diff --git a/clang/lib/Sema/SemaDeclAttr.cpp b/clang/lib/Sema/SemaDeclAttr.cpp
index ae04d3855f01c..2b47459ac4368 100644
--- a/clang/lib/Sema/SemaDeclAttr.cpp
+++ b/clang/lib/Sema/SemaDeclAttr.cpp
@@ -5743,10 +5743,11 @@ bool Sema::CheckCallingConvAttr(const ParsedAttr &Attrs, CallingConv &CC,
   bool IsTargetDefaultMSABI =
       Context.getTargetInfo().getTriple().isOSWindows() ||
       Context.getTargetInfo().getTriple().isUEFI();
+  const TargetInfo &TI = Context.getTargetInfo();
   // TODO: diagnose uses of these conventions on the wrong target.
   switch (Attrs.getKind()) {
   case ParsedAttr::AT_CDecl:
-    CC = CC_C;
+    CC = LangOpts.SYCLIsDevice ? TI.getDefaultCallingConv() : CC_C;
     break;
   case ParsedAttr::AT_FastCall:
     CC = CC_X86FastCall;
@@ -5853,7 +5854,6 @@ bool Sema::CheckCallingConvAttr(const ParsedAttr &Attrs, CallingConv &CC,
   }
 
   TargetInfo::CallingConvCheckResult A = TargetInfo::CCCR_OK;
-  const TargetInfo &TI = Context.getTargetInfo();
   auto *Aux = Context.getAuxTargetInfo();
   // CUDA functions may have host and/or device attributes which indicate
   // their targeted execution environment, therefore the calling convention
diff --git a/clang/lib/Sema/SemaType.cpp b/clang/lib/Sema/SemaType.cpp
index 44ac4f6630690..298e076ea374c 100644
--- a/clang/lib/Sema/SemaType.cpp
+++ b/clang/lib/Sema/SemaType.cpp
@@ -8380,7 +8380,7 @@ static bool handleFunctionTypeAttr(TypeProcessingState &state, ParsedAttr &attr,
   // much ability to diagnose it later.
   if (!supportsVariadicCall(CC)) {
     const FunctionProtoType *FnP = dyn_cast<FunctionProtoType>(fn);
-    if (FnP && FnP->isVariadic()) {
+    if (FnP && FnP->isVariadic() && !S.getLangOpts().SYCLIsDevice) {
       // stdcall and fastcall are ignored with a warning for GCC and MS
       // compatibility.
       if (CC == CC_X86StdCall || CC == CC_X86FastCall)
diff --git a/clang/test/SemaSYCL/sycl-cconv.cpp b/clang/test/SemaSYCL/sycl-cconv.cpp
index 664a4dbf37c49..c018e734253fe 100644
--- a/clang/test/SemaSYCL/sycl-cconv.cpp
+++ b/clang/test/SemaSYCL/sycl-cconv.cpp
@@ -4,14 +4,11 @@
 // Check that there is no error/warning emitted for cdecl functions compiled for
 // SYCL device. Make sure variadic calls from within device code are diagnosed.
 
-// no-aux-warning@+2 {{'__cdecl' calling convention is not supported for this target}}
-// no-aux-error@+1 {{variadic function cannot use spir_function calling convention}}
 __inline __cdecl int printf(char const* const _Format, ...) { return 0; }
 
 // FIXME: that should be diagnosed.
 [[clang::sycl_external]] int foo(int, ...) { return 0; }
 
-// no-aux-warning@+1 {{'__cdecl' calling convention is not supported for this target}}
 __inline __cdecl int moo() { return 0; }
 
 void bar() {
@@ -27,11 +24,24 @@ void sycl_kernel_launch(Args ...args) {}
 
 template<typename KN, typename K>
 [[clang::sycl_kernel_entry_point(KN)]]
-// no-aux-warning@+1 {{'__cdecl' calling convention is not supported for this target}}
 __cdecl void sycl_entry_point(K k) {
   k(); // expected-note {{called by}}
 }
 
+// No errors for deallocation/allocation functions.
+void __cdecl operator delete(void *) noexcept;
+
+// Make sure that function type conversions work.
+typedef void (__cdecl *funcTy)();
+void invoke(funcTy f);
+
+static void callee() noexcept {
+}
+
+void foo() {
+   invoke(callee);
+}
+
 int main() {
   //expected-error@+1 {{SYCL device code does not support variadic functions}}
   sycl_entry_point<class kn>([]() { printf("world\n");