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Re: PR53914, rs6000 constraints and reload queries
- From: Alan Modra <amodra at gmail dot com>
- To: Olivier Hainque <hainque at adacore dot com>
- Cc: gcc at gcc dot gnu dot org, dje dot gcc at gmail dot com, bergner at vnet dot ibm dot com, mrmeissn at us dot ibm dot com, uweigand at de dot ibm dot com
- Date: Wed, 1 Aug 2012 20:48:22 +0930
- Subject: Re: PR53914, rs6000 constraints and reload queries
- References: <20120717153411.GB27761@bubble.grove.modra.org> <F9A05836-D987-495F-8E9C-C992A5B2C27F@adacore.com>
On Wed, Aug 01, 2012 at 10:26:50AM +0200, Olivier Hainque wrote:
> I had made a proposal to help the rs6000_mode_dependent_address
> issue, http://gcc.gnu.org/ml/gcc-patches/2012-04/msg01668.html.
>
> Seems to me that the general idea is still valid:
>
> << a number of places in the compiler use the
> mode_dependent_address_p predicate to actually check for weaker necessary
> conditions
> >>
>
> Opinion on the proposal ?
I like the idea. It is worth pursuing for code improvement we'll see
even if we avoid the "o" constraint everywhere. For example,
long long llo (long long *x) { return x[4095]; }
will generate better powerpc -m32 -O2 code with your patch applied, I
think.
--
Alan Modra
Australia Development Lab, IBM