Index: include/llvm/CodeGen/MachineBasicBlock.h
===================================================================
--- include/llvm/CodeGen/MachineBasicBlock.h
+++ include/llvm/CodeGen/MachineBasicBlock.h
@@ -367,8 +367,8 @@
   /// Update the terminator instructions in block to account for changes to the
   /// layout. If the block previously used a fallthrough, it may now need a
   /// branch, and if it previously used branching it may now be able to use a
-  /// fallthrough.
-  void updateTerminator();
+  /// fallthrough. Return true if the terminator is updated, otherwise false.
+  bool updateTerminator();
 
   // Machine-CFG mutators
 
Index: lib/CodeGen/MachineBasicBlock.cpp
===================================================================
--- lib/CodeGen/MachineBasicBlock.cpp
+++ lib/CodeGen/MachineBasicBlock.cpp
@@ -400,10 +400,10 @@
   getParent()->splice(++NewBefore->getIterator(), getIterator());
 }
 
-void MachineBasicBlock::updateTerminator() {
+bool MachineBasicBlock::updateTerminator() {
   const TargetInstrInfo *TII = getParent()->getSubtarget().getInstrInfo();
   // A block with no successors has no concerns with fall-through edges.
-  if (this->succ_empty()) return;
+  if (this->succ_empty()) return false;
 
   MachineBasicBlock *TBB = nullptr, *FBB = nullptr;
   SmallVector<MachineOperand, 4> Cond;
@@ -415,8 +415,10 @@
     if (TBB) {
       // The block has an unconditional branch. If its successor is now
       // its layout successor, delete the branch.
-      if (isLayoutSuccessor(TBB))
+      if (isLayoutSuccessor(TBB)) {
         TII->RemoveBranch(*this);
+        return true;
+      }
     } else {
       // The block has an unconditional fallthrough. If its successor is not
       // its layout successor, insert a branch. First we have to locate the
@@ -431,12 +433,14 @@
       // If there is no non-landing-pad successor, the block has no
       // fall-through edges to be concerned with.
       if (!TBB)
-        return;
+        return false;
 
       // Finally update the unconditional successor to be reached via a branch
       // if it would not be reached by fallthrough.
-      if (!isLayoutSuccessor(TBB))
+      if (!isLayoutSuccessor(TBB)) {
         TII->InsertBranch(*this, TBB, nullptr, Cond, DL);
+        return true;
+      }
     }
   } else {
     if (FBB) {
@@ -445,12 +449,14 @@
       // conditional branch.
       if (isLayoutSuccessor(TBB)) {
         if (TII->ReverseBranchCondition(Cond))
-          return;
+          return false;
         TII->RemoveBranch(*this);
         TII->InsertBranch(*this, FBB, nullptr, Cond, DL);
+        return true;
       } else if (isLayoutSuccessor(FBB)) {
         TII->RemoveBranch(*this);
         TII->InsertBranch(*this, TBB, nullptr, Cond, DL);
+        return true;
       }
     } else {
       // Walk through the successors and find the successor which is not
@@ -475,7 +481,7 @@
         // if it would not be reached by fallthrough.
         if (!isLayoutSuccessor(TBB))
           TII->InsertBranch(*this, TBB, nullptr, Cond, DL);
-        return;
+        return true;
       }
 
       // The block has a fallthrough conditional branch.
@@ -484,16 +490,19 @@
           // We can't reverse the condition, add an unconditional branch.
           Cond.clear();
           TII->InsertBranch(*this, FallthroughBB, nullptr, Cond, DL);
-          return;
+          return true;
         }
         TII->RemoveBranch(*this);
         TII->InsertBranch(*this, FallthroughBB, nullptr, Cond, DL);
+        return true;
       } else if (!isLayoutSuccessor(FallthroughBB)) {
         TII->RemoveBranch(*this);
         TII->InsertBranch(*this, TBB, FallthroughBB, Cond, DL);
+        return true;
       }
     }
   }
+  return false;
 }
 
 void MachineBasicBlock::validateSuccProbs() const {