Am Mittwoch 03 Februar 2010 16:44:31 schrieb Serge D. Mechveliani:
> Dear GHC team,
>
> It looks like ghc-6.12.1 reports erroneous time profiling --
> when the Main module of the project is made under -O.
>
> This is for ghc-6.12.1 made from source for Debian Linux and
> i386-like.
>
> Main.main calls for Complete.complete, `complete' calls for
> eLoop inside its source.
> eLoop must take almost all the time.
> My whole user library is made under -O -prof, and
> --enable-library-profiling.
> Main is compiled by
> ghc $dmCpOpt -prof --make Main
> and run by ./Main +RTS -M400m -pT -RTS
> For this key, the profiling report Main.prof looks natural and shows
> eLoop -- 97%.
>
> But for ghc $dmCpOpt -O -prof --make Make,
>
> it shows a different thing: zero for eLoop and 99% for `main'.
Could be that eLoop is inlined with -O.
Try
ghc $dmCpOpt -O -prof -auto-all --make
That should show eLoop (if that's a top-level declaration, otherwise you'd
have to insert a pragma {-# SCC "eLoop" #-} manually).
>
> How could this additional -O mislead the compiler?
> Also, as I recall, -O is still by default -- ?
No, default is "comile as fast as possible", no optimisations (-O0).
>
> Could you explain, please?
>
> Regards,
>
> -----------------
> Serge Mechveliani
> mech...@botik.ru
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