[llvm-commits] [PATCH] Add TargetMemoryModel

[greened at obbligato.org]

Hal Finkel <hfinkel at anl.gov> writes:

>> What's TTI?
>
> Look at Analysis/TargetTransformInfo.h.

Ok, I will investigate!

>> I am certainly open to a better approach.  Would it be worth
>> submitting the rest of what I have, reviewing it as-is and trying to
>> commit it so that more people can participate in refining/reworking
>> it?  I have an ongoing interest in these models so it won't be a dump
>> and run.  :)
>
> I'm not sure; but it would be useful to see the rest of what you
> have. This would provide context to what you're proposing.

Ok.  I was waiting for all of my testing runs to finish to make sure
everything works.  I'll hopefully finish that today and post the whole
sequence.

>> > In addition, the prefetcher info should be cache-level specific.
>> > Many systems have different prefetchers for different cache levels.
>> 
>> The prefetcher information is purely configuration information for a
>> software prefetcher.
>
> Okay, interesting; now I understand. Will you be contributing this
> prefetcher as well?

That's a work in progress.  My best guess is that I might be able to
convince our management to allow me to submit a *really* simple version
of it.  I'm working on that.  I doubt I will be able to submit the whole
thing.

The idea was to have a target-agnostic software prefetcher that could be
configured on a target-by-target basis.  Even with a really dumb
software prefetcher, it's not terribly difficult to make it smarter.

>> Maybe I should rework the names to emphasize that this is a
>> configuration model for software prefetchers, not a model of any
>> hardware prefetchers.
>
> Well, do be fair, you did name it TargetSoftwarePrefetcherInfo. It
> might be better just to call it SoftwarePrefetcherInfo (because it is
> not a property of the target). Nevertheless, this should be part of
> TTI so that targets can customize the behavior in the (new) standard
> way.

But it is a property of the target.  The suggested distances are
specified for each target.  Hopefully this will be more clear once I
submit the whole sequence.

                          -David