From: Luke Kenneth Casson Leighton <lkcl@lkcl.net>
Date: Sun, 17 Jan 2021 21:27:01 +0000 (+0000)
Subject: more notes about scalar reduction
X-Git-Tag: convert-csv-opcode-to-binary~427
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=02afa8ec4079703d83040eff1d6f9d448bdea8c0;p=libreriscv.git

more notes about scalar reduction
---

diff --git a/openpower/sv/svp64/appendix.mdwn b/openpower/sv/svp64/appendix.mdwn
index 96f6021ec..c97688080 100644
--- a/openpower/sv/svp64/appendix.mdwn
+++ b/openpower/sv/svp64/appendix.mdwn
@@ -203,6 +203,11 @@ It would be better to use addition followed by one final subtract,
 or in the case of divide, to get better accuracy, to perform a multiply
 cascade followed by a final divide.
 
+Note that single-operand or three-operand scalar-dest reduce is perfectly
+well permitted: both still meet the qualifying characteristics that one
+source operand can also be the destination, which allows the "accumulator"
+to be identified.
+
 ## Vector result reduce mode
 
 1. limited to single predicated dual src operations (add RT, RA, RB).