X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2FsimplCore%2FSetLevels.lhs;h=2d95727e35637c33141f954014bb514a9867c3ba;hb=59c796f8e77325d35f29ddd3e724bfa780466d40;hp=1eacf4db5a1c7d56e4f52b71a454b664fb794419;hpb=5f087cf4add4e140e7df05d896ee6b271133f822;p=ghc-hetmet.git diff --git a/ghc/compiler/simplCore/SetLevels.lhs b/ghc/compiler/simplCore/SetLevels.lhs index 1eacf4d..2d95727 100644 --- a/ghc/compiler/simplCore/SetLevels.lhs +++ b/ghc/compiler/simplCore/SetLevels.lhs @@ -46,6 +46,7 @@ module SetLevels ( setLevels, Level(..), tOP_LEVEL, + LevelledBind, LevelledExpr, incMinorLvl, ltMajLvl, ltLvl, isTopLvl, isInlineCtxt ) where @@ -55,10 +56,11 @@ module SetLevels ( import CoreSyn import CmdLineOpts ( FloatOutSwitches(..) ) -import CoreUtils ( exprType, exprIsTrivial, exprIsBottom, mkPiTypes ) +import CoreUtils ( exprType, exprIsTrivial, exprIsCheap, mkPiTypes ) import CoreFVs -- all of it import Subst -import Id ( Id, idType, mkSysLocal, isOneShotLambda, zapDemandIdInfo, +import Id ( Id, idType, mkSysLocalUnencoded, + isOneShotLambda, zapDemandIdInfo, idSpecialisation, idWorkerInfo, setIdInfo ) import IdInfo ( workerExists, vanillaIdInfo, ) @@ -70,8 +72,9 @@ import OccName ( occNameUserString ) import Type ( isUnLiftedType, Type ) import BasicTypes ( TopLevelFlag(..) ) import UniqSupply -import Util ( sortLt, isSingleton, count ) +import Util ( sortLe, isSingleton, count ) import Outputable +import FastString \end{code} %************************************************************************ @@ -306,6 +309,23 @@ lvlExpr ctxt_lvl env expr@(_, AnnLam bndr rhs) -- but not nearly so much now non-recursive newtypes are transparent. -- [See SetLevels rev 1.50 for a version with this approach.] +lvlExpr ctxt_lvl env (_, AnnLet (AnnNonRec bndr rhs) body) + | isUnLiftedType (idType bndr) + -- Treat unlifted let-bindings (let x = b in e) just like (case b of x -> e) + -- That is, leave it exactly where it is + -- We used to float unlifted bindings too (e.g. to get a cheap primop + -- outside a lambda (to see how, look at lvlBind in rev 1.58) + -- but an unrelated change meant that these unlifed bindings + -- could get to the top level which is bad. And there's not much point; + -- unlifted bindings are always cheap, and so hardly worth floating. + = lvlExpr ctxt_lvl env rhs `thenLvl` \ rhs' -> + lvlExpr incd_lvl env' body `thenLvl` \ body' -> + returnLvl (Let (NonRec bndr' rhs') body') + where + incd_lvl = incMinorLvl ctxt_lvl + bndr' = TB bndr incd_lvl + env' = extendLvlEnv env [bndr'] + lvlExpr ctxt_lvl env (_, AnnLet bind body) = lvlBind NotTopLevel ctxt_lvl env bind `thenLvl` \ (bind', new_env) -> lvlExpr ctxt_lvl new_env body `thenLvl` \ body' -> @@ -317,7 +337,7 @@ lvlExpr ctxt_lvl env (_, AnnCase expr case_bndr alts) alts_env = extendCaseBndrLvlEnv env expr' case_bndr incd_lvl in mapLvl (lvl_alt alts_env) alts `thenLvl` \ alts' -> - returnLvl (Case expr' (case_bndr, incd_lvl) alts') + returnLvl (Case expr' (TB case_bndr incd_lvl) alts') where incd_lvl = incMinorLvl ctxt_lvl @@ -325,13 +345,20 @@ lvlExpr ctxt_lvl env (_, AnnCase expr case_bndr alts) = lvlMFE True incd_lvl new_env rhs `thenLvl` \ rhs' -> returnLvl (con, bs', rhs') where - bs' = [ (b, incd_lvl) | b <- bs ] + bs' = [ TB b incd_lvl | b <- bs ] new_env = extendLvlEnv alts_env bs' \end{code} @lvlMFE@ is just like @lvlExpr@, except that it might let-bind the expression, so that it can itself be floated. +[NOTE: unlifted MFEs] +We don't float unlifted MFEs, which potentially loses big opportunites. +For example: + \x -> f (h y) +where h :: Int -> Int# is expensive. We'd like to float the (h y) outside +the \x, but we don't because it's unboxed. Possible solution: box it. + \begin{code} lvlMFE :: Bool -- True <=> strict context [body of case or let] -> Level -- Level of innermost enclosing lambda/tylam @@ -342,21 +369,19 @@ lvlMFE :: Bool -- True <=> strict context [body of case or let] lvlMFE strict_ctxt ctxt_lvl env (_, AnnType ty) = returnLvl (Type ty) + lvlMFE strict_ctxt ctxt_lvl env ann_expr@(fvs, _) - | isUnLiftedType ty -- Can't let-bind it + | isUnLiftedType ty -- Can't let-bind it; see [NOTE: unlifted MFEs] || isInlineCtxt ctxt_lvl -- Don't float out of an __inline__ context + || exprIsTrivial expr -- Never float if it's trivial || not good_destination - || exprIsTrivial expr -- Is trivial - || (strict_ctxt && exprIsBottom expr) -- Strict context and is bottom - -- e.g. \x -> error "foo" - -- No gain from floating this = -- Don't float it out lvlExpr ctxt_lvl env ann_expr | otherwise -- Float it out! = lvlFloatRhs abs_vars dest_lvl env ann_expr `thenLvl` \ expr' -> newLvlVar "lvl" abs_vars ty `thenLvl` \ var -> - returnLvl (Let (NonRec (var,dest_lvl) expr') + returnLvl (Let (NonRec (TB var dest_lvl) expr') (mkVarApps (Var var) abs_vars)) where expr = deAnnotate ann_expr @@ -364,25 +389,42 @@ lvlMFE strict_ctxt ctxt_lvl env ann_expr@(fvs, _) dest_lvl = destLevel env fvs (isFunction ann_expr) abs_vars = abstractVars dest_lvl env fvs - good_destination = dest_lvl `ltMajLvl` ctxt_lvl -- Escapes a value lambda - || (isTopLvl dest_lvl -- Goes to the top - && floatConsts env - && not strict_ctxt) -- or from a strict context -- A decision to float entails let-binding this thing, and we only do -- that if we'll escape a value lambda, or will go to the top level. - -- - -- Beware: - -- concat = /\ a -> foldr ..a.. (++) [] - -- was getting turned into - -- concat = /\ a -> lvl a - -- lvl = /\ a -> foldr ..a.. (++) [] - -- which is pretty stupid. Hence the strict_ctxt test - -- - -- We are keen to float something to the top level, even if it does not - -- escape a lambda, because then it needs no allocation. But it's controlled - -- by a flag, because doing this too early loses opportunities for RULES - -- which (needless to say) are important in some nofib programs - -- (gcd is an example). + good_destination + | dest_lvl `ltMajLvl` ctxt_lvl -- Escapes a value lambda + = not (exprIsCheap expr) || isTopLvl dest_lvl + -- Even if it escapes a value lambda, we only + -- float if it's not cheap (unless it'll get all the + -- way to the top). I've seen cases where we + -- float dozens of tiny free expressions, which cost + -- more to allocate than to evaluate. + -- NB: exprIsCheap is also true of bottom expressions, which + -- is good; we don't want to share them + -- + -- It's only Really Bad to float a cheap expression out of a + -- strict context, because that builds a thunk that otherwise + -- would never be built. So another alternative would be to + -- add + -- || (strict_ctxt && not (exprIsBottom expr)) + -- to the condition above. We should really try this out. + + | otherwise -- Does not escape a value lambda + = isTopLvl dest_lvl -- Only float if we are going to the top level + && floatConsts env -- and the floatConsts flag is on + && not strict_ctxt -- Don't float from a strict context + -- We are keen to float something to the top level, even if it does not + -- escape a lambda, because then it needs no allocation. But it's controlled + -- by a flag, because doing this too early loses opportunities for RULES + -- which (needless to say) are important in some nofib programs + -- (gcd is an example). + -- + -- Beware: + -- concat = /\ a -> foldr ..a.. (++) [] + -- was getting turned into + -- concat = /\ a -> lvl a + -- lvl = /\ a -> foldr ..a.. (++) [] + -- which is pretty stupid. Hence the strict_ctxt test \end{code} @@ -403,31 +445,26 @@ lvlBind :: TopLevelFlag -- Used solely to decide whether to clone -> LvlM (LevelledBind, LevelEnv) lvlBind top_lvl ctxt_lvl env (AnnNonRec bndr rhs@(rhs_fvs,_)) - | isInlineCtxt ctxt_lvl -- Don't do anything inside InlineMe + | isInlineCtxt ctxt_lvl -- Don't do anything inside InlineMe = lvlExpr ctxt_lvl env rhs `thenLvl` \ rhs' -> - returnLvl (NonRec (bndr, ctxt_lvl) rhs', env) + returnLvl (NonRec (TB bndr ctxt_lvl) rhs', env) | null abs_vars = -- No type abstraction; clone existing binder lvlExpr dest_lvl env rhs `thenLvl` \ rhs' -> cloneVar top_lvl env bndr ctxt_lvl dest_lvl `thenLvl` \ (env', bndr') -> - returnLvl (NonRec (bndr', dest_lvl) rhs', env') + returnLvl (NonRec (TB bndr' dest_lvl) rhs', env') | otherwise = -- Yes, type abstraction; create a new binder, extend substitution, etc lvlFloatRhs abs_vars dest_lvl env rhs `thenLvl` \ rhs' -> newPolyBndrs dest_lvl env abs_vars [bndr] `thenLvl` \ (env', [bndr']) -> - returnLvl (NonRec (bndr', dest_lvl) rhs', env') + returnLvl (NonRec (TB bndr' dest_lvl) rhs', env') where bind_fvs = rhs_fvs `unionVarSet` idFreeVars bndr abs_vars = abstractVars dest_lvl env bind_fvs - - dest_lvl | isUnLiftedType (idType bndr) = destLevel env bind_fvs False `maxLvl` Level 1 0 - | otherwise = destLevel env bind_fvs (isFunction rhs) - -- Hack alert! We do have some unlifted bindings, for cheap primops, and - -- it is ok to float them out; but not to the top level. If they would otherwise - -- go to the top level, we pin them inside the topmost lambda + dest_lvl = destLevel env bind_fvs (isFunction rhs) \end{code} @@ -435,12 +472,12 @@ lvlBind top_lvl ctxt_lvl env (AnnNonRec bndr rhs@(rhs_fvs,_)) lvlBind top_lvl ctxt_lvl env (AnnRec pairs) | isInlineCtxt ctxt_lvl -- Don't do anything inside InlineMe = mapLvl (lvlExpr ctxt_lvl env) rhss `thenLvl` \ rhss' -> - returnLvl (Rec ((bndrs `zip` repeat ctxt_lvl) `zip` rhss'), env) + returnLvl (Rec ([TB b ctxt_lvl | b <- bndrs] `zip` rhss'), env) | null abs_vars = cloneRecVars top_lvl env bndrs ctxt_lvl dest_lvl `thenLvl` \ (new_env, new_bndrs) -> mapLvl (lvlExpr ctxt_lvl new_env) rhss `thenLvl` \ new_rhss -> - returnLvl (Rec ((new_bndrs `zip` repeat dest_lvl) `zip` new_rhss), new_env) + returnLvl (Rec ([TB b dest_lvl | b <- new_bndrs] `zip` new_rhss), new_env) | isSingleton pairs && count isId abs_vars > 1 = -- Special case for self recursion where there are @@ -466,16 +503,17 @@ lvlBind top_lvl ctxt_lvl env (AnnRec pairs) in lvlExpr body_lvl body_env rhs_body `thenLvl` \ new_rhs_body -> newPolyBndrs dest_lvl env abs_vars [bndr] `thenLvl` \ (poly_env, [poly_bndr]) -> - returnLvl (Rec [((poly_bndr,dest_lvl), mkLams abs_vars_w_lvls $ - mkLams new_lam_bndrs $ - Let (Rec [((new_bndr,rhs_lvl), mkLams new_lam_bndrs new_rhs_body)]) - (mkVarApps (Var new_bndr) lam_bndrs))], + returnLvl (Rec [(TB poly_bndr dest_lvl, + mkLams abs_vars_w_lvls $ + mkLams new_lam_bndrs $ + Let (Rec [(TB new_bndr rhs_lvl, mkLams new_lam_bndrs new_rhs_body)]) + (mkVarApps (Var new_bndr) lam_bndrs))], poly_env) | otherwise -- Non-null abs_vars = newPolyBndrs dest_lvl env abs_vars bndrs `thenLvl` \ (new_env, new_bndrs) -> mapLvl (lvlFloatRhs abs_vars dest_lvl new_env) rhss `thenLvl` \ new_rhss -> - returnLvl (Rec ((new_bndrs `zip` repeat dest_lvl) `zip` new_rhss), new_env) + returnLvl (Rec ([TB b dest_lvl | b <- new_bndrs] `zip` new_rhss), new_env) where (bndrs,rhss) = unzip pairs @@ -508,7 +546,7 @@ lvlFloatRhs abs_vars dest_lvl env rhs %************************************************************************ \begin{code} -lvlLamBndrs :: Level -> [CoreBndr] -> (Level, [(CoreBndr, Level)]) +lvlLamBndrs :: Level -> [CoreBndr] -> (Level, [TaggedBndr Level]) -- Compute the levels for the binders of a lambda group -- The binders returned are exactly the same as the ones passed, -- but they are now paired with a level @@ -524,10 +562,10 @@ lvlLamBndrs lvl bndrs | isId bndr && -- Go to the next major level if this is a value binder, not bumped_major && -- and we havn't already gone to the next level (one jump per group) not (isOneShotLambda bndr) -- and it isn't a one-shot lambda - = go new_lvl True ((bndr,new_lvl) : rev_lvld_bndrs) bndrs + = go new_lvl True (TB bndr new_lvl : rev_lvld_bndrs) bndrs | otherwise - = go old_lvl bumped_major ((bndr,old_lvl) : rev_lvld_bndrs) bndrs + = go old_lvl bumped_major (TB bndr old_lvl : rev_lvld_bndrs) bndrs where new_lvl = incMajorLvl old_lvl @@ -612,7 +650,7 @@ floatLams (FloatOutSw float_lams _, _, _, _) = float_lams floatConsts :: LevelEnv -> Bool floatConsts (FloatOutSw _ float_consts, _, _, _) = float_consts -extendLvlEnv :: LevelEnv -> [(Var,Level)] -> LevelEnv +extendLvlEnv :: LevelEnv -> [TaggedBndr Level] -> LevelEnv -- Used when *not* cloning extendLvlEnv (float_lams, lvl_env, subst, id_env) prs = (float_lams, @@ -620,9 +658,9 @@ extendLvlEnv (float_lams, lvl_env, subst, id_env) prs foldl del_subst subst prs, foldl del_id id_env prs) where - add_lvl env (v,l) = extendVarEnv env v l - del_subst env (v,_) = extendInScope env v - del_id env (v,_) = delVarEnv env v + add_lvl env (TB v l) = extendVarEnv env v l + del_subst env (TB v _) = extendInScope env v + del_id env (TB v _) = delVarEnv env v -- We must remove any clone for this variable name in case of -- shadowing. This bit me in the following case -- (in nofib/real/gg/Spark.hs): @@ -646,7 +684,7 @@ extendCaseBndrLvlEnv (float_lams, lvl_env, subst, id_env) (Var scrut_var) case_b extendVarEnv id_env case_bndr ([scrut_var], Var scrut_var)) extendCaseBndrLvlEnv env scrut case_bndr lvl - = extendLvlEnv env [(case_bndr,lvl)] + = extendLvlEnv env [TB case_bndr lvl] extendPolyLvlEnv dest_lvl (float_lams, lvl_env, subst, id_env) abs_vars bndr_pairs = (float_lams, @@ -692,14 +730,14 @@ abstractVars :: Level -> LevelEnv -> VarSet -> [Var] -- whose level is greater than the destination level -- These are the ones we are going to abstract out abstractVars dest_lvl env fvs - = uniq (sortLt lt [var | fv <- varSetElems fvs, var <- absVarsOf dest_lvl env fv]) + = uniq (sortLe le [var | fv <- varSetElems fvs, var <- absVarsOf dest_lvl env fv]) where -- Sort the variables so we don't get -- mixed-up tyvars and Ids; it's just messy - v1 `lt` v2 = case (isId v1, isId v2) of + v1 `le` v2 = case (isId v1, isId v2) of (True, False) -> False (False, True) -> True - other -> v1 < v2 -- Same family + other -> v1 <= v2 -- Same family uniq :: [Var] -> [Var] -- Remove adjacent duplicates; the sort will have brought them together @@ -756,7 +794,7 @@ newPolyBndrs dest_lvl env abs_vars bndrs in returnLvl (extendPolyLvlEnv dest_lvl env abs_vars (bndrs `zip` new_bndrs), new_bndrs) where - mk_poly_bndr bndr uniq = mkSysLocal (_PK_ str) uniq poly_ty + mk_poly_bndr bndr uniq = mkSysLocalUnencoded (mkFastString str) uniq poly_ty where str = "poly_" ++ occNameUserString (getOccName bndr) poly_ty = mkPiTypes abs_vars (idType bndr) @@ -767,7 +805,7 @@ newLvlVar :: String -> LvlM Id newLvlVar str vars body_ty = getUniqueUs `thenLvl` \ uniq -> - returnUs (mkSysLocal (_PK_ str) uniq (mkPiTypes vars body_ty)) + returnUs (mkSysLocalUnencoded (mkFastString str) uniq (mkPiTypes vars body_ty)) -- The deeply tiresome thing is that we have to apply the substitution -- to the rules inside each Id. Grr. But it matters.