[GHC] #15652: SerializedCompact has a [(Ptr a, Word)] instead of a custom datatype

18 Sep 2018

      #15652: SerializedCompact has a [(Ptr a, Word)] instead of a custom datatype
-------------------------------------+-------------------------------------
           Reporter:  chessai        |             Owner:  ezyang
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:  8.8.1
          Component:                 |           Version:  8.4.3
  libraries/compact                  |
           Keywords:  ghc-compact,   |  Operating System:  Unknown/Multiple
  compact regions                    |   Type of failure:  Runtime
       Architecture:  aarch64        |  performance bug
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 {{{#!hs
 data SerializedCompact a = SerializedCompact
   { serializedCompactBlockList :: [(Ptr a, Word)]
   , serializedCompactRoot :: Ptr a
   }
 }}}

 I'm not sure why the first member of {{{SerializedCompact}}} isn't
 something like

 {{{#!hs
 data CompactBlock a = CompactBlock {-# UNPACK #-} (Ptr a) {-# UNPACK #-}
 Word
 }}}

 so the {{{Ptr}}} can unpack into the constructor, which isn't possible
 with {{{(,)}}}. {{{SerializedCompact}}} would then look like

 {{{#!hs
 data SerializedCompact a = SerializedCompact
   { serializedCompactBlockList :: [CompactBlock a]
   , serializedCompactRoot :: Ptr a
   }
 }}}

-- 
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15652
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