[LLVMdev] SIV tests in LoopDependence Analysis, Sanjoy's patch

[Preston Briggs]

On Mon, May 14, 2012 at 1:30 PM, Hal Finkel <hfinkel at anl.gov> wrote:

> Can you explain this comment:
> > With minor algebra, this test can also be used for things like [c1 +
> > a1*i + a2*j][c2].

It's really too simple to deserve mention...
Given a subscript pair, [c1 + a1*i + a2*j] and [c2], we can test for
dependence using the RDIV test by rewriting as [c1 + a1*i] and [c2 -
a2*j].

> I this look good, but, as you say below, we also need to work on the
> top-level infrastructure. It will be hard to validate and evaluate
> this code without a framework in which to use it.

Yep. I've written a simple framework to do tests on my own, but it
needs to be extended to be more generally useful.

> One thing that I would like to mention is that 'use' here should also
> include user feedback. This means being able to pass information back
> to the frontends about which loops are being effectively analyzed, and
> for loops that are not, why not.

Absolutely. I've been thinking in terms of passing info back to the
programmer (see
https://sites.google.com/site/parallelizationforllvm/feedback). It's a
very interesting problem and one where I think there are real research
possibilities.

Preston