diff --git a/llvm/lib/CodeGen/MachineLoopUtils.cpp b/llvm/lib/CodeGen/MachineLoopUtils.cpp
--- a/llvm/lib/CodeGen/MachineLoopUtils.cpp
+++ b/llvm/lib/CodeGen/MachineLoopUtils.cpp
@@ -103,11 +103,10 @@
 
   DebugLoc DL;
   if (Direction == LPD_Front) {
-    Preheader->replaceSuccessor(Loop, NewBB);
+    Preheader->ReplaceUsesOfBlockWith(Loop, NewBB);
     NewBB->addSuccessor(Loop);
     Loop->replacePhiUsesWith(Preheader, NewBB);
-    if (TII->removeBranch(*Preheader) > 0)
-      TII->insertBranch(*Preheader, NewBB, nullptr, {}, DL);
+    Preheader->updateTerminator(Loop);
     TII->removeBranch(*NewBB);
     TII->insertBranch(*NewBB, Loop, nullptr, {}, DL);
   } else {
diff --git a/llvm/lib/CodeGen/ModuloSchedule.cpp b/llvm/lib/CodeGen/ModuloSchedule.cpp
--- a/llvm/lib/CodeGen/ModuloSchedule.cpp
+++ b/llvm/lib/CodeGen/ModuloSchedule.cpp
@@ -1797,10 +1797,10 @@
 
   // Iterate in reverse order over all instructions, remapping as we go.
   for (MachineBasicBlock *B : reverse(Blocks)) {
-    for (auto I = B->getFirstInstrTerminator()->getReverseIterator();
+    for (auto I = B->instr_rbegin();
          I != std::next(B->getFirstNonPHI()->getReverseIterator());) {
-      MachineInstr *MI = &*I++;
-      rewriteUsesOf(MI);
+      MachineBasicBlock::reverse_instr_iterator MI = I++;
+      rewriteUsesOf(&*MI);
     }
   }
   for (auto *MI : IllegalPhisToDelete) {