Disallow applying the sycl_kernel_entry_point attribute to functions with a function-try-block.

The SYCL 2020 specification prohibits the use of C++ exceptions in device
functions. Even if exceptions were not prohibited, it is unclear what the
semantics would be for an exception that escapes the SYCL kernel entry point
function; the boundary between host and device code could be an implicit
noexcept boundary that results in program termination if violated, or the
exception could perhaps be propagated to host code via the SYCL library.
The semantics of function-try-blocks is that an exception raised in the
function body that escapes to a function-try-block handler is implicitly
rethrown. Pending support for C++ exceptions in device code and clear
semantics for handling them at the host-device boundary, this change makes
use of the sycl_kernel_entry_point attribute with a function defined with
a function-try-block an error.

Author: tahonermann

clang/include/clang/Basic/AttrDocs.td

@@ -487,6 +487,7 @@ following requirements.
 * Is not a C variadic function.
 * Is not a coroutine.
 * Is not defined as deleted or as defaulted.
+* Is not defined with a function try block.
 * Is not declared with the ``constexpr`` or ``consteval`` specifiers.
 * Is not declared with the ``[[noreturn]]`` attribute.
 

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -12457,7 +12457,8 @@ def err_sycl_entry_point_invalid : Error<
   "'sycl_kernel_entry_point' attribute cannot be applied to a"
   " %select{non-static member function|variadic function|deleted function|"
            "defaulted function|constexpr function|consteval function|"
-           "function declared with the 'noreturn' attribute|coroutine}0">;
+           "function declared with the 'noreturn' attribute|coroutine|"
+           "function defined with a function try block}0">;
 def err_sycl_entry_point_invalid_redeclaration : Error<
   "'sycl_kernel_entry_point' kernel name argument does not match prior"
   " declaration%diff{: $ vs $|}0,1">;

clang/lib/Sema/SemaDecl.cpp

@@ -15983,6 +15983,10 @@ Decl *Sema::ActOnFinishFunctionBody(Decl *dcl, Stmt *Body,
       Diag(SKEPAttr->getLocation(), diag::err_sycl_entry_point_invalid)
           << /*coroutine*/ 7;
       SKEPAttr->setInvalidAttr();
+    } else if (Body && isa<CXXTryStmt>(Body)) {
+      Diag(SKEPAttr->getLocation(), diag::err_sycl_entry_point_invalid)
+          << /*function defined with a function try block*/ 8;
+      SKEPAttr->setInvalidAttr();
     }
 
     if (Body && !FD->isTemplated() && !SKEPAttr->isInvalidAttr()) {

clang/test/SemaSYCL/sycl-kernel-entry-point-attr-appertainment.cpp

@@ -350,3 +350,12 @@ auto bad36 = [] [[clang::sycl_kernel_entry_point(BADKN<36>)]] static {};
 // expected-error@+1 {{'sycl_kernel_entry_point' attribute cannot be applied to a coroutine}}
 auto bad37 = [] [[clang::sycl_kernel_entry_point(BADKN<37>)]] static -> void { co_return; };
 #endif
+
+// expected-error@+1 {{'sycl_kernel_entry_point' attribute cannot be applied to a function defined with a function try block}}
+[[clang::sycl_kernel_entry_point(BADKN<38>)]]
+void bad38() try {} catch(...) {}
+
+// expected-error@+2 {{'sycl_kernel_entry_point' attribute cannot be applied to a function defined with a function try block}}
+template<typename>
+[[clang::sycl_kernel_entry_point(BADKN<39>)]]
+void bad39() try {} catch(...) {}