diff --git a/llvm/lib/CodeGen/PrologEpilogInserter.cpp b/llvm/lib/CodeGen/PrologEpilogInserter.cpp
--- a/llvm/lib/CodeGen/PrologEpilogInserter.cpp
+++ b/llvm/lib/CodeGen/PrologEpilogInserter.cpp
@@ -1230,6 +1230,10 @@
   if (OnlyUsed)
     for (const MachineBasicBlock &MBB : MF)
       for (const MachineInstr &MI : MBB)
+         // skip debug instructions
+         if (MI.isDebugInstr())
+           continue;
+
         for (const MachineOperand &MO : MI.operands()) {
           if (!MO.isReg())
             continue;