From: lkcl Date: Wed, 29 Mar 2023 15:08:35 +0000 (+0100) Subject: (no commit message) X-Git-Tag: opf_rfc_ls001_v3~2 X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=e854709a1dcdc92c7be3fc59cf7b72c25e26c5f0;p=libreriscv.git --- diff --git a/openpower/sv/rfc/ls010.mdwn b/openpower/sv/rfc/ls010.mdwn index 3cf0c5013..71ffd21ac 100644 --- a/openpower/sv/rfc/ls010.mdwn +++ b/openpower/sv/rfc/ls010.mdwn @@ -34,15 +34,22 @@ and counting up as you move rightwards to the LSB end). All bit ranges are inclu element numbering however is LSB0 ordering** which is a different convention from that used elsewhere in the Power ISA. -64-bit instructions are split into two 32-bit words, the prefix and the -suffix. The prefix always comes before the suffix in PC order. +The SVP64 prefix always comes before the suffix in PC order and must be considered +an independent "Defined word" that augments the behaviour of the following instruction, +but does **not** change the actual Decoding of that following instruction. +**All prefixed instructions retain their non-prefixed encoding and definition**. + +*Architectural Resource Allocation note: it is **prohibited** to accept RFCs which +fundamentally violate this hard requirement. Under no circumstances must the +Suffix space have an alternate instruction encoding allocated within SVP64 that is +entirely different from the non-prefixed Defined Word. Hardware Implementors +critically rely on this inviolate guarantee to implement High-Performance Multi-Issue +micro-architectures that can sustain 100% throughput* | 0:5 | 6:31 | 32:63 | |--------|--------------|--------------| | EXT09 | v3.1 Prefix | v3.0/1 Suffix | -svp64 fits into the "reserved" portions of the v3.1 prefix, making it possible for svp64, v3.0B (or v3.1 including 64 bit prefixed) instructions to co-exist in the same binary without conflict. - Subset implementations in hardware are permitted, as long as certain rules are followed, allowing for full soft-emulation including future revisions. Compliancy Subsets exist to ensure minimum levels of binary