[GHC] #15488: GHC takes up huge amount of memory when compiling accelerate 1.2.0

[GHC]

#15488: GHC takes up huge amount of memory when compiling accelerate 1.2.0
-------------------------------------+-------------------------------------
        Reporter:  noah              |                Owner:  tdammers
            Type:  bug               |               Status:  new
        Priority:  high              |            Milestone:  8.6.1
       Component:  Compiler          |              Version:  8.4.3
      Resolution:                    |             Keywords:
                                     |  accelerate,memory,compile
Operating System:  Linux             |         Architecture:  x86_64
                                     |  (amd64)
 Type of failure:  Compile-time      |            Test Case:  accelerate
  performance bug                    |  1.2.0
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by tdammers):

 So here's an interesting candidate:

 {{{
 -- RHS size: {terms: 27, types: 44, coercions: 4, joins: 0/0}
 encodeConst
 encodeConst
   = \ @ t_areG ds_dtLe ds_dtLf ->
       case ds_dtLe of {
         TypeRunit co_areI ->
           case ds_dtLf `cast` <Co:2> of { () -> mempty $fMonoidBuilder };
         TypeRscalar t_aq5y -> encodeScalarConst t_aq5y ds_dtLf;
         TypeRpair @ a1_areO @ b_areP co_areQ ta_aq5A tb_aq5B ->
           case ds_dtLf `cast` <Co:2> of { (a_aq5C, b_aq5D) ->
           <>
             $fSemigroupBuilder
             (encodeConst ta_aq5A a_aq5C)
             (encodeConst tb_aq5B b_aq5D)
           }
       }
 end Rec }
 }}}

 Perfectly benign, but after simplification, we get:

 {{{
 -- RHS size: {terms: 81,945,
               types: 43,626,
               coercions: 10,191,
               joins: 0/2,111}
 encodeConst1_r4XSg
 encodeConst1_r4XSg
 ...
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15488#comment:8>
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