\begin{code}
module Rules (
- RuleBase, prepareRuleBase, lookupRule,
- addIdSpecialisations,
- ProtoCoreRule(..), pprProtoCoreRule,
- orphanRule
+ RuleBase, emptyRuleBase,
+ extendRuleBase, extendRuleBaseList, addRuleBaseFVs,
+ ruleBaseIds, ruleBaseFVs,
+ pprRuleBase,
+
+ lookupRule, addRule, addIdSpecialisations
) where
#include "HsVersions.h"
import CoreSyn -- All of it
-import OccurAnal ( occurAnalyseExpr, tagBinders, UsageDetails )
-import BinderInfo ( markMany )
-import CoreFVs ( exprFreeVars, idRuleVars, ruleSomeLhsFreeVars )
-import CoreUnfold ( Unfolding(..) )
-import CoreUtils ( whnfOrBottom, eqExpr )
+import OccurAnal ( occurAnalyseRule )
+import CoreFVs ( exprFreeVars, ruleRhsFreeVars, ruleLhsFreeIds )
+import CoreUnfold ( isCheapUnfolding, unfoldingTemplate )
+import CoreUtils ( eqExpr )
import PprCore ( pprCoreRule )
-import Subst ( Subst, InScopeSet, substBndr, lookupSubst, extendSubst,
- mkSubst, substEnv, setSubstEnv,
- unBindSubst, bindSubstList, unBindSubstList,
+import Subst ( Subst, InScopeSet, mkInScopeSet, lookupSubst, extendSubst,
+ substEnv, setSubstEnv, emptySubst, isInScope,
+ bindSubstList, unBindSubstList, substInScope, uniqAway
)
-import Id ( Id, getIdUnfolding,
- getIdSpecialisation, setIdSpecialisation,
- setIdNoDiscard, maybeModifyIdInfo, modifyIdInfo
- )
-import IdInfo ( zapLamIdInfo, setSpecInfo, specInfo )
-import Name ( Name, isLocallyDefined )
-import Var ( isTyVar, isId )
+import Id ( Id, idUnfolding, idSpecialisation, setIdSpecialisation )
+import Var ( isId )
import VarSet
import VarEnv
-import Type ( mkTyVarTy, getTyVar_maybe )
-import qualified Unify ( match )
-import CmdLineOpts ( opt_D_dump_simpl, opt_D_verbose_core2core )
+import TcType ( mkTyVarTy )
+import qualified TcType ( match )
+import TypeRep ( Type(..) ) -- Can see type representation for matching
-import UniqFM
-import ErrUtils ( dumpIfSet )
import Outputable
-import Maybes ( maybeToBool )
-import List ( partition )
+import Maybe ( isJust, isNothing, fromMaybe )
import Util ( sortLt )
\end{code}
%************************************************************************
\begin{code}
-matchRules :: InScopeSet -> [CoreRule] -> [CoreExpr] -> Maybe (FAST_STRING, CoreExpr, [CoreExpr])
+matchRules :: InScopeSet -> [CoreRule] -> [CoreExpr] -> Maybe (RuleName, CoreExpr)
-- See comments on matchRule
matchRules in_scope [] args = Nothing
matchRules in_scope (rule:rules) args
Nothing -> matchRules in_scope rules args
-matchRule :: InScopeSet -> CoreRule -> [CoreExpr] -> Maybe (FAST_STRING, CoreExpr, [CoreExpr])
+matchRule :: InScopeSet -> CoreRule -> [CoreExpr] -> Maybe (RuleName, CoreExpr)
--- If (matchRule rule args) returns Just (name,rhs,args')
+-- If (matchRule rule args) returns Just (name,rhs)
-- then (f args) matches the rule, and the corresponding
--- rewritten RHS is (rhs args').
+-- rewritten RHS is rhs
--
-- The bndrs and rhs is occurrence-analysed
--
-- map (f.g) x) -- rhs
--
-- Then the call: matchRule the_rule [e1,map e2 e3]
--- = Just ("map/map", \f,g,x -> rhs, [e1,e2,e3])
+-- = Just ("map/map", (\f,g,x -> rhs) e1 e2 e3)
--
-- Any 'surplus' arguments in the input are simply put on the end
-- of the output.
--
-- ASSUMPTION (A):
--- No variable free in the template is bound in the target
+-- A1. No top-level variable is bound in the target
+-- A2. No template variable is bound in the target
+-- A3. No lambda bound template variable is free in any subexpression of the target
+--
+-- To see why A1 is necessary, consider matching
+-- \x->f against \f->f
+-- When we meet the lambdas we substitute [f/x] in the template (a no-op),
+-- and then erroneously succeed in matching f against f.
+--
+-- To see why A2 is needed consider matching
+-- forall a. \b->b against \a->3
+-- When we meet the lambdas we substitute [a/b] in the template, and then
+-- erroneously succeed in matching what looks like the template variable 'a' against 3.
+--
+-- A3 is needed to validate the rule that says
+-- (\x->E) matches F
+-- if
+-- (\x->E) matches (\x->F x)
+
-matchRule in_scope (Rule rn tpl_vars tpl_args rhs) args
- = go tpl_args args (mkSubst in_scope emptySubstEnv)
+matchRule in_scope rule@(BuiltinRule match_fn) args = match_fn args
+
+matchRule in_scope rule@(Rule rn tpl_vars tpl_args rhs) args
+ = go tpl_args args emptySubst
+ -- We used to use the in_scope set, but I don't think that's necessary
+ -- After all, the result is going to be simplified again with that in_scope set
where
tpl_var_set = mkVarSet tpl_vars
go (tpl_arg:tpl_args) (arg:args) subst = match tpl_arg arg tpl_var_set (go tpl_args args) subst
-- Two easy ways to terminate
- go [] [] subst = Just (rn, mkLams tpl_vars rhs, mk_result_args subst tpl_vars)
- go [] args subst = Just (rn, mkLams tpl_vars rhs, mk_result_args subst tpl_vars ++ args)
+ go [] [] subst = Just (rn, app_match subst (mkLams tpl_vars rhs) tpl_vars)
+ go [] args subst = Just (rn, app_match subst (mkLams tpl_vars rhs) tpl_vars `mkApps` args)
-- One tiresome way to terminate: check for excess unmatched
-- template arguments
- go tpl_args [] subst
+ go tpl_args [] subst = Nothing -- Failure
+
+
+ -----------------------
+ app_match subst fn vs = foldl go fn vs
+ where
+ senv = substEnv subst
+ go fn v = case lookupSubstEnv senv v of
+ Just (DoneEx ex) -> fn `App` ex
+ Just (DoneTy ty) -> fn `App` Type ty
+ -- Substitution should bind them all!
+
+
+ -----------------------
+{- The code below tries to match even if there are more
+ template args than real args.
+
+ I now think this is probably a bad idea.
+ Should the template (map f xs) match (map g)? I think not.
+ For a start, in general eta expansion wastes work.
+ SLPJ July 99
+
= case eta_complete tpl_args (mkVarSet leftovers) of
Just leftovers' -> Just (rn, mkLams done (mkLams leftovers' rhs),
mk_result_args subst done)
Nothing -> Nothing -- Failure
where
- (done, leftovers) = partition (\v -> maybeToBool (lookupSubstEnv subst_env v))
+ (done, leftovers) = partition (\v -> isJust (lookupSubstEnv subst_env v))
(map zapOccInfo tpl_vars)
-- Zap the occ info
subst_env = substEnv subst
eta_complete other vars = Nothing
- -----------------------
- mk_result_args subst vs = map go vs
- where
- senv = substEnv subst
- go v = case lookupSubstEnv senv v of
- Just (DoneEx ex) -> ex
- Just (DoneTy ty) -> Type ty
- -- Substitution should bind them all!
zapOccInfo bndr | isTyVar bndr = bndr
- | otherwise = maybeModifyIdInfo zapLamIdInfo bndr
+ | otherwise = zapLamIdInfo bndr
+-}
\end{code}
\begin{code}
-type Matcher result = IdOrTyVarSet -- Template variables
+type Matcher result = VarSet -- Template variables
-> (Subst -> Maybe result) -- Continuation if success
-> Subst -> Maybe result -- Substitution so far -> result
-- The *SubstEnv* in these Substs apply to the TEMPLATE only
--- The *InScopeSet* in these Substs gives a superset of the free vars
--- in the term being matched. This set can get augmented, for example
--- when matching against a lambda:
--- (\x.M) ~ N iff M ~ N x
--- but we must clone x if it's already free in N
+-- The *InScopeSet* in these Substs gives variables bound so far in the
+-- target term. So when matching forall a. (\x. a x) against (\y. y y)
+-- while processing the body of the lambdas, the in-scope set will be {y}.
+-- That lets us do the occurs-check when matching 'a' against 'y'
match :: CoreExpr -- Template
-> CoreExpr -- Target
match (Var v1) e2 tpl_vars kont subst
= case lookupSubst subst v1 of
- Nothing | v1 `elemVarSet` tpl_vars -> kont (extendSubst subst v1 (DoneEx e2))
- -- v1 is a template variables
+ Nothing | v1 `elemVarSet` tpl_vars -- v1 is a template variable
+ -> if (any (`isInScope` subst) (varSetElems (exprFreeVars e2))) then
+ match_fail -- Occurs check failure
+ -- e.g. match forall a. (\x-> a x) against (\y. y y)
+ else
+ kont (extendSubst subst v1 (DoneEx e2))
+
- | eqExpr (Var v1) e2 -> kont subst
+ | eqExpr (Var v1) e2 -> kont subst
-- v1 is not a template variable, so it must be a global constant
- Just (DoneEx e2') | eqExpr e2' e2 -> kont subst
+ Just (DoneEx e2') | eqExpr e2' e2 -> kont subst
other -> match_fail
-match (Con c1 es1) (Con c2 es2) tpl_vars kont subst
- | c1 == c2
- = matches es1 es2 tpl_vars kont subst
+match (Lit lit1) (Lit lit2) tpl_vars kont subst
+ | lit1 == lit2
+ = kont subst
match (App f1 a1) (App f2 a2) tpl_vars kont subst
= match f1 f2 tpl_vars (match a1 a2 tpl_vars kont) subst
match (Lam x1 e1) (Lam x2 e2) tpl_vars kont subst
= bind [x1] [x2] (match e1 e2) tpl_vars kont subst
-{- THESE EQUATIONS ARE BOGUS. SLPJ 19 May 99
-- This rule does eta expansion
-- (\x.M) ~ N iff M ~ N x
--- We must clone the binder in case it's already in scope in N
+-- See assumption A3
match (Lam x1 e1) e2 tpl_vars kont subst
- = match e1 (App e2 (mkVarArg x1')) tpl_vars kont' subst'
- where
- (subst', x1') = substBndr subst x1
- kont' subst = kont (unBindSubst subst x1 x1')
+ = bind [x1] [x1] (match e1 (App e2 (mkVarArg x1))) tpl_vars kont subst
-- Eta expansion the other way
-- M ~ (\y.N) iff \y.M y ~ \y.N
-- iff M y ~ N
-- Remembering that by (A), y can't be free in M, we get this
match e1 (Lam x2 e2) tpl_vars kont subst
- = match (App e1 (mkVarArg x2)) e2 tpl_vars kont subst
--}
+ = bind [new_id] [x2] (match (App e1 (mkVarArg new_id)) e2) tpl_vars kont subst
+ where
+ new_id = uniqAway (substInScope subst) x2
+ -- This uniqAway is actually needed. Here's the example:
+ -- rule: foldr (mapFB (:) f) [] = mapList
+ -- target: foldr (\x. mapFB k f x) []
+ -- where
+ -- k = \x. mapFB ... x
+ -- The first \x is ok, but when we inline k, hoping it might
+ -- match (:) we find a second \x.
match (Case e1 x1 alts1) (Case e2 x2 alts2) tpl_vars kont subst
= match e1 e2 tpl_vars case_kont subst
-- (Its occurrence information is not necessarily up to date,
-- so we don't use it.)
match e1 (Var v2) tpl_vars kont subst
- = case getIdUnfolding v2 of
- CoreUnfolding form guidance unfolding
- | whnfOrBottom form
- -> match e1 unfolding tpl_vars kont subst
+ | isCheapUnfolding unfolding
+ = match e1 (unfoldingTemplate unfolding) tpl_vars kont subst
+ where
+ unfolding = idUnfolding v2
- other -> match_fail
-- We can't cope with lets in the template
-- We rename x to y in the template... but then erroneously
-- match y against y. But this can't happen because of (A)
bind vs1 vs2 matcher tpl_vars kont subst
- = ASSERT( all not_in_subst vs1)
+ = WARN( not (all not_in_subst vs1), bug_msg )
matcher tpl_vars kont' subst'
where
kont' subst'' = kont (unBindSubstList subst'' vs1 vs2)
subst' = bindSubstList subst vs1 vs2
-- The unBindSubst relies on no shadowing in the template
- not_in_subst v = not (maybeToBool (lookupSubst subst v))
-
-----------------------------------------
-match_ty ty1 ty2 tpl_vars kont subst
- = case Unify.match ty1 ty2 tpl_vars Just (substEnv subst) of
- Nothing -> match_fail
- Just senv' -> kont (setSubstEnv subst senv')
+ not_in_subst v = isNothing (lookupSubst subst v)
+ bug_msg = sep [ppr vs1, ppr vs2]
----------------------------------------
matches [] [] tpl_vars kont subst
| otherwise = Type (mkTyVarTy v)
\end{code}
+Matching Core types: use the matcher in TcType.
+Notice that we treat newtypes as opaque. For example, suppose
+we have a specialised version of a function at a newtype, say
+ newtype T = MkT Int
+We only want to replace (f T) with f', not (f Int).
+
+\begin{code}
+----------------------------------------
+match_ty ty1 ty2 tpl_vars kont subst
+ = TcType.match ty1 ty2 tpl_vars kont' (substEnv subst)
+ where
+ kont' senv = kont (setSubstEnv subst senv)
+\end{code}
+
+
+
%************************************************************************
%* *
\subsection{Adding a new rule}
%************************************************************************
\begin{code}
-addRule :: Id -> CoreRules -> CoreRule -> CoreRules
+addRule :: CoreRules -> Id -> CoreRule -> CoreRules
-- Insert the new rule just before a rule that is *less specific*
-- than the new one; or at the end if there isn't such a one.
-- We make no check for rules that unify without one dominating
-- the other. Arguably this would be a bug.
-addRule id (Rules rules rhs_fvs) (Rule str tpl_vars tpl_args rhs)
- = Rules (insert rules) (rhs_fvs `unionVarSet` new_rhs_fvs)
- where
- new_rule = Rule str tpl_vars' tpl_args rhs'
- -- Add occ info to tpl_vars, rhs
-
- (rhs_uds, rhs') = occurAnalyseExpr isLocallyDefined rhs
- (rhs_uds1, tpl_vars') = tagBinders rhs_uds tpl_vars
+addRule (Rules rules rhs_fvs) id rule@(BuiltinRule _)
+ = Rules (rule:rules) rhs_fvs
+ -- Put it at the start for lack of anything better
- insert [] = [new_rule]
- insert (rule:rules) | new_is_more_specific rule = (new_rule:rule:rules)
- | otherwise = rule : insert rules
-
- new_is_more_specific rule = maybeToBool (matchRule tpl_var_set rule tpl_args)
-
- tpl_var_set = mkVarSet tpl_vars'
- -- Actually we should probably include the free vars of tpl_args,
- -- but I can't be bothered
-
- new_rhs_fvs = (exprFreeVars rhs' `minusVarSet` tpl_var_set) `delVarSet` id
+addRule (Rules rules rhs_fvs) id rule
+ = Rules (insertRule rules new_rule) (rhs_fvs `unionVarSet` new_rhs_fvs)
+ where
+ new_rule = occurAnalyseRule rule
+ new_rhs_fvs = ruleRhsFreeVars new_rule `delVarSet` id
-- Hack alert!
-- Don't include the Id in its own rhs free-var set.
-- Otherwise the occurrence analyser makes bindings recursive
-- that shoudn't be. E.g.
-- RULE: f (f x y) z ==> f x (f y z)
-addIdSpecialisations :: Id -> [([CoreBndr], [CoreExpr], CoreExpr)] -> Id
-addIdSpecialisations id spec_stuff
- = setIdSpecialisation id new_rules
+insertRule rules new_rule@(Rule _ tpl_vars tpl_args _)
+ = go rules
where
- rule_name = _PK_ ("SPEC " ++ showSDoc (ppr id))
- new_rules = foldr add (getIdSpecialisation id) spec_stuff
- add (vars, args, rhs) rules = addRule id rules (Rule rule_name vars args rhs)
+ tpl_var_set = mkInScopeSet (mkVarSet tpl_vars)
+ -- Actually we should probably include the free vars of tpl_args,
+ -- but I can't be bothered
+
+ go [] = [new_rule]
+ go (rule:rules) | new_is_more_specific rule = (new_rule:rule:rules)
+ | otherwise = rule : go rules
+
+ new_is_more_specific rule = isJust (matchRule tpl_var_set rule tpl_args)
+
+addIdSpecialisations :: Id -> [CoreRule] -> Id
+addIdSpecialisations id rules
+ = setIdSpecialisation id new_specs
+ where
+ new_specs = foldr add (idSpecialisation id) rules
+ add rule rules = addRule rules id rule
\end{code}
%************************************************************************
\begin{code}
-data ProtoCoreRule
- = ProtoCoreRule
- Bool -- True <=> this rule was defined in this module,
- Id -- What Id is it for
- CoreRule -- The rule itself
-
-
-pprProtoCoreRule (ProtoCoreRule _ fn rule) = pprCoreRule (Just fn) rule
-
-lookupRule :: InScopeSet -> Id -> [CoreExpr] -> Maybe (FAST_STRING, CoreExpr, [CoreExpr])
+lookupRule :: InScopeSet -> Id -> [CoreExpr] -> Maybe (RuleName, CoreExpr)
lookupRule in_scope fn args
- = case getIdSpecialisation fn of
+ = case idSpecialisation fn of
Rules rules _ -> matchRules in_scope rules args
-
-orphanRule :: ProtoCoreRule -> Bool
--- An "orphan rule" is one that is defined in this
--- module, but of ran *imported* function. We need
--- to track these separately when generating the interface file
-orphanRule (ProtoCoreRule local fn _)
- = local && not (isLocallyDefined fn)
\end{code}
%************************************************************************
\begin{code}
-type RuleBase = (IdSet, -- Imported Ids that have rules attached
- IdSet) -- Ids (whether local or imported) mentioned on
+data RuleBase = RuleBase
+ IdSet -- Ids with their rules in their specialisations
+ -- Held as a set, so that it can simply be the initial
+ -- in-scope set in the simplifier
+
+ IdSet -- Ids (whether local or imported) mentioned on
-- LHS of some rule; these should be black listed
--- The rule Ids and LHS Ids are black-listed; that is, they aren't inlined
--- so that the opportunity to apply the rule isn't lost too soon
+ -- This representation is a bit cute, and I wonder if we should
+ -- change it to use (IdEnv CoreRule) which seems a bit more natural
-prepareRuleBase :: [CoreBind] -> [ProtoCoreRule] -> ([CoreBind], RuleBase)
-prepareRuleBase binds rules
- = (map zap_bind binds, (imported_rule_ids, rule_lhs_fvs))
- where
- (rule_ids, rule_lhs_fvs) = foldr add_rule (emptyVarSet, emptyVarSet) rules
- imported_rule_ids = filterVarSet (not . isLocallyDefined) rule_ids
-
- -- rule_fvs is the set of all variables mentioned in rules
- rule_fvs = foldVarSet (unionVarSet . idRuleVars) rule_lhs_fvs rule_ids
-
- -- Attach the rules for each locally-defined Id to that Id.
- -- - This makes the rules easier to look up
- -- - It means that transformation rules and specialisations for
- -- locally defined Ids are handled uniformly
- -- - It keeps alive things that are referred to only from a rule
- -- (the occurrence analyser knows about rules attached to Ids)
- -- - It makes sure that, when we apply a rule, the free vars
- -- of the RHS are more likely to be in scope
- --
- -- The LHS and RHS Ids are marked 'no-discard'.
- -- This means that the binding won't be discarded EVEN if the binding
- -- ends up being trivial (v = w) -- the simplifier would usually just
- -- substitute w for v throughout, but we don't apply the substitution to
- -- the rules (maybe we should?), so this substitution would make the rule
- -- bogus.
- zap_bind (NonRec b r) = NonRec (zap_bndr b) r
- zap_bind (Rec prs) = Rec [(zap_bndr b, r) | (b,r) <- prs]
-
- zap_bndr bndr = case lookupVarSet rule_ids bndr of
- Just bndr' -> setIdNoDiscard bndr'
- Nothing | bndr `elemVarSet` rule_fvs -> setIdNoDiscard bndr
- | otherwise -> bndr
-
-add_rule (ProtoCoreRule _ id rule)
- (rule_id_set, rule_fvs)
- = (rule_id_set `extendVarSet` new_id,
- rule_fvs `unionVarSet` extendVarSet lhs_fvs id)
+ruleBaseIds (RuleBase ids _) = ids
+ruleBaseFVs (RuleBase _ fvs) = fvs
+
+emptyRuleBase = RuleBase emptyVarSet emptyVarSet
+
+addRuleBaseFVs :: RuleBase -> IdSet -> RuleBase
+addRuleBaseFVs (RuleBase rules fvs) extra_fvs
+ = RuleBase rules (fvs `unionVarSet` extra_fvs)
+
+extendRuleBaseList :: RuleBase -> [(Id,CoreRule)] -> RuleBase
+extendRuleBaseList rule_base new_guys
+ = foldl extendRuleBase rule_base new_guys
+
+extendRuleBase :: RuleBase -> (Id,CoreRule) -> RuleBase
+extendRuleBase (RuleBase rule_ids rule_fvs) (id, rule)
+ = RuleBase (extendVarSet rule_ids new_id)
+ (rule_fvs `unionVarSet` extendVarSet lhs_fvs id)
where
- new_id = case lookupVarSet rule_id_set id of
- Just id' -> addRuleToId id' rule
- Nothing -> addRuleToId id rule
- lhs_fvs = ruleSomeLhsFreeVars isId rule
- -- Find *all* the free Ids of the LHS, not just
+ new_id = setIdSpecialisation id (addRule old_rules id rule)
+
+ old_rules = idSpecialisation (fromMaybe id (lookupVarSet rule_ids id))
+ -- Get the old rules from rule_ids if the Id is already there, but
+ -- if not, use the Id from the incoming rule. If may be a PrimOpId,
+ -- in which case it may have rules in its belly already. Seems
+ -- dreadfully hackoid.
+
+ lhs_fvs = ruleLhsFreeIds rule
+ -- Finds *all* the free Ids of the LHS, not just
-- locally defined ones!!
-addRuleToId id rule = setIdSpecialisation id (addRule id (getIdSpecialisation id) rule)
+pprRuleBase :: RuleBase -> SDoc
+pprRuleBase (RuleBase rules _) = vcat [ pprCoreRule (ppr id) rs
+ | id <- varSetElems rules,
+ rs <- rulesRules $ idSpecialisation id ]
\end{code}
-
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