[SYCL] gpu_selector not failing when no GPU devices

[jbrodman]

 cl::sycl::queue queue(cl::sycl::gpu_selector{});
  std::cout << "Running on " << queue.get_device().get_info<cl::sycl::info::device::name>() << std::endl;

on a CPU system prints either:

./test1
Running on Intel(R) FPGA Emulation Device

or

env SYCL_DEVICE_TYPE=CPU ./test1
Running on Intel(R) Xeon(R) Platinum 8180 CPU @ 2.50GHz

I think it's supposed to be throwing an exception if there's not an available GPU device...

[KarachunIvan]

I reckon that you observe such behavior because of this line:

llvm/sycl/source/device_selector.cpp

Line 55 in 44954af

(score == dev_score && isDeviceOfPreferredSyclBe(dev))) {

gpu_selector return -1 for every device except for GPU. So dev_score will be -1 (score = -1 by default). Besides, isDeviceOfPreferredSyclBe returns true if the device uses opencl backend.
So, in that case first OpenCL device will be chosen.

[jbrodman]

Probably.

It's still violating the spec. :)

[Ruyk]

I found this problem too while working on NVIDIA OpenCL filtering, i'll fix it as part of that patch

[Ruyk]

In #1689 , devices with score -1 are properly discarded

[romanovvlad]

Will put a fix on review soon.

[romanovvlad]

Should be resolved by #1689. @jbrodman please, check.

[jbrodman]

Looks like it now properly fails.