[GHC] #12227: regression: out of memory with -O2 -ddump-hi on a complex INLINE function

[GHC]

#12227: regression: out of memory with -O2 -ddump-hi on a complex INLINE function
-------------------------------------+-------------------------------------
        Reporter:  j6carey           |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.1
  (CodeGen)                          |
      Resolution:                    |             Keywords:
Operating System:  Linux             |         Architecture:  x86_64
                                     |  (amd64)
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by simonpj):

 I've learned a bit about this example.

 1. It builds big, deeply-nested coercions.

 2. The actual memory exhaustion comes from the pretty printer. Here's a
 dump from `-ticky` of GHC itself, with the `-ddump-hi` on:
 {{{
     Entries      Alloc    Alloc'd  Non-void Arguments      STG Name
 --------------------------------------------------------------------------------
    24320676 1066014032          0   4 MEiM                 $waboveNest{v
 rb81} (ghc-8.1:Pretty) (fun)
    19400250  621778256          0   3 MEM                  beside{v r16q}
 (ghc-8.1:Pretty) (fun)
     2773145  143762232          0   4 EMiL
 ghc-8.1:Pretty.$wsep1{v rb7d} (fun)
     3466978  117540632          0   2 >L
 base-4.9.0.0:GHC.Base.map{v 01X} (fun)
     4143110  114461032          0   1 M                    oneLiner{v
 r16K} (ghc-8.1:Pretty) (fun)
     1939310   97813720          0   1 M
 ghc-8.1:Coercion.coercionKind_go{v rrbv} (fun)
     1475028   66514184          0   3 i.M
 containers-0.5.7.1 at containers-0.5.7.1:Data.IntMap.Base.$winsert{v rnBj}
 (fun)
      902398   65925152          0   2 LL
 ghc-8.1:Util.$wsplitAtList{v rhOj} (fun)
 }}}
   So clearly the pretty printer is behaving very badly when given deeply
 nested things to print.

 3. Aside from that, a tremendous amount of time is spent in
 `coercionKind`.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12227#comment:2>
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