[clang] [SYCL] Basic diagnostics for the sycl_kernel_entry_point attribute. (PR #120327)

[Tom Honermann via cfe-commits]

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@@ -206,3 +208,124 @@ void SemaSYCL::handleKernelEntryPointAttr(Decl *D, const ParsedAttr &AL) {
   D->addAttr(::new (SemaRef.Context)
                  SYCLKernelEntryPointAttr(SemaRef.Context, AL, TSI));
 }
+
+static SourceLocation SourceLocationForType(QualType QT) {
+  SourceLocation Loc;
+  const Type *T = QT->getUnqualifiedDesugaredType();
+  if (const TagType *TT = dyn_cast<TagType>(T))
+    Loc = TT->getDecl()->getLocation();
+  else if (const ObjCInterfaceType *ObjCIT = dyn_cast<ObjCInterfaceType>(T))
+    Loc = ObjCIT->getDecl()->getLocation();
+  return Loc;
+}
+
+static bool CheckSYCLKernelName(Sema &S, SourceLocation Loc,
+                                QualType KernelName) {
+  assert(!KernelName->isDependentType());
+
+  if (!KernelName->isStructureOrClassType()) {
+    // SYCL 2020 section 5.2, "Naming of kernels", only requires that the
+    // kernel name be a C++ typename. However, the definition of "kernel name"
+    // in the glossary states that a kernel name is a class type. Neither
+    // section explicitly states whether the kernel name type can be
+    // cv-qualified. For now, kernel name types are required to be class types
+    // and that they may be cv-qualified. The following issue requests
+    // clarification from the SYCL WG.
+    //   https://github.com/KhronosGroup/SYCL-Docs/issues/568
+    S.Diag(Loc, diag::warn_sycl_kernel_name_not_a_class_type) << KernelName;
+    SourceLocation DeclTypeLoc = SourceLocationForType(KernelName);
+    if (DeclTypeLoc.isValid())
+      S.Diag(DeclTypeLoc, diag::note_entity_declared_at) << KernelName;
+    return true;
+  }
+
+  return false;
+}
+
+void SemaSYCL::CheckSYCLEntryPointFunctionDecl(FunctionDecl *FD) {
+  // Ensure that all attributes present on the declaration are consistent
+  // and warn about any redundant ones.
+  const SYCLKernelEntryPointAttr *SKEPAttr = nullptr;
+  for (auto SAI = FD->specific_attr_begin<SYCLKernelEntryPointAttr>();
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tahonermann wrote:

I don't see how that is an improvement. What is the concern with `specific_attr_iterator`? 

https://github.com/llvm/llvm-project/pull/120327