Introduced in OpenMP 6.0, the device UID shall be a unique identifier of a device on a given system. (Not necessarily a UUID.) Since it is not guaranteed that the (U)UIDs defined by the device vendor libraries, such as HSA, do not overlap with those of other vendors, the device UIDs in offload are always combined with the offload plugin name. In case the vendor library does not specify any device UID for a given device, we fall back to the offload-internal device ID. The device UID can be retrieved using the `llvm-offload-device-info` tool.
Summary: This causes issues with CUDA's teardown order when the init is separated from the total init scope.
Summary: The Offloading library wraps around the underlying plugins. The problem is that we currently initialize all plugins we find, even if they are not needed for the program. This is very expensive for trivial uses, as fully heterogenous usage is quite rare. In practice this means that you will always pay a 200 ms penalty for having CUDA installed. This patch changes the behavior to provide accessors into the plugins and devices that allows them to be initialized lazily. We use a once_flag, this should properly take a fast-path check while still blocking on concurrent use. Making full use of this will require a way to filter platforms more specifically. I'm thinking of what this would look like as an API. I'm thinking that we either have an extra iterate function that takes a callback on the platform, or we just provide a helper to find all the devices that can run a given image. Maybe both? Fixes: https://github.com/llvm/llvm-project/issues/159636
Summary: Need to verify this actually has a device. We really need to rework this to point to a real impolementation, or streamline it to handle this automatically.
Currently, devices store a raw pointer to back to their owning Platform. Platforms are stored directly inside of a vector. Modifying this vector risks invalidating all the platform pointers stored in devices. This patch allocates platforms individually, and changes devices to store a reference to its platform instead of a pointer. This is safe, because platforms are guaranteed to outlive the devices they contain.
Summary: The host plugin is basically OpenMP specific and doesn't work very well. Previously we were skipping over it in the list instead of just not adding it at all.
If olMemAlloc happens to allocate memory that was already allocated elsewhere (possibly by another device on another platform), it is now thrown away and a new allocation generated. A new `AllocBases` vector is now available, which is an ordered list of allocation start addresses.
Summary: This exposes the 'isDeviceCompatible' routine for checking if a binary *can* be loaded. This is useful if people don't want to consume errors everywhere when figuring out which image to put to what device. I don't know if this is a good name, I was thining like `olIsCompatible` or whatever. Let me know what you think. Long term I'd like to be able to do something similar to what OpenMP does where we can conditionally only initialize devices if we need them. That's going to be support needed if we want this to be more generic.