From: Konstantinos Margaritis <konstantinos.margaritis@vectorcamp.gr>
Date: Fri, 28 Apr 2023 16:42:31 +0000 (+0000)
Subject: working version, negatives work also
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=b1050a3f9f3cf9eb8c80f43de98c1f0b37171150;p=libreriscv.git

working version, negatives work also
---

diff --git a/openpower/sv/twin_butterfly.mdwn b/openpower/sv/twin_butterfly.mdwn
index c2014930b..deaf80d29 100644
--- a/openpower/sv/twin_butterfly.mdwn
+++ b/openpower/sv/twin_butterfly.mdwn
@@ -49,12 +49,14 @@ Pseudo-code:
     res1 <- ROTL64(prod1, XLEN-n)
     res2 <- ROTL64(prod2, XLEN-n)
     m <- MASK(n, (XLEN-1))
-    s1 <- res1[0]
-    s2 <- res2[0]
-    smask1 <- ([s1]*XLEN) & ¬m
-    smask2 <- ([s2]*XLEN) & ¬m
-    RT <- res1 & m | smask1
-    RS <- res2 & m | smask2
+    signbit1 <- res1[0]
+    signbit2 <- res2[0]
+    smask1 <- ([signbit1]*XLEN) & ¬m
+    smask2 <- ([signbit2]*XLEN) & ¬m
+    s64_1 <- [0]*(XLEN-1) || signbit1
+    s64_2 <- [0]*(XLEN-1) || signbit2
+    RT <- (res1 & m | smask1) + s64_1
+    RS <- (res2 & m | smask2) + s64_2
 ```
 
 Special Registers Altered: