From: Matthijs Kooijman <matthijs@stdin.nl>
Date: Tue, 30 Mar 2010 12:25:54 +0000 (+0200)
Subject: Pass the context in which an expression occurs to each transformation.
X-Git-Url: https://git.stderr.nl/gitweb?a=commitdiff_plain;h=3deb1d21f696f8495cd99345c9677210e2a2fc79;p=matthijs%2Fmaster-project%2Fc%CE%BBash.git

Pass the context in which an expression occurs to each transformation.

Currently, the only context supported is "Other" and contexts are only
passed around and not yet used anywhere.
---

diff --git "a/c\316\273ash/CLasH/Normalize.hs" "b/c\316\273ash/CLasH/Normalize.hs"
index 31474d5..fa6ae8c 100644
--- "a/c\316\273ash/CLasH/Normalize.hs"
+++ "b/c\316\273ash/CLasH/Normalize.hs"
@@ -48,12 +48,12 @@ import CLasH.Utils.Pretty
 -- η abstraction
 --------------------------------
 eta, etatop :: Transform
-eta expr | is_fun expr && not (is_lam expr) = do
+eta c expr | is_fun expr && not (is_lam expr) = 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 e = return e
+eta c e = return e
 etatop = notappargs ("eta", eta)
 
 --------------------------------
@@ -62,17 +62,17 @@ etatop = notappargs ("eta", eta)
 beta, betatop :: Transform
 -- 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
+beta c (App (Lam x expr) arg) | CoreSyn.isTyVar x = setChanged >> substitute x arg c expr
+                              | otherwise         = setChanged >> substitute_clone x arg c expr
 -- Propagate the application into the let
-beta (App (Let binds expr) arg) = change $ Let binds (App expr arg)
+beta c (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'
+beta 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
-beta expr = return expr
+beta c expr = return expr
 -- Perform this transform everywhere
 betatop = everywhere ("beta", beta)
 
@@ -81,12 +81,12 @@ betatop = everywhere ("beta", beta)
 --------------------------------
 -- 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')
+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 expr = return expr
+castprop c expr = return expr
 -- Perform this transform everywhere
 castproptop = everywhere ("castprop", castprop)
 
@@ -95,7 +95,7 @@ castproptop = everywhere ("castprop", castprop)
 -- perhaps for others as well.
 --------------------------------
 castsimpl, castsimpltop :: Transform
-castsimpl expr@(Cast val ty) = do
+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
@@ -110,7 +110,7 @@ castsimpl expr@(Cast val ty) = do
     else
       return expr
 -- Leave all other expressions unchanged
-castsimpl expr = return expr
+castsimpl c expr = return expr
 -- Perform this transform everywhere
 castsimpltop = everywhere ("castsimpl", castsimpl)
 
@@ -123,11 +123,11 @@ castsimpltop = everywhere ("castsimpl", castsimpl)
 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
+lambdasimpl c 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
+lambdasimpl c expr@(Lam bndr res) = do
   repr <- isRepr res
   local_var <- Trans.lift $ is_local_var res
   if not local_var && repr
@@ -140,7 +140,7 @@ lambdasimpl expr@(Lam bndr res) = do
       return expr
 
 -- Leave all other expressions unchanged
-lambdasimpl expr = return expr
+lambdasimpl c expr = return expr
 -- Perform this transform everywhere
 lambdasimpltop = everywhere ("lambdasimpl", lambdasimpl)
 
@@ -148,7 +148,7 @@ lambdasimpltop = everywhere ("lambdasimpl", lambdasimpl)
 -- let derecursification
 --------------------------------
 letderec, letderectop :: Transform
-letderec expr@(Let (Rec binds) res) = case liftable of
+letderec c expr@(Let (Rec binds) res) = case liftable of
   -- Nothing is liftable, just return
   [] -> return expr
   -- Something can be lifted, generate a new let expression
@@ -164,7 +164,7 @@ letderec expr@(Let (Rec binds) res) = case liftable of
     -- single bind recursive let.
     canlift (bndr, e) = not $ expr_uses_binders bndrs e
 -- Leave all other expressions unchanged
-letderec expr = return expr
+letderec c expr = return expr
 -- Perform this transform everywhere
 letderectop = everywhere ("letderec", letderec)
 
@@ -174,10 +174,10 @@ letderectop = everywhere ("letderec", letderec)
 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
+letsimpl c 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 binds res) = do
+letsimpl c expr@(Let binds res) = do
   repr <- isRepr res
   local_var <- Trans.lift $ is_local_var res
   if not local_var && repr
@@ -191,7 +191,7 @@ letsimpl expr@(Let binds res) = do
       return expr
 
 -- Leave all other expressions unchanged
-letsimpl expr = return expr
+letsimpl c expr = return expr
 -- Perform this transform everywhere
 letsimpltop = everywhere ("letsimpl", letsimpl)
 
@@ -205,9 +205,9 @@ letsimpltop = everywhere ("letsimpl", letsimpl)
 -- 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) = 
+letflat c (Let (NonRec b (Let binds  res')) res) = 
   change $ Let binds (Let (NonRec b res') res)
-letflat (Let (Rec binds) expr) = do
+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
@@ -222,7 +222,7 @@ letflat (Let (Rec binds) expr) = do
     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
+letflat c expr = return expr
 -- Perform this transform everywhere
 letflattop = everywhere ("letflat", letflat)
 
@@ -231,9 +231,9 @@ letflattop = everywhere ("letflat", letflat)
 --------------------------------
 -- Remove empty (recursive) lets
 letremove, letremovetop :: Transform
-letremove (Let (Rec []) res) = change res
+letremove c (Let (Rec []) res) = change res
 -- Leave all other expressions unchanged
-letremove expr = return expr
+letremove c expr = return expr
 -- Perform this transform everywhere
 letremovetop = everywhere ("letremove", letremove)
 
@@ -248,12 +248,12 @@ letremovesimpletop = everywhere ("letremovesimple", inlinebind (\(b, e) -> Trans
 -- Unused let binding removal
 --------------------------------
 letremoveunused, letremoveunusedtop :: Transform
-letremoveunused expr@(Let (NonRec b bound) res) = do
+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 expr@(Let (Rec binds) res) = do
+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
@@ -264,7 +264,7 @@ letremoveunused expr@(Let (Rec binds) res) = do
       -- expressions
       dobind (bndr, _) = any (expr_uses_binders [bndr]) (res:bound_exprs)
 -- Leave all other expressions unchanged
-letremoveunused expr = return expr
+letremoveunused c expr = return expr
 letremoveunusedtop = everywhere ("letremoveunused", letremoveunused)
 
 {-
@@ -275,7 +275,7 @@ letremoveunusedtop = everywhere ("letremoveunused", letremoveunused)
 -- 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
+letmerge c expr@(Let _ _) = do
   let (binds, res) = flattenLets expr
   binds' <- domerge binds
   return $ mkNonRecLets binds' res
@@ -296,7 +296,7 @@ letmerge expr@(Let _ _) = do
       -- Different expressions? Don't change
       | otherwise = return (b2, e2)
 -- Leave all other expressions unchanged
-letmerge expr = return expr
+letmerge c expr = return expr
 letmergetop = everywhere ("letmerge", letmerge)
 -}
 
@@ -344,10 +344,10 @@ inlinetoplevel, inlinetopleveltop :: Transform
 -- an infinite loop in transformation. Not inlining == is really a hack,
 -- but for now it keeps things working with the most common symptom of
 -- this problem.
-inlinetoplevel expr@(Var f) | Name.getOccString f `elem` ["==", "/="] = return expr
+inlinetoplevel c expr@(Var f) | Name.getOccString f `elem` ["==", "/="] = return expr
 -- Any system name is candidate for inlining. Never inline user-defined
 -- functions, to preserve structure.
-inlinetoplevel expr@(Var f) | not $ isUserDefined f = do
+inlinetoplevel c expr@(Var f) | not $ isUserDefined f = do
   body_maybe <- needsInline f
   case body_maybe of
     Just body -> do
@@ -360,7 +360,7 @@ inlinetoplevel expr@(Var f) | not $ isUserDefined f = do
 
 
 -- Leave all other expressions unchanged
-inlinetoplevel expr = return expr
+inlinetoplevel c expr = return expr
 inlinetopleveltop = everywhere ("inlinetoplevel", inlinetoplevel)
   
 -- | Does the given binder need to be inlined? If so, return the body to
@@ -393,14 +393,14 @@ needsInline f = do
 --------------------------------
 -- Inline all top level dictionaries, so we can use them to resolve
 -- class methods based on the dictionary passed. 
-inlinedict expr@(Var f) | Id.isDictId f = do
+inlinedict c expr@(Var f) | Id.isDictId f = do
   body_maybe <- Trans.lift $ getGlobalBind f
   case body_maybe of
     Nothing -> return expr
     Just body -> change body
 
 -- Leave all other expressions unchanged
-inlinedict expr = return expr
+inlinedict c expr = return expr
 inlinedicttop = everywhere ("inlinedict", inlinedict)
 
 --------------------------------
@@ -438,7 +438,7 @@ inlinedicttop = everywhere ("inlinedict", inlinedict)
 -- using $con2tag functions to translate a datacon to an int and compare
 -- that with GHC.Prim.==# . Better to avoid that for now.
 classopresolution, classopresolutiontop :: Transform
-classopresolution expr@(App (App (Var sel) ty) dict) | not is_builtin =
+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
@@ -463,7 +463,7 @@ classopresolution expr@(App (App (Var sel) ty) dict) | not is_builtin =
     is_builtin = elem (Name.getOccString sel) builtinIds
 
 -- Leave all other expressions unchanged
-classopresolution expr = return expr
+classopresolution c expr = return expr
 -- Perform this transform everywhere
 classopresolutiontop = everywhere ("classopresolution", classopresolution)
 
@@ -472,12 +472,12 @@ classopresolutiontop = everywhere ("classopresolution", classopresolution)
 --------------------------------
 scrutsimpl,scrutsimpltop :: Transform
 -- Don't touch scrutinees that are already simple
-scrutsimpl expr@(Case (Var _) _ _ _) = return expr
+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 expr@(Case scrut b ty alts) = do
+scrutsimpl c expr@(Case scrut b ty alts) = do
   repr <- isRepr scrut
   if repr
     then do
@@ -486,7 +486,7 @@ scrutsimpl expr@(Case scrut b ty alts) = do
     else
       return expr
 -- Leave all other expressions unchanged
-scrutsimpl expr = return expr
+scrutsimpl c expr = return expr
 -- Perform this transform everywhere
 scrutsimpltop = everywhere ("scrutsimpl", scrutsimpl)
 
@@ -501,18 +501,18 @@ scrutsimpltop = everywhere ("scrutsimpl", scrutsimpl)
 scrutbndrremove, scrutbndrremovetop :: 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 (Case (Var scrut) bndr ty alts) | bndr_used = do
+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) expr
+      expr' <- substitute bndr (Var scrut) c expr
       return (con, bndrs, expr')
     wild = MkCore.mkWildBinder (Id.idType bndr)
 -- Leave all other expressions unchanged
-scrutbndrremove expr = return expr
+scrutbndrremove c expr = return expr
 scrutbndrremovetop = everywhere ("scrutbndrremove", scrutbndrremove)
 
 --------------------------------
@@ -522,14 +522,14 @@ casesimpl, casesimpltop :: 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 expr@(Case scrut b ty [(con, bndrs, Var x)]) = return expr
+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 expr@(Case scrut bndr ty alts) | not bndr_used = do
+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
@@ -611,7 +611,7 @@ casesimpl expr@(Case scrut bndr ty alts) | not bndr_used = do
             -- Don't simplify anything else
             return (Nothing, expr)
 -- Leave all other expressions unchanged
-casesimpl expr = return expr
+casesimpl c expr = return expr
 -- Perform this transform everywhere
 casesimpltop = everywhere ("casesimpl", casesimpl)
 
@@ -622,11 +622,11 @@ casesimpltop = everywhere ("casesimpl", casesimpl)
 -- 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
+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 expr = return expr
+caseremove c expr = return expr
 -- Perform this transform everywhere
 caseremovetop = everywhere ("caseremove", caseremove)
 
@@ -637,7 +637,7 @@ caseremovetop = everywhere ("caseremove", caseremove)
 appsimpl, appsimpltop :: 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 expr@(App f arg) = do
+appsimpl c expr@(App f arg) = do
   -- Check runtime representability
   repr <- isRepr arg
   local_var <- Trans.lift $ is_local_var arg
@@ -648,7 +648,7 @@ appsimpl expr@(App f arg) = do
     else -- Leave non-representable arguments unchanged
       return expr
 -- Leave all other expressions unchanged
-appsimpl expr = return expr
+appsimpl c expr = return expr
 -- Perform this transform everywhere
 appsimpltop = everywhere ("appsimpl", appsimpl)
 
@@ -662,7 +662,7 @@ argprop, argproptop :: 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 expr@(App _ _) | is_var fexpr = do
+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
@@ -744,7 +744,7 @@ argprop expr@(App _ _) | is_var fexpr = do
           -- 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 expr = return expr
+argprop c expr = return expr
 -- Perform this transform everywhere
 argproptop = everywhere ("argprop", argprop)
 
@@ -757,7 +757,7 @@ argproptop = everywhere ("argprop", argprop)
 -- apply map to a lambda expression This will not conflict with inlinenonrep,
 -- since that only inlines local let bindings, not top level bindings.
 funextract, funextracttop :: Transform
-funextract expr@(App _ _) | is_var fexpr = do
+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.
@@ -795,7 +795,7 @@ funextract expr@(App _ _) | is_var fexpr = do
     doarg arg = return arg
 
 -- Leave all other expressions unchanged
-funextract expr = return expr
+funextract c expr = return expr
 -- Perform this transform everywhere
 funextracttop = everywhere ("funextract", funextract)
 
@@ -805,9 +805,9 @@ funextracttop = everywhere ("funextract", funextract)
 -- 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
+simplrestop c expr@(Lam _ _) = return expr
+simplrestop c expr@(Let _ _) = return expr
+simplrestop c expr = do
   local_var <- Trans.lift $ is_local_var expr
   -- Don't extract values that are not representable, to prevent loops with
   -- inlinenonrep
diff --git "a/c\316\273ash/CLasH/Normalize/NormalizeTools.hs" "b/c\316\273ash/CLasH/Normalize/NormalizeTools.hs"
index b9f4544..b1ca369 100644
--- "a/c\316\273ash/CLasH/Normalize/NormalizeTools.hs"
+++ "b/c\316\273ash/CLasH/Normalize/NormalizeTools.hs"
@@ -37,19 +37,18 @@ everywhere trans = applyboth (subeverywhere (everywhere trans)) trans
 -- Apply the first transformation, followed by the second transformation, and
 -- keep applying both for as long as expression still changes.
 applyboth :: Transform -> (String, Transform) -> Transform
-applyboth first (name, second) expr = do
+applyboth first (name, second) context expr = do
   -- Apply the first
-  expr' <- first expr
+  expr' <- first context expr
   -- Apply the second
-  (expr'', changed) <- Writer.listen $ second expr'
+  (expr'', changed) <- Writer.listen $ second context expr'
   if Monoid.getAny $
         -- trace ("Trying to apply transform " ++ name ++ " to:\n" ++ showSDoc (nest 4 $ ppr expr') ++ "\nType: \n" ++ (showSDoc $ nest 4 $ ppr $ CoreUtils.exprType expr') ++ "\n")
         changed 
     then 
      -- trace ("Applying transform " ++ name ++ " to:\n" ++ showSDoc (nest 4 $ ppr expr') ++ "\nType: \n" ++ (showSDoc $ nest 4 $ ppr $ CoreUtils.exprType expr') ++ "\n"
      --        ++ "Result of applying " ++ name ++ ":\n" ++ showSDoc (nest 4 $ ppr expr'') ++ "\n" ++ "Type: \n" ++ (showSDoc $ nest 4 $ ppr $ CoreUtils.exprType expr'') ++ "\n" ) $
-      applyboth first (name, second)
-        expr'' 
+      applyboth first (name, second) context expr'' 
     else 
       -- trace ("No changes") $
       return expr''
@@ -57,49 +56,49 @@ applyboth first (name, second) expr = do
 -- Apply the given transformation to all direct subexpressions (only), not the
 -- expression itself.
 subeverywhere :: Transform -> Transform
-subeverywhere trans (App a b) = do
-  a' <- trans a
-  b' <- trans b
+subeverywhere trans c (App a b) = do
+  a' <- trans (Other:c) a
+  b' <- trans (Other:c) b
   return $ App a' b'
 
-subeverywhere trans (Let (NonRec b bexpr) expr) = do
-  bexpr' <- trans bexpr
-  expr' <- trans expr
+subeverywhere trans c (Let (NonRec b bexpr) expr) = do
+  bexpr' <- trans (Other:c) bexpr
+  expr' <- trans (Other:c) expr
   return $ Let (NonRec b bexpr') expr'
 
-subeverywhere trans (Let (Rec binds) expr) = do
-  expr' <- trans expr
+subeverywhere trans c (Let (Rec binds) expr) = do
+  expr' <- trans (Other:c) expr
   binds' <- mapM transbind binds
   return $ Let (Rec binds') expr'
   where
     transbind :: (CoreBndr, CoreExpr) -> TransformMonad (CoreBndr, CoreExpr)
     transbind (b, e) = do
-      e' <- trans e
+      e' <- trans (Other:c) e
       return (b, e')
 
-subeverywhere trans (Lam x expr) = do
-  expr' <- trans expr
+subeverywhere trans c (Lam x expr) = do
+  expr' <- trans (Other:c) expr
   return $ Lam x expr'
 
-subeverywhere trans (Case scrut b t alts) = do
-  scrut' <- trans scrut
+subeverywhere trans c (Case scrut b t alts) = do
+  scrut' <- trans (Other:c) scrut
   alts' <- mapM transalt alts
   return $ Case scrut' b t alts'
   where
     transalt :: CoreAlt -> TransformMonad CoreAlt
     transalt (con, binders, expr) = do
-      expr' <- trans expr
+      expr' <- trans (Other:c) expr
       return (con, binders, expr')
 
-subeverywhere trans (Var x) = return $ Var x
-subeverywhere trans (Lit x) = return $ Lit x
-subeverywhere trans (Type x) = return $ Type x
+subeverywhere trans c (Var x) = return $ Var x
+subeverywhere trans c (Lit x) = return $ Lit x
+subeverywhere trans c (Type x) = return $ Type x
 
-subeverywhere trans (Cast expr ty) = do
-  expr' <- trans expr
+subeverywhere trans c (Cast expr ty) = do
+  expr' <- trans (Other:c) expr
   return $ Cast expr' ty
 
-subeverywhere trans expr = error $ "\nNormalizeTools.subeverywhere: Unsupported expression: " ++ show expr
+subeverywhere trans c expr = error $ "\nNormalizeTools.subeverywhere: Unsupported expression: " ++ show expr
 
 -- Apply the given transformation to all expressions, except for direct
 -- arguments of an application
@@ -110,34 +109,34 @@ notappargs trans = applyboth (subnotappargs trans) trans
 -- (but not the expression itself), except for direct arguments of an
 -- application
 subnotappargs :: (String, Transform) -> Transform
-subnotappargs trans (App a b) = do
-  a' <- subnotappargs trans a
-  b' <- subnotappargs trans b
+subnotappargs trans c (App a b) = do
+  a' <- subnotappargs trans (Other:c) a
+  b' <- subnotappargs trans (Other:c) b
   return $ App a' b'
 
 -- Let subeverywhere handle all other expressions
-subnotappargs trans expr = subeverywhere (notappargs trans) expr
+subnotappargs trans c expr = subeverywhere (notappargs trans) c expr
 
 -- Runs each of the transforms repeatedly inside the State monad.
 dotransforms :: [Transform] -> CoreExpr -> TranslatorSession CoreExpr
 dotransforms transs expr = do
-  (expr', changed) <- Writer.runWriterT $ Monad.foldM (flip ($)) expr transs
+  (expr', changed) <- Writer.runWriterT $ Monad.foldM (\e trans -> trans [] e) expr transs
   if Monoid.getAny changed then dotransforms transs expr' else return expr'
 
 -- Inline all let bindings that satisfy the given condition
 inlinebind :: ((CoreBndr, CoreExpr) -> TransformMonad Bool) -> Transform
-inlinebind condition expr@(Let (NonRec bndr expr') res) = do
+inlinebind condition context expr@(Let (NonRec bndr expr') res) = do
     applies <- condition (bndr, expr')
     if applies
       then do
         -- Substitute the binding in res and return that
-        res' <- substitute_clone bndr expr' res
+        res' <- substitute_clone bndr expr' context res
         change res'
       else
         -- Don't change this let
         return expr
 -- Leave all other expressions unchanged
-inlinebind _ expr = return expr
+inlinebind _ context expr = return expr
 
 -- Sets the changed flag in the TransformMonad, to signify that some
 -- transform has changed the result
@@ -161,7 +160,7 @@ changeif False val = return val
 -- Does not set the changed flag.
 substitute :: CoreBndr -> CoreExpr -> Transform
 -- Use CoreSubst to subst a type var in an expression
-substitute find repl expr = do
+substitute find repl context expr = do
   let subst = CoreSubst.extendSubst CoreSubst.emptySubst find repl
   return $ CoreSubst.substExpr subst expr 
 
@@ -170,12 +169,12 @@ substitute find repl expr = do
 -- expression are cloned before the replacement, to guarantee uniqueness.
 substitute_clone :: CoreBndr -> CoreExpr -> Transform
 -- If we see the var to find, replace it by a uniqued version of repl
-substitute_clone find repl (Var var) | find == var = do
+substitute_clone find repl context (Var var) | find == var = do
   repl' <- Trans.lift $ CoreTools.genUniques repl
   change repl'
 
 -- For all other expressions, just look in subexpressions
-substitute_clone find repl expr = subeverywhere (substitute_clone find repl) expr
+substitute_clone find repl context expr = subeverywhere (substitute_clone find repl) context expr
 
 -- Is the given expression representable at runtime, based on the type?
 isRepr :: (CoreTools.TypedThing t) => t -> TransformMonad Bool
diff --git "a/c\316\273ash/CLasH/Normalize/NormalizeTypes.hs" "b/c\316\273ash/CLasH/Normalize/NormalizeTypes.hs"
index 3affc87..a7de6dc 100644
--- "a/c\316\273ash/CLasH/Normalize/NormalizeTypes.hs"
+++ "b/c\316\273ash/CLasH/Normalize/NormalizeTypes.hs"
@@ -14,5 +14,8 @@ import CLasH.Translator.TranslatorTypes
 -- over a single expression and track if the expression was changed.
 type TransformMonad = Writer.WriterT Monoid.Any TranslatorSession
 
+-- | In what context does a core expression occur?
+data CoreContext = Other -- ^ Another context
+
 -- | Transforms a CoreExpr and keeps track if it has changed.
-type Transform = CoreSyn.CoreExpr -> TransformMonad CoreSyn.CoreExpr
+type Transform = [CoreContext] -> CoreSyn.CoreExpr -> TransformMonad CoreSyn.CoreExpr