Check empty dominance frontier.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@52437 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/Analysis/Dominators.h b/include/llvm/Analysis/Dominators.h
index 6ce3260b8f5294bd000afd6f94aab0d7fdee128d..52171d7e12c79044392f326e0d9ede57a2583f29 100644 (file)
--- a/include/llvm/Analysis/Dominators.h
+++ b/include/llvm/Analysis/Dominators.h
@@ -944,6 +944,9 @@ public:
     // itself is not member of NewBB's dominance frontier.
     DominanceFrontier::iterator NewDFI = find(NewBB);
     DominanceFrontier::iterator DFI = find(BB);
+    // If BB was an entry block then its frontier is empty.
+    if (DFI == end())
+      return;
     DominanceFrontier::DomSetType BBSet = DFI->second;
     for (DominanceFrontier::DomSetType::iterator BBSetI = BBSet.begin(),
            BBSetE = BBSet.end(); BBSetI != BBSetE; ++BBSetI) {