From: Luke Kenneth Casson Leighton <lkcl@lkcl.net>
Date: Thu, 14 Feb 2019 10:43:01 +0000 (+0000)
Subject: create and use decode function
X-Git-Tag: ls180-24jan2020~2011
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=5e1a88814def18d3d7f3241363f335d2a82d20f2;p=ieee754fpu.git

create and use decode function
---

diff --git a/src/add/nmigen_add_experiment.py b/src/add/nmigen_add_experiment.py
index 9b0bc87f..417d7f6f 100644
--- a/src/add/nmigen_add_experiment.py
+++ b/src/add/nmigen_add_experiment.py
@@ -15,6 +15,13 @@ class FPNum:
         self.e = Signal((10, True)) # Exponent: 10 bits, signed
         self.s = Signal()           # Sign bit
 
+    def decode(self):
+        v = self.v
+        return [self.m.eq(Cat(0, 0, 0, v[0:23])), # mantissa
+                self.e.eq(Cat(v[23:31]) - 127),   # exponent (take off bias)
+                self.s.eq(Cat(v[31])),            # sign
+                ]
+
     def create(self, s, e, m):
         return [
           self.v[31].eq(s),    # sign
@@ -102,17 +109,8 @@ class FPADD:
 
             with m.State("unpack"):
                 m.next = "special_cases"
-                m.d.sync += [
-                    # mantissa
-                    a.m.eq(Cat(0, 0, 0, a.v[0:23])),
-                    b.m.eq(Cat(0, 0, 0, b.v[0:23])),
-                    # exponent (take off exponent bias, here)
-                    a.e.eq(Cat(a.v[23:31]) - 127),
-                    b.e.eq(Cat(b.v[23:31]) - 127),
-                    # sign
-                    a.s.eq(Cat(a.v[31])),
-                    b.s.eq(Cat(b.v[31]))
-                ]
+                m.d.sync += a.decode()
+                m.d.sync += b.decode()
 
             # ******
             # special cases: NaNs, infs, zeros, denormalised