Allow getting all backend names (pytorch#8520)

Summary:

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

Reviewed By: omerjerk

Differential Revision: D69691354

extension/pybindings/portable_lib.py

@@ -38,6 +38,7 @@
     _create_profile_block,  # noqa: F401
     _dump_profile_results,  # noqa: F401
     _get_operator_names,  # noqa: F401
+    _get_registered_backend_names,  # noqa: F401
     _load_bundled_program_from_buffer,  # noqa: F401
     _load_for_executorch,  # noqa: F401
     _load_for_executorch_from_buffer,  # 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>
@@ -91,6 +92,8 @@ using ::executorch::runtime::DataLoader;
 using ::executorch::runtime::Error;
 using ::executorch::runtime::EValue;
 using ::executorch::runtime::EventTracerDebugLogLevel;
+using ::executorch::runtime::get_backend_name;
+using ::executorch::runtime::get_num_registered_backends;
 using ::executorch::runtime::get_registered_kernels;
 using ::executorch::runtime::HierarchicalAllocator;
 using ::executorch::runtime::Kernel;
@@ -975,6 +978,18 @@ py::list get_operator_names() {
   return res;
 }
 
+py::list get_registered_backend_names() {
+  size_t n_of_registered_backends = get_num_registered_backends();
+  py::list res;
+  for (size_t i = 0; i < n_of_registered_backends; i++) {
+    auto backend_name_res = get_backend_name(i);
+    THROW_IF_ERROR(backend_name_res.error(), "Failed to get backend name");
+    auto backend_name = backend_name_res.get();
+    res.append(backend_name);
+  }
+  return res;
+}
+
 } // namespace
 
 PYBIND11_MODULE(EXECUTORCH_PYTHON_MODULE_NAME, m) {
@@ -1028,6 +1043,10 @@ PYBIND11_MODULE(EXECUTORCH_PYTHON_MODULE_NAME, m) {
             prof_result.num_bytes);
       },
       call_guard);
+  m.def(
+      "_get_registered_backend_names",
+      &get_registered_backend_names,
+      call_guard);
   m.def("_get_operator_names", &get_operator_names);
   m.def("_create_profile_block", &create_profile_block, call_guard);
   m.def(

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/runtime:runtime",
+    ],
+)

extension/pybindings/test/test_backend_pybinding.py

@@ -0,0 +1,14 @@
+import unittest
+
+from executorch.runtime import Runtime
+
+
+class TestBackendsPybinding(unittest.TestCase):
+    def test_backend_name_list(
+        self,
+    ) -> None:
+
+        runtime = Runtime.get()
+        registered_backend_names = runtime.backend_registry.registered_backend_names
+        self.assertGreaterEqual(len(registered_backend_names), 1)
+        self.assertIn("XnnpackBackend", registered_backend_names)

runtime/__init__.py

@@ -42,7 +42,7 @@
 import functools
 from pathlib import Path
 from types import ModuleType
-from typing import Any, BinaryIO, Dict, Optional, Sequence, Set, Union
+from typing import Any, BinaryIO, Dict, List, Optional, Sequence, Set, Union
 
 try:
     from executorch.extension.pybindings.portable_lib import (
@@ -125,6 +125,21 @@ def load_method(self, name: str) -> Optional[Method]:
         return self._methods.get(name, None)
 
 
+class BackendRegistry:
+    """The registry of backends that are available to the runtime."""
+
+    def __init__(self, legacy_module: ModuleType) -> None:
+        # TODO: Expose the kernel callables to Python.
+        self._legacy_module = legacy_module
+
+    @property
+    def registered_backend_names(self) -> List[str]:
+        """
+        Returns the names of all registered backends as a list of strings.
+        """
+        return self._legacy_module._get_registered_backend_names()
+
+
 class OperatorRegistry:
     """The registry of operators that are available to the runtime."""
 
@@ -157,6 +172,7 @@ def get() -> "Runtime":
 
     def __init__(self, *, legacy_module: ModuleType) -> None:
         # Public attributes.
+        self.backend_registry = BackendRegistry(legacy_module)
         self.operator_registry = OperatorRegistry(legacy_module)
         # Private attributes.
         self._legacy_module = legacy_module

runtime/backend/interface.cpp

@@ -55,5 +55,16 @@ Error register_backend(const Backend& backend) {
   return Error::Ok;
 }
 
+size_t get_num_registered_backends() {
+  return num_registered_backends;
+}
+
+Result<const char*> get_backend_name(size_t index) {
+  if (index >= num_registered_backends) {
+    return Error::InvalidArgument;
+  }
+  return registered_backends[index].name;
+}
+
 } // namespace runtime
 } // namespace executorch

runtime/backend/interface.h

@@ -139,6 +139,16 @@ struct Backend {
  */
 ET_NODISCARD Error register_backend(const Backend& backend);
 
+/**
+ * Returns the number of registered backends.
+ */
+size_t get_num_registered_backends();
+
+/**
+ * Returns the backend name at the given index.
+ */
+Result<const char*> get_backend_name(size_t index);
+
 } // namespace runtime
 } // namespace executorch