import HscTypes ( ModGuts(..) )
import WwLib ( mkWorkerArgs )
import DataCon
-import Coercion
+import Coercion hiding( substTy, substCo )
import Rules
-import Type hiding( substTy )
+import Type hiding ( substTy )
import Id
import MkCore ( mkImpossibleExpr )
import Var
import DmdAnal ( both )
import Serialized ( deserializeWithData )
import Util
+import Pair
import UniqSupply
import Outputable
import FastString
we were getting literally hundreds of (mostly unused) specialisations of
a local function.
+In a case like the above we end up never calling the original un-specialised
+function. (Although we still leave its code around just in case.)
+
+However, if we find any boring calls in the body, including *unsaturated*
+ones, such as
+ letrec foo x y = ....foo...
+ in map foo xs
+then we will end up calling the un-specialised function, so then we *should*
+use the calls in the un-specialised RHS as seeds. We call these "boring
+call patterns, and callsToPats reports if it finds any of these.
+
+
Note [Do not specialise diverging functions]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Specialising a function that just diverges is a waste of code.
scSubstTy :: ScEnv -> Type -> Type
scSubstTy env ty = substTy (sc_subst env) ty
+scSubstCo :: ScEnv -> Coercion -> Coercion
+scSubstCo env co = substCo (sc_subst env) co
+
zapScSubst :: ScEnv -> ScEnv
zapScSubst env = env { sc_subst = zapSubstEnv (sc_subst env) }
live_case_bndr = not (isDeadBinder case_bndr)
env1 | Var v <- scrut = extendValEnv env v cval
| otherwise = env -- See Note [Add scrutinee to ValueEnv too]
- env2 | live_case_bndr = extendValEnv env case_bndr cval
+ env2 | live_case_bndr = extendValEnv env1 case_bndr cval
| otherwise = env1
alt_bndrs' | case scrut of { Var {} -> True; _ -> live_case_bndr }
vanilla_args = map Type (tyConAppArgs (idType case_bndr)) ++
varsToCoreExprs alt_bndrs
- zap v | isTyCoVar v = v -- See NB2 above
+ zap v | isTyVar v = v -- See NB2 above
| otherwise = zapIdOccInfo v
scExpr' env (Var v) = case scSubstId env v of
- Var v' -> return (varUsage env v' UnkOcc, Var v')
+ Var v' -> return (mkVarUsage env v' [], Var v')
e' -> scExpr (zapScSubst env) e'
scExpr' env (Type t) = return (nullUsage, Type (scSubstTy env t))
+scExpr' env (Coercion c) = return (nullUsage, Coercion (scSubstCo env c))
scExpr' _ e@(Lit {}) = return (nullUsage, e)
scExpr' env (Note n e) = do (usg,e') <- scExpr env e
return (usg, Note n e')
scExpr' env (Cast e co) = do (usg, e') <- scExpr env e
- return (usg, Cast e' (scSubstTy env co))
+ return (usg, Cast e' (scSubstCo env co))
scExpr' env e@(App _ _) = scApp env (collectArgs e)
scExpr' env (Lam b e) = do let (env', b') = extendBndr env b
(usg, e') <- scExpr env' e
; return (usg', b_occ `combineOcc` scrut_occ, (con, bs2, rhs')) }
scExpr' env (Let (NonRec bndr rhs) body)
- | isTyCoVar bndr -- Type-lets may be created by doBeta
+ | isTyVar bndr -- Type-lets may be created by doBeta
= scExpr' (extendScSubst env bndr rhs) body
| otherwise
fn'@(Lam {}) -> scExpr (zapScSubst env) (doBeta fn' args')
-- Do beta-reduction and try again
- Var fn' -> return (arg_usg `combineUsage` mk_fn_usg fn' args',
+ Var fn' -> return (arg_usg `combineUsage` mkVarUsage env fn' args',
mkApps (Var fn') args')
other_fn' -> return (arg_usg, mkApps other_fn' args') }
doBeta (Lam bndr body) (arg : args) = Let (NonRec bndr arg) (doBeta body args)
doBeta fn args = mkApps fn args
- mk_fn_usg fn' args'
- = case lookupHowBound env fn' of
- Just RecFun -> SCU { scu_calls = unitVarEnv fn' [(sc_vals env, args')]
- , scu_occs = emptyVarEnv }
- Just RecArg -> SCU { scu_calls = emptyVarEnv
- , scu_occs = unitVarEnv fn' evalScrutOcc }
- Nothing -> nullUsage
-
-- The function is almost always a variable, but not always.
-- In particular, if this pass follows float-in,
-- which it may, we can get
; return (combineUsages arg_usgs `combineUsage` fn_usg, mkApps fn' args') }
----------------------
+mkVarUsage :: ScEnv -> Id -> [CoreExpr] -> ScUsage
+mkVarUsage env fn args
+ = case lookupHowBound env fn of
+ Just RecFun -> SCU { scu_calls = unitVarEnv fn [(sc_vals env, args)]
+ , scu_occs = emptyVarEnv }
+ Just RecArg -> SCU { scu_calls = emptyVarEnv
+ , scu_occs = unitVarEnv fn arg_occ }
+ Nothing -> nullUsage
+ where
+ -- I rather think we could use UnkOcc all the time
+ arg_occ | null args = UnkOcc
+ | otherwise = evalScrutOcc
+
+----------------------
scTopBind :: ScEnv -> CoreBind -> UniqSM (ScEnv, CoreBind)
scTopBind env (Rec prs)
| Just threshold <- sc_size env
-- And now the original binding
where
rules = [r | OS _ r _ _ <- specs]
-
-----------------------
-varUsage :: ScEnv -> OutVar -> ArgOcc -> ScUsage
-varUsage env v use
- | Just RecArg <- lookupHowBound env v = SCU { scu_calls = emptyVarEnv
- , scu_occs = unitVarEnv v use }
- | otherwise = nullUsage
\end{code}
Int -- Length of specs; used for numbering them
- (Maybe ScUsage) -- Nothing => we have generated specialisations
- -- from calls in the *original* RHS
- -- Just cs => we haven't, and this is the usage
- -- of the original RHS
+ (Maybe ScUsage) -- Just cs => we have not yet used calls in the
+ -- from calls in the *original* RHS as
+ -- seeds for new specialisations;
+ -- if you decide to do so, here is the
+ -- RHS usage (which has not yet been
+ -- unleashed)
+ -- Nothing => we have
-- See Note [Local recursive groups]
-- One specialisation: Rule plus definition
spec_count' = n_pats + spec_count
; case sc_count env of
Just max | not (sc_force env) && spec_count' > max
- -> pprTrace "SpecConstr" msg $
- return (nullUsage, spec_info)
+ -> if (debugIsOn || opt_PprStyle_Debug) -- Suppress this scary message for
+ then pprTrace "SpecConstr" msg $ -- ordinary users! Trac #5125
+ return (nullUsage, spec_info)
+ else return (nullUsage, spec_info)
where
msg = vcat [ sep [ ptext (sLit "Function") <+> quotes (ppr fn)
, nest 2 (ptext (sLit "has") <+>
dmd_env = go emptyVarEnv dmds pats
go env ds (Type {} : pats) = go env ds pats
+ go env ds (Coercion {} : pats) = go env ds pats
go env (d:ds) (pat : pats) = go (go_one env d pat) ds pats
go env _ _ = env
-- at the call site
-- See Note [Shadowing] at the top
- (tvs, ids) = partition isTyCoVar qvars
+ (tvs, ids) = partition isTyVar qvars
qvars' = tvs ++ ids
-- Put the type variables first; the type of a term
-- variable may mention a type variable
argToPat _env _in_scope _val_env arg@(Type {}) _arg_occ
= return (False, arg)
+
+argToPat _env _in_scope _val_env arg@(Coercion {}) _arg_occ
+ = return (False, arg)
argToPat env in_scope val_env (Note _ arg) arg_occ
= argToPat env in_scope val_env arg arg_occ
-}
argToPat env in_scope val_env (Cast arg co) arg_occ
- | isIdentityCoercion co -- Substitution in the SpecConstr itself
- -- can lead to identity coercions
+ | isReflCo co -- Substitution in the SpecConstr itself
+ -- can lead to identity coercions
= argToPat env in_scope val_env arg arg_occ
| not (ignoreType env ty2)
= do { (interesting, arg') <- argToPat env in_scope val_env arg arg_occ
{ -- Make a wild-card pattern for the coercion
uniq <- getUniqueUs
; let co_name = mkSysTvName uniq (fsLit "sg")
- co_var = mkCoVar co_name (mkCoKind ty1 ty2)
- ; return (interesting, Cast arg' (mkTyVarTy co_var)) } }
+ co_var = mkCoVar co_name (mkCoType ty1 ty2)
+ ; return (interesting, Cast arg' (mkCoVarCo co_var)) } }
where
- (ty1, ty2) = coercionKind co
+ Pair ty1 ty2 = coercionKind co
-- as well, for let-bound constructors!
isValue env (Lam b e)
- | isTyCoVar b = case isValue env e of
+ | isTyVar b = case isValue env e of
Just _ -> Just LambdaVal
Nothing -> Nothing
| otherwise = Just LambdaVal
same (App f1 a1) (App f2 a2) = same f1 f2 && same a1 a2
same (Type {}) (Type {}) = True -- Note [Ignore type differences]
+ same (Coercion {}) (Coercion {}) = True
same (Note _ e1) e2 = same e1 e2 -- Ignore casts and notes
same (Cast e1 _) e2 = same e1 e2
same e1 (Note _ e2) = same e1 e2
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