import CoreSyn -- input
import StgSyn -- output
-import CoreUtils ( coreExprType )
+import CoreUtils ( exprType )
import SimplUtils ( findDefault )
import CostCentre ( noCCS )
-import Id ( Id, mkSysLocal, idType,
- externallyVisibleId, setIdUnique, idName, getIdDemandInfo
+import Id ( Id, mkSysLocal, idType, idStrictness, isExportedId,
+ mkVanillaId, idName, idDemandInfo, idArity, setIdType,
+ idFlavour
)
-import Var ( Var, varType, modifyIdInfo )
-import IdInfo ( setDemandInfo )
-import UsageSPUtils ( primOpUsgTys )
-import DataCon ( DataCon, dataConName, dataConId )
-import Name ( Name, nameModule, isLocallyDefinedName )
-import Module ( isDynamicModule )
-import Const ( Con(..), Literal, isLitLitLit )
+import IdInfo ( StrictnessInfo(..), IdFlavour(..) )
+import DataCon ( dataConWrapId )
+import Demand ( Demand, isStrict, wwLazy )
+import Name ( setNameUnique )
import VarEnv
-import Const ( Con(..), isWHNFCon, Literal(..) )
-import PrimOp ( PrimOp(..), primOpUsg )
+import PrimOp ( PrimOp(..), setCCallUnique )
import Type ( isUnLiftedType, isUnboxedTupleType, Type, splitFunTy_maybe,
- UsageAnn(..), tyUsg, applyTy )
-import TysPrim ( intPrimTy )
-import Demand
-import Unique ( Unique, Uniquable(..) )
+ UsageAnn(..), tyUsg, applyTy, repType, seqType,
+ splitRepFunTys, mkFunTys
+ )
import UniqSupply -- all of it, really
-import Util
+import BasicTypes ( TopLevelFlag(..), isNotTopLevel )
+import UniqSet ( emptyUniqSet )
import Maybes
import Outputable
\end{code}
+ *************************************************
*************** OVERVIEW *********************
+ *************************************************
-The business of this pass is to convert Core to Stg. On the way:
+The business of this pass is to convert Core to Stg. On the way it
+does some important transformations:
-* We discard type lambdas and applications. In so doing we discard
- "trivial" bindings such as
+1. We discard type lambdas and applications. In so doing we discard
+ "trivial" bindings such as
x = y t1 t2
- where t1, t2 are types
+ where t1, t2 are types
+
+2. We get the program into "A-normal form". In particular:
+
+ f E ==> let x = E in f x
+ OR ==> case E of x -> f x
+
+ where E is a non-trivial expression.
+ Which transformation is used depends on whether f is strict or not.
+ [Previously the transformation to case used to be done by the
+ simplifier, but it's better done here. It does mean that f needs
+ to have its strictness info correct!.]
+
+ Similarly, convert any unboxed let's into cases.
+ [I'm experimenting with leaving 'ok-for-speculation' rhss in let-form
+ right up to this point.]
+
+3. We clone all local binders. The code generator uses the uniques to
+ name chunks of code for thunks, so it's important that the names used
+ are globally unique, not simply not-in-scope, which is all that
+ the simplifier ensures.
+
+
+NOTE THAT:
* We don't pin on correct arities any more, because they can be mucked up
by the lambda lifter. In particular, the lambda lifter can take a local
\begin{code}
type StgEnv = IdEnv Id
-data StgFloatBind = StgFloatBind Id StgExpr RhsDemand
+data StgFloatBind = NoBindF
+ | RecF [(Id, StgRhs)]
+ | NonRecF
+ Id
+ StgExpr -- *Can* be a StgLam
+ RhsDemand
+ [StgFloatBind]
+
+-- The interesting one is the NonRecF
+-- NonRecF x rhs demand binds
+-- means
+-- x = let binds in rhs
+-- (or possibly case etc if x demand is strict)
+-- The binds are kept separate so they can be floated futher
+-- if appropriate
\end{code}
A @RhsDemand@ gives the demand on an RHS: strict (@isStrictDem@) and
isOnceDem :: Bool -- True => used at most once
}
-tyDem :: Type -> RhsDemand
--- derive RhsDemand (assuming let-binding)
-tyDem ty = case tyUsg ty of
- UsOnce -> RhsDemand False True
- UsMany -> RhsDemand False False
- UsVar _ -> pprPanic "CoreToStg.tyDem: UsVar unexpected:" $ ppr ty
+mkDem :: Demand -> Bool -> RhsDemand
+mkDem strict once = RhsDemand (isStrict strict) once
+
+mkDemTy :: Demand -> Type -> RhsDemand
+mkDemTy strict ty = RhsDemand (isStrict strict) (isOnceTy ty)
+
+isOnceTy :: Type -> Bool
+isOnceTy ty
+ =
+#ifdef USMANY
+ opt_UsageSPOn && -- can't expect annotations if -fusagesp is off
+#endif
+ case tyUsg ty of
+ UsOnce -> True
+ UsMany -> False
+ UsVar uv -> pprPanic "CoreToStg: unexpected uvar annot:" (ppr uv)
-bdrDem :: Var -> RhsDemand
-bdrDem = tyDem . varType
+bdrDem :: Id -> RhsDemand
+bdrDem id = mkDem (idDemandInfo id) (isOnceTy (idType id))
safeDem, onceDem :: RhsDemand
safeDem = RhsDemand False False -- always safe to use this
later. For this pass
we use @bOGUS_LVs@ and @bOGUS_FVs@ as placeholders.
+When printing out the Stg we need non-bottom values in these
+locations.
+
\begin{code}
bOGUS_LVs :: StgLiveVars
-bOGUS_LVs = panic "bOGUS_LVs" -- emptyUniqSet (used when pprTracing)
+bOGUS_LVs = emptyUniqSet
bOGUS_FVs :: [Id]
-bOGUS_FVs = panic "bOGUS_FVs" -- [] (ditto)
+bOGUS_FVs = []
\end{code}
\begin{code}
coreBindsToStg env [] = returnUs []
coreBindsToStg env (b:bs)
- = coreBindToStg env b `thenUs` \ (new_b, new_env) ->
+ = coreBindToStg TopLevel env b `thenUs` \ (bind_spec, new_env) ->
coreBindsToStg new_env bs `thenUs` \ new_bs ->
- returnUs (new_b ++ new_bs)
+ case bind_spec of
+ NonRecF bndr rhs dem floats
+ -> ASSERT2( not (isStrictDem dem) &&
+ not (isUnLiftedType (idType bndr)),
+ ppr b ) -- No top-level cases!
+
+ mkStgBinds floats rhs `thenUs` \ new_rhs ->
+ returnUs (StgNonRec bndr (exprToRhs dem TopLevel new_rhs)
+ : new_bs)
+ -- Keep all the floats inside...
+ -- Some might be cases etc
+ -- We might want to revisit this decision
+
+ RecF prs -> returnUs (StgRec prs : new_bs)
+ NoBindF -> pprTrace "topCoreBindsToStg" (ppr b) $
+ returnUs new_bs
\end{code}
+
%************************************************************************
%* *
\subsection[coreToStg-binds]{Converting bindings}
%************************************************************************
\begin{code}
-coreBindToStg :: StgEnv
- -> CoreBind
- -> UniqSM ([StgBinding], -- Empty or singleton
- StgEnv) -- Floats
-
-coreBindToStg env (NonRec binder rhs)
- = coreRhsToStg env rhs (bdrDem binder) `thenUs` \ stg_rhs ->
- newLocalId env binder `thenUs` \ (new_env, new_binder) ->
- returnUs ([StgNonRec new_binder stg_rhs], new_env)
-
-coreBindToStg env (Rec pairs)
- = newLocalIds env binders `thenUs` \ (env', binders') ->
- mapUs (\ (bdr,rhs) -> coreRhsToStg env' rhs (bdrDem bdr) )
- pairs `thenUs` \ stg_rhss ->
- returnUs ([StgRec (binders' `zip` stg_rhss)], env')
+coreBindToStg :: TopLevelFlag -> StgEnv -> CoreBind -> UniqSM (StgFloatBind, StgEnv)
+
+coreBindToStg top_lev env (NonRec binder rhs)
+ = coreExprToStgFloat env rhs `thenUs` \ (floats, stg_rhs) ->
+ case (floats, stg_rhs) of
+ ([], StgApp var []) | not (isExportedId binder)
+ -> returnUs (NoBindF, extendVarEnv env binder var)
+ -- A trivial binding let x = y in ...
+ -- can arise if postSimplExpr floats a NoRep literal out
+ -- so it seems sensible to deal with it well.
+ -- But we don't want to discard exported things. They can
+ -- occur; e.g. an exported user binding f = g
+
+ other -> newLocalId top_lev env binder `thenUs` \ (new_env, new_binder) ->
+ returnUs (NonRecF new_binder stg_rhs dem floats, new_env)
+ where
+ dem = bdrDem binder
+
+
+coreBindToStg top_lev env (Rec pairs)
+ = newLocalIds top_lev env binders `thenUs` \ (env', binders') ->
+ mapUs (do_rhs env') pairs `thenUs` \ stg_rhss ->
+ returnUs (RecF (binders' `zip` stg_rhss), env')
where
- (binders, rhss) = unzip pairs
+ binders = map fst pairs
+ do_rhs env (bndr,rhs) = coreExprToStgFloat env rhs `thenUs` \ (floats, stg_expr) ->
+ mkStgBinds floats stg_expr `thenUs` \ stg_expr' ->
+ -- NB: stg_expr' might still be a StgLam (and we want that)
+ returnUs (exprToRhs (bdrDem bndr) top_lev stg_expr')
\end{code}
%************************************************************************
\begin{code}
-coreRhsToStg :: StgEnv -> CoreExpr -> RhsDemand -> UniqSM StgRhs
-
-coreRhsToStg env core_rhs dem
- = coreExprToStg env core_rhs dem `thenUs` \ stg_expr ->
- returnUs (exprToRhs dem stg_expr)
-
-exprToRhs dem (StgLet (StgNonRec var1 rhs) (StgApp var2 []))
- | var1 == var2
- = rhs
- -- This curious stuff is to unravel what a lambda turns into
- -- We have to do it this way, rather than spot a lambda in the
- -- incoming rhs. Why? Because trivial bindings might conceal
- -- what the rhs is actually like.
+exprToRhs :: RhsDemand -> TopLevelFlag -> StgExpr -> StgRhs
+exprToRhs dem _ (StgLam _ bndrs body)
+ = ASSERT( not (null bndrs) )
+ StgRhsClosure noCCS
+ stgArgOcc
+ noSRT
+ bOGUS_FVs
+ ReEntrant -- binders is non-empty
+ bndrs
+ body
{-
We reject the following candidates for 'static constructor'dom:
- any dcon that takes a lit-lit as an arg.
- - [Win32 DLLs only]: any dcon that is (or takes as arg)
- that's living in a DLL.
+ - [Win32 DLLs only]: any dcon that resides in a DLL
+ (or takes as arg something that is.)
These constraints are necessary to ensure that the code
generated in the end for the static constructors, which
constructors (ala C++ static class constructors) which will
then be run at load time to fix up static closures.
-}
-exprToRhs dem (StgCon (DataCon con) args _)
- | not is_dynamic &&
- all (not.is_lit_lit) args = StgRhsCon noCCS con args
- where
- is_dynamic = isDynCon con || any (isDynArg) args
-
- is_lit_lit (StgVarArg _) = False
- is_lit_lit (StgConArg x) =
- case x of
- Literal l -> isLitLitLit l
- _ -> False
-
-exprToRhs dem expr
- = StgRhsClosure noCCS -- No cost centre (ToDo?)
- stgArgOcc -- safe
+exprToRhs dem toplev (StgConApp con args)
+ | isNotTopLevel toplev || not (isDllConApp con args)
+ -- isDllConApp checks for LitLit args too
+ = StgRhsCon noCCS con args
+
+exprToRhs dem _ expr
+ = upd `seq`
+ StgRhsClosure noCCS -- No cost centre (ToDo?)
+ stgArgOcc -- safe
noSRT -- figure out later
bOGUS_FVs
- (if isOnceDem dem then SingleEntry else Updatable)
+ upd
[]
expr
-
-isDynCon :: DataCon -> Bool
-isDynCon con = isDynName (dataConName con)
-
-isDynArg :: StgArg -> Bool
-isDynArg (StgVarArg v) = isDynName (idName v)
-isDynArg (StgConArg con) =
- case con of
- DataCon dc -> isDynCon dc
- Literal l -> isLitLitLit l
- _ -> False
-
-isDynName :: Name -> Bool
-isDynName nm =
- not (isLocallyDefinedName nm) &&
- isDynamicModule (nameModule nm)
-
-
+ where
+ upd = if isOnceDem dem then SingleEntry else Updatable
+ -- HA! Paydirt for "dem"
\end{code}
\begin{code}
coreArgsToStg :: StgEnv -> [(CoreArg,RhsDemand)] -> UniqSM ([StgFloatBind], [StgArg])
--- arguments are all value arguments (tyargs already removed), paired with their demand
+-- Arguments are all value arguments (tyargs already removed), paired with their demand
coreArgsToStg env []
= returnUs ([], [])
coreArgsToStg env ads `thenUs` \ (bs2, as') ->
returnUs (bs1 ++ bs2, a' : as')
--- This is where we arrange that a non-trivial argument is let-bound
coreArgToStg :: StgEnv -> (CoreArg,RhsDemand) -> UniqSM ([StgFloatBind], StgArg)
+-- This is where we arrange that a non-trivial argument is let-bound
coreArgToStg env (arg,dem)
- = let
- ty = coreExprType arg
- dem' = if isUnLiftedType ty -- if it's unlifted, it's definitely strict
- then dem { isStrictDem = True }
- else dem
- in
- coreExprToStgFloat env arg dem' `thenUs` \ (binds, arg') ->
- case (binds, arg') of
- ([], StgCon con [] _) | isWHNFCon con -> returnUs ([], StgConArg con)
- ([], StgApp v []) -> returnUs ([], StgVarArg v)
-
- -- A non-trivial argument: we must let (or case-bind)
- -- We don't do the case part here... we leave that to mkStgBinds
-
- -- Further complication: if we're converting this binding into
- -- a case, then try to avoid generating any case-of-case
- -- expressions by pulling out the floats.
- (_, other) ->
- newStgVar ty `thenUs` \ v ->
- if isStrictDem dem'
- then returnUs (binds ++ [StgFloatBind v arg' dem'], StgVarArg v)
- else returnUs ([StgFloatBind v (mkStgBinds binds arg') dem'], StgVarArg v)
+ = coreExprToStgFloat env arg `thenUs` \ (floats, arg') ->
+ case arg' of
+ StgApp v [] -> returnUs (floats, StgVarArg v)
+ StgLit lit -> returnUs (floats, StgLitArg lit)
+
+ StgConApp con [] -> returnUs (floats, StgVarArg (dataConWrapId con))
+ -- A nullary constructor can be replaced with
+ -- a ``call'' to its wrapper
+
+ other -> newStgVar arg_ty `thenUs` \ v ->
+ returnUs ([NonRecF v arg' dem floats], StgVarArg v)
+ where
+ arg_ty = exprType arg
\end{code}
%************************************************************************
\begin{code}
-coreExprToStg :: StgEnv -> CoreExpr -> RhsDemand -> UniqSM StgExpr
-
-coreExprToStg env (Var var) dem
- = returnUs (StgApp (stgLookup env var) [])
-
+coreExprToStg :: StgEnv -> CoreExpr -> UniqSM StgExpr
+coreExprToStg env expr
+ = coreExprToStgFloat env expr `thenUs` \ (binds,stg_expr) ->
+ mkStgBinds binds stg_expr `thenUs` \ stg_expr' ->
+ deStgLam stg_expr'
\end{code}
%************************************************************************
%* *
-\subsubsection[coreToStg-lambdas]{Lambda abstractions}
+\subsubsection[coreToStg-let(rec)]{Let and letrec expressions}
%* *
%************************************************************************
\begin{code}
-coreExprToStg env expr@(Lam _ _) dem
- = let
- (binders, body) = collectBinders expr
- id_binders = filter isId binders
- body_dem = trace "coreExprToStg: approximating body_dem in Lam"
- safeDem
- in
- newLocalIds env id_binders `thenUs` \ (env', binders') ->
- coreExprToStg env' body body_dem `thenUs` \ stg_body ->
+coreExprToStgFloat :: StgEnv -> CoreExpr
+ -> UniqSM ([StgFloatBind], StgExpr)
+-- Transform an expression to STG. The 'floats' are
+-- any bindings we had to create for function arguments.
+\end{code}
- if null id_binders then -- it was all type/usage binders; tossed
- returnUs stg_body
- else
- case stg_body of
-
- -- if the body reduced to a lambda too...
- (StgLet (StgNonRec var (StgRhsClosure cc bi srt fvs uf args body))
- (StgApp var' []))
- | var == var' ->
- returnUs (StgLet (StgNonRec var
- (StgRhsClosure noCCS
- stgArgOcc
- noSRT
- bOGUS_FVs
- ReEntrant
- (binders' ++ args)
- body))
- (StgApp var []))
-
- other ->
+Simple cases first
+
+\begin{code}
+coreExprToStgFloat env (Var var)
+ = mkStgApp env var [] (idType var) `thenUs` \ app ->
+ returnUs ([], app)
- -- We must let-bind the lambda
- newStgVar (coreExprType expr) `thenUs` \ var ->
- returnUs
- (StgLet (StgNonRec var (StgRhsClosure noCCS
- stgArgOcc
- noSRT
- bOGUS_FVs
- ReEntrant -- binders is non-empty
- binders'
- stg_body))
- (StgApp var []))
+coreExprToStgFloat env (Lit lit)
+ = returnUs ([], StgLit lit)
+
+coreExprToStgFloat env (Let bind body)
+ = coreBindToStg NotTopLevel env bind `thenUs` \ (new_bind, new_env) ->
+ coreExprToStgFloat new_env body `thenUs` \ (floats, stg_body) ->
+ returnUs (new_bind:floats, stg_body)
\end{code}
-%************************************************************************
-%* *
-\subsubsection[coreToStg-let(rec)]{Let and letrec expressions}
-%* *
-%************************************************************************
+Convert core @scc@ expression directly to STG @scc@ expression.
\begin{code}
-coreExprToStg env (Let bind body) dem
- = coreBindToStg env bind `thenUs` \ (stg_binds, new_env) ->
- coreExprToStg new_env body dem `thenUs` \ stg_body ->
- returnUs (foldr StgLet stg_body stg_binds)
+coreExprToStgFloat env (Note (SCC cc) expr)
+ = coreExprToStg env expr `thenUs` \ stg_expr ->
+ returnUs ([], StgSCC cc stg_expr)
+
+coreExprToStgFloat env (Note other_note expr)
+ = coreExprToStgFloat env expr
+\end{code}
+
+\begin{code}
+coreExprToStgFloat env expr@(Type _)
+ = pprPanic "coreExprToStgFloat: tyarg unexpected:" $ ppr expr
\end{code}
%************************************************************************
%* *
-\subsubsection[coreToStg-scc]{SCC expressions}
+\subsubsection[coreToStg-lambdas]{Lambda abstractions}
%* *
%************************************************************************
-Covert core @scc@ expression directly to STG @scc@ expression.
\begin{code}
-coreExprToStg env (Note (SCC cc) expr) dem
- = coreExprToStg env expr dem `thenUs` \ stg_expr ->
- returnUs (StgSCC cc stg_expr)
-\end{code}
-
-\begin{code}
-coreExprToStg env (Note other_note expr) dem = coreExprToStg env expr dem
-\end{code}
+coreExprToStgFloat env expr@(Lam _ _)
+ = let
+ expr_ty = exprType expr
+ (binders, body) = collectBinders expr
+ id_binders = filter isId binders
+ in
+ if null id_binders then -- It was all type/usage binders; tossed
+ coreExprToStgFloat env body
+ else
+ -- At least some value binders
+ newLocalIds NotTopLevel env id_binders `thenUs` \ (env', binders') ->
+ coreExprToStgFloat env' body `thenUs` \ (floats, stg_body) ->
+ mkStgBinds floats stg_body `thenUs` \ stg_body' ->
-The rest are handled by coreExprStgFloat.
+ case stg_body' of
+ StgLam ty lam_bndrs lam_body ->
+ -- If the body reduced to a lambda too, join them up
+ returnUs ([], mkStgLam expr_ty (binders' ++ lam_bndrs) lam_body)
-\begin{code}
-coreExprToStg env expr dem
- = coreExprToStgFloat env expr dem `thenUs` \ (binds,stg_expr) ->
- returnUs (mkStgBinds binds stg_expr)
+ other ->
+ -- Body didn't reduce to a lambda, so return one
+ returnUs ([], mkStgLam expr_ty binders' stg_body')
\end{code}
+
%************************************************************************
%* *
\subsubsection[coreToStg-applications]{Applications}
%************************************************************************
\begin{code}
-coreExprToStgFloat env expr@(App _ _) dem
+coreExprToStgFloat env expr@(App _ _)
= let
- (fun,rads,_) = collect_args expr
- ads = reverse rads
+ (fun,rads,ty,ss) = collect_args expr
+ ads = reverse rads
+ final_ads | null ss = ads
+ | otherwise = zap ads -- Too few args to satisfy strictness info
+ -- so we have to ignore all the strictness info
+ -- e.g. + (error "urk")
+ -- Here, we can't evaluate the arg strictly,
+ -- because this partial application might be seq'd
in
- coreArgsToStg env ads `thenUs` \ (binds, stg_args) ->
+ coreArgsToStg env final_ads `thenUs` \ (arg_floats, stg_args) ->
-- Now deal with the function
case (fun, stg_args) of
- (Var fun_id, _) -> -- A function Id, so do an StgApp; it's ok if
+ (Var fn_id, _) -> -- A function Id, so do an StgApp; it's ok if
-- there are no arguments.
- returnUs (binds,
- StgApp (stgLookup env fun_id) stg_args)
+ mkStgApp env fn_id stg_args ty `thenUs` \ app ->
+ returnUs (arg_floats, app)
(non_var_fun, []) -> -- No value args, so recurse into the function
- ASSERT( null binds )
- coreExprToStg env non_var_fun dem `thenUs` \e ->
- returnUs ([], e)
+ ASSERT( null arg_floats )
+ coreExprToStgFloat env non_var_fun
other -> -- A non-variable applied to things; better let-bind it.
- newStgVar (coreExprType fun) `thenUs` \ fun_id ->
- coreRhsToStg env fun onceDem `thenUs` \ fun_rhs ->
- returnUs (binds,
- StgLet (StgNonRec fun_id fun_rhs) $
- StgApp fun_id stg_args)
+ newStgVar (exprType fun) `thenUs` \ fn_id ->
+ coreExprToStgFloat env fun `thenUs` \ (fun_floats, stg_fun) ->
+ mkStgApp env fn_id stg_args ty `thenUs` \ app ->
+ returnUs (NonRecF fn_id stg_fun onceDem fun_floats : arg_floats,
+ app)
+
where
-- Collect arguments and demands (*in reverse order*)
- collect_args :: CoreExpr -> (CoreExpr, [(CoreExpr,RhsDemand)], Type)
- collect_args (App fun (Type tyarg)) = let (the_fun,ads,fun_ty) = collect_args fun
- in (the_fun,ads,applyTy fun_ty tyarg)
- collect_args (App fun arg ) = let (the_fun,ads,fun_ty) = collect_args fun
- (arg_ty,res_ty) = expectJust "coreExprToStgFloat:collect_args" $
- splitFunTy_maybe fun_ty
- in (the_fun,(arg,tyDem arg_ty):ads,res_ty)
- collect_args (Note (Coerce ty _) e) = let (the_fun,ads,_ ) = collect_args e
- in (the_fun,ads,ty)
- collect_args (Note InlineCall e) = collect_args e
- collect_args (Note (TermUsg _) e) = collect_args e
- collect_args fun = (fun,[],coreExprType fun)
-\end{code}
-
-%************************************************************************
-%* *
-\subsubsection[coreToStg-con]{Constructors}
-%* *
-%************************************************************************
+ -- collect_args e = (f, args_w_demands, ty, stricts)
+ -- => e = f tys args, (i.e. args are just the value args)
+ -- e :: ty
+ -- stricts is the leftover demands of e on its further args
+ -- If stricts runs out, we zap all the demands in args_w_demands
+ -- because partial applications are lazy
-For data constructors, the demand on an argument is the demand on the
-constructor as a whole (see module UsageSPInf). For primops, the
-demand is derived from the type of the primop.
+ collect_args :: CoreExpr -> (CoreExpr, [(CoreExpr,RhsDemand)], Type, [Demand])
-If usage inference is off, we simply make all bindings updatable for
-speed.
+ collect_args (Note (Coerce ty _) e) = let (the_fun,ads,_,ss) = collect_args e
+ in (the_fun,ads,ty,ss)
+ collect_args (Note InlineCall e) = collect_args e
+ collect_args (Note (TermUsg _) e) = collect_args e
-\begin{code}
-coreExprToStgFloat env expr@(Con con args) dem
- = let
- args' = filter isValArg args
- dems' = case con of
- Literal _ -> ASSERT( null args' {-'cpp-} )
- []
- DEFAULT -> panic "coreExprToStgFloat: DEFAULT"
- DataCon c -> repeat (if isOnceDem dem then onceDem else safeDem)
- PrimOp p -> let tyargs = map (\ (Type ty) -> ty) $
- takeWhile isTypeArg args
- (arg_tys,_) = primOpUsgTys p tyargs
- in ASSERT( length arg_tys == length args' {-'cpp-} )
- -- primops always fully applied, so == not >=
- map tyDem arg_tys
- in
- coreArgsToStg env (zip args' dems') `thenUs` \ (binds, stg_atoms) ->
- (case con of -- must change unique if present
- PrimOp (CCallOp (Right _) a b c) -> getUniqueUs `thenUs` \ u ->
- returnUs (PrimOp (CCallOp (Right u) a b c))
- _ -> returnUs con)
- `thenUs` \ con' ->
- returnUs (binds, StgCon con' stg_atoms (coreExprType expr))
+ collect_args (App fun (Type tyarg)) = let (the_fun,ads,fun_ty,ss) = collect_args fun
+ in (the_fun,ads,applyTy fun_ty tyarg,ss)
+ collect_args (App fun arg)
+ = (the_fun, (arg, mkDemTy ss1 arg_ty) : ads, res_ty, ss_rest)
+ where
+ (ss1, ss_rest) = case ss of
+ (ss1:ss_rest) -> (ss1, ss_rest)
+ [] -> (wwLazy, [])
+ (the_fun, ads, fun_ty, ss) = collect_args fun
+ (arg_ty, res_ty) = expectJust "coreExprToStgFloat:collect_args" $
+ splitFunTy_maybe fun_ty
+
+ collect_args (Var v)
+ = (Var v, [], idType v, stricts)
+ where
+ stricts = case idStrictness v of
+ StrictnessInfo demands _ -> demands
+ other -> repeat wwLazy
+
+ collect_args fun = (fun, [], exprType fun, repeat wwLazy)
+
+ -- "zap" nukes the strictness info for a partial application
+ zap ads = [(arg, RhsDemand False once) | (arg, RhsDemand _ once) <- ads]
\end{code}
+
%************************************************************************
%* *
\subsubsection[coreToStg-cases]{Case expressions}
%************************************************************************
\begin{code}
-coreExprToStgFloat env expr@(Case scrut bndr alts) dem
- = coreExprToStgFloat env scrut (bdrDem bndr) `thenUs` \ (binds, scrut') ->
- newEvaldLocalId env bndr `thenUs` \ (env', bndr') ->
+coreExprToStgFloat env (Case scrut bndr alts)
+ = coreExprToStgFloat env scrut `thenUs` \ (binds, scrut') ->
+ newLocalId NotTopLevel env bndr `thenUs` \ (env', bndr') ->
alts_to_stg env' (findDefault alts) `thenUs` \ alts' ->
- returnUs (binds, mkStgCase scrut' bndr' alts')
+ mkStgCase scrut' bndr' alts' `thenUs` \ expr' ->
+ returnUs (binds, expr')
where
scrut_ty = idType bndr
prim_case = isUnLiftedType scrut_ty && not (isUnboxedTupleType scrut_ty)
| prim_case
= default_to_stg env deflt `thenUs` \ deflt' ->
mapUs (prim_alt_to_stg env) alts `thenUs` \ alts' ->
- returnUs (StgPrimAlts scrut_ty alts' deflt')
+ returnUs (mkStgPrimAlts scrut_ty alts' deflt')
| otherwise
= default_to_stg env deflt `thenUs` \ deflt' ->
mapUs (alg_alt_to_stg env) alts `thenUs` \ alts' ->
- returnUs (StgAlgAlts scrut_ty alts' deflt')
+ returnUs (mkStgAlgAlts scrut_ty alts' deflt')
- alg_alt_to_stg env (DataCon con, bs, rhs)
- = coreExprToStg env rhs dem `thenUs` \ stg_rhs ->
- returnUs (con, filter isId bs, [ True | b <- bs ]{-bogus use mask-}, stg_rhs)
+ alg_alt_to_stg env (DataAlt con, bs, rhs)
+ = newLocalIds NotTopLevel env (filter isId bs) `thenUs` \ (env', stg_bs) ->
+ coreExprToStg env' rhs `thenUs` \ stg_rhs ->
+ returnUs (con, stg_bs, [ True | b <- stg_bs ]{-bogus use mask-}, stg_rhs)
-- NB the filter isId. Some of the binders may be
-- existential type variables, which STG doesn't care about
- prim_alt_to_stg env (Literal lit, args, rhs)
+ prim_alt_to_stg env (LitAlt lit, args, rhs)
= ASSERT( null args )
- coreExprToStg env rhs dem `thenUs` \ stg_rhs ->
+ coreExprToStg env rhs `thenUs` \ stg_rhs ->
returnUs (lit, stg_rhs)
default_to_stg env Nothing
= returnUs StgNoDefault
default_to_stg env (Just rhs)
- = coreExprToStg env rhs dem `thenUs` \ stg_rhs ->
+ = coreExprToStg env rhs `thenUs` \ stg_rhs ->
returnUs (StgBindDefault stg_rhs)
-- The binder is used for prim cases and not otherwise
-- (hack for old code gen)
\end{code}
-\begin{code}
-coreExprToStgFloat env expr@(Type _) dem
- = pprPanic "coreExprToStgFloat: tyarg unexpected:" $ ppr expr
-\end{code}
-
-\begin{code}
-coreExprToStgFloat env expr dem
- = coreExprToStg env expr dem `thenUs` \stg_expr ->
- returnUs ([], stg_expr)
-\end{code}
%************************************************************************
%* *
There's not anything interesting we can ASSERT about \tr{var} if it
isn't in the StgEnv. (WDP 94/06)
-\begin{code}
-stgLookup :: StgEnv -> Id -> Id
-stgLookup env var = case (lookupVarEnv env var) of
- Nothing -> var
- Just var -> var
-\end{code}
-
Invent a fresh @Id@:
\begin{code}
newStgVar :: Type -> UniqSM Id
newStgVar ty
= getUniqueUs `thenUs` \ uniq ->
+ seqType ty `seq`
returnUs (mkSysLocal SLIT("stg") uniq ty)
\end{code}
\begin{code}
-newLocalId env id
- | externallyVisibleId id
- = returnUs (env, id)
-
- | otherwise
- = -- Local binder, give it a new unique Id.
- getUniqueUs `thenUs` \ uniq ->
- let
- id' = setIdUnique id uniq
- new_env = extendVarEnv env id id'
+newLocalId TopLevel env id
+ -- Don't clone top-level binders. MkIface relies on their
+ -- uniques staying the same, so it can snaffle IdInfo off the
+ -- STG ids to put in interface files.
+ = let
+ name = idName id
+ ty = idType id
in
- returnUs (new_env, id')
+ name `seq`
+ seqType ty `seq`
+ returnUs (env, mkVanillaId name ty)
--- we overload the demandInfo field of an Id to indicate whether the Id is definitely
--- evaluated or not (i.e. whether it is a case binder). This can be used to eliminate
--- some redundant cases (c.f. dataToTag# above).
-newEvaldLocalId env id
- = getUniqueUs `thenUs` \ uniq ->
+newLocalId NotTopLevel env id
+ = -- Local binder, give it a new unique Id.
+ getUniqueUs `thenUs` \ uniq ->
let
- id' = setIdUnique id uniq `modifyIdInfo` setDemandInfo wwStrict
- new_env = extendVarEnv env id id'
+ name = idName id
+ ty = idType id
+ new_id = mkVanillaId (setNameUnique name uniq) ty
+ new_env = extendVarEnv env id new_id
in
- returnUs (new_env, id')
+ name `seq`
+ seqType ty `seq`
+ returnUs (new_env, new_id)
-newLocalIds :: StgEnv -> [Id] -> UniqSM (StgEnv, [Id])
-newLocalIds env []
+newLocalIds :: TopLevelFlag -> StgEnv -> [Id] -> UniqSM (StgEnv, [Id])
+newLocalIds top_lev env []
= returnUs (env, [])
-newLocalIds env (b:bs)
- = newLocalId env b `thenUs` \ (env', b') ->
- newLocalIds env' bs `thenUs` \ (env'', bs') ->
+newLocalIds top_lev env (b:bs)
+ = newLocalId top_lev env b `thenUs` \ (env', b') ->
+ newLocalIds top_lev env' bs `thenUs` \ (env'', bs') ->
returnUs (env'', b':bs')
\end{code}
+%************************************************************************
+%* *
+\subsection{Building STG syn}
+%* *
+%************************************************************************
+
\begin{code}
-mkStgBinds :: [StgFloatBind] -> StgExpr -> StgExpr
-mkStgBinds binds body = foldr mkStgBind body binds
+mkStgAlgAlts ty alts deflt = seqType ty `seq` StgAlgAlts ty alts deflt
+mkStgPrimAlts ty alts deflt = seqType ty `seq` StgPrimAlts ty alts deflt
+mkStgLam ty bndrs body = seqType ty `seq` StgLam ty bndrs body
+
+mkStgApp :: StgEnv -> Id -> [StgArg] -> Type -> UniqSM StgExpr
+ -- The type is the type of the entire application
+mkStgApp env fn args ty
+ = case idFlavour fn_alias of
+ DataConId dc
+ -> saturate fn_alias args ty $ \ args' ty' ->
+ returnUs (StgConApp dc args')
+
+ PrimOpId (CCallOp ccall)
+ -- Sigh...make a guaranteed unique name for a dynamic ccall
+ -- Done here, not earlier, because it's a code-gen thing
+ -> saturate fn_alias args ty $ \ args' ty' ->
+ getUniqueUs `thenUs` \ uniq ->
+ let ccall' = setCCallUnique ccall uniq in
+ returnUs (StgPrimApp (CCallOp ccall') args' ty')
+
+
+ PrimOpId op
+ -> saturate fn_alias args ty $ \ args' ty' ->
+ returnUs (StgPrimApp op args' ty')
+
+ other -> returnUs (StgApp fn_alias args)
+ -- Force the lookup
+ where
+ fn_alias = case (lookupVarEnv env fn) of -- In case it's been cloned
+ Nothing -> fn
+ Just fn' -> fn'
+
+saturate :: Id -> [StgArg] -> Type -> ([StgArg] -> Type -> UniqSM StgExpr) -> UniqSM StgExpr
+ -- The type should be the type of (id args)
+saturate fn args ty thing_inside
+ | excess_arity == 0 -- Saturated, so nothing to do
+ = thing_inside args ty
+
+ | otherwise -- An unsaturated constructor or primop; eta expand it
+ = ASSERT2( excess_arity > 0 && excess_arity <= length arg_tys,
+ ppr fn <+> ppr args <+> ppr excess_arity <+> parens (ppr ty) <+> ppr arg_tys )
+ mapUs newStgVar extra_arg_tys `thenUs` \ arg_vars ->
+ thing_inside (args ++ map StgVarArg arg_vars) final_res_ty `thenUs` \ body ->
+ returnUs (StgLam ty arg_vars body)
+ where
+ fn_arity = idArity fn
+ excess_arity = fn_arity - length args
+ (arg_tys, res_ty) = splitRepFunTys ty
+ extra_arg_tys = take excess_arity arg_tys
+ final_res_ty = mkFunTys (drop excess_arity arg_tys) res_ty
+\end{code}
-mkStgBind (StgFloatBind bndr rhs dem) body
- | isUnLiftedType bndr_ty
- = ASSERT( not ((isUnboxedTupleType bndr_ty) && (isStrictDem dem==False)) )
- mkStgCase rhs bndr (StgPrimAlts bndr_ty [] (StgBindDefault body))
+\begin{code}
+-- Stg doesn't have a lambda *expression*
+deStgLam (StgLam ty bndrs body)
+ -- Try for eta reduction
+ = ASSERT( not (null bndrs) )
+ case eta body of
+ Just e -> -- Eta succeeded
+ returnUs e
+
+ Nothing -> -- Eta failed, so let-bind the lambda
+ newStgVar ty `thenUs` \ fn ->
+ returnUs (StgLet (StgNonRec fn lam_closure) (StgApp fn []))
+ where
+ lam_closure = StgRhsClosure noCCS
+ stgArgOcc
+ noSRT
+ bOGUS_FVs
+ ReEntrant -- binders is non-empty
+ bndrs
+ body
- | isStrictDem dem == True -- case
- = mkStgCase rhs bndr (StgAlgAlts bndr_ty [] (StgBindDefault body))
+ eta (StgApp f args)
+ | n_remaining >= 0 &&
+ and (zipWith ok bndrs last_args) &&
+ notInExpr bndrs remaining_expr
+ = Just remaining_expr
+ where
+ remaining_expr = StgApp f remaining_args
+ (remaining_args, last_args) = splitAt n_remaining args
+ n_remaining = length args - length bndrs
- | isStrictDem dem == False -- let
- = StgLet (StgNonRec bndr (exprToRhs dem rhs)) body
+ eta (StgLet bind@(StgNonRec b r) body)
+ | notInRhs bndrs r = case eta body of
+ Just e -> Just (StgLet bind e)
+ Nothing -> Nothing
+
+ eta _ = Nothing
+
+ ok bndr (StgVarArg arg) = bndr == arg
+ ok bndr other = False
+
+deStgLam expr = returnUs expr
+
+
+--------------------------------------------------
+notInExpr :: [Id] -> StgExpr -> Bool
+notInExpr vs (StgApp f args) = notInId vs f && notInArgs vs args
+notInExpr vs (StgLet (StgNonRec b r) body) = notInRhs vs r && notInExpr vs body
+notInExpr vs other = False -- Safe
+
+notInRhs :: [Id] -> StgRhs -> Bool
+notInRhs vs (StgRhsCon _ _ args) = notInArgs vs args
+notInRhs vs (StgRhsClosure _ _ _ _ _ _ body) = notInExpr vs body
+ -- Conservative: we could delete the binders from vs, but
+ -- cloning means this will never help
+
+notInArgs :: [Id] -> [StgArg] -> Bool
+notInArgs vs args = all ok args
+ where
+ ok (StgVarArg v) = notInId vs v
+ ok (StgLitArg l) = True
+
+notInId :: [Id] -> Id -> Bool
+notInId vs v = not (v `elem` vs)
+
+
+
+mkStgBinds :: [StgFloatBind]
+ -> StgExpr -- *Can* be a StgLam
+ -> UniqSM StgExpr -- *Can* be a StgLam
+
+mkStgBinds [] body = returnUs body
+mkStgBinds (b:bs) body
+ = deStgLam body `thenUs` \ body' ->
+ go (b:bs) body'
+ where
+ go [] body = returnUs body
+ go (b:bs) body = go bs body `thenUs` \ body' ->
+ mkStgBind b body'
+
+-- The 'body' arg of mkStgBind can't be a StgLam
+mkStgBind NoBindF body = returnUs body
+mkStgBind (RecF prs) body = returnUs (StgLet (StgRec prs) body)
+
+mkStgBind (NonRecF bndr rhs dem floats) body
+#ifdef DEBUG
+ -- We shouldn't get let or case of the form v=w
+ = case rhs of
+ StgApp v [] -> pprTrace "mkStgLet" (ppr bndr <+> ppr v)
+ (mk_stg_let bndr rhs dem floats body)
+ other -> mk_stg_let bndr rhs dem floats body
+
+mk_stg_let bndr rhs dem floats body
+#endif
+ | isUnLiftedType bndr_rep_ty -- Use a case/PrimAlts
+ = ASSERT( not (isUnboxedTupleType bndr_rep_ty) )
+ mkStgCase rhs bndr (StgPrimAlts bndr_rep_ty [] (StgBindDefault body)) `thenUs` \ expr' ->
+ mkStgBinds floats expr'
+
+ | is_whnf
+ = if is_strict then
+ -- Strict let with WHNF rhs
+ mkStgBinds floats $
+ StgLet (StgNonRec bndr (exprToRhs dem NotTopLevel rhs)) body
+ else
+ -- Lazy let with WHNF rhs; float until we find a strict binding
+ let
+ (floats_out, floats_in) = splitFloats floats
+ in
+ mkStgBinds floats_in rhs `thenUs` \ new_rhs ->
+ mkStgBinds floats_out $
+ StgLet (StgNonRec bndr (exprToRhs dem NotTopLevel new_rhs)) body
+
+ | otherwise -- Not WHNF
+ = if is_strict then
+ -- Strict let with non-WHNF rhs
+ mkStgCase rhs bndr (StgAlgAlts bndr_rep_ty [] (StgBindDefault body)) `thenUs` \ expr' ->
+ mkStgBinds floats expr'
+ else
+ -- Lazy let with non-WHNF rhs, so keep the floats in the RHS
+ mkStgBinds floats rhs `thenUs` \ new_rhs ->
+ returnUs (StgLet (StgNonRec bndr (exprToRhs dem NotTopLevel new_rhs)) body)
+
+ where
+ bndr_rep_ty = repType (idType bndr)
+ is_strict = isStrictDem dem
+ is_whnf = case rhs of
+ StgConApp _ _ -> True
+ StgLam _ _ _ -> True
+ other -> False
+
+-- Split at the first strict binding
+splitFloats fs@(NonRecF _ _ dem _ : _)
+ | isStrictDem dem = ([], fs)
+
+splitFloats (f : fs) = case splitFloats fs of
+ (fs_out, fs_in) -> (f : fs_out, fs_in)
+
+splitFloats [] = ([], [])
+\end{code}
+
+
+Making an STG case
+~~~~~~~~~~~~~~~~~~
+
+First, two special cases. We mangle cases involving
+ par# and seq#
+inthe scrutinee.
+
+Up to this point, seq# will appear like this:
+
+ case seq# e of
+ 0# -> seqError#
+ _ -> <stuff>
+
+This code comes from an unfolding for 'seq' in Prelude.hs.
+The 0# branch is purely to bamboozle the strictness analyser.
+For example, if <stuff> is strict in x, and there was no seqError#
+branch, the strictness analyser would conclude that the whole expression
+was strict in x, and perhaps evaluate x first -- but that would be a DISASTER.
+
+Now that the evaluation order is safe, we translate this into
+
+ case e of
+ _ -> ...
+
+This used to be done in the post-simplification phase, but we need
+unfoldings involving seq# to appear unmangled in the interface file,
+hence we do this mangling here.
+
+Similarly, par# has an unfolding in PrelConc.lhs that makes it show
+up like this:
+
+ case par# e of
+ 0# -> rhs
+ _ -> parError#
+
+
+ ==>
+ case par# e of
+ _ -> rhs
+
+fork# isn't handled like this - it's an explicit IO operation now.
+The reason is that fork# returns a ThreadId#, which gets in the
+way of the above scheme. And anyway, IO is the only guaranteed
+way to enforce ordering --SDM.
+
+
+\begin{code}
+-- Discard alernatives in case (par# ..) of
+mkStgCase scrut@(StgPrimApp ParOp _ _) bndr
+ (StgPrimAlts ty _ deflt@(StgBindDefault _))
+ = returnUs (StgCase scrut bOGUS_LVs bOGUS_LVs bndr noSRT (StgPrimAlts ty [] deflt))
+
+mkStgCase (StgPrimApp SeqOp [scrut] _) bndr
+ (StgPrimAlts _ _ deflt@(StgBindDefault rhs))
+ = mkStgCase scrut_expr new_bndr new_alts
where
- bndr_ty = idType bndr
+ new_alts | isUnLiftedType scrut_ty = WARN( True, text "mkStgCase" ) StgPrimAlts scrut_ty [] deflt
+ | otherwise = StgAlgAlts scrut_ty [] deflt
+ scrut_ty = stgArgType scrut
+ new_bndr = setIdType bndr scrut_ty
+ -- NB: SeqOp :: forall a. a -> Int#
+ -- So bndr has type Int#
+ -- But now we are going to scrutinise the SeqOp's argument directly,
+ -- so we must change the type of the case binder to match that
+ -- of the argument expression e.
+
+ scrut_expr = case scrut of
+ StgVarArg v -> StgApp v []
+ -- Others should not happen because
+ -- seq of a value should have disappeared
+ StgLitArg l -> WARN( True, text "seq on" <+> ppr l ) StgLit l
-mkStgCase (StgLet bind expr) bndr alts
- = StgLet bind (mkStgCase expr bndr alts)
mkStgCase scrut bndr alts
- = StgCase scrut bOGUS_LVs bOGUS_LVs bndr noSRT alts
+ = deStgLam scrut `thenUs` \ scrut' ->
+ -- It is (just) possible to get a lambda as a srutinee here
+ -- Namely: fromDyn (toDyn ((+1)::Int->Int)) False)
+ -- gives: case ...Bool == Int->Int... of
+ -- True -> case coerce Bool (\x -> + 1 x) of
+ -- True -> ...
+ -- False -> ...
+ -- False -> ...
+ -- The True branch of the outer case will never happen, of course.
+
+ returnUs (StgCase scrut' bOGUS_LVs bOGUS_LVs bndr noSRT alts)
\end{code}
projects / ghc-hetmet.git / blobdiff