Index: lib/Target/AMDGPU/AMDILCFGStructurizer.cpp
===================================================================
--- lib/Target/AMDGPU/AMDILCFGStructurizer.cpp
+++ lib/Target/AMDGPU/AMDILCFGStructurizer.cpp
@@ -423,7 +423,8 @@
 
 void AMDGPUCFGStructurizer::reversePredicateSetter(
     MachineBasicBlock::iterator I) {
-  while (I--) {
+  assert(static_cast<MachineInstr *>(I) && "Expected valid iterator");
+  for (;; --I) {
     if (I->getOpcode() == AMDGPU::PRED_X) {
       switch (static_cast<MachineInstr *>(I)->getOperand(2).getImm()) {
       case OPCODE_IS_ZERO_INT: