PR53914, rs6000 constraints and reload queries

[Olivier Hainque]

On Aug 1, 2012, at 16:04 , Ulrich Weigand wrote:
> I've been wondering about mode_dependent_address_p myself.  It currently
> appears to cover two quite separate questions:
> 
> - If I have a valid address, will it remain valid if I change its mode to
>  something else?
> 
> - If I have a valid address, and change it mode (resulting in another
>  valid address), will the two address expressions have different
>  "meanings" or side effects?  (E.g. an auto-increment address where
>  the increment depends on the mode size.)
> 
> It seems to me that the first of those questions is rather redundant.
> Instead of speculating whether the address would remain valid if the
> mode were changed, code should IMO rather simply just change the
> address and then check its validity in the usual way (legitimate
> address etc.).  Only the second question really provides any actual
> *new* information ...
> 
> See also the reload patch I recently posted to get rid of some uses
> of offsettable_memref_p in favor of simply doing the change and testing
> its validity afterwards:
> http://gcc.gnu.org/ml/gcc-patches/2012-07/msg01421.html

 I think I see and need to give this further thought ...

 Thanks for your feedback :-)

 Cheers,

 Olivier