[GHC] #10148: Optimization causes repeated computation

[GHC]

#10148: Optimization causes repeated computation
-------------------------------------+-------------------------------------
        Reporter:  akio              |                   Owner:
            Type:  bug               |                  Status:  new
        Priority:  normal            |               Milestone:
       Component:  Compiler          |                 Version:  7.10.1-rc1
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
 Type of failure:  Runtime           |  Unknown/Multiple
  performance bug                    |               Test Case:
      Blocked By:                    |                Blocking:
 Related Tickets:                    |  Differential Revisions:
-------------------------------------+-------------------------------------

Comment (by nomeata):

 Thanks. It still relies on the bang in `gstep`.

 Also funny: Replacing `data Array' a = ALeaf a` by `newtype Array' a =
 ALeaf a` removes
 ''some'' repeated computation, but ''not all''. I’m curious about what
 causes this :-)

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10148#comment:3>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler