[tree-ssa] Re: auto vectorization in gcc

[Daniel Berlin]

On Wednesday, July 23, 2003, at 12:50 PM, Dorit Naishlos wrote:

>
>> This is very much along the same lines as I was envisaging.  Given we
>> currently have some time and resources that could be used on a project
>> like this would you be interested / able tocolaborate on this project?
>
> Sure! (there's a lot to be done...)
>
> We're still at the design phase - trying to decide which
> vectorization scheme we want to implement, what is the minimal
> essential infrastructure required in order to vectorize even
> the simplest loop/code-sequence, and how much of this infrastructure
> is already available, or is being developed and will be available (and
> when).
>
> I understand that Sebastian Pop is working on IV detection,
> and that data dependence analysis will be based on that infrastructure.
> Where does that stand? Sebastian, were you planning to work on the
> dependence graph too?
>
> The project's web page states that loop normalization
> and loop canonicalization are on the todo list. Is someone working
> on that? (Daniel Berlin?)

Is it actually necessary?
A lot of papers i've read recently think it isn't.


> I guess that's pending the IV detection work too?
>

No, it normalized trivial ivs.

You can easily detect trivial iv's in tree-ssa form.

They have a single arity 2 phi node in the first block of the loop, 
with one edge/value coming from a def in the pre-header of that loop, 
and one edge/value coming from the latch block of that loop.