X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=cyclegraph.cc;h=2c3a5936a89d8ac7dbb7e5b43e32b7a1cfd5ec6a;hb=482c7447dd2f63823eb969c37dd6fb4e22991fde;hp=58cb79f22cdd573acf59e24976014c91731e6e7e;hpb=84d49e8de1334a7dad25864c5ba8827de2502947;p=model-checker.git

diff --git a/cyclegraph.cc b/cyclegraph.cc
index 58cb79f..2c3a593 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);
@@ -58,7 +73,7 @@ CycleNode * CycleGraph::getNode(const ModelAction *action)
 CycleNode * CycleGraph::getNode(const Promise *promise)
 {
 	const ModelAction *reader = promise->get_action();
-	CycleNode *node = readerToPromiseNode.get(reader);
+	CycleNode *node = getNode_noCreate(promise);
 	if (node == NULL) {
 		node = new CycleNode(promise);
 		readerToPromiseNode.put(reader, node);
@@ -90,6 +105,89 @@ void CycleGraph::addEdge(const T from, const U to)
 	addNodeEdge(fromnode, tonode);
 }
 
+/**
+ * @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
+ *
+ * @return false if the merge results in a cycle; true otherwise
+ */
+bool CycleGraph::mergeNodes(CycleNode *w_node, CycleNode *p_node,
+		promise_list_t *mustMerge)
+{
+	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;
+	}
+
+	/* 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);
+		}
+	}
+
+	/* 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
@@ -192,12 +290,13 @@ void CycleGraph::dumpGraphToFile(const char *filename) const
 #endif
 
 /**
- * Checks whether one ModelAction can reach another.
+ * Checks whether one ModelAction can reach another ModelAction/Promise
  * @param from The ModelAction from which to begin exploration
- * @param to The ModelAction to reach
+ * @param to The ModelAction or Promise to reach
  * @return True, @a from can reach @a to; otherwise, false
  */
-bool CycleGraph::checkReachable(const ModelAction *from, const ModelAction *to) const
+template <typename T>
+bool CycleGraph::checkReachable(const ModelAction *from, const T *to) const
 {
 	CycleNode *fromnode = actionToNode.get(from);
 	CycleNode *tonode = actionToNode.get(to);
@@ -429,3 +528,19 @@ 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());
+}