Optimizing a branch for a known more-common path

Question

Please consider the following piece of code:

void error_handling();
bool method_impl();

bool method()
{
    const bool res = method_impl();
    if (res == f         


        

Answer 1

You could suggest the compiler that the method_impl() will return true:

void error_handling();
bool method_impl();

bool method()
{
    const bool res = method_impl();
    if (__builtin_expect (res, 0) == false) {
        error_handling();
        return false;
    }
    return true;
}

This will work in GCC.