On 7/14/22 16:25, Erick Ochoa wrote:
>
>
> On Thu, 14 Jul 2022 at 16:10, Martin Liška <[email protected]
> <mailto:[email protected]>> wrote:
>
> On 7/14/22 16:08, Erick Ochoa via Gcc wrote:
> > Last time I checked, value profiling can only track a single value per
> > statement.
>
> Hi.
>
> Take a look at HIST_TYPE_INDIR_CALL which we use for tracking at maximum
> 32
> (#define GCOV_TOPN_MAXIMUM_TRACKED_VALUES 32) and we use for indirect call
> speculative calls which you can see for instance here:
>
> ./gcc/testsuite/g++.dg/tree-prof/indir-call-prof.C
>
>
> Thanks Martin,
>
> I'll give it a read. However, I have mis-spoken. If my understanding is
> correct: multiple values are tracked, but only the values of a single
> variable/expression per statement are tracked. That means that for a gcall
> (which is a single statement and) which has n argument expressions, I believe
> that the naive way to track all argument expressions is not possible without
> extending how histograms are associated to statements. Perhaps canonicalizing
> how callsites work (i.e., only variables are allowed as arguments in call
> sites and then associating a histogram to the definition of the variables
> being used in call sites) would be enough, but I haven't given it much
> thought for the consequences that might follow from this.
Yes, you are correct that we track only one type of histogram per each gimple
statement:
histogram_value
gimple_histogram_value_of_type (struct function *fun, gimple *stmt,
enum hist_type type)
{
histogram_value hist;
for (hist = gimple_histogram_value (fun, stmt); hist;
hist = hist->hvalue.next)
if (hist->type == type)
return hist;
return NULL;
}
but that could be theoretically relaxed for your use-case.
Cheers,
Martin
>
>
>
> Cheers,
> Martin
>
