After a basic block is split into two parts,

second part dominates all the blocks dominated
by original basic block. And first part dominates
second part.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@40035 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 15 insertions, 2 deletions

diff --git a/lib/Transforms/Utils/BasicBlockUtils.cpp b/lib/Transforms/Utils/BasicBlockUtils.cpp
index 520cfeb58b..0ed3ed6ad5 100644
--- a/lib/Transforms/Utils/BasicBlockUtils.cpp
+++ b/lib/Transforms/Utils/BasicBlockUtils.cpp
@@ -165,8 +165,21 @@ BasicBlock *llvm::SplitBlock(BasicBlock *Old, Instruction *SplitPt, Pass *P) {
   if (Loop *L = LI.getLoopFor(Old))
     L->addBasicBlockToLoop(New, LI);
 
-  if (DominatorTree *DT = P->getAnalysisToUpdate<DominatorTree>())
-    DT->addNewBlock(New, Old);
+  if (DominatorTree *DT = P->getAnalysisToUpdate<DominatorTree>()) 
+    {
+      // Old dominates New. New node domiantes 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);
+
+      DomTreeNode *NewNode =   DT->addNewBlock(New,Old);
+
+      for (std::vector<DomTreeNode *>::iterator I = Children.begin(),
+             E = Children.end(); I != E; ++I) 
+        DT->changeImmediateDominator(*I, NewNode);
+    }
 
   if (DominanceFrontier *DF = P->getAnalysisToUpdate<DominanceFrontier>())
     DF->splitBlock(Old);