[SYCL] Functions with variadic arguments should not get a diagnostic …

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -9746,7 +9746,8 @@ def err_sycl_restrict : Error<
   "|call through a function pointer"
   "|allocate storage"
   "|use inline assembly"
-  "|have a class with a virtual function table}0">;
+  "|have a class with a virtual function table"
+  "|call a variadic function}0">;
 def err_sycl_virtual_types : Error<
   "No class with a vtable can be used in a SYCL kernel or any code included in the kernel">;
 def note_sycl_used_here : Note<"used here">;

clang/include/clang/Sema/Sema.h

@@ -11326,7 +11326,8 @@ class Sema {
     KernelCallFunctionPointer,
     KernelAllocateStorage,
     KernelUseAssembly,
-    KernelHavePolymorphicClass
+    KernelHavePolymorphicClass,
+    KernelCallVariadicFunction
  };
   DeviceDiagBuilder SYCLDiagIfDeviceCode(SourceLocation Loc, unsigned DiagID);
   void ConstructOpenCLKernel(FunctionDecl *KernelCallerFunc);

clang/lib/Sema/SemaSYCL.cpp

@@ -317,6 +317,9 @@ class MarkDeviceFunction : public RecursiveASTVisitor<MarkDeviceFunction> {
     if (!Visited.insert(Ty).second)
       return true;
 
+    if (const auto *ATy = dyn_cast<AttributedType>(Ty))
+      return CheckSYCLType(ATy->getModifiedType(), Loc, Visited);
+
     if (const auto *CRD = Ty->getAsCXXRecordDecl()) {
       // If the class is a forward declaration - skip it, because otherwise we
       // would query property of class with no definition, which results in
@@ -354,6 +357,9 @@ class MarkDeviceFunction : public RecursiveASTVisitor<MarkDeviceFunction> {
         }
       }
     } else if (const auto *FPTy = dyn_cast<FunctionProtoType>(Ty)) {
+      if (FPTy->isVariadic() && SemaRef.getLangOpts().SYCLIsDevice)
+	SemaRef.SYCLDiagIfDeviceCode(Loc.getBegin(), diag::err_sycl_restrict)
+            << Sema::KernelCallVariadicFunction;
       for (const auto &ParamTy : FPTy->param_types())
         if (!CheckSYCLType(ParamTy, Loc, Visited))
           return false;

clang/lib/Sema/SemaType.cpp

@@ -7075,11 +7075,6 @@ static bool handleFunctionTypeAttr(TypeProcessingState &state, ParsedAttr &attr,
                << (int)Sema::CallingConventionIgnoredReason::VariadicFunction;
 
       attr.setInvalid();
-      if (S.getLangOpts().SYCLIsDevice) {
-        S.SYCLDiagIfDeviceCode(attr.getLoc(), diag::err_cconv_varargs)
-          << FunctionType::getNameForCallConv(CC);
-        return true;
-      } else
       return S.Diag(attr.getLoc(), diag::err_cconv_varargs)
              << FunctionType::getNameForCallConv(CC);
     }

clang/test/SemaSYCL/sycl-varargs-cconv.cpp

@@ -0,0 +1,24 @@
+// RUN: %clang_cc1 -fsycl-is-device -verify -fsyntax-only -x c++ %s
+
+int __cdecl foo(int, ...); // expected-no-error
+
+float bar(float f, ...) { return ++f; } // expected-no-error
+
+void bar() {
+  foo(5); // expected-no-error
+  bar(7.0f); // expected-no-error
+}
+
+template <typename name, typename Func>
+__attribute__((sycl_kernel)) void kernel_single_task(Func kernelFunc) {
+  kernelFunc();
+}
+
+int main() {
+  //expected-error@+1 {{SYCL kernel cannot call a variadic function}}
+  kernel_single_task<class fake_kernel>([]() { foo(6); });
+  //expected-error@+1 {{SYCL kernel cannot call a variadic function}}
+  kernel_single_task<class fake_kernel>([]() { bar(9.0); });
+  bar();
+  return 0;
+}