The default type legalization generates multiple compares to check
the overflow condition. But on X86 we can just emit an add/sub with
flags output followed by a adc/sbb and check the overflow flag.
I don't think the bug mentioned in the comment I removed applies
anymore. And if it is an issue I don't see why it wouldn't be
an issue with the expanded code we already get for UADDO/USUBO.
clang-format not found in user's PATH; not linting file.