2 % (c) The University of Glasgow 2006
3 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
6 The Desugarer: turning HsSyn into Core.
9 module Desugar ( deSugar, deSugarExpr ) where
21 import CoqPass ( coqPassCoreToString, coqPassCoreToCore )
27 import DsExpr () -- Forces DsExpr to be compiled; DsBinds only
28 -- depends on DsExpr.hi-boot.
34 import CoreMonad ( endPass, CoreToDo(..) )
52 %************************************************************************
54 %* The main function: deSugar
56 %************************************************************************
60 -- | Main entry point to the desugarer.
61 deSugar :: HscEnv -> ModLocation -> TcGblEnv -> IO (Messages, Maybe ModGuts)
62 -- Can modify PCS by faulting in more declarations
66 tcg_env@(TcGblEnv { tcg_mod = mod,
68 tcg_type_env = type_env,
69 tcg_imports = imports,
70 tcg_exports = exports,
72 tcg_rdr_env = rdr_env,
73 tcg_fix_env = fix_env,
74 tcg_inst_env = inst_env,
75 tcg_fam_inst_env = fam_inst_env,
79 tcg_imp_specs = imp_specs,
80 tcg_ev_binds = ev_binds,
85 tcg_fam_insts = fam_insts,
86 tcg_hpc = other_hpc_info })
88 = do { let dflags = hsc_dflags hsc_env
89 ; showPass dflags "Desugar"
91 -- Desugar the program
92 ; let export_set = availsToNameSet exports
93 ; let auto_scc = mkAutoScc dflags mod export_set
94 ; let target = hscTarget dflags
95 ; let hpcInfo = emptyHpcInfo other_hpc_info
99 return (emptyMessages,
100 Just ([], nilOL, [], [], NoStubs, hpcInfo, emptyModBreaks, undefined, undefined
127 (binds_cvr,ds_hpc_info, modBreaks)
129 || target == HscInterpreted)
130 && (not (isHsBoot hsc_src))
131 then addCoverageTicksToBinds dflags mod mod_loc
132 (typeEnvTyCons type_env) binds
133 else return (binds, hpcInfo, emptyModBreaks)
134 initDs hsc_env mod rdr_env type_env $ do
135 do { ds_ev_binds <- dsEvBinds ev_binds
136 ; core_prs <- dsTopLHsBinds auto_scc binds_cvr
137 ; (spec_prs, spec_rules) <- dsImpSpecs imp_specs
138 ; (ds_fords, foreign_prs) <- dsForeigns fords
139 ; ds_rules <- mapMaybeM dsRule rules
140 ; ds_vects <- mapM dsVect vects
141 ; hetmet_brak <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_brak_name else return undefined
142 ; hetmet_esc <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_esc_name else return undefined
143 ; hetmet_flatten <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_flatten_name else return undefined
144 ; hetmet_unflatten <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_unflatten_name else return undefined
145 ; hetmet_flattened_id <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_flattened_id_name else return undefined
146 ; hetmet_PGArrow <- if dopt Opt_F_coqpass dflags then dsLookupTyCon hetmet_PGArrow_name else return undefined
147 ; hetmet_PGArrow_unit <- if dopt Opt_F_coqpass dflags then dsLookupTyCon hetmet_PGArrow_unit_name else return undefined
148 ; hetmet_PGArrow_tensor <- if dopt Opt_F_coqpass dflags then dsLookupTyCon hetmet_PGArrow_tensor_name else return undefined
149 ; hetmet_PGArrow_exponent <- if dopt Opt_F_coqpass dflags then dsLookupTyCon hetmet_PGArrow_exponent_name else return undefined
150 ; hetmet_pga_id <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_id_name else return undefined
151 ; hetmet_pga_comp <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_comp_name else return undefined
152 ; hetmet_pga_first <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_first_name else return undefined
153 ; hetmet_pga_second <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_second_name else return undefined
154 ; hetmet_pga_cancell <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_cancell_name else return undefined
155 ; hetmet_pga_cancelr <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_cancelr_name else return undefined
156 ; hetmet_pga_uncancell <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_uncancell_name else return undefined
157 ; hetmet_pga_uncancelr <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_uncancelr_name else return undefined
158 ; hetmet_pga_assoc <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_assoc_name else return undefined
159 ; hetmet_pga_unassoc <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_unassoc_name else return undefined
160 ; hetmet_pga_copy <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_copy_name else return undefined
161 ; hetmet_pga_drop <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_drop_name else return undefined
162 ; hetmet_pga_swap <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_swap_name else return undefined
163 ; hetmet_pga_applyl <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_applyl_name else return undefined
164 ; hetmet_pga_applyr <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_applyr_name else return undefined
165 ; hetmet_pga_curryl <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_curryl_name else return undefined
166 ; hetmet_pga_curryr <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_curryr_name else return undefined
168 | opt_Hpc = hpcInitCode mod ds_hpc_info
170 ; return ( ds_ev_binds
171 , foreign_prs `appOL` core_prs `appOL` spec_prs
172 , spec_rules ++ ds_rules, ds_vects
173 , ds_fords `appendStubC` hpc_init
174 , ds_hpc_info, modBreaks, hetmet_brak, hetmet_esc
177 , hetmet_flattened_id
179 , hetmet_PGArrow_unit
180 , hetmet_PGArrow_tensor
181 , hetmet_PGArrow_exponent
188 , hetmet_pga_uncancell
189 , hetmet_pga_uncancelr
202 Nothing -> return (msgs, Nothing) ;
203 Just (ds_ev_binds, all_prs, all_rules, ds_vects, ds_fords,ds_hpc_info, modBreaks
204 , hetmet_brak, hetmet_esc
207 , hetmet_flattened_id
209 , hetmet_PGArrow_unit
210 , hetmet_PGArrow_tensor
211 , hetmet_PGArrow_exponent
218 , hetmet_pga_uncancell
219 , hetmet_pga_uncancelr
228 , hetmet_pga_curryr) -> do
230 { -- Add export flags to bindings
231 keep_alive <- readIORef keep_var
232 ; let (rules_for_locals, rules_for_imps)
233 = partition isLocalRule all_rules
234 final_prs = addExportFlagsAndRules target
235 export_set keep_alive rules_for_locals (fromOL all_prs)
237 final_pgm = simplifyBinds $ combineEvBinds ds_ev_binds final_prs
238 -- Notice that we put the whole lot in a big Rec, even the foreign binds
239 -- When compiling PrelFloat, which defines data Float = F# Float#
240 -- we want F# to be in scope in the foreign marshalling code!
241 -- You might think it doesn't matter, but the simplifier brings all top-level
242 -- things into the in-scope set before simplifying; so we get no unfolding for F#!
244 -- Lint result if necessary, and print
245 ; dumpIfSet_dyn dflags Opt_D_dump_ds "Desugared, before opt" $
246 (vcat [ pprCoreBindings final_pgm
247 , pprRules rules_for_imps ])
249 ; ds_binds <- if dopt Opt_F_coqpass dflags
250 then do { us <- mkSplitUniqSupply '~'
251 ; return (coqPassCoreToCore
261 hetmet_PGArrow_tensor
262 hetmet_PGArrow_exponent
281 else return final_pgm
283 ; (ds_binds', ds_rules_for_imps) <- simpleOptPgm dflags ds_binds rules_for_imps
284 -- The simpleOptPgm gets rid of type
285 -- bindings plus any stupid dead code
287 ; dumpIfSet_dyn dflags Opt_D_coqpass "Coq Pass Output" $ text $ coqPassCoreToString ds_binds'
289 ; dumpIfSet_dyn dflags Opt_D_dump_coqpass "After Coq Pass" (text $ showSDoc $ pprCoreBindings ds_binds')
291 ; endPass dflags CoreDesugar ds_binds' ds_rules_for_imps
293 ; let used_names = mkUsedNames tcg_env
294 ; deps <- mkDependencies tcg_env
296 ; let mod_guts = ModGuts {
298 mg_boot = isHsBoot hsc_src,
299 mg_exports = exports,
301 mg_used_names = used_names,
302 mg_dir_imps = imp_mods imports,
303 mg_rdr_env = rdr_env,
304 mg_fix_env = fix_env,
309 mg_fam_insts = fam_insts,
310 mg_inst_env = inst_env,
311 mg_fam_inst_env = fam_inst_env,
312 mg_rules = ds_rules_for_imps,
313 mg_binds = ds_binds',
314 mg_foreign = ds_fords,
315 mg_hpc_info = ds_hpc_info,
316 mg_modBreaks = modBreaks,
317 mg_vect_decls = ds_vects,
318 mg_vect_info = noVectInfo
320 ; return (msgs, Just mod_guts)
323 dsImpSpecs :: [LTcSpecPrag] -> DsM (OrdList (Id,CoreExpr), [CoreRule])
325 = do { spec_prs <- mapMaybeM (dsSpec Nothing) imp_specs
326 ; let (spec_binds, spec_rules) = unzip spec_prs
327 ; return (concatOL spec_binds, spec_rules) }
329 combineEvBinds :: [DsEvBind] -> [(Id,CoreExpr)] -> [CoreBind]
330 -- Top-level bindings can include coercion bindings, but not via superclasses
331 -- See Note [Top-level evidence]
332 combineEvBinds [] val_prs
334 combineEvBinds (LetEvBind (NonRec b r) : bs) val_prs
335 | isId b = combineEvBinds bs ((b,r):val_prs)
336 | otherwise = NonRec b r : combineEvBinds bs val_prs
337 combineEvBinds (LetEvBind (Rec prs) : bs) val_prs
338 = combineEvBinds bs (prs ++ val_prs)
339 combineEvBinds (CaseEvBind x _ _ : _) _
340 = pprPanic "topEvBindPairs" (ppr x)
343 Note [Top-level evidence]
344 ~~~~~~~~~~~~~~~~~~~~~~~~~
345 Top-level evidence bindings may be mutually recursive with the top-level value
346 bindings, so we must put those in a Rec. But we can't put them *all* in a Rec
347 because the occurrence analyser doesn't teke account of type/coercion variables
348 when computing dependencies.
350 So we pull out the type/coercion variables (which are in dependency order),
355 mkAutoScc :: DynFlags -> Module -> NameSet -> AutoScc
356 mkAutoScc dflags mod exports
357 | not opt_SccProfilingOn -- No profiling
359 -- Add auto-scc on all top-level things
360 | dopt Opt_AutoSccsOnAllToplevs dflags
361 = AddSccs mod (\id -> not $ isDerivedOccName $ getOccName id)
362 -- See #1641. This is pretty yucky, but I can't see a better way
363 -- to identify compiler-generated Ids, and at least this should
365 -- Only on exported things
366 | dopt Opt_AutoSccsOnExportedToplevs dflags
367 = AddSccs mod (\id -> idName id `elemNameSet` exports)
371 deSugarExpr :: HscEnv
372 -> Module -> GlobalRdrEnv -> TypeEnv
374 -> IO (Messages, Maybe CoreExpr)
375 -- Prints its own errors; returns Nothing if error occurred
377 deSugarExpr hsc_env this_mod rdr_env type_env tc_expr = do
378 let dflags = hsc_dflags hsc_env
379 showPass dflags "Desugar"
382 (msgs, mb_core_expr) <- initDs hsc_env this_mod rdr_env type_env $
386 Nothing -> return (msgs, Nothing)
390 dumpIfSet_dyn dflags Opt_D_dump_ds "Desugared" (pprCoreExpr expr)
392 return (msgs, Just expr)
395 %************************************************************************
397 %* Add rules and export flags to binders
399 %************************************************************************
402 addExportFlagsAndRules
403 :: HscTarget -> NameSet -> NameSet -> [CoreRule]
404 -> [(Id, t)] -> [(Id, t)]
405 addExportFlagsAndRules target exports keep_alive rules prs
408 add_one bndr = add_rules name (add_export name bndr)
412 ---------- Rules --------
413 -- See Note [Attach rules to local ids]
414 -- NB: the binder might have some existing rules,
415 -- arising from specialisation pragmas
417 | Just rules <- lookupNameEnv rule_base name
418 = bndr `addIdSpecialisations` rules
421 rule_base = extendRuleBaseList emptyRuleBase rules
423 ---------- Export flag --------
424 -- See Note [Adding export flags]
426 | dont_discard name = setIdExported bndr
429 dont_discard :: Name -> Bool
430 dont_discard name = is_exported name
431 || name `elemNameSet` keep_alive
433 -- In interactive mode, we don't want to discard any top-level
434 -- entities at all (eg. do not inline them away during
435 -- simplification), and retain them all in the TypeEnv so they are
436 -- available from the command line.
438 -- isExternalName separates the user-defined top-level names from those
439 -- introduced by the type checker.
440 is_exported :: Name -> Bool
441 is_exported | target == HscInterpreted = isExternalName
442 | otherwise = (`elemNameSet` exports)
446 Note [Adding export flags]
447 ~~~~~~~~~~~~~~~~~~~~~~~~~~
448 Set the no-discard flag if either
449 a) the Id is exported
450 b) it's mentioned in the RHS of an orphan rule
451 c) it's in the keep-alive set
453 It means that the binding won't be discarded EVEN if the binding
454 ends up being trivial (v = w) -- the simplifier would usually just
455 substitute w for v throughout, but we don't apply the substitution to
456 the rules (maybe we should?), so this substitution would make the rule
459 You might wonder why exported Ids aren't already marked as such;
460 it's just because the type checker is rather busy already and
461 I didn't want to pass in yet another mapping.
463 Note [Attach rules to local ids]
464 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
465 Find the rules for locally-defined Ids; then we can attach them
466 to the binders in the top-level bindings
469 - It makes the rules easier to look up
470 - It means that transformation rules and specialisations for
471 locally defined Ids are handled uniformly
472 - It keeps alive things that are referred to only from a rule
473 (the occurrence analyser knows about rules attached to Ids)
474 - It makes sure that, when we apply a rule, the free vars
475 of the RHS are more likely to be in scope
476 - The imported rules are carried in the in-scope set
477 which is extended on each iteration by the new wave of
478 local binders; any rules which aren't on the binding will
482 %************************************************************************
484 %* Desugaring transformation rules
486 %************************************************************************
489 dsRule :: LRuleDecl Id -> DsM (Maybe CoreRule)
490 dsRule (L loc (HsRule name act vars lhs _tv_lhs rhs _fv_rhs))
492 do { let bndrs' = [var | RuleBndr (L _ var) <- vars]
494 ; lhs' <- unsetOptM Opt_EnableRewriteRules $
495 unsetOptM Opt_WarnIdentities $
496 dsLExpr lhs -- Note [Desugaring RULE left hand sides]
498 ; rhs' <- dsLExpr rhs
500 -- Substitute the dict bindings eagerly,
501 -- and take the body apart into a (f args) form
502 ; case decomposeRuleLhs bndrs' lhs' of {
503 Left msg -> do { warnDs msg; return Nothing } ;
504 Right (final_bndrs, fn_id, args) -> do
506 { let is_local = isLocalId fn_id
507 -- NB: isLocalId is False of implicit Ids. This is good becuase
508 -- we don't want to attach rules to the bindings of implicit Ids,
509 -- because they don't show up in the bindings until just before code gen
510 fn_name = idName fn_id
511 final_rhs = simpleOptExpr rhs' -- De-crap it
512 rule = mkRule False {- Not auto -} is_local
513 name act fn_name final_bndrs args final_rhs
518 Note [Desugaring RULE left hand sides]
519 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
520 For the LHS of a RULE we do *not* want to desugar
521 [x] to build (\cn. x `c` n)
522 We want to leave explicit lists simply as chains
523 of cons's. We can achieve that slightly indirectly by
524 switching off EnableRewriteRules. See DsExpr.dsExplicitList.
526 That keeps the desugaring of list comprehensions simple too.
528 Nor do we want to warn of conversion identities on the LHS;
529 the rule is precisly to optimise them:
530 {-# RULES "fromRational/id" fromRational = id :: Rational -> Rational #-}
533 %************************************************************************
535 %* Desugaring vectorisation declarations
537 %************************************************************************
540 dsVect :: LVectDecl Id -> DsM CoreVect
541 dsVect (L loc (HsVect v rhs))
543 do { rhs' <- fmapMaybeM dsLExpr rhs
544 ; return $ Vect (unLoc v) rhs'
546 -- dsVect (L loc (HsVect v Nothing))
547 -- = return $ Vect v Nothing
548 -- dsVect (L loc (HsVect v (Just rhs)))
549 -- = putSrcSpanDs loc $
550 -- do { rhs' <- dsLExpr rhs
551 -- ; return $ Vect v (Just rhs')
559 -- Simplification routines run before the flattener. We can't use
560 -- simpleOptPgm -- it doesn't preserve the order of subexpressions or
561 -- let-binding groups.
563 simplify :: Expr CoreBndr -> Expr CoreBndr
564 simplify (Var v) = Var v
565 simplify (App e1 e2) = App (simplify e1) (simplify e2)
566 simplify (Lit lit) = Lit lit
567 simplify (Note note e) = Note note (simplify e)
568 simplify (Cast e co) = if tcEqType (fst $ coercionKind co) (snd $ coercionKind co)
570 else Cast (simplify e) co
571 simplify (Lam v e) = Lam v (simplify e)
572 simplify (Type t) = Type t
573 simplify (Case e b ty as) = Case (simplify e) b ty (map (\(a,b,e) -> (a,b,simplify e)) as)
574 simplify (Let bind body) = foldr Let (simplify body) (simplifyBind bind)
576 simplifyBind :: Bind CoreBndr -> [Bind CoreBndr]
577 simplifyBind (NonRec b e) = [NonRec b (simplify e)]
578 simplifyBind (Rec []) = []
579 simplifyBind (Rec (rbs@((b,e):rbs'))) =
580 if or $ map (\x -> elemUFM x (exprFreeIds e)) (map fst rbs)
581 then [Rec (map (\(v,e) -> (v,simplify e)) rbs)]
582 else (NonRec b (simplify e)):(simplifyBind $ Rec rbs')
584 simplifyBinds = concatMap simplifyBind