[GHC] #955: more object-code blow-up in ghc-6.8.3 vs. ghc-6.4.2 (both with optimization)

[GHC]

#955: more object-code blow-up in ghc-6.8.3 vs. ghc-6.4.2 (both with
optimization)
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 Reporter:  maeder at tzi.de             |          Owner:          
     Type:  run-time performance bug  |         Status:  closed  
 Priority:  high                      |      Milestone:  6.10.1  
Component:  Compiler                  |        Version:  6.8.3   
 Severity:  normal                    |     Resolution:  fixed   
 Keywords:  object-code blow-up       |     Difficulty:  Unknown 
 Testcase:                            |   Architecture:  Multiple
       Os:  Multiple                  |  
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Comment (by simonpj):

 Just to say that I've now fixed those odd WARNINGs too.
 {{{
 Wed Sep 17 17:29:10 BST 2008  simonpj at microsoft.com
   * Fix nasty infelicity: do not short-cut empty substitution in the
 simplifier

   I was perplexed about why an arity-related WARN was tripping. It took
   me _day_ (sigh) to find that it was because SimplEnv.substExpr was
 taking
   a short cut when the substitution was empty, thereby not subsituting for
   Ids in scope, which must be done (CoreSubst Note [Extending the Subst]).

   The fix is a matter of deleting the "optimisation".  Same with
   CoreSubst.substSpec, although I don't know if that actually caused a
   problem.
 }}}
 Great to have this ticket closed at last.

 Simon

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/955#comment:22>
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