+{-# LANGUAGE PackageImports #-}
--
-- 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 Normalize (normalize) where
+module Normalize (normalizeModule) where
-- Standard modules
import Debug.Trace
-import qualified List
import qualified Maybe
+import qualified "transformers" Control.Monad.Trans as Trans
import qualified Control.Monad as Monad
+import qualified Control.Monad.Trans.Writer as Writer
+import qualified Data.Map as Map
+import qualified Data.Monoid as Monoid
+import Data.Accessor
-- GHC API
import CoreSyn
import qualified CoreUtils
import qualified Type
import qualified Id
-import qualified CoreSubst
+import qualified Var
+import qualified VarSet
+import qualified CoreFVs
+import qualified CoreUtils
+import qualified MkCore
import Outputable ( showSDoc, ppr, nest )
-- Local imports
import NormalizeTypes
import NormalizeTools
import CoreTools
+import Pretty
+
+--------------------------------
+-- Start of transformations
+--------------------------------
+
+--------------------------------
+-- η abstraction
+--------------------------------
+eta, etatop :: Transform
+eta expr | is_fun expr && not (is_lam expr) = do
+ let arg_ty = (fst . Type.splitFunTy . CoreUtils.exprType) expr
+ id <- mkInternalVar "param" arg_ty
+ change (Lam id (App expr (Var id)))
+-- Leave all other expressions unchanged
+eta e = return e
+etatop = notappargs ("eta", eta)
+
+--------------------------------
+-- β-reduction
+--------------------------------
+beta, betatop :: Transform
+-- Substitute arg for x in expr
+beta (App (Lam x expr) arg) = change $ substitute [(x, arg)] expr
+-- Propagate the application into the let
+beta (App (Let binds expr) arg) = change $ Let binds (App expr arg)
+-- Propagate the application into each of the alternatives
+beta (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
+beta expr = return expr
+-- Perform this transform everywhere
+betatop = everywhere ("beta", beta)
+
+--------------------------------
+-- Cast propagation
+--------------------------------
+-- Try to move casts as much downward as possible.
+castprop, castproptop :: Transform
+castprop (Cast (Let binds expr) ty) = change $ Let binds (Cast expr ty)
+castprop 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 expr = return expr
+-- Perform this transform everywhere
+castproptop = everywhere ("castprop", castprop)
+
+--------------------------------
+-- let recursification
+--------------------------------
+letrec, letrectop :: Transform
+letrec (Let (NonRec b expr) res) = change $ Let (Rec [(b, expr)]) res
+-- Leave all other expressions unchanged
+letrec expr = return expr
+-- Perform this transform everywhere
+letrectop = everywhere ("letrec", letrec)
+
+--------------------------------
+-- let simplification
+--------------------------------
+letsimpl, letsimpltop :: Transform
+-- Don't simplifiy lets that are already simple
+letsimpl expr@(Let _ (Var _)) = return expr
+-- Put the "in ..." value of a let in its own binding, but not when the
+-- expression is applicable (to prevent loops with inlinefun).
+letsimpl (Let (Rec binds) expr) | not $ is_applicable expr = do
+ id <- mkInternalVar "foo" (CoreUtils.exprType expr)
+ let bind = (id, expr)
+ change $ Let (Rec (bind:binds)) (Var id)
+-- Leave all other expressions unchanged
+letsimpl expr = return expr
+-- Perform this transform everywhere
+letsimpltop = everywhere ("letsimpl", letsimpl)
+
+--------------------------------
+-- let flattening
+--------------------------------
+letflat, letflattop :: Transform
+letflat (Let (Rec binds) expr) = do
+ -- Turn each binding into a list of bindings (possibly containing just one
+ -- element, of course)
+ bindss <- Monad.mapM flatbind binds
+ -- Concat all the bindings
+ let binds' = concat bindss
+ -- 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, expr) = return [(b, expr)]
+-- Leave all other expressions unchanged
+letflat expr = return expr
+-- Perform this transform everywhere
+letflattop = everywhere ("letflat", letflat)
+
+--------------------------------
+-- Simple let binding removal
+--------------------------------
+-- Remove a = b bindings from let expressions everywhere
+letremovetop :: Transform
+letremovetop = everywhere ("letremove", inlinebind (\(b, e) -> case e of (Var v) | not $ Id.isDataConWorkId v -> True; otherwise -> False))
+
+--------------------------------
+-- Function inlining
+--------------------------------
+-- Remove a = B bindings, with B :: a -> b, or B :: forall x . T, from let
+-- expressions everywhere. This means that any value that still needs to be
+-- applied to something else (polymorphic values need to be applied to a
+-- Type) will be inlined, and will eventually be applied to all their
+-- arguments.
+--
+-- 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 function 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 primitive.
+inlinefuntop :: Transform
+inlinefuntop = everywhere ("inlinefun", inlinebind (is_applicable . snd))
+
+--------------------------------
+-- Scrutinee simplification
+--------------------------------
+scrutsimpl,scrutsimpltop :: Transform
+-- Don't touch scrutinees that are already simple
+scrutsimpl expr@(Case (Var _) _ _ _) = return expr
+-- Replace all other cases with a let that binds the scrutinee and a new
+-- simple scrutinee, but not when the scrutinee is applicable (to prevent
+-- loops with inlinefun, though I don't think a scrutinee can be
+-- applicable...)
+scrutsimpl (Case scrut b ty alts) | not $ is_applicable scrut = do
+ id <- mkInternalVar "scrut" (CoreUtils.exprType scrut)
+ change $ Let (Rec [(id, scrut)]) (Case (Var id) b ty alts)
+-- Leave all other expressions unchanged
+scrutsimpl expr = return expr
+-- Perform this transform everywhere
+scrutsimpltop = everywhere ("scrutsimpl", scrutsimpl)
+
+--------------------------------
+-- Case binder wildening
+--------------------------------
+casewild, casewildtop :: Transform
+casewild expr@(Case scrut b ty alts) = 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 = (Let (Rec bindings) (Case scrut b 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 || length alts == 1 && length bindings == 1 then return expr else change newlet
+ where
+ -- Generate a single wild binder, since they are all the same
+ wild = Id.mkWildId
+ -- 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
+ bindings_maybe <- Monad.zipWithM mkextracts bndrs [0..]
+ let bindings = Maybe.catMaybes bindings_maybe
+ -- We replace the binders with wild binders only. We can leave expr
+ -- unchanged, since the new bindings bind the same vars as the original
+ -- did.
+ let newalt = (con, wildbndrs, expr)
+ return (bindings, newalt)
+ where
+ -- Make all binders wild
+ wildbndrs = map (\bndr -> Id.mkWildId (Id.idType bndr)) bndrs
+ -- Creates a case statement to retrieve the ith element from the scrutinee
+ -- and binds that to b.
+ mkextracts :: CoreBndr -> Int -> TransformMonad (Maybe (CoreBndr, CoreExpr))
+ mkextracts b i =
+ -- TODO: Use free variables instead of is_wild. is_wild is a hack.
+ if is_wild b || Type.isFunTy (Id.idType b)
+ -- Don't create extra bindings for binders that are already wild, or
+ -- for binders that bind function types (to prevent loops with
+ -- inlinefun).
+ then return Nothing
+ else do
+ -- Create on new binder that will actually capture a value in this
+ -- case statement, and return it
+ let bty = (Id.idType b)
+ id <- mkInternalVar "sel" bty
+ let binders = take i wildbndrs ++ [id] ++ drop (i+1) wildbndrs
+ return $ Just (b, Case scrut b bty [(con, binders, Var id)])
+-- Leave all other expressions unchanged
+casewild expr = return expr
+-- Perform this transform everywhere
+casewildtop = everywhere ("casewild", casewild)
+
+--------------------------------
+-- Case value simplification
+--------------------------------
+casevalsimpl, casevalsimpltop :: Transform
+casevalsimpl expr@(Case scrut b ty alts) = do
+ -- Try to simplify each alternative, resulting in an optional binding and a
+ -- new alternative.
+ (bindings_maybe, alts') <- (Monad.liftM unzip) $ mapM doalt alts
+ let bindings = Maybe.catMaybes bindings_maybe
+ -- Create a new let around the case, that binds of the cases values.
+ let newlet = Let (Rec bindings) (Case scrut b ty alts')
+ -- If there were no values that needed and allowed simplification, don't
+ -- change the case.
+ if null bindings then return expr else change newlet
+ where
+ doalt :: CoreAlt -> TransformMonad (Maybe (CoreBndr, CoreExpr), CoreAlt)
+ -- Don't simplify values that are already simple
+ doalt alt@(con, bndrs, Var _) = return (Nothing, alt)
+ -- Simplify each alt by creating a new id, binding the case value to it and
+ -- replacing the case value with that id. Only do this when the case value
+ -- does not use any of the binders bound by this alternative, for that would
+ -- cause those binders to become unbound when moving the value outside of
+ -- the case statement. Also, don't create a binding for applicable
+ -- expressions, to prevent loops with inlinefun.
+ doalt (con, bndrs, expr) | (not usesvars) && (not $ is_applicable expr) = do
+ id <- mkInternalVar "caseval" (CoreUtils.exprType expr)
+ -- We don't flag a change here, since casevalsimpl will do that above
+ -- based on Just we return here.
+ return $ (Just (id, expr), (con, bndrs, Var id))
+ -- Find if any of the binders are used by expr
+ where usesvars = (not . VarSet.isEmptyVarSet . (CoreFVs.exprSomeFreeVars (`elem` bndrs))) expr
+ -- Don't simplify anything else
+ doalt alt = return (Nothing, alt)
+-- Leave all other expressions unchanged
+casevalsimpl expr = return expr
+-- Perform this transform everywhere
+casevalsimpltop = everywhere ("casevalsimpl", casevalsimpl)
+
+--------------------------------
+-- Case removal
+--------------------------------
+-- Remove case statements that have only a single alternative and only wild
+-- binders.
+caseremove, caseremovetop :: Transform
+-- Replace a useless case by the value of its single alternative
+caseremove (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` bndrs))) expr
+-- Leave all other expressions unchanged
+caseremove expr = return expr
+-- Perform this transform everywhere
+caseremovetop = everywhere ("caseremove", caseremove)
+
+--------------------------------
+-- Application simplification
+--------------------------------
+-- Make sure that all arguments in an application are simple variables.
+appsimpl, appsimpltop :: Transform
+-- Don't simplify arguments that are already simple. Do simplify datacons,
+-- however, since we can't portmap literals.
+appsimpl expr@(App f (Var v)) | not $ Id.isDataConWorkId v = return expr
+-- Simplify all non-applicable (to prevent loops with inlinefun) arguments,
+-- except for type arguments (since a let can't bind type vars, only a lambda
+-- can). Do this by introducing a new Let that binds the argument and passing
+-- the new binder in the application.
+appsimpl (App f expr) | (not $ is_applicable expr) && (not $ CoreSyn.isTypeArg expr) = do
+ id <- mkInternalVar "arg" (CoreUtils.exprType expr)
+ change $ Let (Rec [(id, expr)]) (App f (Var id))
+-- Leave all other expressions unchanged
+appsimpl expr = return expr
+-- Perform this transform everywhere
+appsimpltop = everywhere ("appsimpl", appsimpl)
+
+
+--------------------------------
+-- Type argument propagation
+--------------------------------
+-- Remove all applications to type arguments, by duplicating the function
+-- called with the type application in its new definition. We leave
+-- dictionaries that might be associated with the type untouched, the funprop
+-- transform should propagate these later on.
+typeprop, typeproptop :: Transform
+-- Transform any function that is applied to a type argument. Since type
+-- arguments are always the first ones to apply and we'll remove all type
+-- arguments, we can simply do them one by one. We only propagate type
+-- arguments without any free tyvars, since tyvars those wouldn't be in scope
+-- in the new function.
+typeprop expr@(App (Var f) arg@(Type ty)) | not $ has_free_tyvars arg = do
+ body_maybe <- Trans.lift $ getGlobalBind f
+ case body_maybe of
+ Just body -> do
+ let newbody = App body (Type ty)
+ -- Create a new function with the same name but a new body
+ newf <- mkFunction f newbody
+ -- Replace the application with this new function
+ change (Var newf)
+ -- If we don't have a body for the function called, leave it unchanged (it
+ -- should be a primitive function then).
+ Nothing -> return expr
+-- Leave all other expressions unchanged
+typeprop expr = return expr
+-- Perform this transform everywhere
+typeproptop = everywhere ("typeprop", typeprop)
+
+
+--------------------------------
+-- Function-typed argument propagation
+--------------------------------
+-- Remove all applications to function-typed arguments, by duplication the
+-- function called with the function-typed parameter replaced by the free
+-- variables of the argument passed in.
+funprop, funproptop :: 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.
+funprop expr@(App _ _) | is_var fexpr && not (any has_free_tyvars args) = 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 <- mkFunction f newbody
+ -- 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 | is_fun arg = do
+ bndrs <- Trans.lift getGlobalBinders
+ -- 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 interesting var = Var.isLocalVar var && (not $ var `elem` bndrs)
+ let free_vars = VarSet.varSetElems $ CoreFVs.exprSomeFreeVars interesting arg
+ -- Mark the current expression as changed
+ setChanged
+ return (map Var free_vars, free_vars, arg)
+ -- Non-functiontyped arguments can be unchanged. Note that this handles
+ -- both values and types.
+ doarg arg = do
+ -- TODO: preserve original naming?
+ id <- 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
+funprop expr = return expr
+-- Perform this transform everywhere
+funproptop = everywhere ("funprop", funprop)
+
+--------------------------------
+-- 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 inlinefun,
+-- since that only inlines local let bindings, not top level bindings.
+funextract, funextracttop :: Transform
+funextract 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 <- 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 expr = return expr
+-- Perform this transform everywhere
+funextracttop = everywhere ("funextract", funextract)
+
+--------------------------------
+-- End of transformations
+--------------------------------
+
+
+
-- What transforms to run?
-transforms = []
+transforms = [typeproptop, funproptop, funextracttop, etatop, betatop, castproptop, letremovetop, letrectop, letsimpltop, letflattop, casewildtop, scrutsimpltop, casevalsimpltop, caseremovetop, inlinefuntop, appsimpltop]
+
+-- Turns the given bind into VHDL
+normalizeModule ::
+ UniqSupply.UniqSupply -- ^ A UniqSupply we can use
+ -> [(CoreBndr, CoreExpr)] -- ^ All bindings we know (i.e., in the current module)
+ -> [CoreBndr] -- ^ The bindings to generate VHDL for (i.e., the top level bindings)
+ -> [Bool] -- ^ For each of the bindings to generate VHDL for, if it is stateful
+ -> [(CoreBndr, CoreExpr)] -- ^ The resulting VHDL
--- Normalize a core expression by running transforms until none applies
--- anymore. Uses a UniqSupply to generate new identifiers.
-normalize :: UniqSupply.UniqSupply -> CoreExpr -> CoreExpr
-normalize = dotransforms transforms
+normalizeModule uniqsupply bindings generate_for statefuls = runTransformSession uniqsupply $ do
+ -- Put all the bindings in this module in the tsBindings map
+ putA tsBindings (Map.fromList bindings)
+ -- (Recursively) normalize each of the requested bindings
+ mapM normalizeBind generate_for
+ -- Get all initial bindings and the ones we produced
+ bindings_map <- getA tsBindings
+ let bindings = Map.assocs bindings_map
+ normalized_bindings <- getA tsNormalized
+ -- But return only the normalized bindings
+ return $ filter ((flip VarSet.elemVarSet normalized_bindings) . fst) bindings
+normalizeBind :: CoreBndr -> TransformSession ()
+normalizeBind bndr =
+ -- Don't normalize global variables, these should be either builtin
+ -- functions or data constructors.
+ Monad.when (Var.isLocalIdVar bndr) $ do
+ -- Skip binders that have a polymorphic type, since it's impossible to
+ -- create polymorphic hardware.
+ if is_poly (Var bndr)
+ then
+ -- This should really only happen at the top level... TODO: Give
+ -- a different error if this happens down in the recursion.
+ error $ "\nNormalize.normalizeBind: Function " ++ show bndr ++ " is polymorphic, can't normalize"
+ else do
+ normalized_funcs <- getA tsNormalized
+ -- See if this function was normalized already
+ if VarSet.elemVarSet bndr normalized_funcs
+ then
+ -- Yup, don't do it again
+ return ()
+ else do
+ -- Nope, note that it has been and do it.
+ modA tsNormalized (flip VarSet.extendVarSet bndr)
+ expr_maybe <- getGlobalBind bndr
+ case expr_maybe of
+ Just expr -> do
+ -- Introduce an empty Let at the top level, so there will always be
+ -- a let in the expression (none of the transformations will remove
+ -- the last let).
+ let expr' = Let (Rec []) expr
+ -- Normalize this expression
+ trace ("Transforming " ++ (show bndr) ++ "\nBefore:\n\n" ++ showSDoc ( ppr expr' ) ++ "\n") $ return ()
+ expr' <- dotransforms transforms expr'
+ trace ("\nAfter:\n\n" ++ showSDoc ( ppr expr')) $ return ()
+ -- And store the normalized version in the session
+ modA tsBindings (Map.insert bndr expr')
+ -- Find all vars used with a function type. All of these should be global
+ -- binders (i.e., functions used), since any local binders with a function
+ -- type should have been inlined already.
+ let used_funcs_set = CoreFVs.exprSomeFreeVars (\v -> (Type.isFunTy . snd . Type.splitForAllTys . Id.idType) v) expr'
+ let used_funcs = VarSet.varSetElems used_funcs_set
+ -- Process each of the used functions recursively
+ mapM normalizeBind used_funcs
+ return ()
+ -- We don't have a value for this binder. This really shouldn't
+ -- happen for local id's...
+ Nothing -> error $ "\nNormalize.normalizeBind: No value found for binder " ++ pprString bndr ++ "? This should not happen!"
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