1 files changed, 10 insertions, 0 deletions
diff --git a/llvm/lib/CodeGen/DeadMachineInstructionElim.cpp b/llvm/lib/CodeGen/DeadMachineInstructionElim.cpp
index 9a537c859a67..d1529b08f708 100644
--- a/llvm/lib/CodeGen/DeadMachineInstructionElim.cpp
+++ b/llvm/lib/CodeGen/DeadMachineInstructionElim.cpp
@@ -15,6 +15,7 @@
 #include "llvm/CodeGen/MachineRegisterInfo.h"
 #include "llvm/CodeGen/Passes.h"
 #include "llvm/CodeGen/TargetSubtargetInfo.h"
+#include "llvm/InitializePasses.h"
 #include "llvm/Pass.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/raw_ostream.h"
@@ -81,6 +82,15 @@ bool DeadMachineInstructionElim::isDead(const MachineInstr *MI) const {
         if (LivePhysRegs.test(Reg) || MRI->isReserved(Reg))
           return false;
       } else {
+        if (MO.isDead()) {
+#ifndef NDEBUG
+          // Sanity check on uses of this dead register. All of them should be
+          // 'undef'.
+          for (auto &U : MRI->use_nodbg_operands(Reg))
+            assert(U.isUndef() && "'Undef' use on a 'dead' register is found!");
+#endif
+          continue;
+        }
         for (const MachineInstr &Use : MRI->use_nodbg_instructions(Reg)) {
           if (&Use != MI)
             // This def has a non-debug use. Don't delete the instruction!