/compiler/codeGen/StgCmmExtCode.hs

-- | Our extended FCode monad.

-- We add a mapping from names to CmmExpr, to support local variable names in
-- the concrete C-- code.  The unique supply of the underlying FCode monad
-- is used to grab a new unique for each local variable.

-- In C--, a local variable can be declared anywhere within a proc,
-- and it scopes from the beginning of the proc to the end.  Hence, we have
-- to collect declarations as we parse the proc, and feed the environment
-- back in circularly (to avoid a two-pass algorithm).

module StgCmmExtCode (
        CmmParse, unEC,
        Named(..), Env,
        
        loopDecls,
        getEnv,

        newLocal,
        newLabel,
        newBlockId,
        newFunctionName,
        newImport,
        lookupLabel,
        lookupName,

        code,
        emit, emitLabel, emitAssign, emitStore,
        getCode, getCodeR,
        emitOutOfLine,
        withUpdFrameOff, getUpdFrameOff
)

where

import qualified StgCmmMonad as F
import StgCmmMonad (FCode, newUnique)

import Cmm
import CLabel
import MkGraph

-- import BasicTypes
import BlockId
import DynFlags
import FastString
import Module
import UniqFM
import Unique


-- | The environment contains variable definitions or blockids.
data Named      
        = VarN CmmExpr          -- ^ Holds CmmLit(CmmLabel ..) which gives the label type,
                                --      eg, RtsLabel, ForeignLabel, CmmLabel etc. 

        | FunN   PackageId      -- ^ A function name from this package
        | LabelN BlockId                -- ^ A blockid of some code or data.
        
-- | An environment of named things.
type Env        = UniqFM Named

-- | Local declarations that are in scope during code generation.
type Decls      = [(FastString,Named)]

-- | Does a computation in the FCode monad, with a current environment
--      and a list of local declarations. Returns the resulting list of declarations.
newtype CmmParse a      
        = EC { unEC :: Env -> Decls -> FCode (Decls, a) }

type ExtCode = CmmParse ()

returnExtFC :: a -> CmmParse a
returnExtFC a   = EC $ \_ s -> return (s, a)

thenExtFC :: CmmParse a -> (a -> CmmParse b) -> CmmParse b
thenExtFC (EC m) k = EC $ \e s -> do (s',r) <- m e s; unEC (k r) e s'

instance Monad CmmParse where
  (>>=) = thenExtFC
  return = returnExtFC

instance HasDynFlags CmmParse where
    getDynFlags = EC (\_ d -> do dflags <- getDynFlags
                                 return (d, dflags))


-- | Takes the variable decarations and imports from the monad
--      and makes an environment, which is looped back into the computation.  
--      In this way, we can have embedded declarations that scope over the whole
--      procedure, and imports that scope over the entire module.
--      Discards the local declaration contained within decl'
--
loopDecls :: CmmParse a -> CmmParse a
loopDecls (EC fcode) =
      EC $ \e globalDecls -> do
        (_, a) <- F.fixC (\ ~(decls, _) -> fcode (addListToUFM e decls) globalDecls)
        return (globalDecls, a)


-- | Get the current environment from the monad.
getEnv :: CmmParse Env
getEnv  = EC $ \e s -> return (s, e)


addDecl :: FastString -> Named -> ExtCode
addDecl name named = EC $ \_ s -> return ((name, named) : s, ())


-- | Add a new variable to the list of local declarations. 
--      The CmmExpr says where the value is stored. 
addVarDecl :: FastString -> CmmExpr -> ExtCode
addVarDecl var expr = addDecl var (VarN expr)

-- | Add a new label to the list of local declarations.
addLabel :: FastString -> BlockId -> ExtCode
addLabel name block_id = addDecl name (LabelN block_id)


-- | Create a fresh local variable of a given type.
newLocal 
        :: CmmType              -- ^ data type
        -> FastString           -- ^ name of variable
        -> CmmParse LocalReg    -- ^ register holding the value
        
newLocal ty name = do
   u <- code newUnique
   let reg = LocalReg u ty
   addVarDecl name (CmmReg (CmmLocal reg))
   return reg


-- | Allocate a fresh label.
newLabel :: FastString -> CmmParse BlockId
newLabel name = do
   u <- code newUnique
   addLabel name (mkBlockId u)
   return (mkBlockId u)

newBlockId :: CmmParse BlockId
newBlockId = code F.newLabelC

-- | Add add a local function to the environment.
newFunctionName 
        :: FastString   -- ^ name of the function 
        -> PackageId    -- ^ package of the current module
        -> ExtCode
        
newFunctionName name pkg = addDecl name (FunN pkg)
        
        
-- | Add an imported foreign label to the list of local declarations.
--      If this is done at the start of the module the declaration will scope
--      over the whole module.
newImport 
        :: (FastString, CLabel) 
        -> CmmParse ()

newImport (name, cmmLabel) 
   = addVarDecl name (CmmLit (CmmLabel cmmLabel))


-- | Lookup the BlockId bound to the label with this name.
--      If one hasn't been bound yet, create a fresh one based on the 
--      Unique of the name.
lookupLabel :: FastString -> CmmParse BlockId
lookupLabel name = do
  env <- getEnv
  return $ 
     case lookupUFM env name of
        Just (LabelN l) -> l
        _other          -> mkBlockId (newTagUnique (getUnique name) 'L')


-- | Lookup the location of a named variable.
--      Unknown names are treated as if they had been 'import'ed from the runtime system.
--      This saves us a lot of bother in the RTS sources, at the expense of
--      deferring some errors to link time.
lookupName :: FastString -> CmmParse CmmExpr
lookupName name = do
  env    <- getEnv
  return $ 
     case lookupUFM env name of
        Just (VarN e)   -> e
        Just (FunN pkg) -> CmmLit (CmmLabel (mkCmmCodeLabel pkg          name))
        _other          -> CmmLit (CmmLabel (mkCmmCodeLabel rtsPackageId name))


-- | Lift an FCode computation into the CmmParse monad
code :: FCode a -> CmmParse a
code fc = EC $ \_ s -> do 
                r <- fc
                return (s, r)

emit :: CmmAGraph -> CmmParse ()
emit = code . F.emit

emitLabel :: BlockId -> CmmParse ()
emitLabel = code. F.emitLabel

emitAssign :: CmmReg  -> CmmExpr -> CmmParse ()
emitAssign l r = code (F.emitAssign l r)

emitStore :: CmmExpr  -> CmmExpr -> CmmParse ()
emitStore l r = code (F.emitStore l r)

getCode :: CmmParse a -> CmmParse CmmAGraph
getCode (EC ec) = EC $ \e s -> do
  ((s',_), gr) <- F.getCodeR (ec e s)
  return (s', gr)

getCodeR :: CmmParse a -> CmmParse (a, CmmAGraph)
getCodeR (EC ec) = EC $ \e s -> do
  ((s', r), gr) <- F.getCodeR (ec e s)
  return (s', (r,gr))

emitOutOfLine :: BlockId -> CmmAGraph -> CmmParse ()
emitOutOfLine l g = code (F.emitOutOfLine l g)

withUpdFrameOff :: UpdFrameOffset -> CmmParse () -> CmmParse ()
withUpdFrameOff size inner
  = EC $ \e s -> F.withUpdFrameOff size $ (unEC inner) e s

getUpdFrameOff :: CmmParse UpdFrameOffset
getUpdFrameOff = code $ F.getUpdFrameOff