%
% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
\section[CodeGen]{@CodeGen@: main module of the code generator}

This module says how things get going at the top level.

@codeGen@ is the interface to the outside world.  The \tr{cgTop*}
functions drive the mangling of top-level bindings.

%************************************************************************
%*									*
\subsection[codeGen-outside-interface]{The code generator's offering to the world}
%*									*
%************************************************************************

\begin{code}
module CodeGen ( codeGen ) where

#include "HsVersions.h"

-- Kludge (??) so that CgExpr is reached via at least one non-SOURCE
-- import.  Before, that wasn't the case, and CM therefore didn't 
-- bother to compile it.
import CgExpr           ( {-NOTHING!-} )	-- DO NOT DELETE THIS IMPORT

import DriverState	( v_Build_tag )
import StgSyn
import CgMonad
import AbsCSyn
import PrelNames	( gHC_PRIM )
import CLabel		( mkSRTLabel, mkClosureLabel, 
			  mkPlainModuleInitLabel, mkModuleInitLabel )
import PprAbsC		( dumpRealC )
import AbsCUtils	( mkAbstractCs, flattenAbsC )
import CgBindery	( CgIdInfo, addBindC, addBindsC, getCAddrModeAndInfo )
import CgClosure	( cgTopRhsClosure )
import CgCon		( cgTopRhsCon )
import CgConTbls	( genStaticConBits )
import ClosureInfo	( mkClosureLFInfo )
import CmdLineOpts	( DynFlags, DynFlag(..),
			  opt_SccProfilingOn, opt_EnsureSplittableC )
import HscTypes		( ForeignStubs(..), TypeEnv, typeEnvTyCons )
import CostCentre       ( CollectedCCs )
import Id               ( Id, idName, setIdName )
import Name		( nameSrcLoc, nameOccName, nameUnique, isInternalName, mkExternalName )
import OccName		( mkLocalOcc )
import PrimRep		( PrimRep(..) )
import TyCon            ( isDataTyCon )
import Module		( Module )
import BasicTypes	( TopLevelFlag(..) )
import UniqSupply	( mkSplitUniqSupply )
import ErrUtils		( dumpIfSet_dyn, showPass )
import Panic		( assertPanic )

#ifdef DEBUG
import Outputable
#endif

import DATA_IOREF	( readIORef )
\end{code}

\begin{code}
codeGen :: DynFlags
	-> Module
	-> TypeEnv
	-> ForeignStubs
	-> [Module]		-- directly-imported modules
	-> CollectedCCs		-- (Local/global) cost-centres needing declaring/registering.
	-> [(StgBinding,[(Id,[Id])])]	-- Bindings to convert, with SRTs
	-> IO AbstractC		-- Output

codeGen dflags this_mod type_env foreign_stubs imported_mods 
	cost_centre_info stg_binds
  = do	
	showPass dflags "CodeGen"
	fl_uniqs <- mkSplitUniqSupply 'f'
	way <- readIORef v_Build_tag

	let
	    tycons	   = typeEnvTyCons type_env
	    data_tycons    = filter isDataTyCon tycons

	mapM_ (\x -> seq x (return ())) data_tycons

	let

	    cinfo          = MkCompInfo this_mod

	    datatype_stuff = genStaticConBits cinfo data_tycons
	    code_stuff     = initC cinfo (mapCs cgTopBinding stg_binds)
	    init_stuff     = mkModuleInit way cost_centre_info this_mod
				foreign_stubs imported_mods

	    abstractC = mkAbstractCs [ maybeSplitCode,
				       init_stuff, 
				       code_stuff,
				       datatype_stuff]
		-- Put datatype_stuff after code_stuff, because the
		-- datatype closure table (for enumeration types) to
		-- (say) PrelBase_True_closure, which is defined in
		-- code_stuff

	dumpIfSet_dyn dflags Opt_D_dump_absC "Abstract C" (dumpRealC abstractC)

	return $! flattenAbsC fl_uniqs abstractC
\end{code}

%************************************************************************
%*									*
\subsection[codegen-init]{Module initialisation code}
%*									*
%************************************************************************

\begin{code}
mkModuleInit 
	:: String		-- the "way"
	-> CollectedCCs         -- cost centre info
	-> Module
	-> ForeignStubs
	-> [Module]
	-> AbstractC
mkModuleInit way cost_centre_info this_mod foreign_stubs imported_mods
  = let
	(cc_decls, cc_regs) = mkCostCentreStuff cost_centre_info

	register_foreign_exports 
		= case foreign_stubs of
			NoStubs			    -> []
			ForeignStubs _ _ _ fe_bndrs -> map mk_export_register fe_bndrs

	mk_export_register bndr
	  = CMacroStmt REGISTER_FOREIGN_EXPORT [lbl]
	  where
	    lbl = CLbl (mkClosureLabel (idName bndr)) PtrRep
		-- we don't want/need to init GHC.Prim, so filter it out

	mk_import_register mod
	    | mod == gHC_PRIM = AbsCNop
	    | otherwise	      = CMacroStmt REGISTER_IMPORT [
				   CLbl (mkModuleInitLabel mod way) AddrRep
				]

	register_mod_imports = map mk_import_register imported_mods
    in
    mkAbstractCs [
	cc_decls,
        CModuleInitBlock (mkPlainModuleInitLabel this_mod)
			 (mkModuleInitLabel this_mod way)
		         (mkAbstractCs (register_foreign_exports ++
				        cc_regs :
				        register_mod_imports))
    ]
\end{code}

Cost-centre profiling: Besides the usual stuff, we must produce
declarations for the cost-centres defined in this module;

(The local cost-centres involved in this are passed into the
code-generator.)

\begin{code}
mkCostCentreStuff (local_CCs, extern_CCs, singleton_CCSs)
  | not opt_SccProfilingOn = (AbsCNop, AbsCNop)
  | otherwise = 
	( mkAbstractCs (
		map (CCostCentreDecl True)   local_CCs ++
		map (CCostCentreDecl False)  extern_CCs ++
		map CCostCentreStackDecl     singleton_CCSs),
  	  mkAbstractCs (mkCcRegister local_CCs singleton_CCSs)
	)
  where
    mkCcRegister ccs cc_stacks
      = let
	    register_ccs       = mkAbstractCs (map mk_register ccs)
	    register_cc_stacks = mkAbstractCs (map mk_register_ccs cc_stacks)
	in
	[ register_ccs, register_cc_stacks ]
      where
	mk_register cc
	  = CCallProfCCMacro FSLIT("REGISTER_CC") [mkCCostCentre cc]

	mk_register_ccs ccs
	  = CCallProfCCMacro FSLIT("REGISTER_CCS") [mkCCostCentreStack ccs]
\end{code}

%************************************************************************
%*									*
\subsection[codegen-top-bindings]{Converting top-level STG bindings}
%*									*
%************************************************************************

@cgTopBinding@ is only used for top-level bindings, since they need
to be allocated statically (not in the heap) and need to be labelled.
No unboxed bindings can happen at top level.

In the code below, the static bindings are accumulated in the
@MkCgState@, and transferred into the ``statics'' slot by @forkStatics@.
This is so that we can write the top level processing in a compositional
style, with the increasing static environment being plumbed as a state
variable.

\begin{code}
cgTopBinding :: (StgBinding,[(Id,[Id])]) -> Code
cgTopBinding (StgNonRec id rhs, srts)
  = absC maybeSplitCode	  	`thenC`
    maybeExternaliseId id	`thenFC` \ id' ->
    mapM_ (mkSRT [id']) srts	`thenC`
    cgTopRhs id' rhs 	  	`thenFC` \ (id, info) ->
    addBindC id info		`thenC`
	-- Add the un-externalised Id to the envt, so we
	-- find it when we look up occurrences
    nopC

cgTopBinding (StgRec pairs, srts)
  = absC maybeSplitCode		  	`thenC`
    let
        (bndrs, rhss) = unzip pairs
    in
    mapFCs maybeExternaliseId bndrs	`thenFC` \ bndrs' ->
    let
	pairs' = zip bndrs' rhss
    in
    mapM_ (mkSRT bndrs')  srts		`thenC`
    fixC (\ new_binds -> 
		addBindsC new_binds		`thenC`
		mapFCs ( \ (b,e) -> cgTopRhs b e ) pairs'
     )  `thenFC` \ new_binds -> 
     nopC

mkSRT :: [Id] -> (Id,[Id]) -> Code
mkSRT these (id,[])  = nopC
mkSRT these (id,ids)
  = mapFCs remap ids `thenFC` \ ids ->
    remap id	     `thenFC` \ id ->
    absC (CSRT (mkSRTLabel (idName id)) (map (mkClosureLabel . idName) ids))
  where
	-- sigh, better map all the ids against the environment in case they've
	-- been externalised (see maybeExternaliseId below).
    remap id = case filter (==id) these of
		[] ->  getCAddrModeAndInfo id 
				`thenFC` \ (id, _, _) -> returnFC id
		(id':_) -> returnFC id'

-- Urgh!  I tried moving the forkStatics call from the rhss of cgTopRhs
-- to enclose the listFCs in cgTopBinding, but that tickled the
-- statics "error" call in initC.  I DON'T UNDERSTAND WHY!

cgTopRhs :: Id -> StgRhs -> FCode (Id, CgIdInfo)
	-- The Id is passed along for setting up a binding...
	-- It's already been externalised if necessary

cgTopRhs bndr (StgRhsCon cc con args)
  = forkStatics (cgTopRhsCon bndr con args)

cgTopRhs bndr (StgRhsClosure cc bi fvs upd_flag srt args body)
  = ASSERT(null fvs)    -- There should be no free variables
    let 
	srt_label = mkSRTLabel (idName bndr)
	lf_info = mkClosureLFInfo bndr TopLevel [{-no fvs-}] upd_flag args
    in
    setSRTLabel srt_label $ 
      forkStatics (cgTopRhsClosure bndr cc bi srt args body lf_info)
\end{code}


%************************************************************************
%*									*
\subsection{Stuff to support splitting}
%*									*
%************************************************************************

If we're splitting the object, we need to externalise all the top-level names
(and then make sure we only use the externalised one in any C label we use
which refers to this name).

\begin{code}
maybeExternaliseId :: Id -> FCode Id
maybeExternaliseId id
  | opt_EnsureSplittableC, 	-- Externalise the name for -split-objs
    isInternalName name
  = moduleName				 `thenFC` \ mod ->
    returnFC (setIdName id (mkExternalName uniq mod new_occ (nameSrcLoc name)))
  | otherwise		
  = returnFC id
  where
    name       = idName id
    uniq       = nameUnique name
    new_occ    = mkLocalOcc uniq (nameOccName name)
	-- We want to conjure up a name that can't clash with any
	-- existing name.  So we generate
	--	Mod_$L243foo
	-- where 243 is the unique.

maybeSplitCode
  | opt_EnsureSplittableC = CSplitMarker 
  | otherwise             = AbsCNop
\end{code}