commit de53de39d74236b06b59222ba66e9b88cfa7115a
author Scott Wolchok <swolchok@fb.com> Tue Apr 13 13:19:59 2021 -0700
committer Facebook GitHub Bot <facebook-github-bot@users.noreply.github.com> Tue Apr 13 13:23:27 2021 -0700
tree 4a3b62e150159a1025cbb173549392428a778bd8
parent ea446ed6000cf2705601d18203620723f2da5329

[PyTorch] Mark borrowed case as C10_LIKELY in MaybeOwned (#55553)

Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/55553

If this case isn't likely, user code would have been better off with a regular T.
ghstack-source-id: 126369326

Test Plan: Existing CI

Reviewed By: ezyang

Differential Revision: D27630287

fbshipit-source-id: b074af3a65c61dfe9e0246df046cc8c49e8efb03

c10/util/MaybeOwned.h

diff --git a/c10/util/MaybeOwned.h b/c10/util/MaybeOwned.h
index 9d0fc37..63988cc 100644
--- a/c10/util/MaybeOwned.h
+++ b/c10/util/MaybeOwned.h
@@ -1,5 +1,6 @@
 #pragma once
 
+#include <c10/macros/Macros.h>
 #include <c10/util/Exception.h>
 #include <c10/util/in_place.h>
 
@@ -44,7 +45,7 @@
   // chains of borrowing by default! (Note you could get that behavior
   // with MaybeOwned<T>::borrowed(*rhs) if you wanted it.)
   MaybeOwned(const MaybeOwned& rhs) : isBorrowed_(rhs.isBorrowed_) {
-    if (rhs.isBorrowed_) {
+    if (C10_LIKELY(rhs.isBorrowed_)) {
       borrow_ = rhs.borrow_;
     } else {
       new (&own_) T(rhs.own_);
@@ -52,7 +53,7 @@
   }
 
   MaybeOwned& operator=(const MaybeOwned& rhs) {
-    if (!isBorrowed_) {
+    if (C10_UNLIKELY(!isBorrowed_)) {
       if (rhs.isBorrowed_) {
         own_.~T();
         borrow_ = rhs.borrow_;
@@ -61,7 +62,7 @@
         own_ = rhs.own_;
       }
     } else {
-      if (rhs.isBorrowed_) {
+      if (C10_LIKELY(rhs.isBorrowed_)) {
         borrow_ = rhs.borrow_;
       } else {
         new (&own_) T(rhs.own_);
@@ -74,7 +75,7 @@
 
   MaybeOwned(MaybeOwned&& rhs) noexcept(std::is_nothrow_move_constructible<T>::value)
   : isBorrowed_(rhs.isBorrowed_) {
-    if (rhs.isBorrowed_) {
+    if (C10_LIKELY(rhs.isBorrowed_)) {
       borrow_ = rhs.borrow_;
     } else {
       new (&own_) T(std::move(rhs.own_));
@@ -82,7 +83,7 @@
   }
 
   MaybeOwned& operator=(MaybeOwned&& rhs) noexcept(std::is_nothrow_move_assignable<T>::value) {
-    if (!isBorrowed_) {
+    if (C10_UNLIKELY(!isBorrowed_)) {
       if (rhs.isBorrowed_) {
           own_.~T();
           borrow_ = rhs.borrow_;
@@ -91,7 +92,7 @@
         own_ = std::move(rhs.own_);
       }
     } else {
-      if (rhs.isBorrowed_) {
+      if (C10_LIKELY(rhs.isBorrowed_)) {
         borrow_ = rhs.borrow_;
       } else {
         new (&own_) T(std::move(rhs.own_));
@@ -116,7 +117,7 @@
   }
 
   ~MaybeOwned() {
-    if (!isBorrowed_) {
+    if (C10_UNLIKELY(!isBorrowed_)) {
       own_.~T();
     }
   }
@@ -125,14 +126,14 @@
     if (isBorrowed_) {
       TORCH_INTERNAL_ASSERT_DEBUG_ONLY(borrow_ != nullptr);
     }
-    return isBorrowed_ ? *borrow_ : own_;
+    return C10_LIKELY(isBorrowed_) ? *borrow_ : own_;
   }
 
   const T* operator->() const {
     if (isBorrowed_) {
       TORCH_INTERNAL_ASSERT_DEBUG_ONLY(borrow_ != nullptr);
     }
-    return isBorrowed_ ? borrow_ : &own_;
+    return C10_LIKELY(isBorrowed_) ? borrow_ : &own_;
   }
 
   // If borrowed, copy the underlying T. If owned, move from