[slimtensor] Add aoti_torch_new_tensor_handle for SlimTensor (#16926)

This PR was created by the merge bot to help merge the original PR into
the main branch.
ghstack PR number: #16449 by
@Gasoonjia
^ Please use this as the source of truth for the PR details, comments,
and reviews
ghstack PR base:
https://github.com/pytorch/executorch/tree/gh/gasoonjia/91/base
ghstack PR head:
https://github.com/pytorch/executorch/tree/gh/gasoonjia/91/head
Merge bot PR base:
https://github.com/pytorch/executorch/tree/gh/gasoonjia/90/orig
Merge bot PR head:
https://github.com/pytorch/executorch/tree/gh/gasoonjia/91/orig
Differential Revision:
[D90126245](https://our.internmc.facebook.com/intern/diff/D90126245/)
@diff-train-skip-merge

---------

Co-authored-by: gasoonjia <gasoonjia@icloud.com>
Co-authored-by: Gasoonjia <gasoonjia@meta.com>

Author: pytorchbot

backends/cuda/runtime/shims/memory_slim.cpp

@@ -136,6 +136,28 @@ AOTITorchError aoti_torch_delete_tensor_object(Tensor* tensor) {
   return Error::Ok;
 }
 
+AOTITorchError aoti_torch_new_tensor_handle(
+    Tensor* orig_handle,
+    Tensor** new_handle) {
+  ET_CHECK_OR_RETURN_ERROR(
+      orig_handle != nullptr,
+      InvalidArgument,
+      "aoti_torch_new_tensor_handle: orig_handle is null");
+
+  ET_CHECK_OR_RETURN_ERROR(
+      new_handle != nullptr,
+      InvalidArgument,
+      "aoti_torch_new_tensor_handle: new_handle is null");
+
+  // Create a new SlimTensor that shares the same underlying storage.
+  // SlimTensor's copy constructor shares the SharedPtr<Storage>, so both
+  // tensors will reference the same memory. When the last tensor is deleted,
+  // the storage will be freed.
+  *new_handle = new Tensor(*orig_handle);
+
+  return Error::Ok;
+}
+
 } // extern "C"
 
 } // namespace executorch::backends::cuda

backends/cuda/runtime/shims/memory_slim.h

@@ -91,6 +91,21 @@ AOTI_SHIM_EXPORT AOTITorchError aoti_torch_empty_strided(
  */
 AOTI_SHIM_EXPORT AOTITorchError aoti_torch_delete_tensor_object(Tensor* tensor);
 
+/**
+ * Creates a new tensor handle that shares storage with the original tensor.
+ *
+ * The new handle is a copy of the original tensor's metadata (sizes, strides,
+ * dtype, device) and shares the same underlying storage via SharedPtr.
+ * Both tensors will reference the same memory, and the memory will only be
+ * freed when all references are deleted.
+ *
+ * @param orig_handle Pointer to the original tensor (must not be null)
+ * @param new_handle Output parameter for the new tensor handle
+ * @return AOTITorchError error code (Error::Ok on success)
+ */
+AOTI_SHIM_EXPORT AOTITorchError
+aoti_torch_new_tensor_handle(Tensor* orig_handle, Tensor** new_handle);
+
 } // extern "C"
 
 } // namespace executorch::backends::cuda

backends/cuda/runtime/shims/tests/targets.bzl

@@ -74,3 +74,4 @@ def define_common_targets():
     cuda_shim_slim_cpp_unittest("aoti_torch_empty_strided")
     cuda_shim_slim_cpp_unittest("aoti_torch_create_tensor_from_blob_v2")
     cuda_shim_slim_cpp_unittest("aoti_torch_delete_tensor_object")
+    cuda_shim_slim_cpp_unittest("aoti_torch_new_tensor_handle")