[PyTorch] Devirtualize TensorImpl::dim() with macro

aten/src/ATen/SparseTensorImpl.cpp

@@ -69,10 +69,6 @@ void SparseTensorImpl::set_storage_offset(int64_t storage_offset) {
   AT_ERROR("sparse tensors do not have set_storage_offset");
 }
 
-int64_t SparseTensorImpl::dim() const {
-  TORCH_INTERNAL_ASSERT_DEBUG_ONLY(sparse_dim_ + dense_dim_ == TensorImpl::dim());
-  return sparse_dim_ + dense_dim_;
-}
 bool SparseTensorImpl::has_storage() const {
   return false;
 }

aten/src/ATen/SparseTensorImpl.h

@@ -47,7 +47,6 @@ struct TORCH_API SparseTensorImpl : public TensorImpl {
   void set_stride(int64_t dim, int64_t new_stride) override;
   void set_storage_offset(int64_t storage_offset) override;
 
-  int64_t dim() const override;
   bool has_storage() const override;
   const Storage& storage() const override;
   int64_t storage_offset() const override;

c10/core/TensorImpl.cpp

@@ -216,9 +216,11 @@ void TensorImpl::release_resources() {
   }
 }
 
+#ifndef C10_DISABLE_TENSORIMPL_EXTENSIBILITY
 int64_t TensorImpl::dim() const {
   return sizes_.size();
 }
+#endif
 
 int64_t TensorImpl::size(int64_t d) const {
   d = at::maybe_wrap_dim(d, dim(), false);

c10/core/TensorImpl.h

@@ -393,7 +393,14 @@ struct C10_API TensorImpl : public c10::intrusive_ptr_target {
    * Return the number of dimensions of this tensor.  Note that 0-dimension
    * represents a Tensor that is a Scalar, e.g., one that has a single element.
    */
-  virtual int64_t dim() const;
+  TENSORIMPL_MAYBE_VIRTUAL int64_t dim() const
+#ifdef C10_DISABLE_TENSORIMPL_EXTENSIBILITY
+  {
+    return sizes_.size();
+  }
+#else
+  ;
+#endif
 
   /**
    * True if this tensor has storage. See storage() for details.

c10/core/UndefinedTensorImpl.cpp

@@ -20,10 +20,6 @@ int64_t UndefinedTensorImpl::stride(int64_t d) const {
   AT_ERROR("stride(dim) called on an undefined Tensor");
 }
 
-int64_t UndefinedTensorImpl::dim() const {
-  AT_ERROR("dim() called on undefined Tensor");
-}
-
 bool UndefinedTensorImpl::has_storage() const {
   AT_ERROR("has_storage() called on undefined Tensor");
 }

c10/core/UndefinedTensorImpl.h

@@ -21,7 +21,6 @@ struct C10_API UndefinedTensorImpl final : public TensorImpl {
   IntArrayRef strides() const override;
   int64_t size(int64_t d) const override;
   int64_t stride(int64_t d) const override;
-  int64_t dim() const override;
   bool has_storage() const override;
   const Storage& storage() const override;
   int64_t storage_offset() const override;