Re: [PATCH] Redesign jump threading profile updates

[Teresa Johnson <tejohnson@google.com>]

On Wed, Apr 16, 2014 at 10:39 PM, Jeff Law <law@redhat.com> wrote:
> On 03/26/14 17:44, Teresa Johnson wrote:
>>
>> Recently I discovered that the profile updates being performed by jump
>> threading were incorrect in many cases, particularly in the case where
>> the threading path contains a joiner. Some of the duplicated
>> blocks/edges were not getting any counts, leading to incorrect
>> function splitting and other downstream optimizations, and there were
>> other insanities as well. After making a few attempts to fix the
>> handling I ended up completely redesigning the profile update code,
>> removing a few places throughout the code where it was attempting to
>> do some updates.
>
> The profile updates in that code is a mess.  It's never really been looked
> at in any systematic way, what's there is ad-hoc and usually in response to
> someone mentioning the profile data was incorrectly updated.   As we rely
> more and more on that data the ad-hoc updating is going to cause us more and
> more pain.
>
> So any work in this space is going to be greatly appreciated.
>
> I'll have to look at this in some detail.  But I wanted you to know I was
> aware of the work and it's in my queue.

Great, thanks for the update! I realize that it is not a trivial
change so it would take some time to get through. Hopefully it should
address the ongoing profile fixup issues.
Teresa

>
> Thanks!
>
> jeff



-- 
Teresa Johnson | Software Engineer | tejohnson@google.com | 408-460-2413