-fno-inline-small-functions (disable inlining of small functions)

26 Oct 2023

Inlining is a powerful optimization technique used by compilers to improve performance by copying the body of a function directly into its caller. However, there are cases where inlining every function, even small ones, may not always be desired. In such situations, you can use the -fno-inline-small-functions flag in C++ to disable inlining of small functions.

Inlining small functions can lead to larger executable sizes and increased memory usage, as the code for these functions gets duplicated at each call site. Disabling inlining of small functions can help reduce code bloat by keeping these functions separate and called at their original location.

To disable inlining of small functions in your C++ code, follow these steps:

Step 1: Identify Small Functions

First, you need to identify the small functions that you want to prevent from being inlined. Small functions are typically short and don’t contain complex logic.

Step 2: Add the Compiler Flag

To disable inlining of small functions, use the -fno-inline-small-functions flag during the compilation process. This flag instructs the compiler to exclude small functions from the inlining process.

For example, if you’re compiling your code using g++, you can add the following to your compilation command:

g++ -fno-inline-small-functions myfile.cpp -o myfile

By adding this flag, the small functions in myfile.cpp will no longer be inlined during the compilation process.

Step 3: Recompile and Test

Recompile your code with the modified compilation command and test the performance and behavior of your application. By disabling inlining of small functions, you may notice differences in performance, memory usage, or code size.

Conclusion

Disabling inlining of small functions using the -fno-inline-small-functions flag in C++ can help optimize code size and reduce memory usage. However, it’s important to carefully consider the trade-offs between code size, performance, and readability before deciding to disable inlining for specific functions.

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