[project @ 2001-03-14 15:26:00 by simonpj]

[ghc-hetmet.git] / ghc / compiler / simplCore / SimplUtils.lhs

diff --git a/ghc/compiler/simplCore/SimplUtils.lhs b/ghc/compiler/simplCore/SimplUtils.lhs
index 4d9ebd3..f61b513 100644 (file)
--- a/ghc/compiler/simplCore/SimplUtils.lhs
+++ b/ghc/compiler/simplCore/SimplUtils.lhs
@@ -5,9 +5,9 @@
 
 \begin{code}
 module SimplUtils (
-       simplBinder, simplBinders, simplIds,
+       simplBinder, simplBinders, simplRecIds, simplLetId,
        tryRhsTyLam, tryEtaExpansion,
-       mkCase, findAlt, findDefault,
+       mkCase,
 
        -- The continuation type
        SimplCont(..), DupFlag(..), contIsDupable, contResultType,
@@ -23,11 +23,15 @@ import CmdLineOpts  ( switchIsOn, SimplifierSwitch(..),
                          opt_UF_UpdateInPlace
                        )
 import CoreSyn
-import CoreUtils       ( exprIsTrivial, cheapEqExpr, exprType, exprIsCheap, etaExpand, exprEtaExpandArity, bindNonRec )
-import Subst           ( InScopeSet, mkSubst, substBndrs, substBndr, substIds, substExpr )
+import CoreUtils       ( exprIsTrivial, cheapEqExpr, exprType, exprIsCheap, 
+                         etaExpand, exprEtaExpandArity, bindNonRec, mkCoerce,
+                         findDefault
+                       )
+import Subst           ( InScopeSet, mkSubst, substExpr )
+import qualified Subst ( simplBndrs, simplBndr, simplLetId )
 import Id              ( idType, idName, 
                          idUnfolding, idStrictness,
-                         mkVanillaId, idInfo
+                         mkLocalId, idInfo
                        )
 import IdInfo          ( StrictnessInfo(..) )
 import Maybes          ( maybeToBool, catMaybes )
@@ -42,7 +46,7 @@ import Type           ( Type, mkForAllTys, seqType, repType,
 import TyCon           ( tyConDataConsIfAvailable )
 import DataCon         ( dataConRepArity )
 import VarEnv          ( SubstEnv )
-import Util            ( lengthExceeds )
+import Util            ( lengthExceeds, mapAccumL )
 import Outputable
 \end{code}
 
@@ -425,7 +429,7 @@ simplBinders :: [InBinder] -> ([OutBinder] -> SimplM a) -> SimplM a
 simplBinders bndrs thing_inside
   = getSubst           `thenSmpl` \ subst ->
     let
-       (subst', bndrs') = substBndrs subst bndrs
+       (subst', bndrs') = Subst.simplBndrs subst bndrs
     in
     seqBndrs bndrs'    `seq`
     setSubst subst' (thing_inside bndrs')
@@ -434,23 +438,29 @@ simplBinder :: InBinder -> (OutBinder -> SimplM a) -> SimplM a
 simplBinder bndr thing_inside
   = getSubst           `thenSmpl` \ subst ->
     let
-       (subst', bndr') = substBndr subst bndr
+       (subst', bndr') = Subst.simplBndr subst bndr
     in
     seqBndr bndr'      `seq`
     setSubst subst' (thing_inside bndr')
 
 
--- Same semantics as simplBinders, but a little less 
--- plumbing and hence a little more efficient.
--- Maybe not worth the candle?
-simplIds :: [InBinder] -> ([OutBinder] -> SimplM a) -> SimplM a
-simplIds ids thing_inside
+simplRecIds :: [InBinder] -> ([OutBinder] -> SimplM a) -> SimplM a
+simplRecIds ids thing_inside
   = getSubst           `thenSmpl` \ subst ->
     let
-       (subst', bndrs') = substIds subst ids
+       (subst', ids') = mapAccumL Subst.simplLetId subst ids
     in
-    seqBndrs bndrs'    `seq`
-    setSubst subst' (thing_inside bndrs')
+    seqBndrs ids'      `seq`
+    setSubst subst' (thing_inside ids')
+
+simplLetId :: InBinder -> (OutBinder -> SimplM a) -> SimplM a
+simplLetId id thing_inside
+  = getSubst           `thenSmpl` \ subst ->
+    let
+       (subst', id') = Subst.simplLetId subst id
+    in
+    seqBndr id'        `seq`
+    setSubst subst' (thing_inside id')
 
 seqBndrs [] = ()
 seqBndrs (b:bs) = seqBndr b `seq` seqBndrs bs
@@ -605,7 +615,7 @@ tryRhsTyLam rhs                     -- Only does something if there's a let
        let
            poly_name = setNameUnique (idName var) uniq         -- Keep same name
            poly_ty   = mkForAllTys tyvars_here (idType var)    -- But new type of course
-           poly_id   = mkVanillaId poly_name poly_ty 
+           poly_id   = mkLocalId poly_name poly_ty 
 
                -- In the olden days, it was crucial to copy the occInfo of the original var, 
                -- because we were looking at occurrence-analysed but as yet unsimplified code!
@@ -789,14 +799,28 @@ and similar friends.
 mkCase scrut case_bndr alts
   | all identity_alt alts
   = tick (CaseIdentity case_bndr)              `thenSmpl_`
-    returnSmpl scrut
+    returnSmpl (re_note scrut)
   where
-    identity_alt (DEFAULT, [], Var v)     = v == case_bndr
-    identity_alt (DataAlt con, args, rhs) = cheapEqExpr rhs
-                                                       (mkConApp con (map Type arg_tys ++ map varToCoreExpr args))
-    identity_alt other                   = False
-
-    arg_tys = tyConAppArgs (idType case_bndr)
+    identity_alt (con, args, rhs) = de_note rhs `cheapEqExpr` identity_rhs con args
+
+    identity_rhs (DataAlt con) args = mkConApp con (arg_tys ++ map varToCoreExpr args)
+    identity_rhs (LitAlt lit)  _    = Lit lit
+    identity_rhs DEFAULT       _    = Var case_bndr
+
+    arg_tys = map Type (tyConAppArgs (idType case_bndr))
+
+       -- We've seen this:
+       --      case coerce T e of x { _ -> coerce T' x }
+       -- And we definitely want to eliminate this case!
+       -- So we throw away notes from the RHS, and reconstruct
+       -- (at least an approximation) at the other end
+    de_note (Note _ e) = de_note e
+    de_note e         = e
+
+       -- re_note wraps a coerce if it might be necessary
+    re_note scrut = case head alts of
+                       (_,_,rhs1@(Note _ _)) -> mkCoerce (exprType rhs1) (idType case_bndr) scrut
+                       other                 -> scrut
 \end{code}
 
 The catch-all case
@@ -807,22 +831,3 @@ mkCase other_scrut case_bndr other_alts
 \end{code}
 
 
-\begin{code}
-findDefault :: [CoreAlt] -> ([CoreAlt], Maybe CoreExpr)
-findDefault []                         = ([], Nothing)
-findDefault ((DEFAULT,args,rhs) : alts) = ASSERT( null alts && null args ) 
-                                         ([], Just rhs)
-findDefault (alt : alts)               = case findDefault alts of 
-                                           (alts', deflt) -> (alt : alts', deflt)
-
-findAlt :: AltCon -> [CoreAlt] -> CoreAlt
-findAlt con alts
-  = go alts
-  where
-    go []          = pprPanic "Missing alternative" (ppr con $$ vcat (map ppr alts))
-    go (alt : alts) | matches alt = alt
-                   | otherwise   = go alts
-
-    matches (DEFAULT, _, _) = True
-    matches (con1, _, _)    = con == con1
-\end{code}