Esempio n. 1
0
/* Slow, but sure way to check whether a SPLIT pass is needed. */
static int split_needsplit(jit_State *J)
{
  IRIns *ir, *irend;
  IRRef ref;
  for (ir = IR(REF_FIRST), irend = IR(J->cur.nins); ir < irend; ir++)
    if (irt_isint64(ir->t))
      return 1;
  for (ref = J->chain[IR_CONV]; ref; ref = IR(ref)->prev)
    if ((IR(ref)->op2 & IRCONV_SRCMASK) == IRT_I64 ||
	(IR(ref)->op2 & IRCONV_SRCMASK) == IRT_U64)
      return 1;
  return 0;  /* Nope. */
}
Esempio n. 2
0
/* Slow, but sure way to check whether a SPLIT pass is needed. */
static int split_needsplit(jit_State *J)
{
  IRIns *ir, *irend;
  IRRef ref;
  for (ir = IR(REF_FIRST), irend = IR(J->cur.nins); ir < irend; ir++)
    if (LJ_SOFTFP ? irt_is64orfp(ir->t) : irt_isint64(ir->t))
      return 1;
  if (LJ_SOFTFP) {
    for (ref = J->chain[IR_SLOAD]; ref; ref = IR(ref)->prev)
      if ((IR(ref)->op2 & IRSLOAD_CONVERT))
	return 1;
    if (J->chain[IR_TOBIT])
      return 1;
  }
  for (ref = J->chain[IR_CONV]; ref; ref = IR(ref)->prev) {
    IRType st = (IR(ref)->op2 & IRCONV_SRCMASK);
    if ((LJ_SOFTFP && (st == IRT_NUM || st == IRT_FLOAT)) ||
	st == IRT_I64 || st == IRT_U64)
      return 1;
  }
  return 0;  /* Nope. */
}
Esempio n. 3
0
/* Transform the old IR to the new IR. */
static void split_ir(jit_State *J)
{
  IRRef nins = J->cur.nins, nk = J->cur.nk;
  MSize irlen = nins - nk;
  MSize need = (irlen+1)*(sizeof(IRIns) + sizeof(IRRef1));
  IRIns *oir = (IRIns *)lj_str_needbuf(J->L, &G(J->L)->tmpbuf, need);
  IRRef1 *hisubst;
  IRRef ref, snref;
  SnapShot *snap;

  /* Copy old IR to buffer. */
  memcpy(oir, IR(nk), irlen*sizeof(IRIns));
  /* Bias hiword substitution table and old IR. Loword kept in field prev. */
  hisubst = (IRRef1 *)&oir[irlen] - nk;
  oir -= nk;

  /* Remove all IR instructions, but retain IR constants. */
  J->cur.nins = REF_FIRST;
  J->loopref = 0;

  /* Process constants and fixed references. */
  for (ref = nk; ref <= REF_BASE; ref++) {
    IRIns *ir = &oir[ref];
    if ((LJ_SOFTFP && ir->o == IR_KNUM) || ir->o == IR_KINT64) {
      /* Split up 64 bit constant. */
      TValue tv = *ir_k64(ir);
      ir->prev = lj_ir_kint(J, (int32_t)tv.u32.lo);
      hisubst[ref] = lj_ir_kint(J, (int32_t)tv.u32.hi);
    } else {
      ir->prev = ref;  /* Identity substitution for loword. */
      hisubst[ref] = 0;
    }
  }

  /* Process old IR instructions. */
  snap = J->cur.snap;
  snref = snap->ref;
  for (ref = REF_FIRST; ref < nins; ref++) {
    IRIns *ir = &oir[ref];
    IRRef nref = lj_ir_nextins(J);
    IRIns *nir = IR(nref);
    IRRef hi = 0;

    if (ref >= snref) {
      snap->ref = nref;
      split_subst_snap(J, snap++, oir);
      snref = snap < &J->cur.snap[J->cur.nsnap] ? snap->ref : ~(IRRef)0;
    }

    /* Copy-substitute old instruction to new instruction. */
    nir->op1 = ir->op1 < nk ? ir->op1 : oir[ir->op1].prev;
    nir->op2 = ir->op2 < nk ? ir->op2 : oir[ir->op2].prev;
    ir->prev = nref;  /* Loword substitution. */
    nir->o = ir->o;
    nir->t.irt = ir->t.irt & ~(IRT_MARK|IRT_ISPHI);
    hisubst[ref] = 0;

    /* Split 64 bit instructions. */
#if LJ_SOFTFP
    if (irt_isnum(ir->t)) {
      nir->t.irt = IRT_INT | (nir->t.irt & IRT_GUARD);  /* Turn into INT op. */
      /* Note: hi ref = lo ref + 1! Required for SNAP_SOFTFPNUM logic. */
      switch (ir->o) {
      case IR_ADD:
	hi = split_call_ll(J, hisubst, oir, ir, IRCALL_softfp_add);
	break;
      case IR_SUB:
	hi = split_call_ll(J, hisubst, oir, ir, IRCALL_softfp_sub);
	break;
      case IR_MUL:
	hi = split_call_ll(J, hisubst, oir, ir, IRCALL_softfp_mul);
	break;
      case IR_DIV:
	hi = split_call_ll(J, hisubst, oir, ir, IRCALL_softfp_div);
	break;
      case IR_POW:
	hi = split_call_li(J, hisubst, oir, ir, IRCALL_lj_vm_powi);
	break;
      case IR_FPMATH:
	/* Try to rejoin pow from EXP2, MUL and LOG2. */
	if (nir->op2 == IRFPM_EXP2 && nir->op1 > J->loopref) {
	  IRIns *irp = IR(nir->op1);
	  if (irp->o == IR_CALLN && irp->op2 == IRCALL_softfp_mul) {
	    IRIns *irm4 = IR(irp->op1);
	    IRIns *irm3 = IR(irm4->op1);
	    IRIns *irm12 = IR(irm3->op1);
	    IRIns *irl1 = IR(irm12->op1);
	    if (irm12->op1 > J->loopref && irl1->o == IR_CALLN &&
		irl1->op2 == IRCALL_lj_vm_log2) {
	      IRRef tmp = irl1->op1;  /* Recycle first two args from LOG2. */
	      IRRef arg3 = irm3->op2, arg4 = irm4->op2;
	      J->cur.nins--;
	      tmp = split_emit(J, IRT(IR_CARG, IRT_NIL), tmp, arg3);
	      tmp = split_emit(J, IRT(IR_CARG, IRT_NIL), tmp, arg4);
	      ir->prev = tmp = split_emit(J, IRTI(IR_CALLN), tmp, IRCALL_pow);
	      hi = split_emit(J, IRT(IR_HIOP, IRT_SOFTFP), tmp, tmp);
	      break;
	    }
	  }
	}
	hi = split_call_l(J, hisubst, oir, ir, IRCALL_lj_vm_floor + ir->op2);
	break;
      case IR_ATAN2:
	hi = split_call_ll(J, hisubst, oir, ir, IRCALL_atan2);
	break;
      case IR_LDEXP:
	hi = split_call_li(J, hisubst, oir, ir, IRCALL_ldexp);
	break;
      case IR_NEG: case IR_ABS:
	nir->o = IR_CONV;  /* Pass through loword. */
	nir->op2 = (IRT_INT << 5) | IRT_INT;
	hi = split_emit(J, IRT(ir->o == IR_NEG ? IR_BXOR : IR_BAND, IRT_SOFTFP),
			hisubst[ir->op1], hisubst[ir->op2]);
	break;
      case IR_SLOAD:
	if ((nir->op2 & IRSLOAD_CONVERT)) {  /* Convert from int to number. */
	  nir->op2 &= ~IRSLOAD_CONVERT;
	  ir->prev = nref = split_emit(J, IRTI(IR_CALLN), nref,
				       IRCALL_softfp_i2d);
	  hi = split_emit(J, IRT(IR_HIOP, IRT_SOFTFP), nref, nref);
	  break;
	}
	/* fallthrough */
      case IR_ALOAD: case IR_HLOAD: case IR_ULOAD: case IR_VLOAD:
      case IR_STRTO:
	hi = split_emit(J, IRT(IR_HIOP, IRT_SOFTFP), nref, nref);
	break;
      case IR_XLOAD: {
	IRIns inslo = *nir;  /* Save/undo the emit of the lo XLOAD. */
	J->cur.nins--;
	hi = split_ptr(J, oir, ir->op1);  /* Insert the hiref ADD. */
	nref = lj_ir_nextins(J);
	nir = IR(nref);
	*nir = inslo;  /* Re-emit lo XLOAD immediately before hi XLOAD. */
	hi = split_emit(J, IRT(IR_XLOAD, IRT_SOFTFP), hi, ir->op2);
#if LJ_LE
	ir->prev = nref;
#else
	ir->prev = hi; hi = nref;
#endif
	break;
	}
      case IR_ASTORE: case IR_HSTORE: case IR_USTORE: case IR_XSTORE:
	split_emit(J, IRT(IR_HIOP, IRT_SOFTFP), nir->op1, hisubst[ir->op2]);
	break;
      case IR_CONV: {  /* Conversion to number. Others handled below. */
	IRType st = (IRType)(ir->op2 & IRCONV_SRCMASK);
	UNUSED(st);
#if LJ_32 && LJ_HASFFI
	if (st == IRT_I64 || st == IRT_U64) {
	  hi = split_call_l(J, hisubst, oir, ir,
		 st == IRT_I64 ? IRCALL_fp64_l2d : IRCALL_fp64_ul2d);
	  break;
	}
#endif
	lua_assert(st == IRT_INT ||
		   (LJ_32 && LJ_HASFFI && (st == IRT_U32 || st == IRT_FLOAT)));
	nir->o = IR_CALLN;
#if LJ_32 && LJ_HASFFI
	nir->op2 = st == IRT_INT ? IRCALL_softfp_i2d :
		   st == IRT_FLOAT ? IRCALL_softfp_f2d :
		   IRCALL_softfp_ui2d;
#else
	nir->op2 = IRCALL_softfp_i2d;
#endif
	hi = split_emit(J, IRT(IR_HIOP, IRT_SOFTFP), nref, nref);
	break;
	}
      case IR_CALLN:
      case IR_CALLL:
      case IR_CALLS:
      case IR_CALLXS:
	goto split_call;
      case IR_PHI:
	if (nir->op1 == nir->op2)
	  J->cur.nins--;  /* Drop useless PHIs. */
	if (hisubst[ir->op1] != hisubst[ir->op2])
	  split_emit(J, IRT(IR_PHI, IRT_SOFTFP),
		     hisubst[ir->op1], hisubst[ir->op2]);
	break;
      case IR_HIOP:
	J->cur.nins--;  /* Drop joining HIOP. */
	ir->prev = nir->op1;
	hi = nir->op2;
	break;
      default:
	lua_assert(ir->o <= IR_NE || ir->o == IR_MIN || ir->o == IR_MAX);
	hi = split_emit(J, IRTG(IR_HIOP, IRT_SOFTFP),
			hisubst[ir->op1], hisubst[ir->op2]);
	break;
      }
    } else
#endif
#if LJ_32 && LJ_HASFFI
    if (irt_isint64(ir->t)) {
      IRRef hiref = hisubst[ir->op1];
      nir->t.irt = IRT_INT | (nir->t.irt & IRT_GUARD);  /* Turn into INT op. */
      switch (ir->o) {
      case IR_ADD:
      case IR_SUB:
	/* Use plain op for hiword if loword cannot produce a carry/borrow. */
	if (irref_isk(nir->op2) && IR(nir->op2)->i == 0) {
	  ir->prev = nir->op1;  /* Pass through loword. */
	  nir->op1 = hiref; nir->op2 = hisubst[ir->op2];
	  hi = nref;
	  break;
	}
	/* fallthrough */
      case IR_NEG:
	hi = split_emit(J, IRTI(IR_HIOP), hiref, hisubst[ir->op2]);
	break;
      case IR_MUL:
	hi = split_call_ll(J, hisubst, oir, ir, IRCALL_lj_carith_mul64);
	break;
      case IR_DIV:
	hi = split_call_ll(J, hisubst, oir, ir,
			   irt_isi64(ir->t) ? IRCALL_lj_carith_divi64 :
					      IRCALL_lj_carith_divu64);
	break;
      case IR_MOD:
	hi = split_call_ll(J, hisubst, oir, ir,
			   irt_isi64(ir->t) ? IRCALL_lj_carith_modi64 :
					      IRCALL_lj_carith_modu64);
	break;
      case IR_POW:
	hi = split_call_ll(J, hisubst, oir, ir,
			   irt_isi64(ir->t) ? IRCALL_lj_carith_powi64 :
					      IRCALL_lj_carith_powu64);
	break;
      case IR_FLOAD:
	lua_assert(ir->op2 == IRFL_CDATA_INT64);
	hi = split_emit(J, IRTI(IR_FLOAD), nir->op1, IRFL_CDATA_INT64_4);
#if LJ_BE
	ir->prev = hi; hi = nref;
#endif
	break;
      case IR_XLOAD:
	hi = split_emit(J, IRTI(IR_XLOAD), split_ptr(J, oir, ir->op1), ir->op2);
#if LJ_BE
	ir->prev = hi; hi = nref;
#endif
	break;
      case IR_XSTORE:
	split_emit(J, IRTI(IR_HIOP), nir->op1, hisubst[ir->op2]);
	break;
      case IR_CONV: {  /* Conversion to 64 bit integer. Others handled below. */
	IRType st = (IRType)(ir->op2 & IRCONV_SRCMASK);
#if LJ_SOFTFP
	if (st == IRT_NUM) {  /* NUM to 64 bit int conv. */
	  hi = split_call_l(J, hisubst, oir, ir,
		 irt_isi64(ir->t) ? IRCALL_fp64_d2l : IRCALL_fp64_d2ul);
	} else if (st == IRT_FLOAT) {  /* FLOAT to 64 bit int conv. */
	  nir->o = IR_CALLN;
	  nir->op2 = irt_isi64(ir->t) ? IRCALL_fp64_f2l : IRCALL_fp64_f2ul;
	  hi = split_emit(J, IRTI(IR_HIOP), nref, nref);
	}
#else
	if (st == IRT_NUM || st == IRT_FLOAT) {  /* FP to 64 bit int conv. */
	  hi = split_emit(J, IRTI(IR_HIOP), nir->op1, nref);
	}
#endif
	else if (st == IRT_I64 || st == IRT_U64) {  /* 64/64 bit cast. */
	  /* Drop cast, since assembler doesn't care. But fwd both parts. */
	  hi = hiref;
	  goto fwdlo;
	} else if ((ir->op2 & IRCONV_SEXT)) {  /* Sign-extend to 64 bit. */
	  IRRef k31 = lj_ir_kint(J, 31);
	  nir = IR(nref);  /* May have been reallocated. */
	  ir->prev = nir->op1;  /* Pass through loword. */
	  nir->o = IR_BSAR;  /* hi = bsar(lo, 31). */
	  nir->op2 = k31;
	  hi = nref;
	} else {  /* Zero-extend to 64 bit. */
	  hi = lj_ir_kint(J, 0);
	  goto fwdlo;
	}
	break;
	}
      case IR_CALLXS:
	goto split_call;
      case IR_PHI: {
	IRRef hiref2;
	if ((irref_isk(nir->op1) && irref_isk(nir->op2)) ||
	    nir->op1 == nir->op2)
	  J->cur.nins--;  /* Drop useless PHIs. */
	hiref2 = hisubst[ir->op2];
	if (!((irref_isk(hiref) && irref_isk(hiref2)) || hiref == hiref2))
	  split_emit(J, IRTI(IR_PHI), hiref, hiref2);
	break;
	}
      case IR_HIOP:
	J->cur.nins--;  /* Drop joining HIOP. */
	ir->prev = nir->op1;
	hi = nir->op2;
	break;
      default:
	lua_assert(ir->o <= IR_NE);  /* Comparisons. */
	split_emit(J, IRTGI(IR_HIOP), hiref, hisubst[ir->op2]);
	break;
      }
    } else
#endif
#if LJ_SOFTFP
    if (ir->o == IR_SLOAD) {
      if ((nir->op2 & IRSLOAD_CONVERT)) {  /* Convert from number to int. */
	nir->op2 &= ~IRSLOAD_CONVERT;
	if (!(nir->op2 & IRSLOAD_TYPECHECK))
	  nir->t.irt = IRT_INT;  /* Drop guard. */
	split_emit(J, IRT(IR_HIOP, IRT_SOFTFP), nref, nref);
	ir->prev = split_num2int(J, nref, nref+1, irt_isguard(ir->t));
      }
    } else if (ir->o == IR_TOBIT) {
      IRRef tmp, op1 = ir->op1;
      J->cur.nins--;
#if LJ_LE
      tmp = split_emit(J, IRT(IR_CARG, IRT_NIL), oir[op1].prev, hisubst[op1]);
#else
      tmp = split_emit(J, IRT(IR_CARG, IRT_NIL), hisubst[op1], oir[op1].prev);
#endif
      ir->prev = split_emit(J, IRTI(IR_CALLN), tmp, IRCALL_lj_vm_tobit);
    } else if (ir->o == IR_TOSTR) {
      if (hisubst[ir->op1]) {
	if (irref_isk(ir->op1))
	  nir->op1 = ir->op1;
	else
	  split_emit(J, IRT(IR_HIOP, IRT_NIL), hisubst[ir->op1], nref);
      }
    } else if (ir->o == IR_HREF || ir->o == IR_NEWREF) {
      if (irref_isk(ir->op2) && hisubst[ir->op2])
	nir->op2 = ir->op2;
    } else
#endif
    if (ir->o == IR_CONV) {  /* See above, too. */
      IRType st = (IRType)(ir->op2 & IRCONV_SRCMASK);
#if LJ_32 && LJ_HASFFI
      if (st == IRT_I64 || st == IRT_U64) {  /* Conversion from 64 bit int. */
#if LJ_SOFTFP
	if (irt_isfloat(ir->t)) {
	  split_call_l(J, hisubst, oir, ir,
		       st == IRT_I64 ? IRCALL_fp64_l2f : IRCALL_fp64_ul2f);
	  J->cur.nins--;  /* Drop unused HIOP. */
	}
#else
	if (irt_isfp(ir->t)) {  /* 64 bit integer to FP conversion. */
	  ir->prev = split_emit(J, IRT(IR_HIOP, irt_type(ir->t)),
				hisubst[ir->op1], nref);
	}
#endif
	else {  /* Truncate to lower 32 bits. */
	fwdlo:
	  ir->prev = nir->op1;  /* Forward loword. */
	  /* Replace with NOP to avoid messing up the snapshot logic. */
	  nir->ot = IRT(IR_NOP, IRT_NIL);
	  nir->op1 = nir->op2 = 0;
	}
      }
#endif
#if LJ_SOFTFP && LJ_32 && LJ_HASFFI
      else if (irt_isfloat(ir->t)) {
	if (st == IRT_NUM) {
	  split_call_l(J, hisubst, oir, ir, IRCALL_softfp_d2f);
	  J->cur.nins--;  /* Drop unused HIOP. */
	} else {
	  nir->o = IR_CALLN;
	  nir->op2 = st == IRT_INT ? IRCALL_softfp_i2f : IRCALL_softfp_ui2f;
	}
      } else if (st == IRT_FLOAT) {
	nir->o = IR_CALLN;
	nir->op2 = irt_isint(ir->t) ? IRCALL_softfp_f2i : IRCALL_softfp_f2ui;
      } else
#endif
#if LJ_SOFTFP
      if (st == IRT_NUM || (LJ_32 && LJ_HASFFI && st == IRT_FLOAT)) {
	if (irt_isguard(ir->t)) {
	  lua_assert(st == IRT_NUM && irt_isint(ir->t));
	  J->cur.nins--;
	  ir->prev = split_num2int(J, nir->op1, hisubst[ir->op1], 1);
	} else {
	  split_call_l(J, hisubst, oir, ir,
#if LJ_32 && LJ_HASFFI
	    st == IRT_NUM ?
	      (irt_isint(ir->t) ? IRCALL_softfp_d2i : IRCALL_softfp_d2ui) :
	      (irt_isint(ir->t) ? IRCALL_softfp_f2i : IRCALL_softfp_f2ui)
#else
	    IRCALL_softfp_d2i
#endif
	  );
	  J->cur.nins--;  /* Drop unused HIOP. */
	}
      }
#endif
    } else if (ir->o == IR_CALLXS) {
      IRRef hiref;
    split_call:
      hiref = hisubst[ir->op1];
      if (hiref) {
	IROpT ot = nir->ot;
	IRRef op2 = nir->op2;
	nir->ot = IRT(IR_CARG, IRT_NIL);
#if LJ_LE
	nir->op2 = hiref;
#else
	nir->op2 = nir->op1; nir->op1 = hiref;
#endif
	ir->prev = nref = split_emit(J, ot, nref, op2);
      }
      if (LJ_SOFTFP ? irt_is64(ir->t) : irt_isint64(ir->t))
	hi = split_emit(J,
	  IRT(IR_HIOP, (LJ_SOFTFP && irt_isnum(ir->t)) ? IRT_SOFTFP : IRT_INT),
	  nref, nref);
    } else if (ir->o == IR_CARG) {
      IRRef hiref = hisubst[ir->op1];
      if (hiref) {
	IRRef op2 = nir->op2;
#if LJ_LE
	nir->op2 = hiref;
#else
	nir->op2 = nir->op1; nir->op1 = hiref;
#endif
	ir->prev = nref = split_emit(J, IRT(IR_CARG, IRT_NIL), nref, op2);
	nir = IR(nref);
      }
      hiref = hisubst[ir->op2];
      if (hiref) {
#if !LJ_TARGET_X86
	int carg = 0;
	IRIns *cir;
	for (cir = IR(nir->op1); cir->o == IR_CARG; cir = IR(cir->op1))
	  carg++;
	if ((carg & 1) == 0) {  /* Align 64 bit arguments. */
	  IRRef op2 = nir->op2;
	  nir->op2 = REF_NIL;
	  nref = split_emit(J, IRT(IR_CARG, IRT_NIL), nref, op2);
	  nir = IR(nref);
	}
#endif
#if LJ_BE
	{ IRRef tmp = nir->op2; nir->op2 = hiref; hiref = tmp; }
#endif
	ir->prev = split_emit(J, IRT(IR_CARG, IRT_NIL), nref, hiref);
      }
    } else if (ir->o == IR_CNEWI) {
      if (hisubst[ir->op2])
	split_emit(J, IRT(IR_HIOP, IRT_NIL), nref, hisubst[ir->op2]);
    } else if (ir->o == IR_LOOP) {
      J->loopref = nref;  /* Needed by assembler. */
    }
    hisubst[ref] = hi;  /* Store hiword substitution. */
  }
  if (snref == nins) {  /* Substitution for last snapshot. */
    snap->ref = J->cur.nins;
    split_subst_snap(J, snap, oir);
  }

  /* Add PHI marks. */
  for (ref = J->cur.nins-1; ref >= REF_FIRST; ref--) {
    IRIns *ir = IR(ref);
    if (ir->o != IR_PHI) break;
    if (!irref_isk(ir->op1)) irt_setphi(IR(ir->op1)->t);
    if (ir->op2 > J->loopref) irt_setphi(IR(ir->op2)->t);
  }
}
Esempio n. 4
0
/* Transform the old IR to the new IR. */
static void split_ir(jit_State *J)
{
  IRRef nins = J->cur.nins, nk = J->cur.nk;
  MSize irlen = nins - nk;
  MSize need = (irlen+1)*(sizeof(IRIns) + sizeof(IRRef1));
  IRIns *oir = (IRIns *)lj_str_needbuf(J->L, &G(J->L)->tmpbuf, need);
  IRRef1 *hisubst;
  IRRef ref;

  /* Copy old IR to buffer. */
  memcpy(oir, IR(nk), irlen*sizeof(IRIns));
  /* Bias hiword substitution table and old IR. Loword kept in field prev. */
  hisubst = (IRRef1 *)&oir[irlen] - nk;
  oir -= nk;

  /* Remove all IR instructions, but retain IR constants. */
  J->cur.nins = REF_FIRST;

  /* Process constants and fixed references. */
  for (ref = nk; ref <= REF_BASE; ref++) {
    IRIns *ir = &oir[ref];
    if (ir->o == IR_KINT64) {  /* Split up 64 bit constant. */
      TValue tv = *ir_k64(ir);
      ir->prev = lj_ir_kint(J, (int32_t)tv.u32.lo);
      hisubst[ref] = lj_ir_kint(J, (int32_t)tv.u32.hi);
    } else {
      ir->prev = ref;  /* Identity substitution for loword. */
      hisubst[ref] = 0;
    }
  }

  /* Process old IR instructions. */
  for (ref = REF_FIRST; ref < nins; ref++) {
    IRIns *ir = &oir[ref];
    IRRef nref = lj_ir_nextins(J);
    IRIns *nir = IR(nref);
    IRRef hi = 0;

    /* Copy-substitute old instruction to new instruction. */
    nir->op1 = ir->op1 < nk ? ir->op1 : oir[ir->op1].prev;
    nir->op2 = ir->op2 < nk ? ir->op2 : oir[ir->op2].prev;
    ir->prev = nref;  /* Loword substitution. */
    nir->o = ir->o;
    nir->t.irt = ir->t.irt & ~(IRT_MARK|IRT_ISPHI);
    hisubst[ref] = 0;

    /* Split 64 bit instructions. */
    if (irt_isint64(ir->t)) {
      IRRef hiref = hisubst[ir->op1];
      nir->t.irt = IRT_INT | (nir->t.irt & IRT_GUARD);  /* Turn into INT op. */
      switch (ir->o) {
      case IR_ADD:
      case IR_SUB:
	/* Use plain op for hiword if loword cannot produce a carry/borrow. */
	if (irref_isk(nir->op2) && IR(nir->op2)->i == 0) {
	  ir->prev = nir->op1;  /* Pass through loword. */
	  nir->op1 = hiref; nir->op2 = hisubst[ir->op2];
	  hi = nref;
	  break;
	}
	/* fallthrough */
      case IR_NEG:
	hi = split_emit(J, IRTI(IR_HIOP), hiref, hisubst[ir->op2]);
	break;
      case IR_MUL:
	hi = split_call64(J, hisubst, oir, ir, IRCALL_lj_carith_mul64);
	break;
      case IR_DIV:
	hi = split_call64(J, hisubst, oir, ir,
			  irt_isi64(ir->t) ? IRCALL_lj_carith_divi64 :
					     IRCALL_lj_carith_divu64);
	break;
      case IR_MOD:
	hi = split_call64(J, hisubst, oir, ir,
			  irt_isi64(ir->t) ? IRCALL_lj_carith_modi64 :
					     IRCALL_lj_carith_modu64);
	break;
      case IR_POW:
	hi = split_call64(J, hisubst, oir, ir,
			  irt_isi64(ir->t) ? IRCALL_lj_carith_powi64 :
					     IRCALL_lj_carith_powu64);
	break;
      case IR_FLOAD:
	lua_assert(ir->op2 == IRFL_CDATA_INT64);
	hi = split_emit(J, IRTI(IR_FLOAD), nir->op1, IRFL_CDATA_INT64HI);
#if LJ_BE
	ir->prev = hi; hi = nref;
#endif
	break;
      case IR_XLOAD:
	hi = split_emit(J, IRTI(IR_XLOAD), split_ptr(J, nir->op1), ir->op2);
#if LJ_BE
	ir->prev = hi; hi = nref;
#endif
	break;
      case IR_XSTORE:
#if LJ_LE
	hiref = hisubst[ir->op2];
#else
	hiref = nir->op2; nir->op2 = hisubst[ir->op2];
#endif
	split_emit(J, IRTI(IR_XSTORE), split_ptr(J, nir->op1), hiref);
	break;
      case IR_CONV: {  /* Conversion to 64 bit integer. Others handled below. */
	IRType st = (IRType)(ir->op2 & IRCONV_SRCMASK);
	if (st == IRT_NUM || st == IRT_FLOAT) {  /* FP to 64 bit int conv. */
	  hi = split_emit(J, IRTI(IR_HIOP), nir->op1, nref);
	} else if (st == IRT_I64 || st == IRT_U64) {  /* 64/64 bit cast. */
	  /* Drop cast, since assembler doesn't care. */
	  goto fwdlo;
	} else if ((ir->op2 & IRCONV_SEXT)) {  /* Sign-extend to 64 bit. */
	  IRRef k31 = lj_ir_kint(J, 31);
	  nir = IR(nref);  /* May have been reallocated. */
	  ir->prev = nir->op1;  /* Pass through loword. */
	  nir->o = IR_BSAR;  /* hi = bsar(lo, 31). */
	  nir->op2 = k31;
	  hi = nref;
	} else {  /* Zero-extend to 64 bit. */
	  hi = lj_ir_kint(J, 0);
	  goto fwdlo;
	}
	break;
	}
      case IR_PHI: {
	IRRef hiref2;
	if ((irref_isk(nir->op1) && irref_isk(nir->op2)) ||
	    nir->op1 == nir->op2)
	  J->cur.nins--;  /* Drop useless PHIs. */
	hiref2 = hisubst[ir->op2];
	if (!((irref_isk(hiref) && irref_isk(hiref2)) || hiref == hiref2))
	  split_emit(J, IRTI(IR_PHI), hiref, hiref2);
	break;
	}
      default:
	lua_assert(ir->o <= IR_NE);  /* Comparisons. */
	split_emit(J, IRTGI(IR_HIOP), hiref, hisubst[ir->op2]);
	break;
      }
    } else if (ir->o == IR_CONV) {  /* See above, too. */
      IRType st = (IRType)(ir->op2 & IRCONV_SRCMASK);
      if (st == IRT_I64 || st == IRT_U64) {  /* Conversion from 64 bit int. */
	if (irt_isfp(ir->t)) {  /* 64 bit integer to FP conversion. */
	  ir->prev = split_emit(J, IRT(IR_HIOP, irt_type(ir->t)),
				hisubst[ir->op1], nref);
	} else {  /* Truncate to lower 32 bits. */
	fwdlo:
	  ir->prev = nir->op1;  /* Forward loword. */
	  /* Replace with NOP to avoid messing up the snapshot logic. */
	  nir->ot = IRT(IR_NOP, IRT_NIL);
	  nir->op1 = nir->op2 = 0;
	}
      }
    } else if (ir->o == IR_CNEWI) {
      if (hisubst[ir->op2])
	split_emit(J, IRT(IR_HIOP, IRT_NIL), nref, hisubst[ir->op2]);
    } else if (ir->o == IR_LOOP) {
      J->loopref = nref;  /* Needed by assembler. */
    }
    hisubst[ref] = hi;  /* Store hiword substitution. */
  }

  /* Add PHI marks. */
  for (ref = J->cur.nins-1; ref >= REF_FIRST; ref--) {
    IRIns *ir = IR(ref);
    if (ir->o != IR_PHI) break;
    if (!irref_isk(ir->op1)) irt_setphi(IR(ir->op1)->t);
    if (ir->op2 > J->loopref) irt_setphi(IR(ir->op2)->t);
  }

  /* Substitute snapshot maps. */
  oir[nins].prev = J->cur.nins;  /* Substitution for last snapshot. */
  {
    SnapNo i, nsnap = J->cur.nsnap;
    for (i = 0; i < nsnap; i++) {
      SnapShot *snap = &J->cur.snap[i];
      SnapEntry *map = &J->cur.snapmap[snap->mapofs];
      MSize n, nent = snap->nent;
      snap->ref = oir[snap->ref].prev;
      for (n = 0; n < nent; n++) {
	SnapEntry sn = map[n];
	map[n] = ((sn & 0xffff0000) | oir[snap_ref(sn)].prev);
      }
    }
  }
}