import HsSyn -- lots of things
import CoreSyn -- lots of things
import CoreUtils
+import CoreFVs
+import TcHsSyn ( mkArbitraryType ) -- Mis-placed?
+import TcType
import OccurAnal
import CostCentre
import Module
import Id
+import Var ( TyVar )
+import VarSet
import Rules
-import Var ( TyVar, Var )
import VarEnv
import Type
-import TysWiredIn
import Outputable
import SrcLoc
import Maybes
-> HsBind Id
-> DsM [(Id,CoreExpr)] -- Result
-dsHsBind auto_scc rest (VarBind var expr)
- = dsLExpr expr `thenDs` \ core_expr ->
+dsHsBind _ rest (VarBind var expr) = do
+ core_expr <- dsLExpr expr
- -- Dictionary bindings are always VarMonoBinds, so
- -- we only need do this here
- addDictScc var core_expr `thenDs` \ core_expr' ->
- returnDs ((var, core_expr') : rest)
+ -- Dictionary bindings are always VarMonoBinds, so
+ -- we only need do this here
+ core_expr' <- addDictScc var core_expr
+ return ((var, core_expr') : rest)
-dsHsBind auto_scc rest (FunBind { fun_id = L _ fun, fun_matches = matches, fun_co_fn = co_fn })
- = matchWrapper (FunRhs (idName fun)) matches `thenDs` \ (args, body) ->
- dsCoercion co_fn (return (mkLams args body)) `thenDs` \ rhs ->
- returnDs ((fun,rhs) : rest)
+dsHsBind _ rest (FunBind { fun_id = L _ fun, fun_matches = matches,
+ fun_co_fn = co_fn, fun_tick = tick, fun_infix = inf }) = do
+ (args, body) <- matchWrapper (FunRhs (idName fun) inf) matches
+ body' <- mkOptTickBox tick body
+ rhs <- dsCoercion co_fn (return (mkLams args body'))
+ return ((fun,rhs) : rest)
-dsHsBind auto_scc rest (PatBind { pat_lhs = pat, pat_rhs = grhss, pat_rhs_ty = ty })
- = dsGuarded grhss ty `thenDs` \ body_expr ->
- mkSelectorBinds pat body_expr `thenDs` \ sel_binds ->
- returnDs (sel_binds ++ rest)
+dsHsBind _ rest (PatBind { pat_lhs = pat, pat_rhs = grhss, pat_rhs_ty = ty }) = do
+ body_expr <- dsGuarded grhss ty
+ sel_binds <- mkSelectorBinds pat body_expr
+ return (sel_binds ++ rest)
-- Note [Rules and inlining]
-- Common special case: no type or dictionary abstraction
-- Another common case: one exported variable
-- Non-recursive bindings come through this way
dsHsBind auto_scc rest
- (AbsBinds all_tyvars dicts exports@[(tyvars, global, local, prags)] binds)
- = ASSERT( all (`elem` tyvars) all_tyvars )
- ds_lhs_binds NoSccs binds `thenDs` \ core_prs ->
- let
- -- Always treat the binds as recursive, because the typechecker
- -- makes rather mixed-up dictionary bindings
- core_bind = Rec core_prs
- in
- mappM (dsSpec all_tyvars dicts tyvars global local core_bind)
- prags `thenDs` \ mb_specs ->
+ (AbsBinds all_tyvars dicts [(tyvars, global, local, prags)] binds)
+ = ASSERT( all (`elem` tyvars) all_tyvars ) do
+ core_prs <- ds_lhs_binds NoSccs binds
let
- (spec_binds, rules) = unzip (catMaybes mb_specs)
- global' = addIdSpecialisations global rules
- rhs' = mkLams tyvars $ mkLams dicts $ Let core_bind (Var local)
- bind = addInlinePrags prags global' $ addAutoScc auto_scc global' rhs'
- in
- returnDs (bind : spec_binds ++ rest)
+ -- Always treat the binds as recursive, because the typechecker
+ -- makes rather mixed-up dictionary bindings
+ core_bind = Rec core_prs
+
+ mb_specs <- mapM (dsSpec all_tyvars dicts tyvars global local core_bind) prags
+ let
+ (spec_binds, rules) = unzip (catMaybes mb_specs)
+ global' = addIdSpecialisations global rules
+ rhs' = mkLams tyvars $ mkLams dicts $ Let core_bind (Var local)
+ bind = addInlinePrags prags global' $ addAutoScc auto_scc global' rhs'
+
+ return (bind : spec_binds ++ rest)
dsHsBind auto_scc rest (AbsBinds all_tyvars dicts exports binds)
= do { core_prs <- ds_lhs_binds NoSccs binds
-- Rec because of mixed-up dictionary bindings
core_bind = Rec (map do_one core_prs)
- tup_expr = mkTupleExpr locals
+ tup_expr = mkBigCoreVarTup locals
tup_ty = exprType tup_expr
poly_tup_expr = mkLams all_tyvars $ mkLams dicts $
Let core_bind tup_expr
mk_bind ((tyvars, global, local, prags), n) -- locals !! n == local
= -- Need to make fresh locals to bind in the selector, because
- -- some of the tyvars will be bound to voidTy
- do { locals' <- newSysLocalsDs (map substitute local_tys)
+ -- some of the tyvars will be bound to 'Any'
+ do { ty_args <- mapM mk_ty_arg all_tyvars
+ ; let substitute = substTyWith all_tyvars ty_args
+ ; locals' <- newSysLocalsDs (map substitute local_tys)
; tup_id <- newSysLocalDs (substitute tup_ty)
; mb_specs <- mapM (dsSpec all_tyvars dicts tyvars global local core_bind)
prags
rhs = mkLams tyvars $ mkLams dicts $
mkTupleSelector locals' (locals' !! n) tup_id $
mkApps (mkTyApps (Var poly_tup_id) ty_args) dict_args
- ; returnDs ((global', rhs) : spec_binds) }
+ ; return ((global', rhs) : spec_binds) }
where
- mk_ty_arg all_tyvar | all_tyvar `elem` tyvars = mkTyVarTy all_tyvar
- | otherwise = voidTy
- ty_args = map mk_ty_arg all_tyvars
- substitute = substTyWith all_tyvars ty_args
+ mk_ty_arg all_tyvar
+ | all_tyvar `elem` tyvars = return (mkTyVarTy all_tyvar)
+ | otherwise = dsMkArbitraryType all_tyvar
- ; export_binds_s <- mappM mk_bind (exports `zip` [0..])
+ ; export_binds_s <- mapM mk_bind (exports `zip` [0..])
-- don't scc (auto-)annotate the tuple itself.
- ; returnDs ((poly_tup_id, poly_tup_expr) :
+ ; return ((poly_tup_id, poly_tup_expr) :
(concat export_binds_s ++ rest)) }
-mkABEnv :: [([TyVar], Id, Id, [Prag])] -> VarEnv (Id, [Prag])
+mkABEnv :: [([TyVar], Id, Id, [LPrag])] -> VarEnv (Id, [LPrag])
-- Takes the exports of a AbsBinds, and returns a mapping
-- lcl_id -> (gbl_id, prags)
mkABEnv exports = mkVarEnv [ (lcl_id, (gbl_id, prags))
dsSpec :: [TyVar] -> [DictId] -> [TyVar]
-> Id -> Id -- Global, local
- -> CoreBind -> Prag
+ -> CoreBind -> LPrag
-> DsM (Maybe ((Id,CoreExpr), -- Binding for specialised Id
CoreRule)) -- Rule for the Global Id
-- /\b.\(d:Ix b). in f Int b dInt d
-- The idea is that f occurs just once, so it'll be
-- inlined and specialised
-
-dsSpec all_tvs dicts tvs poly_id mono_id mono_bind (InlinePrag {})
+--
+-- Given SpecPrag (/\as.\ds. f es) t, we have
+-- the defn f_spec as ds = let-nonrec f = /\fas\fds. let f_mono = <f-rhs> in f_mono
+-- in f es
+-- and the RULE forall as, ds. f es = f_spec as ds
+--
+-- It is *possible* that 'es' does not mention all of the dictionaries 'ds'
+-- (a bit silly, because then the
+dsSpec _ _ _ _ _ _ (L _ (InlinePrag {}))
= return Nothing
dsSpec all_tvs dicts tvs poly_id mono_id mono_bind
- (SpecPrag spec_expr spec_ty const_dicts inl)
- = do { let poly_name = idName poly_id
+ (L loc (SpecPrag spec_expr spec_ty inl))
+ = putSrcSpanDs loc $
+ do { let poly_name = idName poly_id
; spec_name <- newLocalName poly_name
; ds_spec_expr <- dsExpr spec_expr
- ; let (bndrs, body) = collectBinders ds_spec_expr
- mb_lhs = decomposeRuleLhs (bndrs ++ const_dicts) body
-
- ; case mb_lhs of
- Nothing -> do { warnDs msg; return Nothing }
-
- Just (bndrs', var, args) -> return (Just (addInlineInfo inl spec_id spec_rhs, rule))
- where
- local_poly = setIdNotExported poly_id
+ ; 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 mb_lhs of
+ Nothing -> do { warnDs decomp_msg; return Nothing }
+
+ Just (_, args) -> do
+
+ { f_body <- fix_up (Let mono_bind (Var mono_id))
+
+ ; let local_poly = setIdNotExported poly_id
-- Very important to make the 'f' non-exported,
-- else it won't be inlined!
spec_id = mkLocalId spec_name spec_ty
spec_rhs = Let (NonRec local_poly poly_f_body) ds_spec_expr
- poly_f_body = mkLams (tvs ++ dicts) $
- fix_up (Let mono_bind (Var mono_id))
-
- -- Quantify over constant dicts on the LHS, since
- -- their value depends only on their type
- -- The ones we are interested in may even be imported
- -- e.g. GHC.Base.dEqInt
+ poly_f_body = mkLams (tvs ++ dicts) f_body
+
+ extra_dict_bndrs = filter isDictId (varSetElems (exprFreeVars ds_spec_expr))
+ -- Note [Const rule dicts]
rule = mkLocalRule (mkFastString ("SPEC " ++ showSDoc (ppr poly_name)))
AlwaysActive poly_name
- bndrs' -- Includes constant dicts
- args
+ (extra_dict_bndrs ++ bndrs) args
(mkVarApps (Var spec_id) bndrs)
- }
+ ; return (Just (addInlineInfo inl spec_id spec_rhs, rule))
+ } } }
where
- -- Bind to voidTy any of all_ptvs that aren't
+ -- Bind to Any any of all_ptvs that aren't
-- relevant for this particular function
- fix_up body | null void_tvs = body
- | otherwise = mkTyApps (mkLams void_tvs body)
- (map (const voidTy) void_tvs)
+ fix_up body | null void_tvs = return body
+ | otherwise = do { void_tys <- mapM dsMkArbitraryType void_tvs
+ ; return (mkTyApps (mkLams void_tvs body) void_tys) }
+
void_tvs = all_tvs \\ tvs
- msg = hang (ptext SLIT("Specialisation too complicated to desugar; ignored"))
- 2 (ppr spec_expr)
+ dead_msg bs = vcat [ sep [ptext SLIT("Useless constraint") <> plural bs
+ <+> ptext SLIT("in specialied type:"),
+ nest 2 (pprTheta (map get_pred bs))]
+ , ptext SLIT("SPECIALISE pragma ignored")]
+ get_pred b = ASSERT( isId b ) expectJust "dsSpec" (tcSplitPredTy_maybe (idType b))
+
+ decomp_msg = hang (ptext SLIT("Specialisation too complicated to desugar; ignored"))
+ 2 (ppr spec_expr)
+
+dsMkArbitraryType :: TcTyVar -> DsM Type
+dsMkArbitraryType tv = mkArbitraryType warn tv
+ where
+ warn span msg = putSrcSpanDs span (warnDs msg)
\end{code}
+Note [Unused spec binders]
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+Consider
+ f :: a -> a
+ {-# SPECIALISE f :: Eq a => a -> a #-}
+It's true that this *is* a more specialised type, but the rule
+we get is something like this:
+ f_spec d = f
+ RULE: f = f_spec d
+Note that the rule is bogus, becuase it mentions a 'd' that is
+not bound on the LHS! But it's a silly specialisation anyway, becuase
+the constraint is unused. We could bind 'd' to (error "unused")
+but it seems better to reject the program because it's almost certainly
+a mistake. That's what the isDeadBinder call detects.
+
+Note [Const rule dicts]
+~~~~~~~~~~~~~~~~~~~~~~~
+When the LHS of a specialisation rule, (/\as\ds. f es) has a free dict,
+which is presumably in scope at the function definition site, we can quantify
+over it too. *Any* dict with that type will do.
+
+So for example when you have
+ f :: Eq a => a -> a
+ f = <rhs>
+ {-# SPECIALISE f :: Int -> Int #-}
+
+Then we get the SpecPrag
+ SpecPrag (f Int dInt) Int
+
+And from that we want the rule
+
+ RULE forall dInt. f Int dInt = f_spec
+ f_spec = let f = <rhs> in f Int dInt
+
+
%************************************************************************
%* *
%************************************************************************
\begin{code}
-decomposeRuleLhs :: [Var] -> CoreExpr -> Maybe ([Var], Id, [CoreExpr])
+decomposeRuleLhs :: CoreExpr -> Maybe (Id, [CoreExpr])
-- Returns Nothing if the LHS isn't of the expected shape
--- The argument 'all_bndrs' includes the "constant dicts" of the LHS,
--- and they may be GlobalIds, which we can't forall-ify.
--- So we substitute them out instead
-decomposeRuleLhs all_bndrs lhs
- = go init_env (occurAnalyseExpr lhs) -- Occurrence analysis sorts out the dict
- -- bindings so we know if they are recursive
+decomposeRuleLhs lhs
+ = go emptyVarEnv (occurAnalyseExpr lhs) -- Occurrence analysis sorts out the dict
+ -- bindings so we know if they are recursive
where
-
- -- all_bndrs may include top-level imported dicts,
- -- imported things with a for-all.
- -- So we localise them and subtitute them out
- bndr_prs = [ (id, Var (localise id)) | id <- all_bndrs, isGlobalId id ]
- localise d = mkLocalId (idName d) (idType d)
-
- init_env = mkVarEnv bndr_prs
- all_bndrs' = map subst_bndr all_bndrs
- subst_bndr bndr = case lookupVarEnv init_env bndr of
- Just (Var bndr') -> bndr'
- Just other -> panic "decomposeRuleLhs"
- Nothing -> bndr
-
- -- 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
+ -- 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 (extendVarEnv env dict (simpleSubst env rhs)) body
go env body
- = case collectArgs (simpleSubst env body) of
- (Var fn, args) -> Just (all_bndrs', fn, args)
- other -> Nothing
+ = case collectArgs (simpleSubst env body) of
+ (Var fn, args) -> Just (fn, args)
+ _ -> Nothing
simpleSubst :: IdEnv CoreExpr -> CoreExpr -> CoreExpr
-- Similar to CoreSubst.substExpr, except that
-- (a) takes no account of capture; dictionary bindings use new names
-- (b) can have a GlobalId (imported) in its domain
-- (c) Ids only; no types are substituted
-
+--
+-- (b) is the reason we can't use CoreSubst... and it's no longer relevant
+-- so really we should replace simpleSubst
simpleSubst subst expr
= go expr
where
go (Case scrut bndr ty alts) = Case (go scrut) bndr ty
[(c,bs,go r) | (c,bs,r) <- alts]
-addInlinePrags :: [Prag] -> Id -> CoreExpr -> (Id,CoreExpr)
+addInlinePrags :: [LPrag] -> Id -> CoreExpr -> (Id,CoreExpr)
addInlinePrags prags bndr rhs
- = case [inl | InlinePrag inl <- prags] of
+ = case [inl | L _ (InlinePrag inl) <- prags] of
[] -> (bndr, rhs)
(inl:_) -> addInlineInfo inl bndr rhs
wrap the dict in @_scc_ DICT <dict>@:
\begin{code}
-addDictScc var rhs = returnDs rhs
+addDictScc :: Id -> CoreExpr -> DsM CoreExpr
+addDictScc _ rhs = return rhs
{- DISABLED for now (need to somehow make up a name for the scc) -- SDM
| not ( opt_SccProfilingOn && opt_AutoSccsOnDicts)
|| not (isDictId var)
- = returnDs rhs -- That's easy: do nothing
+ = return rhs -- That's easy: do nothing
| otherwise
- = getModuleAndGroupDs `thenDs` \ (mod, grp) ->
+ = do (mod, grp) <- getModuleAndGroupDs
-- ToDo: do -dicts-all flag (mark dict things with individual CCs)
- returnDs (Note (SCC (mkAllDictsCC mod grp False)) rhs)
+ return (Note (SCC (mkAllDictsCC mod grp False)) rhs)
-}
\end{code}
; return (App expr (Var id)) }
dsCoercion (WpTyApp ty) thing_inside = do { expr <- thing_inside
; return (App expr (Type ty)) }
+dsCoercion WpInline thing_inside = do { expr <- thing_inside
+ ; return (mkInlineMe expr) }
dsCoercion (WpLet bs) thing_inside = do { prs <- dsLHsBinds bs
; expr <- thing_inside
; return (Let (Rec prs) expr) }
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