[SYCL] Suppress warning about cdecl calling convention

Signed-off-by: Premanand M Rao <[email protected]>

Author: premanandrao

clang/lib/Sema/SemaDeclAttr.cpp

@@ -4613,10 +4613,11 @@ bool Sema::CheckCallingConvAttr(const ParsedAttr &Attrs, CallingConv &CC,
     return true;
   }
 
+  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 = TI.getDefaultCallingConv();
     break;
   case ParsedAttr::AT_FastCall:
     CC = CC_X86FastCall;
@@ -4681,7 +4682,6 @@ bool Sema::CheckCallingConvAttr(const ParsedAttr &Attrs, CallingConv &CC,
   }
 
   TargetInfo::CallingConvCheckResult A = TargetInfo::CCCR_OK;
-  const TargetInfo &TI = Context.getTargetInfo();
   // CUDA functions may have host and/or device attributes which indicate
   // their targeted execution environment, therefore the calling convention
   // of functions in CUDA should be checked against the target deduced based

clang/test/SemaSYCL/sycl-cconv.cpp

@@ -1,14 +1,23 @@
 // RUN: %clang_cc1 -triple spir64-unknown-windows-sycldevice -aux-triple x86_64-pc-windows-msvc -fsycl-is-device -fsyntax-only -verify %s
 
-//expected-warning@+1 {{'__cdecl' calling convention is not supported for this target}}
+// expected-no-warning@+1
 __inline __cdecl int printf(char const* const _Format, ...) { return 0; }
+// expected-no-warning@+1
+__inline __cdecl __attribute__((sycl_device)) int foo() { return 0; }
+// expected-no-warning@+1
+__inline __cdecl int moo() { return 0; }
 
 void bar() {
   printf("hello\n"); // expected-no-error
 }
 
 template <typename name, typename Func>
-__attribute__((sycl_kernel)) void kernel_single_task(Func kernelFunc) {
+// expected-no-warning@+1
+__cdecl __attribute__((sycl_kernel)) void kernel_single_task(Func kernelFunc) {
+  // expected-error@+1{{SYCL kernel cannot call a variadic function}}
+  printf("cannot call from here\n");
+  // expected-no-error@+1
+  moo();
   kernelFunc();
 }