From: Luke Kenneth Casson Leighton <lkcl@lkcl.net>
Date: Mon, 25 Apr 2022 20:03:10 +0000 (+0100)
Subject: use shift-and-or rather than mul-and-add in
X-Git-Tag: opf_rfc_ls005_v1~2591
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=1afca349cc91beebe7fd04260e0f9e9dbf85eb06;p=libreriscv.git

use shift-and-or rather than mul-and-add in
construction of 64-bit from 2x32-bit
---

diff --git a/openpower/sv/biginteger/divmnu64.c b/openpower/sv/biginteger/divmnu64.c
index 52e70a116..c77d9b780 100644
--- a/openpower/sv/biginteger/divmnu64.c
+++ b/openpower/sv/biginteger/divmnu64.c
@@ -98,9 +98,9 @@ int divmnu(unsigned q[], unsigned r[], const unsigned u[], const unsigned v[],
         k = 0; // the case of a
         for (j = m - 1; j >= 0; j--)
         {                                 // single-digit
-            uint64_t dig2 = (k * b + u[j]);
+            uint64_t dig2 = (k << 32 ) | u[j];
             q[j] = dig2 / v[0]; // divisor here.
-            k = dig2 % v[0]; // modulo bak into next loop
+            k    = dig2 % v[0]; // modulo back into next loop
         }
         if (r != NULL)
             r[0] = k;