Auto merge of #5138 - alexcrichton:small-opt, r=matklad
authorbors <bors@rust-lang.org>
Wed, 7 Mar 2018 00:02:33 +0000 (00:02 +0000)
committerbors <bors@rust-lang.org>
Wed, 7 Mar 2018 00:02:33 +0000 (00:02 +0000)
Some small optimizations

Found an easy hot spot or two when profiling `./x.py build` in rust-lang/rust, although certainly still lots remaining.


Trivial merge