快速整数类型存储在CPU寄存器中时是否更快？ [英] Are the fast integer types faster when stored in the CPU registers?

问题描述

我一直在考虑快速整数类型：

I have been thinking about the fast integer types:

int_fast8_t ， int_fast16_t ， int_fast32_t ， int_fast64_t ， uint_fast8_t ， uint_fast16_t ， uint_fast32_t ， uint_fast64_t

在过去的几天里，我问了一个关于为什么的问题（如果是的话），这些类型比其他整数类型要快：

over the last days and I asked a question about why (if so) these types are faster than the other integer types:

为什么快速整数类型比其他整数类型快？

我进一步考虑过的问题现在是 if ：

Something I have further thought about now is, if:

1. 更快的类型 在特定环境下（


2. 对象为 regist类的对象，因此该环境反映了此问题的理想环境er 存储在CPU的寄存器中（但通常在使用寄存器类），它们在相同的环境下速度更快，并且



3. CPU的寄存器能够保存所需的整数值

1. Faster types are faster on a certain environment (implementation/architecture-dependent) and thus that environment reflects an ideal environment for this question,
2. Objects with the class of register are stored inside a register of the CPU (but in general do not always need to be stored there when declared with the register class), they are faster on the same environment, and

3. A register of the CPU is capable of holding the required integer value,

• 如果使用寄存器声明，快速整数类型甚至*更快？存储类？

• Are the fast integer types even *faster if declared with the register storage class?

就像：

register int_fastY_t i;

*（表示上面的前提。）

还是它们相互干扰并降低性能？

Or do they interfere with each other and decrease the performance?

推荐答案

寄存器不会导致编译器将值存储在寄存器中。 注册绝对没有任何作用。只有极老的编译器才使用 register 来知道要在寄存器中存储哪些变量。新的编译器会自动执行此操作。甚至20岁的编译器也会自动执行此操作。

register does not cause the compiler to store a value in a register. register does absolutely nothing. Only extremely old compilers used register to know which variables to store in registers. New compilers do it automatically. Even 20-year-old compilers do it automatically.

听起来您正在尝试使程序更快，但您不了解程序的实际作用，因此，您要问的是您听说过的所有与速度有关的事情。

It sounds like you are trying to make a program faster but you don't understand what the program is actually doing, so you are asking about all the speed-related things that you have ever heard about.

我提醒您，例如，如果您使用的是使用GCC的x86-64， ，则 int_fast16_t 与 int64_t 相同，与 int 和 register 绝对没有任何作用，因此 register int_fast16_t 与 int相同。这不是一个神奇的加速命令。

I remind you that if you're on x86-64 using GCC, for example, then int_fast16_t is the same as int64_t, which is the same as int and register does absolutely nothing, so register int_fast16_t is the same as int. It's not a magic speed-up command.

如果您想使用这些技巧来使程序更快，则应先阅读编译器的汇编代码。生产。 GCC信息或 Visual C ++ 。然后，您可以寻找效率低下的汇编代码，找到一些汇编代码后，便可以了解如何加快汇编代码的速度。现在，您在风车上倾斜。

If you want to use these kinds of tricks to make your program faster, you should start by reading the assembly code that your compiler produces. Information for GCC or Visual C++. Then you can look for inefficient assembly code, and when you find some, you can find out how to speed it up. Right now, you are tilting at windmills.

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