This question already has an answer here:
I was browsing through this question and it made me realize a trend: almost all questions which relate to performance improvements are immediately under fire and hotly debated over whether the OP should even bother asking the question. Half of the community will say something like "This doesn't concern you; let the compiler do its job", while the other half rages back, saying, "We can't just ignore performance and hope the optimizer does all the work for us."
The question linked above is a good cross-section of this phenomenon; it has 17 upvotes and 3 close votes as of now.
Hence the question, as there doesn't seem to be a consensus: are these types of questions on-topic or not?
(Also, I know that I need a sample size greater than one to claim that there's a trend, but I don't have time to look up all the other questions I've seen like this at the moment. The one most recently that I remember having similar discussion/debate about was about "the fastest way to tell if two
ints are on the same side of zero" or something.)