[slimtensor] Add aoti_torch__reinterpret_tensor for SlimTensor

Add SlimTensor-based `aoti_torch__reinterpret_tensor()` - Creates a reinterpreted view of a tensor with new sizes, strides, and storage offset using SlimTensor's `as_strided()` method. The view shares the same underlying storage.

Differential Revision: [D90126249](https://our.internmc.facebook.com/intern/diff/D90126249/)

[ghstack-poisoned]

Author: Gasoonjia

backends/cuda/runtime/shims/memory_slim.cpp

@@ -145,6 +145,47 @@ AOTITorchError aoti_torch_new_tensor_handle(
   return Error::Ok;
 }
 
+AOTITorchError aoti_torch__reinterpret_tensor(
+    Tensor* self,
+    int64_t ndim,
+    const int64_t* sizes_ptr,
+    const int64_t* strides_ptr,
+    int64_t storage_offset,
+    Tensor** ret_new_tensor) {
+  ET_CHECK_OR_RETURN_ERROR(
+      self != nullptr,
+      InvalidArgument,
+      "aoti_torch__reinterpret_tensor: self is null");
+
+  ET_CHECK_OR_RETURN_ERROR(
+      ret_new_tensor != nullptr,
+      InvalidArgument,
+      "aoti_torch__reinterpret_tensor: ret_new_tensor is null");
+
+  ET_CHECK_OR_RETURN_ERROR(
+      ndim >= 0,
+      InvalidArgument,
+      "aoti_torch__reinterpret_tensor: ndim must be non-negative, got %lld",
+      static_cast<long long>(ndim));
+
+  ET_CHECK_OR_RETURN_ERROR(
+      !(sizes_ptr == nullptr && ndim > 0),
+      InvalidArgument,
+      "aoti_torch__reinterpret_tensor: sizes_ptr is null but ndim > 0");
+
+  IntArrayRef sizes(sizes_ptr, static_cast<size_t>(ndim));
+  IntArrayRef strides(strides_ptr, static_cast<size_t>(ndim));
+
+  // Create a new tensor view using as_strided. This creates a tensor that
+  // shares the same underlying storage but with different sizes, strides,
+  // and storage offset. SlimTensor::as_strided() handles this via copy
+  // constructor which shares the SharedPtr<Storage>.
+  *ret_new_tensor =
+      new Tensor(self->as_strided(sizes, strides, storage_offset));
+
+  return Error::Ok;
+}
+
 } // extern "C"
 
 } // namespace executorch::backends::cuda

backends/cuda/runtime/shims/memory_slim.h

@@ -103,9 +103,30 @@ AOTI_SHIM_EXPORT AOTITorchError aoti_torch_delete_tensor_object(Tensor* tensor);
  * @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);
+AOTI_SHIM_EXPORT AOTITorchError
+aoti_torch_new_tensor_handle(Tensor* orig_handle, Tensor** new_handle);
+
+/**
+ * Creates a reinterpreted view of a tensor with new sizes, strides, and offset.
+ *
+ * This is equivalent to torch.as_strided() - it creates a new tensor that
+ * shares the same underlying storage but with different view parameters.
+ *
+ * @param self Original tensor to reinterpret (must not be null)
+ * @param ndim Number of dimensions for the new view
+ * @param sizes_ptr Pointer to array of dimension sizes
+ * @param strides_ptr Pointer to array of strides for each dimension
+ * @param storage_offset Storage offset in number of elements
+ * @param ret_new_tensor Output parameter for the reinterpreted tensor view
+ * @return AOTITorchError error code (Error::Ok on success)
+ */
+AOTI_SHIM_EXPORT AOTITorchError aoti_torch__reinterpret_tensor(
+    Tensor* self,
+    int64_t ndim,
+    const int64_t* sizes_ptr,
+    const int64_t* strides_ptr,
+    int64_t storage_offset,
+    Tensor** ret_new_tensor);
 
 } // extern "C"
 

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

@@ -75,3 +75,4 @@ def define_common_targets():
     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")
+    cuda_shim_slim_cpp_unittest("aoti_torch__reinterpret_tensor")