From 7938a50cb26b4465b7d03ca5754b1dbdc8a3d973 Mon Sep 17 00:00:00 2001
From: Alexey Sachkov <alexey.sachkov@intel.com>
Date: Thu, 18 Sep 2025 11:54:09 +0200
Subject: [PATCH 1/2] [SYCL] Fix error with type aliases used as free function
 kernel args

This PR fixes type name that is being printed as free function kernel
argument type in its forward-declaration in the integration header.

Before the change, we used the original argument type name, which could
be an alias - this patch makes use of the canonical type's name to make
sure that all type aliases are "unwrapped".
---
 clang/lib/Sema/SemaSYCL.cpp                   |  8 +--
 .../free-function-kernel-type-alias-arg.cpp   | 53 +++++++++++++++++++
 2 files changed, 57 insertions(+), 4 deletions(-)
 create mode 100644 clang/test/CodeGenSYCL/free-function-kernel-type-alias-arg.cpp

diff --git a/clang/lib/Sema/SemaSYCL.cpp b/clang/lib/Sema/SemaSYCL.cpp
index c86e49a1be33b..b9a5d202af373 100644
--- a/clang/lib/Sema/SemaSYCL.cpp
+++ b/clang/lib/Sema/SemaSYCL.cpp
@@ -6822,13 +6822,13 @@ class FreeFunctionPrinter {
         continue;
       }
 
-      TemplateName TN = TST->getTemplateName();
+      TemplateName CTN = CTST->getTemplateName();
+      CTN.getAsTemplateDecl()->printQualifiedName(ParmListOstream);
+      ParmListOstream << "<";
+
       auto SpecArgs = TST->template_arguments();
       auto DeclArgs = CTST->template_arguments();
 
-      TN.getAsTemplateDecl()->printQualifiedName(ParmListOstream);
-      ParmListOstream << "<";
-
       for (size_t I = 0, E = std::max(DeclArgs.size(), SpecArgs.size()),
                   SE = SpecArgs.size();
            I < E; ++I) {
diff --git a/clang/test/CodeGenSYCL/free-function-kernel-type-alias-arg.cpp b/clang/test/CodeGenSYCL/free-function-kernel-type-alias-arg.cpp
new file mode 100644
index 0000000000000..00dc0abbe0db0
--- /dev/null
+++ b/clang/test/CodeGenSYCL/free-function-kernel-type-alias-arg.cpp
@@ -0,0 +1,53 @@
+// RUN: %clang_cc1 -fsycl-is-device -internal-isystem %S/Inputs -triple spir64-unknown-unknown -sycl-std=2020 -fsycl-int-header=%t.h %s
+// RUN: FileCheck -input-file=%t.h %s
+//
+// The purpose of this test is to ensure that forward declarations of free
+// function kernels are emitted properly.
+// However, this test checks a specific scenario:
+// - free function arguments are type aliases (through using or typedef)
+
+namespace ns {
+
+using IntUsing = int;
+typedef int IntTypedef;
+
+template <typename T>
+struct Foo {};
+
+using FooIntUsing = Foo<int>;
+typedef Foo<int> FooIntTypedef;
+
+template <typename T1, typename T2>
+struct Bar {};
+
+template<typename T1>
+using BarUsing = Bar<T1, float>;
+
+} // namespace ns
+
+[[__sycl_detail__::add_ir_attributes_function("sycl-nd-range-kernel", 2)]]
+void int_using(ns::IntUsing Arg) {}
+
+// CHECK: void int_using(int Arg);
+
+[[__sycl_detail__::add_ir_attributes_function("sycl-nd-range-kernel", 2)]]
+void int_typedef(ns::IntTypedef Arg) {}
+
+// CHECK: void int_typedef(int Arg);
+
+[[__sycl_detail__::add_ir_attributes_function("sycl-nd-range-kernel", 2)]]
+void foo_using(ns::FooIntUsing Arg) {}
+
+// CHECK: void foo_using(ns::Foo<int> Arg);
+
+[[__sycl_detail__::add_ir_attributes_function("sycl-nd-range-kernel", 2)]]
+void foo_typedef(ns::FooIntTypedef Arg) {}
+
+// CHECK: void foo_typedef(ns::Foo<int> Arg);
+
+template<typename T>
+[[__sycl_detail__::add_ir_attributes_function("sycl-nd-range-kernel", 2)]]
+void bar_using(ns::BarUsing<T> Arg) {}
+template void bar_using(ns::BarUsing<int>);
+
+// CHECK: template <typename T> void bar_using(ns::Bar<T, float>);

From e32713371f2b925232dddbf8356596fab10a8efa Mon Sep 17 00:00:00 2001
From: Alexey Sachkov <alexey.sachkov@intel.com>
Date: Thu, 18 Sep 2025 13:06:31 +0200
Subject: [PATCH 2/2] Add one more test case

---
 .../free-function-kernel-type-alias-arg.cpp            | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/clang/test/CodeGenSYCL/free-function-kernel-type-alias-arg.cpp b/clang/test/CodeGenSYCL/free-function-kernel-type-alias-arg.cpp
index 00dc0abbe0db0..d605d8be537bf 100644
--- a/clang/test/CodeGenSYCL/free-function-kernel-type-alias-arg.cpp
+++ b/clang/test/CodeGenSYCL/free-function-kernel-type-alias-arg.cpp
@@ -23,6 +23,11 @@ struct Bar {};
 template<typename T1>
 using BarUsing = Bar<T1, float>;
 
+class Baz {
+public:
+  using type = BarUsing<double>;
+};
+
 } // namespace ns
 
 [[__sycl_detail__::add_ir_attributes_function("sycl-nd-range-kernel", 2)]]
@@ -51,3 +56,8 @@ void bar_using(ns::BarUsing<T> Arg) {}
 template void bar_using(ns::BarUsing<int>);
 
 // CHECK: template <typename T> void bar_using(ns::Bar<T, float>);
+
+[[__sycl_detail__::add_ir_attributes_function("sycl-nd-range-kernel", 2)]]
+void baz_type(ns::Baz::type Arg) {}
+
+// CHECK: void baz_type(ns::Bar<double, float> Arg);