-O3 also makes build times longer (sometimes significantly), and occasionally th... | Hacker News

Hacker News .hnnew | past | comments | ask | show | jobs | submit

		hmry 43 days ago \| parent \| context \| favorite \| on: Show HN: I built a Cargo-like build tool for C/C++ -O3 also makes build times longer (sometimes significantly), and occasionally the resulting program is actually slightly slower than -O2. IME -O3 should only be used if you have benchmarks that show -O3 actually produces a speedup for your specific codebase.

fyrn_ 43 days ago [–]

This various a lot between compilers. Clang for example treats O3 perf regressions a bugs In many cases at least) and is a bit more reasonable with O3 on. GCC goes full mad max and you don't know what it's going to do.

Guidelines | FAQ | Lists | API | Security | Legal | Apply to YC | Contact