基于STM32F103的C与C++的效率对比

class Calculate
{
public:
    float test(float a, float b){
        float tmp1 = a+b;
        double tmp2 = 1000*tmp1;
        
        return tmp2/999.999999;
    }
};

float test(float a, float b)
{
    float tmp1 = a+b;
    double tmp2 = 1000*tmp1;
    
    return tmp2/999.999999;
}

uint32_t tick_1 = 0;
uint32_t tick_2 = 0;
#define CNT_MAX 1000000

Test t;
extern "C" void TestCPlusPlus()
{
    float a = 1.001;
    double b = 1;
    
    tick_1 = HAL_GetTick();
    for(int i = 0; i < CNT_MAX; i++)
    {
        b = t.test(a, b);
    }
    tick_2 = HAL_GetTick();
    SEGGER_RTT_printf(0, "C++:time = %d, b=%drn", tick_2-tick_1, (uint32_t)b);
}


extern "C" void TestC()
{
    float a = 1.001;
    float b = 1;
    
    tick_1 = HAL_GetTick();
    for(int i = 0; i < CNT_MAX; i++)
    {
        b = test(a, b);
    }
    tick_2 = HAL_GetTick();
    SEGGER_RTT_printf(0, "C:time = %d, b=%drn", tick_2-tick_1, (uint32_t)b);
}

运行条件：72MHz，运行结果：
 0> C:time = 5811, b=1000033
 0> C++:time = 6673, b=1000033

结果分析：

完全一样的功能，C++比C多运行862ms