In ExplodedGraphImpl::Trim, prioritize for paths that don't span loops by using

two worklists: for nodes whose locations are block edges with loop terminators
and another for nodes with all other locations.  We only dequeue from the loop
worklist when the other is empty.  Exploration of the graph is still in
reverse-BFS.

llvm-svn: 49791

1 files changed, 34 insertions, 5 deletions

diff --git a/clang/lib/Analysis/ExplodedGraph.cpp b/clang/lib/Analysis/ExplodedGraph.cpp
index 2ba46d77d63..3788551be00 100644
--- a/clang/lib/Analysis/ExplodedGraph.cpp
+++ b/clang/lib/Analysis/ExplodedGraph.cpp
@@ -13,6 +13,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "clang/Analysis/PathSensitive/ExplodedGraph.h"
+#include "clang/AST/Stmt.h"
 #include "llvm/ADT/DenseSet.h"
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/SmallVector.h"
@@ -103,18 +104,30 @@ ExplodedGraphImpl* ExplodedGraphImpl::Trim(ExplodedNodeImpl** BeginSources,
     // Enqueue the source nodes to the first worklist. 
     
     std::list<std::pair<ExplodedNodeImpl*, ExplodedNodeImpl*> > WL1;
+    std::list<std::pair<ExplodedNodeImpl*, ExplodedNodeImpl*> > WL1_Loops;
   
     for (ExplodedNodeImpl** I = BeginSources; I != EndSources; ++I)
       WL1.push_back(std::make_pair(*I, *I));
     
     // Process the worklist.
 
-    while (!WL1.empty()) {
+    while (! (WL1.empty() && WL1_Loops.empty())) {
       
-      ExplodedNodeImpl* N = WL1.back().first;
-      ExplodedNodeImpl* Src = WL1.back().second;
+      ExplodedNodeImpl *N, *Src;
+
+      // Only dequeue from the "loops" worklist if WL1 has no items.
+      // Thus we prioritize for paths that don't span loop boundaries.
       
-      WL1.pop_back();
+      if (WL1.empty()) {
+        N = WL1_Loops.back().first;
+        Src = WL1_Loops.back().second;
+        WL1_Loops.pop_back();
+      }
+      else {
+        N = WL1.back().first;
+        Src = WL1.back().second;
+        WL1.pop_back();
+      }      
       
       if (Pass1.find(N) != Pass1.end())
         continue;
@@ -152,8 +165,24 @@ ExplodedGraphImpl* ExplodedGraphImpl::Trim(ExplodedNodeImpl** BeginSources,
       
       if (VisitPreds)
         for (ExplodedNodeImpl** I=N->Preds.begin(), **E=N->Preds.end();
-             I!=E; ++I)
+             I!=E; ++I) {
+          
+          ProgramPoint P = Src->getLocation();
+          
+          if (const BlockEdge *BE = dyn_cast<BlockEdge>(&P))
+            if (Stmt* T = BE->getSrc()->getTerminator())
+              switch (T->getStmtClass()) {
+                default: break;
+                case Stmt::ForStmtClass:
+                case Stmt::WhileStmtClass:
+                case Stmt::DoStmtClass:
+                  WL1_Loops.push_front(std::make_pair(*I, Src));
+                  continue;
+                  
+              }
+          
           WL1.push_front(std::make_pair(*I, Src));
+        }
     }
   }