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(..) )
48 %************************************************************************
50 %* The main function: deSugar
52 %************************************************************************
55 -- | Main entry point to the desugarer.
56 deSugar :: HscEnv -> ModLocation -> TcGblEnv -> IO (Messages, Maybe ModGuts)
57 -- Can modify PCS by faulting in more declarations
61 tcg_env@(TcGblEnv { tcg_mod = mod,
63 tcg_type_env = type_env,
64 tcg_imports = imports,
65 tcg_exports = exports,
67 tcg_rdr_env = rdr_env,
68 tcg_fix_env = fix_env,
69 tcg_inst_env = inst_env,
70 tcg_fam_inst_env = fam_inst_env,
74 tcg_imp_specs = imp_specs,
75 tcg_ev_binds = ev_binds,
80 tcg_fam_insts = fam_insts,
81 tcg_hpc = other_hpc_info })
83 = do { let dflags = hsc_dflags hsc_env
84 ; showPass dflags "Desugar"
86 -- Desugar the program
87 ; let export_set = availsToNameSet exports
88 ; let auto_scc = mkAutoScc dflags mod export_set
89 ; let target = hscTarget dflags
90 ; let hpcInfo = emptyHpcInfo other_hpc_info
94 return (emptyMessages,
95 Just ([], nilOL, [], [], NoStubs, hpcInfo, emptyModBreaks, undefined, undefined
119 (binds_cvr,ds_hpc_info, modBreaks)
121 || target == HscInterpreted)
122 && (not (isHsBoot hsc_src))
123 then addCoverageTicksToBinds dflags mod mod_loc
124 (typeEnvTyCons type_env) binds
125 else return (binds, hpcInfo, emptyModBreaks)
126 initDs hsc_env mod rdr_env type_env $ do
127 do { ds_ev_binds <- dsEvBinds ev_binds
128 ; core_prs <- dsTopLHsBinds auto_scc binds_cvr
129 ; (spec_prs, spec_rules) <- dsImpSpecs imp_specs
130 ; (ds_fords, foreign_prs) <- dsForeigns fords
131 ; ds_rules <- mapMaybeM dsRule rules
132 ; ds_vects <- mapM dsVect vects
133 ; hetmet_brak <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_brak_name else return undefined
134 ; hetmet_esc <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_esc_name else return undefined
135 ; hetmet_flatten <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_flatten_name else return undefined
136 ; hetmet_unflatten <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_unflatten_name else return undefined
137 ; hetmet_flattened_id <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_flattened_id_name else return undefined
138 ; hetmet_PGArrow <- if dopt Opt_F_coqpass dflags then dsLookupTyCon hetmet_PGArrow_name else return undefined
139 ; hetmet_pga_id <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_id_name else return undefined
140 ; hetmet_pga_comp <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_comp_name else return undefined
141 ; hetmet_pga_first <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_first_name else return undefined
142 ; hetmet_pga_second <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_second_name else return undefined
143 ; hetmet_pga_cancell <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_cancell_name else return undefined
144 ; hetmet_pga_cancelr <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_cancelr_name else return undefined
145 ; hetmet_pga_uncancell <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_uncancell_name else return undefined
146 ; hetmet_pga_uncancelr <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_uncancelr_name else return undefined
147 ; hetmet_pga_assoc <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_assoc_name else return undefined
148 ; hetmet_pga_unassoc <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_unassoc_name else return undefined
149 ; hetmet_pga_copy <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_copy_name else return undefined
150 ; hetmet_pga_drop <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_drop_name else return undefined
151 ; hetmet_pga_swap <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_swap_name else return undefined
152 ; hetmet_pga_applyl <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_applyl_name else return undefined
153 ; hetmet_pga_applyr <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_applyr_name else return undefined
154 ; hetmet_pga_curryl <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_curryl_name else return undefined
155 ; hetmet_pga_curryr <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_curryr_name else return undefined
157 | opt_Hpc = hpcInitCode mod ds_hpc_info
159 ; return ( ds_ev_binds
160 , foreign_prs `appOL` core_prs `appOL` spec_prs
161 , spec_rules ++ ds_rules, ds_vects
162 , ds_fords `appendStubC` hpc_init
163 , ds_hpc_info, modBreaks, hetmet_brak, hetmet_esc
166 , hetmet_flattened_id
174 , hetmet_pga_uncancell
175 , hetmet_pga_uncancelr
188 Nothing -> return (msgs, Nothing) ;
189 Just (ds_ev_binds, all_prs, all_rules, ds_vects, ds_fords,ds_hpc_info, modBreaks
190 , hetmet_brak, hetmet_esc
193 , hetmet_flattened_id
201 , hetmet_pga_uncancell
202 , hetmet_pga_uncancelr
211 , hetmet_pga_curryr) -> do
213 { -- Add export flags to bindings
214 keep_alive <- readIORef keep_var
215 ; let (rules_for_locals, rules_for_imps)
216 = partition isLocalRule all_rules
217 final_prs = addExportFlagsAndRules target
218 export_set keep_alive rules_for_locals (fromOL all_prs)
220 final_pgm = combineEvBinds ds_ev_binds final_prs
221 -- Notice that we put the whole lot in a big Rec, even the foreign binds
222 -- When compiling PrelFloat, which defines data Float = F# Float#
223 -- we want F# to be in scope in the foreign marshalling code!
224 -- You might think it doesn't matter, but the simplifier brings all top-level
225 -- things into the in-scope set before simplifying; so we get no unfolding for F#!
227 -- Lint result if necessary, and print
228 ; dumpIfSet_dyn dflags Opt_D_dump_ds "Desugared, before opt" $
229 (vcat [ pprCoreBindings final_pgm
230 , pprRules rules_for_imps ])
232 ; (ds_binds, ds_rules_for_imps) <- simpleOptPgm dflags final_pgm rules_for_imps
233 -- The simpleOptPgm gets rid of type
234 -- bindings plus any stupid dead code
236 ; ds_binds' <- if dopt Opt_F_coqpass dflags
237 then do { us <- mkSplitUniqSupply '~'
238 ; return (coqPassCoreToCore
267 ; dumpIfSet_dyn dflags Opt_D_coqpass "Coq Pass Output" $ text $ coqPassCoreToString ds_binds'
269 ; dumpIfSet_dyn dflags Opt_D_dump_coqpass "After Coq Pass" (text $ showSDoc $ pprCoreBindings ds_binds')
271 ; endPass dflags CoreDesugar ds_binds' ds_rules_for_imps
273 ; let used_names = mkUsedNames tcg_env
274 ; deps <- mkDependencies tcg_env
276 ; let mod_guts = ModGuts {
278 mg_boot = isHsBoot hsc_src,
279 mg_exports = exports,
281 mg_used_names = used_names,
282 mg_dir_imps = imp_mods imports,
283 mg_rdr_env = rdr_env,
284 mg_fix_env = fix_env,
289 mg_fam_insts = fam_insts,
290 mg_inst_env = inst_env,
291 mg_fam_inst_env = fam_inst_env,
292 mg_rules = ds_rules_for_imps,
293 mg_binds = ds_binds',
294 mg_foreign = ds_fords,
295 mg_hpc_info = ds_hpc_info,
296 mg_modBreaks = modBreaks,
297 mg_vect_decls = ds_vects,
298 mg_vect_info = noVectInfo
300 ; return (msgs, Just mod_guts)
303 dsImpSpecs :: [LTcSpecPrag] -> DsM (OrdList (Id,CoreExpr), [CoreRule])
305 = do { spec_prs <- mapMaybeM (dsSpec Nothing) imp_specs
306 ; let (spec_binds, spec_rules) = unzip spec_prs
307 ; return (concatOL spec_binds, spec_rules) }
309 combineEvBinds :: [DsEvBind] -> [(Id,CoreExpr)] -> [CoreBind]
310 -- Top-level bindings can include coercion bindings, but not via superclasses
311 -- See Note [Top-level evidence]
312 combineEvBinds [] val_prs
314 combineEvBinds (LetEvBind (NonRec b r) : bs) val_prs
315 | isId b = combineEvBinds bs ((b,r):val_prs)
316 | otherwise = NonRec b r : combineEvBinds bs val_prs
317 combineEvBinds (LetEvBind (Rec prs) : bs) val_prs
318 = combineEvBinds bs (prs ++ val_prs)
319 combineEvBinds (CaseEvBind x _ _ : _) _
320 = pprPanic "topEvBindPairs" (ppr x)
323 Note [Top-level evidence]
324 ~~~~~~~~~~~~~~~~~~~~~~~~~
325 Top-level evidence bindings may be mutually recursive with the top-level value
326 bindings, so we must put those in a Rec. But we can't put them *all* in a Rec
327 because the occurrence analyser doesn't teke account of type/coercion variables
328 when computing dependencies.
330 So we pull out the type/coercion variables (which are in dependency order),
335 mkAutoScc :: DynFlags -> Module -> NameSet -> AutoScc
336 mkAutoScc dflags mod exports
337 | not opt_SccProfilingOn -- No profiling
339 -- Add auto-scc on all top-level things
340 | dopt Opt_AutoSccsOnAllToplevs dflags
341 = AddSccs mod (\id -> not $ isDerivedOccName $ getOccName id)
342 -- See #1641. This is pretty yucky, but I can't see a better way
343 -- to identify compiler-generated Ids, and at least this should
345 -- Only on exported things
346 | dopt Opt_AutoSccsOnExportedToplevs dflags
347 = AddSccs mod (\id -> idName id `elemNameSet` exports)
351 deSugarExpr :: HscEnv
352 -> Module -> GlobalRdrEnv -> TypeEnv
354 -> IO (Messages, Maybe CoreExpr)
355 -- Prints its own errors; returns Nothing if error occurred
357 deSugarExpr hsc_env this_mod rdr_env type_env tc_expr = do
358 let dflags = hsc_dflags hsc_env
359 showPass dflags "Desugar"
362 (msgs, mb_core_expr) <- initDs hsc_env this_mod rdr_env type_env $
366 Nothing -> return (msgs, Nothing)
370 dumpIfSet_dyn dflags Opt_D_dump_ds "Desugared" (pprCoreExpr expr)
372 return (msgs, Just expr)
375 %************************************************************************
377 %* Add rules and export flags to binders
379 %************************************************************************
382 addExportFlagsAndRules
383 :: HscTarget -> NameSet -> NameSet -> [CoreRule]
384 -> [(Id, t)] -> [(Id, t)]
385 addExportFlagsAndRules target exports keep_alive rules prs
388 add_one bndr = add_rules name (add_export name bndr)
392 ---------- Rules --------
393 -- See Note [Attach rules to local ids]
394 -- NB: the binder might have some existing rules,
395 -- arising from specialisation pragmas
397 | Just rules <- lookupNameEnv rule_base name
398 = bndr `addIdSpecialisations` rules
401 rule_base = extendRuleBaseList emptyRuleBase rules
403 ---------- Export flag --------
404 -- See Note [Adding export flags]
406 | dont_discard name = setIdExported bndr
409 dont_discard :: Name -> Bool
410 dont_discard name = is_exported name
411 || name `elemNameSet` keep_alive
413 -- In interactive mode, we don't want to discard any top-level
414 -- entities at all (eg. do not inline them away during
415 -- simplification), and retain them all in the TypeEnv so they are
416 -- available from the command line.
418 -- isExternalName separates the user-defined top-level names from those
419 -- introduced by the type checker.
420 is_exported :: Name -> Bool
421 is_exported | target == HscInterpreted = isExternalName
422 | otherwise = (`elemNameSet` exports)
426 Note [Adding export flags]
427 ~~~~~~~~~~~~~~~~~~~~~~~~~~
428 Set the no-discard flag if either
429 a) the Id is exported
430 b) it's mentioned in the RHS of an orphan rule
431 c) it's in the keep-alive set
433 It means that the binding won't be discarded EVEN if the binding
434 ends up being trivial (v = w) -- the simplifier would usually just
435 substitute w for v throughout, but we don't apply the substitution to
436 the rules (maybe we should?), so this substitution would make the rule
439 You might wonder why exported Ids aren't already marked as such;
440 it's just because the type checker is rather busy already and
441 I didn't want to pass in yet another mapping.
443 Note [Attach rules to local ids]
444 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
445 Find the rules for locally-defined Ids; then we can attach them
446 to the binders in the top-level bindings
449 - It makes the rules easier to look up
450 - It means that transformation rules and specialisations for
451 locally defined Ids are handled uniformly
452 - It keeps alive things that are referred to only from a rule
453 (the occurrence analyser knows about rules attached to Ids)
454 - It makes sure that, when we apply a rule, the free vars
455 of the RHS are more likely to be in scope
456 - The imported rules are carried in the in-scope set
457 which is extended on each iteration by the new wave of
458 local binders; any rules which aren't on the binding will
462 %************************************************************************
464 %* Desugaring transformation rules
466 %************************************************************************
469 dsRule :: LRuleDecl Id -> DsM (Maybe CoreRule)
470 dsRule (L loc (HsRule name act vars lhs _tv_lhs rhs _fv_rhs))
472 do { let bndrs' = [var | RuleBndr (L _ var) <- vars]
474 ; lhs' <- unsetOptM Opt_EnableRewriteRules $
475 unsetOptM Opt_WarnIdentities $
476 dsLExpr lhs -- Note [Desugaring RULE left hand sides]
478 ; rhs' <- dsLExpr rhs
480 -- Substitute the dict bindings eagerly,
481 -- and take the body apart into a (f args) form
482 ; case decomposeRuleLhs bndrs' lhs' of {
483 Left msg -> do { warnDs msg; return Nothing } ;
484 Right (final_bndrs, fn_id, args) -> do
486 { let is_local = isLocalId fn_id
487 -- NB: isLocalId is False of implicit Ids. This is good becuase
488 -- we don't want to attach rules to the bindings of implicit Ids,
489 -- because they don't show up in the bindings until just before code gen
490 fn_name = idName fn_id
491 final_rhs = simpleOptExpr rhs' -- De-crap it
492 rule = mkRule False {- Not auto -} is_local
493 name act fn_name final_bndrs args final_rhs
498 Note [Desugaring RULE left hand sides]
499 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
500 For the LHS of a RULE we do *not* want to desugar
501 [x] to build (\cn. x `c` n)
502 We want to leave explicit lists simply as chains
503 of cons's. We can achieve that slightly indirectly by
504 switching off EnableRewriteRules. See DsExpr.dsExplicitList.
506 That keeps the desugaring of list comprehensions simple too.
508 Nor do we want to warn of conversion identities on the LHS;
509 the rule is precisly to optimise them:
510 {-# RULES "fromRational/id" fromRational = id :: Rational -> Rational #-}
513 %************************************************************************
515 %* Desugaring vectorisation declarations
517 %************************************************************************
520 dsVect :: LVectDecl Id -> DsM CoreVect
521 dsVect (L loc (HsVect v rhs))
523 do { rhs' <- fmapMaybeM dsLExpr rhs
524 ; return $ Vect (unLoc v) rhs'
526 -- dsVect (L loc (HsVect v Nothing))
527 -- = return $ Vect v Nothing
528 -- dsVect (L loc (HsVect v (Just rhs)))
529 -- = putSrcSpanDs loc $
530 -- do { rhs' <- dsLExpr rhs
531 -- ; return $ Vect v (Just rhs')