From 90fd2bc78c90147818fe0122eb372afdd5f9dfd0 Mon Sep 17 00:00:00 2001
From: sof <unknown>
Date: Thu, 30 Apr 1998 19:44:49 +0000
Subject: [PATCH] [project @ 1998-04-30 19:44:49 by sof] When floating in, we
have to be careful not to float a specialisation of a binder past a use of
that binder that may later be simplified to use the specialised version that
just floated past (and out of scope.)
Kludgily fix this by including the idSpecVars of a Var in its free
variable set.
---
ghc/compiler/coreSyn/FreeVars.lhs | 26 ++++++++++++++++++--------
1 file changed, 18 insertions(+), 8 deletions(-)
diff --git a/ghc/compiler/coreSyn/FreeVars.lhs b/ghc/compiler/coreSyn/FreeVars.lhs
index a475c3f7a34a..9619f49e2b09 100644
--- a/ghc/compiler/coreSyn/FreeVars.lhs
+++ b/ghc/compiler/coreSyn/FreeVars.lhs
@@ -21,8 +21,9 @@ module FreeVars (
import AnnCoreSyn -- output
import CoreSyn
+import CoreUtils ( idSpecVars )
import Id ( idType, getIdArity, isBottomingId,
- emptyIdSet, unitIdSet, mkIdSet,
+ emptyIdSet, unitIdSet, mkIdSet, unionIdSets,
elementOfIdSet, minusIdSet, unionManyIdSets,
IdSet, Id
)
@@ -36,6 +37,7 @@ import TyVar ( emptyTyVarSet, unitTyVarSet, minusTyVarSet,
import BasicTypes ( Unused )
import UniqSet ( unionUniqSets, addOneToUniqSet )
import Util ( panic, assertPanic )
+
\end{code}
%************************************************************************
@@ -111,6 +113,7 @@ Main public interface:
freeVars :: CoreExpr -> CoreExprWithFVs
freeVars expr = fvExpr noIdCands noTyVarCands expr
+
\end{code}
%************************************************************************
@@ -132,13 +135,18 @@ fvExpr :: IdCands -- In-scope Ids
-> CoreExprWithFVs
fvExpr id_cands tyvar_cands (Var v)
- = (FVInfo (if (v `is_among` id_cands)
- then aFreeId v
- else noFreeIds)
- noFreeTyVars
- leakiness,
- AnnVar v)
+ = (FVInfo fvs noFreeTyVars leakiness, AnnVar v)
where
+ {-
+ ToDo: insert motivating example for why we *need*
+ to include the idSpecVars in the FV list.
+ -}
+ fvs = fvs_v `unionIdSets` mkIdSet (idSpecVars v)
+
+ fvs_v
+ | v `is_among` id_cands = aFreeId v
+ | otherwise = noFreeIds
+
leakiness
| isBottomingId v = lEAK_FREE_BIG -- Hack
| otherwise = case getIdArity v of
@@ -305,9 +313,11 @@ fvExpr id_cands tyvar_cands (Note other_note expr)
-- free vars of the RHS the idSpecVars of the binder,
-- since those are, in truth, free in the definition.
fvRhs id_cands tyvar_cands (bndr,rhs)
- = (FVInfo (fvs `unionIdSets` idSpecVars bndr) ftvs leak, rhs')
+ = (FVInfo fvs' ftvs leak, rhs')
where
(FVInfo fvs ftvs leak, rhs') = fvExpr id_cands tyvar_cands rhs
+ fvs' = fvs `unionIdSets` mkIdSet (idSpecVars bndr)
+
\end{code}
\begin{code}
--
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