More conservative SCC tagging for Haskell libraries #45676
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all-functions
corresponds to-fprof-auto
which places an SCC on every binding. It is well known that SCCs hinder GHC from doing its optimization magic and really slows down profiled code to a point where the profiling reports are completely skewed towards things that were completely optimized away in production settings. Concretely this shows up with things like lenses which do not carry runtime overhead when properly simplified.exported-functions
corresponds to GHCs-fprof-auto-exported
which doesn't put SCCs onINLINE
d code and in turn doesn't influence simplification of this basic but important stuff.This is even more important as per GHC-8.4 SCCs are also put into unfoldings which make you pay for it at each call site.
Motivation for this change
Things done
sandbox
innix.conf
on non-NixOS)nix-shell -p nox --run "nox-review wip"
./result/bin/
)nix path-info -S
before and after)