1. Interest in low‑level optimization
"I really envy programmers who are so skilled at this kind of low‑level optimization." — jdw64
2. Using idiomatic code to help compilers
"I'm not sure it's a 'technique' but the general insight worth taking away from this is that compiler authors often write optimizers to recognize specific patterns so writing your code in a more idiomatic form increases the odds an optimizer will be able to optimize it." — khuey
3. Importance of hardware architecture knowledge
"You could read compiler books, but I would actually recommend reading about CPUs and computer architecture directly." — tux3