[ForkMeOnTinder]

It's described one paragraph earlier.

> I’ve written previously about a processor validation technique called Oracle Serialization that we’ve been using. The idea is to generate two forms of the same randomly generated program and verify their final state is identical.

[1f60c]

Sounds like the real story should be that Google solved the halting problem. :-P

[kadoban]

You're free to solve the halting problem for restricted sets of programs, that doesn't break any rules of the universe.

They also could be just discarding any where it runs for longer than X time, or a bunch of other possibilities.

[tgv]

They might be generating programs that they know will halt. Like: applications with finite loops and such. There are not enough details.