diff --git a/minitests/litex/src.yosys/missing_bit_report.py b/minitests/litex/src.yosys/missing_bit_report.py
new file mode 100644
index 00000000..9fce9091
--- /dev/null
+++ b/minitests/litex/src.yosys/missing_bit_report.py
@@ -0,0 +1,81 @@
+""" Generates a missing feature/bit report for LiteX design.
+
+This script is fairly fragile, because it depends on the specific observation
+that all of the remaining bits appear to either belong to HCLK_IOI or IOI3 
+tiles.  A more general version of this script could be created, but that was
+not the point of this script.
+
+"""
+from fasm import parse_fasm_filename
+
+
+def main():
+    fasm_file = 'top.fasm'
+    fasm_model = list(parse_fasm_filename(fasm_file))
+
+    unknown_bits = {
+        'HCLK_IOI': {},
+        'IOI3': {},
+    }
+
+    total_unknown = 0
+    for l in fasm_model:
+        if l.annotations is None:
+            continue
+
+        annotations = {}
+        for annotation in l.annotations:
+            annotations[annotation.name] = annotation.value
+
+        if 'unknown_bit' not in annotations:
+            continue
+
+        total_unknown += 1
+
+        frame, word, bit = annotations['unknown_bit'].split('_')
+
+        frame = int(frame, 16)
+        word = int(word)
+        bit = int(bit)
+
+        frame_offset = frame % 0x80
+        base_frame = frame - frame_offset
+
+        # All remaining LiteX bits appear to be in this one IO bank, so limit
+        # the tool this this one IO bank.
+        assert base_frame == 0x00401580, hex(frame)
+
+        SIZE = 4
+        INITIAL_OFFSET = -2
+
+        if word == 50:
+            group = 'HCLK_IOI'
+            offset = 50
+        elif word < 50:
+            group = 'IOI3'
+            offset = ((word - INITIAL_OFFSET) // SIZE) * SIZE + INITIAL_OFFSET
+        else:
+            group = 'IOI3'
+            word -= 1
+            offset = ((word - INITIAL_OFFSET) // SIZE) * SIZE + INITIAL_OFFSET
+            offset += 1
+            word += 1
+
+        bit = '{}_{:02d}'.format(
+            frame_offset,
+            (word - offset) * 32 + bit,
+        )
+
+        if bit not in unknown_bits[group]:
+            unknown_bits[group][bit] = 0
+        unknown_bits[group][bit] += 1
+
+    print('Total unknown bits: {}'.format(total_unknown))
+    for group in unknown_bits:
+        print('Group {} (count = {}):'.format(group, len(unknown_bits[group])))
+        for bit in sorted(unknown_bits[group]):
+            print('  {} (count = {})'.format(bit, unknown_bits[group][bit]))
+
+
+if __name__ == "__main__":
+    main()