[analyzer] Break cycles (optionally) when trimming an ExplodedGraph.

Having a trimmed graph with no cycles (a DAG) is much more convenient for
trying to find shortest paths, which is exactly what BugReporter needs to do.

Part of the performance work for <rdar://problem/13433687>.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@177468 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/clang/StaticAnalyzer/Core/PathSensitive/ExplodedGraph.h b/include/clang/StaticAnalyzer/Core/PathSensitive/ExplodedGraph.h
index 5211916407c8f463a6fb4c7d917c6f99714e082f..208c12bd748bb499ef2098f02c8c8c7cb78d9d47 100644 (file)
--- a/include/clang/StaticAnalyzer/Core/PathSensitive/ExplodedGraph.h
+++ b/include/clang/StaticAnalyzer/Core/PathSensitive/ExplodedGraph.h
@@ -363,12 +363,16 @@ public:
   ///
   /// \param Nodes The nodes which must appear in the final graph. Presumably
   ///              these are end-of-path nodes (i.e. they have no successors).
+  /// \param BreakCycles Whether or not the trimmed graph should make an effort
+  ///                    to eliminate cycles. Note that this may result in some
+  ///                    unnecessary nodes being included in the final graph
+  ///                    (i.e. nodes that would have only appeared in a cycle).
   /// \param[out] ForwardMap A optional map from nodes in this graph to nodes in
   ///                        the returned graph.
   /// \param[out] InverseMap An optional map from nodes in the returned graph to
   ///                        nodes in this graph.
   /// \returns The trimmed graph
-  ExplodedGraph *trim(ArrayRef<const NodeTy *> Nodes,
+  ExplodedGraph *trim(ArrayRef<const NodeTy *> Nodes, bool BreakCycles = false,
                       InterExplodedGraphMap *ForwardMap = 0,
                       InterExplodedGraphMap *InverseMap = 0) const;
 

diff --git a/lib/StaticAnalyzer/Core/BugReporter.cpp b/lib/StaticAnalyzer/Core/BugReporter.cpp
index cc67343d340d9db58d9ffd99810a7e0439203b9e..51fdab5c6839f1d96cfc653f7bc6d0cb20453996 100644 (file)
--- a/lib/StaticAnalyzer/Core/BugReporter.cpp
+++ b/lib/StaticAnalyzer/Core/BugReporter.cpp
@@ -1895,7 +1895,8 @@ public:
                ArrayRef<const ExplodedNode *> Nodes) {
     // The trimmed graph is created in the body of the constructor to ensure
     // that the DenseMaps have been initialized already.
-    G.reset(OriginalGraph->trim(Nodes, &ForwardMap, &InverseMap));
+    G.reset(OriginalGraph->trim(Nodes, /*BreakCycles=*/true,
+                                &ForwardMap, &InverseMap));
   }
 
   void createBestReportGraph(ArrayRef<const ExplodedNode *> Nodes,

diff --git a/lib/StaticAnalyzer/Core/ExplodedGraph.cpp b/lib/StaticAnalyzer/Core/ExplodedGraph.cpp
index ca466d89070c82ebafb481c62e3755c9fc18c54c..f9d4345baef680540226591f98d70598f5ae2ae9 100644 (file)
--- a/lib/StaticAnalyzer/Core/ExplodedGraph.cpp
+++ b/lib/StaticAnalyzer/Core/ExplodedGraph.cpp
@@ -331,8 +331,22 @@ ExplodedNode *ExplodedGraph::getNode(const ProgramPoint &L,
   return V;
 }
 
+static bool isDescendent(const ExplodedNode *Parent, const ExplodedNode *Child){
+  SmallVector<const ExplodedNode *, 16> WL;
+  WL.push_back(Parent);
+
+  while (!WL.empty()) {
+    const ExplodedNode *N = WL.pop_back_val();
+    if (N == Child)
+      return true;
+    WL.append(N->succ_begin(), N->succ_end());
+  }
+
+  return false;
+}
+
 ExplodedGraph *
-ExplodedGraph::trim(ArrayRef<const NodeTy *> Sinks,
+ExplodedGraph::trim(ArrayRef<const NodeTy *> Sinks, bool BreakCycles,
                     InterExplodedGraphMap *ForwardMap,
                     InterExplodedGraphMap *InverseMap) const{
 
@@ -429,7 +443,8 @@ ExplodedGraph::trim(ArrayRef<const NodeTy *> Sinks,
          I != E; ++I) {
       Pass2Ty::iterator PI = Pass2.find(*I);
       if (PI != Pass2.end()) {
-        const_cast<ExplodedNode *>(PI->second)->addPredecessor(NewN, *G);
+        if (!BreakCycles || !isDescendent(PI->second, NewN))
+          const_cast<ExplodedNode *>(PI->second)->addPredecessor(NewN, *G);
         continue;
       }