Add missing FORI coercions in recorder.

[luajit-2.0/celess22.git] / src / lj_record.c

/*
** Trace recorder (bytecode -> SSA IR).
** Copyright (C) 2005-2010 Mike Pall. See Copyright Notice in luajit.h
*/

#define lj_record_c
#define LUA_CORE

#include "lj_obj.h"

#if LJ_HASJIT

#include "lj_gc.h"
#include "lj_err.h"
#include "lj_str.h"
#include "lj_tab.h"
#include "lj_state.h"
#include "lj_frame.h"
#include "lj_bc.h"
#include "lj_ff.h"
#include "lj_ir.h"
#include "lj_jit.h"
#include "lj_iropt.h"
#include "lj_trace.h"
#include "lj_record.h"
#include "lj_snap.h"
#include "lj_asm.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))

/* Context for recording an indexed load/store. */
typedef struct RecordIndex {
  TValue tabv;          /* Runtime value of table (or indexed object). */
  TValue keyv;          /* Runtime value of key. */
  TValue valv;          /* Runtime value of stored value. */
  TValue mobjv;         /* Runtime value of metamethod object. */
  GCtab *mtv;           /* Runtime value of metatable object. */
  cTValue *oldv;        /* Runtime value of previously stored value. */
  TRef tab;             /* Table (or indexed object) reference. */
  TRef key;             /* Key reference. */
  TRef val;             /* Value reference for a store or 0 for a load. */
  TRef mt;              /* Metatable reference. */
  TRef mobj;            /* Metamethod object reference. */
  int idxchain;         /* Index indirections left or 0 for raw lookup. */
} RecordIndex;

/* Requested results from rec_call(). */
enum {
  /* Non-negative numbers are number of requested results. */
  CALLRES_MULTI = -1,           /* Return multiple results. */
  CALLRES_TAILCALL = -2,        /* Tail call. */
  CALLRES_PENDING = -3,         /* Call is pending, no results yet. */
  CALLRES_CONT = -4             /* Continuation call. */
};

/* Forward declarations. */
static TRef rec_idx(jit_State *J, RecordIndex *ix);
static int rec_call(jit_State *J, BCReg func, ptrdiff_t cres, ptrdiff_t nargs);

/* -- 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;
  lua_assert(nk <= REF_BIAS && nins >= REF_BIAS && nins < 65536);
  for (i = nins-1; i >= nk; i--) {
    IRIns *ir = IR(i);
    uint32_t mode = lj_ir_mode[ir->o];
    IRRef op1 = ir->op1;
    IRRef op2 = ir->op2;
    switch (irm_op1(mode)) {
    case IRMnone: lua_assert(op1 == 0); break;
    case IRMref: lua_assert(op1 >= nk);
      lua_assert(i >= REF_BIAS ? op1 < i : op1 > i); break;
    case IRMlit: break;
    case IRMcst: lua_assert(i < REF_BIAS); continue;
    }
    switch (irm_op2(mode)) {
    case IRMnone: lua_assert(op2 == 0); break;
    case IRMref: lua_assert(op2 >= nk);
      lua_assert(i >= REF_BIAS ? op2 < i : op2 > i); break;
    case IRMlit: break;
    case IRMcst: lua_assert(0); break;
    }
    if (ir->prev) {
      lua_assert(ir->prev >= nk);
      lua_assert(i >= REF_BIAS ? ir->prev < i : ir->prev > i);
      lua_assert(IR(ir->prev)->o == ir->o);
    }
  }
}

/* Compare frame stack of the recorder and the VM. */
static void rec_check_frames(jit_State *J)
{
  cTValue *frame = J->L->base - 1;
  cTValue *lim = J->L->base - J->baseslot;
  int32_t depth = J->framedepth;
  while (frame > lim) {
    depth--;
    lua_assert(depth >= 0);
    lua_assert((SnapEntry)frame_ftsz(frame) == J->frame[depth]);
    if (frame_iscont(frame)) {
      depth--;
      lua_assert(depth >= 0);
      lua_assert((SnapEntry)frame_ftsz(frame-1) == J->frame[depth]);
    }
    frame = frame_prev(frame);
  }
  lua_assert(depth == 0);
}

/* Sanity check the slots. */
static void rec_check_slots(jit_State *J)
{
  BCReg s, nslots = J->baseslot + J->maxslot;
  int32_t depth;
  lua_assert(J->baseslot >= 1 && J->baseslot < LJ_MAX_JSLOTS);
  lua_assert(nslots < LJ_MAX_JSLOTS);
  for (s = 0; s < nslots; s++) {
    TRef tr = J->slot[s];
    if (s != 0 && (tr & (TREF_CONT|TREF_FRAME)))
      depth++;
    if (tr) {
      IRRef ref = tref_ref(tr);
      lua_assert(ref >= J->cur.nk && ref < J->cur.nins);
      lua_assert(irt_t(IR(ref)->t) == tref_t(tr));
    }
  }
  lua_assert(J->framedepth == depth);
  rec_check_frames(J);
}
#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])
    return J->base[-1];
  lua_assert(J->baseslot == 1);
  return sloadt(J, -1, 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.
*/
static int rec_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_TONUM), a, 0);
        ta = IRT_NUM;
      } else if (ta == IRT_NUM && tb == IRT_INT) {
        b = emitir(IRTN(IR_TONUM), b, 0);
      } else {
        return 2;  /* Two different types are never equal. */
      }
    }
    emitir(IRTG(diff ? IR_NE : IR_EQ, ta), a, b);
  }
  return diff;
}

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

/* Loop event. */
typedef enum {
  LOOPEV_LEAVE,         /* Loop is left or not entered. */
  LOOPEV_ENTER          /* Loop is entered. */
} LoopEvent;

/* Canonicalize slots: convert integers to numbers. */
static void canonicalize_slots(jit_State *J)
{
  BCReg s;
  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_TONUM), tr, 0);
    }
  }
}

/* Stop recording. */
static void rec_stop(jit_State *J, TraceNo lnk)
{
  lj_trace_end(J);
  J->cur.link = (uint16_t)lnk;
  /* Looping back at the same stack level? */
  if (lnk == J->curtrace && 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, cast_num(k));
        } else {
          lua_Number n = proto_knum(J->pt, bc_d(ins));
          if (t == IRT_INT) {
            int32_t k = lj_num2int(n);
            if (n == cast_num(k))  /* -0 is ok here. */
              return lj_ir_kint(J, k);
            return 0;  /* Type mismatch. */
          } else {
            return lj_ir_knum(J, n);
          }
        }
      }
      return 0;  /* Non-constant initializer. */
    }
  }
  return 0;  /* No assignment to this slot found? */
}

/* 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)
{
  TRef tr = find_kinit(J, fori, slot, t);
  if (!tr) {
    tr = J->base[slot];
    if (!tr) {
      if (t == IRT_INT)
        t |= IRT_GUARD;
      tr = sloadt(J, (int32_t)slot, t, IRSLOAD_READONLY|IRSLOAD_INHERIT);
    }
  }
  return tr;
}

/* In-place coercion of FORI arguments. */
static lua_Number for_coerce(jit_State *J, TValue *o)
{
  if (!tvisnum(o) && !(tvisstr(o) && lj_str_tonum(strV(o), o)))
    lj_trace_err(J, LJ_TRERR_BADTYPE);
  return numV(o);
}

/* Simulate the runtime behavior of the FOR loop iterator.
** It's important to exactly reproduce the semantics of the interpreter.
*/
static LoopEvent for_iter(jit_State *J, IROp *op, BCReg ra, int isforl)
{
  TValue *forbase = &J->L->base[ra];
  lua_Number stopv = for_coerce(J, &forbase[FORL_STOP]);
  lua_Number idxv = for_coerce(J, &forbase[FORL_IDX]);
  lua_Number stepv = for_coerce(J, &forbase[FORL_STEP]);
  if (isforl)
    idxv += stepv;
  if ((int32_t)forbase[FORL_STEP].u32.hi >= 0) {
    if (idxv <= stopv) { *op = IR_LE; return LOOPEV_ENTER; }
    *op = IR_GT; return LOOPEV_LEAVE;
  } else {
    if (stopv <= idxv) { *op = IR_GE; return LOOPEV_ENTER; }
    *op = IR_LT; return LOOPEV_LEAVE;
  }
}

/* Record FORL/JFORL or FORI/JFORI. */
static LoopEvent rec_for(jit_State *J, const BCIns *fori, int isforl)
{
  BCReg ra = bc_a(*fori);
  IROp op;
  LoopEvent ev = for_iter(J, &op, ra, isforl);
  TRef *tr = &J->base[ra];
  TRef idx, stop;
  IRType t;
  if (isforl) {  /* Handle FORL/JFORL opcodes. */
    TRef step;
    idx = tr[FORL_IDX];
    if (!idx) idx = sloadt(J, (int32_t)(ra+FORL_IDX), IRT_NUM, 0);
    t = tref_type(idx);
    stop = fori_arg(J, fori, ra+FORL_STOP, t);
    step = fori_arg(J, fori, ra+FORL_STEP, t);
    tr[FORL_IDX] = idx = emitir(IRT(IR_ADD, t), idx, step);
  } else {  /* Handle FORI/JFORI opcodes. */
    BCReg i;
    t = IRT_NUM;
    for (i = FORL_IDX; i <= FORL_STEP; i++) {
      lua_assert(J->base[ra+i] != 0);  /* Assumes the slots are already set. */
      tr[i] = lj_ir_tonum(J, J->base[ra+i]);
    }
    idx = tr[FORL_IDX];
    stop = tr[FORL_STOP];
    if (!tref_isk(tr[FORL_STEP]))  /* Non-const step: need direction guard. */
      emitir(IRTG(((op-IR_LT)>>1)+IR_LT, IRT_NUM),
             tr[FORL_STEP], lj_ir_knum_zero(J));
  }

  tr[FORL_EXT] = idx;
  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), 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);
  lua_assert(J->base[ra] != 0);
  if (!tref_isnil(J->base[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)
{
  J->maxslot = ra;
  J->pc++;
  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 (J->penalty[i].pc == pc) {
      if (J->penalty[i].reason == LJ_TRERR_LLEAVE &&
          J->penalty[i].val >= 2*HOTCOUNT_MIN_PENALTY)
        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) {
    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);
      rec_stop(J, J->curtrace);  /* Root trace forms a loop. */
    } 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 (!innerloopleft(J, pc))
        lj_trace_err(J, LJ_TRERR_LINNER);  /* Root trace hit an inner loop. */
      if ((J->loopref && J->cur.nins - J->loopref > 8) || --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) {  /* 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)
      lnk = J->curtrace;  /* Can form an extra loop. */
    rec_stop(J, lnk);  /* Link to the loop. */
  }  /* Side trace continues across a loop that's left or not entered. */
}

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

/* Prepare to record call to metamethod. */
static BCReg rec_mm_prep(jit_State *J, ASMFunction cont)
{
  BCReg s, top = curr_proto(J->L)->framesize;
  TRef trcont;
  setcont(&J->L->base[top], cont);
#if LJ_64
  trcont = lj_ir_kptr(J, (void *)((int64_t)cont - (int64_t)lj_vm_asm_begin));
#else
  trcont = lj_ir_kptr(J, (void *)cont);
#endif
  J->base[top] = trcont | TREF_CONT;
  for (s = J->maxslot; s < top; s++)
    J->base[s] = TREF_NIL;
  return top+1;
}

/* Record metamethod lookup. */
static int rec_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)) {
    mt = tabref(udataV(&ix->tabv)->metatable);
    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)
      return 0;  /* No metamethod. */
    mix.tab = lj_ir_ktab(J, mt);
    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 = strref(J2G(J)->mmname[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);
    if (isdead(J2G(J), obj2gco(mmstr)))
      flipwhite(obj2gco(mmstr));  /* Need same logic as lj_str_new(). */
    setstrV(J->L, &mix.keyv, mmstr);
    mix.key = lj_ir_kstr(J, mmstr);
    mix.val = 0;
    mix.idxchain = 0;
    ix->mobj = rec_idx(J, &mix);
    return !tref_isnil(ix->mobj);  /* 1 if metamethod found, 0 if not. */
  }
  return 0;  /* No metamethod. */
}

/* Record call to arithmetic metamethod (and MM_len). */
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, lj_cont_ra);
  TRef *base = J->base + func;
  TValue *basev = J->L->base + func;
  base[1] = ix->tab; base[2] = ix->key;
  copyTV(J->L, basev+1, &ix->tabv);
  copyTV(J->L, basev+2, &ix->keyv);
  if (!rec_mm_lookup(J, ix, mm)) {  /* Lookup metamethod on 1st operand. */
    if (mm != MM_len) {
      ix->tab = ix->key;
      copyTV(J->L, &ix->tabv, &ix->keyv);
      if (rec_mm_lookup(J, ix, mm))  /* Lookup metamethod on 2nd operand. */
        goto ok;
    }
    lj_trace_err(J, LJ_TRERR_NOMM);
  }
ok:
  base[0] = ix->mobj;
  copyTV(J->L, basev+0, &ix->mobjv);
  return rec_call(J, func, CALLRES_CONT, 2) ? J->base[func] : 0;
}

/* 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;
  TValue *tv = J->L->base + func;
  base[0] = ix->mobj; base[1] = ix->val; base[2] = ix->key;
  copyTV(J->L, tv+0, &ix->mobjv);
  copyTV(J->L, tv+1, &ix->valv);
  copyTV(J->L, tv+2, &ix->keyv);
  rec_call(J, func, CALLRES_CONT, 2);
  /* It doesn't matter whether this is immediately resolved or not.
  ** Type specialization of the return type suffices to specialize
  ** the control flow.
  */
}

/* 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 (rec_mm_lookup(J, ix, MM_eq)) {  /* Lookup metamethod 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 (!rec_mm_lookup(J, ix, MM_eq) ||
          rec_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 (rec_mm_lookup(J, ix, mm)) {  /* Lookup metamethod 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 (!rec_mm_lookup(J, ix, mm) ||
            rec_objcmp(J, mo1, ix->mobj, &mo1v, &ix->mobjv))
          goto nomatch;
      }
      rec_mm_callcomp(J, ix, op);
      return;
    }
  nomatch:
    /* First 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;
  }
}

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

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

  /* Integer keys are looked up in the array part first. */
  key = ix->key;
  if (tref_isnumber(key)) {
    lua_Number n = numV(&ix->keyv);
    int32_t k = lj_num2int(n);
    lua_assert(tvisnum(&ix->keyv));
    /* Potential array key? */
    if ((MSize)k < LJ_MAX_ASIZE && n == cast_num(k)) {
      TRef asizeref, ikey = key;
      if (!tref_isinteger(ikey))
        ikey = emitir(IRTGI(IR_TOINT), ikey, IRTOINT_INDEX);
      asizeref = emitir(IRTI(IR_FLOAD), ix->tab, IRFL_TAB_ASIZE);
      if ((MSize)k < t->asize) {  /* Currently an array key? */
        TRef arrayref;
        emitir(IRTGI(IR_ABC), asizeref, ikey);  /* Bounds check. */
        arrayref = emitir(IRT(IR_FLOAD, IRT_PTR), ix->tab, IRFL_TAB_ARRAY);
        return emitir(IRT(IR_AREF, IRT_PTR), 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 (tref_isinteger(key))  /* Hash keys are based on numbers, not ints. */
    ix->key = key = emitir(IRTN(IR_TONUM), key, 0);
  if (tref_isk(key)) {
    /* Optimize lookup of constant hash keys. */
    MSize hslot = (MSize)((char *)ix->oldv - (char *)&noderef(t->node)[0].val);
    if (t->hmask > 0 && hslot <= t->hmask*(MSize)sizeof(Node) &&
        hslot <= 65535*(MSize)sizeof(Node)) {
      TRef node, kslot;
      TRef 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_PTR), ix->tab, IRFL_TAB_NODE);
      kslot = lj_ir_kslot(J, key, hslot / sizeof(Node));
      return emitir(IRTG(IR_HREFK, IRT_PTR), node, kslot);
    }
  }
  /* Fall back to a regular hash lookup. */
  return emitir(IRT(IR_HREF, IRT_PTR), 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 i;
      for (i = 0; i <= MM_FAST; i++)
        if (strref(J2G(J)->mmname[i]) == 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. */
static TRef rec_idx(jit_State *J, RecordIndex *ix)
{
  TRef xref;
  IROp xrefop, loadop;
  cTValue *oldv;

  while (!tref_istab(ix->tab)) { /* Handle non-table lookup. */
    lua_assert(ix->idxchain != 0); /* Never call raw rec_idx() on non-table. */
    if (!rec_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;
      TValue *tv = J->L->base + func;
      base[0] = ix->mobj; base[1] = ix->tab; base[2] = ix->key;
      setfuncV(J->L, tv+0, 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);
        rec_call(J, func, CALLRES_CONT, 3);  /* mobj(tab, key, val) */
        return 0;
      } else {
        /* res = mobj(tab, key) */
        return rec_call(J, func, CALLRES_CONT, 2) ? J->base[func] : 0;
      }
    }
    /* 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 && rec_mm_lookup(J, ix, MM_index))
        goto handlemm;
      return TREF_NIL;
    }
  }

  /* Record the key lookup. */
  xref = rec_idx_key(J, ix);
  xrefop = IR(tref_ref(xref))->o;
  loadop = xrefop == IR_AREF ? IR_ALOAD : IR_HLOAD;
  oldv = ix->oldv;

  if (ix->val == 0) {  /* Indexed load */
    IRType t = itype2irt(oldv);
    TRef res = emitir(IRTG(loadop, t), xref, 0);
    if (t == IRT_NIL && ix->idxchain && rec_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);
    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, strref(J2G(J)->mmname[MM_newindex]));
        hasmm = mo && !tvisnil(mo);
      }
      if (hasmm || oldv == niltvg(J2G(J)))
        emitir(IRTG(loadop, IRT_NIL), xref, 0);  /* Guard for nil value. */
      else if (xrefop == IR_HREF)
        emitir(IRTG(IR_NE, IRT_PTR), xref, lj_ir_kptr(J, niltvg(J2G(J))));
      if (ix->idxchain && rec_mm_lookup(J, ix, MM_newindex)) { /* Metamethod? */
        lua_assert(hasmm);
        goto handlemm;
      }
      lua_assert(!hasmm);
      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_TONUM), key, 0);
        xref = emitir(IRT(IR_NEWREF, IRT_PTR), ix->tab, key);
      }
    } 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_PTR), xref, lj_ir_kptr(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. */
        }
      }
    }
    if (tref_isinteger(ix->val))  /* Convert int to number before storing. */
      ix->val = emitir(IRTN(IR_TONUM), ix->val, 0);
    emitir(IRT(loadop+IRDELTA_L2S, tref_type(ix->val)), xref, ix->val);
    if (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_PTR), ix->tab, IRFL_TAB_NOMM);
      emitir(IRT(IR_FSTORE, IRT_U8), fref, lj_ir_kint(J, 0));
    }
    J->needsnap = 1;
    return 0;
  }
}

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

/* Shrink disambiguation hash into an 8 bit value. */
static uint32_t shrink_dhash(uint32_t lo, uint32_t hi)
{
  lo ^= hi; hi = lj_rol(hi, 14);
  lo -= hi; hi = lj_rol(hi, 5);
  hi ^= lo; hi -= lj_rol(lo, 27);
  return (hi & 0xff);
}

/* 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;
  /* Note: this effectively limits LJ_MAX_UPVAL to 127. */
  uv = (uv << 8) | shrink_dhash(uvp->dhash, uvp->dhash-0x04c11db7);
  if (!uvp->closed) {
    /* In current stack? */
    if (uvval(uvp) >= J->L->stack && uvval(uvp) < J->L->maxstack) {
      int32_t slot = (int32_t)(uvval(uvp) - (J->L->base - J->baseslot));
      if (slot >= 0) {  /* Aliases an SSA slot? */
        slot -= (int32_t)J->baseslot;  /* Note: slot number may be negative! */
        /* NYI: add IR to guard that it's still aliasing the same slot. */
        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;
        }
      }
    }
    uref = tref_ref(emitir(IRTG(IR_UREFO, IRT_PTR), fn, uv));
  } else {
    needbarrier = 1;
    uref = tref_ref(emitir(IRTG(IR_UREFC, IRT_PTR), 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. */
    if (tref_isinteger(val))  /* Convert int to number before storing. */
      val = emitir(IRTN(IR_TONUM), val, 0);
    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 fast functions -------------------------------------- */

/* Note: The function and the arguments for the bytecode CALL instructions
** always occupy _new_ stack slots (above the highest active variable).
** This means they must have been stored there by previous instructions
** (MOV, K*, ADD etc.) which must be part of the same trace. This in turn
** means their reference slots are already valid and their types have
** already been specialized (i.e. getslot() would be redundant).
** The 1st slot beyond the arguments is set to 0 before calling recff_*.
*/

/* Data used by handlers to record a fast function. */
typedef struct RecordFFData {
  TValue *argv;         /* Runtime argument values. */
  GCfunc *fn;           /* The currently recorded function. */
  ptrdiff_t nargs;      /* Number of passed arguments. */
  ptrdiff_t nres;       /* Number of returned results (defaults to 1). */
  ptrdiff_t cres;       /* Wanted number of call results. */
  uint32_t data;        /* Per-ffid auxiliary data (opcode, literal etc.). */
  int metacall;         /* True if function was resolved via __call. */
} RecordFFData;

/* Type of handler to record a fast function. */
typedef void (*RecordFunc)(jit_State *J, TRef *res, RecordFFData *rd);

/* Avoid carrying two pointers around. */
#define arg     (res+1)

/* Get runtime value of int argument. */
static int32_t argv2int(jit_State *J, TValue *o)
{
  if (tvisstr(o) && !lj_str_tonum(strV(o), o))
    lj_trace_err(J, LJ_TRERR_BADTYPE);
  return lj_num2bit(numV(o));
}

/* Get runtime value of string argument. */
static GCstr *argv2str(jit_State *J, TValue *o)
{
  if (LJ_LIKELY(tvisstr(o))) {
    return strV(o);
  } else {
    GCstr *s;
    lua_assert(tvisnum(o));
    s = lj_str_fromnum(J->L, &o->n);
    setstrV(J->L, o, s);
    return s;
  }
}

/* Fallback handler for all fast functions that are not recorded (yet). */
static void recff_nyi(jit_State *J, TRef *res, RecordFFData *rd)
{
  UNUSED(res);
  setfuncV(J->L, &J->errinfo, rd->fn);
  lj_trace_err_info(J, LJ_TRERR_NYIFF);
}

LJ_NORET static void recff_err_nyi(jit_State *J, RecordFFData *rd)
{
  setfuncV(J->L, &J->errinfo, rd->fn);
  lj_trace_err_info(J, LJ_TRERR_NYIFFU);
}

/* C functions can have arbitrary side-effects and are not recorded (yet). */
static void recff_c(jit_State *J, TRef *res, RecordFFData *rd)
{
  UNUSED(res);
  setlightudV(&J->errinfo, (void *)rd->fn->c.f);
  lj_trace_err_info(J, LJ_TRERR_NYICF);
}

/* -- Base library fast functions ----------------------------------------- */

static void recff_assert(jit_State *J, TRef *res, RecordFFData *rd)
{
  /* Arguments already specialized. The interpreter throws for nil/false. */
  ptrdiff_t i;
  for (i = 0; arg[i]; i++)  /* Need to pass through all arguments. */
    res[i] = arg[i];
  rd->nres = i;
  UNUSED(J);
}

static void recff_type(jit_State *J, TRef *res, RecordFFData *rd)
{
  /* Arguments already specialized. Result is a constant string. Neat, huh? */
  IRType t = tref_isinteger(arg[0]) ? IRT_NUM : tref_type(arg[0]);
  res[0] = lj_ir_kstr(J, strV(&rd->fn->c.upvalue[t]));
}

static void recff_getmetatable(jit_State *J, TRef *res, RecordFFData *rd)
{
  TRef tr = arg[0];
  if (tref_istab(tr)) {
    RecordIndex ix;
    ix.tab = tr;
    copyTV(J->L, &ix.tabv, &rd->argv[0]);
    if (rec_mm_lookup(J, &ix, MM_metatable))
      res[0] = ix.mobj;
    else
      res[0] = ix.mt;
  }  /* else: Interpreter will throw. */
}

static void recff_setmetatable(jit_State *J, TRef *res, RecordFFData *rd)
{
  TRef tr = arg[0];
  TRef mt = arg[1];
  if (tref_istab(tr) && (tref_istab(mt) || (mt && tref_isnil(mt)))) {
    TRef fref, mtref;
    RecordIndex ix;
    ix.tab = tr;
    copyTV(J->L, &ix.tabv, &rd->argv[0]);
    rec_mm_lookup(J, &ix, MM_metatable); /* Guard for no __metatable field. */
    fref = emitir(IRT(IR_FREF, IRT_PTR), tr, IRFL_TAB_META);
    mtref = tref_isnil(mt) ? lj_ir_knull(J, IRT_TAB) : mt;
    emitir(IRT(IR_FSTORE, IRT_TAB), fref, mtref);
    if (!tref_isnil(mt))
      emitir(IRT(IR_TBAR, IRT_TAB), tr, 0);
    res[0] = tr;
    J->needsnap = 1;
  }  /* else: Interpreter will throw. */
}

static void recff_rawget(jit_State *J, TRef *res, RecordFFData *rd)
{
  if (tref_istab(arg[0]) && arg[1]) {
    RecordIndex ix;
    ix.tab = arg[0]; ix.key = arg[1]; ix.val = 0; ix.idxchain = 0;
    settabV(J->L, &ix.tabv, tabV(&rd->argv[0]));
    copyTV(J->L, &ix.keyv, &rd->argv[1]);
    res[0] = rec_idx(J, &ix);
  }  /* else: Interpreter will throw. */
}

static void recff_rawset(jit_State *J, TRef *res, RecordFFData *rd)
{
  if (tref_istab(arg[0]) && arg[1] && arg[2]) {
    RecordIndex ix;
    ix.tab = arg[0]; ix.key = arg[1]; ix.val = arg[2]; ix.idxchain = 0;
    settabV(J->L, &ix.tabv, tabV(&rd->argv[0]));
    copyTV(J->L, &ix.keyv, &rd->argv[1]);
    copyTV(J->L, &ix.valv, &rd->argv[2]);
    rec_idx(J, &ix);
    res[0] = arg[0];  /* Returns table. */
  }  /* else: Interpreter will throw. */
}

static void recff_rawequal(jit_State *J, TRef *res, RecordFFData *rd)
{
  if (arg[0] && arg[1]) {
    int diff = rec_objcmp(J, arg[0], arg[1], &rd->argv[0], &rd->argv[1]);
    res[0] = diff ? TREF_FALSE : TREF_TRUE;
  }  /* else: Interpreter will throw. */
}

static void recff_tonumber(jit_State *J, TRef *res, RecordFFData *rd)
{
  TRef tr = arg[0];
  if (tref_isnumber_str(tr)) {
    if (arg[1]) {
      TRef base = lj_ir_toint(J, arg[1]);
      if (!tref_isk(base) || IR(tref_ref(base))->i != 10)
        recff_err_nyi(J, rd);
    }
    if (tref_isstr(tr))
      tr = emitir(IRTG(IR_STRTO, IRT_NUM), tr, 0);
  } else {
    tr = TREF_NIL;
  }
  res[0] = tr;
  UNUSED(rd);
}

static void recff_tostring(jit_State *J, TRef *res, RecordFFData *rd)
{
  TRef tr = arg[0];
  if (tref_isstr(tr)) {
    /* Ignore __tostring in the string base metatable. */
    res[0] = tr;
  } else {
    RecordIndex ix;
    ix.tab = tr;
    copyTV(J->L, &ix.tabv, &rd->argv[0]);
    if (rec_mm_lookup(J, &ix, MM_tostring)) {  /* Has __tostring metamethod? */
      if (rd->metacall)  /* Must not use kludge. */
        recff_err_nyi(J, rd);
      res[0] = ix.mobj;
      copyTV(J->L, rd->argv - 1, &ix.mobjv);  /* Kludge. */
      J->framedepth--;
      if (rec_call(J, (BCReg)(res - J->base), 1, 1))
        J->framedepth++;
      else
        rd->cres = CALLRES_PENDING;
      /* Otherwise res[0] already contains the result. */
    } else if (tref_isnumber(tr)) {
      res[0] = emitir(IRT(IR_TOSTR, IRT_STR), tr, 0);
    } else if (tref_ispri(tr)) {
      res[0] = lj_ir_kstr(J, strV(&rd->fn->c.upvalue[tref_type(tr)]));
    } else {
      recff_err_nyi(J, rd);
    }
  }
}

static void recff_ipairs_aux(jit_State *J, TRef *res, RecordFFData *rd)
{
  RecordIndex ix;
  ix.tab = arg[0];
  if (tref_istab(ix.tab)) {
    if (!tvisnum(&rd->argv[1]))  /* No support for string coercion. */
      lj_trace_err(J, LJ_TRERR_BADTYPE);
    setnumV(&ix.keyv, numV(&rd->argv[1])+(lua_Number)1);
    settabV(J->L, &ix.tabv, tabV(&rd->argv[0]));
    ix.val = 0; ix.idxchain = 0;
    ix.key = lj_ir_toint(J, arg[1]);
    res[0] = ix.key = emitir(IRTI(IR_ADD), ix.key, lj_ir_kint(J, 1));
    res[1] = rec_idx(J, &ix);
    rd->nres = tref_isnil(res[1]) ? 0 : 2;
  }  /* else: Interpreter will throw. */
}

static void recff_ipairs(jit_State *J, TRef *res, RecordFFData *rd)
{
  TRef tab = arg[0];
  if (tref_istab(tab)) {
    res[0] = lj_ir_kfunc(J, funcV(&rd->fn->c.upvalue[0]));
    res[1] = tab;
    res[2] = lj_ir_kint(J, 0);
    rd->nres = 3;
  }  /* else: Interpreter will throw. */
}

static void recff_pcall(jit_State *J, TRef *res, RecordFFData *rd)
{
  if (rd->nargs >= 1) {
    BCReg parg = (BCReg)(arg - J->base);
    J->pc = (const BCIns *)(sizeof(TValue) - 4 +
                            (hook_active(J2G(J)) ? FRAME_PCALLH : FRAME_PCALL));
    if (rec_call(J, parg, CALLRES_MULTI, rd->nargs - 1)) {  /* Resolved call. */
      res[0] = TREF_TRUE;  /* Prepend true result. No need to move results. */
      rd->nres = (ptrdiff_t)J->maxslot - (ptrdiff_t)parg + 1;
    } else {  /* Propagate pending call. */
      rd->cres = CALLRES_PENDING;
    }
  }  /* else: Interpreter will throw. */
}

/* Struct to pass context across lj_vm_cpcall. */
typedef struct RecordXpcall {
  ptrdiff_t nargs;
  BCReg parg;
  int resolved;
} RecordXpcall;

static TValue *recff_xpcall_cp(lua_State *L, lua_CFunction dummy, void *ud)
{
  jit_State *J = L2J(L);
  RecordXpcall *rx = (RecordXpcall *)ud;
  UNUSED(dummy);
  rx->resolved = rec_call(J, rx->parg, CALLRES_MULTI, rx->nargs);
  return NULL;
}

static void recff_xpcall(jit_State *J, TRef *res, RecordFFData *rd)
{
  if (rd->nargs >= 2) {
    RecordXpcall rx;
    BCReg parg = (BCReg)(arg - J->base) + 1;
    TRef tmp;
    TValue argv0, argv1;
    ptrdiff_t oargv;
    int errcode;
    /* Swap function and traceback. */
    tmp = arg[0]; arg[0] = arg[1]; arg[1] = tmp;
    copyTV(J->L, &argv0, &rd->argv[0]);
    copyTV(J->L, &argv1, &rd->argv[1]);
    copyTV(J->L, &rd->argv[0], &argv1);
    copyTV(J->L, &rd->argv[1], &argv0);
    oargv = savestack(J->L, rd->argv);
    J->pc = (const BCIns *)(2*sizeof(TValue) - 4 +
                            (hook_active(J2G(J)) ? FRAME_PCALLH : FRAME_PCALL));
    /* Need to protect rec_call because the recorder may throw. */
    rx.parg = parg;
    rx.nargs = rd->nargs - 2;
    errcode = lj_vm_cpcall(J->L, NULL, &rx, recff_xpcall_cp);
    /* Always undo Lua stack swap to avoid confusing the interpreter. */
    rd->argv = restorestack(J->L, oargv);  /* Stack may have been resized. */
    copyTV(J->L, &rd->argv[0], &argv0);
    copyTV(J->L, &rd->argv[1], &argv1);
    if (errcode)
      lj_err_throw(J->L, errcode);  /* Propagate errors. */
    if (rx.resolved) {  /* Resolved call. */
      ptrdiff_t i, nres = (ptrdiff_t)J->maxslot - (ptrdiff_t)parg;
      rd->nres = nres + 1;
      res[0] = TREF_TRUE;  /* Prepend true result. */
      for (i = 1; i <= nres; i++)  /* Move results down. */
        res[i] = res[i+1];
    } else {  /* Propagate pending call. */
      rd->cres = CALLRES_PENDING;
    }
  }  /* else: Interpreter will throw. */
}

/* -- Math library fast functions ----------------------------------------- */

static void recff_math_abs(jit_State *J, TRef *res, RecordFFData *rd)
{
  TRef tr = lj_ir_tonum(J, arg[0]);
  res[0] = emitir(IRTN(IR_ABS), tr, lj_ir_knum_abs(J));
  UNUSED(rd);
}

/* Record rounding functions math.floor and math.ceil. */
static void recff_math_round(jit_State *J, TRef *res, RecordFFData *rd)
{
  if (tref_isinteger(arg[0]))
    res[0] = arg[0];
  else
    res[0] = emitir(IRTN(IR_FPMATH), lj_ir_tonum(J, arg[0]), rd->data);
  /* Note: result is integral (or NaN/Inf), but may not fit into an integer. */
}

/* Record unary math.* functions, mapped to IR_FPMATH opcode. */
static void recff_math_unary(jit_State *J, TRef *res, RecordFFData *rd)
{
  res[0] = emitir(IRTN(IR_FPMATH), lj_ir_tonum(J, arg[0]), rd->data);
}

/* Record binary math.* functions math.atan2 and math.ldexp. */
static void recff_math_binary(jit_State *J, TRef *res, RecordFFData *rd)
{
  TRef tr = lj_ir_tonum(J, arg[0]);
  res[0] = emitir(IRTN(rd->data), tr, lj_ir_tonum(J, arg[1]));
}

/* Record math.asin, math.acos, math.atan. */
static void recff_math_atrig(jit_State *J, TRef *res, RecordFFData *rd)
{
  TRef y = lj_ir_tonum(J, arg[0]);
  TRef x = lj_ir_knum_one(J);
  uint32_t ffid = rd->data;
  if (ffid != FF_math_atan) {
    TRef tmp = emitir(IRTN(IR_MUL), y, y);
    tmp = emitir(IRTN(IR_SUB), x, tmp);
    tmp = emitir(IRTN(IR_FPMATH), tmp, IRFPM_SQRT);
    if (ffid == FF_math_asin) { x = tmp; } else { x = y; y = tmp; }
  }
  res[0] = emitir(IRTN(IR_ATAN2), y, x);
}

static void recff_math_htrig(jit_State *J, TRef *res, RecordFFData *rd)
{
  TRef tr = lj_ir_tonum(J, arg[0]);
  res[0] = lj_ir_call(J, rd->data, tr);
}

static void recff_math_modf(jit_State *J, TRef *res, RecordFFData *rd)
{
  TRef tr = arg[0];
  if (tref_isinteger(tr)) {
    res[0] = tr;
    res[1] = lj_ir_kint(J, 0);
  } else {
    tr = lj_ir_tonum(J, tr);
    res[0] = emitir(IRTN(IR_FPMATH), tr, IRFPM_TRUNC);
    res[1] = emitir(IRTN(IR_SUB), tr, res[0]);
  }
  rd->nres = 2;
}

static void recff_math_degrad(jit_State *J, TRef *res, RecordFFData *rd)
{
  TRef tr = lj_ir_tonum(J, arg[0]);
  res[0] = emitir(IRTN(IR_MUL), tr, lj_ir_knum(J, numV(&rd->fn->c.upvalue[0])));
}

static void recff_math_pow(jit_State *J, TRef *res, RecordFFData *rd)
{
  TRef tr = lj_ir_tonum(J, arg[0]);
  if (!tref_isnumber_str(arg[1]))
    lj_trace_err(J, LJ_TRERR_BADTYPE);
  res[0] = lj_opt_narrow_pow(J, tr, arg[1], &rd->argv[1]);
  UNUSED(rd);
}

static void recff_math_minmax(jit_State *J, TRef *res, RecordFFData *rd)
{
  TRef tr = lj_ir_tonum(J, arg[0]);
  uint32_t op = rd->data;
  BCReg i;
  for (i = 1; arg[i]; i++)
    tr = emitir(IRTN(op), tr, lj_ir_tonum(J, arg[i]));
  res[0] = tr;
}

static void recff_math_random(jit_State *J, TRef *res, RecordFFData *rd)
{
  GCudata *ud = udataV(&rd->fn->c.upvalue[0]);
  TRef tr, one;
  lj_ir_kgc(J, obj2gco(ud), IRT_UDATA);  /* Prevent collection. */
  tr = lj_ir_call(J, IRCALL_lj_math_random_step, lj_ir_kptr(J, uddata(ud)));
  one = lj_ir_knum_one(J);
  tr = emitir(IRTN(IR_SUB), tr, one);
  if (arg[0]) {
    TRef tr1 = lj_ir_tonum(J, arg[0]);
    if (arg[1]) {  /* d = floor(d*(r2-r1+1.0)) + r1 */
      TRef tr2 = lj_ir_tonum(J, arg[1]);
      tr2 = emitir(IRTN(IR_SUB), tr2, tr1);
      tr2 = emitir(IRTN(IR_ADD), tr2, one);
      tr = emitir(IRTN(IR_MUL), tr, tr2);
      tr = emitir(IRTN(IR_FPMATH), tr, IRFPM_FLOOR);
      tr = emitir(IRTN(IR_ADD), tr, tr1);
    } else {  /* d = floor(d*r1) + 1.0 */
      tr = emitir(IRTN(IR_MUL), tr, tr1);
      tr = emitir(IRTN(IR_FPMATH), tr, IRFPM_FLOOR);
      tr = emitir(IRTN(IR_ADD), tr, one);
    }
  }
  res[0] = tr;
}

/* -- Bit library fast functions ------------------------------------------ */

/* Record unary bit.tobit, bit.bnot, bit.bswap. */
static void recff_bit_unary(jit_State *J, TRef *res, RecordFFData *rd)
{
  TRef tr = lj_ir_tobit(J, arg[0]);
  res[0] = (rd->data == IR_TOBIT) ? tr : emitir(IRTI(rd->data), tr, 0);
}

/* Record N-ary bit.band, bit.bor, bit.bxor. */
static void recff_bit_nary(jit_State *J, TRef *res, RecordFFData *rd)
{
  TRef tr = lj_ir_tobit(J, arg[0]);
  uint32_t op = rd->data;
  BCReg i;
  for (i = 1; arg[i]; i++)
    tr = emitir(IRTI(op), tr, lj_ir_tobit(J, arg[i]));
  res[0] = tr;
}

/* Record bit shifts. */
static void recff_bit_shift(jit_State *J, TRef *res, RecordFFData *rd)
{
  TRef tr = lj_ir_tobit(J, arg[0]);
  TRef tsh = lj_ir_tobit(J, arg[1]);
#if !LJ_TARGET_MASKEDSHIFT
  if (!tref_isk(tsh))
    tsh = emitir(IRTI(IR_BAND), tsh, lj_ir_kint(J, 31));
#endif
  res[0] = emitir(IRTI(rd->data), tr, tsh);
}

/* -- String library fast functions --------------------------------------- */

static void recff_string_len(jit_State *J, TRef *res, RecordFFData *rd)
{
  res[0] = emitir(IRTI(IR_FLOAD), lj_ir_tostr(J, arg[0]), IRFL_STR_LEN);
  UNUSED(rd);
}

/* Handle string.byte (rd->data = 0) and string.sub (rd->data = 1). */
static void recff_string_range(jit_State *J, TRef *res, RecordFFData *rd)
{
  TRef trstr = lj_ir_tostr(J, arg[0]);
  TRef trlen = emitir(IRTI(IR_FLOAD), trstr, IRFL_STR_LEN);
  TRef tr0 = lj_ir_kint(J, 0);
  TRef trstart, trend;
  GCstr *str = argv2str(J, &rd->argv[0]);
  int32_t start, end;
  if (rd->data) {  /* string.sub(str, start [,end]) */
    trstart = lj_ir_toint(J, arg[1]);
    trend = tref_isnil(arg[2]) ? lj_ir_kint(J, -1) : lj_ir_toint(J, arg[2]);
    start = argv2int(J, &rd->argv[1]);
    end = tref_isnil(arg[2]) ? -1 : argv2int(J, &rd->argv[2]);
  } else {  /* string.byte(str, [,start [,end]]) */
    if (arg[1]) {
      trstart = lj_ir_toint(J, arg[1]);
      trend = tref_isnil(arg[2]) ? trstart : lj_ir_toint(J, arg[2]);
      start = argv2int(J, &rd->argv[1]);
      end = tref_isnil(arg[2]) ? start : argv2int(J, &rd->argv[2]);
    } else {
      trend = trstart = lj_ir_kint(J, 1);
      end = start = 1;
    }
  }
  if (end < 0) {
    emitir(IRTGI(IR_LT), trend, tr0);
    trend = emitir(IRTI(IR_ADD), emitir(IRTI(IR_ADD), trlen, trend),
                   lj_ir_kint(J, 1));
    end = end+(int32_t)str->len+1;
  } else if ((MSize)end <= str->len) {
    emitir(IRTGI(IR_ULE), trend, trlen);
  } else {
    emitir(IRTGI(IR_GT), trend, trlen);
    end = (int32_t)str->len;
    trend = trlen;
  }
  if (start < 0) {
    emitir(IRTGI(IR_LT), trstart, tr0);
    trstart = emitir(IRTI(IR_ADD), trlen, trstart);
    start = start+(int32_t)str->len;
    emitir(start < 0 ? IRTGI(IR_LT) : IRTGI(IR_GE), trstart, tr0);
    if (start < 0) {
      trstart = tr0;
      start = 0;
    }
  } else {
    if (start == 0) {
      emitir(IRTGI(IR_EQ), trstart, tr0);
      trstart = tr0;
    } else {
      trstart = emitir(IRTI(IR_ADD), trstart, lj_ir_kint(J, -1));
      emitir(IRTGI(IR_GE), trstart, tr0);
      start--;
    }
  }
  if (rd->data) {  /* Return string.sub result. */
    if (end - start >= 0) {
      /* Also handle empty range here, to avoid extra traces. */
      TRef trptr, trslen = emitir(IRTI(IR_SUB), trend, trstart);
      emitir(IRTGI(IR_GE), trslen, tr0);
      trptr = emitir(IRT(IR_STRREF, IRT_PTR), trstr, trstart);
      res[0] = emitir(IRT(IR_SNEW, IRT_STR), trptr, trslen);
    } else {  /* Range underflow: return empty string. */
      emitir(IRTGI(IR_LT), trend, trstart);
      res[0] = lj_ir_kstr(J, lj_str_new(J->L, strdata(str), 0));
    }
  } else {  /* Return string.byte result(s). */
    ptrdiff_t i, len = end - start;
    if (len > 0) {
      TRef trslen = emitir(IRTI(IR_SUB), trend, trstart);
      emitir(IRTGI(IR_EQ), trslen, lj_ir_kint(J, len));
      if (res + len > J->slot + LJ_MAX_JSLOTS)
        lj_trace_err(J, LJ_TRERR_STACKOV);
      rd->nres = len;
      for (i = 0; i < len; i++) {
        TRef tmp = emitir(IRTI(IR_ADD), trstart, lj_ir_kint(J, i));
        tmp = emitir(IRT(IR_STRREF, IRT_PTR), trstr, tmp);
        res[i] = emitir(IRT(IR_XLOAD, IRT_U8), tmp, IRXLOAD_READONLY);
      }
    } else {  /* Empty range or range underflow: return no results. */
      emitir(IRTGI(IR_LE), trend, trstart);
      rd->nres = 0;
    }
  }
}

/* -- Table library fast functions ---------------------------------------- */

static void recff_table_getn(jit_State *J, TRef *res, RecordFFData *rd)
{
  if (tref_istab(arg[0])) {
    res[0] = lj_ir_call(J, IRCALL_lj_tab_len, arg[0]);
  }  /* else: Interpreter will throw. */
  UNUSED(rd);
}

static void recff_table_remove(jit_State *J, TRef *res, RecordFFData *rd)
{
  if (tref_istab(arg[0])) {
    if (!arg[1] || tref_isnil(arg[1])) {  /* Simple pop: t[#t] = nil */
      TRef trlen = lj_ir_call(J, IRCALL_lj_tab_len, arg[0]);
      GCtab *t = tabV(&rd->argv[0]);
      MSize len = lj_tab_len(t);
      emitir(IRTGI(len ? IR_NE : IR_EQ), trlen, lj_ir_kint(J, 0));
      if (len) {
        RecordIndex ix;
        ix.tab = arg[0];
        ix.key = trlen;
        settabV(J->L, &ix.tabv, t);
        setintV(&ix.keyv, len);
        ix.idxchain = 0;
        if (rd->cres != 0) {  /* Specialize load only if result needed. */
          ix.val = 0;
          res[0] = rec_idx(J, &ix);  /* Load previous value. */
          /* Assumes ix.key/ix.tab is not modified for raw rec_idx(). */
        }
        ix.val = TREF_NIL;
        rec_idx(J, &ix);  /* Remove value. */
      } else {
        rd->nres = 0;
      }
    } else {  /* Complex case: remove in the middle. */
      recff_err_nyi(J, rd);
    }
  }  /* else: Interpreter will throw. */
}

static void recff_table_insert(jit_State *J, TRef *res, RecordFFData *rd)
{
  rd->nres = 0;
  if (tref_istab(arg[0]) && arg[1]) {
    if (!arg[2]) {  /* Simple push: t[#t+1] = v */
      TRef trlen = lj_ir_call(J, IRCALL_lj_tab_len, arg[0]);
      GCtab *t = tabV(&rd->argv[0]);
      RecordIndex ix;
      ix.tab = arg[0];
      ix.val = arg[1];
      ix.key = emitir(IRTI(IR_ADD), trlen, lj_ir_kint(J, 1));
      settabV(J->L, &ix.tabv, t);
      setintV(&ix.keyv, lj_tab_len(t) + 1);
      ix.idxchain = 0;
      rec_idx(J, &ix);  /* Set new value. */
    } else {  /* Complex case: insert in the middle. */
      recff_err_nyi(J, rd);
    }
  }  /* else: Interpreter will throw. */
}

/* -- I/O library fast functions ------------------------------------------ */

/* Get FILE* for I/O function. Any I/O error aborts recording, so there's
** no need to encode the alternate cases for any of the guards.
*/
static TRef recff_io_fp(jit_State *J, TRef *res, uint32_t id)
{
  TRef tr, ud, fp;
  if (id) {  /* io.func() */
    tr = lj_ir_kptr(J, &J2G(J)->gcroot[id]);
    ud = emitir(IRT(IR_XLOAD, IRT_UDATA), tr, 0);
  } else {  /* fp:method() */
    ud = arg[0];
    if (!tref_isudata(ud))
      lj_trace_err(J, LJ_TRERR_BADTYPE);
    tr = emitir(IRT(IR_FLOAD, IRT_U8), ud, IRFL_UDATA_UDTYPE);
    emitir(IRTGI(IR_EQ), tr, lj_ir_kint(J, UDTYPE_IO_FILE));
  }
  fp = emitir(IRT(IR_FLOAD, IRT_LIGHTUD), ud, IRFL_UDATA_FILE);
  emitir(IRTG(IR_NE, IRT_LIGHTUD), fp, lj_ir_knull(J, IRT_LIGHTUD));
  return fp;
}

static void recff_io_write(jit_State *J, TRef *res, RecordFFData *rd)
{
  TRef fp = recff_io_fp(J, res, rd->data);
  TRef zero = lj_ir_kint(J, 0);
  TRef one = lj_ir_kint(J, 1);
  ptrdiff_t i = rd->data == 0 ? 1 : 0;
  for (; arg[i]; i++) {
    TRef str = lj_ir_tostr(J, arg[i]);
    TRef buf = emitir(IRT(IR_STRREF, IRT_PTR), str, zero);
    TRef len = emitir(IRTI(IR_FLOAD), str, IRFL_STR_LEN);
    if (tref_isk(len) && IR(tref_ref(len))->i == 1) {
      TRef tr = emitir(IRT(IR_XLOAD, IRT_U8), buf, IRXLOAD_READONLY);
      tr = lj_ir_call(J, IRCALL_fputc, tr, fp);
      if (rd->cres != 0)  /* Check result only if requested. */
        emitir(IRTGI(IR_NE), tr, lj_ir_kint(J, -1));
    } else {
      TRef tr = lj_ir_call(J, IRCALL_fwrite, buf, one, len, fp);
      if (rd->cres != 0)  /* Check result only if requested. */
        emitir(IRTGI(IR_EQ), tr, len);
    }
  }
  res[0] = TREF_TRUE;
}

static void recff_io_flush(jit_State *J, TRef *res, RecordFFData *rd)
{
  TRef fp = recff_io_fp(J, res, rd->data);
  TRef tr = lj_ir_call(J, IRCALL_fflush, fp);
  if (rd->cres != 0)  /* Check result only if requested. */
    emitir(IRTGI(IR_EQ), tr, lj_ir_kint(J, 0));
  res[0] = TREF_TRUE;
}

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

#undef arg

#include "lj_recdef.h"

/* Record return. */
static void rec_ret(jit_State *J, BCReg rbase, ptrdiff_t gotresults)
{
  TValue *frame = J->L->base - 1;
  ptrdiff_t i;
  for (i = 0; i < gotresults; i++)
    getslot(J, rbase+i);  /* Ensure all results have a reference. */
  J->tailcalled = 0;
  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);
    lua_assert(J->baseslot > 1);
    J->base[--rbase] = TREF_TRUE;  /* Prepend true to results. */
    gotresults++;
    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);
    for (i = 0; i < nresults; i++)  /* Adjust results. */
      J->base[i-1] = 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--;
      lua_assert(J->baseslot > cbase+1);
      J->baseslot -= cbase+1;
      J->base -= cbase+1;
    } else if (J->parent == 0) {
      /* Return to lower frame would leave the loop in a root trace. */
      lj_trace_err(J, LJ_TRERR_LLEAVE);
    } else {  /* Return to lower frame. Guard for the target we return to. */
      GCproto *pt = funcproto(frame_func(frame - (cbase+1)));
      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_PTR), trpt, trpc);
      J->retdepth++;
      J->needsnap = 1;
      lua_assert(J->baseslot == 1);
      /* Shift result slots up and clear the slots of the new frame below. */
      memmove(J->base + cbase, J->base-1, sizeof(TRef)*nresults);
      memset(J->base-1, 0, sizeof(TRef)*(cbase+1));
    }
  } 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;
    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) {
      lua_assert(0);
    } else {
      /* Result type already specialized. */
      lua_assert(cont == lj_cont_condf || cont == lj_cont_condt);
    }
  } else {
    lj_trace_err(J, LJ_TRERR_NYIRETL);  /* NYI: handle return to C frame. */
  }
  lua_assert(J->baseslot >= 1);
}

/* Check unroll limits for calls. */
static void check_call_unroll(jit_State *J, GCfunc *fn)
{
  IRRef fref = tref_ref(J->base[-1]);
  int32_t count = 0;
  ptrdiff_t s;
  for (s = (ptrdiff_t)J->baseslot - 1; s > 0; s--)
    if ((J->slot[s] & TREF_FRAME) && tref_ref(J->slot[s]) == fref)
      count++;
  if (bc_op(J->cur.startins) == BC_CALL &&
      funcproto(fn) == &gcref(J->cur.startpt)->pt) {
    if (count + J->tailcalled > J->param[JIT_P_recunroll])
      lj_trace_err(J, LJ_TRERR_NYIRECU);
  } else {
    if (count > J->param[JIT_P_callunroll])
      lj_trace_err(J, LJ_TRERR_CUNROLL);
  }
}

/* Record call. Returns 0 for pending calls and 1 for resolved calls. */
static int rec_call(jit_State *J, BCReg func, ptrdiff_t cres, ptrdiff_t nargs)
{
  RecordFFData rd;
  TRef trfunc, *res = &J->base[func];
  TValue *tv = &J->L->base[func];

  if (tref_isfunc(res[0])) {  /* Regular function call. */
    rd.fn = funcV(tv);
    rd.argv = tv+1;
    rd.metacall = 0;
  } else {  /* Otherwise resolve __call metamethod for called object. */
    RecordIndex ix;
    ptrdiff_t i;
    ix.tab = res[0];
    copyTV(J->L, &ix.tabv, tv);
    if (!rec_mm_lookup(J, &ix, MM_call) || !tref_isfunc(ix.mobj))
      lj_trace_err(J, LJ_TRERR_NOMM);
    /* Update the recorder state, but not the Lua stack. */
    for (i = ++nargs; i > 0; i--)
      res[i] = res[i-1];
    res[0] = ix.mobj;
    rd.fn = funcV(&ix.mobjv);
    rd.argv = tv;  /* The called object is the 1st arg. */
    rd.metacall = 1;
  }

  /* Specialize to the runtime value of the called function. */
  trfunc = lj_ir_kfunc(J, rd.fn);
  emitir(IRTG(IR_EQ, IRT_FUNC), res[0], trfunc);
  res[0] = trfunc | TREF_FRAME;

  /* Add frame links. */
  J->frame[J->framedepth++] = SNAP_MKPC(J->pc+1);
  if (cres == CALLRES_CONT)  /* Continuations need an extra frame stack slot. */
    J->frame[J->framedepth++] = SNAP_MKFTSZ((func+1)*sizeof(TValue)+FRAME_CONT);
    /* NYI: func is wrong if any fast function ever sets up a continuation. */
  if (J->framedepth > LJ_MAX_JFRAME)
    lj_trace_err(J, LJ_TRERR_STACKOV);

  if (isluafunc(rd.fn)) {  /* Record call to Lua function. */
    GCproto *pt = funcproto(rd.fn);
    if ((pt->flags & PROTO_NO_JIT))
      lj_trace_err(J, LJ_TRERR_CJITOFF);
    if ((pt->flags & PROTO_IS_VARARG))
      lj_trace_err(J, LJ_TRERR_NYIVF);
    if (cres == CALLRES_TAILCALL) {
      ptrdiff_t i;
      /* Tailcalls can form a loop, so count towards the loop unroll limit. */
      if (++J->tailcalled > J->loopunroll)
        lj_trace_err(J, LJ_TRERR_LUNROLL);
      for (i = 0; i <= nargs; i++)  /* Move func + args down. */
        J->base[i-1] = res[i];
      J->framedepth--;
      /* Note: the new FRAME is now at J->base[-1] (even for slot #0). */
    } else {  /* Regular call. */
      J->base += func+1;
      J->baseslot += func+1;
    }
    if (J->baseslot + pt->framesize >= LJ_MAX_JSLOTS)
      lj_trace_err(J, LJ_TRERR_STACKOV);
    /* Fill up missing args with nil. */
    while (nargs < pt->numparams)
      J->base[nargs++] = TREF_NIL;
    /* The remaining slots should never be read before they are written. */
    J->maxslot = pt->numparams;
    check_call_unroll(J, rd.fn);
    return 0;  /* No result yet. */
  } else {  /* Record call to C function or fast function. */
    uint32_t m = 0;
    BCReg oldmaxslot = J->maxslot;
    res[1+nargs] = 0;
    rd.nargs = nargs;
    if (rd.fn->c.ffid < sizeof(recff_idmap)/sizeof(recff_idmap[0]))
      m = recff_idmap[rd.fn->c.ffid];
    rd.data = m & 0xff;
    rd.cres = cres;
    rd.nres = 1;  /* Default is one result. */
    (recff_func[m >> 8])(J, res, &rd);  /* Call recff_* handler. */
    J->framedepth--;
    cres = rd.cres;
    if (cres >= 0) {
      /* Caller takes fixed number of results: local a,b = f() */
      J->maxslot = func + (BCReg)cres;
      while (rd.nres < cres)  /* Fill up missing results with nil. */
        res[rd.nres++] = TREF_NIL;
    } else if (cres == CALLRES_MULTI) {
      /* Caller takes any number of results: return 1,f() */
      J->maxslot = func + (BCReg)rd.nres;
    } else if (cres == CALLRES_TAILCALL) {
      /* Tail call: return f() */
      rec_ret(J, func, rd.nres);
    } else if (cres == CALLRES_CONT) {
      /* Note: immediately resolved continuations must not change J->maxslot. */
      J->maxslot = oldmaxslot;
      J->framedepth--;
      res[rd.nres] = TREF_NIL;  /* Turn 0 results into nil result. */
    } else {
      lua_assert(cres == CALLRES_PENDING);
      J->framedepth++;
      return 0;  /* Pending call, no result yet. */
    }
    return 1;  /* Result resolved immediately. */
  }
}

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

static TRef rec_tnew(jit_State *J, uint32_t ah)
{
  uint32_t asize = ah & 0x7ff;
  uint32_t hbits = ah >> 11;
  if (asize == 0x7ff) asize = 0x801;
  return emitir(IRT(IR_TNEW, IRT_TAB), asize, hbits);
}

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

/* Optimize state after comparison. */
static void optstate_comp(jit_State *J, int cond)
{
  BCIns jmpins = J->pc[1];
  const BCIns *npc = J->pc + 2 + (cond ? bc_j(jmpins) : 0);
  SnapShot *snap = &J->cur.snap[J->cur.nsnap-1];
  /* Avoid re-recording the comparison in side traces. */
  J->cur.snapmap[snap->mapofs + snap->nent] = SNAP_MKPC(npc);
  J->needsnap = 1;
  /* Shrink last snapshot if possible. */
  if (bc_a(jmpins) < J->maxslot) {
    J->maxslot = bc_a(jmpins);
    lj_snap_shrink(J);
  }
}

/* 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;

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

  /* 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

  /* 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;
  case BCMnum: { lua_Number n = proto_knum(J->pt, rb);
    setnumV(rbv, n); ix.tab = rb = lj_ir_knumint(J, n); } 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: setitype(rcv, (int32_t)~rc); rc = TREF_PRI(IRT_NIL+rc); break;
  case BCMnum: { lua_Number n = proto_knum(J->pt, rc);
    setnumV(rcv, n); ix.key = rc = lj_ir_knumint(J, n); } 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:
    /* 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_TONUM), ra, 0);
          ta = IRT_NUM;
        } else if (ta == IRT_NUM && tc == IRT_INT) {
          rc = emitir(IRTN(IR_TONUM), rc, 0);
        } else if (!((ta == IRT_FALSE || ta == IRT_TRUE) &&
                     (tc == IRT_FALSE || tc == IRT_TRUE))) {
          break;  /* Interpreter will throw for two different types. */
        }
      }
      lj_snap_add(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(numV(rav), numV(rcv), (IROp)irop)) irop ^= 5;
      } else if (ta == IRT_INT) {
        if (!lj_ir_numcmp(numV(rav), numV(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);
      optstate_comp(J, ((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:
    /* Emit nothing for two non-table, non-udata consts. */
    if (!(tref_isk2(ra, rc) && !(tref_istab(ra) || tref_isudata(ra)))) {
      int diff;
      lj_snap_add(J);
      diff = rec_objcmp(J, ra, rc, rav, rcv);
      if (diff == 1 && (tref_istab(ra) || tref_isudata(ra))) {
        /* Only check __eq if different, but the same type (table or udata). */
        rec_mm_equal(J, &ix, (int)op);
        break;
      }
      optstate_comp(J, ((int)op & 1) == !diff);
    }
    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;

  /* -- 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 (tref_istab(rc)) {
      rc = lj_ir_call(J, IRCALL_lj_tab_len, rc);
    } else {
      ix.tab = rc;
      copyTV(J->L, &ix.tabv, &ix.keyv);
      ix.key = IRT_NIL;
      setnilV(&ix.keyv);
      rc = rec_mm_arith(J, &ix, MM_len);
    }
    break;

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

  case BC_UNM:
    if (tref_isnumber_str(rc)) {
      rc = lj_ir_tonum(J, rc);
      rc = emitir(IRTN(IR_NEG), rc, lj_ir_knum_neg(J));
    } else {
      ix.tab = rc;
      copyTV(J->L, &ix.tabv, &ix.keyv);
      rc = rec_mm_arith(J, &ix, MM_unm);
    }
    break;

  case BC_ADDNV: case BC_SUBNV: case BC_MULNV: case BC_DIVNV: case BC_MODNV:
    ix.tab = rc; ix.key = rc = rb; rb = ix.tab;
    copyTV(J->L, &ix.valv, &ix.tabv);
    copyTV(J->L, &ix.tabv, &ix.keyv);
    copyTV(J->L, &ix.keyv, &ix.valv);
    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)) {
      rb = lj_ir_tonum(J, rb);
      rc = lj_ir_tonum(J, rc);
      rc = emitir(IRTN((int)mm - (int)MM_add + (int)IR_ADD), rb, rc);
    } 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);
    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_pow(J, lj_ir_tonum(J, rb), rc, rcv);
    else
      rc = rec_mm_arith(J, &ix, MM_pow);
    break;

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

  case BC_KSTR: case BC_KNUM: case BC_KPRI: case BC_MOV:
    break;
  case BC_KSHORT:
    rc = lj_ir_kint(J, (int32_t)(int16_t)rc);
    break;
  case BC_KNIL:
    while (ra <= rc)
      J->base[ra++] = TREF_NIL;
    if (rc >= J->maxslot) J->maxslot = rc+1;
    break;

  /* -- 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 = rec_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 = rec_idx(J, &ix);
    break;

  case BC_TNEW:
    rc = rec_tnew(J, rc);
    break;
  case BC_TDUP:
    rc = emitir(IRT(IR_TDUP, IRT_TAB),
                lj_ir_ktab(J, gco2tab(proto_kgc(J->pt, ~(ptrdiff_t)rc))), 0);
    break;

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

  case BC_ITERC:
    J->base[ra] = getslot(J, ra-3);
    J->base[ra+1] = getslot(J, ra-2);
    J->base[ra+2] = getslot(J, ra-1);
    { /* Have to do the actual copy now because rec_call needs the values. */
      TValue *b = &J->L->base[ra];
      copyTV(J->L, b, b-3);
      copyTV(J->L, b+1, b-2);
      copyTV(J->L, b+2, b-1);
    }
    goto callop;

  case BC_CALLMT:
    rb = (TRef)(CALLRES_TAILCALL+1);
    /* fallthrough */
  case BC_CALLM:
    /* L->top is set to L->base+ra+rc+NRESULTS-1+1, see lj_dispatch_ins(). */
    rc = (BCReg)(J->L->top - J->L->base) - ra;
    goto callop;

  case BC_CALLT:
    rb = (TRef)(CALLRES_TAILCALL+1);
    /* fallthrough */
  case BC_CALL:
  callop:
    rec_call(J, ra, (ptrdiff_t)rb-1, (ptrdiff_t)rc-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:
    rec_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:
    lua_assert(bc_op(pc[(ptrdiff_t)rc-BCBIAS_J]) == BC_JFORL);
    if (rec_for(J, pc, 0) != LOOPEV_LEAVE)  /* Link to existing loop. */
      rec_stop(J, 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));
    break;

  case BC_JFORL:
    rec_loop_jit(J, rc, rec_for(J, pc+bc_j(J->trace[rc]->startins), 1));
    break;
  case BC_JITERL:
    rec_loop_jit(J, rc, rec_iterl(J, J->trace[rc]->startins));
    break;
  case BC_JLOOP:
    rec_loop_jit(J, rc, rec_loop(J, ra));
    break;

  case BC_IFORL:
  case BC_IITERL:
  case BC_ILOOP:
    lj_trace_err(J, LJ_TRERR_LBLACKL);
    break;

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

  case BC_CAT:
  case BC_UCLO:
  case BC_FNEW:
  case BC_TSETM:
  case BC_VARG:
  default:
    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) J->maxslot = ra+1;
  }

#undef rav
#undef rbv
#undef rcv

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

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

/* Setup recording for a FORL loop. */
static void rec_setup_forl(jit_State *J, const BCIns *fori)
{
  BCReg ra = bc_a(*fori);
  cTValue *forbase = &J->L->base[ra];
  IRType t = (J->flags & JIT_F_OPT_NARROW) ? lj_opt_narrow_forl(forbase)
                                           : IRT_NUM;
  TRef stop = fori_arg(J, fori, ra+FORL_STOP, t);
  TRef step = fori_arg(J, fori, ra+FORL_STEP, t);
  int dir = (0 <= numV(&forbase[FORL_STEP]));
  lua_assert(bc_op(*fori) == BC_FORI || bc_op(*fori) == BC_JFORI);
  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 (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 (with dead result). */
        emitir(IRTGI(IR_ADDOV), step, stop);
      }
    }
  } else if (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));
  }
  if (t == IRT_INT && !find_kinit(J, fori, ra+FORL_IDX, IRT_INT))
    t |= IRT_GUARD;
  J->base[ra+FORL_EXT] = sloadt(J, (int32_t)(ra+FORL_IDX), t, IRSLOAD_INHERIT);
  J->maxslot = ra+FORL_EXT+1;
}

/* 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:
    lua_assert(bc_op(pc[-1]) == BC_ITERC);
    J->maxslot = ra + bc_b(pc[-1]) - 1;
    J->bc_extent = (MSize)(-bc_j(ins))*sizeof(BCIns);
    pc += 1+bc_j(ins);
    lua_assert(bc_op(pc[-1]) == BC_JMP);
    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;
  default:
    lua_assert(0);
    break;
  }
  return pc;
}

/* Setup recording for a side trace. */
static void rec_setup_side(jit_State *J, Trace *T)
{
  SnapShot *snap = &T->snap[J->exitno];
  SnapEntry *map = &T->snapmap[snap->mapofs];
  MSize n, nent = snap->nent;
  BloomFilter seen = 0;
  /* Emit IR for slots inherited from parent snapshot. */
  for (n = 0; n < nent; n++) {
    SnapEntry sn = map[n];
    IRRef ref = snap_ref(sn);
    BCReg s = snap_slot(sn);
    IRIns *ir = &T->ir[ref];
    TRef tr;
    /* The bloom filter avoids O(nent^2) overhead for de-duping slots. */
    if (bloomtest(seen, ref)) {
      MSize j;
      for (j = 0; j < n; j++)
        if (snap_ref(map[j]) == ref) {
          tr = J->slot[snap_slot(map[j])];
          goto setslot;
        }
    }
    bloomset(seen, ref);
    switch ((IROp)ir->o) {
    /* Only have to deal with constants that can occur in stack slots. */
    case IR_KPRI: tr = TREF_PRI(irt_type(ir->t)); break;
    case IR_KINT: tr = lj_ir_kint(J, ir->i); break;
    case IR_KGC:  tr = lj_ir_kgc(J, ir_kgc(ir), irt_t(ir->t)); break;
    case IR_KNUM: tr = lj_ir_knum_addr(J, ir_knum(ir)); break;
    case IR_KPTR:  tr = lj_ir_kptr(J, ir_kptr(ir)); break;  /* Continuation. */
    /* Inherited SLOADs don't need a guard or type check. */
    case IR_SLOAD:
      tr = emitir_raw(ir->ot & ~IRT_GUARD, s,
             (ir->op2&IRSLOAD_READONLY) | IRSLOAD_INHERIT|IRSLOAD_PARENT);
      break;
    /* Parent refs are already typed and don't need a guard. */
    default:
      tr = emitir_raw(IRT(IR_SLOAD, irt_type(ir->t)), s,
                      IRSLOAD_INHERIT|IRSLOAD_PARENT);
      break;
    }
  setslot:
    J->slot[s] = tr | (sn&(SNAP_CONT|SNAP_FRAME));  /* Same as TREF_* flags. */
    if ((sn & SNAP_FRAME) && s != 0)
      J->baseslot = s+1;
  }
  J->base = J->slot + J->baseslot;
  J->maxslot = snap->nslots - J->baseslot;
  J->framedepth = snap->depth;  /* Copy frames from snapshot. */
  memcpy(J->frame, &map[nent+1], sizeof(SnapEntry)*(size_t)snap->depth);
  lj_snap_add(J);
}

/* 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));
  memset(J->bpropcache, 0, sizeof(J->bpropcache));

  J->baseslot = 1;  /* Invoking function is at base[-1]. */
  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_PTR), 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;

  setgcref(J->cur.startpt, obj2gco(J->pt));
  J->startpc = J->pc;
  if (J->parent) {  /* Side trace. */
    Trace *T = J->trace[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_setup_forl(J, J->pc-1);
        goto sidecheck;
      }
    } else {
      J->startpc = NULL;  /* Prevent forming an extra loop. */
    }
    rec_setup_side(J, T);
  sidecheck:
    if (J->trace[J->cur.root]->nchild >= J->param[JIT_P_maxside] ||
        T->snap[J->exitno].count >= J->param[JIT_P_hotexit] +
                                    J->param[JIT_P_tryside])
      rec_stop(J, TRACE_INTERP);
  } else {  /* Root trace. */
    J->cur.root = 0;
    if (J->pc >= proto_bc(J->pt)) {  /* Not a hot CALL? */
      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.
      */
    } else {
      J->cur.startins = BCINS_ABC(BC_CALL, 0, 0, 0);
    }
    lj_snap_add(J);
    if (bc_op(J->cur.startins) == BC_FORL)
      rec_setup_forl(J, J->pc-1);
    if (1 + J->pt->framesize >= LJ_MAX_JSLOTS)
      lj_trace_err(J, LJ_TRERR_STACKOV);
  }
}

#undef IR
#undef emitir_raw
#undef emitir

#endif