Properly update MachineDominators when splitting critical edge.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@111574 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/MachineBasicBlock.cpp b/lib/CodeGen/MachineBasicBlock.cpp
index d351db5..50f3f67 100644
--- a/lib/CodeGen/MachineBasicBlock.cpp
+++ b/lib/CodeGen/MachineBasicBlock.cpp
@@ -468,8 +468,31 @@
LV->addNewBlock(NMBB, this, Succ);
if (MachineDominatorTree *MDT =
- P->getAnalysisIfAvailable<MachineDominatorTree>())
- MDT->addNewBlock(NMBB, this);
+ P->getAnalysisIfAvailable<MachineDominatorTree>()) {
+ // Update dominator information.
+ MachineDomTreeNode *SucccDTNode = MDT->getNode(Succ);
+
+ bool IsNewIDom = true;
+ for (const_pred_iterator PI = Succ->pred_begin(), E = Succ->pred_end();
+ PI != E; ++PI) {
+ MachineBasicBlock *PredBB = *PI;
+ if (PredBB == NMBB)
+ continue;
+ if (!MDT->dominates(SucccDTNode, MDT->getNode(PredBB))) {
+ IsNewIDom = false;
+ break;
+ }
+ }
+
+ // We know "this" dominates the newly created basic block.
+ MachineDomTreeNode *NewDTNode = MDT->addNewBlock(NMBB, this);
+
+ // If all the other predecessors of "Succ" are dominated by "Succ" itself
+ // then the new block is the new immediate dominator of "Succ". Otherwise,
+ // the new block doesn't dominate anything.
+ if (IsNewIDom)
+ MDT->changeImmediateDominator(SucccDTNode, NewDTNode);
+ }
if (MachineLoopInfo *MLI = P->getAnalysisIfAvailable<MachineLoopInfo>())
if (MachineLoop *TIL = MLI->getLoopFor(this)) {