[SYCL] Fix SYCL Kernel Body Check (#5546)

SYCLKernelAttr can be used to check if a given function is
a SYCL kernel body function or not. A SYCL kernel body function
is the operator() method of a SYCL Kernel Functor or Lambda Function.
The existing check which only tested if a FunctionDecl was an
operator or not, allowed for false positives. This patch adds an
additional check for SYCLKernelAttr, which will be attached to
the kernel body function's parent/ parent's parent (for wrapped
kernels)

Signed-off-by: Elizabeth Andrews <[email protected]>

Author: elizabethandrews

clang/lib/Sema/SemaSYCL.cpp

@@ -823,7 +823,8 @@ class SingleDeviceFunctionTracker {
     // false-positives.
     if (isSYCLKernelBodyFunction(CurrentDecl)) {
       // This is a direct callee of the kernel.
-      if (CallStack.size() == 1) {
+      if (CallStack.size() == 1 &&
+          CallStack.back()->hasAttr<SYCLKernelAttr>()) {
         assert(!KernelBody && "inconsistent call graph - only one kernel body "
                               "function can be called");
         KernelBody = CurrentDecl;

clang/test/SemaSYCL/non-kernel-functor.cpp

@@ -0,0 +1,21 @@
+// RUN: %clang_cc1 -fsycl-is-device -triple spir64-unknown-unknown -verify %s
+
+// Test to verify that non-kernel functors are not processed as SYCL kernel
+// functors
+
+// expected-no-diagnostics
+class First {
+public:
+  void operator()() { return; }
+};
+
+class Second {
+public:
+  First operator()() { return First(); }
+};
+
+SYCL_EXTERNAL
+void foo() {
+  Second NonKernelFunctorObj;
+  NonKernelFunctorObj()();
+}