Inlining replaces instructions that call a function and return from it with the actual instructions of the function being called. Inlining function make your program faster because they execute the function code immediately without the overhead of a function call and return. However, inlining can also make your program larger because the compiler may insert the function's instructions many times throughout your program.
The rest of this section explains how to specify which functions to inline and how the compiler performs the inlining: