(no commit message)

diff --git a/openpower/sv/rfc/ls012.mdwn b/openpower/sv/rfc/ls012.mdwn
index 7107185c7bd226a94bd614fc1225de96ea67a589..2a4e5c910c151d0fca1d6b0c97b7abfffaecc89b 100644 (file)
--- a/openpower/sv/rfc/ls012.mdwn
+++ b/openpower/sv/rfc/ls012.mdwn
@@ -102,6 +102,23 @@ include `pcdec` and the Galois Field arithmetic operations. From a purely
 practical perspective due to the quantity the lower-priority instructions
 were simply left out. However they remain in the Libre-SOC resources.
 
+Some of these SFFS instructions appear to be duplicates of VSX.
+A frequent argument comes up that if instructions
+are in VSX already they should not be added to SFFS, especially if
+they are nominally the same.  The logic that this effectively damages
+performance of an SFFS-only implementation was raised earlier, however
+there is a more subtle reason why the instructions are needed.
+
+Future versions of SVP64 and SVP64Single are expected to be developed
+by future Power ISA Stakeholders on top of VSX.  The decisions made
+there about the meaning of Prefixed Vectorised VSX may be **completely**
+different from those made for Prefixed SFFS instructions.  At which
+point the lack of SFFS equivalents would penalise SFFS implementors
+in a much more severe way, effectively expecting them and SFFS programmers
+to work with a non-orthogonal paradigm, to their detriment.
+The solution is to give the SFFS Subset the space and respect that it deserves
+and allow it to be stand-alone on its own merits.
+
 ## SVP64 Management instructions
 
 These without question have to go in EXT0xx.  Future extended variants,