Index: include/llvm/Analysis/BranchProbabilityInfo.h
===================================================================
--- include/llvm/Analysis/BranchProbabilityInfo.h
+++ include/llvm/Analysis/BranchProbabilityInfo.h
@@ -61,6 +61,9 @@
   BranchProbability getEdgeProbability(const BasicBlock *Src,
                                        const BasicBlock *Dst) const;
 
+  BranchProbability getEdgeProbability(const BasicBlock *Src,
+                                       succ_const_iterator Dst) const;
+
   /// \brief Test if an edge is hot relative to other out-edges of the Src.
   ///
   /// Check whether this edge out of the source block is 'hot'. We define hot
Index: include/llvm/CodeGen/MachineBasicBlock.h
===================================================================
--- include/llvm/CodeGen/MachineBasicBlock.h
+++ include/llvm/CodeGen/MachineBasicBlock.h
@@ -91,13 +91,6 @@
   std::vector<MachineBasicBlock *> Predecessors;
   std::vector<MachineBasicBlock *> Successors;
 
-  /// Keep track of the weights to the successors. This vector has the same
-  /// order as Successors, or it is empty if we don't use it (disable
-  /// optimization).
-  std::vector<uint32_t> Weights;
-  typedef std::vector<uint32_t>::iterator weight_iterator;
-  typedef std::vector<uint32_t>::const_iterator const_weight_iterator;
-
   /// Keep track of the probabilities to the successors. This vector has the
   /// same order as Successors, or it is empty if we don't use it (disable
   /// optimization).
@@ -441,25 +434,15 @@
   // Machine-CFG mutators
 
   /// Add Succ as a successor of this MachineBasicBlock.  The Predecessors list
-  /// of Succ is automatically updated. WEIGHT parameter is stored in Weights
-  /// list and it may be used by MachineBranchProbabilityInfo analysis to
-  /// calculate branch probability.
-  ///
-  /// Note that duplicate Machine CFG edges are not allowed.
-  void addSuccessor(MachineBasicBlock *Succ, uint32_t Weight = 0);
-
-  /// Add Succ as a successor of this MachineBasicBlock.  The Predecessors list
-  /// of Succ is automatically updated. The weight is not provided because BPI
-  /// is not available (e.g. -O0 is used), in which case edge weights won't be
-  /// used. Using this interface can save some space.
-  void addSuccessorWithoutWeight(MachineBasicBlock *Succ);
-
-  /// Add Succ as a successor of this MachineBasicBlock.  The Predecessors list
   /// of Succ is automatically updated. PROB parameter is stored in
-  /// Probabilities list.
+  /// Probabilities list. The default probability is set as unknown. Mixing
+  /// known and unknown probabilities in successor list is not allowed. When all
+  /// successors have unknown probabilities, 1 / N is returned as the
+  /// probability for each successor, where N is the number of successors.
   ///
   /// Note that duplicate Machine CFG edges are not allowed.
-  void addSuccessor(MachineBasicBlock *Succ, BranchProbability Prob);
+  void addSuccessor(MachineBasicBlock *Succ,
+                    BranchProbability Prob = BranchProbability::getUnknown());
 
   /// Add Succ as a successor of this MachineBasicBlock.  The Predecessors list
   /// of Succ is automatically updated. The probability is not provided because
@@ -467,9 +450,6 @@
   /// won't be used. Using this interface can save some space.
   void addSuccessorWithoutProb(MachineBasicBlock *Succ);
 
-  /// Set successor weight of a given iterator.
-  void setSuccWeight(succ_iterator I, uint32_t Weight);
-
   /// Set successor probability of a given iterator.
   void setSuccProbability(succ_iterator I, BranchProbability Prob);
 
@@ -488,7 +468,7 @@
   /// Return the iterator to the element after the one removed.
   succ_iterator removeSuccessor(succ_iterator I);
 
-  /// Replace successor OLD with NEW and update weight info.
+  /// Replace successor OLD with NEW and update probability info.
   void replaceSuccessor(MachineBasicBlock *Old, MachineBasicBlock *New);
 
   /// Transfers all the successors from MBB to this machine basic block (i.e.,
@@ -500,9 +480,6 @@
   /// operands in the successor blocks which refer to FromMBB to refer to this.
   void transferSuccessorsAndUpdatePHIs(MachineBasicBlock *FromMBB);
 
-  /// Return true if any of the successors have weights attached to them.
-  bool hasSuccessorWeights() const { return !Weights.empty(); }
-
   /// Return true if any of the successors have probabilities attached to them.
   bool hasSuccessorProbabilities() const { return !Probs.empty(); }
 
@@ -759,10 +736,6 @@
 
 
 private:
-  /// Return weight iterator corresponding to the I successor iterator.
-  weight_iterator getWeightIterator(succ_iterator I);
-  const_weight_iterator getWeightIterator(const_succ_iterator I) const;
-
   /// Return probability iterator corresponding to the I successor iterator.
   probability_iterator getProbabilityIterator(succ_iterator I);
   const_probability_iterator
@@ -771,11 +744,6 @@
   friend class MachineBranchProbabilityInfo;
   friend class MIPrinter;
 
-  /// Return weight of the edge from this block to MBB. This method should NOT
-  /// be called directly, but by using getEdgeWeight method from
-  /// MachineBranchProbabilityInfo class.
-  uint32_t getSuccWeight(const_succ_iterator Succ) const;
-
   /// Return probability of the edge from this block to MBB. This method should
   /// NOT be called directly, but by using getEdgeProbability method from
   /// MachineBranchProbabilityInfo class.
Index: include/llvm/CodeGen/MachineBranchProbabilityInfo.h
===================================================================
--- include/llvm/CodeGen/MachineBranchProbabilityInfo.h
+++ include/llvm/CodeGen/MachineBranchProbabilityInfo.h
@@ -55,10 +55,15 @@
   uint32_t getEdgeWeight(const MachineBasicBlock *Src,
                          MachineBasicBlock::const_succ_iterator Dst) const;
 
-  // Get sum of the block successors' weights, potentially scaling them to fit
-  // within 32-bits. If scaling is required, sets Scale based on the necessary
-  // adjustment. Any edge weights used with the sum should be divided by Scale.
-  uint32_t getSumForBlock(const MachineBasicBlock *MBB, uint32_t &Scale) const;
+  // Return edge probability.
+  BranchProbability getEdgeProbability(const MachineBasicBlock *Src,
+                                       const MachineBasicBlock *Dst) const;
+
+  // Same as above, but using a const_succ_iterator from Src. This is faster
+  // when the iterator is already available.
+  BranchProbability
+  getEdgeProbability(const MachineBasicBlock *Src,
+                     MachineBasicBlock::const_succ_iterator Dst) const;
 
   // A 'Hot' edge is an edge which probability is >= 80%.
   bool isEdgeHot(const MachineBasicBlock *Src,
@@ -68,15 +73,6 @@
   // NB: This routine's complexity is linear on the number of successors.
   MachineBasicBlock *getHotSucc(MachineBasicBlock *MBB) const;
 
-  // Return a probability as a fraction between 0 (0% probability) and
-  // 1 (100% probability), however the value is never equal to 0, and can be 1
-  // only iff SRC block has only one successor.
-  // NB: This routine's complexity is linear on the number of successors of
-  // Src. Querying sequentially for each successor's probability is a quadratic
-  // query pattern.
-  BranchProbability getEdgeProbability(const MachineBasicBlock *Src,
-                                       const MachineBasicBlock *Dst) const;
-
   // Print value between 0 (0% probability) and 1 (100% probability),
   // however the value is never equal to 0, and can be 1 only iff SRC block
   // has only one successor.
Index: include/llvm/Support/BranchProbability.h
===================================================================
--- include/llvm/Support/BranchProbability.h
+++ include/llvm/Support/BranchProbability.h
@@ -53,6 +53,9 @@
   // Create a BranchProbability object with the given numerator and 1<<31
   // as denominator.
   static BranchProbability getRaw(uint32_t N) { return BranchProbability(N); }
+  // Create a BranchProbability object from 64-bit integers.
+  static BranchProbability getBranchProbability(uint64_t Numerator,
+                                                uint64_t Denominator);
 
   // Normalize given probabilties so that the sum of them becomes approximate
   // one.
@@ -131,10 +134,30 @@
 
   bool operator==(BranchProbability RHS) const { return N == RHS.N; }
   bool operator!=(BranchProbability RHS) const { return !(*this == RHS); }
-  bool operator<(BranchProbability RHS) const { return N < RHS.N; }
-  bool operator>(BranchProbability RHS) const { return RHS < *this; }
-  bool operator<=(BranchProbability RHS) const { return !(RHS < *this); }
-  bool operator>=(BranchProbability RHS) const { return !(*this < RHS); }
+
+  bool operator<(BranchProbability RHS) const {
+    assert(N != UnknownN && RHS.N != UnknownN &&
+           "Unknown probability cannot participate in comparisons.");
+    return N < RHS.N;
+  }
+
+  bool operator>(BranchProbability RHS) const {
+    assert(N != UnknownN && RHS.N != UnknownN &&
+           "Unknown probability cannot participate in comparisons.");
+    return RHS < *this;
+  }
+
+  bool operator<=(BranchProbability RHS) const {
+    assert(N != UnknownN && RHS.N != UnknownN &&
+           "Unknown probability cannot participate in comparisons.");
+    return !(RHS < *this);
+  }
+
+  bool operator>=(BranchProbability RHS) const {
+    assert(N != UnknownN && RHS.N != UnknownN &&
+           "Unknown probability cannot participate in comparisons.");
+    return !(*this < RHS);
+  }
 };
 
 inline raw_ostream &operator<<(raw_ostream &OS, BranchProbability Prob) {
Index: lib/Analysis/BranchProbabilityInfo.cpp
===================================================================
--- lib/Analysis/BranchProbabilityInfo.cpp
+++ lib/Analysis/BranchProbabilityInfo.cpp
@@ -647,6 +647,12 @@
   return BranchProbability(N, D);
 }
 
+BranchProbability
+BranchProbabilityInfo::getEdgeProbability(const BasicBlock *Src,
+                                          succ_const_iterator Dst) const {
+  return getEdgeProbability(Src, Dst.getSuccessorIndex());
+}
+
 raw_ostream &
 BranchProbabilityInfo::printEdgeProbability(raw_ostream &OS,
                                             const BasicBlock *Src,
Index: lib/CodeGen/BranchFolding.cpp
===================================================================
--- lib/CodeGen/BranchFolding.cpp
+++ lib/CodeGen/BranchFolding.cpp
@@ -1099,13 +1099,16 @@
   if (TailMBB.succ_size() <= 1)
     return;
 
-  auto MaxEdgeFreq = *std::max_element(EdgeFreqLs.begin(), EdgeFreqLs.end());
-  uint64_t Scale = MaxEdgeFreq.getFrequency() / UINT32_MAX + 1;
+  auto SumEdgeFreq =
+      std::accumulate(EdgeFreqLs.begin(), EdgeFreqLs.end(), BlockFrequency(0))
+          .getFrequency();
   auto EdgeFreq = EdgeFreqLs.begin();
 
   for (auto SuccI = TailMBB.succ_begin(), SuccE = TailMBB.succ_end();
        SuccI != SuccE; ++SuccI, ++EdgeFreq)
-    TailMBB.setSuccWeight(SuccI, EdgeFreq->getFrequency() / Scale);
+    TailMBB.setSuccProbability(
+        SuccI, BranchProbability::getBranchProbability(EdgeFreq->getFrequency(),
+                                                       SumEdgeFreq));
 }
 
 //===----------------------------------------------------------------------===//
Index: lib/CodeGen/IfConversion.cpp
===================================================================
--- lib/CodeGen/IfConversion.cpp
+++ lib/CodeGen/IfConversion.cpp
@@ -32,6 +32,7 @@
 #include "llvm/Target/TargetLowering.h"
 #include "llvm/Target/TargetRegisterInfo.h"
 #include "llvm/Target/TargetSubtargetInfo.h"
+#include <algorithm>
 
 using namespace llvm;
 
@@ -1151,28 +1152,6 @@
   return true;
 }
 
-/// Scale down weights to fit into uint32_t. NewTrue is the new weight
-/// for successor TrueBB, and NewFalse is the new weight for successor
-/// FalseBB.
-static void ScaleWeights(uint64_t NewTrue, uint64_t NewFalse,
-                         MachineBasicBlock *MBB,
-                         const MachineBasicBlock *TrueBB,
-                         const MachineBasicBlock *FalseBB,
-                         const MachineBranchProbabilityInfo *MBPI) {
-  uint64_t NewMax = (NewTrue > NewFalse) ? NewTrue : NewFalse;
-  uint32_t Scale = (NewMax / UINT32_MAX) + 1;
-  for (MachineBasicBlock::succ_iterator SI = MBB->succ_begin(),
-                                        SE = MBB->succ_end();
-       SI != SE; ++SI) {
-    if (*SI == TrueBB)
-      MBB->setSuccWeight(SI, (uint32_t)(NewTrue / Scale));
-    else if (*SI == FalseBB)
-      MBB->setSuccWeight(SI, (uint32_t)(NewFalse / Scale));
-    else
-      MBB->setSuccWeight(SI, MBPI->getEdgeWeight(MBB, SI) / Scale);
-  }
-}
-
 /// IfConvertTriangle - If convert a triangle sub-CFG.
 ///
 bool IfConverter::IfConvertTriangle(BBInfo &BBI, IfcvtKind Kind) {
@@ -1229,16 +1208,14 @@
   DontKill.clear();
 
   bool HasEarlyExit = CvtBBI->FalseBB != nullptr;
-  uint64_t CvtNext = 0, CvtFalse = 0, BBNext = 0, BBCvt = 0, SumWeight = 0;
-  uint32_t WeightScale = 0;
+  BranchProbability CvtNext, CvtFalse, BBNext, BBCvt;
 
   if (HasEarlyExit) {
-    // Get weights before modifying CvtBBI->BB and BBI.BB.
-    CvtNext = MBPI->getEdgeWeight(CvtBBI->BB, NextBBI->BB);
-    CvtFalse = MBPI->getEdgeWeight(CvtBBI->BB, CvtBBI->FalseBB);
-    BBNext = MBPI->getEdgeWeight(BBI.BB, NextBBI->BB);
-    BBCvt = MBPI->getEdgeWeight(BBI.BB, CvtBBI->BB);
-    SumWeight = MBPI->getSumForBlock(CvtBBI->BB, WeightScale);
+    // Get probabilities before modifying CvtBBI->BB and BBI.BB.
+    CvtNext = MBPI->getEdgeProbability(CvtBBI->BB, NextBBI->BB);
+    CvtFalse = MBPI->getEdgeProbability(CvtBBI->BB, CvtBBI->FalseBB);
+    BBNext = MBPI->getEdgeProbability(BBI.BB, NextBBI->BB);
+    BBCvt = MBPI->getEdgeProbability(BBI.BB, CvtBBI->BB);
   }
 
   if (CvtBBI->BB->pred_size() > 1) {
@@ -1266,22 +1243,24 @@
                                            CvtBBI->BrCond.end());
     if (TII->ReverseBranchCondition(RevCond))
       llvm_unreachable("Unable to reverse branch condition!");
+
+    // Update the edge probability for both CvtBBI->FalseBB and NextBBI.
+    // NewNext = New_Prob(BBI.BB, NextBBI->BB) =
+    //   Prob(BBI.BB, NextBBI->BB) +
+    //   Prob(BBI.BB, CvtBBI->BB) * Prob(CvtBBI->BB, NextBBI->BB)
+    // NewFalse = New_Prob(BBI.BB, CvtBBI->FalseBB) =
+    //   Prob(BBI.BB, CvtBBI->BB) * Prob(CvtBBI->BB, CvtBBI->FalseBB)
+    auto NewTrueBB = getNextBlock(BBI.BB);
+    auto NewNext = BBNext + BBCvt * CvtNext;
+    auto NewTrueBBIter =
+        std::find(BBI.BB->succ_begin(), BBI.BB->succ_end(), NewTrueBB);
+    assert(NewTrueBBIter != BBI.BB->succ_end() &&
+           "NewTrueBB is not a successor of BBI.BB.");
+    BBI.BB->setSuccProbability(NewTrueBBIter, NewNext);
+
+    auto NewFalse = BBCvt * CvtFalse;
     TII->InsertBranch(*BBI.BB, CvtBBI->FalseBB, nullptr, RevCond, dl);
-    BBI.BB->addSuccessor(CvtBBI->FalseBB);
-    // Update the edge weight for both CvtBBI->FalseBB and NextBBI.
-    // New_Weight(BBI.BB, NextBBI->BB) =
-    //   Weight(BBI.BB, NextBBI->BB) * getSumForBlock(CvtBBI->BB) +
-    //   Weight(BBI.BB, CvtBBI->BB) * Weight(CvtBBI->BB, NextBBI->BB)
-    // New_Weight(BBI.BB, CvtBBI->FalseBB) =
-    //   Weight(BBI.BB, CvtBBI->BB) * Weight(CvtBBI->BB, CvtBBI->FalseBB)
-
-    uint64_t NewNext = BBNext * SumWeight + (BBCvt * CvtNext) / WeightScale;
-    uint64_t NewFalse = (BBCvt * CvtFalse) / WeightScale;
-    // We need to scale down all weights of BBI.BB to fit uint32_t.
-    // Here BBI.BB is connected to CvtBBI->FalseBB and will fall through to
-    // the next block.
-    ScaleWeights(NewNext, NewFalse, BBI.BB, getNextBlock(BBI.BB),
-                 CvtBBI->FalseBB, MBPI);
+    BBI.BB->addSuccessor(CvtBBI->FalseBB, NewFalse);
   }
 
   // Merge in the 'false' block if the 'false' block has no other
@@ -1524,7 +1503,7 @@
       MergeBlocks(BBI, TailBBI);
       TailBBI.IsDone = true;
     } else {
-      BBI.BB->addSuccessor(TailBB);
+      BBI.BB->addSuccessor(TailBB, BranchProbability::getOne());
       InsertUncondBranch(BBI.BB, TailBB, TII);
       BBI.HasFallThrough = false;
     }
@@ -1688,21 +1667,26 @@
                                                 FromBBI.BB->succ_end());
   MachineBasicBlock *NBB = getNextBlock(FromBBI.BB);
   MachineBasicBlock *FallThrough = FromBBI.HasFallThrough ? NBB : nullptr;
-
-  // The edge weight from ToBBI.BB to FromBBI.BB, which is only needed when
+  // The edge probability from ToBBI.BB to FromBBI.BB, which is only needed when
   // AddEdges is true and FromBBI.BB is a successor of ToBBI.BB.
-  uint32_t To2FromWeight = 0;
-  // WeightScale and SumWeight are for calculating successor probabilities of
-  // FromBBI.BB.
-  uint32_t WeightScale = 0;
-  uint32_t SumWeight = 0;
+  auto To2FromProb = BranchProbability::getZero();
   if (AddEdges && ToBBI.BB->isSuccessor(FromBBI.BB)) {
-    To2FromWeight = MBPI->getEdgeWeight(ToBBI.BB, FromBBI.BB);
-    // Set the edge weight from ToBBI.BB to FromBBI.BB to zero to avoid the edge
-    // weight being merged to other edges when this edge is removed later.
-    ToBBI.BB->setSuccWeight(
-        std::find(ToBBI.BB->succ_begin(), ToBBI.BB->succ_end(), FromBBI.BB), 0);
-    SumWeight = MBPI->getSumForBlock(FromBBI.BB, WeightScale);
+    To2FromProb = MBPI->getEdgeProbability(ToBBI.BB, FromBBI.BB);
+    // Set the edge probability from ToBBI.BB to FromBBI.BB to zero to avoid the
+    // edge probability being merged to other edges when this edge is removed
+    // later.
+    ToBBI.BB->setSuccProbability(
+        std::find(ToBBI.BB->succ_begin(), ToBBI.BB->succ_end(), FromBBI.BB),
+        BranchProbability::getZero());
+  }
+
+  if (AddEdges && ToBBI.BB->isSuccessor(FromBBI.BB)) {
+    // Set the edge probability from ToBBI.BB to FromBBI.BB to zero to avoid the
+    // edge probability being merged to other edges when this edge is removed
+    // later.
+    ToBBI.BB->setSuccProbability(
+        std::find(ToBBI.BB->succ_begin(), ToBBI.BB->succ_end(), FromBBI.BB),
+        BranchProbability::getZero());
   }
 
   for (unsigned i = 0, e = FromSuccs.size(); i != e; ++i) {
@@ -1711,39 +1695,38 @@
     if (Succ == FallThrough)
       continue;
 
-    uint32_t NewWeight = 0;
+    auto NewProb = BranchProbability::getZero();
     if (AddEdges) {
-      // Calculate the edge weight for the edge from ToBBI.BB to Succ, which is
-      // a portion of the edge weight from FromBBI.BB to Succ. The portion ratio
-      // is the edge probability from ToBBI.BB to FromBBI.BB (if FromBBI is a
-      // successor of ToBBI.BB. See comment below for excepion).
-      NewWeight = MBPI->getEdgeWeight(FromBBI.BB, Succ);
+      // Calculate the edge probability for the edge from ToBBI.BB to Succ,
+      // which is a portion of the edge probability from FromBBI.BB to Succ. The
+      // portion ratio is the edge probability from ToBBI.BB to FromBBI.BB (if
+      // FromBBI is a successor of ToBBI.BB. See comment below for excepion).
+      NewProb = MBPI->getEdgeProbability(FromBBI.BB, Succ);
 
-      // To2FromWeight is 0 when FromBBI.BB is not a successor of ToBBI.BB. This
+      // To2FromProb is 0 when FromBBI.BB is not a successor of ToBBI.BB. This
       // only happens when if-converting a diamond CFG and FromBBI.BB is the
       // tail BB.  In this case FromBBI.BB post-dominates ToBBI.BB and hence we
-      // could just use the weights on FromBBI.BB's out-edges when adding new
-      // successors.
-      if (To2FromWeight > 0) {
-        BranchProbability Prob(NewWeight / WeightScale, SumWeight);
-        NewWeight = Prob.scale(To2FromWeight);
-      }
+      // could just use the probabilities on FromBBI.BB's out-edges when adding
+      // new successors.
+      if (!To2FromProb.isZero())
+        NewProb *= To2FromProb;
     }
 
     FromBBI.BB->removeSuccessor(Succ);
 
     if (AddEdges) {
-      // If the edge from ToBBI.BB to Succ already exists, update the weight of
-      // this edge by adding NewWeight to it. An example is shown below, in
-      // which A is ToBBI.BB and B is FromBBI.BB. In this case we don't have to
-      // set C as A's successor as it already is. We only need to update the
-      // edge weight on A->C. Note that B will not be immediately removed from
-      // A's successors. It is possible that B->D is not removed either if D is
-      // a fallthrough of B. Later the edge A->D (generated here) and B->D will
-      // be combined into one edge. To maintain correct edge weight of this
-      // combined edge, we need to set the edge weight of A->B to zero, which is
-      // already done above. The edge weight on A->D is calculated by scaling
-      // the original weight on A->B by the probability of B->D.
+      // If the edge from ToBBI.BB to Succ already exists, update the
+      // probability of this edge by adding NewWeight to it. An example is shown
+      // below, in which A is ToBBI.BB and B is FromBBI.BB. In this case we
+      // don't have to set C as A's successor as it already is. We only need to
+      // update the edge probability on A->C. Note that B will not be
+      // immediately removed from A's successors. It is possible that B->D is
+      // not removed either if D is a fallthrough of B. Later the edge A->D
+      // (generated here) and B->D will be combined into one edge. To maintain
+      // correct edge probability of this combined edge, we need to set the edge
+      // probability of A->B to zero, which is already done above. The edge
+      // probability on A->D is calculated by scaling the original probability
+      // on A->B by the probability of B->D.
       //
       // Before ifcvt:      After ifcvt (assume B->D is kept):
       //
@@ -1755,11 +1738,11 @@
       //    C  D             C  D
       //
       if (ToBBI.BB->isSuccessor(Succ))
-        ToBBI.BB->setSuccWeight(
+        ToBBI.BB->setSuccProbability(
             std::find(ToBBI.BB->succ_begin(), ToBBI.BB->succ_end(), Succ),
-            MBPI->getEdgeWeight(ToBBI.BB, Succ) + NewWeight);
+            MBPI->getEdgeProbability(ToBBI.BB, Succ) + NewProb);
       else
-        ToBBI.BB->addSuccessor(Succ, NewWeight);
+        ToBBI.BB->addSuccessor(Succ, NewProb);
     }
   }
 
Index: lib/CodeGen/MIRParser/MIParser.cpp
===================================================================
--- lib/CodeGen/MIRParser/MIParser.cpp
+++ lib/CodeGen/MIRParser/MIParser.cpp
@@ -459,8 +459,9 @@
       if (expectAndConsume(MIToken::rparen))
         return true;
     }
-    MBB.addSuccessor(SuccMBB, Weight);
+    MBB.addSuccessor(SuccMBB, BranchProbability::getRaw(Weight));
   } while (consumeIfPresent(MIToken::comma));
+  MBB.normalizeSuccProbs();
   return false;
 }
 
Index: lib/CodeGen/MIRPrinter.cpp
===================================================================
--- lib/CodeGen/MIRPrinter.cpp
+++ lib/CodeGen/MIRPrinter.cpp
@@ -461,8 +461,8 @@
       if (I != MBB.succ_begin())
         OS << ", ";
       printMBBReference(**I);
-      if (MBB.hasSuccessorWeights())
-        OS << '(' << MBB.getSuccWeight(I) << ')';
+      if (MBB.hasSuccessorProbabilities())
+        OS << '(' << MBB.getSuccProbability(I) << ')';
     }
     OS << "\n";
     HasLineAttributes = true;
Index: lib/CodeGen/MachineBasicBlock.cpp
===================================================================
--- lib/CodeGen/MachineBasicBlock.cpp
+++ lib/CodeGen/MachineBasicBlock.cpp
@@ -319,8 +319,8 @@
     OS << "    Successors according to CFG:";
     for (const_succ_iterator SI = succ_begin(), E = succ_end(); SI != E; ++SI) {
       OS << " BB#" << (*SI)->getNumber();
-      if (!Weights.empty())
-        OS << '(' << *getWeightIterator(SI) << ')';
+      if (!Probs.empty())
+        OS << '(' << *getProbabilityIterator(SI) << ')';
     }
     OS << '\n';
   }
@@ -506,34 +506,16 @@
   }
 }
 
-void MachineBasicBlock::addSuccessor(MachineBasicBlock *Succ, uint32_t Weight) {
-  // Weight list is either empty (if successor list isn't empty, this means
-  // disabled optimization) or has the same size as successor list.
-  if (!(Weights.empty() && !Successors.empty()))
-    Weights.push_back(Weight);
-  Successors.push_back(Succ);
-  Succ->addPredecessor(this);
-}
-
-void MachineBasicBlock::addSuccessorWithoutWeight(MachineBasicBlock *Succ) {
-  // We need to make sure weight list is either empty or has the same size of
-  // successor list. When this function is called, we can safely delete all
-  // weight in the list.
-  Weights.clear();
-  Successors.push_back(Succ);
-  Succ->addPredecessor(this);
-}
-
 void MachineBasicBlock::addSuccessor(MachineBasicBlock *Succ,
                                      BranchProbability Prob) {
   // Probability list is either empty (if successor list isn't empty, this means
   // disabled optimization) or has the same size as successor list.
   if (!(Probs.empty() && !Successors.empty())) {
+    assert((Probs.empty() || (Prob.isUnknown() && Probs.back().isUnknown()) ||
+            (!Prob.isUnknown() && !Probs.back().isUnknown())) &&
+           "Successors with both known and unknwon probabilities are not "
+           "allowed.");
     Probs.push_back(Prob);
-    // FIXME: Temporarily use the numerator of the probability to represent edge
-    // weight. This will be removed once all weight-version interfaces in MBB
-    // are replaced with probability-version interfaces.
-    Weights.push_back(Prob.getNumerator());
   }
   Successors.push_back(Succ);
   Succ->addPredecessor(this);
@@ -544,7 +526,6 @@
   // of successor list. When this function is called, we can safely delete all
   // probability in the list.
   Probs.clear();
-  Weights.clear();
   Successors.push_back(Succ);
   Succ->addPredecessor(this);
 }
@@ -558,23 +539,12 @@
 MachineBasicBlock::removeSuccessor(succ_iterator I) {
   assert(I != Successors.end() && "Not a current successor!");
 
-  // If Weight list is empty it means we don't use it (disabled optimization).
-  if (!Weights.empty()) {
-    weight_iterator WI = getWeightIterator(I);
-    Weights.erase(WI);
-  }
-
-  // FIXME: Temporarily comment the following code as probabilities are now only
-  // used during instruction lowering, but this interface is called in later
-  // passes. Uncomment it once all edge weights are replaced with probabilities.
-#if 0
   // If probability list is empty it means we don't use it (disabled
   // optimization).
   if (!Probs.empty()) {
     probability_iterator WI = getProbabilityIterator(I);
     Probs.erase(WI);
   }
-#endif
 
   (*I)->removePredecessor(this);
   return Successors.erase(I);
@@ -611,17 +581,12 @@
   }
 
   // New is already a successor.
-  // Update its weight instead of adding a duplicate edge.
-  if (!Weights.empty())
-    *getWeightIterator(NewI) += *getWeightIterator(OldI);
-  // FIXME: Temporarily comment the following code as probabilities are now only
-  // used during instruction lowering, but this interface is called in later
-  // passes. Uncomment it once all edge weights are replaced with probabilities.
-#if 0
   // Update its probability instead of adding a duplicate edge.
-  if (!Probs.empty())
-    *getProbabilityIterator(NewI) += *getProbabilityIterator(OldI);
-#endif
+  if (!Probs.empty()) {
+    auto ProbIter = getProbabilityIterator(NewI);
+    if (!ProbIter->isUnknown())
+      *ProbIter += *getProbabilityIterator(OldI);
+  }
   removeSuccessor(OldI);
 }
 
@@ -641,13 +606,14 @@
 
   while (!FromMBB->succ_empty()) {
     MachineBasicBlock *Succ = *FromMBB->succ_begin();
-    uint32_t Weight = 0;
 
-    // If Weight list is empty it means we don't use it (disabled optimization).
-    if (!FromMBB->Weights.empty())
-      Weight = *FromMBB->Weights.begin();
+    // If probability list is empty it means we don't use it (disabled optimization).
+    if (!FromMBB->Probs.empty()) {
+      auto Prob = *FromMBB->Probs.begin();
+      addSuccessor(Succ, Prob);
+    } else
+      addSuccessorWithoutProb(Succ);
 
-    addSuccessor(Succ, Weight);
     FromMBB->removeSuccessor(Succ);
   }
 }
@@ -659,10 +625,11 @@
 
   while (!FromMBB->succ_empty()) {
     MachineBasicBlock *Succ = *FromMBB->succ_begin();
-    uint32_t Weight = 0;
-    if (!FromMBB->Weights.empty())
-      Weight = *FromMBB->Weights.begin();
-    addSuccessor(Succ, Weight);
+    if (!FromMBB->Probs.empty()) {
+      auto Prob = *FromMBB->Probs.begin();
+      addSuccessor(Succ, Prob);
+    } else
+      addSuccessorWithoutProb(Succ);
     FromMBB->removeSuccessor(Succ);
 
     // Fix up any PHI nodes in the successor.
@@ -1146,80 +1113,37 @@
   return DL;
 }
 
-/// Return weight of the edge from this block to MBB.
-uint32_t MachineBasicBlock::getSuccWeight(const_succ_iterator Succ) const {
-  if (Weights.empty())
-    return 0;
-
-  return *getWeightIterator(Succ);
-}
-
-/// Return probability of the edge from this block to MBB. If probability list
-/// is empty, return a default probability which is 1/N, where N is the number
-/// of successors. If the probability of the given successor is unknown, then
-/// sum up all known probabilities and return the complement of the sum divided
-/// by the number of unknown probabilities.
+/// Return probability of the edge from this block to MBB.
 BranchProbability
 MachineBasicBlock::getSuccProbability(const_succ_iterator Succ) const {
-  if (Probs.empty())
+  if (Probs.empty() || Probs.back().isUnknown())
     return BranchProbability(1, succ_size());
 
-  auto Prob = *getProbabilityIterator(Succ);
-  assert(!Prob.isUnknown());
-  return Prob;
-}
-
-/// Set successor weight of a given iterator.
-void MachineBasicBlock::setSuccWeight(succ_iterator I, uint32_t Weight) {
-  if (Weights.empty())
-    return;
-  *getWeightIterator(I) = Weight;
+  return *getProbabilityIterator(Succ);
 }
 
 /// Set successor probability of a given iterator.
 void MachineBasicBlock::setSuccProbability(succ_iterator I,
                                            BranchProbability Prob) {
   assert(!Prob.isUnknown());
-  if (Probs.empty() || Weights.empty())
+  if (Probs.empty())
     return;
   *getProbabilityIterator(I) = Prob;
-  // FIXME: Temporarily use the numerator of the probability to represent edge
-  // weight. This will be removed once all weight-version interfaces in MBB
-  // are replaces with probability-version interfaces.
-  *getWeightIterator(I) = Prob.getNumerator();
-}
-
-/// Return wight iterator corresonding to the I successor iterator.
-MachineBasicBlock::weight_iterator MachineBasicBlock::
-getWeightIterator(MachineBasicBlock::succ_iterator I) {
-  assert(Weights.size() == Successors.size() && "Async weight list!");
-  size_t index = std::distance(Successors.begin(), I);
-  assert(index < Weights.size() && "Not a current successor!");
-  return Weights.begin() + index;
 }
 
-/// Return wight iterator corresonding to the I successor iterator.
-MachineBasicBlock::const_weight_iterator MachineBasicBlock::
-getWeightIterator(MachineBasicBlock::const_succ_iterator I) const {
-  assert(Weights.size() == Successors.size() && "Async weight list!");
-  const size_t index = std::distance(Successors.begin(), I);
-  assert(index < Weights.size() && "Not a current successor!");
-  return Weights.begin() + index;
-}
-
-/// Return probability iterator corresonding to the I successor iterator.
-MachineBasicBlock::probability_iterator
-MachineBasicBlock::getProbabilityIterator(MachineBasicBlock::succ_iterator I) {
+/// Return probability iterator corresonding to the I successor iterator
+MachineBasicBlock::const_probability_iterator
+MachineBasicBlock::getProbabilityIterator(
+    MachineBasicBlock::const_succ_iterator I) const {
   assert(Probs.size() == Successors.size() && "Async probability list!");
   const size_t index = std::distance(Successors.begin(), I);
   assert(index < Probs.size() && "Not a current successor!");
   return Probs.begin() + index;
 }
 
-/// Return probability iterator corresonding to the I successor iterator
-MachineBasicBlock::const_probability_iterator
-MachineBasicBlock::getProbabilityIterator(
-    MachineBasicBlock::const_succ_iterator I) const {
+/// Return probability iterator corresonding to the I successor iterator.
+MachineBasicBlock::probability_iterator
+MachineBasicBlock::getProbabilityIterator(MachineBasicBlock::succ_iterator I) {
   assert(Probs.size() == Successors.size() && "Async probability list!");
   const size_t index = std::distance(Successors.begin(), I);
   assert(index < Probs.size() && "Not a current successor!");
Index: lib/CodeGen/MachineBlockPlacement.cpp
===================================================================
--- lib/CodeGen/MachineBlockPlacement.cpp
+++ lib/CodeGen/MachineBlockPlacement.cpp
@@ -380,19 +380,11 @@
   const BranchProbability HotProb(4, 5); // 80%
 
   MachineBasicBlock *BestSucc = nullptr;
-  // FIXME: Due to the performance of the probability and weight routines in
-  // the MBPI analysis, we manually compute probabilities using the edge
-  // weights. This is suboptimal as it means that the somewhat subtle
-  // definition of edge weight semantics is encoded here as well. We should
-  // improve the MBPI interface to efficiently support query patterns such as
-  // this.
-  uint32_t BestWeight = 0;
-  uint32_t WeightScale = 0;
-  uint32_t SumWeight = MBPI->getSumForBlock(BB, WeightScale);
-
-  // Adjust sum of weights by excluding weights on edges pointing to blocks that
-  // is either not in BlockFilter or is already in the current chain. Consider
-  // the following CFG:
+  auto BestProb = BranchProbability::getZero();
+
+  // Adjust edge probabilities by excluding edges pointing to blocks that is
+  // either not in BlockFilter or is already in the current chain. Consider the
+  // following CFG:
   //
   //     --->A
   //     |  / \
@@ -406,7 +398,7 @@
   // HotProb). If we exclude E that is not in BlockFilter when calculating the
   // probability of C->D, D will be selected and we will get A C D B as the
   // layout of this loop.
-  uint32_t AdjustedSumWeight = SumWeight;
+  auto AdjustedSumProb = BranchProbability::getOne();
   SmallVector<MachineBasicBlock *, 4> Successors;
   for (MachineBasicBlock *Succ : BB->successors()) {
     bool SkipSucc = false;
@@ -424,15 +416,16 @@
       }
     }
     if (SkipSucc)
-      AdjustedSumWeight -= MBPI->getEdgeWeight(BB, Succ) / WeightScale;
+      AdjustedSumProb -= MBPI->getEdgeProbability(BB, Succ);
     else
       Successors.push_back(Succ);
   }
 
   DEBUG(dbgs() << "Attempting merge from: " << getBlockName(BB) << "\n");
   for (MachineBasicBlock *Succ : Successors) {
-    uint32_t SuccWeight = MBPI->getEdgeWeight(BB, Succ);
-    BranchProbability SuccProb(SuccWeight / WeightScale, AdjustedSumWeight);
+    BranchProbability SuccProb(
+        MBPI->getEdgeProbability(BB, Succ).getNumerator(),
+        AdjustedSumProb.getNumerator());
 
     // If we outline optional branches, look whether Succ is unavoidable, i.e.
     // dominates all terminators of the MachineFunction. If it does, other
@@ -470,7 +463,7 @@
 
       // Make sure that a hot successor doesn't have a globally more
       // important predecessor.
-      BranchProbability RealSuccProb(SuccWeight / WeightScale, SumWeight);
+      auto RealSuccProb = MBPI->getEdgeProbability(BB, Succ);
       BlockFrequency CandidateEdgeFreq =
           MBFI->getBlockFreq(BB) * RealSuccProb * HotProb.getCompl();
       bool BadCFGConflict = false;
@@ -496,10 +489,10 @@
                  << " (prob)"
                  << (SuccChain.LoopPredecessors != 0 ? " (CFG break)" : "")
                  << "\n");
-    if (BestSucc && BestWeight >= SuccWeight)
+    if (BestSucc && BestProb >= SuccProb)
       continue;
     BestSucc = Succ;
-    BestWeight = SuccWeight;
+    BestProb = SuccProb;
   }
   return BestSucc;
 }
@@ -728,11 +721,6 @@
     MachineBasicBlock *OldExitingBB = ExitingBB;
     BlockFrequency OldBestExitEdgeFreq = BestExitEdgeFreq;
     bool HasLoopingSucc = false;
-    // FIXME: Due to the performance of the probability and weight routines in
-    // the MBPI analysis, we use the internal weights and manually compute the
-    // probabilities to avoid quadratic behavior.
-    uint32_t WeightScale = 0;
-    uint32_t SumWeight = MBPI->getSumForBlock(MBB, WeightScale);
     for (MachineBasicBlock *Succ : MBB->successors()) {
       if (Succ->isEHPad())
         continue;
@@ -746,10 +734,10 @@
         continue;
       }
 
-      uint32_t SuccWeight = MBPI->getEdgeWeight(MBB, Succ);
+      auto SuccProb = MBPI->getEdgeProbability(MBB, Succ);
       if (LoopBlockSet.count(Succ)) {
         DEBUG(dbgs() << "    looping: " << getBlockName(MBB) << " -> "
-                     << getBlockName(Succ) << " (" << SuccWeight << ")\n");
+                     << getBlockName(Succ) << " (" << SuccProb << ")\n");
         HasLoopingSucc = true;
         continue;
       }
@@ -761,7 +749,6 @@
           BlocksExitingToOuterLoop.insert(MBB);
       }
 
-      BranchProbability SuccProb(SuccWeight / WeightScale, SumWeight);
       BlockFrequency ExitEdgeFreq = MBFI->getBlockFreq(MBB) * SuccProb;
       DEBUG(dbgs() << "    exiting: " << getBlockName(MBB) << " -> "
                    << getBlockName(Succ) << " [L:" << SuccLoopDepth << "] (";
@@ -904,21 +891,17 @@
   // edge from the tail of the loop chain.
   SmallVector<std::pair<MachineBasicBlock *, BlockFrequency>, 4> ExitsWithFreq;
   for (auto BB : LoopChain) {
-    uint32_t LargestExitEdgeWeight = 0;
+    auto LargestExitEdgeProb = BranchProbability::getZero();
     for (auto *Succ : BB->successors()) {
       BlockChain *SuccChain = BlockToChain[Succ];
       if (!LoopBlockSet.count(Succ) &&
           (!SuccChain || Succ == *SuccChain->begin())) {
-        uint32_t SuccWeight = MBPI->getEdgeWeight(BB, Succ);
-        LargestExitEdgeWeight = std::max(LargestExitEdgeWeight, SuccWeight);
+        auto SuccProb = MBPI->getEdgeProbability(BB, Succ);
+        LargestExitEdgeProb = std::max(LargestExitEdgeProb, SuccProb);
       }
     }
-    if (LargestExitEdgeWeight > 0) {
-      uint32_t WeightScale = 0;
-      uint32_t SumWeight = MBPI->getSumForBlock(BB, WeightScale);
-      auto ExitFreq =
-          MBFI->getBlockFreq(BB) *
-          BranchProbability(LargestExitEdgeWeight / WeightScale, SumWeight);
+    if (LargestExitEdgeProb > BranchProbability::getZero()) {
+      auto ExitFreq = MBFI->getBlockFreq(BB) * LargestExitEdgeProb;
       ExitsWithFreq.emplace_back(BB, ExitFreq);
     }
   }
@@ -1290,14 +1273,16 @@
       }
 
       // If PrevBB has a two-way branch, try to re-order the branches
-      // such that we branch to the successor with higher weight first.
+      // such that we branch to the successor with higher probability first.
       if (TBB && !Cond.empty() && FBB &&
-          MBPI->getEdgeWeight(PrevBB, FBB) > MBPI->getEdgeWeight(PrevBB, TBB) &&
+          MBPI->getEdgeProbability(PrevBB, FBB) >
+              MBPI->getEdgeProbability(PrevBB, TBB) &&
           !TII->ReverseBranchCondition(Cond)) {
         DEBUG(dbgs() << "Reverse order of the two branches: "
                      << getBlockName(PrevBB) << "\n");
-        DEBUG(dbgs() << "    Edge weight: " << MBPI->getEdgeWeight(PrevBB, FBB)
-                     << " vs " << MBPI->getEdgeWeight(PrevBB, TBB) << "\n");
+        DEBUG(dbgs() << "    Edge probability: "
+                     << MBPI->getEdgeProbability(PrevBB, FBB) << " vs "
+                     << MBPI->getEdgeProbability(PrevBB, TBB) << "\n");
         DebugLoc dl; // FIXME: this is nowhere
         TII->RemoveBranch(*PrevBB);
         TII->InsertBranch(*PrevBB, FBB, TBB, Cond, dl);
Index: lib/CodeGen/MachineBranchProbabilityInfo.cpp
===================================================================
--- lib/CodeGen/MachineBranchProbabilityInfo.cpp
+++ lib/CodeGen/MachineBranchProbabilityInfo.cpp
@@ -28,91 +28,61 @@
 
 void MachineBranchProbabilityInfo::anchor() { }
 
-uint32_t MachineBranchProbabilityInfo::
-getSumForBlock(const MachineBasicBlock *MBB, uint32_t &Scale) const {
-  // First we compute the sum with 64-bits of precision, ensuring that cannot
-  // overflow by bounding the number of weights considered. Hopefully no one
-  // actually needs 2^32 successors.
-  assert(MBB->succ_size() < UINT32_MAX);
-  uint64_t Sum = 0;
-  Scale = 1;
-  for (MachineBasicBlock::const_succ_iterator I = MBB->succ_begin(),
-       E = MBB->succ_end(); I != E; ++I) {
-    uint32_t Weight = getEdgeWeight(MBB, I);
-    Sum += Weight;
-  }
-
-  // If the computed sum fits in 32-bits, we're done.
-  if (Sum <= UINT32_MAX)
-    return Sum;
+uint32_t MachineBranchProbabilityInfo::getEdgeWeight(
+    const MachineBasicBlock *Src,
+    MachineBasicBlock::const_succ_iterator Dst) const {
+  return Src->getSuccProbability(Dst).getNumerator();
+}
 
-  // Otherwise, compute the scale necessary to cause the weights to fit, and
-  // re-sum with that scale applied.
-  assert((Sum / UINT32_MAX) < UINT32_MAX);
-  Scale = (Sum / UINT32_MAX) + 1;
-  Sum = 0;
-  for (MachineBasicBlock::const_succ_iterator I = MBB->succ_begin(),
-       E = MBB->succ_end(); I != E; ++I) {
-    uint32_t Weight = getEdgeWeight(MBB, I);
-    Sum += Weight / Scale;
-  }
-  assert(Sum <= UINT32_MAX);
-  return Sum;
+uint32_t MachineBranchProbabilityInfo::getEdgeWeight(
+    const MachineBasicBlock *Src, const MachineBasicBlock *Dst) const {
+  // This is a linear search. Try to use the const_succ_iterator version when
+  // possible.
+  return getEdgeWeight(Src, std::find(Src->succ_begin(), Src->succ_end(), Dst));
 }
 
-uint32_t MachineBranchProbabilityInfo::
-getEdgeWeight(const MachineBasicBlock *Src,
-              MachineBasicBlock::const_succ_iterator Dst) const {
-  uint32_t Weight = Src->getSuccWeight(Dst);
-  if (!Weight)
-    return DEFAULT_WEIGHT;
-  return Weight;
+BranchProbability MachineBranchProbabilityInfo::getEdgeProbability(
+    const MachineBasicBlock *Src,
+    MachineBasicBlock::const_succ_iterator Dst) const {
+  return Src->getSuccProbability(Dst);
 }
 
-uint32_t MachineBranchProbabilityInfo::
-getEdgeWeight(const MachineBasicBlock *Src,
-              const MachineBasicBlock *Dst) const {
+BranchProbability MachineBranchProbabilityInfo::getEdgeProbability(
+    const MachineBasicBlock *Src, const MachineBasicBlock *Dst) const {
   // This is a linear search. Try to use the const_succ_iterator version when
   // possible.
-  return getEdgeWeight(Src, std::find(Src->succ_begin(), Src->succ_end(), Dst));
+  return getEdgeProbability(Src,
+                            std::find(Src->succ_begin(), Src->succ_end(), Dst));
 }
 
 bool
 MachineBranchProbabilityInfo::isEdgeHot(const MachineBasicBlock *Src,
                                         const MachineBasicBlock *Dst) const {
   // Hot probability is at least 4/5 = 80%
-  // FIXME: Compare against a static "hot" BranchProbability.
-  return getEdgeProbability(Src, Dst) > BranchProbability(4, 5);
+  static BranchProbability HotProb(4, 5);
+  return getEdgeProbability(Src, Dst) > HotProb;
 }
 
 MachineBasicBlock *
 MachineBranchProbabilityInfo::getHotSucc(MachineBasicBlock *MBB) const {
-  uint32_t MaxWeight = 0;
+  auto MaxProb = BranchProbability::getZero();
   MachineBasicBlock *MaxSucc = nullptr;
   for (MachineBasicBlock::const_succ_iterator I = MBB->succ_begin(),
        E = MBB->succ_end(); I != E; ++I) {
-    uint32_t Weight = getEdgeWeight(MBB, I);
-    if (Weight > MaxWeight) {
-      MaxWeight = Weight;
+    auto Prob = getEdgeProbability(MBB, I);
+    if (Prob > MaxProb) {
+      MaxProb = Prob;
       MaxSucc = *I;
     }
   }
 
-  if (getEdgeProbability(MBB, MaxSucc) >= BranchProbability(4, 5))
+  static BranchProbability HotProb(4, 5);
+  if (getEdgeProbability(MBB, MaxSucc) >= HotProb)
     return MaxSucc;
 
   return nullptr;
 }
 
-BranchProbability MachineBranchProbabilityInfo::getEdgeProbability(
-    const MachineBasicBlock *Src, const MachineBasicBlock *Dst) const {
-  uint32_t Scale = 1;
-  uint32_t D = getSumForBlock(Src, Scale);
-  uint32_t N = getEdgeWeight(Src, Dst) / Scale;
-
-  return BranchProbability(N, D);
-}
-
 raw_ostream &MachineBranchProbabilityInfo::printEdgeProbability(
     raw_ostream &OS, const MachineBasicBlock *Src,
     const MachineBasicBlock *Dst) const {
Index: lib/CodeGen/TailDuplication.cpp
===================================================================
--- lib/CodeGen/TailDuplication.cpp
+++ lib/CodeGen/TailDuplication.cpp
@@ -745,12 +745,12 @@
     if (PredTBB)
       TII->InsertBranch(*PredBB, PredTBB, PredFBB, PredCond, DebugLoc());
 
-    uint32_t Weight = MBPI->getEdgeWeight(PredBB, TailBB);
+    auto Prob = MBPI->getEdgeProbability(PredBB, TailBB);
     PredBB->removeSuccessor(TailBB);
     unsigned NumSuccessors = PredBB->succ_size();
     assert(NumSuccessors <= 1);
     if (NumSuccessors == 0 || *PredBB->succ_begin() != NewTarget)
-      PredBB->addSuccessor(NewTarget, Weight);
+      PredBB->addSuccessor(NewTarget, Prob);
 
     TDBBs.push_back(PredBB);
   }
@@ -858,7 +858,7 @@
            "TailDuplicate called on block with multiple successors!");
     for (MachineBasicBlock::succ_iterator I = TailBB->succ_begin(),
            E = TailBB->succ_end(); I != E; ++I)
-      PredBB->addSuccessor(*I, MBPI->getEdgeWeight(TailBB, I));
+      PredBB->addSuccessor(*I, MBPI->getEdgeProbability(TailBB, I));
 
     Changed = true;
     ++NumTailDups;
Index: lib/Support/BranchProbability.cpp
===================================================================
--- lib/Support/BranchProbability.cpp
+++ lib/Support/BranchProbability.cpp
@@ -22,11 +22,14 @@
 const uint32_t BranchProbability::D;
 
 raw_ostream &BranchProbability::print(raw_ostream &OS) const {
+  if (isUnknown())
+    return OS << "?%";
+
   // Get a percentage rounded to two decimal digits. This avoids
   // implementation-defined rounding inside printf.
   double Percent = rint(((double)N / D) * 100.0 * 100.0) / 100.0;
-  OS << format("0x%08" PRIx32 " / 0x%08" PRIx32 " = %.2f%%", N, D, Percent);
-  return OS;
+  return OS << format("0x%08" PRIx32 " / 0x%08" PRIx32 " = %.2f%%", N, D,
+                      Percent);
 }
 
 void BranchProbability::dump() const { print(dbgs()) << '\n'; }
@@ -43,6 +46,19 @@
   }
 }
 
+BranchProbability
+BranchProbability::getBranchProbability64(uint64_t Numerator,
+                                          uint64_t Denominator) {
+  assert(Numerator <= Denominator && "Probability cannot be bigger than 1!");
+  // Scale down Denominator to fit in a 32-bit integer.
+  int Scale = 0;
+  while (Denominator > UINT32_MAX) {
+    Denominator >>= 1;
+    Scale++;
+  }
+  return BranchProbability(Numerator >> Scale, Denominator);
+}
+
 // If ConstD is not zero, then replace D by ConstD so that division and modulo
 // operations by D can be optimized, in case this function is not inlined by the
 // compiler.
Index: lib/Target/AMDGPU/AMDILCFGStructurizer.cpp
===================================================================
--- lib/Target/AMDGPU/AMDILCFGStructurizer.cpp
+++ lib/Target/AMDGPU/AMDILCFGStructurizer.cpp
@@ -1570,8 +1570,7 @@
 
   insertInstrBefore(DstBlk, AMDGPU::WHILELOOP, DebugLoc());
   insertInstrEnd(DstBlk, AMDGPU::ENDLOOP, DebugLoc());
-  DstBlk->addSuccessor(LandMBB);
-  DstBlk->removeSuccessor(DstBlk);
+  DstBlk->replaceSuccessor(DstBlk, LandMBB);
 }
 
 
@@ -1666,8 +1665,7 @@
   replaceInstrUseOfBlockWith(PredMBB, MBB, CloneMBB);
   //srcBlk, oldBlk, newBlk
 
-  PredMBB->removeSuccessor(MBB);
-  PredMBB->addSuccessor(CloneMBB);
+  PredMBB->replaceSuccessor(MBB, CloneMBB);
 
   // add all successor to cloneBlk
   cloneSuccessorList(CloneMBB, MBB);
Index: lib/Target/ARM/ARMConstantIslandPass.cpp
===================================================================
--- lib/Target/ARM/ARMConstantIslandPass.cpp
+++ lib/Target/ARM/ARMConstantIslandPass.cpp
@@ -2274,8 +2274,7 @@
 
   // Update the CFG.
   NewBB->addSuccessor(BB);
-  JTBB->removeSuccessor(BB);
-  JTBB->addSuccessor(NewBB);
+  JTBB->replaceSuccessor(BB, NewBB);
 
   ++NumJTInserted;
   return NewBB;
Index: lib/Target/ARM/ARMISelLowering.cpp
===================================================================
--- lib/Target/ARM/ARMISelLowering.cpp
+++ lib/Target/ARM/ARMISelLowering.cpp
@@ -7346,7 +7346,7 @@
       }
     }
 
-    BB->addSuccessor(DispatchBB);
+    BB->addSuccessor(DispatchBB, BranchProbability::getZero());
 
     // Find the invoke call and mark all of the callee-saved registers as
     // 'implicit defined' so that they're spilled. This prevents code from
Index: lib/Target/Hexagon/HexagonCFGOptimizer.cpp
===================================================================
--- lib/Target/Hexagon/HexagonCFGOptimizer.cpp
+++ lib/Target/Hexagon/HexagonCFGOptimizer.cpp
@@ -186,13 +186,11 @@
 
             if (case1 || case2) {
               InvertAndChangeJumpTarget(MI, UncondTarget);
-              MBB->removeSuccessor(JumpAroundTarget);
-              MBB->addSuccessor(UncondTarget);
+              MBB->replaceSuccessor(JumpAroundTarget, UncondTarget);
 
               // Remove the unconditional branch in LayoutSucc.
               LayoutSucc->erase(LayoutSucc->begin());
-              LayoutSucc->removeSuccessor(UncondTarget);
-              LayoutSucc->addSuccessor(JumpAroundTarget);
+              LayoutSucc->replaceSuccessor(UncondTarget, JumpAroundTarget);
 
               // This code performs the conversion for case 2, which moves
               // the block to the fall-thru case (BB3 in the code above).
Index: lib/Target/Mips/MipsLongBranch.cpp
===================================================================
--- lib/Target/Mips/MipsLongBranch.cpp
+++ lib/Target/Mips/MipsLongBranch.cpp
@@ -262,8 +262,7 @@
       static_cast<const MipsInstrInfo *>(Subtarget.getInstrInfo());
 
   MF->insert(FallThroughMBB, LongBrMBB);
-  MBB->removeSuccessor(TgtMBB);
-  MBB->addSuccessor(LongBrMBB);
+  MBB->replaceSuccessor(TgtMBB, LongBrMBB);
 
   if (IsPIC) {
     MachineBasicBlock *BalTgtMBB = MF->CreateMachineBasicBlock(BB);
Index: test/CodeGen/ARM/ifcvt-branch-weight-bug.ll
===================================================================
--- test/CodeGen/ARM/ifcvt-branch-weight-bug.ll
+++ test/CodeGen/ARM/ifcvt-branch-weight-bug.ll
@@ -14,15 +14,15 @@
   br i1 undef, label %for.end, label %for.body
 
 ; Before if conversion, we have
-; for.body -> lor.lhs.false.i (62)
-;          -> for.cond.backedge (62)
-; lor.lhs.false.i -> for.cond.backedge (1048575)
-;                 -> cond.false.i (1)
+; for.body -> lor.lhs.false.i (50%)
+;          -> for.cond.backedge (50%)
+; lor.lhs.false.i -> for.cond.backedge (100%)
+;                 -> cond.false.i (0%)
 ; Afer if conversion, we have
-; for.body -> for.cond.backedge (130023362)
-;          -> cond.false.i (62)
+; for.body -> for.cond.backedge (100%)
+;          -> cond.false.i (0%)
 ; CHECK: BB#1: derived from LLVM BB %for.body
-; CHECK: Successors according to CFG: BB#2(4294967291) BB#4(2048)
+; CHECK: Successors according to CFG: BB#2(0x7ffffc00 / 0x80000000 = 100.00%) BB#4(0x00000400 / 0x80000000 = 0.00%)
 for.body:
   br i1 undef, label %for.cond.backedge, label %lor.lhs.false.i, !prof !1
 
Index: test/CodeGen/ARM/ifcvt-branch-weight.ll
===================================================================
--- test/CodeGen/ARM/ifcvt-branch-weight.ll
+++ test/CodeGen/ARM/ifcvt-branch-weight.ll
@@ -19,7 +19,7 @@
   br i1 %9, label %return, label %bb2
 
 ; CHECK: BB#2: derived from LLVM BB %bb2
-; CHECK: Successors according to CFG: BB#3(4294967289) BB#4(4294967287)
+; CHECK: Successors according to CFG: BB#3({{[0-9a-fx/= ]+}}50.00%) BB#4({{[0-9a-fx/= ]+}}50.00%)
 
 bb2:
   %v10 = icmp eq i32 %3, 16
Index: test/CodeGen/ARM/ifcvt-iter-indbr.ll
===================================================================
--- test/CodeGen/ARM/ifcvt-iter-indbr.ll
+++ test/CodeGen/ARM/ifcvt-iter-indbr.ll
@@ -1,5 +1,5 @@
 ; RUN: llc < %s -mtriple thumbv7s-apple-darwin  -asm-verbose=false | FileCheck %s
-; RUN: llc < %s -mtriple thumbv7s-apple-darwin  -asm-verbose=false -print-machineinstrs=if-converter 2>&1 | FileCheck --check-prefix=CHECK-WEIGHT %s
+; RUN: llc < %s -mtriple thumbv7s-apple-darwin  -asm-verbose=false -print-machineinstrs=if-converter 2>&1 | FileCheck --check-prefix=CHECK-PROB %s
 
 declare i32 @foo(i32)
 declare i8* @bar(i32, i8*, i8*)
@@ -29,10 +29,10 @@
 ; CHECK-NEXT: [[FOOCALL]]:
 ; CHECK-NEXT:  blx _foo
 ;
-; CHECK-WEIGHT: BB#0:
-; CHECK-WEIGHT: Successors according to CFG: BB#1(1073741824) BB#2(536870912) BB#4(536870912)
-; CHECK-WEIGHT: BB#1:
-; CHECK-WEIGHT: Successors according to CFG: BB#2(1610612736) BB#4(536870912)
+; CHECK-PROB: BB#0:
+; CHECK-PROB: Successors according to CFG: BB#1({{[0-9a-fx/= ]+}}50.00%) BB#2({{[0-9a-fx/= ]+}}25.00%) BB#4({{[0-9a-fx/= ]+}}25.00%)
+; CHECK-PROB: BB#1:
+; CHECK-PROB: Successors according to CFG: BB#2({{[0-9a-fx/= ]+}}75.00%) BB#4({{[0-9a-fx/= ]+}}25.00%)
 
 define i32 @test(i32 %a, i32 %a2, i32* %p, i32* %p2) {
 entry:
Index: test/CodeGen/ARM/tail-merge-branch-weight.ll
===================================================================
--- test/CodeGen/ARM/tail-merge-branch-weight.ll
+++ test/CodeGen/ARM/tail-merge-branch-weight.ll
@@ -9,7 +9,7 @@
 ;                = 0.2 * 0.4 + 0.8 * 0.7 = 0.64
 
 ; CHECK: # Machine code for function test0:
-; CHECK: Successors according to CFG: BB#{{[0-9]+}}(13) BB#{{[0-9]+}}(24)
+; CHECK: Successors according to CFG: BB#{{[0-9]+}}({{[0-9a-fx/= ]+}}20.00%) BB#{{[0-9]+}}({{[0-9a-fx/= ]+}}80.00%)
 ; CHECK: BB#{{[0-9]+}}:
 ; CHECK: BB#{{[0-9]+}}:
 ; CHECK: # End machine code for function test0.
Index: test/CodeGen/ARM/taildup-branch-weight.ll
===================================================================
--- test/CodeGen/ARM/taildup-branch-weight.ll
+++ test/CodeGen/ARM/taildup-branch-weight.ll
@@ -3,7 +3,7 @@
 ; RUN:	| FileCheck %s
 
 ; CHECK: Machine code for function test0:
-; CHECK: Successors according to CFG: BB#1(67108864) BB#2(2080374784)
+; CHECK: Successors according to CFG: BB#1({{[0-9a-fx/= ]+}}3.12%) BB#2({{[0-9a-fx/= ]+}}96.88%)
 
 define void @test0(i32 %a, i32 %b, i32* %c, i32* %d) {
 entry:
@@ -30,7 +30,7 @@
 !0 = !{!"branch_weights", i32 4, i32 124}
 
 ; CHECK: Machine code for function test1:
-; CHECK: Successors according to CFG: BB#1(67108864) BB#2(2080374784)
+; CHECK: Successors according to CFG: BB#1({{[0-9a-fx/= ]+}}3.12%) BB#2({{[0-9a-fx/= ]+}}96.88%)
 
 @g0 = common global i32 0, align 4
 
Index: test/CodeGen/Generic/MachineBranchProb.ll
===================================================================
--- test/CodeGen/Generic/MachineBranchProb.ll
+++ test/CodeGen/Generic/MachineBranchProb.ll
@@ -16,11 +16,11 @@
     i64 5, label %sw.bb1
   ], !prof !0
 ; CHECK: BB#0: derived from LLVM BB %entry
-; CHECK: Successors according to CFG: BB#2(1616928864) BB#4(530554784)
+; CHECK: Successors according to CFG: BB#2({{[0-9a-fx/= ]+}}75.29%) BB#4({{[0-9a-fx/= ]+}}24.71%)
 ; CHECK: BB#4: derived from LLVM BB %entry
-; CHECK: Successors according to CFG: BB#1(252645135) BB#5(277909649)
+; CHECK: Successors according to CFG: BB#1({{[0-9a-fx/= ]+}}47.62%) BB#5({{[0-9a-fx/= ]+}}52.38%)
 ; CHECK: BB#5: derived from LLVM BB %entry
-; CHECK: Successors according to CFG: BB#1(101058054) BB#3(176851595)
+; CHECK: Successors according to CFG: BB#1({{[0-9a-fx/= ]+}}36.36%) BB#3({{[0-9a-fx/= ]+}}63.64%)
 
 sw.bb:
   br label %return
@@ -62,7 +62,7 @@
 ; CHECK-LABEL: Machine code for function left_leaning_weight_balanced_tree:
 ; CHECK: BB#0: derived from LLVM BB %entry
 ; CHECK-NOT: Successors
-; CHECK: Successors according to CFG: BB#8(852677332) BB#9(1294806318)
+; CHECK: Successors according to CFG: BB#8({{[0-9a-fx/= ]+}}39.71%) BB#9({{[0-9a-fx/= ]+}}60.29%)
 }
 
 !1 = !{!"branch_weights",
Index: test/CodeGen/Hexagon/ifcvt-edge-weight.ll
===================================================================
--- test/CodeGen/Hexagon/ifcvt-edge-weight.ll
+++ test/CodeGen/Hexagon/ifcvt-edge-weight.ll
@@ -2,7 +2,7 @@
 ; Check that the edge weights are updated correctly after if-conversion.
 
 ; CHECK: BB#3:
-; CHECK: Successors according to CFG: BB#2(214748365) BB#1(1932735283)
+; CHECK: Successors according to CFG: BB#2({{[0-9a-fx/= ]+}}10.00%) BB#1({{[0-9a-fx/= ]+}}90.00%)
 @a = external global i32
 @d = external global i32
 
Index: test/CodeGen/MIR/X86/newline-handling.mir
===================================================================
--- test/CodeGen/MIR/X86/newline-handling.mir
+++ test/CodeGen/MIR/X86/newline-handling.mir
@@ -35,7 +35,7 @@
 # CHECK-LABEL: name: foo
 # CHECK: body: |
 # CHECK-NEXT: bb.0.entry:
-# CHECK-NEXT: successors: %bb.1.less(0), %bb.2.exit(0)
+# CHECK-NEXT: successors: %bb.1.less(0x40000000 / 0x80000000 = 50.00%), %bb.2.exit(0x40000000 / 0x80000000 = 50.00%)
 # CHECK-NEXT: liveins: %edi
 # CHECK:      CMP32ri8 %edi, 10, implicit-def %eflags
 # CHECK-NEXT: JG_1 %bb.2.exit, implicit killed %eflags
@@ -79,7 +79,7 @@
 # CHECK-LABEL: name: bar
 # CHECK: body: |
 # CHECK-NEXT: bb.0.entry:
-# CHECK-NEXT: successors: %bb.1.less(0), %bb.2.exit(0)
+# CHECK-NEXT: successors: %bb.1.less(0x40000000 / 0x80000000 = 50.00%), %bb.2.exit(0x40000000 / 0x80000000 = 50.00%)
 # CHECK-NEXT: liveins: %edi
 # CHECK:      CMP32ri8 %edi, 10, implicit-def %eflags
 # CHECK-NEXT: JG_1 %bb.2.exit, implicit killed %eflags
Index: test/CodeGen/MIR/X86/successor-basic-blocks-weights.mir
===================================================================
--- test/CodeGen/MIR/X86/successor-basic-blocks-weights.mir
+++ test/CodeGen/MIR/X86/successor-basic-blocks-weights.mir
@@ -1,6 +1,6 @@
 # RUN: llc -march=x86-64 -start-after branch-folder -stop-after branch-folder -o /dev/null %s | FileCheck %s
 # This test ensures that the MIR parser parses basic block successors and
-# weights correctly.
+# probabilities correctly.
 
 --- |
 
@@ -21,10 +21,10 @@
 name:            foo
 body: |
   ; CHECK-LABEL: bb.0.entry:
-  ; CHECK:         successors: %bb.1.less(16), %bb.2.exit(32)
+  ; CHECK:         successors: %bb.1.less({{[0-9a-fx/= ]+}}33.00%), %bb.2.exit({{[0-9a-fx/= ]+}}67.00%)
   ; CHECK-LABEL: bb.1.less:
   bb.0.entry:
-    successors: %bb.1.less (16), %bb.2.exit(32)
+    successors: %bb.1.less (33), %bb.2.exit(67)
     liveins: %edi
 
     CMP32ri8 %edi, 10, implicit-def %eflags
Index: test/CodeGen/MIR/X86/successor-basic-blocks.mir
===================================================================
--- test/CodeGen/MIR/X86/successor-basic-blocks.mir
+++ test/CodeGen/MIR/X86/successor-basic-blocks.mir
@@ -32,7 +32,7 @@
 name:            foo
 body: |
   ; CHECK-LABEL: bb.0.entry:
-  ; CHECK:         successors: %bb.1.less(0), %bb.2.exit(0)
+  ; CHECK:         successors: %bb.1.less(0x40000000 / 0x80000000 = 50.00%), %bb.2.exit(0x40000000 / 0x80000000 = 50.00%)
   ; CHECK-LABEL: bb.1.less:
   bb.0.entry:
     successors: %bb.1.less, %bb.2.exit
@@ -58,7 +58,7 @@
   ; Verify that we can have multiple lists of successors that will be merged
   ; into one.
   ; CHECK-LABEL: bb.0.entry:
-  ; CHECK:         successors: %bb.1(0), %bb.2(0)
+  ; CHECK:         successors: %bb.1(0x80000000 / 0x80000000 = 100.00%), %bb.2(0x00000000 / 0x80000000 = 0.00%)
   bb.0.entry:
     liveins: %edi
     successors: %bb.1
Index: test/CodeGen/X86/MachineBranchProb.ll
===================================================================
--- test/CodeGen/X86/MachineBranchProb.ll
+++ test/CodeGen/X86/MachineBranchProb.ll
@@ -18,9 +18,9 @@
   %or.cond = or i1 %tobool, %cmp4
   br i1 %or.cond, label %for.inc20, label %for.inc, !prof !0
 ; CHECK: BB#1: derived from LLVM BB %for.cond2
-; CHECK: Successors according to CFG: BB#3(32756933) BB#4(2114726715)
+; CHECK: Successors according to CFG: BB#3({{[0-9a-fx/= ]+}}1.53%) BB#4({{[0-9a-fx/= ]+}}98.47%)
 ; CHECK: BB#4: derived from LLVM BB %for.cond2
-; CHECK: Successors according to CFG: BB#3(33264335) BB#2(2114219313)
+; CHECK: Successors according to CFG: BB#3({{[0-9a-fx/= ]+}}1.55%) BB#2({{[0-9a-fx/= ]+}}98.45%)
 
 for.inc:                                          ; preds = %for.cond2
   %shl = shl i32 %bit.0, 1
Index: test/CodeGen/X86/catchpad-weight.ll
===================================================================
--- test/CodeGen/X86/catchpad-weight.ll
+++ test/CodeGen/X86/catchpad-weight.ll
@@ -2,7 +2,7 @@
 
 ; Check if the edge weight to the catchpad is calculated correctly.
 
-; CHECK: Successors according to CFG: BB#3(2147481600) BB#1(2048) BB#4(1024) BB#6(512) BB#8(256)
+; CHECK: Successors according to CFG: BB#3(0x7ffff100 / 0x80000000 = 100.00%) BB#1(0x00000800 / 0x80000000 = 0.00%) BB#4(0x00000400 / 0x80000000 = 0.00%) BB#6(0x00000200 / 0x80000000 = 0.00%) BB#8(0x00000100 / 0x80000000 = 0.00%)
 
 target datalayout = "e-m:w-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64--windows-msvc18.0.0"
Index: test/CodeGen/X86/stack-protector-weight.ll
===================================================================
--- test/CodeGen/X86/stack-protector-weight.ll
+++ test/CodeGen/X86/stack-protector-weight.ll
@@ -2,13 +2,13 @@
 ; RUN: llc -mtriple=x86_64-apple-darwin -print-machineinstrs=expand-isel-pseudos -enable-selectiondag-sp=false %s -o /dev/null 2>&1 | FileCheck %s --check-prefix=IR
 
 ; SELDAG: # Machine code for function test_branch_weights:
-; SELDAG: Successors according to CFG: BB#[[SUCCESS:[0-9]+]](2147481600) BB#[[FAILURE:[0-9]+]](2048)
+; SELDAG: Successors according to CFG: BB#[[SUCCESS:[0-9]+]]({{[0-9a-fx/= ]+}}100.00%) BB#[[FAILURE:[0-9]+]]
 ; SELDAG: BB#[[FAILURE]]:
 ; SELDAG: CALL64pcrel32 <es:__stack_chk_fail>
 ; SELDAG: BB#[[SUCCESS]]:
 
 ; IR: # Machine code for function test_branch_weights:
-; IR: Successors according to CFG: BB#[[SUCCESS:[0-9]+]](2147481600) BB#[[FAILURE:[0-9]+]](2048)
+; IR: Successors according to CFG: BB#[[SUCCESS:[0-9]+]]({{[0-9a-fx/= ]+}}100.00%) BB#[[FAILURE:[0-9]+]]
 ; IR: BB#[[SUCCESS]]:
 ; IR: BB#[[FAILURE]]:
 ; IR: CALL64pcrel32 <ga:@__stack_chk_fail>
Index: test/CodeGen/X86/switch-edge-weight.ll
===================================================================
--- test/CodeGen/X86/switch-edge-weight.ll
+++ test/CodeGen/X86/switch-edge-weight.ll
@@ -34,22 +34,22 @@
 ; CHECK: BB#0:
 ; BB#0 to BB#4: [0, 1133] (65 = 60 + 5)
 ; BB#0 to BB#5: [1134, UINT32_MAX] (25 = 20 + 5)
-; CHECK: Successors according to CFG: BB#4(1550960411) BB#5(596523235)
+; CHECK: Successors according to CFG: BB#4({{[0-9a-fx/= ]+}}72.22%) BB#5({{[0-9a-fx/= ]+}}27.78%)
 ;
 ; CHECK: BB#4:
 ; BB#4 to BB#1: [155, 159] (50)
 ; BB#4 to BB#5: [0, 1133] - [155, 159] (15 = 10 + 5)
-; CHECK: Successors according to CFG: BB#1(1193046470) BB#7(357913941)
+; CHECK: Successors according to CFG: BB#1({{[0-9a-fx/= ]+}}76.92%) BB#7({{[0-9a-fx/= ]+}}23.08%)
 ;
 ; CHECK: BB#5:
 ; BB#5 to BB#1: {1140} (10)
 ; BB#5 to BB#6: [1134, UINT32_MAX] - {1140} (15 = 10 + 5)
-; CHECK: Successors according to CFG: BB#1(238609294) BB#6(357913941)
+; CHECK: Successors according to CFG: BB#1({{[0-9a-fx/= ]+}}40.00%) BB#6({{[0-9a-fx/= ]+}}60.00%)
 ;
 ; CHECK: BB#6:
 ; BB#6 to BB#1: {1134} (10)
 ; BB#6 to BB#2: [1134, UINT32_MAX] - {1134, 1140} (5)
-; CHECK: Successors according to CFG: BB#1(238609294) BB#2(119304647)
+; CHECK: Successors according to CFG: BB#1({{[0-9a-fx/= ]+}}66.67%) BB#2({{[0-9a-fx/= ]+}}33.33%)
 }
 
 ; CHECK-LABEL: test2
@@ -102,7 +102,7 @@
 ; CHECK: BB#0:
 ; BB#0 to BB#6: {0} + [15, UINT32_MAX] (5)
 ; BB#0 to BB#8: [1, 14] (jump table) (65 = 60 + 5)
-; CHECK: Successors according to CFG: BB#6(153391689) BB#8(1994091957)
+; CHECK: Successors according to CFG: BB#6({{[0-9a-fx/= ]+}}7.14%) BB#8({{[0-9a-fx/= ]+}}92.86%
 ;
 ; CHECK: BB#8:
 ; BB#8 to BB#1: {1} (10)
@@ -111,7 +111,7 @@
 ; BB#8 to BB#3: {11} (10)
 ; BB#8 to BB#4: {12} (10)
 ; BB#8 to BB#5: {13, 14} (20)
-; CHECK: Successors according to CFG: BB#1(306783378) BB#6(153391689) BB#2(306783378) BB#3(306783378) BB#4(306783378) BB#5(613566756)
+; CHECK: Successors according to CFG: BB#1({{[0-9a-fx/= ]+}}14.29%) BB#6({{[0-9a-fx/= ]+}}7.14%) BB#2({{[0-9a-fx/= ]+}}14.29%) BB#3({{[0-9a-fx/= ]+}}14.29%) BB#4({{[0-9a-fx/= ]+}}14.29%) BB#5({{[0-9a-fx/= ]+}}28.57%)
 }
 
 ; CHECK-LABEL: test3
@@ -163,7 +163,7 @@
 ; CHECK: BB#0:
 ; BB#0 to BB#6: [0, 9] + [15, UINT32_MAX] {10}
 ; BB#0 to BB#8: [10, 14] (jump table) (50)
-; CHECK: Successors according to CFG: BB#6(357913941) BB#8(1789569705)
+; CHECK: Successors according to CFG: BB#6({{[0-9a-fx/= ]+}}16.67%) BB#8({{[0-9a-fx/= ]+}}83.33%)
 ;
 ; CHECK: BB#8:
 ; BB#8 to BB#1: {10} (10)
@@ -171,7 +171,7 @@
 ; BB#8 to BB#3: {12} (10)
 ; BB#8 to BB#4: {13} (10)
 ; BB#8 to BB#5: {14} (10)
-; CHECK: Successors according to CFG: BB#1(357913941) BB#2(357913941) BB#3(357913941) BB#4(357913941) BB#5(357913941)
+; CHECK: Successors according to CFG: BB#1({{[0-9a-fx/= ]+}}20.00%) BB#2({{[0-9a-fx/= ]+}}20.00%) BB#3({{[0-9a-fx/= ]+}}20.00%) BB#4({{[0-9a-fx/= ]+}}20.00%) BB#5({{[0-9a-fx/= ]+}}20.00%)
 }
 
 ; CHECK-LABEL: test4
@@ -216,12 +216,12 @@
 ; CHECK: BB#0:
 ; BB#0 to BB#6: [0, 110] + [116, UINT32_MAX] (20)
 ; BB#0 to BB#7: [111, 115] (bit test) (50)
-; CHECK: Successors according to CFG: BB#6(613566756) BB#7(1533916890)
+; CHECK: Successors according to CFG: BB#6({{[0-9a-fx/= ]+}}28.57%) BB#7({{[0-9a-fx/= ]+}}71.43%)
 ;
 ; CHECK: BB#7:
 ; BB#7 to BB#2: {111, 114, 115} (30)
 ; BB#7 to BB#3: {112, 113} (20)
-; CHECK: Successors according to CFG: BB#2(920350134) BB#3(613566756)
+; CHECK: Successors according to CFG: BB#2({{[0-9a-fx/= ]+}}60.00%) BB#3({{[0-9a-fx/= ]+}}40.00%)
 }
 
 ; CHECK-LABEL: test5
@@ -273,7 +273,7 @@
 ; CHECK: BB#0:
 ; BB#0 to BB#6: [10, UINT32_MAX] (15)
 ; BB#0 to BB#8: [1, 5, 7, 9] (jump table) (45)
-; CHECK: Successors according to CFG: BB#8(536870912) BB#9(1610612734)
+; CHECK: Successors according to CFG: BB#8({{[0-9a-fx/= ]+}}25.00%) BB#9({{[0-9a-fx/= ]+}}75.00%)
 }
 
 !1 = !{!"branch_weights", i32 10, i32 10, i32 10, i32 10, i32 10, i32 10, i32 10, i32 10, i32 10} 
Index: test/CodeGen/X86/switch-jump-table.ll
===================================================================
--- test/CodeGen/X86/switch-jump-table.ll
+++ test/CodeGen/X86/switch-jump-table.ll
@@ -1,5 +1,5 @@
 ; RUN: llc -mtriple=i686-pc-gnu-linux < %s | FileCheck %s -check-prefix=CHECK
-; RUN: llc -mtriple=i686-pc-gnu-linux -print-machineinstrs=expand-isel-pseudos %s -o /dev/null 2>&1 | FileCheck %s -check-prefix=CHECK-JT-WEIGHT
+; RUN: llc -mtriple=i686-pc-gnu-linux -print-machineinstrs=expand-isel-pseudos %s -o /dev/null 2>&1 | FileCheck %s -check-prefix=CHECK-JT-PROB
 
 
 ; An unreachable default destination is replaced with the most popular case label.
@@ -54,9 +54,9 @@
 ; Check if branch probabilities are correctly assigned to the jump table.
 
 define void @bar(i32 %x, i32* %to) {
-; CHECK-JT-WEIGHT-LABEL: bar:
-; CHECK-JT-WEIGHT: Successors according to CFG: BB#6(306783378) BB#8(1840700268)
-; CHECK-JT-WEIGHT: Successors according to CFG: BB#1(306783378) BB#2(306783378) BB#3(306783378) BB#4(306783378) BB#5(613566756)
+; CHECK-JT-PROB-LABEL: bar:
+; CHECK-JT-PROB: Successors according to CFG: BB#6({{[0-9a-fx/= ]+}}14.29%) BB#8({{[0-9a-fx/= ]+}}85.71%)
+; CHECK-JT-PROB: Successors according to CFG: BB#1({{[0-9a-fx/= ]+}}16.67%) BB#2({{[0-9a-fx/= ]+}}16.67%) BB#3({{[0-9a-fx/= ]+}}16.67%) BB#4({{[0-9a-fx/= ]+}}16.67%) BB#5({{[0-9a-fx/= ]+}}33.33%)
 
 entry:
   switch i32 %x, label %default [