[GHC] #4801: Typechecker performance regression 6.12 -> 7.0.1

[GHC]

#4801: Typechecker performance regression 6.12 -> 7.0.1
----------------------------------------+-----------------------------------
    Reporter:  simonmar                 |        Owner:  simonpj     
        Type:  bug                      |       Status:  new         
    Priority:  high                     |    Milestone:  7.0.2       
   Component:  Compiler (Type checker)  |      Version:  7.0.1       
    Keywords:                           |     Testcase:              
   Blockedby:                           |   Difficulty:              
          Os:  Unknown/Multiple         |     Blocking:              
Architecture:  Unknown/Multiple         |      Failure:  None/Unknown
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Changes (by simonmar):

  * owner:  => simonpj


Comment:

 Latest results:

 6.12.3:
 {{{
    1,411,847,696 bytes allocated in the heap
   Total time    4.56s  (  5.31s elapsed)
 }}}
 HEAD (20101221):
 {{{
    8,229,161,760 bytes allocated in the heap
  Total time    6.30s  (  6.78s elapsed)
 }}}

 So the immediate problem has been fixed, although the compiler is still
 allocating about 6 times as much memory as 6.12.3 on this example.
 Ordinary profiling would probably nail the culprit of that.

 We need to merge whatever patch(es) fixed the main problem into the 7.0.2
 branch.  Simon - which were they?

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4801#comment:3>
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