{-# LANGUAGE CPP #-}
{-# LANGUAGE DataKinds #-}

-----------------------------------------------------------------------------
--
-- Stg to C-- code generation
--
-- (c) The University of Glasgow 2004-2006
--
-----------------------------------------------------------------------------

module GHC.StgToCmm ( codeGen ) where

#include "HsVersions.h"

import GhcPrelude as Prelude

import GHC.StgToCmm.Prof (initCostCentres, ldvEnter)
import GHC.StgToCmm.Monad
import GHC.StgToCmm.Env
import GHC.StgToCmm.Bind
import GHC.StgToCmm.DataCon
import GHC.StgToCmm.Layout
import GHC.StgToCmm.Utils
import GHC.StgToCmm.Closure
import GHC.StgToCmm.Hpc
import GHC.StgToCmm.Ticky

import GHC.Cmm
import GHC.Cmm.CLabel

import GHC.Stg.Syntax
import DynFlags
import ErrUtils

import HscTypes
import CostCentre
import Id
import IdInfo
import GHC.Types.RepType
import DataCon
import TyCon
import Module
import Outputable
import Stream
import BasicTypes
import VarSet ( isEmptyDVarSet )

import OrdList
import GHC.Cmm.Graph

import Data.IORef
import Control.Monad (when,void)
import Util

codeGen :: DynFlags
        -> Module
        -> [TyCon]
        -> CollectedCCs                -- (Local/global) cost-centres needing declaring/registering.
        -> [CgStgTopBinding]           -- Bindings to convert
        -> HpcInfo
        -> Stream IO CmmGroup ()       -- Output as a stream, so codegen can
                                       -- be interleaved with output

codeGen dflags this_mod data_tycons
        cost_centre_info stg_binds hpc_info
  = do  {     -- cg: run the code generator, and yield the resulting CmmGroup
              -- Using an IORef to store the state is a bit crude, but otherwise
              -- we would need to add a state monad layer.
        ; cgref <- liftIO $ newIORef =<< initC
        ; let cg :: FCode () -> Stream IO CmmGroup ()
              cg fcode = do
                cmm <- liftIO . withTimingSilent dflags (text "STG -> Cmm") (`seq` ()) $ do
                         st <- readIORef cgref
                         let (a,st') = runC dflags this_mod st (getCmm fcode)

                         -- NB. stub-out cgs_tops and cgs_stmts.  This fixes
                         -- a big space leak.  DO NOT REMOVE!
                         writeIORef cgref $! st'{ cgs_tops = nilOL,
                                                  cgs_stmts = mkNop }
                         return a
                yield cmm

               -- Note [codegen-split-init] the cmm_init block must come
               -- FIRST.  This is because when -split-objs is on we need to
               -- combine this block with its initialisation routines; see
               -- Note [pipeline-split-init].
        ; cg (mkModuleInit cost_centre_info this_mod hpc_info)

        ; mapM_ (cg . cgTopBinding dflags) stg_binds

                -- 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
        ; let do_tycon tycon = do
                -- Generate a table of static closures for an
                -- enumeration type Note that the closure pointers are
                -- tagged.
                 when (isEnumerationTyCon tycon) $ cg (cgEnumerationTyCon tycon)
                 mapM_ (cg . cgDataCon) (tyConDataCons tycon)

        ; mapM_ do_tycon data_tycons
        }

---------------------------------------------------------------
--      Top-level 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. -}

cgTopBinding :: DynFlags -> CgStgTopBinding -> FCode ()
cgTopBinding dflags (StgTopLifted (StgNonRec id rhs))
  = do  { let (info, fcode) = cgTopRhs dflags NonRecursive id rhs
        ; fcode
        ; addBindC info
        }

cgTopBinding dflags (StgTopLifted (StgRec pairs))
  = do  { let (bndrs, rhss) = unzip pairs
        ; let pairs' = zip bndrs rhss
              r = unzipWith (cgTopRhs dflags Recursive) pairs'
              (infos, fcodes) = unzip r
        ; addBindsC infos
        ; sequence_ fcodes
        }

cgTopBinding dflags (StgTopStringLit id str)
  = do  { let label = mkBytesLabel (idName id)
        ; let (lit, decl) = mkByteStringCLit label str
        ; emitDecl decl
        ; addBindC (litIdInfo dflags id mkLFStringLit lit)
        }

cgTopRhs :: DynFlags -> RecFlag -> Id -> CgStgRhs -> (CgIdInfo, FCode ())
        -- The Id is passed along for setting up a binding...

cgTopRhs dflags _rec bndr (StgRhsCon _cc con args)
  = cgTopRhsCon dflags bndr con (assertNonVoidStgArgs args)
      -- con args are always non-void,
      -- see Note [Post-unarisation invariants] in GHC.Stg.Unarise

cgTopRhs dflags rec bndr (StgRhsClosure fvs cc upd_flag args body)
  = ASSERT(isEmptyDVarSet fvs)    -- There should be no free variables
    cgTopRhsClosure dflags rec bndr cc upd_flag args body


---------------------------------------------------------------
--      Module initialisation code
---------------------------------------------------------------

mkModuleInit
        :: CollectedCCs         -- cost centre info
        -> Module
        -> HpcInfo
        -> FCode ()

mkModuleInit cost_centre_info this_mod hpc_info
  = do  { initHpc this_mod hpc_info
        ; initCostCentres cost_centre_info
        }


---------------------------------------------------------------
--      Generating static stuff for algebraic data types
---------------------------------------------------------------


cgEnumerationTyCon :: TyCon -> FCode ()
cgEnumerationTyCon tycon
  = do dflags <- getDynFlags
       emitRawRODataLits (mkLocalClosureTableLabel (tyConName tycon) NoCafRefs)
             [ CmmLabelOff (mkLocalClosureLabel (dataConName con) NoCafRefs)
                           (tagForCon dflags con)
             | con <- tyConDataCons tycon]


cgDataCon :: DataCon -> FCode ()
-- Generate the entry code, info tables, and (for niladic constructor)
-- the static closure, for a constructor.
cgDataCon data_con
  = do  { dflags <- getDynFlags
        ; let
            (tot_wds, --  #ptr_wds + #nonptr_wds
             ptr_wds) --  #ptr_wds
              = mkVirtConstrSizes dflags arg_reps

            nonptr_wds   = tot_wds - ptr_wds

            dyn_info_tbl =
              mkDataConInfoTable dflags data_con False ptr_wds nonptr_wds

            -- We're generating info tables, so we don't know and care about
            -- what the actual arguments are. Using () here as the place holder.
            arg_reps :: [NonVoid PrimRep]
            arg_reps = [ NonVoid rep_ty
                       | ty <- dataConRepArgTys data_con
                       , rep_ty <- typePrimRep ty
                       , not (isVoidRep rep_ty) ]

        ; emitClosureAndInfoTable dyn_info_tbl NativeDirectCall [] $
            -- NB: the closure pointer is assumed *untagged* on
            -- entry to a constructor.  If the pointer is tagged,
            -- then we should not be entering it.  This assumption
            -- is used in ldvEnter and when tagging the pointer to
            -- return it.
            -- NB 2: We don't set CC when entering data (WDP 94/06)
            do { tickyEnterDynCon
               ; ldvEnter (CmmReg nodeReg)
               ; tickyReturnOldCon (length arg_reps)
               ; void $ emitReturn [cmmOffsetB dflags (CmmReg nodeReg) (tagForCon dflags data_con)]
               }
                    -- The case continuation code expects a tagged pointer
        }
