> > > When a function doesn't contain calls to > > > unknown functions we can be a bit more lenient: we can make it so that > > > GCC simply doesn't touch xmm8-15 at all, then no save/restore is > > > necessary.
One may also take into account that first 8 registers are cheaper to encode than the later 8, so perhaps we may want to choose range that contains both. Honza