lower levels it is preserved with @let@/@letrec@s).
\begin{code}
-module DsBinds ( dsTopLHsBinds, dsLHsBinds, decomposeRuleLhs,
- dsCoercion,
- AutoScc(..)
+module DsBinds ( dsTopLHsBinds, dsLHsBinds, decomposeRuleLhs, dsSpec,
+ dsHsWrapper, dsTcEvBinds, dsEvBinds, wrapDsEvBinds,
+ DsEvBind(..), AutoScc(..)
) where
#include "HsVersions.h"
-import {-# SOURCE #-} DsExpr( dsLExpr, dsExpr )
+import {-# SOURCE #-} DsExpr( dsLExpr )
import {-# SOURCE #-} Match( matchWrapper )
import DsMonad
import HsSyn -- lots of things
import CoreSyn -- lots of things
+import CoreSubst
+import MkCore
import CoreUtils
+import CoreArity ( etaExpand )
+import CoreUnfold
import CoreFVs
+import Digraph
-import TcHsSyn ( mkArbitraryType ) -- Mis-placed?
import TcType
-import OccurAnal
+import Type
+import Coercion
+import TysPrim ( anyTypeOfKind )
import CostCentre
import Module
import Id
-import Var ( TyVar )
+import TyCon ( tyConDataCons )
+import Class
+import DataCon ( dataConRepType )
+import Name ( localiseName )
+import MkId ( seqId )
+import Var
import VarSet
import Rules
import VarEnv
-import Type
import Outputable
import SrcLoc
import Maybes
+import OrdList
import Bag
import BasicTypes hiding ( TopLevel )
import FastString
-import Util ( mapSnd )
+import Util
-import Control.Monad
-import Data.List
+import MonadUtils
\end{code}
%************************************************************************
%************************************************************************
\begin{code}
-dsTopLHsBinds :: AutoScc -> LHsBinds Id -> DsM [(Id,CoreExpr)]
+dsTopLHsBinds :: AutoScc -> LHsBinds Id -> DsM (OrdList (Id,CoreExpr))
dsTopLHsBinds auto_scc binds = ds_lhs_binds auto_scc binds
dsLHsBinds :: LHsBinds Id -> DsM [(Id,CoreExpr)]
-dsLHsBinds binds = ds_lhs_binds NoSccs binds
-
+dsLHsBinds binds = do { binds' <- ds_lhs_binds NoSccs binds
+ ; return (fromOL binds') }
------------------------
-ds_lhs_binds :: AutoScc -> LHsBinds Id -> DsM [(Id,CoreExpr)]
+ds_lhs_binds :: AutoScc -> LHsBinds Id -> DsM (OrdList (Id,CoreExpr))
+
-- scc annotation policy (see below)
-ds_lhs_binds auto_scc binds = foldM (dsLHsBind auto_scc) [] (bagToList binds)
-
-dsLHsBind :: AutoScc
- -> [(Id,CoreExpr)] -- Put this on the end (avoid quadratic append)
- -> LHsBind Id
- -> DsM [(Id,CoreExpr)] -- Result
-dsLHsBind auto_scc rest (L loc bind)
- = putSrcSpanDs loc $ dsHsBind auto_scc rest bind
-
-dsHsBind :: AutoScc
- -> [(Id,CoreExpr)] -- Put this on the end (avoid quadratic append)
- -> HsBind Id
- -> DsM [(Id,CoreExpr)] -- Result
-
-dsHsBind _ rest (VarBind var expr) = do
- core_expr <- dsLExpr expr
-
- -- Dictionary bindings are always VarMonoBinds, so
- -- we only need do this here
- core_expr' <- addDictScc var core_expr
- return ((var, core_expr') : 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 _ 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
--- This is a bit less trivial than you might suppose
--- The naive way woudl be to desguar to something like
--- f_lcl = ...f_lcl... -- The "binds" from AbsBinds
--- M.f = f_lcl -- Generated from "exports"
--- But we don't want that, because if M.f isn't exported,
--- it'll be inlined unconditionally at every call site (its rhs is
--- trivial). That would be ok unless it has RULES, which would
--- thereby be completely lost. Bad, bad, bad.
---
--- Instead we want to generate
--- M.f = ...f_lcl...
--- f_lcl = M.f
--- Now all is cool. The RULES are attached to M.f (by SimplCore),
--- and f_lcl is rapidly inlined away.
---
--- This does not happen in the same way to polymorphic binds,
--- because they desugar to
--- M.f = /\a. let f_lcl = ...f_lcl... in f_lcl
--- Although I'm a bit worried about whether full laziness might
--- float the f_lcl binding out and then inline M.f at its call site
-
-dsHsBind auto_scc rest (AbsBinds [] [] exports binds)
- = do { core_prs <- ds_lhs_binds NoSccs binds
- ; let env = mkABEnv exports
- do_one (lcl_id, rhs) | Just (gbl_id, prags) <- lookupVarEnv env lcl_id
- = addInlinePrags prags gbl_id $
- addAutoScc auto_scc gbl_id rhs
- | otherwise = (lcl_id, rhs)
- locals' = [(lcl_id, Var gbl_id) | (_, gbl_id, lcl_id, _) <- exports]
- ; return (map do_one core_prs ++ locals' ++ rest) }
- -- No Rec needed here (contrast the other AbsBinds cases)
- -- because we can rely on the enclosing dsBind to wrap in Rec
-
- -- Another common case: one exported variable
+ds_lhs_binds auto_scc binds = do { ds_bs <- mapBagM (dsLHsBind auto_scc) binds
+ ; return (foldBag appOL id nilOL ds_bs) }
+
+dsLHsBind :: AutoScc -> LHsBind Id -> DsM (OrdList (Id,CoreExpr))
+dsLHsBind auto_scc (L loc bind)
+ = putSrcSpanDs loc $ dsHsBind auto_scc bind
+
+dsHsBind :: AutoScc -> HsBind Id -> DsM (OrdList (Id,CoreExpr))
+
+dsHsBind _ (VarBind { var_id = var, var_rhs = expr, var_inline = inline_regardless })
+ = do { core_expr <- dsLExpr expr
+
+ -- Dictionary bindings are always VarBinds,
+ -- so we only need do this here
+ ; core_expr' <- addDictScc var core_expr
+ ; let var' | inline_regardless = var `setIdUnfolding` mkCompulsoryUnfolding core_expr'
+ | otherwise = var
+
+ ; return (unitOL (makeCorePair var' False 0 core_expr')) }
+
+dsHsBind auto_scc (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
+ ; wrap_fn' <- dsHsWrapper co_fn
+ ; let rhs = addAutoScc auto_scc fun $ wrap_fn' (mkLams args body')
+ ; return (unitOL (makeCorePair fun False 0 rhs)) }
+
+dsHsBind auto_scc (PatBind { pat_lhs = pat, pat_rhs = grhss, pat_rhs_ty = ty })
+ = do { body_expr <- dsGuarded grhss ty
+ ; sel_binds <- mkSelectorBinds pat body_expr
+ -- We silently ignore inline pragmas; no makeCorePair
+ -- Not so cool, but really doesn't matter
+ ; let sel_binds' = [ (v, addAutoScc auto_scc v expr)
+ | (v, expr) <- sel_binds ]
+ ; return (toOL sel_binds') }
+
+ -- A common case: one exported variable
-- Non-recursive bindings come through this way
-dsHsBind auto_scc rest
- (AbsBinds all_tyvars dicts [(tyvars, global, local, prags)] binds)
- = ASSERT( all (`elem` tyvars) all_tyvars ) do
- core_prs <- ds_lhs_binds NoSccs binds
- let
- -- Always treat the binds as recursive, because the typechecker
- -- makes rather mixed-up dictionary bindings
- core_bind = Rec core_prs
+ -- So do self-recursive bindings, and recursive bindings
+ -- that have been chopped up with type signatures
+dsHsBind auto_scc (AbsBinds { abs_tvs = all_tyvars, abs_ev_vars = dicts
+ , abs_exports = [(tyvars, global, local, prags)]
+ , abs_ev_binds = ev_binds, abs_binds = binds })
+ = ASSERT( all (`elem` tyvars) all_tyvars )
+ do { bind_prs <- ds_lhs_binds NoSccs binds
+ ; ds_ev_binds <- dsTcEvBinds ev_binds
+
+ ; let core_bind = Rec (fromOL bind_prs)
+ rhs = addAutoScc auto_scc global $
+ mkLams tyvars $ mkLams dicts $
+ wrapDsEvBinds ds_ev_binds $
+ Let core_bind $
+ Var local
- 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'
+ ; (spec_binds, rules) <- dsSpecs rhs prags
+
+ ; let global' = addIdSpecialisations global rules
+ main_bind = makeCorePair global' (isDefaultMethod prags)
+ (dictArity dicts) rhs
- return (bind : spec_binds ++ rest)
+ ; return (main_bind `consOL` spec_binds) }
-dsHsBind auto_scc rest (AbsBinds all_tyvars dicts exports binds)
- = do { core_prs <- ds_lhs_binds NoSccs binds
+dsHsBind auto_scc (AbsBinds { abs_tvs = all_tyvars, abs_ev_vars = dicts
+ , abs_exports = exports, abs_ev_binds = ev_binds
+ , abs_binds = binds })
+ = do { bind_prs <- ds_lhs_binds NoSccs binds
+ ; ds_ev_binds <- dsTcEvBinds ev_binds
; let env = mkABEnv exports
- do_one (lcl_id,rhs) | Just (gbl_id, prags) <- lookupVarEnv env lcl_id
- = addInlinePrags prags lcl_id $
- addAutoScc auto_scc gbl_id rhs
+ do_one (lcl_id,rhs) | Just (_, gbl_id, _, _prags) <- lookupVarEnv env lcl_id
+ = (lcl_id, addAutoScc auto_scc gbl_id rhs)
| otherwise = (lcl_id,rhs)
- -- Rec because of mixed-up dictionary bindings
- core_bind = Rec (map do_one core_prs)
-
- tup_expr = mkBigCoreVarTup locals
- tup_ty = exprType tup_expr
- poly_tup_expr = mkLams all_tyvars $ mkLams dicts $
- Let core_bind tup_expr
- locals = [local | (_, _, local, _) <- exports]
- local_tys = map idType locals
-
- ; poly_tup_id <- newSysLocalDs (exprType poly_tup_expr)
-
- ; let dict_args = map Var dicts
-
- 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 'Any'
- do { ty_args <- mapM mk_ty_arg all_tyvars
- ; let substitute = substTyWith all_tyvars ty_args
+ core_bind = Rec (map do_one (fromOL bind_prs))
+ -- Monomorphic recursion possible, hence Rec
+
+ tup_expr = mkBigCoreVarTup locals
+ tup_ty = exprType tup_expr
+ poly_tup_rhs = mkLams all_tyvars $ mkLams dicts $
+ wrapDsEvBinds ds_ev_binds $
+ Let core_bind $
+ tup_expr
+ locals = [local | (_, _, local, _) <- exports]
+ local_tys = map idType locals
+
+ ; poly_tup_id <- newSysLocalDs (exprType poly_tup_rhs)
+
+ ; let mk_bind ((tyvars, global, _, spec_prags), n) -- locals!!n == local
+ = -- Need to make fresh locals to bind in the selector,
+ -- because some of the tyvars will be bound to 'Any'
+ do { let ty_args = map mk_ty_arg all_tyvars
+ 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
- ; let (spec_binds, rules) = unzip (catMaybes mb_specs)
- global' = addIdSpecialisations global rules
- rhs = mkLams tyvars $ mkLams dicts $
+ ; let rhs = mkLams tyvars $ mkLams dicts $
mkTupleSelector locals' (locals' !! n) tup_id $
- mkApps (mkTyApps (Var poly_tup_id) ty_args) dict_args
- ; return ((global', rhs) : spec_binds) }
+ mkVarApps (mkTyApps (Var poly_tup_id) ty_args)
+ dicts
+ full_rhs = Let (NonRec poly_tup_id poly_tup_rhs) rhs
+ ; (spec_binds, rules) <- dsSpecs full_rhs spec_prags
+
+ ; let global' = addIdSpecialisations global rules
+ ; return ((global', rhs) `consOL` spec_binds) }
where
mk_ty_arg all_tyvar
- | all_tyvar `elem` tyvars = return (mkTyVarTy all_tyvar)
+ | all_tyvar `elem` tyvars = mkTyVarTy all_tyvar
| otherwise = dsMkArbitraryType all_tyvar
; export_binds_s <- mapM mk_bind (exports `zip` [0..])
- -- don't scc (auto-)annotate the tuple itself.
+ -- Don't scc (auto-)annotate the tuple itself.
- ; return ((poly_tup_id, poly_tup_expr) :
- (concat export_binds_s ++ rest)) }
+ ; return ((poly_tup_id, poly_tup_rhs) `consOL`
+ concatOL export_binds_s) }
-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))
- | (_, gbl_id, lcl_id, prags) <- exports]
-
-
-dsSpec :: [TyVar] -> [DictId] -> [TyVar]
- -> Id -> Id -- Global, local
- -> CoreBind -> LPrag
- -> DsM (Maybe ((Id,CoreExpr), -- Binding for specialised Id
- CoreRule)) -- Rule for the Global Id
-
--- Example:
--- f :: (Eq a, Ix b) => a -> b -> b
--- {-# SPECIALISE f :: Ix b => Int -> b -> b #-}
---
--- AbsBinds [ab] [d1,d2] [([ab], f, f_mono, prags)] binds
---
--- SpecPrag (/\b.\(d:Ix b). f Int b dInt d)
--- (forall b. Ix b => Int -> b -> b)
---
--- Rule: forall b,(d:Ix b). f Int b dInt d = f_spec b d
---
--- Spec bind: f_spec = Let f = /\ab \(d1:Eq a)(d2:Ix b). let binds in f_mono
--- /\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
---
--- 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
- (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 (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) 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
- (extra_dict_bndrs ++ bndrs) args
- (mkVarApps (Var spec_id) bndrs)
- ; return (Just (addInlineInfo inl spec_id spec_rhs, rule))
- } } }
+--------------------------------------
+data DsEvBind
+ = LetEvBind -- Dictionary or coercion
+ CoreBind -- recursive or non-recursive
+
+ | CaseEvBind -- Coercion binding by superclass selection
+ -- Desugars to case d of d { K _ g _ _ _ -> ... }
+ DictId -- b The dictionary
+ AltCon -- K Its constructor
+ [CoreBndr] -- _ g _ _ _ The binders in the alternative
+
+wrapDsEvBinds :: [DsEvBind] -> CoreExpr -> CoreExpr
+wrapDsEvBinds ds_ev_binds body = foldr wrap_one body ds_ev_binds
where
- -- Bind to Any any of all_ptvs that aren't
- -- relevant for this particular function
- fix_up body | null void_tvs = return body
- | otherwise = do { void_tys <- mapM dsMkArbitraryType void_tvs
- ; return (mkTyApps (mkLams void_tvs body) void_tys) }
+ body_ty = exprType body
+ wrap_one (LetEvBind b) body = Let b body
+ wrap_one (CaseEvBind x k xs) body = Case (Var x) x body_ty [(k,xs,body)]
- void_tvs = all_tvs \\ tvs
+dsTcEvBinds :: TcEvBinds -> DsM [DsEvBind]
+dsTcEvBinds (TcEvBinds {}) = panic "dsEvBinds" -- Zonker has got rid of this
+dsTcEvBinds (EvBinds bs) = dsEvBinds bs
- 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))
+dsEvBinds :: Bag EvBind -> DsM [DsEvBind]
+dsEvBinds bs = return (map dsEvGroup sccs)
+ where
+ sccs :: [SCC EvBind]
+ sccs = stronglyConnCompFromEdgedVertices edges
+
+ edges :: [(EvBind, EvVar, [EvVar])]
+ edges = foldrBag ((:) . mk_node) [] bs
+
+ mk_node :: EvBind -> (EvBind, EvVar, [EvVar])
+ mk_node b@(EvBind var term) = (b, var, free_vars_of term)
+
+ free_vars_of :: EvTerm -> [EvVar]
+ free_vars_of (EvId v) = [v]
+ free_vars_of (EvCast v co) = v : varSetElems (tyCoVarsOfCo co)
+ free_vars_of (EvCoercion co) = varSetElems (tyCoVarsOfCo co)
+ free_vars_of (EvDFunApp _ _ vs) = vs
+ free_vars_of (EvSuperClass d _) = [d]
+
+dsEvGroup :: SCC EvBind -> DsEvBind
+dsEvGroup (AcyclicSCC (EvBind co_var (EvSuperClass dict n)))
+ | isCoVar co_var -- An equality superclass
+ = ASSERT( null other_data_cons )
+ CaseEvBind dict (DataAlt data_con) bndrs
+ where
+ (cls, tys) = getClassPredTys (evVarPred dict)
+ (data_con:other_data_cons) = tyConDataCons (classTyCon cls)
+ (ex_tvs, theta, rho) = tcSplitSigmaTy (applyTys (dataConRepType data_con) tys)
+ (arg_tys, _) = splitFunTys rho
+ bndrs = ex_tvs ++ map mk_wild_pred (theta `zip` [0..])
+ ++ map mkWildValBinder arg_tys
+ mk_wild_pred (p, i) | i==n = ASSERT( p `eqPred` (coVarPred co_var))
+ co_var
+ | otherwise = mkWildEvBinder p
+
+dsEvGroup (AcyclicSCC (EvBind v r))
+ = LetEvBind (NonRec v (dsEvTerm r))
- decomp_msg = hang (ptext (sLit "Specialisation too complicated to desugar; ignored"))
- 2 (ppr spec_expr)
+dsEvGroup (CyclicSCC bs)
+ = LetEvBind (Rec (map ds_pair bs))
+ where
+ ds_pair (EvBind v r) = (v, dsEvTerm r)
+
+dsEvTerm :: EvTerm -> CoreExpr
+dsEvTerm (EvId v) = Var v
+dsEvTerm (EvCast v co) = Cast (Var v) co
+dsEvTerm (EvDFunApp df tys vars) = Var df `mkTyApps` tys `mkVarApps` vars
+dsEvTerm (EvCoercion co) = Coercion co
+dsEvTerm (EvSuperClass d n)
+ = ASSERT( isClassPred (classSCTheta cls !! n) )
+ -- We can only select *dictionary* superclasses
+ -- in terms. Equality superclasses are dealt with
+ -- in dsEvGroup, where they can generate a case expression
+ Var sc_sel_id `mkTyApps` tys `App` Var d
+ where
+ sc_sel_id = classSCSelId cls n -- Zero-indexed
+ (cls, tys) = getClassPredTys (evVarPred d)
+
+------------------------
+makeCorePair :: Id -> Bool -> Arity -> CoreExpr -> (Id, CoreExpr)
+makeCorePair gbl_id is_default_method dict_arity rhs
+ | is_default_method -- Default methods are *always* inlined
+ = (gbl_id `setIdUnfolding` mkCompulsoryUnfolding rhs, rhs)
+
+ | otherwise
+ = case inlinePragmaSpec inline_prag of
+ EmptyInlineSpec -> (gbl_id, rhs)
+ NoInline -> (gbl_id, rhs)
+ Inlinable -> (gbl_id `setIdUnfolding` inlinable_unf, rhs)
+ Inline -> inline_pair
-dsMkArbitraryType :: TcTyVar -> DsM Type
-dsMkArbitraryType tv = mkArbitraryType warn tv
where
- warn span msg = putSrcSpanDs span (warnDs msg)
+ inline_prag = idInlinePragma gbl_id
+ inlinable_unf = mkInlinableUnfolding rhs
+ inline_pair
+ | Just arity <- inlinePragmaSat inline_prag
+ -- Add an Unfolding for an INLINE (but not for NOINLINE)
+ -- And eta-expand the RHS; see Note [Eta-expanding INLINE things]
+ , let real_arity = dict_arity + arity
+ -- NB: The arity in the InlineRule takes account of the dictionaries
+ = ( gbl_id `setIdUnfolding` mkInlineUnfolding (Just real_arity) rhs
+ , etaExpand real_arity rhs)
+
+ | otherwise
+ = pprTrace "makeCorePair: arity missing" (ppr gbl_id) $
+ (gbl_id `setIdUnfolding` mkInlineUnfolding Nothing rhs, rhs)
+
+
+dictArity :: [Var] -> Arity
+-- Don't count coercion variables in arity
+dictArity dicts = count isId dicts
+
+
+------------------------
+type AbsBindEnv = VarEnv ([TyVar], Id, Id, TcSpecPrags)
+ -- Maps the "lcl_id" for an AbsBind to
+ -- its "gbl_id" and associated pragmas, if any
+
+mkABEnv :: [([TyVar], Id, Id, TcSpecPrags)] -> AbsBindEnv
+-- Takes the exports of a AbsBinds, and returns a mapping
+-- lcl_id -> (tyvars, gbl_id, lcl_id, prags)
+mkABEnv exports = mkVarEnv [ (lcl_id, export) | export@(_, _, lcl_id, _) <- exports]
\end{code}
+Note [Rules and inlining]
+~~~~~~~~~~~~~~~~~~~~~~~~~
+Common special case: no type or dictionary abstraction
+This is a bit less trivial than you might suppose
+The naive way woudl be to desguar to something like
+ f_lcl = ...f_lcl... -- The "binds" from AbsBinds
+ M.f = f_lcl -- Generated from "exports"
+But we don't want that, because if M.f isn't exported,
+it'll be inlined unconditionally at every call site (its rhs is
+trivial). That would be ok unless it has RULES, which would
+thereby be completely lost. Bad, bad, bad.
+
+Instead we want to generate
+ M.f = ...f_lcl...
+ f_lcl = M.f
+Now all is cool. The RULES are attached to M.f (by SimplCore),
+and f_lcl is rapidly inlined away.
+
+This does not happen in the same way to polymorphic binds,
+because they desugar to
+ M.f = /\a. let f_lcl = ...f_lcl... in f_lcl
+Although I'm a bit worried about whether full laziness might
+float the f_lcl binding out and then inline M.f at its call site
+
+Note [Specialising in no-dict case]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Even if there are no tyvars or dicts, we may have specialisation pragmas.
+Class methods can generate
+ AbsBinds [] [] [( ... spec-prag]
+ { AbsBinds [tvs] [dicts] ...blah }
+So the overloading is in the nested AbsBinds. A good example is in GHC.Float:
+
+ class (Real a, Fractional a) => RealFrac a where
+ round :: (Integral b) => a -> b
+
+ instance RealFrac Float where
+ {-# SPECIALIZE round :: Float -> Int #-}
+
+The top-level AbsBinds for $cround has no tyvars or dicts (because the
+instance does not). But the method is locally overloaded!
+
+Note [Abstracting over tyvars only]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+When abstracting over type variable only (not dictionaries), we don't really need to
+built a tuple and select from it, as we do in the general case. Instead we can take
+
+ AbsBinds [a,b] [ ([a,b], fg, fl, _),
+ ([b], gg, gl, _) ]
+ { fl = e1
+ gl = e2
+ h = e3 }
+
+and desugar it to
+
+ fg = /\ab. let B in e1
+ gg = /\b. let a = () in let B in S(e2)
+ h = /\ab. let B in e3
+
+where B is the *non-recursive* binding
+ fl = fg a b
+ gl = gg 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), 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
+ number (10), we filter the binding set B by the free
+ variables of the particular RHS. Tiresome.
+
+Why got to this trouble? It's a common case, and it removes the
+quadratic-sized tuple desugaring. Less clutter, hopefullly faster
+compilation, especially in a case where there are a *lot* of
+bindings.
+
+
+Note [Eta-expanding INLINE things]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Consider
+ foo :: Eq a => a -> a
+ {-# INLINE foo #-}
+ foo x = ...
+
+If (foo d) ever gets floated out as a common sub-expression (which can
+happen as a result of method sharing), there's a danger that we never
+get to do the inlining, which is a Terribly Bad thing given that the
+user said "inline"!
+
+To avoid this we pre-emptively eta-expand the definition, so that foo
+has the arity with which it is declared in the source code. In this
+example it has arity 2 (one for the Eq and one for x). Doing this
+should mean that (foo d) is a PAP and we don't share it.
+
+Note [Nested arities]
+~~~~~~~~~~~~~~~~~~~~~
+For reasons that are not entirely clear, method bindings come out looking like
+this:
+
+ AbsBinds [] [] [$cfromT <= [] fromT]
+ $cfromT [InlPrag=INLINE] :: T Bool -> Bool
+ { AbsBinds [] [] [fromT <= [] fromT_1]
+ fromT :: T Bool -> Bool
+ { fromT_1 ((TBool b)) = not b } } }
+
+Note the nested AbsBind. The arity for the InlineRule on $cfromT should be
+gotten from the binding for fromT_1.
+
+It might be better to have just one level of AbsBinds, but that requires more
+thought!
+
+Note [Implementing SPECIALISE pragmas]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Example:
+ f :: (Eq a, Ix b) => a -> b -> Bool
+ {-# SPECIALISE f :: (Ix p, Ix q) => Int -> (p,q) -> Bool #-}
+ f = <poly_rhs>
+
+From this the typechecker generates
+
+ AbsBinds [ab] [d1,d2] [([ab], f, f_mono, prags)] binds
+
+ SpecPrag (wrap_fn :: forall a b. (Eq a, Ix b) => XXX
+ -> forall p q. (Ix p, Ix q) => XXX[ Int/a, (p,q)/b ])
+
+Note that wrap_fn can transform *any* function with the right type prefix
+ forall ab. (Eq a, Ix b) => XXX
+regardless of XXX. It's sort of polymorphic in XXX. This is
+useful: we use the same wrapper to transform each of the class ops, as
+well as the dict.
+
+From these we generate:
+
+ Rule: forall p, q, (dp:Ix p), (dq:Ix q).
+ f Int (p,q) dInt ($dfInPair dp dq) = f_spec p q dp dq
+
+ Spec bind: f_spec = wrap_fn <poly_rhs>
+
+Note that
+
+ * The LHS of the rule may mention dictionary *expressions* (eg
+ $dfIxPair dp dq), and that is essential because the dp, dq are
+ needed on the RHS.
+
+ * The RHS of f_spec, <poly_rhs> has a *copy* of 'binds', so that it
+ can fully specialise it.
+
+\begin{code}
+------------------------
+dsSpecs :: CoreExpr -- Its rhs
+ -> TcSpecPrags
+ -> DsM ( OrdList (Id,CoreExpr) -- Binding for specialised Ids
+ , [CoreRule] ) -- Rules for the Global Ids
+-- See Note [Implementing SPECIALISE pragmas]
+dsSpecs _ IsDefaultMethod = return (nilOL, [])
+dsSpecs poly_rhs (SpecPrags sps)
+ = do { pairs <- mapMaybeM (dsSpec (Just poly_rhs)) sps
+ ; let (spec_binds_s, rules) = unzip pairs
+ ; return (concatOL spec_binds_s, rules) }
+
+dsSpec :: Maybe CoreExpr -- Just rhs => RULE is for a local binding
+ -- Nothing => RULE is for an imported Id
+ -- rhs is in the Id's unfolding
+ -> Located TcSpecPrag
+ -> DsM (Maybe (OrdList (Id,CoreExpr), CoreRule))
+dsSpec mb_poly_rhs (L loc (SpecPrag poly_id spec_co spec_inl))
+ | isJust (isClassOpId_maybe poly_id)
+ = putSrcSpanDs loc $
+ do { warnDs (ptext (sLit "Ignoring useless SPECIALISE pragma for class method selector")
+ <+> quotes (ppr poly_id))
+ ; return Nothing } -- There is no point in trying to specialise a class op
+ -- Moreover, classops don't (currently) have an inl_sat arity set
+ -- (it would be Just 0) and that in turn makes makeCorePair bleat
+
+ | otherwise
+ = putSrcSpanDs loc $
+ do { let poly_name = idName poly_id
+ ; spec_name <- newLocalName poly_name
+ ; wrap_fn <- dsHsWrapper spec_co
+ ; let (bndrs, ds_lhs) = collectBinders (wrap_fn (Var poly_id))
+ spec_ty = mkPiTypes bndrs (exprType ds_lhs)
+ ; case decomposeRuleLhs bndrs ds_lhs of {
+ Left msg -> do { warnDs msg; return Nothing } ;
+ Right (final_bndrs, _fn, args) -> do
+
+ { (spec_unf, unf_pairs) <- specUnfolding wrap_fn spec_ty (realIdUnfolding poly_id)
+
+ ; let spec_id = mkLocalId spec_name spec_ty
+ `setInlinePragma` inl_prag
+ `setIdUnfolding` spec_unf
+ inl_prag | isDefaultInlinePragma spec_inl = idInlinePragma poly_id
+ | otherwise = spec_inl
+ -- Get the INLINE pragma from SPECIALISE declaration, or,
+ -- failing that, from the original Id
+
+ rule = mkRule False {- Not auto -} is_local_id
+ (mkFastString ("SPEC " ++ showSDoc (ppr poly_name)))
+ AlwaysActive poly_name
+ final_bndrs args
+ (mkVarApps (Var spec_id) bndrs)
+
+ spec_rhs = wrap_fn poly_rhs
+ spec_pair = makeCorePair spec_id False (dictArity bndrs) spec_rhs
+
+ ; return (Just (spec_pair `consOL` unf_pairs, rule))
+ } } }
+ where
+ is_local_id = isJust mb_poly_rhs
+ poly_rhs | Just rhs <- mb_poly_rhs
+ = rhs -- Local Id; this is its rhs
+ | Just unfolding <- maybeUnfoldingTemplate (realIdUnfolding poly_id)
+ = unfolding -- Imported Id; this is its unfolding
+ -- Use realIdUnfolding so we get the unfolding
+ -- even when it is a loop breaker.
+ -- We want to specialise recursive functions!
+ | otherwise = pprPanic "dsImpSpecs" (ppr poly_id)
+ -- The type checker has checked that it *has* an unfolding
+
+specUnfolding :: (CoreExpr -> CoreExpr) -> Type
+ -> Unfolding -> DsM (Unfolding, OrdList (Id,CoreExpr))
+{- [Dec 10: TEMPORARILY commented out, until we can straighten out how to
+ generate unfoldings for specialised DFuns
+
+specUnfolding wrap_fn spec_ty (DFunUnfolding _ _ ops)
+ = do { let spec_rhss = map wrap_fn ops
+ ; spec_ids <- mapM (mkSysLocalM (fsLit "spec") . exprType) spec_rhss
+ ; return (mkDFunUnfolding spec_ty (map Var spec_ids), toOL (spec_ids `zip` spec_rhss)) }
+-}
+specUnfolding _ _ _
+ = return (noUnfolding, nilOL)
+
+dsMkArbitraryType :: TcTyVar -> Type
+dsMkArbitraryType tv = anyTypeOfKind (tyVarKind tv)
+\end{code}
+
+%************************************************************************
+%* *
+\subsection{Adding inline pragmas}
+%* *
+%************************************************************************
+
+\begin{code}
+decomposeRuleLhs :: [Var] -> CoreExpr -> Either SDoc ([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 bndrs lhs
+ = -- Note [Simplifying the left-hand side of a RULE]
+ case collectArgs opt_lhs of
+ (Var fn, args) -> check_bndrs fn args
+
+ (Case scrut bndr ty [(DEFAULT, _, body)], args)
+ | isDeadBinder bndr -- Note [Matching seqId]
+ -> check_bndrs seqId (args' ++ args)
+ where
+ args' = [Type (idType bndr), Type ty, scrut, body]
+
+ _other -> Left bad_shape_msg
+ where
+ opt_lhs = simpleOptExpr lhs
+
+ check_bndrs fn args
+ | null (dead_bndrs) = Right (extra_dict_bndrs ++ bndrs, fn, args)
+ | otherwise = Left (vcat (map dead_msg dead_bndrs))
+ where
+ arg_fvs = exprsFreeVars args
+
+ -- Check for dead binders: Note [Unused spec binders]
+ dead_bndrs = filterOut (`elemVarSet` arg_fvs) bndrs
+
+ -- Add extra dict binders: Note [Constant rule dicts]
+ extra_dict_bndrs = [ mkLocalId (localiseName (idName d)) (idType d)
+ | d <- varSetElems (arg_fvs `delVarSetList` bndrs)
+ , isDictId d]
+
+
+ bad_shape_msg = hang (ptext (sLit "RULE left-hand side too complicated to desugar"))
+ 2 (ppr opt_lhs)
+ dead_msg bndr = hang (sep [ ptext (sLit "Forall'd") <+> pp_bndr bndr
+ , ptext (sLit "is not bound in RULE lhs")])
+ 2 (ppr opt_lhs)
+ pp_bndr bndr
+ | isTyVar bndr = ptext (sLit "type variable") <+> quotes (ppr bndr)
+ | isEvVar bndr = ptext (sLit "constraint") <+> quotes (ppr (evVarPred bndr))
+ | otherwise = ptext (sLit "variable") <+> quotes (ppr bndr)
+\end{code}
+
+Note [Simplifying the left-hand side of a RULE]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+simpleOptExpr occurrence-analyses and simplifies the lhs
+and thereby
+(a) sorts dict bindings into NonRecs and inlines them
+(b) substitute trivial lets so that they don't get in the way
+ Note that we substitute the function too; we might
+ have this as a LHS: let f71 = M.f Int in f71
+(c) does eta reduction
+
+For (c) consider the fold/build rule, which without simplification
+looked like:
+ fold k z (build (/\a. g a)) ==> ...
+This doesn't match unless you do eta reduction on the build argument.
+Similarly for a LHS like
+ augment g (build h)
+we do not want to get
+ augment (\a. g a) (build h)
+otherwise we don't match when given an argument like
+ augment (\a. h a a) (build h)
+
+NB: tcSimplifyRuleLhs is very careful not to generate complicated
+ dictionary expressions that we might have to match
+
+Note [Matching seqId]
+~~~~~~~~~~~~~~~~~~~
+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.
+
Note [Unused spec binders]
~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider
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]
+Note [Constant 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
{-# SPECIALISE f :: Int -> Int #-}
Then we get the SpecPrag
- SpecPrag (f Int dInt) Int
+ SpecPrag (f Int dInt)
And from that we want the rule
RULE forall dInt. f Int dInt = f_spec
f_spec = let f = <rhs> in f Int dInt
-
-
-%************************************************************************
-%* *
-\subsection{Adding inline pragmas}
-%* *
-%************************************************************************
-
-\begin{code}
-decomposeRuleLhs :: CoreExpr -> Maybe (Id, [CoreExpr])
--- 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
- where
- -- 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
- = 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 (Var v) = lookupVarEnv subst v `orElse` Var v
- go (Cast e co) = Cast (go e) co
- go (Type ty) = Type ty
- go (Lit lit) = Lit lit
- go (App fun arg) = App (go fun) (go arg)
- go (Note note e) = Note note (go e)
- go (Lam bndr body) = Lam bndr (go body)
- go (Let (NonRec bndr rhs) body) = Let (NonRec bndr (go rhs)) (go body)
- go (Let (Rec pairs) body) = Let (Rec (mapSnd go pairs)) (go body)
- go (Case scrut bndr ty alts) = Case (go scrut) bndr ty
- [(c,bs,go r) | (c,bs,r) <- alts]
-
-addInlinePrags :: [LPrag] -> Id -> CoreExpr -> (Id,CoreExpr)
-addInlinePrags prags bndr rhs
- = case [inl | L _ (InlinePrag inl) <- prags] of
- [] -> (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)
- where
- attach_phase bndr phase
- | isAlwaysActive phase = bndr -- Default phase
- | otherwise = bndr `setInlinePragma` phase
-
- wrap_inline True body = mkInlineMe body
- wrap_inline False body = body
-\end{code}
+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. Likewise it might have an InlineRule or something, which would be
+utterly bogus. So we really make a fresh Id, with the same unique and type
+as the old one, but with an Internal name and no IdInfo.
%************************************************************************
data AutoScc = NoSccs
| AddSccs Module (Id -> Bool)
-- The (Id->Bool) says which Ids to add SCCs to
+-- But we never add a SCC to function marked INLINE
addAutoScc :: AutoScc
-> Id -- Binder
addAutoScc NoSccs _ rhs
= rhs
+addAutoScc _ id rhs | isInlinePragma (idInlinePragma id)
+ = rhs
addAutoScc (AddSccs mod add_scc) id rhs
| add_scc id = mkSCC (mkAutoCC id mod NotCafCC) rhs
| otherwise = rhs
\begin{code}
-dsCoercion :: HsWrapper -> DsM CoreExpr -> DsM CoreExpr
-dsCoercion WpHole thing_inside = thing_inside
-dsCoercion (WpCompose c1 c2) thing_inside = dsCoercion c1 (dsCoercion c2 thing_inside)
-dsCoercion (WpCast co) thing_inside = do { expr <- thing_inside
- ; return (Cast expr co) }
-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 (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) }
+dsHsWrapper :: HsWrapper -> DsM (CoreExpr -> CoreExpr)
+dsHsWrapper WpHole = return (\e -> e)
+dsHsWrapper (WpTyApp ty) = return (\e -> App e (Type ty))
+dsHsWrapper (WpLet ev_binds) = do { ds_ev_binds <- dsTcEvBinds ev_binds
+ ; return (wrapDsEvBinds ds_ev_binds) }
+dsHsWrapper (WpCompose c1 c2) = do { k1 <- dsHsWrapper c1
+ ; k2 <- dsHsWrapper c2
+ ; return (k1 . k2) }
+dsHsWrapper (WpCast co) = return (\e -> Cast e co)
+dsHsWrapper (WpEvLam ev) = return (\e -> Lam ev e)
+dsHsWrapper (WpTyLam tv) = return (\e -> Lam tv e)
+dsHsWrapper (WpEvApp evtrm) = return (\e -> App e (dsEvTerm evtrm))
\end{code}
projects / ghc-hetmet.git / blobdiff