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)
+
--------------------------------
-- Function inlining
--------------------------------
-- 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, letrectop, letsimpltop, letflattop, scrutsimpltop, casesimpltop, caseremovetop, inlinenonreptop, appsimpltop, letremoveunusedtop]
-- | Returns the normalized version of the given function.
getNormalized ::
-- 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 ()
+ trace ("\nAfter:\n\n" ++ showSDoc ( ppr expr'')) $ return ()
return expr''
-- | Get the value that is bound to the given binder at top level. Fails when