Remove useless copy

Author: ShortDevelopment

lib/Runtime/ByteCode/ByteCodeEmitter.cpp

@@ -57,38 +57,40 @@ static void EmitOptionalChainWrapper(ParseNodeUni *pnodeOptChain, ByteCodeGenera
     Js::ByteCodeLabel skipLabel = byteCodeGenerator->Writer()->DefineLabel();
     funcInfo->currentOptionalChainSkipLabel = skipLabel;
 
+    // Acquire slot for the result value
+    Js::RegSlot resultSlot = funcInfo->AcquireLoc(pnodeOptChain);
+
     // Copy values from wrapper to inner expression
     ParseNodePtr innerNode = pnodeOptChain->pnode1;
     innerNode->isUsed = pnodeOptChain->isUsed;
+    innerNode->location = resultSlot;
 
     // emit chain expression
     // Every `?.` node will call `EmitNullPropagation`
     // `EmitNullPropagation` short-circuits to `skipLabel` in case of a nullish value
     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);
+        Assert(resultSlot == innerNode->location);
 
         // Skip short-circuiting logic
-        Js::ByteCodeLabel doneLabel = byteCodeGenerator->Writer()->DefineLabel();
+        doneLabel = byteCodeGenerator->Writer()->DefineLabel();
         byteCodeGenerator->Writer()->Br(doneLabel);
+    }
 
-        // 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
+    if (pnodeOptChain->isUsed)
     {
-        byteCodeGenerator->Writer()->MarkLabel(skipLabel);
+        Assert(innerNode->isUsed);
+        Assert(Js::Constants::NoRegister != resultSlot);
+
+        // Set `undefined` on short-circuiting
+        byteCodeGenerator->Writer()->Reg2(Js::OpCode::Ld_A_ReuseLoc, resultSlot, funcInfo->undefinedConstantRegister);
+        byteCodeGenerator->Writer()->MarkLabel(doneLabel);
     }
     funcInfo->currentOptionalChainSkipLabel = previousSkipLabel;
 }