[SimplifyCFG][BasicBlockUtils] Port SplitBlockPredecessors()/SplitLandingPadPredecessors() to DomTreeUpdater

This is not nice, but it's the best transient solution possible,
and is better than just duplicating the whole function.

The problem is, this function is widely used,
and it is not at all obvious that all the users
could be painlessly switched to operate on DomTreeUpdater,
and somehow i don't feel like porting all those users first.

This function is one of last three that not operate on DomTreeUpdater.

1 files changed, 5 insertions, 8 deletions

diff --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
index a534643..4c0427e 100644
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -1113,7 +1113,7 @@ bool SimplifyCFGOpt::FoldValueComparisonIntoPredecessors(Instruction *TI,
       if (!SafeToMergeTerminators(TI, PTI, &FailBlocks)) {
         for (auto *Succ : FailBlocks) {
           if (!SplitBlockPredecessors(Succ, TI->getParent(), ".fold.split",
-                                      DTU ? &DTU->getDomTree() : nullptr))
+                                      DTU))
             return false;
         }
       }
@@ -1977,8 +1977,7 @@ static bool SinkCommonCodeFromPredecessors(BasicBlock *BB,
     LLVM_DEBUG(dbgs() << "SINK: Splitting edge\n");
     // We have a conditional edge and we're going to sink some instructions.
     // Insert a new block postdominating all blocks we're going to sink from.
-    if (!SplitBlockPredecessors(BB, UnconditionalPreds, ".sink.split",
-                                DTU ? &DTU->getDomTree() : nullptr))
+    if (!SplitBlockPredecessors(BB, UnconditionalPreds, ".sink.split", DTU))
       // Edges couldn't be split.
       return false;
     Changed = true;
@@ -3391,8 +3390,7 @@ static bool mergeConditionalStoreToAddress(
     // branch to QFB and PostBB.
     BasicBlock *TruePred = QTB ? QTB : QFB->getSinglePredecessor();
     BasicBlock *NewBB =
-        SplitBlockPredecessors(PostBB, {QFB, TruePred}, "condstore.split",
-                               DTU ? &DTU->getDomTree() : nullptr);
+        SplitBlockPredecessors(PostBB, {QFB, TruePred}, "condstore.split", DTU);
     if (!NewBB)
       return false;
     PostBB = NewBB;
@@ -4827,9 +4825,8 @@ static void createUnreachableSwitchDefault(SwitchInst *Switch,
                                            DomTreeUpdater *DTU) {
   LLVM_DEBUG(dbgs() << "SimplifyCFG: switch default is dead.\n");
   auto *BB = Switch->getParent();
-  BasicBlock *NewDefaultBlock =
-      SplitBlockPredecessors(Switch->getDefaultDest(), Switch->getParent(), "",
-                             DTU ? &DTU->getDomTree() : nullptr);
+  BasicBlock *NewDefaultBlock = SplitBlockPredecessors(
+      Switch->getDefaultDest(), Switch->getParent(), "", DTU);
   auto *OrigDefaultBlock = Switch->getDefaultDest();
   Switch->setDefaultDest(&*NewDefaultBlock);
   if (DTU)