module ClosureInfo (
	ClosureInfo(..), LambdaFormInfo(..),	-- would be abstract but
	StandardFormInfo(..),			-- mkCmmInfo looks inside
        SMRep,

	ArgDescr(..), Liveness(..), 
	C_SRT(..), needsSRT,

	mkLFThunk, mkLFReEntrant, mkConLFInfo, mkSelectorLFInfo,
	mkApLFInfo, mkLFImported, mkLFArgument, mkLFLetNoEscape,

	mkClosureInfo, mkConInfo, maybeIsLFCon,

	closureSize, closureNonHdrSize,
	closureGoodStuffSize, closurePtrsSize,
	slopSize, 

	infoTableLabelFromCI, entryLabelFromCI,
	closureLabelFromCI,
	isLFThunk, closureUpdReqd,
	closureNeedsUpdSpace, closureIsThunk,
	closureSingleEntry, closureReEntrant, isConstrClosure_maybe,
	closureFunInfo,	isStandardFormThunk, isKnownFun,
        funTag, funTagLFInfo, tagForArity, clHasCafRefs,

	enterIdLabel, enterLocalIdLabel, enterReturnPtLabel,

	nodeMustPointToIt, 
	CallMethod(..), getCallMethod,

	blackHoleOnEntry,

	staticClosureRequired,
	getClosureType,

	isToplevClosure,
	closureValDescr, closureTypeDescr,	-- profiling

	isStaticClosure,
	cafBlackHoleClosureInfo,

	staticClosureNeedsLink,
    ) where

#include "../includes/MachDeps.h"
#include "HsVersions.h"

import StgSyn
import SMRep

import CLabel

import Unique
import StaticFlags
import Var
import Id
import IdInfo
import DataCon
import Name
import Type
import TypeRep
import TcType
import TyCon
import BasicTypes
import FastString
import Outputable
import Constants
import DynFlags

data ClosureInfo
  = ClosureInfo {
	closureName   :: !Name,		  -- The thing bound to this closure
	closureLFInfo :: !LambdaFormInfo, -- NOTE: not an LFCon (see below)
	closureSMRep  :: !SMRep,	  -- representation used by storage mgr
	closureSRT    :: !C_SRT,	  -- What SRT applies to this closure
	closureType   :: !Type,		  -- Type of closure (ToDo: remove)
	closureDescr  :: !String,	  -- closure description (for profiling)
	closureInfLcl :: Bool             -- can the info pointer be a local symbol?
    }

  -- Constructor closures don't have a unique info table label (they use
  -- the constructor's info table), and they don't have an SRT.
  | ConInfo {
	closureCon       :: !DataCon,
	closureSMRep     :: !SMRep
    }

-- C_SRT is what StgSyn.SRT gets translated to... 
-- we add a label for the table, and expect only the 'offset/length' form

data C_SRT = NoC_SRT
	   | C_SRT !CLabel !WordOff !StgHalfWord {-bitmap or escape-}
           deriving (Eq)

needsSRT :: C_SRT -> Bool
needsSRT NoC_SRT       = False
needsSRT (C_SRT _ _ _) = True

instance Outputable C_SRT where
  ppr (NoC_SRT) = ptext (sLit "_no_srt_")
  ppr (C_SRT label off bitmap) = parens (ppr label <> comma <> ppr off <> comma <> text (show bitmap))

data LambdaFormInfo
  = LFReEntrant		-- Reentrant closure (a function)
	TopLevelFlag	-- True if top level
	!Int		-- Arity. Invariant: always > 0
	!Bool		-- True <=> no fvs
	ArgDescr	-- Argument descriptor (should reall be in ClosureInfo)

  | LFCon		-- A saturated constructor application
	DataCon		-- The constructor

  | LFThunk		-- Thunk (zero arity)
	TopLevelFlag
	!Bool		-- True <=> no free vars
	!Bool		-- True <=> updatable (i.e., *not* single-entry)
	StandardFormInfo
	!Bool		-- True <=> *might* be a function type

  | LFUnknown		-- Used for function arguments and imported things.
			--  We know nothing about  this closure.  Treat like
			-- updatable "LFThunk"...
			-- Imported things which we do know something about use
			-- one of the other LF constructors (eg LFReEntrant for
			-- known functions)
	!Bool		-- True <=> *might* be a function type

  | LFLetNoEscape	-- See LetNoEscape module for precise description of
			-- these "lets".
	!Int		-- arity;

  | LFBlackHole		-- Used for the closures allocated to hold the result
			-- of a CAF.  We want the target of the update frame to
			-- be in the heap, so we make a black hole to hold it.


-------------------------
-- An ArgDsecr describes the argument pattern of a function

data ArgDescr
  = ArgSpec		-- Fits one of the standard patterns
	!StgHalfWord	-- RTS type identifier ARG_P, ARG_N, ...

  | ArgGen	 	-- General case
	Liveness	-- Details about the arguments


-------------------------
-- We represent liveness bitmaps as a Bitmap (whose internal
-- representation really is a bitmap).  These are pinned onto case return
-- vectors to indicate the state of the stack for the garbage collector.
-- 
-- In the compiled program, liveness bitmaps that fit inside a single
-- word (StgWord) are stored as a single word, while larger bitmaps are
-- stored as a pointer to an array of words. 

data Liveness
  = SmallLiveness	-- Liveness info that fits in one word
	StgWord		-- Here's the bitmap

  | BigLiveness		-- Liveness info witha a multi-word bitmap
	CLabel		-- Label for the bitmap


-------------------------
-- StandardFormInfo tells whether this thunk has one of 
-- a small number of standard forms

data StandardFormInfo
  = NonStandardThunk
	-- Not of of the standard forms

  | SelectorThunk
	-- A SelectorThunk is of form
	--      case x of
	--	       con a1,..,an -> ak
	-- and the constructor is from a single-constr type.
       WordOff             	-- 0-origin offset of ak within the "goods" of 
			-- constructor (Recall that the a1,...,an may be laid
			-- out in the heap in a non-obvious order.)

  | ApThunk 
	-- An ApThunk is of form
	--	x1 ... xn
	-- The code for the thunk just pushes x2..xn on the stack and enters x1.
	-- There are a few of these (for 1 <= n <= MAX_SPEC_AP_SIZE) pre-compiled
	-- in the RTS to save space.
	Int		-- Arity, n

mkLFReEntrant :: TopLevelFlag	-- True of top level
	      -> [Id]		-- Free vars
	      -> [Id] 		-- Args
	      -> ArgDescr	-- Argument descriptor
	      -> LambdaFormInfo

mkLFReEntrant top fvs args arg_descr 
  = LFReEntrant top (length args) (null fvs) arg_descr

mkLFThunk :: Type -> TopLevelFlag -> [Var] -> UpdateFlag -> LambdaFormInfo
mkLFThunk thunk_ty top fvs upd_flag
  = ASSERT2( not (isUpdatable upd_flag) || not (isUnLiftedType thunk_ty), ppr thunk_ty $$ ppr fvs )
    LFThunk top (null fvs) 
	    (isUpdatable upd_flag)
	    NonStandardThunk 
	    (might_be_a_function thunk_ty)

might_be_a_function :: Type -> Bool
-- Return False only if we are *sure* it's a data type
-- Look through newtypes etc as much as poss
might_be_a_function ty
  = case splitTyConApp_maybe (repType ty) of
	Just (tc, _) -> not (isDataTyCon tc)
	Nothing	     -> True

mkConLFInfo :: DataCon -> LambdaFormInfo
mkConLFInfo con = LFCon con

maybeIsLFCon :: LambdaFormInfo -> Maybe DataCon
maybeIsLFCon (LFCon con) = Just con
maybeIsLFCon _ = Nothing

mkSelectorLFInfo :: Id -> WordOff -> Bool -> LambdaFormInfo
mkSelectorLFInfo id offset updatable
  = LFThunk NotTopLevel False updatable (SelectorThunk offset) 
	(might_be_a_function (idType id))

mkApLFInfo :: Id -> UpdateFlag -> Int -> LambdaFormInfo
mkApLFInfo id upd_flag arity
  = LFThunk NotTopLevel (arity == 0) (isUpdatable upd_flag) (ApThunk arity)
	(might_be_a_function (idType id))

mkLFArgument :: Id -> LambdaFormInfo
mkLFArgument id = LFUnknown (might_be_a_function (idType id))

mkLFLetNoEscape :: Int -> LambdaFormInfo
mkLFLetNoEscape = LFLetNoEscape

mkLFImported :: Id -> LambdaFormInfo
mkLFImported id
  = case idArity id of
      n | n > 0 -> LFReEntrant TopLevel n True (panic "arg_descr")  -- n > 0
      _ -> mkLFArgument id -- Not sure of exact arity

isLFThunk :: LambdaFormInfo -> Bool
isLFThunk (LFThunk _ _ _ _ _)  = True
isLFThunk LFBlackHole          = True
	-- return True for a blackhole: this function is used to determine
	-- whether to use the thunk header in SMP mode, and a blackhole
	-- must have one.
isLFThunk _ = False

mkClosureInfo :: Bool		-- Is static
	      -> Id
	      -> LambdaFormInfo 
	      -> Int -> Int	-- Total and pointer words
	      -> C_SRT
	      -> String		-- String descriptor
	      -> ClosureInfo
mkClosureInfo is_static id lf_info tot_wds ptr_wds srt_info descr
  = ClosureInfo { closureName = name, 
		  closureLFInfo = lf_info,
		  closureSMRep = sm_rep, 
		  closureSRT = srt_info,
		  closureType = idType id,
		  closureDescr = descr,
		  closureInfLcl = isDataConWorkId id }
		    -- Make the _info pointer for the implicit datacon worker binding
		    -- local. The reason we can do this is that importing code always
		    -- either uses the _closure or _con_info. By the invariants in CorePrep
		    -- anything else gets eta expanded.
  where
    name   = idName id
    sm_rep = chooseSMRep is_static lf_info tot_wds ptr_wds

mkConInfo :: Bool	-- Is static
	  -> DataCon	
	  -> Int -> Int	-- Total and pointer words
	  -> ClosureInfo
mkConInfo is_static data_con tot_wds ptr_wds
   = ConInfo {	closureSMRep = sm_rep,
		closureCon = data_con }
  where
    sm_rep = chooseSMRep is_static (mkConLFInfo data_con) tot_wds ptr_wds

closureSize :: ClosureInfo -> WordOff
closureSize cl_info = hdr_size + closureNonHdrSize cl_info
  where hdr_size  | closureIsThunk cl_info = thunkHdrSize
  		  | otherwise      	   = fixedHdrSize
	-- All thunks use thunkHdrSize, even if they are non-updatable.
	-- this is because we don't have separate closure types for
	-- updatable vs. non-updatable thunks, so the GC can't tell the
	-- difference.  If we ever have significant numbers of non-
	-- updatable thunks, it might be worth fixing this.

closureNonHdrSize :: ClosureInfo -> WordOff
closureNonHdrSize cl_info
  = tot_wds + computeSlopSize tot_wds cl_info
  where
    tot_wds = closureGoodStuffSize cl_info

closureGoodStuffSize :: ClosureInfo -> WordOff
closureGoodStuffSize cl_info
  = let (ptrs, nonptrs) = sizes_from_SMRep (closureSMRep cl_info)
    in	ptrs + nonptrs

closurePtrsSize :: ClosureInfo -> WordOff
closurePtrsSize cl_info
  = let (ptrs, _) = sizes_from_SMRep (closureSMRep cl_info)
    in	ptrs

-- not exported:
sizes_from_SMRep :: SMRep -> (WordOff,WordOff)
sizes_from_SMRep (GenericRep _ ptrs nonptrs _)   = (ptrs, nonptrs)
sizes_from_SMRep BlackHoleRep			 = (0, 0)

slopSize :: ClosureInfo -> WordOff
slopSize cl_info = computeSlopSize payload_size cl_info
  where payload_size = closureGoodStuffSize cl_info

computeSlopSize :: WordOff -> ClosureInfo -> WordOff
computeSlopSize payload_size cl_info
  = max 0 (minPayloadSize smrep updatable - payload_size)
  where
	smrep        = closureSMRep cl_info
	updatable    = closureNeedsUpdSpace cl_info

-- we leave space for an update if either (a) the closure is updatable
-- or (b) it is a static thunk.  This is because a static thunk needs
-- a static link field in a predictable place (after the slop), regardless
-- of whether it is updatable or not.
closureNeedsUpdSpace :: ClosureInfo -> Bool
closureNeedsUpdSpace (ClosureInfo { closureLFInfo = 
					LFThunk TopLevel _ _ _ _ }) = True
closureNeedsUpdSpace cl_info = closureUpdReqd cl_info

minPayloadSize :: SMRep -> Bool -> WordOff
minPayloadSize smrep updatable
  = case smrep of
	BlackHoleRep		 		-> min_upd_size
	GenericRep _ _ _ _      | updatable     -> min_upd_size
	GenericRep True _ _ _                   -> 0 -- static
	GenericRep False _ _ _                  -> mIN_PAYLOAD_SIZE
          --       ^^^^^___ dynamic
  where
   min_upd_size =
	ASSERT(mIN_PAYLOAD_SIZE <= sIZEOF_StgSMPThunkHeader)
	0 	-- check that we already have enough
		-- room for mIN_SIZE_NonUpdHeapObject,
		-- due to the extra header word in SMP

chooseSMRep
	:: Bool			-- True <=> static closure
	-> LambdaFormInfo
	-> WordOff -> WordOff	-- Tot wds, ptr wds
	-> SMRep

chooseSMRep is_static lf_info tot_wds ptr_wds
  = let
	 nonptr_wds   = tot_wds - ptr_wds
	 closure_type = getClosureType is_static ptr_wds lf_info
    in
    GenericRep is_static ptr_wds nonptr_wds closure_type	

-- We *do* get non-updatable top-level thunks sometimes.  eg. f = g
-- gets compiled to a jump to g (if g has non-zero arity), instead of
-- messing around with update frames and PAPs.  We set the closure type
-- to FUN_STATIC in this case.

getClosureType :: Bool -> WordOff -> LambdaFormInfo -> ClosureType
getClosureType is_static ptr_wds lf_info
  = case lf_info of
	LFCon _ | is_static && ptr_wds == 0	-> ConstrNoCaf
		  | otherwise			-> Constr
  	LFReEntrant _ _ _ _ 			-> Fun
	LFThunk _ _ _ (SelectorThunk _) _ 	-> ThunkSelector
	LFThunk _ _ _ _ _ 			-> Thunk
	_ -> panic "getClosureType"

nodeMustPointToIt :: LambdaFormInfo -> Bool
nodeMustPointToIt (LFReEntrant top _ no_fvs _)
  = not no_fvs ||   -- Certainly if it has fvs we need to point to it
    isNotTopLevel top
		    -- If it is not top level we will point to it
		    --   We can have a \r closure with no_fvs which
		    --   is not top level as special case cgRhsClosure
		    --   has been dissabled in favour of let floating

		-- For lex_profiling we also access the cost centre for a
		-- non-inherited function i.e. not top level
		-- the  not top  case above ensures this is ok.

nodeMustPointToIt (LFCon _) = True

	-- Strictly speaking, the above two don't need Node to point
	-- to it if the arity = 0.  But this is a *really* unlikely
	-- situation.  If we know it's nil (say) and we are entering
	-- it. Eg: let x = [] in x then we will certainly have inlined
	-- x, since nil is a simple atom.  So we gain little by not
	-- having Node point to known zero-arity things.  On the other
	-- hand, we do lose something; Patrick's code for figuring out
	-- when something has been updated but not entered relies on
	-- having Node point to the result of an update.  SLPJ
	-- 27/11/92.

nodeMustPointToIt (LFThunk _ no_fvs updatable NonStandardThunk _)
  = updatable || not no_fvs || opt_SccProfilingOn
	  -- For the non-updatable (single-entry case):
	  --
	  -- True if has fvs (in which case we need access to them, and we
	  --		    should black-hole it)
	  -- or profiling (in which case we need to recover the cost centre
	  --		 from inside it)

nodeMustPointToIt (LFThunk _ _ _ _ _)
  = True  -- Node must point to any standard-form thunk

nodeMustPointToIt (LFUnknown _)     = True
nodeMustPointToIt LFBlackHole       = True    -- BH entry may require Node to point
nodeMustPointToIt (LFLetNoEscape _) = False 

data CallMethod
  = EnterIt				-- no args, not a function

  | JumpToIt CLabel			-- no args, not a function, but we
					-- know what its entry code is

  | ReturnIt				-- it's a function, but we have
					-- zero args to apply to it, so just
					-- return it.

  | ReturnCon DataCon			-- It's a data constructor, just return it

  | SlowCall				-- Unknown fun, or known fun with
					-- too few args.

  | DirectEntry 			-- Jump directly, with args in regs
	CLabel 				--   The code label
	Int 				--   Its arity

getCallMethod :: DynFlags
              -> Name		-- Function being applied
              -> CafInfo        -- Can it refer to CAF's?
	      -> LambdaFormInfo	-- Its info
	      -> Int		-- Number of available arguments
	      -> CallMethod

getCallMethod _ _ _ lf_info _
  | nodeMustPointToIt lf_info && opt_Parallel
  =	-- If we're parallel, then we must always enter via node.  
	-- The reason is that the closure may have been 	
	-- fetched since we allocated it.
    EnterIt

getCallMethod _ name caf (LFReEntrant _ arity _ _) n_args
  | n_args == 0    = ASSERT( arity /= 0 )
		     ReturnIt	-- No args at all
  | n_args < arity = SlowCall	-- Not enough args
  | otherwise      = DirectEntry (enterIdLabel name caf) arity

getCallMethod _ _ _ (LFCon con) n_args
  | opt_SccProfilingOn     -- when profiling, we must always enter
  = EnterIt                -- a closure when we use it, so that the closure
                           -- can be recorded as used for LDV profiling.
  | otherwise
  = ASSERT( n_args == 0 )
    ReturnCon con

getCallMethod _dflags _name _caf (LFThunk _ _ _updatable _std_form_info is_fun) _n_args
  | is_fun 	-- it *might* be a function, so we must "call" it (which is
                -- always safe)
  = SlowCall	-- We cannot just enter it [in eval/apply, the entry code
		-- is the fast-entry code]

  -- Since is_fun is False, we are *definitely* looking at a data value
  | otherwise
  = EnterIt
    -- We used to have ASSERT( n_args == 0 ), but actually it is
    -- possible for the optimiser to generate
    --   let bot :: Int = error Int "urk"
    --   in (bot `cast` unsafeCoerce Int (Int -> Int)) 3
    -- This happens as a result of the case-of-error transformation
    -- So the right thing to do is just to enter the thing

-- Old version:
--  | updatable || doingTickyProfiling dflags -- to catch double entry
--  = EnterIt
--  | otherwise	-- Jump direct to code for single-entry thunks
--  = JumpToIt (thunkEntryLabel name caf std_form_info updatable)
--
-- Now we never use JumpToIt, even if the thunk is single-entry, since
-- the thunk may have already been entered and blackholed by another
-- processor.


getCallMethod _ _ _ (LFUnknown True) _
  = SlowCall -- Might be a function

getCallMethod _ name _ (LFUnknown False) n_args
  | n_args > 0 
  = WARN( True, ppr name <+> ppr n_args ) 
    SlowCall	-- Note [Unsafe coerce complications]

  | otherwise
  = EnterIt -- Not a function

getCallMethod _ _ _ LFBlackHole _
  = SlowCall	-- Presumably the black hole has by now
		-- been updated, but we don't know with
		-- what, so we slow call it

getCallMethod _ name _ (LFLetNoEscape 0) _
  = JumpToIt (enterReturnPtLabel (nameUnique name))

getCallMethod _ name _ (LFLetNoEscape arity) n_args
  | n_args == arity = DirectEntry (enterReturnPtLabel (nameUnique name)) arity
  | otherwise = pprPanic "let-no-escape: " (ppr name <+> ppr arity)

blackHoleOnEntry :: DynFlags -> ClosureInfo -> Bool
-- Static closures are never themselves black-holed.
-- Updatable ones will be overwritten with a CAFList cell, which points to a 
-- black hole;
-- Single-entry ones have no fvs to plug, and we trust they don't form part 
-- of a loop.

blackHoleOnEntry _ ConInfo{} = False
blackHoleOnEntry dflags (ClosureInfo { closureLFInfo = lf_info, closureSMRep = rep })
  | isStaticRep rep
  = False	-- Never black-hole a static closure

  | otherwise
  = case lf_info of
	LFReEntrant _ _ _ _	  -> False
	LFLetNoEscape _		  -> False
	LFThunk _ no_fvs updatable _ _
	  -> if updatable
	     then not opt_OmitBlackHoling
	     else doingTickyProfiling dflags || not no_fvs
                  -- the former to catch double entry,
                  -- and the latter to plug space-leaks.  KSW/SDM 1999-04.

	_ -> panic "blackHoleOnEntry"	-- Should never happen

isStandardFormThunk :: LambdaFormInfo -> Bool
isStandardFormThunk (LFThunk _ _ _ (SelectorThunk _) _) = True
isStandardFormThunk (LFThunk _ _ _ (ApThunk _) _)	= True
isStandardFormThunk _ 			= False

isKnownFun :: LambdaFormInfo -> Bool
isKnownFun (LFReEntrant _ _ _ _) = True
isKnownFun (LFLetNoEscape _) = True
isKnownFun _ = False

staticClosureNeedsLink :: ClosureInfo -> Bool
-- A static closure needs a link field to aid the GC when traversing
-- the static closure graph.  But it only needs such a field if either
-- 	a) it has an SRT
--	b) it's a constructor with one or more pointer fields
-- In case (b), the constructor's fields themselves play the role
-- of the SRT.
staticClosureNeedsLink (ClosureInfo { closureSRT = srt })
  = needsSRT srt
staticClosureNeedsLink (ConInfo { closureSMRep = sm_rep, closureCon = con })
  = not (isNullaryRepDataCon con) && not_nocaf_constr
  where
    not_nocaf_constr = 
	case sm_rep of 
	   GenericRep _ _ _ ConstrNoCaf -> False
	   _other			-> True

staticClosureRequired
	:: Name
	-> StgBinderInfo
	-> LambdaFormInfo
	-> Bool
staticClosureRequired _ bndr_info
		      (LFReEntrant top_level _ _ _)	-- It's a function
  = ASSERT( isTopLevel top_level )
	-- Assumption: it's a top-level, no-free-var binding
	not (satCallsOnly bndr_info)

staticClosureRequired _ _ _ = True

isStaticClosure :: ClosureInfo -> Bool
isStaticClosure cl_info = isStaticRep (closureSMRep cl_info)

closureUpdReqd :: ClosureInfo -> Bool
closureUpdReqd ClosureInfo{ closureLFInfo = lf_info } = lfUpdatable lf_info
closureUpdReqd ConInfo{} = False

lfUpdatable :: LambdaFormInfo -> Bool
lfUpdatable (LFThunk _ _ upd _ _)  = upd
lfUpdatable LFBlackHole 	   = True
	-- Black-hole closures are allocated to receive the results of an
	-- alg case with a named default... so they need to be updated.
lfUpdatable _ = False

closureIsThunk :: ClosureInfo -> Bool
closureIsThunk ClosureInfo{ closureLFInfo = lf_info } = isLFThunk lf_info
closureIsThunk ConInfo{} = False

closureSingleEntry :: ClosureInfo -> Bool
closureSingleEntry (ClosureInfo { closureLFInfo = LFThunk _ _ upd _ _}) = not upd
closureSingleEntry _ = False

closureReEntrant :: ClosureInfo -> Bool
closureReEntrant (ClosureInfo { closureLFInfo = LFReEntrant _ _ _ _ }) = True
closureReEntrant _ = False

isConstrClosure_maybe :: ClosureInfo -> Maybe DataCon
isConstrClosure_maybe (ConInfo { closureCon = data_con }) = Just data_con
isConstrClosure_maybe _ 				  = Nothing

closureFunInfo :: ClosureInfo -> Maybe (Int, ArgDescr)
closureFunInfo (ClosureInfo { closureLFInfo = lf_info }) = lfFunInfo lf_info
closureFunInfo _ = Nothing

lfFunInfo :: LambdaFormInfo ->  Maybe (Int, ArgDescr)
lfFunInfo (LFReEntrant _ arity _ arg_desc)  = Just (arity, arg_desc)
lfFunInfo _                                 = Nothing

funTag :: ClosureInfo -> Int
funTag (ClosureInfo { closureLFInfo = lf_info }) = funTagLFInfo lf_info
funTag _ = 0

-- maybe this should do constructor tags too?
funTagLFInfo :: LambdaFormInfo -> Int
funTagLFInfo lf
    -- A function is tagged with its arity
  | Just (arity,_) <- lfFunInfo lf,
    Just tag <- tagForArity arity
  = tag

    -- other closures (and unknown ones) are not tagged
  | otherwise
  = 0

tagForArity :: Int -> Maybe Int
tagForArity i | i <= mAX_PTR_TAG = Just i
              | otherwise        = Nothing

clHasCafRefs :: ClosureInfo -> CafInfo
clHasCafRefs (ClosureInfo {closureSRT = srt}) = 
  case srt of NoC_SRT -> NoCafRefs
              _       -> MayHaveCafRefs
clHasCafRefs (ConInfo {}) = NoCafRefs

isToplevClosure :: ClosureInfo -> Bool
isToplevClosure (ClosureInfo { closureLFInfo = lf_info })
  = case lf_info of
      LFReEntrant TopLevel _ _ _ -> True
      LFThunk TopLevel _ _ _ _   -> True
      _ -> False
isToplevClosure _ = False

infoTableLabelFromCI :: ClosureInfo -> CLabel
infoTableLabelFromCI = fst . labelsFromCI

entryLabelFromCI :: ClosureInfo -> CLabel
entryLabelFromCI = snd . labelsFromCI

labelsFromCI :: ClosureInfo -> (CLabel, CLabel) -- (Info, Entry)
labelsFromCI cl@(ClosureInfo { closureName = name,
			       closureLFInfo = lf_info,
			       closureInfLcl = is_lcl })
  = case lf_info of
	LFBlackHole -> (mkCAFBlackHoleInfoTableLabel, mkCAFBlackHoleEntryLabel)

	LFThunk _ _ upd_flag (SelectorThunk offset) _ -> 
		bothL (mkSelectorInfoLabel, mkSelectorEntryLabel) upd_flag offset

	LFThunk _ _ upd_flag (ApThunk arity) _ -> 
		bothL (mkApInfoTableLabel, mkApEntryLabel) upd_flag arity

	LFThunk{}      -> bothL std_mk_lbls name $ clHasCafRefs cl

	LFReEntrant _ _ _ _ -> bothL std_mk_lbls name $ clHasCafRefs cl

	_ -> panic "labelsFromCI"
  where std_mk_lbls = if is_lcl then (mkLocalInfoTableLabel, mkLocalEntryLabel) else (mkInfoTableLabel, mkEntryLabel)

labelsFromCI cl@(ConInfo { closureCon = con, 
			           closureSMRep = rep })
  | isStaticRep rep = bothL (mkStaticInfoTableLabel, mkStaticConEntryLabel)  name $ clHasCafRefs cl
  | otherwise	    = bothL (mkConInfoTableLabel,    mkConEntryLabel)        name $ clHasCafRefs cl
  where
    name = dataConName con

bothL :: (a -> b -> c, a -> b -> c) -> a -> b -> (c, c)
bothL (f, g) x y = (f x y, g x y)

-- ClosureInfo for a closure (as opposed to a constructor) is always local
closureLabelFromCI :: ClosureInfo -> CLabel
closureLabelFromCI cl@(ClosureInfo { closureName = nm }) = mkLocalClosureLabel nm $ clHasCafRefs cl
closureLabelFromCI _ = panic "closureLabelFromCI"

-- thunkEntryLabel is a local help function, not exported.  It's used from both
-- entryLabelFromCI and getCallMethod.

{- UNUSED:
thunkEntryLabel :: Name -> CafInfo -> StandardFormInfo -> Bool -> CLabel
thunkEntryLabel _thunk_id _ (ApThunk arity) is_updatable
  = enterApLabel is_updatable arity
thunkEntryLabel _thunk_id _ (SelectorThunk offset) upd_flag
  = enterSelectorLabel upd_flag offset
thunkEntryLabel thunk_id caf _ _is_updatable
  = enterIdLabel thunk_id caf
-}

{- UNUSED:
enterApLabel :: Bool -> Int -> CLabel
enterApLabel is_updatable arity
  | tablesNextToCode = mkApInfoTableLabel is_updatable arity
  | otherwise        = mkApEntryLabel is_updatable arity
-}

{- UNUSED:
enterSelectorLabel :: Bool -> Int -> CLabel
enterSelectorLabel upd_flag offset
  | tablesNextToCode = mkSelectorInfoLabel upd_flag offset
  | otherwise        = mkSelectorEntryLabel upd_flag offset
-}

enterIdLabel :: Name -> CafInfo -> CLabel
enterIdLabel id
  | tablesNextToCode = mkInfoTableLabel id
  | otherwise        = mkEntryLabel id

enterLocalIdLabel :: Name -> CafInfo -> CLabel
enterLocalIdLabel id
  | tablesNextToCode = mkLocalInfoTableLabel id
  | otherwise        = mkLocalEntryLabel id

enterReturnPtLabel :: Unique -> CLabel
enterReturnPtLabel name
  | tablesNextToCode = mkReturnInfoLabel name
  | otherwise        = mkReturnPtLabel name

cafBlackHoleClosureInfo :: ClosureInfo -> ClosureInfo
cafBlackHoleClosureInfo (ClosureInfo { closureName = nm,
				       closureType = ty })
  = ClosureInfo { closureName   = nm,
		  closureLFInfo = LFBlackHole,
		  closureSMRep  = BlackHoleRep,
		  closureSRT    = NoC_SRT,
		  closureType   = ty,
		  closureDescr  = "",
		  closureInfLcl = False }
cafBlackHoleClosureInfo _ = panic "cafBlackHoleClosureInfo"

closureValDescr, closureTypeDescr :: ClosureInfo -> String
closureValDescr (ClosureInfo {closureDescr = descr}) 
  = descr
closureValDescr (ConInfo {closureCon = con})
  = occNameString (getOccName con)

closureTypeDescr (ClosureInfo { closureType = ty })
  = getTyDescription ty
closureTypeDescr (ConInfo { closureCon = data_con })
  = occNameString (getOccName (dataConTyCon data_con))

getTyDescription :: Type -> String
getTyDescription ty
  = case (tcSplitSigmaTy ty) of { (_, _, tau_ty) ->
    case tau_ty of
      TyVarTy _	       	     -> "*"
      AppTy fun _      	     -> getTyDescription fun
      FunTy _ res      	     -> '-' : '>' : fun_result res
      TyConApp tycon _ 	     -> getOccString tycon
      PredTy sty	     -> getPredTyDescription sty
      ForAllTy _ ty          -> getTyDescription ty
    }
  where
    fun_result (FunTy _ res) = '>' : fun_result res
    fun_result other	     = getTyDescription other

getPredTyDescription :: PredType -> String
getPredTyDescription (ClassP cl _) = getOccString cl
getPredTyDescription (IParam ip _) = getOccString (ipNameName ip)
getPredTyDescription (EqPred _ _)  = "Type equality"