ghci/ByteCodeItbls.hs

    {-# LANGUAGE CPP, MagicHash, ScopedTypeVariables #-}
    {-# OPTIONS_GHC -optc-DNON_POSIX_SOURCE #-}
    --
    --  (c) The University of Glasgow 2002-2006
    --

    -- | ByteCodeItbls: Generate infotables for interpreter-made bytecodes
    module ByteCodeItbls ( mkITbls ) where

    #include "HsVersions.h"

    import ByteCodeTypes
    import GHCi
    import DynFlags
    import HscTypes
    import Name             ( Name, getName )
    import NameEnv
    import DataCon          ( DataCon, dataConRepArgTys, dataConIdentity )
    import TyCon            ( TyCon, tyConFamilySize, isDataTyCon, tyConDataCons )
    import RepType
    import StgCmmLayout     ( mkVirtConstrSizes )
    import StgCmmClosure    ( tagForCon, NonVoid (..) )
    import Util
    import Panic

    {-
      Manufacturing of info tables for DataCons
    -}

    -- Make info tables for the data decls in this module
    mkITbls :: HscEnv -> [TyCon] -> IO ItblEnv
    mkITbls hsc_env tcs =
      foldr plusNameEnv emptyNameEnv <$>
        mapM (mkITbl hsc_env) (filter isDataTyCon tcs)
     where
      mkITbl :: HscEnv -> TyCon -> IO ItblEnv
      mkITbl hsc_env tc
        | dcs `lengthIs` n -- paranoia; this is an assertion.
        = make_constr_itbls hsc_env dcs
           where
              dcs = tyConDataCons tc
              n   = tyConFamilySize tc
      mkITbl _ _ = panic "mkITbl"

    mkItblEnv :: [(Name,ItblPtr)] -> ItblEnv
    mkItblEnv pairs = mkNameEnv [(n, (n,p)) | (n,p) <- pairs]

    -- Assumes constructors are numbered from zero, not one
    make_constr_itbls :: HscEnv -> [DataCon] -> IO ItblEnv
    make_constr_itbls hsc_env cons =
      mkItblEnv <$> mapM (uncurry mk_itbl) (zip cons [0..])
     where
      dflags = hsc_dflags hsc_env

      mk_itbl :: DataCon -> Int -> IO (Name,ItblPtr)
      mk_itbl dcon conNo = do
         let rep_args = [ NonVoid prim_rep
                        | arg <- dataConRepArgTys dcon
                        , prim_rep <- typePrimRep arg ]

             (tot_wds, ptr_wds) =
                 mkVirtConstrSizes dflags rep_args

             ptrs'  = ptr_wds
             nptrs' = tot_wds - ptr_wds
             nptrs_really
                | ptrs' + nptrs' >= mIN_PAYLOAD_SIZE dflags = nptrs'
                | otherwise = mIN_PAYLOAD_SIZE dflags - ptrs'

             descr = dataConIdentity dcon

         r <- iservCmd hsc_env (MkConInfoTable ptrs' nptrs_really
                                  conNo (tagForCon dflags dcon) descr)
         return (getName dcon, ItblPtr r)