alt Hacker Newsxor clears the carry as well? In fact, looks like xor and sub affect the same set of flags!
xor:
> The OF and CF flags are cleared; the SF, ZF, and PF flags are set according to the result. The state of the AF flag is undefined.
sub:
> The OF, SF, ZF, AF, PF, and CF flags are set according to the result.
(I don't have an x64 system handy, but hopefully the reference manual can be trusted. I dimly remembered this, or something like it, tripping me up after coming from programming for the 6502.)
This is a good thing since the pipeline now doesn’t have to track the state of the flags since they all got zero’d.