ljx

lj_record.c (87882B)

---

 /*
 ** Trace recorder (bytecode -> SSA IR).
 ** Copyright (C) 2005-2016 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"
 #include "ljx_bitwise.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;
   lua_assert(nk <= REF_BIAS && nins >= REF_BIAS && nins < 65536);
   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;
     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);
       if (irt_is64(ir->t) && ir->o != IR_KNULL)
 	i++;
       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->o == IR_NOP || IR(ir->prev)->o == ir->o);
     }
   }
 }
 
 /* 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;
   lua_assert(J->baseslot >= 1+LJ_FR2 && J->baseslot < LJ_MAX_JSLOTS);
   lua_assert(J->baseslot == 1+LJ_FR2 || (J->slot[J->baseslot-1] & TREF_FRAME));
   lua_assert(nslots < LJ_MAX_JSLOTS);
   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. */
       if (!LJ_FR2 || ref || !(tr & (TREF_FRAME | TREF_CONT))) {
 	lua_assert(ref >= J->cur.nk && ref < J->cur.nins);
 	ir = IR(ref);
 	lua_assert(irt_t(ir->t) == tref_t(tr));
       }
       if (s == 0) {
 	lua_assert(tref_isfunc(tr));
 #if LJ_FR2
       } else if (s == 1) {
 	lua_assert(0);
 #endif
       } else if ((tr & TREF_FRAME)) {
 	GCfunc *fn = gco2func(frame_gc(tv));
 	BCReg delta = (BCReg)(tv - frame_prev(tv));
 #if LJ_FR2
 	if (ref)
 	  lua_assert(ir_knum(ir)->u64 == tv->u64);
 	tr = J->slot[s-1];
 	ir = IR(tref_ref(tr));
 #endif
 	lua_assert(tref_isfunc(tr));
 	if (tref_isk(tr)) lua_assert(fn == ir_kfunc(ir));
 	lua_assert(s > delta + LJ_FR2 ? (J->slot[s-delta] & TREF_FRAME)
 				      : (s == delta + LJ_FR2));
 	depth++;
       } else if ((tr & TREF_CONT)) {
 #if LJ_FR2
 	if (ref)
 	  lua_assert(ir_knum(ir)->u64 == tv->u64);
 #else
 	lua_assert(ir_kptr(ir) == gcrefp(tv->gcr, void));
 #endif
 	lua_assert((J->slot[s+1+LJ_FR2] & TREF_FRAME));
 	depth++;
       } else {
 	if (tvisnumber(tv))
 	  lua_assert(tref_isnumber(tr));  /* Could be IRT_INT etc., too. */
 	else
 	  lua_assert(itype2irt(tv) == tref_type(tr));
 	if (tref_isk(tr)) {  /* Compare constants. */
 	  TValue tvk;
 	  lj_ir_kvalue(J->L, &tvk, ir);
 	  if (!(tvisnum(&tvk) && tvisnan(&tvk)))
 	    lua_assert(lj_obj_equal(tv, &tvk));
 	  else
 	    lua_assert(tvisnum(tv) && tvisnan(tv));
 	}
       }
     }
   }
   lua_assert(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];
   lua_assert(J->baseslot == 1+LJ_FR2);
   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);
 }
 
 /* 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 = 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]);
   lua_assert(bc_op(*fori) == BC_FORI || bc_op(*fori) == BC_JFORI);
   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;
   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);
       lua_assert(tref_isnumber_str(tr[i]));
       if (tref_isstr(tr[i]))
 	tr[i] = emitir(IRTG(IR_STRTO, IRT_NUM), tr[i], 0);
       if (t == IRT_INT) {
 	if (!tref_isinteger(tr[i]))
 	  tr[i] = emitir(IRTGI(IR_CONV), tr[i], IRCONV_INT_NUM|IRCONV_CHECK);
       } else {
 	if (!tref_isnum(tr[i]))
 	  tr[i] = emitir(IRTN(IR_CONV), tr[i], IRCONV_NUM_INT);
       }
     }
     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)
 {
   if (ra < J->maxslot) 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 (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;
   lua_assert(J->prof_mode == 'f' || J->prof_mode == 'l');
   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;
 }
 
 /* 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] = 0;
   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;
   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);
     lua_assert(J->baseslot > 1+LJ_FR2);
     gotresults++;
     rbase += cbase;
     J->baseslot -= (BCReg)cbase;
     J->base -= cbase;
     J->base[--rbase] = TREF_TRUE;  /* Prepend true to results. */
     frame = frame_prevd(frame);
   }
   /* 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);
     lua_assert(J->baseslot > 1+LJ_FR2);
     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 (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--;
       lua_assert(J->baseslot > cbase+1+LJ_FR2);
       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 {  /* 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;
       lua_assert(J->baseslot == 1+LJ_FR2);
       /* 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. */
 	TValue *b = J->L->base, save;  /* Simulate lower frame and result. */
 	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;
 	copyTV(J->L, b-(2<<LJ_FR2), &save);
       }
       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. */
       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+LJ_FR2);
 }
 
 /* -- 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_USERDATA) {
       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_51
     base[2] = TREF_NIL; setnilV(basev+2);
 #else
     base[2] = tr; copyTV(J->L, basev+2, tv);
 #endif
     lj_record_call(J, func, 2);
   } else {
     if (!LJ_51 && 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_51
     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;
     }
 #else
     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;
 #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 {
     lua_assert(tref_iscdata(ix->key));
     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;
       lua_assert(irt_isint(J->scev.t) && ir->o == IR_SLOAD);
       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. */
 	emitir(IRTG(IR_ABC, IRT_P32), 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(IRTG(IR_ABC, IRT_P32), 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. */
     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, 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, 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;
 
   /* Remember original table before overwriting it. */
   ix->otab = ix->tab;
   ix->otabv = ix->tabv;
 
   while (!tref_istab(ix->tab)) { /* Handle non-table lookup. */
     /* Never call raw lj_record_idx() on non-table. */
     lua_assert(ix->idxchain != 0);
     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 {
         base[3] = ix->otab;
         copyTV(J->L, tv+3, &ix->otabv);
         lj_record_call(J, func, 3);  /* res = mobj(tab, key, origtab) */
 	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)) {
 	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_CONV), key, IRCONV_NUM_INT);
 	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->flags & UV_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_FINALIZED)) {
 	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;
     lua_assert(val == 0);
     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;
   lua_assert((pt->flags & PROTO_VARARG));
   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;
   lua_assert(frame_isvarg(J->L->base-1));
   if (J->framedepth > 0) {  /* Simple case: varargs defined on-trace. */
     ptrdiff_t i;
     if (nvararg < 0) nvararg = 0;
     if (nresults == -1) {
       nresults = nvararg;
       J->maxslot = dst + (BCReg)nvararg;
     } else if (dst + nresults > J->maxslot) {
       J->maxslot = dst + (BCReg)nresults;
     }
     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));
 	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 (dst + (BCReg)nresults > J->maxslot)
 	J->maxslot = dst + (BCReg)nresults;
     } else if (select_detect(J)) {  /* y = select(x, ...) */
       TRef tridx = J->base[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))
 	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 ------------------------------------------------------- */
 
 static TRef rec_cat(jit_State *J, BCReg baseslot, BCReg topslot)
 {
   TRef *top = &J->base[topslot];
   TValue savetv[5];
   BCReg s;
   RecordIndex ix;
   lua_assert(baseslot < topslot);
   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) return tr;  /* Return simple concatenation result. */
     /* Pass partial result. */
     topslot = J->maxslot--;
     *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];
   memcpy(savetv, &J->L->base[topslot-1], sizeof(savetv));  /* Save slots. */
   rec_mm_arith(J, &ix, MM_concat);  /* Call __concat metamethod. */
   memcpy(&J->L->base[topslot-1], savetv, sizeof(savetv));  /* Restore slots. */
   return 0;  /* No result yet. */
 }
 
 /* -- 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: lua_assert(0); break;
     }
     J->postproc = LJ_POST_NONE;
   }
 
   /* Need snapshot before recording next bytecode (e.g. after a store). */
   if (J->needsnap) {
     J->needsnap = 0;
     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_51) {
           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_51 && tref_istab(rc))
       rc = lj_ir_call(J, IRCALL_lj_tab_len, rc);
     else
       rc = rec_mm_len(J, rc, rcv);
     break;
 #if LJ_53
   /* -- Bitwise ops ---------------------------------------------------- */
   case BC_BNOT:
     ix.tab = rc;
     copyTV(J->L, rbv, rcv);
   case BC_IDIV:
   case BC_BAND:
   case BC_BOR:
   case BC_BXOR:
   case BC_SHL:
   case BC_SHR:
   {
     MMS opmm = bcmode_mm(op);
     if (!(rc = ljx_rec_bitwise(J, rb, rc, rbv, rcv, opmm)))
       rc = rec_mm_arith(J, &ix, bcmode_mm(op));
     break;
   }
 #endif
 
   /* -- 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_pow(J, rb, rc, rbv, rcv);
     else
       rc = rec_mm_arith(J, &ix, MM_pow);
     break;
 
   /* -- Miscellaneous ops ------------------------------------------------- */
 
   case BC_CAT:
     rc = rec_cat(J, rb, rc);
     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:
     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);
     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:
     lua_assert(bc_op(pc[(ptrdiff_t)rc-BCBIAS_J]) == BC_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));
     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));
     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:
     lua_assert(0);  /* Cannot happen. No hotcall counting for varag funcs. */
     break;
 
   case BC_FUNCC:
   case BC_FUNCCW:
     lj_ffrecord_func(J);
     break;
 
   default:
     if (op >= BC__MAX) {
       lj_ffrecord_func(J);
       break;
     }
   case BC_UCLO:
     /* No UVs to be closed or none concerning us -> NOP */
     if ((!gcref(J->L->openupval)) ||
         (uvval((gco2uv(gcref(J->L->openupval)))) < (lbase + ra))) {
       if (ra < J->maxslot)
         J->maxslot = ra;  /* Shrink used slots. */
       break;
     }
     /* TBD: Need to close UV -> call lj_func_closeuv */
     /* fallthrough */
   case BC_ITERN:
   case BC_ISNEXT:
   case BC_FNEW:
   case BC_ESETV:
     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. */
   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 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;
   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:
     lua_assert(0);
     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