[GHC] #12900: Common up identical info tables

[GHC]

#12900: Common up identical info tables
-------------------------------------+-------------------------------------
           Reporter:  dobenour       |             Owner:
               Type:  feature        |            Status:  new
  request                            |
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.0.1
           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:
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 Consider

 {{{#!hs
 data Bool' = No | Yes
 }}}

 It is clear that this is identical to `Bool` at runtime, and so GHC should
 be able to reuse `Bool`'s code.  The same holds for all other pairs of
 isomorphic data types.

 I think that a **massive** space savings could be achieved this way.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12900>
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