From 5167e3da69df90afb667c2d09216b620a55fc646 Mon Sep 17 00:00:00 2001
From: "Mrozek, Michal" <michal.mrozek@intel.com>
Date: Fri, 2 Feb 2018 13:46:30 +0100
Subject: [PATCH] [1/n] optimize CPU code.

Limit the amount of atomic operations while decrementing ref count from 2 to 1

Change-Id: I0e9e9f07abd1aa62a3967ce4f83ffe2cc288765a
---
 runtime/utilities/reference_tracked_object.h          | 11 ++++++++---
 .../utilities/reference_tracked_object_tests.cpp      |  7 ++++++-
 2 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/runtime/utilities/reference_tracked_object.h b/runtime/utilities/reference_tracked_object.h
index 165744f7b4..4dbf84f239 100644
--- a/runtime/utilities/reference_tracked_object.h
+++ b/runtime/utilities/reference_tracked_object.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017, Intel Corporation
+ * Copyright (c) 2017 - 2018, Intel Corporation
  *
  * Permission is hereby granted, free of charge, to any person obtaining a
  * copy of this software and associated documentation files (the "Software"),
@@ -54,6 +54,10 @@ class RefCounter {
         return (curr == 0);
     }
 
+    CT decAndReturnCurrent() {
+        return --val;
+    }
+
     bool peekIsZero() const {
         return (val == 0);
     }
@@ -144,8 +148,9 @@ class ReferenceTrackedObject {
 
     unique_ptr_if_unused<DerivedClass> decRefInternal() {
         auto customDeleter = tryGetCustomDeleter();
-        bool unused = refInternal.dec();
-        UNRECOVERABLE_IF(refInternal.peek() < 0);
+        auto current = refInternal.decAndReturnCurrent();
+        bool unused = (current == 0);
+        UNRECOVERABLE_IF(current < 0);
         return unique_ptr_if_unused<DerivedClass>(static_cast<DerivedClass *>(this), unused, customDeleter);
     }
 
diff --git a/unit_tests/utilities/reference_tracked_object_tests.cpp b/unit_tests/utilities/reference_tracked_object_tests.cpp
index f192a1a9a7..76d413d247 100644
--- a/unit_tests/utilities/reference_tracked_object_tests.cpp
+++ b/unit_tests/utilities/reference_tracked_object_tests.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017, Intel Corporation
+ * Copyright (c) 2017 - 2018, Intel Corporation
  *
  * Permission is hereby granted, free of charge, to any person obtaining a
  * copy of this software and associated documentation files (the "Software"),
@@ -45,6 +45,11 @@ TEST(RefCounter, referenceCount) {
     ASSERT_TRUE(rc.peekIsZero());
 }
 
+TEST(RefCounter, givenReferenceTrackedObjectWhenDecAndReturnCurrentIsCalledThenMinusOneIsReturned) {
+    RefCounter<> rc;
+    EXPECT_EQ(-1, rc.decAndReturnCurrent());
+}
+
 TEST(unique_ptr_if_unused, InitializedWithDefaultConstructorAtQueryReturnsNullptr) {
     unique_ptr_if_unused<int> uptr;
     ASSERT_EQ(nullptr, uptr.get());