测试代码：

    static volatile uint32_t cnt;
    cnt = 0;
    uint64_t time = time_spent({
        while (cnt < 1000000)
        {
            cnt++;
        }
    });
    log_info("test time spent: %llu us\r\n", time);

结果：

//未开启Cache
fmc_ram test:
uint32_t spent time: 955963 us
uint64_t spent time: 1091907 us
float spent time: 247405 us
double spent time: 1092104 us
iram test:
uint32_t spent time: 13462 us
uint64_t spent time: 956284 us
float spent time: 1227114 us
double spent time: 1091992 us

//开启Cache
fmc_ram test:
uint32_t spent time: 227392 us
uint64_t spent time: 329214 us
float spent time: 244203 us
double spent time: 353283 us
iram test:
uint32_t spent time: 10476 us
uint64_t spent time: 16780 us
float spent time: 25151 us
double spent time: 37813 us

测试环境：
1. 主频：480MHZ
2. 开启double硬件加速