diff --git a/llvm/lib/Target/AMDGPU/SIInsertWaitcnts.cpp b/llvm/lib/Target/AMDGPU/SIInsertWaitcnts.cpp
--- a/llvm/lib/Target/AMDGPU/SIInsertWaitcnts.cpp
+++ b/llvm/lib/Target/AMDGPU/SIInsertWaitcnts.cpp
@@ -1528,6 +1528,13 @@
   return StrictDom;
 }
 
+static bool isWaitInstr(MachineInstr &Inst) {
+  return Inst.getOpcode() == AMDGPU::S_WAITCNT ||
+         (Inst.getOpcode() == AMDGPU::S_WAITCNT_VSCNT &&
+          Inst.getOperand(0).isReg() &&
+          Inst.getOperand(0).getReg() == AMDGPU::SGPR_NULL);
+}
+
 // Generate s_waitcnt instructions where needed.
 bool SIInsertWaitcnts::insertWaitcntInBlock(MachineFunction &MF,
                                             MachineBasicBlock &Block,
@@ -1563,10 +1570,7 @@
 
     // Track pre-existing waitcnts that were added in earlier iterations or by
     // the memory legalizer.
-    if (Inst.getOpcode() == AMDGPU::S_WAITCNT ||
-        (Inst.getOpcode() == AMDGPU::S_WAITCNT_VSCNT &&
-         Inst.getOperand(0).isReg() &&
-         Inst.getOperand(0).getReg() == AMDGPU::SGPR_NULL)) {
+    if (isWaitInstr(Inst)) {
       if (!OldWaitcntInstr)
         OldWaitcntInstr = &Inst;
       ++Iter;