import DsMonad
import DsGRHSs
import DsUtils
+import OccurAnal
import HsSyn -- lots of things
import CoreSyn -- lots of things
+import MkCore
import CoreUtils
+import CoreUnfold
+import CoreFVs
-import OccurAnal
+import TcHsSyn ( mkArbitraryType ) -- Mis-placed?
+import TcType
import CostCentre
import Module
import Id
+import Var ( Var, TyVar )
+import VarSet
import Rules
-import Var ( TyVar, Var )
import VarEnv
import Type
-import TysWiredIn
import Outputable
import SrcLoc
import Maybes
import Bag
import BasicTypes hiding ( TopLevel )
import FastString
-import Util ( mapSnd )
+import StaticFlags ( opt_DsMultiTyVar )
+import Util ( mapSnd, count, mapAndUnzip, lengthExceeds )
import Control.Monad
import Data.List
------------------------
ds_lhs_binds :: AutoScc -> LHsBinds Id -> DsM [(Id,CoreExpr)]
+
-- scc annotation policy (see below)
ds_lhs_binds auto_scc binds = foldM (dsLHsBind auto_scc) [] (bagToList binds)
-> HsBind Id
-> DsM [(Id,CoreExpr)] -- Result
-dsHsBind auto_scc rest (VarBind var expr)
- = dsLExpr expr `thenDs` \ core_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)
-
-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 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)
-
--- 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 _ rest (VarBind var expr 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 ((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)
+ ar_env = mkArityEnv binds
+ do_one (lcl_id, rhs)
+ | Just (_, gbl_id, _, prags) <- lookupVarEnv env lcl_id
+ = makeCorePair gbl_id (lookupArity ar_env lcl_id) prags $
+ addAutoScc auto_scc gbl_id rhs
+
+ | otherwise = (lcl_id, rhs)
+
locals' = [(lcl_id, Var gbl_id) | (_, gbl_id, lcl_id, _) <- exports]
+ -- Note [Rules and inlining]
; 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
+
+{- 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.
+-}
+
+
+dsHsBind auto_scc rest (AbsBinds tyvars [] exports binds)
+ | opt_DsMultiTyVar -- This (static) debug flag just lets us
+ -- switch on and off this optimisation to
+ -- see if it has any impact; it is on by default
+ = -- Note [Abstracting over tyvars only]
+ do { core_prs <- ds_lhs_binds NoSccs binds
+ ; arby_env <- mkArbitraryTypeEnv tyvars exports
+ ; let (lg_binds, core_prs') = mapAndUnzip do_one core_prs
+ bndrs = mkVarSet (map fst core_prs)
+
+ add_lets | core_prs `lengthExceeds` 10 = add_some
+ | otherwise = mkLets lg_binds
+ add_some rhs = mkLets [ NonRec b r | NonRec b r <- lg_binds
+ , b `elemVarSet` fvs] rhs
+ where
+ fvs = exprSomeFreeVars (`elemVarSet` bndrs) rhs
+
+ ar_env = mkArityEnv binds
+ env = mkABEnv exports
+
+ do_one (lcl_id, rhs)
+ | Just (id_tvs, gbl_id, _, prags) <- lookupVarEnv env lcl_id
+ = let rhs' = addAutoScc auto_scc gbl_id $
+ mkLams id_tvs $
+ mkLets [ NonRec tv (Type (lookupVarEnv_NF arby_env tv))
+ | tv <- tyvars, not (tv `elem` id_tvs)] $
+ add_lets rhs
+ in (NonRec lcl_id (mkTyApps (Var gbl_id) (mkTyVarTys id_tvs)),
+ makeCorePair gbl_id (lookupArity ar_env lcl_id) prags rhs')
+ | otherwise
+ = (NonRec lcl_id (mkTyApps (Var non_exp_gbl_id) (mkTyVarTys tyvars)),
+ (non_exp_gbl_id, mkLams tyvars (add_lets rhs)))
+ where
+ non_exp_gbl_id = setIdType lcl_id (mkForAllTys tyvars (idType lcl_id))
+
+ ; return (core_prs' ++ rest) }
+
-- Another common case: one exported variable
-- Non-recursive bindings come through this way
+ -- So do self-recursive bindings, and recursive bindings
+ -- that have been chopped up with type signatures
dsHsBind auto_scc rest
- (AbsBinds all_tyvars dicts exports@[(tyvars, global, local, prags)] binds)
+ (AbsBinds all_tyvars dicts [(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 ->
- 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)
+ 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
+ inl_arity = lookupArity (mkArityEnv binds) local
+
+ ; mb_specs <- mapM (dsSpec all_tyvars dicts tyvars global
+ local inl_arity core_bind) prags
+
+ ; let (spec_binds, rules) = unzip (catMaybes mb_specs)
+ global' = addIdSpecialisations global rules
+ rhs = addAutoScc auto_scc global $
+ mkLams tyvars $ mkLams dicts $ Let core_bind (Var local)
+ main_bind = makeCorePair global' (inl_arity + length dicts) prags rhs
+
+ ; return (main_bind : spec_binds ++ rest) }
dsHsBind auto_scc rest (AbsBinds all_tyvars dicts 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 lcl_id $
- addAutoScc auto_scc gbl_id rhs
+ ar_env = mkArityEnv binds
+ 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 = mkTupleExpr locals
+ 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
+ inl_prags :: [(Id, SrcSpan)]
+ inl_prags = [(id, loc) | (_, id, _, prags) <- exports
+ , L loc (InlinePrag {}) <- prags ]
+
+ ; mapM_ discardedInlineWarning inl_prags
+
; 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 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)
+ ; mb_specs <- mapM (dsSpec all_tyvars dicts tyvars global local
+ (lookupArity ar_env local) core_bind)
prags
; let (spec_binds, rules) = unzip (catMaybes mb_specs)
global' = addIdSpecialisations global rules
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..])
- -- don't scc (auto-)annotate the tuple itself.
+ ; 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])
+------------------------
+makeCorePair :: Id-> Arity -> [LPrag] -> CoreExpr -> (Id, CoreExpr)
+makeCorePair gbl_id arity prags rhs
+ = (addInline gbl_id arity rhs prags, rhs)
+
+------------------------
+discardedInlineWarning :: (Id, SrcSpan) -> DsM ()
+discardedInlineWarning (id, loc)
+ = putSrcSpanDs loc $
+ warnDs $ sep [ ptext (sLit "Discarding INLINE pragma for") <+> ppr id
+ , ptext (sLit "because it is bound by a pattern, or a mutual recursion") ]
+
+------------------------
+type AbsBindEnv = VarEnv ([TyVar], Id, Id, [LPrag])
+ -- Maps the "lcl_id" for an AbsBind to
+ -- its "gbl_id" and associated pragmas, if any
+
+mkABEnv :: [([TyVar], Id, Id, [LPrag])] -> AbsBindEnv
-- 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]
+-- lcl_id -> (tyvars, gbl_id, lcl_id, prags)
+mkABEnv exports = mkVarEnv [ (lcl_id, export) | export@(_, _, lcl_id, _) <- exports]
+mkArityEnv :: LHsBinds Id -> IdEnv Arity
+ -- Maps a local to the arity of its definition
+mkArityEnv binds = mkVarEnv (mapCatMaybes get_arity (bagToList binds))
+ where
+ get_arity (L _ (FunBind { fun_id = id, fun_matches = ms })) = Just (unLoc id, matchGroupArity ms)
+ get_arity _ = Nothing
+
+lookupArity :: IdEnv Arity -> Id -> Arity
+lookupArity ar_env id = lookupVarEnv ar_env id `orElse` 0
+
+addInline :: Id -> Arity -> CoreExpr -> [LPrag] -> Id
+addInline id arity rhs prags
+ = case [inl | L _ (InlinePrag inl) <- prags] of
+ [] -> id
+ (inl_spec : _) -> addInlineToId id arity rhs inl_spec
+
+addInlineToId :: Id -> Arity -> CoreExpr -> InlineSpec -> Id
+addInlineToId id inl_arity rhs (Inline phase is_inline)
+ = id `setInlinePragma` phase
+ `setIdUnfolding` inline_rule
+ where
+ inline_rule | is_inline = mkInlineRule rhs inl_arity
+ | otherwise = noUnfolding
+------------------------
dsSpec :: [TyVar] -> [DictId] -> [TyVar]
- -> Id -> Id -- Global, local
- -> CoreBind -> Prag
+ -> Id -> Id -> Arity -- Global, local, arity of local
+ -> 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
+dsSpec all_tvs dicts tvs poly_id mono_id inl_arity 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 ds_spec_expr
- mb_lhs = decomposeRuleLhs (bndrs ++ const_dicts) body
+ ; case (decomposeRuleLhs ds_spec_expr) of {
+ Nothing -> do { warnDs decomp_msg; return Nothing } ;
- ; case mb_lhs of
- Nothing -> do { warnDs msg; return Nothing }
+ Just (bndrs, _fn, args) ->
- Just (bndrs', var, args) -> return (Just (addInlineInfo inl spec_id spec_rhs, rule))
- where
- local_poly = setIdNotExported poly_id
+ -- 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))
+
+ ; 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_id1 = addInlineToId spec_id (inl_arity + count isDictId bndrs)
+ spec_rhs inl
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 = [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)))
AlwaysActive poly_name
- bndrs' -- Includes constant dicts
- args
+ (extra_dict_bndrs ++ bndrs) args
(mkVarApps (Var spec_id) bndrs)
- }
+ ; return (Just ((spec_id1, 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)
+
+
+mkArbitraryTypeEnv :: [TyVar] -> [([TyVar], a, b, c)] -> DsM (TyVarEnv Type)
+-- If any of the tyvars is missing from any of the lists in
+-- the second arg, return a binding in the result
+mkArbitraryTypeEnv tyvars exports
+ = go emptyVarEnv exports
+ where
+ go env [] = return env
+ go env ((ltvs, _, _, _) : exports)
+ = do { env' <- foldlM extend env [tv | tv <- tyvars
+ , not (tv `elem` ltvs)
+ , not (tv `elemVarEnv` env)]
+ ; go env' exports }
+
+ extend env tv = do { ty <- dsMkArbitraryType tv
+ ; return (extendVarEnv env tv ty) }
+
+
+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
+
+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.
+
%************************************************************************
%* *
%************************************************************************
\begin{code}
-decomposeRuleLhs :: [Var] -> CoreExpr -> Maybe ([Var], 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
--- 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
+ = case (decomp emptyVarEnv body) of
+ Nothing -> Nothing
+ Just (fn, args) -> Just (bndrs, fn, args)
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
- 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 (all_bndrs', fn, args)
- other -> Nothing
+ 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
+ decomp env (Let (NonRec dict rhs) body)
+ = decomp (extendVarEnv env dict (simpleSubst env rhs)) body
+ decomp 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
+-- (a) Takes no account of capture; at this point there is no shadowing
+-- (b) Can have a GlobalId (imported) in its domain
-- (c) Ids only; no types are substituted
+-- (d) Does not insist (as does CoreSubst.lookupIdSubst) that the
+-- in-scope set mentions all LocalIds mentioned in the argument of the subst
+--
+-- (b) and (d) are the reasons we can't use CoreSubst
+--
+-- (I had a note that (b) is "no longer relevant", and indeed it doesn't
+-- look relevant here. Perhaps there was another caller of simpleSubst.)
simpleSubst subst expr
= go expr
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 :: [Prag] -> Id -> CoreExpr -> (Id,CoreExpr)
-addInlinePrags prags bndr rhs
- = case [inl | 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}
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}
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 (WpCo co) thing_inside = do { expr <- 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 (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 (WpLet bs) thing_inside = do { prs <- dsLHsBinds bs
projects / ghc-hetmet.git / blobdiff