X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2FdeSugar%2FDsBinds.lhs;h=e65da3cf9ba13e161f746f46ea9174e62929e835;hp=57bbd02c7da785311e9ee5592c2fa8898e9daea6;hb=90ce88a0a9b5611416e592a6ff96781ba884975f;hpb=15b860cb80dcc58de964da44ebaf366f66fc7d27 diff --git a/compiler/deSugar/DsBinds.lhs b/compiler/deSugar/DsBinds.lhs index 57bbd02..e65da3c 100644 --- a/compiler/deSugar/DsBinds.lhs +++ b/compiler/deSugar/DsBinds.lhs @@ -23,19 +23,21 @@ import {-# SOURCE #-} Match( matchWrapper ) import DsMonad import DsGRHSs import DsUtils +import OccurAnal import HsSyn -- lots of things import CoreSyn -- lots of things +import MkCore import CoreUtils import CoreFVs -import TcHsSyn ( mkArbitraryType ) -- Mis-placed? +import TcHsSyn ( mkArbitraryType ) -- Mis-placed? import TcType -import OccurAnal import CostCentre import Module import Id -import Var ( TyVar ) +import MkId ( seqId ) +import Var ( Var, TyVar ) import VarSet import Rules import VarEnv @@ -162,14 +164,16 @@ dsHsBind auto_scc rest (AbsBinds [] [] exports binds) where B is the *non-recursive* binding fl = fg a b gl = gg b - h = h a b + h = h a b -- See (b); note shadowing! Notice (a) g has a different number of type variables to f, so we must use the mkArbitraryType thing to fill in the gaps. We use a type-let to do that. (b) The local variable h isn't in the exports, and rather than - clone a fresh copy we simply replace h by (h a b). + clone a fresh copy we simply replace h by (h a b), where + the two h's have different types! Shadowing happens here, + which looks confusing but works fine. (c) The result is *still* quadratic-sized if there are a lot of small bindings. So if there are more than some small @@ -331,24 +335,17 @@ dsSpec all_tvs dicts tvs poly_id mono_id mono_bind do { let poly_name = idName poly_id ; spec_name <- newLocalName poly_name ; ds_spec_expr <- dsExpr spec_expr - ; let (bndrs, body) = collectBinders (occurAnalyseExpr ds_spec_expr) - -- The occurrence-analysis does two things - -- (a) identifies unused binders: Note [Unused spec binders] - -- (b) sorts dict bindings into NonRecs - -- so they can be inlined by decomposeRuleLhs - mb_lhs = decomposeRuleLhs body - - -- Check for dead binders: Note [Unused spec binders] - ; case filter isDeadBinder bndrs of { - bs | not (null bs) -> do { warnDs (dead_msg bs); return Nothing } - | otherwise -> + ; case (decomposeRuleLhs ds_spec_expr) of { + Nothing -> do { warnDs decomp_msg; return Nothing } ; - case mb_lhs of - Nothing -> do { warnDs decomp_msg; return Nothing } + Just (bndrs, _fn, args) -> - Just (_, args) -> do { + -- Check for dead binders: Note [Unused spec binders] + case filter isDeadBinder bndrs of { + bs | not (null bs) -> do { warnDs (dead_msg bs); return Nothing } + | otherwise -> do - f_body <- fix_up (Let mono_bind (Var mono_id)) + { f_body <- fix_up (Let mono_bind (Var mono_id)) ; let local_poly = setIdNotExported poly_id -- Very important to make the 'f' non-exported, @@ -357,7 +354,9 @@ dsSpec all_tvs dicts tvs poly_id mono_id mono_bind spec_rhs = Let (NonRec local_poly poly_f_body) ds_spec_expr poly_f_body = mkLams (tvs ++ dicts) f_body - extra_dict_bndrs = filter isDictId (varSetElems (exprFreeVars ds_spec_expr)) + extra_dict_bndrs = [localiseId d -- See Note [Constant rule dicts] + | d <- varSetElems (exprFreeVars ds_spec_expr) + , isDictId d] -- Note [Const rule dicts] rule = mkLocalRule (mkFastString ("SPEC " ++ showSDoc (ppr poly_name))) @@ -365,7 +364,7 @@ dsSpec all_tvs dicts tvs poly_id mono_id mono_bind (extra_dict_bndrs ++ bndrs) args (mkVarApps (Var spec_id) bndrs) ; return (Just (addInlineInfo inl spec_id spec_rhs, rule)) - } } } + } } } } where -- Bind to Any any of all_ptvs that aren't -- relevant for this particular function @@ -383,6 +382,7 @@ dsSpec all_tvs dicts tvs poly_id mono_id mono_bind decomp_msg = hang (ptext (sLit "Specialisation too complicated to desugar; ignored")) 2 (ppr spec_expr) + mkArbitraryTypeEnv :: [TyVar] -> [([TyVar], a, b, c)] -> DsM (TyVarEnv Type) -- If any of the tyvars is missing from any of the lists in @@ -441,6 +441,9 @@ And from that we want the rule RULE forall dInt. f Int dInt = f_spec f_spec = let f = in f Int dInt +But be careful! That dInt might be GHC.Base.$fOrdInt, which is an External +Name, and you can't bind them in a lambda or forall without getting things +confused. Hence the use of 'localiseId' to make it Internal. %************************************************************************ @@ -450,19 +453,37 @@ And from that we want the rule %************************************************************************ \begin{code} -decomposeRuleLhs :: CoreExpr -> Maybe (Id, [CoreExpr]) +decomposeRuleLhs :: CoreExpr -> Maybe ([Var], Id, [CoreExpr]) +-- Take apart the LHS of a RULE. It's suuposed to look like +-- /\a. f a Int dOrdInt +-- or /\a.\d:Ord a. let { dl::Ord [a] = dOrdList a d } in f [a] dl +-- That is, the RULE binders are lambda-bound -- Returns Nothing if the LHS isn't of the expected shape decomposeRuleLhs lhs - = go emptyVarEnv (occurAnalyseExpr lhs) -- Occurrence analysis sorts out the dict - -- bindings so we know if they are recursive + = case (decomp emptyVarEnv body) of + Nothing -> Nothing + Just (fn, args) -> Just (bndrs, fn, args) where + occ_lhs = occurAnalyseExpr lhs + -- The occurrence-analysis does two things + -- (a) identifies unused binders: Note [Unused spec binders] + -- (b) sorts dict bindings into NonRecs + -- so they can be inlined by 'decomp' + (bndrs, body) = collectBinders occ_lhs + -- Substitute dicts in the LHS args, so that there -- aren't any lets getting in the way -- Note that we substitute the function too; we might have this as -- a LHS: let f71 = M.f Int in f71 - go env (Let (NonRec dict rhs) body) - = go (extendVarEnv env dict (simpleSubst env rhs)) body - go env body + decomp env (Let (NonRec dict rhs) body) + = decomp (extendVarEnv env dict (simpleSubst env rhs)) body + + decomp env (Case scrut bndr ty [(DEFAULT, _, body)]) + | isDeadBinder bndr -- Note [Matching seqId] + = Just (seqId, [Type (idType bndr), Type ty, + simpleSubst env scrut, simpleSubst env body]) + + decomp env body = case collectArgs (simpleSubst env body) of (Var fn, args) -> Just (fn, args) _ -> Nothing @@ -502,17 +523,23 @@ addInlinePrags prags bndr rhs (inl:_) -> addInlineInfo inl bndr rhs addInlineInfo :: InlineSpec -> Id -> CoreExpr -> (Id,CoreExpr) -addInlineInfo (Inline phase is_inline) bndr rhs - = (attach_phase bndr phase, wrap_inline is_inline rhs) +addInlineInfo (Inline prag is_inline) bndr rhs + = (attach_pragma bndr prag, wrap_inline is_inline rhs) where - attach_phase bndr phase - | isAlwaysActive phase = bndr -- Default phase - | otherwise = bndr `setInlinePragma` phase + attach_pragma bndr prag + | isDefaultInlinePragma prag = bndr + | otherwise = bndr `setInlinePragma` prag wrap_inline True body = mkInlineMe body wrap_inline False body = body \end{code} +Note [Matching seq] +~~~~~~~~~~~~~~~~~~~ +The desugarer turns (seq e r) into (case e of _ -> r), via a special-case hack +and this code turns it back into an application of seq! +See Note [Rules for seq] in MkId for the details. + %************************************************************************ %* * @@ -574,8 +601,11 @@ dsCoercion (WpLam id) thing_inside = do { expr <- thing_inside ; return (Lam id expr) } dsCoercion (WpTyLam tv) thing_inside = do { expr <- thing_inside ; return (Lam tv expr) } -dsCoercion (WpApp id) thing_inside = do { expr <- thing_inside - ; return (App expr (Var id)) } +dsCoercion (WpApp v) thing_inside + | isTyVar v = do { expr <- thing_inside + {- Probably a coercion var -} ; return (App expr (Type (mkTyVarTy v))) } + | otherwise = do { expr <- thing_inside + {- An Id -} ; return (App expr (Var v)) } dsCoercion (WpTyApp ty) thing_inside = do { expr <- thing_inside ; return (App expr (Type ty)) } dsCoercion WpInline thing_inside = do { expr <- thing_inside