\section[Specialise]{Stamping out overloading, and (optionally) polymorphism}
\begin{code}
-{-# OPTIONS -w #-}
-- The above warning supression flag is a temporary kludge.
-- While working on this module you are encouraged to remove it and fix
-- any warnings in the module. See
--- http://hackage.haskell.org/trac/ghc/wiki/CodingStyle#Warnings
+-- http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings
-- for details
module Specialise ( specProgram ) where
#include "HsVersions.h"
-import DynFlags ( DynFlags, DynFlag(..) )
-import Id ( Id, idName, idType, mkUserLocal,
- idInlinePragma, setInlinePragma )
+import Id ( Id, idName, idType, mkUserLocal, idCoreRules,
+ idInlinePragma, setInlinePragma, setIdUnfolding,
+ isLocalId )
import TcType ( Type, mkTyVarTy, tcSplitSigmaTy,
tyVarsOfTypes, tyVarsOfTheta, isClassPred,
tcCmpType, isUnLiftedType
)
import CoreSubst ( Subst, mkEmptySubst, extendTvSubstList, lookupIdSubst,
substBndr, substBndrs, substTy, substInScope,
- cloneIdBndr, cloneIdBndrs, cloneRecIdBndrs
+ cloneIdBndr, cloneIdBndrs, cloneRecIdBndrs,
+ extendIdSubst
)
+import CoreUnfold ( mkUnfolding )
+import SimplUtils ( interestingArg )
+import Var ( DictId )
import VarSet
import VarEnv
import CoreSyn
-import CoreUtils ( applyTypeToArgs, mkPiTypes )
+import Rules
+import CoreUtils ( exprIsTrivial, applyTypeToArgs, mkPiTypes )
import CoreFVs ( exprFreeVars, exprsFreeVars, idFreeVars )
-import CoreTidy ( tidyRules )
-import CoreLint ( showPass, endPass )
-import Rules ( addIdSpecialisations, mkLocalRule, lookupRule, emptyRuleBase, rulesOfBinds )
-import PprCore ( pprRules )
import UniqSupply ( UniqSupply,
- UniqSM, initUs_, thenUs, returnUs, getUniqueUs,
- getUs, mapUs
+ UniqSM, initUs_,
+ MonadUnique(..)
)
import Name
import MkId ( voidArgId, realWorldPrimId )
import FiniteMap
-import Maybes ( catMaybes, maybeToBool )
-import ErrUtils ( dumpIfSet_dyn )
-import BasicTypes ( Activation( AlwaysActive ) )
+import Maybes ( catMaybes, isJust )
import Bag
-import List ( partition )
-import Util ( zipEqual, zipWithEqual, cmpList, lengthIs,
- equalLength, lengthAtLeast, notNull )
+import Util
import Outputable
import FastString
-infixr 9 `thenSM`
\end{code}
%************************************************************************
Still, this is no great hardship, because we intend to eliminate
overloading altogether anyway!
-
-
A note about non-tyvar dictionaries
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Some Ids have types like
But it is simpler and more uniform to specialise wrt these dicts too;
and in future GHC is likely to support full fledged type signatures
like
- f ;: Eq [(a,b)] => ...
+ f :: Eq [(a,b)] => ...
%************************************************************************
%************************************************************************
\begin{code}
-specProgram :: DynFlags -> UniqSupply -> [CoreBind] -> IO [CoreBind]
-specProgram dflags us binds
- = do
- showPass dflags "Specialise"
-
- let binds' = initSM us (go binds `thenSM` \ (binds', uds') ->
- returnSM (dumpAllDictBinds uds' binds'))
-
- endPass dflags "Specialise" Opt_D_dump_spec binds'
-
- dumpIfSet_dyn dflags Opt_D_dump_rules "Top-level specialisations"
- (pprRules (tidyRules emptyTidyEnv (rulesOfBinds binds')))
-
- return binds'
+specProgram :: UniqSupply -> [CoreBind] -> [CoreBind]
+specProgram us binds = initSM us (do (binds', uds') <- go binds
+ return (dumpAllDictBinds uds' binds'))
where
-- We need to start with a Subst that knows all the things
-- that are in scope, so that the substitution engine doesn't
-- accidentally re-use a unique that's already in use
-- Easiest thing is to do it all at once, as if all the top-level
-- decls were mutually recursive
- top_subst = mkEmptySubst (mkInScopeSet (mkVarSet (bindersOfBinds binds)))
+ top_subst = mkEmptySubst (mkInScopeSet (mkVarSet (bindersOfBinds binds)))
- go [] = returnSM ([], emptyUDs)
- go (bind:binds) = go binds `thenSM` \ (binds', uds) ->
- specBind top_subst bind uds `thenSM` \ (bind', uds') ->
- returnSM (bind' ++ binds', uds')
+ go [] = return ([], emptyUDs)
+ go (bind:binds) = do (binds', uds) <- go binds
+ (bind', uds') <- specBind top_subst bind uds
+ return (bind' ++ binds', uds')
\end{code}
%************************************************************************
specExpr :: Subst -> CoreExpr -> SpecM (CoreExpr, UsageDetails)
-- We carry a substitution down:
--- a) we must clone any binding that might flaot outwards,
+-- a) we must clone any binding that might float outwards,
-- to avoid name clashes
-- b) we carry a type substitution to use when analysing
-- the RHS of specialised bindings (no type-let!)
---------------- First the easy cases --------------------
-specExpr subst (Type ty) = returnSM (Type (substTy subst ty), emptyUDs)
-specExpr subst (Var v) = returnSM (specVar subst v, emptyUDs)
-specExpr subst (Lit lit) = returnSM (Lit lit, emptyUDs)
-specExpr subst (Cast e co) =
- specExpr subst e `thenSM` \ (e', uds) ->
- returnSM ((Cast e' (substTy subst co)), uds)
-specExpr subst (Note note body)
- = specExpr subst body `thenSM` \ (body', uds) ->
- returnSM (Note (specNote subst note) body', uds)
+specExpr subst (Type ty) = return (Type (substTy subst ty), emptyUDs)
+specExpr subst (Var v) = return (specVar subst v, emptyUDs)
+specExpr _ (Lit lit) = return (Lit lit, emptyUDs)
+specExpr subst (Cast e co) = do
+ (e', uds) <- specExpr subst e
+ return ((Cast e' (substTy subst co)), uds)
+specExpr subst (Note note body) = do
+ (body', uds) <- specExpr subst body
+ return (Note (specNote subst note) body', uds)
---------------- Applications might generate a call instance --------------------
-specExpr subst expr@(App fun arg)
+specExpr subst expr@(App {})
= go expr []
where
- go (App fun arg) args = specExpr subst arg `thenSM` \ (arg', uds_arg) ->
- go fun (arg':args) `thenSM` \ (fun', uds_app) ->
- returnSM (App fun' arg', uds_arg `plusUDs` uds_app)
+ go (App fun arg) args = do (arg', uds_arg) <- specExpr subst arg
+ (fun', uds_app) <- go fun (arg':args)
+ return (App fun' arg', uds_arg `plusUDs` uds_app)
go (Var f) args = case specVar subst f of
- Var f' -> returnSM (Var f', mkCallUDs subst f' args)
- e' -> returnSM (e', emptyUDs) -- I don't expect this!
- go other args = specExpr subst other
+ Var f' -> return (Var f', mkCallUDs f' args)
+ e' -> return (e', emptyUDs) -- I don't expect this!
+ go other _ = specExpr subst other
---------------- Lambda/case require dumping of usage details --------------------
-specExpr subst e@(Lam _ _)
- = specExpr subst' body `thenSM` \ (body', uds) ->
- let
- (filtered_uds, body'') = dumpUDs bndrs' uds body'
- in
- returnSM (mkLams bndrs' body'', filtered_uds)
+specExpr subst e@(Lam _ _) = do
+ (body', uds) <- specExpr subst' body
+ let (filtered_uds, body'') = dumpUDs bndrs' uds body'
+ return (mkLams bndrs' body'', filtered_uds)
where
(bndrs, body) = collectBinders e
(subst', bndrs') = substBndrs subst bndrs
-- More efficient to collect a group of binders together all at once
-- and we don't want to split a lambda group with dumped bindings
-specExpr subst (Case scrut case_bndr ty alts)
- = specExpr subst scrut `thenSM` \ (scrut', uds_scrut) ->
- mapAndCombineSM spec_alt alts `thenSM` \ (alts', uds_alts) ->
- returnSM (Case scrut' case_bndr' (substTy subst ty) alts', uds_scrut `plusUDs` uds_alts)
+specExpr subst (Case scrut case_bndr ty alts) = do
+ (scrut', uds_scrut) <- specExpr subst scrut
+ (alts', uds_alts) <- mapAndCombineSM spec_alt alts
+ return (Case scrut' case_bndr' (substTy subst ty) alts', uds_scrut `plusUDs` uds_alts)
where
(subst_alt, case_bndr') = substBndr subst case_bndr
-- No need to clone case binder; it can't float like a let(rec)
- spec_alt (con, args, rhs)
- = specExpr subst_rhs rhs `thenSM` \ (rhs', uds) ->
- let
- (uds', rhs'') = dumpUDs args uds rhs'
- in
- returnSM ((con, args', rhs''), uds')
- where
- (subst_rhs, args') = substBndrs subst_alt args
+ spec_alt (con, args, rhs) = do
+ (rhs', uds) <- specExpr subst_rhs rhs
+ let (uds', rhs'') = dumpUDs args uds rhs'
+ return ((con, args', rhs''), uds')
+ where
+ (subst_rhs, args') = substBndrs subst_alt args
---------------- Finally, let is the interesting case --------------------
-specExpr subst (Let bind body)
- = -- Clone binders
- cloneBindSM subst bind `thenSM` \ (rhs_subst, body_subst, bind') ->
-
- -- Deal with the body
- specExpr body_subst body `thenSM` \ (body', body_uds) ->
+specExpr subst (Let bind body) = do
+ -- Clone binders
+ (rhs_subst, body_subst, bind') <- cloneBindSM subst bind
+
+ -- Deal with the body
+ (body', body_uds) <- specExpr body_subst body
- -- Deal with the bindings
- specBind rhs_subst bind' body_uds `thenSM` \ (binds', uds) ->
+ -- Deal with the bindings
+ (binds', uds) <- specBind rhs_subst bind' body_uds
- -- All done
- returnSM (foldr Let body' binds', uds)
+ -- All done
+ return (foldr Let body' binds', uds)
-- Must apply the type substitution to coerceions
-specNote subst note = note
+specNote :: Subst -> Note -> Note
+specNote _ note = note
\end{code}
%************************************************************************
UsageDetails) -- And info to pass upstream
specBind rhs_subst bind body_uds
- = specBindItself rhs_subst bind (calls body_uds) `thenSM` \ (bind', bind_uds) ->
- let
- bndrs = bindersOf bind
- all_uds = zapCalls bndrs (body_uds `plusUDs` bind_uds)
- -- It's important that the `plusUDs` is this way round,
+ = do { (bind', bind_uds) <- specBindItself rhs_subst bind (calls body_uds)
+ ; return (finishSpecBind bind' bind_uds body_uds) }
+
+finishSpecBind :: CoreBind -> UsageDetails -> UsageDetails -> ([CoreBind], UsageDetails)
+finishSpecBind bind
+ (MkUD { dict_binds = rhs_dbs, calls = rhs_calls, ud_fvs = rhs_fvs })
+ (MkUD { dict_binds = body_dbs, calls = body_calls, ud_fvs = body_fvs })
+ | not (mkVarSet bndrs `intersectsVarSet` all_fvs)
+ -- Common case 1: the bound variables are not
+ -- mentioned in the dictionary bindings
+ = ([bind], MkUD { dict_binds = body_dbs `unionBags` rhs_dbs
+ -- It's important that the `unionBags` is this way round,
-- because body_uds may bind dictionaries that are
-- used in the calls passed to specDefn. So the
- -- dictionary bindings in bind_uds may mention
+ -- dictionary bindings in rhs_uds may mention
-- dictionaries bound in body_uds.
- in
- case splitUDs bndrs all_uds of
-
- (_, ([],[])) -- This binding doesn't bind anything needed
- -- in the UDs, so put the binding here
- -- This is the case for most non-dict bindings, except
- -- for the few that are mentioned in a dict binding
- -- that is floating upwards in body_uds
- -> returnSM ([bind'], all_uds)
-
- (float_uds, (dict_binds, calls)) -- This binding is needed in the UDs, so float it out
- -> returnSM ([], float_uds `plusUDs` mkBigUD bind' dict_binds calls)
-
-
--- A truly gruesome function
-mkBigUD bind@(NonRec _ _) dbs calls
- = -- Common case: non-recursive and no specialisations
- -- (if there were any specialistions it would have been made recursive)
- MkUD { dict_binds = listToBag (mkDB bind : dbs),
- calls = listToCallDetails calls }
-
-mkBigUD bind dbs calls
- = -- General case
- MkUD { dict_binds = unitBag (mkDB (Rec (bind_prs bind ++ dbsToPairs dbs))),
- -- Make a huge Rec
- calls = listToCallDetails calls }
+ , calls = all_calls
+ , ud_fvs = all_fvs })
+
+ | case bind of { NonRec {} -> True; Rec {} -> False }
+ -- Common case 2: no specialisation happened, and binding
+ -- is non-recursive. But the binding may be
+ -- mentioned in body_dbs, so we should put it first
+ = ([], MkUD { dict_binds = rhs_dbs `unionBags` ((bind, b_fvs) `consBag` body_dbs)
+ , calls = all_calls
+ , ud_fvs = all_fvs `unionVarSet` b_fvs })
+
+ | otherwise -- General case: make a huge Rec (sigh)
+ = ([], MkUD { dict_binds = unitBag (Rec all_db_prs, all_db_fvs)
+ , calls = all_calls
+ , ud_fvs = all_fvs `unionVarSet` b_fvs })
where
- bind_prs (NonRec b r) = [(b,r)]
- bind_prs (Rec prs) = prs
+ all_fvs = rhs_fvs `unionVarSet` body_fvs
+ all_calls = zapCalls bndrs (rhs_calls `unionCalls` body_calls)
+
+ bndrs = bindersOf bind
+ b_fvs = bind_fvs bind
- dbsToPairs [] = []
- dbsToPairs ((bind,_):dbs) = bind_prs bind ++ dbsToPairs dbs
+ (all_db_prs, all_db_fvs) = add (bind, b_fvs) $
+ foldrBag add ([], emptyVarSet) $
+ rhs_dbs `unionBags` body_dbs
+ add (NonRec b r, b_fvs) (prs, fvs) = ((b,r) : prs, b_fvs `unionVarSet` fvs)
+ add (Rec b_prs, b_fvs) (prs, fvs) = (b_prs ++ prs, b_fvs `unionVarSet` fvs)
+
+---------------------------
+specBindItself :: Subst -> CoreBind -> CallDetails -> SpecM (CoreBind, UsageDetails)
-- specBindItself deals with the RHS, specialising it according
-- to the calls found in the body (if any)
-specBindItself rhs_subst (NonRec bndr rhs) call_info
- = specDefn rhs_subst call_info (bndr,rhs) `thenSM` \ ((bndr',rhs'), spec_defns, spec_uds) ->
- let
- new_bind | null spec_defns = NonRec bndr' rhs'
- | otherwise = Rec ((bndr',rhs'):spec_defns)
+specBindItself rhs_subst (NonRec fn rhs) call_info
+ = do { (rhs', rhs_uds) <- specExpr rhs_subst rhs -- Do RHS of original fn
+ ; (fn', spec_defns, spec_uds) <- specDefn rhs_subst call_info fn rhs
+ ; if null spec_defns then
+ return (NonRec fn rhs', rhs_uds)
+ else
+ return (Rec ((fn',rhs') : spec_defns), rhs_uds `plusUDs` spec_uds) }
-- bndr' mentions the spec_defns in its SpecEnv
-- Not sure why we couln't just put the spec_defns first
- in
- returnSM (new_bind, spec_uds)
-
+
specBindItself rhs_subst (Rec pairs) call_info
- = mapSM (specDefn rhs_subst call_info) pairs `thenSM` \ stuff ->
- let
- (pairs', spec_defns_s, spec_uds_s) = unzip3 stuff
- spec_defns = concat spec_defns_s
- spec_uds = plusUDList spec_uds_s
- new_bind = Rec (spec_defns ++ pairs')
- in
- returnSM (new_bind, spec_uds)
-
-
-specDefn :: Subst -- Subst to use for RHS
+ -- Note [Specialising a recursive group]
+ = do { let (bndrs,rhss) = unzip pairs
+ ; (rhss', rhs_uds) <- mapAndCombineSM (specExpr rhs_subst) rhss
+ ; let all_calls = call_info `unionCalls` calls rhs_uds
+ ; (bndrs1, spec_defns1, spec_uds1) <- specDefns rhs_subst all_calls pairs
+
+ ; if null spec_defns1 then -- Common case: no specialisation
+ return (Rec (bndrs `zip` rhss'), rhs_uds)
+ else do -- Specialisation occurred; do it again
+ { (bndrs2, spec_defns2, spec_uds2) <-
+ -- pprTrace "specB" (ppr bndrs $$ ppr rhs_uds) $
+ specDefns rhs_subst (calls spec_uds1) (bndrs1 `zip` rhss)
+
+ ; let all_defns = spec_defns1 ++ spec_defns2 ++ zip bndrs2 rhss'
+
+ ; return (Rec all_defns, rhs_uds `plusUDs` spec_uds1 `plusUDs` spec_uds2) } }
+
+
+---------------------------
+specDefns :: Subst
+ -> CallDetails -- Info on how it is used in its scope
+ -> [(Id,CoreExpr)] -- The things being bound and their un-processed RHS
+ -> SpecM ([Id], -- Original Ids with RULES added
+ [(Id,CoreExpr)], -- Extra, specialised bindings
+ UsageDetails) -- Stuff to fling upwards from the specialised versions
+
+-- Specialise a list of bindings (the contents of a Rec), but flowing usages
+-- upwards binding by binding. Example: { f = ...g ...; g = ...f .... }
+-- Then if the input CallDetails has a specialised call for 'g', whose specialisation
+-- in turn generates a specialised call for 'f', we catch that in this one sweep.
+-- But not vice versa (it's a fixpoint problem).
+
+specDefns _subst _call_info []
+ = return ([], [], emptyUDs)
+specDefns subst call_info ((bndr,rhs):pairs)
+ = do { (bndrs', spec_defns, spec_uds) <- specDefns subst call_info pairs
+ ; let all_calls = call_info `unionCalls` calls spec_uds
+ ; (bndr', spec_defns1, spec_uds1) <- specDefn subst all_calls bndr rhs
+ ; return (bndr' : bndrs',
+ spec_defns1 ++ spec_defns,
+ spec_uds1 `plusUDs` spec_uds) }
+
+---------------------------
+specDefn :: Subst
-> CallDetails -- Info on how it is used in its scope
- -> (Id, CoreExpr) -- The thing being bound and its un-processed RHS
- -> SpecM ((Id, CoreExpr), -- The thing and its processed RHS
- -- the Id may now have specialisations attached
+ -> Id -> CoreExpr -- The thing being bound and its un-processed RHS
+ -> SpecM (Id, -- Original Id with added RULES
[(Id,CoreExpr)], -- Extra, specialised bindings
- UsageDetails -- Stuff to fling upwards from the RHS and its
- ) -- specialised versions
+ UsageDetails) -- Stuff to fling upwards from the specialised versions
-specDefn subst calls (fn, rhs)
+specDefn subst calls fn rhs
-- The first case is the interesting one
| rhs_tyvars `lengthIs` n_tyvars -- Rhs of fn's defn has right number of big lambdas
&& rhs_ids `lengthAtLeast` n_dicts -- and enough dict args
-- See Note [Inline specialisation] for why we do not
-- switch off specialisation for inline functions
- = -- Specialise the body of the function
- specExpr subst rhs `thenSM` \ (rhs', rhs_uds) ->
-
- -- Make a specialised version for each call in calls_for_me
- mapSM spec_call calls_for_me `thenSM` \ stuff ->
- let
- (spec_defns, spec_uds, spec_rules) = unzip3 stuff
-
- fn' = addIdSpecialisations fn spec_rules
- in
- returnSM ((fn',rhs'),
- spec_defns,
- rhs_uds `plusUDs` plusUDList spec_uds)
+ = do { -- Make a specialised version for each call in calls_for_me
+ stuff <- mapM spec_call calls_for_me
+ ; let (spec_defns, spec_uds, spec_rules) = unzip3 (catMaybes stuff)
+ fn' = addIdSpecialisations fn spec_rules
+ ; return (fn', spec_defns, plusUDList spec_uds) }
| otherwise -- No calls or RHS doesn't fit our preconceptions
- = WARN( notNull calls_for_me, ptext SLIT("Missed specialisation opportunity for") <+> ppr fn )
+ = WARN( notNull calls_for_me, ptext (sLit "Missed specialisation opportunity for") <+> ppr fn )
-- Note [Specialisation shape]
- specExpr subst rhs `thenSM` \ (rhs', rhs_uds) ->
- returnSM ((fn, rhs'), [], rhs_uds)
+ return (fn, [], emptyUDs)
where
fn_type = idType fn
(inline_rhs, rhs_inside) = dropInline rhs
(rhs_tyvars, rhs_ids, rhs_body) = collectTyAndValBinders rhs_inside
- rhs_dicts = take n_dicts rhs_ids
- rhs_bndrs = rhs_tyvars ++ rhs_dicts
- body = mkLams (drop n_dicts rhs_ids) rhs_body
+ rhs_dict_ids = take n_dicts rhs_ids
+ body = mkLams (drop n_dicts rhs_ids) rhs_body
-- Glue back on the non-dict lambdas
calls_for_me = case lookupFM calls fn of
Nothing -> []
Just cs -> fmToList cs
+ already_covered :: [CoreExpr] -> Bool
+ already_covered args -- Note [Specialisations already covered]
+ = isJust (lookupRule (const True) (substInScope subst)
+ fn args (idCoreRules fn))
+
+ mk_ty_args :: [Maybe Type] -> [CoreExpr]
+ mk_ty_args call_ts = zipWithEqual "spec_call" mk_ty_arg rhs_tyvars call_ts
+ where
+ mk_ty_arg rhs_tyvar Nothing = Type (mkTyVarTy rhs_tyvar)
+ mk_ty_arg _ (Just ty) = Type ty
+
----------------------------------------------------------
-- Specialise to one particular call pattern
- spec_call :: (CallKey, ([DictExpr], VarSet)) -- Call instance
- -> SpecM ((Id,CoreExpr), -- Specialised definition
- UsageDetails, -- Usage details from specialised body
- CoreRule) -- Info for the Id's SpecEnv
- spec_call (CallKey call_ts, (call_ds, call_fvs))
+ spec_call :: (CallKey, ([DictExpr], VarSet)) -- Call instance
+ -> SpecM (Maybe ((Id,CoreExpr), -- Specialised definition
+ UsageDetails, -- Usage details from specialised body
+ CoreRule)) -- Info for the Id's SpecEnv
+ spec_call (CallKey call_ts, (call_ds, _))
= ASSERT( call_ts `lengthIs` n_tyvars && call_ds `lengthIs` n_dicts )
- -- Calls are only recorded for properly-saturated applications
- -- Suppose f's defn is f = /\ a b c d -> \ d1 d2 -> rhs
- -- Supppose the call is for f [Just t1, Nothing, Just t3, Nothing] [dx1, dx2]
+ -- Suppose f's defn is f = /\ a b c -> \ d1 d2 -> rhs
+ -- Supppose the call is for f [Just t1, Nothing, Just t3] [dx1, dx2]
-- Construct the new binding
- -- f1 = SUBST[a->t1,c->t3, d1->d1', d2->d2'] (/\ b d -> rhs)
+ -- f1 = SUBST[a->t1,c->t3, d1->d1', d2->d2'] (/\ b -> rhs)
-- PLUS the usage-details
-- { d1' = dx1; d2' = dx2 }
- -- where d1', d2' are cloned versions of d1,d2, with the type substitution applied.
+ -- where d1', d2' are cloned versions of d1,d2, with the type substitution
+ -- applied. These auxiliary bindings just avoid duplication of dx1, dx2
--
-- Note that the substitution is applied to the whole thing.
-- This is convenient, but just slightly fragile. Notably:
- -- * There had better be no name clashes in a/b/c/d
- --
- let
- -- poly_tyvars = [b,d] in the example above
+ -- * There had better be no name clashes in a/b/c
+ do { let
+ -- poly_tyvars = [b] in the example above
-- spec_tyvars = [a,c]
- -- ty_args = [t1,b,t3,d]
- poly_tyvars = [tv | (tv, Nothing) <- rhs_tyvars `zip` call_ts]
- spec_tyvars = [tv | (tv, Just _) <- rhs_tyvars `zip` call_ts]
- ty_args = zipWithEqual "spec_call" mk_ty_arg rhs_tyvars call_ts
- where
- mk_ty_arg rhs_tyvar Nothing = Type (mkTyVarTy rhs_tyvar)
- mk_ty_arg rhs_tyvar (Just ty) = Type ty
- rhs_subst = extendTvSubstList subst (spec_tyvars `zip` [ty | Just ty <- call_ts])
- in
- cloneBinders rhs_subst rhs_dicts `thenSM` \ (rhs_subst', rhs_dicts') ->
- let
- inst_args = ty_args ++ map Var rhs_dicts'
-
- -- Figure out the type of the specialised function
- body_ty = applyTypeToArgs rhs fn_type inst_args
- (lam_args, app_args) -- Add a dummy argument if body_ty is unlifted
- | isUnLiftedType body_ty -- C.f. WwLib.mkWorkerArgs
- = (poly_tyvars ++ [voidArgId], poly_tyvars ++ [realWorldPrimId])
- | otherwise = (poly_tyvars, poly_tyvars)
- spec_id_ty = mkPiTypes lam_args body_ty
- in
- newIdSM fn spec_id_ty `thenSM` \ spec_f ->
- specExpr rhs_subst' (mkLams lam_args body) `thenSM` \ (spec_rhs, rhs_uds) ->
- let
+ -- ty_args = [t1,b,t3]
+ poly_tyvars = [tv | (tv, Nothing) <- rhs_tyvars `zip` call_ts]
+ spec_tv_binds = [(tv,ty) | (tv, Just ty) <- rhs_tyvars `zip` call_ts]
+ spec_ty_args = map snd spec_tv_binds
+ ty_args = mk_ty_args call_ts
+ rhs_subst = extendTvSubstList subst spec_tv_binds
+
+ ; (rhs_subst1, inst_dict_ids) <- cloneDictBndrs rhs_subst rhs_dict_ids
+ -- Clone rhs_dicts, including instantiating their types
+
+ ; let (rhs_subst2, dx_binds) = bindAuxiliaryDicts rhs_subst1 $
+ (my_zipEqual rhs_dict_ids inst_dict_ids call_ds)
+ inst_args = ty_args ++ map Var inst_dict_ids
+
+ ; if already_covered inst_args then
+ return Nothing
+ else do
+ { -- Figure out the type of the specialised function
+ let body_ty = applyTypeToArgs rhs fn_type inst_args
+ (lam_args, app_args) -- Add a dummy argument if body_ty is unlifted
+ | isUnLiftedType body_ty -- C.f. WwLib.mkWorkerArgs
+ = (poly_tyvars ++ [voidArgId], poly_tyvars ++ [realWorldPrimId])
+ | otherwise = (poly_tyvars, poly_tyvars)
+ spec_id_ty = mkPiTypes lam_args body_ty
+
+ ; spec_f <- newSpecIdSM fn spec_id_ty
+ ; (spec_rhs, rhs_uds) <- specExpr rhs_subst2 (mkLams lam_args body)
+ ; let
-- The rule to put in the function's specialisation is:
- -- forall b,d, d1',d2'. f t1 b t3 d d1' d2' = f1 b d
- spec_env_rule = mkLocalRule (mkFastString ("SPEC " ++ showSDoc (ppr fn)))
- AlwaysActive (idName fn)
- (poly_tyvars ++ rhs_dicts')
- inst_args
- (mkVarApps (Var spec_f) app_args)
+ -- forall b, d1',d2'. f t1 b t3 d1' d2' = f1 b
+ rule_name = mkFastString ("SPEC " ++ showSDoc (ppr fn <+> ppr spec_ty_args))
+ spec_env_rule = mkLocalRule
+ rule_name
+ inline_prag -- Note [Auto-specialisation and RULES]
+ (idName fn)
+ (poly_tyvars ++ inst_dict_ids)
+ inst_args
+ (mkVarApps (Var spec_f) app_args)
-- Add the { d1' = dx1; d2' = dx2 } usage stuff
- final_uds = foldr addDictBind rhs_uds (my_zipEqual "spec_call" rhs_dicts' call_ds)
+ final_uds = foldr addDictBind rhs_uds dx_binds
- spec_pr | inline_rhs = (spec_f `setInlinePragma` inline_prag, Note InlineMe spec_rhs)
- | otherwise = (spec_f, spec_rhs)
- in
- returnSM (spec_pr, final_uds, spec_env_rule)
+ spec_pr | inline_rhs = (spec_f `setInlinePragma` inline_prag, Note InlineMe spec_rhs)
+ | otherwise = (spec_f, spec_rhs)
+ ; return (Just (spec_pr, final_uds, spec_env_rule)) } }
+ where
+ my_zipEqual xs ys zs
+ | debugIsOn && not (equalLength xs ys && equalLength ys zs)
+ = pprPanic "my_zipEqual" (vcat [ ppr xs, ppr ys
+ , ppr fn <+> ppr call_ts
+ , ppr (idType fn), ppr theta
+ , ppr n_dicts, ppr rhs_dict_ids
+ , ppr rhs])
+ | otherwise = zip3 xs ys zs
+
+bindAuxiliaryDicts
+ :: Subst
+ -> [(DictId,DictId,CoreExpr)] -- (orig_dict, inst_dict, dx)
+ -> (Subst, -- Substitute for all orig_dicts
+ [(DictId, CoreExpr)]) -- Auxiliary bindings
+-- Bind any dictionary arguments to fresh names, to preserve sharing
+-- Substitution already substitutes orig_dict -> inst_dict
+bindAuxiliaryDicts subst triples = go subst [] triples
+ where
+ go subst binds [] = (subst, binds)
+ go subst binds ((d, dx_id, dx) : pairs)
+ | exprIsTrivial dx = go (extendIdSubst subst d dx) binds pairs
+ -- No auxiliary binding necessary
+ | otherwise = go subst_w_unf ((dx_id,dx) : binds) pairs
where
- my_zipEqual doc xs ys
-#ifdef DEBUG
- | not (equalLength xs ys) = pprPanic "my_zipEqual" (vcat
- [ ppr xs, ppr ys
- , ppr fn <+> ppr call_ts
- , ppr (idType fn), ppr theta
- , ppr n_dicts, ppr rhs_dicts
- , ppr rhs])
-#endif
- | otherwise = zipEqual doc xs ys
+ dx_id1 = dx_id `setIdUnfolding` mkUnfolding False dx
+ subst_w_unf = extendIdSubst subst d (Var dx_id1)
+ -- Important! We're going to substitute dx_id1 for d
+ -- and we want it to look "interesting", else we won't gather *any*
+ -- consequential calls. E.g.
+ -- f d = ...g d....
+ -- If we specialise f for a call (f (dfun dNumInt)), we'll get
+ -- a consequent call (g d') with an auxiliary definition
+ -- d' = df dNumInt
+ -- We want that consequent call to look interesting
\end{code}
+Note [Specialising a recursive group]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Consider
+ let rec { f x = ...g x'...
+ ; g y = ...f y'.... }
+ in f 'a'
+Here we specialise 'f' at Char; but that is very likely to lead to
+a specialisation of 'g' at Char. We must do the latter, else the
+whole point of specialisation is lost.
+
+But we do not want to keep iterating to a fixpoint, because in the
+presence of polymorphic recursion we might generate an infinite number
+of specialisations.
+
+So we use the following heuristic:
+ * Arrange the rec block in dependency order, so far as possible
+ (the occurrence analyser already does this)
+
+ * Specialise it much like a sequence of lets
+
+ * Then go through the block a second time, feeding call-info from
+ the RHSs back in the bottom, as it were
+
+In effect, the ordering maxmimises the effectiveness of each sweep,
+and we do just two sweeps. This should catch almost every case of
+monomorphic recursion -- the exception could be a very knotted-up
+recursion with multiple cycles tied up together.
+
+This plan is implemented in the Rec case of specBindItself.
+
+Note [Specialisations already covered]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+We obviously don't want to generate two specialisations for the same
+argument pattern. There are two wrinkles
+
+1. We do the already-covered test in specDefn, not when we generate
+the CallInfo in mkCallUDs. We used to test in the latter place, but
+we now iterate the specialiser somewhat, and the Id at the call site
+might therefore not have all the RULES that we can see in specDefn
+
+2. What about two specialisations where the second is an *instance*
+of the first? If the more specific one shows up first, we'll generate
+specialisations for both. If the *less* specific one shows up first,
+we *don't* currently generate a specialisation for the more specific
+one. (See the call to lookupRule in already_covered.) Reasons:
+ (a) lookupRule doesn't say which matches are exact (bad reason)
+ (b) if the earlier specialisation is user-provided, it's
+ far from clear that we should auto-specialise further
+
+Note [Auto-specialisation and RULES]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Consider:
+ g :: Num a => a -> a
+ g = ...
+
+ f :: (Int -> Int) -> Int
+ f w = ...
+ {-# RULE f g = 0 #-}
+
+Suppose that auto-specialisation makes a specialised version of
+g::Int->Int That version won't appear in the LHS of the RULE for f.
+So if the specialisation rule fires too early, the rule for f may
+never fire.
+
+It might be possible to add new rules, to "complete" the rewrite system.
+Thus when adding
+ RULE forall d. g Int d = g_spec
+also add
+ RULE f g_spec = 0
+
+But that's a bit complicated. For now we ask the programmer's help,
+by *copying the INLINE activation pragma* to the auto-specialised rule.
+So if g says {-# NOINLINE[2] g #-}, then the auto-spec rule will also
+not be active until phase 2.
+
+
Note [Specialisation shape]
~~~~~~~~~~~~~~~~~~~~~~~~~~~
We only specialise a function if it has visible top-level lambdas
Reason: when specialising the body for a call (f ty dexp), we want to
substitute dexp for d, and pick up specialised calls in the body of f.
-This doesn't always work. One example I came across was htis:
+This doesn't always work. One example I came across was this:
newtype Gen a = MkGen{ unGen :: Int -> a }
choose :: Eq a => a -> Gen a
-- in ds1 `union` ds2, bindings in ds2 can depend on those in ds1
-- (Remember, Bags preserve order in GHC.)
- calls :: !CallDetails
+ calls :: !CallDetails,
+
+ ud_fvs :: !VarSet -- A superset of the variables mentioned in
+ -- either dict_binds or calls
}
+instance Outputable UsageDetails where
+ ppr (MkUD { dict_binds = dbs, calls = calls, ud_fvs = fvs })
+ = ptext (sLit "MkUD") <+> braces (sep (punctuate comma
+ [ptext (sLit "binds") <+> equals <+> ppr dbs,
+ ptext (sLit "calls") <+> equals <+> ppr calls,
+ ptext (sLit "fvs") <+> equals <+> ppr fvs]))
+
type DictBind = (CoreBind, VarSet)
-- The set is the free vars of the binding
-- both tyvars and dicts
type DictExpr = CoreExpr
-emptyUDs = MkUD { dict_binds = emptyBag, calls = emptyFM }
-
-type ProtoUsageDetails = ([DictBind],
- [(Id, CallKey, ([DictExpr], VarSet))]
- )
+emptyUDs :: UsageDetails
+emptyUDs = MkUD { dict_binds = emptyBag, calls = emptyFM, ud_fvs = emptyVarSet }
------------------------------------------------------------
type CallDetails = FiniteMap Id CallInfo
newtype CallKey = CallKey [Maybe Type] -- Nothing => unconstrained type argument
-type CallInfo = FiniteMap CallKey
- ([DictExpr], VarSet) -- Dict args and the vars of the whole
- -- call (including tyvars)
- -- [*not* include the main id itself, of course]
- -- The finite maps eliminate duplicates
- -- The list of types and dictionaries is guaranteed to
- -- match the type of f
+
+-- CallInfo uses a FiniteMap, thereby ensuring that
+-- we record only one call instance for any key
+--
+-- The list of types and dictionaries is guaranteed to
+-- match the type of f
+type CallInfo = FiniteMap CallKey ([DictExpr], VarSet)
+ -- Range is dict args and the vars of the whole
+ -- call (including tyvars)
+ -- [*not* include the main id itself, of course]
+
+instance Outputable CallKey where
+ ppr (CallKey ts) = ppr ts
-- Type isn't an instance of Ord, so that we can control which
-- instance we use. That's tiresome here. Oh well
instance Eq CallKey where
- k1 == k2 = case k1 `compare` k2 of { EQ -> True; other -> False }
+ k1 == k2 = case k1 `compare` k2 of { EQ -> True; _ -> False }
instance Ord CallKey where
compare (CallKey k1) (CallKey k2) = cmpList cmp k1 k2
where
- cmp Nothing Nothing = EQ
- cmp Nothing (Just t2) = LT
- cmp (Just t1) Nothing = GT
+ cmp Nothing Nothing = EQ
+ cmp Nothing (Just _) = LT
+ cmp (Just _) Nothing = GT
cmp (Just t1) (Just t2) = tcCmpType t1 t2
unionCalls :: CallDetails -> CallDetails -> CallDetails
unionCalls c1 c2 = plusFM_C plusFM c1 c2
-singleCall :: Id -> [Maybe Type] -> [DictExpr] -> CallDetails
+singleCall :: Id -> [Maybe Type] -> [DictExpr] -> UsageDetails
singleCall id tys dicts
- = unitFM id (unitFM (CallKey tys) (dicts, call_fvs))
+ = MkUD {dict_binds = emptyBag,
+ calls = unitFM id (unitFM (CallKey tys) (dicts, call_fvs)),
+ ud_fvs = call_fvs }
where
call_fvs = exprsFreeVars dicts `unionVarSet` tys_fvs
tys_fvs = tyVarsOfTypes (catMaybes tys)
--
-- We don't include the 'id' itself.
-listToCallDetails calls
- = foldr (unionCalls . mk_call) emptyFM calls
- where
- mk_call (id, tys, dicts_w_fvs) = unitFM id (unitFM tys dicts_w_fvs)
- -- NB: the free vars of the call are provided
-
-callDetailsToList calls = [ (id,tys,dicts)
- | (id,fm) <- fmToList calls,
- (tys, dicts) <- fmToList fm
- ]
-
-mkCallUDs subst f args
- | null theta
+mkCallUDs :: Id -> [CoreExpr] -> UsageDetails
+mkCallUDs f args
+ | not (isLocalId f) -- Imported from elsewhere
+ || null theta -- Not overloaded
|| not (all isClassPred theta)
-- Only specialise if all overloading is on class params.
-- In ptic, with implicit params, the type args
-- *don't* say what the value of the implicit param is!
|| not (spec_tys `lengthIs` n_tyvars)
|| not ( dicts `lengthIs` n_dicts)
- || maybeToBool (lookupRule (\act -> True) (substInScope subst) emptyRuleBase f args)
- -- There's already a rule covering this call. A typical case
- -- is where there's an explicit user-provided rule. Then
- -- we don't want to create a specialised version
- -- of the function that overlaps.
- = emptyUDs -- Not overloaded, or no specialisation wanted
+ || not (any interestingArg dicts) -- Note [Interesting dictionary arguments]
+ -- See also Note [Specialisations already covered]
+ = -- pprTrace "mkCallUDs: discarding" (vcat [ppr f, ppr args, ppr n_tyvars, ppr n_dicts, ppr (map interestingArg dicts)])
+ emptyUDs -- Not overloaded, or no specialisation wanted
| otherwise
- = MkUD {dict_binds = emptyBag,
- calls = singleCall f spec_tys dicts
- }
+ = -- pprTrace "mkCallUDs: keeping" (vcat [ppr f, ppr args, ppr n_tyvars, ppr n_dicts, ppr (map interestingArg dicts)])
+ singleCall f spec_tys dicts
where
(tyvars, theta, _) = tcSplitSigmaTy (idType f)
constrained_tyvars = tyVarsOfTheta theta
mk_spec_ty tyvar ty
| tyvar `elemVarSet` constrained_tyvars = Just ty
| otherwise = Nothing
+\end{code}
-------------------------------------------------------------
+Note [Interesting dictionary arguments]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Consider this
+ \a.\d:Eq a. let f = ... in ...(f d)...
+There really is not much point in specialising f wrt the dictionary d,
+because the code for the specialised f is not improved at all, because
+d is lambda-bound. We simply get junk specialisations.
+
+We re-use the function SimplUtils.interestingArg function to determine
+what sort of dictionary arguments have *some* information in them.
+
+
+\begin{code}
plusUDs :: UsageDetails -> UsageDetails -> UsageDetails
-plusUDs (MkUD {dict_binds = db1, calls = calls1})
- (MkUD {dict_binds = db2, calls = calls2})
- = MkUD {dict_binds = d, calls = c}
+plusUDs (MkUD {dict_binds = db1, calls = calls1, ud_fvs = fvs1})
+ (MkUD {dict_binds = db2, calls = calls2, ud_fvs = fvs2})
+ = MkUD {dict_binds = d, calls = c, ud_fvs = fvs1 `unionVarSet` fvs2}
where
d = db1 `unionBags` db2
c = calls1 `unionCalls` calls2
+plusUDList :: [UsageDetails] -> UsageDetails
plusUDList = foldr plusUDs emptyUDs
-- zapCalls deletes calls to ids from uds
-zapCalls ids uds = uds {calls = delListFromFM (calls uds) ids}
+zapCalls :: [Id] -> CallDetails -> CallDetails
+zapCalls ids calls = delListFromFM calls ids
+mkDB :: CoreBind -> DictBind
mkDB bind = (bind, bind_fvs bind)
+bind_fvs :: CoreBind -> VarSet
bind_fvs (NonRec bndr rhs) = pair_fvs (bndr,rhs)
bind_fvs (Rec prs) = foldl delVarSet rhs_fvs bndrs
where
bndrs = map fst prs
rhs_fvs = unionVarSets (map pair_fvs prs)
+pair_fvs :: (Id, CoreExpr) -> VarSet
pair_fvs (bndr, rhs) = exprFreeVars rhs `unionVarSet` idFreeVars bndr
-- Don't forget variables mentioned in the
-- rules of the bndr. C.f. OccAnal.addRuleUsage
-- type T a = Int
-- x :: T a = 3
-addDictBind (dict,rhs) uds = uds { dict_binds = mkDB (NonRec dict rhs) `consBag` dict_binds uds }
+addDictBind :: (Id,CoreExpr) -> UsageDetails -> UsageDetails
+addDictBind (dict,rhs) uds
+ = uds { dict_binds = db `consBag` dict_binds uds
+ , ud_fvs = ud_fvs uds `unionVarSet` fvs }
+ where
+ db@(_, fvs) = mkDB (NonRec dict rhs)
+dumpAllDictBinds :: UsageDetails -> [CoreBind] -> [CoreBind]
dumpAllDictBinds (MkUD {dict_binds = dbs}) binds
= foldrBag add binds dbs
where
dumpUDs :: [CoreBndr]
-> UsageDetails -> CoreExpr
-> (UsageDetails, CoreExpr)
-dumpUDs bndrs uds body
- = (free_uds, foldr add_let body dict_binds)
+dumpUDs bndrs (MkUD { dict_binds = orig_dbs
+ , calls = orig_calls
+ , ud_fvs = fvs}) body
+ = (new_uds, foldrBag add_let body dump_dbs)
+ -- This may delete fewer variables
+ -- than in priciple possible
where
- (free_uds, (dict_binds, _)) = splitUDs bndrs uds
- add_let (bind,_) body = Let bind body
-
-splitUDs :: [CoreBndr]
- -> UsageDetails
- -> (UsageDetails, -- These don't mention the binders
- ProtoUsageDetails) -- These do
-
-splitUDs bndrs uds@(MkUD {dict_binds = orig_dbs,
- calls = orig_calls})
-
- = if isEmptyBag dump_dbs && null dump_calls then
- -- Common case: binder doesn't affect floats
- (uds, ([],[]))
-
- else
- -- Binders bind some of the fvs of the floats
- (MkUD {dict_binds = free_dbs,
- calls = listToCallDetails free_calls},
- (bagToList dump_dbs, dump_calls)
- )
+ new_uds =
+ MkUD { dict_binds = free_dbs
+ , calls = free_calls
+ , ud_fvs = fvs `minusVarSet` bndr_set}
- where
bndr_set = mkVarSet bndrs
+ add_let (bind,_) body = Let bind body
- (free_dbs, dump_dbs, dump_idset)
- = foldlBag dump_db (emptyBag, emptyBag, bndr_set) orig_dbs
+ (free_dbs, dump_dbs, dump_set)
+ = foldlBag dump_db (emptyBag, emptyBag, bndr_set) orig_dbs
-- Important that it's foldl not foldr;
-- we're accumulating the set of dumped ids in dump_set
- -- Filter out any calls that mention things that are being dumped
- orig_call_list = callDetailsToList orig_calls
- (dump_calls, free_calls) = partition captured orig_call_list
- captured (id,tys,(dicts, fvs)) = fvs `intersectsVarSet` dump_idset
- || id `elemVarSet` dump_idset
+ free_calls = filterCalls dump_set orig_calls
dump_db (free_dbs, dump_dbs, dump_idset) db@(bind, fvs)
| dump_idset `intersectsVarSet` fvs -- Dump it
| otherwise -- Don't dump it
= (free_dbs `snocBag` db, dump_dbs, dump_idset)
+
+filterCalls :: VarSet -> CallDetails -> CallDetails
+-- Remove any calls that mention the variables
+filterCalls bs calls
+ = mapFM (\_ cs -> filter_calls cs) $
+ filterFM (\k _ -> not (k `elemVarSet` bs)) calls
+ where
+ filter_calls :: CallInfo -> CallInfo
+ filter_calls = filterFM (\_ (_, fvs) -> not (fvs `intersectsVarSet` bs))
\end{code}
\begin{code}
type SpecM a = UniqSM a
-thenSM = thenUs
-returnSM = returnUs
-getUniqSM = getUniqueUs
-mapSM = mapUs
+initSM :: UniqSupply -> SpecM a -> a
initSM = initUs_
-mapAndCombineSM f [] = returnSM ([], emptyUDs)
-mapAndCombineSM f (x:xs) = f x `thenSM` \ (y, uds1) ->
- mapAndCombineSM f xs `thenSM` \ (ys, uds2) ->
- returnSM (y:ys, uds1 `plusUDs` uds2)
+mapAndCombineSM :: (a -> SpecM (b, UsageDetails)) -> [a] -> SpecM ([b], UsageDetails)
+mapAndCombineSM _ [] = return ([], emptyUDs)
+mapAndCombineSM f (x:xs) = do (y, uds1) <- f x
+ (ys, uds2) <- mapAndCombineSM f xs
+ return (y:ys, uds1 `plusUDs` uds2)
cloneBindSM :: Subst -> CoreBind -> SpecM (Subst, Subst, CoreBind)
-- Clone the binders of the bind; return new bind with the cloned binders
-- Return the substitution to use for RHSs, and the one to use for the body
-cloneBindSM subst (NonRec bndr rhs)
- = getUs `thenUs` \ us ->
- let
- (subst', bndr') = cloneIdBndr subst us bndr
- in
- returnUs (subst, subst', NonRec bndr' rhs)
-
-cloneBindSM subst (Rec pairs)
- = getUs `thenUs` \ us ->
- let
- (subst', bndrs') = cloneRecIdBndrs subst us (map fst pairs)
- in
- returnUs (subst', subst', Rec (bndrs' `zip` map snd pairs))
-
-cloneBinders subst bndrs
- = getUs `thenUs` \ us ->
- returnUs (cloneIdBndrs subst us bndrs)
-
-newIdSM old_id new_ty
- = getUniqSM `thenSM` \ uniq ->
- let
- -- Give the new Id a similar occurrence name to the old one
- name = idName old_id
- new_id = mkUserLocal (mkSpecOcc (nameOccName name)) uniq new_ty (getSrcSpan name)
- in
- returnSM new_id
+cloneBindSM subst (NonRec bndr rhs) = do
+ us <- getUniqueSupplyM
+ let (subst', bndr') = cloneIdBndr subst us bndr
+ return (subst, subst', NonRec bndr' rhs)
+
+cloneBindSM subst (Rec pairs) = do
+ us <- getUniqueSupplyM
+ let (subst', bndrs') = cloneRecIdBndrs subst us (map fst pairs)
+ return (subst', subst', Rec (bndrs' `zip` map snd pairs))
+
+cloneDictBndrs :: Subst -> [CoreBndr] -> SpecM (Subst, [CoreBndr])
+cloneDictBndrs subst bndrs
+ = do { us <- getUniqueSupplyM
+ ; return (cloneIdBndrs subst us bndrs) }
+
+newSpecIdSM :: Id -> Type -> SpecM Id
+ -- Give the new Id a similar occurrence name to the old one
+newSpecIdSM old_id new_ty
+ = do { uniq <- getUniqueM
+ ; let
+ name = idName old_id
+ new_occ = mkSpecOcc (nameOccName name)
+ new_id = mkUserLocal new_occ uniq new_ty (getSrcSpan name)
+ ; return new_id }
\end{code}
projects / ghc-hetmet.git / blobdiff