Compilation speed regression

[augustss]

Ghc has gotten slower at compiling. Compilation time for our code base in 6.12.4 was 23:40, and with the 7.0.4 it is 29:30. This is a 25% increase in compilation time. Both compilations with the same flags, -O2 being the most important one.

[simonmar]

GHC hasn't got uniformly slower at compiling (we do check when making a release), but sometime what happens is that some crucial bit of code gets inlined where it wasn't before (or vice versa) and that causes knock-on effects.

So to investigate this we'll need more information.

[augustss]

I would think that our compilation is a fairly good benchmark because it is about 200,000 lines of Haskell, so it uses all kinds of features. I can't give you the code, so I'm not sure how to provide more information.

We can let this one rest for now, and we'll check if the regression still exists in 7.2.1.

[igloo]

If you still think there's a problem, please reopen and include some way for us to reproduce the problem.