From 818f5c483785a7e57b900f2796c16c5596def185 Mon Sep 17 00:00:00 2001
From: Peter Collingbourne <peter@pcc.me.uk>
Date: Tue, 15 Jul 2014 04:40:27 +0000
Subject: Give SplitBlockAndInsertIfThen the ability to update a domtree.

llvm-svn: 213045
---
 llvm/lib/Transforms/Utils/BasicBlockUtils.cpp | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

(limited to 'llvm/lib/Transforms/Utils/BasicBlockUtils.cpp')

diff --git a/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp b/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
index 80b7e22baca..602e8ba5510 100644
--- a/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
+++ b/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
@@ -673,7 +673,8 @@ ReturnInst *llvm::FoldReturnIntoUncondBranch(ReturnInst *RI, BasicBlock *BB,
 TerminatorInst *llvm::SplitBlockAndInsertIfThen(Value *Cond,
                                                 Instruction *SplitBefore,
                                                 bool Unreachable,
-                                                MDNode *BranchWeights) {
+                                                MDNode *BranchWeights,
+                                                DominatorTree *DT) {
   BasicBlock *Head = SplitBefore->getParent();
   BasicBlock *Tail = Head->splitBasicBlock(SplitBefore);
   TerminatorInst *HeadOldTerm = Head->getTerminator();
@@ -690,6 +691,20 @@ TerminatorInst *llvm::SplitBlockAndInsertIfThen(Value *Cond,
   HeadNewTerm->setDebugLoc(SplitBefore->getDebugLoc());
   HeadNewTerm->setMetadata(LLVMContext::MD_prof, BranchWeights);
   ReplaceInstWithInst(HeadOldTerm, HeadNewTerm);
+
+  if (DT) {
+    if (DomTreeNode *OldNode = DT->getNode(Head)) {
+      std::vector<DomTreeNode *> Children(OldNode->begin(), OldNode->end());
+
+      DomTreeNode *NewNode = DT->addNewBlock(Tail, Head);
+      for (auto Child : Children)
+        DT->changeImmediateDominator(Child, NewNode);
+
+      // Head dominates ThenBlock.
+      DT->addNewBlock(ThenBlock, Head);
+    }
+  }
+
   return CheckTerm;
 }
 
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