From: Jacob Lifshay <programmerjake@gmail.com>
Date: Fri, 3 Mar 2023 05:41:01 +0000 (-0800)
Subject: add justification for maddedus
X-Git-Tag: opf_rfc_ls001_v3~202
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=0912656f1789cc741450e0385f8420f8f727d51c;p=libreriscv.git

add justification for maddedus
---

diff --git a/openpower/sv/rfc/ls003.mdwn b/openpower/sv/rfc/ls003.mdwn
index 3d7615a9e..2e231eafa 100644
--- a/openpower/sv/rfc/ls003.mdwn
+++ b/openpower/sv/rfc/ls003.mdwn
@@ -91,6 +91,11 @@ TODO: address Jacob's comments: https://libre-soc.org/irclog/%23libre-soc.2022-1
 6. These are all 3-in 2-out instructions. If Power ISA did not already
   have LD/ST-with-update instructions and instructions with `RAp`
   and `RTp` then these instructions would not be proposed.
+7. `maddedus` is the first scalar signed/unsigned multiply instruction, the
+  only other signed/unsigned multiply instruction is `vmsummbm`, which has the
+  drawbacks that it is rather specialist, only working on bytes,
+  requires VSX/VMX, and isn't very suited for big-integer multiplication or
+  other general integer arithmetic.
 
 **Changes**