    {-# LANGUAGE DeriveFunctor #-}

    {-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
    {-# LANGUAGE NamedFieldPuns #-}

    {-
    (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
    -}

    {-| Tidying up Core

    This module's purpose is to prepare the Core program for two distinct purposes:
    * To be serialised into the module's interface file
    * To feed to the code generator

    The most important tasks are:
    * Determine which `Name`s should ultimately be `Internal` and `External`
      (which may differ to whether they were originally `Internal` or `External`).
      See `Note [About the NameSorts]` in GHC.Types.Name.
      For example, in:
              module M where
                f x = x + y
                  where y = factorial 4
      could be optimized during the Core pass to:
              module M where
                y = factorial 4
                f x = x + y
      in which case `y` would be changed from `Internal` to `External`.

    * Rename local identifiers to avoid name clashes, so that unfoldings etc can
      be serialialised using the OccName, without Uniques.

      For example (`x_5` means `x` with a `Unique` of `5`):
              f x_12 x_23 = x_12
      would be changed to:
              f x_12 x1_23 = x_12
    -}
    module GHC.Iface.Tidy
      ( TidyOpts (..)
      , UnfoldingExposure (..)
      , tidyProgram
      , mkBootModDetailsTc
      )
    where

    import GHC.Prelude

    import GHC.Tc.Types
    import GHC.Tc.Utils.Env

    import GHC.Core
    import GHC.Core.Unfold
    -- import GHC.Core.Unfold.Make
    import GHC.Core.FVs
    import GHC.Core.Tidy
    import GHC.Core.Seq         ( seqBinds )
    import GHC.Core.Opt.Arity   ( exprArity, typeArity, exprBotStrictness_maybe )
    import GHC.Core.InstEnv
    import GHC.Core.Type     ( Type, tidyTopType )
    import GHC.Core.DataCon
    import GHC.Core.TyCon
    import GHC.Core.Class
    import GHC.Core.Opt.OccurAnal ( occurAnalyseExpr )

    import GHC.Iface.Tidy.StaticPtrTable
    import GHC.Iface.Env

    import GHC.Utils.Outputable
    import GHC.Utils.Misc( filterOut )
    import GHC.Utils.Panic
    import GHC.Utils.Logger as Logger
    import qualified GHC.Utils.Error as Err

    import GHC.Types.ForeignStubs
    import GHC.Types.Var.Env
    import GHC.Types.Var.Set
    import GHC.Types.Var
    import GHC.Types.Id
    import GHC.Types.Id.Make ( mkDictSelRhs )
    import GHC.Types.Id.Info
    import GHC.Types.Demand  ( isDeadEndAppSig, isNopSig, nopSig, isDeadEndSig )
    import GHC.Types.Basic
    import GHC.Types.Name hiding (varName)
    import GHC.Types.Name.Set
    import GHC.Types.Name.Cache
    import GHC.Types.Avail
    import GHC.Types.Tickish
    import GHC.Types.TypeEnv

    import GHC.Unit.Module
    import GHC.Unit.Module.ModGuts
    import GHC.Unit.Module.ModDetails
    import GHC.Unit.Module.Deps

    import GHC.Data.Maybe

    import Control.Monad
    import Data.Function
    import Data.List        ( sortBy, mapAccumL )
    import qualified Data.Set as S
    import GHC.Types.CostCentre

    {-
    Constructing the TypeEnv, Instances, Rules from which the
    ModIface is constructed, and which goes on to subsequent modules in
    --make mode.

    Most of the interface file is obtained simply by serialising the
    TypeEnv.  One important consequence is that if the *interface file*
    has pragma info if and only if the final TypeEnv does. This is not so
    important for *this* module, but it's essential for ghc --make:
    subsequent compilations must not see (e.g.) the arity if the interface
    file does not contain arity If they do, they'll exploit the arity;
    then the arity might change, but the iface file doesn't change =>
    recompilation does not happen => disaster.

    For data types, the final TypeEnv will have a TyThing for the TyCon,
    plus one for each DataCon; the interface file will contain just one
    data type declaration, but it is de-serialised back into a collection
    of TyThings.

    ************************************************************************
    *                                                                      *
                    Plan A: simpleTidyPgm
    *                                                                      *
    ************************************************************************

    Plan A: mkBootModDetails: omit pragmas, make interfaces small
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    * Ignore the bindings

    * Drop all WiredIn things from the TypeEnv
            (we never want them in interface files)

    * Retain all TyCons and Classes in the TypeEnv, to avoid
            having to find which ones are mentioned in the
            types of exported Ids

    * Trim off the constructors of non-exported TyCons, both
            from the TyCon and from the TypeEnv

    * Drop non-exported Ids from the TypeEnv

    * Tidy the types of the DFunIds of Instances,
      make them into GlobalIds, (they already have External Names)
      and add them to the TypeEnv

    * Tidy the types of the (exported) Ids in the TypeEnv,
      make them into GlobalIds (they already have External Names)

    * Drop rules altogether

    * Tidy the bindings, to ensure that the Arity
      information is correct for each top-level binder; the
      code generator needs it. And to ensure that local names have
      distinct OccNames in case of object-file splitting

    * If this an hsig file, drop the instances altogether too (they'll
      get pulled in by the implicit module import.
    -}

    -- This is Plan A: make a small type env when typechecking only,
    -- or when compiling a hs-boot file, or simply when not using -O
    --
    -- We don't look at the bindings at all -- there aren't any
    -- for hs-boot files

    mkBootModDetailsTc :: Logger -> TcGblEnv -> IO ModDetails
    mkBootModDetailsTc :: Logger -> TcGblEnv -> IO ModDetails
    mkBootModDetailsTc Logger
    logger
            TcGblEnv{ tcg_exports :: TcGblEnv -> [AvailInfo]
    tcg_exports          = [AvailInfo]
    exports,
                      tcg_type_env :: TcGblEnv -> TypeEnv
    tcg_type_env         = TypeEnv
    type_env, -- just for the Ids
                      tcg_tcs :: TcGblEnv -> [TyCon]
    tcg_tcs              = [TyCon]
    tcs,
                      tcg_patsyns :: TcGblEnv -> [PatSyn]
    tcg_patsyns          = [PatSyn]
    pat_syns,
                      tcg_insts :: TcGblEnv -> [ClsInst]
    tcg_insts            = [ClsInst]
    insts,
                      tcg_fam_insts :: TcGblEnv -> [FamInst]
    tcg_fam_insts        = [FamInst]
    fam_insts,
                      tcg_complete_matches :: TcGblEnv -> CompleteMatches
    tcg_complete_matches = CompleteMatches
    complete_matches,
                      tcg_mod :: TcGblEnv -> Module
    tcg_mod              = Module
    this_mod
                    }
      = -- This timing isn't terribly useful since the result isn't forced, but
        -- the message is useful to locating oneself in the compilation process.
        Logger
    -> SDoc -> (ModDetails -> ()) -> IO ModDetails -> IO ModDetails
    forall (m :: * -> *) a.
    MonadIO m =>
    Logger -> SDoc -> (a -> ()) -> m a -> m a
    Err.withTiming Logger
    logger
                       (String -> SDoc
    forall doc. IsLine doc => String -> doc
    text String
    "CoreTidy"SDoc -> SDoc -> SDoc
    forall doc. IsLine doc => doc -> doc -> doc
    <+>SDoc -> SDoc
    forall doc. IsLine doc => doc -> doc
    brackets (Module -> SDoc
    forall a. Outputable a => a -> SDoc
    ppr Module
    this_mod))
                       (() -> ModDetails -> ()
    forall a b. a -> b -> a
    const ()) (IO ModDetails -> IO ModDetails) -> IO ModDetails -> IO ModDetails
    forall a b. (a -> b) -> a -> b
    $
        ModDetails -> IO ModDetails
    forall a. a -> IO a
    forall (m :: * -> *) a. Monad m => a -> m a
    return (ModDetails { md_types :: TypeEnv
    md_types            = TypeEnv
    type_env'
                           , md_insts :: InstEnv
    md_insts            = InstEnv
    insts'
                           , md_fam_insts :: [FamInst]
    md_fam_insts        = [FamInst]
    fam_insts
                           , md_rules :: [CoreRule]
    md_rules            = []
                           , md_anns :: [Annotation]
    md_anns             = []
                           , md_exports :: [AvailInfo]
    md_exports          = [AvailInfo]
    exports
                           , md_complete_matches :: CompleteMatches
    md_complete_matches = CompleteMatches
    complete_matches
                           })
      where
        -- Find the LocalIds in the type env that are exported
        -- Make them into GlobalIds, and tidy their types
        --
        -- It's very important to remove the non-exported ones
        -- because we don't tidy the OccNames, and if we don't remove
        -- the non-exported ones we'll get many things with the
        -- same name in the interface file, giving chaos.
        --
        -- Do make sure that we keep Ids that are already Global.
        -- When typechecking an .hs-boot file, the Ids come through as
        -- GlobalIds.
        final_ids :: [Id]
    final_ids = [ Id -> Id
    globaliseAndTidyBootId Id
    id
                    | Id
    id <- TypeEnv -> [Id]
    typeEnvIds TypeEnv
    type_env
                    , Id -> Bool
    keep_it Id
    id ]

        final_tcs :: [TyCon]
    final_tcs  = (TyCon -> Bool) -> [TyCon] -> [TyCon]
    forall a. (a -> Bool) -> [a] -> [a]
    filterOut TyCon -> Bool
    forall thing. NamedThing thing => thing -> Bool
    isWiredIn [TyCon]
    tcs
                     -- See Note [Drop wired-in things]
        type_env' :: TypeEnv
    type_env'  = [Id] -> [TyCon] -> [PatSyn] -> [FamInst] -> TypeEnv
    typeEnvFromEntities [Id]
    final_ids [TyCon]
    final_tcs [PatSyn]
    pat_syns [FamInst]
    fam_insts
        insts' :: InstEnv
    insts'     = TypeEnv -> InstEnv -> InstEnv
    mkFinalClsInsts TypeEnv
    type_env' (InstEnv -> InstEnv) -> InstEnv -> InstEnv
    forall a b. (a -> b) -> a -> b
    $ [ClsInst] -> InstEnv
    mkInstEnv [ClsInst]
    insts

        -- Default methods have their export flag set (isExportedId),
        -- but everything else doesn't (yet), because this is
        -- pre-desugaring, so we must test against the exports too.
        keep_it :: Id -> Bool
    keep_it Id
    id | Name -> Bool
    isWiredInName Name
    id_name           = Bool
    False
                     -- See Note [Drop wired-in things]
                   | Id -> Bool
    isExportedId Id
    id                 = Bool
    True
                   | Name
    id_name Name -> NameSet -> Bool
    `elemNameSet` NameSet
    exp_names = Bool
    True
                   | Bool
    otherwise                       = Bool
    False
                   where
                     id_name :: Name
    id_name = Id -> Name
    idName Id
    id

        exp_names :: NameSet
    exp_names = [AvailInfo] -> NameSet
    availsToNameSet [AvailInfo]
    exports

    lookupFinalId :: TypeEnv -> Id -> Id
    lookupFinalId :: TypeEnv -> Id -> Id
    lookupFinalId TypeEnv
    type_env Id
    id
      = case TypeEnv -> Name -> Maybe TyThing
    lookupTypeEnv TypeEnv
    type_env (Id -> Name
    idName Id
    id) of
          Just (AnId Id
    id') -> Id
    id'
          Maybe TyThing
    _ -> String -> SDoc -> Id
    forall a. HasCallStack => String -> SDoc -> a
    pprPanic String
    "lookup_final_id" (Id -> SDoc
    forall a. Outputable a => a -> SDoc
    ppr Id
    id)

    mkFinalClsInsts :: TypeEnv -> InstEnv -> InstEnv
    mkFinalClsInsts :: TypeEnv -> InstEnv -> InstEnv
    mkFinalClsInsts TypeEnv
    env = (Id -> Id) -> InstEnv -> InstEnv
    updateClsInstDFuns (TypeEnv -> Id -> Id
    lookupFinalId TypeEnv
    env)

    globaliseAndTidyBootId :: Id -> Id
    -- For a LocalId with an External Name,
    -- makes it into a GlobalId
    --     * unchanged Name (might be Internal or External)
    --     * unchanged details
    --     * VanillaIdInfo (makes a conservative assumption about arity)
    --     * BootUnfolding (see Note [Inlining and hs-boot files] in GHC.CoreToIface)
    globaliseAndTidyBootId :: Id -> Id
    globaliseAndTidyBootId Id
    id
      = (Type -> Type) -> Id -> Id
    updateIdTypeAndMult Type -> Type
    tidyTopType (Id -> Id
    globaliseId Id
    id)
                       Id -> Unfolding -> Id
    `setIdUnfolding` Unfolding
    BootUnfolding

    {-
    ************************************************************************
    *                                                                      *
            Plan B: tidy bindings, make TypeEnv full of IdInfo
    *                                                                      *
    ************************************************************************

    Plan B: include pragmas, make interfaces
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    * Step 1: Figure out which Ids are externally visible
              See Note [Choosing external Ids]

    * Step 2: Gather the externally visible rules, separately from
              the top-level bindings.
              See Note [Finding external rules]

    * Step 3: Tidy the bindings, externalising appropriate Ids
              See Note [Tidy the top-level bindings]

    * Drop all Ids from the TypeEnv, and add all the External Ids from
      the bindings.  (This adds their IdInfo to the TypeEnv; and adds
      floated-out Ids that weren't even in the TypeEnv before.)

    Note [Choosing external Ids]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    See also the section "Interface stability" in the
    recompilation-avoidance commentary:
      https://gitlab.haskell.org/ghc/ghc/wikis/commentary/compiler/recompilation-avoidance

    First we figure out which Ids are "external" Ids.  An
    "external" Id is one that is visible from outside the compilation
    unit.  These are
      a) the user exported ones
      b) the ones bound to static forms
      c) ones mentioned in the unfoldings, workers, or
         rules of externally-visible ones

    While figuring out which Ids are external, we pick a "tidy" OccName
    for each one.  That is, we make its OccName distinct from the other
    external OccNames in this module, so that in interface files and
    object code we can refer to it unambiguously by its OccName.  The
    OccName for each binder is prefixed by the name of the exported Id
    that references it; e.g. if "f" references "x" in its unfolding, then
    "x" is renamed to "f_x".  This helps distinguish the different "x"s
    from each other, and means that if "f" is later removed, things that
    depend on the other "x"s will not need to be recompiled.  Of course,
    if there are multiple "f_x"s, then we have to disambiguate somehow; we
    use "f_x0", "f_x1" etc.

    As far as possible we should assign names in a deterministic fashion.
    Each time this module is compiled with the same options, we should end
    up with the same set of external names with the same types.  That is,
    the ABI hash in the interface should not change.  This turns out to be
    quite tricky, since the order of the bindings going into the tidy
    phase is already non-deterministic, as it is based on the ordering of
    Uniques, which are assigned unpredictably.

    To name things in a stable way, we do a depth-first-search of the
    bindings, starting from the exports sorted by name.  This way, as long
    as the bindings themselves are deterministic (they sometimes aren't!),
    the order in which they are presented to the tidying phase does not
    affect the names we assign.

    Note [Tidy the top-level bindings]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    Next we traverse the bindings top to bottom.  For each *top-level*
    binder

     1. Make it into a GlobalId; its IdDetails becomes VanillaGlobal,
        reflecting the fact that from now on we regard it as a global,
        not local, Id

     2. Give it a system-wide Unique.
        [Even non-exported things need system-wide Uniques because the
        byte-code generator builds a single Name->BCO symbol table.]

        We use the given NameCache as the source of such system-wide uniques.

        For external Ids, use the original-name cache in the NameCache
        to ensure that the unique assigned is the same as the Id had
        in any previous compilation run.

     3. Rename top-level Ids according to the names we chose in step 1.
        If it's an external Id, make it have a External Name, otherwise
        make it have an Internal Name.  This is used by the code generator
        to decide whether to make the label externally visible

     4. Give it its UTTERLY FINAL IdInfo; in ptic,
            * its unfolding, if it should have one

            * its arity, computed from the number of visible lambdas

    Finally, substitute these new top-level binders consistently
    throughout, including in unfoldings.  We also tidy binders in
    RHSs, so that they print nicely in interfaces.

    Note [Always expose compulsory unfoldings]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    We must make absolutely sure that unsafeCoerce# is inlined. You might
    think that giving it a compulsory unfolding is enough. However,
    unsafeCoerce# is put in an interface file just like any other definition.
    So, unless we take special precuations
    - If we compiled Unsafe.Coerce with -O0, we might not put the unfolding
      into the interface file.
    - If we compile a module M, that imports Unsafe.Coerce, with -O0 we might
      not read the unfolding out of the interface file.

    So we need to take care, to ensure that Compulsory unfoldings are written
    and read.  That makes sense: they are compulsory, after all. There are
    three places this is actioned:

    * GHC.Iface.Tidy.addExternal.  Export end: expose compulsory
      unfoldings, even with -O0.

    * GHC.IfaceToCore.tcIdInfo.  Import end: when reading in from
      interface file, even with -O0 (fignore-interface-pragmas.)  we must
      load a compulsory unfolding
    -}

    data UnfoldingExposure
      = ExposeNone -- ^ Don't expose unfoldings
      | ExposeSome -- ^ Only expose required unfoldings
      | ExposeAll  -- ^ Expose all unfoldings
      deriving (Arity -> UnfoldingExposure -> ShowS
    [UnfoldingExposure] -> ShowS
    UnfoldingExposure -> String
    (Arity -> UnfoldingExposure -> ShowS)
    -> (UnfoldingExposure -> String)
    -> ([UnfoldingExposure] -> ShowS)
    -> Show UnfoldingExposure
    forall a.
    (Arity -> a -> ShowS) -> (a -> String) -> ([a] -> ShowS) -> Show a
    $cshowsPrec :: Arity -> UnfoldingExposure -> ShowS
    showsPrec :: Arity -> UnfoldingExposure -> ShowS
    $cshow :: UnfoldingExposure -> String
    show :: UnfoldingExposure -> String
    $cshowList :: [UnfoldingExposure] -> ShowS
    showList :: [UnfoldingExposure] -> ShowS
    Show,UnfoldingExposure -> UnfoldingExposure -> Bool
    (UnfoldingExposure -> UnfoldingExposure -> Bool)
    -> (UnfoldingExposure -> UnfoldingExposure -> Bool)
    -> Eq UnfoldingExposure
    forall a. (a -> a -> Bool) -> (a -> a -> Bool) -> Eq a
    $c== :: UnfoldingExposure -> UnfoldingExposure -> Bool
    == :: UnfoldingExposure -> UnfoldingExposure -> Bool
    $c/= :: UnfoldingExposure -> UnfoldingExposure -> Bool
    /= :: UnfoldingExposure -> UnfoldingExposure -> Bool
    Eq,Eq UnfoldingExposure
    Eq UnfoldingExposure =>
    (UnfoldingExposure -> UnfoldingExposure -> Ordering)
    -> (UnfoldingExposure -> UnfoldingExposure -> Bool)
    -> (UnfoldingExposure -> UnfoldingExposure -> Bool)
    -> (UnfoldingExposure -> UnfoldingExposure -> Bool)
    -> (UnfoldingExposure -> UnfoldingExposure -> Bool)
    -> (UnfoldingExposure -> UnfoldingExposure -> UnfoldingExposure)
    -> (UnfoldingExposure -> UnfoldingExposure -> UnfoldingExposure)
    -> Ord UnfoldingExposure
    UnfoldingExposure -> UnfoldingExposure -> Bool
    UnfoldingExposure -> UnfoldingExposure -> Ordering
    UnfoldingExposure -> UnfoldingExposure -> UnfoldingExposure
    forall a.
    Eq a =>
    (a -> a -> Ordering)
    -> (a -> a -> Bool)
    -> (a -> a -> Bool)
    -> (a -> a -> Bool)
    -> (a -> a -> Bool)
    -> (a -> a -> a)
    -> (a -> a -> a)
    -> Ord a
    $ccompare :: UnfoldingExposure -> UnfoldingExposure -> Ordering
    compare :: UnfoldingExposure -> UnfoldingExposure -> Ordering
    $c< :: UnfoldingExposure -> UnfoldingExposure -> Bool
    < :: UnfoldingExposure -> UnfoldingExposure -> Bool
    $c<= :: UnfoldingExposure -> UnfoldingExposure -> Bool
    <= :: UnfoldingExposure -> UnfoldingExposure -> Bool
    $c> :: UnfoldingExposure -> UnfoldingExposure -> Bool
    > :: UnfoldingExposure -> UnfoldingExposure -> Bool
    $c>= :: UnfoldingExposure -> UnfoldingExposure -> Bool
    >= :: UnfoldingExposure -> UnfoldingExposure -> Bool
    $cmax :: UnfoldingExposure -> UnfoldingExposure -> UnfoldingExposure
    max :: UnfoldingExposure -> UnfoldingExposure -> UnfoldingExposure
    $cmin :: UnfoldingExposure -> UnfoldingExposure -> UnfoldingExposure
    min :: UnfoldingExposure -> UnfoldingExposure -> UnfoldingExposure
    Ord)

    data TidyOpts = TidyOpts
      { TidyOpts -> NameCache
    opt_name_cache        :: !NameCache
      , TidyOpts -> Bool
    opt_collect_ccs       :: !Bool -- ^ Always true if we compile with -prof
      , TidyOpts -> UnfoldingOpts
    opt_unfolding_opts    :: !UnfoldingOpts
      , TidyOpts -> UnfoldingExposure
    opt_expose_unfoldings :: !UnfoldingExposure
          -- ^ Which unfoldings to expose
      , TidyOpts -> Bool
    opt_trim_ids :: !Bool
          -- ^ trim off the arity, one-shot-ness, strictness etc which were
          -- retained for the benefit of the code generator
      , TidyOpts -> Bool
    opt_expose_rules :: !Bool
          -- ^ Are rules exposed or not?
      , TidyOpts -> Maybe StaticPtrOpts
    opt_static_ptr_opts :: !(Maybe StaticPtrOpts)
          -- ^ Options for generated static pointers, if enabled (/= Nothing).
      , TidyOpts -> Bool
    opt_keep_auto_rules :: !Bool
      }

    tidyProgram :: TidyOpts -> ModGuts -> IO (CgGuts, ModDetails)
    tidyProgram :: TidyOpts -> ModGuts -> IO (CgGuts, ModDetails)
    tidyProgram TidyOpts
    opts (ModGuts { mg_module :: ModGuts -> Module
    mg_module           = Module
    mod
                              , mg_exports :: ModGuts -> [AvailInfo]
    mg_exports          = [AvailInfo]
    exports
                              , mg_tcs :: ModGuts -> [TyCon]
    mg_tcs              = [TyCon]
    tcs
                              , mg_insts :: ModGuts -> [ClsInst]
    mg_insts            = [ClsInst]
    cls_insts
                              , mg_fam_insts :: ModGuts -> [FamInst]
    mg_fam_insts        = [FamInst]
    fam_insts
                              , mg_binds :: ModGuts -> CoreProgram
    mg_binds            = CoreProgram
    binds
                              , mg_patsyns :: ModGuts -> [PatSyn]
    mg_patsyns          = [PatSyn]
    patsyns
                              , mg_rules :: ModGuts -> [CoreRule]
    mg_rules            = [CoreRule]
    imp_rules
                              , mg_anns :: ModGuts -> [Annotation]
    mg_anns             = [Annotation]
    anns
                              , mg_complete_matches :: ModGuts -> CompleteMatches
    mg_complete_matches = CompleteMatches
    complete_matches
                              , mg_deps :: ModGuts -> Dependencies
    mg_deps             = Dependencies
    deps
                              , mg_foreign :: ModGuts -> ForeignStubs
    mg_foreign          = ForeignStubs
    foreign_stubs
                              , mg_foreign_files :: ModGuts -> [(ForeignSrcLang, String)]
    mg_foreign_files    = [(ForeignSrcLang, String)]
    foreign_files
                              , mg_hpc_info :: ModGuts -> HpcInfo
    mg_hpc_info         = HpcInfo
    hpc_info
                              , mg_modBreaks :: ModGuts -> Maybe ModBreaks
    mg_modBreaks        = Maybe ModBreaks
    modBreaks
                              , mg_boot_exports :: ModGuts -> NameSet
    mg_boot_exports     = NameSet
    boot_exports
                              }) = do

      let implicit_binds :: CoreProgram
    implicit_binds = (TyCon -> CoreProgram) -> [TyCon] -> CoreProgram
    forall (t :: * -> *) a b. Foldable t => (a -> [b]) -> t a -> [b]
    concatMap TyCon -> CoreProgram
    getImplicitBinds [TyCon]
    tcs
          all_binds :: CoreProgram
    all_binds = CoreProgram
    implicit_binds CoreProgram -> CoreProgram -> CoreProgram
    forall a. [a] -> [a] -> [a]
    ++ CoreProgram
    binds

      (unfold_env, tidy_occ_env) <- TidyOpts
    -> Module
    -> CoreProgram
    -> [CoreRule]
    -> IO (UnfoldEnv, TidyOccEnv)
    chooseExternalIds TidyOpts
    opts Module
    mod CoreProgram
    all_binds [CoreRule]
    imp_rules
      let (trimmed_binds, trimmed_rules) = findExternalRules opts all_binds imp_rules unfold_env

      (tidy_env, tidy_binds) <- tidyTopBinds unfold_env boot_exports tidy_occ_env trimmed_binds

      -- See Note [Grand plan for static forms] in GHC.Iface.Tidy.StaticPtrTable.
      (spt_entries, mcstub, tidy_binds') <- case opt_static_ptr_opts opts of
        Maybe StaticPtrOpts
    Nothing    -> ([SptEntry], Maybe CStub, CoreProgram)
    -> IO ([SptEntry], Maybe CStub, CoreProgram)
    forall a. a -> IO a
    forall (f :: * -> *) a. Applicative f => a -> f a
    pure ([], Maybe CStub
    forall a. Maybe a
    Nothing, CoreProgram
    tidy_binds)
        Just StaticPtrOpts
    sopts -> StaticPtrOpts
    -> Module
    -> CoreProgram
    -> IO ([SptEntry], Maybe CStub, CoreProgram)
    sptCreateStaticBinds StaticPtrOpts
    sopts Module
    mod CoreProgram
    tidy_binds

      -- pprTraceM "trimmed_rules" (ppr trimmed_rules)

      let all_foreign_stubs = case Maybe CStub
    mcstub of
            Maybe CStub
    Nothing    -> ForeignStubs
    foreign_stubs
            Just CStub
    cstub -> ForeignStubs
    foreign_stubs ForeignStubs -> CStub -> ForeignStubs
    `appendStubC` CStub
    cstub

          -- The completed type environment is gotten from
          --      a) the types and classes defined here (plus implicit things)
          --      b) adding Ids with correct IdInfo, including unfoldings,
          --              gotten from the bindings
          -- From (b) we keep only those Ids with External names;
          --          the CoreTidy pass makes sure these are all and only
          --          the externally-accessible ones
          -- This truncates the type environment to include only the
          -- exported Ids and things needed from them, which saves space
          --
          -- See Note [Don't attempt to trim data types]
          final_ids  = [ Bool -> Id -> Id
    trimId (TidyOpts -> Bool
    opt_trim_ids TidyOpts
    opts) Id
    id
                       | Id
    id <- CoreProgram -> [Id]
    forall b. [Bind b] -> [b]
    bindersOfBinds CoreProgram
    tidy_binds
                       , Name -> Bool
    isExternalName (Id -> Name
    idName Id
    id)
                       , Bool -> Bool
    not (Id -> Bool
    forall thing. NamedThing thing => thing -> Bool
    isWiredIn Id
    id)
                       ]   -- See Note [Drop wired-in things]

          final_tcs      = (TyCon -> Bool) -> [TyCon] -> [TyCon]
    forall a. (a -> Bool) -> [a] -> [a]
    filterOut TyCon -> Bool
    forall thing. NamedThing thing => thing -> Bool
    isWiredIn [TyCon]
    tcs
                           -- See Note [Drop wired-in things]
          tidy_type_env  = [Id] -> [TyCon] -> [PatSyn] -> [FamInst] -> TypeEnv
    typeEnvFromEntities [Id]
    final_ids [TyCon]
    final_tcs [PatSyn]
    patsyns [FamInst]
    fam_insts
          tidy_cls_insts = TypeEnv -> InstEnv -> InstEnv
    mkFinalClsInsts TypeEnv
    tidy_type_env (InstEnv -> InstEnv) -> InstEnv -> InstEnv
    forall a b. (a -> b) -> a -> b
    $ [ClsInst] -> InstEnv
    mkInstEnv [ClsInst]
    cls_insts
          tidy_rules     = TidyEnv -> [CoreRule] -> [CoreRule]
    tidyRules TidyEnv
    tidy_env [CoreRule]
    trimmed_rules

          -- See Note [Injecting implicit bindings]
          all_tidy_binds = CoreProgram
    tidy_binds'

          -- Get the TyCons to generate code for.  Careful!  We must use
          -- the untidied TyCons here, because we need
          --  (a) implicit TyCons arising from types and classes defined
          --      in this module
          --  (b) wired-in TyCons, which are normally removed from the
          --      TypeEnv we put in the ModDetails
          --  (c) Constructors even if they are not exported (the
          --      tidied TypeEnv has trimmed these away)
          alg_tycons = (TyCon -> Bool) -> [TyCon] -> [TyCon]
    forall a. (a -> Bool) -> [a] -> [a]
    filter TyCon -> Bool
    isAlgTyCon [TyCon]
    tcs

          local_ccs
            | TidyOpts -> Bool
    opt_collect_ccs TidyOpts
    opts
                  = Module -> CoreProgram -> [CoreRule] -> Set CostCentre
    collectCostCentres Module
    mod CoreProgram
    all_tidy_binds [CoreRule]
    tidy_rules
            | Bool
    otherwise
                  = Set CostCentre
    forall a. Set a
    S.empty

      return (CgGuts { cg_module        = mod
                     , cg_tycons        = alg_tycons
                     , cg_binds         = all_tidy_binds
                     , cg_ccs           = S.toList local_ccs
                     , cg_foreign       = all_foreign_stubs
                     , cg_foreign_files = foreign_files
                     , cg_dep_pkgs      = dep_direct_pkgs deps
                     , cg_hpc_info      = hpc_info
                     , cg_modBreaks     = modBreaks
                     , cg_spt_entries   = spt_entries
                     }
             , ModDetails { md_types            = tidy_type_env
                          , md_rules            = tidy_rules
                          , md_insts            = tidy_cls_insts
                          , md_fam_insts        = fam_insts
                          , md_exports          = exports
                          , md_anns             = anns      -- are already tidy
                          , md_complete_matches = complete_matches
                          }
             )

    ------------------------------------------------------------------------------
    -- Collecting cost centres
    -- ---------------------------------------------------------------------------

    -- | Collect cost centres defined in the current module, including those in
    -- unfoldings.
    collectCostCentres :: Module -> CoreProgram -> [CoreRule] -> S.Set CostCentre
    collectCostCentres :: Module -> CoreProgram -> [CoreRule] -> Set CostCentre
    collectCostCentres Module
    mod_name CoreProgram
    binds [CoreRule]
    rules
      = {-# SCC collectCostCentres #-} (Set CostCentre -> CoreBind -> Set CostCentre)
    -> Set CostCentre -> CoreProgram -> Set CostCentre
    forall b a. (b -> a -> b) -> b -> [a] -> b
    forall (t :: * -> *) b a.
    Foldable t =>
    (b -> a -> b) -> b -> t a -> b
    foldl' Set CostCentre -> CoreBind -> Set CostCentre
    go_bind (Set CostCentre -> Set CostCentre
    go_rules Set CostCentre
    forall a. Set a
    S.empty) CoreProgram
    binds
      where
        go :: Set CostCentre -> Expr Id -> Set CostCentre
    go Set CostCentre
    cs Expr Id
    e = case Expr Id
    e of
          Var{} -> Set CostCentre
    cs
          Lit{} -> Set CostCentre
    cs
          App Expr Id
    e1 Expr Id
    e2 -> Set CostCentre -> Expr Id -> Set CostCentre
    go (Set CostCentre -> Expr Id -> Set CostCentre
    go Set CostCentre
    cs Expr Id
    e1) Expr Id
    e2
          Lam Id
    _ Expr Id
    e -> Set CostCentre -> Expr Id -> Set CostCentre
    go Set CostCentre
    cs Expr Id
    e
          Let CoreBind
    b Expr Id
    e -> Set CostCentre -> Expr Id -> Set CostCentre
    go (Set CostCentre -> CoreBind -> Set CostCentre
    go_bind Set CostCentre
    cs CoreBind
    b) Expr Id
    e
          Case Expr Id
    scrt Id
    _ Type
    _ [Alt Id]
    alts -> Set CostCentre -> [Alt Id] -> Set CostCentre
    go_alts (Set CostCentre -> Expr Id -> Set CostCentre
    go Set CostCentre
    cs Expr Id
    scrt) [Alt Id]
    alts
          Cast Expr Id
    e CoercionR
    _ -> Set CostCentre -> Expr Id -> Set CostCentre
    go Set CostCentre
    cs Expr Id
    e
          Tick (ProfNote CostCentre
    cc Bool
    _ Bool
    _) Expr Id
    e ->
            Set CostCentre -> Expr Id -> Set CostCentre
    go (if CostCentre -> Module -> Bool
    ccFromThisModule CostCentre
    cc Module
    mod_name then CostCentre -> Set CostCentre -> Set CostCentre
    forall a. Ord a => a -> Set a -> Set a
    S.insert CostCentre
    cc Set CostCentre
    cs else Set CostCentre
    cs) Expr Id
    e
          Tick GenTickish 'TickishPassCore
    _ Expr Id
    e -> Set CostCentre -> Expr Id -> Set CostCentre
    go Set CostCentre
    cs Expr Id
    e
          Type{} -> Set CostCentre
    cs
          Coercion{} -> Set CostCentre
    cs

        go_alts :: Set CostCentre -> [Alt Id] -> Set CostCentre
    go_alts = (Set CostCentre -> Alt Id -> Set CostCentre)
    -> Set CostCentre -> [Alt Id] -> Set CostCentre
    forall b a. (b -> a -> b) -> b -> [a] -> b
    forall (t :: * -> *) b a.
    Foldable t =>
    (b -> a -> b) -> b -> t a -> b
    foldl' (\Set CostCentre
    cs (Alt AltCon
    _con [Id]
    _bndrs Expr Id
    e) -> Set CostCentre -> Expr Id -> Set CostCentre
    go Set CostCentre
    cs Expr Id
    e)

        go_bind :: S.Set CostCentre -> CoreBind -> S.Set CostCentre
        go_bind :: Set CostCentre -> CoreBind -> Set CostCentre
    go_bind Set CostCentre
    cs (NonRec Id
    b Expr Id
    e) =
          Set CostCentre -> Expr Id -> Set CostCentre
    go (Set CostCentre -> Id -> Set CostCentre
    do_binder Set CostCentre
    cs Id
    b) Expr Id
    e
        go_bind Set CostCentre
    cs (Rec [(Id, Expr Id)]
    bs) =
          (Set CostCentre -> (Id, Expr Id) -> Set CostCentre)
    -> Set CostCentre -> [(Id, Expr Id)] -> Set CostCentre
    forall b a. (b -> a -> b) -> b -> [a] -> b
    forall (t :: * -> *) b a.
    Foldable t =>
    (b -> a -> b) -> b -> t a -> b
    foldl' (\Set CostCentre
    cs' (Id
    b, Expr Id
    e) -> Set CostCentre -> Expr Id -> Set CostCentre
    go (Set CostCentre -> Id -> Set CostCentre
    do_binder Set CostCentre
    cs' Id
    b) Expr Id
    e) Set CostCentre
    cs [(Id, Expr Id)]
    bs

        do_binder :: Set CostCentre -> Id -> Set CostCentre
    do_binder Set CostCentre
    cs Id
    b = Set CostCentre
    -> (Expr Id -> Set CostCentre) -> Maybe (Expr Id) -> Set CostCentre
    forall b a. b -> (a -> b) -> Maybe a -> b
    maybe Set CostCentre
    cs (Set CostCentre -> Expr Id -> Set CostCentre
    go Set CostCentre
    cs) (Id -> Maybe (Expr Id)
    get_unf Id
    b)

        -- Unfoldings may have cost centres that in the original definion are
        -- optimized away, see #5889.
        get_unf :: Id -> Maybe (Expr Id)
    get_unf = Unfolding -> Maybe (Expr Id)
    maybeUnfoldingTemplate (Unfolding -> Maybe (Expr Id))
    -> (Id -> Unfolding) -> Id -> Maybe (Expr Id)
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . Id -> Unfolding
    realIdUnfolding

        -- Have to look at the RHS of rules as well, as these may contain ticks which
        -- don't appear anywhere else. See #19894
        go_rules :: Set CostCentre -> Set CostCentre
    go_rules Set CostCentre
    cs = (Set CostCentre -> Expr Id -> Set CostCentre)
    -> Set CostCentre -> [Expr Id] -> Set CostCentre
    forall b a. (b -> a -> b) -> b -> [a] -> b
    forall (t :: * -> *) b a.
    Foldable t =>
    (b -> a -> b) -> b -> t a -> b
    foldl' Set CostCentre -> Expr Id -> Set CostCentre
    go Set CostCentre
    cs ((CoreRule -> Maybe (Expr Id)) -> [CoreRule] -> [Expr Id]
    forall a b. (a -> Maybe b) -> [a] -> [b]
    mapMaybe CoreRule -> Maybe (Expr Id)
    get_rhs [CoreRule]
    rules)

        get_rhs :: CoreRule -> Maybe (Expr Id)
    get_rhs Rule { Expr Id
    ru_rhs :: Expr Id
    ru_rhs :: CoreRule -> Expr Id
    ru_rhs } = Expr Id -> Maybe (Expr Id)
    forall a. a -> Maybe a
    Just Expr Id
    ru_rhs
        get_rhs BuiltinRule {} = Maybe (Expr Id)
    forall a. Maybe a
    Nothing

    --------------------------
    trimId :: Bool -> Id -> Id
    -- With -O0 we now trim off the arity, one-shot-ness, strictness
    -- etc which tidyTopIdInfo retains for the benefit of the code generator
    -- but which we don't want in the interface file or ModIface for
    -- downstream compilations
    trimId :: Bool -> Id -> Id
    trimId Bool
    do_trim Id
    id
      | Bool
    do_trim, Bool -> Bool
    not (Id -> Bool
    isImplicitId Id
    id)
      = Id
    id Id -> IdInfo -> Id
    `setIdInfo`      IdInfo
    vanillaIdInfo
           Id -> Unfolding -> Id
    `setIdUnfolding` Id -> Unfolding
    idUnfolding Id
    id
           -- We respect the final unfolding chosen by tidyTopIdInfo.
           -- We have already trimmed it if we don't want it for -O0;
           -- see also Note [Always expose compulsory unfoldings]

      | Bool
    otherwise   -- No trimming
      = Id
    id

    {- Note [Drop wired-in things]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    We never put wired-in TyCons or Ids in an interface file.
    They are wired-in, so the compiler knows about them already.

    Note [Don't attempt to trim data types]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    For some time GHC tried to avoid exporting the data constructors
    of a data type if it wasn't strictly necessary to do so; see #835.
    But "strictly necessary" accumulated a longer and longer list
    of exceptions, and finally I gave up the battle:

        commit 9a20e540754fc2af74c2e7392f2786a81d8d5f11
        Author: Simon Peyton Jones <simonpj@microsoft.com>
        Date:   Thu Dec 6 16:03:16 2012 +0000

        Stop attempting to "trim" data types in interface files

        Without -O, we previously tried to make interface files smaller
        by not including the data constructors of data types.  But
        there are a lot of exceptions, notably when Template Haskell is
        involved or, more recently, DataKinds.

        However #7445 shows that even without TemplateHaskell, using
        the Data class and invoking Language.Haskell.TH.Quote.dataToExpQ
        is enough to require us to expose the data constructors.

        So I've given up on this "optimisation" -- it's probably not
        important anyway.  Now I'm simply not attempting to trim off
        the data constructors.  The gain in simplicity is worth the
        modest cost in interface file growth, which is limited to the
        bits reqd to describe those data constructors.

    ************************************************************************
    *                                                                      *
            Implicit bindings
    *                                                                      *
    ************************************************************************

    Note [Injecting implicit bindings]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    We inject the implicit bindings right at the end, in GHC.Core.Tidy.
    Some of these bindings, notably record selectors, are not
    constructed in an optimised form.  E.g. record selector for
            data T = MkT { x :: {-# UNPACK #-} !Int }
    Then the unfolding looks like
            x = \t. case t of MkT x1 -> let x = I# x1 in x
    This generates bad code unless it's first simplified a bit.  That is
    why GHC.Core.Unfold.mkImplicitUnfolding uses simpleOptExpr to do a bit of
    optimisation first.  (Only matters when the selector is used curried;
    eg map x ys.)  See #2070.

    [Oct 09: in fact, record selectors are no longer implicit Ids at all,
    because we really do want to optimise them properly. They are treated
    much like any other Id.  But doing "light" optimisation on an implicit
    Id still makes sense.]

    At one time I tried injecting the implicit bindings *early*, at the
    beginning of SimplCore.  But that gave rise to real difficulty,
    because GlobalIds are supposed to have *fixed* IdInfo, but the
    simplifier and other core-to-core passes mess with IdInfo all the
    time.  The straw that broke the camels back was when a class selector
    got the wrong arity -- ie the simplifier gave it arity 2, whereas
    importing modules were expecting it to have arity 1 (#2844).
    It's much safer just to inject them right at the end, after tidying.

    Oh: two other reasons for injecting them late:

      - If implicit Ids are already in the bindings when we start tidying,
        we'd have to be careful not to treat them as external Ids (in
        the sense of chooseExternalIds); else the Ids mentioned in *their*
        RHSs will be treated as external and you get an interface file
        saying      a18 = <blah>
        but nothing referring to a18 (because the implicit Id is the
        one that does, and implicit Ids don't appear in interface files).

      - More seriously, the tidied type-envt will include the implicit
        Id replete with a18 in its unfolding; but we won't take account
        of a18 when computing a fingerprint for the class; result chaos.

    There is one sort of implicit binding that is injected still later,
    namely those for data constructor workers. Reason (I think): it's
    really just a code generation trick.... binding itself makes no sense.
    See Note [Data constructor workers] in "GHC.CoreToStg.Prep".
    -}

    getImplicitBinds :: TyCon -> [CoreBind]
    getImplicitBinds :: TyCon -> CoreProgram
    getImplicitBinds TyCon
    tc = CoreProgram
    cls_binds CoreProgram -> CoreProgram -> CoreProgram
    forall a. [a] -> [a] -> [a]
    ++ TyCon -> CoreProgram
    getTyConImplicitBinds TyCon
    tc
      where
        cls_binds :: CoreProgram
    cls_binds = CoreProgram -> (Class -> CoreProgram) -> Maybe Class -> CoreProgram
    forall b a. b -> (a -> b) -> Maybe a -> b
    maybe [] Class -> CoreProgram
    getClassImplicitBinds (TyCon -> Maybe Class
    tyConClass_maybe TyCon
    tc)

    getTyConImplicitBinds :: TyCon -> [CoreBind]
    getTyConImplicitBinds :: TyCon -> CoreProgram
    getTyConImplicitBinds TyCon
    tc
      | TyCon -> Bool
    isDataTyCon TyCon
    tc = (Id -> CoreBind) -> [Id] -> CoreProgram
    forall a b. (a -> b) -> [a] -> [b]
    map Id -> CoreBind
    get_defn ((DataCon -> Maybe Id) -> [DataCon] -> [Id]
    forall a b. (a -> Maybe b) -> [a] -> [b]
    mapMaybe DataCon -> Maybe Id
    dataConWrapId_maybe (TyCon -> [DataCon]
    tyConDataCons TyCon
    tc))
      | Bool
    otherwise      = []
        -- The 'otherwise' includes family TyCons of course, but also (less obviously)
        --  * Newtypes: see Note [Compulsory newtype unfolding] in GHC.Types.Id.Make
        --  * type data: we don't want any code for type-only stuff (#24620)

    getClassImplicitBinds :: Class -> [CoreBind]
    getClassImplicitBinds :: Class -> CoreProgram
    getClassImplicitBinds Class
    cls
      = [ Id -> Expr Id -> CoreBind
    forall b. b -> Expr b -> Bind b
    NonRec Id
    op (Class -> Arity -> Expr Id
    mkDictSelRhs Class
    cls Arity
    val_index)
        | (Id
    op, Arity
    val_index) <- Class -> [Id]
    classAllSelIds Class
    cls [Id] -> [Arity] -> [(Id, Arity)]
    forall a b. [a] -> [b] -> [(a, b)]
    `zip` [Arity
    0..] ]

    get_defn :: Id -> CoreBind
    get_defn :: Id -> CoreBind
    get_defn Id
    id = Id -> Expr Id -> CoreBind
    forall b. b -> Expr b -> Bind b
    NonRec Id
    id (Unfolding -> Expr Id
    unfoldingTemplate (Id -> Unfolding
    realIdUnfolding Id
    id))

    {-
    ************************************************************************
    *                                                                      *
    \subsection{Step 1: finding externals}
    *                                                                      *
    ************************************************************************

    See Note [Choosing external Ids].
    -}

    type UnfoldEnv  = IdEnv (Name{-new name-}, Bool {-show unfolding-})
      -- Maps each top-level Id to its new Name (the Id is tidied in step 2)
      -- The Unique is unchanged.  If the new Name is external, it will be
      -- visible in the interface file.
      --
      -- Bool => expose unfolding or not.

    chooseExternalIds :: TidyOpts
                      -> Module
                      -> [CoreBind]
                      -> [CoreRule]
                      -> IO (UnfoldEnv, TidyOccEnv)
                      -- Step 1 from the notes above

    chooseExternalIds :: TidyOpts
    -> Module
    -> CoreProgram
    -> [CoreRule]
    -> IO (UnfoldEnv, TidyOccEnv)
    chooseExternalIds TidyOpts
    opts Module
    mod CoreProgram
    binds [CoreRule]
    imp_id_rules
      = do { (unfold_env1,occ_env1) <- [(Id, Id)] -> UnfoldEnv -> TidyOccEnv -> IO (UnfoldEnv, TidyOccEnv)
    search [(Id, Id)]
    init_work_list UnfoldEnv
    forall a. VarEnv a
    emptyVarEnv TidyOccEnv
    init_occ_env
           ; let internal_ids = (Id -> Bool) -> [Id] -> [Id]
    forall a. (a -> Bool) -> [a] -> [a]
    filter (Bool -> Bool
    not (Bool -> Bool) -> (Id -> Bool) -> Id -> Bool
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . (Id -> UnfoldEnv -> Bool
    forall a. Id -> VarEnv a -> Bool
    `elemVarEnv` UnfoldEnv
    unfold_env1)) [Id]
    binders
           ; tidy_internal internal_ids unfold_env1 occ_env1 }
     where
      name_cache :: NameCache
    name_cache = TidyOpts -> NameCache
    opt_name_cache TidyOpts
    opts

      -- init_ext_ids is the initial list of Ids that should be
      -- externalised.  It serves as the starting point for finding a
      -- deterministic, tidy, renaming for all external Ids in this
      -- module.
      --
      -- It is sorted, so that it has a deterministic order (i.e. it's the
      -- same list every time this module is compiled), in contrast to the
      -- bindings, which are ordered non-deterministically.
      init_work_list :: [(Id, Id)]
    init_work_list = [Id] -> [Id] -> [(Id, Id)]
    forall a b. [a] -> [b] -> [(a, b)]
    zip [Id]
    init_ext_ids [Id]
    init_ext_ids
      init_ext_ids :: [Id]
    init_ext_ids   = (Id -> Id -> Ordering) -> [Id] -> [Id]
    forall a. (a -> a -> Ordering) -> [a] -> [a]
    sortBy (OccName -> OccName -> Ordering
    forall a. Ord a => a -> a -> Ordering
    compare (OccName -> OccName -> Ordering)
    -> (Id -> OccName) -> Id -> Id -> Ordering
    forall b c a. (b -> b -> c) -> (a -> b) -> a -> a -> c
    `on` Id -> OccName
    forall a. NamedThing a => a -> OccName
    getOccName) ([Id] -> [Id]) -> [Id] -> [Id]
    forall a b. (a -> b) -> a -> b
    $ (Id -> Bool) -> [Id] -> [Id]
    forall a. (a -> Bool) -> [a] -> [a]
    filter Id -> Bool
    is_external [Id]
    binders

      -- An Id should be external if either (a) it is exported,
      -- (b) local rules are exposed and it appears in the RHS of a local rule for
      -- an imported Id, or See Note [Which rules to expose]
      is_external :: Id -> Bool
    is_external Id
    id
        | Id -> Bool
    isExportedId Id
    id       = Bool
    True
        | TidyOpts -> Bool
    opt_expose_rules TidyOpts
    opts = Id
    id Id -> VarSet -> Bool
    `elemVarSet` VarSet
    rule_rhs_vars
        | Bool
    otherwise             = Bool
    False

      rule_rhs_vars :: VarSet
    rule_rhs_vars = (CoreRule -> VarSet) -> [CoreRule] -> VarSet
    forall a. (a -> VarSet) -> [a] -> VarSet
    mapUnionVarSet CoreRule -> VarSet
    ruleRhsFreeVars [CoreRule]
    imp_id_rules

      binders :: [Id]
    binders          = ((Id, Expr Id) -> Id) -> [(Id, Expr Id)] -> [Id]
    forall a b. (a -> b) -> [a] -> [b]
    map (Id, Expr Id) -> Id
    forall a b. (a, b) -> a
    fst ([(Id, Expr Id)] -> [Id]) -> [(Id, Expr Id)] -> [Id]
    forall a b. (a -> b) -> a -> b
    $ CoreProgram -> [(Id, Expr Id)]
    forall b. [Bind b] -> [(b, Expr b)]
    flattenBinds CoreProgram
    binds
      binder_set :: VarSet
    binder_set       = [Id] -> VarSet
    mkVarSet [Id]
    binders

      avoids :: [OccName]
    avoids   = [Name -> OccName
    forall a. NamedThing a => a -> OccName
    getOccName Name
    name | Id
    bndr <- [Id]
    binders,
                                    let name :: Name
    name = Id -> Name
    idName Id
    bndr,
                                    Name -> Bool
    isExternalName Name
    name ]
                    -- In computing our "avoids" list, we must include
                    --      all implicit Ids
                    --      all things with global names (assigned once and for
                    --                                      all by the renamer)
                    -- since their names are "taken".
                    -- The type environment is a convenient source of such things.
                    -- In particular, the set of binders doesn't include
                    -- implicit Ids at this stage.

            -- We also make sure to avoid any exported binders.  Consider
            --      f{-u1-} = 1     -- Local decl
            --      ...
            --      f{-u2-} = 2     -- Exported decl
            --
            -- The second exported decl must 'get' the name 'f', so we
            -- have to put 'f' in the avoids list before we get to the first
            -- decl.  tidyTopId then does a no-op on exported binders.
      init_occ_env :: TidyOccEnv
    init_occ_env = [OccName] -> TidyOccEnv
    initTidyOccEnv [OccName]
    avoids

      search :: [(Id,Id)]    -- The work-list: (external id, referring id)
                             -- Make a tidy, external Name for the external id,
                             --   add it to the UnfoldEnv, and do the same for the
                             --   transitive closure of Ids it refers to
                             -- The referring id is used to generate a tidy
                             ---  name for the external id
             -> UnfoldEnv    -- id -> (new Name, show_unfold)
             -> TidyOccEnv   -- occ env for choosing new Names
             -> IO (UnfoldEnv, TidyOccEnv)

      search :: [(Id, Id)] -> UnfoldEnv -> TidyOccEnv -> IO (UnfoldEnv, TidyOccEnv)
    search [] UnfoldEnv
    unfold_env TidyOccEnv
    occ_env = (UnfoldEnv, TidyOccEnv) -> IO (UnfoldEnv, TidyOccEnv)
    forall a. a -> IO a
    forall (m :: * -> *) a. Monad m => a -> m a
    return (UnfoldEnv
    unfold_env, TidyOccEnv
    occ_env)

      search ((Id
    idocc,Id
    referrer) : [(Id, Id)]
    rest) UnfoldEnv
    unfold_env TidyOccEnv
    occ_env
        | Id
    idocc Id -> UnfoldEnv -> Bool
    forall a. Id -> VarEnv a -> Bool
    `elemVarEnv` UnfoldEnv
    unfold_env = [(Id, Id)] -> UnfoldEnv -> TidyOccEnv -> IO (UnfoldEnv, TidyOccEnv)
    search [(Id, Id)]
    rest UnfoldEnv
    unfold_env TidyOccEnv
    occ_env
        | Bool
    otherwise = do
          (occ_env', name') <- Module
    -> NameCache
    -> Maybe Id
    -> TidyOccEnv
    -> Id
    -> IO (TidyOccEnv, Name)
    tidyTopName Module
    mod NameCache
    name_cache (Id -> Maybe Id
    forall a. a -> Maybe a
    Just Id
    referrer) TidyOccEnv
    occ_env Id
    idocc
          let
              (new_ids, show_unfold) = addExternal opts refined_id

                    -- 'idocc' is an *occurrence*, but we need to see the
                    -- unfolding in the *definition*; so look up in binder_set
              refined_id = case VarSet -> Id -> Maybe Id
    lookupVarSet VarSet
    binder_set Id
    idocc of
                             Just Id
    id -> Id
    id
                             Maybe Id
    Nothing -> Bool -> String -> SDoc -> Id -> Id
    forall a. HasCallStack => Bool -> String -> SDoc -> a -> a
    warnPprTrace Bool
    True String
    "chooseExternalIds" (Id -> SDoc
    forall a. Outputable a => a -> SDoc
    ppr Id
    idocc) Id
    idocc

              unfold_env' = UnfoldEnv -> Id -> (Name, Bool) -> UnfoldEnv
    forall a. VarEnv a -> Id -> a -> VarEnv a
    extendVarEnv UnfoldEnv
    unfold_env Id
    idocc (Name
    name',Bool
    show_unfold)
              referrer' | Id -> Bool
    isExportedId Id
    refined_id = Id
    refined_id
                        | Bool
    otherwise               = Id
    referrer
          --
          search (zip new_ids (repeat referrer') ++ rest) unfold_env' occ_env'

      tidy_internal :: [Id] -> UnfoldEnv -> TidyOccEnv
                    -> IO (UnfoldEnv, TidyOccEnv)
      tidy_internal :: [Id] -> UnfoldEnv -> TidyOccEnv -> IO (UnfoldEnv, TidyOccEnv)
    tidy_internal []       UnfoldEnv
    unfold_env TidyOccEnv
    occ_env = (UnfoldEnv, TidyOccEnv) -> IO (UnfoldEnv, TidyOccEnv)
    forall a. a -> IO a
    forall (m :: * -> *) a. Monad m => a -> m a
    return (UnfoldEnv
    unfold_env,TidyOccEnv
    occ_env)
      tidy_internal (Id
    id:[Id]
    ids) UnfoldEnv
    unfold_env TidyOccEnv
    occ_env = do
          (occ_env', name') <- Module
    -> NameCache
    -> Maybe Id
    -> TidyOccEnv
    -> Id
    -> IO (TidyOccEnv, Name)
    tidyTopName Module
    mod NameCache
    name_cache Maybe Id
    forall a. Maybe a
    Nothing TidyOccEnv
    occ_env Id
    id
          let unfold_env' = UnfoldEnv -> Id -> (Name, Bool) -> UnfoldEnv
    forall a. VarEnv a -> Id -> a -> VarEnv a
    extendVarEnv UnfoldEnv
    unfold_env Id
    id (Name
    name',Bool
    False)
          tidy_internal ids unfold_env' occ_env'

    addExternal :: TidyOpts -> Id -> ([Id], Bool)
    addExternal :: TidyOpts -> Id -> ([Id], Bool)
    addExternal TidyOpts
    opts Id
    id
      | UnfoldingExposure
    ExposeNone <- TidyOpts -> UnfoldingExposure
    opt_expose_unfoldings TidyOpts
    opts
      , Bool -> Bool
    not (Unfolding -> Bool
    isCompulsoryUnfolding Unfolding
    unfolding)
      = ([], Bool
    False)  -- See Note [Always expose compulsory unfoldings]
                     -- in GHC.HsToCore

      | Bool
    otherwise
      = ([Id]
    new_needed_ids, Bool
    show_unfold)

      where
        new_needed_ids :: [Id]
    new_needed_ids = Bool -> Id -> [Id]
    bndrFvsInOrder Bool
    show_unfold Id
    id
        idinfo :: IdInfo
    idinfo         = HasDebugCallStack => Id -> IdInfo
    Id -> IdInfo
    idInfo Id
    id
        unfolding :: Unfolding
    unfolding      = IdInfo -> Unfolding
    realUnfoldingInfo IdInfo
    idinfo
        show_unfold :: Bool
    show_unfold    = Unfolding -> Bool
    show_unfolding Unfolding
    unfolding
        never_active :: Bool
    never_active   = Activation -> Bool
    isNeverActive (InlinePragma -> Activation
    inlinePragmaActivation (IdInfo -> InlinePragma
    inlinePragInfo IdInfo
    idinfo))
        loop_breaker :: Bool
    loop_breaker   = OccInfo -> Bool
    isStrongLoopBreaker (IdInfo -> OccInfo
    occInfo IdInfo
    idinfo)
        bottoming_fn :: Bool
    bottoming_fn   = DmdSig -> Bool
    isDeadEndSig (IdInfo -> DmdSig
    dmdSigInfo IdInfo
    idinfo)

            -- Stuff to do with the Id's unfolding
            -- We leave the unfolding there even if there is a worker
            -- In GHCi the unfolding is used by importers

        show_unfolding :: Unfolding -> Bool
    show_unfolding (CoreUnfolding { uf_src :: Unfolding -> UnfoldingSource
    uf_src = UnfoldingSource
    src, uf_guidance :: Unfolding -> UnfoldingGuidance
    uf_guidance = UnfoldingGuidance
    guidance })
           = TidyOpts -> UnfoldingExposure
    opt_expose_unfoldings TidyOpts
    opts UnfoldingExposure -> UnfoldingExposure -> Bool
    forall a. Eq a => a -> a -> Bool
    == UnfoldingExposure
    ExposeAll
                -- 'ExposeAll' says to expose all
                -- unfoldings willy-nilly

           Bool -> Bool -> Bool
    || UnfoldingSource -> Bool
    isStableSource UnfoldingSource
    src     -- Always expose things whose
                                     -- source is an inline rule

           Bool -> Bool -> Bool
    || Bool -> Bool
    not Bool
    dont_inline
           where
             dont_inline :: Bool
    dont_inline
                | Bool
    never_active = Bool
    True   -- Will never inline
                | Bool
    loop_breaker = Bool
    True   -- Ditto
                | Bool
    otherwise    = case UnfoldingGuidance
    guidance of
                                    UnfWhen {}       -> Bool
    False
                                    UnfIfGoodArgs {} -> Bool
    bottoming_fn
                                    UnfNever {}      -> Bool
    True
             -- bottoming_fn: don't inline bottoming functions, unless the
             -- RHS is very small or trivial (UnfWhen), in which case we
             -- may as well do so For example, a cast might cancel with
             -- the call site.

        show_unfolding (DFunUnfolding {}) = Bool
    True
        show_unfolding Unfolding
    _                  = Bool
    False

    {-
    ************************************************************************
    *                                                                      *
                   Deterministic free variables
    *                                                                      *
    ************************************************************************

    We want a deterministic free-variable list.  exprFreeVars gives us
    a VarSet, which is in a non-deterministic order when converted to a
    list.  Hence, here we define a free-variable finder that returns
    the free variables in the order that they are encountered.

    See Note [Choosing external Ids]
    -}

    bndrFvsInOrder :: Bool -> Id -> [Id]
    bndrFvsInOrder :: Bool -> Id -> [Id]
    bndrFvsInOrder Bool
    show_unfold Id
    id
      = DFFV () -> [Id]
    run (Bool -> Id -> DFFV ()
    dffvLetBndr Bool
    show_unfold Id
    id)

    run :: DFFV () -> [Id]
    run :: DFFV () -> [Id]
    run (DFFV VarSet -> (VarSet, [Id]) -> ((VarSet, [Id]), ())
    m) = case VarSet -> (VarSet, [Id]) -> ((VarSet, [Id]), ())
    m VarSet
    emptyVarSet (VarSet
    emptyVarSet, []) of
                     ((VarSet
    _,[Id]
    ids),()
    _) -> [Id]
    ids

    newtype DFFV a
      = DFFV (VarSet              -- Envt: non-top-level things that are in scope
                                  -- we don't want to record these as free vars
          -> (VarSet, [Var])      -- Input State: (set, list) of free vars so far
          -> ((VarSet,[Var]),a))  -- Output state
        deriving ((forall a b. (a -> b) -> DFFV a -> DFFV b)
    -> (forall a b. a -> DFFV b -> DFFV a) -> Functor DFFV
    forall a b. a -> DFFV b -> DFFV a
    forall a b. (a -> b) -> DFFV a -> DFFV b
    forall (f :: * -> *).
    (forall a b. (a -> b) -> f a -> f b)
    -> (forall a b. a -> f b -> f a) -> Functor f
    $cfmap :: forall a b. (a -> b) -> DFFV a -> DFFV b
    fmap :: forall a b. (a -> b) -> DFFV a -> DFFV b
    $c<$ :: forall a b. a -> DFFV b -> DFFV a
    <$ :: forall a b. a -> DFFV b -> DFFV a
    Functor)

    instance Applicative DFFV where
        pure :: forall a. a -> DFFV a
    pure a
    a = (VarSet -> (VarSet, [Id]) -> ((VarSet, [Id]), a)) -> DFFV a
    forall a.
    (VarSet -> (VarSet, [Id]) -> ((VarSet, [Id]), a)) -> DFFV a
    DFFV ((VarSet -> (VarSet, [Id]) -> ((VarSet, [Id]), a)) -> DFFV a)
    -> (VarSet -> (VarSet, [Id]) -> ((VarSet, [Id]), a)) -> DFFV a
    forall a b. (a -> b) -> a -> b
    $ \VarSet
    _ (VarSet, [Id])
    st -> ((VarSet, [Id])
    st, a
    a)
        <*> :: forall a b. DFFV (a -> b) -> DFFV a -> DFFV b
    (<*>) = DFFV (a -> b) -> DFFV a -> DFFV b
    forall (m :: * -> *) a b. Monad m => m (a -> b) -> m a -> m b
    ap

    instance Monad DFFV where
      (DFFV VarSet -> (VarSet, [Id]) -> ((VarSet, [Id]), a)
    m) >>= :: forall a b. DFFV a -> (a -> DFFV b) -> DFFV b
    >>= a -> DFFV b
    k = (VarSet -> (VarSet, [Id]) -> ((VarSet, [Id]), b)) -> DFFV b
    forall a.
    (VarSet -> (VarSet, [Id]) -> ((VarSet, [Id]), a)) -> DFFV a
    DFFV ((VarSet -> (VarSet, [Id]) -> ((VarSet, [Id]), b)) -> DFFV b)
    -> (VarSet -> (VarSet, [Id]) -> ((VarSet, [Id]), b)) -> DFFV b
    forall a b. (a -> b) -> a -> b
    $ \VarSet
    env (VarSet, [Id])
    st ->
        case VarSet -> (VarSet, [Id]) -> ((VarSet, [Id]), a)
    m VarSet
    env (VarSet, [Id])
    st of
           ((VarSet, [Id])
    st',a
    a) -> case a -> DFFV b
    k a
    a of
                         DFFV VarSet -> (VarSet, [Id]) -> ((VarSet, [Id]), b)
    f -> VarSet -> (VarSet, [Id]) -> ((VarSet, [Id]), b)
    f VarSet
    env (VarSet, [Id])
    st'

    extendScope :: Var -> DFFV a -> DFFV a
    extendScope :: forall a. Id -> DFFV a -> DFFV a
    extendScope Id
    v (DFFV VarSet -> (VarSet, [Id]) -> ((VarSet, [Id]), a)
    f) = (VarSet -> (VarSet, [Id]) -> ((VarSet, [Id]), a)) -> DFFV a
    forall a.
    (VarSet -> (VarSet, [Id]) -> ((VarSet, [Id]), a)) -> DFFV a
    DFFV (\VarSet
    env (VarSet, [Id])
    st -> VarSet -> (VarSet, [Id]) -> ((VarSet, [Id]), a)
    f (VarSet -> Id -> VarSet
    extendVarSet VarSet
    env Id
    v) (VarSet, [Id])
    st)

    extendScopeList :: [Var] -> DFFV a -> DFFV a
    extendScopeList :: forall a. [Id] -> DFFV a -> DFFV a
    extendScopeList [Id]
    vs (DFFV VarSet -> (VarSet, [Id]) -> ((VarSet, [Id]), a)
    f) = (VarSet -> (VarSet, [Id]) -> ((VarSet, [Id]), a)) -> DFFV a
    forall a.
    (VarSet -> (VarSet, [Id]) -> ((VarSet, [Id]), a)) -> DFFV a
    DFFV (\VarSet
    env (VarSet, [Id])
    st -> VarSet -> (VarSet, [Id]) -> ((VarSet, [Id]), a)
    f (VarSet -> [Id] -> VarSet
    extendVarSetList VarSet
    env [Id]
    vs) (VarSet, [Id])
    st)

    insert :: Var -> DFFV ()
    insert :: Id -> DFFV ()
    insert Id
    v = (VarSet -> (VarSet, [Id]) -> ((VarSet, [Id]), ())) -> DFFV ()
    forall a.
    (VarSet -> (VarSet, [Id]) -> ((VarSet, [Id]), a)) -> DFFV a
    DFFV ((VarSet -> (VarSet, [Id]) -> ((VarSet, [Id]), ())) -> DFFV ())
    -> (VarSet -> (VarSet, [Id]) -> ((VarSet, [Id]), ())) -> DFFV ()
    forall a b. (a -> b) -> a -> b
    $ \ VarSet
    env (VarSet
    set, [Id]
    ids) ->
               let keep_me :: Bool
    keep_me = Id -> Bool
    isLocalId Id
    v Bool -> Bool -> Bool
    &&
                             Bool -> Bool
    not (Id
    v Id -> VarSet -> Bool
    `elemVarSet` VarSet
    env) Bool -> Bool -> Bool
    &&
                               Bool -> Bool
    not (Id
    v Id -> VarSet -> Bool
    `elemVarSet` VarSet
    set)
               in if Bool
    keep_me
                  then ((VarSet -> Id -> VarSet
    extendVarSet VarSet
    set Id
    v, Id
    vId -> [Id] -> [Id]
    forall a. a -> [a] -> [a]
    :[Id]
    ids), ())
                  else ((VarSet
    set,                [Id]
    ids),   ())

    dffvExpr :: CoreExpr -> DFFV ()
    dffvExpr :: Expr Id -> DFFV ()
    dffvExpr (Var Id
    v)              = Id -> DFFV ()
    insert Id
    v
    dffvExpr (App Expr Id
    e1 Expr Id
    e2)          = Expr Id -> DFFV ()
    dffvExpr Expr Id
    e1 DFFV () -> DFFV () -> DFFV ()
    forall a b. DFFV a -> DFFV b -> DFFV b
    forall (m :: * -> *) a b. Monad m => m a -> m b -> m b
    >> Expr Id -> DFFV ()
    dffvExpr Expr Id
    e2
    dffvExpr (Lam Id
    v Expr Id
    e)            = Id -> DFFV () -> DFFV ()
    forall a. Id -> DFFV a -> DFFV a
    extendScope Id
    v (Expr Id -> DFFV ()
    dffvExpr Expr Id
    e)
    dffvExpr (Tick (Breakpoint XBreakpoint 'TickishPassCore
    _ Arity
    _ [XTickishId 'TickishPassCore]
    ids Module
    _) Expr Id
    e) = (Id -> DFFV ()) -> [Id] -> DFFV ()
    forall (t :: * -> *) (m :: * -> *) a b.
    (Foldable t, Monad m) =>
    (a -> m b) -> t a -> m ()
    mapM_ Id -> DFFV ()
    insert [Id]
    [XTickishId 'TickishPassCore]
    ids DFFV () -> DFFV () -> DFFV ()
    forall a b. DFFV a -> DFFV b -> DFFV b
    forall (m :: * -> *) a b. Monad m => m a -> m b -> m b
    >> Expr Id -> DFFV ()
    dffvExpr Expr Id
    e
    dffvExpr (Tick GenTickish 'TickishPassCore
    _other Expr Id
    e)    = Expr Id -> DFFV ()
    dffvExpr Expr Id
    e
    dffvExpr (Cast Expr Id
    e CoercionR
    _)           = Expr Id -> DFFV ()
    dffvExpr Expr Id
    e
    dffvExpr (Let (NonRec Id
    x Expr Id
    r) Expr Id
    e) = (Id, Expr Id) -> DFFV ()
    dffvBind (Id
    x,Expr Id
    r) DFFV () -> DFFV () -> DFFV ()
    forall a b. DFFV a -> DFFV b -> DFFV b
    forall (m :: * -> *) a b. Monad m => m a -> m b -> m b
    >> Id -> DFFV () -> DFFV ()
    forall a. Id -> DFFV a -> DFFV a
    extendScope Id
    x (Expr Id -> DFFV ()
    dffvExpr Expr Id
    e)
    dffvExpr (Let (Rec [(Id, Expr Id)]
    prs) Expr Id
    e)    = [Id] -> DFFV () -> DFFV ()
    forall a. [Id] -> DFFV a -> DFFV a
    extendScopeList (((Id, Expr Id) -> Id) -> [(Id, Expr Id)] -> [Id]
    forall a b. (a -> b) -> [a] -> [b]
    map (Id, Expr Id) -> Id
    forall a b. (a, b) -> a
    fst [(Id, Expr Id)]
    prs) (DFFV () -> DFFV ()) -> DFFV () -> DFFV ()
    forall a b. (a -> b) -> a -> b
    $
                                    (((Id, Expr Id) -> DFFV ()) -> [(Id, Expr Id)] -> DFFV ()
    forall (t :: * -> *) (m :: * -> *) a b.
    (Foldable t, Monad m) =>
    (a -> m b) -> t a -> m ()
    mapM_ (Id, Expr Id) -> DFFV ()
    dffvBind [(Id, Expr Id)]
    prs DFFV () -> DFFV () -> DFFV ()
    forall a b. DFFV a -> DFFV b -> DFFV b
    forall (m :: * -> *) a b. Monad m => m a -> m b -> m b
    >> Expr Id -> DFFV ()
    dffvExpr Expr Id
    e)
    dffvExpr (Case Expr Id
    e Id
    b Type
    _ [Alt Id]
    as)      = Expr Id -> DFFV ()
    dffvExpr Expr Id
    e DFFV () -> DFFV () -> DFFV ()
    forall a b. DFFV a -> DFFV b -> DFFV b
    forall (m :: * -> *) a b. Monad m => m a -> m b -> m b
    >> Id -> DFFV () -> DFFV ()
    forall a. Id -> DFFV a -> DFFV a
    extendScope Id
    b ((Alt Id -> DFFV ()) -> [Alt Id] -> DFFV ()
    forall (t :: * -> *) (m :: * -> *) a b.
    (Foldable t, Monad m) =>
    (a -> m b) -> t a -> m ()
    mapM_ Alt Id -> DFFV ()
    dffvAlt [Alt Id]
    as)
    dffvExpr Expr Id
    _other               = () -> DFFV ()
    forall a. a -> DFFV a
    forall (m :: * -> *) a. Monad m => a -> m a
    return ()

    dffvAlt :: CoreAlt -> DFFV ()
    dffvAlt :: Alt Id -> DFFV ()
    dffvAlt (Alt AltCon
    _ [Id]
    xs Expr Id
    r) = [Id] -> DFFV () -> DFFV ()
    forall a. [Id] -> DFFV a -> DFFV a
    extendScopeList [Id]
    xs (Expr Id -> DFFV ()
    dffvExpr Expr Id
    r)

    dffvBind :: (Id, CoreExpr) -> DFFV ()
    dffvBind :: (Id, Expr Id) -> DFFV ()
    dffvBind(Id
    x,Expr Id
    r)
      | Bool -> Bool
    not (Id -> Bool
    isId Id
    x) = Expr Id -> DFFV ()
    dffvExpr Expr Id
    r
      | Bool
    otherwise    = Bool -> Id -> DFFV ()
    dffvLetBndr Bool
    False Id
    x DFFV () -> DFFV () -> DFFV ()
    forall a b. DFFV a -> DFFV b -> DFFV b
    forall (m :: * -> *) a b. Monad m => m a -> m b -> m b
    >> Expr Id -> DFFV ()
    dffvExpr Expr Id
    r
                    -- Pass False because we are doing the RHS right here
                    -- If you say True you'll get *exponential* behaviour!

    dffvLetBndr :: Bool -> Id -> DFFV ()
    -- Gather the free vars of the RULES and unfolding of a binder
    -- We always get the free vars of a *stable* unfolding, but
    -- for a *vanilla* one (VanillaSrc), the flag controls what happens:
    --   True <=> get fvs of even a *vanilla* unfolding
    --   False <=> ignore a VanillaSrc
    -- For nested bindings (call from dffvBind) we always say "False" because
    --       we are taking the fvs of the RHS anyway
    -- For top-level bindings (call from addExternal, via bndrFvsInOrder)
    --       we say "True" if we are exposing that unfolding
    dffvLetBndr :: Bool -> Id -> DFFV ()
    dffvLetBndr Bool
    vanilla_unfold Id
    id
      = do { Unfolding -> DFFV ()
    go_unf (IdInfo -> Unfolding
    realUnfoldingInfo IdInfo
    idinfo)
           ; (CoreRule -> DFFV ()) -> [CoreRule] -> DFFV ()
    forall (t :: * -> *) (m :: * -> *) a b.
    (Foldable t, Monad m) =>
    (a -> m b) -> t a -> m ()
    mapM_ CoreRule -> DFFV ()
    go_rule (RuleInfo -> [CoreRule]
    ruleInfoRules (IdInfo -> RuleInfo
    ruleInfo IdInfo
    idinfo)) }
      where
        idinfo :: IdInfo
    idinfo = HasDebugCallStack => Id -> IdInfo
    Id -> IdInfo
    idInfo Id
    id

        go_unf :: Unfolding -> DFFV ()
    go_unf (CoreUnfolding { uf_tmpl :: Unfolding -> Expr Id
    uf_tmpl = Expr Id
    rhs, uf_src :: Unfolding -> UnfoldingSource
    uf_src = UnfoldingSource
    src })
           | UnfoldingSource -> Bool
    isStableSource UnfoldingSource
    src = Expr Id -> DFFV ()
    dffvExpr Expr Id
    rhs
           | Bool
    vanilla_unfold     = Expr Id -> DFFV ()
    dffvExpr Expr Id
    rhs
           | Bool
    otherwise          = () -> DFFV ()
    forall a. a -> DFFV a
    forall (m :: * -> *) a. Monad m => a -> m a
    return ()

        go_unf (DFunUnfolding { df_bndrs :: Unfolding -> [Id]
    df_bndrs = [Id]
    bndrs, df_args :: Unfolding -> [Expr Id]
    df_args = [Expr Id]
    args })
                 = [Id] -> DFFV () -> DFFV ()
    forall a. [Id] -> DFFV a -> DFFV a
    extendScopeList [Id]
    bndrs (DFFV () -> DFFV ()) -> DFFV () -> DFFV ()
    forall a b. (a -> b) -> a -> b
    $ (Expr Id -> DFFV ()) -> [Expr Id] -> DFFV ()
    forall (t :: * -> *) (m :: * -> *) a b.
    (Foldable t, Monad m) =>
    (a -> m b) -> t a -> m ()
    mapM_ Expr Id -> DFFV ()
    dffvExpr [Expr Id]
    args
        go_unf Unfolding
    _ = () -> DFFV ()
    forall a. a -> DFFV a
    forall (m :: * -> *) a. Monad m => a -> m a
    return ()

        go_rule :: CoreRule -> DFFV ()
    go_rule (BuiltinRule {}) = () -> DFFV ()
    forall a. a -> DFFV a
    forall (m :: * -> *) a. Monad m => a -> m a
    return ()
        go_rule (Rule { ru_bndrs :: CoreRule -> [Id]
    ru_bndrs = [Id]
    bndrs, ru_rhs :: CoreRule -> Expr Id
    ru_rhs = Expr Id
    rhs })
          = [Id] -> DFFV () -> DFFV ()
    forall a. [Id] -> DFFV a -> DFFV a
    extendScopeList [Id]
    bndrs (Expr Id -> DFFV ()
    dffvExpr Expr Id
    rhs)

    {-
    ************************************************************************
    *                                                                      *
                   findExternalRules
    *                                                                      *
    ************************************************************************

    Note [Finding external rules]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    The complete rules are gotten by combining
       a) local rules for imported Ids
       b) rules embedded in the top-level Ids

    There are two complications:
      * Note [Which rules to expose]
      * Note [Trimming auto-rules]

    Note [Which rules to expose]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    The function 'expose_rule' filters out rules that mention, on the LHS,
    Ids that aren't externally visible; these rules can't fire in a client
    module.

    The externally-visible binders are computed (by chooseExternalIds)
    assuming that all orphan rules are externalised (see init_ext_ids in
    function 'search'). So in fact it's a bit conservative and we may
    export more than we need.  (It's a sort of mutual recursion.)

    Note [Trimming auto-rules]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~
    Second, with auto-specialisation we may specialise local or imported
    dfuns or INLINE functions, and then later inline them.  That may leave
    behind something like
       RULE "foo" forall d. f @ Int d = f_spec
    where f is either local or imported, and there is no remaining
    reference to f_spec except from the RULE.

    Now that RULE *might* be useful to an importing module, but that is
    purely speculative, and meanwhile the code is taking up space and
    codegen time.  I found that binary sizes jumped by 6-10% when I
    started to specialise INLINE functions (again, Note [Inline
    specialisations] in GHC.Core.Opt.Specialise).

    So it seems better to drop the binding for f_spec, and the rule
    itself, if the auto-generated rule is the *only* reason that it is
    being kept alive.

    (The RULE still might have been useful in the past; that is, it was
    the right thing to have generated it in the first place.  See Note
    [Inline specialisations] in GHC.Core.Opt.Specialise. But now it has
    served its purpose, and can be discarded.)

    So findExternalRules does this:
      * Remove all bindings that are kept alive *only* by isAutoRule rules
          (this is done in trim_binds)
      * Remove all auto rules that mention bindings that have been removed
          (this is done by filtering by keep_rule)

    NB: if a binding is kept alive for some *other* reason (e.g. f_spec is
    called in the final code), we keep the rule too.

    This stuff is the only reason for the ru_auto field in a Rule.

    We discard auto-rules by default, but keep them if -fkeep-auto-rules is on.

    * Discard by default: in #18532 we looked at keeping auto-rules and it turned out to just make
      compiler performance worse while increasing code sizes at the same time. The
      impact varied. Compiling Cabal got ~3% slower, allocated ~3% more and wrote 15%
      more code to disk.  Nofib only saw 0.7% more compiler allocations and executable
      file size growth. But given there was no difference in runtime for these
      benchmarks it turned out to be flat out worse.  See the ticket for more details.

    * Keep with -fkeep-auto-rules: in #21917 we found cases where we get a lot code
      duplication when we discard specialisations.  Agda is a case in point.  Having
      a flag gives us control over the rule-trimming decision.
    -}

    findExternalRules :: TidyOpts
                      -> [CoreBind]
                      -> [CoreRule] -- Local rules for imported fns
                      -> UnfoldEnv  -- Ids that are exported, so we need their rules
                      -> ([CoreBind], [CoreRule])
    -- See Note [Finding external rules]
    findExternalRules :: TidyOpts
    -> CoreProgram
    -> [CoreRule]
    -> UnfoldEnv
    -> (CoreProgram, [CoreRule])
    findExternalRules TidyOpts
    opts CoreProgram
    binds [CoreRule]
    imp_id_rules UnfoldEnv
    unfold_env
      = (CoreProgram
    trimmed_binds, (CoreRule -> Bool) -> [CoreRule] -> [CoreRule]
    forall a. (a -> Bool) -> [a] -> [a]
    filter CoreRule -> Bool
    keep_rule [CoreRule]
    all_rules)
      where
        imp_rules :: [CoreRule]
    imp_rules | TidyOpts -> Bool
    opt_expose_rules TidyOpts
    opts = (CoreRule -> Bool) -> [CoreRule] -> [CoreRule]
    forall a. (a -> Bool) -> [a] -> [a]
    filter CoreRule -> Bool
    expose_rule [CoreRule]
    imp_id_rules
                  | Bool
    otherwise             = []
        imp_user_rule_fvs :: VarSet
    imp_user_rule_fvs = (CoreRule -> VarSet) -> [CoreRule] -> VarSet
    forall a. (a -> VarSet) -> [a] -> VarSet
    mapUnionVarSet CoreRule -> VarSet
    user_rule_rhs_fvs [CoreRule]
    imp_rules

        user_rule_rhs_fvs :: CoreRule -> VarSet
    user_rule_rhs_fvs CoreRule
    rule | CoreRule -> Bool
    isAutoRule CoreRule
    rule Bool -> Bool -> Bool
    && Bool -> Bool
    not (TidyOpts -> Bool
    opt_keep_auto_rules TidyOpts
    opts)
                                                 = VarSet
    emptyVarSet
                               | Bool
    otherwise       = CoreRule -> VarSet
    ruleRhsFreeVars CoreRule
    rule

        (CoreProgram
    trimmed_binds, VarSet
    local_bndrs, VarSet
    _, [CoreRule]
    all_rules) = CoreProgram -> (CoreProgram, VarSet, VarSet, [CoreRule])
    trim_binds CoreProgram
    binds

        keep_rule :: CoreRule -> Bool
    keep_rule CoreRule
    rule = CoreRule -> VarSet
    ruleFreeVars CoreRule
    rule VarSet -> VarSet -> Bool
    `subVarSet` VarSet
    local_bndrs
            -- Remove rules that make no sense, because they mention a
            -- local binder (on LHS or RHS) that we have now discarded.
            -- (NB: ruleFreeVars only includes LocalIds)
            --
            -- LHS: we have already filtered out rules that mention internal Ids
            --     on LHS but that isn't enough because we might have by now
            --     discarded a binding with an external Id. (How?
            --     chooseExternalIds is a bit conservative.)
            --
            -- RHS: the auto rules that might mention a binder that has
            --      been discarded; see Note [Trimming auto-rules]

        expose_rule :: CoreRule -> Bool
    expose_rule CoreRule
    rule = (Id -> Bool) -> [Id] -> Bool
    forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
    all Id -> Bool
    is_external_id (CoreRule -> [Id]
    ruleLhsFreeIdsList CoreRule
    rule)
                    -- Don't expose a rule whose LHS mentions a locally-defined
                    -- Id that is completely internal (i.e. not visible to an
                    -- importing module).  NB: ruleLhsFreeIds only returns LocalIds.
                    -- See Note [Which rules to expose]

        is_external_id :: Id -> Bool
    is_external_id Id
    id = case UnfoldEnv -> Id -> Maybe (Name, Bool)
    forall a. VarEnv a -> Id -> Maybe a
    lookupVarEnv UnfoldEnv
    unfold_env Id
    id of
                              Just (Name
    name, Bool
    _) -> Name -> Bool
    isExternalName Name
    name Bool -> Bool -> Bool
    && Bool -> Bool
    not (Id -> Bool
    isImplicitId Id
    id)
                              Maybe (Name, Bool)
    Nothing        -> Bool
    False

        trim_binds :: [CoreBind]
                   -> ( [CoreBind]   -- Trimmed bindings
                      , VarSet       -- Binders of those bindings
                      , VarSet       -- Free vars of those bindings + rhs of user rules
                                     -- (we don't bother to delete the binders)
                      , [CoreRule])  -- All rules, imported + from the bindings
        -- This function removes unnecessary bindings, and gathers up rules from
        -- the bindings we keep.  See Note [Trimming auto-rules]
        trim_binds :: CoreProgram -> (CoreProgram, VarSet, VarSet, [CoreRule])
    trim_binds []  -- Base case, start with imp_user_rule_fvs
           = ([], VarSet
    emptyVarSet, VarSet
    imp_user_rule_fvs, [CoreRule]
    imp_rules)

        trim_binds (CoreBind
    bind:CoreProgram
    binds)
           | (Id -> Bool) -> [Id] -> Bool
    forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
    any Id -> Bool
    needed [Id]
    bndrs    -- Keep this binding
           = ( CoreBind
    bind CoreBind -> CoreProgram -> CoreProgram
    forall a. a -> [a] -> [a]
    : CoreProgram
    binds', VarSet
    bndr_set', VarSet
    needed_fvs', [CoreRule]
    local_rules [CoreRule] -> [CoreRule] -> [CoreRule]
    forall a. [a] -> [a] -> [a]
    ++ [CoreRule]
    rules )
           | Bool
    otherwise           -- Discard binding altogether
           = (CoreProgram, VarSet, VarSet, [CoreRule])
    stuff
           where
             stuff :: (CoreProgram, VarSet, VarSet, [CoreRule])
    stuff@(CoreProgram
    binds', VarSet
    bndr_set, VarSet
    needed_fvs, [CoreRule]
    rules)
                           = CoreProgram -> (CoreProgram, VarSet, VarSet, [CoreRule])
    trim_binds CoreProgram
    binds
             needed :: Id -> Bool
    needed Id
    bndr   = Id -> Bool
    isExportedId Id
    bndr Bool -> Bool -> Bool
    || Id
    bndr Id -> VarSet -> Bool
    `elemVarSet` VarSet
    needed_fvs

             bndrs :: [Id]
    bndrs         = CoreBind -> [Id]
    forall b. Bind b -> [b]
    bindersOf  CoreBind
    bind
             rhss :: [Expr Id]
    rhss          = CoreBind -> [Expr Id]
    forall b. Bind b -> [Expr b]
    rhssOfBind CoreBind
    bind
             bndr_set' :: VarSet
    bndr_set'     = VarSet
    bndr_set VarSet -> [Id] -> VarSet
    `extendVarSetList` [Id]
    bndrs

             needed_fvs' :: VarSet
    needed_fvs'   = VarSet
    needed_fvs                                   VarSet -> VarSet -> VarSet
    `unionVarSet`
                             (Id -> VarSet) -> [Id] -> VarSet
    forall a. (a -> VarSet) -> [a] -> VarSet
    mapUnionVarSet Id -> VarSet
    idUnfoldingVars   [Id]
    bndrs       VarSet -> VarSet -> VarSet
    `unionVarSet`
                                  -- Ignore type variables in the type of bndrs
                             (Expr Id -> VarSet) -> [Expr Id] -> VarSet
    forall a. (a -> VarSet) -> [a] -> VarSet
    mapUnionVarSet Expr Id -> VarSet
    exprFreeVars      [Expr Id]
    rhss        VarSet -> VarSet -> VarSet
    `unionVarSet`
                             (CoreRule -> VarSet) -> [CoreRule] -> VarSet
    forall a. (a -> VarSet) -> [a] -> VarSet
    mapUnionVarSet CoreRule -> VarSet
    user_rule_rhs_fvs [CoreRule]
    local_rules
                -- In needed_fvs', we don't bother to delete binders from the fv set

             local_rules :: [CoreRule]
    local_rules  = [ CoreRule
    rule
                            | TidyOpts -> Bool
    opt_expose_rules TidyOpts
    opts
                            , Id
    id <- [Id]
    bndrs
                            , Id -> Bool
    is_external_id Id
    id   -- Only collect rules for external Ids
                            , CoreRule
    rule <- Id -> [CoreRule]
    idCoreRules Id
    id
                            , CoreRule -> Bool
    expose_rule CoreRule
    rule ]  -- and ones that can fire in a client

    {-
    ************************************************************************
    *                                                                      *
                   tidyTopName
    *                                                                      *
    ************************************************************************

    This is where we set names to local/global based on whether they really are
    externally visible (see comment at the top of this module).  If the name
    was previously local, we have to give it a unique occurrence name if
    we intend to externalise it.
    -}

    tidyTopName :: Module -> NameCache -> Maybe Id -> TidyOccEnv
                -> Id -> IO (TidyOccEnv, Name)
    tidyTopName :: Module
    -> NameCache
    -> Maybe Id
    -> TidyOccEnv
    -> Id
    -> IO (TidyOccEnv, Name)
    tidyTopName Module
    mod NameCache
    name_cache Maybe Id
    maybe_ref TidyOccEnv
    occ_env Id
    id
      | Bool
    global Bool -> Bool -> Bool
    && Bool
    internal = (TidyOccEnv, Name) -> IO (TidyOccEnv, Name)
    forall a. a -> IO a
    forall (m :: * -> *) a. Monad m => a -> m a
    return (TidyOccEnv
    occ_env, Name -> Name
    localiseName Name
    name)

      | Bool
    global Bool -> Bool -> Bool
    && Bool
    external = (TidyOccEnv, Name) -> IO (TidyOccEnv, Name)
    forall a. a -> IO a
    forall (m :: * -> *) a. Monad m => a -> m a
    return (TidyOccEnv
    occ_env, Name
    name)
            -- Global names are assumed to have been allocated by the renamer,
            -- so they already have the "right" unique
            -- And it's a system-wide unique too

      -- Now we get to the real reason that all this is in the IO Monad:
      -- we have to update the name cache in a nice atomic fashion

      | Bool
    local  Bool -> Bool -> Bool
    && Bool
    internal = do uniq <- NameCache -> IO Unique
    takeUniqFromNameCache NameCache
    name_cache
                                -- See #19619
                                let new_local_name = OccName
    occ' OccName -> Name -> Name
    forall a b. a -> b -> b
    `seq` Unique -> OccName -> SrcSpan -> Name
    mkInternalName Unique
    uniq OccName
    occ' SrcSpan
    loc
                                return (occ_env', new_local_name)
            -- Even local, internal names must get a unique occurrence.
            -- This is necessary because the byte-code generator the byte-code
            -- generator builds a system-wide Name->BCO symbol table.

      | Bool
    local  Bool -> Bool -> Bool
    && Bool
    external = do new_external_name <- NameCache -> Module -> OccName -> SrcSpan -> IO Name
    allocateGlobalBinder NameCache
    name_cache Module
    mod OccName
    occ' SrcSpan
    loc
                                return (occ_env', new_external_name)
            -- If we want to externalise a currently-local name, check
            -- whether we have already assigned a unique for it.
            -- If so, use it; if not, extend the table.
            -- All this is done by allocateGlobalBinder.
            -- This is needed when *re*-compiling a module in GHCi; we must
            -- use the same name for externally-visible things as we did before.

      | Bool
    otherwise = String -> IO (TidyOccEnv, Name)
    forall a. HasCallStack => String -> a
    panic String
    "tidyTopName"
      where
        !name :: Name
    name       = Id -> Name
    idName Id
    id
        external :: Bool
    external    = Maybe Id -> Bool
    forall a. Maybe a -> Bool
    isJust Maybe Id
    maybe_ref
        global :: Bool
    global      = Name -> Bool
    isExternalName Name
    name
        local :: Bool
    local       = Bool -> Bool
    not Bool
    global
        internal :: Bool
    internal    = Bool -> Bool
    not Bool
    external
        !loc :: SrcSpan
    loc        = Name -> SrcSpan
    nameSrcSpan Name
    name

        old_occ :: OccName
    old_occ     = Name -> OccName
    nameOccName Name
    name
        new_occ :: OccName
    new_occ | Just Id
    ref <- Maybe Id
    maybe_ref
                , Id
    ref Id -> Id -> Bool
    forall a. Eq a => a -> a -> Bool
    /= Id
    id
                = NameSpace -> String -> OccName
    mkOccName (OccName -> NameSpace
    occNameSpace OccName
    old_occ) (String -> OccName) -> String -> OccName
    forall a b. (a -> b) -> a -> b
    $
                       let
                           ref_str :: String
    ref_str = OccName -> String
    occNameString (Id -> OccName
    forall a. NamedThing a => a -> OccName
    getOccName Id
    ref)
                           occ_str :: String
    occ_str = OccName -> String
    occNameString OccName
    old_occ
                       in
                       case String
    occ_str of
                         Char
    '$':Char
    'w':String
    _ -> String
    occ_str
                            -- workers: the worker for a function already
                            -- includes the occname for its parent, so there's
                            -- no need to prepend the referrer.
                         String
    _other | Name -> Bool
    isSystemName Name
    name -> String
    ref_str
                                | Bool
    otherwise         -> String
    ref_str String -> ShowS
    forall a. [a] -> [a] -> [a]
    ++ Char
    '_' Char -> ShowS
    forall a. a -> [a] -> [a]
    : String
    occ_str
                            -- If this name was system-generated, then don't bother
                            -- to retain its OccName, just use the referrer.  These
                            -- system-generated names will become "f1", "f2", etc. for
                            -- a referrer "f".
                | Bool
    otherwise = OccName
    old_occ

        (TidyOccEnv
    occ_env', OccName
    occ') = TidyOccEnv -> OccName -> (TidyOccEnv, OccName)
    tidyOccName TidyOccEnv
    occ_env OccName
    new_occ

    {-
    ************************************************************************
    *                                                                      *
    \subsection{Step 2: top-level tidying}
    *                                                                      *
    ************************************************************************
    -}

    -- TopTidyEnv: when tidying we need to know
    --   * name_cache: The NameCache, containing a unique supply and any pre-ordained Names.
    --        These may have arisen because the
    --        renamer read in an interface file mentioning M.$wf, say,
    --        and assigned it unique r77.  If, on this compilation, we've
    --        invented an Id whose name is $wf (but with a different unique)
    --        we want to rename it to have unique r77, so that we can do easy
    --        comparisons with stuff from the interface file
    --
    --   * occ_env: The TidyOccEnv, which tells us which local occurrences
    --     are 'used'
    --
    --   * subst_env: A Var->Var mapping that substitutes the new Var for the old

    tidyTopBinds :: UnfoldEnv
                 -> NameSet
                 -> TidyOccEnv
                 -> CoreProgram
                 -> IO (TidyEnv, CoreProgram)

    tidyTopBinds :: UnfoldEnv
    -> NameSet
    -> TidyOccEnv
    -> CoreProgram
    -> IO (TidyEnv, CoreProgram)
    tidyTopBinds UnfoldEnv
    unfold_env NameSet
    boot_exports TidyOccEnv
    init_occ_env CoreProgram
    binds
      = do let result :: (TidyEnv, CoreProgram)
    result = TidyEnv -> CoreProgram -> (TidyEnv, CoreProgram)
    tidy TidyEnv
    init_env CoreProgram
    binds
           CoreProgram -> ()
    seqBinds ((TidyEnv, CoreProgram) -> CoreProgram
    forall a b. (a, b) -> b
    snd (TidyEnv, CoreProgram)
    result) () -> IO (TidyEnv, CoreProgram) -> IO (TidyEnv, CoreProgram)
    forall a b. a -> b -> b
    `seq` (TidyEnv, CoreProgram) -> IO (TidyEnv, CoreProgram)
    forall a. a -> IO a
    forall (m :: * -> *) a. Monad m => a -> m a
    return (TidyEnv, CoreProgram)
    result
           -- This seqBinds avoids a spike in space usage (see #13564)
      where
        init_env :: TidyEnv
    init_env = (TidyOccEnv
    init_occ_env, VarEnv Id
    forall a. VarEnv a
    emptyVarEnv)

        tidy :: TidyEnv -> CoreProgram -> (TidyEnv, CoreProgram)
    tidy = (TidyEnv -> CoreBind -> (TidyEnv, CoreBind))
    -> TidyEnv -> CoreProgram -> (TidyEnv, CoreProgram)
    forall (t :: * -> *) s a b.
    Traversable t =>
    (s -> a -> (s, b)) -> s -> t a -> (s, t b)
    mapAccumL (UnfoldEnv -> NameSet -> TidyEnv -> CoreBind -> (TidyEnv, CoreBind)
    tidyTopBind UnfoldEnv
    unfold_env NameSet
    boot_exports)

    ------------------------
    tidyTopBind  :: UnfoldEnv
                 -> NameSet
                 -> TidyEnv
                 -> CoreBind
                 -> (TidyEnv, CoreBind)

    tidyTopBind :: UnfoldEnv -> NameSet -> TidyEnv -> CoreBind -> (TidyEnv, CoreBind)
    tidyTopBind UnfoldEnv
    unfold_env NameSet
    boot_exports
                (TidyOccEnv
    occ_env,VarEnv Id
    subst1) (NonRec Id
    bndr Expr Id
    rhs)
      = (TidyEnv
    tidy_env2,  Id -> Expr Id -> CoreBind
    forall b. b -> Expr b -> Bind b
    NonRec Id
    bndr' Expr Id
    rhs')
      where
        (Id
    bndr', Expr Id
    rhs') = UnfoldEnv -> NameSet -> TidyEnv -> (Id, Expr Id) -> (Id, Expr Id)
    tidyTopPair UnfoldEnv
    unfold_env NameSet
    boot_exports TidyEnv
    tidy_env2 (Id
    bndr, Expr Id
    rhs)
        subst2 :: VarEnv Id
    subst2        = VarEnv Id -> Id -> Id -> VarEnv Id
    forall a. VarEnv a -> Id -> a -> VarEnv a
    extendVarEnv VarEnv Id
    subst1 Id
    bndr Id
    bndr'
        tidy_env2 :: TidyEnv
    tidy_env2     = (TidyOccEnv
    occ_env, VarEnv Id
    subst2)

    tidyTopBind UnfoldEnv
    unfold_env NameSet
    boot_exports (TidyOccEnv
    occ_env, VarEnv Id
    subst1) (Rec [(Id, Expr Id)]
    prs)
      = (TidyEnv
    tidy_env2, [(Id, Expr Id)] -> CoreBind
    forall b. [(b, Expr b)] -> Bind b
    Rec [(Id, Expr Id)]
    prs')
      where
        prs' :: [(Id, Expr Id)]
    prs'      = ((Id, Expr Id) -> (Id, Expr Id))
    -> [(Id, Expr Id)] -> [(Id, Expr Id)]
    forall a b. (a -> b) -> [a] -> [b]
    map (UnfoldEnv -> NameSet -> TidyEnv -> (Id, Expr Id) -> (Id, Expr Id)
    tidyTopPair UnfoldEnv
    unfold_env NameSet
    boot_exports TidyEnv
    tidy_env2) [(Id, Expr Id)]
    prs
        subst2 :: VarEnv Id
    subst2    = VarEnv Id -> [(Id, Id)] -> VarEnv Id
    forall a. VarEnv a -> [(Id, a)] -> VarEnv a
    extendVarEnvList VarEnv Id
    subst1 (((Id, Expr Id) -> Id) -> [(Id, Expr Id)] -> [Id]
    forall a b. (a -> b) -> [a] -> [b]
    map (Id, Expr Id) -> Id
    forall a b. (a, b) -> a
    fst [(Id, Expr Id)]
    prs [Id] -> [Id] -> [(Id, Id)]
    forall a b. [a] -> [b] -> [(a, b)]
    `zip` ((Id, Expr Id) -> Id) -> [(Id, Expr Id)] -> [Id]
    forall a b. (a -> b) -> [a] -> [b]
    map (Id, Expr Id) -> Id
    forall a b. (a, b) -> a
    fst [(Id, Expr Id)]
    prs')
        tidy_env2 :: TidyEnv
    tidy_env2 = (TidyOccEnv
    occ_env, VarEnv Id
    subst2)
        -- This is where we "tie the knot": tidy_env2 is fed into tidyTopPair

    -----------------------------------------------------------
    tidyTopPair :: UnfoldEnv
                -> NameSet
                -> TidyEnv  -- The TidyEnv is used to tidy the IdInfo
                            -- It is knot-tied: don't look at it!
                -> (Id, CoreExpr)   -- Binder and RHS before tidying
                -> (Id, CoreExpr)
            -- This function is the heart of Step 2
            -- The rec_tidy_env is the one to use for the IdInfo
            -- It's necessary because when we are dealing with a recursive
            -- group, a variable late in the group might be mentioned
            -- in the IdInfo of one early in the group

    tidyTopPair :: UnfoldEnv -> NameSet -> TidyEnv -> (Id, Expr Id) -> (Id, Expr Id)
    tidyTopPair UnfoldEnv
    unfold_env NameSet
    boot_exports TidyEnv
    rhs_tidy_env (Id
    bndr, Expr Id
    rhs)
      = -- pprTrace "tidyTop" (ppr name' <+> ppr details <+> ppr rhs) $
        (Id
    bndr1, Expr Id
    rhs1)

      where
        Just (Name
    name',Bool
    show_unfold) = UnfoldEnv -> Id -> Maybe (Name, Bool)
    forall a. VarEnv a -> Id -> Maybe a
    lookupVarEnv UnfoldEnv
    unfold_env Id
    bndr
        !cbv_bndr :: Id
    cbv_bndr = HasDebugCallStack => NameSet -> Id -> Expr Id -> Id
    NameSet -> Id -> Expr Id -> Id
    tidyCbvInfoTop NameSet
    boot_exports Id
    bndr Expr Id
    rhs
        bndr1 :: Id
    bndr1    = IdDetails -> Name -> Type -> IdInfo -> Id
    mkGlobalId IdDetails
    details Name
    name' Type
    ty' IdInfo
    idinfo'
        details :: IdDetails
    details  = Id -> IdDetails
    idDetails Id
    cbv_bndr -- Preserve the IdDetails
        ty' :: Type
    ty'      = Type -> Type
    tidyTopType (Id -> Type
    idType Id
    cbv_bndr)
        rhs1 :: Expr Id
    rhs1     = TidyEnv -> Expr Id -> Expr Id
    tidyExpr TidyEnv
    rhs_tidy_env Expr Id
    rhs
        idinfo' :: IdInfo
    idinfo'  = TidyEnv
    -> Name -> Type -> Expr Id -> Expr Id -> IdInfo -> Bool -> IdInfo
    tidyTopIdInfo TidyEnv
    rhs_tidy_env Name
    name' Type
    ty'
                                 Expr Id
    rhs Expr Id
    rhs1 (HasDebugCallStack => Id -> IdInfo
    Id -> IdInfo
    idInfo Id
    cbv_bndr) Bool
    show_unfold

    -- tidyTopIdInfo creates the final IdInfo for top-level
    -- binders.  The delicate piece:
    --
    --  * Arity.  After CoreTidy, this arity must not change any more.
    --      Indeed, CorePrep must eta expand where necessary to make
    --      the manifest arity equal to the claimed arity.
    --
    tidyTopIdInfo :: TidyEnv -> Name -> Type
                  -> CoreExpr -> CoreExpr -> IdInfo -> Bool -> IdInfo
    tidyTopIdInfo :: TidyEnv
    -> Name -> Type -> Expr Id -> Expr Id -> IdInfo -> Bool -> IdInfo
    tidyTopIdInfo TidyEnv
    rhs_tidy_env Name
    name Type
    rhs_ty Expr Id
    orig_rhs Expr Id
    tidy_rhs IdInfo
    idinfo Bool
    show_unfold
      | Bool -> Bool
    not Bool
    is_external     -- For internal Ids (not externally visible)
      = IdInfo
    vanillaIdInfo       -- we only need enough info for code generation
                            -- Arity and strictness info are enough;
                            --      c.f. GHC.Core.Tidy.tidyLetBndr
            IdInfo -> Arity -> IdInfo
    `setArityInfo`      Arity
    arity
            IdInfo -> DmdSig -> IdInfo
    `setDmdSigInfo`     DmdSig
    final_sig
            IdInfo -> CprSig -> IdInfo
    `setCprSigInfo`     CprSig
    final_cpr
            IdInfo -> Unfolding -> IdInfo
    `setUnfoldingInfo`  Unfolding
    minimal_unfold_info  -- See note [Preserve evaluatedness]
                                                     -- in GHC.Core.Tidy

      | Bool
    otherwise           -- Externally-visible Ids get the whole lot
      = IdInfo
    vanillaIdInfo
            IdInfo -> Arity -> IdInfo
    `setArityInfo`       Arity
    arity
            IdInfo -> DmdSig -> IdInfo
    `setDmdSigInfo`      DmdSig
    final_sig
            IdInfo -> CprSig -> IdInfo
    `setCprSigInfo`      CprSig
    final_cpr
            IdInfo -> OccInfo -> IdInfo
    `setOccInfo`         OccInfo
    robust_occ_info
            IdInfo -> InlinePragma -> IdInfo
    `setInlinePragInfo`  IdInfo -> InlinePragma
    inlinePragInfo IdInfo
    idinfo
            IdInfo -> Unfolding -> IdInfo
    `setUnfoldingInfo`   Unfolding
    unfold_info
                    -- NB: we throw away the Rules
                    -- They have already been extracted by findExternalRules
      where
        is_external :: Bool
    is_external = Name -> Bool
    isExternalName Name
    name

        --------- OccInfo ------------
        robust_occ_info :: OccInfo
    robust_occ_info = OccInfo -> OccInfo
    zapFragileOcc (IdInfo -> OccInfo
    occInfo IdInfo
    idinfo)
        -- It's important to keep loop-breaker information
        -- when we are doing -fexpose-all-unfoldings

        --------- Strictness ------------
        mb_bot_str :: Maybe (Arity, DmdSig, CprSig)
    mb_bot_str = Expr Id -> Maybe (Arity, DmdSig, CprSig)
    exprBotStrictness_maybe Expr Id
    orig_rhs

        sig :: DmdSig
    sig = IdInfo -> DmdSig
    dmdSigInfo IdInfo
    idinfo
        final_sig :: DmdSig
    final_sig | Bool -> Bool
    not (DmdSig -> Bool
    isNopSig DmdSig
    sig)
                  = Bool -> String -> SDoc -> DmdSig -> DmdSig
    forall a. HasCallStack => Bool -> String -> SDoc -> a -> a
    warnPprTrace (DmdSig -> Bool
    _bottom_hidden DmdSig
    sig) String
    "tidyTopIdInfo" (Name -> SDoc
    forall a. Outputable a => a -> SDoc
    ppr Name
    name) DmdSig
    sig

                  -- No demand signature, so try a
                  -- cheap-and-cheerful bottom analyser
                  | Just (Arity
    _, DmdSig
    bot_str_sig, CprSig
    _) <- Maybe (Arity, DmdSig, CprSig)
    mb_bot_str
                  = DmdSig
    bot_str_sig

                  -- No strictness info
                  | Bool
    otherwise = DmdSig
    nopSig

        cpr :: CprSig
    cpr = IdInfo -> CprSig
    cprSigInfo IdInfo
    idinfo
        final_cpr :: CprSig
    final_cpr | Just (Arity
    _, DmdSig
    _, CprSig
    bot_cpr_sig) <- Maybe (Arity, DmdSig, CprSig)
    mb_bot_str
                  = CprSig
    bot_cpr_sig
                  | Bool
    otherwise
                  = CprSig
    cpr

        _bottom_hidden :: DmdSig -> Bool
    _bottom_hidden DmdSig
    id_sig
          = case Maybe (Arity, DmdSig, CprSig)
    mb_bot_str of
              Maybe (Arity, DmdSig, CprSig)
    Nothing            -> Bool
    False
              Just (Arity
    arity, DmdSig
    _, CprSig
    _) -> Bool -> Bool
    not (DmdSig -> Arity -> Bool
    isDeadEndAppSig DmdSig
    id_sig Arity
    arity)

        --------- Unfolding ------------
        -- Force unfold_info (hence bangs), otherwise the old unfolding
        -- is retained during code generation. See #22071

        unf_info :: Unfolding
    unf_info = IdInfo -> Unfolding
    realUnfoldingInfo IdInfo
    idinfo
        !minimal_unfold_info :: Unfolding
    minimal_unfold_info = Unfolding -> Unfolding
    trimUnfolding Unfolding
    unf_info

        !unfold_info :: Unfolding
    unfold_info | Unfolding -> Bool
    isCompulsoryUnfolding Unfolding
    unf_info Bool -> Bool -> Bool
    || Bool
    show_unfold
                     = TidyEnv -> Expr Id -> Unfolding -> Unfolding
    tidyTopUnfolding TidyEnv
    rhs_tidy_env Expr Id
    tidy_rhs Unfolding
    unf_info
                     | Bool
    otherwise
                     = Unfolding
    minimal_unfold_info
         -- NB: use `orig_rhs` not `tidy_rhs` in this call to mkFinalUnfolding
         -- else you get a black hole (#22122). Reason: mkFinalUnfolding
         -- looks at IdInfo, and that is knot-tied in tidyTopBind (the Rec case)

        --------- Arity ------------
        -- Usually the Id will have an accurate arity on it, because
        -- the simplifier has just run, but not always.
        -- One case I found was when the last thing the simplifier
        -- did was to let-bind a non-atomic argument and then float
        -- it to the top level. So it seems more robust just to
        -- fix it here.
        arity :: Arity
    arity = Expr Id -> Arity
    exprArity Expr Id
    orig_rhs Arity -> Arity -> Arity
    forall a. Ord a => a -> a -> a
    `min` Type -> Arity
    typeArity Type
    rhs_ty
                -- orig_rhs: using tidy_rhs would make a black hole, since
                --           exprArity uses the arities of Ids inside the rhs
                --
                -- typeArity: see Note [Arity invariants for bindings]
                --            in GHC.Core.Opt.Arity

    ------------ Unfolding  --------------
    tidyTopUnfolding :: TidyEnv -> CoreExpr -> Unfolding -> Unfolding
    tidyTopUnfolding :: TidyEnv -> Expr Id -> Unfolding -> Unfolding
    tidyTopUnfolding TidyEnv
    _ Expr Id
    _ Unfolding
    NoUnfolding   = Unfolding
    NoUnfolding
    tidyTopUnfolding TidyEnv
    _ Expr Id
    _ Unfolding
    BootUnfolding = Unfolding
    BootUnfolding
    tidyTopUnfolding TidyEnv
    _ Expr Id
    _ (OtherCon {}) = Unfolding
    evaldUnfolding

    tidyTopUnfolding TidyEnv
    tidy_env Expr Id
    _ df :: Unfolding
    df@(DFunUnfolding { df_bndrs :: Unfolding -> [Id]
    df_bndrs = [Id]
    bndrs, df_args :: Unfolding -> [Expr Id]
    df_args = [Expr Id]
    args })
      = Unfolding
    df { df_bndrs = bndrs', df_args = map (tidyExpr tidy_env') args }
      where
        (TidyEnv
    tidy_env', [Id]
    bndrs') = TidyEnv -> [Id] -> (TidyEnv, [Id])
    tidyBndrs TidyEnv
    tidy_env [Id]
    bndrs

    tidyTopUnfolding TidyEnv
    tidy_env Expr Id
    tidy_rhs
         unf :: Unfolding
    unf@(CoreUnfolding { uf_tmpl :: Unfolding -> Expr Id
    uf_tmpl = Expr Id
    unf_rhs, uf_src :: Unfolding -> UnfoldingSource
    uf_src = UnfoldingSource
    src  })
      = -- See Note [tidyTopUnfolding: avoiding black holes]
        Unfolding
    unf { uf_tmpl = tidy_unf_rhs }
      where
        tidy_unf_rhs :: Expr Id
    tidy_unf_rhs | UnfoldingSource -> Bool
    isStableSource UnfoldingSource
    src
                     = TidyEnv -> Expr Id -> Expr Id
    tidyExpr TidyEnv
    tidy_env Expr Id
    unf_rhs    -- Preserves OccInfo in unf_rhs
                     | Bool
    otherwise
                     = Expr Id -> Expr Id
    occurAnalyseExpr Expr Id
    tidy_rhs    -- Do occ-anal

    {- Note [tidyTopUnfolding: avoiding black holes]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    When we are exposing all unfoldings we don't want to tidy the unfolding
    twice -- we just want to use the tidied RHS.  That tidied RHS itself
    contains fully-tidied Ids -- it is knot-tied.  So the uf_tmpl for the
    unfolding contains stuff we can't look at.  Now consider (#22112)
       foo = foo
    If we freshly compute the uf_is_value field for foo's unfolding,
    we'll call `exprIsValue`, which will look at foo's unfolding!
    Whether or not the RHS is a value depends on whether foo is a value...
    black hole.

    In the Simplifier we deal with this by not giving `foo` an unfolding
    in its own RHS.  And we could do that here.  But it's qite nice
    to common everything up to a single Id for foo, used everywhere.

    And it's not too hard: simply leave the unfolding undisturbed, except
    tidy the uf_tmpl field. Hence tidyTopUnfolding does
       unf { uf_tmpl = tidy_unf_rhs }

    Don't mess with uf_is_value, or guidance; in particular don't recompute
    them from tidy_unf_rhs.

    And (unlike tidyNestedUnfolding) don't deep-seq the new unfolding,
    because that'll cause a black hole (I /think/ because occurAnalyseExpr
    looks in IdInfo).

    ************************************************************************
    *                                                                      *
                      Old, dead, type-trimming code
    *                                                                      *
    ************************************************************************

    We used to try to "trim off" the constructors of data types that are
    not exported, to reduce the size of interface files, at least without
    -O.  But that is not always possible: see the old Note [When we can't
    trim types] below for exceptions.

    Then (#7445) I realised that the TH problem arises for any data type
    that we have deriving( Data ), because we can invoke
       Language.Haskell.TH.Quote.dataToExpQ
    to get a TH Exp representation of a value built from that data type.
    You don't even need {-# LANGUAGE TemplateHaskell #-}.

    At this point I give up. The pain of trimming constructors just
    doesn't seem worth the gain.  So I've dumped all the code, and am just
    leaving it here at the end of the module in case something like this
    is ever resurrected.

    Note [When we can't trim types]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    The basic idea of type trimming is to export algebraic data types
    abstractly (without their data constructors) when compiling without
    -O, unless of course they are explicitly exported by the user.

    We always export synonyms, because they can be mentioned in the type
    of an exported Id.  We could do a full dependency analysis starting
    from the explicit exports, but that's quite painful, and not done for
    now.

    But there are some times we can't do that, indicated by the 'no_trim_types' flag.

    First, Template Haskell.  Consider (#2386) this
            module M(T, makeOne) where
              data T = Yay String
              makeOne = [| Yay "Yep" |]
    Notice that T is exported abstractly, but makeOne effectively exports it too!
    A module that splices in $(makeOne) will then look for a declaration of Yay,
    so it'd better be there.  Hence, brutally but simply, we switch off type
    constructor trimming if TH is enabled in this module.

    Second, data kinds.  Consider (#5912)
         {-# LANGUAGE DataKinds #-}
         module M() where
         data UnaryTypeC a = UnaryDataC a
         type Bug = 'UnaryDataC
    We always export synonyms, so Bug is exposed, and that means that
    UnaryTypeC must be too, even though it's not explicitly exported.  In
    effect, DataKinds means that we'd need to do a full dependency analysis
    to see what data constructors are mentioned.  But we don't do that yet.

    In these two cases we just switch off type trimming altogether.

    mustExposeTyCon :: Bool         -- Type-trimming flag
                    -> NameSet      -- Exports
                    -> TyCon        -- The tycon
                    -> Bool         -- Can its rep be hidden?
    -- We are compiling without -O, and thus trying to write as little as
    -- possible into the interface file.  But we must expose the details of
    -- any data types whose constructors or fields are exported
    mustExposeTyCon no_trim_types exports tc
      | no_trim_types               -- See Note [When we can't trim types]
      = True

      | not (isAlgTyCon tc)         -- Always expose synonyms (otherwise we'd have to
                                    -- figure out whether it was mentioned in the type
                                    -- of any other exported thing)
      = True

      | isEnumerationTyCon tc       -- For an enumeration, exposing the constructors
      = True                        -- won't lead to the need for further exposure

      | isFamilyTyCon tc            -- Open type family
      = True

      -- Below here we just have data/newtype decls or family instances

      | null data_cons              -- Ditto if there are no data constructors
      = True                        -- (NB: empty data types do not count as enumerations
                                    -- see Note [Enumeration types] in GHC.Core.TyCon

      | any exported_con data_cons  -- Expose rep if any datacon or field is exported
      = True

      | isNewTyCon tc && isFFITy (snd (newTyConRhs tc))
      = True   -- Expose the rep for newtypes if the rep is an FFI type.
               -- For a very annoying reason.  'Foreign import' is meant to
               -- be able to look through newtypes transparently, but it
               -- can only do that if it can "see" the newtype representation

      | otherwise
      = False
      where
        data_cons = tyConDataCons tc
        exported_con con = any (`elemNameSet` exports)
                               (dataConName con : dataConFieldLabels con)
    -}