You can't do that kind of low level optimizations on PC. You can do that only on consoles (The Last Of Us according to devs had some very serious optimizations done to get the most out of the PS3, but those optimizations do no translate on the PS 4 version due to the different hardware).
PC game development is very limited. A lot of the work is handled by the API driver, and that isn't something a developer can effect. That's why you get new drivers for better performance in games. Optimizations in driver that the dev couldn't do.
You wanna run your game on 8 or more cores? Sorry, drawcalls can't be executed from more than one core in DirectX and OpenGL on PC. You want full control over memory management? Nope. You want to try an alternative to AFR and SFR? Nope, not going to happen.
DirectX 12 will improve that, but it will also increase the work the devs have to do.