Fix fgOptimizeAddition opt for AOT (#94350)

Author: EgorBo

src/coreclr/jit/morph.cpp

@@ -11019,16 +11019,15 @@ GenTree* Compiler::fgOptimizeAddition(GenTreeOp* add)
         GenTreeOp*     addOne   = op1->AsOp();
         GenTreeOp*     addTwo   = op2->AsOp();
         GenTreeIntCon* constOne = addOne->gtGetOp2()->AsIntCon();
-        GenTreeIntCon* constTwo = addTwo->gtGetOp2()->AsIntCon();
 
+        // addOne is now "x + y"
         addOne->gtOp2 = addTwo->gtGetOp1();
         addOne->SetAllEffectsFlags(addOne->gtGetOp1(), addOne->gtGetOp2());
-        DEBUG_DESTROY_NODE(addTwo);
 
-        constOne->SetValueTruncating(constOne->IconValue() + constTwo->IconValue());
-        op2        = constOne;
-        add->gtOp2 = constOne;
-        DEBUG_DESTROY_NODE(constTwo);
+        // addTwo is now "icon1 + icon2" so we can fold it using gtFoldExprConst
+        addTwo->gtOp1 = constOne;
+        add->gtOp2    = gtFoldExprConst(add->gtOp2);
+        op2           = add->gtGetOp2();
     }
 
     // Fold (x + 0) - given it won't change the tree type.