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

c10/core/TensorImpl.cpp

@@ -94,9 +94,11 @@ TensorImpl::TensorImpl(Storage&& storage, DispatchKeySet key_set, const caffe2::
   strides_.push_back(1);
 }
 
+#ifndef C10_DISABLE_TENSORIMPL_EXTENSIBILITY
 IntArrayRef TensorImpl::sizes() const {
   return sizes_;
 }
+#endif
 
 IntArrayRef TensorImpl::strides() const {
   return strides_;

c10/core/TensorImpl.h

@@ -390,7 +390,14 @@ struct C10_API TensorImpl : public c10::intrusive_ptr_target {
    * Return a reference to the sizes of this tensor.  This reference remains
    * valid as long as the tensor is live and not resized.
    */
-  virtual IntArrayRef sizes() const;
+  TENSORIMPL_MAYBE_VIRTUAL IntArrayRef sizes() const
+#ifdef C10_DISABLE_TENSORIMPL_EXTENSIBILITY
+  {
+    return sizes_;
+  }
+#else
+  ;
+#endif
 
   /**
    * Return a reference to the strides of this tensor.  This reference remains

c10/core/UndefinedTensorImpl.cpp

@@ -8,10 +8,6 @@ UndefinedTensorImpl::UndefinedTensorImpl()
 : TensorImpl(DispatchKey::Undefined, caffe2::TypeMeta(), c10::nullopt) {
 }
 
-IntArrayRef UndefinedTensorImpl::sizes() const {
-  AT_ERROR("sizes() called on undefined Tensor");
-}
-
 int64_t UndefinedTensorImpl::size(int64_t d) const {
   AT_ERROR("size(dim) called on an undefined Tensor");
 }

c10/core/UndefinedTensorImpl.h

@@ -17,7 +17,6 @@ struct C10_API UndefinedTensorImpl final : public TensorImpl {
 #endif
     return &_singleton;
   }
-  IntArrayRef sizes() const override;
   IntArrayRef strides() const override;
   int64_t size(int64_t d) const override;
   int64_t stride(int64_t d) const override;