[GHC] #5623: GHC 7.2.1 Performance Regression: Vector

[GHC]

#5623: GHC 7.2.1 Performance Regression: Vector
---------------------------------+------------------------------------------
    Reporter:  dterei            |       Owner:  simonpj                
        Type:  bug               |      Status:  new                    
    Priority:  high              |   Milestone:  7.4.2                  
   Component:  Compiler          |     Version:  7.3                    
    Keywords:                    |          Os:  Unknown/Multiple       
Architecture:  Unknown/Multiple  |     Failure:  Runtime performance bug
  Difficulty:                    |    Testcase:                         
   Blockedby:                    |    Blocking:                         
     Related:                    |  
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Comment(by simonpj@…):

 commit 2112f43c466935818a371c53c706608cfa069d01
 {{{
 Author: Simon Peyton Jones <simonpj at microsoft.com>
 Date:   Wed May 9 11:06:44 2012 +0100

     Be a little less aggressive about inlining (fixes Trac #5623)

     When inlining, we are making a copy of the expression, so we have to
     be careful about duplicating work.  Previously we were using
     exprIsCheap for that, but it is willing to duplicate a cheap primop --
     and that is terribly bad if it happens inside some inner array loop
     (Trac #5623).  So now we use a new function exprIsWorkFree.  Even
     then there is some wiggle room:
        see Note [exprIsWorkFree] in CoreUtils

     This commit does make wheel-sieve1 allocate a lot more, but we decided
     that's just tough; it's more important for inlining to be robust
     about not duplicating work.

  compiler/coreSyn/CoreSyn.lhs    |   12 ++++----
  compiler/coreSyn/CoreUnfold.lhs |   60
 ++++++++++++++++++------------------
  compiler/coreSyn/CoreUtils.lhs  |   64
 ++++++++++++++++++++++++++++++++++++++-
  compiler/coreSyn/PprCore.lhs    |    4 +-
  4 files changed, 101 insertions(+), 39 deletions(-)
 }}}

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5623#comment:13>
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