Fix broken mask when x == y

diff --git a/src/soc/decoder/helpers.py b/src/soc/decoder/helpers.py
index 0efdc439600fab381eb1c3902dfca2d54a4cb251..ef28c7ca7ef77a4386c91302401c0a2e6682ca22 100644 (file)
--- a/src/soc/decoder/helpers.py
+++ b/src/soc/decoder/helpers.py
@@ -53,6 +53,8 @@ def MASK(x, y):
         y = 63-y
         mask_a = ((1 << x) - 1) & ((1 << 64) - 1)
         mask_b = ((1 << y) - 1) & ((1 << 64) - 1)
+    elif x == y:
+        return 1 << (63-x)
     else:
         x = 64-x
         y = 63-y
@@ -109,6 +111,10 @@ class HelperTests(unittest.TestCase):
         # slw 1, 1, 2
         self.assertHex(MASK(32, 63-5), 0xffffffe0)
 
+        self.assertHex(MASK(32, 33), 0xc0000000)
+        self.assertHex(MASK(32, 32), 0x80000000)
+        self.assertHex(MASK(33, 33), 0x40000000)
+
     def test_ROTL64(self):
         # r1 = 0xdeadbeef12345678
         value = 0xdeadbeef12345678