-----------------------------------------------------------------------------
--
-- Code generation for foreign calls.
--
-- (c) The University of Glasgow 2004-2006
--
-----------------------------------------------------------------------------

module StgCmmForeign (
  cgForeignCall, loadThreadState, saveThreadState,
  emitPrimCall, emitCCall,
  emitSaveThreadState, -- will be needed by the Cmm parser
  emitLoadThreadState, -- ditto
  emitOpenNursery,
 ) where

#include "HsVersions.h"

import StgSyn
import StgCmmProf
import StgCmmEnv
import StgCmmMonad
import StgCmmUtils
import StgCmmClosure

import BlockId
import Cmm
import CmmUtils
import MkZipCfgCmm hiding (CmmAGraph)
import Type
import TysPrim
import CLabel
import SMRep
import ForeignCall
import Constants
import StaticFlags
import Maybes
import Outputable
import ZipCfgCmmRep
import BasicTypes

import Control.Monad

-----------------------------------------------------------------------------
-- Code generation for Foreign Calls
-----------------------------------------------------------------------------

cgForeignCall :: [LocalReg]		-- r1,r2  where to put the results
	      -> [ForeignHint]
	      -> ForeignCall		-- the op
	      -> [StgArg]		-- x,y	  arguments
	      -> FCode ()
-- Emits code for an unsafe foreign call:      r1, r2 = foo( x, y, z )

cgForeignCall results result_hints (CCall (CCallSpec target cconv safety)) stg_args
  = do	{ cmm_args <- getFCallArgs stg_args
        ; let ((call_args, arg_hints), cmm_target)
                = case target of
                   StaticTarget lbl mPkgId 
		     -> let labelSource
				= case mPkgId of
					Nothing		-> ForeignLabelInThisPackage
					Just pkgId	-> ForeignLabelInPackage pkgId
			    size	= call_size cmm_args
			in  ( unzip cmm_args
			    , CmmLit (CmmLabel 
					(mkForeignLabel lbl size labelSource IsFunction)))
 
                   DynamicTarget    ->  case cmm_args of
                                           (fn,_):rest -> (unzip rest, fn)
                                           [] -> panic "cgForeignCall []"
              fc = ForeignConvention cconv arg_hints result_hints
              call_target = ForeignTarget cmm_target fc
        
        ; srt <- getSRTInfo NoSRT        -- SLPJ: Not sure what SRT 
                                        -- is right here
                                        -- JD: Does it matter in the new codegen?
        ; emitForeignCall safety results call_target call_args srt CmmMayReturn }
  where
	-- in the stdcall calling convention, the symbol needs @size appended
	-- to it, where size is the total number of bytes of arguments.  We
	-- attach this info to the CLabel here, and the CLabel pretty printer
	-- will generate the suffix when the label is printed.
      call_size args
	| StdCallConv <- cconv = Just (sum (map arg_size args))
	| otherwise            = Nothing

	-- ToDo: this might not be correct for 64-bit API
      arg_size (arg, _) = max (widthInBytes $ typeWidth $ cmmExprType arg) wORD_SIZE

emitCCall :: [(CmmFormal,ForeignHint)]
	  -> CmmExpr 
	  -> [(CmmActual,ForeignHint)]
	  -> FCode ()
emitCCall hinted_results fn hinted_args
  = emitForeignCall PlayRisky results target args
	            NoC_SRT -- No SRT b/c we PlayRisky
              	    CmmMayReturn
  where
    (args, arg_hints) = unzip hinted_args
    (results, result_hints) = unzip hinted_results
    target = ForeignTarget fn fc
    fc = ForeignConvention CCallConv arg_hints result_hints
    

emitPrimCall :: CmmFormals -> CallishMachOp -> CmmActuals -> FCode ()
emitPrimCall res op args
  = emitForeignCall PlayRisky res (PrimTarget op) args NoC_SRT CmmMayReturn

-- alternative entry point, used by CmmParse
emitForeignCall
	:: Safety
	-> CmmFormals		-- where to put the results
	-> MidCallTarget	-- the op
	-> CmmActuals		-- arguments
        -> C_SRT                -- the SRT of the calls continuation
        -> CmmReturnInfo	-- This can say "never returns"
				--   only RTS procedures do this
	-> FCode ()
emitForeignCall safety results target args _srt _ret
  | not (playSafe safety) = do
    let (caller_save, caller_load) = callerSaveVolatileRegs
    emit caller_save
    emit $ mkUnsafeCall target results args
    emit caller_load

  | otherwise = do
    updfr_off <- getUpdFrameOff
    temp_target <- load_target_into_temp target
    emit $ mkSafeCall temp_target results args updfr_off


{-
--	THINK ABOUT THIS (used to happen)
-- we might need to load arguments into temporaries before
-- making the call, because certain global registers might
-- overlap with registers that the C calling convention uses
-- for passing arguments.
--
-- This is a HACK; really it should be done in the back end, but
-- it's easier to generate the temporaries here.
load_args_into_temps = mapM arg_assign_temp
  where arg_assign_temp (e,hint) = do
	   tmp <- maybe_assign_temp e
	   return (tmp,hint)
-}
	
load_target_into_temp :: MidCallTarget -> FCode MidCallTarget
load_target_into_temp (ForeignTarget expr conv) = do 
  tmp <- maybe_assign_temp expr
  return (ForeignTarget tmp conv)
load_target_into_temp other_target@(PrimTarget _) =
  return other_target

maybe_assign_temp :: CmmExpr -> FCode CmmExpr
maybe_assign_temp e
  | hasNoGlobalRegs e = return e
  | otherwise         = do 
	-- don't use assignTemp, it uses its own notion of "trivial"
	-- expressions, which are wrong here.
        -- this is a NonPtr because it only duplicates an existing
	reg <- newTemp (cmmExprType e) --TODO FIXME NOW
	emit (mkAssign (CmmLocal reg) e)
	return (CmmReg (CmmLocal reg))

-- -----------------------------------------------------------------------------
-- Save/restore the thread state in the TSO

-- This stuff can't be done in suspendThread/resumeThread, because it
-- refers to global registers which aren't available in the C world.

saveThreadState :: CmmAGraph
saveThreadState =
  -- CurrentTSO->sp = Sp;
  mkStore (cmmOffset stgCurrentTSO tso_SP) stgSp
  <*> closeNursery
  -- and save the current cost centre stack in the TSO when profiling:
  <*> if opt_SccProfilingOn then
	mkStore (cmmOffset stgCurrentTSO tso_CCCS) curCCS
      else mkNop

emitSaveThreadState :: BlockId -> FCode ()
emitSaveThreadState bid = do
  -- CurrentTSO->sp = Sp;
  emit $ mkStore (cmmOffset stgCurrentTSO tso_SP)
                 (CmmStackSlot (CallArea (Young bid)) (widthInBytes (typeWidth gcWord)))
  emit closeNursery
  -- and save the current cost centre stack in the TSO when profiling:
  when opt_SccProfilingOn $
	emit (mkStore (cmmOffset stgCurrentTSO tso_CCCS) curCCS)

   -- CurrentNursery->free = Hp+1;
closeNursery :: CmmAGraph
closeNursery = mkStore nursery_bdescr_free (cmmOffsetW stgHp 1)

loadThreadState :: LocalReg -> CmmAGraph
loadThreadState tso = do
  -- tso <- newTemp gcWord -- TODO FIXME NOW
  catAGraphs [
	-- tso = CurrentTSO;
  	mkAssign (CmmLocal tso) stgCurrentTSO,
	-- Sp = tso->sp;
	mkAssign sp (CmmLoad (cmmOffset (CmmReg (CmmLocal tso)) tso_SP)
	                      bWord),
	-- SpLim = tso->stack + RESERVED_STACK_WORDS;
	mkAssign spLim (cmmOffsetW (cmmOffset (CmmReg (CmmLocal tso)) tso_STACK)
			            rESERVED_STACK_WORDS),
        openNursery,
        -- and load the current cost centre stack from the TSO when profiling:
        if opt_SccProfilingOn then
	  mkStore curCCSAddr
                  (CmmLoad (cmmOffset (CmmReg (CmmLocal tso)) tso_CCCS) ccsType)
        else mkNop]
emitLoadThreadState :: LocalReg -> FCode ()
emitLoadThreadState tso = emit $ loadThreadState tso

openNursery :: CmmAGraph
openNursery = catAGraphs [
        -- Hp = CurrentNursery->free - 1;
	mkAssign hp (cmmOffsetW (CmmLoad nursery_bdescr_free bWord) (-1)),

        -- HpLim = CurrentNursery->start + 
	--		CurrentNursery->blocks*BLOCK_SIZE_W - 1;
	mkAssign hpLim
	    (cmmOffsetExpr
		(CmmLoad nursery_bdescr_start bWord)
		(cmmOffset
		  (CmmMachOp mo_wordMul [
		    CmmMachOp (MO_SS_Conv W32 wordWidth)
		      [CmmLoad nursery_bdescr_blocks b32],
		    CmmLit (mkIntCLit bLOCK_SIZE)
		   ])
		  (-1)
		)
	    )
   ]
emitOpenNursery :: FCode ()
emitOpenNursery = emit openNursery

nursery_bdescr_free, nursery_bdescr_start, nursery_bdescr_blocks :: CmmExpr
nursery_bdescr_free   = cmmOffset stgCurrentNursery oFFSET_bdescr_free
nursery_bdescr_start  = cmmOffset stgCurrentNursery oFFSET_bdescr_start
nursery_bdescr_blocks = cmmOffset stgCurrentNursery oFFSET_bdescr_blocks

tso_SP, tso_STACK, tso_CCCS :: ByteOff
tso_SP    = tsoFieldB     oFFSET_StgTSO_sp
tso_STACK = tsoFieldB     oFFSET_StgTSO_stack
tso_CCCS  = tsoProfFieldB oFFSET_StgTSO_CCCS

-- The TSO struct has a variable header, and an optional StgTSOProfInfo in
-- the middle.  The fields we're interested in are after the StgTSOProfInfo.
tsoFieldB :: ByteOff -> ByteOff
tsoFieldB off
  | opt_SccProfilingOn = off + sIZEOF_StgTSOProfInfo + fixedHdrSize * wORD_SIZE
  | otherwise          = off + fixedHdrSize * wORD_SIZE

tsoProfFieldB :: ByteOff -> ByteOff
tsoProfFieldB off = off + fixedHdrSize * wORD_SIZE

stgSp, stgHp, stgCurrentTSO, stgCurrentNursery :: CmmExpr
stgSp		  = CmmReg sp
stgHp		  = CmmReg hp
stgCurrentTSO	  = CmmReg currentTSO
stgCurrentNursery = CmmReg currentNursery

sp, spLim, hp, hpLim, currentTSO, currentNursery :: CmmReg
sp		  = CmmGlobal Sp
spLim		  = CmmGlobal SpLim
hp		  = CmmGlobal Hp
hpLim		  = CmmGlobal HpLim
currentTSO	  = CmmGlobal CurrentTSO
currentNursery 	  = CmmGlobal CurrentNursery

-- -----------------------------------------------------------------------------
-- For certain types passed to foreign calls, we adjust the actual
-- value passed to the call.  For ByteArray#/Array# we pass the
-- address of the actual array, not the address of the heap object.

getFCallArgs :: [StgArg] -> FCode [(CmmExpr, ForeignHint)]
-- (a) Drop void args
-- (b) Add foreign-call shim code
-- It's (b) that makes this differ from getNonVoidArgAmodes

getFCallArgs args
  = do	{ mb_cmms <- mapM get args
	; return (catMaybes mb_cmms) }
  where
    get arg | isVoidRep arg_rep 
	    = return Nothing
	    | otherwise
	    = do { cmm <- getArgAmode (NonVoid arg)
		 ; return (Just (add_shim arg_ty cmm, hint)) }
	    where
	      arg_ty  = stgArgType arg
	      arg_rep = typePrimRep arg_ty
	      hint    = typeForeignHint arg_ty

add_shim :: Type -> CmmExpr -> CmmExpr
add_shim arg_ty expr
  | tycon == arrayPrimTyCon || tycon == mutableArrayPrimTyCon
  = cmmOffsetB expr arrPtrsHdrSize

  | tycon == byteArrayPrimTyCon || tycon == mutableByteArrayPrimTyCon
  = cmmOffsetB expr arrWordsHdrSize

  | otherwise = expr
  where	
    tycon = tyConAppTyCon (repType arg_ty)
	-- should be a tycon app, since this is a foreign call
