Re: [PATCH] Discard Scops for which entry==exit

[Richard Biener <richard.guenther@gmail.com>]

On Tue, Jun 30, 2015 at 8:11 AM, Tobias Grosser <tobias@grosser.es> wrote:
> On 06/30/2015 02:09 AM, Sebastian Pop wrote:
>>
>> On Mon, Jun 29, 2015 at 3:04 PM, Aditya Kumar <hiraditya@msn.com> wrote:
>>>
>>> In this patch we discard the scops where entry and exit are the same BB.
>>> This is an effort to remove graphite-scop-detection.c:limit_scops.
>>> Removing the limit_scops function introduces correctness regressions.
>>> We are making relevant changes in incremental steps to fix those bugs,
>>> and finally we intend to remove limit_scops.
>>>
>>> 2015-06-29  Aditya Kumar  <aditya.k7@samsung.com>
>>>              Sebastian Pop <s.pop@samsung.com>
>>>
>>>          * graphite-scop-detection.c (build_scops_1): Discard scops for
>>> which entry==exit
>>
>>
>> Looks good to me.
>> Let's wait on comments from Tobi before pushing this patch.
>
>
> Hi Sebastian,
>
> the commit message should probably give a short reasoning why scops with
> entry == exit need to be discarded. I currently don't see why they would be
> incorrect/problematic (despite being possibly very small/empty).

Dependent on how GRAPHITE initializes loops even a loop can consist of a single
basic-block (without LOOPS_HAVE_SIMPLE_LATCHES where you always have at
least two BBs for a loop).

I suppose GRAPHITE does nothing for non-loops and this is what the check is
about?  (so rather require a backedge in the SCOP?)

Of ocurse I also don't see "correctness" issues here, just maybe a waste of
compile-time?

Richard.

> Tobias