为什么下列程序进行的是无符号乘法？

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unsigned int x1 = 0xaeb1c2aa;
unsigned int x2 = 0xaeb1c2aa;

long long r_whole = (signed long long)x1 * (signed long long)x2;

printf("r_whole = %lldn",r_whole);

输出的结果是无符号乘法的结果：

r_whole = 8590088583138384100

而下面的程序

unsigned int x1 = 0xaeb1c2aa;
unsigned int x2 = 0xaeb1c2aa;

int xx1 = x1;
int xx2 = x2;

long long r_whole = (signed long long)xx1 * (signed long long)xx2;

printf("r_whole = %lldn",r_whole);

输出的事有符号乘法的结果：