to be aware how the Arrays of vec2/3/4 become re-ordered
*and swizzled at the same time*.
-Pack/Unpack applies to
-[[sv/mv.vec]] as well however the uniform relationship and
-the fact that the source and destination subvector length
-must be the same (vec2/3/4) makes things slightly easier to
-understand. The main thing to keep in mind about Pack/Unpack
+Pack/Unpack started out as
+[[sv/mv.vec]] but became its own distinct Mode over time.
+The main thing to keep in mind about Pack/Unpack
is that it engages a swap of the ordering of the VL-SUBVL
nested for-loops, in exactly the same way that Matrix REMAP
-can do. When Pack or Unpack is enabled it is the SUBVL for-loop
-that becomes outermost.
+can do.
+When Pack or Unpack is enabled it is the SUBVL for-loop
+that becomes outermost. A bit of thought shows that this is
+a 2D "Transpose" where Dimension X is VL and Dimension Y is SUBVL.
+However *both* source *and* destination may be independently
+"Transposed", which makes no sense at all until the fact that
+Swizzle can have a *different SUBVL* is taken into account.
+
+Basically Pack/Unpack
# No Scalar GPR Move