Don't try to simplify nested lets.

This would cause loops with letflat (and possibly with itself as well).

diff --git a/cλash/CLasH/Normalize.hs b/cλash/CLasH/Normalize.hs
index 07ded20bbb8d387c38372f749c9c79789d38cdbf..6a4825d42406343c5b6eb94191fdaf5b4ed554e0 100644 (file)
--- a/cλash/CLasH/Normalize.hs
+++ b/cλash/CLasH/Normalize.hs
@@ -146,6 +146,9 @@ letderectop = everywhere ("letderec", letderec)
 -- let simplification
 --------------------------------
 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
 -- 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