Starting about now, after a period of testing, Google is switching over to a mobile-first search index. This means that search results will be based on the content seen on the mobile version of your website even if there is more content on the desktop version, and depending on how you are supporting mobile browsing, that could be a problem.
If you are using Responsive design, with a single, smart template set then you should be OK as there’s only one source of content to index. If you have a multi-template solution, but there is largely parity of content and consistency of canonical URLs between both, then you are OK too. If you don’t really have a mobile specific experience and just serve your desktop website and hope for the best, well at least this is the version that will get indexed but you may suffer some penalty in your search ranking for not being mobile friendly.
But if you’re one of the lazy organisations that half-assed their mobile website using UsableNet or NetBiscuits or some other awful page scraping based solution that frankensteins a mobile site together out of page fragments and cookie cutter templates, then I’m afraid you’re completely fucked. The combination of URL redirects, bad URLs, bad HTML, bad code, and missing content found with these archaic stop-gap solutions is going to completely screw over your search rankings. Your only hope is to turn them off immediately (you should, they’re killing your conversion on mobile anyway) because while Google’s bots could be pointed at your desktop content, they also crawl using generic browser identifications to make sure you’re not serving one set of content to the crawlers and another to visitors, so you will get further penalised if you keep using UsableNet’s terrible solution.