From: lkcl <lkcl@web>
Date: Mon, 18 Apr 2022 21:06:05 +0000 (+0100)
Subject: (no commit message)
X-Git-Tag: opf_rfc_ls005_v1~2717
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=b43442e8019f8a9e8cb4889b666f04deac83945e;p=libreriscv.git

---

diff --git a/openpower/sv/bitmanip/appendix.mdwn b/openpower/sv/bitmanip/appendix.mdwn
index dc1f64c69..643d4e94f 100644
--- a/openpower/sv/bitmanip/appendix.mdwn
+++ b/openpower/sv/bitmanip/appendix.mdwn
@@ -6,7 +6,21 @@ links
 * <https://lists.libre-soc.org/pipermail/libre-soc-dev/2022-April/004700.html>
 * <https://news.ycombinator.com/item?id=21151646>
 
-Row-based multiply using temporary vector
+Row-based multiply using temporary vector. Simple implementation
+of Knuth M: <https://git.libre-soc.org/?p=libreriscv.git;a=blob;f=openpower/sv/bitmanip/mulmnu.c;hb=HEAD>
+
+```
+      for (i = 0; i < m; i++) {
+         unsigned product = u[i]*v[j] + w[i + j];
+         phi[i] = product>>16;
+         plo[i] = product;
+      }
+      for (i = 0; i < m; i++) {
+         t = (phi[i]<<16) | plo[i] + k;
+         w[i + j] = t;          // (I.e., t & 0xFFFF).
+         k = t >> 16;
+      }
+```
 
 # big integer division