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`PRIVATE | ATTACH` maps can be used to represent firstprivate pointers that should be initialized by doing doing the pointee's device address, if its lookup succeeds, or retain the original host pointee's address otherwise. With this, for a test like the following: ```f90 integer, pointer :: p(:) !$omp target map(p(1)) ... print*, p(1) !$omp end target ``` The codegen can look like: ```llvm ; maps for p: ; &p(1), &p(1), sizeof(p(1)), TO|FROM //(1) ; &ref_ptr(p), &p(1), sizeof(ref_ptr(p)), ATTACH //(2) ; &ref_ptr(p), &p(1), sizeof(ref_ptr(p)), PRIVATE|ATTACH|PARAM //(3) call... @__omp_outlined...(ptr %ref_ptr_of_p) ``` * `(1)` maps the pointee `p(1)`. * `(2)` attaches it to the (previously) mapped `ref_ptr(p)`, if present. It can be controlled via OpenMP 6.1's `attach(auto/always/never)` map-type modifiers. * `(3)` privatizes and initializes the local `ref_ptr(p)`, which gets passed in as the kernel argument `%ref_ptr_of_p`. Can be skipped if p is not referenced directly within the region. While similar mapping can be used for C/C++, it's more important/useful for Fortran as we can avoid creating another argument for passing the descriptor, and use that to initialize the private copy in the body of the kernel.
The LLVM/Offload Subproject
The Offload subproject aims at providing tooling, runtimes, and APIs that allow users to execute code on accelerators or other "co-processors" that may or may not match the architecture of their "host". In the long run, all kinds of targets are in scope of this effort, including but not limited to: CPUs, GPUs, FPGAs, AI/ML accelerators, distributed resources, etc.
For OpenMP offload users, the project is ready and fully usable. The final API design is still under development. More content will show up here and on our webpage soon. In the meantime, people are encouraged to participate in our meetings (see below) and check our development board as well as the discussions on Discourse.
Meetings
Every second Wednesday, 7:00 - 8:00am PT, starting Jan 24, 2024. Alternates with the OpenMP in LLVM meeting. invite.ics Meeting Minutes and Agenda