Merge branch 'master' of git://github.com/christiaanb/clash into cλash

[matthijs/master-project/cλash.git] / cλash / CLasH / Normalize.hs

diff --git a/cλash/CLasH/Normalize.hs b/cλash/CLasH/Normalize.hs
index 7571a6f3b0fbf21b33673fe59476bd217ab336ed..9828d5ceea96704f92b979766dd06be5bfcc7523 100644 (file)
--- a/cλash/CLasH/Normalize.hs
+++ b/cλash/CLasH/Normalize.hs
@@ -4,11 +4,12 @@
 -- top level function "normalize", and defines the actual transformation passes that
 -- are performed.
 --
 -- top level function "normalize", and defines the actual transformation passes that
 -- are performed.
 --

-module CLasH.Normalize (getNormalized) where
+module CLasH.Normalize (getNormalized, normalizeExpr, splitNormalized) where

 
 -- Standard modules
 import Debug.Trace
 import qualified Maybe
 
 -- 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 "transformers" Control.Monad.Trans as Trans
 import qualified Control.Monad as Monad
 import qualified Control.Monad.Trans.Writer as Writer


@@ -39,6 +40,7 @@ import CLasH.Normalize.NormalizeTools
 import CLasH.VHDL.VHDLTypes
 import qualified CLasH.Utils as Utils
 import CLasH.Utils.Core.CoreTools
 import CLasH.VHDL.VHDLTypes
 import qualified CLasH.Utils as Utils
 import CLasH.Utils.Core.CoreTools

+import CLasH.Utils.Core.BinderTools

 import CLasH.Utils.Pretty
 
 --------------------------------
 import CLasH.Utils.Pretty
 
 --------------------------------


@@ -51,7 +53,7 @@ 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
 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
   change (Lam id (App expr (Var id)))
 -- Leave all other expressions unchanged
 eta e = return e


@@ -90,14 +92,55 @@ castprop expr = return expr
 castproptop = everywhere ("castprop", castprop)
 
 --------------------------------
 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 (Rec [(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)
+

 --------------------------------
 --------------------------------

-letrec, letrectop :: Transform
-letrec (Let (NonRec b expr) res) = change $ Let (Rec [(b, expr)]) res
+-- let derecursification
+--------------------------------
+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 $ MkCore.mkCoreLets newbinds 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
+    -- Create nonrec bindings for each liftable binding and a single recursive
+    -- binding for all others
+    newbinds = (map (uncurry NonRec) liftable) ++ [Rec nonliftable]
+    -- 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
 -- Leave all other expressions unchanged

-letrec expr = return expr
+letderec expr = return expr

 -- Perform this transform everywhere
 -- Perform this transform everywhere

-letrectop = everywhere ("letrec", letrec)
+letderectop = everywhere ("letderec", letderec)

 
 --------------------------------
 -- let simplification
 
 --------------------------------
 -- let simplification


@@ -112,7 +155,7 @@ letsimpl expr@(Let (Rec binds) res) = do
     then do
       -- If the result is not a local var already (to prevent loops with
       -- ourselves), extract it.
     then do
       -- If the result is not a local var already (to prevent loops with
       -- ourselves), extract it.

-      id <- mkInternalVar "foo" (CoreUtils.exprType res)
+      id <- Trans.lift $ mkBinderFor res "foo"

       let bind = (id, res)
       change $ Let (Rec (bind:binds)) (Var id)
     else
       let bind = (id, res)
       change $ Let (Rec (bind:binds)) (Var id)
     else


@@ -156,6 +199,54 @@ letflattop = everywhere ("letflat", letflat)
 letremovetop :: Transform
 letremovetop = everywhere ("letremove", inlinebind (\(b, e) -> Trans.lift $ is_local_var e))
 
 letremovetop :: Transform
 letremovetop = everywhere ("letremove", inlinebind (\(b, e) -> Trans.lift $ is_local_var e))
 

+--------------------------------
+-- Unused let binding removal
+--------------------------------
+letremoveunused, letremoveunusedtop :: Transform
+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 (Rec binds) res) = do
+  binds' <- domerge binds
+  return (Let (Rec 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
 --------------------------------
 --------------------------------
 -- Function inlining
 --------------------------------


@@ -188,7 +279,7 @@ scrutsimpl expr@(Case scrut b ty alts) = do
   repr <- isRepr scrut
   if repr
     then do
   repr <- isRepr scrut
   if repr
     then do

-      id <- mkInternalVar "scrut" (CoreUtils.exprType scrut)
+      id <- Trans.lift $ mkBinderFor scrut "scrut"

       change $ Let (Rec [(id, scrut)]) (Case (Var id) b ty alts)
     else
       return expr
       change $ Let (Rec [(id, scrut)]) (Case (Var id) b ty alts)
     else
       return expr


@@ -262,7 +353,7 @@ casesimpl expr@(Case scrut b ty alts) = do
             -- Create on new binder that will actually capture a value in this
             -- case statement, and return it.
             let bty = (Id.idType b)
             -- 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))
             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))


@@ -282,7 +373,7 @@ casesimpl expr@(Case scrut b ty alts) = do
         -- prevent loops with inlinenonrep).
         if (not uses_bndrs) && (not local_var) && repr
           then do
         -- 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)
             -- 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)


@@ -322,7 +413,7 @@ appsimpl expr@(App f arg) = do
   local_var <- Trans.lift $ is_local_var arg
   if repr && not local_var
     then do -- Extract representable arguments
   local_var <- Trans.lift $ is_local_var arg
   if repr && not local_var
     then do -- Extract representable arguments

-      id <- mkInternalVar "arg" (CoreUtils.exprType arg)
+      id <- Trans.lift $ mkBinderFor arg "arg"

       change $ Let (Rec [(id, arg)]) (App f (Var id))
     else -- Leave non-representable arguments unchanged
       return expr
       change $ Let (Rec [(id, arg)]) (App f (Var id))
     else -- Leave non-representable arguments unchanged
       return expr


@@ -358,7 +449,7 @@ argprop expr@(App _ _) | is_var fexpr = do
           -- 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
           -- 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
           -- Replace the original application with one of the new function to the
           -- new arguments.
           change $ MkCore.mkCoreApps (Var newf) newargs


@@ -404,7 +495,7 @@ argprop expr@(App _ _) | is_var fexpr = do
           -- Representable types will not be propagated, and arguments with free
           -- type variables will be propagated later.
           -- TODO: preserve original naming?
           -- 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) 
           -- 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) 


@@ -451,7 +542,7 @@ funextract expr@(App _ _) | is_var fexpr = do
       -- by the argument expression.
       let free_vars = VarSet.varSetElems $ CoreFVs.exprFreeVars arg
       let body = MkCore.mkCoreLams free_vars arg
       -- 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.
       Trans.lift $ addGlobalBind id body
       -- Replace the argument with a reference to the new function, applied to
       -- all vars it uses.


@@ -472,7 +563,7 @@ funextracttop = everywhere ("funextract", funextract)
 
 
 -- What transforms to run?
 
 
 -- What transforms to run?

-transforms = [argproptop, funextracttop, etatop, betatop, castproptop, letremovetop, letrectop, letsimpltop, letflattop, scrutsimpltop, casesimpltop, caseremovetop, inlinenonreptop, appsimpltop]
+transforms = [argproptop, funextracttop, etatop, betatop, castproptop, letremovetop, letderectop, letsimpltop, letflattop, scrutsimpltop, casesimpltop, caseremovetop, inlinenonreptop, appsimpltop, letmergetop, letremoveunusedtop, castsimpltop]

 
 -- | Returns the normalized version of the given function.
 getNormalized ::
 
 -- | Returns the normalized version of the given function.
 getNormalized ::


@@ -487,14 +578,23 @@ getNormalized bndr = Utils.makeCached bndr tsNormalized $ do
       error $ "\nNormalize.normalizeBind: Function " ++ show bndr ++ " is polymorphic, can't normalize"
     else do
       expr <- getBinding bndr
       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

       -- 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
       -- 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 ()
+      trace (what ++ " before normalization:\n\n" ++ showSDoc ( ppr expr' ) ++ "\n") $ return ()

       expr'' <- dotransforms transforms expr'
       expr'' <- dotransforms transforms expr'

-      trace ("\nAfter:\n\n" ++ showSDoc ( ppr expr')) $ return ()
+      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
       return expr''
 
 -- | Get the value that is bound to the given binder at top level. Fails when


@@ -507,3 +607,31 @@ 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
   -- 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"
+
+-- | Flattens nested lets into a single list of bindings. The expression
+--   passed does not have to be a let expression, if it isn't an empty list of
+--   bindings is returned.
+flattenLets ::
+  CoreExpr -- ^ The expression to flatten.
+  -> ([Binding], CoreExpr) -- ^ The bindings and resulting expression.
+flattenLets (Let binds expr) = 
+  (bindings ++ bindings', expr')
+  where
+    -- Recursively flatten the contained expression
+    (bindings', expr') =flattenLets expr
+    -- Flatten our own bindings to remove the Rec / NonRec constructors
+    bindings = CoreSyn.flattenBinds [binds]
+flattenLets expr = ([], expr)