[project @ 2003-03-21 13:54:27 by simonmar]

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

diff --git a/ghc/compiler/coreSyn/CoreUtils.lhs b/ghc/compiler/coreSyn/CoreUtils.lhs
index caf04ee..12e0ff8 100644 (file)
--- a/ghc/compiler/coreSyn/CoreUtils.lhs
+++ b/ghc/compiler/coreSyn/CoreUtils.lhs
@@ -18,8 +18,7 @@ module CoreUtils (
        exprIsBottom, exprIsDupable, exprIsTrivial, exprIsCheap, 
        exprIsValue,exprOkForSpeculation, exprIsBig, 
        exprIsConApp_maybe, exprIsAtom,
-       idAppIsBottom, idAppIsCheap,
-
+       idAppIsBottom, idAppIsCheap, rhsIsNonUpd,
 
        -- Arity and eta expansion
        manifestArity, exprArity, 
@@ -34,9 +33,6 @@ module CoreUtils (
        -- Equality
        cheapEqExpr, eqExpr, applyTypeToArgs, applyTypeToArg,
 
-       -- CAF info
-       hasCafRefs, rhsIsNonUpd,
-
        -- Cross-DLL references
        isCrossDllConApp,
     ) where
@@ -59,10 +55,9 @@ import PrimOp                ( PrimOp(..), primOpOkForSpeculation, primOpIsCheap )
 import Id              ( Id, idType, globalIdDetails, idNewStrictness, 
                          mkWildId, idArity, idName, idUnfolding, idInfo,
                          isOneShotLambda, isDataConWorkId_maybe, mkSysLocal,
-                         isDataConWorkId, isBottomingId, idCafInfo
+                         isDataConWorkId, isBottomingId
                        )
-import IdInfo          ( GlobalIdDetails(..), megaSeqIdInfo,
-                         CafInfo(..), mayHaveCafRefs )
+import IdInfo          ( GlobalIdDetails(..), megaSeqIdInfo )
 import NewDemand       ( appIsBottom )
 import Type            ( Type, mkFunTy, mkForAllTy, splitFunTy_maybe,
                          splitFunTy,
@@ -80,7 +75,6 @@ import Outputable
 import TysPrim         ( alphaTy )     -- Debugging only
 import Util             ( equalLength, lengthAtLeast )
 import TysPrim         ( statePrimTyCon )
-import FastTypes       hiding ( fastOr )
 \end{code}
 
 
@@ -1178,58 +1172,11 @@ isCrossDllArg (Lam v e)   = isCrossDllArg e
 
 %************************************************************************
 %*                                                                     *
-\subsection{Figuring out CafInfo for an expression}
+\subsection{Determining non-updatable right-hand-sides}
 %*                                                                     *
 %************************************************************************
 
-hasCafRefs decides whether a top-level closure can point into the dynamic heap.
-We mark such things as `MayHaveCafRefs' because this information is
-used to decide whether a particular closure needs to be referenced
-in an SRT or not.
-
-There are two reasons for setting MayHaveCafRefs:
-       a) The RHS is a CAF: a top-level updatable thunk.
-       b) The RHS refers to something that MayHaveCafRefs
-
-Possible improvement: In an effort to keep the number of CAFs (and 
-hence the size of the SRTs) down, we could also look at the expression and 
-decide whether it requires a small bounded amount of heap, so we can ignore 
-it as a CAF.  In these cases however, we would need to use an additional
-CAF list to keep track of non-collectable CAFs.  
-
 \begin{code}
-hasCafRefs  :: (Var -> Bool) -> Arity -> CoreExpr -> CafInfo
-hasCafRefs p arity expr 
-  | is_caf || mentions_cafs = MayHaveCafRefs
-  | otherwise              = NoCafRefs
- where
-  mentions_cafs = isFastTrue (cafRefs p expr)
-  is_caf = not (arity > 0 || rhsIsNonUpd expr)
-  -- NB. we pass in the arity of the expression, which is expected
-  -- to be calculated by exprArity.  This is because exprArity
-  -- knows how much eta expansion is going to be done by 
-  -- CorePrep later on, and we don't want to duplicate that
-  -- knowledge in rhsIsNonUpd below.
-
-cafRefs p (Var id)
-  | isId id && p id = fastBool (mayHaveCafRefs (idCafInfo id))
-  | otherwise       = fastBool False
-
-cafRefs p (Lit l)           = fastBool False
-cafRefs p (App f a)         = fastOr (cafRefs p f) (cafRefs p) a
-cafRefs p (Lam x e)         = cafRefs p e
-cafRefs p (Let b e)         = fastOr (cafRefss p (rhssOfBind b)) (cafRefs p) e
-cafRefs p (Case e bndr alts) = fastOr (cafRefs p e) (cafRefss p) (rhssOfAlts alts)
-cafRefs p (Note n e)        = cafRefs p e
-cafRefs p (Type t)          = fastBool False
-
-cafRefss p []    = fastBool False
-cafRefss p (e:es) = fastOr (cafRefs p e) (cafRefss p) es
-
--- hack for lazy-or over FastBool.
-fastOr a f x = fastBool (isFastTrue a || isFastTrue (f x))
-
-
 rhsIsNonUpd :: CoreExpr -> Bool
 -- True => Value-lambda, saturated constructor
 -- This is a bit like CoreUtils.exprIsValue, with the following differences: