-- top level function "normalize", and defines the actual transformation passes that
-- are performed.
--
-module CLasH.Normalize (normalizeModule) where
+module CLasH.Normalize (getNormalized, normalizeExpr, splitNormalized) where
-- Standard modules
import Debug.Trace
import qualified Maybe
+import qualified List
import qualified "transformers" Control.Monad.Trans as Trans
import qualified Control.Monad as Monad
import qualified Control.Monad.Trans.Writer as Writer
import qualified CoreUtils
import qualified Type
import qualified TcType
+import qualified Name
import qualified Id
import qualified Var
import qualified VarSet
-- Local imports
import CLasH.Normalize.NormalizeTypes
+import CLasH.Translator.TranslatorTypes
import CLasH.Normalize.NormalizeTools
import CLasH.VHDL.VHDLTypes
+import qualified CLasH.Utils as Utils
import CLasH.Utils.Core.CoreTools
+import CLasH.Utils.Core.BinderTools
import CLasH.Utils.Pretty
--------------------------------
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
+ id <- Trans.lift $ mkInternalVar "param" arg_ty
change (Lam id (App expr (Var id)))
-- Leave all other expressions unchanged
eta e = return e
castproptop = everywhere ("castprop", castprop)
--------------------------------
--- let recursification
+-- Cast simplification. Mostly useful for state packing and unpacking, but
+-- perhaps for others as well.
+--------------------------------
+castsimpl, castsimpltop :: Transform
+castsimpl 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 expr = return expr
+-- Perform this transform everywhere
+castsimpltop = everywhere ("castsimpl", castsimpl)
+
+
+--------------------------------
+-- Lambda simplication
+--------------------------------
+-- Ensure that a lambda always evaluates to a let expressions or a simple
+-- variable reference.
+lambdasimpl, lambdasimpltop :: Transform
+-- Don't simplify a lambda that evaluates to let, since this is already
+-- normal form (and would cause infinite loops).
+lambdasimpl expr@(Lam _ (Let _ _)) = return expr
+-- Put the of a lambda in its own binding, but not when the expression is
+-- already a local variable, or not representable (to prevent loops with
+-- inlinenonrep).
+lambdasimpl expr@(Lam bndr res) = do
+ repr <- isRepr res
+ local_var <- Trans.lift $ is_local_var res
+ if not local_var && repr
+ then do
+ id <- Trans.lift $ mkBinderFor res "res"
+ change $ Lam bndr (Let (NonRec id res) (Var id))
+ else
+ -- If the result is already a local var or not representable, don't
+ -- extract it.
+ return expr
+
+-- Leave all other expressions unchanged
+lambdasimpl expr = return expr
+-- Perform this transform everywhere
+lambdasimpltop = everywhere ("lambdasimpl", lambdasimpl)
+
+--------------------------------
+-- let derecursification
--------------------------------
-letrec, letrectop :: Transform
-letrec (Let (NonRec b expr) res) = change $ Let (Rec [(b, expr)]) res
+letderec, letderectop :: Transform
+letderec expr@(Let (Rec binds) res) = case liftable of
+ -- Nothing is liftable, just return
+ [] -> return expr
+ -- Something can be lifted, generate a new let expression
+ _ -> change $ mkNonRecLets liftable (Let (Rec nonliftable) res)
+ where
+ -- Make a list of all the binders bound in this recursive let
+ bndrs = map fst binds
+ -- See which bindings are liftable
+ (liftable, nonliftable) = List.partition canlift binds
+ -- Any expression that does not use any of the binders in this recursive let
+ -- can be lifted into a nonrec let. It can't use its own binder either,
+ -- since that would mean the binding is self-recursive and should be in a
+ -- single bind recursive let.
+ canlift (bndr, e) = not $ expr_uses_binders bndrs e
-- Leave all other expressions unchanged
-letrec expr = return expr
+letderec expr = return expr
-- Perform this transform everywhere
-letrectop = everywhere ("letrec", letrec)
+letderectop = everywhere ("letderec", letderec)
--------------------------------
-- let simplification
--------------------------------
letsimpl, letsimpltop :: Transform
+-- Don't simplify a let that evaluates to another let, since this is already
+-- normal form (and would cause infinite loops with letflat below).
+letsimpl expr@(Let _ (Let _ _)) = return expr
-- Put the "in ..." value of a let in its own binding, but not when the
-- expression is already a local variable, or not representable (to prevent loops with inlinenonrep).
-letsimpl expr@(Let (Rec binds) res) = do
+letsimpl expr@(Let binds res) = do
repr <- isRepr res
local_var <- Trans.lift $ is_local_var res
if not local_var && repr
then do
-- If the result is not a local var already (to prevent loops with
-- ourselves), extract it.
- id <- mkInternalVar "foo" (CoreUtils.exprType res)
- let bind = (id, res)
- change $ Let (Rec (bind:binds)) (Var id)
+ id <- Trans.lift $ mkBinderFor res "foo"
+ change $ Let binds (Let (NonRec id res) (Var id))
else
-- If the result is already a local var, don't extract it.
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, letflattop :: Transform
+-- Turn a nonrec let that binds a let into two nested lets.
+letflat (Let (NonRec b (Let binds res')) res) =
+ change $ Let binds (Let (NonRec b res') res)
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
+ -- 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.
-- 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 expr = return expr
-- Perform this transform everywhere
letflattop = everywhere ("letflat", letflat)
+--------------------------------
+-- empty let removal
+--------------------------------
+-- Remove empty (recursive) lets
+letremove, letremovetop :: Transform
+letremove (Let (Rec []) res) = change $ res
+-- Leave all other expressions unchanged
+letremove expr = return expr
+-- Perform this transform everywhere
+letremovetop = everywhere ("letremove", letremove)
+
--------------------------------
-- Simple let binding removal
--------------------------------
-- Remove a = b bindings from let expressions everywhere
-letremovetop :: Transform
-letremovetop = everywhere ("letremove", inlinebind (\(b, e) -> Trans.lift $ is_local_var e))
+letremovesimpletop :: Transform
+letremovesimpletop = everywhere ("letremovesimple", inlinebind (\(b, e) -> Trans.lift $ is_local_var e))
+
+--------------------------------
+-- Unused let binding removal
+--------------------------------
+letremoveunused, letremoveunusedtop :: Transform
+letremoveunused expr@(Let (NonRec b bound) res) = do
+ let used = expr_uses_binders [b] res
+ if used
+ then return expr
+ else change res
+letremoveunused 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 expr = return expr
+letremoveunusedtop = everywhere ("letremoveunused", letremoveunused)
+
+{-
+--------------------------------
+-- 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, letmergetop :: Transform
+letmerge 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 expr = return expr
+letmergetop = everywhere ("letmerge", letmerge)
+-}
--------------------------------
-- Function inlining
inlinenonreptop :: Transform
inlinenonreptop = everywhere ("inlinenonrep", inlinebind ((Monad.liftM not) . isRepr . snd))
+inlinetoplevel, inlinetopleveltop :: Transform
+-- Any system name is candidate for inlining. Never inline user-defined
+-- functions, to preserver structure.
+inlinetoplevel expr@(Var f) | not $ isUserDefined f = do
+ -- See if this is a top level binding for which we have a body
+ body_maybe <- Trans.lift $ getGlobalBind f
+ case body_maybe of
+ Just body -> do
+ -- Get the normalized version
+ norm <- Trans.lift $ getNormalized f
+ if needsInline norm
+ then
+ change norm
+ else
+ return expr
+ -- No body, this is probably a local variable or builtin or external
+ -- function.
+ Nothing -> return expr
+-- Leave all other expressions unchanged
+inlinetoplevel expr = return expr
+inlinetopleveltop = everywhere ("inlinetoplevel", inlinetoplevel)
+
+needsInline :: CoreExpr -> Bool
+needsInline expr = case splitNormalized expr of
+ -- Inline any function that only has a single definition, it is probably
+ -- simple enough. This might inline some stuff that it shouldn't though it
+ -- will never inline user-defined functions (inlinetoplevel only tries
+ -- system names) and inlining should never break things.
+ (args, [bind], res) -> True
+ _ -> False
+
--------------------------------
-- Scrutinee simplification
--------------------------------
repr <- isRepr scrut
if repr
then do
- id <- mkInternalVar "scrut" (CoreUtils.exprType scrut)
- change $ Let (Rec [(id, scrut)]) (Case (Var id) b ty alts)
+ 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
(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'))
+ let newlet = mkNonRecLets 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),
(exprbinding_maybe, expr') <- doexpr expr uses_bndrs
-- Create a new alternative
let newalt = (con, newbndrs, expr')
- let bindings = Maybe.catMaybes (exprbinding_maybe : bindings_maybe)
+ let bindings = Maybe.catMaybes (bindings_maybe ++ [exprbinding_maybe])
return (bindings, newalt)
where
-- Make wild alternatives for each binder
-- binding containing a case expression.
dobndr :: CoreBndr -> Int -> TransformMonad (CoreBndr, Maybe (CoreBndr, CoreExpr))
dobndr b i = do
- repr <- isRepr (Var b)
+ 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 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
+ id <- Trans.lift $ mkInternalVar "sel" bty
let binders = take i wildbndrs ++ [id] ++ drop (i+1) wildbndrs
let caseexpr = Case scrut b bty [(con, binders, Var id)]
return (wildbndrs!!i, Just (b, caseexpr))
-- prevent loops with inlinenonrep).
if (not uses_bndrs) && (not local_var) && repr
then do
- id <- mkInternalVar "caseval" (CoreUtils.exprType expr)
+ 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)
local_var <- Trans.lift $ is_local_var arg
if repr && not local_var
then do -- Extract representable arguments
- id <- mkInternalVar "arg" (CoreUtils.exprType arg)
- change $ Let (Rec [(id, arg)]) (App f (Var id))
+ 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
-- 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
+ newf <- Trans.lift $ mkFunction f newbody
-- Replace the original application with one of the new function to the
-- new arguments.
change $ MkCore.mkCoreApps (Var newf) newargs
-- Representable types will not be propagated, and arguments with free
-- type variables will be propagated later.
-- TODO: preserve original naming?
- id <- mkBinderFor arg "param"
+ 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)
-- by the argument expression.
let free_vars = VarSet.varSetElems $ CoreFVs.exprFreeVars arg
let body = MkCore.mkCoreLams free_vars arg
- id <- mkBinderFor body "fun"
+ 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.
-- Perform this transform everywhere
funextracttop = everywhere ("funextract", funextract)
+--------------------------------
+-- Ensure that a function that just returns another function (or rather,
+-- another top-level binder) is still properly normalized. This is a temporary
+-- solution, we should probably integrate this pass with lambdasimpl and
+-- letsimpl instead.
+--------------------------------
+simplrestop expr@(Lam _ _) = return expr
+simplrestop expr@(Let _ _) = return expr
+simplrestop expr = do
+ local_var <- Trans.lift $ is_local_var expr
+ -- Don't extract values that are not representable, to prevent loops with
+ -- inlinenonrep
+ repr <- isRepr expr
+ if local_var || not repr
+ then
+ return expr
+ else do
+ id <- Trans.lift $ mkBinderFor expr "res"
+ change $ Let (NonRec id expr) (Var id)
--------------------------------
-- End of transformations
--------------------------------
-- What transforms to run?
-transforms = [argproptop, funextracttop, etatop, betatop, castproptop, letremovetop, letrectop, letsimpltop, letflattop, scrutsimpltop, casesimpltop, caseremovetop, inlinenonreptop, appsimpltop]
-
--- Turns the given bind into VHDL
-normalizeModule ::
- HscTypes.HscEnv
- -> UniqSupply.UniqSupply -- ^ A UniqSupply we can use
- -> [(CoreBndr, CoreExpr)] -- ^ All bindings we know (i.e., in the current module)
- -> [CoreExpr]
- -> [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)], [(CoreBndr, CoreExpr)], TypeState) -- ^ The resulting VHDL
-
-normalizeModule env uniqsupply bindings testexprs generate_for statefuls = runTransformSession env uniqsupply $ do
- testbinds <- mapM (\x -> do { v <- mkBinderFor' x "test" ; return (v,x) } ) testexprs
- let testbinders = (map fst testbinds)
- -- Put all the bindings in this module in the tsBindings map
- putA tsBindings (Map.fromList (bindings ++ testbinds))
- -- (Recursively) normalize each of the requested bindings
- mapM normalizeBind (generate_for ++ testbinders)
- -- Get all initial bindings and the ones we produced
- bindings_map <- getA tsBindings
- let bindings = Map.assocs bindings_map
- normalized_binders' <- getA tsNormalized
- let normalized_binders = VarSet.delVarSetList normalized_binders' testbinders
- let ret_testbinds = zip testbinders (Maybe.catMaybes $ map (\x -> lookup x bindings) testbinders)
- let ret_binds = filter ((`VarSet.elemVarSet` normalized_binders) . fst) bindings
- typestate <- getA tsType
- -- But return only the normalized bindings
- return $ (ret_binds, ret_testbinds, typestate)
-
-normalizeBind :: CoreBndr -> TransformSession ()
-normalizeBind bndr =
- -- Don't normalize global variables, these should be either builtin
- -- functions or data constructors.
- Monad.when (Var.isLocalId 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.
- bndrs <- getGlobalBinders
- let used_funcs_set = CoreFVs.exprSomeFreeVars (\v -> not (Id.isDictId v) && v `elem` bndrs) 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!"
+transforms = [inlinetopleveltop, argproptop, funextracttop, etatop, betatop, castproptop, letremovesimpletop, letderectop, letremovetop, letsimpltop, letflattop, scrutsimpltop, casesimpltop, caseremovetop, inlinenonreptop, appsimpltop, letremoveunusedtop, castsimpltop, lambdasimpltop, simplrestop]
+
+-- | Returns the normalized version of the given function.
+getNormalized ::
+ CoreBndr -- ^ The function to get
+ -> TranslatorSession CoreExpr -- The normalized function body
+
+getNormalized bndr = Utils.makeCached bndr tsNormalized $ do
+ 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
+ expr <- getBinding bndr
+ normalizeExpr (show bndr) expr
+
+-- | 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
+ -- Normalize this expression
+ trace (what ++ " before normalization:\n\n" ++ showSDoc ( ppr expr ) ++ "\n") $ return ()
+ expr' <- dotransforms transforms expr
+ trace ("\n" ++ what ++ " after normalization:\n\n" ++ showSDoc ( ppr expr')) $ return ()
+ return expr'
+
+-- | Get the value that is bound to the given binder at top level. Fails when
+-- there is no such binding.
+getBinding ::
+ CoreBndr -- ^ The binder to get the expression for
+ -> TranslatorSession CoreExpr -- ^ The value bound to the binder
+
+getBinding bndr = Utils.makeCached bndr tsBindings $ do
+ -- If the binding isn't in the "cache" (bindings map), then we can't create
+ -- it out of thin air, so return an error.
+ error $ "Normalize.getBinding: Unknown function requested: " ++ show bndr
+
+-- | Split a normalized expression into the argument binders, top level
+-- bindings and the result binder.
+splitNormalized ::
+ CoreExpr -- ^ The normalized expression
+ -> ([CoreBndr], [Binding], CoreBndr)
+splitNormalized expr = (args, binds, res)
+ where
+ (args, letexpr) = CoreSyn.collectBinders expr
+ (binds, resexpr) = flattenLets letexpr
+ res = case resexpr of
+ (Var x) -> x
+ _ -> error $ "Normalize.splitNormalized: Not in normal form: " ++ pprString expr ++ "\n"