示例#1
0
static bool
arithmetic_flags_clobber_p (rtx_insn *insn)
{
  rtx pat, x;

  if (!NONJUMP_INSN_P (insn))
    return false;
  pat = PATTERN (insn);
  if (asm_noperands (pat) >= 0)
    return false;

  if (GET_CODE (pat) == PARALLEL && XVECLEN (pat, 0) == 2)
    {
      x = XVECEXP (pat, 0, 0);
      if (GET_CODE (x) != SET)
	return false;
      x = SET_DEST (x);
      if (!REG_P (x))
	return false;

      x = XVECEXP (pat, 0, 1);
      if (GET_CODE (x) == CLOBBER)
	{
	  x = XEXP (x, 0);
	  if (REG_P (x) && REGNO (x) == targetm.flags_regnum)
	    return true;
	}
    }

  return false;
}
示例#2
0
文件: pr47744-3.c 项目: 0day-ci/gcc
void find_reloads (rtx insn, int n_alternatives, int commutative)
{
  register int i, j;
  int noperands;
  char *constraints[10];
  int address_reloaded[10];
  int this_alternative[10];
  char this_alternative_win[10];
  int this_alternative_matches[10];
  int this_alternative_number;
  rtx body = ((insn)->fld[3].rtx);
  int operand_mode[10];
  if (body->code == 1)
    {
      reload_n_operands = noperands = asm_noperands (body);
      n_alternatives = n_occurrences (constraints);
    }
  for (this_alternative_number = 0;
       this_alternative_number < n_alternatives;
       this_alternative_number++)
    for (i = 0;
	 i < noperands;
	 i++)
      {
	register char *p = constraints[i];
	register int win = 0;
	int badop = 1;
	int c;
	register rtx operand = recog_operand[i];
	int force_reload = 0;
	this_alternative_win[i] = 0;
	this_alternative[i] = 1;
	while (*p && (c = *p++) != ',')
	  switch (c)
	    {
	    case '4':
	      c -= '0';
	      this_alternative_matches[i] = c;
	      if ((c != commutative
		   || i != commutative + 1)
		  && operands_match[c][i])
		win = this_alternative_win[c];
	      else
		find_dummy_reload (operand_mode[i], this_alternative[c]);
	      if (! win || force_reload)
		for (j = 0; j < i; j++)
		  if (this_alternative_matches[j]
		      == this_alternative_matches[i])
		    badop = 1;
	      break;
	    case '<':
	      if (operand->code == 2
		  && ! address_reloaded[i]
		  && operand->fld[0].rtx->code == 3)
		win = 1;
	    }
      }
}
示例#3
0
static bool
copyprop_hardreg_forward_1 (basic_block bb, struct value_data *vd)
{
  bool anything_changed = false;
  rtx insn;

  for (insn = BB_HEAD (bb); ; insn = NEXT_INSN (insn))
    {
      int n_ops, i, alt, predicated;
      bool is_asm, any_replacements;
      rtx set;
      bool replaced[MAX_RECOG_OPERANDS];
      bool changed = false;
      struct kill_set_value_data ksvd;

      if (!NONDEBUG_INSN_P (insn))
	{
	  if (DEBUG_INSN_P (insn))
	    {
	      rtx loc = INSN_VAR_LOCATION_LOC (insn);
	      if (!VAR_LOC_UNKNOWN_P (loc))
		replace_oldest_value_addr (&INSN_VAR_LOCATION_LOC (insn),
					   ALL_REGS, GET_MODE (loc),
					   ADDR_SPACE_GENERIC, insn, vd);
	    }

	  if (insn == BB_END (bb))
	    break;
	  else
	    continue;
	}

      set = single_set (insn);
      extract_insn (insn);
      if (! constrain_operands (1))
	fatal_insn_not_found (insn);
      preprocess_constraints ();
      alt = which_alternative;
      n_ops = recog_data.n_operands;
      is_asm = asm_noperands (PATTERN (insn)) >= 0;

      /* Simplify the code below by rewriting things to reflect
	 matching constraints.  Also promote OP_OUT to OP_INOUT
	 in predicated instructions.  */

      predicated = GET_CODE (PATTERN (insn)) == COND_EXEC;
      for (i = 0; i < n_ops; ++i)
	{
	  int matches = recog_op_alt[i][alt].matches;
	  if (matches >= 0)
	    recog_op_alt[i][alt].cl = recog_op_alt[matches][alt].cl;
	  if (matches >= 0 || recog_op_alt[i][alt].matched >= 0
	      || (predicated && recog_data.operand_type[i] == OP_OUT))
	    recog_data.operand_type[i] = OP_INOUT;
	}

      /* Apply changes to earlier DEBUG_INSNs if possible.  */
      if (vd->n_debug_insn_changes)
	note_uses (&PATTERN (insn), cprop_find_used_regs, vd);

      /* For each earlyclobber operand, zap the value data.  */
      for (i = 0; i < n_ops; i++)
	if (recog_op_alt[i][alt].earlyclobber)
	  kill_value (recog_data.operand[i], vd);

      /* Within asms, a clobber cannot overlap inputs or outputs.
	 I wouldn't think this were true for regular insns, but
	 scan_rtx treats them like that...  */
      note_stores (PATTERN (insn), kill_clobbered_value, vd);

      /* Kill all auto-incremented values.  */
      /* ??? REG_INC is useless, since stack pushes aren't done that way.  */
      for_each_rtx (&PATTERN (insn), kill_autoinc_value, vd);

      /* Kill all early-clobbered operands.  */
      for (i = 0; i < n_ops; i++)
	if (recog_op_alt[i][alt].earlyclobber)
	  kill_value (recog_data.operand[i], vd);

      /* Special-case plain move instructions, since we may well
	 be able to do the move from a different register class.  */
      if (set && REG_P (SET_SRC (set)))
	{
	  rtx src = SET_SRC (set);
	  unsigned int regno = REGNO (src);
	  enum machine_mode mode = GET_MODE (src);
	  unsigned int i;
	  rtx new_rtx;

	  /* If we are accessing SRC in some mode other that what we
	     set it in, make sure that the replacement is valid.  */
	  if (mode != vd->e[regno].mode)
	    {
	      if (hard_regno_nregs[regno][mode]
		  > hard_regno_nregs[regno][vd->e[regno].mode])
		goto no_move_special_case;

	      /* And likewise, if we are narrowing on big endian the transformation
		 is also invalid.  */
	      if (hard_regno_nregs[regno][mode]
		  < hard_regno_nregs[regno][vd->e[regno].mode]
		  && (GET_MODE_SIZE (vd->e[regno].mode) > UNITS_PER_WORD
		      ? WORDS_BIG_ENDIAN : BYTES_BIG_ENDIAN))
		goto no_move_special_case;
	    }

	  /* If the destination is also a register, try to find a source
	     register in the same class.  */
	  if (REG_P (SET_DEST (set)))
	    {
	      new_rtx = find_oldest_value_reg (REGNO_REG_CLASS (regno), src, vd);
	      if (new_rtx && validate_change (insn, &SET_SRC (set), new_rtx, 0))
		{
		  if (dump_file)
		    fprintf (dump_file,
			     "insn %u: replaced reg %u with %u\n",
			     INSN_UID (insn), regno, REGNO (new_rtx));
		  changed = true;
		  goto did_replacement;
		}
	      /* We need to re-extract as validate_change clobbers
		 recog_data.  */
	      extract_insn (insn);
	      if (! constrain_operands (1))
		fatal_insn_not_found (insn);
	      preprocess_constraints ();
	    }

	  /* Otherwise, try all valid registers and see if its valid.  */
	  for (i = vd->e[regno].oldest_regno; i != regno;
	       i = vd->e[i].next_regno)
	    {
	      new_rtx = maybe_mode_change (vd->e[i].mode, vd->e[regno].mode,
				       mode, i, regno);
	      if (new_rtx != NULL_RTX)
		{
		  if (validate_change (insn, &SET_SRC (set), new_rtx, 0))
		    {
		      ORIGINAL_REGNO (new_rtx) = ORIGINAL_REGNO (src);
		      REG_ATTRS (new_rtx) = REG_ATTRS (src);
		      REG_POINTER (new_rtx) = REG_POINTER (src);
		      if (dump_file)
			fprintf (dump_file,
				 "insn %u: replaced reg %u with %u\n",
				 INSN_UID (insn), regno, REGNO (new_rtx));
		      changed = true;
		      goto did_replacement;
		    }
		  /* We need to re-extract as validate_change clobbers
		     recog_data.  */
		  extract_insn (insn);
		  if (! constrain_operands (1))
		    fatal_insn_not_found (insn);
		  preprocess_constraints ();
		}
	    }
	}
      no_move_special_case:

      any_replacements = false;

      /* For each input operand, replace a hard register with the
	 eldest live copy that's in an appropriate register class.  */
      for (i = 0; i < n_ops; i++)
	{
	  replaced[i] = false;

	  /* Don't scan match_operand here, since we've no reg class
	     information to pass down.  Any operands that we could
	     substitute in will be represented elsewhere.  */
	  if (recog_data.constraints[i][0] == '\0')
	    continue;

	  /* Don't replace in asms intentionally referencing hard regs.  */
	  if (is_asm && REG_P (recog_data.operand[i])
	      && (REGNO (recog_data.operand[i])
		  == ORIGINAL_REGNO (recog_data.operand[i])))
	    continue;

	  if (recog_data.operand_type[i] == OP_IN)
	    {
	      if (recog_op_alt[i][alt].is_address)
		replaced[i]
		  = replace_oldest_value_addr (recog_data.operand_loc[i],
					       recog_op_alt[i][alt].cl,
					       VOIDmode, ADDR_SPACE_GENERIC,
					       insn, vd);
	      else if (REG_P (recog_data.operand[i]))
		replaced[i]
		  = replace_oldest_value_reg (recog_data.operand_loc[i],
					      recog_op_alt[i][alt].cl,
					      insn, vd);
	      else if (MEM_P (recog_data.operand[i]))
		replaced[i] = replace_oldest_value_mem (recog_data.operand[i],
							insn, vd);
	    }
	  else if (MEM_P (recog_data.operand[i]))
	    replaced[i] = replace_oldest_value_mem (recog_data.operand[i],
						    insn, vd);

	  /* If we performed any replacement, update match_dups.  */
	  if (replaced[i])
	    {
	      int j;
	      rtx new_rtx;

	      new_rtx = *recog_data.operand_loc[i];
	      recog_data.operand[i] = new_rtx;
	      for (j = 0; j < recog_data.n_dups; j++)
		if (recog_data.dup_num[j] == i)
		  validate_unshare_change (insn, recog_data.dup_loc[j], new_rtx, 1);

	      any_replacements = true;
	    }
	}

      if (any_replacements)
	{
	  if (! apply_change_group ())
	    {
	      for (i = 0; i < n_ops; i++)
		if (replaced[i])
		  {
		    rtx old = *recog_data.operand_loc[i];
		    recog_data.operand[i] = old;
		  }

	      if (dump_file)
		fprintf (dump_file,
			 "insn %u: reg replacements not verified\n",
			 INSN_UID (insn));
	    }
	  else
	    changed = true;
	}

    did_replacement:
      if (changed)
	{
	  anything_changed = true;

	  /* If something changed, perhaps further changes to earlier
	     DEBUG_INSNs can be applied.  */
	  if (vd->n_debug_insn_changes)
	    note_uses (&PATTERN (insn), cprop_find_used_regs, vd);
	}

      ksvd.vd = vd;
      ksvd.ignore_set_reg = NULL_RTX;

      /* Clobber call-clobbered registers.  */
      if (CALL_P (insn))
	{
	  unsigned int set_regno = INVALID_REGNUM;
	  unsigned int set_nregs = 0;
	  unsigned int regno;
	  rtx exp;
	  hard_reg_set_iterator hrsi;

	  for (exp = CALL_INSN_FUNCTION_USAGE (insn); exp; exp = XEXP (exp, 1))
	    {
	      rtx x = XEXP (exp, 0);
	      if (GET_CODE (x) == SET)
		{
		  rtx dest = SET_DEST (x);
		  kill_value (dest, vd);
		  set_value_regno (REGNO (dest), GET_MODE (dest), vd);
		  copy_value (dest, SET_SRC (x), vd);
		  ksvd.ignore_set_reg = dest;
		  set_regno = REGNO (dest);
		  set_nregs
		    = hard_regno_nregs[set_regno][GET_MODE (dest)];
		  break;
		}
	    }

	  EXECUTE_IF_SET_IN_HARD_REG_SET (regs_invalidated_by_call, 0, regno, hrsi)
	    if (regno < set_regno || regno >= set_regno + set_nregs)
	      kill_value_regno (regno, 1, vd);

	  /* If SET was seen in CALL_INSN_FUNCTION_USAGE, and SET_SRC
	     of the SET isn't in regs_invalidated_by_call hard reg set,
	     but instead among CLOBBERs on the CALL_INSN, we could wrongly
	     assume the value in it is still live.  */
	  if (ksvd.ignore_set_reg)
	    note_stores (PATTERN (insn), kill_clobbered_value, vd);
	}

      /* Notice stores.  */
      note_stores (PATTERN (insn), kill_set_value, &ksvd);

      /* Notice copies.  */
      if (set && REG_P (SET_DEST (set)) && REG_P (SET_SRC (set)))
	copy_value (SET_DEST (set), SET_SRC (set), vd);

      if (insn == BB_END (bb))
	break;
    }

  return anything_changed;
}
示例#4
0
void
eliminate_regs_in_insn (rtx_insn *insn, bool replace_p, bool first_p,
			HOST_WIDE_INT update_sp_offset)
{
  int icode = recog_memoized (insn);
  rtx old_set = single_set (insn);
  bool validate_p;
  int i;
  rtx substed_operand[MAX_RECOG_OPERANDS];
  rtx orig_operand[MAX_RECOG_OPERANDS];
  struct lra_elim_table *ep;
  rtx plus_src, plus_cst_src;
  lra_insn_recog_data_t id;
  struct lra_static_insn_data *static_id;

  if (icode < 0 && asm_noperands (PATTERN (insn)) < 0 && ! DEBUG_INSN_P (insn))
    {
      lra_assert (GET_CODE (PATTERN (insn)) == USE
		  || GET_CODE (PATTERN (insn)) == CLOBBER
		  || GET_CODE (PATTERN (insn)) == ASM_INPUT);
      return;
    }

  /* Check for setting an eliminable register.	*/
  if (old_set != 0 && REG_P (SET_DEST (old_set))
      && (ep = get_elimination (SET_DEST (old_set))) != NULL)
    {
      for (ep = reg_eliminate; ep < &reg_eliminate[NUM_ELIMINABLE_REGS]; ep++)
	if (ep->from_rtx == SET_DEST (old_set) && ep->can_eliminate)
	  {
	    bool delete_p = replace_p;
	    
#ifdef HARD_FRAME_POINTER_REGNUM
	    if (ep->from == FRAME_POINTER_REGNUM
		&& ep->to == HARD_FRAME_POINTER_REGNUM)
	      /* If this is setting the frame pointer register to the
		 hardware frame pointer register and this is an
		 elimination that will be done (tested above), this
		 insn is really adjusting the frame pointer downward
		 to compensate for the adjustment done before a
		 nonlocal goto.  */
	      {
		rtx src = SET_SRC (old_set);
		rtx off = remove_reg_equal_offset_note (insn, ep->to_rtx);
		
		/* We should never process such insn with non-zero
		   UPDATE_SP_OFFSET.  */
		lra_assert (update_sp_offset == 0);
		
		if (off != NULL_RTX
		    || src == ep->to_rtx
		    || (GET_CODE (src) == PLUS
			&& XEXP (src, 0) == ep->to_rtx
			&& CONST_INT_P (XEXP (src, 1))))
		  {
		    HOST_WIDE_INT offset;
		    
		    if (replace_p)
		      {
			SET_DEST (old_set) = ep->to_rtx;
			lra_update_insn_recog_data (insn);
			return;
		      }
		    offset = (off != NULL_RTX ? INTVAL (off)
			      : src == ep->to_rtx ? 0 : INTVAL (XEXP (src, 1)));
		    offset -= (ep->offset - ep->previous_offset);
		    src = plus_constant (Pmode, ep->to_rtx, offset);
		    
		    /* First see if this insn remains valid when we
		       make the change.  If not, keep the INSN_CODE
		       the same and let the constraint pass fit it
		       up.  */
		    validate_change (insn, &SET_SRC (old_set), src, 1);
		    validate_change (insn, &SET_DEST (old_set),
				     ep->from_rtx, 1);
		    if (! apply_change_group ())
		      {
			SET_SRC (old_set) = src;
			SET_DEST (old_set) = ep->from_rtx;
		      }
		    lra_update_insn_recog_data (insn);
		    /* Add offset note for future updates.  */
		    add_reg_note (insn, REG_EQUAL, src);
		    return;
		  }
	      }
#endif
	    
	    /* This insn isn't serving a useful purpose.  We delete it
	       when REPLACE is set.  */
	    if (delete_p)
	      lra_delete_dead_insn (insn);
	    return;
	  }
    }

  /* We allow one special case which happens to work on all machines we
     currently support: a single set with the source or a REG_EQUAL
     note being a PLUS of an eliminable register and a constant.  */
  plus_src = plus_cst_src = 0;
  if (old_set && REG_P (SET_DEST (old_set)))
    {
      if (GET_CODE (SET_SRC (old_set)) == PLUS)
	plus_src = SET_SRC (old_set);
      /* First see if the source is of the form (plus (...) CST).  */
      if (plus_src
	  && CONST_INT_P (XEXP (plus_src, 1)))
	plus_cst_src = plus_src;
      /* Check that the first operand of the PLUS is a hard reg or
	 the lowpart subreg of one.  */
      if (plus_cst_src)
	{
	  rtx reg = XEXP (plus_cst_src, 0);

	  if (GET_CODE (reg) == SUBREG && subreg_lowpart_p (reg))
	    reg = SUBREG_REG (reg);

	  if (!REG_P (reg) || REGNO (reg) >= FIRST_PSEUDO_REGISTER)
	    plus_cst_src = 0;
	}
    }
  if (plus_cst_src)
    {
      rtx reg = XEXP (plus_cst_src, 0);
      HOST_WIDE_INT offset = INTVAL (XEXP (plus_cst_src, 1));

      if (GET_CODE (reg) == SUBREG)
	reg = SUBREG_REG (reg);

      if (REG_P (reg) && (ep = get_elimination (reg)) != NULL)
	{
	  rtx to_rtx = replace_p ? ep->to_rtx : ep->from_rtx;

	  if (! replace_p)
	    {
	      if (update_sp_offset == 0)
		offset += (ep->offset - ep->previous_offset);
	      if (ep->to_rtx == stack_pointer_rtx)
		{
		  if (first_p)
		    offset -= lra_get_insn_recog_data (insn)->sp_offset;
		  else
		    offset += update_sp_offset;
		}
	      offset = trunc_int_for_mode (offset, GET_MODE (plus_cst_src));
	    }

	  if (GET_CODE (XEXP (plus_cst_src, 0)) == SUBREG)
	    to_rtx = gen_lowpart (GET_MODE (XEXP (plus_cst_src, 0)), to_rtx);
	  /* If we have a nonzero offset, and the source is already a
	     simple REG, the following transformation would increase
	     the cost of the insn by replacing a simple REG with (plus
	     (reg sp) CST).  So try only when we already had a PLUS
	     before.  */
	  if (offset == 0 || plus_src)
	    {
	      rtx new_src = plus_constant (GET_MODE (to_rtx), to_rtx, offset);

	      old_set = single_set (insn);

	      /* First see if this insn remains valid when we make the
		 change.  If not, try to replace the whole pattern
		 with a simple set (this may help if the original insn
		 was a PARALLEL that was only recognized as single_set
		 due to REG_UNUSED notes).  If this isn't valid
		 either, keep the INSN_CODE the same and let the
		 constraint pass fix it up.  */
	      if (! validate_change (insn, &SET_SRC (old_set), new_src, 0))
		{
		  rtx new_pat = gen_rtx_SET (SET_DEST (old_set), new_src);

		  if (! validate_change (insn, &PATTERN (insn), new_pat, 0))
		    SET_SRC (old_set) = new_src;
		}
	      lra_update_insn_recog_data (insn);
	      /* This can't have an effect on elimination offsets, so skip
		 right to the end.  */
	      return;
	    }
	}
    }

  /* Eliminate all eliminable registers occurring in operands that
     can be handled by the constraint pass.  */
  id = lra_get_insn_recog_data (insn);
  static_id = id->insn_static_data;
  validate_p = false;
  for (i = 0; i < static_id->n_operands; i++)
    {
      orig_operand[i] = *id->operand_loc[i];
      substed_operand[i] = *id->operand_loc[i];

      /* For an asm statement, every operand is eliminable.  */
      if (icode < 0 || insn_data[icode].operand[i].eliminable)
	{
	  /* Check for setting a hard register that we know about.  */
	  if (static_id->operand[i].type != OP_IN
	      && REG_P (orig_operand[i]))
	    {
	      /* If we are assigning to a hard register that can be
		 eliminated, it must be as part of a PARALLEL, since
		 the code above handles single SETs.  This reg can not
		 be longer eliminated -- it is forced by
		 mark_not_eliminable.  */
	      for (ep = reg_eliminate;
		   ep < &reg_eliminate[NUM_ELIMINABLE_REGS];
		   ep++)
		lra_assert (ep->from_rtx != orig_operand[i]
			    || ! ep->can_eliminate);
	    }

	  /* Companion to the above plus substitution, we can allow
	     invariants as the source of a plain move.	*/
	  substed_operand[i]
	    = lra_eliminate_regs_1 (insn, *id->operand_loc[i], VOIDmode,
				    replace_p, ! replace_p && ! first_p,
				    update_sp_offset, first_p);
	  if (substed_operand[i] != orig_operand[i])
	    validate_p = true;
	}
    }

  if (! validate_p)
    return;

  /* Substitute the operands; the new values are in the substed_operand
     array.  */
  for (i = 0; i < static_id->n_operands; i++)
    *id->operand_loc[i] = substed_operand[i];
  for (i = 0; i < static_id->n_dups; i++)
    *id->dup_loc[i] = substed_operand[(int) static_id->dup_num[i]];

  /* If we had a move insn but now we don't, re-recognize it.
     This will cause spurious re-recognition if the old move had a
     PARALLEL since the new one still will, but we can't call
     single_set without having put new body into the insn and the
     re-recognition won't hurt in this rare case.  */
  id = lra_update_insn_recog_data (insn);
  static_id = id->insn_static_data;
}
示例#5
0
/* Try to simplify INSN.  */
static void
reload_cse_simplify (rtx insn, rtx testreg)
{
  rtx body = PATTERN (insn);

  if (GET_CODE (body) == SET)
    {
      int count = 0;

      /* Simplify even if we may think it is a no-op.
         We may think a memory load of a value smaller than WORD_SIZE
         is redundant because we haven't taken into account possible
         implicit extension.  reload_cse_simplify_set() will bring
         this out, so it's safer to simplify before we delete.  */
      count += reload_cse_simplify_set (body, insn);

      if (!count && reload_cse_noop_set_p (body))
	{
	  rtx value = SET_DEST (body);
	  if (REG_P (value)
	      && ! REG_FUNCTION_VALUE_P (value))
	    value = 0;
	  delete_insn_and_edges (insn);
	  return;
	}

      if (count > 0)
	apply_change_group ();
      else
	reload_cse_simplify_operands (insn, testreg);
    }
  else if (GET_CODE (body) == PARALLEL)
    {
      int i;
      int count = 0;
      rtx value = NULL_RTX;

      /* Registers mentioned in the clobber list for an asm cannot be reused
	 within the body of the asm.  Invalidate those registers now so that
	 we don't try to substitute values for them.  */
      if (asm_noperands (body) >= 0)
	{
	  for (i = XVECLEN (body, 0) - 1; i >= 0; --i)
	    {
	      rtx part = XVECEXP (body, 0, i);
	      if (GET_CODE (part) == CLOBBER && REG_P (XEXP (part, 0)))
		cselib_invalidate_rtx (XEXP (part, 0));
	    }
	}

      /* If every action in a PARALLEL is a noop, we can delete
	 the entire PARALLEL.  */
      for (i = XVECLEN (body, 0) - 1; i >= 0; --i)
	{
	  rtx part = XVECEXP (body, 0, i);
	  if (GET_CODE (part) == SET)
	    {
	      if (! reload_cse_noop_set_p (part))
		break;
	      if (REG_P (SET_DEST (part))
		  && REG_FUNCTION_VALUE_P (SET_DEST (part)))
		{
		  if (value)
		    break;
		  value = SET_DEST (part);
		}
	    }
	  else if (GET_CODE (part) != CLOBBER)
	    break;
	}

      if (i < 0)
	{
	  delete_insn_and_edges (insn);
	  /* We're done with this insn.  */
	  return;
	}

      /* It's not a no-op, but we can try to simplify it.  */
      for (i = XVECLEN (body, 0) - 1; i >= 0; --i)
	if (GET_CODE (XVECEXP (body, 0, i)) == SET)
	  count += reload_cse_simplify_set (XVECEXP (body, 0, i), insn);

      if (count > 0)
	apply_change_group ();
      else
	reload_cse_simplify_operands (insn, testreg);
    }
}