+ if not repr && not (is_var arg && interesting (exprToVar arg)) && not (has_free_tyvars arg)
+ then do
+ -- Propagate all complex arguments that are not representable, but not
+ -- arguments with free type variables (since those would require types
+ -- not known yet, which will always be known eventually).
+ -- Find interesting free variables, each of which should be passed to
+ -- the new function instead of the original function argument.
+ --
+ -- Interesting vars are those that are local, but not available from the
+ -- top level scope (functions from this module are defined as local, but
+ -- they're not local to this function, so we can freely move references
+ -- to them into another function).
+ let free_vars = VarSet.varSetElems $ CoreFVs.exprSomeFreeVars interesting arg
+ -- Mark the current expression as changed
+ setChanged
+ return (map Var free_vars, free_vars, arg)
+ else do
+ -- Representable types will not be propagated, and arguments with free
+ -- type variables will be propagated later.
+ -- TODO: preserve original naming?
+ id <- 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)
+-- Leave all other expressions unchanged
+argprop expr = return expr
+-- Perform this transform everywhere
+argproptop = everywhere ("argprop", argprop)
+
+--------------------------------
+-- 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
+