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| author | Simon Peyton Jones <simonpj@microsoft.com> | 2014-06-11 19:53:06 +0100 |
|---|---|---|
| committer | Simon Peyton Jones <simonpj@microsoft.com> | 2014-06-11 20:56:38 +0100 |
| commit | 7d9feb264a4fc3c15d1e5f88f2e7a04202ed9743 (patch) | |
| tree | 5005a67f94c508094c0aeb7779fc8a015d96b913 /compiler/stranal | |
| parent | c8295c0bd58485db5572d3c35427d321bdf1b7d0 (diff) | |
| download | haskell-7d9feb264a4fc3c15d1e5f88f2e7a04202ed9743.tar.gz | |
Fix a serious, but rare, strictness analyser bug (Trac #9128)
In a special case for trivial RHSs (see DmdAnal.unpackTrivial),
I'd forgotten to include a demand for the RHS itself.
See Note [Remember to demand the function itself].
Thanks to David Terei for guiding me to the bug,
at PLDI in Edinburgh.
Diffstat (limited to 'compiler/stranal')
| -rw-r--r-- | compiler/stranal/DmdAnal.lhs | 11 |
1 files changed, 10 insertions, 1 deletions
diff --git a/compiler/stranal/DmdAnal.lhs b/compiler/stranal/DmdAnal.lhs index bd7b5c33bf..f240be4cd7 100644 --- a/compiler/stranal/DmdAnal.lhs +++ b/compiler/stranal/DmdAnal.lhs @@ -596,7 +596,16 @@ dmdAnalRhs :: TopLevelFlag dmdAnalRhs top_lvl rec_flag env id rhs | Just fn <- unpackTrivial rhs -- See Note [Demand analysis for trivial right-hand sides] , let fn_str = getStrictness env fn - = (fn_str, emptyDmdEnv, set_idStrictness env id fn_str, rhs) + fn_fv | isLocalId fn = unitVarEnv fn topDmd + | otherwise = emptyDmdEnv + -- Note [Remember to demand the function itself] + -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + -- fn_fv: don't forget to produce a demand for fn itself + -- Lacking this caused Trac #9128 + -- The demand is very conservative (topDmd), but that doesn't + -- matter; trivial bindings are usually inlined, so it only + -- kicks in for top-level bindings and NOINLINE bindings + = (fn_str, fn_fv, set_idStrictness env id fn_str, rhs) | otherwise = (sig_ty, lazy_fv, id', mkLams bndrs' body') |