From 1b2222d691a55eb20b39d3804c71aca19f5577bf Mon Sep 17 00:00:00 2001
From: Brian Demsky <bdemsky@uci.edu>
Date: Sun, 29 Dec 2019 21:43:29 -0800
Subject: [PATCH] handle last action with nop

---
 action.h     |  3 ++-
 execution.cc | 63 +++++++++++++++++++++++++++++++++-------------------
 execution.h  |  1 +
 3 files changed, 43 insertions(+), 24 deletions(-)

diff --git a/action.h b/action.h
index 2b4b4141..1658a83d 100644
--- a/action.h
+++ b/action.h
@@ -77,7 +77,8 @@ typedef enum action_type {
 	ATOMIC_WAIT,	// < A wait action
 	ATOMIC_TIMEDWAIT,	// < A timed wait action
 	ATOMIC_ANNOTATION,	// < An annotation action to pass information to a trace analysis
-	READY_FREE
+	READY_FREE,	// < Write is ready to be freed
+	ATOMIC_NOP	// < Placeholder
 } action_type_t;
 
 
diff --git a/execution.cc b/execution.cc
index 40aa6814..e462748c 100644
--- a/execution.cc
+++ b/execution.cc
@@ -1720,10 +1720,14 @@ ClockVector * ModelExecution::computeMinimalCV() {
 	return cvmin;
 }
 
-//Options...
-//How often to check for memory
-//How much of the trace to always keep
-//Whether to sacrifice completeness...i.e., remove visible writes
+void ModelExecution::fixupLastAct(ModelAction *act) {
+//Create a standin ModelAction
+	ModelAction *newact = new ModelAction(ATOMIC_NOP, std::memory_order_seq_cst, get_thread(act->get_tid()));
+	newact->set_seq_number(get_next_seq_num());
+	newact->create_cv(act);
+	newact->set_last_fence_release(act->get_last_fence_release());
+	add_action_to_lists(newact, false);
+}
 
 void ModelExecution::collectActions() {
 	//Compute minimal clock vector for all live threads
@@ -1777,8 +1781,19 @@ void ModelExecution::collectActions() {
 	}
 	for (sllnode<ModelAction*> * it2 = action_trace.end();it2 != it;it2=it2->getPrev()) {
 		ModelAction *act = it2->getVal();
+		bool islastact = false;
+		ModelAction *lastact = get_last_action(act->get_tid());
+		if (act == lastact) {
+			Thread * th = get_thread(act);
+			islastact = !th->is_complete();
+		}
+
 		if (act->is_read() && act->get_reads_from()->is_free()) {
-			act->set_read_from(NULL);
+			removeAction(act);
+			if (islastact) {
+				fixupLastAct(act);
+			}
+			delete act;
 		}
 	}
 	for (;it != NULL;) {
@@ -1793,31 +1808,33 @@ void ModelExecution::collectActions() {
 		}
 
 		if (act->is_read()) {
-			if (!islastact && act->get_reads_from()->is_free()) {
+			if (act->get_reads_from()->is_free()) {
 				removeAction(act);
+				if (islastact) {
+					fixupLastAct(act);
+				}
 				delete act;
-				continue;
-			}
-			if (islastact && act->get_reads_from()->is_free()) {
-				act->set_read_from(NULL);
-			}
-
-			const ModelAction *rel_fence =act->get_last_fence_release();
-			if (rel_fence != NULL) {
-				modelclock_t relfenceseq = rel_fence->get_seq_number();
-				thread_id_t relfence_tid = rel_fence->get_tid();
-				modelclock_t tid_clock = cvmin->getClock(relfence_tid);
-				//Remove references to irrelevant release fences
-				if (relfenceseq <= tid_clock)
-					act->set_last_fence_release(NULL);
+			} else {
+				const ModelAction *rel_fence =act->get_last_fence_release();
+				if (rel_fence != NULL) {
+					modelclock_t relfenceseq = rel_fence->get_seq_number();
+					thread_id_t relfence_tid = rel_fence->get_tid();
+					modelclock_t tid_clock = cvmin->getClock(relfence_tid);
+					//Remove references to irrelevant release fences
+					if (relfenceseq <= tid_clock)
+						act->set_last_fence_release(NULL);
+				}
 			}
-		} else if (islastact) {
-			continue;
 		} else if (act->is_free()) {
 			removeAction(act);
+			if (islastact) {
+				fixupLastAct(act);
+			}
 			delete act;
 		} else if (act->is_write()) {
 			//Do nothing with write that hasn't been marked to be freed
+		} else if (islastact) {
+			//Keep the last action for non-read/write actions
 		} else if (act->is_fence()) {
 			//Note that acquire fences can always be safely
 			//removed, but could incur extra overheads in
@@ -1839,7 +1856,7 @@ void ModelExecution::collectActions() {
 				delete act;
 			}
 		} else {
-			//need to deal with lock, annotation, wait, notify, thread create, start, join, yield, finish
+			//need to deal with lock, annotation, wait, notify, thread create, start, join, yield, finish, nops
 			//lock, notify thread create, thread finish, yield, finish are dead as soon as they are in the trace
 			//need to keep most recent unlock/wait for each lock
 			if(act->is_unlock() || act->is_wait()) {
diff --git a/execution.h b/execution.h
index 72efcd67..008e1e11 100644
--- a/execution.h
+++ b/execution.h
@@ -124,6 +124,7 @@ private:
 	ModelAction * convertNonAtomicStore(void*);
 	ClockVector * computeMinimalCV();
 	void removeAction(ModelAction *act);
+	void fixupLastAct(ModelAction *act);
 
 #ifdef TLS
 	pthread_key_t pthreadkey;
-- 
2.34.1