[project @ 1998-06-08 11:45:09 by simonpj]

[ghc-hetmet.git] / ghc / compiler / coreSyn / FreeVars.lhs

diff --git a/ghc/compiler/coreSyn/FreeVars.lhs b/ghc/compiler/coreSyn/FreeVars.lhs
index 48185a9..b0b39e3 100644 (file)
--- 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
@@ -254,13 +262,16 @@ fvExpr id_cands tyvar_cands (Case expr alts)
        binder_ftvs = munge_id_ty binder
            -- We need to collect free tyvars from the binder
 
+-- Don't forget to notice that the idSpecVars of the binder
+-- are free in the whole expression; albeit not in the RHS or body
+
 fvExpr id_cands tyvar_cands (Let (NonRec binder rhs) body)
-  = (FVInfo (freeVarsOf rhs'   `combine` body_fvs)
+  = (FVInfo (freeVarsOf rhs'   `combine` body_fvs `combine` mkIdSet (idSpecVars binder))
            (freeTyVarsOf rhs' `combine` freeTyVarsOf body2 `combine` binder_ftvs)
            (leakinessOf rhs' `orLeak` leakinessOf body2),
      AnnLet (AnnNonRec binder rhs') body2)
   where
-    rhs'       = fvExpr id_cands tyvar_cands rhs
+    rhs'       = fvRhs id_cands tyvar_cands (binder, rhs)
     body2      = fvExpr (aFreeId binder `combine` id_cands) tyvar_cands body
     body_fvs   = freeVarsOf body2 `minusIdSet` aFreeId binder
     binder_ftvs = munge_id_ty binder
@@ -275,12 +286,17 @@ fvExpr id_cands tyvar_cands (Let (Rec binds) body)
     (binders, rhss)   = unzip binds
     new_id_cands      = binders_set `combine` id_cands
     binders_set              = mkIdSet binders
-    rhss'            = map (fvExpr new_id_cands tyvar_cands) rhss
+    rhss'            = map (fvRhs new_id_cands tyvar_cands) binds
 
     FVInfo rhss_fvs rhss_tfvs leakiness_of_rhss
        = foldr1 combineFVInfo [info | (info,_) <- rhss']
 
-    binds_fvs        = rhss_fvs `minusIdSet` binders_set
+       -- Don't forget to notice that the idSpecVars of the binder
+       -- are free in the whole expression; albeit not in the RHS or body
+    binds_fvs        = (foldr (unionIdSets . mkIdSet . idSpecVars) rhss_fvs binders)
+                       `minusIdSet`
+                       binders_set
+
     body2            = fvExpr new_id_cands tyvar_cands body
     body_fvs         = freeVarsOf body2 `minusIdSet` binders_set
     binders_ftvs      = foldr (combine . munge_id_ty) noFreeTyVars binders
@@ -300,6 +316,9 @@ fvExpr id_cands tyvar_cands (Note other_note expr)
   = (fvinfo, AnnNote other_note expr2)
   where
     expr2@(fvinfo,_) = fvExpr id_cands tyvar_cands expr
+
+fvRhs id_cands tyvar_cands (bndr,rhs)
+  = fvExpr id_cands tyvar_cands rhs
 \end{code}
 
 \begin{code}