From: Luke Kenneth Casson Leighton <lkcl@lkcl.net>
Date: Sun, 17 Apr 2022 16:43:19 +0000 (+0100)
Subject: add weirdmuladd to bitmanip appendix
X-Git-Tag: opf_rfc_ls005_v1~2754
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=c8bc7a56d9a4dc15ffc0c468c9675447b4c3a6bf;p=libreriscv.git

add weirdmuladd to bitmanip appendix
---

diff --git a/openpower/sv/bitmanip/appendix.mdwn b/openpower/sv/bitmanip/appendix.mdwn
index cdd3d7dba..edf85fea0 100644
--- a/openpower/sv/bitmanip/appendix.mdwn
+++ b/openpower/sv/bitmanip/appendix.mdwn
@@ -113,3 +113,10 @@ may be morphed to:
         }
 
 ```
+
+Transformation of 4-in, 2-out into a pair of operations:
+
+* 3-in, 2-out `msubx RT, RA, RB, RC` producing {RT,RS} where RS=RT+VL
+* 3-in, 2-out `weirdsubx RT, RA, RB` a hidden RS=RT+VL as input *and output*
+
+<img src="/openpower/sv/weirdmuladd.jpg" width=800 />