在IAR下,我想查看函数[mw_shl_code=applescript,true]/**
  * @brief  Returns the HCLK frequency     
  * @note   Each time HCLK changes, this function must be called to update the
  *         right HCLK value. Otherwise, any configuration based on this function will be incorrect.
  * @note   The SystemCoreClock CMSIS variable is used to store System Clock Frequency.
  * @retval HCLK frequency
  */
uint32_t HAL_RCC_GetHCLKFreq(void)
{
  return SystemCoreClock;
}[/mw_shl_code]
但是编译器提示这句话没有作用

这是怎么回事呢?