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Most people do not understand the knowledge points of this article "how to solve the problem of CPU out-of-order execution", so the editor summarizes the following content, detailed content, clear steps, and has a certain reference value. I hope you can get something after reading this article. Let's take a look at this "how to solve the problem of CPU out-of-order execution" article.

To solve the problem of out-of-order execution is a must for high-performance programming, especially lock-free programming in multithreaded environment. The problem of out-of-order execution is caused by compiler optimization and CPU instruction rearrangement at run time.

For the out-of-order execution problem caused by compiler optimization, this is a good solution: where you do not want to be optimized by the compiler and statement rearrangement occurs, you can insert compiler-specific statements. Take gcc as an example, add the following compiler barriers:

Asm volatile ("":: "memory")

Next, we will focus on the implementation of CPU out of order, which is easy to be misunderstood. I think the problem of out-of-order execution of CPU mentioned on the Internet is caused by the rearrangement of CPU instructions. Therefore, it is necessary for us to understand the premise and background of CPU instruction rearrangement in order to avoid unnecessary panic. CPU instruction rearrangement is aimed at micro machine instructions, and our code is composed of relatively macro program statements. There is a mapping relationship from macro to micro, but it is definitely not equivalent. I think one of the misunderstandings about the rearrangement of CPU instructions is that there is no clear distinction between machine instructions and program statements.

CPU instruction rearrangement exists in mainstream CPU, but CPU will be executed strictly according to our program statements (program logic), otherwise it will be a major bug of CPU or compiler. Therefore, from the point of view of the execution of a single thread, although there may be a rearrangement of CPU instructions, corresponding to macroscopic program statements, which statement is executed first and which statement is then executed will not violate our program logic. We must ensure the order of statement execution, otherwise our program will not be able to write.

The above is about the content of this article on "how to solve the problem of CPU out-of-order execution". I believe we all have a certain understanding. I hope the content shared by the editor will be helpful to you. If you want to know more about the relevant knowledge, please pay attention to the industry information channel.

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