Re: RFC: fix think-o in tree-ssa-loop-ivopts.c

[Richard Guenther <richard dot guenther at gmail dot com>]

On Wed, Jun 9, 2010 at 9:59 PM, Eric Botcazou <ebotcazou@adacore.com> wrote:
>> The "cost" is never referred to again in the fallback code, so it seems
>> like deleting the return statement was an unintended mistake.
>
> Indeed, how embarassing. :-( ?This affects 4.5.x as well.
>
>> So, I'm wondering: ?Eric, were the runtime speed improvements you claimed
>> you saw here
>>
>> http://gcc.gnu.org/ml/gcc-patches/2009-05/msg01858.html
>>
>> actually present in the checked-in version of the patch, where the result
>> of the fancy cost computation is simply discarded, or in some other version
>> of the patch that implemented what I presume was the intended behavior?
>
> Probably in both versions, at least partially. ?The main effect (saving 1
> register for loops with non-constant iteration origin) is always present.
>
>> Do we know for sure that the fancy cost computation actually even an
>> improvement over the fallback case?
>
> The "fancy" computation was an improvement, yes.
>
>> 2010-06-09 ?Sandra Loosemore ?<sandra@codesourcery.com>
>>
>> ? ? ? gcc/
>> ? ? ? * tree-ssa-loop-ivopts.c (get_computation_cost_at): Return the
>> ? ? ? computed cost.
>
> I'd add "again". ?Thanks for spotting this.

The patch is ok if it passes bootstrap and regtest.  It's also ok for the
branch after a while.

Thanks,
Richard.

> --
> Eric Botcazou
>