Architecture specific («post-compile» time pass) and chained fixups (link time pass) optimisations are orthogonal, and both can take place. Since a) Bitcode IR

Architecture specific («post-compile» time pass) and chained fixups (link time pass) optimisations are orthogonal, and both can take place. Since a) Bitcode IR is, essentially, an object file; b) the destination platform version is known at the post-processing (i.e. download) time, it is possible to also optimise the executable binary format to make us of whatever enhacements are available, too.