cmm/CLabel.hs

    -----------------------------------------------------------------------------
    --
    -- Object-file symbols (called CLabel for histerical raisins).
    --
    -- (c) The University of Glasgow 2004-2006
    --
    -----------------------------------------------------------------------------

    {-# LANGUAGE CPP #-}

    module CLabel (
            CLabel, -- abstract type
            ForeignLabelSource(..),
            pprDebugCLabel,

            mkClosureLabel,
            mkSRTLabel,
            mkTopSRTLabel,
            mkInfoTableLabel,
            mkEntryLabel,
            mkSlowEntryLabel,
            mkConEntryLabel,
            mkRednCountsLabel,
            mkConInfoTableLabel,
            mkLargeSRTLabel,
            mkApEntryLabel,
            mkApInfoTableLabel,
            mkClosureTableLabel,
            mkBytesLabel,

            mkLocalClosureLabel,
            mkLocalInfoTableLabel,
            mkLocalEntryLabel,
            mkLocalConEntryLabel,
            mkLocalConInfoTableLabel,
            mkLocalClosureTableLabel,

            mkReturnPtLabel,
            mkReturnInfoLabel,
            mkAltLabel,
            mkDefaultLabel,
            mkBitmapLabel,
            mkStringLitLabel,

            mkAsmTempLabel,
            mkAsmTempDerivedLabel,
            mkAsmTempEndLabel,
            mkAsmTempDieLabel,

            mkPlainModuleInitLabel,

            mkSplitMarkerLabel,
            mkDirty_MUT_VAR_Label,
            mkUpdInfoLabel,
            mkBHUpdInfoLabel,
            mkIndStaticInfoLabel,
            mkMainCapabilityLabel,
            mkMAP_FROZEN_infoLabel,
            mkMAP_FROZEN0_infoLabel,
            mkMAP_DIRTY_infoLabel,
            mkSMAP_FROZEN_infoLabel,
            mkSMAP_FROZEN0_infoLabel,
            mkSMAP_DIRTY_infoLabel,
            mkEMPTY_MVAR_infoLabel,
            mkArrWords_infoLabel,

            mkTopTickyCtrLabel,
            mkCAFBlackHoleInfoTableLabel,
            mkCAFBlackHoleEntryLabel,
            mkRtsPrimOpLabel,
            mkRtsSlowFastTickyCtrLabel,

            mkSelectorInfoLabel,
            mkSelectorEntryLabel,

            mkCmmInfoLabel,
            mkCmmEntryLabel,
            mkCmmRetInfoLabel,
            mkCmmRetLabel,
            mkCmmCodeLabel,
            mkCmmDataLabel,
            mkCmmClosureLabel,

            mkRtsApFastLabel,

            mkPrimCallLabel,

            mkForeignLabel,
            addLabelSize,

            foreignLabelStdcallInfo,
            isBytesLabel,
            isForeignLabel,
            mkCCLabel, mkCCSLabel,

            DynamicLinkerLabelInfo(..),
            mkDynamicLinkerLabel,
            dynamicLinkerLabelInfo,

            mkPicBaseLabel,
            mkDeadStripPreventer,

            mkHpcTicksLabel,

            hasCAF,
            needsCDecl, maybeAsmTemp, externallyVisibleCLabel,
            isMathFun,
            isCFunctionLabel, isGcPtrLabel, labelDynamic,

            -- * Conversions
            toClosureLbl, toSlowEntryLbl, toEntryLbl, toInfoLbl, toRednCountsLbl, hasHaskellName,

            pprCLabel
        ) where

    #include "HsVersions.h"

    import IdInfo
    import BasicTypes
    import Packages
    import Module
    import Name
    import Unique
    import PrimOp
    import Config
    import CostCentre
    import Outputable
    import FastString
    import DynFlags
    import Platform
    import UniqSet
    import Util
    import PprCore ( {- instances -} )

    -- -----------------------------------------------------------------------------
    -- The CLabel type

    {-
      | CLabel is an abstract type that supports the following operations:

      - Pretty printing

      - In a C file, does it need to be declared before use?  (i.e. is it
        guaranteed to be already in scope in the places we need to refer to it?)

      - If it needs to be declared, what type (code or data) should it be
        declared to have?

      - Is it visible outside this object file or not?

      - Is it "dynamic" (see details below)

      - Eq and Ord, so that we can make sets of CLabels (currently only
        used in outputting C as far as I can tell, to avoid generating
        more than one declaration for any given label).

      - Converting an info table label into an entry label.
    -}

    data CLabel
      = -- | A label related to the definition of a particular Id or Con in a .hs file.
        IdLabel
            Name
            CafInfo
            IdLabelInfo             -- encodes the suffix of the label

      -- | A label from a .cmm file that is not associated with a .hs level Id.
      | CmmLabel
            UnitId               -- what package the label belongs to.
            FastString              -- identifier giving the prefix of the label
            CmmLabelInfo            -- encodes the suffix of the label

      -- | A label with a baked-in \/ algorithmically generated name that definitely
      --    comes from the RTS. The code for it must compile into libHSrts.a \/ libHSrts.so
      --    If it doesn't have an algorithmically generated name then use a CmmLabel
      --    instead and give it an appropriate UnitId argument.
      | RtsLabel
            RtsLabelInfo

      -- | A 'C' (or otherwise foreign) label.
      --
      | ForeignLabel
            FastString              -- name of the imported label.

            (Maybe Int)             -- possible '@n' suffix for stdcall functions
                                    -- When generating C, the '@n' suffix is omitted, but when
                                    -- generating assembler we must add it to the label.

            ForeignLabelSource      -- what package the foreign label is in.

            FunctionOrData

      -- | A family of labels related to a particular case expression.
      | CaseLabel
            {-# UNPACK #-} !Unique  -- Unique says which case expression
            CaseLabelInfo

      | AsmTempLabel
            {-# UNPACK #-} !Unique

      | AsmTempDerivedLabel
            CLabel
            FastString              -- suffix

      | StringLitLabel
            {-# UNPACK #-} !Unique

      | PlainModuleInitLabel        -- without the version & way info
            Module

      | CC_Label  CostCentre
      | CCS_Label CostCentreStack

      -- | These labels are generated and used inside the NCG only.
      --    They are special variants of a label used for dynamic linking
      --    see module PositionIndependentCode for details.
      | DynamicLinkerLabel DynamicLinkerLabelInfo CLabel

      -- | This label is generated and used inside the NCG only.
      --    It is used as a base for PIC calculations on some platforms.
      --    It takes the form of a local numeric assembler label '1'; and
      --    is pretty-printed as 1b, referring to the previous definition
      --    of 1: in the assembler source file.
      | PicBaseLabel

      -- | A label before an info table to prevent excessive dead-stripping on darwin
      | DeadStripPreventer CLabel

      -- | Per-module table of tick locations
      | HpcTicksLabel Module

      -- | Static reference table
      | SRTLabel !Unique

      -- | Label of an StgLargeSRT
      | LargeSRTLabel
            {-# UNPACK #-} !Unique

      -- | A bitmap (function or case return)
      | LargeBitmapLabel
            {-# UNPACK #-} !Unique

      deriving Eq

    -- This is laborious, but necessary. We can't derive Ord because
    -- Unique doesn't have an Ord instance. Note nonDetCmpUnique in the
    -- implementation. See Note [No Ord for Unique]
    -- This is non-deterministic but we do not currently support deterministic
    -- code-generation. See Note [Unique Determinism and code generation]
    instance Ord CLabel where
      compare (IdLabel a1 b1 c1) (IdLabel a2 b2 c2) =
        compare a1 a2 `thenCmp`
        compare b1 b2 `thenCmp`
        compare c1 c2
      compare (CmmLabel a1 b1 c1) (CmmLabel a2 b2 c2) =
        compare a1 a2 `thenCmp`
        compare b1 b2 `thenCmp`
        compare c1 c2
      compare (RtsLabel a1) (RtsLabel a2) = compare a1 a2
      compare (ForeignLabel a1 b1 c1 d1) (ForeignLabel a2 b2 c2 d2) =
        compare a1 a2 `thenCmp`
        compare b1 b2 `thenCmp`
        compare c1 c2 `thenCmp`
        compare d1 d2
      compare (CaseLabel u1 a1) (CaseLabel u2 a2) =
        nonDetCmpUnique u1 u2 `thenCmp`
        compare a1 a2
      compare (AsmTempLabel u1) (AsmTempLabel u2) = nonDetCmpUnique u1 u2
      compare (AsmTempDerivedLabel a1 b1) (AsmTempDerivedLabel a2 b2) =
        compare a1 a2 `thenCmp`
        compare b1 b2
      compare (StringLitLabel u1) (StringLitLabel u2) =
        nonDetCmpUnique u1 u2
      compare (PlainModuleInitLabel a1) (PlainModuleInitLabel a2) =
        compare a1 a2
      compare (CC_Label a1) (CC_Label a2) =
        compare a1 a2
      compare (CCS_Label a1) (CCS_Label a2) =
        compare a1 a2
      compare (DynamicLinkerLabel a1 b1) (DynamicLinkerLabel a2 b2) =
        compare a1 a2 `thenCmp`
        compare b1 b2
      compare PicBaseLabel PicBaseLabel = EQ
      compare (DeadStripPreventer a1) (DeadStripPreventer a2) =
        compare a1 a2
      compare (HpcTicksLabel a1) (HpcTicksLabel a2) =
        compare a1 a2
      compare (SRTLabel u1) (SRTLabel u2) =
        nonDetCmpUnique u1 u2
      compare (LargeSRTLabel u1) (LargeSRTLabel u2) =
        nonDetCmpUnique u1 u2
      compare (LargeBitmapLabel u1) (LargeBitmapLabel u2) =
        nonDetCmpUnique u1 u2
      compare IdLabel{} _ = LT
      compare _ IdLabel{} = GT
      compare CmmLabel{} _ = LT
      compare _ CmmLabel{} = GT
      compare RtsLabel{} _ = LT
      compare _ RtsLabel{} = GT
      compare ForeignLabel{} _ = LT
      compare _ ForeignLabel{} = GT
      compare CaseLabel{} _ = LT
      compare _ CaseLabel{} = GT
      compare AsmTempLabel{} _ = LT
      compare _ AsmTempLabel{} = GT
      compare AsmTempDerivedLabel{} _ = LT
      compare _ AsmTempDerivedLabel{} = GT
      compare StringLitLabel{} _ = LT
      compare _ StringLitLabel{} = GT
      compare PlainModuleInitLabel{} _ = LT
      compare _ PlainModuleInitLabel{} = GT
      compare CC_Label{} _ = LT
      compare _ CC_Label{} = GT
      compare CCS_Label{} _ = LT
      compare _ CCS_Label{} = GT
      compare DynamicLinkerLabel{} _ = LT
      compare _ DynamicLinkerLabel{} = GT
      compare PicBaseLabel{} _ = LT
      compare _ PicBaseLabel{} = GT
      compare DeadStripPreventer{} _ = LT
      compare _ DeadStripPreventer{} = GT
      compare HpcTicksLabel{} _ = LT
      compare _ HpcTicksLabel{} = GT
      compare SRTLabel{} _ = LT
      compare _ SRTLabel{} = GT
      compare LargeSRTLabel{} _ = LT
      compare _ LargeSRTLabel{} = GT

    -- | Record where a foreign label is stored.
    data ForeignLabelSource

       -- | Label is in a named package
       = ForeignLabelInPackage      UnitId

       -- | Label is in some external, system package that doesn't also
       --   contain compiled Haskell code, and is not associated with any .hi files.
       --   We don't have to worry about Haskell code being inlined from
       --   external packages. It is safe to treat the RTS package as "external".
       | ForeignLabelInExternalPackage

       -- | Label is in the package currenly being compiled.
       --   This is only used for creating hacky tmp labels during code generation.
       --   Don't use it in any code that might be inlined across a package boundary
       --   (ie, core code) else the information will be wrong relative to the
       --   destination module.
       | ForeignLabelInThisPackage

       deriving (Eq, Ord)

    -- | For debugging problems with the CLabel representation.
    --      We can't make a Show instance for CLabel because lots of its components don't have instances.
    --      The regular Outputable instance only shows the label name, and not its other info.
    --
    pprDebugCLabel :: CLabel -> SDoc
    pprDebugCLabel lbl
     = case lbl of
            IdLabel{}       -> ppr lbl <> (parens $ text "IdLabel")
            CmmLabel pkg _name _info
             -> ppr lbl <> (parens $ text "CmmLabel" <+> ppr pkg)

            RtsLabel{}      -> ppr lbl <> (parens $ text "RtsLabel")

            ForeignLabel _name mSuffix src funOrData
                -> ppr lbl <> (parens $ text "ForeignLabel"
                                    <+> ppr mSuffix
                                    <+> ppr src
                                    <+> ppr funOrData)

            _               -> ppr lbl <> (parens $ text "other CLabel)")

    data IdLabelInfo
      = Closure             -- ^ Label for closure
      | SRT                 -- ^ Static reference table (TODO: could be removed
                            -- with the old code generator, but might be needed
                            -- when we implement the New SRT Plan)
      | InfoTable           -- ^ Info tables for closures; always read-only
      | Entry               -- ^ Entry point
      | Slow                -- ^ Slow entry point

      | LocalInfoTable      -- ^ Like InfoTable but not externally visible
      | LocalEntry          -- ^ Like Entry but not externally visible

      | RednCounts          -- ^ Label of place to keep Ticky-ticky  info for this Id

      | ConEntry            -- ^ Constructor entry point
      | ConInfoTable        -- ^ Corresponding info table

      | ClosureTable        -- ^ Table of closures for Enum tycons

      | Bytes               -- ^ Content of a string literal. See
                            -- Note [Bytes label].

      deriving (Eq, Ord)

    data CaseLabelInfo
      = CaseReturnPt
      | CaseReturnInfo
      | CaseAlt ConTag
      | CaseDefault
      deriving (Eq, Ord)

    data RtsLabelInfo
      = RtsSelectorInfoTable Bool{-updatable-} Int{-offset-}  -- ^ Selector thunks
      | RtsSelectorEntry     Bool{-updatable-} Int{-offset-}

      | RtsApInfoTable       Bool{-updatable-} Int{-arity-}    -- ^ AP thunks
      | RtsApEntry           Bool{-updatable-} Int{-arity-}

      | RtsPrimOp PrimOp
      | RtsApFast     FastString    -- ^ _fast versions of generic apply
      | RtsSlowFastTickyCtr String

      deriving (Eq, Ord)
      -- NOTE: Eq on LitString compares the pointer only, so this isn't
      -- a real equality.

    -- | What type of Cmm label we're dealing with.
    --      Determines the suffix appended to the name when a CLabel.CmmLabel
    --      is pretty printed.
    data CmmLabelInfo
      = CmmInfo                     -- ^ misc rts info tabless,     suffix _info
      | CmmEntry                    -- ^ misc rts entry points,     suffix _entry
      | CmmRetInfo                  -- ^ misc rts ret info tables,  suffix _info
      | CmmRet                      -- ^ misc rts return points,    suffix _ret
      | CmmData                     -- ^ misc rts data bits, eg CHARLIKE_closure
      | CmmCode                     -- ^ misc rts code
      | CmmClosure                  -- ^ closures eg CHARLIKE_closure
      | CmmPrimCall                 -- ^ a prim call to some hand written Cmm code
      deriving (Eq, Ord)

    data DynamicLinkerLabelInfo
      = CodeStub                    -- MachO: Lfoo$stub, ELF: foo@plt
      | SymbolPtr                   -- MachO: Lfoo$non_lazy_ptr, Windows: __imp_foo
      | GotSymbolPtr                -- ELF: foo@got
      | GotSymbolOffset             -- ELF: foo@gotoff

      deriving (Eq, Ord)

    -- -----------------------------------------------------------------------------
    -- Constructing CLabels
    -- -----------------------------------------------------------------------------

    -- Constructing IdLabels
    -- These are always local:
    mkSlowEntryLabel :: Name -> CafInfo -> CLabel
    mkSlowEntryLabel        name c         = IdLabel name  c Slow

    mkTopSRTLabel     :: Unique -> CLabel
    mkTopSRTLabel u = SRTLabel u

    mkSRTLabel        :: Name -> CafInfo -> CLabel
    mkRednCountsLabel :: Name -> CLabel
    mkSRTLabel              name c  = IdLabel name  c SRT
    mkRednCountsLabel       name    =
      IdLabel name NoCafRefs RednCounts  -- Note [ticky for LNE]

    -- These have local & (possibly) external variants:
    mkLocalClosureLabel      :: Name -> CafInfo -> CLabel
    mkLocalInfoTableLabel    :: Name -> CafInfo -> CLabel
    mkLocalEntryLabel        :: Name -> CafInfo -> CLabel
    mkLocalClosureTableLabel :: Name -> CafInfo -> CLabel
    mkLocalClosureLabel     name c  = IdLabel name  c Closure
    mkLocalInfoTableLabel   name c  = IdLabel name  c LocalInfoTable
    mkLocalEntryLabel       name c  = IdLabel name  c LocalEntry
    mkLocalClosureTableLabel name c = IdLabel name  c ClosureTable

    mkClosureLabel              :: Name -> CafInfo -> CLabel
    mkInfoTableLabel            :: Name -> CafInfo -> CLabel
    mkEntryLabel                :: Name -> CafInfo -> CLabel
    mkClosureTableLabel         :: Name -> CafInfo -> CLabel
    mkLocalConInfoTableLabel    :: CafInfo -> Name -> CLabel
    mkLocalConEntryLabel        :: CafInfo -> Name -> CLabel
    mkConInfoTableLabel         :: Name -> CafInfo -> CLabel
    mkBytesLabel                :: Name -> CLabel
    mkClosureLabel name         c     = IdLabel name c Closure
    mkInfoTableLabel name       c     = IdLabel name c InfoTable
    mkEntryLabel name           c     = IdLabel name c Entry
    mkClosureTableLabel name    c     = IdLabel name c ClosureTable
    mkLocalConInfoTableLabel    c con = IdLabel con c ConInfoTable
    mkLocalConEntryLabel        c con = IdLabel con c ConEntry
    mkConInfoTableLabel name    c     = IdLabel name c ConInfoTable
    mkBytesLabel name                 = IdLabel name NoCafRefs Bytes

    mkConEntryLabel       :: Name -> CafInfo -> CLabel
    mkConEntryLabel name        c     = IdLabel name c ConEntry

    -- Constructing Cmm Labels
    mkDirty_MUT_VAR_Label, mkSplitMarkerLabel, mkUpdInfoLabel,
        mkBHUpdInfoLabel, mkIndStaticInfoLabel, mkMainCapabilityLabel,
        mkMAP_FROZEN_infoLabel, mkMAP_FROZEN0_infoLabel, mkMAP_DIRTY_infoLabel,
        mkEMPTY_MVAR_infoLabel, mkTopTickyCtrLabel,
        mkCAFBlackHoleInfoTableLabel, mkCAFBlackHoleEntryLabel,
        mkArrWords_infoLabel, mkSMAP_FROZEN_infoLabel, mkSMAP_FROZEN0_infoLabel,
        mkSMAP_DIRTY_infoLabel :: CLabel
    mkDirty_MUT_VAR_Label           = mkForeignLabel (fsLit "dirty_MUT_VAR") Nothing ForeignLabelInExternalPackage IsFunction
    mkSplitMarkerLabel              = CmmLabel rtsUnitId (fsLit "__stg_split_marker")    CmmCode
    mkUpdInfoLabel                  = CmmLabel rtsUnitId (fsLit "stg_upd_frame")         CmmInfo
    mkBHUpdInfoLabel                = CmmLabel rtsUnitId (fsLit "stg_bh_upd_frame" )     CmmInfo
    mkIndStaticInfoLabel            = CmmLabel rtsUnitId (fsLit "stg_IND_STATIC")        CmmInfo
    mkMainCapabilityLabel           = CmmLabel rtsUnitId (fsLit "MainCapability")        CmmData
    mkMAP_FROZEN_infoLabel          = CmmLabel rtsUnitId (fsLit "stg_MUT_ARR_PTRS_FROZEN") CmmInfo
    mkMAP_FROZEN0_infoLabel         = CmmLabel rtsUnitId (fsLit "stg_MUT_ARR_PTRS_FROZEN0") CmmInfo
    mkMAP_DIRTY_infoLabel           = CmmLabel rtsUnitId (fsLit "stg_MUT_ARR_PTRS_DIRTY") CmmInfo
    mkEMPTY_MVAR_infoLabel          = CmmLabel rtsUnitId (fsLit "stg_EMPTY_MVAR")        CmmInfo
    mkTopTickyCtrLabel              = CmmLabel rtsUnitId (fsLit "top_ct")                CmmData
    mkCAFBlackHoleInfoTableLabel    = CmmLabel rtsUnitId (fsLit "stg_CAF_BLACKHOLE")     CmmInfo
    mkCAFBlackHoleEntryLabel        = CmmLabel rtsUnitId (fsLit "stg_CAF_BLACKHOLE")     CmmEntry
    mkArrWords_infoLabel            = CmmLabel rtsUnitId (fsLit "stg_ARR_WORDS")         CmmInfo
    mkSMAP_FROZEN_infoLabel         = CmmLabel rtsUnitId (fsLit "stg_SMALL_MUT_ARR_PTRS_FROZEN") CmmInfo
    mkSMAP_FROZEN0_infoLabel        = CmmLabel rtsUnitId (fsLit "stg_SMALL_MUT_ARR_PTRS_FROZEN0") CmmInfo
    mkSMAP_DIRTY_infoLabel          = CmmLabel rtsUnitId (fsLit "stg_SMALL_MUT_ARR_PTRS_DIRTY") CmmInfo

    -----
    mkCmmInfoLabel,   mkCmmEntryLabel, mkCmmRetInfoLabel, mkCmmRetLabel,
      mkCmmCodeLabel, mkCmmDataLabel,  mkCmmClosureLabel
            :: UnitId -> FastString -> CLabel

    mkCmmInfoLabel      pkg str     = CmmLabel pkg str CmmInfo
    mkCmmEntryLabel     pkg str     = CmmLabel pkg str CmmEntry
    mkCmmRetInfoLabel   pkg str     = CmmLabel pkg str CmmRetInfo
    mkCmmRetLabel       pkg str     = CmmLabel pkg str CmmRet
    mkCmmCodeLabel      pkg str     = CmmLabel pkg str CmmCode
    mkCmmDataLabel      pkg str     = CmmLabel pkg str CmmData
    mkCmmClosureLabel   pkg str     = CmmLabel pkg str CmmClosure

    -- Constructing RtsLabels
    mkRtsPrimOpLabel :: PrimOp -> CLabel
    mkRtsPrimOpLabel primop         = RtsLabel (RtsPrimOp primop)

    mkSelectorInfoLabel  :: Bool -> Int -> CLabel
    mkSelectorEntryLabel :: Bool -> Int -> CLabel
    mkSelectorInfoLabel  upd off    = RtsLabel (RtsSelectorInfoTable upd off)
    mkSelectorEntryLabel upd off    = RtsLabel (RtsSelectorEntry     upd off)

    mkApInfoTableLabel :: Bool -> Int -> CLabel
    mkApEntryLabel     :: Bool -> Int -> CLabel
    mkApInfoTableLabel   upd off    = RtsLabel (RtsApInfoTable       upd off)
    mkApEntryLabel       upd off    = RtsLabel (RtsApEntry           upd off)

    -- A call to some primitive hand written Cmm code
    mkPrimCallLabel :: PrimCall -> CLabel
    mkPrimCallLabel (PrimCall str pkg)
            = CmmLabel pkg str CmmPrimCall

    -- Constructing ForeignLabels

    -- | Make a foreign label
    mkForeignLabel
            :: FastString           -- name
            -> Maybe Int            -- size prefix
            -> ForeignLabelSource   -- what package it's in
            -> FunctionOrData
            -> CLabel

    mkForeignLabel str mb_sz src fod
        = ForeignLabel str mb_sz src  fod

    -- | Update the label size field in a ForeignLabel
    addLabelSize :: CLabel -> Int -> CLabel
    addLabelSize (ForeignLabel str _ src  fod) sz
        = ForeignLabel str (Just sz) src fod
    addLabelSize label _
        = label

    -- | Whether label is a top-level string literal
    isBytesLabel :: CLabel -> Bool
    isBytesLabel (IdLabel _ _ Bytes) = True
    isBytesLabel _lbl = False

    -- | Whether label is a non-haskell label (defined in C code)
    isForeignLabel :: CLabel -> Bool
    isForeignLabel (ForeignLabel _ _ _ _) = True
    isForeignLabel _lbl = False

    -- | Get the label size field from a ForeignLabel
    foreignLabelStdcallInfo :: CLabel -> Maybe Int
    foreignLabelStdcallInfo (ForeignLabel _ info _ _) = info
    foreignLabelStdcallInfo _lbl = Nothing

    -- Constructing Large*Labels
    mkLargeSRTLabel :: Unique -> CLabel
    mkBitmapLabel   :: Unique -> CLabel
    mkLargeSRTLabel uniq            = LargeSRTLabel uniq
    mkBitmapLabel   uniq            = LargeBitmapLabel uniq

    -- Constructin CaseLabels
    mkReturnPtLabel   :: Unique -> CLabel
    mkReturnInfoLabel :: Unique -> CLabel
    mkAltLabel        :: Unique -> ConTag -> CLabel
    mkDefaultLabel    :: Unique -> CLabel
    mkReturnPtLabel uniq            = CaseLabel uniq CaseReturnPt
    mkReturnInfoLabel uniq          = CaseLabel uniq CaseReturnInfo
    mkAltLabel      uniq tag        = CaseLabel uniq (CaseAlt tag)
    mkDefaultLabel  uniq            = CaseLabel uniq CaseDefault

    -- Constructing Cost Center Labels
    mkCCLabel  :: CostCentre      -> CLabel
    mkCCSLabel :: CostCentreStack -> CLabel
    mkCCLabel           cc          = CC_Label cc
    mkCCSLabel          ccs         = CCS_Label ccs

    mkRtsApFastLabel :: FastString -> CLabel
    mkRtsApFastLabel str = RtsLabel (RtsApFast str)

    mkRtsSlowFastTickyCtrLabel :: String -> CLabel
    mkRtsSlowFastTickyCtrLabel pat = RtsLabel (RtsSlowFastTickyCtr pat)

    -- Constructing Code Coverage Labels
    mkHpcTicksLabel :: Module -> CLabel
    mkHpcTicksLabel                = HpcTicksLabel

    -- Constructing labels used for dynamic linking
    mkDynamicLinkerLabel :: DynamicLinkerLabelInfo -> CLabel -> CLabel
    mkDynamicLinkerLabel            = DynamicLinkerLabel

    dynamicLinkerLabelInfo :: CLabel -> Maybe (DynamicLinkerLabelInfo, CLabel)
    dynamicLinkerLabelInfo (DynamicLinkerLabel info lbl) = Just (info, lbl)
    dynamicLinkerLabelInfo _        = Nothing

    mkPicBaseLabel :: CLabel
    mkPicBaseLabel                  = PicBaseLabel

    -- Constructing miscellaneous other labels
    mkDeadStripPreventer :: CLabel -> CLabel
    mkDeadStripPreventer lbl        = DeadStripPreventer lbl

    mkStringLitLabel :: Unique -> CLabel
    mkStringLitLabel                = StringLitLabel

    mkAsmTempLabel :: Uniquable a => a -> CLabel
    mkAsmTempLabel a                = AsmTempLabel (getUnique a)

    mkAsmTempDerivedLabel :: CLabel -> FastString -> CLabel
    mkAsmTempDerivedLabel = AsmTempDerivedLabel

    mkAsmTempEndLabel :: CLabel -> CLabel
    mkAsmTempEndLabel l = mkAsmTempDerivedLabel l (fsLit "_end")
    mkPlainModuleInitLabel :: Module -> CLabel
    mkPlainModuleInitLabel mod      = PlainModuleInitLabel mod

    -- | Construct a label for a DWARF Debug Information Entity (DIE)
    -- describing another symbol.
    mkAsmTempDieLabel :: CLabel -> CLabel
    mkAsmTempDieLabel l = mkAsmTempDerivedLabel l (fsLit "_die")

    -- -----------------------------------------------------------------------------
    -- Convert between different kinds of label

    toClosureLbl :: CLabel -> CLabel
    toClosureLbl (IdLabel n c _) = IdLabel n c Closure
    toClosureLbl (CmmLabel m str _) = CmmLabel m str CmmClosure
    toClosureLbl l = pprPanic "toClosureLbl" (ppr l)

    toSlowEntryLbl :: CLabel -> CLabel
    toSlowEntryLbl (IdLabel n c _) = IdLabel n c Slow
    toSlowEntryLbl l = pprPanic "toSlowEntryLbl" (ppr l)

    toEntryLbl :: CLabel -> CLabel
    toEntryLbl (IdLabel n c LocalInfoTable)  = IdLabel n c LocalEntry
    toEntryLbl (IdLabel n c ConInfoTable)    = IdLabel n c ConEntry
    toEntryLbl (IdLabel n c _)               = IdLabel n c Entry
    toEntryLbl (CaseLabel n CaseReturnInfo)  = CaseLabel n CaseReturnPt
    toEntryLbl (CmmLabel m str CmmInfo)      = CmmLabel m str CmmEntry
    toEntryLbl (CmmLabel m str CmmRetInfo)   = CmmLabel m str CmmRet
    toEntryLbl l = pprPanic "toEntryLbl" (ppr l)

    toInfoLbl :: CLabel -> CLabel
    toInfoLbl (IdLabel n c Entry)          = IdLabel n c InfoTable
    toInfoLbl (IdLabel n c LocalEntry)     = IdLabel n c LocalInfoTable
    toInfoLbl (IdLabel n c ConEntry)       = IdLabel n c ConInfoTable
    toInfoLbl (IdLabel n c _)              = IdLabel n c InfoTable
    toInfoLbl (CaseLabel n CaseReturnPt)   = CaseLabel n CaseReturnInfo
    toInfoLbl (CmmLabel m str CmmEntry)    = CmmLabel m str CmmInfo
    toInfoLbl (CmmLabel m str CmmRet)      = CmmLabel m str CmmRetInfo
    toInfoLbl l = pprPanic "CLabel.toInfoLbl" (ppr l)

    toRednCountsLbl :: CLabel -> Maybe CLabel
    toRednCountsLbl = fmap mkRednCountsLabel . hasHaskellName

    hasHaskellName :: CLabel -> Maybe Name
    hasHaskellName (IdLabel n _ _) = Just n
    hasHaskellName _               = Nothing

    -- -----------------------------------------------------------------------------
    -- Does a CLabel's referent itself refer to a CAF?
    hasCAF :: CLabel -> Bool
    hasCAF (IdLabel _ _ RednCounts) = False -- Note [ticky for LNE]
    hasCAF (IdLabel _ MayHaveCafRefs _) = True
    hasCAF _                            = False

    -- Note [ticky for LNE]
    -- ~~~~~~~~~~~~~~~~~~~~~

    -- Until 14 Feb 2013, every ticky counter was associated with a
    -- closure. Thus, ticky labels used IdLabel. It is odd that
    -- CmmBuildInfoTables.cafTransfers would consider such a ticky label
    -- reason to add the name to the CAFEnv (and thus eventually the SRT),
    -- but it was harmless because the ticky was only used if the closure
    -- was also.
    --
    -- Since we now have ticky counters for LNEs, it is no longer the case
    -- that every ticky counter has an actual closure. So I changed the
    -- generation of ticky counters' CLabels to not result in their
    -- associated id ending up in the SRT.
    --
    -- NB IdLabel is still appropriate for ticky ids (as opposed to
    -- CmmLabel) because the LNE's counter is still related to an .hs Id,
    -- that Id just isn't for a proper closure.

    -- -----------------------------------------------------------------------------
    -- Does a CLabel need declaring before use or not?
    --
    -- See wiki:Commentary/Compiler/Backends/PprC#Prototypes

    needsCDecl :: CLabel -> Bool
      -- False <=> it's pre-declared; don't bother
      -- don't bother declaring Bitmap labels, we always make sure
      -- they are defined before use.
    needsCDecl (SRTLabel _)                 = True
    needsCDecl (LargeSRTLabel _)            = False
    needsCDecl (LargeBitmapLabel _)         = False
    needsCDecl (IdLabel _ _ _)              = True
    needsCDecl (CaseLabel _ _)              = True
    needsCDecl (PlainModuleInitLabel _)     = True

    needsCDecl (StringLitLabel _)           = False
    needsCDecl (AsmTempLabel _)             = False
    needsCDecl (AsmTempDerivedLabel _ _)    = False
    needsCDecl (RtsLabel _)                 = False

    needsCDecl (CmmLabel pkgId _ _)
            -- Prototypes for labels defined in the runtime system are imported
            --      into HC files via includes/Stg.h.
            | pkgId == rtsUnitId         = False

            -- For other labels we inline one into the HC file directly.
            | otherwise                     = True

    needsCDecl l@(ForeignLabel{})           = not (isMathFun l)
    needsCDecl (CC_Label _)                 = True
    needsCDecl (CCS_Label _)                = True
    needsCDecl (HpcTicksLabel _)            = True
    needsCDecl (DynamicLinkerLabel {})      = panic "needsCDecl DynamicLinkerLabel"
    needsCDecl PicBaseLabel                 = panic "needsCDecl PicBaseLabel"
    needsCDecl (DeadStripPreventer {})      = panic "needsCDecl DeadStripPreventer"

    -- | If a label is a local temporary used for native code generation
    --      then return just its unique, otherwise nothing.
    maybeAsmTemp :: CLabel -> Maybe Unique
    maybeAsmTemp (AsmTempLabel uq)          = Just uq
    maybeAsmTemp _                          = Nothing

    -- | Check whether a label corresponds to a C function that has
    --      a prototype in a system header somehere, or is built-in
    --      to the C compiler. For these labels we avoid generating our
    --      own C prototypes.
    isMathFun :: CLabel -> Bool
    isMathFun (ForeignLabel fs _ _ _)       = fs `elementOfUniqSet` math_funs
    isMathFun _ = False

    math_funs :: UniqSet FastString
    math_funs = mkUniqSet [
            -- _ISOC99_SOURCE
            (fsLit "acos"),         (fsLit "acosf"),        (fsLit "acosh"),
            (fsLit "acoshf"),       (fsLit "acoshl"),       (fsLit "acosl"),
            (fsLit "asin"),         (fsLit "asinf"),        (fsLit "asinl"),
            (fsLit "asinh"),        (fsLit "asinhf"),       (fsLit "asinhl"),
            (fsLit "atan"),         (fsLit "atanf"),        (fsLit "atanl"),
            (fsLit "atan2"),        (fsLit "atan2f"),       (fsLit "atan2l"),
            (fsLit "atanh"),        (fsLit "atanhf"),       (fsLit "atanhl"),
            (fsLit "cbrt"),         (fsLit "cbrtf"),        (fsLit "cbrtl"),
            (fsLit "ceil"),         (fsLit "ceilf"),        (fsLit "ceill"),
            (fsLit "copysign"),     (fsLit "copysignf"),    (fsLit "copysignl"),
            (fsLit "cos"),          (fsLit "cosf"),         (fsLit "cosl"),
            (fsLit "cosh"),         (fsLit "coshf"),        (fsLit "coshl"),
            (fsLit "erf"),          (fsLit "erff"),         (fsLit "erfl"),
            (fsLit "erfc"),         (fsLit "erfcf"),        (fsLit "erfcl"),
            (fsLit "exp"),          (fsLit "expf"),         (fsLit "expl"),
            (fsLit "exp2"),         (fsLit "exp2f"),        (fsLit "exp2l"),
            (fsLit "expm1"),        (fsLit "expm1f"),       (fsLit "expm1l"),
            (fsLit "fabs"),         (fsLit "fabsf"),        (fsLit "fabsl"),
            (fsLit "fdim"),         (fsLit "fdimf"),        (fsLit "fdiml"),
            (fsLit "floor"),        (fsLit "floorf"),       (fsLit "floorl"),
            (fsLit "fma"),          (fsLit "fmaf"),         (fsLit "fmal"),
            (fsLit "fmax"),         (fsLit "fmaxf"),        (fsLit "fmaxl"),
            (fsLit "fmin"),         (fsLit "fminf"),        (fsLit "fminl"),
            (fsLit "fmod"),         (fsLit "fmodf"),        (fsLit "fmodl"),
            (fsLit "frexp"),        (fsLit "frexpf"),       (fsLit "frexpl"),
            (fsLit "hypot"),        (fsLit "hypotf"),       (fsLit "hypotl"),
            (fsLit "ilogb"),        (fsLit "ilogbf"),       (fsLit "ilogbl"),
            (fsLit "ldexp"),        (fsLit "ldexpf"),       (fsLit "ldexpl"),
            (fsLit "lgamma"),       (fsLit "lgammaf"),      (fsLit "lgammal"),
            (fsLit "llrint"),       (fsLit "llrintf"),      (fsLit "llrintl"),
            (fsLit "llround"),      (fsLit "llroundf"),     (fsLit "llroundl"),
            (fsLit "log"),          (fsLit "logf"),         (fsLit "logl"),
            (fsLit "log10l"),       (fsLit "log10"),        (fsLit "log10f"),
            (fsLit "log1pl"),       (fsLit "log1p"),        (fsLit "log1pf"),
            (fsLit "log2"),         (fsLit "log2f"),        (fsLit "log2l"),
            (fsLit "logb"),         (fsLit "logbf"),        (fsLit "logbl"),
            (fsLit "lrint"),        (fsLit "lrintf"),       (fsLit "lrintl"),
            (fsLit "lround"),       (fsLit "lroundf"),      (fsLit "lroundl"),
            (fsLit "modf"),         (fsLit "modff"),        (fsLit "modfl"),
            (fsLit "nan"),          (fsLit "nanf"),         (fsLit "nanl"),
            (fsLit "nearbyint"),    (fsLit "nearbyintf"),   (fsLit "nearbyintl"),
            (fsLit "nextafter"),    (fsLit "nextafterf"),   (fsLit "nextafterl"),
            (fsLit "nexttoward"),   (fsLit "nexttowardf"),  (fsLit "nexttowardl"),
            (fsLit "pow"),          (fsLit "powf"),         (fsLit "powl"),
            (fsLit "remainder"),    (fsLit "remainderf"),   (fsLit "remainderl"),
            (fsLit "remquo"),       (fsLit "remquof"),      (fsLit "remquol"),
            (fsLit "rint"),         (fsLit "rintf"),        (fsLit "rintl"),
            (fsLit "round"),        (fsLit "roundf"),       (fsLit "roundl"),
            (fsLit "scalbln"),      (fsLit "scalblnf"),     (fsLit "scalblnl"),
            (fsLit "scalbn"),       (fsLit "scalbnf"),      (fsLit "scalbnl"),
            (fsLit "sin"),          (fsLit "sinf"),         (fsLit "sinl"),
            (fsLit "sinh"),         (fsLit "sinhf"),        (fsLit "sinhl"),
            (fsLit "sqrt"),         (fsLit "sqrtf"),        (fsLit "sqrtl"),
            (fsLit "tan"),          (fsLit "tanf"),         (fsLit "tanl"),
            (fsLit "tanh"),         (fsLit "tanhf"),        (fsLit "tanhl"),
            (fsLit "tgamma"),       (fsLit "tgammaf"),      (fsLit "tgammal"),
            (fsLit "trunc"),        (fsLit "truncf"),       (fsLit "truncl"),
            -- ISO C 99 also defines these function-like macros in math.h:
            -- fpclassify, isfinite, isinf, isnormal, signbit, isgreater,
            -- isgreaterequal, isless, islessequal, islessgreater, isunordered

            -- additional symbols from _BSD_SOURCE
            (fsLit "drem"),         (fsLit "dremf"),        (fsLit "dreml"),
            (fsLit "finite"),       (fsLit "finitef"),      (fsLit "finitel"),
            (fsLit "gamma"),        (fsLit "gammaf"),       (fsLit "gammal"),
            (fsLit "isinf"),        (fsLit "isinff"),       (fsLit "isinfl"),
            (fsLit "isnan"),        (fsLit "isnanf"),       (fsLit "isnanl"),
            (fsLit "j0"),           (fsLit "j0f"),          (fsLit "j0l"),
            (fsLit "j1"),           (fsLit "j1f"),          (fsLit "j1l"),
            (fsLit "jn"),           (fsLit "jnf"),          (fsLit "jnl"),
            (fsLit "lgamma_r"),     (fsLit "lgammaf_r"),    (fsLit "lgammal_r"),
            (fsLit "scalb"),        (fsLit "scalbf"),       (fsLit "scalbl"),
            (fsLit "significand"),  (fsLit "significandf"), (fsLit "significandl"),
            (fsLit "y0"),           (fsLit "y0f"),          (fsLit "y0l"),
            (fsLit "y1"),           (fsLit "y1f"),          (fsLit "y1l"),
            (fsLit "yn"),           (fsLit "ynf"),          (fsLit "ynl"),

            -- These functions are described in IEEE Std 754-2008 -
            -- Standard for Floating-Point Arithmetic and ISO/IEC TS 18661
            (fsLit "nextup"),       (fsLit "nextupf"),      (fsLit "nextupl"),
            (fsLit "nextdown"),     (fsLit "nextdownf"),    (fsLit "nextdownl")
        ]

    -- -----------------------------------------------------------------------------
    -- | Is a CLabel visible outside this object file or not?
    --      From the point of view of the code generator, a name is
    --      externally visible if it has to be declared as exported
    --      in the .o file's symbol table; that is, made non-static.
    externallyVisibleCLabel :: CLabel -> Bool -- not C "static"
    externallyVisibleCLabel (CaseLabel _ _)         = False
    externallyVisibleCLabel (StringLitLabel _)      = False
    externallyVisibleCLabel (AsmTempLabel _)        = False
    externallyVisibleCLabel (AsmTempDerivedLabel _ _)= False
    externallyVisibleCLabel (PlainModuleInitLabel _)= True
    externallyVisibleCLabel (RtsLabel _)            = True
    externallyVisibleCLabel (CmmLabel _ _ _)        = True
    externallyVisibleCLabel (ForeignLabel{})        = True
    externallyVisibleCLabel (IdLabel name _ info)   = isExternalName name && externallyVisibleIdLabel info
    externallyVisibleCLabel (CC_Label _)            = True
    externallyVisibleCLabel (CCS_Label _)           = True
    externallyVisibleCLabel (DynamicLinkerLabel _ _)  = False
    externallyVisibleCLabel (HpcTicksLabel _)       = True
    externallyVisibleCLabel (LargeBitmapLabel _)    = False
    externallyVisibleCLabel (SRTLabel _)            = False
    externallyVisibleCLabel (LargeSRTLabel _)       = False
    externallyVisibleCLabel (PicBaseLabel {}) = panic "externallyVisibleCLabel PicBaseLabel"
    externallyVisibleCLabel (DeadStripPreventer {}) = panic "externallyVisibleCLabel DeadStripPreventer"

    externallyVisibleIdLabel :: IdLabelInfo -> Bool
    externallyVisibleIdLabel SRT             = False
    externallyVisibleIdLabel LocalInfoTable  = False
    externallyVisibleIdLabel LocalEntry      = False
    externallyVisibleIdLabel _               = True

    -- -----------------------------------------------------------------------------
    -- Finding the "type" of a CLabel

    -- For generating correct types in label declarations:

    data CLabelType
      = CodeLabel   -- Address of some executable instructions
      | DataLabel   -- Address of data, not a GC ptr
      | GcPtrLabel  -- Address of a (presumably static) GC object

    isCFunctionLabel :: CLabel -> Bool
    isCFunctionLabel lbl = case labelType lbl of
                            CodeLabel -> True
                            _other    -> False

    isGcPtrLabel :: CLabel -> Bool
    isGcPtrLabel lbl = case labelType lbl of
                            GcPtrLabel -> True
                            _other     -> False

    -- | Work out the general type of data at the address of this label
    --    whether it be code, data, or static GC object.
    labelType :: CLabel -> CLabelType
    labelType (CmmLabel _ _ CmmData)                = DataLabel
    labelType (CmmLabel _ _ CmmClosure)             = GcPtrLabel
    labelType (CmmLabel _ _ CmmCode)                = CodeLabel
    labelType (CmmLabel _ _ CmmInfo)                = DataLabel
    labelType (CmmLabel _ _ CmmEntry)               = CodeLabel
    labelType (CmmLabel _ _ CmmPrimCall)            = CodeLabel
    labelType (CmmLabel _ _ CmmRetInfo)             = DataLabel
    labelType (CmmLabel _ _ CmmRet)                 = CodeLabel
    labelType (RtsLabel (RtsSelectorInfoTable _ _)) = DataLabel
    labelType (RtsLabel (RtsApInfoTable _ _))       = DataLabel
    labelType (RtsLabel (RtsApFast _))              = CodeLabel
    labelType (CaseLabel _ CaseReturnInfo)          = DataLabel
    labelType (CaseLabel _ _)                       = CodeLabel
    labelType (PlainModuleInitLabel _)              = CodeLabel
    labelType (SRTLabel _)                          = DataLabel
    labelType (LargeSRTLabel _)                     = DataLabel
    labelType (LargeBitmapLabel _)                  = DataLabel
    labelType (ForeignLabel _ _ _ IsFunction)       = CodeLabel
    labelType (IdLabel _ _ info)                    = idInfoLabelType info
    labelType _                                     = DataLabel

    idInfoLabelType :: IdLabelInfo -> CLabelType
    idInfoLabelType info =
      case info of
        InfoTable     -> DataLabel
        LocalInfoTable -> DataLabel
        Closure       -> GcPtrLabel
        ConInfoTable  -> DataLabel
        ClosureTable  -> DataLabel
        RednCounts    -> DataLabel
        Bytes         -> DataLabel
        _             -> CodeLabel

    -- -----------------------------------------------------------------------------
    -- Does a CLabel need dynamic linkage?

    -- When referring to data in code, we need to know whether
    -- that data resides in a DLL or not. [Win32 only.]
    -- @labelDynamic@ returns @True@ if the label is located
    -- in a DLL, be it a data reference or not.

    labelDynamic :: DynFlags -> Module -> CLabel -> Bool
    labelDynamic dflags this_mod lbl =
      case lbl of
       -- is the RTS in a DLL or not?
       RtsLabel _           -> (WayDyn `elem` ways dflags) && (this_pkg /= rtsUnitId)

       IdLabel n _ _        -> isDllName dflags this_mod n

       -- When compiling in the "dyn" way, each package is to be linked into
       -- its own shared library.
       CmmLabel pkg _ _
        | os == OSMinGW32 ->
           (WayDyn `elem` ways dflags) && (this_pkg /= pkg)
        | otherwise ->
           True

       ForeignLabel _ _ source _  ->
           if os == OSMinGW32
           then case source of
                -- Foreign label is in some un-named foreign package (or DLL).
                ForeignLabelInExternalPackage -> True

                -- Foreign label is linked into the same package as the
                -- source file currently being compiled.
                ForeignLabelInThisPackage -> False

                -- Foreign label is in some named package.
                -- When compiling in the "dyn" way, each package is to be
                -- linked into its own DLL.
                ForeignLabelInPackage pkgId ->
                    (WayDyn `elem` ways dflags) && (this_pkg /= pkgId)

           else -- On Mac OS X and on ELF platforms, false positives are OK,
                -- so we claim that all foreign imports come from dynamic
                -- libraries
                True

       PlainModuleInitLabel m -> (WayDyn `elem` ways dflags) && this_pkg /= (moduleUnitId m)

       HpcTicksLabel m        -> (WayDyn `elem` ways dflags) && this_mod /= m

       -- Note that DynamicLinkerLabels do NOT require dynamic linking themselves.
       _                 -> False
      where
        os = platformOS (targetPlatform dflags)
        this_pkg = moduleUnitId this_mod

    -----------------------------------------------------------------------------
    -- Printing out CLabels.

    {-
    Convention:

          <name>_<type>

    where <name> is <Module>_<name> for external names and <unique> for
    internal names. <type> is one of the following:

             info                   Info table
             srt                    Static reference table
             srtd                   Static reference table descriptor
             entry                  Entry code (function, closure)
             slow                   Slow entry code (if any)
             ret                    Direct return address
             vtbl                   Vector table
             <n>_alt                Case alternative (tag n)
             dflt                   Default case alternative
             btm                    Large bitmap vector
             closure                Static closure
             con_entry              Dynamic Constructor entry code
             con_info               Dynamic Constructor info table
             static_entry           Static Constructor entry code
             static_info            Static Constructor info table
             sel_info               Selector info table
             sel_entry              Selector entry code
             cc                     Cost centre
             ccs                    Cost centre stack

    Many of these distinctions are only for documentation reasons.  For
    example, _ret is only distinguished from _entry to make it easy to
    tell whether a code fragment is a return point or a closure/function
    entry.

    Note [Closure and info labels]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    For a function 'foo, we have:
       foo_info    : Points to the info table describing foo's closure
                     (and entry code for foo with tables next to code)
       foo_closure : Static (no-free-var) closure only:
                     points to the statically-allocated closure

    For a data constructor (such as Just or Nothing), we have:
        Just_con_info: Info table for the data constructor itself
                       the first word of a heap-allocated Just
        Just_info:     Info table for the *worker function*, an
                       ordinary Haskell function of arity 1 that
                       allocates a (Just x) box:
                          Just = \x -> Just x
        Just_closure:  The closure for this worker

        Nothing_closure: a statically allocated closure for Nothing
        Nothing_static_info: info table for Nothing_closure

    All these must be exported symbol, EXCEPT Just_info.  We don't need to
    export this because in other modules we either have
           * A reference to 'Just'; use Just_closure
           * A saturated call 'Just x'; allocate using Just_con_info
    Not exporting these Just_info labels reduces the number of symbols
    somewhat.

    Note [Bytes label]
    ~~~~~~~~~~~~~~~~~~
    For a top-level string literal 'foo', we have just one symbol 'foo_bytes', which
    points to a static data block containing the content of the literal.
    -}

    instance Outputable CLabel where
      ppr c = sdocWithPlatform $ \platform -> pprCLabel platform c

    pprCLabel :: Platform -> CLabel -> SDoc

    pprCLabel platform (AsmTempLabel u)
     | cGhcWithNativeCodeGen == "YES"
      =  getPprStyle $ \ sty ->
         if asmStyle sty then
            ptext (asmTempLabelPrefix platform) <> pprUniqueAlways u
         else
            char '_' <> pprUniqueAlways u

    pprCLabel platform (AsmTempDerivedLabel l suf)
     | cGhcWithNativeCodeGen == "YES"
       = ptext (asmTempLabelPrefix platform)
         <> case l of AsmTempLabel u -> pprUniqueAlways u
                      _other         -> pprCLabel platform l
         <> ftext suf

    pprCLabel platform (DynamicLinkerLabel info lbl)
     | cGhcWithNativeCodeGen == "YES"
       = pprDynamicLinkerAsmLabel platform info lbl

    pprCLabel _ PicBaseLabel
     | cGhcWithNativeCodeGen == "YES"
       = text "1b"

    pprCLabel platform (DeadStripPreventer lbl)
     | cGhcWithNativeCodeGen == "YES"
       = pprCLabel platform lbl <> text "_dsp"

    pprCLabel _ (StringLitLabel u)
     | cGhcWithNativeCodeGen == "YES"
      = pprUniqueAlways u <> ptext (sLit "_str")

    pprCLabel platform lbl
       = getPprStyle $ \ sty ->
         if cGhcWithNativeCodeGen == "YES" && asmStyle sty
         then maybe_underscore (pprAsmCLbl platform lbl)
         else pprCLbl lbl

    maybe_underscore :: SDoc -> SDoc
    maybe_underscore doc
      | underscorePrefix = pp_cSEP <> doc
      | otherwise        = doc

    pprAsmCLbl :: Platform -> CLabel -> SDoc
    pprAsmCLbl platform (ForeignLabel fs (Just sz) _ _)
     | platformOS platform == OSMinGW32
        -- In asm mode, we need to put the suffix on a stdcall ForeignLabel.
        -- (The C compiler does this itself).
        = ftext fs <> char '@' <> int sz
    pprAsmCLbl _ lbl
       = pprCLbl lbl

    pprCLbl :: CLabel -> SDoc
    pprCLbl (StringLitLabel u)
      = pprUniqueAlways u <> text "_str"

    pprCLbl (CaseLabel u CaseReturnPt)
      = hcat [pprUniqueAlways u, text "_ret"]
    pprCLbl (CaseLabel u CaseReturnInfo)
      = hcat [pprUniqueAlways u, text "_info"]
    pprCLbl (CaseLabel u (CaseAlt tag))
      = hcat [pprUniqueAlways u, pp_cSEP, int tag, text "_alt"]
    pprCLbl (CaseLabel u CaseDefault)
      = hcat [pprUniqueAlways u, text "_dflt"]

    pprCLbl (SRTLabel u)
      = pprUniqueAlways u <> pp_cSEP <> text "srt"

    pprCLbl (LargeSRTLabel u)  = pprUniqueAlways u <> pp_cSEP <> text "srtd"
    pprCLbl (LargeBitmapLabel u)  = text "b" <> pprUniqueAlways u <> pp_cSEP <> text "btm"
    -- Some bitsmaps for tuple constructors have a numeric tag (e.g. '7')
    -- until that gets resolved we'll just force them to start
    -- with a letter so the label will be legal assmbly code.

    pprCLbl (CmmLabel _ str CmmCode)        = ftext str
    pprCLbl (CmmLabel _ str CmmData)        = ftext str
    pprCLbl (CmmLabel _ str CmmPrimCall)    = ftext str

    pprCLbl (RtsLabel (RtsApFast str))   = ftext str <> text "_fast"

    pprCLbl (RtsLabel (RtsSelectorInfoTable upd_reqd offset))
      = sdocWithDynFlags $ \dflags ->
        ASSERT(offset >= 0 && offset <= mAX_SPEC_SELECTEE_SIZE dflags)
        hcat [text "stg_sel_", text (show offset),
              ptext (if upd_reqd
                     then (sLit "_upd_info")
                     else (sLit "_noupd_info"))
            ]

    pprCLbl (RtsLabel (RtsSelectorEntry upd_reqd offset))
      = sdocWithDynFlags $ \dflags ->
        ASSERT(offset >= 0 && offset <= mAX_SPEC_SELECTEE_SIZE dflags)
        hcat [text "stg_sel_", text (show offset),
                    ptext (if upd_reqd
                            then (sLit "_upd_entry")
                            else (sLit "_noupd_entry"))
            ]

    pprCLbl (RtsLabel (RtsApInfoTable upd_reqd arity))
      = sdocWithDynFlags $ \dflags ->
        ASSERT(arity > 0 && arity <= mAX_SPEC_AP_SIZE dflags)
        hcat [text "stg_ap_", text (show arity),
                    ptext (if upd_reqd
                            then (sLit "_upd_info")
                            else (sLit "_noupd_info"))
            ]

    pprCLbl (RtsLabel (RtsApEntry upd_reqd arity))
      = sdocWithDynFlags $ \dflags ->
        ASSERT(arity > 0 && arity <= mAX_SPEC_AP_SIZE dflags)
        hcat [text "stg_ap_", text (show arity),
                    ptext (if upd_reqd
                            then (sLit "_upd_entry")
                            else (sLit "_noupd_entry"))
            ]

    pprCLbl (CmmLabel _ fs CmmInfo)
      = ftext fs <> text "_info"

    pprCLbl (CmmLabel _ fs CmmEntry)
      = ftext fs <> text "_entry"

    pprCLbl (CmmLabel _ fs CmmRetInfo)
      = ftext fs <> text "_info"

    pprCLbl (CmmLabel _ fs CmmRet)
      = ftext fs <> text "_ret"

    pprCLbl (CmmLabel _ fs CmmClosure)
      = ftext fs <> text "_closure"

    pprCLbl (RtsLabel (RtsPrimOp primop))
      = text "stg_" <> ppr primop

    pprCLbl (RtsLabel (RtsSlowFastTickyCtr pat))
      = text "SLOW_CALL_fast_" <> text pat <> ptext (sLit "_ctr")

    pprCLbl (ForeignLabel str _ _ _)
      = ftext str

    pprCLbl (IdLabel name _cafs flavor) = ppr name <> ppIdFlavor flavor

    pprCLbl (CC_Label cc)           = ppr cc
    pprCLbl (CCS_Label ccs)         = ppr ccs

    pprCLbl (PlainModuleInitLabel mod)
       = text "__stginit_" <> ppr mod

    pprCLbl (HpcTicksLabel mod)
      = text "_hpc_tickboxes_"  <> ppr mod <> ptext (sLit "_hpc")

    pprCLbl (AsmTempLabel {})       = panic "pprCLbl AsmTempLabel"
    pprCLbl (AsmTempDerivedLabel {})= panic "pprCLbl AsmTempDerivedLabel"
    pprCLbl (DynamicLinkerLabel {}) = panic "pprCLbl DynamicLinkerLabel"
    pprCLbl (PicBaseLabel {})       = panic "pprCLbl PicBaseLabel"
    pprCLbl (DeadStripPreventer {}) = panic "pprCLbl DeadStripPreventer"

    ppIdFlavor :: IdLabelInfo -> SDoc
    ppIdFlavor x = pp_cSEP <>
                   (case x of
                           Closure          -> text "closure"
                           SRT              -> text "srt"
                           InfoTable        -> text "info"
                           LocalInfoTable   -> text "info"
                           Entry            -> text "entry"
                           LocalEntry       -> text "entry"
                           Slow             -> text "slow"
                           RednCounts       -> text "ct"
                           ConEntry         -> text "con_entry"
                           ConInfoTable     -> text "con_info"
                           ClosureTable     -> text "closure_tbl"
                           Bytes            -> text "bytes"
                          )

    pp_cSEP :: SDoc
    pp_cSEP = char '_'

    instance Outputable ForeignLabelSource where
     ppr fs
      = case fs of
            ForeignLabelInPackage pkgId     -> parens $ text "package: " <> ppr pkgId
            ForeignLabelInThisPackage       -> parens $ text "this package"
            ForeignLabelInExternalPackage   -> parens $ text "external package"

    -- -----------------------------------------------------------------------------
    -- Machine-dependent knowledge about labels.

    underscorePrefix :: Bool   -- leading underscore on assembler labels?
    underscorePrefix = (cLeadingUnderscore == "YES")

    asmTempLabelPrefix :: Platform -> LitString  -- for formatting labels
    asmTempLabelPrefix platform = case platformOS platform of
        OSDarwin -> sLit "L"
        OSAIX    -> sLit "__L" -- follow IBM XL C's convention
        _        -> sLit ".L"

    pprDynamicLinkerAsmLabel :: Platform -> DynamicLinkerLabelInfo -> CLabel -> SDoc
    pprDynamicLinkerAsmLabel platform dllInfo lbl
     = if platformOS platform == OSDarwin
       then if platformArch platform == ArchX86_64
            then case dllInfo of
                 CodeStub        -> char 'L' <> ppr lbl <> text "$stub"
                 SymbolPtr       -> char 'L' <> ppr lbl <> text "$non_lazy_ptr"
                 GotSymbolPtr    -> ppr lbl <> text "@GOTPCREL"
                 GotSymbolOffset -> ppr lbl
            else case dllInfo of
                 CodeStub  -> char 'L' <> ppr lbl <> text "$stub"
                 SymbolPtr -> char 'L' <> ppr lbl <> text "$non_lazy_ptr"
                 _         -> panic "pprDynamicLinkerAsmLabel"

       else if platformOS platform == OSAIX
            then case dllInfo of
                 SymbolPtr -> text "LC.." <> ppr lbl -- GCC's naming convention
                 _         -> panic "pprDynamicLinkerAsmLabel"

       else if osElfTarget (platformOS platform)
            then if platformArch platform == ArchPPC
                 then case dllInfo of
                           CodeStub  -> -- See Note [.LCTOC1 in PPC PIC code]
                                        ppr lbl <> text "+32768@plt"
                           SymbolPtr -> text ".LC_" <> ppr lbl
                           _         -> panic "pprDynamicLinkerAsmLabel"
                 else if platformArch platform == ArchX86_64
                      then case dllInfo of
                           CodeStub        -> ppr lbl <> text "@plt"
                           GotSymbolPtr    -> ppr lbl <> text "@gotpcrel"
                           GotSymbolOffset -> ppr lbl
                           SymbolPtr       -> text ".LC_" <> ppr lbl
                 else if platformArch platform == ArchPPC_64 ELF_V1
                      || platformArch platform == ArchPPC_64 ELF_V2
                      then case dllInfo of
                           GotSymbolPtr    -> text ".LC_"  <> ppr lbl
                                                   <> text "@toc"
                           GotSymbolOffset -> ppr lbl
                           SymbolPtr       -> text ".LC_" <> ppr lbl
                           _               -> panic "pprDynamicLinkerAsmLabel"
            else case dllInfo of
                 CodeStub        -> ppr lbl <> text "@plt"
                 SymbolPtr       -> text ".LC_" <> ppr lbl
                 GotSymbolPtr    -> ppr lbl <> text "@got"
                 GotSymbolOffset -> ppr lbl <> text "@gotoff"
       else if platformOS platform == OSMinGW32
            then case dllInfo of
                 SymbolPtr -> text "__imp_" <> ppr lbl
                 _         -> panic "pprDynamicLinkerAsmLabel"
       else panic "pprDynamicLinkerAsmLabel"