[llvm] r215199 - [AArch64] Add an FP load balancing pass for Cortex-A57

[Tim Northover]

Hi James,

This caused test-failures on Darwin. I've put some kind of fix in
place in r215233. It's ugly, but I think it's correct and couldn't
come up with an obviously cleaner solution off-hand. Feel free to
change it if you can.

Cheers.

Tim.