zero because there is no encoding space to select between -1, 0 and 1, and
0 and max values are more useful.
-# RM Mode Concept:
-
-MVRM-2P-1S1D:
-
-| Field Name | Field bits | Description |
-|------------|------------|----------------------------|
-| Rdest_EXTRA2 | `10:11` | extends Rdest (R\*\_EXTRA2 Encoding) |
-| Rsrc_EXTRA2 | `12:13` | extends Rsrc (R\*\_EXTRA2 Encoding) |
-| PACK_en | `14` | Enable pack |
-| UNPACK_en | `15` | Enable unpack |
-| MASK_SRC | `16:18` | Execution Mask for Source |
-
-The inclusion of a separate src SUBVL allows
-`sv.mv.swiz RT.vecN RA.vecN` to mean zip/unzip (pack/unpack).
-This is conceptually achieved by having both source and
+# Pack/Unpack Mode:
+
+It is possible to apply Pack and Unpack to Vectorised
+swizzle moves, and these instructions are of EXTRA type
+`RM-2P-1S1D-PU`. The interaction requires specific explanation
+because it involves the separate SUBVLs (with destination SUBVL
+being separate). Key to understanding is that the
+source and
destination SUBVL be "outer" loops instead of inner loops,
-exactly as in [[sv/remap]] Matrix mode.
+exactly as in [[sv/remap]] Matrix mode, under the control
+of `PACK_en` and `UNPACK_en`.
Illustrating a
-"normal" SVP64 operation with `SUBVL!=1:` (assuming no elwidth overrides):
+"normal" SVP64 operation with `SUBVL!=1` (assuming no elwidth overrides):
def index():
for i in range(VL):