[project @ 2003-02-04 15:09:38 by simonpj]

[ghc-hetmet.git] / ghc / compiler / basicTypes / Id.lhs

diff --git a/ghc/compiler/basicTypes/Id.lhs b/ghc/compiler/basicTypes/Id.lhs
index 2ef248a..bd9fffb 100644 (file)
--- a/ghc/compiler/basicTypes/Id.lhs
+++ b/ghc/compiler/basicTypes/Id.lhs
@@ -92,7 +92,7 @@ import Var            ( Id, DictId,
                        )
 import qualified Var   ( mkLocalId, mkGlobalId, mkSpecPragmaId )
 import Type            ( Type, typePrimRep, addFreeTyVars, 
-                          usOnce, eqUsage, seqType, splitTyConApp_maybe )
+                          seqType, splitTyConApp_maybe )
 
 import IdInfo 
 
@@ -104,7 +104,6 @@ import Name         ( Name, OccName,
                        ) 
 import OccName         ( EncodedFS, mkWorkerOcc )
 import PrimRep         ( PrimRep )
-import TysPrim         ( statePrimTyCon )
 import FieldLabel      ( FieldLabel )
 import Maybes          ( orElse )
 import SrcLoc          ( SrcLoc )
@@ -464,34 +463,12 @@ idLBVarInfo :: Id -> LBVarInfo
 idLBVarInfo id = lbvarInfo (idInfo id)
 
 isOneShotLambda :: Id -> Bool
-isOneShotLambda id = analysis || hack
-  where analysis = case idLBVarInfo id of
-                     LBVarInfo u    | u `eqUsage` usOnce      -> True
-                     other                                    -> False
-        hack     = case splitTyConApp_maybe (idType id) of
-                     Just (tycon,_) | tycon == statePrimTyCon -> True
-                     other                                    -> False
-
-       -- The last clause is a gross hack.  It claims that 
-       -- every function over realWorldStatePrimTy is a one-shot
-       -- function.  This is pretty true in practice, and makes a big
-       -- difference.  For example, consider
-       --      a `thenST` \ r -> ...E...
-       -- The early full laziness pass, if it doesn't know that r is one-shot
-       -- will pull out E (let's say it doesn't mention r) to give
-       --      let lvl = E in a `thenST` \ r -> ...lvl...
-       -- When `thenST` gets inlined, we end up with
-       --      let lvl = E in \s -> case a s of (r, s') -> ...lvl...
-       -- and we don't re-inline E.
-       --
-       -- It would be better to spot that r was one-shot to start with, but
-       -- I don't want to rely on that.
-       --
-       -- Another good example is in fill_in in PrelPack.lhs.  We should be able to
-       -- spot that fill_in has arity 2 (and when Keith is done, we will) but we can't yet.
+isOneShotLambda id = case idLBVarInfo id of
+                       IsOneShotLambda  -> True
+                       NoLBVarInfo      -> False
 
 setOneShotLambda :: Id -> Id
-setOneShotLambda id = modifyIdInfo (`setLBVarInfo` LBVarInfo usOnce) id
+setOneShotLambda id = modifyIdInfo (`setLBVarInfo` IsOneShotLambda) id
 
 clearOneShotLambda :: Id -> Id
 clearOneShotLambda id