[Openmp-dev] Declare variant + Nvidia Device Offload

[Johannes Doerfert via Openmp-dev]

On 5/20/20 12:26 PM, Jonas Hahnfeld wrote:
> Am Mittwoch, den 20.05.2020, 11:40 -0500 schrieb Johannes Doerfert:
>> On 5/20/20 11:19 AM, Jonas Hahnfeld wrote:
>>> Am Dienstag, den 19.05.2020, 17:50 +0200 schrieb Lukas Sommer via
>>> Openmp-dev:
>>>> Hi Johannes,
>>>>
>>>>> Yes, we need to replace the dot with either of the symbols you
>>>>> mentioned. If we can use the same symbols on the host, I'm fine with
>>>>> chaining it unconditionally.
>>>> I've prototyped this change locally, replacing the dot with a
>>>> dollar-sign in the places you mentioned. With this change, declaring
>>>> variants for offloading to CUDA devices works for my testcase in my
>>>> setup (ARM + Nvidia SM 7.2).
>>>>
>>>> If you want, I could create a patch for that, but do you (or anyone else
>>>> on the list) know whether the other offloading targets (AMDGPU, NEC VE,
>>>> ...) are all able to handle the dollar sign in the mangled name, so we
>>>> could make this change unconditionally? I do not have a setup for each
>>>> of these to test.
>>>>
>>>> I was also wondering if legalizing the mangled name shouldn't be handled
>>>> by the backend (NVPTX in this case) instead of the OpenMP-specific parts.
>>> For some context on this, see the following set of reviews:
>>> https://reviews.llvm.org/D17738
>>> https://reviews.llvm.org/D29883
>>> https://reviews.llvm.org/D39005
>>> https://reviews.llvm.org/D40573
>>>
>>> My favorite statement from the last patch: "This is silly. This bug has
>>> been open for so long that nvidia could've just fixed their toolchain
>>> by now to accept dots in symbol names."
>> Thanks for the links!
>>
>> I think in those reviews people also concluded you cannot/should not
>> modify visible symbol names late.
>>
>> I guess, since we have _$_ in other cases we should do _$_ as separator
>> in Clang too. WDYT?
> Probably depending on the target architecture, see for example
> CGOpenMPRuntime::getOutlinedHelperName() and the override in
> CGOpenMPRuntimeNVPTX for precedence.


I would like to avoid using just __, for c++filt reasons. CGOpenMPRuntime is

going away, if we want to change something this is the time.