3 files changed, 9 insertions, 0 deletions
diff --git a/lib/flow.sail b/lib/flow.sail
index dd917b55..a2f6ed55 100644
--- a/lib/flow.sail
+++ b/lib/flow.sail
@@ -63,4 +63,7 @@ overload __size = {__id}
 
 val __deref = "reg_deref" : forall ('a : Type). register('a) -> 'a effect {rreg}
 
+/* Used to implement bitfield desugaring */
+val __bitfield_deref = "reg_deref" : forall ('a : Type). register('a) -> 'a effect pure
+
 $endif
diff --git a/lib/sail.c b/lib/sail.c
index c3fbe3b4..5530b462 100644
--- a/lib/sail.c
+++ b/lib/sail.c
@@ -323,6 +323,11 @@ void undefined_int(sail_int *rop, const int n)
   mpz_set_ui(*rop, (uint64_t) n);
 }
 
+void undefined_nat(sail_int *rop, const unit u)
+{
+  mpz_set_ui(*rop, 0);
+}
+
 inline
 void undefined_range(sail_int *rop, const sail_int l, const sail_int u)
 {
diff --git a/lib/sail.h b/lib/sail.h
index 87b2c476..b50a5a4c 100644
--- a/lib/sail.h
+++ b/lib/sail.h
@@ -129,6 +129,7 @@ SAIL_INT_FUNCTION(shr_int, sail_int, const sail_int, const sail_int);
  * constraints.
  */
 SAIL_INT_FUNCTION(undefined_int, sail_int, const int);
+SAIL_INT_FUNCTION(undefined_nat, sail_int, const unit);
 SAIL_INT_FUNCTION(undefined_range, sail_int, const sail_int, const sail_int);
 
 /*