[SYCL] Have default_selector consider SYCL_BE

Have the default_selector consider the env var SYCL_BE when rating
device scores to make choosing a backend easier.

Signed-off-by: Alexander Johnston <[email protected]>

Author: Alexander Johnston

sycl/source/device_selector.cpp

@@ -31,6 +31,24 @@ device device_selector::select_device() const {
 }
 
 int default_selector::operator()(const device &dev) const {
+
+  // Take note of the SYCL_BE environment variable when doing default selection
+  const char *SYCL_BE = std::getenv("SYCL_BE");
+  std::string backend = (SYCL_BE ? SYCL_BE : "");
+  if (backend != "") {
+    const std::string DriverVersion = dev.get_info<info::device::driver_version>();
+    // If we have a cuda device but aren't using PI_CUDA, don't use this device
+    if (DriverVersion.find("CUDA") == std::string::npos && backend == "PI_CUDA") {
+      return -1;
+    }
+    // We can't easily check for an OpenCL device as there is no common string
+    // to search for on all devices, so just guarantee we don't choose a cuda
+    // device when PI_OPENCL is used
+    if (DriverVersion.find("CUDA") != std::string::npos && backend == "PI_OPENCL") {
+      return -1;
+    }
+  }
+
   if (dev.is_gpu())
     return 500;