From 17f05ad5e562830127dd06be6c11c10453a86d0e Mon Sep 17 00:00:00 2001
From: Sebastian Messmer <messmer@fb.com>
Date: Thu, 18 Apr 2019 14:07:30 -0700
Subject: [PATCH] Moving at::Tensor into caffe2::Tensor without bumping
 refcount (#19388)

Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/19388

The old implementation forced a refcount bump when converting at::Tensor to caffe2::Tensor.
Now, it is possible to move it without a refcount bump.

Reviewed By: dzhulgakov

Differential Revision: D14986815

fbshipit-source-id: 92b4b0a6f323ed38376ffad75f960cad250ecd9b
---
 aten/src/ATen/core/Tensor.h      | 5 +++++
 aten/src/ATen/templates/Tensor.h | 5 +++++
 caffe2/core/tensor.h             | 4 ++--
 3 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/aten/src/ATen/core/Tensor.h b/aten/src/ATen/core/Tensor.h
index e6552f2..5fbdb4e 100644
--- a/aten/src/ATen/core/Tensor.h
+++ b/aten/src/ATen/core/Tensor.h
@@ -14,6 +14,9 @@
 #include <ATen/core/LegacyTypeDispatch.h>
 #include <ATen/core/DeprecatedTypePropertiesRegistry.h>
 
+namespace caffe2 {
+class Tensor;
+}
 namespace c10{
 struct TensorOptions;
 }
@@ -761,6 +764,8 @@ class CAFFE2_API Tensor {
   friend struct WeakTensor;
 
 protected:
+  friend class ::caffe2::Tensor;
+
   void enforce_invariants();
   c10::intrusive_ptr<TensorImpl, UndefinedTensorImpl> impl_;
 };
diff --git a/aten/src/ATen/templates/Tensor.h b/aten/src/ATen/templates/Tensor.h
index 3944676..f9d9da0 100644
--- a/aten/src/ATen/templates/Tensor.h
+++ b/aten/src/ATen/templates/Tensor.h
@@ -14,6 +14,9 @@
 #include <ATen/core/LegacyTypeDispatch.h>
 #include <ATen/core/DeprecatedTypePropertiesRegistry.h>
 
+namespace caffe2 {
+class Tensor;
+}
 namespace c10{
 struct TensorOptions;
 }
@@ -348,6 +351,8 @@ class CAFFE2_API Tensor {
   friend struct WeakTensor;
 
 protected:
+  friend class ::caffe2::Tensor;
+
   void enforce_invariants();
   c10::intrusive_ptr<TensorImpl, UndefinedTensorImpl> impl_;
 };
diff --git a/caffe2/core/tensor.h b/caffe2/core/tensor.h
index 4846d9a..d6a5030 100644
--- a/caffe2/core/tensor.h
+++ b/caffe2/core/tensor.h
@@ -115,8 +115,8 @@ class CAFFE2_API Tensor final {
    * The tensor will share the same instance (data, strides, sizes, etc) but
    * a different subset of APIs would be available
    */
-  explicit Tensor(const at::Tensor& tensor)
-      : impl_(std::move(tensor.getIntrusivePtr())) {
+  explicit Tensor(at::Tensor tensor)
+      : impl_(std::move(tensor.impl_)) {
     enforce_invariants();
   }
 
-- 
2.7.4