[GHC] #13340: Core top-level bindings no longer deduplicated

[GHC]

#13340: Core top-level bindings no longer deduplicated
-------------------------------------+-------------------------------------
           Reporter:  rwbarton       |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  high           |         Milestone:  8.2.1
          Component:  Compiler       |           Version:  8.1
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 This module
 {{{#!hs
 module Two where

 f :: Int -> Int
 f n = n + 1 + 1

 g :: Int -> Int
 g n = n + 1 + 1
 }}}
 used to (in 8.0) optimize to a definition of `g` plus `f = g`. The Common
 sub-expression phase noticed `f` and `g` were equal.

 That doesn't happen any more in HEAD and we end up with two copies of the
 code. The Common sub-expression pass apparently still runs, it just
 doesn't succeed in removing one of the bindings.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13340>
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