[GHC] #10491: Regression, simplifier explosion with Accelerate, cannot compile, increasing tick factor is not a workaround

[GHC]

#10491: Regression, simplifier explosion with Accelerate, cannot compile,
increasing tick factor is not a workaround
-------------------------------------+-------------------------------------
        Reporter:  robertce          |                   Owner:
            Type:  bug               |                  Status:  new
        Priority:  highest           |               Milestone:  7.10.2
       Component:  Compiler          |                 Version:  7.10.1
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  performance bug                    |               Test Case:
      Blocked By:                    |                Blocking:
 Related Tickets:                    |  Differential Revisions:
-------------------------------------+-------------------------------------

Comment (by George):

 ghc -V
 The Glorious Glasgow Haskell Compilation System, version 7.10.1.20150612

 It seems that the order of the args determines if it succeeds or not.
 {{{
  time ghc -fno-specialise -fforce-recomp -O2 Slice.hs
 [1 of 1] Compiling Data.Array.Accelerate.CUDA.Array.Slice ( Slice.hs,
 Slice.o )
 ghc: panic! (the 'impossible' happened)
   (GHC version 7.10.1.20150612 for x86_64-apple-darwin):
         Simplifier ticks exhausted
   When trying UnfoldingDone $j_s1FS5
   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: 1668604

 Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug


 real    0m19.542s
 user    0m18.451s
 sys     0m0.901s
 bash-3.2$ time ghc -O2 -fno-specialise -fforce-recomp Slice.hs
 [1 of 1] Compiling Data.Array.Accelerate.CUDA.Array.Slice ( Slice.hs,
 Slice.o )

 real    0m3.299s
 user    0m3.085s
 sys     0m0.158s
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10491#comment:29>
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