gcc-8.3/gcc/alter_subreg()

参照元†

gcc-8.3/gcc/alter_subregs()

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説明†

パス: gcc-8.3/gcc/final.c

FIXME: これは何？
- 説明

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引数†

rtx *xp
- gcc-8.3/gcc/rtx
bool final_p

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返り値†

rtx
- gcc-8.3/gcc/rtx

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参考†

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実装†

/* If X is a SUBREG, try to replace it with a REG or a MEM, based on
   the thing it is a subreg of.  Do it anyway if FINAL_P.  */

rtx
alter_subreg (rtx *xp, bool final_p)
{
  rtx x = *xp;
  rtx y = SUBREG_REG (x);

- gcc-8.3/gcc/rtx
- gcc-8.3/gcc/SUBREG_REG()

  /* simplify_subreg does not remove subreg from volatile references.
     We are required to.  */
  if (MEM_P (y))
    {
      poly_int64 offset = SUBREG_BYTE (x);

      /* For paradoxical subregs on big-endian machines, SUBREG_BYTE
	 contains 0 instead of the proper offset.  See simplify_subreg.  */
      if (paradoxical_subreg_p (x))
	offset = byte_lowpart_offset (GET_MODE (x), GET_MODE (y));

      if (final_p)
	*xp = adjust_address (y, GET_MODE (x), offset);
      else
	*xp = adjust_address_nv (y, GET_MODE (x), offset);
    }

  else if (REG_P (y) && HARD_REGISTER_P (y))
    {
      rtx new_rtx = simplify_subreg (GET_MODE (x), y, GET_MODE (y),
				     SUBREG_BYTE (x));

      if (new_rtx != 0)
	*xp = new_rtx;
      else if (final_p && REG_P (y))
	{
	  /* Simplify_subreg can't handle some REG cases, but we have to.  */
	  unsigned int regno;
	  poly_int64 offset;

	  regno = subreg_regno (x);
	  if (subreg_lowpart_p (x))
	    offset = byte_lowpart_offset (GET_MODE (x), GET_MODE (y));
	  else
	    offset = SUBREG_BYTE (x);
	  *xp = gen_rtx_REG_offset (y, GET_MODE (x), regno, offset);
	}
    }