[GHC] #14683: Slow compile times for Happy-generated source
GHC
ghc-devs at haskell.org
Tue Jan 23 13:02:02 UTC 2018
#14683: Slow compile times for Happy-generated source
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Reporter: harpocrates | Owner: (none)
Type: bug | Status: new
Priority: high | Milestone: 8.4.1
Component: Compiler | Version: 8.2.2
Resolution: | Keywords:
Operating System: Unknown/Multiple | Architecture:
Type of failure: Compile-time | Unknown/Multiple
performance bug | Test Case:
Blocked By: | Blocking:
Related Tickets: | Differential Rev(s):
Wiki Page: |
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Comment (by tdammers):
Replying to [comment:12 alexbiehl]:
> Tobias, I saw you mentioning #7258 here.
>
> I ran over `Grammar.hs` with my sampling code from for #14461:
>
> - there are 245 non-toplevel StgRhsClosures
> - the deepest StgRhsClosure is nested 5 levels
> - Of that 245,
> - 168 have 0 free variables
> - 53 have 1 free variables
> - 16 have 2 free variables
> - 6 have 3 free variables
> - 1 has 4 free variables
> - 1 has 7 free variables
> -
> - 206 share 0 free variables with their parent
> - 32 share 1 free variable with their parent
> - 6 share 2 free variables with their parent
> - 1 shares 3 free variables with their parent
>
> I think this is not related to code generation. My timing shows most of
the time is spent before CoreToStg. Codegen is a lot less. Our
pathological cases #7258 had A LOT more (basically around 100
StgRhsClosures sharing around 150 fvs with their parents) free variable
business going on.
Thanks for stepping in, you seem to be much quicker at getting a clearer
picture here than me. Good to know that this isn't the direction to look
in.
--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14683#comment:13>
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