optabs.c

gcc库的原代码,对编程有很大帮助.

	    {
	      register rtx tmp;

	      tmp = op0; op0 = op1; op1 = tmp;
	      tmp = xop0; xop0 = xop1; xop1 = tmp;
	    }
	}

      /* In case the insn wants input operands in modes different from
	 the result, convert the operands.  */

      if (GET_MODE (op0) != VOIDmode
	  && GET_MODE (op0) != mode0
	  && mode0 != VOIDmode)
	xop0 = convert_to_mode (mode0, xop0, unsignedp);

      if (GET_MODE (xop1) != VOIDmode
	  && GET_MODE (xop1) != mode1
	  && mode1 != VOIDmode)
	xop1 = convert_to_mode (mode1, xop1, unsignedp);

      /* Now, if insn's predicates don't allow our operands, put them into
	 pseudo regs.  */

      if (! (*insn_operand_predicate[icode][1]) (xop0, mode0)
	  && mode0 != VOIDmode)
	xop0 = copy_to_mode_reg (mode0, xop0);

      if (! (*insn_operand_predicate[icode][2]) (xop1, mode1)
	  && mode1 != VOIDmode)
	xop1 = copy_to_mode_reg (mode1, xop1);

      if (! (*insn_operand_predicate[icode][0]) (temp, mode))
	temp = gen_reg_rtx (mode);

      pat = GEN_FCN (icode) (temp, xop0, xop1);
      if (pat)
	{
	  /* If PAT is a multi-insn sequence, try to add an appropriate
	     REG_EQUAL note to it.  If we can't because TEMP conflicts with an
	     operand, call ourselves again, this time without a target.  */
	  if (GET_CODE (pat) == SEQUENCE
	      && ! add_equal_note (pat, temp, binoptab->code, xop0, xop1))
	    {
	      delete_insns_since (last);
	      return expand_binop (mode, binoptab, op0, op1, NULL_RTX,
				   unsignedp, methods);
	    }

	  emit_insn (pat);
	  return temp;
	}
      else
	delete_insns_since (last);
    }

  /* If this is a multiply, see if we can do a widening operation that
     takes operands of this mode and makes a wider mode.  */

  if (binoptab == smul_optab && GET_MODE_WIDER_MODE (mode) != VOIDmode
      && (((unsignedp ? umul_widen_optab : smul_widen_optab)
	   ->handlers[(int) GET_MODE_WIDER_MODE (mode)].insn_code)
	  != CODE_FOR_nothing))
    {
      temp = expand_binop (GET_MODE_WIDER_MODE (mode),
			   unsignedp ? umul_widen_optab : smul_widen_optab,
			   op0, op1, NULL_RTX, unsignedp, OPTAB_DIRECT);

      if (temp != 0)
	{
	  if (GET_MODE_CLASS (mode) == MODE_INT)
	    return gen_lowpart (mode, temp);
	  else
	    return convert_to_mode (mode, temp, unsignedp);
	}
    }

  /* Look for a wider mode of the same class for which we think we
     can open-code the operation.  Check for a widening multiply at the
     wider mode as well.  */

  if ((class == MODE_INT || class == MODE_FLOAT || class == MODE_COMPLEX_FLOAT)
      && methods != OPTAB_DIRECT && methods != OPTAB_LIB)
    for (wider_mode = GET_MODE_WIDER_MODE (mode); wider_mode != VOIDmode;
	 wider_mode = GET_MODE_WIDER_MODE (wider_mode))
      {
	if (binoptab->handlers[(int) wider_mode].insn_code != CODE_FOR_nothing
	    || (binoptab == smul_optab
		&& GET_MODE_WIDER_MODE (wider_mode) != VOIDmode
		&& (((unsignedp ? umul_widen_optab : smul_widen_optab)
		     ->handlers[(int) GET_MODE_WIDER_MODE (wider_mode)].insn_code)
		    != CODE_FOR_nothing)))
	  {
	    rtx xop0 = op0, xop1 = op1;
	    int no_extend = 0;

	    /* For certain integer operations, we need not actually extend
	       the narrow operands, as long as we will truncate
	       the results to the same narrowness.   */

	    if ((binoptab == ior_optab || binoptab == and_optab
		 || binoptab == xor_optab
		 || binoptab == add_optab || binoptab == sub_optab
		 || binoptab == smul_optab || binoptab == ashl_optab)
		&& class == MODE_INT)
	      no_extend = 1;

	    xop0 = widen_operand (xop0, wider_mode, mode, unsignedp, no_extend);

	    /* The second operand of a shift must always be extended.  */
	    xop1 = widen_operand (xop1, wider_mode, mode, unsignedp,
				  no_extend && binoptab != ashl_optab);

	    temp = expand_binop (wider_mode, binoptab, xop0, xop1, NULL_RTX,
				 unsignedp, OPTAB_DIRECT);
	    if (temp)
	      {
		if (class != MODE_INT)
		  {
		    if (target == 0)
		      target = gen_reg_rtx (mode);
		    convert_move (target, temp, 0);
		    return target;
		  }
		else
		  return gen_lowpart (mode, temp);
	      }
	    else
	      delete_insns_since (last);
	  }
      }

  /* These can be done a word at a time.  */
  if ((binoptab == and_optab || binoptab == ior_optab || binoptab == xor_optab)
      && class == MODE_INT
      && GET_MODE_SIZE (mode) > UNITS_PER_WORD
      && binoptab->handlers[(int) word_mode].insn_code != CODE_FOR_nothing)
    {
      int i;
      rtx insns;
      rtx equiv_value;

      /* If TARGET is the same as one of the operands, the REG_EQUAL note
	 won't be accurate, so use a new target.  */
      if (target == 0 || target == op0 || target == op1)
	target = gen_reg_rtx (mode);

      start_sequence ();

      /* Do the actual arithmetic.  */
      for (i = 0; i < GET_MODE_BITSIZE (mode) / BITS_PER_WORD; i++)
	{
	  rtx target_piece = operand_subword (target, i, 1, mode);
	  rtx x = expand_binop (word_mode, binoptab,
				operand_subword_force (op0, i, mode),
				operand_subword_force (op1, i, mode),
				target_piece, unsignedp, next_methods);

	  if (x == 0)
	    break;

	  if (target_piece != x)
	    emit_move_insn (target_piece, x);
	}

      insns = get_insns ();
      end_sequence ();

      if (i == GET_MODE_BITSIZE (mode) / BITS_PER_WORD)
	{
	  if (binoptab->code != UNKNOWN)
	    equiv_value
	      = gen_rtx (binoptab->code, mode, copy_rtx (op0), copy_rtx (op1));
	  else
	    equiv_value = 0;

	  emit_no_conflict_block (insns, target, op0, op1, equiv_value);
	  return target;
	}
    }

  /* Synthesize double word shifts from single word shifts.  */
  if ((binoptab == lshr_optab || binoptab == ashl_optab
       || binoptab == ashr_optab)
      && class == MODE_INT
      && GET_CODE (op1) == CONST_INT
      && GET_MODE_SIZE (mode) == 2 * UNITS_PER_WORD
      && binoptab->handlers[(int) word_mode].insn_code != CODE_FOR_nothing
      && ashl_optab->handlers[(int) word_mode].insn_code != CODE_FOR_nothing
      && lshr_optab->handlers[(int) word_mode].insn_code != CODE_FOR_nothing)
    {
      rtx insns, inter, equiv_value;
      rtx into_target, outof_target;
      rtx into_input, outof_input;
      int shift_count, left_shift, outof_word;

      /* If TARGET is the same as one of the operands, the REG_EQUAL note
	 won't be accurate, so use a new target.  */
      if (target == 0 || target == op0 || target == op1)
	target = gen_reg_rtx (mode);

      start_sequence ();

      shift_count = INTVAL (op1);

      /* OUTOF_* is the word we are shifting bits away from, and
	 INTO_* is the word that we are shifting bits towards, thus
	 they differ depending on the direction of the shift and
	 WORDS_BIG_ENDIAN.  */

      left_shift = binoptab == ashl_optab;
      outof_word = left_shift ^ ! WORDS_BIG_ENDIAN;

      outof_target = operand_subword (target, outof_word, 1, mode);
      into_target = operand_subword (target, 1 - outof_word, 1, mode);

      outof_input = operand_subword_force (op0, outof_word, mode);
      into_input = operand_subword_force (op0, 1 - outof_word, mode);

      if (shift_count >= BITS_PER_WORD)
	{
	  inter = expand_binop (word_mode, binoptab,
			       outof_input,
			       GEN_INT (shift_count - BITS_PER_WORD),
			       into_target, unsignedp, next_methods);

	  if (inter != 0 && inter != into_target)
	    emit_move_insn (into_target, inter);

	  /* For a signed right shift, we must fill the word we are shifting
	     out of with copies of the sign bit.  Otherwise it is zeroed.  */
	  if (inter != 0 && binoptab != ashr_optab)
	    inter = CONST0_RTX (word_mode);
	  else if (inter != 0)
	    inter = expand_binop (word_mode, binoptab,
				  outof_input,
				  GEN_INT (BITS_PER_WORD - 1),
				  outof_target, unsignedp, next_methods);

	  if (inter != 0 && inter != outof_target)
	    emit_move_insn (outof_target, inter);
	}
      else
	{
	  rtx carries;
	  optab reverse_unsigned_shift, unsigned_shift;

	  /* For a shift of less then BITS_PER_WORD, to compute the carry,
	     we must do a logical shift in the opposite direction of the
	     desired shift.  */

	  reverse_unsigned_shift = (left_shift ? lshr_optab : ashl_optab);

	  /* For a shift of less than BITS_PER_WORD, to compute the word
	     shifted towards, we need to unsigned shift the orig value of
	     that word.  */

	  unsigned_shift = (left_shift ? ashl_optab : lshr_optab);

	  carries = expand_binop (word_mode, reverse_unsigned_shift,
				  outof_input,
				  GEN_INT (BITS_PER_WORD - shift_count),
				  0, unsignedp, next_methods);

	  if (carries == 0)
	    inter = 0;
	  else
	    inter = expand_binop (word_mode, unsigned_shift, into_input,
				  op1, 0, unsignedp, next_methods);

	  if (inter != 0)
	    inter = expand_binop (word_mode, ior_optab, carries, inter,
				  into_target, unsignedp, next_methods);

	  if (inter != 0 && inter != into_target)
	    emit_move_insn (into_target, inter);

	  if (inter != 0)
	    inter = expand_binop (word_mode, binoptab, outof_input,
				  op1, outof_target, unsignedp, next_methods);
	  
	  if (inter != 0 && inter != outof_target)
	    emit_move_insn (outof_target, inter);
	}

      insns = get_insns ();
      end_sequence ();

      if (inter != 0)
	{
	  if (binoptab->code != UNKNOWN)
	    equiv_value = gen_rtx (binoptab->code, mode, op0, op1);
	  else
	    equiv_value = 0;

	  emit_no_conflict_block (insns, target, op0, op1, equiv_value);
	  return target;
	}
    }

  /* Synthesize double word rotates from single word shifts.  */
  if ((binoptab == rotl_optab || binoptab == rotr_optab)
      && class == MODE_INT
      && GET_CODE (op1) == CONST_INT
      && GET_MODE_SIZE (mode) == 2 * UNITS_PER_WORD
      && ashl_optab->handlers[(int) word_mode].insn_code != CODE_FOR_nothing
      && lshr_optab->handlers[(int) word_mode].insn_code != CODE_FOR_nothing)
    {
      rtx insns, equiv_value;
      rtx into_target, outof_target;
      rtx into_input, outof_input;
      rtx inter;
      int shift_count, left_shift, outof_word;

      /* If TARGET is the same as one of the operands, the REG_EQUAL note
	 won't be accurate, so use a new target.  */
      if (target == 0 || target == op0 || target == op1)
	target = gen_reg_rtx (mode);

      start_sequence ();

      shift_count = INTVAL (op1);

      /* OUTOF_* is the word we are shifting bits away from, and
	 INTO_* is the word that we are shifting bits towards, thus
	 they differ depending on the direction of the shift and
	 WORDS_BIG_ENDIAN.  */

      left_shift = (binoptab == rotl_optab);
      outof_word = left_shift ^ ! WORDS_BIG_ENDIAN;

      outof_target = operand_subword (target, outof_word, 1, mode);
      into_target = operand_subword (target, 1 - outof_word, 1, mode);

      outof_input = operand_subword_force (op0, outof_word, mode);
      into_input = operand_subword_force (op0, 1 - outof_word, mode);

      if (shift_count == BITS_PER_WORD)
	{
	  /* This is just a word swap.  */
	  emit_move_insn (outof_target, into_input);
	  emit_move_insn (into_target, outof_input);
	  inter = const0_rtx;
	}
      else
	{
	  rtx into_temp1, into_temp2, outof_temp1, outof_temp2;
	  rtx first_shift_count, second_shift_count;
	  optab reverse_unsigned_shift, unsigned_shift;

	  reverse_unsigned_shift = (left_shift ^ (shift_count < BITS_PER_WORD)
				    ? lshr_optab : ashl_optab);

	  unsigned_shift = (left_shift ^ (shift_count < BITS_PER_WORD)
			    ? ashl_optab : lshr_optab);

	  if (shift_count > BITS_PER_WORD)
	    {
	      first_shift_count = GEN_INT (shift_count - BITS_PER_WORD);
	      second_shift_count = GEN_INT (2*BITS_PER_WORD - shift_count);
	    }
	  else
	    {
	      first_shift_count = GEN_INT (BITS_PER_WORD - shift_count);
	      second_shift_count = GEN_INT (shift_count);
	    }

	  into_temp1 = expand_binop (word_mode, unsigned_shift,
				     outof_input, first_shift_count,
				     NULL_RTX, unsignedp, next_methods);
	  into_temp2 = expand_binop (word_mode, reverse_unsigned_shift,
				     into_input, second_shift_count,
				     into_target, unsignedp, next_methods);

	  if (into_temp1 != 0 && into_temp2 != 0)
	    inter = expand_binop (word_mode, ior_optab, into_temp1, into_temp2,
				  into_target, unsignedp, next_methods);
	  else
	    inter = 0;

	  if (inter != 0 && inter != into_target)
	    emit_move_insn (into_target, inter);

	  outof_temp1 = expand_binop (word_mode, unsigned_shift,
				      into_input, first_shift_count,
				      NULL_RTX, unsignedp, next_methods);
	  outof_temp2 = expand_binop (word_mode, reverse_unsigned_shift,
				      outof_input, second_shift_count,
				      outof_target, unsignedp, next_methods);

	  if (inter != 0 && outof_temp1 != 0 && outof_temp2 != 0)
	    inter = expand_binop (word_mode, ior_optab,
				  outof_temp1, outof_temp2,
				  outof_target, unsignedp, next_methods);

	  if (inter != 0 && inter != outof_target)
	    emit_move_insn (outof_target, inter);
	}

      insns = get_insns ();
      end_sequence ();

      if (inter != 0)
	{
	  if (binoptab->code != UNKNOWN)
	    equiv_value = gen_rtx (binoptab->code, mode, op0, op1);
	  else
	    equiv_value = 0;

	  /* We can't make this a no conflict block if this is a word swap,
	     because the word swap case fails if the input and output values
	     are in the same register.  */
	  if (shift_count != BITS_PER_WORD)
	    emit_no_conflict_block (insns, target, op0, op1, equiv_value);
	  else
	    emit_insns (insns);


	  return target;
	}
    }

  /* These can be done a word at a time by propagating carries.  */
  if ((binoptab == add_optab || binoptab == sub_optab)
      && class == MODE_INT
      && GET_MODE_SIZE (mode) >= 2 * UNITS_PER_WORD
      && binoptab->handlers[(int) word_mode].insn_code != CODE_FOR_nothing)
    {
      int i;
      rtx carry_tmp = gen_reg_rtx (word_mode);
      optab otheroptab = binoptab == add_optab ? sub_optab : add_optab;
      int nwords = GET_MODE_BITSIZE (mode) / BITS_PER_WORD;
      rtx carry_in, carry_out;
      rtx xop0, xop1;

      /* We can handle either a 1 or -1 value for the carry.  If STORE_FLAG
	 value is one of those, use it.  Otherwise, use 1 since it is the
	 one easiest to get.  */
#if STORE_FLAG_VALUE == 1 || STORE_FLAG_VALUE == -1
      int normalizep = STORE_FLAG_VALUE;
#else
      int normalizep = 1;
#endif

      /* Prepare the operands.  */