> Then, when it fails [...], you can either poke it in the right ways or change your program in the right ways so that it works for you again. This is a horrible way to program; it’s all alchemy and guesswork and you need to become deeply specialized about the nuances of a single [...] implementation

In that post, the blanks reference a compiler’s autovectorizer. But you know what they could also reference? An aggresively opaque and undocumented, very complex CPU or GPU microarchitecture. (Cf. https://purplesyringa.moe/blog/why-performance-optimization-....)