Professional Assembly Language

Chapter 15. Optimizing Routines

If you have been programming professionally using C or C++, you probably picked up this book to learn assembly language to help optimize your applications. Now that you are familiar with assembly language, you are ready to start analyzing your applications and putting your assembly language knowledge to use.

However, just writing functions in assembly language code instead of C or C++ does not necessarily make them perform better. Remember, the GNU compiler already converts all of your high-level language code to assembly language, so writing a function in assembly language just means that you did it instead of the compiler.

To truly optimize high-level language functions, you need to write better assembly language code than the compiler does. This can be quite a challenge. There are several optimization tricks the compiler can be instructed to perform on the generated assembly language code. Before you begin diving into writing your own assembly language functions, it's a good idea to see what techniques the experts use to optimize assembly language code, and then duplicate and possibly even improve on them.

To view optimized assembly language code, you need to know how to generate it from the compiler. This chapter first discusses how to use the various optimization levels when compiling C or C++ programs, and what optimization techniques are utilized within each optimization level. After that, a sample optimization session is shown to acquaint you ...