From 4159ba45e83f6542e3a3320e83bca9fbaf2da3ea Mon Sep 17 00:00:00 2001
From: Brian Norris <banorris@uci.edu>
Date: Fri, 30 Nov 2012 18:46:28 -0800
Subject: [PATCH] model: add get_last_seq_cst_fence

---
 model.cc | 29 +++++++++++++++++++++++++++++
 model.h  |  1 +
 2 files changed, 30 insertions(+)

diff --git a/model.cc b/model.cc
index 39af266a..fc86d5c7 100644
--- a/model.cc
+++ b/model.cc
@@ -1997,6 +1997,35 @@ ModelAction * ModelChecker::get_last_seq_cst_write(ModelAction *curr) const
 	return NULL;
 }
 
+/**
+ * Gets the last memory_order_seq_cst fence (in the total global sequence)
+ * performed in a particular thread, prior to a particular fence.
+ * @param tid The ID of the thread to check
+ * @param before_fence The fence from which to begin the search; if NULL, then
+ * search for the most recent fence in the thread.
+ * @return The last prior seq_cst fence in the thread, if exists; otherwise, NULL
+ */
+ModelAction * ModelChecker::get_last_seq_cst_fence(thread_id_t tid, const ModelAction *before_fence) const
+{
+	/* All fences should have NULL location */
+	action_list_t *list = get_safe_ptr_action(obj_map, NULL);
+	action_list_t::reverse_iterator rit = list->rbegin();
+
+	if (before_fence) {
+		for (; rit != list->rend(); rit++)
+			if (*rit == before_fence)
+				break;
+
+		ASSERT(*rit == before_fence);
+		rit++;
+	}
+
+	for (; rit != list->rend(); rit++)
+		if ((*rit)->is_fence() && (tid == (*rit)->get_tid()) && (*rit)->is_seqcst())
+			return *rit;
+	return NULL;
+}
+
 /**
  * Gets the last unlock operation performed on a particular mutex (i.e., memory
  * location). This function identifies the mutex according to the current
diff --git a/model.h b/model.h
index d0e47d9d..11afba9f 100644
--- a/model.h
+++ b/model.h
@@ -171,6 +171,7 @@ private:
 	void add_action_to_lists(ModelAction *act);
 	ModelAction * get_last_action(thread_id_t tid) const;
 	ModelAction * get_last_seq_cst_write(ModelAction *curr) const;
+	ModelAction * get_last_seq_cst_fence(thread_id_t tid, const ModelAction *before_fence) const;
 	ModelAction * get_last_unlock(ModelAction *curr) const;
 	void build_reads_from_past(ModelAction *curr);
 	ModelAction * process_rmw(ModelAction *curr);
-- 
2.34.1