Fix typo.

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

diff --git a/cλash/CLasH/Normalize.hs b/cλash/CLasH/Normalize.hs
index bd0ec97e2b4a5be52acff046f81ecb7928ce77d7..0d352761dbafec889da2345d1b82bc9dab0b4542 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, normalizeExpr) 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


@@ -22,6 +23,7 @@ import qualified UniqSupply
 import qualified CoreUtils
 import qualified Type
 import qualified TcType
 import qualified CoreUtils
 import qualified Type
 import qualified TcType

+import qualified Name

 import qualified Id
 import qualified Var
 import qualified VarSet
 import qualified Id
 import qualified Var
 import qualified VarSet


@@ -62,8 +64,10 @@ etatop = notappargs ("eta", eta)
 -- β-reduction
 --------------------------------
 beta, betatop :: Transform
 -- β-reduction
 --------------------------------
 beta, betatop :: Transform

--- Substitute arg for x in expr
-beta (App (Lam x expr) arg) = change $ substitute [(x, arg)] expr
+-- Substitute arg for x in expr. For value lambda's, also clone before
+-- substitution.
+beta (App (Lam x expr) arg) | CoreSyn.isTyVar x = setChanged >> substitute x arg expr
+                            | otherwise      = setChanged >> substitute_clone 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
 -- 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


@@ -106,7 +110,7 @@ castsimpl expr@(Cast val ty) = do
       -- Generate a binder for the expression
       id <- Trans.lift $ mkBinderFor val "castval"
       -- Extract the expression
       -- Generate a binder for the expression
       id <- Trans.lift $ mkBinderFor val "castval"
       -- Extract the expression

-      change $ Let (Rec [(id, val)]) (Cast (Var id) ty)
+      change $ Let (NonRec id val) (Cast (Var id) ty)

     else
       return expr
 -- Leave all other expressions unchanged
     else
       return expr
 -- Leave all other expressions unchanged


@@ -114,32 +118,78 @@ castsimpl expr = return expr
 -- Perform this transform everywhere
 castsimpltop = everywhere ("castsimpl", castsimpl)
 
 -- Perform this transform everywhere
 castsimpltop = everywhere ("castsimpl", castsimpl)
 

+

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

--- let recursification
+-- Lambda simplication

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

-letrec, letrectop :: Transform
-letrec (Let (NonRec b expr) res) = change $ Let (Rec [(b, expr)]) res
+-- 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
 -- Leave all other expressions unchanged

-letrec expr = return expr
+lambdasimpl expr = return expr

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

-letrectop = everywhere ("letrec", letrec)
+lambdasimpltop = everywhere ("lambdasimpl", lambdasimpl)
+
+--------------------------------
+-- 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 $ 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
+letderec expr = return expr
+-- Perform this transform everywhere
+letderectop = everywhere ("letderec", letderec)

 
 --------------------------------
 -- let simplification
 --------------------------------
 letsimpl, letsimpltop :: Transform
 
 --------------------------------
 -- 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).
 -- 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.
   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 <- Trans.lift $ 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
     else
       -- If the result is already a local var, don't extract it.
       return expr


@@ -152,13 +202,18 @@ letsimpltop = everywhere ("letsimpl", letsimpl)
 --------------------------------
 -- let flattening
 --------------------------------
 --------------------------------
 -- 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
 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
 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.
   -- 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.


@@ -168,23 +223,40 @@ letflat (Let (Rec binds) expr) = do
     -- into a list with just that binding
     flatbind :: (CoreBndr, CoreExpr) -> TransformMonad [(CoreBndr, CoreExpr)]
     flatbind (b, Let (Rec binds) expr) = change ((b, expr):binds)
     -- 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)
 
     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
 --------------------------------
 -- 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
 
 --------------------------------
 -- 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
 letremoveunused expr@(Let (Rec binds) res) = do
   -- Filter out all unused binds.
   let binds' = filter dobind binds


@@ -199,6 +271,39 @@ letremoveunused expr@(Let (Rec binds) res) = do
 letremoveunused expr = return expr
 letremoveunusedtop = everywhere ("letremoveunused", letremoveunused)
 
 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
 --------------------------------
 --------------------------------
 -- Function inlining
 --------------------------------


@@ -217,6 +322,40 @@ letremoveunusedtop = everywhere ("letremoveunused", letremoveunused)
 inlinenonreptop :: Transform
 inlinenonreptop = everywhere ("inlinenonrep", inlinebind ((Monad.liftM not) . isRepr . snd))
 
 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 preserve structure.
+inlinetoplevel expr@(Var f) | not $ isUserDefined f = do
+  norm <- isNormalizeable f
+  -- See if this is a top level binding for which we have a body
+  body_maybe <- Trans.lift $ getGlobalBind f
+  if norm && Maybe.isJust body_maybe
+    then do
+      -- Get the normalized version
+      norm <- Trans.lift $ getNormalized f
+      if needsInline norm 
+        then do
+          -- Regenerate all uniques in the to-be-inlined expression
+          norm_uniqued <- Trans.lift $ genUniques norm
+          change norm_uniqued
+        else
+          return expr
+    else
+      -- No body or not normalizeable.
+      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
 --------------------------------
 --------------------------------
 -- Scrutinee simplification
 --------------------------------


@@ -231,8 +370,8 @@ scrutsimpl expr@(Case scrut b ty alts) = do
   repr <- isRepr scrut
   if repr
     then do
   repr <- isRepr scrut
   if repr
     then do

-      id <- Trans.lift $ 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
     else
       return expr
 -- Leave all other expressions unchanged


@@ -258,7 +397,7 @@ casesimpl 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
   (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),
   -- 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),


@@ -281,7 +420,7 @@ casesimpl expr@(Case scrut b ty alts) = do
     (exprbinding_maybe, expr') <- doexpr expr uses_bndrs
     -- Create a new alternative
     let newalt = (con, newbndrs, expr')
     (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
     return (bindings, newalt)
     where
       -- Make wild alternatives for each binder


@@ -293,7 +432,7 @@ casesimpl expr@(Case scrut b ty alts) = do
       -- binding containing a case expression.
       dobndr :: CoreBndr -> Int -> TransformMonad (CoreBndr, Maybe (CoreBndr, CoreExpr))
       dobndr b i = do
       -- 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)
         -- 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)


@@ -325,7 +464,7 @@ 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 <- Trans.lift $ 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)


@@ -365,8 +504,8 @@ 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 <- Trans.lift $ 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
     else -- Leave non-representable arguments unchanged
       return expr
 -- Leave all other expressions unchanged


@@ -507,6 +646,25 @@ funextract expr = return expr
 -- Perform this transform everywhere
 funextracttop = everywhere ("funextract", funextract)
 
 -- 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
 --------------------------------
 --------------------------------
 -- End of transformations
 --------------------------------


@@ -515,7 +673,7 @@ 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, letremoveunusedtop, castsimpltop]
+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 ::
 
 -- | Returns the normalized version of the given function.
 getNormalized ::


@@ -539,15 +697,12 @@ normalizeExpr ::
   -> TranslatorSession CoreSyn.CoreExpr -- ^ The normalized expression
 
 normalizeExpr what expr = do
   -> 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
+      expr_uniqued <- genUniques expr

       -- Normalize this expression
       -- Normalize this expression

-      trace ("Transforming " ++ what ++ "\nBefore:\n\n" ++ showSDoc ( ppr expr' ) ++ "\n") $ return ()
-      expr'' <- dotransforms transforms expr'
-      trace ("\nAfter:\n\n" ++ showSDoc ( ppr expr'')) $ return ()
-      return expr''
+      trace (what ++ " before normalization:\n\n" ++ showSDoc ( ppr expr_uniqued ) ++ "\n") $ return ()
+      expr' <- dotransforms transforms expr_uniqued
+      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.
 
 -- | Get the value that is bound to the given binder at top level. Fails when
 --   there is no such binding.


@@ -559,3 +714,16 @@ 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"