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Currently, we return early whenever we've already generated an allocation for intermediate descriptor variables (required in certain cases when we can't directly access the base address of a passes in descriptor function argument due to HLFIR/FIR restrictions). This unfortunately, skips over the presence check and load/store required to set the intermediate descriptor allocations values/data. This is fine in most cases, but if a function happens to have a series of branches with seperate target regions capturing the same input argument, we'd emit the present/load/store into the first branch with the first target inside of it, the secondary (or any preceding) branches would not have the present/load/store, this would lead to the subsequent mapped values in that branch being empty and then leading to a memory access violation on device. The fix for the moment is to emit a present/load/store at the relevant location of every target utilising the input argument, this likely will also lead to fixing possible issues with the input argument being manipulated inbetween target regions (primarily resizing, the data should remain the same as we're just copying an address around, in theory at least). There's possible optimizations/simplifications to emit less load/stores such as by raising the load/store out of the branches when we can, but I'm inclined to leave this sort of optimization to lower level passes such as an LLVM pass (which very possibly already covers it).
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