From 3e0fbb771817ce6759eed8348df327c712dde5e0 Mon Sep 17 00:00:00 2001
From: Michael Sippel <m.sippel@hzdr.de>
Date: Thu, 7 Dec 2023 03:10:31 +0100
Subject: [PATCH] GraphProperty: replace redundant `task` member with address
 calculation through offsetof

---
 redGrapes/task/property/graph.cpp | 23 ++++++++++++++++-------
 redGrapes/task/property/graph.hpp | 16 ++++++++--------
 redGrapes/task/task_space.cpp     |  2 +-
 3 files changed, 25 insertions(+), 16 deletions(-)

diff --git a/redGrapes/task/property/graph.cpp b/redGrapes/task/property/graph.cpp
index 3680c795..4b0e0579 100644
--- a/redGrapes/task/property/graph.cpp
+++ b/redGrapes/task/property/graph.cpp
@@ -1,4 +1,5 @@
-/* Copyright 2019-2022 Michael Sippel
+/* Copyright 2019-2024 The RedGrapes Community
+ * Authors: Michael Sippel
  *
  * This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
@@ -6,19 +7,27 @@
  */
 
 #include <redGrapes/redGrapes.hpp>
-#include <redGrapes/resource/resource_user.hpp>
 #include <redGrapes/scheduler/event.hpp>
 #include <redGrapes/task/property/graph.hpp>
 #include <redGrapes/task/task.hpp>
 #include <redGrapes/task/task_space.hpp>
 #include <redGrapes/util/trace.hpp>
 
+#include <cstddef>
 #include <memory>
 #include <unordered_set>
 
 namespace redGrapes
 {
 
+    Task* GraphProperty::get_task()
+    {
+        /* NOTE: this offsetof gives works because we know that `space` is
+         * the first member that is derived from `GraphProperty`
+         */
+        return (Task*) ((uintptr_t) this - offsetof(Task, space));
+    }
+
     /*! create a new (external) event which precedes the tasks post-event
      */
     scheduler::EventPtr GraphProperty::make_event()
@@ -37,7 +46,7 @@ namespace redGrapes
     void GraphProperty::init_graph()
     {
         TRACE_EVENT("Graph", "init_graph");
-        for(auto r = this->task->unique_resources.rbegin(); r != this->task->unique_resources.rend(); ++r)
+        for(auto r = this->get_task()->unique_resources.rbegin(); r != this->get_task()->unique_resources.rend(); ++r)
         {
             if(r->task_entry != r->resource->users.rend())
             {
@@ -63,7 +72,7 @@ namespace redGrapes
                     if(preceding_task == this->space->parent)
                         break;
 
-                    if(preceding_task->space == this->space && this->space->is_serial(*preceding_task, *this->task))
+                    if(preceding_task->space == this->space && this->space->is_serial(*preceding_task, *this->get_task()))
                     {
                         add_dependency(*preceding_task);
                         if(preceding_task->has_sync_access(r->resource))
@@ -84,7 +93,7 @@ namespace redGrapes
     void GraphProperty::delete_from_resources()
     {
         TRACE_EVENT("Graph", "delete_from_resources");
-        for(auto r = this->task->unique_resources.rbegin(); r != this->task->unique_resources.rend(); ++r)
+        for(auto r = this->get_task()->unique_resources.rbegin(); r != this->get_task()->unique_resources.rend(); ++r)
         {
             // TODO: can this lock be avoided?
             //   corresponding lock to init_graph()
@@ -101,7 +110,7 @@ namespace redGrapes
         // in_edges.push_back(&preceding_task);
 
         // scheduling graph
-        auto preceding_event = SingletonContext::get().scheduler->task_dependency_type(preceding_task, *this->task)
+        auto preceding_event = SingletonContext::get().scheduler->task_dependency_type(preceding_task, *this->get_task())
                                    ? preceding_task->get_pre_event()
                                    : preceding_task->get_post_event();
 
@@ -119,7 +128,7 @@ namespace redGrapes
             scheduler::EventPtr follower = *it;
             if(follower.task)
             {
-                if(!space->is_serial(*this->task, *follower.task))
+                if(!space->is_serial(*get_task(), *follower.task))
                 {
                     // remove dependency
                     // follower.task->in_edges.erase(std::find(std::begin(follower.task->in_edges),
diff --git a/redGrapes/task/property/graph.hpp b/redGrapes/task/property/graph.hpp
index d7d7cadc..1f92ba34 100644
--- a/redGrapes/task/property/graph.hpp
+++ b/redGrapes/task/property/graph.hpp
@@ -49,16 +49,14 @@ namespace redGrapes
     {
         Task& operator*()
         {
-            return *task;
+            return *get_task();
         }
 
         Task* operator->()
         {
-            return task;
+            return get_task();
         }
 
-        Task* task;
-
         //! number of parents
         uint8_t scope_depth;
 
@@ -80,24 +78,26 @@ namespace redGrapes
         scheduler::Event result_set_event;
         scheduler::Event result_get_event;
 
+        Task* get_task();
+
         inline scheduler::EventPtr get_pre_event()
         {
-            return scheduler::EventPtr{scheduler::T_EVT_PRE, this->task};
+            return scheduler::EventPtr{scheduler::T_EVT_PRE, this->get_task()};
         }
 
         inline scheduler::EventPtr get_post_event()
         {
-            return scheduler::EventPtr{scheduler::T_EVT_POST, this->task};
+            return scheduler::EventPtr{scheduler::T_EVT_POST, this->get_task()};
         }
 
         inline scheduler::EventPtr get_result_set_event()
         {
-            return scheduler::EventPtr{scheduler::T_EVT_RES_SET, this->task};
+            return scheduler::EventPtr{scheduler::T_EVT_RES_SET, this->get_task()};
         }
 
         inline scheduler::EventPtr get_result_get_event()
         {
-            return scheduler::EventPtr{scheduler::T_EVT_RES_GET, this->task};
+            return scheduler::EventPtr{scheduler::T_EVT_RES_GET, this->get_task()};
         }
 
         inline bool is_ready()
diff --git a/redGrapes/task/task_space.cpp b/redGrapes/task/task_space.cpp
index c889d539..c2a74a07 100644
--- a/redGrapes/task/task_space.cpp
+++ b/redGrapes/task/task_space.cpp
@@ -70,8 +70,8 @@ namespace redGrapes
     void TaskSpace::submit(Task* task)
     {
         TRACE_EVENT("TaskSpace", "submit()");
+
         task->space = shared_from_this();
-        task->task = task;
 
         ++task_count;