Only apply eta expansion to expressions at the top level.

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

diff --git a/cλash/CLasH/Normalize.hs b/cλash/CLasH/Normalize.hs
index 89b5a8118691d99d9eb63077be7f761734478146..6ee0f0f220481094179a4eab5481863f1eb70d65 100644 (file)
--- a/cλash/CLasH/Normalize.hs
+++ b/cλash/CLasH/Normalize.hs
@@ -45,17 +45,16 @@ import CLasH.Utils.Pretty
 --------------------------------
 
 --------------------------------
--- η abstraction
---------------------------------
+-- η expansion
+--------------------------------
+-- Make sure all parameters to the normalized functions are named by top
+-- level lambda expressions. For this we apply η expansion to the
+-- function body (possibly enclosed in some lambda abstractions) while
+-- it has a function type. Eventually this will result in a function
+-- body consisting of a bunch of nested lambdas containing a
+-- non-function value (e.g., a complete application).
 eta, etatop :: Transform
--- Don't apply to expressions that are applied, since that would cause
--- us to apply to our own result indefinitely.
-eta (AppFirst:_) expr = return expr
--- Also don't apply to arguments, since this can cause loops with
--- funextract. This isn't the proper solution, but due to an
--- implementation bug in notappargs, this is how it used to work so far.
-eta (AppSecond:_) expr = return expr
-eta c expr | is_fun expr && not (is_lam expr) = do
+eta c expr | is_fun expr && not (is_lam expr) && all (== LambdaBody) c = do
   let arg_ty = (fst . Type.splitFunTy . CoreUtils.exprType) expr
   id <- Trans.lift $ mkInternalVar "param" arg_ty
   change (Lam id (App expr (Var id)))
@@ -353,7 +352,7 @@ inlinenonreptop = everywhere ("inlinenonrep", inlinebind ((Monad.liftM not) . is
 -- By not inlining any other reference, we also prevent looping problems
 -- with funextract and inlinedict.
 inlinetoplevel, inlinetopleveltop :: Transform
-inlinetoplevel (LetBinding:_) expr =
+inlinetoplevel (LetBinding:_) expr | not (is_fun expr) =
   case collectArgs expr of
        (Var f, args) -> do
          body_maybe <- needsInline f