mention idea of reserving 25% only of PO9 for non-Vectorised uses

diff --git a/openpower/sv/rfc/ls001.mdwn b/openpower/sv/rfc/ls001.mdwn
index 48c63be0991dfc6547216fe6cb4a24e4d9b7bd58..15c0fd29cc29e820ca312f3da6ad5179f485829d 100644 (file)
--- a/openpower/sv/rfc/ls001.mdwn
+++ b/openpower/sv/rfc/ls001.mdwn
@@ -820,12 +820,10 @@ and reserved areas, QTY 1of 32-bit, and QTY 3of 55-bit, are:
 
 | 0-5 | 6 | 7 | 8-31  | 32-3 | Description               |
 |-----|---|---|-------|------|---------------------------|
-| PO9?| 1 | 0 | 0000  | xx   | `RESERVED1` or EXT300-363      |
-| PO9?| 0 | x | xxxx  | 0b00 | `RESERVED2` or EXT200-216    |
-| PO9?| 0 | x | xxxx  | 0b01 | `RESERVED2` or EXT216-231    |
-| PO9?| 0 | x | xxxx  | 0b10 | `RESERVED2` or EXT232-247   |
-
-Where:
+| PO9?| 1 | 0 | 0000  | xx   | `RESERVED1` or EXT300-363 (32-bit) |
+| PO9?| 0 | x | xxxx  | 0b00 | `RESERVED2` or EXT200-216 (55-bit) |
+| PO9?| 0 | x | xxxx  | 0b01 | `RESERVED2` or EXT216-231 (55-bit) |
+| PO9?| 0 | x | xxxx  | 0b10 | `RESERVED2` or EXT232-247 (55-bit) |
 
 * SVP64Single (`RESERVED3/4`) is *planned* for a future RFC
   (but needs reserving as part of this RFC)
@@ -851,9 +849,21 @@ Bit-allocation Summary:
 * QTY 3of 55-bit spaces also exist for future use (longer by 3 bits
   than opcodes allocated in EXT001)
 * Simple-V EXT2nn is restricted to range EXT248-263
-* non-Simple-V EXT2nn (if ever allocated by a future RFC) is restricted to range EXT200-247
+* non-Simple-V (non-Vectoriseable) EXT2nn (if ever requested in any future RFC) is restricted to range EXT200-247
 * Simple-V EXT0nn takes up 50% of PO9 for this and future Simple-V RFCs
 
+**This however potentially puts SVP64 under pressure (in 5-10 years).**
+Ideas being discussed already include adding LD/ST-with-Shift and variant
+Shift-Immediate operations that require large quantity of Primary Opcodes.
+To ensure that there is room in future,
+it may be better to allocate 25% to `RESERVED`:
+
+| 0-5 | 6 | 7 | 8-31  | 32  | Description               |
+|-----|---|---|-------|-----|---------------------------|
+| PO9?| 1 | 0 | 0000  | x   | EXT300-363 or `RESERVED1` (32-bit) |
+| PO9?| 0 | x | xxxx  | 0b0 | EXT200-232 or `RESERVED2` (56-bit) |
+| PO9?| 0 | x | xxxx  | 0b1 | EXT232-263 and SVP64(/V/S) |
+
 The clear separation between Simple-V and non-Simple-V stops
 conflict in future RFCs, both of which get plenty of space.
 EXT000-063 pressure is reduced in both Vectoriseable and