--- /dev/null
+--
+-- Functions to bring a Core expression in normal form. This module provides a
+-- top level function "normalize", and defines the actual transformation passes that
+-- are performed.
+--
+module CLasH.Normalize (getNormalized, normalizeExpr, splitNormalized) where
+
+-- Standard modules
+import Debug.Trace
+import qualified Maybe
+import qualified List
+import qualified Control.Monad.Trans.Class as Trans
+import qualified Control.Monad as Monad
+import qualified Control.Monad.Trans.Writer as Writer
+import qualified Data.Accessor.Monad.Trans.State as MonadState
+import qualified Data.Monoid as Monoid
+import qualified Data.Map as Map
+
+-- GHC API
+import CoreSyn
+import qualified CoreUtils
+import qualified BasicTypes
+import qualified Type
+import qualified TysWiredIn
+import qualified Id
+import qualified Var
+import qualified Name
+import qualified DataCon
+import qualified VarSet
+import qualified CoreFVs
+import qualified Class
+import qualified MkCore
+import Outputable ( showSDoc, ppr, nest )
+
+-- Local imports
+import CLasH.Normalize.NormalizeTypes
+import CLasH.Translator.TranslatorTypes
+import CLasH.Normalize.NormalizeTools
+import CLasH.VHDL.Constants (builtinIds)
+import qualified CLasH.Utils as Utils
+import CLasH.Utils.Core.CoreTools
+import CLasH.Utils.Core.BinderTools
+import CLasH.Utils.Pretty
+
+----------------------------------------------------------------
+-- Cleanup transformations
+----------------------------------------------------------------
+
+--------------------------------
+-- β-reduction
+--------------------------------
+beta :: Transform
+-- Substitute arg for x in expr. For value lambda's, also clone before
+-- substitution.
+beta c (App (Lam x expr) arg) | CoreSyn.isTyVar x = setChanged >> substitute x arg c expr
+ | otherwise = setChanged >> substitute_clone x arg c expr
+-- Leave all other expressions unchanged
+beta c expr = return expr
+
+--------------------------------
+-- Unused let binding removal
+--------------------------------
+letremoveunused :: Transform
+letremoveunused c expr@(Let (NonRec b bound) res) = do
+ let used = expr_uses_binders [b] res
+ if used
+ then return expr
+ else change res
+letremoveunused c expr@(Let (Rec binds) res) = do
+ -- Filter out all unused binds.
+ let binds' = filter dobind binds
+ -- Only set the changed flag if binds got removed
+ changeif (length binds' /= length binds) (Let (Rec binds') res)
+ where
+ bound_exprs = map snd binds
+ -- For each bind check if the bind is used by res or any of the bound
+ -- expressions
+ dobind (bndr, _) = any (expr_uses_binders [bndr]) (res:bound_exprs)
+-- Leave all other expressions unchanged
+letremoveunused c expr = return expr
+
+--------------------------------
+-- empty let removal
+--------------------------------
+-- Remove empty (recursive) lets
+letremove :: Transform
+letremove c (Let (Rec []) res) = change res
+-- Leave all other expressions unchanged
+letremove c expr = return expr
+
+--------------------------------
+-- Simple let binding removal
+--------------------------------
+-- Remove a = b bindings from let expressions everywhere
+letremovesimple :: Transform
+letremovesimple = inlinebind (\(b, e) -> Trans.lift $ is_local_var e)
+
+--------------------------------
+-- Cast propagation
+--------------------------------
+-- Try to move casts as much downward as possible.
+castprop :: Transform
+castprop c (Cast (Let binds expr) ty) = change $ Let binds (Cast expr ty)
+castprop c expr@(Cast (Case scrut b _ alts) ty) = change (Case scrut b ty alts')
+ where
+ alts' = map (\(con, bndrs, expr) -> (con, bndrs, (Cast expr ty))) alts
+-- Leave all other expressions unchanged
+castprop c expr = return expr
+
+--------------------------------
+-- Cast simplification. Mostly useful for state packing and unpacking, but
+-- perhaps for others as well.
+--------------------------------
+castsimpl :: Transform
+castsimpl c expr@(Cast val ty) = do
+ -- Don't extract values that are already simpl
+ local_var <- Trans.lift $ is_local_var val
+ -- Don't extract values that are not representable, to prevent loops with
+ -- inlinenonrep
+ repr <- isRepr val
+ if (not local_var) && repr
+ then do
+ -- Generate a binder for the expression
+ id <- Trans.lift $ mkBinderFor val "castval"
+ -- Extract the expression
+ change $ Let (NonRec id val) (Cast (Var id) ty)
+ else
+ return expr
+-- Leave all other expressions unchanged
+castsimpl c expr = return expr
+
+--------------------------------
+-- Top level function inlining
+--------------------------------
+-- This transformation inlines simple top level bindings. Simple
+-- currently means that the body is only a single application (though
+-- the complexity of the arguments is not currently checked) or that the
+-- normalized form only contains a single binding. This should catch most of the
+-- cases where a top level function is created that simply calls a type class
+-- method with a type and dictionary argument, e.g.
+-- fromInteger = GHC.Num.fromInteger (SizedWord D8) $dNum
+-- which is later called using simply
+-- fromInteger (smallInteger 10)
+--
+-- These useless wrappers are created by GHC automatically. If we don't
+-- inline them, we get loads of useless components cluttering the
+-- generated VHDL.
+--
+-- Note that the inlining could also inline simple functions defined by
+-- the user, not just GHC generated functions. It turns out to be near
+-- impossible to reliably determine what functions are generated and
+-- what functions are user-defined. Instead of guessing (which will
+-- inline less than we want) we will just inline all simple functions.
+--
+-- Only functions that are actually completely applied and bound by a
+-- variable in a let expression are inlined. These are the expressions
+-- that will eventually generate instantiations of trivial components.
+-- By not inlining any other reference, we also prevent looping problems
+-- with funextract and inlinedict.
+inlinetoplevel :: Transform
+inlinetoplevel (LetBinding:_) expr | not (is_fun expr) =
+ case collectArgs expr of
+ (Var f, args) -> do
+ body_maybe <- needsInline f
+ case body_maybe of
+ Just body -> do
+ -- Regenerate all uniques in the to-be-inlined expression
+ body_uniqued <- Trans.lift $ genUniques body
+ -- And replace the variable reference with the unique'd body.
+ change (mkApps body_uniqued args)
+ -- No need to inline
+ Nothing -> return expr
+ -- This is not an application of a binder, leave it unchanged.
+ _ -> return expr
+
+-- Leave all other expressions unchanged
+inlinetoplevel c expr = return expr
+
+-- | Does the given binder need to be inlined? If so, return the body to
+-- be used for inlining.
+needsInline :: CoreBndr -> TransformMonad (Maybe CoreExpr)
+needsInline f = do
+ body_maybe <- Trans.lift $ getGlobalBind f
+ case body_maybe of
+ -- No body available?
+ Nothing -> return Nothing
+ Just body -> case CoreSyn.collectArgs body of
+ -- The body is some (top level) binder applied to 0 or more
+ -- arguments. That should be simple enough to inline.
+ (Var f, args) -> return $ Just body
+ -- Body is more complicated, try normalizing it
+ _ -> do
+ norm_maybe <- Trans.lift $ getNormalized_maybe False f
+ case norm_maybe of
+ -- Noth normalizeable
+ Nothing -> return Nothing
+ Just norm -> case splitNormalizedNonRep norm of
+ -- The function has just a single binding, so that's simple
+ -- enough to inline.
+ (args, [bind], Var res) -> return $ Just norm
+ -- More complicated function, don't inline
+ _ -> return Nothing
+
+
+----------------------------------------------------------------
+-- Program structure transformations
+----------------------------------------------------------------
+
+--------------------------------
+-- η expansion
+--------------------------------
+-- Make sure all parameters to the normalized functions are named by top
+-- level lambda expressions. For this we apply η expansion to the
+-- function body (possibly enclosed in some lambda abstractions) while
+-- it has a function type. Eventually this will result in a function
+-- body consisting of a bunch of nested lambdas containing a
+-- non-function value (e.g., a complete application).
+eta :: Transform
+eta c expr | is_fun expr && not (is_lam expr) && all (== LambdaBody) c = do
+ let arg_ty = (fst . Type.splitFunTy . CoreUtils.exprType) expr
+ id <- Trans.lift $ mkInternalVar "param" arg_ty
+ change (Lam id (App expr (Var id)))
+-- Leave all other expressions unchanged
+eta c e = return e
+
+--------------------------------
+-- Application propagation
+--------------------------------
+-- Move applications into let and case expressions.
+appprop :: Transform
+-- Propagate the application into the let
+appprop c (App (Let binds expr) arg) = change $ Let binds (App expr arg)
+-- Propagate the application into each of the alternatives
+appprop c (App (Case scrut b ty alts) arg) = change $ Case scrut b ty' alts'
+ where
+ alts' = map (\(con, bndrs, expr) -> (con, bndrs, (App expr arg))) alts
+ ty' = CoreUtils.applyTypeToArg ty arg
+-- Leave all other expressions unchanged
+appprop c expr = return expr
+
+--------------------------------
+-- Let recursification
+--------------------------------
+-- Make all lets recursive, so other transformations don't need to
+-- handle non-recursive lets
+letrec :: Transform
+letrec c expr@(Let (NonRec bndr val) res) =
+ change $ Let (Rec [(bndr, val)]) res
+
+-- Leave all other expressions unchanged
+letrec c expr = return expr
+
+--------------------------------
+-- let flattening
+--------------------------------
+-- Takes a let that binds another let, and turns that into two nested lets.
+-- e.g., from:
+-- let b = (let b' = expr' in res') in res
+-- to:
+-- let b' = expr' in (let b = res' in res)
+letflat :: Transform
+-- Turn a nonrec let that binds a let into two nested lets.
+letflat c (Let (NonRec b (Let binds res')) res) =
+ change $ Let binds (Let (NonRec b res') res)
+letflat c (Let (Rec binds) expr) = do
+ -- Flatten each binding.
+ binds' <- Utils.concatM $ Monad.mapM flatbind binds
+ -- Return the new let. We don't use change here, since possibly nothing has
+ -- changed. If anything has changed, flatbind has already flagged that
+ -- change.
+ return $ Let (Rec binds') expr
+ where
+ -- Turns a binding of a let into a multiple bindings, or any other binding
+ -- into a list with just that binding
+ flatbind :: (CoreBndr, CoreExpr) -> TransformMonad [(CoreBndr, CoreExpr)]
+ flatbind (b, Let (Rec binds) expr) = change ((b, expr):binds)
+ flatbind (b, Let (NonRec b' expr') expr) = change [(b, expr), (b', expr')]
+ flatbind (b, expr) = return [(b, expr)]
+-- Leave all other expressions unchanged
+letflat c expr = return expr
+
+--------------------------------
+-- Return value simplification
+--------------------------------
+-- Ensure the return value of a function follows proper normal form. eta
+-- expansion ensures the body starts with lambda abstractions, this
+-- transformation ensures that the lambda abstractions always contain a
+-- recursive let and that, when the return value is representable, the
+-- let contains a local variable reference in its body.
+
+-- Extract the return value from the body of the top level lambdas (of
+-- which ther could be zero), unless it is a let expression (in which
+-- case the next clause applies).
+retvalsimpl c expr | all (== LambdaBody) c && not (is_lam expr) && not (is_let expr) = do
+ local_var <- Trans.lift $ is_local_var expr
+ repr <- isRepr expr
+ if not local_var && repr
+ then do
+ id <- Trans.lift $ mkBinderFor expr "res"
+ change $ Let (Rec [(id, expr)]) (Var id)
+ else
+ return expr
+-- Extract the return value from the body of a let expression, which is
+-- itself the body of the top level lambdas (of which there could be
+-- zero).
+retvalsimpl c expr@(Let (Rec binds) body) | all (== LambdaBody) c = do
+ -- Don't extract values that are already a local variable, to prevent
+ -- loops with ourselves.
+ local_var <- Trans.lift $ is_local_var body
+ -- Don't extract values that are not representable, to prevent loops with
+ -- inlinenonrep
+ repr <- isRepr body
+ if not local_var && repr
+ then do
+ id <- Trans.lift $ mkBinderFor body "res"
+ change $ Let (Rec ((id, body):binds)) (Var id)
+ else
+ return expr
+-- Leave all other expressions unchanged
+retvalsimpl c expr = return expr
+
+--------------------------------
+-- Representable arguments simplification
+--------------------------------
+-- Make sure that all arguments of a representable type are simple variables.
+appsimpl :: Transform
+-- Simplify all representable arguments. Do this by introducing a new Let
+-- that binds the argument and passing the new binder in the application.
+appsimpl c expr@(App f arg) = do
+ -- Check runtime representability
+ repr <- isRepr arg
+ local_var <- Trans.lift $ is_local_var arg
+ if repr && not local_var
+ then do -- Extract representable arguments
+ id <- Trans.lift $ mkBinderFor arg "arg"
+ change $ Let (NonRec id arg) (App f (Var id))
+ else -- Leave non-representable arguments unchanged
+ return expr
+-- Leave all other expressions unchanged
+appsimpl c expr = return expr
+
+----------------------------------------------------------------
+-- Built-in function transformations
+----------------------------------------------------------------
+
+--------------------------------
+-- Function-typed argument extraction
+--------------------------------
+-- This transform takes any function-typed argument that cannot be propagated
+-- (because the function that is applied to it is a builtin function), and
+-- puts it in a brand new top level binder. This allows us to for example
+-- apply map to a lambda expression This will not conflict with inlinenonrep,
+-- since that only inlines local let bindings, not top level bindings.
+funextract :: Transform
+funextract c expr@(App _ _) | is_var fexpr = do
+ body_maybe <- Trans.lift $ getGlobalBind f
+ case body_maybe of
+ -- We don't have a function body for f, so we can perform this transform.
+ Nothing -> do
+ -- Find the new arguments
+ args' <- mapM doarg args
+ -- And update the arguments. We use return instead of changed, so the
+ -- changed flag doesn't get set if none of the args got changed.
+ return $ MkCore.mkCoreApps fexpr args'
+ -- We have a function body for f, leave this application to funprop
+ Just _ -> return expr
+ where
+ -- Find the function called and the arguments
+ (fexpr, args) = collectArgs expr
+ Var f = fexpr
+ -- Change any arguments that have a function type, but are not simple yet
+ -- (ie, a variable or application). This means to create a new function
+ -- for map (\f -> ...) b, but not for map (foo a) b.
+ --
+ -- We could use is_applicable here instead of is_fun, but I think
+ -- arguments to functions could only have forall typing when existential
+ -- typing is enabled. Not sure, though.
+ doarg arg | not (is_simple arg) && is_fun arg = do
+ -- Create a new top level binding that binds the argument. Its body will
+ -- be extended with lambda expressions, to take any free variables used
+ -- by the argument expression.
+ let free_vars = VarSet.varSetElems $ CoreFVs.exprFreeVars arg
+ let body = MkCore.mkCoreLams free_vars arg
+ id <- Trans.lift $ mkBinderFor body "fun"
+ Trans.lift $ addGlobalBind id body
+ -- Replace the argument with a reference to the new function, applied to
+ -- all vars it uses.
+ change $ MkCore.mkCoreApps (Var id) (map Var free_vars)
+ -- Leave all other arguments untouched
+ doarg arg = return arg
+
+-- Leave all other expressions unchanged
+funextract c expr = return expr
+
+
+
+
+----------------------------------------------------------------
+-- Case normalization transformations
+----------------------------------------------------------------
+
+--------------------------------
+-- Scrutinee simplification
+--------------------------------
+-- Make sure the scrutinee of a case expression is a local variable
+-- reference.
+scrutsimpl :: Transform
+-- Don't touch scrutinees that are already simple
+scrutsimpl c expr@(Case (Var _) _ _ _) = return expr
+-- Replace all other cases with a let that binds the scrutinee and a new
+-- simple scrutinee, but only when the scrutinee is representable (to prevent
+-- loops with inlinenonrep, though I don't think a non-representable scrutinee
+-- will be supported anyway...)
+scrutsimpl c expr@(Case scrut b ty alts) = do
+ repr <- isRepr scrut
+ if repr
+ then do
+ id <- Trans.lift $ mkBinderFor scrut "scrut"
+ change $ Let (NonRec id scrut) (Case (Var id) b ty alts)
+ else
+ return expr
+-- Leave all other expressions unchanged
+scrutsimpl c expr = return expr
+
+--------------------------------
+-- Scrutinee binder removal
+--------------------------------
+-- A case expression can have an extra binder, to which the scrutinee is bound
+-- after bringing it to WHNF. This is used for forcing evaluation of strict
+-- arguments. Since strictness does not matter for us (rather, everything is
+-- sort of strict), this binder is ignored when generating VHDL, and must thus
+-- be wild in the normal form.
+scrutbndrremove :: Transform
+-- If the scrutinee is already simple, and the bndr is not wild yet, replace
+-- all occurences of the binder with the scrutinee variable.
+scrutbndrremove c (Case (Var scrut) bndr ty alts) | bndr_used = do
+ alts' <- mapM subs_bndr alts
+ change $ Case (Var scrut) wild ty alts'
+ where
+ is_used (_, _, expr) = expr_uses_binders [bndr] expr
+ bndr_used = or $ map is_used alts
+ subs_bndr (con, bndrs, expr) = do
+ expr' <- substitute bndr (Var scrut) c expr
+ return (con, bndrs, expr')
+ wild = MkCore.mkWildBinder (Id.idType bndr)
+-- Leave all other expressions unchanged
+scrutbndrremove c expr = return expr
+
+--------------------------------
+-- Case normalization
+--------------------------------
+-- Turn a case expression with any number of alternatives with any
+-- number of non-wild binders into as set of case and let expressions,
+-- all of which are in normal form (e.g., a bunch of extractor case
+-- expressions to extract all fields from the scrutinee, a number of let
+-- bindings to bind each alternative and a single selector case to
+-- select the right value.
+casesimpl :: Transform
+-- This is already a selector case (or, if x does not appear in bndrs, a very
+-- simple case statement that will be removed by caseremove below). Just leave
+-- it be.
+casesimpl c expr@(Case scrut b ty [(con, bndrs, Var x)]) = return expr
+-- Make sure that all case alternatives have only wild binders and simple
+-- expressions.
+-- This is done by creating a new let binding for each non-wild binder, which
+-- is bound to a new simple selector case statement and for each complex
+-- expression. We do this only for representable types, to prevent loops with
+-- inlinenonrep.
+casesimpl c expr@(Case scrut bndr ty alts) | not bndr_used = do
+ (bindingss, alts') <- (Monad.liftM unzip) $ mapM doalt alts
+ let bindings = concat bindingss
+ -- Replace the case with a let with bindings and a case
+ let newlet = mkNonRecLets bindings (Case scrut bndr ty alts')
+ -- If there are no non-wild binders, or this case is already a simple
+ -- selector (i.e., a single alt with exactly one binding), already a simple
+ -- selector altan no bindings (i.e., no wild binders in the original case),
+ -- don't change anything, otherwise, replace the case.
+ if null bindings then return expr else change newlet
+ where
+ -- Check if the scrutinee binder is used
+ is_used (_, _, expr) = expr_uses_binders [bndr] expr
+ bndr_used = or $ map is_used alts
+ -- Generate a single wild binder, since they are all the same
+ wild = MkCore.mkWildBinder
+ -- Wilden the binders of one alt, producing a list of bindings as a
+ -- sideeffect.
+ doalt :: CoreAlt -> TransformMonad ([(CoreBndr, CoreExpr)], CoreAlt)
+ doalt (con, bndrs, expr) = do
+ -- Make each binder wild, if possible
+ bndrs_res <- Monad.zipWithM dobndr bndrs [0..]
+ let (newbndrs, bindings_maybe) = unzip bndrs_res
+ -- Extract a complex expression, if possible. For this we check if any of
+ -- the new list of bndrs are used by expr. We can't use free_vars here,
+ -- since that looks at the old bndrs.
+ let uses_bndrs = not $ VarSet.isEmptyVarSet $ CoreFVs.exprSomeFreeVars (`elem` newbndrs) expr
+ (exprbinding_maybe, expr') <- doexpr expr uses_bndrs
+ -- Create a new alternative
+ let newalt = (con, newbndrs, expr')
+ let bindings = Maybe.catMaybes (bindings_maybe ++ [exprbinding_maybe])
+ return (bindings, newalt)
+ where
+ -- Make wild alternatives for each binder
+ wildbndrs = map (\bndr -> MkCore.mkWildBinder (Id.idType bndr)) bndrs
+ -- A set of all the binders that are used by the expression
+ free_vars = CoreFVs.exprSomeFreeVars (`elem` bndrs) expr
+ -- Look at the ith binder in the case alternative. Return a new binder
+ -- for it (either the same one, or a wild one) and optionally a let
+ -- binding containing a case expression.
+ dobndr :: CoreBndr -> Int -> TransformMonad (CoreBndr, Maybe (CoreBndr, CoreExpr))
+ dobndr b i = do
+ repr <- isRepr b
+ -- Is b wild (e.g., not a free var of expr. Since b is only in scope
+ -- in expr, this means that b is unused if expr does not use it.)
+ let wild = not (VarSet.elemVarSet b free_vars)
+ -- Create a new binding for any representable binder that is not
+ -- already wild and is representable (to prevent loops with
+ -- inlinenonrep).
+ if (not wild) && repr
+ then do
+ caseexpr <- Trans.lift $ mkSelCase scrut i
+ -- Create a new binder that will actually capture a value in this
+ -- case statement, and return it.
+ return (wildbndrs!!i, Just (b, caseexpr))
+ else
+ -- Just leave the original binder in place, and don't generate an
+ -- extra selector case.
+ return (b, Nothing)
+ -- Process the expression of a case alternative. Accepts an expression
+ -- and whether this expression uses any of the binders in the
+ -- alternative. Returns an optional new binding and a new expression.
+ doexpr :: CoreExpr -> Bool -> TransformMonad (Maybe (CoreBndr, CoreExpr), CoreExpr)
+ doexpr expr uses_bndrs = do
+ local_var <- Trans.lift $ is_local_var expr
+ repr <- isRepr expr
+ -- Extract any expressions that do not use any binders from this
+ -- alternative, is not a local var already and is representable (to
+ -- prevent loops with inlinenonrep).
+ if (not uses_bndrs) && (not local_var) && repr
+ then do
+ id <- Trans.lift $ mkBinderFor expr "caseval"
+ -- We don't flag a change here, since casevalsimpl will do that above
+ -- based on Just we return here.
+ return (Just (id, expr), Var id)
+ else
+ -- Don't simplify anything else
+ return (Nothing, expr)
+-- Leave all other expressions unchanged
+casesimpl c expr = return expr
+
+--------------------------------
+-- Case removal
+--------------------------------
+-- Remove case statements that have only a single alternative and only wild
+-- binders.
+caseremove :: Transform
+-- Replace a useless case by the value of its single alternative
+caseremove c (Case scrut b ty [(con, bndrs, expr)]) | not usesvars = change expr
+ -- Find if any of the binders are used by expr
+ where usesvars = (not . VarSet.isEmptyVarSet . (CoreFVs.exprSomeFreeVars (`elem` b:bndrs))) expr
+-- Leave all other expressions unchanged
+caseremove c expr = return expr
+
+--------------------------------
+-- Case of known constructor simplification
+--------------------------------
+-- If a case expressions scrutinizes a datacon application, we can
+-- determine which alternative to use and remove the case alltogether.
+-- We replace it with a let expression the binds every binder in the
+-- alternative bound to the corresponding argument of the datacon. We do
+-- this instead of substituting the binders, to prevent duplication of
+-- work and preserve sharing wherever appropriate.
+knowncase :: Transform
+knowncase context expr@(Case scrut@(App _ _) bndr ty alts) | not bndr_used = do
+ case collectArgs scrut of
+ (Var f, args) -> case Id.isDataConId_maybe f of
+ -- Not a dataconstructor? Don't change anything (probably a
+ -- function, then)
+ Nothing -> return expr
+ Just dc -> do
+ let (altcon, bndrs, res) = case List.find (\(altcon, bndrs, res) -> altcon == (DataAlt dc)) alts of
+ Just alt -> alt -- Return the alternative found
+ Nothing -> head alts -- If the datacon is not present, the first must be the default alternative
+ -- Double check if we have either the correct alternative, or
+ -- the default.
+ if altcon /= (DataAlt dc) && altcon /= DEFAULT then error ("Normalize.knowncase: Invalid core, datacon not found in alternatives and DEFAULT alternative is not first? " ++ pprString expr) else return ()
+ -- Find out how many arguments to drop (type variables and
+ -- predicates like dictionaries).
+ let (tvs, preds, _, _) = DataCon.dataConSig dc
+ let count = length tvs + length preds
+ -- Create a let expression that binds each of the binders in
+ -- this alternative to the corresponding argument of the data
+ -- constructor.
+ let binds = zip bndrs (drop count args)
+ change $ Let (Rec binds) res
+ _ -> return expr -- Scrutinee is not an application of a var
+ where
+ is_used (_, _, expr) = expr_uses_binders [bndr] expr
+ bndr_used = or $ map is_used alts
+
+-- Leave all other expressions unchanged
+knowncase c expr = return expr
+
+
+
+
+----------------------------------------------------------------
+-- Unrepresentable value removal transformations
+----------------------------------------------------------------
+
+--------------------------------
+-- Non-representable binding inlining
+--------------------------------
+-- Remove a = B bindings, with B of a non-representable type, from let
+-- expressions everywhere. This means that any value that we can't generate a
+-- signal for, will be inlined and hopefully turned into something we can
+-- represent.
+--
+-- This is a tricky function, which is prone to create loops in the
+-- transformations. To fix this, we make sure that no transformation will
+-- create a new let binding with a non-representable type. These other
+-- transformations will just not work on those function-typed values at first,
+-- but the other transformations (in particular β-reduction) should make sure
+-- that the type of those values eventually becomes representable.
+inlinenonrep :: Transform
+inlinenonrep = inlinebind ((Monad.liftM not) . isRepr . snd)
+
+--------------------------------
+-- Function specialization
+--------------------------------
+-- Remove all applications to non-representable arguments, by duplicating the
+-- function called with the non-representable parameter replaced by the free
+-- variables of the argument passed in.
+argprop :: Transform
+-- Transform any application of a named function (i.e., skip applications of
+-- lambda's). Also skip applications that have arguments with free type
+-- variables, since we can't inline those.
+argprop c expr@(App _ _) | is_var fexpr = do
+ -- Find the body of the function called
+ body_maybe <- Trans.lift $ getGlobalBind f
+ case body_maybe of
+ Just body -> do
+ -- Process each of the arguments in turn
+ (args', changed) <- Writer.listen $ mapM doarg args
+ -- See if any of the arguments changed
+ case Monoid.getAny changed of
+ True -> do
+ let (newargs', newparams', oldargs) = unzip3 args'
+ let newargs = concat newargs'
+ let newparams = concat newparams'
+ -- Create a new body that consists of a lambda for all new arguments and
+ -- the old body applied to some arguments.
+ let newbody = MkCore.mkCoreLams newparams (MkCore.mkCoreApps body oldargs)
+ -- Create a new function with the same name but a new body
+ newf <- Trans.lift $ mkFunction f newbody
+
+ Trans.lift $ MonadState.modify tsInitStates (\ismap ->
+ let init_state_maybe = Map.lookup f ismap in
+ case init_state_maybe of
+ Nothing -> ismap
+ Just init_state -> Map.insert newf init_state ismap)
+ -- Replace the original application with one of the new function to the
+ -- new arguments.
+ change $ MkCore.mkCoreApps (Var newf) newargs
+ False ->
+ -- Don't change the expression if none of the arguments changed
+ return expr
+
+ -- If we don't have a body for the function called, leave it unchanged (it
+ -- should be a primitive function then).
+ Nothing -> return expr
+ where
+ -- Find the function called and the arguments
+ (fexpr, args) = collectArgs expr
+ Var f = fexpr
+
+ -- Process a single argument and return (args, bndrs, arg), where args are
+ -- the arguments to replace the given argument in the original
+ -- application, bndrs are the binders to include in the top-level lambda
+ -- in the new function body, and arg is the argument to apply to the old
+ -- function body.
+ doarg :: CoreExpr -> TransformMonad ([CoreExpr], [CoreBndr], CoreExpr)
+ doarg arg = do
+ repr <- isRepr arg
+ bndrs <- Trans.lift getGlobalBinders
+ let interesting var = Var.isLocalVar var && (var `notElem` bndrs)
+ if not repr && not (is_var arg && interesting (exprToVar arg)) && not (has_free_tyvars arg)
+ then do
+ -- Propagate all complex arguments that are not representable, but not
+ -- arguments with free type variables (since those would require types
+ -- not known yet, which will always be known eventually).
+ -- Find interesting free variables, each of which should be passed to
+ -- the new function instead of the original function argument.
+ --
+ -- Interesting vars are those that are local, but not available from the
+ -- top level scope (functions from this module are defined as local, but
+ -- they're not local to this function, so we can freely move references
+ -- to them into another function).
+ let free_vars = VarSet.varSetElems $ CoreFVs.exprSomeFreeVars interesting arg
+ -- Mark the current expression as changed
+ setChanged
+ -- TODO: Clone the free_vars (and update references in arg), since
+ -- this might cause conflicts if two arguments that are propagated
+ -- share a free variable. Also, we are now introducing new variables
+ -- into a function that are not fresh, which violates the binder
+ -- uniqueness invariant.
+ return (map Var free_vars, free_vars, arg)
+ else do
+ -- Representable types will not be propagated, and arguments with free
+ -- type variables will be propagated later.
+ -- Note that we implicitly remove any type variables in the type of
+ -- the original argument by using the type of the actual argument
+ -- for the new formal parameter.
+ -- TODO: preserve original naming?
+ id <- Trans.lift $ mkBinderFor arg "param"
+ -- Just pass the original argument to the new function, which binds it
+ -- to a new id and just pass that new id to the old function body.
+ return ([arg], [id], mkReferenceTo id)
+-- Leave all other expressions unchanged
+argprop c expr = return expr
+
+--------------------------------
+-- Non-representable result inlining
+--------------------------------
+-- This transformation takes a function (top level binding) that has a
+-- non-representable result (e.g., a tuple containing a function, or an
+-- Integer. The latter can occur in some cases as the result of the
+-- fromIntegerT function) and inlines enough of the function to make the
+-- result representable again.
+--
+-- This is done by first normalizing the function and then "inlining"
+-- the result. Since no unrepresentable let bindings are allowed in
+-- normal form, we can be sure that all free variables of the result
+-- expression will be representable (Note that we probably can't
+-- guarantee that all representable parts of the expression will be free
+-- variables, so we might inline more than strictly needed).
+--
+-- The new function result will be a tuple containing all free variables
+-- of the old result, so the old result can be rebuild at the caller.
+--
+-- We take care not to inline dictionary id's, which are top level
+-- bindings with a non-representable result type as well, since those
+-- will never become VHDL signals directly. There is a separate
+-- transformation (inlinedict) that specifically inlines dictionaries
+-- only when it is useful.
+inlinenonrepresult :: Transform
+
+-- Apply to any (application of) a reference to a top level function
+-- that is fully applied (i.e., dos not have a function type) but is not
+-- representable. We apply in any context, since non-representable
+-- expressions are generally left alone and can occur anywhere.
+inlinenonrepresult context expr | not (is_fun expr) =
+ case collectArgs expr of
+ (Var f, args) | not (Id.isDictId f) -> do
+ repr <- isRepr expr
+ if not repr
+ then do
+ body_maybe <- Trans.lift $ getNormalized_maybe True f
+ case body_maybe of
+ Just body -> do
+ let (bndrs, binds, res) = splitNormalizedNonRep body
+ if has_free_tyvars res
+ then
+ -- Don't touch anything with free type variables, since
+ -- we can't return those. We'll wait until argprop
+ -- removed those variables.
+ return expr
+ else do
+ -- Get the free local variables of res
+ global_bndrs <- Trans.lift getGlobalBinders
+ let interesting var = Var.isLocalVar var && (var `notElem` global_bndrs)
+ let free_vars = VarSet.varSetElems $ CoreFVs.exprSomeFreeVars interesting res
+ let free_var_types = map Id.idType free_vars
+ let n_free_vars = length free_vars
+ -- Get a tuple datacon to wrap around the free variables
+ let fvs_datacon = TysWiredIn.tupleCon BasicTypes.Boxed n_free_vars
+ let fvs_datacon_id = DataCon.dataConWorkId fvs_datacon
+ -- Let the function now return a tuple with references to
+ -- all free variables of the old return value. First pass
+ -- all the types of the variables, since tuple
+ -- constructors are polymorphic.
+ let newres = mkApps (Var fvs_datacon_id) (map Type free_var_types ++ map Var free_vars)
+ -- Recreate the function body with the changed return value
+ let newbody = mkLams bndrs (Let (Rec binds) newres)
+ -- Create the new function
+ f' <- Trans.lift $ mkFunction f newbody
+
+ -- Call the new function
+ let newapp = mkApps (Var f') args
+ res_bndr <- Trans.lift $ mkBinderFor newapp "res"
+ -- Create extractor case expressions to extract each of the
+ -- free variables from the tuple.
+ sel_cases <- Trans.lift $ mapM (mkSelCase (Var res_bndr)) [0..n_free_vars-1]
+
+ -- Bind the res_bndr to the result of the new application
+ -- and each of the free variables to the corresponding
+ -- selector case. Replace the let body with the original
+ -- body of the called function (which can still access all
+ -- of its free variables, from the let).
+ let binds = (res_bndr, newapp):(zip free_vars sel_cases)
+ let letexpr = Let (Rec binds) res
+
+ -- Finally, regenarate all uniques in the new expression,
+ -- since the free variables could otherwise become
+ -- duplicated. It is not strictly necessary to regenerate
+ -- res, since we're moving that expression, but it won't
+ -- hurt.
+ letexpr_uniqued <- Trans.lift $ genUniques letexpr
+ change letexpr_uniqued
+ Nothing -> return expr
+ else
+ -- Don't touch representable expressions or (applications of)
+ -- dictionary ids.
+ return expr
+ -- Not a reference to or application of a top level function
+ _ -> return expr
+-- Leave all other expressions unchanged
+inlinenonrepresult c expr = return expr
+
+--------------------------------
+-- ClassOp resolution
+--------------------------------
+-- Resolves any class operation to the actual operation whenever
+-- possible. Class methods (as well as parent dictionary selectors) are
+-- special "functions" that take a type and a dictionary and evaluate to
+-- the corresponding method. A dictionary is nothing more than a
+-- special dataconstructor applied to the type the dictionary is for,
+-- each of the superclasses and all of the class method definitions for
+-- that particular type. Since dictionaries all always inlined (top
+-- levels dictionaries are inlined by inlinedict, local dictionaries are
+-- inlined by inlinenonrep), we will eventually have something like:
+--
+-- baz
+-- @ CLasH.HardwareTypes.Bit
+-- (D:Baz @ CLasH.HardwareTypes.Bit bitbaz)
+--
+-- Here, baz is the method selector for the baz method, while
+-- D:Baz is the dictionary constructor for the Baz and bitbaz is the baz
+-- method defined in the Baz Bit instance declaration.
+--
+-- To resolve this, we can look at the ClassOp IdInfo from the baz Id,
+-- which contains the Class it is defined for. From the Class, we can
+-- get a list of all selectors (both parent class selectors as well as
+-- method selectors). Since the arguments to D:Baz (after the type
+-- argument) correspond exactly to this list, we then look up baz in
+-- that list and replace the entire expression by the corresponding
+-- argument to D:Baz.
+--
+-- We don't resolve methods that have a builtin translation (such as
+-- ==), since the actual implementation is not always (easily)
+-- translateable. For example, when deriving ==, GHC generates code
+-- using $con2tag functions to translate a datacon to an int and compare
+-- that with GHC.Prim.==# . Better to avoid that for now.
+classopresolution :: Transform
+classopresolution c expr@(App (App (Var sel) ty) dict) | not is_builtin =
+ case Id.isClassOpId_maybe sel of
+ -- Not a class op selector
+ Nothing -> return expr
+ Just cls -> case collectArgs dict of
+ (_, []) -> return expr -- Dict is not an application (e.g., not inlined yet)
+ (Var dictdc, (ty':selectors)) | not (Maybe.isJust (Id.isDataConId_maybe dictdc)) -> return expr -- Dictionary is not a datacon yet (but e.g., a top level binder)
+ | tyargs_neq ty ty' -> error $ "Normalize.classopresolution: Applying class selector to dictionary without matching type?\n" ++ pprString expr
+ | otherwise ->
+ let selector_ids = Class.classSelIds cls in
+ -- Find the selector used in the class' list of selectors
+ case List.elemIndex sel selector_ids of
+ Nothing -> error $ "Normalize.classopresolution: Selector not found in class' selector list? This should not happen!\nExpression: " ++ pprString expr ++ "\nClass: " ++ show cls ++ "\nSelectors: " ++ show selector_ids
+ -- Get the corresponding argument from the dictionary
+ Just n -> change (selectors!!n)
+ (_, _) -> return expr -- Not applying a variable? Don't touch
+ where
+ -- Compare two type arguments, returning True if they are _not_
+ -- equal
+ tyargs_neq (Type ty1) (Type ty2) = not $ Type.coreEqType ty1 ty2
+ tyargs_neq _ _ = True
+ -- Is this a builtin function / method?
+ is_builtin = elem (Name.getOccString sel) builtinIds
+
+-- Leave all other expressions unchanged
+classopresolution c expr = return expr
+
+--------------------------------
+-- Dictionary inlining
+--------------------------------
+-- Inline all top level dictionaries, that are in a position where
+-- classopresolution can actually resolve them. This makes this
+-- transformation look similar to classoperesolution below, but we'll
+-- keep them separated for clarity. By not inlining other dictionaries,
+-- we prevent expression sizes exploding when huge type level integer
+-- dictionaries are inlined which can never be expanded (in casts, for
+-- example).
+inlinedict c expr@(App (App (Var sel) ty) (Var dict)) | not is_builtin && is_classop = do
+ body_maybe <- Trans.lift $ getGlobalBind dict
+ case body_maybe of
+ -- No body available (no source available, or a local variable /
+ -- argument)
+ Nothing -> return expr
+ Just body -> change (App (App (Var sel) ty) body)
+ where
+ -- Is this a builtin function / method?
+ is_builtin = elem (Name.getOccString sel) builtinIds
+ -- Are we dealing with a class operation selector?
+ is_classop = Maybe.isJust (Id.isClassOpId_maybe sel)
+
+-- Leave all other expressions unchanged
+inlinedict c expr = return expr
+
+
+{-
+--------------------------------
+-- Identical let binding merging
+--------------------------------
+-- Merge two bindings in a let if they are identical
+-- TODO: We would very much like to use GHC's CSE module for this, but that
+-- doesn't track if something changed or not, so we can't use it properly.
+letmerge :: Transform
+letmerge c expr@(Let _ _) = do
+ let (binds, res) = flattenLets expr
+ binds' <- domerge binds
+ return $ mkNonRecLets binds' res
+ where
+ domerge :: [(CoreBndr, CoreExpr)] -> TransformMonad [(CoreBndr, CoreExpr)]
+ domerge [] = return []
+ domerge (e:es) = do
+ es' <- mapM (mergebinds e) es
+ es'' <- domerge es'
+ return (e:es'')
+
+ -- Uses the second bind to simplify the second bind, if applicable.
+ mergebinds :: (CoreBndr, CoreExpr) -> (CoreBndr, CoreExpr) -> TransformMonad (CoreBndr, CoreExpr)
+ mergebinds (b1, e1) (b2, e2)
+ -- Identical expressions? Replace the second binding with a reference to
+ -- the first binder.
+ | CoreUtils.cheapEqExpr e1 e2 = change $ (b2, Var b1)
+ -- Different expressions? Don't change
+ | otherwise = return (b2, e2)
+-- Leave all other expressions unchanged
+letmerge c expr = return expr
+-}
+
+--------------------------------
+-- End of transformations
+--------------------------------
+
+
+
+
+-- What transforms to run?
+transforms = [ ("inlinedict", inlinedict)
+ , ("inlinetoplevel", inlinetoplevel)
+ , ("inlinenonrepresult", inlinenonrepresult)
+ , ("knowncase", knowncase)
+ , ("classopresolution", classopresolution)
+ , ("argprop", argprop)
+ , ("funextract", funextract)
+ , ("eta", eta)
+ , ("beta", beta)
+ , ("appprop", appprop)
+ , ("castprop", castprop)
+ , ("letremovesimple", letremovesimple)
+ , ("letrec", letrec)
+ , ("letremove", letremove)
+ , ("retvalsimpl", retvalsimpl)
+ , ("letflat", letflat)
+ , ("scrutsimpl", scrutsimpl)
+ , ("scrutbndrremove", scrutbndrremove)
+ , ("casesimpl", casesimpl)
+ , ("caseremove", caseremove)
+ , ("inlinenonrep", inlinenonrep)
+ , ("appsimpl", appsimpl)
+ , ("letremoveunused", letremoveunused)
+ , ("castsimpl", castsimpl)
+ ]
+
+-- | Returns the normalized version of the given function, or an error
+-- if it is not a known global binder.
+getNormalized ::
+ Bool -- ^ Allow the result to be unrepresentable?
+ -> CoreBndr -- ^ The function to get
+ -> TranslatorSession CoreExpr -- The normalized function body
+getNormalized result_nonrep bndr = do
+ norm <- getNormalized_maybe result_nonrep bndr
+ return $ Maybe.fromMaybe
+ (error $ "Normalize.getNormalized: Unknown or non-representable function requested: " ++ show bndr)
+ norm
+
+-- | Returns the normalized version of the given function, or Nothing
+-- when the binder is not a known global binder or is not normalizeable.
+getNormalized_maybe ::
+ Bool -- ^ Allow the result to be unrepresentable?
+ -> CoreBndr -- ^ The function to get
+ -> TranslatorSession (Maybe CoreExpr) -- The normalized function body
+
+getNormalized_maybe result_nonrep bndr = do
+ expr_maybe <- getGlobalBind bndr
+ normalizeable <- isNormalizeable result_nonrep bndr
+ if not normalizeable || Maybe.isNothing expr_maybe
+ then
+ -- Binder not normalizeable or not found
+ return Nothing
+ else do
+ -- Binder found and is monomorphic. Normalize the expression
+ -- and cache the result.
+ normalized <- Utils.makeCached bndr tsNormalized $
+ normalizeExpr (show bndr) (Maybe.fromJust expr_maybe)
+ return (Just normalized)
+
+-- | Normalize an expression
+normalizeExpr ::
+ String -- ^ What are we normalizing? For debug output only.
+ -> CoreSyn.CoreExpr -- ^ The expression to normalize
+ -> TranslatorSession CoreSyn.CoreExpr -- ^ The normalized expression
+
+normalizeExpr what expr = do
+ startcount <- MonadState.get tsTransformCounter
+ expr_uniqued <- genUniques expr
+ -- Do a debug print, if requested
+ let expr_uniqued' = Utils.traceIf (normalize_debug >= NormDbgFinal) (what ++ " before normalization:\n\n" ++ showSDoc ( ppr expr_uniqued ) ++ "\n") expr_uniqued
+ -- Normalize this expression
+ expr' <- dotransforms transforms expr_uniqued'
+ endcount <- MonadState.get tsTransformCounter
+ -- Do a debug print, if requested
+ Utils.traceIf (normalize_debug >= NormDbgFinal) (what ++ " after normalization:\n\n" ++ showSDoc ( ppr expr') ++ "\nNeeded " ++ show (endcount - startcount) ++ " transformations to normalize " ++ what) $
+ return expr'
+
+-- | Split a normalized expression into the argument binders, top level
+-- bindings and the result binder. This function returns an error if
+-- the type of the expression is not representable.
+splitNormalized ::
+ CoreExpr -- ^ The normalized expression
+ -> ([CoreBndr], [Binding], CoreBndr)
+splitNormalized expr =
+ case splitNormalizedNonRep expr of
+ (args, binds, Var res) -> (args, binds, res)
+ _ -> error $ "Normalize.splitNormalized: Not in normal form: " ++ pprString expr ++ "\n"
+
+-- Split a normalized expression, whose type can be unrepresentable.
+splitNormalizedNonRep::
+ CoreExpr -- ^ The normalized expression
+ -> ([CoreBndr], [Binding], CoreExpr)
+splitNormalizedNonRep expr = (args, binds, resexpr)
+ where
+ (args, letexpr) = CoreSyn.collectBinders expr
+ (binds, resexpr) = flattenLets letexpr
projects / matthijs / master-project / cλash.git / blobdiff