[GHC] #12620: Allow the user to prevent floating and CSE

[GHC]

#12620: Allow the user to prevent floating and CSE
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        Reporter:  nomeata           |                Owner:
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #9520, #8457      |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by tomjaguarpaw):

 Edsko, it seems to me that the problem that you mention here is quite easy
 to avoid.

 {{{#!hs
 main :: IO ()
 main = retry $ return () >>= \_ -> ni_mapM_ print [1..1000000]
 }}}

 is sufficient, unless I am very much mistaken.  With such a construction
 the list is allocated afresh for each invocation of the `IO` action.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12620#comment:12>
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