[PATCH] [AArch64] Generate tbz/tbnz when comparing against zero.

[Chad Rosier]

>>! In D4440#12, @mcrosier wrote:
> The performance numbers are slightly better, but still less than noise.  All, please take a look.

To be clear, the numbers are slightly better relative to the ADD/SUB only combine.  Overall, we still see a large improvement in eembc/OAv2.

http://reviews.llvm.org/D4440