diff --git a/llvm/lib/CodeGen/DeadMachineInstructionElim.cpp b/llvm/lib/CodeGen/DeadMachineInstructionElim.cpp
--- a/llvm/lib/CodeGen/DeadMachineInstructionElim.cpp
+++ b/llvm/lib/CodeGen/DeadMachineInstructionElim.cpp
@@ -126,7 +126,9 @@
     for (MachineBasicBlock::succ_iterator S = MBB.succ_begin(),
            E = MBB.succ_end(); S != E; S++)
       for (const auto &LI : (*S)->liveins())
-        LivePhysRegs.set(LI.PhysReg);
+        for (MCSubRegIterator SR(LI.PhysReg, TRI, /*IncludeSelf=*/true);
+             SR.isValid(); ++SR)
+          LivePhysRegs.set(*SR);
 
     // Now scan the instructions and delete dead ones, tracking physreg
     // liveness as we go.
diff --git a/llvm/test/CodeGen/Hexagon/dead-code-elim-sub-reg-livein.mir b/llvm/test/CodeGen/Hexagon/dead-code-elim-sub-reg-livein.mir
new file mode 100644
--- /dev/null
+++ b/llvm/test/CodeGen/Hexagon/dead-code-elim-sub-reg-livein.mir
@@ -0,0 +1,35 @@
+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
+# RUN: llc -march=hexagon -run-pass dead-mi-elimination -verify-machineinstrs %s -o - | FileCheck %s
+
+# DeadMachineCodeElimination needs to add the subregisters of the live-ins of a block to avoid
+# deleting instructions writing to parts of a super register.
+# This test is making sure that this happens.
+
+---
+name: livein_sub_reg_not_preserved
+tracksRegLiveness: true
+
+body: |
+  ; CHECK-LABEL: name: livein_sub_reg_not_preserved
+  ; CHECK: bb.0:
+  ; CHECK:   successors: %bb.1(0x80000000)
+  ; CHECK:   liveins: $d0, $r2
+  ; CHECK: bb.1:
+  ; CHECK:   successors: %bb.1(0x80000000)
+  ; CHECK:   liveins: $d0, $r2
+  ; CHECK:   $r0 = A2_tfrsi 1
+  ; CHECK:   A2_nop implicit-def $p0
+  ; CHECK:   J2_jumpt killed $p0, %bb.1, implicit-def dead $pc
+  ; CHECK:   J2_jumpr $r31, implicit-def dead $pc
+  bb.0:
+    liveins: $d0, $r2
+    successors: %bb.1
+
+  bb.1:
+    successors: %bb.1
+    liveins: $d0, $r2
+    $r0 = A2_tfrsi 1
+    A2_nop implicit-def $p0
+    J2_jumpt killed $p0, %bb.1, implicit-def dead $pc
+    J2_jumpr $r31, implicit-def dead $pc
+...