cyclegraph: add full promise resolution, node merging

We now support the interfaces needed for tracking Promise constraints in
CycleGraph.

diff --git a/cyclegraph.cc b/cyclegraph.cc
index 479ddf852fcc0440f1f0850867fca5dd87ddfab3..46b0d4ac4eb803df74d57e53148d0d463f343e26 100644 (file)
--- a/cyclegraph.cc
+++ b/cyclegraph.cc
@@ -90,6 +90,89 @@ 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

diff --git a/cyclegraph.h b/cyclegraph.h
index e7e9380bb7e67e195d3d2ab95b587a44aa0234aa..c0bd7d66167aea6bd71fa323efb29e18a57dfac4 100644 (file)
--- a/cyclegraph.h
+++ b/cyclegraph.h
@@ -19,6 +19,8 @@ class Promise;
 class CycleNode;
 class ModelAction;
 
+typedef std::vector< const Promise *, ModelAlloc<const Promise *> > promise_list_t;
+
 /** @brief A graph of Model Actions for tracking cycles. */
 class CycleGraph {
  public:
@@ -40,12 +42,17 @@ class CycleGraph {
        void dumpGraphToFile(const char *filename) const;
 #endif
 
+       bool resolvePromise(ModelAction *reader, ModelAction *writer,
+                       promise_list_t *mustResolve);
+
        SNAPSHOTALLOC
  private:
        void addNodeEdge(CycleNode *fromnode, CycleNode *tonode);
        void putNode(const ModelAction *act, CycleNode *node);
        CycleNode * getNode(const ModelAction *);
        CycleNode * getNode(const Promise *promise);
+       bool mergeNodes(CycleNode *node1, CycleNode *node2,
+                       promise_list_t *mustMerge);
 
        HashTable<const CycleNode *, const CycleNode *, uintptr_t, 4, model_malloc, model_calloc, model_free> *discovered;