From: lkcl <lkcl@web>
Date: Sat, 11 Dec 2021 21:21:41 +0000 (+0000)
Subject: (no commit message)
X-Git-Tag: opf_rfc_ls005_v1~3285
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=42499e421ea4ebbaed8af2077ca4939fe1064f54;p=libreriscv.git

---

diff --git a/openpower/sv/bitmanip.mdwn b/openpower/sv/bitmanip.mdwn
index 63db85117..d9c836bd9 100644
--- a/openpower/sv/bitmanip.mdwn
+++ b/openpower/sv/bitmanip.mdwn
@@ -462,37 +462,6 @@ uint64_t gorc64(uint64_t RA, uint64_t RB)
 
 ```
 
-# carryless mul
-
-based on RV bitmanip
-see https://en.wikipedia.org/wiki/CLMUL_instruction_set
-
-```
-uint_xlen_t clmul(uint_xlen_t RA, uint_xlen_t RB)
-{
-    uint_xlen_t x = 0;
-    for (int i = 0; i < XLEN; i++)
-        if ((RB >> i) & 1)
-            x ^= RA << i;
-    return x;
-}
-uint_xlen_t clmulh(uint_xlen_t RA, uint_xlen_t RB)
-{
-    uint_xlen_t x = 0;
-    for (int i = 1; i < XLEN; i++)
-        if ((RB >> i) & 1)
-            x ^= RA >> (XLEN-i);
-    return x;
-}
-uint_xlen_t clmulr(uint_xlen_t RA, uint_xlen_t RB)
-{
-    uint_xlen_t x = 0;
-    for (int i = 0; i < XLEN; i++)
-        if ((RB >> i) & 1)
-            x ^= RA >> (XLEN-i-1);
-    return x;
-}
-```
 # Galois Field
 
 see <https://courses.csail.mit.edu/6.857/2016/files/ffield.py>
@@ -611,6 +580,42 @@ def gf_invert(a, mod=0x1B) :
   return g1
 ```
 
+## carryless mul
+
+based on RV bitmanip
+see https://en.wikipedia.org/wiki/CLMUL_instruction_set
+
+these are GF2 operations with the modulo set to 2^degree.
+they are worth adding as their own non-overwrite operations
+(in the same pipeline).
+
+```
+uint_xlen_t clmul(uint_xlen_t RA, uint_xlen_t RB)
+{
+    uint_xlen_t x = 0;
+    for (int i = 0; i < XLEN; i++)
+        if ((RB >> i) & 1)
+            x ^= RA << i;
+    return x;
+}
+uint_xlen_t clmulh(uint_xlen_t RA, uint_xlen_t RB)
+{
+    uint_xlen_t x = 0;
+    for (int i = 1; i < XLEN; i++)
+        if ((RB >> i) & 1)
+            x ^= RA >> (XLEN-i);
+    return x;
+}
+uint_xlen_t clmulr(uint_xlen_t RA, uint_xlen_t RB)
+{
+    uint_xlen_t x = 0;
+    for (int i = 0; i < XLEN; i++)
+        if ((RB >> i) & 1)
+            x ^= RA >> (XLEN-i-1);
+    return x;
+}
+```
+
 # bitmatrix
 
 ```