[LLVMdev] Supporting heterogeneous computing in llvm.

[C Bergström]

On Sun, Jun 7, 2015 at 2:34 AM, Eric Christopher <echristo at gmail.com> wrote:
>
>
> 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.

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