[clang][SYCL] Emit canonical types in integration footer (#16161)

A recent change to sycl headers revealed a bug in integration footer -
missing nns in case of an explicit template specialization in some of
device_global's template arguments.

Author: Fznamznon

clang/lib/Sema/SemaSYCL.cpp

@@ -6969,6 +6969,7 @@ bool SYCLIntegrationFooter::emit(raw_ostream &OS) {
   Policy.adjustForCPlusPlusFwdDecl();
   Policy.SuppressTypedefs = true;
   Policy.SuppressUnwrittenScope = true;
+  Policy.PrintCanonicalTypes = true;
 
   llvm::SmallSet<const VarDecl *, 8> Visited;
   bool EmittedFirstSpecConstant = false;

clang/test/CodeGenSYCL/int_footer_with_explicit_specialization.cpp

@@ -0,0 +1,32 @@
+// RUN: %clang_cc1 -fsycl-is-device -internal-isystem %S/Inputs -triple spir64-unknown-unknown -fsycl-int-footer=%t.footer.h -emit-llvm %s -o -
+// RUN: FileCheck -input-file=%t.footer.h %s --check-prefix=CHECK-FOOTER
+
+// This test checks that integration footer is emitted correctly when a
+// device_global has an explicit template specialization in template arguments.
+
+#include "sycl.hpp"
+
+namespace sycl {
+template <typename T> struct X {};
+template <> struct X<int> {};
+namespace detail {
+struct Y {};
+} // namespace detail
+template <> struct X<detail::Y> {};
+} // namespace sycl
+
+using namespace sycl;
+template <typename T, typename = X<detail::Y>> struct Arg1 { T val; };
+
+using namespace sycl::ext::oneapi;
+template <typename properties_t>
+device_global<properties_t> dev_global;
+
+SYCL_EXTERNAL auto foo() {
+  (void)dev_global<Arg1<int>>;
+}
+
+// CHECK-FOOTER: __sycl_device_global_registration::__sycl_device_global_registration() noexcept {
+// CHECK-FOOTER-NEXT: device_global_map::add((void *)&::dev_global<Arg1<int, sycl::X<sycl::detail::Y>>>, "_Z10dev_globalI4Arg1IiN4sycl1XINS1_6detail1YEEEEE");
+// CHECK-FOOTER-NEXT: }
+// CHECK-FOOTER-NEXT: } // namespace (unnamed)