[SYCL] Warn when number of kernel args exceeds maximum available on GPU

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -10990,6 +10990,9 @@ def err_sycl_restrict : Error<
   "|use a const static or global variable that is neither zero-initialized "
   "nor constant-initialized"
   "}0">;
+def warn_sycl_kernel_too_many_args : Warning<
+  "resulting number of kernel arguments %0 is greater than maximum supported "
+  "on GPU device - %1">;
 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_recursive_function_declared_here: Note<"function implemented using recursion declared here">;

clang/lib/Sema/SemaSYCL.cpp

@@ -56,6 +56,7 @@ enum KernelInvocationKind {
 
 const static std::string InitMethodName = "__init";
 const static std::string FinalizeMethodName = "__finalize";
+const static unsigned GPUMaxKernelArgsNum = 2000;
 
 namespace {
 
@@ -1487,6 +1488,14 @@ class SyclKernelDeclCreator : public SyclKernelFieldHandler {
                    std::back_inserter(ArgTys),
                    [](const ParmVarDecl *PVD) { return PVD->getType(); });
 
+    // TODO: enable template instantiation tree for this diagnostic
+    if (SemaRef.Context.getTargetInfo().getTriple().getSubArch() ==
+        llvm::Triple::SPIRSubArch_gen)
+      if (Params.size() > GPUMaxKernelArgsNum)
+        SemaRef.Diag(KernelDecl->getLocation(),
+                     diag::warn_sycl_kernel_too_many_args)
+            << static_cast<unsigned>(Params.size()) << GPUMaxKernelArgsNum;
+
     QualType FuncType = Ctx.getFunctionType(Ctx.VoidTy, ArgTys, Info);
     KernelDecl->setType(FuncType);
     KernelDecl->setParams(Params);

clang/test/SemaSYCL/num-args-overflow.cpp

@@ -0,0 +1,17 @@
+// RUN: %clang_cc1 -fsycl -triple spir64_gen -DGPU -fsycl-is-device -fsyntax-only -verify %s
+// RUN: %clang_cc1 -fsycl -triple spir64 -fsycl-is-device -fsyntax-only -verify %s
+
+template <typename Name, typename F>
+__attribute__((sycl_kernel)) void kernel(F kernelFunc) {
+  kernelFunc();
+}
+
+void use() {
+  int Arr[2001];
+#ifdef GPU
+  // expected-warning@+4 {{resulting number of kernel arguments 2001 is greater than maximum supported on GPU device - 2000}}
+#else
+  // expected-no-diagnostics
+#endif
+  kernel<class Foo>([=]() { (void)Arr[0]; });
+}