Enable use of default platform context extension (#627)

* Enable use of default platform context extension

Instead of using sycl::context(const sycl::device &D) constructor
to created cached context, use sycl::queue(const sycl::device &D) and
extract context from the queue.

For capable compiler, i.e. the one that supports
https://github.com/intel/llvm/blob/sycl/sycl/doc/extensions/PlatformContext/PlatformContext.adoc

the queue constructor will use platform default context. For other compilers
the sycl::context(D) will get called, so the behavior won't change.

If compiler supports default platform context extension, use that when building the cached.

* Use rfind instead of index to find latest occurrance of usm_type in pickle bytes

* Make sure that testing is done with host device enabled

Author: oleksandr-pavlyk

.github/workflows/conda-package.yml

@@ -151,6 +151,7 @@ jobs:
         run: |
           # echo "libintelocl.so" | tee /etc/OpenCL/vendors/intel-cpu.icd
           export OCL_ICD_FILENAMES=libintelocl.so
+          export SYCL_ENABLE_HOST_DEVICE=1
           # clinfo -l
           python -m pytest --pyargs $MODULE_NAME
 
@@ -208,7 +209,9 @@ jobs:
       - name: Add library
         run: echo "OCL_ICD_FILENAMES=C:\Miniconda\Library\lib\intelocl64.dll" | Out-File -FilePath $env:GITHUB_ENV -Encoding utf8 -Append
       - name: Run tests
-        run: python -m pytest --pyargs ${{ env.MODULE_NAME }}
+        run: |
+          set SYCL_ENABLE_HOST_DEVICE=1
+          python -m pytest --pyargs ${{ env.MODULE_NAME }}
 
   upload_linux:
     needs: test_linux

dpctl-capi/source/dpctl_sycl_device_manager.cpp

@@ -124,7 +124,15 @@ struct DeviceCacheBuilder
                 for (const auto &D : Devices) {
                     if (mRanker(D) < 0)
                         continue;
-                    auto entry = cache_l.emplace(D, D);
+
+                    // Per https://github.com/intel/llvm/blob/sycl/sycl/doc/
+                    // extensions/PlatformContext/PlatformContext.adoc
+                    // sycl::queue(D) would create default platform context
+                    // for capable compiler, sycl::context(D) otherwise
+                    auto Q = queue(D);
+                    auto Ctx = Q.get_context();
+                    auto entry = cache_l.emplace(D, Ctx);
+
                     if (!entry.second) {
                         std::cerr << "Fatal Error during device cache "
                                      "construction.\n";

dpctl/tests/test_sycl_usm.py

@@ -201,7 +201,7 @@ def test_pickling_reconstructor_invalid_type(memory_ctor):
     mobj = memory_ctor(1024, alignment=64)
     good_pickle_bytes = pickle.dumps(mobj)
     usm_types = expected_usm_type(memory_ctor).encode("utf-8")
-    i = good_pickle_bytes.index(usm_types)
+    i = good_pickle_bytes.rfind(usm_types)
     bad_pickle_bytes = good_pickle_bytes[:i] + b"u" + good_pickle_bytes[i + 1 :]
     with pytest.raises(ValueError):
         pickle.loads(bad_pickle_bytes)