[SYCL][COMPAT] Ensure launched kernels are fully inlined (#15941)

This PR defines & uses a custom `syclcompat::detail::apply_helper` with
`[[clang::always_inline]]` to ensure kernels are inlined.

sycl/include/syclcompat/launch_policy.hpp

@@ -192,6 +192,17 @@ launch_policy(dim3, dim3, Ts...) -> launch_policy<
     detail::has_type<local_mem_size, std::tuple<Ts...>>::value>;
 
 namespace detail {
+// Custom std::apply helpers to enable inlining
+template <class F, class Tuple, size_t... Is>
+__syclcompat_inline__ constexpr void apply_expand(F f, Tuple t,
+                                                  std::index_sequence<Is...>) {
+  [[clang::always_inline]] f(get<Is>(t)...);
+}
+
+template <class F, class Tuple>
+__syclcompat_inline__ constexpr void apply_helper(F f, Tuple t) {
+  apply_expand(f, t, std::make_index_sequence<std::tuple_size<Tuple>{}>{});
+}
 
 template <auto F, typename Range, typename KProps, bool HasLocalMem,
           typename... Args>
@@ -211,12 +222,16 @@ struct KernelFunctor {
   operator()(syclcompat::detail::range_to_item_t<Range>) const {
     if constexpr (HasLocalMem) {
       char *local_mem_ptr = static_cast<char *>(
-          _local_acc.template get_multi_ptr<sycl::access::decorated::no>().get());
-      std::apply(
-          [lmem_ptr = local_mem_ptr](auto &&...args) { F(args..., lmem_ptr); },
+          _local_acc.template get_multi_ptr<sycl::access::decorated::no>()
+              .get());
+      apply_helper(
+          [lmem_ptr = local_mem_ptr](auto &&...args) {
+            [[clang::always_inline]] F(args..., lmem_ptr);
+          },
           _argument_tuple);
     } else {
-      std::apply([](auto &&...args) { F(args...); }, _argument_tuple);
+      apply_helper([](auto &&...args) { [[clang::always_inline]] F(args...); },
+                   _argument_tuple);
     }
   }
 

sycl/test/syclcompat/launch/kernel_properties.cpp

@@ -23,7 +23,7 @@
 // We need hardware which can support at least 2 sub-group sizes, since that
 // hardware (presumably) supports the `intel_reqd_sub_group_size` attribute.
 // REQUIRES: sg-32 && sg-16
-// RUN: %clangxx -fsycl -fsycl-targets=%sycl_triple %if cl_options %{/clang:-S /clang:-emit-llvm%} %else %{-S -emit-llvm%} -o - | FileCheck %s
+// RUN: %clangxx -fsycl -fsycl-targets=%sycl_triple %if cl_options %{/clang:-S /clang:-emit-llvm%} %else %{-S -emit-llvm%} %s -o - | FileCheck %s
 #include <sycl/ext/oneapi/kernel_properties/properties.hpp>
 #include <sycl/detail/core.hpp>
 #include <sycl/ext/oneapi/properties/properties.hpp>

sycl/test/syclcompat/launch/launch_inlining.cpp

@@ -0,0 +1,97 @@
+/***************************************************************************
+ *
+ *  Copyright (C) Codeplay Software Ltd.
+ *
+ *  Part of the LLVM Project, under the Apache License v2.0 with LLVM
+ *  Exceptions. See https://llvm.org/LICENSE.txt for license information.
+ *  SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ *
+ *  SYCLcompat API
+ *
+ *  launch_inlining.cpp
+ *
+ *  Description:
+ *    Ensure kernels are inlined
+ **************************************************************************/
+// RUN: %clangxx -fsycl -fgpu-inline-threshold=0 %if cl_options %{/clang:-S /clang:-emit-llvm%} %else %{-S -emit-llvm%} %s -o - | FileCheck %s
+// We set -fgpu-inline-threshold=0 to disable heuristic inlining for the
+// purposes of the test
+#include <sycl/detail/core.hpp>
+#include <sycl/group_barrier.hpp>
+#include <syclcompat/launch.hpp>
+#include <syclcompat/memory.hpp>
+
+namespace compat_exp = syclcompat::experimental;
+namespace sycl_exp = sycl::ext::oneapi::experimental;
+namespace sycl_intel_exp = sycl::ext::intel::experimental;
+
+static constexpr int LOCAL_MEM_SIZE = 1024;
+
+// CHECK: define {{.*}}spir_kernel{{.*}}write_mem_kernel{{.*}} {
+// CHECK-NOT: call {{.*}}write_mem_kernel
+// CHECK: }
+
+template <typename T> void write_mem_kernel(T *data, int num_elements) {
+  const int id =
+      sycl::ext::oneapi::this_work_item::get_nd_item<1>().get_global_id(0);
+  if (id < num_elements) {
+    data[id] = static_cast<T>(id);
+  }
+};
+
+// CHECK: define {{.*}}spir_kernel{{.*}}dynamic_local_mem_typed_kernel{{.*}} {
+// CHECK-NOT: call {{.*}}dynamic_local_mem_typed_kernel
+// CHECK: }
+template <typename T>
+void dynamic_local_mem_typed_kernel(T *data, char *local_mem) {
+  constexpr size_t num_elements = LOCAL_MEM_SIZE / sizeof(T);
+  T *typed_local_mem = reinterpret_cast<T *>(local_mem);
+
+  const int id =
+      sycl::ext::oneapi::this_work_item::get_nd_item<1>().get_global_id(0);
+  if (id < num_elements) {
+    typed_local_mem[id] = static_cast<T>(id);
+  }
+  sycl::group_barrier(sycl::ext::oneapi::this_work_item::get_work_group<1>());
+  if (id < num_elements) {
+    data[id] = typed_local_mem[num_elements - id - 1];
+  }
+};
+
+int test_write_mem() {
+  compat_exp::launch_policy my_dim3_config(syclcompat::dim3{32},
+                                           syclcompat::dim3{32});
+
+  const int memsize = 1024;
+  int *d_a = (int *)syclcompat::malloc(memsize);
+  compat_exp::launch<write_mem_kernel<int>>(my_dim3_config, d_a,
+                                            memsize / sizeof(int))
+      .wait();
+
+  syclcompat::free(d_a);
+  return 0;
+}
+
+int test_lmem_launch() {
+  int local_mem_size = LOCAL_MEM_SIZE;
+
+  size_t num_elements = local_mem_size / sizeof(int);
+  int *d_a = (int *)syclcompat::malloc(local_mem_size);
+
+  compat_exp::launch_policy my_config(
+      sycl::nd_range<1>{{256}, {256}},
+      compat_exp::local_mem_size(local_mem_size));
+
+  compat_exp::launch<dynamic_local_mem_typed_kernel<int>>(my_config, d_a)
+      .wait();
+
+  syclcompat::free(d_a);
+
+  return 0;
+}