From: lkcl <lkcl@web>
Date: Sat, 17 Jun 2023 00:36:41 +0000 (+0100)
Subject: (no commit message)
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=4dfc32a35c24dcd9e0f05010b4e5c1bd1360bf17;p=libreriscv.git

---

diff --git a/openpower/sv/po9_encoding/discussion.mdwn b/openpower/sv/po9_encoding/discussion.mdwn
index 829888f91..e92ae8137 100644
--- a/openpower/sv/po9_encoding/discussion.mdwn
+++ b/openpower/sv/po9_encoding/discussion.mdwn
@@ -104,6 +104,30 @@ Length detection:
 
 # alternative 32-64 encoding (3) **current**
 
+this idea gets even simpler. the 55-bit area is eliminated and may only be
+reintroduced by sacrificing parts of EXT200-263.
+
+```
+|0-5| 6-29   |30 31|32-37   | 38-663 | Description      |
+|---|--------|-----|--------|--------|------------------|
+|PO9| xxxx   | x x | 010001 |  ////  | RESERVED         |
+|PO9| xxxx   | x x | 000001 |  ////  | RESERVED         |
+|PO9| !ZERO  | 1 1 |  !PO9  |     xxxx        | SSingle:EXT232-263 |
+|PO9|  0000  | 1 1 |  !PO9  |     xxxx        | Scalar EXT232-263  |
+|PO9|  SVRM  | 1 0 |  !PO9  |     xxxx        | SVP64:EXT232-263   |
+|PO9|  0000  | 0 1 | Defined Word-instruction | 32-bit EXT300-363  |
+|PO9| !ZERO  | 0 1 | Defined Word-instruction | SSingle:EXT000-063 |
+|PO9|  SVRM  | 0 0 | Defined Word-instruction | SVP64:EXT000-063   |
+```
+* bit 31 is "SSingle"
+* bit 30 is EXT200-263 if set otherwise EXT000-063
+
+This was one of the original early PO9 Encodings.
+
+# alternative **no 32 encoding* (4) **current**
+
+
+
 aim of this idea is to attempt simplification of area identification
 and length.  the 55-bit area is eliminated and may only be reintroduced
 by sacrificing parts of EXT200-231, bear in mind that EXT240 is already