add justification for maddedus

diff --git a/openpower/sv/rfc/ls003.mdwn b/openpower/sv/rfc/ls003.mdwn
index 3d7615a9eb4d502e279641da768d9b29778dbfbc..2e231eafaa2e0d5a733876df4f2dc4d0c6e4fcf2 100644 (file)
--- 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**