Not like Ubuntu works very well on old hardware but hopefully O2 support will still be there. Many people need it.
-O2 vs -O3 adds
-fgcse-after-reload -fipa-cp-clone -floop-interchange -floop-unroll-and-jam -fpeel-loops -fpredictive-commoning -fsplit-loops -fsplit-paths -ftree-loop-distribution -ftree-partial-pre -funswitch-loops -fvect-cost-model=dynamic -fversion-loops-for-strides
I don’t think any of these optimizations require more modern hardware?
Right. GCC -f optimizations are basically like “how hard are we going to try to be clever” and are, I believe, orthogonal to the actual instructions used. Machine dependent args start with -m, like -march or -mavx etc.
How do they avoid the subsequent bugs O3 tends to produce?
op-ti-mize [verb (trans.)]* … (gcc) to modify executable code so that it fails more quickly.
Gentoo users in shambles
