Re: useless_type_conversion_p vs pointer sizes

[Tristan Gingold <gingold at adacore dot com>]

On Jan 13, 2012, at 10:59 PM, DJ Delorie wrote:

> 
>> That should not be necessary as there is a mode check below.  Do you
>> hit the issue only when the VOID_TYPE_P check is true?  In that case
>> simply delete it - it has become obsolete.
> 
> That seems to be happening, yes, but there are other checks
> that might let differing modes through...
> 
>  /* Changes in machine mode are never useless conversions unless we
>     deal with aggregate types in which case we defer to later checks.  */
>  if (TYPE_MODE (inner_type) != TYPE_MODE (outer_type)
>      && !AGGREGATE_TYPE_P (inner_type))
>    return false;
> 
> Later,
> 
>  else if (POINTER_TYPE_P (inner_type)
> 	   && POINTER_TYPE_P (outer_type))
>    {
>      /* Do not lose casts to function pointer types.  */
>      if ((TREE_CODE (TREE_TYPE (outer_type)) == FUNCTION_TYPE
> 	   || TREE_CODE (TREE_TYPE (outer_type)) == METHOD_TYPE)
> 	  && !(TREE_CODE (TREE_TYPE (inner_type)) == FUNCTION_TYPE
> 	       || TREE_CODE (TREE_TYPE (inner_type)) == METHOD_TYPE))
> 	return false;
> 
>      /* We do not care for const qualification of the pointed-to types
> 	 as const qualification has no semantic value to the middle-end.  */
> 
>      /* Otherwise pointers/references are equivalent.  */
>      return true;
>    }
> 
> So two different sized pointers to aggregate types will also have a problem?

No, because pointers are not aggregate types.

> 
> I'm a little paranoid here because TPF uses different sized pointers a
> *lot* so if we can't guarantee that the rest of the logic keeps the
> conversion, I'd rather keep the explicit check.

For the record, what is TPF ?

Tristan.