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 TcType ( tcSplitTyConApp_maybe )
29 import CoreTidy ( tidyRules )
30 import Id ( Id, idUnfolding, isLocalId, isGlobalId, idName,
31 idSpecialisation, idCoreRules, setIdSpecialisation )
32 import IdInfo ( SpecInfo( SpecInfo ) )
34 import VarEnv ( IdEnv, InScopeSet, emptyTidyEnv,
35 emptyInScopeSet, mkInScopeSet, extendInScopeSetList,
36 emptyVarEnv, lookupVarEnv, extendVarEnv,
37 nukeRnEnvL, mkRnEnv2, rnOccR, rnOccL, inRnEnvR,
38 rnBndrR, rnBndr2, rnBndrL, rnBndrs2,
39 rnInScope, extendRnInScopeList, lookupRnInScope )
41 import Name ( Name, NamedThing(..), nameOccName )
43 import Unify ( ruleMatchTyX, MatchEnv(..) )
44 import BasicTypes ( Activation, CompilerPhase, isActive )
47 import Maybes ( isJust, orElse )
50 import Util ( singleton, mapAccumL )
51 import List ( isPrefixOf )
55 %************************************************************************
57 \subsection[specialisation-IdInfo]{Specialisation info about an @Id@}
59 %************************************************************************
61 A @CoreRule@ holds details of one rule for an @Id@, which
62 includes its specialisations.
64 For example, if a rule for @f@ contains the mapping:
66 forall a b d. [Type (List a), Type b, Var d] ===> f' a b
68 then when we find an application of f to matching types, we simply replace
69 it by the matching RHS:
71 f (List Int) Bool dict ===> f' Int Bool
73 All the stuff about how many dictionaries to discard, and what types
74 to apply the specialised function to, are handled by the fact that the
75 Rule contains a template for the result of the specialisation.
77 There is one more exciting case, which is dealt with in exactly the same
78 way. If the specialised value is unboxed then it is lifted at its
79 definition site and unlifted at its uses. For example:
81 pi :: forall a. Num a => a
83 might have a specialisation
85 [Int#] ===> (case pi' of Lift pi# -> pi#)
87 where pi' :: Lift Int# is the specialised version of pi.
90 mkLocalRule :: RuleName -> Activation
91 -> Name -> [CoreBndr] -> [CoreExpr] -> CoreExpr -> CoreRule
92 -- Used to make CoreRule for an Id defined in this module
93 mkLocalRule name act fn bndrs args rhs
94 = Rule { ru_name = name, ru_fn = fn, ru_act = act,
95 ru_bndrs = bndrs, ru_args = args,
96 ru_rhs = rhs, ru_rough = roughTopNames args,
97 ru_orph = Just (nameOccName fn), ru_local = True }
100 roughTopNames :: [CoreExpr] -> [Maybe Name]
101 roughTopNames args = map roughTopName args
103 roughTopName :: CoreExpr -> Maybe Name
104 -- Find the "top" free name of an expression
105 -- a) the function in an App chain (if a GlobalId)
106 -- b) the TyCon in a type
107 -- This is used for the fast-match-check for rules;
108 -- if the top names don't match, the rest can't
109 roughTopName (Type ty) = case tcSplitTyConApp_maybe ty of
110 Just (tc,_) -> Just (getName tc)
112 roughTopName (App f a) = roughTopName f
113 roughTopName (Var f) | isGlobalId f = Just (idName f)
114 | otherwise = Nothing
115 roughTopName other = Nothing
117 ruleCantMatch :: [Maybe Name] -> [Maybe Name] -> Bool
118 -- (ruleCantMatch tpl actual) returns True only if 'actual'
119 -- definitely can't match 'tpl' by instantiating 'tpl'.
120 -- It's only a one-way match; unlike instance matching we
121 -- don't consider unification
123 -- Notice that there is no case
124 -- ruleCantMatch (Just n1 : ts) (Nothing : as) = True
125 -- Reason: a local variable 'v' in the actuals might
126 -- have an unfolding which is a global.
127 -- This quite often happens with case scrutinees.
128 ruleCantMatch (Just n1 : ts) (Just n2 : as) = n1 /= n2 || ruleCantMatch ts as
129 ruleCantMatch (t : ts) (a : as) = ruleCantMatch ts as
130 ruleCantMatch ts as = False
134 %************************************************************************
136 SpecInfo: the rules in an IdInfo
138 %************************************************************************
141 mkSpecInfo :: [CoreRule] -> SpecInfo
142 mkSpecInfo rules = SpecInfo rules (rulesRhsFreeVars rules)
144 extendSpecInfo :: SpecInfo -> [CoreRule] -> SpecInfo
145 extendSpecInfo (SpecInfo rs1 fvs1) rs2
146 = SpecInfo (rs2 ++ rs1) (rulesRhsFreeVars rs2 `unionVarSet` fvs1)
148 addSpecInfo :: SpecInfo -> SpecInfo -> SpecInfo
149 addSpecInfo (SpecInfo rs1 fvs1) (SpecInfo rs2 fvs2)
150 = SpecInfo (rs1 ++ rs2) (fvs1 `unionVarSet` fvs2)
152 addIdSpecialisations :: Id -> [CoreRule] -> Id
153 addIdSpecialisations id rules
154 = setIdSpecialisation id $
155 extendSpecInfo (idSpecialisation id) rules
157 rulesOfBinds :: [CoreBind] -> [CoreRule]
158 rulesOfBinds binds = concatMap (concatMap idCoreRules . bindersOf) binds
162 %************************************************************************
166 %************************************************************************
169 type RuleBase = NameEnv [CoreRule]
170 -- Maps (the name of) an Id to its rules
171 -- The rules are are unordered;
172 -- we sort out any overlaps on lookup
174 emptyRuleBase = emptyNameEnv
176 mkRuleBase :: [CoreRule] -> RuleBase
177 mkRuleBase rules = extendRuleBaseList emptyRuleBase rules
179 extendRuleBaseList :: RuleBase -> [CoreRule] -> RuleBase
180 extendRuleBaseList rule_base new_guys
181 = foldl extendRuleBase rule_base new_guys
183 unionRuleBase :: RuleBase -> RuleBase -> RuleBase
184 unionRuleBase rb1 rb2 = plusNameEnv_C (++) rb1 rb2
186 extendRuleBase :: RuleBase -> CoreRule -> RuleBase
187 extendRuleBase rule_base rule
188 = extendNameEnv_Acc (:) singleton rule_base (ruleIdName rule) rule
190 pprRuleBase :: RuleBase -> SDoc
191 pprRuleBase rules = vcat [ pprRules (tidyRules emptyTidyEnv rs)
192 | rs <- nameEnvElts rules ]
196 %************************************************************************
198 \subsection{Matching}
200 %************************************************************************
203 lookupRule :: (Activation -> Bool) -> InScopeSet
204 -> RuleBase -- Imported rules
205 -> Id -> [CoreExpr] -> Maybe (RuleName, CoreExpr)
206 lookupRule is_active in_scope rule_base fn args
207 = matchRules is_active in_scope fn args rules
209 -- The rules for an Id come from two places:
210 -- (a) the ones it is born with (idCoreRules fn)
211 -- (b) rules added in subsequent modules (extra_rules)
212 -- PrimOps, for example, are born with a bunch of rules under (a)
213 rules = extra_rules ++ idCoreRules fn
214 extra_rules | isLocalId fn = []
215 | otherwise = lookupNameEnv rule_base (idName fn) `orElse` []
217 matchRules :: (Activation -> Bool) -> InScopeSet
219 -> [CoreRule] -> Maybe (RuleName, CoreExpr)
220 -- See comments on matchRule
221 matchRules is_active in_scope fn args rules
222 = case go [] rules of
224 (m:ms) -> Just (case findBest (fn,args) m ms of
225 (rule, ans) -> (ru_name rule, ans))
227 rough_args = map roughTopName args
229 go :: [(CoreRule,CoreExpr)] -> [CoreRule] -> [(CoreRule,CoreExpr)]
231 go ms (r:rs) = case (matchRule is_active in_scope args rough_args r) of
232 Just e -> go ((r,e):ms) rs
235 findBest :: (Id, [CoreExpr])
236 -> (CoreRule,CoreExpr) -> [(CoreRule,CoreExpr)] -> (CoreRule,CoreExpr)
237 -- All these pairs matched the expression
238 -- Return the pair the the most specific rule
239 -- The (fn,args) is just for overlap reporting
241 findBest target (rule,ans) [] = (rule,ans)
242 findBest target (rule1,ans1) ((rule2,ans2):prs)
243 | rule1 `isMoreSpecific` rule2 = findBest target (rule1,ans1) prs
244 | rule2 `isMoreSpecific` rule1 = findBest target (rule2,ans2) prs
246 | otherwise = pprTrace "Rules.findBest: rule overlap (Rule 1 wins)"
247 (vcat [ptext SLIT("Expression to match:") <+> ppr fn <+> sep (map ppr args),
248 ptext SLIT("Rule 1:") <+> ppr rule1,
249 ptext SLIT("Rule 2:") <+> ppr rule2]) $
250 findBest target (rule1,ans1) prs
252 | otherwise = findBest target (rule1,ans1) prs
257 isMoreSpecific :: CoreRule -> CoreRule -> Bool
258 isMoreSpecific (BuiltinRule {}) r2 = True
259 isMoreSpecific r1 (BuiltinRule {}) = False
260 isMoreSpecific (Rule { ru_bndrs = bndrs1, ru_args = args1 })
261 (Rule { ru_bndrs = bndrs2, ru_args = args2 })
262 = isJust (matchN in_scope bndrs2 args2 args1)
264 in_scope = mkInScopeSet (mkVarSet bndrs1)
265 -- Actually we should probably include the free vars
266 -- of rule1's args, but I can't be bothered
268 noBlackList :: Activation -> Bool
269 noBlackList act = False -- Nothing is black listed
271 matchRule :: (Activation -> Bool) -> InScopeSet
272 -> [CoreExpr] -> [Maybe Name]
273 -> CoreRule -> Maybe CoreExpr
275 -- If (matchRule rule args) returns Just (name,rhs)
276 -- then (f args) matches the rule, and the corresponding
277 -- rewritten RHS is rhs
279 -- The bndrs and rhs is occurrence-analysed
284 -- forall f g x. map f (map g x) ==> map (f . g) x
286 -- CoreRule "map/map"
287 -- [f,g,x] -- tpl_vars
288 -- [f,map g x] -- tpl_args
289 -- map (f.g) x) -- rhs
291 -- Then the call: matchRule the_rule [e1,map e2 e3]
292 -- = Just ("map/map", (\f,g,x -> rhs) e1 e2 e3)
294 -- Any 'surplus' arguments in the input are simply put on the end
297 matchRule is_active in_scope args rough_args
298 (BuiltinRule { ru_name = name, ru_try = match_fn })
299 = case match_fn args of
300 Just expr -> Just expr
303 matchRule is_active in_scope args rough_args
304 (Rule { ru_name = rn, ru_act = act, ru_rough = tpl_tops,
305 ru_bndrs = tpl_vars, ru_args = tpl_args,
307 | not (is_active act) = Nothing
308 | ruleCantMatch tpl_tops rough_args = Nothing
310 = case matchN in_scope tpl_vars tpl_args args of
312 Just (binds, tpl_vals, leftovers) -> Just (mkLets binds $
317 rule_fn = occurAnalyseExpr (mkLams tpl_vars rhs)
318 -- We could do this when putting things into the rulebase, I guess
323 -> [Var] -- Template tyvars
324 -> [CoreExpr] -- Template
325 -> [CoreExpr] -- Target; can have more elts than template
326 -> Maybe ([CoreBind], -- Bindings to wrap around the entire result
327 [CoreExpr], -- What is substituted for each template var
328 [CoreExpr]) -- Leftover target exprs
330 matchN in_scope tmpl_vars tmpl_es target_es
331 = do { ((tv_subst, id_subst, binds), leftover_es)
332 <- go init_menv emptySubstEnv tmpl_es target_es
333 ; return (fromOL binds,
334 map (lookup_tmpl tv_subst id_subst) tmpl_vars,
337 init_menv = ME { me_tmpls = mkVarSet tmpl_vars, me_env = init_rn_env }
338 init_rn_env = mkRnEnv2 (extendInScopeSetList in_scope tmpl_vars)
340 go menv subst [] es = Just (subst, es)
341 go menv subst ts [] = Nothing -- Fail if too few actual args
342 go menv subst (t:ts) (e:es) = do { subst1 <- match menv subst t e
343 ; go menv subst1 ts es }
345 lookup_tmpl :: TvSubstEnv -> IdSubstEnv -> Var -> CoreExpr
346 lookup_tmpl tv_subst id_subst tmpl_var
347 | isTyVar tmpl_var = case lookupVarEnv tv_subst tmpl_var of
349 Nothing -> unbound tmpl_var
350 | otherwise = case lookupVarEnv id_subst tmpl_var of
352 other -> unbound tmpl_var
354 unbound var = pprPanic "Template variable unbound in rewrite rule" (ppr var)
358 ---------------------------------------------
359 The inner workings of matching
360 ---------------------------------------------
363 -- These two definitions are not the same as in Subst,
364 -- but they simple and direct, and purely local to this module
366 -- * The domain of the TvSubstEnv and IdSubstEnv are the template
367 -- variables passed into the match.
369 -- * The (OrdList CoreBind) in a SubstEnv are the bindings floated out
370 -- from nested matches; see the Let case of match, below
372 type SubstEnv = (TvSubstEnv, IdSubstEnv, OrdList CoreBind)
373 type IdSubstEnv = IdEnv CoreExpr
375 emptySubstEnv :: SubstEnv
376 emptySubstEnv = (emptyVarEnv, emptyVarEnv, nilOL)
379 -- At one stage I tried to match even if there are more
380 -- template args than real args.
382 -- I now think this is probably a bad idea.
383 -- Should the template (map f xs) match (map g)? I think not.
384 -- For a start, in general eta expansion wastes work.
390 -> CoreExpr -- Template
391 -> CoreExpr -- Target
394 -- See the notes with Unify.match, which matches types
395 -- Everything is very similar for terms
397 -- Interesting examples:
399 -- \x->f against \f->f
400 -- When we meet the lambdas we must remember to rename f to f' in the
401 -- second expresion. The RnEnv2 does that.
404 -- forall a. \b->b against \a->3
405 -- We must rename the \a. Otherwise when we meet the lambdas we
406 -- might substitute [a/b] in the template, and then erroneously
407 -- succeed in matching what looks like the template variable 'a' against 3.
409 -- The Var case follows closely what happens in Unify.match
410 match menv subst (Var v1) e2
411 | Just subst <- match_var menv subst v1 e2
414 -- Here is another important rule: if the term being matched is a
415 -- variable, we expand it so long as its unfolding is a WHNF
416 -- (Its occurrence information is not necessarily up to date,
417 -- so we don't use it.)
418 match menv subst e1 (Var v2)
419 | not (inRnEnvR rn_env v2),
420 -- If v2 is in the RnEnvR, then it's locally bound and can't
421 -- have an unfolding. We must make this check because if it
422 -- is locally bound we must not look it up in the in-scope set
423 -- E.g. (\x->x) where x is already in scope
424 isCheapUnfolding unfolding
425 = match menv subst e1 (unfoldingTemplate unfolding)
428 unfolding = idUnfolding (lookupRnInScope rn_env v2)
429 -- Notice that we look up v2 in the in-scope set
430 -- See Note [Lookup in-scope]
432 match menv subst (Lit lit1) (Lit lit2)
436 match menv subst (App f1 a1) (App f2 a2)
437 = do { subst' <- match menv subst f1 f2
438 ; match menv subst' a1 a2 }
440 match menv subst (Lam x1 e1) (Lam x2 e2)
441 = match menv' subst e1 e2
443 menv' = menv { me_env = rnBndr2 (me_env menv) x1 x2 }
445 -- This rule does eta expansion
446 -- (\x.M) ~ N iff M ~ N x
447 match menv subst (Lam x1 e1) e2
448 = match menv' subst e1 (App e2 (varToCoreExpr new_x))
450 (rn_env', new_x) = rnBndrL (me_env menv) x1
451 menv' = menv { me_env = rn_env' }
453 -- Eta expansion the other way
454 -- M ~ (\y.N) iff M y ~ N
455 match menv subst e1 (Lam x2 e2)
456 = match menv' subst (App e1 (varToCoreExpr new_x)) e2
458 (rn_env', new_x) = rnBndrR (me_env menv) x2
459 menv' = menv { me_env = rn_env' }
461 match menv subst (Case e1 x1 ty1 alts1) (Case e2 x2 ty2 alts2)
462 = do { subst1 <- match_ty menv subst ty1 ty2
463 ; subst2 <- match menv subst1 e1 e2
464 ; let menv' = menv { me_env = rnBndr2 (me_env menv) x1 x2 }
465 ; match_alts menv' subst2 alts1 alts2 -- Alts are both sorted
468 match menv subst (Type ty1) (Type ty2)
469 = match_ty menv subst ty1 ty2
471 match menv subst (Note (Coerce to1 from1) e1) (Note (Coerce to2 from2) e2)
472 = do { subst1 <- match_ty menv subst to1 to2
473 ; subst2 <- match_ty menv subst1 from1 from2
474 ; match menv subst2 e1 e2 }
476 -- Matching a let-expression. Consider
477 -- RULE forall x. f (g x) = <rhs>
478 -- and target expression
479 -- f (let { w=R } in g E))
480 -- Then we'd like the rule to match, to generate
481 -- let { w=R } in (\x. <rhs>) E
482 -- In effect, we want to float the let-binding outward, to enable
483 -- the match to happen. This is the WHOLE REASON for accumulating
484 -- bindings in the SubstEnv
486 -- We can only do this if
487 -- (a) Widening the scope of w does not capture any variables
488 -- We use a conservative test: w is not already in scope
489 -- (b) The free variables of R are not bound by the part of the
490 -- target expression outside the let binding; e.g.
491 -- f (\v. let w = v+1 in g E)
492 -- Here we obviously cannot float the let-binding for w.
494 match menv subst@(tv_subst, id_subst, binds) e1 (Let bind e2)
495 | all freshly_bound bndrs,
496 not (any locally_bound bind_fvs)
497 = match (menv { me_env = rn_env' })
498 (tv_subst, id_subst, binds `snocOL` bind)
502 bndrs = bindersOf bind
503 bind_fvs = varSetElems (bindFreeVars bind)
504 freshly_bound x = not (x `rnInScope` rn_env)
505 locally_bound x = inRnEnvR rn_env x
506 rn_env' = extendRnInScopeList rn_env bndrs
508 -- This is an interesting rule: we simply ignore lets in the
509 -- term being matched against! The unfolding inside it is (by assumption)
510 -- already inside any occurrences of the bound variables, so we'll expand
511 -- them when we encounter them. This gives a chance of matching
512 -- forall x,y. f (g (x,y))
514 -- f (let v = (a,b) in g v)
516 match menv subst e1 (Let bind e2)
517 = match (menv { me_env = rn_env' }) subst e1 e2
519 (rn_env', _bndrs') = mapAccumL rnBndrR (me_env menv) (bindersOf bind)
520 -- It's important to do this renaming, so that the bndrs
521 -- are brought into the local scope. For example:
523 -- forall f,x,xs. f (x:xs)
525 -- f (let y = e in (y:[]))
526 -- We must not get success with x->y! So we record that y is
527 -- locally bound (with rnBndrR), and proceed. The Var case
528 -- will fail when trying to bind x->y
531 -- Everything else fails
532 match menv subst e1 e2 = Nothing
534 ------------------------------------------
535 match_var :: MatchEnv
538 -> CoreExpr -- Target
540 match_var menv subst@(tv_subst, id_subst, binds) v1 e2
541 | v1' `elemVarSet` me_tmpls menv
542 = case lookupVarEnv id_subst v1' of
543 Nothing | any (inRnEnvR rn_env) (varSetElems (exprFreeVars e2))
544 -> Nothing -- Occurs check failure
545 -- e.g. match forall a. (\x-> a x) against (\y. y y)
547 | otherwise -- No renaming to do on e2
548 -> Just (tv_subst, extendVarEnv id_subst v1 e2, binds)
550 Just e2' | tcEqExprX (nukeRnEnvL rn_env) e2' e2
556 | otherwise -- v1 is not a template variable; check for an exact match with e2
558 Var v2 | v1' == rnOccR rn_env v2 -> Just subst
563 v1' = rnOccL rn_env v1
564 -- If the template is
565 -- forall x. f x (\x -> x) = ...
566 -- Then the x inside the lambda isn't the
567 -- template x, so we must rename first!
570 ------------------------------------------
571 match_alts :: MatchEnv
573 -> [CoreAlt] -- Template
574 -> [CoreAlt] -- Target
576 match_alts menv subst [] []
578 match_alts menv subst ((c1,vs1,r1):alts1) ((c2,vs2,r2):alts2)
580 = do { subst1 <- match menv' subst r1 r2
581 ; match_alts menv subst1 alts1 alts2 }
584 menv' = menv { me_env = rnBndrs2 (me_env menv) vs1 vs2 }
586 match_alts menv subst alts1 alts2
590 Matching Core types: use the matcher in TcType.
591 Notice that we treat newtypes as opaque. For example, suppose
592 we have a specialised version of a function at a newtype, say
594 We only want to replace (f T) with f', not (f Int).
597 ------------------------------------------
598 match_ty menv (tv_subst, id_subst, binds) ty1 ty2
599 = do { tv_subst' <- Unify.ruleMatchTyX menv tv_subst ty1 ty2
600 ; return (tv_subst', id_subst, binds) }
604 Note [Lookup in-scope]
605 ~~~~~~~~~~~~~~~~~~~~~~
606 Consider this example
607 foo :: Int -> Maybe Int -> Int
609 foo m (Just n) = foo (m-n) (Just n)
611 SpecConstr sees this fragment:
613 case w_smT of wild_Xf [Just A] {
614 Data.Maybe.Nothing -> lvl_smf;
615 Data.Maybe.Just n_acT [Just S(L)] ->
616 case n_acT of wild1_ams [Just A] { GHC.Base.I# y_amr [Just L] ->
617 $wfoo_smW (GHC.Prim.-# ds_Xmb y_amr) wild_Xf
620 and correctly generates the rule
622 RULES: "SC:$wfoo1" [0] __forall {y_amr [Just L] :: GHC.Prim.Int#
623 sc_snn :: GHC.Prim.Int#}
624 $wfoo_smW sc_snn (Data.Maybe.Just @ GHC.Base.Int (GHC.Base.I# y_amr))
625 = $s$wfoo_sno y_amr sc_snn ;]
627 BUT we must ensure that this rule matches in the original function!
628 Note that the call to $wfoo is
629 $wfoo_smW (GHC.Prim.-# ds_Xmb y_amr) wild_Xf
631 During matching we expand wild_Xf to (Just n_acT). But then we must also
632 expand n_acT to (I# y_amr). And we can only do that if we look up n_acT
633 in the in-scope set, because in wild_Xf's unfolding it won't have an unfolding
636 That is why the 'lookupRnInScope' call in the (Var v2) case of 'match'
640 %************************************************************************
642 \subsection{Checking a program for failing rule applications}
644 %************************************************************************
646 -----------------------------------------------------
648 -----------------------------------------------------
650 We want to know what sites have rules that could have fired but didn't.
651 This pass runs over the tree (without changing it) and reports such.
653 NB: we assume that this follows a run of the simplifier, so every Id
654 occurrence (including occurrences of imported Ids) is decorated with
655 all its (active) rules. No need to construct a rule base or anything
659 ruleCheckProgram :: CompilerPhase -> String -> [CoreBind] -> SDoc
660 -- Report partial matches for rules beginning
661 -- with the specified string
662 ruleCheckProgram phase rule_pat binds
664 = text "Rule check results: no rule application sites"
666 = vcat [text "Rule check results:",
668 vcat [ p $$ line | p <- bagToList results ]
671 results = unionManyBags (map (ruleCheckBind (phase, rule_pat)) binds)
672 line = text (replicate 20 '-')
674 type RuleCheckEnv = (CompilerPhase, String) -- Phase and Pattern
676 ruleCheckBind :: RuleCheckEnv -> CoreBind -> Bag SDoc
677 -- The Bag returned has one SDoc for each call site found
678 ruleCheckBind env (NonRec b r) = ruleCheck env r
679 ruleCheckBind env (Rec prs) = unionManyBags [ruleCheck env r | (b,r) <- prs]
681 ruleCheck :: RuleCheckEnv -> CoreExpr -> Bag SDoc
682 ruleCheck env (Var v) = emptyBag
683 ruleCheck env (Lit l) = emptyBag
684 ruleCheck env (Type ty) = emptyBag
685 ruleCheck env (App f a) = ruleCheckApp env (App f a) []
686 ruleCheck env (Note n e) = ruleCheck env e
687 ruleCheck env (Let bd e) = ruleCheckBind env bd `unionBags` ruleCheck env e
688 ruleCheck env (Lam b e) = ruleCheck env e
689 ruleCheck env (Case e _ _ as) = ruleCheck env e `unionBags`
690 unionManyBags [ruleCheck env r | (_,_,r) <- as]
692 ruleCheckApp env (App f a) as = ruleCheck env a `unionBags` ruleCheckApp env f (a:as)
693 ruleCheckApp env (Var f) as = ruleCheckFun env f as
694 ruleCheckApp env other as = ruleCheck env other
698 ruleCheckFun :: RuleCheckEnv -> Id -> [CoreExpr] -> Bag SDoc
699 -- Produce a report for all rules matching the predicate
700 -- saying why it doesn't match the specified application
702 ruleCheckFun (phase, pat) fn args
703 | null name_match_rules = emptyBag
704 | otherwise = unitBag (ruleAppCheck_help phase fn args name_match_rules)
706 name_match_rules = filter match (idCoreRules fn)
707 match rule = pat `isPrefixOf` unpackFS (ruleName rule)
709 ruleAppCheck_help :: CompilerPhase -> Id -> [CoreExpr] -> [CoreRule] -> SDoc
710 ruleAppCheck_help phase fn args rules
711 = -- The rules match the pattern, so we want to print something
712 vcat [text "Expression:" <+> ppr (mkApps (Var fn) args),
713 vcat (map check_rule rules)]
716 i_args = args `zip` [1::Int ..]
717 rough_args = map roughTopName args
719 check_rule rule = rule_herald rule <> colon <+> rule_info rule
721 rule_herald (BuiltinRule { ru_name = name })
722 = ptext SLIT("Builtin rule") <+> doubleQuotes (ftext name)
723 rule_herald (Rule { ru_name = name })
724 = ptext SLIT("Rule") <+> doubleQuotes (ftext name)
727 | Just _ <- matchRule noBlackList emptyInScopeSet args rough_args rule
728 = text "matches (which is very peculiar!)"
730 rule_info (BuiltinRule {}) = text "does not match"
732 rule_info (Rule { ru_name = name, ru_act = act,
733 ru_bndrs = rule_bndrs, ru_args = rule_args})
734 | not (isActive phase act) = text "active only in later phase"
735 | n_args < n_rule_args = text "too few arguments"
736 | n_mismatches == n_rule_args = text "no arguments match"
737 | n_mismatches == 0 = text "all arguments match (considered individually), but rule as a whole does not"
738 | otherwise = text "arguments" <+> ppr mismatches <+> text "do not match (1-indexing)"
740 n_rule_args = length rule_args
741 n_mismatches = length mismatches
742 mismatches = [i | (rule_arg, (arg,i)) <- rule_args `zip` i_args,
743 not (isJust (match_fn rule_arg arg))]
745 lhs_fvs = exprsFreeVars rule_args -- Includes template tyvars
746 match_fn rule_arg arg = match menv emptySubstEnv rule_arg arg
748 in_scope = lhs_fvs `unionVarSet` exprFreeVars arg
749 menv = ME { me_env = mkRnEnv2 (mkInScopeSet in_scope)
750 , me_tmpls = mkVarSet rule_bndrs }