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,
14 lookupRule, mkLocalRule, roughTopNames
17 #include "HsVersions.h"
19 import CoreSyn -- All of it
20 import OccurAnal ( occurAnalyseExpr )
21 import CoreFVs ( exprFreeVars, exprsFreeVars, bindFreeVars, rulesRhsFreeVars )
22 import CoreUnfold ( isCheapUnfolding, unfoldingTemplate )
23 import CoreUtils ( tcEqExprX )
24 import PprCore ( pprRules )
25 import Type ( TvSubstEnv )
26 import TcType ( tcSplitTyConApp_maybe )
27 import CoreTidy ( tidyRules )
28 import Id ( Id, idUnfolding, isLocalId, isGlobalId, idName,
29 idSpecialisation, idCoreRules, setIdSpecialisation )
30 import IdInfo ( SpecInfo( SpecInfo ) )
32 import VarEnv ( IdEnv, InScopeSet, emptyTidyEnv,
33 emptyInScopeSet, mkInScopeSet, extendInScopeSetList,
34 emptyVarEnv, lookupVarEnv, extendVarEnv,
35 nukeRnEnvL, mkRnEnv2, rnOccR, rnOccL, inRnEnvR,
36 rnBndrR, rnBndr2, rnBndrL, rnBndrs2,
37 rnInScope, extendRnInScopeList, lookupRnInScope )
39 import Name ( Name, NamedThing(..), nameOccName )
41 import Unify ( ruleMatchTyX, MatchEnv(..) )
42 import BasicTypes ( Activation, CompilerPhase, isActive )
45 import Maybes ( isJust, orElse )
48 import Util ( singleton, mapAccumL )
49 import List ( isPrefixOf )
53 %************************************************************************
55 \subsection[specialisation-IdInfo]{Specialisation info about an @Id@}
57 %************************************************************************
59 A @CoreRule@ holds details of one rule for an @Id@, which
60 includes its specialisations.
62 For example, if a rule for @f@ contains the mapping:
64 forall a b d. [Type (List a), Type b, Var d] ===> f' a b
66 then when we find an application of f to matching types, we simply replace
67 it by the matching RHS:
69 f (List Int) Bool dict ===> f' Int Bool
71 All the stuff about how many dictionaries to discard, and what types
72 to apply the specialised function to, are handled by the fact that the
73 Rule contains a template for the result of the specialisation.
75 There is one more exciting case, which is dealt with in exactly the same
76 way. If the specialised value is unboxed then it is lifted at its
77 definition site and unlifted at its uses. For example:
79 pi :: forall a. Num a => a
81 might have a specialisation
83 [Int#] ===> (case pi' of Lift pi# -> pi#)
85 where pi' :: Lift Int# is the specialised version of pi.
88 mkLocalRule :: RuleName -> Activation
89 -> Name -> [CoreBndr] -> [CoreExpr] -> CoreExpr -> CoreRule
90 -- Used to make CoreRule for an Id defined in this module
91 mkLocalRule name act fn bndrs args rhs
92 = Rule { ru_name = name, ru_fn = fn, ru_act = act,
93 ru_bndrs = bndrs, ru_args = args,
94 ru_rhs = rhs, ru_rough = roughTopNames args,
95 ru_orph = Just (nameOccName fn), ru_local = True }
98 roughTopNames :: [CoreExpr] -> [Maybe Name]
99 roughTopNames args = map roughTopName args
101 roughTopName :: CoreExpr -> Maybe Name
102 -- Find the "top" free name of an expression
103 -- a) the function in an App chain (if a GlobalId)
104 -- b) the TyCon in a type
105 -- This is used for the fast-match-check for rules;
106 -- if the top names don't match, the rest can't
107 roughTopName (Type ty) = case tcSplitTyConApp_maybe ty of
108 Just (tc,_) -> Just (getName tc)
110 roughTopName (App f a) = roughTopName f
111 roughTopName (Var f) | isGlobalId f = Just (idName f)
112 | otherwise = Nothing
113 roughTopName other = Nothing
115 ruleCantMatch :: [Maybe Name] -> [Maybe Name] -> Bool
116 -- (ruleCantMatch tpl actual) returns True only if 'actual'
117 -- definitely can't match 'tpl' by instantiating 'tpl'.
118 -- It's only a one-way match; unlike instance matching we
119 -- don't consider unification
121 -- Notice that there is no case
122 -- ruleCantMatch (Just n1 : ts) (Nothing : as) = True
123 -- Reason: a local variable 'v' in the actuals might
124 -- have an unfolding which is a global.
125 -- This quite often happens with case scrutinees.
126 ruleCantMatch (Just n1 : ts) (Just n2 : as) = n1 /= n2 || ruleCantMatch ts as
127 ruleCantMatch (t : ts) (a : as) = ruleCantMatch ts as
128 ruleCantMatch ts as = False
132 %************************************************************************
134 SpecInfo: the rules in an IdInfo
136 %************************************************************************
139 mkSpecInfo :: [CoreRule] -> SpecInfo
140 mkSpecInfo rules = SpecInfo rules (rulesRhsFreeVars rules)
142 extendSpecInfo :: SpecInfo -> [CoreRule] -> SpecInfo
143 extendSpecInfo (SpecInfo rs1 fvs1) rs2
144 = SpecInfo (rs2 ++ rs1) (rulesRhsFreeVars rs2 `unionVarSet` fvs1)
146 addSpecInfo :: SpecInfo -> SpecInfo -> SpecInfo
147 addSpecInfo (SpecInfo rs1 fvs1) (SpecInfo rs2 fvs2)
148 = SpecInfo (rs1 ++ rs2) (fvs1 `unionVarSet` fvs2)
150 addIdSpecialisations :: Id -> [CoreRule] -> Id
151 addIdSpecialisations id rules
152 = setIdSpecialisation id $
153 extendSpecInfo (idSpecialisation id) rules
155 rulesOfBinds :: [CoreBind] -> [CoreRule]
156 rulesOfBinds binds = concatMap (concatMap idCoreRules . bindersOf) binds
160 %************************************************************************
164 %************************************************************************
167 type RuleBase = NameEnv [CoreRule]
168 -- Maps (the name of) an Id to its rules
169 -- The rules are are unordered;
170 -- we sort out any overlaps on lookup
172 emptyRuleBase = emptyNameEnv
174 mkRuleBase :: [CoreRule] -> RuleBase
175 mkRuleBase rules = extendRuleBaseList emptyRuleBase rules
177 extendRuleBaseList :: RuleBase -> [CoreRule] -> RuleBase
178 extendRuleBaseList rule_base new_guys
179 = foldl extendRuleBase rule_base new_guys
181 unionRuleBase :: RuleBase -> RuleBase -> RuleBase
182 unionRuleBase rb1 rb2 = plusNameEnv_C (++) rb1 rb2
184 extendRuleBase :: RuleBase -> CoreRule -> RuleBase
185 extendRuleBase rule_base rule
186 = extendNameEnv_Acc (:) singleton rule_base (ruleIdName rule) rule
188 pprRuleBase :: RuleBase -> SDoc
189 pprRuleBase rules = vcat [ pprRules (tidyRules emptyTidyEnv rs)
190 | rs <- nameEnvElts rules ]
194 %************************************************************************
196 \subsection{Matching}
198 %************************************************************************
201 lookupRule :: (Activation -> Bool) -> InScopeSet
202 -> RuleBase -- Imported rules
203 -> Id -> [CoreExpr] -> Maybe (RuleName, CoreExpr)
204 lookupRule is_active in_scope rule_base fn args
205 = matchRules is_active in_scope fn args rules
207 -- The rules for an Id come from two places:
208 -- (a) the ones it is born with (idCoreRules fn)
209 -- (b) rules added in subsequent modules (extra_rules)
210 -- PrimOps, for example, are born with a bunch of rules under (a)
211 rules = extra_rules ++ idCoreRules fn
212 extra_rules | isLocalId fn = []
213 | otherwise = lookupNameEnv rule_base (idName fn) `orElse` []
215 matchRules :: (Activation -> Bool) -> InScopeSet
217 -> [CoreRule] -> Maybe (RuleName, CoreExpr)
218 -- See comments on matchRule
219 matchRules is_active in_scope fn args rules
220 = case go [] rules of
222 (m:ms) -> Just (case findBest (fn,args) m ms of
223 (rule, ans) -> (ru_name rule, ans))
225 rough_args = map roughTopName args
227 go :: [(CoreRule,CoreExpr)] -> [CoreRule] -> [(CoreRule,CoreExpr)]
229 go ms (r:rs) = case (matchRule is_active in_scope args rough_args r) of
230 Just e -> go ((r,e):ms) rs
233 findBest :: (Id, [CoreExpr])
234 -> (CoreRule,CoreExpr) -> [(CoreRule,CoreExpr)] -> (CoreRule,CoreExpr)
235 -- All these pairs matched the expression
236 -- Return the pair the the most specific rule
237 -- The (fn,args) is just for overlap reporting
239 findBest target (rule,ans) [] = (rule,ans)
240 findBest target (rule1,ans1) ((rule2,ans2):prs)
241 | rule1 `isMoreSpecific` rule2 = findBest target (rule1,ans1) prs
242 | rule2 `isMoreSpecific` rule1 = findBest target (rule1,ans1) prs
244 | otherwise = pprTrace "Rules.findBest: rule overlap (Rule 1 wins)"
245 (vcat [ptext SLIT("Expression to match:") <+> ppr fn <+> sep (map ppr args),
246 ptext SLIT("Rule 1:") <+> ppr rule1,
247 ptext SLIT("Rule 2:") <+> ppr rule2]) $
248 findBest target (rule1,ans1) prs
250 | otherwise = findBest target (rule1,ans1) prs
255 isMoreSpecific :: CoreRule -> CoreRule -> Bool
256 isMoreSpecific (BuiltinRule {}) r2 = True
257 isMoreSpecific r1 (BuiltinRule {}) = False
258 isMoreSpecific (Rule { ru_bndrs = bndrs1, ru_args = args1 })
259 (Rule { ru_bndrs = bndrs2, ru_args = args2 })
260 = isJust (matchN in_scope bndrs2 args2 args1)
262 in_scope = mkInScopeSet (mkVarSet bndrs1)
263 -- Actually we should probably include the free vars
264 -- of rule1's args, but I can't be bothered
266 noBlackList :: Activation -> Bool
267 noBlackList act = False -- Nothing is black listed
269 matchRule :: (Activation -> Bool) -> InScopeSet
270 -> [CoreExpr] -> [Maybe Name]
271 -> CoreRule -> Maybe CoreExpr
273 -- If (matchRule rule args) returns Just (name,rhs)
274 -- then (f args) matches the rule, and the corresponding
275 -- rewritten RHS is rhs
277 -- The bndrs and rhs is occurrence-analysed
282 -- forall f g x. map f (map g x) ==> map (f . g) x
284 -- CoreRule "map/map"
285 -- [f,g,x] -- tpl_vars
286 -- [f,map g x] -- tpl_args
287 -- map (f.g) x) -- rhs
289 -- Then the call: matchRule the_rule [e1,map e2 e3]
290 -- = Just ("map/map", (\f,g,x -> rhs) e1 e2 e3)
292 -- Any 'surplus' arguments in the input are simply put on the end
295 matchRule is_active in_scope args rough_args
296 (BuiltinRule { ru_name = name, ru_try = match_fn })
297 = case match_fn args of
298 Just expr -> Just expr
301 matchRule is_active in_scope args rough_args
302 (Rule { ru_name = rn, ru_act = act, ru_rough = tpl_tops,
303 ru_bndrs = tpl_vars, ru_args = tpl_args,
305 | not (is_active act) = Nothing
306 | ruleCantMatch tpl_tops rough_args = Nothing
308 = case matchN in_scope tpl_vars tpl_args args of
310 Just (binds, tpl_vals, leftovers) -> Just (mkLets binds $
315 rule_fn = occurAnalyseExpr (mkLams tpl_vars rhs)
316 -- We could do this when putting things into the rulebase, I guess
321 -> [Var] -- Template tyvars
322 -> [CoreExpr] -- Template
323 -> [CoreExpr] -- Target; can have more elts than template
324 -> Maybe ([CoreBind], -- Bindings to wrap around the entire result
325 [CoreExpr], -- What is substituted for each template var
326 [CoreExpr]) -- Leftover target exprs
328 matchN in_scope tmpl_vars tmpl_es target_es
329 = do { ((tv_subst, id_subst, binds), leftover_es)
330 <- go init_menv emptySubstEnv tmpl_es target_es
331 ; return (fromOL binds,
332 map (lookup_tmpl tv_subst id_subst) tmpl_vars,
335 init_menv = ME { me_tmpls = mkVarSet tmpl_vars, me_env = init_rn_env }
336 init_rn_env = mkRnEnv2 (extendInScopeSetList in_scope tmpl_vars)
338 go menv subst [] es = Just (subst, es)
339 go menv subst ts [] = Nothing -- Fail if too few actual args
340 go menv subst (t:ts) (e:es) = do { subst1 <- match menv subst t e
341 ; go menv subst1 ts es }
343 lookup_tmpl :: TvSubstEnv -> IdSubstEnv -> Var -> CoreExpr
344 lookup_tmpl tv_subst id_subst tmpl_var
345 | isTyVar tmpl_var = case lookupVarEnv tv_subst tmpl_var of
347 Nothing -> unbound tmpl_var
348 | otherwise = case lookupVarEnv id_subst tmpl_var of
350 other -> unbound tmpl_var
352 unbound var = pprPanic "Template variable unbound in rewrite rule" (ppr var)
356 ---------------------------------------------
357 The inner workings of matching
358 ---------------------------------------------
361 -- These two definitions are not the same as in Subst,
362 -- but they simple and direct, and purely local to this module
364 -- * The domain of the TvSubstEnv and IdSubstEnv are the template
365 -- variables passed into the match.
367 -- * The (OrdList CoreBind) in a SubstEnv are the bindings floated out
368 -- from nested matches; see the Let case of match, below
370 type SubstEnv = (TvSubstEnv, IdSubstEnv, OrdList CoreBind)
371 type IdSubstEnv = IdEnv CoreExpr
373 emptySubstEnv :: SubstEnv
374 emptySubstEnv = (emptyVarEnv, emptyVarEnv, nilOL)
377 -- At one stage I tried to match even if there are more
378 -- template args than real args.
380 -- I now think this is probably a bad idea.
381 -- Should the template (map f xs) match (map g)? I think not.
382 -- For a start, in general eta expansion wastes work.
388 -> CoreExpr -- Template
389 -> CoreExpr -- Target
392 -- See the notes with Unify.match, which matches types
393 -- Everything is very similar for terms
395 -- Interesting examples:
397 -- \x->f against \f->f
398 -- When we meet the lambdas we must remember to rename f to f' in the
399 -- second expresion. The RnEnv2 does that.
402 -- forall a. \b->b against \a->3
403 -- We must rename the \a. Otherwise when we meet the lambdas we
404 -- might substitute [a/b] in the template, and then erroneously
405 -- succeed in matching what looks like the template variable 'a' against 3.
407 -- The Var case follows closely what happens in Unify.match
408 match menv subst (Var v1) e2
409 | Just subst <- match_var menv subst v1 e2
412 -- Here is another important rule: if the term being matched is a
413 -- variable, we expand it so long as its unfolding is a WHNF
414 -- (Its occurrence information is not necessarily up to date,
415 -- so we don't use it.)
416 match menv subst e1 (Var v2)
417 | not (inRnEnvR rn_env v2),
418 -- If v2 is in the RnEnvR, then it's locally bound and can't
419 -- have an unfolding. We must make this check because if it
420 -- is locally bound we must not look it up in the in-scope set
421 -- E.g. (\x->x) where x is already in scope
422 isCheapUnfolding unfolding
423 = match menv subst e1 (unfoldingTemplate unfolding)
426 unfolding = idUnfolding (lookupRnInScope rn_env v2)
427 -- Notice that we look up v2 in the in-scope set
428 -- See Note [Lookup in-scope]
430 match menv subst (Lit lit1) (Lit lit2)
434 match menv subst (App f1 a1) (App f2 a2)
435 = do { subst' <- match menv subst f1 f2
436 ; match menv subst' a1 a2 }
438 match menv subst (Lam x1 e1) (Lam x2 e2)
439 = match menv' subst e1 e2
441 menv' = menv { me_env = rnBndr2 (me_env menv) x1 x2 }
443 -- This rule does eta expansion
444 -- (\x.M) ~ N iff M ~ N x
445 match menv subst (Lam x1 e1) e2
446 = match menv' subst e1 (App e2 (varToCoreExpr new_x))
448 (rn_env', new_x) = rnBndrL (me_env menv) x1
449 menv' = menv { me_env = rn_env' }
451 -- Eta expansion the other way
452 -- M ~ (\y.N) iff M y ~ N
453 match menv subst e1 (Lam x2 e2)
454 = match menv' subst (App e1 (varToCoreExpr new_x)) e2
456 (rn_env', new_x) = rnBndrR (me_env menv) x2
457 menv' = menv { me_env = rn_env' }
459 match menv subst (Case e1 x1 ty1 alts1) (Case e2 x2 ty2 alts2)
460 = do { subst1 <- match_ty menv subst ty1 ty2
461 ; subst2 <- match menv subst1 e1 e2
462 ; let menv' = menv { me_env = rnBndr2 (me_env menv) x2 x2 }
463 ; match_alts menv' subst2 alts1 alts2 -- Alts are both sorted
466 match menv subst (Type ty1) (Type ty2)
467 = match_ty menv subst ty1 ty2
469 match menv subst (Note (Coerce to1 from1) e1) (Note (Coerce to2 from2) e2)
470 = do { subst1 <- match_ty menv subst to1 to2
471 ; subst2 <- match_ty menv subst1 from1 from2
472 ; match menv subst2 e1 e2 }
474 -- Matching a let-expression. Consider
475 -- RULE forall x. f (g x) = <rhs>
476 -- and target expression
477 -- f (let { w=R } in g E))
478 -- Then we'd like the rule to match, to generate
479 -- let { w=R } in (\x. <rhs>) E
480 -- In effect, we want to float the let-binding outward, to enable
481 -- the match to happen. This is the WHOLE REASON for accumulating
482 -- bindings in the SubstEnv
484 -- We can only do this if
485 -- (a) Widening the scope of w does not capture any variables
486 -- We use a conservative test: w is not already in scope
487 -- (b) The free variables of R are not bound by the part of the
488 -- target expression outside the let binding; e.g.
489 -- f (\v. let w = v+1 in g E)
490 -- Here we obviously cannot float the let-binding for w.
492 match menv subst@(tv_subst, id_subst, binds) e1 (Let bind e2)
493 | all freshly_bound bndrs,
494 not (any locally_bound bind_fvs)
495 = match (menv { me_env = rn_env' })
496 (tv_subst, id_subst, binds `snocOL` bind)
500 bndrs = bindersOf bind
501 bind_fvs = varSetElems (bindFreeVars bind)
502 freshly_bound x = not (x `rnInScope` rn_env)
503 locally_bound x = inRnEnvR rn_env x
504 rn_env' = extendRnInScopeList rn_env bndrs
506 -- This is an interesting rule: we simply ignore lets in the
507 -- term being matched against! The unfolding inside it is (by assumption)
508 -- already inside any occurrences of the bound variables, so we'll expand
509 -- them when we encounter them. This gives a chance of matching
510 -- forall x,y. f (g (x,y))
512 -- f (let v = (a,b) in g v)
514 match menv subst e1 (Let bind e2)
515 = match (menv { me_env = rn_env' }) subst e1 e2
517 (rn_env', _bndrs') = mapAccumL rnBndrR (me_env menv) (bindersOf bind)
518 -- It's important to do this renaming, so that the bndrs
519 -- are brought into the local scope. For example:
521 -- forall f,x,xs. f (x:xs)
523 -- f (let y = e in (y:[]))
524 -- We must not get success with x->y! So we record that y is
525 -- locally bound (with rnBndrR), and proceed. The Var case
526 -- will fail when trying to bind x->y
529 -- Everything else fails
530 match menv subst e1 e2 = Nothing
532 ------------------------------------------
533 match_var :: MatchEnv
536 -> CoreExpr -- Target
538 match_var menv subst@(tv_subst, id_subst, binds) v1 e2
539 | v1' `elemVarSet` me_tmpls menv
540 = case lookupVarEnv id_subst v1' of
541 Nothing | any (inRnEnvR rn_env) (varSetElems (exprFreeVars e2))
542 -> Nothing -- Occurs check failure
543 -- e.g. match forall a. (\x-> a x) against (\y. y y)
545 | otherwise -- No renaming to do on e2
546 -> Just (tv_subst, extendVarEnv id_subst v1 e2, binds)
548 Just e2' | tcEqExprX (nukeRnEnvL rn_env) e2' e2
554 | otherwise -- v1 is not a template variable; check for an exact match with e2
556 Var v2 | v1' == rnOccR rn_env v2 -> Just subst
561 v1' = rnOccL rn_env v1
562 -- If the template is
563 -- forall x. f x (\x -> x) = ...
564 -- Then the x inside the lambda isn't the
565 -- template x, so we must rename first!
568 ------------------------------------------
569 match_alts :: MatchEnv
571 -> [CoreAlt] -- Template
572 -> [CoreAlt] -- Target
574 match_alts menv subst [] []
576 match_alts menv subst ((c1,vs1,r1):alts1) ((c2,vs2,r2):alts2)
578 = do { subst1 <- match menv' subst r1 r2
579 ; match_alts menv subst1 alts1 alts2 }
582 menv' = menv { me_env = rnBndrs2 (me_env menv) vs1 vs2 }
584 match_alts menv subst alts1 alts2
588 Matching Core types: use the matcher in TcType.
589 Notice that we treat newtypes as opaque. For example, suppose
590 we have a specialised version of a function at a newtype, say
592 We only want to replace (f T) with f', not (f Int).
595 ------------------------------------------
596 match_ty menv (tv_subst, id_subst, binds) ty1 ty2
597 = do { tv_subst' <- Unify.ruleMatchTyX menv tv_subst ty1 ty2
598 ; return (tv_subst', id_subst, binds) }
602 Note [Lookup in-scope]
603 ~~~~~~~~~~~~~~~~~~~~~~
604 Consider this example
605 foo :: Int -> Maybe Int -> Int
607 foo m (Just n) = foo (m-n) (Just n)
609 SpecConstr sees this fragment:
611 case w_smT of wild_Xf [Just A] {
612 Data.Maybe.Nothing -> lvl_smf;
613 Data.Maybe.Just n_acT [Just S(L)] ->
614 case n_acT of wild1_ams [Just A] { GHC.Base.I# y_amr [Just L] ->
615 $wfoo_smW (GHC.Prim.-# ds_Xmb y_amr) wild_Xf
618 and correctly generates the rule
620 RULES: "SC:$wfoo1" [0] __forall {y_amr [Just L] :: GHC.Prim.Int#
621 sc_snn :: GHC.Prim.Int#}
622 $wfoo_smW sc_snn (Data.Maybe.Just @ GHC.Base.Int (GHC.Base.I# y_amr))
623 = $s$wfoo_sno y_amr sc_snn ;]
625 BUT we must ensure that this rule matches in the original function!
626 Note that the call to $wfoo is
627 $wfoo_smW (GHC.Prim.-# ds_Xmb y_amr) wild_Xf
629 During matching we expand wild_Xf to (Just n_acT). But then we must also
630 expand n_acT to (I# y_amr). And we can only do that if we look up n_acT
631 in the in-scope set, because in wild_Xf's unfolding it won't have an unfolding
634 That is why the 'lookupRnInScope' call in the (Var v2) case of 'match'
638 %************************************************************************
640 \subsection{Checking a program for failing rule applications}
642 %************************************************************************
644 -----------------------------------------------------
646 -----------------------------------------------------
648 We want to know what sites have rules that could have fired but didn't.
649 This pass runs over the tree (without changing it) and reports such.
651 NB: we assume that this follows a run of the simplifier, so every Id
652 occurrence (including occurrences of imported Ids) is decorated with
653 all its (active) rules. No need to construct a rule base or anything
657 ruleCheckProgram :: CompilerPhase -> String -> [CoreBind] -> SDoc
658 -- Report partial matches for rules beginning
659 -- with the specified string
660 ruleCheckProgram phase rule_pat binds
662 = text "Rule check results: no rule application sites"
664 = vcat [text "Rule check results:",
666 vcat [ p $$ line | p <- bagToList results ]
669 results = unionManyBags (map (ruleCheckBind (phase, rule_pat)) binds)
670 line = text (replicate 20 '-')
672 type RuleCheckEnv = (CompilerPhase, String) -- Phase and Pattern
674 ruleCheckBind :: RuleCheckEnv -> CoreBind -> Bag SDoc
675 -- The Bag returned has one SDoc for each call site found
676 ruleCheckBind env (NonRec b r) = ruleCheck env r
677 ruleCheckBind env (Rec prs) = unionManyBags [ruleCheck env r | (b,r) <- prs]
679 ruleCheck :: RuleCheckEnv -> CoreExpr -> Bag SDoc
680 ruleCheck env (Var v) = emptyBag
681 ruleCheck env (Lit l) = emptyBag
682 ruleCheck env (Type ty) = emptyBag
683 ruleCheck env (App f a) = ruleCheckApp env (App f a) []
684 ruleCheck env (Note n e) = ruleCheck env e
685 ruleCheck env (Let bd e) = ruleCheckBind env bd `unionBags` ruleCheck env e
686 ruleCheck env (Lam b e) = ruleCheck env e
687 ruleCheck env (Case e _ _ as) = ruleCheck env e `unionBags`
688 unionManyBags [ruleCheck env r | (_,_,r) <- as]
690 ruleCheckApp env (App f a) as = ruleCheck env a `unionBags` ruleCheckApp env f (a:as)
691 ruleCheckApp env (Var f) as = ruleCheckFun env f as
692 ruleCheckApp env other as = ruleCheck env other
696 ruleCheckFun :: RuleCheckEnv -> Id -> [CoreExpr] -> Bag SDoc
697 -- Produce a report for all rules matching the predicate
698 -- saying why it doesn't match the specified application
700 ruleCheckFun (phase, pat) fn args
701 | null name_match_rules = emptyBag
702 | otherwise = unitBag (ruleAppCheck_help phase fn args name_match_rules)
704 name_match_rules = filter match (idCoreRules fn)
705 match rule = pat `isPrefixOf` unpackFS (ruleName rule)
707 ruleAppCheck_help :: CompilerPhase -> Id -> [CoreExpr] -> [CoreRule] -> SDoc
708 ruleAppCheck_help phase fn args rules
709 = -- The rules match the pattern, so we want to print something
710 vcat [text "Expression:" <+> ppr (mkApps (Var fn) args),
711 vcat (map check_rule rules)]
714 i_args = args `zip` [1::Int ..]
715 rough_args = map roughTopName args
717 check_rule rule = rule_herald rule <> colon <+> rule_info rule
719 rule_herald (BuiltinRule { ru_name = name })
720 = ptext SLIT("Builtin rule") <+> doubleQuotes (ftext name)
721 rule_herald (Rule { ru_name = name })
722 = ptext SLIT("Rule") <+> doubleQuotes (ftext name)
725 | Just _ <- matchRule noBlackList emptyInScopeSet args rough_args rule
726 = text "matches (which is very peculiar!)"
728 rule_info (BuiltinRule {}) = text "does not match"
730 rule_info (Rule { ru_name = name, ru_act = act,
731 ru_bndrs = rule_bndrs, ru_args = rule_args})
732 | not (isActive phase act) = text "active only in later phase"
733 | n_args < n_rule_args = text "too few arguments"
734 | n_mismatches == n_rule_args = text "no arguments match"
735 | n_mismatches == 0 = text "all arguments match (considered individually), but rule as a whole does not"
736 | otherwise = text "arguments" <+> ppr mismatches <+> text "do not match (1-indexing)"
738 n_rule_args = length rule_args
739 n_mismatches = length mismatches
740 mismatches = [i | (rule_arg, (arg,i)) <- rule_args `zip` i_args,
741 not (isJust (match_fn rule_arg arg))]
743 lhs_fvs = exprsFreeVars rule_args -- Includes template tyvars
744 match_fn rule_arg arg = match menv emptySubstEnv rule_arg arg
746 in_scope = lhs_fvs `unionVarSet` exprFreeVars arg
747 menv = ME { me_env = mkRnEnv2 (mkInScopeSet in_scope)
748 , me_tmpls = mkVarSet rule_bndrs }