[PATCH] D138862: [Clang] Do not set offload kind in a freestanding build

[Joseph Huber via Phabricator via cfe-commits]

jhuber6 added a comment.

In D138862#3955339 <https://reviews.llvm.org/D138862#3955339>, @tra wrote:

>> we should expect it to be handled externally.
>
> Can you give more details on how it will work? Something/somewhere would need to generate the glue code to register kernels w/ CUDA runtime.
> Are you saying that we'll have some way to tell the final linking stage that all offloaded functions with unspecified offload kind must be treated as if they need runtime X, and the appropriate glue will be generated for them?
>
> If you mean that it would need to be handled by the end user, it may be problematic as they would need to have access to the GPU binaries, the kernel names they contain and would need to further generate host-side kernel launch stubs matching the kernel names.

So this patch was made because I'm trying to create a generic `libc` runtime for the GPU. The easiest way to build this was to use OpenMP. However, this creates a fatbinary with the kind set to `OpenMP` this means if someone linked with the built `libcgpu.a` for a CUDA application it would lead to the linker wrapper thinking it had to create registration code for both CUDA and OpenMP. So my goal was to allow a way for us to add "Nothing" as the offloading kind. This will result in only registering with the CUDA runtime in the previous example. I figured `-ffreestanding` was the best option to overload for this behaviour because it more or less implies that there is no standard runtime, in this case OpenMP.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D138862/new/

https://reviews.llvm.org/D138862