[SYCL] Fix crash caused by functor without call operator passed as Kernel.

Author: srividya-sundaram

clang/lib/Sema/SemaSYCL.cpp

@@ -2412,6 +2412,11 @@ static bool isESIMDKernelType(const CXXRecordDecl *KernelObjType) {
   return (OpParens != nullptr) && OpParens->hasAttr<SYCLSimdAttr>();
 }
 
+static bool isSYCLKernelDefinedAsAFunctor(const CXXRecordDecl *KernelObjType) {
+  const CXXMethodDecl *OpParens = getOperatorParens(KernelObjType);
+  return (OpParens != nullptr);
+}
+
 class SyclKernelBodyCreator : public SyclKernelFieldHandler {
   SyclKernelDeclCreator &DeclCreator;
   llvm::SmallVector<Stmt *, 16> BodyStmts;
@@ -3457,7 +3462,8 @@ void Sema::CheckSYCLKernelCall(FunctionDecl *KernelFunc, SourceRange CallLoc,
   const CXXRecordDecl *KernelObj =
       GetSYCLKernelObjectType(KernelFunc)->getAsCXXRecordDecl();
 
-  if (!KernelObj) {
+  bool IsKernelAValidFunctor = isSYCLKernelDefinedAsAFunctor(KernelObj);
+  if (!KernelObj || !IsKernelAValidFunctor) {
     Diag(Args[0]->getExprLoc(), diag::err_sycl_kernel_not_function_object);
     KernelFunc->setInvalidDecl();
     return;

clang/test/SemaSYCL/undefined-functor.cpp

@@ -0,0 +1,18 @@
+// RUN: %clang_cc1 -fsycl-is-device -internal-isystem %S/Inputs -sycl-std=2020 -verify -fsyntax-only %s
+
+#include "sycl.hpp"
+
+using namespace sycl;
+queue q;
+
+struct FunctorWithoutCallOperator; // expected-note {{forward declaration of 'FunctorWithoutCallOperator'}}
+
+int main() {
+    // expected-error@#KernelSingleTask {{kernel parameter must be a lambda or function object}}
+  q.submit([&](sycl::handler &cgh) {
+    // expected-error@+2 {{invalid use of incomplete type 'FunctorWithoutCallOperator'}}
+    // expected-note@+1 {{in instantiation of function template specialization}}
+    cgh.single_task(FunctorWithoutCallOperator{});
+  });
+
+}