The Desugarer: turning HsSyn into Core.
\begin{code}
-{-# OPTIONS -w #-}
--- The above warning supression flag is a temporary kludge.
--- While working on this module you are encouraged to remove it and fix
--- any warnings in the module. See
--- http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings
--- for details
-
module Desugar ( deSugar, deSugarExpr ) where
-#include "HsVersions.h"
-
import DynFlags
import StaticFlags
import HscTypes
import Id
import Name
import CoreSyn
-import OccurAnal
+import CoreSubst
+import CoqPass ( coqPassCoreToString, coqPassCoreToCore )
import PprCore
import DsMonad
import DsExpr
import DsExpr () -- Forces DsExpr to be compiled; DsBinds only
-- depends on DsExpr.hi-boot.
import Module
-import UniqFM
-import PackageConfig
import RdrName
import NameSet
-import VarSet
+import NameEnv
import Rules
-import CoreLint
-import CoreFVs
+import CoreMonad ( endPass, CoreToDo(..) )
import ErrUtils
-import ListSetOps
import Outputable
import SrcLoc
-import Maybes
-import FastString
-import Util
import Coverage
-import IOEnv
+import Util
+import MonadUtils
+import OrdList
+import Data.List
import Data.IORef
+import PrelNames
+import UniqSupply
+import UniqFM
+import CoreFVs
+import Type
+import Coercion
\end{code}
%************************************************************************
%************************************************************************
\begin{code}
-deSugar :: HscEnv -> ModLocation -> TcGblEnv -> IO (Maybe ModGuts)
+
+-- | Main entry point to the desugarer.
+deSugar :: HscEnv -> ModLocation -> TcGblEnv -> IO (Messages, Maybe ModGuts)
-- Can modify PCS by faulting in more declarations
deSugar hsc_env
tcg_type_env = type_env,
tcg_imports = imports,
tcg_exports = exports,
- tcg_inst_uses = dfun_uses_var,
- tcg_th_used = th_var,
tcg_keep = keep_var,
tcg_rdr_env = rdr_env,
tcg_fix_env = fix_env,
tcg_inst_env = inst_env,
tcg_fam_inst_env = fam_inst_env,
- tcg_deprecs = deprecs,
+ tcg_warns = warns,
+ tcg_anns = anns,
tcg_binds = binds,
- tcg_fords = fords,
- tcg_rules = rules,
- tcg_insts = insts,
- tcg_fam_insts = fam_insts,
- tcg_hpc = other_hpc_info })
+ tcg_imp_specs = imp_specs,
+ tcg_ev_binds = ev_binds,
+ tcg_fords = fords,
+ tcg_rules = rules,
+ tcg_vects = vects,
+ tcg_insts = insts,
+ tcg_fam_insts = fam_insts,
+ tcg_hpc = other_hpc_info })
= do { let dflags = hsc_dflags hsc_env
; showPass dflags "Desugar"
-- Desugar the program
; let export_set = availsToNameSet exports
- ; let auto_scc = mkAutoScc mod export_set
+ ; let auto_scc = mkAutoScc dflags mod export_set
; let target = hscTarget dflags
; let hpcInfo = emptyHpcInfo other_hpc_info
- ; mb_res <- case target of
- HscNothing -> return (Just ([], [], NoStubs, hpcInfo, emptyModBreaks))
- _ -> do (binds_cvr,ds_hpc_info, modBreaks)
- <- if (opt_Hpc
- || target == HscInterpreted)
- && (not (isHsBoot hsc_src))
- then addCoverageTicksToBinds dflags mod mod_loc (typeEnvTyCons type_env) binds
- else return (binds, hpcInfo, emptyModBreaks)
- initDs hsc_env mod rdr_env type_env $ do
- { core_prs <- dsTopLHsBinds auto_scc binds_cvr
- ; (ds_fords, foreign_prs) <- dsForeigns fords
- ; let all_prs = foreign_prs ++ core_prs
- local_bndrs = mkVarSet (map fst all_prs)
- ; ds_rules <- mappM (dsRule mod local_bndrs) rules
- ; return (all_prs, catMaybes ds_rules, ds_fords, ds_hpc_info, modBreaks)
- }
- ; case mb_res of {
- Nothing -> return Nothing ;
- Just (all_prs, ds_rules, ds_fords,ds_hpc_info, modBreaks) -> do
+ ; (msgs, mb_res)
+ <- case target of
+ HscNothing ->
+ return (emptyMessages,
+ Just ([], nilOL, [], [], NoStubs, hpcInfo, emptyModBreaks, undefined, undefined
+ , undefined
+ , undefined
+ , undefined
+ , undefined
+ , undefined
+ , undefined
+ , undefined
+ , undefined
+ , undefined
+ , undefined
+ , undefined
+ , undefined
+ , undefined
+ , undefined
+ , undefined
+ , undefined
+ , undefined
+ , undefined
+ , undefined
+ , undefined
+ , undefined
+ , undefined
+ , undefined
+ , undefined
+ ))
+ _ -> do
+ (binds_cvr,ds_hpc_info, modBreaks)
+ <- if (opt_Hpc
+ || target == HscInterpreted)
+ && (not (isHsBoot hsc_src))
+ then addCoverageTicksToBinds dflags mod mod_loc
+ (typeEnvTyCons type_env) binds
+ else return (binds, hpcInfo, emptyModBreaks)
+ initDs hsc_env mod rdr_env type_env $ do
+ do { ds_ev_binds <- dsEvBinds ev_binds
+ ; core_prs <- dsTopLHsBinds auto_scc binds_cvr
+ ; (spec_prs, spec_rules) <- dsImpSpecs imp_specs
+ ; (ds_fords, foreign_prs) <- dsForeigns fords
+ ; ds_rules <- mapMaybeM dsRule rules
+ ; ds_vects <- mapM dsVect vects
+ ; hetmet_brak <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_brak_name else return undefined
+ ; hetmet_esc <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_esc_name else return undefined
+ ; hetmet_flatten <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_flatten_name else return undefined
+ ; hetmet_unflatten <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_unflatten_name else return undefined
+ ; hetmet_flattened_id <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_flattened_id_name else return undefined
+ ; hetmet_PGArrow <- if dopt Opt_F_coqpass dflags then dsLookupTyCon hetmet_PGArrow_name else return undefined
+ ; hetmet_PGArrow_unit <- if dopt Opt_F_coqpass dflags then dsLookupTyCon hetmet_PGArrow_unit_name else return undefined
+ ; hetmet_PGArrow_tensor <- if dopt Opt_F_coqpass dflags then dsLookupTyCon hetmet_PGArrow_tensor_name else return undefined
+ ; hetmet_PGArrow_exponent <- if dopt Opt_F_coqpass dflags then dsLookupTyCon hetmet_PGArrow_exponent_name else return undefined
+ ; hetmet_pga_id <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_id_name else return undefined
+ ; hetmet_pga_comp <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_comp_name else return undefined
+ ; hetmet_pga_first <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_first_name else return undefined
+ ; hetmet_pga_second <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_second_name else return undefined
+ ; hetmet_pga_cancell <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_cancell_name else return undefined
+ ; hetmet_pga_cancelr <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_cancelr_name else return undefined
+ ; hetmet_pga_uncancell <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_uncancell_name else return undefined
+ ; hetmet_pga_uncancelr <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_uncancelr_name else return undefined
+ ; hetmet_pga_assoc <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_assoc_name else return undefined
+ ; hetmet_pga_unassoc <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_unassoc_name else return undefined
+ ; hetmet_pga_copy <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_copy_name else return undefined
+ ; hetmet_pga_drop <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_drop_name else return undefined
+ ; hetmet_pga_swap <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_swap_name else return undefined
+ ; hetmet_pga_applyl <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_applyl_name else return undefined
+ ; hetmet_pga_applyr <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_applyr_name else return undefined
+ ; hetmet_pga_curryl <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_curryl_name else return undefined
+ ; hetmet_pga_curryr <- if dopt Opt_F_coqpass dflags then dsLookupGlobalId hetmet_pga_curryr_name else return undefined
+ ; let hpc_init
+ | opt_Hpc = hpcInitCode mod ds_hpc_info
+ | otherwise = empty
+ ; return ( ds_ev_binds
+ , foreign_prs `appOL` core_prs `appOL` spec_prs
+ , spec_rules ++ ds_rules, ds_vects
+ , ds_fords `appendStubC` hpc_init
+ , ds_hpc_info, modBreaks, hetmet_brak, hetmet_esc
+ , hetmet_flatten
+ , hetmet_unflatten
+ , hetmet_flattened_id
+ , hetmet_PGArrow
+ , hetmet_PGArrow_unit
+ , hetmet_PGArrow_tensor
+ , hetmet_PGArrow_exponent
+ , hetmet_pga_id
+ , hetmet_pga_comp
+ , hetmet_pga_first
+ , hetmet_pga_second
+ , hetmet_pga_cancell
+ , hetmet_pga_cancelr
+ , hetmet_pga_uncancell
+ , hetmet_pga_uncancelr
+ , hetmet_pga_assoc
+ , hetmet_pga_unassoc
+ , hetmet_pga_copy
+ , hetmet_pga_drop
+ , hetmet_pga_swap
+ , hetmet_pga_applyl
+ , hetmet_pga_applyr
+ , hetmet_pga_curryl
+ , hetmet_pga_curryr
+ ) }
+
+ ; case mb_res of {
+ Nothing -> return (msgs, Nothing) ;
+ Just (ds_ev_binds, all_prs, all_rules, ds_vects, ds_fords,ds_hpc_info, modBreaks
+ , hetmet_brak, hetmet_esc
+ , hetmet_flatten
+ , hetmet_unflatten
+ , hetmet_flattened_id
+ , hetmet_PGArrow
+ , hetmet_PGArrow_unit
+ , hetmet_PGArrow_tensor
+ , hetmet_PGArrow_exponent
+ , hetmet_pga_id
+ , hetmet_pga_comp
+ , hetmet_pga_first
+ , hetmet_pga_second
+ , hetmet_pga_cancell
+ , hetmet_pga_cancelr
+ , hetmet_pga_uncancell
+ , hetmet_pga_uncancelr
+ , hetmet_pga_assoc
+ , hetmet_pga_unassoc
+ , hetmet_pga_copy
+ , hetmet_pga_drop
+ , hetmet_pga_swap
+ , hetmet_pga_applyl
+ , hetmet_pga_applyr
+ , hetmet_pga_curryl
+ , hetmet_pga_curryr) -> do
{ -- Add export flags to bindings
keep_alive <- readIORef keep_var
- ; let final_prs = addExportFlags target export_set
- keep_alive all_prs ds_rules
- ds_binds = [Rec final_prs]
+ ; let (rules_for_locals, rules_for_imps)
+ = partition isLocalRule all_rules
+ final_prs = addExportFlagsAndRules target
+ export_set keep_alive rules_for_locals (fromOL all_prs)
+
+ final_pgm = simplifyBinds $ combineEvBinds ds_ev_binds final_prs
-- Notice that we put the whole lot in a big Rec, even the foreign binds
-- When compiling PrelFloat, which defines data Float = F# Float#
-- we want F# to be in scope in the foreign marshalling code!
-- You might think it doesn't matter, but the simplifier brings all top-level
-- things into the in-scope set before simplifying; so we get no unfolding for F#!
- -- Lint result if necessary
- ; endPass dflags "Desugar" Opt_D_dump_ds ds_binds
-
- -- Dump output
- ; doIfSet (dopt Opt_D_dump_ds dflags)
- (printDump (ppr_ds_rules ds_rules))
-
- ; used_names <- mkUsedNames tcg_env
+ -- Lint result if necessary, and print
+ ; dumpIfSet_dyn dflags Opt_D_dump_ds "Desugared, before opt" $
+ (vcat [ pprCoreBindings final_pgm
+ , pprRules rules_for_imps ])
+
+ ; (final_pgm', rules_for_imps') <- if dopt Opt_F_simpleopt_before_flatten dflags
+ then simpleOptPgm dflags final_pgm rules_for_imps
+ else return (final_pgm, rules_for_imps)
+
+ ; ds_binds <- if dopt Opt_F_coqpass dflags
+ then do { us <- mkSplitUniqSupply '~'
+ ; let do_flatten = dopt Opt_F_flatten dflags
+ ; let do_skolemize = dopt Opt_F_skolemize dflags
+ ; return (coqPassCoreToCore
+ do_flatten
+ do_skolemize
+ hetmet_brak
+ hetmet_esc
+ hetmet_flatten
+ hetmet_unflatten
+ hetmet_flattened_id
+ us
+ final_pgm'
+ hetmet_PGArrow
+ hetmet_PGArrow_unit
+ hetmet_PGArrow_tensor
+ hetmet_PGArrow_exponent
+ hetmet_pga_id
+ hetmet_pga_comp
+ hetmet_pga_first
+ hetmet_pga_second
+ hetmet_pga_cancell
+ hetmet_pga_cancelr
+ hetmet_pga_uncancell
+ hetmet_pga_uncancelr
+ hetmet_pga_assoc
+ hetmet_pga_unassoc
+ hetmet_pga_copy
+ hetmet_pga_drop
+ hetmet_pga_swap
+ hetmet_pga_applyl
+ hetmet_pga_applyr
+ hetmet_pga_curryl
+ hetmet_pga_curryr)
+ }
+ else return final_pgm
+
+ ; (ds_binds', ds_rules_for_imps) <- if dopt Opt_F_simpleopt_before_flatten dflags
+ then return (ds_binds, rules_for_imps')
+ else simpleOptPgm dflags ds_binds rules_for_imps'
+ -- The simpleOptPgm gets rid of type
+ -- bindings plus any stupid dead code
+
+ ; dumpIfSet_dyn dflags Opt_D_dump_proofs "Coq Pass Output" $ text $ coqPassCoreToString ds_binds'
+
+ ; dumpIfSet_dyn dflags Opt_D_coqpass "After Coq Pass" (text $ showSDoc $ pprCoreBindings ds_binds')
+
+ ; endPass dflags CoreDesugar ds_binds' ds_rules_for_imps
+
+ ; let used_names = mkUsedNames tcg_env
; deps <- mkDependencies tcg_env
; let mod_guts = ModGuts {
mg_dir_imps = imp_mods imports,
mg_rdr_env = rdr_env,
mg_fix_env = fix_env,
- mg_deprecs = deprecs,
+ mg_warns = warns,
+ mg_anns = anns,
mg_types = type_env,
mg_insts = insts,
mg_fam_insts = fam_insts,
mg_inst_env = inst_env,
mg_fam_inst_env = fam_inst_env,
- mg_rules = ds_rules,
- mg_binds = ds_binds,
+ mg_rules = ds_rules_for_imps,
+ mg_binds = ds_binds',
mg_foreign = ds_fords,
mg_hpc_info = ds_hpc_info,
mg_modBreaks = modBreaks,
+ mg_vect_decls = ds_vects,
mg_vect_info = noVectInfo
}
- ; return (Just mod_guts)
+ ; return (msgs, Just mod_guts)
}}}
-mkAutoScc :: Module -> NameSet -> AutoScc
-mkAutoScc mod exports
+dsImpSpecs :: [LTcSpecPrag] -> DsM (OrdList (Id,CoreExpr), [CoreRule])
+dsImpSpecs imp_specs
+ = do { spec_prs <- mapMaybeM (dsSpec Nothing) imp_specs
+ ; let (spec_binds, spec_rules) = unzip spec_prs
+ ; return (concatOL spec_binds, spec_rules) }
+
+combineEvBinds :: [DsEvBind] -> [(Id,CoreExpr)] -> [CoreBind]
+-- Top-level bindings can include coercion bindings, but not via superclasses
+-- See Note [Top-level evidence]
+combineEvBinds [] val_prs
+ = [Rec val_prs]
+combineEvBinds (LetEvBind (NonRec b r) : bs) val_prs
+ | isId b = combineEvBinds bs ((b,r):val_prs)
+ | otherwise = NonRec b r : combineEvBinds bs val_prs
+combineEvBinds (LetEvBind (Rec prs) : bs) val_prs
+ = combineEvBinds bs (prs ++ val_prs)
+combineEvBinds (CaseEvBind x _ _ : _) _
+ = pprPanic "topEvBindPairs" (ppr x)
+\end{code}
+
+Note [Top-level evidence]
+~~~~~~~~~~~~~~~~~~~~~~~~~
+Top-level evidence bindings may be mutually recursive with the top-level value
+bindings, so we must put those in a Rec. But we can't put them *all* in a Rec
+because the occurrence analyser doesn't teke account of type/coercion variables
+when computing dependencies.
+
+So we pull out the type/coercion variables (which are in dependency order),
+and Rec the rest.
+
+
+\begin{code}
+mkAutoScc :: DynFlags -> Module -> NameSet -> AutoScc
+mkAutoScc dflags mod exports
| not opt_SccProfilingOn -- No profiling
= NoSccs
- | opt_AutoSccsOnAllToplevs -- Add auto-scc on all top-level things
- = AddSccs mod (\id -> True)
- | opt_AutoSccsOnExportedToplevs -- Only on exported things
+ -- Add auto-scc on all top-level things
+ | dopt Opt_AutoSccsOnAllToplevs dflags
+ = AddSccs mod (\id -> not $ isDerivedOccName $ getOccName id)
+ -- See #1641. This is pretty yucky, but I can't see a better way
+ -- to identify compiler-generated Ids, and at least this should
+ -- catch them all.
+ -- Only on exported things
+ | dopt Opt_AutoSccsOnExportedToplevs dflags
= AddSccs mod (\id -> idName id `elemNameSet` exports)
| otherwise
= NoSccs
-
deSugarExpr :: HscEnv
-> Module -> GlobalRdrEnv -> TypeEnv
-> LHsExpr Id
- -> IO (Maybe CoreExpr)
+ -> IO (Messages, Maybe CoreExpr)
-- Prints its own errors; returns Nothing if error occurred
-deSugarExpr hsc_env this_mod rdr_env type_env tc_expr
- = do { let dflags = hsc_dflags hsc_env
- ; showPass dflags "Desugar"
+deSugarExpr hsc_env this_mod rdr_env type_env tc_expr = do
+ let dflags = hsc_dflags hsc_env
+ showPass dflags "Desugar"
- -- Do desugaring
- ; mb_core_expr <- initDs hsc_env this_mod rdr_env type_env $
- dsLExpr tc_expr
+ -- Do desugaring
+ (msgs, mb_core_expr) <- initDs hsc_env this_mod rdr_env type_env $
+ dsLExpr tc_expr
- ; case mb_core_expr of {
- Nothing -> return Nothing ;
- Just expr -> do {
+ case mb_core_expr of
+ Nothing -> return (msgs, Nothing)
+ Just expr -> do
- -- Dump output
- dumpIfSet_dyn dflags Opt_D_dump_ds "Desugared" (pprCoreExpr expr)
+ -- Dump output
+ dumpIfSet_dyn dflags Opt_D_dump_ds "Desugared" (pprCoreExpr expr)
- ; return (Just expr) } } }
+ return (msgs, Just expr)
+\end{code}
--- addExportFlags
--- Set the no-discard flag if either
--- a) the Id is exported
--- b) it's mentioned in the RHS of an orphan rule
--- c) it's in the keep-alive set
---
--- It means that the binding won't be discarded EVEN if the binding
--- ends up being trivial (v = w) -- the simplifier would usually just
--- substitute w for v throughout, but we don't apply the substitution to
--- the rules (maybe we should?), so this substitution would make the rule
--- bogus.
-
--- You might wonder why exported Ids aren't already marked as such;
--- it's just because the type checker is rather busy already and
--- I didn't want to pass in yet another mapping.
-
-addExportFlags target exports keep_alive prs rules
- = [(add_export bndr, rhs) | (bndr,rhs) <- prs]
+%************************************************************************
+%* *
+%* Add rules and export flags to binders
+%* *
+%************************************************************************
+
+\begin{code}
+addExportFlagsAndRules
+ :: HscTarget -> NameSet -> NameSet -> [CoreRule]
+ -> [(Id, t)] -> [(Id, t)]
+addExportFlagsAndRules target exports keep_alive rules prs
+ = mapFst add_one prs
where
- add_export bndr
- | dont_discard bndr = setIdExported bndr
+ add_one bndr = add_rules name (add_export name bndr)
+ where
+ name = idName bndr
+
+ ---------- Rules --------
+ -- See Note [Attach rules to local ids]
+ -- NB: the binder might have some existing rules,
+ -- arising from specialisation pragmas
+ add_rules name bndr
+ | Just rules <- lookupNameEnv rule_base name
+ = bndr `addIdSpecialisations` rules
+ | otherwise
+ = bndr
+ rule_base = extendRuleBaseList emptyRuleBase rules
+
+ ---------- Export flag --------
+ -- See Note [Adding export flags]
+ add_export name bndr
+ | dont_discard name = setIdExported bndr
| otherwise = bndr
- orph_rhs_fvs = unionVarSets [ ruleRhsFreeVars rule
- | rule <- rules,
- not (isLocalRule rule) ]
- -- A non-local rule keeps alive the free vars of its right-hand side.
- -- (A "non-local" is one whose head function is not locally defined.)
- -- Local rules are (later, after gentle simplification)
- -- attached to the Id, and that keeps the rhs free vars alive.
-
- dont_discard bndr = is_exported name
+ dont_discard :: Name -> Bool
+ dont_discard name = is_exported name
|| name `elemNameSet` keep_alive
- || bndr `elemVarSet` orph_rhs_fvs
- where
- name = idName bndr
-- In interactive mode, we don't want to discard any top-level
-- entities at all (eg. do not inline them away during
is_exported :: Name -> Bool
is_exported | target == HscInterpreted = isExternalName
| otherwise = (`elemNameSet` exports)
-
-ppr_ds_rules [] = empty
-ppr_ds_rules rules
- = text "" $$ text "-------------- DESUGARED RULES -----------------" $$
- pprRules rules
\end{code}
+Note [Adding export flags]
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+Set the no-discard flag if either
+ a) the Id is exported
+ b) it's mentioned in the RHS of an orphan rule
+ c) it's in the keep-alive set
+
+It means that the binding won't be discarded EVEN if the binding
+ends up being trivial (v = w) -- the simplifier would usually just
+substitute w for v throughout, but we don't apply the substitution to
+the rules (maybe we should?), so this substitution would make the rule
+bogus.
+
+You might wonder why exported Ids aren't already marked as such;
+it's just because the type checker is rather busy already and
+I didn't want to pass in yet another mapping.
+
+Note [Attach rules to local ids]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Find the rules for locally-defined Ids; then we can attach them
+to the binders in the top-level bindings
+
+Reason
+ - It makes the rules easier to look up
+ - It means that transformation rules and specialisations for
+ locally defined Ids are handled uniformly
+ - It keeps alive things that are referred to only from a rule
+ (the occurrence analyser knows about rules attached to Ids)
+ - It makes sure that, when we apply a rule, the free vars
+ of the RHS are more likely to be in scope
+ - The imported rules are carried in the in-scope set
+ which is extended on each iteration by the new wave of
+ local binders; any rules which aren't on the binding will
+ thereby get dropped
+
%************************************************************************
%* *
%************************************************************************
\begin{code}
-dsRule :: Module -> IdSet -> LRuleDecl Id -> DsM (Maybe CoreRule)
-dsRule mod in_scope (L loc (HsRule name act vars lhs tv_lhs rhs fv_rhs))
+dsRule :: LRuleDecl Id -> DsM (Maybe CoreRule)
+dsRule (L loc (HsRule name act vars lhs _tv_lhs rhs _fv_rhs))
= putSrcSpanDs loc $
- do { let bndrs = [var | RuleBndr (L _ var) <- vars]
- ; lhs' <- dsLExpr lhs
- ; rhs' <- dsLExpr rhs
+ do { let bndrs' = [var | RuleBndr (L _ var) <- vars]
+
+ ; lhs' <- unsetOptM Opt_EnableRewriteRules $
+ unsetOptM Opt_WarnIdentities $
+ dsLExpr lhs -- Note [Desugaring RULE left hand sides]
+
+ ; rhs' <- dsLExpr rhs
- ; case decomposeRuleLhs (occurAnalyseExpr lhs') of {
- Nothing -> do { warnDs msg; return Nothing } ;
- Just (fn_id, args) -> do
-
-- Substitute the dict bindings eagerly,
-- and take the body apart into a (f args) form
- { let local_rule = isLocalId fn_id
+ ; case decomposeRuleLhs bndrs' lhs' of {
+ Left msg -> do { warnDs msg; return Nothing } ;
+ Right (final_bndrs, fn_id, args) -> do
+
+ { let is_local = isLocalId fn_id
-- NB: isLocalId is False of implicit Ids. This is good becuase
-- we don't want to attach rules to the bindings of implicit Ids,
-- because they don't show up in the bindings until just before code gen
fn_name = idName fn_id
-
- rule = Rule { ru_name = name, ru_fn = fn_name, ru_act = act,
- ru_bndrs = bndrs, ru_args = args, ru_rhs = rhs',
- ru_rough = roughTopNames args,
- ru_local = local_rule }
+ final_rhs = simpleOptExpr rhs' -- De-crap it
+ rule = mkRule False {- Not auto -} is_local
+ name act fn_name final_bndrs args final_rhs
; return (Just rule)
} } }
- where
- msg = hang (ptext SLIT("RULE left-hand side too complicated to desugar; ignored"))
- 2 (ppr lhs)
+\end{code}
+
+Note [Desugaring RULE left hand sides]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+For the LHS of a RULE we do *not* want to desugar
+ [x] to build (\cn. x `c` n)
+We want to leave explicit lists simply as chains
+of cons's. We can achieve that slightly indirectly by
+switching off EnableRewriteRules. See DsExpr.dsExplicitList.
+
+That keeps the desugaring of list comprehensions simple too.
+
+
+
+Nor do we want to warn of conversion identities on the LHS;
+the rule is precisly to optimise them:
+ {-# RULES "fromRational/id" fromRational = id :: Rational -> Rational #-}
+
+
+%************************************************************************
+%* *
+%* Desugaring vectorisation declarations
+%* *
+%************************************************************************
+
+\begin{code}
+dsVect :: LVectDecl Id -> DsM CoreVect
+dsVect (L loc (HsVect v rhs))
+ = putSrcSpanDs loc $
+ do { rhs' <- fmapMaybeM dsLExpr rhs
+ ; return $ Vect (unLoc v) rhs'
+ }
+-- dsVect (L loc (HsVect v Nothing))
+-- = return $ Vect v Nothing
+-- dsVect (L loc (HsVect v (Just rhs)))
+-- = putSrcSpanDs loc $
+-- do { rhs' <- dsLExpr rhs
+-- ; return $ Vect v (Just rhs')
+-- }
+\end{code}
+
+
+
+\begin{code}
+--
+-- Simplification routines run before the flattener. We can't use
+-- simpleOptPgm -- it doesn't preserve the order of subexpressions or
+-- let-binding groups.
+--
+simplify :: Expr CoreBndr -> Expr CoreBndr
+simplify (Var v) = Var v
+simplify (App e1 e2) = App (simplify e1) (simplify e2)
+simplify (Lit lit) = Lit lit
+simplify (Note note e) = Note note (simplify e)
+simplify (Cast e co) = if tcEqType (fst $ coercionKind co) (snd $ coercionKind co)
+ then simplify e
+ else Cast (simplify e) co
+simplify (Lam v e) = Lam v (simplify e)
+simplify (Type t) = Type t
+simplify (Case e b ty as) = Case (simplify e) b ty (map (\(a,b,e) -> (a,b,simplify e)) as)
+simplify (Let bind body) = foldr Let (simplify body) (simplifyBind bind)
+
+simplifyBind :: Bind CoreBndr -> [Bind CoreBndr]
+simplifyBind (NonRec b e) = [NonRec b (simplify e)]
+simplifyBind (Rec []) = []
+simplifyBind (Rec (rbs@((b,e):rbs'))) =
+ if or $ map (\x -> elemUFM x (exprFreeIds e)) (map fst rbs)
+ then [Rec (map (\(v,e) -> (v,simplify e)) rbs)]
+ else (NonRec b (simplify e)):(simplifyBind $ Rec rbs')
+
+simplifyBinds = concatMap simplifyBind
\end{code}
projects / ghc-hetmet.git / blobdiff