addIdSpecialisations,
-- * Misc. CoreRule helpers
- rulesOfBinds, getRules, pprRulesForUser,
+ rulesOfBinds, getRules, pprRulesForUser,
- lookupRule, mkLocalRule, roughTopNames
+ lookupRule, mkRule, roughTopNames
) where
#include "HsVersions.h"
import CoreSyn -- All of it
-import OccurAnal ( occurAnalyseExpr )
+import CoreSubst
+import OccurAnal ( occurAnalyseExpr )
import CoreFVs ( exprFreeVars, exprsFreeVars, bindFreeVars, rulesFreeVars )
-import CoreUtils ( exprType )
+import CoreUtils ( exprType, eqExpr )
import PprCore ( pprRules )
-import Type ( Type, TvSubstEnv, tcEqTypeX )
+import Type ( Type )
import TcType ( tcSplitTyConApp_maybe )
+import Coercion
import CoreTidy ( tidyRules )
import Id
import IdInfo ( SpecInfo( SpecInfo ) )
-import Var ( Var )
import VarEnv
import VarSet
import Name ( Name, NamedThing(..) )
import NameEnv
import Unify ( ruleMatchTyX, MatchEnv(..) )
-import BasicTypes ( Activation )
+import BasicTypes ( Activation, CompilerPhase, isActive )
import StaticFlags ( opt_PprStyle_Debug )
import Outputable
import FastString
import Maybes
-import OrdList
import Bag
import Util
import Data.List
\end{code}
+Note [Overall plumbing for rules]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+* After the desugarer:
+ - The ModGuts initially contains mg_rules :: [CoreRule] of
+ locally-declared rules for imported Ids.
+ - Locally-declared rules for locally-declared Ids are attached to
+ the IdInfo for that Id. See Note [Attach rules to local ids] in
+ DsBinds
+
+* TidyPgm strips off all the rules from local Ids and adds them to
+ mg_rules, so that the ModGuts has *all* the locally-declared rules.
+
+* The HomePackageTable contains a ModDetails for each home package
+ module. Each contains md_rules :: [CoreRule] of rules declared in
+ that module. The HomePackageTable grows as ghc --make does its
+ up-sweep. In batch mode (ghc -c), the HPT is empty; all imported modules
+ are treated by the "external" route, discussed next, regardless of
+ which package they come from.
+
+* The ExternalPackageState has a single eps_rule_base :: RuleBase for
+ Ids in other packages. This RuleBase simply grow monotonically, as
+ ghc --make compiles one module after another.
+
+ During simplification, interface files may get demand-loaded,
+ as the simplifier explores the unfoldings for Ids it has in
+ its hand. (Via an unsafePerformIO; the EPS is really a cache.)
+ That in turn may make the EPS rule-base grow. In contrast, the
+ HPT never grows in this way.
+
+* The result of all this is that during Core-to-Core optimisation
+ there are four sources of rules:
+
+ (a) Rules in the IdInfo of the Id they are a rule for. These are
+ easy: fast to look up, and if you apply a substitution then
+ it'll be applied to the IdInfo as a matter of course.
+
+ (b) Rules declared in this module for imported Ids, kept in the
+ ModGuts. If you do a substitution, you'd better apply the
+ substitution to these. There are seldom many of these.
+
+ (c) Rules declared in the HomePackageTable. These never change.
+
+ (d) Rules in the ExternalPackageTable. These can grow in response
+ to lazy demand-loading of interfaces.
+
+* At the moment (c) is carried in a reader-monad way by the CoreMonad.
+ The HomePackageTable doesn't have a single RuleBase because technically
+ we should only be able to "see" rules "below" this module; so we
+ generate a RuleBase for (c) by combing rules from all the modules
+ "below" us. That's why we can't just select the home-package RuleBase
+ from HscEnv.
+
+ [NB: we are inconsistent here. We should do the same for external
+ pacakges, but we don't. Same for type-class instances.]
+
+* So in the outer simplifier loop, we combine (b-d) into a single
+ RuleBase, reading
+ (b) from the ModGuts,
+ (c) from the CoreMonad, and
+ (d) from its mutable variable
+ [Of coures this means that we won't see new EPS rules that come in
+ during a single simplifier iteration, but that probably does not
+ matter.]
+
%************************************************************************
%* *
where pi' :: Lift Int# is the specialised version of pi.
\begin{code}
-mkLocalRule :: RuleName -> Activation
- -> Name -> [CoreBndr] -> [CoreExpr] -> CoreExpr -> CoreRule
+mkRule :: Bool -> Bool -> RuleName -> Activation
+ -> Name -> [CoreBndr] -> [CoreExpr] -> CoreExpr -> CoreRule
-- ^ Used to make 'CoreRule' for an 'Id' defined in the module being
-- compiled. See also 'CoreSyn.CoreRule'
-mkLocalRule name act fn bndrs args rhs
+mkRule is_auto is_local name act fn bndrs args rhs
= Rule { ru_name = name, ru_fn = fn, ru_act = act,
ru_bndrs = bndrs, ru_args = args,
- ru_rhs = rhs, ru_rough = roughTopNames args,
- ru_local = True }
+ ru_rhs = occurAnalyseExpr rhs,
+ ru_rough = roughTopNames args,
+ ru_auto = is_auto, ru_local = is_local }
--------------
roughTopNames :: [CoreExpr] -> [Maybe Name]
roughTopName :: CoreExpr -> Maybe Name
roughTopName (Type ty) = case tcSplitTyConApp_maybe ty of
- Just (tc,_) -> Just (getName tc)
- Nothing -> Nothing
+ Just (tc,_) -> Just (getName tc)
+ Nothing -> Nothing
+roughTopName (Coercion _) = Nothing
roughTopName (App f _) = roughTopName f
-roughTopName (Var f) | isGlobalId f = Just (idName f)
- | otherwise = Nothing
+roughTopName (Var f) | isGlobalId f -- Note [Care with roughTopName]
+ , isDataConWorkId f || idArity f > 0
+ = Just (idName f)
roughTopName _ = Nothing
ruleCantMatch :: [Maybe Name] -> [Maybe Name] -> Bool
ruleCantMatch _ _ = False
\end{code}
+Note [Care with roughTopName]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Consider this
+ module M where { x = a:b }
+ module N where { ...f x...
+ RULE f (p:q) = ... }
+You'd expect the rule to match, because the matcher can
+look through the unfolding of 'x'. So we must avoid roughTopName
+returning 'M.x' for the call (f x), or else it'll say "can't match"
+and we won't even try!!
+
+However, suppose we have
+ RULE g (M.h x) = ...
+ foo = ...(g (M.k v))....
+where k is a *function* exported by M. We never really match
+functions (lambdas) except by name, so in this case it seems like
+a good idea to treat 'M.k' as a roughTopName of the call.
+
+
\begin{code}
pprRulesForUser :: [CoreRule] -> SDoc
-- (a) tidy the rules
rulesOfBinds binds = concatMap (concatMap idCoreRules . bindersOf) binds
getRules :: RuleBase -> Id -> [CoreRule]
- -- The rules for an Id come from two places:
- -- (a) the ones it is born with (idCoreRules fn)
- -- (b) rules added in subsequent modules (extra_rules)
- -- PrimOps, for example, are born with a bunch of rules under (a)
+-- See Note [Where rules are found]
getRules rule_base fn
- | isLocalId fn = idCoreRules fn
- | otherwise = WARN( not (isPrimOpId fn) && notNull (idCoreRules fn),
- ppr fn <+> ppr (idCoreRules fn) )
- idCoreRules fn ++ (lookupNameEnv rule_base (idName fn) `orElse` [])
- -- Only PrimOpIds have rules inside themselves, and perhaps more besides
+ = idCoreRules fn ++ imp_rules
+ where
+ imp_rules = lookupNameEnv rule_base (idName fn) `orElse` []
\end{code}
+Note [Where rules are found]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The rules for an Id come from two places:
+ (a) the ones it is born with, stored inside the Id iself (idCoreRules fn),
+ (b) rules added in other modules, stored in the global RuleBase (imp_rules)
+
+It's tempting to think that
+ - LocalIds have only (a)
+ - non-LocalIds have only (b)
+
+but that isn't quite right:
+
+ - PrimOps and ClassOps are born with a bunch of rules inside the Id,
+ even when they are imported
+
+ - The rules in PrelRules.builtinRules should be active even
+ in the module defining the Id (when it's a LocalId), but
+ the rules are kept in the global RuleBase
+
%************************************************************************
%* *
%************************************************************************
%* *
-\subsection{Matching}
+ Matching
%* *
%************************************************************************
-Note [Extra args in rule matching]
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-If we find a matching rule, we return (Just (rule, rhs)),
-but the rule firing has only consumed as many of the input args
-as the ruleArity says. It's up to the caller to keep track
-of any left-over args. E.g. if you call
- lookupRule ... f [e1, e2, e3]
-and it returns Just (r, rhs), where r has ruleArity 2
-then the real rewrite is
- f e1 e2 e3 ==> rhs e3
-
-You might think it'd be cleaner for lookupRule to deal with the
-leftover arguments, by applying 'rhs' to them, but the main call
-in the Simplifier works better as it is. Reason: the 'args' passed
-to lookupRule are the result of a lazy substitution
-
\begin{code}
-- | The main rule matching function. Attempts to apply all (active)
-- supplied rules to this instance of an application in a given
-- context, returning the rule applied and the resulting expression if
-- successful.
-lookupRule :: (Activation -> Bool) -> InScopeSet
+lookupRule :: (Activation -> Bool) -- When rule is active
+ -> IdUnfoldingFun -- When Id can be unfolded
+ -> InScopeSet
-> Id -> [CoreExpr]
-> [CoreRule] -> Maybe (CoreRule, CoreExpr)
-- See Note [Extra args in rule matching]
-- See comments on matchRule
-lookupRule is_active in_scope fn args rules
- = -- pprTrace "matchRules" (ppr fn <+> ppr rules) $
+lookupRule is_active id_unf in_scope fn args rules
+ = -- pprTrace "matchRules" (ppr fn <+> ppr args $$ ppr rules ) $
case go [] rules of
[] -> Nothing
(m:ms) -> Just (findBest (fn,args) m ms)
go :: [(CoreRule,CoreExpr)] -> [CoreRule] -> [(CoreRule,CoreExpr)]
go ms [] = ms
- go ms (r:rs) = case (matchRule is_active in_scope args rough_args r) of
+ go ms (r:rs) = case (matchRule is_active id_unf in_scope args rough_args r) of
Just e -> go ((r,e):ms) rs
Nothing -> -- pprTrace "match failed" (ppr r $$ ppr args $$
- -- ppr [(arg_id, unfoldingTemplate unf) | Var arg_id <- args, let unf = idUnfolding arg_id, isCheapUnfolding unf] )
- go ms rs
+ -- ppr [ (arg_id, unfoldingTemplate unf)
+ -- | Var arg_id <- args
+ -- , let unf = idUnfolding arg_id
+ -- , isCheapUnfolding unf] )
+ go ms rs
findBest :: (Id, [CoreExpr])
-> (CoreRule,CoreExpr) -> [(CoreRule,CoreExpr)] -> (CoreRule,CoreExpr)
(fn,args) = target
isMoreSpecific :: CoreRule -> CoreRule -> Bool
-isMoreSpecific (BuiltinRule {}) _ = True
-isMoreSpecific _ (BuiltinRule {}) = False
+-- This tests if one rule is more specific than another
+-- We take the view that a BuiltinRule is less specific than
+-- anything else, because we want user-define rules to "win"
+-- In particular, class ops have a built-in rule, but we
+-- any user-specific rules to win
+-- eg (Trac #4397)
+-- truncate :: (RealFrac a, Integral b) => a -> b
+-- {-# RULES "truncate/Double->Int" truncate = double2Int #-}
+-- double2Int :: Double -> Int
+-- We want the specific RULE to beat the built-in class-op rule
+isMoreSpecific (BuiltinRule {}) _ = False
+isMoreSpecific (Rule {}) (BuiltinRule {}) = True
isMoreSpecific (Rule { ru_bndrs = bndrs1, ru_args = args1 })
(Rule { ru_bndrs = bndrs2, ru_args = args2 })
- = isJust (matchN in_scope bndrs2 args2 args1)
+ = isJust (matchN id_unfolding_fun in_scope bndrs2 args2 args1)
where
+ id_unfolding_fun _ = NoUnfolding -- Don't expand in templates
in_scope = mkInScopeSet (mkVarSet bndrs1)
-- Actually we should probably include the free vars
-- of rule1's args, but I can't be bothered
noBlackList :: Activation -> Bool
noBlackList _ = False -- Nothing is black listed
+\end{code}
+
+Note [Extra args in rule matching]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+If we find a matching rule, we return (Just (rule, rhs)),
+but the rule firing has only consumed as many of the input args
+as the ruleArity says. It's up to the caller to keep track
+of any left-over args. E.g. if you call
+ lookupRule ... f [e1, e2, e3]
+and it returns Just (r, rhs), where r has ruleArity 2
+then the real rewrite is
+ f e1 e2 e3 ==> rhs e3
-matchRule :: (Activation -> Bool) -> InScopeSet
+You might think it'd be cleaner for lookupRule to deal with the
+leftover arguments, by applying 'rhs' to them, but the main call
+in the Simplifier works better as it is. Reason: the 'args' passed
+to lookupRule are the result of a lazy substitution
+
+\begin{code}
+------------------------------------
+matchRule :: (Activation -> Bool) -> IdUnfoldingFun
+ -> InScopeSet
-> [CoreExpr] -> [Maybe Name]
-> CoreRule -> Maybe CoreExpr
-- Any 'surplus' arguments in the input are simply put on the end
-- of the output.
-matchRule _is_active _in_scope args _rough_args
+matchRule _is_active id_unf _in_scope args _rough_args
(BuiltinRule { ru_try = match_fn })
- = case match_fn args of
+-- Built-in rules can't be switched off, it seems
+ = case match_fn id_unf args of
Just expr -> Just expr
Nothing -> Nothing
-matchRule is_active in_scope args rough_args
+matchRule is_active id_unf in_scope args rough_args
(Rule { ru_act = act, ru_rough = tpl_tops,
ru_bndrs = tpl_vars, ru_args = tpl_args,
ru_rhs = rhs })
| not (is_active act) = Nothing
| ruleCantMatch tpl_tops rough_args = Nothing
| otherwise
- = case matchN in_scope tpl_vars tpl_args args of
- Nothing -> Nothing
- Just (binds, tpl_vals) -> Just (mkLets binds $
- rule_fn `mkApps` tpl_vals)
+ = case matchN id_unf in_scope tpl_vars tpl_args args of
+ Nothing -> Nothing
+ Just (bind_wrapper, tpl_vals) -> Just (bind_wrapper $
+ rule_fn `mkApps` tpl_vals)
where
rule_fn = occurAnalyseExpr (mkLams tpl_vars rhs)
-- We could do this when putting things into the rulebase, I guess
-\end{code}
-\begin{code}
--- For a given match template and context, find bindings to wrap around
--- the entire result and what should be substituted for each template variable.
--- Fail if there are two few actual arguments from the target to match the template
-matchN :: InScopeSet -- ^ In-scope variables
+---------------------------------------
+matchN :: IdUnfoldingFun
+ -> InScopeSet -- ^ In-scope variables
-> [Var] -- ^ Match template type variables
-> [CoreExpr] -- ^ Match template
-> [CoreExpr] -- ^ Target; can have more elements than the template
- -> Maybe ([CoreBind],
+ -> Maybe (BindWrapper, -- Floated bindings; see Note [Matching lets]
[CoreExpr])
+-- For a given match template and context, find bindings to wrap around
+-- the entire result and what should be substituted for each template variable.
+-- Fail if there are two few actual arguments from the target to match the template
-matchN in_scope tmpl_vars tmpl_es target_es
- = do { (tv_subst, id_subst, binds)
- <- go init_menv emptySubstEnv tmpl_es target_es
- ; return (fromOL binds,
- map (lookup_tmpl tv_subst id_subst) tmpl_vars') }
+matchN id_unf in_scope tmpl_vars tmpl_es target_es
+ = do { subst <- go init_menv emptyRuleSubst tmpl_es target_es
+ ; return (rs_binds subst,
+ map (lookup_tmpl subst) tmpl_vars') }
where
(init_rn_env, tmpl_vars') = mapAccumL rnBndrL (mkRnEnv2 in_scope) tmpl_vars
- -- See Note [Template binders]
+ -- See Note [Template binders]
- init_menv = ME { me_tmpls = mkVarSet tmpl_vars', me_env = init_rn_env }
+ init_menv = RV { rv_tmpls = mkVarSet tmpl_vars', rv_lcl = init_rn_env
+ , rv_fltR = mkEmptySubst (rnInScopeSet init_rn_env)
+ , rv_unf = id_unf }
go _ subst [] _ = Just subst
go _ _ _ [] = Nothing -- Fail if too few actual args
- go menv subst (t:ts) (e:es) = do { subst1 <- match menv subst t e
+ go menv subst (t:ts) (e:es) = do { subst1 <- match menv subst t e
; go menv subst1 ts es }
- lookup_tmpl :: TvSubstEnv -> IdSubstEnv -> Var -> CoreExpr
- lookup_tmpl tv_subst id_subst tmpl_var'
- | isTyVar tmpl_var' = case lookupVarEnv tv_subst tmpl_var' of
- Just ty -> Type ty
- Nothing -> unbound tmpl_var'
- | otherwise = case lookupVarEnv id_subst tmpl_var' of
- Just e -> e
- _ -> unbound tmpl_var'
-
+ lookup_tmpl :: RuleSubst -> Var -> CoreExpr
+ lookup_tmpl (RS { rs_tv_subst = tv_subst, rs_id_subst = id_subst }) tmpl_var'
+ | isId tmpl_var' = case lookupVarEnv id_subst tmpl_var' of
+ Just e -> e
+ _ -> unbound tmpl_var'
+ | otherwise = case lookupVarEnv tv_subst tmpl_var' of
+ Just ty -> Type ty
+ Nothing -> unbound tmpl_var'
+
unbound var = pprPanic "Template variable unbound in rewrite rule"
(ppr var $$ ppr tmpl_vars $$ ppr tmpl_vars' $$ ppr tmpl_es $$ ppr target_es)
\end{code}
necessary; the renamed ones are the tmpl_vars'
- ---------------------------------------------
+%************************************************************************
+%* *
+ The main matcher
+%* *
+%************************************************************************
+
+ ---------------------------------------------
The inner workings of matching
---------------------------------------------
\begin{code}
--- These two definitions are not the same as in Subst,
--- but they simple and direct, and purely local to this module
---
-- * The domain of the TvSubstEnv and IdSubstEnv are the template
-- variables passed into the match.
--
--- * The (OrdList CoreBind) in a SubstEnv are the bindings floated out
+-- * The BindWrapper in a RuleSubst are the bindings floated out
-- from nested matches; see the Let case of match, below
--
-type SubstEnv = (TvSubstEnv, IdSubstEnv, OrdList CoreBind)
-type IdSubstEnv = IdEnv CoreExpr
-
-emptySubstEnv :: SubstEnv
-emptySubstEnv = (emptyVarEnv, emptyVarEnv, nilOL)
-
+data RuleEnv = RV { rv_tmpls :: VarSet -- Template variables
+ , rv_lcl :: RnEnv2 -- Renamings for *local bindings*
+ -- (lambda/case)
+ , rv_fltR :: Subst -- Renamings for floated let-bindings
+ -- domain disjoint from envR of rv_lcl
+ -- See Note [Matching lets]
+ , rv_unf :: IdUnfoldingFun
+ }
+
+data RuleSubst = RS { rs_tv_subst :: TvSubstEnv -- Range is the
+ , rs_id_subst :: IdSubstEnv -- template variables
+ , rs_binds :: BindWrapper -- Floated bindings
+ , rs_bndrs :: VarSet -- Variables bound by floated lets
+ }
+
+type BindWrapper = CoreExpr -> CoreExpr
+ -- See Notes [Matching lets] and [Matching cases]
+ -- we represent the floated bindings as a core-to-core function
+
+emptyRuleSubst :: RuleSubst
+emptyRuleSubst = RS { rs_tv_subst = emptyVarEnv, rs_id_subst = emptyVarEnv
+ , rs_binds = \e -> e, rs_bndrs = emptyVarSet }
-- At one stage I tried to match even if there are more
-- template args than real args.
-- SLPJ July 99
-match :: MatchEnv
- -> SubstEnv
+match :: RuleEnv
+ -> RuleSubst
-> CoreExpr -- Template
-> CoreExpr -- Target
- -> Maybe SubstEnv
+ -> Maybe RuleSubst
-- See the notes with Unify.match, which matches types
-- Everything is very similar for terms
-- succeed in matching what looks like the template variable 'a' against 3.
-- The Var case follows closely what happens in Unify.match
-match menv subst (Var v1) e2
- | Just subst <- match_var menv subst v1 e2
- = Just subst
-
-match menv subst e1 (Note _ e2)
- = match menv subst e1 e2
- -- See Note [Notes in RULE matching]
-
-match menv subst e1 (Var v2) -- Note [Expanding variables]
- | not (locallyBoundR rn_env v2) -- Note [Do not expand locally-bound variables]
- , Just e2' <- expandId v2'
- = match (menv { me_env = nukeRnEnvR rn_env }) subst e1 e2'
+match renv subst (Var v1) e2 = match_var renv subst v1 e2
+match renv subst (Note _ e1) e2 = match renv subst e1 e2
+match renv subst e1 (Note _ e2) = match renv subst e1 e2
+ -- Ignore notes in both template and thing to be matched
+ -- See Note [Notes in RULE matching]
+
+match renv subst e1 (Var v2) -- Note [Expanding variables]
+ | not (inRnEnvR rn_env v2) -- Note [Do not expand locally-bound variables]
+ , Just e2' <- expandUnfolding_maybe (rv_unf renv v2')
+ = match (renv { rv_lcl = nukeRnEnvR rn_env }) subst e1 e2'
where
v2' = lookupRnInScope rn_env v2
- rn_env = me_env menv
+ rn_env = rv_lcl renv
-- Notice that we look up v2 in the in-scope set
-- See Note [Lookup in-scope]
-- No need to apply any renaming first (hence no rnOccR)
- -- becuase of the not-locallyBoundR
-
-match menv (tv_subst, id_subst, binds) e1 (Let bind e2)
- | all freshly_bound bndrs -- See Note [Matching lets]
- , not (any (locallyBoundR rn_env) bind_fvs)
- = match (menv { me_env = rn_env' })
- (tv_subst, id_subst, binds `snocOL` bind')
- e1 e2'
+ -- because of the not-inRnEnvR
+
+match renv subst e1 (Let bind e2)
+ | okToFloat (rv_lcl renv) (bindFreeVars bind) -- See Note [Matching lets]
+ = match (renv { rv_fltR = flt_subst' })
+ (subst { rs_binds = rs_binds subst . Let bind'
+ , rs_bndrs = extendVarSetList (rs_bndrs subst) new_bndrs })
+ e1 e2
+ where
+ flt_subst = addInScopeSet (rv_fltR renv) (rs_bndrs subst)
+ (flt_subst', bind') = substBind flt_subst bind
+ new_bndrs = bindersOf bind'
+
+{- Disabled: see Note [Matching cases] below
+match renv (tv_subst, id_subst, binds) e1
+ (Case scrut case_bndr ty [(con, alt_bndrs, rhs)])
+ | exprOkForSpeculation scrut -- See Note [Matching cases]
+ , okToFloat rn_env bndrs (exprFreeVars scrut)
+ = match (renv { me_env = rn_env' })
+ (tv_subst, id_subst, binds . case_wrap)
+ e1 rhs
where
- rn_env = me_env menv
- bndrs = bindersOf bind
- bind_fvs = varSetElems (bindFreeVars bind)
- freshly_bound x = not (x `rnInScope` rn_env)
- bind' = bind
- e2' = e2
- rn_env' = extendRnInScopeList rn_env bndrs
+ rn_env = me_env renv
+ rn_env' = extendRnInScopeList rn_env bndrs
+ bndrs = case_bndr : alt_bndrs
+ case_wrap rhs' = Case scrut case_bndr ty [(con, alt_bndrs, rhs')]
+-}
match _ subst (Lit lit1) (Lit lit2)
| lit1 == lit2
= Just subst
-match menv subst (App f1 a1) (App f2 a2)
- = do { subst' <- match menv subst f1 f2
- ; match menv subst' a1 a2 }
+match renv subst (App f1 a1) (App f2 a2)
+ = do { subst' <- match renv subst f1 f2
+ ; match renv subst' a1 a2 }
-match menv subst (Lam x1 e1) (Lam x2 e2)
- = match menv' subst e1 e2
+match renv subst (Lam x1 e1) (Lam x2 e2)
+ = match renv' subst e1 e2
where
- menv' = menv { me_env = rnBndr2 (me_env menv) x1 x2 }
+ renv' = renv { rv_lcl = rnBndr2 (rv_lcl renv) x1 x2
+ , rv_fltR = delBndr (rv_fltR renv) x2 }
-- This rule does eta expansion
-- (\x.M) ~ N iff M ~ N x
-- It's important that this is *after* the let rule,
-- so that (\x.M) ~ (let y = e in \y.N)
-- does the let thing, and then gets the lam/lam rule above
-match menv subst (Lam x1 e1) e2
- = match menv' subst e1 (App e2 (varToCoreExpr new_x))
+match renv subst (Lam x1 e1) e2
+ = match renv' subst e1 (App e2 (varToCoreExpr new_x))
where
- (rn_env', new_x) = rnBndrL (me_env menv) x1
- menv' = menv { me_env = rn_env' }
+ (rn_env', new_x) = rnEtaL (rv_lcl renv) x1
+ renv' = renv { rv_lcl = rn_env' }
-- Eta expansion the other way
-- M ~ (\y.N) iff M y ~ N
-match menv subst e1 (Lam x2 e2)
- = match menv' subst (App e1 (varToCoreExpr new_x)) e2
+match renv subst e1 (Lam x2 e2)
+ = match renv' subst (App e1 (varToCoreExpr new_x)) e2
where
- (rn_env', new_x) = rnBndrR (me_env menv) x2
- menv' = menv { me_env = rn_env' }
-
-match menv subst (Case e1 x1 ty1 alts1) (Case e2 x2 ty2 alts2)
- = do { subst1 <- match_ty menv subst ty1 ty2
- ; subst2 <- match menv subst1 e1 e2
- ; let menv' = menv { me_env = rnBndr2 (me_env menv) x1 x2 }
- ; match_alts menv' subst2 alts1 alts2 -- Alts are both sorted
+ (rn_env', new_x) = rnEtaR (rv_lcl renv) x2
+ renv' = renv { rv_lcl = rn_env' }
+
+match renv subst (Case e1 x1 ty1 alts1) (Case e2 x2 ty2 alts2)
+ = do { subst1 <- match_ty renv subst ty1 ty2
+ ; subst2 <- match renv subst1 e1 e2
+ ; let renv' = rnMatchBndr2 renv subst x1 x2
+ ; match_alts renv' subst2 alts1 alts2 -- Alts are both sorted
}
-match menv subst (Type ty1) (Type ty2)
- = match_ty menv subst ty1 ty2
+match renv subst (Type ty1) (Type ty2)
+ = match_ty renv subst ty1 ty2
+match renv subst (Coercion co1) (Coercion co2)
+ = match_co renv subst co1 co2
-match menv subst (Cast e1 co1) (Cast e2 co2)
- = do { subst1 <- match_ty menv subst co1 co2
- ; match menv subst1 e1 e2 }
+match renv subst (Cast e1 co1) (Cast e2 co2)
+ = do { subst1 <- match_co renv subst co1 co2
+ ; match renv subst1 e1 e2 }
-- Everything else fails
-match _ _ _e1 _e2 = -- pprTrace "Failing at" ((text "e1:" <+> ppr e1) $$ (text "e2:" <+> ppr e2)) $
- Nothing
+match _ _ _e1 _e2 = -- pprTrace "Failing at" ((text "e1:" <+> ppr _e1) $$ (text "e2:" <+> ppr _e2)) $
+ Nothing
+
+-------------
+match_co :: RuleEnv
+ -> RuleSubst
+ -> Coercion
+ -> Coercion
+ -> Maybe RuleSubst
+match_co renv subst (CoVarCo cv) co
+ = match_var renv subst cv (Coercion co)
+match_co _ _ co1 _
+ = pprTrace "match_co baling out" (ppr co1) Nothing
+
+-------------
+rnMatchBndr2 :: RuleEnv -> RuleSubst -> Var -> Var -> RuleEnv
+rnMatchBndr2 renv subst x1 x2
+ = renv { rv_lcl = rnBndr2 rn_env x1 x2
+ , rv_fltR = delBndr (rv_fltR renv) x2 }
+ where
+ rn_env = addRnInScopeSet (rv_lcl renv) (rs_bndrs subst)
+ -- Typically this is a no-op, but it may matter if
+ -- there are some floated let-bindings
------------------------------------------
-match_var :: MatchEnv
- -> SubstEnv
- -> Var -- Template
- -> CoreExpr -- Target
- -> Maybe SubstEnv
-match_var menv subst@(tv_subst, id_subst, binds) v1 e2
- | v1' `elemVarSet` me_tmpls menv
- = case lookupVarEnv id_subst v1' of
- Nothing | any (inRnEnvR rn_env) (varSetElems (exprFreeVars e2))
- -> Nothing -- Occurs check failure
- -- e.g. match forall a. (\x-> a x) against (\y. y y)
-
- | otherwise -- No renaming to do on e2, because no free var
- -- of e2 is in the rnEnvR of the envt
- -- Note [Matching variable types]
- -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
- -- However, we must match the *types*; e.g.
- -- forall (c::Char->Int) (x::Char).
- -- f (c x) = "RULE FIRED"
- -- We must only match on args that have the right type
- -- It's actually quite difficult to come up with an example that shows
- -- you need type matching, esp since matching is left-to-right, so type
- -- args get matched first. But it's possible (e.g. simplrun008) and
- -- this is the Right Thing to do
- -> do { tv_subst' <- Unify.ruleMatchTyX menv tv_subst (idType v1') (exprType e2)
- -- c.f. match_ty below
- ; return (tv_subst', extendVarEnv id_subst v1' e2, binds) }
+match_alts :: RuleEnv
+ -> RuleSubst
+ -> [CoreAlt] -- Template
+ -> [CoreAlt] -- Target
+ -> Maybe RuleSubst
+match_alts _ subst [] []
+ = return subst
+match_alts renv subst ((c1,vs1,r1):alts1) ((c2,vs2,r2):alts2)
+ | c1 == c2
+ = do { subst1 <- match renv' subst r1 r2
+ ; match_alts renv subst1 alts1 alts2 }
+ where
+ renv' = foldl mb renv (vs1 `zip` vs2)
+ mb renv (v1,v2) = rnMatchBndr2 renv subst v1 v2
- Just e1' | eqExpr (nukeRnEnvL rn_env) e1' e2
- -> Just subst
+match_alts _ _ _ _
+ = Nothing
- | otherwise
- -> Nothing
+------------------------------------------
+okToFloat :: RnEnv2 -> VarSet -> Bool
+okToFloat rn_env bind_fvs
+ = foldVarSet ((&&) . not_captured) True bind_fvs
+ where
+ not_captured fv = not (inRnEnvR rn_env fv)
- | otherwise -- v1 is not a template variable; check for an exact match with e2
- = case e2 of
- Var v2 | v1' == rnOccR rn_env v2 -> Just subst
- _ -> Nothing
+------------------------------------------
+match_var :: RuleEnv
+ -> RuleSubst
+ -> Var -- Template
+ -> CoreExpr -- Target
+ -> Maybe RuleSubst
+match_var renv@(RV { rv_tmpls = tmpls, rv_lcl = rn_env, rv_fltR = flt_env })
+ subst v1 e2
+ | v1' `elemVarSet` tmpls
+ = match_tmpl_var renv subst v1' e2
+
+ | otherwise -- v1' is not a template variable; check for an exact match with e2
+ = case e2 of -- Remember, envR of rn_env is disjoint from rv_fltR
+ Var v2 | v1' == rnOccR rn_env v2
+ -> Just subst
+
+ | Var v2' <- lookupIdSubst (text "match_var") flt_env v2
+ , v1' == v2'
+ -> Just subst
+
+ _ -> Nothing
where
- rn_env = me_env menv
- v1' = rnOccL rn_env v1
+ v1' = rnOccL rn_env v1
-- If the template is
-- forall x. f x (\x -> x) = ...
-- Then the x inside the lambda isn't the
-- template x, so we must rename first!
-
------------------------------------------
-match_alts :: MatchEnv
- -> SubstEnv
- -> [CoreAlt] -- Template
- -> [CoreAlt] -- Target
- -> Maybe SubstEnv
-match_alts _ subst [] []
- = return subst
-match_alts menv subst ((c1,vs1,r1):alts1) ((c2,vs2,r2):alts2)
- | c1 == c2
- = do { subst1 <- match menv' subst r1 r2
- ; match_alts menv subst1 alts1 alts2 }
- where
- menv' :: MatchEnv
- menv' = menv { me_env = rnBndrs2 (me_env menv) vs1 vs2 }
+match_tmpl_var :: RuleEnv
+ -> RuleSubst
+ -> Var -- Template
+ -> CoreExpr -- Target
+ -> Maybe RuleSubst
+
+match_tmpl_var renv@(RV { rv_lcl = rn_env, rv_fltR = flt_env })
+ subst@(RS { rs_id_subst = id_subst, rs_bndrs = let_bndrs })
+ v1' e2
+ | any (inRnEnvR rn_env) (varSetElems (exprFreeVars e2))
+ = Nothing -- Occurs check failure
+ -- e.g. match forall a. (\x-> a x) against (\y. y y)
-match_alts _ _ _ _
- = Nothing
-\end{code}
+ | Just e1' <- lookupVarEnv id_subst v1'
+ = if eqExpr (rnInScopeSet rn_env) e1' e2'
+ then Just subst
+ else Nothing
-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).
+ | otherwise
+ = -- Note [Matching variable types]
+ -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ -- However, we must match the *types*; e.g.
+ -- forall (c::Char->Int) (x::Char).
+ -- f (c x) = "RULE FIRED"
+ -- We must only match on args that have the right type
+ -- It's actually quite difficult to come up with an example that shows
+ -- you need type matching, esp since matching is left-to-right, so type
+ -- args get matched first. But it's possible (e.g. simplrun008) and
+ -- this is the Right Thing to do
+ do { subst' <- match_ty renv subst (idType v1') (exprType e2)
+ ; return (subst' { rs_id_subst = id_subst' }) }
+ where
+ -- e2' is the result of applying flt_env to e2
+ e2' | isEmptyVarSet let_bndrs = e2
+ | otherwise = substExpr (text "match_tmpl_var") flt_env e2
+
+ id_subst' = extendVarEnv (rs_id_subst subst) v1' e2'
+ -- No further renaming to do on e2',
+ -- because no free var of e2' is in the rnEnvR of the envt
-\begin{code}
------------------------------------------
-match_ty :: MatchEnv
- -> SubstEnv
+match_ty :: RuleEnv
+ -> RuleSubst
-> Type -- Template
-> Type -- Target
- -> Maybe SubstEnv
-match_ty menv (tv_subst, id_subst, binds) ty1 ty2
- = do { tv_subst' <- Unify.ruleMatchTyX menv tv_subst ty1 ty2
- ; return (tv_subst', id_subst, binds) }
+ -> Maybe RuleSubst
+-- 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).
+
+match_ty renv subst ty1 ty2
+ = do { tv_subst' <- Unify.ruleMatchTyX menv tv_subst ty1 ty2
+ ; return (subst { rs_tv_subst = tv_subst' }) }
+ where
+ tv_subst = rs_tv_subst subst
+ menv = ME { me_tmpls = rv_tmpls renv, me_env = rv_lcl renv }
\end{code}
Note [Expanding variables]
Note [Notes in RULE matching]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-Look through Notes. In particular, we don't want to
-be confused by InlineMe notes. Maybe we should be more
-careful about profiling notes, but for now I'm just
-riding roughshod over them.
-See Note [Notes in call patterns] in SpecConstr
+Look through Notes in both template and expression being matched. In
+particular, we don't want to be confused by InlineMe notes. Maybe we
+should be more careful about profiling notes, but for now I'm just
+riding roughshod over them. cf Note [Notes in call patterns] in
+SpecConstr
Note [Matching lets]
~~~~~~~~~~~~~~~~~~~~
let { w=R } in (\x. <rhs>) E
In effect, we want to float the let-binding outward, to enable
the match to happen. This is the WHOLE REASON for accumulating
-bindings in the SubstEnv
-
-We can only do this if
- (a) Widening the scope of w does not capture any variables
- We use a conservative test: w is not already in scope
- If not, we clone the binders, and substitute
- (b) The free variables of R are not bound by the part of the
- target expression outside the let binding; e.g.
- f (\v. let w = v+1 in g E)
- Here we obviously cannot float the let-binding for w.
-
-You may think rule (a) would never apply, because rule matching is
-mostly invoked from the simplifier, when we have just run substExpr
-over the argument, so there will be no shadowing anyway.
-The fly in the ointment is that the forall'd variables of the
-RULE itself are considered in scope.
-
-I though of various ways to solve (a). One plan was to
-clone the binders if they are in scope. But watch out!
- (let x=y+1 in let z=x+1 in (z,z)
- --> should match (p,p) but watch out that
- the use of x on z's rhs is OK!
-If we clone x, then the let-binding for 'z' is then caught by (b),
-at least unless we elaborate the RnEnv stuff a bit.
-
-So for we simply fail to match unless both (a) and (b) hold.
-
-Other cases to think about
- (let x=y+1 in \x. (x,x))
- --> let x=y+1 in (\x1. (x1,x1))
- (\x. let x = y+1 in (x,x))
- --> let x1 = y+1 in (\x. (x1,x1)
- (let x=y+1 in (x,x), let x=y-1 in (x,x))
- --> let x=y+1 in let x1=y-1 in ((x,x),(x1,x1))
-
-
+bindings in the RuleSubst
+
+We can only do this if the free variables of R are not bound by the
+part of the target expression outside the let binding; e.g.
+ f (\v. let w = v+1 in g E)
+Here we obviously cannot float the let-binding for w. Hence the
+use of okToFloat.
+
+There are a couple of tricky points.
+ (a) What if floating the binding captures a variable?
+ f (let v = x+1 in v) v
+ --> NOT!
+ let v = x+1 in f (x+1) v
+
+ (b) What if two non-nested let bindings bind the same variable?
+ f (let v = e1 in b1) (let v = e2 in b2)
+ --> NOT!
+ let v = e1 in let v = e2 in (f b2 b2)
+ See testsuite test "RuleFloatLet".
+
+Our cunning plan is this:
+ * Along with the growing substitution for template variables
+ we maintain a growing set of floated let-bindings (rs_binds)
+ plus the set of variables thus bound.
+
+ * The RnEnv2 in the MatchEnv binds only the local binders
+ in the term (lambdas, case)
+
+ * When we encounter a let in the term to be matched, we
+ check that does not mention any locally bound (lambda, case)
+ variables. If so we fail
+
+ * We use CoreSubst.substBind to freshen the binding, using an
+ in-scope set that is the original in-scope variables plus the
+ rs_bndrs (currently floated let-bindings). So in (a) above
+ we'll freshen the 'v' binding; in (b) above we'll freshen
+ the *second* 'v' binding.
+
+ * We apply that freshening substitution, in a lexically-scoped
+ way to the term, although lazily; this is the rv_fltR field.
+
+
+Note [Matching cases]
+~~~~~~~~~~~~~~~~~~~~~
+{- NOTE: This idea is currently disabled. It really only works if
+ the primops involved are OkForSpeculation, and, since
+ they have side effects readIntOfAddr and touch are not.
+ Maybe we'll get back to this later . -}
+
+Consider
+ f (case readIntOffAddr# p# i# realWorld# of { (# s#, n# #) ->
+ case touch# fp s# of { _ ->
+ I# n# } } )
+This happened in a tight loop generated by stream fusion that
+Roman encountered. We'd like to treat this just like the let
+case, because the primops concerned are ok-for-speculation.
+That is, we'd like to behave as if it had been
+ case readIntOffAddr# p# i# realWorld# of { (# s#, n# #) ->
+ case touch# fp s# of { _ ->
+ f (I# n# } } )
+
Note [Lookup in-scope]
~~~~~~~~~~~~~~~~~~~~~~
Consider this example
That is why the 'lookupRnInScope' call in the (Var v2) case of 'match'
is so important.
-\begin{code}
-eqExpr :: RnEnv2 -> CoreExpr -> CoreExpr -> Bool
--- ^ A kind of shallow equality used in rule matching, so does
--- /not/ look through newtypes or predicate types
-
-eqExpr env (Var v1) (Var v2)
- | rnOccL env v1 == rnOccR env v2
- = True
-
--- The next two rules expand non-local variables
--- C.f. Note [Expanding variables]
--- and Note [Do not expand locally-bound variables]
-eqExpr env (Var v1) e2
- | not (locallyBoundL env v1)
- , Just e1' <- expandId (lookupRnInScope env v1)
- = eqExpr (nukeRnEnvL env) e1' e2
-
-eqExpr env e1 (Var v2)
- | not (locallyBoundR env v2)
- , Just e2' <- expandId (lookupRnInScope env v2)
- = eqExpr (nukeRnEnvR env) e1 e2'
-
-eqExpr _ (Lit lit1) (Lit lit2) = lit1 == lit2
-eqExpr env (App f1 a1) (App f2 a2) = eqExpr env f1 f2 && eqExpr env a1 a2
-eqExpr env (Lam v1 e1) (Lam v2 e2) = eqExpr (rnBndr2 env v1 v2) e1 e2
-eqExpr env (Note n1 e1) (Note n2 e2) = eq_note env n1 n2 && eqExpr env e1 e2
-eqExpr env (Cast e1 co1) (Cast e2 co2) = tcEqTypeX env co1 co2 && eqExpr env e1 e2
-eqExpr env (Type t1) (Type t2) = tcEqTypeX env t1 t2
-
-eqExpr env (Let (NonRec v1 r1) e1)
- (Let (NonRec v2 r2) e2) = eqExpr env r1 r2
- && eqExpr (rnBndr2 env v1 v2) e1 e2
-eqExpr env (Let (Rec ps1) e1)
- (Let (Rec ps2) e2) = equalLength ps1 ps2
- && and (zipWith eq_rhs ps1 ps2)
- && eqExpr env' e1 e2
- where
- env' = foldl2 rn_bndr2 env ps2 ps2
- rn_bndr2 env (b1,_) (b2,_) = rnBndr2 env b1 b2
- eq_rhs (_,r1) (_,r2) = eqExpr env' r1 r2
-eqExpr env (Case e1 v1 t1 a1)
- (Case e2 v2 t2 a2) = eqExpr env e1 e2
- && tcEqTypeX env t1 t2
- && equalLength a1 a2
- && and (zipWith (eq_alt env') a1 a2)
- where
- env' = rnBndr2 env v1 v2
-
-eqExpr _ _ _ = False
-
-eq_alt :: RnEnv2 -> CoreAlt -> CoreAlt -> Bool
-eq_alt env (c1,vs1,r1) (c2,vs2,r2) = c1==c2 && eqExpr (rnBndrs2 env vs1 vs2) r1 r2
-
-eq_note :: RnEnv2 -> Note -> Note -> Bool
-eq_note _ (SCC cc1) (SCC cc2) = cc1 == cc2
-eq_note _ (CoreNote s1) (CoreNote s2) = s1 == s2
-eq_note _ _ _ = False
-\end{code}
-
-Auxiliary functions
-
-\begin{code}
-locallyBoundL, locallyBoundR :: RnEnv2 -> Var -> Bool
-locallyBoundL rn_env v = inRnEnvL rn_env v
-locallyBoundR rn_env v = inRnEnvR rn_env v
-
-
-expandId :: Id -> Maybe CoreExpr
-expandId id
- | isExpandableUnfolding unfolding = Just (unfoldingTemplate unfolding)
- | otherwise = Nothing
- where
- unfolding = idUnfolding id
-\end{code}
-
%************************************************************************
%* *
Rule-check the program
\begin{code}
-- | Report partial matches for rules beginning with the specified
-- string for the purposes of error reporting
-ruleCheckProgram :: (Activation -> Bool) -- ^ Rule activation test
+ruleCheckProgram :: CompilerPhase -- ^ Rule activation test
-> String -- ^ Rule pattern
-> RuleBase -- ^ Database of rules
-> [CoreBind] -- ^ Bindings to check in
-> SDoc -- ^ Resulting check message
-ruleCheckProgram is_active rule_pat rule_base binds
+ruleCheckProgram phase rule_pat rule_base binds
| isEmptyBag results
= text "Rule check results: no rule application sites"
| otherwise
vcat [ p $$ line | p <- bagToList results ]
]
where
- results = unionManyBags (map (ruleCheckBind (RuleCheckEnv is_active rule_pat rule_base)) binds)
+ env = RuleCheckEnv { rc_is_active = isActive phase
+ , rc_id_unf = idUnfolding -- Not quite right
+ -- Should use activeUnfolding
+ , rc_pattern = rule_pat
+ , rc_rule_base = rule_base }
+ results = unionManyBags (map (ruleCheckBind env) binds)
line = text (replicate 20 '-')
data RuleCheckEnv = RuleCheckEnv {
rc_is_active :: Activation -> Bool,
+ rc_id_unf :: IdUnfoldingFun,
rc_pattern :: String,
rc_rule_base :: RuleBase
}
ruleCheck _ (Var _) = emptyBag
ruleCheck _ (Lit _) = emptyBag
ruleCheck _ (Type _) = emptyBag
+ruleCheck _ (Coercion _) = emptyBag
ruleCheck env (App f a) = ruleCheckApp env (App f a) []
ruleCheck env (Note _ e) = ruleCheck env e
ruleCheck env (Cast e _) = ruleCheck env e
ruleCheckFun env fn args
| null name_match_rules = emptyBag
- | otherwise = unitBag (ruleAppCheck_help (rc_is_active env) fn args name_match_rules)
+ | otherwise = unitBag (ruleAppCheck_help env fn args name_match_rules)
where
name_match_rules = filter match (getRules (rc_rule_base env) fn)
match rule = (rc_pattern env) `isPrefixOf` unpackFS (ruleName rule)
-ruleAppCheck_help :: (Activation -> Bool) -> Id -> [CoreExpr] -> [CoreRule] -> SDoc
-ruleAppCheck_help is_active fn args rules
+ruleAppCheck_help :: RuleCheckEnv -> Id -> [CoreExpr] -> [CoreRule] -> SDoc
+ruleAppCheck_help env fn args rules
= -- The rules match the pattern, so we want to print something
vcat [text "Expression:" <+> ppr (mkApps (Var fn) args),
vcat (map check_rule rules)]
= ptext (sLit "Rule") <+> doubleQuotes (ftext name)
rule_info rule
- | Just _ <- matchRule noBlackList emptyInScopeSet args rough_args rule
+ | Just _ <- matchRule noBlackList (rc_id_unf env) emptyInScopeSet args rough_args rule
= text "matches (which is very peculiar!)"
rule_info (BuiltinRule {}) = text "does not match"
rule_info (Rule { ru_act = act,
ru_bndrs = rule_bndrs, ru_args = rule_args})
- | not (is_active act) = text "active only in later phase"
+ | not (rc_is_active env act) = text "active only in later phase"
| n_args < n_rule_args = text "too few arguments"
| n_mismatches == n_rule_args = text "no arguments match"
| n_mismatches == 0 = text "all arguments match (considered individually), but rule as a whole does not"
not (isJust (match_fn rule_arg arg))]
lhs_fvs = exprsFreeVars rule_args -- Includes template tyvars
- match_fn rule_arg arg = match menv emptySubstEnv rule_arg arg
+ match_fn rule_arg arg = match renv emptyRuleSubst rule_arg arg
where
- in_scope = lhs_fvs `unionVarSet` exprFreeVars arg
- menv = ME { me_env = mkRnEnv2 (mkInScopeSet in_scope)
- , me_tmpls = mkVarSet rule_bndrs }
+ in_scope = mkInScopeSet (lhs_fvs `unionVarSet` exprFreeVars arg)
+ renv = RV { rv_lcl = mkRnEnv2 in_scope
+ , rv_tmpls = mkVarSet rule_bndrs
+ , rv_fltR = mkEmptySubst in_scope
+ , rv_unf = rc_id_unf env }
\end{code}
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