[Bug ipa/65076] [5 Regression] 16% tramp3d-v4.cpp compile time regression

["hubicka at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65076

--- Comment #54 from Jan Hubicka <hubicka at gcc dot gnu.org> ---
I have full set of firefox talos benchmarks with inline-unit-growth bumped back
to 30 (I did not test default value by accident, but I am running itnow). We
now get back the GCC 4.9 performance on dromaeo_dom/dromaeo_css that was
troubling me most. We also get improvement on tsvgx and the startup time
benchmark (where mainline is already on par with GCC 4.9 after the wrapper
fix).

I am definitely surprised - I originally introduced the relative benefits as a
hack to get around value range limitation in the fixed point badness metric,
but the explanation about many average size functions being better for code
generation that case of some very small and some very big seems reasonable. 
The combined badness metric kind of consider function growth and unit growth to
be both limiting factors as they are.

Given the benchmark results, I think we should go ahead with the change. I will
work out the preferred limits for overall-unit-growth based on firefox
incrementally. Also we need to reconsider FDO metric. It seems that new one
works better for tramp3d and spec, I will re-check how it behaves on firefox.