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  • Glasgow Haskell CompilerGlasgow Haskell Compiler
  • GHCGHC
  • Issues
  • #5654
Closed
Open
Issue created Nov 23, 2011 by Simon Marlow@simonmarDeveloper

Profiling semantics bug

GHC doesn't quite implement the new cost-centre stack semantics correctly. e.g.

{-# NOINLINE f #-}
f :: Int -> Int
f = {-# SCC f #-} g

{-# NOINLINE g #-}
g :: Int -> Int
g x = {-# SCC g #-} x + 1

main = print (f 3)

What we want is

 CAF        Main                    106           0    0.0    0.7     0.0   21.7
  f         Main                    201           1    0.0    0.0     0.0    0.0
  main      Main                    200           1    0.0   20.9     0.0   21.0
   f        Main                    202           0    0.0    0.0     0.0    0.1
    g       Main                    203           1    0.0    0.1     0.0    0.1

but we get

 CAF        Main                    106           0    0.0    0.7     0.0   21.6
  f         Main                    201           1    0.0    0.0     0.0    0.0
  main      Main                    200           1    0.0   20.9     0.0   20.9
   g        Main                    202           1    0.0    0.0     0.0    0.0

The original flat CC profiler used to use IND_PERM indirections to handle this kind of thing, but we aren't doing that now.

Trac metadata
Trac field Value
Version 7.2.1
Type Bug
TypeOfFailure OtherFailure
Priority normal
Resolution Unresolved
Component Profiling
Test case
Differential revisions
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Blocking
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