Index: llvm/tools/llvm-reduce/ReducerWorkItem.cpp
===================================================================
--- llvm/tools/llvm-reduce/ReducerWorkItem.cpp
+++ llvm/tools/llvm-reduce/ReducerWorkItem.cpp
@@ -35,6 +35,11 @@
     for (auto &SrcMI : SrcMBB) {
       for (unsigned I = 0, E = SrcMI.getNumOperands(); I < E; ++I) {
         auto &DMO = SrcMI.getOperand(I);
+        if (DMO.isRegMask()) {
+          DstMRI->addPhysRegsUsedFromRegMask(DMO.getRegMask());
+          continue;
+        }
+
         if (!DMO.isReg())
           continue;
         Register SrcReg = DMO.getReg();