From: Luke Kenneth Casson Leighton <lkcl@lkcl.net>
Date: Fri, 29 Sep 2023 18:31:38 +0000 (+0100)
Subject: code-comments
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=d03d2ad5519baae17e77ab54ccd9aa32ca5bde16;p=openpower-isa.git

code-comments
---

diff --git a/src/openpower/test/bigint/powmod.py b/src/openpower/test/bigint/powmod.py
index 72fc239c..8cdeeabd 100644
--- a/src/openpower/test/bigint/powmod.py
+++ b/src/openpower/test/bigint/powmod.py
@@ -111,14 +111,15 @@ def python_mul_algorithm2(a, b):
             iyl.append((iy+i, i==4))
             il.append(i)
 
-    y = [0] * 8
-    t = [0] * 8
+    y = [0] * 8 # result y and temp t of same size
+    t = [0] * 8 # no need after this to set t[4] to zero
     for iy in range(4):
-        for i in range(4):
+        for i in range(4): # use t[iy+4] as a 64-bit carry
             t[iy+i], t[iy+4] = maddedu(a[iy], b[i], t[iy+4])
         ca = 0
-        for i in range(5):
-            y[iy + i], ca = adde(y[iy + i], t[iy+i], ca)
+        for i in range(5): # add vec t to y with 1-bit carry
+            idx = iy + i
+            y[idx], ca = adde(y[idx], t[idx], ca)
     return y