2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 \section[CoreRules]{Transformation rules}
8 RuleBase, emptyRuleBase, mkRuleBase, extendRuleBaseList,
9 unionRuleBase, pprRuleBase, ruleCheckProgram,
11 mkSpecInfo, extendSpecInfo, addSpecInfo,
12 rulesOfBinds, addIdSpecialisations,
16 lookupRule, mkLocalRule, roughTopNames
19 #include "HsVersions.h"
21 import CoreSyn -- All of it
22 import OccurAnal ( occurAnalyseExpr )
23 import CoreFVs ( exprFreeVars, exprsFreeVars, bindFreeVars, rulesRhsFreeVars )
24 import CoreUnfold ( isCheapUnfolding, unfoldingTemplate )
25 import CoreUtils ( tcEqExprX )
26 import PprCore ( pprRules )
27 import Type ( TvSubstEnv )
28 import Coercion ( coercionKind )
29 import TcType ( tcSplitTyConApp_maybe )
30 import CoreTidy ( tidyRules )
31 import Id ( Id, idUnfolding, isLocalId, isGlobalId, idName,
32 idSpecialisation, idCoreRules, setIdSpecialisation )
33 import IdInfo ( SpecInfo( SpecInfo ) )
35 import VarEnv ( IdEnv, InScopeSet, emptyTidyEnv,
36 emptyInScopeSet, mkInScopeSet, extendInScopeSetList,
37 emptyVarEnv, lookupVarEnv, extendVarEnv,
38 nukeRnEnvL, mkRnEnv2, rnOccR, rnOccL, inRnEnvR,
39 rnBndrR, rnBndr2, rnBndrL, rnBndrs2,
40 rnInScope, extendRnInScopeList, lookupRnInScope )
42 import Name ( Name, NamedThing(..), nameOccName )
44 import Unify ( ruleMatchTyX, MatchEnv(..) )
45 import BasicTypes ( Activation, CompilerPhase, isActive )
48 import Maybes ( isJust, orElse )
51 import Util ( singleton )
52 import List ( isPrefixOf )
56 %************************************************************************
58 \subsection[specialisation-IdInfo]{Specialisation info about an @Id@}
60 %************************************************************************
62 A @CoreRule@ holds details of one rule for an @Id@, which
63 includes its specialisations.
65 For example, if a rule for @f@ contains the mapping:
67 forall a b d. [Type (List a), Type b, Var d] ===> f' a b
69 then when we find an application of f to matching types, we simply replace
70 it by the matching RHS:
72 f (List Int) Bool dict ===> f' Int Bool
74 All the stuff about how many dictionaries to discard, and what types
75 to apply the specialised function to, are handled by the fact that the
76 Rule contains a template for the result of the specialisation.
78 There is one more exciting case, which is dealt with in exactly the same
79 way. If the specialised value is unboxed then it is lifted at its
80 definition site and unlifted at its uses. For example:
82 pi :: forall a. Num a => a
84 might have a specialisation
86 [Int#] ===> (case pi' of Lift pi# -> pi#)
88 where pi' :: Lift Int# is the specialised version of pi.
91 mkLocalRule :: RuleName -> Activation
92 -> Name -> [CoreBndr] -> [CoreExpr] -> CoreExpr -> CoreRule
93 -- Used to make CoreRule for an Id defined in this module
94 mkLocalRule name act fn bndrs args rhs
95 = Rule { ru_name = name, ru_fn = fn, ru_act = act,
96 ru_bndrs = bndrs, ru_args = args,
97 ru_rhs = rhs, ru_rough = roughTopNames args,
98 ru_orph = Just (nameOccName fn), ru_local = True }
101 roughTopNames :: [CoreExpr] -> [Maybe Name]
102 roughTopNames args = map roughTopName args
104 roughTopName :: CoreExpr -> Maybe Name
105 -- Find the "top" free name of an expression
106 -- a) the function in an App chain (if a GlobalId)
107 -- b) the TyCon in a type
108 -- This is used for the fast-match-check for rules;
109 -- if the top names don't match, the rest can't
110 roughTopName (Type ty) = case tcSplitTyConApp_maybe ty of
111 Just (tc,_) -> Just (getName tc)
113 roughTopName (App f a) = roughTopName f
114 roughTopName (Var f) | isGlobalId f = Just (idName f)
115 | otherwise = Nothing
116 roughTopName other = Nothing
118 ruleCantMatch :: [Maybe Name] -> [Maybe Name] -> Bool
119 -- (ruleCantMatch tpl actual) returns True only if 'actual'
120 -- definitely can't match 'tpl' by instantiating 'tpl'.
121 -- It's only a one-way match; unlike instance matching we
122 -- don't consider unification
124 -- Notice that there is no case
125 -- ruleCantMatch (Just n1 : ts) (Nothing : as) = True
126 -- Reason: a local variable 'v' in the actuals might
127 -- have an unfolding which is a global.
128 -- This quite often happens with case scrutinees.
129 ruleCantMatch (Just n1 : ts) (Just n2 : as) = n1 /= n2 || ruleCantMatch ts as
130 ruleCantMatch (t : ts) (a : as) = ruleCantMatch ts as
131 ruleCantMatch ts as = False
135 %************************************************************************
137 SpecInfo: the rules in an IdInfo
139 %************************************************************************
142 mkSpecInfo :: [CoreRule] -> SpecInfo
143 mkSpecInfo rules = SpecInfo rules (rulesRhsFreeVars rules)
145 extendSpecInfo :: SpecInfo -> [CoreRule] -> SpecInfo
146 extendSpecInfo (SpecInfo rs1 fvs1) rs2
147 = SpecInfo (rs2 ++ rs1) (rulesRhsFreeVars rs2 `unionVarSet` fvs1)
149 addSpecInfo :: SpecInfo -> SpecInfo -> SpecInfo
150 addSpecInfo (SpecInfo rs1 fvs1) (SpecInfo rs2 fvs2)
151 = SpecInfo (rs1 ++ rs2) (fvs1 `unionVarSet` fvs2)
153 addIdSpecialisations :: Id -> [CoreRule] -> Id
154 addIdSpecialisations id rules
155 = setIdSpecialisation id $
156 extendSpecInfo (idSpecialisation id) rules
158 rulesOfBinds :: [CoreBind] -> [CoreRule]
159 rulesOfBinds binds = concatMap (concatMap idCoreRules . bindersOf) binds
163 %************************************************************************
167 %************************************************************************
170 type RuleBase = NameEnv [CoreRule]
171 -- Maps (the name of) an Id to its rules
172 -- The rules are are unordered;
173 -- we sort out any overlaps on lookup
175 emptyRuleBase = emptyNameEnv
177 mkRuleBase :: [CoreRule] -> RuleBase
178 mkRuleBase rules = extendRuleBaseList emptyRuleBase rules
180 extendRuleBaseList :: RuleBase -> [CoreRule] -> RuleBase
181 extendRuleBaseList rule_base new_guys
182 = foldl extendRuleBase rule_base new_guys
184 unionRuleBase :: RuleBase -> RuleBase -> RuleBase
185 unionRuleBase rb1 rb2 = plusNameEnv_C (++) rb1 rb2
187 extendRuleBase :: RuleBase -> CoreRule -> RuleBase
188 extendRuleBase rule_base rule
189 = extendNameEnv_Acc (:) singleton rule_base (ruleIdName rule) rule
191 pprRuleBase :: RuleBase -> SDoc
192 pprRuleBase rules = vcat [ pprRules (tidyRules emptyTidyEnv rs)
193 | rs <- nameEnvElts rules ]
197 %************************************************************************
199 \subsection{Matching}
201 %************************************************************************
204 lookupRule :: (Activation -> Bool) -> InScopeSet
205 -> RuleBase -- Imported rules
206 -> Id -> [CoreExpr] -> Maybe (CoreRule, CoreExpr)
207 lookupRule is_active in_scope rule_base fn args
208 = matchRules is_active in_scope fn args rules
210 -- The rules for an Id come from two places:
211 -- (a) the ones it is born with (idCoreRules fn)
212 -- (b) rules added in subsequent modules (extra_rules)
213 -- PrimOps, for example, are born with a bunch of rules under (a)
214 rules = extra_rules ++ idCoreRules fn
215 extra_rules | isLocalId fn = []
216 | otherwise = lookupNameEnv rule_base (idName fn) `orElse` []
218 matchRules :: (Activation -> Bool) -> InScopeSet
220 -> [CoreRule] -> Maybe (CoreRule, CoreExpr)
221 -- See comments on matchRule
222 matchRules is_active in_scope fn args rules
223 = -- pprTrace "matchRules" (ppr fn <+> ppr rules) $
226 (m:ms) -> Just (findBest (fn,args) m ms)
228 rough_args = map roughTopName args
230 go :: [(CoreRule,CoreExpr)] -> [CoreRule] -> [(CoreRule,CoreExpr)]
232 go ms (r:rs) = case (matchRule is_active in_scope args rough_args r) of
233 Just e -> go ((r,e):ms) rs
234 Nothing -> -- pprTrace "match failed" (ppr r $$ ppr args $$
235 -- ppr [(arg_id, unfoldingTemplate unf) | Var arg_id <- args, let unf = idUnfolding arg_id, isCheapUnfolding unf] )
238 findBest :: (Id, [CoreExpr])
239 -> (CoreRule,CoreExpr) -> [(CoreRule,CoreExpr)] -> (CoreRule,CoreExpr)
240 -- All these pairs matched the expression
241 -- Return the pair the the most specific rule
242 -- The (fn,args) is just for overlap reporting
244 findBest target (rule,ans) [] = (rule,ans)
245 findBest target (rule1,ans1) ((rule2,ans2):prs)
246 | rule1 `isMoreSpecific` rule2 = findBest target (rule1,ans1) prs
247 | rule2 `isMoreSpecific` rule1 = findBest target (rule2,ans2) prs
249 | otherwise = pprTrace "Rules.findBest: rule overlap (Rule 1 wins)"
250 (vcat [ptext SLIT("Expression to match:") <+> ppr fn <+> sep (map ppr args),
251 ptext SLIT("Rule 1:") <+> ppr rule1,
252 ptext SLIT("Rule 2:") <+> ppr rule2]) $
253 findBest target (rule1,ans1) prs
255 | otherwise = findBest target (rule1,ans1) prs
260 isMoreSpecific :: CoreRule -> CoreRule -> Bool
261 isMoreSpecific (BuiltinRule {}) r2 = True
262 isMoreSpecific r1 (BuiltinRule {}) = False
263 isMoreSpecific (Rule { ru_bndrs = bndrs1, ru_args = args1 })
264 (Rule { ru_bndrs = bndrs2, ru_args = args2 })
265 = isJust (matchN in_scope bndrs2 args2 args1)
267 in_scope = mkInScopeSet (mkVarSet bndrs1)
268 -- Actually we should probably include the free vars
269 -- of rule1's args, but I can't be bothered
271 noBlackList :: Activation -> Bool
272 noBlackList act = False -- Nothing is black listed
274 matchRule :: (Activation -> Bool) -> InScopeSet
275 -> [CoreExpr] -> [Maybe Name]
276 -> CoreRule -> Maybe CoreExpr
278 -- If (matchRule rule args) returns Just (name,rhs)
279 -- then (f args) matches the rule, and the corresponding
280 -- rewritten RHS is rhs
282 -- The bndrs and rhs is occurrence-analysed
287 -- forall f g x. map f (map g x) ==> map (f . g) x
289 -- CoreRule "map/map"
290 -- [f,g,x] -- tpl_vars
291 -- [f,map g x] -- tpl_args
292 -- map (f.g) x) -- rhs
294 -- Then the call: matchRule the_rule [e1,map e2 e3]
295 -- = Just ("map/map", (\f,g,x -> rhs) e1 e2 e3)
297 -- Any 'surplus' arguments in the input are simply put on the end
300 matchRule is_active in_scope args rough_args
301 (BuiltinRule { ru_name = name, ru_try = match_fn })
302 = case match_fn args of
303 Just expr -> Just expr
306 matchRule is_active in_scope args rough_args
307 (Rule { ru_name = rn, ru_act = act, ru_rough = tpl_tops,
308 ru_bndrs = tpl_vars, ru_args = tpl_args,
310 | not (is_active act) = Nothing
311 | ruleCantMatch tpl_tops rough_args = Nothing
313 = case matchN in_scope tpl_vars tpl_args args of
315 Just (binds, tpl_vals) -> Just (mkLets binds $
316 rule_fn `mkApps` tpl_vals)
318 rule_fn = occurAnalyseExpr (mkLams tpl_vars rhs)
319 -- We could do this when putting things into the rulebase, I guess
324 -> [Var] -- Template tyvars
325 -> [CoreExpr] -- Template
326 -> [CoreExpr] -- Target; can have more elts than template
327 -> Maybe ([CoreBind], -- Bindings to wrap around the entire result
328 [CoreExpr]) -- What is substituted for each template var
330 matchN in_scope tmpl_vars tmpl_es target_es
331 = do { (tv_subst, id_subst, binds)
332 <- go init_menv emptySubstEnv tmpl_es target_es
333 ; return (fromOL binds,
334 map (lookup_tmpl tv_subst id_subst) tmpl_vars) }
336 init_menv = ME { me_tmpls = mkVarSet tmpl_vars, me_env = init_rn_env }
337 init_rn_env = mkRnEnv2 (extendInScopeSetList in_scope tmpl_vars)
339 go menv subst [] es = Just subst
340 go menv subst ts [] = Nothing -- Fail if too few actual args
341 go menv subst (t:ts) (e:es) = do { subst1 <- match menv subst t e
342 ; go menv subst1 ts es }
344 lookup_tmpl :: TvSubstEnv -> IdSubstEnv -> Var -> CoreExpr
345 lookup_tmpl tv_subst id_subst tmpl_var
346 | isTyVar tmpl_var = case lookupVarEnv tv_subst tmpl_var of
348 Nothing -> unbound tmpl_var
349 | otherwise = case lookupVarEnv id_subst tmpl_var of
351 other -> unbound tmpl_var
353 unbound var = pprPanic "Template variable unbound in rewrite rule" (ppr var)
357 ---------------------------------------------
358 The inner workings of matching
359 ---------------------------------------------
362 -- These two definitions are not the same as in Subst,
363 -- but they simple and direct, and purely local to this module
365 -- * The domain of the TvSubstEnv and IdSubstEnv are the template
366 -- variables passed into the match.
368 -- * The (OrdList CoreBind) in a SubstEnv are the bindings floated out
369 -- from nested matches; see the Let case of match, below
371 type SubstEnv = (TvSubstEnv, IdSubstEnv, OrdList CoreBind)
372 type IdSubstEnv = IdEnv CoreExpr
374 emptySubstEnv :: SubstEnv
375 emptySubstEnv = (emptyVarEnv, emptyVarEnv, nilOL)
378 -- At one stage I tried to match even if there are more
379 -- template args than real args.
381 -- I now think this is probably a bad idea.
382 -- Should the template (map f xs) match (map g)? I think not.
383 -- For a start, in general eta expansion wastes work.
389 -> CoreExpr -- Template
390 -> CoreExpr -- Target
393 -- See the notes with Unify.match, which matches types
394 -- Everything is very similar for terms
396 -- Interesting examples:
398 -- \x->f against \f->f
399 -- When we meet the lambdas we must remember to rename f to f' in the
400 -- second expresion. The RnEnv2 does that.
403 -- forall a. \b->b against \a->3
404 -- We must rename the \a. Otherwise when we meet the lambdas we
405 -- might substitute [a/b] in the template, and then erroneously
406 -- succeed in matching what looks like the template variable 'a' against 3.
408 -- The Var case follows closely what happens in Unify.match
409 match menv subst (Var v1) e2
410 | Just subst <- match_var menv subst v1 e2
413 -- Here is another important rule: if the term being matched is a
414 -- variable, we expand it so long as its unfolding is a WHNF
415 -- (Its occurrence information is not necessarily up to date,
416 -- so we don't use it.)
417 match menv subst e1 (Var v2)
418 | not (inRnEnvR rn_env v2),
419 -- If v2 is in the RnEnvR, then it's locally bound and can't
420 -- have an unfolding. We must make this check because if it
421 -- is locally bound we must not look it up in the in-scope set
422 -- E.g. (\x->x) where x is already in scope
423 isCheapUnfolding unfolding
424 = match menv subst e1 (unfoldingTemplate unfolding)
427 unfolding = idUnfolding (lookupRnInScope rn_env v2)
428 -- Notice that we look up v2 in the in-scope set
429 -- See Note [Lookup in-scope]
431 -- Matching a let-expression. Consider
432 -- RULE forall x. f (g x) = <rhs>
433 -- and target expression
434 -- f (let { w=R } in g E))
435 -- Then we'd like the rule to match, to generate
436 -- let { w=R } in (\x. <rhs>) E
437 -- In effect, we want to float the let-binding outward, to enable
438 -- the match to happen. This is the WHOLE REASON for accumulating
439 -- bindings in the SubstEnv
441 -- We can only do this if
442 -- (a) Widening the scope of w does not capture any variables
443 -- We use a conservative test: w is not already in scope
444 -- (b) The free variables of R are not bound by the part of the
445 -- target expression outside the let binding; e.g.
446 -- f (\v. let w = v+1 in g E)
447 -- Here we obviously cannot float the let-binding for w.
449 match menv subst@(tv_subst, id_subst, binds) e1 (Let bind e2)
450 | all freshly_bound bndrs,
451 not (any locally_bound bind_fvs)
452 = match (menv { me_env = rn_env' })
453 (tv_subst, id_subst, binds `snocOL` bind)
457 bndrs = bindersOf bind
458 bind_fvs = varSetElems (bindFreeVars bind)
459 freshly_bound x = not (x `rnInScope` rn_env)
460 locally_bound x = inRnEnvR rn_env x
461 rn_env' = extendRnInScopeList rn_env bndrs
463 match menv subst (Lit lit1) (Lit lit2)
467 match menv subst (App f1 a1) (App f2 a2)
468 = do { subst' <- match menv subst f1 f2
469 ; match menv subst' a1 a2 }
471 match menv subst (Lam x1 e1) (Lam x2 e2)
472 = match menv' subst e1 e2
474 menv' = menv { me_env = rnBndr2 (me_env menv) x1 x2 }
476 -- This rule does eta expansion
477 -- (\x.M) ~ N iff M ~ N x
478 -- It's important that this is *after* the let rule,
479 -- so that (\x.M) ~ (let y = e in \y.N)
480 -- does the let thing, and then gets the lam/lam rule above
481 match menv subst (Lam x1 e1) e2
482 = match menv' subst e1 (App e2 (varToCoreExpr new_x))
484 (rn_env', new_x) = rnBndrL (me_env menv) x1
485 menv' = menv { me_env = rn_env' }
487 -- Eta expansion the other way
488 -- M ~ (\y.N) iff M y ~ N
489 match menv subst e1 (Lam x2 e2)
490 = match menv' subst (App e1 (varToCoreExpr new_x)) e2
492 (rn_env', new_x) = rnBndrR (me_env menv) x2
493 menv' = menv { me_env = rn_env' }
495 match menv subst (Case e1 x1 ty1 alts1) (Case e2 x2 ty2 alts2)
496 = do { subst1 <- match_ty menv subst ty1 ty2
497 ; subst2 <- match menv subst1 e1 e2
498 ; let menv' = menv { me_env = rnBndr2 (me_env menv) x1 x2 }
499 ; match_alts menv' subst2 alts1 alts2 -- Alts are both sorted
502 match menv subst (Type ty1) (Type ty2)
503 = match_ty menv subst ty1 ty2
505 match menv subst (Cast e1 co1) (Cast e2 co2)
506 | (from1, to1) <- coercionKind co1
507 , (from2, to2) <- coercionKind co2
508 = do { subst1 <- match_ty menv subst to1 to2
509 ; subst2 <- match_ty menv subst1 from1 from2
510 ; match menv subst2 e1 e2 }
512 {- REMOVING OLD CODE: I think that the above handling for let is
513 better than the stuff here, which looks
514 pretty suspicious to me. SLPJ Sept 06
515 -- This is an interesting rule: we simply ignore lets in the
516 -- term being matched against! The unfolding inside it is (by assumption)
517 -- already inside any occurrences of the bound variables, so we'll expand
518 -- them when we encounter them. This gives a chance of matching
519 -- forall x,y. f (g (x,y))
521 -- f (let v = (a,b) in g v)
523 match menv subst e1 (Let bind e2)
524 = match (menv { me_env = rn_env' }) subst e1 e2
526 (rn_env', _bndrs') = mapAccumL rnBndrR (me_env menv) (bindersOf bind)
527 -- It's important to do this renaming, so that the bndrs
528 -- are brought into the local scope. For example:
530 -- forall f,x,xs. f (x:xs)
532 -- f (let y = e in (y:[]))
533 -- We must not get success with x->y! So we record that y is
534 -- locally bound (with rnBndrR), and proceed. The Var case
535 -- will fail when trying to bind x->y
538 -- Everything else fails
539 match menv subst e1 e2 = -- pprTrace "Failing at" ((text "e1:" <+> ppr e1) $$ (text "e2:" <+> ppr e2)) $
542 ------------------------------------------
543 match_var :: MatchEnv
546 -> CoreExpr -- Target
548 match_var menv subst@(tv_subst, id_subst, binds) v1 e2
549 | v1' `elemVarSet` me_tmpls menv
550 = case lookupVarEnv id_subst v1' of
551 Nothing | any (inRnEnvR rn_env) (varSetElems (exprFreeVars e2))
552 -> Nothing -- Occurs check failure
553 -- e.g. match forall a. (\x-> a x) against (\y. y y)
555 | otherwise -- No renaming to do on e2
556 -> Just (tv_subst, extendVarEnv id_subst v1 e2, binds)
558 Just e2' | tcEqExprX (nukeRnEnvL rn_env) e2' e2
564 | otherwise -- v1 is not a template variable; check for an exact match with e2
566 Var v2 | v1' == rnOccR rn_env v2 -> Just subst
571 v1' = rnOccL rn_env v1
572 -- If the template is
573 -- forall x. f x (\x -> x) = ...
574 -- Then the x inside the lambda isn't the
575 -- template x, so we must rename first!
578 ------------------------------------------
579 match_alts :: MatchEnv
581 -> [CoreAlt] -- Template
582 -> [CoreAlt] -- Target
584 match_alts menv subst [] []
586 match_alts menv subst ((c1,vs1,r1):alts1) ((c2,vs2,r2):alts2)
588 = do { subst1 <- match menv' subst r1 r2
589 ; match_alts menv subst1 alts1 alts2 }
592 menv' = menv { me_env = rnBndrs2 (me_env menv) vs1 vs2 }
594 match_alts menv subst alts1 alts2
598 Matching Core types: use the matcher in TcType.
599 Notice that we treat newtypes as opaque. For example, suppose
600 we have a specialised version of a function at a newtype, say
602 We only want to replace (f T) with f', not (f Int).
605 ------------------------------------------
606 match_ty menv (tv_subst, id_subst, binds) ty1 ty2
607 = do { tv_subst' <- Unify.ruleMatchTyX menv tv_subst ty1 ty2
608 ; return (tv_subst', id_subst, binds) }
612 Note [Lookup in-scope]
613 ~~~~~~~~~~~~~~~~~~~~~~
614 Consider this example
615 foo :: Int -> Maybe Int -> Int
617 foo m (Just n) = foo (m-n) (Just n)
619 SpecConstr sees this fragment:
621 case w_smT of wild_Xf [Just A] {
622 Data.Maybe.Nothing -> lvl_smf;
623 Data.Maybe.Just n_acT [Just S(L)] ->
624 case n_acT of wild1_ams [Just A] { GHC.Base.I# y_amr [Just L] ->
625 $wfoo_smW (GHC.Prim.-# ds_Xmb y_amr) wild_Xf
628 and correctly generates the rule
630 RULES: "SC:$wfoo1" [0] __forall {y_amr [Just L] :: GHC.Prim.Int#
631 sc_snn :: GHC.Prim.Int#}
632 $wfoo_smW sc_snn (Data.Maybe.Just @ GHC.Base.Int (GHC.Base.I# y_amr))
633 = $s$wfoo_sno y_amr sc_snn ;]
635 BUT we must ensure that this rule matches in the original function!
636 Note that the call to $wfoo is
637 $wfoo_smW (GHC.Prim.-# ds_Xmb y_amr) wild_Xf
639 During matching we expand wild_Xf to (Just n_acT). But then we must also
640 expand n_acT to (I# y_amr). And we can only do that if we look up n_acT
641 in the in-scope set, because in wild_Xf's unfolding it won't have an unfolding
644 That is why the 'lookupRnInScope' call in the (Var v2) case of 'match'
648 %************************************************************************
650 \subsection{Checking a program for failing rule applications}
652 %************************************************************************
654 -----------------------------------------------------
656 -----------------------------------------------------
658 We want to know what sites have rules that could have fired but didn't.
659 This pass runs over the tree (without changing it) and reports such.
661 NB: we assume that this follows a run of the simplifier, so every Id
662 occurrence (including occurrences of imported Ids) is decorated with
663 all its (active) rules. No need to construct a rule base or anything
667 ruleCheckProgram :: CompilerPhase -> String -> [CoreBind] -> SDoc
668 -- Report partial matches for rules beginning
669 -- with the specified string
670 ruleCheckProgram phase rule_pat binds
672 = text "Rule check results: no rule application sites"
674 = vcat [text "Rule check results:",
676 vcat [ p $$ line | p <- bagToList results ]
679 results = unionManyBags (map (ruleCheckBind (phase, rule_pat)) binds)
680 line = text (replicate 20 '-')
682 type RuleCheckEnv = (CompilerPhase, String) -- Phase and Pattern
684 ruleCheckBind :: RuleCheckEnv -> CoreBind -> Bag SDoc
685 -- The Bag returned has one SDoc for each call site found
686 ruleCheckBind env (NonRec b r) = ruleCheck env r
687 ruleCheckBind env (Rec prs) = unionManyBags [ruleCheck env r | (b,r) <- prs]
689 ruleCheck :: RuleCheckEnv -> CoreExpr -> Bag SDoc
690 ruleCheck env (Var v) = emptyBag
691 ruleCheck env (Lit l) = emptyBag
692 ruleCheck env (Type ty) = emptyBag
693 ruleCheck env (App f a) = ruleCheckApp env (App f a) []
694 ruleCheck env (Note n e) = ruleCheck env e
695 ruleCheck env (Cast e co) = ruleCheck env e
696 ruleCheck env (Let bd e) = ruleCheckBind env bd `unionBags` ruleCheck env e
697 ruleCheck env (Lam b e) = ruleCheck env e
698 ruleCheck env (Case e _ _ as) = ruleCheck env e `unionBags`
699 unionManyBags [ruleCheck env r | (_,_,r) <- as]
701 ruleCheckApp env (App f a) as = ruleCheck env a `unionBags` ruleCheckApp env f (a:as)
702 ruleCheckApp env (Var f) as = ruleCheckFun env f as
703 ruleCheckApp env other as = ruleCheck env other
707 ruleCheckFun :: RuleCheckEnv -> Id -> [CoreExpr] -> Bag SDoc
708 -- Produce a report for all rules matching the predicate
709 -- saying why it doesn't match the specified application
711 ruleCheckFun (phase, pat) fn args
712 | null name_match_rules = emptyBag
713 | otherwise = unitBag (ruleAppCheck_help phase fn args name_match_rules)
715 name_match_rules = filter match (idCoreRules fn)
716 match rule = pat `isPrefixOf` unpackFS (ruleName rule)
718 ruleAppCheck_help :: CompilerPhase -> Id -> [CoreExpr] -> [CoreRule] -> SDoc
719 ruleAppCheck_help phase fn args rules
720 = -- The rules match the pattern, so we want to print something
721 vcat [text "Expression:" <+> ppr (mkApps (Var fn) args),
722 vcat (map check_rule rules)]
725 i_args = args `zip` [1::Int ..]
726 rough_args = map roughTopName args
728 check_rule rule = rule_herald rule <> colon <+> rule_info rule
730 rule_herald (BuiltinRule { ru_name = name })
731 = ptext SLIT("Builtin rule") <+> doubleQuotes (ftext name)
732 rule_herald (Rule { ru_name = name })
733 = ptext SLIT("Rule") <+> doubleQuotes (ftext name)
736 | Just _ <- matchRule noBlackList emptyInScopeSet args rough_args rule
737 = text "matches (which is very peculiar!)"
739 rule_info (BuiltinRule {}) = text "does not match"
741 rule_info (Rule { ru_name = name, ru_act = act,
742 ru_bndrs = rule_bndrs, ru_args = rule_args})
743 | not (isActive phase act) = text "active only in later phase"
744 | n_args < n_rule_args = text "too few arguments"
745 | n_mismatches == n_rule_args = text "no arguments match"
746 | n_mismatches == 0 = text "all arguments match (considered individually), but rule as a whole does not"
747 | otherwise = text "arguments" <+> ppr mismatches <+> text "do not match (1-indexing)"
749 n_rule_args = length rule_args
750 n_mismatches = length mismatches
751 mismatches = [i | (rule_arg, (arg,i)) <- rule_args `zip` i_args,
752 not (isJust (match_fn rule_arg arg))]
754 lhs_fvs = exprsFreeVars rule_args -- Includes template tyvars
755 match_fn rule_arg arg = match menv emptySubstEnv rule_arg arg
757 in_scope = lhs_fvs `unionVarSet` exprFreeVars arg
758 menv = ME { me_env = mkRnEnv2 (mkInScopeSet in_scope)
759 , me_tmpls = mkVarSet rule_bndrs }