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,
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 )
52 import List hiding( mapAccumL ) -- Also defined in Util
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_rn_env, tmpl_vars') = mapAccumL rnBndrL (mkRnEnv2 in_scope) tmpl_vars
337 -- See Note [Template binders]
339 init_menv = ME { me_tmpls = mkVarSet tmpl_vars', me_env = init_rn_env }
341 go menv subst [] es = Just subst
342 go menv subst ts [] = Nothing -- Fail if too few actual args
343 go menv subst (t:ts) (e:es) = do { subst1 <- match menv subst t e
344 ; go menv subst1 ts es }
346 lookup_tmpl :: TvSubstEnv -> IdSubstEnv -> Var -> CoreExpr
347 lookup_tmpl tv_subst id_subst tmpl_var'
348 | isTyVar tmpl_var' = case lookupVarEnv tv_subst tmpl_var' of
350 Nothing -> unbound tmpl_var'
351 | otherwise = case lookupVarEnv id_subst tmpl_var' of
353 other -> unbound tmpl_var'
355 unbound var = pprPanic "Template variable unbound in rewrite rule" (ppr var)
358 Note [Template binders]
359 ~~~~~~~~~~~~~~~~~~~~~~~
360 Consider the following match:
361 Template: forall x. f x
363 This should succeed, because the template variable 'x' has nothing to do with
364 the 'x' in the target.
366 To achive this, we use rnBndrL to rename the template variables if necessary;
367 the renamed ones are the tmpl_vars'
370 ---------------------------------------------
371 The inner workings of matching
372 ---------------------------------------------
375 -- These two definitions are not the same as in Subst,
376 -- but they simple and direct, and purely local to this module
378 -- * The domain of the TvSubstEnv and IdSubstEnv are the template
379 -- variables passed into the match.
381 -- * The (OrdList CoreBind) in a SubstEnv are the bindings floated out
382 -- from nested matches; see the Let case of match, below
384 type SubstEnv = (TvSubstEnv, IdSubstEnv, OrdList CoreBind)
385 type IdSubstEnv = IdEnv CoreExpr
387 emptySubstEnv :: SubstEnv
388 emptySubstEnv = (emptyVarEnv, emptyVarEnv, nilOL)
391 -- At one stage I tried to match even if there are more
392 -- template args than real args.
394 -- I now think this is probably a bad idea.
395 -- Should the template (map f xs) match (map g)? I think not.
396 -- For a start, in general eta expansion wastes work.
402 -> CoreExpr -- Template
403 -> CoreExpr -- Target
406 -- See the notes with Unify.match, which matches types
407 -- Everything is very similar for terms
409 -- Interesting examples:
411 -- \x->f against \f->f
412 -- When we meet the lambdas we must remember to rename f to f' in the
413 -- second expresion. The RnEnv2 does that.
416 -- forall a. \b->b against \a->3
417 -- We must rename the \a. Otherwise when we meet the lambdas we
418 -- might substitute [a/b] in the template, and then erroneously
419 -- succeed in matching what looks like the template variable 'a' against 3.
421 -- The Var case follows closely what happens in Unify.match
422 match menv subst (Var v1) e2
423 | Just subst <- match_var menv subst v1 e2
426 -- Here is another important rule: if the term being matched is a
427 -- variable, we expand it so long as its unfolding is a WHNF
428 -- (Its occurrence information is not necessarily up to date,
429 -- so we don't use it.)
430 match menv subst e1 (Var v2)
431 | isCheapUnfolding unfolding
432 = match menv subst e1 (unfoldingTemplate unfolding)
435 unfolding = idUnfolding (lookupRnInScope rn_env (rnOccR rn_env v2))
436 -- Notice that we look up v2 in the in-scope set
437 -- See Note [Lookup in-scope]
438 -- Remember to apply any renaming first (hence rnOccR)
440 -- Matching a let-expression. Consider
441 -- RULE forall x. f (g x) = <rhs>
442 -- and target expression
443 -- f (let { w=R } in g E))
444 -- Then we'd like the rule to match, to generate
445 -- let { w=R } in (\x. <rhs>) E
446 -- In effect, we want to float the let-binding outward, to enable
447 -- the match to happen. This is the WHOLE REASON for accumulating
448 -- bindings in the SubstEnv
450 -- We can only do this if
451 -- (a) Widening the scope of w does not capture any variables
452 -- We use a conservative test: w is not already in scope
453 -- (b) The free variables of R are not bound by the part of the
454 -- target expression outside the let binding; e.g.
455 -- f (\v. let w = v+1 in g E)
456 -- Here we obviously cannot float the let-binding for w.
458 match menv subst@(tv_subst, id_subst, binds) e1 (Let bind e2)
459 | all freshly_bound bndrs,
460 not (any locally_bound bind_fvs)
461 = match (menv { me_env = rn_env' })
462 (tv_subst, id_subst, binds `snocOL` bind)
466 bndrs = bindersOf bind
467 bind_fvs = varSetElems (bindFreeVars bind)
468 freshly_bound x = not (x `rnInScope` rn_env)
469 locally_bound x = inRnEnvR rn_env x
470 rn_env' = extendRnInScopeList rn_env bndrs
472 match menv subst (Lit lit1) (Lit lit2)
476 match menv subst (App f1 a1) (App f2 a2)
477 = do { subst' <- match menv subst f1 f2
478 ; match menv subst' a1 a2 }
480 match menv subst (Lam x1 e1) (Lam x2 e2)
481 = match menv' subst e1 e2
483 menv' = menv { me_env = rnBndr2 (me_env menv) x1 x2 }
485 -- This rule does eta expansion
486 -- (\x.M) ~ N iff M ~ N x
487 -- It's important that this is *after* the let rule,
488 -- so that (\x.M) ~ (let y = e in \y.N)
489 -- does the let thing, and then gets the lam/lam rule above
490 match menv subst (Lam x1 e1) e2
491 = match menv' subst e1 (App e2 (varToCoreExpr new_x))
493 (rn_env', new_x) = rnBndrL (me_env menv) x1
494 menv' = menv { me_env = rn_env' }
496 -- Eta expansion the other way
497 -- M ~ (\y.N) iff M y ~ N
498 match menv subst e1 (Lam x2 e2)
499 = match menv' subst (App e1 (varToCoreExpr new_x)) e2
501 (rn_env', new_x) = rnBndrR (me_env menv) x2
502 menv' = menv { me_env = rn_env' }
504 match menv subst (Case e1 x1 ty1 alts1) (Case e2 x2 ty2 alts2)
505 = do { subst1 <- match_ty menv subst ty1 ty2
506 ; subst2 <- match menv subst1 e1 e2
507 ; let menv' = menv { me_env = rnBndr2 (me_env menv) x1 x2 }
508 ; match_alts menv' subst2 alts1 alts2 -- Alts are both sorted
511 match menv subst (Type ty1) (Type ty2)
512 = match_ty menv subst ty1 ty2
514 match menv subst (Cast e1 co1) (Cast e2 co2)
515 | (from1, to1) <- coercionKind co1
516 , (from2, to2) <- coercionKind co2
517 = do { subst1 <- match_ty menv subst to1 to2
518 ; subst2 <- match_ty menv subst1 from1 from2
519 ; match menv subst2 e1 e2 }
521 {- REMOVING OLD CODE: I think that the above handling for let is
522 better than the stuff here, which looks
523 pretty suspicious to me. SLPJ Sept 06
524 -- This is an interesting rule: we simply ignore lets in the
525 -- term being matched against! The unfolding inside it is (by assumption)
526 -- already inside any occurrences of the bound variables, so we'll expand
527 -- them when we encounter them. This gives a chance of matching
528 -- forall x,y. f (g (x,y))
530 -- f (let v = (a,b) in g v)
532 match menv subst e1 (Let bind e2)
533 = match (menv { me_env = rn_env' }) subst e1 e2
535 (rn_env', _bndrs') = mapAccumL rnBndrR (me_env menv) (bindersOf bind)
536 -- It's important to do this renaming, so that the bndrs
537 -- are brought into the local scope. For example:
539 -- forall f,x,xs. f (x:xs)
541 -- f (let y = e in (y:[]))
542 -- We must not get success with x->y! So we record that y is
543 -- locally bound (with rnBndrR), and proceed. The Var case
544 -- will fail when trying to bind x->y
547 -- Everything else fails
548 match menv subst e1 e2 = -- pprTrace "Failing at" ((text "e1:" <+> ppr e1) $$ (text "e2:" <+> ppr e2)) $
551 ------------------------------------------
552 match_var :: MatchEnv
555 -> CoreExpr -- Target
557 match_var menv subst@(tv_subst, id_subst, binds) v1 e2
558 | v1' `elemVarSet` me_tmpls menv
559 = case lookupVarEnv id_subst v1' of
560 Nothing | any (inRnEnvR rn_env) (varSetElems (exprFreeVars e2))
561 -> Nothing -- Occurs check failure
562 -- e.g. match forall a. (\x-> a x) against (\y. y y)
564 | otherwise -- No renaming to do on e2
565 -> Just (tv_subst, extendVarEnv id_subst v1' e2, binds)
567 Just e2' | tcEqExprX (nukeRnEnvL rn_env) e2' e2
573 | otherwise -- v1 is not a template variable; check for an exact match with e2
575 Var v2 | v1' == rnOccR rn_env v2 -> Just subst
580 v1' = rnOccL rn_env v1
581 -- If the template is
582 -- forall x. f x (\x -> x) = ...
583 -- Then the x inside the lambda isn't the
584 -- template x, so we must rename first!
587 ------------------------------------------
588 match_alts :: MatchEnv
590 -> [CoreAlt] -- Template
591 -> [CoreAlt] -- Target
593 match_alts menv subst [] []
595 match_alts menv subst ((c1,vs1,r1):alts1) ((c2,vs2,r2):alts2)
597 = do { subst1 <- match menv' subst r1 r2
598 ; match_alts menv subst1 alts1 alts2 }
601 menv' = menv { me_env = rnBndrs2 (me_env menv) vs1 vs2 }
603 match_alts menv subst alts1 alts2
607 Matching Core types: use the matcher in TcType.
608 Notice that we treat newtypes as opaque. For example, suppose
609 we have a specialised version of a function at a newtype, say
611 We only want to replace (f T) with f', not (f Int).
614 ------------------------------------------
615 match_ty menv (tv_subst, id_subst, binds) ty1 ty2
616 = do { tv_subst' <- Unify.ruleMatchTyX menv tv_subst ty1 ty2
617 ; return (tv_subst', id_subst, binds) }
621 Note [Lookup in-scope]
622 ~~~~~~~~~~~~~~~~~~~~~~
623 Consider this example
624 foo :: Int -> Maybe Int -> Int
626 foo m (Just n) = foo (m-n) (Just n)
628 SpecConstr sees this fragment:
630 case w_smT of wild_Xf [Just A] {
631 Data.Maybe.Nothing -> lvl_smf;
632 Data.Maybe.Just n_acT [Just S(L)] ->
633 case n_acT of wild1_ams [Just A] { GHC.Base.I# y_amr [Just L] ->
634 $wfoo_smW (GHC.Prim.-# ds_Xmb y_amr) wild_Xf
637 and correctly generates the rule
639 RULES: "SC:$wfoo1" [0] __forall {y_amr [Just L] :: GHC.Prim.Int#
640 sc_snn :: GHC.Prim.Int#}
641 $wfoo_smW sc_snn (Data.Maybe.Just @ GHC.Base.Int (GHC.Base.I# y_amr))
642 = $s$wfoo_sno y_amr sc_snn ;]
644 BUT we must ensure that this rule matches in the original function!
645 Note that the call to $wfoo is
646 $wfoo_smW (GHC.Prim.-# ds_Xmb y_amr) wild_Xf
648 During matching we expand wild_Xf to (Just n_acT). But then we must also
649 expand n_acT to (I# y_amr). And we can only do that if we look up n_acT
650 in the in-scope set, because in wild_Xf's unfolding it won't have an unfolding
653 That is why the 'lookupRnInScope' call in the (Var v2) case of 'match'
657 %************************************************************************
659 \subsection{Checking a program for failing rule applications}
661 %************************************************************************
663 -----------------------------------------------------
665 -----------------------------------------------------
667 We want to know what sites have rules that could have fired but didn't.
668 This pass runs over the tree (without changing it) and reports such.
670 NB: we assume that this follows a run of the simplifier, so every Id
671 occurrence (including occurrences of imported Ids) is decorated with
672 all its (active) rules. No need to construct a rule base or anything
676 ruleCheckProgram :: CompilerPhase -> String -> [CoreBind] -> SDoc
677 -- Report partial matches for rules beginning
678 -- with the specified string
679 ruleCheckProgram phase rule_pat binds
681 = text "Rule check results: no rule application sites"
683 = vcat [text "Rule check results:",
685 vcat [ p $$ line | p <- bagToList results ]
688 results = unionManyBags (map (ruleCheckBind (phase, rule_pat)) binds)
689 line = text (replicate 20 '-')
691 type RuleCheckEnv = (CompilerPhase, String) -- Phase and Pattern
693 ruleCheckBind :: RuleCheckEnv -> CoreBind -> Bag SDoc
694 -- The Bag returned has one SDoc for each call site found
695 ruleCheckBind env (NonRec b r) = ruleCheck env r
696 ruleCheckBind env (Rec prs) = unionManyBags [ruleCheck env r | (b,r) <- prs]
698 ruleCheck :: RuleCheckEnv -> CoreExpr -> Bag SDoc
699 ruleCheck env (Var v) = emptyBag
700 ruleCheck env (Lit l) = emptyBag
701 ruleCheck env (Type ty) = emptyBag
702 ruleCheck env (App f a) = ruleCheckApp env (App f a) []
703 ruleCheck env (Note n e) = ruleCheck env e
704 ruleCheck env (Cast e co) = ruleCheck env e
705 ruleCheck env (Let bd e) = ruleCheckBind env bd `unionBags` ruleCheck env e
706 ruleCheck env (Lam b e) = ruleCheck env e
707 ruleCheck env (Case e _ _ as) = ruleCheck env e `unionBags`
708 unionManyBags [ruleCheck env r | (_,_,r) <- as]
710 ruleCheckApp env (App f a) as = ruleCheck env a `unionBags` ruleCheckApp env f (a:as)
711 ruleCheckApp env (Var f) as = ruleCheckFun env f as
712 ruleCheckApp env other as = ruleCheck env other
716 ruleCheckFun :: RuleCheckEnv -> Id -> [CoreExpr] -> Bag SDoc
717 -- Produce a report for all rules matching the predicate
718 -- saying why it doesn't match the specified application
720 ruleCheckFun (phase, pat) fn args
721 | null name_match_rules = emptyBag
722 | otherwise = unitBag (ruleAppCheck_help phase fn args name_match_rules)
724 name_match_rules = filter match (idCoreRules fn)
725 match rule = pat `isPrefixOf` unpackFS (ruleName rule)
727 ruleAppCheck_help :: CompilerPhase -> Id -> [CoreExpr] -> [CoreRule] -> SDoc
728 ruleAppCheck_help phase fn args rules
729 = -- The rules match the pattern, so we want to print something
730 vcat [text "Expression:" <+> ppr (mkApps (Var fn) args),
731 vcat (map check_rule rules)]
734 i_args = args `zip` [1::Int ..]
735 rough_args = map roughTopName args
737 check_rule rule = rule_herald rule <> colon <+> rule_info rule
739 rule_herald (BuiltinRule { ru_name = name })
740 = ptext SLIT("Builtin rule") <+> doubleQuotes (ftext name)
741 rule_herald (Rule { ru_name = name })
742 = ptext SLIT("Rule") <+> doubleQuotes (ftext name)
745 | Just _ <- matchRule noBlackList emptyInScopeSet args rough_args rule
746 = text "matches (which is very peculiar!)"
748 rule_info (BuiltinRule {}) = text "does not match"
750 rule_info (Rule { ru_name = name, ru_act = act,
751 ru_bndrs = rule_bndrs, ru_args = rule_args})
752 | not (isActive phase act) = text "active only in later phase"
753 | n_args < n_rule_args = text "too few arguments"
754 | n_mismatches == n_rule_args = text "no arguments match"
755 | n_mismatches == 0 = text "all arguments match (considered individually), but rule as a whole does not"
756 | otherwise = text "arguments" <+> ppr mismatches <+> text "do not match (1-indexing)"
758 n_rule_args = length rule_args
759 n_mismatches = length mismatches
760 mismatches = [i | (rule_arg, (arg,i)) <- rule_args `zip` i_args,
761 not (isJust (match_fn rule_arg arg))]
763 lhs_fvs = exprsFreeVars rule_args -- Includes template tyvars
764 match_fn rule_arg arg = match menv emptySubstEnv rule_arg arg
766 in_scope = lhs_fvs `unionVarSet` exprFreeVars arg
767 menv = ME { me_env = mkRnEnv2 (mkInScopeSet in_scope)
768 , me_tmpls = mkVarSet rule_bndrs }