Allow getting all backend names (pytorch#8520)

Summary:

Allow getting all backends name in both python and c++

Reviewed By: tarun292

Differential Revision: D69691354

extension/pybindings/portable_lib.py

@@ -37,6 +37,7 @@
     # Disable "imported but unused" (F401) checks.
     _create_profile_block,  # noqa: F401
     _dump_profile_results,  # noqa: F401
+    _get_backend_names,  # noqa: F401
     _get_operator_names,  # noqa: F401
     _load_bundled_program_from_buffer,  # noqa: F401
     _load_for_executorch,  # noqa: F401

extension/pybindings/pybindings.cpp

@@ -23,6 +23,7 @@
 #include <executorch/extension/data_loader/buffer_data_loader.h>
 #include <executorch/extension/data_loader/mmap_data_loader.h>
 #include <executorch/extension/memory_allocator/malloc_memory_allocator.h>
+#include <executorch/runtime/backend/interface.h>
 #include <executorch/runtime/core/data_loader.h>
 #include <executorch/runtime/core/exec_aten/util/scalar_type_util.h>
 #include <executorch/runtime/executor/method.h>
@@ -87,10 +88,12 @@ using ::executorch::extension::BufferDataLoader;
 using ::executorch::extension::MallocMemoryAllocator;
 using ::executorch::extension::MmapDataLoader;
 using ::executorch::runtime::ArrayRef;
+using ::executorch::runtime::Backend;
 using ::executorch::runtime::DataLoader;
 using ::executorch::runtime::Error;
 using ::executorch::runtime::EValue;
 using ::executorch::runtime::EventTracerDebugLogLevel;
+using ::executorch::runtime::get_registered_backends;
 using ::executorch::runtime::get_registered_kernels;
 using ::executorch::runtime::HierarchicalAllocator;
 using ::executorch::runtime::Kernel;
@@ -975,6 +978,17 @@ py::list get_operator_names() {
   return res;
 }
 
+py::list get_backend_names() {
+  Span<const Backend> backends = get_registered_backends();
+  py::list res;
+  for (const Backend& backend : backends) {
+    if (backend.name != nullptr) {
+      res.append(py::cast(backend.name));
+    }
+  }
+  return res;
+}
+
 } // namespace
 
 PYBIND11_MODULE(EXECUTORCH_PYTHON_MODULE_NAME, m) {
@@ -1029,6 +1043,7 @@ PYBIND11_MODULE(EXECUTORCH_PYTHON_MODULE_NAME, m) {
       },
       call_guard);
   m.def("_get_operator_names", &get_operator_names);
+  m.def("_get_backend_names", &get_backend_names);
   m.def("_create_profile_block", &create_profile_block, call_guard);
   m.def(
       "_reset_profile_results",

extension/pybindings/pybindings.pyi

@@ -211,6 +211,15 @@ def _load_bundled_program_from_buffer(
     """
     ...
 
+@experimental("This API is experimental and subject to change without notice.")
+def _get_backend_names() -> List[str]:
+    """
+    .. warning::
+
+        This API is experimental and subject to change without notice.
+    """
+    ...
+
 @experimental("This API is experimental and subject to change without notice.")
 def _get_operator_names() -> List[str]:
     """

extension/pybindings/test/TARGETS

@@ -47,3 +47,11 @@ runtime.python_test(
         "//executorch/kernels/quantized:aot_lib",
     ],
 )
+
+runtime.python_test(
+    name = "test_backend_pybinding",
+    srcs = ["test_backend_pybinding.py"],
+    deps = [
+        "//executorch/extension/pybindings:portable_lib",
+    ],
+)

extension/pybindings/test/test_backend_pybinding.py

@@ -0,0 +1,12 @@
+import unittest
+
+from executorch.extension.pybindings.portable_lib import _get_backend_names
+
+
+class TestBackendsPybinding(unittest.TestCase):
+    def test_backend_name_list(
+        self,
+    ) -> None:
+        all_backend_name = _get_backend_names()
+        self.assertGreater(len(all_backend_name), 1)
+        self.assertIn("XnnpackBackend", all_backend_name)

runtime/backend/interface.cpp

@@ -55,5 +55,9 @@ Error register_backend(const Backend& backend) {
   return Error::Ok;
 }
 
+Span<const Backend> get_registered_backends() {
+  return {registered_backends, num_registered_backends};
+}
+
 } // namespace runtime
 } // namespace executorch

runtime/backend/interface.h

@@ -18,6 +18,7 @@
 #include <executorch/runtime/core/freeable_buffer.h>
 #include <executorch/runtime/core/memory_allocator.h>
 #include <executorch/runtime/core/result.h>
+#include <executorch/runtime/core/span.h>
 #include <executorch/runtime/platform/compiler.h>
 
 namespace executorch {
@@ -139,6 +140,11 @@ struct Backend {
  */
 ET_NODISCARD Error register_backend(const Backend& backend);
 
+/**
+ * Returns all registered backends.
+ */
+Span<const Backend> get_registered_backends();
+
 } // namespace runtime
 } // namespace executorch