From d3e65e702f45ea3476f3bda2b8f69a3e3729e9e2 Mon Sep 17 00:00:00 2001
From: Rafael Espindola <rafael.espindola@gmail.com>
Date: Wed, 24 Aug 2011 18:07:01 +0000
Subject: [PATCH] Fix a crashing bug in SplitBlock when it is called on a block
 with no dominator information even though dominators were previously
 computed.

Patch by Nick Sumner.

llvm-svn: 138449
---
 llvm/lib/Transforms/Utils/BasicBlockUtils.cpp | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp b/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
index 27120eeeb3ae..a7f9efd562e1 100644
--- a/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
+++ b/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
@@ -299,16 +299,17 @@ BasicBlock *llvm::SplitBlock(BasicBlock *Old, Instruction *SplitPt, Pass *P) {
 
   if (DominatorTree *DT = P->getAnalysisIfAvailable<DominatorTree>()) {
     // Old dominates New. New node dominates all other nodes dominated by Old.
-    DomTreeNode *OldNode = DT->getNode(Old);
-    std::vector<DomTreeNode *> Children;
-    for (DomTreeNode::iterator I = OldNode->begin(), E = OldNode->end();
-         I != E; ++I) 
-      Children.push_back(*I);
+    if (DomTreeNode *OldNode = DT->getNode(Old)) {
+      std::vector<DomTreeNode *> Children;
+      for (DomTreeNode::iterator I = OldNode->begin(), E = OldNode->end();
+           I != E; ++I) 
+        Children.push_back(*I);
 
       DomTreeNode *NewNode = DT->addNewBlock(New,Old);
       for (std::vector<DomTreeNode *>::iterator I = Children.begin(),
              E = Children.end(); I != E; ++I) 
         DT->changeImmediateDominator(*I, NewNode);
+    }
   }
 
   return New;