Allow arguments to builtins to be applications.

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

diff --git a/Normalize.hs b/Normalize.hs
index 9ee919ab524be8a211b99fe4b22bd7a03478079a..ee5ea8be621172a8d5b6269570f6e2b303776401 100644 (file)
--- a/Normalize.hs
+++ b/Normalize.hs
@@ -411,8 +411,56 @@ 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
 
--- TODO: introduce top level let if needed?
+-- Leave all other expressions unchanged
+funextract expr = return expr
+-- Perform this transform everywhere
+funextracttop = everywhere ("funextract", funextract)
 
 --------------------------------
 -- End of transformations
@@ -422,7 +470,7 @@ funproptop = everywhere ("funprop", funprop)
 
 
 -- What transforms to run?
-transforms = [typeproptop, funproptop, etatop, betatop, castproptop, letremovetop, letrectop, letsimpltop, letflattop, casewildtop, scrutsimpltop, casevalsimpltop, caseremovetop, inlinefuntop, appsimpltop]
+transforms = [typeproptop, funproptop, funextracttop, etatop, betatop, castproptop, letremovetop, letrectop, letsimpltop, letflattop, casewildtop, scrutsimpltop, casevalsimpltop, caseremovetop, inlinefuntop, appsimpltop]
 
 -- Turns the given bind into VHDL
 normalizeModule ::