From: Jacob Lifshay <programmerjake@gmail.com>
Date: Thu, 7 Apr 2022 02:59:03 +0000 (-0700)
Subject: change reference algorithm to be more amenable to bitwise operations
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=f86878c336b3155821189648b7b6d142fc87c1e5;p=nmigen-gf.git

change reference algorithm to be more amenable to bitwise operations
---

diff --git a/src/nmigen_gf/hdl/cldivrem.py b/src/nmigen_gf/hdl/cldivrem.py
index 9a89c43..c63ad60 100644
--- a/src/nmigen_gf/hdl/cldivrem.py
+++ b/src/nmigen_gf/hdl/cldivrem.py
@@ -23,16 +23,19 @@ def equal_leading_zero_count_reference(a, b, width):
     assert isinstance(b, int) and 0 <= b < (1 << width)
     eq = True  # both have no leading zeros so far...
     for i in range(width):
-        if (a >> i) & 1:
-            if (b >> i) & 1:
-                eq = True  # both have no leading zeros so far...
-            else:
-                eq = False  # different number of leading zeros
+        a_bit = (a >> i) & 1
+        b_bit = (b >> i) & 1
+        # `both_ones` is set if both have no leading zeros so far
+        both_ones = a_bit & b_bit
+        # `different` is set if there are a different number of leading
+        # zeros so far
+        different = a_bit != b_bit
+        if both_ones:
+            eq = True
+        elif different:
+            eq = False
         else:
-            if (b >> i) & 1:
-                eq = False  # different number of leading zeros
-            else:
-                pass  # propagate results from lower bits
+            pass  # propagate from lower bits
     return eq