#3717: Superfluous seq no eliminated
---------------------------------------------+------------------------------
  Reporter:  rl                              |          Owner:                  
      Type:  bug                             |         Status:  closed          
  Priority:  normal                          |      Milestone:  7.0.2           
 Component:  Compiler                        |        Version:  6.13            
Resolution:  fixed                           |       Keywords:                  
  Testcase:  simplCore/should_compile/T3717  |      Blockedby:                  
Difficulty:                                  |             Os:  Unknown/Multiple
  Blocking:                                  |   Architecture:  Unknown/Multiple
   Failure:  Runtime performance bug         |  
---------------------------------------------+------------------------------
Changes (by simonpj):

  * status:  new => closed
  * resolution:  => fixed


Comment:

 Fixed by
 {{{
 Tue Jan 25 11:05:25 GMT 2011  simo...@microsoft.com
   * Fix Trac #3717 by making exprOkForSpeculation a bit cleverer

   The main change here is to do with dropping redundant seqs.
   See Note [exprOkForSpeculation: case expressions] in CoreUtils.

     M ./compiler/coreSyn/CoreUtils.lhs -5 +14
     M ./compiler/simplCore/Simplify.lhs -36 +47

 Tue Jan 25 11:04:18 GMT 2011  simo...@microsoft.com
   * Improve dataToTag# magic

   dataToTag# is a bit unsatisfactory because it requires
   its argument to be evaluated, and we don't have a good
   way to enforce that. This patch adds some comments, and
   makes exprOkForSpeculation a bit less picky in the case
   of dataToTag# (since the argument may, in fact, not be
   eval'd).

     M ./compiler/coreSyn/CorePrep.lhs -3 +8
     M ./compiler/coreSyn/CoreUtils.lhs +24
 }}}
 No need to merge; putting this in 7.2 is fine.

 Simon

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/3717#comment:5>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler

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