[polly] Memory access based dependency analysis

Tobias Grosser tobias at grosser.es
Tue Jun 24 16:21:47 PDT 2014


On 25/06/2014 01:12, Johannes Doerfert wrote:
> I don't think a single reduction in a statement without anything else needs
> this memory access based dependency tracking.
> However, I found it easier to order the patches this way. Furthermore, the
> patch which will cause the need for this kind of
> Analysis is big enough on its own and I don't really see the point in
> combining them (or changing the order and producing wrong code in between).
>
> So what is the plan now? Do we agree on the need for this patch? Can I
> commit it now? If so, we should also consider the next patch as it will
> bring the compilation time back to normal.

So what is the next patch that requires this one? Can you already post 
it to the mailing list? My hope is that we can find a patch order that 
enables us to enable multi-statement dependences without introducing
incorrectness, but just being very conservatively in the dependences 
(only detect reductions if the statement consists purely of reduction
dependences). After this is committed, we can then use a subsequent 
patch to give the dependence analysis more freedom.

Another point I am not sure about. Even in case of multi-reduction 
statements, is there a test case where per-access dependences will
give more freedom to the scheduler. Or can the increased freedom only be 
exploited together with the reduction aware parallel ast generation?

Tobias




More information about the llvm-commits mailing list