From: Luke Kenneth Casson Leighton <lkcl@lkcl.net>
Date: Thu, 14 Feb 2019 06:20:23 +0000 (+0000)
Subject: add inf special case
X-Git-Tag: ls180-24jan2020~2030
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=0f623094c1018cbaf0945bafa043af3f6e67bc00;p=ieee754fpu.git

add inf special case
---

diff --git a/src/add/nmigen_add_experiment.py b/src/add/nmigen_add_experiment.py
index dcf7195a..2cb31c98 100644
--- a/src/add/nmigen_add_experiment.py
+++ b/src/add/nmigen_add_experiment.py
@@ -99,6 +99,22 @@ class FPADD:
                           z[22].eq(1),      # mantissa top bit: 1
                           z[0:22].eq(0)     # mantissa rest: 0b0000...
                     ]
+                # if a is inf return inf
+                with m.Elif(a_e == 128):
+                    m.next = "put_z"
+                    m.d.sync += [
+                        z[31].eq(a_s),    # sign: a_s
+                        z[23:31].eq(255), # exp: 0b11111...
+                        z[0:23].eq(0)     # mantissa rest: 0b0000...
+                    ]
+                    # if a is inf and signs don't match return NaN
+                    with m.If((b_e == 128) & (a_s != b_s)):
+                        m.d.sync += [
+                          z[31].eq(b_s),    # sign: b_s
+                          z[23:31].eq(255), # exp: 0b11111...
+                          z[22].eq(1),      # mantissa top bit: 1
+                          z[0:22].eq(0)     # mantissa rest: 0b0000...
+                        ]
         return m
 
 """