Re: [PATCH][ARM] Fix costing of sign-extending load in rtx costs

[Kyrill Tkachov <kyrylo dot tkachov at foss dot arm dot com>]

Ping.
Thanks,
Kyrill

On 11/05/16 10:00, Kyrill Tkachov wrote:
> Ping.
> https://gcc.gnu.org/ml/gcc-patches/2016-04/msg01655.html
>
> Thanks,
> Kyrill
>
> On 27/04/16 15:13, Kyrill Tkachov wrote:
> > Hi all,
> >
> > Another costs issue that came out of the investigation for PR 65932 is that
> > sign-extending loads get a higher cost than they should in the arm backend.
> > The problem is that when handling a sign-extend of a MEM we add the cost
> > of the load_sign_extend cost field and then recursively add the cost of the inner MEM
> > rtx, which is bogus. This will end up adding an extra load cost on it.
> >
> > The solution in this patch is to just remove that recursive step.
> > With this patch from various CSE dumps I see much more sane costs assign to these
> > expressions (such as 12 instead of 32 or higher).
> >
> > Bootstrapped and tested on arm-none-linux-gnueabihf.
> >
> > Ok for trunk?
> >
> > Thanks,
> > Kyrill
> >
> > 2016-04-27  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
> >
> >     * config/arm/arm.c (arm_new_rtx_costs, SIGN_EXTEND case):
> >     Don't add cost of inner memory when handling sign-extended
> >     loads.