codeGen/StgCmm.hs

    {-# LANGUAGE CPP #-}

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

    module StgCmm ( codeGen ) where

    #include "HsVersions.h"

    import StgCmmProf (initCostCentres, ldvEnter)
    import StgCmmMonad
    import StgCmmEnv
    import StgCmmBind
    import StgCmmCon
    import StgCmmLayout
    import StgCmmUtils
    import StgCmmClosure
    import StgCmmHpc
    import StgCmmTicky

    import Cmm
    import CmmUtils
    import CLabel

    import StgSyn
    import DynFlags

    import HscTypes
    import CostCentre
    import Id
    import IdInfo
    import RepType
    import DataCon
    import Name
    import TyCon
    import Module
    import Outputable
    import Stream
    import BasicTypes

    import OrdList
    import MkGraph

    import qualified Data.ByteString as BS
    import Data.IORef
    import Control.Monad (when,void)
    import Util

    codeGen :: DynFlags
            -> Module
            -> [TyCon]
            -> CollectedCCs                -- (Local/global) cost-centres needing declaring/registering.
            -> [StgTopBinding]             -- 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 $ 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 -> StgTopBinding -> FCode ()
    cgTopBinding dflags (StgTopLifted (StgNonRec id rhs))
      = do  { id' <- maybeExternaliseId dflags id
            ; let (info, fcode) = cgTopRhs dflags NonRecursive id' rhs
            ; fcode
            ; addBindC info -- Add the *un-externalised* Id to the envt,
                            -- so we find it when we look up occurrences
            }

    cgTopBinding dflags (StgTopLifted (StgRec pairs))
      = do  { let (bndrs, rhss) = unzip pairs
            ; bndrs' <- Prelude.mapM (maybeExternaliseId dflags) bndrs
            ; 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  { id' <- maybeExternaliseId dflags id
            ; let label = mkBytesLabel (idName id')
            ; let (lit, decl) = mkByteStringCLit label (BS.unpack str)
            ; emitDecl decl
            ; addBindC (litIdInfo dflags id' mkLFStringLit lit)
            }

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

    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 UnariseStg

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

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

    {- The module initialisation code looks like this, roughly:

            FN(__stginit_Foo) {
              JMP_(__stginit_Foo_1_p)
            }

            FN(__stginit_Foo_1_p) {
            ...
            }

       We have one version of the init code with a module version and the
       'way' attached to it.  The version number helps to catch cases
       where modules are not compiled in dependency order before being
       linked: if a module has been compiled since any modules which depend on
       it, then the latter modules will refer to a different version in their
       init blocks and a link error will ensue.

       The 'way' suffix helps to catch cases where modules compiled in different
       ways are linked together (eg. profiled and non-profiled).

       We provide a plain, unadorned, version of the module init code
       which just jumps to the version with the label and way attached.  The
       reason for this is that when using foreign exports, the caller of
       startupHaskell() must supply the name of the init function for the "top"
       module in the program, and we don't want to require that this name
       has the version and way info appended to it.

    We initialise the module tree by keeping a work-stack,
            * pointed to by Sp
            * that grows downward
            * Sp points to the last occupied slot
    -}

    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
                -- For backwards compatibility: user code may refer to this
                -- label for calling hs_add_root().
            ; let lbl = mkPlainModuleInitLabel this_mod
            ; emitDecl (CmmData (Section Data lbl) (Statics lbl []))
            }

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

    cgEnumerationTyCon :: TyCon -> FCode ()
    cgEnumerationTyCon tycon
      = do dflags <- getDynFlags
           emitRODataLits (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
            }

    ---------------------------------------------------------------
    --      Stuff to support splitting
    ---------------------------------------------------------------

    maybeExternaliseId :: DynFlags -> Id -> FCode Id
    maybeExternaliseId dflags id
      | gopt Opt_SplitObjs dflags,  -- See Note [Externalise when splitting]
                                    -- in StgCmmMonad
        isInternalName name = do { mod <- getModuleName
                                 ; returnFC (setIdName id (externalise mod)) }
      | otherwise           = returnFC id
      where
        externalise mod = mkExternalName uniq mod new_occ loc
        name    = idName id
        uniq    = nameUnique name
        new_occ = mkLocalOcc uniq (nameOccName name)
        loc     = nameSrcSpan 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.