Number parsing: is fallback necessary?

[piotrrzysko]

I've been working on implementing float parsing in simdjson-java, and while researching the topic, I've noticed that simdjson, in some cases, requires fallback to a more accurate multiplication of multiword integers. According to Fast Number Parsing Without Fallback, the fallback is not necessary.

Do I understand correctly that we can remove the fallback? If that's the case, I'd be happy to submit a PR.

[piotrrzysko]

@lemire Apologies for pinging you. I would appreciate your input on this topic. In simdjson-java, I've entirely skipped the fallback: https://github.com/simdjson/simdjson-java/blob/567af8f7b2e025cf7ac3c7f243a1ab8ac58b3f35/src/main/java/org/simdjson/NumberParser.java#L172.

[lemire]

@piotrrzysko You are correct that the multiplication, after loading 128 bits, is exact. PR invited!