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Re: PR53914, rs6000 constraints and reload queries

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:

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

 Thanks for your feedback :-)




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