[Bug target/64905] unsigned short is loaded with 4-byte load (movl)

["hjl.tools at gmail dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64905

H.J. Lu <hjl.tools at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2015-02-02
                 CC|                            |ubizjak at gmail dot com
          Component|translation                 |target
   Target Milestone|---                         |5.0
     Ever confirmed|0                           |1

--- Comment #1 from H.J. Lu <hjl.tools at gmail dot com> ---
aligned_operand has

  if (MEM_ALIGN (op) >= 32)
    return true;

  op = XEXP (op, 0);

  /* Pushes and pops are only valid on the stack pointer.  */
  if (GET_CODE (op) == PRE_DEC
      || GET_CODE (op) == POST_INC)
    return true;

  /* Decode the address.  */
  ok = ix86_decompose_address (op, &parts);
  gcc_assert (ok);

  if (parts.base && GET_CODE (parts.base) == SUBREG)
    parts.base = SUBREG_REG (parts.base);
  if (parts.index && GET_CODE (parts.index) == SUBREG)
    parts.index = SUBREG_REG (parts.index);

  /* Look for some component that isn't known to be aligned.  */
  if (parts.index)
    {
      if (REGNO_POINTER_ALIGN (REGNO (parts.index)) * parts.scale < 32)
        return false;
    }
  if (parts.base)
    {
      if (REGNO_POINTER_ALIGN (REGNO (parts.base)) < 32)
        return false;
    }
  if (parts.disp)
    {
      if (!CONST_INT_P (parts.disp)
          || (INTVAL (parts.disp) & 3))
        return false;
    }

  /* Didn't find one -- this must be an aligned address.  */
  return true;

It returns true for

(mem:HI (reg/f:DI 6 bp [orig:90 *a_p_2(D) ] [90]) [2 *_3+0 S2 A16])

Why do we need to decompose address when we have MEM_ALIGN (op)?