Comment by wtallis

ffmpeg is a bad example, because it's the kind of project that has lots of infrastructure around incorporating hand-optimized routines with inline assembly or SIMD intrinsics, and runtime detection to dispatch to different optimized code paths. That's not something you can get for free on any C/C++ code base; function multiversioning needs to be explicitly configured per function. By contrast, simply compiling with a newer instruction set permits the compiler's autovectorization use newer instructions whenever and wherever it finds an opportunity.