Add test motivation note

Signed-off-by: Steffen Larsen <[email protected]>

Author: Steffen Larsen

SYCL/Regression/unoptimized_stream.cpp

@@ -3,6 +3,11 @@
 // RUN: %CPU_RUN_PLACEHOLDER %t.out
 // RUN: %GPU_RUN_PLACEHOLDER %t.out
 
+// NOTE: The libclc target used by the CUDA backend used to generate atomic load
+//       variants that were unsupported by NVPTX. Even if they were not used
+//       directly, sycl::stream and other operations would keep the invalid
+//       operations in when optimizations were disabled.
+
 #include <sycl/sycl.hpp>
 
 int main() {