[analyzer] Fix a spurious undef value warning.

When we timeout or exceed a max number of blocks within an inlined
function, we retry with no inlining starting from a node right before
the CallEnter node. We assume the state of that node is the state of the
program before we start evaluating the call. However, the node pruning
removes this node as unimportant. 

Teach the node pruning to keep the predecessors of the call enter nodes.

llvm-svn: 157860

clang/lib/StaticAnalyzer/Core/ExplodedGraph.cpp

@@ -67,6 +67,8 @@ bool ExplodedGraph::shouldCollect(const ExplodedNode *node) {
   // (6) The 'GDM' is the same as the predecessor.
   // (7) The LocationContext is the same as the predecessor.
   // (8) The PostStmt is for a non-consumed Stmt or Expr.
+  // (9) The successor is a CallExpr StmtPoint (so that we would be able to
+  //     find it when retrying a call with no inlining).
 
   // Conditions 1 and 2.
   if (node->pred_size() != 1 || node->succ_size() != 1)
@@ -109,7 +111,13 @@ bool ExplodedGraph::shouldCollect(const ExplodedNode *node) {
       return false;
   }
   
-  return true; 
+  // Condition 9.
+  const ProgramPoint SuccLoc = succ->getLocation();
+  if (const StmtPoint *SP = dyn_cast<StmtPoint>(&SuccLoc))
+    if (isa<CallExpr>(SP->getStmt()))
+      return false;
+
+  return true;
 }
 
 void ExplodedGraph::collectNode(ExplodedNode *node) {