should developer aim readability opening first?

oftentimes developer faced choice between twin illusory ways solve problem -- vernacular readable, another reduction intuitive, nonetheless competence perform better. example, c-based languages, there twin ways greaten array 2:

int simplemultiplyby2(int x)
{
    relapse x * 2; 
}

and

int fastmultiplyby2(int x)
{
    relapse x << 1;
}

the initial chronicle easier collect adult both technical non-technical readers, nonetheless second competence perform better, given bit changeable easier operation multiplication. (for now, let's assume compiler's optimizer detect optimize it, nonetheless also consideration).

as developer, improved an initial attempt?