[SYCL] Implement get_backend_info()

[HPS-1]

Implementing the get_backend_info() functions for our SYCL implementation based on SYCL 2020 spec. (Link here: https://registry.khronos.org/SYCL/specs/sycl-2020/html/sycl-2020.html you may search for "get_backend_info()" there for the spec for these functions)
There're six groups of variations for this function, namely sycl::platform::get_backend_info(), sycl::context::get_backend_info(), sycl::device::get_backend_info(), sycl::queue::get_backend_info(), sycl::eventv::get_backend_info(), and sycl::kernel::get_backend_info()

One known concern: it seems that sycl::platform, sycl::context and sycl::kernel may have multiple associated device, but according to the spec the return type for sycl::xxx::get_backend_info<info::device::version>() should be std::string (i.e. a single device version) so I'm just returning the version of the first associated device in the list. Is this OK?

[AlexeySachkov]

Tests are missing. We should at least add some to sycl/test which would check that we can compile code using new API and/or there could be tests in sycl/test-e2e which would check that the new API behaves as expected

[HPS-1]

Tests are missing. We should at least add some to sycl/test which would check that we can compile code using new API and/or there could be tests in sycl/test-e2e which would check that the new API behaves as expected

Fixed! Added the new e2e test case sycl/test-e2e/backend_info.cpp for this purpose.

[againull]

@HPS-1

One known concern: it seems that sycl::platform, sycl::context and sycl::kernel may have multiple associated device, but according to the spec the return type for sycl::xxx::get_backend_infoinfo::device::version() should be std::string (i.e. a single device version) so I'm just returning the version of the first associated device in the list. Is this OK?

info::device::version is the information descriptor of the sycl::device. Do we have to actually support it for all other classes sycl::platform, sycl::context and sycl::kernel? Maybe it's enough to support it only for sycl::device.

[HPS-1]

@HPS-1

One known concern: it seems that sycl::platform, sycl::context and sycl::kernel may have multiple associated device, but according to the spec the return type for sycl::xxx::get_backend_infoinfo::device::version() should be std::string (i.e. a single device version) so I'm just returning the version of the first associated device in the list. Is this OK?

info::device::version is the information descriptor of the sycl::device. Do we have to actually support it for all other classes sycl::platform, sycl::context and sycl::kernel? Maybe it's enough to support it only for sycl::device.

@againull Hi! Thanks for reviewing the code. And about the question you have, the thing is that the SYCL specification for (all variations of) get_backend_info() says "The type alias Param::return_type must be defined in accordance with the SYCL backend specification.", while the SYCL backend spec (for OpenCL, link here https://registry.khronos.org/SYCL/specs/sycl-2020/html/sycl-2020.html#_backend_specific_information_descriptors) suggest that both info::platform::version and info::device::version are backend-specific info descriptors. I think this means that we should allow the user to query them using all variations of get_backend_info(), including the ones you mentioned such as sycl::context::get_backend_info().

[againull]

@HPS-1

One known concern: it seems that sycl::platform, sycl::context and sycl::kernel may have multiple associated device, but according to the spec the return type for sycl::xxx::get_backend_infoinfo::device::version() should be std::string (i.e. a single device version) so I'm just returning the version of the first associated device in the list. Is this OK?

info::device::version is the information descriptor of the sycl::device. Do we have to actually support it for all other classes sycl::platform, sycl::context and sycl::kernel? Maybe it's enough to support it only for sycl::device.

@againull Hi! Thanks for reviewing the code. And about the question you have, the thing is that the SYCL specification for (all variations of) get_backend_info() says "The type alias Param::return_type must be defined in accordance with the SYCL backend specification.", while the SYCL backend spec (for OpenCL, link here https://registry.khronos.org/SYCL/specs/sycl-2020/html/sycl-2020.html#_backend_specific_information_descriptors) suggest that both info::platform::version and info::device::version are backend-specific info descriptors. I think this means that we should allow the user to query them using all variations of get_backend_info(), including the ones you mentioned such as sycl::context::get_backend_info().

In such case probably we can return the version of the default/selected device.
For example, let's say if we have 3 devices (opencl gpu, l0 gpu, opencl cpu) in the context.
If user didn't set ONEAPI_DEVICE_SELECTOR, then we can return version of the device chosen by default selector - it will be l0 gpu.
If user set ONEAPI_DEVICE_SELECTOR=opencl:cpu, then we can return the version of the opencl cpu device.

But maybe it worth discussing with language group.