I wanted to add just a short comment - while byroot is quite possibly correct in regards to most users
using pre-packaged binaries (probably), there are also folks (like me, and others) who compile ruby
from source. These could benefit from significant speed improvement, e. g. via a configure switch
for building (such as --enable-simd and/or --enable-simd-optimizations and/or --optimizations=LIST).
So perhaps the primary issue is about code maintainability/complexity as such. If only we could write
ruby in ... ruby, then ugly #ifdef macros may not have to be used. :)