Enhance GRBranchNodeBuilderImpl (part of GRCoreEngine) to understand the case
where the true or false CFGBlock* for a branch could be NULL. This will handle
the case where we can determine during CFG construction that a branch is
infeasible.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@76450 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/GRExprEngine.cpp b/lib/Analysis/GRExprEngine.cpp
index 8a1bd18..97e75fa 100644
--- a/lib/Analysis/GRExprEngine.cpp
+++ b/lib/Analysis/GRExprEngine.cpp
@@ -706,16 +706,20 @@
   }
     
   // Process the true branch.
-  if (const GRState *state = PrevState->assume(V, true))
-    builder.generateNode(MarkBranch(state, Term, true), true);
-  else
-    builder.markInfeasible(true);
+  if (builder.isFeasible(true)) {
+    if (const GRState *state = PrevState->assume(V, true))
+      builder.generateNode(MarkBranch(state, Term, true), true);
+    else
+      builder.markInfeasible(true);
+  }
       
   // Process the false branch.  
-  if (const GRState *state = PrevState->assume(V, false))
-    builder.generateNode(MarkBranch(state, Term, false), false);
-  else
-    builder.markInfeasible(false);
+  if (builder.isFeasible(false)) {
+    if (const GRState *state = PrevState->assume(V, false))
+      builder.generateNode(MarkBranch(state, Term, false), false);
+    else
+      builder.markInfeasible(false);
+  }
 }
 
 /// ProcessIndirectGoto - Called by GRCoreEngine.  Used to generate successor