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Re: PR53914, rs6000 constraints and reload queries
- From: Olivier Hainque <hainque at adacore dot com>
- To: Ulrich Weigand <uweigand at de dot ibm dot com>
- Cc: Olivier Hainque <hainque at adacore dot com>, gcc at gcc dot gnu dot org, amodra at gmail dot com, dje dot gcc at gmail dot com, bergner at vnet dot ibm dot com, mrmeissn at us dot ibm dot com
- Date: Thu, 2 Aug 2012 18:30:20 +0200
- Subject: Re: PR53914, rs6000 constraints and reload queries
- References: <201208011404.q71E4pJR020376@d06av02.portsmouth.uk.ibm.com>
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 :-)