    {-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
    {-# LANGUAGE CPP #-}
    {-# LANGUAGE TypeFamilies #-}

    -----------------------------------------------------------------------------
    --
    -- Stg to C-- code generation: expressions
    --
    -- (c) The University of Glasgow 2004-2006
    --
    -----------------------------------------------------------------------------

    module GHC.StgToCmm.Expr ( cgExpr, cgLit ) where

    import GHC.Prelude hiding ((<*>))

    import {-# SOURCE #-} GHC.StgToCmm.Bind ( cgBind )

    import GHC.StgToCmm.Monad
    import GHC.StgToCmm.Heap
    import GHC.StgToCmm.Env
    import GHC.StgToCmm.DataCon
    import GHC.StgToCmm.Prof (saveCurrentCostCentre, restoreCurrentCostCentre, emitSetCCC)
    import GHC.StgToCmm.Layout
    import GHC.StgToCmm.Lit
    import GHC.StgToCmm.Prim
    import GHC.StgToCmm.Hpc
    import GHC.StgToCmm.TagCheck
    import GHC.StgToCmm.Ticky
    import GHC.StgToCmm.Utils
    import GHC.StgToCmm.Closure

    import GHC.Stg.Syntax

    import GHC.Cmm.Graph
    import GHC.Cmm.BlockId
    import GHC.Cmm hiding ( succ )
    import GHC.Cmm.Info
    import GHC.Cmm.Utils ( cmmTagMask, mkWordCLit, mAX_PTR_TAG )
    import GHC.Core
    import GHC.Core.DataCon
    import GHC.Types.ForeignCall
    import GHC.Types.Id
    import GHC.Builtin.PrimOps
    import GHC.Core.TyCon
    import GHC.Core.Type        ( isUnliftedType )
    import GHC.Types.RepType    ( isZeroBitTy, countConRepArgs, mightBeFunTy )
    import GHC.Types.CostCentre ( CostCentreStack, currentCCS )
    import GHC.Types.Tickish
    import GHC.Data.Maybe
    import GHC.Utils.Misc
    import GHC.Data.FastString
    import GHC.Utils.Outputable
    import GHC.Utils.Panic

    import Control.Monad ( unless, void )
    import Control.Arrow ( first )
    import Data.List     ( partition )
    import GHC.Stg.InferTags.TagSig (isTaggedSig)
    import GHC.Platform.Profile (profileIsProfiling)

    ------------------------------------------------------------------------
    --              cgExpr: the main function
    ------------------------------------------------------------------------

    cgExpr  :: CgStgExpr -> FCode ReturnKind

    cgExpr :: CgStgExpr -> FCode ReturnKind
    cgExpr (StgApp Id
    fun [StgArg]
    args)     = Id -> [StgArg] -> FCode ReturnKind
    cgIdApp Id
    fun [StgArg]
    args

    -- seq# a s ==> a
    -- See Note [seq# magic] in GHC.Core.Opt.ConstantFold
    cgExpr (StgOpApp (StgPrimOp PrimOp
    SeqOp) [StgVarArg Id
    a, StgArg
    _] Type
    _res_ty) =
      Id -> [StgArg] -> FCode ReturnKind
    cgIdApp Id
    a []

    -- dataToTagSmall# :: a_levpoly -> Int#
    -- See Note [DataToTag overview] in GHC.Tc.Instance.Class,
    -- particularly wrinkles H3 and DTW4
    cgExpr (StgOpApp (StgPrimOp PrimOp
    DataToTagSmallOp) [StgVarArg Id
    a] Type
    _res_ty) = do
      platform <- FCode Platform
    getPlatform
      emitComment (mkFastString "dataToTagSmall#")

      a_eval_reg <- newTemp (bWord platform)
      _ <- withSequel (AssignTo [a_eval_reg] False) (cgIdApp a [])
      let a_eval_expr = CmmReg -> CmmExpr
    CmmReg (LocalReg -> CmmReg
    CmmLocal LocalReg
    a_eval_reg)
          tag1 = Platform -> CmmExpr -> CmmExpr
    cmmConstrTag1 Platform
    platform CmmExpr
    a_eval_expr

      -- subtract 1 because we need to return a zero-indexed tag
      emitReturn [cmmSubWord platform tag1 (CmmLit $ mkWordCLit platform 1)]

    -- dataToTagLarge# :: a_levpoly -> Int#
    -- See Note [DataToTag overview] in GHC.Tc.Instance.Class,
    -- particularly wrinkles H3 and DTW4
    cgExpr (StgOpApp (StgPrimOp PrimOp
    DataToTagLargeOp) [StgVarArg Id
    a] Type
    _res_ty) = do
      platform <- FCode Platform
    getPlatform
      emitComment (mkFastString "dataToTagLarge#")

      a_eval_reg <- newTemp (bWord platform)
      _ <- withSequel (AssignTo [a_eval_reg] False) (cgIdApp a [])
      let a_eval_expr = CmmReg -> CmmExpr
    CmmReg (LocalReg -> CmmReg
    CmmLocal LocalReg
    a_eval_reg)

      tag1_reg <- assignTemp $ cmmConstrTag1 platform a_eval_expr
      result_reg <- newTemp (bWord platform)
      let tag1_expr = CmmReg -> CmmExpr
    CmmReg (CmmReg -> CmmExpr) -> CmmReg -> CmmExpr
    forall a b. (a -> b) -> a -> b
    $ LocalReg -> CmmReg
    CmmLocal LocalReg
    tag1_reg
          is_too_big_tag = Platform -> CmmExpr -> CmmExpr -> CmmExpr
    cmmEqWord Platform
    platform CmmExpr
    tag1_expr (Platform -> CmmExpr
    cmmTagMask Platform
    platform)

      -- Return the constructor index from the pointer tag
      -- (Used if pointer tag is small enough to be unambiguous)
      return_ptr_tag <- getCode $ do
        emitAssign (CmmLocal result_reg)
          $ cmmSubWord platform tag1_expr (CmmLit $ mkWordCLit platform 1)

      -- Return the constructor index recorded in the info table
      return_info_tag <- getCode $ do
        profile     <- getProfile
        align_check <- stgToCmmAlignCheck <$> getStgToCmmConfig
        emitAssign (CmmLocal result_reg)
          $ getConstrTag profile align_check (cmmUntag platform a_eval_expr)

      emit =<< mkCmmIfThenElse' is_too_big_tag return_info_tag return_ptr_tag (Just False)
      emitReturn [CmmReg $ CmmLocal result_reg]

    cgExpr (StgOpApp StgOp
    op [StgArg]
    args Type
    ty) = StgOp -> [StgArg] -> Type -> FCode ReturnKind
    cgOpApp StgOp
    op [StgArg]
    args Type
    ty
    cgExpr (StgConApp DataCon
    con ConstructorNumber
    mn [StgArg]
    args [[PrimRep]]
    _) = DataCon -> ConstructorNumber -> [StgArg] -> FCode ReturnKind
    cgConApp DataCon
    con ConstructorNumber
    mn [StgArg]
    args
    cgExpr (StgTick StgTickish
    t CgStgExpr
    e)         = StgTickish -> FCode ()
    cgTick StgTickish
    t FCode () -> FCode ReturnKind -> FCode ReturnKind
    forall a b. FCode a -> FCode b -> FCode b
    forall (m :: * -> *) a b. Monad m => m a -> m b -> m b
    >> CgStgExpr -> FCode ReturnKind
    cgExpr CgStgExpr
    e
    cgExpr (StgLit Literal
    lit)          = do cmm_expr <- Literal -> FCode CmmExpr
    cgLit Literal
    lit
                                      emitReturn [cmm_expr]

    cgExpr (StgLet XLet 'CodeGen
    _ GenStgBinding 'CodeGen
    binds CgStgExpr
    expr) = do { GenStgBinding 'CodeGen -> FCode ()
    cgBind GenStgBinding 'CodeGen
    binds;     CgStgExpr -> FCode ReturnKind
    cgExpr CgStgExpr
    expr }
    cgExpr (StgLetNoEscape XLetNoEscape 'CodeGen
    _ GenStgBinding 'CodeGen
    binds CgStgExpr
    expr) =
      do { u <- FCode Unique
    newUnique
         ; let join_id = Unique -> BlockId
    mkBlockId Unique
    u
         ; cgLneBinds join_id binds
         ; r <- cgExpr expr
         ; emitLabel join_id
         ; return r }

    cgExpr (StgCase CgStgExpr
    expr BinderP 'CodeGen
    bndr AltType
    alt_type [GenStgAlt 'CodeGen]
    alts) =
      CgStgExpr
    -> Id -> AltType -> [GenStgAlt 'CodeGen] -> FCode ReturnKind
    cgCase CgStgExpr
    expr Id
    BinderP 'CodeGen
    bndr AltType
    alt_type [GenStgAlt 'CodeGen]
    alts

    ------------------------------------------------------------------------
    --              Let no escape
    ------------------------------------------------------------------------

    {- Generating code for a let-no-escape binding, aka join point is very
    very similar to what we do for a case expression.  The duality is
    between
            let-no-escape x = b
            in e
    and
            case e of ... -> b

    That is, the RHS of 'x' (ie 'b') will execute *later*, just like
    the alternative of the case; it needs to be compiled in an environment
    in which all volatile bindings are forgotten, and the free vars are
    bound only to stable things like stack locations..  The 'e' part will
    execute *next*, just like the scrutinee of a case. -}

    -------------------------
    cgLneBinds :: BlockId -> CgStgBinding -> FCode ()
    cgLneBinds :: BlockId -> GenStgBinding 'CodeGen -> FCode ()
    cgLneBinds BlockId
    join_id (StgNonRec BinderP 'CodeGen
    bndr GenStgRhs 'CodeGen
    rhs)
      = do  { local_cc <- FCode (Maybe LocalReg)
    saveCurrentCostCentre
                    -- See Note [Saving the current cost centre]
            ; (info, fcode) <- cgLetNoEscapeRhs join_id local_cc bndr rhs
            ; fcode
            ; addBindC info }

    cgLneBinds BlockId
    join_id (StgRec [(BinderP 'CodeGen, GenStgRhs 'CodeGen)]
    pairs)
      = do  { local_cc <- FCode (Maybe LocalReg)
    saveCurrentCostCentre
            ; r <- sequence $ unzipWith (cgLetNoEscapeRhs join_id local_cc) pairs
            ; let (infos, fcodes) = unzip r
            ; addBindsC infos
            ; sequence_ fcodes
            }

    -------------------------
    cgLetNoEscapeRhs
        :: BlockId          -- join point for successor of let-no-escape
        -> Maybe LocalReg   -- Saved cost centre
        -> Id
        -> CgStgRhs
        -> FCode (CgIdInfo, FCode ())

    cgLetNoEscapeRhs :: BlockId
    -> Maybe LocalReg
    -> Id
    -> GenStgRhs 'CodeGen
    -> FCode (CgIdInfo, FCode ())
    cgLetNoEscapeRhs BlockId
    join_id Maybe LocalReg
    local_cc Id
    bndr GenStgRhs 'CodeGen
    rhs =
      do { (info, rhs_code) <- Maybe LocalReg
    -> Id -> GenStgRhs 'CodeGen -> FCode (CgIdInfo, FCode ())
    cgLetNoEscapeRhsBody Maybe LocalReg
    local_cc Id
    bndr GenStgRhs 'CodeGen
    rhs
         ; let (bid, _) = expectJust "cgLetNoEscapeRhs" $ maybeLetNoEscape info
         ; let code = do { (_, body) <- FCode () -> FCode ((), CmmAGraphScoped)
    forall a. FCode a -> FCode (a, CmmAGraphScoped)
    getCodeScoped FCode ()
    rhs_code
                         ; emitOutOfLine bid (first (<*> mkBranch join_id) body) }
         ; return (info, code)
         }

    cgLetNoEscapeRhsBody
        :: Maybe LocalReg   -- Saved cost centre
        -> Id
        -> CgStgRhs
        -> FCode (CgIdInfo, FCode ())
    cgLetNoEscapeRhsBody :: Maybe LocalReg
    -> Id -> GenStgRhs 'CodeGen -> FCode (CgIdInfo, FCode ())
    cgLetNoEscapeRhsBody Maybe LocalReg
    local_cc Id
    bndr (StgRhsClosure XRhsClosure 'CodeGen
    _ CostCentreStack
    cc UpdateFlag
    _upd [BinderP 'CodeGen]
    args CgStgExpr
    body Type
    _typ)
      = Id
    -> Maybe LocalReg
    -> CostCentreStack
    -> [NonVoid Id]
    -> CgStgExpr
    -> FCode (CgIdInfo, FCode ())
    cgLetNoEscapeClosure Id
    bndr Maybe LocalReg
    local_cc CostCentreStack
    cc ([Id] -> [NonVoid Id]
    nonVoidIds [Id]
    [BinderP 'CodeGen]
    args) CgStgExpr
    body
    cgLetNoEscapeRhsBody Maybe LocalReg
    local_cc Id
    bndr (StgRhsCon CostCentreStack
    cc DataCon
    con ConstructorNumber
    mn [StgTickish]
    _ts [StgArg]
    args Type
    _typ)
      = Id
    -> Maybe LocalReg
    -> CostCentreStack
    -> [NonVoid Id]
    -> CgStgExpr
    -> FCode (CgIdInfo, FCode ())
    cgLetNoEscapeClosure Id
    bndr Maybe LocalReg
    local_cc CostCentreStack
    cc []
          (DataCon
    -> ConstructorNumber -> [StgArg] -> [[PrimRep]] -> CgStgExpr
    forall (pass :: StgPass).
    DataCon
    -> ConstructorNumber -> [StgArg] -> [[PrimRep]] -> GenStgExpr pass
    StgConApp DataCon
    con ConstructorNumber
    mn [StgArg]
    args (String -> SDoc -> [[PrimRep]]
    forall a. HasCallStack => String -> SDoc -> a
    pprPanic String
    "cgLetNoEscapeRhsBody" (SDoc -> [[PrimRep]]) -> SDoc -> [[PrimRep]]
    forall a b. (a -> b) -> a -> b
    $
                               String -> SDoc
    forall doc. IsLine doc => String -> doc
    text String
    "StgRhsCon doesn't have type args"))
            -- For a constructor RHS we want to generate a single chunk of
            -- code which can be jumped to from many places, which will
            -- return the constructor. It's easy; just behave as if it
            -- was an StgRhsClosure with a ConApp inside!

    -------------------------
    cgLetNoEscapeClosure
            :: Id                   -- binder
            -> Maybe LocalReg       -- Slot for saved current cost centre
            -> CostCentreStack      -- XXX: *** NOT USED *** why not?
            -> [NonVoid Id]         -- Args (as in \ args -> body)
            -> CgStgExpr            -- Body (as in above)
            -> FCode (CgIdInfo, FCode ())

    cgLetNoEscapeClosure :: Id
    -> Maybe LocalReg
    -> CostCentreStack
    -> [NonVoid Id]
    -> CgStgExpr
    -> FCode (CgIdInfo, FCode ())
    cgLetNoEscapeClosure Id
    bndr Maybe LocalReg
    cc_slot CostCentreStack
    _unused_cc [NonVoid Id]
    args CgStgExpr
    body
      = do platform <- FCode Platform
    getPlatform
           let code = FCode () -> FCode ()
    forall a. FCode a -> FCode a
    forkLneBody (FCode () -> FCode ()) -> FCode () -> FCode ()
    forall a b. (a -> b) -> a -> b
    $ Id -> [NonVoid Id] -> FCode () -> FCode ()
    forall a. Id -> [NonVoid Id] -> FCode a -> FCode a
    withNewTickyCounterLNE Id
    bndr [NonVoid Id]
    args (FCode () -> FCode ()) -> FCode () -> FCode ()
    forall a b. (a -> b) -> a -> b
    $ do
                    { Platform -> Maybe LocalReg -> FCode ()
    restoreCurrentCostCentre Platform
    platform Maybe LocalReg
    cc_slot
                    ; arg_regs <- [NonVoid Id] -> FCode [LocalReg]
    bindArgsToRegs [NonVoid Id]
    args
                    ; void $ noEscapeHeapCheck arg_regs (tickyEnterLNE >> cgExpr body) }
           return ( lneIdInfo platform bndr args, code )

    ------------------------------------------------------------------------
    --              Case expressions
    ------------------------------------------------------------------------

    {- Note [Compiling case expressions]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    It is quite interesting to decide whether to put a heap-check at the
    start of each alternative.  Of course we certainly have to do so if
    the case forces an evaluation, or if there is a primitive op which can
    trigger GC.

    NB: things are not settled here: see #8326.

    A more interesting situation is this (a Plan-B situation)

            !P!;
            ...P...
            case x# of
              0#      -> !Q!; ...Q...
              default -> !R!; ...R...

    where !x! indicates a possible heap-check point. The heap checks
    in the alternatives *can* be omitted, in which case the topmost
    heapcheck will take their worst case into account.

    In favour of omitting !Q!, !R!:

     - *May* save a heap overflow test,
       if ...P... allocates anything.

     - We can use relative addressing from a single Hp to
       get at all the closures so allocated.

     - No need to save volatile vars etc across heap checks
       in !Q!, !R!

    Against omitting !Q!, !R!

      - May put a heap-check into the inner loop.  Suppose
            the main loop is P -> R -> P -> R...
            Q is the loop exit, and only it does allocation.
        This only hurts us if P does no allocation.  If P allocates,
        then there is a heap check in the inner loop anyway.

      - May do more allocation than reqd.  This sometimes bites us
        badly.  For example, nfib (ha!) allocates about 30\% more space if the
        worst-casing is done, because many many calls to nfib are leaf calls
        which don't need to allocate anything.

        We can un-allocate, but that costs an instruction

    Neither problem hurts us if there is only one alternative.

    Suppose the inner loop is P->R->P->R etc.  Then here is
    how many heap checks we get in the *inner loop* under various
    conditions

      Alloc   Heap check in branches (!Q!, !R!)?
      P Q R      yes     no (absorb to !P!)
    --------------------------------------
      n n n      0          0
      n y n      0          1
      n . y      1          1
      y . y      2          1
      y . n      1          1

    Best choices: absorb heap checks from Q and R into !P! iff
      a) P itself does some allocation
    or
      b) P does allocation, or there is exactly one alternative

    We adopt (b) because that is more likely to put the heap check at the
    entry to a function, when not many things are live.  After a bunch of
    single-branch cases, we may have lots of things live

    Hence: Two basic plans for

            case e of r { alts }

    ------ Plan A: the general case ---------

            ...save current cost centre...

            ...code for e,
               with sequel (SetLocals r)

            ...restore current cost centre...
            ...code for alts...
            ...alts do their own heap checks

       When using GcInAlts the return point for heap checks and evaluating
       the scrutinee is shared. This does mean we might execute the actual
       branching code twice but it's rare enough to not matter.
       The huge advantage of this pattern is that we do not require multiple
       info tables for returning from gc as they can be shared between all
       cases. Reducing code size nicely.

    ------ Plan B: special case when ---------
      (i)  e does not allocate or call GC
      (ii) either upstream code performs allocation
           or there is just one alternative

      Then heap allocation in the (single) case branch
      is absorbed by the upstream check.
      Very common example: primops on unboxed values

            ...code for e,
               with sequel (SetLocals r)...

            ...code for alts...
            ...no heap check...

       There is a variant B.2 which we use if:

      (i)   e is already evaluated+tagged
      (ii)  We have multiple alternatives
      (iii) and there is no upstream allocation.

      Here we also place one heap check before the `case` which
      branches on `e`. Hopefully to be absorbed by an already existing
      heap check further up. However the big difference in this case is that
      there is no code for e. So we are not guaranteed that the heap
      checks of the alts will be combined with an heap check further up.

      Very common example: Casing on strict fields.

            ...heap check...
            ...assign bindings...

            ...code for alts...
            ...no heap check...

      -- Reasoning for Plan B.2:
       Since the scrutinee is already evaluated there is no evaluation
       call which would force a info table that we can use as a shared
       return point.
       This means currently if we were to do GcInAlts like in Plan A then
       we would end up with one info table per alternative.

       To avoid this we unconditionally do gc outside of the alts with all
       the pros and cons described in Note [Compiling case expressions].
       Rewriting the logic to generate a shared return point before the case
       expression while keeping the heap checks in the alternatives would be
       possible. But it's unclear to me that this would actually be an improvement.

       This means if we have code along these lines:

          g x y = case x of
             True -> Left $ (y + 1,y,y-1)
             False -> Right $! y - (2 :: Int)

       We get these potential heap check placements:

       f = ...
          !max(L,R)!; -- Might be absorbed upstream.
          case x of
             True  -> !L!; ...L...
             False -> !R!; ...R...

       And we place a heap check at !max(L,R)!

       The downsides of using !max(L,R)! are:

       * If f is recursive, and the hot loop wouldn't allocate, but the exit branch does then we do
       a redundant heap check.
       * We use one more instruction to de-allocate the unused heap in the branch using less heap. (Negligible)
       * A small risk of running gc slightly more often than needed especially if one branch allocates a lot.

       The upsides are:
       * May save a heap overflow test if there is an upstream check already.
       * If the heap check is absorbed upstream we can also eliminate its info table.
       * We generate at most one heap check (versus one per alt otherwise).
       * No need to save volatile vars etc across heap checks in !L!, !R!
       * We can use relative addressing from a single Hp to get at all the closures so allocated. (seems neglible)
       * It fits neatly in the logic we already have for handling A/B

       For containers:Data/Sequence/Internal/Sorting.o the difference is
       about 10% in terms of code size compared to using Plan A for this case.
       The main downside is we might put heap checks into loops, even if we
       could avoid it (See Note [Compiling case expressions]).

       Potential improvement: Investigate if heap checks in alts would be an
       improvement if we generate and use a shared return point that is placed
       in the common path for all alts.

    -}

    -------------------------------------
    data GcPlan
      = GcInAlts            -- Put a GC check at the start the case alternatives,
            [LocalReg]      -- which binds these registers
      | NoGcInAlts          -- The scrutinee is a primitive value, or a call to a
                            -- primitive op which does no GC.  Absorb the allocation
                            -- of the case alternative(s) into the upstream check

    -------------------------------------
    cgCase :: CgStgExpr -> Id -> AltType -> [CgStgAlt] -> FCode ReturnKind

    {-
    Note [Scrutinising VoidRep]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~
    Suppose we have this STG code:
       f = \[s : State# RealWorld] ->
           case s of _ -> blah
    This is very odd.  Why are we scrutinising a state token?  But it
    can arise with bizarre NOINLINE pragmas (#9964)
        crash :: IO ()
        crash = IO (\s -> let {-# NOINLINE s' #-}
                              s' = s
                          in (# s', () #))

    Now the trouble is that 's' has VoidRep, and we do not bind void
    arguments in the environment; they don't live anywhere.  See the
    calls to nonVoidIds in various places.  So we must not look up
    's' in the environment.  Instead, just evaluate the RHS!  Simple.

    Note [Dead-binder optimisation]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    Consider:

       case x of (y, z<dead>) -> rhs

    where `z` is unused in `rhs`.  When we return form the eval of `x`,
    GHC.StgToCmm.DataCon.bindConArgs will generate some loads, assuming the the
    value of `x` is returned in R1:
       y := R1[1]
       z := R1[2]

    If `z` is never used, the load `z := R1[2]` is a waste of a memory operation.
    CmmSink (which sinks loads to their usage sites, if any) will eliminate the dead
    load; but
      1. CmmSink only runs with -O
      2. It would save CmmSink work if we simply did not generate the load in the
      first place.

    Hence STG uses dead-binder information, in `bindConArgs` to drop dead loads.
    That's why we preserve occurrence-info on binders in GHC.Core.Tidy (see
    GHC.Core.Tidy.tidyIdBndr).

    So it's important that deadness is accurate.  But StgCse can invalidate it
    (#14895 #24233).  Here is an example:

      map_either :: (a -> b) -> Either String a -> Either String b
      map_either = \f e -> case e of b<dead> {
        Right x -> Right (f x)
        Left  x -> Left x
      }

      The case-binder "b" is dead (not used in the rhss of the alternatives).
      StgCse notices that `Left x` doesn't need to be allocated as we can reuse `b`,
      and we get:

      map_either :: (a -> b) -> Either String a -> Either String b
      map_either = \f e -> case e of b { -- b no longer dead!
        Right x -> Right (f x)
        Left  x -> b
      }

    For now StgCse simply zaps occurrence information on case binders. A more
    accurate update would complexify the implementation and doesn't seem worth it.

    -}

    cgCase :: CgStgExpr
    -> Id -> AltType -> [GenStgAlt 'CodeGen] -> FCode ReturnKind
    cgCase (StgApp Id
    v []) Id
    _ (PrimAlt PrimRep
    _) [GenStgAlt 'CodeGen]
    alts
      | HasDebugCallStack => Type -> Bool
    Type -> Bool
    isZeroBitTy (Id -> Type
    idType Id
    v)  -- See Note [Scrutinising VoidRep]
      , [GenStgAlt{alt_con :: forall (pass :: StgPass). GenStgAlt pass -> AltCon
    alt_con=AltCon
    DEFAULT, alt_bndrs :: forall (pass :: StgPass). GenStgAlt pass -> [BinderP pass]
    alt_bndrs=[BinderP 'CodeGen]
    _, alt_rhs :: forall (pass :: StgPass). GenStgAlt pass -> GenStgExpr pass
    alt_rhs=CgStgExpr
    rhs}] <- [GenStgAlt 'CodeGen]
    alts
      = CgStgExpr -> FCode ReturnKind
    cgExpr CgStgExpr
    rhs

    {- Note [Dodgy unsafeCoerce 1]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    Consider
        case (x :: HValue) |> co of (y :: MutVar# Int)
            DEFAULT -> ...
    We want to generate an assignment
         y := x
    We want to allow this assignment to be generated in the case when the
    types are compatible, because this allows some slightly-dodgy but
    occasionally-useful casts to be used, such as in GHC.Runtime.Heap.Inspect
    where we cast an HValue to a MutVar# so we can print out the contents
    of the MutVar#.  If instead we generate code that enters the HValue,
    then we'll get a runtime panic, because the HValue really is a
    MutVar#.  The types are compatible though, so we can just generate an
    assignment.
    -}
    cgCase (StgApp Id
    v []) Id
    bndr alt_type :: AltType
    alt_type@(PrimAlt PrimRep
    _) [GenStgAlt 'CodeGen]
    alts
      | HasDebugCallStack => Type -> Bool
    Type -> Bool
    isUnliftedType (Id -> Type
    idType Id
    v)  -- Note [Dodgy unsafeCoerce 1]
      = -- assignment suffices for unlifted types
        do { platform <- FCode Platform
    getPlatform
           ; unless (reps_compatible platform) $
               pprPanic "cgCase: reps do not match, perhaps a dodgy unsafeCoerce?"
                        (pp_bndr v $$ pp_bndr bndr)
           ; v_info <- getCgIdInfo v
           ; emitAssign (CmmLocal (idToReg platform (NonVoid bndr)))
                        (idInfoToAmode v_info)
           -- Add bndr to the environment
           ; _ <- bindArgToReg (NonVoid bndr)
           ; cgAlts (NoGcInAlts,AssignedDirectly) (NonVoid bndr) alt_type alts }
      where
        reps_compatible :: Platform -> Bool
    reps_compatible Platform
    platform = Platform -> PrimRep -> PrimRep -> Bool
    primRepCompatible Platform
    platform (Id -> PrimRep
    idPrimRepU Id
    v) (Id -> PrimRep
    idPrimRepU Id
    bndr)

        pp_bndr :: Id -> SDoc
    pp_bndr Id
    id = Id -> SDoc
    forall a. Outputable a => a -> SDoc
    ppr Id
    id SDoc -> SDoc -> SDoc
    forall doc. IsLine doc => doc -> doc -> doc
    <+> SDoc
    dcolon SDoc -> SDoc -> SDoc
    forall doc. IsLine doc => doc -> doc -> doc
    <+> Type -> SDoc
    forall a. Outputable a => a -> SDoc
    ppr (Id -> Type
    idType Id
    id) SDoc -> SDoc -> SDoc
    forall doc. IsLine doc => doc -> doc -> doc
    <+> SDoc -> SDoc
    forall doc. IsLine doc => doc -> doc
    parens (PrimRep -> SDoc
    forall a. Outputable a => a -> SDoc
    ppr (Id -> PrimRep
    idPrimRepU Id
    id))

    {- Note [Dodgy unsafeCoerce 2, #3132]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    In all other cases of a lifted Id being cast to an unlifted type, the
    Id should be bound to bottom, otherwise this is an unsafe use of
    unsafeCoerce.  We can generate code to enter the Id and assume that
    it will never return.  Hence, we emit the usual enter/return code, and
    because bottom must be untagged, it will be entered.  The Sequel is a
    type-correct assignment, albeit bogus.  The (dead) continuation loops;
    it would be better to invoke some kind of panic function here.
    -}
    cgCase scrut :: CgStgExpr
    scrut@(StgApp Id
    v []) Id
    _ (PrimAlt PrimRep
    _) [GenStgAlt 'CodeGen]
    _
      = do { platform <- FCode Platform
    getPlatform
           ; mb_cc <- maybeSaveCostCentre True
           ; _ <- withSequel
                      (AssignTo [idToReg platform (NonVoid v)] False) (cgExpr scrut)
           ; restoreCurrentCostCentre platform mb_cc
           ; emitComment $ mkFastString "should be unreachable code"
           ; l <- newBlockId
           ; emitLabel l
           ; emit (mkBranch l)  -- an infinite loop
           ; return AssignedDirectly
           }

    {- Note [Handle seq#]
    ~~~~~~~~~~~~~~~~~~~~~
    See Note [seq# magic] in GHC.Core.Opt.ConstantFold.
    The special case for seq# in cgCase does this:

      case seq# a s of v
        (# s', a' #) -> e
    ==>
      case a of v
        (# s', a' #) -> e

    (taking advantage of the fact that the return convention for (# State#, a #)
    is the same as the return convention for just 'a')
    -}

    cgCase (StgOpApp (StgPrimOp PrimOp
    SeqOp) [StgVarArg Id
    a, StgArg
    _] Type
    _) Id
    bndr AltType
    alt_type [GenStgAlt 'CodeGen]
    alts
      = -- Note [Handle seq#]
        -- And see Note [seq# magic] in GHC.Core.Opt.ConstantFold
        -- Use the same return convention as vanilla 'a'.
        CgStgExpr
    -> Id -> AltType -> [GenStgAlt 'CodeGen] -> FCode ReturnKind
    cgCase (Id -> [StgArg] -> CgStgExpr
    forall (pass :: StgPass). Id -> [StgArg] -> GenStgExpr pass
    StgApp Id
    a []) Id
    bndr AltType
    alt_type [GenStgAlt 'CodeGen]
    alts

    {-
    Note [Eliminate trivial Solo# continuations]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    If we have code like this:

        case scrut of bndr {
          alt -> Solo# bndr
        }

    The RHS of the only branch does nothing except wrap the case-binder
    returned by 'scrut' in a unary unboxed tuple.  But unboxed tuples
    don't exist at run-time, i.e. the branch is a no-op!  So we can
    generate code as if we just had 'scrut' instead of a case-expression.

    This situation can easily arise for IO or ST code, where the last
    operation a function performs is commonly 'pure $! someExpr'.
    See also #24264 and !11778.  More concretely, as of December 2023,
    when building a stage2 "perf+no_profiled_libs" ghc:

     * The special case is reached 398 times.
     * Of these, 158 have scrutinees that call a function or enter a
       potential thunk, and would need to push a useless stack frame if
       not for this optimisation.

    We might consider rewriting such case expressions in GHC.Stg.CSE as a
    slight extension of Note [All alternatives are the binder].  But the
    RuntimeReps of 'bndr' and 'Solo# bndr' are not exactly the same, and
    per Note [Typing the STG language] in GHC.Stg.Lint, we do expect Stg
    code to remain RuntimeRep-correct.  So we just detect the situation in
    StgToCmm instead.

    Crucially, the return conventions for 'ty' and '(# ty #)' are compatible:
    The returned value is passed in the same register(s) or stack slot in
    both conventions, and the set of allowed return values for 'ty'
    is a subset of the allowed return values for '(# ty #)':

     * For a lifted type 'ty', the return convention for 'ty' promises to
       return an evaluated-properly-tagged heap pointer, while a return
       type '(# ty #)' only promises to return a heap pointer to an object
       that can be evaluated later if need be.

     * If 'ty' is unlifted, the allowed return
       values for 'ty' and '(# ty #)' are identical.
    -}

    cgCase CgStgExpr
    scrut Id
    bndr AltType
    _alt_type [GenStgAlt { alt_rhs :: forall (pass :: StgPass). GenStgAlt pass -> GenStgExpr pass
    alt_rhs = CgStgExpr
    rhs}]
      -- see Note [Eliminate trivial Solo# continuations]
      | StgConApp DataCon
    dc ConstructorNumber
    _ [StgVarArg Id
    v] [[PrimRep]]
    _ <- CgStgExpr
    rhs
      , DataCon -> Bool
    isUnboxedTupleDataCon DataCon
    dc
      , Id
    v Id -> Id -> Bool
    forall a. Eq a => a -> a -> Bool
    == Id
    bndr
      = CgStgExpr -> FCode ReturnKind
    cgExpr CgStgExpr
    scrut

    cgCase CgStgExpr
    scrut Id
    bndr AltType
    alt_type [GenStgAlt 'CodeGen]
    alts
      = -- the general case
        do { platform <- FCode Platform
    getPlatform
           ; up_hp_usg <- getVirtHp        -- Upstream heap usage
           ; let ret_bndrs = Id -> AltType -> [GenStgAlt 'CodeGen] -> [NonVoid Id]
    chooseReturnBndrs Id
    bndr AltType
    alt_type [GenStgAlt 'CodeGen]
    alts
                 alt_regs  = (NonVoid Id -> LocalReg) -> [NonVoid Id] -> [LocalReg]
    forall a b. (a -> b) -> [a] -> [b]
    map (Platform -> NonVoid Id -> LocalReg
    idToReg Platform
    platform) [NonVoid Id]
    ret_bndrs

           ; simple_scrut <- isSimpleScrut scrut alt_type
           ; let do_gc  | CgStgExpr -> Bool
    forall {pass :: StgPass}. GenStgExpr pass -> Bool
    is_cmp_op CgStgExpr
    scrut  = Bool
    False  -- See Note [GC for conditionals]
                        | Bool -> Bool
    not Bool
    simple_scrut = Bool
    True
                        | [GenStgAlt 'CodeGen] -> Bool
    forall a. [a] -> Bool
    isSingleton [GenStgAlt 'CodeGen]
    alts = Bool
    False
                        | RepArity
    up_hp_usg RepArity -> RepArity -> Bool
    forall a. Ord a => a -> a -> Bool
    > RepArity
    0    = Bool
    False
                        | Bool
    otherwise        = Bool
    True
                   -- cf Note [Compiling case expressions]
                 gc_plan = if Bool
    do_gc then [LocalReg] -> GcPlan
    GcInAlts [LocalReg]
    alt_regs else GcPlan
    NoGcInAlts

           ; mb_cc <- maybeSaveCostCentre simple_scrut

           ; let sequel = [LocalReg] -> Bool -> Sequel
    AssignTo [LocalReg]
    alt_regs Bool
    do_gc{- Note [scrut sequel] -}
           ; ret_kind <- withSequel sequel (cgExpr scrut)
           ; restoreCurrentCostCentre platform mb_cc
           ; _ <- bindArgsToRegs ret_bndrs
           ; cgAlts (gc_plan,ret_kind) (NonVoid bndr) alt_type alts
           }
      where
        is_cmp_op :: GenStgExpr pass -> Bool
    is_cmp_op (StgOpApp (StgPrimOp PrimOp
    op) [StgArg]
    _ Type
    _) = PrimOp -> Bool
    isComparisonPrimOp PrimOp
    op
        is_cmp_op GenStgExpr pass
    _                             = Bool
    False

    {- Note [GC for conditionals]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    For comparison operators (`is_cmp_op`) it seems that we have always done
    NoGcInAlts.  It's odd, and it's flagrantly inconsistent with the rules described
    Note [Compiling case expressions].  However, that's the way it has been for ages
    (there was some long-gone history involving tagToEnum#; see #13397, #8317, #8326).

    Note [scrut sequel]
    ~~~~~~~~~~~~~~~~~~~
    The job of the scrutinee is to assign its value(s) to alt_regs.
    Additionally, if we plan to do a heap-check in the alternatives (see
    Note [Compiling case expressions]), then we *must* retreat Hp to
    recover any unused heap before passing control to the sequel.  If we
    don't do this, then any unused heap will become slop because the heap
    check will reset the heap usage. Slop in the heap breaks LDV profiling
    (+RTS -hb) which needs to do a linear sweep through the nursery.

    Note [Inlining out-of-line primops and heap checks]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    If shouldInlinePrimOp returns True when called from GHC.StgToCmm.Expr for the
    purpose of heap check placement, we *must* inline the primop later in
    GHC.StgToCmm.Prim. If we don't things will go wrong.
    -}

    -----------------
    maybeSaveCostCentre :: Bool -> FCode (Maybe LocalReg)
    maybeSaveCostCentre :: Bool -> FCode (Maybe LocalReg)
    maybeSaveCostCentre Bool
    simple_scrut
      | Bool
    simple_scrut = Maybe LocalReg -> FCode (Maybe LocalReg)
    forall a. a -> FCode a
    forall (m :: * -> *) a. Monad m => a -> m a
    return Maybe LocalReg
    forall a. Maybe a
    Nothing
      | Bool
    otherwise    = FCode (Maybe LocalReg)
    saveCurrentCostCentre

    -----------------
    isSimpleScrut :: CgStgExpr -> AltType -> FCode Bool
    -- Simple scrutinee, does not block or allocate; hence safe to amalgamate
    -- heap usage from alternatives into the stuff before the case
    -- NB: if you get this wrong, and claim that the expression doesn't allocate
    --     when it does, you'll deeply mess up allocation
    isSimpleScrut :: CgStgExpr -> AltType -> FCode Bool
    isSimpleScrut (StgOpApp StgOp
    op [StgArg]
    args Type
    _) AltType
    _         = StgOp -> [StgArg] -> FCode Bool
    isSimpleOp StgOp
    op [StgArg]
    args
    isSimpleScrut (StgLit Literal
    _)           AltType
    _         = Bool -> FCode Bool
    forall a. a -> FCode a
    forall (m :: * -> *) a. Monad m => a -> m a
    return Bool
    True       -- case 1# of { 0# -> ..; ... }
    isSimpleScrut (StgApp Id
    _ [])    (PrimAlt PrimRep
    _)   = Bool -> FCode Bool
    forall a. a -> FCode a
    forall (m :: * -> *) a. Monad m => a -> m a
    return Bool
    True       -- case x# of { 0# -> ..; ... }
    isSimpleScrut (StgApp Id
    f [])   AltType
    _
      | Just TagSig
    sig <- Id -> Maybe TagSig
    idTagSig_maybe Id
    f
      , TagSig -> Bool
    isTaggedSig TagSig
    sig  -- case !x of { ... }
      = if Type -> Bool
    mightBeFunTy (Id -> Type
    idType Id
    f)
          -- See Note [Evaluating functions with profiling] in rts/Apply.cmm
          then Bool -> Bool
    not (Bool -> Bool) -> (Profile -> Bool) -> Profile -> Bool
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . Profile -> Bool
    profileIsProfiling (Profile -> Bool) -> FCode Profile -> FCode Bool
    forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
    <$> FCode Profile
    getProfile
          else Bool -> FCode Bool
    forall a. a -> FCode a
    forall (f :: * -> *) a. Applicative f => a -> f a
    pure Bool
    True
    isSimpleScrut CgStgExpr
    _                    AltType
    _         = Bool -> FCode Bool
    forall a. a -> FCode a
    forall (m :: * -> *) a. Monad m => a -> m a
    return Bool
    False

    isSimpleOp :: StgOp -> [StgArg] -> FCode Bool
    -- True iff the op cannot block or allocate
    isSimpleOp :: StgOp -> [StgArg] -> FCode Bool
    isSimpleOp (StgFCallOp (CCall (CCallSpec CCallTarget
    _ CCallConv
    _ Safety
    safe)) Type
    _) [StgArg]
    _ = Bool -> FCode Bool
    forall a. a -> FCode a
    forall (m :: * -> *) a. Monad m => a -> m a
    return (Bool -> FCode Bool) -> Bool -> FCode Bool
    forall a b. (a -> b) -> a -> b
    $! Bool -> Bool
    not (Safety -> Bool
    playSafe Safety
    safe)
    -- dataToTagSmall#/dataToTagLarge# evaluate an argument;
    -- see Note [DataToTag overview] in GHC.Tc.Instance.Class
    isSimpleOp (StgPrimOp PrimOp
    DataToTagSmallOp) [StgArg]
    _ = Bool -> FCode Bool
    forall a. a -> FCode a
    forall (m :: * -> *) a. Monad m => a -> m a
    return Bool
    False
    isSimpleOp (StgPrimOp PrimOp
    DataToTagLargeOp) [StgArg]
    _ = Bool -> FCode Bool
    forall a. a -> FCode a
    forall (m :: * -> *) a. Monad m => a -> m a
    return Bool
    False
    isSimpleOp (StgPrimOp PrimOp
    op) [StgArg]
    stg_args                  = do
        arg_exprs <- [StgArg] -> FCode [CmmExpr]
    getNonVoidArgAmodes [StgArg]
    stg_args
        cfg       <- getStgToCmmConfig
        -- See Note [Inlining out-of-line primops and heap checks]
        return $! shouldInlinePrimOp cfg op arg_exprs
    isSimpleOp (StgPrimCallOp PrimCall
    _) [StgArg]
    _                           = Bool -> FCode Bool
    forall a. a -> FCode a
    forall (m :: * -> *) a. Monad m => a -> m a
    return Bool
    False

    -----------------
    chooseReturnBndrs :: Id -> AltType -> [CgStgAlt] -> [NonVoid Id]
    -- These are the binders of a case that are assigned by the evaluation of the
    -- scrutinee.
    -- They're non-void, see Note [Post-unarisation invariants] in GHC.Stg.Unarise.
    chooseReturnBndrs :: Id -> AltType -> [GenStgAlt 'CodeGen] -> [NonVoid Id]
    chooseReturnBndrs Id
    bndr (PrimAlt PrimRep
    _) [GenStgAlt 'CodeGen]
    _alts
      = [Id] -> [NonVoid Id]
    assertNonVoidIds [Id
    bndr]

    chooseReturnBndrs Id
    _bndr (MultiValAlt RepArity
    n) [GenStgAlt 'CodeGen
    alt]
      = Bool -> SDoc -> [NonVoid Id] -> [NonVoid Id]
    forall a. HasCallStack => Bool -> SDoc -> a -> a
    assertPpr ([Id]
    [BinderP 'CodeGen]
    ids [Id] -> RepArity -> Bool
    forall a. [a] -> RepArity -> Bool
    `lengthIs` RepArity
    n) (RepArity -> SDoc
    forall a. Outputable a => a -> SDoc
    ppr RepArity
    n SDoc -> SDoc -> SDoc
    forall doc. IsDoc doc => doc -> doc -> doc
    $$ [Id] -> SDoc
    forall a. Outputable a => a -> SDoc
    ppr [Id]
    [BinderP 'CodeGen]
    ids SDoc -> SDoc -> SDoc
    forall doc. IsDoc doc => doc -> doc -> doc
    $$ Id -> SDoc
    forall a. Outputable a => a -> SDoc
    ppr Id
    _bndr) ([NonVoid Id] -> [NonVoid Id]) -> [NonVoid Id] -> [NonVoid Id]
    forall a b. (a -> b) -> a -> b
    $
        [Id] -> [NonVoid Id]
    assertNonVoidIds [Id]
    [BinderP 'CodeGen]
    ids     -- 'bndr' is not assigned!
        where ids :: [BinderP 'CodeGen]
    ids = GenStgAlt 'CodeGen -> [BinderP 'CodeGen]
    forall (pass :: StgPass). GenStgAlt pass -> [BinderP pass]
    alt_bndrs GenStgAlt 'CodeGen
    alt

    chooseReturnBndrs Id
    bndr (AlgAlt TyCon
    _) [GenStgAlt 'CodeGen]
    _alts
      = [Id] -> [NonVoid Id]
    assertNonVoidIds [Id
    bndr]  -- Only 'bndr' is assigned

    chooseReturnBndrs Id
    bndr AltType
    PolyAlt [GenStgAlt 'CodeGen]
    _alts
      = [Id] -> [NonVoid Id]
    assertNonVoidIds [Id
    bndr]  -- Only 'bndr' is assigned

    chooseReturnBndrs Id
    _ AltType
    _ [GenStgAlt 'CodeGen]
    _ = String -> [NonVoid Id]
    forall a. HasCallStack => String -> a
    panic String
    "chooseReturnBndrs"
                                 -- MultiValAlt has only one alternative

    -------------------------------------
    cgAlts :: (GcPlan,ReturnKind) -> NonVoid Id -> AltType -> [CgStgAlt]
           -> FCode ReturnKind
    -- At this point the result of the case are in the binders
    cgAlts :: (GcPlan, ReturnKind)
    -> NonVoid Id
    -> AltType
    -> [GenStgAlt 'CodeGen]
    -> FCode ReturnKind
    cgAlts (GcPlan, ReturnKind)
    gc_plan NonVoid Id
    _bndr AltType
    PolyAlt [GenStgAlt 'CodeGen
    alt]
      = (GcPlan, ReturnKind) -> FCode ReturnKind -> FCode ReturnKind
    forall a. (GcPlan, ReturnKind) -> FCode a -> FCode a
    maybeAltHeapCheck (GcPlan, ReturnKind)
    gc_plan (CgStgExpr -> FCode ReturnKind
    cgExpr (CgStgExpr -> FCode ReturnKind) -> CgStgExpr -> FCode ReturnKind
    forall a b. (a -> b) -> a -> b
    $ GenStgAlt 'CodeGen -> CgStgExpr
    forall (pass :: StgPass). GenStgAlt pass -> GenStgExpr pass
    alt_rhs GenStgAlt 'CodeGen
    alt)

    cgAlts (GcPlan, ReturnKind)
    gc_plan NonVoid Id
    _bndr (MultiValAlt RepArity
    _) [GenStgAlt 'CodeGen
    alt]
      = (GcPlan, ReturnKind) -> FCode ReturnKind -> FCode ReturnKind
    forall a. (GcPlan, ReturnKind) -> FCode a -> FCode a
    maybeAltHeapCheck (GcPlan, ReturnKind)
    gc_plan (CgStgExpr -> FCode ReturnKind
    cgExpr (CgStgExpr -> FCode ReturnKind) -> CgStgExpr -> FCode ReturnKind
    forall a b. (a -> b) -> a -> b
    $ GenStgAlt 'CodeGen -> CgStgExpr
    forall (pass :: StgPass). GenStgAlt pass -> GenStgExpr pass
    alt_rhs GenStgAlt 'CodeGen
    alt)
            -- Here bndrs are *already* in scope, so don't rebind them

    cgAlts (GcPlan, ReturnKind)
    gc_plan NonVoid Id
    bndr (PrimAlt PrimRep
    _) [GenStgAlt 'CodeGen]
    alts
      = do  { platform <- FCode Platform
    getPlatform

            ; tagged_cmms <- cgAltRhss gc_plan bndr alts

            ; let bndr_reg = LocalReg -> CmmReg
    CmmLocal (Platform -> NonVoid Id -> LocalReg
    idToReg Platform
    platform NonVoid Id
    bndr)
                  (DEFAULT,deflt) = head tagged_cmms
                    -- PrimAlts always have a DEFAULT case
                    -- and it always comes first

                  tagged_cmms' = [(Literal
    lit,CmmAGraphScoped
    code)
                                 | (LitAlt Literal
    lit, CmmAGraphScoped
    code) <- [(AltCon, CmmAGraphScoped)]
    tagged_cmms]
            ; emitCmmLitSwitch (CmmReg bndr_reg) tagged_cmms' deflt
            ; return AssignedDirectly }

    cgAlts (GcPlan, ReturnKind)
    gc_plan NonVoid Id
    bndr (AlgAlt TyCon
    tycon) [GenStgAlt 'CodeGen]
    alts
      = do  { platform <- FCode Platform
    getPlatform

            ; (mb_deflt, branches) <- cgAlgAltRhss gc_plan bndr alts

            ; let !fam_sz   = TyCon -> RepArity
    tyConFamilySize TyCon
    tycon
                  !bndr_reg = LocalReg -> CmmReg
    CmmLocal (Platform -> NonVoid Id -> LocalReg
    idToReg Platform
    platform NonVoid Id
    bndr)
                  !ptag_expr = Platform -> CmmExpr -> CmmExpr
    cmmConstrTag1 Platform
    platform (CmmReg -> CmmExpr
    CmmReg CmmReg
    bndr_reg)
                  !branches' = (RepArity -> RepArity)
    -> (RepArity, CmmAGraphScoped) -> (RepArity, CmmAGraphScoped)
    forall b c d. (b -> c) -> (b, d) -> (c, d)
    forall (a :: * -> * -> *) b c d.
    Arrow a =>
    a b c -> a (b, d) (c, d)
    first RepArity -> RepArity
    forall a. Enum a => a -> a
    succ ((RepArity, CmmAGraphScoped) -> (RepArity, CmmAGraphScoped))
    -> [(RepArity, CmmAGraphScoped)] -> [(RepArity, CmmAGraphScoped)]
    forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
    <$> [(RepArity, CmmAGraphScoped)]
    branches
                  !maxpt = Platform -> RepArity
    mAX_PTR_TAG Platform
    platform
                  (!via_ptr, !via_info) = partition ((< maxpt) . fst) branches'
                  !small = Platform -> RepArity -> Bool
    isSmallFamily Platform
    platform RepArity
    fam_sz

                    -- Is the constructor tag in the node reg?
                    -- See Note [Tagging big families]
            ; if small || null via_info
               then -- Yes, bndr_reg has constructor tag in ls bits
                   emitSwitch ptag_expr branches' mb_deflt 1
                     (if small then fam_sz else maxpt)

               else -- No, the get exact tag from info table when mAX_PTR_TAG
                    -- See Note [Double switching for big families]
                  do
                    profile     <- getProfile
                    align_check <- stgToCmmAlignCheck <$> getStgToCmmConfig
                    let !untagged_ptr = Platform -> CmmExpr -> CmmExpr
    cmmUntag Platform
    platform (CmmReg -> CmmExpr
    CmmReg CmmReg
    bndr_reg)
                        !itag_expr = Profile -> Bool -> CmmExpr -> CmmExpr
    getConstrTag Profile
    profile Bool
    align_check CmmExpr
    untagged_ptr
                        !info0 = (RepArity -> RepArity)
    -> (RepArity, CmmAGraphScoped) -> (RepArity, CmmAGraphScoped)
    forall b c d. (b -> c) -> (b, d) -> (c, d)
    forall (a :: * -> * -> *) b c d.
    Arrow a =>
    a b c -> a (b, d) (c, d)
    first RepArity -> RepArity
    forall a. Enum a => a -> a
    pred ((RepArity, CmmAGraphScoped) -> (RepArity, CmmAGraphScoped))
    -> [(RepArity, CmmAGraphScoped)] -> [(RepArity, CmmAGraphScoped)]
    forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
    <$> [(RepArity, CmmAGraphScoped)]
    via_info
                    if null via_ptr then
                      emitSwitch itag_expr info0 mb_deflt 0 (fam_sz - 1)
                    else do
                      infos_lbl <- newBlockId
                      infos_scp <- getTickScope

                      let spillover = (RepArity
    maxpt, (BlockId -> CmmAGraph
    mkBranch BlockId
    infos_lbl, CmmTickScope
    infos_scp))

                      (mb_shared_deflt, mb_shared_branch) <- case mb_deflt of
                          (Just (CmmAGraph
    stmts, CmmTickScope
    scp)) ->
                              do lbl <- FCode BlockId
    forall (m :: * -> *). MonadUnique m => m BlockId
    newBlockId
                                 return ( Just (mkLabel lbl scp <*> stmts, scp)
                                        , Just (mkBranch lbl, scp))
                          Maybe CmmAGraphScoped
    _ -> (Maybe CmmAGraphScoped, Maybe CmmAGraphScoped)
    -> FCode (Maybe CmmAGraphScoped, Maybe CmmAGraphScoped)
    forall a. a -> FCode a
    forall (m :: * -> *) a. Monad m => a -> m a
    return (Maybe CmmAGraphScoped
    forall a. Maybe a
    Nothing, Maybe CmmAGraphScoped
    forall a. Maybe a
    Nothing)
                      -- Switch on pointer tag
                      emitSwitch ptag_expr (spillover : via_ptr) mb_shared_deflt 1 maxpt
                      join_lbl <- newBlockId
                      emit (mkBranch join_lbl)
                      -- Switch on info table tag
                      emitLabel infos_lbl
                      emitSwitch itag_expr info0 mb_shared_branch
                        (maxpt - 1) (fam_sz - 1)
                      emitLabel join_lbl

            ; return AssignedDirectly }

    cgAlts (GcPlan, ReturnKind)
    _ NonVoid Id
    _ AltType
    _ [GenStgAlt 'CodeGen]
    _ = String -> FCode ReturnKind
    forall a. HasCallStack => String -> a
    panic String
    "cgAlts"
            -- UbxTupAlt and PolyAlt have only one alternative

    -- Note [Double switching for big families]
    -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    --
    -- An algebraic data type can have a n >= 0 summands
    -- (or alternatives), which are identified (labeled) by
    -- constructors. In memory they are kept apart by tags
    -- (see Note [Data constructor dynamic tags] in GHC.StgToCmm.Closure).
    -- Due to the characteristics of the platform that
    -- contribute to the alignment of memory objects, there
    -- is a natural limit of information about constructors
    -- that can be encoded in the pointer tag. When the mapping
    -- of constructors to the pointer tag range 1..mAX_PTR_TAG
    -- is not injective, then we have a "big data type", also
    -- called a "big (constructor) family" in the literature.
    -- Constructor tags residing in the info table are injective,
    -- but considerably more expensive to obtain, due to additional
    -- memory access(es).
    --
    -- When doing case analysis on a value of a "big data type"
    -- we need two nested switch statements to make up for the lack
    -- of injectivity of pointer tagging, also taking the info
    -- table tag into account. The exact mechanism is described next.
    --
    -- In the general case, switching on big family alternatives
    -- is done by two nested switch statements. According to
    -- Note [Tagging big families], the outer switch
    -- looks at the pointer tag and the inner dereferences the
    -- pointer and switches on the info table tag.
    --
    -- We can handle a simple case first, namely when none
    -- of the case alternatives mention a constructor having
    -- a pointer tag of 1..mAX_PTR_TAG-1. In this case we
    -- simply emit a switch on the info table tag.
    -- Note that the other simple case is when all mentioned
    -- alternatives lie in 1..mAX_PTR_TAG-1, in which case we can
    -- switch on the ptr tag only, just like in the small family case.
    --
    -- There is a single intricacy with a nested switch:
    -- Both should branch to the same default alternative, and as such
    -- avoid duplicate codegen of potentially heavy code. The outer
    -- switch generates the actual code with a prepended fresh label,
    -- while the inner one only generates a jump to that label.
    --
    -- For example, let's assume a 64-bit architecture, so that all
    -- heap objects are 8-byte aligned, and hence the address of a
    -- heap object ends in `000` (three zero bits).
    --
    -- Then consider the following data type
    --
    --   > data Big = T0 | T1 | T2 | T3 | T4 | T5 | T6 | T7 | T8
    --   Ptr tag:      1    2    3    4    5    6    7    7    7
    --   As bits:    001  010  011  100  101  110  111  111  111
    --   Info pointer tag (zero based):
    --                 0    1    2    3    4    5    6    7    8
    --
    -- Then     \case T2 -> True; T8 -> True; _ -> False
    -- will result in following code (slightly cleaned-up and
    -- commented -ddump-cmm-from-stg):
    {-
               R1 = _sqI::P64;  -- scrutinee
               if (R1 & 7 != 0) goto cqO; else goto cqP;
           cqP: // global       -- enter
               call (I64[R1])(R1) returns to cqO, args: 8, res: 8, upd: 8;
           cqO: // global       -- already WHNF
               _sqJ::P64 = R1;
               _cqX::P64 = _sqJ::P64 & 7;  -- extract pointer tag
               switch [1 .. 7] _cqX::P64 {
                   case 3 : goto cqW;
                   case 7 : goto cqR;
                   default: {goto cqS;}
               }
           cqR: // global
               _cr2 = I32[I64[_sqJ::P64 & (-8)] - 4]; -- tag from info pointer
               switch [6 .. 8] _cr2::I64 {
                   case 8 : goto cr1;
                   default: {goto cr0;}
               }
           cr1: // global
               R1 = GHC.Types.True_closure+2;
               call (P64[(old + 8)])(R1) args: 8, res: 0, upd: 8;
           cr0: // global     -- technically necessary label
               goto cqS;
           cqW: // global
               R1 = GHC.Types.True_closure+2;
               call (P64[(old + 8)])(R1) args: 8, res: 0, upd: 8;
           cqS: // global
               R1 = GHC.Types.False_closure+1;
               call (P64[(old + 8)])(R1) args: 8, res: 0, upd: 8;
    -}
    --
    -- For 32-bit systems we only have 2 tag bits in the pointers at our disposal,
    -- so the performance win is dubious, especially in face of the increased code
    -- size due to double switching. But we can take the viewpoint that 32-bit
    -- architectures are not relevant for performance any more, so this can be
    -- considered as moot.

    -- Note [alg-alt heap check]
    -- ~~~~~~~~~~~~~~~~~~~~~~~~~
    --
    -- In an algebraic case with more than one alternative, we will have
    -- code like
    --
    -- L0:
    --   x = R1
    --   goto L1
    -- L1:
    --   if (x & 7 >= 2) then goto L2 else goto L3
    -- L2:
    --   Hp = Hp + 16
    --   if (Hp > HpLim) then goto L4
    --   ...
    -- L4:
    --   call gc() returns to L5
    -- L5:
    --   x = R1
    --   goto L1

    -- Note [Tagging big families]
    -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~
    --
    -- Both the big and the small constructor families are tagged,
    -- that is, greater unions which overflow the tag space of TAG_BITS
    -- (i.e. 3 on 32 resp. 7 constructors on 64 bit archs).
    --
    -- For example, let's assume a 64-bit architecture, so that all
    -- heap objects are 8-byte aligned, and hence the address of a
    -- heap object ends in `000` (three zero bits).  Then consider
    -- > data Maybe a = Nothing | Just a
    -- > data Day a = Mon | Tue | Wed | Thu | Fri | Sat | Sun
    -- > data Grade = G1 | G2 | G3 | G4 | G5 | G6 | G7 | G8 | G9 | G10
    --
    -- Since `Grade` has more than 7 constructors, it counts as a
    -- "big data type" (also referred to as "big constructor family" in papers).
    -- On the other hand, `Maybe` and `Day` have 7 constructors or fewer, so they
    -- are "small data types".
    --
    -- Then
    --   * A pointer to an unevaluated thunk of type `Maybe Int`, `Day` or `Grade` will end in `000`
    --   * A tagged pointer to a `Nothing`, `Mon` or `G1` will end in `001`
    --   * A tagged pointer to a `Just x`, `Tue` or `G2`  will end in `010`
    --   * A tagged pointer to `Wed` or `G3` will end in `011`
    --       ...
    --   * A tagged pointer to `Sat` or `G6` will end in `110`
    --   * A tagged pointer to `Sun` or `G7` or `G8` or `G9` or `G10` will end in `111`
    --
    -- For big families we employ a mildly clever way of combining pointer and
    -- info-table tagging. We use 1..MAX_PTR_TAG-1 as pointer-resident tags where
    -- the tags in the pointer and the info table are in a one-to-one
    -- relation, whereas tag MAX_PTR_TAG is used as "spill over", signifying
    -- we have to fall back and get the precise constructor tag from the
    -- info-table.
    --
    -- Consequently we now cascade switches, because we have to check
    -- the pointer tag first, and when it is MAX_PTR_TAG, fetch the precise
    -- tag from the info table, and switch on that. The only technically
    -- tricky part is that the default case needs (logical) duplication.
    -- To do this we emit an extra label for it and branch to that from
    -- the second switch. This avoids duplicated codegen. See #14373.
    -- See Note [Double switching for big families] for the mechanics
    -- involved.
    --
    -- Also see Note [Data constructor dynamic tags]
    -- and the wiki https://gitlab.haskell.org/ghc/ghc/wikis/commentary/rts/haskell-execution/pointer-tagging
    --

    -------------------
    cgAlgAltRhss :: (GcPlan,ReturnKind) -> NonVoid Id -> [CgStgAlt]
                 -> FCode ( Maybe CmmAGraphScoped
                          , [(ConTagZ, CmmAGraphScoped)] )
    cgAlgAltRhss :: (GcPlan, ReturnKind)
    -> NonVoid Id
    -> [GenStgAlt 'CodeGen]
    -> FCode (Maybe CmmAGraphScoped, [(RepArity, CmmAGraphScoped)])
    cgAlgAltRhss (GcPlan, ReturnKind)
    gc_plan NonVoid Id
    bndr [GenStgAlt 'CodeGen]
    alts
      = do { tagged_cmms <- (GcPlan, ReturnKind)
    -> NonVoid Id
    -> [GenStgAlt 'CodeGen]
    -> FCode [(AltCon, CmmAGraphScoped)]
    cgAltRhss (GcPlan, ReturnKind)
    gc_plan NonVoid Id
    bndr [GenStgAlt 'CodeGen]
    alts

           ; let { mb_deflt = case [(AltCon, CmmAGraphScoped)]
    tagged_cmms of
                               ((AltCon
    DEFAULT,CmmAGraphScoped
    rhs) : [(AltCon, CmmAGraphScoped)]
    _) -> CmmAGraphScoped -> Maybe CmmAGraphScoped
    forall a. a -> Maybe a
    Just CmmAGraphScoped
    rhs
                               [(AltCon, CmmAGraphScoped)]
    _other              -> Maybe CmmAGraphScoped
    forall a. Maybe a
    Nothing
                                -- DEFAULT is always first, if present

                  ; branches = [ (DataCon -> RepArity
    dataConTagZ DataCon
    con, CmmAGraphScoped
    cmm)
                               | (DataAlt DataCon
    con, CmmAGraphScoped
    cmm) <- [(AltCon, CmmAGraphScoped)]
    tagged_cmms ]
                  }

           ; return (mb_deflt, branches)
           }

    -------------------
    cgAltRhss :: (GcPlan,ReturnKind) -> NonVoid Id -> [CgStgAlt]
              -> FCode [(AltCon, CmmAGraphScoped)]
    cgAltRhss :: (GcPlan, ReturnKind)
    -> NonVoid Id
    -> [GenStgAlt 'CodeGen]
    -> FCode [(AltCon, CmmAGraphScoped)]
    cgAltRhss (GcPlan, ReturnKind)
    gc_plan NonVoid Id
    bndr [GenStgAlt 'CodeGen]
    alts = do
      platform <- FCode Platform
    getPlatform
      let
        base_reg = Platform -> NonVoid Id -> LocalReg
    idToReg Platform
    platform NonVoid Id
    bndr
        cg_alt :: CgStgAlt -> FCode (AltCon, CmmAGraphScoped)
        cg_alt GenStgAlt{alt_con :: forall (pass :: StgPass). GenStgAlt pass -> AltCon
    alt_con=AltCon
    con, alt_bndrs :: forall (pass :: StgPass). GenStgAlt pass -> [BinderP pass]
    alt_bndrs=[BinderP 'CodeGen]
    bndrs, alt_rhs :: forall (pass :: StgPass). GenStgAlt pass -> GenStgExpr pass
    alt_rhs=CgStgExpr
    rhs}
          = FCode AltCon -> FCode (AltCon, CmmAGraphScoped)
    forall a. FCode a -> FCode (a, CmmAGraphScoped)
    getCodeScoped             (FCode AltCon -> FCode (AltCon, CmmAGraphScoped))
    -> FCode AltCon -> FCode (AltCon, CmmAGraphScoped)
    forall a b. (a -> b) -> a -> b
    $
            (GcPlan, ReturnKind) -> FCode AltCon -> FCode AltCon
    forall a. (GcPlan, ReturnKind) -> FCode a -> FCode a
    maybeAltHeapCheck (GcPlan, ReturnKind)
    gc_plan (FCode AltCon -> FCode AltCon) -> FCode AltCon -> FCode AltCon
    forall a b. (a -> b) -> a -> b
    $
            do { _ <- AltCon -> LocalReg -> [NonVoid Id] -> FCode [LocalReg]
    bindConArgs AltCon
    con LocalReg
    base_reg ([Id] -> [NonVoid Id]
    assertNonVoidIds [Id]
    [BinderP 'CodeGen]
    bndrs)
                        -- alt binders are always non-void,
                        -- see Note [Post-unarisation invariants] in GHC.Stg.Unarise
               ; _ <- cgExpr rhs
               ; return con }
      forkAlts (map cg_alt alts)

    maybeAltHeapCheck :: (GcPlan,ReturnKind) -> FCode a -> FCode a
    maybeAltHeapCheck :: forall a. (GcPlan, ReturnKind) -> FCode a -> FCode a
    maybeAltHeapCheck (GcPlan
    NoGcInAlts,ReturnKind
    _)  FCode a
    code = FCode a
    code
    maybeAltHeapCheck (GcInAlts [LocalReg]
    regs, ReturnKind
    AssignedDirectly) FCode a
    code =
      [LocalReg] -> FCode a -> FCode a
    forall a. [LocalReg] -> FCode a -> FCode a
    altHeapCheck [LocalReg]
    regs FCode a
    code
    maybeAltHeapCheck (GcInAlts [LocalReg]
    regs, ReturnedTo BlockId
    lret RepArity
    off) FCode a
    code =
      [LocalReg] -> BlockId -> RepArity -> FCode a -> FCode a
    forall a. [LocalReg] -> BlockId -> RepArity -> FCode a -> FCode a
    altHeapCheckReturnsTo [LocalReg]
    regs BlockId
    lret RepArity
    off FCode a
    code

    -----------------------------------------------------------------------------
    --      Tail calls
    -----------------------------------------------------------------------------

    cgConApp :: DataCon -> ConstructorNumber -> [StgArg] -> FCode ReturnKind
    cgConApp :: DataCon -> ConstructorNumber -> [StgArg] -> FCode ReturnKind
    cgConApp DataCon
    con ConstructorNumber
    mn [StgArg]
    stg_args
      | DataCon -> Bool
    isUnboxedTupleDataCon DataCon
    con       -- Unboxed tuple: assign and return
      = do { arg_exprs <- [StgArg] -> FCode [CmmExpr]
    getNonVoidArgAmodes [StgArg]
    stg_args
           ; tickyUnboxedTupleReturn (length arg_exprs)
           ; emitReturn arg_exprs }

      | Bool
    otherwise   --  Boxed constructors; allocate and return
      = Bool -> SDoc -> FCode ReturnKind -> FCode ReturnKind
    forall a. HasCallStack => Bool -> SDoc -> a -> a
    assertPpr ([StgArg]
    stg_args [StgArg] -> RepArity -> Bool
    forall a. [a] -> RepArity -> Bool
    `lengthIs` DataCon -> RepArity
    countConRepArgs DataCon
    con)
                  (DataCon -> SDoc
    forall a. Outputable a => a -> SDoc
    ppr DataCon
    con SDoc -> SDoc -> SDoc
    forall doc. IsLine doc => doc -> doc -> doc
    <> SDoc -> SDoc
    forall doc. IsLine doc => doc -> doc
    parens (RepArity -> SDoc
    forall a. Outputable a => a -> SDoc
    ppr (DataCon -> RepArity
    countConRepArgs DataCon
    con)) SDoc -> SDoc -> SDoc
    forall doc. IsLine doc => doc -> doc -> doc
    <+> [StgArg] -> SDoc
    forall a. Outputable a => a -> SDoc
    ppr [StgArg]
    stg_args) (FCode ReturnKind -> FCode ReturnKind)
    -> FCode ReturnKind -> FCode ReturnKind
    forall a b. (a -> b) -> a -> b
    $
        do  { (idinfo, fcode_init) <- Id
    -> ConstructorNumber
    -> Bool
    -> CostCentreStack
    -> DataCon
    -> [NonVoid StgArg]
    -> FCode (CgIdInfo, FCode CmmAGraph)
    buildDynCon (DataCon -> Id
    dataConWorkId DataCon
    con) ConstructorNumber
    mn Bool
    False
                                         CostCentreStack
    currentCCS DataCon
    con ([StgArg] -> [NonVoid StgArg]
    assertNonVoidStgArgs [StgArg]
    stg_args)
                                         -- con args are always non-void,
                                         -- see Note [Post-unarisation invariants] in GHC.Stg.Unarise
                    -- The first "con" says that the name bound to this
                    -- closure is "con", which is a bit of a fudge, but
                    -- it only affects profiling (hence the False)

            ; emit =<< fcode_init
            ; tickyReturnNewCon (length stg_args)
            ; emitReturn [idInfoToAmode idinfo] }

    cgIdApp :: Id -> [StgArg] -> FCode ReturnKind
    cgIdApp :: Id -> [StgArg] -> FCode ReturnKind
    cgIdApp Id
    fun_id [StgArg]
    args = do
        platform       <- FCode Platform
    getPlatform
        fun_info       <- getCgIdInfo fun_id
        cfg            <- getStgToCmmConfig
        self_loop      <- getSelfLoop
        let profile        = StgToCmmConfig -> Profile
    stgToCmmProfile  StgToCmmConfig
    cfg
            fun_arg        = Id -> StgArg
    StgVarArg Id
    fun_id
            fun_name       = Id -> Name
    idName    Id
    fun_id
            fun            = CgIdInfo -> CmmExpr
    idInfoToAmode CgIdInfo
    fun_info
            lf_info        = CgIdInfo -> LambdaFormInfo
    cg_lf         CgIdInfo
    fun_info
            n_args         = [StgArg] -> RepArity
    forall a. [a] -> RepArity
    forall (t :: * -> *) a. Foldable t => t a -> RepArity
    length [StgArg]
    args
        case getCallMethod cfg fun_name fun_id lf_info n_args (cg_loc fun_info) self_loop of
                -- A value in WHNF, so we can just return it.
            CallMethod
    ReturnIt
              | HasDebugCallStack => Type -> Bool
    Type -> Bool
    isZeroBitTy (Id -> Type
    idType Id
    fun_id) -> [CmmExpr] -> FCode ReturnKind
    emitReturn []
              | Bool
    otherwise                -> [CmmExpr] -> FCode ReturnKind
    emitReturn [CmmExpr
    fun]

            -- A value infered to be in WHNF, so we can just return it.
            CallMethod
    InferedReturnIt
              | HasDebugCallStack => Type -> Bool
    Type -> Bool
    isZeroBitTy (Id -> Type
    idType Id
    fun_id) -> FCode ()
    trace FCode () -> FCode ReturnKind -> FCode ReturnKind
    forall a b. FCode a -> FCode b -> FCode b
    forall (m :: * -> *) a b. Monad m => m a -> m b -> m b
    >> [CmmExpr] -> FCode ReturnKind
    emitReturn []
              | Bool
    otherwise                   -> FCode ()
    trace FCode () -> FCode () -> FCode ()
    forall a b. FCode a -> FCode b -> FCode b
    forall (m :: * -> *) a b. Monad m => m a -> m b -> m b
    >> FCode ()
    assertTag FCode () -> FCode ReturnKind -> FCode ReturnKind
    forall a b. FCode a -> FCode b -> FCode b
    forall (m :: * -> *) a b. Monad m => m a -> m b -> m b
    >>
                                                        [CmmExpr] -> FCode ReturnKind
    emitReturn [CmmExpr
    fun]
                where
                  trace :: FCode ()
    trace = do
                    FCode ()
    tickyTagged
                    use_id <- FCode Unique
    newUnique
                    _lbl <- emitTickyCounterTag use_id (NonVoid fun_id)
                    tickyTagSkip use_id fun_id

                    -- pprTraceM "WHNF:" (ppr fun_id <+> ppr args )
                  assertTag :: FCode ()
    assertTag = FCode () -> FCode ()
    whenCheckTags (FCode () -> FCode ()) -> FCode () -> FCode ()
    forall a b. (a -> b) -> a -> b
    $ do
                      mod <- FCode Module
    getModuleName
                      emitTagAssertion (showPprUnsafe
                          (text "TagCheck failed on entry in" <+> ppr mod <+> text "- value:" <> ppr fun_id <+> pdoc platform fun))
                          fun

            CallMethod
    EnterIt -> Bool -> SDoc -> FCode ReturnKind -> FCode ReturnKind
    forall a. HasCallStack => Bool -> SDoc -> a -> a
    assertPpr ([StgArg] -> Bool
    forall a. [a] -> Bool
    forall (t :: * -> *) a. Foldable t => t a -> Bool
    null [StgArg]
    args) (Id -> SDoc
    forall a. Outputable a => a -> SDoc
    ppr Id
    fun_id SDoc -> SDoc -> SDoc
    forall doc. IsDoc doc => doc -> doc -> doc
    $$ [StgArg] -> SDoc
    forall a. Outputable a => a -> SDoc
    ppr [StgArg]
    args) (FCode ReturnKind -> FCode ReturnKind)
    -> FCode ReturnKind -> FCode ReturnKind
    forall a b. (a -> b) -> a -> b
    $  -- Discarding arguments
                       CmmExpr -> FCode ReturnKind
    emitEnter CmmExpr
    fun

            CallMethod
    SlowCall -> do      -- A slow function call via the RTS apply routines
                    { LambdaFormInfo -> [StgArg] -> FCode ()
    tickySlowCall LambdaFormInfo
    lf_info [StgArg]
    args
                    ; FastString -> FCode ()
    emitComment (FastString -> FCode ()) -> FastString -> FCode ()
    forall a b. (a -> b) -> a -> b
    $ String -> FastString
    mkFastString String
    "slowCall"
                    ; CmmExpr -> [StgArg] -> FCode ReturnKind
    slowCall CmmExpr
    fun [StgArg]
    args }

            -- A direct function call (possibly with some left-over arguments)
            DirectEntry CLabel
    lbl RepArity
    arity -> do
                    { RepArity -> [StgArg] -> FCode ()
    tickyDirectCall RepArity
    arity [StgArg]
    args
                    ; if Profile -> LambdaFormInfo -> Bool
    nodeMustPointToIt Profile
    profile LambdaFormInfo
    lf_info
                         then Convention -> CLabel -> RepArity -> [StgArg] -> FCode ReturnKind
    directCall Convention
    NativeNodeCall   CLabel
    lbl RepArity
    arity (StgArg
    fun_argStgArg -> [StgArg] -> [StgArg]
    forall a. a -> [a] -> [a]
    :[StgArg]
    args)
                         else Convention -> CLabel -> RepArity -> [StgArg] -> FCode ReturnKind
    directCall Convention
    NativeDirectCall CLabel
    lbl RepArity
    arity [StgArg]
    args }

            -- Let-no-escape call or self-recursive tail-call
            JumpToIt BlockId
    blk_id [LocalReg]
    lne_regs -> do
              { FCode ()
    adjustHpBackwards -- always do this before a tail-call
              ; cmm_args <- [StgArg] -> FCode [CmmExpr]
    getNonVoidArgAmodes [StgArg]
    args
              ; emitMultiAssign lne_regs cmm_args
              ; emit (mkBranch blk_id)
              ; return AssignedDirectly }

    -- Note [Self-recursive tail calls]
    -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    --
    -- Self-recursive tail calls can be optimized into a local jump in the same
    -- way as let-no-escape bindings (see Note [What is a non-escaping let] in
    -- "GHC.CoreToStg"). Consider this:
    --
    -- foo.info:
    --     a = R1  // calling convention
    --     b = R2
    --     goto L1
    -- L1: ...
    --     ...
    -- ...
    -- L2: R1 = x
    --     R2 = y
    --     call foo(R1,R2)
    --
    -- Instead of putting x and y into registers (or other locations required by the
    -- calling convention) and performing a call we can put them into local
    -- variables a and b and perform jump to L1:
    --
    -- foo.info:
    --     a = R1
    --     b = R2
    --     goto L1
    -- L1: ...
    --     ...
    -- ...
    -- L2: a = x
    --     b = y
    --     goto L1
    --
    -- This can be done only when function is calling itself in a tail position
    -- and only if the call passes number of parameters equal to function's arity.
    -- Note that this cannot be performed if a function calls itself with a
    -- continuation.
    --
    -- This in fact implements optimization known as "loopification". It was
    -- described in "Low-level code optimizations in the Glasgow Haskell Compiler"
    -- by Krzysztof Woś, though we use different approach. Krzysztof performed his
    -- optimization at the Cmm level, whereas we perform ours during code generation
    -- (Stg-to-Cmm pass) essentially making sure that optimized Cmm code is
    -- generated in the first place.
    --
    -- Implementation is spread across a couple of places in the code:
    --
    --   * FCode monad stores additional information in its reader
    --     environment (stgToCmmSelfLoop field). This `SelfLoopInfo`
    --     record tells us which function can tail call itself in an
    --     optimized way (it is the function currently being compiled),
    --     its RepArity, what is the label of its loop header (L1 in
    --     example above) and information about which local registers
    --     should receive arguments when making a call (this would be a
    --     and b in the example above).
    --
    --   * Whenever we are compiling a function, we set that information to reflect
    --     the fact that function currently being compiled can be jumped to, instead
    --     of called. This is done in closureCodyBody in GHC.StgToCmm.Bind.
    --
    --   * We also have to emit a label to which we will be jumping. We make sure
    --     that the label is placed after a stack check but before the heap
    --     check. The reason is that making a recursive tail-call does not increase
    --     the stack so we only need to check once. But it may grow the heap, so we
    --     have to repeat the heap check in every self-call. This is done in
    --     do_checks in GHC.StgToCmm.Heap.
    --
    --   * When we begin compilation of another closure we remove the additional
    --     information from the environment. This is done by forkClosureBody
    --     in GHC.StgToCmm.Monad. Other functions that duplicate the environment -
    --     forkLneBody, forkAlts, codeOnly - duplicate that information. In other
    --     words, we only need to clean the environment of the self-loop information
    --     when compiling right hand side of a closure (binding).
    --
    --   * When compiling a call (cgIdApp) we use getCallMethod to decide what kind
    --     of call will be generated. getCallMethod decides to generate a self
    --     recursive tail call when (a) environment stores information about
    --     possible self tail-call; (b) that tail call is to a function currently
    --     being compiled; (c) number of passed arguments is equal to
    --     function's unarised arity. (d) loopification is turned on via
    --     -floopification command-line option.
    --
    --   * Command line option to turn loopification on and off is implemented in
    --     DynFlags, then passed to StgToCmmConfig for this phase.

    emitEnter :: CmmExpr -> FCode ReturnKind
    emitEnter :: CmmExpr -> FCode ReturnKind
    emitEnter CmmExpr
    fun = do
      { platform <- FCode Platform
    getPlatform
      ; profile  <- getProfile
      ; adjustHpBackwards
      ; sequel      <- getSequel
      ; updfr_off   <- getUpdFrameOff
      ; align_check <- stgToCmmAlignCheck <$> getStgToCmmConfig
      ; case sequel of
          -- For a return, we have the option of generating a tag-test or
          -- not.  If the value is tagged, we can return directly, which
          -- is quicker than entering the value.  This is a code
          -- size/speed trade-off: when optimising for speed rather than
          -- size we could generate the tag test.
          --
          -- Right now, we do what the old codegen did, and omit the tag
          -- test, just generating an enter.
          Sequel
    Return -> do
            { let entry :: CmmExpr
    entry = Platform -> CmmExpr -> CmmExpr
    entryCode Platform
    platform
                    (CmmExpr -> CmmExpr) -> CmmExpr -> CmmExpr
    forall a b. (a -> b) -> a -> b
    $ Platform -> Bool -> CmmExpr -> CmmExpr
    closureInfoPtr Platform
    platform Bool
    align_check
                    (CmmExpr -> CmmExpr) -> CmmExpr -> CmmExpr
    forall a b. (a -> b) -> a -> b
    $ CmmReg -> CmmExpr
    CmmReg (Platform -> CmmReg
    nodeReg Platform
    platform)
            ; CmmAGraph -> FCode ()
    emit (CmmAGraph -> FCode ()) -> CmmAGraph -> FCode ()
    forall a b. (a -> b) -> a -> b
    $ Profile
    -> Convention -> CmmExpr -> [CmmExpr] -> RepArity -> CmmAGraph
    mkJump Profile
    profile Convention
    NativeNodeCall CmmExpr
    entry
                            [Platform -> CmmExpr -> CmmExpr
    cmmUntag Platform
    platform CmmExpr
    fun] RepArity
    updfr_off
            ; ReturnKind -> FCode ReturnKind
    forall a. a -> FCode a
    forall (m :: * -> *) a. Monad m => a -> m a
    return ReturnKind
    AssignedDirectly
            }

          -- The result will be scrutinised in the sequel.  This is where
          -- we generate a tag-test to avoid entering the closure if
          -- possible.
          --
          -- The generated code will be something like this:
          --
          --    R1 = fun  -- copyout
          --    if (fun & 7 != 0) goto Lret else goto Lcall
          --  Lcall:
          --    call [fun] returns to Lret
          --  Lret:
          --    fun' = R1  -- copyin
          --    ...
          --
          -- Note in particular that the label Lret is used as a
          -- destination by both the tag-test and the call.  This is
          -- because Lret will necessarily be a proc-point, and we want to
          -- ensure that we generate only one proc-point for this
          -- sequence.
          --
          -- Furthermore, we tell the caller that we generated a native
          -- return continuation by returning (ReturnedTo Lret off), so
          -- that the continuation can be reused by the heap-check failure
          -- code in the enclosing case expression.
          --
          AssignTo [LocalReg]
    res_regs Bool
    _ -> do
           { lret  <- FCode BlockId
    forall (m :: * -> *). MonadUnique m => m BlockId
    newBlockId
           ; lcall <- newBlockId
           ; updfr_off   <- getUpdFrameOff
           ; align_check <- stgToCmmAlignCheck <$> getStgToCmmConfig
           ; let (off, _, copyin) = copyInOflow profile NativeReturn (Young lret) res_regs []
           ; let area = BlockId -> Area
    Young BlockId
    lret
           ; let (outArgs, regs, copyout) = copyOutOflow profile NativeNodeCall Call area
                                              [fun] updfr_off []
             -- refer to fun via nodeReg after the copyout, to avoid having
             -- both live simultaneously; this sometimes enables fun to be
             -- inlined in the RHS of the R1 assignment.
           ; let node = CmmReg -> CmmExpr
    CmmReg (CmmReg -> CmmExpr) -> CmmReg -> CmmExpr
    forall a b. (a -> b) -> a -> b
    $ Platform -> CmmReg
    nodeReg Platform
    platform
                 entry = Platform -> CmmExpr -> CmmExpr
    entryCode Platform
    platform (Platform -> Bool -> CmmExpr -> CmmExpr
    closureInfoPtr Platform
    platform Bool
    align_check CmmExpr
    node)
                 the_call = CmmExpr
    -> Maybe BlockId
    -> RepArity
    -> RepArity
    -> RepArity
    -> [GlobalReg]
    -> CmmAGraph
    toCall CmmExpr
    entry (BlockId -> Maybe BlockId
    forall a. a -> Maybe a
    Just BlockId
    lret) RepArity
    updfr_off RepArity
    off RepArity
    outArgs [GlobalReg]
    regs
           ; tscope <- getTickScope
           ; emit $
               copyout <*>
               mkCbranch (cmmIsTagged platform node)
                         lret lcall Nothing <*>
               outOfLine lcall (the_call,tscope) <*>
               mkLabel lret tscope <*>
               copyin
           ; return (ReturnedTo lret off)
           }
      }

    ------------------------------------------------------------------------
    --              Ticks
    ------------------------------------------------------------------------

    -- | Generate Cmm code for a tick. Depending on the type of Tickish,
    -- this will either generate actual Cmm instrumentation code, or
    -- simply pass on the annotation as a @CmmTickish@.
    cgTick :: StgTickish -> FCode ()
    cgTick :: StgTickish -> FCode ()
    cgTick StgTickish
    tick
      = do { platform <- FCode Platform
    getPlatform
           ; case tick of
               ProfNote   CostCentre
    cc Bool
    t Bool
    p -> CostCentre -> Bool -> Bool -> FCode ()
    emitSetCCC CostCentre
    cc Bool
    t Bool
    p
               HpcTick    Module
    m RepArity
    n    -> CmmAGraph -> FCode ()
    emit (Platform -> Module -> RepArity -> CmmAGraph
    mkTickBox Platform
    platform Module
    m RepArity
    n)
               SourceNote RealSrcSpan
    s LexicalFastString
    n    -> CmmTickish -> FCode ()
    emitTick (CmmTickish -> FCode ()) -> CmmTickish -> FCode ()
    forall a b. (a -> b) -> a -> b
    $ RealSrcSpan -> LexicalFastString -> CmmTickish
    forall (pass :: TickishPass).
    RealSrcSpan -> LexicalFastString -> GenTickish pass
    SourceNote RealSrcSpan
    s LexicalFastString
    n
               StgTickish
    _other            -> () -> FCode ()
    forall a. a -> FCode a
    forall (m :: * -> *) a. Monad m => a -> m a
    return () -- ignore
           }