[GHC] #10459: -fsimple-tick-factor required

[GHC]

#10459: -fsimple-tick-factor required
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        Reporter:  mikehat           |                   Owner:
            Type:  bug               |                  Status:  new
        Priority:  normal            |               Milestone:
       Component:  Compiler          |                 Version:  7.6.3
      Resolution:                    |                Keywords:  fsimple-
                                     |  tick-factor
Operating System:  Linux             |            Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |               Test Case:
      Blocked By:                    |                Blocking:
 Related Tickets:                    |  Differential Revisions:
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Comment (by thomie):

 Here is the offending code from the SFML package, comment:1:
 {{{#!haskell
 module T10459 where

 data Transform = Transform
     { m00 :: !Float, m10 :: !Float, m20 :: !Float
     , m01 :: !Float, m11 :: !Float, m21 :: !Float
     , m02 :: !Float, m12 :: !Float, m22 :: !Float
     }

 abs_ (Transform a00 a01 a02 a03 a04 a05 a06 a07 a08) =
      (Transform (abs a00) (abs a01) (abs a02) (abs a03)
                 (abs a04) (abs a05) (abs a06) (abs a07) (abs a08))
 }}}

 Fails with 7.8.4 and higher, but not with 7.6.3.
 {{{
 $ ghc-7.8.4 T10459.hs -fsimpl-tick-factor=200 -O -fforce-recomp
 [1 of 1] Compiling T10459           ( T10459.hs, T10459.o )
 ghc: panic! (the 'impossible' happened)
   (GHC version 7.8.4 for x86_64-unknown-linux):
         Simplifier ticks exhausted
     When trying UnfoldingDone $j_s1vT{v} [lid]
     To increase the limit, use -fsimpl-tick-factor=N (default 100)
     If you need to do this, let GHC HQ know, and what factor you needed
     To see detailed counts use -ddump-simpl-stats
     Total ticks: 73282
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10459#comment:2>
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