ghc-7.8-rc2 in -O2 mode eats all stack and RAM on pandoc-, citeproc / highlighting-kate

Michal J. Gajda mjgajda at
Thu Apr 10 06:26:11 UTC 2014

Dear Devs,

On 04/10/2014 09:09 AM, ghc-devs-request at wrote:
> Filed the reproducer as a new ticket:
> [ Looks like highlighting-kate asks to be added to
>   compiler performance benchmarks (are there such ones?)
>   It tends to stress ghc all the time:
> ]
Please consider adding hPDB too, if you want to stress the optimizer.
It shows GHC optimizer at its best, with at least 10-20% improvement in
every major version of
the compiler since 6.12. Unfortunately at cost of very long compile times.
Please let me know if I should submit a driver code for automatic
benchmarks it (it is in hPDB-examples.) Thanks!
>> > SpecConstr is too aggressive: it sometimes blows up the program badly and we have no good
solution.  See Trac #7898, #7068, #7944, #5550, #8836.
And #8960, where GHC runs out of memory. (Only in 7.8.) Should be easy
to reproduce by just `cabal install hPDB`.
>> > I notice that the latter three are actually fixed in 7.8, so worth trying that.  If it
still fails, do add instructions to reproduce to one of the above open
tickets, or make a new one.
>> >
>> > Meanwhile you can use -fno-spec-constr to simply switch it off for
offending modules.  That should get you going. 
  Best regards

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