[LLVMdev] Supporting heterogeneous computing in llvm.

[C Bergström]

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*.

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.