深入理解计算机系统 2.73

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转自：https://github.com/darrenhp/Practise/blob/master/csapp/ch02/2_73.c
加法处理，正溢出输出TMax,负溢出输出Tmin.
#include<stdio.h>
#include<limits.h>

int saturating_add(int x, int y)
{
int mask = INT_MIN;
int sum = x + y;
int w = (sizeof(int)<<3)-1;
int tmin = ( ((x&mask)&&(y&mask)&&!(sum&mask)) << w >> w ) & INT_MIN;
int tmax = ( ((~x&mask)&&(~y&mask)&&(sum&mask)) << w >> w) & INT_MAX;
return (sum& ~(!(tmin|tmax))) | tmin | tmax;
}

void show_saturating_add(int x, int y)
{
printf("saturating_add(0x%08X, 0x%08X) = 0x%08X:%d\n", 
x, y, saturating_add(x, y), saturating_add(x, y) );
printf("%d + %d = %d\n", x, y, x+y);
printf("    \n");
}


int main()
{
show_saturating_add(0xFFFFFFFF, 0x80000000);
show_saturating_add(0xFFFFFFFF, 0xFFFFFFFF);
show_saturating_add(0x7FFFFFF0, 0x0000000F);
show_saturating_add(0x7FFFFFF5, 0x0000000F);
show_saturating_add(0x55555555, 0x55555555);
show_saturating_add(0x55555555, 0x33333333);
show_saturating_add(0x55555555, 0x23333333);
show_saturating_add(0x55555555, 0x2FFFFFFF);
}