[SYCL] Follow-up for #19990

Downstream CI uncovered another scenario where
`detail::CompileTimeKernelInfo<KernelName>.Name` might be empty (other
than non-SYCL compilation in some of the [unit]tests). That happens when
compiling the same TU using multiple offload models (e.g., both SYCL and
OMP) and the device compilation for non-SYCL model doesn't use SYCL
integration header to provide kernel information.

Also, my previous comments about `__usmfill` turned out to be incorrect.
We do NOT unconditionally instantiate any of those in the
`sycl/handler.hpp`, it was individual unittests that did that.

Author: aelovikov-intel

sycl/include/sycl/handler.hpp

@@ -836,26 +836,28 @@ class __SYCL_EXPORT handler {
                                               Dims>());
 #endif
 
-    // SYCL unittests are built without sycl compiler, so "host" information
-    // about kernels isn't provided (e.g., via integration headers or compiler
-    // builtins).
-    //
-    // However, some copy/fill USM operation are implemented via SYCL kernels
-    // and are instantiated resulting in all the `static_assert` checks being
-    // exercised. Without kernel information that would fail, so we explicitly
-    // disable such checks when this macro is defined. Note that the unittests
-    // don't actually execute those operation, that's why disabling
-    // unconditional `static_asserts`s is enough for now.
-#ifndef __SYCL_UNITTESTS_BYPASS_KERNEL_NAME_CHECK
     constexpr auto Info = detail::CompileTimeKernelInfo<KernelName>;
 
-    static_assert(Info.Name != std::string_view{}, "Kernel must have a name!");
+    // Ideally, the following should be a `static_assert` but cannot do that as
+    // it would fail in at least two scenarios:
+    //
+    //  * Our own unittests that are compiled with an arbitrary host compiler
+    //    without SYCL knowledge (i.e., no integration headers
+    //    generated/supplied). Those that don't have to supply any stub kernel
+    //    information test exceptions thrown before kernel enqueue, so having a
+    //    run-time assert here doesn't affect them.
+    //
+    //  * Mixed SYCL/OpenMP compilation, device code generation for OpenMP in
+    //  * particular. For that scenario this code is compiled but never
+    //  * executed.
+    assert(Info.Name != std::string_view{} && "Kernel must have a name!");
 
     // Some host compilers may have different captures from Clang. Currently
     // there is no stable way of handling this when extracting the captures,
     // so a static assert is made to fail for incompatible kernel lambdas.
     static_assert(
-        sizeof(KernelType) == Info.KernelSize,
+        Info.Name == std::string_view{} ||
+            sizeof(KernelType) == Info.KernelSize,
         "Unexpected kernel lambda size. This can be caused by an "
         "external host compiler producing a lambda with an "
         "unexpected layout. This is a limitation of the compiler."
@@ -866,7 +868,6 @@ class __SYCL_EXPORT handler {
         "In case of MSVC, passing "
         "-fsycl-host-compiler-options='/std:c++latest' "
         "might also help.");
-#endif
 
     setDeviceKernelInfo<KernelName>((void *)MHostKernel->getPtr());
 

sycl/test/lit.cfg.py

@@ -126,9 +126,7 @@
 llvm_symbolizer = os.path.join(config.llvm_build_bin_dir, "llvm-symbolizer")
 llvm_config.with_environment("LLVM_SYMBOLIZER_PATH", llvm_symbolizer)
 
-sycl_host_only_options = (
-    "-std=c++17 -Xclang -fsycl-is-host -D__SYCL_UNITTESTS_BYPASS_KERNEL_NAME_CHECK=1"
-)
+sycl_host_only_options = "-std=c++17 -Xclang -fsycl-is-host"
 for include_dir in [
     config.sycl_include,
     config.level_zero_include_dir,

sycl/unittests/CMakeLists.txt

@@ -9,8 +9,6 @@ endforeach()
 
 add_compile_definitions(SYCL2020_DISABLE_DEPRECATION_WARNINGS SYCL_DISABLE_FSYCL_SYCLHPP_WARNING)
 
-add_compile_definitions(__SYCL_UNITTESTS_BYPASS_KERNEL_NAME_CHECK)
-
 # suppress warnings which came from Google Test sources
 if (CXX_SUPPORTS_SUGGEST_OVERRIDE_FLAG)
   add_compile_options("-Wno-suggest-override")