X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=cyclegraph.cc;h=eaddc8e1714629f8834a5b11c891f8009b2e1237;hb=00b14c0561d3838aeb798d3c22f4136f8c4d136b;hp=49c462f5375c0695bb07d10b18f82ee156a73b29;hpb=07aa7bafa42e3909d74889e5ed70fff3ab05d0f0;p=model-checker.git

diff --git a/cyclegraph.cc b/cyclegraph.cc
index 49c462f..eaddc8e 100644
--- a/cyclegraph.cc
+++ b/cyclegraph.cc
@@ -31,14 +31,29 @@ void CycleGraph::putNode(const ModelAction *act, CycleNode *node)
 #endif
 }
 
+/** @return The corresponding CycleNode, if exists; otherwise NULL */
+CycleNode * CycleGraph::getNode_noCreate(const ModelAction *act) const
+{
+	return actionToNode.get(act);
+}
+
+/** @return The corresponding CycleNode, if exists; otherwise NULL */
+CycleNode * CycleGraph::getNode_noCreate(const Promise *promise) const
+{
+	return readerToPromiseNode.get(promise->get_action());
+}
+
 /**
  * @brief Returns the CycleNode corresponding to a given ModelAction
+ *
+ * Gets (or creates, if none exist) a CycleNode corresponding to a ModelAction
+ *
  * @param action The ModelAction to find a node for
  * @return The CycleNode paired with this action
  */
 CycleNode * CycleGraph::getNode(const ModelAction *action)
 {
-	CycleNode *node = actionToNode.get(action);
+	CycleNode *node = getNode_noCreate(action);
 	if (node == NULL) {
 		node = new CycleNode(action);
 		putNode(action, node);
@@ -47,40 +62,122 @@ CycleNode * CycleGraph::getNode(const ModelAction *action)
 }
 
 /**
- * @brief Adds an edge between objects
+ * @brief Returns a CycleNode corresponding to a promise
  *
- * This function will add an edge between any two objects which can be
- * associated with a CycleNode. That is, if they have a CycleGraph::getNode
- * implementation.
+ * Gets (or creates, if none exist) a CycleNode corresponding to a promised
+ * value.
  *
- * The object to is ordered after the object from.
+ * @param promise The Promise generated by a reader
+ * @return The CycleNode corresponding to the Promise
+ */
+CycleNode * CycleGraph::getNode(const Promise *promise)
+{
+	const ModelAction *reader = promise->get_action();
+	CycleNode *node = getNode_noCreate(promise);
+	if (node == NULL) {
+		node = new CycleNode(promise);
+		readerToPromiseNode.put(reader, node);
+	}
+	return node;
+}
+
+/**
+ * @return false if the resolution results in a cycle; true otherwise
+ */
+bool CycleGraph::resolvePromise(ModelAction *reader, ModelAction *writer,
+		promise_list_t *mustResolve)
+{
+	CycleNode *promise_node = readerToPromiseNode.get(reader);
+	CycleNode *w_node = actionToNode.get(writer);
+	ASSERT(promise_node);
+
+	if (w_node)
+		return mergeNodes(w_node, promise_node, mustResolve);
+	/* No existing write-node; just convert the promise-node */
+	promise_node->resolvePromise(writer);
+	readerToPromiseNode.put(reader, NULL); /* erase promise_node */
+	putNode(writer, promise_node);
+	return true;
+}
+
+/**
+ * @brief Merge two CycleNodes that represent the same write
+ *
+ * Note that this operation cannot be rolled back.
+ *
+ * @param w_node The write ModelAction node with which to merge
+ * @param p_node The Promise node to merge. Will be destroyed after this
+ * function.
+ * @param mustMerge Return (pass-by-reference) any additional Promises that
+ * must also be merged with w_node
  *
- * @param to The edge points to this object, of type T
- * @param from The edge comes from this object, of type U
+ * @return false if the merge results in a cycle; true otherwise
  */
-template <typename T, typename U>
-void CycleGraph::addEdge(const T from, const U to)
+bool CycleGraph::mergeNodes(CycleNode *w_node, CycleNode *p_node,
+		promise_list_t *mustMerge)
 {
-	ASSERT(from);
-	ASSERT(to);
+	ASSERT(!w_node->is_promise());
+	ASSERT(p_node->is_promise());
+	const Promise *promise = p_node->getPromise();
+	if (!promise->is_compatible(w_node->getAction())) {
+		hasCycles = true;
+		return false;
+	}
 
-	CycleNode *fromnode = getNode(from);
-	CycleNode *tonode = getNode(to);
+	/* Transfer back edges to w_node */
+	while (p_node->getNumBackEdges() > 0) {
+		CycleNode *back = p_node->removeBackEdge();
+		if (back != w_node) {
+			if (back->is_promise()) {
+				if (checkReachable(w_node, back)) {
+					/* Edge would create cycle; merge instead */
+					mustMerge->push_back(back->getPromise());
+					if (!mergeNodes(w_node, back, mustMerge))
+						return false;
+				} else
+					back->addEdge(w_node);
+			} else
+				addNodeEdge(back, w_node);
+		}
+	}
+
+	/* Transfer forward edges to w_node */
+	while (p_node->getNumEdges() > 0) {
+		CycleNode *forward = p_node->removeEdge();
+		if (forward != w_node) {
+			if (forward->is_promise()) {
+				if (checkReachable(forward, w_node)) {
+					mustMerge->push_back(forward->getPromise());
+					if (!mergeNodes(w_node, forward, mustMerge))
+						return false;
+				} else
+					w_node->addEdge(forward);
+			} else
+				addNodeEdge(w_node, forward);
+		}
+	}
 
-	addNodeEdge(fromnode, tonode);
+	/* erase p_node */
+	readerToPromiseNode.put(promise->get_action(), NULL);
+	delete p_node;
+
+	return !hasCycles;
 }
 
 /**
  * Adds an edge between two CycleNodes.
  * @param fromnode The edge comes from this CycleNode
  * @param tonode The edge points to this CycleNode
+ * @return True, if new edge(s) are added; otherwise false
  */
-void CycleGraph::addNodeEdge(CycleNode *fromnode, CycleNode *tonode)
+bool CycleGraph::addNodeEdge(CycleNode *fromnode, CycleNode *tonode)
 {
+	bool added;
+
 	if (!hasCycles)
 		hasCycles = checkReachable(tonode, fromnode);
 
-	if (fromnode->addEdge(tonode))
+	if ((added = fromnode->addEdge(tonode)))
 		rollbackvector.push_back(fromnode);
 
 	/*
@@ -92,9 +189,12 @@ void CycleGraph::addNodeEdge(CycleNode *fromnode, CycleNode *tonode)
 		if (!hasCycles)
 			hasCycles = checkReachable(tonode, rmwnode);
 
-		if (rmwnode->addEdge(tonode))
+		if (rmwnode->addEdge(tonode)) {
 			rollbackvector.push_back(rmwnode);
+			added = true;
+		}
 	}
+	return added;
 }
 
 /**
@@ -171,23 +271,6 @@ void CycleGraph::dumpGraphToFile(const char *filename) const
 }
 #endif
 
-/**
- * Checks whether one ModelAction can reach another.
- * @param from The ModelAction from which to begin exploration
- * @param to The ModelAction to reach
- * @return True, @a from can reach @a to; otherwise, false
- */
-bool CycleGraph::checkReachable(const ModelAction *from, const ModelAction *to) const
-{
-	CycleNode *fromnode = actionToNode.get(from);
-	CycleNode *tonode = actionToNode.get(to);
-
-	if (!fromnode || !tonode)
-		return false;
-
-	return checkReachable(fromnode, tonode);
-}
-
 /**
  * Checks whether one CycleNode can reach another.
  * @param from The CycleNode from which to begin exploration
@@ -218,6 +301,7 @@ bool CycleGraph::checkReachable(const CycleNode *from, const CycleNode *to) cons
 	return false;
 }
 
+/** @return True, if the promise has failed; false otherwise */
 bool CycleGraph::checkPromise(const ModelAction *fromact, Promise *promise) const
 {
 	std::vector< CycleNode *, ModelAlloc<CycleNode *> > queue;
@@ -230,9 +314,9 @@ bool CycleGraph::checkPromise(const ModelAction *fromact, Promise *promise) cons
 		CycleNode *node = queue.back();
 		queue.pop_back();
 
-		if (promise->eliminate_thread(node->getAction()->get_tid())) {
+		if (!node->is_promise() &&
+				promise->eliminate_thread(node->getAction()->get_tid()))
 			return true;
-		}
 
 		for (unsigned int i = 0; i < node->getNumEdges(); i++) {
 			CycleNode *next = node->getEdge(i);
@@ -409,3 +493,19 @@ bool CycleNode::setRMW(CycleNode *node)
 	hasRMW = node;
 	return false;
 }
+
+/**
+ * Convert a Promise CycleNode into a concrete-valued CycleNode. Should only be
+ * used when there's no existing ModelAction CycleNode for this write.
+ *
+ * @param writer The ModelAction which wrote the future value represented by
+ * this CycleNode
+ */
+void CycleNode::resolvePromise(const ModelAction *writer)
+{
+	ASSERT(is_promise());
+	ASSERT(promise->is_compatible(writer));
+	action = writer;
+	promise = NULL;
+	ASSERT(!is_promise());
+}