test_caller_bcd: mention reference implementation

diff --git a/src/openpower/decoder/isa/test_caller_bcd.py b/src/openpower/decoder/isa/test_caller_bcd.py
index 12b00b55288d7b343a062408c21370a8d54539e9..5cf3f2efd6678ebf2ed3cee8c6ff12dfcc43d4db 100644 (file)
--- a/src/openpower/decoder/isa/test_caller_bcd.py
+++ b/src/openpower/decoder/isa/test_caller_bcd.py
@@ -319,6 +319,8 @@ class BCDTestCase(FHDLTestCase):
         self.run_tst("cbcdtd", mapping)
 
     def test_addg6s(self):
+        # Reference implementation for addg6s, adopted to Python.
+        # https://github.com/antonblanchard/microwatt/blob/master/execute1.vhdl
         def addg6s(a, b):
             def bits(value, bits):
                 lsb = [((value >> bit) & 1) for bit in range(bits, -1, -1)]