add -fflatten and -funsafe-skolemize flags

[ghc-hetmet.git] / compiler / deSugar / Desugar.lhs

diff --git a/compiler/deSugar/Desugar.lhs b/compiler/deSugar/Desugar.lhs
index 64fff0d..f219c01 100644 (file)
--- a/compiler/deSugar/Desugar.lhs
+++ b/compiler/deSugar/Desugar.lhs
@@ -17,6 +17,8 @@ import MkIface
 import Id
 import Name
 import CoreSyn
 import Id
 import Name
 import CoreSyn

+import CoreSubst
+import CoqPass ( coqPassCoreToString, coqPassCoreToCore )

 import PprCore
 import DsMonad
 import DsExpr
 import PprCore
 import DsMonad
 import DsExpr

@@ -27,16 +29,24 @@ import DsExpr               ()      -- Forces DsExpr to be compiled; DsBinds only
 import Module
 import RdrName
 import NameSet
 import Module
 import RdrName
 import NameSet

+import NameEnv

 import Rules
 import CoreMonad       ( endPass, CoreToDo(..) )
 import ErrUtils
 import Outputable
 import SrcLoc
 import Rules
 import CoreMonad       ( endPass, CoreToDo(..) )
 import ErrUtils
 import Outputable
 import SrcLoc

-import Maybes
-import FastString

 import Coverage
 import Coverage

-
+import Util
+import MonadUtils
+import OrdList
+import Data.List

 import Data.IORef
 import Data.IORef

+import PrelNames
+import UniqSupply
+import UniqFM
+import CoreFVs
+import Type
+import Coercion

 \end{code}
 
 %************************************************************************
 \end{code}
 
 %************************************************************************

@@ -46,6 +56,7 @@ import Data.IORef
 %************************************************************************
 
 \begin{code}
 %************************************************************************
 
 \begin{code}

+

 -- | Main entry point to the desugarer.
 deSugar :: HscEnv -> ModLocation -> TcGblEnv -> IO (Messages, Maybe ModGuts)
 -- Can modify PCS by faulting in more declarations
 -- | Main entry point to the desugarer.
 deSugar :: HscEnv -> ModLocation -> TcGblEnv -> IO (Messages, Maybe ModGuts)
 -- Can modify PCS by faulting in more declarations

@@ -65,11 +76,14 @@ deSugar hsc_env
                            tcg_warns        = warns,
                            tcg_anns         = anns,
                            tcg_binds        = binds,
                            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"
 
   = do { let dflags = hsc_dflags hsc_env
         ; showPass dflags "Desugar"

@@ -83,44 +97,204 @@ deSugar hsc_env
               <- case target of
                   HscNothing ->
                        return (emptyMessages,
               <- case target of
                   HscNothing ->
                        return (emptyMessages,

-                               Just ([], [], NoStubs, hpcInfo, emptyModBreaks))
+                               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))
                    _        -> 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 
+                              then addCoverageTicksToBinds dflags mod mod_loc
+                                                           (typeEnvTyCons type_env) binds 

                               else return (binds, hpcInfo, emptyModBreaks)
                      initDs hsc_env mod rdr_env type_env $ do
                               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
-                        ds_rules <- mapM dsRule rules
-                        return (all_prs, catMaybes ds_rules, ds_fords, ds_hpc_info, modBreaks)
-
-       ; case mb_res of {
-          Nothing -> return (msgs, Nothing) ;
-          Just (all_prs, ds_rules, ds_fords,ds_hpc_info, modBreaks) -> 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
 
        {       -- Add export flags to bindings
          keep_alive <- readIORef keep_var

-       ; let final_prs = addExportFlags target export_set
-                                 keep_alive all_prs 
-             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#!
 
        -- 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 CoreDesugar ds_binds ds_rules
-
-       -- 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 ])
+
+        ; 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) <- 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 {     
        ; deps <- mkDependencies tcg_env
 
         ; let mod_guts = ModGuts {     

@@ -139,16 +313,49 @@ deSugar hsc_env
                mg_fam_insts    = fam_insts,
                mg_inst_env     = inst_env,
                mg_fam_inst_env = fam_inst_env,
                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_foreign      = ds_fords,
                mg_hpc_info     = ds_hpc_info,
                 mg_modBreaks    = modBreaks,

+                mg_vect_decls   = ds_vects,

                 mg_vect_info    = noVectInfo
               }
         ; return (msgs, Just mod_guts)
        }}}
 
                 mg_vect_info    = noVectInfo
               }
         ; return (msgs, Just mod_guts)
        }}}
 

+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
 mkAutoScc :: DynFlags -> Module -> NameSet -> AutoScc
 mkAutoScc dflags mod exports
   | not opt_SccProfilingOn     -- No profiling

@@ -187,36 +394,45 @@ deSugarExpr hsc_env this_mod rdr_env type_env tc_expr = do
         dumpIfSet_dyn dflags Opt_D_dump_ds "Desugared" (pprCoreExpr expr)
 
         return (msgs, Just expr)
         dumpIfSet_dyn dflags Opt_D_dump_ds "Desugared" (pprCoreExpr 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 :: HscTarget -> NameSet -> NameSet -> [(Id, t)]
-               -> [(Id, t)]
-addExportFlags target exports keep_alive prs
-  = [(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
   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
 
        | otherwise         = bndr
 

-    dont_discard bndr = is_exported name
+    dont_discard :: Name -> Bool
+    dont_discard name = is_exported name

                     || name `elemNameSet` keep_alive
                     || name `elemNameSet` keep_alive

-                    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
 
        -- In interactive mode, we don't want to discard any top-level
        -- entities at all (eg. do not inline them away during

@@ -228,15 +444,44 @@ addExportFlags target exports keep_alive prs
     is_exported :: Name -> Bool
     is_exported | target == HscInterpreted = isExternalName
                | otherwise                = (`elemNameSet` exports)
     is_exported :: Name -> Bool
     is_exported | target == HscInterpreted = isExternalName
                | otherwise                = (`elemNameSet` exports)

-
-ppr_ds_rules :: [CoreRule] -> SDoc
-ppr_ds_rules [] = empty
-ppr_ds_rules rules
-  = blankLine $$ text "-------------- DESUGARED RULES -----------------" $$
-    pprRules rules

 \end{code}
 
 
 \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
+

 
 %************************************************************************
 %*                                                                     *
 
 %************************************************************************
 %*                                                                     *

@@ -250,28 +495,28 @@ dsRule (L loc (HsRule name act vars lhs _tv_lhs rhs _fv_rhs))
   = putSrcSpanDs loc $ 
     do { let bndrs' = [var | RuleBndr (L _ var) <- vars]
 
   = putSrcSpanDs loc $ 
     do { let bndrs' = [var | RuleBndr (L _ var) <- vars]
 

-       ; lhs'  <- unsetOptM Opt_EnableRewriteRules $
-                  dsLExpr lhs  -- Note [Desugaring RULE lhss]
+        ; lhs' <- unsetOptM Opt_EnableRewriteRules $
+                  unsetOptM Opt_WarnIdentities $
+                  dsLExpr lhs   -- Note [Desugaring RULE left hand sides]

 
 

-       ; rhs'  <- dsLExpr rhs
+       ; rhs' <- dsLExpr rhs

 
        -- Substitute the dict bindings eagerly,
        -- and take the body apart into a (f args) form
 
        -- Substitute the dict bindings eagerly,
        -- and take the body apart into a (f args) form

-       ; case decomposeRuleLhs (mkLams bndrs' lhs') of {
-               Nothing -> do { warnDs msg; return Nothing } ;
-               Just (bndrs, fn_id, args) -> do
+       ; case decomposeRuleLhs bndrs' lhs' of {
+               Left msg -> do { warnDs msg; return Nothing } ;
+               Right (final_bndrs, fn_id, args) -> do

        
        

-       { let local_rule = isLocalId fn_id
+       { 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
                -- 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    = mkRule local_rule name act fn_name bndrs args rhs' 
+             fn_name   = idName fn_id
+             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)
        } } }
        ; 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]
 \end{code}
 
 Note [Desugaring RULE left hand sides]

@@ -283,3 +528,62 @@ 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.
 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}
\ No newline at end of file