[GHC] #12737: T12227 is failing on ghc-8.0

[GHC]

#12737: T12227 is failing on ghc-8.0
-------------------------------------+-------------------------------------
        Reporter:  ezyang            |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.0.2
       Component:  Visual Haskell    |              Version:  8.0.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Runtime           |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by bgamari):

 According to ticky, it looks like the primary differences between `master`
 (namely 2cb8cc26df6af431d30b6964710ea2d859ca2bcd) and `ghc-8.0` (namely
 a32221830e478bb7c282ff325d9f62cc16af40da, which is admittedly quite far
 removed chronologically from the cherry-picked commit) are indeed in
 `Pretty`,
 {{{
 | Change        | alloc A   | alloc B    | name
 |
 |---------------|-----------|------------|------------------------------------------------------------------|
 | +3474432240.0 | 262333536 | 3736765776 | beside (ghc:Pretty)
 |
 | +951367008.0  | 221431440 | 1172798448 | $waboveNest (ghc:Pretty)
 |
 | +140163848.0  | 91135776  | 231299624  |  (ghc:Coercion.coercionKind_go)
 |
 | +118356184.0  | 63778576  | 182134760  | $wsplitAtList (ghc:Util.)
 |
 | +111367360.0  | 640       | 111368000  | $w$cput_6 (ghc:Binary.)
 |
 | +94517880.0   | 18616520  | 113134400  | $wunpack (ghc:Encoding)
 |
 | +85860960.0   | 13610200  | 99471160   | $windent (ghc:Pretty)
 |
 | +45853128.0   | 13206856  | 59059984   | $s$wget1 (ghc:Pretty)
 |
 | +31953400.0   | 8224616   | 40178016   | $wsep1 (ghc:Pretty.)
 |
 | +29843944.0   | 8127648   | 37971592   | $wpprName (ghc:Name.)
 |
 | +29057288.0   | 20964736  | 50022024   | $wsubstTyWith (ghc:TyCoRep.)
 |
 | +22840864.0   | 11732016  | 34572880   | $wtyCoFVsOfType (ghc:TyCoRep.)
 |
 | +22640112.0   | 17493648  | 40133760   |
 (ghc:TyCon.expandSynTyCon_maybe)                                |
 | +22354288.0   | 5551864   | 27906152   | $wlay2 (ghc:Pretty)
 |
 | +19673016.0   | 14129160  | 33802176   |  (ghc:Unify.liftCoMatch)
 |
 | +16728760.0   | 9231400   | 25960160   |  (ghc:Unify.ty_co_match)
 |
 | +15683720.0   | 9053800   | 24737520   | $wcoercionKindRole
 (ghc:Coercion.)                               |
 | +15627024.0   | 3566736   | 19193760   |
 (ghc:IfaceType.toIfaceTcArgs_go)                                |
 | +15499856.0   | 3545152   | 19045008   | $wget (ghc:Pretty)
 |
 | +15113200.0   | 5327048   | 20440248   |  (ghc:IfaceType.toIfaceType)
 |
 | +14813696.0   | 3417088   | 18230784   | $wppr_iface_tc_app
 (ghc:IfaceType)                               |
 | +14507168.0   | 2747264   | 17254432   |  (ghc:Name.pprModulePrefix)
 |
 | +13158528.0   | 2774064   | 15932592   | $wxs1 (ghc:Pretty)
 |
 | +12767416.0   | 5934000   | 18701416   |  (ghc:OptCoercion.opt_co4)
 |
 | +11420416.0   | 2612848   | 14033264   | $wlay1 (ghc:Pretty)
 |
 | +11400448.0   | 7529920   | 18930368   | $ssubst_ty
 (ghc:TyCoRep.composeTCvSubst_)                        |
 | +10744600.0   | 79480     | 10824080   | $w$cput_7 (ghc:IfaceType.)
 |
 | +10555272.0   | 3780088   | 14335360   |  (ghc:IfaceType.toIfaceTcArgs)
 |
 | +10380952.0   | 6663952   | 17044904   | isAxiom_maybe (ghc:OptCoercion)
 |
 ...
 }}}

 Working on why this is the case will require some more effort.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12737#comment:5>
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