Semiconductor Manufacturing International Corp.’s stock has more than doubled over the past two months on an expected boost from China’s self-reliance push, even amid risks tied to competition and geopolitical tensions. Shanghai-listed shares of China’s largest outsourced chipmaker are up 120% from a September low, trouncing global sector names including Nvidia Corp. and Taiwan Semiconductor Manufacturing Co. The mainland stock has outperformed SMIC’s Hong Kong shares by almost 50 percentage poi...