[LLVMdev] Supporting heterogeneous computing in llvm.

[Eric Christopher]

On Sat, Jun 6, 2015 at 12:31 PM C Bergström <cbergstrom at pathscale.com>
wrote:

> On Sun, Jun 7, 2015 at 2:22 AM, Eric Christopher <echristo at gmail.com>
> wrote:
> >
> >
> > On Sat, Jun 6, 2015 at 5:02 AM C Bergström <cbergstrom at pathscale.com>
> wrote:
> >>
> >> On Sat, Jun 6, 2015 at 6:24 PM, Christos Margiolas
> >> <chrmargiolas at gmail.com> wrote:
> >> > Hello,
> >> >
> >> > Thank you a lot for the feedback. I believe that the heterogeneous
> >> > engine
> >> > should be strongly connected with parallelization and vectorization
> >> > efforts.
> >> > Most of the accelerators are parallel architectures where having
> >> > efficient
> >> > parallelization and vectorization can be critical for performance.
> >> >
> >> > I am interested in these efforts and I hope that my code can help you
> >> > managing the offloading operations. Your LLVM instruction set
> extensions
> >> > may
> >> > require some changes in the analysis code but I think is going to be
> >> > straightforward.
> >> >
> >> > I am planning to push my code on phabricator in the next days.
> >>
> >> If you're doing the extracting at the loop and llvm ir level - why
> >> would you need to modify the IR? Wouldn't the target level lowering
> >> happen later?
> >>
> >> How are you actually determining to offload? Is this tied to
> >> directives or using heuristics+some set of restrictions?
> >>
> >> Lastly, are you handling 2 targets in the same module or end up
> >> emitting 2 modules and dealing with recombining things later..
> >>
> >
> > It's not currently possible to do this using the current structure
> without
> > some significant and, honestly, icky patches.
>
> What's not possible? I agree some of our local patches and design may
> not make it upstream as-is, but we are offloading to 2+ targets using
> llvm ir *today*.
>
>
I'm not sure how much more clear I can be. It's not possible, in the same
module, to handle multiple targets at the same time.


> IMHO - you must (re)solve the problem about handling multiple targets
> concurrently. That means 2 targets in a single Module or 2 Modules
> basically glued one after the other.
>

Patches welcome.

-eric
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