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| author | Simon Peyton Jones <simonpj@microsoft.com> | 2016-10-14 12:05:46 +0100 |
|---|---|---|
| committer | Simon Peyton Jones <simonpj@microsoft.com> | 2016-10-17 08:41:19 +0100 |
| commit | 692c8df03969ee6a0de5158f05907b16689945d0 (patch) | |
| tree | f0609951e365407e009520c15f4679633b722554 /compiler/stranal/WorkWrap.hs | |
| parent | 82b54fcf815ccd80be8887401dd69ab7a488386e (diff) | |
| download | haskell-692c8df03969ee6a0de5158f05907b16689945d0.tar.gz | |
Fix shadowing in mkWwBodies
This bug, exposed by Trac #12562 was very obscure, and has been
lurking for a long time. What happened was that, in the
worker/wrapper split
a tyvar binder for a worker function
accidentally shadowed an in-scope term variable
that was mentioned in the body of the function
It's jolly hard to provoke, so I have not even attempted to make
a test case. There's a Note [Freshen WW arguments] to explain.
Interestingly, fixing the bug (which meant fresher type variables)
revealed a second lurking bug: I'd failed to apply the substitution to
the coercion in the second last case of mkWWArgs, which introduces a
Cast.
Diffstat (limited to 'compiler/stranal/WorkWrap.hs')
| -rw-r--r-- | compiler/stranal/WorkWrap.hs | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/compiler/stranal/WorkWrap.hs b/compiler/stranal/WorkWrap.hs index 80d966b392..9acc461c20 100644 --- a/compiler/stranal/WorkWrap.hs +++ b/compiler/stranal/WorkWrap.hs @@ -10,6 +10,7 @@ module WorkWrap ( wwTopBinds ) where import CoreSyn import CoreUnfold ( certainlyWillInline, mkWwInlineRule, mkWorkerUnfolding ) import CoreUtils ( exprType, exprIsHNF ) +import CoreFVs ( exprFreeVars ) import Var import Id import IdInfo @@ -365,7 +366,7 @@ splitFun :: DynFlags -> FamInstEnvs -> Id -> IdInfo -> [Demand] -> DmdResult -> splitFun dflags fam_envs fn_id fn_info wrap_dmds res_info rhs = WARN( not (wrap_dmds `lengthIs` arity), ppr fn_id <+> (ppr arity $$ ppr wrap_dmds $$ ppr res_info) ) do -- The arity should match the signature - stuff <- mkWwBodies dflags fam_envs fun_ty wrap_dmds res_info + stuff <- mkWwBodies dflags fam_envs rhs_fvs fun_ty wrap_dmds res_info case stuff of Just (work_demands, wrap_fn, work_fn) -> do work_uniq <- getUniqueM @@ -432,6 +433,7 @@ splitFun dflags fam_envs fn_id fn_info wrap_dmds res_info rhs Nothing -> return [(fn_id, rhs)] where + rhs_fvs = exprFreeVars rhs fun_ty = idType fn_id inl_prag = inlinePragInfo fn_info rule_match_info = inlinePragmaRuleMatchInfo inl_prag |