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This article will explain in detail the example analysis of gcc optimization level in Linux environment. The editor thinks it is very practical, so I share it with you for reference. I hope you can get something after reading this article.

Gcc-o1 first of all, there is an o0 on o1, which does not provide any optimization and will hardly be used in the project, while o1 is widely used. O1 is the most basic optimization, mainly optimizing branches of code, expressions, and constants. The compiler will make the code shorter in a short period of time, so it will become smaller and reduce memory usage. It is faster when memory is scheduled by the operating system. But there is no absolute advantage, when a large program is broken down, the memory footprint will be greatly increased, because most of today's systems are multithreaded, there will be stutters and response delays.

The optimization level of gcc-o2 is an advanced level of o1, which will be more strictly subdivided on the basis of the previous level, and most importantly, the use of registers will be added. Register is an important part of cpu, in addition, there are arithmetic units and controllers. As the name implies, computers need to carry out all kinds of complex calculations. Because the speed of cpu is fast, the intermediate results of calculation will be saved in registers, which can greatly improve the efficiency of the system. However, registers are expensive and limited, so generally speaking, programs will not be placed in registers. Another way to put code in a register is to use register to decorate variables, which are suitable for variables that are called frequently.

Gcc-o3 is a very powerful optimization because the compiler makes predictions for each layer of the loop in order to split the loop and improve execution efficiency. The compiler will also try to replace unknown values with existing values, and will also use addition instead of multiplication, which is complex and time-consuming because of the nature of the operator. Of course, the most obvious disadvantage of o3 is that it may make errors when trying to predict the direction of the program, leading to errors and irreversible trends of the program. Therefore, o3 is not recommended in general.

These are the three levels of optimization, for optimization, system optimization or mechanical, programmers for a deep understanding of the language, clever algorithms may be more meaningful.

This is the end of this article on "sample Analysis of gcc Optimization level in Linux". I hope the above content can be of some help to you, so that you can learn more knowledge. if you think the article is good, please share it for more people to see.

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