[Bug middle-end/50481] builtin to reverse the bit order

[hoganmeier at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=50481

--- Comment #4 from krux <hoganmeier at gmail dot com> ---
+1
The builtins already produce better code than a generic bitreverse
implementation:
https://godbolt.org/z/Um2Tit

But using special hardware instructions automatically is even more important
imho.