Index: llvm/include/llvm/Analysis/BranchProbabilityInfo.h
===================================================================
--- llvm/include/llvm/Analysis/BranchProbabilityInfo.h
+++ llvm/include/llvm/Analysis/BranchProbabilityInfo.h
@@ -189,6 +189,9 @@
   /// unset for source.
   void copyEdgeProbabilities(BasicBlock *Src, BasicBlock *Dst);
 
+  /// Swap outgoing edges probabilities for \p Src with branch terminator
+  void swapSuccEdgesProbabilities(const BasicBlock *Src);
+
   static BranchProbability getBranchProbStackProtector(bool IsLikely) {
     static const BranchProbability LikelyProb((1u << 20) - 1, 1u << 20);
     return IsLikely ? LikelyProb : LikelyProb.getCompl();
Index: llvm/lib/Analysis/BranchProbabilityInfo.cpp
===================================================================
--- llvm/lib/Analysis/BranchProbabilityInfo.cpp
+++ llvm/lib/Analysis/BranchProbabilityInfo.cpp
@@ -1175,6 +1175,14 @@
   }
 }
 
+void BranchProbabilityInfo::swapSuccEdgesProbabilities(const BasicBlock *Src) {
+  assert(Src->getTerminator()->getNumSuccessors() == 2);
+  if (!Probs.contains(std::make_pair(Src, 0)))
+    return; // No probability is set for edges from Src
+  assert(Probs.contains(std::make_pair(Src, 1)));
+  std::swap(Probs[std::make_pair(Src, 0)], Probs[std::make_pair(Src, 1)]);
+}
+
 raw_ostream &
 BranchProbabilityInfo::printEdgeProbability(raw_ostream &OS,
                                             const BasicBlock *Src,