From 4d34c747aad8cff48a6f0ef0ef4c6380d08bcae4 Mon Sep 17 00:00:00 2001
From: Luke Kenneth Casson Leighton <lkcl@lkcl.net>
Date: Thu, 14 Feb 2019 08:36:46 +0000
Subject: [PATCH] add code comments

---
 src/add/nmigen_add_experiment.py | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/add/nmigen_add_experiment.py b/src/add/nmigen_add_experiment.py
index 601b56e9..6628d766 100644
--- a/src/add/nmigen_add_experiment.py
+++ b/src/add/nmigen_add_experiment.py
@@ -188,16 +188,19 @@ class FPADD:
                 with m.State("add_0"):
                     m.next = "add_1"
                     m.d.sync += z_e.eq(a_e)
+                    # same-sign (both negative or both positive) add mantissas
                     with m.If(a_s == b_s):
                         m.d.sync += [
                             tot.eq(a_m + b_m),
                             z_s.eq(a_s)
                         ]
+                    # a mantissa greater than b, use a
                     with m.Else(a_m >= b_m):
                         m.d.sync += [
                             tot.eq(a_m - b_m),
                             z_s.eq(a_s)
                         ]
+                    # b mantissa greater than a, use b
                     with m.Else():
                         m.sync += [
                             tot.eq(b_m - a_m),
-- 
2.30.2