Remove useless copy

Author: ShortDevelopment

lib/Runtime/ByteCode/ByteCodeEmitter.cpp

@@ -67,29 +67,29 @@ static void EmitOptionalChainWrapper(ParseNodeUni *pnodeOptChain, ByteCodeGenera
     emitChainContent(innerNode);
     funcInfo->ReleaseLoc(innerNode);
 
-    if (innerNode->isUsed)
+    Js::ByteCodeLabel doneLabel = Js::Constants::NoRegister;
+    if (pnodeOptChain->isUsed)
     {
-        Assert(Js::Constants::NoRegister != innerNode->location);
-
-        // Acquire slot for the result value
-        Js::RegSlot resultSlot = funcInfo->AcquireLoc(pnodeOptChain);
-        // Copy chain result
-        byteCodeGenerator->Writer()->Reg2(Js::OpCode::Ld_A, resultSlot, innerNode->location);
+        Assert(innerNode->isUsed);
 
         // Skip short-circuiting logic
-        Js::ByteCodeLabel doneLabel = byteCodeGenerator->Writer()->DefineLabel();
+        doneLabel = byteCodeGenerator->Writer()->DefineLabel();
         byteCodeGenerator->Writer()->Br(doneLabel);
+    }
+
+    byteCodeGenerator->Writer()->MarkLabel(skipLabel);
+
+    if (pnodeOptChain->isUsed)
+    {
+        // Acquire slot for the result value
+        Js::RegSlot resultSlot = funcInfo->AcquireLoc(pnodeOptChain);
+        Assert(Js::Constants::NoRegister != resultSlot);
+        Assert(resultSlot == innerNode->location);
 
         // Set `undefined` on short-circuiting
-        byteCodeGenerator->Writer()->MarkLabel(skipLabel);
         byteCodeGenerator->Writer()->Reg2(Js::OpCode::Ld_A_ReuseLoc, resultSlot, funcInfo->undefinedConstantRegister);
-
         byteCodeGenerator->Writer()->MarkLabel(doneLabel);
     }
-    else
-    {
-        byteCodeGenerator->Writer()->MarkLabel(skipLabel);
-    }
     funcInfo->currentOptionalChainSkipLabel = previousSkipLabel;
 }