From: Jacob Lifshay <programmerjake@gmail.com>
Date: Fri, 18 Mar 2022 02:48:52 +0000 (-0700)
Subject: reduce RS for consistency in gfbtmadd
X-Git-Tag: opf_rfc_ls005_v1~3017
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=f78ea6039307bda2e3c2af0d0a5773da5a7264f5;p=libreriscv.git

reduce RS for consistency in gfbtmadd
---

diff --git a/openpower/sv/bitmanip.mdwn b/openpower/sv/bitmanip.mdwn
index ab2c7e2a9..ad120459e 100644
--- a/openpower/sv/bitmanip.mdwn
+++ b/openpower/sv/bitmanip.mdwn
@@ -701,7 +701,8 @@ c = (RC)
 # read all inputs before writing to any outputs in case
 # an input overlaps with an output register.
 (RT) = gfbmadd(a, (RB), c)
-(RS) = a ^ c
+# use gfbmadd again since it reduces the result
+(RS) = gfbmadd(a, 1, c) # "a * 1 + c"
 ```
 
 ## `gfbinv` -- Binary Galois Field `GF(2^m)` Inverse