) {
      rc = lj_opt_narrow_unm(J, rc, rcv);
    } else {
      ix.tab = rc;
      copyTV(J->L, &ix.tabv, rcv);
      rc = rec_mm_arith(J, &ix, MM_unm);
    }
    break;

  case BC_ADDNV: case BC_SUBNV: case BC_MULNV: case BC_DIVNV: case BC_MODNV:
    /* Swap rb/rc and rbv/rcv. rav is temp. */
    ix.tab = rc; ix.key = rc = rb; rb = ix.tab;
    copyTV(J->L, rav, rbv);
    copyTV(J->L, rbv, rcv);
    copyTV(J->L, rcv, rav);
    if (op == BC_MODNV)
      goto recmod;
    /* fallthrough */
  case BC_ADDVN: case BC_SUBVN: case BC_MULVN: case BC_DIVVN:
  case BC_ADDVV: case BC_SUBVV: case BC_MULVV: case BC_DIVVV: {
    MMS mm = bcmode_mm(op);
    if (tref_isnumber_str(rb) && tref_isnumber_str(rc))
      rc = lj_opt_narrow_arith(J, rb, rc, rbv, rcv,
                               (int)mm - (int)MM_add + (int)IR_ADD);
    else
      rc = rec_mm_arith(J, &ix, mm);
    break;
    }

  case BC_MODVN: case BC_MODVV:
  recmod:
    if (tref_isnumber_str(rb) && tref_isnumber_str(rc))
      rc = lj_opt_narrow_mod(J, rb, rc, rbv, rcv);
    else
      rc = rec_mm_arith(J, &ix, MM_mod);
    break;

  case BC_POW:
    if (tref_isnumber_str(rb) && tref_isnumber_str(rc))
      rc = lj_opt_narrow_arith(J, rb, rc, rbv, rcv, IR_POW);
    else
      rc = rec_mm_arith(J, &ix, MM_pow);
    break;

  /* -- Miscellaneous ops ------------------------------------------------- */

  case BC_CAT:
    rc = rec_cat(J, rb, rc);
    if (rc >= 0xffffff00)
      lj_err_throw(J->L, -(int32_t)rc);  /* Propagate errors. */
    break;

  /* -- Constant and move ops --------------------------------------------- */

  case BC_MOV:
    /* Clear gap of method call to avoid resurrecting previous refs. */
    if (ra > J->maxslot) {
#if LJ_FR2
      memset(J->base + J->maxslot, 0, (ra - J->maxslot) * sizeof(TRef));
#else
      J->base[ra-1] = 0;
#endif
    }
    break;
  case BC_KSTR: case BC_KNUM: case BC_KPRI:
    break;
  case BC_KSHORT:
    rc = lj_ir_kint(J, (int32_t)(int16_t)rc);
    break;
  case BC_KNIL:
    if (LJ_FR2 && ra > J->maxslot)
      J->base[ra-1] = 0;
    while (ra <= rc)
      J->base[ra++] = TREF_NIL;
    if (rc >= J->maxslot) J->maxslot = rc+1;
    break;
#if LJ_HASFFI
  case BC_KCDATA:
    rc = lj_ir_kgc(J, proto_kgc(J->pt, ~(ptrdiff_t)rc), IRT_CDATA);
    break;
#endif

  /* -- Upvalue and function ops ------------------------------------------ */

  case BC_UGET:
    rc = rec_upvalue(J, rc, 0);
    break;
  case BC_USETV: case BC_USETS: case BC_USETN: case BC_USETP:
    rec_upvalue(J, ra, rc);
    break;

  /* -- Table ops --------------------------------------------------------- */

  case BC_GGET: case BC_GSET:
    settabV(J->L, &ix.tabv, tabref(J->fn->l.env));
    ix.tab = emitir(IRT(IR_FLOAD, IRT_TAB), getcurrf(J), IRFL_FUNC_ENV);
    ix.idxchain = LJ_MAX_IDXCHAIN;
    rc = lj_record_idx(J, &ix);
    break;

  case BC_TGETB: case BC_TSETB:
    setintV(&ix.keyv, (int32_t)rc);
    ix.key = lj_ir_kint(J, (int32_t)rc);
    /* fallthrough */
  case BC_TGETV: case BC_TGETS: case BC_TSETV: case BC_TSETS:
    ix.idxchain = LJ_MAX_IDXCHAIN;
    rc = lj_record_idx(J, &ix);
    break;
  case BC_TGETR: case BC_TSETR:
    ix.idxchain = 0;
    rc = lj_record_idx(J, &ix);
    break;

  case BC_TSETM:
    rec_tsetm(J, ra, (BCReg)(J->L->top - J->L->base), (int32_t)rcv->u32.lo);
    J->maxslot = ra;  /* The table slot at ra-1 is the highest used slot. */
    break;

  case BC_TNEW:
    rc = rec_tnew(J, rc);
    break;
  case BC_TDUP:
    rc = emitir(IRTG(IR_TDUP, IRT_TAB),
                lj_ir_ktab(J, gco2tab(proto_kgc(J->pt, ~(ptrdiff_t)rc))), 0);
#ifdef LUAJIT_ENABLE_TABLE_BUMP
    J->rbchash[(rc & (RBCHASH_SLOTS-1))].ref = tref_ref(rc);
    setmref(J->rbchash[(rc & (RBCHASH_SLOTS-1))].pc, pc);
    setgcref(J->rbchash[(rc & (RBCHASH_SLOTS-1))].pt, obj2gco(J->pt));
#endif
    break;

  /* -- Calls and vararg handling ----------------------------------------- */

  case BC_ITERC:
    J->base[ra] = getslot(J, ra-3);
    J->base[ra+1+LJ_FR2] = getslot(J, ra-2);
    J->base[ra+2+LJ_FR2] = getslot(J, ra-1);
    { /* Do the actual copy now because lj_record_call needs the values. */
      TValue *b = &J->L->base[ra];
      copyTV(J->L, b, b-3);
      copyTV(J->L, b+1+LJ_FR2, b-2);
      copyTV(J->L, b+2+LJ_FR2, b-1);
    }
    lj_record_call(J, ra, (ptrdiff_t)rc-1);
    break;

  /* L->top is set to L->base+ra+rc+NARGS-1+1. See lj_dispatch_ins(). */
  case BC_CALLM:
    rc = (BCReg)(J->L->top - J->L->base) - ra - LJ_FR2;
    /* fallthrough */
  case BC_CALL:
    lj_record_call(J, ra, (ptrdiff_t)rc-1);
    break;

  case BC_CALLMT:
    rc = (BCReg)(J->L->top - J->L->base) - ra - LJ_FR2;
    /* fallthrough */
  case BC_CALLT:
    lj_record_tailcall(J, ra, (ptrdiff_t)rc-1);
    break;

  case BC_VARG:
    rec_varg(J, ra, (ptrdiff_t)rb-1);
    break;

  /* -- Returns ----------------------------------------------------------- */

  case BC_RETM:
    /* L->top is set to L->base+ra+rc+NRESULTS-1, see lj_dispatch_ins(). */
    rc = (BCReg)(J->L->top - J->L->base) - ra + 1;
    /* fallthrough */
  case BC_RET: case BC_RET0: case BC_RET1:
#if LJ_HASPROFILE
    rec_profile_ret(J);
#endif
    lj_record_ret(J, ra, (ptrdiff_t)rc-1);
    break;

  /* -- Loops and branches ------------------------------------------------ */

  case BC_FORI:
    if (rec_for(J, pc, 0) != LOOPEV_LEAVE)
      J->loopref = J->cur.nins;
    break;
  case BC_JFORI:
    lj_assertJ(bc_op(pc[(ptrdiff_t)rc-BCBIAS_J]) == BC_JFORL,
               "JFORI does not point to JFORL");
    if (rec_for(J, pc, 0) != LOOPEV_LEAVE)  /* Link to existing loop. */
      lj_record_stop(J, LJ_TRLINK_ROOT, bc_d(pc[(ptrdiff_t)rc-BCBIAS_J]));
    /* Continue tracing if the loop is not entered. */
    break;

  case BC_FORL:
    rec_loop_interp(J, pc, rec_for(J, pc+((ptrdiff_t)rc-BCBIAS_J), 1));
    break;
  case BC_ITERL:
    rec_loop_interp(J, pc, rec_iterl(J, *pc));
    break;
  case BC_LOOP:
    rec_loop_interp(J, pc, rec_loop(J, ra, 1));
    break;

  case BC_JFORL:
    rec_loop_jit(J, rc, rec_for(J, pc+bc_j(traceref(J, rc)->startins), 1));
    break;
  case BC_JITERL:
    rec_loop_jit(J, rc, rec_iterl(J, traceref(J, rc)->startins));
    break;
  case BC_JLOOP:
    rec_loop_jit(J, rc, rec_loop(J, ra,
                                 !bc_isret(bc_op(traceref(J, rc)->startins))));
    break;

  case BC_IFORL:
  case BC_IITERL:
  case BC_ILOOP:
  case BC_IFUNCF:
  case BC_IFUNCV:
    lj_trace_err(J, LJ_TRERR_BLACKL);
    break;

  case BC_JMP:
    if (ra < J->maxslot)
      J->maxslot = ra;  /* Shrink used slots. */
    break;

  /* -- Function headers -------------------------------------------------- */

  case BC_FUNCF:
    rec_func_lua(J);
    break;
  case BC_JFUNCF:
    rec_func_jit(J, rc);
    break;

  case BC_FUNCV:
    rec_func_vararg(J);
    rec_func_lua(J);
    break;
  case BC_JFUNCV:
    /* Cannot happen. No hotcall counting for varag funcs. */
    lj_assertJ(0, "unsupported vararg hotcall");
    break;

  case BC_FUNCC:
  case BC_FUNCCW:
    lj_ffrecord_func(J);
    break;

  default:
    if (op >= BC__MAX) {
      lj_ffrecord_func(J);
      break;
    }
    /* fallthrough */
  case BC_ITERN:
  case BC_ISNEXT:
  case BC_UCLO:
  case BC_FNEW:
    setintV(&J->errinfo, (int32_t)op);
    lj_trace_err_info(J, LJ_TRERR_NYIBC);
    break;
  }

  /* rc == 0 if we have no result yet, e.g. pending __index metamethod call. */
  if (bcmode_a(op) == BCMdst && rc) {
    J->base[ra] = rc;
    if (ra >= J->maxslot) {
#if LJ_FR2
      if (ra > J->maxslot) J->base[ra-1] = 0;
#endif
      J->maxslot = ra+1;
    }
  }

#undef rav
#undef rbv
#undef rcv

  /* Limit the number of recorded IR instructions and constants. */
  if (J->cur.nins > REF_FIRST+(IRRef)J->param[JIT_P_maxrecord] ||
      J->cur.nk < REF_BIAS-(IRRef)J->param[JIT_P_maxirconst])
    lj_trace_err(J, LJ_TRERR_TRACEOV);
}

/* -- Recording setup ----------------------------------------------------- */

/* Setup recording for a root trace started by a hot loop. */
static const BCIns *rec_setup_root(jit_State *J)
{
  /* Determine the next PC and the bytecode range for the loop. */
  const BCIns *pcj, *pc = J->pc;
  BCIns ins = *pc;
  BCReg ra = bc_a(ins);
  switch (bc_op(ins)) {
  case BC_FORL:
    J->bc_extent = (MSize)(-bc_j(ins))*sizeof(BCIns);
    pc += 1+bc_j(ins);
    J->bc_min = pc;
    break;
  case BC_ITERL:
    lj_assertJ(bc_op(pc[-1]) == BC_ITERC, "no ITERC before ITERL");
    J->maxslot = ra + bc_b(pc[-1]) - 1;
    J->bc_extent = (MSize)(-bc_j(ins))*sizeof(BCIns);
    pc += 1+bc_j(ins);
    lj_assertJ(bc_op(pc[-1]) == BC_JMP, "ITERL does not point to JMP+1");
    J->bc_min = pc;
    break;
  case BC_LOOP:
    /* Only check BC range for real loops, but not for "repeat until true". */
    pcj = pc + bc_j(ins);
    ins = *pcj;
    if (bc_op(ins) == BC_JMP && bc_j(ins) < 0) {
      J->bc_min = pcj+1 + bc_j(ins);
      J->bc_extent = (MSize)(-bc_j(ins))*sizeof(BCIns);
    }
    J->maxslot = ra;
    pc++;
    break;
  case BC_RET:
  case BC_RET0:
  case BC_RET1:
    /* No bytecode range check for down-recursive root traces. */
    J->maxslot = ra + bc_d(ins) - 1;
    break;
  case BC_FUNCF:
    /* No bytecode range check for root traces started by a hot call. */
    J->maxslot = J->pt->numparams;
    pc++;
    break;
  case BC_CALLM:
  case BC_CALL:
  case BC_ITERC:
    /* No bytecode range check for stitched traces. */
    pc++;
    break;
  default:
    lj_assertJ(0, "bad root trace start bytecode %d", bc_op(ins));
    break;
  }
  return pc;
}

/* Setup for recording a new trace. */
void lj_record_setup(jit_State *J)
{
  uint32_t i;

  /* Initialize state related to current trace. */
  memset(J->slot, 0, sizeof(J->slot));
  memset(J->chain, 0, sizeof(J->chain));
#ifdef LUAJIT_ENABLE_TABLE_BUMP
  memset(J->rbchash, 0, sizeof(J->rbchash));
#endif
  memset(J->bpropcache, 0, sizeof(J->bpropcache));
  J->scev.idx = REF_NIL;
  setmref(J->scev.pc, NULL);

  J->baseslot = 1+LJ_FR2;  /* Invoking function is at base[-1-LJ_FR2]. */
  J->base = J->slot + J->baseslot;
  J->maxslot = 0;
  J->framedepth = 0;
  J->retdepth = 0;

  J->instunroll = J->param[JIT_P_instunroll];
  J->loopunroll = J->param[JIT_P_loopunroll];
  J->tailcalled = 0;
  J->loopref = 0;

  J->bc_min = NULL;  /* Means no limit. */
  J->bc_extent = ~(MSize)0;

  /* Emit instructions for fixed references. Also triggers initial IR alloc. */
  emitir_raw(IRT(IR_BASE, IRT_PGC), J->parent, J->exitno);
  for (i = 0; i <= 2; i++) {
    IRIns *ir = IR(REF_NIL-i);
    ir->i = 0;
    ir->t.irt = (uint8_t)(IRT_NIL+i);
    ir->o = IR_KPRI;
    ir->prev = 0;
  }
  J->cur.nk = REF_TRUE;

  J->startpc = J->pc;
  setmref(J->cur.startpc, J->pc);
  if (J->parent) {  /* Side trace. */
    GCtrace *T = traceref(J, J->parent);
    TraceNo root = T->root ? T->root : J->parent;
    J->cur.root = (uint16_t)root;
    J->cur.startins = BCINS_AD(BC_JMP, 0, 0);
    /* Check whether we could at least potentially form an extra loop. */
    if (J->exitno == 0 && T->snap[0].nent == 0) {
      /* We can narrow a FORL for some side traces, too. */
      if (J->pc > proto_bc(J->pt) && bc_op(J->pc[-1]) == BC_JFORI &&
          bc_d(J->pc[bc_j(J->pc[-1])-1]) == root) {
        lj_snap_add(J);
        rec_for_loop(J, J->pc-1, &J->scev, 1);
        goto sidecheck;
      }
    } else {
      J->startpc = NULL;  /* Prevent forming an extra loop. */
    }
    lj_snap_replay(J, T);
  sidecheck:
    if (traceref(J, J->cur.root)->nchild >= J->param[JIT_P_maxside] ||
        T->snap[J->exitno].count >= J->param[JIT_P_hotexit] +
                                    J->param[JIT_P_tryside]) {
      lj_record_stop(J, LJ_TRLINK_INTERP, 0);
    }
  } else {  /* Root trace. */
    J->cur.root = 0;
    J->cur.startins = *J->pc;
    J->pc = rec_setup_root(J);
    /* Note: the loop instruction itself is recorded at the end and not
    ** at the start! So snapshot #0 needs to point to the *next* instruction.
    */
    lj_snap_add(J);
    if (bc_op(J->cur.startins) == BC_FORL)
      rec_for_loop(J, J->pc-1, &J->scev, 1);
    else if (bc_op(J->cur.startins) == BC_ITERC)
      J->startpc = NULL;
    if (1 + J->pt->framesize >= LJ_MAX_JSLOTS)
      lj_trace_err(J, LJ_TRERR_STACKOV);
  }
#if LJ_HASPROFILE
  J->prev_pt = NULL;
  J->prev_line = -1;
#endif
#ifdef LUAJIT_ENABLE_CHECKHOOK
  /* Regularly check for instruction/line hooks from compiled code and
  ** exit to the interpreter if the hooks are set.
  **
  ** This is a compile-time option and disabled by default, since the
  ** hook checks may be quite expensive in tight loops.
  **
  ** Note this is only useful if hooks are *not* set most of the time.
  ** Use this only if you want to *asynchronously* interrupt the execution.
  **
  ** You can set the instruction hook via lua_sethook() with a count of 1
  ** from a signal handler or another native thread. Please have a look
  ** at the first few functions in luajit.c for an example (Ctrl-C handler).
  */
  {
    TRef tr = emitir(IRT(IR_XLOAD, IRT_U8),
                     lj_ir_kptr(J, &J2G(J)->hookmask), IRXLOAD_VOLATILE);
    tr = emitir(IRTI(IR_BAND), tr, lj_ir_kint(J, (LUA_MASKLINE|LUA_MASKCOUNT)));
    emitir(IRTGI(IR_EQ), tr, lj_ir_kint(J, 0));
  }
#endif
}

#undef IR
#undef emitir_raw
#undef emitir

#endif

tarantool / luajit / 30088298194

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