最快的方式从无符号整数（C ++）中读取最左边的位？ [英] Fastest way to read Left-Most bit from unsigned int (C++)?

问题描述

从无符号整数读取最左位的最快速方式是什么？

What is the fastest way to read the Left-Most bit from unsigned int ?

感谢，

SW

Thanks,
SW

推荐答案

i >> (sizeof(unsigned int) * CHAR_BIT - 1)

code>，乘法和减法将由编译时由任何合理的编译器计算，所以这应该成为一个右移指令，这是大约与你会得到的一样快。

The sizeof, multiplication, and subtraction will be computed at compile-time by any reasonable compiler, so this should become a single right-shift instruction, which is about as fast as you will get.

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