Re: [GOOGLE] Iterative AutoFDO

[Dehao Chen <dehao at google dot com>]

Patch updated.

Thanks,
Dehao

On Wed, Oct 9, 2013 at 10:45 PM, Xinliang David Li <davidxl@google.com> wrote:
>  > /* Program behavior changed, original promoted (and inlined) target is not
>  > hot any more. Will avoid promote the original target.  */
>  > if (total >= info->first * 0.5)
>  >   return false;
>
> This part is still not clear: Difference between OLD_INFO and INFO,
> factor 0.5 comes from where etc.
>
>> gcov_type autofdo_source_profile::get_callsite_total_count (
>>    struct cgraph_edge *edge) const
>
> Formatting and missing documentation -- there are other cases like
> this in the source.
>
>>     /* No need to promoted the stmt if its in promoted_stmts (means
>>       it is already been promoted in the previous iterations).  */
>
> Make it clear that ic promotion and early-inline-2 is done in multiple
> iterations.
>
>> This is needed because an indirect call might be promoted and
>
> might have been
>
>  >    inlined in the profiled binary. If we do not promote and inline
>  >    these indirect calls before annothation, the profile for these
>
> annothation --> annotation.
>
>>   for (int i = 0; i < PARAM_VALUE (PARAM_EARLY_INLINER_MAX_ITERATIONS); i++)
>>   {
>>     if (!flag_value_profile_transformations
>>         || !autofdo::afdo_vpt_for_early_inline (&promoted_stmts))
>>      break;
>>    early_inliner ();
>
> Does it leave any indirect call sites not promoted after this loop? In
> other words, is there a need to keep the value profile transformation
> after the cfg annotation?

That's still needed because the IC_promotion happened before
annotation is only for those promoted in the profiling runs. We still
need to promote those newly exposed opportunities.

>
> A related question -- for indirect callsites that are not
> promoted/inlined in the profiled binary, will indirect call promotion
> and inlining before cfg annotation cause problems? The inline instance
> won't find profile anymore.

Those callsites will still be promoted after annotation, thus no problem.

Dehao

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