#1547: Arity can decrease with -prof
---------------------------------------+------------------------------------
Reporter: igloo | Owner:
Type: bug | Status: new
Priority: high | Milestone: 6.10 branch
Component: Profiling | Version: 6.6.1
Severity: normal | Resolution:
Keywords: | Difficulty: Unknown
Testcase: stm package/tests/conc052 | Architecture: Unknown
Os: Unknown |
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Changes (by simonpj):
* testcase: => stm package/tests/conc052
* summary: conc052 core lint errors in profc/profasm ways => Arity can
decrease with -prof
* milestone: 6.8 branch => 6.10 branch
Old description:
> The conc052 test (in the stm package) on amd64/Linux is giving core lint
> errors for the profc/profasm ways.
>
> Part of #1546 might be the same problem.
New description:
Something like
{{{
f = \p\q.body
x = scc "foo" f (\y.e)
}}}
shows f having arity 2, and hence x having arity 1. But when we inline f,
we get
{{{
x = scc "foo" let p = \x.e in \q.body
}}}
and the cheap-and-cheerful arity discovery function (`exprArity`) detects
arity of 0, not 1. And then !CoreLint complains about the inconsistency
of arity and strictness info.
This is unpleasant but not actually a problem.
It shows up in the `conc052` test (in the stm package).
Part of #1546 might be the same problem.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/1547#comment:1>
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