[llvm] r212100 - [PeepholeOptimizer] Advanced rewriting of copies to avoid cross register banks

[Amara Emerson]

Hi Quentin,

> +    // However, some code could theoritically generates a single
Typo s/theoritically/theoretically, no big deal.

Sorry, looked at this earlier but didn't have time to reply. The rest
of the changes look OK from what I can tell.

Cheers,
Amara