[GHC] #11195: New pattern-match check can be non-performant

[GHC]

#11195: New pattern-match check can be non-performant
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        Reporter:  goldfire          |                Owner:  goldfire
            Type:  bug               |               Status:  new
        Priority:  highest           |            Milestone:  8.0.1
       Component:  Compiler          |              Version:  7.11
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  crash                              |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by bgamari):

 {{{
 $ inplace/bin/ghc-stage2 Test.hs -package ghc -O +RTS -s
 [1 of 1] Compiling Test             ( Test.hs, Test.o )
   22,902,711,336 bytes allocated in the heap
   33,446,941,712 bytes copied during GC
    2,960,993,984 bytes maximum residency (21 sample(s))
       15,073,104 bytes maximum slop
             7835 MB total memory in use (0 MB lost due to fragmentation)

                                      Tot time (elapsed)  Avg pause  Max
 pause
   Gen  0       530 colls,     0 par   16.236s  61.556s     0.1161s
 29.5767s
   Gen  1        21 colls,     0 par    8.853s  69.183s     3.2944s
 61.3812s

   TASKS: 4 (1 bound, 3 peak workers (3 total), using -N1)

   SPARKS: 0 (0 converted, 0 overflowed, 0 dud, 0 GC'd, 0 fizzled)

   INIT    time    0.001s  (  0.001s elapsed)
   MUT     time    6.645s  ( 60.820s elapsed)
   GC      time   25.089s  (130.739s elapsed)
   EXIT    time    0.251s  (  1.432s elapsed)
   Total   time   31.996s  (192.991s elapsed)

   Alloc rate    3,446,736,733 bytes per MUT second

   Productivity  21.6% of total user, 3.6% of total elapsed

 gc_alloc_block_sync: 0
 whitehole_spin: 0
 gen[0].sync: 0
 gen[1].sync: 0
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11195#comment:3>
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