[SYCL] Skip device diagnostics for unevaluated functions (#1093)

Do not produce an error if some restricted feature
(e.g. exceptions) is used by a function only referenced
in unevaluated context(e.g. in decltype expression)

In order to do that, skip such functions when extracting
device part of the code.

Signed-off-by: Ilya Stepykin <[email protected]>

Author: Ilya Stepykin

clang/lib/Sema/SemaSYCL.cpp

@@ -1425,6 +1425,12 @@ Sema::DeviceDiagBuilder Sema::SYCLDiagIfDeviceCode(SourceLocation Loc,
 
 void Sema::checkSYCLDeviceFunction(SourceLocation Loc, FunctionDecl *Callee) {
   assert(Callee && "Callee may not be null.");
+
+  // Errors in unevaluated context don't need to be generated,
+  // so we can safely skip them.
+  if (isUnevaluatedContext())
+    return;
+
   FunctionDecl *Caller = dyn_cast<FunctionDecl>(getCurLexicalContext());
 
   // If the caller is known-emitted, mark the callee as known-emitted.

clang/test/SemaSYCL/unevaluated-function.cpp

@@ -0,0 +1,50 @@
+// RUN: %clang_cc1 -fcxx-exceptions -fsycl-is-device -verify -fsyntax-only %s
+
+// Check that a function used in an unevaluated context is not subject
+// to delayed device diagnostics.
+
+bool foo1() {
+  // Throw exception which is not allowed on device. Error is expected
+  // only when the function is called in evaluated context.
+  // expected-error@+1 1{{SYCL kernel cannot use exceptions}}
+  throw 10;
+
+  return false;
+}
+
+template <typename T>
+T foo2(T t) {
+  throw t;
+  return t;
+}
+
+bool foo3() {
+  __float128 a;
+  return false;
+}
+
+template <typename Name, typename Func>
+__attribute__((sycl_kernel)) void kernel_single_task(Func kernelFunc) {
+  // expected-note@+1 1{{called by}}
+  kernelFunc();
+}
+
+int main() {
+  using T1 = decltype(foo1());
+  kernel_single_task<class fake_kernel>([]() {
+    using T2 = decltype(foo1());
+
+    // expected-note@+1 1{{called by}}
+    auto S1 = foo1();
+    auto S2 = sizeof(foo1());
+
+    using T3 = decltype(foo2(decltype(foo1()){}));
+    using T4 = decltype(foo3());
+
+    T1 f1;
+    T2 f2;
+    T3 f3;
+    T4 f4;
+  });
+  return 0;
+}