Rethink Inlining?
ref https://github.com/pandas-dev/pandas/pull/33886#discussion_r418637034

We use the `inline` keyword pretty liberally in our Cython extensions, with the thought that this probably improves performance. However, running GCC with `-Winline` as a flag produces a ton of warnings that we aren't actually inlining things. Some of these _may_ even do more harm than good (just a hunch, I have no expertise with inline)

I've attached warnings from a clean build on master. Not sure all of these are necessarily even just from pandas but may be worth a look for anyone interested

[warnings.log.zip](https://github.com/pandas-dev/pandas/files/4565443/warnings.log.zip)
