Re: [AutoFDO] prevent head_count of 0 with AFDO profile.

Hell,
this is OK,
thanks
Honza

On Thu, Aug 20, 2026 at 1:01 AM Kugan Vivekanandarajah <
[email protected]> wrote:

> Hi Honza,
>
> Thanks for the review.
>
> > On 4 Aug 2026, at 5:07 pm, Jan Hubička <[email protected]> wrote:
> >
> > External email: Use caution opening links or attachments
> > Kugan,
> > I apologize for late reaction. I finally got to reproduce this.
> > I think we want to set the entry block count to
> >  MAX (1, afdo_count_scale / 2)
> > Receiving 0 samples on code that is known to be executed means that the
> real value should be somewhere between 0 and 1, so 1/2 is good estimate.
> Setting count 1 will make all basic blocks to appear very hot and confuse
> the logic computing BB frequency.
> >
> > Also I think you can do that just once in  afdo_calculate_branch_prob
> > just after calling afdo_adjust_guessed_profile instead of doing it as a
> > part of the fixup algorithm (which is already bit complicated).
>
> Yes, this helps. I have added in one place as you suggested and this fixes
> the ICE.
> If you don't have any objections, I will commit this patch.
>
> Thanks,
> Kugan
>
>