Index: lib/Target/AMDGPU/SIInsertWaitcnts.cpp
===================================================================
--- lib/Target/AMDGPU/SIInsertWaitcnts.cpp
+++ lib/Target/AMDGPU/SIInsertWaitcnts.cpp
@@ -1558,7 +1558,8 @@
 MachineBasicBlock *SIInsertWaitcnts::loopBottom(const MachineLoop *Loop) {
   MachineBasicBlock *Bottom = Loop->getHeader();
   for (MachineBasicBlock *MBB : Loop->blocks())
-    if (MBB->getNumber() > Bottom->getNumber())
+    if (MBB->getNumber() > Bottom->getNumber() &&
+        MBB->isSuccessor(Loop->getHeader()))
       Bottom = MBB;
   return Bottom;
 }