From: lkcl <lkcl@web>
Date: Wed, 9 Mar 2022 23:40:17 +0000 (+0000)
Subject: (no commit message)
X-Git-Tag: opf_rfc_ls005_v1~3105
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=b8a3ca2f5e23ad80d7b789377bdfb6af300e023d;p=libreriscv.git

---

diff --git a/openpower/sv/bitmanip.mdwn b/openpower/sv/bitmanip.mdwn
index 6b3277bb3..3ed51ae91 100644
--- a/openpower/sv/bitmanip.mdwn
+++ b/openpower/sv/bitmanip.mdwn
@@ -736,6 +736,21 @@ uint_xlen_t clmulr(uint_xlen_t RA, uint_xlen_t RB)
     return x;
 }
 ```
+## carryless Twin Butterfly (Tukey-Cooley) Mul-add-sub
+
+used in combination with SV FFT REMAP to perform
+a full NTT in-place. possible by having 3-in 2-out,
+to avoid the need for a temp register.  RS is written
+to as well as RT.
+
+    clfmadd  RT,RA,RC,RB (Rc=0)
+    clfmadd. RT,RA,RC,RB (Rc=1)
+
+Pseudo-code:
+
+    RT <- CLMUL(RA, RC) ^ RB
+    RS <- CLMUL(RA, RC) ^ RB
+
 
 # bitmatrix