From: Luke Kenneth Casson Leighton <lkcl@lkcl.net>
Date: Thu, 9 May 2019 10:37:59 +0000 (+0100)
Subject: reduce ANDing chain (using NOR) in group picker
X-Git-Tag: div_pipeline~2093
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=b01ab17fcb948edb4dda903195a6b3a2f688371e;p=soc.git

reduce ANDing chain (using NOR) in group picker
---

diff --git a/src/scoreboard/group_picker.py b/src/scoreboard/group_picker.py
index 333d5b1b..022543f0 100644
--- a/src/scoreboard/group_picker.py
+++ b/src/scoreboard/group_picker.py
@@ -16,14 +16,15 @@ class PriorityPicker(Elaboratable):
         m = Module()
 
         res = []
+        ni = Signal(self.wid, reset_less = True)
+        m.d.comb += ni.eq(~self.i)
         for i in range(0, self.wid):
             t = Signal(reset_less = True)
             res.append(t)
             if i == 0:
-                m.d.comb += t.eq(self.i[0])
+                m.d.comb += t.eq(self.i[i])
             else:
-                m.d.comb += t.eq((~res[-2]) & self.i[i])
-            res.append(t)
+                m.d.comb += t.eq(~Cat(ni[i], *self.i[:i]).bool())
         
         # we like Cat(*xxx).  turn lists into concatenated bits
         m.d.comb += self.o.eq(Cat(*res))