From: lkcl <lkcl@web>
Date: Thu, 8 Sep 2022 15:37:41 +0000 (+0100)
Subject: (no commit message)
X-Git-Tag: opf_rfc_ls005_v1~614
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=87f543be39b9e6f8b10ded67c182a1cfbde03a60;p=libreriscv.git

---

diff --git a/openpower/sv/rfc/ls001.mdwn b/openpower/sv/rfc/ls001.mdwn
index cc22c2043..65fb4e507 100644
--- a/openpower/sv/rfc/ls001.mdwn
+++ b/openpower/sv/rfc/ls001.mdwn
@@ -137,6 +137,24 @@ Supercomputing ISAs.
 * Parallel Reduction REMAP, performs an automatic map-reduce using *any suitable
   scalar operation*.
 
+# Scalar Operations.
+
+The primary reason for mentioning the additional Scalar operations is because
+they are so numerous, with Power ISA not having advanced in the *general purpose*
+compute area in the past 12 years, that some considerable care is needed.
+
+Summary: **to fit everything at least 75% of 3 Major Opcodes is required**
+
+Candidates include:
+
+* EXT006 (80% free)
+* EXT017 (75% free but not recommended)
+* EXT001 (50% free)
+* EXT009 (100% free)
+* EXT005 (100% free)
+* brownfield space in EXT019 (25% but NOT recommended)
+
+
 [^extend]: Prefix opcode space **must** be reserved in advance to do so, in order to avoid the catastrophic binary-incompatibility mistake made by RISC-V RVV and ARM SVE/2
 [^likeext001]: SVP64-Single is remarkably similar to the "bit 1" of EXT001 being set to indicate that the 64-bits is to be allocated in full to a new encoding, but in fact it still embeds v3.0 Scalar operations.
 [^pseudorewrite] elwidth overrides does however mean that all SFS / SFFS pseudocode will need rewriting to be in terms of XLEN. This has the indirect side-effect of automatically making a 32-bit Scalar Power ISA Specification possible, as well as a future 128-bit one (Cross-reference: RISC-V RV32 and RV128)