From 9a01c127a8d47c08eab55c4b9b75fceddc6c2605 Mon Sep 17 00:00:00 2001
From: Alexey Sachkov <alexey.sachkov@intel.com>
Date: Thu, 20 Nov 2025 15:45:21 +0100
Subject: [PATCH 1/2] [SYCL] Fix one more bug in int-header generation

When free function kernel defined as a template has an argument whose
type is an alias, we need to look into the underlying type, or otherwise
we emit nonsense.
---
 clang/lib/Sema/SemaSYCL.cpp                   |  9 +++++--
 .../free-function-kernel-type-alias-arg.cpp   | 25 +++++++++++++++++++
 2 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/clang/lib/Sema/SemaSYCL.cpp b/clang/lib/Sema/SemaSYCL.cpp
index ba08bb279d44f..fc5145a2805de 100644
--- a/clang/lib/Sema/SemaSYCL.cpp
+++ b/clang/lib/Sema/SemaSYCL.cpp
@@ -6814,13 +6814,18 @@ class FreeFunctionPrinter {
       QualType T = Param->getType();
       QualType CT = T.getCanonicalType();
 
-      auto *TST = dyn_cast<TemplateSpecializationType>(T.getTypePtr());
-      auto *CTST = dyn_cast<TemplateSpecializationType>(CT.getTypePtr());
+      const auto *TST = dyn_cast<TemplateSpecializationType>(T.getTypePtr());
+      const auto *CTST = dyn_cast<TemplateSpecializationType>(CT.getTypePtr());
       if (!TST || !CTST) {
         ParmListOstream << T.getAsString(Policy);
         continue;
       }
 
+      const TemplateSpecializationType *TSTAsNonAlias =
+          TST->getAsNonAliasTemplateSpecializationType();
+      if (TSTAsNonAlias)
+        TST = TSTAsNonAlias;
+
       TemplateName CTN = CTST->getTemplateName();
       CTN.getAsTemplateDecl()->printQualifiedName(ParmListOstream);
       ParmListOstream << "<";
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 d605d8be537bf..ca18c4c50abb8 100644
--- a/clang/test/CodeGenSYCL/free-function-kernel-type-alias-arg.cpp
+++ b/clang/test/CodeGenSYCL/free-function-kernel-type-alias-arg.cpp
@@ -23,11 +23,18 @@ struct Bar {};
 template<typename T1>
 using BarUsing = Bar<T1, float>;
 
+template<typename T1, typename T2>
+using BarUsing2 = Bar<Foo<T2>, T1>;
+
 class Baz {
 public:
   using type = BarUsing<double>;
 };
 
+template <typename T1, typename T2, typename T3 = BarUsing2<T1, T2>,
+          typename T4 = BarUsing<T2>>
+struct AliasAsDefaultArg {};
+
 } // namespace ns
 
 [[__sycl_detail__::add_ir_attributes_function("sycl-nd-range-kernel", 2)]]
@@ -57,7 +64,25 @@ template void bar_using(ns::BarUsing<int>);
 
 // CHECK: template <typename T> void bar_using(ns::Bar<T, float>);
 
+template<typename T1, typename T2>
+[[__sycl_detail__::add_ir_attributes_function("sycl-nd-range-kernel", 2)]]
+void bar_using2(ns::BarUsing2<T1, T2> Arg) {}
+template void bar_using2(ns::BarUsing2<int, float>);
+
+// CHECK: template <typename T1, typename T2> void bar_using2(ns::Bar<ns::Foo<T2>, T1>);
+
 [[__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);
+
+#if 0
+// This test case fails, but it is added here in advance to add a record of a
+// known bug.
+template<typename T1, typename T2>
+[[__sycl_detail__::add_ir_attributes_function("sycl-nd-range-kernel", 2)]]
+void alias_as_default_template_arg(ns::AliasAsDefaultArg<T1, T2> Arg) {}
+template void alias_as_default_template_arg(ns::AliasAsDefaultArg<int, float>);
+
+// CHECK-DISABLED: template <typename T1, typename T2> void alias_as_default_template_arg(ns::AliasAsDefaultArg<T1, T2, ns::Bar<ns::Foo<T2>, T1>, ns::Bar<T2, float>>);
+#endif

From 99174d62ca92a454e8dabba9cac8290dd8f3a059 Mon Sep 17 00:00:00 2001
From: Alexey Sachkov <alexey.sachkov@intel.com>
Date: Fri, 21 Nov 2025 11:14:28 +0100
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 ca18c4c50abb8..5d6ea216d7d38 100644
--- a/clang/test/CodeGenSYCL/free-function-kernel-type-alias-arg.cpp
+++ b/clang/test/CodeGenSYCL/free-function-kernel-type-alias-arg.cpp
@@ -26,6 +26,9 @@ using BarUsing = Bar<T1, float>;
 template<typename T1, typename T2>
 using BarUsing2 = Bar<Foo<T2>, T1>;
 
+template <typename T1>
+using BarUsingBarUsing2 = BarUsing2<T1, int>;
+
 class Baz {
 public:
   using type = BarUsing<double>;
@@ -71,6 +74,13 @@ template void bar_using2(ns::BarUsing2<int, float>);
 
 // CHECK: template <typename T1, typename T2> void bar_using2(ns::Bar<ns::Foo<T2>, T1>);
 
+template<typename T1>
+[[__sycl_detail__::add_ir_attributes_function("sycl-nd-range-kernel", 2)]]
+void bar_using_bar_using2(ns::BarUsingBarUsing2<T1> Arg) {}
+template void bar_using_bar_using2(ns::BarUsingBarUsing2<int>);
+
+// CHECK: template <typename T1> void bar_using_bar_using2(ns::Bar<ns::Foo<int>, T1>);
+
 [[__sycl_detail__::add_ir_attributes_function("sycl-nd-range-kernel", 2)]]
 void baz_type(ns::Baz::type Arg) {}