ghci -fobject-code -O2 doesn't do the same optimisations as ghc --make -O2
From IRC:
I have a module that takes around 10 seconds to compile on ghc --make -O2, but only around 3 seconds on ghci -fobject-code -O2.
bgamari: that is surprising
I've put the -v timing output of the two cases into https://gist.github.com/nh2/e9bc4732111bfe422d8e606c10f8f0ac
I'm comparing the 2 files with meld for spotting differences easily.
Check e.g. Result size of Tidy Core which seems to have 3x as many terms for ghc, and Simplifier [Mymodule] doesn't seem to run in ghci
The first time terms are different is at Desugar, the first time a factor 3 comes in is after Specialize`.
bgamari: wow, it sounds like the simplifier isn't getting run as aggressively in GHCi
I'm running this on Ubuntu 16.04 inside nix (but happens the same way outside nix).
Trac metadata
| Trac field | Value |
|---|---|
| Version | 8.0.1 |
| Type | Bug |
| TypeOfFailure | OtherFailure |
| Priority | normal |
| Resolution | Unresolved |
| Component | Compiler |
| Test case | |
| Differential revisions | |
| BlockedBy | |
| Related | |
| Blocking | |
| CC | nh2 |
| Operating system | |
| Architecture |