    -----------------------------------------------------------------------------
    --
    -- Code generation for profiling
    --
    -- (c) The University of Glasgow 2004-2006
    --
    -----------------------------------------------------------------------------

    module StgCmmProf (
    	initCostCentres, ccType, ccsType,
    	mkCCostCentre, mkCCostCentreStack,

    	-- Cost-centre Profiling
    	dynProfHdr, profDynAlloc, profAlloc, staticProfHdr, initUpdFrameProf,
    	enterCostCentre, enterCostCentrePAP, enterCostCentreThunk,
    	chooseDynCostCentres,
    	costCentreFrom,
    	curCCS, curCCSAddr,
    	emitSetCCC, emitCCS,

    	saveCurrentCostCentre, restoreCurrentCostCentre,

    	-- Lag/drag/void stuff
    	ldvEnter, ldvEnterClosure, ldvRecordCreate
      ) where

    #include "HsVersions.h"
    #include "../includes/MachDeps.h"
     -- For WORD_SIZE_IN_BITS only.
    #include "../includes/rts/Constants.h"
    	-- For LDV_CREATE_MASK, LDV_STATE_USE
    	-- which are StgWords
    #include "../includes/DerivedConstants.h"
    	-- For REP_xxx constants, which are MachReps

    import StgCmmClosure
    import StgCmmUtils
    import StgCmmMonad
    import SMRep

    import MkZipCfgCmm
    import Cmm
    import CmmUtils
    import CLabel

    import Id
    import qualified Module
    import CostCentre
    import StgSyn
    import StaticFlags
    import FastString
    import Module
    import Constants	-- Lots of field offsets
    import Outputable

    import Data.Char
    import Control.Monad

    -----------------------------------------------------------------------------
    --
    -- Cost-centre-stack Profiling
    --
    -----------------------------------------------------------------------------

    -- Expression representing the current cost centre stack
    ccsType :: CmmType 	-- Type of a cost-centre stack
    ccsType = bWord

    ccType :: CmmType 	-- Type of a cost centre
    ccType = bWord

    curCCS :: CmmExpr
    curCCS = CmmLoad curCCSAddr ccsType

    -- Address of current CCS variable, for storing into
    curCCSAddr :: CmmExpr
    curCCSAddr = CmmLit (CmmLabel (mkCmmDataLabel rtsPackageId (fsLit "CCCS")))

    mkCCostCentre :: CostCentre -> CmmLit
    mkCCostCentre cc = CmmLabel (mkCCLabel cc)

    mkCCostCentreStack :: CostCentreStack -> CmmLit
    mkCCostCentreStack ccs = CmmLabel (mkCCSLabel ccs)

    costCentreFrom :: CmmExpr 	-- A closure pointer
    	       -> CmmExpr	-- The cost centre from that closure
    costCentreFrom cl = CmmLoad (cmmOffsetB cl oFFSET_StgHeader_ccs) ccsType

    staticProfHdr :: CostCentreStack -> [CmmLit]
    -- The profiling header words in a static closure
    -- Was SET_STATIC_PROF_HDR
    staticProfHdr ccs = ifProfilingL [mkCCostCentreStack ccs,
    			  	  staticLdvInit]

    dynProfHdr :: CmmExpr -> [CmmExpr]
    -- Profiling header words in a dynamic closure
    dynProfHdr ccs = ifProfilingL [ccs, dynLdvInit]

    initUpdFrameProf :: CmmExpr -> FCode ()
    -- Initialise the profiling field of an update frame
    initUpdFrameProf frame_amode
      = ifProfiling $	-- frame->header.prof.ccs = CCCS
        emit (mkStore (cmmOffsetB frame_amode oFFSET_StgHeader_ccs) curCCS)
    	-- frame->header.prof.hp.rs = NULL (or frame-header.prof.hp.ldvw = 0)
    	-- is unnecessary because it is not used anyhow.

    ---------------------------------------------------------------------------
    -- 	Saving and restoring the current cost centre
    ---------------------------------------------------------------------------

    {-	Note [Saving the current cost centre]
    	~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    The current cost centre is like a global register.  Like other
    global registers, it's a caller-saves one.  But consider
    	case (f x) of (p,q) -> rhs
    Since 'f' may set the cost centre, we must restore it
    before resuming rhs.  So we want code like this:
    	local_cc = CCC  -- save
    	r = f( x )
    	CCC = local_cc  -- restore
    That is, we explicitly "save" the current cost centre in
    a LocalReg, local_cc; and restore it after the call. The
    C-- infrastructure will arrange to save local_cc across the
    call.

    The same goes for join points;
    	let j x = join-stuff
    	in blah-blah
    We want this kind of code:
    	local_cc = CCC  -- save
    	blah-blah
         J:
            CCC = local_cc  -- restore
    -}

    saveCurrentCostCentre :: FCode (Maybe LocalReg)
    	-- Returns Nothing if profiling is off
    saveCurrentCostCentre
      | not opt_SccProfilingOn
      = return Nothing
      | otherwise
      = do	{ local_cc <- newTemp ccType
    	; emit (mkAssign (CmmLocal local_cc) curCCS)
    	; return (Just local_cc) }

    restoreCurrentCostCentre :: Maybe LocalReg -> FCode ()
    restoreCurrentCostCentre Nothing
      = return ()
    restoreCurrentCostCentre (Just local_cc)
      = emit (mkStore curCCSAddr (CmmReg (CmmLocal local_cc)))

    -------------------------------------------------------------------------------
    -- Recording allocation in a cost centre
    -------------------------------------------------------------------------------

    -- | Record the allocation of a closure.  The CmmExpr is the cost
    -- centre stack to which to attribute the allocation.
    profDynAlloc :: ClosureInfo -> CmmExpr -> FCode ()
    profDynAlloc cl_info ccs
      = ifProfiling $
        profAlloc (CmmLit (mkIntCLit (closureSize cl_info))) ccs

    -- | Record the allocation of a closure (size is given by a CmmExpr)
    -- The size must be in words, because the allocation counter in a CCS counts
    -- in words.
    profAlloc :: CmmExpr -> CmmExpr -> FCode ()
    profAlloc words ccs
      = ifProfiling $
        emit (addToMemE alloc_rep
    		(cmmOffsetB ccs oFFSET_CostCentreStack_mem_alloc)
    	  	(CmmMachOp (MO_UU_Conv wordWidth (typeWidth alloc_rep)) $
    		  [CmmMachOp mo_wordSub [words,
    					 CmmLit (mkIntCLit profHdrSize)]]))
    		-- subtract the "profiling overhead", which is the
    		-- profiling header in a closure.
     where
    	alloc_rep =  REP_CostCentreStack_mem_alloc

    -- ----------------------------------------------------------------------
    -- Setting the cost centre in a new closure

    chooseDynCostCentres :: CostCentreStack
    		     -> [Id] 	        -- Args
    		     -> StgExpr		-- Body
    		     -> FCode (CmmExpr, CmmExpr)
    -- Called when allocating a closure
    -- Tells which cost centre to put in the object, and which
    -- to blame the cost of allocation on
    chooseDynCostCentres ccs args body = do
      -- Cost-centre we record in the object
      use_ccs <- emitCCS ccs

      -- Cost-centre on whom we blame the allocation
      let blame_ccs
    	| null args && isBox body = CmmLit (mkCCostCentreStack overheadCCS)
    	| otherwise		  = use_ccs

      return (use_ccs, blame_ccs)

    -- Some CostCentreStacks are a sequence of pushes on top of CCCS.
    -- These pushes must be performed before we can refer to the stack in
    -- an expression.
    emitCCS :: CostCentreStack -> FCode CmmExpr
    emitCCS ccs = push_em (ccsExpr ccs') (reverse cc's)
      where
    	(cc's, ccs') = decomposeCCS ccs

    	push_em ccs [] = return ccs
    	push_em ccs (cc:rest) = do
      	  tmp <- newTemp ccsType
    	  pushCostCentre tmp ccs cc
    	  push_em (CmmReg (CmmLocal tmp)) rest

    ccsExpr :: CostCentreStack -> CmmExpr
    ccsExpr ccs
      | isCurrentCCS ccs = curCCS
      | otherwise        = CmmLit (mkCCostCentreStack ccs)

    isBox :: StgExpr -> Bool
    -- If it's an utterly trivial RHS, then it must be
    -- one introduced by boxHigherOrderArgs for profiling,
    -- so we charge it to "OVERHEAD".
    -- This looks like a GROSS HACK to me --SDM
    isBox (StgApp _ []) = True
    isBox _             = False

    -- -----------------------------------------------------------------------
    -- Setting the current cost centre on entry to a closure

    -- For lexically scoped profiling we have to load the cost centre from
    -- the closure entered, if the costs are not supposed to be inherited.
    -- This is done immediately on entering the fast entry point.

    -- Load current cost centre from closure, if not inherited.
    -- Node is guaranteed to point to it, if profiling and not inherited.

    enterCostCentre
       :: ClosureInfo
       -> CostCentreStack
       -> StgExpr	-- The RHS of the closure
       -> FCode ()

    -- We used to have a special case for bindings of form
    --	f = g True
    -- where g has arity 2.  The RHS is a thunk, but we don't
    -- need to update it; and we want to subsume costs.
    -- We don't have these sort of PAPs any more, so the special
    -- case has gone away.

    enterCostCentre closure_info ccs body
      = ifProfiling $
        ASSERT2(not (noCCSAttached ccs), ppr (closureName closure_info) <+> ppr ccs)
        enter_cost_centre closure_info ccs body

    enter_cost_centre :: ClosureInfo -> CostCentreStack -> StgExpr -> FCode ()
    enter_cost_centre closure_info ccs body
      | isSubsumedCCS ccs
      = ASSERT(isToplevClosure closure_info)
        ASSERT(re_entrant)
        enter_ccs_fsub

      | isDerivedFromCurrentCCS ccs
      = do {
    	if re_entrant && not is_box
        	  then
    		enter_ccs_fun node_ccs
        	  else
    	  	emit (mkStore curCCSAddr node_ccs)

    	-- don't forget to bump the scc count.  This closure might have been
    	-- of the form   let x = _scc_ "x" e in ...x..., which the SCCfinal
    	-- pass has turned into simply  let x = e in ...x... and attached
    	-- the _scc_ as PushCostCentre(x,CCCS) on the x closure.  So that
    	-- we don't lose the scc counter, bump it in the entry code for x.
    	-- ToDo: for a multi-push we should really bump the counter for
    	-- each of the intervening CCSs, not just the top one.
           ; when (not (isCurrentCCS ccs)) $
    		emit (bumpSccCount curCCS)
           }

      | isCafCCS ccs
      = ASSERT(isToplevClosure closure_info)
        ASSERT(not re_entrant)
        do	{ 	-- This is just a special case of the isDerivedFromCurrentCCS
    		-- case above.  We could delete this, but it's a micro
    		-- optimisation and saves a bit of code.
    	  emit (mkStore curCCSAddr enc_ccs)
    	; emit (bumpSccCount node_ccs)
    	}

      | otherwise
      = panic "enterCostCentre"
      where
        enc_ccs    = CmmLit (mkCCostCentreStack ccs)
        re_entrant = closureReEntrant closure_info
        node_ccs   = costCentreFrom (cmmOffsetB (CmmReg nodeReg) (-node_tag))
        is_box     = isBox body

        -- if this is a function, then node will be tagged; we must subract the tag
        node_tag = funTag closure_info

    -- set the current CCS when entering a PAP
    enterCostCentrePAP :: CmmExpr -> FCode ()
    enterCostCentrePAP closure =
      ifProfiling $ do
        enter_ccs_fun (costCentreFrom closure)
        enteringPAP 1

    enterCostCentreThunk :: CmmExpr -> FCode ()
    enterCostCentreThunk closure =
      ifProfiling $ do
        emit $ mkStore curCCSAddr (costCentreFrom closure)

    enter_ccs_fun :: CmmExpr -> FCode ()
    enter_ccs_fun stack = emitRtsCall rtsPackageId (fsLit "EnterFunCCS") [(stack,AddrHint)] False
    			-- ToDo: vols

    enter_ccs_fsub :: FCode ()
    enter_ccs_fsub = enteringPAP 0

    -- When entering a PAP, EnterFunCCS is called by both the PAP entry
    -- code and the function entry code; we don't want the function's
    -- entry code to also update CCCS in the event that it was called via
    -- a PAP, so we set the flag entering_PAP to indicate that we are
    -- entering via a PAP.
    enteringPAP :: Integer -> FCode ()
    enteringPAP n
      = emit (mkStore (CmmLit (CmmLabel (mkCmmDataLabel rtsPackageId (fsLit "entering_PAP"))))
    		  (CmmLit (CmmInt n cIntWidth)))

    ifProfiling :: FCode () -> FCode ()
    ifProfiling code
      | opt_SccProfilingOn = code
      | otherwise	       = nopC

    ifProfilingL :: [a] -> [a]
    ifProfilingL xs
      | opt_SccProfilingOn = xs
      | otherwise	       = []

    ---------------------------------------------------------------
    --	Initialising Cost Centres & CCSs
    ---------------------------------------------------------------

    initCostCentres :: CollectedCCs -> FCode CmmAGraph
    -- Emit the declarations, and return code to register them
    initCostCentres (local_CCs, ___extern_CCs, singleton_CCSs)
      = getCode $ whenC opt_SccProfilingOn $
        do	{ mapM_ emitCostCentreDecl local_CCs
      	; mapM_ emitCostCentreStackDecl  singleton_CCSs
    	; emit $ catAGraphs $ map mkRegisterCC local_CCs
    	; emit $ catAGraphs $ map mkRegisterCCS singleton_CCSs }

    emitCostCentreDecl :: CostCentre -> FCode ()
    emitCostCentreDecl cc = do
      { label <- mkStringCLit (costCentreUserName cc)
      ; modl  <- mkStringCLit (Module.moduleNameString
                   	               (Module.moduleName (cc_mod cc)))
                    -- All cost centres will be in the main package, since we
                    -- don't normally use -auto-all or add SCCs to other packages.
                    -- Hence don't emit the package name in the module here.
      ; let lits = [ zero,   	-- StgInt ccID,
    	      	 label,	-- char *label,
    	      	 modl,	-- char *module,
                  	 zero,	-- StgWord time_ticks
                  	 zero64,	-- StgWord64 mem_alloc
    	      	 subsumed, -- StgInt is_caf
    	      	 zero	-- struct _CostCentre *link
    	       ]
      ; emitDataLits (mkCCLabel cc) lits
      }
      where
    	subsumed | isCafCC cc = mkIntCLit (ord 'c')  -- 'c' == is a CAF
    		 | otherwise  = mkIntCLit (ord 'B')  -- 'B' == is boring

    emitCostCentreStackDecl :: CostCentreStack -> FCode ()
    emitCostCentreStackDecl ccs
      = case maybeSingletonCCS ccs of
    	Just cc -> emitDataLits (mkCCSLabel ccs) (mk_lits cc)
    	Nothing -> pprPanic "emitCostCentreStackDecl" (ppr ccs)
      where
         mk_lits cc = zero :
    		  mkCCostCentre cc :
    		  replicate (sizeof_ccs_words - 2) zero
    	-- Note: to avoid making any assumptions about how the
    	-- C compiler (that compiles the RTS, in particular) does
    	-- layouts of structs containing long-longs, simply
    	-- pad out the struct with zero words until we hit the
    	-- size of the overall struct (which we get via DerivedConstants.h)

    zero :: CmmLit
    zero = mkIntCLit 0
    zero64 :: CmmLit
    zero64 = CmmInt 0 W64

    sizeof_ccs_words :: Int
    sizeof_ccs_words
        -- round up to the next word.
      | ms == 0   = ws
      | otherwise = ws + 1
      where
       (ws,ms) = SIZEOF_CostCentreStack `divMod` wORD_SIZE

    -- ---------------------------------------------------------------------------
    -- Registering CCs and CCSs

    --   (cc)->link = CC_LIST;
    --   CC_LIST = (cc);
    --   (cc)->ccID = CC_ID++;

    mkRegisterCC :: CostCentre -> CmmAGraph
    mkRegisterCC cc
      = withTemp cInt $ \tmp ->
        catAGraphs [
         mkStore (cmmOffsetB cc_lit oFFSET_CostCentre_link)
    		 (CmmLoad cC_LIST bWord),
         mkStore cC_LIST cc_lit,
         mkAssign (CmmLocal tmp) (CmmLoad cC_ID cInt),
         mkStore (cmmOffsetB cc_lit oFFSET_CostCentre_ccID) (CmmReg (CmmLocal tmp)),
         mkStore cC_ID (cmmRegOffB (CmmLocal tmp) 1)
       ]
      where
    	cc_lit = CmmLit (CmmLabel (mkCCLabel cc))

    --  (ccs)->prevStack = CCS_LIST;
    --  CCS_LIST = (ccs);
    --  (ccs)->ccsID = CCS_ID++;

    mkRegisterCCS :: CostCentreStack -> CmmAGraph
    mkRegisterCCS ccs
      = withTemp cInt $ \ tmp ->
        catAGraphs [
         mkStore (cmmOffsetB ccs_lit oFFSET_CostCentreStack_prevStack)
    			(CmmLoad cCS_LIST bWord),
         mkStore cCS_LIST ccs_lit,
         mkAssign (CmmLocal tmp) (CmmLoad cCS_ID cInt),
         mkStore (cmmOffsetB ccs_lit oFFSET_CostCentreStack_ccsID) (CmmReg (CmmLocal tmp)),
         mkStore cCS_ID (cmmRegOffB (CmmLocal tmp) 1)
       ]
      where
        ccs_lit = CmmLit (CmmLabel (mkCCSLabel ccs))

    cC_LIST, cC_ID :: CmmExpr
    cC_LIST = CmmLit (CmmLabel (mkCmmDataLabel rtsPackageId (fsLit "CC_LIST")))
    cC_ID   = CmmLit (CmmLabel (mkCmmDataLabel rtsPackageId (fsLit "CC_ID")))

    cCS_LIST, cCS_ID :: CmmExpr
    cCS_LIST = CmmLit (CmmLabel (mkCmmDataLabel rtsPackageId (fsLit "CCS_LIST")))
    cCS_ID   = CmmLit (CmmLabel (mkCmmDataLabel rtsPackageId (fsLit "CCS_ID")))

    -- ---------------------------------------------------------------------------
    -- Set the current cost centre stack

    emitSetCCC :: CostCentre -> FCode ()
    emitSetCCC cc
      | not opt_SccProfilingOn = nopC
      | otherwise = do
        tmp <- newTemp ccsType -- TODO FIXME NOW
        ASSERT( sccAbleCostCentre cc )
          pushCostCentre tmp curCCS cc
        emit (mkStore curCCSAddr (CmmReg (CmmLocal tmp)))
        when (isSccCountCostCentre cc) $
    	 emit (bumpSccCount curCCS)

    pushCostCentre :: LocalReg -> CmmExpr -> CostCentre -> FCode ()
    pushCostCentre result ccs cc
      = emitRtsCallWithResult result AddrHint
    	rtsPackageId
    	(fsLit "PushCostCentre") [(ccs,AddrHint),
    				(CmmLit (mkCCostCentre cc), AddrHint)]
            False

    bumpSccCount :: CmmExpr -> CmmAGraph
    bumpSccCount ccs
      = addToMem REP_CostCentreStack_scc_count
    	 (cmmOffsetB ccs oFFSET_CostCentreStack_scc_count) 1

    -----------------------------------------------------------------------------
    --
    --		Lag/drag/void stuff
    --
    -----------------------------------------------------------------------------

    --
    -- Initial value for the LDV field in a static closure
    --
    staticLdvInit :: CmmLit
    staticLdvInit = zeroCLit

    --
    -- Initial value of the LDV field in a dynamic closure
    --
    dynLdvInit :: CmmExpr
    dynLdvInit =     -- (era << LDV_SHIFT) | LDV_STATE_CREATE
      CmmMachOp mo_wordOr [
          CmmMachOp mo_wordShl [loadEra, CmmLit (mkIntCLit lDV_SHIFT) ],
          CmmLit (mkWordCLit lDV_STATE_CREATE)
      ]

    --
    -- Initialise the LDV word of a new closure
    --
    ldvRecordCreate :: CmmExpr -> FCode ()
    ldvRecordCreate closure = emit $ mkStore (ldvWord closure) dynLdvInit

    --
    -- Called when a closure is entered, marks the closure as having been "used".
    -- The closure is not an 'inherently used' one.
    -- The closure is not IND or IND_OLDGEN because neither is considered for LDV
    -- profiling.
    --
    ldvEnterClosure :: ClosureInfo -> FCode ()
    ldvEnterClosure closure_info = ldvEnter (cmmOffsetB (CmmReg nodeReg) (-tag))
      where tag = funTag closure_info
            -- don't forget to substract node's tag

    ldvEnter :: CmmExpr -> FCode ()
    -- Argument is a closure pointer
    ldvEnter cl_ptr
      = ifProfiling $
         -- if (era > 0) {
         --    LDVW((c)) = (LDVW((c)) & LDV_CREATE_MASK) |
         --                era | LDV_STATE_USE }
        emit (mkCmmIfThenElse (CmmMachOp mo_wordUGt [loadEra, CmmLit zeroCLit])
    		(mkStore ldv_wd new_ldv_wd)
    		mkNop)
      where
            -- don't forget to substract node's tag
        ldv_wd = ldvWord cl_ptr
        new_ldv_wd = cmmOrWord (cmmAndWord (CmmLoad ldv_wd bWord)
    				       (CmmLit (mkWordCLit lDV_CREATE_MASK)))
    		 (cmmOrWord loadEra (CmmLit (mkWordCLit lDV_STATE_USE)))

    loadEra :: CmmExpr
    loadEra = CmmMachOp (MO_UU_Conv cIntWidth wordWidth)
    	  [CmmLoad (mkLblExpr (mkCmmDataLabel rtsPackageId (fsLit "era"))) cInt]

    ldvWord :: CmmExpr -> CmmExpr
    -- Takes the address of a closure, and returns
    -- the address of the LDV word in the closure
    ldvWord closure_ptr = cmmOffsetB closure_ptr oFFSET_StgHeader_ldvw

    -- LDV constants, from ghc/includes/Constants.h
    lDV_SHIFT :: Int
    lDV_SHIFT = LDV_SHIFT
    --lDV_STATE_MASK :: StgWord
    --lDV_STATE_MASK   = LDV_STATE_MASK
    lDV_CREATE_MASK :: StgWord
    lDV_CREATE_MASK  = LDV_CREATE_MASK
    --lDV_LAST_MASK :: StgWord
    --lDV_LAST_MASK    = LDV_LAST_MASK
    lDV_STATE_CREATE :: StgWord
    lDV_STATE_CREATE = LDV_STATE_CREATE
    lDV_STATE_USE :: StgWord
    lDV_STATE_USE    = LDV_STATE_USE