-march=native will still give you better performance. It's not just about the instruction set, but also heuristics taking into account cache size, latencies, to

-march=native will still give you better performance. It's not just about the instruction set, but also heuristics taking into account cache size, latencies, topology and other things. Intel for example has this quirk that aligning functions (and other jump targets) at 32 byte boundaries speeds up funct8 calls and jumps. I haven't tested it but I suspect you'd gain more from -mtune=native with the generic x86_64 target than -march=native. Some loops that can be autovectorized with AVX instructions will probably be faster though. But cache size especially is important for deciding if some optimization is beneficial or just leads to stalls due to thrashing.