Expose the compute number of elements helper function.

runtime/core/exec_aten/exec_aten.h

@@ -87,6 +87,11 @@ using IntArrayRef = at::IntArrayRef;
 template <typename T>
 using OptionalArrayRef = c10::OptionalArrayRef<T>;
 
+inline ssize_t compute_numel(const SizesType* sizes, ssize_t dim) {
+  return static_cast<ssize_t>(
+      c10::multiply_integers(c10::ArrayRef<SizesType>(sizes, dim)));
+}
+
 #else // Use executor types
 
 using Tensor = torch::executor::Tensor;
@@ -127,9 +132,12 @@ template <typename T>
 using OptionalArrayRef =
     torch::executor::optional<torch::executor::ArrayRef<T>>;
 
+using torch::executor::compute_numel;
+
 #endif // Use executor types
 
 } // namespace exec_aten
+
 namespace torch {
 namespace executor {
 using TensorList = exec_aten::TensorList;

runtime/core/exec_aten/util/scalar_type_util.h

@@ -28,6 +28,7 @@
 #include <type_traits>
 
 #include <executorch/runtime/platform/assert.h>
+
 #ifdef USE_ATEN_LIB
 // Note that a lot of the macros/functions defined in this ScalarTypeUtil.h file
 // are also defined in c10/core/ScalarType.h, which is included via
@@ -39,14 +40,14 @@
 namespace exec_aten {
 using ScalarType = at::ScalarType;
 }
-#else
+#else // !USE_ATEN_LIB
 #include <executorch/runtime/core/portable_type/scalar_type.h>
 #include <executorch/runtime/core/portable_type/string_view.h>
 namespace exec_aten {
 using ScalarType = torch::executor::ScalarType;
 using string_view = torch::executor::string_view;
 } // namespace exec_aten
-#endif
+#endif // USE_ATEN_LIB
 
 namespace executorch {
 namespace runtime {
@@ -1361,6 +1362,14 @@ inline exec_aten::ScalarType promoteTypes(
 } // namespace runtime
 } // namespace executorch
 
+namespace exec_aten {
+#ifdef USE_ATEN_LIB
+using ::at::elementSize;
+#else // USE_ATEN_LIB
+using ::executorch::runtime::elementSize;
+#endif // USE_ATEN_LIB
+} // namespace exec_aten
+
 namespace torch {
 namespace executor {
 // TODO(T197294990): Remove these deprecated aliases once all users have moved

runtime/core/portable_type/tensor_impl.cpp

@@ -20,7 +20,6 @@
 namespace torch {
 namespace executor {
 
-namespace {
 /**
  * Compute the number of elements based on the sizes of a tensor.
  */
@@ -39,7 +38,6 @@ ssize_t compute_numel(const TensorImpl::SizesType* sizes, ssize_t dim) {
   }
   return numel;
 }
-} // namespace
 
 TensorImpl::TensorImpl(
     ScalarType type,

runtime/core/portable_type/tensor_impl.h

@@ -253,5 +253,20 @@ class TensorImpl {
   const TensorShapeDynamism shape_dynamism_;
 };
 
+/**
+ * Compute the number of elements based on the sizes of a tensor.
+ */
+ssize_t compute_numel(
+    const ::torch::executor::TensorImpl::SizesType* sizes,
+    ssize_t dim);
+
 } // namespace executor
 } // namespace torch
+
+namespace executorch {
+namespace runtime {
+// TODO(T197294990): Remove these deprecated aliases once all users have moved
+// to the new `::executorch` namespaces.
+using torch::executor::compute_numel;
+} // namespace runtime
+} // namespace executorch