#1168: Optimisation sometimes decreases sharing in IO code
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Reporter: simonmar | Owner:
Type: bug | Status: new
Priority: normal | Milestone: _|_
Component: Compiler | Version: 6.6
Severity: normal | Resolution:
Keywords: | Difficulty: Unknown
Testcase: nofib/spectral/calendar | Architecture: Unknown
Os: Unknown |
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Comment (by simonpj):
I agree that the current behaviour sometimes bites badly, as it did for
you here. Trouble is, removing the hack has (or used to have) a
significant negative effect on performance of lots of programs.
Still, I think that there are various other possibilities to try. For
example, compiling the I/O libraries (only) with the state-hack on, and
with it off by default elsewhere, might gather most of the benefits
without the costs. Or restricting it to top level functions. Or
something like that.
It needs someone who's willing to do some measurements and try variations.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/1168#comment:8>
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