From 5e92edc851c7c60fa84bd81938cb123c80bd10bf Mon Sep 17 00:00:00 2001
From: Luke Kenneth Casson Leighton <lkcl@lkcl.net>
Date: Sun, 23 Feb 2020 00:26:23 +0000
Subject: [PATCH] skip shiftermask when bitwid=0

---
 src/ieee754/part_shift/part_shift_dynamic.py | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/ieee754/part_shift/part_shift_dynamic.py b/src/ieee754/part_shift/part_shift_dynamic.py
index 4f75cc86..93188618 100644
--- a/src/ieee754/part_shift/part_shift_dynamic.py
+++ b/src/ieee754/part_shift/part_shift_dynamic.py
@@ -140,10 +140,13 @@ class PartitionedDynamicShift(Elaboratable):
         # partition varies dynamically.
         shifter_masks = []
         for i in range(len(b_intervals)):
+            bwid = b_intervals[i].shape()[0]
             bitwid = pwid-i
+            if bitwid == 0:
+                shifter_masks.append(C((1<<min_bits)-1, bwid))
+                continue
             max_bits = math.ceil(math.log2(width-intervals[i][0]))
-            sm = ShifterMask(bitwid, b_intervals[i].shape()[0],
-                             max_bits, min_bits)
+            sm = ShifterMask(bitwid, bwid, max_bits, min_bits)
             setattr(m.submodules, "sm%d" % i, sm)
             if bitwid != 0:
                 comb += sm.gates.eq(gates[i:pwid])
-- 
2.30.2