Index: llvm/trunk/lib/Target/WebAssembly/WebAssemblyExplicitLocals.cpp
===================================================================
--- llvm/trunk/lib/Target/WebAssembly/WebAssemblyExplicitLocals.cpp
+++ llvm/trunk/lib/Target/WebAssembly/WebAssemblyExplicitLocals.cpp
@@ -284,8 +284,11 @@
           }
           if (UseEmpty[TargetRegisterInfo::virtReg2Index(OldReg)]) {
             unsigned Opc = getDropOpcode(RC);
-            BuildMI(MBB, InsertPt, MI.getDebugLoc(), TII->get(Opc))
-                .addReg(NewReg);
+            MachineInstr *Drop =
+                BuildMI(MBB, InsertPt, MI.getDebugLoc(), TII->get(Opc))
+                    .addReg(NewReg);
+            // After the drop instruction, this reg operand will not be used
+            Drop->getOperand(0).setIsKill();
           } else {
             unsigned LocalId = getLocalId(Reg2Local, CurLocal, OldReg);
             unsigned Opc = getSetLocalOpcode(RC);
@@ -294,6 +297,9 @@
                 .addReg(NewReg);
           }
           MI.getOperand(0).setReg(NewReg);
+          // This register operand is now being used by the inserted drop
+          // instruction, so make it undead.
+          MI.getOperand(0).setIsDead(false);
           MFI.stackifyVReg(NewReg);
           Changed = true;
         }
Index: llvm/trunk/test/CodeGen/WebAssembly/explicit-locals.mir
===================================================================
--- llvm/trunk/test/CodeGen/WebAssembly/explicit-locals.mir
+++ llvm/trunk/test/CodeGen/WebAssembly/explicit-locals.mir
@@ -0,0 +1,23 @@
+# RUN: llc -mtriple=wasm32-unknown-unknown -run-pass wasm-explicit-locals %s -o - | FileCheck %s
+
+# When a drop instruction is inserted to drop a dead register operand, the
+# original operand should be marked not dead anymore because it is now used by
+# the new drop instruction. And the operand to the new drop instruction should
+# be marked killed instead.
+---
+name: drop_test
+liveins:
+  - { reg: '$arguments' }
+tracksRegLiveness: true
+body: |
+  bb.0:
+    successors: %bb.1
+    liveins: $arguments
+
+  bb.1:
+  ; predecessors: %bb.0
+    ; CHECK-NOT: dead %{{[0-9]+}}
+    ; CHECK: DROP_I32 killed %{{[0-9]+}}
+    dead %0:i32 = CONST_I32 0, implicit-def dead $arguments, implicit $sp32, implicit $sp64
+    RETURN_VOID implicit-def dead $arguments
+...