% % (c) The University of Glasgow 2002 % \section[ByteCodeGen]{Generate bytecode from Core} \begin{code} module ByteCodeGen ( UnlinkedBCO, byteCodeGen, coreExprToBCOs ) where #include "HsVersions.h" import ByteCodeInstr import ByteCodeFFI ( mkMarshalCode, moan64 ) import ByteCodeAsm ( CompiledByteCode(..), UnlinkedBCO, assembleBCO, assembleBCOs, iNTERP_STACK_CHECK_THRESH ) import ByteCodeLink ( lookupStaticPtr ) import Outputable import Name ( Name, getName, mkSystemVarName ) import Id import FiniteMap import ForeignCall ( ForeignCall(..), CCallTarget(..), CCallSpec(..) ) import HscTypes ( TypeEnv, typeEnvTyCons, typeEnvClasses ) import CoreUtils ( exprType ) import CoreSyn import PprCore ( pprCoreExpr ) import Literal ( Literal(..), literalType ) import PrimOp ( PrimOp(..) ) import CoreFVs ( freeVars ) import Type ( isUnLiftedType, splitTyConApp_maybe ) import DataCon ( DataCon, dataConTag, fIRST_TAG, dataConTyCon, isUnboxedTupleCon, isNullaryRepDataCon, dataConWorkId, dataConRepArity ) import TyCon ( TyCon, tyConFamilySize, isDataTyCon, tyConDataCons, isUnboxedTupleTyCon ) import Class ( Class, classTyCon ) import Type ( Type, repType, splitFunTys, dropForAlls, pprType ) import Util import DataCon ( dataConRepArity ) import Var ( isTyVar ) import VarSet ( VarSet, varSetElems ) import TysPrim ( arrayPrimTyCon, mutableArrayPrimTyCon, byteArrayPrimTyCon, mutableByteArrayPrimTyCon ) import DynFlags ( DynFlags, DynFlag(..) ) import ErrUtils ( showPass, dumpIfSet_dyn ) import Unique ( mkPseudoUniqueE ) import FastString ( FastString(..), unpackFS ) import Panic ( GhcException(..) ) import SMRep ( typeCgRep, arrWordsHdrSize, arrPtrsHdrSize, StgWord, CgRep(..), cgRepSizeW, isFollowableArg, idCgRep ) import Bitmap ( intsToReverseBitmap, mkBitmap ) import OrdList import Constants ( wORD_SIZE ) import Data.List ( intersperse, sortBy, zip4, zip6, partition ) import Foreign ( Ptr, castPtr, mallocBytes, pokeByteOff, Word8, withForeignPtr ) import Foreign.C ( CInt ) import Control.Exception ( throwDyn ) import GHC.Exts ( Int(..), ByteArray# ) import Control.Monad ( when ) import Data.Char ( ord, chr ) -- ----------------------------------------------------------------------------- -- Generating byte code for a complete module byteCodeGen :: DynFlags -> [CoreBind] -> [TyCon] -> IO CompiledByteCode byteCodeGen dflags binds tycs = do showPass dflags "ByteCodeGen" let flatBinds = [ (bndr, freeVars rhs) | (bndr, rhs) <- flattenBinds binds] (BcM_State final_ctr mallocd, proto_bcos) <- runBc (mapM schemeTopBind flatBinds) when (notNull mallocd) (panic "ByteCodeGen.byteCodeGen: missing final emitBc?") dumpIfSet_dyn dflags Opt_D_dump_BCOs "Proto-BCOs" (vcat (intersperse (char ' ') (map ppr proto_bcos))) assembleBCOs proto_bcos tycs -- ----------------------------------------------------------------------------- -- Generating byte code for an expression -- Returns: (the root BCO for this expression, -- a list of auxilary BCOs resulting from compiling closures) coreExprToBCOs :: DynFlags -> CoreExpr -> IO UnlinkedBCO coreExprToBCOs dflags expr = do showPass dflags "ByteCodeGen" -- create a totally bogus name for the top-level BCO; this -- should be harmless, since it's never used for anything let invented_name = mkSystemVarName (mkPseudoUniqueE 0) FSLIT("ExprTopLevel") invented_id = mkLocalId invented_name (panic "invented_id's type") (BcM_State final_ctr mallocd, proto_bco) <- runBc (schemeTopBind (invented_id, freeVars expr)) when (notNull mallocd) (panic "ByteCodeGen.coreExprToBCOs: missing final emitBc?") dumpIfSet_dyn dflags Opt_D_dump_BCOs "Proto-BCOs" (ppr proto_bco) assembleBCO proto_bco -- ----------------------------------------------------------------------------- -- Compilation schema for the bytecode generator type BCInstrList = OrdList BCInstr type Sequel = Int -- back off to this depth before ENTER -- Maps Ids to the offset from the stack _base_ so we don't have -- to mess with it after each push/pop. type BCEnv = FiniteMap Id Int -- To find vars on the stack ppBCEnv :: BCEnv -> SDoc ppBCEnv p = text "begin-env" $$ nest 4 (vcat (map pp_one (sortBy cmp_snd (fmToList p)))) $$ text "end-env" where pp_one (var, offset) = int offset <> colon <+> ppr var <+> ppr (idCgRep var) cmp_snd x y = compare (snd x) (snd y) -- Create a BCO and do a spot of peephole optimisation on the insns -- at the same time. mkProtoBCO :: name -> BCInstrList -> Either [AnnAlt Id VarSet] (AnnExpr Id VarSet) -> Int -> Int -> [StgWord] -> Bool -- True <=> is a return point, rather than a function -> [Ptr ()] -> ProtoBCO name mkProtoBCO nm instrs_ordlist origin arity bitmap_size bitmap is_ret mallocd_blocks = ProtoBCO { protoBCOName = nm, protoBCOInstrs = maybe_with_stack_check, protoBCOBitmap = bitmap, protoBCOBitmapSize = bitmap_size, protoBCOArity = arity, protoBCOExpr = origin, protoBCOPtrs = mallocd_blocks } where -- Overestimate the stack usage (in words) of this BCO, -- and if >= iNTERP_STACK_CHECK_THRESH, add an explicit -- stack check. (The interpreter always does a stack check -- for iNTERP_STACK_CHECK_THRESH words at the start of each -- BCO anyway, so we only need to add an explicit on in the -- (hopefully rare) cases when the (overestimated) stack use -- exceeds iNTERP_STACK_CHECK_THRESH. maybe_with_stack_check | is_ret = peep_d -- don't do stack checks at return points; -- everything is aggregated up to the top BCO -- (which must be a function) | stack_overest >= 65535 = pprPanic "mkProtoBCO: stack use won't fit in 16 bits" (int stack_overest) | stack_overest >= iNTERP_STACK_CHECK_THRESH = STKCHECK stack_overest : peep_d | otherwise = peep_d -- the supposedly common case stack_overest = sum (map bciStackUse peep_d) -- Merge local pushes peep_d = peep (fromOL instrs_ordlist) peep (PUSH_L off1 : PUSH_L off2 : PUSH_L off3 : rest) = PUSH_LLL off1 (off2-1) (off3-2) : peep rest peep (PUSH_L off1 : PUSH_L off2 : rest) = PUSH_LL off1 (off2-1) : peep rest peep (i:rest) = i : peep rest peep [] = [] argBits :: [CgRep] -> [Bool] argBits [] = [] argBits (rep : args) | isFollowableArg rep = False : argBits args | otherwise = take (cgRepSizeW rep) (repeat True) ++ argBits args -- ----------------------------------------------------------------------------- -- schemeTopBind -- Compile code for the right-hand side of a top-level binding schemeTopBind :: (Id, AnnExpr Id VarSet) -> BcM (ProtoBCO Name) schemeTopBind (id, rhs) | Just data_con <- isDataConWorkId_maybe id, isNullaryRepDataCon data_con = -- Special case for the worker of a nullary data con. -- It'll look like this: Nil = /\a -> Nil a -- If we feed it into schemeR, we'll get -- Nil = Nil -- because mkConAppCode treats nullary constructor applications -- by just re-using the single top-level definition. So -- for the worker itself, we must allocate it directly. emitBc (mkProtoBCO (getName id) (toOL [PACK data_con 0, ENTER]) (Right rhs) 0 0 [{-no bitmap-}] False{-not alts-}) | otherwise = schemeR [{- No free variables -}] (id, rhs) -- ----------------------------------------------------------------------------- -- schemeR -- Compile code for a right-hand side, to give a BCO that, -- when executed with the free variables and arguments on top of the stack, -- will return with a pointer to the result on top of the stack, after -- removing the free variables and arguments. -- -- Park the resulting BCO in the monad. Also requires the -- variable to which this value was bound, so as to give the -- resulting BCO a name. schemeR :: [Id] -- Free vars of the RHS, ordered as they -- will appear in the thunk. Empty for -- top-level things, which have no free vars. -> (Id, AnnExpr Id VarSet) -> BcM (ProtoBCO Name) schemeR fvs (nm, rhs) {- | trace (showSDoc ( (char ' ' $$ (ppr.filter (not.isTyVar).varSetElems.fst) rhs $$ pprCoreExpr (deAnnotate rhs) $$ char ' ' ))) False = undefined | otherwise -} = schemeR_wrk fvs nm rhs (collect [] rhs) collect xs (_, AnnNote note e) = collect xs e collect xs (_, AnnLam x e) = collect (if isTyVar x then xs else (x:xs)) e collect xs (_, not_lambda) = (reverse xs, not_lambda) schemeR_wrk fvs nm original_body (args, body) = let all_args = reverse args ++ fvs arity = length all_args -- all_args are the args in reverse order. We're compiling a function -- \fv1..fvn x1..xn -> e -- i.e. the fvs come first szsw_args = map idSizeW all_args szw_args = sum szsw_args p_init = listToFM (zip all_args (mkStackOffsets 0 szsw_args)) -- make the arg bitmap bits = argBits (reverse (map idCgRep all_args)) bitmap_size = length bits bitmap = mkBitmap bits in schemeE szw_args 0 p_init body `thenBc` \ body_code -> emitBc (mkProtoBCO (getName nm) body_code (Right original_body) arity bitmap_size bitmap False{-not alts-}) fvsToEnv :: BCEnv -> VarSet -> [Id] -- Takes the free variables of a right-hand side, and -- delivers an ordered list of the local variables that will -- be captured in the thunk for the RHS -- The BCEnv argument tells which variables are in the local -- environment: these are the ones that should be captured -- -- The code that constructs the thunk, and the code that executes -- it, have to agree about this layout fvsToEnv p fvs = [v | v <- varSetElems fvs, isId v, -- Could be a type variable v `elemFM` p] -- ----------------------------------------------------------------------------- -- schemeE -- Compile code to apply the given expression to the remaining args -- on the stack, returning a HNF. schemeE :: Int -> Sequel -> BCEnv -> AnnExpr' Id VarSet -> BcM BCInstrList -- Delegate tail-calls to schemeT. schemeE d s p e@(AnnApp f a) = schemeT d s p e schemeE d s p e@(AnnVar v) | not (isUnLiftedType v_type) = -- Lifted-type thing; push it in the normal way schemeT d s p e | otherwise = -- Returning an unlifted value. -- Heave it on the stack, SLIDE, and RETURN. pushAtom d p (AnnVar v) `thenBc` \ (push, szw) -> returnBc (push -- value onto stack `appOL` mkSLIDE szw (d-s) -- clear to sequel `snocOL` RETURN_UBX v_rep) -- go where v_type = idType v v_rep = typeCgRep v_type schemeE d s p (AnnLit literal) = pushAtom d p (AnnLit literal) `thenBc` \ (push, szw) -> let l_rep = typeCgRep (literalType literal) in returnBc (push -- value onto stack `appOL` mkSLIDE szw (d-s) -- clear to sequel `snocOL` RETURN_UBX l_rep) -- go schemeE d s p (AnnLet (AnnNonRec x (_,rhs)) (_,body)) | (AnnVar v, args_r_to_l) <- splitApp rhs, Just data_con <- isDataConWorkId_maybe v, dataConRepArity data_con == length args_r_to_l = -- Special case for a non-recursive let whose RHS is a -- saturatred constructor application. -- Just allocate the constructor and carry on mkConAppCode d s p data_con args_r_to_l `thenBc` \ alloc_code -> schemeE (d+1) s (addToFM p x d) body `thenBc` \ body_code -> returnBc (alloc_code `appOL` body_code) -- General case for let. Generates correct, if inefficient, code in -- all situations. schemeE d s p (AnnLet binds (_,body)) = let (xs,rhss) = case binds of AnnNonRec x rhs -> ([x],[rhs]) AnnRec xs_n_rhss -> unzip xs_n_rhss n_binds = length xs fvss = map (fvsToEnv p' . fst) rhss -- Sizes of free vars sizes = map (\rhs_fvs -> sum (map idSizeW rhs_fvs)) fvss -- the arity of each rhs arities = map (length . fst . collect []) rhss -- This p', d' defn is safe because all the items being pushed -- are ptrs, so all have size 1. d' and p' reflect the stack -- after the closures have been allocated in the heap (but not -- filled in), and pointers to them parked on the stack. p' = addListToFM p (zipE xs (mkStackOffsets d (nOfThem n_binds 1))) d' = d + n_binds zipE = zipEqual "schemeE" -- ToDo: don't build thunks for things with no free variables build_thunk dd [] size bco off arity = returnBc (PUSH_BCO bco `consOL` unitOL (mkap (off+size) size)) where mkap | arity == 0 = MKAP | otherwise = MKPAP build_thunk dd (fv:fvs) size bco off arity = do (push_code, pushed_szw) <- pushAtom dd p' (AnnVar fv) more_push_code <- build_thunk (dd+pushed_szw) fvs size bco off arity returnBc (push_code `appOL` more_push_code) alloc_code = toOL (zipWith mkAlloc sizes arities) where mkAlloc sz 0 = ALLOC_AP sz mkAlloc sz arity = ALLOC_PAP arity sz compile_bind d' fvs x rhs size arity off = do bco <- schemeR fvs (x,rhs) build_thunk d' fvs size bco off arity compile_binds = [ compile_bind d' fvs x rhs size arity n | (fvs, x, rhs, size, arity, n) <- zip6 fvss xs rhss sizes arities [n_binds, n_binds-1 .. 1] ] in do body_code <- schemeE d' s p' body thunk_codes <- sequence compile_binds returnBc (alloc_code `appOL` concatOL thunk_codes `appOL` body_code) schemeE d s p (AnnCase scrut bndr _ [(DataAlt dc, [bind1, bind2], rhs)]) | isUnboxedTupleCon dc, VoidArg <- typeCgRep (idType bind1) -- Convert -- case .... of x { (# VoidArg'd-thing, a #) -> ... } -- to -- case .... of a { DEFAULT -> ... } -- becuse the return convention for both are identical. -- -- Note that it does not matter losing the void-rep thing from the -- envt (it won't be bound now) because we never look such things up. = --trace "automagic mashing of case alts (# VoidArg, a #)" $ doCase d s p scrut bind2 [(DEFAULT, [], rhs)] True{-unboxed tuple-} | isUnboxedTupleCon dc, VoidArg <- typeCgRep (idType bind2) = --trace "automagic mashing of case alts (# a, VoidArg #)" $ doCase d s p scrut bind1 [(DEFAULT, [], rhs)] True{-unboxed tuple-} schemeE d s p (AnnCase scrut bndr _ [(DataAlt dc, [bind1], rhs)]) | isUnboxedTupleCon dc -- Similarly, convert -- case .... of x { (# a #) -> ... } -- to -- case .... of a { DEFAULT -> ... } = --trace "automagic mashing of case alts (# a #)" $ doCase d s p scrut bind1 [(DEFAULT, [], rhs)] True{-unboxed tuple-} schemeE d s p (AnnCase scrut bndr _ alts) = doCase d s p scrut bndr alts False{-not an unboxed tuple-} schemeE d s p (AnnNote note (_, body)) = schemeE d s p body schemeE d s p other = pprPanic "ByteCodeGen.schemeE: unhandled case" (pprCoreExpr (deAnnotate' other)) -- Compile code to do a tail call. Specifically, push the fn, -- slide the on-stack app back down to the sequel depth, -- and enter. Four cases: -- -- 0. (Nasty hack). -- An application "GHC.Prim.tagToEnum# unboxed-int". -- The int will be on the stack. Generate a code sequence -- to convert it to the relevant constructor, SLIDE and ENTER. -- -- 1. The fn denotes a ccall. Defer to generateCCall. -- -- 2. (Another nasty hack). Spot (# a::VoidArg, b #) and treat -- it simply as b -- since the representations are identical -- (the VoidArg takes up zero stack space). Also, spot -- (# b #) and treat it as b. -- -- 3. Application of a constructor, by defn saturated. -- Split the args into ptrs and non-ptrs, and push the nonptrs, -- then the ptrs, and then do PACK and RETURN. -- -- 4. Otherwise, it must be a function call. Push the args -- right to left, SLIDE and ENTER. schemeT :: Int -- Stack depth -> Sequel -- Sequel depth -> BCEnv -- stack env -> AnnExpr' Id VarSet -> BcM BCInstrList schemeT d s p app -- | trace ("schemeT: env in = \n" ++ showSDocDebug (ppBCEnv p)) False -- = panic "schemeT ?!?!" -- | trace ("\nschemeT\n" ++ showSDoc (pprCoreExpr (deAnnotate' app)) ++ "\n") False -- = error "?!?!" -- Case 0 | Just (arg, constr_names) <- maybe_is_tagToEnum_call = pushAtom d p arg `thenBc` \ (push, arg_words) -> implement_tagToId constr_names `thenBc` \ tagToId_sequence -> returnBc (push `appOL` tagToId_sequence `appOL` mkSLIDE 1 (d+arg_words-s) `snocOL` ENTER) -- Case 1 | Just (CCall ccall_spec) <- isFCallId_maybe fn = generateCCall d s p ccall_spec fn args_r_to_l -- Case 2: Constructor application | Just con <- maybe_saturated_dcon, isUnboxedTupleCon con = case args_r_to_l of [arg1,arg2] | isVoidArgAtom arg1 -> unboxedTupleReturn d s p arg2 [arg1,arg2] | isVoidArgAtom arg2 -> unboxedTupleReturn d s p arg1 _other -> unboxedTupleException -- Case 3: Ordinary data constructor | Just con <- maybe_saturated_dcon = mkConAppCode d s p con args_r_to_l `thenBc` \ alloc_con -> returnBc (alloc_con `appOL` mkSLIDE 1 (d - s) `snocOL` ENTER) -- Case 4: Tail call of function | otherwise = doTailCall d s p fn args_r_to_l where -- Detect and extract relevant info for the tagToEnum kludge. maybe_is_tagToEnum_call = let extract_constr_Names ty | Just (tyc, []) <- splitTyConApp_maybe (repType ty), isDataTyCon tyc = map (getName . dataConWorkId) (tyConDataCons tyc) -- NOTE: use the worker name, not the source name of -- the DataCon. See DataCon.lhs for details. | otherwise = panic "maybe_is_tagToEnum_call.extract_constr_Ids" in case app of (AnnApp (_, AnnApp (_, AnnVar v) (_, AnnType t)) arg) -> case isPrimOpId_maybe v of Just TagToEnumOp -> Just (snd arg, extract_constr_Names t) other -> Nothing other -> Nothing -- Extract the args (R->L) and fn -- The function will necessarily be a variable, -- because we are compiling a tail call (AnnVar fn, args_r_to_l) = splitApp app -- Only consider this to be a constructor application iff it is -- saturated. Otherwise, we'll call the constructor wrapper. n_args = length args_r_to_l maybe_saturated_dcon = case isDataConWorkId_maybe fn of Just con | dataConRepArity con == n_args -> Just con _ -> Nothing -- ----------------------------------------------------------------------------- -- Generate code to build a constructor application, -- leaving it on top of the stack mkConAppCode :: Int -> Sequel -> BCEnv -> DataCon -- The data constructor -> [AnnExpr' Id VarSet] -- Args, in *reverse* order -> BcM BCInstrList mkConAppCode orig_d s p con [] -- Nullary constructor = ASSERT( isNullaryRepDataCon con ) returnBc (unitOL (PUSH_G (getName (dataConWorkId con)))) -- Instead of doing a PACK, which would allocate a fresh -- copy of this constructor, use the single shared version. mkConAppCode orig_d s p con args_r_to_l = ASSERT( dataConRepArity con == length args_r_to_l ) do_pushery orig_d (non_ptr_args ++ ptr_args) where -- The args are already in reverse order, which is the way PACK -- expects them to be. We must push the non-ptrs after the ptrs. (ptr_args, non_ptr_args) = partition isPtrAtom args_r_to_l do_pushery d (arg:args) = pushAtom d p arg `thenBc` \ (push, arg_words) -> do_pushery (d+arg_words) args `thenBc` \ more_push_code -> returnBc (push `appOL` more_push_code) do_pushery d [] = returnBc (unitOL (PACK con n_arg_words)) where n_arg_words = d - orig_d -- ----------------------------------------------------------------------------- -- Returning an unboxed tuple with one non-void component (the only -- case we can handle). -- -- Remember, we don't want to *evaluate* the component that is being -- returned, even if it is a pointed type. We always just return. unboxedTupleReturn :: Int -> Sequel -> BCEnv -> AnnExpr' Id VarSet -> BcM BCInstrList unboxedTupleReturn d s p arg = do (push, sz) <- pushAtom d p arg returnBc (push `appOL` mkSLIDE sz (d-s) `snocOL` RETURN_UBX (atomRep arg)) -- ----------------------------------------------------------------------------- -- Generate code for a tail-call doTailCall :: Int -> Sequel -> BCEnv -> Id -> [AnnExpr' Id VarSet] -> BcM BCInstrList doTailCall init_d s p fn args = do_pushes init_d args (map atomRep args) where do_pushes d [] reps = do ASSERT( null reps ) return () (push_fn, sz) <- pushAtom d p (AnnVar fn) ASSERT( sz == 1 ) return () returnBc (push_fn `appOL` ( mkSLIDE ((d-init_d) + 1) (init_d - s) `appOL` unitOL ENTER)) do_pushes d args reps = do let (push_apply, n, rest_of_reps) = findPushSeq reps (these_args, rest_of_args) = splitAt n args (next_d, push_code) <- push_seq d these_args instrs <- do_pushes (next_d + 1) rest_of_args rest_of_reps -- ^^^ for the PUSH_APPLY_ instruction returnBc (push_code `appOL` (push_apply `consOL` instrs)) push_seq d [] = return (d, nilOL) push_seq d (arg:args) = do (push_code, sz) <- pushAtom d p arg (final_d, more_push_code) <- push_seq (d+sz) args return (final_d, push_code `appOL` more_push_code) -- v. similar to CgStackery.findMatch, ToDo: merge findPushSeq (PtrArg: PtrArg: PtrArg: PtrArg: PtrArg: PtrArg: rest) = (PUSH_APPLY_PPPPPP, 6, rest) findPushSeq (PtrArg: PtrArg: PtrArg: PtrArg: PtrArg: rest) = (PUSH_APPLY_PPPPP, 5, rest) findPushSeq (PtrArg: PtrArg: PtrArg: PtrArg: rest) = (PUSH_APPLY_PPPP, 4, rest) findPushSeq (PtrArg: PtrArg: PtrArg: rest) = (PUSH_APPLY_PPP, 3, rest) findPushSeq (PtrArg: PtrArg: rest) = (PUSH_APPLY_PP, 2, rest) findPushSeq (PtrArg: rest) = (PUSH_APPLY_P, 1, rest) findPushSeq (VoidArg: rest) = (PUSH_APPLY_V, 1, rest) findPushSeq (NonPtrArg: rest) = (PUSH_APPLY_N, 1, rest) findPushSeq (FloatArg: rest) = (PUSH_APPLY_F, 1, rest) findPushSeq (DoubleArg: rest) = (PUSH_APPLY_D, 1, rest) findPushSeq (LongArg: rest) = (PUSH_APPLY_L, 1, rest) findPushSeq _ = panic "ByteCodeGen.findPushSeq" -- ----------------------------------------------------------------------------- -- Case expressions doCase :: Int -> Sequel -> BCEnv -> AnnExpr Id VarSet -> Id -> [AnnAlt Id VarSet] -> Bool -- True <=> is an unboxed tuple case, don't enter the result -> BcM BCInstrList doCase d s p (_,scrut) bndr alts is_unboxed_tuple = let -- Top of stack is the return itbl, as usual. -- underneath it is the pointer to the alt_code BCO. -- When an alt is entered, it assumes the returned value is -- on top of the itbl. ret_frame_sizeW = 2 -- An unlifted value gets an extra info table pushed on top -- when it is returned. unlifted_itbl_sizeW | isAlgCase = 0 | otherwise = 1 -- depth of stack after the return value has been pushed d_bndr = d + ret_frame_sizeW + idSizeW bndr -- depth of stack after the extra info table for an unboxed return -- has been pushed, if any. This is the stack depth at the -- continuation. d_alts = d_bndr + unlifted_itbl_sizeW -- Env in which to compile the alts, not including -- any vars bound by the alts themselves p_alts = addToFM p bndr (d_bndr - 1) bndr_ty = idType bndr isAlgCase = not (isUnLiftedType bndr_ty) && not is_unboxed_tuple -- given an alt, return a discr and code for it. codeALt alt@(DEFAULT, _, (_,rhs)) = schemeE d_alts s p_alts rhs `thenBc` \ rhs_code -> returnBc (NoDiscr, rhs_code) codeAlt alt@(discr, bndrs, (_,rhs)) -- primitive or nullary constructor alt: no need to UNPACK | null real_bndrs = do rhs_code <- schemeE d_alts s p_alts rhs returnBc (my_discr alt, rhs_code) -- algebraic alt with some binders | ASSERT(isAlgCase) otherwise = let (ptrs,nptrs) = partition (isFollowableArg.idCgRep) real_bndrs ptr_sizes = map idSizeW ptrs nptrs_sizes = map idSizeW nptrs bind_sizes = ptr_sizes ++ nptrs_sizes size = sum ptr_sizes + sum nptrs_sizes -- the UNPACK instruction unpacks in reverse order... p' = addListToFM p_alts (zip (reverse (ptrs ++ nptrs)) (mkStackOffsets d_alts (reverse bind_sizes))) in do rhs_code <- schemeE (d_alts+size) s p' rhs return (my_discr alt, unitOL (UNPACK size) `appOL` rhs_code) where real_bndrs = filter (not.isTyVar) bndrs my_discr (DEFAULT, binds, rhs) = NoDiscr {-shouldn't really happen-} my_discr (DataAlt dc, binds, rhs) | isUnboxedTupleCon dc = unboxedTupleException | otherwise = DiscrP (dataConTag dc - fIRST_TAG) my_discr (LitAlt l, binds, rhs) = case l of MachInt i -> DiscrI (fromInteger i) MachFloat r -> DiscrF (fromRational r) MachDouble r -> DiscrD (fromRational r) MachChar i -> DiscrI (ord i) _ -> pprPanic "schemeE(AnnCase).my_discr" (ppr l) maybe_ncons | not isAlgCase = Nothing | otherwise = case [dc | (DataAlt dc, _, _) <- alts] of [] -> Nothing (dc:_) -> Just (tyConFamilySize (dataConTyCon dc)) -- the bitmap is relative to stack depth d, i.e. before the -- BCO, info table and return value are pushed on. -- This bit of code is v. similar to buildLivenessMask in CgBindery, -- except that here we build the bitmap from the known bindings of -- things that are pointers, whereas in CgBindery the code builds the -- bitmap from the free slots and unboxed bindings. -- (ToDo: merge?) bitmap = intsToReverseBitmap d{-size-} (sortLe (<=) rel_slots) where binds = fmToList p rel_slots = concat (map spread binds) spread (id, offset) | isFollowableArg (idCgRep id) = [ rel_offset ] | otherwise = [] where rel_offset = d - offset - 1 in do alt_stuff <- mapM codeAlt alts alt_final <- mkMultiBranch maybe_ncons alt_stuff let alt_bco_name = getName bndr alt_bco = mkProtoBCO alt_bco_name alt_final (Left alts) 0{-no arity-} d{-bitmap size-} bitmap True{-is alts-} -- in -- trace ("case: bndr = " ++ showSDocDebug (ppr bndr) ++ "\ndepth = " ++ show d ++ "\nenv = \n" ++ showSDocDebug (ppBCEnv p) ++ -- "\n bitmap = " ++ show bitmap) $ do scrut_code <- schemeE (d + ret_frame_sizeW) (d + ret_frame_sizeW) p scrut alt_bco' <- emitBc alt_bco let push_alts | isAlgCase = PUSH_ALTS alt_bco' | otherwise = PUSH_ALTS_UNLIFTED alt_bco' (typeCgRep bndr_ty) returnBc (push_alts `consOL` scrut_code) -- ----------------------------------------------------------------------------- -- Deal with a CCall. -- Taggedly push the args onto the stack R->L, -- deferencing ForeignObj#s and adjusting addrs to point to -- payloads in Ptr/Byte arrays. Then, generate the marshalling -- (machine) code for the ccall, and create bytecodes to call that and -- then return in the right way. generateCCall :: Int -> Sequel -- stack and sequel depths -> BCEnv -> CCallSpec -- where to call -> Id -- of target, for type info -> [AnnExpr' Id VarSet] -- args (atoms) -> BcM BCInstrList generateCCall d0 s p ccall_spec@(CCallSpec target cconv safety) fn args_r_to_l = let -- useful constants addr_sizeW = cgRepSizeW NonPtrArg -- Get the args on the stack, with tags and suitably -- dereferenced for the CCall. For each arg, return the -- depth to the first word of the bits for that arg, and the -- CgRep of what was actually pushed. pargs d [] = returnBc [] pargs d (a:az) = let arg_ty = repType (exprType (deAnnotate' a)) in case splitTyConApp_maybe arg_ty of -- Don't push the FO; instead push the Addr# it -- contains. Just (t, _) | t == arrayPrimTyCon || t == mutableArrayPrimTyCon -> pargs (d + addr_sizeW) az `thenBc` \ rest -> parg_ArrayishRep arrPtrsHdrSize d p a `thenBc` \ code -> returnBc ((code,NonPtrArg):rest) | t == byteArrayPrimTyCon || t == mutableByteArrayPrimTyCon -> pargs (d + addr_sizeW) az `thenBc` \ rest -> parg_ArrayishRep arrWordsHdrSize d p a `thenBc` \ code -> returnBc ((code,NonPtrArg):rest) -- Default case: push taggedly, but otherwise intact. other -> pushAtom d p a `thenBc` \ (code_a, sz_a) -> pargs (d+sz_a) az `thenBc` \ rest -> returnBc ((code_a, atomRep a) : rest) -- Do magic for Ptr/Byte arrays. Push a ptr to the array on -- the stack but then advance it over the headers, so as to -- point to the payload. parg_ArrayishRep hdrSize d p a = pushAtom d p a `thenBc` \ (push_fo, _) -> -- The ptr points at the header. Advance it over the -- header and then pretend this is an Addr#. returnBc (push_fo `snocOL` SWIZZLE 0 hdrSize) in pargs d0 args_r_to_l `thenBc` \ code_n_reps -> let (pushs_arg, a_reps_pushed_r_to_l) = unzip code_n_reps push_args = concatOL pushs_arg d_after_args = d0 + sum (map cgRepSizeW a_reps_pushed_r_to_l) a_reps_pushed_RAW | null a_reps_pushed_r_to_l || head a_reps_pushed_r_to_l /= VoidArg = panic "ByteCodeGen.generateCCall: missing or invalid World token?" | otherwise = reverse (tail a_reps_pushed_r_to_l) -- Now: a_reps_pushed_RAW are the reps which are actually on the stack. -- push_args is the code to do that. -- d_after_args is the stack depth once the args are on. -- Get the result rep. (returns_void, r_rep) = case maybe_getCCallReturnRep (idType fn) of Nothing -> (True, VoidArg) Just rr -> (False, rr) {- Because the Haskell stack grows down, the a_reps refer to lowest to highest addresses in that order. The args for the call are on the stack. Now push an unboxed Addr# indicating the C function to call. Then push a dummy placeholder for the result. Finally, emit a CCALL insn with an offset pointing to the Addr# just pushed, and a literal field holding the mallocville address of the piece of marshalling code we generate. So, just prior to the CCALL insn, the stack looks like this (growing down, as usual): ... Addr# address_of_C_fn (must be an unboxed type) The interpreter then calls the marshall code mentioned in the CCALL insn, passing it (& ), that is, the addr of the topmost word in the stack. When this returns, the placeholder will have been filled in. The placeholder is slid down to the sequel depth, and we RETURN. This arrangement makes it simple to do f-i-dynamic since the Addr# value is the first arg anyway. The marshalling code is generated specifically for this call site, and so knows exactly the (Haskell) stack offsets of the args, fn address and placeholder. It copies the args to the C stack, calls the stacked addr, and parks the result back in the placeholder. The interpreter calls it as a normal C call, assuming it has a signature void marshall_code ( StgWord* ptr_to_top_of_stack ) -} -- resolve static address get_target_info = case target of DynamicTarget -> returnBc (False, panic "ByteCodeGen.generateCCall(dyn)") StaticTarget target -> ioToBc (lookupStaticPtr target) `thenBc` \res -> returnBc (True, res) in get_target_info `thenBc` \ (is_static, static_target_addr) -> let -- Get the arg reps, zapping the leading Addr# in the dynamic case a_reps -- | trace (showSDoc (ppr a_reps_pushed_RAW)) False = error "???" | is_static = a_reps_pushed_RAW | otherwise = if null a_reps_pushed_RAW then panic "ByteCodeGen.generateCCall: dyn with no args" else tail a_reps_pushed_RAW -- push the Addr# (push_Addr, d_after_Addr) | is_static = (toOL [PUSH_UBX (Right static_target_addr) addr_sizeW], d_after_args + addr_sizeW) | otherwise -- is already on the stack = (nilOL, d_after_args) -- Push the return placeholder. For a call returning nothing, -- this is a VoidArg (tag). r_sizeW = cgRepSizeW r_rep d_after_r = d_after_Addr + r_sizeW r_lit = mkDummyLiteral r_rep push_r = (if returns_void then nilOL else unitOL (PUSH_UBX (Left r_lit) r_sizeW)) -- generate the marshalling code we're going to call r_offW = 0 addr_offW = r_sizeW arg1_offW = r_sizeW + addr_sizeW args_offW = map (arg1_offW +) (init (scanl (+) 0 (map cgRepSizeW a_reps))) in ioToBc (mkMarshalCode cconv (r_offW, r_rep) addr_offW (zip args_offW a_reps)) `thenBc` \ addr_of_marshaller -> recordMallocBc addr_of_marshaller `thenBc_` let -- Offset of the next stack frame down the stack. The CCALL -- instruction needs to describe the chunk of stack containing -- the ccall args to the GC, so it needs to know how large it -- is. See comment in Interpreter.c with the CCALL instruction. stk_offset = d_after_r - s -- do the call do_call = unitOL (CCALL stk_offset (castPtr addr_of_marshaller)) -- slide and return wrapup = mkSLIDE r_sizeW (d_after_r - r_sizeW - s) `snocOL` RETURN_UBX r_rep in --trace (show (arg1_offW, args_offW , (map cgRepSizeW a_reps) )) $ returnBc ( push_args `appOL` push_Addr `appOL` push_r `appOL` do_call `appOL` wrapup ) -- Make a dummy literal, to be used as a placeholder for FFI return -- values on the stack. mkDummyLiteral :: CgRep -> Literal mkDummyLiteral pr = case pr of NonPtrArg -> MachWord 0 DoubleArg -> MachDouble 0 FloatArg -> MachFloat 0 _ -> moan64 "mkDummyLiteral" (ppr pr) -- Convert (eg) -- GHC.Prim.Char# -> GHC.Prim.State# GHC.Prim.RealWorld -- -> (# GHC.Prim.State# GHC.Prim.RealWorld, GHC.Prim.Int# #) -- -- to Just IntRep -- and check that an unboxed pair is returned wherein the first arg is VoidArg'd. -- -- Alternatively, for call-targets returning nothing, convert -- -- GHC.Prim.Char# -> GHC.Prim.State# GHC.Prim.RealWorld -- -> (# GHC.Prim.State# GHC.Prim.RealWorld #) -- -- to Nothing maybe_getCCallReturnRep :: Type -> Maybe CgRep maybe_getCCallReturnRep fn_ty = let (a_tys, r_ty) = splitFunTys (dropForAlls fn_ty) maybe_r_rep_to_go = if isSingleton r_reps then Nothing else Just (r_reps !! 1) (r_tycon, r_reps) = case splitTyConApp_maybe (repType r_ty) of (Just (tyc, tys)) -> (tyc, map typeCgRep tys) Nothing -> blargh ok = ( ( r_reps `lengthIs` 2 && VoidArg == head r_reps) || r_reps == [VoidArg] ) && isUnboxedTupleTyCon r_tycon && case maybe_r_rep_to_go of Nothing -> True Just r_rep -> r_rep /= PtrArg -- if it was, it would be impossible -- to create a valid return value -- placeholder on the stack blargh = pprPanic "maybe_getCCallReturn: can't handle:" (pprType fn_ty) in --trace (showSDoc (ppr (a_reps, r_reps))) $ if ok then maybe_r_rep_to_go else blargh -- Compile code which expects an unboxed Int on the top of stack, -- (call it i), and pushes the i'th closure in the supplied list -- as a consequence. implement_tagToId :: [Name] -> BcM BCInstrList implement_tagToId names = ASSERT( notNull names ) getLabelsBc (length names) `thenBc` \ labels -> getLabelBc `thenBc` \ label_fail -> getLabelBc `thenBc` \ label_exit -> zip4 labels (tail labels ++ [label_fail]) [0 ..] names `bind` \ infos -> map (mkStep label_exit) infos `bind` \ steps -> returnBc (concatOL steps `appOL` toOL [LABEL label_fail, CASEFAIL, LABEL label_exit]) where mkStep l_exit (my_label, next_label, n, name_for_n) = toOL [LABEL my_label, TESTEQ_I n next_label, PUSH_G name_for_n, JMP l_exit] -- ----------------------------------------------------------------------------- -- pushAtom -- Push an atom onto the stack, returning suitable code & number of -- stack words used. -- -- The env p must map each variable to the highest- numbered stack -- slot for it. For example, if the stack has depth 4 and we -- tagged-ly push (v :: Int#) on it, the value will be in stack[4], -- the tag in stack[5], the stack will have depth 6, and p must map v -- to 5 and not to 4. Stack locations are numbered from zero, so a -- depth 6 stack has valid words 0 .. 5. pushAtom :: Int -> BCEnv -> AnnExpr' Id VarSet -> BcM (BCInstrList, Int) pushAtom d p (AnnApp f (_, AnnType _)) = pushAtom d p (snd f) pushAtom d p (AnnNote note e) = pushAtom d p (snd e) pushAtom d p (AnnLam x e) | isTyVar x = pushAtom d p (snd e) pushAtom d p (AnnVar v) | idCgRep v == VoidArg = returnBc (nilOL, 0) | isFCallId v = pprPanic "pushAtom: shouldn't get an FCallId here" (ppr v) | Just primop <- isPrimOpId_maybe v = returnBc (unitOL (PUSH_PRIMOP primop), 1) | Just d_v <- lookupBCEnv_maybe p v -- v is a local variable = returnBc (toOL (nOfThem sz (PUSH_L (d-d_v+sz-2))), sz) -- d - d_v the number of words between the TOS -- and the 1st slot of the object -- -- d - d_v - 1 the offset from the TOS of the 1st slot -- -- d - d_v - 1 + sz - 1 the offset from the TOS of the last slot -- of the object. -- -- Having found the last slot, we proceed to copy the right number of -- slots on to the top of the stack. | otherwise -- v must be a global variable = ASSERT(sz == 1) returnBc (unitOL (PUSH_G (getName v)), sz) where sz = idSizeW v pushAtom d p (AnnLit lit) = case lit of MachLabel fs _ -> code NonPtrArg MachWord w -> code NonPtrArg MachInt i -> code PtrArg MachFloat r -> code FloatArg MachDouble r -> code DoubleArg MachChar c -> code NonPtrArg MachStr s -> pushStr s where code rep = let size_host_words = cgRepSizeW rep in returnBc (unitOL (PUSH_UBX (Left lit) size_host_words), size_host_words) pushStr s = let getMallocvilleAddr = case s of FastString _ n _ fp _ -> -- we could grab the Ptr from the ForeignPtr, -- but then we have no way to control its lifetime. -- In reality it'll probably stay alive long enoungh -- by virtue of the global FastString table, but -- to be on the safe side we copy the string into -- a malloc'd area of memory. ioToBc (mallocBytes (n+1)) `thenBc` \ ptr -> recordMallocBc ptr `thenBc_` ioToBc ( withForeignPtr fp $ \p -> do memcpy ptr p (fromIntegral n) pokeByteOff ptr n (fromIntegral (ord '\0') :: Word8) return ptr ) other -> panic "ByteCodeGen.pushAtom.pushStr" in getMallocvilleAddr `thenBc` \ addr -> -- Get the addr on the stack, untaggedly returnBc (unitOL (PUSH_UBX (Right addr) 1), 1) pushAtom d p other = pprPanic "ByteCodeGen.pushAtom" (pprCoreExpr (deAnnotate (undefined, other))) foreign import ccall unsafe "memcpy" memcpy :: Ptr a -> Ptr b -> CInt -> IO () -- ----------------------------------------------------------------------------- -- Given a bunch of alts code and their discrs, do the donkey work -- of making a multiway branch using a switch tree. -- What a load of hassle! mkMultiBranch :: Maybe Int -- # datacons in tycon, if alg alt -- a hint; generates better code -- Nothing is always safe -> [(Discr, BCInstrList)] -> BcM BCInstrList mkMultiBranch maybe_ncons raw_ways = let d_way = filter (isNoDiscr.fst) raw_ways notd_ways = sortLe (\w1 w2 -> leAlt (fst w1) (fst w2)) (filter (not.isNoDiscr.fst) raw_ways) mkTree :: [(Discr, BCInstrList)] -> Discr -> Discr -> BcM BCInstrList mkTree [] range_lo range_hi = returnBc the_default mkTree [val] range_lo range_hi | range_lo `eqAlt` range_hi = returnBc (snd val) | otherwise = getLabelBc `thenBc` \ label_neq -> returnBc (mkTestEQ (fst val) label_neq `consOL` (snd val `appOL` unitOL (LABEL label_neq) `appOL` the_default)) mkTree vals range_lo range_hi = let n = length vals `div` 2 vals_lo = take n vals vals_hi = drop n vals v_mid = fst (head vals_hi) in getLabelBc `thenBc` \ label_geq -> mkTree vals_lo range_lo (dec v_mid) `thenBc` \ code_lo -> mkTree vals_hi v_mid range_hi `thenBc` \ code_hi -> returnBc (mkTestLT v_mid label_geq `consOL` (code_lo `appOL` unitOL (LABEL label_geq) `appOL` code_hi)) the_default = case d_way of [] -> unitOL CASEFAIL [(_, def)] -> def -- None of these will be needed if there are no non-default alts (mkTestLT, mkTestEQ, init_lo, init_hi) | null notd_ways = panic "mkMultiBranch: awesome foursome" | otherwise = case fst (head notd_ways) of { DiscrI _ -> ( \(DiscrI i) fail_label -> TESTLT_I i fail_label, \(DiscrI i) fail_label -> TESTEQ_I i fail_label, DiscrI minBound, DiscrI maxBound ); DiscrF _ -> ( \(DiscrF f) fail_label -> TESTLT_F f fail_label, \(DiscrF f) fail_label -> TESTEQ_F f fail_label, DiscrF minF, DiscrF maxF ); DiscrD _ -> ( \(DiscrD d) fail_label -> TESTLT_D d fail_label, \(DiscrD d) fail_label -> TESTEQ_D d fail_label, DiscrD minD, DiscrD maxD ); DiscrP _ -> ( \(DiscrP i) fail_label -> TESTLT_P i fail_label, \(DiscrP i) fail_label -> TESTEQ_P i fail_label, DiscrP algMinBound, DiscrP algMaxBound ) } (algMinBound, algMaxBound) = case maybe_ncons of Just n -> (0, n - 1) Nothing -> (minBound, maxBound) (DiscrI i1) `eqAlt` (DiscrI i2) = i1 == i2 (DiscrF f1) `eqAlt` (DiscrF f2) = f1 == f2 (DiscrD d1) `eqAlt` (DiscrD d2) = d1 == d2 (DiscrP i1) `eqAlt` (DiscrP i2) = i1 == i2 NoDiscr `eqAlt` NoDiscr = True _ `eqAlt` _ = False (DiscrI i1) `leAlt` (DiscrI i2) = i1 <= i2 (DiscrF f1) `leAlt` (DiscrF f2) = f1 <= f2 (DiscrD d1) `leAlt` (DiscrD d2) = d1 <= d2 (DiscrP i1) `leAlt` (DiscrP i2) = i1 <= i2 NoDiscr `leAlt` NoDiscr = True _ `leAlt` _ = False isNoDiscr NoDiscr = True isNoDiscr _ = False dec (DiscrI i) = DiscrI (i-1) dec (DiscrP i) = DiscrP (i-1) dec other = other -- not really right, but if you -- do cases on floating values, you'll get what you deserve -- same snotty comment applies to the following minF, maxF :: Float minD, maxD :: Double minF = -1.0e37 maxF = 1.0e37 minD = -1.0e308 maxD = 1.0e308 in mkTree notd_ways init_lo init_hi -- ----------------------------------------------------------------------------- -- Supporting junk for the compilation schemes -- Describes case alts data Discr = DiscrI Int | DiscrF Float | DiscrD Double | DiscrP Int | NoDiscr instance Outputable Discr where ppr (DiscrI i) = int i ppr (DiscrF f) = text (show f) ppr (DiscrD d) = text (show d) ppr (DiscrP i) = int i ppr NoDiscr = text "DEF" lookupBCEnv_maybe :: BCEnv -> Id -> Maybe Int lookupBCEnv_maybe = lookupFM idSizeW :: Id -> Int idSizeW id = cgRepSizeW (typeCgRep (idType id)) unboxedTupleException :: a unboxedTupleException = throwDyn (Panic ("Bytecode generator can't handle unboxed tuples. Possibly due\n" ++ "\tto foreign import/export decls in source. Workaround:\n" ++ "\tcompile this module to a .o file, then restart session.")) mkSLIDE n d = if d == 0 then nilOL else unitOL (SLIDE n d) bind x f = f x splitApp :: AnnExpr' id ann -> (AnnExpr' id ann, [AnnExpr' id ann]) -- The arguments are returned in *right-to-left* order splitApp (AnnApp (_,f) (_,a)) | isTypeAtom a = splitApp f | otherwise = case splitApp f of (f', as) -> (f', a:as) splitApp (AnnNote n (_,e)) = splitApp e splitApp e = (e, []) isTypeAtom :: AnnExpr' id ann -> Bool isTypeAtom (AnnType _) = True isTypeAtom _ = False isVoidArgAtom :: AnnExpr' id ann -> Bool isVoidArgAtom (AnnVar v) = typeCgRep (idType v) == VoidArg isVoidArgAtom (AnnNote n (_,e)) = isVoidArgAtom e isVoidArgAtom _ = False atomRep :: AnnExpr' Id ann -> CgRep atomRep (AnnVar v) = typeCgRep (idType v) atomRep (AnnLit l) = typeCgRep (literalType l) atomRep (AnnNote n b) = atomRep (snd b) atomRep (AnnApp f (_, AnnType _)) = atomRep (snd f) atomRep (AnnLam x e) | isTyVar x = atomRep (snd e) atomRep other = pprPanic "atomRep" (ppr (deAnnotate (undefined,other))) isPtrAtom :: AnnExpr' Id ann -> Bool isPtrAtom e = atomRep e == PtrArg -- Let szsw be the sizes in words of some items pushed onto the stack, -- which has initial depth d'. Return the values which the stack environment -- should map these items to. mkStackOffsets :: Int -> [Int] -> [Int] mkStackOffsets original_depth szsw = map (subtract 1) (tail (scanl (+) original_depth szsw)) -- ----------------------------------------------------------------------------- -- The bytecode generator's monad data BcM_State = BcM_State { nextlabel :: Int, -- for generating local labels malloced :: [Ptr ()] } -- ptrs malloced for current BCO -- Should be free()d when it is GCd newtype BcM r = BcM (BcM_State -> IO (BcM_State, r)) ioToBc :: IO a -> BcM a ioToBc io = BcM $ \st -> do x <- io return (st, x) runBc :: BcM r -> IO (BcM_State, r) runBc (BcM m) = m (BcM_State 0 []) thenBc :: BcM a -> (a -> BcM b) -> BcM b thenBc (BcM expr) cont = BcM $ \st0 -> do (st1, q) <- expr st0 let BcM k = cont q (st2, r) <- k st1 return (st2, r) thenBc_ :: BcM a -> BcM b -> BcM b thenBc_ (BcM expr) (BcM cont) = BcM $ \st0 -> do (st1, q) <- expr st0 (st2, r) <- cont st1 return (st2, r) returnBc :: a -> BcM a returnBc result = BcM $ \st -> (return (st, result)) instance Monad BcM where (>>=) = thenBc (>>) = thenBc_ return = returnBc emitBc :: ([Ptr ()] -> ProtoBCO Name) -> BcM (ProtoBCO Name) emitBc bco = BcM $ \st -> return (st{malloced=[]}, bco (malloced st)) recordMallocBc :: Ptr a -> BcM () recordMallocBc a = BcM $ \st -> return (st{malloced = castPtr a : malloced st}, ()) getLabelBc :: BcM Int getLabelBc = BcM $ \st -> return (st{nextlabel = 1 + nextlabel st}, nextlabel st) getLabelsBc :: Int -> BcM [Int] getLabelsBc n = BcM $ \st -> let ctr = nextlabel st in return (st{nextlabel = ctr+n}, [ctr .. ctr+n-1]) \end{code}