这是更快：X＆所述;＆。1或X;小于10？ [英] Which is faster: x<<1 or x<<10?

问题描述

我不希望优化什么，我发誓，我只想问这个问题是出于好奇。
我知道，在大多数硬件上有位移（如 SHL ， SHR ）的集合命令，这是一个单一的命令。但它的问题（纳秒的角度来看，还是CPU-圆通明智的），你有多少位转移。换句话说，要么是下列任何CPU上更快吗？

I don't want to optimize anything, I swear, I just want to ask this question out of curiosity. I know that on most hardware there's an assembly command of bit-shift (e.g. shl, shr), which is a single command. But does it matter (nanosecond-wise, or CPU-tact-wise) how many bits you shift. In other words, is either of the following faster on any CPU?

x << 1;

和

x << 10;

和请不要恨我这个问题。 ：）

And please don't hate me for this question. :)

推荐答案

潜在取决于CPU。

然而，所有现代的CPU（X86，ARM）使用一个桶式移位器 - 一个硬件模块专为在固定时间内执行任意移

However, all modern CPUs (x86, ARM) use a "barrel shifter" -- a hardware module specifically designed to perform arbitrary shifts in constant time.

因此​​，底线是...没有。没有什么区别。

So the bottom line is... no. No difference.

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