《C++ Footprint and Performance Optimization》读书笔记

P75

// hmjtestasm.cpp : 定义控制台应用程序的入口点。
//

#include "stdafx.h"
#include "stdio.h"
long MulOperator(void);
int DoWop(int dow,int op);

struct A{char a;long b;char c;long d;};
#pragma pack(push,1)
struct B{char a;long b;char c;long d;};
#pragma pack(pop)
int _tmain(int argc, _TCHAR* argv[])
{
    char vara;
    int varb;
    varb=DoWop(1,2);//result : varb=3
    printf("varb is :%d\n",varb);
    printf("%d is \n",MulOperator());//turn to shift

    printf("size of struct a : %d\n",sizeof(A));//16
    printf("size of struct b :%d\n",sizeof(B));//10
    vara=getchar();
    return 0;
}

long MulOperator(void)
{
    long i,j=1031;
    for (i=0;i<20000000;i++)
    {
        j*=2;
        //j*=3;//生成的汇编代码不同
    }
    return j;
}
inline int DoWop(int dow,int op)
{//在微软开发平台内联汇编
    __asm
    {
        mov eax,dow;
        add eax,op;
    }
}

 书中源码下载：http://is.gd/cppfootprint

本书出版社地址：http://www.informit.com/store/c-plus-plus-footprint-and-performance-optimization-9780672319044