From: lkcl 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